Super absorbent polymer

Abstract

The present invention relates to a polyacrylic acid (salt)-based super absorbent polymer having a surface area–to–apparent volume ratio of 45 mm-1 or more and exhibiting a deodorization rate of 40% or more for dimethyl disulfide (DMDS) or dimethyl trisulfide according to the following Equation 1. [Equation 1] Deodorization rate (%) = (1 x Cs / Co) x 100 (In Equation 1, Cs is a peak area of an odor standard substance in a gas chromatography-mass spectrometry (GC-MS) graph for an odor standard substance solution that has been in contact with a super absorbent polymer at 35°C for 2 hours, and Co is a peak area of an odor standard substance in a gas chromatography-mass spectrometry graph for an odor standard substance solution that has been in contact with a control group at 35°C for 2 hours.)

Description

superabsorbent resin

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0100100, filed July 29, 2024, and U.S. Patent Application No. 19 / 258,113, filed July 2, 2025, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a superabsorbent resin having both excellent absorption performance and deodorizing effect against odor-causing substances.

[0004] Super absorbent polymer (SAP) is a synthetic polymer material that can absorb 500 to 1,000 times its own weight in water. Different developers call it by different names, such as SAM (Super Absorbency Material) and AGM (Absorbent Gel Material). The above super absorbent polymer began to be put to practical use in products such as diapers and hygiene products, and is currently widely used as a soil conditioner for horticulture, a water-stopping material for civil engineering and construction, a sheet for nursery cultivation, and a freshness-preserving agent and material for steaming in the food distribution industry.

[0005] In particular, superabsorbent polymers are widely used in sanitary products such as diapers and sanitary pads, so they need to exhibit not only high absorption performance but also a fast absorption rate.

[0006] Furthermore, to provide thinner products, the development of so-called pulpless products, which reduce pulp content or even eliminate pulp altogether, is actively underway. As a result, these products contain a relatively high percentage of superabsorbent polymer, and the superabsorbent polymer particles are inevitably embedded in multiple layers. Consequently, the importance of the absorption rate of superabsorbent polymers is increasing.

[0007] For this purpose, a method of forming a porous structure within the base resin powder by including a foaming agent in the monomer composition and proceeding with crosslinking polymerization to increase the surface area of ​​the superabsorbent resin is generally used.

[0008] However, the use of a foaming agent resulted in a problem in which various properties of the superabsorbent resin, such as surface tension, permeability, or bulk density, were reduced.

[0009] In addition, the environment in which superabsorbent resins are used is one in which microorganisms that are harmful to the human body and cause odors, such as bacteria and mold, can easily proliferate, and thus, during the use process, an unpleasant odor may be generated by the microorganisms, and therefore, deodorizing effects are additionally required for the superabsorbent resins.

[0010] However, when the structure or properties of superabsorbent resins are adjusted for deodorizing function, the overall absorption performance is reduced, and thus, no superabsorbent resin that satisfies all of these required properties has been introduced yet.

[0011] Therefore, there is a continuous demand for the development of new superabsorbent resins that maintain the excellent absorption performance of superabsorbent resins while simultaneously having deodorizing effects against various odor-causing substances.

[0012] The present invention aims to provide a superabsorbent resin having both excellent absorption performance and deodorizing effect against odor-causing substances.

[0013] The present invention has a surface area of ​​45 mm relative to the actual volume. -1 The present invention provides a superabsorbent resin having a deodorizing rate of 40% or more according to the following formula 1 for dimethyl disulfide (DMDS) or dimethyl trisulfide (DMTS):

[0014] [Formula 1]

[0015] Deodorization rate (%) = (1- Cs / Co) × 100

[0016] In the above equation 1,

[0017] Cs is the peak area of ​​the odor standard substance in the gas chromatography-mass spectrometry (GC-MS) graph for the odor standard substance solution that was in contact with the superabsorbent resin at 35°C for 2 hours, and Co is the peak area of ​​the odor standard substance in the gas chromatography-mass spectrometry graph for the odor standard substance solution that was in contact with the control at 35°C for 2 hours.

[0018] The superabsorbent resin of the present invention not only has excellent absorption performance with a surface area to actual volume ratio of a certain level or higher, but also has a deodorizing effect against dimethyl disulfide or dimethyl trisulfide.

[0019] Figure 1 shows the setting values ​​of the Sample Dispersion Unit in Malvern Panalytical's morphologi 4.

[0020] Figure 2 shows the illumination setting values ​​in Malvern Panalytical's morphologi 4.

[0021] Figure 3 shows the Optics Selection setting values ​​in Malvern Panalytical's morphologi 4.

[0022] Figure 4 shows the Scan Area setting values ​​in Malvern Panalytical's morphologi 4.

[0023] According to one embodiment of the present invention, as a polyacrylic acid (salt)-based superabsorbent resin,

[0024] Surface area to actual volume is 45 mm -1 That's all,

[0025] A superabsorbent resin having a deodorizing rate of 40% or more according to the following formula 1 for dimethyl disulfide (DMDS) or dimethyl trisulfide (DMTS) can be provided:

[0026] [Formula 1]

[0027] Deodorization rate (%) = (1- Cs / Co) × 100

[0028] In the above equation 1,

[0029] Cs is the peak area of ​​the odor standard substance in the gas chromatography-mass spectrometry (GC-MS) graph for the odor standard substance solution that was in contact with the superabsorbent resin at 35°C for 2 hours, and Co is the peak area of ​​the odor standard substance in the gas chromatography-mass spectrometry graph for the odor standard substance solution that was in contact with the control at 35°C for 2 hours.

[0030] Unless otherwise defined herein, all technical and scientific terms used herein are used merely to describe exemplary embodiments and are not intended to be limiting of the present invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, it should be understood that terms such as "comprise," "include," or "have" specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0031] The present invention is susceptible to various modifications and takes various forms. Specific embodiments are illustrated and described in detail below. However, this is not intended to limit the present invention to specific disclosed forms, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

[0032] The technical terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the present invention. Furthermore, the singular forms "singular" and "in" also include plural forms, unless the context clearly dictates otherwise.

[0033] The term "polymer" or "high molecular weight polymer" as used in the specification of the present invention means a polymerized state of a water-soluble ethylenically unsaturated monomer, and may encompass any moisture content range or particle size range.

[0034] In addition, the term "superabsorbent resin" is used to encompass, depending on the context, a base resin in powder form consisting of a crosslinked polymer, superabsorbent resin particles obtained by pulverizing the crosslinked polymer, or a crosslinked polymer or base resin that has undergone an additional process, such as drying, pulverization, classification, or surface crosslinking, to make it suitable for commercialization.

[0035] Additionally, the term "fine particles" refers to particles having a particle size of less than 150 μm among superabsorbent resin particles. The particle size of such resin particles can be measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 220.3 method.

[0036] Additionally, the term "chopping" is used to refer to cutting the hydrogel polymer into small pieces on the order of millimeters to increase drying efficiency, as distinguished from grinding to the micrometer or normal particle level.

[0037] Additionally, the term "micronizing" is used to differentiate it from "chopping", as it refers to grinding a hydrogel polymer into particle sizes of tens to hundreds of micrometers.

[0038] Additionally, the term "free swelling" refers to a state in which a superabsorbent polymer can swell without a restraining load when absorbing a specific solution.

[0039] In this specification, the element symbols used are those described in the periodic table.

[0040] Hereinafter, a superabsorbent resin and a method for manufacturing the same according to specific embodiments of the invention will be described in more detail.

[0041] Ⅰ. Polyacrylic acid (salt)-based superabsorbent resin

[0042] The superabsorbent resin of the present invention is a polyacrylic acid (salt)-based superabsorbent resin, having a surface area relative to the actual volume of 45 mm -1 In addition, it is characterized by a deodorizing rate of 40% or more according to the following formula 1 for dimethyl disulfide (DMDS) or dimethyl trisulfide (DMTS).

[0043] [Formula 1]

[0044] Deodorization rate (%) = (1- Cs / Co) × 100

[0045] In the above equation 1,

[0046] Cs is the peak area of ​​the odor standard substance in the gas chromatography-mass spectrometry (GC-MS) graph for the odor standard substance solution that was in contact with the superabsorbent resin at 35°C for 2 hours, and Co is the peak area of ​​the odor standard substance in the gas chromatography-mass spectrometry graph for the odor standard substance solution that was in contact with the control at 35°C for 2 hours.

[0047] The superabsorbent resin of the present invention has a surface area of ​​45 mm relative to its actual volume. -1 As described above, the superabsorbent resin has many curves on its surface, so it has a large surface area and thus maintains excellent absorption performance, while at the same time having excellent deodorizing effects against various odor-causing substances, especially dimethyl disulfide or dimethyl trisulfide.

[0048] The superabsorbent resin having a deodorizing effect means that the superabsorbent resin reduces the amount of at least one odor standard substance in the deodorizing rate evaluation.

[0049] The above deodorization rate evaluation is an evaluation in which the superabsorbent resin is brought into contact with the odor standard substance in a physiological saline solution in which the odor standard substance exists, and the specific method of conducting the deodorization rate evaluation will be described in more detail in the experimental example section described below.

[0050] The odor standard substances applied to the above deodorization rate evaluation include sulfur compounds such as dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS), ketones such as diacetyl, and isovaleraldehyde generated from amino acids such as leucine.

[0051] The superabsorbent resin according to the present invention has an odor reduction effect for dimethyl disulfide (DMDS) or dimethyl trisulfide (DMTS), among the above odor standard substances.

[0052] Specifically, the superabsorbent resin according to the present invention can have a deodorizing rate of 40% or more for dimethyl disulfide (DMDS) or dimethyl trisulfide (DMTS).

[0053] For example, the superabsorbent resin according to the present invention may have a deodorization rate of 40% or more, 42% or more, or 45% or more for dimethyl disulfide (DMDS) or dimethyl trisulfide (DMTS). Preferably, the superabsorbent resin may exhibit a deodorization rate of 47% or more, 50% or more, or 52% or more for either dimethyl disulfide (DMDS) or dimethyl trisulfide (DMTS).

[0054] In addition, the superabsorbent resin according to the present invention can have an odor reduction effect for diacetyl and / or isovaleraldehyde.

[0055] That is, the superabsorbent resin according to the present invention has a deodorizing effect against dimethyl disulfide (DMDS) or dimethyl trisulfide (DMTS), and in addition, can exhibit a deodorizing effect against at least one or both of diacetyl and isovaleraldehyde.

[0056] In particular, the superabsorbent resin according to the present invention can exhibit deodorizing efficacy against dimethyl disulfide (DMDS) or dimethyl trisulfide (DMTS) among the four odor standard substances, dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), diacetyl, and isovaleraldehyde, even when all four odor standard substances are mixed, and can exhibit deodorizing efficacy against at least one or both of diacetyl and isovaleraldehyde.

[0057] According to one embodiment of the invention, the superabsorbent resin may exhibit a deodorization rate of 10% or more, 12% or more, or 14% or more with respect to diacetyl among the malodor standard substances in the deodorization rate evaluation. There is no particular limitation on the upper limit of the deodorization rate, but may be, for example, 100% or less, 95% or less, 90% or less, 85% or less, or 80% or less. Such a deodorization rate may be exhibited even when all four types of malodor standard substances are in contact with the superabsorbent resin at the same time.

[0058] According to one embodiment of the invention, the superabsorbent resin may exhibit a deodorization rate of 10% or more, 12% or more, or 14% or more for isovaleraldehyde among the malodor standard substances in the deodorization rate evaluation. Preferably, the superabsorbent resin may exhibit a deodorization rate of 16% or more, 18% or more, or 19% or more, and there is no particular limitation on the upper limit of the deodorization rate, but may be, for example, 100% or less, 95% or less, 90% or less, 85% or less, or 80% or less. Such a deodorization rate may be exhibited even when all four types of malodor standard substances and the superabsorbent resin are in contact at the same time.

[0059] The above deodorization rate is a value determined according to the following formula 1 based on the results of the deodorization rate evaluation.

[0060] [Formula 1]

[0061] Deodorization rate (%) = (1- Cs / Co) × 100

[0062] In the above formula 1, Cs is the peak area of ​​the odor standard substance in the gas chromatography-mass spectrometry (GC-MS) graph for the odor standard substance solution that was in contact with the superabsorbent resin according to one embodiment of the present invention at 35°C for 2 hours, and Co is the peak area of ​​the odor standard substance in the gas chromatography-mass spectrometry graph for the odor standard substance solution that was in contact with the control group at 35°C for 2 hours.

[0063] The above odor standard material solution is a solution in which dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), diacetyl, and isovaleraldehyde are dissolved in physiological saline.

[0064] As the control group, LG Chemical's GS4800, a general-purpose superabsorbent resin, was used.

[0065] The specific method of evaluating the deodorization rate to confirm the above deodorization rate will be explained in more detail in the experimental example described below.

[0066] According to one embodiment of the invention, a superabsorbent resin can exhibit a deodorization rate of a certain level or higher for dimethyl disulfide (DMDS) or dimethyl trisulfide (DMTS) among the above four types of odor standard substances when in contact with all of them simultaneously, and at the same time, can exhibit a deodorization rate of a certain level or higher for one or more types, or two or more types, of odor standard substances other than dimethyl disulfide (DMDS) or dimethyl trisulfide (DMTS).

[0067] In one embodiment of the present invention, the surface area to actual volume of the superabsorbent resin is 45 mm -1 Ideally 46 mm -1 It may be ideal. In addition, the surface area to actual volume is 65 mm -1 Below, preferably 62 mm -1 Less than or equal to 60 mm, more preferably -1 It could be as follows:

[0068] In this specification, the surface area to actual volume refers to a value obtained by dividing the total surface area of ​​the superabsorbent resin by the total volume of the superabsorbent resin within a specific reference volume.

[0069] The surface area to actual volume of the present invention is a value obtained by dividing the total surface area of ​​the superabsorbent resin by the total volume of the superabsorbent resin within a specific reference volume. In the present invention, a large surface area to actual volume of the superabsorbent resin means that the surface of the superabsorbent resin has many curves and thus has a large surface area.

[0070] That is, the present invention has a large surface area compared to the conventional superabsorbent resin, and thus has a large surface area relative to the actual volume, and by having this structure, it forms an absorption path for various fluids, thereby helping to have excellent absorption performance while simultaneously having a deodorizing effect on odor-causing substances.

[0071] However, although a larger surface area relative to the actual volume may help to achieve a deodorizing effect against odor-causing substances, the surface area relative to the actual volume and the deodorizing effect are not necessarily proportional. In other words, a larger surface area relative to the actual volume does not necessarily mean a higher deodorizing effect, and vice versa.

[0072] The surface area to actual volume ratio can be derived using a 3D X-ray microscope (XRM).

[0073] In the case of XRM, a cross-sectional image can be obtained by rotating a sample and irradiating it with X-rays, and three-dimensional data can be obtained based on this. This is called 3D reconstruction. Conversely, a two-dimensional (2D) cross-sectional image can be extracted from the obtained three-dimensional (3D) data, noise can be removed, the measurement target can be separated, and this can be converted back into three-dimensional (3D) volume data. When the measurement target is separated from the XRM 2D cross-sectional image and converted back into a three-dimensional volume, the measurement target can be precisely observed in a three-dimensional form. In this way, when using XRM, superabsorbent resins can be analyzed in either a three-dimensional or a two-dimensional form.

[0074] Specifically, the surface area to actual volume ratio can be derived using the following method.

[0075] <Method for deriving surface area from actual volume>

[0076] - Step 1) Drying and sampling of superabsorbent resin

[0077] The superabsorbent resin is dried at about 100°C for about 12 hours, and the dried superabsorbent resin is sampled in a size of 1.5 cm x 1.5 cm x 1.5 cm (width x length x height).

[0078] - Step 2) Image extraction

[0079] The sampled superabsorbent resin is analyzed using XRM (ZEISS Xradia 620 Versa) under the following conditions to derive a 3D image of the superabsorbent resin (3D reconstruction).

[0080] <Conditions>

[0081] X-Ray Energy: 70 kV

[0082] detector: Flat Pane

[0083] Voxel Size: 5 ㎛

[0084] Measurement time: 0.05 s / frame

[0085] Total images: 4501

[0086] - Step 3) Surface area to actual volume (S) SAP / V C ) is derived

[0087] ① Set the area of ​​interest (measurement area) in the 2D image of the XRM cross-section of the 3D reconstructed superabsorbent resin and cut it out.

[0088] ② Apply Gaussian blur to the cropped 2D cross-sectional image to remove noise. Next, Otsu's thresholding method is used to convert the 2D cross-sectional image into a binarized image to distinguish between the background image and the superabsorbent resin particle image. This process is repeatedly applied to all 2D images of the measurement target to obtain a 2D cross-sectional image showing the separated superabsorbent resin particles.

[0089] ③ Stack the above multiple 2D cross-sectional images and perform 3D rendering.

[0090] ④ The volume of the entire superabsorbent resin particle (V) is calculated from the 3D rendered volume data. C ) is measured. In addition, considering the connectivity of the 3D rendered volume data, the surface area of ​​the superabsorbent resin particles excluding the surface area of ​​the closed pore region (S SAP ) is measured. At this time, the area of ​​the outer surface (cut cross-section) of the 3D rendered data is excluded. The surface area (S) of the superabsorbent resin particles SAP ) is the volume of the total particles of superabsorbent resin (V C ) to derive the surface area per actual volume of the superabsorbent resin.

[0091] In the process of measuring the surface area relative to the actual volume, the pretreatment of drying the superabsorbent resin at about 100°C for about 12 hours is performed to measure the surface area relative to the actual volume of the superabsorbent resin without being affected by the moisture content.

[0092] The superabsorbent resin according to the present invention has excellent absorption performance and can simultaneously have a deodorizing effect against odor-causing substances by comprehensively combining the above-described surface area to actual volume characteristics as well as the convexity, CE diameter, etc. described below.

[0093] In one embodiment of the present invention, the superabsorbent resin may have an average value of convexity calculated by Equation 2 below for all particles of 0.94 or less.

[0094] [Formula 2]

[0095] M c = L s / L

[0096] In the above equation 2,

[0097] M c is convexity,

[0098] L s refers to the length of an elastic band when it is assumed that the 3D image of the 3D particle to be measured is surrounded by an imaginary elastic band that stretches around the contour of the captured 2D image.

[0099] L represents the actual circumference of the image captured as a 2D image of the 3D image of the 3D particle to be measured.

[0100] The above total particles refer to superabsorbent resin particles with no limitation on particle size.

[0101] The above convexity is a parameter for measuring the particle outline and surface roughness of the particle with a value of 0 to 1. The closer the convexity is to 1, the more the particle can be seen as having a very smooth outline, and the closer the convexity is to 0, the more the particle can be seen as having a rough or uneven outline.

[0102] The superabsorbent resin according to the present invention can have a convexity of 0.94 or less, and a low convexity means a large specific surface area, and thus can have an excellent absorption rate.

[0103] At this time, the average value of the convexity is measured after particles are randomly scattered on the stage by vacuum within the measuring device, and a statistical result is derived by securing n of 200 or more and averaging them.

[0104] In one embodiment of the present invention, the average value of the convexity of all particles of the superabsorbent resin may be 0.80 or more, 0.83 or more, 0.85 or more, or 0.87 or more, and 0.94 or less, 0.93 or less, or 0.92 or less.

[0105] In one embodiment of the present invention, the superabsorbent resin may have an average CE diameter (Circle Equivalent diameter) of 220 ㎛ to 450 ㎛.

[0106] The above CE diameter refers to the diameter of a circle having the same area as that of an image obtained by capturing a 3D image of a particle as a 2D image, and the size of the particle can be indicated through the CE diameter. The average value of the CE diameter of the superabsorbent resin may be 220 ㎛ or more, 230 ㎛ or more, or 240 ㎛ or more, and 450 ㎛ or less, 440 ㎛ or less, or 430 ㎛ or less.

[0107] If the average value of the CE diameter of the above-mentioned superabsorbent resin is less than 220 ㎛, there is a concern that the amount of fine particles will be high due to the large number of fine particles, and the absorption characteristics will be low. If it exceeds 450 ㎛, there may be a problem that the absorption speed will be low. Therefore, it is preferable that the average value of the CE diameter of the above-mentioned superabsorbent resin be within the above-mentioned range.

[0108] The average value of the above CE diameter is measured after randomly scattering the particles on the stage by vacuum within the measuring device, and a statistical result is derived by securing n numbers of 200 or more and averaging them.

[0109] When the particle size of the superabsorbent resin according to the present invention is such, a superabsorbent resin having a fast absorption rate and excellent absorption properties can be manufactured.

[0110] Additionally, convexity and CE diameter can be measured using several commercial instruments that quantify and analyze particle morphology based on image analysis of the particles. For example, these parameters can be measured using the Malvern Panalytical Morphologi 4, which is specifically measured through the following four steps, which are described in more detail in the experimental examples below.

[0111] 1) Sample Preparation: Prepare the superabsorbent resin particles to be measured. When measuring the convexity of particles with a specific particle size range, prepare the sample by classifying the particles with the specific particle size using a Retsch classifier at 1.0 amplitude for 10 minutes.

[0112] At this time, the particle size of the superabsorbent resin particles can be measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 220.3 method.

[0113] 2) Image acquisition: After setting the prepared sample on the stage within the equipment, scan it at 2.5x magnification to acquire images of individual particles.

[0114] 3) Image processing: For the acquired images, the 3D image of the 3D particle for each particle is captured as a 2D image, and parameter values ​​such as CE diameter (Circle Equivalent diameter), shortest diameter, longest diameter, actual particle perimeter, and convex hull perimeter are measured.

[0115] 4) Based on the data analyzed for each particle, convexity and CE diameter values ​​for all particles included in the sample were obtained.

[0116] In order to obtain the superabsorbent resin of the present invention having a deodorizing rate higher than a certain value for dimethyl disulfide or dimethyl trisulfide and a surface area to actual volume value higher than a certain value, the inventors adjusted the manufacturing process conditions of the superabsorbent resin. For example, by adjusting the type or content of additives in the surface crosslinking process, or adjusting the conditions of the polymerization and pulverization processes, the superabsorbent resin of the present invention has a deodorizing rate higher than a certain value for dimethyl disulfide or dimethyl trisulfide and satisfies a surface area to actual volume value higher than a certain value.

[0117] For example, by controlling the type and content of the monomer composition in the polymerization process, the type and content of the internal cross-linking agent, the type, amount and timing of introduction of the surfactant in the neutralization and atomization steps, the type, amount and timing of introduction of the neutralizing agent, the type of atomization device, the rotation speed, the hole size, the number of atomizations, etc., the superabsorbent resin can be controlled to have a deodorizing rate for dimethyl disulfide or dimethyl trisulfide of a certain value or higher and a surface area to actual volume value of a certain value or higher.

[0118] Meanwhile, the superabsorbent resin of the present invention may have a water retention capacity (CRC) measured according to EDANA method WSP 241.3 of about 28 g / g or more, about 29 g / g or more, or about 30 g / g or more, and about 50 g / g or less, about 45 g / g or less, or about 40 g / g or less.

[0119] In addition, the superabsorbent polymer of the present invention may have an absorbency under pressure (AUP) of about 25 g / g or more, about 27 g / g or more, about 28 g / g or more, or about 29 g / g or more, and about 45 g / g or less, about 42 g / g or less, or about 40 g / g or less at 2.07 kPa (0.3 psi) as measured according to EDANA method WSP 242.3.

[0120] The superabsorbent resin of the present invention may have a vortex time of 40 seconds or less as measured by a vortex measurement method at 24.0°C.

[0121] More specifically, the vortex time may be 40 seconds or less, 39 seconds or less, 38 seconds or less, or 37 seconds or less. In addition, the vortex time is better the smaller the value, so the lower limit of the vortex time is theoretically 0 seconds, but may be 10 seconds or more, for example.

[0122] The method for measuring the water retention capacity, pressurized absorption capacity and absorption rate of the above superabsorbent resin is described in more detail in the experimental examples described below.

[0123] In addition, when the superabsorbent resin of the present invention is swollen with water having an electrical conductivity of 100 to 130 μS / cm for 1 minute, the maximum capacity of water that the superabsorbent resin can hold (free swell capacity) may be 130 g or more, 132 g or more, 135 g or more, or 138 g or more, and 230 g or less, 225 g or less, or 220 g or less. This is a value showing the absorption capacity of the superabsorbent resin.

[0124] Even when the same superabsorbent resin is used, the absorption behavior in water with an electrical conductivity of 100 to 130 μS / cm and the absorption behavior in 0.9% salt water with an electrical conductivity of approximately 16,100 μS / cm are bound to be different.

[0125] That is, it can be said that the absorption capacity, which is the maximum capacity of water, has an independent meaning when using water with an electrical conductivity value of 100 to 130 μS / cm and when using 0.9% salt water with an electrical conductivity of about 16,100 μS / cm.

[0126] The present inventors determined the maximum capacity of water that a superabsorbent polymer can hold by using water having an electrical conductivity of 100 to 130 μS / cm at 24°C, which is lower in ion concentration than the 0.9% salt water and is about 1 / 100 of the electrical conductivity of 0.9% salt water at 24°C of about 16,100 μS / cm. In the examples, water having an electrical conductivity of 110 μS / cm at 24°C was used. For water within the range of 100 to 130 μS / cm in electrical conductivity, there is no significant difference in absorption characteristics depending on electrical conductivity.

[0127] Accordingly, the inventors of the present invention sought to develop a superabsorbent resin having an excellent absorption rate and absorption capacity for water having an electrical conductivity of 100 to 130 μS / cm, which has a lower ion concentration and electrical conductivity than 0.9% salt water, that is, an electrical conductivity of about 1 / 100 of 0.9% salt water, and implemented this by manufacturing the superabsorbent resin so that it has a deodorizing rate of a certain value or higher for dimethyl disulfide or dimethyl trisulfide and at the same time satisfies a surface area to actual volume value of a certain value or higher.

[0128] The method for measuring the absorption capacity in water having an electrical conductivity value of 100 to 130 μS / cm will be described in more detail in the experimental examples section described below.

[0129] Meanwhile, the superabsorbent resin according to the present invention can be produced by appropriately controlling manufacturing process conditions, such as the components / content of the superabsorbent resin, polymerization process conditions of the superabsorbent resin, or crushing process conditions. That is, by controlling these process conditions, it is possible to produce a superabsorbent resin having a deodorizing rate of a certain value or higher and a surface area to actual volume value of a predetermined value or higher.

[0130] For example, by controlling the type and content of the monomer composition in the polymerization process, the type and content of the internal cross-linking agent, the type, amount and timing of injection of the surfactant in the neutralization and atomization steps, the type, amount and timing of injection of the neutralizing agent, the type of atomization device, the rotation speed, the hole size, the number of atomizations, etc., the superabsorbent resin can be controlled to have a deodorizing rate of a certain value or higher for dimethyl disulfide or dimethyl trisulfide and a surface area to actual volume value of a certain value or higher.

[0131] Below, each component that makes up the superabsorbent resin will be explained in more detail.

[0132] A polyacrylic acid (salt)-based superabsorbent resin of one embodiment of the invention comprises a base resin comprising a crosslinked polymer of a water-soluble ethylenically unsaturated monomer having an acidic group and an internal crosslinking agent. The crosslinked polymer can preferably be formed by polymerizing a monomer composition comprising components such as a monomer, an internal crosslinking agent, and a polymerization initiator.

[0133] Here, the water-soluble ethylenically unsaturated monomer may be any monomer commonly used in the production of superabsorbent resins. As a non-limiting example, the water-soluble ethylenically unsaturated monomer may be a compound represented by the following chemical formula 1:

[0134] [Chemical Formula 1]

[0135] R-COOM'

[0136] In the above chemical formula 1,

[0137] R is an alkyl group having 2 to 5 carbon atoms containing an unsaturated bond,

[0138] M' is a hydrogen atom, a monovalent or divalent metal, an ammonium group, or an organic amine salt.

[0139] Preferably, the monomer may be at least one selected from the group consisting of (meth)acrylic acid, and monovalent (alkali) metal salts, divalent metal salts, ammonium salts, and organic amine salts of these acids.

[0140] In this way, when (meth)acrylic acid and / or its salt is used as a water-soluble ethylenically unsaturated monomer, a superabsorbent resin with improved absorbency can be obtained, which is advantageous. In addition, as the monomers, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacryloylethane sulfonic acid, 2-(meth)acryloylpropanesulfonic acid or 2-(meth)acrylamide-2-methyl propane sulfonic acid, (meth)acrylamide, N-substituted (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, (N,N)-dimethylaminoethyl (meth)acrylate, (N,N)-dimethylaminopropyl (meth)acrylamide, etc. can be used.

[0141] The above-mentioned water-soluble ethylenically unsaturated monomer has acidic groups. Meanwhile, in the production of superabsorbent resins, a monomer in which at least a portion of the acidic groups are neutralized by a neutralizing agent is crosslinked and polymerized to form a polymer. However, in the present invention, the acidic groups are preferably not neutralized during polymerization, but can be neutralized after the polymer is formed. More specific details regarding this will be described in the section on the production method of superabsorbent resins.

[0142] The concentration of the water-soluble ethylenically unsaturated monomer in the monomer composition may be appropriately adjusted in consideration of polymerization time, reaction conditions, etc., and may be about 20 to about 60 wt%, or about 20 to about 40 wt%.

[0143] The term 'internal crosslinking agent' used in this specification is a term used to distinguish it from a surface crosslinking agent for performing a crosslinking reaction on the surface of superabsorbent resin particles described below, and it serves to form a polymer including a crosslinked structure by introducing crosslinking bonds between unsaturated bonds of the water-soluble ethylenically unsaturated monomers described above.

[0144] The crosslinking in the above step is carried out without distinction between the surface and the interior, but when the surface crosslinking process of the superabsorbent resin particles described later is carried out, the surface of the finally manufactured superabsorbent resin particles may include a structure newly crosslinked by the surface crosslinking agent, and the interior of the superabsorbent resin particles may maintain the structure crosslinked by the internal crosslinking agent.

[0145] According to one embodiment of the present invention, the internal crosslinking agent may include at least one of a multifunctional acrylate compound, a multifunctional allyl compound, or a multifunctional vinyl compound.

[0146] Non-limiting examples of multifunctional acrylate compounds include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butanediol di(meth)acrylate, butylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol di(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol Examples thereof include tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, trimethylolpropane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, glycerin di(meth)acrylate, and glycerin tri(meth)acrylate, and these may be used alone or in combination of two or more.

[0147] Non-limiting examples of polyfunctional allyl compounds include ethylene glycol diallyl ether, diethylene glycol diallyl ether, triethylene glycol diallyl ether, tetraethylene glycol diallyl ether, polyethylene glycol diallyl ether, propylene glycol diallyl ether, tripropylene glycol diallyl ether, polypropylene glycol diallyl ether, butanediol diallyl ether, butylene glycol diallyl ether, hexanediol diallyl ether, pentaerythritol diallyl ether, pentaerythritol triallyl ether, pentaerythritol tetraallyl ether, dipentaerythritol diallyl ether, dipentaerythritol triallyl ether, dipentaerythritol tetraallyl ether, dipentaerythritol pentaallyl ether, trimethylolpropane diallyl ether, Examples include trimethylolpropane triallyl ether, glycerin diallyl ether, and glycerin triallyl ether, and they can be used alone or in combination of two or more.

[0148] Non-limiting examples of polyfunctional vinyl compounds include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, tetraethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, tripropylene glycol divinyl ether, polypropylene glycol divinyl ether, butanediol divinyl ether, butylene glycol divinyl ether, hexanediol divinyl ether, pentaerythritol divinyl ether, pentaerythritol trivinyl ether, pentaerythritol tetravinyl ether, dipentaerythritol divinyl ether, dipentaerythritol trivinyl ether, dipentaerythritol tetravinyl ether, dipentaerythritol pentavinyl ether, trimethylolpropane divinyl ether, trimethylolpropane Examples thereof include trivinyl ether, glycerin divinyl ether, and glycerin trivinyl ether, and these may be used singly or in combination of two or more. Preferably, pentaerythritol triallyl ether may be used.

[0149] The above-described multifunctional allyl compound or multifunctional vinyl compound can form a cross-linked structure during the polymerization process by having two or more unsaturated groups included in the molecule bond with the unsaturated bonds of water-soluble ethylenically unsaturated monomers or the unsaturated bonds of other internal cross-linking agents, and unlike an acrylate compound including an ester bond (-(C=O)O-) in the molecule, the cross-linked bond can be more stably maintained even during the neutralization process after the polymerization reaction described below.

[0150] Accordingly, the gel strength of the superabsorbent resin being manufactured can be increased, process stability can be improved during the discharging process after polymerization, and the amount of water-soluble components can be minimized.

[0151] Crosslinking polymerization of the water-soluble ethylenically unsaturated monomer in the presence of such an internal crosslinking agent can be carried out in the presence of a polymerization initiator, a thickener if necessary, a plasticizer, a preservative stabilizer, an antioxidant, etc.

[0152] In the monomer composition, the internal cross-linking agent may be used in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. For example, the internal cross-linking agent may be used in an amount of 0.01 parts by weight or more, 0.05 parts by weight or more, or 0.1 parts by weight or more, and 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or 0.7 parts by weight or less, based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. If the content of the internal cross-linking agent is too low, cross-linking may not occur sufficiently, making it difficult to achieve a strength higher than an appropriate level, and if the content of the internal cross-linking agent is too high, the internal cross-linking density may increase, making it difficult to achieve a desired water retention capacity. In particular, within the above range, the superabsorbent resin according to the present invention is suitable for implementation so as to have a deodorizing rate of a certain value or higher for dimethyl disulfide or dimethyl trisulfide and a surface area to actual volume value of a certain value or higher.

[0153] Meanwhile, when a low content of internal cross-linking agent is used to ensure that the base resin has a high centrifugal retention capacity (CRC), the gel strength of the formed polymer may be reduced, and the low gel strength may make it difficult to operate a shredder or the like when cutting the hydrogel polymer. In this case, by mixing two or more types of internal cross-linking agents and using them for the operation of a high-speed rotary shredder or the like, the gel strength can be increased, thereby improving the operational stability of the shredder or the like.

[0154] The above-formed functional gel polymer can change the shape of the particles depending on the degree of internal crosslinking, and the polymer formed using such an internal crosslinking agent can have a three-dimensional network structure in which the main chains formed by polymerizing the water-soluble ethylenically unsaturated monomers are crosslinked by the internal crosslinking agent.

[0155] In this way, when the polymer has a three-dimensional network structure, the overall properties of the superabsorbent resin, such as water retention capacity and pressure absorption capacity, can be significantly improved compared to the case of a two-dimensional linear structure that is not further crosslinked by an internal crosslinking agent.

[0156] The above polymer is a polymer in which a monomer and an internal crosslinking agent are polymerized in the presence of a polymerization initiator. The type of the polymerization initiator is not particularly limited, but preferably, the polymerization can be performed using a thermal polymerization method in a batch reactor, and accordingly, a thermal polymerization initiator can be used as the polymerization initiator.

[0157] As the above thermal polymerization initiator, one or more selected from the group of initiators consisting of persulfate initiators, azo initiators, hydrogen peroxide, and ascorbic acid can be used. Specifically, examples of persulfate initiators include sodium persulfate (Na2S2O8), potassium persulfate (K2S2O8), and ammonium persulfate ((NH4)2S2O8), and examples of azo initiators include 2,2-azobis-(2-amidinopropane) dihydrochloride, 2,2-azobis-(N,N-dimethylene)isobutyramidine dihydrochloride, 2-(carbamoylazo)isobutylonitril, Examples include 2,2-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, 4,4-azobis-(4-cyanovaleric acid), etc. A more diverse range of thermal polymerization initiators is well described in Odian's book, 'Principle of Polymerization (Wiley, 1981), p203, and is not limited to the examples described above.

[0158] Such polymerization initiator may be used in an amount of 2 parts by weight or less relative to 100 parts by weight of the water-soluble ethylenically unsaturated monomer. That is, if the concentration of the polymerization initiator is excessively low, the polymerization rate may be slowed and a large amount of residual monomer may be extracted from the final product, which is not preferable. Conversely, if the concentration of the polymerization initiator is higher than the above range, the polymer chains forming the network may become shorter, which may increase the content of water-soluble components and lower the pressure absorbency, thereby deteriorating the physical properties of the resin, which is not preferable.

[0159] Meanwhile, in one embodiment of the present invention, polymerization can be initiated by adding the aforementioned polymerization initiator and a reducing agent forming a redox couple together to the monomer composition.

[0160] Specifically, the initiator and reducing agent react with each other to form radicals when introduced into a polymer solution.

[0161] The formed radicals react with the monomer, and since the oxidation-reduction reaction between the initiator and reducing agent is highly reactive, polymerization is initiated even when only a small amount of initiator and reducing agent is added, so there is no need to increase the process temperature, low-temperature polymerization is possible, and changes in the physical properties of the polymer solution can be minimized.

[0162] The polymerization reaction utilizing the above oxidation-reduction reaction can occur smoothly even at temperatures near room temperature (25°C) or lower. For example, the polymerization reaction can be performed at a temperature of 5°C or higher and 25°C or lower, or 5°C or higher and 20°C or lower.

[0163] In one embodiment of the present invention, when a persulfate-based initiator is used as the initiator, the reducing agent may be at least one selected from the group consisting of sodium metabisulfite (Na2S2O5); tetramethyl ethylenediamine (TMEDA); a mixture of iron (II) sulfate and EDTA (FeSO4 / EDTA); sodium formaldehyde sulfoxylate; and disodium 2-hydroxy-2-sulfinoacetate.

[0164] For example, potassium persulfate may be used as the initiator and disodium 2-hydroxy-2-sulfinoacetate may be used as the reducing agent; ammonium persulfate may be used as the initiator and tetramethylethylenediamine may be used as the reducing agent; or sodium persulfate may be used as the initiator and sodium formaldehyde sulfoxylate may be used as the reducing agent.

[0165] In another embodiment of the present invention, when a hydrogen peroxide-based initiator is used as the initiator, the reducing agent may be at least one selected from the group consisting of ascorbic acid; sucrose; sodium sulfite (Na2SO3), sodium metabisulfite (Na2S2O5); tetramethyl ethylenediamine (TMEDA); a mixture of iron (II) sulfate and EDTA (FeSO4 / EDTA); sodium formaldehyde sulfoxylate; disodium 2-hydroxy-2-sulfinoacteate; and disodium 2-hydroxy-2-sulfoacteate.

[0166] The above monomer composition may further include additives such as a thickener, a plasticizer, a preservative stabilizer, and an antioxidant, as needed.

[0167] And, the monomer composition including the monomer may be in a solution state dissolved in a solvent such as water, for example, and the solid content in the monomer composition in the solution state, i.e., the concentration of the monomer, internal crosslinking agent, and polymerization initiator, may be appropriately adjusted in consideration of the polymerization time, reaction conditions, etc. For example, the solid content in the monomer composition may be 10 to 80 wt%, 15 to 60 wt%, or 30 to 50 wt%.

[0168] The solvent that can be used at this time can be used without limitation in its composition as long as it can dissolve the above-mentioned components, and for example, one or more selected from water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate, and N,N-dimethylacetamide can be used in combination.

[0169] The polymer obtained by this method can form a polymer with a high molecular weight and uniform molecular weight distribution by polymerizing it using an ethylenically unsaturated monomer in an unsaturated state. This reduces the content of water-soluble components, thereby improving the performance of the superabsorbent resin.

[0170] Additionally, the polymer may have a moisture content of 30 to 80 wt%. For example, the moisture content of the polymer may be at least 30 wt%, at least 45 wt%, or at least 50 wt%, but at most 80 wt%, at most 70 wt%, or at most 60 wt%.

[0171] If the moisture content of the polymer is too low, it may be difficult to secure an appropriate surface area in the subsequent grinding step, and thus the polymer may not be effectively ground. If the moisture content of the polymer is too high, the pressure applied in the subsequent grinding step may increase, making it difficult to grind to the desired particle size.

[0172] Meanwhile, throughout this specification, "moisture content" refers to the content of moisture in relation to the total weight of the polymer, which is the value obtained by subtracting the weight of the polymer in a dry state from the weight of the polymer. Specifically, the moisture content is defined as a value calculated by measuring the weight loss due to moisture evaporation in the polymer during the drying process by raising the temperature of the polymer in a crumbly state through infrared heating. At this time, the drying conditions are such that the temperature is raised from room temperature to about 180°C and then maintained at 180°C, and the total drying time is set to 40 minutes, including 5 minutes for the temperature rising step, to measure the moisture content.

[0173] A superabsorbent resin according to one embodiment of the invention comprises a base resin powder comprising a crosslinked polymer of a water-soluble ethylenically unsaturated monomer having an acidic group as described above and an internal crosslinking agent; and a surface crosslinked layer formed on the base resin powder by further crosslinking the crosslinked polymer via a surface crosslinking agent.

[0174] The above surface cross-linking layer is formed on at least a portion of the surface of the base resin powder, and may be formed by additional cross-linking of a cross-linking polymer included in the base resin powder via a surface cross-linking agent.

[0175] As the surface cross-linking agent, any surface cross-linking agent that has been conventionally used in the production of superabsorbent resins can be used without particular limitation. For example, the surface cross-linking agent may be at least one polyol selected from the group consisting of ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,2-hexanediol, 1,3-hexanediol, 2-methyl-1,3-propanediol, 2,5-hexanediol, 2-methyl-1,3-pentanediol, 2-methyl-2,4-pentanediol, tripropylene glycol, and glycerol; at least one carbonate compound selected from the group consisting of ethylene carbonate, propylene carbonate, and glycerol carbonate; an epoxy compound such as ethylene glycol diglycidyl ether; an oxazoline compound such as oxazolidinone; a polyamine compound; mono-, di- or polyoxazolidinone compounds; or cyclic urea compounds; etc.

[0176] Specifically, one or more, two or more, or three or more of the surface cross-linking agents described above may be used as the surface cross-linking agent, for example, ethylene carbonate-propylene carbonate (ECPC), propylene glycol, and / or glycerol carbonate may be used.

[0177] Such surface cross-linking agent may be used in an amount of 0.001 to 0.5 parts by weight per 100 parts by weight of the superabsorbent resin particles. In this case, 100 parts by weight of the superabsorbent resin particles is based on a dried state. In addition, the content refers to the total amount of the surface cross-linking agent used.

[0178] For example, the surface cross-linking agent may be used in an amount of 0.005 parts by weight or more, 0.01 parts by weight or more, or 0.05 parts by weight or more, based on 100 parts by weight of the superabsorbent resin particles. In addition, the surface cross-linking agent may be used in an amount of 3.0 parts by weight or less, 2.5 parts by weight or less, 2.0 parts by weight or less, 1.5 parts by weight or less, 1.0 parts by weight or less, 0.5 parts by weight or less, 0.4 parts by weight or less, or 0.2 parts by weight or less, based on 100 parts by weight of the superabsorbent resin particles. By adjusting the content range of the surface cross-linking agent within the above-described range, a superabsorbent resin exhibiting excellent overall absorption properties can be manufactured.

[0179] By adjusting the content range of the surface cross-linking agent within the above-described range, a superabsorbent resin exhibiting excellent absorption properties can be manufactured. In particular, within the above range, the superabsorbent resin according to the present invention is suitable for implementing a deodorizing rate of dimethyl disulfide or dimethyl trisulfide of a certain value or higher, and at the same time, a surface area to actual volume value of a predetermined value or higher.

[0180] Additionally, the surface cross-linking layer can be formed by adding an inorganic substance to the surface cross-linking agent. That is, in the presence of the surface cross-linking agent and the inorganic substance, the surface of the base resin powder can be further cross-linked to form a surface cross-linking layer.

[0181] As such inorganic materials, one or more inorganic materials selected from the group consisting of silica, clay, alumina, silica-alumina composites, titania, zinc oxide, and aluminum sulfate can be used. The inorganic material can be used in powder or liquid form, and in particular, can be used as alumina powder, silica-alumina powder, titania powder, or nano silica solution. In addition, the inorganic material can be used in an amount of about 0.001 to about 1 part by weight based on 100 parts by weight of superabsorbent resin particles.

[0182] As described above, a superabsorbent resin including a base resin powder and a surface cross-linking layer formed on the base resin powder can absorb body fluid or water at a high rate, and can also absorb a relatively large amount initially, thereby preventing problems such as body fluid or water not being absorbed but pooling or leaking out.

[0183] Ⅱ. Manufacturing method of superabsorbent resin

[0184] Conventional superabsorbent polymers are manufactured by crosslinking and polymerizing a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups in the presence of an internal crosslinking agent and a polymerization initiator to form a hydrogel polymer, drying the hydrogel polymer formed in this manner, and then pulverizing it to a desired particle size. Typically, a chopping process is performed before the drying process to cut the hydrogel polymer into particles several millimeters in size in order to facilitate drying of the hydrogel polymer and increase the efficiency of the pulverization process. However, in this chopping process, due to the adhesiveness of the hydrogel polymer, the hydrogel polymer cannot be pulverized to a micro-sized particle level, but instead becomes an aggregated gel. When this aggregated gel-type hydrogel polymer is dried, a plate-shaped dried body is formed, and in order to pulverize it to a micro-sized particle level, it must go through a multi-stage pulverization process that lowers the adhesiveness of the polymer. This process has been problematic in that a lot of fine dust is generated.

[0185] To address this issue, a method has been used to reuse the separated fine particles by mixing them with an appropriate amount of water, reassembling the fine particles, and then adding them to the chopping or pre-drying step. However, this process of reusing the fine particles has led to problems such as increased equipment load and / or energy consumption. Furthermore, even after reuse, the remaining fine particles, which were not classified, have deteriorated the properties of the superabsorbent polymer.

[0186] To solve this problem, as a result of repeated research, it was confirmed that, instead of performing polymerization in a state where the acidic groups of a water-soluble ethylenically unsaturated monomer are neutralized, as in the conventional method for producing superabsorbent resins, polymerization is first performed in a state where the acidic groups are not neutralized to form a polymer, and then the hydrogel polymer is micronized in the presence of a surfactant and then the acidic groups of the polymer are neutralized, or the hydrogel polymer is formed by neutralizing the acidic groups of the polymer and then the hydrogel polymer is micronized in the presence of a surfactant, or the acidic groups present in the polymer are neutralized simultaneously with the micronization, so that the surfactant is present in a large amount on the surface of the polymer and can sufficiently play a role in lowering the high adhesiveness of the polymer, preventing the polymer from excessively agglomerating, and controlling the agglomeration state to a desired level.

[0187] Meanwhile, the superabsorbent resin according to the present invention can be implemented by controlling the resin components and content, polymerization conditions, or grinding process conditions, etc. For example, by controlling the type and content of the monomer composition in the polymerization process, the type and content of the internal cross-linking agent, the type, amount and timing of the surfactant in the neutralization and atomization steps, the type, amount and timing of the neutralizing agent, the type of the atomization device, the rotation speed, the hole size, the number of atomizations, the components and content of the surface cross-linking solution, etc., the superabsorbent resin can be controlled to have a deodorizing rate of a certain value or higher for dimethyl disulfide or dimethyl trisulfide and a surface area to actual volume value of a certain value or higher.

[0188] In particular, when performing a polymerization process, atomization method, and a surface cross-linking process in the manufacturing process of a superabsorbent resin, the superabsorbent resin can be controlled to have a deodorizing rate for dimethyl disulfide or dimethyl trisulfide of a certain value or higher and a surface area to actual volume value of a certain value or higher by controlling the neutralization time and polymerization conditions, whether to apply an ultra-fine chain process, controlling the components and content of the surface cross-linking solution, controlling the hole size, or controlling the number of times of atomization.

[0189] Hereinafter, each step of the method for manufacturing a superabsorbent resin according to an embodiment will be described in more detail.

[0190] Step 1: Polymerization stage

[0191] First, polymerization is performed on a monomer composition including a water-soluble ethylenically unsaturated monomer having an acidic group and an internal crosslinking agent, thereby producing a base resin powder including a polymer in which the water-soluble ethylenically unsaturated monomer having an acidic group and the internal crosslinking agent are crosslinked.

[0192] The above step may be comprised of a step of preparing a monomer composition by mixing the water-soluble ethylenically unsaturated monomer having the acidic group, an internal crosslinking agent, and a polymerization initiator, and a step of polymerizing the monomer composition to form a polymer.

[0193] Here, the contents of each component can be equally applied to the contents described in the superabsorbent resin of the aforementioned item Ⅰ.

[0194] Meanwhile, the water-soluble ethylenically unsaturated monomer has an acidic group. As explained above, in the production of conventional superabsorbent resins, a monomer in which at least a portion of the acidic groups are neutralized by a neutralizing agent is crosslinked and polymerized to form a polymer. Specifically, in the step of mixing the water-soluble ethylenically unsaturated monomer having the acidic group, an internal crosslinking agent, a polymerization initiator, and a neutralizing agent, at least a portion of the acidic groups of the water-soluble ethylenically unsaturated monomer are neutralized.

[0195] However, according to one embodiment of the present invention, polymerization is first performed in a state where the acidic group of the water-soluble ethylenically unsaturated monomer is not neutralized to form a polymer.

[0196] Water-soluble ethylenically unsaturated monomers (e.g., acrylic acid) whose acid groups are not neutralized are liquid at room temperature and have high miscibility with the solvent (water), so they exist as a mixed solution in the monomer composition. However, water-soluble ethylenically unsaturated monomers whose acid groups are neutralized are solid at room temperature and have different solubility depending on the temperature of the solvent (water), with the solubility decreasing at lower temperatures.

[0197] In this way, a water-soluble ethylenically unsaturated monomer in which the acidic groups are not neutralized has a higher solubility or miscibility in a solvent (water) than a monomer in which the acidic groups are neutralized, and thus does not precipitate even at low temperatures, and is therefore advantageous for long-term polymerization at low temperatures. Accordingly, a water-soluble ethylenically unsaturated monomer in which the acidic groups are not neutralized can be used for long-term polymerization to stably form a polymer having a higher molecular weight and a uniform molecular weight distribution.

[0198] In addition, since it is possible to form a polymer with a longer chain, it is possible to achieve the effect of reducing the content of water-soluble components that are not crosslinked due to incomplete polymerization or crosslinking, and accordingly, it is suitable for implementing a superabsorbent resin having a deodorizing rate of a certain value or higher for dimethyl disulfide or dimethyl trisulfide and a surface area to actual volume value of a certain value or higher.

[0199] In addition, if polymerization is first performed in a state where the acidic groups of the monomer are not neutralized to form a polymer, and then the polymer is micronized in the presence of a surfactant after neutralization, or the polymer is micronized in the presence of a surfactant and then neutralized, or the acidic groups present in the polymer are neutralized simultaneously with the micronization, the surfactant can sufficiently play a role in reducing the adhesiveness of the polymer by being present in large quantities on the surface of the polymer.

[0200] According to one embodiment of the present invention, the step of performing polymerization on the monomer composition to form a polymer can be performed for 1 hour or more in a batch type reactor.

[0201] In the manufacturing method of a typical superabsorbent resin, the polymerization method is largely divided into thermal polymerization and photopolymerization depending on the polymerization energy source. When thermal polymerization is performed, it can be performed in a reactor with a stirring shaft such as a kneader, and when photopolymerization is performed, it can be performed in a flat-bottomed container.

[0202] Meanwhile, when the polymerization is performed as a continuous polymerization, for example, when the polymerization is performed in a reactor equipped with a conveyor belt, a new monomer composition is supplied to the reactor as the polymerization product moves, so that polymerization is performed continuously, and thus polymers having different polymerization rates are mixed, and accordingly, it is difficult to achieve even polymerization throughout the entire monomer composition, which may result in a deterioration of the overall physical properties.

[0203] However, according to one embodiment of the present invention, since polymerization is carried out in a static manner in a batch reactor, there is less concern that polymers with different polymerization rates will be mixed, and thus a polymer with consistent quality can be obtained.

[0204] In addition, the polymerization step is performed in a batch reactor having a predetermined volume, and the polymerization reaction is performed for a longer period of time, for example, 1 hour or more, 3 hours or more, or 6 hours or more, than when polymerization is performed continuously in a reactor equipped with a conveyor belt. Despite the long polymerization reaction time as described above, since the polymerization is performed on a water-soluble ethylenically unsaturated monomer in an unneutralized state, the monomer does not precipitate easily even if the polymerization is performed for a long period of time, and therefore, it is advantageous for long-term polymerization.

[0205] Meanwhile, since polymerization in the batch reactor of the present invention utilizes a thermal polymerization method, the polymerization initiator uses a thermal polymerization initiator, and the description of the corresponding component is as described above.

[0206] Steps 2 and 3: Atomization and neutralization steps

[0207] Next, the method includes a step (step 2) of producing a mixture including the micronized functional gel polymer by micronizing the functional gel polymer in the presence of a surfactant.

[0208] The above-mentioned micronization step is a step of micronizing the polymer in the presence of a surfactant, and is a step in which micronization and agglomeration into sizes of tens to hundreds of micrometers occur simultaneously, rather than chopping the polymer into sizes of millimeters.

[0209] That is, this is a step for manufacturing secondary aggregated particles in the form of aggregated primary particles that are finely divided into tens to hundreds of micrometers in size by imparting appropriate adhesiveness to the polymer. The secondary aggregated particles, which are hydrophilic superabsorbent resin particles manufactured through this step, have a normal particle size distribution while significantly increasing their surface area, which can significantly improve their absorption rate.

[0210] Meanwhile, when a high-intensity mechanical shear force is applied in the above-mentioned micronization step to perform ultra-fine grinding at a rotation speed of 500 rpm to 4,000 rpm, coagulated functional gel particles having finer pores can be formed.

[0211] At this time, when ultra-fine grinding is performed at a rotation speed of 500 rpm to 4,000 rpm, a high-strength mechanical shear force is applied, so that micropores of 100 μm or less are easily formed in the polymer, thereby increasing the surface roughness, and significantly increasing the total surface area of ​​the polymer due to the pores formed inside and outside the polymer particles. Since the micropores are formed in a stable form compared to the pores formed using a foaming agent in the polymerization step, the degree of fine powder generation due to the pores in the subsequent process can be significantly reduced. The superabsorbent resin particles manufactured by this step can have a significantly increased surface area, so that the absorption rate can be significantly improved, and accordingly, the superabsorbent resin of the present invention is suitable for implementing a deodorizing rate of a certain value or higher for dimethyl disulfide or dimethyl trisulfide and a surface area to actual volume value of a certain value or higher.

[0212] The above ultra-fine grinding process is performed at a rotation speed of 500 rpm to 4,000 rpm. If the rotation speed of the process is less than 500 rpm, it is difficult to form sufficient pores to the desired degree, making it difficult to expect a fast absorption speed and securing the desired level of productivity. In addition, if it exceeds 4,000 rpm, the polymer chains may be damaged due to excessive shear force, and accordingly, the water-soluble component may increase, which may slightly deteriorate the overall physical properties of the manufactured superabsorbent resin. Preferably, the above ultra-fine grinding process can be performed at 1,000 rpm to 3,500 rpm, or 2,000 rpm to 3,000 rpm. Within this range, it is easy to form the desired micropores without the aforementioned problems.

[0213] According to one embodiment of the present invention, the atomization step is performed by an atomization device, and the atomization device may include a body part including a transport space into which a polymer is transported; a screw member rotatably installed inside the transport space to move the polymer; a driving motor providing a rotational driving force to the screw member; a cutter member installed in the body part to pulverize the polymer; and a porous plate having a plurality of holes formed therein, which discharges the polymer pulverized by the cutter member to the outside of the body part.

[0214] At this time, the hole size provided in the porous plate of the atomization device may be 1 mm to 25 mm, 5 mm to 20 mm, or 5 mm to 15 mm.

[0215] In this way, when the polymer mixed with the surfactant is atomized while controlling agglomeration using a micronizing device, a smaller particle size distribution is realized, so that subsequent drying and grinding processes can be performed under milder conditions, thereby preventing the generation of fine particles and improving the properties of the superabsorbent resin. In addition, if ultra-fine grinding is performed, the absorption rate can be improved by simultaneously forming appropriate micropores on the surface of the polymer and increasing the surface area.

[0216] The above atomization step may be performed one or more times, preferably one to six times, one to four times, or one to three times. This may be performed using a plurality of atomization devices, a single atomization device comprising a plurality of porous plates and / or a plurality of cutter elements, or some of the plurality of atomization devices may comprise a plurality of porous plates and / or a plurality of cutter elements.

[0217] According to one embodiment of the present invention, a surfactant may be additionally used in the atomization step, whereby agglomeration between polymer particles can be effectively controlled, thereby reducing the load on the equipment used in the pulverization process and further improving productivity.

[0218] Preferably, the surfactant may be a compound represented by the following chemical formula 2 or a salt thereof, but the present invention is not limited thereto:

[0219] [Chemical Formula 2]

[0220]

[0221] In the above chemical formula 2,

[0222] A1, A2 and A3 are each independently a single bond, carbonyl, , or and, provided that at least one of these is carbonyl or , wherein, m1, m2 and m3 are each independently an integer from 1 to 8, are each connected to an adjacent oxygen atom, are connected to adjacent R1, R2 and R3 respectively,

[0223] R1, R2 and R3 are each independently hydrogen, straight or branched chain alkyl having 6 to 18 carbon atoms or straight or branched chain alkenyl having 6 to 18 carbon atoms,

[0224] n is an integer from 1 to 9.

[0225] The above surfactant is added so that the atomization step can be easily achieved without agglomeration by mixing with the polymer.

[0226] The surfactant represented by the above chemical formula 2 is a nonionic surfactant, and has excellent surface adsorption performance by hydrogen bonding even with a polymer that is not neutralized, and is therefore suitable for implementing the desired coagulation control effect. On the other hand, in the case of anionic surfactants, not nonionic surfactants, when mixed with a polymer that has been neutralized with a neutralizing agent such as NaOH or Na2SO4, the Na ionized in the carboxyl group substituent of the polymer + It is adsorbed through ions, and when mixed with an unsaturated polymer, there is a problem that the adsorption efficiency for the polymer is relatively reduced due to competition with the anion of the carboxyl group substituent of the polymer.

[0227] Specifically, in the surfactant represented by the above chemical formula 2, the hydrophobic functional group is the terminal functional group R1, R2, R3 portion (if not hydrogen), and the hydrophilic functional group is the glycerol-derived portion in the chain and the terminal hydroxyl group (A n is a single bond, and at the same time R n When the polymer is hydrogen, n=1~3) is further included, and the glycerol-derived portion and the terminal hydroxyl group serve as hydrophilic functional groups to improve the adsorption performance on the polymer surface. Accordingly, the aggregation of superabsorbent resin particles can be effectively suppressed.

[0228] In the above chemical formula 2, the hydrophobic functional groups R1, R2, and R3 (if not hydrogen) are each independently a straight-chain or branched alkyl having 6 to 18 carbon atoms or a straight-chain or branched alkenyl having 6 to 18 carbon atoms. In this case, if the R1, R2, and R3 portions (if not hydrogen) are alkyl or alkenyl having less than 6 carbon atoms, there is a problem that the agglomeration control of the pulverized particles is not effectively performed due to the short chain length, and if the R1, R2, and R3 portions (if not hydrogen) are alkyl or alkenyl having more than 18 carbon atoms, the mobility of the surfactant may be reduced so that it may not be effectively mixed with the polymer, and there may be a problem that the unit price of the composition increases due to the increase in the cost of the surfactant.

[0229] Preferably, R1, R2, R3 may be hydrogen, or, if it is a straight-chain or branched alkyl having 6 to 18 carbon atoms, 2-methylhexyl, n-heptyl, 2-methylheptyl, n-octyl, n-nonyl, n-decanyl, n-undecanyl, n-dodecanyl, n-tridecanyl, n-tetradecanyl, n-pentadecanyl, n-hexadecanyl, n-heptadecanyl, or n-octadecanyl, or, if it is a straight-chain or branched alkenyl having 6 to 18 carbon atoms, 2-hexenyl, 2-heptenyl, 2-octenyl, 2-nonenyl, n-dekenyl, 2-undekenyl, 2-dodekenyl, 2-tridekenyl, 2-tetradekenyl, 2-pentadekenyl, 2-hexadekenyl, It can be 2-heptadekenyl or 2-octadekenyl.

[0230] The surfactant may be selected from compounds represented by the following chemical formulas 2-1 to 2-14, but is not limited thereto:

[0231] [Chemical Formula 2-1]

[0232]

[0233] [Chemical Formula 2-2]

[0234]

[0235] [Chemical Formula 2-3]

[0236]

[0237] [Chemical Formula 2-4]

[0238]

[0239] [Chemical Formula 2-5]

[0240]

[0241] [Chemical Formula 2-6]

[0242]

[0243] [Chemical Formula 2-7]

[0244]

[0245] [Chemical Formula 2-8]

[0246]

[0247] [Chemical Formula 2-9]

[0248]

[0249] [Chemical Formula 2-10]

[0250]

[0251] [Chemical Formula 2-11]

[0252]

[0253] [Chemical Formula 2-12]

[0254]

[0255] [Chemical Formula 2-13]

[0256]

[0257] [Chemical Formula 2-14]

[0258] .

[0259] Meanwhile, the amount of the surfactant used is not particularly limited, but may be used in an amount of 0.06 g to 0.48 g per 1,000 g of the functional gel polymer depending on productivity or device load conditions.

[0260] If the surfactant is used in an excessively small amount, the surfactant may not be evenly adsorbed on the polymer surface, resulting in re-agglomeration of particles after grinding, or absorption performance, such as water retention capacity and absorbency under pressure, may deteriorate due to the surfactant sharing a large amount with the polymer. On the other hand, if the surfactant is used in an excessive amount, the overall physical properties of the final superabsorbent resin may deteriorate due to a decrease in surface tension.

[0261] Therefore, for example, the surfactant may be used in an amount of 0.06 g or more, 0.1 g or more, or 0.2 g or more, and 0.48 g or less, 0.45 g or less, or 0.4 g or less per 1,000 g of the functional gel polymer. In this case, it is easy to control the superabsorbent resin to have a deodorizing rate of a certain value or more for dimethyl disulfide or dimethyl trisulfide and a surface area to actual volume value of a certain value or more.

[0262] The method for mixing these surfactants into the polymer is not particularly limited, and any method capable of evenly mixing them into the polymer may be appropriately employed. Specifically, the surfactants may be mixed dry, dissolved in a solvent and then mixed in a solution state, or melted and then mixed.

[0263] For example, the surfactant may be mixed in a solution state dissolved in a solvent. Any type of solvent, whether inorganic or organic, may be used, but water is most suitable considering the ease of the drying process and the cost of the solvent recovery system. Furthermore, the solution may be prepared by mixing the surfactant and polymer in a reactor, placing the polymer in a mixer and spraying the solution, or continuously supplying the polymer and solution to a continuously operating mixer for mixing.

[0264] Meanwhile, when the surfactant is mixed in a solution state dissolved in water, it can be used by diluting it into an aqueous solution having a concentration of about 0.01% to 90%.

[0265] For example, if the surfactant is to be used at 0.1 g per 1,000 g of the hydrogel polymer, 100 g of an aqueous solution having a concentration of 0.1%, in which 0.1 g of the surfactant is dissolved in 99.9 g of water, may be used. Alternatively, 10 g of an aqueous solution having a concentration of 1%, in which 0.1 g of the surfactant is dissolved in 9.9 g of water, may be used.

[0266] That is, when using the same amount of surfactant, the water content can be increased or decreased to create an aqueous solution having a desired concentration, and the concentration can be appropriately adjusted in consideration of the properties of the superabsorbent resin to be ultimately manufactured.

[0267] According to one embodiment of the invention, a step of neutralizing at least a portion of the acidic groups of the polymer (step 3) is performed, wherein the atomizing step of step 2 and the neutralizing step of step 3 described above may be performed sequentially, alternately, or simultaneously.

[0268] That is, a neutralizing agent may be added to the polymer to first neutralize the acidic groups, and then a surfactant may be added to the neutralized polymer to micronize the polymer mixed with the surfactant (performed in the order of Step 3->Step 2), or the neutralizing agent and the surfactant may be added to the polymer simultaneously to neutralize and micronize the polymer (perform Steps 2 and 3 simultaneously). Alternatively, the surfactant may be added first and the neutralizing agent may be added later (performed in the order of Step 2->Step 3). Alternatively, the neutralizing agent and the surfactant may be added alternately in a cross-sectional manner. Alternatively, the surfactant may be added first to micronize, the neutralizing agent may be added to neutralize, and then an additional surfactant may be added to the neutralized hydrogel polymer to further perform the micronization process.

[0269] Here, if the neutralization step is performed independently from the atomization step of step 2, it can be performed in a manner in which the additive is added while pulverizing the polymer at the same time. More specifically, a screw-type extruder including a porous plate having a plurality of holes formed therein can be used. The screw-type extruder is a device that performs pulverization under milder conditions compared to the atomization device used in the atomization step described above, and the rotation speed can be about 150 rpm to 500 rpm, and the holes of the porous plate can be about 3 mm to 25 mm, but are not limited thereto.

[0270] The rotation speed of the screw-type extruder and the size of the perforated plate holes affect the discharge state of the superabsorbent resin discharged from the extruder, and the particle shape of the superabsorbent resin may change depending on the discharge state.

[0271] In particular, by adjusting the rotation speed of the screw-type extruder to 150 rpm to 500 rpm, the superabsorbent resin can be controlled to have a deodorizing rate of a certain value or higher for dimethyl disulfide or dimethyl trisulfide and a surface area to actual volume value of a certain value or higher.

[0272] At this time, a basic substance such as sodium hydroxide, potassium hydroxide, or ammonium hydroxide that can neutralize acid groups can be used as a neutralizing agent.

[0273] In addition, the degree of neutralization, which refers to the degree of neutralization of acidic groups contained in the polymer by the neutralizing agent, may be 50 to 90 mol%, 60 to 85 mol%, 65 to 85 mol%, or 65 to 80 mol%. The range of the degree of neutralization may vary depending on the final physical properties, and the absorption rate and absorption performance may be controlled by controlling the degree of neutralization.

[0274] At this time, if the degree of neutralization is excessively high, the absorption capacity of the superabsorbent resin may decrease, and if the concentration of carboxyl groups on the particle surface is excessively low, it may be difficult to properly perform surface cross-linking in subsequent processes, which may reduce the pressure-absorbent properties or liquid permeability. Conversely, if the degree of neutralization is excessively low, not only will the polymer's absorption capacity significantly decrease, but it may also exhibit properties similar to elastic rubber that are difficult to handle.

[0275] Meanwhile, it may be desirable to leave a certain time gap between the introduction of the neutralizing agent and the atomization process to ensure even neutralization of the entire polymer.

[0276] Step 4: Drying

[0277] Next, a step (step 4) is performed to dry the above-mentioned micronized and neutralized polymer to prepare a base resin powder.

[0278] The above step is a step of drying the moisture in the base resin powder, which is a polymer obtained by neutralizing at least a portion of the acidic groups of the polymer and pulverizing the polymer.

[0279] In a conventional method for manufacturing a superabsorbent resin, the drying step is performed so that the moisture content of the base resin powder is about 4 to 20 wt%, about 4 to about 15 wt%, or about 6 to about 13 wt%. However, the present invention is not limited thereto.

[0280] The above step 4 can be performed in a fixed-bed type drying method, a moving type drying method, or a combination thereof.

[0281] According to one embodiment of the invention, step 4 can be performed by static drying.

[0282] The above-mentioned static drying method refers to a method in which the material to be dried is placed on a perforated iron plate or other permeable floor, and hot air is passed through the material from below to dry it.

[0283] Since static drying dries in a plate-like shape without particle movement, it is difficult to achieve uniform drying with a simple flow of hot air. Therefore, static drying requires delicate control of hot air and temperature to obtain a uniform, high-moisture content dried body. In the present invention, by changing the direction of hot air from bottom to top, warping of the plate-like dried body during drying was prevented, thereby preventing hot air from leaking out. In addition, the drying temperature was changed section by section so that the upper, middle, and lower layers within the dried body could be dried uniformly with a moisture content deviation of less than 5%.

[0284] As a device capable of drying using the above-mentioned political drying method, a belt-type dryer may be used, but is not limited thereto.

[0285] In the above-described static drying step, the drying process may be performed at a temperature of about 80°C to 200°C, preferably 90°C to 190°C or 100°C to 180°C. If the drying temperature is lower than 80°C, the drying time may be excessively long, and if the drying temperature is excessively high, exceeding 200°C, a superabsorbent resin having a moisture content lower than the desired moisture content may be obtained. Meanwhile, the drying temperature may refer to the temperature of the hot air used or the internal temperature of the device during the drying process.

[0286] According to one embodiment of the invention, step 4 may be performed by fluid drying.

[0287] The fluidized drying method described above refers to a method of drying in which the material is mechanically stirred during the drying process. The direction in which the hot air passes through the material may be the same as or different from the direction in which the material circulates. Alternatively, the material can be dried by circulating the heat-generating fluid (heat-generating oil) within the dryer and passing it through a separate pipe outside the dryer.

[0288] Devices capable of drying using this fluid drying method include a horizontal-type mixer, a rotary kiln, a paddle dryer, a steam tube dryer, or a generally used fluid dryer.

[0289] In the case of the above-mentioned fluid drying step, the drying process can be performed at a temperature of about 100°C to 300°C, preferably 120°C to 280°C or 150°C to 250°C. If the drying temperature is too low, such as below 100°C, the drying time may be too long, and if the drying temperature is too high, such as exceeding 300°C, the superabsorbent resin polymer chain may be damaged, resulting in a decline in overall physical properties and a superabsorbent resin having a moisture content lower than the desired moisture content may be obtained.

[0290] Step 5: Grinding Stage

[0291] Next, a step of grinding the dried base resin powder is performed.

[0292] Specifically, the above grinding step can be performed by grinding the dry base resin powder to have a particle size of a normal particle level, i.e., a particle size of 150 μm to 850 μm.

[0293] The crusher used for this purpose may be, specifically, a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, a cutter mill, a disc mill, a shred crusher, a crusher, a chopper, or a disc cutter, but is not limited to the examples described above.

[0294] Alternatively, a grinder such as a pin mill, hammer mill, screw mill, roll mill, disc mill or jog mill may be used, but is not limited to the examples described above.

[0295] Meanwhile, in the manufacturing method of the present invention, superabsorbent resin particles having a smaller particle size distribution than in the conventional chopping step can be realized in the micronization step, and since the moisture content after drying is maintained relatively high, even if the pulverization is performed under mild conditions with less pulverizing force, a superabsorbent resin having a very high content of normal particle size of 150 ㎛ to 850 ㎛ can be formed, and the fine powder generation ratio can be greatly reduced.

[0296] The superabsorbent resin particles manufactured as described above may contain superabsorbent resin particles having a particle size of 150 ㎛ to 850 ㎛, i.e., normal particles, in an amount of 80 wt% or more, 85 wt% or more, 89 wt% or more, 90 wt% or more, 92 wt% or more, 93 wt% or more, 94 wt% or more, or 95 wt% or more, based on the total weight. The particle size of these resin particles may be measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 220.3 method.

[0297] In addition, the superabsorbent resin particles may include fine particles having a particle size of less than 150 μm in an amount of about 20 wt% or less, about 18 wt% or less, about 15 wt% or less, about 13 wt% or less, about 12 wt% or less, about 11 wt% or less, about 10 wt% or less, about 9 wt% or less, about 8 wt% or less, or about 5 wt% or less, relative to the total weight. This is in contrast to having fine particles in an amount of more than about 20 wt% to about 30 wt% when producing a superabsorbent resin according to a conventional manufacturing method.

[0298] Additive injection stage

[0299] Meanwhile, according to one embodiment of the invention, a step of adding an additive to the atomized and neutralized polymer may be further included before the drying step (step 4).

[0300] The above additive injection process is a process for improving properties by using additional additives within a range that does not impede the desired effect, and the types of the additives are not particularly limited, and examples thereof include, but are not limited to, a polymerization initiator for removing residual monomers, a permeability improver for improving absorption properties, a fine powder anti-caking agent for recycling the generated fine powder, a fluidity improver, an antioxidant, a neutralizer, a surfactant, etc.

[0301] The above additive injection step may be performed simultaneously with step 2, simultaneously with step 3, after steps 2 and 3, or in at least one or more of these steps. The above additive injection step may be performed multiple times as needed, and may also be performed at least once in each step.

[0302] If the above additive injection step is performed independently from steps 2 and 3, i.e., after steps 2 and 3 and before step 4, it can be performed in such a way that the additive is injected simultaneously with the polymer being crushed.

[0303] The above grinding can be applied in the same manner as the grinding step of step 5 described above, and the additive can be added once or multiple times in the grinding step and mixed with the polymer.

[0304] Classification stage

[0305] Next, after the step of crushing the base resin powder (step 5), a step of classifying the crushed superabsorbent resin particles according to particle size may be further included.

[0306] Surface cross-linking step

[0307] In addition, a step of forming a surface cross-linking layer on at least a portion of the surface of the base resin particles may be further included in the presence of a surface cross-linking agent after the base resin powder has been pulverized (step 5) and / or classified. By this step, the cross-linking polymer contained in the base resin powder may be further cross-linked via the surface cross-linking agent, thereby forming a surface cross-linking layer on at least a portion of the surface of the base resin powder.

[0308] The description of the above surface cross-linking agent can be applied equally to all of the above.

[0309] In addition, there is no limitation on the composition of the method for mixing the surface cross-linking agent with the base resin powder. For example, a method of mixing a composition containing the surface cross-linking agent and the base resin powder by placing them in a reaction tank, a method of spraying the surface cross-linking agent onto the composition, a method of continuously supplying the resin composition and the surface cross-linking agent to a continuously operating mixer, and the like can be used.

[0310] When mixing the surface crosslinking agent and base resin powder, water and methanol may be additionally mixed and added. Adding water and methanol has the advantage of ensuring that the surface crosslinking agent is evenly dispersed throughout the resin composition. The amount of water and methanol added can be appropriately adjusted to ensure even dispersion of the surface crosslinking agent, prevent clumping of the resin composition, and optimize the depth of surface penetration of the crosslinking agent.

[0311] The above surface cross-linking process may be performed at a temperature of about 80°C to about 250°C. More specifically, the surface cross-linking process may be performed at a temperature of about 100°C to about 220°C, or about 120°C to about 200°C, for about 20 minutes to about 2 hours, or about 40 minutes to about 80 minutes. When the above-described surface cross-linking process conditions are met, the surface of the superabsorbent resin particles may be sufficiently cross-linked, thereby increasing the absorbency under pressure.

[0312] The temperature raising means for the above surface crosslinking reaction is not particularly limited.

[0313] Heating can be achieved by supplying a heat medium or directly supplying a heat source. At this time, available heat mediums include, but are not limited to, heated fluids such as steam, hot air, and hot oil. Furthermore, the temperature of the supplied heat medium can be appropriately selected considering the heat medium source, heating rate, and target temperature. Meanwhile, directly supplied heat sources include, but are not limited to, heating via electricity or gas.

[0314] Post-processing step

[0315] According to one embodiment of the present invention, after the step of forming a surface cross-linking layer on at least a portion of the surface of the base resin powder, the method may further include at least one of a cooling step of cooling the superabsorbent resin particles on which the surface cross-linking layer has been formed, a watering step of adding water to the superabsorbent resin particles on which the surface cross-linking layer has been formed, and a post-treatment step of adding an additive to the superabsorbent resin particles on which the surface cross-linking layer has been formed. In this case, the cooling step, the watering step, and the post-treatment step may be performed sequentially or simultaneously.

[0316] In the above-described water step, water or brine can be used, thereby controlling the amount of water generated, etc. The amount of water used can be appropriately adjusted in consideration of the moisture content of the desired final product, etc., and preferably, 0.1 to 10 wt%, 0.5 to 8 wt%, or 1 to 5 wt% can be used relative to the absorbent resin, but is not limited thereto.

[0317] Additionally, after the above-mentioned singer step, a further maturation step can be performed.

[0318] When using brine in the above-mentioned water step, the solution absorption rate is relatively low due to the conductivity of the brine, so that the brine is evenly distributed during the maturation step, enabling even absorption into the absorbent resin. The maturation step may be performed using a commonly used method without any particular limitation, and may be performed, for example, using a rotary stirring device, at a temperature of 100°C or lower, 80°C or lower, and preferably 50°C or lower for 10 minutes to 1 hour.

[0319] The additives added in the above post-processing step may include surfactants, inorganic salts, permeability improvers, anti-caking agents, fluidity improvers, and antioxidants, but the present invention is not limited thereto.

[0320] By selectively performing the above cooling step, water step, and post-treatment step, the moisture content of the final superabsorbent resin can be improved by controlling the occurrence of moisture, etc., and a higher quality superabsorbent resin product can be manufactured.

[0321] The description of the method for producing the superabsorbent resin of the present invention can be applied to the superabsorbent resin of the present invention described above.

[0322] Hereinafter, the functions and effects of the invention will be described in more detail through specific examples. However, these examples are provided merely as examples of the invention and do not define the scope of the invention.

[0323] <Example>

[0324] 1) Example 1

[0325] (Step 1: Polymerization step - Manufacturing step of functional gel polymer)

[0326] In a 2 L glass vessel equipped with a stirrer and a thermometer, 1,000 g of acrylic acid, 2.5 g of pentaerythritol triallyl ether (PETTAE) as an internal cross-linking agent, and 2,260 g of water were mixed with stirring. The reaction temperature was maintained at 5°C. 1,000 cc / min of nitrogen was introduced into the glass vessel containing the mixture for 1 hour to replace the inside of the glass vessel with nitrogen. Thereafter, 13.0 g of a 0.3% aqueous hydrogen peroxide solution, 15.0 g of a 1% aqueous ascorbic acid solution, and 30.0 g of a 2% aqueous 2,2'-azobis amidinopropane dihydrochloride solution were introduced as polymerization initiators. Simultaneously, 15.0 g of a 0.01% aqueous ferrous sulfate solution, as a reducing agent, was added and mixed to initiate polymerization. A polymerization reaction was initiated in the above mixture, and after the temperature of the polymer reached 85°C, a functional gel polymer was manufactured by polymerizing in an oven at 90±2°C for about 6 hours.

[0327] (Steps 2 and 3: Atomization and Neutralization Steps)

[0328] 1,000 g of the hydrogel polymer obtained in Step 1 and 0.1 g of glycerol monolaurate (GML) were dissolved in water at 60°C or higher and fed into a cylindrical grinder in the form of an aqueous solution. Thereafter, the hydrogel polymer was pushed out at a rotation speed of 1,700 rpm through a porous plate having multiple holes of 10 mm in diameter using a high-speed rotary chopper (F-150 / Karl Schnell) mounted inside the cylindrical grinder. Subsequently, the hydrogel polymer was further pushed out at a rotation speed of 1,800 rpm through a porous plate having multiple holes of 10 mm in diameter to obtain a pulverized gel-type hydrogel polymer. Thereafter, the pulverized gel-type hydrogel polymer was pushed out three times through a porous plate having multiple holes of 6 mm in diameter using a screw-type extruder mounted inside the cylindrical grinder at a rotation speed of 250 rpm to obtain hydrogel superabsorbent resin particles.

[0329] At this time, 450 g of a 32% NaOH aqueous solution was added for the first pass through the perforated plate, and 42.8 g of a 0.5% Na2S2O8 aqueous solution (SPS aqueous solution) was added for the second pass and pushed through the perforated plate. For the third pass, the solution was passed through the perforated plate without adding any additives.

[0330] (Step 4: Drying Stage)

[0331] The superabsorbent resin particles obtained as a result of the above grinding were placed on a porous plate capable of vertically transferring airflow, and dried at 120°C for 40 minutes using an air-flow oven.

[0332] Hot air of 200°C and 100°C was sequentially flowed from the top to the bottom for 5 minutes and 10 minutes, respectively, so that the moisture content of the dried superabsorbent resin was approximately 10%, and then hot air of 100°C was flowed from the bottom to the top for 15 minutes to uniformly dry the water-absorbent resin particles, thereby obtaining a dried body.

[0333] (Step 5: Crushing and Classification Stage)

[0334] The above dried body is crushed by a grinder (GRAN-U-LIZER) TM , MPE) and then sieved through a standard mesh sieve of ASTM standards to obtain base resin powder with a size of 150 to 850 μm.

[0335] (Step 6: Surface cross-linking step)

[0336] Next, as described in Table 1 below, for 100 g of the base resin powder, a surface cross-linking agent aqueous solution containing 4 g of water, 6 g of methanol, 0.08 g of ethylene glycol diglycidyl ether (EJ-1030S), 0.1 g of propylene glycol, 0.2 g of aluminum sulfate, and 0.1 g of silica particles (Aerosil 200) was added and mixed. At this time, the surface cross-linking agent aqueous solution was mixed so as to be evenly distributed on the superabsorbent resin powder.

[0337] Next, the base resin powder mixed with the surface cross-linking solution was placed in a surface cross-linking reactor, and a surface cross-linking reaction was performed to obtain a surface-cross-linked superabsorbent resin.

[0338] Specifically, within the surface crosslinking reactor, the base resin powder underwent a surface crosslinking reaction at 140°C for 50 minutes.

[0339] After the surface cross-linking step, the surface-cross-linked superabsorbent resin was classified through a standard mesh sieve according to ASTM standards to produce a superabsorbent resin having a particle size of 150 μm to 850 μm.

[0340] 2) Example 2

[0341] (Step 1: Polymerization step - Manufacturing step of functional gel polymer)

[0342] A functional gel polymer was prepared using the same method as in Example 1.

[0343] (Steps 2 and 3: Atomization and Neutralization Steps)

[0344] 1,000 g of the hydrogel polymer obtained in Step 1 and 0.1 g of glycerol monolaurate (GML) were dissolved in water at 60°C or higher and fed into a cylindrical grinder in the form of an aqueous solution. Thereafter, the hydrogel polymer was extruded at a rotation speed of 1,500 rpm through a porous plate having multiple holes of 8 mm in diameter using a high-speed rotary chopper (F-150 / Karl Schnell) mounted inside the cylindrical grinder. Subsequently, the hydrogel polymer was further extruded at a rotation speed of 2,600 rpm through a porous plate having multiple holes of 10 mm in diameter to obtain a pulverized gel-type hydrogel polymer. Thereafter, the pulverized gel-type hydrogel polymer was extruded three times through a porous plate having multiple holes of 6 mm in diameter using a screw-type extruder mounted inside the cylindrical grinder at a rotation speed of 250 rpm to obtain hydrogel superabsorbent resin particles.

[0345] At this time, 385 g of 32% NaOH aqueous solution was added for the first pass through the perforated plate, and 42.8 g of 0.5% Na2S2O8 aqueous solution (SPS aqueous solution) was added for the second pass and pushed through the perforated plate. For the third pass, the solution was passed through the perforated plate without adding any additives.

[0346] (Step 4: Drying Stage)

[0347] The functional superabsorbent resin particles were uniformly dried in the same manner as in Example 1 to obtain a dried product.

[0348] (Step 5: Crushing and Classification Stage)

[0349] The above dried body is crushed by a grinder (GRAN-U-LIZER) TM , MPE) and then sieved through a standard mesh sieve of ASTM standards to obtain base resin powder with a size of 150 to 850 μm.

[0350] (Step 6: Surface cross-linking step)

[0351] The superabsorbent resin of Example 2 was manufactured by carrying out the surface crosslinking step in the same manner as in Example 1, except that the components and contents of the surface crosslinking agent aqueous solution were prepared as described in Table 1 below.

[0352] 3) Example 3

[0353] (Step 1: Polymerization step - Manufacturing step of functional gel polymer)

[0354] A functional gel polymer was prepared using the same method as in Example 1.

[0355] (Steps 2 and 3: Atomization and Neutralization Steps)

[0356] In Example 1, superabsorbent resin particles were obtained in the same manner as in Example 1, except that instead of adding 450 g of 32% NaOH aqueous solution per pass through the porous plate in Example 1, 420 g of 32% NaOH aqueous solution was added.

[0357] (Step 4: Drying Stage)

[0358] The functional superabsorbent resin particles were uniformly dried in the same manner as in Example 1 to obtain a dried product.

[0359] (Step 5: Crushing and Classification Stage)

[0360] The above dried body is crushed by a grinder (GRAN-U-LIZER) TM , MPE) and then sieved through a standard mesh sieve of ASTM standards to obtain base resin powder with a size of 150 to 850 μm.

[0361] (Step 6: Surface cross-linking step)

[0362] The superabsorbent resin of Example 3 was manufactured by carrying out the surface crosslinking step in the same manner as in Example 1, except that the components and contents of the surface crosslinking agent aqueous solution were prepared as described in Table 1 below.

[0363] 4) Comparative Example 1

[0364] (Step 1: Polymerization step - Manufacturing step of functional gel polymer)

[0365] A functional gel polymer was prepared using the same method as in Example 1.

[0366] (Steps 2 and 3: Atomization and Neutralization Steps)

[0367] 1,000 g of the hydrogel polymer obtained in Step 1 and 0.1 g of glycerol monolaurate (GML) were dissolved in water at 60°C or higher and fed into a cylindrical grinder in the form of an aqueous solution. Thereafter, the hydrogel polymer was extruded at a rotation speed of 1,800 rpm through a porous plate having multiple holes of 10 mm in diameter using a high-speed rotary chopper (F-150 / Karl Schnell) mounted inside the cylindrical grinder. Subsequently, the hydrogel polymer was further extruded at a rotation speed of 2,200 rpm through a porous plate having multiple holes of 10 mm in diameter to obtain a pulverized gel-type hydrogel polymer. Thereafter, the pulverized gel-type hydrogel polymer was extruded three times through a porous plate having multiple holes of 6 mm in diameter using a screw-type extruder mounted inside the cylindrical grinder at a rotation speed of 250 rpm to obtain hydrogel superabsorbent resin particles.

[0368] At this time, 330 g of 32% NaOH aqueous solution was added for the first pass through the perforated plate, and 42.8 g of 0.5% Na2S2O8 aqueous solution (SPS aqueous solution) was added for the second pass and pushed through the perforated plate. For the third pass, the solution was passed through the perforated plate without adding any additives.

[0369] (Step 4: Drying Stage)

[0370] The functional superabsorbent resin particles were uniformly dried in the same manner as in Example 1 to obtain a dried product.

[0371] (Step 5: Crushing and Classification Stage)

[0372] The above dried body is crushed by a grinder (GRAN-U-LIZER) TM, MPE) and then sieved through a standard mesh sieve of ASTM standards to obtain base resin powder with a size of 150 to 850 μm.

[0373] (Step 6: Surface cross-linking step)

[0374] A superabsorbent resin of Comparative Example 1 was manufactured by carrying out the surface crosslinking step in the same manner as in Example 1, except that the components and contents of the surface crosslinking agent aqueous solution were prepared as described in Table 1 below.

[0375] 5) Comparative Example 2

[0376] (Step 1: Polymerization step - Manufacturing step of functional gel polymer)

[0377] A functional gel polymer was prepared using the same method as in Example 1.

[0378] (Steps 2 and 3: Atomization and Neutralization Steps)

[0379] In Example 1, superabsorbent resin particles were obtained in the same manner as in Example 1, except that instead of adding 450 g of a 32% NaOH aqueous solution per pass through the porous plate in Example 1, 310 g of a 32% NaOH aqueous solution was added.

[0380] (Step 4: Drying Stage)

[0381] The functional superabsorbent resin particles were uniformly dried in the same manner as in Example 1 to obtain a dried product.

[0382] (Step 5: Crushing and Classification Stage)

[0383] The above dried body is crushed by a grinder (GRAN-U-LIZER) TM , MPE) and then sieved through a standard mesh sieve of ASTM standards to obtain base resin powder with a size of 150 to 850 μm.

[0384] (Step 6: Surface cross-linking step)

[0385] A superabsorbent resin of Comparative Example 2 was manufactured by carrying out the surface crosslinking step in the same manner as in Example 1, except that the components and contents of the surface crosslinking agent aqueous solution were prepared as described in Table 1 below.

[0386] 6) Comparative Example 3

[0387] (Step 1: Polymerization step - Manufacturing step of functional gel polymer)

[0388] A functional gel polymer was prepared using the same method as in Example 1.

[0389] (Steps 2 and 3: Atomization and Neutralization Steps)

[0390] 1,000 g of the hydrogel polymer obtained in Step 1 and 0.1 g of glycerol monolaurate (GML) were dissolved in water at 60°C or higher and fed into a cylindrical grinder in the form of an aqueous solution. Thereafter, the hydrogel polymer was pushed out at a rotation speed of 1,500 rpm through a porous plate having multiple holes of 10 mm in diameter using a high-speed rotary chopper (F-150 / Karl Schnell) mounted inside the cylindrical grinder. Subsequently, the hydrogel polymer was further pushed out at a rotation speed of 2,700 rpm through a porous plate having multiple holes of 8 mm in diameter to obtain a pulverized gel-type hydrogel polymer. Thereafter, the pulverized gel-type hydrogel polymer was pushed out three times through a porous plate having multiple holes of 6 mm in diameter using a screw-type extruder mounted inside the cylindrical grinder at a rotation speed of 250 rpm to obtain hydrogel superabsorbent resin particles.

[0391] At this time, 325 g of 32% NaOH aqueous solution was added for the first pass through the perforated plate, and 42.8 g of 0.5% Na2S2O8 aqueous solution (SPS aqueous solution) was added for the second pass and pushed through the perforated plate. For the third pass, the solution was passed through the perforated plate without adding any additives.

[0392] (Step 4: Drying Stage)

[0393] The functional superabsorbent resin particles were uniformly dried in the same manner as in Example 1 to obtain a dried product.

[0394] (Step 5: Crushing and Classification Stage)

[0395] The above dried body is crushed by a grinder (GRAN-U-LIZER) TM , MPE) and then sieved through a standard mesh sieve of ASTM standards to obtain base resin powder with a size of 150 to 850 μm.

[0396] (Step 6: Surface cross-linking step)

[0397] A superabsorbent resin of Comparative Example 3 was manufactured by carrying out the surface crosslinking step in the same manner as in Example 1, except that the components and contents of the surface crosslinking agent aqueous solution were prepared as described in Table 1 below.

[0398] ABCDEFG Example 1460.080.10.2-0.1 Example 2560.080.10.20.030.25 Example 3460.080.1-0.10.15 Comparative Example 1660.10.1--0.25 Comparative Example 2560.10.10.40.030.1 Comparative Example 3560.10.10.10.20.05

[0399] The materials A to G in the above Table 1 are as follows, and in the above Table 1, '-' means a component not included in the surface cross-linking agent aqueous solution, and the unit of each number is g. That is, the above Table 1 means the amount of material used per 100 g of the base resin powder. A: Water

[0400] B: Methanol

[0401] C: Ethylene glycol diglycidyl ether

[0402] D: Propylene glycol

[0403] E: Aluminum sulfate

[0404] F: Sucrose stearate

[0405] G: Silica

[0406] <Experimental Example 1> - Deodorization Rate Evaluation

[0407] The deodorizing efficacy of superabsorbent resin was evaluated for four types of odor standard substances.

[0408] Dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), diacetyl, and isovaleraldehyde were used as odor standards.

[0409] A mixed solution was prepared by sufficiently dissolving dimethyl disulfide (DMDS, CAS No.: 624-92-0), dimethyl trisulfide (DMTS, CAS No.: 3658-80-8), diacetyl (Diacetyl, CAS No.: 431-03-8), and isovaleraldehyde (isovaleraldehyde, CAS 58-41 2022-07-26 No. 590-86-3) in physiological saline solution to have a concentration within the range of 30 μg / mL to 250 μg / mL, respectively.

[0410] Next, a solution of an odor standard substance was prepared by mixing it with a 0.9 wt% NaCl aqueous solution at a volume ratio of 1:1000 (mixed solution: NaCl aqueous solution). A 0.9 wt% NaCl solution was used as the physiological saline solution.

[0411] Next, 80 mg of the superabsorbent resin of Example 1 was placed in a 20 mL vial, and 2 mL of the odor standard substance solution was injected.

[0412] The above vial was sealed and maintained at a temperature of 35°C for approximately 2 hours. The injection of the above odor standard material solution and the maintenance at 35°C for 2 hours were performed using a PAL RTC automatic injection system from CTC.

[0413] Using the Solid Phase Micro Extraction (SPME) Arrow (Carbon WR / PDMS Fiber) mounted on the above PAL RTC automatic injection system, the odor standard substance was adsorbed at a temperature in the range of 30°C to 40°C for about 15 minutes, and the peak area of ​​the odor standard substance after the adsorption was confirmed using Gas Chromatography-Mass Spectrometry (GC-MS). As the GC-MS system, the 8890 GC / 5977B MSD from Agilent was used. The SPME Arrow mounted on the PAL RTC was injected into the Split / Splitless inlet, and the DB-624 Ultra Inert (UI) was used as the column.

[0414] During the measurement, He gas was used as the mobile phase, and the sample adsorbed in SPME (Solid Phase Micro Extraction) was desorbed by setting the heater temperature of the sample inlet to around 250°C during injection.

[0415] Afterwards, the deodorization rate for each odor standard substance was confirmed using Equation 1 below.

[0416] [Formula 1]

[0417] Deodorization rate (%) = (1- Cs / Co) Х 100

[0418] In the above formula 1, Cs is the peak area of ​​the odor standard substance in the gas chromatography-mass spectrometry (GC-MS) graph for the odor standard substance solution that was in contact with the superabsorbent resin of Example 1 for 2 hours at 35°C, and Co is the peak area of ​​the odor standard substance in the gas chromatography-mass spectrometry graph for the odor standard substance solution that was in contact with the control group for 2 hours at 35°C.

[0419] As the control group, LG Chemical's GS4800, a general-purpose superabsorbent resin, was used.

[0420] The deodorization rate was obtained using the same method for the superabsorbent resins of Examples 2 and 3 and Comparative Examples.

[0421] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 DMDS-23-61558-55-36 DMTS63522-8-60-58 Diacetyl 144675-143-2 Isovaleraldehyde 196183-30-22-45

[0422] <Experimental Example 2> - Measurement of surface area relative to actual volume of superabsorbent resin

[0423] The surface area per actual volume of the superabsorbent resin of Example 1 was obtained according to steps 1 to 3 below.

[0424] - Step 1) Drying and sampling of superabsorbent resin

[0425] The superabsorbent resin of Example 1 was dried at about 100°C for about 12 hours, and the dried superabsorbent resin was sampled in a size of 1.5 cm x 1.5 cm x 1.5 cm (width x length x height).

[0426] - Step 2) Image extraction

[0427] The superabsorbent resin of the sampled Example 1 was analyzed using XRM (ZEISS Xradia 620 Versa) under the following conditions to derive a 3D image of the superabsorbent resin.

[0428] <Conditions>

[0429] X-Ray Energy: 70 kV

[0430] detector: Flat Pane

[0431] Voxel Size: 5 ㎛

[0432] Measurement time: 0.05 s / frame

[0433] Total images: 4501

[0434] - Step 3) Surface area to actual volume (S) SAP / V C ) is derived

[0435] 1) The area of ​​interest (measurement area) was set and cut out from the 2D image of the XRM cross-section of the superabsorbent resin of Example 1 that was 3D reconstructed.

[0436] 2) Apply Gaussian blur to the cropped 2D cross-sectional image to remove noise. Next, Otsu's thresholding method is used to convert the 2D cross-sectional image into a binarized image to distinguish the background image from the superabsorbent resin particle image. This process is repeatedly applied to all 2D images of the measurement target to obtain a 2D cross-sectional image showing the separated superabsorbent resin particles.

[0437] 3) The above multiple 2D cross-sectional images were stacked and 3D rendering was performed.

[0438] 4) The volume (V) of the entire particles of the superabsorbent resin of Example 1 was calculated from the 3D rendered volume data. C ) was measured. In addition, considering the connectivity of the 3D rendered image, the surface area (S) of the entire superabsorbent resin particles of Example 1 excluding the surface area of ​​the closed pore region was measured. SAP ) was measured. The surface area (S) of the superabsorbent resin particles of Example 1 SAP ) is the volume (V) of the total particles of the superabsorbent resin of Example 1. C ) was divided into the actual volume and the surface area of ​​the superabsorbent resin of Example 1 was derived.

[0439] The results are shown in Table 3 below.

[0440] The surface area per actual volume was obtained for the superabsorbent resins of Examples 2 and 3 and Comparative Examples using the same method.

[0441] Surface area to actual volume (mm) -1 )Example 154.2Example 247.3Example 355.3Comparative Example 134.7Comparative Example 239.9Comparative Example 335.1

[0442] <Experimental Example 3> - Measurement of convexity and CE diameter

[0443] Additionally, the convexity and CE diameter of the superabsorbent resin particles manufactured in the above examples and comparative examples were measured using the following method, and the results are listed in Table 3 below.

[0444] Unless otherwise specified, all of the following property evaluations were conducted under constant temperature and humidity (23±1℃, relative humidity 50±10%), and saline solution or saline refers to a 0.9 wt% sodium chloride (NaCl) aqueous solution.

[0445] After the sample to be measured was left under constant temperature and humidity conditions for 24 hours, each property was evaluated.

[0446] For the superabsorbent resins of the above examples and comparative examples, the convexity and CE diameter were measured using a morphologi 4 from Malvern Panalytical using the following method.

[0447] 1) Sample Preparation: A 1 g particle sample of the superabsorbent resin to be measured was prepared. At this time, the superabsorbent resin was classified using a particle classifier from Retsch at 1.0 amplitude for 10 minutes to separate 1 g of the sample into individual particles with a particle size of 300 μm to 600 μm without damage to the particles. The setting values ​​of the Sample Dispersion Unit at this time are as shown in Fig. 1.

[0448] 2) Image acquisition: The prepared sample was placed on the stage within the equipment and scanned at 2.5x magnification to acquire images of individual particles. At this time, the Illumination Setting value and Optics Selection Setting value were as shown in Figures 2 and 3, respectively.

[0449] 3) Image processing: For the acquired images, the parameter values ​​such as the 3D image of the 3D particle for each particle was captured as a 2D image, the CE diameter (Circle Equivalent diameter), the shortest diameter, the longest diameter, the actual particle perimeter, and the convex hull perimeter were measured. At this time, the Scan Area setting value was as shown in Fig. 4, and the particle was measured without setting the Filtering value.

[0450] 4) Based on the data analyzed for each particle, convexity and CE diameter values ​​for all particles included in the sample were obtained.

[0451] Among these, the average value of convexity and CE diameter (Circle Equivalent diameter) calculated by Equation 2 below are listed in Table 4 below.

[0452] [Formula 2]

[0453] M c = L s / L

[0454] In the above equation 2,

[0455] M c is convexity,

[0456] L s refers to the length of an elastic band when it is assumed that the 3D image of the 3D particle to be measured is surrounded by an imaginary elastic band that stretches around the contour of the captured 2D image.

[0457] L represents the actual circumference of the image captured as a 2D image of the 3D image of the 3D particle to be measured.

[0458] Convexity Average CE Diameter Average (㎛) Example 10.87412 Example 20.88425 Example 30.91399 Comparative Example 10.92321 Comparative Example 20.92326 Comparative Example 30.91420

[0459] <Experimental Example 4> - Physical Property Evaluation

[0460] The properties of the superabsorbent resins manufactured in the above examples and comparative examples were evaluated using the following methods and are listed in Table 4 below.

[0461] Unless otherwise specified, all of the following property evaluations were conducted under constant temperature and humidity (23±1℃, relative humidity 50±10%), and saline solution or saline refers to a 0.9 wt% sodium chloride (NaCl) aqueous solution.

[0462] After the sample to be measured was left under constant temperature and humidity conditions for 24 hours, each property was evaluated.

[0463] (1) Centrifuge Retention Capacity (CRC, g / g)

[0464] The water retention capacity of the superabsorbent resins of the above examples and comparative examples by the absorption rate under no load was measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 241.3.

[0465] Measurements were performed at a temperature of 23±2℃ and a relative humidity of 45±15% as described in EDANA WSP 241.0.

[0466] Specifically, the superabsorbent resin W0(g) (approximately 0.2 g) obtained through each of the examples and comparative examples was uniformly placed in a non-woven bag, sealed, and then immersed in a saline solution (0.9 wt%) at room temperature. After 30 minutes, water was removed from the bag for 3 minutes using a centrifuge at 250 G, and the mass W2(g) of the bag was measured. In addition, the same operation was performed without using the resin, and the mass W1(g) at that time was measured.

[0467] Using each mass obtained, CRC (g / g) was calculated according to the following mathematical formula 1.

[0468] [Mathematical Formula 1]

[0469] CRC (g / g) = {[W2(g) - W1(g)] / W0(g)} - 1

[0470] The above measurement was repeated five times, and the average value and standard deviation were calculated.

[0471] (2) Absorbency under Pressure (AUP: Absorbency under Pressure, g / g)

[0472] The pressurized absorption capacity of 2.07 kPa (0.3 psi) of the superabsorbent resins of the above examples and comparative examples was measured according to the EDANA method WSP 242.3.

[0473] Measurements were performed at a temperature of 23±2℃ and a relative humidity of 45±15% as described in EDANA WSP 242.0.

[0474] Specifically, a 400-mesh stainless steel wire mesh was installed on the bottom of a plastic cylinder with an inner diameter of 25 mm. Under conditions of room temperature and 50% humidity, superabsorbent resin W3 (g) (0.9 g) was uniformly sprayed on the wire mesh, and a piston capable of uniformly applying a load of 2.07 kPa (0.3 psi) was installed on top of it, with an outer diameter slightly smaller than 25 mm, without a gap with the inner wall of the cylinder, and without impeding up-and-down movement. At this time, the weight W4 (g) of the device was measured.

[0475] A glass filter with a diameter of 90 mm and a thickness of 5 mm was placed inside a petri dish with a diameter of 150 mm, and a saline solution consisting of 0.9 wt% sodium chloride was placed so that it was level with the upper surface of the glass filter. A sheet of filter paper with a diameter of 90 mm was placed on top of it. The measuring device was placed on the filter paper, and the liquid was absorbed under a load for 1 hour. After 1 hour, the measuring device was lifted, and its weight W5 (g) was measured.

[0476] Using each mass obtained, the pressurized absorbency (g / g) was calculated according to the following mathematical formula 2.

[0477] [Equation 2]

[0478] AUP(g / g) = [W5(g) - W4(g)] / W3(g)

[0479] The above measurement was repeated five times, and the average value and standard deviation were calculated.

[0480] (3) Vortex time

[0481] The vortex time of the superabsorbent resins of the above examples and comparative examples was measured by the following method.

[0482] 1) First, 50 mL of 0.9% saline solution was added to a 100 mL beaker with a flat bottom using a 100 mL mass cylinder.

[0483] 2) Next, the beaker was placed in the center of the magnetic stirrer, and a circular magnetic bar (diameter 30 mm) was placed inside the beaker.

[0484] 3) Afterwards, the stirrer was operated so that the magnetic bar stirred at 600 rpm, and the lowest part of the vortex created by stirring was made to touch the top of the magnetic bar.

[0485] 4) After confirming that the temperature of the brine in the beaker reached 24.0℃, 2±0.01 g of superabsorbent resin sample was added, and the stopwatch was simultaneously operated. The time until the vortex disappeared and the liquid surface became completely horizontal was measured in seconds, and this was designated as the vortex time.

[0486] (4) 1-minute water absorption capacity (WFA) in water with an electrical conductivity value of 110 μS / cm 110 )

[0487] For the superabsorbent resins of the examples and comparative examples, the 1-minute absorption capacity (WFA) in water having an electrical conductivity value of 110 μS / cm at 24°C was measured using the following method. 110 ) was measured. The specific measurement process was as follows.

[0488] 1.0 g (W6) of the superabsorbent resins of the examples and comparative examples were placed in a nonwoven bag (18 cm Х 28 cm) and immersed in 1000 mL of water having an electrical conductivity of 110 μS / cm at 24°C for 1 minute. After 1 minute, the bag was taken out of the water having an electrical conductivity of 110 μS / cm, hung, and left for 1 minute. Thereafter, the mass (W8) of the bag was measured. In addition, the same operation was performed without using the superabsorbent resin, and the mass at that time (W7) was measured. Using each mass thus obtained, the 1-minute absorbency (g / g) in water having an electrical conductivity of 110 μS / cm was calculated according to the following mathematical equation 3.

[0489] [Equation 3]

[0490] WFA 110 (g / g) = {[W8(g) - W7(g) - W6(g)] / W6(g)}

[0491] CRC (g / g)AUP (g / g)Vortex time (sec)WFA 110 (g / g) Example 1 38.7 32.2 17 190 Example 2 31.3 29.12 3 143 Example 3 35.2 33.135 185 Comparative Example 1 40.5 22.14 3 111 Comparative Example 2 39.12 6.0 40 102 Comparative Example 3 38.12 7.6 4 2 120

[0492] As can be seen from Tables 2 to 5 above, the superabsorbent resin according to the embodiment of the present invention has a deodorizing effect for dimethyl disulfide or dimethyl trisulfide, and at the same time has excellent absorption performance such as water retention capacity, pressurized absorption capacity, and absorption speed with a surface area relative to the actual volume being at a certain level or higher.

[0493] The present invention can be applied to superabsorbent resins.

Claims

1. As a polyacrylic acid (salt)-based superabsorbent resin, Surface area to actual volume is 45 mm -1 That's all, A super absorbent resin having a deodorizing rate of 40% or more according to the following formula 1 for dimethyl disulfide (DMDS) or dimethyl trisulfide (DMTS): [Formula 1] Deodorization rate (%) = (1- Cs / Co) × 100 In the above equation 1, Cs is the peak area of ​​the odor standard substance in the gas chromatography-mass spectrometry (GC-MS) graph for the odor standard substance solution that was in contact with the superabsorbent resin at 35°C for 2 hours, and Co is the peak area of ​​the odor standard substance in the gas chromatography-mass spectrometry graph for the odor standard substance solution that was in contact with the control at 35°C for 2 hours.

2. In paragraph 1, The above superabsorbent resin is a superabsorbent resin having a deodorizing rate of 10% or more for diacetyl.

3. In paragraph 1, The above superabsorbent resin is a superabsorbent resin having a deodorizing rate for isovaleraldehyde of 10% or more.

4. In paragraph 1, The surface area relative to the actual volume is 65 mm -1 Below, super absorbent resin.

5. In paragraph 1, The above superabsorbent resin is a superabsorbent resin in which the average value of convexity calculated by the following equation 2 for all particles is 0.94 or less: [Formula 2] M c = L s / L In the above equation 2, M c is convexity, L s refers to the length of an elastic band when it is assumed that the 3D image of the 3D particle to be measured is surrounded by an imaginary elastic band that stretches around the contour of the captured 2D image. L represents the actual circumference of the image captured as a 2D image of the 3D image of the 3D particle to be measured.

6. In paragraph 1, The above superabsorbent resin is a superabsorbent resin having an average CE diameter (Circle Equivalent diameter) of 220 ㎛ to 450 ㎛.

7. In paragraph 1, The above superabsorbent resin is a superabsorbent resin having a water retention capacity (CRC) of 28 g / g or more as measured according to the method of EDANA method WSP 241.

3.

8. In paragraph 1, The above superabsorbent resin is a superabsorbent resin having an absorbency under pressure (AUP) of 25 g / g or more as measured under 2.07 kPa (0.3 psi) according to EDANA method WSP 242.

3.

9. In paragraph 1, A superabsorbent resin, wherein when the superabsorbent resin is swelled in water having an electrical conductivity of 100 to 130 μS / cm for 1 minute, the maximum capacity of water that the superabsorbent resin can hold (Free Swell Capacity) is 130 g / g or more.

Images