Improvements in aminoplastic resins

摘要

1,145,831. Aminoplast coating compositions. BRITISH INDUSTRIAL PLASTICS Ltd. 16 May, 1966 [20 May, 1965], No. 21388/65. Headings C3B and C3R. [Also in Division C7] Alkylated aminoresins, derived from the alkyl esters of aminoplast precondensates, or the precondensates themselves are at least partially transesterified by reaction with a hydroxycarboxylic acid. The resins or precondensates may be obtained by reaction of HCHO with urea, melamine or benzoguanamine; they may be alkylated by reaction with methyl, ethyl, propyl or butyl alcohol. The hydroxycarboxylic acid may contain more hydroxyl than carboxylic groups, e.g. gallic acid or dimethylolpropionic acid. Other suitable acids are glycollic acid, lactic acid or acids obtained by condensing a glycol with a dicarboxylic acid or anhydride. The hydroxycarboxylic acid and resin or precondensate may be reacted together in the absence of solvent (optionally in vacuo) until the evolution of alcohol ceases; sufficient acid may be used to provide one OH group for each mole of alkylated resin or precondensate. The resins of the invention may be used to form ionized aqueous solutions (e.g. having a pH from 6À5 to 9À0) in which the anion is derived from the resin and the cation is provided by ammonia or an organic base (e.g. triethylamine or dimethylaminoethanol). Such solutions may be used together with water soluble alkyd resins and pigments in the formation of enamels which may be coated by electrodeposition (see Division C7).