Phosphate ester aqueous polymer and preparation method therefor and use thereof

Abstract

The present application provides a phosphate ester aqueous polymer, and a preparation method therefor and a use thereof. The phosphate ester aqueous polymer is prepared by polymerizing the following monomers: a monovinyl ether, a vinylbenzene monomer, an allyl polyoxyethylene methyl-terminated polyether, and phosphorus pentoxide. The phosphate ester aqueous polymer of the present application can be used for dispersion of aqueous nano titanium dioxide, and can prepare a titanium dioxide dispersion liquid having low particle size, narrow distribution, and good stability.

Description

A waterborne polymer based on phosphate esters, its preparation method and application Technical Field

[0001] This application belongs to the field of polymer materials technology, and relates to a phosphate ester aqueous polymer, its preparation method and application. Background Technology

[0002] Dispersants, as pigment dispersing aids, possess properties such as reducing pigment particle size, increasing coating gloss, improving leveling, and enhancing the color and hiding power of coatings. They are essential raw materials in coating production. Traditional dispersants are typically low-molecular-weight surfactants with relatively simple molecular structures and few anchoring groups. This structure makes it difficult to provide stable adsorption capacity and steric hindrance effect on the pigment particle surface. Superdispersants, on the other hand, are high-molecular-weight dispersants with more complex molecular structures, containing multiple and various types of anchoring groups and abundant solvation segments. They can provide stable adsorption capacity on the pigment particle surface and corresponding steric protection effect, forming a stable protective layer and effectively preventing pigment particle aggregation and sedimentation.

[0003] Phosphate ester groups, as ionic groups with a unique structure, possess both hydrophilic and hydrophobic properties. When phosphate ester groups come into contact with a solid surface, their hydrophilic groups adhere to the solid surface, while the hydrophobic groups extend outwards into the liquid, thereby reducing the surface tension of the liquid and making it easier for the liquid to spread on the solid surface, forming a uniform coating. As a polymer dispersant containing phosphate groups, its unique structure enables polymers to possess excellent wetting, emulsifying, and solubilizing properties. It effectively improves the dispersibility of pigments, increases the uniformity of materials, prevents particle aggregation, and enhances the stability of materials.

[0004] Therefore, a polymer dispersant containing phosphate ester groups has been developed, which has broad application prospects in the coatings field. Summary of the Invention

[0005] This application provides a phosphate ester-based aqueous polymer, its preparation method, and its application.

[0006] In a first aspect, this application provides a phosphate ester-based aqueous polymer, which is prepared by polymerization of the following monomers: monovinyl ether, vinylbenzene monomer, allyl polyoxyethylene methyl-terminated polyether, and phosphorus pentoxide.

[0007] The phosphate ester-based aqueous polymer of this application can be used for the dispersion of aqueous nano-titanium dioxide, and can prepare titanium dioxide dispersions with low particle size, narrow distribution and good stability.

[0008] Preferably, the molar ratio of the monovinyl ether, vinylbenzene, allyl polyoxyethylene methyl-terminated polyether, and phosphorus pentoxide is (1-2):(2-5):(3-5):(2-3). In this application, the molar ratio of the monovinyl ether (1-2) can be 1, 1.2, 1.4, 1.6, 1.8, or 2; the molar ratio of the vinylbenzene (2-5) can be 2, 2.3, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.3, 4.5, 4.8, or 5; the molar ratio of the allyl polyoxyethylene methyl-terminated polyether (3-5) can be 3, 3.3, 3.5, 3.8, 4, 4.3, 4.5, 4.8, or 5; and the molar ratio of the phosphorus pentoxide (2-3) can be 2, 2.3, 2.5, 2.8, or 3.

[0009] Preferably, the monovinyl ether is selected from one or a combination of at least two of ethylene glycol monovinyl ether, diethylene glycol monovinyl ether, or 4-hydroxybutylvinyl ether.

[0010] Preferably, the vinylbenzene monomer is selected from one or a combination of at least two of styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene or α-methylstyrene.

[0011] Preferably, the allyl polyoxyethylene methyl-terminated polyether has the following general formula: CH2=CHCH2O(CH2CH2O) n CH3, where n is an integer from 4 to 20 (e.g., 4, 6, 8, 10, 12, 15, 18 or 20, etc.).

[0012] Preferably, the polymerization is carried out under the initiation of an initiator.

[0013] Preferably, the initiator is selected from azo initiators.

[0014] Preferably, the amount of the azo initiator is 2-10% of the total mass of the monovinyl ether, vinylbenzene monomer and allyl polyoxyethylene methyl-terminated polyether, such as 2%, 3%, 5%, 8% or 10%.

[0015] Preferably, the azo initiator is selected from one or a combination of at least two of azobisisobutyronitrile, azobisisoheptanenitrile, azobisisovalerate, or dimethyl azobisisobutyrate.

[0016] Preferably, the weight-average molecular weight of the phosphate ester aqueous polymer is 5000–20000 g / mol, for example 5000 g / mol, 6000 g / mol, 7000 g / mol, 8000 g / mol, 9000 g / mol, 10000 g / mol, 12000 g / mol, 14000 g / mol, 16000 g / mol, 18000 g / mol, or 20000 g / mol.

[0017] In this application, the polymer molecular weight was determined by gel permeation chromatography (GPC) using polyethylene oxide as the calibration standard and a water / acetonitrile mixture as the eluent.

[0018] Secondly, this application provides a method for preparing the phosphate ester aqueous polymer as described above, the preparation method comprising the following steps:

[0019] (1) Mix monovinyl ether, vinylbenzene and part of allyl polyoxyethylene methyl-terminated polyether to obtain mixture A, and dissolve the initiator in the solvent to obtain mixture B;

[0020] (2) Mix mixture A and mixture B and the remaining allyl polyoxyethylene methyl-terminated polyether and react to obtain intermediate polymer;

[0021] (3) Add phosphorus pentoxide to the system containing intermediate polymer obtained in step (2) and react to obtain the phosphate ester aqueous polymer.

[0022] Preferably, the portion of allyl polyoxyethylene methyl-terminated polyether in step (1) is 40-60% of the total mass of allyl polyoxyethylene methyl-terminated polyether, for example, 40%, 43%, 45%, 48%, 50%, 53%, 55%, 58% or 60%.

[0023] In this application, by reacting the monovinyl ether, vinylbenzene and a portion of allyl polyoxyethylene methyl-terminated polyether in step (1), and then reacting the mixture A and mixture B with the remaining allyl polyoxyethylene methyl-terminated polyether, the molecular weight of the polymer can be better controlled, and the copolymerization rate of the polymer can be adjusted, so that the polymer rate is controllable, the polymerization product has good uniformity, and the reaction is prevented from being too fast and the polymer molecular weight is too high.

[0024] Preferably, the initiator in step (1) is selected from azo initiators.

[0025] Preferably, the amount of the azo initiator is 2-10% of the total mass of the monovinyl ether, vinylbenzene monomer and allyl polyoxyethylene methyl-terminated polyether, such as 2%, 3%, 5%, 8% or 10%.

[0026] Preferably, the azo initiator is selected from one or a combination of at least two of azobisisobutyronitrile, azobisisoheptanenitrile, azobisisovalerate, or dimethyl azobisisobutyrate.

[0027] Preferably, the solvent in step (1) is selected from one or a combination of at least two of ethylene glycol dimethyl ether, ethylene glycol dipropyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether or tetraethylene glycol dimethyl ether.

[0028] Preferably, in step (2), mixture A and mixture B are simultaneously added to the remaining allyl polyoxyethylene methyl-terminated polyether and mixed to carry out the reaction.

[0029] Preferably, the addition is done by dripping.

[0030] Preferably, the dripping is completed within 1 to 4 hours (e.g., 1 hour, 1.3 hours, 1.5 hours, 1.8 hours, 2 hours, 2.3 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours).

[0031] Preferably, before mixing in step (2), the remaining allyl polyoxyethylene methyl-terminated polyether is heated to 60-100°C (e.g., 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C), and then mixed solution A and mixed solution B are added while stirring.

[0032] Preferably, the reaction temperature in step (2) is 60 to 100°C, for example 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C, and the reaction time is 1 to 3 hours, for example 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours.

[0033] Preferably, in step (3), the temperature is controlled at 50-100°C (e.g., 50°C, 60°C, 70°C, 80°C, 90°C or 100°C), phosphorus pentoxide is added to the system containing intermediate polymer obtained in step (2), and then the reaction is kept at this temperature for 3-10 hours (e.g., 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours).

[0034] Preferably, the phosphorus pentoxide is added to the system in batches and evenly over a period of 1 to 3 hours (e.g., 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours).

[0035] Thirdly, this application provides an aqueous nano-titanium dioxide dispersion, wherein the aqueous nano-titanium dioxide dispersion includes a dispersant, and the dispersant is an aqueous polymer of phosphate ester as described above.

[0036] In this application, phosphate ester-based aqueous polymers are used as dispersants for aqueous nano-titanium dioxide, which can yield titanium dioxide dispersions with low particle size, narrow distribution, and good stability.

[0037] Compared with the prior art, this application has the following advantages:

[0038] The phosphate ester-based aqueous polymer of this application can be used for the dispersion of aqueous nano-titanium dioxide, and can prepare titanium dioxide dispersions with low particle size, narrow distribution and good stability. Detailed Implementation

[0039] The technical solution of this application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely to help understand this application and should not be regarded as specific limitations on this application.

[0040] Example 1

[0041] This embodiment provides a phosphate ester-based aqueous polymer, the preparation method of which includes the following steps:

[0042] Step 1: Mix 88g of ethylene glycol monovinyl ether, 210g of styrene and 800g of allyl polyoxyethylene methyl-terminated polyether (Mw: 500g / mol) (Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.) evenly to obtain mixture A; dissolve 37g of azobisisobutyronitrile in 185g of ethylene glycol dimethyl ether to obtain mixture B.

[0043] Step 2: Add 800g of allyl polyoxyethylene methyl-terminated polyether (Mw: 500g / mol) to a reaction flask with stirring, temperature control, and condensation. After heating to 60℃, while stirring, add mixtures A and B dropwise to the flask simultaneously over 2 hours. After the addition is complete, keep the temperature for 1.5 hours to obtain the intermediate polymer.

[0044] Step 3: Control the reaction temperature to 50℃, and add 284g of phosphorus pentoxide into the flask in batches evenly over 1 hour according to the ratio; after the addition is complete, keep the temperature and react for 3 hours (take samples every ten minutes to measure the acid value change difference <5mgKOH / g, which is regarded as the reaction endpoint), to obtain the final phosphate ester waterborne polymer dispersant.

[0045] The molecular weights of the polymers were determined by gel permeation chromatography (GPC) using polyethylene oxide as the calibration standard and a water / acetonitrile mixture as the eluent, with a weight-average molecular weight of 19357 g / mol.

[0046] Example 2

[0047] Step 1: Mix 132g of ethylene glycol monovinyl ether, 312g of styrene and 850g of allyl polyoxyethylene methyl-terminated polyether (Mw: 350g / mol) (Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.) evenly to obtain mixture A; dissolve 260g of azobisisovalerate in 2300g of diethylene glycol dimethyl ether solvent to obtain mixture B.

[0048] Step 2: Add the remaining 850g of allyl polyoxyethylene methyl-terminated polyether (Mw: 350g / mol) to a reaction flask that is stirred, temperature controlled, and condensed. After heating to 90℃, while stirring, add mixtures A and B dropwise to the flask simultaneously over 4 hours. After the addition is complete, keep the temperature for 3 hours to obtain the intermediate polymer.

[0049] Step 3: Control the reaction temperature at 100℃, and add 220g of phosphorus pentoxide into the flask in batches evenly over 3 hours according to the ratio; after the addition is complete, keep the temperature for 10 hours (take samples every ten minutes to measure the acid value change difference <5mgKOH / g, which is regarded as the reaction endpoint), and obtain the final phosphate ester waterborne polymer dispersant.

[0050] The molecular weight of the polymers was determined by gel permeation chromatography (GPC) using polyethylene oxide as the calibration standard and a water / acetonitrile mixture as the eluent. The weight-average molecular weight was 7584 g / mol.

[0051] Example 3

[0052] Step 1: Mix 233g of 4-hydroxybutyl vinyl ether, 591g of 2-methylstyrene and 750g of allyl polyoxyethylene methyl-terminated polyether (Mw: 500g / mol) (Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.) evenly to obtain mixture A; dissolve 450g of azobisisoheptanenitrile in 4500g of tetraethylene glycol dimethyl ether solvent to obtain mixture B.

[0053] Step 2: Add 750g of allyl polyoxyethylene methyl-terminated polyether (Mw: 500g / mol) to a reaction flask with stirring, temperature control, and condensation. After heating to 100℃, while stirring, add mixtures A and B dropwise to the flask simultaneously over 4 hours. After the addition is complete, keep the temperature for 1 hour to obtain the intermediate polymer.

[0054] Step 3: Control the reaction temperature at 100℃, and add phosphorus pentoxide into the flask in batches evenly within 1 hour according to the ratio; after the addition is complete, keep the temperature for 3 hours, and take samples every ten minutes to measure the acid value change. If the difference is <5mgKOH / g, it is considered as the reaction endpoint, and the final phosphate ester waterborne polymer dispersant is obtained.

[0055] The molecular weights of the polymers were determined by gel permeation chromatography (GPC) using polyethylene oxide as the calibration standard and a water / acetonitrile mixture as the eluent, with a weight-average molecular weight of 10553 g / mol.

[0056] Example 4

[0057] This embodiment provides a phosphate ester-based aqueous polymer, the preparation method of which includes the following steps:

[0058] Step 1: Mix 260g of diethylene glycol monovinyl ether, 472g of α-methylstyrene and 1000g of allyl polyoxyethylene methyl-terminated polyether (Mw: 500g / mol) (Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.) evenly to obtain mixture A; dissolve 283g of azobisisoheptanenitrile in 2000g of ethylene glycol dipropyl ether solvent to obtain mixture B.

[0059] Step 2: Add the remaining 1000g of allyl polyoxyethylene methyl-terminated polyether (Mw: 500g / mol) to a reaction flask with stirring, temperature control, and condensation. After heating to 90℃, while stirring, add mixtures A and B dropwise to the flask simultaneously over 2 hours. After the addition is complete, keep the temperature for 2 hours to obtain the intermediate polymer.

[0060] Step 3: Control the reaction temperature to 80℃, and add phosphorus pentoxide into the flask in batches over 2.5 hours according to the ratio; after the addition is complete, keep the reaction at the temperature for 5 hours, and take samples every ten minutes to measure the acid value change. If the difference is <5mgKOH / g, it is considered the reaction endpoint, and the final phosphate ester waterborne polymer dispersant is obtained.

[0061] The molecular weights of the polymers were determined by gel permeation chromatography (GPC) using polyethylene oxide as the calibration standard and a water / acetonitrile mixture as the eluent, with a weight-average molecular weight of 14691 g / mol.

[0062] Comparative Example 1

[0063] The only difference from Example 1 is that styrene monomer was not included in the preparation, and the weight-average molecular weight of the polymer obtained was 17891 g / mol.

[0064] Comparative Example 2

[0065] The only difference from Example 1 is that the ethylene glycol monovinyl ether is replaced with an equimolar amount of ethyl vinyl ether, and the resulting polymer has a weight-average molecular weight of 15493 g / mol.

[0066] Comparative Example 3

[0067] The only difference from Example 1 is that the styrene was replaced with an equimolar amount of 2-vinylnaphthalene, and the resulting polymer had a weight-average molecular weight of 11583 g / mol.

[0068] Comparative Example 4

[0069] The only difference from Example 1 is that allyl polyoxyethylene methyl-terminated polyether (Mw: 500 g / mol) was not included in the preparation, and the weight-average molecular weight of the polymer obtained was 8754 g / mol.

[0070] Comparative Example 5

[0071] The only difference from Example 1 is that the amount of ethylene glycol monovinyl ether added in the preparation is 20g, and the weight-average molecular weight of the polymer obtained is 13532g / mol.

[0072] Comparative Example 6

[0073] The only difference from Example 1 is that the amount of phosphorus pentoxide added in the preparation is 74g, and the weight-average molecular weight of the polymer obtained is 17834g / mol.

[0074] Test case

[0075] The polymers obtained in the examples and comparative examples were used for the dispersion of aqueous nano-titanium dioxide.

[0076] Using a laboratory sand mill, 100 parts of the slurry formulation were prepared, and the polymer dispersant, pH stabilizer monoethanolamine, and 20nm-nano titanium dioxide were added sequentially according to the proportions of Examples 1-4 and Comparative Examples 1-4. After stirring evenly, 200g of zirconium beads with a particle size of 1-1.2mm were added and sealed in a glass jar. The mixture was shaken for 10 hours and then filtered to obtain the color paste. The viscosity, particle size, and storage stability of the color paste were tested.

[0077] The formula is shown in Table 1 below.

[0078] Table 1

[0079] 1. Particle size: Tested using a BT-90 laser particle size analyzer, Dandong Better Instruments Co., Ltd.

[0080] 2. Storage stability: After storing at 55℃ for 7 days, the change in particle size was detected.

[0081] The specific test results are shown in Table 2 below.

[0082] Table 2

[0083] As can be seen from the test results above, the phosphate ester aqueous polymer prepared in this application can be used as a dispersant for aqueous nano-titanium dioxide to obtain a titanium dioxide dispersion with low particle size, narrow distribution and good stability.

[0084] The applicant declares that this application illustrates the phosphate ester-based aqueous polymer, its preparation method, and its application through the above embodiments. However, this application is not limited to the above embodiments, meaning that this application does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this application, equivalent substitutions of raw materials for the product, addition of auxiliary components, and selection of specific methods, etc., all fall within the protection and disclosure scope of this application.

[0085] 1. A phosphate ester-based aqueous polymer, prepared by polymerization of the following monomers: monovinyl ether, vinylbenzene monomer, allyl polyoxyethylene methyl-terminated polyether, and phosphorus pentoxide.

[0086] 2. The phosphate ester aqueous polymer according to claim 1, wherein the molar ratio of the monovinyl ether, vinylbenzene, allyl polyoxyethylene methyl-terminated polyether, and phosphorus pentoxide is (1-2):(2-5):(3-5):(2-3).

[0087] 3. The phosphate ester aqueous polymer according to claim 1 or 2, wherein the monovinyl ether is selected from one or a combination of at least two of ethylene glycol monovinyl ether, diethylene glycol monovinyl ether, and 4-hydroxybutylvinyl ether;

[0088] Preferably, the vinylbenzene monomer is selected from one or a combination of at least two of styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene or α-methylstyrene;

[0089] Preferably, the allyl polyoxyethylene methyl-terminated polyether has the following general formula: CH2=CHCH2O(CH2CH2O) n CH3, where n is an integer from 4 to 20.

[0090] 4. The aqueous phosphate polymer according to any one of claims 1-3, wherein the polymerization is carried out under the initiation of an initiator;

[0091] Preferably, the initiator is selected from azo initiators;

[0092] Preferably, the amount of the azo initiator is 2-10% of the total mass of the monovinyl ether, vinylbenzene monomer, and allyl polyoxyethylene methyl-terminated polyether;

[0093] Preferably, the azo initiator is selected from one or a combination of at least two of azobisisobutyronitrile, azobisisoheptanenitrile, azobisisovalerate, or dimethyl azobisisobutyrate.

[0094] 5. The aqueous phosphate polymer according to any one of claims 1-4, wherein the weight-average molecular weight of the aqueous phosphate polymer is 5000-20000 g / mol.

[0095] 6. A method for preparing a phosphate ester aqueous polymer according to any one of claims 1-5, comprising the following steps:

[0096] (1) Mix monovinyl ether, vinylbenzene and part of allyl polyoxyethylene methyl-terminated polyether to obtain mixture A, and dissolve the initiator in the solvent to obtain mixture B;

[0097] (2) Mix mixture A and mixture B and the remaining allyl polyoxyethylene methyl-terminated polyether and react to obtain intermediate polymer;

[0098] (3) Add phosphorus pentoxide to the system containing intermediate polymer obtained in step (2) and react to obtain the phosphate ester aqueous polymer.

[0099] 7. The preparation method according to claim 6, wherein the portion of allyl polyoxyethylene methyl-terminated polyether in step (1) is 40-60% of the total mass of allyl polyoxyethylene methyl-terminated polyether.

[0100] 8. The preparation method according to claim 6, wherein the initiator in step (1) is selected from azo initiators;

[0101] Preferably, the amount of the azo initiator is 2-10% of the total mass of the monovinyl ether, vinylbenzene monomer, and allyl polyoxyethylene methyl-terminated polyether;

[0102] Preferably, the azo initiator is selected from one or a combination of at least two of azobisisobutyronitrile, azobisisoheptanenitrile, azobisisovalerate, or dimethyl azobisisobutyrate.

[0103] 9. The preparation method according to claim 6, wherein the solvent in step (1) is selected from one or a combination of at least two of ethylene glycol dimethyl ether, ethylene glycol dipropyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether or tetraethylene glycol dimethyl ether;

[0104] Preferably, in step (2), mixture A and mixture B are simultaneously added to the remaining allyl polyoxyethylene methyl-terminated polyether and mixed to carry out the reaction;

[0105] Preferably, the addition is done by dripping.

[0106] Preferably, the dripping is completed within 1 to 4 hours;

[0107] Preferably, before mixing in step (2), the remaining allyl polyoxyethylene methyl-terminated polyether is heated to 60-100°C, and then mixed solution A and mixed solution B are added while stirring.

[0108] Preferably, the temperature of the reaction in step (2) is 60-100°C, and the reaction time is 1-3 hours;

[0109] Preferably, in step (3), the temperature is controlled at 50-100°C, phosphorus pentoxide is added to the system containing intermediate polymer obtained in step (2), and then the reaction is kept at the temperature for 3-10 hours.

[0110] Preferably, the phosphorus pentoxide is added to the system in batches and evenly over 1 to 3 hours.

[0111] 10. An aqueous nano-titanium dioxide dispersion comprising a dispersant, wherein the dispersant is an aqueous polymer of a phosphate ester as described in any one of claims 1-5.

Claims

1. A phosphate ester-based aqueous polymer, prepared by polymerization of the following monomers: monovinyl ether, vinylbenzene monomer, allyl polyoxyethylene methyl-terminated polyether, and phosphorus pentoxide.

2. The phosphate ester-based waterborne polymer of claim 1, wherein, The molar ratio of the monovinyl ether, vinylbenzene, allyl polyoxyethylene methyl-terminated polyether, and phosphorus pentoxide is (1-2):(2-5):(3-5):(2-3).

3. The phosphate ester-based waterborne polymer according to claim 1 or 2, wherein, The monovinyl ether is selected from one or a combination of at least two of ethylene glycol monovinyl ether, diethylene glycol monovinyl ether, and 4-hydroxybutylvinyl ether; Preferably, the vinylbenzene monomer is selected from one or a combination of at least two of styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene or α-methylstyrene; Preferably, the allyl polyoxyethylene methyl-terminated polyether has the following general formula: CH2=CHCH2O(CH2CH2O) n CH3, where n is an integer from 4 to 20.

4. The phosphate ester-based waterborne polymer according to any one of claims 1 to 3, wherein, The polymerization is carried out under the initiation of an initiator; Preferably, the initiator is selected from azo initiators; Preferably, the amount of the azo initiator is 2-10% of the total mass of the monovinyl ether, vinylbenzene monomer, and allyl polyoxyethylene methyl-terminated polyether; Preferably, the azo initiator is selected from one or a combination of at least two of azobisisobutyronitrile, azobisisoheptanenitrile, azobisisovalerate, or dimethyl azobisisobutyrate.

5. The phosphate ester-based waterborne polymer according to any one of claims 1 to 4, wherein, The weight-average molecular weight of the phosphate ester aqueous polymer is 5000–20000 g / mol.

6. A method for preparing a phosphate ester aqueous polymer according to any one of claims 1-5, comprising the following steps: (1) Mix monovinyl ether, vinylbenzene and part of allyl polyoxyethylene methyl-terminated polyether to obtain mixture A, and dissolve the initiator in the solvent to obtain mixture B; (2) Mix mixture A and mixture B and the remaining allyl polyoxyethylene methyl-terminated polyether and react to obtain intermediate polymer; (3) Add phosphorus pentoxide to the system containing intermediate polymer obtained in step (2) and react to obtain the phosphate ester aqueous polymer.

7. The production method according to claim 6, wherein The portion of allyl polyoxyethylene methyl-terminated polyether mentioned in step (1) is 40-60% of the total mass of allyl polyoxyethylene methyl-terminated polyether.

8. The production method according to claim 6, wherein The initiator mentioned in step (1) is selected from azo initiators; Preferably, the amount of the azo initiator is 2-10% of the total mass of the monovinyl ether, vinylbenzene monomer, and allyl polyoxyethylene methyl-terminated polyether; Preferably, the azo initiator is selected from one or a combination of at least two of azobisisobutyronitrile, azobisisoheptanenitrile, azobisisovalerate, or dimethyl azobisisobutyrate.

9. The production method according to claim 6, wherein The solvent in step (1) is selected from one or a combination of at least two of ethylene glycol dimethyl ether, ethylene glycol dipropyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether or tetraethylene glycol dimethyl ether; Preferably, in step (2), mixture A and mixture B are simultaneously added to the remaining allyl polyoxyethylene methyl-terminated polyether and mixed to carry out the reaction; Preferably, the addition is done by dripping. Preferably, the dripping is completed within 1 to 4 hours; Preferably, before mixing in step (2), the remaining allyl polyoxyethylene methyl-terminated polyether is heated to 60-100°C, and then mixed solution A and mixed solution B are added while stirring. Preferably, the temperature of the reaction in step (2) is 60-100°C, and the reaction time is 1-3 hours; Preferably, in step (3), the temperature is controlled at 50-100°C, phosphorus pentoxide is added to the system containing intermediate polymer obtained in step (2), and then the reaction is kept at the temperature for 3-10 hours. Preferably, the phosphorus pentoxide is added to the system in batches and evenly over 1 to 3 hours.

10. An aqueous nano-titanium dioxide dispersion comprising a dispersant, wherein the dispersant is an aqueous phosphate polymer as described in any one of claims 1-5.

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