GB1459843A - Contact adhesive - Google Patents

Abstract

1459843 Aqueous phenolic resin dispersion/ acrylate latex contact adhesives UNION CARBIDE CORP 29 April 1974 [30 April 1973] 18730/74 Headings C3R and C3P A contact adhesive composition comprises an aqueous mixed dispersion containing: (a) an alkyl acrylate polymer resin latex having a second order transition temperature not greater than 30‹ C.; and (b) an aqueous phenolic resole dispersion having a weight average M.Wt. of from 200 to 3000 and comprising either: (i) a first resole formed by the alkaline condensation of an aldehyde and a phenol and which is employed in the dispersion as solid particles suspended in water, substantially all of which have diameters of less than 60 microns; or (ii) a second resole comprising the alkaline condensed reaction product of formaldehyde and a difunctional phenol and having a labile formaldehyde content of from 0 to 12% wt., based on the weight of the second resole and wherein the second resole is employed in the dispersion as a solution in a water-immiscible organic solvent. The acrylate polymer preferably comprises at least 25% wt. of units derived from alkyl acrylates; and preferably has a mean average ultimate elongation of at least 500%. The first resole dispersion may be prepared by condensing at least one phenol selected from phenol itself, trifunctional monohydric mono- or dimeta-substituted C 1 -C 9 alkyl or alkoxy, or halo-phenols, and bisphenols with formaldehyde or furfural in the presence of an alkaline catalyst and optionally a mixture of gum arabic and at least one polysaccharide gum having mannose and galactose units or D-mannuronic and L-guluronic acid units. The second resole dispersion may be prepared by reacting a para-substituted phenol preferably a para-C 1 -C 12 alkyl-phenol with formaldehyde in the presence of an alkaline catalyst and emulsifying the resole formed with up to 50% wt. of a water-immiscible solvent e.g. an aromatic or aliphatic hydrocarbon, before adding it to water to form the dispersion optionally in the presence of an emulsifier such as an alkali metal salt of a C 12 -C 24 aliphatic fatty acid alone or together with the corresponding amine or ammonium salt or with casein, ammoniated casein and various gums. The composition preferably comprises 5-45 wt. per cent phenolic resin solids and 95-55 wt. per cent acrylate resin solids, based on the combined weight of the resins and optionally up to 50 wt. per cent of a filler or pigment determined on a solids basis of the total formulation. In the examples adhesives are prepared from (1) either (i) a latex copolymer of ethyl acrylate, acrylonitrile, acrylic acid and N-methylol acrylamide alone or in admixture with an acrylate latex copolymer (B) of vinyl acetate and isobutyl acrylate, or (ii) an acrylate latex prepared by adding an aqueous dispersion of a copolymer of ethylene and acrylic acid partially neutralized with N,N-dimethylolethanolamine to an acrylate copolymer latex of ethyl acrylate, methyl methacrylate and methacrylic acid and then heating, alone or in admixture with acrylate latex (B), and (2) either (i) a bisphenol-AHCHO resin aqueous dispersion prepared in presence of gum arabic and "Jaguar" (R.T.M.) gum, or (ii) a phenol-HCHO resin aqueous dispersion prepared in the presence of gum arabic and either guar gum or a gum comprising galactose units, or (iii) an aqueous dispersion of either p-tert-butylphenol-HCHO resin having a labile HCHO content of 6À3% wt., or an aqueous phenol-cresol-HCHO dispersion each containing oleic acid, NaOH, ammoniated casein, gum arabic and an organic solvent.