Modification of wood with hydrophilic prepolymers
A composition for modification of wood products is disclosed. The composition contains a prepolymer formed by the reaction of a polyfunctional hydrophilic polymer of high molecular weight and a crosslinking agent. The composition may also contain a prepolymer formed by the reaction of a sugar and a crosslinking agent. Modification of the wood product may result in one or more of: improved stiffness, strength, surface hardness, dimensional stability, water resistance, flame retardancy, and biological resistance.
1. A wood product-modifying composition comprising:
A) a shelf-stable prepolymer formed by the reaction of:
(i) a polyfunctional hydrophilic polymer, selected from a vinyl polymer, a polyamide, a polysaccharide, a lignin derivative, a cellulose derivative, a polyol, a polylactic acid, a polycaprolactone, and a mixture thereof, the polyfunctional hydrophilic polymer having a weight-average molecular weight of between 3,000 Da and 100,000 Da; and
(ii) a crosslinking agent selected from an amino resin and a compound containing two or more functional groups selected from hydroxymethyl, alkoxymethyl, epoxide, vinyl, aldehyde, alcohol, carboxylic acid, ester, anhydride, acyl halide groups, and a mixture thereof; the composition being further characterized in that the ratio of said polyfunctional hydrophilic polymer to crosslinking agent is in the weight range of substantially 0.5:1 to 10:1; and
(iii) optionally additionally comprising one or more components selected from a catalyst for promoting crosslinking, a water miscible solvent, a surfactant, a preservative and a dye, wherein the prepolymer stability ranges for a time period from 24 hours to 5 months.
2. The composition as claimed in claim 1 wherein the ratio of polyfunctional hydrophilic polymer to crosslinking agent is in the weight range of substantially 0.5:1 to 5:1.
3. The composition as claimed in claim 1 wherein the vinyl polymer is selected from a polyvinyl alcohol, polyvinyl acetate, polyvinyl pyrrolidone, polyacrylic acid, polyacrylamide, or mixtures, derivatives or salts thereof, or a copolymer of polyvinyl alcohol, polyvinyl acetate, polyvinyl pyrrolidone, polyacrylic acid, polyacrylamide and derivatives thereof, and wherein the vinyl polymer is polyvinyl alcohol having a degree of hydrolysis in the range from about 80% to about 100%.
4. The composition as claimed in claim 1 wherein the polyamide is a synthetic polyamide, a polypeptide, or derivatives thereof.
5. The composition as claimed in claim 1 wherein the amino resin is a hydroxymethyl or alkoxymethyl derivative of melamine, benzoguanamine, urea, glycoluril, dihydroxyethylene urea, acrylamide or methacrylamide.
6. The composition as claimed in claim 1 wherein the water miscible solvent is selected from an alcohol, a glycol, an ether alcohol, ester, amine, alkanolamine and amine oxide.
7. The composition as claimed in claim 6 wherein the water miscible solvent is present at substantially 0.1-60% by weight, up to a concentration that will not adversely affect the solubility of other components of the composition.
8. The composition as claimed in claim 1 , further comprising:
B) a prepolymer formed by the reaction of:
(i) a sugar selected from sucrose, maltose, lactose, trehalose, cellobiose, chitobiose, glucose, fructose, galactose, mannose, and chemical derivatives thereof; and
(ii) a crosslinking agent selected from an amino resin and a compound containing two or more functional groups selected from hydroxymethyl, alkoxymethyl, epoxide, vinyl, aldehyde, alcohol, carboxylic acid, ester, anhydride, acyl halide groups and a mixture thereof; and
(iii) optionally additionally comprising one or more components selected from a catalyst for promoting crosslinking, and a water miscible solvent.
9. The composition as claimed in claim 8 wherein the crosslinking agent in Part B) is an amino resin selected from a hydroxymethyl or alkoxymethyl derivative of melamine, benzoguanamine, urea, glycoluril, dihydroxyethylene urea, acrylamide and methacrylamide.
10. The composition as claimed in claim 8 wherein the ratio of sugar to crosslinking agent is in the weight range of substantially 0.5:1 to 10:1.
11. The composition as claimed in claim 8 wherein the ratio of prepolymer A) to prepolymer B) is in the weight range of substantially 0.1:1 to 10:1.
12. The composition as claimed in claim 1 wherein prepolymers A) and B) are formed in separate reactions then combined, or are formed concurrently or sequentially in the same reaction medium.
13. A wood product resulting from a method as claimed in claim 1 .
14. A wood product-modifying composition comprising:
A) a shelf-stable prepolymer formed by the reaction of:
(i) a polyfunctional hydrophilic polymer having a weight-average molecular weight of between 3,000 Da and 250,000 Da;
(ii) a first crosslinking agent, the shelf-stable prepolymer being further characterized in that the ratio of said polyfunctional hydrophilic polymer to first crosslinking agent is in the weight range of substantially 0.5:1 to 10:1;
B) a pre-polymer formed by the reaction of
(i) a sugar comprising at least one of a monosaccharide or a disaccharide;
(ii) a second crosslinking agent being further characterized in that the ratio of said sugar to crosslinking agent is in the weight range of substantially 0.5:1 to 10:1;
C) a catalyst capable of promoting a crosslinking reaction for at least one of component A) and component B); and
D) a surfactant, wherein the shelf-stable prepolymer stability ranges for a time period from 24 hours to 5 months.
15. The composition as claimed in claim 14 , wherein the polyfunctional hydrophilic polymer has a weight-average molecular weight of between 10,000 and 100,000 Da.
16. The composition as claimed in claim 14 , wherein the surfactant is an acidic surfactant present in an amount ranging from 0.1 wt.% to 1.0 wt.% of the composition.
17. A wood product-modifying composition comprising:
A) a shelf-stable prepolymer having a composition including the reaction products of
(i) a polyfunctional hydrophilic polymer having a weight-average molecular weight of between 10,000 Da and 100,000 Da;
(ii) a first crosslinking agent; and
B) a catalyst capable of promoting a crosslinking reaction of component A), wherein the shelf-stable prepolymer stability ranges for a time period from 7 days to 5 months.
18. The composition as claimed in claim 17 , further comprising a prepolymer having a composition including the reaction products of a second crosslinking agent with at least one of a monosaccharide and disaccharide.
19. The composition as claimed in claim 18 , wherein the prepolymer composition includes at least one of the prepolymer having a sugar-melamine composition and the shelf-stable prepolymer having an alcohol-melamine composition.
20. The composition as claimed in claim 1 , wherein the polyfunctional hydrophilic polymer having a weight-average molecular weight of between 10,000 Da and 100,000 Da.