Water-soluble, carboxyl-containing copolymers, the preparation t

Details Water-soluble, carboxyl-containing copolymers, the preparation t Water-soluble, carboxyl-containing copolymers, the preparation t

1996-02-20

1998-05-05

Schofer, Joseph L.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

526332, 526319, 526347, 526348, 210701, C08F22002, C08F22006, C08F21612, C08F21804, C08F21206

Patent

active

057476195

DESCRIPTION:

BRIEF SUMMARY
The invention relates to water-soluble, carboxyl-containing copolymers, to a process for the preparation of the copolymers by polymerization of monoethylenically unsaturated carboxylic acids and other copolymerizable monoethylenically unsaturated monomers in the presence of free-radical polymerization initiators and to the use of the copolymers as scale inhibitor.
U.S. Pat. No. 3,756,257 discloses the use of homopolymers of acrylic acid as scale inhibitor. GB-A-1 411 063 discloses the use of hydrolyzed polymaleic anhydrides in water treatment. Suitable polymers are prepared, for example, by polymerizing maleic anhydride in xylene using benzoyl peroxide as initiator and subsequently hydrolyzing the polymaleic anhydride obtained in this way.
EP-B-0 009 169 discloses a process for the suspension copolymerization of maleic anhydride and C.sub.6 -C.sub.10 -alkenes in excess alkenes as suspending medium. In this case, poly-C.sub.1 -C.sub.20 -alkyl vinyl ethers are used as dispersants.
EP-A-0 260 386 discloses the preparation of olefin-maleic anhydride copolymers in powder form by free-radical polymerization of olefins and maleic anhydride in aromatic solvents in the presence of copolymers of ethylene and vinyl acetate or polystyrene as dispersant.
GB-A-1 454 657 and EP-A-0 261 589 disclose the use of hydrolyzed copolymers of maleic anhydride as scale inhibitor.
According to EP-A-0 276 464, water-soluble copolymers of maleic acid are prepared by copolymerization of maleic anhydride with a maximum of up to 20% by weight of another monoethylenically unsaturated monomer which is copolymerizable therewith in an aromatic hydrocarbon in the presence of peroxy esters as polymerization initiators. The copolymerization can, according to the statements in the application, also be carried out in the presence of protective colloids. After removal of the solvent and hydrolysis of the anhydride groups, the copolymers are used as water-treatment agents for preventing deposition of scale and separation out of water hardness in water-conveying systems.
As disclosed in the abovementioned references, aggregation and deposition of polymers on parts of the polymerization apparatus during the precipitation polymerization is avoided or substantially prevented on use of protective colloids. However, in this case, the copolymers result in more or less coarse form and can often be dissolved completely in water in the form of the salts only with difficulty. In most cases, cloudy salt solutions of the copolymers are obtained. However, when such cloudy solutions are metered with the aid of metering pumps, blockages in the metering pumps occur. Another problem in the use of copolymers of, for example, maleic anhydride and olefins is that aqueous solutions of the copolymers foam greatly on use as scale inhibitor.
It is an object of the present invention to provide novel substances which, for example when used as scale inhibitor, form clear solutions even on dissolving in seawater and which virtually do not foam in seawater desalination by the multistage flash evaporation process.
We have found that this object is achieved by water-soluble, carboxyl-containing copolymers when they comprise -carboxylic acids, their anhydrides and/or their water-soluble salts, C.sub.1 -C.sub.10 -alkyl vinyl ethers and/or vinyl esters of saturated C.sub.1 -C.sub.10 -monocarboxylic acids and C.sub.1 -C.sub.30 -alcohols method of H. Fikentscher on 1% by weight aqueous solutions of the sodium salts of the copolymers at 25.degree. C. and pH 7.5).
The object is additionally achieved by a process for preparing water-soluble copolymers by copolymerization of -carboxylic acids, their anhydrides and/or water-soluble salts, C.sub.1 -C.sub.10 -alkyl vinyl ethers and/or vinyl esters of saturated C.sub.1 -C.sub.10 -monocarboxylic acids and C.sub.1 -C.sub.30 -alcohols
The invention additionally relates to the use of the copolymers described above as scale inhibitor.
The water-soluble copolymers comprise as monomers of group (a) from 30 to 80, preferably 40 to 75, mol % of monoe

REFERENCES:
patent: 3756257 (1973-09-01), Rice et al.
patent: 4872995 (1989-10-01), Chen et al.
patent: 5086142 (1992-02-01), Fock et al.
Abstract of L.

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