Patent GB-575131-A (GB)
Title: New synthetic drying oils and coating compositions
Filed: 1943-06-25
Abstract: Synthetic drying oils are prepared by the simultaneous interaction of one or more naturally occurring glycerides, glycerol, and one or more a , b -unsaturated monofunctional monocarboxylic acids.  These latter acids may be any monofunctional monocarboxylic acid having an ethylenic double bond between the a - and b -carbon atoms provided there be no thienyl group attached to either of these two atoms; the term "monofunctional" means that the acid contains no group capable of undergoing reaction with the single carboxyl group under normal esterification conditions.  Examples of such acids are b -(2-furyl) acrylic acid, hexadien-2 : 4-oic acid, b -benzoylacrylic acid, a -vinyl cinnamic acid, cinnamalacetic acid, a -methacrylic acid, octatrien-2 : 4 : 6-oic acid, 5-cyclohexylpentadien-2 : 4-oic acid, 6-phenylhexadien-2 : 4-oic acid, a  : b -di-(2-furyl) acrylic acid, b -(3-furyl) acrylic acid, b -[2-(5 - chlorofuryl)] acrylic acid, cinnamic acid, b -acetyl acrylic acid, and 2-cyanohexadien-2 : 4-oic acid.  The glycerides are preferably drying or semidrying oils, though non-drying oils such as coconut and corn oils may be used. The products of the invention are glycerol mixed esters and may be prepared by fusion or solution methods.  In the solution method, the natural oil and a stoichiometric mixture of glycerol and a ,b -unsaturated monofunctional monocarboxylic acid and a sufficient amount of hydrocarbon solvent such as xylene or toluene to produce boiling at about 200 DEG  C. are heated in the presence of a small amount of esterification catalyst such as sodium hydrogen sulphate monohydrate or, in general, alkali metal partial salts of inorganic salts.  The water of esterification is distilled off with solvent and the solvent separated and returned to the reaction mixture continuously.  The final product may be freed of solvent if desired by distillation or blowing with carbon dioxide. Operating temperatures of 180-225 DEG  C. are generally satisfactory.  When using fusion methods, a slight excess of the a ,b -unsaturated acid is advantageous.  Improved colour of the product is obtained by blanketing the reaction with an inert gas such as carbon dioxide. The preferred products contain (theoretically) 5-60 per cent of the a ,b -unsaturated acid glycerol ester.  There may be present in the reaction mixture other monofunctional monocarboxylic acids which do not contain an a ,b -ethylenic double bond; these acids may be aromatic or aliphatic; monocyclic polycyclic, homocyclic or heterocyclic; saturated or unsaturated; straight or branched chain; and substituted or not by other groups or atoms such as ether, ketone, or halogen which do not interfere in the esterification. Thus, cottonseed oil, coconut oil, oleic, furoic, lauric, p-toluic, quinolinic and phenoxy acetic acids may be used for this purpose. The products of the invention are useful ingredients for coating compositions in paints and varnishes.  Such coating compositions may comprise the esters only or may also contain natural resins, for example kauri, congo, manilla, damar and shellac; synthetic resins such as hydrogenated rosin, ester gum, phenolic extended ester gums, phenol aldehyde resins, polyacrylates and methacrylates, and vinyl resins generally; cellulose derivatives, for example nitrocellulose, cellulose acetate and cellulose esters and ethers generally; waxes; natural drying oils; fillers; corks; bitumins and solvents.  These compositions may be applied to metal, wood, paper, linen, silk, cotton, leather or regenerated cellulose wrapping foil.  The mixed glycerol esters may be used as impregnating agents for paper, board and pressed wood materials, as artificial leather coatings, textile lubricants, lubricating oil modifiers, water-proofing agents, binders for plaster and in adhesives, printing inks, wood stains and fillers, putty and caulking compositions.  Paints formulated from red lead and the mixed glycerol esters, especially those obtained from soya bean oil and b -(2-furyl) acrylic acid make useful primers; aluminium paints may also be prepared.  In examples: (1) a glycerol mixed ester of linseed oil acids and b -(2-furyl) acrylic acid is prepared by heating glycerol, alkali refined linseed oil and b -(2-furyl) acrylic acid in the presence of sodium hydrogen sulphate as catalyst and toluene according to the solution method described above.  This product, with cobalt naphthenate drier, air-dries to give clear tack-free films.  A typical white enamel comprises the mixed glyceride, titanium dioxide, antimony oxide, mineral spirits and cobalt drier.  A black enamel comprises the mixed glyceride, carbon black, mineral spirits and cobalt naphthenate drier; (2) the mixed glyceride of (1) above is prepared by the fusion method, using the same reactants, but omitting the toluene; a composition giving tack-free films comprises the mixed ester, limed rosin, mineral spirits and cobalt drier; (3) a mixed glyceride of b -(2-furyl) acrylic acid and soya bean oil acids is prepared from the acrylic acid, soya bean oil and glycerol as in (1) above and is compatible with an equal weight of soya bean oil.  Other mixed glycerides are prepared similarly by fusion or solution methods from glycerol; and (4) linseed oil and hexadien-2 : 4-oic acid; (5) corn oil and b -(2-furyl) acrylic acid; (6) soya bean oil, linseed oil and b -(2-furyl) acrylic acid; (7) chinawood oil, linseed oil, and b -(2-furyl) acrylic acid; (8) linseed oil and b -benzoylacrylic acid; (9) linseed oil and a -vinylcinnamic acid; (10) linseed oil and cinnamalacetic acid; and (11) linseed oil and a -methacrylic acid; all these mixed esters give tack-free films with added cobalt.  Other glycerides specified are oiticica oil, perilla oil, castor oil, cottonseed oil, and menhaden oil.  The toluene employed as a solvent may be replaced by p-cymene, amylbenzene, anisol, cyclohexanone and tetrachlorethane.  Of the a  : b -unsaturated acids specified above, b -benzoyl acrylic acid is prepared from benzene and maleic anhydride, a -vinyl cinnamic acid is prepared by condensing benzaldehyde and crotonic aldehyde in the presence of triethylamine, and cinnamalacetic acid is prepared by heating together cinnamaldehyde, malonic acid and pyridine and treating the product with 20 per cent sulphuric acid; the other acids are obtainable by reacting an aldehyde with an acid anhydride according to Perkin's method.  The Specification as open to inspection under Sect. 91 relates also to the preparation of similar esters, using in place of glycerol, other polyhydric alcohols, including diethylene glycol, decamethylene glycol, erythritol, sorbitol, methyltrimethylolmethane, p : p-di-(2-hydroxyethyl) benzene and cyclohexyl-1 : 2-dicarbinol. This subject-matter does not appear in the Specification as accepted. Reference has been directed by the Comptroller to Specification 569,404.