JP2018174986A - Absorption structure and absorbent article comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an absorbent raw material in which an environmental load is reduced in whole product life cycle in a discharge amount of carbon dioxide.SOLUTION: An absorption structure of the invention is formed of a porous body comprising acidic polysaccharide to which pyruvic acid is bound, and polysaccharide other than acidic polysaccharide to which pyruvic acid is bound, and is used for liquid absorption, in the liquid, water is included as a component. The polysaccharide other than the acidic polysaccharide to which pyruvic acid is bound is preferably a nonionic polysaccharide or amphoteric polysaccharide. The polysaccharide other than the acidic polysaccharide to which pyruvic acid is bound is preferably nonionic polysaccharide including three or more pieces of mannose in a repeating unit skeleton. The absorption structure preferably further includes water insoluble particles.SELECTED DRAWING: None

Description

  The present invention relates to an absorbent structure and an absorbent article provided with the same.

  BACKGROUND ART Absorbent articles such as disposable diapers and sanitary napkins contain an absorbent polymer which is a material for absorbing and holding liquid. As an absorptive polymer, a polyacrylate cross-linked body is widely used. In addition to the above-described cross-linked polyacrylate, various substances have been proposed as absorbable polymers.

  For example, Patent Document 1 proposes a layered absorbent composed of a water-swellable polymer component A and a foamed water-soluble polymer component B. In this layered absorbent, component A is integrated or fixed in a defined manner in sheet component designed matrix component B. As the component A, guar seed powder, carboxymethylcellulose, xanthan, alginate, gum arabic and chitin are used. As the component B, (meth) acrylic acid, (meth) acrylonitrile, (meth) acrylamide, vinyl acetate, vinyl alcohol and the like are used.

  Patent Document 2 discloses a gelling agent comprising a polysaccharide capable of thickening in the presence of polyvalent metal ions, a substance capable of supplying polyvalent metal ions, and an organic acid and / or a polyvalent metal ion scavenger. Absorbers are described. As polysaccharides that can be thickened in the presence of polyvalent metal ions, guar gum, locust bean gum and xanthan gum are exemplified.

Japanese Patent Application Publication No. 11-506384 JP, 2011-019566, A

  In light of recent environmental problems, there is a demand for materials with low carbon dioxide emissions and low environmental impact. The above absorbent articles are more often discarded after use than repeated use due to the nature of the product, so if the amount of carbon dioxide emissions resulting from disposal can be reduced, the burden on the environment will be reduced. . In particular, when the absorbent article is incinerated, the absorbent polymer composed of the polyacrylate cross-linked body tends to have a large amount of carbon dioxide generated by combustion because the incineration load is high. Therefore, it would be advantageous to be able to provide new types of absorbable polymers in terms of Life Cycle Assessment (LCA).

  Although the materials described in each of the above-mentioned documents use absorbent materials other than the polyacrylate cross-linked body, they are not environmentally-designed, so they can not be said to be sufficient from the viewpoint of LCA. .

  Accordingly, an object of the present invention is to provide an absorbent material with reduced environmental load in terms of LCA.

  The present invention is an absorbent structure used for absorbing a liquid containing water as a component, which is a porous material containing an acidic polysaccharide to which pyruvic acid is bound and a polysaccharide other than an acidic polysaccharide to which pyruvic acid is bound. It is intended to provide an absorbent structure consisting of a body.

  The present invention also provides an absorbent article provided with the above-mentioned absorbent structure.

  According to the present invention, an absorbent material is provided with reduced environmental impact throughout the product life cycle with respect to carbon dioxide emissions.

  The present invention will be described below based on its preferred embodiments. The absorbent structure of the present invention is a solid having a certain form. The absorbent structure of the present invention comprising a solid substance has the structure of a porous body. In addition, the absorbent structure of the present invention is non-powdery and has a certain outer shape. Specifically, the absorbent structure of the present invention has an appearance such as, for example, a plate, a massive, a fibrous, a sheet or a strand. As apparent from the preferred method of manufacturing the absorbent structure described later, the absorbent structure can be formed into various shapes by methods such as extrusion molding and mold molding. That is, the absorbent structure of the present invention has free formability and has a high degree of freedom in forming. Therefore, it is possible to easily obtain a laminated body in which a plurality of absorbing structures having complicated three-dimensional shapes are laminated, or an integrally formed body in which each member constituting the laminated body is integrated with each other. When the absorbent structure of the present invention is a plate, at least one of the main surfaces of the pair of main surfaces of the plate may have a concavo-convex structure. As an example of this concavo-convex structure, a block structure etc. which consist of a crevice which consists of a slot which intersects perpendicularly in all directions, and a convex part of a plane view rectangle shape surrounded by the slot are mentioned.

  When the absorbent structure of the present invention is, for example, a plate-like body or a massive body, it is preferable that the plate-like body or the massive body itself has a porous structure. On the other hand, when the absorbent structure of the present invention is a fibrous body, the fibrous body itself has a porous structure, or the fibrous body itself does not have a porous structure, but a plurality of the fibers It is preferable that the bodies are intertwined to form a network structure, and a part of the network in the network structure forms a porous structure.

  The porous structure in the absorbent structure of the present invention may be an open cell type or a part may be a closed cell type. When the absorbent structure of the present invention is produced, for example, by the lyophilization method described later, an open-cell type porous structure absorbent structure is obtained. The size of the pores in the porous structure (median diameter determined by the measurement method described later) is preferably 20 μm or more in at least a part of the absorbent structure from the viewpoint of efficiently performing absorption and retention of water, More preferably, it is 30 μm or more, and more preferably 50 μm or more. The thickness is preferably 500 μm or less, more preferably 400 μm or less, and still more preferably 300 μm or less. The size of these pores may be different in each part of the absorbent structure, for example, in the front and back, in the middle and in the end, and / or in the longitudinal front and rear of the absorbent structure. The size of the pores may be varied.

  By setting the pore size to the above-mentioned lower limit value or more, it is possible to achieve excrement containing solid contents such as menstrual blood, cormorants, watery feces etc. and water without clogging the solid contents. It can absorb well. In addition, by setting the pore size to the above-mentioned upper limit value or less, the contact efficiency between the low viscosity liquid such as urine and sweat and the surface of the polysaccharide is improved, and the liquid can be efficiently immobilized.

  The pore size can be measured, for example, using a mercury porosimeter, Autopore IV 9500 series (Shimadzu Corporation), in accordance with the mercury intrusion method (JIS R 1655).

  The mercury porosimetry is a method for obtaining information on the physical shape of the absorbent structure by measuring the size and volume of the pores of the porous structure. The principle of the mercury intrusion method is to apply pressure to mercury and inject it into the pores of the object to be measured, and measure the relationship between the pressure applied at that time and the injected mercury volume. Below, about the measuring method of pore diameter distribution of the absorption structure using a mercury porosimeter, absorbent articles, such as a diaper and a sanitary napkin, are demonstrated as an example. In addition, "pore diameter" is synonymous with "size of pore".

[Method of Measuring Pore Size Distribution of Absorbent Structure]
First, the absorbent structure is taken out of the absorbent article (product including the absorbent structure). At this time, it is important to take out without destroying the structure of the absorbent structure. Generally, hot melt adhesives are used in the assembly of absorbent articles, so it is preferable to take them out after cooling the absorbent structure. As a cooling method, for example, a method of spraying a suitable amount of cold spray (for example, Nichiban Co., Ltd. sport cooling spray, CS480), or a method of sufficiently cooling the whole absorbent article in liquid nitrogen can be employed. It may be devised in accordance with the properties of the absorbent article. This method is also common to the other measurements herein.

Next, the taken out absorbent structure is cut into 5 mm × 10 mm × 3 mm to make a sample. The cut samples are set in a sample cell of a mercury porosimeter (Shimadzu Corporation), and a pore size distribution of 1 to 600 μm is measured. Based on the pore distribution curve (differentiation and integral curve) of the resulting absorbent structure, the total pore volume over a pore diameter of 1 to 600 μm is taken as the total pore volume, and the above of the pore volume in the region of 100 μm or less of pore diameter Determine the ratio to the total pore volume. Furthermore, based on the pore distribution curve (differential / integral curve) of the resulting absorbent structure, the ratio of the pore volume of the region with a pore diameter of 1 to 100 μm to the total pore volume is determined. The measurement is performed at five points, and the average value of the three points excluding the maximum and minimum measurement values is taken as the measurement value. The size of the sample of the absorbent structure to be subjected to the measurement can be appropriately adjusted according to the amount of pores and the distribution of the absorbent structure.

  The absorbent structure of the present invention is used to absorb a liquid containing water as a component. The liquid containing water as a component refers to various liquids containing water as a component having fluidity at the temperature of use of the absorbent structure of the present invention in addition to water itself. Fluidity is the property of having a constant volume but no inherent profile. The liquid containing water as a component may be a natural product or a synthetic product. Natural products include those produced in the natural world as well as those produced or excreted from a living body. Urine, menstrual blood, feces (so-called watery feces containing a large amount of water, soft feces, diarrhea feces etc.), stools, sweat, exudates from wounds, breast milk, meat are produced or excreted from the living body And drips from fish fillets.

  The term "absorption" in the present invention includes not only uptake into the interior of the absorbent structure but also substantial migration of the liquid by permeation or diffusion into the pores possessed by the absorbent structure. The difficulty in moving refers to a state in which the liquid does not move even when an external force is applied under the use conditions of the absorbing structure. For example, it means that the liquid is held by thickening, gelation, or the interaction between a part of the absorbent structure and water. Due to the difficulty in moving the liquid, movement of the liquid is less likely to occur even when an external force such as tilting of the absorbent structure acts, and leakage of the liquid can be suppressed.

  The absorbent structure of the present invention is a porous body as described above, and has the property of being able to retain water in the pores of the porous body. This property is due to the action on the water of the material constituting the absorbent structure. Specific examples of this action include phenomena such as hydration, thickening and gelation. Therefore, the absorbent structure of the present invention does not show an extreme volume increase even after absorbing and holding water. In contrast to this property, the cross-linked polyacrylate which is widely used for absorption and retention of water absorbs and retains water by ion osmotic pressure, and exhibits a large volume increase by absorption and retention of water. And unlike the absorption structure of the present invention, the polyacrylate cross-linked body does not need to be a porous body.

  The absorbent structure of the present invention is mainly composed of polysaccharides. In detail, the absorbent structure of the present invention comprises a porous body containing an acidic polysaccharide to which pyruvic acid, which is one of polysaccharides, is bound, and a polysaccharide other than an acidic polysaccharide to which pyruvic acid is bound. It is. In the following description, for convenience of explanation, the acid polysaccharide to which pyruvate is bound may be referred to as “polysaccharide A”, and polysaccharides other than the acid polysaccharide to which pyruvate is bound may be referred to as “polysaccharide It may be called "sugar B". Since the absorbent structure of the present invention is mainly composed of polysaccharides, the absorbent structure has reduced environmental impact over the entire product life cycle with respect to carbon dioxide emissions. In the present specification, “acidic”, “anionic” and “anionic” are respectively synonymous, and “basic”, “cation” and “cationic” are also the same, and these expressions are It can be read as appropriate. Further, in the present specification, "polysaccharides other than acidic polysaccharides to which pyruvate is bound" refer to "polysaccharides that are not" acidic polysaccharides to which pyruvate is bound ", and pyruvic acid is bound to them. No acidic polysaccharides or polysaccharides to which pyruvic acid is bound but which are not acidic polysaccharides.

  The absorption structure of the present invention microscopically forms a macroscopic structure by physically cross-linking the molecular chain of polysaccharide A and the molecular chain of polysaccharide B. Physical crosslinking is a term used in contrast to chemical crosslinking. In contrast to the cross-linking mode in which chemical crosslinks link polymer chains together by strong chemical bonds such as covalent bonds, physical crosslinks crosslink modes in which polymer chains are linked by relatively weak bonds such as hydrogen bonds. It is. In addition, the absorbent structure of the present invention having physical crosslinks can be reversibly changed between the gel state and the sol state. The absorbent structure of the present invention contains polysaccharide A and polysaccharide B, and due to physical cross-linking between them, it is possible to significantly thicken and retain water by absorbing water. . As apparent from the results of Comparative Examples described later, even if other polysaccharide combinations are adopted, the remarkable thickening effect exhibited in the present invention is not exhibited.

  The physical crosslinking according to the present invention can be considered as follows. Here, xanthan gum will be described as an example of one of pyruvic acid-bound acidic polysaccharides. That is, at the use temperature of the absorbent structure of the present invention, for example, around the body temperature, a part of molecular chains of xanthan gum takes a helical structure in an aqueous solution. The helical structure portion and the smooth portion (the portion with a small amount of galactose residues) of the main chain of polysaccharide B are associated by hydrogen bonding to form a crosslinked region. Alternatively, a part of the helical structure is changed to produce a structure in which the molecular chain of polysaccharide B is sandwiched or an entangled structure. The interaction between the helical structure site of these xanthan gums and other polysaccharides results in a state in which the movement of the molecular chains of each other is partially restricted. Due to the state in which the molecular chain is partially constrained, the effect of thickening and gelation when interaction with water takes place becomes greater than that using polysaccharide alone. Also, an improvement in the compressive strength of the obtained gel is observed. Furthermore, in contrast to chemical crosslinking in acrylate crosslinks, according to the absorption structure of the present invention, heating weakens the interaction of molecular chains with each other to cause reversible sol-gel transition and dissolution.

  Xanthan gum, which is a kind of polysaccharide A contained in the absorbent structure of the present invention, is composed of repeating units containing, as basic skeletons, a total of five polysaccharides of two glucose, two mannose and one glucuronic acid as shown below It is a polymer. The main chain of xanthan gum is the β-1,4 bond of D-glucose, and this bond has the same bonding mode as cellulose. The side chain contains one glucuronic acid between the two mannoses. The side chains are located at every other glucose and are attached to the 3-position of glucose. The D-mannose at the side of the side chain has a pyruvate structure, and some of the D-mannose at the side of the side chain have ketal bonds with pyruvate at the 4- and 6-positions. The terminal D-mannose is acetylated at the 6-position.

  The xanthan gum used in the present invention is not particularly limited in its molecular weight as long as the absorbent structure can absorb and retain the liquid. The general mass average molecular weight of available xanthan gum is 100,000 or more and 50 million or less.

  In contrast to the polysaccharide B contained in the absorbent structure of the present invention, the above-mentioned acidic polysaccharide to which pyruvic acid as polysaccharide A is bound is an anionic polysaccharide derived from a carboxyl group, For example, being non-ionic polysaccharide or amphoteric polysaccharide, separation of polysaccharide A and polysaccharide B is less likely to occur, and heterogeneous gelation of polysaccharide A and polysaccharide B is less likely to occur. It is preferable from However, the use of anionic polysaccharides other than acidic polysaccharides to which pyruvic acid is bound is not disturbed as polysaccharide B. Polysaccharide B can be used individually by 1 type or in combination of 2 or more types.

  By alone is meant that the polysaccharide uses a particular structure, for example a polysaccharide having the above-mentioned structure, without being mixed with a polysaccharide having another structure. Therefore, polysaccharides and structural isomers that have the same structure but different molecular weight distribution, or low molecular weight saccharides of monosaccharides and disaccharides (glucose, lactose, dextrin or maltose), drugs used in the process of separation and purification of the polysaccharides It is acceptable to include isopropanol, which is a kind of When two different main structures are mixed and used in combination, it is expressed as two or more types.

  When an acidic polysaccharide to which pyruvic acid, which is a type of polyanionic polysaccharide, is mixed in an aqueous solution, from the viewpoint of suppressing formation of polyion complex and aggregation due to electrostatic interaction, polysaccharide B is a non-ionic system It is preferable to use the following polysaccharides or amphoteric polysaccharides. By suppressing the aggregation, the structure of the absorbent structure becomes uniform, mechanical strength can be secured in both the dry and wet cases, and the structure of the absorbent structure can be maintained during use. In addition, as described above, the absorbent structure of the present invention makes it difficult to move the liquid due to the affinity with water of the material, so that the liquid retention of the absorbent structure can be achieved by maintaining the structure of the absorbent structure. You can keep

  Specific examples of the polysaccharide B used in the present invention include locust bean gum which is a non-ionic polysaccharide, guar gum, tara gum, galactomannan, tamarind seed gum, starches (corn starch, corn grits, corn flour, wheat starch ( Wheat flour), rice starch (rice flour), potato starch, sweet potato starch, tapioca starch, sorghum starch, or chemically treated ones, chemically modified modified starches, etc.). Further, specific examples of the polysaccharide B include cationized xanthan gum which is amphoteric polysaccharide, cationized gellan gum, cationized pectin, cationized carrageenan, cationized karaya gum and the like.

  In the case of using a non-ionic polysaccharide as polysaccharide B, separation of polysaccharide A and polysaccharide B becomes more difficult to occur by using a structure having a structure containing three or more mannoses in the repeating unit skeleton. Moreover, it is preferable from the point which heterogeneous gelatinization with the polysaccharide A and the polysaccharide B becomes difficult to occur. Examples of polysaccharides having such a structure include locust bean gum, cod gum and the like. For example, locust bean gum has a structure having mannose and galactose in a repeating ratio of 4: 1 in the repeating unit as shown below. In addition, tara gum has a structure having mannose and galactose in a unit ratio of 3: 1.

  In the absorption structure of the present invention, a physical cross-linking region is formed by hydrogen bonding of the helical structure portion of the acidic polysaccharide to which pyruvic acid is bound and the portion having a small amount of galactose residues which is a smooth portion of polysaccharide B main chain. It is preferable to form The portion low in galactose residues refers to, in other words, mannose residues in the repeating unit skeleton. Due to the large number of mannose residues, the number of interaction sites with the helical structure of the pyruvate-linked acidic polysaccharide increases, and the repulsion of galactose residues is suppressed to facilitate interaction, and the desired performance is achieved. Is likely to be expressed.

  The mixing ratio of polysaccharide A and polysaccharide B in the absorbent structure of the present invention may be appropriately set according to the water absorption and retention performance required for the absorbent structure and the shape of the absorbent structure. For example, the ratio of polysaccharide A to the total amount of polysaccharide A and polysaccharide B is preferably 20% by mass or more, more preferably 30% by mass or more, and further preferably 40% by mass or more. preferable. Further, the content is preferably 80% by mass or less, more preferably 70% by mass or less, and still more preferably 60% by mass or less. By setting the ratio of polysaccharide A to the total amount of polysaccharide A and polysaccharide B in this range, physical crosslinks of polysaccharide A and polysaccharide B are sufficiently formed, and the thickening effect and gelling effect, Water retention performance such as improvement of compression resistance is suitably exhibited.

  With regard to polysaccharide B, the ratio of polysaccharide B to the total amount of polysaccharide A and polysaccharide B is preferably 20% by mass or more, more preferably 30% by mass or more, and 40% by mass or more It is more preferable to Further, the content is preferably 80% by mass or less, more preferably 70% by mass or less, and still more preferably 60% by mass or less. By setting the ratio of polysaccharide B to the total amount of polysaccharide A and polysaccharide B in this range, physical crosslinks are sufficiently generated, and water such as thickening effect, gelling effect, compression resistance improvement, etc. The retention performance is suitably exhibited.

The mixing ratio of polysaccharide A and polysaccharide B can be determined, for example, by the following method.
In order to remove water insolubles from the absorbent structure, 1 part by mass of the weighed sample is placed in 300 parts by mass of 90 ° C. hot water and stirred, and filtration is performed using a glass filter. Thereafter, pyruvic acid derived from the acidic polysaccharide to which pyruvic acid as polysaccharide A is bound is quantified by the following method, and the ratio is calculated from the ratio of the total amount of sugar to the quantitative value.

[Detection of polysaccharides]
The presence of an acidic polysaccharide such as pyruvic acid-bound acidic polysaccharide can be monitored by directly dropping Alcian blue staining solution onto a sample and observing with a microscope. If coloring can be confirmed by this operation, it means that an acidic polysaccharide is present.

  Alcian blue staining solution can be prepared as follows. 0.01 g of Alcian Blue 8GX (manufactured by Wako Pure Chemical Industries, Ltd.) is dissolved in 20 mL of a 50% (v / v) aqueous solution of ethanol, to which hydrochloric acid or sodium dihydrogen phosphate is appropriately added and pH adjusted. The resulting solution can be filtered through filter paper (No. 5B) to obtain a 0.05% 50% (v / v) aqueous ethanol solution.

  Alcian blue staining solution is known to bind to both a carboxyl group and a sulfate group at pH 2.5 and to bind only a sulfate group at pH 1.0. For this reason, it can be confirmed that a color is developed at pH 2.5 and a carboxyl group is present if color is not developed at pH 1.0. Moreover, if color development occurs at pH 1.0, it is known that the polysaccharide has a sulfate group. When the degree of color development is not sufficient due to the interference from the coexisting substance or the amount of contained sugar and the observation with the naked eye is difficult, the concentration of ethanol or alcian blue can be appropriately adjusted.

  Whether xanthan gum is included as an acidic polysaccharide can be confirmed by the presence of pyruvate at the end of xanthan gum. That is, the amount of pyruvate obtained is measured after hydrolyzing pyruvate with hydrochloric acid according to the following method.

  A sample of 0.600 g is precisely weighed and dissolved in 100 mL of deionized water in a beaker while heating with a 90 ° C. water bath. After accurately making up to 100 mL with a volumetric flask, 10 mL of the solution is put into the flask, 20 mL of 1 mol / L hydrochloric acid is added, the mass is precisely weighed, and heated in a 90 ° C. water bath for 4 hours. After cooling, the mass of the flask contents is corrected with deionized water to the mass before heating. Weigh exactly 2 mL of this solution, add exactly 10 mL of a solution of 2,4-dinitrophenylhydrazine in 2 mol / L hydrochloric acid (1 in 200), and shake. After standing for 5 minutes, extract twice with 5 mL of ethyl acetate. Combine the ethyl acetate extracts, extract three times with 5 mL portions of sodium carbonate solution (1 → 10), transfer the extract to a volumetric flask, add sodium carbonate solution (1 → 10) to make exactly 100 mL, Let it be a liquid. Separately, 0.360 g of pyruvic acid is taken and water is added to make exactly 100 mL. Pipet 1 mL of this solution, add water to make exactly 100 mL. Accurately measure 2 mL of this solution, add exactly 10 mL of a solution (1 → 200) in which 2,4-dinitrophenylhydrazine is dissolved in 2 mol / L hydrochloric acid, and operate in the same manner as the test solution to obtain a comparison solution. For these solutions, the absorbance at a wavelength of 375 mL is measured using water as a control.

  The amount of constituent sugar derived from xanthan gum can be calculated by equivalent calculation from the amount of pyruvic acid obtained. In addition, free sugars are obtained in advance by high performance liquid chromatography (HPLC) method, and then the sample is acid hydrolyzed, and similarly, by HPLC method, the sum of free sugars + component sugars derived from polysaccharide is obtained. Ask. By subtracting the amount of free existing sugar determined separately, it is possible to determine the sum of the constituent sugars derived from polysaccharides.

The structures of polysaccharides other than acidic polysaccharides can be identified by the following means. HPLC measurement, for example, column for sugar analysis: Shodex SUGARSP 0810 (8.0 mm × 300 mm, Shodex), mobile phase: H ₂ O, flow rate: 1.0 mL / min, thermostat bath temperature: 80 ° C., detection: Shodex RI Injection volume: 10 μL, Standard sample of various sugars as internal standard substance (monosaccharide, disaccharide, fructose, rhamnose, glucose, sucrose, sucrose, lactose, lactose, xylose, mannose, rhamnose, arabinose, ribose, galactose, fucose The above can be used for Wako Pure Chemical Industries, Ltd.). The amount of polysaccharides present can be estimated by subtracting the amount of constituent sugars derived from xanthan gum determined from the amount of pyruvic acid from the amount of constituent sugars obtained by HPLC.

  The absorbent structure of the present invention may contain other components in order to enhance various performances of the absorbent structure, in addition to containing the above-mentioned polysaccharide A and polysaccharide B. Examples of such components include water-insoluble particles, and specific examples include mica, bentonite, diatomaceous earth, zeekrite, calcium carbonate, zinc oxide, barium sulfate, polyethylene, methyl methacrylate, silicone etc. Molecular particles, activated carbon, silica gel, activated alumina, various aluminosilicate clay minerals such as natural or synthetic zeolite, sepiolite, sepiolite, Mizukanite, zeolite, cancrinite-like mineral, crosslinkable vinyl monomer and vinyl monomer having hetero aromatic ring The deodorizing particle etc. which are obtained by copolymerizing a monomer component are mentioned. These components can be used individually by 1 type or in combination of 2 or more types.

  By incorporating the water-insoluble particles into the absorbent structure of the present invention, it has been found that the gel strength is improved when the absorbent structure absorbs water and becomes a hydrogel. From this point of view, further studies were conducted, and it was found that gel strength tends to increase when particles having a small contact angle with deionized water on the surface, that is, particles having high hydrophilicity, are used as the particles. It was also found that the water-insoluble particles of the inorganic substance tend to have higher gel strength than the water-insoluble particles of the organic substance. From this viewpoint, it is preferable to use inorganic particles as the water-insoluble particles, and it is preferable to use inorganic particles having a contact angle to deionized water of 110 degrees or less, particularly 100 degrees or less, and particularly 80 degrees or less . Further, by incorporating water-insoluble particles in the absorbent structure, an open cell type porous structure can be formed in the absorbent structure, and the pore size distribution can be controlled.

  When water-insoluble particles are contained in the absorbent structure of the present invention, when obtaining the absorbent structure of the present invention, a step of dissolving and dispersing polysaccharide and water-insoluble particles in water can be provided. In this case, the entire system can be made substantially uniform by stirring etc. However, the viscosity of the system and the specific gravity of the water-insoluble particles are appropriately selected to precipitate the water-insoluble particles, and the proportion of water-insoluble particles in the system Can also be unevenly distributed. As a result, the pore size and pore distribution can be changed in the obtained absorbent structure. As the content of water insoluble particles increases, the cell size tends to be smaller and more uniform.

  The water-insoluble particles to be added preferably have a contact angle of 110 degrees or less with respect to the ion-exchanged water, because the mixing property with the polysaccharide is good and the particles can be dispersed uniformly. As a result, the porous structure in the absorbent structure becomes uniform and has a good appearance, the surface or internal strength is improved, and the surface of the absorbent structure has appropriate hydrophilicity so that the liquid can be absorbed successfully. . In addition, uniform dispersion of particles in these polysaccharides has an advantage that the strength improvement effect of the entire structure bottom can be obtained.

  The above-mentioned "water-insoluble" means that the dissolved amount after 10 minutes of stirring after adding particles precisely weighed to 2.00 g to 100 g of water at 25 ° C. is 10% by mass or less. Also, the contact angle to deionized water is measured at 25 ° C. as follows. That is, a double-sided tape (manufactured by Nichiban Co., Ltd., ny stack NW-5S) is pasted on a slide glass for 30 mm. Water insoluble particles to be measured are dispersed on the adhesive surface of the double-sided tape so that the adhesive surface does not come out, and a flat surface of the particle assembly is created. To the obtained surface, 20 μL of deionized water is dropped, and the contact angle is measured under a magnifying glass observation. When the contact angle changes with time, a value of 60 seconds after dropping is measured, and an average value of 10 points in total is adopted.

  When water-insoluble particles are mixed in the absorbent structure, the absorbent structure is placed in 90 ° C. hot water of 300 times or more the sample amount, stirred for 30 minutes while stirring with a stirring blade, and filtered; Water insoluble particles are isolated. The water-insoluble particles on the filter medium are washed with hot water and then dried at room temperature to obtain a measurement sample. If fibers or other large particle size powder are contained in the absorbent structure, they are separated, for example, by sieving.

  Water-insoluble particles which are particularly preferably used include, for example, various aluminosilicate clay minerals such as silica, bentonite, mica, zinc oxide, diatomaceous earth, zyklite, calcium carbonate, barium sulfate, activated alumina, natural or synthetic zeolite, sepiolite, There may be mentioned Mizukanite, zeolite, and cancrinite-like minerals. These inorganic particles can be used singly or in combination of two or more.

  It is preferable from the viewpoint of effective water absorption retention that the water-insoluble particles have a particle size equal to or less than the size of the pores in the porous body described above. In particular, the particle size of the water-insoluble particles is preferably 20 μm or less, more preferably 10 μm or less, and 5 μm or less, provided that the particle size is equal to or less than the size of the pores in the porous body. More preferred. The lower limit of the particle size is not particularly limited, but from the viewpoint of safety, the size of the secondary particles is preferably 100 nm or more. The particle size of the water-insoluble particles is measured using a laser diffraction / scattering particle size distribution measuring apparatus (LA-920, manufactured by Horiba, Ltd.) for the particles isolated by the above-mentioned method.

  For compositional analysis of water-insoluble particles, elemental analysis of the particles is performed using an energy dispersive X-ray analyzer (EDX) attached to a scanning electron microscope (SEM). In the EDX operation, the X-ray extraction angle is 30 °, the X-ray folding time is 30 minutes, and a Si (Li) semiconductor detector can be used for X-ray detection.

  The proportion of water-insoluble particles contained in the absorbent structure of the present invention is preferably 1% by mass or more, and more preferably 3% by mass or more, based on the total amount of polysaccharide A and polysaccharide B. Preferably, it is more preferably 5% by mass or more. The content is preferably 400% by mass or less, more preferably 200% by mass or less, and still more preferably 150% by mass or less. By using water-insoluble particles in this range, necessary and sufficient gel strength can be obtained. When the addition amount of water-insoluble particles is 1% by mass or more, the cell diameter of the porous body can be homogenized, and when the addition amount is 400% by mass or less, bonding between particles is sufficiently performed and absorption The strength of the structure can be improved. Furthermore, the proportion of polysaccharides involved in the difficulty in liquid migration is increased, and a small amount of absorbent structure can be used.

  The optimum range of the amount of water-insoluble particles added is appropriately selected depending on the desired outer shape of the absorbent structure, the molding method of the absorbent structure, and the purpose of particle addition, provided that the above ratio range is satisfied. Can be determined. The mass of the water-insoluble particles contained in the absorbent structure may be measured after isolating the particles by the method described above.

  In order to compensate for the strength of the absorbent structure of the present invention, other fibrous materials such as pulp, semi-synthetic fibers or synthetic fibers can be mixed with the absorbent structure. Examples of pulp include softwood bleached kraft pulp (hereinafter also referred to as NBKP), hardwood bleached kraft pulp (hereinafter also referred to as LBKP), wood pulp such as used paper pulp, etc. bulky chemistry such as mercerized pulp and crosslinked pulp. Treated pulp, cotton is preferred. As the semi-synthetic fiber, rayon, lyocell and tencel are preferable. Further, as the synthetic fibers, polyolefin fibers (polyethylene, polypropylene, polyethylene terephthalate etc.), polylactic acid fibers, polyvinyl alcohol fibers etc. are preferable. In the case of mixing synthetic fibers, it is more preferable to mix polyolefin fibers derived from biomass, polylactic acid fibers, and biodegradable fibers. The various fibers can be used singly or in combination of two or more.

  The absorbent structure of the present invention is formed of a polysaccharide as a skeleton, but in the case of mixing polyolefin fiber or polylactic acid fiber, a fiber aggregate having such a fiber as a skeleton, for example, a non-woven fabric, etc. May be applied or impregnated. The fiber diameter of the synthetic fiber preferably includes a fiber of 4 dtex or more and 30 dtex or less (hereinafter, also referred to as a thick fiber) from the viewpoint of mixing with the polysaccharide. In order to obtain the strength of the fiber assembly, fibers of 1.5 dtex or more and 4 detx or less (hereinafter also referred to as thin fibers) containing a resin modified to have a low melting point may be mixed. It is preferable that the mixing ratio of the thick fiber and the thin fiber is thick fiber (% by mass) / thin fiber (% by mass) = 90/10 to 50/50. Favorable strength can be acquired as the mixing ratio of a thin fiber is 10 mass% or more, the pore diameter of a fiber assembly becomes large as it is 50 mass% or less, and liquid can be absorbed efficiently.

  Various surfactants can be added to the absorbent structure for the purpose of liquid permeability to the absorbent structure, mixing properties of polysaccharides, particle dispersibility, viscosity reduction in extrusion foaming, and the like. As surfactant, an anionic surfactant, a cationic surfactant, a nonionic surfactant etc. are mentioned, for example. Among these, it is preferable to add a nonionic surfactant. Specific examples of the nonionic surfactant include higher alcohols and fatty acid sorbitan esters (any of mono, di and tri esters), alkyl glucosides, polyglycerin fatty acid esters, sucrose fatty acid esters and the like. The surfactants can be used alone or in combination of two or more.

  An equilibrium moisture regulator can be added to the absorbent structure to improve the flexibility of the absorbent structure. As the equilibrium moisture regulator, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, polyglycerin, propylene glycol, diethanolamine, polyoxypropylene, trimethylolpropane, pentaerythritol, 1,3-propanediol, 1, Polyols such as 3-butylene glycol and sorbitol are mentioned.

  Since the dissolution of polysaccharide, gelling temperature, gel strength and the like are affected by the amount of metal ion contained in the system, a metal ion scavenger may be contained as appropriate. Examples of the metal ion scavenger include tetrasodium ethylenediaminetetraacetic acid (EDTA), ethylenediamine-N, N'-disuccinic acid (EDDS), trisodium nitrilotriacetic acid (NTA), pentasodium diethylenetriaminepentaacetic acid (DTPA), hydroxy Aminocarboxylate metal ion scavengers such as ethyl ethylenediaminetriacetic acid (HEDTA) trisodium, L-glutamic acid diacetic acid (GLDA) tetrasodium, 3-hydroxy-2,2'-iminodisuccinic acid tetrasodium (HIDS); hydroxy Phosphate-based metal ion scavengers such as ethylidene diphosphonic acid (HEDP) tetrasodium; Polymerized phosphate-based metal ion scavengers such as sodium tripolyphosphate (STPP), sodium pyrophosphate (TSPP), sodium hexametaphosphate; Builders for polymeric detergents such as sodium polyacrylate and acrylic acid / maleic acid copolymer; Other organic metal ion scavengers such as trisodium citrate and ammonium citrate; Zeolite (crystalline aluminosilicate), sodium silicate etc. An inorganic type metal ion trapping agent etc. are mentioned, It can use individually by 1 type in these, or in combination of 2 or more types. Among these, ethylenediaminetetraacetic acid (EDTA) tetrasodium, trisodium citrate, sodium tripolyphosphate, sodium acrylate and zeolite are preferable, and trisodium citrate and ethylenediamine-N, N'-disuccinic acid (EDDS), 3- Hydroxy-2,2'-iminodisuccinic acid tetrasodium (HIDS) is preferred in view of low environmental impact. These components can be used individually by 1 type or in combination of 2 or more types.

  The absorbent structure of the present invention can be manufactured in various ways. For example, in the case where the absorbent structure is a plate or a lump, an absorbent structure having a porous structure can be obtained by subjecting an aqueous solution containing polysaccharide A and polysaccharide B to a lyophilization method. Alternatively, an absorbent structure having a porous structure can be obtained by a foam molding method. When water-insoluble particles are added, it may be added to an aqueous solution containing polysaccharide A and polysaccharide B. In this case, it is possible to obtain an absorbent structure having various cross-sectional shapes by adopting extrusion foam molding using an extruder or the like and combining profile extrusion such as changing the shape of the die.

  When the freeze-drying method is used, a hydrogel containing polysaccharide A and polysaccharide B is frozen to a predetermined shape, and then vacuum dried to sublime water to obtain an absorption structure of the target shape. Be For example, in the case of obtaining a plate-like absorbent structure, a hydrogel containing polysaccharide A and polysaccharide B may be placed in a flat-bottomed container and frozen, and the frozen body may be vacuum dried. By making the bottom of the container flat, an absorbent structure having a flat structure can be obtained. If a recess or a protrusion is provided on the bottom of the container, it is possible to obtain an absorbent structure having the corresponding unevenness or the block shape (male-female shape with the container as a mold) or the like. In the case of obtaining an absorbent structure composed of a fibrous body, a hydrogel containing polysaccharide A and polysaccharide B is extruded from a die to form a striatum, which is frozen and then dried if necessary. Just do it.

  Below, an example of the conditions of extrusion molding by an extruder is demonstrated. However, the conditions for extrusion molding are not limited to the following, and appropriate conditions can be set in consideration of the extrusion molding apparatus to be used, the type or amount of material, the shape of the desired composition, and the like.

  The feed screw speed of the extruder is preferably 100 rpm or more, more preferably 130 rpm or more, and preferably 150 rpm or less. The rotation speed of the main screw is preferably 150 rpm or more, more preferably 180 rpm or more, and preferably 230 rpm or less, more preferably 220 rpm or less. When the barrel temperature of the extruder is controlled in four temperature ranges, when the barrel temperature is 1, the barrel temperature 2, the barrel temperature 3, and the barrel temperature 4 from the upstream toward the downstream, the barrel temperature 1 Is preferably 60 ° C. or more, more preferably 70 ° C. or more, and preferably 100 ° C. or less, more preferably 90 ° C. or less. The barrel temperature 2 is preferably 110 ° C. or more, more preferably 120 ° C. or more, and preferably 150 ° C. or less, more preferably 140 ° C. or less. The barrel temperature 3 is preferably 100 ° C. or more, more preferably 110 ° C. or more, and preferably 130 ° C. or less, more preferably 120 ° C. or less. The barrel temperature 4 is preferably 100 ° C. or more, more preferably 110 ° C. or more, and preferably 130 ° C. or less, more preferably 120 ° C. or less. The discharge diameter of the die is preferably 5 mm or more, more preferably 8 mm or more, and preferably 20 mm or less, more preferably 15 mm or less.

  In the above steps, in order to adjust the size of the pores of the porous structure in the absorbent structure, for example, in the case of lyophilization, the concentration of the aqueous polysaccharide solution, the freezing temperature and the freezing rate may be changed. In the case of extrusion foam molding, the nozzle pressure, the molding temperature, the addition amount of water when using steam as the principle of foaming, the addition amount of the water-insoluble particles, the type and the like may be appropriately selected. In addition, the obtained absorbent structure may be subjected to post-processing, and may be subjected to larger holes, slits, emboss, punching or cutting for changing the outer shape.

  The absorbent structure thus obtained can be used as it is for absorbing a liquid containing water as a component. Alternatively, it can be used in the form of an absorbent article incorporating this absorbent structure. The absorbent articles include, for example, disposable diapers, liners for cloth diapers, sanitary napkins, panty liners, incontinence pads, breast milk pads, pet litter sheets, surgical blood absorbing articles, surgical clothes, bandages, bandages, bed sheets, Pillow covers, absorbent paper for underarm pads, shoe insoles, poultices, and meat and fish meat juice absorbing sheets, etc. may be mentioned.

  Specific examples of the above-mentioned absorbent articles include disposable diapers, which are absorbent articles of body fluid discharged from the human body, sanitary napkins, panty liners, incontinence pads and the like. These body fluid absorbent articles are provided with a skin facing side sheet located closer to the skin of the wearer and a non-skin facing side sheet located farther from the wearer's skin, and the absorbent structure of the present invention It is preferable that the body has a structure disposed between the skin-facing side sheet and the non-skin-facing side sheet. As a skin opposing surface side sheet, the liquid-permeable top sheet which is a sheet located, for example in the side nearest to a wearer's skin is mentioned. Moreover, the sublayer sheet | seat which is a liquid-permeable sheet | seat arrange | positioned adjacent to this surface sheet as a skin opposing surface side sheet | seat is mentioned. On the other hand, as the non-skin facing side sheet, there may be mentioned a liquid impermeable or liquid impervious back sheet, for example, a resin film, a liquid impervious nonwoven fabric and the like.

  Examples of the liquid-permeable top sheet include various nonwoven fabrics and perforated films. Examples of the liquid-permeable sublayer sheet include various nonwoven fabrics. Regardless of the type of surface sheet or sublayer sheet, in the absorbent article provided with the absorbent structure of the present invention, the absorbent structure is preferably in direct contact with the skin-facing side sheet. In this case, when the skin facing side sheet is only the surface sheet, the surface sheet is in direct contact with the absorbent structure. When the skin-facing side sheet includes a top sheet and a sublayer sheet, the sublayer sheet is in direct contact with the absorbent structure. By adopting such a configuration, absorption and retention of the liquid by the thickening effect of the absorbent structure can be efficiently performed.

  From the viewpoint of improving the stability of the outer shape of the absorbent core, the fixability of the pulp and the acrylate crosslinked material, and the transportability of the absorbent core in the production line, an absorbent core composed of a mixture of conventional pulp / acrylate crosslinked materials The entire absorbent core is covered with a sheet material such as nonwoven fabric or tissue paper having an average pore diameter of 20 μm or less to form an absorbent. Having such a configuration in the absorbent article has the advantage that it is possible to add functional agents to the sheet material to add value, but it also impedes the permeability of the liquid from the sheet to the absorbent core. It is a factor. On the other hand, since the whole absorbent structure of the present invention is integrated, the absorbent structure of the present invention can maintain a stable outer shape and can be manufactured. There is no need to cover the outer surface of the absorbent structure with a sheet material. Therefore, the improvement of the liquid absorption speed and the uptake characteristic of the highly viscous liquid can be sufficiently expressed by utilizing the design of the pore size of the absorbent structure.

  Although the present invention has been described above based on its preferred embodiments, the present invention is not limited to the embodiments. For example, although it is preferable that the absorbent article provided with the absorbent structure of the present invention includes the skin facing surface side sheet and the non-skin facing surface side sheet as described above, in addition to this, the specific application of the absorbent article Accordingly, it is possible to provide leak-barrier cuffs extending along the longitudinal direction on both sides along the longitudinal direction on the skin facing surface side. Moreover, you may provide the adhesion layer for fixation with clothing on the surface of a non-skin opposing surface.

  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 specified, "%" and "parts" mean "mass%" and "parts by mass".

Example 1
Polysaccharide A and polysaccharide B shown in Table 1 below were mixed with water at a ratio shown in the same table to obtain an aqueous solution. The aqueous solution was frozen in a flat-bottomed container. The obtained frozen body was vacuum dried to remove water, to obtain an absorbent structure comprising a plate-like body having a porous structure. Specifically, 1.5 parts of polysaccharide A (xanthan gum, made by DSP Gokyo Food & Chemical Co., Ltd., Labour gum GS-C) and polysaccharide B (locust bean gum, made by Unitech Foods Co., Ltd., in a 500 mL beaker, 97 parts of deionized water was added to 1.5 parts of VIDOGUM L175 HQ) to prepare a total of 300 g of a polysaccharide mixture. The beaker was stirred with a stirring blade for 1 hour while warming the periphery of the beaker with a 90 ° C. water bath, and was dissolved so as to be uniform visually. The top of the beaker was covered with a lid to suppress water evaporation. Then put 50 g into a metal mold (Sansho long stainless steel long bat deep mold 12 type, length x width x depth = 120 mm x 72 mm x 53 mm), naturally cool to room temperature, and then -80 ° C freezer Frozen for 1 hour. Thereafter, the lyophilization was performed for approximately two days and night until the lyophilizer completed the drying. As a freezer, Kanowo chiller, Deep freezer LAB-11 was used, and as a freeze dryer, a freeze dryer FDU-1200 manufactured by Tokyo Rika Kikai Co., Ltd. was used.

[Examples 2 and 3, 8 and 9]
An absorbent structure was obtained in the same manner as in Example 1 except that polysaccharide A and polysaccharide B shown in Table 1 below were used in the proportions shown in the same table. In Table 1, as the cationized xanthan gum, Raball gum CX manufactured by DSP Gokyo Food & Chemical Co., Ltd. was used. As cod gum, MT-120 manufactured by Mitsubishi Chemical Foods Co., Ltd. was used.

[Examples 4 to 7]
Polysaccharide A and polysaccharide B shown in Table 1 below were used in the proportions shown in the same Table. Also, water-insoluble particles shown in the same table and the following were added to the aqueous solution in the proportions shown in the same table. An absorbent structure was obtained in the same manner as in Example 1 except that the amount of deionized water to be added was reduced by the mass of the water-insoluble particles.
・ Hydrophilic fumed silica (EVONIK INSDUSTRIES, Aerosil 200)
・ Bentnight (made by Hojun Co., Ltd., Ben Bell)
・ Mica (made by Katakura Coop Agri Co., Ltd., MEE)
・ Zinc oxide (made by Hakusui Tech Co., Ltd., zincox super F1)
・ Silica (manufactured by AGC SITEC Co., Ltd., Sunsphere L51)

[Comparative Examples 1 to 9]
An absorbent structure was obtained in the same manner as in Example 1 except that polysaccharide A and polysaccharide B shown in Table 1 below were used in the proportions shown in the same table. In Table 1, as the xanthan gum, Raball gum GS-C manufactured by DSP Gokyo Food & Chemical Co., Ltd. was used. As carboxymethylcellulose sodium salt (abbreviated as CMC-Na in the table), CMC 1390 manufactured by Daicel Co., Ltd. was used. Kimica algin IL-2 manufactured by Kimica Co., Ltd. was used as sodium alginate (abbreviated as sodium alginate in the table). As a cationized guar gum, Raball gum CG-M manufactured by DSP Gokyo Food & Chemical Co., Ltd. was used. As the cationized starch, Neotac 40T: cationized tapioca starch manufactured by Nippon Food Chemical Co., Ltd. was used.

[Comparative Examples 10 and 11]
Polysaccharide A and polysaccharide B shown in Table 1 below were used in the proportions shown in the same Table. Also, water-insoluble particles shown in the same table and the following were added to the aqueous solution in the proportions shown in the same table. An absorbent structure was obtained in the same manner as Example 1 except for the above.
・ Hydrophilic fumed silica (EVONIK INSDUSTRIES, Aerosil 200)
・ Bentnight (made by Hojun Co., Ltd., Ben Bell)
・ Methyl siloxane cross-linked product (Momentive Performance Materials Japan KK, Tospearl 3120)

[Evaluation]
The uniformity after mixing polysaccharides A and B with water was visually evaluated about each Example and each comparative example. In addition, for each example and each comparative example, while measuring the pore size, the viscosity when absorbing and holding 100 parts of deionized water by the absorbing structure is taken as a measure of the viscosity (30 ° C.) of the liquid. It was measured with a B-type viscometer (B-type viscometer B8M type, manufactured by Tokyo Keiki Co., Ltd.). The results are shown in Table 2 below. In Examples and Comparative Examples containing water-insoluble particles in Table 2, the water-insoluble particles do not dissolve in the system but disperse. Therefore, evaluation of uniformity in these Examples and Comparative Examples is evaluated as "uniform" when aggregation of particles, partial gelation of polysaccharides, precipitation, etc. is not observed, and aggregation or aggregation of particles is evaluated. When partial gelation of saccharides is observed, it is evaluated as "non-uniform", and when sedimentation of particles is observed, it is evaluated as "sedimentation", and aqueous solution mixed with polysaccharides A and B and water insoluble particles When separation was observed, it was evaluated as "complete separation".

  As apparent from the results shown in Table 2, in each example, mixing of polysaccharide A and polysaccharide B can be uniformly performed, and the obtained absorbent structure can stably hold deionized water. I understand.

Claims (9)

An absorbent structure used for absorbing a liquid containing water as a component, comprising:
An absorbent structure comprising a porous body containing an acidic polysaccharide to which pyruvic acid is bound and a polysaccharide other than an acidic polysaccharide to which pyruvic acid is bound.   The absorbent structure according to claim 1, wherein the polysaccharide other than the acidic polysaccharide to which pyruvic acid is bound is a nonionic or amphoteric polysaccharide.   The absorbent structure according to claim 1 or 2, wherein the polysaccharide other than the acidic polysaccharide to which pyruvic acid is bound is a nonionic polysaccharide containing three or more mannoses in the repeating unit skeleton.   The absorbent structure according to any one of claims 1 to 3, wherein the pyruvic acid-bound acidic polysaccharide is xanthan gum.   5. Absorbent structure according to any one of the preceding claims further comprising water insoluble particles.   An absorbent article provided with the absorbent structure according to any one of claims 1 to 5. And a non-skin facing side sheet located on the side far from the wearer's skin, and a non-skin facing side sheet located on the side closer to the wearer's skin, and
The absorbent according to claim 6, wherein the absorbent structure is disposed between the skin-facing side sheet and the non-skin-facing side sheet, and is in direct contact with the skin-facing side sheet. Sex goods.   The absorbent article according to claim 7, wherein the skin-facing side sheet is a surface sheet located on the side closest to the skin of the wearer.   The absorbent article according to claim 7, wherein the skin-facing side sheet is a sublayer sheet disposed adjacent to a surface sheet positioned on the side closer to the skin of the wearer.