Phosphorus-free composite scale inhibitor and preparation method thereof

Abstract

The present application belongs to the technical field of scale inhibitors, and particularly relates to a phosphorus-free composite scale inhibitor and a preparation method thereof. The phosphorus-free composite scale inhibitor comprises, in terms of mass fraction, 4.5-9.5 parts of beta-CD grafted hyperbranched polyglycidyl ether, 8-20 parts of AA / AMPS copolymer, 15-30 parts of PESA, 18-30 parts of CETSA, 6.5-10.5 parts of 2,4,6-trithiol-1,3,5-triazine, 3-6 parts of sodium molybdate dihydrate, 5-12 parts of sodium polyacrylate, 2-6 parts of N-octadecyl-D-glucosamide, 1.2-3 parts of ureido pyrimidone derivative containing isocyanate groups, 0.5-1.2 parts of 2,6-pyridine dicarboxamide, and 65-85 parts of water. The preparation method comprises the following steps: stirring raw materials such as beta-CD grafted hyperbranched polyglycidyl ether and water, adjusting pH, and keeping warm, then adding ureido pyrimidone derivative containing isocyanate groups and 2,6-pyridine dicarboxamide, and mixing uniformly to obtain the phosphorus-free composite scale inhibitor. The present application solves the problem of poor scale inhibition and corrosion inhibition effect of the phosphorus-free scale inhibitor in sewage containing high concentrations of calcium silicate and magnesium silicate components by reasonable compounding.

Description

Technical Field

[0001] This invention belongs to the technical field of scale inhibitors and descaling agents, specifically relating to a phosphorus-free composite scale inhibitor and its preparation method. Background Technology

[0002] In cooling water systems, reverse osmosis membrane systems, or boiler water systems of industries such as power, chemical, petroleum, and metallurgy, calcium and magnesium ions in the water can form hard scale over long-term use. This scale adheres to the surfaces of heat exchangers, pipes, and other equipment. This hard scale has poor thermal conductivity, severely impacting heat exchange efficiency. By adding scale inhibitors at the equipment dosing points, the scale inhibitors can inhibit the formation of hard scale through chelation and dispersion. Furthermore, with increasingly stringent water pollution control requirements, the preparation of phosphorus-free scale inhibitors can effectively reduce phosphate emissions from factories, preventing eutrophication and other water problems.

[0003] Because phosphorus-free scale inhibitors do not contain phosphorus, under certain water quality conditions, such as wastewater containing high concentrations of calcium silicate and magnesium silicate, the calcium silicate / magnesium scale typically forms an amorphous or dense network structure. Compared to other types of scale, such as carbonate scale, it is harder and less easily penetrated by polymer chains. The long-chain structure of the scale inhibitor cannot effectively contact, adsorb, and thus participate in lattice distortion. Therefore, the scale inhibition and corrosion inhibition effects of phosphorus-free scale inhibitors are not good. It is necessary to adjust the raw material ratio for such water quality and find a product suitable for factory production that can solve the problem of poor scale inhibition and corrosion inhibition effects of phosphorus-free scale inhibitors in wastewater containing high concentrations of calcium silicate and magnesium silicate.

[0004] Chinese patent CN105800802A discloses a composite phosphorus-free corrosion and scale inhibitor, which is composed of the following raw materials by weight: 20-30 parts of S-carboxyethyl thiosuccinic acid, 10-15 parts of sodium gluconate, 5-8 parts of sodium benzoate, 10-20 parts of hydroxypropyl acrylate, 5-10 parts of zinc sulfate, and 35-45 parts of water. Another Chinese patent CN109264878A discloses a composite phosphorus-free corrosion and scale inhibitor, which contains the following raw materials by weight: 5-10 parts of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, 2-6 parts of hydrolyzed polymaleic anhydride, 4-6 parts of zinc sulfate, 1-3 parts of sodium molybdate, 5-10 parts of polyepoxysuccinic acid, 1-3 parts of maleic acid-acrylic acid copolymer, and 0.5-2 parts of benzotriazole. The two patents mentioned above use zinc sulfate, which easily forms zinc scale in alkaline or high-hardness water, leading to secondary scaling. In addition, excessive discharge of zinc salts can cause water pollution.

[0005] Chinese patent CN109133389A discloses a phosphorus-free composite scale inhibitor, which is composed of a dendritic polymer, sodium polyepoxysuccinate, sodium polyaspartate, IA-AMPS, and water. The dendritic polymer is a polyamide-amine dendritic polymer (EDA-PAMAM) with ethylenediamine as the core and amine groups as end groups. IA-AMPS is a copolymer formed by free radical polymerization of itaconic acid and 2-acrylamido-2-methylpropanesulfonic acid as monomers. The dendritic polymer is a 1.0 generation scale inhibitor, EDA-PAMAM, which is obtained by reacting a diamine compound with an unsaturated fatty acid ester in an organic solvent; the reaction product is then reacted with the diamine compound in an organic solvent. IA-AMPS is prepared from the following raw materials in parts by weight: 1-10 parts itaconic acid, 10-30 parts 2-acrylamido-2-methylpropanesulfonic acid, 20-60 parts deionized water, 0.1-5 parts ammonium persulfate, 1-5 parts sodium bisulfite, and 10-40 parts sodium hydroxide.

[0006] According to the patent's embodiments, EDA-PAMAM requires two generations of synthesis, with each generation requiring 8-12 hours of reaction time, resulting in a long reaction cycle that is not conducive to factory production. Summary of the Invention

[0007] The purpose of this invention is to provide a phosphorus-free composite scale inhibitor to solve the problem of poor scale inhibition and corrosion inhibition effects of phosphorus-free scale inhibitors in wastewater containing high concentrations of calcium silicate and magnesium silicate. This invention also provides a method for preparing the phosphorus-free composite scale inhibitor.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The phosphorus-free composite scale inhibitor of the present invention comprises the following components by weight:

[0010] The composition includes 4.5-9.5 parts of β-cyclodextrin-grafted hyperbranched polyglycidyl ether, 8-20 parts of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, 15-30 parts of polyepoxysuccinic acid, 18-30 parts of S-carboxyethyl thiosuccinic acid, 6.5-10.5 parts of 2,4,6-trimercapto-1,3,5-triazine, 3-6 parts of sodium molybdate dihydrate, 5-12 parts of sodium polyacrylate, 2-6 parts of N-octadecyl-D-glucosamide, 1.2-3 parts of isocyanate-containing ureidopyrimidinone derivative, 0.5-1.2 parts of 2,6-pyridinedicarboxamide, and 65-85 parts of water.

[0011] in:

[0012] The polyepoxysuccinic acid has a number average molecular weight of 800~1200 Da; the acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer has a number average molecular weight of 2500~3500 Da.

[0013] The method for preparing the isocyanate-containing ureidopyrimidinone derivative is to react pyrimidine monomer, isocyanate monomer and catalyst in an inert atmosphere to obtain a crude product, and then to obtain the isocyanate-containing ureidopyrimidinone derivative by post-treatment.

[0014] The mass ratio of the pyrimidine monomer, isocyanate monomer, and catalyst is 125:(580~1100):(35~55), the pyrimidine monomer is 2-amino-4-hydroxy-6-methylpyrimidine, the isocyanate monomer is hexamethylene diisocyanate, and the catalyst is N-methylpyrrolidone or pyridine.

[0015] The reaction temperature is 100~115℃, and the reaction time is 7~10h.

[0016] The post-processing includes sedimentation, filtration, washing, and drying. Sedimentation refers to adding the crude product to a solvent for sedimentation, wherein the solvent is one of n-pentane, n-hexane, or petroleum ether.

[0017] The mass ratio of the pyrimidine monomer to the solvent is 125:(600~700).

[0018] The preparation method of the phosphorus-free composite scale inhibitor of the present invention includes the following steps:

[0019] β-Cyclodextrin-grafted hyperbranched polyglycidyl ether, acrylate-2-acrylamide-2-methylpropanesulfonic acid copolymer, polyepoxysuccinic acid, S-carboxyethylthiosuccinic acid, 2,4,6-trimercapto-1,3,5-triazine, sodium molybdate dihydrate, sodium polyacrylate, N-octadecyl-D-glucosamide, and water were weighed, and the mixture was stirred, pH adjusted, and kept at a constant temperature. Then, ureidopyrimidinone derivatives containing isocyanate groups and 2,6-pyridinedicarboxamide were weighed and mixed to prepare a phosphorus-free composite scale inhibitor.

[0020] in:

[0021] The stirring rate is 100~150 rpm, the stirring temperature is 50~60℃, and the stirring time is 8~20 min.

[0022] The pH is adjusted to 7.8~8.2, the stirring rate is 20~70 rpm during heat preservation, the heat preservation temperature is 40~60℃, and the heat preservation time is 20~40 min.

[0023] The beneficial effects of this invention are as follows:

[0024] β-Cyclodextrin-grafted hyperbranched polyglycidyl ether (HPG-g-CD) is an amphiphilic core-shell structure formed by grafting hyperbranched polyglycidyl ether onto a β-cyclodextrin core. The β-cyclodextrin core is hydrophobic, while the outer layer features long, regularly distributed branches with irregularly branched hydroxyl groups. The N-octadecyl-D-glucamide moiety includes both alkyl hydrophobic long chains and a hydrophilic glucamide portion. The hydrophobic cavity of the β-cyclodextrin in HPG-g-CD can encapsulate the alkyl group. The hydrophobic long chain and hydrophilic glucose group can anchor to the surface of hard limescale (referring to calcium silicate and magnesium silicate scale). HPG-g-CD and N-octadecyl-D-glucamide form complex micelles on the surface of hard limescale. With the help of the amphiphilic structure and long branched chain of HPG-g-CD, it can capture molecules such as 2,4,6-trimercapto-1,3,5-triazine, polyepoxysuccinic acid, S-carboxyethyl thiosuccinic acid, and acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer. The HPG-g-CD forms a network structure through hydrogen bonding, which provides a certain degree of slow release and avoids the dosage threshold of reagents such as polyepoxysuccinic acid (the scale inhibition effect is not significant when excessive). Secondly, the long-branched hydrophilic groups of HPG-g-CD and the hydrophilic ends of glucosamide work synergistically to form continuous hydrophilic channels, guiding polyepoxysuccinic acid, S-carboxyethyl thiosuccinic acid, etc., to penetrate deep into hard scale. The composite micelles coat the surface of hard scale, promoting the contact between polyepoxysuccinic acid, S-carboxyethyl thiosuccinic acid, etc. and hard scale, and jointly improving scale inhibition efficiency. Thirdly, the composite micelles can ensure that polyepoxysuccinic acid, S-carboxyethyl thiosuccinic acid, etc. can remain stable in various types of use scenarios, such as high temperature or high salt conditions, and maintain their chelating ability. On the other hand, the chelates formed by polyepoxysuccinic acid and other reagents with calcium and magnesium salts and the loose scale layer can adhere to the hydrophilic groups of HPG-g-CD branches. With the help of the irregular branching distribution, a large steric hindrance can be formed, effectively reducing the risk of secondary scaling.

[0025] 2,4,6-Trithio-1,3,5-triazine is a small molecule with highly polar thiol groups. The three thiol groups are rotate symmetrically distributed, which can efficiently complex silicates. At the same time, with the assistance of the sulfonic acid groups of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, a polar system is formed, which can better adsorb onto the surface of calcium silicate, magnesium silicate, and other calcium and magnesium salt scales. It can better exert the lattice distortion effect, interfere with the normal crystal growth, make the scale layer loose and brittle, and make it difficult to adhere to the equipment surface. Acrylic acid can also better inhibit scale formation. In addition, 2,4,6-trithio-1,3,5-triazine, together with polyepoxysuccinic acid and S-carboxyethylthiosuccinic acid, forms a mixed ligand complex with hard scale, which enhances the distortion and dispersion of scale crystals and promotes the desorption and disintegration of silicate scale.

[0026] Because the pyridine nitrogen atom in 2,6-pyridinedicarboxamide forms a parallel conformation with the two symmetrically distributed amide groups, and the isocyanate-containing ureidopyrimidinone derivative contains a long-chain alkyl group and a terminal UPy group, the UPy group, with 2,6-pyridinedicarboxamide as a bridge, further forms a three-dimensional AADD tetrahydrobonded network structure, forming an ordered molecular self-assembly on the surface of hard scale; 2,6-pyridinedicarboxamide and isocyanate-containing ureidopyrimidinone derivative can form multidirectional hydrogen bonding through the outer ring hydrophilic core-shell structure of HPG-g-CD, thereby guiding HPG-g-CD (and the complex formed with polyepoxysuccinic acid, etc.) to closely contact hard scale, accelerating the formation of complex micelles. Detailed Implementation

[0027] The present invention will now be described and illustrated in detail with reference to the embodiments.

[0028] The basic raw materials used in the following examples and comparative examples are all commercially available products. Among them, β-cyclodextrin-grafted hyperbranched polyglycidyl ether was provided by Xi'an Qiyue Biotechnology Co., Ltd., polyepoxysuccinic acid was provided by Hubei Haili Environmental Protection Technology Co., Ltd., and acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer was provided by Shandong Kairui Chemical Co., Ltd.

[0029] Example 1

[0030] 1.25 parts of 2-amino-4-hydroxy-6-methylpyrimidine, 5.8 parts of hexamethylene diisocyanate, and 0.45 parts of N-methylpyrrolidone were heated to 100°C under a nitrogen atmosphere and reacted for 9 hours. The mixture was then cooled to room temperature to obtain a crude product. The crude product was added to 6.2 parts of n-pentane and stirred for 5 minutes. The mixture was allowed to stand for 15 minutes to settle. The solid phase was then filtered and collected. The solid phase was washed three times with acetone and dried under vacuum to constant weight to obtain a ureidylpyrimidinone derivative containing isocyanate groups.

[0031] Weigh out 4.5 parts by weight of β-cyclodextrin-grafted hyperbranched polyglycidyl ether, 8 parts of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer (number average molecular weight approximately 3000 Da), 30 parts of polyepoxysuccinic acid (number average molecular weight approximately 800 Da), 30 parts of S-carboxyethyl thiosuccinic acid, 6.5 parts of 2,4,6-trimercapto-1,3,5-triazine, 3.5 parts of sodium molybdate dihydrate, 5 parts of sodium polyacrylate, 2 parts of N-octadecyl-D-glucosamide, and 85 parts of water. Add these to a stirred tank and stir at 150 rpm and 50°C for 12 min, controlling the pH to 7.8~8.2. Keep the mixture at 40 rpm and 40°C for 33 min, then cool to room temperature. Add 3 parts of isocyanate-containing ureidopyrimidinone derivative and 0.5 parts of 2,6-pyridinedicarboxamide and mix well to obtain the phosphorus-free composite scale inhibitor.

[0032] Example 2

[0033] 1.25 parts of 2-amino-4-hydroxy-6-methylpyrimidine, 8.2 parts of hexamethylene diisocyanate, and 0.35 parts of pyridine were heated to 105°C under a nitrogen atmosphere and reacted for 10 h. The mixture was then cooled to room temperature to obtain a crude product. The crude product was added to 6 parts of n-hexane and stirred for 5 min. The mixture was allowed to stand for 15 min to settle, then filtered and the solid phase was collected. The solid phase was washed three times with acetone and dried under vacuum to constant weight to obtain a ureidylpyrimidinone derivative containing isocyanate groups.

[0034] Weigh out 9.5 parts by weight of β-cyclodextrin-grafted hyperbranched polyglycidyl ether, 20 parts of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer (number average molecular weight approximately 3500 Da), 20 parts of polyepoxysuccinic acid (number average molecular weight approximately 1000 Da), 20 parts of S-carboxyethyl thiosuccinic acid, 8.5 parts of 2,4,6-trimercapto-1,3,5-triazine, 3 parts of sodium molybdate dihydrate, 12 parts of sodium polyacrylate, 6 parts of N-octadecyl-D-glucosamide, and 65 parts of water. Add these to a stirred tank and stir at 120 rpm and 60°C for 8 min, controlling the pH to 7.8~8.2. Keep the mixture at 70 rpm and 50°C for 40 min, then cool to room temperature. Add 2.2 parts of isocyanate-containing ureidopyrimidinone derivative and 1.2 parts of 2,6-pyridinedicarboxamide and mix well to obtain the phosphorus-free composite scale inhibitor.

[0035] Example 3

[0036] 1.25 parts of 2-amino-4-hydroxy-6-methylpyrimidine, 11 parts of hexamethylene diisocyanate, and 0.55 parts of N-methylpyrrolidone were heated to 115°C under a nitrogen atmosphere and reacted for 7 h. The mixture was then cooled to room temperature to obtain a crude product. The crude product was added to 7 parts of petroleum ether and stirred for 5 min. The mixture was allowed to stand for 15 min to settle. The solid phase was then filtered and collected. The solid phase was washed three times with acetone and dried under vacuum to constant weight to obtain a ureidylpyrimidinone derivative containing isocyanate groups.

[0037] Weigh out 7.5 parts by weight of β-cyclodextrin-grafted hyperbranched polyglycidyl ether, 15 parts of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer (number average molecular weight approximately 2500 Da), 15 parts of polyepoxysuccinic acid (number average molecular weight approximately 1200 Da), 18 parts of S-carboxyethyl thiosuccinic acid, 10.5 parts of 2,4,6-trimercapto-1,3,5-triazine, 6 parts of sodium molybdate dihydrate, 9.5 parts of sodium polyacrylate, 3.5 parts of N-octadecyl-D-glucosamide, and 80 parts of water. Add these to a stirred tank and stir at 100 rpm and 55°C for 20 min, controlling the pH to 7.8~8.2. Keep the mixture at 20 rpm and 60°C for 20 min, then cool to room temperature. Add 1.2 parts of isocyanate-containing ureidopyrimidinone derivative and 1 part of 2,6-pyridinedicarboxamide and mix well to obtain the phosphorus-free composite scale inhibitor.

[0038] Comparative Example 1

[0039] Without adding β-cyclodextrin grafted hyperbranched polyglycidyl ether, the remaining steps and raw materials are the same as in Example 1.

[0040] Comparative Example 2

[0041] Without adding 2,4,6-trimercapto-1,3,5-triazine, the remaining steps and raw materials used are the same as in Example 1.

[0042] Comparative Example 3

[0043] Without adding N-octadecyl-D-glucosamide, the remaining steps and raw materials used are the same as in Example 1.

[0044] Comparative Example 4

[0045] Without adding isocyanate-containing ureidopyrimidinone derivatives, the remaining steps and raw materials are the same as in Example 1.

[0046] Comparative Example 5

[0047] Without adding 2,6-pyridinedicarboxamide, the remaining steps and raw materials used are the same as in Example 1.

[0048] Implementation effect evaluation

[0049] After fully dissolving calcium chloride, magnesium chloride, and sodium silicate in water, ammonia was added to adjust the pH to 9.6-9.8 to obtain a high-concentration test solution, in which the calcium ion concentration was 800 mg / L and the magnesium ion concentration was 400 mg / L.

[0050] 125 mg of the phosphorus-free composite scale inhibitor obtained in Example 1 was mixed with 1 L of high-concentration test solution and recorded as the test group; another 1 L of high-concentration test solution was recorded as the blank group. The dosing group and the blank group were added to an autoclave, and pretreated carbon steel plates (80×100×2.5 mm in size, polished to Ra=0.8 μm) were immersed in the autoclave. The temperature was raised to 145℃ and the pressure was 1.3 MPa. During the process, the pH was maintained at 9.6~9.8, and the mixture was stirred and kept at the temperature for 24 h. After 24 h, stirring was stopped, and the temperature was lowered to room temperature. The aqueous solutions of the dosing group and the blank group were used to test the scale inhibition rate. The plates were immersed in 10 wt% HCl and repeatedly washed for 2 min. They were then removed, rinsed with clean water, and dried until there was no change in weight. The corrosion rate was then tested. The specific data are shown in Table 1.

[0051] Formula for calculating scale inhibition rate (%): ;

[0052] C0 represents the calcium and magnesium ion concentration at the endpoint of the blank group (without the addition of phosphorus-free composite scale inhibitor); C1 represents the calcium and magnesium ion concentration at the endpoint of the test group (with the addition of phosphorus-free composite scale inhibitor); C2 represents the calcium and magnesium ion concentration of the high-concentration test solution (calcium ion concentration 800 mg / L, magnesium ion concentration 400 mg / L).

[0053] Formula for calculating annual average corrosion rate (mm / a): ;

[0054] ρ is the density of the hanging strips, and A is the exposed area of ​​the hanging strips (cm²). 2 ), t is time (h), m0 is the initial mass of the hanging piece, and m1 is the mass of the hanging piece after the experiment, in kg. Specific data are shown in Table 1.

[0055] Table 1 Performance test results of phosphorus-free composite scale inhibitor

[0056]

[0057] As shown in Table 1, Examples 1-3 of the present invention achieve the effect of virtually no scaling with high concentration silicates using a small amount of the present invention.

Claims

1. A phosphorus-free composite scale inhibitor, characterized in that, The product comprises, by weight parts, the following components: 4.5-9.5 parts of β-cyclodextrin-grafted hyperbranched polyglycidyl ether, 8-20 parts of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, 15-30 parts of polyepoxysuccinic acid, 18-30 parts of S-carboxyethyl thiosuccinic acid, 6.5-10.5 parts of 2,4,6-trimercapto-1,3,5-triazine, 3-6 parts of sodium molybdate dihydrate, 5-12 parts of sodium polyacrylate, 2-6 parts of N-octadecyl-D-glucosamide, 1.2-3 parts of isocyanate-containing ureidopyrimidinone derivative, 0.5-1.2 parts of 2,6-pyridinedicarboxamide, and 65-85 parts of water.

2. The phosphorus-free composite scale inhibitor according to claim 1, characterized in that, The number average molecular weight of polyepoxysuccinic acid is 800~1200 Da; the number average molecular weight of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer is 2500~3500 Da.

3. The phosphorus-free composite scale inhibitor according to claim 1, characterized in that, The preparation method of ureidopyrimidinone derivatives containing isocyanate groups involves reacting pyrimidine monomers, isocyanate monomers, and catalysts in an inert atmosphere to obtain a crude product. The crude product is then post-treated to obtain ureidopyrimidinone derivatives containing isocyanate groups.

4. The phosphorus-free composite scale inhibitor according to claim 3, characterized in that, The mass ratio of pyrimidine monomer, isocyanate monomer and catalyst is 125:(580~1100):(35~55), the pyrimidine monomer is 2-amino-4-hydroxy-6-methylpyrimidine, the isocyanate monomer is hexamethylene diisocyanate, and the catalyst is N-methylpyrrolidone or pyridine.

5. The phosphorus-free composite scale inhibitor according to claim 3, characterized in that, The reaction temperature is 100~115℃, and the reaction time is 7~10h.

6. The phosphorus-free composite scale inhibitor according to claim 3, characterized in that, Post-treatment includes sedimentation, filtration, washing and drying. Sedimentation refers to adding the crude product to a solvent for sedimentation. The solvent is one of n-pentane, n-hexane or petroleum ether.

7. The phosphorus-free composite scale inhibitor according to claim 6, characterized in that, The mass ratio of pyrimidine monomer to solvent is 125:(600~700).

8. A method for preparing the phosphorus-free composite scale inhibitor according to any one of claims 1-7, characterized in that, Includes the following steps: β-Cyclodextrin-grafted hyperbranched polyglycidyl ether, acrylate-2-acrylamide-2-methylpropanesulfonic acid copolymer, polyepoxysuccinic acid, S-carboxyethylthiosuccinic acid, 2,4,6-trimercapto-1,3,5-triazine, sodium molybdate dihydrate, sodium polyacrylate, N-octadecyl-D-glucosamide, and water were weighed, and the mixture was stirred, pH adjusted, and kept at a constant temperature. Then, ureidopyrimidinone derivatives containing isocyanate groups and 2,6-pyridinedicarboxamide were weighed and mixed to prepare a phosphorus-free composite scale inhibitor.

9. The method for preparing the phosphorus-free composite scale inhibitor according to claim 8, characterized in that, The stirring temperature is 50~60℃, and the stirring time is 8~20min.

10. The method for preparing the phosphorus-free composite scale inhibitor according to claim 8, characterized in that, Adjust the pH to 7.8~8.2, keep the temperature at 40~60℃, and keep the temperature for 20~40 minutes.

Images