JPH08246395A - Absorbing sheet and its production - Google Patents

Abstract

PURPOSE: To obtain a thin absorbing sheet of a paper state capable of surely fixing a highly absorbing polymer to the interior of an absorbing sheet without damaging absorbing characteristics of the highly absorbing polymer of its own, not making the highly absorbing polymer cause gel blocking even in the case of repeated absorption of a liquid and developing absorbing characteristics of the highly absorbing polymer of its own. CONSTITUTION: The absorption characteristics of this absorbing sheet containing at least hydrophilic fibers, thermally fusible bondable fibers or a paper strength reinforcing agent and a highly absorbing polymer are established when the highly absorbing polymer does not exist on the absorption surface in which the absorbing sheet absorbs a liquid, the highly absorbing polymer is dispersed and arranged in the interior of the absorbing sheet and bonded and fixed to the hydrophilic fibers constituting the absorbing sheet. The highly absorbing polymer has 5-300g/m2 dispersed weight and the absorbing sheet has 0.3-1.5mm thickness.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a drip sheet,
The present invention relates to an absorbent sheet used for kitchen absorbent sheets, household cleaning sheets, pet undersheets, and the like, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Various methods for obtaining an absorbent sheet by fixing a superabsorbent polymer in an absorbent structure are known. For example, U.S. Pat. No. 3,070,095 discloses that a super absorbent polymer 16 is sprinkled on a tissue 30 and another tissue 31 is laminated on the tissue 30 by a roller, as shown in FIG. It is disclosed to press the superabsorbent polymer into the tissue by crimping. However, in this method, the superabsorbent polymer is only fixed in layers between the tissue layers, and a large amount of superabsorbent polymer cannot be fixed. Therefore, when such an absorbent sheet is used as an absorbent body of an absorbent article, for example, the highly absorbent 16 polymer is converted into the tissues 30, 3 by movement of the wearer.
There is a case where the liquid separates from No. 1 and a space is formed between the tissues 30 and 31, and the liquid stays there.

US Pat. No. 3,670,731 discloses a method in which a superabsorbent polymer is dispersed between two paper layers,
It is disclosed to be embossed or quilted to hold the superabsorbent polymer in place. However, this method also has the same drawbacks as the above-mentioned roller pressure bonding method.

Further, Japanese Patent Publication No. 59-26467, Japanese Patent Laid-Open No. 54-123293, and Japanese Patent Laid-Open No. 54-141.
No. 099 gazette discloses that by spraying steam or spraying water on a tissue to moisten the tissue and then spraying a superabsorbent polymer to give tackiness to the superabsorbent polymer. Immobilizing superabsorbent polymers is disclosed. According to this method
Although the superabsorbent polymer can be fixed to some extent, it cannot completely be prevented from falling off, and the fixing amount is still insufficient. Further, upon absorbing a liquid, the superabsorbent polymer swells in a layered form, and in some cases, absorption inhibition may occur due to gel blocking or the like.

Further, in Japanese Patent Laid-Open No. 61-132697.
In the papermaking process, is a highly absorbent polymer on the paper before drying.
After spraying the polymer, dry it
A method for producing absorbent paper containing mer is described.
It According to this method, a certain amount of superabsorbent polymer
Can be fixed in the paper, but the fixed amount is at most 10 g / m
²It is a degree, and it cannot be said that the amount is sufficient. Also, profit
In the absorptive absorbent sheet, even on the surface that absorbs liquid
Due to the presence of superabsorbent polymers, such high absorption
The absorbable polymer is produced by dynamic action such as friction.
It has the drawback that it can easily fall off.

Furthermore, a method is known in which a hot melt adhesive is applied to the entire surface of a tissue or the like and the superabsorbent polymer is fixed by the adhesive. According to this method, the superabsorbent polymer can be reliably fixed. However, since most of the surface of the superabsorbent polymer is covered with the hot melt adhesive, the swelling of the superabsorbent polymer and the absorption of liquid are inhibited.

As another method for fixing the superabsorbent polymer using the hot melt adhesive, there is a method of applying the hot melt adhesive in a spiral shape. According to this method, the above-mentioned swelling inhibition and absorption inhibition are small, and moreover, the superabsorbent polymer can be fixed efficiently. However, the spiral coating of the hot melt adhesive complicates the manufacturing process and equipment. Furthermore, since a large amount of superabsorbent polymer is fixed in a layered form, gel blocking of the superabsorbent polymer occurs when absorbing the liquid, and swelling inhibition of the liquid occurs.

On the other hand, an absorbent sheet using wood pulp produced by the dry method is also known. In such an absorbent sheet, if an attempt is made to increase the sheet strength by using a chemical binder, a highly-blended synthetic pulp, a low melting point synthetic fiber, or the like, the absorbent sheet becomes hydrophobic and the absorption rate is reduced. When the sheet strength is low, there is a drawback that when absorbing a liquid, the superabsorbent polymer swells, breaks the absorbent sheet and protrudes to the outside. Further, in order to increase the surface strength of the absorbent sheet, crepe paper may be laminated, but in this case, there is a problem that the cost becomes high.
Moreover, in any case, the fixation of the superabsorbent polymer to the wood pulp is insufficient, and the problem that the superabsorbent polymer is likely to fall off is not solved. Further, when the absorbent sheet is strongly compressed, there is a problem that the liquid absorption rate is unavoidably reduced.

In addition to the above-mentioned absorbent sheet, there is also known a method in which a superabsorbent polymer is directly polymerized on a non-woven fabric as a base material and fixed on the non-woven fabric to obtain an absorbent sheet. However, when a non-woven fabric composed of hydrophilic fibers is used as the non-woven fabric, the superabsorbent polymer obtained as a result of the polymerization does not become particulate and is immobilized almost uniformly on the entire non-woven fabric, so the amount of liquid absorbed Has the disadvantage that it will decrease. On the other hand, when a non-woven fabric composed of hydrophobic fibers is used as the non-woven fabric, unlike the above-mentioned non-woven fabric composed of hydrophilic fibers, the superabsorbent polymer obtained as a result of the polymerization becomes particulate, but the whole absorbent sheet Since it is hydrophobic, it has a drawback that the absorption rate of liquid is slow. Moreover, in these methods, the unreacted monomer remains inevitable, so that the use of the absorbent sheet is limited from the viewpoint of safety of the monomer to the human body.

Further, US Pat. Nos. 4,605,402 and 5,021,050 are manufactured by superposing a fiber layer on a fiber web sprinkled with a superabsorbent polymer. Also disclosed is an absorbent body in which a superabsorbent polymer is dispersed and adhered to fibers in the central portion in the thickness direction. Although these absorbers are compressed and thinned at the time of manufacturing, they are not formed into a sheet and are still thick for use in various applications. Also, since the density is low, the surface absorbency is weak. Furthermore, when absorbing and wetting a liquid, the elasticity of the synthetic fibers is used to recover the original thickness in order to obtain an absorption space, which is insufficient for thinning the absorbent article.

Accordingly, it is an object of the present invention to provide a thin absorbent sheet in the form of paper in which the superabsorbent polymer is securely fixed without impairing the original absorption characteristics of the superabsorbent polymer.

Further, an object of the present invention is to provide an absorbent sheet which does not cause gel blocking by the superabsorbent polymer even when repeatedly absorbing a liquid, and can exhibit the original absorption characteristics of the superabsorbent polymer. is there.

A further object of the present invention is to provide a method for easily manufacturing the absorbent sheet.

[0014]

Means for Solving the Problems As a result of intensive investigations, the inventors of the present invention have buried a superabsorbent polymer in a space formed between fibers in a state where the fibers constituting the absorbent sheet are wet. It has been found that by doing so, gel blocking of the superabsorbent polymer can be effectively prevented, and a large amount of the superabsorbent polymer can be immobilized.

The present invention has been made based on the above findings, and in an absorbent sheet containing at least a hydrophilic fiber and a heat-meltable adhesive fiber or a paper strength reinforcing agent and a superabsorbent polymer; the superabsorbent polymer is The absorbent sheet does not exist on the absorbent surface that absorbs liquid, is dispersed and arranged inside the absorbent sheet, and is adhered and fixed to the hydrophilic fibers constituting the absorbent sheet. A spray basis weight of the superabsorbent polymer is 5 to 300 g / m ² ; the absorbent sheet has a thickness of 0.3 to 1.5 mm; The above-mentioned object is achieved.

The present invention also provides, as a preferred method for producing the above-mentioned absorbent sheet, a method for producing an absorbent sheet containing at least a hydrophilic fiber, a heat-meltable adhesive fiber or a paper-strengthening agent, and a superabsorbent polymer. , A water slurry containing at least a hydrophilic fiber and a heat-meltable adhesive fiber or a paper-strengthening agent, which is formed by wet papermaking, and a superabsorbent polymer is sprinkled onto a wet fiber web, on which a hydrophilic fiber and It is intended to provide a method for producing an absorbent sheet, which comprises a step of superposing a fiber assembly containing a heat-meltable adhesive fiber or a paper-strengthening agent, and drying and integrating them.

Further, the present invention comprises a fibrous structure formed of bulky hydrophilic fibers and heat-meltable adhesive fibers or a paper-strengthening agent, and superabsorbent polymer particles. Does not exist on the absorbent surface where the absorbent sheet absorbs liquid, is dispersed and fixed in the fibrous structure, and the thickness of the absorbent sheet is 0.3 to 1.5.
mm, and the spreading basis weight of the superabsorbent polymer is 20 to
The absorbent sheet is characterized by having a weight of 70 g / m ² .

In the present specification, the "fiber web" means
In the wet state before spraying the superabsorbent polymer, the constituent fibers are not restrained at all with each other, or are restrained only slightly due to mechanical entanglement and frictional force and have a very high degree of freedom. And, after the drying, the constituent fibers mean an aggregate of fibers in which the constituent fibers are strongly bound to each other to form a sheet, and the "fiber aggregate" is formed mainly of fibers and is in a sheet form. In addition to ordinary paper, non-woven fabric, woven fabric, and the like, it also includes the above fiber web, and the "fiber structure" means the above fiber web and the above fiber assembly. It means a sheet-like material of fibers integrally constituted mainly of.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the absorbent sheet of the present invention will be described in detail with reference to the drawings. Here, FIG. 1 is a schematic view showing a cross section of the absorbent sheet of the present invention, and FIG. 2 is a schematic view showing a cross section of a preferred absorbent sheet of the present invention.

As shown in FIG. 1, the absorbent sheet 10 of the present invention contains at least a hydrophilic fiber, a hot-melt adhesive fiber or a paper reinforcing agent, and a superabsorbent polymer 16. Further, the absorbent sheet 10 has an absorbent surface 12 that absorbs liquid, and the superabsorbent polymer 16 does not exist on the absorbent surface 12, and the superabsorbent polymer 16 is included in the absorbent sheet 10. It is distributed inside. The super absorbent polymer 16 is used in the absorbent sheet 1
It is adhered to the above-mentioned hydrophilic fibers constituting 0.

The absorbent sheet 10 of the present invention preferably comprises a fiber assembly 15 and a fiber web 18 as shown in FIG. The fiber assembly 15 has an absorbent surface 12 and does not include the superabsorbent polymer 16 on the absorbent surface 12 side. On the other hand, the fiber web 18 is composed of at least hydrophilic fibers.
Further, as shown in FIG. 2, the fiber aggregate 15 and the fiber web 18 are integrated. Furthermore, the superabsorbent polymer 16 is mainly arranged inside the fibrous web 18.

As described above, the preferred embodiment of the absorbent sheet 10 of the present invention is the fiber assembly 15 and the fiber web 1.
One of the features is that it has a monolithic structure including 8 and a superabsorbent polymer 16 contained therein. More specifically, in the absorbent sheet 10 of the present invention, the mechanical entanglement between the fibers forming the fiber assembly 15 and the fibers forming the fiber web 18, hydrogen bonding (and paper reinforcing agent), and The fiber assembly 15 and the fiber web 18 are integrated by heat fusion or the like. By having such a structure, the superabsorbent polymer 16 can be reliably fixed inside the absorbent sheet, and can be prevented from falling off. Moreover, the permeability of the liquid absorbed from the absorbing surface 12 is further improved, and the liquid reaches the superabsorbent polymer 16 smoothly. Further, gel blocking of the superabsorbent polymer 16 which has absorbed the liquid can be suppressed.
Therefore, the absorbent sheet 10 of the present invention has a completely different structure from the conventional absorbent sheet (FIG. 6) in which a superabsorbent polymer is sandwiched between two sheets of absorbent paper (that is,
The conventional absorbent sheet has two plies, but the absorbent sheet 10 of the present invention is one sheet). Such integration is preferably achieved by superposing wet papermaking, as described below.

The fibrous web 18 is in a wet state before the superabsorbent polymer 16 is sprinkled, and it is important that the fibers constituting the fibrous web 18 have an extremely high degree of freedom with respect to each other. . Fiber web 1 in this state
By dispersing the superabsorbent polymer 16 on the surface 8, the superabsorbent polymer 16 is three-dimensionally dispersed and fixed in the fibrous web 18, that is, from the surface to the inside. Further, the fibrous web 18 has such strength that the superabsorbent polymer 16 does not deposit on the surface of the absorbent sheet 10 after the fibrous web 18 and the fiber assembly 15 are integrated. That is also important. For this purpose, the fibrous web 18 is JIS-P-8.
The wet strength measured by 113 is preferably 50 g or more, more preferably 100 g or more.
In order to impart wet strength to the fibrous web 18, as will be described later, a hot-melt adhesive fiber or a paper-strengthening agent is blended. It is also preferable to further mix wood pulp or non-wood pulp that forms hydrogen bonds.

[0024] The fiber web 18, the basis weight is preferably from ^{10g / m 2 ~200g / m 2} , and more preferably a ^{10g / m 2 ~100g / m 2} , more preferably 20 g / m ² ~ It is 80 g / m ² . The basis weight is 1
If it is less than 0 g / m ² , the superabsorbent polymer 16 will be swelled when the superabsorbent polymer 16 is swollen.
May protrude and fall off. On the other hand, when the basis weight exceeds 200 g / m ² , the density of the fibrous web increases too much, the absorbent sheet 10 becomes too hard, and the superabsorbent polymer 16 cannot be fixed three-dimensionally, or liquid Since the transparency may be deteriorated or the wearing feeling may be deteriorated, it is preferably within the above range.

The fibrous web contains at least hydrophilic fibers. As such a hydrophilic fiber, any fiber having a hydrophilic surface can be used without particular limitation as long as it can form a fiber web in which the fibers have extremely high degrees of freedom in the wet state. Examples of such hydrophilic fibers include wood pulp such as softwood kraft pulp and hardwood kraft pulp, natural cellulose fibers such as cotton pulp and straw pulp, regenerated cellulose fibers such as rayon and cupra, polyvinyl alcohol fibers and polyacrylonitrile fibers. Examples thereof include hydrophilic synthetic fibers such as, and synthetic fibers such as polyethylene fibers, polypropylene fibers, and polyester fibers that have been hydrophilized with a surfactant, but are not limited thereto. These hydrophilic fibers may be used alone or in combination of two or more.

The hydrophilic fiber is the same as the fiber web 100 described above.
It is preferably contained in an amount of 30 parts by weight or more, more preferably 50 parts by weight or more, based on parts by weight.

Of the above hydrophilic fibers, preferred ones are
Cellulose fiber. Cellulose fibers are preferred because they have a stable hydrophilic surface and maintain hydrophilicity, especially after wetting. In particular, bulky cellulose fibers such as natural cellulose fibers and regenerated cellulose fibers are preferable. From the viewpoint of cost, it is preferable to use wood pulp, and particularly softwood kraft pulp is preferable. By using such bulky cellulose fibers, not only the dispersibility and degree of immobilization of the superabsorbent polymer are further improved, but also the drainage of the fiber web during wet papermaking can be more easily controlled. . Further, since the bulky cellulose fiber can form a bulky and highly voided fiber web,
It is easy for the superabsorbent polymer to be three-dimensionally embedded, dispersed and fixed in the fiber web, and the gel blocking of the superabsorbent polymer can be suppressed. The average fiber length of the bulky cellulose fibers is not particularly limited, but is generally 1 to 20 mm as a general range. Further, fibers obtained by hydrophilizing synthetic fibers such as PET, PE and PP are also preferably used in the present invention as bulky hydrophilic fibers. In the present specification, the term “bulky fiber” means that the fiber shape has a three-dimensional structure such as a twist structure, a crimp structure, a bending and / or a branch structure, or a fiber cross section that is extremely thick (for example, the fiber roughness is 0.3 m
g / m or more).

The bulky cellulose fibers are contained in an amount of preferably 30 parts by weight or more, more preferably 50 to 99 parts by weight, based on 100 parts by weight of the fiber web.

Examples of preferable bulky cellulose fibers include cellulose fibers having a fiber roughness of 0.3 mg / m or more. Cellulose fibers having a fiber roughness of 0.3 mg / m or more are preferable because the cellulose fibers are accumulated in a bulky state, and a bulky network structure is easily formed in the fiber web. Further, it is preferable because the movement resistance of the liquid is small and the passing speed of the liquid is high.

In the present invention, "fiber roughness" means a fiber having a non-uniform thickness, such as wood pulp,
It is used as a scale showing the thickness of the fiber, and for example, a fiber roughness meter (FS-200, KAJANNI ELECTRONIC
S LTD.).

As described above, the bulky cellulose fiber preferably has a fiber roughness of 0.3 mg / m or more, more preferably a fiber roughness of 0.3 to 2 mg / m, and a further preferable fiber. The roughness is 0.32 to 1 mg / m.

Examples of cellulose fibers having a fiber roughness of 0.3 mg / m 2 or more include softwood kraft pulp [Federal
"ALBACEL" (trade name) made by Paper Board Co., and PT
Inti Indorayon Utama's "INDORAYON" (brand name)] and the like.

Another preferred example of the bulky cellulose fiber is a cellulose fiber having a roundness of the fiber cross section of 0.5 to 1, and particularly preferably 0.55 to 1. Cellulose fibers having a circularity of the fiber cross section of 0.5 to 1 are preferable because they have low liquid movement resistance and high liquid permeation rate. The method for measuring the roundness of the fiber cross section will be described later.

As mentioned above, it is preferable to use wood pulp as the cellulose fiber, but in general, the cross section of the wood pulp is flat due to the delignification treatment, and most of the roundness thereof is less than 0.5. In order to make the roundness of such wood pulp 0.5 or more, for example, the wood pulp may be mercerized to swell the cross section of the wood pulp.

Thus, as the bulky cellulose fiber, mercerized pulp having a circularity of 0.5 to 1 obtained by mercerizing wood pulp is also preferable.
An example of a commercially available mercerized pulp that can be used in the present invention is "FILTRAN I" manufactured by ITT Rayonier Inc.
"ER" (brand name) and "POROSANIER" (brand name) manufactured by the same company.

When the fiber roughness is 0.3 mg / m or more,
Moreover, it is preferable to use a cellulose fiber having a roundness of a fiber cross section of 0.5 to 1 because a bulky network structure is more easily formed and a liquid passing speed is further increased.

Another preferable example of the above bulky cellulose fiber is a crosslinked cellulose fiber obtained by crosslinking the inside and / or the inside of the cellulose fiber. Such crosslinked cellulose fibers are preferable because they can maintain a bulky structure even in a wet state.

The method for crosslinking the cellulose fibers is not particularly limited, and examples thereof include a crosslinking method using a crosslinking agent. Examples of such cross-linking agents include N-methylol compounds such as dimethylol ethylene urea and dimethylol dihydroxy ethylene urea; polycarboxylic acids such as citric acid, tricarballylic acid and butane tetracarboxylic acid; polyols such as dimethyl hydroxyethylene urea. ;
Examples thereof include cross-linking agents for polyglycidyl ether compounds. In particular, a cross-linking agent of a polycarboxylic acid or a polyglycidyl ether-based compound that does not generate formalin or the like which is harmful to the human body during cross-linking is preferable.

The amount of the cross-linking agent used is preferably 0.2 to 20 parts by weight with respect to 100 parts by weight of the cellulose fibers. If the amount used is less than 0.2 parts by weight, the cross-linking density of the cellulose fibers is low, so the elastic modulus may decrease significantly when wet, and if the amount used exceeds 20 parts by weight, the cellulose fibers will be Since the cellulose fiber may become too rigid and become brittle when stressed, the above range is preferable.

In order to crosslink the above-mentioned cellulose fibers using the above-mentioned crosslinker, for example, an aqueous solution of the above-mentioned crosslinker, to which a catalyst is added if necessary, is impregnated with the above-mentioned cellulose fibers to design an aqueous solution of the crosslinker. The cellulose fibers are dehydrated so that the adhesion amount is obtained, and then heated to the crosslinking temperature, or
Alternatively, an aqueous solution of a cross-linking agent is sprayed onto the above-mentioned cellulose fibers by spraying or the like so as to have a designed adhesion amount, and then heated to a cross-linking temperature to cause a cross-linking reaction.

The commercially available cross-linked cellulose fibers include “High Bulk Additiv” manufactured by Weyerhaeuser Paper Co.
e ”and the like.

In addition to the above-mentioned bulky cellulose fibers, bulky cellulose obtained by crosslinking the inside and / or the inside of the cellulose fibers such as pulp having a fiber roughness of 0.3 mg / m or more by the above-mentioned method. Fibers are also preferred.

Further, bulky cellulose fibers obtained by cross-linking the inside and / or between the molecules of pulp having a roundness of the fiber cross section of 0.5 to 1 by the above-mentioned method are also preferable.

Further, bulky cellulose fibers obtained by crosslinking the mercerized pulp having a roundness of the fiber cross section of 0.5 to 1 in the molecule and / or between the molecules by the above method are also preferable.

The more preferred bulky cellulose fibers are those obtained by crosslinking the pulp having a fiber roughness of 0.3 mg / m or more and a roundness of the fiber cross section of 0.5 to 1 by the above-mentioned method. is there.

The particularly preferred bulky cellulose fibers are pulps having a fiber roughness of 0.3 mg / m 2 or more and having a roundness of 0.5 to 1 by mercerization and then crosslinked by the above-mentioned method. is there.

In order to keep the structure of the absorbent sheet of the present invention stable even when it is wet, it is necessary to impart wet strength to the above-mentioned fibrous web. For this reason, the heat-meltable adhesive fiber is required. Alternatively, a paper strengthening agent is added.

Further, in order to strengthen the hydrogen bond between the fibers of the cellulose fiber and improve the strength of the absorbent sheet, the ordinary cellulose fiber, that is, wood pulp, is used in place of the heat-meltable adhesive fiber or the paper-strengthening agent. It is also effective to add non-wood pulp or the like. However, in order to sufficiently obtain the strength of the absorbent sheet when it is wet, it is preferable to use it in combination with the hot-melt adhesive fiber or the paper-strengthening agent.

As the above-mentioned heat-meltable adhesive fibers, fibers which are melted by heating and adhere to each other can be used. Specifically, for example, polyolefin fibers such as polyethylene, polypropylene and polyvinyl alcohol, polyester fibers, Polyethylene-polypropylene conjugate fiber, polyethylene-polyester conjugate fiber, low melting point polyester-polyester conjugate fiber, polyvinyl alcohol-polypropylene conjugate fiber whose fiber surface is hydrophilic,
In addition, polyvinyl alcohol-polyester composite fiber and the like can be mentioned. When the conjugate fiber is used, both the core-sheath type conjugate fiber and the side-by-side type conjugate fiber can be used. These heat-meltable adhesive fibers may be used alone or in combination of two or more. Examples of the heat-meltable adhesive fiber preferably used in the present invention include polyvinyl alcohol fiber soluble in hot water and core-sheath type polyester fiber.

Generally, the above-mentioned heat-meltable adhesive fiber preferably has a fiber length of 2 to 60 mm and a fiber diameter of 0.
It is preferably 1 to 3 denier (particularly 0.5 to 3 denier).

As described above, the fiber web has
A polyamine / epichlorohydrin resin, a dialdehyde starch, sponge, carboxymethylcellulose, etc., as a paper strength agent are added. These paper strength agents are
0.01 to 30 parts by weight, preferably 0.01 to 20 parts by weight, can be added based on 100 parts by weight of the fiber web.

When the heat-melting adhesive fiber is used, the fiber web contains 30 to 99 parts by weight of the hydrophilic fiber and 1 to 50 parts by weight of the heat-melting adhesive fiber based on 100 parts by weight of the fiber web. It is preferable that More preferably, based on 100 parts by weight of the fiber web, 50 to 97 parts by weight of the hydrophilic fiber and 3 to 3 parts of the heat-meltable adhesive fiber are used.
It comprises 30 parts by weight.

The fibrous web is, for example, preferably
It comprises 1 to 10 parts by weight of vinylon fiber (polyvinyl alcohol fiber), and more preferably 2 to 5 parts by weight. As the vinylon fiber, it is preferable to use a vinylon fiber that is melted by wet heat.

As another example, the fibrous web preferably contains 1 to 30 parts by weight, more preferably 5 to 20 parts by weight, of the hot-melt adhesive fiber having a core-sheath structure.
Specific examples of the heat-meltable adhesive fiber having a core-sheath structure include a polyethylene-vinyl acetate resin having a melting point of 70 ° C. to 150 ° C., a polyethylene resin, or a modified polyester resin or a wet heat-soluble polyvinyl alcohol as a sheath portion, Moreover, a synthetic fiber having a core-sheath structure having a polypropylene resin or a polyester resin as a core can be mentioned.

On the other hand, when the above paper strength reinforcing agent is used, 3 parts by weight of the hydrophilic fiber is added based on 100 parts by weight of the fiber web.
It is preferable that 0 to 100 parts by weight, 0 to 50 parts by weight of other fibers, and 0.01 to 30 parts by weight of the paper strength agent are contained. More preferably, based on 100 parts by weight of the fiber web, 50 to 100 parts by weight of the hydrophilic fiber, 0 to 20 parts by weight of the other fiber, and 0.01 of the paper-strengthening agent are used.
~ 20 parts by weight.

For example, the fibrous web may include 30 to 99 parts by weight of the bulky cellulose fibers, 1 to 70 parts by weight of the wood pulp or non-wood pulp, and the paper strength based on 100 parts by weight of the fibrous web. Reinforcing agent 0.01 to 30
It is preferable to comprise by weight. More preferably, based on 100 parts by weight of the fiber web, 50 to 95 parts by weight of the bulky cellulose fiber, 5 to 50 parts by weight of the wood pulp or non-wood pulp, and 0.0% of the paper strength reinforcing agent.
It comprises 1 to 20 parts by weight.

Next, the superabsorbent polymer 16 contained in the absorbent sheet 10 of the present invention will be described.
As shown in FIG. 1, the superabsorbent polymer 16 is contained inside the absorbent sheet 10 and is dispersed in a space formed between fibers constituting the absorbent sheet 10. More specifically, as shown in FIG. 2, the superabsorbent polymer 16 is mainly contained inside the fibrous web 18, that is, from the interface between the fibrous web 18 and the fibrous assembly 15 of the fibrous web 18. It is preferably contained in the inside and dispersed in the space formed between the fibers constituting the fiber web 18. As a result, the superabsorbent polymer 16 is reliably fixed in the absorbent sheet and gel blocking is suppressed. Note that, here, “the superabsorbent polymer is contained inside the absorbent sheet” does not mean that the superabsorbent polymer does not exist on the surface of the absorbent sheet at all, and will be described later. In the preferred manufacturing method of the absorbent sheet, a trace amount of the superabsorbent polymer unavoidably present on the surface of the absorbent sheet is acceptable, and most of the superabsorbent polymer is inside the absorbent sheet. It exists.

The superabsorbent polymer 16 is adhered to the hydrophilic fibers forming the absorbent sheet 10, preferably the hydrophilic fibers forming the fibrous web 18. Therefore, the immobilization of the superabsorbent polymer 16 becomes stronger and the gel blocking thereof is further suppressed.
Here, the superabsorbent polymer 16 is mainly adhered to hydrophilic fibers, but other fibers constituting the absorbent sheet,
For example, there is no problem even if it is adhered to the hot-melt fiber. Also, not all of the particles need be adhered to the fiber. Based on the total amount of the superabsorbent polymer 16,
50% by weight or more is preferably adhered to the fiber,
In particular, 70% by weight or more is preferably adhered to the fiber. The method of adhering the superabsorbent polymer 16 to the fibers will be described later.

When a particle-aggregation-type superabsorbent polymer is used as the superabsorbent polymer, in which a spherical polymer is used as primary particles to aggregate them into secondary particles, all of the primary particles are fibers. If the secondary particles partially adhere to the fiber, the superabsorbent polymer will be fixed to the fiber.

Preferably, the above superabsorbent polymer 16
Are not dispersed in layers in the absorbent sheet 10, but are dispersed in three dimensions as shown in FIG. Therefore, the superabsorbent polymer can be dispersed in a large amount. That is, the upper limit of the spray basis weight of the superabsorbent polymer in the conventional absorbent sheet in which the superabsorbent polymer 16 is dispersed in a layered form (that is, two-dimensional form) is generally about 50 to 50.
100 g / m ² while the above-mentioned absorbent sheet 1
At 0, the superabsorbent polymer 16 can be dispersed three-dimensionally.
The upper limit of the spray basis weight can be about 200 to 300 g / m ^2, and the spray basis weight of the superabsorbent polymer 16 can be increased to about 3 times that of the conventional absorbent sheet. Therefore, the absorptive sheet 10 dramatically increases the amount of liquid absorbed as compared with the conventional absorptive sheet. Furthermore, since the superabsorbent polymer 16 is three-dimensionally dispersed,
The original absorption performance of the superabsorbent polymer 16 is more effectively exhibited. That is, even when the same amount of superabsorbent polymer as that of the conventional absorbent sheet is used, the absorbent performance can be further improved and the absorbent sheet can be made extremely thin. In addition, since it is possible to increase the spray basis weight, it can be suitably used as an absorbent body such as a disposable diaper that requires a large absorbent capacity.

The superb absorbent polymer has a spray basis weight of 5 to 300 g / m ² , and preferably 10 to 250 g / m ² . In addition, when used for applications where the amount of liquid absorbed is not large, in order to make the absorbent sheet extremely thin,
It is preferably ²⁰ to 70 g / m ² . If the spray basis weight is less than 5 g / m ² , the water absorption capacity is insufficient and sufficient function cannot be exhibited. On the other hand, when the spray basis weight is more than 300 g / m ² , the adhesive force between the fiber web and the fiber assembly is lowered, and the superabsorbent polymer is likely to fall off. Therefore, it is preferably within the above range.

The superabsorbent polymer 16 is preferably one capable of absorbing and retaining 20 times or more of its own weight of liquid and capable of gelling. The shape is not particularly limited, and it is spherical, lumpy, grape-like, powdery or fibrous, and preferably has a size of 1
It is in the form of particles of ˜1000 μm (more preferably 10 to 500 μm). Examples of such superabsorbent polymers include starch, cross-linked carboxymethyl cellulose, polymers or copolymers of acrylic acid or alkali metal salts of acrylic acid, polyacrylic acid and its salts, and polyacrylate graft weight. You can list coalescence.
As the polyacrylic acid salt, sodium salt can be preferably used. In addition, acrylic acid is added to maleic acid, itaconic acid, acrylamide, 2-acrylamide-2-
A copolymer obtained by copolymerizing a comonomer such as methyl propane sulfonic acid, 2- (meth) acryloylethane sulfonic acid, 2-hydroxyethyl (meth) acrylate or styrene sulfonic acid within a range not deteriorating the performance of the superabsorbent polymer is also available. It can be preferably used.

Next, the fiber assembly 15 having the absorbent surface 12 in the absorbent sheet 10 of the present invention will be described. Here, the above-mentioned "absorption surface" refers to a surface that first absorbs liquid mainly when the absorbent sheet 10 of the present invention absorbs liquid. That is, in a preferred embodiment of the absorbent sheet 10 of the present invention, the liquid is mainly absorbed from the fiber assembly 15 side.

The fiber assembly does not contain the superabsorbent polymer on the absorbent surface side (the superabsorbent polymer does not exist). Here, "does not contain superabsorbent polymer" does not mean that the fiber assembly does not contain the superabsorbent polymer on its absorbent surface side at all, and is preferable for the absorbent sheet described below. A trace amount of superabsorbent polymer which is inevitably mixed in the production method means that the superabsorbent polymer does not substantially exist on the absorption surface side although it is tolerable.

The above-mentioned fiber assembly is obtained by mechanical entanglement, physical entanglement, thermal bonding, etc. of fibers, and for example, paper or non-woven fabric can be used.
As the paper, it is possible to use paper obtained by wet papermaking, crepe-processed paper, or the like. On the other hand, as the non-woven fabric, various non-woven fabrics such as a card method non-woven fabric, a spunbonded non-woven fabric, and a spunlace non-woven fabric which are mainly composed of synthetic cellulose fibers such as rayon and cupra and natural cellulose fibers such as cotton can be used.

The above fiber assembly preferably contains hydrophilic fibers. As such a hydrophilic fiber, the same as that used in the above-mentioned fiber web can be used. The hydrophilic fiber is contained in an amount of preferably 30 parts by weight or more, and more preferably 50 to 99 parts by weight, based on 100 parts by weight of the fiber assembly.

It is preferable that the fiber assembly is imparted with a wet strength like the fiber web. By imparting the wet strength, the form can be stably maintained even when the absorbent sheet is wet.
Regarding the wet strength of the fiber assembly, the wet strength measured according to JIS-P-8113 is preferably 50 g or more, and more preferably 100 g or more. In order to impart wet strength to the fiber assembly, as in the case of the fiber web, the heat-meltable adhesive fiber or the paper reinforcing agent is blended. It is also preferable to further mix wood pulp or non-wood pulp that forms hydrogen bonds. In this case, the heat-meltable adhesive fiber is preferably contained in an amount of 1 to 50 parts by weight, more preferably 3 to 30 parts by weight, based on 100 parts by weight of the fiber assembly. Further, the paper strength reinforcing agent is preferably contained in an amount of 0.01 to 30 parts by weight, and more preferably 0.02 to 20 parts by weight, based on 100 parts by weight of the fiber aggregate.

The above fiber aggregate is particularly preferably formed by the same composition as the fibers and components forming the above fiber web.

It is also preferable that the fiber assembly is made of a non-woven fabric, and particularly preferably a dry process non-woven fabric, for example, a card process non-woven fabric.

The fiber aggregate has a basis weight of 10 to 20.
It is preferably 0 g / m ² , and 10 to 100 g / m
More preferably, it is ² . The basis weight is 10 g / m ²
If it does not satisfy the above condition, the superabsorbent polymer may project from the fiber assembly and fall off during swelling of the superabsorbent polymer. On the other hand, if the basis weight is more than 200 g / m ² , the density of the fiber assembly may be too high and the absorbent sheet may be too hard.

The fiber assembly may be produced in advance before producing the fiber web, or may be produced simultaneously with the fiber web when producing the absorbent sheet of the present invention. .

In the absorbent sheet of the present invention, the fiber aggregate has a basis weight of 10 to 200 g / m ² , and the superabsorbent polymer has a spray basis weight of 5 to 300 g / m ² , and the fibers are The basis weight of the web is preferably 10 to 200 g / m ² , and the basis weight of the fiber assembly is 10 to 10
It was 0 g / m ^2, sprayed basis weight of the superabsorbent polymer is 5 to 200 g / m ^2, the basis weight of the fiber web 1
It is more preferably 0 to 100 g / m ² .

The total basis weight of the absorbent sheet of the present invention is preferably 21 to 500 g / m ² ,
More preferably from 30 to 300 g / m ² , and 50
More preferably, it is about 200 g / m ² .

The absorbent sheet of the present invention preferably has a fiber density of 0.1 g / cm ³ or more,
More preferably from 0.1 to 0.4 g / cm ³ ,
More preferably, it is 0.1 to 0.2 g / cm ³ .
By setting the fiber density in such a range, gel blocking of the superabsorbent polymer can be more effectively prevented. The fiber density in such a range can be easily realized by using bulky hydrophilic fibers (particularly bulky cellulose fibers).

A particularly preferred embodiment of the absorbent sheet of the present invention is composed of a fiber structure formed from bulky hydrophilic fibers and heat-meltable adhesive fibers or a paper-strengthening agent, and superabsorbent polymer particles. The superabsorbent polymer particles are not present on the absorbent surface that absorbs the liquid of the absorbent sheet and are dispersed and fixed in the fibrous structure, and the thickness of the absorbent sheet is 0.3 to 1 The absorbent sheet is 0.5 mm, and the basis weight of the superabsorbent polymer is 20 to 70 g / m ² . Such an absorbent sheet is extremely thin. Further, if a large amount of liquid is not absorbed, the thickness hardly increases even after absorbing the liquid.
Therefore, when such an absorbent sheet is used, for example, as the absorbent layer of a sanitary napkin, a comfortable fit can be obtained even after absorbing menstrual blood.

When the absorbent sheet of the present invention is used as an absorbent body of a sanitary napkin, the basis weight of the superabsorbent polymer dispersed in the absorbent sheet is preferably 10 to 100.
g / m ^2, more preferably from 20 to 70 g / m ^2,
The basis weight of the fiber assembly is preferably 10 to 80 g / m ² , more preferably 15 to 50 g / m ² , and the basis weight of the fiber web is preferably 10 to 80 g / m ² , and more preferably 15 to 50 g / m ² . m ² and the thickness of the absorbent sheet is preferably 0.3 to 1.5 mm. On the other hand, when the absorbent sheet of the present invention is used as an absorbent body for holding multiple liquids such as disposable diapers, the basis weight of the superabsorbent polymer dispersed in the absorbent sheet is preferably 50 to 300 g / m ² ,
It is more preferably 100 to 250 g / m ² , the basis weight of the fiber assembly is preferably 20 to 200 g / m ² , more preferably 20 to 100 g / m ² , and the basis weight of the fiber web is preferably 20 to 200 g / m ^2. 200 g / m ^2, more preferably from 20 to 100 g / m ^2, the thickness of the absorbent sheet is preferably 0.5 to 1.5 mm.

The thickness of the absorbent sheet of the present invention can be reduced because the absorption efficiency is good because the superabsorbent polymer is dispersed and adhered to the fibers. In particular, the use of bulky cellulose fibers is preferable because the dispersed state of the superabsorbent polymer is further improved. That is, the absorbent sheet of the present invention has a weight of 2.5 g.
/ Cm ² the thickness under load is 0.3 to 1.5 mm,
It is preferably 0.5 to 1.2 mm. Thus, the absorbent sheet of the present invention is extremely thin. Moreover, the increase in thickness is small even after absorbing the liquid. The reason for this is that when a liquid is absorbed, the superabsorbent polymer becomes large and the inter-fiber distance is widened, and as a result, the thickness of the absorbent sheet only increases, and US Pat. This is because the elasticity of the fibers and the thickness of the superabsorbent polymer do not increase due to the opening of the fibers as in No. 5,021,050.

The thickness of the absorbent sheet of the present invention is the thickness after the fiber assembly 15 and the fiber web 18 are integrated, and this thickness is thinner than before the integration. This integration largely contributes to the hot-melt adhesive fiber or the paper-strengthening agent blended in the absorbent sheet. In addition, in the absorbent sheet of the present invention, as described above, since the superabsorbent polymer is dispersed and adhered to the fibers, the absorbent sheet has good absorption efficiency, and thus can be thinned. In particular, the use of bulky cellulose fibers is preferable because the dispersed state of the superabsorbent polymer is further improved. Since the super absorbent polymer is in close contact with the fibers and the fiber assembly 15 and the fiber web 18, the liquid can be smoothly transferred to the super absorbent polymer. In addition, the fiber assembly 15
Since the fibrous web 18 and the fibrous web 18 are bonded to each other by a heat-melting adhesive fiber or a paper-strengthening agent, the structure is kept stable even when wet, and the liquid transferability to the superabsorbent polymer and the superabsorbent polymer It has excellent fixability. The thickness of the absorbent sheet of the present invention is, as described above, US Pat.
Unlike No. 402, No. 5,021,050, etc., it does not easily increase after wetting. In particular, when bulky cellulose fibers are used as hydrophilic fibers, the density becomes low and spaces are formed by the fibers, so the superabsorbent polymer has excellent dispersibility and liquid transfer properties, and is particularly useful for absorbing liquids with high viscosity. Excel. Further, since the space is secured by the fibers, the liquid absorbency after wetting is excellent without the thickness increasing significantly. As described above, in the absorbent sheet of the present invention, the immobilization property and the absorption efficiency of the superabsorbent polymer are improved, so that it is possible to reduce the thickness. In addition, the integration of the fiber assembly 15 and the fiber web 18 into a sheet, and the use of a heat-melting adhesive fiber or a paper-strengthening agent that contributes to the stabilization of the structure when wet is one of the factors for reducing the thickness. Is one.

Next, a preferred method for producing the absorbent sheet of the present invention will be described with reference to the drawings. Here, FIG. 3 is a schematic view showing an apparatus preferably used for producing the absorbent sheet of the present invention. This method is a method for producing an absorbent sheet containing at least a hydrophilic fiber and a heat-meltable adhesive fiber or a paper-strengthening agent, and a superabsorbent polymer, which is at least a hydrophilic fiber and a heat-meltable adhesive fiber or a paper-strength reinforcing agent. A fiber assembly containing a hydrophilic fiber and a heat-melting adhesive fiber or a paper-strengthening agent, on which a superabsorbent polymer is sprinkled on a wet fibrous web formed by wet papermaking with an aqueous slurry containing an agent. Overlaid,
The method is characterized by including a step of drying and integrating these. According to such a method, it is possible to easily disperse the superabsorbent polymer inside the absorbent sheet without causing the absorbent sheet to exist on the absorbent surface for absorbing the liquid. Further, the super absorbent polymer can be easily adhered and fixed to the hydrophilic fibers constituting the absorbent sheet. Furthermore, it becomes easy to make the thickness of the absorbent sheet as thin as 0.3 to 1.5 mm.

The above method will be described in detail. First, the fiber web containing the hydrophilic fibers is formed. The method for forming the fibrous web is not particularly limited, and for example, a dry papermaking method can be used, but a wet papermaking method is preferably used. This is because, as will be described later, when the superabsorbent polymer is applied to the fiber web, the fiber web must be in a wet state and the degree of freedom of the fibers must be extremely high. This is because when the web is formed, it immediately realizes the wet state, and therefore it is possible to save the trouble of making the wet state in another step. Further, in the fiber web obtained by the wet papermaking method, the fibers are not sufficiently bonded to each other before being dried. It also has the advantage that it is easy to be three-dimensionally embedded in the space formed in, and a large amount of superabsorbent polymer can be dispersed.

When the above fibrous web is subjected to wet papermaking,
The fibers and components forming the fibrous web, preferably the hydrophilic fibers and the heat-melting adhesive fibers or the paper-strengthening agent, etc., are dispersed in water to a predetermined concentration to form a slurry. . The concentration of the hydrophilic fiber, the heat-meltable adhesive fiber, the paper-strengthening agent, and the like in the slurry may be the concentration in general wet papermaking. Further, the relative blending ratio between the hydrophilic fiber and the heat-melting adhesive fiber, the paper-strength reinforcing agent, or the like is such that the blending ratio thereof in the fiber web obtained by wet papermaking falls within the above-mentioned range. You can do this.

On the fibrous web thus obtained, the superabsorbent polymer is sprinkled in the wet state. The wet state of the fibrous web is preferably about 20 to 500 parts by weight of water based on 100 parts by weight of the dry fibrous web, and more preferably 50 to 300 parts by weight of water.
If the amount of water is less than 20 parts by weight, the superabsorbent polymer that has been sprayed absorbs water and wets it, making it impossible to obtain tackiness. If the amount exceeds 500 parts by weight, the superabsorbent polymer may be excessively absorbed, resulting in poor drying in the drying step described later.

The superabsorbent polymer is sprinkled on a wet fibrous web. As a result, the superabsorbent polymer absorbs water and becomes tacky, is embedded in the fibers constituting the fibrous web, and is adhered and fixed to the fibers by subsequent drying. Further, since the fibers forming the wet web have a degree of freedom because they are not yet bonded to each other, the superabsorbent polymer can be dispersed three-dimensionally. Therefore, as compared with the conventional absorbent sheet, a larger amount of superabsorbent polymer can be stably fixed. When the superabsorbent polymer is sprayed, the superabsorbent polymer may be evenly sprayed on the entire surface of the wet fibrous web, or if necessary, the wet fibrous web may be spaced in the longitudinal direction. It is also possible to disperse the fibers in a striped manner or intermittently disperse the wetted fibrous web in a shot form in the longitudinal direction.

Next, the fiber assembly is superposed on the surface of the fiber web on which the superabsorbent polymer is sprayed. At this point, the fibers in the fibrous web still have a degree of freedom, so that the superabsorbent polymer is further embedded in the fibrous web and the fibers in the fibrous web and in the fibrous aggregate. Easily intertwined with other fibers.

Subsequently, by drying the superposed body of the fiber web and the fiber aggregate, the fibers are entangled with each other, and further, the action of hydrogen bonding and heat fusion is added, so that the fiber web and the fiber are attached. The superabsorbent polymer which is integrated with the aggregate and adheres to the fibers is dried and fixed, whereby the absorbent sheet of the present invention is obtained. The drying temperature is
The temperature is preferably 100 to 180 ° C., more preferably 1 to 1, although it depends on the kind of fibers to be used.
It is in the range of 05 to 150 ° C. By drying and integrating,
The fiber web and the fiber aggregate are integrated, and the fibers forming the fiber web are bonded to each other to form a sheet. The drying means is not particularly limited, and, for example, a Yankee dryer or an air through dryer can be used.

Particularly preferably, the absorbent sheet of the present invention is produced by an in-line single step using a wet paper machine. That is, as shown in FIG. 3, the fibrous web 18 is formed in the forming part 40 of the wet paper machine, and the fibrous web 18 is dewatered in the suction dewatering step 42 (20 to 20 parts of water based on 100 parts by weight of the dried fibrous web). (Dehydrated to the extent of including 500 parts by weight), the superabsorbent polymer 16 is sprinkled on the fiber web 18 immediately before the press part 44, and the fiber assembly 15 is superposed on the superposed polymer 16, and then the conveyer 45 is applied to the dryer 46. Guide them and dry them with a dryer 46 to integrate them. By such a method, the absorbent sheet 10 of the present invention can be manufactured easily at high speed.

As the wet paper machine, an ordinary paper machine can be used, and examples of such a paper machine include a Fourdrinier paper machine and a round net paper machine. As for the steps other than those described above, the steps in the ordinary papermaking method can be appropriately used.

Although the method of manufacturing the absorbent sheet of the present invention has been described based on its preferred embodiment, it goes without saying that the method of manufacturing the absorbent sheet of the present invention is not limited to such a method.

In the absorbent sheet of the present invention, the superabsorbent polymer is less likely to fall off, and tearing of the sheet due to swelling of the superabsorbent polymer can be prevented. Therefore, the absorbent sheet of the present invention alone can be used as a final absorbent product. The absorbent sheet of the present invention may be mixed with a deodorant, a bactericide and the like at the time of production to enhance other functions of the product.

[0090]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but it goes without saying that the present invention is not limited to these Examples. In the following description, “part” means “part by weight” unless otherwise specified.

[Example 1] Fiber roughness of 0.18 mg / m 2,
Chemical pulp with a roundness of the fiber cross section of 0.32 [Softwood kraft pulp, SKEENA PRIME manufactured by Skeena Cellulose Co.
(Trade name)] and dispersed and mixed in water, and a paper-strength reinforcing agent [polyamide epichlorohydrin resin, trade name; Kamen WS-570, company name; Japan PMC Co., Ltd.] is further added to 100 parts by dry weight of the pulp. One part of the resin component was dispersed and mixed in water, and the dispersion mixture was formed into a fibrous web with a forming part of a wet paper machine so that the dry basis weight was 40 g / m ² . Then, the fiber web was put into a suction box to obtain a moisture content of 20 based on 100 parts of the dry fiber web.
The fibrous web was dewatered to 0 parts. Then, immediately before the press part, the superabsorbent polymer [Polymer Q (trade name) of Kao Corporation] was placed on the wet, moistened fiber web.
Was sprayed substantially uniformly at a basis weight of 50 g / m ² .

Absorbent paper (basis weight: 40 g / m 2) having a composition similar to that of the above-mentioned fiber web as a fiber aggregate on the surface of the above-mentioned fiber web on which the above-mentioned superabsorbent polymer has been sprayed. ² ) are superposed, and the superposed body of the fiber web and the absorbent paper is introduced into a dryer, and 1
By drying and integrating at a temperature of 30 ° C., a single absorbent sheet having a superabsorbent polymer fixed therein was obtained.

The fiber roughness and the roundness of the fiber cross section of the chemical pulp used in the fiber web and the absorbent paper were measured as follows.

<Measurement of fiber roughness> Fiber roughness meter FS-20
0 (manufactured by KAJAANI ELECTRONICS LTD.) Was used.
First, in order to determine the true weight of the chemical pulp, the chemical pulp is dried in a vacuum dryer at 100 ° C. for 1 hour to remove the water present in the chemical pulp.
Approximately 1 g of the above chemical pulp within ± 0.1 mg accuracy
Accurately measure. Next, in order not to damage the chemical pulp, the chemical pulp was completely disintegrated in 150 ml of water with a mixer attached to the fiber roughness meter, and this was 5,000 ml.
It was diluted with water until it became, and 50 ml was accurately measured from the obtained diluted solution, which was used as a fiber roughness measuring solution, and the fiber roughness was determined according to the operation procedure of the fiber roughness meter.

<Measurement of Roundness of Fiber Cross Section> The cross section of the chemical pulp was sliced perpendicularly to the cross sectional direction so as not to change the area, and a cross sectional photograph was taken with an electron microscope. [Avio E manufactured by Nippon Avionics Co., Ltd.
XCEL ”(trade name)], and the roundness of the fiber cross section of the chemical pulp was determined using the formula shown below. The roundness was an average value obtained by measuring 100 points on the fiber cross section of the above chemical pulp.

[0096]

[Equation 1]

[Example 2] A mercerized pulp having a fiber roughness of 0.36 mg / m and a roundness of a fiber cross section of 0.80 [ITT RA
"POROSANIER-J" (brand name) made by YONIER INC.] 95
Part, and 5 parts of polyvinyl alcohol fiber (heat-melting adhesive fiber, Fibribond (trade name) manufactured by Sansho Co., Ltd., hereinafter referred to as "PVA fiber") having a thickness of 1 denier and a length of 3 mm are dispersed and mixed in water. After adjusting the concentration to a predetermined value, the dry basis weight of the dispersion mixture is 40 g in the forming part of the wet paper machine.
A fibrous web was formed to have a thickness of / m ² . Then, the fiber web was dehydrated by a suction box until the water content became 150 parts based on 100 parts of the dry fiber web. Immediately before the press part, a superabsorbent polymer [Polymer Q (trade name) of Kao Corporation] was sprinkled on the wet fibrous web after dehydration to a basis weight of 50 g / m 2.
Sprayed almost evenly with ² .

Absorbent paper (basis weight: 40 g / m 2) having a composition similar to that of the above-mentioned fiber web as a fiber aggregate, on the surface of the above-mentioned fiber web on which the above-mentioned superabsorbent polymer has been sprayed. ² ) are superposed, and the superposed body of the fiber web and the absorbent paper is introduced into a dryer, and 1
By drying and integrating at a temperature of 30 ° C., a single absorbent sheet having a superabsorbent polymer fixed therein was obtained.

Example 3 Fiber roughness of 0.32 mg / m, fiber
Cross-linked pulp with a circular cross section of 0.30 [Weyerhau
"High Bulk Additive HBA-S" made by ser Paper
(Product name)] 70 parts, fiber roughness 0.18, fiber cross section
Coniferous kraft pulp with a roundness of 0.32 [Skeena C
"SKEENA PRIME" (trade name) manufactured by ellulose Co.] 30 copies
Is mixed and dispersed in water, and the dry weight of the mixed pulp is further added.
Paper strength reinforcing agent [polyamide epichloro
Hydrin resin, trade name; Kaimen WS-570, company
Name: Japan PMC Co., Ltd.] with a resin component, 1 part dispersed in water
After mixing and adjusting to a predetermined concentration, the dispersion mixture is wet-processed.
40 g / m dry basis weight in the forming part of the paper machine²To
To form a fibrous web. Then, the fiber web
The dry fiber web 100 with a suction box
The fiber web is removed until the water content is 100 parts based on the parts.
Watered Next, immediately before the press part, wetting after dehydration
A high-absorbency polymer [Kao Corporation
Limmer Q (product name)] sprayed basis weight 50g / m ²Almost uniform
Sprinkled on one.

On the surface of the above-mentioned fibrous web on which the above-mentioned superabsorbent polymer has been sprinkled, as a fiber assembly, an absorbent paper (paper basis weight of 40 g / m 2) having a similar composition to that of the above-mentioned fibrous web is prepared. ² ) are superposed, and the superposed body of the fiber web and the absorbent paper is introduced into a dryer, and 1
By drying and integrating at a temperature of 30 ° C., a single absorbent sheet having a superabsorbent polymer fixed therein was obtained.

[Example 4] A cross-linked pulp having a fiber roughness of 0.32 mg / m and a roundness of the fiber cross section of 0.30 [Weyerhau
"High Bulk Additive HBA-S" made by ser Paper
(Brand name)] 95 parts and 5 parts of the PVA fiber are dispersed and mixed in water to a predetermined concentration, and the dispersion mixture is dried in a forming part of a wet paper machine to give a dry basis weight of 40 g / m ^2.
Was formed into a fibrous web. Then, the fiber web is dried in a suction box to form a dry fiber web 10
The fibrous web was dehydrated to a moisture content of 100 parts based on 0 parts. Then, immediately before the press part, a superabsorbent polymer [Polymer Q (trade name) of Kao Corporation] was sprayed on the wet fibrous web after dehydration substantially uniformly at a basis weight of 50 g / m ² .

On the surface of the above-mentioned fibrous web on which the superabsorbent polymer has been sprinkled, as a fiber aggregate, an absorbent paper (paper basis weight of 40 g / m 2) having the same composition and composition as that of the above-mentioned fibrous web is prepared. ² ) are superposed, and the superposed body of the fiber web and the absorbent paper is introduced into a dryer, and 1
By drying and integrating at a temperature of 30 ° C., a single absorbent sheet having a superabsorbent polymer fixed therein was obtained.

Example 5 Fiber roughness 0.32 mg / m, fiber
Cross-linked pulp with a circular cross section of 0.30 [Weyerhau
"High Bulk Additive HBA-S" made by ser Paper
(Product name)] 90 parts, thickness 1.1 denier, length 5
mm low melting point polyester adhesive fiber [TM manufactured by Teijin Ltd.
-07N (trade name)] is dispersed and mixed in water and prescribed
After the concentration of
Drying basis weight of 40 g / m ²Fiber to be
Weaved web formed. Then, the fiber web is cut into pieces.
Water on the basis of 100 parts of dry fiber web
The fibrous web was dewatered to a fraction of 100 parts. Next
Just before the press part, the wet fibrous web after dehydration
In addition, super absorbent polymer [Polymer Q of Kao Corporation (commercial
Product name)] spraying basis weight 50g / m²Spread almost evenly with
Was.

Of the above-mentioned fiber webs, the surface on which the above-mentioned superabsorbent polymer has been sprayed has been subjected to a hydrophilization treatment, and has a thickness of 2.2 denier and a polyethylene / polypropylene composite fiber of length 38 mm [made by Chisso Co., Ltd.]. ], A dry heat-bonded nonwoven fabric manufactured by a card machine (basis weight: 40 g / m ² )
And the superposed body of the fibrous web and the non-woven fabric is introduced into a dryer and dried at a temperature of 130 ° C.
By integrating, a single absorbent sheet having a superabsorbent polymer fixed therein was obtained.

Comparative Example 1 Chemical pulp used in Example 1 having a fiber roughness of 0.18 mg / m and a roundness of the fiber cross section of 0.32 [SKEENA PRIME (trade name) manufactured by Skeena Cellulose Co.] An absorbent sheet was produced using an absorbent paper which was previously made with a basis weight of 40 g / m ² . That is, on the absorbent paper,
Water is sprinkled based on 100 parts of the absorbent paper (dry) to 200 parts. Then, a superabsorbent polymer [Polymer Q (trade name) manufactured by Kao Corporation] is applied on the wet absorbent paper.
Was sprayed substantially uniformly at a basis weight of 50 g / m ² .

Among the absorbent papers, an absorbent paper having a basis weight of 40 g / m ² having the same composition as the absorbent paper was superposed on the surface on which the superabsorbent polymer was sprayed, and the ^two absorbent papers were combined. The superposed bodies were pressure-bonded and integrated, and then dried with a dryer to obtain an absorbent sheet having a total basis weight of 130 g / m ² . In this absorbent sheet, the absorbent paper on which the superabsorbent polymer has been dispersed is not in the form of a wet fiber web, but the pulp fibers are strongly bound to each other, and the absorbent paper between the two absorbent papers is high. The absorbent polymer is sandwiched in layers.

Comparative Example 2 Water was sprinkled on the same absorbent paper as in Comparative Example 1 until 100 parts of the absorbent paper (dry) was reached to 10 parts. Then, a superabsorbent polymer [Polymer Q (trade name) manufactured by Kao Corporation] is applied on the wet absorbent paper.
Was sprayed substantially uniformly at a basis weight of 50 g / m ² .

Among the absorbent papers, an absorbent paper having a basis weight of 40g / m ² having the same composition as the absorbent paper was superposed on the surface on which the superabsorbent polymer was sprayed, and the two absorbent papers Emboss crimping the overlapped body through a lattice embossing roll that is divided into 5 mm sections in the vertical and horizontal directions.
After being integrated, it is dried with a dryer and the total basis weight is 13
An absorbent sheet of 0 g / m ² was obtained. In this absorbent sheet, the absorbent paper on which the superabsorbent polymer has been dispersed is not in the form of a wet fiber web, but the pulp fibers are strongly bound to each other, and the absorbent paper between the two absorbent papers is high. The absorbent polymer is pressure-bonded by embossing.

Comparative Example 3 On the same absorbent paper as in Comparative Example 1, an adhesive [Movinyl 710 manufactured by Hoechst Synthetic Co., Ltd. was used.
(Trade name)] at a basis weight of 20 g / m ² , and then a super-absorbent polymer [Polymer Q (trade name) of Kao Co., Ltd.] is sprayed at a basis weight of 50 g / m ² to be substantially uniform. Sprayed.

Of the absorbent paper, an absorbent paper having a basis weight of 40 g / m ² having the same composition as the absorbent paper was superposed on the surface of the absorbent paper on which the superabsorbent polymer was sprayed. The superposed bodies were pressure-bonded and integrated, and then dried with a dryer to obtain an absorbent sheet having a total basis weight of 150 g / m ² . In this absorbent sheet, the absorbent paper on which the superabsorbent polymer has been dispersed is not in the form of a wet fiber web, but the pulp fibers are strongly bound to each other, and the absorbent paper between the two absorbent papers is high. The absorbent polymer is fixed in layers by an adhesive.

Comparative Example 4 A dry absorbent sheet containing synthetic pulp and a super absorbent polymer was produced. That is, a pulp sheet consisting of 25 parts of polyethylene synthetic pulp and 75 parts of chemical pulp [softwood pulp, manufactured by Hercules Co., Ltd.] was defibrated with a hammer mill to obtain a basis weight of 80 g / m ^2.
Super absorbent polymer [Aqualic CAW-4 (trade name) manufactured by Nippon Shokubai Co., Ltd.] when forming a dry absorbent sheet of
Was mixed into the raw material so as to be 50 g / m ² , and then polyethylene synthetic pulp was fused and integrated by hot air treatment. The dry absorbent sheet has a super absorbent polymer on its surface.

Comparative Example 5 A superabsorbent polymer [Aqua manufactured by Nippon Shokubai Co., Ltd.] was used between pulp sheets [coniferous pulp, manufactured by Hapix Co., Ltd.] having a basis weight of 45 g / m ² formed by the air laid method. Rick CAW-4 (product name)] is basis weight 5
The absorbent sheet was sprayed so that the amount became 0 g / m ² , and then the pulp was fixed with a chemical binder to produce an absorbent sheet.

Tables 1 and 2 show the compounding compositions and manufacturing methods of the absorbent sheets of the present invention in Examples 1 to 5 and the absorbent sheets of Comparative Examples 1 to 5, respectively.

[0114]

[Table 1]

[0115]

[Table 2]

Various tests were conducted on each absorbent sheet by the methods described below. The results are shown in Table 3.
Shown in

<Thickness> A 2.5 g / cm ² load was applied to the upper surface of the absorbent sheet cut into an appropriate size with a load area of 10 cm ² (disc having a radius of 17.8 mm), and the thickness was measured with a thickness meter. It was measured. The average value of 10 points in total was taken as the thickness.

<Detachment test of superabsorbent polymer> 70 × 2
After measuring the weight of the absorbent sheet cut out to 00 mm,
This is put in a plastic bag with a chuck having a length of 280 mm and a width of 200 mm, and in this state, shaking is performed by shaking 50 times by hand. After the test, the weight change of the absorbent sheet was measured, and the colored water dyed with Blue No. 1 (0.3
(100 g of water / 100 ml of water) is added to a plastic bag to swell the superabsorbent polymer, and the degree of dropout is visually determined. ○: Almost no dropout of the superabsorbent polymer was observed. Δ: Some dropout of the superabsorbent polymer is observed. X: The dropout of the superabsorbent polymer is considerably observed. The measurement was performed 10 times, and the average value was defined as the amount of dropout.

<Sheet strength of absorbent sheet when wet> 2
Hold the absorbent sheet cut out to a size of 00 mm x 200 mm in your hand, and put on the desk colored water dyed with Blue No. 1 (0.3 g / water 1
(00 ml) was dripped, and the colored water was wiped off with an absorbent sheet held in the hand. A wiping test was repeated three times in total (a total of 30 g of the absorbent sheet was absorbed), and a tearing of the sheet on the surface of the absorbent sheet and a dropout test of the superabsorbent polymer were performed. ○: The surface of the absorbent sheet is not broken, and the superabsorbent polymer does not fall off. Δ: The surface of the absorbent sheet is slightly broken, but the superabsorbent polymer does not fall off. X: The surface of the absorbent sheet was torn and the superabsorbent polymer was dropped off.

<Saturated absorption amount> A 5 cm square absorbent sheet was placed in a bag made of non-woven fabric, and the entire bag was immersed in ion-exchanged water for 10 minutes. After removing the bag from the ion-exchanged water, it was hung in the air for 1 hour to remove the adhering water, and then the weight was measured, and the increase in the weight per 1 g of the absorbent sheet was measured as the saturated absorption amount (g / g). ).

<Absorption Rate> As shown in FIG. 4, a hole having a diameter of 1 cm was formed in the center of the 15 cm square absorbent sheet 10.
The time required for absorption of physiological saline by injecting 20 ml of physiological saline through the above holes with a 0 cm square transparent acrylic plate 20 and a weight 22 placed on the absorbent sheet 10 under a load of 5 g / cm ^2. Was taken as the absorption rate. The absorption rate was measured twice, but the second injection (resorption rate) was 1
The measurement was performed 1 minute after the first measurement.

<Measurement of Liquid Return> After measuring the absorption rate, 10
As shown in FIG. 5, 15 minutes have passed on the absorbent sheet.
10 pieces of cm square filter paper 24 (Toyo Filter Paper TYPE2) are piled up, and a 15 cm square acrylic plate 26 and a weight 22 are further placed on it.
Apply a load of g / cm ² for 1 minute, then filter paper 24
Was taken out, and the weight of the physiological saline absorbed by the filter paper 24 was used as the liquid return amount.

[0123]

[Table 3]

As is clear from the results shown in Table 3, the absorbent sheet of the present invention is an absorbent sheet produced by conventional water spraying, embossing integration or integration with an adhesive, synthetic pulp, chemical binder, etc. Compared with the above-mentioned absorbent sheet, it is superior in immobilization of superabsorbent polymer and surface strength of the sheet. Moreover, it can be seen that the absorption characteristics are excellent such that the absorption rate is high and the amount of liquid returned is small.

In particular, the absorbent sheet of the present invention (Example 1) composed of chemical pulp and superabsorbent polymer and two absorbent papers of the same chemical pulp are fixed in a layered manner. As is clear from the comparison of the results with the conventional absorbent sheets (Comparative Examples 1 to 3), the absorbent sheet of the present invention has excellent immobilization ability for superabsorbent polymers and absorption characteristics (particularly reabsorption). It turns out that it is excellent in speed).

Further, as the hydrophilic fiber constituting the absorbent sheet, a bulky cellulose fiber capable of expressing a bulky structure even when wet, for example, when the fiber roughness in Example 2 is 0.30 mg / m 2 or more. Further, when the mercerized pulp having a roundness of the fiber cross section of 0.5 or more and the crosslinked pulp in Examples 3 to 5 are used, the absorption characteristics are further improved, and particularly the absorption rate and the liquid return property are more improved. It can be seen that it will be further improved.

An important feature of the absorbent sheet of the present invention is that the superabsorbent polymer is dispersed and adhered between the fibers constituting the fiber web dispersed with the superabsorbent polymer. Very little loss of the superabsorbent polymer, and even when the superabsorbent polymer absorbs and swells, the superabsorbent polymer is difficult to gel-block, and as a result, has excellent absorption characteristics such as reabsorption rate. Moreover, the liquid can be reliably fixed with the superabsorbent polymer, and the amount of liquid returned is small. Furthermore, according to the preferable method for producing the absorbent sheet of the present invention, the absorbent sheet of the present invention can be produced more rapidly and easily.

[0128]

The absorbent sheet of the present invention is capable of reliably fixing the superabsorbent polymer in the sheet, the superabsorbent polymer is hardly detached, and the superabsorbent polymer is less likely to undergo gel blocking. Excellent in speed and liquid fixability. Further, the absorbent sheet of the present invention has a high absorbency despite being extremely thin.

Therefore, according to the present invention, it is possible to obtain an ultrathin absorbent sheet in which the loss of the superabsorbent polymer is remarkably improved and the absorption rate and the absorption capacity are excellent.

Further, according to the preferable method for producing the superabsorbent sheet of the present invention, the production process is remarkably accelerated as compared with the conventional method for producing the absorbent sheet.
In addition, a complicated processing process for fixing the superabsorbent polymer is not required, which greatly simplifies the manufacturing process.

Further, according to the above-mentioned manufacturing method, not only the superabsorbent polymer can be sprinkled all over the absorbent sheet, but it can also be partially streaked in the longitudinal direction or intermittently sprinkled in the longitudinal direction. Therefore, the range in which the superabsorbent polymer is sprayed can be set according to the application, and the absorbent sheet can be manufactured more economically.

[Brief description of drawings]

FIG. 1 is a schematic view showing a cross section of an absorbent sheet of the present invention.

FIG. 2 is a schematic view showing a cross section of a preferred absorbent sheet of the present invention.

FIG. 3 is a schematic diagram showing a preferred method for producing the absorbent sheet of the present invention.

FIG. 4 is a schematic diagram showing measurement of absorption rate.

FIG. 5 is a schematic diagram showing measurement of a liquid return amount.

FIG. 6 is a schematic view showing a cross section of a conventional absorbent sheet.

[Explanation of symbols]

 10 Absorbent Sheet 12 Absorbing Surface 15 Fiber Aggregate 16 Super Absorbent Polymer 18 Fiber Web 30, 31 Tissue 40 Forming Part 42 Suction Dewatering Step 44 Press Part 46 Dryer

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location A61F 13/18 307C A41B 13/02 Z (72) Inventor Mari Kaganoi 2264-2 (72) Asakura, Kochi City, Kochi Prefecture ) Minoru Nakanishi 23-3-11 Midori, Minamikawachi-cho, Kawachi-gun, Tochigi Prefecture (72) Inventor Mitsuji Hamajima 1172-8 Yokoyama-cho, Utsunomiya-shi, Tochigi Prefecture (72) Koyu Yamamoto Akabane, Kai-cho, Haga-gun, Tochigi Prefecture 2606-6 Kao Akabane Dormitory (72) Inventor Hironori Kawasaki 4954 Kaohashi, Kaigamachi, Haga-gun, Tochigi Kao Castle Dormitory

Claims (10)

[Claims] 1. An absorbent sheet comprising at least a hydrophilic fiber and a hot-melt adhesive fiber or paper reinforcing agent and a superabsorbent polymer; said superabsorbent polymer being an absorbent surface on which said absorbent sheet absorbs liquid. Is not present in the absorbent sheet, is dispersed and arranged inside the absorbent sheet, and is fixed by being adhered to the hydrophilic fibers constituting the absorbent sheet; ~ 300g /
m ² ; the absorbent sheet has a thickness of 0.3 to 1.5
mm .; an absorbent sheet, characterized in that 2. The absorbent sheet is composed of a fiber assembly and a fiber web, and the fiber assembly and the fiber web are integrated, and the fiber assembly has the absorbent surface. The absorbent surface side does not contain the superabsorbent polymer, the fiber web is formed of at least the hydrophilic fiber, and the superabsorbent polymer is mainly dispersed and arranged in the fiber web. The absorbent sheet according to claim 1. 3. The fiber assembly has a basis weight of 10 to 200 g.
/ M ² , and the basis weight of the fiber web is 10 to 200 g / m ² .
The absorbent sheet according to claim 2. 4. The absorbent sheet according to claim 1, wherein the hydrophilic fibers are bulky cellulose fibers. 5. The absorbent sheet according to claim 4, wherein the bulky cellulose fiber has a fiber roughness of 0.3 mg / m or more. 6. The absorbent sheet according to claim 4, wherein the bulky cellulose fiber has a roundness of a fiber cross section of 0.5 to 1. 7. The absorbent sheet according to claim 4, wherein the bulky cellulose fibers are crosslinked cellulose fibers. 8. A fibrous structure formed from bulky hydrophilic fibers and heat-meltable adhesive fibers or a paper-strengthening agent, and superabsorbent polymer particles, wherein the superabsorbent polymer particles are the absorbent particles. The sheet does not exist on the absorption surface that absorbs liquid, is dispersed and fixed in the fiber structure, and the thickness of the absorbent sheet is 0.3 to 1.5 mm,
The basis weight of the superabsorbent polymer is 20 to 70 g / m ²
Absorbent sheet characterized by being. 9. A method for producing an absorbent sheet comprising at least hydrophilic fibers and heat-meltable adhesive fibers or paper-strengthening agent and superabsorbent polymer, which comprises at least hydrophilic fibers and heat-meltable adhesive fibers or paper-strength. A fiber aggregate containing a hydrophilic fiber and a heat-meltable adhesive fiber or a paper-strengthening agent, on which a superabsorbent polymer is sprinkled on a moistened fibrous web formed by wet papermaking with an aqueous slurry containing a reinforcing agent. A method for producing an absorbent sheet, which comprises the steps of stacking bodies and drying and integrating them. 10. The fiber web is formed in a forming part, the fiber web is dehydrated in a suction dehydration step, the superabsorbent polymer is sprinkled on the fiber web immediately before the press part, and the fiber aggregate is formed thereon. The manufacturing method according to claim 9, comprising a step of stacking the bodies and then drying and integrating them with a dryer.