METHOD FOR PRODUCING A WATER-IN-WATER POLYMER DISPERSION USING A SHEAR PROFILE

Abstract

The invention relates to processes for producing a polymer dispersion, polymer dispersions, and their use. The processes for producing a water-in-water polymer dispersion utilize a batch reactor that provides a specific shear profile. The processes comprise a step in which an aqueous reaction mixture is subjected to radical polymerization to synthesize a dispersed polymer and form the water-in-water polymer dispersion. This aqueous reaction mixture comprises (a) a polymeric dispersant and (b) a monomer composition comprising radically polymerizable monomers. The radically polymerizable monomers are selected from the group consisting of one or more nonionic ethylene-unsaturated monomers, cationic ethylene-unsaturated monomers, and amphiphilic ethylene-unsaturated monomers.

Description

[0001] The invention relates to processes for producing a water-in-water polymer dispersion, polymer dispersions and their use.

[0002] The primary goal is to unlock the potential of water and renewable resources to create a safer, healthier, and more sustainable world. Countless industrial processes are water-based. The replacement of environmentally harmful substances or their volume reduction in water-based processes forms the basis for more sustainable solutions. The invention addresses this primary goal in the field of water-in-water (W / W) polymer dispersions. Improvements to W / W polymer dispersions directly correlate with sustainability in downstream applications, such as the papermaking process. The better such WW polymer dispersions function as additives in water-based processes, such as the papermaking process, the fewer such process additives need to be used. Furthermore, the replacement of hydrocarbons supports the primary goal.

[0003] In addition to applications in other technical fields, the water-in-water polymer dispersions are suitable as flocculants, drainage aids, and retention aids in papermaking. Paper is produced by first preparing an aqueous slurry of cellulose fibers with a water content of more than 95 wt.%. The finished paper sheet has a water content of less than 5 wt.%. Drainage and retention are crucial steps in papermaking and are important for an efficient papermaking process. High-performance water-in-water polymer dispersions are a key factor in the papermaking process.

[0004] A well-known flocculant is a w / w polymer dispersion produced by copolymerizing ethylenically unsaturated monomers in an aqueous system containing a polymer dispersant, resulting in a dispersion containing the polymer dispersant and the synthesized copolymer. US8476391 B2 and 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 polymer dispersants, on the other, leads to products with completely different properties than the w / w polymer dispersions disclosed in the above-mentioned patent documents. Copolymerization within a system containing the polymer dispersant is required to obtain high-performance flocculant products, e.g., for papermaking.

[0005] These circumstances make the production of water-in-water polymer dispersions a multi-parameter system. The type of ethylenically unsaturated monomer, its ratio, and the type of polymer dispersant are just a few of the parameters that influence the properties of the water-in-water polymer dispersion. Improving the properties of the final water-in-water polymer dispersion product has been the subject of numerous research and development efforts.

[0006] Those skilled in the art know how to radically polymerize monomers in a reaction mixture. Efforts are being made to find parameters that have a beneficial effect on complex polymer systems and offer the possibility of improving their properties. Beyond the properties of the final product, the w / w polymer dispersion, there is also a need to improve the process itself. In this context, there is a need to improve the process in terms of efficiency. There is a need to use raw materials efficiently. However, all measures applied to the process should not be associated with a loss of quality in the final product.

[0007] The object underlying the invention is to overcome the disadvantages of the prior art. In particular, the object underlying the invention relates to providing a process for producing a water-in-water polymer dispersion that results in a product that ensures improved handling and improved raw material-mediated efficiency. Furthermore, the object underlying the invention relates to providing a process for producing a water-in-water polymer dispersion that ensures a high degree of stability during the production process and a high storage life under adverse conditions such as fluctuating temperatures.

[0008] The objects underlying the invention are solved by the subject matter of claim 1. Thus, according to a first aspect, the invention relates to a process for producing a water-in-water polymer dispersion using a batch reactor, which comprises a step in which an aqueous reaction mixture is subjected to a radical polymerization in order to synthesize a dispersed polymer and form the water-in-water polymer dispersion, wherein the aqueous reaction mixture comprises a) a polymeric dispersant and 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; wherein the batch reactor comprises a stirrer which supplies a specific power input to the aqueous reaction mixture by stirring during the subjecting step, characterized in that the subjecting step comprises at least a first time phase and a second time phase, wherein the first time phase starts from an initiation of the radical polymerization and the second time phase follows the first time phase, wherein the specific power input in the first time phase is lower than the specific power input in the second time phase.

[0009] The process for preparing a water-in-water polymer dispersion utilizes a batch reactor providing a specific shear profile, the processes comprising a step of subjecting an aqueous reaction mixture to radical polymerization to synthesize a dispersed polymer and form the water-in-water polymer dispersion, wherein the aqueous reaction mixture comprises (a) a polymeric dispersant and (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. The polymer dispersions prepared by the process of the invention are referred to as water-in-water (W / W) polymer dispersions.

[0010] The process comprises providing a reaction mixture comprising the monomers to be copolymerized and a polymeric dispersant. The monomers are polymerized in the presence of the polymeric dispersant in an aqueous medium. According to well-known technical knowledge, a polymer dispersion obtained by the process according to the invention cannot be obtained by subjecting the monomer composition to copolymerization, followed by the addition of the polymeric dispersant after copolymerization. By applying the process according to the invention, unique properties are imparted to the polymer dispersion, with the polymer dispersion representing the final product comprising the copolymer obtained from the radically polymerizable monomers together with the polymeric dispersant.

[0011] In recent years, it has been discovered that the energy input to the reaction mixtures influences polymerizations. For example, WO 2011 / 110484 A1 discloses a process for the catalytic production of polyetherols, wherein the power input is within a predetermined range, based on the reactor volume, by means of at least one stirrer or by means of at least one stirrer and a pump, and deflections are used to influence the power input.

[0012] According to the state of the art, polymer synthesis is often carried out in a way that achieves effective homogenization. However, in the production of water-in-water polymer dispersions, a high power input throughout the entire process to effectively homogenize the reaction mixture is not the most advantageous way of conducting the polymerization.

[0013] According to the present invention, the object underlying the invention is achieved by a process for producing a polymer dispersion, comprising the reaction of a reaction mixture, wherein the reaction is carried out in a reactor vessel with stirring, wherein a specific power input into the reaction mixture is increased in a second time phase compared to a first time phase after initiation of the polymerization. In particular, it has been observed that the reaction profile feature according to claim 1 leads to improved efficiency of the initiation process. The increase in the supplied power can therefore take place after the initiation of the polymerization has been completed.

[0014] The expression "the second time phase follows the first time phase" means that the first time phase has ended, and the second time phase represents a time phase that is carried out after the first time phase has ended. The second time phase can follow immediately after the first time phase, but it can also follow with a time delay. This can be achieved, for example, by gradually increasing the specific power input in a time window between the first time phase and the second time phase.

[0015] The first time phase begins with the injection of an initiator. This means that the first time phase begins when the initiator is loaded into the batch reactor.

[0016] It has surprisingly been found that carrying out the method in such a way that the specific power input is changed according to claim 1 is associated with the advantageous effects.

[0017] The specific power input is the power input, the calculation of which depends on the type of flow, i.e., whether the flow in the reaction vessel is turbulent or laminar. The specific power input (P / V) is expressed as the power input (P) divided by the volume of the reaction mixture (V) and is calculated as follows: a) for the turbulent flow regime, the specific power input is calculated using: P / V=Ne*n3*d5*Density / V with Ne = Newtonian number of the reactor; n = stirrer speed; d = stirrer diameter; density of the reaction mixture, V = filling volume (this is the volume of the reaction mixture at the end of the reaction) and b) for the laminar flow regime, the specific power input is calculated using: P / V=C*n2*d3*Viscosity / V with C = Re*Ne and Re = Reynolds number of the stirrer used to mix the reaction mixture and Ne is the Newton number of the reactor.

[0018] The method can be carried out such that the stirrer generates a laminar flow or a turbulent flow during the first time phase, and / or the stirrer generates a laminar flow or a turbulent flow during the second time phase. Preferably, the method is carried out such that the stirrer generates a laminar flow during the first time phase and / or the stirrer generates a turbulent flow during the second time phase. The power input is calculated accordingly.

[0019] The power input can be determined by measuring the electrical power consumed by the stirrer motor or calculated from rheological parameters, stirrer type, reactor internal geometry, and stirring speed as described above. The calculation is described in the chapter "Stirring" by M. Zlokarnik in Ullmann's Encyclopedia of Industrial Chemistry, 2012, Wiley-VCH Verlag Weinheim.

[0020] In practice, the increase in specific power input in the process according to the invention is achieved by increasing the electrical power input. Before the start of the reaction, immediately before the initiator is loaded into the batch reactor, the power supply is low compared to the power supply in the second time phase. After the polymerization has been initiated, the power supply is increased. In the second time phase, the positive effect associated with more vigorous stirring takes effect.

[0021] In a preferred embodiment, the first time phase begins with the injection of the initiator and the second time phase begins 1 to 25 minutes, preferably 2 to 15 minutes, particularly preferably 5 to 8 minutes after the start of the first time phase.

[0022] According to preferred embodiments, the process is characterized in that the step of subjecting an aqueous reaction mixture to radical polymerization is carried out by sequentially or simultaneously adding a redox initiator system. The redox initiator system preferably consists of an oxidizing agent and a reducing agent. If the initiator is added sequentially to the batch reactor, the first time phase begins by definition with the injection of the first portion of the initiator. The second time phase only begins when all of the initiator used to initiate the polymerization has been injected into the batch reactor; however, the portions of the initiator injected to destroy residual monomers do not count towards the start of the second time phase.

[0023] According to a preferred embodiment, the process is characterized in that the oxidizing agent has a redox potential of 0.6 to 2.0 V. Preferred oxidizing agents used in the redox initiator system to control the adiabatic conditions are peroxydiphosphates; hydrogen peroxide (1.14 V); alkyl hydroperoxides, particularly preferably t-butyl hydroperoxide; or aryl hydroperoxides, particularly preferably cumene hydroperoxide. According to a particularly highly preferred embodiment, the process is characterized in that the oxidizing agent is selected from alkyl hydroperoxides, particularly t-butyl hydroperoxide, or aryl hydroperoxides, particularly cumene hydroperoxide.

[0024] Persulfates can also be used as agents in an initiator system. However, it has been shown that persulfates with a redox potential of 2.01 V do not influence the manufacturing process sufficiently to meet the requirement that the process be carried out under controlled adiabatic conditions. If persulfates are used as initiators in the present process, another oxidizing agent with a potential of 2 V or less and 0.6 V or more is used in the redox initiator system. In a preferred embodiment, however, the redox initiator system is free of a persulfate salt.

[0025] In a preferred embodiment, the process is characterized in that the reducing agent has a redox potential of -2 to 0.3 V. Preferred reducing agents are selected from sodium bisulfite, potassium bisulfite, ammonium bisulfite, sodium sulfite (-1.12 V), potassium sulfite, ammonium sulfite, a hydrogen sulfite (-0.08 V); a thiosulfate (-0.017 V); an amine; an acid, particularly preferably ascorbic acid (0.127 V) or erythorbic acid (0.127 V). Particularly preferred reducing agents are bisulfites, in particular sodium bisulfite, potassium bisulfite, or ammonium bisulfite.

[0026] The redox potential is determined using standard methods known to those skilled in the art.

[0027] In a very preferred embodiment, the redox initiator system comprises an alkyl / aryl hydroperoxide together with a bisulfite.

[0028] In a preferred embodiment, more oxidizing agent is used than reducing agent by mass. According to a preferred embodiment, the process is characterized in that the weight ratio between the reducing agent and the oxidizing agent is below 35:1 and above 2:1, preferably below 15:1 and above 3:1, particularly preferably below 9:1 and above 4:1.

[0029] In a further preferred embodiment, the process is characterized in that the polymerization step is carried out by stirring while measuring the torque of a motor-driven stirrer. Alternatively, the process is characterized in that step B of the polymerization is carried out by stirring and the torque of a motor-driven stirrer is kept below 65 N / cm.

[0030] In a preferred process, the monomer composition comprises the radically polymerizable monomers selected from the group consisting of one or more of the following: i. a non-ionic monomer of formula (I)wherein R 1 hydrogen or methyl; R 2 and R 3 are independently hydrogen, C1-C5 alkyl or C1-C5 hydroxyalkyl, ii. a cationic monomer of formula (II) wherein R 1 hydrogen or methyl; Z1 is O, NH, NR4, where R4 is C1-C4 alkyl, preferably methyl. Y is one of Y0 and Y1 are a C1-C6 alkylene group optionally substituted with one or more hydroxyl groups, preferably ethylene or propylene optionally substituted with a hydroxyl group; Y2, Y3, Y5, Y6, Y7 are each independently C1-C6 alkyl, preferably methyl; and Z- a counterion, preferably a halogen, pseudohalogen, acetate or SO4CH3 - ; iii. an amphiphilic monomer of formula (III) or (IV) wherein Z1 is O, NH, NR4, where R4 is C1-C4 alkyl, preferably methyl R 1 hydrogen or methyl, R8 is a C1-C6 alkylene group, preferably ethylene or propylene, R5 and R6 are each independently C1-C6 alkyl, preferably methyl, R7 a C8-C 32 -alkyl, optionally substituted by one or more hydroxyl groups, preferably C 12 -C 20 -alkyl, optionally substituted with a hydroxyl group, and Z - a counterion, preferably a halogen, pseudohalogen, acetate or SO4CH3 - ; orwherein Z1 is O, NH, NR4, where R4 is C1-C4 alkyl, preferably methyl R 1 hydrogen or methyl, R 10 Hydrogen, C8-C32 -Alkyl, C8-C 32 -aryl and / or C8-C 32 -aralkyl, preferably C 12 -C 20 -Alkyl means R9 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, more preferably between 3 and 15, most preferably between 4 and 8; and iv. an ethylenically unsaturated crosslinker having 2, 3, 4 or 5 ethylenically unsaturated groups.

[0031] In the context of the present invention, a cationic monomer is a monomer that permanently carries a positive charge.

[0032] According to the preferred embodiment, one or more of the above monomers mentioned under points i. to iv. are used as monomers in the monomer composition to be polymerized. It is preferred that a copolymer is polymerized, i.e., that two of the monomers mentioned above under points i. to iv. are provided for the monomer composition to be polymerized. It is preferred that one monomer from point i. and one monomer from point ii. are provided for the monomer composition subjected to copolymerization. In a preferred embodiment, the radically polymerizable monomers comprise a radically polymerizable non-ionic monomer according to the general formula (I); and a radically polymerizable cationic monomer according to the general formula (II). These copolymerized monomers are advantageous for achieving the above objects.

[0033] More preferably, a monomer of item i., a monomer of item ii., and a monomer of item iv. are provided for the monomer composition subjected to copolymerization.

[0034] 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 wherein R 1 hydrogen or methyl, and R 2 and R 3 both are 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 wherein R 1 is hydrogen or methyl and Z1 is O, NH or NR4, wherein R4 is methyl, Y1 is C2-C6 alkylene, preferably ethylene or propylene, Y5, Y6 and Y7 are all methyl, and Z - is a halogen.

[0035] In a preferred embodiment, the radically polymerizable monomers comprise a radically polymerizable non-ionic 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.

[0036] In a further preferred embodiment, the radically polymerizable monomers comprise a radically polymerizable cationic monomer according to general formula (II) selected from the group consisting of trimethylammonium C2-C6 alkyl (meth)acrylate halides and trimethylammonium C2-C6 alkyl (meth)acrylamide halides. In a particularly highly preferred embodiment, the monomer composition comprises a radically polymerizable monomer which is (meth)acrylamide, together with a radically polymerizable monomer selected from trimethylammonium C2-C6 alkyl (meth)acrylate halides, in particular an acryloyloxyethyl trimethylammonium halide.

[0037] According to a preferred embodiment, the monomer composition comprising free-radically polymerizable monomers contains a crosslinker. Crosslinkers are known to those skilled in the art. In this preferred embodiment, the monomer composition preferably contains 0.0001 to 1.25 wt. % of one or more preferably ethylenically unsaturated crosslinkers, based on the total weight of the monomers. If ethylenically unsaturated crosslinkers are present, they contain 2, 3, 4, or 5 ethylenically unsaturated groups that are free-radically polymerizable.

[0038] Examples of crosslinkers with two radically polymerizable, ethylenically unsaturated groups are: (1) Alkenyl di(meth)acrylates, such as 1,6-hexanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, 1,18-octadecanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, methylene di(meth)acrylate, 2,2'-bis(hydroxymethyl)-1,3-propanediol di(meth)acrylate, and preferably ethylene glycol di(meth)acrylate, 1,3-propanediol di(meth)acrylate, 1,3-butanediol di(meth)acrylate and 1,4-butanediol di(meth)acrylate; (2) Alkylenedi(meth)acrylamides, e.g. N-methylenedi(meth)acrylamide, N,N'-3-methylbutylidenebis(meth)acrylamide, N,N'-(1,2-dihydroxyethylene)bis(meth)acrylamide, and preferably N,N'-hexamethylenebis(meth)acrylamide, and particularly preferably N,N'-methylenebis(meth)acrylamide; (3) Polyalkoxydi(meth)acrylates according to the general formula (V)wherein R 10 is hydrogen or methyl; R 11 is selected from -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2- or -CH2CH2CH2CH2CH2CH2-; andm is an integer in the range 2-50.

[0039] Examples of crosslinkers according to the general formula (V) are polypropylene glycol di(meth)acrylates with m in the range of 4-25; polybutylene glycol di(meth)acrylates with m in the range of 5-40; and preferably polyethylene glycol di(meth)acrylates with m in the range of 2-45, e.g. diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate; and, more preferably, polyethylene glycol di(meth)acrylates with m in the range of 5-20; (4) Examples of other di(meth)acrylates that can be used are benzylidene di(meth)acrylate, bisphenol A di(meth)acrylate, 1,3-di(meth)acryloyloxy-Z-propanol, hydroquinone di(meth)acrylate, ethanedithiol di(meth)acrylate, propanedithiol di(meth)acrylate, polyethylenedithiol di(meth)acrylate and polypropylenedithiol di(meth)acrylate; (5) Divinyl compounds, e.g. 1,4-butanediol divinyl ether, divinylbenzene, butadiene, 1,6-hexadiene; di(meth)allyl compounds, such as di(meth)allyl phthalate or di(meth)allylsuccinate; vinyl(meth)acrylic compounds, e.g. vinyl(meth)acrylate; or preferably (meth)allyl(meth)acrylic compounds, e.g. allyl(meth)acrylate.

[0040] Examples of crosslinkers with 3 or more ethylenically unsaturated, radically polymerizable groups are glycerol tri(meth)acrylate, 2,2-dihydroxymethyl-1-butanol tri(meth)acrylate, trimethylolpropane triethoxytri(meth)acrylate, trimethacrylamide, (meth)allylidene di(meth)acrylate, 3-allyloxy-1,2-propanediol di(meth)acrylate, triallylamine, triallyl cyanurate or triallyl isocyanurate; and (as representative compounds with more than 3 ethylenically unsaturated, radically polymerizable groups) pentaerythritol tetra(meth)acrylate and N,N,N'N'-tetra(meth)acryloyl-1,5-pentanediamine.

[0041] An example of a crosslinker with 5 ethylenically unsaturated, radically polymerizable groups is dipentaerithritol pentaacrylate.

[0042] Particularly preferred crosslinkers are selected from the group consisting of methylenebisacrylamide, polyethylene glycol diacrylate and triallylamine.

[0043] Other preferred crosslinkers are asymmetrically crosslinkable monomers, i.e., crosslinkable monomers that rely on different functional groups for incorporation into the polymer backbone and the crosslinking reaction. Examples of such asymmetrically crosslinkable monomers are N'-methylolacrylamide, N'-methylolmethacrylamide, and glycidyl (meth)acrylate.

[0044] Crosslinkers of this type have the advantage that crosslinking can be initiated sequentially. Thus, crosslinking can occur under different conditions than the radical polymerization of the main backbone. Preferably, crosslinking is initiated after changing the reaction conditions, e.g., 6-9% of the pH (addition of acid or base), the temperature, and the like. Optionally, the monomer composition further comprises a hydrophobic monomer, preferably a hydrophobic C4-18 alkyl (meth)acrylate, and / or an ethylenically unsaturated monomer.

[0045] In a preferred embodiment, the process is characterized in that the radically polymerizable monomers are selected from the non-ionic monomer of formula (I) and / or the cationic monomer of formula (II), wherein the amount of radically polymerizable monomers selected from the non-ionic monomer of formula (I) and / or the cationic monomer of formula (II) is between 80 and less than 100 wt.%, preferably 85 and 99 wt.%, most preferably 90 and 95 wt.%, 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 the ethylenically unsaturated crosslinker having 2, 3, 4 or 5 ethylenically unsaturated groups.

[0046] The sum of the values ​​in wt. % need not be 100 wt. %, since, in addition to the monomers of formulas (I) and / or (II), other ethylenically unsaturated monomers may be present in the monomer composition, i.e., the reaction mixture, which must be taken into account when determining the total amount of monomers. In a preferred embodiment, however, the monomer composition consists of monomers (a) and (b), so that the sum of the two values ​​in wt. % is 100 wt. %, i.e., no further monomers are present.

[0047] In a preferred embodiment, the monomer composition comprises - at least 5% by weight, preferably at least 20% by weight of the non-ionic monomer of formula (I)wherein R 1 hydrogen or methyl; R 2 and R 3 are independently hydrogen, C1-C5 alkyl or C1-C5 hydroxyalkyl; - at least 5% by weight, preferably at least 20% by weight, particularly preferably 25 to 47% by weight, most preferably 50.5 to 80% by weight, of the cationic monomer of formula (II)wherein R 1 hydrogen or methyl; Z1 is O, NH, NR4, where R4 is C1-C4 alkyl, preferably methyl Y is one ofwhere Y0 and Y1 are a C1-C6 alkylene group optionally substituted with one or more hydroxyl groups, preferably ethylene or propylene optionally substituted with a hydroxyl group; Y2, Y3, Y5, Y6, Y7 are each independently C1-C6 alkyl, preferably methyl; and Z - a counterion, preferably a halogen, pseudohalogen, acetate or SO4CH3 - ; - 0.0001 to 1.25% by weight, preferably 0.0005 to 1% by weight of the ethylenically unsaturated crosslinker having 2, 3, 4 or 5 ethylenically unsaturated groups; and - optionally further ethylenically unsaturated monomers.

[0048] Here, too, the sum of the values ​​in wt. % need not be 100 wt. %, since, in addition to the monomers of formulas (I) and / or (II), further ethylenically unsaturated monomers may be present in the monomer composition, i.e., in the reaction mixture, which must be taken into account when determining the total amount of monomers. In a preferred embodiment, however, the monomer composition consists of monomers (a) and (b), so that the sum of the two values ​​in wt. % is 100 wt. %, i.e., no further monomers are present.

[0049] In the present application, all percentages relating to the monomer composition refer to the total amount of monomers.

[0050] According to the invention, the copolymerization is carried out in the presence of a polymeric dispersant.

[0051] According to the prior art, alternative aqueous polymer systems are stabilized by low-molecular-weight salts. A high salt content ensures the stability of the polymer system. In contrast to these systems, the stabilization of the inventive W / W polymer dispersion is fundamentally ensured by the polymeric dispersant. This system eliminates the need for a high salt concentration, as is common in prior-art aqueous polymer systems. In a preferred embodiment, the polymer dispersion has a salt content of less than 15 wt. %, particularly preferably a salt content of 0.1 to 10 wt. %, most preferably 1 to 5 wt. %, based on the polymer dispersion. The term "salt content" refers to salts with low molecular weight. The polymeric electrolytes are not taken into account when calculating the salt content.

[0052] In a preferred embodiment, the cationic polymeric dispersant is substantially linear, ie, it is not derived from monomer mixtures with crosslinkers.

[0053] In a preferred embodiment, the polymeric dispersant is derived from one or more radically polymerizable, ethylenically unsaturated monomers. Preferably, the polymeric dispersant is derived from one type of radically polymerizable, ethylenically unsaturated monomer, i.e., the polymeric dispersant is essentially a homopolymer. The term "essentially" in this context means that no second type of monomer is intentionally added during the synthesis of the polymeric dispersant.

[0054] Preferably, the polymeric dispersant is derived from one or more cationic monomers, more preferably from a single cationic monomer.

[0055] In a further preferred embodiment, the process is characterized in that the polymeric dispersant is a homopolymer prepared from the cationic monomer of formula (II) wherein R 1 hydrogen or methyl; Z1 is O, NH, NR4, where R4 is C1-C4 alkyl, preferably methyl. Y is one of Y0 and Y1 are a C1-C6 alkylene group optionally substituted with one or more hydroxyl groups, preferably ethylene or propylene optionally substituted with a hydroxyl group; Y2, Y3, Y5, Y6, Y7 are each independently C1-C6 alkyl, preferably methyl; and Z - a counterion, preferably a halogen, pseudohalogen, acetate or SO4CH3 - .

[0056] Preferably, Y1, Y2 and Y3 are identical, preferably methyl. In a preferred embodiment, Z1 is O or NH, Y0 is ethylene or propylene, R 1Hydrogen or methyl, and Y1, Y2, and Y3 are methyl. The cationic monomer according to general formula (II) can be an ester (Z1 = O), such as trimethylammonium ethyl (meth)acrylate (ADAME quat.). However, the cationic monomer according to general formula (I) is preferably an amide (Z1 = NH), in particular trimethylammonium propylacrylamide (DIMAPA quat).

[0057] Bevorzugte radikalisch polymerisierbare kationische Monomere nach allgemeiner Formel (II) umfassen quaternierte Dialkylaminoalkyl(meth)acrylate oder Dialkylaminoalkyl(meth)acrylamide mit 1 bis 3 C-Atomen in den Alkyl- oder Alkylengruppen, besonders bevorzugt das Methylchloridquaternierte Ammoniumsalz von Dimethylaminomethyl(meth)acrylat, Dimethylaminoethyl(meth)acrylat, Dimethylaminopropyl(meth)acrylat, Diethylaminomethyl(meth)acrylat, Diethylaminoethyl-(meth)acrylat, Diethylaminopropyl(meth)acrylat, Dimethylaminomethyl(meth)acrylamid, Dimethylaminoethyl(meth)acrylamid, Dimethylaminopropyl(meth)acrylamid, Diethylaminomethyl(meth)acrylamid, Diethylaminoethyl(meth)acrylamid, Diethylaminopropyl(meth)-acrylamid.

[0058] Quaternized dimethylaminoethyl acrylate and dimethylaminopropylacrylamide are particularly preferred. Quaternization can be influenced by the use of dimethyl sulfate, diethyl sulfate, methyl chloride, or ethyl chloride. In a preferred embodiment, monomers are quaternized with methyl chloride.

[0059] In a preferred embodiment, the polymeric dispersant is a homopolymer of trimethylammonium propylacrylamide chloride (DIMAPA quat), which is referred to by IUPAC as (3-acrylamidopropyl)trimethylammonium chloride (APTAC).

[0060] Preferably, the polymeric dispersant is derived from a monomer composition comprising 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 comprising a cationic monomer selected from the group consisting of trimethylammonium alkyl(meth)acrylate halides, trimethylammonium alkyl(meth)acrylamide halides, and diallyldialkylammonium halides.Preferably, the aforementioned cationic monomers comprise 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.

[0061] In a further preferred embodiment, the polymeric dispersant is derived from a dialkenyldialkylammonium halide, preferably a diallyldimethylammonium halide (DADMAC).

[0062] According to a preferred embodiment, the process is characterized in that the polymeric dispersant is a homopolymer prepared from a (meth)acryloylamidopropyltrimethylammonium salt or a (meth)acryloyloxyethyltrimethylammonium salt. For the purposes of this disclosure, a homopolymer of a (meth)acrylate means that the homopolymer is either a methacrylate or an acrylate.

[0063] For the purposes of this application, the halide may be any acceptable halide, such as chloride, bromide, or iodide; the counterions of the salts may be any acceptable counterions, such as halides, methosulfates, sulfates, or others.

[0064] According to a preferred embodiment, the process is characterized in that the polymeric dispersant has a weight-average molecular weight M determined by size exclusion chromatography. w from 40,000 to less than 150,000 g / mol, preferably 50,000 to 140,000 g / mol, particularly preferably 60,000 to 130,000, most preferably 85,000 to 120,000 g / mol.

[0065] In a preferred embodiment, the process is characterized in that the viscosity of the polymer dispersion is 1,800 mPas to less than 6,700 mPas, preferably 2,000 mPas to 6,000 mPas, particularly preferably 2,200 mPas to 5,500 mPas, most preferably 2,500 mPas to 5,000 mPas, measured with a Brookfield viscometer with spindle 4 at 20°C and an angular speed of 10 rpm.

[0066] The viscosity is preferably the volume viscosity, which refers to the viscosity immediately after receiving the cooled product.

[0067] According to a preferred embodiment, the ratio of the polymeric dispersant to the dispersed polymer in the polymer dispersion is in the range of 0.45:1 to 1:0.9, preferably in the range of 0.5:1 to 1:1, particularly preferably in the range of 0.55:1 to less than 1:1, even more preferably in the range of 0.6:1 to 0.99:1, in particular in the range of 0.65:1 to 0.9:1.

[0068] The invention is particularly effective when 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 wt.%, preferably 12 to 26 wt.%, particularly preferably 14 to 24 wt.%, even more preferably 16 to 22 wt.%. According to a further embodiment, the process is characterized in that the total weight of the polymeric dispersant, based on the total weight of the polymer dispersion, is between 18 and 26 wt.%, preferably 19 to 25 wt.%.

[0069] According to a preferred embodiment, the process comprises step C) reducing the residual monomer content by adding an initiator to the reaction mixture approximately at the time the maximum temperature (T max). In a particularly preferred embodiment, step C) is carried out isothermally, even more preferably step C is carried out by maintaining the temperature during step C at a level above 55°C and below 80°C, most preferably above 60°C and below 70°C.

[0070] The initiator used to reduce the residual monomer content can be one of the additional initiators mentioned above. However, it is preferred that the initiator be selected from a peroxide or an azo compound, more preferably selected from the group consisting of a hydroperoxide, a dialkyl peroxide, a diacyl peroxide, and an azo compound substituted by tertiary carbon atoms, preferably bearing alkyl groups, nitrile groups, and / or ester groups. In particular, the initiator used in step C is 2,2'-azobis(2-amidinopropane) dihydrochloride (V-50).

[0071] The objects underlying the invention are further achieved by the subject matter of claim 14. Thus, according to a second aspect, the invention relates to a polymer dispersion obtained by a process for preparing the polymer dispersion according to the invention, 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, 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; B) subjecting the monomer composition in the reaction mixture to a radical polymerization in order to synthesize a dispersed polymer and form the polymer dispersion,wherein the batch reactor has a stirrer which delivers a specific power input by stirring into the aqueous reaction mixture during the subjection step, characterized in that the subjection step comprises at least two time phases, wherein a first time phase starts from an initiation of the radical polymerization and a second time phase follows the first time phase, wherein the specific power input in the first time phase is lower than the specific power input in the second time phase.

[0072] According to a preferred embodiment, the polymer dispersion is obtained by a process for preparing the polymer dispersion, wherein the polymeric dispersant has a weight-average molecular weight M determined by size exclusion chromatography w from 40,000 to less than 150,000 g / mol, preferably 50,000 to 140,000 g / mol, particularly preferably 60,000 to 130,000, most preferably 85,000 to 120,000 g / mol.

[0073] According to a preferred embodiment, the polymer dispersion is obtained by a process for preparing the polymer dispersion, wherein the polymer dispersion has a volume viscosity below 6,700 mPas, preferably below 6,000 mPas, particularly preferably below 5,500 mPas, most preferably below 5,000 mPas, measured at 20°C using a Brookfield viscometer with spindle 4 and a speed of 10 rpm.

[0074] According to preferred embodiments, the polymer dispersion is obtained by a process for preparing the polymer dispersion, wherein the polymer dispersion has a volume viscosity above 1,800 mPas, preferably above 2,000 mPas, particularly preferably above 2,200 mPas, even more preferably above 2,500 mPas, most preferably above 3,000 mPas, measured at 20°C using a Brookfield viscometer with spindle 4 and a speed of 10 rpm.

[0075] The objects underlying the invention are further achieved by the subject matter of claim 15. Thus, according to a third aspect, the invention relates to the use of the polymer dispersion according to the invention a. as a flocculant in the sedimentation, flotation or filtration of solids, b. as a thickener, c. as a pollution control agent, d. as a dry strength aid, retention agent or drainage aid in papermaking.

[0076] Features relating to preferred embodiments of the first aspect of the present invention, which are disclosed exclusively with respect to the first aspect of the invention, also represent preferred embodiments of the second and third embodiments.

[0077] In the following, exemplary embodiments (A) to (E) are disclosed, which represent particularly preferred embodiments. (A)

[0078] A process for preparing a water-in-water polymer dispersion using a batch reactor, comprising a step of subjecting an aqueous reaction mixture to radical polymerization to synthesize a dispersed polymer and form the water-in-water polymer dispersion, said aqueous reaction mixture comprising a) a polymeric dispersant and 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; wherein the batch reactor has a stirrer which, by stirring, delivers a specific power input to the aqueous reaction mixture during the subjecting step, characterized in that the subjecting step comprises at least a first time phase and a second time phase, wherein the first time phase starts from an initiation of the radical polymerization by injecting an initiator into the batch reactor and the second time phase follows the first time phase, wherein the specific power input in the first time phase is lower than the specific power input in the second time phase. (B)

[0079] A process for preparing a water-in-water polymer dispersion using a batch reactor, comprising a step of subjecting an aqueous reaction mixture to radical polymerization to synthesize a dispersed polymer and form the water-in-water polymer dispersion, said aqueous reaction mixture comprising a) a polymeric dispersant and 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;wherein the batch reactor has a stirrer which delivers a specific power input by stirring into the aqueous reaction mixture during the subjecting step, characterized in that the subjecting step comprises at least a first time phase and a second time phase, wherein the first time phase starts from an initiation of the radical polymerization by injecting an initiator into the batch reactor and the second time phase follows the first time phase, wherein the specific power input in the first time phase is lower than the specific power input in the second time phase, wherein the polymeric dispersant is a homopolymer prepared from the cationic monomer of the formula (II) wherein; R 1 hydrogen or methyl; Z1 is O, NH, NR4, where R4 is C1-C4 alkyl, preferably methyl. Y is one of Y0 and Y1 are a C1-C6 alkylene group optionally substituted with one or more hydroxyl groups, preferably ethylene or propylene optionally substituted with a hydroxyl group; Y2, Y3, Y5, Y6, Y7 are each independently C1-C6 alkyl, preferably methyl; and Z - a counterion, preferably a halogen, pseudohalogen, acetate or SO4CH3 - . (C)

[0080] A process for preparing a water-in-water polymer dispersion using a batch reactor, comprising a step of subjecting an aqueous reaction mixture to radical polymerization to synthesize a dispersed polymer and form the water-in-water polymer dispersion, said aqueous reaction mixture comprising a) a polymeric dispersant and 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;wherein the batch reactor has a stirrer which delivers a specific power input by stirring into the aqueous reaction mixture during the subjecting step, characterized in that the subjecting step comprises at least a first time phase and a second time phase, wherein the first time phase starts from an initiation of the radical polymerization by injecting an initiator into the batch reactor and the second time phase follows the first time phase, wherein the specific power input in the first time phase is lower than the specific power input in the second time phase, wherein the polymeric dispersant is a homopolymer prepared from a (meth)acryloylamidopropyltrimethylammonium salt or a (meth)acryloyloxyethyltrimethylammonium salt.; (D)

[0081] A process for preparing a water-in-water polymer dispersion using a batch reactor, comprising a step of subjecting an aqueous reaction mixture to radical polymerization to synthesize a dispersed polymer and form the water-in-water polymer dispersion, said aqueous reaction mixture comprising a) a polymeric dispersant and 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;wherein the batch reactor has a stirrer which delivers a specific power input by stirring into the aqueous reaction mixture during the subjecting step, characterized in that the subjecting step comprises at least a first time phase and a second time phase, wherein the first time phase starts from an initiation of the radical polymerization by injecting an initiator into the batch reactor and the second time phase follows the first time phase, wherein the specific power input in the first time phase is lower than the specific power input in the second time phase, wherein the specific power input is adjusted by changing the electrical power input supplied to the stirrer.; (E)

[0082] A process for preparing a water-in-water polymer dispersion using a batch reactor, comprising a step of subjecting an aqueous reaction mixture to radical polymerization to synthesize a dispersed polymer and form the water-in-water polymer dispersion, said aqueous reaction mixture comprising a) a polymeric dispersant and 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;wherein the batch reactor has a stirrer which delivers a specific power input by stirring into the aqueous reaction mixture during the subjecting step, characterized in that the subjecting step comprises at least a first time phase and a second time phase, wherein the first time phase starts from an initiation of the radical polymerization by injecting an initiator into the batch reactor and the second time phase follows the first time phase, wherein the specific power input in the first time phase is lower than the specific power input in the second time phase, wherein the specific power input is adjusted by changing the electrical power input supplied to the stirrer, and wherein the second time phase begins 1 to 25 minutes, preferably 5 to 15 minutes, after the start of the first time phase. EXAMPLES

[0083] The test methods used are described in detail below: The volume viscosity is measured as follows: Use the product directly for measurement. Spindle No. 4 is slowly immersed in the product and the viscosity is determined using a Brookfield RVT viscometer at 10 rpm. The measurement is terminated when the reading remains constant for a period of 30 seconds.

[0084] The viscosity of the solution is measured in deionized water and determined as follows: A 5 wt% solution in water is prepared. 323.0 ± 0.1 g of demineralized water is weighed into a 400 ml beaker. Then, 17.0 ± 0.1 g of the product (22 ± 3 °C) are added while stirring at 300 rpm. The dissolution time is 60 min at 300 ± 10 rpm. The solution must then rest for 5 minutes. Spindle No. 2 is then slowly immersed, and the viscosity is determined using a Brookfield RFT viscometer at 10 rpm. The measurement is stopped when the measured value remains constant for a period of 30 seconds.

[0085] The salt viscosity is measured in a 10% NaCl solution and determined as follows: Weigh 289.0 ± 0.1 g of demineralized water into a 400 ml beaker. Then, 17.0 ± 0.1 g of the product (22 ± 3 °C) are added while stirring at 300 rpm. The dissolution time is 45 minutes at 300 ± 10 rpm, after which 34.0 ± 0.1 g of NaCl are added. The solution is stirred for another 15 minutes. The solution must then stand for 5 minutes. Spindle No. 1 is then slowly immersed, and the viscosity is determined using a Brookfield RVT viscometer at 10 rpm. The measurement is stopped when the measured value remains constant for a period of 30 seconds.

[0086] The molecular weight is measured using size exclusion chromatography (SEC).

[0087] The measurement is carried out in particular to determine the molecular weight of the dispersant.

[0088] Molecular weights are characterized by aqueous SEC using pullulan standards for calibration.

[0089] Sample preparation: The samples are diluted with the eluent (polymer make-down in a volumetric flask) and filtered through a 1µm filter (M&N) (via syringe) before injection. If the instrument is equipped with an autosampler, filter the solution through a 1µm filter into a vial.

[0090] Parameters used: Device: SEC (Agilent) Column: Novema 3000 (PSS) Detector: RI Eluent: 1.5 wt% formic acid in water Flow rate: 1 ml / min Calibration standards: Pullulan with different Mw

[0091] The following examples further illustrate the process for preparing the W / W polymer dispersion. However, the following examples should not be construed as limiting the invention. Example 1: Synthesis of the polymeric dispersant:

[0092] First, 294.06 g of water, 666.7 g of acryloylamidopropyltrimethylammonium chloride (DIMAPA quat.) (60 wt%), and sulfuric acid (50 wt%) were weighed into a 2-liter vessel to adjust the pH to 5.0 ± 0.2. The monomer solution was then purged with nitrogen for 30 min by stirring. After 3 minutes of stirring at low power input, the power input was increased. The aqueous solution was then heated to 65°C, and 2-mercaptoethanol and V-50 (2,2'-azobis(2-amidinopropane) dihydrochloride) were added to the solution. After reaching Tmax, the vessel was cooled to ≤ 80°C. Two additional portions of the initiator (V-50) were then added to the product within 10 minutes to burn off the remaining monomer. The product was stirred at 70°C for 1 h. The final aqueous product was cooled to 30 °C. The dispersants were provided in 40 wt% aqueous solutions.

[0093] Specifications: - Product viscosity [mPas]: 110-180 - pH value (pure): 4.9-5.3 - Total solids [%]: 40-43 - Mw SEC [g / mol]: 70000-110000 Example 2: Synthesis of polymer dispersion (charge density 15 mol%)

[0094] 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 aqueous phase was prepared at 200 rpm.

[0095] First, 206.90 kg of soft water, 261.80 kg of bio-acrylamide (49 wt%), 77.20 kg of acryloyloxyethyltrimethylammonium chloride (ADAME quat) (80 wt%), 412.50 kg of polymeric dispersant from Example 1, 10.00 kg of ammonium sulfate, and 0.20 kg of Trilon C were charged into the reaction vessel. The pH was adjusted to 5.0±0.2 with approximately 0.10 kg of sulfuric acid (50%). The vessel was evacuated five times before being vented with nitrogen. The initiator composition was added at a vacuum of 0.5 bar and maximum stirrer speed. Initiation began at 22±1 °C with the addition of 0.34 kg of V-50 in 3.05 kg of soft water, 0.025 kg of sodium persulfate in 0.47 kg of soft water, 0.014 kg of sodium bisulfite in 0.27 kg of soft water, and 0.003 kg of t-butyl hydroperoxide (70%) in 1 kg of soft water. The vessel was then re-aerated with nitrogen.After reaching the maximum temperature, a solution of 0.17 kg of V-50 in 1.53 kg of soft water was added to reduce the monomer content. After a one-hour post-reaction period, the product was cooled to a temperature below 40°C. Subsequently, 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 below 30°C.

[0096] Alternatively, in all of the above examples and embodiments, efficiency can be increased by operating the stirrer (or stirring) at 20% power during oxygen release (at higher power, a vortex is created and the nitrogen passes through). Then, the stirring power is set to 100%, and the initiators can be added to start the reaction. This can now be done in such a way that the stirring profile is always the same. If the stirring power was lower than when the initiators were added, significant differences in stirring power and stirring times can occur later on. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This 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

[0000] US 8476391 B2

[0004] US 7323510B2

[0004] WO 2011 / 110484 A1

[0011] Cited non-patent literature

[0000] Stirring” by M. Zlokarnik in Ullmann's Encyclopedia of Industrial Chemistry, 2012, Wiley-VCH Verlag Weinheim

[0019]

Claims

[1] A process for producing a water-in-water polymer dispersion using a batch reactor, comprising a step of subjecting an aqueous reaction mixture to radical polymerization to synthesize a dispersed polymer and form the water-in-water polymer dispersion, said aqueous reaction mixture comprising a) a polymeric dispersant and 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; wherein the batch reactor has a stirrer which provides a certain power input by stirring into the aqueous reaction mixture during the subjection step, characterized bythat the subjecting step comprises at least a first time phase and a second time phase, wherein the first time phase starts from an initiation of the radical polymerization and the second time phase follows the first time phase, where the specific power input in the first time phase is lower than the specific power input in the second time phase. [2] Method according to claim 1, characterized by that the specific power input is given by the formula P=Ne × n 3 × d 5 × ς, where Ne is the Newton number, n is the stirrer speed in revolutions / minute (rpm), d is the stirrer diameter and ς is the density of the reaction mixture. [3] Method according to claim 1, characterized by that the specific power input is given by the formula P / V = C × n 2 × d 3× viscosity / V, where C = Re × Ne and Re is the Reynolds number of the stirrer used to mix the aqueous reaction mixture and Ne is the Newton number of the reactor. [4] Method according to one of claims 1 to 3, characterized by that the batch reactor is free of a baffle. [5] Method according to one of claims 1 to 4, characterized by that the specific power input is adjusted by changing the electrical power input supplied to the stirrer. [6] Method according to one of claims 1 to 5, characterized by that the stirrer induces turbulent flow during the step of subjecting the aqueous reaction mixture to radical polymerization. [7] Method according to one of claims 1 to 6, characterized by that the monomer composition comprising the radically polymerizable monomers is selected from the group consisting of one or more of the following: i. a non-ionic monomer of formula (I)wherein R 1 hydrogen or methyl; R 2 and R 3 are independently hydrogen, C1-C5 alkyl or C1-C5 hydroxyalkyl, ii. a cationic monomer of formula (II)wherein R 1 hydrogen or methyl; Z1 is O, NH, NR4, where R4 is C1-C4 alkyl, preferably methyl. Y is one of Y0 and Y1 are a C1-C6 alkylene group optionally substituted with one or more hydroxyl groups, preferably ethylene or propylene optionally substituted with a hydroxyl group; Y2, Y3, Y5, Y6, Y7 are each independently C1-C6 alkyl, preferably methyl; and Z - a counterion, preferably a halogen, pseudohalogen, acetate or SO4CH3 - ; iii. an amphiphilic monomer of formula (III) or (IV) wherein Z1 is O, NH, NR4, where R4 is C1-C4 alkyl, preferably methyl R 1 hydrogen or methyl, R8 is a C1-C6 alkylene group, preferably ethylene or propylene, R5 and R6 are each independently C1-C6 alkyl, preferably methyl, R7 a C8-C 32 -alkyl, optionally substituted by one or more hydroxyl groups, preferably C 12 -C 20 -alkyl, optionally substituted with a hydroxyl group, and Z - a counterion, preferably a halogen, pseudohalogen, acetate or SO4CH3 - ; orwherein Z1 is O, NH, NR4, where R4 is C1-C4 alkyl, preferably methyl, R1 is hydrogen or methyl, R 10 Hydrogen, C8-C 32 -Alkyl, C8-C 32 -aryl and / or C8-C 32 -aralkyl, preferably C 12 -C 20 -Alkyl means R9 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 3 and 15, most preferably 4 and 8; and iv. an ethylenically unsaturated crosslinker having 2, 3, 4 or 5 ethylenically unsaturated groups. [8] Method according to one of claims 1 to 7, characterized by that the monomer composition comprising the radically polymerizable monomers comprises the nonionic monomer of formula (I) selected from those wherein R 1 hydrogen or methyl, and R 2 and R 3 both are 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 wherein R 1is hydrogen or methyl and Z1 is O, NH or NR4, wherein R4 is methyl, Y1 is C2-C6 alkylene, preferably ethylene or propylene, Y5, Y6 and Y7 are all methyl, and Z - is a halogen, most preferably the monomer composition comprising the radically polymerizable monomers comprises at least the nonionic monomer of formula (I) as (meth)acrylamide and the cationic monomer of formula (II) as (meth)acryloylamidopropyltrimethylammonium chloride or (meth)acryloyloxyethyltrimethylammonium chloride. [9] Method according to one of claims 1 to 8, characterized by that the monomer composition comprising the radically polymerizable monomers comprises - at least 5% by weight, preferably at least 20% by weight of the non-ionic monomer of formula (I)wherein R 1 hydrogen or methyl; R 2 and R 3are independently hydrogen, C1-C5 alkyl or C1-C5 hydroxyalkyl; - at least 5% by weight, preferably at least 20% by weight, particularly preferably 25 to 47% by weight, most preferably 50.5 to 80% by weight, of the cationic monomer of formula (II)wherein R 1 hydrogen or methyl; Z1 is O, NH, NR4, where R4 is C1-C4 alkyl, preferably methyl. Y is one of Y0 and Y1 are a C1-C6 alkylene group optionally substituted with one or more hydroxyl groups, preferably ethylene or propylene optionally substituted with a hydroxyl group; Y2, Y3, Y5, Y6, Y7 are each independently C1-C6 alkyl, preferably methyl; and Z - a counterion, preferably a halogen, pseudohalogen, acetate or SO4CH3 - ; - 0 to 1.25 wt.%, preferably 0.0001 to 1 wt.%, particularly preferably 0.001 to 0.5 wt.% of the ethylenically unsaturated crosslinker having 2, 3, 4 or 5 ethylenically unsaturated groups; and - optionally further ethylenically unsaturated monomers. [10] Method according to one of claims 1 to 9, characterized by that the polymeric dispersant is a homopolymer prepared from the cationic monomer of formula (II) wherein R 1 hydrogen or methyl; Z1 is O, NH, NR4, where R4 is C1-C4 alkyl, preferably methyl. Y is one of Y0 and Y1 are a C1-C6 alkylene group optionally substituted with one or more hydroxyl groups, preferably ethylene or propylene optionally substituted with a hydroxyl group; Y2, Y3, Y5, Y6, Y7 are each independently C1-C6 alkyl, preferably methyl; and Z -a counterion, preferably a halogen, pseudohalogen, acetate or SO4CH3 - . [11] Method according to one of claims 1 to 10, characterized by that the polymeric dispersant is a homopolymer of a (meth)acryloylamidopropyltrimethylammonium salt or a (meth)acryloyloxyethyltrimethylammonium salt. [12] Method according to one of claims 1 to 11, characterized by that the ratio of the polymeric dispersant to the dispersed polymer in the polymer dispersion is in the range of 0.45:1 to 1:0.9, preferably in the range of 0.5:1 to 1:1, particularly preferably in the range of 0.55:1 to less than 1:1, even more preferably in the range of 0.6:1 to 0.99:1, in particular in the range of 0.65:1 to 0.9:

1. [13] Method according to one of claims 1 to 12, characterized bythat the polymer dispersion has a salt content of less than 15 wt.%, preferably a salt content of 0.1 to 10 wt.%, particularly preferably a salt content of 1 to 5 wt.%, based on the total weight of the polymer dispersion. [14] A polymer dispersion obtained by a process for producing the polymer dispersion according to any one of claims 1 to 13, wherein the process uses a batch reactor and the process comprises a step of subjecting an aqueous reaction mixture to radical polymerization to synthesize a dispersed polymer and form the water-in-water polymer dispersion, said aqueous reaction mixture comprising a) a polymeric dispersant and 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; wherein the batch reactor comprises a stirrer which delivers a certain power input by stirring into the aqueous reaction mixture during the subjecting step, characterized by that the subjecting step comprises at least two time phases, wherein a first time phase starting from an initiation of the radical polymerization and a second time phase after the first time phase, wherein the specific power input in the first time phase is lower than the specific power input in the second time phase. [15] Use of the polymer dispersion according to claim 14 a. as a flocculant in the sedimentation, flotation or filtration of solids, b. as a thickener, c. as a pollution control agent, d. as a dry strength aid, retention agent or drainage aid in papermaking.