It is a well-known problem when abrading soft materials, especially painted surfaces, that the abrasive material becomes clogged with debris from the abraded surface. Harder materials abrade in the form of dust or easily removed discrete particles but softer materials can melt under the conditions of high temperature and pressure generated by the abrasion process to form a discontinuous coating on the abrasive surface. As the coating builds up, the abrasive material rapidly becomes unusable. This phenomenon is known as "loading" and is a particular problem when cellulose-based paints are involved, especially nitrocellulose paints which are commonly used on car bodies.
Various lubricants and surface treatments have been applied to abrasive materials in order to minimise loading problems, for example, as disclosed in U.S. Pat. Nos. 2,050,992, 2,278,158, 2,780,534, 2,882,064, 3,043,673, 3,089,763 and 3,795,496. The most commonly used lubricants are the metal salts of long chain fatty acids as disclosed in U.S. Pat. Nos. 2,768,886 and 2,893,854. The fatty acid metal salts are generally applied in combination with a binder and optional coating additives such as wetting agents, thickeners, defoamers etc., as a dispersion in either aqueous or organic media. Current preference is directed to aqueous formulations, for example, as disclosed in Japanese Patent Application No. 56-69074.
U.S. Pat. No. 3,042,508 discloses metal backed abraders formed by brazing tungsten carbide abrasive particles to a steel substrate with copper brazing metal. The abrasive surface is coated with a sintered layer of a polymer selected from polytetrafluoroethylene, polytrifluorochloroethylene and co-polymers thereof, cured to a hard durable coating by heat treatment, typically in excess of 250.degree. F. The abraders are said to resist loading during use.
U.S. Pat. Nos. 3,779,727 and 3,868,232 disclose the use of poly(tetrafluoroethylene), poly(tetrafluoro ethylene-hexafluoropropylene) and fluorinated graphite as a solid lubricant for addition (in particulate form) to the binder matrix of grinding wheels and the size layer of abrasive belts and discs.
U.S. Pat. No. 3,868,233 discloses the use of poly(tetrafluoroethylene) as a solid lubricant for addition to the central core of cup-type grinding wheels.
U.S. Pat. No. 3,869,834 discloses the use of a surface deposit of poly(tetrafluoroethylene) or poly(trifluorochloroethylene) particles, either loosely or compactly applied, onto the cutting surface of abrasive belts and grinding wheels.
U.S. Pat. No. 4,343,628 discloses the use of poly(tetrafluoroethylene) or a copolymer of poly(tetrafluoroethylene-hexafluoropropylene) as a binder matrix for diamond containing grinding wheels.
U.S. Pat. No. 4,720,941 discloses the use of poly(tetrafluoroethylene) or poly(trifluorochloroethylene) as a binder matrix for abrasive elements such as grinding wheels and cups, abrasive discs, sheets and pads.
Japanese Patent No. 71-032912 discloses the addition of pulverised fluorinated resins such as poly(tetrafluoro ethylene) or a copolymer of poly(tetrafluoroethylene-hexafluoroethylene) to the size or supersize layer of abrasive cloths and paper.
There has now been found an abrasive material having improved anti-loading properties.