GB777494A - Improvements relating to polystyrene plastic materials - Google Patents

Abstract

A composition comprises polystyrene, up to 20 per cent by weight of the polystyrene of an unvulcanized natural or synthetic rubber, e.g. butadiene-styrene copolymer, and a small proportion of a 2,4,6-trialkyl phenol as an antioxidant. Pale crepe, reclaim or powdered natural rubbers may be used. The alkyl phenols preferably contain an alkyl group having 3 to 12 carbon atoms, e.g. propyl, butyl, t-butyl, hexyl or octyl in the ortho position the remainder being methyl, e.g. 2,4-dimethyl-6-t-butyl phenol, 2,4-dimethyl-6-octyl phenol and 2,6-dit-butyl)-4-methyl phenol. The polystyrene and rubber are blended with the aid of heat by working in a mill, mixer or extruder and pelleted. The phenol is introduced alone or in admixture with polystyrene before or during the blending, or a master-batch with higher proportions of trialkyl phenol may be prepared for further blending with the polystyrene as required. Alternatively the rubber may be incorporated in styrene monomer which is polymerized by heat and a catalyst, e.g. di-t-butyl peroxide, and the phenol then added. Colouring materials and softeners, e.g. high boiling alkyl benzene and butyl stearate may be included. Specifications 745,901, 766,585 and 776,048 are referred to.ALSO:A composition comprises polystyrene, up to 20 per cent by weight of the polystyrene of an unvulcanized natural rubber and a small proportion of a 2 : 4 : 6 trialkyl phenol as an antioxidant. Pale crepe, reclaim or powdered rubber may be used and the alkyl phenols preferably contain an alkyl group having 3 to 12 carbon atoms e.g. propyl, butyl, t-butyl, hexyl or octyl in the ortho position the remainder being methyl, e.g. 2 : 4 - dimethyl - 6 - t - butyl phenol, 2 : 4 - dimethyl - 6 - octyl phenol, and 2 : 6 di(t - butyl) 4 - methyl phenol. The polystyrene and rubber is blended with the aid of heat by working in a mill, mixer or extruder and pelleted. The phenol is introduced alone or in admixture with polystyrene before or during the blending, or a master-batch with higher proportions of trialkyl phenol may be prepared for further blending with polystyrene as required. Alternatively the rubber may be incorporated in styrene monomer which is polymerized by heat and a catalyst e.g. di-t-butyl peroxide and the phenol then added. Colouring materials and softeners e.g. high boiling alkyl benzene and butyl stearate may be included. Specifications 745,901 [Group IV(a)], 766,585 and 776,048 [Group IV(a)] are referred to.