WO1992010433A1

WO1992010433A1 - Use of water-soluble natural graft polymers as water-treatment agents

Info

Publication number: WO1992010433A1
Application number: PCT/EP1991/002225
Authority: WO
Inventors: Walter Denzinger; Heinrich Hartmann; Charalampos Grousetis; Karl-Heinz Buechner
Original assignee: Basf Aktiengesellschaft
Priority date: 1990-12-06
Filing date: 1991-11-26
Publication date: 1992-06-25
Also published as: DE4038908A1

Abstract

Described is the use, as water-treatment agents, of water-soluble graft polymers obtained by the radical-initiated polymerization of (A) monomer mixtures containing as monomers monoethylenically unsaturated carboxylic acids, their alkali-metal salts and/or their ammonium salts, in the presence of (B) monosaccharides, oligosaccharides, polysaccharides, oxidatively, hydrolytically or enzymatically degraded polysaccharides, chemically modified mono-, oligo- or polysaccharides, or mixtures of these compounds, in the ratio, by mass, of A:B of (95 to 20):(5 to 80).

Description

Use of water-soluble grafted natural substances as water treatment agents

description

The invention relates to the use of water-soluble grafted natural products which can be obtained as water treatment agents by polymerizing monoethylene-unsaturated carboxylic acids and optionally other monomers in the presence of monosaccharides, oligosaccharides, polysaccharides and / or derivatives thereof.

From US Pat. No. 3,810,834 it is known that hydrolyzed polymaleic anhydrides, which have a molecular weight of 300 to 5000 before hydrolysis, or whose water-soluble salts can be used as water treatment agents in order to largely suppress or suppress the formation of scale prevent. The polymers suitable for this are prepared by polymerizing maleic anhydride in toluene using benzoyl peroxide and subsequent hydrolysis of the polymaleic anhydride obtained in this way. Since the polymerization of the maleic anhydride is not complete and the separation of unpolymerized maleic anhydride from the polymer is difficult, the polymaleic acids still contain considerable amounts of maleic acid.

Low-molecular-weight copolymers are known from US Pat. No. 3,755,264, which contain 85 to 99 mol% of maleic anhydride and, in addition to 100 mol% of acrylic acid, vinyl acetate, styrene or mixtures thereof, copolymerized. The copolymers are prepared by copolymerizing maleic anhydride in dry organic solvents with the monomers mentioned at temperatures from 100 to 145 ° C. in the presence of peroxides. Examples of suitable peroxides are di-tertiary-butyl peroxide, acetyl peroxide, dicumyl peroxide, diisopropyl percarbonate and, in particular, benzoyl peroxide. The anhydride groups of the copolymer can be hydrolyzed to acid groups or converted into the salts after the polymerization. The water-soluble copolymers are used to prevent scale deposition. The ones obtainable by this procedure

Products have a very high content of unpolymerized maleic anhydride. The use of low molecular weight polymers of acrylic acid for water treatment or as a scale inhibitor is known, for example, from US Pat. No. 3,904,522 and US Pat. No. 3,514,376. From US Pat. No. 3,709816 it is known that copolymers containing acrylamido propanesulfonic acid are suitable as water treatment agents. For example, copolymers of 2-acrylamidopropanesulfonic acid and Acryla id, which is partially hydrolyzed. The disadvantage here is that residual monomer fractions of acrylamide inevitably remain in the polymers, so that their use can only be recommended to a very limited extent. In contrast, homopolymeric acids of acrylic acid show a satisfactory effect only against covering types that are relatively easy to suppress, such as calcium carbonate.

JP-A-61/031 498 discloses detergents which contain 0.5 to 50% by weight of graft polymers of a monosaccharide and / or an oligosaccharide and a water-soluble ethylenically unsaturated monomer as binders. According to the examples, acrylic acid was grafted onto sucrose or glucose.

From the unpublished DE-A-4003 172 graft copolymers of monosaccharides, oligosaccharides, polysaccharides and their derivatives are known. The graft copolymers are obtainable by free-radical copolymerization of

(A) monomer mixtures

(a) 90 to 10 wt .-% monoethylenically unsaturated C ^ - to Ce dicarboxylic acids, their anhydrides or

Alkali and / or ammonium salts,

(b) 10 to 90% by weight of monoethylenically unsaturated C ₃ to Cio carboxylic acids or their alkali and / or ammonium salts,

(c) 0 to 40% by weight of other monoethylenically unsaturated monomers which can be copolymerized with monomers (a) and (b), and (d) 0 to 5% by weight of at least two ethylenically unsaturated non-conjugated double bonds in the molecule having monomers

in the presence of

(B) monosaccharides, oligosaccharides, polysaccharides, oxidatively, hydrolytically or enzymatically degraded polysaccharides, oxidized hydrolytically or oxidized enzymatically degraded polysaccharides, chemically modified mono-, oligo- and polysaccharides or mixtures of the compounds mentioned

in the weight ratio (A) :( B) from (95 to 20): (5 to 80). The graft copolymers are used as additives for washing and cleaning agents in amounts of 0.1 to 20% by weight, based on the respective formulations.

The invention is based on the object of providing agents for water treatment which achieve or even exceed the effect of the polymers based on acrylic acid used hitherto and which can be prepared with the partial use of renewable raw materials.

The object is achieved according to the invention with the use of water-soluble graft polymers of monosaccharides, oligosaccharides, polysaccharides and their derivatives which can be obtained by free-radically initiated polymerization of

(A) Mixtures of monomers

(a) 40 to 100% by weight of monoethylenically unsaturated C3 to Ci _Q monocarboxylic acids and / or monoethylenically unsaturated C4 to Cβ dicarboxylic acids, their anhydrides, alkali metal salts and / or ammonium salts

(b) 0 to 60% by weight of other monoethylenically unsaturated monomers which are copolymerizable with the monomers (a), and

(c) 0 to 5% by weight of at least 2 ethylenically unsaturated, non-conjugated double bonds in the molecule comprising monomers in the presence of

(B) monosaccharides, oligosaccharides, polysaccharides, oxidative, hydrolytically or enzymatically degraded polysaccharides, oxidized hydrolytically or oxidized enzymatically degraded polysaccharides, chemically modified mono-, oligo- and polysaccharides or mixtures of the compounds mentioned

in the weight ratio (A): (B) from (95 to 20) :( 5 to 80) as water treatment agent.

The graft polymers can be obtained by homo- or copolymerization of the monomers (A) in the presence of the natural products (B).

Monoethylenically unsaturated C3- to Cio-monocarboxylic acids and their alkali and / or ammonium salts are suitable as monomers of group (a). These monomers include, for example, acrylic acid, methacrylic acid, diethyl acrylic acid, ethyl acrylic acid, allylacetic acid and vinyl acetic acid. From this group of monomers, preference is given to using acrylic acid, methacrylic acid, their mixtures and the sodium, potassium or ammonium salts or mixtures thereof. These monomers are used either alone or in a mixture with monoethylenically unsaturated dicarboxylic acids or their anhydrides in the presence of

Natural substances (B) poly erized. Such dicarboxylic acids contain 4 to 8 carbon atoms, for example maleic acid, fumaric acid, itaconic acid, mesaconic acid, methylene malonic acid, citraconic acid, maleic acid anyhdrid, itaconic acid anhydride and methylene malonic acid anhydride. The monoethylenically unsaturated C4- to Cβ-dicarboxylic acids can be used in the form of the free acids or in a form neutralized with alkali metal bases, ammonia or amines in the graft polymerization. Of the dicarboxylic acids or their anhydrides in question, maleic acid, maleic anhydride, itaconic acid or itaconic anhydride and the sodium, potassium or ammonium salts of maleic acid or itaconic acid are preferably used. These salts can be obtained, for example, from maleic anhydride or itaconic anhydride if the anhydrides mentioned are neutralized in aqueous solution with sodium hydroxide solution, potassium hydroxide solution or ammonia or amines. The cited dicarboxylic acids or their anhydrides or their salts can also be polymerized alone in the presence of the natural substances (B). Of particular interest are those graft polymers which are obtained by copolymerization of

(1) 10 to 90, preferably 12 to 80% by weight of monoethylenically unsaturated C4 to Cβ dicarboxylic acids, their anhydrides, salts or mixtures with

(2) 90 to 10, preferably 88 to 20% by weight of monoethylenically unsaturated C ₃ to Cio-monocarboxylic acids, their alkali or ammonium salts or mixtures of the free acids and the salts

are available in the presence of natural substances (B). Technically interesting are in particular graft copolymers, which by copolymerization of

(1) 15 to 60% by weight of maleic acid, itaconic acid or their alkali or ammonium salts

(2) 85 to 40% by weight of acrylic acid, methacrylic acid, mixtures of acrylic acid and methacrylic acid, their alkali or ammonium salts or mixtures of the free acids and the salts

are available in the presence of natural substances (B).

The monomers of group (a) can optionally be subjected to the graft copolymerization together with (b) other monoethylenically unsaturated monomers which can be copolymerized with the monomers (a). The proportion of the monomers (a) in the monomer mixture (A) is 40 to 100% by weight, while the monomers (b) can be present in it up to 60% by weight.

The monomers of group (b) which may be used in the graft copolymerization include, for example, C 1 -C 6 -alkyl and hydroxyalkyl esters of the compounds mentioned under (a), for example methyl acrylate, ethyl acrylate, n-butyl acrylate, methyl ethacrylate, maleic acid monomethyl ester, maleic acid dimethyl ester, maleic acid monoethyl ester, maleic acid diethyl ester, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate and hydroxypropyl methacrylate. In addition, the amides and N-substituted alkylamides of the compounds given under (a) come as monomers Group (b), for example acrylamide, methacrylic acid, NA kylacrylamide with 1 to 18 carbon atoms in the alkyl group, such as N-methylacrylamide, N, N-dimethylacrylamide, N-tert-butylacrylamide, N-octadecylacrylamide, Maleic acid monoethylhexylamide, maleic acid monododecylamide, dimethylaminopropyl methacrylic acid and acrylamidoglycolic acid. Likewise suitable as monomers (b) are alkyl inoalkyl (meth) acrylates, for example dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, dimethyla inopropyl acrylate and dimethylaminopropyl methacrylate.

Also suitable as monomers of group (b) are monomers containing sulfo groups, such as, for example, vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, styrene sulfonic acid, 3-sulfopropyl acrylate, 3-sulfopropyl methacrylate and acrylic idomethylpropanesulfonic acid and monomers containing phosphonic acid groups, such as vinylphosphonic acid and acrylamide, allyl phosphonic acid . This group of monomers also includes N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylformamide, N-vinyl-N-methylformamide, 1-vinylimidazole, 1-vinyl-2-methylimidazole, vinyl acetate and vinyl propionate. Also suitable as monomers of group (b) are the esters of alkoxylated C 1 -C 14 -alcohols which have been reacted with 2 to 50 mol of ethylene oxide, propylene oxide, butylene oxide or mixtures thereof, with the monoethylenically unsaturated carboxylic acids of group (a), e.g. the esters of acrylic acid, methacrylic acid or maleic acid with a Cχ3 / Ci5 oxo alcohol which has been reacted with different amounts of ethylene oxide, e.g. 3 moles, 5 moles, 7 moles, 10 moles or 30 moles of ethylene oxide.

Both the mono- and the diesters of the esters of dicarboxylic acids come into consideration. The basic monomers are preferably in the form of salts with mineral acids, e.g. Hydrochloric acid, sulfuric acid or nitric acid, or used in quaternized form (suitable quaternizing agents are, for example, dimethyl sulfate, diethyl sulfate, methyl chloride, ethyl chloride or benzyl chloride).

Also come as monomers of group (b) amides of monoethylenically unsaturated C ₃ - to Cβ-carboxylic acids with Aid groups of the structure Rl / -CO-N (I)

\ R2

considered in the

Rl = R_o- (CH-CH-0) _n _ι-CH-CH-,

I I I I R3 * R * R3 R4

R3, R = H, CH ₃ , C ₂ H ₅ ,

R = C ** .- to C ₂ 8-alkyl,

n = 2 to 100 and

R2 = H, Rl

mean.

The preferred monomers of group (b) are hydroxyethyl acrylate, hydroxypropyl acrylates, vinyl acetate, N-vinylpyrrolidone, acrylamidomethylpropanesulfonic acid and N-vinylimidazole.

A further modification of the graft copolymers can be achieved by carrying out the graft polymerization in the presence of monomers from group (c). In this case, the monomer mixtures contain up to 5% by weight of a monomer having at least two ethylenically unsaturated non-conjugated double bonds in the molecule. These compounds are usually used as crosslinkers in copolymerizations. They can be added to the monomers of group (a) used for the copolymerization or to the monomer mixtures from (a) and (b). If they are used, the amount of monomers (c) used is preferably 0.05 to 2% by weight. The use of the monomers of group (c) during the copolymerization causes an increase in the K values of the copolymers. Suitable compounds of this type are, for example, methylene bisacrylamide, esters of acrylic acid and methacrylic acid with polyhydric alcohols, for example glycol diacrylate, glycerol triacrylate, glycol dimethacrylate, glycerol trimethacrylate, and at least polyols esterified with acrylic acid or methacrylic acid, such as pentaerythritol and Glucose. Suitable crosslinkers are also divinylbenzene, divinyldioxane, pentaerythritol triallyl ether and pentaallylsucrose. From this group of compounds, preference is given to using water-soluble monomers, such as glycol diacrylate or glycol diacrylates of polyethylene glycols having a molecular weight of up to 3,000.

The monomers (a) and, if appropriate, additionally (b) and (c) are polymerized in the presence of natural products based on polysaccharides, oligosaccharides, monosaccharides and their derivatives. The natural substances are e.g. Saccharides of vegetable or animal origin or products of the metabolism of microorganisms and their degradation and modification products which are already dispersible or soluble in water or alkalis or during the polymerization of the monomers (a) and optionally (b) and (c) become dispersible or soluble directly or partially or completely neutralized with alkalis, ammonia or amines.

These are, for example, pectin, algin, chitin, chitosan, heparin, carrageenan, agar, gum arabic, tragacanth, karaya gum, ghatti gum, locust bean gum, guar gum, tara gum, inulin, xanthan, dextran, nigeran and pentosans such as xylan and araban, the main components of which are D-glucuronic acid, D-galacturonic acid, D-galacturonic acid methyl ester, D-mannuronic acid, L-guluronic acid, D- and L-galactose, 3,6-anhydro-D-galactose, L-arabinose , LR-hamnose, D-glucuronic acid, D-xylose, L-fucose, D-mannose, D-fructose and D-glucose, 2-amino-2-deoxi-D-glucose and 2-amino-2-deoxi-D -Galactose and their N-acetyl derivatives.

From an economic point of view, the polysaccharides of component (B) used in the graft copolymerization are preferably starch, thermally and / or mechanically treated starch, oxidatively, hydrolytically or enzymatically degraded starches, oxidized hydrolytically or oxidized enzymatically degraded starches, and chemically modified starches and chemically modified starches Monosaccharides and oligosaccharides. In principle, all strengths are suitable. However, starches from corn, wheat, rice, tapioca and in particular starch from potatoes are preferred. The starches are practically insoluble in water and can be prepared in a known manner by thermal and / or mechanical treatment or by an enzymatic or an acid-catalyzed degradation in a water-soluble form. Oxidatively degraded starches are also suitable as component (B). The following compounds may be mentioned as starch breakdown products, which are obtainable either by oxidative, hydrolytic or enzymatic breakdown of starch: dextrins, such as white and yellow dextrins, maltodextrins, glucose syrups, maltose syrups, hydrolysates with a high content of D-glucose, starch saccharification products and the like Maltose and D-glucose and their iso erization product fructose. Mono- and oligosaccharides, such as galactose, mannose, ribose, sucrose, raffinose, lactose and trehalose, and cellulose degradation products, for example cellobiose and its oligomers, are of course also suitable as component (B).

Oxidized starches, such as e.g. Dialdehyde starch and oxidized starch degradation products, such as gluconic acid, glucaric acid and glucuronic acid. Such compounds are obtained, for example, by oxidizing starch with periodate, chromic acid, hydrogen peroxide, nitrogen dioxide, nitrogen tetroxide, nitric acid or hypochlorite.

Also suitable as component (B) are chemically modified polysaccharides, in particular chemically modified starches, for example starches and starch degradation products converted with acids to esters and with alcohols to ethers. The esterification of these substances is possible both with inorganic and with organic acids, their anhydrides or chlorides. In the case of direct esterification, the water released leads to acid-catalyzed cleavage of glycosidic bonds. Phosphated and acetylated starches and starch breakdown products are of particular technical interest. The most common method for etherifying starch is to treat the starch and starch degradation products with organic halogen compounds, epoxides or sulfates in aqueous alkaline solution. Starch ethers are, for example, the alkyl ether, hydroxyalkyl ether, carboxyalkyl ether and allyl ether of starch. Chemically modified starches according to component (B) are also to be understood as meaning cationically modified starches, for example starches reacted with 2,3-epoxypropyltrimethylammonium chloride, as described, for example, in US Pat. No. 3,649,616. Chemically modified polysaccharides also include, for example, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl hydroxyethyl cellulose, sulfoethyl cellulose, carboxymethyl sulfoethyl cellulose, hydroxypropyl sulfoethyl cellulose, hydroxyethyl sulfoethyl cellulose, methyl sulfoethyl cellulose and ethyl sulfo cellulose.

Chemically modified degraded starches are also suitable as component (B), for example hydrogenation products of starch hydrolysates such as sorbitol and mannitol, maltitol and hydrogenated glucose syrups or oxidized hydrolytically degraded or oxidized enzymatically degraded starches.

The products of acid-catalyzed or enzymatic transglycosidation or glycosidation, such as e.g. Methyl glucose.

To prepare the graft copolymers, the monomers (a) and optionally (b) and / or (c) are radically polymerized in the presence of compounds of component (B). In some cases it may be favorable for the effect of the graft polymer formed to use two or more of the compounds indicated under (B), e.g. Mixtures of acid-catalytically or enzymatically degraded starches and gluconic acid, mixtures of a monosaccharide and an oligosaccharide, mixtures of an enzymatically degraded starch and a monosaccharide or mixtures of glucose and sucrose or mannose. The polymerization can be carried out in the presence or in the absence of inert solvents or inert diluents. Since the polymerization in the absence of inert solvents or diluents usually leads to inconsistent graft polymers, the graft polymerization in an inert solvent or diluent is preferred. Suitable inert diluents are, for example, in which the compounds indicated under (B) can be suspended and which dissolve the monomers (A). In these cases, the graft polymers are in suspended form after the polymerisation and can easily be isolated by filtration in solid form. Suitable inert diluents are, for example, toluene, o-, m-, p-xylene and

Isomer mixtures, ethylbenzene, aliphatic hydrocarbons, such as pentane, hexane, heptane, octane, nonane, DodeGan, cyclohexane, Cyclooctane, methylcyclohexane and mixtures of the hydrocarbons mentioned or gasoline fractions which do not contain any polymerizable monomers. Chlorinated hydrocarbons such as chloroform, carbon tetrachloride, hexachloroethane, dichloroethane and tetrachloroethane are also suitable. In the procedure described above, in which the compounds of component (B) are suspended in an inert diluent, preferably anhydrous compounds of component (B) are used and the anhydrides from the group of monomers (a) are preferably used. A preferred way of producing the graft polymers is solution polymerization, the compounds of component (B), the monomers (A) and the graft copolymer formed being at least dispersed, preferably in dissolved form. Inert solvents, such as methanol, ethanol, isopropanol, n-propanol, n-butanol, sec-butanol, tetrahydrofuran, dioxane, and mixtures of the inert solvents mentioned are suitable, for example, for solution polymerization. The copolymerization can be carried out continuously or batchwise. As already mentioned above, components (A) and (B) can also be copolymerized in the absence of inert diluents or solvents. Continuous polymerization at temperatures of 160 to 250 ° C. is particularly suitable for this. If necessary, it is possible to work in the absence of polymerization initiators. However, preference is also given to using catalysts which form free radicals under the polymerization conditions, for example inorganic and organic peroxides, persulfates, azo compounds and so-called redox catalysts.

The graft polymers are generally prepared using free-radical initiators.

Suitable radical initiators are preferably all those compounds which have a half-life of less than 3 hours at the polymerization temperature chosen in each case. If you start the polymerization initially at a lower temperature and at a higher temperature to an end, it is expedient to work with at least two decompose at different temperatures ver¬ initiators, namely, first one at a relatively low temperature decomposed ^• falling for initiating use the polymerization and then end the main polymerization with an initiator lead, which disintegrates at a higher temperature. Water-soluble and water-insoluble initiators or mixtures of water-soluble and water-insoluble initiators can be used. The water-insoluble initiators are then soluble in the organic phase. The initiators listed for this purpose can be used, for example, for the temperature ranges specified below.

Temperature: 40 to 60 ° C: acetylcyclohexanesulfonyl peroxide, diacetyl peroxidicarbonate,

Dicyclohexyl peroxidicarbonate, di-2-ethylhexyl peroxidicarbonate, tert-butyl perneodecanoate, 2,2'-azobis- (4-methoxy-2,4-dimethyl-valeronitrile), 2,2'-azobis- (2-methyl-N-pheπylpropionamidine) - dihydrochloride, 2,2'-azobis- (2-π_ethylpropionamidine) dihydrochloride.

Temperature: 60 to 80 ° C: tert-butyl perpivalate, dioctanoyl peroxide, dilauroyl peroxide,

2 _r 2'-Azobϊs- (2,4-dimethylvaleronitrile).

Temperature: 80 to 100 ° C:

Dibenzoyl peroxide, tert-butyl per-2-ethylhexanoate, tert-butyl permaleinate, 2,2'-azobis (isobutyronitrile), dimethyl-2, 2'-azobisisobutyrate, sodium persulfate, potassium persulfate, ammonium persulfate.

Temperature: 100 to 120 ° C:

Bis- (tert-butylperoxy) cyclohexane, tert-butylperoxiisopropyl carbonate, tert-butyl peracetate, hydrogen peroxide.

Temperature: 120 to 140 ° C:

2,2-bis (tert-butyl peroxy) butane, dicumyl eroxi,

Di-tert-amyl peroxide, di-tert-butyl peroxide.

Temperature:> 140 ° C p-menthane hydroperoxide, pinane hydroperoxide, cumene hydroperoxide and tert-butyl hydroperoxide.

In addition to the initiators mentioned, salts or complexes of heavy metals, for example copper, cobalt, manganese, iron, vanadium, cerium, nickel and chromium salts or organic compounds such as benzoin, dimethylaniline or Ascorbic acid, the half-lives of the radical initiators indicated can be reduced. For example, tert-butyl hydroperoxide with the addition of 5 ppm copper II acetylacetonate can already be activated in such a way that polymerisation can take place at 100 ° C. The reducing component of redox catalysts can also be formed, for example, from compounds such as sodium sulfite, sodium bisulfite, sodium formaldehyde sulfoxylate and hydrazine. Based on the monomers used in the polymerization, 0.01 to 20, preferably 0.05 to 10,% by weight of a polymerization initiator or a mixture of several polymerization initiators is used. 0.01 to 5% of the reducing compounds are added as redox components. Heavy metals are used in the range of 0.1 to 100 ppm, preferably 0.5 to 10 ppm. It is often advantageous to use a combination of peroxide, reducing agent and heavy metal as a redox catalyst.

The polymerization of the monomers (a) and the optionally used monomers (b) and / or (c) can also be carried out by the action of ultraviolet radiation, if appropriate in the presence of UV initiators. For the polymerization under the action of UV rays, the photoinitiators or sensitizers that are normally used are used. These are, for example, compounds such as benzoin and benzoin ether, α-methylbenzoin or α-phenylbenzoin. So-called triplet sensitizers, such as benzene diketals, can also be used. In addition to high-energy UV lamps, such as carbon arc lamps, mercury vapor lamps or xenon lamps, low-UV light sources, such as fluorescent tubes with a high proportion of blue, also serve as UV radiation sources.

In order to produce polymers with a low K value, the graft polymerization is advantageously carried out in the presence of regulators. Suitable regulators are, for example, mercapto compounds, such as mercaptoethanol, mercaptopropanol, mercapto-butanol, mercaptoacetic acid, mercaptopropionic acid, butyl mercaptan and dodecyl mercaptan. Also suitable as regulators are allyl compounds, such as allyl alcohol, aldehydes, such as formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde and isobutyraldehyde, formic acid, ammonium formate, propionic acid, hydrazine sulfate and butenols. If the polymerization is in the presence of regulators is carried out, 0.05 to 20% by weight, based on the monomers used in the polymerization, are required.

In order to prepare colorless or only slightly colored graft polymers from components (A) and (B), the polymerization is carried out in the presence of water-soluble phosphorus compounds in which the phosphorus has an oxidation number of 1 to 4, the water-soluble alkali metal or ammonium salts, water-soluble Compounds containing PO (OH) 2 groups and / or their water-soluble salts. Phosphorous acid is preferably used. The phosphorus compounds in question are used to reduce the discoloration of the graft copolymers in amounts of from 0.01 to 5% by weight, based on the monomers (A) used. The phosphorus compounds in question are described in EP-A-0 175317.

The copolymerization of components (A) and (B) is usually carried out in an inert gas atmosphere with the exclusion of atmospheric oxygen. Good mixing of the reactants is generally ensured during the polymerization. In the case of smaller batches in which a reliable removal of the heat of polymerization is ensured, the reaction participants, which are preferably present in an inert diluent, can be copolymerized discontinuously by heating the reaction mixture to the polymerization temperature. These temperatures are in the range of 40 to 150 ° C. With this method, however, graft copolymers are obtained which, when using dicarboxylic acids, have a relatively high content of unpolymerized dicarboxylic acid. In order to be able to better control the course of the polymerization reaction, the monomers (A) are therefore added to the polymerizing mixture continuously or batchwise after the polymerization has started, to the extent that the graft polymerization can be easily controlled in the desired temperature range . A type of addition of the monomers of component (A) is preferred in which the compounds of component (B) or at least some of the compounds of component (B) are first combined with at least one monomer of group (a ) placed in the reactor and heated to the desired polymerization temperature with stirring. As soon as this temperature is reached, the remaining monomers of group (a) are added over a period of about 1 to 10, preferably 2 to 8 hours. and optionally the monomers (b) and optionally (c) and the initiator and optionally a regulator. Such a procedure is used, for example, when polymerizing components (A) and (B) in an inert diluent in which component (B) is suspended and also in graft copolymerization carried out in solution.

The graft copolymers are preferably prepared by suspension or solution polymerization of components (A) and (B) in an aqueous medium, with solution polymerization in water being particularly preferred. In solution polymerization in an aqueous medium, the procedure is, for example, that the monomers (a) and at least some of the compounds of component (B) are initially introduced in an aqueous medium and, if appropriate, the remaining monomers of group (a) and, if appropriate, the

Monomers (b) and, if appropriate, the monomers (c) are added continuously or batchwise to the polymerizing reaction mixture and copolymerized in such a way that the degree of neutralization of the copolymerized monomer units (1) and (2) of the monomers of group (a) after completion of the graft copolymerization, ie when at least 95, preferably 98-99% of the monomers have polymerized, is 20 to 80%. The monomers (1) of group (a) are preferably used in at least 20% neutralized form at the start of the polymerization. In the graft copolymerization in an aqueous medium, the entire amount of the compounds of component (B) or only a part, for example 50%, of the compounds of component (B) together with the monomers (1) of group (a) and the remainder Add amounts of compounds of component (B) to the polymerizing reaction mixture together with the monomers (2) from group (a) and, if appropriate, the monomers (b) and / or (c) continuously or batchwise. In order to obtain graft copolymers with a low residual content of unpolymerized monomer (1) from group (a), ie in particular maleic acid, it is important to control the degree of neutralization of the monomers during the copolymerization. It should be 20 to 80%, preferably 30 to 70%, during the graft copolymerization. For this purpose, for example, the monomers (1) and (2) of group (a) can be partially neutralized so that their degree of neutralization is in each case in the range specified. However, it is also possible to completely or approximately 90% of the monomers (1) from group (a) introduced in the reactor and to neutralize the monomers Add (2) to group (a) in non-neutralized form so that the total degree of neutralization of the monomers (1) and (2) of group (a) and optionally (b), ie if (b) contains an acid group Monomer is used, for example acrylamido methyl propanesulfonic acid or vinylphosphonic acid, during the

Polymerization initially reduced from approximately 100% or approximately 90% to values in the range from 20 to 80%. To maintain a certain degree of neutralization within this range of the monomers (1) and (2) of group (a), a base, e.g. Add sodium hydroxide solution, potassium hydroxide solution, ammonia or ethanolamine. Depending on the composition of the graft copolymer, the main amount, i.e. 60 to 80% of the monomers (1) and (2) of group (a) polymerized at a degree of neutralization of 20 to 80%. The solution copolymerization is particularly preferably carried out with hydrogen peroxide, sodium persulfate or mixtures in any ratio as initiator. This requires 0.5 to 20% by weight of initiator, based on the monomers (A). If the monomer mixture (A) consists of a small proportion of the monomers (1) of group (a), a relatively low amount of initiator is used and if the proportion of monomers (1) of group (a) is high, a larger amount of initiator is used, e.g. for 90% by weight of monomer (1) of group (a) about 15 to 18% by weight of initiator. Here too, the procedure is such that at least a portion of component (B) is initially introduced together with the monomers (1) from group (a), which are preferably at least 90% neutralized, and the monomers (2) from the group (a) and optionally the monomers (b) and / or (c) while maintaining the required degree of neutralization of 20 to 80%. The monomers (2) of group (a) can be neutralized either by adding appropriate amounts of base separately or by adding partially neutralized monomers (2) from group (a) to the reaction mixture. The degree of neutralization of the partially neutralized monomers (2) of group (a) is then in the range from 20 to 80%.

As already mentioned, polysaccharides in aqueous suspension can be subjected to the graft copolymerization. However, graft copolymers from polysaccharides are preferably prepared by first converting a water-insoluble polysaccharide in aqueous suspension with the addition of enzymes and / or acids to a water-soluble form, and the aqueous solution of the degraded polysaccharide obtained in this way Subject to graft copolymerization. Here, a water-insoluble polysaccharide, such as potato starch, is first suspended in water and broken down. This degradation can be carried out under the action of enzymes, for example α- or β-amylase, or of debranching enzymes, for example pullulanase, or by the action of inorganic or organic acids in a known manner. Suitable inorganic acids are, for example, phosphoric acid, sulfuric acid, hydrochloric acid and nitric acid. Suitable organic acids are, for example, saturated or unsaturated carboxylic acids, for example formic acid, acetic acid, propionic acid, acrylic acid, methacrylic acid, maleic acid, itaconic acid, p-toluenesulfonic acid and benzenesulfonic acid. The conversion of the polysaccharides into a water-soluble form is preferably carried out with a monomer (a), which is then used in the graft copolymerization. For example, potato starch or maize starch can be hydrolytically degraded in an aqueous suspension by adding acrylic acid, methacrylic acid, maleic acid or itaconic acid in the temperature range from 50 to 150 ° C. As soon as the starch has reached the desired degree of degradation, the added monocarboxylic acid or maleic acid or itaconic acid is neutralized to at least 20, preferably 90%, and by adding the remaining monomers of group (a) and optionally monomers (b) and, if appropriate (c) the graft copolymerization was carried out.

The enzymatic degradation of starch is carried out in the temperature range from 30 to 120 ° C, while the hydrolytic degradation of the starch is carried out at temperatures from 50 to 150 ° C. The hydrolytic degradation takes about 5 minutes to 10 hours, the degree of hydrolytic degradation of the starch depending on the selected temperature, pH and time. Further information on the breakdown of starch can be found in the specialist literature, cf. e.g. Günther Tegge, starch and starch derivatives, Behr's Verlag, Hamburg 1984. In some cases it has proven advantageous to use at least one of the phosphorus compounds already in the enzymatic or hydrolytic degradation of the starch, which according to the teaching of EP-A-0 175 317 lead to polymers which are not or only very slightly colored.

In the graft copolymerization, the temperatures are usually in the range from 40 to 180, preferably 60 to 150 ° C. As soon as the temperature in the copolymerization is above the boiling points of the inert diluent or solvent or the monomers, the copolymerization is carried out under pressure. The concentration of components (A) and (B) in the copolymerization in the presence of inert solvents or inert diluents is 10 to 80, preferably 20 to 70,% by weight. The graft copolymers can be prepared in the customary polymerization devices. For this purpose, for example, stirred kettles are used which are equipped with an anchor, blade, impeller or multi-stage impulse countercurrent stirrer. In particular in the case of graft copolymerization in the absence of diluents, it can be advantageous to carry out the graft copolymerization in kneaders. It may also be necessary to polymerize in a kneader when working at high concentrations or when the natural products are high molecular weight and initially swell strongly.

This gives water-soluble graft copolymers with K values of 8 to 70, preferably 10 to 40, (measured on 1% strength aqueous solutions of the copolymers at pH 7 and 25 ° C.). The graft copolymers which can be prepared by the processes given above are colorless to brownish-colored products. When polymerizing in an aqueous medium, they are present as dispersions or polymer solutions. Depending on the particular composition and the concentration of the graft copolymers, these are low-viscosity to pasty aqueous solutions or dispersions. The graft polymers described above are more biodegradable due to the natural substance content than the previously used copolymers based on ethylenically unsaturated monomers, but at least can be eliminated with the sewage sludge from sewage treatment plants.

The aqueous copolymer solutions obtainable in this way can be used directly as water treatment agents for reducing scale deposition and water hardness excretion in water-bearing systems. It is possible to combine the polymers according to the invention with other dispersants, such as phosphonates, phosphonoalkane carboxylic acids etc.

The mode of action of the graft polymers as so-called scale inhibitors for water treatment consists in the formation of crystals of the hardener salts, such as calcium carbonate, To prevent magnesium oxide, magnesium carbonate, calcium, barium or strontium sulfate, calcium phosphate (apatite) and the like in the sub-stoichiometric dosage range or to influence the formation of these precipitates in such a way that no hard and stone-like deposits are formed, but rather easy-to-wash out, finely divided precipitates are formed become. In this way, the surfaces of, for example, heat exchangers, pipes or pump components are kept free of deposits and their tendency to corrode is reduced. In particular, the risk of pitting corrosion under these coverings is reduced. Furthermore, the growth of microorganisms on these metal surfaces is made more difficult. Due to the influence of the deposit inhibitors, the lifespan of such systems can be increased and downtimes for cleaning system parts can be considerably reduced. The amounts of deposit inhibitor required for this are 0.1 to 100, preferably 0.5 to 25 ppm, based on the respective amount of water. The water-carrying systems are, for example, open or closed cooling circuits, for example of power plants or chemical plants, such as reactors, distillation apparatuses and similar components, in which heat has to be removed. These deposit inhibitors can also be used in boiler water and steam generators, preferably in the range of water temperatures below 150 ° C. A preferred application of the scale inhibitors to be used according to the invention is also the desalination of sea and brackish water by distillation or membrane processes, such as reverse osmosis or electrodialysis. For example, in the so-called MSF distillation process (multi-day rash evaporation), thickened sea water is circulated at elevated temperature for desalination. The deposit preventers effectively prevent the excretion of hardness-forming agents, such as brucite, and their caking on plant components.

In membrane processes, damage to the membranes by crystallizing hardness agents can be effectively prevented. In this way, these deposit preventers enable higher thickening factors, improved yield of pure water and longer membrane life. A further application of the deposit inhibitor is, for example, when evaporating sugar juices from cane or beet sugar. In contrast to the applications described above, the sugar thin juice is cleaned here, for example, calcium hydroxide, carbon dioxide, sulfur dioxide. if phosphoric acid is added. After filtration in the sugar juice, the remaining slightly soluble calcium salts, such as calcium carbonate, sulfate or phosphate, precipitate out during the evaporation process and can appear as rock hard deposits on heat exchanger surfaces. This also applies to accompanying substances in sugar, such as silica or calcium salts of organic acids, such as oxalic acid.

The same applies to processes that follow sugar extraction, e.g. the production of alcohol from residues from sugar production.

The copolymers which can be used according to the invention as deposit inhibitors are able to largely prevent the above-mentioned deposit formation, so that downtimes of the systems for cleaning, e.g. by boiling out, can be significantly reduced. An important aspect here is the considerable energy saving by avoiding the heat-insulating coverings mentioned.

The amounts of deposit inhibitor required in the applications described are different, but are between 0.1 and 100 ppm, based on the cooling water, boiler water, process water or e.g. Sugar juice.

The products to be used according to the invention have better dispersion compared to hardness-forming salts, such as calcium carbonate, calcium sulfate and calcium phosphate, and are also more compatible with calcium ions than acrylic acid copolymer.

The K values of the copolymers were determined according to H. Fikentscher, Cellulosechemie, Vol. 13, 48 to 64 and 71 to 74 (1932) in aqueous solution at a pH of 7, a temperature of 25 ° C and a polymer concentration of the sodium salt of Copolymer determined from 1 wt.%. The percentages relate to the weight of the fabrics. Examples

Production of the graft polymers

Graft polymer 1

In a heatable reactor which is provided with a stirrer, reflux condenser, thermometer, feed devices, nitrogen inlet and outlet devices, 309.4 g of the 80.7% solution of a starch sugar product obtained by two-stage enzyme conversion with a composition of approx. 10% dextrose, approx. 11% maltose, approx. 14% maltotriose and 65% higher sugar, 354.6 g water and 1.8 g phosphorous acid heated to 95 ° C. in a weak nitrogen stream and metered in parallel within 4 hours, 294.6 g acrylic acid, 35.35 g

2-mercaptoethanol dissolved in 50 g water and 2.94 g sodium per sulfate dissolved in 70 g water. It is then cooled to 80 ° C. and a solution of 0.3 g of 2,2′-azobis (2-methylpropionamidine) dihydrochloride in 30 g of water is metered in uniformly at 80 ° within 1 hour. Then at 80 ° C with 296 g

50% sodium hydroxide solution neutralized. Then a solution of 0.9 g of sodium disulfite in 15 g of water and 9.8 g of 30% hydrogen peroxide are added in succession and the mixture is reheated at 80 ° C. for 1 hour. The yellowish polymer solution obtained has a solids content of 46.8% and a pH of 7.0. The K value of the graft polymer is 14.6.

Graft polymer 2

In a heatable reactor equipped with a stirrer, thermometer,

Feed devices, and a distillation device is provided, 1056 g of a mixture of isopropanol and water in a ratio of 75:25, 806.46 g of maltodextrin with a DE value (according to Luff-Schoorl) of 11 to 14, 94% and 47, 16 g of 30% hydrogen peroxide are initially charged. The reactor is then pressed off 3 times with 3 bar nitrogen and expanded again and then heated to 120 ° C., a pressure of 3 bar being established. Now, at 120 ° C., 1137 g of acrylic acid are dissolved uniformly within 6 hours in 966 g of a mixture of isopropanol and water in a ratio of 75:25, and within 8 hours, 80 g of 30% hydrogen peroxide dissolved in 304 g a mixture of isopropanol and water in a ratio of 75:25. The mixture is then reheated at 120 ° C. for a further 2 hours. The mixture is then cooled to 100 °, decompressed and the isopropanol is distilled off by introducing steam until a boiling point of 100 ° is reached. The mixture is then neutralized to a pH of 8 by adding 882 g of 50% strength aqueous sodium hydroxide solution. Now it is cooled and the 54.6% almost clear solution is adjusted to 45% by dilution with water, the K value of the graft polymer is 19.5.

Graft polymer 3

is produced according to the recipe for graft polymer 2, with the exception that the acrylic acid solution is metered in uniformly in 3 hours and the hydrogen peroxide in 4 hours. The K value of the graft polymer obtained is 21.7.

Graft polymer 4

In the reactor in which the graft polymer 1 was produced, 290 g of maltodextrin with a DE value (according to Luff-Schoorl) of 11 to 14, 94%, 470 g of water, 101.4 g of maleic anhydride, 4. 2 ml of a 0.1% solution of iron (II) ammonium sulfate in water and 74.5 g of sodium hydroxide are heated to boiling, within 5 hours a mixture of 120 g of acrylic acid and 114.4 g of 58% is added. aqueous solution of the sodium salt of acrylamidomethylpropanesulfonic acid and within 6 hours 80 g of 30% strength hydrogen peroxide and a solution of 24 g of sodium persulfate in 72 g of water uniformly under boiling conditions. The reaction mixture is then boiled under reflux for a further 2 hours and then neutralized with cooling with 155 g of 50% strength aqueous sodium hydroxide solution. The brown, clear solution obtained has a solids content of 42.3% and a pH of 7.0. The K value of the graft polymer is 27.6.

Graft polymer 5

In the reactor in which the graft polymer 1 was prepared, 127.2 g of maltodextrin with a DE value (according to Luff-Schoorl) of 11 to 14, 370 g of water, 3.8 g of phosphorous acid in a gentle stream of nitrogen to 95 ° C heated and

^* Within 4 hours, a mixture of 407 g of acrylic acid, 35 g of water and 101.8 g of N-vinylimidazole and one Mixture of 25.44 g of 2-mercaptoethanol and 78.5 g of water as well as a solution of 3.2 g of sodium persulfate in 75 g of water and a solution of 3.2 g of 2,2'-azobis (2-methylpropionamidine) dihydro- chloride in 65 g of water evenly metered in at 95 ° C. The mixture is then heated for a further 2 hours, cooled to 40 ° C. and neutralized with 378 g of 50% strength aqueous sodium hydroxide solution. The yellowish solution has a solids content of 45.8% and a pH of 7.1. The K value of the graft polymer is 26.9.

Graft polymer 6

235.4 g of maltodextrin with a DE value of 11 to 14, 230 g of water, 117.54 g of maleic anhydride and 173 g of 50% strength aqueous sodium hydroxide solution are placed in the reactor described in Example 1 and heated to boiling. The degree of neutralization of the resulting maleic acid is 90.1%. Immediately after the start of boiling, ma adds a solution of 139.2 g of 97% acrylic acid and 300 g of water within 5 hours and, separately, solutions of 3.2 g of sodium per sulfate in 80 g of water and 10.14 g within 6 hours 30% water peroxide in 60 g of water evenly and polymerized at the boiling point of the reaction mixture. The maleic acid and acrylic acid units contained in the graft copolymer have a degree of neutralization of 50.6%. After the hydrogen peroxide addition has ended, the reaction mixture is heated to boiling for a further hour and neutralized by adding 137 g of 50% strength aqueous sodium hydroxide solution. A clear, viscous, brown solution with a solids content of 39% is obtained. The graft copolymer has a K value of 31.5.

Graft polymer 7

1056 g of a mixture of isopropanol and water in a ratio of 75:25 and 806.46 g of maltodextrin with a DE value (according to Luff-Schoorl) are placed in a heatable reactor which is provided with a stirrer, thermometer, feed devices and a distillation device. from 11 to 14, 94% strength and 47.16 g of hydrogen peroxide 30% strength. The reactor is then pressed off 3 times with 3 bar of nitrogen and expanded again and then heated to 120 ° C., a pressure of 3 bar being established. Now at 120 ° C evenly within 6 hours. 682.2 g of acrylic acid, 227.4 g of N-vinylimidazole and 227.4 g of acrylamidomethylpropanesulfonic acid dissolved in 966 g of a mixture of isopropanol and water in a ratio of 75:25, and within 8 hours, 80 g of 30% hydrogen peroxide dissolved in 304 g of a mixture of isopropanol and water in a ratio of 75:25, metered in. The mixture is then reheated at 120 ° C. for a further 2 hours. The mixture is then cooled to 100 °, decompressed and the isopropanol is distilled off by introducing steam until a boiling point of 100 ° is reached. The mixture is then neutralized to a pH of 8 by adding 50% aqueous sodium hydroxide solution. Now it is cooled and the 50.6% almost clear solution is adjusted to 45% by dilution with water, the K value of the graft polymer is 23.5.

Water treatment agent 1

Commercial homopolymer of acrylic acid with a K value of 15.

Water treatment agent 2 Commercial homopolymer of acrylic acid with a K value of 20.

Water treatment agent 3

Commercial homopolymer of acrylic acid with a K value of 25.

The graft polymers described above are subjected to the following tests for their suitability as water treatment agents and compared with commercially available water treatment agents.

Examples according to the invention and comparative examples

CaS04 test

500 ml of a saturated CaSO 4 solution are evaporated to 200 g at 200 ° C. in a drying cabinet. The mixture is left to stand overnight and filtered the next day through a membrane filter (0.45 µm).

50 ml of the filtrate is washed with an aqueous 0.2 M solution of

Na2H ₂ EDTA (EDTA = ethylenediaminetetraacetic acid) titrated and the still dissolved Ca content determined. The inhibition when adding 1 ppm polymer is calculated against a blank test without addition of polymer.

/ mg CaSO ^ on filter (with 1 ppm polymer% inhibition: 100 - (l

V mg CaS0 on filter (blind verse, without polymer)

CaC03 ~ test

An aqueous test solution is prepared from components A and B.

A: 3.36 g NaHC0 ₃ / l B: 1.58 g CaCl ₂ -2H ₂ 0 / l 0.88 g MgSO ^ / l

100 ml each of the above solutions A and B are pipetted into a 250 ml bottle, 5 ppm of graft polymer are added, sealed and stored at 86 ° C. for 16 hours. After cooling to room temperature and filtration, the solution is titrated with a 0.2 M solution of Na ₂ H2-EDTA.

mg CaO on filter (with 1 ppm polymer)% inhibition: 100 - (1 mg CaO on filter (blind verse, without polymer)

Ca ₃ (P0) 2 test

100 ml of a solution with the following concentrations are prepared:

1.095 g / 1 CaCl ₂ '6H ₂ 0 0.019 g / 1 NaHP04-2H ₂ 0 2 ppm _. polymer

The pH is adjusted to 8.6 with a borax buffer. The solution is then stirred at 70 ° C. for 3 hours and left to stand for 24 hours. After this time, the light transmittance (LD, white light) is measured with a photometer. The photometer is previously set to 100% LD with distilled water. 100 - LD with 2 ppm polymer% inhibition: 100 * (1st

100 - LD of a blank without polymer

The data on polymer refer to 100% substance.

The test results are given in the table.

% Inhibition

Example of graft polymer K-value CaC03 CaS04 Ca3 (P0) ₂

Comparative water treatment example medium

47

30th

49

As can be seen from the table, the graft polymers have an improved effectiveness in comparison with the homopolymers of acrylic acid with a comparable K value.

Claims

1. Use of water-soluble graft polymers of monosaccharides, oligosaccharides, polysaccharides and their derivatives, which are obtainable by free-radically initiated polymerization of

(A) monomer mixtures

(a) 40 to 100% by weight monoethylenically unsaturated

C3- to Cio-monocarboxylic acids and / or monoethylenically unsaturated C4 to Cβ-dicarboxylic acids, their anhydrides, alkali salts and / or ammonium salts,

(c) 0 to 5% by weight of at least 2 ethylenically unsaturated, non-conjugated double bonds in the molecule having monomers

in the presence of

in the weight ratio (A) :( B) of (95 to 20): (5 to 80) as a water treatment agent.

Use according to claim 1, characterized in that component (A)

(a) acrylic acid, methacrylic acid, maleic acid or mixtures thereof and (b) acrylamidomethylpropanesulfonic acid or N-vinylimidazole or mixtures thereof

starts.

3. Use according to claim 1 or 2, characterized in that starch saccharification products or hydrogenated starch hydrolysates are used as component (B).

4. scale inhibitors, characterized in that they are obtainable by radical-initiated polymerization of

(A) monomer mixtures

(a) 40 to 100% by weight monoethylenically unsaturated

C ₃ - to Cio-monocarboxylic acids and / or monoethylene-unsaturated C ₄ - to Cβ-dicarboxylic acids, their anhydrides, alkali salts and / or ammonium salts,

in the presence of

in the weight ratio (A) :( B) from (95 to 20): (5 to 80). CHANGED REQUIREMENTS

[1-4 replaced with the International Bureau on 23 April 1992 (23.04.92) eingegangen- originally ^ü ngl ⁱ che claims by amended claims 1-4 (2 pages)]

1. Use of water-soluble graft polymers of monosaccharides, oligosaccharides, polysaccharides and their 5 derivatives, which are obtainable by free-radically initiated polymerization of

(A) monomer mixtures

10 (a) 40 to 100% by weight monoethylenically unsaturated

C3- to CiQ-monocarboxylic acids and / or monoethylenically unsaturated C4 to Cβ-dicarboxylic acids, their anhydrides, alkali salts and / or ammonium salts,

15

20 (c) 0 to 5% by weight of at least 2 ethylenically unsaturated, non-conjugated double bonds in the molecule having monomers

in the presence of

25

(B) monosaccharides, oligosaccharides, polysaccharides, oxidatively, hydrolytically or enzymatically degraded polysaccharides, oxidized hydrolytically or oxidized enzymatically degraded polysaccharides, 30 chemically modified mono-, oligo- and polysaccharides or mixtures of the compounds mentioned

in the weight ratio (A): (B) of (95 to 20): (5 to 80) as water treatment agent, with the exception of oxidatively degraded graft polymers of maleic anhydride and (meth) acrylic acid on polysaccharides.

2. Use according to claim 1, characterized in that as component (A)

40

(a) acrylic acid, methacrylic acid, maleic acid or mixtures thereof and (b) Acrylamϊdomethylpropansulfonsäure or N-vinylimidazole or mixtures thereof

starts.

(A) monomer mixtures

(a) 40 to 100% by weight monoethylenically unsaturated

C3- to Cιo ~ monocarboxylic acids and / or monoethylenically unsaturated C4 to Cs-dicarboxylic acids, their anhydrides, alkali salts and / or ammonium salts,

in the presence of

to 20) in a weight ratio (A) :( B) of (95: are (5 taken through 80), said oxidatively degraded graft polymers of maleic anhydride and (meth) acrylic acid to be ^¬ polysaccharides. INARTICLE 19 CERTIFICATE

On the basis of the EP-A-0 404 377 determined in the international search report, a new disclaimer was included in the new patent claims 1 to 4, with which graft polymers of maleic anhydride and (meth) acrylic acid on polysaccharides subjected to oxidative degradation are excluded from the claimed use. EP-A-0 404 377 is to be regarded as a publication which was published before the international filing date but after the claimed priority date.