Synthetic resin and anodic coating method

摘要

Coating material is anodically deposited from an aqueous bath, having dispersed therein a synthetic resin which is produced by reacting an organic polymer having a plurality of hydroxyl groups with trimellitic anhydride, by immersing a first electrode in the bath while it is in electrical connection with a second electrode which is apart from the first, and passing a direct current through the bath. In the drawing a tank 11 contains the bath 13 and acts as the negative electrode; the article to be coated 19 is suspended from conveyer 35 by hangers 21 and 23 insulated at 25 and 27; the article 19 is in electrical connection over sliding members 29 and 31 with bus-bar 33 and serves as the positive electrode.ALSO:An organic polymer having a plurality of hydroxyl groups is reacted with trimellitie anhydride, i.e. the 1,2-anhydride of 1,2,4-benzene tricarboxylic acid. The polymer may be a copolymer of styrene and allyl alcohol, may have a molecular weight of above 1000 and have 2-10 hydroxyl groups/molecule. The reaction may be carried out at over 330 DEG F. and sufficient anhydride used, e.g. at least 2 mol./ mol. resin, to provide at least one carboxyl group/600 units of molecular weight in the polymer. The reaction may also be carried out in xylene in the presence of soya fatty acids, tall oil fatty acids or linseed fatty acids, or the polymer may be reacted first with these acids and then with the anhydride: the reacted polymer may be blended with one of the foregoing fatty acids. The reacted polymer may be dispersed in water containing ammonia or triisopropanolamine, or may be made into a paint by mixing with methyl ethyl ketone pine oil, polyethylene glycol red iron oxide, basic lead chromate coated silicate and/or china clay.