Calcium phosphonate scale inhibition

Claim 2

A composition comprising at least one primary phosphonate scale inhibitor and at least one secondary copolymer scale inhibitor in the respective weight ratio of from 100:1 to 1:100 said primary scale inhibitor is effective as a threshold inhibition agent against calcium carbonate scale whereas said secondary scale inhibitor is effective as a threshold inhibition agent against calcium phosphonate scale; said primary scale inhibitor is selected from amino phosphonic acids, diphosphonic acids, phosphonotricarboxylic acids polyphosphoric acids, polyol phosphate esters, amino phosphonates, and mixtures thereof; and said secondary scale inhibitor is selected from copolymers containing 40 to 99 weight parts of at least one polymerized monounsaturated monocarboxylic acid containing 3 to 4 carbon atoms with remainder being at least one other copolymerizable monomer.

Claim 3

Composition of claim 1 wherein said acid in said secondary scale inhibitor is selected from acrylic acid, methacrylic acid, and mixtures thereof; said copolymerizable monomer is selected from at least one comonomer selected from substituted and unsubstituted acrylamides, substituted and unsubstituted alkyl acrylates and methacrylates, alkoxyalkyl acrylates and methacrylates, acrylamido alkane sulfonic acids and salts thereof, acrylamido alkane carboxylic acids and salts thereof, hydroxyalkyl acrylates and methacrylates, allyloxy hydroxy alkane sulfonic acids and salts thereof, alkyl itaconates, styrene sulfonic acids and salts thereof, maleic acid as well as maleic anhydride and salts of maleic acid, and mixtures of said comonomers.

Claim 4

Composition of claim 2 wherein the weight ratio of said primary scale inhibitor to said secondary scale inhibitor is from 5:1 to 1:5; wherein said primary scale inhibitor is 1-hydroxyethane-­1,1-diphosphonic acid; and wherein said secondary scale inhibitor is selected from copolymers of an acid selected from acrylic acid, methacrylic acid and mixtures of such acids, and at least one comonomer selected from substituted acrylamides containing substituents on the nitrogen atom selected from isopropyl, t-butyl, methyl, and mixtures thereof, alkoxyalkyl acrylates wherein said alkyl group contains 1 to 6 carbon atoms and said alkoxy groups also contains 1 to 6 carbon atoms, and acrylamidoalkane sulfonic acids wherein said alkane group contains 1 to 4 carbon atoms.

Claim 5

Method for inhibiting precipitation of calcium phosphonate scale by means of threshold inhibition comprising adding to an aqueous medium at least an effective amount of at least one primary phosphonate scale inhibitor and at least an effective amount of at least one secondary copolymer scale inhibitor in the relative weight ratio of from 100:1 to 1:100, said aqueous medium containing calcium and carbonate ions whereby said primary scale inhibitor is effective in inhibiting precipitation of calcium carbonate scale and whereby said primary scale inhibitor has the capacity to form water-insoluble calcium phosphonate scale, precipitation of which is inhibited by said secondary scale inhibitor.

Claim 6

Method for inhibiting precipitation of calcium phosphonate scale by means of threshold inhibition comprising adding to an aqueous medium at least an effective amount of at least one primary phosphonate scale inhibitor and at least an effective amount of at least one secondary copolymer scale inhibitor in the relative weight ratio of from 100:1 to 1:100, said aqueous medium containing calcium and carbonate ions whereby said primary scale inhibitor is effective in inhibiting precipitation of calcium carbonate scale and whereby said primary scale inhibitor has the capacity to form water-insoluble calcium phosphonate scale, precipitation of which is inhibited by said secondary scale inhibitor.

Claim 7

Method of claim 4 wherein the weight ratio of said primary scale inhibitor to said secondary scale inhibitor to said secondary scale inhibitor is from 5:1 to 1:5; wherein said primary and said secondary scale inhibitors are soluble in water at least to the extent of up to about 20% solids; wherein amount of said secondary scale inhibitor is 0.1 to 50 ppm; wherein said primary scale inhibitor is selected from amino phosphonic acids, diphosphonic acids, phosphonotricarboxylic acids, polyphosphoric acids, polyol phosphate esters, amino phosphonates, and mixtures thereof; and wherein said secondary scale inhibitor is selected from copolymers containing 50 to 95 weight parts of at least one polymerized monounsaturated monocarboxylic acid containing 3 to 4 carbon atoms with remainder being at least one copolymerizable monomer selected from substituted acrylamides, alkoxyalkyl acrylates and methacrylates, alkyl acrylates and methacrylates, acrylamido alkane sulfonic acids, acrylamido alkane carboxylic acids, hydroxyalkyl acrylates and methacrylates, allyloxy hydroxyalkanesulfonic acids, alkyl itaconates, and mixtures thereof.

Claim 8

Method of claim 5 wherein said amino phosphonic acids are defined as follows: wherein R³ and R⁴ are individually selected from hydrogen and organic radicals, R¹ and R² are individually selected from hydrogen, organic radicals, and alkylene phosphonic radicals; said diphosphonic acids are defined as follows: wherein R is selected from alkyl radicals of 1 to 5 carbon atoms; said phosphonotricarboxylic acids are defined as follows: where R is selected from hydrogen, alkyl groups of 1 to 5 carbon atoms, and carboxyl groups and R¹ is selected from hydrogen and methyl groups; said polyphosphoric acids are selected from pyrophosphates, metaphosphates, and complex phosphates; said polyol phosphate esters contain at least one 2-hydroxyethyl group and at least one of the following groups: and said amino phosphonates are defined as follows: and R¹ is R or -CH₂-CH₂-OH and R² is R, - CH₂-CH₂-OH or where M is hydrogen, ammonium, alkali metal or a combination thereof, and n is 1 to 6; and wherein said primary scale inhibitor also includes water soluble salts of said amino phosphonic acids, diphosphonic acids, phosphonotricarboxylic acids, polyphosphoric acids, polyol phosphonate esters, amino phosphonates, and mixtures thereof.

Claim 9

Method of claim 6 wherein said alkyl acrylates contain 1 to 12 carbon atoms; substituted acrylamide monomers are defined as follows: where R¹ is selected from hydrogen and methyl, and R² and R³ are individually selected from hydrogen, alkyl and substituted alkyl groups with each alkyl or substituted alkyl group containing a total of 1 to 8 carbon atoms, provided that both R² and R³ are not hydrogens, substituents on the R² and R³ groups being selected from alkyl, aryl, carboxylic acid, and keto groups; said alkoxyalkyl acrylates are defined as follows: where R is hydrogen, R¹ and R² are individually selected from alkyl groups of 1 to 6 carbon atoms, and n is a number from 1 to 6; said acrylamido sulfonic acids are defined as follows: where R is selected from hydrogen and methyl and R¹ and R² are individually selected from H or alkyl groups containing 1 to 4 carbon atoms; said hydroxyalkyl acrylates are characterized by the presence of the following repeating units: where R is selected from hydrogen and alkyl groups of 1 to 3 carbon atoms; R² is selected from alkyl groups of 2 to 6 carbon atoms; and said alkyl itaconates are defined as follows: where R² and R³ are individually selected from hydrogen and alkyl groups of 1 to 12 carbon atoms provided that at least R² or R³ is an alkyl group.

Claim 10

Method of claim 7 wherein said secondary scale inhibitors have molecular weight in the range of 1,000 to 50,000 and are selected from substituted acrylamides wherein R² and R³ are individually selected from unsubstituted alkyl groups of 2 to 6 carbon atoms and substituted alkyl groups of 1 to 8 carbon atoms containing a carboxylic acid or a keto substituent group; alkoxy alkyl acrylates where R¹ and R² are individually selected from alkyl groups of 2 to 4 carbon atoms and n is 2 to 4; acrylamido alkane sulfonic acids where R is hydrogen and R¹ and R² are individually selected from alkyl groups of 1 to 2 carbon atoms; and hydroxyalkyl acrylates where R is selected from hydrogen and alkyl groups of 1 to 3 carbon atoms, and R¹ is selected from alkyl groups of 2 to 6 carbon atoms.

Claim 11

Method for inhibiting precipitation of calcium phosphonate scale by means of threshold inhibition comprising adding to an aqueous medium at least an effective amount of at least one primary phosphonate scale inhibitor and at least an effective amount of at least one secondary copolymer scale inhibitor in the relative weight ratio of from 100:1 to 1:100, said aqueous medium containing calcium and carbonate ions, said primary scale inhibitor is effective in inhibiting precipitation of calcium carbonate scale and said primary scale inhibitor has the capacity to form water-insoluble calcium phosphonate scale, precipitation of which is inhibited by said secondary scale inhibitor; wherein said secondary scale inhibitor is selected from copolymers of a carboxylic acid and a copolymerizable monomer, said acid selected from acrylic acid, methacrylic acid, and mixtures thereof; and wherein said copolymerizable monomer is selected from at least one comonomer selected from substituted acrylamides, alkyl acrylates and methacrylates, alkoxyalkyl acrylates and methacrylates, acrylamido alkane sulfonic acids, acrylamido alkane carboxylic acids, hydroxyalkyl acrylates and methacrylates, allyloxyhydroxyalkanesulfonic acids, alkyl itaconates, and mixtures thereof, provided that said copolymers containing acrylamidoalkane sulfonic acid are composed of at least three comonomers.

Claim 12

Method for inhibiting precipitation of calcium phosphonate scale by means of threshold inhibition comprising adding to an aqueous medium at least an effective amount of at least one primary phosphonate scale inhibitor and at least an effective amount of at least one secondary copolymer scale inhibitor in the relative weight ratio of from 100:1 to 1:100, said aqueous medium containing calcium and carbonate ions, said primary scale inhibitor is effective in inhibiting precipitation of calcium carbonate scale and said primary scale inhibitor has the capacity to form water-insoluble calcium phosphonate scale, precipitation of which is inhibited by said secondary scale inhibitor; wherein said secondary scale inhibitor is selected from copolymers of a carboxylic acid and a copolymerizable monomer, said acid selected from acrylic acid, methacrylic acid, and mixtures thereof; and wherein said copolymerizable monomer is selected from at least one comonomer selected from substituted acrylamides, alkyl acrylates and methacrylates, alkoxyalkyl acrylates and methacrylates, acrylamido alkane sulfonic acids, acrylamido alkane carboxylic acids, hydroxyalkyl acrylates and methacrylates, allyloxyhydroxyalkanesulfonic acids, alkyl itaconates, and mixtures thereof, provided that said copolymers containing acrylamidoalkane sulfonic acid are composed of at least three comonomers.

Claim 13

Method of claim 9 wherein the weight ratio of said primary scale inhibitor to said secondary scale inhibitor is from 5:1 to 1:5; wherein said primary and said secondary scale inhibitors are soluble in water at least to the extent of up to about 20% solids; wherein said primary scale inhibitor is selected from aminotri(methylene phosphonic acid), hexamethylene-diamine tetra(methylene phosphonic acid), hydroxyalkane-­1,1-diphosphonic acids containing 1 to 5 carbon atoms in the alkane group, phosphonoalkane tricarboxylic acids containing 2 to 6 carbon atoms in the alkane groups, glycerine phosphate esters, water-soluble salts of said primary scale inhibitors, and mixtures thereof; wherein said secondary scale inhibitor consists essentially of a copolymer of an acid and at least one principal comonomer, said acid is selected from acrylic acid, methacrylic acid, and mixtures thereof wherein amount of acrylic acid predominates and said comonomer is selected from substituted acrylamides wherein one or both of the substituent groups are selected from methyl, isopropyl, t-butyl and isobutyl radicals; 2-(2-ethoxyethoxy)ethyl acrylate; 2-acrylamido-2-methylpropane sulfonic acid; and 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate; and water-soluble salts thereof; wherein said secondary scale inhibitor contains 50 to 95 weight parts of said polymerized acid or a mixture thereof; wherein amount of said secondary scale inhibitor is 0.1 to 50 ppm; and wherein said aqueous medium is selected from recirculating cooling water and desalination water.