GB500769A - Improvements in the polymerisation of dienes - Google Patents

Abstract

500,769. Synthetic rubber. I. G. FARBENINDUSTRIE AKT.-GES. March 24, 1938, No. 9049. Convention date, March 25, 1937. [Class 2 (iii)] Polymers of dienes which may be mobile liquids similar to drying oils, rubber-like bodies or solid horny substances are produced by polymerizing dienes in the liquid phase with anhydrous hydrogen halides at temperatures below -20‹ C.; separating from the product those constituents which boil without decomposition under a pressure of 10 mm. by distillation or selective solvents, and subjecting the remainder , to further polymerization. The second polymerization may be effected by heating to 100-200‹ C. and additional hydrogen halide or other halides such as iron, tin or magnesium chloride or oxygen-transferring, agents such as persulphates, perborates or hydrogen peroxide may be added. Organic chlorine compounds such as unsaturated chlorine compounds obtainable from chlorinated paraffins having more than three carbon atoms may also be added to accelerate the second polymerization. In examples: (1) pure butadiene is cooled to -60‹ C. and mixed with liquid anhydrous hydrogen chloride and maintained at that temperature for 4 hours; the low-boiling-point constituents of the product are distilled off at 10 mm. pressure and the remaining rubber-like polymer which is free from chlorine is heated to cause any desired degree of further polymerization ; alternatively the first polymerization product may be isolated by precipitation with methanol at room temperature and is then polymerized further as described above or with the addition of the unsaturated halogen hydrocarbons referred to above ; (2) a mixture of butadiene, butylene, and propylene obtained by splitting hydrogen chloride from dichlorbutane is treated at -60‹ C. with hydrogen chloride as in the first example, followed by distillation under 10 mm. pressure and further heating of the residue as described above, The Specification as open to inspection under Sect. 91 includes the use of gaseous hydrogen halides and is not limited to a process in which there is a second polymerization. An example describes the polymerization of pure liquid isoprene with anhydrous hydrogen bromide at 20‹ C. in a pressure bomb. This subjectmatter does not appear in the Specification as accepted.