Improvements in or relating to the manufacture of oil-modified alkyd resins

In making fatty oil-modified alkyd resins wherein an incompletely esterified polyhydric alcohol composition made by alcoholysis of a fatty oil with one or more polyhydric alcohols and containing in solution a calcium salt of a fatty acid is esterified with phthalic acid or anhydride, with or without maleic anhydride, clear haze-free resins are obtained by adding to the polyhydric alcohol composition an inorganic phosphate, which is soluble therein at any stage prior to the esterification in amount at least sufficient to precipitate the calcium salts present. Phosphates specified are phosphoric acid, ammonium phosphate, and sodium- and potassium - dihydrogen phosphates. The precipitated calcium salts may be removed mechanically before the esterification. According to the examples, in making a linseed oil-modified pentaerythritol phthalate, calcium formate (present as impurity) is removed by addition of (1) phosphoric acid, (3) potassium dihydrogen phosphate, and (4) sodium dihydrogen phosphate; and (2) in making a linseed oil-modified glycerol phthalate, calcium acetate (present as catalyst) is removed by adding phosphoric acid.