GB649217A - Improvements in practice golf ball - Google Patents

Abstract

A practice golf ball having substantially the dimensions, shape and appearance of a standard golf ball is made of closed-cell expanded plasticized polyvinyl chloride. The ball may be made by forming a paste of finely-divided polyvinyl chloride and a plasticizer therefor, mixing the plasticized resin with a chemical blowing agent capable of generating a gas on the application of heat, heating the mixture in an undersized mould to effect gelation and generation of gas, cooling and removing the miniature moulded ball, expanding it in hot water or an air oven to approximate golf ball size, and dimpling the expanded ball by heating it in a golf ball mould. The dimpling may be accomplished in the miniature mould if desired. The blowing agent may be a ,a 1-azobisisobutyronitrile, diazoaminobenzene, 1,31-bis-(o-xenyl)-triazene or 1,3-bis-(p-xenyl)-triazene, and the plasticizer may be dioctyl phthalate, tricresyl phosphate, dibutyl phthalate, or dicapryl phthalate. A small quantity of calcium stearate may be incorporated as stabilizer. Fillers and pigments, preferably white in colour, may be incorporated. Specification 500,298 is referred to.ALSO:A practice golf ball of closed-cell expanded plasticized polyvinyl chloride is made by forming a paste of finely-divided polyvinyl chloride and a plasticizer therefor, mixing the plasticized resin with a chemical blowing agent capable of generating a gas on the application of heat, heating the mixture in an undersized mould to effect gelation and generation of gas, this heating being preferably carried out at a temperature of from 250 DEG to 350 DEG F. for from 6 to 15 minutes, cooling and removing the miniature moulded ball, expanding it in hot water or an air oven to approximate golf ball size, and dimpling the expanded ball by heating it in a golf ball mould. The dimpling may be accomplished in the miniature mould. In an example the undersized mould has a cavity 3/4 inch in diameter and the filled and closed mould is heated for eight minutes at 330 DEG F. and a mould-closing pressure of 3600 p.s.i. The mould is cooled for seven minutes and the ball removed, being about 7/8 inch in diameter. The ball is heated in water at 85 DEG C. for 15 minutes and then dimpled in a golf ball mould by heating it for 12 minutes at 230 DEG F. Specification 500,298, [Group IV], is referred to.