GB1069625A - Improvements in or relating to the manufacture of synthetic resin articles reinforced with fibrous material - Google Patents

Abstract

Sheet materials which may subsequently be moulded and used to form laminates comprise sheeted cellulosic fibrous materials, impregnated with a composition comprising a hardenable synthetic resin and a blowing agent which is stable at normal storage temperatures. The fibrous sheet materials may be impregnated with a solution or dispersion containing the resin and blowing agent in a volatile carrier and dried at a temperature sufficient to remove the carrier, e.g. an alcohol or water, but insufficient to cause hardening of the resin and decomposition of the blowing agent. Alternatively the fibrous sheet material may be impregnated with a liquid resin comprising the blowing agent, the resin being reacted to a solid, still fusible state while in situ in the material at a temperature below that at which the blowing agent decomposes. If the fibrous sheet material is a felt the powdered synthetic resin and powdered blowing agent may be incorporated therein during its manufacture. Suitable synthetic resins are phenolic, epoxy, polyester and urea- or melamineformaldehyde resins. The blowing agent may be dinitrosopentamethylenetetramine, p,p1-oxybis (benzene sulphonyl hydrazide), benzene sulphonyl hydrazide, urea oxalate or an inorganic blowing agent. The composition may also contain salicylic acid, stearic acid, dyes, pigments, fillers, waxes and surfactants. Fibre-reinforced expanded synthetic resin articles may subsequently be produced by heating in or on a mould one or more of the impregnated fibrous sheet materials at a temperature above the decomposition temperature of the blowing agent and the hardening temperature of the resin. The fibrous sheet material may be in the form of knitted fabrics, cross-creped paper, loosely woven or netted fabric, felts, paper creped only in one direction or tightly woven fabrics depending upon the amount of extension required during the subsequent moulding process. Fabrics comprising cotton fibres alone or in admixture with wool and viscose rayon fibres may be treated.ALSO:Sheet materials which may subsequently be moulded and used to form laminates comprise sheeted cellulosic fibrous materials impregnated with a composition comprising a hardenable synthetic resin and a blowing agent which is stable at normal storage temperatures. The fibrous sheet materials may be impregnated with a solution or dispersion containing the resin and blowing agent in a volatile carrier and dried at a temperature sufficient to remove the carrier, e.g. an alcohol or water but insufficient to cause hardening of the resin and decomposition of the blowing agent. Alternatively the fibrous sheet material may be impregnated with a liquid resin comprising the blowing agent, the resin being reacted to a solid, still fusible state while in situ in the material at a temperature below that at which the blowing agent decomposes. If the fibrous sheet material is a felt the powdered synthetic resin and powdered blowing agent may be incorporated therein during its manufacture. Suitable synthetic resins are phenolic, epoxy, polyester and urea- or melamineformaldehyde resins. The blowing agent may be dinitrosopentamethylenetetramine, P P1- oxybis (benzene sulphonyl hydrazide), benzene sulphonyl hydrazide, urea oxalate or an inorganic blowing agent. The composition may also contain salicylic acid, stearic acid, dyes, pigments, fillers, waxes and surfactants. Fibre-reinforced expanded synthetic resin articles may subsequently be produced by heating in or on a mould one or more of the impregnated fibrous sheet materials at a temperature above the decomposition temperature of the blowing agent and the hardening temperature of the resin. The fibrous sheet material may be in the form of knitted fabrics, cross-creped paper, loosely woven or netted fabric, felts, paper creped only in one direction or tightly woven fabrics depending upon the amount of extension required during the subsequent moulding process. Fabrics comprising cotton fibres alone or in admixture with wool and viscose rayon fibres may be treated.