GB816913A - Preparation of 2,2-methylene-bis-(4,6-dialkyl phenols) - Google Patents

Abstract

Compounds of general formula <FORM:0816913/IV (b)/1> where R1 is a straight-chain alkyl radical of 1 to 3 carbon atoms, and R2 is a tertiary alkyl radical of from 4 to 8 carbon atoms, are prepared by condensing the corresponding dialkyl phenol with formaldehyde, in an aqueous medium, in the presence of an anionic dispersing agent, and adding to the reaction mixture, after the reaction is substantially complete, a cationic surface-active agent, and then separating the 2,21-methylene bis-(4,6-dialkyl phenol). Suitable cationic surface-active agents are amine salts such as alkylol substituted alkyl guanidine salts, or a mixture of octadecyl amide and octadecyl guanidine salts of octadecyl carbamic acid reacted with ethylene oxide, or quaternary ammonium compounds, such as a 50 per cent solution of stearamidopropyl dimethyl betahydroxyethyl ammonium chloride or a stearamidopropyl dimethyl beta-hydroxyethyl dihydrogen phosphate as a 35 per cent solution in an isopropyl-water mixture. The amount of cationic agent used is 0.3-3.0 parts, preferably 1.0-2.5 parts, per 1 part of anionic agent. The anionic agent is preferably in a concentration of about 0.5 to about 1.5 grams real per mol. of dialkyl phenol, and suitable anionic agents are sodium alkyl benzene sulphonates in which the aliphatic side-chain contains at least 10 carbon atoms, e.g. sodium dodecyl benzene sulphonate, and sodium dialkyl naphthalene sulphonates in which the two aliphatic side-chains contain at least 5 carbon atoms, e.g. sodium diamyl naphthalene sulphonate. At least 150 mls., preferably 500 mls., of water per mol. of dialkyl phenol should be used in the reaction medium, and from 1-3 per cent of an organic solvent by weight of the reaction mixture in the aqueous medium may also be added. Suitable acid catalysts are sulphuric or phosphoric acid, which are employed in various amounts depending upon the strength of the acid used, e.g. about 2 grs. to about 20 grs. of 98 per cent sulphuric acid per litre of water may be used. The condensation is preferably conducted by adding with agitation, the formaldehyde to, a mixture of a dialkyl phenol, acid catalyst, dispersing agent, and water with or without an organic solvent present, preferably at an elevated temperature for some time, e.g. 4 hours. After completion of the reaction at a temperature, preferably below 95 DEG C., sodium hydroxide or another suitable neutralizing agent may be introduced and the contents cooled. The reaction mixture may then be centrifuged or filtered to separate the solid product, which is then washed with water and dried. The addition of the cationic agent may be made at various times, after the condensation reaction is substantially complete, e.g. before or after the cooling of the reaction mixture, or during the actual separation. Examples are given of the preparation of 2,21-methylene bis(4-methyl-6-tertiary-butylphenol) and 2,21-methylene bis(4-ethyl-6-tertiary-butyl phenol). Specifications 654,163 and 776,518 are referred to. Reference has been directed by the Comptroller to Specification 711,122.