Polymerization process

Abstract

A process for the production and treatment of a stereoregular polypropylene, such as isotactic polypropylene in which a polymerization reactor is operated under conditions to react propylene supplied to the reactor to produce a stereoregular propylene polymer fluff. A product stream containing the fluff and unreacted propylene is withdrawn from the reactor and at least a portion of the unreacted propylene is separated from the product stream. The propylene polymer fluff is heated to a temperature sufficient to melt the propylene polymer, and a lactone is incorporated into the propylene polymer. The lactone is a 5,7 dialkyl-3-(2,3 dialkyl phenyl)-3H-benzofuran-2-one, in which the 5,7 and 2,3 substituents are of relatively low molecular weights. The phenyl alkyl substituents, each contain 1 or 2 carbon atoms, and the 5,7 alkyl substituents each contain from 2 to 5 carbon atoms. After the heating and incorporation of the lactone, the heated polymer fluff containing the lactone is extruded to produce particles of the propylene polymer. The polymer particles containing the lactone can be heated to a molten state and then extruded to form a fiber preform. The fiber preform is subject to spinning and drawing at differential spinning and drawing speeds to provide a draw ratio sufficient to form a continuous polypropylene fiber.