GB743353A - Polystyrene rubber compositions - Google Patents

Abstract

A vulcanized composition of polystyrene or copolymers thereof, with a major proportion of rubber and 5 to 25 parts per 100 parts of styrene of an ester plasticizer such as dibutyl and dioctyl phthalates and tricresyl phosphate is prepared by mixing part of the rubber with the other ingredients at an elevated temperature and compounding the product with more rubber and vulcanizing agents, and finally vulcanizing. The products, of increased hardness and elasticity, may be used for shoe soleing, flooring, extrusion, insulating and translucent materials.ALSO:An ester plasticizer such as dibutyl phthalate, dioctyl phthalate or tricresyl phosphate is incorporated in a mix of polystyrene and rubber to make them compatible, the mix containing a major proportion of rubber to allow of its being vulcanized and containing 5 to 25 parts by weight of ester to 100 parts of polystrene. The mix is preferably made by mixing polystyrene with the plasticizer and some of the rubber to give a homogeneous intermediate product containing 1 to 3 parts of polystyrene to 1 part of rubber, which is then mixed with the remainder of the rubber and the vulcanizing and compounding agents. The polystyrene may be wholly or in part replaced by a copolymer of styrene containing a major proportion of styrene units in its molecular structure. In an example the initial composition was, in parts by weight, pale crepe rubber 100, polystyrene 200, dibutyl phthalate 10. The rubber was masticated for 3 minutes at a temperature of 35-40 DEG C. and mixed with powdered polystyrene and plasticizer. The mixture was then heated to 150 DEG C. to gell the polystyrene and was further milled for 5 minutes. The resulting composition was then mixed with rubber and vulcanizing ingredients to give a final composition, in parts by weight, pale crepe rubber 90 or 80, polystyrene/rubber/composition 30 or 60, zinc oxides 5, sulphur 3, stearic acid 2, cyclohexyl benzthiazyl sulphonamide 1. An alternative method of preparing the intermediate composition and a further example using an initial composition of 100 parts crepe rubber, 100 parts polystyrene and 10 parts dibutyl phthalate, are given.