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

A fiber mat having good tensile properties comprising said fibers bound together with a cured binder, said binder 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 polymer having a bi-modal molecular weight and comprising a first molecular weight species and a second molecular weight species.

A method of 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 comprising as a major component a thermosetting urea-formaldehyde resin and as a minor component a water-soluble an additive comprising 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 polymer having a bi-modal molecular weight and comprising a first molecular weight species and a second molecular weight species to said wet fiber mat, and curing the binder composition at an elevated temperature, wherein the binder, before curing, contains about 0.1 to about 10 wt % solids based on total urea-formaldehyde resin and additive solids, and wherein said elevated temperature is from about 135° C. to about 300° C.