Process for the manufacture of finely divided insoluble and infusible solids of large surface area

摘要

Finely-divided, insoluble, infusible solid substances having a specific surface area greater than 10 square metres per gram are obtained by forming from an aqueous solution of melamine and formaldehyde in a molar ratio of 1 to 1.5-6 at a pH of 0-6 and a temperature of 0-140 DEG C. in the presence of one or more surface-active substances a solid phase, which is freed from inorganic salts, dried at 30-160 DEG C., and comminuted to an average particle size of less than 5m . The solid phase is preferably formed from a precondensate prepared at a pH of 5-10, in the presence of a buffer substance, e.g. potassium hydrogen phthalate, an ammonium or monoethanolamine phosphate or a neutral ammonium tartrate, and one or more surface-active substances, e.g. quaternary ammonium salts, fatty alcohol sulphonates, alkylarylsulphonates, salts of sulphosuccinic acid esters, monoglyceride sulphates or polyalkylene ethers or tragacanth. The dehydration may be by spray-drying, or, preferably, by azeotropic distillation using a hydrocarbon or halohydrocarbon boiling at 30-160 DEG C., e.g. benzene, toluene, xylene, methylene, chloride, chloroform, carbon tetrachloride, 1,2-dichlorethane or trichlorethylene. The comminution may be by ball mill, roller mill, hammer mill or air jet mill, or may be performed as a wet grinding operation before, e.g. spray-drying. The powder may be used as a filler or reinforcing agent for rubber or synthetic resins. In Examples 18 and 24 rubber is milled with ZnO, S, stearic acid, a vulcanization accelerator and a powder of the invention (and in Example 24 with a plasticizer and diethylene glycol also). In Examples 25 and 26 a P.V.C. resin is milled with dioctyl phthalate, Ba and Cd laurates and a powder of the invention, then gelled to give a foil. In Example 27 mat rayon fibres are prepared from a dope into which has been incorporated a suspension of 1m particles of the invention. These powders may also be used as vehicles and bases for pesticide and cosmetic powders and pastes, as supports for ion exchange resins, and as fillers for paper.