Method for synthesizing maleic acid-acrylic acid copolymer by using oxalic acid and hydrogen peroxide

Abstract

The invention discloses a method for synthesizing a maleic acid-acrylic acid copolymer by using oxalic acid and hydrogen peroxide. The method comprises the following steps: providing an acrylic monomer solution, an oxalic acid aqueous solution and hydrogen peroxide; the method comprises the following steps: putting reverse osmosis water and maleic anhydride monomers into a reactor, heating to 30-60 DEG C, slowly dropwise adding an acrylic monomer solution, an oxalic acid aqueous solution and hydrogen peroxide under a constant temperature condition, reacting for 2-6 hours by dropwise adding, and preserving heat for 1-4 hours after dropwise adding is finished; and after the reaction is finished, cooling to obtain the maleic acid-acrylic acid copolymer. The obtained product is controllable in molecular weight and excellent in scale inhibition performance, has the advantages of being environmentally friendly, low in energy consumption and low in cost, and is suitable for the field of industrial water treatment and the field of electronic-grade chemicals.

Description

Technical Field

[0001] The invention relates to the fields of water treatment agents and electronic-grade chemicals, and in particular to a method for synthesizing a maleic acid-acrylic acid copolymer by utilizing oxalic acid and hydrogen peroxide. Background Art

[0002] Maleic acid-acrylic acid copolymer (MA-AA) is a highly effective water treatment agent. Traditional synthesis methods often use persulfates (such as ammonium persulfate and sodium persulfate) as initiators, which have the following drawbacks: ① High temperature requirement: Persulfate needs to be decomposed at high temperatures (>70°C) to generate free radicals, which consumes a lot of energy; ② Byproduct pollution: Sulfate residues can easily cause eutrophication of water bodies; ③ High cost: Persulfate is expensive, and industrial production costs are high.

[0003] To address the above problems, the present invention proposes to use oxalic acid (H2C2O4) and hydrogen peroxide (H2O2) as a redox initiation system to efficiently initiate the MA-AA copolymerization reaction under mild conditions, which has the advantages of environmental protection, low energy consumption and low cost, and expands its application field - electronic-grade chemicals. Summary of the Invention

[0004] To address the energy consumption issues associated with conventional high-temperature processes for preparing maleic acid-acrylic acid copolymers, the present invention provides a method for synthesizing maleic acid-acrylic acid copolymers using oxalic acid and hydrogen peroxide. The resulting maleic acid-acrylic acid copolymers are suitable for use as scale inhibitors and dispersants in water treatment and as electronic-grade chemicals.

[0005] The first object of the present invention is to provide a method for synthesizing a maleic acid-acrylic acid copolymer using oxalic acid and hydrogen peroxide, comprising the following steps:

[0006] Provide an acrylic acid monomer solution, an oxalic acid aqueous solution and hydrogen peroxide;

[0007] Put reverse osmosis water and maleic anhydride monomer into the reactor, increase the temperature, slowly add acrylic acid monomer solution, oxalic acid aqueous solution, and hydrogen peroxide solution dropwise under constant temperature, and react for 2-6 hours. After the addition is complete, keep the temperature for 1-4 hours;

[0008] After the reaction is completed, the mixture is cooled to obtain the maleic acid-acrylic acid copolymer.

[0009] In some embodiments of the present invention, the heating temperature is 30-60°C. For example, it can be 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, etc., or any interval value between any two values.

[0010] In some embodiments of the present invention, the concentration of the acrylic acid monomer solution is 60 wt % to 90 wt %. For example, it can be 60 wt %, 65 wt %, 70 wt %, 75 wt %, 80 wt %, 85 wt %, 90 wt %, or any range between any two values.

[0011] In some embodiments of the present invention, the hydrogen peroxide solution is added after the acrylic acid monomer solution and the oxalic acid aqueous solution by 5-30 minutes. The core purpose of delaying the initiator addition in the present invention is to improve product properties, such as molecular weight distribution, monomer conversion, and composition uniformity, by controlling the timing and rate of initiator addition.

[0012] In some embodiments of the present invention, the mass ratio of acrylic acid monomer to maleic anhydride monomer is 1:1-1:4. For example, it can be 1:1, 1:2, 1:3, 1:4, etc., or any interval between any two values.

[0013] In some embodiments of the present invention, the reverse osmosis water is primary reverse osmosis water, secondary reverse osmosis water or ultrapure water.

[0014] In some embodiments of the present invention, the concentration of the oxalic acid aqueous solution is 5wt%-8.5wt%, and illustratively, it can be 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, 8.5wt%, etc., or any interval value between any two values; the amount of oxalic acid is 0.5%-3.0% of the total mass of the acrylic acid and maleic anhydride monomers, and illustratively, it can be 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3.0wt%, etc., or any interval value between any two values.

[0015] In some embodiments of the present invention, the mass concentration of the hydrogen peroxide is 27.5%-35.0%, for example, 27.5wt%, 28wt%, 28.5wt%, 29wt%, 29.5wt%, 30wt%, 30.5wt%, 31wt%, 32wt%, 33wt%, 34wt%, 35wt%, etc., or any interval value between any two values; the amount of hydrogen peroxide used is acrylic acid and maleic anhydride monomers. 3.0%-30.0% of the total mass, illustratively, can be 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, etc., or any interval value between any two values.

[0016] In some embodiments of the present invention, the mass ratio of reverse osmosis water to maleic anhydride monomer is 1:1-4:1. For example, it can be 1:1, 1:2, 1:3, 1:4, etc., or any interval between any two values.

[0017] In some embodiments of the present invention, the molecular weight of the maleic acid-acrylic acid copolymer is 2,000-10,000.

[0018] The present invention generates hydroxyl radicals (·OH) through the redox reaction of oxalic acid and hydrogen peroxide, and initiates monomer polymerization under mild conditions (30-60° C.), thereby solving the energy consumption problem of traditional high-temperature processes.

[0019] Its core principles are as follows:

[0020] Oxalic acid (reducing agent) and hydrogen peroxide (oxidizing agent) undergo redox reaction under acidic or neutral conditions to generate highly active hydroxyl radicals (·OH) and carbon dioxide (CO2). The reaction formula is as follows: H2C2O4+H2O2→2CO2+2H2O+2·OH.

[0021] Hydroxyl radical (·OH): As a primary free radical, it attacks the double bonds in monomer molecules (such as acrylic acid, maleic anhydride, etc.) and initiates a chain polymerization reaction.

[0022] From the above reaction principle, we know that the reaction generates carbon dioxide and water, does not introduce by-products into the system, and has low energy consumption and low cost.

[0023] In the present invention, when hydrogen peroxide (H2O2) and the more commonly used persulfate are used as initiators, both initiate polymerization by generating free radicals, but their reaction mechanisms, initiation conditions, and applicable scenarios are significantly different. In particular, there are significant differences in the reaction principle: hydrogen peroxide mainly generates hydroxyl radicals in the redox system; persulfate mainly generates sulfate radicals (·SO4 - ). In terms of by-products, hydrogen peroxide decomposes to produce water and oxygen, and persulfate decomposes to produce sulfate.

[0024] Advantages of hydrogen peroxide: ① The decomposition products of hydrogen peroxide are only water (H2O) and oxygen (O2), with no toxic residues; sulfates will generate sulfate ions, leading to eutrophication of water bodies. ② It complies with the principles of green chemistry, reduces environmental pollution, and is suitable for sustainable development processes. ③ Low temperature and high efficiency: After forming a redox system with a reducing agent (such as oxalic acid), it can efficiently initiate the reaction at 30-60°C, and the energy consumption is reduced by more than 40% compared with traditional thermal initiators (such as ammonium persulfate requiring >70°C). ④ Low cost: The cost of oxalic acid and hydrogen peroxide is 50% lower than that of persulfate. ⑤ Controllable molecular weight and high efficiency: By adjusting the initiator ratio and reaction time, the molecular weight of the copolymer can be precisely controlled (2000-10000), and its scale inhibition rate is >90%, which is especially suitable for treating high hardness and high alkalinity water, and its performance is better than traditional scale inhibitors (scale inhibition rate between 85%-90%).

[0025] The above technical solution of the present invention has the following advantages over the prior art:

[0026] (1) Green and environmentally friendly, highly efficient initiation system: Oxalic acid reacts with hydrogen peroxide to generate hydroxyl radicals (·OH), eliminating sulfate residues. The reaction byproducts are only CO2 and H2O. This meets green chemistry requirements, significantly improves environmental friendliness, and eliminates the burden of wastewater treatment.

[0027] (2) Low-temperature energy saving and economic optimization: The reaction temperature is as low as 30°C, and the energy consumption is reduced by more than 40% compared with the traditional high-temperature process. The cost of oxalic acid and hydrogen peroxide is reduced by 50% compared with persulfate, and the overall production cost is reduced by 20%, which is suitable for large-scale industrial production.

[0028] (3) Controllable molecular weight and high efficiency: By adjusting the initiator ratio and reaction time, the molecular weight of the copolymer can be precisely controlled (2000-10000), and its scale inhibition rate is >90%, which is especially suitable for high hardness and high alkalinity water treatment. Its performance is better than traditional scale inhibitors (scale inhibition rate is between 85%-90%). BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0030] Figure 1 This is the ICP full scan result of the product in Example 1 of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0032] Example 1

[0033] This embodiment provides a method for synthesizing a maleic acid-acrylic acid copolymer using oxalic acid and hydrogen peroxide, as shown below:

[0034] (1) 333 g of acrylic acid was dissolved in 60 g of secondary reverse osmosis water (ultrapure water), and the mixture was stirred to obtain an acrylic acid solution for later use; 15 g of oxalic acid was dissolved in 172 g of secondary reverse osmosis water, and the mixture was stirred until the solution was completely dissolved to obtain an oxalic acid aqueous solution for later use; and 150 g of hydrogen peroxide (27.5 wt %) was prepared as an initiator for the polymerization reaction.

[0035] (2) 167 g of maleic anhydride and 167 g of secondary reverse osmosis water were added to a reactor, and the temperature was raised to 60° C. The acrylic acid monomer solution (dropping speed of 1.75 g / min), initiator hydrogen peroxide (dropping speed of 0.63 g / min), and oxalic acid aqueous solution (dropping speed of 0.85 g / min) were slowly added dropwise, and the reaction was carried out at a constant temperature of 60±2° C. for 4 hours; wherein, the initiator hydrogen peroxide dropwise addition time lagged behind the monomer solution and oxalic acid aqueous solution by 15 minutes.

[0036] (3) After the addition is complete, heat for 2 hours; after the heat preservation is completed, cool to room temperature and add secondary reverse osmosis water to dilute to a solid content of 50%, thereby obtaining a maleic acid-acrylic acid copolymer product. The obtained maleic acid-acrylic acid copolymer product was subjected to ICP testing. The experimental results are shown in FIG. Figure 1 ,Depend on Figure 1 It can be seen that the contents of target metal ions (such as Na, K, Fe, Cu, Ni, etc.) and harmful elements (such as Pb, Cd, As, Hg) in the obtained maleic acid-acrylic acid copolymer product are lower than the instrument detection limit (LOD), meeting the quality standards of high-purity electronic-grade chemicals.

[0037] Example 2

[0038] This embodiment provides a method for synthesizing a maleic acid-acrylic acid copolymer using oxalic acid and hydrogen peroxide, as shown below:

[0039] (1) Dissolve 400 g of acrylic acid in 70 g of secondary reverse osmosis water, stir evenly to obtain an acrylic acid solution, which is set aside; dissolve 10 g of oxalic acid in 115 g of secondary reverse osmosis water, stir until completely dissolved to obtain an oxalic acid aqueous solution, which is set aside; and simultaneously prepare 140 g of hydrogen peroxide (27.5%) as an initiator for the polymerization reaction.

[0040] (2) 100 g of maleic anhydride and 165 g of secondary reverse osmosis water were added to a reactor, and the temperature was raised to 60° C. The acrylic acid monomer solution (dropping speed of 1.75 g / min), initiator hydrogen peroxide (dropping speed of 0.63 g / min), and oxalic acid aqueous solution (dropping speed of 0.85 g / min) were slowly added dropwise. The addition was continued dropwise at a constant temperature of 60±2° C. for 5 hours. The addition time of the initiator hydrogen peroxide lagged behind that of the acrylic acid monomer solution and the oxalic acid aqueous solution by 15 minutes.

[0041] (3) After the addition is complete, heat preservation is performed for 2 hours; after the heat preservation is completed, the mixture is cooled to room temperature and diluted with secondary reverse osmosis water to a solid content of 50%, thereby obtaining a maleic acid-acrylic acid copolymer product.

[0042] Comparative Example 1

[0043] This comparative example provides a method for producing a maleic acid-acrylic acid copolymer, which is specifically as follows:

[0044] (1) Dissolve 333 g of acrylic acid in 60 g of secondary reverse osmosis water, stir evenly to obtain an acrylic acid solution, and set aside; dissolve 15 g of sodium persulfate in 135 g of secondary reverse osmosis water, stir until completely dissolved to obtain a sodium persulfate aqueous solution, and set aside; dissolve 5 g of sodium bisulfite in 95 g of secondary reverse osmosis water, stir until completely dissolved, and set aside.

[0045] (2) 167 g of maleic anhydride and 167 g of secondary reverse osmosis water were added to a reactor, the temperature was raised to 95° C., and acrylic acid monomer solution (dropping rate of 1.75 g / min), initiator sodium persulfate solution (dropping rate of 0.63 g / min), and sodium bisulfite aqueous solution (0.44 g / min) were slowly added dropwise, and the reaction was continued for 4 hours; wherein, the sodium persulfate solution was added dropwise 15 minutes later than the monomer solution and sodium bisulfite solution.

[0046] (3) After the addition is complete, heat preservation is performed for 2 hours; after the heat preservation is completed, the mixture is cooled to room temperature and diluted with secondary reverse osmosis water to a solid content of 50%, thereby obtaining a maleic acid-acrylic acid copolymer product.

[0047] Performance Testing

[0048] The viscosity average molecular weight and performance tests of Examples 1, 2 and Comparative Example 1 were performed, and the results are shown in the following table:

[0049] Table 1

[0050] Sample source Viscosity average molecular weight Calcium carbonate scale inhibition rate, % Example 1 4098 92.3 Example 2 4134 92 Comparative Example 1 5149 87.2

[0051] Note: The scale inhibition rate of calcium carbonate is tested in accordance with GB / T16632-2019 "Determination of scale inhibition performance of water treatment agents - Calcium carbonate precipitation method".

[0052] It can be clearly seen from the data in Table 1 that the viscosity-average molecular weight of Example 1 and Example 2 is lower than that of Comparative Example 1, and the calcium carbonate scale inhibition rate corresponding to the examples is also higher than that of the comparative example. The root of this difference lies in the choice of initiator. Comparative Example 1 uses persulfate as an initiator. After the reaction is completed, sulfate ions will remain in the product, which undoubtedly reduces the purity of the product. In contrast, Examples 1 and 2 of the present invention use hydrogen peroxide as an initiator. The products after the reaction are only the target product, water and oxygen, and no additional impurities are introduced, which greatly improves the purity of the final product. High-purity products have a more stable structure and a higher content of effective ingredients. In the calcium carbonate scale inhibition experiment, they can play a more full role. Therefore, the calcium carbonate scale inhibition rate corresponding to the examples must be higher than that of the comparative example.

[0053] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for synthesizing a maleic acid-acrylic acid copolymer using oxalic acid and hydrogen peroxide, characterized in that: The following steps are involved: Provide an acrylic acid monomer solution, an oxalic acid aqueous solution and hydrogen peroxide; Put reverse osmosis water and maleic anhydride monomer into the reactor, raise the temperature to 30-60°C, add acrylic acid monomer solution, oxalic acid aqueous solution and hydrogen peroxide dropwise under constant temperature, and react for 2-6 hours. After the addition is complete, keep warm for 1-4 hours; After the reaction is completed, the mixture is cooled to obtain the maleic acid-acrylic acid copolymer.

2. The method for synthesizing a maleic acid-acrylic acid copolymer using oxalic acid and hydrogen peroxide according to claim 1, wherein: The concentration of the acrylic acid monomer solution is 60 wt%-90 wt%.

3. The method for synthesizing a maleic acid-acrylic acid copolymer using oxalic acid and hydrogen peroxide according to claim 1, wherein: The time of adding hydrogen peroxide solution to the acrylic acid monomer solution and the oxalic acid aqueous solution is delayed by 5-30 minutes.

4. The method for synthesizing a maleic acid-acrylic acid copolymer using oxalic acid and hydrogen peroxide according to claim 1, wherein: The mass ratio of acrylic acid monomer to maleic anhydride monomer is 1:1-1:

4.

5. The method for synthesizing a maleic acid-acrylic acid copolymer using oxalic acid and hydrogen peroxide according to claim 1, wherein: Reverse osmosis water is primary reverse osmosis water, secondary reverse osmosis water or ultrapure water.

6. The method for synthesizing a maleic acid-acrylic acid copolymer using oxalic acid and hydrogen peroxide according to claim 1, wherein: The concentration of the oxalic acid aqueous solution is 5 wt%-8.5 wt%.

7. The method for synthesizing a maleic acid-acrylic acid copolymer using oxalic acid and hydrogen peroxide according to claim 1, wherein: The amount of oxalic acid used is 0.5%-3.0% of the total mass of acrylic acid and maleic anhydride monomers.

8. The method for synthesizing a maleic acid-acrylic acid copolymer using oxalic acid and hydrogen peroxide according to claim 1, wherein: The mass concentration of the hydrogen peroxide is 27.5%-35.0%; the amount of hydrogen peroxide used is 3.0%-30.0% of the total mass of acrylic acid and maleic anhydride monomers.

9. The method for synthesizing a maleic acid-acrylic acid copolymer using oxalic acid and hydrogen peroxide according to claim 1, wherein: The mass ratio of reverse osmosis water to maleic anhydride monomer is 1:1-4:

1.

10. The method for synthesizing a maleic acid-acrylic acid copolymer using oxalic acid and hydrogen peroxide according to claim 1, wherein: The molecular weight of the maleic acid-acrylic acid copolymer is 2000-10000.

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