JPH08120567A - Bulky crosslinked cellulose fiber - Google Patents

Abstract

PURPOSE: To produce a cellulose fiber having low compression set in wet state, keeping the bulkiness and sufficient strength, exhibiting high absorptivity unattainable by conventional cellulose fiber and resistant to slippage. CONSTITUTION: This bulky crosslinked cellulose fiber is produced by the intramolecular and/or intermolecular crosslinking of a cellulose fiber having a fiber fineness of >=0.30mg/m, especially 0.33-1mg/m with a crosslinking agent. The crosslinking agent is e.g. an N-methylol compound, a polycarboxylic acid or a polyglycidyl ether compound and the amount of the agent is 0.2-20 pts.wt. based on 100 pts.wt. of the cellulose fiber. The cellulose fiber preferably has a roundness of >=0.5, especially 0.55-1.0 and is produced preferably by mercerizing wood pulp having fiber fineness of >=0.3mg/m to increase the roundness of the crosssection and crosslinking the mercerized product. The bulky crosslinked cellulose fiber has a compression set of preferably <40%, especially <35% in wet state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bulky and highly liquid-absorbent cellulose fiber, and more specifically, to a crosslinked cellulose obtained by crosslinking the inside and / or the inside of the cellulose fiber with a suitable crosslinking agent. Regarding fibers.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
Many proposals have been made for absorbent articles aimed at improving the absorbability of body fluids, and many improvements have been made. Most of these improvements have been in improving the liquid absorption rate, preventing the liquid from returning from the absorber to the surface material, preventing liquid leakage, and reducing the stickiness of the absorbent article to the body.

For example, regarding the material of the absorbent body, instead of using hydrophilic absorbent paper or pulp which absorbs and holds the liquid in the physical fine space, the liquid is subjected to a physicochemical action, that is, It has been proposed to use a super-absorbent polymer that improves the liquid absorption capacity by absorbing and holding the liquid by ionic osmotic pressure and prevents the liquid from returning after absorbing the liquid. The use of the superabsorbent polymer improves the absorbency of the liquid, and at present, most absorbent articles use an absorbent body in which pulp and a superabsorbent polymer are used in combination.

However, even with such an absorbent article, liquid leakage prevention is still insufficient, as suggested by the fact that the first dissatisfaction with the absorbent article is liquid leakage.

In other words, a superabsorbent polymer that absorbs and retains a liquid by ionic osmotic pressure has a limited liquid absorption rate, and the superabsorbent polymer cannot absorb the liquid unless it is wet with the liquid. Had to be used in combination with pulp having a high liquid absorption rate. However, pulp has a problem in that when a flexible fluff absorbent layer is formed as an absorber, it locally absorbs liquid, and thus the diffusivity for efficiently utilizing the entire absorber is poor.

[0006] Further, while pulp exhibits a certain degree of compression recovery and bending recovery when it is dried, its strength is extremely reduced when it is wet, and it hardly shows those recovery properties. Therefore, when stress is applied to the wet pulp, Compressive deformation of pulp (hereinafter,
The liquid absorption space is significantly reduced.
As a result, the once absorbed liquid easily returns to the body side due to the twist, which causes stickiness and liquid leakage.

Further, the liquid absorption space is reduced due to this twisting, whereby the movement resistance when the liquid moves to the polymer is increased. As a result, not only the liquid absorption efficiency of the polymer is lowered, but also the re-absorption rate of the entire absorbent body after twisting is significantly reduced, which often causes liquid leakage.

In order to improve the poor diffusivity of these fluff pulps and the reduction of the liquid absorption space due to twisting, there is also a proposal to improve the diffusivity and the liquid return property by compressing / densifying the pulp. Have been reported up to. However, these proposals not only solve the essential problem that the strength of pulp becomes extremely weak when it gets wet, but conversely, the distance between fibers of the pulp becomes too close, so that liquid becomes a polymer. The movement resistance at the time of movement greatly increases, resulting in a disadvantage that the liquid absorption efficiency of the polymer deteriorates.

Accordingly, the object of the present invention is to have a small amount of compressive deformation when wet, retain bulkiness, have sufficient strength, and have a high absorbency that cannot be achieved by conventional cellulose fibers. And to provide a cellulose fiber that is resistant to twisting.

[0010]

Means for Solving the Problems As a result of intensive investigations aimed at achieving the above object, the present inventors have found that cross-linking a specific cellulose fiber prevents twisting / settling even when wet, and It was found that the liquid permeability and absorption can be improved.

The present invention has been made on the basis of the above findings, and is characterized in that the inside and / or between the molecules of the cellulose fiber having a fiber roughness of 0.30 mg / m 2 or more are crosslinked with a crosslinking agent. The above object is achieved by providing a bulky crosslinked cellulose fiber.

The bulky cross-linked cellulose fiber of the present invention is particularly useful as an absorbent body in absorbent articles such as sanitary napkins, incontinence pads and disposable diapers, and especially as absorbent paper used in the absorbent body in absorbent articles. It is useful.

[0013]

The bulky cross-linked cellulose fiber of the present invention has little twisting / staining even when wetted with a liquid, and can stably maintain a liquid absorbing space for temporarily absorbing the liquid. In addition, the liquid absorption space formed by the bulky highly crosslinked cellulose fibers of the present invention allows the liquid to pass therethrough quickly.

The bulky highly crosslinked cellulose fiber of the present invention will be described in more detail below.

The highly bulky crosslinked cellulose fiber of the present invention is a cellulose fiber having a fiber roughness of 0.30 mg / m or more, which is obtained by crosslinking the inside and / or the inside of the molecule with a crosslinking agent. As the cellulose fibers, any of natural cellulose fibers such as wood pulp and cotton and regenerated cellulose fibers such as rayon and cupra may be used. From the viewpoint of cost, it is preferable to use wood pulp, and particularly softwood pulp (NBKP) is preferably used. These cellulose fibers may be used alone or in combination of two or more.

Examples of the cross-linking agent used for cross-linking cellulose fibers 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: Examples include polyols such as dimethylhydroxyethylene urea; polyglycidyl ether-based crosslinking agents, and the like. These cross-linking agents may be used alone or in combination of two or more.

The amount of the crosslinking agent used is 100
It is preferably 0.2 to 20 parts by weight with respect to parts by weight. If the amount is less than 0.2 parts by weight, the crosslinking density is low,
The elastic modulus when wet is low, and twisting / sagging may occur. When it exceeds 20 parts by weight, the cellulose fiber becomes too rigid, and when stress is applied, the fiber may become brittle, which is not preferable. .

In order to cross-link cellulose fibers using such a cross-linking agent, for example, an aqueous solution of the cross-linking agent to which a catalyst is added if necessary is impregnated with the cellulose fibers, and the cross-linking agent aqueous solution has a designed adhesion amount. In this way, dehydration and heating to the crosslinking temperature are carried out, or an aqueous solution of the crosslinking agent is sprayed onto the cellulose fibers by spraying or the like in a designed adhesion amount, and then heated to the crosslinking temperature to carry out the crosslinking reaction.

The highly bulky crosslinked cellulose fiber of the present invention is one in which the intramolecular and / or intermolecular crosslinkage of the cellulose fiber is crosslinked. As a result, twisting / sagging does not occur when the bulky crosslinked cellulose fibers are wet with liquid. Further, the cross-linking makes it difficult for the bulky cross-linked cellulose fiber itself to absorb the liquid, and as a result, the fiber itself becomes difficult to swell, so that the fiber can be kept stable. In the present invention, due to the synergistic effect of both of them, it becomes possible to keep the distance between the fibers stable even when the bulky crosslinked cellulose fibers are wet with a liquid. Therefore, it is more preferable that the bulky crosslinked cellulose fiber is crosslinked both inside and between the molecules of the cellulose fiber.

In the present invention, the fiber roughness is 0.3 mg /
Crosslink the cellulose fibers having a size of m or more. Preferably, the fiber roughness is 0.3-2 mg / m, 0.33-1
More preferably, it is mg / m. Fiber roughness is 0.3mg
Cellulose fibers of less than / m are thin and supple,
The effect of cross-linking is difficult to manifest. Cellulose fibers having a fiber roughness of more than 2 mg / m are not preferable because the rigidity may become too high.

In the present invention, "fiber roughness" means
It is used as a scale for expressing the thickness of fibers such as wood pulp in which the thickness of the fibers is not uniform. For example, a fiber roughness meter (FS-200, KAJAANI ELEC
TRONICS LTD.).

Cellulose fibers having a fiber roughness of 0.3 mg / m 2 or more include, for example, softwood kraft pulp (Fe
"ALBACEL" (brand name) made by deral Paper Board Co.,
And "INDORAYON" (trade name) manufactured by PT Inti Indorayon Utama.

Generally, in absorbent paper used for absorbent articles, the closer the fiber cross section is to a perfect circle, the smaller the movement resistance when the liquid moves through the absorbent paper. Also,
The closer the cross-sectional shape of the cellulose fiber is to a perfect circle, the more easily the effect of cross-linking when cross-linked with the cross-linking agent is exhibited. Therefore, in the present invention, it is more preferable that the cross-sectional shape of the cross-linked cellulose fiber is close to a perfect circle. Specifically, the roundness of the cellulose fiber is preferably 0.5 or more, and more preferably 0.55 to 1.0.
In the present invention, particularly advantageous effects can be obtained when the fiber roughness of the cross-linked cellulose fiber is 0.3 mg / m or more and the circularity is 0.5 or more.

As described above, in the present invention, it is preferable to use wood pulp as the cellulose fiber,
Generally, the cross section of 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.

As described above, the bulky crosslinked cellulose fibers of the present invention are mercerized crosslinked pulp obtained by crosslinking mercerized pulp having a roundness of 0.5 or more obtained by mercerizing ordinary wood pulp. Is preferred.

The mercerized crosslinked pulp can be obtained, for example, by mercerizing the above-mentioned wood pulp having a fiber roughness of 0.3 mg / m or more to increase the roundness of its cross section and then crosslinking it. It is also possible to obtain the mercerized pulp of, and cross-link it.

Commercially available mercerized pulp that can be used in the present invention includes "FILTRANIER" (trade name) manufactured by ITT Rayonier Inc. and "POROSANIER" manufactured by the same company.
(Product name) and the like.

The bulky cross-linked cellulose fiber of the present invention preferably has a small twist / sag when wet with a liquid.
That is, it is preferable that the residual strain when the bulky crosslinked cellulose fibers are compressed when wet is small. The smaller the compressive residual strain, the better. Specifically, the compressive residual strain of the bulky crosslinked cellulose fibers when wet is preferably less than 40%, and more preferably less than 35%. When the compressive residual strain of the bulky crosslinked cellulose fibers when wet is 40% or more, the liquid absorption rate when absorbing a liquid and the liquid absorption capacity may decrease, and the twist / sag when wet may increase. As a result, the liquid absorption space is reduced, the distance between the fibers is reduced, and it may be difficult to keep the bulky crosslinked cellulose fiber of the present invention stable, which is not preferable.

Stable compressive residual strain of cellulose fiber 4
In order to maintain the distance between the cellulose fibers to be less than 0% and to keep the distance between the cellulose fibers stable, it is an important requirement to adjust the thickness of the bulky crosslinked cellulose fibers in addition to crosslinking the cellulose fibers. The reason is that the thicker the bulky crosslinked cellulose fiber, the easier it is to stabilize the compression residual strain of the bulky crosslinked cellulose fiber at a low value when wet, and the interfiber distance does not decrease. Because. Since the thickness of the bulky crosslinked cellulose fiber depends on the thickness of the cellulose fiber to be crosslinked, the thickness of the bulky crosslinked cellulose fiber may be adjusted as appropriate to adjust the thickness of the bulky crosslinked cellulose fiber. As described above, since the fiber roughness is a measure of the thickness of the fiber, in the present invention,
A bulky cross-linked cellulose fiber obtained by cross-linking the inside and / or the inter-molecule of a cellulose fiber having a fiber roughness of 0.30 mg / m or more with a compressive residual strain when wet of 40.
%, It is preferable to use a cross-linking agent inside and / or between the cellulose fibers having a fiber roughness of 0.30 mg / m or more and a roundness of 0.5 or more. It is preferable to use crosslinked bulky highly crosslinked cellulose fibers having a compression residual strain of less than 40% when wet.

As described above, the bulky crosslinked cellulose fiber of the present invention is particularly useful as the absorbent body itself of an absorbent article or as an absorbent paper used for the absorbent body. As such an absorbent paper, there is a permeable absorbent paper which has a large liquid absorbing space and can quickly absorb / permeate the liquid, and a diffusible absorbent paper which can quickly diffuse the liquid into a large area. Hereinafter, the transparent absorbent paper and the diffusive absorbent paper will be described.

The permeable absorbent paper comprises 50 to 98 parts by weight of the bulky crosslinked cellulose fiber of the present invention, preferably 70 to 98.
Parts by weight and 2 to 50 parts by weight, and preferably 2 to 30 parts by weight of the hot-melt adhesive fiber. The basis weight is preferably 20 to 60 g / m ² , and more preferably 20 to 50.
g / m ² . In the above permeable absorbent paper, when the bulky crosslinked cellulose fiber of the present invention is less than 50 parts by weight, the resulting permeable absorbent paper has an insufficient permeation rate, and when it exceeds 98 parts by weight, it becomes difficult to form a sheet. Further, in the above permeable absorbent paper, when the heat-melting adhesive fiber is less than 2 parts by weight, the strength as the permeable absorbent paper is insufficient and it becomes difficult to form a sheet, and when it exceeds 50 parts by weight, the permeable absorbent paper is absorbed. Permeability of the paper is reduced and the rigidity of the entire sheet becomes too high.

As the heat-melting adhesive fiber, fibers which are melted by heating and adhere to each other can be used. Specific examples thereof include polyolefin fibers such as polyethylene, polypropylene and polyvinyl alcohol, polyester fibers, polyethylene. -Polypropylene composite fiber, polyethylene-polyester composite fiber, low melting point polyester-polyester composite fiber, polyvinyl alcohol-polypropylene composite fiber having a hydrophilic fiber surface, 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 and polyester.

The heat-meltable adhesive fiber generally has a fiber length of 2 to 60 mm and a fiber diameter of 0.5 to 3 denier.

The method for producing the above-mentioned permeable absorbent paper is not particularly limited, and for example, a commonly used wet or dry papermaking method can be used. When the wet papermaking method is used, the bulky highly crosslinked cellulose fibers and the heat-meltable adhesive fibers of the present invention are dispersed in water, and if necessary, other components are added to form a slurry, and the slurry is used on a paper machine. To make paper. After papermaking, calendering or crepe processing can be carried out if necessary.

Examples of the other components include other pulps such as softwood pulp, hardwood pulp and straw pulp, and dialdehyde starch, sponge, sodium carboxymethyl cellulose and the like as a strong auxiliary agent. These components can be added in an amount of 0 to 20 parts by weight.

The permeable absorbent paper thus produced has a thickness of 0.2 to 2.0 under a load of 2.5 g / m ^2.
It is preferably mm. The reason for this is that the absorption / permeation space for temporarily absorbing body fluid can be made sufficiently large as long as the thickness is within the above range.
Particularly preferably, the thickness is 0.3 to 1.5 mm.

Furthermore, it is preferable that the permeable absorbent paper has a fast liquid passage time. In particular, the permeable absorbent paper preferably has a transit time of 10 g of an aqueous 85% by weight glycerin solution of 50 seconds or less, and more preferably 5 to 40 seconds. If the passage time exceeds 50 seconds, it becomes difficult for the liquid to move quickly in the permeable absorbent paper, and the liquid may not be absorbed by the permeable absorbent paper and may remain on the surface for a long time. In addition to having the permeation time as described above, the permeable absorbent paper further preferably has the thickness as described above from the viewpoint of rapid liquid permeation. The method of measuring the transit time will be described later.

Most of the conventional absorbent papers used for absorbent articles are prepared by wet-making natural pulp such as ordinary softwood pulp, and the absorbent paper obtained by wet-making such natural pulp is In the process of dehydration / wet pressure / drying during papermaking, when water is dehydrated from the paper layer and the paper layer is dried, the interfacial tension of water acting between pulp fibers and hydrogen bonding cause very strong tightening between pulp fibers. Power works. Since the distance between the pulp fibers is shortened by the tightening force, the conventional absorbent paper is very slow in liquid absorption / permeation, and further, the liquid absorption space is reduced, resulting in deterioration of liquid permeability. Was there. On the other hand, in the above permeable absorbent paper, by blending the bulky crosslinked cellulose fibers of the present invention, hydrogen bonds that act between fibers during wet papermaking are suppressed, and the tightening force that acts between fibers is weakened, The liquid absorption space is enlarged and the liquid flow of absorbing / permeating / diffusing the liquid is controlled.

Next, the diffusive absorbent paper will be described. The diffusible absorbent paper is 20 to 80 parts by weight, preferably 30 to 70 parts by weight of the bulky crosslinked cellulose fibers of the present invention, 80 to 20 parts by weight of hydrophilic fine cellulose fibers, preferably 70 to 30 parts by weight, and heat. Meltable adhesive fiber 0-30
Parts by weight, preferably 0 to 20 parts by weight and having a basis weight of 20 to 60 g / m ² , preferably 20 to 50 g / m ² .
² In the above-mentioned diffusible absorbent paper, when the bulky highly crosslinked cellulose fibers of the present invention are less than 20 parts by weight or the hydrophilic fine fibers exceed 80 parts by weight, a strong tightening force acts between the fibers during paper making, and the liquid absorption space becomes small, The space where the liquid can be substantially diffused is reduced. In the above diffusible absorbent paper, the bulky crosslinked cellulose fiber of the present invention is 80
If the amount exceeds 5 parts by weight or the hydrophilic fine fibers are less than 20 parts by weight, the distance between the fibers becomes large and the ability to diffuse body fluid becomes insufficient, which is not preferable.

As the hydrophilic fine fibers, fibers having a hydrophilic surface and a large surface area can be used, and the fiber roughness is preferably less than 0.2 mg / m, preferably 0.01 to 0. 0.2 mg / m, and the circularity is 0.
Less than 5, preferably 0.1 to 0.4, or fiber surface area of 1.0 m ² / g or more, preferably hydrophilic fibers is 1-20 m ² / g are preferably exemplified. Such hydrophilic fine fibers generally have a fiber length of 0.5 to 15 mm.

The hydrophilic fine fibers are not particularly limited as long as they have the above-mentioned physical properties, and for example, wood pulp,
Examples thereof include cellulosic fibers such as cotton and rayon, and synthetic fibers having a hydrophilic group such as acrylonitrile and polyvinyl alcohol. In particular, wood pulp can be used preferably because it is available at a very low cost and the surface area of the fiber can be controlled by controlling the beating conditions. As such wood pulp, NBK
P (for example, "SKEENAPRIM made by Skeena cellulose Co.
Finely beaten "E" (brand name), LBKP
(“PRIME ALBERT ASP” manufactured by Waferuser Paper Co., Ltd.
EN HANDWOOD "(trade name), and straw pulp. The hydrophilic fine fibers may be used alone or in combination of two or more.

The diffusible absorbent paper preferably contains up to 30 parts by weight of hot-melt adhesive fibers. If the amount of the heat-meltable adhesive fiber exceeds 30 parts by weight, the hydrophilicity of the diffusive absorbent paper may be lowered, and the diffusibility and permeability of the liquid may be lowered. By including the heat-melting adhesive fiber in the diffusive absorbent paper, the effect of further stabilizing the fiber space when wet is further produced. More preferably, the diffusible absorbent paper comprises up to 20 parts by weight, particularly preferably 2 to 20 parts by weight of hot-melt adhesive fibers. As the heat-melting adhesive fiber, the same ones as the heat-melting adhesive fiber described for the permeable absorbent paper can be used.

The method for producing the diffusible absorbent paper is not particularly limited, and for example, a commonly used wet or dry papermaking method can be used. When the wet papermaking method is used, the bulky highly crosslinked cellulose fiber, the hydrophilic fine fiber and the heat-meltable adhesive fiber of the present invention are dispersed in water, and further, if necessary, other components are added to form a slurry. The slurry is made into paper using a paper machine. After papermaking, calendering or crepe processing can be carried out if necessary.

Examples of the above-mentioned other components include dialdehyde starch, sponge, sodium carboxymethyl cellulose and the like. These ingredients are
0 to 20 parts by weight can be added.

The diffusive absorbent paper produced as described above has a thickness of 0.2 to 0.8 under a load of 2.5 g / m ^2.
It is preferably mm. The reason is that if the thickness is less than 0.2 mm, the space for diffusing the liquid is small and the capacity is insufficient, and if the thickness exceeds 0.8 mm, the thickness becomes too thick and it becomes difficult to transmit the body fluid to the superabsorbent polymer. is there. Particularly preferably, the thickness is 0.3 to 0.6 m.
m.

Furthermore, the diffusible absorbent paper is required to have a function of quickly diffusing a liquid into a large area. Therefore, it is preferable that the diffusible absorbent paper has a creme absorption height after 50 minutes of physiological saline of 50 mm or more and a creme absorption height after 10 minutes of 100 mm or more. If the creme absorption height is less than these values, the diffusibility of the liquid will be poor.
More preferably, the creme absorption height after 1 minute with respect to physiological saline is 60 to 120 mm. The creme absorption height after 10 minutes is 120 to 300 mm.

As described above, it is necessary that the diffusive absorbent paper has a function of diffusing a liquid quickly, and in addition to this, it is desirable that the liquid absorbing speed is also high. That is, the diffusible absorbent paper preferably has a transit time of 10 g of an aqueous 85% by weight glycerin solution of 100 g or less, and more preferably 10 to 80 seconds. Such a diffusive absorbent paper exhibits particularly excellent performance with respect to the diffusion and absorption of liquid.

Further, as another example of the absorbent paper using the bulky cross-linked cellulose fiber of the present invention, a composite obtained by integrating the permeable absorbent paper 2c and the diffusible absorbent paper 2d as shown in FIG. There is an absorbent paper 2f. The composite absorbent paper will be described below.

The method for integrating the transparent absorbing paper and the diffusion absorbing paper is not particularly limited as long as they can be integrated. For example, the transparent absorption paper and the diffusion absorption paper may be overlapped and passed through a pair of embossing rolls to integrate the two, or they may be integrated by an adhesive or an adhesive represented by hot melt or the like. You can Preferably, the transparent absorbent paper and the diffusion absorbent paper are produced by a wet papermaking method, and then they are integrated by a papermaking process. When the two are integrated by such a method, the fibers of the both are more closely entangled with each other, and the movement of the liquid between the two is smoothly performed.

In one embodiment of integrating the transparent absorbent paper and the diffusion absorbent paper in a papermaking process, the slurry for forming the transparent absorbent paper is fed to a paper machine to form a paper layer on the wire. Separately from this, the slurry for forming the diffusive absorbent paper is supplied to another paper machine to form a paper layer on the wire. These paper layers are picked up from the respective wires, they are overlapped, and then they are squeezed, dehydrated and dried to obtain the composite absorbent paper in which the permeable absorbent paper and the diffusive absorbent paper are integrated.

In another embodiment, the slurry for forming the permeable absorbent paper and the slurry for forming the diffusive absorbent paper are supplied onto the wire at once from two rows of paper making nozzles, respectively. Form a layered paper layer. Then, the paper layer is taken out from the wire, squeezed and dehydrated, and dried to obtain the composite absorbent paper in which the permeable absorbent paper and the diffusive absorbent paper are integrated.

The composite absorbent paper in which the permeable absorbent paper and the diffusive absorbent paper are integrated is
The liquid is not absorbed between the two and is quickly absorbed,
In addition, it diffuses quickly throughout the composite absorbent body.

As described above, the composite absorbent paper is a combination of the permeable absorbent paper and the diffusive absorbent paper, but other papers may be further used for integration. For example, as shown in FIG. 2, in addition to the permeable absorbent paper 2c and the diffusible absorbent paper 2d, another paper is superposed so as to be in contact with the diffusible absorbent paper, and these are integrated to form It may be 2 g of composite absorbent paper.

As such another paper, there is a polymer dispersion paper 2e for enhancing the dispersibility of the super absorbent polymer. The polymer-dispersed paper is preferably composed mainly of the bulky and highly crosslinked cellulose fibers of the present invention that do not get wet when wet, and is one that fluffs at a low density in order to bury the superabsorbent polymer. Specifically, the bulky crosslinked cellulose fiber of the present invention is 70 to 100 parts by weight, preferably 80 to 100 parts by weight and the heat-melting adhesive fiber is 0 to 30 parts by weight, preferably 0.
.About.20 parts by weight, and the basis weight is 10 to 50 g / m.
² , preferably 10 to 30 g / m ² . The polymer-dispersed paper is to prevent the super-absorbent polymers from coagulating with each other when the super-absorbent polymer is dispersed on the polymer-dispersed paper, and thereby more effectively prevent gel blocking of the super-absorbent polymer. It is possible to suppress and further improve the liquid flow property between the particles of the superabsorbent polymer.

The polymer-dispersed paper preferably contains up to 30 parts by weight of a hot-melt adhesive adhesive fiber in addition to the bulky crosslinked cellulose fiber of the present invention. By using such a heat-meltable adhesive fiber, the effect of further stabilizing the inter-fiber distance when wet is further produced. More preferably, the polymer-dispersed paper contains up to 20 parts by weight, particularly preferably 2 to 20 parts by weight of hot-melt adhesive fibers. As the heat-melting adhesive fiber, the same heat-melting adhesive fiber as described for the permeable absorbent paper and the diffusible absorbent paper can be used.

The method for producing the polymer-dispersed paper is not particularly limited, and for example, a commonly used wet or dry papermaking method can be used. When the wet papermaking method is used, the bulky highly crosslinked cellulose fibers of the present invention and, if necessary, the heat-meltable adhesive fibers are dispersed in water, and if necessary, other components are added to form a slurry. Is made using a paper machine. After papermaking, calendering or crepe processing can be carried out if necessary.

As the above-mentioned other components, for example, softwood kraft pulp (NBKP) and hardwood kraft pulp (L
BKP), dialdehyde starch, sponge, and the like. These components can be added in an amount of 0 to 20 parts by weight.

The polymer-dispersed paper thus produced has a thickness of 0.2 to 1.0 m under a load of 2.5 g / m ^2.
It is preferably m. The reason for this is that the thickness is 0.
If the thickness is less than 2 mm, the effect of dispersing the polymer may be insufficient, and if the thickness exceeds 1.0 mm, the thickness may be too thick and an extremely thin absorbent article may not be obtained, which is not preferable. Particularly preferably, the thickness is 0.2
~ 0.6 mm.

In order to produce the composite absorbent paper comprising the permeable absorbent paper, the diffusible absorbent paper and the polymer dispersed paper, the permeable absorbent paper and the diffusible absorbent paper are provided. The method for producing the composite absorbent paper can be appropriately used.

The permeable absorbent paper, the diffusive absorbent paper and the composite absorbent paper are particularly useful as an absorbent body for absorbent articles. Below, an absorbent article using these absorbent papers will be described.

First, an absorbent article using the permeable absorbent paper and the diffusive absorbent paper will be described. The absorbent article comprises a liquid-permeable surface material, a liquid-impermeable leak-proof material, and a liquid-retaining absorber interposed between the surface material and the leak-proof material. A body is characterized by comprising the permeable absorbent paper and the diffusive absorbent paper.

As an example of the absorbent article, the sanitary napkin shown in FIG. 3 will be described as an example. The sanitary napkin 10 shown in FIG. 3 has a liquid-permeable surface material 1 and a liquid-impermeable leak preventive material 3. And a liquid-retaining absorber 2 interposed between the surface material and the leak preventer.

More specifically, the sanitary napkin 10 is formed substantially vertically long, and when the sanitary napkin 10 is worn, the surface material 1 is located on the side in contact with the skin and the leak preventive material 3 is provided. The absorber 2 is located on the side in contact with the underwear, and the absorber 2 is interposed between the surface material 1 and the leak preventer 3. Further, as shown in FIG. 3, the absorber 2 is covered with the leak preventive material 3 on the back surface, all side surfaces and the peripheral portion of the front surface, and further, the entire surface thereof is covered with the surface material 1. The central portion of the surface of the absorbent body 2 is directly covered with the surface material 1, and the body fluid is directly transmitted to the absorbent body 2. Further, on the back surface side of the surface material 1, three adhesive parts 4 are linearly formed in the longitudinal direction, and the adhesive parts 4 are protected by a release paper 5. Incidentally, in FIG. 3, reference numeral 6 denotes a joining portion made of hot melt. The absorbent body 2 in the absorbent article 10 shown in FIG. 3 is formed by covering the high-absorbent polymer 2b with the diffusible absorbent paper 2d and further covering it with the permeable absorbent paper 2c. is there. As a result, the absorbent article has high absorbency and high permeability.

Next, a sanitary napkin using the composite absorbent paper will be described with reference to FIG. The same points as those in FIG. 3 will not be described in detail, but the description in detail with respect to FIG. 3 is appropriately applied. In addition, in FIG.
The same reference numerals are given to the same members as. The absorbent body 2 in the sanitary napkin shown in FIG. 4 is formed by covering the super absorbent polymer 2b with the composite absorbent paper 2f. As shown in FIG. 1, the composite absorbent paper 2f is formed by integrating the transparent absorbent paper 2c and the diffusive absorbent paper 2d. When covering the super absorbent polymer 2b, the composite absorbent paper 2 is used.
The fluctuating absorbent paper 2d side of f is brought into contact with the superabsorbent polymer 2b.

Sanitary napkin 10 having such a structure
In the above, the body fluid that has permeated the permeable absorbent paper 2c is smoothly absorbed inside the absorbent body 2 without staying in each absorbent paper, and diffused throughout the absorbent body 2 by the diffusible absorbent paper 2d. It is completely immobilized with the absorbent polymer 2b.

By using such a composite absorbent paper 2f, an absorbent body can be constituted by only one sheet of absorbent paper and superabsorbent polymer, and a superabsorbent and ultrathin absorbent body can be obtained very easily. be able to.

Another embodiment of an absorbent article using the above composite absorbent paper will be described by taking a sanitary napkin as an example with reference to FIG. The same points as those in FIG. 3 will not be described in detail, but the description in detail with respect to FIG. 3 is appropriately applied. Further, in FIG. 5, the same members as those in FIG. 3 are designated by the same reference numerals.

In the sanitary napkin 10 shown in FIG. 5, the absorbent body 2 is formed by covering the super absorbent polymer 2b with the composite absorbent paper 2g. As shown in FIG. 2, the composite absorbent paper 2g is formed by integrating the permeable absorbent paper 2c, the diffusive absorbent paper 2d, and the polymer dispersed paper 2e. When covering the superabsorbent polymer 2b, the polymer-dispersed paper 2e side of the composite absorbent paper 2g is in contact with the superabsorbent polymer 2b.

The polymer-dispersed paper 2e is for covering the super-absorbent polymer 2b with the composite absorbent paper 2g so that the super-absorbent polymer 2b does not aggregate with each other even if they are integrated. Thus, gel blocking of the superabsorbent polymer 2b can be suppressed more effectively, and the liquid flowability between the particles of the superabsorbent polymer 2b can be further improved.

When the absorbent body 2 having the structure shown in FIG. 5 is used as the absorbent article, an absorbent article exhibiting a high absorption performance can be obtained even when excreting particularly.
Particularly preferred.

The absorbent article comprising the absorbent paper using the bulky highly cross-linked cellulose fiber of the present invention has excellent high absorption performance, particularly excellent re-absorption rate / holding capacity after repeated excretion, and excellent absorption performance. Even if it is thinner than an article, it can be obtained, has high excretion, and is highly comfortable with no liquid return, stickiness, or leakage even when worn for a long time. Further, an absorbent paper mainly composed of the highly bulky cross-linked cellulose fiber of the present invention (body-absorbent paper,
By using the above-mentioned diffusion absorbent paper and the above composite absorbent paper, it becomes possible to very easily obtain an absorber having extremely high absorption performance.

[0072]

EXAMPLES Next, the present invention will be described in more detail based on Examples and Comparative Examples, but it goes without saying that the scope of the present invention is not limited to such Examples.

[Example 1] Fiber roughness is 0.36 mg / m
And mercerized pulp whose fiber roundness is 0.80 (trade name: "POROSANIER-J", ITT Rayonier Inc.
100 g as a cross-linking agent, dimethylol dihydroxyethylene urea (trade name; “Sumitex Resin NS-19
, 5% by weight of Sumitomo Chemical Co., Ltd., 3% by weight of a metal catalyst (trade name; "Sumitex Accelerator X-110", manufactured by Sumitomo Chemical Co., Ltd.) as a crosslinking agent aqueous solution 1000
g, and the mercerized pulp was impregnated with a crosslinking agent. Then, after removing the excess aqueous solution of the crosslinking agent from the mercerized pulp so that the amount of the aqueous solution of the crosslinking agent with respect to the mercerized pulp is 200% by weight, it is heated in an electric dryer at 135 ° C. for 10 minutes, The cellulose molecules were crosslinked and the pulp fibers were crosslinked to obtain a mercerized crosslinked pulp. This is designated as cellulose fiber (A).

Example 2 Fiber roughness is 0.35 mg / m
And a coniferous wood pulp NBKP (trade name; "INDORAYON", PT Inti Indo, whose roundness of the fiber cross section is 0.28)
100 g of rayon Utama) is used as a cross-linking agent, and dimethylol dihydroxyethylene urea (trade name; “Sumitex Re
sin NS-19 ", 5% by weight of Sumitomo Chemical Co., Ltd., 5% by weight of a metal catalyst (trade name;" Sumitex Accelerator X-110 ", Sumitomo Chemical Co., Ltd.) And the kraft pulp was impregnated with a crosslinking agent.
Then, the amount of the cross-linking agent aqueous solution to the pulp is 2
After the excess aqueous solution of the crosslinking agent was removed from the pulp so as to be 100% by weight, the pulp was heated in an electric dryer at 135 ° C. for 10 minutes to crosslink the cellulose molecules in the pulp and the pulp fibers to obtain a crosslinked pulp. It was This is designated as cellulose fiber (B).

Example 3 Fiber roughness of 0.78 mg / m
In the same manner as in Production Example 1, except that rayon (trade name: "Corona SB rayon", manufactured by Daiwabo Rayon Co., Ltd.) having a roundness of fiber cross section of 0.68 and a length of 8 mm was used. Then, a crosslinked rayon fiber was obtained. This is designated as cellulose fiber (C).

Comparative Example 1 Fiber roughness is 0.18 mg / m
And, the softness of kraft pulp NBKP (trade name; "SKEENA PRIME", Skeena C
ellulose Co.) was used, and a crosslinking reaction was performed in the same manner as in Production Example 1 to obtain a crosslinked pulp. This is designated as cellulose fiber (D).

[Comparative Example 2] Fiber roughness is 0.18 mg / m.
And, the softness of kraft pulp NBKP (trade name; "SKEENA PRIME", Skeena C
ellulose Co.) was prepared. This is designated as cellulose fiber (E).

[Comparative Example 3] Fiber roughness is 0.24 mg / m.
And, a coniferous kraft pulp NBKP (trade name; "HARMAC-R", MacMillan Bl with a roundness of the fiber cross section of 0.34)
oedel Ltd.) was prepared. This is called cellulose fiber (F).

The fiber roughness, the roundness of the fiber cross section and the compression residual strain when wet of the above cellulose fibers (A) to (F) were measured by the following methods. Table 1 shows the results.

<Measurement of fiber roughness> Fiber roughness meter FS-20
0 (manufactured by KAJAANI ELECTRONICS LTD.) Was used.
First, in order to obtain the true weight of the cellulose fiber, the cellulose fiber is dried in a vacuum dryer at 100 ° C. for 1 hour to remove the water content existing in the cellulose fiber.
Approximately 1 g of cellulosic fiber with an accuracy of ± 0.1 g
Accurately measure. Next, the cellulose fiber was completely disintegrated in 150 ml of water with a mixer attached to the fiber roughness meter so as not to damage the cellulose fiber.
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> The circularity of the cross section of the cellulose fiber is measured by first slicing the cellulose fiber in a direction perpendicular to the cross section so that the area of the cross section of the cellulose fiber does not change, and measuring the cross section by an electron microscope. Take a picture and take a picture of the cross section with an image analyzer (manufactured by Nippon Avionics, trade name;
"Avio EXCEL"), and the roundness of the cellulose fiber cross section was determined using the formula shown below. The roundness was an average value obtained by measuring 100 points on any cross section of cellulose fiber.

[Equation 1]

<Measurement of Compressive Residual Strain When Wet> Crosslinked cellulose fibers were sheeted into a size of 50 mm × 50 mm at a basis weight of 500 g / m ² and a load of 5 g / cm ² and 5.0 ±.
The thickness L ₀ is adjusted to 0.1 mm. Then, assuming that the body fluid is excreted, 12.5 g of physiological saline (about 10 times the sheet weight) is applied to the entire sheet almost uniformly, and the entire sheet is wet. Then, in a Tensilon compression tester, a compression area of 10 cm ² (radius 1.78
cm disk), compression speed 10 mm / min, maximum load 200
after compression to g / cm ² (ie 2000 g total),
Decompress at a constant speed. At this time, by compressing, the physiological saline solution overflowing from the pulp is absorbed and removed by a tissue or the like. This operation was repeated 10 times in total, and the thickness L ₁ under a load of 5 g / cm ² after the compression measurement was determined, and the compression residual strain was determined using the formula shown below.

[Equation 2]

[0083]

[Table 1]

As is clear from Table 1, the fiber roughness is 0.
By cross-linking 3 mg / m or more of cellulose fibers,
It can be seen that the compressive residual strain when wet can be kept below 40%. However, the fiber roughness is 0.3 mg / m
With respect to the following cellulose fibers and crosslinked cellulose fibers obtained by crosslinking cellulose fibers having a fiber roughness of 0.3 mg / m or less, the compression residual strain when wet cannot be kept below 40%. It has been shown to be a cellulosic fiber that is very fragile to compression when wet. Therefore, when absorbing body fluid, it is not possible to maintain the fiber space formed by the cellulose fibers, and it is not preferable because the distance between the fibers cannot be kept stable.

[0085]

EFFECTS OF THE INVENTION According to the highly bulky crosslinked cellulose fiber of the present invention, swelling when wet is small and the distance between fibers can be kept stable, so that there is little twisting / sagging when wet. It is possible to stably maintain the absorption space that temporarily absorbs the body fluid, and the body fluid can quickly pass through the absorption space. Further, since the absorption space has excellent liquid flowability even during rewetting, it is possible to extremely stably / effectively absorb body fluid without deteriorating the absorption performance even during repeated excretion.

[Brief description of drawings]

FIG. 1 is a diagram showing a composite absorbent paper in which a transparent absorbent paper and a diffusive absorbent paper are integrated.

FIG. 2 is a diagram showing a composite absorbent paper in which a transparent absorbent paper, a diffusive absorbent paper and a polymer absorbent paper are integrated.

FIG. 3 is a diagram showing a cross section in the longitudinal direction of an absorbent article using a permeable absorbent paper and a diffusive absorbent paper.

FIG. 4 is a view showing a cross section in the longitudinal direction of an absorbent article using the composite absorbent paper shown in FIG.

5 is a view showing a cross section in the longitudinal direction of an absorbent article using the composite absorbent paper shown in FIG.

[Explanation of symbols]

 1 Surface Material 2 Absorber 2b High Absorbent Polymer 2c Permeable Absorbent Paper 2d Diffusive Absorbent Paper 2e Polymer Dispersed Paper 2f 2g Composite Absorbent Paper 3 Leakage Preventer 4 Adhesive 5 Release Paper 6 Joint 10 10 Sanitary Napkin

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display part D21H 11/20 A41B 13/02 D A61F 13/18 303

Claims (5)

[Claims] 1. A bulky crosslinked cellulose fiber characterized in that the inside and / or between the molecules of a cellulose fiber having a fiber roughness of 0.30 mg / m or more are crosslinked with a crosslinking agent. 2. The bulky highly crosslinked cellulose fiber according to claim 1, wherein the roundness of the cellulose fiber is 0.5 or more. 3. The bulky crosslinked cellulose fiber according to claim 2, wherein the cellulose fiber is pulp. 4. The bulky crosslinked cellulose fiber according to claim 3, wherein the pulp is a mercerized pulp. 5. The bulky highly crosslinked cellulose fiber according to claim 1, which has a compressive residual strain when wet of less than 40%.