Patent GB-576563-A (GB)
Title: New synthetic drying oils and coating compositions
Filed: 1943-06-25
Abstract: Drying oils comprise the esters of glycerol with one or more monofunctional thienyl acrylic acids as hereinafter defined, and, if desired, one or more monofunctional aliphatic monocarboxylic acids. The esters may be simple esters or be mixed esters of different thienylacrylic acids or of a thienylacrylic acid and a monofunctional aliphatic monocarboxylic acid, preferably an unsaturated acid such as a drying oil acid.  The expression "a thienylacrylic acid" is used to include any monocarboxylic acid having an a ,b -ethylenic double bond and a thienyl group attached to either or both of the a - and b -carbon atoms; the thienyl group may be attached at any position on the thiophene ring and these acids can have nonesterifiable substituents on the a - or b -carbon atoms or on the thiophene ring. The term "monofunctional" means that the acid does not contain groups reactive with the carboxyl group.  The simple esters are prepared by direct esterification of glycerol with the thienylacrylic acid, an example being the glyceride of b -thienyl acrylic acid. Mixed esters may be prepared by reacting glycerol, a glycerol ester such as a drying or semi-drying oil and sufficient thienyl acrylic acid to esterify the remaining free hydroxyl groups present in the mixture. Another method involves the partial alcoholysis of the glycerol ester of either the thienylacrylic acid or the monofunctional aliphatic monocarboxylic acid followed by esterification with the remaining acid; this may be carried out with an inert solvent present to remove the water formed in the reaction and, preferably, an ester-interchange catalyst is used, for example litharge, sodium hydroxide or sodium alcoholate.  The mixed esters may also be prepared by blending a mixed ester having a higher thienylacrylic acid content than is desired with a drying oil or other ester to give a final product having the desired thienylacrylic acid content. Desirably, the reactions should be carried out in an inert oxygen-free atmosphere and the use of materials liable to liberate oxygen in the reaction, e.g. old samples of petroleum naphtha or turpentine, should be avoided. The reaction temperature for the alcoholysis may be from 150 DEG  to 300 DEG  C.  In an example, 400 parts linseed oil, 95 parts of b -thienylacrylic acid, 19 parts of glycerol and 50 parts of toluene are refluxed in a deoxidised nitrogen atmosphere, the water-toluene vapours evolved being condensed and the toleuene returned to the reaction; finally, an inert gas is blown through the heated product to remove solvent yielding a mixed ester product containing theoretically 80 per cent thienyl acrylic acid glyceride and 20 per cent linseed oil glyceride. The toluene may be replaced by xylene, cymene, amyl benzene, tetrachlorethane, anisol and cyclohexanone, or, in general, aromatic hydrocarbons, chlorinated solvents, ethers and ketones.  Other specified thienyl acrylic acids are a -methyl-b -(2-thienyl) acrylic acid, b -(3-thienyl) acrylic acid, a -(2-thienyl)-b -phenylacrylic acid, and b -[2-(5-methyl) thienyl] acrylic acid, all obtainable by reacting an aldehyde with an acid anhydride according to Perkin's method; b -thienyl acrylic acid is prepared by condensing 2-thienylaldehyde with methyl acetate in the presence of sodium methoxide followed by hydrolysis.  Other monofunctional aliphatic monocarboxylic acids are the acids derived from perilla oil, oiticica oil, chinawood oil, dehydrated castor oil, soya bean oil, corn oil, cottonseed oil and coconut oil, oleic acid, stearic acid, lauric acid, butyric acid, crotonic acid and sorbic acids. In general, these latter acids may be saturated or unsaturated; straight or branched chain; and substituted or not by other groups or atoms such as ether, ketone or halogen.  The thienylacrylic acids may contain aliphatic or aromatic radicals, the latter being homo- or hetero-cyclic, the radicals being saturated or unsaturated, and substituted or not by such inert groups as ether, halogen ketone or sulphide.  The products may be employed in drying oils, paints, varnishes and enamels (see Group III).  Thus, coating compositions may be formulated with these esters and cellulose derivatives such as nitrocellulose, cellulose acetate, cellulose aceto-propionate and ethyl cellulose. Reference is made to Specification 569,404.