GB597144A - Improvements in or relating to synthetic resinous adhesive compositions - Google Patents

Abstract

A resinous binder for bonding wood, laminated plastics and metal plates, comprises from 10 to 100 parts by weight of a soluble partial reaction product of 1 mol. of a polyhydroxybenzene having at least two hydroxyl groups in the 1-, 3-, 5-positions and from 1 to 1.17 mols. of formaldehyde in the form of a solid polymer, combined with 100 parts by weight of a vinyl thermoplastic resin. The partial reaction product is prepared by refluxing the polyhydroxybenzene and solid polymer of formaldehyde in substantially anhydrous methanol or ethanol in the presence of a catalyst in an amount of less than 1 per cent of the weight of the polyhydroxybenzene, the catalyst being neutralized after the reaction. The vinyl resin may be vinyl acetate, vinyl acetate-butyrate, polyvinyl alcohols, particularly those produced from a vinyl ester hydrolysed less than 50 per cent, polyvinyl formal, polyvinyl acetal, polyvinyl butyral and simple substituted vinyls such as acrylates, methyl- and propyl-methacrylates. Suitable polyhydroxybenzenes are resorcinol and phloroglucinol, 1,3-polyhydroxybenzenes with one methyl, ethyl or other group attached to the benzene ring. The catalyst may be a mineral acid, a strongly acid-reacting salt, such as ferric chloride or a basic substance. In the preparation of the phenol-formaldehyde resin, resorcinol, paraformaldehyde, anhydrous methyl or ethyl alcohol and hydrochloric acid are heated at about the reflux temperature of the alcohol until a clear viscous resin results, when the viscosity is adjusted by the addition of alcohol and the acid catalyst neutralized with alkali. In the examples: (1) a resorcinol resin solution in methanol having a 60 per cent solids content was mixed with polyvinylacetate of medium molecular weight dissolved in acetone; (2) a similar resin solution was combined with a high molecular weight polyvinyl acetate in acetone, in (3) low molecular weight polyvinyl acetate dissolved in benzene/ethanol solution was mixed with a 60 per cent solid content resorcinol formaldehyde resin in ethanol. Up to 10 per cent of a basic hardening catalyst such as ammonium hydroxide, ethylene diamine and hexamethylenetetramine can be added to the above compositions. In example (4) 15 per cent hydrolysed polyvinylacetate of medium molecular weight dissolved in a mixture of equal parts of acetone and ethyl acetate to yield a 20 per cent solution was combined with a 50 per cent resorcinol-formaldehyde resin solution in ethanol. In the Specification as open to inspection under Sect. 91, acetaldehyde or butyraldehyde may be used in the condensation in place of formaldehyde. This subject-matter does not appear in the Specification as accepted.