Patent GB-909322-A (GB)
Title: Coating compositions
IPC: C08L63/00
Filed: 1960-09-14
Abstract: Sheet metal, e.g. steel, chromium plate, brass, nickel or aluminium is coated with a composition containing the following (all parts and percentages by weight): (a) 20-50% of a copolymer having in 100 parts: 50-85 of styrene; at least 3 of methacrylic acid, acrylic acid or a mixture thereof; at least 5 of at least one C1-C4 alkanol ester of acrylic and/or methacrylic acid; (b) 20-50% of an ester containing, per 100 parts: at least 40 parts of epoxy hydroxy polyether of a polyhydric phenol having on average more than one epoxy group/molecule and 15-60 parts of C12-C22 fatty acid including at least 15 of at least one C16-C22 polyunsaturated fatty acid; (c) 10-40% of one or more urea-melamine- and/or benzoguanamine - formaldehyde condensate modified with C1-C4 alkanol, all in solution in a volatile organic solvent.  Pigments may be added. The coatings may be applied by, e.g. spraying, brushing, dipping, roller-coating or flow-coating.  They are dried and cured at 250 DEG -400 DEG F., 350 DEG F. for 15-20 min. or 280 DEG F. for 30-40 min. being preferred.  In Example 1, "Bonderized" (Registered Trade Mark) steel is primed to provide a coating ca. 0,8 mil. thick on curing at 350 DEG F. for 20 min., and given a 1 mil. topcoat with a commercial baking enamel with 20 min. curing at 350 DEG F.  In Example 2, steel panels primed as in Example 1 are topcoated with compositions according to the invention, curing at 300 DEG F. for 30 min., and another sheet is primed with the composition of Example 1, flash-dried for 5 min. at room temperature, top-coated with composition of Example 2, and cured at 300 DEG F. for 30 min. Specifications 483,399, 686,234 and U.S.A. Specification 2,456,408 are referred to.ALSO:A coating composition contains as its chief ingredients: (a) 20-50%, preferably 25-45% by weight of a copolymer of: 50-85 parts styrene; at least 3 parts acrylic or methacrylic acid or mixture; at least 5 parts of a C1-C4 alkanol ester of one of said acids or mixture of such esters, the total being 100 parts by weight, (b) 20-50%, preferably 25-45% of mixture containing per 100 parts: (i) at least 40 parts preferably 50 - 75, of epoxyhydroxy polyether of a polyhydric phenol with on average more than one epoxy group and several OH groups per molecule, (ii) 15-60, preferably 25-50 parts of a C12-C22 fatty acid or mixture containing at least 15 parts of at least one C16-C22 polyunsaturated acid, the acid being esterified by the epoxyhydroxy polyether largely through the hydroxy groups, with as little esterification of epoxy groups as possible, (c) 10-40%, preferably 20-35%, of one or more C1-C4 alkanol-modified urea-, melamine-, or benzoguanamine-formaldehyde condensates in solution in a volatile organic solvent.  1%-200% of a pigment, based on above solids, may be added, as may grinding aids, curing accelerators, bodying agents, flow control agents, surface-active agents, inhibitors, slip agents, plasticizers, and polyethylene or vegetable waxes for abrasion-resistance.  Component (a) is preferably of the following composition per 100 parts by weight: 65-75 parts styrene; 8-12 parts methacrylic acid; 15-25 parts of one or more C1-C4 alkanol (ethanol preferred) esters of acrylic acid.  They have a relative viscosity of 1,05-1,20, preferably 1,07-1,15.  They are prepared by solution polymerization at 125 DEG -200 DEG C. for 1/2 -8 hours in aromatic hydrocarbons.  0,1-2%, based on weight of monomers, of a catalyst, e.g. cumene hydroperoxide, di-t-butyl peroxide, t-butyl peracetate, benzaldehyde peroxide, 2,2-bis(t-butyl peroxy) butane, or diazoaminobenzene is preferably added. Conventional additives (activators, chain-transfer agents, inhibitors, or surface-active agents) may be present.  The removal of inhibitors from commercial monomers is not essential.  The solvent may be toluol, xylol, benzol, mixtures of these with minor amounts of aliphatics, petroleum naphthas of aniline point below 40 DEG C. when diluted with 1 vol. n-heptane, and should boil at 80 DEG -250 DEG C., preferably below 225 DEG C. 25-400% by weight, based on monomers, of the solvent may be present, 33-150% being preferred. p  Reflux at 140 DEG -170 DEG C. is the preferred temperature for the polymerization.  Component (b) is prepared by varnish-cooking at 300 DEG -500 DEG F. the epoxyhydroxy polyether with the fatty acids per se or with a glyceride drying oil.  Saturated or mono-olefinic acids may be present, and exert a plasticizing effect.  Suitable oils and acids are listed.  The polyether is prepared by reacting an aliphatic halohydrin, e.g. epichlorhydrin or glycerol dichlorohydrin, with a polyhydric phenol (preferably bis-phenol-alkylene type) in the presence of caustic alkali. Suitable polyethers are described in U.S.A.  Specification 2,456,408.  The mol. wt. may vary widely; ca. 3,000 is preferred; the epoxy equivalent weight is preferably not much more than 1,500; the esterification equivalent weight (OH and epoxy groups) is preferably 125-200.  Component (c) is a normal modified aminoplast, and may contain other modifiers, e.g. aryl sulphonamides or polyamines. Specifications 483,399 and 686,234 also are referred to.