Alkali-soluble thickening agent as well as preparation method and application thereof

Abstract

The invention discloses an alkali-soluble thickening agent as well as a preparation method and application thereof. The alkali-soluble thickening agent is prepared from the following raw material components: 90 to 95 parts of unsaturated monomer, 3 to 5 parts of functional monomer, 1 to 3 parts of cross-linking agent, 0.1 to 5 parts of emulsifier and 0.1 to 1 part of initiator. The functional monomer is polyoxyethylene 20 oleyl ether acrylate; the cross-linking agent is prepared from an amino alcohol acid reagent and triphenylmethane triisocyanate through a nucleophilic substitution reaction. The thickening agent provided by the invention can improve the shear viscosity of the coating and improve the flowability and leveling property of the coating under the condition of relatively low dosage, has relatively good stability, can avoid the layering phenomenon possibly occurring in the storage process of the coating, and can also solve the sagging problem existing in the use process.

Description

Technical Field

[0001] The invention belongs to the field of coatings and relates to an alkali-soluble thickener and a preparation method and application thereof. Background Art

[0002] As an important chemical additive, thickeners have been widely used in many fields such as coatings, inks, adhesives and cosmetics. Among the many thickeners, alkali-swellable associative thickeners have attracted widespread attention due to their unique thickening mechanism and excellent performance.

[0003] Alkali-swellable thickeners are polymers with carboxyl functional groups obtained by free radical polymerization of ethylene unsaturated monomers. This type of polymer is essentially insoluble in water at low pH values, but will show viscosity-increasing and thickening properties when dissolved or swelled in water under highly ionized conditions. Due to the good thickening ability, rheological adjustment effect and simple application operation (especially emulsions) of alkali-swellable thickeners, they have brought great industrial value, so many alkali-swellable thickener invention patents have been applied for and authorized. Alkali-swellable thickeners are used in latex paints, carpet backings, adhesives, coatings, pesticide products, personal care, household and industrial cleaners, oil field drilling operations, etc.

[0004] CN115160481A discloses a shear-resistant alkali-swellable associative thickener and a preparation method thereof. The associative thickener is prepared by continuous seed emulsion polymerization of the following components in weight: carboxyl acrylate monomer: 7.5-15%; acrylic acid C1-C4 alkyl ester monomer: 10-20%; bifunctional unsaturated vinyl crosslinking monomer: 0.01-0.5%; functional monomer: 0.1-3.0%; acrylamide monomer: 0.5-5.0%; anionic emulsifier: 0.5-1.0%; nonionic emulsifier: 0.1-0.5%; initiator: 0.05-0.5%; and deionized water: the balance. The acrylate thickener emulsion prepared in the application has the characteristics of both thickening efficiency and low thixotropy, but its viscosity after thickening still needs to be improved.

[0005] Therefore, it is still of great significance to develop a new type of alkali-soluble thickener and its preparation method. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention aims to provide an alkali-soluble thickener and a preparation method thereof.

[0007] To achieve this object, the present invention adopts the following technical solutions: One of the objects of the present invention is to provide an alkali-soluble thickener, wherein the raw material components of the alkali-soluble thickener include 90-95 parts by weight of unsaturated monomers (for example, 90 parts by weight, 91 parts by weight, 92 parts by weight, 93 parts by weight, 94 parts by weight, 95 parts by weight, etc.), 3-5 parts by weight of functional monomers (for example, 3 parts by weight, 4 parts by weight, 5 parts by weight, etc.), 1-3 parts by weight of cross-linking agents (for example, 1 part by weight, 2 parts by weight, 3 parts by weight, etc.), 0.1-5 parts by weight of emulsifiers (for example, 0.1 parts by weight, 0.5 parts by weight, 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, etc.), and 0.1-1 parts by weight of initiators (for example, 0.1 parts by weight, 0.2 parts by weight, 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, 1 part by weight, etc.); The functional monomer is polyoxyethylene 20 oleyl ether acrylate; The preparation method of the cross-linking agent comprises: A1. Under the protection of nitrogen, 3-aminoglutaric acid is placed in formic acid to obtain a first solution; A2. Under nitrogen protection, add the chlorobenzene solution of triphenylmethane triisocyanate to the first solution, mix at 30-40°C (e.g., 30°C, 32°C, 35°C, 37°C, 40°C, etc.) for 10-30 min (e.g., 10 min, 15 min, 20 min, 25 min, 30 min, etc.), then add 1,2-dichloroethane, react for 5-10 h, to obtain a second solution; A3. Wash the second solution with ethyl acetate, and vacuum dry at 50-60°C (e.g., 50°C, 52°C, 55°C, 57°C, 60°C, etc.) to obtain a cross-linking agent.

[0008] Preferably, in the first solution in step A1, the concentration of 3-aminoglutaric acid is 2-4 mol / L, for example, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, etc.

[0009] Preferably, the molar ratio of triphenylmethane triisocyanate to 3-aminoglutaric acid in step A2 is 1:(2-4); for example, 1:2, 1:3, 1:4, etc.

[0010] Preferably, based on the added volume of 1,2-dichloroethane in step A2 being 1 L, the molar addition amount of triphenylmethane triisocyanate is 0.1-0.5 mol, for example, 0.1 mol, 0.2 mol, 0.3 mol, 0.4 mol, 0.5 mol, etc.

[0011] The alkali-soluble thickener in the present invention is obtained by emulsion polymerization of unsaturated monomers, specific functional monomers, specific crosslinking agents, emulsifiers and initiators. The thickener of the present invention can increase the shear viscosity of the coating at a relatively low dosage, improve the fluidity and leveling of the coating, and has good stability. It can avoid the stratification phenomenon that may occur in the coating during storage, and solve the sagging problem that exists during use.

[0012] In the present invention, a specific polyoxyethylene 20 oleyl ether acrylate is used as a functional monomer, which contains hydrophilic and hydrophobic amphiphilic chain segments. Through the association and adsorption of hydrophobic groups and hydrophilic groups with other ions, a network structure with a large fluid dynamic volume is formed, which connects different continuous phase or dispersed phase particles, thereby enhancing the low shear structural viscosity and changing the flow characteristics of the coating; in particular, it contains a long alkyl chain, which has good anti-water separation performance while ensuring viscosity and fluidity.

[0013] In the present invention, a specific type of cross-linking agent is used, which is prepared by a nucleophilic substitution reaction of an amino alcohol acid reagent and triphenylmethane triisocyanate. The cross-linking agent has a multi-site structure and can form a stable multi-structure with other particles, thereby increasing the network cross-linking volume, increasing the stability of the cross-linking, and reducing the amount of thickener used. In addition, cyclic rigid groups such as benzene rings are introduced therein, which can cooperate with functional monomers to regulate the curling behavior of molecular chains under polymerization conditions.

[0014] Preferably, the unsaturated monomer is acrylic acid or methacrylic acid.

[0015] Preferably, the preparation method of polyoxyethylene 20 oleyl ether acrylate comprises: B1. Mix polyoxyethylene 20 oleyl ether, triethylamine and dichloromethane at 10-20°C (e.g., 10°C, 12°C, 15°C, 17°C, 20°C, etc.) for 1-3 h (e.g., 1 h, 1.5 h, 2 h, 2.5 h, 3 h, etc.) to obtain a mixed solution; B2. Add dichloromethane and acryloyl chloride to the mixed solution, and react at 15-35°C (e.g., 15°C, 20°C, 25°C, 30°C, 35°C, etc.) for 12-24 h (e.g., 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, etc.) to obtain polyoxyethylene 20 oleyl ether acrylate.

[0016] Preferably, based on the addition amount of polyoxyethylene 20 oleyl ether being 105-125 g, the addition amount of triethylamine described in B1 is 18-25 g (for example, 18 g, 19 g, 20 g, 21 g, 22 g, 23 g, 24 g, 25 g, etc.), and the addition amount of dichloromethane is 200-250 mL (for example, 200 mL, 210 mL, 220 mL, 230 mL, 240 mL, 250 mL, etc.).

[0017] Preferably, based on the addition amount of triethylamine being 18-25 g (e.g., 18 g, 19 g, 20 g, 21 g, 22 g, 23 g, 24 g, 25 g, etc.), the addition amount of acryloyl chloride described in B2 is 32-40 g, and the addition amount of dichloromethane is 100-120 mL (e.g., 100 mL, 105 mL, 110 mL, 115 mL, 120 mL, etc.).

[0018] Preferably, the emulsifier is any one of polyoxyethylene ether sulfate, alkyl sulfate or alkylbenzene sulfonate.

[0019] Preferably, the initiator is any one of ammonium persulfate, sodium persulfate or potassium persulfate.

[0020] The second object of the present invention is to provide a method for preparing the alkali-soluble thickener as described in the first object, the preparation method comprising the following steps: (1) adding 20-30% (e.g., 20%, 22%, 25%, 28%, 30%, etc.) of an emulsifier into water to prepare an emulsion, and then adding an unsaturated monomer, a functional monomer and a cross-linking agent to mix to obtain a mixed solution 1; (2) adding the remaining 70-80% (e.g., 70%, 72%, 75%, 78%, 80%, etc.) of the emulsifier into water to prepare an emulsion, and then adding the initiator to obtain a mixed solution 2; (3) Mixed solution 1 and mixed solution 2 are mixed and reacted to obtain an alkali-soluble thickener.

[0021] Preferably, the mixing temperature in step (1) is 60-80°C (e.g., 60°C, 65°C, 70°C, 75°C, 80°C, etc.), and the mixing time is 1-5 h (e.g., 1 h, 2 h, 3 h, 4 h, 5 h, etc.).

[0022] The temperature of the mixed reaction in step (3) is 60-80°C (e.g., 60°C, 65°C, 70°C, 75°C, 80°C, etc.), and the time of the mixed reaction is 1-2 h (e.g., 1 h, 1.2 h, 1.5 h, 1.8 h, 2 h, etc.).

[0023] The third object of the present invention is to provide an application of the alkali-soluble thickener as described in the first object in coatings.

[0024] Compared with the prior art, the present invention has at least the following beneficial effects: The alkali-soluble thickener in the present invention is obtained by emulsion polymerization of unsaturated monomers, specific functional monomers, specific crosslinking agents, emulsifiers and initiators. The thickener of the present invention can increase the shear viscosity of the coating at a relatively low dosage, improve the fluidity and leveling of the coating, and has good stability. It can avoid the stratification phenomenon that may occur in the coating during storage, and solve the sagging problem that exists during use.

[0025] In the present invention, a specific polyoxyethylene 20 oleyl ether acrylate is used as a functional monomer, which contains hydrophilic and hydrophobic amphiphilic chain segments. Through the association and adsorption of hydrophobic groups and hydrophilic groups with other ions, a network structure with a large fluid dynamic volume is formed, which connects different continuous phase or dispersed phase particles, thereby enhancing the low shear structural viscosity and changing the flow characteristics of the coating; in particular, it contains a long alkyl chain, which has good anti-water separation performance while ensuring viscosity and fluidity.

[0026] In the present invention, a specific type of cross-linking agent is used, which is prepared by a nucleophilic substitution reaction of an amino alcohol acid reagent and triphenylmethane triisocyanate. The cross-linking agent has a multi-site structure and can form a stable multi-structure with other particles, thereby increasing the network cross-linking volume, increasing the stability of the cross-linking, and reducing the amount of thickener used. In addition, cyclic rigid groups such as benzene rings are introduced therein, which can cooperate with functional monomers to regulate the curling behavior of molecular chains under polymerization conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the structure of the cross-linking agent prepared in Preparation Example 1 of the present invention; Figure 2 The water distribution of the thickener prepared in Example 1 of the present invention after being placed at different temperatures for 30 days; Figure 3 The water separation of the thickener prepared in Comparative Example 3 of the present invention after being placed at 25°C for 30 days; Figure 4 This is the water separation of the thickener prepared in Comparative Example 3 of the present invention after being placed at 50° C. for 30 days. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments recorded herein are specific embodiments of the present invention, which are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limitations on the embodiments of the present invention and the scope of protection of the present invention. In addition to the embodiments recorded herein, those skilled in the art can also adopt other obvious technical solutions based on the contents disclosed in the claims of this application and its specification, including technical solutions that adopt any obvious replacements and modifications to the embodiments recorded herein.

[0029] The raw materials used in the preparation of the cross-linking agent, triphenylmethane triisocyanate, 2-amino-1,3-propanediol, 3-aminoglutaric acid, and L-threonine, were all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., and the solvents, formic acid, 1,2-dichloroethane, and ethyl acetate, were all purchased from Shanghai Sinopharm Chemical Reagent Co., Ltd.

[0030] The raw materials used in the preparation of polyoxyethylene 20 oleyl ether acrylate, polyoxyethylene 20 oleyl ether, triethylamine, dichloromethane, and acryloyl chloride were all purchased from Merck Life Sciences Ltd.

[0031] Acrylic acid, ammonium persulfate and sodium persulfate used in the preparation of alkali-soluble thickeners were purchased from Merck Life Sciences Ltd., polyoxyethylene ether sulfate sodium salt was purchased from Gaide Chemical Co., Ltd., and ethoxylated alkyl sulfate sodium salt was purchased from China Light Industry Co., Ltd.

[0032] Preparation Example 1 This preparation example provides a method for preparing a cross-linking agent, comprising: (1) Under nitrogen protection and stirring conditions, 0.03 mol of 3-aminoglutaric acid was dissolved in 10 mL of formic acid to obtain a first solution; (2) Under nitrogen protection and stirring conditions, triphenylmethane triisocyanate solution (20wt% chlorobenzene solution, wherein the amount of triphenylmethane triisocyanate is 0.01 mol) is slowly dripped into the first solution. After complete dissolution under continuous magnetic stirring, 60 mL of 1,2-dichloroethane is added dropwise under 35°C water bath conditions, nitrogen protection, and stirring conditions to carry out nucleophilic substitution reaction between isocyanate group and amino group to generate urea group. The reaction is stirred for 5 hours under nitrogen protection to obtain a second solution; (3) The second solution is washed with ethyl acetate, dried under vacuum at 50° C., and then ground to obtain a cross-linking agent.

[0033] Figure 1 The structure of the cross-linking agent prepared in Preparation Example 2 shows that it has 6 binding sites and can be effectively cross-linked with other particles.

[0034] Preparation Example 2 This preparation example provides a preparation method of polyoxyethylene 20 oleyl ether acrylate, comprising: (1) Add 115 g of polyoxyethylene 20 oleyl ether and 20.4 g of triethylamine into a three-necked flask containing 200 mL of dichloromethane and stir at 200 r / min for 2 h at 10 °C; (2) 100 mL of dichloromethane and 36 g of acryloyl chloride were placed in a dropping funnel and added dropwise to a three-necked flask at a rate of 60 d / min. The mixture was stirred for 5 h at 10 °C and then reacted at 25 °C for 12 h. After the reaction, triethylamine hydrochloride was removed by vacuum filtration using a G4 sand core funnel (pressure of -0.1 MPa, time of 30 min), and dichloromethane was removed by rotary evaporation at a speed of 100 r / min. The rotary evaporation product was precipitated with 200 mL of ether and allowed to stand for 3 h. The triethylamine hydrochloride precipitate was then filtered using a G4 sand core funnel and the ether was removed by rotary evaporation. The purified product was light yellow and was vacuum dried at 25 °C and vacuum degree of -0.6 MPa for 48 h to obtain polyoxyethylene 20 oleyl ether acrylate.

[0035] Example 1

[0036] This embodiment provides an alkali-soluble thickener, and its raw material composition is as follows: 95 parts of unsaturated monomer acrylic acid, 4 parts of functional monomer polyoxyethylene 20 oleyl ether acrylate, 2 parts of crosslinking agent, 3 parts of emulsifier polyoxyethylene ether sulfate sodium salt, 0.5 parts of initiator ammonium persulfate; Wherein, the functional monomer and the cross-linking agent are both obtained through Preparation Example 1 and Preparation Example 2.

[0037] This embodiment also provides a method for preparing an alkali-soluble thickener, comprising: (1) Under stirring conditions, 25% of an emulsifier was added to water to prepare an emulsion (concentration of 15%), and then an unsaturated monomer, a functional monomer and a cross-linking agent were added and mixed at 70°C for 3 h to obtain a mixed solution 1; (2) Under stirring conditions, the remaining 75% of the emulsifier is added to water to prepare an emulsion (concentration is 2%), and then the initiator is added to obtain a mixed solution 2; (3) Mixture 1 and mixture 2 were mixed and reacted at 70° C. for 1.5 h under stirring to obtain an alkali-soluble thickener.

[0038] Example 2

[0039] This embodiment provides an alkali-soluble thickener, and its raw material composition is as follows: 90 parts of unsaturated monomer acrylic acid, 3 parts of functional monomer polyoxyethylene 20 oleyl ether acrylate, 1 part of crosslinking agent, 0.1 parts of emulsifier polyoxyethylene ether sulfate, and 0.1 parts of initiator ammonium persulfate; Wherein, the functional monomer and the cross-linking agent are both obtained through Preparation Example 1 and Preparation Example 2.

[0040] This embodiment also provides a method for preparing an alkali-soluble thickener, comprising: (1) Under stirring conditions, 20% of an emulsifier was added to water to prepare an emulsion (concentration of 15%), and then an unsaturated monomer, a functional monomer and a cross-linking agent were added and mixed at 60°C for 5 h to obtain a mixed solution 1; (2) Under stirring conditions, the remaining 80% of the emulsifier is added to water to prepare an emulsion (concentration is 2%), and then the initiator is added to obtain a mixed solution 2; (3) Mixture 1 and mixture 2 were mixed and reacted at 60° C. for 2 h under stirring to obtain an alkali-soluble thickener.

[0041] Example 3

[0042] This embodiment provides an alkali-soluble thickener, and its raw material composition is as follows: 95 parts of unsaturated monomer acrylic acid, 5 parts of functional monomer polyoxyethylene 20 oleyl ether acrylate, 3 parts of crosslinking agent, 5 parts of emulsifier polyoxyethylene ether sulfate, 1 part of initiator ammonium persulfate; Wherein, the functional monomer and the cross-linking agent are both obtained through Preparation Example 1 and Preparation Example 2.

[0043] This embodiment also provides a method for preparing an alkali-soluble thickener, comprising: (1) Under stirring conditions, 30% of an emulsifier was added to water to prepare an emulsion (concentration of 15%), and then an unsaturated monomer, a functional monomer and a cross-linking agent were added and mixed at 80°C for 1 h to obtain a mixed solution 1; (2) Under stirring conditions, the remaining 70% of the emulsifier is added to water to prepare an emulsion (concentration is 2%), and then the initiator is added to obtain a mixed solution 2; (3) Mixture 1 and mixture 2 were mixed and reacted at 80° C. for 1 h under stirring to obtain an alkali-soluble thickener.

[0044] Example 4

[0045] The difference from Example 1 is that the emulsifier is ethoxylated alkyl sulfate sodium salt.

[0046] Example 5

[0047] The difference from Example 1 is that the initiator is sodium persulfate.

[0048] The alkali-soluble thickeners obtained in Examples 1-5 were tested, and it was found that the solid content was 29-31%, the pH was 2-3.5, and the viscosity was less than 50 mPa·s.

[0049] Comparative Example 1 The only difference from Example 1 is that no functional monomer is included.

[0050] Comparative Example 2 The only difference from Example 1 is that no crosslinking agent is included.

[0051] Comparative Example 3 The only difference from Example 1 is that the cross-linking agent is replaced by a conventional cross-linking agent, diallyl phthalate.

[0052] Comparative Example 4 The only difference from Example 1 is that the functional monomer is replaced by acrylic acid ester.

[0053] Test Method The thickeners obtained in Examples 1-5 and Comparative Examples 1-4 were subjected to emulsion thickening tests: the thickening property was tested in styrene-acrylic emulsion 998A (Brookfield viscosity of 1200 mPa·s, 3#60r, solid content of 48%), the dilution ratio of styrene-acrylic emulsion to water was 1:2, the pH was adjusted to 8.5-9.0 with Amp-95, the amount of thickener added was 2%, the shear viscosity was 60 KU with a Stormer viscometer (test method: in accordance with GB / T9269-2009 Stormer viscometer method for determination of coating viscosity), and the rotational viscosity was tested with a Brookfield DV-S viscometer, see Table 1: Table 1 Performance test results of thickeners obtained from Examples 1-5 and Comparative Examples 1-4

[0054] By comparing Examples 1-5 and Comparative Examples 1-4, it can be seen that when the technical solution of the present application is adopted, the obtained thickener has good shear viscosity and rotational viscosity; when the thickener raw material does not include a functional monomer or a cross-linking agent, the shear viscosity and rotational viscosity of the obtained thickener will be greatly reduced; when the thickener raw material does not select the functional monomer or cross-linking agent specified in the present application, the shear viscosity and rotational viscosity of the obtained thickener will also be greatly reduced.

[0055] The thickeners obtained in Examples 1-5 and Comparative Examples 1-4 were subjected to emulsion thickening stability tests. It was found that after the thickeners prepared in Examples 1-5 were subjected to emulsion thickening, they were placed at 4°C, 25°C and 50°C for 30 days, respectively. Figure 2After the thickener obtained in Example 1 was subjected to emulsion thickening, it was found that no stratification occurred when placed at 4°C, 25°C and 50°C for 30 days; similarly, it was found that no stratification occurred when Examples 2-5 were placed at 4°C, 25°C and 50°C for 30 days; and after the thickeners prepared in Comparative Examples 1-4 were subjected to emulsion thickening, they were placed at 4°C, 25°C and 50°C for 30 days, respectively, and it was found that at 25°C, Comparative Examples 1-2 showed obvious stratification, and Comparative Examples 3-4 showed slight stratification ( Figure 3 The thickener prepared in Comparative Example 3 was placed at 25°C for 30 days, and slight stratification was found. At 4°C and 50°C, Comparative Examples 1-4 all showed obvious stratification ( Figure 4 The thickener prepared in Comparative Example 3 was placed at 50°C for 30 days and showed obvious stratification.

[0056] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. An alkali-soluble thickener, characterized in that: The raw material components of the alkali-soluble thickener include 90-95 parts by weight of unsaturated monomer, 3-5 parts by weight of functional monomer, 1-3 parts by weight of crosslinking agent, 0.1-5 parts by weight of emulsifier, and 0.1-1 parts by weight of initiator; The functional monomer is polyoxyethylene 20 oleyl ether acrylate; The preparation method of the cross-linking agent comprises: A1. Under the protection of nitrogen, 3-aminoglutaric acid is placed in formic acid to obtain a first solution; A2. Under nitrogen protection, add the chlorobenzene solution of triphenylmethane triisocyanate to the first solution, mix at 30-40° C. for 10-30 min, then add 1,2-dichloroethane, and react for 5-10 h to obtain a second solution; A3. Wash the second solution with ethyl acetate and dry it in vacuo at 50-60°C to obtain a cross-linking agent.

2. The alkali-soluble thickener according to claim 1, characterized in that Step A1: In the first solution, the concentration of 3-aminoglutaric acid is 2-4 mol / L; The molar ratio of triphenylmethane triisocyanate to 3-aminoglutaric acid in step A2 is 1:(2-4); Based on the added volume of 1,2-dichloroethane in step A2 being 1 L, the molar amount of triphenylmethane triisocyanate added is 0.1-0.5 mol.

3. The alkali-soluble thickener according to claim 1, characterized in that The unsaturated monomer is acrylic acid or methacrylic acid.

4. The alkali-soluble thickener according to claim 1, characterized in that The preparation method of polyoxyethylene 20 oleyl ether acrylate comprises: B1. Mix polyoxyethylene 20 oleyl ether, triethylamine and dichloromethane at 10-20° C. for 1-3 h to obtain a mixed solution; B2. Add dichloromethane and acryloyl chloride to the mixed solution and react at 15-35°C for 12-24 h to obtain polyoxyethylene 20 oleyl ether acrylate.

5. The alkali-soluble thickener according to claim 4, characterized in that Based on the addition amount of polyoxyethylene 20 oleyl ether being 105-125 g, the addition amount of triethylamine in B1 is 18-25 g, and the addition amount of dichloromethane is 200-250 mL; Based on the addition amount of triethylamine being 18-25 g, the addition amount of acryloyl chloride in B2 is 32-40 g, and the addition amount of dichloromethane is 100-120 mL.

6. The alkali-soluble thickener according to claim 1, characterized in that The emulsifier is any one of polyoxyethylene ether sulfate, alkyl sulfate or alkyl benzene sulfonate.

7. The alkali-soluble thickener according to claim 1, characterized in that The initiator is any one of ammonium persulfate, sodium persulfate or potassium persulfate.

8. The method for preparing an alkali-soluble thickener according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: (1) 20-30% of an emulsifier is added to water to prepare an emulsion, and then an unsaturated monomer, a functional monomer and a cross-linking agent are added and mixed to obtain a mixed solution 1; (2) adding the remaining 70-80% of the emulsifier into water to prepare an emulsion, and then adding the initiator to obtain a mixed solution 2; (3) Mixed solution 1 and mixed solution 2 are mixed and reacted to obtain an alkali-soluble thickener.

9. The method for preparing an alkali-soluble thickener according to claim 8, characterized in that: The mixing temperature in step (1) is 60-80°C and the mixing time is 1-5 h; The temperature of the mixed reaction in step (3) is 60-80° C., and the time of the mixed reaction is 1-2 h.

10. Use of the alkali-soluble thickener according to any one of claims 1 to 7 in coatings.

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