| 摘要 |
A viscous liquid mixture of a monomer or monomers and a polymer or copolymer of styrene and/or nuclear substituted styrene containing at least 40 per cent by weight of polymer or copolymer is introduced, in uniform discrete portions, into a heated inert liquid medium with which the monomeric part is not miscible and in which the polymer or copolymer is not soluble, the said portions being maintained in suspension in said heated medium till polymerization is substantially complete. Nuclear substituted styrenes specified are p-methyl, o-methyl, p-chloro and o-chloro styrenes and dimethyl and dichlorostyrenes. Other ethenoid compounds such as acrylic and methacrylic acid derivatives such as methyl methacrylate and ethylene glycol di-methacrylate, methyl vinyl ketone, divinyl benzene and vinyl crotonate may be present with the styrene compound monomers. Plasticizers, and/or filler and/or dyestuff which are insoluble in the heated inert medium may be mixed with the monomer. Heat and/or light and/or catalysts such as benzoyl and m-toluyl peroxides may be used. The viscous liquid may be obtained by mixing polymeric and monomeric materials or by partial polymerisation. The complete process may be made continuous. Inert liquids specified are water, glycol, glycerol or mixtures of these. Gentle agitation, co- or counter-current flow of the heated inert liquid may be used and the specific gravity may be adjusted by adding thickeners to cause the discrete portions to rise or fall at a predetermined rate in a column of the inert liquid; thus, calcium chloride, sodium silicate, sorbitol, sugar, starch, alginates, methyl cellulose carboxylate, methyl cellulose, cellulose hydroxy ethyl ether, polyvinyl alcohol, polyethylene oxide or polyvinyl methyl ether may be used. By using a conical tower to hold the inert liquid the rate of flow of the liquid may be varied to allow for the changing gravity of the discrete beads. Cutting devices for obtaining the discrete beads of the viscous liquid are described.
|
