| 摘要 |
<p>1,235,660. Acrylic enamel coatings. E. I. DU PONT DE NEMOURS & CO. 27 Oct., 1969 [29 Nov., 1968], No. 52423/69. Heading B2E. [Also in Division C3] Coating compositions suitable for use as thermosetting acrylic enamels contain 10- 60% by weight of a film-forming polymer blend, and a solvent for the polymer blend, said blend comprising (1) from 50-80% (by weight of the blend) of an acrylic polymer of (a) 0-25% (by weight) styrene units, (b) 25-55% methyl methacrylate units, (c) 38- 48% of units of a C 2 -C 4 -alkyl acrylate or methacrylate, (d) 5-20% of units of a C 1 -C 8 - hydroxyalkyl acrylate or methacrylate and (e) 1-5% of units of anα, #-ethylenically unsaturated monocarboxylic acid, the polymer having a relative viscosity (in ethylene dichloride) of 1.04 to 1.10; (2) from 5-45% of cellulose acetate butyrate having a butyryl content of 45-55% by weight and a viscosity at 25‹C of from 0.1 to 8 sec; and (3) 5-45% of a compatible thermosetting N-containing condensation resin. The acid component (e) of the acrylic polymer may be acrylic, methacrylic, ethacrylic,α-propylacrylic,α-isopropylacrylic or crotomic acid. Preferred as the condensation resin (3) are alkylated melamineformaldehyde resins or mixtures thereof with urea-formaldehyde resins. Suitable solvents for the polymer blends include toluene, xylene, butyl acetate, acetone, methyl isobutyl ketone, methyl ethyl ketone, ethylene glycol monoethyl ether acetate, isopropyl alcohol and butyl alcohol. Optional components include polymeric plasticisers, e.g. oil-free and oil-modified alkyds and polyesters, non-polymeric plasticisers, e.g. epoxidised soya bean oil, phthalates, phosphates, pentaerythritol esters, diglycol dibenzoate, tetrabutylthiodisuccinate, butyl phthalyl butyl glycolate, acetyl tributyl citrate, dibenzyl sebacate and toluene ethyl sulphonamide, and pigments, e.g. metal flakes, e.g. aluminium metal oxides and hydroxides such as titanium dioxide and zinc oxide, chromates such as lead chromate, sulphides, sulphates, carbonates, carbon black, silica, talc, china clay, iron blues and organic dyes. The compositions can be applied to various substrates, e.g. wood, glass, car and truck bodies and are particularly suitable for glass fibre-reinforced plastics substrates. Application can be affected by methods such as spraying, dipping, brushing and flow coating. When applied to metal substrates, the latter are preferably primed with a pigmented alkyl or epoxy primer. Coatings are preferably cured at 125-175‹C for 15-30 minutes. In Examples, the compositions are applied, by spraying, onto primed steel panels.</p> |
