GB1242658A - Adhesive films - Google Patents

Abstract

1,242,658. Honeycomb laminates. CHISSO CORP. 1 July, 1969 [19 July, 1968; 22 Oct., 1968], No. 33092/69. Heading B5N. [Also in Divisions B2 and C3] An adhesive film, suitable for use in the manufacture of honeycomb sandwich structures, is produced by impregnating a porous web substrate, e.g. a glass fibre fabric, paper, cloth or mat of synthetic fibres, non-woven fabric, victorian lawn or gauze, with a resin solution containing a phenol-formaldehyde resin and polyethylene glycol and/or polypropylene glycol, coating at least one surface of the impregnated substrate with a powdered thermoplastic resin and then drying at a temperature below the curing temperature of the phenol-formaldehyde resin, e.g. at below 80‹ C. for 2-3 minutes. The polyethylene glycol or polypropylene glycol, which may be used in an amount of 1-100 parts per 100 parts by weight of phenol formaldehyde resin, may have a molecular weight of 200-4000. The solvent used in the resin solution may be methanol, ethanol, chloroform, acetone, benzene or dichloroethane. The resin solution may also contain an acid hardening catalyst for the phenol-formaldehyde resin, e.g. toluene, xylene or benzene sulphonic acid, in an amount of 1-10 parts per 100 parts by weight of the mixture of phenol-formaldehyde resin and polyethylene glycol and/or polypropylene glycol, and sufficient of an alkaline substance, e.g. sodium or potassium hydroxide or an amine, to adjust the pH of the solution to 3-6. The thermoplastic resin which may have a particle size of less than 42 (Tyler) mesh may be polyvinyl formal, acetal, butyral, isobutyral, acetate or alcohol, and may be used in an amount of at least 40 parts per 100 parts by weight of the mixture of phenol-formaldehyde resin and polyethylene glycol and/or polypropylene glycol. The adhesive film may be covered for storage with strippable films or sheets, e.g. polyolefin films, regenerated cellulose films or release papers. Honeycomb sandwich structures may be produced by placing the adhesive films between the honeycomb core which may be of paper and surface sheets, e.g. of aluminium, and then applying heat and pressure.