Patent GB-915638-A (GB)
Title: Substituted o-aminophenols and their use in rubber technology
IPC: C08K5/18
Filed: 1960-04-14
Abstract: Natural and synthetic rubbers vulcanizates are rendered less susceptible to cracking by adding to mixture to be vulcanized 0,4 to 6% by weight of a substituted o-aminophenol of the general formula <FORM:0915638/IV(a)/1> wherein R1 is a hydrogen atom or a hydrocarbon group containing up to 16 carbon atoms, R2 is a hydrocarbon group containing up to 16 carbon atoms, and R3 and R4 represent a tertiary C4 to C9 hydrocarbon group, or by adding 0,4 to 6% by weight of a bisaminophenol having the structure obtained by substituting the radical <FORM:0915638/IV(a)/2> (wherein R8 and R6 are tertiary C4 to C9 hydrocarbon groups, and R5, R6 and R7 each represent a hydrogen atom or a hydrocarbon group containing up to 16 carbon atoms) in place of R2 in the first formula.  All the examples relate to the resistance to cracking, under stretching, in the presence of ozonized air, of vulcanizates of pale crepe to which had been added specific substituted o-aminophenols or bis-aminophenols and various other additives.  The specified aminophenols used in these tests were 2-methylamino-4,6-di-tert.-butyl phenol, and the corresponding 2-ethylamino-, n-propylamino-, 2-sec. butylamino-, 2-n-dodecylamino-, 2-phenylamino-, and 2-cyclohexylamino-compounds, also N-methyl-2-hydroxy-41-methyl-3,5-di -tert.-butyl-diphenylamine, N,N1-methylene-bis-(2-n-propylamino-4,6-di-tert.-butyl phenol) and the corresponding 2-tert.-butylaminocompound, N,N1-C-methyl-methylene-bis-(2-cyclohexylamino-4, 6-di-tert.-butyl phenol), N,N-C-isopropyl - methylene - bis - (2 - methylamino - 4,6-di-tert.-butyl phenol) and N,N1-methylene-bis[2-ethylamino - 4,6 - di - (alpha - methylcyclohexyl)-phenol].  Examples of synthetic rubbers which may be stabilized against the action of ozone by these compounds are polymers obtained from butadiene, dimethyl butadiene, and isoprene, and copolymers of such conjugated diolefines with styrene, alpha-methylstyrene, acrylonitrile, methacrylonitrile, acrylates or methacrylates, copolymers of isobutylene with small quantities of conjugated diolefines.ALSO:Substituted o-aminophenols of the general formula <FORM:0915638/IV (b)/1> wherein R1 is a hydrogen atom or a hydrocarbon group containing up to 16 carbon atoms, R2 is a hydrocarbon group containing up to 16 carbon atoms, and R3 and R4 each represent a tertiary C4 to C9 hydrocarbon group, are produced by reacting a 1,2-dihydroxybenzene, substituted in the 4-, 6-positions by the appropriate tertiary hydrocarbon groups, with a primary amine in the presence of oxygen, followed if necessary (i.e. when R1 is to be a hydrocarbon group) by alkylation. Bisaminophenols having the structure obtained by substituting the radical <FORM:0915638/IV (b)/2> (wherein R8 and R9 are tertiary C4 to C9 hydrocarbon groups, and R5, R6 and R7 each represent a hydrogen atom or a hydrocarbon group) in place of R2 in the first formula (R1 = H), are prepared by reacting the appropriate o-aminophenol (prepared as above) with an aliphatic aldehyde.  In Example 1, isobutylamine is added to a suspension of 4,6-di-tert.-butylpyrocatechol in light benzene, and the mixture is then stirred for 7 hours in an open vessel.  After drying with sodium sulphate, and removing the solvent in vacuo, there is obtained 2-sec.-butylamino-4,6-di-tert.-butylphenol, which may be converted into its hydrochloride.  Example 3 describes the preparation of the corresponding (a) ethylamino- (b) n-propylamino- and (c) cyclohexylamino-compounds; and Example 4 describes the preparation of the corresponding dodecylamino-and phenylamino-compounds.  When the reaction is effected with a primary arylamine, it is advantageous to work in the presence of a secondary or tertiary amine or an alkali metal hydroxide.  Example 4 also describes the preparation of N-methyl-2-hydroxy-41-methyl-3,5-di-tert.-butyl diphenylamine by the action of dimethyl sulphate on 4,6-di-tert.-butyl-2-(N-p-tolyl)-aminophenol.  Example 5 describes the preparation of N,N1-methylene-bis-(2-tert.-butylamino-4,6 - di-tert.-butyl-2-(N-tert.-butyl)-aminophenol with formaldehyde. It is stated that N,N1 - C - methyl-methylene-bis-(2-cyclohexylamino-4,6-di-tert.-butyl phenol) may be prepared, in an analogous manner, using acetaldehyde.  These substituted o-aminophenols have use as anti-ozonants for natural and synthetic rubber (Group IV(a)).  A list of suitable compounds is given; this list includes 2-(p-methoxyphenylamino)-4,6-di-tert.-butyl phenol and the corresponding ethoxyphenylamino-, phenoxy-phenylamino-, chlorophenylamino-, gamma-dimethyl-alpha-amino-, propylamino-, beta-hydroxyethylamino-, pyrenylamino-, and naphthylamino-compounds.