JP3552336B2 - Absorbent articles - Google Patents

Description

【００３５】
表１から分かるように、本発明の吸収性物品の一つである使いすて紙おむつは、人工尿の吸収速度が３回目とも３０秒以下にあって、しかもウェットバック量がいずれも０．７ｇ以下にあり、共に極めて優れている。更に、本発明の吸収性物品に用いられた拡散層は、坪量が２００ｇ／ｍ^２で比較すると、圧縮しても３．０ｍｍ以上の厚さを有しており、圧縮復元性に優れ、液体を吸収するための空隙を多く持っている上、優れた拡散層の液体吸収性によってトップシートに残留する液体が殆どなく、ドライタッチ性に優れており、ドライ感がある。又、拡散層が保持する水分は、１０ｇ以下にあり、液体の放出性が許容範囲にある（実施例１〜４）。
これに対して、拡散層がＮＢＫＰ１００％の場合、液体の吸収性と放出性が悪い（比較例１）。カールや捻れのような変形が付与、固定されていない繊維内架橋結合を有するパルプ繊維で構成される拡散層では、乾燥状態での復元性には優れるが、液体を吸収させた後に液体の逆戻りが生じ（ウェットバック量が多い）、ドライタッチ性にもやや劣る（比較例２）。
【００３６】
拡散層の原料として不織布材料を用いると、液体の透過性が良いため吸収速度には優れるが、不織布そのものには液体の吸収性が全くといって良いほどないので、ドライタッチ性は極めて悪い（比較例３）。
一方、繊維内架橋結合を有し、変形が付与、固定されたパルプ繊維１００％から構成される拡散層であっても、坪量が余りにも低いと、拡散層自体に嵩高さがなく、液体の保持性に劣りウェットバック量が多くなるので適さない（比較例４）。ＮＢＫＰの使用割合を多くし、逆に、繊維内架橋結合を有し、変形が付与、固定されたパルプ繊維の使用割合が少なくなり過ぎると、徐々に液体の吸収速度が悪くなり、拡散層の水分保持量が多くなって、液体の放出性が悪くなる（比較例５）。
【００３７】
【発明の効果】
本発明は、吸収性物品のトップシートと吸収体の間に、繊維内架橋結合を有し、カールや捻れのような変形が付与、固定されたセルロース繊維を含有するシート状或いはウェブ状の拡散層が配置された構成を有するため、拡散層自体の圧縮に対する復元性が優れ、それによって吸収性物品のトップシートからの液体の吸収速度が顕著に改善されるので、拡散層から吸収体への液体の放出性も優れたものとなり、ドライタッチ性が顕著に優れた吸収性物品を提供するという効果を奏する。
【図面の簡単な説明】
【図１】本発明の吸収性物品の一つとしての使いすて紙おむつの図２及び図３のｘ−ｘ’線における断面図である。
【図２】本発明の吸収性物品の一つとしての使いすて紙おむつの一部切り欠き平面図である。
【図３】本発明の吸収性物品の一つとしての使いすて紙おむつの図２とは別の一部切り欠き平面図である。
【符号の説明】
１．液透過性のトップシ−ト
２．拡散層
３．液不透過性のバックシ−ト
４．吸収体
５．綿状パルプ
６．ＳＡＰ（高吸収性ポリマー）
７．親水性シ−ト
８．伸縮性弾性体[0001]
[Industrial applications]
The present invention provides a diffusion layer containing a cellulose fiber, in which mechanical stirring is performed between a liquid-permeable top sheet and a liquid-retentive absorbent body, the fibers have cross-linking bonds, and the deformation is imparted. The present invention relates to an absorbent article which is disposed, has excellent liquid absorbability and release property, has excellent dry touch properties, and is preferably used for disposable diapers, pads for incontinent persons, sanitary napkins, bed sheets and the like. .
[0002]
[Prior art]
A disposable disposable diaper, which is one of the known absorbent articles, has a cotton-like pulp, a superabsorbent polymer (hereinafter referred to as SAP), between a liquid-permeable topsheet and a liquid-impermeable backsheet. An absorbent body made of a hydrophilic sheet or the like is arranged, and urine is absorbed by the absorbent body through the top sheet. At this time, the absorber needs to quickly receive and absorb a liquid such as urine or body fluid, and hold the liquid without re-wetting the skin.
In recent years, disposable diapers have been progressively thinned from the viewpoint of ease of use and reduction of manufacturing costs, and as a result, the usage ratio of large-volume cotton-like pulp used in absorbent materials has been reduced, resulting in smaller volume and larger absorption capacity. There is a tendency to increase the proportion of SAP.
However, since SAP absorbs urine and body fluid at a low rate, an absorbent article such as a disposable disposable diaper composed of a thin absorbent having a high proportion of SAP absorbs urine and body fluid from the top sheet ( This causes a problem that urine and body fluid leak out of the absorbent article.
[0003]
In order to solve the problem of a decrease in the absorption rate of an absorbent article using the thin absorbent, it has been proposed to further provide a diffusion layer between the liquid-permeable top sheet and the absorbent. Examples of the structure of the diffusion layer include a net-like structural member made of a hydrophobic elastic foam (JP-A-59-228001) and a diffusion sheet made of a hydrophilic synthetic fiber and a hot-melt fiber (JP-A-60-198152). ), A fiber assembly layer in which each fiber is fused at an intersection to maintain a web form (Japanese Patent Laid-Open No. 62-276003), and has a first phase in an unlofted state and a second phase in a lofted state. A diffusion sheet made of a non-woven material with particle adhesion (Japanese Patent Application Laid-Open No. 63-220867) can be used.
However, the diffusion layer made of these synthetic fibers has a high absorption rate, but does not have the ability to absorb and hold the liquid on the top sheet all at once, so that some urine or body fluid remains on the top sheet surface, As a result, a phenomenon in which the skin of the human body is given a wet feeling and the dry touch property of the top sheet is not good is observed. Deterioration of the dry touch property causes discomfort to the user, and may cause skin irritation in the case of an infant.
[0004]
On the other hand, conventionally known cellulose pulp fibers have been widely used as members of absorbers. This is due to the nature of pulp fibers, which have high liquid holding power and low release performance of absorbed liquid. However, such a pulp fiber has a problem that the absorption rate is gradually decreased when the liquid is repeatedly absorbed, and the diffusion layer which is required to have an excellent liquid release property because the liquid release performance is low. Not used.
Further, since the pulp fibers are not rigid, sheets or webs using the pulp fibers have low recoverability even when the pressure is released when the sheet is compressed and compressed. Since the density does not return to the original state and the density remains high, there is a problem that the absorption rate is also reduced.
[0005]
In order to solve the problem of compression recovery of pulp fibers, for example, Japanese Patent Publication No. Hei 5-71702 discloses a cellulose fiber using a C2 to C8 dialdehyde and a C2 to C8 monoaldehyde having an acid functionality. Discloses a method for producing a cellulose fiber in which the inside of the cellulose fiber is crosslinked by reacting with at least two hydroxyl groups on the cellulose chain of the cellulose fiber, thereby adjusting the liquid absorbency.
Also, JP-A-3-206174, JP-A-3-206175 and JP-A-3-206176 disclose that the inside of the cellulose fiber is cross-linked by using a C2 to C9 polycarboxylic acid to adjust the liquid absorbency. A method for producing a crosslinked cellulose fiber is disclosed.
Certainly, the absorbent sheet or web composed of the cellulose fibers obtained by these cross-linking treatment methods has an improved compression recovery property as compared with that of the untreated cellulose fibers, so that the absorbent material has When used as a member, the release of liquid was significantly improved. However, since no curl or twist is imparted to the fiber, there is a problem that the bulk is lost when the liquid is absorbed, the release of the liquid is impaired, and the fiber cannot be used as a diffusion layer.
[0006]
[Problems to be solved by the invention]
On the other hand, after the cross-linking agent is reacted with the cellulose fiber, or simultaneously with the reaction, mechanical stirring is performed, then fluffing and heat treatment are performed, so that the fiber has intra-fiber cross-linking, and at the same time, such as curling and twisting. Cellulose fibers that have been deformed and fixed have a high curl factor (the degree to which the fibers are curled or twisted) especially when wet with a liquid. It has been found that when a liquid is absorbed, it exhibits extremely excellent liquid absorption and release properties (Japanese Patent Application No. 7-16042).
In view of this situation, the present inventors have an absorber between a liquid-permeable topsheet and a liquid-impermeable backsheet, and a diffusion layer is disposed between the topsheet and the absorber. As a result of intensive studies on a material suitable for a diffusion layer capable of quickly absorbing a liquid, having excellent liquid holding properties even when compressed, and rapidly diffusing the absorbed liquid to an absorbent body, the above-described fiber Absorption with a diffusion layer composed of a cellulose fiber sheet or web that has cross-linking and imparts deformation such as curl or twist to the fibers by mechanical stirring, and contains a fixed amount of fixed cellulose fibers. The present invention has been completed by the conclusion that the sexual article can achieve the intended purpose. An object of the present invention is to quickly absorb a liquid such as urine or body fluid on a top sheet even under pressurized compression, and to quickly diffuse and release the absorbed liquid to the absorber without substantially retaining the absorbed liquid. The diffusion layer is configured on the absorber provided between the liquid-permeable top sheet and the liquid-impermeable back sheet, and has excellent liquid absorption, release and dry touch properties. An object of the present invention is to provide an absorbent article.
[0007]
[Means for Solving the Problems]
A first aspect of the present invention is that an absorbent is provided between a liquid-permeable topsheet and a liquid-impermeable backsheet, and a diffusion layer is further disposed between the topsheet and the absorbent. In absorbent articles,The absorber is formed by wrapping a cotton-like pulp and a highly absorbent polymer with a hydrophilic sheet,The diffusion layer is formed of a fiber containing a cellulose fiber which has a cross-linking agent added to the cellulose fiber, is subjected to mechanical stirring, fluffing and heat treatment, has a cross-linking within the fiber, is deformed, and is fixed. An absorbent article characterized in that: In the second aspect of the present invention, the cellulose fibers forming the diffusion layer are prepared such that the weight-weighted average fiber length is 3.0 mm or more, and the fibers having a length of less than 2.0 mm are less than 10% by weight. After the addition of a cross-linking agent, mechanical stirring, fluffing and heat treatment are performed to have intra-fiber cross-linking, deformed, and fixed cellulose fibers. An absorbent article according to one of the claims. A third aspect of the present invention is that the diffusion layer is 50 to 200 g / m2.²The absorbent article according to the first or second aspect of the present invention, which is constituted by a sheet or a web having a basis weight of: A fourth aspect of the present invention is the first, second, or fourth aspect of the present invention, wherein the diffusion layer has an intra-fiber cross-linking, and contains at least 40% by weight of a deformed and fixed cellulose fiber. An absorbent article according to item 3.
[0008]
Hereinafter, the configuration of the absorbent article of the present invention will be described in detail with reference to the drawings, taking a disposable disposable diaper as one of the absorbent articles as an example, but the present invention is not limited to these.
FIG. 1 is a cross-sectional view taken along line XX ′ of FIGS. 2 and 3 of the disposable disposable diaper, and FIGS. 2 and 3 are plan views in which a part of the disposable diaper is cut out. As described above, the diffusion layer 2 and the absorber 4 are provided between the liquid-permeable top sheet 1 and the liquid-impermeable back sheet 3.
The back sheet 3 is made of a liquid impermeable film such as polyethylene or polypropylene, or a material in which a nonwoven fabric, a woven fabric, or the like is laminated on the liquid impermeable film.
In FIG. 1, an absorbent body 4 is sandwiched between a top sheet 1 and a back sheet 3, and comprises a cotton-like pulp 5 and an SAP 6 wrapped by a hydrophilic sheet 7. The diffusion layer 2 is further disposed between the absorbers 4 on the absorber 4.
[0009]
Hereinafter, the components used in the present invention will be further described.
Top sheet
The top sheet is appropriately selected from hydrophilic and liquid-permeable nonwoven fabrics, woven fabrics, porous plastic films, and the like, and is used as the resin of the fiber, such as polypropylene, polyethylene, or polyester alone or in combination. Composite fibers composed of two or more components may be used, and composite fibers such as polyester / polyester, polyester / polyethylene, and polypropylene / polyethylene are particularly desirable from the viewpoint of strength, but are not particularly limited.
Diffusion layer
The diffusion layer is formed by a known chemical pulping method such as kraft pulping method, sulfite kraft pulping method, or thermomechanical pulping method using cellulose fibers, especially softwood materials such as pine, cedar, and cypress. Non-wood pulp such as wood pulp, hemp pulp, and bast fiber obtained by a mechanical pulping method such as a pulping method is used alone or in a mixed state, and further in a bleached or unbleached state. In addition, a cross-linking agent is added, and mechanical stirring, fluffing, and heat treatment are applied to the fiber to impart intra-fiber cross-linking and deformation, and a fixed pulp fiber is used to form a sheet or web. .
[0010]
The pulp fibers are described in J. TAPPI paper pulp test method No. A pulp fiber prepared by classifying fibers having a weight-weighted average fiber length of not less than 3.0 mm and less than 2.0 mm to be less than 10% by weight as measured according to No. 52 As described above, a cross-linking agent is added thereto in the same manner as above, and mechanical stirring, fluffing and heat treatment are performed to give a cross-linking bond and deformation in the fiber, and a sheet or web using the fixed pulp fiber is used. It is preferable to use such a composition because more excellent liquid absorption, retention and release properties can be obtained.
The method of classifying the fibers is not particularly limited, and widely used known fractionators, extractors, screw presses, thickeners and the like can be used alone or in combination.
[0011]
As the cross-linking agent added to the cellulose fiber, known ones can be used as they are, for example, formalin-based cross-linking agents such as formaldehyde, urea-formalin resin and melanin-urea formalin resin, and bifunctional aldehydes such as glyoxal and dialdehyde compounds. A crosslinker of a polycarboxylic acid type, a crosslinker of an ethylene urea type, or the like can be used, and one or more of them are appropriately selected from these. A crosslinking aid that promotes crosslinking may be used as needed for the crosslinking agent.
The addition ratio of these cross-linking agents is preferably 1 to 10% in terms of solid content based on the weight of the absolutely dried cellulose fiber. The method of addition is preferably a method of adding to a suspension of cellulose fibers before mechanical stirring, or a method of adding simultaneously with mechanical stirring.
Mechanical treatment imparts deformations, such as curl and twist, to the cellulosic fibers and, in conjunction with cross-linking, such deformations are fixed, thereby allowing the fibers to have shape retention, especially containing these fibers The sheet or web absorbs the liquid and is subjected to compression by pressurization, and when the pressurization is released, resilience is imparted so that the shape can be maintained in a bulky state, whereby the liquid of the sheet or web is provided. Is essential because it can significantly enhance the absorption, retention and liquid-releasing properties.
[0012]
Next, the cellulose fibers subjected to the mechanical treatment are heated at a certain temperature in order to promote an intra-fiber crosslinking reaction between the added crosslinking agent and the cellulose fibers and to fix deformation such as curl and twist given by the mechanical treatment. However, in order to enhance the effect of this heat treatment, fluffing is performed prior to the heat treatment so that the cellulose fibers do not interact with each other and the cellulose fibers themselves are not restrained. It is necessary to keep.
The moisture contained in the cellulose fibers at the time of fluffing is an important factor because it affects the fiber length of the cellulose fibers after fluffing, and is preferably 30 to 60%. If the water content is less than 30%, the fibers are greatly damaged, and the amount of fine fibers increases. If the water content exceeds 60%, unfluffed cellulose fibers remain, which is not preferable.
As the conditions for the heat treatment, the temperature may be 105 to 250 ° C., preferably 130 to 230 ° C., and the time may be a time necessary for the water content according to JIS P 8127 to be 4% by weight or less. When the temperature is lower than 105 ° C., the heat treatment takes too much time, and the crosslinking reaction does not proceed. When the temperature exceeds 250 ° C., although the treatment is completed in a short time, the deterioration of the cellulose fibers and the crosslinking agent due to heat progresses and the number of fine fibers increases, which is not preferable.
[0013]
Cellulose fibers having intra-fiber cross-linking used in the diffusion layer of the present invention and imparting deformation, and fixed, contain many fibers in which deformations such as curl and twist are more strongly fixed, so that the fibers The sheet or web containing such fibers is excellent in absorbing, retaining and releasing the liquid, and is used as a diffusion layer of the absorbent article. When used between the topsheet and the absorber, it can quickly absorb liquids such as urine and bodily fluids from the topsheet, temporarily hold the liquid by itself, and then quickly diffuse and release the liquid As a result, liquid is hardly left on the top sheet and the diffusion layer itself because the liquid is transferred to the absorber side. For this reason, the amount of wet back in which the liquid returns to the top sheet from the diffusion layer is reduced, and since no liquid remains on the top sheet, there is no wet feeling and the dry touch property is improved.
A sheet or web as a diffusion layer containing pulp fibers having cross-linked bonds within fibers, deformed and fixed, is 50 to 200 g / m2.²The desired effect can be obtained when such fibers are contained in an amount of 40% by weight or more. For thinning, a diffusion layer having a low basis weight is preferably used.
[0014]
The basis weight of the diffusion layer is 50 g / m²If it is less than 10, the resilience to compression becomes worse, and the apparent density becomes higher, so that the absorption speed becomes worse, and the wet back amount of the liquid tends to increase. In addition, the basis weight is 200 g / m²If it is larger than that, the thickness of the sheet exceeds 5 mm, so that the usability becomes poor, which is not preferable.
Furthermore, in a diffusion layer having cross-linked fibers and having a deformed and fixed cellulose fiber content of less than 40% by weight, the resilience to compression deteriorates, the liquid absorption rate decreases, and the diffusion rate decreases. The liquid retention of the layer itself is significantly increased and the layer also lacks release properties. In order to increase the internal strength of the sheet-like or web-like diffusion layer, 3 to 60% by weight of the heat-fusible fiber may be mixed with the cellulose fiber as needed, and then thermocompression-bonded.
Further, as shown in FIGS. 2 and 3, the diffusion layer is used by being arranged on the absorber, but its size may be equal to or smaller than the absorber. When used, if a place from which a liquid such as urine or bodily fluid is excreted can be specified in advance, a diffusion layer may be provided only in that part.
[0015]
Absorber
As the absorbent used in the present invention, a known absorbent can be applied as it is. For example, the most commonly used absorbent is one in which cotton-like pulp and a superabsorbent polymer are uniformly mixed, and the mixture is wrapped with a hydrophilic sheet. General-purpose ones can be used. In this case, 3 to 60% by weight of a heat-fusible substance may be mixed with the cotton-like pulp and thermocompression-bonded.
The flocculent pulp is a known chemical pulp sheet, for example, a sheet made of bleached softwood kraft pulp or a fiber having a fiber length of 5 mm or less obtained by defibrating a mechanical pulp sheet with a crusher. The pulp raw material is not limited to softwood, and non-wood pulp such as hardwood, straw, bamboo, and kenaf can also be used.
The amount of the pulp used varies depending on the intended absorber, for example, depending on whether it is used alone, a plurality of layers are used, or another absorbent is used in combination, but the basis weight is 50 to 400 g / m2.²  Is appropriately selected from the range.
[0016]
Examples of the SAP include known starch, cellulose, and synthetic polymer. More specifically, these SAPs include starch-acrylic acid (salt) graft copolymers, saponified starch-ethyl acrylate graft copolymers, and saponified starch-methyl methacrylate graft copolymers. Saponified starch-acrylonitrile graft copolymer, saponified starch-acrylamide graft copolymer, saponified starch-acrylonitrile 2-acrylamide-2-methylpropanesulfonic acid graft copolymer, acrylic acid (salt) There are a polymer, a polyethylene oxide cross-linked with acrylic acid, a cross-linked product of sodium carboxymethyl cellulose, a cross-linked product of a polyvinyl alcohol-maleic anhydride reactant, and the like, which are appropriately selected and used.
In particular, from the viewpoint of the absorption performance of absorbing urine, bodily fluid, and water that is 20 times or more its own weight, a sodium polyacrylate-based SAP is most suitable as a commonly used SAP.
The amount of the SAP used is 10 to 500%, preferably 15 to 300% of the total weight of the bone-dry cotton-like pulp, and such an amount of the SAP is used by being substantially uniformly distributed in the cotton-like pulp. . Such SAPs are such that when the polymer absorbs and swells the liquid, the particles themselves have minimal interference with each other and are less likely to come into continuous contact to form a liquid permeation barrier; Excellent absorption can be obtained because it can be easily transmitted and diffused in the three-dimensional direction and transferred to another SAP that has not yet absorbed the liquid.
[0017]
The hydrophilic sheet may be a hydrophilic sheet such as a tissue, an absorbent paper, a hydrophilic nonwoven fabric, or the like. A mat or pad in which SAP is uniformly distributed in the cotton-like pulp of a predetermined size is covered with a hydrophilic sheet so as to be used as an absorber. This absorber has a total unit weight of 80 to 250 g / m.², Preferably 100 to 200 g / m²It is selected and used in the range. Further, such an absorber is compressed under pressure in order to have an appropriate thickness.
The most general method of compressing an absorber is to compress the absorber by passing the absorber between two rolls, but the density of the absorber is substantially evenly distributed over the whole. The peripheral surface of the roll may be a continuous smooth surface so that the peripheral surface is uneven, the density of the absorber is partially different, and liquid such as urine or bodily fluid is oblique to the vertical direction. An embossing roll having a pattern arrangement designed to guide in the direction may be used.
When an embossing roll is used, the compression section and the non-compression section may be continuous or discontinuous.
[0018]
The above-described members include, for example, a hot-melt adhesive or a water-soluble glue such as a starch-based or CMC (carboxymethylcellulose) or a highly fluid adhesive between the top sheet and the diffusion layer and between the diffusion layer and the absorber. Adhesion with an agent or the like may be performed entirely or partially.
In the absorbent article of the present invention, the sheet-like or web-like diffusion layer containing cellulose fibers having a cross-linked bond within the fiber and having a deformed and fixed cellulose fiber is provided between the liquid-permeable top sheet and the absorber. The diffusion layer is provided in a sheet or web shape which is strongly deformed such as curl and twist and contains a large amount of fixed cellulose fibers and has excellent resilience to compression. Excellent absorption, retention and release properties, quickly absorb liquids such as urine and bodily fluids from the topsheet, temporarily hold the liquids themselves, then quickly diffuse and release the liquids Thus, it can be shifted to the absorber side.
For this reason, liquid hardly remains on the top sheet and the diffusion layer itself, and the amount of wet back in which the liquid returns to the top sheet is reduced. Further, since no liquid remains on the top sheet as described above, the human body It has no wet feeling even when it touches the skin, has excellent dry touch properties, and gives the user uncomfortable feeling and the problem of skin rash on the human body is improved.
[0019]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples, but of course, the present invention is not limited thereto.
[0020]
Example 1
A disposable diaper was prepared as an absorbent article by the following procedure.
Top sheet
A composite fiber composed of polyester / polyethylene was used as the hydrophilic fiber, and the basis weight was 23.0 g / m.²  A non-woven fabric having a size of 30 cm × 40 cm and a central portion cut out as shown in FIG. 2 was prepared and used as a top sheet.
Diffusion layer
Softwood bleached kraft pulp (hereinafter referred to as NBKP) is used as the cellulose fiber, and a non-formaldehyde crosslinking agent (trademark: Sumitex NF-500K, active ingredient 40%, manufactured by Sumitomo Chemical Co., Ltd.) and a crosslinking assistant (trademark: Sumitex Accelerator X-60, active ingredient 25%, manufactured by Sumitomo Chemical Co., Ltd.) were added at a solid content of 3.0% and 1.5%, respectively, based on the absolutely dry pulp weight, and then water was added to adjust the pulp concentration to 30%. After the adjustment, the mixture was placed in a double-arm kneader (model: S1-1, double-arm rotation speed: 60 rpm, 100 rpm, manufactured by Moriyama Seisakusho), and subjected to stirring at room temperature for 30 minutes.
Thereafter, the pulp was taken out of the kneader, the pulp was loosened by hand, and then put into a blow dryer at 50 ° C. to adjust the pulp moisture to 55%. The pulp with adjusted water content was immediately separated by an experimental waring blender until the fiber mass disappeared to obtain a fluffed pulp.
Further, the fluffed pulp is put into a blow dryer at 150 ° C., and is subjected to a heat treatment for 30 minutes to reduce the water content to 3.5%. Got.
Next, from 100% of this pulp fiber, the basis weight is 200 g / m2.²Was prepared and subjected to a roll press with a clearance of 0.05 mm, and the obtained sheet was used as a diffusion layer.
[0021]
Absorber
NBKP was weighed to 300 g / m on a paper machine.²The pulp sheet obtained by papermaking is subjected to a defibrating machine, and dry weight is used to obtain a basis weight of 200 g / m.²Was prepared. At that time, 200 g / m of SAP made of sodium polyacrylate (Sunwet, manufactured by Sanyo Chemical Co., Ltd.) was used.²  , And then wrapped in a piece of tissue paper and passed between plain rolls with a gap of 0.05 mm to a tension of 0.10 g / cm.³  And used as an absorber. The size of the absorber was 15 cm × 35 cm.
Back sheet
As a back sheet, a polyester sheet having a thickness of 30 μm and a size of 30 cm × 40 cm with a central portion cut out as shown in FIG. 2 was used.
Production of disposable paper diapers
An absorber is placed on the back sheet prepared as described above, then a diffusion layer is placed thereon, and a top sheet is further placed so as to cover the whole, and three elastic elastic members 8 are provided on both sides. The disposable diaper having the configuration shown in FIGS. 1 and 2 was set and adhered and fixed, and used so that the top sheet side was in contact with the skin of a human body. In addition, between the top sheet and the diffusion layer, and between the diffusion layer and the absorber, point bonding was performed at intervals of 10 mm using a hot melt adhesive (JHL-105-89, manufactured by Nippon Fuller Company), and fixed.
[0022]
Testing and evaluation
The following methods were used to evaluate and evaluate the restored thickness and moisture retention of the diffusion layer used in the prepared disposable disposable diaper, the absorption rate and wet back amount of the disposable diaper, and the dry touch property of the top sheet.
(1) Restored thickness of diffusion layer
The restoration thickness of the diffusion layer means the thickness (mm) after applying a roll press with a clearance of 0.05 mm to the diffusion layer before being incorporated into the disposable diaper, and this indicates the restoration property of the diffusion layer in a dry state. It is shown. Since the thickness changes depending on the basis weight of the diffusion layer, only the diffusion layer having the same basis weight (200 g / m 2) is used in the present invention.²) Were used for comparison. This restored thickness serves as an indicator of whether or not the layer structure has voids.
[0023]
(2) Water retention amount of diffusion layer
The amount of water retained in the diffusion layer is 645 g, a size of 100 mm x 100 mm, a thickness of 9 mm, and a 25 mm diameter hole of a stainless steel plate placed in the center of the top sheet side of the disposable diaper. 50 ml of urine was injected, and one minute later, the diffusion layer was taken out, and the amount of water (g) contained in the diffusion layer was determined from the increase in the weight of the diffusion layer, which was defined as the water retention amount.
Artificial urine composition (% by weight)
Urea 1.9%
NaCl 0.8%
CaCl₂      0.1%
MgSO₄      0.1%
The rest is water
(3) Absorption rate
The absorption rate is as follows. A stainless plate with a weight of 645 g, a size of 100 mm x 100 mm, a thickness of 9 mm, and a hole diameter of 25 mm is used and placed in the center of the top sheet side of the disposable diaper. And the time (seconds) until urine was absorbed into the diaper. The absorption rate was measured three times every 30 minutes.
[0024]
(4) Wet back amount
The amount of wet back was determined by measuring the absorption rate in (1) (30 ml of artificial urine was absorbed three times). After using the disposable diaper for 60 minutes, a 10 cm × 10 cm square was placed at the center of the top sheet side of the diaper. Put 10 sheets of filter paper on top of each other, and then 0.05kg / cm²  , And the amount of liquid transferred to the filter paper was measured, and wet back was evaluated based on the amount of the liquid. The smaller the measured liquid volume, the better the liquid does not return and the liquid has been transferred to the absorber, but is excellent, but the diffusion layer has excellent releasability and the absorbed liquid can be transferred to the absorber quickly. It is known that the wet-back amount is small when the liquid is strongly retained in the diffusion layer itself, even if the release property of the diffusion layer is poor.
(5) Dry touch properties
For the dry touch property, the absorption rate was measured in (1) (30 ml of artificial urine was absorbed three times), and then the surface of the top sheet was lightly touched by hand, and the dryness (dry touch property) was evaluated by sensory evaluation. Judged. It is known that the better the liquid absorptivity of the diffusion layer, the better the dry touch property.
The criterion was indicated in the following three stages (○, Δ, ×).
○: Dry
△: Wet
×: Very wet
[0025]
Example 2
NBKP was used as a cellulose fiber, and the NBKP was passed through a Bauer-Macnet sieving tester equipped with a 24-mesh wire mesh at a pulp concentration of 1% at 11 liter / minute to classify, and the fibers remaining without passing through the wire mesh. Was collected and the fibers that passed through the wire mesh were discarded.
The fiber length distribution of the classified fibers is measured by a fiber length distribution measuring device (model: FS-200, manufactured by Kajani), and the weight-weighted average fiber length is 3.98 mm, and the fiber length is less than 2 mm. The rate was 3.2% by weight.
When forming a diffusion layer, the classified NBKP was used in the same manner as in Example 1 except that pulp fibers having intra-fiber cross-linking, deformation, and immobilization were prepared using the classified NBKP. Disposable diapers were made and their quality was evaluated.
[0026]
Example 3
The diffusion layer has a basis weight of 60 g / m.²A disposable diaper was prepared in the same manner as in Example 2 except that the diaper was used, and the quality was evaluated in the same manner as in Example 1.
[0027]
Example 4
Example 1 was different from Example 1 in that a diffusion layer was prepared using a mixed pulp of 50% by weight of the pulp fiber obtained in Example 2 and 50% by weight of NBKP, which had a cross-linkage within the fiber, was deformed and fixed, and was obtained in Example 2. In the same manner, disposable diapers were prepared and their quality was evaluated.
[0028]
Comparative Example 1
A disposable diaper was prepared in the same manner as in Example 1 except that the diffusion layer was made of 100% NBKP, and the quality was evaluated.
[0029]
Comparative Example 2
When producing pulp fibers cross-linked in a fiber, NBKP is subjected to a cross-linking reaction, fluffing and heat treatment in the same manner as in Example 1 except that mechanical stirring is not performed, so that curl and twist are imparted and fixed. No pulp fibers were made.
A disposable diaper was prepared in the same manner as in Example 1 except that the diffusion layer was made of 100% of the pulp fiber, and the quality was evaluated.
[0030]
Comparative Example 3
The diffusion layer is made of a particle-bonded non-woven material having a first phase in an unlofted state and a second phase in a lofted state, and has a basis weight of 25 g / m 2.²A paper diaper was prepared in the same manner as in Example 1 except that the sheet was replaced with a sheet (see JP-A-63-220867), and the quality was evaluated.
[0031]
Comparative Example 4
The diffusion layer has intra-fiber cross-linking, is deformed and fixed, and uses the classified pulp fiber obtained in Example 2, and has a basis weight of 40 g / m 2.²A diaper was prepared in the same manner as in Example 1 except that the disposable diaper was prepared, and the quality was evaluated.
[0032]
Comparative Example 5
Except that the diffusion layer was formed using a mixed pulp of 30% by weight of the classified pulp fiber obtained in Example 2 and 70% by weight of NBKP, which had an intra-fiber cross-linking, was deformed and fixed, and was obtained in Example 2. A disposable diaper was prepared in the same manner as in Example 1, and the quality was evaluated.
[0033]
Table 1 shows the results obtained in Examples 1 to 4 and Comparative Examples 1 to 5.
[0034]
[Table 1]

[0035]
As can be seen from Table 1, the disposable disposable diaper, which is one of the absorbent articles of the present invention, has an artificial urine absorption rate of 30 seconds or less for the third time and a wet back amount of 0.7 g for all. The following are both excellent. Further, the diffusion layer used in the absorbent article of the present invention has a basis weight of 200 g / m2.²In comparison with the above, it has a thickness of 3.0 mm or more even when compressed, has excellent compression restoring properties, has many voids for absorbing liquid, and has excellent liquid absorbing properties of the diffusion layer. There is almost no liquid remaining on the top sheet, excellent dry touch properties, and a dry feeling. In addition, the moisture retained by the diffusion layer is 10 g or less, and the release of liquid is within an allowable range (Examples 1 to 4).
On the other hand, when the diffusion layer is 100% NBKP, the liquid has poor absorption and release properties (Comparative Example 1). Diffusion layers composed of pulp fibers that have intra-fiber crosslinks that are not fixed and deformed such as curl and twist are excellent in resilience in the dry state, but the liquid reverts after absorbing the liquid (A large amount of wet back), and the dry touch property is slightly inferior (Comparative Example 2).
[0036]
When a nonwoven fabric material is used as a raw material of the diffusion layer, the liquid permeability is good and the absorption rate is excellent, but the nonwoven fabric itself has almost no liquid absorbability, so the dry touch property is extremely poor ( Comparative Example 3).
On the other hand, even if the diffusion layer is formed of 100% pulp fibers having cross-linking within the fiber and being deformed and fixed, if the basis weight is too low, the diffusion layer itself will not be bulky, (Comparative Example 4). When the use ratio of NBKP is increased, and conversely, the use ratio of the pulp fiber having cross-linkage in the fiber and being deformed and fixed is too small, the absorption rate of the liquid gradually decreases, and the diffusion layer The water retention is increased, and the liquid release property is deteriorated (Comparative Example 5).
[0037]
【The invention's effect】
The present invention has an intra-fiber cross-linking between a top sheet and an absorbent body of an absorbent article, and imparts a deformation such as curl or twist to a sheet-like or web-like diffusion containing fixed cellulose fibers. Since the layer has a configuration in which the layers are arranged, the resilience to the compression of the diffusion layer itself is excellent, thereby significantly improving the absorption rate of the liquid from the top sheet of the absorbent article. The liquid release properties are also excellent, and the effect of providing an absorbent article with remarkably excellent dry touch properties is provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view taken along line x-x ′ of FIGS. 2 and 3 of a disposable paper diaper as one of the absorbent articles of the present invention.
FIG. 2 is a partially cutaway plan view of a disposable paper diaper as one of the absorbent articles of the present invention.
FIG. 3 is a partially cutaway plan view of a disposable paper diaper as one of the absorbent articles of the present invention, which is different from FIG.
[Explanation of symbols]
1. Liquid permeable topsheet
2. Diffusion layer
3. Liquid-impermeable backsheet
4. Absorber
5. Floc pulp
6. SAP (super absorbent polymer)
7. Hydrophilic sheet
8. Elastic elastic body

Claims (4)

An absorbent article comprising an absorbent between a liquid-permeable topsheet and a liquid-impermeable backsheet and further comprising a diffusion layer between the topsheet and the absorbent. The body is formed by wrapping the cotton-like pulp and the superabsorbent polymer with a hydrophilic sheet, and the diffusion layer adds a cross-linking agent to the cellulose fiber, and performs mechanical stirring, fluffing and heat treatment to obtain the fiber. An absorbent article characterized by being composed of fibers containing cellulose fibers having internal cross-linking, deformed and fixed. After the cellulose fibers forming the diffusion layer are prepared so that the weight-weighted average fiber length is 3.0 mm or more and the fibers having a length of less than 2.0 mm are less than 10% by weight, a crosslinking agent is added. 2. The absorbent article according to claim 1, wherein the absorbent article is made of cellulose fibers which have been subjected to mechanical stirring, fluffing and heat treatment to have intra-fiber cross-linking, deformation, and fixation. 3. The absorbent article according to claim 1, wherein the diffusion layer comprises a sheet or a web having a basis weight of 50 to 200 g / m ^{2. 4} . 4. The absorbent article according to claim 1, wherein the diffusion layer has intra-fiber cross-linking, and contains at least 40% by weight of deformed and fixed cellulose fibers.

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