Patent GB-565431-A (GB)
Title: Modification of drying or semi-drying oils
Filed: 1942-11-16
Abstract: The properties of drying or semi-drying oils, other than those containing conjugated double or triple bonds, the corresponding acids or the mono- or di-glycerides of the acids are modified by heating them, e.g. at 90-150 DEG  C., with maleic anhydride, maleic acid or the half ester of maleic acid with a monohydric alcohol, e.g. methyl, ethyl, propyl, butyl or amyl, while passing a current of air or oxygen containing gas through the mixture.  Suitable oils are linseed, perilla, soya bean, safflower, hempseed, walnut, poppy seed, rubber seed, stillingia, candle nut, niger seed, cotton seed, sesame, maize, wheat, sunflower seeds, herring, pilchard, sardine, menhaden or whale oil, or mixtures thereof.  A proportion of the material being treated may be in the oxidized form.  In general, not more than 1 mol. of the modifying agent should be used per mol. of fatty acid in the material being treated.  The time of heating may vary from 2-10 hours.  It should be accompanied by agitation.  When modifying oils with maleic acid or anhydride, the proportion of modifying agent should be smaller than usual to avoid gelation, but must not be less than .5 mol. of modifying agent per mol. of oil.  In the case of fatty acids from linseed perilla or marine oils, not more than .5 mol. of maleic and/or anhydride should be used for 3 mols. of fatty acids.  The products of the modification reaction may be esterified with a polyhydric alcohol or a partial ester thereof with a drying or semi-drying oil fatty acid if they contain excess carboxylic acid groups, or with a drying or semi-drying oil fatty acid if they contain excess hydroxyl groups, oils modified with between half and 1 mol. of maleic acid or anhydride per mol. of fatty acid or the oil cannot be fully esterified with a trihydric alcohol, such as glycerol without gelation, but can be esterified with a dihydric alcohol, e.g. mono-, di- or tri-ethylene glycol, a polyhydric alcohol partly esterified with a drying oil acid and containing not more than two hydroxyl groups, e.g. mono- or di-glycerides of drying oil acids, or with a mixture of a trihydric and a dihydric alcohol.  When a half ester of maleic acid is the modifying agent the products are usually thin liquids which on esterification have good film-forming properties.  When maleic acid is used as the modifier, some may be converted to fumaric acid which may deposit and need to be separated. The products of the invention usually increase in viscosity on storage and may gel.  This effect may be minimised in the case of the ester products by heating them with a natural resin esterified with a polyhydric alcohol, e.g. glycerol.  Heating should be stopped when the viscosity reaches a minimum.  Examples describe (1) modification of linseed oil by heating with maleic anhydride and formation of a varnish by adding cobalt naphthenate to the product and diluting with white spirit.  (2) Esterification of the modified oil of example (1) with a monoglyceride from linseed oil and formation of a varnish as in example (1).  (3) Modification of soya bean oil with maleic anhydride as in example (1).  Esterification and making of a varnish from the product as in example (2).  (4) A mixture of pilchard oil and sardine oil is modified with maleic anhydride and a varnish formed from the product as in example (1).  (5) Esterification of the modified oils of example (4) with linseed oil monoglyceride and formation as in example (1) of a varnish from the product.  (6) Modification of linseed oil fatty acids with maleic anhydride, esterification of the product with linseed oil monoglyceride and varnish formation as in example (1).  (7) Modification of linseed oil monoglyceride with maleic anhydride, esterification of the product with linseed oil fatty acids and varnish formation as in example (1). (8) Modification of linseed oil with maleic acid, esterification of the product with the monoglyceride of linseed oil and varnish formation as in example (1).  (9) Modification of linseed oil with monobutyl maleate, esterification of the product with the monoglyceride of linseed oil and varnish formation as in example (1). (10) Modification of linseed oil containing a small proportion of oxidised linseed oil with maleic anhydride and formation of a varnish as in example (1).  (11) and (12) Similar to example (1).  (13) Modification of linseed oil containing a small proportion of oxidised linseed oil with maleic anhydride, esterification of she product with the monoglyceride of linseed oil, and stabilization of the product against gelation on storage by heating with ester gum.  (14) Stabilization of the ester product of example (13) with ester gum. In all the examples, a stream of air is bubbled through the reaction mixture during modification reactions.  Esterification and stabilization are carried out in an inert atmosphere.  Specifications 446,658, [Group III], and 565,432 are referred to.