Alpha-Methylstyrene → Alpha-Methylstyrene

Participants

Reaction Conditions

Reaction Steps

Copolymers of styrene and alpha-methylstyrene are prepared by anionic polymerization substantially according to the following process steps. A feed stream comprising alpha-methylstyrene, phenylacetylene free styrene and ethylbenzene solvent is distilled and contacted with an alumina bed to remove water, oxygen and benzaldehyde impurities. The purified feed stream is pumped to a 2-liter Paar reactor, equipped with a hollow auger agitator, the hollow auger comprising a cylinder slightly shorter in length than the interior of the reactor and slightly smaller in diameter. A land is helically disposed on the outside of the cylinder. The land is sized such that the cylinder generated by rotation of the hollow cylinder and land is slightly less than the internal volume of the reactor. Such an agitator is described in U.S. Pat. No. 4,239,863, the teachings of which are herewith incorporated by reference thereto. Hot water under pressure is employed to heat the reactor to 95° C. The purified feed stream and initiator are introduced into the side of the reactor at a rate to give a two-hour residence time. The initiator is normal-butyllithium pumped at a rate to provide a concentration of about 60 ppm. The pressure within the reactor is maintained at about 50 pounds per square inch gauge using a pressure control valve at the outlet. The stream from the reactor is fed to a terminator coil of 1 inch inside diameter, 316 Stainless Steel tubing connected in a square configuration and having an internal volume of about 467 cubic centimeters. Material is recirculated within the terminator coil while a solution of 1 weight percent ethanol in ethylbenzene is fed to the terminator coil at a rate about twice that of the normal-butyllithium fed to the polymerizing vessel. Effluent from the terminator coil is then pressure fed into a devolatilizer equipped with a flat plate heater and a screw extruder substantially according to that described in U.S. Pat. No. 3,014,702, the teaching of which is incorporated by reference thereto. The exterior of the heater is maintained at a pressure of less than 20 millimeters of mercury and the product mixture is heated to a temperature of about 250° C. to provide a polymer containing about 0.3 weight percent volatiles. The molecular weight of the resultant styrene alpha-methylstyrene polymer over a 24-hour period is maintained at plus or minus 5,000 of 140,000. By varying the amount of alpha-methylstyrene in the monomer feed the amount of alpha-methylstyrene in the resulting copolymer may be varied up to a maximum content of about 70 percent by weight.

Provenance & Evidence