GB617333A - Improvements in or relating to abrasive articles and methods of producing the same - Google Patents

Abstract

617,333. Flexible abrasive articles. MINNESOTA MINING & MANUFACTURING CO. Oct. 4, 1945, No. 25797. Convention date, Feb. 24, 1942. [Class 60] [Also in Group XI] A flexible abrasive article is made by applying a layer of abrasive particles upon a backing such as paper, vulcanised fibre, or cloth coated with a thermosetting resin, and curing the resin by heat induced therein by a highfrequency alternating electric field, the heating being controlled so that the temperature of the abrasive particles does not exceed that of the resin. Alternatively, heat may be induced by a high-frequency alternating electric field in a thermosetting resinous sand-sizing adhesive applied over the abrasive particles, which are secured to the backing by a similar or different adhesive, e.g. a protein such as glue, casein, or soya bean meal. The thermosetting resin may be a phenol-, urea-, thiourea-, or melamine-aldehyde resin or an alkyd resin. The thermosetting resin may be partly set, e.g. by external heat, before exposure to the high-frequency field. Ranges of frequency are specified for use with silicon carbide and aluminium oxide abrasive grains. The abrasive particles may be coated with graphite or powdered metal, or the resin may contain, as a filler, silica, graphite, or metal in finely-divided form, to alter its electrical properties. The abrasive-coated web W, Fig. 2, may be caused to travel between bare or insulated, flat metal plate electrodes 5 and 6 which are connected to a source of high frequency alternating potential. The lines of force may be set up in and parallel to the plane of the travelling web, by having strip electrodes positioned close to its longitudinal edges, or by passing the web over spaced tubular electrodes 9, 10, Fig. 6, electrodes 9 being connected to one terminal and electrodes 10 to the other terminal of a source of high-frequency potential. The abrasive-coated web, after a preliminary incomplete cure by external heat, may be subjected to the high-frequency field as a coiled-up roll. As shown in Fig. 9 the abrasive coated material W is wound up on a metal drum 11 serving as one electrode, and is covered by an outer metal sleeve 12 serving as the other electrode. Alternatively the web W, Fig. 10, may be wound on a non-conducting core 13, and placed between flat electrodes 14 and 15 which may be bare or insulated. The roll W may be wrapped in a blanket of heat-insulating material.