[001] This invention relates to a thermoplastic adhesive antimicrobial composition comprising a thermoplastic adhesive and at least one antimicrobial. This invention also relates to products and fabrics incorporating a layer of the thermoplastic adhesive composition.

[002] Background

[003] It is known to incorporate antimicrobials into consumer products in order to inhibit the growth of, for example, bacteria and/or fungi and/or viruses. However, the selection of a suitable antimicrobial depends significantly on the product into which it is to be incorporated. This invention seeks to provide a thermoplastic polymer composition comprising an antimicrobial which can be utilised in a wide range of products, and in particular which can be applied as a layer to fabrics, in particular absorbent fabrics.

[004] Statement of invention

[005] This invention relates to a thermoplastic adhesive antimicrobial composition comprising:

(a) a thermoplastic adhesive, and

(b) at least one antimicrobial.

By providing an antimicrobial composition in the form of a thermoplastic adhesive, a layer of an antimicrobial composition can be applied to a wide range of substrates.

[006] In relation to this invention, the term "thermoplastic adhesive" is used to refer to a polymer which is thermoplastic (ie which becomes pliable or moldable above a specific temperature and which returns to a solid state upon cooling) and which is capable of adhering to a substrate. [007] In relation to this invention, the term "antimicrobial" is used to refer to a substance that can kill microorganisms or inhibit their growth. Examples of antimicrobials include germicides, antibiotics, antibacterials, antivirals and antifungals. It is preferred that the antimicrobial provides up to a log 4 reduction in the number of cells of the microorganism in question. For example, a reduction in the number of cells from 10 ⁸ to 10 ⁴ would be a log 4 reduction (ie killing of 99.9% of the cells in question).

[008] It is preferred that the composition comprises l-50wt% of the at least one antimicrobial, preferably l-20wt%, more preferably 5-15wt%, even more preferably about 10wt%. In some embodiments, the remainder of the composition comprises the thermoplastic adhesive.

[009] It is preferred that the thermoplastic adhesive is ethylene vinyl acetate. It is preferred that the ethylene vinyl acetate is "low melt", ie it has a melting point of 50- 100°C, preferably 60-80°C.

[0010] It is preferred that the at least one antimicrobial is a quaternary ammonium compound. The quaternary ammonium compound is preferably a quaternary ammonium alkyl compound. More preferably, the quaternary ammonium alkyl compound is benzalkonium chloride or didecyldimethylammonium chloride. Alternative antimicrobials that may be used in the compositions of the invention include polyhexanides, preferably polyhexamethylene biguanide, and/or chlorophenols, preferably 4-chloro-3,5-dimethylphenol, 2 -chloro-3 -methyl-phenol, 2,4-dichloro-3,5-dimethylphenol, 2,4-dichloro-5-methylphenol, 4-chloro-3- methylphenol and/or 2,4,6-trichlorophenol.

[0011] The at least one antimicrobial is preferably benzalkonium chloride, 2-bromo- 2-nitropropane-l,3-diol and/or polyhexamethylene biguanide. It has surprisingly been found that these antimicrobials perform particularly well in the compositions of the invention. In some embodiments, the at least one antimicrobial comprises two antimicrobials. In some embodiments, it is preferred that the two antimicrobials are benzalkonium chloride and 2-bromo-2-nitropropane-l,3-diol.

[0012] In some embodiments, the composition additionally comprises an anionic surfactant. The inclusion of an anionic surfactant can assist in allowing the release of the antimicrobial when the composition is contacted with water. As described below, the inclusion of an anionic surfactant can be advantageous when the composition is incorporated into, for example, a mop head or surface wipe. This is because it can allow the antimicrobial to be released from the composition and deposited on the surface being cleaned. This can then provide the clean surface with antimicrobial activity for a period of time after it has been cleaned. It is preferred that the anionic surfactant is sodium lauryl ether sulphate, sodium lauryl sulphate, linear alkyl benzene sulphonic acid and/or sodium dodecylbenzenesulfonate. In a preferred embodiment, the anionic surfactant is sodium lauryl sulphate and the antimicrobial is polyhexamethylene biguanide. This anionic surfactant has been found to be particularly effective in allowing the release of the polyhexamethylene biguanide from the composition when the composition comes into contact with water. [0013] It is preferred that the composition comprises 1-5 wt% of the anionic surfactant, preferably about 2wt%. In some embodiments, the remainder of the composition comprises the thermoplastic adhesive and the antimicrobial.

[0014] This invention also relates to a method of preparing a composition as described above, comprising the step of mixing a thermoplastic adhesive powder and at least one antimicrobial powder. In some embodiments, the method comprises the step of mixing a thermoplastic adhesive powder and two antimicrobial powders. In some embodiments, the mixing step includes mixing an anionic surfactant powder. In some embodiments, the method comprises the step of mixing a thermoplastic adhesive powder, an antimicrobial powder and an anionic surfactant powder. [0015] This invention also relates to a method of forming a layer of a composition as described above on a substrate, the method comprising the steps of:

(a) applying to a substrate a thermoplastic adhesive microbial composition comprising a thermoplastic adhesive and at least one antimicrobial, and

(b) melting the thermoplastic adhesive antimicrobial composition.

[0016] After step (b), the method normally comprises the step of allowing the melted composition to cool. As a result, the melted composition will solidify. In step (a) of applying the composition to the substrate, the composition may be in the form of a powder (which may, for example, be scattered on the substrate). Melting step (b) may be carried out by compressing the composition and substrate between heated rollers. [0017] In some embodiments, the thermoplastic adhesive antimicrobial composition comprises a thermoplastic adhesive and two antimicrobials. In some embodiments, the thermoplastic adhesive antimicrobial composition comprises an anionic surfactant. [0018] The substrate is preferably a woven or nonwoven fabric. The substrate may alternatively comprise other water-permeable and/or air-permeable materials, which may also be capable of absorbing water. In some embodiments, the woven fabric comprises loops of fibre, such as terry towelling. In some embodiments, the nonwoven fabric comprises polypropylene and/or viscose (eg spun bond viscose).

[0019] In some embodiments, the method additionally comprises, after step (b), the step of: (c) applying a thermoplastic polymer to the thermoplastic adhesive antimicrobial composition. Step (c) can be carried out before or after the composition has cooled and solidified. It is preferred that the thermoplastic polymer is polyethylene, preferably low-density polyethylene (LDPE). Other suitable polymers include those that are capable of forming a film, for example polyester. The thermoplastic polymer can be applied in the form of a film or sheet. [0020] This invention also relates product comprising a substrate as defined above, preferably a woven or nonwoven fabric, having a layer of the composition as defined above adhered to it. Examples of suitable products include mattress protectors, pillow protectors, mop heads or surface wipes.

[0021] In some embodiments, the product additionally comprises a layer comprising a thermoplastic polymer as described above on the layer of the thermoplastic adhesive antimicrobial composition.

[0022] This invention also relates to a method of cleaning a surface comprising the steps of:

(a) wetting a mop head or surface wipe as described above with water, and

(b) wiping the surface with the wetted mop head or surface wipe.

[0023] This invention will be further described by reference to the following Figures which are not intended to limit the scope of the invention claimed, in which:

Figure 1 shows a photograph of testing of the antimicrobial activity of the composition of the invention when applied to nonwoven polypropylene,

Figure 2 shows a photograph of testing of the antimicrobial activity of the composition of the invention when applied to terry towelling,

Figure 3 shows a photograph of testing of the antimicrobial activity of the composition of the invention when applied to spun bond viscose,

Figure 4 shows a photograph of testing of the antimicrobial activity of the composition of the invention when incorporated in a mattress protector,

Figure 5 shows a further photograph of testing of the antimicrobial activity of the composition of the invention when incorporated in a mattress protector, and

Figure 6 shows a photograph of testing of the antimicrobial activity of the composition of the invention when incorporated in a mop head. [0024] Example 1

[0025] Laminated fabric samples were prepared by sprinkling a thermoplastic adhesive antimicrobial composition comprising ethylene vinyl acetate, polyhexamethylene biguanide and sodium lauryl sulphate onto the fabrics listed below and then compressing the fabric and composition layer between two heated rollers in order to melt the composition and adhere it to the fabric:

(1) White nonwoven polypropylene,

(2) White terry towelling, and

(3) White spun bond viscose.

[0026] For test sample 2, ie the terry towelling, a layer of LDPE was applied as a film to the thermoplastic adhesive antimicrobial composition. [0027] The resulting fabric swatches were all in good visible condition.

[0028] 25x25mm swatches of the above samples were transferred onto a surface of suitable culture media pre-seeded with the test species listed below (Tryptone Soya Agar (TSA) for bacteria and Sabouraud Dextrose Agar (SDA) for fungi). The swatches were then moistened with 0.5 ml of sterile water and incubated, the TSA samples at 35°C for 24 hours for bacteria and the SDA samples at 25°C for 2 to 5 days for yeasts and moulds.

[0029] Test species: (i) Escherichia coli (NCIMB 8879)

(ii) Staphylococcus aureus (ATCC 6538)

(iii) Staphylococcus aureus MRSA (NCIMB 11939)

(iv) Candida albicans (NCYC 597)

(v) Aspergillus niger (IMI 149007) [0030] The test results are set out in Table 1 below and in Figures 1-3. Figure 1 shows a photograph of the five Petri dishes used to test sample 1 against the five different test species (i)-(v). Identical photographs for samples 2 and 3 are shown in Figures 2 and 3 respectively.

Table 1

[0031] The results in Table 1 above show the size of the clear zone of no growth in mm, including the 25mm fabric swatch. These results are normally graded as follows:

Grade 0 = no clear zone - growth on swatch

Grade 1 = 1-10% growth on swatch

Grade 2 = 10-30% growth on swatch

Grade 3 = 30-50% growth on swatch

Grade 4 = 50-70% growth on swatch

Grade 5 = complete overgrowth

[0032] These test results show that the laminated swatches demonstrated clear zones of no growth around each swatch, indicating good antimicrobial activity. [0033] Example 2

[0034] A mattress protector was manufactured, comprising a layer of nonwoven polypropylene onto which was sprinkled a thermoplastic adhesive antimicrobial composition comprising ethylene vinyl acetate, polyhexamethylene biguanide and sodium lauryl sulphate. The fabric and composition layer were then compressed between two heated rollers in order to melt the composition and adhere it to the fabric. A layer of low-density polyethylene (LDPE) film was then applied on top of the thermoplastic adhesive antimicrobial composition. The sample was in good visible condition. [0035] 1. Modified AATCC 30 Method

[0036] 25x25mm duplicate swatches from the sample were transferred onto the surface of suitable culture media, which for bacteria is Tryptone Soya Agar (TSA). The swatches and culture media were then overlaid with a thin layer of the specified culture media pre-seeded with test species as detailed below. The plates were then incubated for 24 hours at 35°C (for bacteria).

[0037] Test species: (i) Escherichia coli (NCIMB 8879)

(ii) Staphylococcus aureus MRSA (NCIMB 11939)

[0038] 2. Modified Kirby-Bauer

[0039] The surface of suitable culture media, TSA for bacteria and SDA for fungi, were surface inoculated (using a sterile swab) with 0.5ml of the test species as detailed below. The inoculated plates were allowed to stand for 5 minutes to allow the inoculum to soak into the media (with the lid closed). 25x25mm duplicate swatches from the sample were transferred onto the surface of the inoculated culture media. The plates were then incubated 48 hours at 35°C for bacteria, 48 hours at 25°C for the yeast, and 5 days at 25°C for mould.

[0040] Test species: (i) Escherichia coli (NCIMB 8879)

(ii) Staphylococcus aureus MRSA (NCIMB 11939)

[0041] The results for tests 1 and 2 described above are shown in Table 2 below. In addition, Figures 4 and 5 each show photographs of two Petri dishes. Figure 4 shows dishes for test 1 (Modified AATCC 30) against the two test species (i) and (ii), and Figure 5 shows dishes for test 1 (Modified Kirby Bauer) against the two test species (i) and (ii).

ASSESSMENT OF GROWTH

Modified AATCC 30 Modified Kirby Bauer E.coli MRSA E.coli MRSA

32mm 33mm 29mm 30mm

Table 2

[0042] The results in Table 2 above show the size of the clear zone of no growth in mm, including the 25mm fabric swatch. These results are normally graded as follows:

Grade 0 = no clear zone - no growth under swatch

Grade 1 = <10% growth under swatch

Grade 2 = 10-30% growth under swatch

Grade 3 = > 30% growth under swatch

Grade 4 = >60% growth on swatch

[0043] These test results show that the mattress protector demonstrated clear zones of no growth around each swatch, indicating good antimicrobial activity.

[0044] 3. Simulated In-use Test

[0045] Discs 90mm diameter were cut from the mattress protector sheet and transferred to sterile Petri dishes.

[0046] The discs were inoculated with 1ml of the test species as detailed in Table 3 below and spread over the surface using a sterile L shaped spreader. After 1 minute the surface of the disc was swabbed with a dry sterile swab and the number of survivors determined by serial dilution and plate counting ("Swab" result in Table 3 below). 10 ml of sterile saline solution was then added to the Petri dish and mixed by rotating the dish 5 x clockwise, 5 x anticlockwise, 5 x forward and 5 x backward to release any bacteria remaining on the test surface, the number of survivors was determined by serial dilution and plates counting (the "Swatch" result below).

[0047] This was repeated on fresh discs with a 5 minute contact time. TEST SPECIES INITIAL INOCULUM LEVEL

Colony forming units per ml

Escherichia coli (NCIMB 8879) 2.9xl0 ⁶

Staphylococcus aureus MRSA (NCIMB 11939) 1.3xl0 ⁷

Table 3

[0048] The test results are shown in Table 4 below, and the calculated percentage reduction in the test species from the initial number inoculated is shown in Table 5 below.

Table 4

Table 5

[0049] The results in Tables 4 and 5 above show that the mattress protector including a layer of a composition according to the invention demonstrated a reduced number of survivors on the swatch with an increase in activity at 5 minutes for both E.coli and MRSA. The test results indicate that the mattress protector reduced the numbers of E.coli and MRSA by >90%.

[0050] Example 3

[0051] A strip roll of mop head material was manufactured, comprising a layer of viscose onto which was sprinkled a thermoplastic adhesive antimicrobial composition comprising ethylene vinyl acetate, polyhexamethylene biguanide and sodium lauryl sulphate. A further layer of viscose was then applied on top of the thermoplastic adhesive antimicrobial composition to give a sandwich-type structure. This structure was then compressed between two heated rollers in order to melt the composition and adhere it to the two layers of fabric. The sample was in good visible condition. [0052] Five strips 50mm long were cut from the roll and stapled together (at one end) to form mop heads. One mop head was used dry. Mop heads were used after 1, 3 and 5 washes, in sterile water (10ml).

[0053] Sterile tiles (100mm x 100mm) 1-5 were inoculated with 1ml of a cocktail of the test species as detailed in Table 6 below and spread over the surface using a sterile L shaped spreader.

[0054] Tile 1 was immediately swabbed with a dry mop head and the number of survivors determined by serial dilution and plate counting (the "mop head" result in Table 7 below). The tile was then swabbed with a sterile moistened swab to determine the number of survivors remaining on the tile surface (the "sterile swab" result in Table 7 below).

[0055] The remaining tiles were allowed to air dry. One tile was swabbed with a mop head after 1 wash and then by a sterile moistened swab, the number of survivors on the mop head and sterile swab was determined by serial dilution and plate counting. [0056] This was repeated for the mop heads after 3 and 5 washes. A control tile, which was not wiped with a mop head, was swabbed with a sterile moistened swab.

Table 6

[0057] The test results are shown in Table 7 below.

Table 7 [0058] The results in Table 7 show that the dry mop head demonstrated a reduction in the number of survivors. However, this reduction was not as great the mop heads which had been wetted in sterile water before use. This is believed to be because the wetting of the mop head provides improved release of the antimicrobial(s). Since the mop head was dry the activity from the mop head was not released to its full capacity.

[0059] The mop heads after 1 and 3 washes demonstrated significant reductions indicating the release of the active (ie the antimicrobial) from the mop head.

[0060] The mop head after 5 washes demonstrated better reduction than the dry mop head but the activity was reducing indicating possible depletion of the active.

[0061] Under laboratory conditions, the test results indicate that adding moisture to the mop head improves release of the active. The activity was most effective after 1 to 3 washes of the mop heads, with a slight reduction in activity after 5 washes. However, all tested mop head samples provided a good reduction in activity.

[0062] Example 4

[0063] Further testing was carried out on a sample of triangular mop head. The mop head was formed from the same material as that described in Example 3 above. However, in this example the mop head had areas of black dirt and cleaner areas indicating that the mop head had been used. The test species used is set out below.

[0064] Test species: Staphylococcus aureus (ATCC 6538)

[0065] A lower layer, 10 ml of culture media (TSA), was poured into sterile Petri dishes and allowed to set. Culture media (TSA) pre-cooled to approximately 45°C was inoculated with the test bacteria and poured over the lower layer to form an upper layer and allowed to set. [0066] Panels 25 x 25 mm were cut from "clean" and "dirty" areas of the sample and aseptically transferred, mop head down, onto the two-layer agar plates and incubated at 35°C for 24 hours.

[0067] The level of antibacterial activity was assessed by examining the extent of the bacterial growth in the contact zone between the agar and the test swatch. Inhibition zones were calculated using the following formula:

H = (D - d)/2

where H is the inhibition zone in mm

D is the total diameter of the swatch and the inhibition zone

d is the diameter of the swatch in mm

[0068] The test results are set out in Table 8 below. In addition, Figure 6 shows a photograph of two Petri dishes, (i) showing the testing of the clean area of the mop head, and (if) showing the testing of the dirty area of the mop head.

Table 8 [0069] According to the EN ISO 20645, standard inhibition zones > 1 mm and no growth under the specimen are accepted as effective. 0 mm inhibition and slight growth are evaluated as having limited effect.

[0070] The test results clearly show that the mop head including the composition of the invention demonstrates effective protection both when it is clean and when it is "dirty".