Preparation method of modified polyacrylate resin with high water absorption

Abstract

The invention relates to the technical field of polyacrylic resin, and discloses a preparation method of modified polyacrylate resin with high water absorbability, and the modified polyacrylate resin with high water absorbability is obtained by reacting deionized water, acrylic acid, sodium hydroxide, an allyl cation UPy monomer and an initiator. The modified polyacrylate resin is self-crosslinked in water to form a gelatinous substance with a network structure, a chemical crosslinking agent does not need to be added, and the modified polyacrylate resin contains hydrophilic quaternary ammonium salt groups, so that the water absorption rate of the resin is remarkably improved. The prepared quaternary ammonium salt adsorbent has good adsorption performance, has more adsorption sites, contains a large number of quaternary ammonium salt cations, can effectively adsorb anionic dyes sunset yellow and reactive blue 19, and remarkably improves the adsorption performance on the anionic dyes.

Description

Technical Field

[0001] The invention relates to the technical field of polyacrylic acid resins, in particular to a method for preparing a highly water-absorbent modified polyacrylic acid salt resin. Background Art

[0002] Polyacrylic acid resins are highly hydrophilic and have excellent adsorption properties, making them widely used. Typically, during resin preparation, crosslinking agents such as N,N'-methylenebisacrylamide and ethylene glycol methacrylate are added to form a crosslinked network, resulting in excellent water absorption and adsorption properties. These crosslinked networks have important practical applications in soil water conservation and wastewater treatment. Patent Publication No. CN118703010A discloses a high-strength hydrogel with physical and chemical synergistic crosslinking, as well as its preparation method and application. Using acrylic acid, acrylamide, chitosan quaternary ammonium salt, a chemical crosslinker, and lithiasis earth as raw materials, the hydrogels prepared exhibit excellent adsorption properties for cationic dyes. However, the hydrogels described in this patent require the additional addition of a chemical crosslinker, do not exhibit high water absorption, and lack good adsorption properties for anionic dyes. Summary of the Invention

[0003] The invention provides a preparation method of a highly water-absorbent modified polyacrylic acid resin, which solves the problems of low water absorption of polyacrylic acid resin and poor adsorption performance for anionic dyes.

[0004] The technical solution of the present invention is: a method for preparing a highly water-absorbent modified polyacrylate resin, wherein deionized water and acrylic acid are added to a flask, sodium hydroxide is added to the solution after stirring, and then a compound having the structural formula Allyl cationic UPy monomer (R is Cl or Br) and an initiator are added, nitrogen is introduced, and the reaction is stirred. The solution is cooled in an ice-water bath, filtered, and the product is washed with water and ethanol in sequence, and dried to obtain a highly water-absorbent modified polyacrylate resin.

[0005] Furthermore, sodium hydroxide is added to control the neutralization degree of the solution to 50-80%.

[0006] Furthermore, the reaction is carried out at 65-80° C. for 3-4 h.

[0007] Furthermore, the ratio of acrylic acid, allyl cationic UPy monomer, and initiator is (0.65-0.8) mol: (0.2-0.35) mol: (5-6.2) mmol.

[0008] Furthermore, the initiator is potassium persulfate or ammonium persulfate.

[0009] Furthermore, the preparation method of the allyl cationic UPy monomer is as follows: dichloromethane and the structural formula The Upy-HDI monomer has the structural formula N-(2-hydroxyethyl)-N,N-dimethylprop-2-ene-1-ammonium halide and dibutyltin dilaurate are added, nitrogen is introduced, heated to 40-45°C, stirred, condensed and refluxed for 2-3 hours, dichloromethane is removed by rotary evaporation, and petroleum ether is washed. The product is recrystallized and purified in a mixed solution of acetone and isopropanol to obtain an allyl cationic UPy monomer.

[0010] Furthermore, the ratio of dichloromethane, Upy-HDI monomer, and dibutyltin dilaurate is 1 mol: (1-1.1) mol: (0.8-1.3) mmol.

[0011] The beneficial technical effect of the present invention is that an allyl cationic UPy monomer is polymerized with acrylic acid to obtain a highly water-absorbent modified polyacrylic acid salt resin. The modified polyacrylic acid salt resin contains a UPy structure, which forms quadruple hydrogen bonds between polyacrylic acid salt molecular chains to form a primary crosslink. The modified polyacrylic acid salt resin also contains sodium carboxylate anions and quaternary ammonium salt cations to form an electrostatic interaction to form a secondary crosslink. No chemical crosslinking agent is required, so that the polyacrylic acid salt resin self-crosslinks in water to form a gel-like substance with a network structure. The modified polyacrylic acid salt resin also contains hydrophilic quaternary ammonium salt groups, which significantly improves the water absorption rate of the resin.

[0012] The modified polyacrylic acid salt resin of the present invention is cross-linked in water to form a gel-like substance with a network structure, has more adsorption sites, and contains a large amount of quaternary ammonium salt cations, which can effectively adsorb anionic dyes such as sunset yellow and reactive blue 19, and significantly improve the resin's adsorption performance for these anionic dyes. DETAILED DESCRIPTION

[0013] The present application is described in detail below. However, these embodiments do not limit the present application, and any structural, methodological, or functional changes made by a person skilled in the art based on these embodiments are all included in the scope of protection of the present application.

[0014] Add 54.4g hexamethylene diisocyanate and 5.82g 2-amino-4-hydroxy-6-methylpyrimidine (CAS No. 3977-29-5) to the flask, introduce nitrogen, heat to 100°C, reflux under condensation for 12h, cool, add petroleum ether for precipitation, filter, wash with petroleum ether, and dry to obtain Upy-HDI monomer with the structural formula: .

[0015] In an ice bath, 20 mL of acetonitrile, 0.89 g of N,N-dimethylethanolamine (CAS No. 108-01-0), and 0.92 g of 3-chloropropylene were added to a flask and stirred for 1 h. The mixture was then heated to 60°C and reacted for 12 h. The mixture was rotary evaporated and the product was recrystallized from a solution of acetonitrile and n-hexane to obtain N-(2-hydroxyethyl)-N,N-dimethylprop-2-en-1-ammonium chloride, with the structural formula: .

[0016] In an ice bath, 20 mL of acetonitrile, 0.89 g of N,N-dimethylethanolamine (CAS No. 108-01-0), and 1.46 g of 3-bromopropylene were added to a flask and stirred for 1 h. The mixture was then heated to 60°C and reacted for 5 h. The mixture was rotary evaporated and the product was recrystallized from a solution of acetonitrile and n-hexane to obtain N-(2-hydroxyethyl)-N,N-dimethylprop-2-en-1-ammonium chloride, with the structural formula: . Example

[0017] (1) 120 mL of dichloromethane, 40 mmol of Upy-HDI monomer, 40 mmol of N-(2-hydroxyethyl)-N,N-dimethylprop-2-en-1-ammonium chloride, and 0.052 mmol of dibutyltin dilaurate were added to a flask. The mixture was heated to 40 °C in a nitrogen atmosphere and stirred under reflux for 3 h. The dichloromethane was removed by rotary evaporation and the mixture was washed with petroleum ether. The product was recrystallized and purified in a mixed solution of acetone and isopropanol to obtain an allyl cationic UPy monomer.

[0018] (2) Add 600 mL of deionized water and 80 mmol of acrylic acid into a flask, stir, and then add sodium hydroxide to the solution to control the neutralization degree of the solution to 65%. Then add 20 mmol of allyl cationic UPy monomer and 0.057 mmol of ammonium persulfate, introduce nitrogen, heat to 70 ° C, stir and react for 4 hours, cool the solution in an ice water bath, filter, wash with water and ethanol in turn, and dry to obtain a highly water-absorbent modified polyacrylate resin. Example

[0019] (1) 150 mL of dichloromethane, 40 mmol of Upy-HDI monomer, 44 mmol of N-(2-hydroxyethyl)-N,N-dimethylprop-2-en-1-ammonium bromide, and 0.032 mmol of dibutyltin dilaurate were added to a flask. The mixture was heated to 45 °C in a nitrogen atmosphere and stirred under reflux for 2 h. The dichloromethane was removed by rotary evaporation and the mixture was washed with petroleum ether. The product was recrystallized and purified in a mixed solution of acetone and isopropanol to obtain an allyl cationic UPy monomer.

[0020] (2) Add 600 mL of deionized water and 75 mmol of acrylic acid into a flask, stir, and then add sodium hydroxide to the solution to control the neutralization degree of the solution to 50%. Then add 25 mmol of allyl cationic UPy monomer and 0.062 mmol of ammonium persulfate, introduce nitrogen, heat to 65 ° C, stir and react for 4 hours, cool the solution in an ice water bath, filter, wash with water and ethanol in turn, and dry to obtain a highly water-absorbent modified polyacrylate resin. Example

[0021] (1) 600 mL of deionized water and 70 mmol of acrylic acid were added to a flask. After stirring, sodium hydroxide was added to the solution to control the neutralization degree of the solution to 70%. Then, 30 mmol of allyl cationic UPy monomer (prepared in Example 1) and 0.05 mmol of potassium persulfate were added. Nitrogen was introduced, and the mixture was heated to 65° C. and stirred for 4 h. The solution was cooled in an ice-water bath, filtered, washed with water and ethanol in sequence, and dried to obtain a highly water-absorbent modified polyacrylate resin. Example

[0022] (1) 700 mL of deionized water and 65 mmol of acrylic acid were added to a flask. After stirring, sodium hydroxide was added to the solution to control the neutralization degree of the solution to 80%. Then, 35 mmol of allyl cationic UPy monomer (prepared in Example 1) and 0.053 mmol of ammonium persulfate were added. Nitrogen was introduced, and the mixture was heated to 80°C and stirred for 3 hours. The solution was cooled in an ice-water bath, filtered, washed with water and ethanol in sequence, and dried to obtain a highly water-absorbent modified polyacrylate resin.

[0023] Comparative Example 1: This comparative example differs from Example 1 in that acrylic acid is used instead of the allyl cationic UPy monomer.

[0024] (1) Add 600 mL of deionized water and 100 mmol of acrylic acid into a flask. After stirring, add sodium hydroxide to the solution to control the neutralization degree of the solution to 65%. Then add 0.057 mmol of ammonium persulfate, introduce nitrogen, heat to 70°C, stir and react for 4 hours, cool the solution in an ice-water bath, filter, wash with water and ethanol in sequence, and dry to obtain a polyacrylate resin.

[0025] Comparative Example 2: This comparative example differs from Example 1 in that N-(2-hydroxyethyl)-N,N-dimethylprop-2-en-1-ammonium chloride is used instead of the allyl cationic UPy monomer.

[0026] (1) Add 600 mL of deionized water and 80 mmol of acrylic acid into a flask, stir, and add sodium hydroxide to the solution to control the neutralization degree of the solution to 65%. Then add 20 mmol of allyl cationic UPy monomer and 0.057 mmol of ammonium persulfate, introduce nitrogen, heat to 70 ° C, stir and react for 4 hours, cool the solution in an ice water bath, filter, wash with water and ethanol in sequence, and dry to obtain a modified polyacrylate resin.

[0027] In comparative example 3, the allyl cationic UPy monomer was replaced by a methacrylate UPy monomer.

[0028] (1) Add 20 mL of dimethyl sulfoxide solvent and 1.48 g of 2-amino-4-hydroxy-6-methylpyrimidine to a flask, heat to 150 ° C, stir to dissolve, and then cool to room temperature. Add 2 g of isocyanoethyl methacrylate and stir to react for 2 h. Heat and distill under reduced pressure to remove dimethyl sulfoxide. The product is added to acetone, filtered, washed with acetone, and dried to obtain methacrylate UPy monomer with the structural formula: .

[0029] (2) Add 600 mL of deionized water and 80 mmol of acrylic acid to a flask, stir, and add sodium hydroxide to the solution to control the neutralization degree of the solution to 65%. Then add 20 mmol of methyl acrylate UPy monomer and 0.057 mmol of ammonium persulfate, introduce nitrogen, heat to 70 ° C, stir and react for 4 hours, cool the solution in an ice water bath, filter, wash with water and ethanol in turn, and dry to obtain a modified polyacrylate resin.

[0030] Weigh the dried polyacrylate resin and add it to 2 L of deionized water. Stir and let it stand for 6 hours. Filter and hang it for 10 minutes to drain any remaining water. Weigh it and calculate the water absorption rate W, where W = m0 / m. m0 is the mass before water absorption and m is the mass after water absorption.

[0031] Add 20 mg of sunset yellow to 1 L of deionized water and stir to prepare a 20 mg / L solution. Then, add 200 mg of polyacrylate resin and allow adsorption at 20°C for 3 h. The upper layer of the solution was collected and the absorbance and concentration of sunset yellow were measured using a UV spectrophotometer. The sunset yellow removal efficiency, Q, was calculated as (C0 - C0) / C0 × 100%. C0 is the concentration of sunset yellow in the solution before adsorption, and C is the concentration of sunset yellow in the solution after adsorption.

[0032] Add 20 mg of Reactive Blue 19 to 1 L of deionized water and stir to prepare a 20 mg / L solution. Then, add 250 mg of polyacrylate resin and allow to adsorb at 20°C for 3 h with stirring. The upper layer of solution was collected and the absorbance and concentration of Reactive Blue 19 were measured using a UV spectrophotometer. The Reactive Blue 19 removal rate, Q, was calculated as (C0 - C0) / C0 × 100%. C0 is the concentration of Reactive Blue 19 in the solution before adsorption, and C is the concentration of Reactive Blue 19 in the solution after adsorption.

[0033] Table 1 Properties of polyacrylate resin After testing, the modified polyacrylate resin prepared in each embodiment has a high water absorption rate and a high removal rate for anionic dyes sunset yellow and reactive blue 19, mainly because the modified polyacrylate resin contains UPy structure ( ), forming quadruple hydrogen bonds between polyacrylate molecular chains, creating a primary crosslink. The presence of sodium carboxylate anions and quaternary ammonium cations creates electrostatic interactions, resulting in a secondary crosslink. This allows the polyacrylate resin to self-crosslink in water to form a gel-like substance with a network structure. The presence of hydrophilic quaternary ammonium groups significantly increases the resin's water absorption. The gel also possesses more adsorption sites and contains a large number of quaternary ammonium cations, effectively adsorbing the anionic dyes Sunset Yellow and Reactive Blue 19, significantly improving the resin's adsorption performance for these anionic dyes.

[0034] The polyacrylic acid salt in comparative example 1 is highly water-soluble, dissolves in water, and has no water absorption rate. In addition, the polyacrylic acid salt is a linear molecular chain, has no cross-linked network, and does not contain cationic groups. It has poor adsorption performance for anionic dyes such as sunset yellow and reactive blue 19, and the removal rate is very low.

[0035] Comparative Example 2: N-(2-hydroxyethyl)-N,N-dimethylprop-2-ene-1-ammonium chloride is polymerized with acrylic acid. The resulting modified polyacrylate resin does not contain a UPy structure and cannot be cross-linked through quadruple hydrogen bonds. It relies solely on the electrostatic interaction between anions and quaternary ammonium cations, making it difficult to cross-link to form a gel-like substance with a network structure. As a result, it dissolves in water, has no water absorption rate, and has fewer adsorption sites. As a result, the adsorption performance for sunset yellow and reactive blue 19 is poor, and the removal rate is low.

[0036] In Comparative Example 3, a modified polyacrylate resin obtained by polymerization reaction of methacrylate UPy monomer and acrylic acid does not contain quaternary ammonium cations, is cross-linked only by quadruple hydrogen bonds, and does not form secondary cross-links through electrostatic interactions. The cross-linking degree is low, and a gel-like substance with a good network structure is not formed, resulting in a low water absorption rate. In addition, the resin does not contain quaternary ammonium cations, and has poor adsorption performance for sunset yellow and reactive blue 19, resulting in a low removal rate.

[0037] The above description of the present disclosure is provided to enable any person skilled in the art to implement or use the present disclosure. Various modifications to the present disclosure will be apparent to those skilled in the art.

Claims

1. A method for preparing a highly water-absorbent modified polyacrylate resin, characterized in that: The preparation method comprises the following steps: adding deionized water and acrylic acid into a flask, stirring, adding sodium hydroxide to the solution, then adding allyl cationic UPy monomer and initiator, introducing nitrogen, stirring for reaction, cooling the solution, filtering, washing the product, and drying to obtain a highly water-absorbent modified polyacrylate resin; The structural formula of the allyl cationic UPy monomer is as follows: , R is Cl or Br.

2. The method for preparing a highly water-absorbent modified polyacrylate resin according to claim 1, wherein: The sodium hydroxide is added to control the neutralization degree of the solution to be 50-80%.

3. The method for preparing a highly water-absorbent modified polyacrylate resin according to claim 1, wherein: The reaction was carried out at 65-80°C for 3-4 h.

4. The method for preparing a highly water-absorbent modified polyacrylate resin according to claim 1, wherein: The ratio of acrylic acid, allyl cationic UPy monomer and initiator is (0.65-0.8) mol: (0.2-0.35) mol: (5-6.2) mmol.

5. The method for preparing the highly water-absorbent modified polyacrylate resin according to claim 4, wherein: The initiator is potassium persulfate or ammonium persulfate.

6. The method for preparing a highly water-absorbent modified polyacrylate resin according to claim 4, wherein: The preparation method of the allyl cationic UPy monomer comprises: adding dichloromethane, Upy-HDI monomer, N-(2-hydroxyethyl)-N,N-dimethylprop-2-en-1-ammonium halide, and dibutyltin dilaurate into a flask, introducing nitrogen, stirring for reaction, and then rotary evaporating to remove dichloromethane, washing with petroleum ether, and recrystallizing and purifying the product in a mixed solution of acetone and isopropanol to obtain the allyl cationic UPy monomer; The structural formula of the Upy-HDI monomer is ; The structural formula of the N-(2-hydroxyethyl)-N,N-dimethylprop-2-ene-1-ammonium halide is: , R is Cl or Br.

7. The method for preparing a highly water-absorbent modified polyacrylate resin according to claim 6, wherein: The ratio of the dichloromethane, Upy-HDI monomer, and dibutyltin dilaurate is 1 mol: (1-1.1) mol: (0.8-1.3) mmol.

8. The method for preparing a highly water-absorbent modified polyacrylate resin according to claim 6, wherein: In the allyl cationic UPy monomer, the reaction is carried out at 40-45° C. and refluxed under condensation for 2-3 hours.

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