Expanded plastics moulding, esp. abrasive disc prodn. - by treating dry grains with water and then reactive expandable plastics

摘要

Prodn. of mouldings from expanded plastics (I) with granular inserts (II), esp. (unsupported) abrasive discs, is carried out with (I) which reacts with water. (II) is dried and then treated with a definite amt. of water and treated with expandable (I), which reacts with water to form a cellular material with a number of cells starting from the surface of (II). The dimensions and pore structure are very regular and the abrasive properties are improved, since the (II) surface is cleaner than usual. (I) pref. is a polyisocyanate or prepolymer for urethane foam. A primer can be added to promote adhesion between (I) and (II). In an example, 1200 g. (II), pref. treated with 60 g. primer, were dried, impregnated with 36 g. water contg. 5 g. bicarbonate, mixed with 600 g. polyisocyanate or prepolymer for urethane foam and cast, giving a stiff abrasive disc.