GB1267198A - - Google Patents

Abstract

1,267,198. Seaming. W. R. GRACE & CO. 27 May, 1969 [29 May, 1968], No. 25754/68. Heading B5K. [Also in Divisions B8 and C3] A method of effecting adhesion between two articles, such as a bottle and closure both made of plastics, comprises interposing between them, and in contact with a surface of each, a thermally activatable adhesive composition, made for instance of a thermoplastics hot melt or a thermosetting synthetic resin, plasticized or unplasticized, and containing carbon particles, and subjecting the assembly of articles to be bonded to the action of a high-frequency magnetic field until the adhesive composition has been heated sufficiently to become activated. The carbon particles, of average size of 1 mm. diameter, may be amorphous carbon, e.g. carbon black, graphite, or a coating on an inert, electrically non-conducting, support such as glass beads the ratio of carbon to adhesive being in the range of from 5:95 to 80:20, and the adhesive being chosen which has an affinity for the surfaces being joined. The magnetic field frequency is in the range of from 0À5-100 megacycles/second and preferably between 15 and 30 mc/s., the power being from 0À1-30 kw. and preferably 2À5 kw. Examples given of thermoplastic adhesive materials are olefin polymers such as polyethylene, polypropylene, ethylene/propylene copolymers, and polystyrene, and vinyl polymers. Examples of hot melt compositions include high molecular weight linear polyamides. Thermosetting resin compositions include cross-linking polyesters, phenol-formaldehyde, urea-formaldehyde, and melamine-formaldehyde resins. As shown, the assembly to be bonded is supported on a carriage 6 to extend into a work coil 4 which is cooled by a closed circuit, distilled water, cooling system 5 and which is supplied with a highfrequency magnetic field of 27À12 mc/s. at 5 kw. by a generator 1 controlled by an electrically operated timing device, not shown.