COATING COMPOSITIONS CONTAINING ACRYLIC POLYMERS AND PHENOXY RESINS

摘要

1,272,239. Coatings. E.I. DU PONT DE NEMOURS & CO. 24 Nov., 1969 [12 Dec., 1968], No. 57358/69. Heading B2E. [Also in Division C3] Liquid coating compositions comprise from 5-50% by weight of film-forming constituents and a solvent for said constituents, which constituents comprise (1) at least 50% by weight (based on the constituents) of an acrylic polymer derived from one or more alkyl methacrylates and/or acrylates in which the alkyl group has 1-8 carbon atoms and having copolymerised therein from 0-5% by weight (based on the acrylic polymer) of anα, #- ethylenically unsaturated monocarboxylic acid and greater than 0% and up to 50% by weight of the acrylic polymer being provided by pendent adhesion-promoting groups attached to the polymer backbone, said groups being of the formula: in which n is 1 or 2, R1, R2 and R3 which may be the same or different are H, C 1 -C 4 alkyl or aryl, and R4 together with the adjacent N atom forms a heterocyclic group optionally containing a hetero atom other than the said N atom; (2) at least 5% by weight of a phenoxy resin having the formula: in which n is an integer such that the resin has a molecular weight of at least 20,000, R5 is a divalent aromatic radical, R6, R7 and R8 which may be the same or different are H or C 1 -C 5 alkyl, and R9 is a C 1 -C 5 alkylene group; and (3) 0-40% by weight of an organic plasticiser; with the proviso that components (1), (2) and (3) are not used in amounts of 50%, 50% and 0% by weight respectively. Preferred proportions of (1), (2) and (3) are 50-70%, 10-30% and 20-40% by weight respectively. The optional acid component of the acrylic polymer may be, for example acrylic, methacrylic or crotonic acid. Suitable monomers for providing the adhesion, promoting groups include amino alkyl methacrylates and their N-alkyl and N, N-dialkyl derivatives, hydroxy-amino-alkyl methacrylates, N-(hydroxyalkyl)-methacrylamides, 2-(1-aziridinyl)-ethyl methacrylate and, preferably, the monomer of the formula: Preferred as the phenoxy resin component are reaction products of epichlorohydrin with bisphenol A or bisphenol F (4, 4'-methylene-bisphenol). Suitable plasticisers include epoxidised soya bean oil, oil-free or oil-modified alkyds and polyesters, phthalate esters, triphenyl or tricresyl phosphate, pentaerythritol mixed esters, glycol dibenzoates, succinate, sebacate and citrate esters and toluene ethyl sulphonamide; benzyl butyl phthalate is a preferred plasticiser. Specified solvents are toluene, xylene, butyl acetate, acetone, methyl isobutyl ketone, methyl ethyl ketone, butyl alcohol, isopropanol, ethylene glycol monoethyl ether and ethylene glycol monoethyl ether acetate. Inorganic or organic pigments can be included in the compositions, e.g. titanium dioxide magnesium silicate, barytes, talc, silica and carbon black. The compositions are particularly useful as sealer or primer compositions and adhere to unprimed metal surfaces and also to enamelled or lacquered surfaces. They can be applied to substrates such as metal, glass or plastics (e.g. styrene copolymers) by methods such as spraying, dipping, brushing or flow coating. Coatings can be air-dried or baked at 93- 150‹C. In the Examples coatings are applied to primed steel panels.