A method for preparing super absorbent resin by metal enzyme catalysis

Abstract

The present invention discloses a method for preparing a superabsorbent resin using metalloenzyme catalysis, and relates to the technical field of resin material preparation. The method comprises the following steps: incubating a protein and a metal salt in deionized water at room temperature, adjusting the pH with an alkaline solution, allowing to stand at room temperature, and then centrifuging. Finally, washing with deionized water and drying the resulting metalloenzyme obtains the metalloenzyme; and mixing a resin monomer, a neutralizing solution, a metalloenzyme, acetylacetone, and a crosslinking agent in deionized water, allowing the mixture to stand at room temperature to obtain a resin colloid. Granulation and drying obtain the superabsorbent resin. The present invention utilizes an artificially synthesized metalloenzyme instead of a natural laccase to carry out the polymerization reaction. The metalloenzyme has a low preparation cost, and the amount of metalloenzyme used to oxidize acetylacetone is less than that of the natural laccase. Furthermore, the metalloenzyme-driven free radical polymerization can generate free radicals to complete resin polymerization without requiring external high-temperature stimulation. This method reduces preparation costs without affecting the resin's high water absorption and water retention, thereby achieving green synthesis of superabsorbent resin at room temperature.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of resin materials, and in particular to a method for preparing highly absorbent resin by metal enzyme catalysis. Background Art

[0002] Super absorbent polymer (SAP) is a novel functional organic polymer material with a three-dimensional network structure due to a low degree of cross-linking. SAP's molecular chains are rich in hydrophilic groups, allowing it to absorb hundreds to thousands of times its own weight in water. SAP not only has a strong water absorption capacity but also an outstanding water retention capacity. Even after absorbing water, it does not lose water even when pressurized, hence its name, "high water retention material."

[0003] The water absorption and swelling rate of SAP is typically affected by the solution's pH and ion concentration. Due to its unique properties, it is widely used in various fields. In agriculture, superabsorbent resins can be used to control the release of substances such as water, fertilizers, pesticides, and herbicides, and to protect soil from impacts that can cause soil hardening. In industry, they can be used for the adsorption and filtration of toxic heavy metals or dyes from industrial wastewater, the treatment of radioactive uranium ions, coal dehydration, and food packaging. In the biomedical field, they are used in tissue engineering, biosensors, drug delivery systems, and wound dressings. Superabsorbent polymers also play an important role in secondary energy storage, thermal energy storage, and artificial snowmaking. Currently, over 90% of SAP is used in disposable sanitary materials.

[0004] Polyacrylic acid is currently the most commonly used SAP material. The two most common polyacrylic acid polymers are sodium polyacrylate, formed by neutralizing acrylic acid with sodium hydroxide, and potassium polyacrylate, formed by neutralizing acrylic acid with potassium hydroxide. Free radical polymerization is a common method for SAP polymerization. The general steps involve neutralizing acrylic acid, distilled water, and alkaline solution in an ice-water bath. After removing oxygen, a peroxide initiator and a crosslinker are added at high temperature to form a gel. The SAP is then crushed and dried to obtain. Peroxide initiators include ammonium persulfate, potassium persulfate, and benzoyl peroxide, while crosslinkers include N,N-methylenebisacrylamide and divinylbenzene.

[0005] In recent years, the emerging enzyme-catalyzed free radical polymerization technology is more environmentally friendly than traditional free radical polymerization technology. For example, enzymes with peroxidase-like activity can catalyze peroxide initiators such as ammonium persulfate to produce hydroxyl radicals at room temperature to induce the polymerization of acrylic acid or acrylamide monomers. This type of strategy of using enzymes to initiate free radical polymerization at room temperature meets the requirements of green chemistry and has broad prospects. Acetylacetone, i.e., 2,4-pentanedione, is a redox mediator in enzyme-catalyzed free radical chemistry. It is not only widely present in plants but also an inexpensive and low-toxic industrial chemical. Acetylacetone is used as a redox mediator to construct a horseradish peroxidase-acetylacetone-hydrogen peroxide ternary catalytic system to achieve green synthesis of acrylamide. In the laccase system, acetylacetone is oxidized to carbon radicals to induce the polymerization of acrylamide, accompanied by the reduction of oxygen to water.

[0006] Currently, the existing document "FH, YG, CT, et al. Evaluation of the Laccase from Myceliophthora thermophila as Industrial Biocatalyst for Polymerization Reactions[J]. Macromolecules, 2008, 41(22): 8520-8524." discloses a system using laccase (derived from the thermophilic fungus Myceliophthora thermophila) to catalyze the polymerization of acrylamide. The system uses molecular oxygen as an electron acceptor to oxidize acetylacetone to generate carbon free radicals for polymerization to prepare polymerized acrylamide. The cost of catalyzing acrylamide polymerization by this system is extremely high. Specifically, laccase is expensive as a natural extract, the laccase enzyme activity is insufficient, and a high concentration of enzyme raw material is required to ensure a significant polymerization yield. The article points out that the cost of enzyme raw materials per kilogram of polyacrylamide produced by this strategy reaches 10 euros, while the cost of polyacrylamide produced by cheap industrial products such as persulfate as a catalytic reagent is about 8 yuan per kilogram (the price of Henan Yushuifeng Environmental Protection Technology Co., Ltd. on May 15, 2024). The cost disadvantage of the laccase strategy is too great. At the same time, laccase requires 50°C to exert its optimal enzyme activity, and the heat energy consumed is close to the persulfate hot start temperature of 60°C. In addition, the patent number is "202111242722.4" and the patent name is "A method for preparing a super absorbent resin". A method for obtaining a super absorbent resin is disclosed by mixing sodium hydroxide, acrylic acid, acrylamide, a cross-linking agent and ammonium persulfate, adding cyclohexane and Span 60, and stirring to 70°C for reaction for 2 hours. The use of persulfate in this preparation method to initiate polymerization at high temperature consumes huge energy, which is specifically manifested in that the reactants need to be reacted at 70°C for 2 hours. In view of the problems of high cost and large energy consumption in the existing enzyme-catalyzed free radical polymerization technology, the present invention provides a method for preparing a super absorbent resin by metal enzyme catalysis. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for preparing a super absorbent resin by metalloenzyme catalysis, which reduces costs by replacing natural laccase with artificially designed synthetic metalloenzymes. At the same time, the green synthesis of super absorbent resin at room temperature is achieved without affecting the high water absorption and water retention of the resin.

[0008] To achieve the above object, the present invention provides a method for preparing a super absorbent resin by metalloenzyme catalysis, comprising the following steps:

[0009] S1. Preparation of Metalloenzymes

[0010] The protein and metal salt are placed in deionized water and incubated at room temperature, and then the pH value is adjusted with an alkaline solution. The metal enzyme is then centrifuged after standing at room temperature and finally washed with deionized water and dried.

[0011] S2. Preparation of super absorbent resin

[0012] The resin monomer, neutralizing solution, metal enzyme, acetylacetone and cross-linking agent are placed in deionized water and mixed evenly, and allowed to stand at room temperature to obtain resin colloid, which is granulated and dried to obtain highly absorbent resin.

[0013] Preferably, in said S1, the room temperature range is 16°C-40°C, the room temperature incubation time is 1 hour, the pH is adjusted to 9-11, and the mixture is allowed to stand at room temperature for 7 hours.

[0014] Preferably, in S1, the protein is one or more of bovine serum albumin and soy protein; and the metal salt is one or more of manganese acetate, manganese chloride, manganese sulfate, ferric chloride and ferric sulfate.

[0015] Preferably, in said S1, the protein concentration is 0-0.1%, and the metal salt concentration is 1-10 mM.

[0016] Preferably, in S2, the room temperature range is 16°C-40°C, and the mixture is allowed to stand at room temperature for 6 hours.

[0017] Preferably, in S2, the resin monomer is one or more of acrylic acid and acrylamide; the neutralizing solution is one or more of sodium hydroxide and potassium hydroxide; and the cross-linking agent is one or more of methylene acrylamide, divinylbenzene, and ethylene glycol dimethacrylate.

[0018] Preferably, in S2, the resin monomer concentration is 20%-40%, the neutralizing solution concentration is 0-90%, the metalloenzyme concentration is 0.05%-1%, the acetylacetone concentration is 0.5%-2%, and the crosslinking agent concentration is 1%-5% of the resin monomer concentration.

[0019] Therefore, the present invention provides a method for preparing a super absorbent resin by metal enzyme catalysis, and the specific beneficial effects are as follows:

[0020] (1) The metalloenzyme preparation process used in the present invention only requires mixing protein, metal salt and deionized water at room temperature and letting it stand, waiting for the protein to adsorb metal ions, adjusting the pH to 9-11 with alkaline solution, and incubating at room temperature for 7 hours to obtain the enzyme. In addition, the super absorbent resin polymerization process does not require heating or the use of peroxide reagents, which meets the requirements of green chemistry.

[0021] (2) The present invention utilizes an artificially synthesized metalloenzyme instead of natural laccase to perform the polymerization reaction. On the one hand, the cost of the synthetic raw materials for the metalloenzyme is low, and the synthesis steps are simple, making the preparation cost of the metalloenzyme much lower than the extraction cost of natural laccase. On the other hand, because the relative enzymatic activity of the metalloenzyme in oxidizing acetylacetone is much higher than that of natural laccase, the amount of metalloenzyme consumed in the synthesis process is much lower than that of natural laccase. Therefore, the cost of using metalloenzymes for resin synthesis is lower than that of natural laccase.

[0022] (3) The preparation process of the super absorbent resin of the present invention is green and environmentally friendly, and the free radical polymerization driven by metal enzymes can generate free radicals to complete the resin polymerization without external high temperature stimulation.

[0023] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is an electron paramagnetic resonance spectrum of carbon free radicals in the polymerization of super absorbent resin catalyzed by metalloenzyme prepared in Example 1 of the present invention;

[0025] Figure 2 The following are Fourier infrared spectra of the enzyme-catalyzed super absorbent resin products prepared in Example 2 of the present invention and the comparative example. DETAILED DESCRIPTION

[0026] The present invention provides a method for preparing a super absorbent resin by metalloenzyme catalysis. Based on the principle of enzyme catalysis, the metalloenzyme is used to oxidize acetylacetone to generate carbon free radicals for polymerization of resin monomers. The preparation method specifically comprises the following steps:

[0027] S1. Preparation of Metalloenzymes

[0028] The protein, metal salt and deionized water were incubated at room temperature for 1 hour. Subsequently, the pH was adjusted to 9-11 with an alkaline solution. After standing at room temperature for 7 hours, the product was centrifuged, washed with deionized water and dried to obtain the metalloenzyme, which was stored at 4°C for a long time.

[0029] In the present invention, the room temperature range is 16° C.-40° C.; the protein is one or more of bovine serum albumin and soy protein, and the protein concentration is 0-0.1%; the metal salt is one or more of manganese acetate, manganese chloride, manganese sulfate, ferric chloride, and ferric sulfate, and the metal salt concentration is 1-10 mM.

[0030] S2. Preparation of super absorbent resin

[0031] The resin monomer, neutralizing solution, metal enzyme, acetylacetone and cross-linking agent are placed in deionized water and mixed evenly, and allowed to stand at room temperature for 6 hours to obtain a resin colloid, which is granulated and dried to obtain a highly absorbent resin.

[0032] In the present invention, the room temperature range is 16°C-40°C; the resin monomer is one or more of acrylic acid and acrylamide, and the resin monomer concentration is 20%-40%; the neutralizing solution is one or more of sodium hydroxide and potassium hydroxide, and the neutralizing solution concentration is 0-90%; the crosslinking agent is one or more of methylene acrylamide, divinylbenzene, and ethylene glycol dimethacrylate, and the crosslinking agent concentration is 1%-5% of the resin monomer concentration; the metal enzyme concentration is 0.05%-1%, and the acetylacetone concentration is 0.5%-2%.

[0033] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only intended to illustrate the present invention and are not intended to limit the scope of the present invention. Any other changes, modifications, substitutions, combinations, or simplifications made without violating the spirit and principles of the present invention should all be equivalent replacement methods and are included within the scope of protection of the present invention. It should also be understood that after reading the contents of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims appended to this application and all belong to the scope of protection of the present invention.

[0034] References to "embodiments" herein mean that the specific features, structures, or characteristics described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the word "embodiment" in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or relevance to other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the various technical features mentioned in the embodiments can be combined in any manner to form a corresponding implementable technical solution.

[0035] Unless otherwise defined, the technical terms used herein have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms herein is only for describing specific embodiments and is not intended to limit this application.

[0036] Unless otherwise specified, the reagents, instruments, and equipment used in the present invention are all commonly used by those skilled in the art. The main raw materials were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. and were of analytical grade.

[0037] Example 1

[0038] This embodiment provides a method for preparing a super absorbent resin with a neutralization degree of 0 by metalloenzyme catalysis, comprising the following steps:

[0039] S1. Preparation of Metalloenzymes

[0040] 0.05 g of bovine serum albumin and 0.25 g of manganese acetate tetrahydrate were added to 0.5 L of deionized water, mixed and incubated at room temperature for 1 h. Under stirring, the pH was adjusted to 10 with 0.5 M sodium hydroxide solution. After standing for 7 h, the product was centrifuged, washed, and dried for later use.

[0041] S2. Preparation of super absorbent resin

[0042] Under stirring at room temperature, 0.6 g of metalloenzyme, 10 mL of acetylacetone, 100 g of acrylic acid and 1 g of methylenebisacrylamide were added to 400 mL of deionized water, mixed and allowed to stand for 6 hours to obtain a resin colloid, which was then granulated and dried to obtain a highly absorbent resin.

[0043] The absorption and water retention of deionized water and saline solution by superabsorbent resins were evaluated with reference to the national standard GB / T 22875-2018. The experimental results show that the superabsorbent resin prepared in this example with a degree of neutralization of 0 has a deionized water absorption of 200±40 g / g and a water retention of 24±3 g / g, and a saline absorption of 25±3 g / g and a water retention of 17±2 g / g.

[0044] The product of acetylacetone oxidation by metalloenzyme was characterized by paramagnetic electron spin resonance spectroscopy. The steps were as follows: 10 mg of metalloenzyme was mixed with 0.1 mL of acetylacetone and 1 mL of 25 mg / mL 5-dimethyl-1-pyrroline oxide in 2 mL of deionized water, and then paramagnetic electron spin resonance spectroscopy was performed. The results were as follows: Figure 1 As shown by Figure 1 It can be seen that carbon free radicals are generated in the mixture of metalloenzyme and acetylacetone, indicating that metalloenzyme can replace natural laccase to oxidize acetylacetone to produce carbon free radicals.

[0045] Example 2

[0046] This embodiment provides a method for preparing a super absorbent resin with a neutralization degree of 60% by metalloenzyme catalysis, comprising the following steps:

[0047] S1. Preparation of Metalloenzymes

[0048] 0.05 g of bovine serum albumin and 0.25 g of manganese acetate tetrahydrate were added to 0.5 L of deionized water, mixed and incubated at room temperature for 1 h. Under stirring, the pH was adjusted to 10 with 0.5 M sodium hydroxide solution. After standing for 7 h, the product was centrifuged, washed, and dried for later use.

[0049] S2. Preparation of super absorbent resin

[0050] Under stirring in an ice-water bath, 33 g of sodium hydroxide was added to 400 mL of deionized water. After the solution was mixed and cooled, 100 g of acrylic acid was slowly added. After mixing, 0.6 g of metalloenzyme, 10 mL of acetylacetone and 1 g of methylene bisacrylamide were added and mixed. The mixture was allowed to stand at room temperature for 6 h to obtain a resin colloid, which was then granulated and dried to obtain a highly absorbent resin.

[0051] The absorption and water retention of superabsorbent resins for deionized water and saline were evaluated with reference to the national standard GB / T 22875-2018. The experimental results show that the superabsorbent resin prepared in this example with a neutralization degree of 60% has a deionized water absorption capacity of 410±30 g / g and a water retention capacity of 34±5 g / g, and a saline absorption capacity of 45±5 g / g and a water retention capacity of 27±3 g / g.

[0052] The super absorbent resin prepared by metalloenzyme catalysis in this example is designated as SAP1, and the super absorbent resin prepared by ammonium persulfate catalysis at high temperature is designated as SAP2 for comparison.

[0053] Comparative Example SAP2

[0054] Under stirring in an ice-water bath, 33 g of sodium hydroxide was added to 400 mL of deionized water. After the solution was mixed and cooled, 100 g of acrylic acid was slowly added. After mixing, 1 g of methylene bisacrylamide and 0.5 g of ammonium persulfate were added and mixed. The mixture was allowed to stand at 70 ° C for 6 h to obtain a resin colloid. After granulation and drying, a highly absorbent resin was obtained.

[0055] The spectrum of SAP1 and SPA2 was analyzed by Fourier infrared spectrometer. Figure 2 As shown. Figure 2 It can be seen that the Fourier transform infrared spectra of SAP1 catalyzed by metalloenzyme and SAP2 catalyzed by ammonium persulfate at 70℃ are basically the same. Both SAP1 and SAP2 have the 3500-2500 cm -1 Directional OH, 2924cm -1 Directed -CH2, 1703cm -1 Directed C=O, 1453cm -1 The -COO directed to the metal is the metal coordination of the metalloenzyme, which is manifested as SAP1 at 1620 cm -1 and 1048cm -1 The metal coordination peak of SAP2 is not present, indicating that the structure of the superabsorbent polymerized by metalloenzyme is basically the same as that of the product catalyzed by conventional ammonium persulfate heating.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a super absorbent resin by metalloenzyme catalysis, characterized in that: The following steps are involved: S1. Preparation of Metalloenzymes The protein and metal salt are placed in deionized water and incubated at room temperature, and then the pH value is adjusted with an alkaline solution. The metal enzyme is then centrifuged after standing at room temperature and finally washed with deionized water and dried. S2. Preparation of super absorbent resin The resin monomer, neutralizing solution, metal enzyme, acetylacetone and cross-linking agent are placed in deionized water and mixed evenly, and allowed to stand at room temperature to obtain resin colloid, which is granulated and dried to obtain highly absorbent resin.

2. The method for preparing a super absorbent resin by metalloenzyme catalysis according to claim 1, characterized in that: In the S1, the room temperature range is 16° C.-40° C., the room temperature incubation time is 1 hour, the pH is adjusted to 9-11, and the mixture is allowed to stand at room temperature for 7 hours.

3. The method for preparing a super absorbent resin by metalloenzyme catalysis according to claim 1, characterized in that: In the above-mentioned S1, the protein is one or more of bovine serum albumin and soy protein; the metal salt is one or more of manganese acetate, manganese chloride, manganese sulfate, ferric chloride and ferric sulfate.

4. The method for preparing a super absorbent resin by metalloenzyme catalysis according to claim 1, characterized in that: In the S1, the protein concentration is 0-0.1%, and the metal salt concentration is 1-10 mM.

5. The method for preparing a super absorbent resin by metalloenzyme catalysis according to claim 1, characterized in that: In the S2, the room temperature range is 16°C-40°C, and the mixture is allowed to stand at room temperature for 6 hours.

6. The method for preparing a super absorbent resin by metalloenzyme catalysis according to claim 1, characterized in that: In S2, the resin monomer is one or more of acrylic acid and acrylamide; the neutralizing solution is one or more of sodium hydroxide and potassium hydroxide; and the cross-linking agent is one or more of methylene acrylamide, divinylbenzene, and ethylene glycol dimethacrylate.

7. The method for preparing a super absorbent resin by metalloenzyme catalysis according to claim 1, characterized in that: In the S2, the resin monomer concentration is 20%-40%, the neutralizing solution concentration is 0-90%, the metal enzyme concentration is 0.05%-1%, the acetylacetone concentration is 0.5%-2%, and the crosslinking agent concentration is 1%-5% of the resin monomer concentration.

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