Polyvinyl chloride

The invention claimed is polyvinyl chloride having a density greater than 1,406 and less than 1,424. The Specification states that such polyvinyl chloride may be prepared by polymerizing vinyl chloride at -20 DEG to 60 DEG C. using a redox catalyst comprising a tertiary hydrocarbon hydroperoxide, an iron compound capable of producing ferrous ions in the reaction medium, and ascorbic acid or a lactone thereof. The reaction may be carried out in a common solvent for the monomer and catalyst, e.g. methanol or ethanol, or in aqueous dispersion containing an "antifreeze agent", e.g. methanol, ethanol, glycol or glycerol, and an emulsifying agent. Suitable hydroperoxides have one of the formulae X-R1 CR2-OOH or HOOO-R1 CR2-X-R3 CR4-OOH where R1-4 are C1-C4 alkyl groups and X is an aromatic group. Suitable iron compounds are ferrous sulphate, ferrous ammonium sulphate and ferrous chloride. The vinyl chloride may constitute 20 to 50 vol. per cent of the reaction mixture, the hydroperoxide 0,05 to 0,15 wt. per cent of the vinyl chloride, the ascorbic acid 75 to 300 molar per cent of the hydroperoxide and the iron compound 0,001 to 0,02 wt. per cent of the vinyl chloride. Some or all of the catalyst components and/or the monomer may be added in increments as the reaction proceeds. The molecular weight of the product may be kept relatively low by using a chain-stopping agent such as bromo and/or chloro methanes. Preferred products have a softening point (B.S.I.) above 100 DEG C. Examples illustrate polymerization in aqueous dispersion using a mixture of C10-18 mono-alkyl sulphates as emulsifier and in methanol solution. Reference has been directed by the Comptroller to Specification 895,153.