| 摘要 |
A process is disclosed for preparing a polyacrylate-modified polyvinyl chloride processing aid for polyvinyl chloride by sequentially polymerizing the vinyl chloride and the desired acrylate ester monomer. Thus, a conventional vinyl chloride suspension polymerization is conducted at a controlled rate of agitation and in the presence of a specified concentration of an alkyl, hydroxyalkyl or carboxyalkyl modified cellulose suspending agent and is then halted at or near its completion; unreacted vinyl chloride monomer is removed, the suspension of polyvinyl chloride particles is cooled, a minor proportion of an acrylate ester monomer, e.g., methyl methacrylate, is then added with a fresh supply of a free radical initiating catalyst to the cooled suspension, the cooling being sufficient to retard polymerization of the acrylate, and polymerization is then resumed by heating the suspension and continued until the acrylate ester monomer polymerizes in and/or on the particles of the previously polymerized polyvinyl chloride. The polyacrylate-modified PVC thereby recovered is an effective aid for processing conventional PVC, or it can be processed per se since it is suitable for calendering or extruding. |
