Bacteriostatic super absorbent resin and preparation method thereof

Abstract

The invention discloses antibacterial super absorbent resin and a preparation method thereof. The antibacterial super absorbent resin is prepared by surface post-treatment of a quaternary ammonium salt-epoxy functional polymer. Specifically, a quaternary ammonium salt monomer with double bonds and glycidyl methacrylate are subjected to free radical polymerization to form a polymer containing quaternary ammonium cations and active epoxy groups at the same time, then the polymer is subjected to spraying process post-treatment on polyacrylate super absorbent resin, so that the polyacrylate super absorbent resin and carboxyl of the resin are subjected to cross-linking reaction, and the super absorbent resin is obtained. A three-dimensional network structure is constructed on the surface of the resin, the problem of gel blockage of the super absorbent resin is solved, the saline water absorption rate, the absorption speed and the gel strength of the resin are remarkably improved, and meanwhile, the super absorbent resin is endowed with excellent broad-spectrum antibacterial performance by utilizing the synergistic effect of quaternary ammonium groups and epoxy groups; the antibacterial rates of the super absorbent resin prepared by the invention on escherichia coli, staphylococcus aureus and candida albicans are all greater than 99.9%, and the super absorbent resin belongs to a non-dissolution antibacterial material.

Description

An antibacterial superabsorbent resin and its preparation method Technical Field

[0001] This invention belongs to the field of functional polymer materials, specifically relating to an antibacterial superabsorbent resin and its preparation method. Background Technology

[0002] Superabsorbent polymers (SAPs) are a new type of functional polymer material capable of absorbing hundreds or even thousands of times their own weight in water, and have wide applications in many fields. However, traditional SAPs typically lack antibacterial properties. In some applications with high hygiene requirements, such as medical and food preservation, bacteria can easily grow during use, affecting product safety and lifespan.

[0003] For the development of antibacterial superabsorbent polymers (SAPs), most domestic and foreign SAP companies introduce natural antibacterial components or organic antibacterial agents and copolymerize them with acrylic acid or prepare SAPs through grafting reactions. Research results show that substances with antibacterial effects can participate in polymerization or grafting reactions, but the grafting process is often complex, costly, and difficult to control, resulting in a significant reduction in antibacterial performance. Some companies also post-treat SAPs by spraying organic antibacterial agents such as biguanides and compound quaternary ammonium salts. However, these organic antibacterial agents can dissolve from the SAP to achieve a bactericidal effect. The dissolved antibacterial agents may enter the reproductive system or the skin surface, thereby disrupting the stable microbial environment of the skin and causing certain irritation and toxic side effects.

[0004] In developed countries, particularly Japan, the antibacterial agents used are mostly inorganic, such as silver-based, zinc-based, and copper-based agents. Inorganic antibacterial agents often contain heavy metal ions, which are easily absorbed by the body through skin contact, posing a significant health hazard. Japanese companies such as Sumitomo, Sangoku, and Mitsubishi Chemical are actively researching antibacterial superabsorbent materials, but their antibacterial performance does not meet the requirements of the new national standards in China, thus preventing their widespread market application. Currently, there are no relatively mature antibacterial superabsorbent resin products on the domestic market that simultaneously meet the requirements for non-leaching antibacterial properties and the new national standards. Therefore, developing an antibacterial superabsorbent resin with a simple preparation process, long-lasting antibacterial performance, and excellent water absorption is of significant practical importance.

[0005] This invention introduces a functional polymer containing quaternary ammonium salts and epoxy groups. On the one hand, through a post-processing step, the polymer undergoes a cross-linking reaction with the carboxyl groups on the surface of polyacrylate superabsorbent resin, constructing a three-dimensional network structure on the resin surface. This solves the problem of gel clogging in superabsorbent resin, significantly improving the resin's salt absorption ratio, absorption rate, and gel strength. At the same time, the synergistic effect of the quaternary ammonium groups and epoxy groups endows the superabsorbent resin with excellent broad-spectrum antibacterial properties. Summary of the Invention

[0006] This invention aims to overcome the shortcomings of the aforementioned problems and provide a superabsorbent resin with good saline absorption performance, fast absorption speed, good gel strength, antibacterial effect, excellent bacteriostatic properties, and no dissolution of antibacterial components, as well as a method for its preparation. The technical solution of this invention is as follows:

[0007] A method for preparing an antibacterial superabsorbent resin includes the following steps: (1) Mixing deionized water and acrylic acid evenly, adding sodium hydroxide aqueous solution for neutralization, controlling the degree of neutralization of acrylic acid to 75%, adding 0.01 wt% of crosslinking agent polyethylene glycol diacrylate to the acrylic acid neutralization solution, stirring evenly, and then adding 0.05 wt% of redox initiator of acrylic acid to obtain a water-absorbing resin colloid, which is then cut, dried, crushed, and sieved to obtain water-absorbing resin particles; (2) Treating the above water-absorbing resin particles by surface spraying with quaternary ammonium salt-epoxy polymer, drying at 180°C for 40 min, and sieving to obtain an antibacterial superabsorbent resin.

[0008] The preparation method described above, specifically the preparation of the quaternary ammonium salt-epoxy polymer, involves adding glycidyl methacrylate and a quaternary ammonium salt monomer with double bonds in a molar ratio of 1:1 to 1:3 to a reaction vessel containing a mixed solvent of N,N-dimethylformamide and toluene in a volume ratio of 1:1. The pH of the system is then adjusted to 6-8 using a phosphate buffer solution. Next, azobisisobutyramidine hydrochloride, the initiator, is added dropwise at a flow rate of 0.5-2 mL / h. The reaction is carried out under nitrogen protection at 30-60°C with stirring for 2-4 hours. Then, 0.05 wt%-0.2 wt% hydroquinone (by weight of the total system mass) is added to terminate the free radical reaction. Finally, the mixed solvent is removed by vacuum distillation to obtain the quaternary ammonium salt-epoxy polymer, with the following structural formula:

[0009]

[0010] The structure of R in the formula is: CH2N + (CH3)3、COOCH2CH2N + (CH3)3、N + For any one of (CH2=CHCH2)(CH3)2, the value of m ranges from 1 to 3, and the value of n ranges from 1 to 9.

[0011] In the preparation method of the quaternary ammonium salt-epoxy polymer, the amount of initiator used is 0.02wt%-0.05wt% of the total monomer mass.

[0012] The post-treatment method can be either impregnation or spraying.

[0013] In the preparation method described above, the amount of quaternary ammonium salt-epoxy polymer added is 1wt%-4wt% of the superabsorbent resin.

[0014] The beneficial effects of this invention are:

[0015] (1) The preparation method of the antibacterial superabsorbent resin of the present invention does not require a post-crosslinking process. The three-dimensional network structure of the superabsorbent resin can be effectively constructed by the reaction of the introduced epoxy groups with the carboxyl groups on the surface of the polyacrylate superabsorbent resin. A "core-shell" structure can be formed on the surface. The low degree of crosslinking of the "core" can maintain the high water absorption ratio of the resin, while the high degree of crosslinking of the "shell" can increase the pressure absorption of the resin, so that the superabsorbent resin can still maintain a high gel strength after absorbing liquid, reduce the probability of gel blockage, and keep the sanitary products dry. In addition, due to the presence of quaternary ammonium groups, its cationic properties can enhance the binding force between the polymer and the surface of the superabsorbent resin through electrostatic interaction, further stabilizing the crosslinking structure. Therefore, the synergistic effect of quaternary ammonium groups and epoxy groups makes the superabsorbent resin prepared by the present invention have high water absorption and water retention properties, fast absorption speed, and good gel strength.

[0016] (2) The superabsorbent resin prepared in this invention has excellent broad-spectrum antibacterial properties and belongs to non-leaching antibacterial materials. This invention introduces a functional polymer containing epoxy groups and quaternary ammonium groups. On the one hand, the quaternary ammonium groups can destroy the structure and function of microorganisms through various pathways such as electrostatic adsorption and cell membrane disruption, inhibition of enzyme activity and metabolic interference, thereby achieving highly efficient antibacterial activity. On the other hand, the quaternary ammonium salt-epoxy polymer crosslinks with the carboxyl groups on the resin surface through a ring-opening reaction, firmly fixing the quaternary ammonium groups on the resin surface, so that the antibacterial components will not dissolve from the superabsorbent resin, thereby preventing the dissolved antibacterial components from entering the reproductive system or the skin surface and disrupting the originally stable bacterial environment.

[0017] (3) This invention prepares a low-polymerization-degree quaternary ammonium salt-epoxy polymer by optimizing process parameters such as initiator dosage, monomer concentration, and chain terminator. The low molecular weight quaternary ammonium salt-epoxy polymer can effectively prevent it from forming a film on the surface of superabsorbent resin. The higher the molecular weight of the polymer, the easier it is to form a film on the surface of superabsorbent resin, resulting in a decrease in the absorption performance of superabsorbent resin. In addition, the low-polymerization-degree quaternary ammonium salt-epoxy polymer has low steric hindrance and can quickly diffuse to the surface of bacterial cell membrane. It can destroy the membrane structure through electrostatic interaction, leading to leakage of intracellular substances and death. In contrast, the diffusion rate of high molecular weight polymers is reduced due to molecular chain entanglement, and they require a longer contact time to exert their effect.

[0018] (4) The present invention does not require special equipment, the raw materials are readily available, the cost is low, and the preparation process is simple. The high-performance superabsorbent resin prepared by the present invention can be widely used in medical supplies, soil water retention, packaging materials, oil extraction and other fields, and is especially suitable for disposable hygiene products such as diapers (pads, pads) and sanitary napkins. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0020] Example 1

[0021] (1) Mix deionized water and acrylic acid evenly, add sodium hydroxide aqueous solution to neutralize, control the degree of neutralization of acrylic acid to 75%, add 0.01 wt% of crosslinking agent polyethylene glycol diacrylate to acrylic acid neutralization solution, stir evenly, add 0.05 wt% of acrylic acid ammonium persulfate and sodium bisulfite to obtain water-absorbing resin colloid, and obtain water-absorbing resin particles by cutting, drying, crushing and sieving.

[0022] (2) Glycidyl methacrylate and allyltrimethylammonium chloride were added in a molar ratio of 1:1 to a reaction vessel containing a mixture of N,N-dimethylformamide and toluene in a volume ratio of 1:1. The pH of the system was then adjusted to 6.5 with phosphate buffer solution. Then, 0.02 wt% of the initiator azobisisobutyramidine hydrochloride was added dropwise at a flow rate of 0.5 mL / h. The reaction was stirred at 40 °C for 2 h under nitrogen protection. Hydroquinone was added to terminate the free radical reaction. Finally, the mixed solvent was removed by vacuum distillation to obtain the quaternary ammonium salt-epoxy polymer.

[0023] (3) The superabsorbent resin was treated by spraying with 1wt% quaternary ammonium salt-epoxy polymer, dried at 180℃ for 40 min, and then screened to obtain antibacterial superabsorbent resin.

[0024] Example 2

[0025] (1) Mix deionized water and acrylic acid evenly, add sodium hydroxide aqueous solution to neutralize, control the degree of neutralization of acrylic acid to 75%, add 0.01 wt% of crosslinking agent polyethylene glycol diacrylate to acrylic acid neutralization solution, stir evenly, add 0.05 wt% of initiator ammonium persulfate and sodium bisulfite to obtain water-absorbing resin colloid, and obtain water-absorbing resin particles by cutting, drying, crushing and sieving.

[0026] (2) Glycidyl methacrylate and allyltrimethylammonium chloride were added to a reaction vessel containing a mixture of N,N-dimethylformamide and toluene in a volume ratio of 1:1 at a molar ratio of 1:1. The pH of the system was then adjusted to 6.5 with phosphate buffer solution. Then, 0.02 wt% of the initiator azobisisobutyramidine hydrochloride was added dropwise at a flow rate of 0.5 mL / h. The reaction was stirred at 40 °C for 2 h under nitrogen protection. Then, 0.05 wt% of hydroquinone was added to terminate the free radical reaction. Finally, the mixed solvent was removed by vacuum distillation to obtain the quaternary ammonium salt-epoxy polymer.

[0027] (3) The superabsorbent resin was treated by spraying with 3wt% quaternary ammonium salt-epoxy polymer, dried at 180℃ for 40 min, and then screened to obtain antibacterial superabsorbent resin.

[0028] Example 3

[0029] (1) Mix deionized water and acrylic acid evenly, add sodium hydroxide aqueous solution to neutralize, control the degree of neutralization of acrylic acid to 75%, add 0.01 wt% of crosslinking agent polyethylene glycol diacrylate to acrylic acid neutralization solution, stir evenly, add 0.05 wt% of acrylic acid ammonium persulfate and sodium bisulfite to obtain water-absorbing resin colloid, and obtain water-absorbing resin particles by cutting, drying, crushing and sieving.

[0030] (2) Glycidyl methacrylate and allyltrimethylammonium chloride were added to a reaction vessel containing a mixture of N,N-dimethylformamide and toluene in a volume ratio of 1:1 at a molar ratio of 1:3. The pH of the system was then adjusted to 7 with phosphate buffer solution. Then, 0.02 wt% of initiator azobisisobutyramidine hydrochloride was added dropwise at a flow rate of 0.5 mL / h. The reaction was stirred at 50 °C for 3 h under nitrogen protection. Then, 0.05 wt% of hydroquinone was added to terminate the free radical reaction. Finally, the mixed solvent was removed by vacuum distillation to obtain the quaternary ammonium salt-epoxy polymer.

[0031] (3) The superabsorbent resin was treated by spraying with 3wt% quaternary ammonium salt-epoxy polymer, dried at 180℃ for 40 min, and then screened to obtain antibacterial superabsorbent resin.

[0032] Example 4

[0033] This embodiment evaluates the absorption and antibacterial properties of the superabsorbent resins prepared in Examples 1, 2, 3 and Comparative Examples 1 and 2, and determines whether they are dissolved or not.

[0034] Molecular weight determination: The molecular weight is calculated after testing using end-group analysis.

[0035] Absorption performance test: The absorption capacity (physiological saline), water retention capacity and pressure absorption capacity of superabsorbent resin were tested in accordance with GB / T22875-2018 "Superabsorbent Resins for Diapers and Sanitary Napkins". The test results are shown in Table 1.

[0036] Absorption rate test method: Add 50.0±0.5g of physiological saline to a 100mL beaker, adjust the magnetic stirrer to a speed of 600rpm, accurately weigh 2.00g of superabsorbent resin and add it to the physiological saline, and use a stopwatch to time the process. When the solution vortex disappears and the liquid surface becomes horizontal, the endpoint is recorded. Three sets of data are tested in parallel for each sample, and the average value is taken as the test result. The test results are shown in Table 1.

[0037] Dissolution / non-dissolution determination test: Soak 1.0±0.01g of sample in sterile distilled water for 24h, take the soaking solution and refer to the antibacterial performance test of antibacterial agent E.6.1 in 15979-2024 "Hygienic Requirements for Disposable Sanitary Products". If there is no antibacterial effect, it means that the sample is a non-dissolution antibacterial material.

[0038] Antibacterial performance test method: The antibacterial performance of non-leaching superabsorbent materials was tested in accordance with GB15979-2024 "Hygienic requirements for disposable sanitary products" (there is no test method for leaching superabsorbent materials in the standard). The test results are shown in Table 3.

[0039] Comparative Example 1

[0040] Deionized water and acrylic acid were mixed evenly, and sodium hydroxide aqueous solution was added for neutralization to control the degree of acrylic acid neutralization to 75%. 0.01 wt% of crosslinking agent polyethylene glycol diacrylate was added to the acrylic acid neutralization solution. After stirring evenly, 0.05 wt% of ammonium persulfate and sodium bisulfite were added to obtain a water-absorbing resin colloid. After cutting, drying, crushing, and sieving, a superabsorbent resin was obtained.

[0041] Comparative Example 2

[0042] (1) Mix deionized water and acrylic acid evenly, add sodium hydroxide aqueous solution to neutralize, control the degree of neutralization of acrylic acid to 75%, add 0.01 wt% of crosslinking agent polyethylene glycol diacrylate to acrylic acid neutralization solution, stir evenly, add 0.05 wt% of acrylic acid ammonium persulfate and sodium bisulfite to obtain water-absorbing resin colloid, and obtain water-absorbing resin particles by cutting, drying, crushing and sieving.

[0043] (2) The superabsorbent resin was treated by surface spraying with a mixture of 3wt% glycidyl methacrylate and allyltrimethylammonium chloride, dried at 180℃ for 40 min, and then sieved to obtain the superabsorbent resin.

[0044] Comparative Example 3

[0045] (1) Mix deionized water and acrylic acid evenly, add sodium hydroxide aqueous solution to neutralize, control the degree of neutralization of acrylic acid to 75%, add 0.01 wt% of crosslinking agent polyethylene glycol diacrylate to acrylic acid neutralization solution, stir evenly, add 0.05 wt% of acrylic acid ammonium persulfate and sodium bisulfite to obtain water-absorbing resin colloid, and obtain water-absorbing resin particles by cutting, drying, crushing and sieving.

[0046] (2) Glycidyl methacrylate and allyltrimethylammonium chloride were added to a reaction vessel containing a mixture of N,N-dimethylformamide and toluene in a volume ratio of 1:1 at a molar ratio of 1:3. The pH of the system was then adjusted to 7 with phosphate buffer solution. Then, 0.05 wt% of initiator azobisisobutyramidine hydrochloride was added dropwise at a flow rate of 0.5 mL / h. The reaction was carried out under nitrogen protection at 50 °C with stirring for 3 h. Finally, the mixed solvent was removed by vacuum distillation to obtain the quaternary ammonium salt-epoxy polymer.

[0047] (3) The superabsorbent resin was treated by spraying with 3wt% quaternary ammonium salt-epoxy polymer, dried at 180℃ for 40 min, and then screened to obtain antibacterial superabsorbent resin.

[0048] The following are the performance tests conducted on the superabsorbent resins prepared in Examples 1, 2, 3 and Comparative Examples 1, 2 and 3, including absorption capacity (physiological saline), water retention capacity, pressurized absorption capacity, and absorption rate. The results are shown in Table 1.

[0049] Table 1. Test results of superabsorbent resin absorption performance

[0050] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Molecular Weight (g / mol) 1000 2000 5000 50000 Absorbance (g / g) 68.61 68.64 70.31 49.31 61.13 55.25 Absorption Rate (s) 36 38 42 55 48 53 Pressure Absorbance (g / g) 30.12 34.54 37.46 7.65 20.23 33.41 surface

[0051] As shown in Table 1, the addition of quaternary ammonium salt-epoxy polymer significantly improves the absorption capacity, absorption rate, and pressure absorption capacity of superabsorbent resin. With increasing post-treatment quaternary ammonium salt-epoxy polymer dosage, the pressure absorption capacity gradually increases, while the absorption rate decreases. This is because more and more epoxy groups react with carboxyl groups, reducing the carboxyl group content on the resin surface and weakening its hydrophilicity. Comparative Example 3 and Example 3 show that quaternary ammonium salt-epoxy polymers with excessively high molecular weights easily form films on the surface of superabsorbent resin, causing blockage of the pore structure and thus reducing the absorption performance of the superabsorbent resin.

[0052] The following are the leaching and non-leaching determination tests conducted on the superabsorbent resins prepared in Examples 1, 2, 3 and Comparative Examples 2, 3. The results are shown in Table 2.

[0053] Table 2. Test results of antibacterial properties of superabsorbent resin soaking solution

[0054]

[0055] As shown in Table 2, the antibacterial rate of the soaking solution of the superabsorbent resin prepared in Examples 1, 2 and 3 is 0%, indicating that the quaternary ammonium salt-epoxy polymer crosslinks with the carboxyl groups on the resin surface through a ring-opening reaction, firmly fixing the quaternary ammonium groups on the resin surface, so that the antibacterial components will not dissolve from the superabsorbent resin, and the samples are non-leaching antibacterial materials.

[0056] The following are the antibacterial performance tests conducted on the superabsorbent resins prepared in Examples 1, 2, 3 and Comparative Example 3, and the results are shown in Table 3.

[0057] Table 3. Test results of antibacterial properties of superabsorbent resin

[0058]

[0059] As can be seen from the examples and comparative examples, the superabsorbent resin prepared by the present invention has good antibacterial stability and excellent antibacterial effect. This is mainly because the molecular weight of the quaternary ammonium salt-epoxy polymer prepared by the present invention is appropriately controlled, so that it can exert its antibacterial effect to the maximum extent.

[0060] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an antibacterial superabsorbent resin, characterized in that, The process includes the following steps: (1) Mixing deionized water and acrylic acid evenly, adding sodium hydroxide aqueous solution for neutralization, controlling the degree of acrylic acid neutralization to 75%, adding 0.01 wt% of crosslinking agent polyethylene glycol diacrylate to the acrylic acid neutralization solution, stirring evenly, and then adding 0.05 wt% of redox initiator to obtain water-absorbing resin colloid, which is then cut, dried, crushed, and sieved to obtain water-absorbing resin particles; (2) Treating the above water-absorbing resin particles with quaternary ammonium salt-epoxy polymer through a finishing process, drying at 180℃ for 40 min, and sieving to obtain antibacterial super absorbent resin. The preparation method of the quaternary ammonium salt-epoxy polymer is as follows: glycidyl methacrylate is added to the quaternary ammonium salt-epoxy polymer. Oil ether and a quaternary ammonium salt monomer with double bonds were added to a reaction vessel containing a mixed solvent of N,N-dimethylformamide and toluene in a volume ratio of 1:1 to 1:3 at a molar ratio of 1:

1. The pH of the system was then adjusted to 6-8 with phosphate buffer solution. Azobisisobutyramidine hydrochloride, an initiator, was then added dropwise at a flow rate of 0.5-2 mL / h, with the amount of initiator being 0.02 wt%-0.05 wt% of the total monomer mass. The reaction was carried out under nitrogen protection at 30-60°C with stirring for 2-4 h. Hydroquinone, accounting for 0.05 wt%-0.2 wt% of the total system mass, was then added to terminate the free radical reaction. Finally, the mixed solvent was removed by vacuum distillation to obtain the quaternary ammonium salt-epoxy polymer with the following structural formula: The structure of R in the formula is: CH2N + (CH3)3、COOCH2CH2N + (CH3)3、N + For any one of (CH2=CHCH2)(CH3)2, the value of m ranges from 1 to 3, and the value of n ranges from 1 to 9.

2. The preparation method according to claim 1, characterized in that, The finishing method can be either impregnation or spraying, and the amount of quaternary ammonium salt-epoxy polymer added is 1wt%-4wt% of the superabsorbent resin.

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