WO2018116849A1

WO2018116849A1 - Absorbent sheet and absorbent article

Info

Publication number: WO2018116849A1
Application number: PCT/JP2017/043992
Authority: WO
Inventors: 亮太蔵前
Original assignee: 花王株式会社
Priority date: 2016-12-22
Filing date: 2017-12-07
Publication date: 2018-06-28
Also published as: CN109963537B; CN109963537A

Abstract

This absorbent article (20) is provided with: an absorbent sheet (10) which is obtained by affixing a water absorbent polymer (12) to a substrate sheet (11); and a cover sheet (21) which covers at least one surface of the absorbent sheet (10). The absorbent sheet (10) has a water absorbent polymer fixation rate of 40% or more. Since this absorbent article (20) exhibits high fixation performance of the water absorbent polymer (12) to the substrate sheet (11), falling-off of the water absorbent polymer (12) is not likely to occur even after absorption of a liquid. The water absorbent polymer (12) is preferably affixed to the substrate sheet (11), with an adhesive (13) for substrate sheet fixation being interposed therebetween. The adhesive (13) is preferably an acrylic, silicone-based or rubber-based adhesive, and is preferably a hot melt adhesive.

Description

Absorbent sheet and absorber

The present invention relates to an absorbent sheet used for liquid absorption, and more particularly to an absorbent sheet suitably used as an absorbent body of absorbent articles such as sanitary napkins and disposable diapers.

As an absorbent sheet used as an absorbent body of an absorbent article, a sheet in which a water-absorbing polymer is fixed to a base sheet is known. Since the absorbent sheet having such a configuration is thinner and less bulky than an absorbent body including a pile of fiber materials such as pulp fibers, it is mainly used for thin absorbent articles.

Patent Documents 1 and 2 describe an absorbent sheet in which a large number of water-absorbing polymer particles are fixed on one surface of a base sheet made of a nonwoven fabric or the like with a hot melt adhesive. With respect to the hot melt adhesive for fixing the water-absorbing polymer particles to the base sheet, Patent Document 1 can reliably fix the water-absorbing polymer particles swollen after liquid absorption, and the enormous amount of water-absorbing polymer particles due to swelling. It is described that acrylic elastomers and rubber-based ones are preferable as those having easiness of elongation that can follow the process. Patent Document 2 further describes silicone-based hot melt adhesives. .

US Patent Application Publication No. 2002/0115969 European Patent Application No. 1447067

The present invention is an absorbent sheet in which a water-absorbing polymer is fixed to a base sheet, and the water-absorbing polymer fixing rate is 40% or more.

The present invention is also an absorbent body comprising the absorbent sheet of the present invention and a covering sheet that covers at least one surface of the absorbent sheet.

Further, the present invention is the absorbent sheet according to the present invention, wherein the water-absorbing polymer is fixed to the base sheet via a base sheet fixing adhesive, It is a manufacturing method of an absorptive sheet which has a process of applying an adhesive to one side of a substrate sheet, and then spraying a small piece of a water-absorbing polymer on the one side.

FIG. 1 is a perspective view schematically showing one embodiment of the absorbent sheet of the present invention. FIG. 2 is a cross-sectional view schematically showing a part of a cross section taken along line II of FIG. Fig.3 (a) is sectional drawing which shows typically the cross section along the thickness direction in the state before liquid absorption of one Embodiment of the absorber of this invention, FIG.3 (b) shows in Fig.3 (a). It is the same sectional view in the state after liquid absorption of an absorber.

Detailed Description of the Invention

The conventional absorbent sheet has low fixing performance with respect to the base sheet of the water-absorbing polymer. Therefore, for example, when the water-absorbing polymer is in the form of particles, there may be a situation in which a considerable number of water-absorbing polymer particles have already dropped from the base sheet before use. Further, for example, when the absorbent sheet is used as an absorbent body of an absorbent article, the water absorbent polymer particles may fall off the base sheet due to swelling of the water absorbent polymer particles accompanying absorption of body fluid such as urine. there were. The water-absorbing polymer particles dropped from the absorbent sheet in the absorbent article may be agglomerated and cause the absorbent article wearer to feel hardness, and may give a jerky feeling due to rubbing of the particles. Yes, it can cause a decrease in wearing feeling. Further, in the region where the water-absorbing polymer has fallen off in the absorbent sheet, the absorption performance deteriorates, so there is a concern about liquid leakage or liquid return.

Therefore, the present invention relates to providing an absorbent sheet and an absorbent body that have a high ability to fix a water-absorbing polymer to a base sheet, and that the water-absorbing polymer does not easily fall off even after liquid absorption.

Hereinafter, the present invention will be described based on preferred embodiments with reference to the drawings. 1 and 2 show an absorbent sheet 10 which is an embodiment of the absorbent sheet of the present invention. The absorbent sheet 10 includes a base sheet 11 having one surface 11 a and another surface 11 b, and a water absorbent polymer 12 fixed to the base sheet 11. The absorbent sheet 10 has a longitudinal direction X and a width direction Y which is a direction perpendicular thereto.

In the absorbent sheet 10, both

surfaces

11a and 11b of the base material sheet 11 are substantially flat (macroscopically). The water absorbent polymer 12 is fixed to one surface 11 a of the flat base sheet 11 via an adhesive 13, and the water absorbent polymer 12 is not fixed to the other surface 11 b of the base sheet 11. In the absorbent sheet 10, the one surface 11 a side of the base sheet 11 that is the fixed surface side of the water-absorbing polymer 12 functions as a liquid absorbing surface. Such a configuration that “the water absorbent polymer 12 is fixed to the one surface 11a of the base sheet 11 via the adhesive 13 and the water absorbent polymer 12 is not fixed to the other surface 11b” will be described later. It is preferable because it can promote the formation of a gap due to the curvature of the base sheet 11 after liquid absorption / swelling of the water-absorbing polymer 12, and can contribute to improvement of absorption performance.

The base sheet 11 may be a sheet-like material to which the water-absorbing polymer 12 can be fixed, and may be liquid permeable or liquid impermeable. Examples of the base sheet 11 include resin films, foams, nets, and the like in addition to fibrous structures such as nonwoven fabrics, woven fabrics, knitted fabrics, and papers. In particular, from the viewpoint of thinning the absorbent sheet 10 and improving flexibility, the base sheet 11 preferably includes a non-woven fabric or a resin film, that is, the base sheet 11 is composed of only one of them. Or a composite sheet comprising both is preferred.

As the nonwoven fabric constituting the base sheet 11, those produced by various production methods can be used without particular limitation. For example, air-through nonwoven fabric, heat roll nonwoven fabric, spunlace nonwoven fabric, spunbond nonwoven fabric, meltblown nonwoven fabric, spunbond-meltblown-spun A bond (SMS) nonwoven fabric is mentioned. These non-woven fabrics may be hydrophilic non-woven fabrics made of fibers subjected to hydrophilic treatment. Among these non-woven fabrics, the SMS non-woven fabric is particularly effective for reducing the thickness of the absorbent sheet 10 and improving the flexibility, and is therefore preferably used as the base material sheet 11.

Examples of the resin film material constituting the base sheet 11 include polyurethane resins, polyester resins such as polyethylene terephthalate (PET), polyolefin resins such as polyethylene (PE) and polypropylene (PP), polyamide resins, Examples thereof include polyvinyl alcohol, modified products and copolymers thereof. The resin film may be provided with a plurality of apertures penetrating in the thickness direction from the viewpoint of improving liquid permeability. Among these resin films, polyolefin resin is particularly preferably used as the substrate sheet 11 because it is excellent in flexibility and workability.

In the absorbent sheet 10, the water-absorbing polymer 12 is in the form of particles, and a large number of particulate water-absorbing polymers 12 are fixed to one surface 11 a of the base sheet 11. The shape of the particulate water-absorbing polymer 12 is not particularly limited, and examples thereof include a spherical shape, a block shape, a bowl shape, and an indefinite shape. The average particle diameter of the particulate water-absorbing polymer 12 is not particularly limited, but is preferably 50 μm or more, more preferably 200 μm or more, and preferably 800 μm or less, more preferably, from the viewpoint of the balance between fixability and absorption performance. 500 μm or less.

In the present invention, the form of the water-absorbing polymer is not limited to particles, and various forms can be adopted. The present invention has been made in view of the problem that the contact area with the substrate sheet (the area of the portion fixed to the substrate sheet) is relatively small, and therefore the water-absorbing polymer is likely to fall off from the substrate sheet. Therefore, as a form of the water-absorbing polymer according to the present invention, a small piece sufficiently smaller than the base sheet is typical as a form in which such a problem is particularly likely to occur. As such a water-absorbing polymer piece, in addition to the above-mentioned particle shape, a fiber shape, a sheet shape, and the like can be exemplified, and a sheet-like water-absorbing polymer may be finely cut into a predetermined shape such as a strip shape.

As the water-absorbing polymer 12, those usable in this type of absorbent sheet can be used without particular limitation, such as polyacrylic acid soda, (acrylic acid-vinyl alcohol) copolymer, polyacrylic acid soda crosslinking. Body, (starch-acrylic acid) graft polymer, (isobutylene-maleic anhydride) copolymer and saponified product thereof, potassium polyacrylate, cesium polyacrylate, etc. Two or more kinds can be used in combination.

The water-absorbing polymer 12 preferably has a high water-absorbing property. However, when the water-absorbing property increases, the degree of swelling due to water absorption increases, which may lead to the falling off of the water-absorbing polymer 12. From such a viewpoint, when the centrifugal retention amount is used as the water absorption index of the water absorbent polymer used in the present invention, the centrifugal retention amount of the water absorbent polymer is preferably 10 g / g or more, more preferably 20 g / g or more. More preferably, it is 30 g / g or more, and preferably 60 g / g or less, and more preferably 50 g / g or less. The centrifugal retention amount (water absorption amount) of the water absorbent polymer is measured by the following method.

<Measurement method of centrifugal retention amount of water-absorbing polymer>
The measurement of the centrifugal retention amount is performed according to JIS K 7223 (1996). Nylon woven fabric (sold by Sanriki Seisakusho, product name: nylon net, standard: 250 mesh) is cut into a rectangle with a width of 10 cm and a length of 40 cm, folded in half at the center in the longitudinal direction, and heat sealed at both ends to a width of 10 cm A nylon bag having an inner dimension of 9 cm and a length of 20 cm is prepared. Next, 1.00 g of the water-absorbing polymer as a measurement sample is precisely weighed and placed uniformly at the bottom of the produced nylon bag. Next, the nylon bag containing the sample is immersed in physiological saline (0.9 mass% sodium chloride aqueous solution) adjusted to 25 ° C. After 1 hour from the start of immersion, the nylon bag is taken out from the physiological saline, suspended in a vertical state for 1 hour and drained, and then dehydrated using a centrifugal dehydrator (model H-130C special model manufactured by Kokusan Co., Ltd.). The dehydration condition is 143 G (800 rpm) for 10 minutes. After dehydration, the mass of the sample is measured, and the target centrifugal retention amount (water absorption amount) is calculated according to the following formula.
Centrifugal retention amount (g / g) = (a′−bc) / c
In the above formula, a ′ is the total mass (g) of the sample and the nylon bag after centrifugal dehydration, b is the mass (g) before water absorption (when dried) of the nylon bag, and c is before water absorption (when dry) of the sample. Represents mass (g).
The measurement is performed 5 times (n = 5), the values at each of the upper and lower points are deleted, and the average value of the remaining three points is taken as the measured value. Further, the measurement is performed at 23 ± 2 ° C. and humidity 50 ± 5%, and the sample is measured after being stored in the same environment for 24 hours or more.

One of the main characteristics of the absorbent sheet 10 is that the water-absorbing polymer fixing rate is 40% or more. The water-absorbing polymer fixing ratio indicates the ratio of the water-absorbing polymer that does not fall off even when the absorbent sheet to be measured is put into the physiological saline (0.9% by mass saline) being stirred at a predetermined rotation speed. It can be used as an index of the fixing property of the water-absorbing / swelled water-absorbing polymer to the base sheet, and the larger the value of the water-absorbing polymer fixing rate, the higher the fixing property of the water-absorbing polymer to the base sheet. This indicates that the water-absorbing polymer is unlikely to fall off before use and even after liquid absorption. The water-absorbing polymer fixing rate is measured according to the following procedures 1 to 5.

(Procedure 1) A 5 cm square absorbent sheet having a square shape in plan view is prepared as a measurement sample. After gripping the end of the measurement sample and once hanging the measurement sample vertically, the weight of the measurement sample (initial sample weight) is measured.
(Procedure 2) The whole measurement sample is immersed in physiological saline, and 30 minutes after the start of immersion, the measurement sample is taken out from the physiological saline.
(Procedure 3) A cylindrical stirrer having a diameter of 35 mm and an axial length of 12 mm and physiological saline 300 ml are placed in a beaker having a capacity of 300 ml, and the stirrer is rotated at a rotational speed of 600 ± 5 rpm using a magnetic stirrer. Stir the saline. The measurement sample that has undergone the procedure 2 is put into the stirring physiological saline, and the measurement sample is taken out from the physiological saline 30 seconds after the addition.
(Procedure 4) After the measurement sample in the wet state that has undergone the above-mentioned procedure 3 is allowed to stand for 12 hours in the bath of the thermostatic bath set at 105 ° C., the weight of the measurement sample in the dry state ( Measure the sample weight after stirring.
(Procedure 5) The total weight of members other than the water-absorbing polymer is subtracted from the initial sample weight and the sample weight after the stirring treatment, respectively, and the initial water-absorbing polymer weight (W0) and the water-absorbing polymer weight (W1) after the stirring treatment are obtained. Calculate each. And the water absorption polymer fixed rate of a measurement sample (absorbent sheet) is computed by following Formula.
Fixed rate of water-absorbing polymer (%) = (W1 / W0) × 100

In the above procedure 1, the reason for holding the end of the measurement sample (5 cm square square-shaped absorbent sheet in plan view) and once hanging it vertically is that it is placed unfixed on the base sheet. This is for removing non-fixed substances such as a water-absorbing polymer (for example, a water-absorbing polymer that is not fixed with an adhesive and is simply sprinkled from above the base sheet). In the operation of suspending the measurement sample, it is only necessary to hold the end of the measurement sample and suspend it approximately vertically for about 3 to 5 seconds, and the suspended measurement sample is not hit or shaken greatly. When suspending a measurement sample, first, grasp the end of the measurement sample using tweezers and suspend it for 3 to 5 seconds, and then suspend the measurement sample on the side opposite to the end that was gripped during the suspension. Hold the end and hang for 3-5 seconds.
Moreover, in the said procedure 1, when a 5 cm square absorbent sheet cannot be prepared as a measurement sample (for example, when the size of a measurement sample is less than 5 cm square because the size of the absorbent sheet is small), the evaluation object A plurality of small measurement samples having a size less than 5 cm square are collected from the sheet, and the total area of one side of the plurality of measurement samples is 25 cm ² . Then, for each of the plurality of measurement samples, the water-absorbing polymer fixing rate is measured according to the above procedures 1 to 5, and the average value of the plurality of water-absorbing polymer fixing rates thus obtained is determined as the water-absorbing polymer of the absorbent sheet A fixed rate.

Examples of the measuring instrument used in the procedure 3 include the following.
-Magnetic stirrer: HI-304N (manufactured by HANNA, inverted stirrer)
・ Stirrer: Starhead NALGENE (6600-0035) [35φ × 12mm]
・ Beaker: 300ml [78φ × 103mm]

The absorbent sheet of the present invention is not limited as long as the water-absorbing polymer is fixed to the base sheet and the water-absorbing polymer fixing ratio is 40% or more. A typical example of such fixing means is an adhesive. In the absorbent sheet 10, as described above, the water-absorbing polymer 12 is fixed to the surface (one surface 11a) of the base sheet 11 via the adhesive 13. ing. From the viewpoint of achieving a water-absorbing polymer fixing rate of 40% or more, the water-absorbing polymer is preferably fixed to the base sheet via the base sheet fixing adhesive, and the type of the adhesive is appropriately selected. By doing so, a higher water-absorbing polymer fixing rate, for example, 60% or higher, and further 80% or higher water-absorbing polymer fixing rate can be realized. The adhesive according to the present invention has the properties of both “liquid and solid” and “adhesive in a narrow sense that becomes liquid when pasted with a non-adhesive substance” in a liquid state (with fluidity) before use. Both “adhesives that always keep the wet state stable” are included.

As a fixing form of the water-absorbing polymer using other fixing means other than the adhesive, for example, the water-absorbing polymer is directly attached to the surface of the base sheet without passing through other members such as an adhesive. A form is mentioned. This directly adhering form of the water-absorbing polymer can be obtained by carrying out production (polymerization reaction) of the water-absorbing polymer on the base sheet.

In addition, the absorbent sheet of the present invention has not only a form in which the water-absorbing polymer is fixed on the surface of the base sheet, but also, for example, particulate water-absorbing polymer pieces are embedded and supported inside the base sheet. Are also included. Here, the water-absorbing polymer piece is embedded and supported in the interior of the base sheet. The water-absorbing polymer piece enters the inter-fiber gap of the base sheet, and stress is applied to the base sheet from the outside. In this case, the water-absorbing polymer piece is less likely to move or drop off. At this time, the water-absorbing polymer piece adheres to the constituent fiber due to its own stickiness, or the constituent fiber is entangled with the water-absorbing polymer piece. Or it is stuck. However, from the viewpoint of more surely achieving a water-absorbing polymer fixing rate of 40% or more, the water-absorbing polymer pieces are bonded via an adhesive rather than the form in which the water-absorbing polymer pieces are embedded and supported inside the base sheet. The form fixed to the surface of the material sheet is preferred.

As the adhesive 13 which is an adhesive for fixing the base material sheet of the water absorbent polymer 12 in the absorbent sheet 10, it is preferable that the adhesive 13 has a flexibility capable of extending following the swelling change accompanying the liquid absorption of the water absorbent polymer 12. Specifically, acrylic, silicone or rubber, and olefin are preferred. Regarding the flexibility of the adhesive, the maximum elongation (elongation at the time of cutting) of the adhesive measured according to the Japan Adhesive Industry Association Standard JAI7-1999 can be used as an index. It can be evaluated that the larger the size, the higher the flexibility of the adhesive. Such maximum elongation of the adhesive 13 is preferably 200% or more, more preferably 300% or more. The maximum elongation, that is, the flexibility of the adhesive 13 is preferably as high as possible, but the upper limit of the maximum elongation is preferably 3000% or less, more preferably 2500% or less.

Examples of the material (base polymer) of the acrylic adhesive include (co) polymers of vinyl monomers whose main component is 2-ethylhexyl acrylate, butyl acrylate, ethyl acrylate, cyanoacrylate, vinyl acetate, methyl methacrylate, or the like. Examples thereof include those composed of (ethylene vinyl acetate copolymer and the like).
Examples of the material (base polymer) of the silicone-based adhesive include a polydimethylsiloxane polymer polymer.
Examples of the rubber adhesive material (base polymer) include natural rubber, polyisoprene, styrene-butadiene copolymer (SBR), styrene-isoprene-styrene block copolymer (SIS), and styrene-butadiene-styrene. Examples thereof include a block copolymer (SBS), a styrene-ethylene-butadiene-styrene block copolymer (SEBS), and a styrene-ethylene-propylene-styrene block copolymer (SEPS).

The adhesive 13 is preferably a hot melt adhesive that is used by heating and melting from the viewpoint of processability and the like. Hot melt adhesives usually contain a base polymer, a tackifier and a plasticizer. Specific examples of the base polymer are as described above. For example, when the adhesive 13 is a hot melt adhesive having SBS as a base polymer, the polystyrene block (hard segment) in the base polymer mainly contributes to the expression of the cohesive force of the adhesive, and the base polymer The polybutadiene block (soft segment) in contributes to the rubber elasticity of the adhesive. Therefore, in order to achieve the water-absorbing polymer fixing ratio of 40% or more, a method of increasing the ratio of styrene in SBS is effective.

As the tackifier constituting the hot melt adhesive (adhesive 13), those which are solid at room temperature can be preferably used. For example, C5 petroleum resin, C9 petroleum resin, dicyclopentadiene petroleum resin, rosin Based petroleum resin, polyterpene resin, and terpene phenol resin can be used, and one of these can be used alone or in combination of two or more.
As a plasticizer which comprises a hot-melt-adhesive (adhesive 13), paraffin type oil and naphthenic oil are mentioned, for example, These 1 type can be used individually or in combination of 2 or more types.

The hot melt adhesive (adhesive 13) can contain other components other than the base polymer, tackifier and plasticizer, if necessary. Examples of other components include phenolic, amine-based, Examples thereof include phosphorus-based and benzimidazole-based antioxidants, and these can be used alone or in combination of two or more.

The content of the base polymer in the hot melt adhesive (adhesive 13) is preferably 10 parts by mass when the total amount of the tackifier and the plasticizer contained in the hot melt adhesive is 100 parts by weight. As mentioned above, More preferably, it is 20 mass parts or more, Preferably it is 60 mass parts or less, More preferably, it is 40 mass parts or less.
The content of the tackifier in the hot melt adhesive (adhesive 13) is preferably 20% by mass or more, more preferably 40% by mass or more, and preferably 80% with respect to the total mass of the hot melt adhesive. It is at most 70% by mass, more preferably at most 70% by mass.
The content of the plasticizer in the hot melt adhesive (adhesive 13) is preferably 0% by mass or more, more preferably 10% by mass or more, and preferably 40% by mass with respect to the total mass of the hot melt adhesive. % Or less, more preferably 25% by mass or less.

The adhesive 13 for fixing the water-absorbing polymer 12 to the base sheet 11 is used after the liquid absorption / swelling of the water-absorbing polymer 12 in order to achieve the water-absorbing polymer fixing rate of 40% or more. It is required to be able to maintain the fixing against. As a result of various studies on adhesives that can meet such demands, the present inventors have found that such adhesives can be stretched following the swelling of the water-absorbing polymer, and the swelling property of the water-absorbing polymer. As a result of studying the adhesive, it was found that the water-absorbing polymer does not fall off from the base sheet even when external force is applied, and resistance (residual stress) is necessary. Regarding the residual stress when added, it was found that there is a specific range in which the achievement of the water-absorbing polymer fixing ratio of 40% or more can be made more reliable. Based on the above knowledge, the residual stress of the base sheet fixing adhesive such as the adhesive 13 is preferably 3 kPa or more, more preferably 5 kPa or more, and preferably 18 kPa or less, more preferably, by the following method. Is 15 kPa or less.

<Measurement method of residual stress of adhesive>
Using a rotary rheometer (manufactured by Anton paar, model “Physica MCR301”), a circular receiving plate for supporting a measurement sample from below, and a flat surface opposed to the upper side of the receiving plate An adhesive to be measured is interposed between the pressing plate having a circular shape. The adhesive in this state has a circular shape in plan view, and has a thickness of 1.5 mm, a diameter of 12 mm, and a temperature of 30 ° C. Then, the pressing plate is rotated from such a state to apply a strain of 30% to the adhesive. After 20 minutes have passed since the distortion of the adhesive, the shear stress of the adhesive is measured, and the measured value is taken as the residual stress of the adhesive.

In the measurement of the residual stress, when the adhesive to be measured is unused (when it is not applied to the base sheet and is not a constituent element of the absorbent sheet), the unused adhesive is used. The agent is used for measurement as it is. On the other hand, when the adhesive to be measured is a constituent element of the absorbent sheet, the adhesive is collected from the absorbent sheet by the following solvent extraction method, and the collected adhesive is used as the measurement target. That is, the residual stress of the adhesive for fixing the base sheet such as the adhesive 13 is within the above preferred range in at least one of the unused state and the used state (the state applied to the base sheet 11). That's fine.

<Adhesive solvent extraction method>
First, an absorbent sheet containing an adhesive and a solvent capable of dissolving the adhesive are mixed in a container such as a beaker to obtain an adhesive solution in which the adhesive is dissolved in the solvent. Next, the adhesive solution is collected from the container, and the adhesive solution is obtained by drying the adhesive solution under reduced pressure using a rotary evaporator to remove the solvent from the adhesive solution. The adhesive thus obtained is used as a measurement target in the measurement of the residual stress. What is necessary is just to select the solvent used for melt | dissolution of an adhesive agent suitably according to the kind etc. of adhesive agent. When the adhesive to be measured is an adhesive (hot melt adhesive or the like) that can be used as, for example, the adhesive 13 (adhesive for fixing the base sheet) described above, as a solvent used for dissolving the adhesive, , Toluene, methyl ethyl ketone, and heptane.

For example, when the base sheet fixing adhesive such as the adhesive 13 is a hot melt adhesive, the residual stress of the hot melt adhesive can be adjusted by appropriately adjusting the composition of the base polymer, the content of the plasticizer, and the like. It can be adjusted.
For example, when the adhesive 13 is a hot melt adhesive having an SBS base polymer, as a method of increasing the residual stress of the adhesive, a method of increasing the ratio of styrene forming a cross-linked domain in the SBS is used. Is mentioned. By increasing the styrene ratio, the cross-linked domain is strengthened, and stress relaxation due to the butadiene chain is less likely to occur, resulting in an increase in the residual stress of the adhesive. On the contrary, in order to reduce the residual stress of the hot melt adhesive having SBS as a base polymer, the ratio of styrene may be decreased.
When the base sheet fixing adhesive such as the adhesive 13 is a hot melt adhesive, a method of increasing the residual stress of the adhesive includes a method of reducing the ratio of a plasticizer such as paraffin oil. It is done. On the contrary, in order to reduce the residual stress of the hot melt adhesive, the ratio of the plasticizer may be reduced.

The absorbent sheet 10 is formed by applying an adhesive (preferably a hot melt adhesive) 13 to one surface 11a of the base sheet 11, and then applying a water absorbent polymer 12 (water absorbent polymer piece) to the one surface 11a which is the adhesive application surface. It can be manufactured by spraying. The application pattern of the adhesive 13 is not particularly limited, and may be applied to the entire surface 11a of the base sheet 11 or may be partially applied. For example, the absorbent sheet 10 absorbs the absorbent article. When used as a body, from the viewpoint of minimizing the decrease in absorption performance due to the adhesive 13, partial application, that is, the application portion and the non-application portion of the adhesive 13 on the one surface 11 a of the base sheet 11. It is preferable that the adhesive 13 is applied so that. The application method of the adhesive 13 is not particularly limited, and a known application method such as a slot spray method, a curtain spray method, a spiral spray method, a coater spray method, an omega spray method, a summit spray method, or the like can be used. The coating amount of the adhesive 13 is preferably 1 g / m ² or more, more preferably 5 g / m ² or more, and preferably 30 g / m ² or less, more preferably 20 g / m ² or less, in terms of solid content.

The thickness and basis weight of the base sheet 11 and the basis weight (adhesion amount per unit area) of the water-absorbing polymer 12 are not particularly limited, and an appropriate value is selected according to the specific use of the absorbent sheet 10. Is done. When the absorbent sheet 10 is used as an absorbent body of an absorbent article, for example, it is characterized by being thin even though the basis weight of the water absorbent polymer 12 is relatively large. Specifically, when the absorbent sheet 10 is used as an absorbent body of an absorbent article, the basis weight of the water-absorbing polymer 12 has a sufficient absorption capacity, and from the point of obtaining a thin and flexible absorbent body, Preferably it is 30 g / m ² or more, more preferably 100 g / m ² or more, and preferably 600 g / m ² or less, more preferably 400 g / m ² or less.

From the same viewpoint, the thickness (substantial thickness) of the base sheet 11 is preferably 0.01 mm or more, more preferably 0.03 mm or more, and preferably 0.8 mm or less, more preferably 0.2 mm or less. . In the present specification, unless otherwise specified, “sheet thickness” means a thickness (thickness under a load of 0.5 cN / cm ² (= 0.05 kPa)) measured by the following method.
From the same viewpoint, the basis weight of the base sheet 11 is preferably 5 g / m ² or more, more preferably 8 g / m ² or more, and preferably 40 g / m ² or less, more preferably 25 g / m ² or less. is there.

<Measuring method of sheet thickness>
A circular plate having a weight of 2.5 g and a radius of 12.5 mm is placed on the measurement table, and the position of the upper surface of the circular plate in this state is set as a reference point A for measurement. Next, the circular plate is removed, the object to be measured is placed on the measurement table, the circular plate is placed again thereon, and the position of the upper surface of the circular plate in that state is set as position B. A laser displacement meter (manufactured by Keyence Corporation, CCD laser displacement sensor LK-080) is used as a measuring instrument. The difference between the reference point A and the position B is the thickness of the measurement object, that is, the thickness of the absorber under a pressure of 0.5 cN / cm ² (= 0.05 kPa).

In addition, when the sheet | seat (base material sheet) of a measuring object is integrated in the absorbent article, the taking-out method of the sheet | seat of the measuring object from the absorbent article is as follows. Cold spray (made by Nichiban Co., Ltd., trade name) is sprayed from the surface sheet side of the absorbent article. Thereafter, the constituent members of the absorbent article other than the measurement target are carefully peeled off from the absorbent article.

The absorbent sheet 10 can be used alone for absorbing liquid. For example, it can be used as a drip sheet, a sheet placed under food, a pet sheet, and the like. It is also used as an absorbent in various hygiene products such as medical pads and breast milk sheets. Particularly preferably, it is used as an absorbent in absorbent articles such as sanitary napkins and disposable diapers. Such an absorbent article generally includes a top sheet located on the side close to the wearer's skin and a back sheet located on the side far from the wearer's skin, and the absorbent sheet 10 is disposed between both sheets. The The absorbent article provided with the absorbent sheet 10 has high performance for fixing the water-absorbing polymer 12 to the base sheet 11, and even after liquid absorption, the water-absorbing polymer 12 is unlikely to fall off the base sheet 11. Inconvenience due to such falling off of the water-absorbing polymer 12, for example, the feeling of wearing of the absorbent article by causing the wearer of the absorbent article to feel hardness or a jerky feeling due to rubbing of the dropped water-absorbing polymer 12 Liquid leakage or liquid return due to a decrease or a decrease in absorption performance is unlikely to occur.

FIG. 3 shows an absorbent body 20 which is an embodiment of the absorbent body of the present invention. In the embodiment of the present invention to be described later, components different from those of the absorbent sheet 10 of the above embodiment will be mainly described, and the same components will be denoted by the same reference numerals and description thereof will be omitted. The description of the absorbent sheet 10 is applied as appropriate to components that are not specifically described.

As shown in FIG. 3A, the absorbent body 20 includes an absorbent sheet 10 and a covering sheet 21 that covers at least one surface of the absorbent sheet 10. The absorbent sheet 10 is arranged on the absorbent article such that the longitudinal direction X thereof coincides with the longitudinal direction of the absorbent article corresponding to the longitudinal direction of the absorbent article wearer, and the width direction Y of the absorbent sheet 10 is , Which coincides with the horizontal direction orthogonal to the vertical direction. The cover sheet 21 functions as a sheet for receiving the absorbent sheet 10 when the absorbent body 20 is manufactured, and plays a role of wrapping and shaping the absorbent sheet 10 after the manufacture. Further, as described above, the absorbent sheet 10 is unlikely to cause the water-absorbing polymer 12 to drop off. However, in the unlikely event that the water-absorbing polymer 12 is dropped, the covering sheet 21 has the dropped water-absorbing polymer 12 removed. 12 plays a role of preventing leakage to the outside of the absorbent body 20.

In the absorbent sheet 10, the one surface 11 a side of the base sheet 11, which is the fixed surface side of the water absorbent polymer 12, is a skin facing surface, and the other surface 11 b side is a non-skin facing surface. In the present specification, the “skin facing surface” refers to a surface of the absorbent article or a component thereof (for example, the absorbent sheet 10) that is directed toward the wearer's skin when the absorbent article is worn, that is, relatively. It is the side close to the skin of the wearer, and the “non-skin facing surface” is the surface of the absorbent article or its constituent members that is directed to the side opposite to the skin side (clothing side) when the absorbent article is worn, that is, relative It is the side far from the wearer's skin. Here, “when worn” means a state in which a normal proper wearing position is maintained.

The covering sheet 21 covers the skin facing surface and the non-skin facing surface of the absorbent sheet 10. In the absorbent body 20, as shown in FIG. 3A, the covering sheet 21 includes a skin side portion that covers the skin facing surface (the fixed surface side of the water absorbent polymer 12) of the absorbent sheet 10, and the absorbent sheet. The non-skin side part which covers 10 non-skin opposing surfaces is comprised, and this sheet | seat side part and this non-skin side part comprise one continuous sheet | seat. More specifically, in the absorbent body 20, a single continuous covering sheet 21 having a width that is two to three times the length of the absorbent sheet 10 in the width direction Y is employed. As shown in FIG. 3A, the sheet of covering sheet 21 covers the whole area of the skin-facing surface of the absorbent sheet 10 and extends outward in the lateral direction Y from both ends in the lateral direction Y of the absorbent sheet 10. The extended portion and the extended portion are rolled down below the absorbent sheet 10 to cover the entire area of the non-skin facing surface of the absorbent sheet 10. And in this one coating sheet 21, the part which coat | covers the skin opposing surface of the absorbent sheet 10 is the said skin side part, and the part which coat | covers the non-skin opposing surface of the absorbent sheet 10 is the said non-skin side part. . As the covering sheet 21, a water-permeable sheet material can be used. For example, paper, a nonwoven fabric, etc. can be used. The basis weight of the covering sheet 21 is preferably 8 g / m ² or more, more preferably 12 g / m ² or more, and preferably 30 g / m ² or less, more preferably 20 g / m ² or less.

In the absorbent body 20, as shown in FIG. 3A, the water absorbent polymer 12 in the absorbent sheet 10 is fixed to the covering sheet 21 via the covering sheet fixing adhesive 22. That is, the water-absorbing polymer 12 is fixed to the one surface 11a (skin facing surface) of the base sheet 11 via the base sheet fixing adhesive 13 applied to the one surface 11a. 21 is fixed to the covering sheet 21 via the covering sheet fixing adhesive 22 applied to the non-skin facing surface on the non-skin facing surface of the skin side portion (the facing surface of the base sheet 11). The two

sheets

11 and 21 facing each other are fixed via

adhesives

13 and 22. In addition, between the other surface 11b (non-skin facing surface) of the base material sheet 11 and the skin facing surface of the non-skin side portion of the covering sheet 21, the same adhesive (not shown) as the adhesive 22 is interposed. It is fixed.

FIG. 3B shows a state after the absorber 20 has absorbed liquid. As shown in FIG. 3B, in the state where the water absorbent polymer 12 in the absorbent sheet 10 is swollen by liquid absorption, the degree of curvature of the base sheet 11 in the absorbent sheet 10 is before the water absorbent polymer 12 is swollen. As a result, the apparent thickness T of the base sheet 11 (the protruding height of the part protruding to the skin facing surface 11a side in the base sheet 11) is larger than that before the water absorbent polymer 12 is swollen. It has increased. As described above, the absorbent sheet 10 has a water-absorbing polymer fixing ratio of 40% or more with respect to the curvature of the base sheet 11 after the water absorption / swelling of the water-absorbing polymer 12 and the accompanying increase in the apparent thickness T. This is due to the fact that That is, in the absorbent sheet 10 having a water-absorbing polymer fixing rate of 40% or more, even after the water-absorbing polymer 12 absorbs body fluid such as urine and menstrual blood and swells, most of the surface 11a of the base sheet 11 is swollen. Since the water-absorbing polymer 12 in the fixed state swells relatively narrowly, the surface 11a of the base sheet 11 is swollen with the swelling of the water-absorbing polymer 12 in the fixed state. While the side is extended in the plane direction, the other surface 11b side of the base sheet 11 is not extended in the plane direction because the water-absorbing polymer 12 is not fixed. Due to the difference in the degree of elongation on the 11b side, the base material sheet 11 is convexly curved toward the one surface 11a side, that is, the wearer's skin side. On the other hand, in the conventional absorbent sheet in which the water-absorbing polymer fixing ratio of 40% or more has not been achieved, among the water-absorbing polymers constituting the absorbent sheet, the ratio of those that fall off due to liquid absorption / swelling is not small. Even if the water-absorbing polymer that is fixed to the base sheet without falling off swells, the base sheet does not greatly extend in the surface direction, and the base sheet as shown in FIG. It is unlikely that bending or increase in apparent thickness will occur.

In the state where the water-absorbing polymer 12 is swollen by liquid absorption, as shown in FIG. 3B, the base sheet 11 is convexly curved toward the skin facing surface, and the apparent thickness T of the base sheet 11 is the water-absorbing polymer. 12 is increased as compared with that before the swelling of 12, a gap may be formed between the other surface 11 b (non-skin facing surface) of the base sheet 11 and the covering sheet 21. Since it leads to the improvement of the uptake | capture property of body fluids, such as menstrual blood, the liquid absorption performance of the absorber 20 can improve.

Further, in the absorbent body 20, in a state where the water absorbent polymer 12 is swollen by liquid absorption, the adhesive force of the adhesive 22 fixing the water absorbent polymer 12 to the covering sheet 21 is higher than that before the water absorbent polymer 12 is swollen. In such a state, as shown in FIG. 3 (b), the fixing of the covering sheet 21 to the water-absorbing polymer 12 is released, and as a result, the material and basis weight of the covering sheet 21 are reduced. Alternatively, depending on the material, basis weight, and the like of a surface sheet (not shown) arranged closer to the wearer's skin than the covering sheet 21, it is between the water absorbent polymer 12 and the covering sheet 21 (the skin side portion). There can also be gaps. The gap that may occur on the skin side of the base sheet 11 is also effective in improving the uptake of body fluid such as urine and menstrual blood, similar to the gap that may occur on the non-skin side. Improvement of liquid absorption performance can be expected.

Thus, the adhesive 13 for fixing the base sheet and the adhesive 22 for fixing the covering sheet are different in the wet state, and the former is stronger in the wet state than the latter. As the adhesive 22, a hot melt adhesive that is usually used for bonding an absorbent core such as an absorbent sheet and a covering sheet covering the absorbent core in this type of absorbent body can be used. The adhesive 22 has a smaller residual stress measured by the above method than the adhesive 13, and the preferable residual stress of the adhesive 13 is 3 kPa or more and 18 kPa or less as described above, whereas the adhesive 22 has a residual stress. The stress is usually less than 3 kPa.

In addition, the above-mentioned “state in which the apparent thickness T of the base sheet 11 in the absorbent sheet 10 is increased as compared with that before the water absorbent polymer 12 swells”, that is, the base sheet after the water absorbent polymer 12 swells. In the state where 11 is curved, as a form of the curvature, as shown in FIG. 3B, not only the whole base sheet 11 is curved but also the base sheet 11 is partially curved. There is also a possibility. That is, a form in which a plurality of curved portions in which a part of the base sheet 11 is convexly curved toward the skin facing surface side is scattered on the one surface 11a of the base sheet 11 after liquid absorption and swelling of the water-absorbing polymer 12. possible. Such a difference in the curved form of the base sheet 11 results from the basis weight and arrangement pattern of the water-absorbing polymer 12, the type of the base sheet 11, and the like. Even if the base sheet 11 has such a partially curved portion, as described above, a gap can be formed between the absorbent sheet 10 and the opposing member. Can be done.

As shown in FIG. 3B, the base sheet 11 preferably has flexibility from the viewpoint of more reliably performing deformation (curvature) after liquid absorption of the absorbent sheet 10; Specifically, the bending rigidity is preferably 10 cN or less, particularly 5 cN or less, and further preferably 3 cN or less. The bending stiffness is measured by the following method.

<Measurement method of bending stiffness>
For the measurement of the bending stiffness, a HOM-2 handle ohmmeter tester manufactured by Seisakusho Co., Ltd., which conforms to JIS L1096 (general fabric test method, confirmation 2004) stiffness / softness E method is used. A measurement sample having a rectangular shape in plan view of 100 mm × 50 mm is prepared, and the measurement sample is placed on the sample stage of a testing machine in which the slit interval is set to 30 mm so that the measurement site of the measurement sample is positioned at the center between the slits. Place horizontally. At this time, the measurement sample is not fixed to the sample stage. A blade adjusted so as to descend to a position (lowermost position) 8 mm below the surface of the sample stage is lowered from above the measurement sample at a constant speed of 200 mm / min. Then, the maximum value (cN) indicated by the indicator (load meter) when the measurement sample is pressed back and forth with the blade in the length direction is read. The measurement is performed three times with different measurement samples for the same type of measurement target (base material sheet), and the average value is calculated as the bending rigidity of the measurement target. The measurement is performed at 23 ± 2 ° C. and humidity 50 ± 5%.

As mentioned above, although this invention was demonstrated based on the embodiment, this invention can be changed suitably, without being restrict | limited to the said embodiment.
For example, in the said embodiment, although the water absorbing polymer 12 was fixed only to the one surface 11a of the base material sheet 11, it may be fixed only to the other surface 11b, and may be fixed to both

surfaces

11a and 11b. The structure in which the water-absorbing polymer 12 is fixed to both

surfaces

11a and 11b of the base sheet 11 is more water-absorbing polymer 12 than the structure in which the water-absorbing polymer 12 is fixed only to one

side

11a or 11b. Can be carried, which is preferable. Moreover, in the said embodiment, although one continuous sheet | seat was employ | adopted as the coating sheet 21, it replaces with this and the skin side coating sheet which coat | covers the skin opposing surface of the absorbent sheet 10, and the absorbent sheet 10 You may employ | adopt a total of two sheets with the non-skin-side sheet | seat which coat | covers the non-skin opposing surface.
In addition, the absorbent article to which the absorbent sheet and the absorbent body of the present invention are applied widely includes articles used for absorption of body fluids (urine, loose stool, menstrual blood, sweat, etc.) discharged from the human body, for example, An unfolded disposable diaper, a pants-type disposable diaper, a sanitary napkin, a sanitary short, and the like are also included. The following additional notes are disclosed with respect to the embodiment of the present invention described above.

<1>
An absorbent sheet in which a water-absorbing polymer is fixed to a base sheet, wherein the water-absorbing polymer fixing rate measured according to the following procedures 1 to 5 is 40% or more.
(Procedure 1) A 5 cm square absorbent sheet having a square shape in plan view is prepared as a measurement sample. After gripping the end of the measurement sample and once hanging the measurement sample vertically, the weight of the measurement sample (initial sample weight) is measured.
(Procedure 2) The whole measurement sample is immersed in physiological saline, and 30 minutes after the start of immersion, the measurement sample is taken out from the physiological saline.
(Procedure 3) A cylindrical stirrer having a diameter of 35 mm and an axial length of 12 mm and physiological saline 300 ml are placed in a beaker having a capacity of 300 ml, and the stirrer is rotated at a rotational speed of 600 ± 5 rpm using a magnetic stirrer. Stir the saline. The measurement sample that has undergone the procedure 2 is put into the stirring physiological saline, and the measurement sample is taken out from the physiological saline 30 seconds after the addition.
(Procedure 4) After the measurement sample in the wet state that has undergone the above-mentioned procedure 3 is allowed to stand for 12 hours in the bath of the thermostatic bath set at 105 ° C., the weight of the measurement sample in the dry state ( Measure the sample weight after stirring.
(Procedure 5) The total weight of members other than the water-absorbing polymer is subtracted from the initial sample weight and the sample weight after the stirring treatment, respectively, and the initial water-absorbing polymer weight (W0) and the water-absorbing polymer weight (W1) after the stirring treatment are obtained. Calculate each. And the water absorption polymer fixed rate of a measurement sample (absorbent sheet) is computed by following Formula.
Fixed rate of water-absorbing polymer (%) = (W1 / W0) × 100

<2>
The absorbent sheet according to <1>, wherein the water-absorbing polymer is fixed to the base sheet via an adhesive for fixing the base sheet.
<3>
The absorbent sheet according to <2>, wherein the adhesive for fixing the base sheet is acrylic, silicone or rubber.
<4>
The absorbent sheet according to <2> or <3>, wherein the base sheet fixing adhesive is a hot melt adhesive.
<5>
The maximum elongation of the adhesive for fixing the base sheet according to Japan Adhesive Industry Association Standard JAI7-1999 is preferably 200% or more, more preferably 300% or more, and preferably 3000% or less, more preferably 2500. % Of the absorbent sheet according to any one of the above items <2> to <4>.

<6>
Any one of the above items <2> to <5>, wherein the base sheet fixing adhesive contains a base polymer, a tackifier, and a plasticizer, and the base polymer is a styrene-butadiene-styrene block copolymer. The absorbent sheet according to item 1.
<7>
<6> wherein the tackifier is at least one selected from the group consisting of C5 petroleum resins, C9 petroleum resins, dicyclopentadiene petroleum resins, rosin petroleum resins, polyterpene resins and terpene phenol resins. Absorbent sheet as described in 1.
<8>
The absorbent sheet according to <6> or <7>, wherein the plasticizer is at least one selected from the group consisting of paraffinic oil and naphthenic oil.
<9>
The content of the base polymer in the base sheet fixing adhesive is preferably 10 parts by mass when the total amount of the tackifier and the plasticizer contained in the adhesive is 100 parts by weight. The absorbent sheet according to any one of <6> to <8>, more preferably 20 parts by mass or more, and preferably 60 parts by mass or less, and more preferably 40 parts by mass or less.
<10>
The content of the tackifier in the base sheet fixing adhesive is preferably 20% by mass or more, more preferably 40% by mass or more, and preferably 80% by mass with respect to the total mass of the adhesive. The absorbent sheet according to any one of <6> to <9>, further preferably 70% by mass or less.
<11>
The content of the plasticizer in the adhesive for fixing the base sheet is preferably 0% by mass or more, more preferably 10% by mass or more, and preferably 40% by mass or less with respect to the total mass of the adhesive. The absorbent sheet according to any one of <6> to <10>, more preferably 25% by mass or less.
<12>
Any one of the above items <2> to <11>, wherein the residual stress of the base sheet fixing adhesive is preferably 3 kPa or more, more preferably 5 kPa or more, and preferably 18 kPa or less, more preferably 15 kPa or less. The absorbent sheet according to item.
<13>
The coating amount of the base sheet fixing adhesive is preferably 1 g / m ² or more, more preferably 5 g / m ² or more, and preferably 30 g / m ² or less, more preferably 20 g / m in terms of solid content. The absorbent sheet according to any one of the above items <2> to <12>, which is ² or less.

<14>
The absorbent sheet according to any one of <2> to <13>, wherein both surfaces of the base sheet are flat.
<15>
The water-absorbing polymer is fixed to one surface of the base sheet through the base sheet fixing adhesive, and the water-absorbing polymer is not fixed to the other surface of the base sheet <14 > Absorbent sheet of description.
<16>
The absorbent sheet according to any one of <1> to <14>, wherein the water-absorbing polymer is fixed to both surfaces of the base sheet.
<17>
<1> The basis weight of the water-absorbing polymer is preferably 30 g / m ² or more, more preferably 100 g / m ² or more, and preferably 400 g / m ² or less, more preferably 300 g / m ² or less. The absorbent sheet according to any one of to <16>.
<18>
The centrifugal retention amount of the water-absorbing polymer is preferably 10 g / g or more, more preferably 20 g / g or more, more preferably 30 g / g or more, and preferably 60 g / g or less, more preferably 50 g / g or less. The absorbent sheet according to any one of the above items <1> to <17>.
<19>
The absorbent sheet according to any one of <1> to <18>, wherein the base sheet includes a nonwoven fabric or a resin film.
<20>
The absorbent sheet according to any one of <1> to <19>, wherein the base sheet has a flexural rigidity of preferably 10 cN or less, more preferably 5 cN or less, more preferably 3 cN or less.
<21>
The thickness of the base sheet is preferably 0.01 mm or more, more preferably 0.03 mm or more, and preferably 0.8 mm or less, more preferably 0.2 mm or less. The absorptive sheet given in any 1 paragraph.
<22>
The basis weight of the base sheet is preferably 5 g / m ² or more, more preferably 8 g / m ² or more, and preferably 40 g / m ² or less, more preferably 25 g / m ² or less <1>. The absorbent sheet according to any one of to <21>.
<23>
The absorbent sheet according to any one of <1> to <22>, wherein the base sheet is a nonwoven fabric.
<24>
The absorbent sheet according to any one of <1> to <23>, wherein the base sheet is a spunbond-meltblown-spunbond nonwoven fabric.
<25>
Any one of the above items <1> to <24>, wherein the water-absorbing polymer is in the form of particles and has an average particle size of preferably 50 μm or more, more preferably 200 μm or more, and preferably 800 μm or less, more preferably 500 μm or less. The absorbent sheet of Claim 1.

<26>
An absorbent body comprising the absorbent sheet according to any one of the above items <1> to <25> and a covering sheet that covers at least one surface of the absorbent sheet.
<27>
In the state where the water-absorbing polymer in the absorbent sheet is swollen by liquid absorption, the apparent thickness of the base sheet in the absorbent sheet is increased as compared with that before the water-absorbing polymer is swollen <26 The absorber as described in>.
<28>
The water-absorbing polymer is fixed to the covering sheet via an adhesive for fixing the covering sheet,
The absorbent body according to <27>, wherein in the state where the water-absorbing polymer is swollen by liquid absorption, the adhesive strength of the adhesive for fixing the covering sheet is lower than that before the water-absorbing polymer is swollen.

<29>
In the absorbent sheet, the water-absorbing polymer is fixed to the base sheet through an adhesive for fixing the base sheet,
The adhesive for fixing the base sheet and the adhesive for fixing the covering sheet have different adhesive strengths in a wet state, and the adhesive for fixing the base sheet is wetter than the adhesive for fixing the covering sheet. The absorbent material according to <28>, wherein the adhesive strength in a state is strong.
<30>
The water-absorbing polymer is fixed to the base sheet via a base sheet fixing adhesive,
The said covering sheet fixing adhesive is an absorber as described in said <28> or <29> with a small residual stress compared with the said base material sheet fixing adhesive.
<31>
The basis weight of the covering sheet is preferably 8 g / m ² or more, more preferably 12 g / m ² or more, and preferably 30 g / m ² or less, more preferably 20 g / m ² or less. <30> The absorber according to any one of the above.
<32>
The covering sheet covers the entire skin-facing surface of the absorbent sheet and extends laterally outward from both lateral ends of the absorbent sheet, and the extending portion is a non-skin of the absorbent sheet. The absorbent body according to any one of <26> to <31>, wherein the absorbent body is wound down toward the facing surface side and covers the entire area of the non-skin facing surface.
<33>
The absorbent according to any one of <26> to <32>, wherein the water-absorbing polymer fixing ratio is 60% or more, more preferably 80% or more.

<34>
The method for producing an absorbent sheet according to any one of the above <1> to <25>,
The manufacturing method of an absorptive sheet which has a process of apply | coating an adhesive agent to one surface of a base material sheet, and spraying the small piece of a water absorbing polymer on this one surface.
<35>
The method for producing an absorbent sheet according to <34>, wherein the adhesive has a residual stress of 3 kPa to 18 kPa.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to such examples.

[Examples 1 to 6 and Comparative Examples 1 and 2]
An absorbent sheet having the same configuration as the absorbent sheet 10 shown in FIGS. 1 and 2 was produced. As the base sheet, an SMS nonwoven fabric having a basis weight of 10 g / m ² was used in Examples 1 to 5 and Comparative Examples 1 and 2, and a PET film having a basis weight of 35 g / m ² was used in Example 6. As the water-absorbing polymer, a particulate polyacrylate water-absorbing polymer (average particle size 400 μm, centrifugal retention 27 g / g) was used. Examples 1-2 and 6 and Comparative Examples 1 and 2 are rubber-based hot-melt adhesives for fixing the water-absorbing polymer to the base sheet, and ethylene vinyl acetate copolymer is used in Example 3. A hot melt adhesive, a silicone adhesive in Example 4, and an acrylic adhesive in Example 5, were used, respectively, and the basis weight of the adhesive was 20 g / m ^{2 in} terms of solid content.

[Evaluation Test 1]
With respect to the absorbent sheets of the examples and comparative examples, the water-absorbing polymer fixing rate was measured according to the procedures 1 to 5. The results are shown in Table 1 below together with the residual stresses measured by the above methods for the adhesives for fixing the base sheet used in each Example and Comparative Example.

In addition, disposable diapers were prepared using the absorbent sheets of the examples and comparative examples. Specifically, an absorbent core (such as pulp fiber and water-absorbing polymer covered with a covering sheet) is removed from a disposable diaper (trade name “Merry's”, released in 2016) manufactured by Kao Corporation. The absorbent sheets of the examples and comparative examples having the same shape and dimensions as the removed absorbent core were wrapped in a covering sheet in the same manner as the absorbent core and incorporated into the diaper. About the disposable diaper produced in this way, the water absorbing polymer fixability at the time of absorbent article wear was evaluated by the following method. The results are shown in Table 1 below.

<Evaluation method of water-absorbing polymer fixability when wearing absorbent articles>
The diaper to be evaluated is folded vertically in the vertical direction with the skin-facing surface, that is, the top sheet, inside, and the sides of the central part of the absorbent body, which is the artificial urine injection scheduled part, are gripped with fingers and alternately in the vertical direction Move to. After repeating this up-and-down motion 50 times, each part of the diaper is stretched and spread in a flat shape, and the artificial urine is placed on the top sheet in the center of the absorbent body with the top sheet facing upward and fixed on the horizontal plane. 120 g was injected and absorbed, and then allowed to stand for 3 minutes in a natural state.
Next, the up-and-down movement performed before the artificial urine is injected is performed again on the diaper. This up-and-down movement assumes movement of a wearer's leg while wearing a diaper. After repeating this up-and-down motion 20 times, the covering sheet in the diaper is cut open, the state of the absorbent sheet is visually observed, and no dropout or movement of the water-absorbing polymer is seen or only a small part is seen. The case was A (highest evaluation), and the other cases were B.

The composition of the artificial urine used in the measurement method is as follows. 1.94% by mass of urea, 0.7954% by mass of sodium chloride, 0.11058% by mass of magnesium sulfate (septahydrate), 0.06208% by mass of calcium chloride (dihydrate), 0.19788% by mass of potassium sulfate , Polyoxyethylene lauryl ether 0.0035 mass% and ion-exchanged water (remaining amount).

As shown in Table 1, the absorbent sheet of each Example having a water-absorbing polymer fixing rate of 40% or more or an absorbent body using the same has high water-absorbing polymer fixing property when the absorbent article is worn. Even if it moves after excretion of body fluids such as urine, the water-absorbing polymer does not easily fall off or move, and the shape retention as an absorber is excellent. On the other hand, each comparative example in which the water-absorbing polymer fixing rate does not reach 40% has a low water-absorbing polymer fixing property when the absorbent article is worn, and in such an evaluation test of the water-absorbing polymer fixing property, It was confirmed that large unevenness was formed as the absorbent body due to remarkable dropout and movement. From the above results, each example is less likely to give a sense of incongruity when wearing an absorbent article due to the dropping of the water-absorbing polymer as compared with each comparative example, and can stably exhibit excellent absorption performance. It is obvious.

[Examples 7 to 10]
An absorbent sheet having the same configuration as the absorbent sheet 10 shown in FIGS. 1 and 2 was produced. A nonwoven fabric or a resin film shown in Table 2 below was used as the base sheet, and a particulate polyacrylate-based water-absorbing polymer (average particle size 400 μm) was used as the water-absorbing polymer. A rubber-based hot melt adhesive was used as the base sheet fixing adhesive for fixing the water-absorbing polymer to the base sheet, and the basis weight of the adhesive was 20 g / m ^{2 in} terms of solid content.

[Evaluation Test 2]
Using the absorbent sheets of Examples 7 to 10, a disposable diaper was prepared in the same manner as described above, and the diaper was fixed on a horizontal surface with the top sheet facing upward, at the center of the absorbent body. On the surface sheet, 120 g of artificial urine was injected and absorbed, and then allowed to stand for 3 minutes in a natural state. And the apparent thickness of the base material sheet after liquid absorption (The protrusion height of the part which protrudes in the skin opposing surface side in a base material sheet. The thickness shown by the code | symbol T in FIG.3 (b)) was measured. The results are shown in Table 2 below together with the substantial thickness of the base sheet, which was measured in advance according to the above <Method for measuring thickness of sheet> before liquid absorption (before injection of artificial urine).
In any of the absorbent sheets of Examples 7 to 10, the water-absorbing polymer fixing rate measured according to the procedures 1 to 5 was 40% or more.

As described above, the formation of the gap accompanying the curvature of the base sheet after liquid absorption / swelling of the water-absorbing polymer can improve body fluid uptake, and from the viewpoint of improving the absorption performance of the absorbent sheet Is a favorable event. This gap corresponds to “amount of change in thickness of substrate sheet” in Table 2 below (= apparent thickness of substrate sheet after liquid absorption−substantial thickness of substrate sheet). It can be evaluated that the gap is large and the body fluid uptake is excellent.
As shown in Table 2, since the difference in the amount of change in the thickness of the base sheet was remarkable in Examples 7 and 8 and Example 9, the flexural rigidity of the base sheet was about 6 cN or less, especially about 3 cN or less. Is preferable.

According to the present invention, there are provided an absorbent sheet and an absorbent body, which have a high performance of fixing the water-absorbing polymer to the base sheet, and the water-absorbing polymer does not easily fall off even after liquid absorption. When the absorbent sheet or the absorbent body of the present invention is used for an absorbent article, the falling off of the water-absorbing polymer is effectively suppressed, so that the wearer does not feel uncomfortable and the absorption performance is stably exhibited. Is done.

Claims

An absorbent sheet in which a water-absorbing polymer is fixed to a base sheet, and the water-absorbing polymer fixing rate is 40% or more.
The absorbent sheet according to claim 1, wherein the water-absorbing polymer is fixed to the base sheet through an adhesive for fixing the base sheet.
The absorbent sheet according to claim 2, wherein the adhesive for fixing the base sheet is acrylic, silicone or rubber.
The absorbent sheet according to claim 2 or 3, wherein the base sheet fixing adhesive is a hot melt adhesive.
The absorbent sheet according to any one of claims 2 to 4, wherein the base sheet fixing adhesive has a maximum elongation in accordance with Japan Adhesive Industry Association Standard JAI7-1999 of 200% or more and 3000% or less.
6. The base sheet fixing adhesive according to claim 2, wherein the base sheet fixing adhesive contains a base polymer, a tackifier and a plasticizer, and the base polymer is a styrene-butadiene-styrene block copolymer. The absorbent sheet as described.
The tackifier is at least one selected from the group consisting of C5 petroleum resins, C9 petroleum resins, dicyclopentadiene petroleum resins, rosin petroleum resins, polyterpene resins and terpene phenol resins. The absorbent sheet as described.
The absorbent sheet according to claim 6 or 7, wherein the plasticizer is at least one selected from the group consisting of paraffinic oil and naphthenic oil.
When the total amount of the tackifier and the plasticizer contained in the adhesive is 100 parts by weight, the content of the base polymer in the base sheet fixing adhesive is 10 parts by mass or more and 60 parts by mass. The absorbent sheet according to any one of claims 6 to 8, wherein the absorbent sheet is not more than part by mass.
10. The content of the tackifier in the base sheet fixing adhesive is 20% by mass to 80% by mass with respect to the total mass of the adhesive. Absorbent sheet.
The content of the plasticizer in the base sheet fixing adhesive is 0% by mass or more and 40% by mass or less with respect to the total mass of the adhesive. Absorbent sheet.
The absorbent sheet according to any one of claims 2 to 11, wherein a residual stress of the adhesive for fixing the base sheet is 3 kPa or more and 18 kPa or less.
The absorbent sheet according to any one of claims 2 to 12, wherein an application amount of the adhesive for fixing the base sheet is 1 g / m 2 or more and 30 g / m 2 or less in terms of solid content.
The absorbent sheet according to any one of claims 2 to 13, wherein both surfaces of the base sheet are flat.
The water-absorbing polymer is fixed to one surface of the base sheet through the base sheet fixing adhesive, and the water-absorbing polymer is not fixed to the other surface of the base sheet. Absorbent sheet as described in 1.
The absorbent sheet according to any one of claims 1 to 14, wherein the water-absorbing polymer is fixed to both surfaces of the base sheet.
The absorbent sheet according to any one of claims 1 to 16, wherein a basis weight of the water-absorbing polymer is 30 g / m 2 or more and 400 g / m 2 or less.
The absorbent sheet according to any one of claims 1 to 17, wherein a centrifugal retention amount of the water-absorbing polymer is 10 g / g or more and 60 g / g or less.
The absorbent sheet according to any one of claims 1 to 18, wherein the base sheet comprises a nonwoven fabric or a resin film.
The absorbent sheet according to any one of claims 1 to 19, wherein the bending rigidity of the base sheet is 10 cN or less.
The absorbent sheet according to any one of claims 1 to 20, wherein the base sheet has a thickness of 0.01 mm or more and 0.8 mm or less.
The absorbent sheet according to any one of claims 1 to 21, wherein a basis weight of the base sheet is 5 g / m 2 or more and 40 g / m 2 or less.
The absorbent sheet according to any one of claims 1 to 22, wherein the base sheet is a nonwoven fabric.
The absorbent sheet according to any one of claims 1 to 23, wherein the base sheet is a spunbond-meltblown-spunbond nonwoven fabric.
The absorbent sheet according to any one of claims 1 to 24, wherein the water-absorbing polymer is in the form of particles and has an average particle diameter of 50 µm to 800 µm.
An absorbent comprising the absorbent sheet according to any one of claims 1 to 25 and a covering sheet that covers at least one surface of the absorbent sheet.
27. In a state where the water absorbent polymer in the absorbent sheet is swollen by liquid absorption, the apparent thickness of the base sheet in the absorbent sheet is increased as compared with that before the water absorbent polymer is swollen. The absorber as described in.
The water-absorbing polymer is fixed to the covering sheet via an adhesive for fixing the covering sheet,
The absorbent body according to claim 27, wherein the adhesive strength of the adhesive for fixing the covering sheet is lower than that before the water absorbent polymer is swollen in a state where the water absorbent polymer is swollen by liquid absorption.
In the absorbent sheet, the water-absorbing polymer is fixed to the base sheet through an adhesive for fixing the base sheet,
The adhesive for fixing the base sheet and the adhesive for fixing the covering sheet have different adhesive strengths in a wet state, and the adhesive for fixing the base sheet is wetter than the adhesive for fixing the covering sheet. The absorbent body according to claim 28, wherein the adhesive strength in a state is strong.
The water-absorbing polymer is fixed to the base sheet via a base sheet fixing adhesive,
30. The absorbent body according to claim 28 or 29, wherein the covering sheet fixing adhesive has a smaller residual stress than the base sheet fixing adhesive.
The absorbent body according to any one of claims 26 to 30, wherein the basis weight of the covering sheet is 8 g / m 2 or more and 30 g / m 2 or less.
The covering sheet covers the entire skin-facing surface of the absorbent sheet and extends laterally outward from both lateral ends of the absorbent sheet, and the extending portion is a non-skin of the absorbent sheet. The absorbent body according to any one of claims 26 to 31, wherein the absorbent body is wound down to the facing surface side and covers the entire area of the non-skin facing surface.
The absorbent body according to any one of claims 26 to 32, wherein the water-absorbing polymer fixing ratio is 60% or more.
A method for producing an absorbent sheet according to any one of claims 1 to 25,
The manufacturing method of an absorptive sheet which has a process of apply | coating an adhesive agent to one surface of a base material sheet, and spraying the small piece of a water absorbing polymer on this one surface.
The method for producing an absorbent sheet according to claim 34, wherein the residual stress of the adhesive is 3 kPa or more and 18 kPa or less.