Patent GB-1408197-A (GB)
Title: Coating of polyamides
IPC: C08J7/046
Filed: 1972-08-23
Abstract: 1408197 Coating polyamide surfaces HOECHST AG 23 Aug 1972 [3 Sept 1971] 39328/72 Heading B2E A process of coating a polyamide surfaced article comprising applying to at least a part of the poylamide surface a composition comprising (i) a binder consisting of 3 to 20% by wt. of a phenol-formaldehyde resol, 1 to 10% by wt of an amino-formaldehyde resin, 1 to 8% by weight of an epoxide resin and 3 to 15% by weight of a polyvinyl acetal, (ii) a hardener for said binder and (iii) a solvent, wherein the total amount of the four components of the binder is not more than 35% by wt of the coating composition. In Examples, suitable polyamides are hexamethylene diamine adipate, polycaprolactam, the condensation product of omega-aminoundecanoic acid and of octamethylene diamine with sebacic acid. The article may be of polyamide or polyamide and metal, in which case the metal surface may also be coated. The composition may be pigmented and filled. A list of inorganic, Cr, Sr, Ba, Pb, Ca, Mn and Zn compounds being listed as pigments. Other fillers and pigments listed are kaolin, iron red, ultramarine blue, TiO 2  BaSO 4 , asbestos flour, carbon black, phthalocyanin, mica, quartz flour and ground shale. Talc may additionally be present. Suitable phenol-formaldehyde resoles are based on phenol, cresols, or alkyl phenols with up to 12 alkyl carbon atoms; suitable aminoformaldehyde resins include urea, melamine and benzoguanamine resins: suitable epoxide resins include the reaction products of 4, 4'- dihidroxydiphenol methane and/or propane, and epichlorohydrin, aliphatic epoxy resins, e.g. based on cyclobutane derivatives, and the reaction products of epoxy resins with fatty acids such as ricinoleic acid; and suitable polyvinylacetals include polyvinylbutyral and products acetalised with butyraldehyde and other aldehydes which may contain hydroxy and carboxy groups. Hardening agents of the composition are preferably acids and acid esters, examples of which are given. The composition may be applied in solution by spraying, dipping, immersing or brushing. It is stated that the composition adheres well to metals such as iron, steel, copper aluminium and brass. An overcoat may be applied from solution over the composition layer and may comprise (i) a physically drying lacquer such as copolymers of (meth)acrylic esters with monomers such as styrene, (meth)acrylic acid and/or maleic acid or an anhydride thereof, or copolymers of vinyl chloride with vinyl acetate, rubber, chlorinated rubber, chloropropylene, or nitrocellulose, or (2) an oxidatively drying lacquer based on alkyd resins or drying oils, or (3) reaction lacquers such as alkyd amino resins, acid hardening acrylic amino resins, epoxide amino resin, alkyd amino resins, alkyd isocyanate resin and/or acid hardening phenol amino resin combinations or (4) stoving lacquers such as alkyd amino resin combinations, self-cross-linking resins e.g. those based on acrylic or methacrylic acid, hydroxy alkyl esters or (meth) acrylic acid alkylol amides, further acrylic/amino resin combinations, epoxide/phenol resin combinations, or epoxide/ amino resin combinations. A further overcoat may be applied from solution consisting of a pigmented oil/alkyd drying resin.