| 摘要 |
A moulding composition comprises a refractory polyvinyl acetal resin and a petroleum hydrocarbon insoluble pine-wood resin. There may be added yacca gum, coumarone or coumarone-indene resins; lead, aluminium, calcium, zinc, lithium, caesium and rubidium stearates; canauba and "Ceranova" waxes; chlorinated naphthalene; pitch; carbon black, calcium carbonate, diatomaceous earths; plasticizers, e.g. dibutyl phthalate, dimethoxyethyl phthalate, dibutyl sebacate, o-nitrodiphenyl and methyl phthalyl p ethyl glycollate. Acetals specified are polyvinyl formal, acetal, butyral and benzal. Mixing may be carried out with vigorous mastication, e.g. in a heated Banbury mixer or extruder. The composition may be used for making gramophone records having a thickness of 40 mils. or less. Specification 351,082 is referred to. |
