Stabilization of iron in aqueous systems

Claim 3

Method of claim l wherein said aqueous system is a recirculating water system containing at least about l ppm of soluble iron (III).

Claim 4

Method of claim l wherein amount of said copolymer in said aqueous system is about l to 200 ppm and said copolymer is water-soluble and essentially non-crosslinked random copolymer wherein weight ratio of said substituted acrylamides is respectively 50 to 90 weight parts, based on a total of l00 weight parts of comonomers, and said copolymer has molecular weight in the range of 2,000 to 20,000.

Claim 5

Method of claim 3 wherein said acids are selected from acrylic acids, polymerized units of which are defined by the following formula: where m is in the range of about l0 to 700, subject to the molecular weight limitation; R is selected from hydrogen and methyl; X is selected from hydrogen, sodium, potassium, calcium, ammonium, and magnesium; and the substituents on the substituted alkyl groups R² and/or R³ are selected from alkyl, aryl, hydroxyl, hydroxyalkyl, and keto groups.

Claim 6

Method of claim 3 wherein said acid is selected from acrylic acid itself and methacrylic acid; said substituted acrylamides are selected from diacetone acrylamide, N,N-dialkylacrylamides, and N-monoalkylacrylamides containing l to 8 carbons in each alkyl group; and said aqueous system has pH of about 5 and above.

Claim 7

Method of claim 3 wherein said copolymer contains up to about 30 weight parts of one or more other suitable monomers copolymerizable with said acids and said substituted acrylamides, based on l00 weight parts of all monomers.

Claim 8

Method for inhibiting the precipitation of scale-forming salts in an aqueous system containing an alkaline earth metal salt or mixtures thereof, said aqueous system also containing solubilized iron, the method comprising the step of adding to said aqueous system an effective amount of a copolymer of 40 to 95 weight parts of one or more monounsaturated monocarboxylic acids containing 3 to 4 carbon atoms and 5 to 60 weight parts of one or more substituted acrylamides, on the basis of a total of l00 weight parts of all monomers, amount of said copolymer being sufficient to inhibit precipitation of said salts, said copolymer having weight average molecular weight of about l,000 to 50,000 and the polymerized units of said substituted acrylamide are defined by the following formula: where n is in the range of about 0.l to 350, subject to the molecular weight limitation; R¹ is selected from hydrogen and methyl; and R² and R³ are individually selected from hydrogen and substituted and unsubstituted alkyl groups each containing a total of l to 8 carbon atoms, provided that either R² and/or R³ is other than hydrogen.

Claim 9

Method for inhibiting the precipitation of scale-forming salts in an aqueous system containing an alkaline earth metal salt or mixtures thereof, said aqueous system also containing solubilized iron, the method comprising the step of adding to said aqueous system an effective amount of a copolymer of 40 to 95 weight parts of one or more monounsaturated monocarboxylic acids containing 3 to 4 carbon atoms and 5 to 60 weight parts of one or more substituted acrylamides, on the basis of a total of l00 weight parts of all monomers, amount of said copolymer being sufficient to inhibit precipitation of said salts, said copolymer having weight average molecular weight of about l,000 to 50,000 and the polymerized units of said substituted acrylamide are defined by the following formula: where n is in the range of about 0.l to 350, subject to the molecular weight limitation; R¹ is selected from hydrogen and methyl; and R² and R³ are individually selected from hydrogen and substituted and unsubstituted alkyl groups each containing a total of l to 8 carbon atoms, provided that either R² and/or R³ is other than hydrogen.

Claim 10

Method of claim 7 wherein the aqueous system is a recirculating water system containing at least about l ppm of soluble iron (III), amount of said copolymer in said aqueous system is about l to 200 ppm, said copolymer is water soluble and essentially non-crosslinked random copolymer wherein weight ratio of said acids to said substituted acrylamides is respectively 50 to 90 weight parts to l0 to 50 weight parts, and said copolymer has molecular weight in the range of 2,000 to 20,000.

Claim 11

Method of claim 7 wherein said acids are selected from acrylic acids, polymerized units of which are defined by the following formula: where m is in the range of about l0 to 700, subject to the molecular weight limitation; R is selected from hydrogen and methyl; X is selected from hydrogen, sodium, potassium, calcium, ammonium, and magnesium; the substituents on the substituted alkyl groups R² and/or R³ are selected from alkyl, aryl, hydroxyl, hydroxyalkyl and keto groups; and wherein said copolymer contains up to about 30 weight parts of one or more other suitable monomers copolymerizable with said acids and said substituted acrylamides, based on l00 weight parts of all monomers to be polymerized.

Claim 12

l0. Method of claim 9 wherein said acids are selected from acrylic acid itself and methacrylic acid; said substituted acrylamides are selected from diacetone acrylamide, N,N-dialkylacrylamides, and N-monoalkylacrylamides containing l to 8 carbons in each alkyl group; and said aqueous system is at pH of about 5 and above and contains l to 5 ppm of solubilized iron (III) as well as scales selected from the group consisting of calcium carbonate, calcium phosphate, calcium sulfate, magnesium hydroxide, and mixtures thereof.

Claim 13

Method of claim 7 wherein said copolymer is selected from an 80/20 copolymer of acrylic acid and t-butyl acrylamide, and an 60/20/20 copolymer of acrylic acid, t-butyl acrylamide, and methacrylic acid, on weight basis.

Claim 14

Method of claim 9 wherein said copolymer is water-soluble and essentially non-crosslinked random copolymer wherein weight ratio of said substituted acrylamide is respectively 50 to 90 weight parts, based on a total of l00 weight parts of comonomers.