Patent GB-612429-A (GB)
Title: Process for the manufacture of isoprene
IPC: C07C4/00
Filed: 1946-01-14
Abstract: Isoprene is prepared by contacting small particles of rubber or similar substances such as gutta-percha, balata and natural or synthetic olefin polymers containing more than 100 molecules of C5 monomer, in a dissolved, molten, solid or dispersed condition, with a surface at a temperature of 700-750 DEG  C., and rapidly withdrawing the pyrolysis products by means of an auxiliary gas.  This may be nitrogen, hydrogen or water vapour, which can be used as a carrier for the powdered rubber, or the vapour of a solvent in which the rubber is dissolved.  Natural rubber latex or concentrated latex may be used which is preferably preheated prior to admission to the cracking zone with precautions to avoid coagulation.  The feed to the pyrolyser may be by means of an injector or atomizer.  The cracking zone may contain a catalyst such as Cu, Pt, Co, Ni or Fe in the form of shavings or gauze.  In examples, plasticized first latex crepe in toluene or mesitylene, and latex, either preconcentrated or not, are dropped into a cracking zone which may contain copper shavings, at pressures varying from 1 atmos. down to 4 mm., in one case a nitrogen current also being used.  The condensate is fractionated to give isoprene.  Higher boiling fractions may serve as rubber solvents to give increased yields.  The Specification as open to inspection under Sect. 91 comprises other methods for rapid withdrawal of pyrolysis products such as the application of low pressure.  Additional examples describe the pyrolysis of plasticized crepe by heating to 200 DEG  or 250 DEG  C. and dropping on to hot copper in a tube under a pressure of 2 mm. This subject-matter does not appear in the Specification as accepted.ALSO:Isoprene is prepared by contacting small particles of rubber or similar substances such as gutta-percha, balata, and natural or synthetic olefin polymers containing more than 100 molecules of C5 monomer, in a dissolved, molten, solid or dispersed condition, with a surface at a temperature of 700-750 DEG C., and rapidly withdrawing the pyrolysis products by means of an auxiliary gas.  This may be nitrogen, hydrogen or water vapour, which can be used as a carrier for the powdered rubber, or the vapour of a solvent in which the rubber is dissolved.  Natural rubber latex or concentrated latex may be used, which is preferably preheated prior to admission to the cracking zone with precautions to avoid coagulation.  The feed to the pyrolyser may be by means of an injector or atomizer.  The cracking zone may contain a catalyst such as Cu, Pt, Co, Ni or Fe in the form of shavings or gauze.  In examples, plasticized first latex crepe in toluene or mesitylene and latex, either preconcentrated or not, are dropped into a cracking zone which may contain copper shavings, at pressures varying from 1 atmos. down to 4 mm., in one case a nitrogen current also being used. The condensate is fractionated to give isoprene.  Higher boiling fractions may serve as rubber solvents to give increased yields.  The Specification as open to inspection under Sect. 91 comprises other methods for rapid withdrawal of pyrolysis products such as the application of low pressure.  Additional examples describe the pyrolysis of plasticized crepe by heating to 200 or 250 DEG  C. and dropping on to hot copper in a tube under a pressure of 2 mm. This subject-matter does not appear in the Specification as accepted.