Patent GB-859470-A (GB)
Title: Difunctional polymers and methods for their preparation
IPC: C08F36/04
Filed: 1959-08-11
Abstract: A polymeric dimercaptan is prepared by polymerizing, to a number average degree of polymerization of at least 10, at least one monomer containing at least one H2C=C<group in the presence of a xanthogen disulphide having the formula; <FORM:0859470/IV(a)/1> , wherein in R is an aliphatic aralkyl or alicyclic radical, to form a polymeric bis xanthate ester and hydrolyzing said ester groups to produce a polymeric dimercaptan.  Monomers specified are styrene, acrylonitrile, acrylic and methacrylic acids and their alkyl esters, butadiene, isoprene, dimethyl butadiene, chlorobutadiene, ethyl butadiene and phenyl butadiene, chloro-bromo- and fluorostyrenes and methyl styrenes, methyl ethyl, methoxy, ethoxy and dialkylamino sytrenes and vinyl pyridines and their methyl and ethyl derivatives. Xanthogen disulphides specified are those in which R in the above formula represents radicals such as methyl, ethyl, propyl, isopropyl, amyl, lauryl phenyl, methyl phenyl, mono- or dichloro-phenyl benzyl, phenethyl, alpha or beta naphthyl, anthracyl, cyclobutyl, cyclopentyl and cyclohexel.  Polymerization may be carried out by conventional bulk or aqueous emulsion techniques employing peroxy or azo catalysts, which may be activated by a pyrophosphate/ferric sulphate/cobaltous chloride mixture, and emulsifiers.  In aqueous emulsion polymerization additional xanthogen disulphide and activator may be provided during the course of the reaction.  The hydrolysis of the xanthate ester groups in the polymer may be effected by means of alcoholic potash, a secondary amine or acids. The resulting polymer containing mercaptan end-groups may be further reacted in a number of ways, e.g. (i) with ethylene chlorhydrin or a cyclic oxide such as ethylene, propylene, butylene, butadiene, cyclohexene or vinyl cyclohexene oxide to yield a polymeric glycol (ii) with an oxidizing agent such as iodine to yield a polymeric disulphide, (iii) with a ketone or aldehyde to yield a polymeric thioketal or thioacetal, (iv) with phosgene to yield a polymeric dithiocarbonate, (v) with acrylonitrile followed by reduction to the diamine or hydrolysis to the dicarboxylate, and (vi) with diisocyanates; the products thus obtained may themselves be further reacted.  The examples describe the preparation of polystyrene, polybutadiene and butadiene/styrene copolymer dimercaptans.  In the case of polystyrene dimercaptans there are described the following further reactions: (a) the oxidation of the mercaptan groups with iodine to produce a polymeric mercaptan, which is reduced with zinc dust and acid to regenerate the dimercaptan which is treated with alcoholic potash while exposed to the atmosphere, this reconverting it to the dimercaptan; (b) the reaction of the mercaptan groups with ethylene oxide to produce a polymeric glycol which is further reacted with diphenylmethane diisocyanate; (c) the reaction of the mercaptan groups with phenylene diisocyanate; and (d) reaction with diiodopentane in the presence of alcoholic potash.  In the case of the polybutadiene dimercaptan these are described: (a) the reaction of the mercaptan groups with diphenyl methane diisocyanate which converts the polymers from an oily to a rubbery form; and (b) the reaction of the mercaptan groups with ethylene oxide to produce a polymeric glycol which is further reacted with tolylene diisocyanate to yield a soft rubbery material.  In the case of the butadiene/styrene copolymer dimercaptan reaction of the mercaptan groups with diphenylmethane diisocyanate is described, which converts the polymer from an oily to a rubbery form.  When the above reactions result in the joining of polymer molecules through their end groups the products are described as block polymers.