Calcium carbonate scale inhibitor having organophosphonate, water soluble acrylic or maleic copolymer and citric acid

Claim 1

An inhibitor of the formation of scale in an aqueous system, comprising; (a) an organophosphonic acid- or salt thereof having a scale inhibiting property, said organophosphonic acid being selected from the group consisting of 2-phosphonobutane-1,2,4-tricarboxylic acid, 1-hydroxyethylidene-1,1-diphosphonic acid and aminomethylenephosphonic acid; (b) a water soluble copolymer comprising: (1) at least two different vinyl monomers each having a carboxyl group represented by formula (I): ##STR4## where R 1 represents a hydrogen atom or a methyl group; R 2 represents a hydrogen atom, a methyl group, a second carboxyl group, or said second carboxyl group together with said carboxyl group forming a maleic acid anhydride ring; or (2) by at least a combination of the vinyl monomer (I) and a vinyl monomer having another polar group represented by the formula (II): ##STR5## where R 3 represents a hydrogen atom or a methyl group; R 4 represents --COOR 5 SO 3 H: --COOR 5 OH, --CONHR 5 SO 3 H, --CONHR 2 OH, --R 5 SO 3 H, --C 6 H 4 --SO 3 H or --R 5 O(R 6 O) n H, wherein R 5 represents a C 1-4 alkylene group, R 6 represents a C 1-3 alkylene group, and n represents an integer between 0 to 100; wherein said carboxyl group containing monomer is contained in an amount of at least 30 mol % in said water-soluble copolymer; and wherein an average molecular weight of said water-soluble copolymer (b) is between about 500 to about 100,000; and (c) citric acid or a salt thereof; wherein a blending ratio by weight of said water-soluble copolymer component (b) to said organophosphonic acid component (a) is 0.4-20:1, and a blending ratio of said citric acid component (c) to said water-soluble copolymer component (a) and said organophosphonic acid component (b) together is 0.3-3.0:1.