Moulding Compositions

1,187,504. Synthetic resin compositions. BRITISH INDUSTRIAL PLASTICS Ltd. 26 April, 1967 [29 April, 1966; 7 Dec., 1966], Nos. 18869/66 and 54769/66. Headings C3P and C3R. A thermosetting moulding composition comprises an unsaturated polyester resin, a copolymerizable monomer and a finely divided filler, at least part of which, providing at least 10 wt. per cent of the composition, is a substantially water-insoluble metal borate. The composition may also include a fibrous reinforcing filler and a mould lubricant. The resins are condensates of a glycol, and optionally a polyol, e.g. pentaerythritol, and a mixture of an unsaturated dibasic acid, e.g. maleic or fumaric, and a saturated dibasic acid, e.g. phthalic or adipic. Specified comonomers are styrene, vinyl toluene, diallyl phthalate and a mixture of styrene and methyl methacrylate. Specified borates are those of Ca, Mn, Zn, Sr, Cu++ and Mg; the hydrated borates are preferred but basic borates may also be used. Other finely divided fillers mentioned are Mg, Zn and Ca carbonates, slate powder, magnesium fluosilicate, NH 4 , Ca and Mn sulphates, Mg and Ti oxides, Ca oxalate, Zn sulphite, boric acid, Ni hydroxide, asbestos, quartz, fluorspar, Na metaphosphate, tribasic zinc phosphate, dicyandiamide, Ca cyanamide, talc, guanamines, melamine and aminoplast resins, e.g. urea- or melamineformaldehyde resins which may be spraydried. The fibrous reinforcing filler may be glass, asbestos, nylon, polyester, polyacrylonitrile, polyvinyl alcohol or acetate or polypropylene. The mould lubricant may be stearic acid or zinc or magnesium stearate. In examples, the resin is 2 parts of propylene glycol maleate phthalate in 1 part styrene catalysed with 1À5% benzoyl peroxide and the fillers are Ca metaborate, Zn borate, anhydrous Zn borate, basic Mg borate or Mn borate together with “ in. glass fibres, polypropylene or nylon flock and various of the other fillers mentioned above and alumina and antimony oxide; zinc stearate is included in all examples. The compositions are useful for moulding electrical apparatus, e.g. insulators and arc-suppressing devices.