US 5,516,432 AGranted

Method for prevention of scale formation in aqueous systems

AssigneeRohm and Haas Company

InventorsKathleen J. King, William M. Hann, Barry Weinstein

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Abstract

A process for stabilizing aqueous systems containing scale-forming salts by adding to such systems an effective amount of selected low molecular weight water-soluble polymers containing from 30 to 60 weight percent unsaturated sulfonic acid units, from 35 to 65 weight percent carboxylic acid units and optionally up to 10 weight percent of one or more units selected from non-ionizable monomers, is provided. The polymers used in the process provide improved phosphate and iron stabilization at high temperature conditions. A polymer composition based on 50/50 weight/weight 2-acrylamido-2-methyl-1-propanesulfonic acid/acrylic acid is particularly preferred for use at high temperatures, for example, from 80.degree. to 100.degree. C.

Claims16

Dependent claims

A method for stabilizing an aqueous system by inhibiting the precipitation of phosphate salts comprising adding to the aqueous system an effective amount of a water-soluble polymer comprising monomer units of:

(a) from 40 to 60 percent by weight of an unsaturated sulfonic acid selected from one or more of 2-acrylamido-2-methyl-1-propanesulfonic acid, 2-methacrylamido-2-methyl-1-propanesulfonic acid, 3-methacrylamido-2-hydroxy-1-propanesulfonic acid or salts thereof;
and
(b) from 40 to 60 percent by weight of an unsaturated carboxylic monomer selected from acrylic acid or methacrylic acid or salts thereof;
wherein the weight average molecular weight of the polymer is from about 3,000 to about 7,410;
wherein the aqueous system comprises calcium, iron and phosphate ions in amounts from 100 to 1000 parts per million, zero to 3 parts per million, and 2 to 30 parts per million, respectively, wherein the amounts are parts per million by weight of the aqueous system;
and wherein the aqueous system is maintained at a temperature greater than about 80.degree. C.

3 more elements

(a) from 30 to 60 percent by weight of an unsaturated sulfonic acid selected from one or more of 2-acrylamido-2-methyl-1-propanesulfonic acid, 2-methacrylamido-2-methyl-1-propanesulfonic acid, 3-methacrylamido-2-hydroxy-1-propanesulfonic acid or salts thereof;
(b) from 35 to 65 percent by weight of an unsaturated carboxylic monomer selected from acrylic acid or methacrylic acid or salts thereof;
and
(c) from 5 to 10 percent by weight of an unsaturated non-ionizable monomer selected from one or more of tert-butylacrylamide, tert-octylacrylamide, dimethylacrylamide, acrylamide, acryloyl morpholine, styrene, ethyl acrylate, butyl acrylate, hydroxyethyl methacrylate or hydroxypropyl acrylate;
wherein the weight average molecular weight of the polymer is from about 3,000 to about 12,000;
wherein the aqueous system comprises calcium, iron and phosphate ions in amounts from 100 to 1000 parts per million, zero to 3 parts per million, and 2 to 30 parts per million, respectively, wherein the amounts are parts per million by weight of the aqueous system;
and wherein the aqueous system is maintained at a temperature greater than about 80.degree. C.

4 more elements

Dependencies are inferred from the claim text.