Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
ANTIMICROBIAL TRIBOELECTRIC MATERIAL
Document Type and Number:
WIPO Patent Application WO/2018/068100
Kind Code:
A1
Abstract:
The present disclosure generally provides antimicrobial triboelectric filtration material comprising a blend of positively charged wool fibres and negatively charged polypropylene fibres that form a triboelectric charge in the material. The triboelectric filtration material, for example the blend or wool fibres, also comprises an antimicrobial agent consisting of at least one of polyhexamethylene biguanide (PHMB) and quaternary ammonium compound (QAC). One advantage is that the material can be washed after use while still retaining its antimicrobial and triboelectric properties.

Inventors:
GAO, Yuan (c/- Commonwealth Scientific and Industrial Research Organisation, Clunies Ross StActon, Australian Capital Territory 2601, 2601, AU)
SCHUTZ, Jurg Arthur (c/- Commonwealth Scientific and Industrial Research Organisation, Clunies Ross StreetActon, Australian Capital Territory 2601, 2601, AU)
Application Number:
AU2017/051113
Publication Date:
April 19, 2018
Filing Date:
October 13, 2017
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
COMMONWEALTH SCIENTIFIC AND INDUSTRIAL RESEARCH ORGANISATION (Clunies Ross St, Acton, Australian Capital Territory 2601, 2601, AU)
International Classes:
D06M16/00; A41D13/11; A62B7/10; A62B23/02; B01D39/08
Foreign References:
US20070048356A12007-03-01
EP3061864A12016-08-31
FR2984176A12013-06-21
US20150061464A12015-03-05
US20130260625A12013-10-03
Download PDF:
Claims:
CLAIMS

1. An antimicrobial triboelectric filtration material comprising:

a blend of positively charged wool fibres and negatively charged polypropylene fibres that form a triboelectric charge in the material; and

an antimicrobial agent consisting of at least one of polyhexamethylene biguanide (PHMB) and quaternary ammonium compound (QAC);

wherein at least the wool fibres are impregnated or coated with an antimicrobial effective amount of the antimicrobial agent.

2. The antimicrobial triboelectric filtration material of claim 1, wherein the material is capable of maintaining elevated levels of electrostatic charge and exhibiting antimicrobial activity for a pre-determined time of at least 6 months. 3. The antimicrobial triboelectric filtration material of claim 1 or claim 2, wherein the antimicrobial agent consists of PHMB.

4. The antimicrobial triboelectric filtration material of any one of claims 1 to 3, wherein the amount of PHMB in the material based on total weight % of the wool fibre component, is at least 1.0 wt. %.

5. The antimicrobial triboelectric filtration material of any one of claims 1 to 4, wherein the amount of PHMB in the material based on total weight % of the wool fibre component, is at least 2.0 wt. %.

6. The antimicrobial triboelectric filtration material of any one of claims 1 to 5, wherein the material optionally comprises one or more additives.

7. The antimicrobial triboelectric filtration material of claim 6, wherein the one or more additives is a non-charge depleting agent.

8. The antimicrobial triboelectric filtration material of claim 7, wherein the non- charge depleting agent is a lanolin, suint, inorganic dirt, vegetable matter on wool fibres (VM), rosin, pine sap, colourant, dye, fragrance, washing agent, knitting wax, paraffin, carnauba wax, lanolin, anionic fabric scouring agent, hydrocarbon alkane oil, or hydrocarbon alkene oil.

9. The antimicrobial triboelectric filtration material of claim 7, wherein the non- charge depleting agent is a resin.

10. The antimicrobial triboelectric filtration material of any one of claims 6 to 9, wherein the one or more additives, if present in the material, are in a total amount based on total weight % of the material, of less than about 5 wt. %.

11. The antimicrobial triboelectric filtration material of any one of claims 1 to 10, wherein the material optionally comprises one or more incidental impurity.

12. The antimicrobial triboelectric filtration material of claim 11, wherein the one or more incidental impurity is an aliphatic fatty ester or ethoxylate, antistatic compound, texturizing agent, fabric softening agent, or lubricating agent. 13. The antimicrobial triboelectric filtration material of claim 12, wherein the antistatic compound is a hydrophilic antistatic agent.

14. The antimicrobial triboelectric filtration material of any one of claims 11 to 13, wherein the one or more incidental impurities, if present in the material, are in a total amount based on weight % of the material, of less than about 2 wt. %.

15. The antimicrobial triboelectric filtration material of any one of claims 1 to 14, wherein the amount of antimicrobial reduction according to AATCC Method 100 is at least 90%.

16. The antimicrobial triboelectric filtration material of any one of claims 1 to 15, wherein the pressure drop (in Pa) across the material (using PCFTI testing or specify specific instrument and conditions) is less than about 250 Pa. 17. The antimicrobial triboelectric filtration material of any one of claims 1 to 16, wherein the quality factor, Q, at 0.15 ms"1 face velocity for a 0.3 to 0.5 μιη potassium chloride particle size (Q.0.3) measured using a PCFTI instrument is at least about 22kPa

1

18. The antimicrobial triboelectric filtration material of any one of claims 1 to 17, wherein the quality factor, Qx, for a 0.3 to 0.5 μιη potassium chloride particle size (Q.0.3) measured using a PCFTI instrument is at least about 55 nm (e.g., 55 χ 10" metres).

19. The antimicrobial triboelectric filtration material of any one of claims 1 to 18, wherein the quality factor, Q, at zero dust loading is at least 3 times that of the value of the fully loaded antimicrobial filtration material.

20. The antimicrobial triboelectric filtration material of any one of claims 1 to 19, wherein the positively charged wool fibres are Bunte salt pre-treated wool fibres comprising the antimicrobial agent.

21. The antimicrobial triboelectric filtration material of claim 20, wherein the Bunte salt pre-treated wool fibres comprise at least a portion of the wool fibres bearing at least one of -S-S03" and -S-S03"Na+ functionality.

22. The antimicrobial triboelectric filtration material of claim 21, wherein at least about 50% of the wool fibres in the triboelectric filtration material bear at least one of -S-SO3" and -S03"Na+ functionality. 23. The antimicrobial triboelectric filtration material of any one of claims 1 to 22, wherein the ratio of total surface area of wool fibres to polypropylene fibres in the material is in a range of 30:70 to 70:30.

24. The antimicrobial triboelectric filtration material of any one of claims 1 to 23, wherein the wool fibres and polypropylene fibres each independently have fibre diameters in the range of about 5 to 100 microns.

25. The antimicrobial triboelectric filtration material of any one of claims 1 to 24, wherein the wool fibres and polypropylene fibres each independently have individual fibre lengths of between about 10 to 150 mm.

26. The antimicrobial triboelectric filtration material of any one of claims 1 to 25, wherein the material is a fabric. 27. The antimicrobial triboelectric filtration material of any one of claims 1 to 26, wherein the material is a woven fabric, a non-woven felt, a knitted fabric, or a fibrous composite structure. The antimicrobial triboelectric filtration material of any one of claims 1 to 27, in the material has a thickness of between about 1 mm to 10 mm. 29. The antimicrobial triboelectric filtration material of any one of claims 1 to 28, wherein the material has a basis weight (gem 2) of between about 30 and 800 gem"2, or a packing density of between about 0.8% and 40%.

30. The antimicrobial triboelectric filtration material of any one of claims 1 to 29, wherein the filtration efficiency is between about 25% and about 99.97%.

31. A fabric, garment or respirator device comprising the antimicrobial triboelectric filtration material according to any one of claims 1 to 30. 32. A respiratory filter or respiratory face mask comprising the antimicrobial triboelectric filtration material according to any one of claims 1 to 31.

33. An antimicrobial triboelectric filtration material consisting of a blend of positively charged wool fibres and negatively charged polypropylene fibres that form a triboelectric charge in the material; and an antimicrobial agent selected from at least one of polyhexamethylene biguanide (PHMB) and quaternary ammonium compound (QAC), wherein at least the wool fibres are impregnated or coated with an

antimicrobial effective amount of the antimicrobial agent; and other than any incidental impurities optionally one or more additives.

34. An antimicrobial triboelectric filtration material consisting of:

a blend of positively charged wool fibres and negatively charged polypropylene fibres that form a triboelectric charge in the material; and

an antimicrobial agent selected from at least one of polyhexamethylene biguanide (PHMB) and quaternary ammonium compound (QAC), wherein at least the wool fibres are impregnated or coated with an antimicrobial effective amount of the antimicrobial agent; and

the one or more additives are selected from non-charge depleting agents provided in a total amount based on total weight % of the material of less than about 5 wt.%; and the incidental impurities are selected from one or more charge depleting agents provided in a total amount based on total weight % of the material of less than about 2 wt. %. 35. A method for preparing an antimicrobial triboelectric filtration material comprising a blend of positively charged wool fibres and negatively charged polypropylene fibres, comprising:

applying an antimicrobial agent consisting of at least one of polyhexamethylene biguanide (PHMB) and quaternary ammonium compound (QAC) to wool fibres to at least impregnate or coat the wool fibres with an antimicrobial effective amount of the antimicrobial agent, and blending the wool fibres with polypropylene fibres to form an antimicrobial triboelectric filtration material; or

applying an antimicrobial agent consisting of at least one of polyhexamethylene biguanide (PHMB) and quaternary ammonium compound (QAC) to a triboelectric filtration material comprising a blend of untreated wool fibres and polypropylene fibres to at least impregnate or coat the material with an antimicrobial effective amount of the antimicrobial agent wherein at least the wool fibres comprise untreated wool fibres that have initially undergone a pre-treatment process. 36. The method of claim 35, wherein the wool fibres have initially undergone the pre-treatment process and the polypropylene fibres have not initially undergone the pre-treatment process.

37. The method of claim 35, wherein the blend of untreated wool fibres and polypropylene fibres has initially undergone the pre-treatment process.

38. The method of any one of claims 35 to 37, wherein the pre-treatment process comprises: contacting the untreated wool fibres or blend of untreated wool fibres and polypropylene fibres with a sulfate composition; and

then contacting the resultant wool fibres or blend of wool fibres and polypropylene fibres with a sulfite composition.

39. The method of claim 38, wherein the resultant wool fibres or blend of wool fibres and polypropylene fibres are rinsed between the contact with the sulfate composition and the contact with the sulfite composition.

40. The method of claim 38 or claim 39, wherein contacting the untreated wool fibres or blend of untreated wool fibres and polypropylene fibres with the sulfate composition occurs in the presence of a surfactant. 41. The method of any one of claims 38 to 40, wherein the sulfate composition comprises potassium peroxymonosulfate (PMS).

42. The method of any one of claims 38 to 41, wherein the sulfite composition comprises sodium sulfite.

43. The method of claim 42, wherein the sodium sulfite is initially adjusted to a pH or between about 8.0 and 8.5.

44. The method of any one of claims 38 to 43, wherein the surfactant comprises Triton X-100.

45. The method of any one of claims 38 to 44, wherein the pre-treatment process comprises finally rinsing the wool fibres or blend of wool fibres and polypropylene fibres with water and optionally drying.

46. The method of any one of claims 38 to 45, wherein the pre-treatment process results in at least a portion of the wool fibres bearing -S-S03" functionality or wool fibres bearing -S-S03~Na+ functionality. 47. The method of claim 46, wherein at least about 50% of the wool fibres in the triboelectric filtration material bear -S-S03" functionality or -S-S03~Na+ functionality.

48. The method of claim 46 or claim 47, wherein the -S-S03" functionality or -S-S03 Na+ is detected by Fourier-transform infrared spectroscopy (FTI ).

49. The method of any one of claims 35 to 48, wherein the antimicrobial agent is applied at a pH of about 6.5 to about 7.5.

50. The method of any one of claims 34 to 49, wherein the antimicrobial agent is applied at a pH of about 7.0.

51. The method of any one of claims 35 to 50, wherein the method further comprises drying the antimicrobial triboelectric filtration material to facilitate electrostatic re-charging. 52. An antimicrobial triboelectric filtration material prepared according to the method of any one of claims 35 to 51.

53. A use of an antimicrobial triboelectric filtration material according to any one of claims 1 to 34, as a filter of particulates in a respiratory device, fabric, garment, carpet, drapes, bedding material, automotive fabric or material, or aircraft fabric or material.

54. The use according to claim 53, wherein the use is as a respiratory filter or respiratory face mask.

Description:
ANTIMICROBIAL TRIBOELECTRIC MATERIAL

FIELD

The present disclosure relates to an antimicrobial triboelectric filtration material, a method of preparing an antimicrobial triboelectric filtration material, a garment or device comprising an antimicrobial triboelectric filtration material, or use of an antimicrobial triboelectric filtration material as a respiratory filter.

BACKGROUND

Antimicrobial treatments of textiles have attracted considerable attention in recent years, and it is estimated that antimicrobial textiles are one of the fastest growing sectors of the textile market. The antimicrobial treatments serve to inhibit the growth of, or kill, microorganisms on the textile. This provides not only health and hygienic benefits to users of the textile, but also protects the textile from discoloration and physical deterioration that can arise from bacterial growth. Ideally, the antimicrobial should be effective against a broad spectrum of bacterial and fungal species, but at the same time, exhibit low toxicity to consumers.

Textiles that have been treated with an antimicrobial find use in several applications, including, for example, respiratory filters, automotive textiles, home furnishings, medical textiles, clothing, and both domestic and commercial bedding materials (i.e. mattress protectors, bed sheets, pillow covers). Such textiles may be knitted, woven or non-woven in nature.

Electrostatic charge may increase the particle collection efficiency of a textile, provided the charge is applied, stored and preserved inside the textile structure in a suitable manner. Electrostatic charge may be imparted onto a textile through triboelectric charging, in which certain materials become electrically charged after they come into frictional contact with a different material. The polarity and strength of the charges produced differs according to the properties of the material, and material may be approximately ranked on a "Triboelectric scale" in terms of its tendency to be positively or negatively charged. The triboelectric material carries electric charges that attract airborne particles carried by an airflow passing through the material, so as to enhance filtration efficiency without increasing air flow resistance. That is, the electrostatic effects within the filtration material augment the mechanical capture of airborne particles and therefore achieve higher particle collection efficiencies, while maintaining a low resistance to air flow.

Triboelectric properties in filtration materials are extremely sensitive to disruption by even small amounts of incidental impurities or the presence of additive compounds. It is not possible to predict which compounds that are applied to specific triboelectric materials will result in a depletion of electrostatic charge for that material, and significant research and development is required to determine if any particular compound can be added to provide additional beneficial properties that also do not damage or degrade the electrostatic charge properties of the triboelectric material.

It is generally desirable that textiles that have been treated with any beneficial additives can be laundered. Following laundering, it is desirable that the textile retains both its filtering ability and beneficial properties. Furthermore, it is desirable that the textiles do not shrink or lose shape as a result of laundering. In the instance of knitted, woven and non-woven textiles made of triboelectric materials, it is also desirable that the electrostatic charge is maintained or at least regenerated following laundering.

Consequently, there is a need to develop a triboelectric filtration material that that can also provide other beneficial properties such as antimicrobial properties while still being able to regenerate its electrostatic charge, for example after washing and/or drying, such that filtration performance is retained while still providing antimicrobial properties, or to at least provide the public with a useful alternative.

SUMMARY

The present disclosure generally provides antimicrobial triboelectric filtration material comprising a blend of positively charged wool fibres and negatively charged polypropylene fibres that form a triboelectric charge in the material. The triboelectric filtration material, for example the blend or wool fibres, also comprises an antimicrobial agent consisting of at least one of polyhexamethylene biguanide (PHMB) and quaternary ammonium compound (QAC). One advantage is that the material can be washed after use while still retaining its antimicrobial and triboelectric properties. Further advantages and embodiments are described herein.

In one aspect, there is provided an antimicrobial triboelectric filtration material comprising a blend of positively charged wool fibres and negatively charged polypropylene fibres that form a triboelectric charge in the material, and an antimicrobial agent consisting of at least one of polyhexamethylene biguanide (PHMB) and quaternary ammonium compound (QAC); wherein at least the wool fibres are impregnated or coated with an antimicrobial effective amount of the antimicrobial agent.

In another aspect, there is provided an antimicrobial triboelectric filtration material consisting of a blend of positively charged wool fibres and negatively charged polypropylene fibres that form a triboelectric charge in the material; and an antimicrobial agent selected from at least one of polyhexamethylene biguanide (PHMB) and quaternary ammonium compound (QAC), wherein at least the wool fibres are impregnated or coated with an antimicrobial effective amount of the antimicrobial agent; and other than any incidental impurities optionally one or more additives.

In an embodiment of the above aspects, the antimicrobial triboelectric filtration material is capable of maintaining elevated levels of electrostatic charge and exhibiting antimicrobial activity for a pre-determined time of at least six months.

In an embodiment of the above aspects, the antimicrobial agent consists of PHMB. The amount of PHMB in the material based on total weight % of the wool component may be at least 1.0 wt. % or at least 2.0 wt. %.

In a further embodiment, the antimicrobial agent consists of QAC. The amount of QAC in the material based on total weight % of the wool component may be at least 5.0 wt. %.

The antimicrobial triboelectric filtration material may optionally comprise or further consist of one or more additives. The one or more additives may be a non- charge depleting agent. The non-charge depleting agent may be a lanolin, suint, inorganic dirt, vegetable matter on wool fibres (VM), rosin, pine sap, colourant, dye, fragrance, washing agent, knitting wax, paraffin, carnauba wax, lanolin, anionic fabric scouring agent, hydrocarbon alkane oil, or hydrocarbon alkene oil. The non-charge depleting agent may also be a resin. The one or more additives, if present in the material, may be in a total amount based on total weight % of the material, of less than about 5 wt. %.

The antimicrobial triboelectric filtration material may optionally comprise or further consist of one or more incidental impurity. The one or more incidental impurity may be an aliphatic fatty ester or ethoxylate, antistatic compound, texturizing agent, fabric softening agent, or lubricating agent The antistatic compound may be a hydrophilic antistatic agent. In an embodiment, the one or more incidental impurities, if present in the material, are in a total amount based on weight % of the material, of less than about 2 wt. %.

The amount of antimicrobial reduction according to AATCC Method 100 may be at least 90%.

In an embodiment of the antimicrobial triboelectric filtration material, the pressure drop (in Pa) across the material (using PCFTI testing or specify specific instrument and conditions) may be less than about 250 Pa.

In an embodiment of the antimicrobial triboelectric filtration material, the quality factor, Q, at 0.15 ms "1 face velocity for a 0.3 to 0.5 μιη potassium chloride particle size (Q0.3) measured using a PCFTI instrument may be at least about 22kPa _1 . In an embodiment of the antimicrobial triboelectric filtration material, the quality factor, Qx, for a 0.3 to 0.5 μιη potassium chloride particle size (0.0.3) measured using a PCFTI instrument may be at least about 55 nm (e.g., 55 χ 10 "9 metres).

In an embodiment of the antimicrobial triboelectric filtration material, the quality factor, Q, at zero dust loading may be at least 3 times that of the value of the fully loaded antimicrobial filtration material.

In an embodiment of the antimicrobial triboelectric filtration material, the positively charged wool fibres are Bunte salt pre-treated wool fibres comprising the antimicrobial agent. The Bunte salt pre-treated wool fibres may comprise or further consist of at least a portion of the wool fibres bearing at least one of -S-SO3 " and -S- S0 3 " Na + functionality. At least about 50% of the wool fibres in the triboelectric filtration material may bear at least one of -S-SO3 " and -S0 3 " Na + functionality.

The ratio of total surface area of wool fibres to polypropylene fibres in the material may be in a range of 30:70 to 70:30.

In an embodiment of the antimicrobial triboelectric filtration material, the wool fibres and polypropylene fibres each independently have fibre diameters in the range of about 5 to 100 microns.

In an embodiment of the antimicrobial triboelectric filtration material, the wool fibres and polypropylene fibres each independently have individual fibre lengths of between about 10 to 150 mm.

In an embodiment of the antimicrobial triboelectric filtration material, the material is a fabric. The material may be a woven fabric, a non-woven felt, a knitted fabric, or a fibrous composite structure. The material may have a thickness of between about 1 mm to 10 mm. In an embodiment, the material has a basis weight (gem 2 ) of between about 30 and 800 gem "2 , or a packing density of between about 0.8% and 40%.

In an embodiment of the antimicrobial triboelectric filtration material, the filtration efficiency is between about 25% and about 99.97%.

In another aspect, there is provided a fabric, garment or respirator device comprising the antimicrobial triboelectric filtration material.

In another aspect, there is provided a respiratory filter or respiratory face mask comprising the antimicrobial triboelectric filtration material.

In another aspect, there is provided an antimicrobial triboelectric filtration material consisting of: a blend of positively charged wool fibres and negatively charged polypropylene fibres that form a triboelectric charge in the material; and an antimicrobial agent selected from at least one of polyhexamethylene biguanide (PHMB) and quaternary ammonium compound (QAC), wherein at least the wool fibres are impregnated or coated with an antimicrobial effective amount of the antimicrobial agent; and the one or more additives are selected from non-charge depleting agents provided in a total amount based on total weight % of the material of less than about 5 wt.%; and the incidental impurities are selected from one or more charge depleting agents provided in a total amount based on total weight % of the material of less than about 2 wt. %.

In another aspect, there is provided an antimicrobial triboelectric filtration material consisting of a blend of positively charged wool fibres and negatively charged polypropylene fibres that form a triboelectric charge in the material; and an antimicrobial agent selected from at least one of polyhexamethylene biguanide

(PHMB) and quaternary ammonium compound (QAC), wherein at least the wool fibres are impregnated or coated with an antimicrobial effective amount of the antimicrobial agent; and other than any incidental impurities optionally one or more additives selected from non-charge depleting agents, wherein the non-charge depleting agents are selected from lanolin, suint, inorganic dirt (e.g., Si0 2 ) vegetable matter on wool

(VM), lubricants, texturizing agents, dyes, fabric softeners, fragrances, scouring agents, and washing agents; and the incidental impurities are selected from charge depleting agents, wherein the charge depleting agents are selected from spin finishers or residues, aliphatic esters or ethoxylates, antistatic compounds, texturizing agents, fabric softening agents, and lubricating agents.

In an embodiment of the above aspect, the one or more non-charge depleting agents are provided in a total amount based on total weight % of the material of less than about 5 wt.% selected from lanolin, suint, inorganic dirt (e.g., Si0 2 ) vegetable matter on wool (VM), lubricants, texturizing agents, dyes, fabric softeners, fragrances, scouring agents, washing agents; and the one or more charge depleting agents are provided in a total amount based on total weight % of the material of less than about 2 wt. % selected from spin finishers or residues, aliphatic esters or ethoxylates, antistatic compounds, texturizing agents, fabric softening agents, and lubricating agents.

In another aspect, there is provided a method for preparing an antimicrobial triboelectric filtration material comprising a blend of positively charged wool fibres and negatively charged polypropylene fibres, comprising applying an antimicrobial agent consisting of at least one of polyhexamethylene biguanide (PHMB) and quaternary ammonium compound (QAC) to wool fibres to at least impregnate or coat the wool fibres with an antimicrobial effective amount of the antimicrobial agent, and blending the wool fibres with polypropylene fibres to form an antimicrobial triboelectric filtration material; or applying an antimicrobial agent consisting of at least one of polyhexamethylene biguanide (PHMB) and quaternary ammonium compound (QAC) to a triboelectric filtration material comprising a blend of wool fibres and polypropylene fibres to at least impregnate or coat the material with an antimicrobial effective amount of the antimicrobial agent; wherein at least the wool fibres comprise untreated wool fibres that have initially undergone a pre-treatment process.

In an embodiment, the antimicrobial triboelectric filtration material comprises wool fibres that have initially undergone the pre-treatment process and polypropylene fibres that have not initially undergone the pre-treatment process. In another embodiment, the blend of untreated wool fibres and polypropylene fibres has initially undergone the pre-treatment process.

In an embodiment, the method for preparing an antimicrobial triboelectric filtration material comprises the pre-treatment process comprising contacting the untreated wool fibres or blend of wool fibres and polypropylene fibres with a sulfate composition; and then contacting the resultant wool fibres or blend of wool fibres and polypropylene fibres with a sulfite composition.

In an embodiment, the method for preparing an antimicrobial triboelectric filtration material comprises the resultant wool fibres or blend of wool fibres and polypropylene fibres being rinsed between the contact with the sulfate composition and the contact with the sulfite composition.

In an embodiment, the method for preparing an antimicrobial triboelectric filtration material comprises contacting the untreated wool fibres or blend of untreated wool fibres and polypropylene fibres with the sulfate composition in the presence of a surfactant. The sulfate composition may comprise potassium peroxymonosulfate (PMS). The sulfite composition may comprise sodium sulfite. The sodium sulfite may initially be adjusted to a pH or between about 8.0 and 8.5. The surfactant may comprise Triton X-100.

In an embodiment, the method for preparing an antimicrobial triboelectric filtration material comprises the pre-treatment process comprising finally rinsing the wool fibres or blend of wool fibres and polypropylene fibres with water and optionally drying.

In an embodiment, the method for preparing an antimicrobial triboelectric filtration material comprises the pre-treatment process that results in at least a portion of the wool fibres bearing -S-S0 3 " functionality or wool fibres bearing -S-S0 3 ~ Na + functionality. At least about 50% of the wool fibres in the triboelectric filtration material may bear -S-S0 3 " functionality or -S-S0 3 ~ Na + functionality. The -S-S0 3 " functionality or -S-S0 3 " Na + may be detected by Fourier-transform infrared

spectroscopy (FTI ). In an embodiment, the method for preparing an antimicrobial triboelectric filtration material comprises the antimicrobial agent being applied at a pH of about 6.5 to about 7.5. The antimicrobial agent may be applied at a pH of about 7.0.

In an embodiment, the method for preparing an antimicrobial triboelectric filtration material further comprises drying the antimicrobial triboelectric filtration material to facilitate electrostatic re-charging.

In another aspect, there is provided an antimicrobial triboelectric filtration material prepared according to any one or more embodiments or examples as described herein.

In another aspect, there is provided a use of the antimicrobial triboelectric filtration material, according to any one or more embodiments or examples described herein, as a filter of particulates in a respiratory device, fabric, garment, carpet, drapes, bedding material, automotive fabric or material, or aircraft fabric or material.

In an embodiment, the use of the antimicrobial triboelectric filtration material is as a respiratory filter or respiratory face mask.

It will be appreciated that further aspects and embodiments are described herein, which may include one or more of the features as described above.

DETAILED DESCRIPTION

The present disclosure describes the following, various non-limiting embodiments, which relate to the surprising finding that pre-treated wool fibres at least impregnated or coated with an antimicrobial agent of polyhexamethylene biguanide (PH M B) and/or quaternary ammonium compounds (QACs) can be blended with polypropylene fibres to provide a triboelectric filtration material that unexpectedly can regenerate its electrostatic charge, for example after washing and/or drying, such that filtration performance is retained while still providing antimicrobial properties.

The selection of fibres in the preparation of an effective triboelectric material is highly unpredictable, and although there are many options known in which to try to select compatible negatively chargeable fibres and positively chargeable fibres for forming a triboelectric material, in practice, it is necessary to determine whether an effective triboelectric material is formed from the particular combination of fibres. That is, the preparation of a triboelectric material is itself highly unpredictable, and many combinations of particular fibres that might be considered worthwhile trying, simply do not provide any triboelectric properties long term, let alone triboelectric properties that are regenerated after washing and/or drying. Even further, small amounts of contaminants or charge-depleting agents present on the associated fibres can result in an ineffective material.

For the present triboelectric material, the wool fibres essentially provide a positively chargeable fibre and the polypropylene fibres provide a negatively chargeable fibre, which for example enables an electrostatic capability to facilitate capture and filtration of airborne particulates. As mentioned, it is unexpected for triboelectric filtration materials to exhibit high performance levels after being exposed to various additional agents. For example, many fabric treatment processes and fibre coatings commonly used in the treatment of wool disrupt the ability of the fibre to retain an electrostatic charge when blended with a particular compatible fibre, thereby deteriorating the wool fibres' effectiveness as a positively chargeable fibre in a triboelectric filter material. As also mentioned, triboelectric properties are highly sensitive to the presence of other agents and are readily damaged or degraded by the presence of even small amounts of additives or contaminants.

Surprisingly, the present disclosure has identified that antimicrobial properties can be introduced in to the triboelectric material using PHMB and/or QAC, which can be impregnated or coated on the wool fibres and yet unexpectedly (and in contrast to many other various potentially suitable additives) the filtration material, at least according to some embodiments, not only retains its triboelectric properties, but also provides effective antimicrobial properties. Further, according to at least some embodiments, the antimicrobial compounds can retain at least some shrink resistance to the material. According to at least some embodiments the properties of the triboelectric material can be retained even after repeated washing and drying cycles. It has also been found that fibres impregnated or coated with PHMB and/or QAC, at least according to some embodiments, provide essentially no attributable toxicity, allergy or irritation upon contact to an individual.

TERMS

After considering this description it will be apparent to one skilled in the art how the invention is implemented in various alternative embodiments and alternative applications. However, although various embodiments of the present invention will be described herein, it is understood that these embodiments are presented by way of example only, and not limitation. As such, this description of various alternative embodiments should not be construed to limit the scope or breadth of the present invention. Furthermore, statements of advantages or other aspects may apply only to specific exemplary embodiments, and not necessarily to all embodiments covered by the claims. As used herein, the term "wool fibre" is intended to mean any fibre (whether used directly from the animal or twisted into a yarn or textile fibre) that is elastic and obtained from an animal such as a sheep. The term wool fibre used in the specification is aimed at describing wool that is pre-treated according to the method provided to enable exhaustion with PHMB or QAC. Preferably, the wool fibres are Bunte salt pre- treated wool fibres. The term "untreated wool fibre" denotes wool that is not pre- treated.

The term "reclaiming" used herein with respect to the electrostatic charge of the fibre is intended to mean that an electrostatic charge on the fibre prior to a washing and/or drying procedure is present after that procedure. The term is not intended to be construed narrowly to mean that the level of charge, or the polarity of charge, or the distribution of charge, or any other charge-related characteristic is unchanged. While it is contemplated that there may be an increase or decrease or other alteration in the electrostatic charge, the medium nevertheless retains the ability to function as a filter.

Where reference is made to an "electrostatic charge", the intention is not to mean a permanent electrostatic charge. Typically, the electrostatic charge is a "quasi- permanent" charge of the kind associated with electrets or otherwise highly charged materials.

Reference to "triboelectric" material refers to where an electrostatic charge is separated by some process and deposited by polarity onto two different types of materials, and a separation of charge can occur without electrical means, simply by an application of mechanical friction or during evaporation of a liquid from fibre surfaces. It is a type of contact electrification where certain materials become electrically charged following frictional contact with a different material. The polarity and strength of the produced charges may differ according to the various properties of the materials.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. Throughout the description and the claims of this specification the term "consisting of" and variations of the term, such as "consists of" is intended to be construed exhaustively to exclude other additives, components, integers or steps. Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Triboelectric Filtration Material

A triboelectric filtration material comprises a blend of wool fibres and polypropylene fibres. It would be appreciated that, in terms of the triboelectric series, wool fibres can bear a relatively positive charge, whereas polypropylene fibres can bear a relatively negative charge. It is these charges on the surface of the fibres that can result in an electrostatic field across the triboelectric filter material, which aids to attract airborne particles carried by an airflow passing through the material, so as to enhance filtration efficiency without increasing air flow resistance.

The antimicrobial triboelectric filtration material may be capable of maintaining elevated levels of electrostatic charge and exhibiting antimicrobial activity for a pre-determined time. That is, the antimicrobial filtration material may be capable of simultaneously maintaining elevated levels of electrostatic charge and exhibiting antimicrobial activity for a pre-determined time. By elevated levels of electrostatic charge, it is meant that the levels of electrostatic charge are such that the

antimicrobial triboelectric filtration material is capable of attracting airborne particles carried by an airflow passing through the filter material, so as to enhance filtration efficiency without increasing air flow resistance. The pre-determined time is characterised typically by a tripling of penetration over a period of the first ten years.

The ratio of the total weight of wool fibre to polypropylene fibre in the antimicrobial triboelectric filtration material may be chosen according to any desired characteristic of the resultant filtration medium. Blends of wool fibres and polypropylene fibres may have a ratio of the total weight of wool fibres to

polypropylene fibres in the range of 20:80 to 80:20 (w/w), 30:70 to 70:30 (w/w), 40:60 to 60:40 (w/w), or 55:45 to 45:55 (w/w). The antimicrobial triboelectric filtration material comprising a blend of wool fibres and polypropylene fibres may contain at least about 20, 30, 40, 50, 55, 60, 70 or 80%, by weight (wt. %), of wool fibres (the balance being polypropylene fibres). The antimicrobial triboelectric filtration material comprising a blend of wool fibres and polypropylene fibres may contain less than about 90, 80, 70, 60, 50, 40, or 30%, by weight (wt. %), of wool fibres (the balance being polypropylene fibres). The ratio of the total weight of the wool fibre to polypropylene fibre in the antimicrobial triboelectric filtration material may be provided by any range or value at or within these ranges and values. In one embodiment, the antimicrobial triboelectric filtration material comprises a blend of wool fibres and polypropylene fibres in a ratio of the total weight of wool fibres to polypropylene fibres in the range of 50:50 to 70:30 (w/w). In another embodiment, the antimicrobial triboelectric filtration material comprises a blend of wool fibres and polypropylene fibres containing less than about 70 wt. % of wool fibres (the balance being polypropylene fibres). In another embodiment, the antimicrobial triboelectric filtration material comprises greater than about 50 wt. % of wool fibres (the balance being polypropylene fibres).

The ratio of the total surface area of wool fibre to polypropylene fibre in the antimicrobial triboelectric filtration material may be chosen according to any desired characteristic of the resultant filtration medium. Blends of wool fibres and

polypropylene fibres may have a ratio of the total surface area of wool fibre to polypropylene fibre in the range of about 20:80 to 80:20, 30:70 to 70:30, 40:60 to 60:40, or 55:45 to 45:55. The antimicrobial triboelectric filtration material comprising a blend of wool fibres and polypropylene fibres may contain at least about 20, 30, 40, 50, 55, 60, 70 or 80%, by total surface area, of wool fibres (the balance being polypropylene fibres). The antimicrobial triboelectric filtration material comprising a blend of wool fibres and polypropylene fibres may contain less than about 90, 80, 70, 60, 50, 40, 30%, by total surface area, of wool fibres (the balance being polypropylene fibres). In one embodiment, blends of wool fibres and polypropylene fibres may have a ratio of the total surface area of wool fibres to polypropylene fibres in the range of about 50:50. In another embodiment, the antimicrobial triboelectric filtration material comprising a blend of wool fibres and polypropylene fibres may contain at least 50%, by total surface area, of wool fibres (the balance being polypropylene fibres). In another embodiment, the antimicrobial triboelectric filtration material comprising a blend of wool fibres and polypropylene fibres may contain less than 60%, by total surface area, of wool fibres (the balance being polypropylene fibres).

Each wool fibre and polypropylene fibre may, independently, be of a particular diameter. The average diameter (in micrometres, μιη) of the fibres may be in the range of 5 to 100 μιη, 10 to 50 μιη, or 15 to 30 μιη. The average diameter (in micrometres) of the fibres may be at least about 5, 10, 15, 20, 22, 25, 30, 50, 75, 100, or 150 μιη. The average diameter (in micrometres) of the fibres may be less than about 200, 150, 100, 50, 40, 30, 20, or 10 μηη. The diameter (in micrometres, μηη) of the fibres may be provided in any range or value at or within these ranges and values. In an embodiment, the average diameter (in micrometres, μιη) of the fibres is at least about 15 μιη. In another embodiment, the average diameter (in micrometres, μιη) of the fibres is in the range of about 15 to 30 μιη. In another embodiment, the average diameter (in micrometres, μιη) of the fibres is less than about 30 μιη. In another embodiment, the average diameter (in micrometres, μιη) of the fibres is in the range of about 20 to 24 μιη, or about 22 μιη.

Each wool fibre and polypropylene fibre may, independently, be of a particular length. The average length (in millimetres, mm) of the fibres may be in the range of 5 to 200 mm, 20 to 100 mm, or 40 to 70 mm. The average length (in millimetres) of the fibres may be at least about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 100, 125, 150, 175, 200, 225, 250, or 275 mm. The average length of the fibres may be less than about 300, 275, 250, 225, 200, 175, 150, 125, 100, 80, 70, 60, 50, 40, 30, 20, or 10 mm. The average length of the fibres may be provided in any range or value at or within these ranges or values. In an embodiment, the average length (in millimetres) of the fibres is at least about 40 mm. In another embodiment, the average length of the fibres is in the range of about 40 to 70 mm. In another embodiment, the average length of the fibres is less than about 80 mm. In another embodiment, the average length of the fibres is about 60 mm.

It will be appreciated that the antimicrobial triboelectric filtration material can be made into non-woven felt, woven fabric, non-woven fabric, or knitted fabric, comprising a plurality of fibres. It will be appreciated that knitted fabric may be made by various known techniques involving worsted or woollen yarns and may be brushed or raised in order to augment the cover of the knitted structure, which can improve filtration performance. Typically, the non-woven material is a felt, made by forming a fibre-web from carding or air-laying the fibre blend, which may furthermore be augmented in volume by cross-lapping, followed by various consolidation processes including a wet felting process (e.g. foulard, spun-lace) or a dry felting process (e.g. needle-punching), as would be understood by the person skilled in the art. It will also be appreciated that the antimicrobial triboelectric filtration material can be made into a fibrous composite structure. A fibrous composite structure may include a felt with lofty core (to maximise electrostatic performance) and one or two high-density surfaces (to improve abrasion resistance), a combination of non-woven felt and woven fabric, a combination of non-woven felts and knitted fabric, a combination of woven and knitted fabric, multiple layer structures made of non- woven, woven or knitted layers, multiple layer structures comprising non-woven, woven or knitted outer layers with meltblown, electrospun or micro-fibre layers in between, multi-layer structures where individual layers are consolidated by needle- punching, multi-layer structures where individual layers are held together by sewing, gluing or thermal bonding, as would be understood by the person skilled in the art.

The antimicrobial triboelectric filtration material may be of a particular thickness. The thickness (in millimetres) of the antimicrobial triboelectric filtration material may be in the range of about 0.5 to 200 mm, 1 to 100 mm, 2 to 50 mm, 3 to 20 mm, 4 to 10 mm, or 5 to 6 mm. The thickness (in millimetres) of the antimicrobial triboelectric filtration material may be at least about 0.5, 1, 2, 3, 4, 5, 6, 10, 20, 50, 100, 150, 200, or 250 mm. The thickness (in millimetres) of the antimicrobial triboelectric filtration material may be less than about 300, 250, 200, 150, 100, 75, 50, 20 10, 6, 5, 4, 3, 2, or 1 mm. The thickness of the antimicrobial triboelectric filtration material may be provided in any range or value at or within these ranges and values. In an embodiment, the thickness (in millimetres) of the triboelectric filter material is at least about 3 mm. In another embodiment, the thickness (in millimetres) of the antimicrobial triboelectric filtration material is less than about 10 mm. In another embodiment, the thickness (in millimetres) of the antimicrobial triboelectric filtration material is the range of about 4 to 10 mm. In another embodiment, the thickness (in millimetres) of the antimicrobial triboelectric filtration material is about 5 mm.

The antimicrobial triboelectric filtration material may be of a particular basis weight. The basis weight (in grams per square centimetre, g/cm 2 ) of the antimicrobial triboelectric filtration material may be in the range of about 30 to 800 g/cm 2 , 40 to 500 g/cm 2 , 50 to 250 g/cm 2 , 60 to 150 g/cm 2 , or 70 to 100 g/cm 2 . The basis weight (in grams per square centimetre, g/cm 2 ) of the antimicrobial triboelectric filtration material may be at least about 30, 40, 50, 60, 70, 100, 150, 250, 500 or 800 g/cm 2 . The basis weight (in grams per square centimetre, g/cm 2 ) of the antimicrobial triboelectric filtration material may be less than about 1000, 900, 800, 500, 250, 150, 100, 70, 60, 50 or 40 g/cm 2 . The weight basis (in grams per square centimetre, g/cm 2 ) of the antimicrobial triboelectric filtration material may be provided in ranges or values at or within these values. In an embodiment, the basis weight (in grams per square centimetre, g/cm 2 ) is in the range of about 30 to 800 g/cm 2 .

The antimicrobial triboelectric filtration material may be of a particular packing density. The packing density (representing the portion of the total volume in percent that is taken up by fibres of the antimicrobial triboelectric filtration material) may be in the range of 0.8 to 40%, 1.0 to 35%, 1.5 to 30%, 2 to 20%, 3 to 20%, or 3 to 10%. The packing density (in percent) of the antimicrobial triboelectric filtration material may be at least about 0.8, 1, 2, 3, 10, 20, 30, 35, or 40%. The packing density (in percent) of the antimicrobial triboelectric filtration material may be less than about 70, 60, 50, 40, 30, 20, 15, 10, 5 or 1%. The packing density (in percent) of the antimicrobial triboelectric filtration material may be provided in ranges or values at or within these values. In an embodiment, the antimicrobial triboelectric filtration material has a packing density (in percent) of less than about 15%. In another embodiment, the antimicrobial triboelectric filtration material has a packing density (in percent) of at least about 3%. In another embodiment, the antimicrobial triboelectric filtration material has a packing density (in percent) in the range of about 3 to 20%.

The antimicrobial triboelectric filtration material may have a pressure drop (in Pascals, Pa) across the material, when measured using PCFTI testing, and may be in the range of about 1 to 250 Pa, 2 to 100 Pa, 3 to 50 Pa, 4 to 20 Pa, or 5 to 10 Pa. The antimicrobial triboelectric filtration material may have a pressure drop (in Pascals, Pa) across the material, when measured using PCFTI testing, of at least about 0.5, 1, 2, 3, 4, 5, 10, 20, 50, 100, 150, 200, or 250 Pa. In an embodiment, the antimicrobial triboelectric filtration material has a pressure drop (in Pascals, Pa) across the material, when measured using PCFTI testing, of less than about 10 Pa. In another embodiment, the antimicrobial triboelectric filtration material has a pressure drop (in Pascals, Pa) across the material, when measured using PCFTI testing, is in the range of about 5 to 10 Pa. In another embodiment, the antimicrobial triboelectric filtration material has a pressure drop (in Pascals, Pa) across the material, when measured using PCFTI testing, of at least about 5 Pa.

The antimicrobial triboelectric filtration material may have a particular Q. value.

The "Q factor" refers to the quality factor of the filtration material. Since filtration efficiency and pressure drop are both affected by properties such as fabric thickness or fabric density, it is generally useful to calculate the quality factor (Q factor) in units of kPa "1 (kilo-Pascal) as follows: In this equation, P denotes penetration, which is equal to (1 - FE/100), with FE denoting filtration efficiency in percent, ln() the natural logarithm, and Δρ the pressure drop.

A modified definition of the quality factor in units of 10 "9 m (nano-metres) is used that accounts for the influence of face velocity, v^

Qx = Q. vf. r) (2)

The dynamic viscosity, η, is introduced because this extension is based on Darcy's Law.

The quality factor, Q, for purely mechanical nonwoven filter media without electrostatic charge has an upper ceiling value of approximately 20 kPa 1 for the 0.3 to 0.5 μιη particle size bin (Q.0.3) if measured with this Particle Counter Filter Test Instrument (PCFTI). The equivalent value for Qx is 55 10 ~9 m. It is fairly independent of fibre diameter (ranging from 100 nm to 50 μιη) and packing density (within 3% to 20%) and provides therefore a general benchmark for filtration performance. Deviations of the quality factor, Q, from the ceiling value, if measured at a fixed face velocity, are due to compromises in evenness (accounting for a lower value) or the presence of electrostatic charge (leading to a higher value). The quality factor, Q, therefore allows comparisons to be made between different media in terms of the quality of the filtration medium (e.g. evenness) and strongly suppresses the influence of thickness, fabric weight, or packing density.

The antimicrobial triboelectric filtration material may have a Q value, when measured at 0.15 ms "1 face velocity for a 0.3 to 0.5 μιη potassium chloride particle size (Q.0.3), and when measured using a PCFTI instrument, of at least about 20, 30, 50, 60, 80, 100, 150, 200, 250, 300, 350, 400 or 450 kPa The antimicrobial triboelectric filtration material according to the present invention may have a Q value, when measured at 0.15 ms "1 face velocity for a 0.3 to 0.5 μιη potassium chloride particle size, and when measured using a PCFTI instrument, of less than about 500, 450, 400, 350, 300, 250, 200, 150, 100, 80, 60, 50, 30 kPa "1 . The antimicrobial triboelectric filtration material according to the present invention may have a Q value, when measured at 0.15 ms "1 face velocity for a 0.3 to 0.5 μιη potassium chloride particle size, and when measured using a PCFTI instrument, in the range of about 15 to 500, 20 to 350, 25 to 150, 30 to 89 or 35 to 60 kPa "1 . The Q value of the antimicrobial triboelectric filtration material may be provided in any range or value at or within these ranges and values. In an embodiment, the Q value, when measured at 0.15 ms "1 face velocity for a 0.3 to 0.5 μιη potassium chloride particle size, and when measured using a PCFTI instrument, is at least about 30 kPa "1 . The antimicrobial triboelectric filtration material may have a quality factor, Q, at zero dust loading, of at least about 1.5, 2, 2.5, 3, 4, 5, 8, 10, 15, 20 times that of the quality factor, Q, of the fully loaded filtration material. A fully loaded filtration material may be referred to as a clogged filtration material. The antimicrobial triboelectric filtration material according to the present invention may have a quality factor, Q, at zero dust loading, of between about 1.5 and 20, 2 and 15, 2.5 and 10, 3 and 8, or 4 and 5 times that of the quality factor, Q, of the fully loaded filtration material. The quality factor, Q, of the antimicrobial triboelectric filtration material may be provided in any range or value at or within these ranges and values. In an embodiment, the quality factor, Q, at zero dust loading, is at least three times that of the value of the fully loaded filtration material.

The antimicrobial triboelectric filtration material may have a particular quality factor Q. Filtration potential is a measure of the actual measured quality factor (Q actual) relative to the ceiling potential quality factor (Q ceiling potential):

Fpot = (Q actual) / (Q ceiling potential) (3)

The ceiling potential for uncharged filter media is in the vicinity of Q = 22 kPa "1 for nonwoven media over a vast range of fibre diameters (4-40 μιη) and packing densities (3 - 20%). Wool-polypropylene filter media typically reach ceiling values of 150-500 kPa "1 , depending on packing density and type of wool fibre used.

The antimicrobial triboelectric filtration material may have a filtration efficiency, FE, of at least about 5, 10, 15, 20, 25, 30, 35, 40, 50, 60, 70, 80, 90, 95, 98, 99, 99.5, 99.9, 99.95, or 99.97%. The antimicrobial triboelectric filtration material may have a filtration efficiency, FE, in a range provided by any two of these previously mentioned values. The filtration efficiency, FE, of the antimicrobial triboelectric filtration material may be provided in any range or value at or within these ranges and values. In an embodiment, the filtration efficiency, FE, of the antimicrobial triboelectric filtration material is between 25 and 99.97%.

A non-woven process comprising carding and needle-punching may be used to manufacture the antimicrobial triboelectric filtration material. This process provides considerable opportunity for triboelectric charging of the fibres. In one embodiment, the antimicrobial triboelectric filtration material comprising a blend of wool fibres and polypropylene fibres is produced using a small-scale manufacturing route consisting of fibre cleaning, blending and carding using a sample card, and finally, consolidation by needle punching. The small size of the manufacturing route may allow processing of batch weights in a typical range of 100 to 150 grams. Across various sizes of carding machines with cross-lapper the processing range may span from 30 to 1500 g/m 2 basis weight for needle felts. The batch weight for stand-alone cards is 50 - 500 grams depending on size of the machine used. Processing on a nonwovens line with cross- lapper is continuous and can reach 100 or several hundred kilograms per hour.

The antimicrobial triboelectric filtration material may be tested both before and after washing to establish its ability to substantially reclaim triboelectric properties and filtration performance. A number of methods are typically used in the industry for measuring particulate filtration performance, with one method being used herein for the examples. Various analyses may be undertaken to quantitatively define filtration performance, in addition to those explicitly described herein. It is therefore to be understood that filtration performance may be established using methods other than those described herein with a view to demonstrating the reclamation of electrostatic charge, and therefore the ability to retain airborne particulates.

The filtration performance of the antimicrobial triboelectric filtration material before washing as compared with after washing may be greater than about 50, 60, 70, 80, 90, 95, 98 or 99% for fine particles in the 0.3-0.5 μιη particle size range when utilising the performance measurement method described herein. In one

embodiment, the performance is at least about 80% for fine particles in the 0.3-0.5 μιη particle size range when utilising the performance measurement method described herein. This 80% performance satisfies the requirements for a PI performance rating (Committee SF/10 Respiratory Protection, AS/NZS 1716:1994 Respiratory Protective Devices, 1994, Standards Australia). A nonwoven felt of 300-350 g/m basis weight is generally sufficient to achieve more than 94% filtration efficiency to satisfy the Class P2 rating according to AS/NZS 1716 or Class FFP2 rating according to EN 149:2001+A1 or filter class ISO 15 E according to ISO 29463-l:2011(E).

The washing and/or drying procedure employed may be a domestic laundering procedure, optionally followed by a domestic tumble drying procedure. The washing process may be carried out at a water temperature of at least about 20, 25, 30, 35, 40, 45, 50, 55, 60, 65 or 70 degrees Celsius (°C). The washing process may be carried out at a water temperature less than about 100, 90, 80, 70, 60, 50, 40, 30 or 20 degrees Celsius (°C). The washing process may be carried out at a water temperature in the range of about 20 to 100, 25 to 90, 30 to 80, or 40 to 60 degrees Celsius (°C). The washing process may be carried out in the presence of a domestic laundry detergent. Detergents may for example comprise at least one of the following: a

detergent/surfactant (such as an alkylbenzenesulfonate), a water softening agent or builder (such as sodium carbonate), a bleach (such as sodium perborate), and an enzyme (such as an amylase or a protease). The washing and drying procedures may be as described in ISO 6330:2000/AMD.l:2008(E) Textiles - Domestic Washing And Drying Procedures For Textile Testing, 2008, International Organization For Standardization (ISO). In addition to the resin-coated wool fibre, the present material includes a synthetic polymeric fibre, i.e. polypropylene.

The antimicrobial triboelectric filtration material may also be resistant to shrinkage following the washing and/or drying procedure employed, for example, a domestic laundering procedure optionally followed by a domestic tumble drying procedure. The antimicrobial triboelectric filtration material, following five washing and drying procedures according to ISO 6330:2000/AMD.l:2008(E) Textiles - Domestic Washing And Drying Procedures For Textile Testing, 2008, International Organization For Standardization (ISO), has a shrinkage of less than about 2, 5, 7, 10, 15, 20, 25, 50, 75 or 90% of the material size prior to the initial washing and drying procedure. The antimicrobial triboelectric filtration material, following five washing and drying procedures according to ISO 6330:2000/AMD.l:2008(E) Textiles - Domestic Washing and Drying Procedures for Textile Testing, 2008, International Organization For Standardization (ISO), has a shrinkage in the range of about 2 to 90%, 5 to 75%. 7 to 50% or 10 to 25% of the material size prior to the initial washing and drying procedure. In an embodiment, the antimicrobial triboelectric filtration material, following five washing and drying procedures according to ISO 6330:2000/AMD.l:2008(E) Textiles - Domestic Washing and Drying Procedures for Textile Testing, 2008, International Organization For Standardization (ISO), has a shrinkage of less than about 10% of the material size prior to the initial washing and drying procedure.

The antimicrobial triboelectric filtration material finds application in several areas, including, for example, particle filter components for respirator canisters, cartridges or (clip-on) modules; particle barriers made from nonwovens, wovens (optionally raised) or knits (optionally brushed), including facial masks, respirator masks (up to FFP3, P3 or N100 ratings), scarfs, bandannas, shrouds, head coverings, ponchos, jackets, shirts with collars, and turtle-neck shirts; highly fire-resistant masks for fire-fighting; odour suppressing socks, t-shirts, and undergarments; allergen- suppressing or allergen-locking furnishings, including carpets, curtains, bed covers, pillows, sofa coverings, and fabrics for chairs; vacuum cleaner bags, vacuum cleaner filter cartridges or panels, vacuum cleaner outlet filters (replacing micro-filters), outlet pre-filters for extraction systems in hazardous environments (e.g., asbestos removal), inlet filters for snorkel systems, pre-filters for fume cabinets, and filters for laminar flow cabinets; cabin filters for cars, trucks, buses, trains, trams, airplanes, ships, and submarines; sheet filter material or flat panels for box air-conditioners, and semi-split and split system air-conditioners; pleated air-conditioning panels or modules for domestic air-conditioning, industrial air-conditioning such as airports, trucks in mining or earth movement, general laboratories, test laboratories or set-ups, physical containment laboratories Level 2 (PC2) or higher, and air intakes for plants; bag filters for large installations such as shopping centres, office complexes, public buildings, sports complexes and arenas, and airports; multi-active particle filter for

antimicrobial/antiviral/antifungal media and applications (e.g., in conjunction with photoactive titanium-dioxide particles); and particle-scavenging garments or undergarments for physical containment laboratories, used in conjunction with protective coveralls or full protective suits.

The antimicrobial triboelectric filtration material is particularly (although not exclusively) applicable as a filter of particulates in a respiratory device. The antimicrobial triboelectric filtration material has been shown to provide high filtration efficiency of particulates, and at least according to some embodiments at

exceptionally low breathing resistance. In an embodiment, the triboelectric filtration material may be used as a filter of particulates in a respiratory mask. In another embodiment, the triboelectric filtration material may be used as a filter of particulates in a respiratory device that is incorporated into a garment. This may be, for example, an additional segment of fabric incorporated into an item of clothing that can be positioned over the mouth and/or nose of the wearer, so as to filter particulates during respiration. The clothing item may be, for example, a shirt, wherein the segment of fabric is incorporated into the collar, and can be positioned over the mouth and/or nose of the wearer, so as to filter particulates during respiration.

The antimicrobial triboelectric filtration material is applicable as a filter of particulates in any one or more of the following: fabric, garment, carpet, drapes, bedding material, automotive fabric or material, or aircraft fabric or material. They can be used for air-conditioning or other high-flow applications as frame-mounted filter bags or with wire-mesh support in pleated filter panels.

Wool Fibre

A triboelectric filtration material comprises a blend of wool fibres and polypropylene fibres. In the triboelectric filtration material, the wool fibres can provide the positively charged fibres.

The wool fibres may be obtained from pre-treatment of wool according to the methods provided. Suitable wool can be from any animal, for example sheep, goats, alpacas, muskoxen, rabbits and camelids. The wool fibres of the triboelectric filter material may be from a single animal, for example, sheep wool fibres. Alternatively, the wool fibres of the triboelectric filter material may be a blend of any one or more wool fibres, for example, sheep and goat wool fibres, sheep and alpaca wool fibres, or goat and alpaca fibres. The wool fibres may also be a blend of fibres from one or more animals, for example, a blend of sheep and goat wool fibres. In an embodiment, the wool fibres of the triboelectric filter material are sheep wool fibres.

Each untreated wool fibre may be of a particular diameter. The average diameter (in micrometres, μιη) of un-treated wool fibres may be in the range of about 5 to 100 μιη, 10 to 50 μιη, or 15 to 30 μιη. The average diameter (in micrometres, μιη) of untreated wool fibres may be at least about 10, 15, 20, 22, 25, 30, 50, or 75 μιη. The average diameter (in micrometres, μιη) of untreated wool fibres may be less than about 100, 75, 50, 30, or 25 μιη. The untreated wool fibres may be provided in any range or value at or within these ranges and values. In an embodiment, the average diameter (in micrometres, μιη) of untreated wool fibres is at least about 15 μιη. In another embodiment, average diameter (in micrometres, μιη) of untreated wool fibres is in the range of about 15 to 30 μιη. In another embodiment, average diameter (in micrometres, μιη) of untreated wool fibres is in the range of about 20 to 24 μιη, or about 22 μιη.

Each untreated wool fibre may be of a particular length. The average length (in millimetres, mm) of untreated wool fibres may be in the range of 5 to 200 mm, 20 to 100 mm, or 40 to 70 mm. The average length (in millimetres, mm) of untreated wool fibres may be at least about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 100, 125, 150, 175, or 200 mm. The average length (in millimetres, mm) of untreated wool fibres may be less than 300, 275, 250, 225, 200, 175, 150, 125, 100, 75, 50, 40, 30 or 20 mm. The untreated wool fibres may be provided in any range or value at or within these ranges and values. In an embodiment, the average length (in millimetres, mm) of untreated wool fibres is at least about 40 mm. In another embodiment, the average length (in millimetres, mm) of untreated wool fibres is in the range of about 40 to 70 mm. In another embodiment, the average length (in millimetres, mm) of untreated wool fibres is about 60 mm.

Each untreated wool fibre may be of a particular crimp. Reference to wool "crimp" refers to the waviness of the wool fire, particularly the bends along the length of the wool fibre. Crimp is measured in crimps per centimetre. Fine wools have more crimps per unit length of the wool fibre, whereas coarser wools have less crimps per unit length of the wool fibre. The average crimp of untreated wool fibres may be in the range of about 1 to 20, 2 to 15, 3 to 10, 4 to 8, or 5 to 6, crimps per centimetre length of untreated wool fibre. The average crimp of untreated wool fibres may be at least about 1, 2, 3, 4, 5, 6, 8, 10, 15 or 20, crimps per centimetre length of the fibre. The average crimp of the untreated wool fibre may be less than about 30, 25, 20, 15, 10, 8, 6, or 4, crimps per centimetre length of the fibre. The untreated wool fibres may be provided in any range or value at or within these ranges and values. It will be appreciated that a range of crimp frequencies and crimp-depths can be tolerated for carding; although uniformity and well-expressed crimp provide particular advantages.

Polypropylene Fibre

A triboelectric filtration material comprises a blend of wool fibres and polypropylene fibres. In the triboelectric filtration material, the polypropylene fibres can provide the negatively charged fibres. Polypropylene (PP), also referred to as polyprene, is a thermoplastic polymer made from repeating propylene monomers:

Each polypropylene fibre may be of a particular diameter. The average diameter (in micrometres, μιη) of the polypropylene fibres may be in the range of about 5 to 100 μιη, 10 to 50 μιη, or 15 to 30 μιη. The average diameter (in micrometres) of the polypropylene fibres may be at least about 5, 10, 15, 20, 22, 25, 30, 50, 75, 125, 150, or 175 μιη. The average diameter (in micrometres) of the polypropylene fibres may be less than about 200, 175, 150, 125, 100, 75, 50, 30, 25 or 20 μιη. The polypropylene fibres may be provided in any range or value at or within these ranges and values. In an embodiment, the average diameter (in micrometres) of the polypropylene fibres is at least about 15 μιη. in another embodiment, the average diameter (in micrometres) of the polypropylene fibres in the range of about 15 to 30 μιη. In another embodiment, the average diameter (in micrometres) of the polypropylene fibres is in the range of about 22 to 24 μιη, or about 22 μιη.

Each polypropylene fibre may be of a particular length. The average length (in millimetres, mm) of the polypropylene fibres may be in the range of 5 to 200 mm, 20 to 100 mm, or 40 to 70 mm. The average length (in millimetres) of the polypropylene fibres may be at least about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 100, 125, 150, 175, 200, 225, 250, or 275 mm. The average length (in millimetres) of the polypropylene fibres may be less than about 300, 275, 250, 225, 200, 175, 150, 125, 100, 75, 50m 30, 25, or 20 mm. The polypropylene fibres may be provided in any range or value at or within these ranges and values. In an embodiment, the average length (in millimetres) of the polypropylene fibres is at least about 40 mm. In another embodiment, the average length (in millimetres) of the polypropylene fibres is in the range of about 40 to 70 mm. In another embodiment, the average length (in millimetres) of the polypropylene fibres is about 60 mm.

Each polypropylene fibre may be of a particular crimp. Reference to polypropylene "crimp" refers to the waviness of the polypropylene fire, particularly the bends along the length of the polypropylene fibre. Crimp is measured in crimps per centimetre. Fine polypropylene fibres have more crimps per unit length of the polypropylene fibre, whereas coarser polypropylene fibres have less crimps per unit length of the polypropylene fibre. The average crimp of the polypropylene fibres may be in the range of 1 to 20, 2 to 15, 3 to 10, 4 to 8, or 5 to 6, crimps per centimetre length of polypropylene fibre. The average crimp of the polypropylene fibres may be at least about 1, 2, 3, 4, 5, 6, 8, 10, 15 or 20, crimps per centimetre length of polypropylene fibre. The average crimp of the polypropylene fibres may be less than about 30, 25, 20, 15, 10, 8, 5, 4 or 3, crimps per centimetre length of polypropylene fibre. The polypropylene fibres may be provided in ranges or values at or within these values.

It will be appreciated that in the antimicrobial triboelectric filtration material, the polypropylene fibres may comprise other polymeric fibres. For example, the polypropylene fibres may comprise a portion of polypropylene amide fibres (i.e., a blend of polypropylene and polypropylene amide fibres). That is, the blend of wool and polypropylene fibres that form the triboelectric filtration material may include wool and a blend of polypropylene fibres and other polymer fibres (e.g.,

polypropylene amide fibres). The polypropylene fibres may comprise any portion of other polymeric fibres so long as when blended with wool, a triboelectric filtration material forms due to the charge association.

Polyhexamethylene Biguanide (PHMB)

Polyhexamethylene biguanide (PH MB), also referred to as polyhexanide, is heterodisperse mixture of polyhexamethylene biguanides with an average molecular weight of approximately 2500 Daltons (Da), and is a polymer of (C 8 Hi 7 N 5 ) n according to the following structure:

PHMB is a strong, fast acting, and broad spectral antimicrobial agent exhibiting antimicrobial properties, including antiviral and antifungal properties, with low toxicity to humans. The term "antimicrobial agent", as used herein, refers to an agent that is active against microbes. For example, an antimicrobial agent may inhibit the replication of microbes. A microbe refers to a microorganism that is capable of causing disease, and includes, for example, bacteria, viruses and fungi. The safety of PHMB has been well established, as it has been used as a disinfectant in the food industry, for sanitisation of swimming pools, and has been explored as a biocide in mouth washes and wound dressings. PHMB exerts its bactericidal activity by impairing the integrity of the cell bacteria membrane.

Specifically, it is the cationic charge of PHMB that interacts with the bacteria cell wall, leading to bacteria death. The attachment of PHMB to textile substrates can be through both ionic and hydrogen bonding interactions between the cationic PHMB and a fibre surface. PHMB is sold under various trade names, including Vantocil ® (20% w/w solution). The PHMB may be selected from a commercial grade PHMB. While antimicrobial properties of PHMB are known, there are no known textiles consisting of PHMB with both antimicrobial and triboelectric properties.

The fibres of the antimicrobial triboelectric filtration material may be impregnated or coated with an antimicrobial effective amount of PHMB. The amount of PHMB in the antimicrobial triboelectric filtration material based on the total weight percentage of the material (wt.%) may be in the range of about 0.1 to 100 wt.%, 0.5 to 75 wt.%, 1 to 50%, 2 to 20%, or 3 to 10 wt.%. The amount of PHMB in the

antimicrobial triboelectric filtration material based on the total weight percentage of the material (wt.%) may be at least about 0.1, 0.5, 1, 2, 3, 4, 5, 10, 20, 50, or 75 wt.%. The amount of PHMB in the triboelectric filtration material based on the total weight percentage of the material (wt.%) may be less than about 100, 75, 50, 40, 30, 20, 10, 5, 2.5 or 1 wt. %. The amount of PHMB in the antimicrobial triboelectric filtration material may be provided in any range or value at or within these ranges and values. In an embodiment, the amount of PHMB in the antimicrobial triboelectric filtration material based on the total weight percentage of the material (wt.%) is at least about 0.1 wt. %. In an embodiment, the amount of PHMB in the antimicrobial triboelectric filtration material based on the total weight percentage of the material (wt. %) is between about 1 wt. % and about 20 wt. %.

The wool fibres of the antimicrobial triboelectric filtration material may be impregnated or coated with an antimicrobial effective amount of PHMB. That is, the wool fibres may be separately impregnated or coated with an antimicrobial effective amount of PHMB prior to being blended with the polypropylene fibres. The amount of PHMB in the antimicrobial triboelectric filtration material based on the total weight percentage of the wool fibres in the material (wt.%) may be in the range of about 0.1 to 100 wt.%, 0.5 to 75 wt.%, 1 to 50%, 2 to 20%, or 3 to 10 wt.%. The amount of PHMB in the antimicrobial triboelectric filtration material based on the total weight percentage of the wool fibres in the material (wt.%) may be at least about 0.1, 0.5, 1, 2, 3, 4, 5, 10, 20, 50, or 75 wt.%. The amount of PHMB in the triboelectric filtration material based on the total weight percentage of the wool fibres in the material (wt.%) may be less than about 100, 75, 50, 40, 30, 20, 10, 5, 2.5 or 1 wt. %. The amount of PHMB in the antimicrobial triboelectric filtration material may be provided in any range or value at or within these ranges and values. In an embodiment, the amount of PHMB in the antimicrobial triboelectric filtration material based on the total weight percentage of the wool fibres in the material (wt. %) is at least about 0.1 wt. %. In an embodiment, the amount of PHMB in the antimicrobial triboelectric filtration material based on the total weight percentage of the wool fibres in the material (wt. %) is between about 1 wt. % and about 20 wt. %.

An advantage of the antimicrobial triboelectric filtration material when impregnated or coated with PHMB, according to at least some embodiments, is that PHMB may provide a non-toxic and/or non-irritant antimicrobial agent to the material.

Quaternary Ammonium Compounds (QACs)

Quaternary ammonium salt compounds (QACs) have been shown to have good antimicrobial and/or disinfectant activity. QACs carry a positive charge at the nitrogen atom in solution, and inflict a variety of detrimental effects on microbes, including damage to cell membranes, denaturation of proteins and disruption of the cell structure.

The phrase "quaternary ammonium salt compound" as used herein, refers to complexes of a quaternary ammonium compound and a counter-ion. The salts may be organic or inorganic salts of the quaternary ammonium compound. The quaternary ammonium compound comprises at least one amino group, and accordingly acid addition salts can be formed with this amino group. Exemplary salts include, but are not limited, to sulfate, citrate, acetate, oxalate, chloride, bromide, iodide, nitrate, bisulfate, phosphate, acid phosphate, isonicotinate, lactate, salicylate, acid citrate, tartrate, oleate, tannate, pantothenate, bitartrate, ascorbate, succinate, maleate, gentisinate, fumarate, gluconate, glucuronate, saccharate, formate, benzoate, glutamate, methanesulfonate, ethanesulfonate, benzenesulfonate, p- toluenesulfonate, and pamoate (i.e., l,l'-methylene-bis-(2-hydroxy-3-naphthoate)) salts. An acceptable salt may involve the inclusion of another molecule such as an acetate ion, a succinate ion or other counter-ion. The counter-ion may be any organic or inorganic moiety that stabilizes the charge on the quaternary ammonium compound. Furthermore, an acceptable salt may have more than one charged atom in its structure. Instances where multiple charged atoms are part of the acceptable salt can have multiple counter ions. Hence, an acceptable salt can have one or more charged atoms and/or one or more counter-ion. The salt may be selected from a pharmaceutically acceptable salt.

The QACs that exhibit antimicrobial and/or disinfectant activity include, but are not limited to, those that contain long alkyl chains. Examples of QACs that exhibit antimicrobial and/or disinfectant activity include, but are not limited to, 3- trimethoxysilylpropyldimethylactadecyl ammonium chloride, benzalkonium chloride, benzethonium chloride, methylbenzethonium chloride, cetalkonium chloride, cetylpyridinium chloride, cetrimonium, cetrimide, dofanium chloride,

tetraethylammonium bromide, didecyldimethylammonium chloride and domiphen bromide. In one example, the antimicrobial triboelectric filtration material is impregnated or coated with an antimicrobial effective amount of benzalkonium chloride. In one example, the antimicrobial triboelectric filtration material is impregnated or coated with an antimicrobial effective amount of cetylpyridinium chloride. While antimicrobial properties of QACs are known, there are no known textiles consisting of QAC with both antimicrobial and triboelectric properties.

The fibres of the antimicrobial triboelectric filtration material may be impregnated or coated with an antimicrobial effective amount of one or more QACs. The amount of QACs in the antimicrobial triboelectric filtration material based on the total weight percentage of the material (wt.%) may be in the range of about 0.1 to 99 wt.%, 0.5 to 75 wt.%, 1 to 50%, 2 to 20%, or 3 to 10 wt.%. The amount of QACs in the antimicrobial triboelectric filtration material based on the total weight percentage of the material (wt.%) may be at least about 0.1, 0.5, 1, 2, 3, 4, 5, 10, 20, 50, or 75 wt.%. The amount of QACs in the antimicrobial triboelectric filtration material based on the total weight percentage of the material (wt.%) may be less than about 100, 75, 50, 40, 30, 20, 10, 5, 2.5 or 1 wt. %. The amount of QACs in the antimicrobial triboelectric filtration material may be provided in any range or value at or within these ranges and values. In an embodiment, the amount of QACs in the antimicrobial triboelectric filtration material based on the total weight percentage of the material (wt.%) is at least about 5 wt. %. In an embodiment, the amount of QACs in the antimicrobial triboelectric filtration material based on the total weight percentage of the material (wt. %) is between about 1 wt. % and about 20 wt. %.

The wool fibres of the antimicrobial triboelectric filtration material may be impregnated or coated with an antimicrobial effective amount of QACs. That is, the wool fibres may be separately impregnated or coated with an antimicrobial effective amount of QACs prior to being blended with the polypropylene fibres. The amount of QACs in the antimicrobial triboelectric filtration material based on the total weight percentage of the wool fibres in the material (wt.%) may be in the range of about 0.1 to 99 wt.%, 0.5 to 75 wt.%, 1 to 50 wt.%, 2 to 20 wt.%, or 3 to 10 wt.%. The amount of QACs in the antimicrobial triboelectric filtration material based on the total weight percentage of the wool fibres in the material (wt.%) may be at least about 0.1, 0.5, 1, 2, 3, 4, 5, 10, 20, 50, or 75 wt.%. The amount of QACs in the triboelectric filtration material based on the total weight percentage of the wool fibres in the material (wt.%) may be less than about 100, 75, 50, 40, 30, 20, 10, 5, 2.5 or 1 wt. %. The amount of QACs in the antimicrobial triboelectric filtration material may be provided in any range or value at or within these ranges and values. In an embodiment, the amount of QACs in the antimicrobial triboelectric filtration material based on the total weight percentage of the wool fibres in the material (wt. %) is at least about 0.1 wt. %. In an embodiment, the amount of QACs in the antimicrobial triboelectric filtration material based on the total weight percentage of the wool fibres in the material (wt. %) is between about 1 wt. % and about 20 wt. %.

An advantage of the antimicrobial triboelectric filtration material when impregnated or coated with QACs, according to at least some embodiments, is that QACs may provide a non-toxic and/or non-irritant antimicrobial agent to the material.

Antimicrobial Triboelectric Filtration Material

The antimicrobial triboelectric material comprises a blend of wool fibres and polypropylene fibres. Accordingly, one or both of the fibres may be impregnated and/or coated with the antimicrobial effective amount of PHMB and/or QAC. In an embodiment, the wool fibres are impregnated and/or coated with the antimicrobial effective amount of PHMB and/or QAC. In another embodiment, the polypropylene fibres are impregnated and/or coated with an antimicrobial effective amount of PHMB and/or QAC. In another embodiment, both the wool fibres and the polypropylene fibres are impregnated and/or coated with an antimicrobial effective amount of PHMB and/or QAC.

It has been surprisingly found that PHMB and QAC, when impregnated and/or coated onto the antimicrobial triboelectric filtration material, allow for the triboelectric filtration properties of the material to be maintained. That is, PHMB and QAC do not result in a depletion of the triboelectric charge so much that the triboelectric charge is lost and filtering ability is compromised. The impregnation and/or coating of the triboelectric filtration material with alternative and/or additional antimicrobial agents may results in the depletion of the triboelectric charge.

Accordingly, the PHMB and/or QAC antimicrobial agents are the sole antimicrobial agents impregnated and/or coated onto the antimicrobial triboelectric filtration material. That is, no other antimicrobial agents may be impregnated and/or coated onto the antimicrobial triboelectric filtration material. In one embodiment, the antimicrobial triboelectric filtration material is impregnated and/or coated with PHMB as the sole antimicrobial agent. In one embodiment, the antimicrobial triboelectric filtration material is impregnated and/or coated with QAC as the sole antimicrobial agent. In one embodiment, the antimicrobial triboelectric filtration material is impregnated and/or coated with a combination of PHMB and QAC as the sole antimicrobial agents. When both PHMB and QAC are impregnated and/or coated onto the triboelectric filtration material, the antimicrobial agents may be present in any ratio so as to provide an antimicrobial triboelectric filtration material (i.e., to have antimicrobial efficacy). For example, the amount of PHMB and QAC impregnated and/or coated onto the triboelectric filtration material may be in a ratio of about 5:95, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30, 80:20, 90:10, or 95:5 of PHMB/QAC.

Additives

In some circumstances the wool and/or polypropylene fibres may contain one or more additives for imparting various processing or textile properties that may harm or degrade the triboelectric properties of the antimicrobial triboelectric filtration material. Such an additive does not contribute to the triboelectric charge of the filtration material, nor does in contribute to the antimicrobial activity of the filtration material.

The additives may be charge or non-charge depleting agents. In one embodiment, the antimicrobial triboelectric filtration material comprises or consists of one or more additives. The additive may be present in a total amount of several percent, on a weight basis of the material (wt. %), but it may be desirable to keep levels of such agents low for other reasons such as enticing or hygienic reasons. The total amount of additive in the antimicrobial triboelectric filtration material based on the total weight percentage of the antimicrobial triboelectric filtration material (wt. %) may be in the range of about 0.1 to 99 wt.%, 0.5 to 75 wt.%, 1 to 50 wt.%, 1.5 to 25 wt.%, 2 to 10 wt.% or 3 to 5 wt.%. The total amount additive in the antimicrobial triboelectric filtration material based on the total weight percentage of the antimicrobial triboelectric filtration material (wt. %) may be at least about 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 10, 25, 50, 75 wt.%. The total amount of additive in the antimicrobial triboelectric filtration material based on the total weight percentage of the antimicrobial triboelectric filtration material (wt. %) may be less than about 100, 75, 50, 25, 10, 5, 4, 3, 2, 1, 0.5 wt.%. The total amount of additive in the antimicrobial triboelectric filtration material based on the total weight percentage of the antimicrobial triboelectric filtration material (wt. %) may be provided in any range or value at or within these ranges and values. In one example, the total amount of additive in the antimicrobial triboelectric filtration material based on the total weight percentage of the antimicrobial triboelectric filtration material (wt. %) is less than 5 wt.%. In one embodiment, the antimicrobial triboelectric filtration material comprises or consists of one or more charge-depleting agents or non-charge depleting agent.

In the instance of non-charge depleting agents, the triboelectric charge of the material is not depleted or substantially degraded by the presence of the non-charge depleting agent. In one embodiment, the antimicrobial triboelectric filtration material comprises or consists of a non-charge depleting agent. Examples of non-charge- depleting agents include those present on the fibre prior to any treatment, such as lanolin, suint, inorganic dirt (e.g., Si0 2 ), and vegetable matter on wool fibres (VM). Examples of non-charge depleting agents also include those deliberately imparted onto the fibre during treatment, such as rosins, pine saps, colourants, dyes, fragrances, washing agents, knitting waxes, paraffins, natural products including carnauba waxes or lanolins, anionic fabric scouring agents, hydrocarbon alkane oils, and hydrocarbon alkene oils.

In one embodiment, the triboelectric filtration material comprises or consists of lanolin. In one embodiment, the triboelectric filtration material comprises or consists of suint. In one embodiment, the triboelectric filtration material comprises or consists of inorganic dirt (e.g., Si0 2 ). In one embodiment, the triboelectric filtration material comprises or consists of vegetable matter on wool fibres (VM). In one embodiment, the triboelectric filtration material comprises or consists of a rosin. In one

embodiment, the triboelectric filtration material comprises or consists of a pine sap. In one embodiment, the triboelectric filtration material comprises or consists of a colourant. In one embodiment, the triboelectric filtration material comprises or consists of a dye. In one embodiment, the triboelectric filtration material comprises or consists of a fragrance. In one embodiment, the triboelectric filtration material comprises or consists of a washing agent. In one embodiment, the triboelectric filtration material comprises or consists of a knitting wax. In one embodiment, the triboelectric filtration material comprises or consists of a paraffin. In one embodiment, the triboelectric filtration material comprises or consists of a carnauba wax. In one embodiment, the triboelectric filtration material comprises or consists of a lanolin. In one embodiment, the triboelectric filtration material comprises or consists of an anionic fabric scouring agent. In one embodiment, the triboelectric filtration material comprises or consists of a hydrocarbon alkane oil. In one embodiment, the triboelectric filtration material comprises or consists of a hydrocarbon alkene oil. Examples of non-charge depleting agents also include resins. Such resins may impart a specific technical effect onto the fabric, for example, shrink-proof and shrink- resistance properties. In one embodiment, the triboelectric filtration material comprises or consists of a shrink-proof resin. In one embodiment, the triboelectric filtration material comprises or consists of shrink-resistant resin. An example of a shrink-proofing resin that is particularly useful on the triboelectric filtration material is polyamide-epichlorohydrin polymer. Such a polyamide-epichlorohydrin polymer is also referred to as "superwash", and is sold commercially as "Hercosett". Wool fibres may be subjected to polyamide-epichlorohydrin polymer as part of a chlor-Hercosett treatment, typically employed to impart shrink-proof properties onto the fibre. In one embodiment, the triboelectric filtration material comprises or consists of a polyamide- epichlorohydrin polymer. In one embodiment, the triboelectric filtration material comprises or consists of Hercosett. An example of a shrink-resistant resin that is particularly useful on the triboelectric filtration material is a self-crosslinking acrylic latex. Such a self-crosslinking acrylic latex is that sold commercially by Rohm and Haas as "Primal HA8". In one embodiment, the triboelectric filtration material comprises or consists of a self-crosslinking acrylic latex. In one embodiment, the triboelectric filtration material comprises or consists of Primal HA8.

The total amount of the non-charge depleting agent in the wool fibre, polypropylene fibre, or the triboelectric filtration material, may be in an amount that is effective for processing, e.g. carding or fibre delivery systems in general. The non- charge depleting agent may be present in a total amount of several percent, on a weight basis of the material (wt. %), but it may be desirable to keep levels of such agents low for other reasons such as enticing or hygienic reasons. The total amount of non-charge depleting agent in the antimicrobial triboelectric filtration material based on the total weight percentage of the antimicrobial triboelectric filtration material (wt. %) may be in the range of about 0.1 to 99 wt.%, 0.5 to 75 wt.%, 1 to 50 wt.%, 1.5 to 25 wt.%, 2 to 10 wt.% or 3 to 5 wt.%. The total amount of non-charge depleting agent in the antimicrobial triboelectric filtration material based on the total weight percentage of the antimicrobial triboelectric filtration material (wt. %) may be at least about 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 10, 25, 50, 75 wt.%. The total amount of non-charge depleting agent in the antimicrobial triboelectric filtration material based on the total weight percentage of the antimicrobial triboelectric filtration material (wt. %) may be less than about 100, 75, 50, 25, 10, 5, 4, 3, 2, 1, 0.5 wt.%. The total amount of non-charge depleting agent in the antimicrobial triboelectric filtration material based on the total weight percentage of the antimicrobial triboelectric filtration material (wt. %) may be provided in any range or value at or within these ranges and values. In one example, the total amount of non-charge depleting agent in the antimicrobial triboelectric filtration material based on the total weight percentage of the antimicrobial triboelectric filtration material (wt. %) is less than 5 wt.%.

In the instance of charge depleting agents, also referred to as incidental impurities, the triboelectric charge of the material is partially or completely depleted or degraded by the presence of the charge depleting agent. In one embodiment, the antimicrobial triboelectric filtration material comprises or consists of a charge depleting agent. It will be appreciated that any incidental charge depleting agents is present at a low level, and levels of such agents can be reduced for example by aqueous scouring prior to forming the material, or by recharging during drying.

Examples of charge depleting agents include spin finishers or residues from processing belonging to the broader chemical groups of aliphatic fatty esters or ethoxylates, antistatic compounds, texturizing agents, fabric softening agents, and lubricating agents. The charge depleting agents may be hydrophilic antistatic agents, particularly those that can be removed effectively by aqueous scouring. In one embodiment, the triboelectric filtration material comprises or consists of a spin finisher. In one embodiment, the triboelectric filtration material comprises or consists of an aliphatic ester compound. In one embodiment, the triboelectric filtration material comprises or consists of an ethoxylate compound. In one embodiment, the triboelectric filtration material comprises or consists of an antistatic compound. In one embodiment, the triboelectric filtration material comprises or consists of a texturizing agent. In one embodiment, the triboelectric filtration material comprises or consists of a fabric softening agent. In one embodiment, the triboelectric filtration material comprises or consists of a lubricating agent. In one embodiment, the triboelectric filtration material comprises or consists of a hydrophilic antistatic agent.

The charge depleting agent may be present in a total amount of several percent, on a weight basis of the material (wt. %), and it is desirable to keep levels of such agents low for maintaining the charge of the triboelectric filtration material. The total amount of charge depleting agent in the antimicrobial triboelectric filtration material based on the total weight percentage of the antimicrobial triboelectric filtration material (wt. %) may be in the range of about 0.1 to 99 wt.%, 0.5 to 75 wt.%, 1 to 50 wt.%, 1.5 to 25 wt.%, 2 to 10 wt.% or 3 to 5 wt.%. The total amount of charge depleting agent in the antimicrobial triboelectric filtration material based on the total weight percentage of the antimicrobial triboelectric filtration material (wt. %) may be at least about 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 10, 25, 50, 75 wt.%. The total amount of charge depleting agent in the antimicrobial triboelectric filtration material based on the total weight percentage of the antimicrobial triboelectric filtration material (wt. %) may be less than about 100, 75, 50, 25, 10, 5, 4, 3, 2, 1, 0.5 wt.%. The total amount of charge depleting agent in the antimicrobial triboelectric filtration material based on the total weight percentage of the antimicrobial triboelectric filtration material (wt. %) may be provided in any range or value at or within these ranges and values. In one example, the total amount of charge depleting agent in the antimicrobial triboelectric filtration material based on the total weight percentage of the antimicrobial triboelectric filtration material (wt. %) is less than 5 wt.%.

Fibres for triboelectric filtration materials preferentially have any charge depleting agents removed from the fibre surface before the triboelectric charge is applied. If the charge depleting agents are not sufficiently removed from the fibres, there may be a reduced or no triboelectric enhancement of filtration performance. The charge depleting agents if present in the fibres may be removed or substantially reduced by pre-treatment, for example by washing. Method of Preparing Antimicrobial Triboelectric Filtration

The present disclosure also provides methods for preparing an antimicrobial triboelectric filtration material comprising a blend of positively charged wool fibres and negatively charged polypropylene fibres, comprising:

applying an antimicrobial agent consisting of at least one of polyhexamethylene biguanide (PHMB) and quaternary ammonium compound (QAC) to wool fibres to at least impregnate or coat the wool fibres with an antimicrobial effective amount of the antimicrobial agent, and blending the wool fibres with polypropylene fibres to form an antimicrobial triboelectric filtration material; or

applying an antimicrobial agent consisting of at least one of polyhexamethylene biguanide (PHMB) and quaternary ammonium compound (QAC) to a triboelectric filtration material comprising a blend of wool fibres and polypropylene fibres to at least impregnate or coat the material with an antimicrobial effective amount of the antimicrobial agent;

wherein at least the wool fibres have initially undergone a pre-treatment process.

The wool fibres used in the triboelectric filtration material may be carbonised or scoured wool fibres. Such processes serve to remove organic matter from the surface of the wool fiber, such as waxes and vegetable matter. The fibres may be additionally cleaned by applying any one or more of detergent in water, petroleum ether, dichloromethane, or methanol. Alternatively, the wool fibres used in the triboelectric filtration material may be directly used once obtained from the animal. In one example, the triboelectric filtration material comprises a blend of positively charged scoured wool fibres and negatively charged polypropylene fibres. In one example, the triboelectric filtration material comprises a blend of positively charged carbonised wool fibres and negatively charged polypropylene fibres.

In an embodiment, the wool fibres have initially undergone the pre-treatment process. That is, the wool fibres, prior to blending with the polypropylene fibres, are pre-treated. In an embodiment, the blend of wool fibres and polypropylene fibres has initially undergone the pre-treatment process. That is, the wool fibres and

polypropylene fibres are blended and the blend is then pre-treated. It is therefore possible that, in a triboelectric filtration material comprising wool and polypropylene fibres, the wool fibres have alone been subjected to the pre-treatment process.

Similarly, it is also possible that, in a triboelectric filtration material comprising wool and polypropylene fibres, both the wool fibres and polypropylene fibres have been subjected to the pre-treatment process.

The pre-treatment process comprises contacting the wool fibres or blend of wool fibres and polypropylene fibres with a sulfate composition, and then contacting the wool fibres or blend of wool fibres and polypropylene fibres with a sulfite composition. In one example, wool fibres are contacted with a sulfate composition, and then contacted with a sulfite composition. In one example, the blend of wool fibres and polypropylene fibres is contacted with a sulfate composition, and then contacted with a sulfite composition.

The pre-treatment process serves to install Bunte salts on the surface of the wool fiber. A Bunte salt typically is an -S-SO3 " functional group, which is generally installed as the sodium salt (i.e., -S-SO3 " Na + ). It will be understood that the Bunte salt may be installed in a form other than the sodium salt, so long as -S-SO3 " is present on the surface of the wool fibre. Accordingly, the surface of the wool fibre bears such functional groups (i.e., wool-S-S0 3 " Na + or wool-S-S0 3 " ). Advantageously, the presence of Bunte salts on the surface of the wool fibre may result in greater adherence or exhaustion of the antimicrobial agent, for example PHMB or a QAC, to the triboelectric filtration material. Further advantageously, the presence of Bunte salts on the surface of the wool fibre may result in decreased wash-out of the antimicrobial agent, for example PHMB or a QAC, from the triboelectric filtration material. That is, the antimicrobial agent may remain associated with the surface of the wool fibre when the triboelectric filtration material is subjected to washing for a greater number of wash cycles in comparison to a wool fiber treated with an antimicrobial agent, for example PHMB or a QAC, in the absence of Bunte salts on the surface of the wool fibres (i.e., not having been subjected to the pre-treatment process). Therefore, the pre-treatment process may advantageously provide a triboelectric filtration material that exhibits greater adherence to or exhaustion onto the antimicrobial agent for a longer duration, particularly when the triboelectric filtration material is subjected to wash cycles. In one embodiment, the pre-treatment process results in at least a portion of the wool fibres bearing -S-S0 3 " functionality or wool fibres bearing -S-S0 3 " Na + functionality. The amount of wool fibres in the triboelectric filtration material bearing Bunte salts may be in the rage of about 5 to 95%, 20 to 80%, 30 to 70%, or 40 to 60%. The amount of wool fibres in the triboelectric filtration material bearing Bunte salts may be at least about 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 95%. The amount of wool fibres in the triboelectric filtration material bearing Bunte salts may be less than about 100, 90, 80, 70, 60, or 50%. In one example, the amount of wool fibres in the triboelectric filtration material bearing Bunte salts is at least about 50%. The amount of wool fibres in the triboelectric filtration material bearing Bunte salts may be provided in any range or value at or within these ranges and values. The presence of Bunte salts on the surface of the wool fibre may be detected by Fourier-transform infrared spectroscopy (FTI ).

The two-part pre-treatment process consists of an initial oxidation step, followed by a subsequent reduction step. The sulfate composition is used in the pre- treatment process may be any sulfate composition capable of effecting such an oxidation step. In one example, the sulfate composition is potassium

peroxymonosulfate (PMS), also referred to as potassium monopersulfate, and sold under the trade name of Oxone. The subsequent reduction step of the pre-treatment process may be effected by any sulfite composition capable of effecting such a reduction step. In one example, the sulfite composition is sodium sulfite. The sulfite composition is initially adjusted to a pH of between about 6 .0 and about 10.0, preferably between about 7.0 and about 9.0, more preferably between about 8.0 and about 8.5.

The concentration of the sulfate composition and the sulfite composition used in the pre-treatment process are such that the Bunte salts are installed onto the surface of the wool fiber, as would be understood by the person skilled in the art.

The pre-treatment process may optionally include a rinsing step. In one embodiment, the wool fibres or blend of wool fibres and polypropylene fibres are rinsed between the contact with the sulfate composition and the contact with the sulfite composition. This rinsing may occur with water, and serves to remove excess sulfate from the fibres prior to contacting the fibres with the sulfite composition.

The pre-treatment process may optionally comprise the use of a surfactant. In one embodiment, contacting the wool fibres or blend of wool fibres and

polypropylene fibres with the sulfate composition occurs in the presence of a surfactant. In one example, the surfactant is Triton X-100. The pre-treatment process may optionally comprise finally rinsing the wool fibres or blend of wool fibres and polypropylene fibres bearing the Bunte salt, with water. The rinsed wool fibres or blend of wool fibres and polypropylene fibres bearing the Bunte salt, may then be optionally dried prior to adhesion or exhaustion of the antimicrobial agent onto the triboelectric filtration material.

If the wool fibres alone had initially undergone the pre-treatment, then the method for preparing an antimicrobial triboelectric filtration material may next include either of (1) blending the pre-treated wool fibres with polypropylene fibres to form an antimicrobial triboelectric filtration material, and then applying the antimicrobial agent to the triboelectric filtration material to at least impregnate or coat the wool fibres with an antimicrobial effective amount of the antimicrobial agent, or (2) applying the antimicrobial agent to the wool fibres alone to at least impregnate or coat the wool fibres with an antimicrobial effective amount of the antimicrobial agent, and then blending the wool fibres with polypropylene fibres to form an antimicrobial triboelectric filtration material.

Alternatively, if the blend of wool fibres and polypropylene fibres had initially undergone the pre-treatment, then the method for preparing an antimicrobial triboelectric filtration material includes applying the antimicrobial agent to the triboelectric filtration material to at least impregnate or coat the wool fibres with an antimicrobial effective amount of the antimicrobial agent.

Therefore, the antimicrobial agent is applied to either the pre-treated wool fibres alone or to the pre-treated blend of wool fibres and polypropylene fibres. The application of the antimicrobial agent is also referred to as "exhaustion". Exhaustion may be carried out by contacting the pre-treated wool fibres or blend of wool fibres and polypropylene fibres with a solution containing the antimicrobial agent. The solution containing the antimicrobial agent may be pH adjusted prior to exhaustion. In one example, a solution containing the antimicrobial agent, PHMB, is adjusted to a pH of between about 5.5 and about 8.5, preferably between about 6.0 and about 8.0, more preferably between about 6.5 and about 7.5. Exhaustion may occur by contacting the pre-treated wool fibres or blend of wool fibres and polypropylene fibres at room temperature or at an elevated temperature (i.e., a temperature greater than room temperature). In one example, exhaustion occurs at room temperature. In another example, exhaustion occurs at about 20 °C and about 40 °C. The pre-treated wool fibres or blend of wool fibres and polypropylene fibres may be contacted with the solution containing the antimicrobial solution for a period of time sufficient so as to at least impregnate or coat the wool fibres with an antimicrobial effective amount of the antimicrobial agent. The pre-treated wool fibres or blend of wool fibres and polypropylene fibres may be contacted with the solution containing the antimicrobial solution for a period of time in the range of about 60 seconds and 100 minutes, about 5 minutes and about 90 minutes, about 10 minutes and about 75 minutes, or 15 minutes and about 60 minutes. The pre-treated wool fibres or blend of wool fibres and polypropylene fibres may be contacted with the solution containing the antimicrobial solution for a period of time of at least about 60 seconds, 5 minutes, 10 minutes, 15 minutes, 30 minutes, or 60 minutes. The pre-treated wool fibres or blend of wool fibres and polypropylene fibres may be contacted with the solution containing the antimicrobial solution for a period of time of less than about 24 hours, 12 hours, 100 minutes, 90 minutes, 60 minutes, 30 minutes, or 15 minutes. In one example, the pre- treated wool fibres or blend of wool fibres and polypropylene fibres may be contacted with the solution containing the antimicrobial solution for a period of time of between about 15 minutes and about 60 minutes. The pre-treated wool fibres or blend of wool fibres and polypropylene fibres may be contacted with the solution containing the antimicrobial solution for a period of time in any range or value at or within these ranges and values.

The exhaustion process may optionally occur in the presence of a surfactant. In one embodiment, the exhaustion process occurs in the presence of a surfactant. In one example, the surfactant is Triton X-100.

Following exhaustion, the wool fibres or blend of wool fibres and polypropylene fibres are optionally rinsed in water to remove excess antimicrobial solution. The wool fibres or blend of wool fibres and polypropylene fibres are then dried. Drying of the antimicrobial wool fibres may assist in the blending of the wool fibres with the polypropylene fibres to form the antimicrobial triboelectric filtration material.

Otherwise, drying of the blend of wool fibres and polypropylene fibres may facilitate the restoration of the triboelectric charge in the antimicrobial triboelectric filtration material. Drying options may include:

• Tumble dryers: some machines have different settings with higher/lower

temperatures and longer/shorter treatment times per cycle.

· Bonding ovens: Temperature should probably remain between 100 - 110

degrees Celsius, because lower temperature will dry more slowly and higher ones may affect fibres in terms of mechanical damage or getting too close to glass temperatures. But the transport speed can be increased to increase the level of dryness; residence time should be at least 3 minutes.

· Control of residual water after washing is also important: remove water using a centrifugal dehydrator when washed in a winch. There is no need for this if the liquor is expressed via hydraulic high-pressure pad rollers of a foulard. BRIEF DESCRIPTION OF DRAWINGS

In the examples, reference will be made to the accompanying drawings, in which:

Figure 1 shows duplicate plates with colonies from the untreated wool- polypropylene substrate and of treated filter media AM02 and AM04 at lOx (top) as well as lOOOx (bottom) dilution; and

Figures 2a-f show dust loading results from triboelectric wool filter media with and without antimicrobial treatment. EXAMPLES

The present disclosure provides the following non-limiting examples according to various embodiments as described above.

Materials

Scoured wool (long-staple, 20.4 μιη wool) or carbonised (carbonised and machine-scoured 21.8 μιη wool) wool was used as the substrate for the antimicrobial treatment. Peroxymonosulfate (PMS) was purchased from DuPont. Sodium sulfite was purchased from Sigma Aldrich. Polyhexamethylene biguanide (PHMB) 20% aqueous solution was purchased from Arch chemicals. All other reagents were purchased from Sigma Aldrich.

Pre-Treatment

Wool was pre-treated prior to exhaustion with PHMB. In this pre-treatment, also referred to as PMS/sulfite pre-treatment, wool was treated with 2 g/L PMS and 1 mL/L Triton X-100 as surfactant for 15 min at 20 °C to 40 °C (liquor ratio = 40 on weight of wool), and was then rinsed in water. The wool was then treated with 10 g/L sodium sulfite (adjusted to pH 8.2-8.5 with 2 M sulfuric acid) for 15 min at 20 °C to 40 °C (liquor ratio = 40 on weight of wool), and was then rinsed in water. The treated and rinsed wool fibre was either used immediately for PHMB or QAC uptake, or was dried in air or in an oven at 80 °C and stored at room temperature before further use.

PHMB Exhaustion

The pH of the PHMB aqueous solution (20%) was adjusted to neutral pH with sodium hydroxide (NaOH). The pre-treated wool fibre was contacted with a solution containing PHMB (8% on weight of wool) at 20 °C to 40 °C for 15 to 60 min. During this treatment, the liquor to wool fibre ratio was about 20:1 to about 50:1, and a non-ionic surfactant (e.g., Triton X-100, 0.1% v/v) is optionally included in the PHMB solution. The wool fibre was then optionally rinsed in water. The wool fibre was squeezed and dried in air or in an oven at 80 °C for 1 h to overnight for subsequent felt

manufacturing.

QAC Exhaustion

The pH of the QAC solution can be adjusted to neutral pH. The pre-treated wool fibre can be contacted with a solution containing QAC (8% on weight of wool) at 20 °C to 40 °C for 15 to 60 min. During this treatment, the liquor to wool fibre ratio can be about 20:1 to about 50:1, and a non-ionic surfactant (e.g., Triton X-100, 0.1% v/v) can optionally be included in the QAC solution. The wool fibre can then be optionally rinsed in water. The wool fibre can be squeezed and dried in air or in an oven at 80 °C for 1 h to overnight for subsequent felt manufacturing.

Fabrication of Non-Woven Media for Air Filters

Air filter media were made from a blend of wool fibres and polypropylene fibres in a ratio of 60:40. The polypropylene fibres consisted of scoured hydrophilic polypropylene of 3 denier fineness (equivalent to an average fibre diameter of 22.9 μιη) and 64 mm stable length. The wool fibres were untreated and unchlorinated

Australian Merino wool and had an average fibre diameter of 19 μιη. The wool fibres were treated with antimicrobial treatment, as described above. Polypropylene fibres and wool fibres were blended manually on the bench and processed by the

Memmingen card in two passes. The triboelectric filtration material was 60:40 % wool- PP by weight. The resultant batch weight was 225 g and had a processing width of 30 cm. Carded webs were subsequently consolidated by needle punching on the Hunter Fibrelocker at 125 insertions/cm2 from each side. The felts were formed by carding without lubricant and consolidated by needle punching. Triboelectric filtration media were subsequently characterised by their thickness and fabric weight, as determined from circular filter samples of 109 mm diameter.

Antimicrobial Properties

Antimicrobial tests were performed using the quantitative antimicrobial assays on the triboelectric filtration media as per the AATCC Test Method 100, using the bacterial species E. coli. In the test, 0.25 mL inoculum in the nutrient media LB

(containing lxlO 7 cells) was applied to ~0.4 g filter media. The total number of live E. coli cells after incubation for 4 h at 37°C in a sealed jar was counted by serial dilution and plating. The percentage of growth reduction was calculated as follows:

Reduction (%) = 100 (C-A)/C; where A is the number colonies from test fabrics after 5 hrs incubation; C is the number of colonies from an untreated fabric at time Zero. If A is greater than C, there is no reduction. Samples AM01-AM05 were prepared according to the following:

AM01: carbonized wool and polypropylene were scoured. The wool and

polypropylene fibres were blended, carded and subjected to needle punching.

AM02: carbonized wool and polypropylene were scoured. The wool fibres were pre- treated, and had PHMB applied. The wool and polypropylene fibres were blended, carded and subjected to needle punching.

AM03: scoured wool was used, and polypropylene was separately scoured. The wool and polypropylene fibres were blended, carded and subjected to needle punching. AM04: scoured wool was used, and polypropylene was separately scoured. The wool fibres were pre-treated, and had PHMB applied. The wool and polypropylene fibres were blended, carded and subjected to needle punching.

AM05: carbonized wool and polypropylene were scoured. The wool fibres were pre- treated, and had PHMB applied. The wool and polypropylene fibres were blended, carded and subjected to needle punching.

Manufactured felt substrate: carbonized wool and polypropylene were scoured. The wool and polypropylene fibres were blended, carded and subjected to needle punching.

Water application: carbonized wool and polypropylene were scoured. The wool and polypropylene fibres were blended, carded and subjected to needle punching. Water was applied to the felt, and the felt was dried.

Table 1 shows the results of the antimicrobial assays. The triboelectric filtration media made of PHMB-treated wool, either scoured or carbonized, exhibited strong antimicrobial ability, killing almost all the bacterial inoculated into the media, while the control media (wool without PHMB treatment) lacked such antimicrobial activity. The spread of colonies on plates is shown in Figure 1.

Table 1. Antimicrobial property of the PHMB treated wool fibre air filter media.

Testing of triboelectric Testing of triboelectric filtration media in 2006 filtration media in 2016

Triboelectric PHMB No. of No. of Bacteri No. of No. of Bacteri filtration media (% wt. of bacteri bacteri al bacteri bacteri al (60:40 wool al al reducti al al reducti wool/polypropy fibre coloni coloni on coloni coloni on lene fibre by compone es at t es at t es at t es at t

weight) nt) = 0 = 4 h = 0 = 4 h

Sample AM 01 No No (carbonized 0 268 285 reducti 312 >500 reducti wool) on on

Sample AM02

(carbonized 7.66 268 0 > 99.9% 312 0 >99.9% wool)

No

Sample AM 03

0 268 396 reducti ND* ND* ND* (scoured wool)

on

Sample AM04

5.35 268 0 > 99.9% 312 0 >99.9% (scoured wool)

Sample AM05

(carbonized 5.00 268 7 97.4% ND* ND* ND* wool)

*not determined

Filter Performance

Two circular samples (i.e., Sample 1 and Sample 2) of 109 mm diameter were cut from each medium and characterised by weight and thickness prior to testing (Table 2).

Table 2. Fabric properties of treated and untreated triboelectric filtration media samples.

Triboelectric Circular Fabric weight Thickness Packing filtration sample no. [g/m 2 ] [mm] density [%] media

1 340.6 4.75 6.24

AM01

2 287.3 4.35 5.74

1 248.0 4.17 5.17

AM02

2 274.7 4.35 5.49

1 289.1 4.30 5.85

AM03

2 274.6 4.21 5.67

1 292.6 4.34 5.86

AM 04

2 266.8 4.14 5.61

AM05 1 252.5 4.37 5.02 2 220.5 3.68 5.21

The samples were subsequently subjected to the following filter tests:

• No. 1 samples were subjected to particle counter tests (PCFTI) that were carried out shortly after manufacturing and repeated at least once, 2 to 3 weeks later;

• No. 2 samples were tested first (non-destructively) on the PCFTI before they were subjected to a dust loading test on the Methylene Blue Filter Test Instrument (MBFTI). Another PCFTI test was carried out after dust loading in order to establish the respective filter performance of the loaded filter medium.

The PCFTI is operating non-destructively with particle concentrations of 10 "7 to 10 "9 particles/cm 3 by number count, or 0.01-0.60 mg/m 3 by mass. The MBFTI is loading filter media with fine dust using a particle concentration of 1 χ 10 11 to 5 x 10 11 particles/cm 3 by number count, or 10-50 mg/m 3 by mass. Results from PCFTI tests conducted on the No. 1 samples are summarised in Table 3.

Table 3. Repeated testing from the Particle Counter Filter Test Instrument (PCFTI) conducted on No. 1 samples: filtration efficiency, FE, for different particle sizes (0.3, 0.5, 1.0 and 5.0 μm particle diameter), pressure drop, P d „ and quality factor, Q, (also for different particle sizes).

Time

Circula from

Triboelectr r Chargin FEo. P d Qo.3 Qo.5 Ql.O ic filtration sampl g 3 FEo.5 FEi.0 FE5.0 [Pa [kPa [kPa [kPa media e no. [days] [%] [%] [%] [%] ] - 1 ] - 1 ] - 1 ]

97. 100. 20. 180. 233. 313.

0.1 3 99.1 99.8 0 0 8 8 3

97. 100. 19. 186. 242. 328.

6.1 1 99.0 99.8 0 1 6 6 7

AM01 1

97. 100. 19. 185. 240. 313.

13.0 1 99.0 99.8 0 2 5 1 9

91. 28. 116. 154.

3549.1 2 96.4 98.8 99.7 4 85.7 8 8

93. 100. 14. 191. 247. 345.

0.1 6 97.2 99.3 0 4 3 5 6

AM02 1

94. 100. 13. 211. 272. 369.

0.9 0 97.3 99.3 0 3 4 0 1 94. 100. 14. 199. 255. 343.

6.0 0 97.3 99.2 0 2 0 8 6

94. 100. 13. 214. 272. 370.

12.9 1 97.3 99.2 0 2 3 7 4

88. 20. 108. 147. 205.

3549.0 2 94.7 98.4 99.7 0 3 5 4

98. 100. 18. 215. 276. 379.

0.0 1 99.4 99.9 0 5 2 6 7

98. 100. 17. 230. 301. 420.

6.0 1 99.4 99.9 0 1 7 6 4

AM03 1

98. 100. 17. 241. 302. 424.

12.9 4 99.4 99.9 0 0 5 7 8

95. 100. 25. 127. 173. 222.

3549.0 9 98.7 99.6 0 0 7 0 3

98. 100. 100. 18. 242. 311. 248.

0.0 9 99.7 0 0 8 7 2 5

99. 100. 100. 17. 267. 342. 349.

5.9 0 99.7 0 0 4 8 9 8

AM04 1

98. 100. 100. 19. 234. 301. 410.

12.9 8 99.7 0 0 0 2 5 0

96. 100. 25. 135. 187. 241.

3549.0 9 99.2 99.8 0 7 6 0 6

95. 100. 15. 197. 255. 365.

0.1 3 98.1 99.6 0 5 1 1 1

95. 100. 13. 234. 304. 403.

6.0 4 98.2 99.5 0 2 0 8 7

AM05 1

95. 100. 16. 188. 238. 319.

13.0 0 97.8 99.4 0 0 2 0 4

88. 22. 139. 186.

3549.1 9 95.5 98.4 99.7 3 99.9 4 5

All triboelectric filtration media exhibit very little change over a time period of 13 days, which indicates that electrostatic properties are stable over time. Quality factor, Q, provides a benchmark for assessing filter performance, and is dependent on the mechanical properties of the fabric. Results for 0.3, 0.5 and 1.0 μιη particle size exhibit only insignificant differences between treated (AM02/AM05 and AM04) and untreated (AM01 and AM03) triboelectric filtration media. Triboelectric filtration media made from scoured wool appear to perform slightly better than those made from carbonised wool. The dust loading performances of the same triboelectric filtration media were assessed via the respective No. 2 samples. These tests were conducted using the Methylene Blue Filter Test Instrument (MBFTI). Results from tests conducted on the media made from carbonised wool (AM01 and AM02) and from scoured wool (AM03 and AM04) are shown in Figure 2.

Antimicrobial treatment of the wool fibre component increased filtration efficiency but at the same time led to a higher pressure drop (Figure 2). The quality factor, Q, exhibited no significant differences between treated and untreated wool, except maybe at the very beginning, at practically zero dust loads, where treated fabrics appear to exhibit better performances.

In the comparison of carbonised wool and scoured wool, the electrostatic enhancement of the triboelectric filtration media filter performance appears to dissipate more quickly for scoured wool, as expressed by a more accentuated drop in the quality factor. Results obtained from additional samples taken from another part of AM02, which are not shown here, however suggest that this deviation may be due to a slightly lower fabric weight, rather than be the result of a difference between the two types of wool.

An indication of long-term performance is demonstrated by an additional measurement conducted nearly 10 years after manufacture of the media (3549 days). It shows fairly consistently that the penetration is approximately tripled over this period of time, while the respective quality factor is halved.

The results should be considered in the typical broader context that the vast majority of surface coatings applied to wool fibres negatively affect triboelectric properties, and hence filtration efficiency, of the resulting wool-polypropylene blend. This is illustrated by a range of polymers (Table 4), which were applied to an already formed wool-polypropylene triboelectric felt and charged automatically during subsequent drying in a vented oven.

Table 4. Fibre identification and polymer treatments applied to the non-woven wool polypropylene substrate.

Wool Coating Solids content

Medium Manufacturer

Component polymer (%)

Manufactured Carbonised

None N/A - felt substrate Wool

Water Carbonised

Water only N/A - application Wool Carbonised

Antistatic CFE 1122 14 Flexichem

Wool

NonCarbonised

DC 200 100 Dow Corning functional Wool

Carbonised

Epoxy JG 7293 40 Flexichem

Wool

Carbonised

Amino SM 8709 33 Dow Corning

Wool

Low amine Carbonised Wacker

Finish CT 34E 50

No. Wool Chemicals

High amine Carbonised Wacker

Finish CT 95E 25

No. Wool Chemicals

The untreated wool-substrate (labelled "Manufactured felt substrate") is equivalent to control medium AM01 that was characterised in Tables 1 to 3. The wet- treatment was applied to the already blended wool-polypropylene felt after formation. The felts were subsequently dried while still wet in a vented oven at 105 °C temperature for 4 hours, which restored a significant amount of the electrostatic charge, but not all of it. The need to restore electrostatic charge from the wet is the main difference to the process used for AM02 and AM05, where the wool component only was treated before the nonwoven felt was formed. But wool-polypropylene felts are quite capable of restoring charge during drying, with the amount of charge recovered increasing as the drying rate is accelerated.

Measured filtration results of the wool-polypropylene substrate and of the wet-treated felts are shown in Table 5. The control for this series is represented by a wet-treated substrate where no polymer was used (medium labelled "Water application") and filtration test results illustrate how much of the electrostatic performance was recovered during the drying process. It is particularly useful in this regard to observe changes in the quality factor Q 0 3 , which dropped from

approximately 130 kPa 1 to 80 kPa

Table 5. Initial and 2-day delayed testing from the Particle Counter Filter Test Instrument (PCFTI) conducted on wool-polypropylene felts wet-treated with various different compounds. media e no. g

[days]

100. 133. 177. 257.

0.0 93.0 97.1 99.4 20.0

0 3 7 0

1

Manufact 129. 166. 239.

1.9 92.5 96.5 99.2 99.9 20.1

ured 3 7 3 felt 129. 169. 244.

0.1 92.7 96.7 99.3 99.8 20.2

substrate 9 0 1

2

100. 128. 163. 233.

1.9 92.0 96.0 99.0 19.7

0 7 7 0

105. 148.

0.0 83.0 89.5 95.8 99.8 21.4 83.0

7 2

1

118.

Water 2.2 79.3 85.3 94.2 99.8 24.0 65.7 80.1

7 applicatio

104. 149. n 0.0 83.2 89.8 96.1 99.6 21.8 82.0

6 1

2

100. 131.

2.2 82.3 87.6 95.5 23.5 73.7 89.0

0 7

0.1 26.5 34.6 48.6 83.9 21.7 14.3 19.7 30.8

1

Antistatic 2.1 14.6 17.3 33.3 80.8 22.0 7.2 8.6 18.4 CFE 1122 0.1 26.0 33.0 46.7 87.8 22.5 13.4 17.8 28.0

2

2.1 14.5 15.5 35.0 81.0 23.7 6.7 7.2 18.2

0.1 11.2 17.7 29.2 73.5 19.4 6.1 10.1 17.9

Non1

2.1 15.1 16.5 31.3 75.3 21.7 7.6 8.3 17.3 functional

0.1 10.4 19.2 31.3 78.0 19.2 5.8 11.1 19.6 DC 200 2

2.1 12.5 14.0 29.9 80.9 22.9 5.9 6.7 15.6

0.1 22.5 29.3 42.9 87.1 24.1 10.8 14.6 23.4

1

Epoxy 2.0 17.1 18.7 36.2 84.5 23.3 8.1 8.9 19.3 JG 7293 0.1 28.1 32.8 45.5 85.7 22.2 14.8 18.0 27.4

2

2.0 19.7 18.5 35.3 79.5 22.3 9.8 9.2 19.5

0.1 20.6 28.5 39.6 86.7 22.3 10.4 15.1 22.6

Epoxy 1

2.0 17.8 18.2 33.6 78.4 21.5 9.1 9.3 19.1 (rpt)

0.1 27.5 32.8 44.5 86.0 21.4 15.2 18.7 27.7 JG 7293 2

2.0 16.7 18.0 34.5 84.3 23.1 7.9 8.6 18.3

0.1 43.0 49.7 64.3 91.8 24.0 23.4 28.7 43.0

1

Amino 2.1 16.0 18.0 33.7 81.2 23.9 7.3 8.3 17.2 SM 8709 0.1 46.5 53.2 68.0 94.8 22.2 28.2 34.2 51.4

2

2.1 17.8 19.2 36.3 81.4 23.5 8.4 9.1 19.2

Low 0.0 53.1 60.1 75.4 96.1 23.0 33.0 40.0 61.0

1

amine No. 1.9 15.3 18.2 33.5 83.2 20.4 8.2 9.9 20.1 Finish CT 0.0 60.6 68.2 82.2 97.6 23.3 40.0 49.2 74.1

2

34 E 1.9 14.9 16.2 32.1 75.2 20.8 7.8 8.5 18.6

High 0.1 42.7 49.5 64.4 94.7 21.3 26.2 32.2 48.6

1

amine No. 2.2 20.4 20.5 38.1 84.0 21.9 10.4 10.5 21.9 Finish CT 0.1 32.0 39.0 53.6 86.9 22.6 17.1 22.0 34.1

2

95E 2.2 17.0 19.6 36.9 83.1 22.6 8.3 9.7 20.4

Taking triboelectric filtration media "Water application" as reference, it becomes apparent that all polymer compounds used in the experimental trial were depleting filtration performance significantly. Of those that depleted filtration performance, the highest quality factor was achieved by compound "Low amino No.", with Qo.3 reaching an initial value of 30-40 kPa "1 that dropped to about 8 kPa "1 within about 2 days from processing.

This experimental trial illustrates a common finding that the majority of chemicals applied to wool-polypropylene felts will deplete the electrostatic charging capacity of the medium. It is quite unusual that a chemical has no measurable negative effect on charging, as is demonstrably the case for PHMB.

Triboelectric Charge Recovery

The degree of charge recovery after washing is characterised in the following for an optimised blend of wool with polypropylene, and a blend of Kermel (enhanced with co-extruded beige pigment) with polypropylene. This is to demonstrate the charge recovery performance of wool-polypropylene with an all-polymeric alternative. Card/NP: The performance reference is provided by the carded and needle punched nonwoven formed from a clean fibre blend of Kermel beige / polypropylene or wool / polypropylene.

Wet/Dried: Complete wetting out of the nonwoven felts after formation was achieved by submerging the fabric in a water bath, removing the fabric from the water and expressing the water from the nonwoven using a foulard. The wetted out nonwoven was subsequently dried using a bonding oven at 105 °C. This process has been described in WO 2006/128237A.

Recharged/Low: The Wet/Dried nonwoven was needle punched at 45 insertions/cm 2 . Recharged/High: The Recharged/Low nonwoven fabric was needle punched for a second time at 220 insertions/cm 2 (Kermel beige) or 110 insertions/cm 2 (wool), respectively.

Table 6: Mechanical fabric properties and PCFTI filtration test results for medium weight electrostatic fabrics made from clean fibre. Kermel(beige)-polypropylene blended fabrics are compared to wool-polypropylene blended fabric at different stages of post processing.

Kermel (beige) - polypropylene blend

Card

3.99 176.1 3.96 97.3 98.6 99.7 100.0 7.8 473.4 560.2 749.5 0.0 NP

Wet

2.80 173.9 5.58 40.6 47.3 59.9 86.4 11.8 45.5 55.5 79.0 177.4 Dried

Recharged

2.73 191.4 6.29 69.9 67.4 85.6 98.5 17.5 71.7 68.1 114.4 219.4 Low

Recharged

2.20 142.0 5.77 87.8 92.3 96.9 99.7 12.1 176.0 214.7 289.8 309.4 High

Wool - polypropylene blend

Card

3.82 147.6 3.39 79.6 83.3 92.0 98.7 5.6 287.0 323.3 455.9 621.7 NP

Wet

4.81 185.1 3.61 51.7 53.4 64.0 86.1 7.2 102.5 107.7 144.0 284.4 Dried

Recharged

3.08 175.0 4.99 70.9 74.7 85.4 96.3 6.5 211.0 236.4 329.4 569.3 Low

Recharged

2.76 166.6 5.30 82.8 87.7 94.5 99.5 8.7 204.2 243.2 335.8 395.3 High

Filtration tests show that both blends are active (filtration efficiency and Q) after the Wet/Dried treatment. Looking at the Q-factors, high level recharging

imparted on wool-polypropylene is recovering 70-75% of the performance, while for Kermel(beige)-polypropylene it is about 38%. This result illustrates the superior re- chargeability of wool-polypropylene blends over all-polymeric Kermel(beige)- polypropylene blends.