GB786796A - Wax modified polystyrene compositions and process of manufacture - Google Patents

Abstract

In the process for making round records of the parent Specification, the wax and additional polystyrene which is added is obtained by precipitating a mixture of aqueous wax and polystyrene emulsions, drying, and mechanically working at between 160 DEG and 225 DEG C., before incorporating in the basic polystyrenecarbide composition. The wax emulsions may be prepared from carnauba, candelilla, montan, esparto, oricury, beeswax, cotton wax, insect wax, japan wax; a synthetic wax made by hydrogenating vegetable, marine or animal oils; or mineral waxes such as paraffin and microcrystalline waxes, ozokerite, or ceresin. The emulsions may contain zinc stearate and polyethylene glycol oleyl ether. The polystyrene emulsions may be prepared by polymerizing styrene by heating in aqueous emulsion with a potassium persulphate catalyst, a sodium soap of dehydrogenated rosin, t-dodecyl mercaptan and sodium hydroxide under nitrogen, preferably to give Standinger molecular weights of 40,000 to 150,000. The mixed emulsions may be precipitated by aqueous sodium chloridehydrochloric acid solution, aqueous isopropanol or aqueous acetic acid, and the coagulum dehydrated by exposure to air or heat. The mechanical working is carried out in a heated screw extrusion, Banbury or multi-parallel roller mixer. The product is diced and blended with fillers, e.g. diatomaceous silica, slate flour and calcium carbonate, pigments, e.g. carbon black and soaps such as zinc and calcium stearates, and moulded.