| 摘要 |
<p>A rigid sheet comprises a polymeric constituent formed from monomers in which vinyl chloride predominates and reinforcing fibres, the polymeric constituent being rigid at room temperature when not reinforced, and the fibres being uniformly dispersed throughout and all lying in or substantially in the plane of the sheet. In one embodiment the polymeric constituent comprises a dispersion or emulsion of polyvinyl chloride in water together with a solution of a vinyl chloride copolymer in an organic solvent e.g. a vinyl chloride/vinylidene chloride copolymer dissolved in toluene or a vinyl chloride/vinyl acetate copolymer dissolved in methyl ethyl Ketone and, optionally, a hydrocarbon fraction. Alternatively, the polymeric constituent comprises a mixture of the said copolymers, one being dispersed in a solution of the other e.g. the vinyl acetate copolymer is dispersed in a toluene solution of the vinylidene chloride copolymer. Asbestos and/or glass or organic fibres are added. In the first example toluene solutions of a vinyl chloride/vinylidene chloride copolymer and of a styrene/diester of maleic acid and a C8 alcohol copolymer are mixed with additional toluene, powdered polyvinyl chloride, an aqueous polyvinyl chloride latex, stabilizers, talc, asbestos and pigment. This mixture is used to form the base layer of a laminated sheet and a similar mixture, without the styrene copolymer and containing a greater proportion of polyvinyl chloride, is used to form the body layer. The aqueous phase of both mixtures may contain a minor amount of another latex e.g. a butadiene/acrylonitrile copolymer latex. In the second example the body layer comprises a toluene solution of a vinyl chloride/vinylidene chloride copolymer, a vinyl chloride/vinyl acetate copolymer, asbestos stabilizers, talc and water.</p> |
