Method of manufacturing a water-in-water polymer dispersion applying a shearing profile

Abstract

The invention relates to methods for manufacturing a polymer dispersion, to polymer dispersions and their use. The methods of manufacturing a water-in-water polymer dispersion make use of a batch reactor supplying a specific shearing profile wherein the methods comprise a step of subjection of an aqueous reaction mixture to a radical polymerization to synthesize a dispersed polymer and to form the water-in-water polymer dispersion, which 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 of a non-ionic ethylenically unsaturated monomer, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer.

Description

[0001] METHOD OF MANUFACTURING A WATER-IN-WATER POLYMER DISPERSION APPLYING A

[0002] SHEARING PROFILE

[0003] The invention relates to methods for manufacturing a water-in-water polymer dispersion, to polymer dispersions and their use.

[0004] The foremost objective is to unlock the potential of water and renewable resources to build a safer, healthier, more sustainable world. Numberless industrial processes are water-based processes. The replacement of environmental harmful substances or their volume reduction in water-based processes form the basis towards more sustainable solutions. The invention aims at this foremost objective in the field of water-in-water polymer dispersions (w / w polymer dispersions). The improvements of w / w polymer dispersions directly correlate with the sustainability in downstream applications, as e.g. in the paper making process. The better such w / w polymer dispersion work as additives in water-based processes, like in the paper making process, the less of such process additives are to be used. Furthermore, the substitution of hydrocarbons supports the foremost objective.

[0005] The water-in-water polymer dispersions are useful as flocculants, dewatering (drainage) aids and retention aids in papermaking besides applications in other technical fields. Paper is manufactured by firstly making an aqueous slurry of cellulosic fibers which slurry has a water content of more than 95 wt-%. The final paper sheet has a water content of less than 5 wt-%. The dewatering (drainage) and retention represent crucial steps in papermaking and are important for an efficient paper making process. High-performance w / w polymer dispersions represent a key factor in the paper making process.

[0006] A well-known flocculant is given by a w / w polymer dispersion, which is produced by copolymerizing ethy lenically unsaturated monomers in an aqueous system comprising a polymeric dispersant resulting in a dispersion comprising the polymeric dispersant and the synthesized copolymer. The US8476391 B2 and US7323510B2 represent early publications of such w / w polymer dispersions. It is well-accepted knowledge in this technical field that the addition of separately synthesized copolymers on the one hand and polymer dispersants on the other hand results in a products having completely different properties compared to the w / w polymer dispersions as disclosed in the above patent documents. It requires the copolymerization within a system comprising the polymeric dispersant in order to obtain high-performance flocculant products e.g. for the paper making process.

[0007] These circumstances make the manufacturing of the w / w polymer dispersions to a multi-parameter systems. The kind of the ethylenically unsaturated monomer, their ratio, the kind of the polymer dispersant are only a very few parameters influencing the properties of the w / w polymer dispersion. An improvement of the properties of the final product of the w / w polymer dispersion has been subject of numberless attempts in research and development. The skilled person knows how to radically polymerize monomers in a reaction mixture. There are put efforts in finding those parameters having a beneficial impact on complex polymer systems and offering the possibility to improve their properties. Apart from the properties of the final product of the w / w polymer dispersion, there is also the need for improving the process as such. In this regard, there is a need for improving the process in view of efficiency. There is a need of efficiently use the raw materials. However, all measures applied to the process should not be associated with a loss of quality of the final product.

[0008] The invention’s underlaying problem relates to overcoming the drawbacks of the state of the art. In particular, the invention’s underlaying problem relates to the provision of a process for manufacturing a w / w polymer dispersion resulting in a product ensuring an improved handling and an improved efficiency imparted by the raw materials. Further, the invention’s underlaying problem relates to the provision of a process for manufacturing a w / w polymer dispersion ensuring a high degree of stability during the manufacturing process and ensuring a high shelf-life under unfavorable circumstances like e. g. alternating temperatures.

[0009] The invention’s underlaying problems are solved by the subject-matter of claim 1. Thus, according to a first aspect, the invention relates a method of manufacturing a water-in-water polymer dispersion making use of a batch reactor comprising a step of subjection of an aqueous reaction mixture to a radical polymerization to synthesize a dispersed polymer and to form the water-in-water polymer dispersion, which 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 of a non-ionic ethylenically unsaturated monomer, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer; wherein the batch reactor comprises an agitator supplying a specific power input by stirring to the aqueous reaction mixture during the step of subjection, characterized in that the step of subjection 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.

[0010] The method of manufacturing a water-in-water polymer dispersion makes use of a batch reactor supplying a specific shearing profile wherein the methods comprise a step of subjection of an aqueous reaction mixture to a radical polymerization to synthesize a dispersed polymer and to form the water- in-water polymer dispersion, which 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 of a non-ionic ethylenically unsaturated monomer, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer. The polymer dispersions are designated as water-in-water (w / w) polymer dispersions being produced by the method according to the invention.

[0011] The method comprises the provision of a reaction mixture comprising the monomers to be copolymerized and a polymeric dispersant. The monomers are polymerized in presence of the polymeric dispersant in an aqueous medium. According to well-established technical knowledge, a polymer dispersion obtained by the method according to the invention cannot be obtained in that the monomer composition is subjected to a copolymerization, whereupon subsequently after the copolymerization, the polymeric dispersant is added. Unique properties are conferred to the polymer dispersion by applying the method according to the invention, which polymer dispersion represents the final product comprising the copolymer obtained from the radically polymerizable monomers together with the polymeric dispersant.

[0012] In recent years, the power input to reaction mixtures have been found as a parameter having an influence on polymerizations. As such, the WO 2011 / 110484 A1 , for instance, discloses a process for the catalytic preparation of polyetherols, wherein the power input by means of at least one stirrer or by means of at least one stirrer and one pump, based on the reactor volume, is in a specified range, wherein baffles are used influencing the power input.

[0013] In the state of the art, polymer synthesis is often performed such that an effective homogenization is accomplished. However, in the manufacture of w / w polymer dispersions, a high power input throughout the whole process in order to effectively homogenize the reaction mixture does not represent the most beneficial way of conducting the polymerization.

[0014] According to the present invention, the invention’s underlaying problem is achieved by a method for manufacturing a polymer dispersion comprising the reaction of a reaction mixture, wherein the reaction is conducted in a reactor vessel under stirring with a specific power input into the reaction mixture being increased in a second time phase compared to a first time phase after initiation of the polymerization. In particular, it was observed that the reaction profile feature as given by claim 1 results in an improved efficiency of the initiation process. Therefore, the increase of the supplied power can be performed after the initiation of the polymerization has been accomplished.

[0015] The term “the second time phase follows the first time phase” means that the first time phase has been finished and then the second time phase represents a time phase being performed after having finished the first time phase. The second time phase may follow immediately after the first time phase, however, the second time phase may follow after a delay of time. This may be accomplished e.g. in that a gradual increase in the specific power input is applied in a time frame between the first time phase and the second time phase.

[0016] The first time phase starts with the injection of an initiator. This means that the first time phase begins when the initiator is loaded into the batch reactor. It was surprisingly found that conducting the process such that the specific power input is changed in the manner as given by claim 1 is associated with the beneficial effects.

[0017] The specific power input is the power input per can be calculated which calculation depends on the kind of streaming, i.e. whether the streaming in the reaction vessel is turbulent or laminar. The specific power input (PA / ) is expressed by the power input (P) over volume of the reaction mixture (V) and is calculated as follows: a) for the turbulent flow range, the specific power input is calculated with:

[0018] P / V = Ne * n3* d5* density / V with Ne = Newton number of the reactor; n = agitator speed; d = agitator diameter; density of the reaction mixture, V = filling volume (which is the volume of the reaction mixture at the end of the reaction), and b) for the laminar flow range, the specific power input is calculated with:

[0019] P / V = C * n2* d3* viscosity I with C = Re*Ne and Re = Reynolds number of the agitator used for mixing the reaction mixture, and Ne is the Newton number of the reactor.

[0020] The method may be conducted such that the agitator induces a laminar streaming or a turbulent streaming during the first time phase, and / or the agitator induces a laminar streaming or a turbulent streaming during the second time phase. It is preferred that the method is conducted such that the agitator induces a laminar streaming during the first time phase, and / or the agitator induces a turbulent streaming during the second time phase. The calculation of the power input is calculated accordingly.

[0021] The power input may be determined by measuring the electrical power consumed by the stirring motor or calculated from rheological parameters, agitator type, geometry of reactor internals and the stirring speed as given above. The calculation is described in the chapter “Stirring” by M. Zlokarnik as part of Ullmann’s Encyclopedia of Industrial Chemistry, 2012, Wiley — VCH Verlag Weinheim.

[0022] In practice, the increase in the specific power input during the method according to the invention is accomplished by an increase in the electrical power input. Before the beginning of the reaction, right 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 having accomplished the initiation of the polymerization, the power supply is increased. In the second time phase, the positive effect associated with a more vigorous stirring comes into place.

[0023] In a preferred embodiment, the first time phase starts with the injection of the initiator and the second time phase starts 1 to 25 Minutes, preferably 2 to 15 Minutes, more preferred 5 to 8 Minutes after starting the first time phase.

[0024] According to preferred embodiments, the method is characterized in that the step of subjection of an aqueous reaction mixture to a radical polymerization is performed by sequentially or simultaneously adding a redox initiator system. The redox initiator system preferably comprises an oxidizing agent and a reducing agent. When the initiator is sequentially added to the batch reactor, the first time phase starts per definition with the injection of the first part of the initiator. The second time phase does not start before all of the initiator used for the initiation of the polymerization has been injected into the batch reactor, whereupon however those parts of the initiator injected for destroying residual monomers do not count for the start of the second time phase.

[0025] According to a preferred embodiment, the method is characterized in that the oxidizing agent has a redox potential of from 0.6 to 2.0 V. Preferred oxidizing agents being used in the redox initiator system for controlling the adiabatic conditions are peroxydiphosphates; hydrogen peroxide (1.14 V); alkyl hydroperoxides, more preferred t-butyl hydroperoxide; or aryl hydroperoxides, more preferred cumene hydroperoxide. According to a most preferred embodiment, the method is characterized in that the oxidizing agent is selected from alkyl hydroperoxides, in particular t-butyl hydroperoxide, or aryl hydroperoxides, in particular cumene hydroperoxide.

[0026] Persulfates as agents in an initiator system may also be used. However, it has been found that persulfates with a redox potential of 2.01 V does not have such an impact on the method of manufacturing that it is able to fulfill the feature according to which the method is conducted under controlled adiabatic conditions. If persulfates are used as initiators in the present method, there is used a further oxidizing agent in the redox initiator system having a potential of 2 V or less and 0.6 V or more. However, in a preferred embodiment, the redox initiator system is devoid of a persulfate salt.

[0027] In a preferred embodiment, the method is characterized in that the reducing agent has a redox potential of from -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 (-.017 V); an amine; an acid, more preferred ascorbic acid (0.127 V) or erythorbic acid (0.127 V). More preferred reducing agents are bisulfites, in particular sodium bisulfite, potassium bisulfite, or ammonium bisulfite.

[0028] The redox potential is determined according to standard methods known by a skilled person.

[0029] In a most preferred embodiment, the redox initiator system comprises an alkyl / aryl hydroperoxide together with a bisulfite.

[0030] In a preferred embodiment, more oxidizing agent is used than reducing agent in terms of mass. According to a preferred embodiment, the method 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 , more preferred below 9 : 1 and above 4 : 1.

[0031] In a further preferred embodiment, the method is characterized in that the step of polymerizing is performed by agitating while measuring torque of a motor-driven agitator. Alternatively, the method is characterized in that the step B of polymerizing is performed by agitating and torque of a motor-driven agitator is kept below 65 N / cm.

[0032] In a preferred method, the monomer composition comprising the radically polymerizable monomers which are selected from the group consisting of one or more of the following: i. a non-ionic monomer of formula (I)

[0033] , where

[0034] R1means hydrogen or methyl;

[0035] R2and R3are, independently of each other, hydrogen, Ci-Cs-alkyl or C1-C5- hydroxyalkyl, ii. a cationic monomer of formula (II)

[0036] (lb , where

[0037] R1means hydrogen or methyl;

[0038] Z1 is O, NH or NR4, wherein R4 means Ci-C4-alkyl, preferably methyl, and

[0039] Y is one of , where

[0040] Yo and Y1 are a C1-C6 alkylene group, optionally substituted with one or more hydroxy groups, preferably ethylene or propylene, optionally substituted with one hydroxy group;

[0041] Y2, Y3, Y5, Y6, Y7 independently of each other, are each Ci-Ce-alkyl, preferably methyl; and

[0042] Z is a counterion, preferably a halogen, pseudo-halogen, acetate, or SO4CH3-;

[0043] Hi. an amphiphilic monomer of formulae (III) or (IV) aiii

[0044] , where

[0045] Z1 is O, NH, NR4, wherein R4 means Ci-C4-alkyl, preferably methyl,

[0046] R1 means hydrogen or methyl, Rs is a Ci-Ce alkylene group, preferably ethylene or propylene,

[0047] R5 and Re are, independently of each other, each Ci-Ce-alkyl, preferably methyl,

[0048] R7 is a C8-C32 alkyl, optionally substituted with one or more hydroxy groups, preferably C12-C20 alkyl, optionally substituted with one hydroxy group, and Z is a counterion, preferably a halogen, pseudo-halogen, acetate, or SO4CH3-; or

[0049] , where

[0050] Z1 is O, NH, NR4, wherein R4 means Ci-C4-alkyl, preferably methyl, R1 means hydrogen or methyl,

[0051] R10 means hydrogen, C8-C32 alkyl, C8-C32 aryl and / or C8-C32 aralkyl, preferably C12-C20 alkyl,

[0052] R9 is a Ci-Ce alkylene group, preferably an ethylene group or propylene group, and n is an integer between 1 and 50, preferably between 2 and 30, more preferred 3 and 15, most preferred 4 and 8; and iv. an ethylenically unsaturated cross-linker containing 2, 3, 4 or 5 ethylenically unsaturated groups.

[0053] In the framework of the present invention, a cationic monomer is a monomer carrying permanently a positive charge.

[0054] According to the preferred embodiment, one or more of the above monomers given under items 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 above monomers given under items i. to iv. are provided for the monomer composition to be polymerized. It is preferred that one monomer of item i. and one monomer of item ii. are provided for the monomer composition subjected to the copolymerization. In a preferred embodiment, the radically polymerizable monomers comprise a radically polymerizable nonionic monomer according to general formula (I); and a radically polymerizable cationic monomer according to general formula (II). These monomers being copolymerized are beneficial for solving the above problems.

[0055] Even further, it is preferred that one monomer of item i. one monomer of item ii. and one monomer of item iv. are provided for the monomer composition subjected to the copolymerization. In a preferred embodiment, the method is characterized in that the monomer composition comprising the radically polymerizable monomers at least comprises the non-ionic monomer of formula (I) being selected from those in which R1means hydrogen or methyl, and R2and R3are both hydrogen, hydrogen and C1 -C3 alkyl, hydrogen and hydroxyethyl, or both C1-C3 alkyl, and / or the cationic monomer of formula (II) being selected from those in which R1means hydrogen or methyl, and Z1 is O, NH or NR4, wherein R4 means methyl, Y1 is C2-C6 alkylene, preferably ethylene or propylene, Ys, Ye and Y7 are all methyl, and Z is a halogen.

[0056] In a preferred embodiment, the radically polymerizable monomers comprise a radically polymerizable non-ionic monomer according to 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.

[0057] In another preferred embodiment, the radically polymerizable monomers comprise a radically polymerizable cationic monomer according to 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 most preferred embodiment, the monomer composition comprises a radically polymerizable monomer being (meth)acrylamide together with a radically polymerizable monomer selected from trimethylammonium-C2-C6-alkyl(meth)acrylate halides, in particular being an acryloyl oxyethyl trimethylammonium halide.

[0058] According to a preferred embodiment, the monomer composition comprising radically polymerizable monomers comprises a cross-linker. Cross — linkers are known to the skilled person. In this preferred embodiment, the monomer composition preferably contains 0.0001 to 1 .25 wt.-% of one or more preferably ethylenically unsaturated cross-linkers, based on the total weight of monomers. If ethy lenically unsaturated cross-linkers are present, they contain 2, 3, 4 or 5 ethylenically unsaturated groups that are radically polymerizable.

[0059] Examples of cross-linkers with two radically polymerizable ethylenically unsaturated groups include:

[0060] (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-propane-diol di(meth)acrylate, 1 ,3-butanediol di(meth)acrylate, and 1 ,4-butanediol di(meth)acrylate;

[0061] (2) Alkylene di(meth)acrylamides, e.g. N-methylene di(meth)acrylamide, N,N'-3-methyl-butylidene bis(meth)acrylamide, N,N'-(1 ,2-dihydroxyethylene) bis(meth)acrylamide, and preferably N,N'- hexamethylene bis(meth)acrylamide, and particularly preferably N,N'-methylene bis(meth)acrylamide; (3) Polyalkoxydi(meth)acrylates according to general formula (V)

[0062] R10is hydrogen or methyl;

[0063] R11is selected from -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2- or -CH2CH2CH2CH2CH2CH2-; and m is an integer in the range 2-50.

[0064] Examples of cross-linkers according to general formula (V) include polypropylene glycol di(meth)acrylates with m in the range 4-25; polybutylene glycol di(meth)acrylates with m in the range 5-40; and, preferably, polyethylene glycol di(meth)acrylates with m in the range 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 inthe range 5-20;

[0065] (4) Examples of additional di(meth)acrylates which may be used include benzylidene di-(meth)- acrylate, bisphenol-A di(meth)acrylate, 1 ,3-di(meth)acryloyloxy-Z-propanol, hydro-quinone di(meth)acrylate, ethanedithiol di(meth)acrylate, propanedithiol di(meth)acrylate, polyethylene dithiol di(meth)acrylate, and polypropylene dithiol di(meth)acrylate;

[0066] (5) Divinyl compounds, for example, 1 ,4-butanediol divinyl ether, divinylbenzene, butadiene, 1 ,6- hexadiene; di(meth)a| ly I compounds, such as, for example, di(meth)allyl phthalate or di(meth)ally I succinate; vinyl (meth)acrylic compounds, for example, vinyl (meth)acrylate; or preferably (meth)allyl (meth)acrylic compounds, for example, allyl (meth)acrylate.

[0067] Examples of cross-linkers having 3 or more ethylenically unsaturated radically polymerizable groups include glycerin tri(meth)acrylate, 2, 2-dihydroxymethyl-1 -butanol tri(meth)acrylate, trimethylolpropane triethoxy tri(meth)acrylate, trimethacrylamide, (meth)allylidene di(meth)-acrylate, 3-allyloxy-1 ,2- propanediol di(meth)acrylate, triallyl amine, triallyl cyanurate or triallyl isocyanurate; and also (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.

[0068] An example of a cross-linker having 5 ethylenically unsaturated radically polymerizable groups is dipentaerithritol-pentaacrylate.

[0069] Particularly preferred cross-linkers are selected from the group constsiting of methylene bisacrylamide, polyethylene glycol diacrylate and triallylamine.

[0070] Further preferred cross-linkers include asymmetrically cross-linkable monomers, i.e. cross-linkable monomers which rely on different functional groups with respect to the incorporation reaction into the polymer backbone and the cross-linking reaction. Examples of such asymmetrically cross-linkable monomers include N'-methylol acrylamide, N'-methylol methacrylamide and glycidyl(meth)acrylate.

[0071] Cross-linkers of this type have the advantage that cross-linking may be initiated subsequently. Thus, cross-linking may be performed under different conditions than the radical polymerization of the main- backbone. Preferably, cross-linking is initiated after changing the reaction conditions, 6.9. the pH value (addition of acid or base), the temperature, and the like. Optionally, the monomer composition further comprises a hydrophobic monomer, preferably a hydrophobic (meth)acrylic acid C4-18-alkyl ester; and / or an ethy lenically unsaturated monomer.

[0072] In a preferred embodiment, the method 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 the radically polymerizable monomers being 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-%, preferred 85 and 99 wt-%, most preferred 90 and 95 wt-% based on the total amount of radically polymerizable monomers, wherein the remainder is 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 cross-linker containing 2, 3, 4 or 5 ethylenically unsaturated groups.

[0073] In this regard, the sum of the values in wt-% needs not to amount to 100 wt-%, since further ethylenically unsaturated monomers besides the monomers of formulae (I) and / or (II) may be contained in the monomer composition, i.e. in the reaction mixture, which have to be taken into account when determining the total amount of monomers. In one preferred embodiment, however, the monomer composition consists of monomers (a) and (b) so that the sum of the two values in wt-% amounts to 100 wt-%, i.e. no further monomers are present.

[0074] In a preferred embodiment, the monomer composition comprises at least 5 wt.-%, preferably at least 20 wt.-% of the non-ionic monomer of formula (I)

[0075] , where

[0076] R1means hydrogen or methyl;

[0077] R2and R3are, independently of each other, hydrogen, Ci-Cs-alkyl or Ci-Cs-hydroxyalkyl; at least 5 wt.-%, preferably at least 20 wt.-%, more preferred 25 to 47 wt.-%, most preferred 50.5 to 80 wt.-%, of the cationic monomer of formula (II) fin

[0078] R1means hydrogen or methyl;

[0079] Zi is O, NH or NR4, wherein R4 means Ci-C4-alkyl, preferably methyl, and

[0080] Y is one of

[0081] Yo and Y1 are a C1-C6 alkylene group, optionally substituted with one or more hydroxy groups, preferably ethylene or propylene, optionally substituted with one hydroxy group;

[0082] Y2, Y3, Y5, Y6, Y7 independently of each other, are each Ci-Ce-alkyl, preferably methyl; and Z is a counterion, preferably a halogen, pseudo-halogen, acetate, or SC CHs-;

[0083] 0.0001 to 1.25 wt.-%, preferably 0.0005 to 1 wt.-% of the ethylenically unsaturated cross-linker containing 2, 3, 4 or 5 ethylenically unsaturated groups; and optionally, further ethylenically unsaturated monomers.

[0084] In this regard again, the sum of the values in wt-% needs not to amount to 100 wt-%, since further ethylenically unsaturated monomers besides the monomers of formulae (I) and / or (II) may be contained in the monomer composition, i.e. in the reaction mixture, which have to be taken into account when determining the total amount of monomers. In one preferred embodiment, however, the monomer composition consists of monomers (a) and (b) so that the sum of the two values in wt-% amounts to 100 wt-%, i.e. no further monomers are present.

[0085] In the present application, all percentages with regard to the monomer composition is based on the total amount of monomers.

[0086] According to the invention, the copolymerization is performed in the presence of a polymeric dispersant.

[0087] In the state of the art, alternative aqueous polymeric systems are stabilized by low molecular weight salts. A high salt content ensures the stability of the polymeric system. Distinguishing from these systems, the stabilization of the w / w polymer dispersion according to the invention is basically ensured by the polymeric dispersant. This system renders moot a high salt concentration as in state of the art aqueous polymeric systems. In a preferred embodiment, the polymer dispersion has a salt content of less than 15 wt.%, more preferred a salt content of 0.1 to 10 wt.-%, most preferred 1 to 5 wt.-% based on the polymer dispersion. With the term “salt content”, low molecular weight salts are meant. The polymeric electrolytes do not count for the calculation of the salt content. In a preferred embodiment, the cationic polymeric dispersant is substantially linear, i.e. is not derived from monomer mixtures containing cross-linkers.

[0088] In a preferred embodiment, the polymeric dispersant is derived from one or more radically polymerizable, ethy lenically unsaturated monomers. Preferably, the polymeric dispersant is derived from one type of a radically polymerizable, ethylenically unsaturated monomer, i.e. the polymeric dispersant is essentially a homopolymer. The term “essentially” means in this regard, that no second type of a monomer is purposely added when synthesizing the polymeric dispersant.

[0089] Preferably, the polymeric dispersant is derived from one or more cationic monomers, more preferably from a single cationic monomer.

[0090] In a further preferred embodiment, the method is characterized in that the polymeric dispersant is a homopolymer made of the cationic monomer of formula (II) , where

[0091] R1means hydrogen or methyl;

[0092] Zi is O, NH or NR4, wherein R4 means Ci-C4-alkyl, preferably methyl, and

[0093] Y is one of

[0094] Yo and Y1 are a C1-C6 alkylene group, optionally substituted with one or more hydroxy groups, preferably ethylene or propylene, optionally substituted with one hydroxy group;

[0095] Y2, Y3, Y5, Y6, Y7 independently of each other, are each Ci-Ce-alkyl, preferably methyl; and

[0096] Z is a counterion, preferably a halogen, pseudo-halogen, acetate, or SO4CH3-.

[0097] Preferably, Y1, Y2 and Y3 are identical, preferably methyl. In a preferred embodiment, Z1 is O or NH, Yo is ethylene or propylene, R1is hydrogen or methyl, and Y1, Y2 and Y3 are methyl. The cationic monomer according to general formula (II) may be an ester (Z1 = O), such as trimethylammonium- ethyl(meth)acrylate (ADAME quat.). Preferably, however, the cationic monomer according to general formula (I) is an amide (Z1 = NH), particularly trimethylammonium-propyl acrylamide (DIMAPA quat). Preferred radically polymerizable cationic monomers according to general formula (II) include quaternized dialkylaminoalkyl (meth)acrylates or dialkylaminoalkyl(meth)acrylamides with 1 to 3 C atoms in the alkyl or alkylene groups, more preferably the methyl chloride-quaternized ammonium salt of dimethylamino methyl(meth)acrylate, dimethylamino ethyl(meth)acrylate, dimethylamino propyl(meth)acrylate, diethylamino methyl(meth)acrylate, diethylamino ethyl-(meth)acrylate, diethylamino propyl(meth)acrylate, dimethylamino methyl(meth)acrylamide, dimethylamino ethyl(meth)acrylamide, dimethylamino propyl(meth)acrylamide, diethylamino methyl(meth)acrylamide, diethylamino ethyl(meth)acrylamide, diethylamino propyl(meth)-acrylamide.

[0098] Quaternized dimethylaminoethyl acrylate and dimethylaminopropylacrylamide are particularly preferred. Quaternization may be affected using dimethyl sulfate, diethyl sulfate, methyl chloride or ethyl chloride. In a preferred embodiment, monomers are quaternized with methyl chloride.

[0099] In a preferred embodiment, the polymeric dispersant is a homopolymer of trimethylammonium-propyl acrylamide chloride (DIMAPA quat) designated by IUPAC as (3-acrylamidopropyl)trimethylammonium chloride (APTAC).

[0100] Preferably, the polymeric dispersant is derived from a monomer composition comprising a cationic monomer selected from the group consisting of (alk)acrylamidoalkyltrialkyl ammonium halides (e.g., trimethylammonium-alkyl(meth)acrylamide halides), (alk)acryloyloxyalkyl trialkyl ammonium halides (e.g., trimethylammoniumalkyl(meth)acrylate halides), alkenyl trialkyl ammonium halides and dialkenyl dialkyl ammonium 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, trimethylammoniumalkyl(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 in particular 8 to 12 carbon atoms.

[0101] In a further preferred embodiment, the polymeric dispersant is derived from a dialkenyl dialkyl ammonium halide, preferably a diallyl dimethyl ammonium halide (DADMAC).

[0102] According to a preferred embodiment, the method is characterized in that the polymeric dispersant is a homopolymer made of a (meth)acryloyl amidopropyl trimethylammonium salt or a (meth)acryloyl oxyethyl trimethylammonium salt. In the framework of this disclosure, a homopolymer of a (meth)acrylate means, that either the homopolymer is a methacrylate or an acrylate.

[0103] In the framework of this application, the halide may be any acceptable halide as e.g. chloride, bromide or iodide; the counter ions of the salts may be any acceptable counter ions as e.g. halides, methosulfate, sulfate or others. According to a preferred embodiment, the method is characterized in that the polymeric dispersant has a weight average molecular weight Mwas determined by size exclusion chromatography of 40.000 to less than 150.000 g / mol, preferred 50.000 to 140.000 g / mol, more preferred 60.000 to 130.000, most preferred 85.000 to 120.000 g / mol.

[0104] In a preferred embodiment, the method is characterized in that the viscosity of the polymer dispersion amounts to 1 .800 mPas to less than 6.700 mPas , preferably 2.000 mPas to 6.000 mPas, more preferred 2.200 mPas to 5.500 mPas, most preferred 2.500 mPas to 5.000 mPas, as measured with a Brookfield viscometer with spindle 4 at 20°C and an angle speed of 10 rpm.

[0105] The viscosity is preferably the bulk viscosity which refers to the viscosity right after having obtained the cooled down product.

[0106] 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, preferred in the range of 0.5 : 1 to 1 : 1 , more preferred in the range of 0.55 : 1 to less than 1 : 1 , even more preferred in the range of 0.6 : 1 to 0.99 : 1 , in particular in the range of 0.65 : 1 to 0.9 : 1 .

[0107] The invention is in particular efficient if the method is 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 wt.-%, preferred 12 to 26 wt.%, more preferred 14 to 24 wt.-%, even more preferred 16 to 22 wt.-%. According to a further embodiment, the method 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.-%, preferred 19 to 25 wt.-%.

[0108] According to a preferred embodiment, the method comprises the step of C) reducing the residual monomer content by adding to the reaction mixture an initiator at about the time of reaching the maximum temperature (Tmax). In a more preferred embodiment, step C) is conducted isothermally, even more preferred, step C is performed by holding the temperature during step C on a level above 55°C and below 80°C, most preferred above 60°C and below 70°C.

[0109] The initiator used for reducing the residual monomer content could be any of the above additional initiators. However, it is preferred that the initiator is selected from a peroxide or an azo-compound, even more preferred selected from the group consisting of a hydroperoxide, a dialkylperoxide, a diacylperoxide and an azo-compound being substituted by tertiary carbon atoms, preferably carrying 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). The invention’s underlaying problems are further solved by the subject-matter of claim 14. Thus, according to a second aspect, the invention relates to a polymer dispersion obtained by a method for manufacturing the polymer dispersion according to the invention comprising the steps of

[0110] 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 of a non-ionic ethylenically unsaturated monomer, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer;

[0111] B) subjecting the monomer composition in the reaction mixture to a radical polymerization to synthesize a dispersed polymer and to form the polymer dispersion, wherein the batch reactor comprises an agitator supplying a specific power input by stirring to the aqueous reaction mixture during the step of subjection, characterized in that the step of subjection comprises at least two time phases wherein a first time phase starting from an initiation of the radical polymerization and a second time phase following 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.

[0112] According to a preferred embodiment, the polymer dispersion is obtained by a method for manufacturing the polymer dispersion wherein the polymeric dispersant has a weight average molecular weight Mwas determined by size exclusion chromatography of 40.000 to less than 150.000 g / mol, preferred 50.000 to 140.000 g / mol, more preferred 60.000 to 130.000, most preferred 85.000 to 120.000 g / mol.

[0113] According to a preferred embodiment, the polymer dispersion is obtained by a method for manufacturing the polymer dispersion wherein the polymer dispersion has a bulk viscosity below 6.700 mPas, preferably below 6.000 mPas, more preferred below 5.500 mPas, most preferred below 5.000 mPas as measured at 20°C with a Brookfield viscometer with spindle 4 and a speed of 10 rpm.

[0114] According to preferred embodiments, the polymer dispersion is obtained by a method for manufacturing the polymer dispersion wherein the polymer dispersion has a bulk viscosity above 1 .800 mPas, preferably above 2.000 mPas, more preferred above 2.200 mPas, even more preferred above 2.500 mPas, most preferred above 3.000 mPas as measured at 20°C with a Brookfield viscometer with spindle 4 and a speed of 10 rpm.

[0115] The invention’s underlaying problems are further solved 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 contaminant control, d. as a dry strength aid, retention agent or drainage aid in papermaking. Features relating to preferred embodiments of the first aspect of the present invention, which are solely disclosed relating to the first aspect of the invention represent preferred embodiments of the second and third embodiment as well.

[0116] In the following, exemplary embodiments (A) to (O) are disclosed which represent particularly preferred embodiments.

[0117] (A)

[0118] Method of manufacturing a water-in-water polymer dispersion making use of a batch reactor comprising a step of subjection of an aqueous reaction mixture to a radical polymerization to synthesize a dispersed polymer and to form the water-in-water polymer dispersion, which 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 of a non-ionic ethylenically unsaturated monomer, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer; wherein the batch reactor comprises an agitator supplying a specific power input by stirring to the aqueous reaction mixture during the step of subjection, characterized in that the step of subjection 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.

[0119] (B)

[0120] Method of manufacturing a water-in-water polymer dispersion making use of a batch reactor comprising a step of subjection of an aqueous reaction mixture to a radical polymerization to synthesize a dispersed polymer and to form the water-in-water polymer dispersion, which 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 of a non-ionic ethylenically unsaturated monomer, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer; wherein the batch reactor comprises an agitator supplying a specific power input by stirring to the aqueous reaction mixture during the step of subjection, characterized in that the step of subjection 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 made of the cationic monomer of formula (II)

[0121] (II) , where

[0122] R1means hydrogen or methyl;

[0123] Zi is O, NH or NR4, wherein R4 means Ci-C4-alkyl, preferably methyl, and

[0124] Y is one of , where

[0125] Yo and Y1 are a C1-C6 alkylene group, optionally substituted with one or more hydroxy groups, preferably ethylene or propylene, optionally substituted with one hydroxy group;

[0126] Y2, Y3, Y5, Y6, Y7 independently of each other, are each Ci-Ce-alkyl, preferably methyl; and

[0127] Z is a counterion, preferably a halogen, pseudo-halogen, acetate, or SO4CH3-.

[0128] (C)

[0129] Method of manufacturing a water-in-water polymer dispersion making use of a batch reactor comprising a step of subjection of an aqueous reaction mixture to a radical polymerization to synthesize a dispersed polymer and to form the water-in-water polymer dispersion, which 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 of a non-ionic ethylenically unsaturated monomer, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer; wherein the batch reactor comprises an agitator supplying a specific power input by stirring to the aqueous reaction mixture during the step of subjection, characterized in that the step of subjection 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 made of a (meth)acryloyl amidopropyl trimethylammonium salt or a (meth)acryloyl oxyethyl trimethylammonium salt.

[0130] (D)

[0131] Method of manufacturing a water-in-water polymer dispersion making use of a batch reactor comprising a step of subjection of an aqueous reaction mixture to a radical polymerization to synthesize a dispersed polymer and to form the water-in-water polymer dispersion, which 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 of a non-ionic ethylenically unsaturated monomer, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer; wherein the batch reactor comprises an agitator supplying a specific power input by stirring to the aqueous reaction mixture during the step of subjection, characterized in that the step of subjection 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 agitator.

[0132] (E)

[0133] Method of manufacturing a water-in-water polymer dispersion making use of a batch reactor comprising a step of subjection of an aqueous reaction mixture to a radical polymerization to synthesize a dispersed polymer and to form the water-in-water polymer dispersion, which 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 of a non-ionic ethylenically unsaturated monomer, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer; wherein the batch reactor comprises an agitator supplying a specific power input by stirring to the aqueous reaction mixture during the step of subjection, characterized in that the step of subjection 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 agitator, and wherein the second time phase starts 1 to 25 Minutes, preferably 5 to 15 Minutes after starting the first time phase.

[0134] EXAMPLES

[0135] In the following, the applied test methods are described in detail:

[0136] The bulk viscosity is measured as follows:

[0137] Use the product directly for the measurement. The spindle No. 4 is slowly immersed into the product and the viscosity determined with a Brookfield RVT viscometer at 10 rpm. The measurement is terminated when the reading remains constant for a period of 30 sec.

[0138] The solution viscosity is measured in DI Water and determined as follows:

[0139] A solution of 5 wt-% in water is prepared. In a 400 ml beaker 323.0 ± 0.1 g demineralised water is weighed. Then 17.0 ± 0.1 g of the product are added (22 ± 3°C) under stirring at 300 rpm. The dissolving time amounts to 60 min. at 300 ±10 rpm. Thereafter, the solution has to rest for 5 min. Now the spindle No. 2 is slowly immersed, and the viscosity determined with a Brookfield RFT viscometer at 10 rpm. The measurement is terminated when the reading remains constant for a period of 30 sec.

[0140] The salt viscosity is measured in a 10% NaCI solution and determined as follows:

[0141] In a 400 ml beaker 289.0 ± 0.1 g demineralized water is weighed. Then 17.0 ± 0.1 g of the product are added (22 ± 3°C) under stirring at 300 rpm. The dissolving time amounts to 45 min. at 300 ± 10 rpm and then 34.0 ± 0.1 g NaCI is added. The solution is stirred for further 15 min. After this the solution has to rest for 5 min. Now the spindle No. 1 is slowly immersed, and the viscosity determined with a Brookfield RVT viscometer at 10 rpm. The measurement is terminated when the reading remains constant for a period of 30 sec.

[0142] The molar mass is measured via Size Exclusion Chromatography (SEC).

[0143] The measurement is in particular performed for the determination of the molecular weight of the dispersant.

[0144] The molecular weights are characterized via aqueous SEC using Pullulan standards for the calibration.

[0145] Sample Preparation:

[0146] The samples are diluted with the eluent (polymer make-down in a measuring flask) and filtered through a 1 pm filter (M&N) (via syringe) before they are injected.

[0147] If the machine is equipped with an autosampler filter the solution through a 1 pm filter into a vial.

[0148] Used parameters: apparatus: SEC (Agilent) column: Novema 3000 (PSS) detector: Rl eluent: 1 .5 wt% formic acid in water flow rate: 1 ml / min calibration standards: pullulan with different Mw

[0149] The following examples further illustrate the method of manufacturing the w / w polymer dispersion. The following examples are however not to be construed as limiting the invention.

[0150] Example 1 : Synthesis of the polymeric dispersant:

[0151] At first, 294.06 g water, 666.7 g acryloyl amidopropyl trimethylammonium chloride (DIMAPA quat.) (60wt%) and sulfuric acid (50wt%) to adjust the pH to 5.0 ± 0.2 were weighed in a 2 L vessel. Then the monomer solution was sparged with nitrogen for 30 min by stirring. After 3 Minutes of stirring with a low power input, the power input is increased. Subsequently, the aqueous solution was heated up 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 is cooled down to < 80°C. Then, two additional portions of initiator (V-50) were given to the product in between 10 min for residual monomer burn out. The product was stirred for 1 h at 70°C. The final aqueous product was cooled down to 30°C. The dispersants were provided in 40 wt.-% aqueous solutions.

[0152] Specifications:

[0153] Product viscosity [mPas]: 1 10-180 pH (neat): 4.9-5.3

[0154] - Total solids [%]: 40-43

[0155] MWSEC [g / mol]: 70000-110000

[0156] Example 2: Synthesis of polymer dispersion (charge density 15 mole%)

[0157] In a discontinuous process (batch size 1 ,000 kg), acrylamide and acryloyl oxyethyl trimethylammonium chloride (ADAME quat.) were polymerized in an aqueous solution in the presence of homopoly acryloyl amidopropyl trimethylammonium chloride (polymeric dispersant). The water-phase was prepared at 200 rpm.

[0158] Firstly, 206.90 kg soft water, 261.80 kg Bio-acryl amide (49 wt.-%), 77.20 kg acryloyl oxyethyl trimethylammonium chloride (ADAME quat) (80 wt%), 412.50 kg polymeric dispersant of Example 1 , 10.00 kg ammonium sulphate and 0.20 kg Trilon C were loaded into the reaction vessel. The pH value was adjusted to pH 5.0±0.2 with approximately 0.10 kg of sulphuric acid (50 %). The vessel was evacuated five times before being aerated with nitrogen. The initiator composition was added at a negative pressure of 0.5 bar and maximum agitator speed. Initiating started 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 f-butylhydroperoxide (70 %) in 1 kg soft water. Afterwards the vessel was aerated 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 down to a temperature below 40°C. Then, 8.30 kg citric acid and 0.82 kg of the biocide Acticide SPX were added and the product was cooled down to a temperature below 30°C.

[0159] Alternatively, in all of the above examples and embodiments, an efficiency may be increased by running the stirrer (or applying the agitation) at 20% power during the oxygen liberation (at higher power, a vortex is created and the nitrogen goes through). Then the stirring power is set to 100% and the initiators may be added to start the reaction. This may now be done in such a way that the stirring profile is always the same. When the agitation power was lower than that when the initiators were added, there may occur large differences in the agitation powers and agitation (stirring) times in the further run.

Claims

Claims1. Method of manufacturing a water-in-water polymer dispersion making use of a batch reactor comprising a step of subjection of an aqueous reaction mixture to a radical polymerization to synthesize a dispersed polymer and to form the water-in-water polymer dispersion, which 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 of a non-ionic ethylenically unsaturated monomer, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer; wherein the batch reactor comprises an agitator supplying a specific power input by stirring to the aqueous reaction mixture during the step of subjection, characterized in that the step of subjection 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.

2. Method according to claim 1 , characterized in that the specific power input is defined by the formula P=Ne x n3x d5x <;, wherein Ne is the Newton number, n is the agitator speed in rounds / minute (rpm), d is the agitator diameter, and is the density of the reaction mixture.

3. Method according to claim 1 , characterized in that the specific power input is defined by the formula P / V = C x n2x d3x viscosity / V, wherein C = Re x Ne and Re is Reynolds number of the agitator used for mixing the aqueous reaction mixture, and Ne is the Newton number of the reactor.

4. Method according to any one of claims 1 to 3, characterized in that the batch reactor is devoid of a baffle.

5. Method according to any one of claims 1 to 4, characterized in that the specific power input is adjusted by changing the electrical power input supplied to the agitator.

6. Method according to any one of claims 1 to 5, characterized in that the agitator induces a turbulent flow during the step of subjection of the aqueous reaction mixture to the radical polymerization.Method according to any one of claims 1 to 6, characterized in that the monomer composition comprising the radically polymerizable monomers are selected from the group consisting of one or more of the following: i. a non-ionic monomer of formula (I)R1means hydrogen or methyl;R2and R3are, independently of each other, hydrogen, Ci-Cs-alkyl or C1-C5- hydroxyalkyl, ii. a cationic monomer of formula (II) fibR1means hydrogen or methyl;Z1 is O, NH or NR4, wherein R4 means Ci-C4-alkyl, preferably methyl, andY is one of, whereYo and Y1 are a C1-C6 alkylene group, optionally substituted with one or more hydroxy groups, preferably ethylene or propylene, optionally substituted with one hydroxy group;Y2, Y3, Y5, Y6, Y7 independently of each other, are each Ci-Ce-alkyl, preferably methyl; andZ is a counterion, preferably a halogen, pseudo-halogen, acetate, or SO4CH3-;Hi. an amphiphilic monomer of formulae (III) or (IV) am, whereZ1 is O, NH, NR4, wherein R4 means Ci-C4-alkyl, preferably methyl,R1 means hydrogen or methyl,Ra is a Ci-Ce alkylene group, preferably ethylene or propylene,Rs and Re are, independently of each other, each Ci-Ce-alkyl, preferably methyl,R7 is a C8-C32 alkyl, optionally substituted with one or more hydroxy groups, preferably C12-C20 alkyl, optionally substituted with one hydroxy group, and Z is a counterion, preferably a halogen, pseudo-halogen, acetate, or SO4CH3-; or(IV)Z1 is O, NH, NR4, wherein R4 means Ci-C4-alkyl, preferably methyl, R1 means hydrogen or methyl,R10 means hydrogen, C8-C32 alkyl, C8-C32 aryl and / or C8-C32 aralkyl, preferably C12-C20 alkyl,R9 is a Ci-Ce alkylene group, preferably an ethylene group or propylene group, and n is an integer between 1 and 50, preferably between 2 and 30, more preferred 3 and 15, most preferred 4 and 8; and iv. an ethylenically unsaturated cross-linker containing 2, 3, 4 or 5 ethylenically unsaturated groups.

8. Method according to any one of claims 1 to 7, characterized in that the monomer composition comprising the radically polymerizable monomers comprises the non-ionic monomer of formula (I) being selected from those in which R1means hydrogen or methyl, and R2and R3are both hydrogen, hydrogen and C1 -C3 alkyl, hydrogen and hydroxyethyl, or both C1-C3 alkyl, and / or the cationic monomer of formula (II) being selected from those in which R1means hydrogen or methyl, and Z1 is O, NH or NR4, wherein R4 means methyl, Y1 is C2-C6 alkylene, preferably ethylene or propylene, Ys, Ye and Y7 are all methyl, and Z is a halogen; wherein most preferred the monomer composition comprising the radically polymerizable monomers at least comprises the non-ionic monomer of formula (I) being (meth)acrylamide and the cationic monomer of formula (II) being (meth)acryloyl amidopropyl trimethylammonium chloride or (meth)acryloyl oxyethyl trimethylammonium chloride.

9. Method according to any one of claims 1 to 8, characterized in that the monomer composition comprising the radically polymerizable monomers comprises at least 5 wt.-%, preferably at least 20 wt.-% of the non-ionic monomer of formula (I)R1means hydrogen or methyl;R2and R3are, independently of each other, hydrogen, Ci-Cs-alkyl or C1-C5- hydroxyalkyl; at least 5 wt.-%, preferably at least 20 wt.-%, more preferred 25 to 47 wt.-%, most preferred 50.5 to 80 wt.-%, of the cationic monomer of formula (II)(III, whereR1means hydrogen or methyl;Z1 is O, NH or NR4, wherein R4 means Ci-C4-alkyl, preferably methyl, andY is one of, whereYo and Y1 are a C1-C6 alkylene group, optionally substituted with one or more hydroxy groups, preferably ethylene or propylene, optionally substituted with one hydroxy group;Y2, Y3, Y5, Y6, Y7 independently of each other, are each Ci-Ce-alkyl, preferably methyl; andZ is a counterion, preferably a halogen, pseudo-halogen, acetate, or SC CHs-; 0 to 1 .25 wt.-%, preferably 0.0001 to 1 wt.-%, more preferred 0.001 to 0.5 wt.-% of the ethylenically unsaturated cross-linker containing 2, 3, 4 or 5 ethy lenically unsaturated groups; and optionally, further ethylenically unsaturated monomers.Method according to any one of claims 1 to 9, characterized in that the polymeric dispersant is a homopolymer made of the cationic monomer of formula (II)(Hi, whereR1means hydrogen or methyl;Zi is O, NH or NR4, wherein R4 means Ci-C4-alkyl, preferably methyl, andY is one of, whereYo and Y1 are a C1-C6 alkylene group, optionally substituted with one or more hydroxy groups, preferably ethylene or propylene, optionally substituted with one hydroxy group;Y2, Y3, Y5, Y6, Y7 independently of each other, are each Ci-Ce-alkyl, preferably methyl; andZ is a counterion, preferably a halogen, pseudo-halogen, acetate, or SO4CH3-.11 . Method according to any one of claims 1 to 10, characterized in that the polymeric dispersant is a homopolymer made of a (meth)acryloyl amidopropyl trimethylammonium salt or a (meth)acryloyl oxyethyl trimethylammonium salt.

12. Method according to any one of claims 1 to 11 , characterized in that the ratio of the polymeric dispersant to the dispersed polymer in the polymer dispersion is in the range of 0.45 : 1 to1 : 0.9, preferred in the range of 0.5 : 1 to 1 : 1 , more preferred in the range of 0.55 : 1 to less than 1 : 1 , even more preferred 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 any one of claims 1 to 12, characterized in that the polymer dispersion has a salt content of less than 15 wt.%, preferably a salt content of 0.1 to 10 wt.-%, more preferred a salt content of 1 to 5 wt.-%, based on the total weight of the polymer dispersion.

14. A polymer dispersion obtained by a method for manufacturing the polymer dispersion according to any one of claims 1 to 13, wherein the method makes use of a batch reactor and the method comprises a step of subjection of an aqueous reaction mixture to a radical polymerization to synthesize a dispersed polymer and to form the water-in-water polymer dispersion, which 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 of a non-ionic ethylenically unsaturated monomer, a cationic ethylenically unsaturated monomer and an amphiphilic ethylenically unsaturated monomer; wherein the batch reactor comprises an agitator supplying a specific power input by stirring to the aqueous reaction mixture during the step of subjection, characterized in that the step of subjection comprises at least two time phases wherein a first time phase starting from an initiation of the radical polymerization and a second time phase following the first time phase, 1wherein 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 contaminant control, d. as a dry strength aid, retention agent or drainage aid in papermaking.

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