GB1076130A - A process for increasing the hardness of synthetic and natural elastic foam and sponge mateials - Google Patents

Abstract

The hardness of elastic foams is increased by treating an elastic foam with a mixture of a latex of a polymer containing reactive groups, an aqueous colloidal dispersion of silica and a cross-linking or vulcanising agent. Examples of elastic foams are polyether, polyester, polyvinyl chloride, natural or synthetic latex, sponge rubber and naturally occuring foams such as sponge rubber. The polymer may comprise 60 to 70% butadiene, 0 to 36% styrene, 0 to 36% acrylonitrile and 4 to 20% methacrylic acid, and the solids content of the latex may be 20 to 50%. The colloidal dispersion of silica may contain a stabilising additive and the silicon dioxide particles may have sizes from 0.01 to 0.3m . The ratio of the dry silicon dioxide to the solids content of the latex may be 1:2 to 2:1. The cross-linking agent may be a metal oxide, e.g. zinc, magnesium oxide, or a melamine resin. The foam material may be immersed in the mixture of latex and colloidal silica, wrung out and left to dry, immersion and drying being carried out at 10 to 85 DEG C. Only parts of the foam, say the edges, may be hardened by applying the mixture only to those areas to be hardened, e.g. by spreading with a brush, or spraying with a spray gun. In the Example cubes of the foam material are treated and the compression hardness measured.