| 摘要 |
A polishing enamel comprises a pigment and a vehicle including as a binder an aminoplast resin I and II the reaction product of an acidic copolymer (as hereinafter defined) and 5-20% by weight (based on the copolymer plus the epoxide) of oxirane, an alkyl- or aryl-substituted oxirane or an ether or an ester each containing only one 3-membered epoxide group, the amount of epoxide within its range being sufficient to give an acid value of 5 to 25, and the amount of I employed being 15 to 35% by weight of I plus II. The acidic copolymers are defined as being A, B, C or D where A is the reaction product of 40 to 80% of methyl, or ethyl methacrylate, and 15 to 40% of acrylic or methacrylic acid: B is the reaction product of 5 to 89% of methyl or ethyl methacrylate, 5 to 40% of acrylic or methacrylic acid and 5 to 35% of a vinyl aromatic compound having a single vinyl group A acrylonitrile or vinylpyrrolidone; C is the reaction product of 10 to 50% of methyl or ethyl methacrylate, 5 to 40% of acrylic or methacrylic acid and 30 to 55% of a C3 to C8 methacrylate or a C1 to C8 acrylate; and D is the reaction product of 10 to 50% of methyl or ethyl methacrylate, 5 to 40% of acrylic or methacrylic acid, 30 to 55% of a C3 to C8 methacrylate or a C1 to C8 acrylate and 1 to 40% of a vinyl aromatic compound having a single vinyl group, acrylonitrile or vinylpyrrolidone, the percentages being by weight of the total weight of comonomers + epoxide. The monoepoxide and the acidic monomer may have been reacted together before the copolymerization. Organic and inorganic pigments may be used. The aminoplast resins are the alkylated condensates formed by the reaction of amines and amides with aldehydes in the presence of alcohols. Specified are urea, thiourea, melamine, benzoguanamine and p-toluenesulphonamide-formaldehyde resins alkylated by propyl, butyl, isobutyl octyl and decyl alcohol. The vehicle may also contain acid catalysts and solvents such as aromatic hydrocarbons, alcohols and ketones or their mixtures. In comparative examples the aminoplast are replaced by alkyd resins. Copolymers are prepared by solution polymerization in an organic solvent using cumene hydroperoxide as the catalyst. The comonomers may be added in two batches. The additional comonomers exemplified are methyl, ethyl, butyl and 2-ethyl-hexyl acrylates and butyl methacrylate. The copolymers are reacted with the oxiranes in the presence of benzyltrimethylammonium methoxide, oxiranes exemplified being propylene oxide, butylene oxide and styrene oxide.ALSO:Automotive polishing enamels comprising a pigment and a vehicle including as a binder an aminoplast resin and a copolymer comprising methyl or ethyl methacrylate and acrylic or methacrylic acid with as optional comonomers, C1-8 acrylates, C3-8 methacrylates, vinyl aromatic compounds having a single vinyl group, acrylonitrile or vinylpyrrolidone, in which some but not all of the carboxyl groups have been reacted with oxirane, an alkyl or aryl oxirane, or an ether or ester containing only one oxirane group (see Division C3) are sprayed on to panels of steel and cured by baking at 250 DEG F. |
