JP4993479B2 - Absorbent articles - Google Patents

Description

  The present invention relates to an absorbent body used for various absorbent articles such as disposable diapers and sanitary napkins, and a method for producing the same.

  Absorbent articles such as disposable diapers, sanitary napkins, incontinence pads, etc. are absorbent that absorbs and retains body fluids excreted from the body, such as urine, loose stool, menstrual blood, etc., and flexible that is placed on the side in contact with the body A liquid-permeable top sheet, and a liquid-impermeable back sheet disposed on the opposite side in contact with the body. Absorbents usually contain pulp fibers and superabsorbent polymers as main components, and when used in absorbent articles, body fluids such as urine that have entered through the surface sheet are temporarily retained by the pulp fibers. After that, the body fluid is retained with the water-absorbing polymer. It is desirable that the absorbent has a high absorption capacity, but in order to increase the absorption capacity, a large amount of pulp must be used. As a result, the absorbent becomes thick and the feeling of wearing of the absorbent article is reduced. Resulting in. Although the thickness of the absorber can be reduced to some extent by compressing the absorber, the absorber obtained by compression is generally hardened with increased hardness. However, an excellent wearing feeling cannot be obtained.

Regarding the improvement technique of the absorbent body, Patent Document 1 discloses an absorbent layer mainly composed of a highly water-absorbent resin, a non-woven substrate carrying the highly water-absorbent resin, and between the superabsorbent resin and the superabsorbent water. A non-woven fabric base material, and a non-woven base material having a relatively hydrophilic layer and a high density fiber layer, There is described a sheet-like absorbent body composed of a nonwoven fabric having a multilayer structure composed of an acquisition layer composed of a fiber layer having low hydrophilicity and low density.
However, since the absorbent body described in Patent Document 1 does not include a layer containing pulp fibers and a superabsorbent polymer, there is a concern that a body fluid may have insufficient absorption capacity, and liquid return is likely to occur. The liquid return is a phenomenon in which the liquid once absorbed by the absorbent body through the surface sheet returns to the surface sheet again in the absorbent article having the above configuration, and is one of the problems to be solved in the technical field.

Patent Document 2 includes an upper layer, a lower layer, and two layers disposed between both layers, and one of these two layers is formed from a nonwoven fabric containing a superabsorbent polymer. An absorbent laminate core is described in which the other layer contains pulp fibers and superabsorbent polymer.
However, the absorber described in Patent Document 2 cannot be said to have a sufficiently short liquid absorption time, and there is room for improvement in terms of the amount of liquid return.
As described above, an absorbent body that is thin, flexible, has good liquid absorbability, and can exhibit excellent wear feeling and liquid leakage prevention properties when used in an absorbent article has not yet been provided. .

Japanese Patent No. 3090266 JP 2005-515020 A

  Accordingly, an object of the present invention is to provide an absorber having a small thickness, being flexible, and having good liquid absorbability, and a method for producing the same.

  The present invention comprises a lower absorbent layer comprising pulp fibers and a superabsorbent polymer, and an upper absorbent layer made of a nonwoven fabric laminated on the lower absorbent layer and comprising a superabsorbent polymer. The object is achieved by providing an absorber in which the lower layer has a higher fiber density than the uppermost layer.

  The present invention also comprises a lower absorbent layer comprising pulp fibers and a superabsorbent polymer, and an upper absorbent layer made of a nonwoven fabric laminated on the lower absorbent layer and comprising a superabsorbent polymer, the upper absorbent layer The lowermost layer is a method for manufacturing an absorbent body having a fiber density higher than that of the uppermost layer, and a nonwoven fabric manufactured using a net is disposed on the net when the nonwoven fabric is manufactured. A step of laminating on the precursor so as to face the precursor of the absorbent layer, a step of spraying the superabsorbent polymer from the surface of the nonwoven fabric opposite to the net surface, and the lower absorbent layer The object is achieved by providing a method for producing an absorbent body comprising a step of pressurizing a laminate of a precursor and the nonwoven fabric from the upper and lower surfaces thereof.

  According to the present invention, it is possible to provide an absorbent body that is thin, flexible, and has good liquid absorption. When the absorbent body having such features is used as an absorbent body of various absorbent articles such as disposable diapers and sanitary napkins, for example, it is possible to realize excellent wear feeling and liquid leakage prevention properties.

Hereinafter, the absorber of the present invention is explained based on the preferred embodiment with reference to drawings.
The absorbent body 1 of this embodiment is used as an absorbent body for various absorbent articles such as disposable diapers and sanitary napkins. As shown in FIGS. 1 and 2, pulp fibers and superabsorbent polymers are used. A lower absorbent layer 2 including the upper absorbent layer 3, and an upper absorbent layer 3 that is laminated on the lower absorbent layer 2 and made of a nonwoven fabric containing a superabsorbent polymer.

  The absorber 1 is substantially vertically long. The lower absorbent layer 2 is substantially vertically long, and has an hourglass shape with a central portion in the longitudinal direction as a whole. The upper absorbent layer 3 has a vertically long rectangular shape (rectangular shape). In the present embodiment, the lower absorbent layer 2 and the upper absorbent layer 3 have the same length in the longitudinal direction, but are different in length in the width direction. That is, the length of the upper absorbent layer 3 in the width direction is larger than the width of the narrow portion of the lower absorbent layer 2 (the minimum width in the constricted portion at the center in the longitudinal direction) and the width of the wide portion of the lower absorbent layer 2. Smaller than (maximum width). The absorbent body 1 is entirely covered with a covering sheet 4 except for both end faces in the longitudinal direction of the absorbent body 1.

The lower absorbent layer 2 has an action of absorbing and holding body fluids such as urine and soft stool that have permeated through the upper absorbent layer 3, and includes pulp fibers and a superabsorbent polymer. The total content of the pulp fiber and the superabsorbent polymer is preferably 70 to 100% by weight, more preferably 85 to 100% by weight, based on the total weight of the lower absorbent layer 2, from the viewpoint of ensuring such an effect. %.
Further, the weight ratio of the pulp fiber to the superabsorbent polymer in the lower absorbent layer 2 is as follows: from the viewpoint of sufficiently holding and fixing urine, loose stool, menstrual blood, and the like, pulp fiber: superabsorbent polymer = 7: 3 to 3: 7 is preferable, and pulp fiber: superabsorbent polymer = 6: 4 to 3: 7 is more preferable.

As a pulp fiber used for the lower absorption layer 2, what is normally used in the said technical field can be used suitably. Examples thereof include natural fibers such as wood pulp and plant pulp, and these can be used alone or in admixture of two or more.
Moreover, although there is no restriction | limiting in particular in the average fiber length of the pulp fiber used for the lower absorption layer 2, It is preferable that it is 1-5 mm as a general range.
Furthermore, from the viewpoint of maintaining bulkiness that does not inhibit the liquid absorption swelling of the superabsorbent polymer, the pulp fiber preferably has a fiber roughness of 0.3 mg / m or more. “Fiber roughness” is used as a measure of fiber thickness in fibers with non-uniform fiber thickness such as wood pulp. For example, fiber roughness meter (FS-200, KAJANNI ELECTRONICS LTD.).

  As the superabsorbent polymer used for the lower absorbent layer 2, those usually used in the technical field can be appropriately used. For example, poly (sodium acrylate), (acrylic acid-vinyl alcohol) copolymer, cross-linked poly (sodium acrylate), (starch-acrylic acid) graft polymer, (isobutylene-maleic anhydride) copolymer and saponified product thereof, Examples include potassium polyacrylate, cesium polyacrylate, and the like. One of these can be used alone, or two or more can be mixed and used.

The superabsorbent polymer used for the lower absorbent layer 2 is usually a particulate polymer, but may be a fibrous polymer. The particulate superabsorbent polymer includes an amorphous type, a block type, a bowl type, a spherical particle aggregation type, a spherical type, and the like due to the difference in shape, and any type can be used.
Volume of distribution of the superabsorbent polymer in the lower absorbent layer 2 is preferably 100 to 300 g / m ^2, more preferably, 100 to 200 g / m ^2, more preferably from 130~180g / m ^2.

  The lower absorbent layer 2 does not contain a binder component for binding the superabsorbent polymer to the fiber component (pulp fiber) contained in the lower absorbent layer 2, and the superabsorbent polymer has no binder component in the lower part. It is carried on the absorption layer 2. Here, the “binder component” is a fiber component and a superabsorbent polymer which are added to bind and fix the fiber component in the absorbent layer and the superabsorbent polymer in the conventional absorbent layer of this type. Is a separate component, and examples thereof include a fused fiber (binder fiber), a hot melt pressure-sensitive adhesive, and a synthetic binder. The lower absorbent layer 2 does not contain such a binder component.

  Further, “the superabsorbent polymer is supported by the absorbent layer” means that the superabsorbent polymer enters the space formed by the fiber component contained in the absorbent layer, and enters the absorbent layer. On the other hand, it means a state in which the polymer is unlikely to move or fall off even when stress is applied from the outside. At this time, the fiber component is entangled or caught in the superabsorbent polymer, or the superabsorbent polymer adheres to the constituent fibers by developing its own tackiness. It is not chemically bonded to the polymer.

  For example, in the manufacturing process of the absorbent body 1, the superabsorbent polymer is supported as described below, after the superabsorbent polymer is sprayed on the fiber web constituting the absorbent layer, and then pressure is applied to the fiber web. Alternatively, it can be produced by spraying a superabsorbent polymer on a fiber web sprayed with water. In addition, it is particularly effective for producing the supported state to use softwood fluff pulp as the pulp fiber and to use a massive polymer with many surface irregularities as the superabsorbent polymer.

The lower absorbent layer 2 may contain components other than the pulp fiber and the superabsorbent polymer as necessary. Examples of other components that can be contained in the lower absorbent layer 2 include various additives such as a pH buffer material, hydrophilic fine powder, and deodorant, and natural fibers other than pulp, regenerated fibers, and synthetic fibers. These 1 type can be used individually or in mixture of 2 or more types.
However, as described above, from the viewpoint of realizing a state in which the superabsorbent polymer is supported in the lower absorbent layer 2, the lower absorbent layer 2 includes a binder component such as a fused fiber (binder fiber), a hot melt, or a synthetic binder. It is preferable not to contain.

The basis weight of the lower absorbent layer 2, from the viewpoint of adapted to effectively hold fixed the urine or loose feces or the like, preferably 140~750g / m ^2, more preferably a 250~520g / m ^2.
Moreover, the thickness of the lower absorption layer 2 is preferably 1.0 to 2.5 mm, more preferably 1.5 to 2.0 mm, from the viewpoint of realizing a thin diaper.

  The upper absorbent layer 3 is a layer that is laminated on the lower absorbent layer 2 and first contacts the liquid that the absorbent body 1 should absorb. For example, when the absorbent body 1 is used in an absorbent article such as a disposable diaper, It has the effect | action which permeate | transmits body fluids, such as urine and a loose stool, to the lower absorption layer 2 located in the downward direction, the effect | action which hold | maintains a body fluid as it is, and also the effect | action which absorbs the liquid which returned from the lower absorption layer 2. The upper absorbent layer 3 is made of a nonwoven fabric containing a superabsorbent polymer.

The upper absorbent layer 3 (nonwoven fabric) has a fiber density higher in the lowermost layer than in the uppermost layer. The lowermost layer is a lower layer region extending from a lower surface of the upper absorbent layer 3 (a contact surface with the lower absorbent layer 2) to a location separated by a distance corresponding to 30% of the entire thickness of the upper absorbent layer 3 in the thickness direction. Means. The uppermost layer is separated from the upper surface of the upper absorbent layer 3 (the surface opposite to the contact surface with the lower absorbent layer 2) by a distance corresponding to 30% of the total thickness of the upper absorbent layer 3 in the thickness direction. It means the upper layer region over the part. The uppermost layer where the fiber density is relatively low is a region where the assembly of the constituent fibers is relatively sparse, and the lowermost layer where the fiber density is relatively high is the relatively dense assembly of the constituent fibers. This is the area where
In FIG. 2, the upper absorbent layer 3 is shown as if it has a two-layer configuration with different fiber densities. However, in actuality, the upper absorbent layer 3 is not necessarily divided into two layers depending on the fiber density. It is not clearly divided into

  The fiber densities of the uppermost layer and the lowermost layer of the upper absorbent layer 3 can be compared by the average deviation (hereinafter referred to as SMD) of the surface roughness of the upper and lower surfaces of the upper absorbent layer 3. That is, since the nonwoven fabric used in the upper absorbent layer 3 is thin as will be described later, the SMD on the upper surface can be regarded as the SMD of the uppermost layer including the upper surface, and the SMD on the lower surface can be regarded as the lower surface SMD. It can be regarded as the SMD of the lowermost layer constituted by including. Therefore, the fiber density of the uppermost layer and the lowermost layer can be determined by determining the SMDs of the upper and lower surfaces of the upper absorbent layer 3, respectively.

  In general, the higher the fiber density, the smaller the gap between the fibers, so the SMD becomes smaller. Therefore, as described above, in the present embodiment in which the lowermost layer has a fiber density higher than that of the uppermost layer, the lowermost layer (the lower surface of the upper absorbent layer 3) is the uppermost layer (the upper surface of the upper absorbent layer 3). ) Is smaller than SMD.

  SMD is measured using KESFB4-AUTO-A (trade name) manufactured by Kato Tech Co., Ltd. with reference to the method described in the following book “Standardization and analysis of texture evaluation”. Specifically, it is measured by the following measurement method. Book: Kakio Kawabata, “Standardization and analysis of texture evaluation”, 2nd edition, Japan Textile Opportunity Association, Texture Measurement and Standardization Research Committee, issued July 10, 1980

[Measurement method of mean deviation of surface roughness (SMD)]
A non-woven fabric of an arbitrary size is cut out from the absorbent body and attached to a smooth metal flat test bench. The contact is pressed against the test piece with 9.8 cN (within ± 0.49 cN error). The specimen is moved 2 cm horizontally at a constant speed of 0.1 cm / sec. The specimen is given a uniaxial tension of 19.6 cN / cm. The contact consists of a 0.5 mm diameter piano wire bent in a U shape with a width of 5 mm, and a test piece is crimped at 9.8 cN. The contact is crimped with a spring. The spring constant is 24.5 cN / mm (within an error of ± 0.98 cN / mm), and the resonance frequency is 30 Hz or more in a state away from the surface contact. The measured value of the average deviation of the surface roughness is represented by the SMD value. This measurement is performed for both MD and CD, and an average value is obtained from the following formula (1), which is defined as an average deviation (SMD) of the surface roughness.
Average deviation of surface roughness SMD = {(SMD _MD ² + SMD _CD ² ) / 2} ^1/2 (1)
In addition, MD (Machine Direction) is a flow direction of the fiber web (nonwoven fabric precursor) at the time of manufacturing the nonwoven fabric, and CD (Cross machine Direction) is a direction orthogonal to MD.

In the upper absorbent layer 3 (nonwoven fabric), the lowermost layer has a higher fiber density than the uppermost layer, that is, the lowermost layer (lower surface of the upper absorbent layer 3) is the uppermost layer (upper surface of the upper absorbent layer 3). Since the SMD is smaller than that, the fixability and dispersibility of the superabsorbent polymer contained in the upper absorbent layer 3 are improved, and as a result, the liquid absorption rate is improved and the liquid return amount is reduced. .
In particular, when the SMD of the lowermost layer (the lower surface of the upper absorbent layer 3) is smaller than the SMD of the uppermost layer (the upper surface of the upper absorbent layer 3) by 0.01 μm or more, particularly 0.1 μm or more, the above-mentioned effect is exhibited. Is preferable in that it becomes more reliable.

The SMD of the uppermost layer (the upper surface of the upper absorbent layer 3) is preferably 0.5 to 4.0 μm, more preferably 2.5 to 3.5 μm.
The SMD of the lowermost layer (the lower surface of the upper absorbent layer 3) is preferably 0.1 to 3.5 μm, more preferably 2.0 to 3.2 μm.

In order to impart the fiber density difference as described above to the upper absorbent layer 3, it is preferable to use a nonwoven fabric having a density difference in which the fiber density differs in the thickness direction as the nonwoven fabric constituting the upper absorbent layer 3.
From such a viewpoint, in this embodiment, as a nonwoven fabric which comprises the upper absorption layer 3, a high-pressure water stream is applied from the one surface side of the web comprised from the air laid nonwoven fabric, the air through nonwoven fabric, or the fibrous material. One of spunlace nonwoven fabric (single-side treated spunlace nonwoven fabric) is used.
As is well known, these non-woven fabrics have a step of forming a web by dropping and depositing fibers placed in an air stream on the net at the time of manufacture, and / or the net surface side with respect to the web on the net. Non-woven fabric that is subjected to web bonding by passing high-temperature air or high-pressure water flow from the opposite side, that is, a non-woven fabric manufactured using a net. The surface of the net that was in contact with the net at the time of manufacture (disposed on the net) and the surface that was not in contact with the net and was directly exposed to high-temperature air or high-pressure water (air) Surface). The nonwoven fabric having such a net surface and air surface has a higher fiber density on the net surface side than on the air surface side.
When the finished nonwoven fabric is viewed from a cross section, the fuzzy surface is the air surface and the smooth surface is the net surface.

  In the present embodiment, the net surface of the nonwoven fabric having such a net surface is opposed to the lower absorbent layer 2. Therefore, the uppermost layer of the absorbent body 1 is the air surface side of the nonwoven fabric having a relatively low fiber density. By arranging the nonwoven fabric having the net surface and the air surface in this way, the upper absorbent layer 3 composed of the nonwoven fabric has a fiber density higher in the lowermost layer than in the uppermost layer.

In addition, the nonwoven fabric which comprises the upper absorption layer 3 is not restrict | limited to the nonwoven fabric of 2 layer structure which consists of an upper layer and a lower layer, The nonwoven fabric which has three or more layers may be sufficient.
Moreover, the method of giving the fiber density difference as described above to the upper absorbent layer 3 is not limited to the above-described method using a nonwoven fabric (such as an airlaid nonwoven fabric) manufactured using a net. A method in which the fiber diameter of the fibers constituting the lowermost layer (the layer adjacent to the lower absorbent layer 2) is made smaller than the fiber diameter of the fibers constituting the other layers, or 2) the basis weight of the lowermost layer is set to the other layers. It is possible to realize the fiber density difference as described above also by a method of increasing the number relatively.

  As a fiber used for the nonwoven fabric which comprises the upper absorption layer 3, a thermoplastic fiber is mentioned. Examples of the thermoplastic fiber include polypropylene, high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, polyolefins such as crystalline propylene copolymer composed of propylene and α-olefin; polyamides; polyethylene terephthalate , Polybutylene terephthalate, low melting point polyester copolymerized with diol and terephthalic acid / isophthalic acid, synthetic fiber using a single resin such as polyester such as polyester elastomer, or two or more of these resins were used Examples include composite fibers (core-sheath type, side-by-side type, etc.). Among these, from the viewpoint of efficiently supporting the superabsorbent polymer, polyolefin composite fibers are preferable.

  Moreover, as a fiber used for the said nonwoven fabric, from a viewpoint of carrying | supporting a superabsorbent polymer efficiently, a fineness becomes like this. Preferably it is 0.5-13 dtex, More preferably, it is 2.2-6.7 dtex, and fiber length is A short fiber of preferably 64 mm or less, more preferably 3 to 64 mm is preferred.

As the superabsorbent polymer used for the upper absorbent layer 3, the same polymer as that used for the lower absorbent layer 2 can be used.
The content of the superabsorbent polymer is preferably 50 to 90% by weight, more preferably 70 to 90% by weight, based on the total weight of the upper absorbent layer 3.
The distribution amount of the superabsorbent polymer in the upper absorbent layer 3 is preferably 75 to 200 g / m ² , more preferably 90 to 160 g / m ² .

The upper absorbent layer 3 does not include a binder component for binding the superabsorbent polymer to the fiber component (fiber component constituting the nonwoven fabric) contained in the upper absorbent layer 3, and the superabsorbent polymer is a binder. It is carried on the upper absorbent layer 3 without any components. The “binder component” and “support of the superabsorbent polymer” for the upper absorbent layer 3 are the same as those for the lower absorbent layer 2 described above. Applied.
Using the airlaid nonwoven fabric, air-through nonwoven fabric or single-side treated spunlace nonwoven fabric described above as the nonwoven fabric constituting the upper absorbent layer 3, and using a massive polymer with many surface irregularities as the superabsorbent polymer, the preparation of the supported state It is particularly effective.

  The upper absorbent layer 3 may contain components other than the nonwoven fabric and the superabsorbent polymer as necessary. About this other component, it is the same as that of the other component used for the lower absorption layer 2 mentioned above.

The basis weight of the upper absorbent layer 3, from the viewpoint of transmitting the urine or loose feces or the like to effectively lower absorbent layer 2, preferably 80~250g / m ^2, more preferably a 150 to 200 g / m ^2.
The thickness of the upper absorbent layer 3 is preferably 0.1 to 2.0 mm, and more preferably 0.4 to 0.8 mm, from the viewpoint of realizing thinning of the diaper.

  The lowermost layer of the upper absorbent layer 3 preferably has a lower fiber density than the uppermost layer of the lower absorbent layer 2 (a layer adjacent to the lowermost layer of the upper absorbent layer 3). With such a configuration, the capillary force increases as the absorbent body 1 moves downward, and the liquid drawability is further improved. The fiber density here is as described above. Further, the uppermost layer of the lower absorbent layer 2 is separated from the upper surface of the lower absorbent layer 2 (the contact surface with the upper absorbent layer 3) by a distance corresponding to 30% of the total thickness of the lower absorbent layer 2 in the thickness direction. It means the upper layer region over the part.

The absorber 1 is covered with a covering sheet 4 as shown in FIG. The covering sheet 4 is a liquid-permeable sheet, and in the present embodiment, the covering sheet 4 is composed of two sheets having different dimensions. One sheet is an upper covering sheet 4a having the same dimensions as the length in the longitudinal direction and the width direction of the absorbent body 1 (the length in the width direction of the absorbent body 1 here means the maximum length in the width direction). The other sheet is a lower covering sheet 4b wider than the upper covering sheet 4a. The upper covering sheet 4a is disposed to face the upper surface of the upper absorbent layer 3 (the surface opposite to the contact surface with the lower absorbent layer 2). The lower covering sheet 4b is arranged to face the lower surface of the lower absorbent layer 2 (the surface opposite to the contact surface with the upper absorbent layer 3), and the portions extending from both side edges of the lower absorbent layer 2 are The upper covering layer 4 is wound up on the upper covering sheet 4 a that covers the upper surface of the upper absorbent layer 3. The upper cover sheet 4a and the upper surface of the upper absorbent layer 3 and the lower cover sheet 4b and the lower surface of the lower absorbent layer 2 are joined together by a joining means such as a hot melt adhesive.
Covering the absorbent body 1 with the covering sheet 4 as in the present embodiment is effective in improving the shape stability of the absorbent body 1, and the high absorption in each of the lower absorbent layer 2 and the upper absorbent layer 3 described above. It is considered to be effective for maintaining the supporting state of the conductive polymer.

  As the covering sheet 4, for example, a fiber material sheet or a perforated film can be used. From the viewpoint of good liquid permeation, the covering sheet 4 is preferably made of a hydrophilic fiber sheet. As the hydrophilic fiber sheet, paper such as tissue paper and various non-woven fabrics can be used. Examples of the non-woven fabric include non-woven fabrics made of hydrophilic fibers such as cotton and rayon, and non-woven fabrics made by subjecting synthetic resin fibers to a hydrophilic treatment. Specific examples include a spunbond nonwoven fabric, a spunlace nonwoven fabric, an airlaid nonwoven fabric, and an air-through nonwoven fabric treated with a surfactant.

Appropriate values are selected for the basis weight and thickness of the absorbent body 1 according to the specific application of the absorbent article to which the absorbent body 1 is applied. For example, when used as an absorber of a disposable diaper for infants, basis weight 400~650g / m ^2, preferably in particular 450~550g / m ^2, thickness 1.5 to 3.5 mm, in particular It is preferable that it is 1.8-2.5 mm. In addition, the basic weight and thickness of the absorber 1 here are basic weight and thickness which do not include the coating sheet 4. FIG.

The absorber 1 is desirably flexible. As an evaluation of flexibility, a measured value by a handle-ometer can be used. This measured value is preferably 1 N or less, particularly preferably 0.6 N or less. The absorbent body 1 of the present embodiment has the above-described configuration, and the upper absorbent layer 3 that is a part of the absorbent body 1 is composed of a nonwoven fabric, so that it has high flexibility, and the measured value Falls within the above range.
The measured value by the handle-ometer can be measured by a measuring method according to JIS L1096 (flexibility measurement method). That is, an absorbent body cut in the longitudinal direction by 140 mm and in the width direction by 100 mm is arranged in a direction perpendicular to the grooves on a support base in which a groove having a width of 30 mm is carved. The force required when the center of the absorber is pushed by a blade having a thickness of 2 mm is measured. The apparatus used in the present invention is a texture testing machine (handle-of-meter method), HOM-3 type, manufactured by Daiei Kagaku Seiki Seisakusho. The average value of the three points is taken as the measured value.

  Next, the manufacturing method of the absorber 1 is demonstrated, referring FIG. The apparatus 10 shown in FIG. 3 is an absorber manufacturing apparatus capable of continuously producing the absorber 1 described above at a high speed.

  When the manufacturing apparatus 10 is operated, a belt-like sheet 4b ′, which is a precursor of the lower covering sheet 4b (covering sheet 4), is continuously fed out and transported by a transport mechanism (not shown). Then, the adhesive application device 11 applies an adhesive such as a hot melt adhesive in a predetermined application pattern such as a spiral shape to a predetermined location including the central portion in the width direction of the sheet 4b ′.

  Subsequently, a mixed product fiber 2 ′ of pulp fibers and a superabsorbent polymer, which is a precursor of the lower absorbent layer 2 separately manufactured according to a conventional method, is continuously provided in the center in the width direction of the continuously conveyed sheet 4b ′. It is mounted. The mixed fiber body 2 ′ has an hourglass shape and is formed narrower than the sheet 4b ′. The mixed fiber 2 'is bonded and fixed onto the sheet 4b' by the adhesive.

  Next, the pressure-sensitive adhesive is sprayed by the pressure-sensitive adhesive spraying device 12 on the upper surface of the mixed fiber 2 ′ placed on the sheet 4 b ′.

  Next, a nonwoven fabric 3 ′ (nonwoven fabric not containing a superabsorbent polymer), which is a precursor of the upper absorbent layer 3 separately manufactured according to a conventional method, is overlaid and laminated on the mixed fiber 2 ′ being conveyed. The The nonwoven fabric 3 ′ is an air-through nonwoven fabric and has a rectangular shape, and the central portion in the longitudinal direction is not bundled like the mixed product fiber 2 ′. The long side of the rectangular nonwoven fabric 3 ′ has the same length as the longitudinal direction of the mixed product fiber 2 ′, and the short side of the nonwoven fabric 3 ′ is the width of the wide part of the hourglass shaped mixed product 2 ′. It has a length between the (maximum width) and the width of the narrow portion (minimum width in the constricted portion at the central portion in the longitudinal direction). The nonwoven fabric 3 ′ is laminated on the mixed fiber 2 ′ so that its net surface faces the mixed fiber 2 ′. Thus, a laminated body 30 is formed by laminating the nonwoven fabric 3 ′ (precursor of the upper absorbent layer 3) on the mixed fiber 2 ′ (precursor of the lower absorbent layer 2). The uppermost layer of the laminate 30 is formed from the air surface side, which is a layer having a relatively low fiber density in the nonwoven fabric 3 ′.

  Next, the superabsorbent polymer is uniformly sprayed on the nonwoven fabric 3 ′ in the laminate 30 by the polymer spraying device 13. The dispersed superabsorbent polymer penetrates into the nonwoven fabric 3 ′ from the air surface side of the nonwoven fabric 3 ′ having a relatively low fiber density, and is supported on the nonwoven fabric 3 ′. Thus, spraying the superabsorbent polymer from the air surface side of the nonwoven fabric is effective in imparting good liquid absorbency to the upper absorbent layer 3 in terms of the distribution state of the superabsorbent polymer in the upper absorbent layer 3. In order to obtain a stable distribution state, it is preferable.

  Next, a belt-like sheet 4a ′, which is a precursor of the upper covering sheet 4a (covering sheet 4), is continuously fed out and conveyed by a conveying mechanism (not shown), on the nonwoven fabric 3 ′ in the laminate 30 being conveyed. Overlaid and stacked. Before the sheet 4a ′ is overlaid on the nonwoven fabric 3 ′, an adhesive such as a hot melt adhesive is applied to the predetermined portion including the central portion in the width direction of the surface facing the nonwoven fabric 3 ′ by the adhesive coating device 14. It is applied in a predetermined application pattern such as a spiral shape, and the sheet 4a ′ and the nonwoven fabric 3 ′ are joined by the adhesive. 4 schematically shows a cross section in the width direction (cross section corresponding to the cross section taken along line II in FIG. 1) of the transported object obtained in the above-described process (the transported object at the position indicated by X in FIG. 3). Indicate.

Next, portions 4b′a and 4b′a extending from both side edges of the laminate 30 of the sheet 4b ′ are wound up to the upper surface of the sheet 4a ′ forming the uppermost surface of the laminate 30 by the folding device 15, respectively. Folded toward the center in the width direction. In this way, the absorber continuous body 1 ′ is obtained.
The folding device 15 includes a pressing means (a roller and / or a guide plate) (not shown) that pressurizes the central portion in the width direction of the sheet 4b ′ in a state where tension is applied to the sheet 4b ′, and is pressurized by this pressing. Guide means (rollers and / or guide plates, etc.) (not shown) for bending both side portions 4b′a and 4b′a of the sheet 4b ′ standing up on both sides of the portion toward the center in the width direction of the sheet 4b ′. is doing.

  Next, the absorber continuum 1 ′ is pressed by the press device 16 from the upper and lower surface sides. The press device 16 is a known pressurizing unit that pressurizes a member to be pressed at a nip portion between a pair of rubber rolls. By this pressurization step, the configuration of the absorbent continuum 1 ′ is stabilized. In particular, the laminated product 30 of the mixed product 2 'and the nonwoven fabric 3', which is the precursor of the lower absorbent layer 2, is pressed from above and below by this pressurizing step. The superabsorbent polymer contained in each of 2 ′ and non-woven fabric 3 ′ firmly bites into each layer, and as a result, the above-described superabsorbent polymer is supported. From the viewpoint of reliably producing the supported state, the pressurizing step is preferably performed at a linear pressure of 100 to 800 N / cm.

  The absorber continuous body 1 ′ thus pressurized is cut into a predetermined length by the cutting device 17, and the intended absorber 1 is obtained.

The absorbent body 1 of this embodiment is interposed between a liquid-permeable top sheet and a liquid-impermeable back sheet, for example, and is used in combination with disposable diapers, sanitary napkins, incontinence pads, and diapers. It is preferably used as an absorbent body of various absorbent articles such as absorbent articles for absorbing body fluids (including urine). In order to maximize the performance of the absorbent body 1, the absorbent body 1 is arranged so that the upper absorbent layer 3 is positioned on the skin contact surface side of the absorbent article (the lower absorbent layer 2 is non-skin contact of the absorbent article). It is preferable that the absorbent article is disposed so as to be located on the surface side. As described above, in the upper absorbent layer 3 that first comes into contact with the liquid, the lowermost layer located on the non-skin contact surface side has a higher fiber density than the uppermost layer located on the skin contact surface side. Therefore, favorable liquid absorptivity is obtained by arranging the absorber 1 as described above.
In addition, in this specification, a skin contact surface is a surface turned to a wearer's skin side at the time of wear among both surfaces of the absorptive article extended in flat shape, and a non-skin contact surface is flat. Of both surfaces of the expanded absorbent article, the surface is directed to the underwear side (the side opposite to the wearer's skin side) when worn.

According to the absorbent body 1 of the present embodiment, since it is thin, flexible, and has good liquid absorbency, when used as an absorbent body of various absorbent articles, excellent wear feeling and liquid leakage prevention properties are realized. it can.
That is, the absorbent body 1 of the present embodiment is greatly reduced in thickness and flexibility by adopting the upper absorbent layer 3 made of non-woven fabric as compared with an absorbent body mainly composed of conventional pulp fibers. When used for absorbent articles, an excellent wearing feeling can be provided. In addition, the use of a non-woven fabric contains a sufficient amount of superabsorbent polymer to develop an excellent liquid absorbency, so that the liquid absorbency is also good. In addition, the use of a non-woven fabric provides good spot absorptivity (capability of absorbing the liquid without spreading in the plane direction). This spot absorptivity is more reliably exhibited when the constituent fibers of the nonwoven fabric are short fibers.

Further, since the lowermost layer of the upper absorbent layer 3 has a fiber density higher than that of the uppermost layer, the fixability of the superabsorbent polymer contained in the upper absorbent layer 3 and the superabsorbent polymer in the upper absorbent layer 3 As a result, the liquid absorption rate is improved (liquid absorption time is shortened), and the liquid return amount is reduced.
Moreover, since the lower absorbent layer 2 has higher fiber density than the upper absorbent layer 3 and contains highly hydrophilic pulp fibers, the absorbed liquid can be quickly drawn and fixed. For this reason, the absorption amount of the absorber 1 as a whole increases, and wetback is reduced.

  FIG. 5 is a diagram illustrating an example in which the absorbent body 1 having the above-described configuration is used as an absorbent body of a disposable diaper. A disposable diaper 50 shown in FIG. 5 includes a liquid-permeable top sheet 51, a liquid-impermeable back sheet 52, and the absorbent body 1 disposed between the sheets 51 and 52, and substantially includes The diaper is formed in a vertically long shape from one end to the other in the longitudinal direction of the diaper, and is disposed on the back side of the wearer at the time of wearing, and is disposed opposite to the liquid excretion portion of the wearer. It has an opposing part B and an abdominal side part C arranged on the ventral side in order. The absorbent body 1 has the upper absorbent layer 3 facing the skin contact surface side of the diaper 50 (the upper surface of the upper absorbent layer 3 is opposed to the non-skin contact surface of the topsheet 51), and the longitudinal direction of the diaper 50 is It is clamped and fixed between both sheets 51 and 52 so as to coincide with the longitudinal direction. The diaper 50 is a so-called unfolded diaper in which a pair of fastening tapes 53, 53 are provided on the right and left side edges of the back side A, and is provided on the outer surface (non-skin contact surface) of the abdominal side C. The landing tapes 54 corresponding to the fastening tapes 53 are provided. Solid gathers (not shown) are formed on both sides of the diaper 50 in the longitudinal direction.

  Since the disposable diaper 50 includes the absorbent body 1 having the above-described configuration, the disposable diaper 50 exhibits excellent wear feeling and liquid leakage prevention properties. In the disposable diaper 50, various materials conventionally used for disposable diapers can be used without particular limitation as the forming material of each member excluding the absorbent body 1 respectively.

The absorber of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, the shape of the absorber is not particularly limited. Further, the shape and size (size) of the lower absorption layer 2 and the upper absorption layer 3 may be the same, or the shape and / or size of the lower absorption layer 2 and the upper absorption layer 3 are different. Also good.
In the above embodiment, both end faces in the longitudinal direction of the absorbent body 1 are not covered with the covering sheet 4. However, these faces are also covered with the covering sheet 4, that is, the entire absorbent body 1 is covered. The sheet 4 may be covered. The absorbent body of the present invention may not be covered with a covering sheet.
In addition, the absorbent article to which the absorbent body of the present invention can be applied is not limited to the unfolded diaper configured as shown in FIG. 5, but a so-called pants-type diaper, a sanitary napkin, a panty liner (cage sheet), It is also suitable as an absorbent body such as an incontinence pad.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to these.

[Example 1]
The absorber having the form shown in FIGS. 1 and 2 was manufactured as follows, and the obtained absorber was used as a sample of Example 1.
First, 100 parts by weight of the opened fluff pulp and 100 parts by weight of a superabsorbent polymer were uniformly mixed in an air stream to obtain an hourglass-shaped lower absorbent layer having a basis weight of 330 g / m ² and a thickness of 1.8 mm. The basis weight of the fluff pulp and the superabsorbent polymer in this lower absorbent layer was 165 g / m ² , respectively.
Subsequently, a rectangular air-through nonwoven fabric as an upper absorbent layer was disposed on the lower absorbent layer to obtain a laminate. At this time, the air-through nonwoven fabric was disposed so that its net surface was opposed to the lower absorbent layer. This nonwoven fabric is composed of a core-sheath type composite fiber (thickness: 3.3 dtex, surface-treated with a surfactant, hydrophilic) having a core made of polyethylene terephthalate and a sheath made of polyethylene, and has a basis weight of 26 g / m ² and a thickness. Was 0.5 mm. Subsequently, the superabsorbent polymer was uniformly dispersed from above the upper absorbent layer (air-through nonwoven fabric) to the air surface (upper surface) side. At this time, the dispersion of the superabsorbent polymer was adjusted so that the distribution amount of the superabsorbent polymer in the upper absorbent layer was 147 g / m ² .
Furthermore the whole of the laminate, hot melt adhesive 5 g / m ² is wrapped in tissue paper of spray coating has been a basis weight 16g / m ^2, to obtain an absorbent. In this absorber, the lower absorbent layer 2 is located on the side of the face farthest from the skin. The basis weight of the entire absorbent body was 545 g / m ² and the thickness was 2.4 mm. The size of this absorber is 360 mm in the longitudinal direction (the same for both the upper and lower absorbent layers), and the width direction is 100 mm for the rectangular upper absorbent layer and the width of the wide portion for the hourglass-shaped lower absorbent layer ( The maximum width) was 125 mm, and the width of the narrow portion (the minimum width at the constricted portion in the central portion in the longitudinal direction) was 70 mm. The SMD of the upper surface of the upper absorbent layer (the uppermost layer of the upper absorbent layer) was 2.84 μm, and the SMD of the lower surface (the lowermost layer of the upper absorbent layer) was 2.81 μm.

[Example 2]
In Example 1, an absorbent body was produced in the same manner as in Example 1 except that the thickness of the core-sheath composite fiber constituting the nonwoven fabric of the upper absorbent layer was 6.7 dtex. did. In the absorber of Example 2, the SMD of the upper surface of the upper absorbent layer (the uppermost layer of the upper absorbent layer) was 3.28 μm, and the SMD of the lower surface (the lowermost layer of the upper absorbent layer) was 3.04 μm.

[Comparative Example 1]
In Example 1, the upper absorbent layer (air-through nonwoven fabric) was placed upside down (the air-through nonwoven fabric was placed so that its air surface faces the lower absorbent layer). This was manufactured as a sample of Comparative Example 1.

[Comparative Example 2]
100 parts by weight of the opened fluff pulp and 100 parts by weight of the superabsorbent polymer were uniformly mixed in an air stream to obtain a mixture having a basis weight of 520 g / m ² . The shape of this mixture was an hourglass shape similar to that of the lower absorbent layer of Example 1. The basis weights of fluff pulp and superabsorbent polymer in this mixture were 260 g / m ² , respectively. The whole of the resulting mixture, the hot-melt adhesive 5 g / m ² is wrapped in tissue paper of spray coating has been a basis weight 16g / m ^2, obtaining an absorbent, and a sample of Comparative Example 2 this. The basis weight of the absorbent body of Comparative Example 2 is 562 g / m ² and the thickness is 3.7 mm. Also, the width of the wide portion (maximum width) and the width of the narrow portion (constriction of the central portion in the longitudinal direction) of this absorbent body. The minimum width in the part) was the same as that of the lower absorption layer in Example 1.

[Performance evaluation]
About the absorber obtained by the Example and the comparative example, the absorptivity (absorption time), the liquid return amount, the softness | flexibility, and thickness were evaluated with the following method, respectively. These results are shown in Table 1 below.

<Absorptivity (absorption time)>
While pressurizing the obtained absorbent from above at 2 kPa, 40 g of physiological saline was injected into the absorbent three times, and a total of 120 g of physiological saline was injected. The time (absorption time) from when the physiological saline was injected for the third time until the physiological saline was completely absorbed was measured and evaluated in the following three stages.
○: Absorption time is 300 seconds or less.
(Triangle | delta): Absorption time exceeds 300 second and is 500 second or less.
X: Absorption time exceeds 500 seconds.

<Liquid return amount>
After the measurement of the absorption time, a 10 cm × 10 cm filter paper was placed in the physiological saline injection part of the absorber, and a load of 3.5 kPa was applied from above the filter paper and left for 2 minutes. The liquid return amount was calculated from the weight increase of the filter paper due to the transfer of the physiological saline in the absorbent body to the filter paper, and evaluated in the following three stages.
○: Liquid return amount is 1 g or less.
(Triangle | delta): The liquid return amount exceeds 1 g and is 3 g or less.
X: The liquid return amount exceeds 3 g.

<Flexibility>
The obtained absorber was subjected to the handle-ometer test, and the flexibility was evaluated in the following three stages. The smaller the measured value of the steering wheel, the softer and more flexible it is.
○: The measured value of the handle o meter is 0.6 N or less.
(Triangle | delta): The measured value of a handle ohm meter exceeds 0.6N, and is 1N or less.
X: The measured value of the handle o meter exceeds 1N.

<Thickness>
The thickness of the obtained absorbent under pressure at 2.5 g / m ² was measured and evaluated in the following three stages.
○: The thickness is 2.5 mm or less.
(Triangle | delta): Thickness exceeds 2.5 mm and is 3 mm or less.
X: Thickness exceeds 3 mm.

It is a perspective view which shows the absorber which is one Embodiment of this invention. (A) is the II sectional view schematic diagram of FIG. 1, (b) is the II-II sectional schematic view of FIG. It is a schematic diagram which shows the example of the apparatus which enforces the manufacturing method of the absorber shown in FIG. It is a schematic diagram of the cross section (cross section of the location equivalent to the II line cross section in FIG. 1) of the to-be-conveyed object (intermediate product) in the location shown by X of FIG. FIG. 2 is a plan view showing a skin contact surface side (surface sheet side) in a developed state of an absorbent article using the absorbent body shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Absorber 2 Lower absorption layer 3 Upper absorption layer 4 Cover sheet 4a Upper cover sheet 4b Lower cover sheet 50 Disposable diaper 51 Top sheet 52 Back sheet 53 Fastening tape 54 Landing tape A Dorsal part B Excretion part opposite part C Abdominal part

Claims (4)

In an absorbent article comprising an absorber,
The absorbent body includes a lower absorbent layer containing pulp fibers and a superabsorbent polymer, and an upper absorbent layer made of a nonwoven fabric laminated on the lower absorbent layer and containing a superabsorbent polymer, fiber density than the lowermost layer is the uppermost layer is rather high, and
The absorbent is disposed in the absorbent article such that a layer that comes into contact with the liquid excreted by a wearer of the absorbent article in the absorbent body first becomes the uppermost layer of the upper absorbent layer. Sex goods . The non-woven fabric is either an air-laid non-woven fabric, an air-through non-woven fabric, or a spunlace non-woven fabric formed by applying a high-pressure water flow from one side of a web made of fibrous material. The absorbent article according to claim 1, wherein a net surface that has been formed is opposed to the lower absorbent layer. The lower absorbent layer and the upper absorbent layer do not contain a binder component for binding the superabsorbent polymer to the fiber component contained in these absorbent layers, and the superabsorbent polymer is not contained in the binder. The absorbent article of Claim 1 or 2 currently carry | supported by these absorption layers without a component. The lower surface of the upper absorbent layer, which is a contact surface with the lower absorbent layer, has an average surface roughness deviation of 0.01 μm compared to the upper surface of the upper absorbent layer, which is the surface opposite to the lower surface. The absorbent article as described in any one of Claims 1-3 small above.

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