JP2019084075A - Absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an absorber which is thin, has a small amount of liquid return, and has high flexibility. An absorber 16 has a base sheet 12 and an absorbent core 14. The absorbent core 14 contains a water-absorbent resin, a non-fibrous water-soluble polymer and a polyhydric alcohol. The water-absorbent resin is contained in the absorbent core in an amount of 40% by mass or more and 95% by mass or less. The non-fibrous water-soluble polymer is contained in an amount of 0.1% by mass or more and 5% by mass or less with respect to the water-absorbent resin contained in the absorbent core. The polyhydric alcohol is contained in an amount of 110% by mass or more and 1500% by mass or less with respect to the non-fibrous water-soluble polymer contained in the absorbent core. The water-absorbent resin has a median diameter of 150 μm or more and 500 μm or less. [Selection diagram] Fig. 1

Description

  The present invention relates to an absorber. The absorber of the present invention is particularly suitable as an absorber for an absorbent article.

  As absorbent bodies for absorbent articles, a laminated body of water-absorbent fibers such as pulp, a laminated body of a mixture of the water-absorbent fibers and particles of a superabsorbent polymer, etc. are widely used. Since the absorbers made of these materials are relatively bulky, absorbers aiming at thinning and downsizing have been proposed. Examples of such an absorbent body include those obtained by dispersing a superabsorbent polymer and a fibrous binder in a liquid and applying the dispersion to a sheet-like substrate (see Patent Documents 1 to 3). ).

  Patent Document 1 discloses a composite comprising water-swellable solid-body particles and water-swellable solid-body particles obtained from cellulose, wherein the water-swellable solid-body particles are bound to each other by the microfibrils. The composition is described. Patent Document 2 describes a water-absorbent composite sheet comprising a composite composed of particulate SAP and a fibrous binder, and a sheet-like base material supporting the composite. This composite contains inorganic powders such as alumina, silica, zeolite, bentonite and kaolin. In Patent Document 3, an absorbent layer containing a highly water-absorptive resin, a non-woven fabric-like substrate supporting a highly water-absorptive resin, and a mutually highly water-absorptive resin, and a bond between the highly water-absorptive resin and the substrate A multi-functional sheet-like absorber comprising a binder component is disclosed.

  Patent Document 4 discloses a porous sponge-like absorbent composed of a superabsorbent polymer, a fiber and an alkylene oxide polymer. Patent Document 5 describes a liquid absorbent sheet in which a sheet-shaped liquid absorbent layer is composed of a superabsorbent polymer, a filter aid, fibers, and an alkylene oxide polymer. As a filter aid, diatomaceous earth, activated carbon, talc, perlite, etc. are used.

JP 10-168230 A JP-A-9-299399 JP 2000-201975 A WO 94/07599 pamphlet JP-A-8-80318

  The absorbers described in Patent Documents 1 to 4 are concerned with deformation due to the occurrence of warpage at the time of manufacture or at the time of water absorption because the fiber component is an essential element. When the absorbent body is warped, local pressure is applied to the body of the person wearing the absorbent article, which causes discomfort and reduces the feeling of wearing.

  In particular, in the technology described in Patent Document 4, the alkylene oxide polymer is essential as a binder between the superabsorbent polymer and the fiber, and a large amount of the alkylene oxide polymer is required to exhibit its function. In fact, in the example of the same document, an alkylene oxide polymer having a mass of 5 times the water absorbing resin is added. It is considered that when the absorbent body becomes hard due to this, or when the absorbent body is used for an absorbent article such as a diaper, the uncomfortable feeling at the time of wearing occurs and the absorption performance is lowered. Moreover, since the absorber described in the same document is described as a sponge-like structure, it is considered to be bulky and to be thick. Furthermore, the sponge-like absorbent body described in the same document is considered to have a high ratio of pores to the highly water-absorbent polymer, and it is speculated that the liquid will return to the surface when the absorbent is pressurized after water absorption. It is possible and may cause discomfort to the user.

  In the technique described in Patent Document 5, the absorber becomes hard due to the high proportion of the powder contained as the filter aid, and the liquid return amount increases.

  Accordingly, an object of the present invention is to improve the absorber, and more specifically, to provide an absorber which is thin, has a small amount of liquid return, and is highly flexible.

The present invention relates to a substrate sheet and an absorbent body having an absorbent core on the substrate sheet,
The absorbent core comprises a water absorbing resin, a non-fibrous water soluble polymer and a polyhydric alcohol,
The water absorbing resin is contained in the absorbent core in an amount of 40% by mass to 95% by mass.
The non-fibrous water-soluble polymer is contained in an amount of 0.1% by mass to 5% by mass with respect to the water absorbent resin.
The polyhydric alcohol is contained in an amount of 110% by mass or more and 1500% by mass or less based on the non-fibrous water-soluble polymer.
The water-absorbent resin provides an absorber having a median diameter of 150 μm to 500 μm.

  According to the present invention, an absorbent having a small amount of liquid return and high flexibility is provided. In particular, when it is used as an absorbent for an absorbent article, an absorbent which has a good fit and is less likely to cause discomfort when worn is provided.

FIG. 1 is a perspective view showing an apparatus suitably used for producing the absorbent of the present invention. Fig.2 (a) and (b) is a perspective view which shows another apparatus suitably used for manufacture of the absorber of this invention, respectively.

  The present invention will be described below based on its preferred embodiments. The absorber of the present invention comprises a substrate sheet and an absorbent core located on at least one side of the substrate sheet. The substrate sheet is used for the purpose of holding the absorbent core to enhance the shape retention of the absorber or to improve the handleability of the absorber. Moreover, a base material sheet is used also as an application | coating base material at the time of manufacturing an absorptive core by the method mentioned later. On the other hand, the absorbent core is a main liquid absorption site in the absorber, and has a function of absorbing and holding the liquid.

  As a base material sheet, a thing of the material which can hold an absorptive core is used. The substrate sheet may be liquid permeable or may be liquid impermeable to liquid impermeable. The base sheet can be composed of, for example, non-woven fabric, paper, woven fabric, and film. You may use the laminated body of these 2 or more types of materials as a base material sheet. From the viewpoint of diffusing the liquid in the planar direction, the substrate sheet is preferably made of a liquid-permeable fiber sheet.

  As the non-woven fabric, those obtained by various manufacturing methods can be used without particular limitation. Examples of nonwoven fabrics include spunlace nonwoven fabrics, spunbond nonwoven fabrics, air-through nonwoven fabrics, meltblown nonwoven fabrics, needle-punched nonwoven fabrics and resin-bonded nonwoven fabrics. These non-woven fabrics can be used alone or in the form of a laminate of two or more non-woven fabrics.

  As the woven fabric, one having various fiber systems can be used. As paper, the paper-made fiber can be used as a raw material, and what was obtained by the wet papermaking method or the dry papermaking method can be used. As the film, for example, one obtained by being formed by T-die method or inflation method and uniaxially or biaxially stretched can be used.

  The various materials described above constituting the substrate sheet may be, for example, synthetic polymer materials such as various thermoplastic resins, and natural polymer materials such as cellulose such as pulp. Examples of the thermoplastic resin include polyolefin fibers such as polyethylene (PE) and polypropylene (PP), polyester fibers such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), and polyacrylics such as polyacrylic acid and polymethacrylic acid ester. Acid based fibers, vinyl based fibers such as polystyrene and polyvinyl chloride can be used. These resins may be used alone or in combination of two or more. When fibers are formed from these resins, fibers of a single resin may be formed, or core-sheath type or side-by-side type composite fibers may be formed.

The base sheet preferably has a basis weight of 10 g / m ² or more, and 15 g / m ² or more from the viewpoint of shape retention of the absorber holding the absorbent core and handleability of the absorber. Is more preferable, and 20 g / m ² or more is more preferable. The base sheet is preferably 70 g / m ² or less, more preferably 65 g / m ² or less, and more preferably 60 g / m ² or less from the viewpoint of thinness and flexibility of the absorber. More preferred. Specifically, the base sheet preferably has a basis weight of 10 g / m ² or more and 70 g / m ² or less, more preferably 15 g / m ² or more and 65 g / m ² or less, and 20 g / m 2 it is more preferably ² or more 60 g / ^{m 2} or less.

  An absorbent core is located on at least one side of the base sheet. The absorbent core may be located on the substrate sheet in direct contact with the substrate sheet, or one or more members or layers may be provided between the substrate sheet and the absorbent core. In the interposed state, the base sheet and the absorbent core may be indirectly adjacent to each other.

  The absorbent core is characterized by being thin. Due to the thinness of the absorbent core, the absorber as a whole is flexible. From the viewpoint of sufficiently enhancing the flexibility of the absorbent, the thickness of the absorbent core is preferably 5 mm or less, more preferably 4.5 mm or less, and still more preferably 4 mm or less. Moreover, in view of achieving sufficient absorption performance despite being thin, the thickness is preferably 0.3 mm or more, more preferably 0.4 mm or more, and 0.5 mm or more Is more preferred. Specifically, the thickness of the absorbent core is preferably 0.3 mm or more and 5 mm or less, more preferably 0.4 mm or more and 4.5 mm or less, and preferably 0.5 mm or more and 4 mm or less More preferred.

  The absorbent core contains a water absorbent resin, a non-fibrous water soluble polymer and a polyhydric alcohol as its constituent material. By forming the absorbent core from these materials, the absorbent core can be made thin, and the problem of warpage that has occurred in the conventional thin absorbent core can be solved. The details of each material will be described below.

  The water absorbing resin plays a role as a main water absorbing material in the absorbent core. The water-absorbent resin is made of a material that can swell upon contact with water to absorb and retain water. The water-absorbent resin is preferably one that can absorb and hold 20 mass times or more its own weight of water. In addition, it is preferable that the water-absorbent resin be capable of absorbing and holding 20 times or more, particularly 30 times or more of its own weight if the object is urine, and 1 time or more, preferably 3 times or more if it is blood. The one that can be done is preferable. There is no particular limitation on the upper limit value of water absorption and retention in the water-absorbent resin, but 1000 mass times of its own weight can be used as a guideline for the upper limit. As a water-absorbent resin, various hydrogel materials such as crosslinked polymers of acrylic acid or acrylic acid alkali metal salt or copolymer, polyacrylic acid and salts thereof, crosslinked products of polyacrylate graft polymer, starch Or crosslinked product of carboxymethylated cellulose, crosslinked product of hydrolysis product of starch-acrylate graft copolymer, crosslinked product of vinyl alcohol-acrylate copolymer, crosslinked product of maleic anhydride grafted polyvinyl alcohol, A crosslinked isobutylene-maleic anhydride copolymer, a saponified vinyl acetate-acrylic acid ester copolymer, or the like can be used. These water absorbent resins can be used singly or in combination of two or more.

  The water-absorbent resin is generally in the form of particles, but may be in the form of fibers. When a particulate water-absorbent resin is used, its shape may be spherical, massive, bowl-like or amorphous.

  The water-absorbent resin is preferably contained in an amount of 40% by mass or more, and more preferably 45% by mass or more, from the viewpoint of sufficiently enhancing the absorption performance of the absorbent core. It is more preferable that it is contained by mass% or more. In addition, from the viewpoint of flexibility of the absorbent core, the absorbent core preferably contains 95% by mass or less, more preferably 93% by mass or less, and 91% by mass or less Is more preferable. Specifically, the water-absorbent resin is preferably contained in the absorbent core in an amount of 40% by mass to 95% by mass, and more preferably 45% by mass to 93% by mass, and more preferably 50 More preferably, it is contained by mass% or more and 91 mass% or less.

  In relation to the content ratio of the absorbent core contained in the absorber, the ratio of the area of the absorbent core to the area of the absorber is 50 area% or more from the viewpoint of sufficiently enhancing the absorption capacity of the absorber Is more preferably 60 area% or more, and still more preferably 70 area% or more. The ratio of the area of the absorbent core to the area of the absorbent is preferably 100 area% or less, more preferably 95 area% or less, from the viewpoint of the diffusibility of the liquid in the absorbent core. It is more preferable that the area% or less. Specifically, the ratio of the area of the absorbent core to the area of the absorber is preferably 50 area% or more and 100 area% or less, more preferably 60 area% or more and 95 area% or less, 70 More preferably, the area% or more and 90 area% or less. In addition, "the area of an absorber" and the "area of an absorptive core" are each area in the surface by which the absorptive core was provided on the base material sheet. That the ratio of the area of the absorbent core to the area of the absorbent is 100 area% means that the absorbent core is disposed on the entire surface of the base sheet.

  The ratio of the area of the absorbent core to the area of the absorbent is measured by the method described below. The length in the longitudinal direction and the width direction of the substrate sheet is measured to calculate the area. And the length of the longitudinal direction and width direction of the absorptive core on a substrate sheet is measured, and area is computed. The ratio of the area of the absorbent core to the area of the substrate sheet is calculated to determine the ratio.

  As a result of studies by the present inventor, it has been found that it is preferable that the water absorbent resin has a controlled particle size from the viewpoint of reduction in liquid return. The reason is as follows. In the case of a thin absorber such as the absorber of the present invention, it is necessary to increase the surface area of the water absorbent resin to increase the absorption rate or to reduce the amount of liquid return. For this purpose, it is considered that the water-absorbent resin is pulverized and / or classified by operation such as classification and the like to increase its surface area.

From the viewpoint of reducing the amount of liquid return while controlling the particle size and particle size distribution of the water-absorbent resin and increasing the absorption rate, it is preferable to use a particulate water-absorbent resin, in which case the particle size is The particle diameter D ₅₀ at a cumulative volume of 50% measured by the diffractive particle size distribution method, that is, the median diameter is preferably 150 μm or more, more preferably 160 μm or more, and still more preferably 170 μm or more. The median diameter is preferably 500 μm or less, more preferably 450 μm or less, and still more preferably 400 μm or less. Specifically, the median diameter is preferably 150 μm or more and 500 μm or less, more preferably 160 μm or more and 450 μm or less, and still more preferably 170 μm or more and 400 μm or less.

When the water absorbing resin is crushed and / or classified, the particles of the water absorbing resin after the operation have a particle size distribution. In this case, it has been found as a result of the study of the inventor that when the distribution of the fine particles is large, in other words, when the base on the small particle diameter side in the particle size distribution curve is wide, the liquid return amount of the absorber increases. The reason for this is considered to be due to the reduction of the gap in the absorbent by the water absorbent resin of small particle size. In this respect, in the particle size distribution of the water-absorbing resin, if the particle diameter at 10% cumulative volume measured by a laser diffraction particle size distribution method and D _10, the particle diameter at the cumulative volume of 90% was D _90, ( The value of D ₉₀ -D ₁₀ ) / D ₅₀ is preferably 0.10 or more, more preferably 0.20 or more, and still more preferably 0.30 or more. The value of (D ₉₀ -D ₁₀ ) / D ₅₀ is preferably 1.60 or less, more preferably 1.50 or less, and still more preferably 1.40 or less. Specifically, the value of (D ₉₀ -D ₁₀ ) / D ₅₀ is preferably 0.10 or more and 1.60 or less, more preferably 0.20 or more and 1.50 or less, and 0.30 It is further more preferable that it is 1.40 or less.

  The non-fibrous water-soluble polymer contained in the absorbent core is mainly used for the purpose of immobilizing the water absorbent resin in the absorbent core. The “non-fibrous water-soluble polymer” refers to, for example, a polymer such as microfibrils of cellulose described in the above-mentioned Patent Documents 1 to 3 that maintains a fibrous form even after liquid absorption. It is meant to be excluded from the scope. Therefore, even if the state before absorption is fibrous, the water-soluble polymer which is dissolved in water by absorption and becomes non-fibrous is included in the non-fibrous water-soluble polymer according to the present invention Be done. The term "water-soluble" means that the solubility in 100 g of water at 25 ° C is preferably 1 g or more, more preferably 5 g or more, and still more preferably 10 g or more. As a measurement method, a predetermined amount of the object is added to and mixed with 50 mL ion-exchanged water at 25 ° C. in a 100 mL glass beaker (5 mm)), and a 20 mm long and 7 mm wide stirrer chip is inserted. Stir at 600 rpm using HPS-100. If the total amount of the added object dissolves in water within 24 hours, it is determined that the object has "water solubility" twice that of the predetermined amount. In the present invention, as the more preferable solubility, the entire amount is preferably dissolved in water within 3 hours, and it is more preferable that the entire amount is dissolved in water within 30 minutes.

  The inventors of the present invention examined the cause of the occurrence of warpage in conventionally known thin absorbers, such as Patent Documents 1 to 3 described above. As a result, it is possible to use microfibrillar as a binder contained in the absorber. It was speculated that cellulose (hereinafter also referred to as "MFC") is associated with the occurrence of warpage. In detail, the MFC immobilizes the MFCs and the MFC and the water absorbing resin by hydrogen bonding. Therefore, when water transfer due to water retention or evaporation occurs when manufacturing an absorber or absorbing a liquid, the hydrogen-bonded fibers are likely to be deformed. As a result, it is considered that distortion occurs in the absorber and warpage occurs. In addition, since hydrogen bonding by MFC does not immediately break immediately after the absorbent absorbs water, it is considered that the MFC is deformed along with the swelling of the water-absorbent resin, and that the absorber itself is warped.

  On the other hand, in the absorber of the present invention, a non-fibrous water-soluble polymer is contained in the absorbent core, and the polymer is used as a binder. Due to this, the absorber of the present invention can effectively suppress the occurrence of warpage even if water migration occurs in the absorbent core during its production or liquid absorption. In addition, since the non-fibrous water-soluble polymer is dissolved by contact with water, there is also an advantage that the absorbent core is easily deformed following the external force at the time of liquid absorption. From this viewpoint, in the absorbent of the present invention, the absorbent core preferably contains no fibrous binder.

  On the other hand, as described in Patent Document 4 described above, when a binder component is used to bond the water-absorbent resin and the fiber, a large amount of binder component is required, and as a result, the surface of the water-absorbent resin becomes a binder component. As a result, the water absorption performance of the water absorbent resin becomes difficult to express. In the technique of Patent Document 4, although a porous sponge-like structure can be obtained by fibers and liquid can be held in the porous portion, when body pressure is applied, the body fluid can not be held and leaks out.

  In the present invention, from the viewpoint of making the above-mentioned various advantages attributable to the use of the non-fibrous water-soluble polymer more remarkable, the non-fibrous water-soluble polymer is capable of absorbing water in the absorbent core. The content is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and still more preferably 0.5% by mass or more based on the resin. For the same reason, the non-fibrous water-soluble polymer is preferably contained in the absorbent core in an amount of 5% by mass or less, more preferably 4% by mass or less, based on the water absorbing resin. It is more preferable to include the following. Specifically, the non-fibrous water-soluble polymer is preferably contained in the absorbent core in an amount of 0.1% by mass or more and 5% by mass or less with respect to the water-absorbent resin, and 0.3% by mass or more More preferably, it is contained by mass% or less, more preferably 0.5 mass% or more and 3 mass% or less. The “ratio of non-fibrous water-soluble polymer to water-absorbent resin” is calculated using the mass of the water-absorbent resin contained in the absorbent core as the denominator and the non-fibrous water-soluble polymer as molecules. It is a ratio.

  Moreover, from the viewpoint of making the above-mentioned various advantages resulting from using a non-fibrous water-soluble polymer more remarkable, examples of the water-soluble polymer include polyvinyl pyrrolidone, polyvinyl alcohol, polyvinyl butyral, dextrin And polyethylene oxide, water-soluble nylon, etc., and among them, one or more selected from polyvinyl pyrrolidone, polyvinyl butyral and dextrin are preferable. These non-fibrous water-soluble polymers can be used alone or in combination of two or more. Among these non-fibrous water-soluble polymers, polyvinyl pyrrolidone in particular, in terms of solubility in water and alcohols, and in terms of binding power, among the grades of polyvinyl pyrrolidone, among others, K-15, K-30, K-60 or K-90 It is preferred to use polyvinyl pyrrolidone.

  In the context of using a non-fibrous water-soluble polymer, in the absorber of the present invention, it is preferred that the absorbent core be free of fiber material. Examples of the fiber material include natural fibers such as wood pulp and kenaf, synthetic fibers such as olefin type and polyester type, and regenerated fibers such as rayon. As a result, the occurrence of warpage in the absorber is more effectively prevented. The fiber material is a deformable material having a shape in which the length L is sufficiently long with respect to the thickness D. For example, materials having a shape in which the value of L / D is 3 or more are included in the category of fiber materials.

  The polyhydric alcohol which is a component contained in the absorbent core in addition to the water-absorbent resin and the non-fibrous water-soluble polymer described above is mainly used for the purpose of imparting flexibility to the absorbent core. The polyhydric alcohol is preferably one having higher wettability (hydration property) than the non-fibrous water-soluble polymer described above, from the viewpoint of improving the diffusivity of the liquid in the absorbent core. The level of wettability (hydration) is determined, for example, by the spreading area of water in a certain time when a fixed amount of water is dropped on a circularly spread polyhydric alcohol having a certain area on a smooth glass plate. It can be determined. It can be determined that the wettability (hydration property) is higher as the area in which the water spreads is larger, and it can be determined that the wettability (hydration property) is lower as the area in which the water spreads is smaller. As an example of a specific determination method, for example, the polyhydric alcohol is spread on a 50 mm square so as to be as uniform as possible on a smooth glass plate. Then, after dropping 1 drop (50 μg) of water on the center of the polyhydric alcohol surface, the area after 5 seconds is measured. The area may be measured as an image.

  As polyhydric alcohols, any of aliphatic polyhydric alcohols and aromatic polyhydric alcohols can be used. Among these, from the viewpoint of further improving the flexibility of the absorbent core, it is preferable to use an aliphatic polyhydric alcohol. As aliphatic polyhydric alcohols, saturated aliphatic polyhydric alcohols and unsaturated aliphatic polyhydric alcohols can be used. In particular, it is preferable to use a saturated aliphatic polyhydric alcohol from the viewpoint of further improving the flexibility of the absorbent core. As the saturated aliphatic polyhydric alcohol, for example, one or more selected from glycerin, propylene glycol and polyethylene glycol can be used, and one or more of these can be blended. Among these, it is particularly preferable to use glycerin.

  From the viewpoint of imparting flexibility to the absorbent core, the polyhydric alcohol is preferably contained in the absorbent core in an amount of 110% by mass or more, preferably 200% by mass or more, based on the non-fibrous water-soluble polymer. Is more preferable, and 300% by mass or more is more preferable. For the same reason, the polyhydric alcohol is preferably contained in the absorbent core in an amount of 1500% by mass or less, more preferably 1250% by mass or less, based on the non-fibrous water-soluble polymer, further preferably 1000% by mass. It is more preferable to include the following. Specifically, the polyhydric alcohol is preferably contained in the absorbent core in an amount of 110% by mass or more and 1500% by mass or less, and 200% by mass or more and 1250% by mass or less based on the non-fibrous water-soluble polymer. It is more preferable to be contained, and it is further preferable to contain 300% by mass to 1000% by mass.

  In addition to the above components, the absorbent core can also contain, if necessary, components capable of improving various performances of the absorbent core. Such components include, for example, thickeners, pH adjusters and the like.

  In the absorber of the present invention, the absorbent core may be formed continuously on at least one surface of the base sheet without gaps, or may be formed so that a part of the surface of the base sheet is exposed. It may be done. For example, if the substrate sheet is rectangular, the absorbent core can be formed only in the region between the left and right side regions. Alternatively, a plurality of absorbent cores may be formed to extend linearly in one direction, and the surface of the base sheet may be exposed in the region between adjacent absorbent cores. Additionally, the absorbent core may be arranged in a checkerboard pattern.

  It is preferable that the thickness of an absorptive core is the value mentioned above even if the shape in planar view of an absorptive core is any of the above-mentioned cases.

The thickness of the absorbent core is measured by the following method. That is, the absorbent core at the measurement target site is placed on a horizontal place without wrinkles or bending, and the thickness under a load of 5 cN / cm ² is measured. Specifically, for example, a thickness meter (PEACOCK (registered trademark) DIAL UPRIGHT GAUGES R5-C) manufactured by Ozaki Mfg. Co., Ltd. is used to measure the thickness. At this time, a planar-view circular or square plate (acrylic having a thickness of about 5 mm) whose size is adjusted so that the load is 5 cN / cm ² between the tip of the thickness gauge and the object to be measured Place the plate and measure the thickness. The thickness of the absorber and the thickness of the substrate sheet are measured, and the difference value is taken as the thickness of the absorbent core.

  Although the above description is for the case where the absorbent core is basically of a single layer, in the present invention, the absorbent core has the same composition or 2 different compositions. It may have a layered structure portion of layers or more. Even in such a case, it is preferable that the shape of the absorbent core in plan view and the thickness of the absorbent core (thickness at the maximum thickness part) be as described above.

  The absorber of the present invention can be suitably obtained by applying a paint for producing an absorbent core on at least one surface of a substrate sheet. FIG. 1 shows an apparatus 10 suitable for producing an absorbent in this way. The absorber manufacturing apparatus 10 shown in the figure includes a paint supply unit 20, a paint application unit 30, and a paint drying unit 40. Each part will be described below.

  The supply unit 20 includes a paint storage tank 21. The paint 11 is stored in the tank 21. The paint 11 in the tank 21 is stirred by the stirring blade 22 and homogenized. The stirring blade 22 is connected to a rotational drive source 24 such as a motor via a shaft 23. One end of a conduit 25 is connected to the bottom of the tank 21. The other end of the conduit 25 is connected to the application unit 30.

  The coating unit 30 includes a coating head 31. The coating head 31 applies the paint supplied from the storage tank 21 via the pipe line 25 on one surface of the elongated base sheet 12 continuously transported along the one direction D. It is. As the coating head 31, what can apply | coat a fluid is used. Although the die coater etc. are mentioned as an example of such a coating head 31, It is not restricted to this. In FIG. 1, a coating material is apply | coated to the area | region between the both-sides area | regions 12a and 12a of the base material sheet 12 by the coating head 31, and a mode that the coating body 13 of a wet state is formed is shown.

  When viewed along the conveyance direction D of the base sheet 12, the drying unit 40 is disposed downstream of the application unit 30. The drying unit 40 includes a drying device 41. The drying device 41 dries the coated body 13 formed by the coating unit 30 to remove volatile components, and fixes the absorbent core 14 which is a dried body of the coated body 13 to the base sheet 12. As the drying device 41, one having means capable of removing volatile matter from the wet coated body 13 is used. Examples of such a drying device 41 include, but are not limited to, an infrared radiation device, a heated hot air blowing device, and the like.

  In this manner, the absorbent 16 in which the absorbent core 14 is formed on one surface of the base sheet 12 is obtained. The absorber 16 is subjected to post-processing as needed. As post-processing, for example, a step of cutting the long absorber 16 along its width direction and processing it into an absorber of each leaf, a step of incorporating the absorber 16 into a final product such as an absorbent article, an absorber The process of winding up 16 and making it original is mentioned.

  According to the above method, there is an advantage that the target absorbent core and absorbent can be obtained by a simple process of applying the paint to the substrate sheet. In addition to this, there is an advantage that the load on the device and the operation load are light. Furthermore, there are advantages that the investment in the apparatus can be reduced since the number of processes is small. And, in the absorber manufactured by the above method, since the absorbent core is made higher in density than in the past, it is easy to make it thinner while maintaining high absorption performance, and it is easy to make the absorber and it It is possible to make the equipped product compact. Moreover, in the absorber manufactured by the above method, the thickness and the basis weight of the absorbent core become highly controlled, and local variations in the basis weight and the thickness do not easily occur. Due to that, the absorber exhibits stable absorption performance. Furthermore, in the absorber manufactured by the above method, it is possible to form the absorbent core extremely thin. Furthermore, the basis weight of the absorbent core can be optionally changed in a wide area on the substrate sheet. Moreover, the surface of the absorbent core can be planarized. As a result, in the absorber manufactured by the above method, the flexibility can be made extremely high. In addition, regardless of the basis weight of the water-absorbent resin, the water-absorbent resin can be reliably fixed in the absorbent core.

  The flatness of the surface of the absorbent core is measured from the surface image of the absorbent core taken with a microscope (VHX-5000, manufactured by KEYENCE CORPORATION). The maximum height roughness Rz of the surface exhibiting the maximum unevenness difference measured from the image of the absorbent core is preferably 1.5 mm or less, more preferably 1.25 mm or less, and 1.0 mm or less Is more preferred. Due to the flat surface of the absorbent core, for example, when the absorbent article provided with the absorbent core is mounted, a good wearing feeling can be obtained. The maximum height roughness Rz of the surface is an index based on JIS B 0601: 2013. The smaller the maximum height roughness Rz, the better, and the closer to 0, the better. However, a specific lower limit is 0.01 mm.

  From the viewpoint of making the above effects more remarkable, the paint to be used is one obtained by dispersing or dissolving the above-described water-absorbent resin, non-fibrous water-soluble polymer and polyhydric alcohol in a solvent Is preferred. The paint may contain water to such an extent that the water-absorbent resin does not swell, but in order to prevent the water-absorbent resin from absorbing or swelling in the paint, it is preferred that the paint not contain water. The absence of water is intended to exclude the purpose of intentionally adding a significant amount of water to the paint. Therefore, the presence of a trace amount of water unavoidably mixed as an impurity of the raw material and a trace amount of water unavoidably mixed from the atmosphere is acceptable.

  The ratio of the water-absorbent resin, the non-fibrous water-soluble polymer and the polyhydric alcohol contained in the paint is the ratio of the water-absorbent resin, the non-fibrous water-soluble polymer and the polyhydric alcohol contained in the absorbent core It can be the same as Moreover, it is preferable that the paint does not contain a fiber material.

  A non-aqueous solvent is suitably used as the solvent contained in the paint. As such non-aqueous solvent, for example, ethanol, methanol, isopropyl alcohol, acetone, methyl ethyl ketone, butyl acetate and the like can be mentioned. These non-aqueous solvents can be used singly or in combination of two or more. Among these non-aqueous solvents, it is preferable to use ethanol in terms of availability, versatility, and safety.

  The proportion of the non-aqueous solvent in the paint is preferably 30% by mass or more, more preferably 35% by mass or more, and still more preferably 40% by mass or more from the viewpoint of performing coating application successfully and efficiently. is there. From the same viewpoint, the proportion of the non-aqueous solvent in the paint is preferably 70% by mass or less, more preferably 65% by mass or less, and still more preferably 60% by mass or less. Specifically, the proportion of the non-aqueous solvent in the paint is preferably 30% by mass to 70% by mass, more preferably 35% by mass to 65% by mass, and still more preferably 40% by mass to 60%. It is less than mass%.

  FIGS. 2a and 2b show another device different from the device 10 shown in FIG. In the apparatus 10A shown in FIG. 2A, the structure of the coating head 31A provided in the coating unit 30A is different from the structure of the coating head 31 shown in FIG. The coating head 31A shown in FIG. 2A has a structure capable of intermittently forming the coated body 13A along the transport direction D of the base sheet 12 and along the width direction W orthogonal to the transport direction. doing. As a result, according to the present apparatus 10A, a plurality of coating body rows 15A including a plurality of coating bodies 13A formed at intervals along the transport direction D are formed at intervals along the width direction W. Ru.

  In the apparatus 10B shown in FIG. 2B, the coating section 30B is provided with two coating heads 31B and 31C. The coating heads 31 </ b> B and 31 </ b> C are arranged in series along the conveyance direction D of the base sheet 12. When viewed along the transport direction D, the coating head 31B is disposed on the upstream side, and the coating head 31C is disposed on the downstream side thereof. The coating head 31 </ b> B applies a paint to the region between the side regions 12 a and 12 a of the base sheet 12 to form a first coated body 13 </ b> B. On the other hand, the coating head 31C forms a second coated body 13C narrower than the first coated body 13B on the first coated body 13B. The second applying body 13C is formed on the center in the width direction of the first applying body 13B. The paint used to form the first coated body 13B and the paint used to form the second coated body 13C may have the same or different compositions. It is also good. As a result, according to this device 10B, when the absorber is viewed along the width direction W, the central region has a plurality of absorbent core structures such as a two-layer structure, and the side located on both sides thereof The area has a single layer structure. As a result, in the absorber, the thickness is different between the central area and the side area, and the absorption performance is also different. Although two coating heads are arranged in series in the apparatus 10B shown in FIG. 2 (b), two layers may be discharged by one coating head. Alternatively, the second layer may not be formed at the central portion. Alternatively, the second layer may be a plurality of layers. Also, three or more layers may be stacked instead of two.

  The absorber of the present invention obtained by each of the above methods is suitably used, for example, as an absorber for various absorbent articles such as disposable diapers and sanitary napkins. These absorbent articles generally comprise a liquid-permeable top sheet, a liquid-impermeable to hard-permeable back sheet, and a liquid-retaining absorbent body positioned between both sheets, as the absorbent body By using the absorbent of the present invention, the absorbent article has good fit to the body regardless of whether the absorbent is dry or wet, and a comfortable fit can be obtained. Become.

In connection with the embodiment described above, the present invention further discloses the following absorbent.
<1>
A substrate sheet and an absorbent body having an absorbent core on the substrate sheet,
The absorbent core comprises a water absorbing resin, a non-fibrous water soluble polymer and a polyhydric alcohol,
The water absorbing resin is contained in the absorbent core in an amount of 40% by mass to 95% by mass.
The non-fibrous water-soluble polymer is contained in an amount of 0.1% by mass to 5% by mass with respect to the water absorbent resin.
The polyhydric alcohol is contained in an amount of 110% by mass or more and 1500% by mass or less based on the non-fibrous water-soluble polymer.
The said water absorbent resin is an absorber whose median diameter is 150 micrometers or more and 500 micrometers or less.

<2>
The absorbent core according to the above <1>, wherein the thickness of the absorbent core is preferably 0.3 mm to 5 mm, more preferably 0.4 mm to 4.5 mm, and still more preferably 0.5 mm to 4 mm. .
<3>
The ratio of the area of the absorbent core to the area of the absorber is 50% to 100%, preferably 60% to 95%, and more preferably 70% to 90%. The absorber as described in <2>.
<4>
The absorbent according to any one of <1> to <3>, wherein the absorbent core does not contain a fiber material.
<5>
In the particle size distribution of the water-absorbent resin, the water-absorbent resin has a particle size at 10% of cumulative volume measured by a laser diffraction particle size distribution method as D ₁₀ and a particle size at 90% of cumulative volume as D ₉₀ The absorber according to any one of <1> to <4>, wherein the value of (D ₉₀ -D ₁₀ ) / D ₅₀ is 0.10 or more and 1.60 or less.
<6>
The value of (D ₉₀ -D ₁₀ ) / D ₅₀ of the water-absorbent resin is more preferably 0.20 or more and 1.50 or less, and still more preferably 0.30 or more and 1.40 or less. Absorbent as described in.
<7>
More preferably, the water-absorbent resin has a median diameter of 160 μm to 450 μm, and more preferably 170 μm to 400 μm.

  Hereinafter, the present invention will be described in more detail by way of examples. However, the scope of the present invention is not limited to such embodiments. Unless otherwise stated, "%" means "mass%".

[Examples 1 to 3 and Comparative Examples 1 and 2]
Coating solutions having the compositions shown in Table 1 below were prepared. The details of the raw materials shown in the same table and the preparation method of the coating solution are as follows. A 0.3 mm thick metal plate opened in a 200 mm × 80 mm square was placed on a 280 × 120 mm base sheet, and the prepared coating solution was applied to the size of the square. The sheet coated with the coating solution was dried for about 10 minutes in an electric drying oven set at 80 ° C., and then allowed to stand for about 10 minutes in a normal temperature environment. The thus obtained absorber was cut into the size of an 182 mm × 60 mm absorbent core to prepare a sample for evaluation. The substrate sheet was used WJ35-TRLD (manufactured by Venus Paper Co.) (basis weight 35 g / ^{m 2).} As a water absorbing resin, polyacrylic acid sodium salt polymer (ST-500D ^* manufactured by Sanyo Chemical Industries, Ltd.) was used, and this was pulverized by Labomill LM-05 (manufactured by Dalton Co., Ltd.). The median diameter and the particle size distribution were adjusted by variously changing the grinding conditions (hammer rotation number, collecting section screen hole diameter).

<Raw material>
A solution in which the water-absorbent resin is dispersed in a solution in which the agents 1 to 3 are dissolved in a solvent is used as a coating solution.
[Solvent] Ethanol: manufactured by Japan Synthetic Alcohol Co., Ltd.
[Agent 1] Polyvinyl pyrrolidone: manufactured by BASF, Luviskol (registered trademark) K90
[Agent 2] Glycerin: Kao Corporation, concentrated glycerin for cosmetics
[Agent 3] Hydroxypropyl Cellulose: HPC-H manufactured by Nippon Soda Co., Ltd.

[Evaluation]
The liquid reversion amount and the softness of the absorbers obtained in Examples and Comparative Examples were measured by the following methods. The results are shown in Table 2 below.

[Liquid return amount]
The measurement sample of the absorber is a rectangle of 182 mm × 60 mm. The basis weight of the water-absorbent resin contained in the above-mentioned absorbent measurement sample at the time of evaluation was 200 g / m ² . This measurement sample is inserted into a surface member used for a water absorption pad for light incontinence (for Laurier Sara Pure (registered trademark) 50cc, Kao Corporation), and 50cc of artificial urine is injected at 5 g / sec. Left for 2 minutes. The injected measurement sample was pressurized at 2.25 kPa for 3 minutes through an acrylic plate, and then the pressurization was stopped and left for 30 seconds. Next, filter paper No. A stack of 20 sheets of 4A (manufactured by Advantec Co., Ltd.) was sandwiched between the measurement sample and the surface member and pressurized again at 2.25 kPa for 2 minutes. The mass of the filter paper before and after pressurization was measured, and the amount of liquid return was calculated by calculating according to the following equation.

  Liquid return amount (g) = (mass of filter paper after injection pressure (g))-(mass of filter paper before injection (g))

[Flexibility]
The value of the flexural rigidity of the absorber was divided by the basis weight of the water absorbent resin to give a measure of flexibility. The flexural rigidity of the absorber can be evaluated by a three-point bending load. As the value of the bending load is smaller, it can be judged that the flexibility is higher, that is, the bending rigidity is lower. The measurement of the three-point bending load is performed as follows. The measuring instrument uses a hand lometer.

The measurement sample of the absorber is a rectangle of 182 mm × 60 mm. This measurement sample is placed between a pair of plate-like supports. The distance between the supports is 20 mm. The plate-like pusher is pushed into the measurement sample from above the measurement sample placed between the supports. The plate-like pusher has a width of 2 mm and a length longer than the length of the measurement sample. The position where the plate-like pressing body is pressed is an intermediate position between the pair of supports. The plate-like push-in body is pushed in 15 mm with respect to the support, and the maximum value of the load generated during the movement amount is taken as a three-point bending load. This was measured in the direction (CD) orthogonal to the machine direction, and the bending stiffness (gf = N × 10 ⁻³ ) was evaluated. Furthermore, the flexibility was calculated by dividing the measured flexural rigidity by the basis weight (g / m ² = gsm) of the water-absorbent resin in the measurement sample. The following is the conversion formula for flexibility.

Flexibility (N x 10 ^-3 / gsm) = (bending stiffness (N x 10 ^-3 )) / (basis weight of water-absorbent resin (gsm))

  As apparent from the results shown in Table 2, it can be seen that the absorbers of the respective examples have a smaller amount of liquid return and higher flexibility as compared with the absorbers of the comparative examples.

DESCRIPTION OF SYMBOLS 10 Manufacturing apparatus 11 Paint 12 Base material sheet 13 Application body 14 Absorbent core 16 Absorbent body 20 Supply part 30 Application part 40 Drying part

Claims (5)

A substrate sheet and an absorbent body having an absorbent core on the substrate sheet,
The absorbent core comprises a water absorbing resin, a non-fibrous water soluble polymer and a polyhydric alcohol,
The water absorbing resin is contained in the absorbent core in an amount of 40% by mass to 95% by mass.
The non-fibrous water-soluble polymer is contained in an amount of 0.1% by mass to 5% by mass with respect to the water absorbent resin.
The polyhydric alcohol is contained in an amount of 110% by mass or more and 1500% by mass or less based on the non-fibrous water-soluble polymer.
The said water absorbent resin is an absorber whose median diameter is 150 micrometers or more and 500 micrometers or less.   The absorber according to claim 1, wherein the thickness of the absorbent core is 0.3 mm or more and 5 mm or less.   The absorber according to claim 1 or 2, wherein the ratio of the area of the absorbent core to the area of the absorber is 50 area% or more and 100 area% or less.   The absorbent according to any one of claims 1 to 3, wherein the absorbent core does not contain a fiber material. In the particle size distribution of the water-absorbent resin, the water-absorbent resin has a particle size at 10% of cumulative volume measured by a laser diffraction particle size distribution method as D ₁₀ and a particle size at 90% of cumulative volume as D ₉₀ , _{(D 90} -D 10) _{/ D 50} of the absorption body according to any one of claims 1 0.10 or more 1.60 or less 4.