Water-absorbing resin and its manufacturing method

Abstract

This invention provides a water-absorbing resin and a method for manufacturing the same. The method includes subjecting a water-absorbing resin composition to a free radical polymerization reaction to obtain a gel, wherein the water-absorbing resin composition comprises an unsaturated monomer aqueous solution, a polymerization initiator, and a free radical polymerization crosslinking agent. The method further includes shearing the gel using a shredder to obtain multiple water-absorbing resin particles, wherein the shredder's outlet includes blades and a perforated disc, the blades having a parallelogram cross-section, and the perforated disc containing multiple holes. The method also includes performing a surface crosslinking reaction on the water-absorbing resin particles to obtain the water-absorbing resin. This improves the surface porosity, absorption rate, and liquid conductivity of the obtained water-absorbing resin.

Description

Technical Field

[0001] This invention relates to a water-absorbing resin and a method for manufacturing the same, and more particularly to a water-absorbing resin obtained using a shredder with special blades and a method for manufacturing the same. Background Technology

[0002] Superabsorbent polymer (SAP) is a type of polymer that is not water-soluble. It is mainly used in various fields such as absorbent products like diapers and sanitary napkins, water-retaining agents for agriculture, forestry and horticulture, and industrial waterproofing agents.

[0003] The preparation of absorbent polymers (APPs) requires a large amount of monomers and hydrophilic polymers. Industrially, the main production method is polyacrylic acid (salt)-based PAPs, which use acrylic acid and / or its salts as monomers. With the increasing demand for high-performance absorbents, particularly in diapers, there are more functional requirements for PAPs (e.g., high cost-effectiveness). Specifically, in addition to basic physical properties such as absorbency under no pressure and absorbency under pressure, PAPs are also required to meet various physical properties including gel strength, water-soluble content, moisture content, absorption rate, antibacterial properties, abrasion resistance, powder flowability, deodorization, colorfastness, low dust, and low residual monomers. Especially in the application of hygiene products such as diapers, the trend towards thinner products necessitates further improvements in the absorption rate of PAPs.

[0004] Generally, industrial manufacturing methods for powdered or granular superabsorbent polymers include the following processes: polymerization; gel pulverization (granulation) during or after polymerization; drying of the granulated gel; pulverization of the dried product; sieving of the pulverized product; and surface crosslinking of the graded superabsorbent polymer powder. Currently proposed methods for manufacturing superabsorbent polymers include those that simultaneously perform polymerization and gel pulverization using a polymerization apparatus equipped with pulverizing equipment. In these methods, the generated hydrogel is pulverized while the liquid monomer undergoes polymerization, and the granulated hydrogel is discharged from the polymerization apparatus. Specifically, existing technologies utilize intermittent or continuous kneaders for pulverization.

[0005] However, the gel particles obtained by the aforementioned apparatus are approximately several millimeters to several centimeters in size. To further increase the water absorption rate, the aforementioned gel particle size is insufficient, necessitating the addition of a gel pulverizing device. For example, intermittent and continuous kneaders can be used to wet-mill the superabsorbent resin into gel particles with a specific particle size or relatively smaller. However, existing gel pulverizing devices are too large to be easily applied in industrial production lines.

[0006] In view of this, there is an urgent need to provide a water-absorbing resin and a method for manufacturing the same, so as to pulverize the gel into a size that meets the requirements during the process. Summary of the Invention

[0007] One aspect of the present invention is to provide a method for manufacturing a water-absorbing resin, which uses a special blade of a shredder to crush the gel, thereby improving the absorption rate and liquid conductivity of the resulting water-absorbing resin.

[0008] Another aspect of the present invention is to provide a water-absorbing resin, which is prepared by the above-described aspect.

[0009] According to one aspect of the present invention, a method for manufacturing a water-absorbing resin is provided. The method includes subjecting a water-absorbing resin composition to a free radical polymerization reaction to obtain a gel, wherein the water-absorbing resin composition comprises an aqueous solution of an unsaturated monomer, a polymerization initiator, and a free radical polymerization crosslinking agent. The method further includes shearing the gel using a shredder to obtain a plurality of water-absorbing resin particles, wherein the discharge port of the shredder includes blades and a perforated disc, the blades having a parallelogram cross-section, and the perforated disc containing a plurality of holes. The method further includes performing a surface crosslinking reaction on the water-absorbing resin particles to obtain the water-absorbing resin.

[0010] According to an embodiment of the present invention, the parallelogram has a first side length and a second side length that are parallel to each other in a first direction, the endpoints of the first side length and the second side length on the same side are the first endpoint and the second endpoint, respectively, the first side length is equal to the sum of the first length and the second length, the first length is the distance between the first endpoint of the first side length and the second endpoint of the second side length in the first direction, and the ratio of the first length to the second length is 0.1 to 0.8.

[0011] According to one embodiment of the present invention, the first side length has an angle with the adjacent side, and the tangent of the angle is 0.1 to 0.9.

[0012] According to one embodiment of the present invention, the first length is 40 mm to 120 mm, and the second length is 190 mm to 210 mm.

[0013] According to one embodiment of the present invention, each of the above-mentioned holes has a diameter, and the diameter is from 8 mm to 22 mm.

[0014] According to one embodiment of the present invention, the blade is spaced from the orifice by a distance of 0.01 mm to 0.09 mm.

[0015] According to one embodiment of the present invention, the specific mechanical energy of the above-mentioned shredder is 25 kWh / t to 65 kWh / t.

[0016] According to one embodiment of the present invention, before carrying out the above-mentioned surface crosslinking reaction, the method further includes adding a surface crosslinking agent and an aluminum salt compound to the water-absorbing resin particles.

[0017] According to one embodiment of the present invention, based on the above-mentioned water-absorbing resin being 100 wt%, the amount of aluminum salt compound added is 0.1 wt% to 1.0 wt%.

[0018] According to one embodiment of the present invention, the above-mentioned aluminum salt compound comprises aluminum sulfate, aluminum lactate, aluminum citrate, or any combination thereof.

[0019] According to another aspect of the present invention, a water-absorbing resin is provided, which is prepared by the above method.

[0020] The water-absorbing resin and its manufacturing method of the present invention are used to crush the gel by a shredder with a variable diameter orifice disc to improve the compactness and surface roughness of the gel, thereby improving the surface porosity, absorption rate and liquid conductivity of the obtained water-absorbing resin, and reducing the water-soluble content. Attached Figure Description

[0021] A better understanding of the present invention will be obtained by reading the following detailed description in conjunction with the accompanying drawings. It should be noted that, as is standard practice in the industry, many features are not drawn to scale. In fact, for clarity of discussion, the dimensions of many features may be arbitrarily scaled.

[0022] Figure 1 A flowchart illustrating a method for manufacturing a water-absorbing resin according to some embodiments of the present invention is provided.

[0023] Figure 2A A top view is provided to illustrate the blades of a shredder according to some embodiments of the present invention.

[0024] Figure 2B A side view of the blades of a shredder according to some embodiments of the present invention is shown.

[0025] Figure 2C A cross-sectional view of the blades of a shredder according to some embodiments of the present invention is shown. Detailed Implementation

[0026] As used in this article, “around,” “about,” “approximately,” or “substantially” generally mean within 20 percent, 10 percent, or 5 percent of the stated value or range.

[0027] The manufacture and use of embodiments of the present invention are discussed in detail below. However, it will be understood that the embodiments provide many applicable inventive concepts that can be implemented in a wide variety of specific contexts. The specific embodiments discussed are for illustrative purposes only and are not intended to limit the scope of the invention.

[0028] Existing methods for manufacturing superabsorbent polymers involve pulverizing cross-linked hydrogels before drying and grinding them to increase drying efficiency. This pulverization step can be performed, for example, after polymerization using a screw extruder or meat grinder, or by using the cutter of a kneader during polymerization, or by chopping the hydrogel in a laboratory using scissors or a utility knife, or by pressing a circular cutting blade against a roller to chop it.

[0029] As described above, the present invention provides a water-absorbing resin and a method for manufacturing the same. The gel is pulverized by a shredder with special blades to improve the compactness and surface roughness of the gel, thereby improving the surface porosity, absorption rate and liquid conductivity of the resulting water-absorbing resin, and reducing water-soluble content.

[0030] Please see Figure 1 This is a flowchart illustrating a method 100 for manufacturing a water-absorbing resin according to some embodiments of the present invention. First, operation 110 is performed to subject the water-absorbing resin composition to a free radical polymerization reaction to obtain a gel. In some embodiments, the water-absorbing resin composition comprises an aqueous solution of an unsaturated monomer, a polymerization initiator, and a free radical polymerization crosslinking agent.

[0031] The term "unsaturated monomer" as used in this invention refers to a water-soluble monomer having unsaturated double bonds. In some embodiments, the aqueous solution of unsaturated monomers in the absorbent resin composition includes a water-soluble monomer having an acid group, such as acrylic acid. In some embodiments, the aqueous solution of unsaturated monomers may also be methacrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, maleic acid (maleic acid), maleic anhydride, fumaric acid (trans-butenedioic acid), and trans-butenedioic anhydride. The aqueous solution of unsaturated monomers may contain, but is not limited to, one monomer, and may also contain two or more of the above-mentioned monomers in aqueous solution.

[0032] In some embodiments, based on the 100 wt% water-absorbing resin composition, the concentration of the unsaturated monomer aqueous solution can be, but is not limited to, 20 wt% to 55 wt%, preferably 30 wt% to 45 wt%. Generally, when the concentration of the unsaturated monomer aqueous solution is 20 wt% to 55 wt%, the viscosity of the polymerized product is moderate, making it easier to machine, and the heat of reaction during free radical polymerization is also easier to control.

[0033] In other embodiments, other hydrophilic monomers with unsaturated double bonds may be selectively added, such as acrylamide, methacrylamide, 2-carboxyethyl acrylate, 2-carboxyethyl methacrylate, methyl acrylate, ethyl acrylate, dimethylamine acrylamide, and chloroacrylamidotrimethylamine. However, the amount of the above-mentioned hydrophilic monomers added is based on the principle of not impairing the physical properties of the absorbent resin (e.g., holding power and absorption rate).

[0034] In some embodiments, water-soluble polymers may be selectively added to the absorbent resin composition to reduce preparation costs. These water-soluble polymers may be partially or fully saponified polyvinyl alcohol, polyethylene glycol, polyacrylic acid, polyacrylamide, starch, or starch derivatives (e.g., methylcellulose, methylcellulose acrylate, ethylcellulose), etc., preferably starch and partially or fully saponified polyvinyl alcohol used alone or in combination. In the foregoing embodiments, the molecular weight of the water-soluble polymer is not limited, and when the amount of unsaturated monomer aqueous solution is 100 wt%, the amount of water-soluble polymer added is based on the principle of not reducing the physical properties of the absorbent resin, typically not exceeding 20 wt%, preferably not exceeding 10 wt%, and more preferably not exceeding 5 wt%.

[0035] In some embodiments, the unsaturated monomer aqueous solution can be directly subjected to polymerization; or it can be partially neutralized first using a neutralizing agent to make the unsaturated monomer aqueous solution neutral or weakly acidic before polymerization. In these embodiments, the neutralizing agent comprises hydroxides or carbonates of alkali metals or alkaline earth metals (e.g., sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate), amines, and combinations thereof. In some embodiments, the neutralization concentration of the unsaturated monomer aqueous solution is 45 mol% to 85 mol%, preferably 50 mol% to 75 mol%. When the neutralization concentration is within the aforementioned range, the unsaturated monomer aqueous solution can have a suitable pH value and is less likely to cause harm if accidentally exposed to human body. It should be noted that the neutralization concentration described herein is defined as the ratio of the number of moles of alkaline solution to the number of moles of unsaturated monomer aqueous solution, and can also be regarded as the percentage of acidic groups in the unsaturated monomer aqueous solution that are neutralized. In some embodiments, the pH value of the unsaturated monomer aqueous solution is 5.5 to 7.0, preferably 5.5 to 6.5. If the pH value of the unsaturated monomer aqueous solution is between 5.5 and 7.0, then a large amount of unreacted monomer is less likely to remain in the aqueous solution after polymerization, and the water-absorbing resin subsequently prepared has better physical properties and a larger absorption capacity.

[0036] The prepolymerization reaction begins with the generation of free radicals from the decomposition of the polymerization initiator. In some embodiments, based on the amount of the unsaturated monomer aqueous solution being 100 wt%, the appropriate amount of the polymerization initiator is 0.001 wt% to 10 wt%, preferably 0.1 wt% to 5 wt%. If the amount of the polymerization initiator is within the aforementioned range, the rate of the free radical polymerization reaction is more appropriate, the economic benefits are better, the heat of reaction is easier to control, and the formation of a gel-like solid due to overpolymerization can be avoided.

[0037] In some embodiments, the polymerization initiator comprises a thermally decomposable initiator, a redox initiator, or a combination thereof. In some embodiments, the thermally decomposable initiator comprises peroxides [e.g., hydrogen peroxide, di-tert-butyl peroxide, peroxyamide, or persulfates (including ammonium and alkali metal salts)] and azo compounds [e.g., 2,2-azobis(2-amidinylpropane) dihydrochloride, 2,2-azobis(N,N-diethylmethylisobutylamidinyl) dihydrochloride]. In some embodiments, the redox initiator comprises acidic sulfites, ascorbic acid, or ferrous salts. The polymerization initiator is preferably used in combination with both a thermally decomposable initiator and a redox initiator, which first reacts the redox initiator to generate free radicals. When these free radicals transfer to the monomer, the polymerization reaction is initiated, and the large amount of heat released by the polymerization reaction raises the temperature. When a specific temperature is reached, the thermally decomposable initiator can be further decomposed to make the polymerization reaction more complete, thus avoiding leaving excessive unreacted monomers.

[0038] Free radical polymerization crosslinking agents in absorbent resin compositions can impart appropriate crosslinking degrees to the composition, thereby improving its processability after polymerization. In some embodiments, the free radical polymerization crosslinking agent may be a compound containing two or more unsaturated double bonds, such as N,N-bis(2-propenyl)amine, N,N-methylenebisacrylamide, N,N-methylenebismethylacrylamide, propylene acrylate, ethylene glycol diacrylate, polyethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, glycerol trimethacrylate, glycerol-added ethylene oxide triacrylate or trimethacrylate, trimethylol Propane trimethacrylate, trimethylolpropane triacrylate, N,N,N-tris(2-propenyl)amine, ethylene glycol diacrylate, polyoxyethylene glycerol triacrylate, diethyl polyoxyethylene glycerol triacrylate, dipropylene triethylene glycol ester, etc.; compounds containing two or more epoxy groups may also be selected, such as sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, dipropylene glycol polyglycidyl ether, etc. Two or more free radical polymerization crosslinking agents can be used alone or in combination. In some embodiments, the unsaturated monomer aqueous solution is 100 wt%, and the free radical polymerization crosslinking agent is 0.001 wt% to 5 wt%, preferably 0.01 wt% to 3 wt%. If the amount of free radical polymerization crosslinking agent added is within the aforementioned range, the viscosity of the polymer aqueous solution after the reaction is moderate, making it easier to mechanically process, and the water absorption of the subsequently obtained water-absorbing resin is better.

[0039] In some embodiments, the free radical polymerization reaction described above can be carried out in a batch reaction vessel (such as a batch reactor) or a conveyor belt reactor.

[0040] Next, operation 120 is performed, using a shredder to shear the gel to obtain absorbent resin particles. The discharge port of the aforementioned shredder includes special blades and a perforated disc. This shredder with special blades can compress the gel, increasing its roughness and compactness, thereby increasing the short-term absorption rate of the absorbent resin particles, reducing water-soluble substances, and improving liquid conductivity.

[0041] Please see Figures 2A to 2C , Figure 2A To illustrate a top view of the blade 200 of a shredder according to some embodiments of the present invention, Figure 2B To illustrate a side view of the blade 200 of a shredder according to some embodiments of the present invention, Figure 2CThe diagram illustrates a cross-section 210 of the blade 200 of a shredder according to some embodiments of the present invention. Compared to existing blades composed of cuboids, the blade 200 is composed of two parallelogram-shaped blades, and unlike existing blades with rectangular cross-sections, the cross-section 210 of the blade 200 used in this invention is a parallelogram, such as... Figure 2B As shown. When the cross section 210 is a parallelogram, there is greater friction and extrusion force when cutting the gel, and more friction occurs between the gel particles. Therefore, the roughness and compactness of the obtained water-absorbing resin particles can be increased, thereby increasing the apparent specific gravity and absorption rate of the obtained water-absorbing resin particles.

[0042] Section 210 has a first side length 215 and a second side length 220 that are parallel to each other in the X direction, wherein the endpoints of the first side length 215 and the second side length 220 on the same side are a first endpoint P1 and a second endpoint P2, respectively. The first side length 215 is composed of a first length R1 and a second length R2, wherein the first length R1 is the distance between the first endpoint P1 and the second endpoint P2 in the X direction. In some embodiments, the first length R1 is about 40 mm to about 120 mm, and the second length R2 is about 190 mm to about 210 mm (preferably about 200 mm).

[0043] In some embodiments, the ratio R1 / R2 of the first length R1 to the second length R2 is from about 0.1 to about 0.8, preferably from about 0.2 to about 0.7. When the ratio R1 / R2 is within the aforementioned range, the shredder can have appropriate compressive and shearing forces and better specific mechanical properties.

[0044] Section 210 has an adjacent side 225 that intersects the first side length 215 at the first endpoint P1, and the first side length 215 and the adjacent side 225 form an angle θ. In some embodiments, the tangent of the angle θ (i.e., tanθ) is about 0.1 to about 0.9, preferably about 0.2 to about 0.6. When tanθ is within the aforementioned range, the shredder can have appropriate friction and shear force, and better specific mechanical energy.

[0045] The shredder's perforated disc has multiple holes, and in some embodiments, the hole diameter is from about 8 mm to about 22 mm, preferably from about 10 mm to about 20 mm. When the hole diameter is within the aforementioned range, the shredder's operating time can be reduced, and appropriate frictional force can be applied to the gel.

[0046] The blades and the orifice disc are connected and spaced apart. In some embodiments, the spacing is from about 0.01 mm to about 0.09 mm, preferably from about 0.02 mm to about 0.08 mm. When the spacing is within the aforementioned range, the shredder can apply appropriate shearing and frictional forces to the gel, thus possessing suitable specific mechanical energy to effectively shear the gel and avoid the generation of iron filings from the blades or orifice disc. It should be noted that the specific mechanical energy is the output power of the shredder's motor divided by the throughput of the gel. In some embodiments, the specific mechanical energy of the shredder is from about 25 kWh / t to about 65 kWh / t, preferably from about 25 kWh / t to 60 kWh / t. The aforementioned suitable specific mechanical energy allows for effective shearing of the gel.

[0047] In some embodiments, the small gels obtained after shearing with a shredder must undergo further steps such as drying, pulverizing, and screening. In the aforementioned embodiments, the drying temperature is from about 100°C to about 250°C. Using the aforementioned temperature range for the drying process can effectively control the drying time and the degree of crosslinking, thereby avoiding the retention of a large amount of unreacted monomers.

[0048] In some embodiments, the screening step described above is to screen out small gels with an average particle size of no more than about 2.0 mm, preferably from about 0.05 mm to about 1.50 mm. Gels with an average particle size greater than 2.0 mm must be returned to the shredder for further shredding. The particle size must be controlled within the aforementioned range to avoid generating a high amount of fine powder in subsequent processes, to ensure better thermal conductivity, and to avoid excessive residues of unreacted monomers, which would result in poor physical properties. Generally, the narrower the particle size distribution of the small gels, the better the physical properties, and the easier it is to control the drying time and temperature.

[0049] In some embodiments, the small gels are dried again after the screening step, and the small gels may be selectively subjected to a second drying process. In the foregoing embodiments, the drying process is carried out at a temperature of about 100°C to about 180°C. Using the aforementioned temperature range for the drying process can effectively control the drying time and the degree of crosslinking, thereby avoiding the retention of a large amount of unreacted monomers.

[0050] In some embodiments, the particle size of the absorbent resin particles is selected from 0.06 mm to 1.00 mm, preferably from 0.10 mm to 0.85 mm. Controlling the particle size of the absorbent resin particles to the aforementioned range can reduce the amount of fine powder in the finished product and improve the absorption performance of the absorbent resin.

[0051] In some embodiments, the resulting water-absorbing resin particles have a holding power of about 33.0 g / g to about 35.0 g / g, a 1-minute water absorption ratio of about 120 g / g to about 150 g / g, a 1-hour water soluble content of about 5.0% to about 7.0%, a surface porosity of about 0.030 cc / g to about 0.050 cc / g, and a free swelling rate of about 0.30 g / g / s to about 0.50 g / g / s.

[0052] Then, step 130 is performed to conduct a surface crosslinking reaction on the absorbent resin particles to obtain an absorbent resin. Since absorbent resin is an insoluble hydrophilic polymer with a uniform bridging structure inside, generally, further bridging is performed on the resin surface to improve absorption rate, colloidal strength, anti-caking properties, and volume permeability. The surface crosslinking reaction is carried out using a surface crosslinking agent with functional groups that can react with acid groups. In some embodiments, the surface crosslinking agent includes a polyol, a polyamine, a compound having two or more epoxy groups, and a hydrocarbon ester, wherein the polyol may be, for example, glycerol, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, and propylene glycol; the polyamine may be, for example, ethylenediamine, diethylenediamine, and triethylenediamine; and the epoxy-containing compound may be, for example, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, and diglycerol. Polyglycidyl ether; hydrocarbon carbonates may include, for example, ethylene glycol carbonate, 4-methyl-1,3-dioxacyclopentan-2-one, 4,5-dimethyl-1,3-dioxacyclopentan-2-one, 4,4-dimethyl-1,3-dioxacyclopentan-2-one, 4-ethyl-1,3-dioxacyclopentan-2-one, 1,3-dioxacyclohexane-2-one, 4,6-dimethyl-1,3-dioxacyclohexane-2-one, and 1,3-dioxacycloheptane-2-one. The reaction can be carried out alone or in combination with two or more surface crosslinking agents. Furthermore, depending on the surface crosslinking agent selected, it can be added directly, or the surface crosslinking agent can be prepared into an aqueous solution or a hydrophilic organic solution before addition. Hydrophilic organic solvents include, but are not limited to, methanol, ethanol, propanol, isobutanol, acetone, dimethyl ether, and diethyl ether.

[0053] In some embodiments, with a total solid content of 100 wt% of reactants, the amount of surface crosslinking agent added is from about 0.001 wt% to about 10 wt%, preferably from about 0.005 wt% to about 5 wt%. When the amount of surface crosslinking agent added is within the aforementioned range, the surface of the absorbent resin can have a crosslinked structure, thereby achieving better absorption performance.

[0054] In some embodiments, the surface crosslinking reaction further includes the simultaneous addition of an aluminum salt compound when adding the surface crosslinking agent to further enhance the liquid conductivity of the superabsorbent resin. In some specific examples, the aluminum salt compound comprises aluminum sulfate, aluminum lactate, aluminum citrate, or a combination thereof. In some embodiments, based on 100 wt% of superabsorbent resin particles, the amount of aluminum salt compound added is 0.1 wt% to 1.0 wt%, preferably about 0.3 wt% to about 0.7 wt%, and most preferably about 0.6 wt%. Adding the aforementioned range of amounts of aluminum salt compound can improve the pressure absorption ratio and liquid conductivity of the resulting superabsorbent resin.

[0055] As described above, the water-absorbing resin prepared by the above-described method 100 can have a high absorption rate, low water soluble content, and high surface porosity. In some embodiments, the water soluble content of the water-absorbing resin of the present invention after 16 hours is about 5.0% to about 8.0%, and the surface porosity is about 0.030 cc / g to about 0.050 cc / g.

[0056] Furthermore, the superabsorbent resin must possess good centrifuge retention capacity (CRC) and absorption against pressure (AAP) to ensure that after absorbing liquid, the superabsorbent resin will not be damaged or have its liquid absorption capacity affected by external pressure applied to the absorbent. In some embodiments, the centrifuge retention capacity of the superabsorbent resin of the present invention is not less than 28 g / g, preferably about 28.0 g / g to about 31.0 g / g. In some embodiments, the absorption against pressure of the superabsorbent resin of the present invention is greater than 23.0 g / g, preferably about 25.0 g / g to 27.0 g / g. The effective capacity (EFFC) of the superabsorbent resin is the average of the centrifuge retention capacity and the absorption against pressure, which can be calculated using the following formula:

[0057] EFFC = CRC + AAP / 2.

[0058] In some embodiments, the EFFC value of the water-absorbing resin of the present invention is from about 27.6 g / g to about 28.5 g / g.

[0059] The ability of a dry, absorbent resin to absorb liquid upon initial contact with it can be expressed by its T20 value. A lower T20 value indicates that the dry, absorbent resin readily absorbs liquid. The T20 value of the absorbent resin of this invention is no greater than about 150 seconds, for example, about 90 seconds to about 130 seconds. It should be further noted that the T20 value is defined as the time required for 1 gram of absorbent resin to absorb 20 grams of physiological saline and 0.01 wt% of an aqueous solution of an alcohol ethoxylated compound at a pressure of 0.3 psi, wherein the alcohol ethoxylated compound has 12 to 14 carbon atoms.

[0060] The permeability of absorbent resins can be detected using urine permeability measurement (UPM). UPM typically measures the flow resistance of the pre-swelled layer of the absorbent resin. Therefore, absorbent resins with a high UPM value exhibit better permeability when wetted by liquid. The absorbent resin of this invention has a UPM value of approximately 20 × 10⁻⁶. -7 cm 3 -s / g to approximately 50×10 -7 cm 3 -s / g.

[0061] In addition, the liquid conductivity of the superabsorbent resin can also be detected using fixed height absorption (FHA) and free swell gel bed permeability (free swell GBP). The FHA value measures the amount of fluid absorbed by the superabsorbent resin when it draws fluid to a specific height under conditions of gravity. In some embodiments, the FHA value of the superabsorbent resin prepared using method 100 is about 20 g / g to about 30 g / g. Free swell gel bed permeability is used to determine the permeability of the swellable substrate of the superabsorbent resin. It should be understood that the term "free swell" means that the superabsorbent resin is allowed to swell without any swelling-limiting load. In some embodiments, the free swell gel bed permeability of the superabsorbent resin prepared using method 100 is about 5 × 10⁻⁶. -9 cm 2 Approximately 20×10 -9 cm 2 .

[0062] The following examples illustrate the application of the present invention, but are not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention.

[0063] Preparation of water-absorbing resin

[0064] Preparation Example

[0065] Take 437.5g of 48wt% sodium hydroxide aqueous solution and slowly add it to a 2000cc Erlenmeyer flask containing 540g acrylic acid and 583.2g water. The sodium hydroxide / acrylic acid dropping ratio is in the range of 0.85 to 0.95, the dropping time is 2 hours, and the temperature of the neutralization reaction system in the flask is maintained in the range of 15℃ to 40℃. A monomer aqueous solution with a monomer concentration of 42 parts by weight is obtained, in which 70mol% of acrylic acid is neutralized to sodium acrylate, and then added to a 2-liter batch reactor (manufactured by Jinlei Precision).

[0066] Next, 0.9 g of N,N'-methylenebisacrylamide (a crosslinking agent for free radical polymerization) was added to the unsaturated monomer aqueous solution, the temperature was maintained at about 20°C, and nitrogen gas was injected through the pipeline to deoxygenate for 30 minutes.

[0067] Then, 0.3g of hydrogen peroxide, 3.6g of sodium bisulfite, 23.4g of 10% sodium carbonate foaming agent, and 3.6g of ammonium persulfate were added as polymerization initiators to carry out free radical polymerization. After standing for 30 minutes, a gel was obtained.

[0068] Example 1

[0069] The gel prepared in this example was sheared using a shredder (CT-122 model manufactured by Kaohsiung Chiao Teng Co., Ltd.). The blades (manufactured by Chin Lei Precision Machinery) and the perforated plate at the discharge port of the shredder had the following characteristics: the first length R1 was 100 mm, the second length R2 was 200 mm, the ratio R1 / R2 was 0.5, tanθ was 0.330, the diameter of the holes in the perforated plate was 16 mm, the distance between the blades and the perforated plate was 0.05 mm, and the specific mechanical energy was 25 kWh / t.

[0070] Gel particles with a diameter of less than 2 mm were screened out. Then, the gel was dried at 130°C for 2 hours. Finally, it was screened using a fixed-size sieve (0.1 mm to 0.85 mm) to obtain water-absorbing resin particles.

[0071] Next, 100g of the water-absorbing resin granules were weighed and mixed with an aqueous solution of 5g of ethylene glycol, 1,4-butanediol (manufactured by Formosa Plastics Corporation), and methanol in a volume ratio of 1:1:0.5 as a surface crosslinking agent. Additionally, 70wt% aluminum lactate aqueous solution was added, at a concentration of 0.6wt% of the water-absorbing resin granules. The mixture was then heated at 200°C for 1 hour. After cooling, the water-absorbing resin was obtained.

[0072] Examples 2 to 11

[0073] The water-absorbing resins of Examples 2 to 11 were prepared using a process similar to that of Example 1. The difference lies in the following characteristics of the shredder blades and perforated disc: first length R1, second length R2, ratio R1 / R2, tanθ, aperture of the perforated disc holes, distance between the blades and the perforated disc, and specific mechanical energy. The characteristics of the shredder blades and perforated discs of Examples 2 to 11 are shown in Table 1.

[0074] Comparative Example 1

[0075] According to the method in Chinese Patent CN 1206365A, a monomer aqueous solution was prepared by mixing 83.2 parts of acrylic acid, 1662.8 parts of a 37% by weight sodium acrylate aqueous solution, 5.5 parts of polyethylene glycol diacrylate (with an average total molar amount of ethylene oxide (EO) of 8), and 654.5 parts of deionized water. The neutralization rate of acrylic acid in the monomer aqueous solution was 85%, and the monomer concentration was 30%. Nitrogen gas was blown into the monomer aqueous solution to remove dissolved oxygen, while the temperature of the monomer aqueous solution was maintained at 24°C.

[0076] Next, 77 parts of a 10 wt% solution of 2,2'-azobis(2-methylpropanediamine) dihydrochloride were added while simultaneously stirring the monomer aqueous solution. Three minutes after stirring began, the monomer aqueous solution containing the 2,2'-azobis(2-methylpropanediamine) dihydrochloride solution turned into a white mist, producing white granular solids with an average particle size of approximately 9 μm. These granular solids were 2,2'-azobis(2-methylpropanediamine) diacrylate, which served as a blowing agent. Five minutes after stirring began, 10.8 parts of a 10 wt% aqueous solution of sodium persulfate and 0.5 parts of a 1 wt% aqueous solution of L-ascorbic acid, acting as initiators for free radical polymerization, were added under nitrogen atmosphere while simultaneously stirring the monomer aqueous solution. After thorough stirring, the monomer aqueous solution was allowed to stand. Three minutes after the addition of the 10 wt% aqueous solution of sodium persulfate and the 1 wt% aqueous solution of L-ascorbic acid, the polymerization reaction began. The polymerization reaction was carried out in a hot water bath, with the temperature of the hot water bath controlled as the temperature of the monomer aqueous solution increased. Twenty-six minutes after adding 10% sodium persulfate aqueous solution to the monomer aqueous solution, the temperature of the monomer aqueous solution reached 97°C. The monomer aqueous solution was then allowed to stand for another 20 minutes, maintaining its temperature between 70°C and 90°C, to allow the polymerization reaction of the acrylate monomer to proceed completely. A bubble-filled crosslinked hydrogel polymer (hereinafter referred to as hydrogel (A)) was obtained as a porous crosslinked polymer.

[0077] The resulting hydrogel (A) was continuously pulverized using a rotary pulverizer as shown in Chinese Patent CN1206365A. During pulverization, the average residence time of the hydrogel (A) in the rotary pulverizer 31, i.e., the pulverization time, was approximately 0.25 minutes. The particle size range of the hydrogel particles obtained by pulverizing the hydrogel (A) was approximately 1-15 mm. The pulverized hydrogel was dried at 160°C for 1 hour using a circulating hot air dryer. Subsequently, the dried hydrogel was milled using a roller mill and sieved using a standard sieve according to JIS standards. Particles passing through a sieve with a mesh size of 850 μm but not through a sieve with a mesh size of 150 μm were obtained as water-absorbing resin particles.

[0078] Next, a secondary crosslinking treatment solution is applied to carry out a surface crosslinking reaction, thereby obtaining a water-absorbing resin. Specifically, the water-absorbing resin is obtained by mixing 100 parts of water-absorbing resin particles and a treatment solution for secondary crosslinking, and then heating the resulting mixture at 195°C for 30 minutes. The secondary crosslinking treatment solution is prepared with the following composition: a mixture of 0.05 parts of ethylene glycol glycidyl ether, 0.5 parts of lactic acid, 0.02 parts of polyoxyethylene dehydrated sorbitan monostearate, 0.75 parts of isopropanol, and 3 parts of water.

[0079] Comparative Example 2

[0080] According to the method in Chinese Patent CN104936989A, a 42.7 wt% acrylic acid / sodium acrylate solution with a degree of neutralization of 69.0 mol% was prepared by continuously mixing water, 50 wt% sodium hydroxide solution, and acrylic acid. After mixing, the monomer solution was cooled to 30°C using a heat exchanger and degassed using nitrogen. The polyene-bonded unsaturated crosslinking agent used was 3-deethoxylated glycerol triacrylate (purity approximately 85 wt%), used in an amount of 0.35 wt% based on the acrylic acid (boaa). To initiate the free radical polymerization reaction, the following components were used in the following amounts: 0.0008 wt% hydrogen peroxide (boaa) added in a 2.5 wt% aqueous solution; 0.13 wt% sodium persulfate (boaa) added in a 15 wt% aqueous solution; and 0.0023 wt% ascorbic acid (boaa) added in a 0.5 wt% aqueous solution. The flux of the monomer solution is 800 kg / h.

[0081] The components were continuously metered into a List ORP 250 Contikneter continuous kneading reactor (LISTAG, Arisdorf, Switzerland). In the first third of the reactor, an additional 26.3 kg / h of removed sieve bottom material with a particle size less than 150 μm was added. The feed temperature of the reaction solution was 30°C. The residence time of the reaction mixture in the reactor was approximately 15 minutes.

[0082] The polymer gel obtained above was extruded using an SLRE 75R extruder (SelaMaschinen GmbH; Harbke; Germany). During extrusion, the polymer gel temperature was 95°C. The perforated plate had 12 holes with a diameter of 8 mm. The thickness of the perforated plate was 16 mm. The length-to-diameter ratio (L / D) of the extruder was 4. The specific mechanical energy (SME) of the extrusion was 26 kWh / t. The extruded polymer gel was dispersed on a metal plate and dried in an air-circulating drying chamber at 175°C for 90 minutes. The polymer gel loading on the metal plate was 0.81 g / cm³. 2 .

[0083] The dried polymer gel was milled using a single-stage roller mill (milling runs were performed three times, with a gap width of 1000 μm for the first run, 600 μm for the second run, and 400 μm for the third run). The milled, dried polymer gel was graded and mixed with a synthetic particle size distribution (PSD) having the following composition:

[0084] 600μm to 710μm: 10.6% by weight;

[0085] 500μm to 600μm: 27.9% by weight;

[0086] 300μm to 500μm: 42.7% by weight;

[0087] 200μm to 300μm: 13.8% by weight; and

[0088] 150μm to 200μm: 5.0% by weight, to obtain raw material polymer A (water-absorbing resin particles).

[0089] Next, at 23°C and a shaft speed of 200 rpm, 54.6 g of the mixture was applied to 1.2 kg of the aforementioned raw material polymer A using a dual-material nozzle in a plowshare mixer (Gebr. Maschinenbau GmbH; Paderborn, Germany) with a heated jacket. The mixture was a mixture of 0.07 wt% N-hydroxyethyl-2-oxazolidinone, 0.07 wt% 1,3-propanediol, 0.7 wt% propylene glycol, 2.27 wt% 22 wt% aqueous aluminum lactate solution, 0.448 wt% 0.9 wt% aqueous sorbitan monolaurate solution, and 0.992 wt% isopropanol, each of the aforementioned weight percentages being based on raw material polymer A.

[0090] After spraying, the product temperature was raised to 185°C and maintained at this temperature and shaft speed of 50 rpm for 35 minutes. The resulting product was cooled to ambient temperature and reclassified using a 710 μm sieve. Performance analysis was performed on the water-absorbing resin with a particle size smaller than 710 μm.

[0091] Comparative Examples 3 to 10

[0092] The water-absorbing resins of Comparative Examples 3 to 10 were also prepared using a process similar to that of Example 1. The difference lies in the following characteristics of the shredder blades and perforated disc: first length R1, second length R2, ratio R1 / R2, tanθ, aperture of the perforated disc holes, distance between the blades and the perforated disc, and specific mechanical energy. The characteristics of the blades and perforated discs of the shredders of Comparative Examples 3 to 10 are shown in Table 1.

[0093] Evaluation method

[0094] To evaluate the properties of the absorbent resin of the present invention, its physical properties were analyzed by the following test methods. Unless otherwise specified, all measurements were performed at room temperature of 23±2°C and relative humidity of 45±10%. The absorbent resin should be thoroughly mixed before analysis.

[0095] Holding force

[0096] Centrifuge Retention Capacity (CRC) was tested according to the test method ERT 241.2(12) specified by the European Disposables and Nonwovens Association (EDANA). The results of the retention capacity tests for the absorbent resin particles and the absorbent resin are shown in Tables 2 and 3, respectively.

[0097] 1-minute water absorption rate

[0098] The 1-minute water absorption rate was tested according to the test method of EDANA ERT 240.2(12), in which saline was replaced with deionized water (purified water) and the absorption time was changed from 30 minutes to 1 minute. The test results of the 1-minute water absorption rate of water-absorbing resin particles and water-absorbing resin are shown in Table 2 and Table 3, respectively.

[0099] Surface porosity

[0100] Surface porosity is measured using a mercury micromeritics instrument. The test was conducted using IV 9520, with a standard filling pressure of approximately 4 kPa. The test results for the water-absorbing resin particles and the water-absorbing resin are shown in Tables 2 and 3, respectively.

[0101] Free swelling rate

[0102] The free swell rate (FSR, unit: g / g / s) was measured and calculated according to the method described in patent number WO 2012 / 174026A1. First, 4g of absorbent resin was dried at 23±2℃ and a pressure not exceeding 0.01 torr for 48 hours. Then, approximately 1g was weighed and placed in a beaker, dispersed at the bottom. Next, 20g of a 0.9wt% sodium chloride aqueous solution was poured in. The time elapsed from the liquid contacting the absorbent resin until the liquid was completely absorbed by the resin was measured. The free swell rate was calculated by dividing the liquid volume by the weight of the absorbent resin, and then by the elapsed time. The average values ​​obtained from three repetitions of the absorbent resin particles and the absorbent resin itself are shown in Tables 2 and 3, respectively.

[0103] Water absorption ratio under pressure

[0104] The absorption against pressure (AAP) was tested according to the test method ERT442.3(10) specified by EDANA, at a pressure of 4.9 kPa for 60 minutes against a 0.9% sodium chloride aqueous solution. The test results of the water-absorbing resin are shown in Table 3.

[0105] Effective Capacity (EFFC)

[0106] The EFFC value refers to the water absorption ratio under holding force and pressure, which is obtained by summing the values ​​and dividing by 2. The EFFC values ​​of superabsorbent resins are shown in Table 3.

[0107] Water-soluble content at 1 hour and 16 hours

[0108] The 1-hour and 16-hour water extractable content were tested according to the test method ERT470.2(02) specified by EDANA. The test results of the 1-hour water extractable content of the water-absorbing resin particles and the 16-hour water extractable content of the water-absorbing resin are shown in Table 2 and Table 3, respectively.

[0109] T20 value

[0110] The T20 value (in seconds) is measured and calculated according to the method described in US Patent No. 9,285,302. It is the time required for 1 gram of the absorbent resin to absorb 20 grams of physiological saline and 0.01 wt% of an aqueous solution of an alcohol ethoxylate compound at a pressure of 0.3 psi, wherein the alcohol ethoxylate compound has 12 to 14 carbon atoms. The average results of three repeated tests of the absorbent resin are shown in Table 3.

[0111] Urine osmolarity measurement

[0112] Urine permeability measurement (UPM) was performed according to the method described in patent number WO2012 / 174026A1. The test results for absorbent resin are shown in Table 3.

[0113] Fixed height absorption value

[0114] The fixed height absorption (FHA) was tested according to the method described in US Patent 7,108,916. The test results for the water-absorbing resin are shown in Table 3.

[0115] Free expansion gel bed permeability

[0116] The free swell gel bed permeability (free swell GBP) was tested according to the method described in US Patent 8,021,998B2. The test results for the water-absorbing resin are shown in Table 3.

[0117] Table 1

[0118]

[0119] Table 2

[0120]

[0121] Table 3

[0122]

[0123]

[0124] According to Tables 2 and 3, the absorbent properties of the water-absorbing resins prepared using the prior art in Comparative Examples 1 and 2 are inferior to those in Examples 1 to 11, and the water-soluble content of Comparative Examples 1 and 2 is significantly higher. The tanθ of Comparative Example 3 is too large, and the ratio R1 / R2 of Comparative Example 4 is too large, both making it difficult to form a water-absorbing resin with better absorbent properties. The distance between the blade and the perforated plate in Comparative Examples 6 to 8 is too large, with the pore size of the perforated plate in Comparative Example 7 being too small and the pore size of the perforated plate in Comparative Example 8 being too large, all resulting in poor absorption speed and other properties of the prepared water-absorbing resins. In Comparative Examples 9 and 10, the first length R1 is equal to the second length R2, resulting in insufficient friction, thus lower porosity of the water-absorbing resin particles and surface, higher water-soluble content, and poor absorbent properties.

[0125] According to Table 2, compared with Comparative Examples 1 to 10, the water-absorbing resin particles of Examples 1 to 11 have significantly lower water soluble content and higher one-minute water absorption ratio, surface porosity and free swelling rate.

[0126] According to Table 3, compared to Comparative Examples 1 to 10, the superabsorbent resins of Examples 1 to 11 all exhibit higher surface porosity, EFFC value, urine permeability (UPM), fixed height absorbent value (FHA), and free expansion bed permeability (GBP), and lower T20 value and water soluble content. Therefore, the superabsorbent resins of Examples 1 to 11 readily absorb liquids in a dry state, and also exhibit better liquid permeability and conductivity.

[0127] Therefore, by applying the manufacturing method of the water-absorbing resin of the present invention, the gel is sheared by a shredder with special blades to improve the compactness and surface roughness of the gel, thereby improving the surface porosity, absorption rate and liquid conductivity of the resulting water-absorbing resin, and reducing water-soluble content.

[0128] Although the present invention has been disclosed above with reference to several embodiments, it is not intended to limit the present invention. Those skilled in the art to which this invention pertains can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

[0129] [Symbol Explanation]

[0130] 100: Method

[0131] 110, 120, 130: Operation

[0132] 200: Blade

[0133] 210: Section

[0134] 215: First side length

[0135] 220: Second side length

[0136] 225: Adjacent edges

[0137] R1: First length

[0138] R2: Second length

[0139] P1: First endpoint

[0140] P2: Second endpoint

[0141] X: Direction

[0142] θ: included angle.

Claims

1. A method for manufacturing a water-absorbing resin, characterized in that, Include: A water-absorbing resin composition is subjected to a free radical polymerization reaction to obtain a gel, wherein the water-absorbing resin composition comprises an unsaturated monomer aqueous solution, a polymerization initiator, and a free radical polymerization crosslinking agent; The gel is sheared using a shredder to obtain multiple water-absorbing resin particles, wherein the discharge port of the shredder includes blades and a perforated disc, the blades having a parallelogram cross-section and the perforated disc containing multiple holes; and The plurality of water-absorbing resin particles are subjected to a surface crosslinking reaction to obtain the water-absorbing resin.

2. The method for manufacturing the water-absorbing resin according to claim 1, characterized in that, The parallelogram has a first side length and a second side length that are parallel to each other in a first direction. The endpoints of the first side length and the second side length on the same side are the first endpoint and the second endpoint, respectively. The first side length is equal to the sum of the first length and the second length. The first length is the distance between the first endpoint of the first side length and the second endpoint of the second side length in the first direction. The ratio of the first length to the second length is 0.1 to 0.

8.

3. The method for manufacturing the water-absorbing resin according to claim 2, characterized in that, The parallelogram has an adjacent side that intersects the first side length at the first endpoint, and there is an angle between the first side length and the adjacent side, with the tangent value of the angle being 0.1 to 0.

9.

4. The method for manufacturing the water-absorbing resin according to claim 2, characterized in that, The first length is 40mm to 120mm, and the second length is 190mm to 210mm.

5. The method for manufacturing the water-absorbing resin according to claim 1, characterized in that, Each of the plurality of holes has an aperture, and the aperture is between 8 mm and 22 mm.

6. The method for manufacturing the water-absorbing resin according to claim 1, characterized in that, The blade is spaced apart from the orifice by a distance of 0.01 mm to 0.09 mm.

7. The method for manufacturing the water-absorbing resin according to claim 1, characterized in that, The specific mechanical energy of the shredder is 25 kWh / t to 65 kWh / t.

8. The method for manufacturing the water-absorbing resin according to claim 1, wherein, prior to carrying out the surface crosslinking reaction, it is characterized in that, Also includes: A surface crosslinking agent and an aluminum salt compound are added to the plurality of water-absorbing resin particles.

9. The method for manufacturing the water-absorbing resin according to claim 8, characterized in that, Based on the fact that the water-absorbing resin particles are 100 wt%, the amount of aluminum salt compound added is 0.1 wt% to 1.0 wt%.

10. The method for manufacturing the water-absorbing resin according to claim 8, characterized in that, The aluminum salt compound comprises aluminum sulfate, aluminum lactate, aluminum citrate, or any combination thereof.

11. A water-absorbing resin, characterized in that, It is produced by the manufacturing method according to any one of claims 1 to 10.

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