Latex binder compositions have been used in a wide variety of applications such as adhering paper coatings to cellulosic substrates, in carpet and rug backings, and in various non-woven products which have gained broad acceptance as replacements for woven fabrics, including such articles as facings or top sheets in diapers, incontinence pads, sanitary napkins, hospital gowns, and other single and multiple-use non-woven products.
Conventional latex binders have generally been prepared from acrylic polymers, styrene/acrylate copolymers, or styrene/butadiene copolymers containing N-methylol functionality which, upon curing, generate substantial quantities of formaldehyde, typically from 200 to 500 ppm or more. It is desirable to use binders which are essentially free of formaldehyde generation. Formaldehyde-free latex binders include various urethane polymers, acrylic polymers, styrene/acrylate copolymers, and the like, such as those disclosed in U.S. Pat. Nos. 2,837,462; 4,207,367; 4,381,332; 5,030,507, and others. However, none of the prior art discloses a suitable conjugated diene/vinyl-substituted aromatic copolymer latex binder which is free of formaldehyde formation, and which also exhibits superior coagulation stability and mechanical stability while imparting excellent wet tensile strength to cellulosic articles such as paper.