Urea-formaldehyde resin binders containing acrylic bi-modal molecular weight solution polymer

1. A fiber mat comprising fibers bound together with a cured binder composition, wherein the binder composition, prior to curing, comprises an aqueous binder composition comprising:

as a major component, a thermosetting urea-formaldehyde resin, and

as a minor component, a water-soluble additive comprising:

at least one styrene/acrylate solution bi-modal polymer comprising a first molecular weight species having a molecular weight of 1,000 daltons to 100,000 daltons and a second molecular weight species having a molecular weight greater than 100,000 daltons.

2. The fiber mat of claim 1 , wherein the aqueous binder composition comprises about 0.1 wt % to about 10 wt % solids of the styrene/acrylate solution bi-modal polymer, based on total binder solids.

3. The fiber mat of claim 1 , wherein the fibers are selected from the group consisting of glass fibers, mineral fibers, graphite fibers, metal fibers, metal coated glass fibers, metal coated graphite fibers, acrylic fibers, aromatic polyamide fibers, polyester fibers, cellulosic fibers, and polyolefin fibers.

4. The fiber mat of claim 1 , wherein the fiber mat contains about 60 wt % to about 90 wt % of the fibers and about 10 wt % to about 40 wt % of the cured binder composition, based on a dry weight of the fiber mat.

5. The fiber mat of claim 4 , wherein the fiber mat contains about 15 wt % to about 25 wt % of the cured binder composition, based on a dry weight of the fiber mat.

6. A method for making a fiber mat, comprising:

dispersing fibers in an aqueous medium to form a slurry;

forming the slurry into a wet fiber mat;

applying an aqueous binder composition to the wet fiber mat, wherein the aqueous binder composition comprises as a major component a thermosetting urea-formaldehyde resin and as a minor component a water-soluble additive containing at least one styrene/acrylate solution bi-modal polymer comprising a first molecular weight species having a molecular weight of 1,000 daltons to 100,000 daltons and a second molecular weight species having a molecular weight greater than 100,000 daltons, wherein the styrene/acrylate solution bimodal polymer is present in the aqueous binder composition in an amount of about 0.1 wt % to about 10 wt %, based on total binder solids, and

curing the binder composition at an elevated temperature of about 135° C. to about 300° C. to provide a fiber mat comprising fibers bound together with the cured binder composition.

7. The fiber mat of claim 1 , wherein a ratio of the first molecular weight species to the second molecular weight species is from about 95:5 to about 5:95.

8. The fiber mat of claim 1 , wherein a ratio of the first molecular weight species to the second molecular weight species is from 50:50 to 70:30.

9. The fiber mat of claim 1 , wherein a ratio of the first molecular weight species to the second molecular weight species is about 60:40.

10. The fiber mat of claim 1 , wherein the first molecular weight species has a molecular weight of 3,000 daltons to 7,000 daltons and the second molecular weight species has a molecular weight greater than 100,000 daltons to 3,000,000 daltons.

11. The fiber mat of claim 1 , wherein the first molecular weight species has a molecular weight of 3,000 daltons to 7,000 daltons, the second molecular weight species has a molecular weight greater than 100,000 daltons to 3,000,000 daltons, and a ratio of the first molecular weight species to the second molecular weight species is from 50:50 to 70:30.

12. The fiber mat of claim 1 , wherein the first molecular weight species has a molecular weight of 3,000 daltons to 7,000 daltons, the second molecular weight species has a molecular weight greater than 100,000 daltons to 3,000,000 daltons, a ratio of the first molecular weight species to the second molecular weight species is from 50:50 to 70:30, and the aqueous binder composition comprises about 0.1 wt % to about 10 wt % solids of the styrene/acrylate solution bi-modal polymer, based on total binder solids.

13. The fiber mat of claim 1 , wherein the first molecular weight species has a molecular weight of 3,000 daltons to 7,000 daltons, the second molecular weight species has a molecular weight greater than 100,000 daltons to 3,000,000 daltons, a ratio of the first molecular weight species to the second molecular weight species is from 50:50 to 70:30, and the aqueous binder composition comprises about 0.1 wt % to about 5 wt % solids of the styrene/acrylate solution bi-modal polymer, based on total binder solids.

14. The fiber mat of claim 1 , wherein the first molecular weight species has a molecular weight of 3,000 daltons to 7,000 daltons, the second molecular weight species has a molecular weight greater than 100,000 daltons to 3,000,000 daltons, a ratio of the first molecular weight species to the second molecular weight species is from 50:50 to 70:30, and the aqueous binder composition comprises about 0.1 wt % to about 3 wt % solids of the styrene/acrylate solution bi-modal polymer, based on total binder solids.

15. The fiber mat of claim 1 , wherein the first molecular weight species has a molecular weight of 3,000 daltons to 7,000 daltons, the second molecular weight species has a molecular weight greater than 100,000 daltons to 3,000,000 daltons, a ratio of the first molecular weight species to the second molecular weight species is about 60:40, and the aqueous binder composition comprises about 0.1 wt % to about 3 wt % solids of the styrene/acrylate solution bi-modal polymer, based on total binder solids.

16. The fiber mat of claim 1 , wherein the styrene/acrylate solution bi-modal polymer comprises an acrylate of the formula:

CH 2 ═CR 1 COOR 2 or

CH 2 ═CR 1 CONR 3 R 4

wherein:

each R 1 is independently hydrogen or —CH 3 ,

R 2 is hydrogen or an optionally substituted ester moiety, and

R 3 and R 4 are each independently hydrogen, an alkyl, or an alkanol.

17. The fiber mat of claim 1 , wherein the acrylate is methyl methacrylate.

18. The method of claim 6 , wherein a ratio of the first molecular weight species to the second molecular weight species is from about 95:5 to about 5:95.

19. The method of claim 6 , wherein a ratio of the first molecular weight species to the second molecular weight species is from 50:50 to 70:30.

20. The method of claim 6 , wherein a ratio of the first molecular weight species to the second molecular weight species is about 60:40.

21. The method of claim 6 , wherein the first molecular weight species has a molecular weight of 3,000 daltons to 7,000 daltons and the second molecular weight species has a molecular weight greater than 100,000 daltons to 3,000,000 daltons.

22. The method of claim 6 , wherein the first molecular weight species has a molecular weight of 3,000 daltons to 7,000 daltons, the second molecular weight species has a molecular weight greater than 100,000 daltons to 3,000,000 daltons, and a ratio of the first molecular weight species to the second molecular weight species is from 50:50 to 70:30.

23. The method of claim 6 , wherein the first molecular weight species has a molecular weight of 3,000 daltons to 7,000 daltons, the second molecular weight species has a molecular weight greater than 100,000 daltons to 3,000,000 daltons, a ratio of the first molecular weight species to the second molecular weight species is from 50:50 to 70:30, and the aqueous binder composition comprises about 0.1 wt % to about 10 wt % solids of the styrene/acrylate solution bi-modal polymer, based on total binder solids.

24. The method of claim 6 , wherein the first molecular weight species has a molecular weight of 3,000 daltons to 7,000 daltons, the second molecular weight species has a molecular weight greater than 100,000 daltons to 3,000,000 daltons, a ratio of the first molecular weight species to the second molecular weight species is from 50:50 to 70:30, and the aqueous binder composition comprises about 0.1 wt % to about 5 wt % solids of the styrene/acrylate solution bi-modal polymer, based on total binder solids.

25. The method of claim 6 , wherein the first molecular weight species has a molecular weight of 3,000 daltons to 7,000 daltons, the second molecular weight species has a molecular weight greater than 100,000 daltons to 3,000,000 daltons, a ratio of the first molecular weight species to the second molecular weight species is from 50:50 to 70:30, and the aqueous binder composition comprises about 0.1 wt % to about 3 wt % solids of the styrene/acrylate solution bi-modal polymer, based on total binder solids.

26. The method of claim 6 , wherein the first molecular weight species has a molecular weight of 3,000 daltons to 7,000 daltons, the second molecular weight species has a molecular weight greater than 100,000 daltons to 3,000,000 daltons, a ratio of the first molecular weight species to the second molecular weight species is about 60:40, and the aqueous binder composition comprises about 0.1 wt % to about 3 wt % solids of the styrene/acrylate solution bi-modal polymer, based on total binder solids.

27. The method of claim 6 , wherein the styrene/acrylate solution bi-modal polymer comprises an acrylate of the formula:

CH 2 ═CR 1 COOR 2 or

CH 2 ═CR 1 CONR 3 R 4

wherein:

each R 1 is independently hydrogen or —CH 3 ,

R 2 is hydrogen or an optionally substituted ester moiety, and

R 3 and R 4 are each independently hydrogen, an alkyl, or an alkanol.