| 摘要 |
1314340 Electro-deposition coating compositions IMPERIAL CHEMICAL INDUSTRIES Ltd 27 Aug 1970 [10 Sept 1969] 44777/69 Heading C7B [Also in Division C 3 ] An electrically conductive article, connected as the anode, is coated by electro-deposition using as the coating bath an aqueous composition comprising a weak base having a dissociation exponent (pKb) greater than 7 and a polycarboxylic acid resin binder at least partially neutralized by a strong base having a pKb of less than 6, the weak base being soluble in the resin binder when in unneutralized form. The pH of the bath is preferably from 7 to 9. Examples of suitable weak bases are aniline, N-methylaniline, N, N- dimethyl aniline, o-toluidine, halogen ring - substituted anilines, pyridine, the picolines, quinoline, isoquinoline and acridine. The strong bases include the caustic alkalis; primary, secondary and tertiary alkyl amines and their hydroxy-substituted derivatives; and morpholine, pyrrolidine and piperidine. Useful resin binders include maleinised oils, alkyl resins prepared from drying and semi-drying oils, esters of polyols and epoxides with drying oil or semidrying oil fatty acids, and addition polymers of monomers of which at least one contains one or more carboxyl groups. The binder may be used in conjunction with a cross-linking agent, e.g. a highly etterified melamine-formaldehyde resin or a phenol-formaldehyde resin. The compositions may additionally include additives such as pigments (e.g. titanium dioxide, red iron oxide), pigment dispersants, plasticizers and organic liquids (e.g. isopropanol). In one embodiment the pH of the bath is maintained by use of a membrane of ion-exchange material between the electrodes. In Examples the binders used are (a) copolymers of acrylic acid, 2- hydroxyethyl methacrylate, methyl methacrylate, 2-ethylhexyl and styrene which may be in combination with a butylated melamine-formaldehyde resin and (b) an epoxyester resin as in Example X of specification 1069841 but having its acidity neutralized to the extent of 60% with aqueous KOH; and the coatings are deposited on phosphated steel panels at 150 volts and on an aluminium substrate at 230 volts. In some Examples the coatings are stoved. |
