JP4863830B2 - Fabric-like high-speed absorbent composite and its production method - Google Patents

Description

  The present invention relates to a thin and lightweight sheet-like absorbent composite, a method for producing the same, and a body fluid absorbent article using the absorbent composite. This absorbent composite is an absorbent composite having a cloth-like feel, an excellent absorption rate, and a high diffusing capacity, so that it can be suitably used particularly in the field of hygiene materials such as disposable diapers and sanitary napkins. it can. Moreover, since it is excellent in form stability, it is related with the absorptive composite_body | complex which is excellent also in workability.

  Water-absorbing polymers have been used in a wide range of fields such as sanitary materials such as sanitary products, diapers, water retention agents in the agricultural field, soil conditioners, artificial snow for artificial ski resorts, and scrubs for face wash. Water-absorbing polymers are usually in the form of particles, have poor molding and processability, and use conditions are limited. Among these uses, when used for sanitary materials such as sanitary products and diapers, it is preferable that the water absorption rate is high and that the material is flexible because it is used in contact with the skin. Moreover, it is preferable that it is a sheet form from a viewpoint of workability.

It is known that the water-absorbing polymer particles become sticky on the surface after water absorption, the liquid permeability between the particles decreases due to gel blocking, and the water absorption rate decreases. Further, generally used dry particles of a water-absorbing polymer produced by crosslinking polymerization of acrylic acid or an alkali metal acrylate are hard and unpreferable in touch.

  As a method for increasing the water absorption rate of a water-absorbing polymer, there is porous water-absorbing polymer particles obtained by making an O / W / O emulsion of an aqueous phase containing a monomer and polymerizing it (see, for example, Patent Document 1). By increasing the surface area due to porosity, the water absorption rate of one particle is improved, but the above-described gel blocking is not improved, so the water absorption rate is not sufficient.

  In addition, there is a porous absorbent polymer macrostructure in which a hydrogel is formed into a sheet by cross-linking between particles (for example, see Patent Document 2). Since this sheet-like macrostructure is a sheet obtained by cross-linking between particles, there is a problem that the strength as a sheet is low and it is easily broken during molding or use.

  There is also a method for producing a superabsorbent resin sheet produced by carrying a water-absorbing polymer in a foamable polyurethane resin and cutting (see, for example, Patent Documents 3 and 4). However, since the polyurethane foam inhibits the swelling of the water-absorbing polymer, the amount of water absorption is not sufficient, and the water-absorbing polymer drops off from the polyurethane resin as the water is absorbed, so that there is a problem that the touch is poor during use.

  There is also a sheet-like composition of a porous absorbent polymer coated with a silicone compound (see, for example, Patent Document 5). However, the absorbent polymer sheet-like composition swells in all directions when the liquid is absorbed. In particular, it is unsuitable when absorption and swelling in the thickness direction is required in a predetermined area such as sanitary goods. In addition, since the movement of water inside the absorbent polymer is not fast, when only a part comes into contact with the liquid, only the contact part tries to swell, but it is thought that the absorption rate decreases due to the influence of the hard dry part .

  In order to control the shape stability and the absorption direction, a method of fixing an absorbent resin to a support carrier has been studied. For example, a method of embossing the absorbent body, a method of including a thermoplastic binder fiber in an absorbent body composed of an absorbent resin and a hydrophilic fiber and heat-sealing the absorbent body, a synthetic resin having a high recovery rate from strain A method of heat-sealing the absorbent by containing it in an absorbent comprising an absorbent resin and a hydrophilic fiber (see, for example, Patent Document 6 and Patent Document 7), and the surface of the absorbent resin having an anionic group is cationic. A method of coating a polymer and adhering and fixing particles through swelling (for example, see Patent Document 8 and Patent Document 9), a method of immobilizing an absorbent resin and a hydrophilic fiber using an emulsion binder, For example, a method of fixing an absorbent resin to a substrate using a hot-melt adhesive (see, for example, Patent Document 10 and Patent Document 11). In such an example, since it is necessary to use a large amount of binder, there arises a problem of regulation of the swelling of the absorbent resin due to restriction of the binder force. In particular, when the absorbent resin and the hydrophilic fiber are fixed with a thermoplastic binder or emulsion, there is a problem that the absorbent ability inherently possessed by the absorbent resin cannot be sufficiently exhibited.

  There is also an example in which an absorbent resin is immobilized on a base material without using a binder. For example, there is a method (see, for example, Patent Document 12) in which absorptive polymer particles during polymerization are attached to a fibrous base material and polymerization is performed on the fibrous base material. In this method, the fibrous base material enters the polymer particles and is firmly fixed, but it is difficult to complete the reaction in the base material, and it is considered that there are many residual monomers and residual crosslinking agents. There is also an example (for example, see Patent Document 13) in which a certain amount or more of an aqueous monomer solution is supported in a fine particle form on a nonwoven fabric that has been subjected to raising treatment, and then polymerized and thermally compressed. In this example, since the amount of the absorbent resin is large, the absorption performance as a composite is high, and since the nonwoven fabric is used, movement is less likely to occur compared to pulp. However, in this example as well, the residual monomer becomes a problem because of polymerization in the nonwoven fabric. Further, the absorbent resin is impregnated with an aqueous solution of an unpolymerized monomer again, applied onto the base material, and the impregnated monomer is polymerized to bond the absorbent resin and the base material (for example, Patent Document 14). However, it is difficult to completely polymerize the residual monomer after adhesion to the substrate, and a large amount of residual monomer becomes a problem. Similarly, there is another example (see, for example, Patent Document 15) in which an absorbent resin is applied as a slurry to a base material. In this case, the productivity is certainly improved by applying the slurry, but it is necessary to use an expensive microfibril as a dispersion medium, and it is considered that the adhesive force is not sufficient.

As described above, an absorber having a high absorption rate and excellent form stability and processability has not been obtained.
Japanese Patent Laid-Open No. 62-106902 Japanese National Patent Publication No. 5-506681 JP-A-1-282223 JP-A-2-62208 JP 2003-301007 A JP-A-10-118114 JP-A-10-118115 JP-A-5-31362 JP-A-6-370 JP 2000-238161 A Japanese National Patent Publication No. 10-510447 JP 2003-11118 A JP 2004-124303 A JP-A-11-137600 Japanese Patent Laid-Open No. 9-239912

  An object of the present invention is to provide an absorptive composite that is thin, lightweight, excellent in form stability and processing characteristics, and has a high absorption rate. In particular, an object is to provide an absorbent composite that can be suitably used for sanitary goods such as disposable diapers, sanitary napkins, and incontinence pads.

As a result of earnest studies to achieve the above-mentioned problems, the absorption rate of the resin is dramatically increased by using a specific amount of the absorbent resin adjusted to the predetermined average particle size and combining it with the base material. As a result, the present inventors have found that the texture is improved and that a good tactile sensation is exhibited. That is, the present invention is an absorbent composite as described below, a method for producing the absorbent composite, and a body fluid absorbent article using the composite.

[1] A composite in which a base material and a particulate absorbent resin are bonded,
An absorbent composite produced by absorbing a base material and / or an absorbent resin, bringing the resin into contact with the base material, then dehydrating and drying, and satisfying the following conditions.
(1) The substrate is composed of cellulosic hydrophilic fibers.
(2) The average basis weight of the absorbent resin with respect to the plane is 10 to 150 g / m ² .
(3) 50% or more of the absorbent resin is directly bonded to the base material,
(4) The residual monomer in the absorbent resin is 200 ppm or less,
(5) The average particle diameter of the absorbent resin is 10 to 300 μm.
(6) The basis weight of at least one base material is 28 to 100 g / m ² .
(7) A compound having two or more functional groups capable of reacting with a carboxyl group coexists in the absorbent resin.
(8) The surface strength of the absorbent resin particles before adhering onto the substrate is 0.1 to 5.5N.
[ 2 ] The absorbent composite according to [1 ] , which is an absorbent composite using a plurality of substrates, and an average basis weight of the resin on the surface of the absorbent composite is 0 to 20 g / m ^2. Sex complex.
[ 3 ] The absorbency according to any one of [1] to [ 2 ], wherein two substrates are used, and the substrates are bonded to each other by a resin layer disposed between the substrates. Complex.
[ 4 ] The absorbent composite as described in any one of [1] to [ 3 ], wherein the ratio of the weight of the absorbent resin to the weight of the substrate is 35 to 300%.
[ 5 ] The absorbent resin is a resin having a carboxylic acid group in the side chain, and 50% or more of the acid groups in the absorbent resin are neutralized in the form of an ammonium salt. 1]-[ 4 ] The absorptive complex in any one.
[ 6 ] The absorbent composite as described in any one of [1] to [ 5 ], wherein the absorbent resin is a copolymer mainly composed of polyacrylate.
[ 7 ] The method according to any one of [1] to [ 6 ], wherein the substrate and / or the absorptive resin is made to absorb water, and then the resin and the substrate are brought into contact with each other and then dehydrated and dried. The manufacturing method of the absorptive complex of description.
[ 8 ] The method for producing an absorbent composite according to [ 7 ], wherein a resin is disposed between a plurality of water-containing base materials, and is adhered and then dehydrated and dried.
[ 9 ] A body fluid-absorbing article comprising the liquid-permeable sheet, the liquid-impermeable sheet, and the absorbent composite according to any one of [1] to [6] between the two.

ADVANTAGE OF THE INVENTION According to this invention, it is a cloth-like absorptive composite body with which the absorptive particle is fix | immobilized by the base material, and can provide the absorber with the high absorption speed of a liquid. By using such an absorber as a sanitary material, the manufacturing process of the sanitary material can be simplified.

The present invention will be described in detail below.
1. Structure / Performance of the Composite of the Present Invention In the present invention, a structure in which an absorbent resin and a substrate are bonded is called an absorbent composite. Resin does not change position and has excellent shape stability. Therefore, the base material can maintain the sheet shape. It is preferable to mix the absorbent composite with short fibers such as pulp and other sheet-like materials to adjust the performance as an absorber. An absorbent resin that is not immobilized may be combined with the absorbent composite, but it may cause blocking and reduce the performance of the absorbent composite. It is preferably 50% or less, more preferably 30% or less, still more preferably 10% or less, and most preferably 5% or less with respect to the weight of the composite.

  The absorbent composite of the present invention is a composite in which an absorbent resin is combined and adhered on a substrate to improve the absorption rate. By directly adhering to the base material constituting fiber, the liquid could be passed through the resin through the adhesive fiber. Thereby, the wettability of resin improves. In addition, the fiber shape change accompanying the contact of the fiber with water may apply a certain force to the resin to which the fiber is adhered, and the absorption speed is dramatically improved. Since the fiber of the base material becomes a liquid passage, it is essential that it is hydrophilic.

In the present invention, since the substrate is in the form of a sheet, one substrate has a front surface, a back surface, and two planes. In this invention, it is necessary for the average basic weight of the absorptive resin with respect to a plane to be 10-150 g / m < ² >. If the particles are in contact with each other when the resin is placed on the base material, a blocking problem occurs at the time of water absorption, but by keeping the amount of particles placed on the flat surface of the base material within a certain range, The adhesion point with the base fiber can be secured. That is, even if a blocking phenomenon occurs between the particles, the absorbent resin absorbs through the base fiber, so that it can be absorbed at high speed without causing liquid flow inhibition. If a higher absorption capacity is required and the amount of absorbent resin used needs to be increased, use multiple absorbent composites, or use a composite with multiple substrates, and the area of the plane We can cope by increasing.

  It is preferable that the absorbent resin is bonded to the base material because the absorbent resin can be prevented from moving during transportation or liquid absorption. The bonding method is not particularly limited, but a method that does not use an adhesive is preferable, and it is more preferable to bond in a form in which some of the fibers of the base material are incorporated in the absorbent resin. It is preferable that 50% by weight or more of the absorbent resin in the bonded absorbent resin is bonded in a form in which a part of the fiber is taken into the absorbent resin, more preferably 70% by weight or more. Preferably 90% by weight or more, most preferably 95% by weight or more of the absorbent resin adheres in this form. If an adhesive is not used, it is preferable because it is not subjected to swelling regulation during liquid absorption. It is preferable that a part of the fibers are bonded in a form incorporated in the absorbent resin because the liquid can be fed into the absorbent resin through the fibers and the absorption speed is improved. On the other hand, in order to develop a high absorption capacity as a composite, it is preferable that the absorption capacity of the resin is also high at the same time. That is, it is preferable that the average absorption rate of the absorbent resin to be used is 50 g / g or more. Absorbent resins having such a high absorption ratio usually tend to cause gel blocking, and until now, hard and low absorption ratio resins having a high degree of cross-linking on the surface and inside have been used. In the present invention, since the influence of blocking is eliminated by passing the liquid from the fiber, a high absorption rate can be achieved even if a soft resin having a high absorption capacity is used.

  Furthermore, since the composite absorbent body of the present invention has high liquid diffusibility depending on the base material and can exhibit the absorption performance of all absorbent resins, the absorbent composite can be used without using extra absorbent resin. The weight can be reduced.

  Among various performances, there is a demand for a low residual monomer content that is regulated in the voluntary standards for absorbent resins of the Japan Sanitary Materials Industry Association. One of the features of the absorbent composite according to the present invention is that it is lowered to a remarkably low value. This is a value that is difficult to achieve by a polymerization method on a resin base material used in a general base material-resin direct bonding method. That is, this is achieved because the resin used is polymerized in advance and a resin having a predetermined low residual monomer state is used as the resin for the composite. It is preferable to use as absorptive resin a resin that has been polymerized in an aqueous solution and the resulting mass is granulated in a process including a crushing process, or a particle aggregate that has been polymerized in advance by a reverse phase suspension polymerization method. .

2. About adhesion In the present invention, the adhesion between the base material and the absorbent resin means that the absorbent resin is fixed to the base material, and the positional relationship between the base material and the absorbent resin does not substantially change. To express. In the present invention, holding one side of the absorbent composite by hand, shaking in the direction of the side in a state where the plane direction of the composite is vertical, swinging for 1 minute at a speed of one reciprocation per second with a width of 20 cm, Assume that particles that are not detached are adhered. The detached particles are considered to be mixed in the absorbent complex and are not included in the absorbent complex. There is no problem even if the absorbent composite is mixed with an unbonded absorbent resin that is detached in this test, but the unbonded absorbent resin is 50% of the weight of the absorbent composite. Or less, more preferably 30% or less, still more preferably 10% or less, and most preferably 1% or less. If the positional relationship between the base material and the absorbent resin does not change, the performance of the absorbent composite does not change due to transportation before use or the like, which is preferable from the viewpoint of repeated liquid absorption.

  In the present invention, there is no particular limitation on the form of adhesion to all particles, adhesion by an adhesive, adhesion by a chemical bond between a base material and an absorbent resin, adhesion by a physical interaction, and fibers have entered the absorbent resin. Adhesion in the form may be sufficient. However, it is preferable that 50% by weight or more of the absorbent resin used is in a form in which the substrate and the resin are in direct contact. More preferably 70% or more, still more preferably 90% or more, and most preferably 95% or more is in a directly adhered form. Here, “directly bonded” refers to bonding without using a base material such as an adhesive, water absorbent resin particles, or components other than these components. However, in the case where an adhesive is used together to such an extent that swelling control does not occur, it is included in direct adhesion. The ratio of the particles that are directly bonded can be determined by measuring the amount of water-absorbing resin particles that are still bonded after the absorbent composite is immersed in a solvent that dissolves the adhesive for 1 hour.

There is no particular limitation on the direct bonding method, and bonding by chemical bonding between the substrate and the water-absorbing resin particles, bonding by physical interaction, bonding in a form in which fibers are contained in the water-absorbing resin, etc. may be used. Adhesion in a form in which fibers are contained in the conductive resin is preferable. Specifically, it is preferable that 50% by weight or more of all water-absorbing resin particles are bonded in a form in which fibers are taken into the water-absorbing resin. Preferably, 60% by weight or more, more preferably 70% by weight or more, and still more preferably 90% by weight or more of particles are adhered in this form.

  The form in which the fibers are contained in the water absorbent resin represents a state in which the fibers in the substrate are present in the water absorbent resin matrix. The shape and length of the fibers that enter are not particularly limited. When bonded in this form, water can be taken into the water-absorbent resin through the fiber, so that excellent performance is exhibited in terms of absorption amount and absorption speed. It can be confirmed with an electron microscope whether or not the fibers are bonded in the form of entering the water-absorbent resin. Any 30 adhered particles can be extracted, peeled off, and observed with an electron microscope to determine the ratio.

  In the present invention, as long as 50% by weight or more of all the water-absorbing resin particles are directly bonded to the substrate, the bonding method of the remaining water-absorbing resin particles is not particularly limited.

  However, it is preferable not to perform adhesion using an adhesive from the viewpoint of preventing swelling control during liquid absorption. Use of an adhesive is not preferable because it may inhibit swelling of the water absorbent resin. Examples of the adhesive include thermoplastic fibers and polymers, emulsion binders, and hot melt adhesives.

  The resin may be bonded to only one side of the substrate, or may be bonded to both sides of the substrate. Since the amount of particles that can be arranged on one plane is limited, when a faster absorption rate and a larger amount of absorption are required, and it is necessary to increase the amount of resin to be used, it is preferable to arrange them on both sides. Further, when it is desired to increase the amount of resin to be used, it is preferable to use a plurality of absorbent composites in order to increase the resin layer. When processing becomes complicated by using multiple absorbent composites, it is possible to integrate multiple absorbent composites with an adhesive. The liquid permeability between the absorbent composites may be deteriorated depending on the agent. In this case, it can be improved by bonding the substrates to each other through one resin layer. That is, when the number of base materials is an arbitrary number n, it is preferable to use an integral absorbent composite having n−1 to n + 1 resin layers. In the case of using a plurality of substrates, it is not necessary that all the substrates are hydrophilic fibers, and they can be used properly according to the purpose. When it is desired to prevent leakage to the outside, it is preferable to use a hydrophobic substrate on the outermost side. However, from the viewpoint of securing the water absorption rate of the resin layer, one resin layer is preferably in contact with at least one hydrophilic substrate, and more preferably is in contact with two hydrophilic substrates.

  The higher the value of the number of hydrophilic substrates / the number of water-absorbing resin layers, the greater the contribution of the hydrophilic substrate to the resin layer, so the absorption rate can be increased efficiently. The value of the number of hydrophilic substrates / the number of water-absorbing resin layers is preferably 1.3 or more, more preferably 1.5 or more, and most preferably 2. That is, it is most preferable to provide a resin layer adhered to both base materials between two hydrophilic base materials. At this time, since the two base materials are bonded by the resin layer, the shape stability is excellent, and the touch becomes thin and cloth-like.

The surface of the absorbent composite in the present invention refers to a flat surface that is exposed to the outside. All absorbent composites have two surfaces. The resin present on the surface may be detached when a force is applied after swelling. For this reason, in applications where desorption is not preferred, it is preferable to limit the amount of resin on the surface. By reducing the amount of resin per plane, the base material area for one particle increases, so that the adhesive strength can be increased. The smaller the amount of resin on the surface of the absorbent composite, the better. Specifically, it is preferable that an average basis weight of 0~20g / ^{m 2,} more preferably 0 to 10 g / ^{m 2,} more preferably from 0~5g / ^{m 2,} 0~1g / M ² is most preferred.
3. About the average basic weight of resin The average basic weight in this invention is defined as the weight per unit area of the absorbent resin in one plane. The weight of the absorbent resin is measured with all particles removed. The average basis weight is essential to be 10 to 150 g / ^{m 2,} is preferably 30~130g / ^{m 2,} more preferably from 40 to 120 g / ^{m 2,} in 50~110g / m2 More preferably, it is most preferably 60 to 90 g / m ² . If the basis weight of the resin is too small, it is difficult to completely transfer the liquid in the substrate to the resin, which may cause the liquid to return. If the basis weight of the resin is too large, the amount of resin that is not in contact with the base fiber increases, so that the influence of blocking cannot be avoided. When a larger amount of resin is required, it can be handled by increasing the plane. Also in this case, it is preferable that the amount of resin in the plane between the base materials satisfies the above range.
4). Absorbent resin particles (absorbent resin)
First, the absorbent resin that constitutes the absorbent resin particles in the present invention will be described.

  In the present invention, the absorbent resin preferably has a residual monomer concentration of 200 ppm or less with respect to the weight of the absorbent resin, more preferably 100 ppm or less, still more preferably 50 ppm or less, and most preferably 10 ppm or less. When there are many residual monomers, there are many elution components at the time of liquid absorption, and it is not preferable in terms of performance.

  Residual monomer can be reduced by heat treatment at the time of production or after completion of the absorbent composite to complete the polymerization, but the residual monomer concentration of the absorbent resin before contact with the substrate may be 5% or less. Preferably, it is 1% or less, more preferably 0.1% or less, and most preferably 0.05% or less. If an absorbent resin with a large amount of residual monomer is used as a starting material, it is difficult to complete the polymerization reaction of the residual monomer at the time of producing the composite, and a large amount of residual monomer tends to remain in the end, which is not preferable. Further, depending on the reaction method, the texture of the substrate may be impaired, which is not preferable.

  For this reason, in the present invention, the absorbent resin is produced by an aqueous solution polymerization method, and then formed into an amorphous particle by a production method including a crushing step and / or a reverse phase suspension polymerization method. It is preferable to use prepared particles.

  The amount of residual monomer can be quantified using the following method.

  The absorbent resin is added to 0.9% physiological saline of 250 times the weight of the resin, extracted for about 6 hours with stirring at room temperature, and then filtered. The filtrate is quantified using a liquid chromatography method.

  In the present invention, the type of the absorbent resin is not particularly limited, and any absorbent resin may be used. It is preferably an absorbent resin having an acid group in the side chain, and more preferably a resin having a carboxylic acid group in the side chain. 50% or more of the acid groups are preferably neutralized in the form of a salt, and more preferably 50% or more of the acid groups are neutralized in the form of an ammonium salt. Absorbent resins having acid groups in the side chains are preferred because electrostatic repulsion between acid groups occurs during liquid absorption and the absorption rate is increased. It is preferable that the acid group is neutralized because the liquid is absorbed into the absorbent resin by osmotic pressure. When neutralized in the form of an ammonium salt, the ammonium salt is preferable because of its high affinity for water and an increased amount of absorption.

  Examples of the absorbent resin include a polyacrylic acid partially neutralized crosslinked product (see, for example, JP-A-55-84304) and a hydrolyzate of starch-acrylonitrile graft polymer (see, for example, JP-B-49-43395). ), Neutralized starch-acrylic acid graft polymer (see, for example, JP-A No. 51-125468), saponified vinyl acetate-acrylic acid ester copolymer (see, for example, JP-A-52-14689) There are many known hydrolysates of acrylonitrile copolymer or acrylamide copolymer (for example, see JP-B-53-15959), polyglutamate (for example, see JP-A-2003-192794), and the like.

  From the viewpoint of absorption performance, cost, and the like, polyacrylate copolymers and polyacrylic acid partially neutralized crosslinked products that are usually used for hygiene materials are preferred.

  Below, the polyacrylic acid crosslinked body and its manufacturing method are demonstrated as a preferable example of the absorptive resin to be used.

  In the crosslinked polyacrylic acid, 50 mol% or more of the repeating units in the polymer molecular chain are preferably carboxyl group-containing units. More preferably, it is 80 mol% or more, More preferably, it is 90 mol% or more. If the carboxyl group-containing unit among the repeating units is 50 mol% or less, a decrease in absorption performance is observed, which is not preferable.

  The carboxyl group in the polymer molecular chain is preferably partially neutralized, and examples of the salt include alkali metals such as sodium, potassium and lithium, and nitrogen-containing basic substances such as ammonia. 50% or more of the carboxyl groups are preferably neutralized, and more preferably 70% or more are neutralized. As a kind of salt, it is preferable to be partially neutralized with at least one kind including ammonia, and most preferably partially neutralized with ammonia alone. From the viewpoint of absorption performance, 50 mol% or more of the carboxyl group neutralized salts in the polymer molecular chain are preferably ammonium salts, more preferably 70 mol% or more, still more preferably 90 mol% or more, and most preferably all ammonium salts. Neutralized with A high proportion of the ammonium salt is preferable in terms of absorption capacity and adhesion to the substrate. In addition, the ratio of the ammonium salt in an absorptive resin can be calculated by calculating | requiring the total amount of nitrogen atoms in an absorptive resin. The total amount of nitrogen atoms in the absorbent resin can be determined by the Kjeldahl method.

  As monomers constituting the absorbent resin, (meth) acrylic acid, ethacrylic acid, itaconic acid, maleic acid, crotonic acid, fumaric acid, sorbic acid, cinnamic acid, their anhydrides, unsaturated carboxylic acid Although the neutralized salt of a monomer is mentioned, Preferably the neutralized salt of (meth) acrylic acid is used. The type of the neutralized salt is preferably an alkali metal salt such as lithium, sodium or potassium, or a nitrogen-containing basic substance such as ammonia. Other monomers may be copolymerized, and unsaturated monomers that may be copolymerized include (meth) acrylic acid, ethacrylic acid, itaconic acid, maleic acid, crotonic acid, sorbic acid, cinnamic acid, Their anhydrides, vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, vinyl toluene sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, 2- (meth) acryloylethane sulfonic acid, 2- ( Anionic unsaturated monomers such as (meth) acryloylpropane sulfonic acid, 2-hydroxylethyl acryloyl phosphate, 2-hydroxylethyl methacryloyl phosphate, phenyl-2-acryloyloxyethyl phosphate, vinyl phosphate, and salts thereof, acrylamide , Methacrylamide, N-eth (Meth) acrylamide, Nn-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate Nonionic hydrophilic group-containing unsaturated monomers such as methoxypolyethylene glycol (meth) acrylate, polyethylene glycol mono (meth) acrylate, N-vinylpyrrolidone, N-acryloylpiperidine, N-acryloylpyrrolidine, and methyl You may use the hydrophilic monomer which forms an absorptive resin by hydrolysis of the functional group after superposition | polymerization like (meth) acrylate, ethyl (meth) acrylate, vinyl acetate. Examples of the hydrophobic monomer that can be used in combination include styrene, vinyl chloride, butadiene, isobutene, ethylene, propylene, stearyl (meth) acrylate, lauryl (meth) acrylate, and the like. More than one type can be added.

  A crosslinking agent may be allowed to coexist in the monomer. As the crosslinking agent, a method in which a condensation type crosslinking agent is used to react with a functional group in the resin to crosslink, a polymerizable crosslinking agent is used. A method of crosslinking by copolymerizing with an unsaturated monomer, a method of crosslinking by irradiating the resin with an electron beam or radiation, etc. are raised, preferably a method using condensation type crosslinking, more preferably a functional group of the resin. This is a method in which a polymerizable crosslinking agent and an unsaturated monomer are copolymerized in the presence of a condensation type crosslinking agent that reacts with.

  As the condensation type crosslinking agent, ethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, (poly) glycerin polyglycidyl ether, diglycerin polyglycidyl ether, glycidyl ether compounds such as propylene glycol diglycidyl ether; (poly) glycerin, (Poly) ethylene glycol, propylene glycol, 1,3-propanediol, polyoxyethylene glycol, triethylene glycol, tetraethylene glycol, diethanolamine, triethanolamine and other polyhydric alcohols; ethylenediamine, diethylenediamine, polyethyleneimine, hexa Multivalent amines such as methylenediamine; Multivalent ions such as zinc, calcium, magnesium, and aluminum Is, these crosslinking agents may be used two or more.

  Examples of unsaturated monomer polymerizable crosslinking agents include diethylene glycol diacrylate, N, N′-methylenebisacrylamide, polyethylene glycol diacrylate, polypropylene glycol diacrylate, trimethylolpropane diallyl ether, allyl glycidyl ether, and pentaerythritol triallyl. Examples include ether, pentaerythritol diacrylate monostearate, bisphenol diacrylate, isocyanuric acid diacrylate, tetraallyloxyethane, diallyloxyacetate, and the like. Two or more of these crosslinking agents may be used.

  The solvent of the monomer solution is not particularly limited as long as it has excellent solubility. Particularly preferred is water alone, but hydrophilic solvents such as ethanol, methanol, acetone and the like may be used alone or in combination. If necessary, salts such as sodium chloride, basic compounds such as ammonia for pH control, and a suspending agent may be added in the case of reverse phase suspension polymerization.

  The polymerization method of the unsaturated monomer is not particularly limited, and generally used methods such as aqueous solution polymerization, reverse phase suspension polymerization, reverse phase emulsion polymerization, spray polymerization, and belt polymerization can be applied. The polymerization initiation method is not particularly limited, and polymerization by a radical polymerization initiator, polymerization by irradiation with radiation, an electron beam, or ultraviolet polymerization by a photosensitizer can be performed. Examples of the initiator used for such radical polymerization include persulfates such as potassium persulfate, ammonium persulfate and sodium persulfate; hydrogen peroxide; organics such as cumene hydroperoxide, t-butyl hydroperoxide and peracetic acid. Examples thereof include known initiators such as oxide oxides. When an oxidizing radical polymerization initiator is used, a reducing agent such as L-ascorbic acid or Rongalite may be used in combination.

  It is preferable to perform a deoxygenation operation in the monomer solution in advance before the start of polymerization. As a specific method, there is a method of removing dissolved oxygen by bubbling with an inert gas for a sufficient time. In addition, it is preferable that the atmosphere in the reactor is replaced with an inert gas such as nitrogen or helium. The inside of the reactor may be any of reduced pressure, normal pressure, and increased pressure. The polymerization start temperature is usually preferably in the range of 0 to 100 ° C. More preferably, it is the range of 20-70 degreeC. If the starting temperature is too high, heat polymerization occurs before the initiator is added, which is not preferable. On the other hand, if the starting temperature is too low, it takes too much time to start the reaction, which is not preferable. The temperature in the reactor during the reaction may depend on the outcome, and the temperature may be controlled by cooling or heating from the outside. The temperature rising rate and the maximum temperature during the polymerization are not particularly problematic, and there is no problem even if the maximum temperature exceeds 100 ° C. The maximum temperature during polymerization is usually 20 to 140 ° C, preferably 40 to 120 ° C. The concentration of the monomer solution is preferably 10 to 80%, more preferably 30 to 70%. If the concentration is too high, the reaction tends to run away, which is not preferable. If the concentration is too low, it takes too much time for the reaction, and the subsequent drying process is also burdened, which is not preferable. The polymerization time is preferably set in the vicinity of the time when heat generation from the reaction solution stops. Since there are heating processes such as a drying process and a post-crosslinking process as post-processes after the polymerization, the polymerization may be terminated before the heat generation from the reaction solution stops. Further, after completion of heat generation, it may be heated and kept for several hours.

  When the polymer obtained after the polymerization is a hydrogel, drying is performed. Although this drying method is not particularly limited, for example, azeotropic dehydration, fluidized drying, hot air drying, vacuum drying and the like are preferably used, and hot air drying and vacuum drying are particularly preferable. The moisture content is 30% by weight or less, preferably 10% by weight or less. Drying may be performed with any form of hydrogel, but it is preferable to dry after coarsely crushing to increase the surface area. The drying temperature is preferably in the range of 70 to 180 ° C, more preferably 100 to 140 ° C.

  The particle size of the polymer after drying is adjusted by operations such as pulverization and classification as required. In the polyacrylic acid crosslinked body, the polymer after drying controlled to a predetermined particle diameter may be heated. In the heat treatment, it is preferable that a compound having two or more functional groups capable of reacting with the carboxyl group to be used coexists. When such a compound coexists, the influence of blocking between particles is reduced, which is advantageous in terms of absorption rate. A compound having two or more functional groups capable of reacting with a carboxyl group may be added before polymerization, may be added during aging after polymerization, or when particles are aggregated. It may be added to the agglomeration step or may be added to the dried particles before the heat treatment. When put before heat processing, it is preferable to dissolve in hydrophilic solvents, such as water, alcohols, and ethers, and to spread on the surface. Although the temperature of heat processing is not specifically limited, Preferably it is the range of 120-250 degreeC. More preferably, it is 150-240 degreeC, More preferably, it is 170-230 degreeC. The heat treatment may be performed continuously in the same apparatus after completion of drying, or may be a step independent of the drying step. When the heating process is included in the manufacturing process of the absorbent composite, it is preferable to perform heating at the time of manufacturing the composite.

  For the above heat treatment, a normal dryer or a heating furnace can be used. For example, a groove type mixer / dryer, a rotary dryer, a disk dryer, a fluidized bed dryer, an airflow dryer, an infrared dryer, etc. Can be mentioned.

  Absorbent resin, deodorant, fragrance, various inorganic powders, foaming agent, pigment, dye, antibacterial agent, hydrophilic short fiber, plasticizer, adhesive, surfactant, fertilizer, oxidizing agent, reducing as required Agents, chelating agents, antioxidants, heat stabilizers, ultraviolet absorbers, light stabilizers, water, salts and the like may be added.

  Examples of the inorganic powder include fine particles of various inorganic compounds inert to water and hydrophilic organic solvents, fine particles of clay mineral, and the like. In particular, the inorganic powder preferably has an appropriate affinity for water and is insoluble or hardly soluble in water, such as metal oxides such as silicon dioxide and titanium oxide, natural zeolite, synthetic zeolite, etc. Silicic acid (salt), kaolin, talc, clay, bentonite and the like.

The usage-amount of the said inorganic powder is 0.001-10 weight part normally with respect to 100 weight part of absorbent resins, Preferably it is 0.01-5 weight part. There is no restriction | limiting in particular in the mixing method of an absorptive resin and inorganic powder, and it carries out by the dry blend method, the wet mixing method, etc.
(Particle shape)
The shape of the absorbent resin particles may be any shape, and examples include spherical particles, irregular particles, agglomerated particles, short fibers, long fibers, and sheets that are widely used in absorbent compositions. It is done. It may be in an irregularly crushed shape, a particle aggregate shape (for example, a bunch of cocoons), a scale shape, or a granular shape. Particle aggregation, spherical particle, and irregular particle shape are preferred.
(Salt concentration near the surface)
Next, the absorbent resin particles before adhering to the substrate preferably have a salt concentration in the vicinity of the surface (hereinafter referred to as “surface salt concentration”) of 50 mol% or more, more preferably 60 mol%. More preferably, it is 70 mol%, and most preferably 80 mol% or more. If the surface salt concentration before adhering onto the substrate is too low, the adhesion of the particles is reduced.

  The surface salt concentration of the absorbent resin particles in the absorbent composite after adhesion to the final substrate is not particularly limited, but is preferably 90 mol% or less, more preferably 80 mol% or less, and even more preferably 60 mol%. It is as follows. A lower surface salt concentration of the absorbent resin particles in the final composite is advantageous because it is less likely to cause stickiness even when exposed to moist air. Further, even when the particles are brought into contact with each other during swelling after absorption of the aqueous solution, it is very preferable because the aqueous solution diffusibility in the absorbent composite can be maintained high. In order to maintain a high absorption ratio, it is necessary to increase the salt concentration of the entire absorbent resin particle, but in order to maintain a high liquid diffusibility in the composite, the salt concentration in the vicinity of the surface may be decreased. desired. That is, it is preferable to increase only the surface salt concentration and increase the internal salt concentration. Specifically, it is preferable to lower the surface salt concentration by 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 mol% or more, compared to the salt concentration at the center of the resin. The vicinity of the surface means an outer layer portion having a thickness of about 1 μm in the depth direction from the surface. The adjustment of the salt concentration in the vicinity of the surface is preferable because it can be performed at the same time as the adhesion on the base material, so that the adhesive force and the absorbing power can be balanced at a high level.

  Absorbent resin usually consists of acid groups such as carboxyl groups and sulfonic acid groups and neutralized salts thereof, basic groups such as amino groups and neutralized salts thereof, etc. What is the surface salt concentration of absorbent resin particles? The ratio of the neutralized group of the surface part of an absorptive resin particle is represented. In the present invention, the salt concentration in the vicinity of the surface of the resin particle is determined by measuring by a microscopic ATR method which is one of infrared absorption analysis methods. In this ATR method, structural information having a surface layer depth of 1 μm is usually obtained, so that the neutralization rate of the resin particle surface can be directly measured by the microscopic ATR method. The internal portion is measured by a micro ATR method after cleaving the resin by using an ultramicrotome (ULTRACUT N manufactured by Reichert) to expose the central portion. As a measuring device, FTS-575 manufactured by Bio-Rad is used.

Hereinafter, a polyacrylic acid-based absorbent resin will be described as an example. As an indicator for defining the composition ratio of carboxylic acid and carboxylate, 1,695 cm ^-1 (carboxylate νC = 0 Baseline 1774~1616cm ^-1) and 1558cm ^{-1 -} peak of (carboxylate νCOO baseline 1616~1500cm ^-1) An area ratio (1695/1558 cm ⁻¹ ) was calculated, and separately prepared by measuring and preparing 10 mol%, 30 mol%, 50 mol%, 70 mol%, 90 mol%, 100 mol% ammonia-neutralized partially crosslinked polyacrylic acid as a standard sample The composition ratio is obtained from the line.

(Surface strength)
Next, the absorbent resin particles before adhering onto the substrate preferably have a surface strength of 0.1 to 5.5N, more preferably 0.1 to 5N, and even more preferably 0.2 to 4N. Most preferably, it is 0.2-3N. The surface strength is a parameter representing the ease of deformation of the particle surface. When absorbent resin particles that have been swollen after absorbing at a specific magnification are put in a container and a load is applied, the gel moves and deforms so as to fill the gaps in the absorbent resin particles that have been filled in the container. I will do it. Since the surface strength is an elastic modulus when the absorbed resin particles that have been absorbed reach an actual volume, it means the magnitude of interaction between gel particles and the ease of surface deformation. A high surface strength indicates that the absorbent resin particles are not easily deformed. That it is hard to deform | transform will mean that an absorbent resin particle will absorb and swell, whereas it will have a strong negative force, and will thereby reduce the absorption capacity. Further, if the surface is not easily deformed, the adhesion surface between the resin and the substrate becomes small, and the particles are likely to be detached from the composite, which is not preferable. The surface strength of the absorbent resin particles of the present invention is determined as follows.

Equipment: Shimadzu Autograph AG-1
Sample: 0.10 g of absorptive resin particles were precisely weighed and uniformly placed in the bottom of a cylindrical container having an inner diameter of 20.5 mm and a height of 50 mm, with a nylon sheet having a pore diameter of 75 μm attached to the bottom surface. A 50φ petri dish was prepared, 0.90 g of physiological saline was added, and the cylindrical container containing the absorbent resin particles was left to stand for absorption swelling for 1 hour.
Measurement: A 1 kN load cell was used, and a cylindrical shaft having a diameter of 19.7 mm was attached. The measurement range is set to 0.2 kN, and is set so that the load cell is lowered at a constant speed of 0.6 mm / min according to the height at which no load is applied to the load cell. The pressure applied to the load cell was recorded over time. Here, the surface strength represents the load (N) when the actual volume is reached. The actual volume of the absorbent resin particles was calculated using the specific gravity of physiological saline 1.010 g / cm ³ and the specific gravity of the absorbent resin particles.

(Absorption capacity)
Next, in the present invention, the average absorption rate of the absorbent resin particles in the composite needs to be 50 g / g or more. More preferably, it is 60 g / g or more, and 70 g / g or more is still more preferable.
The absorbent resin particles in the present invention preferably have an absorption capacity under load of the absorbent resin at 0.8 psi of preferably 20 g / g or more, more preferably 25 g / g or more, and 30 g / g or more most. Preferably. A higher absorption ratio of the absorbent resin particles is preferable because the amount of the absorbent resin particles to be used can be reduced.

  In the present invention, the absorption capacity of the absorbent resin particles refers to an amount capable of freely swelling and absorbing 0.9% physiological saline in a state where no load is applied to the absorbent resin particles. The absorption capacity of the absorbent resin particles is measured by the following method.

Absorbent resin particles 0.05 g are uniformly placed in a non-woven tea bag bag (60 × 40 mm) and immersed in 0.9% physiological saline at 23 ° C. After 180 minutes, the bag is taken out, the corner of the tea bag is fixed, suspended for 10 minutes in an oblique state, drained, and then weighed. The same operation is performed without using the absorbent resin particles, and the weight is measured to obtain a blank. The absorption rate is calculated according to (Equation 4). The measurement is performed three times, and the average value is taken as the absorption magnification.
(Formula 4)
Absorption capacity of absorbent resin particles (g / g) = {(weight of tea bag after absorption) − (weight of blank tea bag after absorption) − (weight of absorbent resin particles)} / (absorbent resin) Particle weight)

The absorption capacity under pressure of the absorbent resin particles of the present invention is measured by the following method. Put 0.02 g of absorbent resin particles in an acrylic resin cylinder with an inner diameter of 25 mm, a height of 30 mm, and a 250 mesh nylon nonwoven fabric at the bottom, and put a smoothly moving cylinder inside the cylinder to make a measuring device and measure the weight. To do. A load of 278.33 g corresponding to 0.8 psi is placed on the upper part of the cylinder of the measuring device to obtain a load, which is placed in a petri dish with an inner diameter of 120 mm containing 60 g of 0.9% physiological saline. After 60 minutes, it is taken out and left on a Kim towel for 3 seconds to drain water, the weight of the device after removing the load is measured, and the absorption capacity under pressure is calculated according to (Equation 5).
(Formula 5)
Absorption capacity under load of absorbent resin particles (g / g) = (weight of device after absorption (g) −weight of device before absorption (g)) / (weight of absorbent resin particles)

Absorptive composite with tensile breaking strength of 0.6 (N / 20 mm) or more composed of absorbent resin particles having an absorption ratio of 70 g / g or more and an absorption capacity of 20 g / g or more under a 0.8 psi load Is preferable for sanitary materials such as paper diapers because it exhibits excellent absorption characteristics under pressure and without pressure. At this time, the absorbent composite is preferably composed of absorbent resin particles and paper and / or cloth, and the absorbent resin particles may be separated so that the absorbent resin particles do not block each other. More preferably, 90% or more of the absorbent resin particles are most preferably adhered to paper and / or cloth. Absorbent resin particles having a non-pressurized absorption rate of 70 g / g or more and an absorption rate of 20 g / g or more under a 0.8 psi load can be obtained by the following method. By polymerizing unsaturated carboxylic acid monomers in which 70% or more is acrylic acid and 50% or more of the carboxyl groups are neutralized as ammonium salts, and a total of 70% or more is neutralized. Obtainable. In this case, a monomer containing 0.0005 to 0.1 mol% of a compound having two or more unsaturated groups in one molecule serving as a crosslinking agent is used. You may use 0.1-3 weight part of compounds which have two or more functional groups which can react a carboxyl group before superposition | polymerization or in any process after superposition | polymerization. Radical polymerization is performed using a redox initiator, and 0.005 to 0.5 mol% is used as the radical polymerization initiator with respect to the amount of the unsaturated monomer. A reducing agent shall be 0.0001-1g with respect to 1 mol of monomers. If necessary, heating is performed under a heating condition that satisfies the following (Formula 6). This heating is preferably performed at the same time when the absorbent composite is produced, rather than by the absorbent resin particles alone.
(Formula 6)
Y = −1.6X + 345
Where Y is the heating time (minutes) and X is the heating temperature (° C.)
Absorbent resin particles obtained by such a method are prone to blocking, so when applying an evaluation method in which the absorptive resin particles are in close contact with each other in the past, in particular, the water absorption rate or under pressure is applied. The absorption performance is inferior. However, in the above-described measurement method in the present invention assuming the state of the resin particles in the absorbent composite, the performance of the absorbent resin particles can be exhibited. Excellent absorption capacity.

(Particle size)
Next, the weight average particle diameter of the absorbent resin particles used in the present invention is preferably 10 to 300 μm, more preferably 20 to 260 μm, still more preferably 30 to 230 μm, and most preferably 40 to 200 μm. If the average particle size is too small, it is not preferable in terms of water absorption performance. On the other hand, if it is too large, the absorption rate is inferior and the feel of the particles becomes conspicuous.

  In the present invention, the particle size of the absorbent resin particles is 32 μm, 38 μm, 45 μm, 53 μm, 63 μm, 75 μm, 90 μm, 106 μm, 125 μm, 150 μm, 180 μm, 212 μm, 250 μm, 300 μm, 355 μm, 425 μm, 500 μm. , 600 μm, 710 μm, 850 μm, 1000 μm, 1180 μm, 1400 μm, 1700 μm and 2500 μm. In the present invention, the particle diameter is an intermediate value between the opening of a sieve that can pass and the opening of a sieve that cannot pass. In addition, about what passed the 32 micrometers sieve, it is set to 16 micrometers, and about what remained on the 2500 micrometers sieve, it shall be 2700 micrometers. By this operation, 16 μm, 35 μm, 41.5 μm, 49 μm, 58 μm, 69 μm, 82.5 μm, 98 μm, 115.5 μm, 137.5 μm, 165 μm, 196 μm, 231 μm, 275 μm, 327.5 μm, 390 μm, 462.5 μm, The particle sizes are classified into 550 μm, 655 μm, 780 μm, 925 μm, 1090 μm, 1290 μm, 1550 μm, 1850 μm, 2100 μm and 2700 μm.

  Further, the absorbent resin particles in the composite of the present invention are preferably 50% or less, more preferably 30% or less, and still more preferably 10% of the particles that cannot pass through a sieve having an opening of 500 μm. It is as follows. Particles that cannot pass through a 300 μm sieve are preferably 50% or less, more preferably 30% or less, and even more preferably 10% or less. When a large amount of particles that are too large are present, the tactile sensation of the particles becomes noticeable in the composite, which is not preferable.

6). About Base Material In the present invention, the base material refers to a material that can maintain a sheet shape.
(Material)
In the present invention, the substrate is in the form of a sheet and may be any material as long as it is hydrophilic, but is preferably paper and / or cloth. In the present invention, the hydrophilic substrate means a substrate having an absorption rate of 0.2 mg / second or more described later. Paper refers to paper in a broad sense defined by JISP0001, and cloth is a generic term for sheet-like fiber products defined by JISL0206. The cloth is classified into a woven fabric, a knitted fabric, a braided article, a lace, a net, and a non-woven fabric according to the means for forming the sheet. The fabric used in the present invention is preferably a woven fabric, a knitted fabric, or a non-woven fabric, and more preferably a non-woven fabric. Paper and / or cloth is preferred because of its excellent shape stability. Nonwoven fabric is defined by JIS L 0222.

  The raw material for the substrate is not limited, and a plurality of combinations of substrates may be used. The base fiber includes both natural fiber and synthetic fiber, and a combination of a plurality of fibers may be used. The length of the fiber may be short fiber or long fiber. A treatment may be applied for strengthening or imparting hydrophilicity. Long fibers are preferred when diffusibility is desired. Short fibers are preferred from the viewpoint of capture power. In particular, since pulp has an excellent capturing power, a base material in which the pulp is cloth-like is preferable.

  Of the hydrophilic substrates, cellulose-based substrates are particularly preferable. The cellulosic substrate in the present invention refers to a fabric and / or paper containing cellulose as a main raw material, and among these, a fabric and / or paper composed of cellulosic fibers, particularly a cellulose nonwoven fabric is preferred. Cellulose may be derivatized by treatment such as esterification or etherification. Moreover, what was mixed with the other fiber may be used. Examples of cellulose include natural fibers such as cotton and hemp, and regenerated fibers such as rayon, polynosic, lyocell, and cupra. As the fiber, a regenerated fiber is preferable, and a fiber obtained by regenerating a cotton seed which is an annual grass is more preferable.

(shape)
The shape of the substrate is not particularly limited, and the thickness per sheet is preferably 0.001 mm or more, more preferably 0.01 mm or more, further preferably 0.05 mm or more, and most preferably 0.1 mm. That's it. The basis weight per one substrate is preferably from 28~100g / ^{m 2,} more preferably from 35~80g / ^{m 2,} and still more preferably from 40 to 60 g / ^{m 2.} Those that are too thin are not preferred in terms of strength. The thicker the thickness, the larger the space for holding the resin, the less likely the contact between the resins occurs, and the greater the contact between the resin and the fiber, which is preferable from the viewpoint of absorption speed. In addition, the surface of the base material is more preferable than the smooth surface since the number of contact points between the resin and the base fiber increases as the number of irregularities increases. About too light thing, since the fiber quantity used as a water flow path with respect to an absorptive resin runs short, it is not preferable. When the resin is too heavy, the ratio of the fibers to the resin becomes too high, and if the resin cannot absorb the liquid in the fibers, it may cause reversal, which is not preferable.

  In the case of using a plurality of base materials, it is preferable that at least one base material satisfies the aforementioned basis weight. When there are a plurality of resin layers, it is preferable that at least one base material satisfies the basis weight described above for each resin layer.

  There may be any number of base materials and resin layers, but when the ratio between the total weight of the absorbent resin and the total weight of the base material is within a certain range, the balance between the absorption speed and the reversibility is particularly good. The ratio of the absorbent resin to the substrate is preferably 35 to 300%, more preferably 42 to 250%, still more preferably 50 to 200%, and 60 to 140%. Most preferred.

(Tensile strength at break)
In the present invention, the tensile breaking strength after physiological saline is preferably 0.6 N / 20 mm or more, more preferably 0.6 to 5000 N / 20 mm, and further preferably 0.7 to 500 N / 20 mm. Yes, more preferably 0.85 to 100 N / 20 mm, and most preferably 1 to 100 N / 20 mm.

  In the present invention, the direction in which the intensity is maximum is the vertical direction, and the direction perpendicular to the vertical direction is the horizontal direction, but in the horizontal direction (that is, in both the vertical direction and the horizontal direction) preferable.

  In the present invention, the tensile strength at break after absorption of physiological saline by the substrate represents the tensile strength at break after absorption of physiological saline by the substrate. In sanitary materials, they may be used as they are without being replaced immediately after liquid absorption. Moreover, after liquid absorption, liquid absorption over several times may be calculated | required. If the use is continued after absorbing once, a load is applied in a state where moisture exists in the absorber. If the substrate breaks due to the load, the liquid permeability and liquid diffusibility are lowered, and the performance of the absorber is deteriorated. It can be said that a base material that maintains a high strength even after absorption of physiological saline is preferable in terms of durability of the absorbent body. Further, in the case of a process in which the base material contains water at the time of production, there may be a problem if the strength when containing water is low, and it can be said that the higher the strength of the base material is, the more preferable. However, even if the strength is too high, there is virtually no difference in performance.

The tensile strength at break after absorption of physiological saline is determined as follows.
Sample: 15 cm × 2 cm rectangular base material (preparing several types by changing direction)
Equipment: Tensile tester (Shimadzu autograph)
Method: 700 g of 0.9% saline is taken in a 1 L beaker and the substrate is immersed for 10 minutes. The substrate is pulled up, left on a Kim towel for 1 minute, and a portion of 2.5 cm is set from both ends so that the distance is 10 cm, and the substrate is pulled until it breaks at a speed of 10 mm / min. The force at this time is recorded, and the maximum value is the strength N / 20 mm. If there is a direction, change the direction and measure several points.

(Absorption capacity)
In the present invention, the absorption rate of the base material is a value measured by measuring how many times the base material absorbs 0.9% physiological saline in 60 minutes, and is specifically as follows. Measure by method.
The substrate is cut into a circle having a diameter of 59.5 mm, and the weight is recorded. Then, a wire is passed through the circumferential portion at a distance of 1 cm. 500 g or more of 23 ° C. physiological saline is prepared in a 1 L beaker, and the substrate is dipped in the physiological saline together with the wire. After 60 minutes, the substrate together with the wire is taken out from the physiological saline and suspended for 10 minutes so that the substrate does not come into contact with the other. Ten minutes later, the wire is removed and the total weight of the water-containing base material and the attached water is measured.

The absorption capacity of the base material is shown by the formula (7).
(Formula 7)
Absorption capacity of substrate (g / g) = weight after absorption (g) / weight before absorption (g)
In the present invention, the absorption capacity of the substrate is preferably from 6 g / g to 200 g / g, more preferably from 8 g / g to 100 g / g, still more preferably from 10 g / g to 50 g / g. Most preferably, it is 12 g / g or more and 30 g / g.

  In the absorbent composite, the fiber absorbs faster than the absorbent resin particles, so that the substrate absorbs in the early stage of absorption and the absorbent resin particles absorb in the later stage. A higher absorption rate of the substrate is preferable because an initial liquid absorption rate is increased. Usually, the absorption of the substrate is due to capillary action, and when a load is applied, the liquid may return or may cause stuffiness during use. Therefore, when the resin particles are bonded in the form of taking in the fibers of the base material, the absorbent resin absorbs the liquid in the form of taking the liquid from the base material. For this reason, it is unlikely that the liquid will return due to the load or stuffy during use.

(Absorption rate)
As an index representing the hydrophilicity and liquid permeability of the substrate, there is an absorption rate.
In the present invention, the absorption rate of the substrate represents a rate at which the substrate having a width of 2 cm absorbs 0.9% physiological saline in the vertical direction.

  The absorption rate of the substrate is preferably 0.2 mg / second or more and 100 mg / second or less, more preferably 0.3 mg / second or more and 50 mg / second or less, further preferably 0.40 mg / second or more and 30 mg / second or less, Most preferably, it is 0.5 mg / second or more and 10 mg / second or less.

Specifically, the absorption rate of the substrate is measured as follows.
Sample: 10 cm × 2 cm rectangular substrate
For those with vertical and horizontal directions, change the direction and prepare two or more points: Electronic balance, Petri dish with a diameter of 90 mm Method: Place the petri dish on the electronic balance and suspend the substrate vertically from 10 cm above the petri dish. The petri dish is taken from the electronic balance, and 60 g of 0.9% physiological saline is weighed with another balance. Hold the lower part of the base material by hand and place the petri dish again on the electronic balance so as not to touch the physiological saline, and set the value of the balance to 0 point. The substrate is gently soaked in physiological saline, and the value of the electronic balance is recorded over time. The time (second) and the absolute value (mg) of the value of the electronic balance are plotted on a graph, and the slope (mg / second) between 120 seconds and 240 seconds is taken as the absorption rate. If the substrate has a direction, change the direction, measure several points, and take the fastest value as the absorption rate.

It can be said that it is preferable that the substrate has directions with different absorption rates. When a direction exists in the substrate, the liquid permeability in a specific direction is excellent and the liquid is easily diffused in the specific direction, so that the balance of absorption in the absorber can be controlled.
(Longitudinal and transverse tensile elongation at break, strength ratio)
When a direction exists in the base material, strength and elongation change in each direction. As described above, in the present invention, the direction in which the intensity is maximum is the vertical direction, and the direction perpendicular thereto is the horizontal direction.

  The ratio between the tensile strength at break in the machine direction and the transverse direction is preferably 1.2: 1 or more, more preferably 1.5: 1 or more, still more preferably 2: 1 or more, and 10: 1 or less.

  The ratio of the tensile elongation at break in the machine direction and the transverse direction is preferably 1: 1.2 or more, more preferably 1: 1.5 or more, still more preferably 1: 2 or more, and 1:10 or less. The elongation and strength of the base material can be determined by conducting a tensile test in a dry state without being immersed in physiological saline in the same manner as the strength of the base material after absorption of physiological saline. The tensile test is performed until the base material breaks, and the force at the maximum strength is defined as the strength of the base material, and the distance stretched at that time is defined as the elongation.

(Contact angle)
The base material in the present invention is preferably a nonwoven fabric having a contact angle of 130 degrees or less.
The contact angle in the present invention is defined as an angle formed after 10 seconds after contacting a substrate with a 44% ammonium polyacrylate aqueous solution having a viscosity of 74 cp at room temperature. The measurement is performed using a contact angle meter (CA-X150 type) manufactured by FACE (Kyowa Interface Science Co., Ltd.). The liquid is a Wako Pure Chemicals 44% ammonium polyacrylate aqueous solution (70 to 110 cp), which is used after adjusting the viscosity with water. Viscosity is measured using a rotating disk viscometer.

  The contact angle is preferably 130 degrees or less, more preferably 120 degrees or less, still more preferably 110 degrees or less, and most preferably 100 degrees or less. The smaller the contact angle, the higher the affinity between the base material and water and the base material and the absorbent resin, which is preferable in terms of absorbency and adhesiveness.

7). Production method of absorbent composite The absorbent composite in the present invention is preferably produced by a production method including a step of adhering the absorbent resin particles to the substrate using the absorbent resin particles and the substrate as raw materials.
The adhesion method is not particularly limited, and an adhesion method that satisfies the above-described conditions may be performed. Examples of the bonding method include a method in which an absorbent resin is entangled in a base material and a method in which an adhesive is used. A preferable method is that 10 to 3000 parts by weight of water is added to 100 parts by weight of the absorbent resin. In this method, the absorbent resin and / or the base material is absorbed, and then dehydrated in a state where the absorbent resin and the base material are in contact with each other. The amount of water is preferably 20 to 2000 parts by weight and more preferably 50 to 1000 parts by weight with respect to 100 parts by weight of the absorbent resin particles. Adhesion by this method is preferable because it is not necessary to use an adhesive as an impurity. Moreover, since adhesion | attachment is carried out by this method, since a part of fiber is taken in in an absorptive resin, it is preferable at the point of the absorption rate or an absorption magnification. The larger the amount of water, the higher the adhesiveness and the better. However, too much water is inefficient because it takes too long to dry.

  The water can be absorbed by either the base material or the absorbent resin, but it is preferable that the water is absorbed by the base material. The water content of the base material when the base material is water-containing and then brought into contact with the absorbent resin particles is preferably in the range of 50 to 500% by weight. In order to increase the adhesiveness between the absorbent resin particles and the substrate, it is preferable that the water content is high, but if it is too high, it takes time to dry. Of course, if the water content is too low, there is a problem that the adhesion between the substrate and the resin is lowered. Therefore, the range of a preferable moisture content is 50 to 200% by weight, and more preferably 80 to 150% by weight. When using a plurality of base materials, it is preferable to hydrate all the base materials.

  As a water-containing method for bonding, a method in which water for bonding is included in the absorbent resin particles may be employed, but in that case, the absorbent resin tends to stick to parts other than the base material. The absorbent resin particles before contact are preferably dried to such an extent that they do not adhere to other substances or adhere to each other. In this case, the water content of the absorbent resin particles is preferably 1 to 50% by weight. More preferably, it is 5 to 30% by weight.

  Examples of the contact method include a method of spraying absorbent resin particles from above on a substrate, and a method of spraying the absorbent resin together with air. A method capable of arranging the absorbent resin particles so that the overlap between the absorbent resin particles is smaller is preferable from the viewpoint of adhesiveness. Furthermore, it is preferable that the method increases the entanglement between the base fiber and the resin because the absorption rate is improved. As a method of increasing the entanglement between the base fiber and the resin, there are a method of raising the base material and a method of applying a press to improve the adhesion between the base material and the resin after contact. When pressing is performed, the resin may adhere to a portion where the press machine and the resin are in contact with each other. Therefore, it is preferable that the contact portion is made of a material that does not easily adhere to the resin. The material that does not easily adhere is a hydrophobic material, and examples thereof include polyolefins and Teflon (registered trademark), and Teflon (registered trademark) is particularly preferable. A Teflon (registered trademark) sheet may be rubbed or coated. The most preferable method for preventing the adhesion of the resin is not to dispose the resin on the surface. In other words, one more base material than the resin layer is used, and the resin is completely sandwiched between the base materials.

  The water to be hydrated may contain impurities. Examples of the impurities include cations such as sodium ion, ammonium ion and iron ion, anions such as chlorine ion, water-soluble organic compounds such as acetone, alcohols, ethers and amines. For adjusting the pH of the absorbent resin and / or the absorbent complex, an acidic or basic one may be used. From the viewpoint of the contact property between the absorbent resin and the substrate and the absorption capacity, it is preferable to use distilled water or ion-exchanged water free from these impurities alone.

  In addition, it is a preferable method to impart a function to the absorbent composite produced by dissolving and / or dispersing a substance having a function such as deodorization in water. Examples of deodorants that can be used here include organic and inorganic deodorants. When using a deodorant insoluble in water, it is preferable to use a dispersant or a surfactant as necessary. In addition, inorganic deodorants can be dispersed in water without using a dispersant by reducing the particle size to the nano level. It is preferred to use without.

  There is no restriction | limiting in particular in the water-containing method. For example, a method of attaching to a water bath, a method of spraying water, a method of contacting with a water-containing body, a method of exposing to a humidified state and the like can be mentioned. Among these, the water spray method, which is industrially simple and easy to adjust the water content, is a preferred method. As the water spraying method, it is preferable to adopt a method in which the moisture content of the substrate such as cloth is uniform. If there is a large variation in the moisture content at each location on the base material, the amount of water absorbed by the absorbent resin particles will vary depending on the location after contacting the absorbent resin and before the dehydration drying process. The accompanying foaming behavior is different, and the resin particle size in the absorbent composite after drying becomes inhomogeneous. An absorptive complex in which resin particles having a non-uniform particle size are arranged may deteriorate the texture.

  Any method of dehydration may be used. Examples of the method include drying by heating, a method of spraying dry air or nitrogen, vacuum drying, freeze drying, azeotropic dehydration, fluidized drying, and microwave, and drying by heating is preferable. The heating condition is preferably 70 to 350 ° C. for 1 second to 1000 seconds, more preferably 100 to 340 ° C. for 1 second to 1000 seconds, and still more preferably 120 to 330 ° C. for 1 second to 1000 seconds. Most preferably, it is 150 to 300 ° C. for 1 to 1000 seconds. The higher the temperature, the shorter the drying time is. However, when the heating is performed for a long time at a high temperature, the absorption performance may be lowered depending on the type of the resin. Simultaneously with the drying, a surface treatment such as surface crosslinking may be performed. The dehydration may be performed at any time until the final product is obtained, but it is preferable to perform the dehydration promptly after the hydration from the viewpoint of deterioration of the absorbent resin.

  Since an absorptive complex is a sheet form and a substrate is also a sheet form, it is preferred to manufacture a roll absorptive complex using a roll substrate. That is, it is to hydrate the base material that has flowed from the base material roll, place the dried absorbent resin, dry it, and then roll it again on the roll. Considering the slipperiness when spread on a roll, it is preferable that no resin is present on the surface. That is, it can be said that a production method in which two base rolls are prepared, resin is arranged on one base, and another base is stacked and dried simultaneously is preferable. At this time, it is preferable that the base material to be stacked later is also hydrated. Moreover, it is also preferable to press after overlapping. By increasing the number of base rolls and increasing the number of devices to place the resin, the number of resin layers and bases can be increased, but considering the thickness of the product roll and the ease of drying, the number of resin layers is limited to two. Preferably, it is a single layer.

8). Absorbent composite performance (absorption capacity)
In the present invention, the absorption capacity of the absorbent complex is the amount absorbed after 3 hours when 0.9% physiological saline is freely absorbed. Specifically, a circular absorptive composite absorbent body having a diameter of 59.5 mm is prepared, and measurement is performed using a method similar to the above-described absorption capacity of the substrate. However, when desorption occurs, the absorbent resin particles are collected by filtration, left to stand on the Kimwipe for 10 seconds or more, drained, and the weight is added for calculation. When it contains absorbent resin particles that are not bonded, it is measured after removing.

The absorption capacity of the absorbent composite is preferably 30 g / g or more, more preferably 40 g / g or more, and still more preferably 50 g / g or more.
(Absorption per area)
The amount of absorption per area is important as an index of the absorption performance of the absorbent composite. The amount of absorption per area can be calculated according to (Equation 8) from the above measurement results.
(Formula 8)
Absorbed amount per area (g / cm ² ) = ((total weight after absorption (g) −weight of absorbent composite (g)) / area of absorbent composite (cm ² )
The larger the amount of absorption per area, the more preferably 0.2 g / cm ² or more, more preferably 0.4 g / cm ² or more, and still more preferably 0.6 g / cm ² or more.
(Absorption capacity under pressure)
The absorbency against pressure of the absorbent composite of the present invention is represented by the amount absorbed after 3 hours when 0.9% physiological saline is absorbed under a load. Specifically, the measurement is performed as follows using a circular absorbent composite having a diameter of 59.5 mm.

First, the measurement apparatus will be briefly described below with reference to FIG. As shown in FIG. 1, the measuring apparatus includes a balance 1, a container 2 having a predetermined capacity placed on the balance 1, an outside air intake pipe 3, a conduit 4, a glass filter 6, and the glass filter 6. It consists of the measurement part 5 mounted on the top. The container 2 has an opening 2a at the top and an opening 2b at the side, and the outside air intake pipe 3 is fitted into the opening 2a, while the conduit 4 is attached to the opening 2b. It has been. The container 2 contains a predetermined amount of physiological saline 12. The lower end of the outside air intake pipe 3 is submerged in the physiological saline 12. The glass filter 6 is formed with a diameter of 70 mm. The container 2 and the glass filter 6 are communicated with each other by a conduit 4. Further, the glass filter 6 is adjusted to be the same height as the lower end of the outside air intake pipe 3. As shown in FIG. 2, the measurement unit 5 includes a filter paper 7, a support cylinder 9, and a weight 11. As the filter paper 7, Advantech No. 2 having a diameter of 60 mm is used. The measuring unit 5 includes a filter paper 7 and a support cylinder 9 placed in this order on a glass filter 6, and a weight 11 is placed inside the support cylinder 9. The support cylinder 9 has an inner diameter of 60 mm. The weight of the weight 11 is adjusted so that a load of 0.8 psi can be uniformly applied to the absorbent composite 13. Using the measuring apparatus having the above-described configuration, the absorption capacity under pressure of the absorbent composite was measured. The measurement method will be described below. First, predetermined preparatory operations such as putting a predetermined amount of physiological saline 12 into the container 2 and fitting the outside air suction pipe 3 into the container 2 were performed. Next, the filter paper 7 was placed on the glass filter 6. On the other hand, in parallel with these placing operations, the absorbent composite 13 was placed inside the support cylinder 9, and the weight 11 was placed on the absorbent composite 13. Next, the support cylinder 9 was placed such that the center portion thereof coincided with the center portion of the glass filter 6. And the weight W (g) of the physiological saline 12 which the absorptive complex 13 absorbed every 10 seconds from the time of placing the support cylinder 9 was measured using the balance 1. The absorption capacity under pressure of the absorbent composite is determined according to (Equation 9).
(Formula 9)
Absorption capacity of absorbent composite under pressure (g / g) = weight W (g) / weight of absorbent composite (g)
The absorption capacity under pressure of the absorbent composite under a 0.8 psi load is preferably 8 g / g or more, more preferably 11 g / g or more, and further preferably 14 g / g or more. Even under pressure, the amount of absorption per area can be determined as in the case of no pressure. The amount of absorption per area under 0.8 psi pressure is preferably 0.1 g / cm ² , more preferably 0.15 g / cm ² or more, and still more preferably 0.2 g / cm ² or more.

(Absorption after 1 minute)
Absorption after 1 minute represents the initial liquid absorption rate. In hygiene material applications such as paper diapers, since it is required to absorb body fluid instantly, a larger absorption rate after 1 minute is preferable. The absorption capacity after 1 minute is determined according to (Equation 10). Specifically, it is measured by the following method.
The absorbent composite is cut into a length of 2 cm and a width of 7 cm, and the weight is measured. Place 700 cc of physiological saline in a 1000 cc glass beaker. First, the weight of 80 cm long and 70 cm wide T-Bag is measured, water is absorbed for 1 minute in the state of only T-Bag, and then the weight is measured. By dividing this weight by the weight of T-Bag before water absorption, the absorption capacity after 1 minute of T-Bag is determined. The T-Bag of the same size is weighed and the absorbent complex is placed in the T-Bag. In order to quickly draw T-Bag from the liquid, prepare a clip with a string, attach it to the T-Bag, and immerse it quickly and carefully in the liquid so that the cloth does not break or get entangled. After 1 minute of soaking, quickly pull up with a string. Then remove the clip, centrifuge at 150 G for 3 minutes, and measure the weight. The absorption capacity after 1 minute is determined by subtracting the water absorption of T-Bag from the total weight and dividing by the weight of the absorbent composite before water absorption. The period from the lifting of the absorbent complex to the start of centrifugation is within 15 seconds.
(Formula 10)
Absorption rate after 1 minute (g-raw food / g) = (weight after centrifugation (g) -weight of T-Bag (g) * absorption rate after 1 minute of T-Bag) / weight of absorbent complex (G)
(Flexibility)
The bending and softness of the absorbent composite is performed by the bending and softness D method (heart loop method) described in JIS standard L1096. When the particle size and distribution of the particles are different between the front and the back, the values are different, but in the present invention, the harder, that is, the smaller value is regarded as the bending resistance. The bending resistance is preferably 40 mm or more, more preferably 50 mm or more, and further preferably 60 mm or more.

9. About the usage method of an absorptive complex The usage as a component of a bodily fluid absorption article is mentioned as a preferable usage method of the absorptive complex of this invention. The case where it uses as a component of a bodily fluid absorption article below is demonstrated.
(Body fluid absorbent article)
The bodily fluid absorbent article of the present invention is a bodily fluid absorbent article composed of a liquid permeable sheet, a liquid impermeable sheet, and an absorbent composite interposed therebetween, and refers to all articles having the ability to absorb bodily fluids. The body fluid to be absorbed in the present invention is not particularly limited, and examples thereof include urine, menstrual blood, breast milk, and loose stool. The shape of the article is not particularly limited, but a pad shape, a tape type, a pants type, or the like is preferably used. Specific examples include diapers, sanitary napkins, urine pads, breast milk pads, and the like.

  When the absorbent composite of the present invention is combined with a liquid-permeable sheet and a liquid-impermeable sheet, a body fluid-absorbing article that is thin and lightweight and has a high absorption rate can be constituted. In addition, since the absorber does not easily shift or move in the body fluid absorbent article during use, the body fluid can be stably absorbed.

  In the present invention, the liquid-permeable sheet is a sheet shape, and any sheet may be used as long as it allows water to pass through when the sheet is sprayed with water, but a cloth as defined in JISL0206. It is preferable that Fabrics are classified into woven fabrics, knitted fabrics, braided fabrics, laces, nets, and non-woven fabrics according to the means for forming the sheet. However, the fabrics used in the liquid-permeable sheet of the present invention are preferably woven fabrics, knitted fabrics, and non-woven fabrics. preferable. In order to eliminate the moist feeling of the part in contact with the skin and make the touch comfortable, a sheet having a low water absorption capacity made of a polyolefin such as polyethylene and polypropylene is preferable. It is preferable that it is a polyolefin system which has been subjected to hydrophilization treatment.

  In the present invention, the liquid-impervious sheet may be any sheet as long as it has a sheet shape and does not transmit water. From the viewpoint of preventing dampness, a material having good air permeability is preferable.

  In the bodily fluid absorbent article of the present invention, there is no problem as long as there is at least an absorbent composite interposed between the liquid permeable sheet and the liquid impermeable sheet, but between the liquid permeable sheet and the absorbent composite, and / or Alternatively, other members may exist between the liquid-impermeable sheet and the absorbent composite. Further, other members may exist outside the liquid-permeable sheet and the liquid-impermeable sheet.

  Examples of the member used here include fibrous materials such as pulp, particulate materials such as absorbent resin, and sheet materials such as tissue, cloth, and paper. These members may be bonded to the absorbent composite of the present invention. As an adhesion method, it may be adhered using an adhesive, or may be directly adhered to the absorbent resin particles in the absorbent composite of the present invention. In the body fluid absorbent article, in addition to the liquid permeable sheet, liquid impermeable sheet, and absorbent composite, for example, tape and rubber for fixing to the body, gathers for preventing side leakage, etc. It is preferable that there is.

  The shape of the bodily fluid absorbent article of the present invention may be a square, a perfect circle, a rectangle, an ellipse, a trapezoid, or an indefinite shape. In the case of a diaper, sanitary product, urine collection pad, etc., the shape of a rectangle or ellipse, or a shape that has a longitudinal direction and a transverse direction (direction perpendicular to the longitudinal direction) similar to that of a rectangle or ellipse. It is preferable because it can be attached together. An example of the shape of the absorbent composite having the longitudinal direction is shown in FIG. There may be a part to be used for bonding the absorbent composite to other members.

  In addition, although there may be a marginal portion where the absorbent resin does not exist in the absorbent composite, in such a case, the basis weight of the absorbent resin of the absorbent composite is in a state where the portion is omitted, It is preferable that the preferable range of conditions for the absorbent composite is satisfied.

The number of absorbent composites used may be one, or a plurality of sheets may be used. In order to construct a thin article, it is preferable to use only one sheet. It is preferable to use a plurality of sheets in order to construct an article having a higher absorbency. When using a plurality of sheets, they may be used in a stacked manner, or may be used side by side. Moreover, the thing of the completely same shape may be used, and the thing of a different shape may be used. In order to improve the absorption capacity without waste, it is preferable to use only the part where the body fluid is secreted, and when it is desired to prevent leakage, it is preferable to use the part that is likely to leak.
The state of the absorbent composite in the body fluid absorbent article is not particularly limited, and the absorbent composite sheet may be in a fully stretched state, in a wrinkled state, or in a folded state.

(Performance evaluation of body fluid absorbent articles)
・ Evaluation of returnability (rewetting property) and liquid diffusion length Place a sufficiently wide wooden board on a horizontal test bench, and on the four corners of the body fluid-absorbing article, so that the article does not wrinkle. Secure with a thumbtack in the stretched state. 20 g of physiological saline warmed to 37 ° C. is weighed and added dropwise to the central portion of the absorbent composite over 2 seconds. After 15 seconds from the start of dropping, Advantech No. 2 filter paper having a diameter of 150 mm cut into a square with a side of 10 cm is piled up to about 100 g and left at the bottom of the droplet. A 3.5 kg load is applied thereon. Remove the load 3 minutes after setting the load, measure the weight of the filter paper, and use the increased weight as the return amount. Five minutes after the start of dropping the liquid, the length of diffusion in the vertical direction is measured, and this is defined as the liquid diffusion length.
The same operation is performed except that the filter paper is placed 5 minutes after the start of dropping the droplet, and this is set as the return amount after 5 minutes.

Specific examples and comparative examples of the present invention are shown below, but the present invention is not limited to the following examples.

Production Example 1
Acrylic acid was manufactured by Wako Pure Chemical Industries, Ltd. and was used after being purified by distillation. 100 g of reagent acrylic acid was dissolved in 91.02 g of water. The aqueous solution was cooled in an ice bath, and while maintaining the liquid temperature at 30 ° C. or lower, 117.94 g of a 25% by mass ammonia aqueous solution was gradually added with stirring to obtain a 40% by mass ammonium acrylate aqueous solution (neutralization rate). 100%).
90 g of this 40 mass% ammonium acrylate aqueous solution and 0.0187 g of N, N′-methylenebisacrylamide are added to a 300 ml separable flask. The flask is bathed in a water bath so that the liquid temperature is maintained at 30 ° C. The aqueous solution was deaerated by bubbling with nitrogen gas, and the reaction system was purged with nitrogen. Next, 0.43 g of 42 mass% glycerin aqueous solution was added with a syringe, and after stirring well, 0.0917 g of 30 mass% hydrogen peroxide aqueous solution and 0.0415 g of Rongalite each dissolved in 1 g of water were added to initiate polymerization. The internal temperature starts from 30 ° C and rises to 100 ° C in 5 minutes from the start of the reaction. Then, it heats in a water bath for 3 hours so that internal temperature may be maintained at 70 degreeC. Thereafter, the gel is taken out from the Separa flask and roughly crushed, and then dried at 100 ° C. for 4 hours using an inert oven. After drying, the mixture was pulverized with a homogenizer. This is designated as absorbent resin 1. The surface strength of this resin was 0.5N. The total ammonium salt concentration was 96%, the surface salt concentration was 90%, and the central salt concentration was 97%.

Production Example 2
The water absorbent resin produced in Production Example 1 was subjected to a heat treatment at 180 ° C. for 10 minutes using an inert oven. This is designated as absorbent resin 2. The surface salt strength was 2.7N. The total ammonium salt concentration was 70%, the surface salt concentration was 30%, and the central salt concentration was 95%.

Production Example 3
To a 300 ml flask, 81.73 g of reagent acrylic acid (manufactured by Wako Pure Chemical, special grade reagent), 185.71 g of water, and 31.78 g of sodium hydroxide were slowly added while cooling with ice so that the liquid temperature did not exceed 30 ° C. (Salt concentration 70%). 90 g of this monomer solution and 0.0561 g of N, N′-methylenebisacrylamide are added to a 300 ml separable flask. The flask is bathed in a water bath so that the liquid temperature is maintained at 30 ° C. The aqueous solution was deoxygenated by bubbling with nitrogen gas, and the reaction system was purged with nitrogen. Polymerization is started by adding 0.0826 g of 30% by mass dissolved in 1 g of water and 0.0518 g of Rongalite respectively. The internal temperature starts from 30 ° C and increases to 70 ° C in 10 minutes from the start of the reaction. Heat in a water bath for 3 hours so that the internal temperature is maintained at 75 ° C. 5 minutes after recording the maximum temperature. After a predetermined time has elapsed, the gel is taken out from the separable flask and roughly crushed, and then dried at 100 ° C. using an inert oven for 4 hours. After drying, the mixture was pulverized with a homogenizer. This is designated as absorbent resin 3. The surface strength of this resin was 0.9N.

Production Example 4
A mixed solution of 0.6 g of isopropyl alcohol, 0.02 g of glycerin, and 0.06 g of water was made and sprayed uniformly on 2 g of the water absorbent resin produced in Production Example 3. This was heated at 180 ° C. for 10 minutes using an inert oven. This is designated as absorbent resin 4. The surface strength of this resin was 5.9N.

Production Example 5
Acrylic acid was manufactured by Wako Pure Chemical Industries, Ltd. and was used after being purified by distillation. 753 g of purified acrylic acid is cooled in an ice bath and kept at a liquid temperature of 30 ° C. or lower, and 625 g of a 25% by weight reagent aqueous solution made by Wako Pure Chemical Industries, Ltd. is gradually added with stirring to a 66% by weight aqueous ammonium acrylate solution. (Neutralization rate 100%) was obtained. To this was added 0.0395 g of N, N′-methylenebisacrylamide dissolved in 1 g of water, dissolved by stirring, and then deaerated by bubbling with nitrogen gas.

  In advance, 4.3 L of cyclohexane and 7.8785 g of sorbitan monostearate as a surfactant were added to a 12 L autoclave with a nitrogen atmosphere inside, and the mixture was stirred and dissolved at room temperature. Then, the reaction system was degassed under a reduced pressure of 65 kPa. I care. It heated until the internal temperature became 60 degreeC with the pressure reduction state. An aqueous solution in which 0.7186 g of ammonium persulfate was dissolved in 50 g of water was added to the above-mentioned ammonium acrylate aqueous solution. After the internal temperature of the reaction system reached 60 ° C., the prepared ammonium acrylate aqueous solution was added to the system, and stirred and suspended at 120 rpm while flowing nitrogen. Thereafter, the inside of the reaction system was maintained at 65 kPa and the internal temperature was 60 ° C., and the polymerization was started. The polymerization was completed for 2 hours while maintaining the stirring speed at 120 rpm to obtain an emulsion containing a hydrous gel. After making the inside of the reaction system normal pressure with nitrogen, the inside of the system was sealed and heated at an internal temperature of 80 ° C., the stirring speed was set to 400 rpm, and 108.8 g of Wako Pure Chemical's special grade ethanol and 8.35 g of glycerin were mixed. The solution was added over 15 minutes. The inside of the system was pressurized with nitrogen, heated until the internal temperature reached 80 ° C., and held for 3 hours with stirring. Thereafter, after the pressure in the system was reduced to normal pressure, the hydrous gel produced at a temperature of 40 ° C. was washed three times using 2 L of cyclohexane.

  The produced hydrogel was collected by filtration, dried and collected at 70 ° C. full vacuum. Dry at 70 ° C. using an inert oven for 6 hours. After drying, the mixture was pulverized with a homogenizer. This is designated as absorbent resin 5. The absorption capacity of this resin was 70 times. The surface strength of this resin was 0.4N. The total ammonium salt concentration was 95%, the surface salt concentration was 88%, and the central salt concentration was 97%.

Production Example 6
In Production Example 5 , the same operation as in Production Example 5 was performed, except that the stirring speed during polymerization was changed from 120 rpm to 400 rpm. The absorbent resin 6 obtained here was used. The absorption capacity of this resin was 80 times. The surface strength of this resin was 0.4N. The total ammonium salt concentration was 95%, the surface salt concentration was 87%, and the central salt concentration was 97%.

Production Example 7
Acrylic acid manufactured by Wako Pure Chemical Industries, Ltd. was used as a reagent special grade. Reagent acrylic acid 2557.8 g was dissolved in water 2087.3 g. This aqueous solution was cooled in an ice bath, and while maintaining the liquid temperature at 30 ° C. or lower, 3507.0 g of 40.5 wt% NaOH aqueous solution was gradually added with stirring to obtain 40 wt% sodium acrylate aqueous solution.

  1733.0 g of the sodium acrylate aqueous solution obtained above was dissolved in 341.5 g of water. 227.7g of acrylic acid was added to this sodium acrylate aqueous solution, and 2302.2g of 40 weight% sodium acrylate / acrylic acid = 70/30 aqueous solution was obtained. After adding and dissolving 2.5 g of N, N′-methylenebisacrylamide as a cross-linking agent, it was deaerated by bubbling with nitrogen gas.

  In advance, 4.3 L of cyclohexane and 7.8785 g of sorbitan monostearate as a surfactant were added to a 12 L autoclave with a nitrogen atmosphere inside the system, and the mixture was stirred and dissolved at room temperature. I care. It heated until the internal temperature became 60 degreeC with the pressure reduction state. An aqueous solution in which 0.7186 g of ammonium persulfate was dissolved in 50 g of water was added to the aqueous sodium acrylate solution described above. After the reaction system internal temperature reached 60 ° C., the adjusted sodium acrylate aqueous solution was added to the system, and the mixture was stirred and suspended at 400 rpm while flowing nitrogen. Thereafter, the inside of the reaction system was maintained at 65 kPa and the internal temperature was 60 ° C., and the polymerization was started. The polymerization was completed for 2 hours while maintaining the stirring speed at 400 rpm to obtain an emulsion containing a hydrous gel. After making the inside of the reaction system normal pressure with nitrogen, the inside of the system was sealed and heated at an internal temperature of 80 ° C., the stirring speed was set to 400 rpm, and 108.8 g of Wako Pure Chemicals grade ethanol and 4.2 g of glycerin were mixed. The solution was added over 15 minutes. The inside of the system was pressurized with nitrogen, heated until the internal temperature reached 80 ° C., and held for 3 hours with stirring. Thereafter, after the pressure in the system was reduced to normal pressure, the hydrous gel produced at a temperature of 40 ° C. was washed three times using 2 L of cyclohexane.

  The produced hydrogel was collected by filtration, dried and collected at 70 ° C. full vacuum. After drying, the mixture was pulverized with a homogenizer. This is designated as absorbent resin 7. The absorption capacity of this resin was 55 times. The surface strength of this resin was 1.2N.

Production Example 8
Acrylic acid manufactured by Wako Pure Chemical Industries, Ltd. was used as a reagent special grade. Reagent acrylic acid 2557.8 g was dissolved in water 2087.3 g. This aqueous solution was cooled in an ice bath, and while maintaining the liquid temperature at 30 ° C. or lower, 3507.0 g of 40.5 wt% NaOH aqueous solution was gradually added with stirring to obtain 40 wt% sodium acrylate aqueous solution.

  1733.0 g of the sodium acrylate aqueous solution obtained above was dissolved in 341.5 g of water. 227.7g of acrylic acid was added to this sodium acrylate aqueous solution, and 2302.2g of 40 weight% sodium acrylate / acrylic acid = 70/30 aqueous solution was obtained. After adding and dissolving 2.5 g of N, N′-methylenebisacrylamide as a cross-linking agent, it was deaerated by bubbling with nitrogen gas.

  In advance, 4.3 L of cyclohexane and 7.8785 g of sorbitan monostearate as a surfactant were added to a 12 L autoclave with a nitrogen atmosphere inside the system, and the mixture was stirred and dissolved at room temperature. I care. It heated until the internal temperature became 60 degreeC with the pressure reduction state. An aqueous solution in which 0.7186 g of ammonium persulfate was dissolved in 50 g of water was added to the aqueous sodium acrylate solution described above. After the reaction system internal temperature reached 60 ° C., the adjusted sodium acrylate aqueous solution was added to the system, and the mixture was stirred and suspended at 400 rpm while flowing nitrogen. Thereafter, the inside of the reaction system was maintained at 65 kPa and the internal temperature was 60 ° C., and the polymerization was started. The polymerization was completed for 2 hours while maintaining the stirring speed at 400 rpm to obtain an emulsion containing a hydrous gel. After making the inside of the reaction system normal pressure with nitrogen, the inside of the system was sealed and heated at an internal temperature of 80 ° C., the stirring speed was set to 400 rpm, and 108.8 g of Wako Pure Chemical's special grade ethanol was added over 15 minutes. The inside of the system was pressurized with nitrogen, heated until the internal temperature reached 80 ° C., and held for 3 hours with stirring. Thereafter, after the pressure in the system was reduced to normal pressure, the hydrous gel produced at a temperature of 40 ° C. was washed three times using 2 L of cyclohexane.

  The produced hydrogel was collected by filtration, dried and collected at 70 ° C. full vacuum. After drying, the mixture was pulverized with a homogenizer. This is designated as absorbent resin 8. The absorption capacity of this resin was 57 times. The surface strength of this resin was 1.1N.

Example 1
Two pieces of rayon spunlace having a basis weight of 45 g / m ² were cut into a size of 16 cm in length and 8 cm in width. On one sheet, out of the resin of Production Example 1, only a resin that passed through a 300 μm sieve but could not pass through a 106 μm sieve was taken out. The average particle size of this resin was 180 μm. 1.0 g of this resin was uniformly sprayed on one rayon spunlace. Water was sprayed over the resin using a spray bottle. The other rayon spunlace was sprayed with water using a spray bottle and placed so as to overlap the resin surface. After applying a load from above and making it adhere, drying was performed at 180 ° C. for 10 minutes using an inert oven. The two rayon spunlaces were firmly bonded through the absorbent resin. This is Example 1.

Reference example 2
An absorbent composite was produced in the same manner as in Example 1 except that the resin of Production Example 3 was used. The average particle size of this resin was 190 μm. This is referred to as Reference Example 2.

Example 3
An absorbent composite was produced in the same manner as in Example 1 except that only the resin passing through a 300 μm sieve was used among the resins of Production Example 5 and the heating condition was 180 ° C. for 7 minutes. The average particle size at this time was 210 μm. This is Example 3.

Example 4
Among the resins of Production Example 6, an absorbent composite was produced in the same manner as in Example 1 except that only a resin that passed through a 200 μm sieve was used and the heating condition was 180 ° C. for 7 minutes. The average particle size at this time was 60 μm. This is Example 4.

Example 5
An absorbent composite was produced in the same manner as in Example 3 except that the resin of Production Example 7 was used. The average particle size at this time was 50 μm. This is Example 5.

Example 6
An absorbent composite was produced in the same manner as in Example 3 except that the resin of Production Example 8 was used. At this time, the average particle size was 110 μm. This is Example 6.

Example 7
An absorbent composite was produced in the same manner as in Example 4 except that the base material was 25 g / m <2> rayon. This is Example 7.

Reference Example 8
A nylon “Spunbond” registered trademark manufactured by Asahi Kasei Fibers Co., Ltd. was cut into a length of 16 cm and a width of 8 cm. Of the resin of Production Example 6, 1 g of the resin passing through a 200 μm sieve was sprayed on the substrate. After spraying water with a mist sprayer, a Teflon (registered trademark) sheet was covered and applied under load. The absorbent composite was manufactured by heating at 150 ° C. for 30 minutes in an inert oven. There are particles that do not adhere and are not included in the composite. This is designated as Reference Example 8.

Example 9
An absorptive composite was produced in the same manner as in Example 4 except that “Oji Kinocross KS-40” registered trademark manufactured by Oji Kinocross Co. was used. This is Example 9.

Example 10
One piece of rayon spunlace having a basis weight of 45 g / m 2 was cut into a size of 16 cm in length and 8 cm in width. ^Two rayon spunlaces having a basis weight of 25 g / m ² were cut out. Of the resin of Production Example 6, only the resin that passed through the 200 μm sieve was taken out. 0.5 g of this resin was uniformly sprayed on ^two 25 g / m ² rayon spunlaces. Water was sprayed over the resin using a spray bottle. Water was sprayed on both sides of another 45 g / m ² rayon spunlace using a spray bottle. The resin side of the ^two 25 g / m ² rayon spunlaces prepared previously was brought into contact so that the resin overlapped on both sides of the 45 g / m ² rayon spunlace. It has a sandwich structure of 25 g / m ² rayon spun lace on the surface layer and 45 g / m ² rayon spun lace at the center through the resin layer. After applying a load from above, it was dried at 180 ° C. for 8 minutes using an inert oven. The three rayon spunlaces were firmly bonded through the absorbent resin. This is Example 10.

Example 11
One piece of rayon spunlace having a basis weight of 45 g / m 2 was cut into a size of 16 cm in length and 8 cm in width. One rayon spun lace having a basis weight of 25 g / m ² was cut out. Of the resin of Production Example 6, only the resin that passed through the 200 μm sieve was taken out. 0.5 g of this resin was sprayed uniformly on two rayon spunlaces. Water was sprayed over the resin using a spray bottle. In the case of the 45 g / m ² rayon spunlace, water was sprayed on the surface without particles, and the sprinkled surface and the particles on the 25 g / m ² rayon spunlace were overlapped. A Teflon (registered trademark) sheet was covered from above and adhered by applying a load so that the particles did not peel off, followed by drying at 180 ° C. for 8 minutes using an inert oven. Compared to Example 10, the composite has one less base. This is Example 11. Since the surface layer has a large amount of resin layer, the particles after absorption were easily peeled off.

Example 12
Only the amount of resin used was changed from Example 11 to produce an absorbent composite. The on rayon 45g / ^{m 2} 0.1g, it is on rayon 25 g / ^{m 2} was 0.9 g. This is Example 12. Although there was a resin layer on the surface, there was almost no peeling of the particles after absorption due to the small amount.

Example 13
An absorptive composite was produced in the same manner as in Example 10, except that three 45 g / m ² rayon spunlaces were used and the amount of resin was 0.35 g each. This is Example 13. The weight ratio of the absorbent resin to the substrate is low, and the reversibility is poor.

Example 14
A registered trademark of “Oji Kinocross KS-40” manufactured by Oji Kinocross Co., Ltd. was cut into a length of 16 cm and a width of 8 cm. After water was evenly sprayed, 1 g of the resin of Production Example 1 that passed through a 300 μm sieve but could not pass through a 106 μm sieve was sprayed. A Teflon (registered trademark) sheet was placed thereon and brought into close contact with a load. Water was sprayed again on the surface without resin, and 1 g of resin was sprayed in the same manner. After a Teflon (registered trademark) sheet was covered and adhered, drying was performed at 180 ° C. for 10 minutes using an inert open. This is Example 14. Although the weight ratio of the absorbent resin is high, the absorption rate is not improved for a large amount of resin used.

Comparative Example 1
An absorptive composite was produced in the same manner as in Example 8 except that the base material was a “Spunbond” registered trademark manufactured by Asahi Kasei Fibers Corporation. This is referred to as Comparative Example 1. There are particles that do not adhere and are not included in the composite.

Comparative Example 2
A composite was produced in the same manner as in Example 4 except that the amount of resin was 3 g. This is referred to as Comparative Example 2.

Comparative Example 3
A composite was produced in the same manner as in Example 4 except that the resin amount was 0.13 g. This is referred to as Comparative Example 3.

Comparative Example 4
To a 300 ml flask, 81.73 g of reagent acrylic acid (manufactured by Wako Pure Chemical, special grade reagent), 185.71 g of water, and 31.78 g of sodium hydroxide were slowly added while cooling with ice so that the liquid temperature did not exceed 30 ° C. (Salt concentration 70%). In a nitrogen box, 90 g of this monomer solution was sprayed and 0.0561 g of N, N′-methylenebisacrylamide was added. The aqueous solution was deoxygenated by bubbling with nitrogen gas. 1 ml of a solution obtained by dissolving 0.022 g of iron (III) chloride hexahydrate in 100 g of water, 1 ml of 30% by weight of hydrogen peroxide water, and a solution obtained by dissolving 0.12 g of L-ascorbic acid in 1 ml of water The mixture was quickly added, stirred, and sprayed onto Spunbond Ertask Limp (registered trademark) PC8020 manufactured by Asahi Kasei Fibers. Using a hot plate, the whole nonwoven fabric was heated to 60 ° C. and polymerized for 1 hour, and then the temperature was raised to 120 ° C. and held for 30 minutes to complete the polymerization. When vacuum drying was performed at 100 ° C. and the residual monomer was measured, it was 1000 ppm or more.

Comparative Example 5
Among the resins of Production Example 6, an absorbent composite was produced in the same manner as in Example 1 by using only a resin that passed through a 600 μm sieve but could not pass through a 400 μm sieve. This is referred to as Comparative Example 5. The average particle size of the resin at this time was 520 μm.

Comparative Example 6
Two pieces of rayon spunlace having a basis weight of 45 g / m ² were cut into a size of 16 cm in length and 8 cm in width. Of the resin of Production Example 2, 0.9 g of only the resin that passed through the 300 μm sieve but could not pass through the 106 μm sieve was taken out. The average particle size of this resin was 180 μm. This is uniformly dispersed between the two substrates, and this is referred to as Comparative Example 6.

Comparative Example 7
Only the absorber part is taken out from 15 cc of Lifely Refreshing Pads manufactured by Unicharm, and used as Comparative Example 7. It is an absorber having a structure in which the particulate absorbent resin is arranged without being fixed to a bag partitioned into compartments.

Comparative Example 8
Only the absorber part is taken out from the safety pad super light manufactured by Ribdou Co., Ltd. The absorbent resin is fixed to the base material using an adhesive.

Explanatory drawing of the measuring apparatus of the absorption magnification under pressure of the absorptive complex of the present invention. FIG. 2 is an enlarged explanatory view of a measurement unit 5 in FIG. An example of the shape of an absorbent composite with a longitudinal direction An electron micrograph showing how fibers penetrate into and adhere to the absorbent resin. The state in which the fibers penetrated and adhered to the absorbent particles was shown by an electron microscope (magnification 150 times) photograph. The part surrounded by a circle is the joint between the absorbent resin and the fiber. From the point where it looks black, the upper right is an absorbent resin, the lower left is the fiber part of the base material, and the fibers penetrate into and bind to the black part.

Claims (9)

A composite in which a base material and particulate absorbent resin are bonded,
An absorbent composite produced by absorbing a base material and / or an absorbent resin, bringing the resin into contact with the base material, then dehydrating and drying, and satisfying the following conditions.
(1) The substrate is composed of cellulosic hydrophilic fibers.
(2) The average basis weight of the absorbent resin with respect to the plane is 10 to 150 g / m ² .
(3) 50% or more of the absorbent resin is directly bonded to the base material,
(4) The residual monomer in the absorbent resin is 200 ppm or less,
(5) The average particle diameter of the absorbent resin is 10 to 300 μm.
(6) The basis weight of at least one base material is 28 to 100 g / m ² .
(7) A compound having two or more functional groups capable of reacting with a carboxyl group coexists in the absorbent resin.
(8) The surface strength of the absorbent resin particles before adhering onto the substrate is 0.1 to 5.5N. An absorbent composite using a plurality of substrates, the absorbent composite according to claim 1, wherein the average basis weight of the resin on the surface of the absorbent composite is characterized in that it is a 0~20g / m ² . The absorbent composite according to claim 1, wherein two substrates are used, and the substrates are bonded to each other by a resin layer disposed between the substrates. The ratio of the absorbent resin weight with respect to a base material weight is 35 to 300%, The absorbent composite in any one of Claims 1-3 characterized by the above-mentioned. The absorbent resin is a resin having a carboxylic acid group in the side chain, and 50% or more of the acid groups in the absorbent resin are neutralized in the form of an ammonium salt. 5. The absorptive complex according to any one of 4 . The absorbent resin according to any one of claims 1 to 5 , wherein the absorbent resin is a copolymer mainly composed of polyacrylate. The absorbent composite according to any one of claims 1 to 6 , wherein the absorbent composite is produced by making the base material and / or the absorbent resin absorb water, bringing the resin into contact with the base material, and then dehydrating and drying. Body manufacturing method. 8. The method for producing an absorbent composite according to claim 7 , wherein a resin is disposed between a plurality of water-containing base materials, and the resin is adhered and then dehydrated and dried. A body fluid-absorbing article comprising the liquid-permeable sheet, the liquid-impermeable sheet, and the absorbent composite according to any one of claims 1 to 6 between them.

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