A scale inhibitor, its preparation method and application

Abstract

This invention belongs to the field of water treatment technology, specifically relating to a scale inhibitor, its preparation method, and its application. The preparation method is as follows: Iminodimethylphosphoric acid, 1,4-dichloro-2-butene, and ethanol are added to a four-necked flask. The mixture is heated and kept at a constant temperature. After cooling to below 50°C, 2-aminobenzene-1,3,5-tricarboxylic acid is added, and the mixture is heated under reflux. The mixture is then distilled under reduced pressure to obtain a viscous solid. Distilled water is added and stirred to dissolve the solid. (2-Acryloylaminoethyl)phosphonic acid and a buffer salt are added and stirred until homogeneous. An initiator is added dropwise. After the addition is complete, the mixture is stirred and kept at a constant temperature to obtain a viscous mixture. The mixture is then cooled to below 40°C, dried, and granulated to obtain the scale inhibitor. The scale inhibitor of this invention has the advantages of widely available raw materials, simple synthesis process, no pollution, and good scale inhibition effect.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a scale inhibitor, its preparation method, and its application. Background Technology

[0002] With the rapid development of industry, industrial water consumption is constantly increasing, making water recycling increasingly important. After repeated use, circulating cooling water is prone to developing inorganic calcium scale, such as calcium carbonate, calcium sulfate, and barium sulfate. This scale adheres to the inner surface of pipes, significantly reducing the cooling efficiency of the circulating cooling water and causing concentration cell corrosion and localized thermal corrosion, which are extremely detrimental to industrial production. Therefore, improving the recycling rate of industrial cooling water is urgently needed.

[0003] Adding scale inhibitors to circulating water is an effective method. Scale inhibitors have chelating, dispersing, and lattice distortion effects on scale, effectively inhibiting its formation. Scale inhibitors have been widely used in many applications such as industrial circulating cooling water, seawater desalination, boilers, geothermal resource development, and oil and gas field development to slow down and prevent the precipitation and scaling of insoluble substances on metal surfaces, thus maintaining the service life and heat transfer efficiency of metal equipment.

[0004] Tie Chengjun et al. synthesized the MA / AM / HPA copolymer scale inhibitor in their paper "Performance of Copolymer Scale Inhibitor MA / AM / HPA" and conducted comprehensive testing in oilfield water environment. They investigated the inhibition efficiency of the polymer on calcium carbonate, calcium sulfate, barium sulfate, and strontium sulfate under different pH, temperature, sodium chloride content and other factors. In indoor tests in oilfield water, the scale inhibition rate of 25 mg / L polymer after being kept at 60℃ for 24 h can reach more than 90%.

[0005] Chinese patent CN102838215A discloses a composite scale inhibitor composed of polyepoxysuccinic acid, ethylenediaminetetramethylenephosphonic acid, itaconic acid-maleic acid-acrylate-methyl acrylate polymer, and dendritic polyamide-amine. The weight percentages of the components of this scale inhibitor are: polyepoxysuccinic acid 22-32%, ethylenediaminetetramethylenephosphonic acid 10-18%, itaconic acid-maleic acid-acrylate-methyl acrylate polymer 35-50%, dendritic polyamide-amine 10-18%, and the remainder being water.

[0006] These products generally have some common problems when used, such as either excessive dosage or poor effect. Therefore, it is very necessary to develop efficient and low-dosage scale inhibitors for water treatment. Summary of the Invention

[0007] This invention addresses the shortcomings of existing technologies by providing a scale inhibitor, its preparation method, and its application. The scale inhibitor of this invention has the advantages of wide availability of raw materials, simple synthesis process, no pollution, and good scale inhibition effect.

[0008] To achieve the above objectives:

[0009] The first aspect of this invention discloses a scale inhibitor, the molecular formula of which is as follows:

[0010]

[0011] Where m = 1000 - 10000;

[0012] n = 200 - 4000.

[0013] Preferably, the viscosity-average molecular weight of the antiscalant is 100,000-300,000.

[0014] In another aspect, the present invention discloses a method for preparing an antiscalant, the specific steps of which are as follows:

[0015] (1) Add iminodi(methylphosphoric acid), 1,4-dichloro-2-butene and ethanol to a four-necked flask, adjust the pH to 9-10 with sodium hydroxide solution, heat and keep the reaction at the temperature, and maintain the pH at 9-10 with sodium hydroxide solution during the reaction; cool down to below 50℃, add 2-aminobenzene-1,3,5-tricarboxylic acid, adjust the pH to 8-9 with sodium hydroxide solution, heat and reflux the reaction, and maintain the pH at 8-9 with sodium hydroxide solution during the reaction. After the reaction is complete, distill the mixed liquid under reduced pressure to obtain a viscous solid.

[0016] (2) Add distilled water, stir to dissolve, add (2-acryloylaminoethyl)phosphonic acid and buffer salt, stir evenly, and adjust the pH to 7-8 with sodium hydroxide solution;

[0017] (3) Add the initiator dropwise to the above four-necked flask. After the addition is complete, stir the reaction until the solution begins to become viscous. Raise the temperature to 70°C and continue to keep the reaction at the temperature for 1-2 hours to obtain a viscous mixture. Cool the temperature to below 40°C and adjust the pH to 7-8 with sodium hydroxide.

[0018] (4) The above viscous mixture is dried and granulated to obtain the scale inhibitor.

[0019] In this invention, preferably, based on 1 mole of iminodi(methylphosphoric acid), the amounts of 1,4-dichloro-2-butene, 2-aminophenyl-1,3,5-tricarboxylic acid, and (2-acryloylaminoethyl)phosphonic acid are 0.8-1.2:0.8-1.2:0.2-0.4 moles, respectively.

[0020] In this invention, preferably, the mass ratio of ethanol to iminodi(methylphosphoric acid) in step (1) is 10-15:1.

[0021] In this invention, preferably, the temperature of the heat preservation reaction in step (1) is 50-70°C and the time is 1-4h, and the time of the reflux reaction is 2-6h.

[0022] In this invention, preferably, the mass ratio of distilled water to iminodi(methylphosphoric acid) in step (2) is 15-20:1.

[0023] In this invention, preferably, the buffer salt in step (2) is one of sodium dihydrogen phosphate, potassium dihydrogen phosphate, and ammonium dihydrogen phosphate, and the mass ratio of the buffer salt to iminodi(methyl phosphate) is 0.1-0.2:1.

[0024] In this invention, preferably, the initiator in step (3) is a mixed solution of persulfate and sodium bisulfite, wherein the concentration of persulfate is 10-12 wt%, the concentration of sodium bisulfite is 3-5 wt%, and the mass ratio of initiator to iminodi(methylphosphoric acid) is 0.2-0.5:1.

[0025] In a preferred embodiment, the persulfate is one of sodium persulfate or ammonium persulfate.

[0026] The reaction equation for the synthesis of the scale inhibitor of the present invention is as follows:

[0027]

[0028] The third objective of this invention is to disclose the application of the above-mentioned scale inhibitor in wastewater treatment.

[0029] The scale inhibitor of this invention is a linear polymer compound. Therefore, its grain growth is disrupted and distorted, resulting in finer grains and a softer scale layer that is easily washed away by water. The polymer contains a large amount of phosphonic acid, which has excellent chelating ability and thermal stability, forming stable complexes with metal ions such as calcium, magnesium, and iron, preventing them from combining with carbonate, sulfate, and other anions to form scale. It also contains a large number of carboxyl functional groups, which can chelate with calcium, magnesium, and other metal ions in water to form stable water-soluble complexes, preventing metal ions from forming scale deposits. Simultaneously, the polycarboxylic acid polymer also has a dispersing effect, dispersing already formed microparticles in the water and preventing them from agglomerating into large scale clumps.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] (1) The scale inhibitor of the present invention has a wide range of raw material sources, a simple synthesis process, and is a one-pot synthesis method with no by-products and no environmental pollution.

[0032] (2) The scale inhibitor of the present invention has a good scale inhibition effect. When the concentration is 3 mg / L, the scale inhibition rate is 90% or more; when the concentration is 5 mg / L, the scale inhibition rate can reach 93% or more; when the concentration is 8 mg / L, the scale inhibition rate can reach 96% or more. Detailed Implementation

[0033] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0034] The present invention will be further described below with reference to specific embodiments:

[0035] Example 1

[0036] (1) In a four-necked flask, add 50 mmol of iminodi(methylphosphoric acid), 40 mmol of 1,4-dichloro-2-butene, and 102.5 g of ethanol. Adjust the pH to 9-10 with sodium hydroxide solution, heat to 60°C, and maintain the reaction temperature for 1 h. During the reaction, maintain the pH at 9-10 with sodium hydroxide solution. Cool to below 50°C, add 45 mmol of 2-aminophenyl-1,3,5-tricarboxylic acid, adjust the pH to 8-9 with sodium hydroxide solution, and heat under reflux for 2 h. During the reaction, maintain the pH at 8-9 with sodium hydroxide solution. After the reaction is complete, distill the mixture under reduced pressure to obtain a viscous solid.

[0037] (2) Add 153.75g of distilled water, stir to dissolve, add 10mmol of (2-acryloylaminoethyl)phosphonic acid and 1.03g of sodium dihydrogen phosphate, stir evenly, and adjust the pH to 7-8 with sodium hydroxide solution.

[0038] (3) Add 2.05 g of initiator dropwise to the above four-necked flask. The initiator is a mixture of sodium persulfate and sodium bisulfite, wherein the concentration of sodium persulfate is 12 wt% and the concentration of sodium bisulfite is 5 wt%. After the addition is complete, stir the reaction until the solution begins to become viscous. Raise the temperature to 70°C and continue to keep the reaction at this temperature for 1 hour to obtain a viscous mixture. Cool the temperature to below 40°C and adjust the pH to 7-8 with sodium hydroxide.

[0039] (4) The above viscous mixture is dried and granulated to obtain the scale inhibitor.

[0040] Example 2

[0041] (1) In a four-necked flask, add 50 mmol of iminodi(methylphosphoric acid), 60 mmol of 1,4-dichloro-2-butene, and 142.5 g of ethanol. Adjust the pH to 9-10 with sodium hydroxide solution, heat to 50°C, and maintain the reaction temperature for 4 h. During the reaction, maintain the pH at 9-10 with sodium hydroxide solution. Cool to below 50°C, add 40 mmol of 2-aminophenyl-1,3,5-tricarboxylic acid, adjust the pH to 8-9 with sodium hydroxide solution, and heat under reflux for 3 h. During the reaction, maintain the pH at 8-9 with sodium hydroxide solution. After the reaction is complete, distill the mixture under reduced pressure to obtain a viscous solid.

[0042] (2) Add 169g of distilled water, stir to dissolve, add 20mmol (2-acryloylaminoethyl)phosphonic acid and 1.44g sodium dihydrogen phosphate, stir evenly, and adjust the pH to 7-8 with sodium hydroxide solution.

[0043] (3) Add 3.46 g of initiator dropwise to the four-necked flask. The initiator is a mixture of sodium persulfate and sodium bisulfite, with a sodium persulfate concentration of 11 wt% and a sodium bisulfite concentration of 4 wt%. After the addition is complete, stir the reaction until the solution begins to thicken. Raise the temperature to 70°C and continue the reaction for 2 hours to obtain a viscous mixture. Cool the temperature to below 40°C and adjust the pH to 7-8 with sodium hydroxide.

[0044] (4) The above viscous mixture is dried and granulated to obtain the scale inhibitor.

[0045] Example 3

[0046] (1) In a four-necked flask, add 50 mmol of iminodi(methylphosphoric acid), 44 mmol of 1,4-dichloro-2-butene, and 138 g of ethanol. Adjust the pH to 9-10 with sodium hydroxide solution, heat to 70°C, and maintain the reaction temperature for 1 h. During the reaction, maintain the pH at 9-10 with sodium hydroxide solution. Cool to below 50°C, add 60 mmol of 2-aminophenyl-1,3,5-tricarboxylic acid, adjust the pH to 8-9 with sodium hydroxide solution, and heat under reflux for 4 h. During the reaction, maintain the pH at 8-9 with sodium hydroxide solution. After the reaction is complete, distill the mixture under reduced pressure to obtain a viscous solid.

[0047] (2) Add 188g of distilled water, stir to dissolve, add 18mmol of (2-acryloylaminoethyl)phosphonic acid and 1.68g of potassium dihydrogen phosphate, stir evenly, and adjust the pH to 7-8 with sodium hydroxide solution.

[0048] (3) Add 2.88 g of initiator dropwise to the above four-necked flask. The initiator is a mixture of sodium persulfate and sodium bisulfite, wherein the concentration of sodium persulfate is 12 wt% and the concentration of sodium bisulfite is 4 wt%. After the addition is complete, stir the reaction until the solution begins to become viscous. Raise the temperature to 70°C and continue to keep the reaction at this temperature for 1.5 h to obtain a viscous mixture. Cool the temperature to below 40°C and adjust the pH to 7-8 with sodium hydroxide.

[0049] (4) The above viscous mixture is dried and granulated to obtain the scale inhibitor.

[0050] Example 4

[0051] (1) In a four-necked flask, add 50 mmol of iminodi(methylphosphoric acid), 48 mmol of 1,4-dichloro-2-butene, and 153 g of ethanol. Adjust the pH to 9-10 with sodium hydroxide solution, heat to 65°C, and maintain the reaction temperature for 2 h. During the reaction, maintain the pH at 9-10 with sodium hydroxide solution. Cool to below 50°C, add 55 mmol of 2-aminophenyl-1,3,5-tricarboxylic acid, adjust the pH to 8-9 with sodium hydroxide solution, and heat under reflux for 4 h. During the reaction, maintain the pH at 8-9 with sodium hydroxide solution. After the reaction is complete, distill the mixture under reduced pressure to obtain a viscous solid.

[0052] (2) Add 205g of distilled water, stir to dissolve, add 16mmol (2-acryloylaminoethyl)phosphonic acid and 1.03g sodium dihydrogen phosphate, stir evenly, and adjust the pH to 7-8 with sodium hydroxide solution.

[0053] (3) Add 3.66 g of initiator dropwise to the above four-necked flask. The initiator is a mixture of sodium persulfate and sodium bisulfite, wherein the concentration of sodium persulfate is 11 wt% and the concentration of sodium bisulfite is 5 wt%. After the addition is complete, stir the reaction until the solution begins to become viscous. Raise the temperature to 70°C and continue to keep the reaction at this temperature for 1.2 h to obtain a viscous mixture. Cool the temperature to below 40°C and adjust the pH to 7-8 with sodium hydroxide.

[0054] (4) The above viscous mixture is dried and granulated to obtain the scale inhibitor.

[0055] Example 5

[0056] (1) In a four-necked flask, add 50 mmol of iminodi(methylphosphoric acid), 55 mmol of 1,4-dichloro-2-butene, and 153.5 g of ethanol. Adjust the pH to 9-10 with sodium hydroxide solution, heat to 65°C, and maintain the reaction temperature for 2 h. During the reaction, maintain the pH at 9-10 with sodium hydroxide solution. Cool to below 50°C, add 43 mmol of 2-aminophenyl-1,3,5-tricarboxylic acid, adjust the pH to 8-9 with sodium hydroxide solution, and heat under reflux for 5 h. During the reaction, maintain the pH at 8-9 with sodium hydroxide solution. After the reaction is complete, distill the mixture under reduced pressure to obtain a viscous solid.

[0057] (2) Add 200g of distilled water, stir to dissolve, add 14mmol (2-acryloylaminoethyl)phosphonic acid and 1.7g potassium dihydrogen phosphate, stir evenly, and adjust the pH to 7-8 with sodium hydroxide solution.

[0058] (3) Add 3.88 g of initiator dropwise to the four-necked flask. The initiator is a mixture of ammonium persulfate and sodium bisulfite, wherein the concentration of ammonium persulfate is 10 wt% and the concentration of sodium bisulfite is 3 wt%. After the addition is complete, stir the reaction until the solution begins to become viscous. Raise the temperature to 70°C and continue to keep the reaction at this temperature for 1.8 h to obtain a viscous mixture. Cool the temperature to below 40°C and adjust the pH to 7-8 with sodium hydroxide.

[0059] (4) The above viscous mixture is dried and granulated to obtain the scale inhibitor.

[0060] Example 6

[0061] (1) In a four-necked flask, add 50 mmol of iminodi(methylphosphoric acid), 52 mmol of 1,4-dichloro-2-butene, and 150 g of ethanol. Adjust the pH to 9-10 with sodium hydroxide solution, heat to 60°C, and maintain the reaction temperature for 3 h. During the reaction, maintain the pH at 9-10 with sodium hydroxide solution. Cool to below 50°C, add 50 mmol of 2-aminophenyl-1,3,5-tricarboxylic acid, adjust the pH to 8-9 with sodium hydroxide solution, and heat under reflux for 6 h. During the reaction, maintain the pH at 8-9 with sodium hydroxide solution. After the reaction is complete, distill the mixture under reduced pressure to obtain a viscous solid.

[0062] (2) Add 186g of distilled water, stir to dissolve, add 12mmol (2-acryloylaminoethyl)phosphonic acid and 1.8g sodium dihydrogen phosphate, stir evenly, and adjust the pH to 7-8 with sodium hydroxide solution.

[0063] (3) Add 1.88 g of initiator dropwise to the above four-necked flask. The initiator is a mixture of ammonium persulfate and sodium bisulfite, wherein the concentration of ammonium persulfate is 10 wt% and the concentration of sodium bisulfite is 3 wt%. After the addition is complete, stir the reaction until the solution begins to become viscous. Raise the temperature to 70°C and continue to keep the reaction at this temperature for 1.6 h to obtain a viscous mixture. Cool the temperature to below 40°C and adjust the pH to 7-8 with sodium hydroxide.

[0064] (4) The above viscous mixture is dried and granulated to obtain the scale inhibitor.

[0065] Example 7

[0066] (1) Add 50 mmol of iminodi(methylphosphoric acid), 50 mmol of 1,4-dichloro-2-butene, and 138 g of ethanol to a four-necked flask. Adjust the pH to 9-10 with sodium hydroxide solution, heat to 60°C, and maintain the reaction temperature for 3 h. During the reaction, maintain the pH at 9-10 with sodium hydroxide solution. Cool to below 50°C, add 52 mmol of 2-aminophenyl-1,3,5-tricarboxylic acid, adjust the pH to 8-9 with sodium hydroxide solution, and heat under reflux for 5 h. During the reaction, maintain the pH at 8-9 with sodium hydroxide solution. After the reaction is complete, distill the mixture under reduced pressure to obtain a viscous solid.

[0067] (2) Add 190g of distilled water, stir to dissolve, add 12mmol (2-acryloylaminoethyl)phosphonic acid and 1.92g sodium dihydrogen phosphate, stir evenly, and adjust the pH to 7-8 with sodium hydroxide solution.

[0068] (3) Add 5.13g of initiator dropwise to the above four-necked flask. The initiator is a mixture of sodium persulfate and sodium bisulfite, wherein the concentration of sodium persulfate is 10wt% and the concentration of sodium bisulfite is 4wt%. After the addition is complete, stir the reaction until the solution begins to become viscous. Raise the temperature to 70℃ and continue to keep the reaction at this temperature for 2 hours to obtain a viscous mixture. Cool the temperature to below 40℃ and adjust the pH to 7-8 with sodium hydroxide.

[0069] (4) The above viscous mixture is dried and granulated to obtain the scale inhibitor.

[0070] Example 8: Evaluation of Scale Inhibition Effect

[0071] The scale inhibitors of this invention (Examples 1-7) were evaluated in the laboratory using the method described in GB / T 16632-2019 "Determination of Scale Inhibition Performance of Water Treatment Agents - Calcium Carbonate Deposition Method". The scale inhibitor dosages were 3, 5, and 8 mg / L. Circulating water from a chemical plant was used as the evaluation water, and EDTA was used as the control sample. The test results are shown in Table 1.

[0072] Table 1. Results of scale inhibition rate determination (%) of scale inhibitor

[0073] 3mg / L 5mg / L 8mg / L Example 1 90 93.9 96.3 Example 2 90.5 94 96.5 Example 3 90.5 94.2 96.6 Example 4 90.2 94 96.7 Example 5 90.4 94.2 96.7 Example 6 91 94.5 96.9 Example 7 90.8 94.3 96.8 Comparative Example 58 73 81.9

[0074] As can be seen from Table 1:

[0075] (1) The scale inhibitor of the present invention (Examples 1-7) has a scale inhibition rate of 90% or more when the concentration is 3 mg / L, and the highest rate is 91% (Example 6), while the comparative example is 58%, which is significantly lower than that of the present invention;

[0076] (2) The scale inhibitor of the present invention (Examples 1-7) has a scale inhibition rate of more than 93% when the concentration is 5 mg / L, and the highest reaches 94.5% (Example 6), while the comparative example is 73%, which is significantly lower than that of the present invention;

[0077] (3) The scale inhibitor of the present invention (Examples 1-7) has a scale inhibition rate of more than 96% when the concentration is 8 mg / L, and the highest rate reaches 96.9% (Example 6), while the comparative example is 81.9%, which is significantly lower than that of the present invention;

[0078] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0079] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0080] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a scale inhibitor, characterized in that, The specific steps of the preparation method are as follows: (1) Add iminodi(methylphosphoric acid), 1,4-dichloro-2-butene and ethanol to a four-necked flask, adjust the pH to 9-10 with sodium hydroxide solution, heat and keep the reaction at the temperature, and maintain the pH at 9-10 with sodium hydroxide solution during the reaction; cool down to below 50℃, add 2-aminobenzene-1,3,5-tricarboxylic acid, adjust the pH to 8-9 with sodium hydroxide solution, heat and reflux the reaction, and maintain the pH at 8-9 with sodium hydroxide solution during the reaction. After the reaction is completed, distill the mixed liquid under reduced pressure to obtain a viscous solid. (2) Add distilled water, stir to dissolve, then add (2-acryloylaminoethyl)phosphonic acid, Add buffer salt, stir well, and adjust the pH to 7-8 with sodium hydroxide solution; (3) Add the initiator dropwise to the above four-necked flask. After the addition is complete, stir the reaction until the solution begins to become viscous. Raise the temperature to 70°C and continue to keep the reaction at this temperature for 1-2 hours to obtain a viscous mixture. Cool the temperature to below 40°C and adjust the pH to 7-8 with sodium hydroxide. (4) The above viscous mixture is dried and granulated to obtain the scale inhibitor product; Based on 1 mole of iminodi(methylphosphoric acid), the amounts of 1,4-dichloro-2-butene, 2-aminophenyl-1,3,5-tricarboxylic acid, and (2-acryloylaminoethyl)phosphonic acid are 0.8-1.2:0.8-1.2:0.2-0.4 moles, respectively.

2. The preparation method according to claim 1, characterized in that, The mass ratio of ethanol to iminodi(methylphosphoric acid) in step (1) is 10-15:

1.

3. The preparation method according to claim 1, characterized in that, The temperature of the heat preservation reaction in step (1) is 50-70℃ and the time is 1-4h, and the time of the reflux reaction is 2-6h.

4. The preparation method according to claim 1, characterized in that, The mass ratio of distilled water to iminodi(methylphosphoric acid) in step (2) is 15-20:

1.

5. The preparation method according to claim 1, characterized in that, The buffer salt mentioned in step (2) is one of sodium dihydrogen phosphate, potassium dihydrogen phosphate, and ammonium dihydrogen phosphate, and the mass ratio of the buffer salt to iminodi(methyl phosphate) is 0.1-0.2:

1.

6. The preparation method according to claim 1, characterized in that, The initiator mentioned in step (3) is a mixed solution of persulfate and sodium bisulfite, wherein the concentration of persulfate is 10-12 wt%, the concentration of sodium bisulfite is 3-5 wt%, and the mass ratio of initiator to iminodi(methylphosphoric acid) is 0.2-0.5:

1.

7. The preparation method according to claim 6, characterized in that, The persulfate is either sodium persulfate or ammonium persulfate.

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