GB1408250A - Electrocoating process and composition - Google Patents

Abstract

1408250 Compositions for electrocoating M & T CHEMICALS Inc 24 Aug 1973 [6 Sept 1972] 40268/73 Headings C3R C3B and C3P [Also in Division C7] A cross-linkable aqueous polymer composition suitable for cathodic electrocoating consists of an aqueous dispersion containing as filmforming components: (a) an amine-containing polymer wherein at least some of the amino radicals are present as the ammonium salt of a carboxylic acid, the repeating units containing the amino radicals constituting from 2-50 mole per cent based on the total number of moles of repeating groups in the polymer; and (b) a heat reactive condensation product of formaldehyde with a phenol or a substituted aromatic hydrocarbon, said product containing an average of at least 2 methylol radicals per molecule, the weight ratio of (a) to (b) being from 1 : 9 to 9 : 1 and components (a) and (b) together comprise from 2-25% wt. of the aqueous polymer composition. Component (a) may be prepared by addition polymerization of a mixture of unsaturated monomers containing 2-50 mole per cent of amine groups or by condensation polymerization of di- or tri-basic organic acids with polyfunctional amines or hydroxyamines. Component (b) is preferably the reaction product of HCHO with phenol, an alkyl or alkylene ether of phenol or an aromatic hydrocarbon containing at least 2 alkyl substituents such as xylene. Component (b) mau be prereacted with a diglycidyl ether of an aromatic or aliphatic dihydroxy compound. Optional components include pigments, stabilizers, fillers, catalysts and organic solvents. In the examples compositions are prepared by mixing (1) an acrylic polymer solution in methylethylketone prepared from methyl methacrylate, t-butylaminoethyl-methacrylate, n-butylacrylate using azo-bis-isobutyronitrile as polymerization initiator with a product obtained by reacting a diglycidyl ether of bisphenol A with the condensate of allylphenyl ether and HCHO using triethylamine as catalyst. then adding toluene and then diluting with the monomethylether of ethylene glycol and 2-ethylhexanol, the product optionally containing TiO 2 and carbon black; (2) an acrylic polymer solution in methylethylketone prepared from ethyl acrylate, methyl methacrylate, hydroxylpropyl methacrylate, styrene and t-butylaminoethyl methacrylate using azobis-isobutyronitrile as initiator with a product obtained by reacting a solid bisphenolepichlorohydrin type epoxy resin with a xyleneformaldehyde condensate; (3) an acrylic polymer solution in the monomethylether of ethylene glycol prepared from methylmethacrylate, t - butylaminoethyl methacrylate and butyl acrylate with a partially polymerized mixture of the allylethers of mono-, di- and tri-methylol phenols; (4) a polyamide resin derived from dimeric linoleic acid and diethylene triamine and the partially polymerized mixture of Example (3). The amine groups are then at least partially neutralized with formic or acetic acid and water is then gradually added to form an emulsion. The compositions thus obtained are used to electrocoat a zinc phosphate coated steel panel which acts as the cathode of a direct current electrical circuit.