Method of controlling monomer loss during the production of a fiber-thermoplastic matrix by in situ bulk polymerization

Abstract

An improved method of controlling monomer loss during the production of a fiber-thermoplastic matrix by in situ bulk polymerization is described, the improvement allowing polymerization to greater than 25% polymer content by weight of the matrix within less than eight minutes. A fibrous web of less than 0.25-inch thickness, saturated with a liquid phase polymerizable composition containing a vinyl monomer and a thermally activated free radical initiator at 1/2-10% by weight of the composition is polymerized under controlled conditions in which the matrix is: (a) confined between heat transfer surfaces at 0.2-20 psig; (b) heated to a temperature sufficient to initiate polymerization but below the boiling point of the composition; (c) increased in temperature as the boiling point of the composition increases during polymerization while still maintaining the temperature below the boiling point of the composition; and (d) increased in temperature above the boiling point of the composition when the desired polymer content is obtained in order to evaporate residual monomer from the matrix. The resulting matrix is suitable for molding by the application pressure into useful products.

Dependencies are inferred from the claim text.