DE102022114641A1 - HIGH MOLECULAR POLYMER DISPERSIONS WITH TAILORED MOLECULAR WEIGHT OF THE POLYMER DISPERSION AGENT - Google Patents

Abstract

The invention relates to processes for producing a polymer dispersion, to polymer dispersions and their use. The methods for preparing the polymer dispersion include the steps of providing a reaction mixture in an aqueous medium comprising a polymeric dispersant and a monomer composition comprising radically polymerizable monomers, and subjecting the monomer composition in the reaction mixture to radical polymerization to form a dispersed polymer synthesize to form the polymer dispersion, wherein the weight average molecular weight of the dispersed polymer is within a certain narrow range. These polymer dispersions are referred to as water-in-water (w/w) polymer dispersions.

Description

The invention relates to processes for producing a polymer dispersion, to polymer dispersions and their use. The methods for preparing the polymer dispersion include the steps of providing a reaction mixture in an aqueous medium comprising a polymeric dispersant and a monomer composition comprising radically polymerizable monomers, and subjecting the monomer composition in the reaction mixture to radical polymerization to synthesize a dispersed polymer, to form the polymer dispersion, wherein the polymeric dispersant has a weight average molecular weight M _w of 40,000 to less than 150,000 g/mol. These polymer dispersions are referred to as water-in-water (w/w) polymer dispersions.

The water-in-water polymer dispersions are suitable as flocculants, drainage aids and retention aids in paper production and in other technical areas. To produce paper, an aqueous slurry of cellulose fibers is first produced that has a water content of more than 95% by weight. The finished paper sheet has a water content of less than 5 percent by weight. Drainage and retention are crucial steps in papermaking and are important for an efficient papermaking process. High-performance w/w polymer dispersions are a key factor in the papermaking process.

A known flocculant is a w/w polymer dispersion prepared by copolymerizing ethylenically unsaturated monomers in an aqueous system containing a polymeric dispersant, thereby forming a dispersion containing the polymeric dispersant and the synthesized copolymer. The US8476391B2 and the US7323510B2 are early publications of such w/w polymer dispersions. It is well known in this technical field that the addition of separately synthesized copolymers on the one hand and polymeric dispersants on the other hand results in products which have completely different properties than the w/w polymer dispersions disclosed in the above-mentioned patent documents. Copolymerization in a system containing the polymeric dispersant is necessary to obtain high performance flocculant products, for example for papermaking.

These circumstances make the production of the w/w polymer dispersions a multi-parameter system. The type of ethylenically unsaturated monomers, their ratio and the type of polymer dispersant are just a few parameters that influence the properties of the w/w polymer dispersion. Improving the properties of the end product of the w/w polymer dispersion has been the subject of numerous research and development attempts.

There is still a need to improve the properties of W/W polymer dispersions. A desired improvement in product performance relates to the dispersibility of the polymer components in the w/w polymer dispersions. After identifying the parameters that have an influence on the properties mentioned, development work was carried out to adjust the parameters in such a way that an improvement in the dispersibility of the w/w polymer dispersions is achieved.

Another disadvantage of the w/w polymer dispersions produced in this way is that the products exhibit instabilities after the manufacturing process has been completed. Such instabilities are supported, for example, by changing temperatures during storage.

The object underlying the invention is to provide a process for producing w/w polymer dispersions which ensures high stability of the w/w polymer dispersions, particularly under unfavorable conditions such as. B. changing temperatures. In particular, the degree of stability refers to the ratio of batches with insufficient stability to batches with sufficient stability, which should be equal to zero. Another problem according to the invention is to improve the dispersibility of polymeric components of the w/w polymer dispersions. The object underlying the invention relates to solving the disadvantages described above.

1. A) Bereitstellen einer Reaktionsmischung in einem wässrigen Medium, umfassend
   1. a) ein polymeres Dispergiermittel und
   2. b) eine Monomerzusammensetzung, die radikalisch polymerisierbare Monomere umfasst, wobei die radikalisch polymerisierbaren Monomere aus der Gruppe ausgewählt sind, die aus einem oder mehreren nichtionischen ethylenisch ungesättigten Monomeren, einem kationischen ethylenisch ungesättigten Monomer und einem amphiphilen ethylenisch ungesättigten Monomer besteht;
2. B) Unterwerfen der Monomerzusammensetzung in der Reaktionsmischung einer radikalischen Polymerisation, um ein dispergiertes Polymer zu synthetisieren und die Polymerdispersion zu bilden, wobei das polymere Dispersionsmittel ein gewichtsmittleres Molekulargewicht M_w, bestimmt durch Größenausschlusschromatographie, von 40.000 bis weniger als 150.000 g/mol, bevorzugt 50.000 bis 140.000 g/mol, noch bevorzugter 60.000 bis 130.000, am meisten bevorzugt 85.000 bis 125.000 g/mol, aufweist.

The problems underlying the invention are solved by the subject matter of claim 1. Thus, according to a first aspect, the invention relates to a method for producing a polymer dispersion, comprising the steps

1. A) Providing a reaction mixture in an aqueous medium, comprising
   1. a) a polymeric dispersant and
   2. b) a monomer composition comprising radically polymerizable monomers, wherein the radically polymerizable monomers are selected from the group consisting of one or more nonionic ethylenically unsaturated monomers, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer;
2. B) subjecting the monomer composition in the reaction mixture to radical polymerization to synthesize a dispersed polymer and form the polymer dispersion, wherein the polymeric dispersant has a weight average molecular weight M _w , determined by size exclusion chromatography, of from 40,000 to less than 150,000 g / mol, preferably 50,000 to 140,000 g/mol, more preferably 60,000 to 130,000, most preferably 85,000 to 125,000 g/mol.

The process includes providing a reaction mixture containing the monomers to be copolymerized and a polymeric dispersant. The monomers are polymerized in an aqueous medium in the presence of the polymeric dispersant. According to the prior art, a polymer dispersion obtained by the process according to the invention cannot be obtained by subjecting the monomer composition to copolymerization and then adding the polymeric dispersant after the copolymerization. By using the process according to the invention, the polymer dispersion is given unique properties, the polymer dispersion representing the end product which comprises the copolymer obtained from the free-radically polymerizable monomers together with the polymeric dispersant.

It was surprisingly found that the weight-average molecular weight in the range according to the invention provides polymer dispersions with excellent stability. In the prior art, polymer dispersion products have a higher weight-average molecular weight of the dispersants, for example more than 150,000 g/mol and up to 350,000 g/mol.

Polymer dispersions that are produced using a manufacturing process according to the invention have increased stability, which can be demonstrated by the stability sedimentation centrifuge test. This test is carried out by subjecting the prepared polymer dispersion to the action of a centrifuge. After this treatment, the supernatant above the sedimentation phase is examined for the content of polymeric dispersants. The higher the content in the supernatant, the less polymeric dispersant is active for dispersing the dispersed polymer, i.e. H. the less stable the polymer dispersion is. It has surprisingly been found that reducing the molecular weight of the polymeric dispersant improves the stability of the polymer dispersion.

Stability can be determined by visual inspection. 1 shows a stable dispersion in the sense of the invention. 2 shows unstable polymer dispersions with visually observable phase separation.

1. i. ein nichtionisches Monomer der Formel (I)
   
   , in der R¹ Wasserstoff oder Methyl bedeutet; R² und R³ sind unabhängig voneinander Wasserstoff, C1-C5-Alkyl oder C1-C5-Hydroxyalkyl,
2. ii. ein kationisches Monomer der Formel (II)
   
   , wobei R¹ Wasserstoff oder Methyl bedeutet; Z₁ O, NH oder NR⁴ ist, wobei R⁴ C1-C4-Alkyl, vorzugsweise Methyl, bedeutet, und Y eine der folgenden Bedeutungen hat
   
   , wobei Y₀ und Y₁ sind eine C1-C6-Alkylengruppe, gegebenenfalls substituiert mit einer oder mehreren Hydroxygruppen, vorzugsweise Ethylen oder Propylen, gegebenenfalls substituiert mit einer Hydroxygruppe; Y₂, Y₃, Y₅, Y₆, Y₇ unabhängig voneinander jeweils C1-C6-Alkyl, vorzugsweise Methyl, bedeuten; und Z^- ein Gegenion ist, vorzugsweise ein Halogen, Pseudohalogen, Acetat oder SO₄CH₃ ^-; und
3. iii. ein amphiphiles Monomer der Formeln (III) oder (IV)
   
   , wobei Z₁ O, NH, NR⁴ ist, wobei R⁴ C1-C4-Alkyl, vorzugsweise Methyl, bedeutet, R¹ Wasserstoff oder Methyl bedeutet, R₈ eine C1-C6-Alkylengruppe ist, vorzugsweise Ethylen oder Propylen, R₈ und R₆ unabhängig voneinander jeweils C1-C6-Alkyl sind, vorzugsweise Methyl, R₇ ein C8-C32-Alkyl ist, gegebenenfalls substituiert mit einer oder mehreren Hydroxygruppen, vorzugsweise C12-C20-Alkyl, gegebenenfalls substituiert mit einer Hydroxygruppe, und Z^- ein Gegenion ist, vorzugsweise ein Halogen, Pseudohalogen, Acetat oder SO₄CH₃ ^-; oder
   
   ist, wobei Z₁ O, NH, NR⁴ ist, wobei R⁴ C1-C4-Alkyl, vorzugsweise Methyl bedeutet, R¹ Wasserstoff oder Methyl bedeutet, R₁₀ Wasserstoff, C8-C32-Alkyl, C8-C32-Aryl und/oder C8-C32-Aralkyl, vorzugsweise C12-C20-Alkyl bedeutet, R₉ eine C1-C6-Alkylengruppe ist, vorzugsweise eine Ethylengruppe oder Propylengruppe, und n eine ganze Zahl zwischen 1 und 50, vorzugsweise zwischen 2 und 30, besonders bevorzugt zwischen 3 und 15, besonders bevorzugt zwischen 4 und 8 ist.

In a preferred process, the monomer composition comprises the radically polymerizable monomers selected from the group consisting of one or more of the following:

1. i. a nonionic monomer of the formula (I)
   
   , in which R ¹ represents hydrogen or methyl; R ² and R ³ are independently hydrogen, C1-C5 alkyl or C1-C5 hydroxyalkyl,
2. ii. a cationic monomer of the formula (II)
   
   , where R ¹ represents hydrogen or methyl; Z ₁ is O, NH or NR ⁴ , where R ⁴ is C1-C4 alkyl, preferably methyl, and Y has one of the following meanings
   
   , where Y ₀ and Y ₁ are a C1-C6 alkylene group, optionally substituted with one or more hydroxy groups, preferably ethylene or propylene, optionally substituted with a hydroxy group; Y ₂ , Y ₃ , Y ₅ , Y ₆ , Y ₇ each independently represent C1-C6 alkyl, preferably methyl; and Z ^- is a counterion, preferably a halogen, pseudohalogen, acetate or SO ₄ CH ₃ ^- ; and
3. iii. an amphiphilic monomer of the formulas (III) or (IV)
   
   , where Z ₁ is O, NH, NR ⁴ , where R ⁴ is C1-C4 alkyl, preferably methyl, R ¹ is hydrogen or methyl, R ₈ is a C1-C6 alkylene group, preferably ethylene or propylene, R ₈ and R ₆ are each independently C1-C6 alkyl, preferably methyl, R ₇ is a C8-C32 alkyl, optionally substituted with one or more hydroxy groups, preferably C12-C20 alkyl, optionally substituted with a hydroxy group, and Z ^- is a counterion, preferably a halogen, pseudohalogen, acetate or SO ₄ CH ₃ ^- ; or
   
   is, where Z ₁ is O, NH, NR ⁴ , where R ⁴ is C1-C4 alkyl, preferably methyl, R ¹ is hydrogen or methyl, R ₁₀ is hydrogen, C8-C32 alkyl, C8-C32 aryl and/ or C8-C32 aralkyl, preferably C12-C20 alkyl, R ₉ is a C1-C6 alkylene group, preferably an ethylene group or propylene group, and n is an integer between 1 and 50, preferably between 2 and 30, particularly preferably between 3 and 15, particularly preferably between 4 and 8.

In the context of the present invention, a cationic monomer is a monomer that permanently carries a positive charge, or the monomer carries a positive charge through protonation.

According to a preferred embodiment, one or more of the above under i. to iii. mentioned monomers are used as monomers in the monomer composition to be polymerized. A copolymer is preferably polymerized, i.e. two of the above under i. to iii. mentioned monomers are provided for the monomer composition to be polymerized. It is even more preferred that the monomer composition subjected to copolymerization is a monomer from point i. and a monomer from point ii. to be provided. In a preferred embodiment, the radically polymerizable monomers comprise a radically polymerizable nonionic monomer according to the general formula (I); and a radically polymerizable cationic monomer according to the general formula (II). A copolymer prepared from these monomers is advantageous for solving the above-mentioned problems.

In a preferred embodiment, the process is characterized in that the monomer composition comprising the radically polymerizable monomers comprises at least the nonionic monomer of formula (I) selected from those in which R ¹ is hydrogen or methyl and R ² and R ³ are both hydrogen, hydrogen and C1-C3 alkyl, hydrogen and hydroxyethyl or both are C1-C3 alkyl, and/or the cationic monomer of formula (II) selected from those in which R ¹ is hydrogen or Methyl and Z ₁ is O, NH or NR ⁴ , where R ⁴ is methyl, Y ₁ is C2-C6 alkylene, preferably ethylene or propylene, Y ₅ , Y ₆ and Y ₇ are all methyl and Z ^- is a halogen .

In a preferred embodiment, the radically polymerizable monomers comprise a radically polymerizable nonionic monomer according to the general formula (I), which is selected from the group consisting of (meth)acrylamide, N-methyl (meth)acrylamide, N,N-dimethyl (meth )acrylamide, N-ethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-methyl-N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide and N-hydroxyethyl(meth)acrylamide.

In a further preferred embodiment, the radically polymerizable monomers comprise a radically polymerizable cationic monomer according to the general formula (II), which is selected from the group consisting of trimethylammonium C2-C6 alkyl (meth)acrylate halides and trimethylammonium C2-C6 alkyl (meth) acrylamide halides. In a particularly preferred embodiment, the monomer composition comprises a radically polymerizable monomer that is (meth)acrylamide, together with a radically polymerizable monomer selected from trimethylammonium C2-C6 alkyl (meth)acrylate halides, which is in particular it is an acryloyloxyethyltrimethylammonium halide.

Optionally, the monomer composition may further contain a crosslinker, preferably an ethylenically unsaturated crosslinker, and/or a hydrophobic monomer, preferably a hydrophobic (meth)acrylic acid C4-18 alkyl ester, and/or an ethylenically unsaturated monomer.

In a preferred embodiment, the process is characterized in that the radically polymerizable monomers are selected from the non-ionic monomer of the formula (I) and/or the cationic monomer of the formula (II), the amount of the radically polymerizable monomers being selected from the non-ionic monomer of the formula (I) and/or the cationic monomer of the formula (II) are selected, is between 80 and less than 100% by weight, preferably 85 and 99% by weight, most preferably 90 and 95% by weight, based on the total amount of radically polymerizable monomers, the remainder being selected from the group consisting of any other ethylenically polymerizable monomer, a monomer of formula (III), a monomer of formula (IV) and a bifunctional ethylenically polymerizable monomer.

The sum of the values in% by weight does not have to be 100% by weight, since the monomer composition, i.e. in the reaction mixture, may contain further ethylenically unsaturated monomers (e), which must be taken into account when determining the total amount of monomers . However, the monomer composition preferably consists of the monomers (a) and (b), so that the sum of the two values in% by weight is 100% by weight, i.e. no further monomers are present.

1. (a) mindestens 5 Gew.-%, vorzugsweise mindestens 20 Gew.-% eines radikalisch polymerisierbaren nichtionischen Monomers der allgemeinen Formel (I);
2. (b) mindestens 5 Gew.-%, vorzugsweise mindestens 15 Gew.-%, stärker bevorzugt mindestens 20 Gew.-% oder 25 Gew.-%; vorzugsweise 10 bis 30 Gew.-% oder 40 bis 60 Gew.-%, stärker bevorzugt 15 bis 25 Gew.-% oder 23 bis 32 Gew.-% oder 45 bis 55 Gew.-%, eines radikalisch polymerisierbaren kationischen Monomers gemäß der allgemeinen Formel (II);
3. (c) gegebenenfalls bis zu 1,25 Gew.-% eines vorzugsweise ethylenisch ungesättigten Vernetzers;
4. (d) gegebenenfalls bis zu 1,25 Gew.-% eines hydrophoben (Meth)acrylsäure-C4-18-Alkylesters; und
5. (e) gegebenenfalls weitere ethylenisch ungesättigte Monomere.

In a preferred embodiment, the monomer composition comprises

1. (a) at least 5% by weight, preferably at least 20% by weight, of a free-radically polymerizable nonionic monomer of the general formula (I);
2. (b) at least 5% by weight, preferably at least 15% by weight, more preferably at least 20% or 25% by weight; preferably 10 to 30% by weight or 40 to 60% by weight, more preferably 15 to 25% by weight or 23 to 32% by weight or 45 to 55% by weight, of a radically polymerizable cationic monomer according to general formula (II);
3. (c) optionally up to 1.25% by weight of a preferably ethylenically unsaturated crosslinker;
4. (d) optionally up to 1.25% by weight of a hydrophobic (meth)acrylic acid C4-18 alkyl ester; and
5. (e) optionally further ethylenically unsaturated monomers.

Here too, the sum of the values in% by weight does not have to be 100% by weight, since further ethylenically unsaturated monomers (e) can be contained in the monomer composition, i.e. in the reaction mixture, which are used when determining the total amount of monomers must be taken into account. However, the monomer composition preferably consists of the monomers (a) and (b), so that the sum of the two values in% by weight is 100% by weight, i.e. no further monomers are present.

In the present application, all percentages relating to the monomer composition refer to the total amount of monomers.

According to the invention, the copolymerization is carried out in the presence of a polymeric dispersant.

In a preferred embodiment, the process is characterized in that the polymeric dispersant is selected from the group consisting of a cellulose derivative, polyvinyl acetate, starch, starch derivative, dextran, polyvinylpyrrolidone, polyvinylpyridine, polyethyleneimine, polyamine, polyvinylimidazole, polyvinylsuccinimide, polyvinyl-2-methylsuccinimide, Polyvinyl-1,3-oxazolidone-2, polyvinyl-2-methylimidazoline, itaconic acid, (meth)acrylic acid, (meth)acrylic acid ester, (meth)acrylic acid amide; preferably a (meth)acryloylamidoalkyltrialkylammonium halide or a (meth)acryloxyalkyltrialkylammonium halide.

Preferably the polymeric dispersant is derived from one or more cationic monomers, most preferably from a single cationic monomer.

In a preferred embodiment, the polymeric dispersant is derived from one or more radically polymerizable, ethylenically unsaturated monomers.

ist, wobei
R¹ Wasserstoff oder Methyl bedeutet;
Z₁ O, NH oder NR⁴ ist, wobei R⁴ C1-C4-Alkyl, vorzugsweise Methyl, bedeutet, und Y ist eines von

ist, wobei
Y₀ und Y₁ eine C1-C6-Alkylengruppe sind, gegebenenfalls substituiert mit einer oder mehreren Hydroxygruppen, vorzugsweise Ethylen oder Propylen, gegebenenfalls substituiert mit einer Hydroxygruppe;
Y₂, Y₃, Y₅, Y₆, Y₇ unabhängig voneinander jeweils C1-C6-Alkyl, vorzugsweise Methyl, bedeuten; und
Z^- ein Gegenion ist, vorzugsweise ein Halogen, Pseudohalogen, Acetat oder SO₄CH₃ ^-.In a further preferred embodiment, the process is characterized in that the polymeric dispersant is a homopolymer consisting of the cationic monomer of the formula (II)

is, where
R ¹ represents hydrogen or methyl;
Z ₁ is O, NH or NR ⁴ , where R ⁴ is C1-C4 alkyl, preferably methyl, and Y is one of

is, where
Y ₀ and Y ₁ are a C1-C6 alkylene group, optionally substituted with one or more hydroxy groups pen, preferably ethylene or propylene, optionally substituted with a hydroxy group;
Y ₂ , Y ₃ , Y ₅ , Y ₆ , Y ₇ each independently represent C1-C6 alkyl, preferably methyl; and
Z ^- is a counterion, preferably a halogen, pseudohalogen, acetate or SO ₄ CH ₃ ^- .

Preferably Y ₁ , Y ₂ and Y ₃ are identical, preferably methyl. In a preferred embodiment, Z ₁ is O or NH, Y ₀ is ethylene or propylene, R ¹ is hydrogen or methyl, and Y ₁ , Y ₂ and Y ₃ are methyl. The cationic monomer according to the general formula (II) can be an ester (Z ₁ = O), such as trimethylammonium ethyl (meth)acrylate (ADAME quat.). However, the cationic monomer according to the general formula (I) is preferably an amide (Z ₁ =NH), in particular trimethylammoniumpropylacrylamide (DIMAPA quat.).

Preferred radically polymerizable cationic monomers according to the general formula (II) are quaternized dialkylaminoalkyl (meth)acrylates or dialkylaminoalkyl (meth)acrylamides with 1 to 3 carbon atoms in the alkyl or alkylene groups, particularly preferably the methyl chloride-quaternized ammonium salt of dimethylaminomethyl (meth )acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, diethylamino-methyl (meth)acrylate, diethylamino-ethyl (meth)acrylate, diethylamino-propyl (meth)acrylate, dimethylamino-methyl (meth)acrylamide, dimethylaminoEthyl( meth)acrylamide, dimethylamino-propyl (meth) acrylamide, diethylamino-methyl (meth) acrylamide, diethylamino-ethyl (meth) acrylamide, diethylamino-propyl (meth) acrylamide.

Quaternized dimethylaminoethyl acrylate and dimethylaminopropylacrylamide are particularly preferred. Quaternization can be carried out with dimethyl sulfate, diethyl sulfate, methyl chloride or ethyl chloride. In a preferred embodiment, the monomers are quaternized with methyl chloride.

In a preferred embodiment, the polymeric dispersant is a homopolymer of trimethylammonium propylacrylamide (DIMAPA quat).

Preferably, the polymeric dispersant is derived from a monomer composition containing a cationic monomer selected from the group consisting of (alk)acrylamidoalkyltrialkylammonium halides (e.g., trimethylammonium alkyl-(meth)acrylamide halides), (alk)acryloyloxyalkyltrialkylammonium halides (e.g., trimethylammonium alkyl (meth)acrylate halides), alkenyltrialkylammonium halides and dialkenyldialkylammonium halides (e.g. diallyldialkylammonium halides). More preferably, the polymeric dispersant is a cationic polymer derived from a monomer composition containing a cationic monomer selected from the group consisting of trimethylammonium alkyl (meth)acrylate halides, trimethylammonium alkyl (meth)acrylamide halides and diallyldialkyl ammonium halides. Preferably, the aforementioned cationic monomers contain 6 to 25 carbon atoms, more preferably 7 to 20 carbon atoms, most preferably 7 to 15 carbon atoms and especially 8 to 12 carbon atoms.

In a preferred embodiment, the polymeric dispersant is derived from a dialkenyl dialkylammonium halide, preferably a diallyldimethyl ammonium halide (DADMAC).

According to a preferred embodiment, the process is characterized in that the polymeric dispersant is a homopolymer of a (meth)acryloylamidopropyltrimethylammonium salt or a (meth)acryloyloxyethyltrimethylammonium salt.

In this application, the halide may be any acceptable halide such as chloride, bromide or iodide; the counterions of the salts can be any acceptable counterions such as halides, methosulfate, sulfate or others.

The invention is particularly efficient if the process is characterized in that the total weight of the polymeric dispersant, based on the total weight of the polymer dispersion, is in the range from 10 to 28% by weight, preferably 12 to 26% by weight, more preferably 14 to 24% by weight, even more preferably 16 to 22% by weight. Compared to the processes known from the prior art for producing polymeric dispersants, the amount of polymeric dispersant used in the process according to the invention is higher.

It has surprisingly been found that the combination of the features according to which the weight average molecular weight is within the claimed range, together with the above-mentioned total weight of the polymeric dispersant, enhances the beneficial effects. If the low weight-average molecular weight is combined with a comparably high amount of polymeric dispersants, the advantageous technical effects associated with the present invention are enhanced. The stability of the polymer dispersions produced using such processes is improved.

In a preferred embodiment, the method is carried out by adding in step B) the reaction mixture successively or simultaneously at least a part of a predetermined amount of a redox initiator system which comprises an oxidizing agent and a reducing agent, at least a part of a predetermined amount of a first radical initiator and at least one Part of a predetermined amount of a second radical initiator is added.

• C) Verringerung des Restmonomergehalts durch Zugabe des Rests der vorbestimmten Menge des Redox-Initiatorsystems, des Rests der vorbestimmten Menge des ersten Radikalinitiators und/oder des Rests der vorbestimmten Menge des zweiten Radikalinitiators und/oder eines dritten Radikalinitiators zu dem Reaktionsgemisch.

According to a preferred embodiment, the method comprises the step

• C) Reducing the residual monomer content by adding the remainder of the predetermined amount of the redox initiator system, the remainder of the predetermined amount of the first radical initiator and/or the remainder of the predetermined amount of the second radical initiator and/or a third radical initiator to the reaction mixture.

The addition of these initiators allows the monomer to be removed so that they do not have any adverse effects on the stability of the dispersion obtained.

According to a preferred embodiment, the process is characterized in that the charge density of the dispersed polymer is 5 to 40 mol%, preferably 8 to 35 mol%, more preferably 10 to 30 mol%, most preferably 12 to 28 mol% . While the charge density of the polymeric dispersant is preferably 100 mol%, i.e. the polymeric dispersant is a 100 mol% polyelectrolyte, the dispersed polymer obtained by the copolymerization in step B) is partly a polyelectrolyte. The charge density is calculated from the monomer components, whereby the number of monomer components that carry a formal charge per total number of monomer components results in the molar proportion of the charge density. The charge density is therefore calculated from the monomeric components of the dispersed polymer.

If the charge density is in the above-mentioned range, the positive effect in terms of stability and viscosity is increased. In particular, the combination of the ratio of the polymeric dispersant to the dispersed polymer in the polymer dispersion and the charge density solves the problems mentioned above. Without being bound by theory, one might assume that the dispersibility of the polymeric dispersant depends on this ratio along with the charge density property.

In a preferred embodiment, the process is characterized in that step B is carried out by stirring.

According to a further preferred embodiment, the viscosity of the polymer dispersion obtained is 2,800 mPas to 6,500 mPas, preferably 3,000 mPas to 5,600 mPas, even more preferably 3,200 mPas to 5,400 mPas, most preferably 3,400 mPas to 4,000 mPas, measured with a Brookfield viscometer with spindle 4 at 20°C and an angular speed of 10 rpm.

It is known to those skilled in the art that the product viscosity differs from the viscosity of the reaction mixture during the manufacturing process. The viscosity of the product has an important influence on its usability for the desired application. If the product has a viscosity in the above-mentioned ranges, the polymer dispersion can be handled appropriately.

In a further preferred embodiment, the method is characterized in that step B is carried out by stirring while measuring the torque of a motor-driven agitator. Alternatively, the method is characterized in that step B is carried out by stirring and the torque of a motor-driven agitator is kept below 65 N/cm. At a torque of 65 N/cm or more, gelling is observed, resulting in a final product that does not have the required flocculant properties.

1. a) ein polymeres Dispergiermittel und
2. b) ein dispergiertes Polymer, das von einer Monomerzusammensetzung abgeleitet ist, die radikalisch polymerisierbare Monomere umfasst, wobei die radikalisch polymerisierbaren Monomere aus der Gruppe ausgewählt sind, die aus einem oder mehreren nicht-ionischen ethylenisch ungesättigten Monomeren, einem kationischen ethylenisch ungesättigten Monomer und einem amphiphilen ethylenisch ungesättigten Monomer besteht;

wobei das polymere Dispergiermittel ein gewichtsmittleres Molekulargewicht M_w, bestimmt durch Größenausschlusschromatographie, von 40.000 bis weniger als 150.000 g/mol, bevorzugt 50.000 bis 140.000 g/mol, weiter bevorzugt 60.000 bis 130.000, am meisten bevorzugt 85.000 bis 125.000 g/mol aufweist.The problems on which the invention is based are further solved by the subject matter of claim 12. According to a second aspect, the invention relates to a polymer dispersion comprising

1. a) a polymeric dispersant and
2. b) a dispersed polymer derived from a monomer composition comprising radically polymerizable monomers, wherein the radically polymerizable monomers are selected from the group consisting of one or more nonionic ethylenically unsaturated monomers, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer;

wherein the polymeric dispersant has a weight-average molecular weight M _w , determined by size exclusion chromatography, of 40,000 to less than 150,000 g/mol, preferably 50,000 to 140,000 g/mol, more preferably 60,000 to 130,000, most preferably 85,000 to 125,000 g/mol.

1. a) ein polymeres Dispergiermittel und
2. b) eine Monomerzusammensetzung, die radikalisch polymerisierbare Monomere umfasst, wobei die radikalisch polymerisierbaren Monomere aus der Gruppe ausgewählt sind, die aus einem oder mehreren nichtionischen ethylenisch ungesättigten Monomeren, einem kationischen ethylenisch ungesättigten Monomer und einem amphiphilen ethylenisch ungesättigten Monomer besteht;
3. B) Unterwerfen der Monomerzusammensetzung in der Reaktionsmischung einer radikalischen Polymerisation, um ein dispergiertes Polymer zu synthetisieren und die Polymerdispersion zu bilden,

wobei das polymere Dispersionsmittel ein gewichtsmittleres Molekulargewicht M_w, bestimmt durch Größenausschlusschromatographie, von 40.000 bis weniger als 150.000 g/mol, bevorzugt 50.000 bis 140.000 g/mol, noch bevorzugter 60.000 bis 130.000, am meisten bevorzugt 85.000 bis 125.000 g/mol, aufweist.The problems on which the invention is based are further solved by the subject matter of claim 13. Thus, according to a third aspect, the invention relates to a polymer dispersion which is obtained by a process for producing the polymer dispersion according to the invention, which comprises the following steps: A) providing a reaction mixture in an aqueous medium

1. a) a polymeric dispersant and
2. b) a monomer composition comprising radically polymerizable monomers, wherein the radically polymerizable monomers are selected from the group consisting of one or more nonionic ethylenically unsaturated monomers, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer;
3. B) subjecting the monomer composition in the reaction mixture to radical polymerization to synthesize a dispersed polymer and form the polymer dispersion,

wherein the polymeric dispersant has a weight-average molecular weight M _w , determined by size exclusion chromatography, of 40,000 to less than 150,000 g/mol, preferably 50,000 to 140,000 g/mol, more preferably 60,000 to 130,000, most preferably 85,000 to 125,000 g/mol.

1. a. als Flockungsmittel bei der Sedimentation, Flotation oder Filtration von Feststoffen,
2. b. als Verdickungsmittel,
3. c. zur Kontrolle von Verunreinigungen,
4. d. als Trockenfestigkeitsmittel, Retentionsmittel oder Entwässerungshilfe bei der Papierherstellung.

The problems underlying the invention are further solved by the subject matter of claim 14. According to a fourth aspect, the invention relates to the use of the polymer dispersion according to the invention

1. a. as a flocculant in the sedimentation, flotation or filtration of solids,
2. b. as a thickener,
3. c. to control contamination,
4. d. as a dry strength agent, retention agent or drainage aid in paper production.

Features that relate to preferred embodiments of the first aspect of the present invention and that are disclosed solely with respect to the first aspect of the invention also represent preferred embodiments of the second and third embodiments.

Exemplary embodiments (A) to (F) are disclosed below, which represent particularly preferred embodiments.

(A)

1. A) Bereitstellen einer Reaktionsmischung in einem wässrigen Medium, umfassend
   1. a) ein polymeres Dispersionsmittel und
   2. b) eine Monomerzusammensetzung, die radikalisch polymerisierbare Monomere umfasst, wobei die radikalisch polymerisierbaren Monomere aus der Gruppe ausgewählt sind, die aus einem oder mehreren nichtionischen ethylenisch ungesättigten Monomeren, einem kationischen ethylenisch ungesättigten Monomer und einem amphiphilen ethylenisch ungesättigten Monomer besteht;
2. B) Unterziehen der Monomerzusammensetzung einer Radikalpolymerisation zur Synthese eines dispergierten Polymers und zur Bildung der Polymerdispersion,

wobei das polymere Dispersionsmittel ein gewichtsmittleres Molekulargewicht M_w, bestimmt durch Größenausschlusschromatographie, von 40.000 bis weniger als 150.000 g/mol, bevorzugt 50.000 bis 140.000 g/mol, noch bevorzugter 60.000 bis 130.000, am meisten bevorzugt 85.000 bis 125. 000 g/mol; wobei die Monomerzusammensetzung, die die radikalisch polymerisierbaren Monomere umfaßt, mindestens das nichtionische Monomer der Formel (I) umfaßt, das aus denjenigen ausgewählt ist, in denen R¹ Wasserstoff oder Methyl bedeutet und R² und R³ beide Wasserstoff, Wasserstoff und C1-C3-Alkyl, Wasserstoff und Hydroxyethyl sind, oder beide C1-C3-Alkyl sind, und/oder das kationische Monomer der Formel (II), das aus denjenigen ausgewählt ist, in denen R¹ Wasserstoff oder Methyl bedeutet und Z₁ O, NH oder NR⁴ ist, wobei R⁴ Methyl bedeutet, Y₁ C2-C6-Alkylen, vorzugsweise Ethylen oder Propylen ist, Y₅, Y₆ und Y₇ alle Methyl sind und Z^- ein Halogen ist.Process for producing a polymer dispersion, comprising the steps

1. A) Providing a reaction mixture in an aqueous medium, comprising
   1. a) a polymeric dispersant and
   2. b) a monomer composition comprising radically polymerizable monomers, wherein the radically polymerizable monomers are selected from the group consisting of one or more nonionic ethylenically unsaturated monomers, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer;
2. B) subjecting the monomer composition to radical polymerization to synthesize a dispersed polymer and form the polymer dispersion,

wherein the polymeric dispersant has a weight average molecular weight M _w , determined by size exclusion chromatography, of 40,000 to less than 150,000 g/mol, preferably 50,000 to 140,000 g/mol, more preferably 60,000 to 130,000, most preferably 85,000 to 125,000 g/mol; wherein the monomer composition comprising the radically polymerizable monomers comprises at least the nonionic monomer of formula (I) selected from those in which R ¹ is hydrogen or methyl and R ² and R ³ are both hydrogen, hydrogen and C1-C3 -alkyl, hydrogen and hydroxyethyl, or both are C1-C3 alkyl, and/or the cationic monomer of formula (II) selected from those in which R ¹ is hydrogen or methyl and Z _{1 is} O, NH or NR ⁴ is where R ⁴ is methyl, Y ₁ is C2-C6 alkylene, preferably ethylene or propylene, Y ₅ , Y ₆ and Y ₇ are all methyl and Z ^- is a halogen.

(B)

1. A) Bereitstellen einer Reaktionsmischung in einem wässrigen Medium, umfassend
   1. a) ein polymeres Dispersionsmittel und
   2. b) eine Monomerzusammensetzung, die radikalisch polymerisierbare Monomere umfasst, wobei die radikalisch polymerisierbaren Monomere aus der Gruppe ausgewählt sind, die aus einem oder mehreren nicht-ionischen ethylenisch ungesättigten Monomeren, einem kationischen ethylenisch ungesättigten Monomer und einem amphiphilen ethylenisch ungesättigten Monomer besteht;
2. B) Unterziehen der Monomerzusammensetzung einer Radikalpolymerisation zur Synthese eines dispergierten Polymers und zur Bildung der Polymerdispersion,

wobei das polymere Dispergiermittel ein gewichtsmittleres Molekulargewicht M_w, bestimmt durch Größenausschlusschromatographie, von 40.000 bis weniger als 150.000 g/mol, bevorzugt 50.000 bis 140.000 g/mol, noch bevorzugter 60.000 bis 130.000, am meisten bevorzugt 85.000 bis 125.000 g/mol aufweist;
wobei die Monomerzusammensetzung, die die radikalisch polymerisierbaren Monomere umfaßt, mindestens das nichtionische Monomer der Formel (I) umfaßt, das aus denjenigen ausgewählt ist, in denen R¹ Wasserstoff oder Methyl bedeutet und R² und R³ beide Wasserstoff, Wasserstoff und C1-C3-Alkyl, Wasserstoff und Hydroxyethyl sind, oder beide C1-C3-Alkyl sind, und/oder das kationische Monomer der Formel (II) ausgewählt ist aus denen, in denen R¹ Wasserstoff oder Methyl bedeutet und Z₁ O, NH oder NR⁴ ist, wobei R⁴ Methyl bedeutet, Y₁ C2-C6-Alkylen, vorzugsweise Ethylen oder Propylen ist, Y₅, Y₆ und Y₇ alle Methyl sind und Z^- ein Halogen ist,
und wobei das polymere Dispergiermittel ausgewählt ist aus der Gruppe bestehend aus einem Cellulosederivat, Polyvinylacetat, Stärke, Stärkederivat, Dextran, Polyvinylpyrrolidon, Polyvinylpyridin, Polyethylenimin, Polyamin, Polyvinylimidazol, Polyvinylsuccinimid, Polyvinyl-2-methylsuccinimid, Polyvinyl-1,3-oxazolidon-2, Polyvinyl-2-methylimidazolin, Itaconsäure, (Meth)acrylsäure, (Meth)acrylsäureester, (Meth)acrylsäureamid; vorzugsweise ein (Meth)acryloylamidoalkyltrialkylammoniumhalogenid oder ein (Meth)acryloxyalkyltrialkylammoniumhalogenidProcess for producing a polymer dispersion, comprising the steps

1. A) Providing a reaction mixture in an aqueous medium, comprising
   1. a) a polymeric dispersant and
   2. b) a monomer composition comprising radically polymerizable monomers, wherein the radically polymerizable monomers are selected from the group consisting of one or more nonionic ethylenically unsaturated monomers, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer;
2. B) subjecting the monomer composition to radical polymerization to synthesize a dispersed polymer and form the polymer dispersion,

wherein the polymeric dispersant has a weight average molecular weight M _w , determined by size exclusion chromatography, of 40,000 to less than 150,000 g/mol, preferably 50,000 to 140,000 g/mol, more preferably 60,000 to 130,000, most preferably 85,000 to 125,000 g/mol;
wherein the monomer composition comprising the radically polymerizable monomers comprises at least the nonionic monomer of formula (I) selected from those in which R ¹ is hydrogen or methyl and R ² and R ³ are both hydrogen, hydrogen and C1-C3 -alkyl, hydrogen and hydroxyethyl, or both are C1-C3-alkyl, and/or the cationic monomer of formula (II) is selected from those in which R ¹ is hydrogen or methyl and Z _{1 is} O, NH or NR ⁴ is, where R ⁴ is methyl, Y ₁ is C2-C6-alkylene, preferably ethylene or propylene, Y ₅ , Y ₆ and Y ₇ are all methyl and Z ^- is a halogen,
and wherein the polymeric dispersant is selected from the group consisting of a cellulose derivative, polyvinyl acetate, starch, starch derivative, dextran, polyvinylpyrrolidone, polyvinylpyridine, polyethyleneimine, polyamine, polyvinylimidazole, polyvinylsuccinimide, polyvinyl-2-methylsuccinimide, polyvinyl-1,3-oxazolidone-2 , polyvinyl-2-methylimidazoline, itaconic acid, (meth)acrylic acid, (meth)acrylic acid ester, (meth)acrylic acid amide; preferably a (meth)acryloylamidoalkyltrialkylammonium halide or a (meth)acryloxyalkyltrialkylammonium halide

(C)

1. A) Bereitstellen einer Reaktionsmischung in einem wässrigen Medium, umfassend
   1. a) ein polymeres Dispersionsmittel und
   2. b) eine Monomerzusammensetzung, die radikalisch polymerisierbare Monomere umfasst, wobei die radikalisch polymerisierbaren Monomere aus der Gruppe ausgewählt sind, die aus einem oder mehreren nichtionischen ethylenisch ungesättigten Monomeren, einem kationischen ethylenisch ungesättigten Monomer und einem amphiphilen ethylenisch ungesättigten Monomer besteht;
2. B) Unterziehen der Monomerzusammensetzung einer Radikalpolymerisation zur Synthese eines dispergierten Polymers und zur Bildung der Polymerdispersion,

wobei das polymere Dispersionsmittel ein gewichtsmittleres Molekulargewicht M_w, bestimmt durch Größenausschlusschromatographie, von 40.000 bis weniger als 150.000 g/mol, bevorzugt 50.000 bis 140.000 g/mol, noch bevorzugter 60.000 bis 130.000, am meisten bevorzugt 85.000 bis 125.000 g/mol, aufweist;
wobei die radikalisch polymerisierbaren Monomere ein radikalisch polymerisierbares nichtionisches Monomer gemäß der allgemeinen Formel (I) umfassen, das ausgewählt ist aus der Gruppe bestehend aus (Meth)acrylamid, N-Methyl(meth)acrylamid, N,N-Dimethyl(meth)acrylamid, N-Ethyl(meth)acrylamid, N,N-Diethyl(meth)acrylamid, N-Methyl-N-ethyl(meth)acrylamid, N-Isopropyl(meth)acrylamid und N-Hydroxyethyl(meth)acrylamid und ein radikalisch polymerisierbares kationisches Monomer gemäß der allgemeinen Formel (II), das ausgewählt ist aus der Gruppe bestehend aus Trimethylammonium-C2-C6-alkyl(meth)acrylathalogeniden und Trimethylammonium-C2-C6-alkyl(meth)acrylamidhalogeniden,
und wobei das polymere Dispergiermittel ein Homopolymer aus einem (Meth)acryloylamidopropyl-Trimethylammoniumsalz oder einem (Meth)acryloyl-Oxyethyl-Trimethylammoniumsalz ist.Process for producing a polymer dispersion, comprising the steps

1. A) Providing a reaction mixture in an aqueous medium, comprising
   1. a) a polymeric dispersant and
   2. b) a monomer composition comprising radically polymerizable monomers, wherein the radically polymerizable monomers are selected from the group consisting of one or more nonionic ethylenically unsaturated monomers, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer;
2. B) subjecting the monomer composition to radical polymerization to synthesize a dispersed polymer and form the polymer dispersion,

wherein the polymeric dispersant has a weight average molecular weight M _w , determined by size exclusion chromatography, of 40,000 to less than 150,000 g/mol, preferably 50,000 to 140,000 g/mol, more preferably 60,000 to 130,000, most preferably 85,000 to 125,000 g/mol;
where the radically polymerizable monomers are a radically polymerizable nonionic monomer according to the general formula (I), which is selected from the group consisting of (meth)acrylamide, N-methyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-ethyl (meth)acrylamide, N, N-Diethyl (meth) acrylamide, N-methyl-N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide and N-hydroxyethyl (meth) acrylamide and a radically polymerizable cationic monomer according to the general formula (II), which is selected from the group consisting of trimethylammonium C2-C6 alkyl (meth) acrylate halides and trimethyl ammonium C2-C6 alkyl (meth) acrylamide halides,
and wherein the polymeric dispersant is a homopolymer of a (meth)acryloylamidopropyl trimethyl ammonium salt or a (meth)acryloyl oxyethyl trimethyl ammonium salt.

(D)

1. A) Bereitstellen einer Reaktionsmischung in einem wässrigen Medium, umfassend
   1. a) ein polymeres Dispersionsmittel und
   2. b) eine Monomerzusammensetzung, die radikalisch polymerisierbare Monomere umfasst, wobei die radikalisch polymerisierbaren Monomere aus der Gruppe ausgewählt sind, die aus einem oder mehreren nichtionischen ethylenisch ungesättigten Monomeren, einem kationischen ethylenisch ungesättigten Monomer und einem amphiphilen ethylenisch ungesättigten Monomer besteht;
2. B) Unterziehen der Monomerzusammensetzung einer Radikalpolymerisation zur Synthese eines dispergierten Polymers und zur Bildung der Polymerdispersion,

wobei das polymere Dispersionsmittel ein gewichtsmittleres Molekulargewicht M_w, bestimmt durch Größenausschlusschromatographie, von 40.000 bis weniger als 150.000 g/mol, bevorzugt 50.000 bis 140.000 g/mol, noch bevorzugter 60.000 bis 130.000, am meisten bevorzugt 85.000 bis 125.000 g/mol, aufweist;
wobei die Monomerzusammensetzung ein radikalisch polymerisierbares Monomer umfasst, das (Meth)acrylamid ist, zusammen mit einem radikalisch polymerisierbaren Monomer, das aus Trimethylammonium-C2-C6-alkyl(meth)acrylathalogeniden ausgewählt ist, wobei es sich vorzugsweise um ein Acryloyloxyethyltrimethylammoniumhalogenid handelt,
und wobei das polymere Dispergiermittel ein Homopolymer aus einem (Meth)acryloylamidopropyltrimethylammoniumsalz oder einem
(Meth)acryloyloxyethyltrimethylammoniumsalz ist.A process for producing a polymer dispersion, comprising the following steps

1. A) Providing a reaction mixture in an aqueous medium, comprising
   1. a) a polymeric dispersant and
   2. b) a monomer composition comprising radically polymerizable monomers, wherein the radically polymerizable monomers are selected from the group consisting of one or more nonionic ethylenically unsaturated monomers, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer;
2. B) subjecting the monomer composition to radical polymerization to synthesize a dispersed polymer and form the polymer dispersion,

wherein the polymeric dispersant has a weight average molecular weight M _w , determined by size exclusion chromatography, of 40,000 to less than 150,000 g/mol, preferably 50,000 to 140,000 g/mol, more preferably 60,000 to 130,000, most preferably 85,000 to 125,000 g/mol;
wherein the monomer composition comprises a radically polymerizable monomer that is (meth)acrylamide, together with a radically polymerizable monomer selected from trimethylammonium C2-C6 alkyl (meth)acrylate halides, which is preferably an acryloyloxyethyltrimethylammonium halide,
and wherein the polymeric dispersant is a homopolymer of a (meth)acryloylamidopropyltrimethylammonium salt or a
(Meth)acryloyloxyethyltrimethylammonium salt.

(E)

1. A) Bereitstellen einer Reaktionsmischung in einem wässrigen Medium, umfassend
   1. a) ein polymeres Dispersionsmittel und
   2. b) eine Monomerzusammensetzung, die radikalisch polymerisierbare Monomere umfasst, wobei die radikalisch polymerisierbaren Monomere aus der Gruppe ausgewählt sind, die aus einem oder mehreren nichtionischen ethylenisch ungesättigten Monomeren, einem kationischen ethylenisch ungesättigten Monomer und einem amphiphilen ethylenisch ungesättigten Monomer besteht;
   3. B) Unterwerfen der Monomerzusammensetzung in der Reaktionsmischung einer radikalischen Polymerisation, um ein dispergiertes Polymer zu synthetisieren und die Polymerdispersion zu bilden,

wobei das polymere Dispergiermittel ein gewichtsmittleres Molekulargewicht M_w, bestimmt durch Größenausschlusschromatographie, von 40.000 bis weniger als 150.000 g/mol, bevorzugt 50.000 bis 140.000 g/mol, noch bevorzugter 60.000 bis 130.000, am meisten bevorzugt 85.000 bis 125.000 g/mol aufweist;
wobei die radikalisch polymerisierbaren Monomere ein radikalisch polymerisierbares nichtionisches Monomer gemäß der allgemeinen Formel (I) umfassen, das ausgewählt ist aus der Gruppe bestehend aus (Meth)acrylamid, N-Methyl(meth)acrylamid, N,N-Dimethyl(meth)acrylamid, N-Ethyl(meth)acrylamid, N,N-Diethyl(meth)acrylamid, N-Methyl-N-ethyl(meth)acrylamid, N-Isopropyl(meth)acrylamid und N-Hydroxyethyl(meth)acrylamid und ein radikalisch polymerisierbares kationisches Monomer gemäß der allgemeinen Formel (II), das ausgewählt ist aus der Gruppe bestehend aus Trimethylammonium-C2-C6-alkyl(meth)acrylathalogeniden und Trimethylammonium-C2-C6-alkyl(meth)acrylamidhalogeniden,
wobei das polymere Dispergiermittel ein Homopolymer aus einem (Meth)acryloylamidopropyl-Trimethylammoniumsalz oder einem (Meth)acryloyl-Oxyethyl-Trimethylammoniumsalz ist,
und wobei das Gesamtgewicht des polymeren Dispergiermittels, bezogen auf das Gesamtgewicht der Polymerdispersion, im Bereich von 10 bis 28 Gew.-%, bevorzugt 12 bis 26 Gew.-%, noch bevorzugter 14 bis 24 Gew.-% und noch bevorzugter 16 bis 22 Gew.-% liegt.A process for producing a polymer dispersion, comprising the following steps

1. A) Providing a reaction mixture in an aqueous medium, comprising
   1. a) a polymeric dispersant and
   2. b) a monomer composition comprising radically polymerizable monomers, wherein the radically polymerizable monomers are selected from the group consisting of one or more nonionic ethylenically unsaturated monomers, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer;
   3. B) subjecting the monomer composition in the reaction mixture to radical polymerization to synthesize a dispersed polymer and form the polymer dispersion,

wherein the polymeric dispersant has a weight average molecular weight M _w , determined by size exclusion chromatography, of 40,000 to less than 150,000 g/mol, preferably 50,000 to 140,000 g/mol, more preferably 60,000 to 130,000, most preferably 85,000 to 125,000 g/mol;
wherein the radically polymerizable monomers comprise a radically polymerizable nonionic monomer according to the general formula (I), which is selected from the group consisting of (meth)acrylamide, N-methyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-ethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-methyl-N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide and N-hydroxyethyl (meth) acrylamide and a radically polymerizable cationic Monomer according to the general formula (II), which is selected from the group consisting of trimethylammonium C2-C6 alkyl (meth) acrylate halides and trimethyl ammonium C2-C6 alkyl (meth) acrylamide halides,
wherein the polymeric dispersant is a homopolymer of a (meth)acryloylamidopropyl-trimethylammonium salt or a (meth)acryloyl-oxyethyl-trimethylammonium salt,
and wherein the total weight of the polymeric dispersant, based on the total weight of the polymer dispersion, is in the range of 10 to 28% by weight, preferably 12 to 26% by weight, more preferably 14 to 24% by weight and even more preferably 16 to 22 % by weight.

(F)

1. A) Bereitstellen einer Reaktionsmischung in einem wässrigen Medium, umfassend
   1. a) ein polymeres Dispergiermittel und
   2. b) eine Monomerzusammensetzung, die radikalisch polymerisierbare Monomere umfasst,

wobei die radikalisch polymerisierbaren Monomere aus der Gruppe ausgewählt sind, die aus einem oder mehreren nichtionischen ethylenisch ungesättigten Monomeren, einem kationischen ethylenisch ungesättigten Monomer und einem amphiphilen ethylenisch ungesättigten Monomer besteht;

1. B) Unterwerfen der Monomerzusammensetzung in der Reaktionsmischung einer radikalischen Polymerisation, um ein dispergiertes Polymer zu synthetisieren und die Polymerdispersion zu bilden,

wobei das polymere Dispergiermittel ein gewichtsmittleres Molekulargewicht M_w, bestimmt durch Größenausschlusschromatographie, von 40.000 bis weniger als 150.000 g/mol, bevorzugt 50.000 bis 140.000 g/mol, noch bevorzugter 60.000 bis 130.000, am meisten bevorzugt 85.000 bis 125.000 g/mol aufweist;
wobei die Viskosität der Polymerdispersion 2.800 mPas bis 6.500 mPas, vorzugsweise 3.000 mPas bis 5.600 mPas, bevorzugter 3.200 mPas bis 5.400 mPas, am meisten bevorzugt 3.400 mPas bis 4.000 mPas beträgt, gemessen mit einem Brookfield-Viskosimeter mit Spindel 4 bei 20°C und einer Winkelgeschwindigkeit von 10 U/min;
wobei die radikalisch polymerisierbaren Monomere ein radikalisch polymerisierbares nichtionisches Monomer gemäß der allgemeinen Formel (I) umfassen, das ausgewählt ist aus der Gruppe bestehend aus (Meth)acrylamid, N-Methyl(meth)acrylamid, N,N-Dimethyl(meth)acrylamid, N-Ethyl(meth)acrylamid, N,N-Diethyl(meth)acrylamid, N-Methyl-N-ethyl(meth)acrylamid, N-Isopropyl(meth)acrylamid und N-Hydroxyethyl(meth)acrylamid und ein radikalisch polymerisierbares kationisches Monomer gemäß der allgemeinen Formel (II), das ausgewählt ist aus der Gruppe bestehend aus Trimethylammonium-C2-C6-alkyl(meth)acrylathalogeniden und Trimethylammonium-C2-C6-alkyl(meth)acrylamidhalogeniden,
wobei das polymere Dispergiermittel ein Homopolymer aus einem (Meth)acryloylamidopropyl-Trimethylammoniumsalz oder einem (Meth)acryloyl-Oxyethyl-Trimethylammoniumsalz ist,
und wobei das Gesamtgewicht des polymeren Dispergiermittels, bezogen auf das Gesamtgewicht der Polymerdispersion, im Bereich von 10 bis 28 Gew.-%, bevorzugt 12 bis 26 Gew.-%, noch bevorzugter 14 bis 24 Gew.-% und noch bevorzugter 16 bis 22 Gew.-% liegt.Process for producing a polymer dispersion, comprising the steps

1. A) Providing a reaction mixture in an aqueous medium, comprising
   1. a) a polymeric dispersant and
   2. b) a monomer composition which comprises free-radically polymerizable monomers,

wherein the radically polymerizable monomers are selected from the group consisting of one or more nonionic ethylenically unsaturated monomers, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer;

1. B) subjecting the monomer composition in the reaction mixture to radical polymerization to synthesize a dispersed polymer and form the polymer dispersion,

wherein the polymeric dispersant has a weight average molecular weight M _w , determined by size exclusion chromatography, of 40,000 to less than 150,000 g/mol, preferably 50,000 to 140,000 g/mol, more preferably 60,000 to 130,000, most preferably 85,000 to 125,000 g/mol;
wherein the viscosity of the polymer dispersion is 2,800 mPas to 6,500 mPas, preferably 3,000 mPas to 5,600 mPas, more preferably 3,200 mPas to 5,400 mPas, most preferably 3,400 mPas to 4,000 mPas, measured with a Brookfield viscometer with spindle 4 at 20 ° C and a angular velocity of 10 rpm;
wherein the radically polymerizable monomers comprise a radically polymerizable nonionic monomer according to the general formula (I), which is selected from the group consisting of (meth)acrylamide, N-methyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-ethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-methyl-N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide and N-hydroxyethyl (meth) acrylamide and a radically polymerizable cationic Monomer according to the general formula (II), which is selected from the group consisting of trimethylammonium C2-C6 alkyl (meth) acrylate halides and trimethyl ammonium C2-C6 alkyl (meth) acrylamide halides,
wherein the polymeric dispersant is a homopolymer of a (meth)acryloylamidopropyl-trimethylammonium salt or a (meth)acryloyl-oxyethyl-trimethylammonium salt,
and wherein the total weight of the polymeric dispersant, based on the total weight of the polymer dispersion, is in the range of 10 to 28% by weight, preferably 12 to 26% by weight, more preferably 14 to 24% by weight and even more preferably 16 to 22 % by weight.

EXAMPLES

• Die Stabilität wird durch zwei unterschiedliche Methoden bestimmt: (a) Zentrifugation und (b) Ofentest. Die Tests werden wie folgt durchgeführt:
  1. (a) 100 ± 0,1 g der Dispersion werden in ein Zentrifugationsröhrchen eingewogen. Das Röhrchen wird in eine Laborzentrifuge (Hermle Z300) gestellt und 1 Stunde lang bei 4000 U/min zentrifugiert. Anschließend wird der flüssige Teil der Probe innerhalb von 3 Minuten ausgephast und das Sediment im Zentrifugationsröhrchen gewogen. Ein höheres Sediment bedeutet eine geringere Phasenstabilität.
  2. (b) Die Probe wird 3 Tage lang bei 40°C im Trockenschrank gelagert. Das Aussehen wird visuell kontrolliert.

The test methods used are described in detail below:

• Stability is determined by two different methods: (a) centrifugation and (b) oven test. The tests are carried out as follows:
  1. (a) 100 ± 0.1 g of the dispersion are weighed into a centrifugation tube. The tube is placed in a laboratory centrifuge (Hermle Z300) and centrifuged at 4000 rpm for 1 hour. The liquid part of the sample is then phased out within 3 minutes and the sediment in the centrifugation tube is weighed. Higher sediment means lower phase stability.
  2. (b) The sample is stored in a drying cabinet at 40°C for 3 days. The appearance is checked visually.

The molar mass is measured using gel permeation chromatography (GPC or SEC). The measurement is carried out in particular to determine the molecular weight of the dispersant.

Molecular weights are characterized by aqueous SEC using pullulan standards for calibration.

Sample preparation:

The samples are diluted with the eluent (polymer make-down in a volumetric flask) and filtered through a 1µm filter (M&N) (using a syringe) before injection. If the device is equipped with an autosampler, the solution is filtered through a 1µm filter into a vial. Parameters used: Device: SEC (Agilent) Pillar: Novema 3000 (PSS) Detector: R.I Eluent: 1.5% by weight formic acid in water Flow rate: 1 ml/min Calibration standards: Pullulan with different M _w

• Verwenden Sie das Produkt direkt für die Messung. Die Spindel Nr. 5 wird langsam in das Produkt getaucht und die Viskosität mit einem Brookfield RVT-Viskosimeter bei 10 U/min bestimmt. Die Messung wird beendet, wenn der Messwert über einen Zeitraum von 30 Sekunden konstant bleibt.

The viscosity of the product is measured as follows:

• Use the product directly for measurement. Spindle #5 is slowly dipped into the product and the viscosity is determined using a Brookfield RVT viscometer at 10 rpm. The measurement is stopped when the measured value remains constant over a period of 30 seconds.

• In ein 400-ml-Becherglas werden 323,0 ± 0,1 g demineralisiertes Wasser eingewogen. Dann werden 17,0 ± 0,1 g des Produkts unter Rühren bei 300 U/min zugegeben (22 ± 3°C). Die Auflösungszeit beträgt 60 Minuten bei 300 ± 10 U/min. Danach muss die Lösung 5 min ruhen. Nun wird die Spindel Nr. 2 langsam eingetaucht und die Viskosität mit einem Brookfield-RFT-Viskosimeter bei 10 U/min bestimmt. Die Messung wird beendet, wenn der Messwert 30 Sekunden lang konstant bleibt.

The viscosity of the solution is measured in DI water and determined as follows:

• 323.0 ± 0.1 g of demineralized water are weighed into a 400 ml beaker. Then 17.0 ± 0.1 g of the product are added while stirring at 300 rpm (22 ± 3 ° C). The dissolution time is 60 minutes at 300 ± 10 rpm. The solution must then rest for 5 minutes. Now spindle No. 2 is slowly immersed and the viscosity is determined with a Brookfield RFT viscometer at 10 rpm. The measurement will stop when the reading remains constant for 30 seconds.

• In ein 400-ml-Becherglas werden 289,0 ± 0,1 g demineralisiertes Wasser eingewogen. Dann werden 17,0 ± 0,1 g des Produkts unter Rühren bei 300 U/min zugegeben (22 ± 3°C). Die Auflösungszeit beträgt 45 Minuten bei 300 ± 10 U/min. und dann werden 34,0 ± 0,1 g NaCl zugegeben. Die Lösung wird weitere 15 min gerührt. Danach muss die Lösung 5 min ruhen. Nun wird die Spindel Nr. 1 langsam eingetaucht und die Viskosität mit einem Brookfield RVT-Viskosimeter bei 10 U/min bestimmt. Die Messung ist beendet, wenn der Messwert über einen Zeitraum von 30 Sekunden konstant bleibt.

The salt viscosity is measured in a 10% NaCl solution and determined as follows:

• 289.0 ± 0.1 g of demineralized water are weighed into a 400 ml beaker. Then 17.0 ± 0.1 g of the product are added while stirring at 300 rpm (22 ± 3 ° C). The dissolution time is 45 minutes at 300 ± 10 rpm. and then 34.0 ± 0.1 g of NaCl are added. The solution is stirred for another 15 minutes. The solution must then rest for 5 minutes. Now spindle No. 1 is slowly immersed and the viscosity is determined with a Brookfield RVT viscometer at 10 rpm. The measurement is finished when the measured value remains constant over a period of 30 seconds.

The following examples further illustrate the invention but are not to be construed as limiting its scope.

Example 1: Synthesis of a low molecular weight polymeric dispersant:

First, 294.06 g of water, 666.7 g of acryloylamidopropyltrimethylammonium chloride (DIMAPA quat.) (60% by weight) and sulfuric acid (50% by weight) were added to adjust the pH to 5.0 ± 0.2 Weighed out 2 liter container. The monomer solution was then purged with nitrogen while stirring for 30 minutes. The aqueous solution was then heated to 60 °C and 2-mercaptoethanol and V-50 (2,2'-azobis(2-amidinopropane) dihydrochloride) were added. After the T _max was reached, two further portions of the initiator (V-50) were added to the product at intervals of 10 minutes in order to burn off the residual monomer. The product was stirred at 85 °C for 2 hours. The aqueous end product was then cooled to 30°C. The dispersants were provided in 40% by weight aqueous solutions.

• - Viskosität des Produkts [mPas]: 110-180
• - pH-Wert (unverdünnt): 4,9 - 5,3
• - Gesamtfeststoffgehalt [%]: 40 - 43
• - M_w SEC [g/mol]: 70000 - 110000

Specifications:

• - Product viscosity [mPas]: 110-180
• - pH value (undiluted): 4.9 - 5.3
• - Total solids content [%]: 40 - 43
• - M _w SEC [g/mol]: 70000 - 110000

The M _w is adjusted by varying the chain transfer agent 2-mercaptoethanol (2-ME).

Example 2: Synthesis of a polymer dispersion (charge density of the dispersed polymer 15 mol%)

In a batch process (batch size 1,000 kg), acrylamide and acryloyloxyethyltrimethylammonium chloride (ADAME quat.) were polymerized in an aqueous solution in the presence of homopolyacryloylamidopropyltrimethylammonium chloride (polymeric dispersant). The water phase was prepared at 200 rpm.

First, 206.90 kg of soft water, 261.80 kg of bio-acrylamide (49% by weight), 77.20 kg of acryloyl-oxyethyl-trimethylammonium chloride (ADAME quat) (80% by weight), 412.50 kg of polymers Dispersant from Example 1, 10.00 kg of ammonium sulfate and 0.20 kg of Trilon C were added to the reaction container. The pH was adjusted to pH 5.0 ± 0.2 with approximately 0.10 kg of sulfuric acid (50%). The vessel was heated to 30 °C and evacuated five times before venting with nitrogen. The initiator composition was added at a negative pressure of 0.5 bar and maximum stirrer speed. Initiation began at 22 ± 1°C with the addition of 0.34 kg V-50 in 3.05 kg soft water, 0.025 kg sodium persulfate in 0.47 kg soft water, 0.014 kg sodium bisulfite in 0.27 kg soft water and 0.003 kg t-butyl hydroperoxide (70%) in 1 kg soft water. The vessel was then ventilated again with nitrogen. After reaching the maximum temperature, a solution of 0.17 kg V-50 in 1.53 kg soft water was added to reduce the monomer content. After a one-hour post-reaction time, the product was cooled to a temperature below 40 °C. Then 8.30 kg of citric acid and 0.82 kg of the biocide Acticide SPX were added and the product was cooled to a temperature of below 30 ° C. Table 1: Dry DP-742*1) [%] 16.5 Active ingredients [%] 19.0 Batch hMw [% by weight] 32.5 Total charge [% by weight] 68.6 *1) Polymer from Example 1, calculated as dry content

• - Produktviskosität [mPas]: <6000
• - Viskosität der Lösung [mPas]: 400 - 2000
• - Salz-Viskosität [mPas]: 400 - 700
• - Rest Acrylamid [ppm]: <95
• - pH-Wert (unverdünnt): 3 - 4

Specifications:

• - Product viscosity [mPas]: <6000
• - Viscosity of the solution [mPas]: 400 - 2000
• - Salt viscosity [mPas]: 400 - 700
• - Residual acrylamide [ppm]: <95
• - pH value (undiluted): 3 - 4

• Es wurden die folgenden Polymerdispersionen hergestellt: Die erfindungsgemäßen Polymerdispersionen mit der Probenbezeichnung „PC8915“ und „PC8925“, sowie zwei Polymerdispersionen mit der Probenbezeichnung „PK2320“ als Referenzbeispiele. Das Molekulargewicht der erfindungsgemäßen Polymerdispersionen beträgt etwa 100.000 g/mol. Das Molekulargewicht der erfindungsgemäßen Polymerdispersion gemäß dem Referenzbeispiel beträgt mehr als 300.000 g/mol.

The following evaluates the effect of the weight average molecular weight of the dispersant on product performance:

• The following polymer dispersions were produced: The polymer dispersions according to the invention with the sample designation “PC8915” and “PC8925”, as well as two polymer dispersions with the sample designation “PK2320” as reference examples. The molecular weight of the polymer dispersions according to the invention is approximately 100,000 g/mol. The molecular weight of the polymer dispersion according to the invention according to the reference example is more than 300,000 g/mol.

As can be seen from Table 2, the viscosity of the polymer dispersion and the stability of the polymer dispersion are improved.

The stability is evaluated by the centrifuge test. This test is carried out by subjecting the prepared polymer dispersion to the action of a centrifuge. After this treatment, the supernatant above the sediment phase is examined for the polymeric dispersant content. The higher the content in the supernatant, the less polymeric dispersant is active for dispersing the dispersed polymer, i.e. H. the less stable the polymer dispersion is.

The advantageous technical effects are further enhanced when the amount of the polymeric dispersant is increased to a certain extent.

Sample PK2320 has a very low dispersant to dispersed phase ratio and a high weight average molecular weight. The product viscosity is very high and the stability is significantly worse than samples in which the weight-average molecular weight is in the range according to the invention.

A batch of sample PK2320 was prepared with subsequent addition of dispersant. The addition of the dispersant is done to reduce the viscosity of the product and meet the specification required by the applicants. Table 2: sample pAPTAC dispersant [%] AETAC-AM dispersed phase [%] Ratio of dispersant to dispersed phase M _w dispersant [g/mol] Product viscosity [mPas] Stability sediment centrifuge PC8915 16.5 19.0 0.868 90-120,000 approx. 4000 15 PC8925 20.0 19.2 1,041 90-120,000 approx. 5000 15 PK2320 9.0 10.4 19.0 17.8 0.474 0.584 300-400,000 300-400,000 approx. 11000; with subsequent addition of dispersant 40

Stability can be determined by visual inspection. 1 shows a stable dispersion in the sense of the invention. 2 shows unstable polymer dispersions with visually observable phase separation.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 8476391 B2 [0003]
• US 7323510 B2 [0003]

Claims (14)

A process for producing a polymer dispersion, comprising the steps A) providing a reaction mixture in an aqueous medium, comprising a) a polymeric dispersant and b) a monomer composition comprising radically polymerizable monomers, the radically polymerizable monomers being selected from the group consisting of one or more nonionic ethylenically unsaturated monomers, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer; B) subjecting the monomer composition to radical polymerization to synthesize a dispersed polymer and to form the polymer dispersion, wherein the polymeric dispersant has a weight-average molecular weight M _w , determined by size exclusion chromatography, of 40,000 to less than 150,000 g/mol, preferably 50,000 to 140,000 g/mol, more preferably 60,000 to 130,000, most preferably 85,000 to 125,000 g/mol. Procedure according to Claim 1 , characterized in that the monomer composition comprising the radically polymerizable monomers is selected from the group consisting of one or more of the following: i. a nonionic monomer of the formula (I)

, in which R ¹ represents hydrogen or methyl; R ² and R ³ are independently hydrogen, C1-C5 alkyl or C1-C5 hydroxyalkyl, ii. a cationic monomer of the formula (II)

, where R ¹ represents hydrogen or methyl; Z ₁ is O, NH or NR ⁴ , where R ⁴ is C1-C4 alkyl, preferably methyl, and Y has one of the following meanings

, where Y ₀ and Y ₁ are a C1-C6 alkylene group, optionally substituted with one or more hydroxy groups, preferably ethylene or propylene, optionally substituted with a hydroxy group; Y ₂ , Y ₃ , Y ₅ , Y ₆ , Y ₇ each independently represent C1-C6 alkyl, preferably methyl; and Z ^- is a counterion, preferably a halogen, pseudohalogen, acetate or SO ₄ CH ₃ ^- ; and iii. an amphiphilic monomer of the formulas (III) or (IV)

, where Z ₁ is O, NH, NR ⁴ , where R ⁴ is C1-C4 alkyl, preferably methyl, R ¹ is hydrogen or methyl, R ₈ is a C1-C6 alkylene group, preferably ethylene or propylene, R ₈ and R ₆ are each independently C1-C6 alkyl, preferably methyl, R ₇ is a C8-C32 alkyl, optionally substituted with one or more hydroxy groups, preferably C12-C20 alkyl, optionally substituted with a hydroxy group, and Z ^- is a counterion, preferably a halogen, pseudohalogen, acetate or SO ₄ CH ₃ ^- ; or

is, where Z ₁ is O, NH, NR ⁴ , where R ⁴ is C1-C4 alkyl, preferably methyl, R ¹ is hydrogen or methyl, R ₁₀ is hydrogen, C8-C32 alkyl, C8-C32 aryl and/ or C8-C32 aralkyl, preferably C12-C20 alkyl, R ₉ is a C1-C6 alkylene group, preferably an ethylene group or propylene group, and n is an integer between 1 and 50, preferably between 2 and 30, particularly preferably between 3 and 15, particularly preferably between 4 and 8. Procedure according to Claim 1 or Claim 2 , characterized in that the monomer composition comprising the radically polymerizable monomers comprises at least the nonionic monomer of formula (I) selected from those in which R ¹ is hydrogen or methyl and R ² and R ³ are both hydrogen, hydrogen and are C1-C3 alkyl, hydrogen and hydroxyethyl or both are C1-C3 alkyl, and/or the cationic monomer of formula (II) selected from those in which R ¹ is hydrogen or methyl and Z ₁ is O , NH or NR ⁴ , where R ⁴ is methyl, Y ₁ is C2-C6 alkylene, preferably ethylene or propylene, Y ₅ , Y ₆ and Y ₇ are all methyl and Z ^- is a halogen. Procedure according to Claim 1 or Claim 3 , characterized in that the free-radically polymerizable monomers are selected from the non-ionic monomer of the formula (I) and/or the cationic monomer of the formula (II), the amount of the free-radically polymerizable monomers being selected from the non-ionic monomer of the formula ( I) and/or the cationic monomer of the formula (II), is between 80 and less than 100% by weight, preferably 85 and 99% by weight, most preferably 90 and 95% by weight, based on the total amount of radically polymerizable monomers, the remainder being selected from the group consisting of any other ethylenically polymerizable monomer, a monomer of formula (III), a monomer of formula (IV) and a bifunctional ethylenically polymerizable monomer. Procedure according to one of the Claims 1 until 4 , characterized in that the polymeric dispersant is selected from the group consisting of a cellulose derivative, polyvinyl acetate, starch, starch derivative, dextran, polyvinylpyrrolidone, polyvinylpyridine, polyethyleneimine, polyamine, polyvinylimidazole, polyvinylsuccinimide, polyvinyl-2-methylsuccinimide, polyvinyl-1,3- oxazolidone-2, polyvinyl-2-methylimidazoline, itaconic acid, (meth)acrylic acid, (meth)acrylic acid ester, (meth)acrylic acid amide; preferably a (meth)acryloylamidoalkyltrialkylammonium halide or a (meth)acryloxyalkyltrialkylammonium halide. Procedure according to one of the Claims 1 until 5 , characterized in that the polymeric dispersant is a homopolymer consisting of the cationic monomer of formula (II)

is, where R ¹ represents hydrogen or methyl; Z ₁ is O, NH or NR ⁴ , where R ⁴ is C1-C4 alkyl, preferably methyl, and Y is one of

is, where Y ₀ and Y ₁ are a C1-C6 alkylene group, optionally substituted with one or more hydroxy groups, preferably ethylene or propylene, optionally substituted with a hydroxy group; Y ₂ , Y ₃ , Y ₅ , Y ₆ , Y ₇ each independently represent C1-C6 alkyl, preferably methyl; and Z ^- is a counterion, preferably a halogen, pseudohalogen, acetate or SO ₄ CH ₃ ^- . Procedure according to one of the Claims 1 until 6 , characterized in that the polymeric dispersant is a homopolymer of a (meth)acryloylamidopropyltrimethylammonium salt or a (meth)acryloyloxyethyltrimethylammonium salt. Procedure according to one of the Claims 1 until 7 , characterized in that the charge density of the dispersed polymer is 5 to 40 mol%, preferably 8 to 35 mol%, more preferably 10 to 30 mol%, most preferably 12 to 28 mol%. Procedure according to one of the Claims 1 until 8th , characterized in that the total weight of the polymeric dispersant, based on the total weight of the polymer dispersion, is in the range of 10 to 28% by weight, preferably 12 to 26% by weight, more preferably 14 to 24% by weight, even stronger is preferably 16 to 22% by weight. Procedure according to one of the Claims 1 until 9 , characterized in that step B) is carried out by adding to the reaction mixture successively or simultaneously at least a portion of a predetermined amount of a redox initiator system comprising an oxidizing agent and a reducing agent, at least a portion of a predetermined amount of a first radical initiator and at least a portion of a predetermined amount of a second radical initiator is added. Procedure according to one of the Claims 1 until 10 , characterized in that the method comprises the step C) reducing the residual monomer content by adding the remainder of the predetermined amount of the redox initiator system, the remainder of the predetermined amount of the first radical initiator and / or the remainder of the predetermined amount of the second radical initiator and / or a third radical initiator to the reaction mixture. Polymer dispersion comprising a) a polymeric dispersant and b) dispersed polymer derived from a monomer composition comprising radically polymerizable monomers, wherein the radically polymerizable monomers are selected from the group consisting of one or more non-ionic ethylenically unsaturated monomers, cationic ethylenically unsaturated monomers and amphiphilic ethylenically unsaturated monomers consists; wherein the polymeric dispersant has a weight-average molecular weight M _w , determined by size exclusion chromatography, of 40,000 to less than 150,000 g/mol, preferably 50,000 to 140,000 g/mol, more preferably 60,000 to 130,000, most preferably 85,000 to 125,000 g/mol. Polymer dispersion obtained by a process for producing the polymer dispersion according to one of Claims 1 until 11 , comprising the steps A) providing a reaction mixture in an aqueous medium, comprising a) a polymeric dispersant and b) a monomer composition which comprises radically polymerizable monomers, the radically polymerizable monomers being selected from the group consisting of one or more non- ionic ethylenically unsaturated monomers, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer; B) subjecting the monomer composition to radical polymerization to synthesize a dispersed polymer and to form the polymer dispersion, wherein the polymeric dispersant has a weight-average molecular weight M _w , determined by size exclusion chromatography, of 40,000 to less than 150,000 g/mol, preferably 50,000 to 140,000 g/mol, more preferably 60,000 to 130,000, most preferably 85,000 to 140,000 g/mol. Use of the polymer dispersion after Claim 12 or Claim 13 a. as a flocculant in the sedimentation, flotation or filtration of solids, b. as a thickener, c. to control contamination, i.e. as a dry strength agent, retention agent or drainage aid in paper production.