Coated abrasive having brittle agglomerates of abrasive grain and a process of producing the latter

A coated abrasive product has abrasive grits secured to a flexible backing by maker and size coats, each abrasive grit consisting essentially of an agglomerate (10) of fine abrasive grains (12) having an average diameter less ihan about 200 microns and an inorganic, brittle, matrix (14). The weight percent of the matrix (14) in each agglomerate (10) is over 35% of the total weight of the agglomerate (10), and the agglomerates (10) are sufficiently fragile so that they can be broken down by rubbing between the thumb and forefinger. The agglomerates (10) are essentially free of microporosity, so that the matrix (14) has a relatively high thermal capacity and a relatively high thermal conductivity. The agglomerates (10) have an irregular surface permitting a bond to the maker and size coats which is stronger than the crush strength of the agglomerates (10) to permit gradual wearing down of the agglomerates (10) during grinding by gradual removal of dulled abrasive grains (12) from the agglomerates (10). A process of preparing agglomerates (10) consists in mixing a fusible inorganic salt and finely divided abrasive grains (12), fusing said inorganic salt, freezing said salt and crushing the resultant mixture to agglomerates (10). Another process of preparing agglomerates (10) consists in mixing a solution of a "polymeric" inorganic salt with finely divided abrasive grains (12), casting said inorganic salt and abrasive mixture in a thin layer, heating the layer to drive off water, hardening the layer and crushing the resultant hardened layer to agglomerates (10).