| abstract |
Copolymers which are substantially completely soluble in water at the low concentration in which they are used to treat process water, include copolymers of acrylic acid ("AA") or methacrylic acid ("MAA") and salts thereof (together referred to herein as "(meth)acrylic acid", and for brevity as "(M)AA"), and a lower alkenyl carboxylate ("LAC") such as vinyl acetate or propionate, optionally together with a salt of a lower alkenyl sulfonate ("SLAS"). Typical copolymers are those of (M)AA and vinyl acetate ("VOAc") present in a molar ratio in the range from 95:5 to about 60:40; and those of (M)AA, VOAc and sodium vinyl sulfonate ("SVS") in a molar ratio in the range from 95:4.9:0.1 to about 50:25:25. If desired, the foregoing copolymers may be hydrolyzed for use as their hydrolyzates, or the copolymers may be at least partially hydrolyzed, prior to or, during use as for example when used in alkaline boiler water systems. The compositions are useful to inhibit the deposition of particulate matter in mud suspended in the process water, and also of scale due to salts dissolved in various process water streams, particularly in boiler water and cooling water. The compositions are therefore not only excellent dispersants but also exhibit unexpected threshold and sequestering effects. They are conventionally formed and have a relatively low molecular weight, preferably in the range from about 1000 to about 25,000. The molar ratio of the reactants is such that (M)AA is always present in a molar amount which is at least 50 mole percent relative to the remaining constituent(s) of the copolymer. |