GB841521A - Improvements in or relating to processes for the preparation of esters of acrylic and methacrylic acids - Google Patents

Abstract

Monomeric esters of acrylic or methacrylic acid with higher alcohols containing at least 9 carbon atoms are prepared by reacting together the higher alcohol with a methyl or ethyl ester of acrylic or methacrylic acid, which ester may contain an amount of polymerization inhibitor sufficient only to prevent its polymerization at ambient temperature, in the presence of an acidic esterification catalyst containing hexavalent sulphur and a quinone having an oxidation potential of not less than 0.4 volts, the quinone being present in an amount of from 0.03 gms. to 0.20 gms. per gm. mol. of the ester, stripping the reaction mixture free of unchanged methyl or ethyl ester, neutralizing the products, drying if necessary, and then filtering off separated solids. Specified quinones are p-benzo quinone, p-toluquinone, duroquinone, phenanthrene quinone, dipheno quinone, trichloro quinone, chloranil, o-xylo quinone, 1 : 4-naphtho quinone, quinhydrone and 4 : 7-hydrindene quinone. Specified acid catalysts are sulphuric acid, alkane-sulphonic acids, benzene sulphonic acid, p-toluene sulphonic acid and sulpho salicylic acid. The reaction is preferably effected by continuously distilling off an azeotrope of liberated methyl or ethyl alcohol and methyl or ethyl ester and passing it into the base of a column containing an upper layer of the starting ester on a lower aqueous layer and withdrawing ester from the upper layer for continuous recycling to the reactor; the aqueous layer preferably contains sodium chloride or other dissolved inorganic salt and a small amount of a polymerization inhibitor, which may be other than a quinone, e.g. toluene. During the reaction air may be blown through or over the reaction mixture. Examples illustrate the preparation of lauryl and 3 : 5 : 5-trimethyl hexyl methacrylates and the acrylic and methacrylic esters of a mixture of cetyl and stearyl alcohols from methyl or ethyl acrylate or methacrylate which in some instances contains 0.1% hydroquinone. Comparative experiments are described using hydroquinone or anthraquinone. Other higher alcohols specified are straight chain primary alcohols containing more than 18 carbon atoms, cycloaliphatic alcohols and wool wax alcohols. The acrylates and methacrylates of the higher alcohols may be polymerized. According to the Provisional Specification, the alcoholysis may be effected with higher alcohols containing at least 4 carbon atoms, such as n-butyl, n-hexyl, n-octyl, 2-ethyl hexyl, n-decyl and myristyl alcohols using an amount of the quinone which is sufficient to prevent polymerization during the alcoholysis but insufficient to necessitate its removal by special treatment. Specification 686,624 is referred to.