Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
WAX EMULSIONS INCORPORATING FORMALDEHYDE SCAVENGERS AND METHODS OF PREPARATION THEREOF
Document Type and Number:
WIPO Patent Application WO/2010/054467
Kind Code:
A1
Abstract:
Stable emulsions having hydrophobing and formaldehyde scavenging properties comprise a continuous aqueous phase comprising a formaldehyde scavenger and a dispersed non-aqueous phase comprising a wax. A method of preparing the emulsions is also provided wherein the formulations comprising the aqueous and non-aqueous phase are prepared separately and wherein the non-aqueous formulation is mixed into the aqueous formulation. The emulsions of the invention have a high wax content, with the dispersed non-aqueous phase comprising at least 45 wt% of the emulsion. In one aspect, the formaldehyde scavengers are provided in an amount of at least 10 wt%. The formaldehyde scavenges are preferably urea and urea-based derivatives. The emulsions are adapted for use in various processes such as the manufacture of composite wood panels or fibreglass insulation batts or rolls.

Inventors:
SINNIGE LAURENCE ANTHONY (CA)
RACOTA MARIA (CA)
Application Number:
PCT/CA2009/001602
Publication Date:
May 20, 2010
Filing Date:
November 11, 2009
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
WALKER IND HOLDINGS LTD (CA)
SINNIGE LAURENCE ANTHONY (CA)
RACOTA MARIA (CA)
International Classes:
C09K23/08; B27N7/00
Domestic Patent References:
WO2009062312A12009-05-22
Foreign References:
CA2547751A12006-11-20
US4043829A1977-08-23
US3819530A1974-06-25
US4239800A1980-12-16
US20070287018A12007-12-13
CA2603565A12008-03-28
US5698108A1997-12-16
Other References:
SCHAFER ET AL.: "On the formaldehyde release of wood.", EUROPEAN JOURNAL OF WOOD AND WOOD PRODUCTS, vol. 58, no. 4, 27 November 2000 (2000-11-27), pages 259 - 296
Attorney, Agent or Firm:
CHARI, Santosh, K. et al. (Cassels & Graydon LLP199 Bay Street,Suite 2800, Box 25,Commerce Court Wes, Toronto ON M5L 1A9, CA)
Download PDF:
Claims:
Ref 67632/00076

WE CLAIM:

1. A stable emulsion for use as a formaldehyde scavenger, the emulsion comprising a non-aqueous phase dispersed within a continuous aqueous phase, wherein the continuous aqueous phase comprises a formaldehyde scavenger and the dispersed non-aqueous phase comprises a wax.

2. The emulsion according to claim 1 , wherein the emulsion has a solids content greater than 65 wt%.

3. The emulsion according to claim 1 , wherein the dispersed phase comprises at least 45 wt% of the emulsion.

4. The emulsion according to claim 1 , wherein the formaldehyde scavenger comprises at least 10 wt% of the emulsion.

5. The emulsion according to claim 1 , further comprising an emulsifier.

6. The emulsion according to any one of claims 1 to 5 wherein the formaldehyde scavenger is urea, a urea derivative, a urea resin, a urea-formaldehyde resin, a melamine- urea-formaldehyde resin, an ethylene urea compound, carbohydrazide, a natural polyphenol^, tannin, lignin, lignosulphonate, or a combination thereof.

7. The emulsion according to claim 6 wherein the wax is a petroleum derived wax, a vegetable derived wax, a paraffin wax, a triglyceride wax, a natural oil, a petroleum base oil, bright stock, process oil, petrolatum or a combination thereof.

8. The emulsion according to claim 5 wherein the emulsifier is a lignosulphonate or a combination of one or more fatty acids or maleated hydrocarbons and one or more water- soluble alkaline compounds.

9. The emulsion according to claim 8 wherein said water-soluble alkaline compound is an alkali metal hydroxide, an amine, an ammonium solution, or a combination thereof.

10. The emulsion according to claim 1 , wherein the non-aqueous phase further comprises at least one hydrophobic element.

21936097 3 21 Ref 67632/00076

1 1. The emulsion according to claim 10 wherein the hydrophobic element is a fatty acid or a maleated hydrocarbon.

12. A method of preparing an emulsion for use as a formaldehyde scavenger, the emulsion comprising a wax and a formaldehyde scavenger, the method comprising: a) providing an aqueous formulation comprising the formaldehyde scavenger; b) providing a non-aqueous formulation comprising the wax; and, c) mixing the non-aqueous formulation into the aqueous formulation and forming an emulsion comprising a continuous formaldehyde scavenger -containing aqueous phase and a dispersed wax-containing non-aqueous phase.

13. The method according to claim 12, wherein the emulsion has a solids content greater than 65 wt%.

14. The method according to claim 12, wherein the dispersed phase comprises at least 45 wt% of the emulsion.

15. The method according to claim 12, wherein the formaldehyde scavenger comprises at least 10 wt% of the emulsion.

16. The method according to claim 12, further comprising adding an emulsifier.

17. The method according to any one of claims 12 to 16, wherein the formaldehyde scavenger is urea, a urea derivative, a urea resin, a urea-formaldehyde resin, a melamine- urea-formaldehyde resin, an ethylene urea compound, carbohydrazide, a natural polyphenol^, tannin, lignin, lignosulphonate, or a combination thereof.

18. The method according to any one of claims 12 to 16, wherein the wax is a petroleum derived wax, a vegetable derived wax, a paraffin wax, a triglyceride wax, a natural oil, a petroleum base oil, bright stock, process oil, petrolatum or a combination thereof.

19. The method according to claim 16, wherein the emulsifier is a lignosulphonate, or a combination of one or more fatty acids or maleated hydrocarbons and one or more water- soluble alkaline compounds.

20. The method according to claim 19, wherein said water-soluble alkaline compound is an alkali metal hydroxide, an amine, an ammonium solution, or a combination thereof.

21936097 3 22 Ref 67632/00076

21. The method according to claim 12, wherein step (a) further comprises combining one or more other hydrophilic components into the aqueous component.

22. The method according to claim 21 , wherein the hydrophilic component is a lignosulphonate, an alkaline compound or a combination thereof.

23. The method according to claim 22, wherein the alkaline compound is an alkali metal hydroxide, an amine, an ammonium solutions, or a combination thereof.

24. The method according to claim 12, wherein step (b) further comprises combining at least one hydrophobic element with the wax in the non-aqueous component.

25. The method according to claim 24 wherein the hydrophobic element is a fatty acid or a maleated hydrocarbon.

26. The method according to any one of claims 12 to 25 wherein the wax has a melting point of between 45°C and 900C.

27. The emulsion formed according to the method of any one of claims 12 to 26.

28. Use of the emulsion according to any one of claims 1 to 1 1 or 27 in the manufacture of composite wood panels or fibreglass insulation batts or rolls.

29. A method of manufacturing a composite wood panel having incorporated therein a formaldehyde scavenger and water repelling characteristics, the method comprising:

- forming a mat comprising wood material, a formaldehyde-based adhesive and an emulsion according to any one of claims 1 to 1 1 or 27; and

- pressing, heating and forming the mat to form said panel.

30. A composite wood panel incorporating the emulsion of any one of claims 1 to 1 1 or 27.

31. A woven or non-woven fibreglass product incorporating the emulsion of any one of claims 1 to 1 1 or 27.

21936097 3 23

Description:
Ref 67632/00076

WAX EMULSIONS INCORPORATING FORMALDEHYDE SCAVENGERS AND METHODS OF PREPARATION THEREOF

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority from US application number 61/1 13,968, filed November 12, 2008, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

[0002] In one aspect, the present invention relates to wax emulsions and methods of formulating same. In another aspect, the invention relates to stable wax emulsions incorporating formaldehyde scavengers.

BACKGROUND OF THE INVENTION

[0003] The manufacture of wood based panels such as particleboard, fibreboard (MDF and HDF) and the like (collectively referred to herein as "composite wood panels") generally first comprises combining wood chips or particles and an adhesive. The mixture is then formed into a mat, which is then heated under pressure to cure the adhesive and to form the desired panel. Formaldehyde based resins, such as urea-formaldehyde (UF), are typical adhesives used in the manufacture of such panels.

[0004] In order to impart water repelling, or hydrophobing characteristics to composite wood panels, it is known to include a wax or similar hydrophobic component into the panel manufacturing process. Thus, once the panel is made, the hydrophobic component serves to repel water from being absorbed, thereby preventing deterioration of the panel.

[0005] Composite wood panels manufactured with formaldehyde based adhesives are known to result in formaldehyde emissions both during manufacture and later over time. It is generally known that formaldehyde is a strong irritant and an allergenic agent. Formaldehyde is known to cause serious ailments in humans ranging from irritation of skin, eyes, and lungs to triggering asthma. Formaldehyde has also been classified as a known carcinogen in humans by the State of California and the World Health Organization's International Agency for Research on Cancer. It has therefore been a goal to absorb or "scavenge" the formaldehyde contained in composite wood panels and/or generated during the manufacture of such panels. In this regard, various restrictions on formaldehyde

21936097 3 -| Ref 67632/00076

emissions from composite wood panels have been proposed, and in some cases implemented, by governmental authorities.

[0006] Various formaldehyde absorbing additives, or "scavengers", have been proposed. Some examples of known scavengers are disclosed in US patent numbers: 4,501 ,628; 4,528,309; and 5,684,1 18. As known in the art, urea functions as an inexpensive and effective formaldehyde scavenger. For example, as disclosed in US patent number 5,684,1 18, urea has been found to be a formaldehyde scavenger both during manufacturing of composite wood panels and subsequent to such manufacture. However, the use of urea also results in various production problems in the manufacturing of composite wood panels. For example as explained in US patent number 5,684, 1 18, urea is added directly to the formaldehyde resin to reduce the concentration of free formaldehyde. As a result, the resin must be cured at a lower temperature thereby affecting the physical properties of the panels (i.e. the boards are of reduced strength) and/or increasing process time for manufacturing such boards. It was also noted that the higher urea concentration reduces the stability of the resin.

[0007] The prior art mentioned above provides various scavenger additives for combining with formaldehyde resin to reduce formaldehyde emissions. However, such additives are often more expensive than urea and, therefore, result in higher product costs. U.S. patent number 4,528,309 teaches the use of urea as a formaldehyde scavenger. However, according to this reference, a two stage process is employed and the urea (formaldehyde scavenger) is maintained separated from the formaldehyde-based adhesive during the curing phase. As taught in this reference, in the first stage, a urea composition is applied to the wood particles and allowed to impregnate therein. After this, in the second stage, the formaldehyde-based adhesive resin is applied and the panel manufacturing process is continued as normal. In this way, the urea scavenger is prevented from mixing with the resin and from affecting the curing process. In one example provided in this reference, where the wood material has a low moisture content, the scavenger may be applied in combination with other non-adhesive formulations such as curing agents, preservatives etc. It is also indicated that, in such formulation, the scavenger should be combined with a hydrophobic component such as a wax. In this regard, the '309 patent teaches that urea is mixed into a wax dispersion and applied to wood particles. However, as known in the art, mixing of a urea solution into a wax emulsion results in dilution of the strength and the overall solids content of the final mixture. Further, addition of urea in dry form can result in instability of the final formulation. In addition, this reference does not

21936097 3 O Ref 67632/00076

teach a single step panel forming method wherein the formaldehyde scavenger composition is applied together with the binding resin (or "glue").

[0008] Que et al (Effects Of Urea-Formaldehyde Resin Mole Ratio On The Properties Of Particleboard; Bldg. and Envir., 2007, 42, pp. 1257-1263) studied varying mole ratios of formaldehyde:urea resins. In such study, it was found that varying the ratio of these two components to reduce formaldehyde emissions, resulted in deterioration of the physical characteristics of the composite wood panel, as measured by the modulus of rupture (MOR), internal bond strength (IB), thickness swelling (TS), and water absorption (WA). The study further concluded that compensation for the deterioration could be provided through a higher dosage of resin or through the modification of UF resin. However, both alternatives meant that the final product would be more expensive.

[0009] The above discussion has focussed on scavenging of formaldehyde added during the manufacture of wood panels. However, a similar problem is encountered in the manufacture of fibreglass insulation products. Specifically, formaldehyde based resins, such as phenol-formaldehyde (PF) resins, are commonly used in the manufacture of fibreglass insulation. Such resins are used to bind glass fibres together to form the fibreglass batts and rolls that are used for insulation purposes. The use of PF resins has been found to allow such batts and rolls to recover or spring back to their original size after being compression packaged. Significant formaldehyde emissions have been found to result from fibreglass batt insulation once such batts are installed (Lent, T., Formaldehyde Emissions from Fibreglass Insulation with Phenol Formaldehyde Binder, 2009, Healthy Building Network). The emitted formaldehyde generally comprises that portion of the added amount that is not reacted or otherwise eliminated during the manufacturing process. Thus, there is a need to scavenge the residual formaldehyde from the fibreglass insulation manufacturing process.

[0010] US Patent No. 5,578,371 discusses the issue of formaldehyde emissions from fibreglass insulation and also notes that urea has been used as a cost effective formaldehyde scavenger in that industry. However, as pointed out in this reference, excess quantities of urea lead to further undesirable issues. Thus, the '371 patents proposes a different solution wherein a bisulfite compound is mixed into the PF resin composition prior to reacting with the glass fibres. The addition of such compound was found to reduce formaldehyde emissions from the fibreglass insulation once formed.

[0011] As discussed above, the use of urea as a formaldehyde scavenger is known as is the use of wax emulsions for imparting hydrophobing characteristics to wood panels.

21936097 3 r> Ref 67632/00076

However, there exists a need for an effective formaldehyde scavenger that can be used in various manufacturing processes. There also exists a need to provide an effective and economical formaldehyde scavenger, comprising a urea-based formulation. There also exists a need for a stable, high solids content wax emulsion incorporating a formaldehyde scavenger that can be used efficiently in manufacturing processes for reducing formaldehyde emissions and imparting hydrophobing characteristics to the finished products.

SUMMARY OF THE INVENTION

[0012] In one aspect, the present invention provides a stable wax emulsion for use as a formaldehyde scavenger, the emulsion comprising a non-aqueous phase dispersed within a continuous aqueous phase, wherein the continuous aqueous phase comprises a formaldehyde scavenger and the dispersed non-aqueous phase comprises a wax.

[0013] In another aspect, the emulsion is used in manufacturing various products such as composite wood panels (i.e. particle board) and fibreglass insulation. For example, with regard to composite wood panels, the emulsions of the invention may be used to impart formaldehyde scavenging and water repelling characteristics to such panels.

[0014] In another aspect, the invention provides an efficient method of preparing the stable emulsions of the present invention.

[0015] In one aspect, the formaldehyde scavenger is: urea; a urea derivative; a urea resin; a urea-formaldehyde resin; a melamine-urea-formaldehyde resin; an ethylene urea compound; carbohydrazide; or a natural polyphenol^ such as tannin, lignin, lignosulphonate, or a combination thereof.

[0016] In another aspect, the wax is a petroleum derived wax, a vegetable derived wax, a paraffin wax, a triglyceride wax, a natural oil, a petroleum base oil, bright stock, process oil, petrolatum or a combination thereof.

[0017] In another aspect, the invention provides a method of preparing an emulsion for use as a formaldehyde scavenger, the emulsion comprising a wax and a formaldehyde scavenger, the method comprising:

a) providing an aqueous formulation comprising the formaldehyde scavenger; b) providing a non-aqueous formulation comprising the wax; and,

21936097 3 Ref 67632/00076

c) mixing the non-aqueous formulation into the aqueous formulation and forming an emulsion comprising a continuous formaldehyde scavenger -containing aqueous phase and a dispersed wax-containing non-aqueous phase.

[0018] In another aspect, the invention provides a stable emulsion for use in manufacturing composite wood panels comprising a wax and a formaldehyde scavenger and, optionally, an emulsifier, the emulsion having a solids content greater than 65% w/w.

[0019] In another aspect, the invention provides a wax and urea emulsion having a dispersed phase comprising at least 45 wt%, and preferably at least 55 wt%, of the emulsion.

[0020] In a further aspect, the invention provides a composite wood panel and a method of manufacturing a composite wood panel incorporating the emulsions described herein.

[0021] In another aspect, the invention provides a method of manufacturing a composite wood panel having incorporated therein a formaldehyde scavenger and water repelling characteristics, the method comprising: - forming a mat comprising wood material, a formaldehyde-based adhesive and an emulsion as described herein; and - pressing, heating and forming the mat to form said panel.

DETAILED DESCRIPTION OF THE INVENTION

[0022] As used herein, the following terms will be understood to have the following meanings.

[0023] "Composite wood panel", or "panel", as used herein, will be understood to mean any form of wood or cellulosic material-based panel. "Composite wood panel" will be understood to include particleboard, fibreboard, such as medium density fibreboard (MDF) and high density fibreboard (HDF), flakeboard, chipboard, oriented strand board (OSB), waferboard and other similar products wherein wood based material is mixed with adhesive and formed into a flat panel.

[0024] "Wood particles" will be understood to mean known wood or cellulosic material commonly used in manufacturing composite wood panels. This term will, therefore, be understood to include wood particles, wood chips, wood shavings, wood wafers, wood strands, sawdust or other similar materials.

21936097 3 R Ref 67632/00076

[0025] "Dispersion", as used with respect to the present invention, will be understood to mean a wax emulsion comprising a continuous aqueous phase and dispersed phase comprising the wax material. As known, the term "dispersion" may be used in the reverse, namely, to identify an aqueous phase dispersed within a continuous non-aqueous phase. However, for the purposes of the present description, the invention will be described in terms of the former meaning.

[0026] "Solids" or "solids content" as used herein will be understood to refer to the amount (expressed as a weight percentage) of non-volatile material in the emulsion. More accurately, these terms refer to the total amount of material (including wax, urea, emulsifiers and stabilizers) that remain after evaporation or drying to a constant weight.

[0027] "Fibreglass" or "fibreglass insulation" as used herein will be understood to mean known woven or non-woven fibreglass insulation products such as batts or rolls and the like, formed using glass fibres and a binder resin, more specifically a phenol formaldehyde (PF) resin.

[0028] The present invention is directed in one aspect to a stable wax emulsion comprising a formaldehyde scavenger and a wax and a method of making such emulsion. In one aspect, the formaldehyde scavenger is urea or a urea derivative. In one aspect, the invention provides a formulation comprising such emulsion for use in the manufacture of composite wood panels or fibreglass batts etc. In another aspect, the formulation of the invention comprises a urea and wax containing emulsion. The invention provides various advantages including an effective and inexpensive means of reducing formaldehyde emissions commonly associated with the manufacture of composite wood panels or fibreglass insulation. The formulation of the invention does not interfere to any substantial degree with the function of the formaldehyde-based adhesives or binders typically used in the manufacture of composite wood panels or fibreglass batts. For example, incorporating the emulsions of the invention into the manufacture of composite wood panels does not alter to a significant degree the physical or strength characteristics of the formed panels

[0029] The invention also provides a urea-wax formulation that has a high degree of stability. In another aspect, the formulation of the invention provides an emulsion comprising a wax and a formaldehyde scavenger wherein the emulsion has a high solids content.

[0030] As will be understood, the high wax content in the emulsion allows a more efficient means of manufacturing a composite wood panel with a desired amount of both a

21936097 3 R Ref 67632/00076

formaldehyde scavenger and wax content. As known in the art, the wax content increases the water repelling characteristics of the panel

[0031] According to one aspect, the formulation of the invention comprises an emulsion formed of a continuous aqueous phase, comprising water and a formaldehyde scavenging additive, and a dispersed wax phase. With such an emulsion, a high total solids content by weight (not volume) is achieved, thereby making such formulation economical for the uses contemplated herein. An emulsifier is preferably included in the formulation and would generally be concentrated at the interface of the wax and aqueous phases.

[0032] In one aspect of the invention, the emulsion provided herein comprises a solids content of greater than 65% and, preferably, greater than 75% (w/w).

[0033] Waxes

[0034] The waxes that can be used in the formulations of the present invention may comprise any known waxes that are suitable for use in manufacturing composite wood panels. For example, the wax component of the emulsion may comprise any natural wax, such as petroleum or vegetable derived waxes, or synthetic waxes. In one preferred embodiment, the invention comprises petroleum or vegetable derived waxes. The petroleum wax may comprise a paraffin wax in the form of a scale wax or slack wax, as obtained from petroleum distillation processes. In one aspect, the wax is a paraffin wax or a triglyceride wax. In a further aspect, the wax has a melting point of 45°C to 90 0 C. The invention also contemplates the use of petroleum waxes modified with various polymers such as polyethylene or copolymers such as ethylene-vinyl acetate copolymers, alpha-olefin maleic anhydride copolymers and similar polymeric materials. In addition, the invention provides for the use of various natural waxes such as vegetable-based waxes, beeswax, etc. In another embodiment, which is particularly suited for the manufacture of fiberglass batts, the "wax" of the invention may comprise other oil or oil-like materials such as bright stock, process oil, or petrolatum (or petroleum jelly). The invention also provides for the use of any mixtures of waxes including those listed above.

[0035] In one embodiment, the wax of the present invention comprises hydrogenated vegetable oil. Hydrogenated vegetable oils are fatty acids which have been saturated with hydrogen molecules. Suitable hydrogenated vegetable oils include hydrogenated soybean oil, hydrogenated palm oil, hydrogenated sunflower oil, hydrogenated canola oil, hydrogenated corn oil, hydrogenated olive oil, hydrogenated peanut oil, hydrogenated safflower oil or mixtures thereof. The use of vegetable based waxes is known to have

21936097 3 J Ref 67632/00076

various economic and environmental advantages. Similarly, emulsions that are used in the fiberglass industry generally tend to be oil based, which denotes a different physical characteristic than would be typically associated with the term "wax". Thus, the invention may incorporate any wax or wax-like material that would normally be used in the art, such as in the manufacture of composite wood panels or fiberglass insulation batts etc.

[0036] Emulsifiers

[0037] Various emulsifiers that can be used in the formulation of the invention will be known to persons skilled in the art. Some examples of suitable emulsifiers include lignosulphonates such as sodium, ammonium, potassium, calcium or magnesium salts of lignosulphonic acids. The emulsifiers of the invention may also comprise one or more fatty acids or maleated hydrocarbons in combination with one or more water-soluble alkaline compounds. Some examples of such water-soluble alkaline compounds include:

[0038] i) alkali metal hydroxides (such as, but not limited to, lithium hydroxide, sodium hydroxide or potassium hydroxide);

[0039] ii) amines, such as, but not limited to, ethanolamines (such as, but not limited to, triethanolamine, diethanolamine, monoethanolamine or methyldiethanolamine); and,

[0040] iii) ammonium solutions (such as, but not limited to, ammonium hydroxide and solutions of ammonium compounds or salts).

[0041] A combination of one or more of such alkaline compounds may also be used. The amount of the aforementioned water-soluble alkaline compound would typically be within a range of 0.5 to 3 times the amount required for the neutralization of the fatty acid or maleated hydrocarbon. Various other emulsifiers will be known to persons skilled in the art and it will be understood that the present invention is not limited to any particular emulsifier.

[0042] Formaldehyde Scavenger

[0043] In general, the scavenger of the invention comprises various formaldehyde sequestering agents or additives that are known in the art. In one aspect, urea, (NH 2 ^CO, is the preferred scavenger component due to its effectiveness as a formaldehyde scavenger, low cost, and high solubility in water. Other urea compounds such as low mole ratio urea- formaldehyde or melamine-urea-formaldehyde resins, ethylene urea and carbohydrazide (1 ,3-diaminourea) may also be used in the invention. Unitan™ wood board additives including vegetable tannin extracts such as Colatan™ GT5, GT 100 and GT10 may also be

21936097 3 8 Ref 67632/00076

used in the invention. Nitrogen containing aromatic heterocyclics such as pyrrole, indole and triazoles are also effective scavengers, as are many other chemicals well known to those in the industry. Such compounds may also be used in the present invention.

[0044] In one aspect, the invention also provides for formaldehyde scavengers comprising natural polyphenols such as tannin, lignin, or lignosulphonate. As will be known to persons skilled in the art, compounds such as lignosulphonates can also serve as emulsifiers as indicated above.

[0045] In one aspect of the invention, the formaldehyde scavenger is urea, a high mole urea based resin or a combination of same. The urea or urea based resin may be present in an amount greater than 10% by weight of the total formulation, and more particularly, in an amount greater than 20% by weight of the total formulation.

[0046] Methodology of Formulation

[0047] As discussed further below, the invention provides, in one aspect, a method of preparing a stable wax in water emulsion comprising a formaldehyde scavenger, for use in various processes such as the manufacture of composite wood panels or fiberglass insulation. It will be understood that the method of preparing the emulsion is not related to the manner in which the resulting emulsion is used. In general, the method comprises the separate formulation of aqueous and non-aqueous compositions and the subsequent mixing of the non-aqueous composition into the aqueous solution. This results in a continuous aqueous phase and a dispersed non-aqueous phase. Further, the method of the invention allows for the manufacture of a stable formulation having a high solids (i.e. wax) content.

[0048] As known in the art, in the formulation of wax emulsions, a limit is known to exist with respect to the amount of wax that can be practicably dispersed in a water solution. That is, a "dispersed" wax content of greater than 60% by weight results in radical changes in viscosity, stability, and ultimately complete inversion of the emulsion. The term "inversion" refers to the conversion of the aqueous continuous phase being converted to the dispersed phase within a continuous non-aqueous phase.

[0049] Thus, the mixing of the aqueous and non-aqueous phases of the wax emulsion must be done in a manner that allows a sufficiently high amount of wax while maintaining the stability of the formulation.

[0050] Adding urea to a prepared emulsion will result in a reduction of hydrophobing properties. Further, in the case of a urea solution, this will also result in dilution of the overall

21936097 3 9 Ref 67632/00076

solids content of the wax dispersion. For example, if a 50 wt% solution of urea in water is added to a 58 wt% solids wax emulsion at a 1 :1 ratio, the formulation summarized in Table 1 will result.

[0051] Table 1

[0052] As indicated in Table 1 , the total solids in the final emulsion is effectively reduced to 53.25 wt%, and the dispersed phase comprises only 28.25 wt% of the emulsion.

[0053] If, on the other hand, the urea is added to the dispersion in neat or dry form, the overall solids of the dispersion will not be reduced, but there is an added risk of reduced stability due to the handling and mixing procedures required to mix dry materials into a liquid dispersion. Such method will also result in a reduction in the dispersed phase content. If urea is added in dry form to the same control sample as discussed above, at a rate of 5Og urea to 100g emulsion, assuming 100 wt% solids for the urea, the formulation summarized in Table 2 will result.

[0054] Table 2

[0055] As noted in Table 2, while the overall solids content is 71 wt% in final emulsion sample, the dispersed phase content, which is effective at providing water resistance and dimensional stability to the composite panels, is now reduced to 37.67 wt%.

21936097 3 10 Ref 67632/00076

[0056] The method of the invention, however, results in a wax and urea emulsion having a high solids content. In one aspect, the method provides an emulsion having a dispersed non-aqueous phase that makes up at least 45% (w/w) of the total emulsion. In a particular aspect, the invention provides an emulsion comprising a dispersed phase comprising at least 55% (w/w) of the emulsion.

[0057] In one aspect, the invention provides a method of preparing a wax and urea emulsion having a high wax content (as measured by "solids"), while maintaining stability. As discussed herein, the method of the invention provides such an emulsion by first separately forming an aqueous formulation comprising a formaldehyde scavenger and a non-aqueous formulation comprising the wax component. The non-aqueous formulation is then mixed into the aqueous formulation, whereby an emulsion is formed comprising a continuous aqueous phase and a dispersed non-aqueous phase.

[0058] The aqueous formulation may further comprise an emulsifier and, optionally, stabilizers. The non-aqueous formulation may further comprise stabilizers. In the case where the emulsifier comprises a combination of fatty acids and/or maleated hydrocarbons and one or more water-soluble alkaline compounds, the fatty acid/maleated hydrocarbon component may be contained in the non-aqueous formulation while the alkaline compound may be contained in the aqueous formulation.

[0059] As will be understood, the invention differs from prior art methods, wherein urea is added to the formulation after the emulsification step. As will be understood, in order to maintain an emulsion having a dispersed phase (wax + fatty acid) content of greater than 55 wt% and achieve a urea concentration of 21 wt%, the original emulsion would need to contain greater than 70 wt% dispersed solids by weight. However, a wax emulsion with a dispersed phase content over 60 wt% starts to create severe issues with viscosity, and with a dispersed phase content over 65 wt%, the emulsion becomes highly unstable and tends to form an "invert" emulsion. Therefore, using even a highly unstable wax content of 65 wt% to start, the addition of 26.6g of dry urea to 10Og of such emulsion would result in a product having 21 wt% urea (26.6g/126.6g) and a maximum wax content of 51.3%. The method of the invention, however, provides a higher wax content without the stability issues mentioned above.

[0060] In the present description, the formulations (i.e. emulsions of wax and one or more formaldehyde scavengers) have been defined as having a specific utility in the manufacturing of wood panels, fibreglass insulation and the like. However, in general, the formulations of the present invention can be used in various other applications where

21936097 3 -| -| Ref 67632/00076

formaldehyde scavenging properties are needed. For example, one other area is in the manufacture of textiles.

[0061] With regard to the manufacture of fibreglass insulation, the emulsions of the invention can be either incorporated into the binder solution directly or can be sprayed onto, for example, mats of the glass fibres.

[0062] Examples

[0063] The invention will now be described in terms of specific examples. It will be understood that the purpose of all examples contained herein is solely to illustrate the invention and that such examples are not intended to limit the invention in any way.

[0064] As illustrated below, the wax formulations of the present invention have been found to effectively reduce formaldehyde emissions in composite wood panels without affecting the curing ability of the adhesive resin (i.e. urea-formaldehyde resin). In addition, it was also noted that the wax formulations of the invention also resulted in improved internal bond strength within the composite wood panel samples. It is believed that the latter effect may be due to the fact that the urea added as a scavenger within a wax emulsion according to the invention, is not immediately available to react with react with the resin, thereby allowing the urea to act as a scavenger after the resin has cured. This is a feature of the invention, since, as described above, resins that contain high levels of urea often result in lower board strength properties. It should be noted that the above discussed possible mode of action in resulting in improved IB values is believed to be accurate but is not intended to limit the invention in any way.

[0065] Example 1 : Preparation of formulations

[0066] Two formulations of the invention were prepared, identified herein as formulations A and B, along with a control, formulation C. Generally, in preparing the formulations, the wax and other hydrophobic components were prepared separately from the aqueous solution comprising the hydrophilic components (i.e. water, emulsifier(s) etc.). The hydrophobic preparation was then mixed into the aqueous solution to result in a continuous aqueous phase and a dispersed wax phase. In some cases, more than one formulation of the same composition may have been made but, for convenience, such sets of formulations will be identified herein in the singular.

[0067] More specifically, for each of formulations A, B and C, a non-aqueous composition was made by blending paraffin wax (high melt slack wax from PetroCanada)

21936097 3 -| 2 Ref 67632/00076

and fatty acids. An aqueous solution was made separately by adding to water, the emulsifier(s) (i.e. the amine compounds) and, for formulations A and B, urea. The non- aqueous mixture was then mixed into the aqueous solution so as to form an emulsion comprising a non-aqueous dispersed phase within a continuous aqueous phase. The resulting coarse emulsion was then further processed with a homogenizer at a temperature of 75 to 95°C. The final emulsion was then rapidly cooled to a temperature below that of the melt point of the wax.

[0068] The relative amounts of continuous phase, dispersed phase and urea scavenger are shown in Table 3 (wt% shown).

[0069] Table 3

[0070] As shown in Table 3, formulation A was formed to provide an emulsion having a solids content of roughly 57% w/w (i.e. ~ 27.5% + 29.2%) and a urea content of 27.5% w/w, based on total weight. Formulation B was formed to provide an emulsion having a solids content of roughly 78% and a urea content of 21 % w/w. The "control" comprised the same wax and emulsifier as used in formulations A and B and had solids content of approximately 56.5% w/w. No other additives were used in preparing the controls.

[0071] Thus, formulation B was formed to include a higher wax content that formulation

A.

[0072] In summary, the final formulations A, B and C were found to have the properties shown in Table 4.

21936097 3 13 Ref 67632/00076

[0073] Table 4

[0074] In addition to formulations A and B described above, a further set of formulations, identified herein as formulation "D", were also prepared. The set comprising formulation D was made without including the aqueous amine component as part of the surfactant and scavenger composition. Thus, formulation D comprised the composition (in wt%) shown in Table 3a.

[0075] Table 3a

[0076] Surprisingly, formulation D, made without the amine component, but with a urea content higher than 10wt% was found to be as stable as the control sample C.

[0077] Other formulation samples were prepared using lignosulfonates and urea in combination as formaldehyde scavengers and these formulations were also found to be stable without the addition of further surfactants.

[0078] Example 2: Preparation and testing of sample composite wood panels

[0079] Using the above two formulations and the control, particleboard samples were prepared. The purpose of this test was to evaluate the formaldehyde scavenging effects of

21936097 3 -| 4 Ref 67632/00076

the wax emulsion formulations A and B as discussed above. Following the manufacture of the board samples, formaldehyde emission tests were performed. In addition, the internal bond (IB) strength of the manufactured boards was evaluated.

[0080] Materials

[0081] A urea-formaldehyde resin (TL-224™) manufactured by Hexion was used. The resin had a solids content of 69% w/w.

[0082] The ratio of core to surface layer particles was 0.6:0.4. The wood particles used were from Sayabec, Quebec and were composed of SPF (spruce, pine, and fir).

[0083] Wax emulsion formulations A and B as indicated above, and a control C, were used. The solids content (w/w) of the three formulations was found to be 56.85%, 78.05% and 56.5%, respectively.

[0084] Particleboard manufacture

[0085] Particleboard samples, in duplicate, were produced using the following parameters:

- Resin dosage: 10% (w/w) UF resin based on dry wood. - Wax/formaldehyde scavenger emulsion dosage: 1 % (w/w) solids wax based on dry wood. - Board construction: homogenous or one layer. - Size of board: 71.1 cm x 71.1 cm x 16 mm. - Platen temperature: 185°C - Target density of board: 640 kg/m 3 . - Pressing time: 225 sec. (3.75 mins.)

[0086] The wood particles, resin and formaldehyde scavenging emulsion were mixed together and formed into a mat, which was subsequently pressed and heated as would be known to persons skilled in the art. A total of six boards were produced. Test specimens for formaldehyde emission tests were cut from the boards after 24 hours of conditioning at 20 0 C and 64% relative humidity (RH). The remaining portions of the boards were conditioned for a week at the same conditions prior to testing for IB strength.

21936097 3 -| 5 Ref 67632/00076

[0087] Formaldehyde emission test

[0088] Test specimens of 10.5 cm x 10.5 cm were cut in the middle of each particleboard after 24 hours of conditioning. The specimens were again conditioned for one week prior to testing for formaldehyde emission following the ASTM standard ASTM D-6007- 06, "Standard Test Method For Determining Formaldehyde Concentration From Wood Products Using A Small Scale Chamber". The test specimens were placed in a chamber, of 53 litres capacity, with an air exchange rate of 440 cm 3 /min for 24 hours. The air from the chamber was absorbed by a sodium bisulfite solution, which was analyzed by the chromotropic acid test procedure. A total of six test specimens were evaluated. Only one test specimen was exposed to the chamber per test.

[0089] Internal bond (IB) strength test

[0090] Sixteen test specimens were cut from each board and the density of each specimen was calculated from its weight and volume. Eight test specimens with similar or with close density values were selected for the internal bond strength (IB) test. Prior to the IB test, the density of each specimen was measured using an x-ray densitometer. The IB test was conducted following the ASTM standard ASTM D-1037-1999, "Standard Test Methods For Evaluating Properties Of Wood-Base Fiber And Particle Panel Materials".

[0091] Results

[0092] Board physical properties

[0093] The average thickness and density of the boards after hot pressing are shown Table 5 below. The thicknesses were found to have small deviations from the nominal thickness of 16 mm.

[0094] Table 5: Sample panel properties

21936097 3 16 Ref 67632/00076

[0095] Formaldehyde emission

[0096] As shown in Table 6, the results were found to have good reproducibility between duplicates of the same formulation and were within a 20% variation. The panels made with formulation A were found to have the lowest formaldehyde emission level followed closely by the panel made with formulation B. The panels made with the control formulations, C, were found to have the highest emission levels. The values for the duplicate samples (i.e. A1 and A2) were averaged and provided in Table 6.

[0097] Table 6: Formaldehyde emission results

[0098] Internal bond strength

[0099] As shown in Table 7 below, panels made with wax formulation B exhibited the highest IB strength values followed by the panels made with wax formulation A. The boards made with the control formulations were found to have the lowest IB values.

[00100] Table 7: IB Values

[00101] Example 3: Thickness swell tests of sample particleboards

[00102] The sample particleboards of Example 2 were subjected to a water absorption test pursuant to ASTM D1037-1999 "Standard Test Methods for Evaluating Properties of Wood-Base Fiber and Particle Panel Materials". Briefly, the test involves first submerging the samples horizontally under 2.54 cm (1 ") of water for 24 hours. The specimens were then removed and, after wiping excess water, were suspended vertically and allowed to drain for 10 mins. The specimens were then measured and weighed. The thicknesses were measured using a digital micrometer at four points midway along each side of the test

21936097 3 17 Ref 67632/00076

panels, 2.54 cm (1 inch) from the edge. Water absorption was obtained by determining differences in sample weight before and after submersion.

[00103] Two samples were used for each test and the averaged results of the thickness swell tests are summarized in Table 8.

[00104] Table 8: Thickness swell results

[00105] This test serves to evaluate the degree of water repellent characteristics imparted to the particle board primarily as a result of the wax component of the formulation. As indicated above, the wax emulsions were added to provide a 1 % w/w total solids on dry wood.

[00106] Conclusions from Examples 2 and 3

[00107] As shown above, boards manufactured using the wax emulsion of formulation B had much better physical characteristics than boards manufactured with formulation A, although both formulations performed well on the formaldehyde emission tests. The modified wax formulations A and B performed better than the control in scavenging formaldehyde in particleboards and were found to result in higher internal bond strengths. As indicated above, the boards manufactured with formulation A were found to control

21936097 3 18 Ref 67632/00076

formaldehyde emissions slightly better than boards manufactured with formulation B. This difference may be attributable to the higher urea content in formulation A.

[00108] These results demonstrate the benefit of a formulation having a high solids content and a high wax content. In the above test, the panels were produced using 1 % of solids on board fibre. Therefore, the sample with high wax and solids, formulation B, performed very well in moisture resistant testing (thickness swell and water absorption). Surprisingly the internal bond, which is a measure of board strength, was not only maintained but actually improved with both scavenger wax formulations. This is in contrast to what would be expected if the urea were added to the resin to provide a "low mole ratio" resin. The low mole ratio reflects a lower ratio of formaldehyde to urea (F/U). It is normally expected that both IB and thickness swell would be impaired with lower mole ratios of F/U.

[00109] Thus, the invention comprises at least the following aspects:

[00110] 1) A stable wax/formaldehyde scavenger emulsion having a continuous aqueous phase and a dispersed non-aqueous phase, the aqueous phase comprising the formaldehyde scavenger and the non-aqueous phase comprising the wax. The emulsion having a high (i.e. greater than 65 wt%) solids content. The aqueous phase may optionally contain an aqueous emulsifier or a water-soluble alkaline component. The non-aqueous phase may optionally contain a fatty acid or maleated hydrocarbon component.

[00111] 2) A stable wax/formaldehyde scavenger emulsion having a continuous aqueous phase and a dispersed non-aqueous phase, the aqueous phase comprising the formaldehyde scavenger and the non-aqueous phase comprising the wax and one or more fatty acids or maleated hydrocarbons.

[00112] 3) A method of forming a stable wax/formaldehyde scavenger emulsion comprising the addition of a non-aqueous wax formulation into an aqueous scavenger formulation.

[00113] 4) A wood composite panel or fibreglass batt or roll formed using the above emulsions.

[00114] 5) A method of forming a composite wood panel comprising combining forming a mat of wood particles, a binder or resin, and the wax/formaldehyde scavenger emulsion of the invention and pressing and heating the mat.

21936097 3 -| 9 Ref 67632/00076

[00115] 6) As discussed above, the wax emulsions of the present invention can be used to impart hydrophobic properties to manufactured products (such as composite wood panels) and also to serve as an effective formaldehyde scavenger.

[00116] Although the invention has been described with reference to certain specific embodiments, various modifications thereof will be apparent to those skilled in the art without departing from the purpose and scope of the invention as outlined in the claims appended hereto. Any examples provided herein are included solely for the purpose of illustrating the invention and are not intended to limit the invention in any way. Any drawings provided herein are solely for the purpose of illustrating various aspects of the invention and are not intended to be drawn to scale or to limit the invention in any way. The disclosures of all prior art recited herein are incorporated herein by reference in their entirety.

21936097 3 20