US Patent 8652579 Processes of making fiber-containing composites from polyamic acid-containing binder compositions

Processes are described for binding a fibrous material. The processes may include applying to a surface of the fibrous material an aqueous binding composition to form a coated fibrous material. The binding composition may include: (a) a water-soluble polyamic acid, and (b) an organic crosslinking agent capable of undergoing a covalent crosslinking reaction with the water-soluble polyamic acid when heated. The water-soluble polyamic acid may be formed by the reaction of: a (i) a polycarboxylic acid or polyanhydride having a molecular weight of at least 150 g/mol, and (ii) ammonia or an amine compound. The processes may further include heating the coated fibrous material to crosslink the water-soluble polyamic acid with the organic crosslinking agent to form a cured binder. One or more adjoining fibers of the fibrous material may be bound to each other at cross over points by the cured binder.