Patent GB-793047-A (GB)
Title: Improvements relating to polymerizable unsaturated esters
IPC: C07C69/54
Filed: 1955-03-07
Abstract: Polymerizable unsaturated esters of polyhydric alcohols are obtained by reacting at elevated temperatures, and in solution in a hydrocarbon solvent, a polyhydric alcohol and an aliphatic monohydric alcohol ester of an unsaturated aliphatic monocarboxylic acid, in the presence of a basic alcoholysis catalyst, while bubbling air through the reaction mixture at a rate in the range 400 to 2000 c.c. per minute for each 200 to 300 gm. of reaction mixture present, including the weight of solvent. In a modification oxygen, instead of air, is bubbled through the reaction mixture at a rate one-fifth of that which would be employed if air were used.  Specified polyhydric alcohols are diethylene glycol, triethylene glycol, tetraethylene glycol, di-, tri- and tetra-propylene glycols, dipentamethylene glycol, glycerol, diglycerol, sorbitol, and pentaerythritol.  The unsaturated esters are preferably those of the formula M-O-Z, where M is an unsaturated aliphatic acyl radical and Z is a C1-C10 alkyl radical, e.g. methyl, ethyl, or propyl, specified esters being the methyl, ethyl, and propyl esters of acrylic, methacrylic, crotonic, isocrotonic, a -methyl-acrylic acid, b -ethyl acrylic acid, b ,b -dimethyl acrylic acid, allylacetic acid, angelic acid, tiglic acid, and hydrosorbic acid. The products may be completely or partially esterified depending on the quantities of reactants employed and the completeness of the reaction.  It is preferred to use from 0.5 to 3 mols. of starting ester per mol. of polyhydric alcohol and reaction temperatures in the range 70 DEG  to 125 DEG  C. are preferred. Specified basic alcoholysis catalysts are sodium carbonate, sodium metal, sodium hydride, sodium methylate, mixtures of sodium hydride and sodium methylate, potassium tert.-butoxide, potassium hydroxide, and caesium hydroxide.  Specified hydrocarbon solvents are benzene, heptane, octane, iso-octane, toluene, xylene, and mesitylene. Examples are given for the reaction of (1) methyl methacrylate with tetraethylene glycol to form the dimethacrylate of the glycol; (2) methyl acrylate with tetraethylene glycol to form the diacrylate of the glycol; (3) methyl methacrylate and tripropylene glycol to form a mixed product comprising tripropylene glycol methacrylate and dimethacrylate; (4) methyl methacrylate and glycerol to form a mixture of glycerol mono- and dimethacrylates; (6) and (7) methyl methacrylate and tetraethylene glycol to give products having different saponification values.  In each case the reaction is carried out in the presence of benzene as solvent and is generally effected in a heated reaction vessel equipped with a fractional distillation column, air being passed into the reaction mixture throughout the reaction.  In Examples (1) to (4), sodium hydride is used as catalyst whilst in (6) a mixture of sodium hydride and sodium methyate is used and in (7) sodium methylate alone is used.  In a comparative example, (5), methyl methacrylate is reacted with tetraethylene glycol in the presence of benzene and of sulphuric acid as alcoholysis catalyst, a small amount of di-tert.-butyl di-perphthalate being also present as oxidation catalyst.  Air is bubbled through the reaction mixture during the reaction but the product is obtained in lower yield and contains 0.31 per cent active oxygen.  Specification 724,188 is referred to.