Patent GB-565432-A (GB)
Title: Modification of drying or semi-drying oils or derivatives of these
Filed: 1942-11-25
Abstract: Mixtures containing drying oils, semi-drying oils, their acids or the mono- or di-glycerides thereof, excluding those compounds with conjugated double or triple bonds, and a small proportion of the same components in oxidised form are heated, e.g. at 90-150 DEG  C., with maleic acid, maleic anhydride or a half ester of maleic acid with a monohydric alcohol, e.g. methyl, ethyl, propyl, butyl or amyl alcohol.  Products of the invention which contain excess acid groups may be esterified with polyhydric alcohols or with a partial ester of a polyhydric alcohol with a drying or semi-drying oil fatty acid. Products containing excess hydroxyl group may be esterified with drying oil or semi-drying oil fatty acids. Modified oils or complete esters of oil acids with polyhydric alcohols, whether esterified or not and the other products after esterification are stable, and dry to durable and elastic films. Suitable drying oils are linseed, perilla, soya bean, safflower, hemp seed, walnut, poppy seed, rubber seed, stillingia, candlenut, niger seed, cotton seed, sesame, maize, wheat, sunflower seed, herring, pilchard, sardine, menhaden or whale oil.  The oxidised component of the reaction mixture is formed as usual by blowing with air.  Heating should be accompanied by agitation and last from 2 to 20 hours.  In general, not more than 1 mol. of maleic acid, anhydride or half ester should be used per mol. of fatty acid present.  When treating oils with maleic acid or anhydride, the proportion should be smaller to avoid gelation and in the case of fatty acids from linseed, perilla or marine oils should not be more than 1/2 mol. of acid or anhydride per 3 mols. of acid. Oils modified with 1/3 to 1 mol. of maleic acid or anhydride per mol. of fatty acid in the oil can only be partly esterified with a trihydric alcohol such as glycerol before gelation occurs. They can usually be completely esterified with a dihydric alcohol such as mono-, di- or tri-ethylene glycol or a polyhydric alcohol itself esterified with a drying or semi-drying oil fatty acid so that not more than two hydroxy groups remain in the moleculer, p  e.g. the mono- or di-glyceride of drying oil acids, or with a mixture of a trihydric and a dihydric alcohol.  When maleic and half esters are used for the reaction, the products are usually thin mobile liquids which, after further esterification, dry to form films.  Maleic acid during the course of the reaction may isomerize to fumaric acid which may have to be separated from the mixture.  The products usually increase in viscosity and may gel on standing.  This may be obviated in the case of the esterified products by heating them with about 5-15 per cent by weight of a natural resin or resin ester.  The heating should be stopped when the viscosity of the reaction mixture reaches a minimum.  Examples describe: (1) and (2) Modification of a mixture of linseed oil and oxidised linseed oil with maleic anhydride.  (3) Esterification of the product of example (2) with a partial glyceride of linseed oil acids.  Thinning the ester with white spirit and addition of cobalt naphthenate yields a varnish. (4) Modification of a mixture of soya bean oil and oxidised soya bean oil with maleic anhydride, esterification of the product with the monoglyceride of linseed oil fatty acids and formation of a varnish from the ester as in example (3).  (5) As in examples (1) and (3). (6) Modification of the monoglyceride from linseed oil and a proportion of the oxidised component with maleic anhydride, esterification of the product with linseed oil fatty acids and formation of a varnish as in example (3).  (7) As in example (1) with maleic acid in place of the anhydride.  (8) Modification of a mixture of linseed oil and oxidised linseed oil with monobutyl maleate, esterification of the product with the monoglyceride of linseed oil acids and formation of a varnish as in example (3). (9) As in examples (1) and (3).  The esterified product is modified by mixing with ester gum and heating for 1 hour at 260 DEG  C. in an inert atmosphere.  This improves storage (10).  The esterified product of example (9) is bodied by heating at 260 DEG  C. in an inert atmosphere and then stabilized by heating with ester gum. Specifications 446,658, [Group III], and 565,431 are referred to.