GB724683A - Improvements in or relating to a boiler water treating composition - Google Patents

Abstract

A boiler-water treating composition comprises from 0.5 to 50 per cent by weight of a water-soluble salt of a polyacrylic acid and from 50 to 99.5 per cent of one or more water-softening agents selected from alkali metal carbonates, bicarbonates, orthophosphates and polyphosphates. Polyacrylic acids of a molecular weight ranging from 1000 to 80,000 may be used. The preferred salts are alkali metal and ammonium, of a molecular weight such thas a water solution of 25 per cent polymer solidt content has a viscosity at 78 DEG C. of at least 750 and preferably between 1000 and 10,000 centipoises. A solution of the acid may be neutralized with the hydroxide of the desired radical, the resulting solution being combined with the water softening agent directly or the salt being first isolated. The acid solution may be treated with a large excess of, for example, sodium carbonate, the excess of the latter above that required to neutralize the acid constituting the water-softening constituent of the resulting liquid water-treating composition. Preferred concentrations of the polyacrylate based on total weight of composition lie in the range 2 to 5 per cent. In use the optimum concentration is such as to provide from 0.25 to 5.0 parts per million parts of feed water. Example: 4 per cent sodium polyacrylate plus 96 per cent soda ash; saturated trisodium phosphate solution containing 0.5 per cent sodium polyacrylate; 10 per cent sodium polyacrylate plus 20 per cent trisodium phosphate plus 70 per cent soda ash.ALSO:A boiler-water treating composition comprises from 0.5 to 50 per cent by weight of a water-soluble salt of a polyacrylic acid and from 50 to 99.5 per cent of one or more water-softening agents selected from alkali metal carbonates, bicarbonates, orthophosphates and polyphosphates. Polyacrylic acids of a moleular weight ranging from 1,000 to 80,000 may be used. The preferred salts are alkali metal and ammonium, of a molecular weight such that a water solution of 25 per cent polymer solids content has a viscosity at 78 DEG C. of at least 750 and preferably between 1,000 and 10,000 centipoises. A solution of the acid may be neutralised with the hydroxide of the desired radical, the resulting solution being combined with the water softening agent directly or the salt being first isolated. The acid solution may be treated with a large excess of, for example, sodium carbonate, the excess of the latter above that required to neutralise the acid constituting the water-softening constituent of the resulting liquid water-treating composition. Preferred concentrations of the polyacrylate based on total weight of composition lie in the range 2 to 5 per cent. In use the optimum concentration is such as to provide from 0.25 to 5.0 parts per million parts of feed water. Examples: 4 per cent sodium polyacrylate plus 96 per cent soda ash; saturated trisodium phosphate solution containing 0.5 per cent sodium polyacrylate; 10 per cent sodium polyacrylate plus 20 per cent trisodium phosphate plus 70 per cent soda ash.