Method for preparing water-in-water polymer dispersions using shear distribution

Abstract

The invention relates to a method for producing a polymer dispersion, to a polymer dispersion and to the use thereof. The method for preparing a water-in-water polymer dispersion utilizes a batch reactor that provides a specific shear distribution wherein the method comprises the step of free radical polymerization of an aqueous reaction mixture to synthesize a dispersed polymer and form a water-in-water polymer dispersion, the aqueous reaction mixture comprises (a) a polymeric dispersant and (b) a monomer composition comprising a radically polymerizable monomer, wherein the radically polymerizable monomer is selected from one or more of a nonionic ethylenically unsaturated monomer, a cationic ethylenically unsaturated monomer, and an amphiphilic ethylenically unsaturated monomer.

Description

[0001] This invention relates to a method for preparing water-in-water polymer dispersions, the polymer dispersions themselves, and their uses.

[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 beneficial effects 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 necessary. In this regard, improvements to the method are needed from an efficiency perspective. The efficient use of raw materials is required. However, all measures taken in this method should not lead to a decline in the quality of the final product.

[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 a method for preparing water-in-water polymer dispersions, the product of which ensures improved operational performance and fully utilizes the efficiency advantages of the raw materials. Furthermore, the fundamental problem of this invention relates to providing a method for preparing water-in-water polymer dispersions that ensures high stability during the preparation process and a long shelf life under adverse environments (such as alternating temperature changes).

[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 method for preparing a water-in-water polymer dispersion using a batch reactor, 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) Polymer dispersants, and b) A monomer composition comprising a free radical polymerizable monomer, wherein the free radical polymerizable monomer is selected from one or more of the following: nonionic olefin unsaturated monomers, cationic olefin unsaturated monomers and amphiphilic olefin unsaturated monomers. The batch reactor includes a stirrer that provides specific power input (specific power consumption) to the aqueous reaction mixture by stirring during the proceeding step. The proceeding step is characterized by comprising at least a first time period and a second time period, wherein the first time period begins with the initiation of free radical polymerization, and the second time period immediately follows the first time period, wherein the specific power input during the first time period is lower than the specific power input during the second time period.

[0009] A method for preparing water-in-water polymer dispersions utilizes a batch reactor that provides a specific shearing profile. 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 comprises (a) a polymer dispersant and (b) a monomer composition containing a free radical polymerizable monomer selected from one or more of the following: nonionic olefinic unsaturated monomers, cationic olefinic unsaturated monomers, and amphiphilic olefinic unsaturated monomers. These polymer dispersions are referred to as water-in-water (w / w) polymer dispersions, prepared by the method according to the invention.

[0010] 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 known technical knowledge, it is impossible to obtain the polymer dispersion obtained by the method of the present invention by copolymerizing the monomer composition and then adding the polymeric dispersant after the copolymerization reaction. By applying the method of the present invention, the polymer dispersion is endowed with unique properties; the polymer dispersion refers to the final product comprising a copolymer obtained from a free radical polymerizable monomer and a polymeric dispersant.

[0011] In recent years, it has been found that the power input to the reaction mixture is a parameter affecting polymerization. For example, WO 2011 / 110484 A1 discloses a method for the catalytic preparation of polyether alcohols, wherein the input power provided by at least one stirrer or by at least one stirrer and a pump is within a specific range based on the reactor volume, wherein a baffle is used to regulate the power input.

[0012] In existing technologies, polymer synthesis is typically carried out in a manner that achieves efficient homogenization. However, in the preparation of water-in-water polymer dispersions, employing high power input throughout the process to effectively homogenize the reaction mixture is not the most advantageous approach for polymerization.

[0013] According to the present invention, the fundamental problem is solved by a method for preparing a polymer dispersion, the method comprising reacting a reaction mixture, wherein the reaction is carried out in a reactor vessel under stirring, and wherein the power input per unit time period after polymerization initiation is increased compared to the first time period. In particular, the reaction profile feature as described in claim 1 is observed to lead to improved initiation efficiency. Therefore, the power can be increased after polymerization initiation is complete.

[0014] The term "second time period immediately following the first time period" means that the first time period has ended, and the second time period is the time period executed after the end of the first time period. The second time period can begin immediately after the first time period; however, it can also begin after a certain delay. This can be achieved, for example, by applying a gradual increase in unit power input within the time range between the first and second time periods.

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

[0016] Surprisingly, it was found that implementing the method by changing the unit power input in the manner described in claim 1 can yield beneficial effects.

[0017] Unit power input is the power input per volume, and its calculation depends on the type of flow, i.e., whether the flow in the reaction vessel is turbulent or laminar. Unit power input (P / V) is expressed as power input (P) divided by the volume of the reaction mixture (V), and is calculated as follows: a) For the turbulent range, the unit power input is calculated using the following formula: P / V = Ne n³ d 5 Density / V Where Ne = reactor Newton number; n = stirrer speed; d = stirrer diameter; density = density of the reaction mixture; V = filling volume (i.e., the volume of the reaction mixture at the end of the reaction), and b) For the laminar flow range, the unit power input is calculated using the following formula: P / V = C n² d³ Viscosity / V Where C = Re Ne, Re = Reynolds number of the stirrer used to mix the reaction mixture, Ne is the Newton number of the reactor.

[0018] The method can be performed as follows: during a first time period, the agitator induces laminar or turbulent flow, and / or during a second time period, the agitator induces laminar or turbulent flow. Preferably, the method is performed as follows: during the first time period, the agitator induces laminar flow, and / or during the second time period, the agitator induces turbulent flow. Power input is calculated accordingly.

[0019] The power input can be determined by measuring the electrical power consumed by the stirring motor, or calculated based on rheological parameters, stirrer type, geometry of the reactor's internal components, and the stirring speed given above. For details of this calculation method, see the chapter "Stirring" by M. Zlokarnik, included in Ullmann's Encyclopedia of Industrial Chemistry, 2012, Wiley-VCH Verlag Weinheim.

[0020] In practice, the increase in unit power input during the method according to the invention is achieved by increasing the electrical power input. Before the reaction begins, i.e., before the initiator is loaded into the batch reactor, the power supply level is relatively low compared to the second time period. After polymerization initiation is complete, the power supply is increased. During the second time period, the positive effects associated with more vigorous stirring begin to appear.

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

[0022] According to a preferred embodiment, the method is characterized by a step of radical polymerization of the aqueous reaction mixture by sequentially or simultaneously adding a redox initiator system. The redox initiator system preferably comprises an oxidant and a reductant. When the initiators are 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 initiators used to initiate polymerization have 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.

[0023] According to a preferred embodiment, the method is characterized in that the redox potential of the oxidant is 0.6 to 2.0 V. The preferred oxidant used in the redox initiator system for controlling adiabatic conditions is peroxydiphosphate; hydrogen peroxide (1.14 V); alkyl hydroperoxide, more preferably tert-butyl hydroperoxide; or aryl hydroperoxide, more preferably cumene hydroperoxide. 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.

[0024] 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.

[0025] 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.

[0026] The redox potential was determined according to standard methods known to the technician.

[0027] In a preferred embodiment, the redox initiator system comprises alkyl / aryl hydroperoxides and bisulfites.

[0028] 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.

[0029] 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.

[0030] In a preferred method, the monomer composition comprising a free radical polymerizable monomer is 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, and 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.

[0031] Within the framework of this invention, a cationic monomer is a monomer that is permanently positively charged.

[0032] 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.

[0033] Furthermore, the monomer composition for copolymerization preferably provides a monomer of item i, a monomer of item ii, and a monomer of item iv.

[0034] 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 C1-C3 alkyl, hydrogen and hydroxyethyl, or all are C1-C3 alkyl, and / or selected from the following formula (II) cationic monomers: wherein R 1 Z1 represents hydrogen or methyl, where R4 represents methyl, Y1 is a C2-C6 alkylene group, preferably ethylene or propylene, Y5, Y6, and Y7 are all methyl, and Z... - It is halogen.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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 general formula (V) (V), in R 10 It is hydrogen or methyl; R 11Selected from -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2-, or -CH2CH2CH2CH2CH2CH2-; and m is an integer in the range of 2-50.

[0039] Examples of crosslinking agents according to general formula (V) 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.

[0040] 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.

[0041] An example of a crosslinking agent having five olefinically unsaturated free radical polymerizable groups is dipentaerythritol pentaacrylate.

[0042] The preferred crosslinking agent is selected from methylenebisacrylamide, polyethylene glycol diacrylate and triallylamine.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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 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. - ; - 0.0001 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.

[0048] 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.

[0049] In this application, all percentages of monomer compositions are based on total monomer content.

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

[0051] 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 present invention is essentially ensured by the polymer dispersant. This system eliminates the high salt concentration problem found in existing aqueous polymer systems. 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.

[0052] In a preferred embodiment, the cationic polymer dispersant is substantially linear, i.e., not derived from a monomer mixture containing a crosslinking agent.

[0053] In a preferred embodiment, the polymer dispersant is derived from one or more free-radical polymerizable olefinic unsaturated monomers. Preferably, the polymer dispersant is derived from one type of free-radical polymerizable olefinic unsaturated monomer, i.e., the polymer dispersant is substantially a homopolymer. In this respect, the term "substantially" means that no second type of monomer was intentionally added during the synthesis of the polymer dispersant.

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

[0055] 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. - .

[0056] Preferably, Y1, Y2, and Y3 are the same, and preferably methyl. In a preferred embodiment, Z1 is O or NH, Y0 is ethylene or propylene, and R... 1 It is hydrogen or methyl, and Y1, Y2 and Y3 are methyl. According to general formula (II), the cationic monomer 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), especially trimethylammonium-propylacrylamide (DIMAPA quaternary ammonium salt).

[0057] 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.

[0058] Quaternized dimethylaminoethyl acrylate and dimethylaminopropylacrylamide 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.

[0059] 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.

[0060] 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.

[0061] In another preferred embodiment, the polymer dispersant is derived from diallyl dialkylammonium halides, preferably diallyl dimethylammonium halide (DADMAC).

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] The viscosity is preferably the bulk viscosity, which refers to the viscosity of the product immediately after it has cooled.

[0067] 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.

[0068] 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% by weight, preferably 12 to 26% by weight, more preferably 14 to 24% by weight, and even more preferably 16 to 22% by weight. 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% by weight, preferably 19 to 25% by weight.

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

[0070] The initiator used to reduce the residual monomer content can be any of the other 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 14. Therefore, according to a second aspect, the present invention relates to a polymer dispersion obtained by a method for preparing a polymer dispersion according to the present invention, the method comprising the steps of: A) A reaction mixture is provided in an aqueous medium, the reaction mixture comprising: a) Polymer dispersants, and b) A monomer composition comprising a free radical polymerizable monomer, wherein the free radical polymerizable monomer is selected from one or more of the following: nonionic olefin unsaturated monomers, cationic olefin unsaturated monomers and amphiphilic olefin unsaturated monomers. B) Allow the monomer composition in the reaction mixture to undergo free radical polymerization to synthesize a dispersed polymer and form the polymer dispersion. The batch reactor includes a stirrer that provides unit power input to the aqueous reaction mixture by stirring during the proceeding step, characterized in that the proceeding step includes at least two time periods, wherein a first time period begins from the initiation of free radical polymerization and a second time period immediately follows the first time period, wherein the unit power input in the first time period is lower than the unit power input in the second time period.

[0072] According to a preferred embodiment, the polymer dispersion is obtained by a method for preparing a polymer dispersion, wherein the weight-average molecular weight Mw of the polymer dispersion 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.

[0073] According to a preferred embodiment, the polymer dispersion is obtained by a method for preparing a polymer dispersion, wherein the bulk viscosity of the polymer dispersion is less than 6,700 mPa·s, preferably less than 6,000 mPa·s, more preferably less than 5,500 mPa·s, and most preferably less than 5,000 mPa·s, measured at 20°C using a Brookfield viscometer, a No. 4 rotor, and a rotation speed of 10 rpm.

[0074] According to a preferred embodiment, the polymer dispersion is obtained by a method for preparing a polymer dispersion, wherein the bulk viscosity of the polymer dispersion is higher than 1,800 mPa·s, preferably higher than 2,000 mPa·s, more preferably higher than 2,200 mPa·s, even more preferably higher than 2,500 mPa·s, and most preferably higher than 3,000 mPa·s, measured at 20°C using a Brookfield viscometer, a No. 4 rotor, and a rotation speed of 10 rpm.

[0075] The fundamental problem of the present invention is also solved by the subject matter of claim 15. Therefore, according to a third aspect, the present invention relates to the use of the polymer dispersion 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.

[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] Exemplary embodiments (A) to (E) representing particularly preferred embodiments are disclosed below.

[0078] (A) A method for preparing a water-in-water polymer dispersion using a batch reactor 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, wherein the aqueous reaction mixture comprises: a) Polymer dispersants, and b) A monomer composition comprising a free radical polymerizable monomer, wherein the free radical polymerizable monomer is selected from one or more of the following: nonionic olefin unsaturated monomers, cationic olefin unsaturated monomers and amphiphilic olefin unsaturated monomers. The batch reactor includes a stirrer that provides unit power input to the aqueous reaction mixture by stirring during the proceeding step, characterized in that the proceeding step includes at least a first time period and a second time period, wherein the first time period is initiated from the initiation of free radical polymerization by injecting an initiator into the batch reactor, and the second time period immediately follows the first time period, wherein the unit power input in the first time period is lower than the unit power input in the second time period.

[0079] (B) A method for preparing a water-in-water polymer dispersion using a batch reactor 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, wherein the aqueous reaction mixture comprises: a) Polymer dispersants, and b) A monomer composition comprising a free radical polymerizable monomer, wherein the free radical polymerizable monomer is selected from one or more of the following: nonionic olefin unsaturated monomers, cationic olefin unsaturated monomers and amphiphilic olefin unsaturated monomers. The batch reactor includes a stirrer that provides unit power input to the aqueous reaction mixture by stirring during the proceeding step. The proceeding step is characterized by comprising at least a first time period and a second time period, wherein the first time period is initiated from the free radical polymerization by injecting an initiator into the batch reactor, and the second time period immediately follows the first time period, wherein the unit power input during the first time period is lower than the unit power input during the second time period. The polymer dispersant therefrom is a homopolymer made from a 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. - .

[0080] (C) A method for preparing a water-in-water polymer dispersion using a batch reactor 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, wherein the aqueous reaction mixture comprises: a) Polymer dispersants, and b) A monomer composition comprising a free radical polymerizable monomer, wherein the free radical polymerizable monomer is selected from one or more of the following: nonionic olefin unsaturated monomers, cationic olefin unsaturated monomers and amphiphilic olefin unsaturated monomers. The batch reactor includes a stirrer that provides unit power input to the aqueous reaction mixture by stirring during the proceeding step. The proceeding step is characterized by comprising at least a first time period and a second time period, wherein the first time period is initiated from the free radical polymerization by injecting an initiator into the batch reactor, and the second time period immediately follows the first time period, wherein the unit power input during the first time period is lower than the unit power input during the second time period. The polymer dispersant thereon is a homopolymer made of (meth)acryloylaminopropyltrimethylammonium salt or (meth)acryloyloxyethyltrimethylammonium salt.

[0081] (D) A method for preparing a water-in-water polymer dispersion using a batch reactor 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, wherein the aqueous reaction mixture comprises: a) Polymer dispersants, and b) A monomer composition comprising a free radical polymerizable monomer, wherein the free radical polymerizable monomer is selected from one or more of the following: nonionic olefin unsaturated monomers, cationic olefin unsaturated monomers and amphiphilic olefin unsaturated monomers. The batch reactor includes a stirrer that provides unit power input to the aqueous reaction mixture by stirring during the proceeding step. The proceeding step comprises at least a first time period and a second time period, wherein the first time period begins with the initiation of free radical polymerization by injecting an initiator into the batch reactor, and the second time period immediately follows the first time period, wherein the unit power input during the first time period is lower than the unit power input during the second time period, and wherein the unit power input is adjusted by changing the electrical power input supplied to the stirrer.

[0082] (E) A method for preparing a water-in-water polymer dispersion using a batch reactor 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, wherein the aqueous reaction mixture comprises: a) Polymer dispersants, and b) A monomer composition comprising a free radical polymerizable monomer, wherein the free radical polymerizable monomer is selected from one or more of the following: nonionic olefin unsaturated monomers, cationic olefin unsaturated monomers and amphiphilic olefin unsaturated monomers. The batch reactor includes a stirrer that provides unit power input to the aqueous reaction mixture by stirring during the proceeding step. The proceeding step is characterized by comprising at least a first time period and a second time period, wherein the first time period begins with the initiation of free radical polymerization by injecting an initiator into the batch reactor, the second time period immediately following the first time period, wherein the unit power input during the first time period is lower than the unit power input during the second time period, wherein the unit power input is adjusted by changing the electrical power input supplied to the stirrer, and wherein the second time period begins 1 to 25 minutes, preferably 5 to 15 minutes, after the start of the first time period. Example

[0083] 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.

[0084] 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.

[0085] 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.

[0086] Molar mass was measured by size exclusion chromatography (SEC).

[0087] This measurement is specifically used to determine the molecular weight of dispersants.

[0088] Molecular weight was characterized using an aqueous SEC calibrated with Pullulan standards.

[0089] 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.

[0090] If the instrument is equipped with an autosampler filter, the solution is filtered into a vial through a 1µm filter cartridge.

[0091] 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.

[0092] 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. After stirring at low power input for 3 minutes, the power input was increased. 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.

[0093] 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 (1,000 kg batch size), 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.

[0094] 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.

[0095] Alternatively, in all the above embodiments and implementations, efficiency can be improved by operating the stirrer (or applying agitation) at 20% power during deoxygenation (at higher power, eddies are generated and nitrogen passes through). The stirring power is then set to 100%, and an initiator can be added to begin the reaction. This method can now be used to keep the stirring profile consistent at all times. When the stirring power is lower when the initiator is added, significant differences in stirring power and stirring (mixing) time may occur in subsequent runs.

Claims

1. A method for preparing a water-in-water polymer dispersion using a batch reactor, 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, wherein the aqueous reaction mixture comprises: a) Polymer dispersants, and b) A monomer composition comprising a free radical polymerizable monomer, wherein the free radical polymerizable monomer is selected from one or more of the following: nonionic olefin unsaturated monomers, cationic olefin unsaturated monomers and amphiphilic olefin unsaturated monomers. The batch reactor described herein includes a stirrer that provides a unit power input to the aqueous reaction mixture by stirring during the described step, characterized in that... The process includes at least a first time period and a second time period, wherein the first time period begins with the initiation of free radical polymerization, and the second time period immediately follows the first time period, wherein the unit power input in the first time period is lower than the unit power input in the second time period.

2. The method according to claim 1, characterized in that, The unity power input is given by the formula P = Ne × n 3 ×d 5 × Defined as follows, where Ne is the Newton number, n is the stirrer speed in revolutions per minute (rpm), and d is the stirrer diameter. It is the density of the reaction mixture.

3. The method according to claim 1, characterized in that, The unity power input is given by the formula P / V = C × n 2 × d 3 × Viscosity / V is defined as follows, where C = Re × Ne, Re is the Reynolds number of the agitator used to mix the aqueous reaction mixture, and Ne is the Newton number of the reactor.

4. The method according to any one of claims 1 to 3, characterized in that, The batch reactor has no baffles.

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

6. The method according to any one of claims 1 to 5, characterized in that, During the step of free radical polymerization of the aqueous reaction mixture, the stirrer induces turbulence.

7. The method according to any one of claims 1 to 6, characterized in that, The monomer composition containing a free radical polymerizable monomer is 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: or ,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, and 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.

8. The method according to any one of claims 1 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 C1-C3 alkyl, hydrogen and hydroxyethyl, or all are C1-C3 alkyl, and / or selected from the following formula (II) cationic monomers: wherein R 1 Z1 represents hydrogen or methyl, where R4 represents methyl, Y1 is a C2-C6 alkylene group, preferably ethylene or propylene, Y5, Y6 and Y7 are all methyl, and Z - It is a 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 1 to 8, 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.

10. The method according to any one of claims 1 to 9, 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. - .

11. The method according to any one of claims 1 to 10, characterized in that, The polymer dispersant is a homopolymer made of (meth)acryloylaminopropyltrimethylammonium salt or (meth)acryloyloxyethyltrimethylammonium salt.

12. The method according to any one of claims 1 to 11, 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.

13. The method according to any one of claims 1 to 12, characterized in that, Based on the total weight of the polymer dispersion, the salt content of the polymer dispersion is less than 15% by weight, preferably 0.1 to 10% by weight, and more preferably 1 to 5% by weight.

14. A polymer dispersion obtained by a method for preparing a polymer dispersion according to any one of claims 1 to 13, wherein the method utilizes 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, said aqueous reaction mixture comprising: a) Polymer dispersants, and b) A monomer composition comprising a free radical polymerizable monomer, wherein the free radical polymerizable monomer is selected from one or more of the following: nonionic olefin unsaturated monomers, cationic olefin unsaturated monomers and amphiphilic olefin unsaturated monomers. The batch reactor described herein includes a stirrer that provides a unit power input to the aqueous reaction mixture by stirring during the described step, characterized in that... The process includes at least two time periods, wherein the first time period begins with the initiation of free radical polymerization and the second time period immediately follows the first time period, wherein the unit power input in the first time period is lower than the unit power input in the second time period.

15. Use of the polymer dispersion according to claim 14 in the following respects: 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.

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