High molecular weight polymer dispersions prepared in batch reactors

Abstract

The present invention relates to a batch reactor comprising an aqueous reaction mixture for the preparation of a water-in-water polymer dispersion by free radical polymerization wherein the batch reactor comprises a stirrer treated by a grinding and polishing technique or wherein the batch reactor is free of baffles. Furthermore, the invention relates to a method for producing a water-in-water polymer dispersion by free-radical polymerization in said batch reactor. Furthermore, the invention relates to the use of said batch reactor in a method for producing a water-in-water polymer dispersion.

Description

[0001] This invention relates to a batch reactor comprising an aqueous reaction mixture for preparing a water-in-water polymer dispersion by free radical polymerization, wherein the batch reactor includes a stirrer treated with a grinding and polishing technique, or wherein the batch reactor is baffle-free. Furthermore, this invention relates to a method for preparing a water-in-water polymer dispersion by carrying out free radical polymerization in the batch reactor. Even further, this invention relates to the use of the batch reactor in the method for preparing water-in-water polymer dispersions.

[0002] The primary objective is to unlock the potential of water and renewable resources to build a safer, healthier, and more sustainable world. Countless industrial processes are water-based. Replacing or reducing the use of environmentally harmful substances in water-based processes is fundamental to achieving more sustainable solutions. This invention aims to achieve this primary objective in the field of water-in-water polymer dispersions (w / w polymer dispersions). Improvements in water-in-water polymer dispersions are directly related to the sustainability of downstream applications, such as papermaking processes. The better such water-in-water polymer dispersions perform as additives in water-based processes (such as papermaking), the less additive is needed in these processes. Furthermore, the substitution of hydrocarbons also supports this primary objective.

[0003] Besides applications in other technological fields, water-in-water polymer dispersions can be used as flocculants, dewatering (filtration) aids, and retention aids in papermaking. Papermaking begins with the preparation of an aqueous pulp of cellulose fibers with a water content greater than 95% by weight. The final paper has a water content of less than 5% by weight. Dewatering (filtration) and retention are key steps in papermaking and are essential for an efficient papermaking process. High-performance water-in-water polymer dispersions are a critical factor in the papermaking process.

[0004] A well-known flocculant is a water-in-water polymer dispersion, prepared by copolymerizing an olefinically unsaturated monomer in an aqueous system containing a polymer dispersant, resulting in a dispersion comprising the polymer dispersant and a synthesized copolymer. US8476391B2 and US7323510B2 are early publications of this type of water-in-water polymer dispersion. It is known in the art that products obtained by mixing separately synthesized copolymers and polymer dispersants have entirely different properties compared to the water-in-water polymer dispersions disclosed in the aforementioned patent documents. To obtain, for example, high-performance flocculant products for use in papermaking processes, copolymerization is required within a system containing the polymer dispersant.

[0005] These factors make the preparation of water-in-water polymer dispersions a multi-parameter system. The types of olefinic unsaturated monomers, their proportions, and the type of polymer dispersant are only a small subset of the parameters affecting the properties of water-in-water polymer dispersions. Improving the performance of the final product from water-in-water polymer dispersions has been the subject of countless research and development attempts.

[0006] Technicians know how to induce free radical polymerization of monomers in the reaction mixture. Efforts are focused on identifying parameters that have a beneficial effect on complex polymer systems and offer the potential for improved performance. Beyond the properties of the final water-in-water polymer dispersion, improvements to the method itself are needed. In this regard, improvements in efficiency are required. The less standby time, the more efficient the method. Agglomeration and deposition have been found during the preparation of water-in-water polymer dispersions, with deposits requiring maintenance and cleaning. Furthermore, small amounts of agglomerated particles have been found to detach from the agitator or from components of the reactor near no-flow areas or no-streaming areas. Even small amounts of detached material can cause problems in the post-processing of the polymer dispersion or in downstream applications.

[0007] The fundamental problem of this invention relates to overcoming the shortcomings of the prior art. In particular, the fundamental problem of this invention relates to providing means in a method for preparing a water-in-water polymer dispersion, thereby obtaining an improved product and ensuring improved operability and increased efficiency of the method for preparing the water-in-water polymer dispersion.

[0008] The fundamental problem of the present invention is solved by the subject matter of claim 1. Therefore, according to a first aspect, the present invention relates to a batch reactor comprising an aqueous reaction mixture for preparing a water-in-water polymer dispersion by free radical polymerization, wherein the aqueous reaction mixture comprises: a) a polymer dispersant; b) a monomer composition comprising a free radical polymerizable monomer selected from one or more of: nonionic olefinic unsaturated monomers, cationic olefinic unsaturated monomers, and amphiphilic olefinic unsaturated monomers; and c) an initiator, wherein the batch reactor includes a stirrer treated with a grinding and polishing technique, or wherein the batch reactor is baffle-free.

[0009] Two alternative features bring about technical improvements and solve the fundamental problems of the present invention described above. The first alternative feature refers to a batch reactor comprising a stirrer treated with a grinding and polishing technique. This means that the stirrer has been treated accordingly before being used in the batch reactor for the application of the method for preparing water-in-water polymer dispersions. This treatment alters the surface of the stirrer. In prior art literature, stirrers are sometimes covered with a layer of enamel. However, the enamel can peel off from the surface of the metal stirrer. This can lead to impurities in the product, resulting in significant defects. On the other hand, if the stirrer is not treated, there is the disadvantage of deposition, which requires periodic maintenance of the batch reactor, thus making the process inefficient.

[0010] The second alternative feature involves the absence of baffles in the batch reactor. Baffles cause mixing of the reaction mixture. However, this creates areas of no flow or very low flow velocities. These areas may be referred to as no-flow zones or flow-free areas. Agglomeration can occur on surfaces near these areas. This agglomeration can reduce the quality of the final product, or if deposited on the surfaces of the batch reactor, such deposits may require maintenance. This maintenance again reduces process efficiency.

[0011] These two alternative features are characteristics of batch reactors. The benefits of these two features are related to the type of reaction that occurs in a batch reactor. Therefore, these benefits are those of batch reactors in which the reaction to prepare water-in-water polymer dispersions takes place.

[0012] Two alternative features—a polished agitator and a batch reactor without baffles—can be implemented in a single batch reactor. Therefore, according to a preferred embodiment, the batch reactor includes a polished agitator and is baffle-free.

[0013] The method includes providing a reaction mixture comprising a monomer to be copolymerized and a polymeric dispersant. The monomer is polymerized in an aqueous medium in the presence of the polymeric dispersant. According to accepted technical knowledge, it is impossible to obtain the polymer dispersion obtained by applying this method in a batch reactor having the two alternative characteristics by copolymerizing the monomer composition and then adding the polymeric dispersant after the copolymerization reaction. By applying this method in such a batch reactor having the two alternative characteristics, the polymer dispersion acquires unique properties representing a final product comprising a copolymer obtained from a free radical polymerizable monomer and a polymeric dispersant.

[0014] According to a preferred embodiment, the batch reactor includes a stirrer treated with a grinding and polishing technique, wherein the grinding and polishing technique represents electropolishing. According to a non-constraint theory, electropolishing exhibits beneficial effects due to the surface structure it induced. The type of product produced, combined with this treated stirrer, solves the aforementioned problems.

[0015] Electrochemical polishing, also known as anodic polishing or electrolytic polishing, is an electrochemical process that removes material from metal workpieces, reducing surface roughness and improving surface finish by smoothing out micro-peaks and valleys. Electropolishing is often compared to electrochemical machining, but they are distinctly different. It is used for polishing, passivating, and deburring metal parts.

[0016] According to a preferred embodiment, the batch reactor includes an electropolished agitator, and the inner wall of the batch reactor is at least partially covered with enamel. The immovable parts of the batch reactor can be covered with enamel because the risk of enamel peeling is very low.

[0017] The batch reactor comprises an aqueous reaction mixture containing a polymer dispersant, a monomer composition, and an initiator. These components are described in conjunction with aspects of the invention described below.

[0018] The fundamental problem of the present invention is also solved by the subject matter of claim 4. Therefore, according to a second aspect, the present invention relates to a method for preparing a water-in-water polymer dispersion, wherein the method is carried out in a batch reactor, and the method comprises the step of subjecting an aqueous reaction mixture to free radical polymerization to synthesize a dispersed polymer and form a water-in-water polymer dispersion, the aqueous reaction mixture comprising: a) a polymer dispersant; b) a monomer composition comprising a free radical polymerizable monomer, wherein the free radical polymerizable monomer is selected from one or more of: nonionic olefinic unsaturated monomers, cationic olefinic unsaturated monomers, and amphiphilic olefinic unsaturated monomers; and c) an initiator, wherein the batch reactor comprises a stirrer treated with a grinding and polishing technique, or wherein the batch reactor is baffle-free.

[0019] As described above, the method for preparing water-in-water polymer dispersions, and the water-in-water polymer dispersions obtained by the method according to the invention, are both improved due to the characteristics of the batch reactor. According to a preferred embodiment, the grinding and polishing technique represents electropolishing. According to another preferred embodiment, the batch reactor includes a stirrer treated with electropolishing technology, and the inner wall of the batch reactor is at least partially covered with enamel.

[0020] According to the present invention, the aqueous reaction mixture comprises a monomer composition containing a free radical polymerizable monomer.

[0021] In a preferred method, the monomer composition comprises a radical-polymerizable monomer selected from one or more of the following: i. Nonionic monomers of formula (I) ,in R 1 Indicates hydrogen or methyl; R 2 and R 3 Each of them is independently hydrogen, C1-C5-alkyl, or C1-C5-hydroxyalkyl. ii. Formula (II) cationic monomer ,in R 1 Indicates hydrogen or methyl; Z1 is O, NH, or NR4, where R4 represents a C1-C4-alkyl group, preferably methyl, and Y is one of the following groups: ,in Y0 and Y1 are C1-C6 alkylene groups, optionally substituted with one or more hydroxyl groups, preferably ethylene or propylene, optionally substituted with one hydroxyl group; Y2, Y3, Y5, Y6, and Y7 are each independently a C1-C6-alkyl group, preferably methyl; and Z - It is a counterion, preferably a halogen, a halogen-like ion, an acetate ion, or SO4CH3. - ; iii. Amphiphilic monomers of formula (III) or (IV) ,in Z1 is O, NH, or NR4, where R4 represents a C1-C4-alkyl group, preferably methyl. R¹ represents 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 is C8-C 32 Alkyl groups, optionally substituted with one or more hydroxyl groups, preferably C10. 12 -C 20 Alkyl group, optionally substituted with a hydroxyl group, and Z - It is a counterion, preferably a halogen, a halogen-like ion, an acetate ion, or SO4CH3. - ;or ,in Z1 is O, NH, or NR4, where R4 represents a C1-C4-alkyl group, preferably methyl. R1 represents hydrogen or methyl. R 10 Indicates hydrogen, C8-C 32 Alkyl, C8-C 32 Aryl and / or C8-C 32 Aryl alkyl group, preferably C 12 -C 20 alkyl, R9 is a C1-C6 alkylene group, preferably ethylene or propylene. n is an integer from 1 to 50, preferably from 2 to 30, more preferably from 3 to 15, and most preferably from 4 to 8; and iv. An olefinically unsaturated crosslinking agent containing 2, 3, 4 or 5 olefinically unsaturated groups.

[0022] Within the framework of this invention, a cationic monomer is a monomer that is permanently positively charged.

[0023] According to a preferred embodiment, one or more monomers given in items i. to iv. above are used as monomers in the monomer composition to be polymerized. Preferably, a copolymer is used, i.e., the monomer composition to be polymerized provides two monomers given in items i. to iv. above. Preferably, the monomer composition undergoing the copolymerization reaction provides a monomer of item i. and a monomer of item ii. In a preferred embodiment, the radical-polymerizable monomer comprises a radical-polymerizable nonionic monomer according to general formula (I); and a radical-polymerizable cationic monomer according to general formula (II). These copolymerized monomers are advantageous for solving the aforementioned problems.

[0024] Furthermore, the monomer composition for copolymerization preferably provides a monomer of item i, a monomer of item ii, and a monomer of item iv.

[0025] In a preferred embodiment, the method is characterized in that the monomer composition comprising a free radical polymerizable monomer comprises at least a nonionic monomer selected from formula (I) of the following: wherein R 1 R represents hydrogen or methyl. 2 and R 3 All are hydrogen, hydrogen and C 1- C3 alkyl, hydrogen and hydroxyethyl, or all of them are C3 1- C3 alkyl, and / or selected from the following formula (II) cationic monomers: wherein R¹ represents hydrogen or methyl, Z1 is O, NH or NR4, wherein R4 represents methyl, Y1 is C2-C6 alkylene, preferably ethylene or propylene, Y5, Y6 and Y7 are all methyl, and Z- It is halogen.

[0026] In a preferred embodiment, the radical-polymerizable monomer comprises a radical-polymerizable nonionic monomer according to general formula (I), selected from: (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.

[0027] In another preferred embodiment, the radical-polymerizable monomer comprises a radical-polymerizable cationic monomer according to general formula (II), selected from: trimethylammonium-C2-C6-alkyl (meth)acrylate halides and trimethylammonium-C2-C6-alkyl (meth)acrylamide halides. In a most preferred embodiment, the monomer composition comprises (meth)acrylamide as a radical-polymerizable monomer and a radical-polymerizable monomer selected from trimethylammonium-C2-C6-alkyl (meth)acrylate halides, particularly acryloyloxyethyltrimethylammonium halides.

[0028] According to a preferred embodiment, the monomer composition comprising a free radical polymerizable monomer includes a crosslinking agent. Crosslinking agents are known to those skilled in the art. In this preferred embodiment, the monomer composition preferably contains 0.0001 to 1.25% by weight of one or more preferred olefinically unsaturated crosslinking agents based on the total weight of the monomers. If olefinically unsaturated crosslinking agents are present, they contain 2, 3, 4, or 5 free radical polymerizable olefinically unsaturated groups.

[0029] Examples of crosslinking agents having two free radical polymerizable olefinic unsaturated groups include: (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) Alkylene di(meth)acrylamide, such as N-methylene di(meth)acrylamide, N,N'-3-methyl-butylene 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 the following general formula , in R 10 It is hydrogen or methyl; R 11 Selected from -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2- or -CH2CH2CH2CH2CH2CH2-; and m is an integer in the range of 2-50.

[0030] Examples of crosslinking agents according to the above general formula include polypropylene glycol di(meth)acrylate with m ranging from 4 to 25; polybutylene glycol di(meth)acrylate with m ranging from 5 to 40; and preferably, polyethylene glycol di(meth)acrylate with m ranging from 2 to 45, such as diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate; and more preferably, polyethylene glycol di(meth)acrylate with m ranging from 5 to 20. (4) Other examples of di(meth)acrylates that may be used include benzyl di(meth)acrylate, bisphenol A di(meth)acrylate, 1,3-di(meth)acryloyloxy-2-propanol, hydroquinone di(meth)acrylate, ethylene dithiol di(meth)acrylate, propylene dithiol di(meth)acrylate, polyethylene dithiol di(meth)acrylate and polypropylene dithiol di(meth)acrylate; (5) Divinyl compounds, such as 1,4-butanediol divinyl ether, divinylbenzene, butadiene, 1,6-hexadiene; di(meth)allyl compounds, such as di(meth)allyl phthalate or di(meth)allyl succinate; vinyl(meth)acrylic acid compounds, such as vinyl(meth)acrylate; or preferably (meth)allyl(meth)acrylic acid compounds, such as allyl(meth)acrylate.

[0031] Examples of crosslinking agents having three or more olefinically unsaturated free radical polymerizable groups include glycerol tri(meth)acrylate, 2,2-dimethylol-1-butanol tri(meth)acrylate, trimethylolpropane triethoxytri(meth)acrylate, trimethacrylamide, (meth)allylide di(meth)acrylate, 3-allyloxy-1,2-propanediol di(meth)acrylate, triallylamine, triallyl cyanurate, or triallyl isocyanurate; and also (as representative compounds having more than three olefinically unsaturated free radical polymerizable groups) pentaerythritol tetra(meth)acrylate and N,N,N',N'-tetra(meth)acryloyl-1,5-pentanediamine.

[0032] An example of a crosslinking agent having five olefinically unsaturated free radical polymerizable groups is dipentaerythritol pentaacrylate.

[0033] The preferred crosslinking agent is selected from methylenebisacrylamide, polyethylene glycol diacrylate and triallylamine.

[0034] Further preferred crosslinking agents include asymmetric crosslinkable monomers, i.e., crosslinkable monomers that rely on different functional groups for main chain introduction and crosslinking reactions. Examples of such asymmetric crosslinkable monomers include N'-hydroxymethylacrylamide, N'-hydroxymethylmethacrylamide, and glycidyl (meth)acrylate.

[0035] The advantage of this type of crosslinking agent is that it can subsequently initiate crosslinking. Therefore, crosslinking can occur under conditions different from those of main-chain free radical polymerization. Preferably, crosslinking is initiated after changing the reaction conditions, such as pH (addition of acid or alkali), temperature, etc. Optionally, the monomer composition also comprises a hydrophobic monomer, preferably a hydrophobic (meth)acrylic acid C4- 18 -Alkyl esters; and / or olefinic unsaturated monomers.

[0036] In a preferred embodiment, the method is characterized in that the free radical polymerizable monomer is selected from nonionic monomers of formula (I) and / or cationic monomers of formula (II), wherein, based on the total amount of free radical polymerizable monomers, the amount of free radical polymerizable monomers selected from nonionic monomers of formula (I) and / or cationic monomers of formula (II) is 80 to less than 100 wt%, preferably 85 to 99 wt%, most preferably 90 to 95 wt%, and the balance is selected from any other olefin polymerizable monomers, monomers of formula (III), monomers of formula (IV), and olefin unsaturated crosslinking agents containing 2, 3, 4, or 5 olefin unsaturated groups.

[0037] In this regard, the sum of the values ​​expressed as % by weight need not reach 100% by weight, because in addition to the monomers of formula (I) and / or (II), the monomer composition (i.e., the reaction mixture) may contain other olefinically unsaturated monomers, which must be taken into account when determining the total amount of monomers. However, in a preferred embodiment, the monomer composition consists of (a) and (b), so the sum of the two % by weight values ​​is 100% by weight, meaning that no other monomers are present.

[0038] In a preferred embodiment, the monomer composition comprises: - At least 5% by weight, preferably at least 20% by weight, of the nonionic monomer of formula (I). ,in R 1 Indicates hydrogen or methyl; R 2 and R 3 Each of them is independently hydrogen, C1-C5-alkyl, or C1-C5-hydroxyalkyl; - At least 5% by weight, preferably at least 20% by weight, more preferably 25 to 47% by weight, and most preferably 50.5 to 80% by weight of the cationic monomer of formula (II). ,in R¹ represents hydrogen or methyl; Z1 is O, NH, or NR4, where R4 represents a C1-C4-alkyl group, preferably methyl, and Y is one of the following groups: ,in Y0 and Y1 are C1-C6 alkylene groups, optionally substituted with one or more hydroxyl groups, preferably ethylene or propylene, optionally substituted with one hydroxyl group; Y2, Y3, Y5, Y6, and Y7 are each independently a C1-C6-alkyl group, preferably methyl; and Z - It is a counterion, preferably a halogen, a halogen-like ion, an acetate ion, or SO4CH3. - ; - 0.0001 to 1.25% by weight, preferably 0.0005 to 1% by weight, of an olefinically unsaturated crosslinking agent containing 2, 3, 4, or 5 olefinically unsaturated groups; and - Optional other olefinic unsaturated monomers.

[0039] To reiterate in this regard, the sum of the values ​​expressed as % by weight need not reach 100% by weight, because in addition to the monomers of formula (I) and / or (II), the monomer composition (i.e., the reaction mixture) may contain other olefinically unsaturated monomers, which must be taken into account when determining the total amount of monomers. However, in a preferred embodiment, the monomer composition consists of (a) and (b), so the sum of the two % by weight values ​​is 100% by weight, meaning that no other monomers are present.

[0040] In this application, all percentages of monomer compositions are based on total monomer content.

[0041] According to the present invention, the aqueous reaction mixture comprises a polymeric dispersant.

[0042] In the prior art, alternative aqueous polymer systems are stabilized using low molecular weight salts. High salt content ensures the stability of the polymer system. Unlike these systems, the stability of the water-in-water polymer dispersion according to the invention is essentially ensured by the polymer dispersant. Compared to prior art aqueous polymer systems, this system makes high salt concentrations unnecessary. In a preferred embodiment, the salt content of the polymer dispersion is less than 15% by weight, more preferably 0.1 to 10% by weight, and most preferably 1 to 5% by weight, based on the polymer dispersion. The term "salt content" refers to low molecular weight salts. Polymer electrolytes are not included in the calculation of salt content.

[0043] In a preferred embodiment, the cationic polymer dispersant is substantially linear, i.e., not derived from a monomer mixture containing a crosslinking agent.

[0044] In a preferred embodiment, the polymeric dispersant is derived from one or more free-radical polymerizable olefinic unsaturated monomers. Preferably, the polymeric dispersant is derived from one type of free-radical polymerizable olefinic unsaturated monomer, i.e., the polymeric dispersant is substantially a homopolymer. In this regard, the term "substantially" means that no second type of monomer was intentionally added during the synthesis of the polymeric dispersant.

[0045] Preferably, the polymer dispersant is derived from one or more cationic monomers, more preferably from a single cationic monomer.

[0046] In another preferred embodiment, the method is characterized in that the polymer dispersant is a homopolymer made from a cationic monomer of formula (II). ,in R 1 Indicates hydrogen or methyl; Z1 is O, NH, or NR4, where R4 represents a C1-C4-alkyl group, preferably methyl, and Y is one of the following groups: ,in Y0 and Y1 are C1-C6 alkylene groups, optionally substituted with one or more hydroxyl groups, preferably ethylene or propylene, optionally substituted with one hydroxyl group; Y2, Y3, Y5, Y6, and Y7 are each independently a C1-C6-alkyl group, preferably methyl; and Z - It is a counterion, preferably a halogen, a halogen-like ion, an acetate ion, or SO4CH3. - .

[0047] Preferably, Y1, Y2, and Y3 are identical, and preferably methyl. In a preferred embodiment, Z1 is O or NH, Y0 is ethylene or propylene, R¹ is hydrogen 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 quaternary ammonium salt). However, preferably, the cationic monomer according to general formula (II) is an amide (Z1 = NH), particularly trimethylammonium-propylacrylamide (DIMAPA quaternary ammonium salt).

[0048] Preferred free radical polymerizable cationic monomers according to general formula (II) include quaternized dialkylaminoalkyl (meth)acrylates or dialkylaminoalkyl (meth)acrylamides having 1 to 3 C atoms in an alkyl or alkylene group, more preferably ammonium salts of the following substances quaternized with chloromethane: dimethylaminomethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, diethylaminomethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, diethylaminopropyl (meth)acrylate, dimethylaminomethyl (meth)acrylamide, dimethylaminoethyl (meth)acrylamide, dimethylaminopropyl (meth)acrylamide, diethylaminomethyl (meth)acrylamide, diethylaminoethyl (meth)acrylamide, diethylaminopropyl (meth)acrylamide.

[0049] Quaternized dimethylaminoethyl acrylate and dimethylaminopropyl acrylamide are particularly preferred. Quaternization can be carried out using dimethyl sulfate, diethyl sulfate, chloromethane, or chloroethane. In a preferred embodiment, the monomer is quaternized with chloromethane.

[0050] In a preferred embodiment, the polymer dispersant is a homopolymer of trimethylammonium-propylacrylamide chloride (DIMAPA quaternary ammonium salt), which is named (3-acrylamidopropyl)trimethylammonium chloride (APTAC) by IUPAC.

[0051] Preferably, the polymer dispersant is derived from a monomer composition comprising a cationic monomer selected from: (alkyl)acrylamidoalkyltrialkylammonium halides (e.g., trimethylammonium-alkyl(meth)acrylamide halides), (alkyl)acryloyloxyalkyltrialkylammonium halides (e.g., trimethylammonium-alkyl(meth)acrylate halides), alkenyltrialkylammonium halides, and diallyldialkylammonium halides (e.g., diallyldialkylammonium halides). More preferably, the polymer dispersant is a cationic polymer derived from a monomer composition comprising a cationic monomer selected from: trimethylammonium-alkyl(meth)acrylate halides, trimethylammonium-alkyl(meth)acrylamide halides, and diallyldialkylammonium halides. Preferably, the aforementioned cationic monomer comprises 6 to 25 carbon atoms, more preferably 7 to 20 carbon atoms, most preferably 7 to 15 carbon atoms, and particularly 8 to 12 carbon atoms.

[0052] In another preferred embodiment, the polymer dispersant is derived from diallyl dialkylammonium halides, preferably diallyl dimethylammonium halide (DADMAC).

[0053] According to a preferred embodiment, the method is characterized in that the polymer dispersant is a homopolymer made of (meth)acryloylaminopropyltrimethylammonium salt or (meth)acryloyloxyethyltrimethylammonium salt. Within the framework of this disclosure, a homopolymer of (meth)acrylate means that the homopolymer is a methacrylate or an acrylate.

[0054] Within the framework of this application, the halide can be any acceptable halide, such as chloride, bromide or iodide; the counter ion of the salt can be any acceptable counter ion, such as halide ion, methylsulfate, sulfate or others.

[0055] According to a preferred embodiment, the method is characterized in that the weight-average molecular weight Mw of the polymer dispersant is 40,000 to less than 150,000 g / mol, preferably 50,000 to 140,000 g / mol, more preferably 60,000 to 130,000 g / mol, and most preferably 85,000 to 120,000 g / mol, as determined by size exclusion chromatography.

[0056] In a preferred embodiment, the method is characterized in that the viscosity of the polymer dispersion is from 1,800 mPa·s to less than 6,700 mPa·s, preferably from 2,000 mPa·s to 6,000 mPa·s, more preferably from 2,200 mPa·s to 5,500 mPa·s, and most preferably from 2,500 mPa·s to 5,000 mPa·s, measured using a Brookfield viscometer with a No. 4 rotor at 20°C and an angular velocity of 10 rpm.

[0057] The viscosity is preferably the bulk viscosity, which refers to the viscosity of the product immediately after it has cooled.

[0058] According to a preferred embodiment, the ratio of polymer dispersant to dispersing 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, more 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, and particularly in the range of 0.65:1 to 0.9:1.

[0059] The invention is particularly effective if the method is characterized in that, based on the total weight of the polymer dispersion, the total weight of the polymer dispersant is in the range of 10 to 28 wt%, preferably 12 to 26 wt%, more preferably 14 to 24 wt%, and even more preferably 16 to 22 wt%. According to another embodiment, the method is characterized in that, based on the total weight of the polymer dispersion, the total weight of the polymer dispersant is between 18 and 26 wt%, preferably 19 to 25 wt%.

[0060] Furthermore, the aqueous reaction mixture contains an initiator. According to a preferred embodiment, the initiator is a redox initiator system comprising an oxidant and a reductant.

[0061] According to a preferred embodiment, the method is characterized by carrying out a step of free radical polymerization of the aqueous reaction mixture by sequentially or simultaneously adding a redox initiator system comprising an oxidant and a reductant. When the initiator is sequentially added to the batch reactor, by definition, a first time period begins with the injection of a first portion of the initiator. A second time period does not begin until all the initiator used to initiate polymerization has been injected into the batch reactor; however, the portion of initiator injected to remove residual monomers is not included in the start time of the second time period.

[0062] According to a preferred embodiment, the method is characterized in that the redox potential of the oxidant is 0.6 to 2.0 V. Preferred oxidants used in the redox initiator system for controlling adiabatic conditions are peroxydiphosphate; hydrogen peroxide (1.14 V); alkyl hydroperoxides, more preferably tert-butyl hydroperoxide; or aryl hydroperoxides, more preferably cumene hydroperoxides. According to a most preferred embodiment, the method is characterized in that the oxidant is selected from alkyl hydroperoxides, particularly tert-butyl hydroperoxide, or aryl hydroperoxides, particularly cumene hydroperoxide.

[0063] Persulfate can also be used as a reagent in the initiator system. However, it has been found that the effect of persulfate with a redox potential of 2.01 V on the preparation method is insufficient to enable the method to be carried out under controlled adiabatic conditions. If persulfate is used as the initiator in this method, another oxidant with a potential of 2 V or lower and 0.6 V or higher is required in the redox initiator system. However, in a preferred embodiment, the redox initiator system does not contain persulfate.

[0064] In a preferred embodiment, the method is characterized in that the redox potential of the reducing agent is -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, bisulfite (-0.08 V); thiosulfates (-0.17 V); amines; acids, more preferably ascorbic acid (0.127 V) or isoascorbic acid (0.127 V). Even more preferred reducing agents are bisulfites, particularly sodium bisulfite, potassium bisulfite, or ammonium bisulfite.

[0065] The redox potential was determined according to standard methods known to the technician.

[0066] In a preferred embodiment, the redox initiator system comprises alkyl / aryl hydroperoxides and bisulfites.

[0067] In a preferred embodiment, the oxidant used is greater than the reducing agent by weight. According to a preferred embodiment, the method is characterized in that the weight ratio of reducing agent to oxidant is less than 35:1 and greater than 2:1, preferably less than 15:1 and greater than 3:1, more preferably less than 9:1 and greater than 4:1.

[0068] In another preferred embodiment, the method is characterized in that the polymerization step is carried out by stirring while the torque of the motor-driven stirrer is measured. Alternatively, the method is characterized in that polymerization step B is carried out by stirring, and the torque of the motor-driven stirrer is maintained below 65 N / cm.

[0069] According to a preferred embodiment, the method includes reaching a maximum temperature (T0) at approximately max The step of adding an initiator to the reaction mixture to reduce the residual monomer content. In a more preferred embodiment, this step is carried out isothermally, and even more preferably, this step is carried out by maintaining the temperature above 55°C and below 80°C, most preferably above 60°C and below 70°C during this step.

[0070] The initiator used to reduce the residual monomer content can be any of the additional initiators mentioned above. However, the preferred initiator is selected from peroxides or azo compounds, and even more preferably from free hydroperoxides, dialkyl peroxides, diacyl peroxides, and azo compounds substituted with tertiary carbon atoms (preferably with alkyl, nitrile, and / or ester groups). In particular, the initiator used in step C is 2,2'-azobis(2-amidinylpropane) dihydrochloride (V-50).

[0071] The fundamental problem of the present invention is also solved by the subject matter of claim 12. Therefore, according to a third aspect, the present invention relates to the use of a batch reactor in a method for preparing a water-in-water polymer dispersion, said method comprising the step of subjecting an aqueous reaction mixture to free radical polymerization to synthesize a dispersed polymer and form a water-in-water polymer dispersion, said aqueous reaction mixture comprising: a) a polymer dispersant; b) a monomer composition comprising a free radical polymerizable monomer, said free radical polymerizable monomer being selected from one or more of: nonionic olefinic unsaturated monomers, cationic olefinic unsaturated monomers, and amphiphilic olefinic unsaturated monomers; and c) an initiator, wherein said batch reactor comprises a stirrer treated with a grinding and polishing technique, or wherein said batch reactor is baffle-free.

[0072] Another aspect of the invention disclosed herein relates to the use of the polymer dispersions according to the invention in the following aspects: a. Used as a flocculant in solid sedimentation, flotation, or filtration. b. Used as a thickener c. Used as a pollutant control agent, d. Used as a dry strength agent, retention aid, or filter aid in papermaking.

[0073] The preferred embodiment of this aspect is characterized in that its disclosed features are combined with any one of the first to third aspects of the present invention.

[0074] Another aspect of the present invention disclosed herein relates to water-in-water polymer dispersions obtained by the method described in the second aspect of the present invention.

[0075] The preferred embodiment of this aspect is characterized in that its disclosed features are combined with the features disclosed in any one of the first to third aspects of the present invention.

[0076] Features relating to the preferred embodiments of the first aspect of the invention (these features are disclosed only with respect to the first aspect of the invention) also constitute features of the preferred embodiments of the second and third aspects of the invention.

[0077] In the following, exemplary embodiments (A) to (H) representing particularly preferred embodiments are disclosed.

[0078] (A) A batch reactor comprising an aqueous reaction mixture for preparing a water-in-water polymer dispersion by free radical polymerization, wherein the aqueous reaction mixture comprises: a) Polymer dispersants; b) A monomer composition comprising a radically polymerizable monomer, wherein the radically polymerizable monomer is selected from one or more of the following: nonionic olefinic unsaturated monomers, cationic olefinic unsaturated monomers, and amphiphilic olefinic unsaturated monomers; and c) Initiator, The batch reactor mentioned above includes a stirrer treated with electropolishing technology, or The batch reactor includes an electropolished agitator and does not contain baffles.

[0079] (B) A batch reactor comprising an aqueous reaction mixture for preparing a water-in-water polymer dispersion by free radical polymerization, wherein the aqueous reaction mixture comprises: a) Polymer dispersants; b) A monomer composition comprising a radically polymerizable monomer, wherein the radically polymerizable monomer is selected from one or more of the following: nonionic olefinic unsaturated monomers, cationic olefinic unsaturated monomers, and amphiphilic olefinic unsaturated monomers; and c) Initiator, The batch reactor mentioned above includes a stirrer treated with electropolishing technology, or The batch reactor mentioned above does not contain baffles; The polymer dispersant therefrom is a homopolymer made from a cationic monomer of formula (II). ,in R 1 Indicates hydrogen or methyl; Z1 is O, NH, or NR4, where R4 represents a C1-C4-alkyl group, preferably methyl, and Y is one of the following groups: ,in Y0 and Y1 are C1-C6 alkylene groups, optionally substituted with one or more hydroxyl groups, preferably ethylene or propylene, optionally substituted with one hydroxyl group; Y2, Y3, Y5, Y6, and Y7 are each independently a C1-C6-alkyl group, preferably methyl; and Z - It is a counterion, preferably a halogen, a halogen-like ion, an acetate ion, or SO4CH3. - .

[0080] (C) A batch reactor comprising an aqueous reaction mixture for preparing a water-in-water polymer dispersion by free radical polymerization, wherein the aqueous reaction mixture comprises: a) Polymer dispersants; b) A monomer composition comprising a radically polymerizable monomer, wherein the radically polymerizable monomer is selected from one or more of the following: nonionic olefinic unsaturated monomers, cationic olefinic unsaturated monomers, and amphiphilic olefinic unsaturated monomers; and c) Initiator, The batch reactor mentioned above includes a stirrer treated with electropolishing technology, or The batch reactor mentioned above does not contain baffles; The polymer dispersant thereon is a homopolymer made of (meth)acryloylaminopropyltrimethylammonium salt or (meth)acryloyloxyethyltrimethylammonium salt.

[0081] (D) A batch reactor comprising an aqueous reaction mixture for preparing a water-in-water polymer dispersion by free radical polymerization, wherein the aqueous reaction mixture comprises: a) Polymer dispersants; b) A monomer composition comprising a radically polymerizable monomer, wherein the radically polymerizable monomer is selected from one or more of the following: nonionic olefinic unsaturated monomers, cationic olefinic unsaturated monomers, and amphiphilic olefinic unsaturated monomers; and c) Initiator, The batch reactor mentioned above includes a stirrer treated with electropolishing technology, or The batch reactor mentioned above does not contain baffles; The polymer dispersant is a homopolymer made of (meth)acryloylaminopropyltrimethylammonium salt or (meth)acryloyloxyethyltrimethylammonium salt; and The monomer composition comprising a free radical polymerizable monomer contains at least two of the following monomers: - At least 5% by weight, preferably at least 20% by weight, of the nonionic monomer of formula (I). ,in R 1 Indicates hydrogen or methyl; R 2 and R 3 Each of them is independently hydrogen, C1-C5-alkyl, or C1-C5-hydroxyalkyl; At least 5% by weight, preferably at least 20% by weight, more preferably 25 to 47% by weight, and most preferably 50.5 to 80% by weight of the cationic monomer of formula (II). ,in R 1 Indicates hydrogen or methyl; Z1 is O, NH, or NR4, where R4 represents a C1-C4-alkyl group, preferably methyl, and Y is one of the following groups: ,in Y0 and Y1 are C1-C6 alkylene groups, optionally substituted with one or more hydroxyl groups, preferably ethylene or propylene, optionally substituted with one hydroxyl group; Y2, Y3, Y5, Y6, and Y7 are each independently a C1-C6-alkyl group, preferably methyl; and Z - It is a counterion, preferably a halogen, a halogen-like ion, an acetate ion, or SO4CH3. - .

[0082] (E) A method for preparing a water-in-water polymer dispersion, wherein the method is carried out in a batch reactor, and the method includes the step of subjecting an aqueous reaction mixture to free radical polymerization to synthesize a dispersed polymer and form a water-in-water polymer dispersion, the aqueous reaction mixture comprising: a) Polymer dispersants; b) A monomer composition comprising a radically polymerizable monomer, wherein the radically polymerizable monomer is selected from one or more of the following: nonionic olefinic unsaturated monomers, cationic olefinic unsaturated monomers, and amphiphilic olefinic unsaturated monomers; and c) Initiator, The batch reactor mentioned above includes a stirrer treated with electropolishing technology, or The batch reactor includes an electropolished agitator and does not contain baffles.

[0083] (F) A method for preparing a water-in-water polymer dispersion, wherein the method is carried out in a batch reactor, and the method includes the step of subjecting an aqueous reaction mixture to free radical polymerization to synthesize a dispersed polymer and form a water-in-water polymer dispersion, the aqueous reaction mixture comprising: a) Polymer dispersants; b) A monomer composition comprising a radically polymerizable monomer, wherein the radically polymerizable monomer is selected from one or more of the following: nonionic olefinic unsaturated monomers, cationic olefinic unsaturated monomers, and amphiphilic olefinic unsaturated monomers; and c) Initiator, The batch reactor mentioned above includes a stirrer treated with electropolishing technology, or The batch reactor mentioned above does not contain baffles; The polymer dispersant therefrom is a homopolymer made from a cationic monomer of formula (II). ,in R 1 Indicates hydrogen or methyl; Z1 is O, NH, or NR4, where R4 represents a C1-C4-alkyl group, preferably methyl, and Y is one of the following groups: ,in Y0 and Y1 are C1-C6 alkylene groups, optionally substituted with one or more hydroxyl groups, preferably ethylene or propylene, optionally substituted with one hydroxyl group; Y2, Y3, Y5, Y6, and Y7 are each independently a C1-C6-alkyl group, preferably methyl; and Z - It is a counterion, preferably a halogen, a halogen-like ion, an acetate ion, or SO4CH3. - .

[0084] (G) A method for preparing a water-in-water polymer dispersion, wherein the method is carried out in a batch reactor, and the method includes the step of subjecting an aqueous reaction mixture to free radical polymerization to synthesize a dispersed polymer and form a water-in-water polymer dispersion, the aqueous reaction mixture comprising: a) Polymer dispersants; b) A monomer composition comprising a radically polymerizable monomer, wherein the radically polymerizable monomer is selected from one or more of the following: nonionic olefinic unsaturated monomers, cationic olefinic unsaturated monomers, and amphiphilic olefinic unsaturated monomers; and c) Initiator, The batch reactor mentioned above includes a stirrer treated with electropolishing technology, or The batch reactor mentioned above does not contain baffles; The polymer dispersant thereon is a homopolymer made of (meth)acryloylaminopropyltrimethylammonium salt or (meth)acryloyloxyethyltrimethylammonium salt.

[0085] (H) A method for preparing a water-in-water polymer dispersion, wherein the method is carried out in a batch reactor, and the method includes the step of subjecting an aqueous reaction mixture to free radical polymerization to synthesize a dispersed polymer and form a water-in-water polymer dispersion, the aqueous reaction mixture comprising: a) Polymer dispersants; b) A monomer composition comprising a radically polymerizable monomer, wherein the radically polymerizable monomer is selected from one or more of the following: nonionic olefinic unsaturated monomers, cationic olefinic unsaturated monomers, and amphiphilic olefinic unsaturated monomers; and c) Initiator, The batch reactor mentioned above includes a stirrer treated with electropolishing technology, or The batch reactor mentioned above does not contain baffles; The polymer dispersant is a homopolymer made of (meth)acryloylaminopropyltrimethylammonium salt or (meth)acryloyloxyethyltrimethylammonium salt; and The monomer composition comprising a free radical polymerizable monomer contains at least two of the following monomers: - At least 5% by weight, preferably at least 20% by weight, of the nonionic monomer of formula (I). ,in R 1 Indicates hydrogen or methyl; R 2 and R 3 Each of them is independently hydrogen, C1-C5-alkyl, or C1-C5-hydroxyalkyl; - At least 5% by weight, preferably at least 20% by weight, more preferably 25 to 47% by weight, and most preferably 50.5 to 80% by weight of the cationic monomer of formula (II). ,in R 1 Indicates hydrogen or methyl; Z1 is O, NH, or NR4, where R4 represents a C1-C4-alkyl group, preferably methyl, and Y is one of the following groups: ,in Y0 and Y1 are C1-C6 alkylene groups, optionally substituted with one or more hydroxyl groups, preferably ethylene or propylene, optionally substituted with one hydroxyl group; Y2, Y3, Y5, Y6, and Y7 are each independently a C1-C6-alkyl group, preferably methyl; and Z - It is a counterion, preferably a halogen, a halogen-like ion, an acetate ion, or SO4CH3. - . Example

[0086] The testing methods used are described in detail below: Bulk viscosity measurements are as follows: Use the product directly for measurement. Slowly immerse rotor #4 into the product and measure the viscosity using a Brookfield RVT viscometer at 10 rpm. Stop the measurement when the reading remains constant for 30 seconds.

[0087] The viscosity of the solution was measured in deionized water, and the determination method is as follows: Prepare a 5% (w / w) aqueous solution. Weigh 323.0 ± 0.1 g of deionized water into a 400 ml beaker. Then add 17.0 ± 0.1 g of the product (22 ± 3°C) while stirring at 300 rpm. Dissolve for 60 minutes at a stirring speed of 300 ± 10 rpm. Afterward, allow the solution to stand for 5 minutes. Then slowly immerse the solution in rotor #2 and measure the viscosity using a Brookfield RFT viscometer at 10 rpm. Stop the measurement when the reading remains constant for 30 seconds.

[0088] Salt viscosity was measured in a 10% NaCl solution, and the determination method is as follows: Weigh 289.0 ± 0.1 g of deionized water into a 400 ml beaker. Then add 17.0 ± 0.1 g of the product (22 ± 3°C) while stirring at 300 rpm. Dissolve for 45 minutes at 300 ± 10 rpm, then add 34.0 ± 0.1 g of NaCl. Stir the solution for another 15 minutes. After that, let the solution stand for 5 minutes. Then slowly immerse the solution in rotor #1 and measure the viscosity using a Brookfield RVT viscometer at 10 rpm. Stop the measurement when the reading remains constant for 30 seconds.

[0089] Molar mass was measured by size exclusion chromatography (SEC).

[0090] This measurement is specifically used to determine the molecular weight of dispersants.

[0091] Molecular weight was characterized using an aqueous SEC calibrated with Pullulan standards.

[0092] Sample preparation: The sample was diluted with eluent (the polymer was dissolved in a volumetric flask) and filtered through a 1µm filter cartridge (M&N) (using a syringe) before injection.

[0093] If the instrument is equipped with an autosampler filter, the solution is filtered into a vial through a 1µm filter cartridge.

[0094] Parameters used: Instrument: SEC (Agilent) Column: Novema 3000 (PSS) Detector: RI Eluent: 1.5 wt% formic acid aqueous solution Flow rate: 1 ml / min Calibration standards: Pullland of different Mw The following examples further illustrate the method for preparing water-in-water polymer dispersions. However, these examples should not be construed as limiting the invention.

[0095] Example 1: Synthesis of Polymer Dispersants First, 294.06 g of water, 666.7 g of acrylamidopropyltrimethylammonium chloride (DIMAPA quaternary ammonium salt) (60 wt%), and sulfuric acid (50 wt%) were weighed into a 2 L container to adjust the pH to 5.0 ± 0.2. Then, the monomer solution was purged with nitrogen for 30 minutes with stirring. Subsequently, the aqueous solution was heated to 65°C, and 2-mercaptoethanol and V-50 (2,2'-azobis(2-amidinylpropane) dihydrochloride) were added to the solution. After reaching Tmax, the container was cooled to ≤ 80°C. Then, additional initiator (V-50) was added to the product in two portions over 10 minutes to consume the residual monomer. The product was stirred at 70°C for 1 hour. The final aqueous product was cooled to 30°C. The dispersant was provided as a 40 wt% aqueous solution.

[0096] Specification: Product viscosity [mPa·s]: 110-180 pH (pure product): 4.9-5.3 Total solids content [%]: 40-43 Mw(SEC) [g / mol]: 70000-110000 Example 2: Synthesis of polymer dispersion (charge density 15 mol%) In a batch process (batch size 1,000 kg) carried out in a batch reactor without baffles and including an electropolished stirrer, acrylamide and acryloyloxyethyltrimethylammonium chloride (ADAME quaternary ammonium salt) were polymerized in an aqueous solution in the presence of homopolymeric polyacrylamide-propyltrimethylammonium chloride (polymer dispersant). The aqueous phase was prepared at 200 rpm.

[0097] First, 206.90 kg of soft water, 261.80 kg of bio-based acrylamide (49 wt%), 77.20 kg of acryloyloxyethyltrimethylammonium chloride (ADAME quaternary ammonium salt) (80 wt%), 412.50 kg of the polymer dispersant from Example 1, 10.00 kg of ammonium sulfate, and 0.20 kg of Trilon C were added to the reaction vessel. The pH was adjusted to pH 5.0 ± 0.2 with approximately 0.10 kg of sulfuric acid (50%). The vessel was evacuated five times before being purged with nitrogen. The initiator composition was added under a negative pressure of 0.5 bar and at maximum stirrer speed. Initiation was started at 22±1°C by adding 0.34 kg of V-50 dissolved in 3.05 kg of soft water, 0.025 kg of sodium persulfate dissolved in 0.47 kg of soft water, 0.014 kg of sodium bisulfite dissolved in 0.27 kg of soft water, and 0.003 kg of tert-butyl hydroperoxide (70%) dissolved in 1 kg of soft water. The container was then purged with nitrogen again. After reaching the maximum temperature, 0.17 kg of V-50 solution dissolved in 1.53 kg of soft water was added to reduce the monomer content. After a one-hour post-reaction time, the product was cooled to below 40°C. Then, 8.30 kg of citric acid and 0.82 kg of the fungicide Acticide SPX were added, and the product was cooled to below 30°C.

Claims

1. A batch reactor comprising an aqueous reaction mixture, said batch reactor being used to prepare a water-in-water polymer dispersion via free radical polymerization, wherein said aqueous reaction mixture comprises: a) Polymer dispersants; b) A monomer composition comprising a radically polymerizable monomer, wherein the radically polymerizable monomer is selected from one or more of the following: nonionic olefinic unsaturated monomers, cationic olefinic unsaturated monomers, and amphiphilic olefinic unsaturated monomers; and c) Initiator, The batch reactor mentioned above includes a stirrer that has been treated with grinding and polishing technology, or The batch reactor mentioned therein does not contain baffles.

2. The batch reactor according to claim 1, wherein the grinding and polishing technology represents electropolishing technology.

3. The batch reactor of claim 1, wherein the batch reactor includes an electropolished agitator, and the inner wall of the batch reactor is at least partially covered with enamel.

4. A method for preparing a water-in-water polymer dispersion, wherein the method is carried out in a batch reactor, and the method includes the step of subjecting an aqueous reaction mixture to free radical polymerization to synthesize a dispersed polymer and form a water-in-water polymer dispersion, the aqueous reaction mixture comprising: a) Polymer dispersants; b) A monomer composition comprising a radically polymerizable monomer, wherein the radically polymerizable monomer is selected from one or more of the following: nonionic olefinic unsaturated monomers, cationic olefinic unsaturated monomers, and amphiphilic olefinic unsaturated monomers; and c) Initiator, The batch reactor mentioned above includes a stirrer that has been treated with grinding and polishing technology, or The batch reactor mentioned therein does not contain baffles.

5. The method according to claim 4, wherein the grinding and polishing technique represents electropolishing.

6. The method of claim 4, wherein the batch reactor includes an electropolished agitator, and the inner wall of the batch reactor is at least partially covered with enamel.

7. The method according to any one of claims 4 to 6, characterized in that, The monomer composition comprising a free radical polymerizable monomer includes: - At least 5% by weight, preferably at least 20% by weight, of the nonionic monomer of formula (I). ,in R 1 Indicates hydrogen or methyl; R 2 and R 3 Each of them is independently hydrogen, C1-C5-alkyl, or C1-C5-hydroxyalkyl; - At least 5% by weight, preferably at least 20% by weight, more preferably 25 to 47% by weight, and most preferably 50.5 to 80% by weight of the cationic monomer of formula (II). ,in R 1 Indicates hydrogen or methyl; Z1 is O, NH, or NR4, where R4 represents a C1-C4-alkyl group, preferably methyl, and Y is one of the following groups: ,in Y0 and Y1 are C1-C6 alkylene groups, optionally substituted with one or more hydroxyl groups, preferably ethylene or propylene, optionally substituted with one hydroxyl group; Y2, Y3, Y5, Y6, and Y7 are each independently a C1-C6-alkyl group, preferably methyl; and Z - It is a counterion, preferably a halogen, a halogen-like ion, an acetate ion, or SO4CH3. - ; - 0 to 1.25% by weight, preferably 0.0001 to 1% by weight, more preferably 0.001 to 0.5% by weight of an olefinically unsaturated crosslinking agent containing 2, 3, 4, or 5 olefinically unsaturated groups; and - Optional other olefinic unsaturated monomers.

8. The method according to any one of claims 4 to 7, characterized in that, The monomer composition comprising a free radical polymerizable monomer contains a nonionic monomer selected from the following formula (I): wherein R 1 R represents hydrogen or methyl. 2 and R 3 All are hydrogen, hydrogen and C 1- C3 alkyl, hydrogen and hydroxyethyl, or all of them are C3 1- C3 alkyl, and / or selected from the following formula (II) cationic monomers: wherein R 1 Z1 represents hydrogen or methyl, R4 represents methyl, Y1 is a C2-C6 alkylene, preferably ethylene or propylene, Y5, Y6 and Y7 are all methyl, and Z⁻ is halogen; wherein most preferably, the monomer composition comprising a free radical polymerizable monomer comprises at least a nonionic monomer of formula (I) as (meth)acrylamide and a cationic monomer of formula (II) as (meth)acrylamidopropyltrimethylammonium chloride or (meth)acryloyloxyethyltrimethylammonium chloride.

9. The method according to any one of claims 4 to 8, characterized in that, The polymer dispersant is a homopolymer made from a cationic monomer of formula (II). ,in R 1 Indicates hydrogen or methyl; Z1 is O, NH, or NR4, where R4 represents a C1-C4-alkyl group, preferably methyl, and Y is one of the following groups: ,in Y0 and Y1 are C1-C6 alkylene groups, optionally substituted with one or more hydroxyl groups, preferably ethylene or propylene, optionally substituted with one hydroxyl group; Y2, Y3, Y5, Y6, and Y7 are each independently a C1-C6-alkyl group, preferably methyl; and Z⁻ is a counter ion, preferably a halogen, halogen-like ion, acetate, or SO₄CH₃. - .

10. The method according to any one of claims 4 to 9, characterized in that, The polymer dispersant is a homopolymer made of (meth)acryloylaminopropyltrimethylammonium salt or (meth)acryloyloxyethyltrimethylammonium salt.

11. The method according to any one of claims 4 to 10, characterized in that, The ratio of polymer dispersant to dispersing 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, more 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, and particularly in the range of 0.65:1 to 0.9:

1.

12. Use of a batch reactor in a method for preparing a water-in-water polymer dispersion, wherein the method includes the step of subjecting an aqueous reaction mixture to free radical polymerization to synthesize a dispersed polymer and form a water-in-water polymer dispersion, said aqueous reaction mixture comprising: a) Polymer dispersants; b) A monomer composition comprising a radically polymerizable monomer, wherein the radically polymerizable monomer is selected from one or more of the following: nonionic olefinic unsaturated monomers, cationic olefinic unsaturated monomers, and amphiphilic olefinic unsaturated monomers; and c) Initiator, The batch reactor mentioned above includes a stirrer that has been treated with grinding and polishing technology, or The batch reactor mentioned therein does not contain baffles.

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