METHOD FOR THE PREPARATION OF VINYL CHLORIDE RESINS BY SUSPENSION POLYMERISATION

摘要

The invention provides means for preventing polymer scale deposition on the reactor walls during the suspension polymerization of vinyl chloride monomer in an aqueous medium.The method of the invention comprises (a) coating of the reactor walls, prior to polymerization, with an aqueous coating solution containing an organic dye having sulfonic acid groups or carboxylic acid groups in the alkali metal or ammonium salt form or an alkali metal or ammonium salt of an organic sulfonic acid or carboxylic acid having at least one pair of conjugated double bonds per molecule, followed by drying, and (b) adding a water-soluble thiocyanate to the polymerization mixture. Previously, the use of an organic peroxide with a relatively large solubility in water as initiator in the reaction had led to large scale deposition on the reactor walls but this is avoided under the conditions specified above. Use of such an organic peroxide is advantageous in improving the thermal stability and initial colouring of the resin products.