Patent GB-476838-A (GB)
Title: Improvements in vulcanization of rubber
IPC: E01C7/35
Filed: 1936-11-13
Abstract: The vulcanization of rubber is accelerated by the addition to the mix of the reaction product of a mercapto-aryl-thiazole, formaldehyde and a phenolic compound.  The accelerators of the present invention are resinous products of unknown constitution. Possible constitutions are, however, suggested.  The accelerators are made by heating the ingredients together in the presence of a resinifying catalyst until a resinous product forms.  Instead of adding the formaldehyde and the mercapto - aryl thiazole separately, their preformed reaction product may be used.  Instead p  of ordinary aqueous formaldehyde, there may be used formaldehyde forming materials such as para-formaldehyde and other polymeric forms of formaldehyde.  The proportions of the reactants are preferably molecular but suitable products may also be made by varying the amounts from \ba1/2\be to 1\ba1/2\be mols. Resinifying catalysts mentioned are alkaline materials such as sodium or calcium hydroxides, acidic materials such as hydrochloric, sulphuric or benzene sulphonic acids and sodium or potassium bisulphite, metal salts such as ammonium aluminium or zinc chloride, calcium cresylate, sodium or potassium salicylate, organic materials such as hexamethylenetetramine, urea and acetamide.  The preferred catalyst is hexamethylenetetramine.  The catalyst may be used in widely varying amounts, all with satisfactory results.  A list of mercapto-aryl-thiazoles is given of which the following is typical: 1-mercapto-5-nitro-benzothiazole, 1-mercapto-5-chlor-benzothiazole, 1-mercapto-4-nitro-5-chlor-benzothiazole, and 1-mercapto-a - or b -naphtha-thiazoles.  A list of phenolic compounds is also given of which the following is typical : phenol, b -naphthol, cresylic acid, resorcinol, catechol, chloro-phenol, hydroquinone, salicylic acid, guaiacol, alkoxy phenols, and 8-hydroxy-quinoline. The preferred compounds are the mono-hydroxy phenols.  In examples: (1) hydroxy methyl benzothiazyl sulphide is heated with phenol in the presence of sodium hydroxide at 140--150 DEG  C. for several hours to give a brittle resin; (2) hydroxy methyl benzothiazyl sulphide is heated with b -naphthol in the presence of glacial acetic acid; (3) hydroxy methyl benzothiazyl sulphide and phenol are heated together for 1 hour and then a gram of sodium hydroxide powder added.  The reaction which follows results in a semi-crystal resin; (4) hydroxy methyl benzothiazyl sulphide and phenol are heated in the presence of aqueous sodium hydroxide to give an amber yellow solid; (5) hydroxy methyl benzothiazyl sulphide and phenol are heated in the presence of hexamethylenetetramine to give a brittle amber resin; (6) hydroxy methyl benzothiazyl sulphide and phenol are heated in the presence of acetamide to give a cherry red solid; (7) a mixture of 1-mercaptobenzothiazole, mixed cresols, and para-formaldehyde is heated in the presence of zinc chloride to give a yellow resinous product; (8) a mixture of hydroxy methyl benzothiazyl sulphide and mixed cresols is heated in the presence of hexamethylene tetramine to give a canary yellow resin; (9) the procedure of example 8 is followed using varying quantities of hexamethylene tetramine with increasing amounts of catalysts, decreasing reaction times where necessary, the products being very similar; (10) a mixture of 1-mercaptobenzothiazole, paraformaldehyde and mixed cresols is heated in the presence of hexamethylenetetramine to give a clear resin; (11) the procedure of example 10 is followed except that an additional quantity of the catalyst is introduced after the start of the reaction.  The amount of catalyst used is also increased. A yellow resin results; (12) 1-mercaptobenzothiazole, formaldehyde and mixed cresols are melted together, concentrated aqueous hydrochloric acid added, and the mixture heated.  A hard opaque resin is obtained; (13) a mixture of mercaptobenzothiazole, paraformaldehyde, hexamethylene-tetramine and high boiling cresols, consisting mostly of xylenols is heated to produce a yellow resin; (14) a mixture of mercaptobenzothiazole, paraformaldehyde and b -naphthol is heated in the presence of hexamethylene-tetramine to give a brown resin.  The accelerators of the present invention may be used either alone or in the presence of nitrogen containing activating accelerators such as diphenylguanidine dibenzylamine, ammonia, di-o-tolyl guanidine, 2 : 4-diaminodiphenylamine, and salts of diphenylguanidine such as the neutral succinate, or the neutral phthalate.  Examples are given to show the efficiency of the accelerators in a typical rubber mix.  It is stated that the accelerators of the present invention possess considerable value as delayed action accelerators.ALSO:The vulcanization of rubber is accelerated by the addition to the mix of reaction product of a mercapto-aryl-thiazole, formaldehyde and a phenolic compound.  The accelerators of the present invention are resinous products of unknown constitution. Possible constitutions are, however, suggested.  The accelerators are made by heating the ingredients together in the presence of a resinifying catalyst until a resinous product forms.  Instead of adding the formaldehyde and the mercapto-aryl thiazole separately, their preformed reaction product may be used.  Instead of ordinary aqueous formaldehyde, there may be used formaldehyde forming materials such as para formaldehyde and other polymeric forms of formaldehyde.  The proportions of the reactants are preferably molecular but suitable products may also be made by varying the amounts from 1/2 to 1 1/2 mols.  Resinifying catalysts mentioned are alkaline materials such as sodium or calcium hydroxide, acidic materials such as hydrochloric, sulphuric or benzene sulphonic acids and sodium or potassium bisulphite, metal salts such as ammonium aluminium or zinc chloride, calcium cresylate, sodium or potassium salicylate, organic materials such as hexamethylenetetramine, urea and acetamide.  The preferred catalyst is hexamethylenetetramine.  The catalyst may be used in widely varying amounts, all with satisfactory results.  A list of mercapto-aryl thiazoles is given of which the following is typical:-1 - mercapto - 5 - nitro - benzothiazole, 1-mercapto-5-chlor-benzothiazole, 1-mercapto - 4 - nitro - 5 - chlor - benzothiazole, and 1 mercapto-a - or b -naphtha-thiazoles.  A list of phenolic compounds is also given of which the following is typical:-phenol b -naphthol, cresylic acid, resorcinol, catechol, chloro-phenol, hydroquinone, salicyclic acid, guaiacol, alkoxy phenols, and 8-hydroxyquinoline.  The preferred compounds are the mono-hydroxy phenols.  In examples: (1) hydroxy methyl benzothiazyl sulphide is heated with phenol in the presence of sodium hydroxide at 140-150 DEG  C. for several hours to give a brittle resin; (2) hydroxy methyl benzothiazyl sulphide is heated with b -naphthol in the presence of glacial acetic acid; (3) hydroxy methyl benzothiazyl sulphide and phenol are heated together for 1 hour and then a gram of sodium hydroxide powder added.  The reaction which follows results in a semi-crystal resin; (4) hydroxy methyl benzothiazyl sulphide and phenol are heated in the presence of aqueous sodium hydroxide to give an amber yellow solid; (5) hydroxy methyl benzothiazyl sulphide and phenol are heated in the presence of hexamethylenetetramine to give a brittle amber resin; (6) hydroxy methyl benzothiazyl sulphide and phenol are heated in the presence of acetamide to give a cherry red solid; (7) a mixture of 1-mercaptobenzothiazole, mixed cresols, and para-formaldehyde is heated in the presence of zinc chloride to give a yellow resinous product; (8) a mixture of hydroxy methyl benzothiazyl sulphide and mixed cresols is heated in the presence of hexamethylene tetramine to give a canary yellow resin; (9) the procedure of example (8) is followed using varying quantities of hexamethylene tetramine with increasing amounts of catalysts, decreasing reaction times where necessary, the products being very similar; (10) a mixture of 1-mercaptobenzothiazole, paraformaldehyde and mixed cresols is heated in the presence of hexamethylenetetramine to give a clear resin; (11) the procedure of example (10) is followed except that an additional quantity of the catalyst is introduced after the start of the reaction.  The amount of catalyst used is also increased.  A yellow resin results; (12) 1-mercaptobenzothiazole, formaldehyde and mixed cresols are melted together, concentrated aqueous hydrochloric acid added, and the mixture heated.  A hard opaque resin is obtained; (13) a mixture of mercaptobenzothiazole, paraformaldehyde, hexamethylene-tetramine and high boiling cresols, consisting mostly of xylenols is heated to produce a yellow resin; (14) a mixture of mercaptobenzothiazole, paraformaldehyde and b -naphthol is heated in the presence of hexamethylenetetramine to give a brown resin.  The accelerators of the present invention may be used either alone or in the presence of nitrogen containing activating accelerators such as diphenylguanidine, dibenzylamine, ammonia, di-o-tolyl guanidine, 2 : 4-diaminodiphenylamine, and salts of diphenylguanidine such as the neutral succinate, or the neutral phthalate.  Examples are given to show the efficiency of the accelerators in a typical rubber mix.  It is stated that the accelerators of the present invention possess considerable value as delayed action accelerators.