Use of an aqueous binding agent devoid of formaldehyde for substrates
The present invention relates to formaldehyde-free aqueous binders for substrates, having a broad molecular weight distribution and comprising (A) from 0 to 100% by weight of an ethylenically unsaturated acid anhydride or ethylenically unsaturated dicarboxylic acid whose carboxylic acid groups can form an anhydride group, or mixtures thereof, (B) from 100 to 0% by weight of an ethylenically unsaturated compound, (C) at least one polyfunctional crosslinker or mixtures thereof, the polymers of A) and B) obtained by free-radical addition polymerization, when classified in a coordinate system by way of their average molecular weight Mw and their polydispersity, being situated in the area above a straight line which is defined by the linear equation y=1.25x+20 000 and has been shifted in y direction parallelwise by at least +3 000, the x axis denoting the weight-average molecular weight and the y axis the polydispersity times 10 000.
1. A formaldehyde-free aqueous binder having a broad molecular weight distribution and comprising a mixture of polymers composed of monomers A) and B), comprising
(A) from 5 to 50% by weight of an ethylenically unsaturated acid anhydride or ethylenically unsaturated dicarboxylic acid whose carboxylic acid groups can form an anhydride group, or mixtures thereof [monomers A)],
(B) from 50 to 95% by weight of at least one ethylenically unsaturated compound different from monomers A) [monomers B)], and
(C) at least one polyfunctional crosslinker or mixtures thereof,
the polymers of monomers A) and B) obtained by free-radical addition polymerization, when classified in a coordinate system by way of their average molecular weight Mw and their polydispersity, being situated in the area above a straight line which is defined by the linear equation y=1.25x+20 000 and has been shifted in y direction parallelwise by at least +3 000, the x axis denoting the weight-average molecular weight and the y axis the polydispersity times 10 000, wherein the polymers are prepared:
(a) in situ in one step by first synthesizing either a low molecular mass fraction at a particular initiator concentration and temperature and then, after lowering the initiator concentration in the reaction mixture and/or reducing the temperature, synthesizing a high molecular mass fraction, or by first synthesizing a high molecular mass fraction at a particular initiator concentration and temperature and then, after raising the initiator concentration in the reaction mixture and/or increasing the temperature, synthesizing a low molecular mass fraction,
(b) by mixing polymers having different molecular weights, or
(c) by synthesizing one polymer of low or high molecular weight in the presence of a second polymer with high or low molecular weight, respectively.
2. The formaldehyde-free aqueous binder according to claim 1 , wherein the aqueous binder comprises less than 1.5% by weight, based on the sum of A), B) and C), of a phosphorus-comprising reaction accelerant.
3. The formaldehyde-free aqueous binder according to claim 1 , wherein the polymer of A) and B) comprises from 5 to 50% by weight of maleic acid.
4. The formaldehyde-free aqueous binder according to claim 3 , wherein the polymer of A) and B) comprises acrylic acid and maleic acid.
5. The formaldehyde-free aqueous binder according to claim 1 , wherein the at least one polyfunctional crosslinker C) is a compound of the formula I
where R 1 is hydrogen, C 1 -C 10 alkyl or C 1 -C 10 hydroxyalkyl and R 2 and R 3 are each C 1 -C 10 hydroxyalkyl.
6. The formaldehyde-free aqueous binder according to claim 1 , wherein the at least one polyfunctional crosslinker C) is triethanolamine.
7. A method for binding an article comprising applying the formaldehyde-free aqueous binder as claimed in claim 1 to the article.
8. The method as claimed in claim 7 , wherein the article is at least one selected from the group consisting of fiber, a fiber mat, a fiber web, glass fiber, a glass fiber web, a glass fiber mat, a mineral fiber, a mineral fiber web and a mineral fiber mat.
9. A process for producing a bonded fiber web, comprising coating, spraying or impregnating the fiber web with the formaldehyde-free aqueous binder as claimed in claim 1 and subsequently drying the fiber web.
10. The process according to claim 9 for producing bonded glass fiber webs or mats.
11. A bonded fiber web or mat obtained by the method as claimed in claim 8 .
12. A bonded glass fiber web or mat obtained by the method as claimed in claim 8 .
13. A roofing membrane comprising the bonded fiber web or mat as claimed in claim 11 .
14. A roofing membrane comprising the bonded glass fiber web or mat as claimed in claim 12 .
15. An insulating material comprising the bonded fiber web or mat as claimed in claim 11 .
16. A floor covering comprising the bonded fiber web or mat as claimed in claim 11 .
17. An insulating material comprising the bonded glass fiber web or mat as claimed in claim 12 .
18. A floor covering comprising the bonded glass fiber web or mat as claimed in claim 12 .
19. A method for producing a molding comprising combining the formaldehyde-free aqueous binder as claimed in claim 1 with fibers, chips or shavings.
20. The method as claimed in claim 19 , wherein the fibers, chips or shavings are composed of renewable raw materials.
21. The method as claimed in claim 19 , wherein the fibers are natural or synthetic fibers or mixtures thereof.
22. The method as claimed in claim 19 , wherein the substrates are wood fibers, wood chips, jute, sisal, flax, hemp or kenaf.
23. The method as claimed in claim 19 , wherein the substrates are wood chipboard panels.
24. A filter material comprising the formaldehyde-free aqueous binder as claimed in claim 1 and a filter medium.
25. An abrasive comprising the formaldehyde-free aqueous binder as claimed in claim 1 and an abrasive material.
26. A cork product comprising the formaldehyde-free aqueous binder as claimed in claim 1 and cork.
27. The formaldehyde-free aqueous binder according to claim 1 , wherein the polymers are prepared in situ in one step by first synthesizing either a low molecular mass fraction at a particular initiator concentration and temperature and then, after lowering the initiator concentration in the reaction mixture and/or reducing the temperature, synthesizing a high molecular mass fraction, or first synthesizing a high molecular mass fraction at a particular initiator concentration and temperature and then, after raising the initiator concentration in the reaction mixture and/or increasing the temperature, synthesizing a low molecular mass fraction.
28. The formaldehyde-free aqueous binder according to claim 1 , wherein the polymers are prepared by mixing polymers having different molecular weights.
29. The formaldehyde-free aqueous binder according to claim 1 , wherein the polymers are prepared by synthesizing one polymer of low or high molecular weight in the presence of a second polymer with high or low molecular weight, respectively.