GB898345A - Improved aminoplast-alkyd coating compositions and substituted melamine-formaldehyde condensates for use therein - Google Patents

Abstract

A coating composition comprises a solution in an organic solvent of (1) an oil modified alkyd resin and (2) either (a) an etherified condensation product of N,N1-dicyclohexyl-and/or N,N1,N11-tricyclohexyl-melamine and formaldehyde or (b) N,N1-dicyclohexyl- and/or N, N1,N11-tricyclohexyl-melamine or a methylol derivative thereof used in conjunction with an etherified melamine-formaldehyde condensation product, said condensation products having been etherified with an alkanol having not more than six carbon atoms. The alkyds used in the coating compositions are the reaction products of polyhydric alcohols such as glycols, glycerol, sorbitol and pentaerythritol with polybasic acids or their anhydrides such as phthalic acid or its anhydride, isophthalic acid, maleic acid or its anhydride, fumaric acid, adipic acid and azelaic acid, modified with drying, semi-drying and non-drying oils such as coconut oil, castor oil, dehydrated castor oil, soya-bean oil, linseed oil, tung oil or with the acids or partial glycerides derived therefrom. Suitable p solvents are hydrocarbons, e.g. xylol and petroleum aliphatic hydrocarbons; alcohols, e.g. butanol; ethers; ketones; esters; and mixtures thereof, e.g. xylol-butanol and aliphatic hydrocarbon-butanol mixtures. Pigments, e.g. titanium droxide and lampblack, and driers, e.g. cobalt naphtherate may also be present. The aminoplast constituent of the composition may be subject to various modifications. The compositions may be applied to wooden, paper or metal, e.g. steel, surfaces by brushing, spraying, roller coating or dipping, and the films may be cured by heating for short periods at 180 DEG -400 DEG F. Examples 16-23 illustrate the compositions.ALSO:Methylol melamine or etherified methylol melamine condensation products having N,N1-dicyclohexyl melamine and/or N,N1,N11-tricyclohexyl melamine units in the molecule are prepared by heating N,N1-dicyclohexylmelamine and/or N,N1,N11-tricyclohexylmelamine, mine and/or N,N1,N11-tricyclohexylmelamine, alone or together with urea or with a melamine free from such N-substituents or both, and formaldehyde, or a substance which acts as a source of formaldehyde, under aqueous alkaline conditions, and if required etherifying, under acid conditions, with an alkanol having 1-6 carbon atoms. Examples 1-15 describe the preparation of condensation products of this type, in each case etherification with n-butanol or iso-butanol being effected. The above substituted melamine condensation products may be used in conjunction with oil-modified alkyds and organic solvents in coating compositions; alternatively, the aminoplast constituent of the composition may be a mixture of one or more substances which act as a source of N,N1-dicyclohexylmelamine or N,N1,N11-tricyclohexylmelamine units together with an etherified melamine-formaldehyde condensation product which does not contain such units and which has been etherified with an alkanol having not more than six carbon atoms. In the alternative procedure, the source of the units may be N,N1-dicyclohexylmelamine itself, N,N1,N11-tricyclohexylmelamine itself, a mixture thereof or a methylol derivative thereof. The alkyds used in the coating compositions are the reaction products of polyhydric alcohols such as glycols, glycerol, sorbitol and pentaerythritol with polybasic acids or their anhydrides such as phthalic acid or its anhydride, isophthalic acid, maleic acid or its anhydride, fumaric acid, adipic acid and azelaic acid, modified with drying, semi-drying and non-drying oils such as coconut oil, castor oil, dehydrated castor oil, soyabean oil, linseed oil, tung oil or with the acids or partial glycerides derived therefrom. Suitable solvents are hydrocarbons, e.g. xylol and petroleum aliphatic hydrocarbons; alcohols, e.g. butanol; ethers; ketones; esters; and mixtures thereof, e.g. xylol-butanol and aliphatic hydrocarbon-butanol mixtures. Pigments, e.g. titanium dioxide and lampblack and driers, e.g. cobalt naphthenate may also be present. The aminoplast constituent of the coating composition may be subject to various modifications, e.g. (1) an etherified unsubstituted melamine-formaldehyde condensate or an etherified methylol urea condensate may be used in addition to the etherified condensate containing the cyclohexyl units and (2) an aryl sulphonamide may be included with the melamine in making the additional film-former as in (1) or in making the etherified melamine formaldehyde condensate for the alternative procedure. Exemplified coating compositions are to be found in Examples 16-23.