GB723991A - Manufacture of polymers and copolymers of vinyl chloride - Google Patents

Abstract

Suspension polymerization of vinyl chloride or a mixture of vinyl chloride with a copolymerizable monomer is effected continuously in the presence of a non-solvent dispersing medium for the polymer and under pressure, the polymerization and the discharge of polymerization product being carried out in separate vessels which can be connected together. The discharge can be carried out in a continuous or discontinuous manner and at least two discharging vessels may be used which are filled alternately from the polymerization vessel and discharged when disconnected therefrom. The copolymerizable monomer may be vinyl formate, acetate, propionate, butyrate, benzoate or stearate, methyl, ethyl or propyl acrylate or methacrylate, maleic, fumaric or crotonic acid or an ester thereof, vinyl bromide or fluoride, vinylidene chloride or acrylonitrile. The dispersing medium may be water, an organic liquid such as a paraffin hydrocarbon, e.g. petroleum ether, methanol or ethanol or mixtures thereof, a mixture of water and methanol, ethanol, propanol, isopropanol, butanol, acetone, dioxane, tetrahydrofurane, formic acid or acetic acid, or monomeric vinyl chloride. Polymerization in an aqueous phase is preferably effected in the presence of a protective colloid such as polyvinyl alcohol, an alginate or a water-soluble salt of a maleic acid copolymer in the presence as catalyst of hydrogen peroxide, a persulphate or a perchlorate, or a redox system in which the reducing agent is sodium formaldehyde sulphoxylate, a hydrosulphite or bisulphite, a sulphinic acid or a salt thereof, didihydroxy-acetone, or sugar; one component of the redox system may be added to the aqueous liquid and the other to the monomer before introduction into the reaction vessel. When polymerizing in an organic liquid or monomeric vinyl chloride the catalyst may be benzoyl, para-chloro-benzoyl, toluyl, acetyl, acetylbenzoyl, or tetrahydronaphthalene peroxide, or azo-isobutyric acid dinitrile, which may be used in combination with a reducing agent such as a mercaptan or sulphinic acid or a hydroxycarbonyl compound such as benzoin used in the presence of a dissolved iron salt. The polymer may be obtained in the form of granules. Further polymerization may take place in the discharging vessel. Specification 694,253 is referred to.