Preparation method of super absorbent resin

Abstract

The invention provides a preparation method of super absorbent resin, and relates to the technical field of super absorbent resin. The preparation method comprises the following steps: diluting acrylic acid with water, and adding alkali liquor for neutralization to obtain a neutralized solution; mixing an emulsifying agent, a thickening agent and foaming carbonate to obtain a foaming promoting auxiliary agent; adding a cross-linking agent, a photoinitiator and a temperature initiator into the neutralization solution to obtain a polymerization mother solution; uniformly mixing a foaming promoting auxiliary agent with the polymerization mother liquor, and initiating polymerization of the polymerization mother liquor under a UV illumination condition to obtain acrylate polymer gel; drying the acrylate polymer gel, and crushing and screening to obtain basic particles; and spraying a surface cross-linking treatment liquid on the surfaces of the basic particles, initiating a surface cross-linking reaction of the basic particles through heat treatment, and adding an inert filler after the surface cross-linking reaction to prepare the super absorbent resin finished product particles. The super absorbent resin disclosed by the invention has the characteristics of high reaction efficiency, high liquid absorption speed, good liquid passing performance, excellent reverse osmosis resistance and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of super absorbent resins, and in particular to a method for preparing super absorbent resins. Background Art

[0002] High absorption resin is one of the core materials of diapers. It has extremely strong water absorption capacity, can absorb hundreds to thousands of times its own weight in water, and has strong water retention. It is made of starch and acrylate, is non-toxic and harmless, can quickly absorb and lock urine, and keep diapers dry. Nowadays, people have put forward more requirements for the quality of diapers. Not only do they need to absorb more urine at a time, but they also need a higher liquid retention capacity, the ability to repeatedly absorb liquid, and good dryness. At the same time, they also need to achieve the optimal liquid absorption speed to prevent urine leakage. However, the high absorbent resin prepared by the current conventional method is difficult to implement in the case of large particle size, and its liquid absorption speed and strong liquid permeability are both achieved. For this purpose, a preparation method for a high absorbent resin specially used for the upper layer of diapers is provided, which has excellent comprehensive properties such as strong liquid permeability, fast liquid absorption speed, and water retention. Summary of the Invention

[0003] In view of the above problems existing in the prior art, the present invention provides a super absorbent resin to improve the problem that the existing resin cannot balance the liquid absorption speed and liquid permeability.

[0004] To achieve the above-mentioned object and other related objects, the present invention provides a method for preparing a super absorbent resin, the method comprising the following steps:

[0005] Diluting acrylic acid with water and neutralizing it with alkali solution to obtain a neutralized solution;

[0006] The emulsifier, thickener and foaming carbonate are mixed evenly and diluted and dissolved with pure water to obtain a foaming promoter;

[0007] adding a crosslinking agent, a photoinitiator and a temperature initiator to the neutralized solution to obtain a polymerization mother solution;

[0008] Deoxygenating the polymerization mother solution with nitrogen, uniformly mixing the foaming promoting agent with the nitrogen-deoxygenated polymerization mother solution, and initiating polymerization of the polymerization mother solution under UV irradiation to obtain an acrylate polymer gel;

[0009] drying the acrylate polymer gel, and crushing and screening it to obtain base particles;

[0010] A surface cross-linking treatment liquid is sprayed on the surface of the base particles, a surface cross-linking reaction of the base particles is initiated by heat treatment, and an inert filler is added after the surface cross-linking reaction to obtain finished super absorbent resin particles.

[0011] In one embodiment of the present invention, the mass concentration of the acrylic acid is 15-45%, and the neutralization degree of the neutralization solution is 20-85%.

[0012] In one embodiment of the present invention, the mass of the emulsifier is 0.022-0.044% of the mass of the acrylic acid, the mass of the thickener is 0.011-0.022% of the mass of the acrylic acid, and the mass of the foaming carbonate is 0.044-0.066% of the mass of the acrylic acid.

[0013] In one embodiment of the present invention, the mass of the cross-linking agent is 0.05 to 5.00% of the mass of the acrylic acid, the mass of the photoinitiator is 0.001 to 0.1% of the mass of the acrylic acid, and the temperature initiator includes a high-temperature initiator and a low-temperature initiator, the mass of the high-temperature initiator is 0.01 to 2.00% of the mass of the acrylic acid, and the mass of the low-temperature initiator is 0.001 to 1.000% of the mass of the acrylic acid.

[0014] In one embodiment of the present invention, drying the acrylate polymer gel and crushing and screening to obtain base particles comprises the following steps:

[0015] extruding and granulating the acrylate polymer gel to obtain gel particles;

[0016] The gel particles are dehydrated and dried, and then crushed and sieved to obtain base particles.

[0017] In one embodiment of the present invention, a carbonate aqueous solution and an auxiliary agent for reducing residual monomers are uniformly added to the acrylate polymer gel during the extrusion granulation process of the acrylate polymer gel, the mass of the auxiliary agent for reducing residual monomers is 0.1-1.0% of the mass of the acrylic acid, the concentration of the carbonate aqueous solution is 1-40%, and the mass of the carbonate in the carbonate aqueous solution is 1-30% of the mass of the acrylic acid. When the gel particles are dehydrated and dried, the drying temperature is 90-250°C and the drying time is 15-120 minutes.

[0018] In one embodiment of the present invention, when the polymerization mother solution is polymerized, the polymerization starting temperature is 12-18° C., and the UV irradiation time is 6-9 minutes.

[0019] In one embodiment of the present invention, the surface of the base particles is heat-treated at a temperature of 130 to 160° C. for a time of 25 to 35 minutes during cross-linking.

[0020] In one embodiment of the present invention, the surface cross-linking treatment liquid includes propylene glycol, ethylene glycol diglycidyl ether and sulfate, the mass of the propylene glycol is 0.01 to 2% of the mass of the base particles, the mass of the ethylene glycol diglycidyl ether is 0.001 to 0.5% of the mass of the base particles, the mass of the sulfate is 0.1 to 4.0% of the mass of the base particles, and the propylene glycol includes any one of 1,3-propylene glycol and 1,2-propylene glycol.

[0021] In one embodiment of the present invention, the mass of the inert filler is 0.01-1.0% of the mass of the base particles.

[0022] The superabsorbent resin of the present invention incorporates a foaming-promoting aid at the initial stage of the reaction, resulting in a gel with dense pores. This allows for a faster liquid absorption rate despite the larger particle size, i.e., a relatively small surface area. Furthermore, while the average particle size of the base particles is relatively large, the addition of an inert filler helps disperse the resin particles, improving the resin's fluid permeability and ensuring the smooth passage of secondary, tertiary, and multiple liquids to the lower layer for absorption, fully meeting the performance requirements of superabsorbent resins for diaper top layers. The superabsorbent resin prepared by the present invention exhibits rapid absorption, excellent fluid permeability, and a strong overall fluid absorption capacity, making it suitable for use as a superabsorbent resin in the top layers of diapers for infants, adults, and pets. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 is a flow chart for preparing a super absorbent resin according to one embodiment of the present invention;

[0025] Figure 2 for Figure 1 Step S5 in the illustrated embodiment is a flow chart in an exemplary embodiment. DETAILED DESCRIPTION

[0026] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following examples and the features in the examples can be combined with each other unless they conflict. It should also be understood that the terms used in the examples of the present invention are for the purpose of describing specific embodiments, not for the purpose of limiting the scope of protection of the present invention. The test methods for which specific conditions are not specified in the following examples are generally carried out under conventional conditions or under the conditions recommended by the manufacturers.

[0027] When numerical ranges are given in the examples, it should be understood that unless otherwise specified herein, both endpoints of each numerical range and any value between the two endpoints may be used. Unless otherwise defined, all technical and scientific terms used herein are consistent with the prior art as understood by those skilled in the art and the description of the present invention. Any prior art methods, devices, and materials similar or equivalent to those in the examples of the present invention may also be used to implement the present invention.

[0028] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0029] See also Figure 1 The present application provides a method for preparing a super absorbent resin, which comprises the following steps:

[0030] S1. diluting acrylic acid with water and adding alkali solution to neutralize it to obtain a neutralized solution;

[0031] S2. Evenly mix the emulsifier, thickener, and foaming carbonate and dilute and dissolve them with pure water to obtain a foaming promoting agent;

[0032] S3, adding a crosslinking agent, a photoinitiator and a temperature initiator to the neutralized solution to obtain a polymerization mother solution;

[0033] S4, nitrogen deoxygenating the polymerization mother solution, uniformly mixing the foaming promoting agent with the nitrogen deoxygenated polymerization mother solution, and initiating polymerization of the polymerization mother solution under UV light conditions to obtain an acrylate polymer gel;

[0034] S5, drying the acrylate polymer gel, and crushing and screening to obtain base particles;

[0035] S6. Spraying a surface crosslinking treatment liquid on the surface of the base particles, initiating a surface crosslinking reaction of the base particles through heat treatment, and adding an inert filler after the surface crosslinking reaction to obtain finished super absorbent resin particles.

[0036] In step S1, the concentration of acrylic acid is 15-45%, preferably 20-40%; the neutralization degree of the neutralization solution is 20-85%, and further, the neutralization degree of the neutralization solution is 35-80%.

[0037] In step S2, the emulsifier can not only reduce the interfacial tension, promote the formation of a stable gas-liquid interface of the bubble nucleus, and form uniform bubbles, but also form an elastic interface film to prevent the bubbles from merging or crowding out each other. The mass of the emulsifier is 0.022 to 0.044% of the mass of the acrylic acid, preferably 0.025 to 0.040%. Exemplarily, the emulsifier can be selected from polyoxyethylene stearate, polyoxyethylene oleate, polyoxyethylene lauryl ether, polyoxyethylene octylphenol ether, polyoxyethylene nonylphenol ether, polyoxyethylene cetyl ether, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan monostearate, polyoxyethylene hydrogenated castor oil, polyoxyethylene polyoxypropylene block copolymer, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monoole ... Any one of polyol anhydride monooleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, propylene glycol monostearate, propylene glycol monolaurate, polyglycerol monostearate, polyglycerol monooleate, xylitol monostearate, xylitol monolaurate, pentaerythritol monostearate, pentaerythritol monooleate, sucrose monolaurate, and sucrose monostearate.

[0038] The thickener can not only increase the viscosity of the system, slow down the rising rate of bubbles, inhibit the rupture of the rising process, enhance the strength of the foam skeleton, and prolong the life of the foam, but also form a three-dimensional network structure and fix the bubbles. The mass of the thickener is 0.011 to 0.022% of the mass of acrylic acid, preferably 0.012 to 0.020%. Exemplary, the thickener is any one or a combination of two of sodium carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC), hydroxypropylmethylcellulose (HPMC), methylcellulose (MC), ethylcellulose (EC), microcrystalline cellulose (MCC), hydroxypropylcellulose (HPC), carboxymethylhydroxyethylcellulose (CMHEC), polyquaternium-10, nanocellulose, polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), cross-linked polyacrylic acid (Carbomer), polyacrylate copolymer, ammonium polyacrylate, ammonium salt of polyacrylic acid, polyhydroxyethyl acrylate (HEA), and polyhydroxypropyl acrylate (HPA).

[0039] The foaming carbonate decomposes upon exposure to acid or heat to release CO, providing the foaming gas. The decomposition rate is controlled to prevent excessive bubble growth or collapse. The mass of the foaming carbonate is 0.044-0.066% of the mass of the acrylic acid, preferably 0.048-0.060%. Exemplarily, the foaming carbonate is any one of calcium carbonate, sodium carbonate, sodium bicarbonate, potassium carbonate, and magnesium carbonate.

[0040] The incorporation of a foaming promoter at the initial stage of the reaction results in a densely packed gel with small pores. This results in faster liquid absorption despite the larger particle size and relatively small surface area. The synergistic effect of the emulsifier, thickener, and foaming carbonate controls the formation of small pores in the subsequently prepared acrylate polymer gel, achieving viscosity-gas release matching. The high viscosity of the thickener slows CO release, resulting in a finer, more stable foam structure and enhanced interfacial stability. The emulsifier adsorbs at the gas-liquid interface, while the hydration of the thickener strengthens the interfacial film, thus doubly stabilizing the bubbles. The decomposition of the carbonate may alter the pH of the system, necessitating the selection of emulsifiers and thickeners with good pH tolerance.

[0041] In the foaming promoting agent, the amount of emulsifier should cover the reaction interface, and excessive amount may cause system instability; the viscosity of the thickener should be 500-2000 cP; the carbonate ratio should be adjusted according to the gas demand. It is also possible to control the reaction kinetics by adding a slow-release acid or embedding carbonates to achieve a gradual release of CO. In some embodiments, a compatibility test is performed before selecting the thickener to avoid the incompatibility of ionic thickeners (such as carrageenan) with high-valent metal ions (such as Ca 2 +) Binding results in precipitation.

[0042] In step S3, the mass of the cross-linking agent is 0.05 to 5.00% of the mass of the acrylic acid, preferably 0.10 to 3.00%. Exemplarily, the cross-linking agent is any one or a combination of two of triethoxylated glycerol triacrylate, pentaerythritol triacrylate, pentaerythritol triallyl ether, dipentaerythritol pentaacrylate, polyethylene glycol (200) diacrylate, polyethylene glycol 300) diacrylate, polyethylene glycol 400) diacrylate, polyethylene glycol 600) diacrylate, polyethylene glycol 800) diacrylate, polyethylene glycol 1000) diacrylate, ethoxylated trimethylolpropane triacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, propoxylated neopentyl glycol diacrylate, ethoxylated neopentyl glycol diacrylate, ethylene glycol diglycidyl ether, and N,N-methylenebisacrylamide.

[0043] The mass of the photoinitiator is 0.001% to 0.1% of the mass of the acrylic acid, preferably 0.005% to 0.05%. Exemplarily, the photoinitiator is any one of benzaldehyde-formaldehyde trimer (BPB), ketone amine photoinitiator (KAP), acrylcarboxylic acid diester (Irgacure 2959), oxazolidinone photoinitiator (BAPO), and titanate photoinitiator (TINUVIN).

[0044] In some embodiments, the temperature initiator includes a high temperature initiator and a low temperature initiator. The mass of the high temperature initiator is 0.01 to 2.00% of the mass of the acrylic acid, preferably 0.02 to 1.00%. Exemplarily, the high-temperature initiator is any one or more combinations of 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide, 4,4'azobis(4-cyanovaleric acid), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropylimidazole) dihydrochloride, 2,2'-azobis[N-(2-hydroxyethyl)-2-methylpropionamidine] tetrahydrate, 1-hydroxycyclohexylphenyl ketone, and 2,2-dimethoxy-2-phenylacetophenone. The mass of the low-temperature initiator is 0.001 to 1.000% of the mass of acrylic acid, preferably 0.005 to 0.500%. Exemplarily, the low-temperature initiator is any one or a combination of two of ascorbic acid, sodium bisulfite, sodium sulfite, sodium hypobisulfite, and sodium metabisulfite.

[0045] In step S4, UV light-assisted initiation can effectively shorten the polymerization induction time and reaction time compared with a simple redox initiation system. The initiation process is completed in multiple stages, including low-temperature redox initiation, medium-temperature initiation, and high-temperature initiation. This can maintain high activity throughout the reaction process, which is beneficial to improving the monomer conversion rate.

[0046] By adding a foaming promoter to the polymerization mother solution before initiation of polymerization, on the one hand, the carbon dioxide generated by the reaction of the foaming promoter and the polymerization monomer can replace the dissolved oxygen in the polymerization solution, thereby increasing the reaction activity of the polymerization solution, suppressing the inhibitory factor, and increasing the reaction rate. On the other hand, the carbon dioxide generated by the reaction has a certain solubility in the low-temperature polymerization solution. After the polymerization reaction starts, the temperature of the polymerization system rises, and the carbon dioxide will precipitate due to the decrease in solubility, thereby forming microbubbles or pores in the acrylate polymer gel.

[0047] In some embodiments, the polymerization starting temperature during polymerization of the polymerization mother solution is 12-18° C., and the UV irradiation time is 6-9 minutes.

[0048] In some embodiments, step S5 involves drying the acrylate polymer gel, crushing and screening to obtain base particles, comprising the following steps:

[0049] S51, extruding and granulating the acrylate polymer gel to obtain gel particles;

[0050] S52, dehydrating and drying the gel particles, and crushing and screening to obtain basic particles.

[0051] In step S51, the extrusion granulation method can be any one of single-screw extrusion granulation, twin-screw extrusion granulation, shear granulation or kneading granulation. Exemplarily, the number of extrusion granulation is 1 to 5 times, preferably 2 to 4 times. The granulation process adopts the effect of multiple granulation, which can make the surface of the gel rougher under the action of multiple extrusion forces and shear forces, and the gel particle size more uniform. In some embodiments, during the extrusion granulation of the acrylate polymer gel, a carbonate aqueous solution and an auxiliary agent for reducing residual monomers are uniformly added. The carbonate aqueous solution can not only neutralize acrylic acid twice, but also, by adding carbonate in the form of an aqueous solution during the multiple granulation processes, the carbonate aqueous solution can penetrate into the surface of the gel particles, and then react with the gel to generate gas, thereby forming a cavity below the surface of the gel particles. On the one hand, the cavity can be connected with the microbubbles inside the gel to form a channel. On the other hand, after drying, the cavity can form a certain depth of pits on the surface of the particles, further improving the surface roughness and specific surface area of the particles. Exemplarily, the carbonate aqueous solution is an aqueous solution of any one of sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate, and ammonium bicarbonate, or a combination thereof. In one embodiment, the concentration of the carbonate aqueous solution is 1-40%, preferably 10-30%, and the mass of the carbonate in the carbonate aqueous solution is 1-30%, preferably 2-15%, of the mass of the acrylic acid. The degree of neutralization of the acrylic acid in the secondary neutralization is 10-30%, preferably 15-25%.

[0052] The residual monomer reduction agent can remove some of the residual monomers. In some embodiments, the weight of the residual monomer reduction agent is 0.1-1.0% of the weight of the acrylic acid, preferably 0.2-0.6%. Exemplarily, the residual monomer reduction agent is any one of anhydrous sodium sulfite, sodium metabisulfite, and sodium thiosulfate, or a combination thereof.

[0053] In step S52, hot air drying is selected for dehydration and drying treatment, and the drying temperature is 90 to 250°C, preferably 120 to 210°C; the drying time is 15 to 120 minutes, preferably 25 to 80 minutes. Exemplarily, the particle size of the base particles is 30 to 50 meshes. In the process of crushing and screening the gel particles after dehydration and drying, resin powder will be produced. In the production process, the resin powder can be added to the acrylate polymer gel during the extrusion and granulation of the gel particles. It can not only recover the by-products produced by grinding, but also absorb the moisture of the gel to assist in drying. Exemplarily, the mass of the resin powder is 1 to 8% of the mass of the acrylate polymer gel, preferably 2 to 6%.

[0054] In step S6, the surface crosslinking treatment liquid includes propylene glycol, ethylene glycol diglycidyl ether, and sulfate. The mass of propylene glycol is 0.01-2% of the mass of the base particles, the mass of ethylene glycol diglycidyl ether is 0.001-0.5% of the mass of the base particles, and the mass of sulfate is 0.1-4.0% of the mass of the base particles. The propylene glycol includes either 1,3-propylene glycol or 1,2-propylene glycol.

[0055] In some embodiments, the surface of the base particles is heat-treated at a temperature of 130 to 160° C. for a time of 25 to 35 minutes during surface cross-linking.

[0056] Under the premise that the average particle size of the base particles is relatively large, an inert filler that aids dispersion is added. The inert filler is evenly dispersed between the resin particles, effectively increasing the gaps between adjacent resin particles through its physical isolation effect. The increase in gaps can significantly reduce the packing density of the resin particle stack, optimize the pore structure between the resin particles, and thus enhance the liquid permeability of the resin particles, meeting the requirements for secondary, tertiary, and multiple liquids to pass smoothly to the lower layer for absorption, meeting the performance requirements of superabsorbent resins for diaper upper layers. The mass of the inert filler is 0.01-1.0% of the mass of the base particles, preferably 0.05-0.5%. Exemplarily, the inert filler is any one of potassium dihydrogen phosphate, fumed silica, and silicate.

[0057] The superabsorbent resin prepared in this application has a high surface area during the liquid absorption and swelling process. At the same time, the absorbed liquid can accelerate the penetration into the interior of the gel through the pores formed inside, making the water absorption process more efficient and ultimately achieving a fast absorption rate. The superabsorbent resin of this application has the characteristics of high reaction efficiency, fast liquid absorption rate, good liquid permeability, and excellent anti-re-seepage performance. It is suitable for use in the fields of fast-absorbing baby diapers, sanitary napkins, and adult incontinence products, and is used to fill their liquid absorption upper structure.

[0058] The technical solutions of the present invention are described in detail below through several specific examples. Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by conventional methods in the art, and the instruments used in the examples are all commercially available.

[0059] Example 1

[0060] The preparation method of the super absorbent resin in this embodiment is as follows: (1) taking 250 parts of acrylic acid, adding 180 parts of water to dilute, and then adding 190 parts of 48% sodium hydroxide to neutralize to obtain a neutralized solution, wherein the mass concentration of acrylic acid in the neutralized solution is 40% and the neutralization degree is 65%; (2) 0.06 parts of emulsifier, 0.01 parts of thickener, and 0.03 parts of foaming carbonate are mixed evenly and diluted and dissolved with pure water to obtain a foaming promoter, and the concentration of the foaming promoter is 30%; (3) 0.2 parts of cross-linking agent, 0.025 parts of photoinitiator, and 1.05 parts of high-temperature initiator are added to the neutralized solution, and after stirring evenly, 0.02 parts of low-temperature initiator are added to obtain a polymerization mother solution; (4) the polymerization mother solution is subjected to nitrogen deoxygenation treatment, and the foaming promoter and the nitrogen deoxygenated polymerization mother solution are mixed evenly, and the mixture is stirred at room temperature. The polymerization mother solution was polymerized under UV light conditions to obtain an acrylate polymer gel, the UV light exposure time was 9 minutes, and the starting temperature of the polymerization was 12°C; (5) the acrylate polymer gel was added to a single-screw rubber cutting granulator for extrusion granulation, and the granulation was continued for 3 times. During the extrusion granulation, 0.7 parts of a carbonate aqueous solution with a carbonate content of 60 parts as a residual monomer reduction auxiliary agent was evenly added to obtain modified devolatilized gel particles; (6) the gel particles were dried at a temperature of 180°C for 60 minutes, and crushed and sieved to obtain 401 parts of basic particles with an average particle size of 35 mesh; (7) a surface crosslinking treatment liquid was sprayed on the surface of the basic particles, and a surface crosslinking reaction was initiated by heat treatment at 150°C for 28 minutes. Finally, 0.2 parts of an inert filler were added to obtain finished super absorbent resin particles.

[0061] In this embodiment, the emulsifier is xylitol monostearate, the thickener is sodium polyacrylate, the foaming carbonate in step (1) is sodium bicarbonate, the crosslinking agent is polyethylene glycol 600) diacrylate, the photoinitiator is a ketamine photoinitiator, the high-temperature initiator includes 0.15 parts of 2,2'-azobis[2-(2-imidazoline-2-yl)propane] dihydrochloride and 0.9 parts of ammonium persulfate, the low-temperature initiator is sodium sulfite, the residual monomer reduction auxiliary agent is anhydrous sodium sulfite, the carbonate aqueous solution is a sodium carbonate aqueous solution, the surface crosslinking treatment solution includes 1.2 parts of 1,2-propylene glycol, 0.06 parts of ethylene glycol diglycidyl ether, 2.6 parts of sulfate and 6 parts of deionized water, and the inert filler is potassium dihydrogen phosphate.

[0062] Example 2

[0063] The preparation method of the super absorbent resin in this embodiment is as follows: (1) 250 parts of acrylic acid are diluted with 180 parts of water, and then 150 parts of 50% sodium hydroxide are added to neutralize to obtain a neutralized solution. The mass concentration of acrylic acid in the neutralized solution is 43%, and the neutralization degree is 54%; (2) 0.07 parts of emulsifier, 0.01 parts of thickener, and 0.04 parts of foaming carbonate are mixed evenly and diluted and dissolved with pure water to obtain a foaming promoter, and the concentration of the foaming promoter is 30%; (3) 0.22 parts of cross-linking agent, 0.02 parts of photoinitiator, and 1.1 parts of high-temperature initiator are added to the neutralized solution, and after stirring evenly, 0.018 parts of low-temperature initiator are added to obtain a polymerization mother solution; (4) the polymerization mother solution is subjected to nitrogen deoxygenation treatment, and the foaming promoter and the nitrogen-deoxygenated polymerization mother solution are mixed evenly, and the mixture is heated under UV The polymerization mother solution was polymerized under light conditions to obtain an acrylate polymer gel, the UV irradiation time was 8 minutes, and the starting temperature of the polymerization was 17°C; (5) the acrylate polymer gel was added to a single-screw rubber cutting granulator for extrusion granulation, and the granulation was continued for 3 times. During the extrusion granulation process, 0.8 parts of a carbonate aqueous solution with a carbonate content of 70 parts as a residual monomer reduction auxiliary agent was evenly added to obtain modified devolatilized gel particles; (6) the gel particles were dried at a temperature of 250°C for 15 minutes, and crushed and sieved to obtain 397 parts of basic particles with an average particle size of 35 mesh; (7) a surface crosslinking treatment liquid was sprayed on the surface of the basic particles, and a surface crosslinking reaction was initiated by heat treatment at 160°C for 25 minutes. Finally, 0.15 parts of an inert filler were added to obtain finished super absorbent resin particles.

[0064] In this embodiment, the emulsifier is sucrose monolaurate, the thickener is ammonium polyacrylate, the foaming carbonate is sodium carbonate, the cross-linking agent includes 0.10 parts of polyethylene glycol 210 and 0.12 parts of pentaerythritol triacrylate, the photoinitiator is acryloyl carboxylic acid diester, the high-temperature initiator includes 0.2 parts of 2,2-dimethoxy-2-phenylacetophenone and 0.6 parts of sodium persulfate, the low-temperature initiator is sodium bisulfite, the residual monomer reduction auxiliary agent is sodium metabisulfite, the carbonate aqueous solution is sodium carbonate aqueous solution, the surface cross-linking treatment liquid includes 1.5 parts of 1,3-propylene glycol, 0.07 parts of ethylene glycol diglycidyl ether, 3 parts of sulfate and 6 parts of deionized water, and the inert filler is silicate.

[0065] Example 3

[0066] The preparation method of the super absorbent resin in this embodiment is as follows: (1) 240 parts of acrylic acid are diluted with 160 parts of water, and then 160 parts of 50% sodium hydroxide are added to neutralize to obtain a neutralized solution, wherein the mass concentration of acrylic acid in the neutralized solution is 41% and the neutralization degree is 60%; (2) 0.06 parts of emulsifier, 0.01 parts of thickener, and 0.03 parts of foaming carbonate are mixed evenly and diluted and dissolved with pure water to obtain a foaming promoter, wherein the concentration of the foaming promoter is 30%; (3) 0.2 parts of cross-linking agent, 0.025 parts of photoinitiator, and 0.89 parts of high-temperature initiator are added to the neutralized solution, and after stirring evenly, 0.005 parts of low-temperature initiator are added to obtain a polymerization mother solution; (4) the polymerization mother solution is subjected to nitrogen deoxygenation treatment, and the foaming promoter and the nitrogen deoxygenated polymerization mother solution are mixed evenly, and the mixture is stirred at room temperature. The polymerization mother solution is polymerized under UV light conditions to obtain an acrylate polymer gel, the UV light exposure time is 6 minutes, and the starting temperature of the polymerization is 18°C; (5) the acrylate polymer gel is added to a single-screw rubber cutting granulator for extrusion granulation, and the granulation is continuous for 3 times. During the extrusion granulation process, 0.6 parts of a carbonate aqueous solution with a carbonate content of 55 parts as an auxiliary agent for reducing residual monomers is evenly added to obtain modified devolatilized gel particles; (6) the gel particles are dried at a temperature of 200°C for 80 minutes, and crushed and sieved to obtain 370 parts of basic particles with an average particle size of 35 mesh; (7) a surface crosslinking treatment liquid is sprayed on the surface of the basic particles, and a surface crosslinking reaction is initiated by heat treatment at 140°C for 32 minutes. Finally, 0.15 parts of an inert filler are added to obtain finished super absorbent resin particles.

[0067] In this embodiment, the emulsifier is sucrose monostearate, the thickener is polyacrylic acid, the foaming carbonate is calcium carbonate, the crosslinking agent is polyethylene glycol 400 diacrylate, the photoinitiator is an azole aniline photoinitiator, the high-temperature initiator includes 0.14 parts of 1-hydroxycyclohexyl phenyl ketone and 0.75 parts of sodium persulfate, the low-temperature initiator is ascorbic acid, the residual monomer reduction auxiliary agent is anhydrous sodium sulfite, the carbonate aqueous solution is a sodium carbonate aqueous solution, the surface crosslinking treatment liquid includes 1.2 parts of 1,2-propylene glycol, 0.05 parts of ethylene glycol diglycidyl ether, 2.4 parts of sulfate and 5.5 parts of deionized water, and the inert filler is fumed silica.

[0068] Example 4

[0069] The preparation method of the super absorbent resin in this embodiment is as follows: (1) 280 parts of acrylic acid are added to 200 parts of water for dilution, and then 160 parts of 50% sodium hydroxide are added for neutralization to obtain a neutralized solution, wherein the mass concentration of acrylic acid in the neutralized solution is 43.7% and the neutralization degree is 50%; (2) 0.1232 parts of emulsifier, 0.0308 parts of thickener and 0.154 parts of foaming carbonate are mixed evenly and diluted and dissolved with pure water to obtain a foaming promoter, wherein the concentration of the foaming promoter is 30%; (3) 14 parts of cross-linking agent, 0.28 parts of photoinitiator and 0.504 parts of high temperature initiator are added to the neutralized solution, and after stirring evenly, 2.8 parts of low temperature initiator are added to obtain a polymerization mother solution; (4) the polymerization mother solution is subjected to nitrogen deoxygenation treatment, and the foaming promoter and the nitrogen deoxygenated polymerization mother solution are mixed evenly, and then the mixture is stirred at room temperature. The polymerization mother solution was polymerized under UV irradiation conditions to obtain an acrylate polymer gel, the UV irradiation time was 7 minutes, and the starting temperature of the polymerization was 15°C; (5) the acrylate polymer gel was added to a single-screw rubber cutting granulator for extrusion granulation, and the granulation was continued for 3 times. During the extrusion granulation process, 2.38 parts of a carbonate aqueous solution with a carbonate content of 2.8 parts as a residual monomer reduction auxiliary agent was evenly added to obtain modified devolatilized gel particles; (6) the gel particles were dried at a temperature of 90°C for 120 minutes, and crushed and sieved to obtain 422 parts of basic particles with an average particle size of 35 mesh; (7) a surface crosslinking treatment liquid was sprayed on the surface of the basic particles, and a surface crosslinking reaction was initiated by heat treatment at 130°C for 35 minutes. Finally, 4.22 parts of an inert filler were added to obtain finished super absorbent resin particles.

[0070] In this embodiment, the emulsifier is polyoxyethylene oleate, the thickener is ethyl cellulose, the foaming carbonate is calcium carbonate, the crosslinking agent is dipentaerythritol pentaacrylate, the photoinitiator is a titanate photoinitiator, the high-temperature initiator is 2,2'-azobis(2-methylbutyronitrile), the low-temperature initiator is sodium metabisulfite, the auxiliary agent for reducing residual monomers is sodium thiosulfate, the carbonate aqueous solution is potassium bicarbonate aqueous solution, the surface crosslinking treatment liquid includes 0.0422 parts of 1,2-propylene glycol, 0.844 parts of ethylene glycol diglycidyl ether, 8.44 parts of sulfate and 5.5 parts of deionized water, and the inert filler is fumed silica.

[0071] Example 5

[0072] The preparation method of the super absorbent resin in this embodiment is as follows: (1) 240 parts of acrylic acid are diluted with 190 parts of water, and then 160 parts of 50% sodium hydroxide are added to neutralize to obtain a neutralized solution, wherein the mass concentration of acrylic acid in the neutralized solution is 43.7% and the neutralization degree is 60%; (2) 0.0528 parts of emulsifier, 0.0528 parts of thickener, and 0.1584 parts of foaming carbonate are mixed uniformly and diluted and dissolved with pure water to obtain a foaming promoter, wherein the concentration of the foaming promoter is 30%; (3) 0.12 parts of cross-linking agent, 0.0024 parts of photoinitiator, and 0.024 parts of high-temperature initiator are added to the neutralized solution, and after stirring uniformly, 0.0024 parts of low-temperature initiator are added to obtain a polymerization mother solution; (4) the polymerization mother solution is subjected to nitrogen deoxygenation treatment, and the foaming promoter is mixed with the nitrogen deoxygenated polymerization mother solution. The acrylate polymer gel was uniformly prepared, and the polymerization mother solution was initiated to polymerize under UV light conditions to obtain acrylate polymer gel. The UV light time was 9 minutes and the starting temperature of the polymerization was 12°C. (5) The acrylate polymer gel was added to a single-screw rubber cutting granulator for extrusion granulation, and the granulation was continuous for 3 times. During the extrusion granulation process, 2.4 parts of a carbonate aqueous solution with a carbonate content of 24 parts as a residual monomer reduction auxiliary agent were uniformly added to obtain modified devolatilized gel particles. (6) The gel particles were dried at a temperature of 180°C for 60 minutes, and crushed and sieved to obtain 422 parts of basic particles with an average particle size of 50 mesh. (7) A surface cross-linking treatment liquid was sprayed on the surface of the basic particles, and a surface cross-linking reaction was initiated by heat treatment at 140°C for 32 minutes. Finally, 0.0422 parts of an inert filler were added to obtain finished super absorbent resin particles.

[0073] In this embodiment, the emulsifier is polyoxyethylene nonylphenol ether, the thickener is microcrystalline cellulose, the foaming carbonate is sodium carbonate, the crosslinking agent is dipentaerythritol pentaacrylate, the high-temperature initiator is 2,2'-azobis(2-methylbutyronitrile), the photoinitiator is benzaldehyde-formaldehyde trimer, the low-temperature initiator is ascorbic acid, the auxiliary agent for reducing residual monomers includes 1 part of sodium thiosulfate and 1.4 parts of anhydrous sodium sulfite, the carbonate aqueous solution is ammonium carbonate aqueous solution, the surface crosslinking treatment liquid includes 8.44 parts of 1,2-propylene glycol, 2.11 parts of ethylene glycol diglycidyl ether, 16.88 parts of sulfate and 5.5 parts of deionized water, and the inert filler is fumed silica.

[0074] Example 6

[0075] The preparation method of the super absorbent resin in this embodiment is as follows: (1) 270 parts of acrylic acid are diluted with 220 parts of water, and then 160 parts of 50% sodium hydroxide are added to neutralize to obtain a neutralized solution, wherein the mass concentration of acrylic acid in the neutralized solution is 38% and the neutralization degree is 53%; (2) 0.108 parts of emulsifier, 0.054 parts of thickener, and 0.1188 parts of foaming carbonate are mixed evenly and diluted and dissolved with pure water to obtain a foaming promoter, wherein the concentration of the foaming promoter is 30%; (3) 0.081 parts of cross-linking agent, 0.135 parts of photoinitiator, and 5.4 parts of high-temperature initiator are added to the neutralized solution, and after stirring evenly, 0.081 parts of low-temperature initiator are added to obtain a polymerization mother liquor; (4) the polymerization mother liquor is subjected to nitrogen deoxygenation treatment, and the foaming promoter and the nitrogen-deoxygenated polymerization mother liquor are mixed evenly. The polymerization mother solution is polymerized under UV irradiation conditions to obtain an acrylate polymer gel, the UV irradiation time is 6 minutes, and the starting temperature of the polymerization is 18°C; (5) the acrylate polymer gel is added to a single-screw rubber cutting granulator for extrusion granulation, and the granulation is continuous for 5 times. During the extrusion granulation process, 0.27 parts of a carbonate aqueous solution with a carbonate content of 50 parts as a residual monomer reduction auxiliary agent is evenly added to obtain modified devolatilized gel particles; (6) the gel particles are dried at a temperature of 180°C for 60 minutes, and crushed and sieved to obtain 410 parts of basic particles with an average particle size of 50 mesh; (7) a surface crosslinking treatment liquid is sprayed on the surface of the basic particles, and a surface crosslinking reaction is initiated by heat treatment at 160°C for 25 minutes. Finally, 2.05 parts of an inert filler are added to obtain finished super absorbent resin particles.

[0076] In this embodiment, the emulsifier is sorbitan monolaurate, the thickener is a polyacrylate copolymer, the foaming carbonate is potassium carbonate, the crosslinking agent is ethoxylated trimethylolpropane triacrylate, the photoinitiator is acryloyl carboxylic acid diester, the high-temperature initiator is 2,2'-azobis[2-(2-imidazoline-2-yl)propane] dihydrochloride, the low-temperature initiator is sodium hyposulfite, the auxiliary agent for reducing residual monomers is sodium thiosulfate, the carbonate aqueous solution is an ammonium bicarbonate aqueous solution, the surface crosslinking treatment liquid includes 4.1 parts of 1,2-propylene glycol, 0.0041 parts of ethylene glycol diglycidyl ether, 4.1 parts of sulfate and 5.5 parts of deionized water, and the inert filler is fumed silica.

[0077] The super absorbent resin finished particles prepared in Examples 1 to 6 were sieved respectively to remove particles with a particle size smaller than 50 meshes to ensure that the particle size of the super absorbent resin finished particles was 30-50 meshes.

[0078] The performance of the super absorbent resins prepared in Examples 1 to 6 was tested, and the test results are shown in Table 1:

[0079] Table 1 Properties of super absorbent resins prepared in Examples 1 to 6

[0080]

[0081] As can be seen from Table 1, the super absorbent resin prepared in the present application has good performance in liquid absorption speed, liquid flow rate and physiological saline absorption times, and can take into account both good liquid absorption speed and strong liquid flow performance.

[0082] The super absorbent resin of the present invention is implanted with a foaming-promoting auxiliary agent at the initial stage of the reaction, so that the gel obtained in the initial stage has dense small pores, and a faster liquid absorption speed is obtained on the basis of a larger particle size, that is, a relatively small surface area; at the same time, under the premise of selecting a larger average particle size in the grinding stage, an inert filler that helps to disperse is added, and a stronger liquid permeability can be obtained, which satisfies the smooth passage of secondary, tertiary, and multiple liquids to the lower layer for absorption, and meets the performance requirements of the super absorbent resin for the upper layer of diapers. The present application prepares the hydrogel by aqueous solution polymerization, and finally obtains the finished product through the processes of extrusion granulation, drying, grinding and crushing to select the particle size, surface cross-linking reaction treatment, etc. The prepared super absorbent resin has the characteristics of fast absorption speed, excellent liquid permeability, and strong comprehensive liquid absorption capacity, and is suitable for the upper layer of diapers for infants, adults, and pets. Therefore, the present invention effectively overcomes some practical problems in the prior art and has high utilization value and use significance.

[0083] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for preparing a super absorbent resin, characterized in that: The steps include: Diluting acrylic acid with water and neutralizing it with alkali solution to obtain a neutralized solution; The emulsifier, thickener and foaming carbonate are evenly mixed and diluted and dissolved with pure water to obtain a foaming promoter; adding a crosslinking agent, a photoinitiator and a temperature initiator to the neutralized solution to obtain a polymerization mother solution; Deoxygenating the polymerization mother solution with nitrogen, uniformly mixing the foaming promoting agent with the nitrogen-deoxygenated polymerization mother solution, and initiating polymerization of the polymerization mother solution under UV irradiation to obtain an acrylate polymer gel; drying the acrylate polymer gel, and crushing and screening it to obtain base particles; A surface cross-linking treatment liquid is sprayed on the surface of the base particles, a surface cross-linking reaction of the base particles is initiated by heat treatment, and an inert filler is added after the surface cross-linking reaction to obtain finished super absorbent resin particles.

2. The preparation method according to claim 1, characterized in that The mass concentration of the acrylic acid is 15-45%, and the neutralization degree of the neutralization solution is 20-85%.

3. The preparation method according to claim 1, characterized in that The mass of the emulsifier is 0.022-0.044% of the mass of the acrylic acid, the mass of the thickener is 0.011-0.022% of the mass of the acrylic acid, and the mass of the foaming carbonate is 0.044-0.066% of the mass of the acrylic acid.

4. The preparation method according to claim 1, characterized in that The mass of the cross-linking agent is 0.05-5.00% of the mass of the acrylic acid, the mass of the photoinitiator is 0.001-0.1% of the mass of the acrylic acid, and the temperature initiator includes a high-temperature initiator and a low-temperature initiator. The mass of the high-temperature initiator is 0.01-2.00% of the mass of the acrylic acid, and the mass of the low-temperature initiator is 0.001-1.000% of the mass of the acrylic acid.

5. The preparation method according to claim 1, characterized in that The acrylate polymer gel is dried, crushed and sieved to obtain basic particles, comprising the following steps: extruding and granulating the acrylate polymer gel to obtain gel particles; The gel particles are dehydrated and dried, and then crushed and sieved to obtain base particles.

6. The preparation method according to claim 5, characterized in that During the extrusion granulation process of the acrylate polymer gel, a carbonate aqueous solution and an auxiliary agent for reducing residual monomers are uniformly added to the acrylate polymer gel, wherein the mass of the auxiliary agent for reducing residual monomers is 0.1 to 1.0% of the mass of the acrylic acid, the concentration of the carbonate aqueous solution is 1 to 40%, and the mass of the carbonate in the carbonate aqueous solution is 1 to 30% of the mass of the acrylic acid. When the gel particles are dehydrated and dried, the drying temperature is 90 to 250° C. and the drying time is 15 to 120 minutes.

7. The preparation method according to claim 1, characterized in that When the polymerization mother solution is polymerized, the polymerization starting temperature is 12-18° C., and the UV irradiation time is 6-9 minutes.

8. The preparation method according to claim 1, characterized in that The surface of the base particles is heat-treated at a temperature of 130 to 160° C. for a time of 25 to 35 minutes during cross-linking.

9. The preparation method according to claim 1, characterized in that The surface cross-linking treatment liquid includes propylene glycol, ethylene glycol diglycidyl ether and sulfate, the mass of the propylene glycol is 0.01 to 2% of the mass of the base particles, the mass of the ethylene glycol diglycidyl ether is 0.001 to 0.5% of the mass of the base particles, the mass of the sulfate is 0.1 to 4.0% of the mass of the base particles, and the propylene glycol includes any one of 1,3-propylene glycol and 1,2-propylene glycol.

10. The preparation method according to claim 1, characterized in that The mass of the inert filler is 0.01 to 1.0% of the mass of the base particles.

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