JP2023502826A - Anionic Copolymers Suitable as Scaling Inhibitors for Sulfide-Containing Scale - Google Patents

Abstract

The present invention relates to anionic copolymers suitable as scaling inhibitors in hydrous systems, particularly as inhibitors of antimony(III) sulfide-containing scale formation. The present invention also relates to a method for reducing sulfide scaling in water-containing systems, particularly in circulating water systems of geothermal power plants where the formation of sulfide-containing scale, especially antimony(III) sulfide-containing scale, can occur. This anionic copolymer has the following properties. 1) This copolymer consists of the following a and b. a: polymerized units of monomer M1 which is a primary amide of a monoethylenically unsaturated monocarboxylic acid having 3 to 6 carbon atoms b: a monoethylenically unsaturated monomer having a sulfonic acid group and/or a sulfuric acid group, carboxyl 2) The copolymer has an anionic charge density of 0.5 to 6.0 mol/kg. Range. 3) The sodium salt of this copolymer has a weight average molecular weight Mw of at least 10000 g/mol as determined by gel permeation chromatography.

Description

The present invention relates to anionic copolymers which are suitable as inhibitors of scaling of sulfide-containing scale, especially antimony(III) sulfide-containing scale, in hydrous systems. The present invention also relates to a method for reducing sulfide-containing scaling in water-containing systems, particularly in circulating water systems of geothermal power plants where the formation of sulfide-containing scale, especially antimony(III) sulfide-containing scale, can occur.

The growing need for clean and renewable energy leads to ever-increasing investments in geothermal power generation. Efficient use of geothermal brines is generally limited by dissolved salts, which are particularly troublesome as they form deposits, also called "scale", on the surface area of the geothermal fluid circulation system. Scaling or fouling causes degradation of the performance of power plant components such as pipes, pumps, and heat exchangers, which inevitably leads to reduced efficiency and can even lead to failure of the entire power plant. Additional maintenance is required for scale removal. The use of suitable additives suppresses its formation and promotes smooth operation.

Hydrous systems, such as geothermal power station hypersalinity water circulation systems, require mitigation of common scales based on silicates, calcium carbonate, calcium sulfate or barium sulfate. Apart from that, less common scales such as sulfides, especially antimony and arsenic sulfides, can cause fouling problems, especially in high-salinity water circulation systems of geothermal power plants. Despite the low concentration of antimony in water in most hydrous systems, the quantitative precipitation of antimony(III) sulfide due to its very low solubility in water below pH 9 suggests the presence of antimony and sulfide in water. can be very problematic with respect to fouling. In hydrous systems, antimony(III) sulfide usually crystallizes in the form of fine needles that loosely clog the inner surface of the hydrous system and form a porous layer that can trap highly saline water. As a result, heat transfer coefficients may be reduced and/or clogged pipes may occur. See K. Brown, Proceedings International Workshop on Mineral Scaling 2011, Manila, Philippines, May 25-27, 2011, pp. 103-106. Removal of stibnite-containing scale is difficult and rarely achievable by chemical means. Therefore, stibnite-containing scale is usually removed mechanically, which is time consuming and requires maintenance to remove the stibnite scale.

Certain polyphosphates, polyacrylic acids, polymethacrylic acids, lignosulfonic acids and their salts, tannins, naphthalenesulfonic acid formaldehyde condensation products, polyphosphates such as tripolyphosphates and hexametaphosphates, phosphonic acids, polymaleic acids , hydrolyzed copolymers and terpolymers of maleic anhydride and salts of these acids, and salts of these acids, have been proposed as useful additives to aqueous systems. The use of these scale inhibitors, especially polyacrylic acid and maleic acid polymers, is effective in controlling scale deposits in general, especially silicate, calcium carbonate, barium sulfate, calcium phosphate and calcium sulfate scale deposits. It is widely recognized that there is

Although the formation of scale in general can be alleviated with the above-mentioned antimony additives, the formation of sulfide-containing scale, particularly antimony (III) sulfide-containing scale (hereinafter also referred to as stibnite-containing scale), still occurs when water is added to antimony. is a serious problem in hydrous units containing sulfides and sulfides. Since the solubility of antimony(III) sulfide decreases with decreasing pH and decreasing temperature, the particular risk of formation of stibnite-containing scale is at pH up to 9, especially up to pH 8.5 and/or up to 120°C. at a temperature of Conditions favorable to the formation of sulfide-bearing scale, especially stibnite-bearing scale, are usually met in high-salinity water circulation systems of geothermal power plants. However, the problem of the formation of sulfide-containing scale, especially stibnite-containing scale, is that the water contains heavy metal salts, especially antimony salts, and sulfides, and the operation is carried out under conditions suitable for the formation of water-insoluble sulfides such as stibnite. can occur in other hydrous systems as well.

U.S. Pat. No. 4,224,151 injects an oxygen-containing gas into a geothermal fluid such that the hydrogen sulfide contained in the fluid is partially oxidized to water-soluble oxidation products with an oxidation number of sulfur less than +6. A method for preventing scale deposition from hydrogen sulfide-bearing geothermal fluids is described.

J. S. Gill et al., GRC Transactions Vol.37, 2013, reported that certain anionic copolymers with high charge density and low molecular weight reduced the particle size of precipitated stibnite, imparted anionic charge to the stibnite particles, and dispersal may reduce the formation of stibnite-containing scale. Similar results were presented by L. Muller et al., Proceedings World Geothermal Congress 2015, Melbourne, Australia, April 19-25, 2015, pp. 1-11.

US Pat. No. 5,032,298 describes low molecular weight copolymers of acrylic acid and acrylamide having a molecular weight distribution such that at least 60% by weight of the copolymer has a molecular weight of less than 500 Daltons. These copolymers have been suggested to be suitable for anti-scaling of the inner walls of petroleum and geothermal equipment. The copolymers described there are not particularly suitable for controlling the formation of sulfide scale.

U.S. Pat. No. 5,403,493 states that copolymers having carboxylate and/or sulfonate groups may be suitable as scale inhibitors which are said to be suitable for geothermal retention. disclosed. This copolymer is used in combination with a carbohydrazide to achieve better corrosion protection. The copolymers described there are not suitable for controlling the formation of sulfide scale.

US Pat. No. 5,256,303 discloses a method of inhibiting calcium sulfate scale formation and deposition and/or dispersing iron from a feed stream passing through a reverse osmosis system. The copolymers described therein contain acrylamide and acrylic acid units, but their use described therein is limited to sulfate scale inhibitors in a particular system, namely reverse osmosis systems. . Furthermore, this document does not provide any evidence or suggestion that the copolymers described therein are suitable for inhibiting the formation of sulfide scale.

US Pat. No. 4,801,388 discloses a method of controlling scale deposits by adding hydrocarbon copolymers or terpolymers of (meth)acrylic acid and sulfoalkyl(meth)acrylamides. The copolymers or terpolymers described there are particularly suitable for calcium phosphate, calcium carbonate, iron phosphate, barium sulfate and magnesium phosphate. However, this document does not provide any evidence or suggestion that the copolymers described therein are suitable for inhibiting sulfide scale formation.

It is widely accepted in the art that general scale inhibitors that inhibit all types of scale with similar performance are not available, and probably not. Rather, most known scale inhibitors are specific with respect to scale type. For example, in the proceedings of the 2013 EUROCORR conference, Hater et al. show that aminotrimethylene phosphonate (ATMP) exhibits 100% inhibition against calcium carbonate, but much lower inhibition against potassium sulfate and potassium phosphate. It shows up to 20% suppression. In contrast to ATMP, a homopolymer of aspartic acid (PASP) exhibits 80% inhibition on calcium sulfate, but little inhibition on calcium phosphate. Neither homopolymers nor copolymers are suitable for controlling all types of scale. For example, according to Hater et al., copolymers of acrylic acid (AA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) can be used to convert calcium sulfate, calcium phosphate, or iron oxide into calcium carbonate scale (less than 40% (approximately 70% to 80% inhibition) and suppressed much better than (suppression of ). A study in Amjad in Materials Performance, Volume 55, No.6, 2016 (NACE International) also reports different performance of scale inhibitors on different scales. For example, inhibition of calcium carbonate by 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) reaches almost 100%, whereas inhibition of calcium phosphate by HEDP is only about 30%. Such research results indicate that the high inhibitory effect of scale inhibitors on certain scales is not transferable to other scale types. In other words, even if a scale inhibitor shows 100% inhibition of a particular scale, e.g., calcium carbonate, the assurance that this scale inhibitor will show the same inhibition effect on other types of scale, such as zinc hydroxide. no. Therefore, inhibitory effects at a particular scale cannot be predicted or extrapolated from inhibitory effects at other scales.

U.S. Patent Application Publication No. 2018/0327294 discloses the addition of sulfide and sulfide in a salty water circulation system of a geothermal power plant comprising injecting an aqueous composition comprising a sulfide scale inhibitor and a silica scale inhibitor into the salty water. A method for inhibiting the formation of silica scale is disclosed. The sulfide scale inhibitor is a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and the silica scale inhibitor is a copolymer of acrylic acid and hydroxypolyethoxyallyl ether. The copolymers described there are not particularly suitable for suppressing the formation of stibnite scale.

It is an object of the present invention to provide a scale inhibitor which, at low doses, effectively reduces or even inhibits the formation of sulfide-containing scale, particularly stibnite-containing scale and/or arsenic sulfide-containing scale.

Surprisingly, these and further problems are
a: polymerized units of the monomer M1 which is a primary amide of a monoethylenically unsaturated monocarboxylic acid having 3 to 6 carbon atoms, and b: a monoethylenically unsaturated monomer having a sulfonic acid group and/or a sulfuric acid group. , a monoethylenically unsaturated monomer having a carboxyl group, and a monoethylenically unsaturated monomer M2 selected from mixtures thereof,
Anion charge density in the range of 0.5-6.0 mol/kg or 0.5-5.0 mol/kg, especially 0.8-5.0 mol/kg or 0.8-4.0 mol/kg or 1.0 in the range of ~4.0 mol/kg, especially in the range of 0.5-3.0 mol/kg, 0.8-3.0 mol/kg or 1.0-3.0 mol/kg;
Anions which, in the form of their sodium salts, have a weight-average molecular weight Mw determined by gel permeation chromatography of at least 10 000 g/mol, in particular at least 15 000 g/mol, more particularly at least 20 000 g/mol, especially at least 22 000 g/mol or at least 25 000 g/mol It has been found that the problem is solved by a sexual copolymer.

These copolymers provide very good control of sulfide-containing scale, especially stibnite-containing scale, and are therefore useful in hydrous systems, especially sulfide-containing scale, especially stibnite-containing scale and/or arsenic sulfide-containing scale. It is particularly suitable for applications in water-containing systems where the formation of

Accordingly, a first aspect of the present invention provides a method for reducing the formation of sulfide-containing scale in a hydrous system, particularly stibnite-containing scale and/or A method for reducing the formation of arsenic sulfide-containing scale.
This anionic copolymer is
c: polymerized units of the monomer M1 which is a primary amide of a monoethylenically unsaturated monocarboxylic acid having 3 to 6 carbon atoms, and d: a monoethylenically unsaturated monomer having a sulfonic acid group and/or a sulfuric acid group. , a monoethylenically unsaturated monomer having a carboxyl group, and a monoethylenically unsaturated monomer M2 selected from mixtures thereof,
Anion charge density in the range of 0.5 to 6.0 or 0.5 to 5.0 mol/kg, especially 0.8 to 5.0 or 0.8 to 4.0 mol/kg or 1.0 to 4.0 mol /kg, especially in the range of 0.5-3.0 mol/kg, 0.8-3.0 or 1.0-3.0 mol/kg,
As the sodium salt form, it has a weight average molecular weight Mw determined by gel permeation chromatography of at least 10 000 g/mol, in particular at least 15 000 g/mol, more in particular at least 20 000 g/mol, especially at least 22 000 g/mol or at least 25 000 g/mol.

A second aspect of the present invention is particularly to reduce the formation of sulfide-containing scale, especially stibnite-containing scale and/or arsenic sulfide-containing scale in water-containing systems, especially in hypersaline water circulation systems of geothermal power plants. comprising polymerized units of monomer M1 and monomer M2 as defined herein and having the charge density and molecular weight defined herein in their deprotonated form.

A third aspect of the present invention provides an anionic copolymer, in deprotonated form, comprising polymerized units of monomer M1 and monomer M2 as defined herein, in which 0.5 to 5.0 mol/kg range, especially 0.8-5.0 mol/kg or 1.0-5.0 mol/kg, more especially 0.5-4.0 mol/kg, 0.8-4.0 mol/kg or 1.0-4 .0 mol/kg, especially in the range of 0.5-3.0 mol/kg, 0.8-3.0 mol/kg or 1.0-3.0 mol/kg, of the sodium salt. in the form weight in the range from 15 000 to 500 000 g/mol, or often in the range from 20 000 to 500 000 g/mol, especially in the range from 22 000 to 300 000 g/mol, especially in the range from 25 000 to 250 000 g/mol, determined by gel permeation chromatography It relates to anionic copolymers with an average molecular weight Mw.

The invention is associated with several advantages. First and foremost, the anionic copolymers defined herein are those which inhibit the formation of sulfide-containing scale, particularly stibnite-containing scale and/or arsenic sulfide-containing scale in aqueous systems susceptible to sulfide-containing scale formation. Provides efficient reduction or suppression. The copolymers defined herein do not require the phosphorus-containing antiscaling agents normally required to achieve efficient reduction or inhibition of sulfide-containing scale formation. Moreover, the copolymers of the present invention are readily prepared from readily available and inexpensive monomers by standard copolymerization techniques.

Detailed description of the invention

The following statements apply to any of the aspects disclosed herein.

Here and hereinafter, the term "scale" refers to deposits on the inner walls of a water-containing system. The terms "scale" and "sediment" are used synonymously.

Here and below, sulfide-containing scale refers to scale containing solid metal sulfides, including in particular antimony and arsenic sulfides.

Here and below, stibnite-containing scale refers to scale containing solid antimony(III) sulfide, ie stibnite or Sb ₂ S ₃ respectively. In particular, the stibnite-containing scale predominantly comprises or consists essentially of crystalline stibnite. This crystalline stibnite is usually present in the form of fine needles.

Here and below, the phrase "reduction or inhibition of the formation of sulfide-containing scale" refers to the formation of sulfide-containing scale, particularly stibnite-containing scale, and also antimony (V) sulfide-containing scale and/or arsenic sulfide-containing scale, in hydrous systems. Formation is meant to be significantly reduced by at least 15%, in particular by at least 20% or by at least 25% compared to hydrous systems without antiscaling agents.

Here and below, the terms "scale" and "scaling" are used synonymously.

Here and below, the terms "antiscaling agent" and "antiscaling agent" are used synonymously.

Here and below, the term "sulphide-containing scale" relates to scale comprising or consisting of inorganic sulphides, in particular containing or consisting of antimony(III) sulphide, antimony(V) sulphide and arsenic(III) sulphide. . The term "sulfide-containing scaling" relates to the formation of sulfide-containing scale.

Here and below, the term "carboxyl group" refers to a COOH group. The term "sulfonate group" refers to an _SO3- group attached to a carbon atom. The term "sulfate group" refers to a -O-SO ₃ - group in which the left oxygen atom is attached to the carbon atom of the monomer.

Here and below, the term "monoethylenically unsaturated monomer" means that the monomer has exactly one ethylenically unsaturated double bond capable of undergoing free-radical copolymerization.

Here and below, the term "water-containing system" means any device with internal surfaces in contact with water, such as tubes, heat exchangers, boilers, steam generators, turbines, pumps, wells, fracking devices, etc. (device) or arrangement of equipment (device). These devices may be part of plants such as power plants, in particular geothermal power plants, desalination plants, paper mills, crushing plants and the like.

Here and below, the term "copolymer in deprotonated form" means that the acidic groups of the copolymer, i.e. the carboxyl and sulfonate groups of the polymerized units of monomer M2, are completely deprotonated and thus the anionic means that it exists in the form of

Under those conditions of use to reduce or inhibit scaling, the copolymers usually exist in a partially or fully deprotonated form. The carboxyl groups of the polymerized units of monomer M2 are usually present in at least partially or completely deprotonated form, ie as CO ₂ ^— groups, whereas the sulfonate groups are usually in completely deprotonated form, That is, it exists as an SO ₃ ^-group . Thus, the polymerized units of monomer M2 impart an anionic charge to the copolymer. When the carboxyl groups and sulfonate groups of the polymerized units of monomer M2 are completely deprotonated, the copolymer has a concentration in the range of 0.5 to 5.0 mol/kg, especially 0.8 to 5.0 mol/kg or 1 0-5.0 mol/kg, especially 0.5-4.0 mol/kg, 0.8-4.0 mol/kg or 1.0-4.0 mol/kg, and especially 0.5-3. It has an anionic charge density in the range of 0 mol/kg, 0.8-3.0 mol/kg or 1.0-3.0 mol/kg.

The anionic charge density of the deprotonated form of the copolymer correlates with the relative molar amount of polymerized units of monomer M1. The anionic charge density _QA of a copolymer containing polymerized units of monomers M1 and M2 and optionally one or more neutral monomers M3 can be calculated by the following equation (1).
Q _A =1000×[M2]/
([M1] x Mw (M1) + [M2] x Mw (M2) + [M3] x Mw (M3))
(1)

The variables in equation (1) mean the following.
[M1] is the relative molar amount of monomer M1 in mol %.
[M2] is the relative molar amount of monomer M2 in mol %.
[M3] is the relative molar amount of monomer M3 in mol %.
Mw (M1) is the molecular weight (g/mol) of monomer M1.
Mw (M2) is the molecular weight (g/mol) of the monomer M2. and Mw (M3) is the molecular weight (g/mol) of the monomer M3.

Those skilled in the art will readily recognize that the term [M3]×Mw(M3) is 0 if the copolymer does not contain polymerized units of monomer M3. Those skilled in the art will also readily recognize that the charge density of copolymers containing two different monomers M2a and M2b can be calculated by the modified equation (1a).
Q _A =1000×A/
([M1]×Mw(M1)+B+[M3]×Mw(M3)) (1a)

where A is [M2a] + [M2b],
B is [M2a]×Mw(M2a)+[M2b]×Mw(M2b),
[M2a] and [M2b] are the relative molar amounts of monomers M2a and M2b, respectively, in mol %.
and Mw (M2a) and Mw (M2b) are the molecular weights of the monomers M2a and M2b respectively in g/mol.

If the copolymer contains polymerized units of the monomers M1 and M2 and, in addition to the optional monomer M3, of the cationic monomer M4, the copolymer is zwitterionic in its deprotonated form. However, the net anionic charge density will be in the above range. Net anionic charge density can be calculated by the following equation (1b).
Q _A =1000×([M2]−[M4])/C (1b)

here,
C = ([M1] x Mw (M1) + [M2] x Mw (M2) + [M3] x Mw (M3) + [M4] x Mw (M4))
[M4] is the relative molar amount of monomer M4 in mol %.
Mw (M4) is the molecular weight (g/mol) of monomer M4. And here,
[M1], [M2], [M3], Mw(M1), Mw(M2), and Mw(M3) are as defined in formula (1).

The anionic charge density of the deprotonated form of the copolymer can also be determined experimentally by titration. For example, the total charge of a polymer can be determined, eg, by colloidal charge titration. This means detection of the streaming potential and titration to zero potential using a reverse potential polyelectrolyte titrant, here a cationic polyelectrolyte such as Polydadomac (polydiallyldimethylammonium chloride). Colloidal charge titration is a well-established technique for determining the surface charge of colloidal particles and can be applied by analogy (e.g. LH Mikkelsen, Wat. Res., (2003) Vol 37, 2458-2466 and K. Ueno et al., J. Chem. The amount of carboxyl groups can be determined by acid/base titration, while the amount of sulfonate groups can be determined spectroscopically, eg via ¹ H-NMR spectroscopy.

With respect to the ability to reduce or inhibit the formation of sulfide-containing scale, the copolymers of the present invention have a concentration of at least 15,000 g/mol by gel permeation chromatography of the sodium salt of the copolymer, particularly in buffered water at pH 7.0. It is advantageous to have a weight-average molecular weight Mw of at least 20 000 g/mol, more especially at least 22 000 g/mol, especially at least 25 000 g/mol or at least 30 000 g/mol. Frequently, the weight-average molecular weight Mw of the copolymers according to the invention does not exceed ¹⁰ g/mol, especially determined by gel permeation chromatography of the sodium salt of the copolymer in buffered water at pH 7.0, preferably at most 5×10 ⁶ g/mol, in particular at most 10 ⁶ g/mol, more especially at most 500 000 g/mol or at most 300 000 g/mol, especially at most 250 000 g/mol. In particular, the copolymers of the invention have a concentration measured by gel permeation chromatography in the range from 15000 to 10 ⁶ g/mol, more preferably in the range from 15000 to 500000 g/mol, from 20000 to 500000 g/mol or from 22000 to 300000 g/mol. /mol, especially in the range from 25000 to 250000 g/mol.

The number-average molecular weight Mn of the copolymers according to the invention in the form of sodium salts, determined by gel permeation chromatography, is often in the range from 2000 to 10 ⁶ g/mol, preferably from 3000 to 500 000 g/mol or from 4000 to 300 000 g/mol. mol range, more preferably in the range from 7000 to 250000 g/mol, especially in the range from 10000 to 200000 g/mol. Frequently, the ratio of the weight-average molecular weight Mw to the number-average molecular weight Mn of the copolymer in sodium salt form, ie the ratio Mw/Mn, is in the range 1.1-10, especially in the range 2-6.

Both the weight average molecular weight (Mw) and number average molecular weight (Mn) referred to herein relate to the molecular weight of the sodium salt of the respective copolymer and are determined by gel permeation chromatography, hereinafter abbreviated as GPC. . Gel permeation chromatography is typically performed using a cross-linked acrylate copolymer of defined pore size as the stationary phase, water buffered to pH 7 as the eluent, and polyacrylic acid sodium salt as the standard. GPC details are provided in the experimental section below.

With respect to the ability of the copolymer to reduce or inhibit the formation of sulfide-containing scale, the amount of polymerized units of monomer M1 preferably ranges from 55 to 95 mol %, based on the total molar amount of polymerized units in the copolymer. , especially in the range of 60-95 mol % or 60-90 mol %, especially in the range of 65-95 mol % or 65-90 mol % or 65-88 mol % or 70-88 mol %.

Examples of suitable monomers M1 are acrylamide and methacrylamide and mixtures thereof. Preferably, the polymerized units of monomer M1 comprise polymerized units of methacrylamide. In particular, at least 50 mol % or at least 80 mol % or at least 100 mol % of the polymerized units of monomer M1 are polymerized units of methacrylamide.

With respect to the ability of the copolymer to reduce or inhibit the formation of sulfide-containing scale, the amount of polymerized units of monomer M2 preferably ranges from 5 to 45 mol %, based on the total molar amount of polymerized units in the copolymer. , especially in the range of 5-40 mol % or 10-40 mol %, especially in the range of 5-35 mol % or 10-35 mol % or 12-35 mol % or 12-30 mol %.

According to the invention, the monomers M2 are monoethylenically unsaturated monomers having sulfonic acid or sulfate groups, hereinafter referred to as monomers M21, and monoethylenically unsaturated monomers having carboxyl groups, hereinafter referred to as monomers M22. is selected from the group consisting of

Suitable monomers M21 with sulfonate groups are, for example, vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, allyloxy-2-hydroxypropanesulfonic acid, vinylbenzenesulfonic acid and monomers of the formula (I) and salts thereof , especially the ammonium and alkali metal salts, especially the sodium salts thereof.

here,
R is H or C ₁ -C ₃ alkyl, such as methyl, ethyl or n-propyl, especially H or methyl;
X is O or NH, and Z is 1,2-ethanediyl, 1,2-propanediyl, 1,3-propanediyl, 2-methyl-1,2-propanediyl, 1,4-butanediyl, 1 , 2-butanediyl, 2-methyl-1,2-butanediyl and the like, C ₂ -C ₆ alkanediyl, etc.

Suitable monomers M21 with sulfate groups are, for example, allyl polyether sulfates, such as allyl sulfate and allyl polyethoxy sulfate, ie monomers of formula (II).
_CH2 =CH-CH2-(O- _{CH2 - CH2} ) _n -OS(=O)-OH (II)

Here, n is in the range from 2 to 20 and salts thereof, especially ammonium salts and alkali metal salts, especially sodium salts thereof.

Among the monomers M21, preference is given to monomers having sulfonate groups, especially monomers of the formula (I), salts thereof, especially alkali metal salts and especially sodium salts. Particularly preferred are the monomers of formula (I), wherein R is H or CH ₃ , X is N, Z is C ₂ -C ₄ alkanediyl, N-acrylamido-C ₂ -C Also called ₄ -alkylsulfonic acids and N-methacrylamide-C ₂ -C ₄ -alkylsulfonic acids and salts thereof, especially alkali metal salts and especially sodium salts, and R is H or CH ₃ , X is N, Z is C ₂ -C ₄ alkanediyl, which are also called acryloxy-C ₂ -C ₄ -alkylsulfonic acids and methacryloxy-C ₂ -C ₄ -alkylsulfonic acids and salts thereof, especially alkali metal salts, especially sodium salts. Examples of monomers M21 of formula (I) are 2-acryloxyethylethanesulfonic acid, 3-acryloxypropanesulfonic acid, 2-acryloxypropanesulfonic acid, 2-acrylamidoethanesulfonic acid, 2-acrylamidopropanesulfonic acid and 2-Acrylamido-2-methylpropanesulfonic acid and salts of the aforementioned monomers, especially alkali metal salts, especially sodium salts. In particular, monomer M21 is 2-acrylamido-2-methylpropanesulfonic acid or its salts, especially its ammonium and alkali metal salts, especially its sodium salt.

Suitable monomers M22 are, in particular, semi-esters of acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, maleic acid or fumaric acid, such as monomethyl maleate, monoethyl fumarate, monoethyl maleate, monoethyl fumarate and acryloxyacetic acid. , are monoethylenically unsaturated monocarboxylic acids having 3 to 6 carbon atoms. Suitable monomers M22 are also monoethylenically unsaturated dicarboxylic acids having 4 to 6 carbon atoms, such as fumaric acid, maleic acid, itaconic acid and citraconic acid. Preferred monomers M22 are monoethylenically unsaturated monocarboxylic acids having 3 to 6 carbon atoms, acrylic acid, methacrylic acid and mixtures thereof being particularly preferred.

In addition to polymerized units of monomer M1 and monomer M2, the copolymer may contain polymerized units of neutral monoethylenic monomer M3. The amount of polymerized units of monomer M3 can be at most 20 mol %, but at most 5 mol %, especially at most 2 mol %, based on the total molar amount of polymerized units of the copolymer. At most 1 mol %, or even 0 mol %, based on the total molar amount of polymerized units therein. Examples of such monomers include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate or hydroxypropyl methacrylate, N-vinyllactams such as N-vinylpyrrolidone and N-vinylcaprolactam. hydroxy-C ₂ -C ₄ -alkyl esters of monoethylenically unsaturated monocarboxylic acids having atoms.

In addition to polymerized units of monomer M1 and monomer M2, the copolymer may contain polymerized units of cationic monoethylenic monomer M4. the amount of polymerized units of monomer M4 can be as high as 20 mol %, but not more than 5 mol %, especially not more than 2 mol %, based on the total molar amount of polymerized units in the copolymer;
At most 1 mol %, or even 0 mol %, based on the total molar amount of polymerized units in the copolymer. Examples of such monomers M4 include N—C ₁ -C ₄ -alkyl-N′-vinylimidazolium salts such as N-methyl-N′-vinylimidazolium salts, N-methyl-vinylpyridinium salts. N—C ₁ -C ₄ -Alkyl-vinylpyridinium salts, especially the chlorides, sulfates, hydrogensulfates, methosulfates and ethosulfates thereof, and the monomers of formula (III), such as Not limited.

wherein R′ is H or C ₁ -C ₃ alkyl such as methyl, ethyl or n-propyl, especially H or methyl;
X' is O or NH, and Z' is 1,2-ethanediyl, 1,2-propanediyl, 1,3-propanediyl, 2-methyl-1,2-propanediyl, 1,4-butanediyl, 1 C ₂ -C ₆ alkanediyl such as ,2-butanediyl, 2-methyl-1,2-butanediyl, etc.
R ^a , R ^b , R ^c are the same or different and are C ₁ -C ₃ alkyl, especially methyl or ethyl;
A ⁻ is a counter-anion equivalent such as chloride, methosulfate, ethosulfate, hydrogensulfate, half-sulfate.

In addition to polymerized units of monomer M1 and monomer M2, the copolymer has polymerized units of monomer M5 having more than one ethylenically unsaturated double bond, such as from 2 to 5 ethylenically unsaturated double bonds. may include The amount of polymerized units of monomer M5 is often at most 1 mol %, especially at most 0.5 mol %, but at least 0.1 mol %, especially 0 mol %, based on the total molar amount of polymerized units in the copolymer. is. Examples of such monomers M5 include, but are not limited to, divinylbenzene, ethylene glycol diacrylate, propanediol diacrylate, butanediol diacrylate, hexanediol diacrylate, diethylene glycol diacrylate, triethylene glycol triacrylate, triethylene glycol triacrylate, Methylolpropane triacrylate, di(trimethylolpropane)tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate and the corresponding di-, tri-, and tetramethacrylates.

Preferred for copolymers are copolymers consisting of at least 95 mol %, especially at least 98 mol %, especially at least 99 mol %, of the polymerized units of monomer M1 and polymerized monomer M2, based on the total molar amount of polymerized units in the copolymer. It is a polymer.

Copolymers containing no more than 1000 ppm of phosphorus, especially less than 500 ppm of phosphorus, are particularly preferred.

A preferred group 1 of embodiments is polymerized units of monomer M21, ie polymerized units of monoethylenically unsaturated monomers having a sulfonate group, especially of at least one monomer of formula (I), especially 2-acrylamido-2-methylpropanesulfone. It relates to copolymers containing polymerized units of acid. In these preferred groups of embodiments, the polymerized units of monomer M21 may be the only polymerized units of monomer M2. In this preferred embodiment group 1, the copolymer comprises at least 95 mol %, especially at least 98 mol %, especially at least 99 mol % of units of polymerized monomer M1 and of monomer M21, based on the total molar amount of polymerized units of the copolymer. It preferably consists of units.

Among the copolymers of embodiment group 1, particularly preferred are copolymers consisting of at least 95 mol %, especially at least 98 mol %, especially at least 99 mol %, based on the total molar amount of polymerized units in the copolymer: It is a polymer.
- 55 to 95 mol% or 60 to 95 mol% of the polymerized units of at least one monomer M1 preferably selected from acrylamide, methacrylamide and mixtures thereof, based on the total molar amount of polymerized units in the copolymer, especially 60-90 mol %, especially 65-95 mol % or 65-90 mol % or 65-88 mol % or 70-88 mol %
- based on the total molar amount of polymerized units in the copolymer, polymerized units of at least one monomer M21, preferably selected from monomers of formula (I), especially 2-acrylamido-2-methylpropanesulfonic acid of the

Another preferred group 2 of embodiments are polymerized units of monomers M22, i.e. polymerized units of monoethylenically unsaturated monomers having a carboxyl group, in particular monoethylenically unsaturated monocarboxylic acids having 3 to 6 carbon atoms, In particular, it relates to copolymers containing polymerized units of acrylic acid and/or methacrylic acid. In these preferred copolymers, the polymerized unit of monomer M22 can be the only polymerized unit of monomer M2. In this preferred embodiment group 2, the copolymer preferably comprises at least 95 mol %, especially at least 98 mol %, especially at least 99 mol % of polymerized units of monomer M1 and monomers, based on the total molar amount of polymerized units of the copolymer. It consists of polymerized units of M22.

Among the copolymers of embodiment group 2, particularly preferred are copolymers consisting of at least 95 mol %, especially at least 98 mol %, especially at least 99 mol %, based on the total molar amount of polymerized units of the copolymer: It is a coalescence.
- 55 to 95 mol% or 60 to 95 mol% of the polymerized units of at least one monomer M1 preferably selected from acrylamide, methacrylamide and mixtures thereof, based on the total molar amount of polymerized units in the copolymer, especially 60-90 mol %, especially 65-95 mol % or 65-90 mol % or 65-88 mol % or 70-88 mol %
- preferably selected from monoethylenically unsaturated monocarboxylic acids having 3 to 6 carbon atoms, especially acrylic acid, methacrylic acid and mixtures thereof, based on the total molar amount of polymerized units in the copolymer; 5 to 45 mol % or 5 to 40 mol %, especially 10 to 40 mol %, especially 5 to 35 mol % or 10 to 35 mol % or 12 to 35 mol % or 12 to 30 mol % of the polymerized units of at least one monomer M22 in

A particularly preferred group 3 of embodiments are copolymers comprising polymerized units of both monomers M21 and monomers M22, i.e. a combination of polymerized units of at least one monomer M21 and at least one monomer M22, in particular the following combinations of polymerized units Regarding.
- at least one monomer M21 selected from the monomers of formula (I) and salts thereof, especially polymerized units of 2-acrylamido-2-methylpropanesulfonic acid; at least one monomer M22 selected from saturated monocarboxylic acids, especially acrylic acid, methacrylic acid and mixtures thereof

In this preferred embodiment group 3, the copolymer preferably comprises at least 95 mol of polymerized units of monomer M1, polymerized units M21 of monomer M1 and polymerized units of monomer M22, based on the total molar amount of polymerized units of the copolymer. %, especially at least 98 mol %, especially at least 99 mol %. In this particular group of embodiments 3, the molar ratio of polymerized units of monomer M21 to polymerized units of monomer M22 is often in the range 1:10 to 10:1, especially in the range 1:5 to 5:1, especially 1: It ranges from 3 to 3:1.

Among the copolymers of embodiment group 3, particularly preferred are copolymers consisting of at least 95 mol %, especially at least 98 mol %, especially at least 99 mol %, based on the total molar amount of polymerized units of the copolymer be.
- 55 to 95 mol% or 60 to 95 mol% of the polymerized units of at least one monomer M1 preferably selected from acrylamide, methacrylamide and mixtures thereof, based on the total molar amount of polymerized units in the copolymer, especially 60-90 mol %, especially 65-95 mol % or 65-90 mol % or 65-88 mol % or 70-88 mol %
- 5 to 45 mol% or 5 to 40 mol%, especially 10 to 40 mol%, especially 5 to 35 mol% or 10 to 35 mol% or 12 to 35 mol% or 12 to 45 mol%, based on the total molar amount of polymerized units in the copolymer 30 mol % polymerized units of at least one monomer M21, preferably selected from monomers of formula (I), especially 2-acrylamido-2-methylpropanesulfonic acid, and preferably 3 to 6 carbon atoms at least one monomer M22 selected from monoethylenically unsaturated monocarboxylic acids, in particular acrylic acid, methacrylic acid and/or mixtures thereof, wherein the molar ratio of polymerized units of monomer M21 to monomer M22 is , often in the range 1:10 to 10:1, especially in the range 1:5 to 5:1, especially in the range 1:3 to 3:1.

The deprotonated copolymers of embodiment groups 1, 2 and 3 are in particular in the range from 0.8 to 4.0 mol/kg or from 1.0 to 4.0 mol/kg, especially from 0.5 to 3.0,0 .8-3.0 mol/kg or 1.0-3.0 mol/kg anion charge density as described above.

The sodium salts of the copolymers of embodiment groups 1, 2 and 3 have a weight-average molecular weight Mw as determined by gel permeation chromatography, particularly in the range from 15000 to ¹⁰ g/mol, more particularly from 15000 to 500000 g/mol. mol range or in the range from 200 000 to 500 000 g/mol, or in the range from 22 000 to 300 000 g/mol, especially in the range from 25 000 to 250 000 g/mol. The sodium salts of the copolymers of embodiment groups 1, 2 and 3 have the number average molecular weight Mn measured by gel permeation chromatography, particularly in the range of 3000 to 500000 g/mol or 4000 to 300000 g/mol, more preferably has a number average molecular weight Mn in the range from 7000 to 250 000 g/mol, especially from 10 000 to 200 000 g/mol.

Although the copolymers of the invention can have any molecular structure, they are preferably random copolymers. Random copolymers are understood as copolymers in which the distribution in the chain of polymerized units of different monomers, here monomers M1 and M2 and optionally one or more further monomers M3, M4 and/or M5, follows a dispersive distribution. . In other words, the ratio of monomers in the compartment corresponds to the molar ratio of monomers (random distribution). The copolymer may have a linear or branched structure, but is preferably linear in nature. The copolymers are in particular random copolymers with a linear structure. However, the copolymer may also have an alternating or gradient structure.

The copolymers of the invention are prepared by copolymerization of at least one monomer M1 and at least one monomer M2 and optionally one or more further monomers M3, M4 and/or M5, for example according to S. Koltzenburg, M. Maskos, O. for copolymerizing the above ethylenically unsaturated monomers, as described in Nuyken (Springer-Verlag 2017) and D. Braun et al., "Polymer Chemistry", "Praktikum der Makromolekularen Stoffe" and the literature cited therein. can be prepared analogously to known methods of The copolymers of the invention are prepared by polymerization of at least one monomer M1 and optionally one or more further monomers M3, M4 and/or M5, analogously to known methods for copolymerizing ethylenically unsaturated monomers. , followed by partial hydrolysis of the polymerized units of monomer M1. The primary amide groups of polymerized monomer M1 are thereby converted to carboxyl groups. Partial hydrolysis is carried out such that the degree of conversion corresponds to the desired anionic charge density of the copolymer. Partial hydrolysis can be performed as described herein.

In many cases, the copolymers described here are obtained by free-radical aqueous copolymerization of monomers M1 and M2 and optionally one or more further monomers M3, M4 and/or M5. Alternatively, the copolymers described herein are prepared by free radical aqueous polymerization of at least one monomer M1 and optionally at least one monomer M2 and optionally one or more further monomers M3, M4 and/or M5 followed by It can be obtained by partial hydrolysis of polymerized units of monomer M1.

The term free-radical polymerization refers to the polymerization of ethylenically unsaturated monomers, here acrylic acid and C ₁ -C ₃ alkyl acrylates, in the presence of a polymerization initiator that forms radicals under the polymerization conditions by thermal decomposition or redox reaction. is understood to be performed by Solution polymerization means that a solution of the monomers in a solvent that can also dissolve the copolymer is polymerized by free radical polymerization, ie in the presence of a polymerization initiator.

Suitable solvents for carrying out solution polymerizations include water and polar organic solvents, and mixtures thereof with water. Suitable polar organic solvents are those that are at least partially miscible with water, preferably to the extent of at least 100 g/L at 20° C. and ambient pressure. Suitable organic solvents include, but are not limited to, C ₁ -C ₄ solvents such as methanol, ethanol, propanol, isopropanol (=2-propanol), n-butanol, sec-butanol (=2-butanol) or isobutanol. alkanols, dimethylsulfoxide, and ethyl acetate. Preferred organic solvents are selected from C ₁ -C ₄ alkanols such as methanol, ethanol, propanol, isopropanol, n-butanol, sec-butanol or isobutanol, preferably isopropanol or sec-butanol. In particular, the solvent for carrying out the solution polymerization is selected from water and mixtures of water with at least one polar organic solvent, preferably water and mixtures of water with one or more C ₁ -C ₄ alkanols. In particular, the solvent used for the free-radical polymerization of the monomers forming the copolymer or its precursors comprises at least 50% by volume, especially at least 70% by volume, based on the total amount of solvent.

When the polymerization of the monomers forming the copolymer or its precursors is carried out as solution polymerization, the concentration of the monomers in the polymerization reaction may vary. In particular, the weight ratio of monomer to solvent is in the range from 1:20 to 1.2:1, especially in the range from 1:10 to 1:1, especially in the range from 1:8 to 1:1.5.

The polymerization of the monomers forming the copolymer or its precursor is preferably a free-radical copolymerization and is therefore induced by a free-radical polymerization initiator (free-radical initiator). These can in principle be peroxides or azo compounds. Of course, redox initiation systems can also be used.

Suitable peroxides are in principle inorganic peroxides such as hydrogen peroxide or peroxodisulfates, for example mono- or dialkali metal or ammonium salts of peroxodisulfate, for example mono- and disodium, potassium or ammonium salts. substances such as diisopropyl peroxydicarbonate, t-amyl perneodecanoate, t-butyl perneodecanoate, t-butyl perpivalate, t-amyl perpivalate, bis(2,4-dichlorobenzoyl) peroxide, diisononanoyl peroxide, Didecanoyl peroxide, dioctanoyl peroxide, dilauroyl peroxide, bis(2-methylbenzoyl) peroxide, disuccinoyl peroxide, diacetyl peroxide, dibenzoyl peroxide, t-butyl per-2-ethylhexanoate, 2-ethylhexanoic acid t-butyl, bis(4-chlorobenzoyl) peroxide, t-butyl perisobutyrate, t-butyl permaleate, 1,1-bis(t-butylperoxy)cyclohexane, t-butylperoxyisopropyl carbonate, t - peroxyacids and esters of peroxyacids, such as butyl perisononanoate, t-butyl peracetate, t-amyl perbenzoate, 3-(t-butylperoxy)-3-phenylphthalide or t-butyl perbenzoate; 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, 2,2-bis(t-butylperoxy)butane (di-t-butylperoxide), 2,2-bis-10- (t-butylperoxy)propane, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, di(t-amyl)peroxide, α,α'-bis(t-butylperoxyisopropyl)benzene, 3,5-bis(t-butylperoxy)-3,5-dimethyl-1,2-dioxolane, di(t-butyl)peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne , 3,3,6,6,9,9-hexamethyl-1,2,4,5-tetraoxacyclononane, p-menthane hydroperoxide, alkyl and cycloalkyl peroxides such as pinane hydroperoxide, dicumyl peroxide, diisopropyl It can be an organic peroxide such as an aromatic peroxide such as benzene, mono-α-hydroperoxide or cumene hydroperoxide. A suitable peroxide may be hydrogen peroxide.

Typical azo initiators are, for example, 4,4′-azobis-4-cyanovaleric acid (ACVA), 2,2′-azobis(2-methylpropionamidine) dihydrochloride, 2,2′-azobis ( 2-methylpropionitrile) (AIBN), 2,2′-azobis(2-methylbutanenitrile), 2,2′-azobis(2,4-dimethylvaleronitrile), 1,1′-azobis(cyanocyclohexane ), 1,1′-azobis(N,N-dimethylformamide), 2,2′-azobis(2-methylbutyronitrile), 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile ), 2,2′-azobis(2,4,4-trimethylpentane), 2,2′-azobisisobutyronitrile, 2,2′-azobis(2-methylbutyronitrile), 2,2′ -azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis(1-cyclohexanecarbonitrile), 2,2' -azobis(isobutyramide) dihydrate, 2-phenylazo-2,4-dimethyl-4-methoxyvaleronitrile, dimethyl 2,2'-azobisisobutyrate, 2-(carbamoylazo)isobutyronitrile, 2,2′-azobis(2,4,4-trimethylpentane), 2,2′-azobis(2-methylpropane), 2,2′-azobis(N,N′-dimethyleneisobutylamidine), 2, 2'-azobis(N,N'-dimethyleneisobutylamidine) hydrochloride, 2,2'-azobis(2-amidinopropane), 2,2'-azobis(2-amidinopropane) hydrochloride, 2,2' -azobis(2-methyl-N-[1,1-bis(hydroxymethyl)ethyl]propionamide), azobis(2-amidopropane) dihydrochloride or 2,2′-azobis(2-methyl-N[1 , 1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide).

Typical redox initiators are mixtures of oxidizing and reducing agents such as, for example, hydrogen peroxide, peroxodisulfates or the aforementioned peroxide compounds. Corresponding reducing agents that can be used are, for example, the following low oxidation state sulfur compounds: alkali metal sulfites such as ammonium sulfite and alkali metal sulfite, e.g. potassium and/or sodium sulfite, ammonium bisulfite and alkali metal bisulfite, such as potassium and/or sodium bisulfite, ammonium metabisulfite and alkali metal metabisulfite, For example, potassium and/or sodium metabisulfite, formaldehyde sulfoxylates, such as potassium and/or sodium formaldehyde sulfoxylate, aliphatic sulfinic acid ammonium salts and alkali metal salts, especially potassium and/or sodium salts, and alkali metal hydrogen sulfide, such as potassium and/or sodium hydrogen sulfide, salts of polyvalent metals, especially Co(II) salts and Fe(II) salts, such as iron(II) sulfate, iron(II) ammonium sulfate or iron phosphate ( II) as well as dihydroxymaleic acid, benzoin and/or ascorbic acid, and reducing sugars such as sorbose, glucose, fructose and/or dihydroxyacetone.

Preferably, the free-radical polymerization initiator comprises an inorganic peroxide, in particular a peroxodisulfate such as a mono- or dialkali metal or ammonium salt of peroxodisulfate. In particular, radical polymerization initiators are redox initiators which contain inorganic peroxides as oxidizing agents, in particular peroxodisulfates such as mono- or dialkali metal or ammonium salts of peroxodisulfate. In these redox initiators, the reducing agent is an alkali metal sulfite such as potassium and/or sodium sulfite, an alkali metal bisulfite such as potassium bisulfite and/or sodium bisulfite, an alkali metal metabisulfite such as potassium and/or sodium bisulfite. or sodium metabisulfite, formaldehyde sulfoxylates, e.g. potassium and/or sodium formaldehyde sulfoxylate, alkali metal salts of aliphatic sulfinic acids, in particular potassium and/or sodium salts, and alkali metal hydrogen sulfides, e.g. It is preferably selected from the group of low oxidation state sulfur compounds such as potassium and/or sodium hydrogen sulfide. In these redox initiators, the molar amount of reducing agent exceeds the molar amount of oxidizing agent. In particular, the molar ratio of reducing agent to oxidizing agent is in the range from 1.5:1 to 100:1, especially in the range from 2:1 to 50:1.

The molecular weight of the copolymer can be adjusted by choosing the appropriate relative amount of free radical polymerization initiator to the monomers to be polymerized. As a rule of thumb, increasing the relative amount of free radical polymerization initiator decreases molecular weight, and decreasing the relative amount of free radical polymerization initiator increases molecular weight. When the free-radical polymerization initiator is selected from redox initiators, increasing the molar ratio of reducing agent to oxidizing agent will likewise lead to a decrease in molecular weight and vice versa. Typically, the amount of free radical polymerization initiator is in the range 0.02 to 20 mmol, especially 0.5 to 5.0 mmol per mol of monomer to be copolymerized. For redox initiators, these ranges refer to oxidizing agents.

The polymerization of the monomers forming the copolymer or its precursors is usually carried out at temperatures in the range of 25-150°C. The temperatures used are often in the range 40-120°C, especially in the range 50-110°C, especially in the range 60-90°C.

Polymerization of the monomers forming the copolymer or its precursors can be carried out at pressures of less than, equal to or greater than 1 atmosphere (atmospheric pressure), so that the polymerization temperature is greater than 100°C and may be up to 150°C. . Polymerization of the monomers is usually carried out at ambient pressure, but can also be carried out under elevated pressure. In this case the pressure may take values between 1.1 and 15 bar (absolute) or even more. Frequently, the free radical polymerizations of the present invention are carried out at ambient pressure (about 1 atmosphere) with the exclusion of oxygen, for example under an inert gas atmosphere, such as nitrogen or argon.

Polymerization of the monomers to form the copolymer or its precursors is carried out, for example, by batch or semi-batch procedures or continuous procedures. In a batch procedure, the monomers to be polymerized and optionally the solvent used in the polymerization procedure are charged to a reaction vessel and most or all of the polymerization initiator is added to the reaction vessel during the course of the polymerization reaction. In a semi-batch procedure, at least a portion of the total amount of free-radical polymerization initiator and solvent, and optionally a small amount of monomer, are charged to the reaction vessel, and the majority of the monomer that will polymerize during the course of the polymerization reaction is added to the reaction vessel. In a continuous process, monomers, polymerization initiator and solvent are continuously added to the reaction vessel and the resulting copolymer is continuously discharged from the polymerization vessel. Preferably, the polymerization of the monomers forming the copolymer or its precursors is carried out in a semi-batch procedure. In particular, at least 90% of the monomers to be polymerized are added to the reaction vessel during the course of the polymerization reaction.

Polymerization of the monomers to form the copolymer or its precursors can be carried out in a step in which residual monomers are removed, i.e. physical means such as distillation, or forced radical polymerization, e.g. at least 90% of the monomers to be polymerized have reacted. Chemical means using a second free-radical polymerization initiator that is later added to the polymerization reaction may also be included. Preferably, the second free radical polymerization initiator is a hydroperoxide or persulfate.

If the monomers polymerized in the polymerization reaction do not contain monomer M2, a precursor polymer is usually obtained which contains no or only an insufficient amount of polymerized units of monomer M2. These polymers then undergo partial hydrolysis to achieve partial conversion of the carboxylamide groups of polymerized monomer M1 to carboxyl or carboxylate groups. Partial hydrolysis can be performed by various methods known to those skilled in the art. Partial hydrolysis is usually carried out by dissolving the polymer in water and adjusting the pH to acidic or alkaline conditions. This includes heating the polymer solution to increase the hydrolysis rate. Acidic hydrolysis is preferably carried out in the presence of a strong acid such as hydrochloric acid or sulfuric acid. The amount of acid is preferably chosen such that the initial pH value is in the range from pH 4 to pH-1, in particular from pH 2 to pH 0. Alternatively, partial hydrolysis can be carried out in an alkaline environment, preferably in the range pH 8 to pH 14, especially in the range pH 9 to pH 12. The pH is then adjusted by the addition of strong bases such as alkali metal hydroxides. The temperature required for hydrolysis of the aqueous polymer solution can be room temperature (20° C.) or even below. Partial hydrolysis at room temperature may be considered an extended maturation stage of the product and may last for days, weeks or months. Once the desired properties are obtained, the pH is adjusted to neutrality, eg pH 5-8. Preferably, the hydrolysis is carried out at a temperature of 20-180°C, particularly preferably 30-100°C. The degree of conversion depends on temperature, pH of the reaction medium and reaction time. Those skilled in the art will routinely find conditions for carrying out the partial hydrolysis to achieve the desired degree of conversion.

Partial hydrolysis may also occur under the polymerization conditions if the polymerization of the monomers is carried out in water or a solvent containing water. However, when the monomers to be polymerized do not contain monomer M2, the amount of carboxyl groups formed during polymerization is usually not sufficient to achieve anionic charge densities in the above ranges. It is also possible to subject a copolymer already containing polymerized units of monomers M1 and M2 to partial hydrolysis. For example, a copolymer containing polymerized units of monomer M1 and monomer M21 is subjected to partial hydrolysis to produce a copolymer containing polymerized units of monomer M1, monomer M21 and monomer M22.

The copolymer is typically separated from the resulting polymerization mixture or the reaction mixture resulting from partial hydrolysis by relatively conventional methods such as precipitation or distillation. However, it is also possible or preferred to use a solution of the copolymer obtained by the polymerization reaction or subsequent partial hydrolysis, especially when the solvent is or contains water. Often the concentration of the copolymer in such solutions is in the range 10-50% by weight, especially in the range 15-40% by weight, based on the total weight of the solution.

The copolymers of the present invention are in permanent contact with water-containing systems, especially water treatment equipment, especially antimony- and sulfide-containing waters, and therefore have a high risk of forming antimony sulfide-containing scale, especially stibnite-containing scale. It is also particularly useful in reducing or inhibiting the formation of arsenic sulfide (As ₂ S ₃ )-containing scale, particularly stibnite-containing scale, in process equipment.

Accordingly, the present invention also relates to a method of reducing or inhibiting the formation of sulfide-containing scale, particularly stibnite-containing scale, in a hydrous system comprising the addition of a copolymer as defined herein to the water contained in the hydrous system.
The present invention also relates to a method of reducing or inhibiting the formation of arsenic sulfide-containing scale in a hydrous system comprising adding a copolymer as defined herein to water contained in the hydrous system.

As noted above, the risk of sulfide-containing scale is associated with any water-containing system, particularly those containing sulfides, particularly those containing both antimony and/or arsenic sulfide and sulfides, the latter of which is stibnite-containing scale and/or Or it is present because the formation of arsenic sulfide-containing scale is likely to occur.

Since the solubility of antimony(III) sulfide decreases with decreasing pH and decreasing temperature, e.g. when measured at 22° C., the water in a hydrous system has a pH of up to 9, especially up to a pH of 8.5, e.g. or in the range of pH 5 to pH 8.5 and/or in the temperature of the water system no more than 120°C, for example in the range of 40-120°C, a temperature drop of at least 40K can occur. In some cases, there is a certain risk of formation of scale containing stibnite. Accordingly, certain embodiments of the invention relate to uses and methods of the invention in which at least one of the following conditions is met.
- the water to be treated contains antimony ions and sulfides, in particular an antimony concentration of at least 1 ppm calculated as elemental antimony and a sulfide ion concentration of at least 1 ppm calculated as elemental sulfur.
- the hydrous system is operated at a pH of up to 9, especially up to pH 8.5, measured at 22°C, eg in the range from pH 4 to pH 9, or in the range from pH 5 to pH 8.5.
- The temperature of the water contained in the hydrous system is or tends to be up to 120°C, especially in the range of 40-120°C.
- A temperature drop of at least 40K occurs or is likely to occur.

The use and method of the copolymers of the present invention are not limited to any particular hydrous system, and therefore may be used in any hydrous system in which the formation of sulfide-containing scale, particularly stibnite-containing scale or arsenic sulfide-containing scale, is prone to occur. be able to.

Conditions favorable to the formation of sulfide-containing scale, in particular stibnite-containing scale and/or arsenic sulfide-containing scale, are usually met in the hypersalinized water circulation systems of geothermal power plants such as dry steam stations, flash steam stations, binary cycle stations, etc. be However, the problem of the formation of stibnite-containing scale and/or arsenic sulfide-containing scale arises from the fact that other It can also occur in hydrous systems. A further example of a hydrous system in which stibnite-containing scale and/or arsenic sulfide-containing scale formation may occur is a hydrous system used in a fracking process.

Accordingly, a particular group of embodiments of the present invention are those in which the copolymer is added to the salinity water circulation system contained in the salinity water circulation system of a geothermal power plant such as a dry steam station, a flash steam station, a binary cycle station, etc. to the uses and methods described herein. Geothermal power plant high-salinity water circulation systems include various parts where scale formation can occur, such as wells, steam pipes, condensers, separators, heat exchangers, pumps, nozzles, tubes, etc. There is Scale formation, in particular stibnite formation, is particularly prevalent in high-salinity water circulation systems where heat is removed from the high-salinity water, especially those above-ground components such as heat exchangers and condensers, as well as nozzles, pumps, tubes, etc. It is likely to occur in other above-ground parts where saline water is cooled.

In order to effectively reduce or inhibit the formation of sulfide-containing scale, particularly stibnite-containing scale and/or arsenic sulfide-containing scale, the copolymer is generally used at a concentration of at least 1 g/m ³ of copolymer in water, In particular, it is added to the water of the hydrous system in an amount of at least 2 g/m ³ , for example in the range of 1-100 g/m ^{3 , or in the range of 2-50 g/m 3 .}

The copolymer may be added to water as such, but is preferably added as an aqueous composition. Frequently, the concentration of copolymer in such aqueous compositions is in the range 1-40% by weight, especially in the range 5-30% by weight, based on the total weight of the composition. The aqueous compositions contain additional additives such as corrosion inhibitors, biocides, surfactants, gas hydrate inhibitors, hydrogen sulfide scavengers, inert fluorescent tracers, and additional antiscaling agents conventionally used in such compositions. It may contain additives.

The copolymer may be added to the water at any point in the water-containing system, particularly where sulfide-containing scale formation is likely to occur, or upstream of this point. Similarly, in a geothermal power plant, the copolymer may be added to the salinity water at any point within the geothermal power plant's salinity water circulation system. However, it is preferable to add the composition to the high salt water at a point upstream of where scaling is likely to occur, eg, upstream of the heat exchanger.

The copolymers defined herein are compatible with antiscaling agents commonly used to reduce or inhibit scale formation in hydrous systems, particularly high-salinity water circulation systems of geothermal power plants. Thus, the copolymers defined herein are further antiscaling agents conventionally used to reduce or inhibit the formation of common scales such as scale based on silicates, calcium carbonate, calcium phosphate, calcium sulfate or barium sulfate. can be used in combination with These scale inhibitors include scale inhibitors, i.e., compounds that inhibit the formation of insoluble scale and scale dispersants, i.e., scale inhibitors, i.e., scale inhibitors that help disperse insoluble inorganic materials that may form in water treatment units. is included.

Examples of such antiscaling additives commonly used to reduce or inhibit the formation of common scale are ATMP (aminotris(methylene phosphonic acid)), PBTC (phosphonobutane tricarboxylic acid), DTPMP ( diethylenetriaminepenta(methylenephosphonic acid)), phosphonates such as HEBP ((1-hydroxyethylidene)bisphosphonic acid), polyacrylic acid, copolymers of acrylic acid and AMPS, ternary copolymers of acrylic acid, AMPS and tert-butylacrylamide Polymers, polymethacrylic acid, polymaleic acid, hydrolyzed copolymers and terpolymers of maleic anhydride, and salts of these acids.

The use of the copolymers of the present invention may be combined with conventional mechanical cleaning such as sponge ball cleaning or water jet injection cleaning.

I. Abbreviations:
AA acrylic acid AM acrylamide AMPS-Na sodium salt of 2-acrylamido-2-methylpropanesulfonic acid APTAC 3-acrylamidopropyltrimethylammonium chloride ATMP aminotris (methylene phosphonic acid)
b. w. by weight DI water Deionized water DTPMP Diethylenetriamine penta(methylene phosphonic acid)
GPC gel permeation chromatography HEBP (1-hydroxyethylidene)bisphosphonic acid Mw weight average molecular weight Mn number average molecular weight MAA methacrylic acid MAM methacrylamide MEHQ 4-methoxyphenol NaBS sodium bisulfite (NaHSO ₃ )
_NaPS sodium persulfate _{( Na2S2O8} )
PBTC Phosphonobutane tricarboxylic acid PP Polypropylene PTFE Poly(tetrafluoroethene)
rpm revolutions per minute

II. Polymer analysis:
1) GPC:
GPC was performed using an Agilent 1200er series equipped with a PSS security degasser and a column oven adjusted to 35° C. and a detection system that measures refractive index. Column used (direction of flow):
1. PSS Suprema Guard column 2 . PSS Suprema 3000A
3. PSS Suprema 100A
The flow rate was 1 ml/min.

As eluent, ultrapure water (Merck Millipore) adjusted to pH 7 with 0.1 M NaNO ₃ and 0.01 M NaH ₂ PO ₄ /Na ₂ HPO ₄ buffers was used. Before use, the eluent was filtered through a 0.45 μm cellulose acetate filter membrane.

Polymer samples were diluted with deionized water at a ratio of 1/10 and adjusted to pH 7 by addition of 10% sodium hydroxide solution.

Samples were diluted with an eluent containing the internal standard ethylene glycol to give a polymer concentration of 3-5 g/L. Samples were filtered with a 0.45 μm cellulose acetate (or hydrophilized PTFE) syringe filter prior to measurement.

Narrow disperse poly(methylacrylic acid) sodium salt standards from PSS (Polymer Standard Service GmbH Germany) with the following peak molecular weights in Daltons were used for calibration.
1.1310
2.3480
3.8210
4.34900
5.72900
6.163000
7.326000
8.549000
(All molecular weights refer to the sodium salt of poly(methacrylic acid).)

For calibration, the Win GPC UniChrom software from PSS (Polymer Standard Service GmbH Germany) was used to analyze the GPC curve of the dispersive standard for retention of the refractive index intensity peak. A calibration correlation curve was generated by polynomial fitting (polynomial 3).

2) Viscosity:
The viscosity of the polymer solution was measured at 20° C.±0.5° C. using a Brookfield digital viscometer (Brookfield Engineering Laboratories, Inc.) equipped with spindle 61 or 62 at a rotation speed of 60 rpm.

3) pH measurement:
pH was measured by direct measurement at 20°C ± 0.5°C using a Mettler Toledo In lab constant pH electrode connected to a WTW 3210 pH meter (WTW Germany) calibrated with WTW buffer.

4) Measurement of charge density:
4.1. Determination of the amount of carboxyl groups The amount of carboxyl/carboxylate groups was determined by back titration with 0.1N NaOH solution of samples acidified with hydrochloric acid.

Typically 15% b.i.d. of 2 g. w. The polymer solution was weighed into a 150ml beaker. 55 ml of DI water and 150-200 μl of 16%b. w. of aqueous hydrochloric acid was added, the sample was homogenized by stirring for 5 minutes before titrating with 0.1 NaOH. Automated titrations were performed using a Methrom Ti-Touch 916 equipped with a pH electrode (Mettler Toledo DG115-SC composite glass pH electrode).
Two to three equivalence points are observed, depending on the composition of the sample.

The first equivalence point (EP1), which occurs at voltages of about +130 to +210 mV, marks the end of the strong mineral acid buffer region (e.g. HCl/NaCl) and the beginning of the carboxylic acid/carboxylate buffer region (-COOH/-COONa). represents The second equivalence point (EP2), occurring at voltages between 0 and -70 mV, represents the end of the carboxylic acid/carboxylate buffer region. Therefore, the difference between equivalent points 2 and 1 can be used to calculate the carboxylate concentration of the sample. For samples that have undergone partial hydrolysis of the amide groups, a third equivalence point is observed that can correspond to the presence of ammonia/ammonium formed in this step.

4.2 Determination of Copolymer Total Charge The total net charge of the polymer was determined by colloidal charge titration. Thus, the current potential was detected while the polymer solution was titrated with an oppositely charged 0.001 N-polyelectrolyte titrant (cationic titrant), here PolyDadmac, to the point of zero charge.

The equipment consists of a Mutek PCD-02 particle charge detector equipped with an automatic dosing/titration unit (Mettler DL 21).

All polymer samples were pre-adjusted to pH 7.5-8.0 and 0.1% solutions were prepared. 1 ml of each solution was placed in a PTFE measuring cell, made up to 10 ml with DI water to completely cover the gold electrode of the instrument, and the solution was titrated with 0.001 N Poly-Dadmac solution until the endpoint (0 mV current potential) was reached. was done.

III. Commercially available copolymers Commercially available copolymers useful as conventional scale inhibitors:
Polymer V1: 43% of a copolymer of free acid form of acrylic acid and AMPS with a molecular weight Mw of 4500 g b. w. Aqueous solution (Acumer® 2000)
Polymer V2: 45% of a terpolymer of acrylic acid, AMPS and N-tert-butylacrylamide with a molecular weight Mw of 5000-7000 g/molb. w. Aqueous solution (Acumer® 5000)
Polymer V3: 31% of poly(sodium acrylate) homopolymer at pH 8 (Mw of 800,000-100,000 g/mol as sodium salt)b. w. Aqueous solution (Flosperse® AZ-10)

Commercially available copolymers suitable for the method and use of the invention:
Polymer P1: 20% of an anionic acrylamide copolymerb. w. Aqueous dispersion:
Terpolymer of about 70 mol % AM and about 30 mol % total of anionic monomers (acrylic acid plus AMPS) (Ferrocryl 8704) with molecular weight Mw>10 ⁶ g/mol and anionic charge density of about 3.0 mol/kg
Polymer P2: Copolymer of 92 mol % AM and 8 mol % acrylic acid (solid powder) (Ferrocryl 8720) with molecular weight Mw>10 ⁶ g/mol and anion charge density of about 0.99 mol/kg.
Polymer P3: 21% of a copolymer of 87 mol % AM and 13 mol % AMPS with a molecular weight Mw>10 ⁶ g/mol and an anionic charge density of about 1.33 mol/kg b. w. Aqueous solution (Kurifloc DA 4020)

IV. Preparation example:
The following polymerization reactions were carried out in a 1000 ml double-jacketed glass reactor equipped with a stainless steel agitator, a condenser connected to a bubble counter outlet, and ports for pipe fittings. The reactor was connected to a heating bath circulation thermostat. All polymerizations were carried out under a nitrogen atmosphere. The reactor is hermetically sealed except for the condenser outlet.

Preparation Example 1: 85:15 molar ratio copolymer of MAM and AMPS An initiator mixture was prepared and filled into a disposable PP syringe fitted with a PTFE tube (1 mm internal diameter) and attached to a syringe pump.
1. Syringe 1: 6.31 g of 39.1%b. w. Aqueous solution of sodium bisulfite 2 . Syringe 2: Aqueous solution of 0.32 g sodium persulfate in 20 ml water

A solution of 108.45 g MAM and 51.55 g AMPS-Na in 593.6 g water containing 300 ppm MEHQ was charged into a glass cylinder connected to a double piston pump.

Water (180.0 g) and 10% b.i. w. of aqueous sulfuric acid (0.3 g) was added to the reactor and heated to 70° C. with stirring (stirring speed: 200 rpm). When the internal temperature of the reactor reached the target temperature of 70°C, about 0.76 g of aqueous sodium bisulfite solution was charged into the reactor. The reactor temperature was set to automatic control with a target temperature of 70°C. The feeds of the monomer and initiator solutions (syringes 1 and 2) were started simultaneously within 1 minute at their respective feed rates from this point. Feeds were added through separate dosing nozzles.

Feeding/dosing times for individual solutions are: 40%b. w. Aqueous sodium bisulfite solution: 180 minutes Sodium persulfate in water: 220 minutes Monomer solution: 180 minutes.

Ten minutes after the end of the last feed (sodium persulfate solution), the pH of the reaction mixture was reduced to 0.65 g of 50% b.i. It was adjusted to 10 by slow addition (10 min) of w of aqueous NaOH. Stirring was continued at 70° C. for 3 hours. After cooling to less than 40°C, 30% b.p. of 0.6. w. Aqueous hydrogen peroxide was added to remove remaining _SO2 . Then 9.8 g of 70%b.i. The pH was adjusted to 6.6 by the addition of w of sulfuric acid. 25 ml of 1M disodium citrate buffer was added for pH stabilization. Water was added to complete the batch to a total mass of 1000 g.

The resulting polymer solution had the following properties:
pH: 5.3 (20°C)
Viscosity (Brookfield): 15 mPas
Solids content: 14.5%b. w. (15% b.w. copolymer)
Mw: 30000 [g/mol]
Mn: 7800 [g/mol]

The copolymer had an anionic charge density of 1.52 mol/kg based on solids content.

Preparative Example 2: 85:15 molar ratio copolymer of MAM and AMPS The copolymer of Preparative Example 2 was prepared analogously to the procedure of Preparative Example 1. The amount of initiator was increased compared to Example 1. The amount of sodium persulfate was 0.63 g and the total amount of 40% sodium bisulfite solution was 13.8 g. In this case, 1.8 g of 50% sodium hydroxide were added within 10 minutes to adjust the pH to 10 and stirring was continued at 70° C. for 3 hours. After cooling below 40° C., 1.09 g of 30% b.i.d. was added to remove remaining SO ₂ . w. Aqueous hydrogen peroxide was added. Then 7.3 g of 70%b.i. The pH was adjusted to 7.0 by the addition of w of sulfuric acid. Water was added to complete the batch to a total mass of 1000 g.

The resulting polymer solution had the following properties:
pH: 7.0 (20°C)
Viscosity (Brookfield): 11 mPas
Solids content: 14.9%b. w.
Mw: 17100 [g/mol]
Mn: 2460 [g/mol]

The copolymer had an anionic charge density of 1.4 mol/kg based on solids content.

Preparative Example 3: 85:15 Mole Ratio Copolymer of Partially Hydrolyzed MAM and AMPS The copolymer of Preparative Example 3 was prepared analogously to the procedure of Preparative Example 1. The amount of sodium persulfate was 0.16 g, 40% b.p. w. The total amount of sodium bisulfite solution was 3.45 g. In this case, the sample was cooled to a temperature below 40° C. after the NaPS feed was finished. Then 1.8 g of 5% b.i.d. w. After the aqueous solution of the isothiazolinone preservative was added, 0.61 g of 50% b.i.d. w. An aqueous solution of sodium hydroxide was added. 42 g of water were added to complete the batch and bring the total mass to 1000 g. Immediately after synthesis, the pH of the product solution was 9.2. Samples were stored at 30°C for 3 months before testing.

The polymer solution obtained after storage had the following properties:
pH: 9.8 (20°C)
Viscosity (Brookfield): 30 mPas
Solids content: 15.7%b. w.
Mw: 86400 [g/mol]
Mn: 25000 [g/mol]

The copolymer had an anionic charge density of 2.4 mol/kg based on solids content.

The amount of carboxyl groups was 0.165 mol/kg (1.06 mol/kg based on solids content) in the product solution.

Preparative Example 4: 85:15 Mole Ratio Copolymer of Partially Hydrolyzed AM and AMPS The copolymer of Preparative Example 4 was prepared analogously to the procedure of Preparative Example 3. The monomer feed solution was 409 g of freshly prepared 50% b.i. w. aqueous acrylamide solution and 233 g of 50% b.i.d. w. It is an AMPS-Na aqueous solution. The amount of sodium persulfate was 0.35 g, 40% b.p. w. The aqueous sodium bisulfite feed was 7.1 g. Before starting the monomer feed, 0.73 g of 40% b.i.d. w. An aqueous sodium bisulfite solution was placed in the reactor. The reaction mixture was cooled to a temperature below 40°C. After the end of the NaPS feed, 0.61 g of 50%b.i. w. After adding the sodium hydroxide solution, 1.8 g of 5% b.i.d. w. An aqueous solution of an isothiazolinone preservative was added. Immediately after polymerization, the pH of the product solution was 9.7. Water was added to complete the batch to a total mass of 1000 g. Samples were stored at 30°C for 3 months before testing.

The resulting polymer solution had the following properties:
pH: 10.2 (20°C)
Viscosity (Brookfield): 580 mPas
Solids content: 33.5%b. w.
Mw: 46700 [g/mol]
Mn: 10700 [g/mol]

The copolymer had an anionic charge density of 2.04 mol/kg based on solids content.

The amount of carboxyl groups was 0.16 mol/kg (0.47 mol/kg based on solids content) in the product solution.

Preparative Example 5: Copolymer with 70:30 molar ratio of MAM and AMPS-Na The copolymer of Preparative Example 5 was prepared analogously to the procedure of Preparative Example 1. The monomer and initiator amounts are summarized in Table 1 below. After the last feed was completed (NaPS), the pH of the polymer solution was adjusted to 0.36 g of 50% b.p. before cooling below 40°C. w. The pH was immediately adjusted to about pH 6 by the addition of aqueous NaOH. Then 1.63 g of 30% b.i.d. w. Aqueous hydrogen peroxide was added to remove remaining _SO2 . Then 1.8 g of 5% b.i.d. w. After adding an aqueous solution of the isothiazolinone preservative, 0.61 g of 50% b.i.d. w. Sodium hydroxide solution was added to readjust the pH to about 6. Water was added to complete the batch to a total mass of 1000 g.

The resulting polymer solution had the following properties:
pH: 6.22 (20°C)
Viscosity (Brookfield): 12.5 mPas
Solid content: 16.0%b. w.
Mw: 32000 [g/mol]
Mn: 6800 [g/mol]

This copolymer had an anionic charge density of 2.44 mol/kg based on solids content.

The amount of carboxyl groups was 0.003 mol/kg in the product solution (0.019 mol/kg based on solids).

Preparative Example 6: Copolymer of MAM and AMPS-Na and AA in a 70:15:15 molar ratio The copolymer of Preparative Example 6 was prepared analogously to the procedure of Preparative Example 1. In this example, an additional monomer feed of acrylic acid (16.5 g) was added simultaneously in parallel to the aqueous solution of methacrylamide and AMPS using a syringe pump. The total amounts of monomer and initiator are summarized in Table 1. After the last feed was completed, the product solution was cooled to below 40°C and immediately charged with 18.7 g of 50%b. w. The pH was adjusted to about 7-8 by the addition of an aqueous NaOH solution. Then 1.22 g of 30% b.i.d. w. Aqueous hydrogen peroxide was added to remove remaining _SO2 . Finally, 1.8 g of 5% b.i.d. w. After the aqueous solution of the isothiazolinone preservative was added, 3.4 g of 10% b.i.d. to readjust the pH to 6.7. w. Aqueous sulfuric acid was added. Water was added to complete the batch to a total mass of 1000 g.

The resulting polymer solution had the following properties:
pH: 6.73 (20°C)
Viscosity (Brookfield): 22.0 mPas
Solids content: 16.3%b. w
Mw: 53000 [g/mol]
Mn: 16000 [g/mol]

The copolymer had an anionic charge density of 2.65 mol/kg based on solids content.

Preparative Example 7: Copolymer with 70:30 molar ratio of MAM and AA The copolymer of Preparative Example 7 was prepared analogously to the procedure of Preparative Example 6. In this example, a monomer feed of acrylic acid (41.26 g) was added simultaneously in parallel to an aqueous solution of AMPS-Na free methacrylamide. The total amounts of monomer and initiator are summarized in Table 1. After the last feed was completed, the product solution was cooled to below 40° C. and 46 g of 50% b.i.d. w. Addition of aqueous NaOH immediately adjusted the pH to about 7-10. Then 30% b.p. of 1.05. w. of aqueous hydrogen peroxide solution was added to remove remaining _SO2 . Finally, 1.8 g of 5% b.i.d. w. After the aqueous solution of the isothiazolinone preservative was added, 11.2 g of 10% b.i.d. was added to readjust the pH to 6.8. w. Aqueous sulfuric acid was added. Water was added to complete the batch to a total mass of 1000 g.

The resulting polymer solution had the following properties:
pH: 6.84 (20°C)
Viscosity (Brookfield): 39.0 mPas
Solids: 16.6%b. w
Mw: 63000 [g/mol]
Mn: 17700 [g/mol]

The copolymer had an anionic charge density of 3.81 mol/kg based on solids content.

The amount of carboxyl groups was 0.63 mol/kg in the product solution (3.80 mol/kg based on solids content).

Preparative Example 8: Copolymer of MAM, AMPS-Na, and MAA with a 73:15:12 molar ratio The copolymer of Preparative Example 8 was prepared analogously to the procedure of Preparative Example 1. In this example, an additional monomer feed of methacrylic acid was added simultaneously in parallel with the methacrylamide and AMPS aqueous solution using a syringe pump (feed time 180 minutes). The total amounts of monomer and initiator are summarized in Table 1. After the last feed was completed, the product solution was cooled to below 40° C. followed immediately by 12.9 g of 50% b.i.d. w. The pH was adjusted to about 6 by the addition of an aqueous NaOH solution. Then 2.04 g of 30% b.i.d. w. Aqueous hydrogen peroxide was added to remove remaining _SO2 . Finally, 1.8 g of 5% b.i.d. w. An aqueous solution of an isothiazolinone preservative was added. Water was added to complete the batch to a total mass of 1000 g.

The resulting polymer solution had the following properties:
pH: 6.1 (20°C)
Viscosity (Brookfield): 15.0 mPas
Solids content: 14.2%b. w
Mw: 51400 [g/mol]
Mn: 14200 [g/mol]

The copolymer had an anionic charge density of 2.64 mol/kg based on solids content.
The amount of carboxyl groups was 0.185 mol/kg in the product solution (1.30 mol/kg based on solids content).

Preparative Example 9: Partially hydrolyzed copolymer of MAM and AMPS at a molar ratio of 85:15

The copolymer of Preparative Example 9 was prepared analogously to the procedure of Preparative Example 1. The amount of sodium persulfate was 0.32 g, 40% b.p. The total amount of w sodium bisulfite solution was 5.45 g. In this case, the sample was cooled to a temperature below 40° C. after the NaPS feed was finished. Then 1.8 g of 5% b.i.d. w. An aqueous solution of the isothiazolinone preservative was added followed by 0.81 g of 50% b.i. w. of aqueous sodium hydroxide solution was added. Water was added to complete the batch to a total mass of 1000 g. The pH of the product solution immediately after synthesis was 9.6. Samples were stored at 30°C for 40 days before testing.

The resulting polymer solution had the following properties:
pH: 9.7 (20°C)
Viscosity (Brookfield): 24 mPas
Solids content: 15.7%b. w.
Mw: 73500 [g/mol]
Mn: 17000 [g/mol]

The copolymer had an anionic charge density of 2.02 mol/kg based on solids content.

The amount of carboxyl groups was 0.102 mol/kg in the product solution (0.65 mol/kg based on solids).

Preparative Example 10: Copolymer with 75:25 Mole Ratio of MAM and AMPS The copolymer of Preparative Example 10 was prepared analogously to the procedure of Preparative Example 1. Total monomer and initiator amounts are summarized in Table 1. This monomer solution was split at a ratio of 60:40 parts. In this case the amount of water used in the reaction mixture was reduced to 60.0 g, while 10%b. w The sulfuric acid aqueous solution was increased to 0.7 g. The reaction mixture was then preheated to 80° C. with stirring at the same stirring speed as in Example 1 and topped up with 60 parts of the above monomer solution (532.9 g). After reaching the target temperature of 92° C., a reduced amount of aqueous sodium bisulfite solution (approximately 0.51 g) was charged to the reactor. The reactor temperature for this reaction was set at 95°C.

The feeding/dosing times of the separate solutions were varied compared to Example 1 as follows:
Sodium bisulfite aqueous solution: 220 minutes Sodium persulfate in water: 300 minutes Monomer solution - 40 fractions (355.3 g): 100 minutes

In this case, the reaction mixture was cooled to 50° C. 10 minutes after the last feed had ended. 1 g of citric acid monohydrate was then added and the reaction mixture was further cooled to 40°C. The pH of the reaction mixture was adjusted to 3.3 g of 20% b.i.d. w. Adjusted to 6.1 by slow addition of aqueous NaOH (10 min). Unlike Example 1, 30% _b.i.d. w. 0.78 of aqueous hydrogen peroxide was added. Then 1.0 g of 20% b.i.d. w. The pH was adjusted to 6.1 by addition of aqueous NaOH and 0.7 g water was added to complete the batch to a total mass of 1000 g.

The resulting polymer solution had the following properties:
pH: 6.1 (20°C)
Viscosity (Brookfield): 68 mPas
Solids content: 20.8%b. w.
Mw: 52000 [g/mol]
Mn: 9500 [g/mol]

The charge density of the copolymer has not been determined but corresponds to a theoretical value of 2.0 mol/kg.

Comparative Preparative Example C1: Low Molecular Weight Copolymer of MAM and AMPS with a Molar Ratio of 85:15

The polymer of Preparative Comparative Example C1 was prepared analogously to the procedure of Preparative Example 1. The amount of initiator was increased compared to Examples 1 and 2. The total amounts of monomer and initiator are summarized in Table 1. The amount of sodium persulfate was 1.26 and the total amount of 40% bw sodium bisulfite aqueous solution was 28.13 g. To adjust the pH to 10, 4.26 g of 50% b.i.d. w. Aqueous sodium hydroxide solution was added within 10 minutes and stirring was continued at 70° C. for 3 hours. After cooling to below 40° C., 1.71 g of 30% b.i.d. w. Aqueous hydrogen peroxide was added to remove remaining _SO2 . Then 9.41 g of 70%b.i. The pH was adjusted to 7.0 by the addition of w sulfuric acid.

The resulting polymer solution had the following properties:
pH: 7.1 (20°C)
Viscosity (Brookfield): 7 mPas
Solids: 16.7%b. w.
Mw: 5100 [g/mol]
Mn: 900 [g/mol]

The polymer had an anionic charge density of 1.59 mol/kg based on solids content.

Comparative Preparative Example C2 (High Charge): High Charge Density Copolymer with 50:35:15 Molar Ratio of MAA, MAM and AMPS The polymer of Comparative Example C2 was prepared analogously to the procedure of Preparative Example 1. In this example, an additional monomer feed of methacrylic acid was added simultaneously in parallel with the methacrylamide and AMPS aqueous solution using a syringe pump (feed time 180 minutes). Five minutes after the start of the methacrylic acid feed, 126.8 g of 20% b.i.d. w. Aqueous sodium hydroxide was added continuously with a syringe pump within 175 minutes. The total amounts of monomer and initiator are summarized in Table 1. After cooling below 40° C., 0.3 g of 30% hydrogen peroxide solution was added to remove residual SO ₂ . Finally, 1.8 g of 5% b.i.d. w. After the aqueous solution of the isothiazolinone preservative was added, 19.8 g of 20% b.i.d. was added to adjust the pH to 6.6. w. Aqueous sodium hydroxide was added. Water was added to complete the batch to a total mass of 1000 g.

The resulting polymer solution had the following properties:
pH: 6.6 (20°C)
Viscosity (Brookfield): 22.5 mPas
Solids: 16.8%b. w
Mw: 111300 [g/mol]
Mn: 30000 [g/mol]

The polymer had an anionic charge density of 6.1 mol/kg based on solids content.

Preparative Comparative Example C3 (High Charge): Copolymer with High Charge Density of 85:15 Molar Ratio of MAA and AMPS The polymer of Comparative Example C3 was prepared analogously to the procedure of Comparative Example C2. The total amounts of monomer and initiator are summarized in Table 1. In this example, no sodium hydroxide was added during the monomer feed. After cooling below 40° C., 2.35 of 30% aqueous hydrogen peroxide was added to remove remaining SO ₂ . Then 1.8 g of 5% b.i.d. w. An aqueous solution of an isothiazolinone preservative was added. The pH of the solution was pH 1.9 and 90.0 g of 50% b.i.d. w. The pH was adjusted to about 6 by the addition of aqueous sodium hydroxide. Water was added to complete the batch to a total mass of 1000 g.

The resulting polymer solution had the following properties:
pH: 6.2 (20°C)
Viscosity (Brookfield): 29.1 mPas
Solids content: 17.1%b. w
Mw: 270000 [g/mol]
Mn: 38000 [g/mol]

The polymer had an anionic charge density of 7.73 mol/kg based on solids content.

Water was added to complete the batch to a total mass of 1000 g.

V. Stability Test of Stibnite in Aqueous Solution Each of the copolymer solutions obtained in each of the above preparation examples and the commercial polymer solution were diluted with deionized water to a copolymer concentration of 1.5 g/L, followed by caustic soda or The pH was adjusted to pH 7.5 by any addition of sulfuric acid. These solutions are used as stabilizer stock solutions.

Appropriate amounts of magnesium sulfate heptahydrate ( _MgSO4.7H2O ), calcium chloride _dihydrate ( _CaCl2.2H2O ) and sodium bicarbonate ( _NaHCO3 ) _were dissolved in deionized water and tested. An aqueous solution was prepared.

To perform the stabilization test, the test water was supplemented with 20 ppm antimony(III) sulfide.

For this, 28.7 mL of commercially available 5% b.i.d. w. After antimony (III) chloride aqueous solution was added to 10 L of test water, the pH was adjusted to 6.3 (±0.1). This solution was used as the test stock solution. Stabilizer stock solution was added with stirring to the desired stabilizer concentration to 1 liter of test stock solution, followed by 275 μl of a commercial 5% b.i. w. An aqueous solution of sodium sulfide was added with stirring to the desired antimony(III) chloride concentration of 20 ppm. Stirring was stopped 15 minutes after the addition of sodium sulfide.

The solution thus obtained was visually observed at 1 hour, 3 hours, 4 hours and 24 hours after the addition of the aqueous sodium sulfide solution. The test solution was not stirred during observation. A strong yellow color indicated the formation of a stable soluble complex of antimony sulfide and inhibitor and the formation of a precipitate indicated the formation of a solid of antimony(III) sulfide. Stabilizer quality was ranked for each stabilizer concentration according to the following grades (Table 3).

The results after 24 hours are summarized in Table 4 below.

The copolymer was also tested in deionized water adjusted to pH 7.5 and supplemented with 175 ppm antimony sulfide, similar to the procedure above. Similar results were observed.

Claims (23)

consisting of the following a and b,
an anionic copolymer having an anionic charge density in the range of 0.5 to 6.0 mol/kg and having, in the form of the sodium salt, a weight average molecular weight Mw of at least 10000 g/mol as determined by gel permeation chromatography; A method for reducing sulfide-containing scaling in a hydrous system by adding it to water in the hydrous system.
e: polymerized units of monomer M1 which is a primary amide of a monoethylenically unsaturated monocarboxylic acid having 3 to 6 carbon atoms f: a monoethylenically unsaturated monomer having a sulfonic acid group and/or a sulfuric acid group, carboxyl Polymerized units of monoethylenically unsaturated monomers M2 selected from monoethylenically unsaturated monomers having groups and mixtures thereof 2. The method of claim 1, wherein said copolymer, in the form of sodium salt, has a weight average molecular weight Mw determined by gel permeation chromatography ranging from 15000 to 10 ⁶ g/mol. The method of any one of the preceding claims, wherein said copolymer has an anionic charge density in the range of 0.8-5.0 mol/kg. The method of any one of the preceding claims, wherein the amount of polymerized units of monomer M1 ranges from 55 to 95 mol% relative to the total molar amount of polymerized units in the copolymer. The method of any one of the preceding claims, wherein the amount of polymerized units of monomer M2 ranges from 5 to 45 mol% relative to the total molar amount of polymerized units in the copolymer. 4. The method of any one of the preceding claims, wherein the total amount of polymerized units of monomers M1 and M2 is at least 95 mol%, relative to the total molar amount of polymerized units in the copolymer. The method of any one of the preceding claims, wherein said monomer M1 is selected from acrylamide and methacrylamide. The method of any one of the preceding claims, wherein said monomer M2 consists of a monoethylenically unsaturated monomer having a carboxyl group. 4. The method of any one of the preceding claims, wherein the monomer M2 is a combination of a monoethylenically unsaturated monomer having sulfonate groups and a monoethylenically unsaturated monomer having carboxyl groups. 4. The method of any one of the preceding claims, wherein the monoethylenically unsaturated monomers containing carboxyl groups are selected from acrylic acid, methacrylic acid, and mixtures thereof. Monoethylenically unsaturated monomers with sulfonate groups are N-acrylamido-C ₂ -C ₄ -alkylsulfonic acids, N-methacrylamido-C ₂ -C ₄ -alkylsulfonic acids, acryloxy-C ₂ -C ₄ - The method of any one of the preceding claims, selected from alkylsulfonic acids, methacryloxy-C ₂ -C ₄ -alkylsulfonic acids, and mixtures thereof. 4. The method of any one of the preceding claims, wherein said copolymer is a random copolymer. Said copolymer is obtained by a free-radical aqueous solution copolymerization process of at least one monomer M1 and at least one monomer M2, or a free-radical aqueous solution polymerization of at least one monomer M1 and optionally at least one monomer M2, followed by A process according to any one of the preceding claims, obtained by a process of partial hydrolysis of polymerized units of monomer M1. 4. The method of any one of the preceding claims, wherein the hydrous system is a circulating water system of a geothermal power plant. The method of any one of the preceding claims, wherein said copolymer is added to said water such that the concentration of copolymer in water ranges from 1 to 100 g/m ³ . 4. The method of any one of the preceding claims, wherein the water comprises antimony and/or arsenic salts and sulfides. A method according to any one of the preceding claims, wherein the water in the aqueous system has a pH level, measured at 22°C, in the range of pH 4-9, in particular pH 5-8.5. Use of a copolymer as defined in any one of claims 1 to 14 for controlling sulfide-containing scale formation in hydrous systems, in particular in brine loops of geothermal power plants. 19. Use according to claim 18, wherein the sulfide-containing scale formation comprises in particular the formation of stibnite-containing scale. polymerized units of monomer M1 which is a primary amide of a monoethylenically unsaturated monocarboxylic acid having 3 to 6 carbon atoms;
Consisting of polymerized units of a monoethylenically unsaturated monomer M2 selected from a monoethylenically unsaturated monomer having a sulfonic acid group and/or a sulfuric acid group, a monoethylenically unsaturated monomer having a carboxyl group, and a mixture thereof,
An anionic copolymer having an anionic charge density in the range of 0.5 to 5.0 mol/kg and a weight average molecular weight Mw measured by gel permeation chromatography in the form of a sodium salt in the range of 15000 to 500000 g/mol. Combined. The amount of polymerized units of monomer M1 is in the range of 60 to 95 mol%, and the amount of polymerized units of monomer M2 is in the range of 5 to 40 mol%, relative to the total molar amount of polymerized units in the copolymer. 21. The anionic copolymer of claim 20. An anionic copolymer according to claim 20 or 21, wherein said copolymer has an anionic charge density in the range of 0.8-4.0 mol/kg. An anionic copolymer according to any one of claims 20-22 having at least one of the characteristics of claims 6-13.