JP4868832B2 - Body fluid absorbent article - Google Patents

Description

The present invention relates to a bodily fluid absorbent article such as a disposable diaper, a sanitary napkin, a urine absorbing pad and a breast milk pad that absorbs and holds bodily fluids. In particular, the present invention relates to a body fluid-absorbing article that is thin and lightweight, has a sufficient absorption rate and absorption capacity, is excellent in liquid diffusibility, and does not easily leak.

  In body fluid absorbent articles used for sanitary materials such as disposable diapers and sanitary napkins, absorbent bodies that absorb fluids such as body fluids, and flexible liquid-permeable surface sheets (top sheets) disposed on the side in contact with the body And a liquid-impermeable back sheet (back sheet) disposed on the opposite side in contact with the body.

  In recent years, there has been an increasing demand for thinner and lighter sanitary materials due to design problems, distribution problems, and dust problems. In order to cope with this, as a method generally used in the current sanitary material, there is a method in which the water-absorbing resin supporting carrier in the sanitary material such as fiber is reduced and a large amount of the water-absorbing resin is used. Hygienic materials with a reduced ratio of hydrophilic fibers and increased water-absorbing resin are preferable from the standpoint of simply storing liquids, but do not distribute or diffuse liquids in actual diaper usage. If you think about it, you will have problems. That is, a large amount of the water-absorbing resin becomes a soft gel upon absorption, causing a so-called gel blocking phenomenon that greatly hinders liquid diffusion. In order to avoid such problems and maintain the absorption characteristics of the absorbent body, the ratio of hydrophilic fibers to water-absorbent resin is naturally limited, and there is a limit in reducing hydrophilic fibers and making sanitary materials thinner. come.

  In the sanitary material, pulp is generally used as a fiber. However, clean virgin pulp is usually used among the pulps. If a large amount of fiber is used, it imposes a load on forest resources.

  As a means for reducing fibers and preventing gel blocking that occurs when a large amount of water-absorbent resin is used, a method of using two types of water-absorbent resins having different absorption performances (for example, see Patent Document 1), cationic ion exchange. A method using a composition containing a hydrogel-forming polymer and an anionic ion-exchange hydrogel-forming polymer (see, for example, Patent Document 2), and a method using a water-absorbing resin having a high surface crosslink density (see, for example, Patent Document 3). A method of foaming and extruding a mixture of a water-absorbent resin and a thermoplastic resin to form a sheet (for example, see Patent Document 4) has been proposed, but is unsatisfactory as an absorbent having a high water-absorbent resin concentration. There is a problem such as there is a high price. In addition, in these methods, the relative amount of hydrophilic fibers that have been responsible for fixing the water-absorbent resin is reduced, and thus there arises a problem that the particles of the water-absorbent resin are biased before use or move during use. Come. In this way, the water-absorbent resin is displaced from the designed position of the absorbent article, causing the mold to lose shape, and then the discharged urine or other liquid does not come into contact with the water-absorbent resin in the absorbent article, leading to leakage. Will arise. There is also a method (for example, refer to Patent Document 5) in which a mixing method of fibers and the water absorbent resin is devised in order to prevent blocking between the water absorbent resins and suppress bias. In this method, the water-absorbing resin and pulp are mixed together with water, and a mixture obtained by dry-mixing with hydrophilic fibers is air-formed on the web. Therefore, it can be said that the degree of mixing is high. However, the clogging of the water-absorbing resin becomes a problem in the process of air-making on a web. When clogging of the water-absorbent resin occurs, it is necessary to discharge from the drum, which leads to a decrease in productivity. In addition, in order to easily prevent clogging and discharge when clogged, it is necessary to use a water-absorbent resin having high hardness. Usually, a water-absorbing resin having a high hardness tends to have a small absorption capacity, and a large amount of water-absorbing resin is required to absorb a target amount of liquid. In addition, this method is not sufficient in terms of preventing the movement and bias of the water-absorbent resin in the product.

  In order to improve these problems, in particular, the problem of movement and bias of the water-absorbing resin, a method of fixing the water-absorbing resin to the support carrier has been studied. For example, a method of embossing the absorber, a method of including a thermoplastic binder fiber in an absorber composed of a water-absorbent resin and a hydrophilic fiber, and heat-sealing the absorber, a synthetic resin having a high recovery rate from strain A method of heat-sealing the absorber by containing it in an absorber composed of a water-absorbent resin and hydrophilic fibers (see, for example, Patent Document 6 and Patent Document 7), and the surface of the water-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 Literature 8 and Patent Literature 9), a method of immobilizing a water-absorbent resin and a hydrophilic fiber using an emulsion binder, A method of fixing a water-absorbent resin to a substrate using a hot-melt adhesive (see, for example, Patent Document 10 and Patent Document 11). However, when the water-absorbing resin is fixed to the base material using the binder as described above, there arises a problem of restriction of swelling of the water-absorbing resin due to restriction of the binder force. In particular, when the water-absorbing resin and the hydrophilic fiber are fixed with a thermoplastic binder or emulsion, there is a problem that the absorbing ability of the water-absorbing resin cannot be sufficiently exhibited. As a technique for relaxing the swelling restriction of the water-absorbent resin by such immobilization, the water-absorbent resin partially encapsulated inside the bulky nonwoven fabric and coated with fine cellulose fibers is removed with a net-like hot melt fiber. Absorbent composite coated from the surface (see, for example, Patent Document 12), a water-absorbent resin partially encapsulated inside a bulky nonwoven fabric and partially exposed from the surface is made of double layers with different net meshes. An absorbent composite sheet (see, for example, Patent Document 13) coated from the outer surface with a net-like hot melt fiber is also known. However, these methods relax the swelling regulation, but have a problem that the absorption characteristics change due to immobilization. As the absorption characteristics of the water-absorbent resin, in addition to the well-known absorption ratio, absorption rate, absorption ratio under pressure, diffusion absorption ratio under pressure, liquid permeability of swollen gel, etc., There is an absorption characteristic (for example, see Patent Document 14 and Patent Document 15) based on the capillary force of the particle gap, which is the capillary absorption magnification. It has been found that the absorption characteristics of the water-absorbing resin, such as the capillary absorption rate, are greatly influenced by the conventional immobilization means. That is, even when a high-performance water-absorbent resin is used, the absorption characteristics of the absorbent body obtained by immobilization often cannot reflect the absorption characteristics of the original water-absorbent resin. In addition, there is a description that the performance of a water absorbent resin that can be used as long as a certain minimum performance is satisfied (for example, see Patent Document 16). Differences in properties were less likely to appear and it was difficult to differentiate the absorber.

  There is also an example in which an absorbent gel is bonded to a chemically stiffened cellulose fiber using an adhesive (see, for example, Patent Document 17). In this method, the chemically stiffened cellulose fiber secures the swelling space of the absorbent gel, the water-absorbing resins are substantially separated from each other, and the performance of the original water-absorbing resin is easily exhibited. it is conceivable that. However, the fibers are not fixed to each other, and the movement of the fiber in the absorbent body is inevitable, and as a result, the movement of the absorbent gel is considered to occur. In addition, it is necessary to wrap the absorbent gel with cellulose fibers to ensure a swelling space, to use a large amount of cellulose, and the swelling space is not sufficient. Furthermore, since an adhesive is also necessary, it is considered that the regulation of swelling is inevitable. There is an example (for example, refer to Patent Document 18) in which the base material and the crosslinking agent are used for adhesion. In this method, it seems that an absorptive complex having good liquid permeability is obtained by using a crosslinking agent having no swelling restriction, making particles low in basis weight, preventing gel blocking. However, a cross-linking agent is required for adhesion, and it is considered that the absorption capacity of the particles is reduced by partially cross-linking the particles. Further, there is a description that the performance under load is improved by increasing the surface cross-linking degree, and it is considered that the anti-blocking effect is not sufficient. Furthermore, since the particles are used so as to have a low basis weight, the absorbability as a composite is low.

There is also an example in which a water-absorbing resin is immobilized on a substrate without using a binder. For example, there is a method (see, for example, Patent Document 19) in which absorbent 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 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 undergone napping treatment, and then polymerized and thermally compressed (see, for example, Patent Document 20). In this example, since the amount of the water-absorbing resin is large, the absorption performance as a composite is high, and since a nonwoven fabric is used, movement is less likely to occur than with pulp. However, in this example as well, the residual monomer becomes a problem because of polymerization in the nonwoven fabric. There is also an example in which a water-absorbent resin is applied as a slurry to a substrate (for example, see Patent Document 21). By applying as a slurry, the productivity is surely increased, but it is necessary to use expensive microfibrils as a dispersion medium, and it is considered that the adhesive force is not sufficient. In absorbent articles such as thin sanitary materials with an increased ratio of water-absorbing resin, the amount of water-absorbing resin used is increased, and depending on the arrangement position, the resin may swell after liquid absorption, resulting in considerable bulkiness. is there. There is also a problem that the body pressure due to the bulkiness tends to increase as the water-absorbent resin is firmly fixed.
In addition, sanitary materials are required to have less stuffiness in addition to leakage in terms of wearing feeling. Conventionally, an absorbent article has been proposed in which an increase in humidity during wearing is suppressed to reduce stuffiness (see, for example, Patent Document 22 and Patent Document 23). The technologies described in these publications include an absolutely dry pulp, a large amount of superabsorbent polymer, a hygroscopic material such as silica gel and lithium chloride in the absorber, and a combination of a moisture permeable back sheet. is there. There is also an absorbent article using a moisture-permeable back sheet (see, for example, Patent Document 24). By combining two sheets having moisture permeability, it is a technique that prevents the liquid from oozing out through the moisture-permeable back sheet even under pressure. However, even in these techniques, the excreted body fluid remains as a liquid that is not fixed between the fibers of paper and pulp, so that when the amount of fluid excreted is large, water vapor is generated from the liquid that is not fixed. This tends to cause stuffiness. In addition, a sanitary napkin (for example, a liquid that is prevented from returning from the absorbent by using an absorbent having a centrifugal retention capacity and a simulated blood permeation rate after the equilibrium absorption and swelling of the simulated blood, respectively, of a predetermined value or more. Patent Document 25) or a multilayer absorbent paper made by mixing bulky cellulose fibers and having a surface layer in contact with the liquid first and one or more base layers layered thereon (see, for example, Patent Document 26) )), An absorbent sheet containing hydrophilic fine fibers or hydrophilic fine powder in an absorbent sheet containing a superabsorbent polymer and bulky cellulose fibers (see, for example, Patent Document 27) is also proposed. Has been. However, in these publications, even when the excretion amount (liquid absorption amount) is large, the generation of water vapor can be remarkably suppressed and the structure of the absorbent article that can remarkably suppress the generation of stuffiness is not described at all. . As a method for suppressing the occurrence of stuffiness, there is also a method using a fiber having a small water holding amount in the absorbent layer (see, for example, Patent Document 28). Although this method certainly reduces stuffiness, since the fibers hardly function as an absorber, it relies on absorption of a water-absorbing resin having a low absorption rate, and the absorption rate becomes slow. Moreover, since there is little expansion | swelling of a fiber at the time of swelling, it is easy to raise | generate gel blocking and it is hard to exhibit the performance of a water absorbing resin.

  In this way, a disposable body fluid absorbent article that uses a thin absorbent body that can simplify the manufacturing process of sanitary materials and that also has a high ability to retain liquid, is thin and lightweight, and has a high body fluid retaining ability. It was not done.

  In addition, it consists of a flexible liquid-permeable top sheet (top sheet) placed on the side in contact with the body, a liquid-impermeable back sheet (back sheet) placed on the opposite side in contact with the body, and an absorbent body In the body fluid absorbent article to be used, there is a problem of deviation or bias of the absorbent body itself in the article during transportation or wearing. As a means for preventing the absorber from being displaced or biased during transportation or use, the absorber is generally fixed with a hot-melt adhesive. (For example, refer to Patent Documents 29 and 30.) However, in this method, if the amount of the adhesive is small, the core and the tissue paper are easily peeled off. If the amount of the adhesive is increased, the flexibility of the sheet is lowered and the water permeability of the crossing portion of the adhesive is hindered. There is a problem. There is also an example in which the adhesive application method is devised to balance the adhesive strength and flexibility (see, for example, Patent Document 31). However, although the balance between adhesive strength and flexibility is improved, it is difficult to say that the level is satisfactory. Furthermore, since the mixture of fibrous materials, such as a pulp, and a water absorbing resin is used as an absorber, a fiber and a water absorbing resin move easily inside an absorber, and it is difficult to exhibit absorptive performance stably. In addition, there is a problem that fibers and water-absorbent resins are likely to leak onto the surface of the body fluid absorbent article. In order to suppress leakage, the absorbent core is used by being embraced with a tissue or the like, but the tissue is easily broken and cannot be said to be sufficient.

  In the body fluid absorbent article, not only the absorbent capacity of the absorbent body but also the reversibility of the absorbent once absorbed is important. A technique for providing a liquid-absorbent core by providing a fiber aggregate layer on the upper surface of the absorbent core for providing an effect such as cushioning and prevention of reverse return of the absorbent is known. For example, the liquid retaining layer is composed of pulp fibers and 10 to 60% by weight superabsorbent polymer particles, and a tissue paper layer and a short fiber fluff layer are sequentially stacked on the upper surface, and if necessary, a tissue paper layer is further formed thereon. There is a technique in which the whole is covered with a surface material such as a nonwoven fabric to form a liquid-absorbent core (for example, see Patent Document 32). Also, there is a technique in which an aggregate of cotton-like pulp containing a superabsorbent polymer is coated with tissue paper to form a liquid retaining layer, and a fiber aggregate layer having a required compression elastic recovery rate is provided on the upper surface (for example, Patent Document 33). reference.). However, in these techniques, the liquid-retaining layer in which the superabsorbent polymer particles occupy 30% by weight or more and the pulp becomes 70% by weight or less is obtained even if the pulp is molded under pressure. The entanglement is blocked by polymer particles, making it very brittle. When a liquid-absorbent core composed of such a liquid-retaining layer is used, there is a problem that the liquid-retaining layer is finely loosened by the movement of a person and hinders diffusion and rapid absorption of body fluids. In order to prevent the liquid-absorbent core from being deformed, there is an example in which the liquid retaining layer and the fiber assembly layer are simultaneously wrapped and joined with tissue paper (see, for example, Patent Document 34). However, the liquid retaining layer is also a mixture of pulp and water-absorbing resin, and the liquid retaining layer itself is easy to move and it is difficult to stably exhibit the liquid absorbing performance, so it can be said that the reversible performance is satisfactory. Absent. Furthermore, the diffusion relies on a small amount of tissue for the absorber, and it is considered that the utilization efficiency of the absorber is inferior. In particular, considering the strength of the tissue once absorbed, it is considered that there is a problem in the diffusibility after absorbing.

  A preferable performance for the body fluid absorbent article is that it does not leak. As a means for preventing leakage, those provided with gathers along the edges of articles have become mainstream. Although effective in the sense of physically clogging bodily fluids, there is a problem of leakage when there is a large amount of bodily fluids or when the fit with the body is poor. Some articles control the flow of bodily fluids before reaching the gathers by devising the surface sheet (see, for example, Patent Document 35). However, since many body fluids pass through the top sheet and are absorbed into the absorber core, there is a problem of leakage after diffusing inside the absorber. There has been proposed a sanitary napkin in which both sides of an absorbent body are bonded and fixed to a surface sheet via a liquid-impermeable adhesive film and liquid leakage is prevented by using the adhesive film (for example, a patent) Reference 36). However, in this napkin, the adhesive for forming the adhesive film may pass through the surface sheet, so that the outer surface of the napkin may become sticky, or the touch at the time of adhesion may deteriorate due to the cured adhesive. there were. There is also an absorptive article which has a leak-proof part which applied hot melt adhesive to both sides of the longitudinal direction of an absorber (for example, refer to patent documents 37). This method is excellent in terms of reducing the number of members used and improving the feeling of use, but it is considered difficult to completely prevent leakage with an adhesive alone. There is also a pad in which a liquid retaining part capable of forming gel blocking is formed on the outer peripheral part of the absorber (see, for example, Patent Document 38). Although this method has a great effect of preventing leakage, there is a problem that the water-absorbing resin is used in an amount more than necessary for absorption.

Thus, a body fluid absorbent article that is thin and lightweight without using unnecessary materials, is excellent in liquid absorption speed and absorption capacity, has excellent liquid diffusibility, and has almost no leakage. It did not exist.
JP 2001-252307 A International Publication No. 98/037149 Pamphlet Japanese Patent Laid-Open No. 06-057010 International Publication No. 01/64153 Pamphlet Japanese Patent Laid-Open No. 5-230747 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 2001-96654 A JP 2001-171027 A Japanese Patent Application No. 2002-72476 Japanese Patent Application No. 2001-375375 JP 2001-96654 A Japanese Patent Laid-Open No. 10-512183 Japanese National Patent Publication No. 10-508528 JP 2003-11118 A JP 2004-124303 A JP-A-11-137600 JP-A-6-218007 JP-A-7-132126 Japanese National Patent Publication No. 10-508521 Japanese Patent Laid-Open No. 7-184958 JP-A-6-28788 Japanese Patent Laid-Open No. 9-156013 JP 2002-165837 A JP-A-8-196559 JP 2001-95837 A JP 2004-201719 A Japanese Utility Model Publication No. 52-99046 Japanese Patent Publication No. 6-38818 Japanese Patent No. 3333979 JP 2004-121701 A JP-A-8-280737 JP 2001-190594 A Japanese Patent No. 3385183

  An object of the present invention is to provide a bodily fluid absorbent article that is thin and lightweight, has a high absorption rate, and does not easily leak. Furthermore, since it is excellent in liquid absorptivity and liquid diffusibility, it is providing the bodily fluid absorption article with high utilization efficiency of an absorber.

As a result of earnest studies to achieve the above-mentioned problem, an absorbent composite obtained by combining a base material and a water-absorbent resin under specific conditions is used between a liquid-permeable sheet and a liquid-impermeable sheet, It was found that by folding the end portion of the absorbent composite, a body fluid absorbent article that is thin and lightweight, has high liquid absorbability, excellent liquid diffusibility, and hardly leaks can be provided. The article of the present invention is a body fluid absorbent article as follows.
(1) A body fluid absorbent article composed of a liquid-permeable sheet, a liquid-impermeable sheet, and an absorbent composite interposed therebetween, and the absorbent composite is disposed on and bonded to a substrate and one or both sides thereof. A resin ratio of 80% by mass to 99% by mass, a resin area filling rate of 20 to 70%, a total surface area coefficient of 0.3 to 0.78, A bodily fluid absorbent article in which 50% or more of the total water-absorbent resin is adhered to the base material, the weight-average particle diameter of the water-absorbent resin is 300 to 2000 μm, and the base material of the absorbent composite has a contact angle A bodily fluid-absorbing article, wherein the absorbent composite is a cloth and / or paper having an angle of 130 degrees or less, wherein the end portion of the absorbent composite is folded back.
(1) The water absorbent resin is cross-linked by reacting with a functional group in the resin using a condensation type cross-linking agent.
(2) Absorbency in which the water-absorbent resin has a particle shape, and 50% or more of the particles adhere without using a part of the base fiber in the water-absorbent resin particles. A complex,
(3) The surface strength of the water absorbent resin in the absorbent composite is 0.1 N or more and 5.5 N or less, and the non-pressure absorption capacity of the water absorbent resin is 55 g / g or more.
(4) The base material of an absorptive composite is a cellulose type.
(2) The body fluid absorbent article according to (1), wherein an adhesive is used for the folded portion.
(3) The body fluid-absorbing article according to (2), wherein the adhesive is a hydrophobic adhesive.
(4) The body fluid-absorbing article according to any one of (2) to (3), wherein the adhesive is a hot melt adhesive.
(5) The water absorbent resin in the absorbent composite is a resin having a carboxylic acid group in the side chain, and 50% or more of the acid groups in the water absorbent resin are neutralized in the form of an ammonium salt. (1)-The bodily fluid absorption article in any one of (4).
(6) The body fluid-absorbing article according to any one of (1) to (5), wherein the water-absorbing resin is a polyacrylate copolymer.

According to the present invention, it is possible to provide a disposable body fluid absorbent article that is thin and lightweight, has a high absorption rate, has a high liquid absorption capacity, is excellent in liquid diffusibility, does not easily leak, and is comfortable to use.

The present invention will be described in detail below.
(About body fluid absorbing articles)
The bodily fluid absorbing article in the present invention 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, and breast milk pads.

  The bodily fluid absorbent article in the present invention is composed of a liquid-permeable sheet, a liquid-impermeable sheet, and an absorbent composite interposed therebetween. The end portion of the absorbent composite in the present invention is preferably folded. The absorbent composite used in the present invention is in the form of a sheet and is stable in form, and since it is difficult for the absorbent composite to shift and move in the body fluid absorbent article during use, the body fluid is stably diffused, Can be absorbed. When the liquid diffuses through the sheet, if the liquid reaches the end of the absorber, leakage easily occurs. If the end portion of the absorber is folded, the liquid can be damped and absorbed, and thus leakage can be prevented.

  The absorptive composite used in the present invention is sheet-like and has a stable form, and has a high absorption rate and a high absorption power despite being thin and light. When this absorptive composite is combined with a liquid-permeable sheet and a liquid-impermeable sheet, a body fluid-absorbing article having a high absorption rate and a high liquid-absorbing ability can be configured while being thin and light. 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. Furthermore, compared with the conventional body fluid absorbent article, since the ratio of the absorbent resin is high, the amount of liquid that has been absorbed once when a load is applied, that is, the return amount is small. Therefore, the mounting portion can be kept comfortable.

  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 body fluid absorbent article of the present invention, there is no problem as long as there is an absorbent composite interposed between at least the liquid permeable sheet and the liquid impermeable sheet, but between the liquid permeable sheet and the absorbent composite, and Other members may be present 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 a water-absorbing resin, and sheet materials such as tissue, cloth, and paper. 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.

  In the present invention, the absorbent composite may have any shape as long as the absorbent composite is interposed between the liquid-permeable sheet and the liquid-impervious sheet. For example, the shape may be a combination of a square, a perfect circle, a rectangle, an ellipse, or a trapezoid, or an indefinite shape. In the case of an article to be worn on the crotch such as a diaper, sanitary product, urine collection pad, etc., it can be fitted according to the shape of the crotch if it is a rectangle, an ellipse, or a shape having a longitudinal direction and a transverse direction similar to it Therefore, it is preferable. An example of the shape of the absorbent body 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, there may be a marginal portion where the absorbent resin does not exist in the absorbent composite, but the absorbent composite ratio and area filling rate of the absorbent composite are omitted in the state where the absorbent composite is omitted. It is preferable that the preferable range of conditions for the body 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.
(About wrapping)
The edge part of the absorptive composite in the present invention refers to the area within 15 cm from the outer peripheral part of the sheet-like absorber. The part where the folding is present is not particularly limited as long as it is within 15 cm from the outer peripheral part, but is preferably within 12 cm, more preferably within 8 cm, further preferably within 5 cm, more preferably 3 cm. Is most preferably within. In the present invention, when the absorbent body is folded, it means that when the absorbent article is stretched to the extent that excessive force is not applied, it is attached to the plate using a thumbtack, and the part that is off the plane of the base material It means to exist. The direction of folding may be the liquid-permeable sheet as shown in FIG. 8, or the liquid-impervious sheet side as shown in FIG. Further, if there is a part that further deviates from the plane when folded as shown in FIG. 10, this part is regarded as the second folding. The number of wrapping may be one time, two times, or a plurality of times of wrapping. Although the effect of preventing leakage is higher when the diffraction is performed more than once, since the thickness is increased, it is preferable to fold the number of times so as not to impair the shape. Even in the case of multiple folding, the direction and angle of folding may be determined freely. 11 may be alternately folded in a bellows shape as in FIG. 11, or may be continuously folded in a certain direction as in FIG. A portion that has been folded once as shown in FIG. 13 may be folded so as to be doubled. Triple or more may be used. As shown in FIG. 14, the folding may not form a plane. It is preferable that the end portion of the absorbent composite has a fold because the portion has a thickness and can function as a physical weir when the liquid diffuses to prevent leakage. Furthermore, since the folded portion has higher absorption capacity than the non-folded portion, leakage can be prevented even after the liquid reaches the folded portion. The part to be folded may be the entire end part of the absorber or only a part thereof. When using an absorptive composite that has a rectangular or elliptical shape, or a shape that has a longitudinal direction and a lateral direction similar to the rectangular shape, leakage in the lateral direction is likely to occur, so it corresponds to the long side of the absorbent composite. It is preferable to fold only the part because leakage can be prevented with the minimum wrapping. In that case, it is preferable to form an absorbent body having a portion for folding as shown in FIG. 2 (a), or to be folded with a cut as shown in FIG. 2 (b). When the absorption point of the body fluid is known, it is preferable to fold the end in the vicinity thereof because the effect of preventing leakage is high. The length of the portion where the folding is present is not particularly limited, but is preferably 2 cm or more, more preferably 5 cm or more, further preferably 7 cm or more, and most preferably 10 cm or more. The longer the folded portion, the higher the effect of preventing leakage. The folded portion may be one place or a plurality of places. The folded portion may be continuous, or a plurality of folded portions may be formed at intervals.

  The width of the folding may be any length, but the width of the folded and overlapping portion is preferably 0.1 to 100 mm, more preferably 1 to 70 mm, and 5 to 40 mm. Is more preferable, and it is most preferable that it is 5-20 mm. If the width is too small, the effect of preventing leakage is reduced, and if it is too large, there is no difference in effect.

In the present invention, when four or more corners of an article are fixed using a thumbtack in a state in which the body fluid absorbent article is spread on a horizontal plate to an extent that an unreasonable load is applied, immediately before the article is removed from the plane of the absorber. The angle formed by the straight line connecting the point (2), the point farthest from the plane, and the plane of the absorber is the folding angle. If there are multiple turns, consider only the first turn. The folding angle is shown in FIG. The folding angle is preferably larger than 0 degree, more preferably 30 degrees or more, further preferably 60 degrees or more, and most preferably 90 degrees or more.

  The folded portion may be fixed using an adhesive. It is preferable to use an adhesive at the folded portion and fix the folded portion, since the absorber can be prevented from shifting or twisting. Adhesives may be used on the folded inner side to bond the absorbers together, or used on the outer side to absorb the absorbent body and liquid-permeable sheet, absorbent body and liquid-impermeable sheet, absorbent body and other members And may be adhered.

For folding, only the absorbent composite may be folded, or other members and the absorbent composite may be folded simultaneously. In the case of folding back at the same time as the other members, the other members are also preferably sheet-like.
(About the absorbent complex)
In the present invention, a combination of a water-absorbing resin and a substrate is called an absorbent composite. In this case, the method of combination is not particularly limited, and may be bonded, a substrate may be entangled with a water-absorbing resin, or may be just mixed. The water-absorbent resin and the base material may be combined one by one or a plurality of combinations. Moreover, you may combine short fibers, such as a pulp, and another material simultaneously.

In the absorbent composite according to the present invention, the resin ratio is preferably 65% by mass to 99% by mass with respect to the total composite weight, and 50% or more of the total water-absorbing resin is preferably bonded to the substrate. Furthermore, the total surface area coefficient is preferably 0.3 to 3, and the resin area filling rate is more preferably 5 to 90%. Such an absorptive composite is preferable because it is thin and lightweight and has excellent absorption speed and absorption capacity. In the absorbent composite in the present invention, the relationship between the base material and the water-absorbent resin is very important. If the weight ratio of the water-absorbent resin is too low with respect to the weight of the entire absorbent composite, it is not preferable because the amount of absorption as the absorbent composite decreases. In order to increase the resin ratio, it is conceivable to use particles having a relatively large particle diameter, or to superimpose particles having a relatively small particle diameter. It is not preferable that many particles overlap each other or are arranged without gaps because blocking is likely to occur and the absorption performance of the water-absorbent resin cannot be sufficiently exhibited. In order to prevent blocking, it is preferable to arrange at a density of the water-absorbent resin such that the area filling rate is 5 to 90%. The area filling rate represents the ratio of the area where the resin is arranged, and if the portion where the resin is not arranged is 10% or more, it will not be an obstacle to diffusing the liquid in the initial stage, and the base material will be blocked before blocking. The liquid can be diffused and the absorption ability can be exhibited. If the area filling rate meets the predetermined value, it can exhibit absorption capacity with almost no inhibition, but in order to demonstrate absorption capacity in the shortest time without waste, it is more necessary to arrange to avoid contact between particles as much as possible Preferably, it is more preferable to dispose the water-absorbing resin at a certain interval. Moreover, it is preferable to arrange | position to one layer so that a water absorbing resin may not overlap, and it is preferable to arrange | position a particle | grain on both surfaces of a base material in order to raise a particle ratio. Since the water-absorbing resin arranged in this manner can sufficiently exhibit the absorption performance without being inhibited from swelling, it can exhibit high absorption performance as an absorbent composite.
It is desirable for a body fluid absorbing article to absorb body fluid quickly. In order to increase the absorption rate of body fluids, increasing the absorption rate of the absorbent complex is an important factor. In order to increase the absorption rate of the absorbent composite, the total surface area coefficient is preferably 0.3 to 3.

  In the present invention, it is essential that 50% or more of the water-absorbing resin is adhered. More preferably, 70% or more, still more preferably 90% or more, and most preferably 95% or more of the water-absorbing resin is adhered. It is preferable that the water absorbent resin is bonded to the base material because the water 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 a part of the fibers of the base material is incorporated in the water-absorbent resin. It is preferable that 50% or more of the water-absorbing resin in the bonded water-absorbing resin is bonded in a form in which a part of the fiber is taken into the water-absorbing resin, more preferably 70% or more, and still more preferably. 90% or more, most preferably 95% or more of the water-absorbing resin is bonded in this form. If an adhesive is not used, it is preferable because it is not subjected to swelling regulation during liquid absorption. If a part of the fibers are bonded in a form incorporated in the water-absorbent resin, the fiber becomes a water passage when the water-absorbent resin absorbs the liquid, and the absorption speed is improved. For this reason, a water absorbent resin having a relatively large particle size, which was not preferred for use in an absorber, can be used. When a water absorbent resin having a large particle diameter is used, the ratio of the water absorbent resin can be increased without increasing the area filling rate, so that the absorbent composite can have high absorption performance. In addition, it is preferable to use a water-absorbent resin having a large particle size because the amount of swelling in the vertical direction also increases, so that the amount of absorption per area can be improved. When a part of the fibers are bonded in a form incorporated in the water absorbent resin, the absorbency under pressure, which is regarded as important as the performance of the water absorbent resin, is also improved. In order to increase the absorption capacity of the water-absorbent resin under pressure, a hard resin with a low absorption capacity has been used in the past, but in the present invention, blocking is avoided by the arrangement, and further, there is a water passage in the resin. Even when a soft resin having a high capacity is used, a high absorbency under pressure can be exhibited. As a result, an absorptive complex having a high absorption capacity can be obtained both under no pressure and under pressure. When blocking between water-absorbing resins occurs, liquid diffusion is also hindered, but the composite absorbent body of the present invention has high liquid diffusibility and can exhibit the absorption performance of all water-absorbing resins, so that excess water absorption The absorbent composite can be reduced in weight without using an absorbent resin.

(About the base material)
In the present invention, the base material refers to a material that can maintain a sheet shape. In the present invention, the base material may be any material as long as it is in sheet form, but is preferably paper and / or cloth. 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 fabric, 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 most preferably a non-woven fabric. Paper and / or cloth is preferable because it has excellent shape stability unlike short fibers such as pulp. Nonwoven fabric is defined by JISL0222. The shape of the substrate is not particularly limited, and the thickness is preferably 0.001 mm to 1 cm, more preferably 0.01 mm to 5 mm, still more preferably 0.05 mm to 3 mm, and most preferably 0.1 mm to 1 mm. Weight preferably ^{0.1g / m 2 ~1kg / m 2} , more preferably from ^{0.5g / m 2 ~500kg / m 2} , more preferably ^{1g / m 2 ~100g / m 2} . Those that are too thin or light are not preferred from the standpoint of strength. In the present invention, the tensile strength at break after physiological saline is preferably 0.6 to 5000 N / 20 mm, more preferably 0.7 to 500 N / 20 mm, and 0.85 to 100 N / 20 mm. Is more preferable, and most preferably 1 to 100 N / 20 mm. In the present invention, the tensile strength at break after absorption of physiological saline represents the tensile strength at break after the substrate has absorbed physiological saline. 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. Moreover, 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 at the time of water inclusion is low. 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 make several points, and use the lowest value as the strength.

  Any raw material may be used for the base material, and a plurality of combinations of base materials 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. Hydrophilic materials are more preferable than hydrophobic materials because they are superior in liquid absorption and water permeability. In addition, continuous long fibers are more preferable than short fibers because they are superior in liquid permeability. Of the hydrophilic substrates, cellulose-based substrates are particularly preferable. The cellulosic substrate in the present invention represents a cloth and / or paper having cellulose as a main raw material. 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 plant is more preferable.

  As an index indicating the hydrophilicity and liquid permeability of the substrate, there are an absorption rate and an absorption rate. This will be described next.

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.
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 2 g / g or more and 200 g / g or less, more preferably 4 g / g or more and 100 g / g or less, still more preferably 8 g / g or more and 50 g / g or less. Most preferably, it is 12 g / g or more and 30 g / g. In the absorbent composite, the fiber absorbs faster than the water-absorbent resin, so that the base material absorbs at the initial stage of absorption and the water-absorbent resin absorbs at 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. However, in the absorptive composite of the present invention, since the resin is bonded in the form of taking in the fibers of the base material, the water-absorbing resin absorbs 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.

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 0.35 mg / second or more and 100 mg / second or less, more preferably 0.45 mg / second or more and 50 mg / second or less, further preferably 0.55 mg / second or more and 30 mg / second or less, Most preferably, it is 0.65 mg / second or more and 10 mg / second or less.
Specifically, the absorption rate of the substrate is measured as follows.
Sample: For a 10 cm x 2 cm rectangular base material 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 a petri dish on the electronic balance and place the base material on the petri dish Suspend vertically from 10cm above. 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. Normally, in the body fluid absorbent article, the shape of the absorbent body is not a shape having no directionality such as a square or a circle, but a shape having a longitudinal direction and a short direction such as a rectangle. At this time, if the liquid diffuses concentrically, leakage from the short direction is likely to occur, and it is preferable that the diffusion in the long axis direction occurs preferentially.

When a direction exists in the base material, strength and elongation change in each direction. In the present invention, the direction having the maximum intensity is defined as the longitudinal direction, and the direction perpendicular thereto is defined as the lateral direction. The ratio of the strength in the vertical direction and the horizontal direction is preferably 1.2 times or more, more preferably 1.5 times or more, and most preferably 2 times or more. The ratio of elongation in the longitudinal direction to the transverse direction is preferably 1.2 times or more, more preferably 1.5 times or more, and most preferably 2 times or more. 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.
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 a 44% ammonium polyacrylate aqueous solution having a viscosity of 74 cp is brought into contact with a substrate at 25 ° C. 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 water-absorbent resin, which is preferable in terms of absorbability and adhesiveness.

(Description of water absorbent resin)
In the water absorbent resin used in the present invention, the residual monomer concentration relative to the weight of the water absorbent resin is preferably 1% by mass or less, more preferably 0.1% by mass or less, still more preferably 0.05% by mass or less, More preferably, it is 0.01 mass% or less, Most preferably, it is 0.005 mass% 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. The residual monomer concentration of the water absorbent resin as a starting material is preferably 10% or less, more preferably 5% or less, still more preferably 1% or less, and most preferably 0.1% or less. preferable. If a water-absorbing resin having a large amount of residual monomer is used, it is difficult to complete the reaction, and depending on the reaction method, the texture of the substrate may be impaired, which is not preferable.
The kind of the water absorbent resin of the present invention is not particularly limited, and any water absorbent resin may be used. A water-absorbing resin having an acid group in the side chain is preferred, and a resin having a carboxylic acid group in the side chain is more preferred. 50% or more of the acid groups are preferably neutralized in the form of a salt, and more preferably 50% of the acid groups are neutralized in the form of an ammonium salt. A water-absorbent resin having an acid group in the side chain is preferable because an electrostatic repulsion between acid groups occurs during liquid absorption and the absorption speed is increased. It is preferable that the acid group is neutralized because the liquid is absorbed into the water-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 water-absorbing resin include a crosslinked polyacrylic acid partially neutralized 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 (see, for example, Japanese Patent Publication No. 53-15959), polyglutamate (see, for example, Japanese Patent Application Laid-Open No. 2003-192794). From the viewpoints of absorption performance, cost, etc., a polyacrylic acid partial neutralized product crosslinked product usually used for hygiene materials is preferred. The shape of the water-absorbing resin may be any shape, may be an irregularly crushed shape, a tuft shape of a cocoon, a spherical shape, or the like, a slurry shape, a liquid shape, a fiber shape, or a sheet shape. The particulate form is preferable in terms of form stability after water absorption and water absorption speed.
Below, the manufacturing method of the polyacrylic acid partial neutralized material crosslinked body is mention | raise | lifted as a preferable example of the water absorbing resin to be used.

  In the polyacrylic acid crosslinked product, preferably 50 mol% or more of the repeating units in the polymer molecular chain are carboxyl group-containing units. More preferably, it is 80 mol% or more, and most preferably 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 a water absorbing resin can be calculated by calculating | requiring the total amount of nitrogen atoms in a water absorbing resin. The total amount of nitrogen atoms in the water-absorbent resin can be determined by the Kjeldahl method.

  There is no particular problem with the shape of the water-absorbent resin, and examples thereof include spherical particulate powders, irregular particulate powders, short fiber shapes, long fiber shapes, and sheet shapes that are widely used in absorbent compositions. Spherical particulate powder or amorphous particulate powder is preferable, and the particle size is preferably 10 to 3000 μm, more preferably 50 to 2800 μm, still more preferably 100 to 2500 μm, and most preferably 200 to 1500 μm.

  Monomers constituting the water-absorbing resin include (meth) acrylic acid, ethacrylic acid, itaconic acid, maleic acid, crotonic acid, fumaric acid, sorbic acid, cinnamic acid, their anhydrides, and unsaturated carboxylic acids. A neutralized salt of a monomer is exemplified, and a neutralized salt of (meth) acrylic acid is preferably 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 a water absorbing 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, most 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 Polyvalent amines such as methylenediamine; multivalent ions such as zinc, calcium, magnesium, and aluminum Which may be used those crosslinking agents of 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, a salt such as sodium chloride, a basic compound such as ammonia for pH control, or a suspending agent may be added during reverse phase suspension polymerization.

  The polymerization method of the unsaturated monomer is not particularly limited, and generally used methods such as (water) solution polymerization, reverse layer 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 initiation temperature is usually preferably in the range of 0 to 70 ° C. More preferably, it is the range of 10-40 degreeC. If the starting temperature is too high, polymerization by heat 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 ° C to 120 ° C. The concentration of the monomer solution is preferably 10 to 70%, and most preferably 30 to 50%. 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 mass or less, preferably 10% by mass 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 ° C to 180 ° C, particularly preferably 100 to 140 ° C.

  The particle size of the polymer after drying is adjusted by operations such as pulverization and classification as required. The shape may be various shapes such as spherical, scaly, irregularly crushed, and granular, but the weight average particle diameter is preferably 100 to 3000 μm, more preferably 200 to 2800 μm, most preferably. Is 300-2500. If the particle size is too small, it becomes fine powder, and it becomes easy to scatter.

  In the polyacrylic acid crosslinked product, the polymer after drying controlled to a predetermined particle size 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. A compound having two or more functional groups capable of reacting with a carboxyl group may be added before polymerization, or may be added to particles before 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. 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.

  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.

  In the water-absorbing resin thus obtained, if necessary, deodorants, fragrances, various inorganic powders, foaming agents, pigments, dyes, antibacterial agents, hydrophilic short fibers, plasticizers, adhesives, surfactants, Fertilizers, oxidizing agents, reducing agents, chelating agents, antioxidants, heat stabilizers, UV absorbers, light stabilizers, water, salts, etc. may be added.

  Examples of the inorganic powder include fine particles of various inorganic compounds that are 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 water absorbing resin, Preferably it is 0.01-5 weight part. There is no restriction | limiting in particular in the mixing method of water absorbing resin and inorganic powder, It carries out by the dry blend method, the wet mixing method, etc.

  If necessary, the particle diameter of the water-absorbent resin is finally adjusted by operations such as grinding and classification. The shape may be various shapes such as spherical, scaly, irregularly crushed, and granular, but the weight average particle diameter is preferably 100 to 3000 μm, more preferably 200 to 2800 μm, most preferably. Is 300-2500.

The water-absorbing resin in the present invention is preferably polymerized until the residual monomer amount is 1% or less. When there are many residual monomers, the elution from an absorber will increase and it is unpreferable in performance. The water-absorbent resin as a starting material is preferably polymerized to a residual monomer content of 10% or less. If the amount of residual monomer is large, it is difficult to complete the polymerization on the nonwoven fabric, and a large amount of residual monomer tends to remain in the end, which is not preferable. The amount of residual monomer can be quantified using the following method. The water-absorbing resin cut to a size of 2 to 3 mm or less is added to 0.9% physiological saline, which is 250 times the weight of the resin, and extracted with stirring for about 6 hours, followed by filtration. The filtrate is quantified using a liquid chromatography method.
The water-absorbent resin before adhering to the substrate in the present invention preferably has a surface salt concentration of 50 mol% or more, more preferably 60 mol% or more, more preferably 70 mol%, most preferably the water-absorbent resin. It is 80 mol% or more. If the surface salt concentration before adhering onto the substrate is too low, the adhesion of the particles will be reduced. There is no particular limitation on the surface salt concentration of the water-absorbent resin portion in the composite after final adhesion to the substrate, but it is preferably 90 mol% or less, more preferably 80 mol% or less, and most preferably 60 mol% or less. is there. A lower surface salt concentration of the water-absorbent resin in the final composite is advantageous because it hardly causes stickiness even when exposed to moist air. The water-absorbent resin is usually composed of an acid group such as a carboxyl group or a sulfonic acid group and a neutralized salt thereof, a basic group such as an amino group and a neutralized salt thereof, and the surface salt concentration of the water-absorbent resin is: The ratio of the neutralized group of the surface part of a water absorbing resin is represented. In the present invention, the surface salt concentration of the resin is determined by measuring by a microscopic ATR method which is one of infrared absorption analysis methods. The neutralization rate of the resin 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 water-absorbing resin will be described as an example. Peaks of 1695 cm ⁻¹ (carboxylic acid νC = 0 baseline 1774 to 1616 cm ⁻¹ ) and 1558 cm ⁻¹ (carboxylate νCOO− baseline 1616 to 1500 cm ⁻¹ ) as indices defining the composition ratio of carboxylic acid and carboxylate 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%, and 100 mol% partially neutralized polyacrylic acid neutralized with ammonia as a standard sample The composition ratio is obtained from the line.
The water absorbent resin in the present invention preferably has a surface strength of 0.1 to 5.5N, more preferably 0.1 to 5N, still more preferably 0.2 to 4N, and most preferably 0.2 to 3N. It is. The surface strength is a parameter representing the ease of deformation of the particle surface. When a water absorbent resin that has been absorbed and swollen at a specific magnification is put into a container and a load is applied, the gel moves and deforms so as to fill the gap of the water absorbent resin that is filled with a gap in the container. Go. Since the surface strength is an elastic modulus when the absorbed water-absorbing resin reaches 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 water-absorbent resin is not easily deformed. The fact that it is difficult to deform means that the water-absorbing resin absorbs and swells, whereas the negative force is strong, and consequently the absorption capacity is lowered. Further, if the surface is not easily deformed, it is not preferable because the adhesion surface becomes small and particles are likely to be detached from the composite. The surface strength of the water absorbent resin of the present invention is determined as follows.
Equipment: Shimadzu Autograph AG-1
Sample: 0.10 g of water-absorbing resin was precisely weighed and placed uniformly 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 water-absorbent resin was left to stand for absorption and 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 water-absorbent resin was calculated using the specific gravity of physiological saline 1.010 g / cm ³ and the specific gravity of the water-absorbent resin.

The particle diameter of the water absorbent resin used in the present invention is preferably 10 to 3000 μm, more preferably 500 to 2500 μm, still more preferably 100 to 2000 μm, and most preferably 100 to 1500 μm. As used herein, the particle size refers to particles that pass through the upper limit interval sieve and remain on the adjustment interval sieve. In the water-absorbent resin of the present invention, the number of particles passing through a sieve having an opening of 300 μm is preferably 70% or less, more preferably 60% or less, still more preferably 50% or less, and most preferably 40% or less. is there. Particles that cannot pass through a sieve having an opening of 3000 μm are preferably 10% or less, more preferably 5% or less.
The average particle diameter in the present invention is preferably 100 to 3000 μm, more preferably 200 to 2500 μm, and most preferably 300 to 1500 μm. The average particle size is determined by sieving. The smaller the average particle size, the higher the absorption rate as particles. Moreover, the larger the average particle size, the larger the swelling in the direction perpendicular to the nonwoven fabric, and the higher the amount of absorption per area. In addition, when particles having the same weight are placed, it can be said that the larger the particle size, the lower the area filling rate of the resin and the less the swelling inhibition. If the particle size alone is too large, the absorption rate will be slow, but the particles in the composite of the present invention will significantly improve the absorption rate even with large particle size due to the composite effect with the fiber, It is also preferable to use relatively large particles. From the viewpoint of achieving both the water absorption force and the water absorption speed, it is preferable to use both particles having a relatively large particle diameter of 600 μm or more and particles having a relatively small particle diameter of 300 μm or less, and two or more in the particle size distribution. It is preferable that the distribution has such a peak. The two peaks are preferably different in particle size by 2 times or more, more preferably 3 times or more, and most preferably 4 times or more. If there is a difference in particle diameter, it becomes close to fine packing, and large particles and small particles have small contact during swelling, and can exhibit each other's performance.

  In the present invention, the non-pressurized absorption capacity of the water absorbent resin is preferably 55 g / g or more, more preferably 60 g / g or more, and most preferably 70 g / g or more. In the water-absorbent resin of the present invention, the absorption capacity under pressure of the water-absorbent resin at 0.8 psi is preferably 20 g / g or more, more preferably 25 g / g or more, and most preferably 30 g / g or more. . A higher absorption capacity of the water absorbent resin is preferable because the amount of the water absorbent resin to be used can be reduced.

  The non-pressurized absorption capacity of the water-absorbent resin of the present invention is an amount capable of freely swelling and absorbing 0.9% physiological saline in a state where no load is applied to the water-absorbent resin. The non-pressure absorption capacity of the water absorbent resin is measured by the following method.

0.05 g of water-absorbent resin is 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 water absorbent resin, and the weight is measured to obtain a blank. Absorption capacity is calculated according to (Equation 1). The measurement is performed three times, and the average value is defined as the non-pressurized absorption ratio (1).
(Formula 1)
Absorption capacity of non-pressurized water absorbent resin (g / g) = {(weight of tea bag after absorption) − (weight of blank tea bag after absorption) − (weight of water absorbent resin)} / (absorption) Resin weight)
The absorption capacity under pressure of the water absorbent resin of the present invention is measured by the following method. Put 0.02 g of water-absorbing resin 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 into the cylinder to make a measuring device and measure the weight. . 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 2).
(Formula 2)
Absorption capacity under load of water absorbent resin (g / g) = (weight of device after absorption (g) −weight of device before absorption (g)) / (weight of absorption resin)
(About resin ratio)
The resin ratio in the present invention indicates the ratio of the water-absorbing resin in the composite absorbent body, and is specifically determined as shown in (Formula 3).
(Formula 3)
Resin ratio (% by mass) = A / B × 100
However, the weight of the water absorbent resin in the composite is A (g), and the total weight of the composite is B (g).
It is essential that the resin ratio is 65% by mass or more and less than 99%, preferably 70% by mass or more and 99% by mass or less, and more preferably 80% by mass or more and 99% by mass or less. A higher resin ratio is preferable because the total absorption amount as a composite increases. The weight of the water-absorbent resin is measured with all particles removed.

(About resin area filling rate)
The resin area filling rate in the present invention is an index representing the ease of contact between particles when the water absorbent resin absorbs a liquid. In the present invention, the resin area filling rate is measured as follows.
A photograph of the surface of the composite is measured with an optical microscope or an electron microscope. At this time, the measurement condition and the magnification are selected so that the water-absorbent resin and the substrate can be distinguished, and a photograph can be taken with 10 or more water-absorbent resin particles in one photograph. The photograph is enlarged and copied, the water-absorbing resin portion and the base material portion are cut out, the weight is measured, and calculation is performed according to the following (Equation 4). 5 or more arbitrary points in the absorber are photographed, and the average value is defined as the area filling rate. In the case where the water-absorbent resin is adhered to both surfaces of the substrate, the measurement is performed separately on each surface.
(Formula 4)
Resin area filling rate (%) = weight of water-absorbing resin portion / total weight × 100
The resin area filling rate is preferably 5 to 90 (%), more preferably 10 to 80, still more preferably 15 to 75, and most preferably 20 to 70. If the area filling rate is too high, the water-absorbing resins come into contact with each other when the water-absorbing resins swell, blocking occurs, and the ability of the water-absorbing resin cannot be fully exhibited. Moreover, when the resin area filling rate is too low, the amount of absorption per area in the composite absorbent body is reduced, which is not preferable. In addition, the area filling factor also affects the stiffness of the substrate. When the area occupied by the resin is large, a strain is produced compared to the original base material. In sanitary materials, if the substrate is too soft, it will be difficult to insert the absorbent body. Therefore, it is not preferable that the area filling rate is too low.

(About the total surface area coefficient)
The total surface area coefficient in this invention is an parameter | index showing the surface area of the water absorbing resin per unit area of a composite_body | complex. A larger total surface area coefficient is preferable because the absorption rate of the composite increases. The total surface area coefficient is preferably A to D, more preferably B to D, and still more preferably C to D. The total surface area coefficient in the present invention is determined by (Equation 5) by collecting the water-absorbent resin used in the composite, dividing it into predetermined particle diameters, measuring the particle weight and bulk specific gravity for each particle diameter.

・ ・・（式５）
Ｗｒは粒子径がｒ（ｃｍ）である粒子の重量の合計（ｇ）
Ｃｒは粒子径がｒ（ｃｍ）である粒子のかさ比重（ｇ／ｃｍ２）
Ｓは複合体の面積（ｃｍ２）
吸水性樹脂の粒子径とかさ比重は、複合体から吸水性樹脂のみを引き剥がし回収して測定するが、その際、繊維等が吸水性樹脂表面についている場合は、繊維を取り除いて測定する。吸水性樹脂中に繊維が浸入している場合は、粒子表面の繊維を切り取り測定する。吸水性樹脂表面に接着剤などが塗布されている場合は、吸水性樹脂が吸収することのできない溶剤を用いて、接着剤を除去する。
本発明における吸水性樹脂の粒子径は、目の開きが１０６μｍ、２１２μｍ、３００μｍ、４２５μｍ、５００μｍ、６００μｍ、７１０μｍ、８５０μｍ、１０００μｍ、１１８０μｍ、１４００μｍ、２０００μｍ、２５００μｍの篩を使用して篩い分けすることによって求める。本発明においては、通過することのできた篩の目の開きと通過することのできない篩の目の開きの中間の値を粒子径とする。なお、１０６μｍの篩を通過したものについては、５３μｍとし、２５００μｍの篩の上に残ったものについては、２７００μｍとする。この操作により、５３μｍ、１５９μｍ、２５６μｍ、３６２．５μｍ、４６２．５μｍ、５５０μｍ、６５５μｍ、７８０μｍ、９２５μｍ、１０９０μｍ、１２９０μｍ、１７００μｍ、２２５０μｍ、２７００μｍの粒径へと分類される。

(5)
Wr is the total weight (g) of particles whose particle diameter is r (cm)
Cr is the bulk specific gravity (g / cm 2) of particles whose particle diameter is r (cm)
S is the area of the composite (cm2)
The particle diameter and bulk specific gravity of the water-absorbent resin are measured by peeling off and collecting only the water-absorbent resin from the composite, and when the fiber or the like is on the surface of the water-absorbent resin, the fiber is removed. When the fiber has penetrated into the water-absorbent resin, the fiber on the particle surface is cut and measured. When an adhesive or the like is applied to the surface of the water absorbent resin, the adhesive is removed using a solvent that the water absorbent resin cannot absorb.
The particle diameter of the water-absorbent resin in the present invention is sieved using a sieve having an opening of 106 μm, 212 μm, 300 μm, 425 μm, 500 μm, 600 μm, 710 μm, 850 μm, 1000 μm, 1180 μm, 1400 μm, 2000 μm, 2500 μm. Ask for. 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 through the 106 micrometers sieve, it shall be 53 micrometers, and what remained on the 2500 micrometers sieve shall be 2700 micrometers. By this operation, the particle size is classified into 53 μm, 159 μm, 256 μm, 362.5 μm, 462.5 μm, 550 μm, 655 μm, 780 μm, 925 μm, 1090 μm, 1290 μm, 1700 μm, 2250 μm and 2700 μm.

Bulk density of the water-absorbent resin in the present invention, by using the volumetric flask 2 cm ³ weighed 2 cm ³ min of the water-absorbent resin was weighed and its weight is determined by dividing by 2 the weight. The measurement is performed 5 times and an average value is taken. Bulk specific gravity is measured at each particle size after sieving.
The total surface area coefficient is preferably 0.3 to 3, more preferably 0.4 to 3, and still more preferably 0.5 to 3. A larger total surface area is preferable because the water absorption speed is improved.

(About adhesion)
In the present invention, the adhesion between the base material and the water absorbent resin means that the water absorbent resin is fixed to the base material and the positional relationship between the base material and the water absorbent resin does not substantially change. In the present invention, the end of the absorber is held and fixed by hand, the surface where the adhesive particles are present is faced down, and the particles that are not detached are bonded by shaking at a speed of 2 reciprocations per second for 2 seconds at a width of 20 cm. Suppose you are. The ratio of the adhered particles can be determined by measuring the weight of the detached particles and the force by peeling off the adhered particles with forceps. At this time, when the particles take in the fibers of the base material, or when the fibers are stuck around the particles, the measurement is performed by removing the fibers as much as possible. If the positional relationship between the base material and the water-absorbent resin does not change, the performance of the absorber 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, it is essential that 50% or more of the water-absorbing resin is adhered, preferably 70% or more, more preferably 90% or more, and most preferably 99% or more. 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 substrate and a water absorbent resin, adhesion by a physical interaction, and fibers have entered the water absorbent resin. Although adhesion in a form or the like may be sufficient, it is preferable that 50% or more of the water-absorbent resin is bonded in a form in which fibers are taken into the water-absorbent resin. Preferably 60% or more, more preferably 70% or more, and most preferably 90% or more of the water-absorbing resin adheres in this form. It is preferable to avoid the use of an adhesive that remarkably impedes liquid flow from the fiber to the water-absorbent resin on the adhesive surface between the water-absorbent resin and the substrate. Inhibition of liquid flow from the fiber to the water-absorbent resin is caused by the presence of a large amount of hydrophobic components on the adhesive surface between the water-absorbent resin and the substrate. An amount of hydrophobic adhesive that does not significantly impede the flow of liquid from the fiber to the water-absorbent resin, or a hydrophilic adhesive that does not impede the flow of liquid may be used. Adhesives that may impede liquid permeability include hydrophobic thermoplastic polymers and hydrophobic emulsion binders. It is more preferable not to use a hydrophobic adhesive, and it is even more preferable not to use a hydrophilic adhesive.
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.

The arrangement of the bonded water-absorbing resin is not particularly problematic as long as the above-mentioned resin area filling rate is satisfied, but the water-absorbing resin is arranged and bonded so that it does not come into contact when absorbing the assumed liquid amount. And, a water-absorbent resin is preferable because it easily exhibits absorption performance. Further, the water-absorbing resin may be adhered to only one surface of the substrate, or may be adhered to both surfaces of the substrate. Adhering to both sides is preferable because the amount of absorption per area increases.
(About manufacturing method of composite)
The absorbent composite in the present invention comprises a step of using a water absorbent resin and a base material as raw materials and adhering the water absorbent resin to the base material. 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 a water-absorbing resin is entangled in a substrate 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 water-absorbing resin. In this method, the water-absorbent resin and / or the base material is absorbed and then dehydrated from the state where the water-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 water absorbent resin. 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 into a water absorbing resin, it is preferable at the point of an absorption speed or an absorptive power. The larger the amount of water, the higher the adhesiveness and the better. However, if the amount is too high, drying takes too much time, which is inefficient.

  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. In order to adjust the pH of the water-absorbent resin and / or the absorbent composite, an acidic or basic one may be used. Considering the contact between the water-absorbent resin and the nonwoven fabric 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 preferable to use without.

  There is no restriction | limiting in particular in the water-containing method. For example, the method of putting on a water bath, the method of spraying water, the method of contacting with a water-containing body, the method of exposing to a humidified state, etc. are mentioned. Of these, the water spray method, which is industrially simple and easily adjusts 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 cloth is uniform. If the water content at each location in the cloth-like hydrophilic support varies greatly, the amount of water absorbed by the absorbent resin between the absorbent resin and the dehydration drying process varies depending on the location, and the drying process. The foaming behavior that accompanies dehydration differs, and the resin size in the absorbent composite after drying becomes inhomogeneous. Absorbent composites in which resin particles having heterogeneous sizes are arranged may deteriorate the texture.

  Either one or both of the water-absorbing resin and the substrate may be in a water-containing state, or both may be in a dry state. If water-absorbing resin is contained in water, it will be easy to stick to parts other than the base material, so the water-absorbing resin before contact is dry to the extent that there is no adhesion to other substances or adhesion between particles preferable. Examples of the contact method include a method of spraying a water-absorbing resin from the top onto a substrate, a method of discharging and contacting the water-absorbing resin scraped with a drum with pressure, and filling a drum roll with the water-absorbing resin. For example, a method of discharging and contacting with pressure may be used. A method in which the water-absorbing resins can be arranged so that they do not come into contact with each other when the water-absorbing resin swells is preferable because the performance of the water-absorbing resin is easily exhibited without waste.

Any method of dehydration may be used. Examples of the method include drying by heating, drying by heating gas circulation, spraying dry air or nitrogen, vacuum drying, freeze drying, azeotropic dehydration, fluidized drying, microwave drying, etc., drying by heating, heating Drying by gas flow is preferred. 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 hydration from the viewpoint of deterioration of the water absorbent resin.
(Preferable production example of composite)
A preferred production example of the composite is shown in FIG. a is a source roll (cloth-like hydrophilic support), b is a water sprayer, c is cloth and / or paper, d1 and d2 are absorbent resin particle hoppers, e1 and e2 are drums for particle adhesion, and f is an absorbent. Resin particles, g represents a drying device, h represents a composite roll, and I represents a hopper for spraying small particle diameter particles.

  An example of the production method of the present invention will be briefly described. The cloth-like hydrophilic support taken out from the source roll (a) is made into a water-containing cloth-like hydrophilic support (c) by using a device such as a water sprayer (b), and then indented on the drum. From the particle adhering drum (e1) in which the particles are placed on the part, the water-containing cloth-like hydrophilic support is sprayed and adhered to one side of the cloth-like hydrophilic support, and then the surface on which the particles are not adhered. Particles are sprayed from the particle adhering drum (e2) in which the particles are placed in the recesses on the drum, and particles with a small particle diameter are more evenly dispersed than (i), and the particles are adhered to both sides. The cloth-like hydrophilic support is dried through a drier to produce a composite in which particles are firmly bonded.

  In the production method of the present invention, the drum structure in which the absorbent resin particles are arranged on the cloth-like hydrophilic support is an important point. On the surface of the drum, there is a recess where an absorbent resin cannot be inserted in an arbitrarily determined portion. It is preferable that the depressions are arranged so as to reduce the probability that the installed absorbent resins are in contact with each other. In order to improve the absorption performance of the absorbent composite produced by the production method of the present invention, there is an optimal dent arrangement. That is, it is in a state where there is a space between neighboring resin particles so that the absorbent resin can swell by absorption, and more absorbent resin is placed on the cloth-like hydrophilic support.

  In the production method of the present invention, the outer diameter of the entrance of the dent on the drum surface to be used needs to be 1 to 3 times the particle size of the large particle of the absorbent resin used. Preferably it is 1.2 to 2 times. The outer diameter of the recess entrance referred to in the present invention is the distance between the longest points on the edge line of the drum surface of the recess entrance. As for the structure of the indentation, the drum surface can be of any shape, such as a non-square shape represented by a circle, an ellipse, etc., a square shape represented by a triangle, a rectangle, a pentagon, etc., or an indefinite shape not defined as a specific shape. I do not care. From the viewpoint of drum production, a non-square or square fixed shape is preferable. The rectangular shape is preferable because of ease of manufacturing the drum and ease of insertion and discharge of the particles into the recess. In addition, as a structure from the drum surface edge toward the inside of the dent, the space is narrowed from the surface to the inside even if it is a dent structure so as to have the same space from the surface to the inside or a dent structure so that the space extends from the surface to the inside. A concave structure may be used. From the viewpoint of easy insertion and discharge of the absorbent resin particles, it is preferable to have a hollow structure in which the space is narrowed from the surface to the inside. In addition, the particle size of the large particle in the present invention means that 20% by weight is taken out from the larger particle diameter side of the entire absorbent resin particle placed on the absorbent composite produced by the production method of the present invention. The average particle size of the particles. The particle diameter measuring method here uses the upper limit, the lower limit, and the average value of the particles passing through the upper limit interval sieve and remaining on the lower limit interval sieve as the particle size of the particles. However, the difference between the upper limit and the lower limit of the interval between the meshes to be used needs to be 400 μm or less. If the outer diameter of the recess entrance is too large, a large number of absorbent resin particles may be inserted into the recess, or the absorbent resin particles after insertion may easily fall out of the recess, resulting in stable Driving becomes difficult. Also, if the outer diameter of the drum entrance is too small, a process of removing absorbent resin particles adhering to places other than the depression due to static electricity or the like even if the absorbent resin particles are sucked by using a suction force Even the absorbent resin particles present in the depression may be removed.

  Moreover, it is preferable that the depth of the hollow of this drum is 0.3 to 2 times the average particle diameter of the granular absorbent resin to be used. More preferably, it is 0.5-1.5 times, More preferably, it is 0.7-1.2 times. If the depth of the dent is shallow, use a suction force to absorb the dent-absorbing resin particles, and remove the absorbent resin particles that have adhered to places other than the dent due to static electricity. Even existing absorbent resin particles may be removed. In addition, if the depth of the recess is too deep, it is difficult to adjust the amount of resin to be adhered on the manufactured absorbent composite because a large number of absorbent resin particles are inserted into the recess, or after insertion. These absorbent resin particles are difficult to be discharged, and stable operation becomes difficult.

  The drum used in the production method of the present invention preferably has a hole through which the gas for blowing out the absorbent resin particles can pass at the bottom of the indentation on the drum surface. The inner diameter of the hole is preferably smaller than the particle diameter of the small particle of the absorbent resin to be used. If the hole is larger than the small particle, the particle having a particle size smaller than the hole often passes through the hole and enters the drum and is not sprayed onto the cloth-like hydrophilic composite. In many cases, it may cause problems in operation. Further, the hole structure may be any structure as long as it substantially fulfills the function of blowing gas from the inside of the drum to the outside of the drum. In order to prevent clogging of the absorbent resin particles into the hole as much as possible, it is preferable that the hole expands toward the inside of the drum.

  Further, when the absorbent resin particles are inserted into the drum, it is preferable that the inside of the drum is in a reduced pressure state and inserted in a suction state. At this time, the pressure difference between the outside and inside of the drum is preferably in the range of 0.01 to 500 Torr. If this pressure difference is too small, particles inserted into the recess may easily fall off, while if too large, many particles may enter the recess and be difficult to discharge. Therefore, the preferable range of this pressure difference is 0.05 to 100 Torr, more preferably 0.1 to 50 Torr, and most preferably 0.5 to 5 Torr. The effect of this suction is not only the improvement of the establishment of the insertion of the absorbent resin particles into the recess, but also the time between the insertion of the absorbent resin particles into the recess and the spraying onto the cloth-like hydrophilic support on the drum. This is a very preferable method because it is possible to prevent the absorbent resin particles from dropping out of the recess due to the operation of removing the absorbent resin particles attached to a place other than the recess.

  Absorbent resin adhering on the drum other than the recess after the absorbent resin particles are inserted into the recess on the drum used in the production method of the present invention and before being sprayed onto the cloth-like hydrophilic support. It is preferable to provide equipment for removing particles. The removal method is not particularly limited, but examples of specific methods include a method of scraping with a brush, a method of blowing a gas, a method of applying vibration, and the like. Among these methods, the method of blowing gas is the most preferable method.

  In addition, since the drum generates static electricity during operation and may destabilize the movement of the absorbent resin particles, it is preferable to install a device for removing static electricity.

  After arranging the resin having a large particle diameter by the drum, it is preferable to spray the resin having a small particle diameter so as to satisfy the total surface area coefficient. The spraying may be performed on only one side, and it is also preferable to spray on both sides with the cloth reversed. In order to reduce detachment, it is preferable to spray the substrate again with water before spraying the small particle size. The method for spraying the small particle diameter is not particularly limited, but a method that can be controlled as uniformly as possible is preferable.

In the method of the present invention, it is preferable to move the cloth-like hydrophilic support. The moving method at this time is not particularly limited. Specific examples of the moving method include movement in a state where there is no support on the upper and lower portions of the cloth-like hydrophilic support, and a method in which a support such as a belt conveyor is provided at the lower portion and moves according to the movement of the support. When the absorbent resin is bonded to both surfaces of the cloth-like hydrophilic support, it is preferable to adopt a belt conveyor type moving method when passing the drum surface in the bonding process to the surface to be bonded last. This is because the resin adhering to the back surface of the cloth-like hydrophilic support is prevented from falling off when the absorbent resin particles are sprayed from the drum. Moreover, it is preferable to employ | adopt a belt conveyor type moving method at the time of the dehydration drying process of the last process. This is because some cloth-like hydrophilic supports shrink during dehydration and drying, so that the shrinkage is minimized.
(Composite performance)
-About the non-pressure absorption capacity | capacitance of a composite_body | complex The non-pressure absorption capacity | capacitance of the composite_body | complex of this invention shall be the quantity absorbed after 3 hours, when 0.9% physiological saline was made to absorb freely. Specifically, a circular composite absorbent body having a diameter of 59.5 mm is prepared, and measurement is performed using the same method as the above-described absorption rate of the nonwoven fabric. However, if it contains a non-adhered water-absorbing resin, or if detachment occurs, collect the water-absorbing resin by filtration, leave it on the Kimwipe for 10 seconds or more, drain it, The weight will be added to the calculation. Moreover, in the case of the absorber which is not fixed at all, it measures by putting an absorber in T-Bag according to the measuring method of the absorption capacity of a water absorbent resin.
The non-pressure absorption capacity of the composite is preferably 40 g / g or more, more preferably 45 g / g or more, and most preferably 50 g / g or more.
As an index of the absorption performance of the composite, the amount of absorption per area is important. The amount of absorption per area can be calculated according to (Equation 6) from the above measurement results.
(Formula 6)
Non-pressure absorption per area (g / cm ² ) = ((total weight after absorption (g) −weight of composite (g)) / area of composite (cm ² )
The pressureless absorption amount per area is preferably 0.4 g / cm ^2, more preferably 0.7 g / cm ² or more, and most preferably 1 g / cm ² or more.
-Absorption capacity under pressure of the complex The absorption capacity under pressure of the complex of the present invention is expressed by the amount absorbed after 3 hours when 0.9% physiological saline is absorbed in a loaded state. The Specifically, the measurement is performed as follows using a circular 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. 4, the measuring device 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. 5, the measurement unit 5 includes a filter paper 7 and a support cylinder 9 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 absorber. The absorption capacity under pressure of the composite was measured using the measuring apparatus having the above configuration. 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 placement operations, an absorber was placed inside the support cylinder 9 and a weight 11 was placed on the absorber. Next, the support cylinder 9 was placed such that the center portion thereof coincided with the center portion of the glass filter 6. Then, the weight W (g) of the physiological saline 12 absorbed by the water absorbent resin every 10 seconds from the time when the support cylinder 9 was placed was measured using the balance 1. The absorption capacity under pressure of the composite is determined according to (Equation 7).
(Formula 7)
Absorption capacity under pressure of composite (g / g) = weight W (g) / weight of composite (g)
The absorption capacity under load under 0.8 psi load of the composite is preferably 15 g / g or more, more preferably 16 g / g or more, and most preferably 18 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 most preferably 0.2 g / cm ² or more.

Measurement of absorption capacity after 1 minute of the composite The composite is cut into 2 cm length and 7 cm width, 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 same size T-Bag is weighed and the 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 150G 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 absorber before water absorption. The period from the lifting of the complex to the start of centrifugation is within 15 seconds. 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 instantaneously, the higher the absorption speed, the better.
(Formula 8)
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 complex (g )
Measurement of the stiffness of the composite The stiffness of the composite is measured by the stiffness / 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 softer, that is, the larger value is regarded as the bending resistance. The bending resistance is preferably 90 mm or less, and more preferably 85 mm or less.
(About the adhesive that bonds the absorbent composite to other members)
In the present invention, the absorbent body and the liquid-permeable sheet and / or the liquid-impermeable sheet and the adhesive are preferably fixed with an adhesive. The absorbent composite is excellent in form stability, but by fixing with an adhesive, it is possible to prevent the absorber from being twisted or displaced and to exhibit the absorption performance stably. The absorbent body and the liquid-permeable sheet and / or liquid-impermeable sheet are preferably directly bonded, but another sheet-like substance is interposed between the sheet-like substance, the absorbent composite, and the sheet-like substance. And a liquid-permeable sheet and / or a liquid-impermeable sheet may be adhered. In addition, the sheet-like substance may be bonded to the liquid-permeable sheet and / or the liquid-impermeable sheet in a state where the absorber is included in the sheet-like substance and the movement of the absorber in the sheet-like substance is restricted. . In order to reliably prevent twisting and shifting, it is preferable that the absorbent body and at least the liquid-permeable sheet or liquid-impermeable sheet are directly bonded.

  In the present invention, the adhesive to be bonded to the absorbent composite refers to an adhesive that can bond the absorbent composite to other substances. The property of the adhesive is not particularly limited, and may be liquid or solid. Only one type of adhesive may be used, or a plurality of adhesives may be used in combination. The type of the adhesive is not particularly limited, and examples thereof include solvent-based, water-dispersed, hot-melt, and reaction systems. Specific examples include urea resin-based adhesives, melamine resin-based adhesives, and phenol resins. Adhesive, resorcin adhesive, α-olefin adhesive, water-soluble polymer-isocyanate adhesive, vinyl acetate resin emulsion adhesive, acrylic emulsion adhesive, vinyl acetate resin adhesive, chloroprene rubber adhesive Agent, nitrile rubber adhesive, SBR adhesive, natural rubber adhesive, epoxy resin adhesive, cyanoacrylate adhesive, polyurethane adhesive, acrylic resin adhesive, anaerobic adhesive, modified silicone type Examples thereof include an adhesive, an inorganic adhesive, and a paste. When a hydrophilic adhesive is used, it is easy to diffuse and it becomes difficult to control the adhesive surface. Therefore, a hydrophobic adhesive is preferable. It is preferable to use a hot melt adhesive because of the ease of the manufacturing process. Hot-melt adhesive refers to all adhesives that are solid at room temperature but are heated and melted, and solidify and adhere when cooled. Specifically, for example, ethylene vinyl acetate copolymer resin, polyamide, polyester, Examples thereof include those containing atactic polypropylene, thermoplastic elastomer and the like as main components and rosin resin, petroleum resin, etc. as tackifiers, and waxes, antioxidants, inorganic fillers, plasticizers and the like.

  In the present invention, the amount of the adhesive is not a problem as long as the absorbent composite adheres to the liquid-permeable sheet and / or liquid-impermeable sheet. The amount of adhesive per unit length is preferably 0.000001 to 0.1 g / cm, more preferably 0.00001 to 0.01 g / cm, and 0.00003 to 0.0045 g / cm. Is more preferable. The coating amount of the adhesive with respect to the area of the absorbent composite is preferably 0.2 to 1000 g / m2, and more preferably 2.0 to 100 g / m2. If the amount of the adhesive is too large, the swelling of the water-absorbent resin is inhibited, the absorption performance is lowered, and the texture is impaired, which is not preferable. Moreover, even if there is too little adhesive agent, it is unpreferable from the point of adhesive strength.

The adhesive pattern in the present invention may be a general coating method such as a wavy bent line, dot, or vertical stripe. Body fluid absorbent article, when the major axis direction of the absorbent body is defined as vertical and the minor axis direction is defined as horizontal, the liquid is applied to flow preferentially in the vertical direction rather than the horizontal direction in which leakage usually occurs. This is preferable because it is difficult for leakage to occur. As an example of the shape of the absorber and its directionality, the vertical direction is shown by arrows in FIG. 1, but the shape of the absorber is not limited to this.
(Performance evaluation of body fluid absorbent articles)
-Evaluation of returnability (rewetting property) and liquid diffusion length Evaluation of returnability and liquid diffusion length in the present invention is performed as follows. On a wooden board having a sufficient width, the body fluid absorbent article is fixed with a thumbtack in a state where the four corners of the article are stretched so as not to be wrinkled. A cylindrical pipe having a diameter of 60 mm and a weight of 53.5 g is installed at the center of the absorber. 80 g of physiological saline warmed to 37 ° C. is weighed and added dropwise to the central portion of the absorber at a rate of 7 to 8 ml / second. After confirming that physiological saline is no longer visible on the upper surface of the top sheet, remove the cylinder. 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. One minute after the start of dropping the droplet, Advantech No. 2 filter paper with a diameter of 150 mm was cut into a square with a side of 10 cm so as to be approximately 90 g and placed at the bottom of the droplet. Apply a load of 5 kg. Three minutes after applying the load, the load is removed, the filter paper is removed from the article, and the weight is measured. At this time, the weight increased from the weight of the original filter paper is taken as the first return amount.

  Place the cylinder again 9 minutes after the drop. After 10 minutes from the bottom of the droplet, 80 g is dropped again and the same operation as the first time is repeated. The increase in the weight of the filter paper at this time is taken as the second return amount.

  A cylinder is installed 19 minutes after the first droplet, 80 g is dropped again 20 minutes after the first droplet, and the same operation is repeated. The increase in the weight of the filter paper at this time is taken as the third return amount.

  The return amount is an index representing the feeling of use when the body fluid absorbent article is used. If the amount of return is large, the skin gets wet and the attachment is uncomfortable. It can be said that the smaller the return amount, the better because the surface of the article dries and becomes comfortable. Furthermore, the amount of return when the number of times is repeated represents the feeling of use when the body fluid absorbent article is continuously worn and the body fluid is repeatedly absorbed, and the second and third times the amount of return is reduced, the wear is continued. This is also preferable because it shows an excellent wearing feeling. The first return amount is preferably 15 g or less, more preferably 10 g or less, further preferably 5 g or less, and most preferably 1 g or less. The amount of the second return is preferably 30 g or less, more preferably 20 g or less, further preferably 15 g or less, and most preferably 8 g or less. The third return amount is preferably 40 g or less, more preferably 32 g or less, further preferably 25 g or less, and most preferably 20 g or less.

  The liquid diffusion length represents the length used for absorbing the liquid in the absorber, and it can be said that the longer the liquid diffusion length, the higher the utilization efficiency of the absorber. When the utilization efficiency of the absorbent body is high, the necessary absorbent capacity can be exhibited even with a small absorbent body weight, and the absorbent article can be resource-saving. Moreover, since the thickness of the absorption layer after liquid absorption will become thin when the liquid diffusion length is long, it is difficult for the absorber to be displaced and the wearer's wearing feeling is reduced, which is preferable. The liquid diffusion length is preferably 180 mm or more, more preferably 200 mm or more, further preferably 230 mm or more, and most preferably 250 mm or more.

(Leakage measurement)
The leak measurement in the present invention is performed as follows. A cross mark of about 1 cm is marked with a magic at the center of the absorbent part of the body fluid absorbent article. It fixes on a horizontal board using a thumbtack on a line drawn perpendicularly from the center to the long axis direction as shown in FIG. At this time, if gathers or the like are attached, the gathers are fixed together so that the end portions of the absorber can be seen from above. Subsequently, as shown in FIG. 6B, a plastic plate is inserted, and the article is fixed using a tape so that the angle with the fixed point is 30 degrees. At this time, the absorber is stretched so as not to be wrinkled.
To the central part marked earlier, physiological saline colored with red food is added dropwise at a rate of 0.1 ml / second. The dripping amount of the liquid at the time when the liquid diffuses and the liquid starts to diffuse outside the end portion of the absorber is read, and this is taken as the leakage dripping amount.
The leakage dripping amount is preferably 100 ml or more, more preferably 120 ml or more, still more preferably 135 ml or more, and most preferably 150 ml or more. By increasing the thickness and increasing the weight of the absorber, the value of the amount of dripping can be increased, but the absorbent article is preferably thin and light. Therefore, in the present invention, the leakage coefficient is defined as the following (Equation 9) from the leakage absorption amount, the weight of the absorber, and the area of the absorber as an index of the difficulty of leakage per unit amount.
(Formula 9)
Leakage coefficient = leakage dripping amount (ml) / (weight of absorbent (g) / area of absorbent (cm ² ))
Regarding the weight of the absorber and the area of the absorber, the value of the entire absorber is measured. In the absorber of the same weight and the same area, the larger the leakage coefficient, the more difficult it is to leak. The leakage coefficient is preferably 1000 or more, more preferably 2000 or more, still more preferably 3000 or more, and most preferably 4000 or more. This range of the leakage coefficient is preferably satisfied simultaneously with the preferable range of the leakage dripping amount described above.

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 the drying, the mixture was pulverized with a homogenizer and classified using a sieve of 106 μm, 212 μm, 300 μm, 425 μm, 500 μm, 600 μm, 710 μm, 850 μm, 1000 μm, 1180 μm, 1400 μm, 2000 μm and 2500 μm. This is designated as water absorbent resin 1. The surface strength of this resin was 0.5N. The surface salt concentration was 90%.
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 water absorbent resin 2. The surface salt strength was 2.7N. The total ammonium salt concentration was 70% and the surface salt concentration was 30%.
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 reaching 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, and classified using sieves of 106 μm, 212 μm, 300 μm, 425 μm, 500 μm, 600 μm, 710 μm, 850 μm, 1000 μm, 1180 μm, 1400 μm, 2000 μm, and 2500 μm. This is designated as water 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 water absorbent resin 4. The surface strength of this resin was 5.9N.

Example 1
“Benlyse” registered trademark manufactured by Asahi Kasei Fibers Co., Ltd. was cut to 37 cm in the longitudinal direction and 21 cm in the lateral direction. Benrise is a continuous long fiber nonwoven fabric made of 100% cellulose. Cellulosic nonwoven fabric with excellent water absorption characteristics. Moreover, since it is a continuous long fiber, it has sufficient strength when it contains water, and it has excellent liquid diffusibility. Similarly, cut a sheet of Teflon (registered trademark) to a length of 37 cm and a width of 21 cm, and draw a line having a length of 35 cm and a width of 19 cm. Two of these were prepared. 6.6 g of the resin remaining on the 1000 μm sieve of Production Example 1 was uniformly sprayed inside the line of one sheet using a 1180 μm sieve. Further, 6.65 g of the resin remaining on the 212 μm sieve was uniformly sprayed using a 300 μm sieve. On the other sheet, 6.7 g of the resin remaining on the 1000 μm sieve was sprayed in the same manner. Using a spray bottle, sprinkle 8 g of water on the Benize and place it on the resin. Furthermore, 2 g of water is sprayed on the Benize and the resin is adhered to the back surface. A weight was placed on the resin-free portion and fixed, and after 3 g of water was sprayed, drying was performed at 180 ° C. for 10 minutes using an inert oven while suppressing the shrinkage of Benize.
Unicharm's "Mooney Blue Fit M Size" registered trademark was prepared, and only the top sheet and the back sheet were recovered by dissolving the hot melt adhesive by the heat of the dryer. The manufactured absorbent composite was sandwiched between them, and the body fluid-absorbing article was produced by folding and adhering as shown in FIG. 7 using an adhesive manufactured by GE Toshiba Silicone Co., Ltd. and a non-corrosion quick-drying adhesive sealing material TSE397. This is Example 1.

Example 2
A body fluid absorbent article was prepared in the same manner as in Example 1 except that water repellent hot melt adhesive manufactured by NSC Japan and ME117 were used as the adhesive. This is Example 2.
Example 3
A bodily fluid absorbent article was produced in the same manner as in Example 1 except that 6.65 g of the resin remaining on the 500 μm sieve was used on each side to produce an absorbent composite. This is Example 3.
Example 4
The same method as in Example 1, except that 4.65 g of the resin remaining on the 710 μm sieve is used on both sides and 10 g of the particles remaining on the 300 μm sieve are used on only one side to produce an absorbent composite. A body fluid absorbent article was prepared. This is Example 3.

Reference example 1
Spunbond Ertas (registered trademark) polypropylene P03020 manufactured by Asahi Kasei Fibers Co., Ltd. was cut in a vertical direction of 33 cm and a horizontal direction of 17 cm. The weight was 1.1 g. Of the water absorbent resin 1 of Production Example 1, 13.3 g of the component remaining on the 1000 μm sieve and 6.65 g of the component remaining on the 212 μm sieve were taken out and heated at 180 ° C. for 10 minutes in an inert oven. . The particles remaining on the 1000 μm sieve were divided in half and dispersed uniformly on a Teflon (registered trademark) sheet in the same manner as in Example 1. Furthermore, the particles on the 212 μm sieve were uniformly sprayed on only one sheet. Instead of water on the nonwoven fabric, a power split stick glue made by KOKUYO Co., Ltd. was thinly applied, and after the entire coating, a water-absorbent resin was adhered to both sides of the nonwoven fabric in the same manner as in Example 1. Thereafter, the body fluid-absorbing article was produced in the same manner as in Example 1 after being left at room temperature for a while and drying the glue. This is referred to as Reference Example 1 .

Reference example 2
A bodily fluid absorbent article was produced in the same manner as in Example 1 except that the resin of Production Example 3 was used. This is referred to as Reference Example 2 .
Reference example 3
A body fluid absorbent article was produced in the same manner as in Example 1 except that the resin of Production Example 4 was used. This is referred to as Reference Example 3 .

Comparative Example 1
A bodily fluid absorbent article was prepared in the same manner as in Example 1 except that 10 g of the resin remaining on the 1000 μm sieve of Production Example 1 was used on both sides. This is referred to as Comparative Example 1. Slow speed due to low total surface area coefficient.
Comparative Example 2
A bodily fluid absorbent article was produced in the same manner as in Example 1 except that water was not sprayed. Even after heating in the oven, the Benlyse and the particles were hardly adhered, so the particles were biased in the body fluid absorbent article. In the case of such an absorber, performance cannot be stably exhibited, and it is considered difficult to obtain reproducibility in each measurement. This is referred to as Comparative Example 2.

Comparative Example 3
A bodily fluid absorbent article was prepared in the same manner as in Example 1 except that 1.8 g of the resin remaining on the 212 μm sieve of Production Example 1 was used on each side. This is referred to as Comparative Example 3. Low water absorption capacity due to low particle ratio.
Comparative Example 4
A body fluid absorbent article was produced in the same manner as in Example 1 except that the horizontal length of the composite was 17 cm and no folding was made. This is referred to as Comparative Example 4. Since there is no wrapping, the ability to prevent leakage is low.

Comparative Example 5
The M size of Mooney's Blue Fit (registered trademark) manufactured by Unicharm Corporation is referred to as Comparative Example 5. The absorption state is a mixture of pulp and water-absorbent resin, has poor diffusibility, and easily leaks.
Comparative Example 6
The M size of Pampers Cotton Care (registered trademark) manufactured by P & G Corporation is referred to as Comparative Example 6. The absorption state is a mixture of pulp and water-absorbent resin, has poor diffusibility, and easily leaks.

Explanatory drawing of the shape and directionality of the absorptive complex in this invention. Explanatory drawing of the folding in the bodily fluid absorption article of this invention. The preferable example of a manufacturing method of the absorptive complex in this invention. Explanatory drawing of the measuring apparatus used for this invention. Explanatory drawing of a measurement part same as the above. Explanatory drawing of a leak measurement of the bodily fluid absorption article in this invention. Explanatory drawing of the folding in the bodily fluid absorption article of Example 1. FIG. Explanatory drawing of the folding angle | corner in the bodily fluid absorption article of this invention. Same as above. Same as above. Same as above. Same as above. Same as above. Same as above.

Claims (6)

A body fluid absorbent article comprising a liquid permeable sheet, a liquid impermeable sheet, and an absorbent composite interposed therebetween, wherein the absorbent composite is disposed and bonded to a substrate and one or both sides thereof. It is composed of a resin, and the resin ratio is 80% by mass to 99% by mass with respect to the total absorbent composite weight, the resin area filling rate is 20 to 70%, the total surface area coefficient is 0.3 to 0.78, and the total water absorption is A body fluid absorbent article in which 50% or more of the resin is bonded to a base material, the weight average particle diameter of the water absorbent resin is 300 to 2000 μm, and the base material of the absorbent composite has a contact angle of 130 degrees. A body fluid-absorbing article comprising the following absorbent fabric and / or paper, wherein an end portion of the absorbent composite is folded back.
(1) The water absorbent resin is cross-linked by reacting with a functional group in the resin using a condensation type cross-linking agent.
(2) The water-absorbent resin has a particle shape, and 50% or more of the particles are bonded without using an adhesive in a form in which a part of the fiber of the base material is taken into the water-absorbent resin particles. Is an absorptive complex,
(3) The surface strength of the water absorbent resin in the absorbent composite is 0.1 N or more and 5.5 N or less, and the non-pressure absorption capacity of the water absorbent resin is 55 g / g or more.
(4) The base material of an absorptive composite is a cellulose type. The body fluid absorbent article according to claim 1, wherein an adhesive is used for the folded portion. The body fluid-absorbing article according to claim 2, wherein the adhesive is a hydrophobic adhesive. The body fluid absorbent article according to any one of claims 2 to 3, wherein the adhesive is a hot melt adhesive. The water-absorbing resin in the absorbent composite is a resin having a carboxylic acid group in the side chain, and 50% or more of the acid groups in the water-absorbing resin are neutralized in the form of an ammonium salt. The bodily fluid absorption article in any one of -4. The body fluid-absorbing article according to any one of claims 1 to 5, wherein the water-absorbent resin is a polyacrylate copolymer.

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