Continuous preparation process of water-absorbent resin particles and water-absorbent resin particles

Abstract

The invention provides a continuous preparation process of water-absorbent resin particles and the water-absorbent resin particles, the preparation process comprises the following steps: (1) dispersing a surfactant in a hydrocarbon dispersion medium, then adding a first monomer aqueous solution, a first initiator, a first cross-linking agent and a first thickening agent, and carrying out a first polymerization reaction; wherein the mass of the first thickening agent is 0.002-0.02% of the mass of the first monomer, so that the particle size of a product of the first polymerization reaction is controlled to be 50-900 microns; (2) separating and removing 50-80% of water in the material subjected to the first polymerization reaction, and performing swelling treatment; (3) adding a second monomer aqueous solution and a second initiator to carry out a second polymerization reaction; and after the reaction is completed, separating and drying to obtain water-absorbent resin particles. The water-absorbent resin particles disclosed by the invention have excellent free absorption capacity and pressurized absorption capacity, and are high in pressurized absorption stability and high in market application value; the continuous preparation process simplifies the technological process and improves the production efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a continuous preparation process of water-absorbing resin particles and the water-absorbing resin particles. Background Art

[0002] Superabsorbent polymer (SAP) is a functional polymer material with a large number of hydrophilic groups. It is primarily formed by cross-linking water-soluble ethylenically unsaturated monomers. Cross-linked polymers of partially neutralized polyacrylic acid are widely used due to their excellent water absorption properties. SAP has shown promising application prospects in the sanitary materials field, particularly in diapers, sanitary napkins, and incontinence pads.

[0003] Compared with the aqueous solution polymerization process route of directly carrying out cross-linking polymerization of acrylic acid (sodium) and the like in an aqueous solution and then crushing and screening, the process route of dispersing the aqueous solution of acrylic acid (sodium) and the like in an oily organic dispersed phase for reverse suspension polymerization has certain advantages: the reverse suspension polymerization process can prepare water-absorbing resins with higher water absorption rates, thereby meeting the composite core market's pursuit of ultra-thinness; the large amount of heat generated by the free radical polymerization of monomer molecules during the reaction process of the reverse suspension polymerization process can be conveniently removed in the form of heat exchange through the azeotropic co-existence of organic solvents and / or water, thereby reducing the difficulty of operation and simplifying the process flow.

[0004] As SAP application scenarios continue to refine, in addition to higher requirements for its free absorption capacity, SAP absorption capacity under load has also become a key performance consideration. For example, in the field of sanitary products, measuring the pressurized absorption capacity of absorbent resins helps ensure that the product can quickly absorb and lock in liquids during actual use, improving the product's dryness and comfort. In the field of medical care products, stable SAP pressurized absorption capacity ensures that the product can still effectively absorb and retain liquids when the patient is active or bedridden for long periods of time, reducing the frequency of caregiver changes and improving the patient's user experience.

[0005] Patent CN1023486C provides a method for producing a water-absorbent resin. This method uses multi-step reverse suspension polymerization, with the first step of polymerization being carried out first. After cooling and precipitation of the surfactant, a monomer solution is added for subsequent polymerization. Through multi-step polymerization and cooling precipitation, a water-absorbent resin with large particle size, narrow particle size distribution, and low fine powder is obtained. However, this method is complex and requires multiple cooling and heating cycles, which may increase production costs. In addition, this method does not focus on the pressurized absorption capacity of the water-absorbent resin.

[0006] Patent CN1060962C discloses a method for preparing a superabsorbent polymer. This method disperses fine particles of the superabsorbent polymer in a liquid hydrocarbon, introduces a monomer aqueous solution containing a thickener and a surfactant, and polymerizes the polymer. By using a hydrophilic additive and operating directly at the polymerization temperature, the generation of fine particles is reduced and the water absorption performance of the polymer is improved. Complex cooling / heating cycles are avoided. However, this method does not involve increasing the load absorption capacity of the absorbent polymer.

[0007] Patent CN111995706A discloses water-absorbent resin particles, a preparation method, and absorbent products. By optimizing the type and dosage of a surface crosslinking agent and controlling the water content of the hydrous crosslinked polymer particles, the method achieves a dry feel on the surface of the absorbent article under pressure, while also improving the gel liquid flow rate. This method involves multiple crosslinking steps, including preparation, surface crosslinking, and drying of the hydrous crosslinked polymer particles. This method requires further alignment and surface crosslinking after the hydrous crosslinked polymer particles are prepared, increasing production costs and process complexity. Furthermore, the method does not address the optimization of the absorbent resin's pressure-absorbing stability.

[0008] Previous studies have found that in the inverse suspension process for preparing water-absorbent resin particles, there is a conflict between increasing the free absorption capacity and the pressurized absorption capacity under load. This is manifested in the following: when the free absorption capacity of the water-absorbent resin increases, its pressurized absorption capacity often decreases; and when the pressurized absorption capacity of the water-absorbent resin increases, its free absorption capacity decreases significantly. Existing techniques often optimize the performance of water-absorbent resins by adjusting the concentration of the aqueous ethylenically unsaturated monomer solution, the concentration of the internal crosslinker, and post-crosslinking (surface crosslinking) processes. However, these methods are not satisfactory in achieving a balanced improvement in both free absorption capacity and pressurized absorption capacity. Summary of the Invention

[0009] In view of the deficiencies in the prior art, the present invention discloses a continuous preparation process for water-absorbent resin particles and the water-absorbent resin particles. The preparation process simplifies the process flow, and the prepared water-absorbent resin particles have excellent free absorption capacity and pressurized absorption capacity, and their pressurized absorption stability is high.

[0010] In order to achieve the above technical objectives, the present invention provides a continuous preparation process of water-absorbent resin particles, comprising the following steps:

[0011] (1) dispersing a surfactant in a hydrocarbon dispersion medium, and then adding a first monomer aqueous solution, a first initiator, a first crosslinking agent, and a first thickener to carry out a first polymerization reaction; wherein the mass of the first thickener is 0.002% to 0.02% of the mass of the first monomer, so as to control the particle size of the product of the first polymerization reaction to be between 50 μm and 900 μm;

[0012] (2) separating and removing 50% to 80% of the water contained in the material after the first polymerization reaction and performing a swelling treatment;

[0013] (3) adding a second monomer aqueous solution and a second initiator to carry out a second polymerization reaction; after the reaction is completed, the water-absorbing resin particles are obtained by separation and drying.

[0014] Through extensive experiments, the research and development team of the present invention discovered that water-absorbent resins produced by the inverse suspension polymerization process will undergo significant swelling (expansion) during the absorption of simulated liquids, and their resin particles may undergo structural disintegration in water. In other words, due to the weak binding force between the micron-sized basic units, the hydrophilic components of the secondary structure aggregates are dissociated by water, causing the primary structure microspheres to separate from the microspheres and form separate water-absorbing microspheres. This reduces the water retained in the secondary structure due to interfacial tension, making it difficult to increase the pressurized absorption capacity. The primary structure refers to the micron-sized basic units formed after monomer polymerization, and the secondary structure refers to the aggregates formed after a certain number of the aforementioned basic units are re-polymerized.

[0015] Based on this discovery, in the above technical solution, the amount of thickener is controlled in the primary polymerization so that the particle size of the product of the first polymerization reaction is within a specific particle size range, and after the completion of the primary polymerization, the material after the reaction is subjected to a water swelling operation, so that the second monomer aqueous solution enters the primary polymerization product more efficiently during the secondary polymerization to undergo a cross-linking reaction, thereby forming a more stable cross-linked network and a more uniform particle structure. The step (1) is conducive to forming a more compact secondary structure agglomerate after the second polymerization reaction by controlling the particle size of the product of the first polymerization reaction within the range of 50μm-900μm, thereby maximizing the pressure absorption capacity of the obtained water-absorbent resin while ensuring sufficient natural absorption capacity; the step (2) is able to separate and remove part of the water contained in the material after the reaction, so that the water absorption of the polymer referred to in step (1) is within a specific range, thereby further regulating the amount of the second monomer polymerized during the secondary polymerization, thereby achieving the improvement of the free water absorption capacity and pressure absorption capacity of the resin. In addition, the preparation process of the present invention does not require separation, drying, and other operations on the materials after the primary polymerization, and the entire process can be carried out in the same container or in different containers, thereby greatly simplifying the operation process and improving process efficiency.

[0016] The examples of the present invention demonstrate that the water-absorbent resin particles produced by the present invention not only exhibit a high natural absorption capacity but also maintain their structure under pressure, preventing water from being squeezed out. Furthermore, the particles are less susceptible to breakage during pressure application, preventing the collapse of the secondary structure. The water-absorbent resin exhibits excellent pressurized water absorption performance and stability of the pressurized water absorption performance.

[0017] The examples of the present invention demonstrate that in the continuous preparation process of the water-absorbent resin particles of the present invention, when the particle size of the product of the first polymerization reaction is 50 μm to 900 μm, the average particle size is 250 to 700 μm, preferably 410 to 530 μm, and more preferably 450 to 500 μm.

[0018] It should be noted that the present invention is not limited to the specific operation of separating and removing the water contained in the material after the primary polymerization reaction in the step (2). For example, methods such as filtering water, separating water by standing and stratifying, separating water by centrifugation, separating water by evaporation or separating water by adsorption can be selected. Those skilled in the art can choose according to actual needs, and the scope of protection of the present invention is not limited thereby.

[0019] The above technical solution controls the removal ratio of the water contained in the material after the first polymerization reaction in step (2) to 50% to 80%, that is, the water absorption of the polymer obtained after the first polymerization reaction is controlled to 77% to 30%, which is more conducive to the full cross-linking reaction between the second monomer and the monomer after the first polymerization during the second polymerization process, thereby increasing the free absorption capacity and pressurized absorption capacity of the water-absorbent resin particles obtained. Wherein, water absorption = (mass after water absorption - mass before water absorption) / mass before water absorption × 100%. In a further example of the present invention, the ratio of the water contained in the material after the first polymerization reaction separated and removed in step (2) is explored and optimized. Optionally, in step (2), 60% to 70% of the water contained in the material after the first polymerization reaction is separated and removed, preferably 65% ​​to 70% of the water contained in the material after the first polymerization reaction is separated and removed. The embodiments of the present invention and the comparative examples illustrate this exploration and optimization process.

[0020] In a further example of the present invention, the temperature of the swelling treatment may be selected from 50 to 90° C., preferably from 60 to 80° C., and more preferably from 65 to 75° C.; the treatment time may be selected from 10 to 120 min, preferably from 30 to 90 min, and more preferably from 45 to 75 min. The embodiments and comparative examples of the present invention show the preparation process of the water-absorbent resin under different swelling operating conditions; the control of the swelling conditions is conducive to improving the process efficiency while ensuring the product performance.

[0021] In a further example of the present invention, the temperature of the first polymerization reaction can be selected from 70 to 90°C, preferably 71 to 85°C, and more preferably 72 to 81°C; the reaction time can be selected from 10 to 180 minutes, preferably 30 to 120°C, and more preferably 45 to 75°C.

[0022] In a further example of the present invention, the temperature of the second polymerization reaction can be selected from 70 to 90° C., preferably 71 to 85° C., and more preferably 72 to 81° C.; the reaction time can be selected from 10 to 180 min, preferably 30 to 120 min, and more preferably 45 to 75 min.

[0023] On the basis of the above technical solution, the optimization of the polymerization reaction control conditions can not only improve the reaction efficiency, but also adjust the structure and properties of the obtained water-absorbent resin, thereby promoting the formation of a stable cross-linked network and ultimately improving the water absorption performance and pressurized water absorption performance of the obtained water-absorbent resin.

[0024] In a further example of the present invention, the types and amounts of the first monomer and the second monomer are explored.

[0025] Optionally, the first monomer and the second monomer are ethylenically unsaturated monomers. Further optionally, the first monomer and the second monomer are independently selected from at least one of acrylic acid monomers, acrylamide monomers, vinyl acetate, ethylene sulfonic acid monomers, and vinylbenzenesulfonic acid monomers (and their salts). Wherein, the acrylic acid monomers include (meth)acrylic acid and its salts, acrylamide monomers include (meth)acrylamide, ethylene sulfonic acid monomers include ethylene sulfonic acid (and its salts), and vinylbenzenesulfonic acid monomers include vinylbenzenesulfonic acid (and its salts). Wherein, the salt of the monomer is not limited to the potassium salt, sodium salt or ammonium salt of the monomer.

[0026] Optionally, the concentration of the first monomer aqueous solution is 10% to 50%, preferably 15% to 45%. Optionally, the neutralization degree of the first monomer aqueous solution is 70% to 80%, which is conducive to balancing the hydrophilicity and cross-linking network elasticity of the product of the first polymerization reaction.

[0027] Optionally, the concentration of the second monomer aqueous solution is 10% to 50%, preferably 15% to 45%.

[0028] Optionally, the molar ratio of the first monomer to the second monomer is (5-20):1, preferably (9-19):1. This embodiment illustrates a continuous process for preparing water-absorbent resin particles using different types and amounts of the first and second monomers. Optimizing the relative amounts of the first and second monomers can improve the pressure absorption capacity of the resulting water-absorbent resin particles.

[0029] In a further example of the present invention, the type and amount of the surfactant were explored.

[0030] Optionally, the surfactant includes at least one of sucrose fatty acid ester, polyglycerol fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerol fatty acid ester, sorbitol fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, alkyl allyl formaldehyde condensation polyoxyethylene ether, polyoxyethylene polyoxypropylene block copolymer, polyoxyethylene polyoxypropyl alkyl ether, polyethylene glycol fatty acid ester, alkyl glucoside, N-alkyl glucose amide, polyoxyethylene fatty acid amide, polyoxyethylene alkylamine, phosphate ester of polyoxyethylene alkyl ether, and phosphate ester of polyoxyethylene alkyl allyl ether.

[0031] Optionally, the mass of the surfactant is 1 / 1000 to 5 / 1000 of the mass of the hydrocarbon dispersion medium, which facilitates simplification of the process and improves stability.

[0032] In a further example of the present invention, the type and amount of the hydrocarbon dispersion medium are explored. Optionally, the hydrocarbon dispersion medium includes at least one of a chain aliphatic hydrocarbon, an alicyclic hydrocarbon, and an aromatic hydrocarbon; preferably, the chain aliphatic hydrocarbon is a chain aliphatic hydrocarbon with 6 to 8 carbon atoms; further preferably, the chain aliphatic hydrocarbon includes at least one of n-hexane, n-heptane, 2-methylhexane, 3-methylhexane, 2,3-dimethylpentane, 3-ethylpentane, and n-octane; preferably, the alicyclic hydrocarbon is an alicyclic hydrocarbon with 6 to 8 carbon atoms; further preferably, the alicyclic hydrocarbon includes at least one of cyclohexane, methylcyclohexane, cyclopentane, methylcyclopentane, trans-1,2-dimethylcyclopentane, cis-1,3-dimethylcyclopentane, and trans-1,3-dimethylcyclopentane; preferably, the aromatic hydrocarbon includes at least one of benzene, toluene, and xylene. Optionally, the mass of the hydrocarbon dispersion medium is 1 to 3 times the mass of the first monomer, which can provide a stable reaction environment and promote sufficient mixing and reaction of the reaction raw materials to obtain a uniform polymer molecular structure and network structure.

[0033] In a further example of the present invention, the types and amounts of the first and second initiators are explored. This example shows a continuous preparation process of water-absorbing resin particles with different initiators, ie, initiator amounts.

[0034] Optionally, the first initiator and the second initiator are independently selected from one or more of persulfates, peroxides, and azo water-soluble free radical initiators. Preferably, the peroxide includes methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide, di-tert-butyl peroxide, tert-butyl isopropyl peroxide, tert-butyl peracetate, tert-butyl peroxyisobutyrate, tert-butyl peroxypivalate, and hydrogen peroxide; preferably, the azo water-soluble free radical initiator includes 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(N-phenylamidino)propane] dihydrochloride, 2,2'-azobis[2-(N-allylamidino)propane] dihydrochloride, )propane] dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane} dihydrochloride, 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide}, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], 4,4'-azobis(4-cyanovaleric acid).

[0035] Optionally, the molar ratio of the first initiator to the first monomer is (0.0002-0.001):1, preferably (0.0003-0.0005):1.

[0036] Optionally, the molar ratio of the second initiator to the second monomer is (0.0002-0.001):1, preferably (0.0003-0.0005):1.

[0037] In a further example of the present invention, the type and amount of the first cross-linking agent are explored. Optionally, the first cross-linking agent includes polyols such as ethylene glycol, propylene glycol, 1,4-butanediol, trimethylolpropane, glycerol, polyethylene glycol diglycidyl ether, polyglycerol diglycidyl ether, polyglycerol triglycidyl ether, trimethylolpropane triglycidyl ether, polypropylene glycol polyglycidyl ether, polyglycerol polyglycidyl ether, etc.; halogenated epoxy compounds such as epichlorohydrin, epibromohydrin, α-methylepichlorohydrin; 2,4-toluene diisocyanate, hexamethylene At least one of an isocyanate compound such as diisocyanate; an oxetane compound such as 3-methyl-3-oxetanemethanol, 3-ethyl-3-oxetanemethanol, 3-butyl-3-oxetanemethanol, 3-methyl-3-oxetaneethanol, 3-ethyl-3-oxetaneethanol, and 3-butyl-3-oxetaneethanol; an oxazoline compound such as 1,2-ethylenebisoxazoline; a carbonate compound such as ethylene carbonate; and a hydroxyalkylamide compound such as bis[N,N-bis(β-hydroxyethyl)]adipamide. Optionally, the first crosslinking agent is added in an amount of 0.01% to 0.03% by mass of the first monomer.

[0038] In a further example of the present invention, the type and amount of the first thickener are explored. Optionally, the first thickener includes at least one of ethyl cellulose, hydroxypropyl cellulose, methyl cellulose, carboxymethyl cellulose, polyacrylic acid, polyacrylic acid (partially) neutralized, polyethylene glycol, polyacrylamide, polyethyleneimine, dextrin, sodium alginate, polyvinyl alcohol, polyvinyl pyrrolidone, and polyethylene oxide. Optionally, the first thickener is added in an amount of 0.005% to 0.01% of the mass of the first monomer, thereby regulating the viscosity of the overall mixture to control the particle size of the product of the first polymerization reaction to be between 100 μm and 800 μm, thereby promoting the preparation of water-absorbing resin particles with uniform particle size distribution.

[0039] In a further example of the present invention, a second cross-linking agent and / or a second thickener may be optionally added when adding the second monomer aqueous solution and the second initiator, thereby integrating the second polymerization and the surface cross-linking into one process, thereby ensuring a balanced increase in the free absorption capacity and the pressurized absorption capacity, completing the surface cross-linking and maintaining other capabilities of the water-absorbent resin particles, and improving product performance without adding additional production processes.

[0040] Optionally, the second cross-linking agent includes polyols such as ethylene glycol, propylene glycol, 1,4-butanediol, trimethylolpropane, glycerol, polyethylene glycol diglycidyl ether, polyglycerol diglycidyl ether, polyglycerol triglycidyl ether, trimethylolpropane triglycidyl ether, polypropylene glycol polyglycidyl ether, polyglycerol polyglycidyl ether, etc.; halogenated epoxy compounds such as epichlorohydrin, epibromohydrin, α-methylepichlorohydrin; 2,4-toluene diisocyanate, hexamethylene At least one of an isocyanate compound such as diisocyanate; an oxetane compound such as 3-methyl-3-oxetanemethanol, 3-ethyl-3-oxetanemethanol, 3-butyl-3-oxetanemethanol, 3-methyl-3-oxetaneethanol, 3-ethyl-3-oxetaneethanol, and 3-butyl-3-oxetaneethanol; an oxazoline compound such as 1,2-ethylenebisoxazoline; a carbonate compound such as ethylene carbonate; and a hydroxyalkylamide compound such as bis[N,N-bis(β-hydroxyethyl)]adipamide. Optionally, the second crosslinking agent is added in an amount of 0% to 0.03% by mass of the second monomer.

[0041] Optionally, the second thickener includes at least one of ethyl cellulose, hydroxypropyl cellulose, methyl cellulose, carboxymethyl cellulose, polyacrylic acid, partially neutralized polyacrylic acid, polyethylene glycol, polyacrylamide, polyethyleneimine, dextrin, sodium alginate, polyvinyl alcohol, polyvinyl pyrrolidone, and polyethylene oxide. Optionally, the second thickener is added in an amount of 0% to 0.01% by weight of the second monomer.

[0042] On the other hand, the present invention provides water-absorbent resin particles, which are prepared by the above-mentioned continuous preparation process of water-absorbent resin particles.

[0043] Optionally, the particle size of the water-absorbing resin particles is 300 to 800 μm.

[0044] Compared with the prior art, the present invention has the following beneficial effects: the continuous preparation process of the water-absorbent resin particles of the present invention controls the particle size of the product after the first polymerization reaction within a specific particle size range, and after the first polymerization reaction is completed, separates a specific proportion of the water contained in the post-reaction material and performs a swelling operation, which is conducive to the monomer entering the polymer during the second polymerization reaction to form a stable cross-linked network and a uniform particle structure, thereby improving the free water absorption performance and pressurized water absorption performance of the prepared water-absorbent resin particles, so that after absorbing and swelling in water, it will not disintegrate into a primary structure and can still well maintain its original secondary structure. The water-absorbent resin particles of the present invention have excellent free absorption capacity and pressurized absorption capacity, and their pressurized absorption stability is high, and have wide market application value. The continuous preparation process of the water-absorbent resin particles of the present invention simplifies the process flow and improves production efficiency. DETAILED DESCRIPTION

[0045] To facilitate understanding of the present invention, the present invention will be described in more detail below, with preferred embodiments of the present invention provided. However, it should be understood that these embodiments are merely for the purpose of further explanation and are not to be construed as limiting the present invention in any form, i.e., they are not intended to limit the scope of protection of the present invention.

[0046] Unless otherwise defined, the technical terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which this invention belongs. The experimental reagents used in the following examples, unless otherwise specified, are conventional biochemical reagents; the experimental methods described, unless otherwise specified, are conventional methods.

[0047] Test method: In the present invention, a 0.9% sodium chloride aqueous solution is used as a simulated urine solution to measure the product's physiological saline absorption capacity (g / g) and pressurized absorption capacity (g / g) according to the test method specified in GB / T 22875-2018. The pressurized absorption capacity I is determined under a load of 2.07 kPa, and the pressurized absorption capacity II of the absorbent resin is determined under a load of 4.14 kPa.

[0048] Example 1

[0049] A continuous preparation process for water-absorbent resin particles comprises the following steps:

[0050] (1) 3.5 g of Span 60 was dispersed in 300 g of cyclohexane, and then 300 g of a 75% neutralized sodium acrylate aqueous solution (prepared by neutralizing 90.6 g of acrylic acid, 90.6 g of water, and 118 g of a 32% by mass sodium hydroxide solution), 0.15 g of potassium persulfate, 0.05 g of ethylene glycol diglycidyl ether, and 0.015 g of hydroxyethyl cellulose were added. The first polymerization reaction was carried out at 70°C for 1 h.

[0051] (2) 60% (about 97 g) of the water contained in the material after the first polymerization reaction was separated and removed by filtration, and a swelling treatment was performed at 50° C. for 1 hour.

[0052] (3) 100 g of sodium acrylate aqueous solution (the same as that used in step 1) and 0.05 g of potassium persulfate were added, and a second polymerization reaction was carried out at 70° C. for 1 hour. After the reaction was completed, the water-absorbent resin particles were separated and dried to obtain the water-absorbent resin particles, having a particle size of 124 μm to 687 μm (average particle size of 410 μm). The water-absorbent resin particles of this embodiment had a natural absorption capacity of 63, a pressurized absorption capacity I of 43, and a pressurized absorption capacity II of 35.

[0053] Comparative Example 1

[0054] This comparative example illustrates a process for preparing a water-absorbent resin. The raw materials and control method used in this method are the same as those in Example 1, except that, in step (2) of this comparative example, no separation and removal of water is performed, and the average particle size of the water-absorbent resin particles is 426 μm. The water-absorbent resin particles of this comparative example have a natural absorption capacity of 53 g / g, a pressurized absorption capacity I of 21 g / g, and a pressurized absorption capacity II of 14 g / g.

[0055] Comparative Example 2

[0056] This comparative example illustrates a process for preparing a water-absorbent resin. The process utilizes the same raw materials and control methods as in Example 1, except that step (2) is omitted. The water-absorbent resin prepared in this comparative example has an average particle size of 409 μm. The water-absorbent resin particles in this comparative example exhibit a natural absorption capacity of 55 g / g, a pressurized absorption capacity I of 19 g / g, and a pressurized absorption capacity II of 13 g / g.

[0057] Example 2

[0058] Based on the continuous preparation process for water-absorbent resin particles described in Example 1, this example explored and optimized the effects of the amount of the first thickener used in step (1) and the particle size of the product after the first polymerization reaction. Specifically, the amount of the first thickener used, the particle size of the product after the first polymerization reaction, and the natural absorption capacity, pressurized absorption capacity I, and pressurized absorption capacity II of the resulting water-absorbent resin particles are shown in Table 1.

[0059] Table 1

[0060]

[0061] Table 1 demonstrates that, in the continuous preparation process of the water-absorbent resin particles of the present invention, by adding an appropriate amount of the first thickener in step (1), the particle size of the product of the first polymerization reaction can be controlled within a range of 50 μm to 900 μm, i.e., its average particle size is within a range of 250 to 700 μm, thereby achieving both good natural absorption capacity and pressure absorption capacity, with the pressure absorption capacity being pressure-stable. Optionally, the mass of the first thickener is 0.002% to 0.02% of the mass of the first monomer, preferably 0.005% to 0.01%, and more preferably 0.007%.

[0062] Example 3

[0063] Based on the continuous preparation process for water-absorbent resin particles described in Example 1, this example explored and optimized the water separation and removal ratio of the post-polymerization reaction material in step (2). Specifically, the natural absorption capacity, pressurized absorption capacity I, and pressurized absorption capacity II of the water-absorbent resin particles obtained under different control ranges are shown in Table 2.

[0064] Table 2

[0065] Serial number Step (2) separation water ratio / % Natural absorption Pressurized absorption capacity I Pressurized Absorption Capacity II Example 3.1 50 64 36 31 Example 1 60 63 43 35 Example 3.3 65 64 35 32 Example 3.4 70 64 35 32 Example 3.5 80 63 33 30 Comparative Example 6.1 5 62 15 9 Comparative Example 6.2 95 61 8 7

[0066] Table 2 demonstrates that, in step (2) of the continuous preparation process for the water-absorbent resin particles of the present invention, removing a specific proportion of water from the material after the first polymerization reaction is beneficial for improving the pressure absorption performance of the water-absorbent resin particles while ensuring a good natural absorption capacity, while also improving the stability of pressure absorption. Alternatively, in step (2), 50% to 80% of the water contained in the material after the first polymerization reaction may be separated and removed and then subjected to a swelling treatment. Furthermore, in step (2), 60% to 70% of the water contained in the material after the first polymerization reaction may be separated and removed, preferably 65% ​​to 70% of the water contained in the material after the first polymerization reaction may be separated and removed.

[0067] Example 4

[0068] Based on the continuous preparation process for water-absorbent resin particles described in Example 1, this example explores the preparation of water-absorbent resin particles under different swelling control conditions. Specifically, the absorption capacity, pressurized absorption capacity I, and pressurized absorption capacity II of the resulting water-absorbent resins under different swelling control conditions are shown in Table 3.

[0069] Table 3

[0070] Serial number Swelling temperature / ℃ Residence time / min Natural absorption Pressurized absorption capacity I Pressurized Absorption Capacity II Example 4.1 50 10 64 33 35 Example 4.2 60 30 64 35 32 Example 4.3 70 60 64 35 32 Example 4.4 80 90 63 34 31 Example 4.5 90 120 63 33 30 Comparative Example 7.1 25 60 63 15 9 Comparative Example 7.2 60 1 63 13 9

[0071] Table 3 demonstrates that, in the continuous preparation process of the water-absorbent resin particles of the present invention, if the swelling operation temperature is too low or the swelling time is too short, the improvement effect of the second polymerization reaction on the pressurized absorption capacity I and II of the prepared water-absorbent resin particles may be affected. Considering that the temperature control of the water swelling operation can preheat the second polymerization reaction materials, the swelling treatment temperature of the present invention is 50-90°C, preferably 60-80°C, and more preferably 65-75°C; the treatment time is 10-120 min, preferably 30-90 min, and more preferably 45-75 min.

[0072] Example 5

[0073] Based on the continuous preparation process for water-absorbent resin particles described in Example 1, this example explores the production of water-absorbent resin particles using different types of first and second monomers. Specifically, the natural absorption capacity, pressurized absorption capacity I, and pressurized absorption capacity II of the various monomers and the resulting water-absorbent resins are shown in Table 4.

[0074] Table 4

[0075] Example First monomer type Second monomer type Natural absorption Pressurized absorption capacity I Pressurized Absorption Capacity II Example 1 Acrylamide Sodium acrylate 63 43 35 Example 5.1 Sodium methacrylate Methacrylic acid 63 43 35 Example 5.2 Sodium vinyl sulfonate Potassium acrylate 64 35 32

[0076] Table 4 shows that the continuous process for preparing water-absorbent resin particles of the present invention has good raw material applicability.

[0077] Example 6

[0078] Based on the continuous preparation process for water-absorbent resin particles described in Example 1, this example explored the effect of the concentration of the first monomer aqueous solution on the preparation of water-absorbent resin particles. Specifically, the natural absorption capacity, pressurized absorption capacity I, and pressurized absorption capacity II of the resulting water-absorbent resins at different first monomer concentrations are shown in Table 5.

[0079] Table 5

[0080]

[0081] Table 5 shows that in the continuous preparation process of water-absorbent resin particles of the present invention, the concentration of the first monomer aqueous solution is 10% to 50%, preferably 15% to 45%; the concentration of the second monomer aqueous solution is 10% to 50%, preferably 15% to 45%.

[0082] Example 7

[0083] Based on the continuous preparation process for water-absorbent resin particles described in Example 1, this example explores the effects of the control conditions in step (3) on the preparation of water-absorbent resin particles. Specifically, the absorption capacity, pressurized absorption capacity I, and pressurized absorption capacity II of the resulting water-absorbent resins under different control conditions are shown in Table 5.

[0084] Table 6

[0085]

[0086] As can be verified from Table 6, the temperature of the second polymerization reaction in the continuous preparation process of the water-based resin particles of the present invention is 70-90° C., preferably 71-85° C., and more preferably 72-81° C.; the reaction time is 10-180 min, preferably 30-120 min, and more preferably 45-75 min.

[0087] Example 8

[0088] Based on the continuous preparation process for water-absorbent resin particles described in Example 1, this example further includes the addition of a second crosslinking agent and / or a second thickener during the addition of the second aqueous monomer solution and the second initiator. This example illustrates the process for producing water-absorbent resin particles with the addition of a second crosslinking agent and / or a second thickener, wherein the second crosslinking agent is of the same type as the first crosslinking agent, and the second thickener is of the same type as the first thickener. Specific control of the second crosslinking agent and / or second thickener, as well as the absorption capacity, pressurized absorption capacity I, and pressurized absorption capacity II of the resulting water-absorbent resin particles, are shown in Table 7.

[0089] Table 7

[0090]

[0091] Table 7 demonstrates that in the continuous preparation process of the water-absorbent resin particles of the present invention, a second crosslinking agent and / or a second thickener can be optionally added when adding the second monomer aqueous solution and the second initiator. The amount of the second crosslinking agent added is 0% to 0.03% by weight of the second monomer, preferably 0.01% to 0.03% by weight; and the amount of the second thickener added is 0% to 0.01% by weight of the second monomer, preferably 0.005% to 0.01% by weight.

[0092] Example 9

[0093] Based on the continuous preparation process for water-absorbent resin particles described in Example 1, this example illustrates the process for preparing water-absorbent resin particles using different hydrocarbon dispersion media and first initiator types. Specifically, the types of hydrocarbon dispersion media and first initiators, as well as the natural absorption capacity, pressurized absorption capacity I, and pressurized absorption capacity II of the resulting water-absorbent resins, are shown in Table 8.

[0094] Table 8

[0095]

[0096] It should be noted that the above is a further detailed description of the present invention in conjunction with specific embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, several simple improvements can be made without departing from the concept of the present invention, and all of these should be considered to fall within the scope of protection of the present invention.

Claims

1. A continuous preparation process for water-absorbent resin particles, characterized in that: The following steps are involved: (1) dispersing a surfactant in a hydrocarbon dispersion medium, and then adding a first monomer aqueous solution, a first initiator, a first crosslinking agent, and a first thickener to carry out a first polymerization reaction; wherein the mass of the first thickener is 0.002% to 0.02% of the mass of the first monomer, so as to control the particle size of the product of the first polymerization reaction to be between 50 μm and 900 μm; (2) separating and removing 50% to 80% of the water contained in the material after the first polymerization reaction and performing a swelling treatment; (3) adding a second monomer aqueous solution and a second initiator to carry out a second polymerization reaction; after the reaction is completed, the water-absorbing resin particles are obtained by separation and drying.

2. The continuous preparation process of water-absorbent resin particles according to claim 1, characterized in that: In the step (2), 60% to 70% of the water contained in the material after the first polymerization reaction is separated and removed, preferably 65% ​​to 70% of the water contained in the material after the first polymerization reaction is separated and removed.

3. The continuous preparation process of water-absorbent resin particles according to claim 1, characterized in that: The swelling treatment temperature is 50-90°C, preferably 60-80°C, more preferably 65-75°C; the treatment time is 10-120 min, preferably 30-90 min, more preferably 45-75 min; and / or, the temperature of the first polymerization reaction is 70 to 90° C., preferably 71 to 85° C., more preferably 72 to 81° C.; The reaction time is 10 to 180 minutes, preferably 30 to 120°C, more preferably 45 to 75°C; and / or, the temperature of the second polymerization reaction is 70 to 90° C., preferably 71 to 85° C., more preferably 72 to 81° C.; The reaction time is 10 to 180 min, preferably 30 to 120 min, and more preferably 45 to 75 min.

4. The continuous preparation process of water-absorbent resin particles according to claim 1, characterized in that: The first monomer and the second monomer are ethylenically unsaturated monomers; Preferably, the first monomer and the second monomer are independently selected from at least one of acrylic acid monomers, acrylamide monomers, vinyl acetate, vinyl sulfonic acid monomers, and vinylbenzene sulfonic acid monomers (and their salts); Preferably, the acrylic acid monomers include (meth)acrylic acid and its salts, the acrylamide monomers include (meth)acrylamide, the vinyl sulfonic acid monomers include vinyl sulfonic acid (and its salts), and the vinylbenzenesulfonic acid monomers include vinylbenzenesulfonic acid (and its salts); and / or, the mass concentration of the first monomer aqueous solution is 10% to 50%, preferably 15% to 45%; and / or, the mass concentration of the second monomer aqueous solution is 10% to 50%, preferably 15% to 45%; And / or, the molar ratio of the first monomer to the second monomer is (5-20):1, preferably (9-19):

1.

5. The continuous preparation process of water-absorbent resin particles according to claim 1, characterized in that: The surfactant includes at least one of sucrose fatty acid ester, polyglycerol fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerol fatty acid ester, sorbitol fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, alkyl allyl formaldehyde condensation polyoxyethylene ether, polyoxyethylene polyoxypropylene block copolymer, polyoxyethylene polyoxypropyl alkyl ether, polyethylene glycol fatty acid ester, alkyl glucoside, N-alkylglucamide, polyoxyethylene fatty acid amide, polyoxyethylene alkylamine, phosphate ester of polyoxyethylene alkyl ether, and phosphate ester of polyoxyethylene alkyl allyl ether; And / or, the mass of the surfactant is 1 / 1000 to 5 / 1000 of the mass of the hydrocarbon dispersion medium.

6. The continuous preparation process of water-absorbent resin particles according to claim 1, characterized in that: The hydrocarbon dispersion medium includes at least one of chain aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons; Preferably, the chain aliphatic hydrocarbon is a chain aliphatic hydrocarbon having 6 to 8 carbon atoms; Further preferably, the chain aliphatic hydrocarbon includes at least one of n-hexane, n-heptane, 2-methylhexane, 3-methylhexane, 2,3-dimethylpentane, 3-ethylpentane, and n-octane; Preferably, the alicyclic hydrocarbon is an alicyclic hydrocarbon having 6 to 8 carbon atoms; Further preferably, the alicyclic hydrocarbon includes at least one of cyclohexane, methylcyclohexane, cyclopentane, methylcyclopentane, trans-1,2-dimethylcyclopentane, cis-1,3-dimethylcyclopentane, and trans-1,3-dimethylcyclopentane; Preferably, the aromatic hydrocarbon includes at least one of benzene, toluene, and xylene; And / or, the mass of the hydrocarbon dispersion medium is 1 to 3 times the mass of the first monomer.

7. The continuous preparation process of water-absorbent resin particles according to claim 1, characterized in that: The first initiator and the second initiator are independently selected from one or more of persulfates, peroxides, and azo water-soluble free radical initiators; Preferably, the peroxide includes methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide, di-tert-butyl peroxide, tert-butyl isopropyl benzene peroxide, tert-butyl peracetate, tert-butyl peroxyisobutyrate, tert-butyl peroxypivalate and hydrogen peroxide; Preferably, the azo water-soluble free radical initiator includes 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(N-phenylamidino)propane] dihydrochloride, 2,2'-azobis[2-(N-allylamidino)propane] dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane} dihydrochloride, 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide}, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], and 4,4'-azobis(4-cyanovaleric acid); and / or, the molar ratio of the first initiator to the first monomer is (0.0002-0.001):1, preferably (0.0003-0.0005):1; And / or, the molar ratio of the second initiator to the second monomer is (0.0002-0.001):1, preferably (0.0003-0.0005):

1.

8. The continuous preparation process of water-absorbent resin particles according to claim 1, characterized in that: The first cross-linking agent includes polyols such as ethylene glycol, propylene glycol, 1,4-butanediol, trimethylolpropane, glycerol, polyethylene glycol diglycidyl ether, polyglycerol diglycidyl ether, polyglycerol triglycidyl ether, trimethylolpropane triglycidyl ether, polypropylene glycol polyglycidyl ether, polyglycerol polyglycidyl ether, etc.; halogenated epoxy compounds such as epichlorohydrin, epibromohydrin, α-methylepichlorohydrin; 2,4-toluene diisocyanate, hexamethylene diisocyanate, etc. Isocyanate compounds such as cyanate; oxetane compounds such as 3-methyl-3-oxetanemethanol, 3-ethyl-3-oxetanemethanol, 3-butyl-3-oxetanemethanol, 3-methyl-3-oxetaneethanol, 3-ethyl-3-oxetaneethanol, and 3-butyl-3-oxetaneethanol; oxazoline compounds such as 1,2-ethylenebisoxazoline; carbonate compounds such as ethylene carbonate; and at least one of hydroxyalkylamide compounds such as bis[N,N-bis(β-hydroxyethyl)]adipamide; and / or, the amount of the first cross-linking agent added is 0.01% to 0.03% by mass of the first monomer; and / or, the first thickener comprises at least one of ethyl cellulose, hydroxypropyl cellulose, methyl cellulose, carboxymethyl cellulose, polyacrylic acid, (partially) neutralized polyacrylic acid, polyethylene glycol, polyacrylamide, polyethyleneimine, dextrin, sodium alginate, polyvinyl alcohol, polyvinyl pyrrolidone, and polyethylene oxide; And / or, the first thickener is added in an amount of 0.005% to 0.01% of the mass of the first monomer, so as to control the particle size of the product of the first polymerization reaction to be 100 μm to 800 μm.

9. The continuous preparation process of water-absorbent resin particles according to any one of claims 1 to 8, characterized in that: The method further comprises adding a second cross-linking agent and / or a second thickener when adding the second monomer aqueous solution and the second initiator; preferably, the second cross-linking agent comprises ethylene glycol, propylene glycol, 1,4-butanediol, trimethylolpropane, glycerol, polyoxyethylene glycol, polyoxypropylene glycol, polyglycerol and other polyols, polyethylene glycol diglycidyl ether, polyglycerol diglycidyl ether, polyglycerol triglycidyl ether, trimethylolpropane triglycidyl ether, polypropylene glycol polyglycidyl ether, polyglycerol polyglycidyl ether and other polyglycidyl compounds; halogenated epoxy compounds such as epichlorohydrin, epibromohydrin, α-methyl epichlorohydrin and the like. Compounds; isocyanate compounds such as 2,4-toluene diisocyanate and hexamethylene diisocyanate; oxetane compounds such as 3-methyl-3-oxetanemethanol, 3-ethyl-3-oxetanemethanol, 3-butyl-3-oxetanemethanol, 3-methyl-3-oxetaneethanol, 3-ethyl-3-oxetaneethanol, and 3-butyl-3-oxetaneethanol; oxazoline compounds such as 1,2-ethylenebisoxazoline; carbonate compounds such as ethylene carbonate; and at least one of hydroxyalkylamide compounds such as bis[N,N-bis(β-hydroxyethyl)]adipamide; Preferably, the amount of the second cross-linking agent added is 0% to 0.03% of the mass of the second monomer; Preferably, the second thickener comprises at least one of ethyl cellulose, hydroxypropyl cellulose, methyl cellulose, carboxymethyl cellulose, polyacrylic acid, (partially) neutralized polyacrylic acid, polyethylene glycol, polyacrylamide, polyethyleneimine, dextrin, sodium alginate, polyvinyl alcohol, polyvinyl pyrrolidone, and polyethylene oxide; Preferably, the amount of the second thickener added is 0% to 0.01% of the mass of the second monomer.

10. A water-absorbent resin particle, characterized in that: Prepared by the continuous preparation process of water-absorbent resin particles according to any one of claims 1 to 9; Preferably, the particle size of the water-absorbing resin particles is 300 μm to 800 μm.

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