Method for producing laminated sheet, laminated sheet, and absorbent article

Abstract

Provided is a method for producing a laminated sheet, the method comprising a step for dispersing a particulate water absorbent into the first fiber layer side of a nonwoven fabric in which a first fiber layer containing adhesive composite fibers and non-adhesive fibers and a second fiber layer containing adhesive composite fibers are laminated into a single article, wherein the ratio of the fiber density of the second fiber layer to the fiber density of the first fiber layer is 2× to 10×. As a result, even without the use of an adhesive or with just the use of a small amount of adhesive, a laminated sheet can be provided that can satisfactorily retain a particulate water absorbent and that exhibits excellent water absorbency.

Description

Method for manufacturing laminated sheet, laminated sheet and absorbent article

[0001] The present invention relates to a method for producing a laminated sheet, a laminated sheet, and an absorbent article.

[0002] A super absorbent polymer (SAP) is a water-swellable, water-insoluble polymer gelling agent that has the ability to absorb liquids and is used in a variety of applications, including hygiene materials such as disposable diapers, sanitary napkins, and adult incontinence products, soil water retention agents for agricultural and horticultural use, industrial waterproofing agents, pet diapers, pet sheets, disposable toilet materials, cleaning wipers, and nursing care products.

[0003] Generally, water-absorbent resins are in powder form and are used as particulate water-absorbing agents. The particulate water-absorbing agents swell when absorbing liquid and become a sticky hydrogel. Such particulate water-absorbing agents are dispersed on a sheet-like substrate such as a nonwoven fabric or paper, and / or immobilized between two sheet-like substrates, to produce and use a laminated water-absorbent sheet (laminate sheet).

[0004] The laminated sheet may be, for example, a laminated sheet having a structure in which a particulate water-absorbing agent and a predetermined amount of adhesive are sandwiched between two or more sheets of nonwoven fabric, such as a water-absorbent sheet composition having a structure in which a particulate water-absorbing agent and a hot-melt adhesive in an amount of 0.10 to 1.0 times the mass of the particulate water-absorbing agent are sandwiched between two or more sheets of hydrophilic nonwoven fabric (Patent Document 1).

[0005] International Publication No. 2010 / 004895

[0006] As described above, the water-absorbent sheet composition described in Patent Document 1 contains a predetermined amount of adhesive to prevent the particulate water-absorbing agent from falling off from the water-absorbent sheet composition.

[0007] However, the adhesive generally contains a hydrophobic material such as a thermoplastic resin. The water-absorbent sheet composition described in Patent Document 1 contains a predetermined amount of adhesive, and the hydrophobicity of the adhesive slows the penetration rate of liquids such as water into the water-absorbent sheet composition, resulting in insufficient absorption of the liquid. Furthermore, when the water-absorbent sheet composition is applied to a cleaning wiper or the like, if the liquid to be absorbed contains an organic solvent and oil, the adhesive dissolves in the organic solvent and oil, making it impossible to maintain adhesion by the adhesive. Therefore, the water-absorbent sheet composition has the problem of being unable to fully exhibit the performance of a water-absorbent sheet.

[0008] On the other hand, when the amount of the adhesive contained in the laminate sheet is extremely small or when the adhesive is not contained at all, the particulate water-absorbing agent is likely to fall off from the laminate sheet. Furthermore, in these cases, the particulate water-absorbing agent is not sufficiently fixed within the laminate sheet. Therefore, when the laminate sheet is used, the particulate water-absorbing agent moves within the laminate sheet and becomes unevenly distributed in specific locations, resulting in an uneven distribution of the particulate water-absorbing agent in the laminate sheet. As a result, the quality of the laminate sheet becomes unstable, and problems such as a loss of properties such as water absorption occur. Here, "the particulate water-absorbing agent falls off from the laminate sheet" means that the particulate water-absorbing agent slides off from the nonwoven fabric and / or permeates through the nonwoven fabric and is separated from the nonwoven fabric.

[0009] In view of the above, there is a demand for a technique that can sufficiently hold a particulate water-absorbing agent in a laminated sheet even when no adhesive is used or when the amount of adhesive used is small.

[0010] The object of the present invention is to solve the above problems and provide a laminated sheet and a manufacturing method thereof that can sufficiently hold a particulate water-absorbing agent even when no adhesive is used or when only a small amount of adhesive is used, and that does not impair the original performance of the nonwoven fabric and particulate water-absorbing agent that constitute the laminated sheet.

[0011] As a result of extensive research, the inventors discovered that a laminated sheet having a structure in which a particulate water-absorbing agent is dispersed on a nonwoven fabric having a specific structure can solve the above-mentioned problems, and arrived at the present invention.

[0012] That is, one embodiment of the present invention is a method for producing a laminated sheet, which includes a water-absorbing agent spraying step of spraying a particulate water-absorbing agent from the first fiber layer side of a nonwoven fabric formed by laminating and integrating a first fiber layer and a second fiber layer, wherein the first fiber layer includes first adhesive conjugate fibers and non-adhesive fibers obtained using at least two types of resin components having different melting points, the second fiber layer includes second adhesive conjugate fibers obtained using at least two types of resin components having different melting points, and the ratio of the fiber density of the second fiber layer to the fiber density of the first fiber layer is 2 times or more and 10 times or less.

[0013] Another embodiment of the present invention is a laminated sheet comprising a particulate water-absorbing agent and a nonwoven fabric, the nonwoven fabric being formed by laminating together a first fiber layer and a second fiber layer, the first fiber layer comprising a first adhesive composite fiber and a non-adhesive fiber obtained by using at least two types of resin components having different melting points, the second fiber layer comprising a second adhesive composite fiber obtained by using at least two types of resin components having different melting points, and the ratio of the fiber density of the second fiber layer to the fiber density of the first fiber layer is 2 times or more and 10 times or less.

[0014] The method for producing a laminate sheet according to one embodiment of the present invention can sufficiently hold the particulate water-absorbing agent in the laminate sheet even when no adhesive is used or when the amount of adhesive used is small. Therefore, the method has the effect of being able to produce a laminate sheet with no restrictions on the amount of particulate water-absorbing agent used compared to conventional methods. Furthermore, the method for producing a laminate sheet has the effect of being able to produce a laminate sheet with the effects described below.

[0015] Furthermore, the laminate sheet according to one embodiment of the present invention can sufficiently retain the particulate water-absorbing agent even when it does not contain an adhesive or when the adhesive content is small. Therefore, the particulate water-absorbing agent is less likely to be unevenly distributed in the laminate sheet even when subjected to vibration, etc., and the particulate water-absorbing agent is less likely to become unevenly distributed. Therefore, the laminate sheet has stable quality. Furthermore, the laminate sheet is less affected by the hydrophobicity of the adhesive. Therefore, the laminate sheet has the effect of maximizing the characteristics of the nonwoven fabric and the particulate water-absorbing agent that constitute the laminate sheet.

[0016] Fig. 1 is a schematic diagram showing the structure of a nonwoven fabric according to one embodiment of the present invention, and Fig. 2 is a schematic diagram showing the structure of a laminated sheet according to one embodiment of the present invention.

[0017] An embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to the configurations described below, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. In this specification, unless otherwise specified, "A to B" representing a numerical range means "greater than or equal to A and less than or equal to B."

[0018] [1. Definition of Terms] [1-1. Water-Absorbent Resin] In this specification, the term "water-absorbent resin" refers to a polymer gelling agent having a water swelling capacity (CRC) as defined by NWSP 241.0.R2(15) of 5 g / g or more and a water-soluble component (Ext) as defined by NWSP 270.0.R2(15) of 70 wt% or less.

[0019] Incidentally, "NWSP" stands for "Non-Woven Standard Procedures-Edition 2015." NWSP was jointly published by EDANA (European Disposables And Nonwovens Association) and INDA (Association of the Nonwoven Fabrics Industry) to standardize evaluation methods for nonwoven fabrics and their products in the United States and Europe, and also includes standard measurement methods for water-absorbent resins. Unless otherwise specified, in this specification, the physical properties of a water-absorbent resin are measured in accordance with NWSP.

[0020] In this specification, the term "water-absorbent resin" is not limited to an embodiment in which the total amount (100% by weight) is the water-absorbent resin alone, but may also refer to a water-absorbent resin composition containing additives, etc. Furthermore, in this specification, the term "water-absorbent resin" may also include a water-absorbent resin in a hydrogel state in which water is taken in.

[0021] [1-2. Water-absorbing agent, particulate water-absorbing agent] In this specification, the term "water-absorbing agent" refers to an absorbent gelling agent containing a water-absorbing resin as a main component, for absorbing water vapor (humidity) contained in a solution (liquid) or air. Here, the solution (liquid) is not limited to water, but is any liquid. Examples of liquids that can be absorbed by the laminate sheet according to one embodiment of the present invention include urine, menstrual blood, sweat, physiological saline, oil, organic solvents, waste liquid, and water (running water). Furthermore, the laminate sheet according to one embodiment of the present invention may absorb water vapor (humidity) contained in air.

[0022] In this specification, the term "particulate water absorbing agent" refers to a particulate (powdered) water absorbing agent (since the water absorbing agent contains a water absorbent resin as a main component, it corresponds to a particulate water absorbing resin). The concept of "particulate water absorbing agent" includes both a single particle of particulate water absorbing agent and an aggregate of a plurality of particulate water absorbing agents. In this specification, "particulate" means having a particle shape. Here, "particle" refers to a relatively small divided body of a substance, having a size of 0.1 nm to several mm (see "particle", McGraw-Hill Scientific and Technical Dictionary, Third Edition, edited by the McGraw-Hill Scientific and Technical Dictionary Editorial Committee, Nikkan Kogyo Shimbun, Ltd., 1996, p. 1929). In this specification, the term "particulate water absorbing agent" may be simply referred to as "water absorbing agent".

[0023] The particulate water-absorbing agent contains a water-absorbent resin as a polymer (also referred to as a particulate water-absorbent resin or water-absorbent resin particles) as a main component. The particulate water-absorbing agent contains 60 to 100 mass %, preferably 70 to 100 mass %, more preferably 80 to 100 mass %, even more preferably 90 to 100 mass %, and particularly preferably 95 to 100 mass % of the water-absorbent resin as a polymer. The remainder of the particulate water-absorbing agent may optionally contain components such as water and additives (inorganic fine particles, polyvalent metal cations, etc.). The particulate water-absorbing agent used in the examples of the present application contains 80 to 100 mass % of the water-absorbent resin.

[0024] That is, the upper limit of the water-absorbent resin in the particulate water-absorbing agent is, for example, 100 mass %, 99 mass %, 97 mass %, 95 mass %, or 90 mass %. In addition to the water-absorbent resin, the particulate water-absorbing agent may contain 0 to 15 mass % of components, particularly components such as water and additives (inorganic fine particles, polyvalent metal cations, etc.).

[0025] The particulate water-absorbing agent preferably has a water content of 0 to 15 mass %. As described above, the "particulate water-absorbing agent" also includes a water-absorbing resin composition in which components such as water and additives are integrated with and / or mixed with the water-absorbing resin.

[0026] [1-3. Laminated Sheet, Absorbent Article] In this specification, both "laminate sheet" and "absorbent article" refer to a sheet and an article that contain a particulate water-absorbing agent, and thus have a water-absorbent resin as a constituent material, and as a result, have liquid-absorbing properties. The "laminate sheet" and the "absorbent article" generally contain pulp, nonwoven fabric, plastic, etc. as constituent materials other than the particulate water-absorbing agent. The absorbent article is not particularly limited, and examples thereof include sanitary materials such as disposable diapers, incontinence pads, and sanitary napkins; sanitary materials such as masks, gowns, and surgical gowns; interior materials such as wall sheets, shoji paper, and flooring; daily life materials such as cover cloths, cleaning wipers, and food waste covers; toiletry products such as disposable toilets and toilet covers; pet supplies such as pet sheets, pet diapers, and pet towels; industrial materials such as wiping materials, filters, cushioning materials, oil and / or solvent adsorbents, and ink tank adsorbents; general medical materials; bedding materials; nursing care products; soil water retention materials for agricultural and horticultural use; industrial water-stopping materials; waste liquid solidification materials; humidity conditioners; and dehumidifiers.

[0027] Furthermore, the "laminated sheet" is not particularly limited and can be used as an absorbent that constitutes a variety of absorbent articles, such as sanitary materials such as diapers, napkins, or incontinence pads; sanitary materials such as masks, gowns, or surgical gowns; interior materials such as wall sheets, shoji paper, or flooring; daily life materials such as cover cloths, cleaning wipers, or food waste covers; toiletry products such as disposable toilets or toilet covers; pet supplies such as pet sheets, pet diapers, or pet towels; industrial materials such as wiping materials, filters, cushioning materials, oil and / or solvent adsorbents, or ink tank adsorbents; general medical materials; bedding materials; nursing care products; soil water retention materials for agricultural and horticultural use; industrial water-stopping materials; waste liquid solidification materials; humidity conditioners; dehumidifiers; etc. The aforementioned "having liquid absorption properties" means having the function of being able to absorb liquid. The liquid is not particularly limited, and examples thereof include urine, menstrual blood, sweat, physiological saline, oil, organic solvents, waste liquid, water (running water), and combinations thereof.

[0028] [1-4. Others] In this specification, "acid (salt)" means "acid and / or its salt". "(Meth)acrylic" means "acrylic and / or methacrylic". "Poly...-based water-absorbent resin" means a water-absorbent resin mainly composed of a constituent unit derived from a monomer described in "..." as a constituent unit. Specifically, it means a water-absorbent resin in which the ratio (molar ratio) of the number of moles of the constituent unit derived from the monomer described in "..." to the total number of moles of the constituent units derived from the monomer (excluding the crosslinking agent) is preferably 50 to 100 mol%, more preferably 70 to 100 mol%, even more preferably 90 to 100 mol%, and particularly preferably substantially 100 mol%.

[0029] [2. Manufacturing Method of Laminated Sheet] A manufacturing method of a laminated sheet according to one embodiment of the present invention (hereinafter referred to as "the manufacturing method of the laminated sheet of the present invention") includes a water-absorbing agent spraying step of spraying a particulate water-absorbing agent from the first fiber layer side of a nonwoven fabric formed by integrally laminating a first fiber layer and a second fiber layer, wherein the first fiber layer contains first adhesive conjugate fibers and non-adhesive fibers obtained using at least two types of resin components having different melting points, the second fiber layer contains second adhesive conjugate fibers obtained using at least two types of resin components having different melting points, and the ratio of the fiber density of the second fiber layer to the fiber density of the first fiber layer is 2 to 10 times.

[0030] Conventional laminated sheets can be manufactured by, for example, spraying a particulate water-absorbing agent onto a substrate such as a nonwoven fabric containing a predetermined amount of adhesive. On the other hand, in the manufacturing method of the laminated sheet of the present invention, the first fiber layer can incorporate and retain the particulate water-absorbing agent therein, as will be described later. Therefore, the particulate water-absorbing agent sprayed in the water-absorbing agent spraying step penetrates into and is retained inside the first fiber layer.

[0031] Therefore, according to the method for producing a laminate sheet of the present invention, it is possible to produce a laminate sheet that can sufficiently retain a particulate water-absorbing agent using a smaller amount of adhesive than that used in conventional methods for producing laminate sheets, or without using any adhesive. Therefore, the method for producing a laminate sheet of the present invention makes it possible to produce a laminate sheet with no restrictions on the amount of particulate water-absorbing agent used, as compared to conventional methods.

[0032] Furthermore, the method for producing a laminate sheet of the present invention can produce a laminate sheet containing less adhesive than that contained in conventional laminate sheets, or a laminate sheet containing no adhesive. Meanwhile, since the laminate sheet can sufficiently retain the particulate water-absorbing agent, the particulate water-absorbing agent is less likely to be unevenly distributed due to vibration or the like, and the distribution of the particulate water-absorbing agent in the laminate sheet is less likely to become uneven. As a result, the method for producing a laminate sheet of the present invention can prevent a decrease in water absorption performance due to the adhesive and can produce a sheet with stable quality.

[0033] Furthermore, in the conventional manufacturing method of the laminated sheet, since it was necessary to fix the particulate water-absorbing agent to the nonwoven fabric with an adhesive, it was essential to use a certain amount of adhesive. Therefore, when the amount of the particulate water-absorbing agent used was small, the amount of adhesive used relative to the particulate water-absorbing agent was large, so that the adhesive had a large effect on the laminated sheet, and as mentioned above, the performance of the laminated sheet could not be fully exhibited.

[0034] In addition, there is a limit (upper limit) to the amount of the particulate water-absorbing agent that can be fixed to one layer of nonwoven fabric with an adhesive, and therefore, when increasing the amount of the particulate water-absorbing agent used, it is necessary to increase the adhesive surface of the nonwoven fabric by, for example, making the sheet structure multi-layered, which poses problems in terms of cost and manufacturing process.

[0035] As described above, conventional methods for producing laminate sheets have had limitations on the amount of particulate water-absorbing agent used. On the other hand, the method for producing a laminate sheet of the present invention can retain a water-absorbing resin inside the nonwoven fabric, so that a laminate sheet can be produced with a basis weight suited to the intended use of the laminate sheet without complicating the sheet structure and production process.

[0036] The method of spraying the particulate water-absorbing agent in the water-absorbing agent spraying step is not particularly limited as long as it is a method that can spray the particulate water-absorbing agent from the first fiber layer side of the nonwoven fabric, and any known spraying method can be used.

[0037] Here, "spraying the particulate water-absorbing agent from the first fiber layer side" means spraying the particulate water-absorbing agent from above the surface of the nonwoven fabric on the first fiber layer side. In the water-absorbing agent spraying step, it is preferable to spray the particulate water-absorbing agent so that the amount of sprayed per unit area of ​​the nonwoven fabric is approximately uniform over the entire surface on the first fiber layer side, from the viewpoint of uniformity of the obtained laminated sheet.

[0038] In the method for producing a laminate sheet of the present invention, the amount of the particulate water-absorbing agent to be sprayed in the water-absorbing agent spraying step can be adjusted appropriately depending on the intended use of the laminate sheet.

[0039] The amount of the particulate water-absorbing agent retained in the nonwoven fabric varies depending on factors such as the structure of the nonwoven fabric. Therefore, the structure of the nonwoven fabric to be used and the amount of the particulate water-absorbing agent to be sprayed can be appropriately determined depending on the factors and the method of use of the laminate sheet. Furthermore, it is preferable to adjust the amount of the particulate water-absorbing agent to be sprayed so that the basis weight of the particulate water-absorbing agent in the laminate sheet to be manufactured falls within a range suitable for the intended method of use of the laminate sheet.

[0040] In the water-absorbing agent spraying step, for example, it is preferable to adjust the amount of the particulate water-absorbing agent sprayed so that the content of the particulate water-absorbing agent in the resulting laminate sheet falls within the range described below.

[0041] The method for producing a laminated sheet of the present invention preferably further comprises, after the water-absorbing agent spraying step, a water-absorbing agent incorporating step in which the particulate water-absorbing agent located on the surface of the nonwoven fabric on the side of the first fiber layer is incorporated into the nonwoven fabric.

[0042] Here, a part of the particulate water-absorbing agent sprayed in the water-absorbing agent spraying step may be located on the surface of the first fiber layer side without being incorporated into the nonwoven fabric. In this case, it is preferable to incorporate the particulate water-absorbing agent into the nonwoven fabric from the viewpoint of stably holding the particulate water-absorbing agent.

[0043] In the method for producing a laminated sheet of the present invention, by further including the water-absorbing agent incorporating step, the particulate water-absorbing agent located on the surface on the side of the first fiber layer is incorporated into the nonwoven fabric, and is prevented from falling off from the laminated sheet.

[0044] The method for carrying out the water-absorbing agent incorporating step is not particularly limited as long as it is a method that can incorporate the particulate water-absorbing agent located on the surface of the first fiber layer side into the inside of the nonwoven fabric. Examples of the method include the following methods (a) and (b). Note that "incorporating into the inside of the nonwoven fabric" more specifically means incorporating into the inside of the first fiber layer.

[0045] (a) A method in which the nonwoven fabric onto which the particulate water-absorbing agent has been dispersed is vibrated by transporting the nonwoven fabric using a conveyor or the like.

[0046] (b) A method of reducing the air pressure applied to the second fiber layer of the nonwoven fabric after the water-absorbing agent spraying step, so that the air pressure applied to the second fiber layer is lower than the air pressure applied to the first fiber layer.

[0047] In particular, when the method (a) is carried out, the vibration causes at least a part of the particulate water-absorbing agent located on the surface of the first fiber layer side to move in the planar direction of the nonwoven fabric due to the applied force. As a result, at least a part of the particulate water-absorbing agent moves onto pores present on the surface of the first fiber layer side. Therefore, at least a part of the particulate water-absorbing agent is taken into the interior of the nonwoven fabric through the pores.

[0048] Furthermore, when the method (b) is carried out, an air flow from the first fiber layer side to the second fiber layer side occurs inside the nonwoven fabric due to the difference in air pressure between the first fiber layer and the second fiber layer. The air flow applies a force toward the inside of the nonwoven fabric to the particulate water-absorbing agent located on the surface of the first fiber layer side. As a result, at least a portion of the particulate water-absorbing agent is taken into the inside of the nonwoven fabric.

[0049] The laminate sheet obtained by the laminate sheet manufacturing method of the present invention undergoes the above-mentioned manufacturing steps, and thereby the particulate water-absorbing agent is sufficiently incorporated and retained inside the nonwoven fabric. Therefore, according to the manufacturing method, it is possible to suppress the particulate water-absorbing agent from falling off from the nonwoven fabric and moving within the nonwoven fabric without using an excessive amount of adhesive, which was previously required. As a result, it is possible to manufacture a laminate sheet with a low rate of particulate water-absorbing agent falling off and an excellent retention rate of the particulate water-absorbing agent.

[0050] In the manufacturing method of the laminated sheet of the present invention, in addition to the nonwoven fabric and the particulate water-absorbing agent, a nonwoven fabric, a wrapping sheet, etc. may be additionally used. The laminated sheet manufactured by the manufacturing method may be, for example, in a form in which an additional nonwoven fabric is superimposed on the nonwoven fabric on which the particulate water-absorbing agent is sprayed, or in a form in which the nonwoven fabric on which the particulate water-absorbing agent is sprayed is wrapped with a wrapping sheet.

[0051] Furthermore, when a small amount of adhesive is used in the above-described manufacturing method, the adhesive is not particularly limited, and a hot melt adhesive containing a thermoplastic resin as a main component is preferred from the viewpoints of eliminating the trouble of solvent removal and the problem of residual solvent, and of excellent productivity.

[0052] In the method for producing the laminate sheet of the present invention, an example of a method using a small amount of hot melt adhesive is a method comprising the following steps (i) to (iii).

[0053] (i) Spray a hot-melt adhesive onto the additional nonwoven fabric (hereinafter also referred to as "additional nonwoven fabric") or wrapping sheet.

[0054] (ii) The additional nonwoven fabric is placed on the nonwoven fabric or the wrapping sheet is wrapped around the nonwoven fabric so that the portion of the additional nonwoven fabric or the wrapping sheet onto which the hot melt adhesive has been sprayed comes into contact with the nonwoven fabric onto which the particulate water-absorbing agent has been sprayed.

[0055] (iii) The additional nonwoven fabric or the wrapping sheet laminated in step (ii) is pressed against the nonwoven fabric to produce a laminated sheet.

[0056] The hot melt adhesive used in one embodiment of the present invention can be appropriately selected, and preferably, one or more types selected from an ethylene-vinyl acetate copolymer adhesive, a styrene-based elastomer adhesive, a polyolefin-based adhesive, a polyester-based adhesive, and the like can be appropriately used.

[0057] Each member used in the method for producing the laminate sheet of the present invention will be described in detail below.

[0058] [Water-absorbent resin, particulate water-absorbing agent] The water-absorbent resin, which is the main component of the particulate water-absorbing agent used in the method for producing the laminated sheet of the present invention, is not particularly limited and may be appropriately selected depending on the properties such as the water absorption performance of the target laminated sheet.

[0059] Examples of the water-absorbing resin include polyacrylic acid (salt)-based resins, polysulfonic acid (salt)-based resins, maleic anhydride (salt)-based resins, polyacrylamide-based resins, polyvinyl alcohol-based resins, polyethylene oxide-based resins, polyaspartic acid (salt)-based resins, polyglutamic acid (salt)-based resins, polyalginic acid (salt)-based resins, starch-based resins, and cellulose-based resins. Among these, polyacrylic acid (salt)-based resins are preferably used as the water-absorbing resin.

[0060] The "polyacrylic acid (salt)" refers to polyacrylic acid and / or its salt. The polyacrylic acid (salt) is a polymer containing, as a main component, structural units derived from acrylic acid and / or its salt (hereinafter referred to as "acrylic acid (salt)"), and further containing, as an optional component, a structure derived from an internal crosslinking agent. The polyacrylic acid (salt) can be obtained by, for example, polymerizing acrylic acid (salt) or hydrolyzing polymers that serve as raw materials for polyacrylamide, polyacrylonitrile, etc. Preferably, the polyacrylic acid (salt) is obtained by polymerizing acrylic acid (salt).

[0061] Here, "contained as a main component" means that the amount of acrylic acid (salt) used when polymerizing polyacrylic acid (salt) is usually 50 to 100 mol %, preferably 70 to 100 mol %, more preferably 90 to 100 mol %, and even more preferably substantially 100 mol %, based on the total amount of monomers (excluding the internal crosslinking agent) used in the polymerization.

[0062] In the method for producing a laminate sheet of the present invention, the particulate water-absorbing agent preferably has an irregularly pulverized particle shape. Here, the irregularly pulverized particle shape refers to particles that are not uniformly shaped. Compared to spherical particles obtained by reversed-phase suspension polymerization or gas-phase polymerization, the irregularly pulverized particles can be more easily fixed to a substrate.

[0063] The particulate water-absorbing agent is preferably a pulverized product obtained by pulverizing and drying a hydrogel obtained by polymerization of a monomer aqueous solution, and is an irregularly pulverized particle. On the other hand, when a pulverization step is not performed, typically, spherical particles or granulated spherical particles obtained by methods such as reverse-phase suspension polymerization and droplet polymerization in which a polymerization monomer is sprayed and polymerized are not irregularly pulverized. In one embodiment of the present invention, when the particulate water-absorbing agent has an irregularly pulverized shape, the particles incorporated into the nonwoven fabric are more likely to become entangled with fibers inside the nonwoven fabric than particles with a high average circularity (e.g., spherical particles), and the particles are less likely to be unevenly distributed within the laminate sheet and to fall off. In one embodiment of the present invention, the average circularity of the particulate water-absorbing agent is preferably 0.70 or less, more preferably 0.60 or less, and even more preferably 0.55 or less.

[0064] The average circularity is calculated as follows. 100 or more particulate water absorbing agents are randomly selected, and each particulate water absorbing agent is photographed with an electron microscope (VE-9800 manufactured by Keyence Corporation) (magnification: 50x) to obtain an image of the particulate water absorbing agent, and the perimeter and area of ​​each particle are calculated using the attached image analysis software. Thereafter, based on the measured values ​​of the perimeter and area, the circularity of each particle is calculated using the following formula (1), and the average value of the obtained values ​​is calculated as the average circularity. Circularity = 4 x π x (area) / (perimeter) ２(1) The particle diameter of the particulate water-absorbing agent (or particulate water-absorbing resin, water-absorbing resin particles) used in the manufacturing method of the laminate sheet of the present invention is a weight average particle diameter obtained in accordance with the measurement method of "PSD" specified in NWSP 220.0.R2(15). The particle diameter is preferably 150 to 600 μm. Furthermore, in the particulate water-absorbing agent, the proportion of particles having a particle diameter of less than 150 μm is preferably 15% by weight or less, and the proportion of particles having a particle diameter of 850 μm or more is preferably 5% by weight or less. Furthermore, the logarithmic standard deviation of the particle size distribution of the particulate water-absorbing agent is preferably 0.20 to 0.50.

[0065] In the method for producing a laminated sheet of the present invention, it is preferable that the weight average particle diameter of the particulate water-absorbing agent is within the above-mentioned range, from the viewpoint of being able to more suitably retain the particulate water-absorbing agent inside the nonwoven fabric, more specifically inside the first fiber layer.

[0066] In the method for producing a laminate sheet of the present invention, a commercially available particulate water absorbing agent having desired physical properties may be used as the particulate water absorbing agent, or a particulate water absorbing agent having desired physical properties may be separately prepared and used. The method for preparing the particulate water absorbing agent is not particularly limited. As the preparation method, for example, known methods for preparing particulate water absorbing agents, such as aqueous solution polymerization, reverse phase suspension polymerization, gas phase droplet polymerization, and other polymerization methods, may be used.

[0067] Therefore, the particulate water-absorbing agent can be prepared by employing at least one of the preparation methods and then appropriately changing the preparation conditions according to the desired physical properties.

[0068] [Nonwoven Fabric] The configuration of the nonwoven fabric used in the method for producing a laminated sheet of the present invention will be described in detail below with reference to Fig. 1. Fig. 1 is a schematic diagram showing the structure of a nonwoven fabric in one embodiment of the present invention.

[0069] <Nonwoven Fabric 10> The nonwoven fabric 10 is formed by laminating together a first fiber layer 20 containing first adhesive conjugate fibers and non-adhesive fibers and a second fiber layer 30 containing second adhesive conjugate fibers. The first adhesive conjugate fibers are fibers obtained using at least two resin components with different melting points. The second adhesive conjugate fibers are fibers obtained using at least two resin components with different melting points. The ratio of the fiber density of the second fiber layer 30 to the fiber density of the first fiber layer 20 is 2 to 10 times.

[0070] The nonwoven fabric 10 thus constructed has a first fiber layer 20 with a mixture of bonded and non-bonded points, and therefore is highly flexible, bulky, and has excellent scraping properties. In other words, when the nonwoven fabric 10 comes into contact with a foreign object, the non-adhesive fibers in the first fiber layer 20 can move, causing the voids in the first fiber layer 20 to deform in accordance with the shape and size of the foreign object, making it easy to trap the foreign object. Furthermore, because the non-adhesive fibers in the first fiber layer 20 become entangled with the trapped foreign object, the nonwoven fabric 10 also has high retention properties for the foreign object.

[0071] In this specification, the "foreign matter" includes the particulate water-absorbing agent. Therefore, in the method for producing a laminated sheet of the present invention, the particulate water-absorbing agent sprayed in the water-absorbing agent spraying step is taken into the first fiber layer 20 and held in the first fiber layer 20.

[0072] Therefore, according to the method for producing a laminate sheet of the present invention, it is possible to produce a laminate sheet that can sufficiently retain a particulate water-absorbing agent using a smaller amount of adhesive than that used in conventional methods for producing a laminate sheet, or without using any adhesive. The laminate sheet produced by the method for producing a laminate sheet of the present invention also includes a first fiber layer and a second fiber layer.

[0073] The nonwoven fabric 10 is an integral laminate of a first fiber layer 20 and a second fiber layer 30. The nonwoven fabric 10 is preferably a through-air nonwoven fabric produced by overlapping the fiber aggregate of the first fiber layer 20 and the fiber aggregate of the second fiber layer 30 and passing hot air through them to thermally melt the adhesive component and form adhesive points.

[0074] The thickness of the nonwoven fabric 10 can be appropriately selected depending on the application and is not particularly limited. The lower limit of the thickness of the nonwoven fabric 10 is, for example, 2.0 mm or more, preferably 3.0 mm or more, and particularly preferably 3.5 mm or more. The upper limit of the thickness is, for example, 20 mm or less, preferably 15 mm or less, and particularly preferably 10 mm or less.

[0075] The lower limit of the basis weight of the nonwoven fabric 10 is, for example, 10 g / m ２ More than 20 g / m ２ More preferably, 25 g / m ２ or more, and most preferably 30 g / m ２ The upper limit of the basis weight is, for example, 100 g / m ２ Preferably 60 g / m or less ２ Particularly preferably 50 g / m ２ The following is the result.

[0076] The lower limit of the specific volume (thickness / basis weight) of the nonwoven fabric 10 is, for example, 90 cm ３ / g or more, preferably 95 cm ３ / g or more, particularly preferably 100 cm ３ / g or more, most preferably 110 cm ３ The upper limit of the specific volume is, for example, 300 cm ３ / g or less, preferably 250 cm ３ / g or less, particularly preferably 200 cm ３ / g or less, most preferably 150 cm ３ / g or less.

[0077] The ratio of the fiber density of the second fiber layer 30 to the fiber density of the first fiber layer 20 is 2 times or more, preferably 2.2 times or more, particularly preferably 2.3 times or more, and most preferably 2.4 times or more, and is 10 times or less, preferably 8 times or less, and particularly preferably 7 times or less. The "fiber density" refers to the number of fibers per unit area of ​​the cross section. The fiber density can be measured by the method described in the Examples below.

[0078] <First Fiber Layer 20> The first fiber layer 20 is a layer produced by heat-treating a fiber assembly containing a blend of first adhesive conjugate fibers that bond to adjacent fibers and non-adhesive fibers that do not contribute to bonding, thereby melting the low-melting-point component of the first adhesive conjugate fibers and forming bonded points. In particular, the first fiber layer 20 is preferably produced by passing hot air through the blend to melt the low-melting-point component of the first adhesive conjugate fibers and form bonded points. In other words, the contact points between the fibers of the first fiber layer 20 include a mixture of bonded points and non-bonded points.

[0079] The lower limit of the fiber density of the first fiber layer (the number of fibers per unit area of ​​the cross section (the sum of the first adhesive composite fibers and the non-adhesive fibers)) is, for example, 5 fibers / mm ２ More than 10 pieces / mm, preferably ２ More preferably, 12 lines / mm ２ More preferably, 15 lines / mm ２ The upper limit of the fiber density is, for example, 30 fibers / mm ２ Preferably 25 lines / mm or less ２ Particularly preferably 20 pieces / mm or less ２ The following is the result.

[0080] The fiber density of the first fiber layer is 5 fibers / mm ２ When the fiber density of the first fiber layer is 30 fibers / mm or more, the fibers constituting the first fiber layer can be appropriately entangled with the particulate water-absorbing agent that has been taken in. ２ When the thickness is equal to or less than this, the bulkiness of the first fiber layer 20 can be appropriately ensured.

[0081] The thickness of the first fiber layer 20 is not particularly limited. The lower limit of the ratio of the thickness of the first fiber layer 20 to the overall thickness of the nonwoven fabric 10 is, for example, 60% or more, preferably 70% or more, and particularly preferably 80% or more. The upper limit of this ratio is, for example, 95% or less, preferably 90% or less, and particularly preferably 85% or less. The thickness of the first fiber layer 20 can be appropriately selected depending on the shape and size of the particulate water-absorbing agent to be incorporated into the first fiber layer. The specific lower limit of the thickness of the first fiber layer 20 is, for example, 2.5 mm or more, preferably 3.0 mm or more, and particularly preferably 3.3 mm or more. The upper limit of the thickness is, for example, 15 mm or less, preferably 12 mm or less, and particularly preferably 9 mm or less.

[0082] The lower limit of the basis weight of the first fiber layer 20 is, for example, 15 g / m ２ or more, preferably 16 g / m ２ More preferably, 17 g / m ２ The upper limit of the basis weight is, for example, 50 g / m ２ Preferably 40 g / m or less ２ Below 30 g / m, particularly preferably ２ Below 25 g / m, most preferably ２ The following is the result.

[0083] The basis weight of the first fiber layer 20 is 15 g / m ２ When the basis weight of the first fiber layer 20 is 50 g / m or more, the retention of the particulate water-absorbing agent incorporated in the first fiber layer 20 is improved. ２ If the thickness is equal to or less than this, sufficient voids can be secured in the first fiber layer 20, and therefore the first fiber layer 20 can more easily take in the particulate water-absorbing agent.

[0084] The lower limit of the specific volume (thickness / basis weight) of the first fiber layer 20 is, for example, 80 cm ３ / g or more, preferably 100 cm ３ / g or more, more preferably 120 cm ３ / g or more, particularly preferably 140 cm ３ / g or more, most preferably 160 cm ３ The upper limit of the specific volume is, for example, 250 cm ３ / g or less, preferably 220 cm３ / g or less, particularly preferably 200 cm ３ / g or less.

[0085] The specific volume of the first fiber layer 20 is 80 cm ３ / g or more, the particulate water-absorbing agent taken into the first fiber layer 20 can be well retained. ３ When the pore size is 0.1 / g or less, the voids in the first fiber layer 20 can be sufficiently secured, and therefore the first fiber layer 20 can easily take in the particulate water-absorbing agent.

[0086] The lower limit of the weight ratio of the first adhesive conjugate fiber to the weight of the first fiber layer 20 is, for example, 20% by weight or more, preferably 30% by weight or more, and particularly preferably 40% by weight or more. The upper limit of this ratio is, for example, 80% by weight or less, preferably 70% by weight or less, particularly preferably 60% by weight or less, and most preferably 55% by weight or less.

[0087] The lower limit of the weight ratio of the non-adhesive fibers to the weight of the first fiber layer 20 is, for example, 20% by weight or more, preferably 30% by weight or more, particularly preferably 40% by weight or more, and most preferably 45% by weight or more. The upper limit of this ratio is, for example, 80% by weight or less, preferably 70% by weight or less, and particularly preferably 60% by weight or less.

[0088] Increasing the weight ratio of the non-adhesive fibers in the first fiber layer 20 allows the first fiber layer 20 to acquire good bulkiness and good flexibility, and also improves the scraping ability of the particulate water-absorbing agent in the first fiber layer 20. On the other hand, decreasing the weight ratio of the non-adhesive fibers improves the durability of the first fiber layer 20.

[0089] <First adhesive conjugate fiber> The first adhesive conjugate fiber is a fiber that contributes to bonding between fibers in the first fiber layer 20, and is obtained using at least two resin components with different melting points. A preferred combination of resin components constituting the first adhesive conjugate fiber is a combination of a resin component with a high melting point and a resin component with a melting point that is 15°C or more lower than the melting point of the resin component with a high melting point.

[0090] The resin component constituting the first adhesive conjugate fiber is not particularly limited, and examples thereof include polyester-based resins and polyolefin-based resins. Examples of the polyester-based resins include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polylactic acid, polybutylene succinate, polybutylene adipate terephthalate, and copolymers thereof. Examples of the polyolefin-based resins include homopolymers such as polyethylene and polypropylene, and copolymers containing propylene as a main component. The polyester-based resin and the polyolefin-based resin may each be one type of resin or two or more types of resins.

[0091] Examples of the combination of resin components constituting the first adhesive conjugate fiber (resin component with a high melting point / resin component with a low melting point) include combinations of polyester resin / polyolefin resin, polyolefin resin / polyolefin resin, and polyester resin / polyester resin. Among these combinations, the combination of polyethylene terephthalate / polyethylene or polypropylene / polyethylene is particularly preferred.

[0092] The fineness of the first adhesive conjugate fiber can be selected taking into consideration imparting bulkiness to the first fiber layer 20. The fineness of the first adhesive conjugate fiber is preferably larger than the fineness of the second adhesive conjugate fiber of the second fiber layer 30. A specific lower limit of the fineness of the first adhesive conjugate fiber is, for example, 2 dtex or more, preferably 3 dtex or more, and particularly preferably 4 dtex or more. Note that when the fineness of the first adhesive conjugate fiber is set to a certain value or less, the texture of the first fiber layer 20 becomes good. Therefore, a specific upper limit of the fineness of the first adhesive conjugate fiber is, for example, 20 dtex or less, preferably 15 dtex or less, and particularly preferably 10 dtex or less.

[0093] The fineness can be measured by a method in accordance with JIS L 1015. The fineness can be adjusted by adjusting the fineness of the undrawn yarn and the drawing ratio in the drawing step.

[0094] The structure of the first adhesive conjugate fiber may be a concentric sheath-core type, an eccentric sheath-core type, a side-by-side type, or a radial type. Among these structures, a sheath-core type in which a resin component having a low melting point serves as the sheath component and a resin component having a high melting point serves as the core component is preferred, and a concentric sheath-core type is particularly preferred. The structure can be adjusted, for example, by changing the cross-sectional shape of the nozzle used in the spinning process.

[0095] When the first adhesive conjugate fiber is a sheath-core type, the weight ratio of the sheath component (resin component with a low melting point) to the core component (resin component with a high melting point) (weight of the sheath component:weight of the core component) is, for example, 10:90 to 90:10. Furthermore, the weight ratio in the first adhesive conjugate fiber is preferably 30:70 to 70:30, and particularly preferably 40:60 to 60:40.

[0096] <Non-adhesive fibers> The non-adhesive fibers are fibers that do not undergo thermal changes such as melting or softening during heat treatment applied to the fiber aggregate of the first fiber layer 20. The heat treatment is, for example, a treatment using hot air. In other words, the non-adhesive fibers are fibers that do not contribute to adhesion between fibers in the first fiber layer 20 but provide fiber mobility within the first fiber layer 20.

[0097] The fineness of the non-adhesive fiber is not particularly limited. The lower limit of the fineness is, for example, 2 dtex or more, preferably 3 dtex or more, and particularly preferably 4 dtex or more. The upper limit of the fineness is, for example, 15 dtex or less, preferably 12 dtex or less, and particularly preferably 10 dtex or less.

[0098] The lower limit of the fineness of the non-adhesive fibers is, for example, at least 1 time the fineness of the first adhesive conjugate fibers, preferably at least 1.2 times the fineness of the first adhesive conjugate fibers, and particularly preferably at least 1.3 times the fineness of the first adhesive conjugate fibers. The upper limit of the fineness of the non-adhesive fibers is, for example, at most 2 times the fineness of the first adhesive conjugate fibers. By making the fineness of the non-adhesive fibers at least the fineness of the first adhesive conjugate fibers, it is possible to reduce the intersection of the first adhesive conjugate fibers in the first fiber layer 20.

[0099] Examples of the non-adhesive fibers include natural fibers such as wood fibers and cotton; recycled fibers such as rayon; semi-synthetic fibers such as acetate; chemical fibers; and synthetic fibers such as polypropylene, polyester, acrylic, nylon, and vinyl chloride. The non-adhesive fibers are preferably fibers made of a single component, such as cotton, rayon, polypropylene, or a polyester-based resin. Using fibers made of polyethylene terephthalate as the non-adhesive fibers is preferable because it can impart bulkiness and flexibility, such as smoothness and texture, to the first fiber layer 20. Polyethylene terephthalate corresponds to a fiber made of a single component of a polyester-based resin.

[0100] <Second Fiber Layer 30> The second fiber layer 30 is a layer produced by subjecting a fiber aggregate containing second adhesive conjugate fibers to heat treatment to thermally melt the low-melting-point component of the second adhesive conjugate fibers and form bonded points between the fibers. The heat treatment is, for example, a treatment using hot air. In other words, in the second fiber layer 30, the bonded points are generally the contact points between the fibers. The second fiber layer 30 contributes to improving the strength of the nonwoven fabric 10 and the laminated sheet including the nonwoven fabric 10.

[0101] The fiber density (number of fibers per unit area of ​​the cross section) of the second fiber layer 30 is at least two times but not more than ten times the fiber density of the first fiber layer 20. The lower limit of the fiber density of the second fiber layer 30 is, for example, 20 fibers / mm ２ More than 30 pieces / mm, preferably 30 pieces / mm ２ More preferably, 35 pieces / mm ２ More preferably, 40 pieces / mm ２ More than 45 lines / mm, most preferably ２ The upper limit of the fiber density of the second fiber layer 30 is, for example, 60 fibers / mm ２ Preferably 55 lines / mm or less ２ Particularly preferably 50 pieces / mm or less ２ is.

[0102] The fiber density of the second fiber layer 30 is 20 fibers / mm ２In this case, the strength of the nonwoven fabric 10 and the laminated sheet including the nonwoven fabric 10 can be more satisfactorily ensured.

[0103] The fiber density of the second fiber layer 30 is 60 fibers / mm ２ If it is equal to or less than this, the processability of the nonwoven fabric 10 and the laminated sheet including the nonwoven fabric 10 can be ensured better.

[0104] There are no particular limitations on the thickness of the second fiber layer 30. The thickness of the second fiber layer 30 is preferably thinner than the thickness of the first fiber layer 20. This allows the nonwoven fabric 10 and the laminated sheet including the nonwoven fabric 10 to be made thinner.

[0105] The lower limit of the ratio of the thickness of the second fiber layer 30 to the total thickness of the nonwoven fabric 10 is, for example, 5% or more, preferably 8% or more, more preferably 13% or more, particularly preferably 16% or more, and most preferably 18% or more. The upper limit of this ratio is, for example, 40% or less, preferably 30% or less, and particularly preferably 20% or less.

[0106] The lower limit of the thickness of the second fiber layer 30 is, for example, 0.1 mm or more, preferably 0.3 mm or more, and particularly preferably 0.4 mm or more. The upper limit of the thickness is, for example, 2.0 mm or less, preferably 1.5 mm or less, and particularly preferably 1.0 mm or less.

[0107] The lower limit of the basis weight of the second fiber layer 30 is, for example, 5 g / m ２ More than 8 g / m ２ More preferably, 11 g / m ２ More preferably, 14 g / m ２ More than 17 g / m, most preferably ２ The upper limit of the basis weight is, for example, 30 g / m ２ Preferably 25 g / m or less ２ Below 20 g / m, particularly preferably ２ The following is the result.

[0108] The basis weight of the second fiber layer 30 is preferably the same as or smaller than the basis weight of the first fiber layer 20. Specifically, the lower limit of the ratio of the basis weight of the second fiber layer 30 to the basis weight of the first fiber layer 20 is, for example, 0.2 times or more, preferably 0.7 times or more, and particularly preferably 0.8 times or more. The upper limit of this ratio is, for example, 1.5 times or less, preferably 1.3 times or less, and particularly preferably 1.2 times or less. The difference between the basis weight of the first fiber layer 20 and the basis weight of the second fiber layer 30: {(basis weight of the first fiber layer 20) - (basis weight of the second fiber layer 30)} is, for example, 0 to 40 g / m ２ , preferably 0 to 30 g / m ２ , more preferably 0 to 25 g / m ２ is.

[0109] The lower limit of the specific volume (thickness / basis weight) of the second fiber layer 30 is, for example, 20 cm ３ / g or more, preferably 25 cm ３ / g or more, more preferably 30 cm ３ / g or more, particularly preferably 35 cm ３ / g or more, most preferably 40 cm ３ The upper limit of the specific volume is, for example, 100 cm ３ / g or less, preferably 80 cm ３ / g or less, more preferably 70 cm ３ / g or less, particularly preferably 60 cm ３ / g or less, most preferably 50 cm ３ / g or less.

[0110] The specific volume of the second fiber layer 30 is 20 cm ３ / g or more, the strength of the second fiber layer 30 and the laminate sheet including the second fiber layer 30 can be improved. ３ When the elastic modulus is 1 / g or less, good processability of the nonwoven fabric 10 and the laminated sheet including the nonwoven fabric 10 is ensured.

[0111] <Second adhesive conjugate fiber> The second adhesive conjugate fiber is obtained using at least two resin components with different melting points. A preferred combination of the resin components is a combination of a resin component with a high melting point and a resin component with a melting point 15°C or more lower than the melting point of the resin component.

[0112] The resin component constituting the second adhesive conjugate fiber is not particularly limited, and examples thereof include polyester-based resins and polyolefin-based resins. Examples of the polyester-based resins include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polylactic acid, polybutylene succinate, polybutylene adipate terephthalate, and copolymers thereof. Examples of the polyolefin-based resins include homopolymers such as polyethylene and polypropylene, and copolymers containing propylene as a main component. The polyester-based resin and the polyolefin-based resin may each be one type of resin or two or more types of resins.

[0113] Examples of the combination of resin components constituting the second adhesive conjugate fiber (resin component with a high melting point / resin component with a low melting point) include combinations of polyester resin / polyolefin resin, polyolefin resin / polyolefin resin, and polyester resin / polyester resin. Among these combinations, the combination of polyethylene terephthalate / polyethylene or polypropylene / polyethylene is particularly preferred.

[0114] Furthermore, it is preferable to use a resin component as the sheath component of the second adhesive conjugate fiber that has the same melting point as the resin component of the sheath component of the first adhesive conjugate fiber or one whose melting point difference is within 5°C, and it is more preferable to use the same resin component as the resin component of the sheath component of the first adhesive conjugate fiber. In particular, it is preferable to use the same combination of resin components for the first adhesive conjugate fiber and the second adhesive conjugate fiber.

[0115] The fineness of the second adhesive conjugate fibers can be selected taking into consideration thinning the second fiber layer 30 and improving smoothness. The fineness of the second adhesive conjugate fibers is preferably smaller than the fineness of the first adhesive conjugate fibers in the first fiber layer 20. The lower limit of the ratio of the fineness of the first adhesive conjugate fibers to the fineness of the second adhesive conjugate fibers is, for example, 1.1 times or more, preferably 1.5 times or more, particularly preferably 2 times or more, and most preferably 2.5 times or more. The upper limit of the ratio is, for example, 25 times or less, preferably 15 times or less, and particularly preferably 10 times or less.

[0116] The lower limit of the fineness of the second adhesive conjugate fiber is, for example, 0.5 dtex or more, preferably 1 dtex or more, particularly preferably 1.5 dtex or more, and the upper limit of the fineness of the second adhesive conjugate fiber is, for example, 5 dtex or less, preferably 3 dtex or less, particularly preferably 2.5 dtex or less.

[0117] The structure of the second adhesive conjugate fiber can be a concentric sheath-core type, an eccentric sheath-core type, a side-by-side type, a radial type, etc. Among the structures of the second adhesive conjugate fiber, a sheath-core type in which a resin component with a low melting point is used as the sheath component and a resin component with a high melting point is used as the core component is preferred, and a concentric sheath-core type is particularly preferred. The structure of the second adhesive conjugate fiber can be adjusted, for example, by the cross-sectional shape of the nozzle used in the spinning process.

[0118] When the second adhesive conjugate fiber is a sheath-core type, the weight ratio of the sheath component (resin component with a low melting point) to the core component (resin component with a high melting point) (weight of the sheath component:weight of the core component) is, for example, 10:90 to 90:10. The weight ratio is preferably 30:70 to 70:30, and particularly preferably 40:60 to 50:50.

[0119] <Method for manufacturing nonwoven fabric> The nonwoven fabric can be manufactured by employing a known method for manufacturing nonwoven fabrics and appropriately selecting manufacturing conditions. The nonwoven fabric can be a through-air nonwoven fabric. When the nonwoven fabric is a through-air nonwoven fabric, the nonwoven fabric can be manufactured by employing, for example, a manufacturing method including the following steps (1) to (4).

[0120] (1) A process of mixing first adhesive conjugate fibers of an appropriate fiber length and non-adhesive conjugate fibers of an appropriate fiber length and carding the mixture to obtain a mixed fiber carded web that will become the fiber aggregate of the first fiber layer.

[0121] (2) On the other hand, a step of carding second adhesive conjugate fibers having an appropriate fiber length to obtain a carded web that will become the fiber aggregate of the second fiber layer.

[0122] (3) A step of laminating the two card webs obtained by steps (1) and (2) to form a laminated web.

[0123] (4) A step of placing the laminated web on a transport support such as a belt conveyor and feeding it into a heat treatment device.

[0124] After step (4), the laminated web is heated in the heat treatment device to a temperature at which only the low-melting-point resin among the resins constituting the first adhesive conjugate fiber, the non-adhesive conjugate fiber, and the second adhesive conjugate fiber melts. This causes the fibers composed of the molten low-melting-point resin to bond (thermally bond) to each other. As a result, the intersections of the fibers are fused, producing a through-air nonwoven fabric having a three-dimensional structure. The heating method is not particularly limited, and for example, a heating method in which hot air is blown onto the stacked card webs from above the transport support can be used.

[0125] The nonwoven fabric may be raised by employing a known method for producing raised nonwoven fabric, and then the raised portion may be shaved to make the surface smooth.

[0126] 1 has the first fiber layer 20 and the second fiber layer 30 adjacent to each other. On the other hand, the nonwoven fabric used in the method for producing a laminated sheet of the present invention may be a nonwoven fabric obtained by interposing a fiber layer other than the first fiber layer and the second fiber layer between the first fiber layer and the second fiber layer, as long as the effect of the present invention is not impaired.

[0127] The nonwoven fabric 10 shown in FIG. 1 may carry functional particles such as inorganic fine particles, as long as the effects of the present invention are not impaired.

[0128] [3. Laminated Sheet] A laminated sheet according to one embodiment of the present invention (hereinafter referred to as "the laminated sheet of the present invention") comprises a particulate water-absorbing agent and a nonwoven fabric, the nonwoven fabric being formed by integrally laminating a first fiber layer and a second fiber layer, the first fiber layer comprising a first adhesive conjugate fiber and a non-adhesive fiber obtained using at least two types of resin components having different melting points, the second fiber layer comprising a second adhesive conjugate fiber obtained using at least two types of resin components having different melting points, and a ratio of the fiber density of the second fiber layer to the fiber density of the first fiber layer being 2 times or more and 10 times or less.

[0129] For the "nonwoven fabric" and the "particulate water-absorbing agent" constituting the laminate sheet of the present invention, the descriptions regarding the "nonwoven fabric" and the "particulate water-absorbing agent" explained in the section [2. Manufacturing method of laminate sheet] above are incorporated herein by reference.

[0130] The laminate sheet of the present invention can be produced by the method for producing a laminate sheet of the present invention.

[0131] The structure of the laminate sheet of the present invention will now be described in detail with reference to Fig. 2. Fig. 2 is a schematic diagram showing the structure of a laminate sheet according to one embodiment of the present invention.

[0132] The laminated sheet 100 of the present invention includes a first fiber layer 20, a second fiber layer 30, a nonwoven fabric 10 consisting of the first fiber layer 20 and the second fiber layer 30, and a particulate water-absorbing agent 40. These components correspond to the "first fiber layer," "second fiber layer," "nonwoven fabric," and "particulate water-absorbing agent" described in the section [2. Manufacturing method of laminated sheet] above.

[0133] As shown in FIG. 2, the laminated sheet 100 has a structure in which a particulate water-absorbing agent 40 is embedded and held inside a first fiber layer 20 constituting a nonwoven fabric.

[0134] By providing the above structure, the laminate sheet 100 can prevent the particulate water-absorbing agent from falling off and can sufficiently retain the particulate water-absorbing agent. Furthermore, the laminate sheet 100 can reduce the amount of adhesive contained in conventional laminate sheets to prevent the particulate water-absorbing agent from falling off, or can eliminate the adhesive. As a result, the laminate sheet 100 reduces the amount of deterioration in water absorption performance due to the hydrophobicity of the adhesive, or prevents the deterioration in water absorption performance, allowing the nonwoven fabric and particulate water-absorbing agent constituting the laminate sheet to exhibit their original performance. Furthermore, the laminate sheet of the present invention is less likely to have uneven distribution of the particulate water-absorbing agent, even when subjected to vibration, and the particulate water-absorbing agent is less likely to become unevenly distributed. As a result, the laminate sheet according to one embodiment of the present invention has stable quality.

[0135] The basis weight of the particulate water-absorbing agent 40 in the laminate sheet 100 can be controlled by adjusting the amount of the particulate water-absorbing agent sprayed in the manufacturing method of the laminate sheet of the present invention. There are no particular restrictions on the basis weight of the particulate water-absorbing agent in the laminate sheet of the present invention. For example, the basis weight may be set to 10 to 500 g / m2 depending on the intended use of the laminate sheet. ２ The range can be exemplified as follows.

[0136] Generally, a laminate sheet with a small basis weight of the particulate water-absorbing agent (a small amount used) is more likely to be affected by the adhesive. Furthermore, a laminate sheet with a large amount of the particulate water-absorbing agent (a large basis weight) is more likely to have uneven distribution of the particulate water-absorbing agent within the laminate sheet. On the other hand, the laminate sheet according to the present invention can retain the particulate water-absorbing agent inside the nonwoven fabric. Therefore, when the basis weight of the particulate water-absorbing agent is small, the laminate sheet can avoid the influence of the adhesive, and when the laminate sheet uses a large amount of the particulate water-absorbing agent, uneven distribution of the particulate water-absorbing agent is prevented. As a result, the laminate sheet according to the present invention can maximize the performance of the nonwoven fabric and the particulate water-absorbing agent, regardless of the basis weight (amount used) of the particulate water-absorbing agent.

[0137] 2, the particulate water absorbing agent 40 is entirely held inside the first fiber layer 20. On the other hand, it is sufficient that at least a part of the particulate water absorbing agent 40 contained in the laminated sheet 100 is held inside the first fiber layer 20. That is, the laminated sheet 100 also includes an embodiment in which a part of the particulate water absorbing agent 40 is held on the surface of the first fiber layer 20 and / or inside the second fiber layer 30. Furthermore, when the laminated sheet 100 includes the other fiber layer, it also includes an embodiment in which a part of the particulate water absorbing agent 40 is held inside the other fiber layer.

[0138] The first fiber layer 20 and / or the second fiber layer 30 of the laminate sheet 100 may contain a small amount of adhesive. Here, the small amount of adhesive means an amount of adhesive that is smaller than the amount of adhesive typically contained in a laminate sheet containing a conventional adhesive. A specific amount of the small amount of adhesive may be, for example, an amount less than 0.10 times (less than 0.10 times) the mass of the particulate water-absorbing agent, as shown in Patent Document 1.

[0139] [5. Absorbent Article] An absorbent article according to one embodiment of the present invention (hereinafter referred to as "absorbent article of the present invention") includes the laminate sheet of the present invention.

[0140] The absorbent article of the present invention has the effect of being provided with excellent water absorption performance by including the laminate sheet of the present invention.

[0141] The absorbent article of the present invention is not particularly limited as long as it is an absorbent article containing a laminated sheet, and general absorbent articles can be selected.Specific examples of the absorbent article of the present invention include hygiene materials such as diapers, napkins, or incontinence pads; hygiene materials such as masks, gowns, or surgical gowns; interior materials such as wall sheets, shoji paper, or flooring; daily-use materials such as cover cloths, cleaning wipers, or food waste covers; toiletry products such as disposable toilets or toilet covers; pet supplies such as pet sheets, pet diapers, or pet towels; industrial materials such as wiping materials, filters, cushioning materials, oil and / or solvent adsorbents, or ink tank adsorbents; general medical materials; bedding materials; nursing care products; soil water-retaining materials for agricultural and horticultural use; industrial water-stopping materials; waste liquid solidification materials; humidity control agents; dehumidifying agents; etc.

[0142] The absorbent article can be manufactured by appropriately employing a known method and appropriately arranging the components constituting the absorbent article, including the laminate sheet, in such a manner that the first fiber layer of the laminate sheet faces the skin of the user.

[0143] An embodiment of the present invention may include the following inventions [1] to [9].

[0144] [1] A method for manufacturing a laminated sheet, comprising a water-absorbing agent spraying step of spraying a particulate water-absorbing agent from the first fiber layer side of a nonwoven fabric formed by laminating and integrating a first fiber layer and a second fiber layer, wherein the first fiber layer contains first adhesive composite fibers and non-adhesive fibers obtained by using at least two types of resin components having different melting points, and the second fiber layer contains second adhesive composite fibers obtained by using at least two types of resin components having different melting points, and the ratio of the fiber density of the second fiber layer to the fiber density of the first fiber layer is 2 times or more and 10 times or less.

[0145] [2] The method for producing a laminated sheet according to [1], wherein the basis weight of the second fiber layer is 0.2 times or more and 1.5 times or less than the basis weight of the first fiber layer.

[0146] [3] The method for producing a laminated sheet according to [1] or [2], wherein the fineness of the first adhesive conjugate fiber is 1.1 times or more and 25 times or less the fineness of the second adhesive conjugate fiber.

[0147] [4] The method for producing a laminate sheet according to any one of [1] to [3], wherein the non-adhesive fiber is a polyester-based single fiber having a fineness of 2.0 dtex or more and 15.0 dtex or less.

[0148] [5] A laminated sheet comprising a particulate water-absorbing agent and a nonwoven fabric, wherein the nonwoven fabric is formed by laminating together a first fiber layer and a second fiber layer, wherein the first fiber layer comprises first adhesive conjugate fibers and non-adhesive fibers obtained by using at least two types of resin components having different melting points, and the second fiber layer comprises second adhesive conjugate fibers obtained by using at least two types of resin components having different melting points, and wherein the ratio of the fiber density of the second fiber layer to the fiber density of the first fiber layer is 2 times or more and 10 times or less.

[0149] [6] The laminated sheet according to [5], wherein the basis weight of the second fiber layer is 0.2 times or more and 1.5 times or less than the basis weight of the first fiber layer.

[0150] [7] The laminated sheet according to [5] or [6], wherein the fineness of the first adhesive conjugate fiber is 1.1 times or more and 25 times or less the fineness of the second adhesive conjugate fiber.

[0151] [8] The laminate sheet according to any one of [5] to [7], wherein the non-adhesive fiber is a polyester-based single fiber having a fineness of 2.0 dtex or more and 15.0 dtex or less.

[0152] [9] An absorbent article comprising the laminated sheet according to any one of [5] to [8].

[0153] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0154] <Measurement Methods> The physical properties of the nonwoven fabrics and laminate sheets described in Production Examples 1 to 8, Examples 1 to 8, and Comparative Examples 1 to 4 described below were measured by the methods shown below.

[0155] <Fineness> The fineness of the sample fiber was measured in accordance with JIS L 1015 using a single yarn physical property measuring device (FAVIMAT) manufactured by Textechno.

[0156] <Basis Weight> Pieces measuring 100 mm x 100 mm were cut out from the nonwoven fabrics prepared in Production Examples 1 to 8 to obtain samples for measuring the basis weight of the nonwoven fabric. The weight of the sample for measuring the basis weight was measured, and the value converted per unit area was used to calculate the basis weight (g / m ２ The measurement of the basis weight was carried out twice for the same sample for basis weight measurement, and the average value of the two measured values ​​was calculated, and this average value was taken as the basis weight of the nonwoven fabric.

[0157] <Nonwoven Fabric Thickness and Fiber Density> (1) Observation Sample Preparation Method The nonwoven fabrics prepared in Production Examples 1 to 8 were placed in an oven and heated at 80°C for 5 minutes to reset the stress history of the nonwoven fabric. The nonwoven fabrics were then cut into 1 cm (machine direction; machine direction) x 2 cm (cross direction; CD) sections. The sections were then thoroughly impregnated with a photocurable resin (UV-LED Resin Hoshi no Shizuku [Soft] manufactured by PADICO Co., Ltd.) and cured by UV irradiation. After the photocurable resin had cured, the sections were then cut using a microtome (RM2265 manufactured by Leica BIOSYSTEMS) to a thickness of 10 μm in the machine direction, yielding observation samples measuring 10 μm (machine direction) x 2 cm (CD).

[0158] (2) Measurement of Fiber Density Using a microscope (VHX-6000 manufactured by KEYENCE Corporation) and a polarizing plate, the microtome cut surface of the observation sample was observed at 20 to 50 magnifications to measure the thickness of the first fiber layer and the second fiber layer, and the number of fibers per area (fibers / mm ２ The thickness and fiber density of each layer were measured twice and the average value was used.

[0159] <Specific Volume of Nonwoven Fabric> Based on the basis weight and thickness values ​​obtained by the above-mentioned methods, the specific volume of the nonwoven fabric was calculated using the following formula (2). ３ / g) = {thickness of nonwoven fabric (mm) / basis weight of nonwoven fabric (g / m ２ )}×1000 (2) <Fiber Density Ratio> Based on the fiber density value obtained by the above-mentioned method, the fiber density ratio was calculated using the following formula (3): Fiber density ratio = fiber density (threads / mm ２ ) / fiber density of first fiber layer (counts / mm ２ ) (3) <Transmittance of Particulate Water-Absorbing Agent> The laminated sheets described in Examples 1 to 8 and Comparative Examples 1 to 4, which will be described later, were produced in a vat. In each of the Examples and Comparative Examples, the weight of the dispersed particulate water-absorbing agent was designated Wa (g). The produced laminated sheet was held on both short sides and slowly lifted up from the vat while keeping the laminated sheet horizontal to the bottom of the vat, and then moved above a flat plate (220 × 160 mm) placed on another plane, and then placed on the flat plate. Thereafter, the weight of the particulate water-absorbing agent that had fallen into the vat was measured and designated Wb (g).

[0160] From the measured Wa and Wb, the "permeability of the particulate water-absorbing agent" was calculated using the following formula (4). The "permeability of the particulate water-absorbing agent" means the ratio of the weight of the particulate water-absorbing agent that has permeated the nonwoven fabric and fallen off to the weight of the particulate water-absorbing agent that has been dispersed on the nonwoven fabric.

[0161] (Wb / Wa) x 100 = Transmittance (%) of Particulate Water Absorbing Agent (4) <Retention Rate of Particulate Water Absorbing Agent> After measuring the "transmittance of the particulate water absorbing agent" by the above-mentioned method, the short sides of the laminate sheet placed on the flat plate were fixed to the flat plate using 50 mm wide masking tape cut to a length of 100 mm. At this time, the overlap between the masking tape and the laminate sheet was 10 mm. Thereafter, a tray large enough to accommodate the flat plate was prepared on a test stand. Next, the flat plate was moved into the tray with the laminate sheet still placed thereon. When moving the flat plate, the flat plate was moved while maintaining the horizontality with respect to the test stand. Next, the laminate sheet was slowly tilted over 5 seconds so that the long sides of the laminate sheet were vertical, until the flat plate and the laminate sheet were perpendicular to the test stand. Thereafter, the state in which the test table, the flat plate, and the laminated sheet were perpendicular to each other was maintained for 10 seconds, and then the flat plate and the laminated sheet were slowly returned to a horizontal state relative to the test table over a period of 5 seconds.

[0162] Thereafter, the flat plate was placed outside the bat while still in a horizontal position, and the weight of the particulate water-absorbing agent that had fallen into the bat was measured and designated as Wc (g). Based on Wa and Wb described in the above-mentioned "Transmittance of the Particulate Water-Absorbing Agent" and the above-mentioned Wc, the "falling rate of the particulate water-absorbing agent" was calculated using the following formula (5): Wc / (Wa-Wb)=falling rate of the particulate water-absorbing agent (5) In this case, the falling rate indicates the proportion of the particulate water-absorbing agent that cannot be held by the nonwoven fabric used, that is, the proportion of the particulate water-absorbing agent that can move freely within the laminate sheet, and can be understood as the proportion of the particulate water-absorbing agent that leads to uneven distribution of the particulate water-absorbing agent within the laminate sheet.

[0163] Furthermore, the "retention rate of the particulate water-absorbing agent" was calculated using the following formula (6).

[0164] The "retention rate of particulate water-absorbing agent" means the weight ratio of the particulate water-absorbing agent retained in the nonwoven fabric to the particulate water-absorbing agent dispersed from the first fiber layer side of the nonwoven fabric. 100 - [{(Wb + Wc) / Wa} × 100] = Retention rate of particulate water-absorbing agent (%) (6) [Production Example 1] As a first adhesive composite fiber, a concentric sheath-core composite fiber having a fineness of 9.0 dtex was prepared, in which high-density polyethylene was used for the sheath and polyethylene terephthalate was used for the core in a weight ratio (sheath:core) of 50:50.

[0165] As the non-adhesive fiber, a fiber made of a single component of polyethylene terephthalate and having a fineness of 9.0 dtex was prepared.

[0166] As the second adhesive conjugate fiber, a concentric sheath-core type conjugate fiber having a fineness of 1.7 dtex was prepared, in which the sheath was made of high density polyethylene and the core was made of polyethylene terephthalate in a weight ratio (sheath:core) of 40:60.

[0167] Next, card web 1 was prepared by mixing the first adhesive conjugate fiber and the non-adhesive fiber in a weight ratio of 30 / 70, and card web 2 was prepared by mixing the second adhesive conjugate fiber. Card web 2 was laminated on card web 1, and hot air at 130°C and 0.9 m / sec was blown onto the card web from above using a hot air circulation dryer, thereby obtaining a nonwoven fabric. The nonwoven fabric obtained in Production Example 1 was designated nonwoven fabric (1). The surface of nonwoven fabric (1) opposite to the surface onto which hot air was blown during production was designated the surface on the first fiber layer side.

[0168] [Manufacturing Example 2] A nonwoven fabric was obtained in the same manner as in Manufacturing Example 1, except that the fineness of the first adhesive conjugate fiber was 4.4 dtex and the fineness of the non-adhesive fiber was 6.0 dtex. The nonwoven fabric obtained in Manufacturing Example 2 was designated nonwoven fabric (2). Of the surfaces of nonwoven fabric (2), the surface opposite to the surface onto which hot air was blown during manufacturing was designated the surface on the first fiber layer side.

[0169] [Manufacturing Example 3] A nonwoven fabric was obtained in the same manner as in Manufacturing Example 1, except that the first adhesive fibers and non-adhesive fibers were mixed in a weight ratio of 70 / 30 to form the card web 1. The nonwoven fabric obtained in Manufacturing Example 3 was designated nonwoven fabric (3). Of the surfaces of nonwoven fabric (3), the surface opposite to the surface onto which hot air was blown during manufacturing was designated the surface on the first fiber layer side.

[0170] [Production Example 4] A nonwoven fabric was obtained in the same manner as in Production Example 2, except that fibers consisting solely of rayon and having a fineness of 5.6 dtex were used as the non-adhesive fibers. The nonwoven fabric obtained in Production Example 4 was designated nonwoven fabric (4). Of the surfaces of nonwoven fabric (4), the surface opposite to the surface onto which hot air was blown during production was designated the surface on the first fiber layer side.

[0171] [Manufacturing Example 5] A nonwoven fabric was obtained in the same manner as in Manufacturing Example 2, except that the first adhesive fiber and the non-adhesive fiber were mixed in a weight ratio of 50 / 50 to form card web 1, and the basis weight ratio between card web 1 and card web 2 was changed. The nonwoven fabric obtained in Manufacturing Example 5 was designated nonwoven fabric (5). Of the surfaces of nonwoven fabric (5), the surface opposite to the surface onto which hot air was blown during manufacturing was designated the surface on the first fiber layer side.

[0172] [Production Example 6] A nonwoven fabric was obtained in the same manner as in Production Example 1, except that no non-adhesive fibers were used as the card web 1. The nonwoven fabric obtained in Production Example 6 was designated as comparative nonwoven fabric (1). Of the surfaces of the comparative nonwoven fabric (1), the surface opposite to the surface onto which hot air was blown during production was designated as the surface on the first fiber layer side.

[0173] [Production Example 7] A nonwoven fabric was obtained in the same manner as in Production Example 2, except that no non-adhesive fibers were used for the card web 1. The nonwoven fabric obtained in Production Example 7 was designated as comparative nonwoven fabric (2). Of the surfaces of the comparative nonwoven fabric (2), the surface opposite to the surface onto which hot air was blown during production was designated as the surface on the first fiber layer side.

[0174] [Production Example 8] A nonwoven fabric was obtained in the same manner as in Production Example 5, except that the fineness of the first adhesive conjugate fiber was 1.7 dtex and the weight ratio of sheath to core (sheath:core) was 40:60. The nonwoven fabric obtained in Production Example 8 was designated comparative nonwoven fabric (3). Of the surfaces of comparative nonwoven fabric (3), the surface opposite to the surface onto which hot air was blown during production was designated the surface on the first fiber layer side.

[0175] [Production Example 9] A 2-liter polypropylene vessel was charged with 343.4 g of acrylic acid, 0.919 g (0.036 mol % relative to the carboxyl group-containing unsaturated monomer) of polyethylene glycol diacrylate (molecular weight 523) as an internal crosslinking agent, 2.15 g of a 1.0 wt % aqueous solution of diethylenetriaminepentaacetic acid trisodium (DTPA 3Na), 144.9 g of a 48.5 wt % aqueous solution of sodium hydroxide, and 337.6 g of deionized water (ion-exchanged water), and the mixture was mixed to prepare an aqueous monomer solution (a').

[0176] Next, the aqueous monomer solution (a') was cooled with stirring. When the liquid temperature of the aqueous monomer solution (a') reached 40.0°C, 148.9 g of a 48.5 wt% aqueous sodium hydroxide solution adjusted to 40°C was added to the aqueous monomer solution (a') and mixed. In this way, an aqueous monomer solution (a) was prepared.

[0177] Next, 13.77 g of a 4.5 wt % aqueous sodium persulfate solution was added to the aqueous monomer solution (a) while stirring the aqueous monomer solution (a). The mixture (liquid) of the aqueous monomer solution (a) and the aqueous sodium persulfate solution was then immediately poured into a stainless steel bat-shaped container (bottom 340 x 340 mm, height 25 mm, inner surface; Teflon (registered trademark) coated) in an open-to-air system. The bat-shaped container had been heated to a surface temperature of 40°C using a hot plate (NEO HOTPLATE HI-1000 / manufactured by Iuchi Seieido Co., Ltd. (now AS ONE Corporation)) before the mixture was poured into it.

[0178] The polymerization reaction started 60 seconds after the mixture was poured into the vat-shaped container. Three minutes after the start of the polymerization reaction, the hydrogel-like crosslinked polymer (hereinafter referred to as "hydrogel") (1) was removed from the vat-shaped container. This series of operations was carried out in an open-air system.

[0179] The hydrogel (1) obtained by the polymerization reaction was cut into strips and fed into a screw extruder for gel pulverization to obtain particulate hydrogel (1).

[0180] This particulate hydrogel (1) was spread on a 50-mesh wire mesh and dried with hot air at 190°C for 30 minutes to obtain a dried product. The dried product was pulverized using a roll mill (WML type roll pulverizer / manufactured by Inokuchi Giken Co., Ltd.) to obtain a pulverized product. The pulverized product was then sieved using JIS sieves with mesh sizes of 850 μm, 600 μm, 500 μm, 300 μm, or 150 μm. Thereafter, fractions of the pulverized product sieved using each JIS sieve were compounded to obtain an irregularly pulverized precursor water-absorbent resin (A) having a weight-average particle diameter of 340 μm and a logarithmic standard deviation of the particle size distribution of 0.33.

[0181] A surface crosslinking agent solution consisting of 0.025 parts by weight of ethylene glycol diglycidyl ether, 0.31 parts by weight of 1,4-butanediol, 0.5 parts by weight of propylene glycol, and 2.0 parts by weight of deionized water was uniformly mixed with 100 parts by weight of a precursor water absorbent resin (A). Subsequently, the mixture of the surface crosslinking agent solution and the precursor water absorbent resin (A) was heated at 190°C for 30 minutes, thereby obtaining a particulate water absorbing agent A in which the precursor water absorbent resin (A) was surface crosslinked.

[0182] Example 1 A piece measuring 18 cm x 10 cm was cut from a nonwoven fabric (1) to obtain a nonwoven fabric piece (1). The nonwoven fabric piece (1) was placed on a tray (inner diameter 26 cm x 20 cm) with the first fiber layer side facing up. Next, a frame with an inner diameter of 16 cm x 8 cm and four sides each having a width of 1 cm was placed on the nonwoven fabric piece (1) so that it did not extend beyond the periphery of the nonwoven fabric piece (1). Next, 6.40 g of particulate water-absorbing agent A was sprayed from above the nonwoven fabric piece (1) so as to be approximately uniform within the area inside the frame of the nonwoven fabric piece (1), and then the frame was removed. A laminated sheet (1) was obtained with the nonwoven fabric piece (1) placed in the tray.

[0183] Example 2 A laminated sheet (2) was obtained in the same state as in Example 1, while being placed in the vat, except that the amount of the particulate water-absorbing agent A to be sprayed was changed to 1.02 g.

[0184] [Example 3] A laminated sheet (3) was obtained in the same state as in Example 1, except that the nonwoven fabric (2) was used instead of the nonwoven fabric (1) and the amount of the particulate water-absorbing agent A to be sprayed was changed to 0.38 g.

[0185] [Example 4] A laminated sheet (4) was obtained in the same state as in Example 1, except that the nonwoven fabric (2) was used instead of the nonwoven fabric (1) and the amount of the particulate water-absorbing agent A to be sprayed was changed to 5.12 g.

[0186] [Example 5] A laminated sheet (5) was obtained in the same state as in Example 1, except that the nonwoven fabric (3) was used instead of the nonwoven fabric (1) and the amount of the particulate water-absorbing agent A to be sprayed was changed to 1.28 g.

[0187] [Example 6] A laminated sheet (6) was obtained in the same state as in Example 1, except that the nonwoven fabric (4) was used instead of the nonwoven fabric (1) and the amount of the particulate water-absorbing agent A to be sprayed was changed to 3.20 g.

[0188] [Example 7] A laminated sheet (7) was obtained in the same state as in Example 1, except that the nonwoven fabric (4) was used instead of the nonwoven fabric (1) and the amount of the particulate water-absorbing agent A to be sprayed was changed to 0.64 g.

[0189] [Example 8] A laminated sheet (8) was obtained in the same state as in Example 1, except that the nonwoven fabric (5) was used instead of the nonwoven fabric (1) and the amount of the particulate water-absorbing agent A to be sprayed was changed to 1.92 g.

[0190] [Comparative Example 1] A comparative laminated sheet (1) was obtained in the same manner as in Example 1, except that a comparative nonwoven fabric (1) was used instead of the nonwoven fabric (1) and the amount of the particulate water-absorbing agent A to be sprayed was changed to 0.64 g.

[0191] [Comparative Example 2] A comparative laminated sheet (2) was obtained in the same manner as in Example 1, except that the comparative nonwoven fabric (1) was used instead of the nonwoven fabric (1) and the amount of the particulate water-absorbing agent A to be sprayed was changed to 5.76 g.

[0192] [Comparative Example 3] A comparative laminated sheet (3) was obtained in the same state as in Example 1, except that the comparative nonwoven fabric (2) was used instead of the nonwoven fabric (1) and the amount of the particulate water-absorbing agent A to be sprayed was changed to 2.56 g.

[0193] [Comparative Example 4] A comparative laminated sheet (4) was obtained in the same state as in Example 1, except that the comparative nonwoven fabric (3) was used instead of the nonwoven fabric (1) and the amount of the particulate water-absorbing agent A to be sprayed was changed to 1.28 g.

[0194] [Results] In Examples 1 to 8, the physical properties of the nonwoven fabrics used and the laminate sheets produced were measured by the methods described above, and the results are shown in Table 1. Similarly, in Comparative Examples 1 to 4, the physical properties of the comparative nonwoven fabrics used and the comparative laminate sheets produced were measured, and the results are shown in Table 2.

[0195] The laminated sheets (1) to (8) described in Examples 1 to 8 were produced by a method including a water-absorbing agent spraying step of spraying a particulate water-absorbing agent from the first fiber layer side of a nonwoven fabric formed by integrally laminating a first fiber layer and a second fiber layer. This method corresponds to the laminated sheet production method of the present invention.

[0196] Furthermore, as shown in Table 1, the first fiber layer of the nonwoven fabrics used in Examples 1 to 8 contained first adhesive conjugate fibers and non-adhesive fibers obtained using at least two types of resin components with different melting points, the second fiber layer contained second adhesive conjugate fibers obtained using at least two types of resin components with different melting points, and the ratio of the fiber density of the second fiber layer to the fiber density of the first fiber layer was 2 to 10 times (hereinafter referred to as "Requirement A"), and these laminate sheets (1) to (8) also contained a nonwoven fabric satisfying Requirement A and a particulate water-absorbing agent, and therefore correspond to the laminate sheets of the present invention.

[0197] On the other hand, the comparative nonwoven fabrics (1) and (2) used in Comparative Examples 1 to 3 do not contain non-adhesive fibers in the first fiber layer. Furthermore, the comparative nonwoven fabric (3) used in Comparative Example 4 has a ratio of the fiber density of the second fiber layer to the fiber density of the first fiber layer of 1.0, which is outside the range of 2 to 10 times. As described above, the comparative nonwoven fabrics (1) to (3) do not satisfy requirement A. Therefore, the manufacturing methods for laminate sheets described in Comparative Examples 1 to 4 do not fall under the manufacturing method for laminate sheets of the present invention. Furthermore, the comparative laminate sheets (1) to (4) do not fall under the laminate sheet of the present invention.

[0198] Furthermore, as shown in Tables 1 and 2, the laminate sheets (1) to (8) have a lower permeability of the particulate water-absorbing agent, a lower falling rate of the particulate water-absorbing agent, and a higher retention rate of the particulate water-absorbing agent compared to the comparative laminate sheets (1) to (4). In addition, the laminate sheets (1) to (8) do not contain an adhesive. Therefore, even though the laminate sheets (1) to (8) do not contain an adhesive, the particulate water-absorbing agent is prevented from falling off from the laminate sheets. In other words, the laminate sheets (1) to (8) can sufficiently retain the particulate water-absorbing agent within the laminate sheets even without using an adhesive.

[0199] From the above, the laminate sheet manufacturing method of the present invention can prevent the particulate water-absorbing agent from falling off the laminate sheet and manufacture a laminate sheet that can sufficiently retain the particulate water-absorbing agent. Therefore, it can be said that this manufacturing method can manufacture a laminate sheet with less restriction on the amount of particulate water-absorbing agent used than in the past. Furthermore, the laminate sheet manufacturing method of the present invention can prevent uneven distribution of the particulate water-absorbing agent, thereby manufacturing a laminate sheet with stable quality. Furthermore, the laminate sheet manufacturing method of the present invention can retain the water-absorbing resin inside the nonwoven fabric, so it can manufacture a laminate sheet with a basis weight that suits the intended use of the laminate sheet without complicating the sheet structure and manufacturing process.

[0200] In addition, the laminated sheet of the present invention has stable quality because the particulate water-absorbing agent is sufficiently retained, and the characteristics of the nonwoven fabric and particulate water-absorbing agent that constitute the laminated sheet can be maximized.

[0201] The laminate sheet manufacturing method and laminate sheet according to one embodiment of the present invention contain less adhesive than conventional methods or do not contain any adhesive, so that the nonwoven fabric and particulate water-absorbing agent constituting the laminate sheet can exhibit their inherent performance. Examples of absorbent articles containing the laminate sheet include hygiene materials such as diapers, napkins, and incontinence pads; hygiene materials such as masks, gowns, and surgical gowns; interior materials such as wall sheets, shoji paper, and flooring; household materials such as cover cloths, cleaning wipers, and food waste covers; toiletry products such as disposable toilets and toilet covers; pet supplies such as pet sheets, pet diapers, and pet towels; industrial materials such as wiping materials, filters, cushioning materials, oil and / or solvent adsorbents, and ink tank adsorbents; general medical materials; bedding materials; nursing care products; soil water-retaining materials for agricultural and horticultural use; industrial water-stopping materials; waste liquid solidification materials; humidity conditioners; dehumidifiers; etc.

[0202] REFERENCE SIGNS LIST 10 Nonwoven fabric 20 First fiber layer 30 Second fiber layer 40 Particulate water-absorbing agent 100 Laminated sheet

Claims

1. The process includes a water-absorbing agent spraying step in which a particulate water-absorbing agent is sprayed from the first fiber layer side of a nonwoven fabric formed by laminating and integrating a first fiber layer and a second fiber layer. The first fiber layer includes first adhesive composite fibers and non-adhesive fibers obtained using at least two resin components with different melting points. The second fiber layer includes a second adhesive composite fiber obtained using at least two resin components with different melting points. A method for manufacturing a laminated sheet, wherein the ratio of the fiber density of the second fiber layer to the fiber density of the first fiber layer is 2 times or more and 10 times or less.

2. The method for manufacturing a laminated sheet according to claim 1, wherein the basis weight of the second fiber layer is 0.2 times or more and 1.5 times or less the basis weight of the first fiber layer.

3. The method for manufacturing a laminated sheet according to claim 1, wherein the fineness of the first adhesive composite fiber is 1.1 times or more and 25 times or less the fineness of the second adhesive composite fiber.

4. A method for manufacturing a laminated sheet according to any one of claims 1 to 3, wherein the non-adhesive fiber is a polyester single fiber having a fineness of 2.0 dtex or more and 15.0 dtex or less.

5. Containing particulate water absorbent and nonwoven fabric, The nonwoven fabric is formed by laminating and integrating a first fiber layer and a second fiber layer. The first fiber layer includes first adhesive composite fibers and non-adhesive fibers obtained using at least two resin components with different melting points. The second fiber layer includes a second adhesive composite fiber obtained using at least two resin components with different melting points. A laminated sheet in which the ratio of the fiber density of the second fiber layer to the fiber density of the first fiber layer is 2 times or more and 10 times or less.

6. The laminated sheet according to claim 5, wherein the basis weight of the second fiber layer is 0.2 times or more and 1.5 times or less the basis weight of the first fiber layer.

7. The laminated sheet according to claim 5, wherein the fineness of the first adhesive composite fiber is 1.1 times or more and 25 times or less the fineness of the second adhesive composite fiber.

8. The laminated sheet according to claim 5, wherein the non-adhesive fiber is a polyester single fiber having a fineness of 2.0 dtex or more and 15.0 dtex or less.

9. An absorbent article comprising a laminated sheet according to any one of claims 5 to 8.