Patent GB-475453-A (GB)
Title: Improvements in vulcanization of rubber
IPC: C08K5/00
Filed: 1936-11-04
Abstract: The vulcanization of rubber is accelerated by the addition to the mix of an addition product of a zinc aromatic thiazyl mercaptide and an organic amine or ammonia.  It is stated that such addition products are more powerful accelerators, than the zinc aromatic thiazoles themselves, and are in addition usually more soluble in petroleum hydrocarbons and in rubber.  The addition products according to the invention may be prepared by bringing the organic amine or ammonia and the zinc salts of the mercapto aromatic thiazole together, preferably in a liquid dispersion, and generally in suspension or solution in water.  In some cases a small amount of heat is applied. The preferred zinc aromatic thiazyl mercaptides are those of the benzene and naphthalene series, and of the amines, the primary and secondary saturated amines which are only to a small extent volatile at room temperature are preferred.  A number of zinc aromatic thiazyl mercaptides are mentioned of which the following are typical:--1 - mercapto - 3 - methylbenzothiazole, 1 - mercapto - 3 : 5 - dimethyl benzothiazole 1 - mercapto - 5 - chlor benzothiazole, 1 - mercapto - 3 - methoxy benzothiazole and the corresponding naphthathiazoles.  A considerable list of suitable organic amines is given, but in general the amines used are as follows: Alicyclic, phenalkyl, furfuryl, and tetrahydro-furfuryl primary amines, aliphatic primary amines having not more than ten carbon atoms, N-alkyl alicyclic secondary amines in which the alkyl group has not more than five carbon atoms, dialkyl alkylene diamines in which the alkyl and alkylene groups have not more than five carbon atoms each.  N-alkyl phenalkyl secondary amines in which the alkyl group has not more than five carbon atoms, dialkyl amines having not more than eight carbon atoms, N-alkyl tetrahydro-furfuryl secondary amines in which the alkyl group has not more than five carbon atoms, and polymethylene secondary amines in which the polymethylene chain may be interrupted by an oxygen atom. A few of the amines specifically mentioned are:--diethylamine, methyl amyl amine, N-methyl cyclohexylamine, hexahydrobenzylamine, n-butyl amine, piperidine, pyrollidine, morpholine, tetrahydro-alpha-furfuryl amine and N-methyl beta phenethyl amine. In examples, (1) zinc benzothiazyl mercaptide is added to an aqueous solution of ethylene diamine and the mixture heated to boiling.  The aqueous layer is separated from the oil, and on cooling a solid separates which is an addition product of 3 mols. of the amine with 1 mol. of the mercaptide.  The oil is a less pure form of the same material; (2) an aqueous suspension of zinc benzothiazyl mercaptide is heated to boiling with cyclohexylamine to yield a yellow solid product; (3) excess of ammonia is passed over finely divided zinc benzothiazyl mercaptide to give an addition product; (4) the addition of mixed amyl primary amines to zinc benzoythiazyl mercaptide produces an exothermic reaction, and upon a small amount of additional heating, an oil was obtained which on extraction with water gave a fairly pure addition product; (5) zinc benzothiazyl mercaptide and tetrahydro-alpha furfuryl amine are warmed together to cause the addition product to be formed; (6) a petroleum ether suspension of zinc benzothiazyl mercaptide and piperidine is stirred for one hour to give a light yellow addition product; (7) a petroleum ether solution of n-butyl amine has added to it a quantity of zinc benzothiazyl mercaptide. a tan sticky semi-solid results.  The efficiency of the products as accelerators when incorporated in a rubber mix is shown in tubular form.ALSO:The vulcanization of rubber is accelerated by the addition to the mix of an addition product of a zinc aromatic thiazyl mercaptide and an organic amine or ammonia.  It is stated that such addition products are more powerful accelerators than the zinc aromatic thiazoles themselves, and are in addition usually more soluble in petroleum hydrocarbons and in rubber.  The addition products according to the invention may be prepared by bringing the organic amine or ammonia together, preferably in a liquid dispersion, and generally in a suspension or solution in water.  In some cases a small amount of heat is applied.  The preferred zinc aromatic thiazyl mercaptides are those of the benzene and naphthalene series, and of the amines the primary and secondary saturated amines which are only to a small extent volatile at room temperature are preferred.  A number of zinc aromatic thiazyl mercaptides are mentioned of which the following are typical: 1-mercapto-3-methylbenzothiazole, 1-mercapto-3 : 5-dimethyl benzothiazole, 1-mercapto 5-chlor-benzothiazole, 1-mercapto-3-methoxy benzothiazole, and the corresponding naphthathiazoles.  A considerable list of suitable organic amines is given, but in general the amines used are as follows: alicyclic phenalkyl, furfuryl and tetrahydrofurfuryl primary amines, aliphatic primary amines having not more than ten carbon atoms, N-alkyl alicyclic secondary amines in which the alkyl group has not more than five carbon atoms, dialkyl alkylene diamines in which the alkyl and alkylene groups have not more than five carbon atoms each, N-alkyl phenalkyl secondary amines in which the alkyl group has not more than five carbon atoms, dialkyl amines having not more than eight carbon atoms, N-alkyl tetrahydrofurfuryl secondary amines in which the alkyl group has not more than five carbon atoms, and polymethylene secondary amines in which the polymethylene chain may be interrupted by an oxygen atom. A few of the amines specifically mentioned are: diethylamine, methyl amyl amine, N-methyl cyclohexylamine, hexahydro-benzylamine, n-butylamine, piperidine, pyrollidine, morpholine tetrahydro-alpha-furfurylamine, and N-methylbeta-phenethyl amine. In examples, there are described the formation of addition compounds of (1) zinc benzothiazyl mercaptide and ethylene diamine, (2) zinc benzothiazyl mercaptide and cyclohexylamine, (3) zinc benzothiazyl mercaptide and ammonia, (4) zinc benzothiazyl mercaptide and mixed primary aryl amines, (5) zinc benzothiazyl mercaptide and tetrahydro-alpha-furfurylamine, (6) zinc benzothiazyl mercaptide and piperidine, (7) zinc benzothiazyl mercaptide and n butylamine.  The efficiency of the products as accelerators when incorporated in a rubber mix is shown in tabular form.