Low odor binders curable at room temperature
View Patent ↗Topically-applied binder materials for imparting wet strength to soft, absorbent paper sheets, such as are useful as household paper towels and the like, include an epoxy-reactive polymer, such as a carboxyl-functional polymer, and an epoxy-functional polymer. These binder materials can be cured at ambient temperature over a period of days and do not impart objectionable odor to final product when wetted.
1. A method of increasing the strength of a fibrous web comprising:
(a) adding alkali to an aqueous emulsion of a water-soluble epoxy-functional polymer, whereby the pH of the emulsion is raised to about 11 or greater;
(b) mixing the emulsion of the water-soluble epoxy-functional polymer with an epoxy-reactive polymer to form an aqueous binder composition, wherein the amount of the epoxy-functional polymer relative to the amount of the epoxy-reactive polymer is from about 0.5 to about 25 weight percent on a solids basis;
(c) topically applying the aqueous binder composition to one or both outer surfaces of the web, wherein the elapsed time between mixing the epoxy-functional polymer with the epoxy-reactive polymer and applying the resulting binder composition to the web is about a day or less; and
(d) curing the aqueous binder composition on the web.
2. The method of claim 1 wherein the aqueous binder composition is cured at a temperature of 120° C. or less.
3. The method of claim 1 wherein the aqueous binder composition is cured at a temperature of 100° C. or less.
4. The method of claim 1 wherein the aqueous binder composition is cured at a temperature of 40° C. or less.
5. The method of claim 1 wherein the aqueous binder composition is cured at a temperature of from about 20 to about 120° C.
6. The method of claim 1 wherein the aqueous binder composition is cured without the emission of formaldehyde.
7. The method of claim 1 wherein the elapsed time is about 12 hours or less.
8. The method of claim 1 wherein the elapsed time is about 3 hours or less.
9. The method of claim 1 wherein the elapsed time is about 30 minutes or less.