Electro-deposition paint. II.

Abstract

Phosphoric acid ester of fatty acid-modified epoxy resin, which can be obtained by the esterification of epoxy resin with fatty acid in the first step and then with phosphoric acid, becomes a resin for use of paint which is perfectly emulsifiable in the water when the ester is neutralized with organic amine. An even coated film of the resin can be separated out on the surface of metal products when the metal piece immersed into aqueous dispersion of the resin is put on electric circuit by connecting the metal piece being cathode and iron piece being anode and with direct current of 30-60 volt.
Authors investigated the composition and the conditions of the resin for coating by means of electrophoresis. In this report, the authors used an epoxy resin of epichlorohydrin-diphenylolpropane type (Epikote # 834, of Shell Chemical). As the fatty acid for esterification, lauric acid, palmitic acid, stearic acid, oleic acid, linolic acid and fatty acid of dehydrated castor oil, etc were selected, and each one mol of the fatty acid was used for one mol of epoxy resin for esterification, and subsequent estrification was made with one mol of phosphoric acid. Thus prepared ester was neutralized with triethanolamine and was dispersed into water so as the nonvolatile matter becomes 10%. Thus obtained emulsion was investigated for difference of electro-deposition property to be caused by the kind of fatty acid, and for characteristic of the film after dried. And additional investigation was made for the water soluble phenol resin to be used linking agent of the phosphoric acid ester of fatty acid-modified epoxy resin, thus prepared, in order to make clear that the phenolic resin merely mixed at a constant ratio into the emulsified aqueous solution of resin thus synthesized would be found in the electro-deposited film at the same mixed ratio as compared with that before coating. Upon experiments the following facts were made clear by the authors.
1) As for the fatty acid, the oleic acid, linolic acid and fatty acid of dehydrated castor oily each of which is unsaturated fatty acid 18 of carbon numbers, were superior.
2) In this synthesized product, the ratio of water soluble phenolic resin to the emulsified aqueous solution, at any optional mixing ratio, was approximately the same with that ratio contained in the electro-deposited film, and which was confiemed from log I₀/I (1500 cm^-1, 810 cm^-1) of infrared spectrum for the coated film separated out.
3) The electro-deposited film, which was prepared from phosphoric acid ester of linolic acid-modified epoxy resin by the neutralization with triethanolamine and then by mixing thereinto with 4-5 parts of water soluble phenolic resin to the 5-6 parts of thus neutralized product, was stable against boiling water for more than 50 hours.