Absorbent materials and hygiene products

Abstract

The present invention relates to an absorbent body and a sanitary product that can contribute to making the absorbent body and the sanitary product thinner by appropriately fixing highly absorbent resin particles in the absorbent body and the sanitary product without using pulp, and that exhibits excellent shape retention even after absorbing moisture, and a sanitary product containing the absorbent body.

Description

[Technical Field]

[0001] [Cross-reference of related applications] This application claims priority rights based on Korean Patent Application No. 10-2022-0153919 dated November 16, 2022, and Korean Patent Application No. 10-2023-0159226 dated November 16, 2023, and all content disclosed in the documents of said Korean Patent Applications is incorporated herein by reference.

[0002] The present invention relates to an absorbent material and sanitary product that can appropriately fix superabsorbent polymer particles within the absorbent material and sanitary product without using pulp, thereby contributing to the thinning of the absorbent material and sanitary product, and that exhibits excellent shape retention even after moisture absorption. [Background technology]

[0003] Generally, various types of sanitary products such as diapers, sanitary napkins, or incontinence pads contain an absorbent material with super absorbent polymer particles. However, such absorbent materials typically consist mainly of these super absorbent polymer particles, and pulp is used to maintain the shape of the absorbent material and the sanitary product while properly fixing these particles.

[0004] However, the presence of such pulp made it difficult to slim down and thin absorbent materials and sanitary products, resulting in problems such as sweat accumulating between the user's skin and the product, leading to poor wearing comfort. Moreover, the need to use large quantities of the aforementioned pulp, which is mainly obtained from wood, goes against the recent trend of environmental protection and has become one of the main reasons for the increased manufacturing cost of the absorbent layers and sanitary products.

[0005] Therefore, many attempts have been made to reduce the amount of pulp used in the absorbent layer and sanitary products, or to provide sanitary products such as so-called pulpless diapers that do not use pulp.

[0006] However, when the amount of pulp used is excessively reduced, the binding strength is low, resulting in multiple tears in the absorbent material. Furthermore, because the superabsorbent polymer particles are not properly fixed within the absorbent material and sanitary products, the absorbent material shifts to specific parts during the transportation of the sanitary products, causing uneven absorption performance and preventing the sanitary products from maintaining their shape properly.

[0007] On the other hand, conventional sanitary products that do not use pulp, such as pulpless diapers, primarily use liquid adhesive compositions to fix the superabsorbent polymer particles instead of pulp. This aims to achieve thinner and slimmer absorbents and sanitary products, as well as lower unit costs due to the absence of pulp. However, in conventional sanitary products, if an excessive amount of adhesive is used, there are disadvantages such as a decrease in the performance of the superabsorbent polymer particles and the absorbent material containing them due to the adhesive, or process problems caused by the migration of the adhesive.

[0008] Conversely, when the amount of adhesive used is reduced, the superabsorbent polymer particles are not properly fixed within the absorbent material and sanitary product, resulting in disadvantages such as uneven absorption performance due to particle migration. Furthermore, the problem of the absorbent material and sanitary product not being able to properly maintain their shape after moisture absorption by the superabsorbent polymer particles has not been resolved.

[0009] Due to these problems with conventional technologies, there is a continuing need for technological development regarding absorbent materials and sanitary products that can appropriately fix superabsorbent polymer particles within the absorbent material and sanitary product without performance degradation, while either eliminating the use of fluff pulp or significantly reducing its use, and that exhibit excellent shape retention even after moisture absorption. [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] This invention relates to an absorbent material that can appropriately fix superabsorbent polymer particles within absorbent materials and sanitary products without using pulp, thereby contributing to the thinning of absorbent materials and sanitary products, and exhibiting excellent shape retention even after moisture absorption.

[0011] The present invention also relates to a sanitary product that includes the absorbent material. [Means for solving the problem]

[0012] To solve the aforementioned problems, the present invention provides First nonwoven fabric and, The second nonwoven fabric, The first and second nonwoven fabrics are interposed to form a superabsorbent resin layer, The superabsorbent resin layer is bonded to the first and second nonwoven fabrics via an adhesive, and does not contain pulp. The following conditions (1) and (2) must be met: Absorbent material.

[0013] (1) The absorbent was vibrated 100 times at a frequency of 65 times / min and an amplitude of 15 mm, and the amount of superabsorbent resin remaining in the absorbent without leakage was measured, and the fixation rate was 90% or more. (2) After dyeing the absorbent material with a dye and drying it, and after confirming that only the superabsorbent resin portion has been selectively dyed, the area of ​​the dyed portion is measured with a colorimeter and the filling rate is 90% or more.

[0014] Furthermore, the present invention provides a sanitary product containing the absorbent material. [Effects of the Invention]

[0015] According to the present invention, an absorbent material is provided that, without using pulp, appropriately fixes a superabsorbent polymer, has excellent shape retention even after moisture absorption, and also has excellent absorption performance. Since the absorbent material does not use pulp, it can have a slimmer and thinner structure, and the manufacturing cost can also be reduced.

[0016] Therefore, the present invention can contribute to slimming, thinning, and enhancing the performance of sanitary products such as diapers, improving the wearing comfort, and significantly reducing the manufacturing cost.

Brief Description of the Drawings

[0017] [Figure 1] FIG. 1 relates to the cross-section of the absorbent body of Example 1 to Example 3, and shows an absorbent body in which a first non-woven fabric 1, an adhesive layer 3, a first coating layer 4 of a superabsorbent resin, a first coating layer 5 of an adhesive, a second coating layer 6 of a superabsorbent resin, a second coating layer 7 of an adhesive, a third coating layer 8 of a superabsorbent resin, an adhesive layer 9, and a second non-woven fabric 2 are sequentially laminated. The above 4 to 8 are superabsorbent resin layers.

Modes for Carrying Out the Invention

[0018] The terms used in this specification are merely used to explain exemplary embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "including", "comprising", or "having" are intended to specify the presence of implemented features, steps, components, or combinations thereof, and it should not be understood that the presence or addition possibility of one or more other features, steps, components, or combinations thereof is precluded in advance.

[0019] The present invention can be subjected to various modifications and can have various forms. Therefore, specific embodiments are illustrated and described in detail below. However, this is not intended to limit the present invention to specific disclosed forms, and it should be understood to include all modifications, equivalents, or alternatives included in the spirit and technical scope of the present invention.

[0020] Also, the technical terms used in this specification are merely for referring to specific embodiments and are not intended to limit the present invention. And the singular forms used here include plural forms unless the context clearly indicates the contrary meaning.

[0021] In the present invention, terms such as first, second, third, etc. are used to describe various components, and these terms are used only for the purpose of distinguishing one component from another.

[0022] The term "polymer" or "macromolecule" used in the specification of the present invention means a state in which an acrylic acid monomer, which is a water-soluble ethylenically unsaturated monomer, is polymerized, and can include any moisture content range or particle size range. Among the polymers, those in the state before drying after polymerization and having a water content (moisture content) of about 40% by weight or more can be referred to as water-containing gel polymers, and particles obtained by pulverizing and drying such water-containing gel polymers can be referred to as crosslinked polymers.

[0023] Also, the term "superabsorbent resin particles" refers to particulate substances containing a crosslinked polymer obtained by polymerizing an acrylic acid monomer containing an acidic group and at least a part of which the acidic group is neutralized and crosslinked with an internal crosslinking agent.

[0024] Also, the term "superabsorbent resin" means, depending on the context, a crosslinked polymer obtained by polymerizing an acrylic acid monomer containing an acidic group and at least a part of which the acidic group is neutralized, or a powdery base resin composed of superabsorbent resin particles obtained by pulverizing the crosslinked polymer, or includes all states in which the crosslinked polymer or the base resin has been made suitable for commercialization through additional processes such as surface crosslinking, micropowder regranulation, drying, pulverization, classification, etc. Therefore, the term "superabsorbent resin" can be interpreted as including a plurality of superabsorbent resin particles.

[0025] As the demand for thin and light diapers increases, research on pulpless diapers that do not contain pulp is being conducted. In pulpless diapers, superabsorbent resin (SAP) must be fixed within the absorbent body of the diaper even when the pulp is removed.

[0026] Therefore, the inventors of the present invention have confirmed that the absorbent material has excellent shape retention and absorption performance by applying an adhesive and a superabsorbent resin sequentially multiple times without using pulp, thereby increasing the fixation rate of the superabsorbent resin, and by uniformly applying the superabsorbent resin inside the absorbent material to improve the filling rate, thereby completing the present invention.

[0027] The absorbent material and sanitary products will be described in more detail below with specific examples of the invention.

[0028] absorbent material An absorbent material according to one embodiment of the present invention comprises a first nonwoven fabric, a second nonwoven fabric, and a superabsorbent resin layer between the first and second nonwoven fabrics, wherein the superabsorbent resin layer is bonded to the first and second nonwoven fabrics via an adhesive, does not contain pulp, and satisfies the following (1) and (2).

[0029] (1) The absorbent was vibrated 100 times at a frequency of 65 times / min and an amplitude of 15 mm, and the amount of superabsorbent resin remaining in the absorbent without leakage was measured, and the fixation rate was 90% or more. (2) After dyeing the absorbent material with a dye and drying it, and after confirming that only the superabsorbent resin portion has been selectively dyed, the area of ​​the dyed portion is measured with a colorimeter and the filling rate is 90% or more.

[0030] Specifically, the absorbent material does not contain pulp, but the superabsorbent resin and adhesive are applied alternately two or more times, allowing the superabsorbent resin to be more firmly fixed within the absorbent material, and this structure can increase the filling rate of the superabsorbent resin within the absorbent material. Therefore, when applying the absorbent material of this embodiment, the movement of the superabsorbent resin particles is suppressed without using pulp or the like, so that the absorbent material and sanitary products exhibit uniform absorption performance, thereby greatly contributing to the thinning, slimming, and lowering of the unit price of the absorbent material and sanitary products containing it.

[0031] At the same time, by applying a structure in which the adhesive and the superabsorbent resin particles are applied alternately, the superabsorbent resin particles can be stably positioned even when using less adhesive composition than before, improving the fixation rate and filling rate, and eliminating the risk of deterioration of the physical properties of the superabsorbent resin particles that occurs when a large amount of adhesive composition is used.

[0032] Therefore, it was confirmed that this particular absorbent material solves the problems of pulp-free hygiene products such as known pulpless diapers, and demonstrates excellent performance, shape retention, and wearing comfort, making it a significant contributor to the thinning and slimming of hygiene products.

[0033] In the absorbent material of the above embodiment, the nonwoven fabric is not particularly limited as long as it is a nonwoven fabric commonly used in absorbents. For example, the nonwoven fabric may consist of a polypropylene nonwoven fabric, a polyethylene nonwoven fabric or a polyolefin multi-component nonwoven fabric (e.g., a PE / PP two-component nonwoven fabric layer), a PLA (Polylactic acid) / PBS (Poly Butyl Succinate) nonwoven fabric, or a variety of other nonwoven fabrics. Since each of these nonwoven fabrics can be manufactured directly by conventional nonwoven fabric manufacturing methods or obtained commercially and used, no further explanation is provided.

[0034] Preferably, the nonwoven fabric does not contain nap. The term "napping" refers to a method of creating fluff on the surface of a fabric by scraping or pulling out fibers, and is not particularly limited as long as it falls under the category of a method typically used for napped fabrics. If the nonwoven fabric contains nap and a superabsorbent polymer is supported between the napped fibers, the fixation rate of the supported superabsorbent polymer may decrease. In a form in which a superabsorbent polymer is supported between the napped fibers, the fixation of the superabsorbent polymer depends solely on adsorption to the napped fibers, but there are limitations to fixing the superabsorbent polymer by adsorption alone.

[0035] The superabsorbent resin layer is constructed by alternately applying and laminating the superabsorbent resin and the adhesive, preferably two or more times, or three or more times, and alternately applying 10 or fewer times, 8 or fewer times, 6 or fewer times, or 5 or fewer times. Furthermore, since the superabsorbent resin layer is bonded to the nonwoven fabric via the adhesive, preferably the uppermost and lowermost layers of the superabsorbent resin layer are coated with superabsorbent resin.

[0036] Preferably, the superabsorbent resin layer may be formed by sequentially laminating a first coating layer of superabsorbent resin, a first coating layer of adhesive, a second coating layer of superabsorbent resin, a second coating layer of adhesive, and a third coating layer of superabsorbent resin.

[0037] Preferably, the thickness of the superabsorbent resin layer may be 5 mm or less, 4 mm or less, or 3 mm or less. The thinner the superabsorbent resin layer, the better the wearing comfort, but as an example, it may be 1 mm or more. If the thickness of the superabsorbent resin layer exceeds 5 mm, there is a problem that it becomes difficult to make the sanitary product thinner and slimmer.

[0038] Preferably, the superabsorbent resin layer has a unit area (m²). 2 It may contain 100g or more of superabsorbent polymer per meter. Preferably, it may be 110g or more, 120g or more, 130g or more, 140g or more, or 150g or more, and 300g or less, 250g or less, 240g or less, 230g or less, 220g or less, 210g or less, or 200g or less. The unit area (m²) of the superabsorbent polymer layer. 2 If the amount of superabsorbent polymer per unit area (m²) is less than 100g, the absolute amount of superabsorbent polymer may be insufficient, potentially reducing absorption performance. 2 If the superabsorbent polymer content per unit exceeds 300g, the volume of the superabsorbent polymer layer increases, making it difficult to thin and slim down the absorbent.

[0039] On the other hand, the fixation rate is 90% or more when the absorbent is vibrated 100 times at a frequency of 65 times / min and an amplitude of 15 mm, and the amount of superabsorbent resin remaining in the absorbent without leakage is measured. Preferably, the fixation rate may be 95% or more, 97% or more, 98% or more, 99% or more, or 99.1% or more, or 100% or less.

[0040] After dyeing the absorbent material with a dye and drying it, and confirming that only the superabsorbent resin portion has been selectively dyed, the filling rate measured by colorimeter of the dyed portion is 90% or more. Preferably, the filling rate may be 95% or more, 97% or more, 98% or more, 99% or more, or 99.5% or more, or 100% or less.

[0041] On the other hand, the superabsorbent resin contained in the absorbent material of the present invention is as follows.

[0042] The superabsorbent resin comprises a base resin containing an acrylic acid monomer and an internal crosslinking agent, wherein the acidic groups are neutralized in part, and the crosslinked polymer comprises an acrylic acid monomer and an internal crosslinking agent, and a surface crosslinked layer formed on the base resin, wherein the crosslinked polymer is further crosslinked via a surface crosslinking agent.

[0043] The superabsorbent polymer may have a water retention capacity (CRC) of 32 g / g to 40 g / g as measured by EDANA NWSP 241.0.R2(15). Preferably, the water retention capacity of the superabsorbent polymer may be 32 g / g or more, 33 g / g or more, or 33.4 g / g or more, and 40 g / g or less, 39 g / g or less, or 38.7 g / g or less. If the water retention capacity of the superabsorbent polymer is less than 32 g / g, there is a problem that the rewetting performance and absorbency will decrease. If the water retention capacity of the superabsorbent polymer is more than 40 g / g, there is a problem that not only is it difficult to manufacture the superabsorbent polymer, but the pressurizing performance will decrease and the rewetting characteristics will deteriorate.

[0044] The superabsorbent polymer may have a water-soluble component of 10% by weight or less as measured after 16 hours of swelling, as measured by EDANA NWSP 270.0.R2(15). Preferably, the water-soluble component of the superabsorbent polymer as measured after 16 hours of swelling may be 9% by weight or less, 8% by weight or less, or 7.7% by weight or less, and also 1% by weight or more, 3% by weight or more, or 5% by weight or more.

[0045] The superabsorbent polymer may have an absorption rate (vortex time) of 30 seconds or less by the vortex method. Preferably, it may be 29 seconds or less, or 28 seconds or less. Furthermore, the smaller the absorption rate, the better the performance. Theoretically, the lower limit of the absorption rate is 0 seconds, but as an example, it may be 10 seconds or more, 15 seconds or more, 18 seconds or more, 20 seconds or more, 21 seconds or more, or 22 seconds or more. If the absorption rate of the superabsorbent polymer exceeds 30 seconds, there is a problem that the rewetting performance will also decrease. Superabsorbent polymers with an absorption rate of less than 10 seconds are not only difficult to manufacture, but also difficult to diffuse inside the diaper during manufacturing, so they are absorbed locally, and there is a risk that the core will rupture or aggregate. In this case, the method for measuring the absorption rate of the superabsorbent polymer will be explained in more detail in the experimental examples described later.

[0046] The superabsorbent polymer may have a bulk density of 0.55 g / ml or more and 0.65 g / ml or less, as measured by EDANA NWSP 251.0.R2(15). Preferably, the bulk density of the superabsorbent polymer may be 0.56 g / ml or more, 0.57 g / ml or more, or 0.58 g / ml or more, and 0.63 g / ml or less, 0.62 g / ml or less, or 0.60 g / ml or less.

[0047] Since the same weight of superabsorbent polymer is used in the manufacture of diapers, if the bulk density is less than 0.55 g / ml, the volume of the superabsorbent polymer may increase, potentially causing gel blocking. If it exceeds 0.65 g / ml, the particle volume within the same weight may decrease, potentially reducing the absorption rate.

[0048] On the other hand, the acrylic acid monomer is a compound represented by the following chemical formula 1.

[0049] [Chemical formula 1] R 1 -COOM 1

[0050] In the aforementioned chemical formula 1, R 1 This is an alkyl group having 2 to 5 carbon atoms and containing an unsaturated bond. M 1 This is a hydrogen atom, a monovalent or divalent metal, an ammonium group, or an organic amine salt.

[0051] Preferably, the acrylic acid monomer comprises acrylic acid, methacrylic acid, and one or more selected from the group consisting of monovalent metal salts, divalent metal salts, ammonium salts, and organic amine salts thereof.

[0052] Here, the acrylic acid monomer may have an acidic group, and at least a portion of the acidic group may be neutralized. Preferably, the monomer may be partially neutralized with an alkaline substance such as sodium hydroxide, potassium hydroxide, or ammonium hydroxide. In this case, the degree of neutralization of the acrylic acid monomer may be 40 to 95 mol%, or 40 to 80 mol%, or 45 to 75 mol%. The range of the degree of neutralization can be adjusted depending on the final physical properties. However, if the degree of neutralization is excessively high, the neutralized monomer may precipitate, making polymerization difficult. Conversely, if the degree of neutralization is excessively low, not only will the absorption capacity of the polymer decrease significantly, but it may also exhibit properties similar to an elastic rubber that is difficult to handle.

[0053] The concentration of the acrylic acid monomer may be about 20 to about 60% by weight, preferably about 40 to about 50% by weight, relative to the monomer composition containing the raw materials and solvent of the superabsorbent resin, and may be an appropriate concentration considering the polymerization time and reaction conditions. However, if the concentration of the monomer is lowered too much, the yield of the superabsorbent resin may be low, which may cause economic problems. Conversely, if the concentration is too high, some of the monomer may precipitate, or the grinding efficiency of the polymerized water-containing gel polymer may be low, which may cause process problems and potentially degrade the physical properties of the superabsorbent resin.

[0054] Furthermore, the term "internal crosslinking agent" as used herein is used to distinguish it from a surface crosslinking agent used to crosslink the surface of superabsorbent polymer particles, as described later, and plays the role of crosslinking and polymerizing the unsaturated bonds of the aforementioned water-soluble ethylene-based unsaturated monomer. Crosslinking in the above step is performed without distinction between surface and internal crosslinking, but when the surface crosslinking step for superabsorbent polymer particles described later is performed, the surface of the particles of the final manufactured superabsorbent polymer consists of a structure crosslinked by the surface crosslinking agent, and the interior consists of a structure crosslinked by the internal crosslinking agent.

[0055] Any compound can be used as the internal crosslinking agent, as long as it enables the introduction of crosslinking bonds during the polymerization of the acrylic acid-based unsaturated monomer. Specifically, the internal crosslinking agent can be a crosslinking agent having one or more functional groups that can react with the water-soluble substituents of the acrylic acid-based unsaturated monomer and one or more ethylenically unsaturated groups; or a crosslinking agent having two or more functional groups that can react with the water-soluble substituents of the monomer and / or water-soluble substituents formed by the hydrolysis of the monomer. As an example, the internal crosslinking agent may be an epoxy compound.

[0056] Any compound can be used as the internal crosslinking agent, as long as it enables the introduction of crosslinking bonds during the polymerization of the acrylic acid-based unsaturated monomer. Specifically, the internal crosslinking agent can be a crosslinking agent having one or more functional groups that can react with the water-soluble substituents of the acrylic acid-based unsaturated monomer and one or more ethylenically unsaturated groups; or a crosslinking agent having two or more functional groups that can react with the water-soluble substituents of the monomer and / or water-soluble substituents formed by the hydrolysis of the monomer.

[0057] The internal crosslinking agent may be an epoxy compound or a polyethylene glycol polymer. Non-limiting examples of the internal crosslinking agent include N,N'-methylenebisacrylamide, trimethylpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol (meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycol (meth)acrylate, butanediol di(meth)acrylate, butylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentaacrylate, and glycerin tri(meth)acrylate. Acrylate compounds such as pentaerythritol tetraacrylate; epoxy compounds such as ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol polyglycidyl ether, and polyglycerol polyglycidyl ether; triarylamines; propylene glycol; glycerin; or polyfunctional crosslinking agents such as ethylene carbonate may be used alone or in combination of two or more, but are not limited thereto.

[0058] According to one example, the epoxy compound can be used as the internal crosslinking agent. For example, a divalent or higher polyvalent epoxy compound, such as ethylene glycol diglycidyl ether, can be used as the internal crosslinking agent. In this case as well, the hydrophobic particles can stably perform foaming by the foaming agent.

[0059] In the monomer composition, such an internal crosslinking agent can be used in an amount of 0.01 to 5 parts by weight per 100 parts by weight of the acrylic acid monomer. For example, the internal crosslinking agent can be used in an amount of 0.01 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight or more, and 0.15 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, per 100 parts by weight of the water-soluble ethylene-based unsaturated monomer. If the content of the internal crosslinking agent is excessively low, crosslinking may not occur sufficiently, making it difficult to achieve a strength above an appropriate level. If the content of the internal crosslinking agent is excessively high, the internal crosslinking density may become high, making it difficult to achieve the desired water retention capacity.

[0060] The crosslinking polymerization of the water-soluble ethylene-based unsaturated monomer in the presence of such an internal crosslinking agent may be carried out by thermal polymerization, photopolymerization, or hybrid polymerization in the presence of a polymerization initiator, and optionally a thickener, plasticizer, preservative stabilizer, antioxidant, etc., but the specific details will be described later.

[0061] Furthermore, the superabsorbent polymer further includes a surface crosslinked layer formed by additional crosslinking of a crosslinked polymer contained in the base resin via a surface crosslinking agent on at least a portion of the surface of the base resin. This is to increase the surface crosslinking density of the superabsorbent polymer, and when the superabsorbent polymer further includes a surface crosslinked layer as described above, it has a structure in which the crosslinking density is higher on the outside than on the inside.

[0062] As the surface crosslinking agent, any surface crosslinking agent that has been conventionally used in the production of superabsorbent polymers can be used without any special restrictions. For example, the surface crosslinking agent may include one or more selected from the group consisting of polyhydric alcohol compounds, polyhydric epoxy compounds, polyamine compounds, haloepoxy compounds, condensation products of haloepoxy compounds, oxazoline compounds, and alkylene carbonate compounds.

[0063] Specifically, the polyhydric alcohol compounds that can be used include mono-, di-, tri-, tetra- or polyethylene glycol, monopropylene glycol, 1,3-propanediol, dipropylene glycol, 2,3,4-trimethyl-1,3-pentanediol, polypropylene glycol, glycerol, polyglycerol, 2-butene-1,4-diol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, or 1,2-cyclohexanedimethanol.

[0064] Furthermore, as the polyvalent epoxy compound, ethylene glycol diglycidyl ether or glycidol can be used.

[0065] Furthermore, as the polyamine compound, ethylenediamine, diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, or polyamide polyamine can be used.

[0066] Furthermore, as the halo-epoxy compound, epichlorohydrin, epibromohydrin, or α-methylepichlorohydrin can be used.

[0067] Furthermore, mono-, di-, or polyoxazolidinones can be used as oxazoline compounds.

[0068] Furthermore, as the alkylene carbonate compound, ethylene carbonate, propylene carbonate, or glycerol carbonate can be used.

[0069] More specifically, the surface crosslinking agent can be one of the aforementioned surface crosslinking agents used alone or in combination with others. As an example, an alkylene carbonate compound such as ethylene carbonate can be used as the surface crosslinking agent.

[0070] On the other hand, such a superabsorbent resin may contain 10% by weight or less of particles with a particle size of 710 μm or more and 850 μm or less relative to the superabsorbent resin. Alternatively, it may contain 10% by weight or less of particles with a particle size of 150 μm or less relative to the superabsorbent resin. The particle size of such superabsorbent resin particles may be measured by the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 220.3 method.

[0071] If the content of particles with a particle size of 710 μm or more and 850 μm or less exceeds 10% by weight, the pulpless diapers, which are generally thinner, may feel hard, potentially causing tactile problems such as poor wearing comfort, and the absorption rate may also decrease. Furthermore, if the content of particles with a particle size of 150 μm or less exceeds 10% by weight, a large amount of fine powder may cause filter clogging during the process, resulting in the disadvantage of a worse working environment.

[0072] On the other hand, the rewet value measured for the absorbent containing the superabsorbent resin may be 3 g or less. Preferably, the rewet value may be 1 g or more, 1.5 g or more, 2.0 g or more, or 2.4 g or more, and 3 g or less, 2.9 g or less, or 2.7 g or less.

[0073] The rewetting value can be obtained by measuring it from the absorbent material. 85 mL of a 0.9 wt% sodium chloride aqueous solution (physiological saline) is injected into the center of an absorbent material (350 mm x 100 mm in size). After 2 minutes, a piece of paper measuring 300 mm x 90 mm (300 gsm filter paper) is placed on the absorbent material. After another 2 minutes, the amount of saline solution that has seeped from the absorbent material onto the paper is measured, and the paper is removed. Fifteen minutes after the injection of the physiological saline solution, a weight is placed on the absorbent material, and while applying a pressure of 0.42 psi, another 85 mL of physiological saline solution is injected into the same position. After 15 minutes, the weight placed on the absorbent material is removed for a while, then a new piece of paper is placed on the absorbent material, and the weight is placed on the paper again, positioning the paper between the absorbent material and the weight. After 2 minutes, the amount of saline solution that has seeped from the absorbent material onto the paper is measured, and the rewetting amount (g) is calculated using the following mathematical formula 3.

[0074] [Mathematical formula 3] Rewetting amount (g)=(W5(g)-W6(g))+(W7(g)-W6(g))

[0075] In the above mathematical formula 3, W5(g) is the weight of the paper that absorbed the liquid seeping out of the absorbent material for 2 minutes after injecting physiological saline solution into the absorbent material under no pressure; W6(g) is the initial weight of the paper; and W7(g) is the weight of the paper that absorbed the liquid seeping out of the absorbent sheet for 2 minutes under a load (0.42 psi) after injecting physiological saline solution into the absorbent sheet under both no pressure and pressure.

[0076] Furthermore, the superabsorbent polymer may also contain hydrophobic particles. Here, hydrophobic particles mean particles with a contact angle of 50° or more with respect to water, or water-insoluble particles that do not dissolve in water. Particles with a contact angle of less than 50° with respect to water and water-soluble particles can dissolve in monomer compositions in aqueous solution form and are less likely to play a role in capturing bubbles generated during the polymerization process. In contrast, hydrophobic particles are located at the interface between the neutralization solution and bubbles such as carbon dioxide that exhibit hydrophobicity within the neutralization solution, and can effectively capture and stabilize the bubbles.

[0077] Therefore, the hydrophobic particles have a contact angle with water of 50° or more. More specifically, the hydrophobic particles may have a contact angle with water of 70° or more, 100° or more, 120° or more, or 130° or more, and 175° or less.

[0078] In this case, the contact angles of the hydrophobic particles may be measured by the following method. First, a coating solution is prepared by dispersing the hydrophobic particles in a methylene chloride solvent at a concentration of 5% by weight. Next, this coating solution is spin-coated onto a wafer with no surface roughness, and then dried at room temperature to remove any remaining solvent. After that, water is dropped onto the coating layer by dropwise measurement, and the contact angle is measured and defined as the contact angle of each hydrophobic particle.

[0079] Furthermore, while the hydrophobic particles have an average particle size of 0.2 μm to 50 μm, if the average particle size of the hydrophobic particles is less than 0.2 μm, it is difficult to effectively capture air bubbles generated during the manufacturing process, resulting in the problem of not being able to create uniform pores. If the hydrophobic particles have an average particle size exceeding 50 μm, the size of the pores created may become excessively large, making it difficult to improve the absorption rate of the superabsorbent polymer. Specifically, for example, the hydrophobic particles may have an average particle size (μm) of 0.3 or more, 0.5 or more, 1 or more, 2 or more, or 3 or more, and also be 40 or less, 35 or less, or 30 or less.

[0080] Here, D50 represents the average particle size of the hydrophobic particles, and "particle size Dn" represents the particle size at the n% point of the cumulative particle number distribution by particle size. In other words, D50 is the particle size at the 50% point of the cumulative particle number distribution by particle size, D90 is the particle size at the 90% point of the cumulative particle number distribution by particle size, and D10 is the particle size at the 10% point of the cumulative particle number distribution by particle size. Dn can be measured using the laser diffraction method. Specifically, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac S3500), and the particle size distribution is calculated by measuring the difference in diffraction patterns due to particle size as the particles pass through the laser beam. D10, D50, and D90 can be measured by calculating the particle diameter at the points that represent the 10%, 50%, and 90% of the cumulative particle number distribution by particle size in the measuring device.

[0081] Such hydrophobic particles may be one or more selected from the group consisting of hydrophobic silica, metal salts of fatty acids having 7 to 24 carbon atoms, and hydrophobic organic particles.

[0082] Here, hydrophobic silica refers to silica that has a low silanol (-SiOH) content on its surface and therefore has a contact angle with water of 50° or more, and hydrophobic silica known in the art can be used without limitation.

[0083] Furthermore, a metal salt of a fatty acid having 7 to 24 carbon atoms refers to a compound in which a metal cation is bonded to the carboxyl group at the end of an unsaturated or saturated fatty acid having 7 to 24 carbon atoms in the molecule and a linear structure, instead of a hydrogen ion. In this case, the metal salt may be a monovalent metal salt or a polyvalent metal salt with two or more carbon atoms. In this case, if the hydrophobic particles are a metal salt of a fatty acid having less than 7 carbon atoms, it may not be possible to capture the bubbles that are generated in particle form by ionization in an aqueous solution. If the hydrophobic particles are a metal salt of a fatty acid having more than 24 carbon atoms, the fatty acid chain may become long, making dispersion difficult.

[0084] Specifically, if the metal salt of the fatty acid is a monovalent metal salt, it has a structure in which one fatty acid carboxylate anion is bonded to an alkali ion, which is a monovalent metal cation. If the metal salt of the fatty acid is a polyvalent metal salt with two or more valencies, it has a structure in which a number of fatty acid carboxylate anions equal to the valence of the metal cation are bonded to the metal cation.

[0085] In one embodiment, the hydrophobic particles may be metal salts of saturated fatty acids having 12 to 20 carbon atoms. For example, the hydrophobic particles may be metal salts of one or more saturated fatty acids selected from the group consisting of: metal salt of lauric acid containing 12 carbon atoms in the molecule; metal salt of tridecyl acid containing 13 carbon atoms in the molecule; metal salt of myristic acid containing 14 carbon atoms in the molecule; metal salt of pentadecanoic acid containing 15 carbon atoms in the molecule; metal salt of palmitic acid containing 16 carbon atoms in the molecule; metal salt of margaric acid containing 17 carbon atoms in the molecule; metal salt of stearic acid containing 18 carbon atoms in the molecule; metal salt of nonadecyl acid containing 19 carbon atoms in the molecule; and metal salt of arachidic acid containing 20 carbon atoms in the molecule.

[0086] Preferably, the metal salt of the fatty acid may be a metal salt of stearate, but it may also be one or more metal salts of stearate selected from the group consisting of, for example, calcium stearate, magnesium stearate, sodium stearate, zinc stearate, and potassium stearate.

[0087] Furthermore, the hydrophobic organic particles may be one or more hydrophobic polymer particles selected from the group consisting of ethylene polymers, propylene polymers, styrene polymers, butadiene polymers, styrene-butadiene copolymers, alkyl acrylate polymers, alkyl methacrylate polymers, alkyl acrylate-acrylonitrile copolymers, acrylonitrile-butadiene copolymers, acrylonitrile-butadiene-styrene copolymers, acrylonitrile-alkyl acrylate-styrene copolymers, alkyl methacrylate-butadiene-styrene copolymers, and alkyl acrylate-alkyl methacrylate copolymers.

[0088] Furthermore, the hydrophobic particles may be present in the aqueous dispersion at a concentration of 10 to 70% by weight based on the total weight of the aqueous dispersion. If the content of the hydrophobic particles in the hydrophobic aqueous dispersion is excessively low or excessively high, the hydrophobic particles may not be dispersed and stabilized, potentially leading to problems such as aggregation of particles with each other or sedimentation due to gravity.

[0089] Furthermore, in the aqueous dispersion of hydrophobic particles, any surfactant known in the art that can stabilize the dispersion of the hydrophobic particles can be used without limitation as the surfactant that plays a role in dispersing the hydrophobic particles. For example, one or more surfactants selected from the group consisting of cationic surfactants, anionic surfactants, amphoteric surfactants, and nonionic surfactants can be used as the surfactant. Preferably, two or more surfactants can be used in terms of stabilizing the dispersion of the hydrophobic particles. More specifically, considering the morphology of the hydrophobic particles, for example, the metal salt form of saturated fatty acids, such a surfactant can be used together with a nonionic surfactant and anionic surfactant, for example, a nonionic surfactant to which a long-chain hydrocarbon having 10 or more carbon atoms is bonded, and a sulfate-based anionic surfactant, in order to more effectively disperse such hydrophobic particles in water.

[0090] Examples of cationic surfactants include dialkyldimethylammonium salts and alkylbenzylmethylammonium salts; examples of anionic surfactants include alkylpolyoxyethylene sulfates, monoalkyl sulfates, alkylbenzene sulfonates, monoalkyl phosphates, long-chain hydrocarbons such as sodium lauryl sulfate, sodium dodecyl sulfate, or sodium laureth sulfate, or sulfates having a sodium salt-containing functional group thereof; examples of amphoteric surfactants include alkyl sulfobetaine and alkyl carboxybetaine; and examples of nonionic surfactants include, but are not limited to, polyoxyethylene alkyl ethers such as polyethylene glycol, polyoxyalkylene alkylphenyl ethers, polyoxyethylene arylphenyl ethers, sorbitan monopalmitate, fatty acid sorbitan esters, or fatty acid esters such as glycerin monostearate, alkyl monoglyceryl ethers, alkanolamides, and alkyl polyglycosides.

[0091] Furthermore, the hydrophobic particle aqueous dispersion may have a pH of 7 or higher. If the pH of the hydrophobic particle aqueous dispersion is less than 7, it will become acidic, making it difficult to stabilize the hydrophobic particles, which are metal salts of fatty acids, and therefore unsuitable.

[0092] On the other hand, the hydrophobic particles are used in an amount of 0.01 to 0.5 parts by weight per 100 parts by weight of the acrylic acid monomer. If the content of the hydrophobic particles is excessively low, the foam stabilization effect may be insufficient and the absorption rate may slow down. If the content of the hydrophobic particles is excessively high, the amount of surfactant used to stabilize the hydrophobic particles in the aqueous dispersion of hydrophobic particles may increase, potentially reducing the surface tension. For example, the hydrophobic particles can be used in an amount of 0.01 or more, 0.03 or more, 0.05 or more, or 0.08 or more, and 0.5 parts by weight or less, 0.4 parts by weight or less, 0.3 parts by weight or less, or 0.2 parts by weight or less, per 100 parts by weight of the acrylic acid monomer.

[0093] Furthermore, the carbonate-based foaming agent plays a role in increasing the surface area by forming pores within the water-containing gel polymer through foaming during polymerization. As an example, one or more carbonates selected from the group consisting of sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, calcium bicarbonate, calcium carbonate, magnesium bicarbonate, and magnesium carbonate can be used.

[0094] The carbonate-based blowing agent can be used in an amount of 0.005 to 1 part by weight per 100 parts by weight of the acrylic acid monomer. If the amount of the blowing agent is less than 0.005 parts by weight, its role as a blowing agent may be negligible, and if the amount of the blowing agent exceeds 1 part by weight, the gel strength of the superabsorbent polymer produced may decrease due to an excessive number of pores in the crosslinked polymer, resulting in a lower density and potentially causing problems in distribution and storage. For example, the carbonate-based blowing agent may be 0.01 parts by weight or more, 0.05 parts by weight or more, and 0.5 parts by weight or less, 0.3 parts by weight or less, or 0.2 parts by weight or less per 100 parts by weight of the acrylic acid monomer.

[0095] Furthermore, such carbonate-based blowing agents and hydrophobic particles can be used in a weight ratio of 1:0.1 to 1:2. If the hydrophobic particles are used in an excessively low content compared to the carbonate-based blowing agent, it will be difficult to effectively capture the generated bubbles, and if they are used in an excessively high content compared to the blowing agent, various physical properties such as water retention capacity and absorption rate may decrease. Specifically, the carbonate-based blowing agent and the hydrophobic particles can be used in a weight ratio of 1:0.4 or higher, 1:0.6 or higher, or 1:0.8 or higher, and 1:1.7 or lower, 1:1.5 or lower, or 1:1.2 or lower. As an example, the carbonate-based blowing agent and the hydrophobic particles can be used in a weight ratio of 1:1.

[0096] On the other hand, a bubble generator can be used as a substitute for the foaming agent. Such a bubble generator can be any type of microbubble generator that has been used for foaming monomer compositions in the manufacturing process of superabsorbent polymers, without any special restrictions. One example of such a microbubble generator may be one in which the monomer composition is passed through a tubular channel with a plurality of protruding pins installed inside at a predetermined supply speed, for example, 50 to 1500 (L / min), and the monomer composition is foamed by colliding with the protruding pins. An example of such a microbubble generator is disclosed in Korean Patent Publication No. 2020-0128969, and it goes without saying that the commercial product used in the examples described later can be obtained and applied.

[0097] Preferably, the adhesive may be applied uniformly or randomly without any particular pattern.

[0098] The adhesive may be applied by a number of methods known to those skilled in the art. For example, the adhesive may be sprayed, rolled, or spun onto the surface of the non-woven fabric or the superabsorbent resin. There are no particular restrictions on the type of adhesive, as long as it is an adhesive commonly used in absorbents. As an example, the adhesive may be hydrophilic, hydrophobic, biodegradable, bio-derived, or a combination thereof. Preferably, when the adhesive is applied, the superabsorbent resin layer and the non-woven fabric are continuously present without bond sites being separated between the superabsorbent resin layer and the non-woven fabric. If the absorbent has separated bond sites, bond sites such as grids are formed on a fabric such as a non-woven fabric through ultrasonic bonding or the like, and the superabsorbent resin is fixed by being filled between the bond sites. Such a method of fixing the superabsorbent resin can improve the fixing rate of the superabsorbent resin, but there may be a disadvantage that the superabsorbent resin can move between the bond sites and the filling rate is poor.

[0099] On the other hand, preferably, the single application amount of an adhesive (product name: FLC7228AZP, manufacturer: HB Fuller) on a non-woven fabric of 350 cm 2 is 0.3 to 3 g, and the total application amount may vary depending on the number of application times. Preferably, the total application amount of an adhesive (product name: FLC7228AZP, manufacturer: HB Fuller) on a non-woven fabric of 350 cm 2 may be 0.3 to 10 g.

[0100] On the other hand, the absorbent may be manufactured by a manufacturing method including: a first step of applying an adhesive and a superabsorbent resin onto a first non-woven fabric two or more times to form a superabsorbent resin layer; a second step of applying an adhesive onto the superabsorbent resin; a third step of attaching and sealing a second non-woven fabric onto the first non-woven fabric after the second step is completed.

[0101] The application, attachment, and sealing methods in each manufacturing step may be performed by a number of methods known to those skilled in the art, and there are no particular restrictions as long as they are commonly used methods.

[0102] sanitary products On the other hand, according to another embodiment of the invention, a sanitary product is provided which includes the absorbent of the above-described embodiment. Such a sanitary product may include, for example, a liquid-permeable upper sheet formed on the upper part of the absorbent (e.g., in the direction that contacts the user's skin) and a waterproof back sheet formed on the lower part of the absorbent (e.g., in the direction opposite to the direction that contacts the user's skin), along with the absorbent.

[0103] In such a sanitary product configuration, the liquid-permeable top sheet may include a material that is generally soft to the touch and does not irritate the user's skin. Furthermore, it is appropriate that the top sheet includes a material that allows liquid bodily secretions, such as urine, to pass quickly through the absorbent. Considering these points, the top sheet can be manufactured and used from a wide range of materials, such as porous resin films, natural fibers, synthetic fibers, or mixtures of natural and synthetic fibers.

[0104] Furthermore, since the waterproof back sheet is impermeable to liquids, it needs to exhibit properties that prevent bodily secretions absorbed and contained in the absorbent material from contaminating the user's clothing, bed sheets, and other hygiene products that come into contact with them. Considering these points, it is appropriate that the back sheet contains a material that is impermeable to liquids but permeable to gases, and may, for example, contain a resin film or a material to which a nonwoven fabric is further attached.

[0105] The aforementioned sanitary product, by including an absorbent material as described in one example, can have a slimmer and thinner structure that does not contain fluff pulp, and its unit cost can also be reduced. Furthermore, the movement of superabsorbent polymer particles within such an absorbent layer and sanitary product is effectively suppressed by the porous nonwoven fabric layer, resulting in more uniform performance and the ability to maintain an appropriate shape even after absorbing a large amount of moisture. In addition, the deterioration of the physical properties of the superabsorbent polymer particles due to large amounts of adhesive can also be suppressed, allowing for the maintenance of excellent absorption performance.

[0106] Such hygiene products can be any personal hygiene product such as diapers, sanitary napkins, or incontinence pads, and may have a standard configuration depending on the type of hygiene product, in addition to the configuration described above.

[0107] The present invention will be described in more detail below for better understanding. However, the following examples are for illustrative purposes only, and the content of the present invention is not limited to the following examples.

[0108] Manufacturing Example 1: Production of Hydrophobic Silica Aqueous Dispersion After adding 100g of water to a high shear mixer, hydrophobic silica with an average particle size of 0.3μm and a contact angle to water of 130°, and hydrophobic silica with an average particle size of 3μm and a contact angle to water of 130° were gradually added while stirring at 5000rpm, so that they constituted 0.2% by weight and 2% by weight, respectively, based on the total weight of the final aqueous dispersion. Once the silica had been completely added, the mixture was stirred at 8000rpm at a temperature of 45°C for 30 minutes. At this time, the pH of the obtained hydrophobic silica aqueous dispersion was 9.

[0109] Manufacturing Example 2: Manufacturing of Superabsorbent Polymer (Step 1) A monomer solution was prepared by mixing 100 parts by weight of acrylic acid with 0.01 parts by weight of PEGDA 400 (polyethylene glycol diacrylate 400) as an internal crosslinking agent and 0.1 parts by weight of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide as a photoinitiator. Next, while continuously supplying the monomer solution to a metering pump, 160 parts by weight of 24% sodium hydroxide aqueous solution was continuously added at the same time to prepare a monomer composition by high-speed line mixing of 3 parts by weight of 4% sodium persulfate aqueous solution, 5 parts by weight of 4% ethylene glycol diglycidyl ether (EJ1030s), 5 parts by weight of 4% sodium bicarbonate aqueous solution, and 5 parts by weight of a hydrophobic silica aqueous dispersion containing 0.2% by weight of hydrophobic silica with an average particle size of 0.3 μm and 2% by weight of hydrophobic silica with an average particle size of 3 μm, which were prepared in Production Example 1. Through this transfer process, the monomer composition was introduced into a polymerization reactor consisting of a moving conveyor belt, and UV polymerization was carried out for 3 minutes by irradiating it with ultraviolet light through a UV irradiation device to produce a sheet-like hydrated gel polymer.

[0110] (Step 2) The water-containing gel polymer was cut to an average size of approximately 300 mm or less, and then fed into a pulverizer (equipped with a porous plate containing multiple holes with a diameter of 15 mm) to cut the water-containing gel. Next, the pulverized water-containing gel was dried in a dryer in which the airflow direction could be changed vertically. Hot air at 180°C was flowed through the water-containing gel to uniformly dry it so that the moisture content of the dried powder was approximately 5% or less.

[0111] (Step 3) The dried resin was pulverized in a pulverizer and then classified to obtain base resins with a size of 150 to 850 μm. A FRITSCH PULVERISETTE 19 pulverizer was used. A 12 mm sieve cassette was installed in the pulverizer, and the dried, water-containing gel was pulverized in the first stage. Mesh numbers 24 / 32 / 48 / 100 / pan were sequentially installed from the following sieves (WSTylor, 8” STAINLESS-STAINLESS TEST SIEVE), and the pulverized particles were placed in the upper #24 mesh, fixed in a sieve shaker, and classified at 1.5 amplitude for 10 minutes.

[0112] [Table 1]

[0113] After classification was complete, the resin content of the upper layer of the #24 mesh was measured, and particles exceeding 50% by weight were found compared to the total amount of dry, water-containing gel added.

[0114] The particles in the upper layer of the #24 mesh underwent secondary grinding. For secondary grinding, a 1.0 mm sieve cassette was installed in the grinder, and the dried, water-containing gel was ground. Sieves (WSTylor, 8” STAINLESS-STAINLESS TEST SIEVE) with mesh numbers 20 / 32 / 48 / 100 / pan were installed sequentially. After the secondary-ground particles were placed in the upper layer of the #20 mesh, they were fixed in a sieve shaker and classified at 1.5 amplitude for 10 minutes.

[0115] The particle weight after classification can be obtained by calculating as follows.

[0116] Particle size distribution by particle size = {(Sieve weight + dried material after classification) - (empty Sieve weight)} / (dried material after grinding) × 100

[0117] (Step 4) 100 parts by weight of the classified base resin powder was sprayed with 8 parts by weight of an aqueous surface crosslinking agent solution containing 1.2 parts by weight of ethylene carbonate, 0.5 parts by weight of propylene carbonate, 0.5 parts by weight of propylene glycol, and 0.5 parts by weight of hydrophilic water-dispersible silica (snotex). The mixture was stirred at room temperature to ensure that the surface crosslinking solution was evenly distributed on the base resin powder. Next, the base resin powder mixed with the surface crosslinking solution was placed in a surface crosslinking reactor and the surface crosslinking reaction was carried out.

[0118] In this surface crosslinking reactor, the base resin powder was observed to gradually increase in temperature from an initial temperature of around 80°C, and the reactor was operated to reach a maximum reaction temperature of 190°C after 30 minutes. After reaching this maximum reaction temperature, the reaction was allowed to continue for an additional 15 minutes, and then a sample of the final produced superabsorbent polymer was taken. After the surface crosslinking step, the sample was classified using an ASTM standard sieve to produce the superabsorbent polymer of Example 1 having a particle size of 150 μm to 850 μm.

[0119] Experimental Example 1 The superabsorbent polymer produced in Production Example 2 was evaluated for its physical properties using the following method, and the results are shown in Table 1 below. Unless otherwise noted, all physical property evaluations below were performed at room temperature (23±1℃) and relative humidity of 45±1%. Physiological saline or brine refers to a 0.9 wt% sodium chloride (NaCl) aqueous solution, and brine at 23±1℃ was used.

[0120] (1) Bulk density (g / ml): Measurement of particles with a particle size of 150-850 μm. Approximately 100 g of the superabsorbent polymer from the above examples and comparative examples was placed in a funnel-shaped bulk density measuring device and poured into a 100 ml container. The weight of the superabsorbent polymer in the container was then measured. The bulk density was calculated as (weight of superabsorbent polymer) / (container volume, 100 ml).

[0121] Bulk density measurements were performed according to the EDANA NWSP 251.0.R2(15) method.

[0122] The density cup used was made of cylindrical stainless steel, had a capacity of (ISO / TR 15510) (100.0 ± 0.5 ml), an internal diameter of 45.0 ± 0.1 mm, and an internal height of 63.1 ± 0.1 mm.

[0123] The funnel is made of stainless steel, and its detailed design conforms to ISO / TR 15510. a) The orifice has an internal diameter of (10.00 ± 0.01) mm, an inclination angle of cone generatrix of 20°, and a height of (145.0 ± 0.5 mm).

[0124] Bulk density analysis was performed at (23±2℃) and (45±15)% relative humidity.

[0125] First, a density cup was placed under the funnel, and 100g of SAP was filled into the funnel, which was closed with an orifice. A timer was started while opening the orifice, and the time taken for all the SAP to fall out of the funnel was measured. After removing the SAP that overflowed into the density cup, its weight was measured (W2). The weight of the empty density cup (W1) was measured, and by calculating the difference between the two weights, the weight of the SAP in the density cup could be determined.

[0126] The bulk density (ρ, g / ml) is calculated using the formula "ρ = (W2 - W1) / 100", where 100 (ml) is the volume of the density cup.

[0127] (2) Water-soluble components measured after 16 hours of swelling (16hr EC, %): Particles with a particle size of 150-850 μm were measured. The water-soluble components of the above examples and comparative examples were measured by the method of EDANA NWSP 270.0.R2(15).

[0128] (3) Centrifuge Retention Capacity (CRC: g / g): Measurement of particles with a particle size of 150-850 μm. The water retention capacity of each resin, based on its absorption ratio under no load, was measured using EDANA NWSP 241.0.R2(15).

[0129] Specifically, superabsorbent polymer W0 (g) (approximately 0.2g) was uniformly placed in a nonwoven fabric envelope, sealed, and then immersed in physiological saline (0.9 wt%) at room temperature. After 30 minutes, the envelope was drained for 3 minutes under 250G conditions using a centrifuge, and the weight of the envelope W2 (g) was measured. The same procedure was then performed without using the polymer, and the weight W1 (g) was measured. Using the obtained weights, the CRC (g / g) was calculated using the following formula.

[0130] [Mathematical formula 1] CRC(g / g)={[W2(g)-W1(g)] / W0(g)}-1

[0131] (3) Absorption capacity under pressure (0.7 AUP: g / g): Measured for particles with a particle size of 150 to 850 μm. The 0.7 psi pressure absorption capacity of each resin was measured using EDANA NWSP 242.0.R2(15).

[0132] Specifically, a 400-mesh stainless steel mesh was attached to the bottom of a 60mm inner diameter plastic cylinder. Under normal temperature and 50% humidity conditions, a superabsorbent polymer W0(g) (0.90g) was uniformly spread on the mesh, and a piston capable of uniformly applying a load of 0.3 psi was placed on top of it. The piston was slightly smaller than the 60mm outer diameter, with no gap between it and the inner wall of the cylinder, so that its vertical movement was not hindered. At this time, the weight W3(g) of the device was measured.

[0133] A glass filter with a diameter of 90 mm and a thickness of 5 mm was placed inside a 150 mm diameter petroleum dish, and physiological saline solution composed of 0.9 wt% sodium chloride was poured in until it was level with the top surface of the glass filter. A sheet of filter paper with a diameter of 90 mm was placed on top of that. The measuring device was placed on top of the filter paper and allowed to absorb the liquid under load for 1 hour. After 1 hour, the measuring device was lifted and its weight W4 (g) was measured.

[0134] Using the obtained weights, the pressure absorption capacity (g / g) was calculated using the following formula.

[0135] [Mathematical formula 2] AUP(g / g) = [W4(g) - W3(g)] / W0(g)

[0136] (4) Absorption rate (Vortex time, s): Measurement of particles with a particle size of 150-850 μm. The absorption rate (vortex time) of the superabsorbent resins in the above examples and comparative examples was measured by the following method.

[0137] (i) 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. (ii) Next, the beaker was placed in the center of the magnetic stirrer, and a circular magnetic bar (30 mm in diameter) was placed inside the beaker. (iii) Subsequently, the agitator was operated so that the magnetic bar agitated at 600 rpm, so that the lowest part of the vortex generated by the agitation struck the magnetic bar. (iv) After confirming that the temperature of the salt water in the beaker reached 24.0°C, 2 ± 0.01 g of the superabsorbent polymer sample was added while simultaneously operating a stopwatch. The time taken in seconds until the vortex disappeared and the liquid surface became completely horizontal was measured and defined as the absorption rate.

[0138] [Table 2]

[0139] Example 1 A 350mm x 100mm first nonwoven fabric (product name: Softhann®, manufacturer: Sambo) 1 was uniformly coated with 0.4g of adhesive (product name: FLC7228AZP, manufacturer: HB Fuller) (adhesive layer, 3) using a hot melt sprayer. Then, 4g of the superabsorbent resin produced in the above manufacturing example was uniformly applied at a feed rate of 2g / s to produce the first coating layer 4 of the superabsorbent resin. 0.4g of adhesive was then applied on top of this to produce the first coating layer 5 of the adhesive. Subsequently, the manufacturing process of the first coating layer 4 of the superabsorbent resin and the first coating layer 5 of the adhesive was repeated two more times to produce the second coating layer 6 of the superabsorbent resin, the second coating layer 7 of the adhesive, the third coating layer 8 of the superabsorbent resin, and the adhesive layer 4. Finally, the second nonwoven fabric (product name: Softhann®, manufacturer: Sambo) 2 was attached to produce the absorbent body. The amount of adhesive used in each adhesive layer was the same at 0.4g, and the amount of superabsorbent resin used in each superabsorbent resin layer was the same at 4g.

[0140] Example 2 The absorbent was manufactured in the same manner as in Example 1, except that 0.8g of adhesive was applied to each.

[0141] Example 3 The absorbent was manufactured in the same manner as in Example 1, except that 1.6 g of adhesive was applied to each of the materials.

[0142] Comparative Example 1 A 350mm x 100mm nonwoven fabric (product name: Softhann®, manufacturer: Sambo) was uniformly coated with 0.6g of adhesive (product name: FLC7228AZP, manufacturer: HB Fuller) (adhesive layer) using a hot melt sprayer. Then, 12g of the superabsorbent resin produced in the above manufacturing example was uniformly applied at a feed rate of 2g / s to produce a superabsorbent resin coating layer. An adhesive layer was then produced by applying 0.6g of adhesive in the same manner on top of this layer, and finally, the second nonwoven fabric (product name: Softhann®, manufacturer: Sambo) was attached to produce an absorbent body.

[0143] Comparative Example 2 After applying 12g of the superabsorbent resin produced in the above manufacturing example onto a first nonwoven fabric measuring 350mm x 100mm (product name: Softhann®, manufacturer: Sambo), heat was applied using a thermal bonding device (product name: SK110, manufacturer: LOVERO) at a temperature of 100°C to 150°C for 10 to 30 seconds to fix the superabsorbent resin in a lattice structure through thermal bonding and produce an absorbent material.

[0144] Experimental Example 2 The physical properties of the absorbers produced in the above examples and comparative examples were evaluated using the following method and are shown in Table 2 below.

[0145] (1) Percentage of superabsorbent polymer layer fixation rate (by weight) within the absorbent material The fixation rate of the superabsorbent polymer layer within the nonwoven fabric was determined by testing the amount of core superabsorbent polymer that leaked out of the nonwoven fabric. The absorbers of each of the above examples and comparative examples were vibrated 100 times at a frequency of 65 times / min and an amplitude of 15 mm, and the amount of superabsorbent polymer remaining in the absorber without leakage was measured and expressed as a percentage by weight.

[0146] (2) Super absorbent resin filling rate (%) The superabsorbent polymer filling rate refers to the area ratio occupied by the superabsorbent polymer within the absorbent material, and is measured as follows.

[0147] The absorber was stained with a dye (product name: FD&C BLUE NO.1 POWDER, manufacturer: SENSIENT) and then dried. After confirming that only the superabsorbent polymer portion was selectively stained, the area of ​​the stained portion was measured using a colorimeter (instrument name: Labscan XE, manufacturer: Hunter lab) under conditions of a spectral range of 400 nm to 700 nm and a wavelength resolution of <3 nm.

[0148] (3) Rewet (g) To evaluate the rewetting characteristics under pressurized conditions, the rewetting characteristics were measured using the following method.

[0149] Two minutes after injecting 85 mL of a 0.9 wt% sodium chloride aqueous solution (physiological saline) into the center of an absorbent material (350 mm x 100 mm x 3 mm) manufactured by the above method, a piece of paper measuring 300 mm x 90 mm (300 gsm filter paper (S-300, HANKUK PAPER), approximately 1.5 g per sheet (W6 (g))) was placed in the center of the absorbent material. Two minutes later, the weight of the paper (W5 (g)) was measured to determine the amount of saline solution that had seeped from the absorbent material into the paper, and the paper was removed. Fifteen minutes after the injection of the physiological saline, a weight was placed in the center of the absorbent material, and while applying a pressure of 0.42 psi, another 85 mL of physiological saline was injected into the same position. After 15 minutes, the weight placed on the absorbent was temporarily removed, and a new sheet of paper (300gsm filter paper (S-300, HANKUK PAPER), approximately 1.5g per sheet (W6(g))) was placed on top of the absorbent. The weight was then placed back on the paper, positioning it between the absorbent and the weight. After 2 minutes, the weight of the paper (W7(g)) was measured to determine the amount of saltwater that had seeped from the absorbent into the paper, and the amount of re-wetting (g) was calculated using the following mathematical formula 3.

[0150] [Mathematical formula 3] Rewetting amount (g)=(W5(g)-W6(g))+(W7(g)-W6(g))

[0151] In the above mathematical formula 3, W5(g) is the weight of the paper that absorbed the liquid seeping out of the absorbent material for 2 minutes after injecting physiological saline solution into the absorbent material under no pressure; W6(g) is the initial weight of the paper; and W7(g) is the weight of the paper that absorbed the liquid seeping out of the absorbent sheet for 2 minutes under a load (0.42 psi) after injecting physiological saline solution into the absorbent sheet under both no pressure and pressure.

[0152] [Table 3] [Explanation of Symbols]

[0153] 1: 1st nonwoven fabric 2:Second nonwoven fabric 3: Adhesive layer 4: First coating layer of superabsorbent resin 5: First coating layer of adhesive 6: Second coating layer of superabsorbent resin 7: Second coating layer of adhesive 8: Third coating layer of superabsorbent resin 9: Adhesive layer

Claims

1. First nonwoven fabric and, Second nonwoven fabric and The first and second nonwoven fabrics are interposed to form a superabsorbent resin layer, The superabsorbent resin layer comprises a superabsorbent resin and an adhesive. The superabsorbent resin layer is bonded to the first and second nonwoven fabrics via an adhesive, and does not contain pulp. The superabsorbent resin layer is formed by sequentially laminating a first coating layer of superabsorbent resin, a first coating layer of adhesive, a second coating layer of superabsorbent resin, a second coating layer of adhesive, and a third coating layer of superabsorbent resin. The following conditions (1) and (2) must be met: Absorbent material. (1) The absorbent was vibrated 100 times at a frequency of 65 times / min and an amplitude of 15 mm, and the amount of superabsorbent resin remaining in the absorbent without leakage was measured. The fixation rate was 90% or more. (2) After dyeing the absorbent material with a dye and drying it, and after confirming that only the superabsorbent resin portion has been selectively dyed, the area of ​​the dyed portion is measured with a colorimeter and the filling rate is 90% or more.

2. The superabsorbent resin layer is formed by applying the superabsorbent resin and adhesive alternately two or more times. The absorbent according to claim 1.

3. The thickness of the superabsorbent resin layer is 5 mm or less. The absorbent according to claim 1.

4. The superabsorbent resin layer has a unit area (m²). ２ ) Contains 100g or more of superabsorbent polymer per serving, The absorbent according to claim 1.

5. The aforementioned superabsorbent resin is A base resin comprising an acrylic acid monomer containing acidic groups, in which at least a portion of the acidic groups are neutralized, and a crosslinked polymer of an internal crosslinking agent, A superabsorbent resin comprising a surface crosslinked layer formed on the base resin, wherein the crosslinked polymer is further crosslinked via a surface crosslinking agent, The following conditions 1) through 4) must be met: The absorbent according to claim 1. 1) The water retention capacity (CRC) measured by EDANA NWSP 241.

0. R2(15) is 32 g / g to 40 g / g. 2) The water-soluble component measured after 16 hours of swelling by EDANA NWSP 270.

0. R2(15) is 10% by weight or less. 3) The absorption rate by the vortex method (vortex time) is 30 seconds or less. 4) Bulk density measured by EDANA NWSP 251.

0. R2(15) is 0.50 g / ml or more and 0.65 g / ml or less.

6. The rewetting value of the absorbent material is 3 g or less. The absorbent according to claim 1.

7. The adhesive is applied without a pattern. The absorbent according to claim 1.

8. A sanitary product comprising the absorbent material described in claim 1.

9. The sanitary product according to claim 8, comprising the absorbent body, a liquid-permeable upper sheet formed on the upper part of the absorbent body, and a waterproof back sheet formed on the lower part of the absorbent body.

10. The sanitary product according to claim 8, which can be used as a diaper, sanitary napkin, or incontinence pad.

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