Poly (vinyl alcohol)—based formaldehyde-free curable aqueous composition
View Patent ↗A formaldehyde-free curable aqueous composition containing polyvinyl alcohol, a multi-functional crosslinking agent, and, optionally, a catalyst. The composition may be used as a binder for non-woven products such as fiberglass insulation. The non-woven products are formed by contacting the formaldehyde-free curable aqueous composition with fibrous components and the mixture is cured to form a rigid thermoset polymer providing excellent strength and water resistance of the cured nonwoven product.
1. A curable aqueous composition prepared by a process comprising combining the following components:
(a) a hydroxy-containing polymer which is a combination of polyvinyl alcohol and at least one member selected from the group consisting of starch, modified starch and a sugar;
(b) a multi-functional crosslinking agent which includes citric acid as a first nonpolymeric polyacid and optionally at least one selected from the group consisting of a second nonpolymeric polyacid, salts thereof, an anhydride, and a nonpolymeric polyaldehyde, and optionally
(c) a catalyst;
wherein the weight ratio of (a):(b) is from 95:5 to about 35:65,
wherein the pH of the curable composition is increased in a positive direction to at least 1.25 upon addition of a nitrogenous base,
wherein said polyvinyl alcohol has a viscosity up to 10 centipoise when in a 4% aqueous solution at 20° C.
2. The curable aqueous composition of claim 1 , wherein sufficient nitrogenous base is added to raise the pH to be in the range of about 2.5 to about 6.5.
3. The curable aqueous composition of claim 1 , wherein the polyvinyl alcohol has a number average molecular weight in the range of greater than 7,000.
4. The curable aqueous composition of claim 3 , wherein the polyvinyl alcohol has a number average molecular weight in the range of 12,000 to 85,000.
5. The curable aqueous composition of claim 3 , wherein the polyvinyl alcohol has a number average molecular weight in the range of greater than 13,000 to 45,000.
6. The curable aqueous composition of claim 1 , having a nonvolatile content greater than 30 wt %.
7. The curable aqueous composition of claim 1 , having a nonvolatile content of 32-43 wt %.
8. The curable aqueous composition of claim 1 , wherein said hydroxy-containing polymer is a combination of polyvinyl alcohol and starch and the catalyst is present in the composition and is ammonium sulfate.
9. The curable aqueous composition of claim 8 , wherein the polyvinyl alcohol is formed by hydrolyzing polyvinyl acetate or a copolymer of ethenol and vinyl acetate, wherein the final polymer is 70 mole % to 99 mole % hydrolyzed.
10. The curable aqueous composition of claim 1 , wherein the multi-functional crosslinking agent further comprises a blocked nonpolymeric polyaldehyde.
11. The curable aqueous composition of claim 10 , wherein the blocked nonpolymeric polyaldehyde is blocked with a blocking agent which is at least one selected from the group consisting of urea, ethylene urea, sorbitol, and ethylene glycol.
12. A cured composition comprising a nonwoven fiber in a cured binder wherein the cured composition is formed in a process comprising combining nonwoven fibers with the curable aqueous composition of claim 1 to form a mixture and curing the mixture.
13. The cured composition according to claim 12 , wherein the process includes a step of diluting the curable aqueous composition with sufficient water so the curable aqueous composition has 5% by weight of nonvolatiles prior to the curing step.
14. The cured composition according to claim 12 , wherein the nonwoven fiber is fiberglass.
15. The curable aqueous composition of claim 1 , wherein the multi-functional crosslinking agent further comprises maleic anhydride.
16. A method of forming a curable aqueous composition comprising the following steps:
a step of combining (a) a hydroxy-containing polymer with (b) a multi-functional crosslinking agent which includes citric acid as a first nonpolymeric polyacid and optionally at least one selected from the group consisting of a second nonpolymeric polyacid, salts thereof, an anhydride, and a nonpolymeric polyaldehyde, and optionally
(c) a catalyst to form a curable aqueous composition; and
a step of adding sufficient nitrogenous base to raise the pH in a positive direction to at least 1.25;
wherein the weight ratio of (a):(b) is from 95:5 to about 35:65; and
wherein said hydroxy-containing polymer is a combination of polyvinyl alcohol and at least one member selected from the group consisting of starch, modified starch and a sugar,
wherein said polyvinyl alcohol has a viscosity up to 10 centipoise when in a 4% aqueous solution at 20° C.
17. The method according to claim 16 , wherein the multifunctional crosslinking agent further comprises a blocked nonpolymeric polyaldehyde or an anhydride.
18. The method according to claim 16 , wherein the polyvinyl alcohol has a number average molecular weight in the range of greater than 7,000.
19. The method according to claim 16 , wherein sufficient nitrogenous base is added to raise the pH to be in the range of about 2.5 to about 6.5.
20. The method according to claim 16 , wherein the multi-functional crosslinking agent further comprises maleic anhydride, and wherein said hydroxy-containing polymer is a combination of polyvinyl alcohol and starch and the catalyst is present in the composition and is ammonium sulfate.
21. A method for forming a nonwoven material comprising the following steps:
combining (a) a hydroxy-containing polymer with (b) a multi-functional crosslinking agent which includes citric acid as a first nonpolymeric polyacid and optionally at least one selected from the group consisting of a second nonpolymeric polyacid, salts thereof, an anhydride, and a nonpolymeric polyaldehyde, and optionally (c) a catalyst to form a curable aqueous composition; and
a step of adding sufficient nitrogenous base to raise the pH in a positive direction to at least 1.25; and
combining the curable aqueous composition with nonwoven fiber, and
heating the curable aqueous composition and nonwoven fiber at 130° C. to 250° C. for sufficient time to effect cure,
wherein the weight ratio of (a):(b) is from 95:5 to about 35:65; and
wherein said hydroxy-containing polymer is a combination of polyvinyl alcohol and at least one member selected from the group consisting of starch, modified starch and a sugar,
wherein said polyvinyl alcohol has a viscosity up to 10 centipoise when in a 4% aqueous solution at 20° C.
22. The method for preparing the nonwoven material of claim 21 , further comprising a step of diluting the curable aqueous composition with sufficient water so the curable aqueous composition has 95% by weight of water prior to the heating step.
23. The method for preparing the nonwoven material of claim 21 , wherein the nonwoven fiber is fiberglass.
24. The method for preparing the nonwoven material of claim 21 , wherein sufficient nitrogenous base is added to raise the pH to be in the range of about 2.5 to about 6.5.
25. The method for preparing the nonwoven material of claim 21 , wherein the multi-functional crosslinking agent further comprises maleic anhydride, and wherein said hydroxy-containing polymer is a combination of polyvinyl alcohol and starch and the catalyst is present in the composition and is ammonium sulfate.
26. A curable aqueous composition prepared by a process comprising combining the following components:
(a) a hydroxy-containing polymer which is a combination of polyvinyl alcohol and at least one member selected from the group consisting of starch, modified starch and a sugar;
(b) a multi-functional crosslinking agent which includes citric acid as a first nonpolymeric polyacid and optionally at least one selected from the group consisting of a second nonpolymeric polyacid, salts thereof, an anhydride, and a nonpolymeric polyaldehyde,
(c) a base, and optionally
(d) a catalyst;
wherein the weight ratio of (a):(b) is from 95:5 to about 35:65,
wherein the pH of the curable composition is increased in a positive direction to at least 1.25 upon addition of a nitrogenous base,
wherein said polyvinyl alcohol has a viscosity up to 10 centipoise when in a 4% aqueous solution at 20° C.
27. The curable aqueous composition of claim 26 , wherein the multi-functional crosslinking agent further comprises maleic anhydride, and wherein said hydroxy-containing polymer is a combination of polyvinyl alcohol and starch and the catalyst is present in the composition and is ammonium sulfate.
28. The curable aqueous composition of claim 26 , wherein sufficient nitrogenous base is added to raise the pH to be in the range of about 2.5 to about 6.5.