GB708640A - Improvements in or relating to dihydroxy diaryl methanes - Google Patents

Abstract

The invention comprises compounds of the formula <FORM:0708640/IV (b)/1> in which the group <FORM:0708640/IV (b)/2> is derived from an aldehyde having the general formula R.CHO and containing only carbon, hydrogen and oxygen in the molecule, R1 is an alkyl group containing at least 4 carbon atoms and R2 is an alkyl group. Such compounds are obtained by reacting, in the presence of an acidic condensation catalyst, an aldehyde having the formula R.CHO and containing only carbon, hydrogen and oxygen in the molecule and a 3,6-dialkyl phenol wherein the 6-substituent is an alkyl group containing at least 4 carbon atoms, with the elimination of water as a by-product of the condensation. Preferably the compounds are obtained from an aliphatic aldehyde which contains at least two carbon atoms, e.g. acetaldehyde, propionaldehyde, butyraldehyde and a -ethyl-b -methyl acrolein, and R1 is preferably a tertiary alkyl group. Other aldehydes specified are formaldehyde, paraldehyde, aldol, n-valeraldehyde, n-heptaldehyde, crotonaldehyde, a -ethyl-b -propyl-acrolein, pyruvic aldehyde, a -furfuraldehyde, benzaldehyde, p - hydroxy - benzaldehyde and cinnamaldehyde. The phenols used may be prepared by reacting a 3-alkyl-phenol with an appropriate tertiary alcohol or olefin in the presence of sulphuric or phosphoric acid as a catalyst. Phenols mentioned are 3-methyl phenols having as 6-substituent a tert.-butyl-, tert.-amyl, n- or sec.-butyl-, iso- or sec.-amyl-, n-hexyl-, iso-hexyl-, n-heptyl-, n-octyl-, n-decyl-, n-dodecyl-, 2,4-dimethylbutyl-, or sec.-octyl radical, 3-ethyl-phenols having as 6-substituent a tert.- or n-butylradical, and 3,6-di-tert.-butyl phenol. The phenol and aldehyde are usually reacted in the molar ratio 2 : 1 with an acidic condensation catalyst, e.g. HCl. In examples: (1) n - propyl bis - (2 - methyl - 4 - hydroxy - 5 - tert. - butyl - phenyl) methane is prepared by reacting 3-methyl-6-tert.-butyl phenol and butyraldehyde; (2) iso-propyl-bis-(2 - methyl - 4 - hydroxy - 5 - tert. - butylphenyl) methane is prepared by reacting 3-methyl-6-tert.-butyl-phenol and isobutyraldehyde; (3) n - propyl bis - (2 - ethyl - 4 - hydroxy - 5 - n - butyl-phenyl) methane is obtained by reacting 6 - n - butyl - 3 - ethyl - phenol and n - butyraldehyde. Similarly prepared from 3-methyl-6-tert.-octyl-phenol is n-propyl-bis-(2-methyl-4-hydroxy-5-tert.-octyl-phenyl) methane, in each case with hydrochloric acid as catalyst. Also described are compounds prepared in a similar manner from other aldehydes listed above and 3 - methyl - 6 - tert. - butyl - phenol, and also from n-butyraldehyde and 3-methyl-6-tert.-amyl phenol or 3-methyl-6-n-butyl-phenol. The application of the products as antioxidants in rubber compositions is described (see Group V).ALSO:Rubber compositions comprise as an antioxidant a compound of the formula <FORM:0708640/V/1> in which the group <FORM:0708640/V/2> is derived from an aldehyde having the general formula R-CHO and containing only carbon, hydrogen and oxygen in the molecule, R1 is an alkyl group containing at least 4 carbon atoms, and R2 is an alkyl group. Examples describe compositions of pale crepe rubber, zinc oxide, lithopone, sulphur, diphenyl guanidine phthalate, benzothiazyl thiobenzoate, paraffin, and as antioxidant, compounds of the above formula in which R2 is a methyl group, R1 is a tert. butyl group and the group <FORM:0708640/V/3> is derived from acetaldehyde, n-butyraldehyde, n-heptaldehyde, benzaldehyde, isobutyraldehyde, pyruvic aldehyde, a -ethyl-b -methylacrolein, and formaldehyde respectively, and also the compounds n-propyl bis (2-methyl-(or ethyl)-4-hydroxy-5-n-butylphenyl) methane, and npropyl bis (2-methyl-4-hydroxy-5-tert. amyl-(or octyl) phenyl) methane. Other antioxidants described are a -methyl-ethenyl bis (2-methyl-4-hydroxy-5-tert. butylphenyl) methane (from a -methyl acrolein), p-hydroxyphenyl-bis (2-methyl-4-hydroxy-5-tert. butyl phenyl) methane (from p-hydroxy-benzaldehyde) and a -ethyl-a -pentenyl-bis (2-methyl-4-hydroxy-5-tert. butyl phenyl) methane (from a -ethyl-b -propyl acrolein). The residue <FORM:0708640/V/4> may also be derived from paraformaldehyde, paraldehyde, aldol, n-valeraldehyde, crotonaldehyde, a -furfuraldehyde, and cinnamaldehyde. The preparation of the antioxidants is described (see Group IV (b)).