JP2009148322A - Low-diffusivity permeable paper and absorbent article using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide low-diffusivity permeable paper which exhibits a low liquid diffusivity and a high liquid permeation when it is used for an absorbent article and to provide the absorbent article using it. <P>SOLUTION: The low-diffusivity permeable paper for absorbent articles is obtained by a wet paper making method. The average pore diameter by pore diameter distribution measurement of the low-diffusivity permeable paper is 30 μm or more. In addition, the pore superficial area in a region of pores whose diameter is 0.7-1.3 times as large as the average pore diameter occupies 70% or more of the whole pore superficial area of the low-diffusivity permeable paper. In addition, the pore superficial area in a region of pores whose diameter is 20 μm or less occupies 10% or less of the whole pore superficial area of the low-diffusivity permeable paper. Preferably, the low-diffusivity permeable paper includes hydrophilic fibers and is treated by a sizing agent. Also, the absorbent article 10 is provided with the low-diffusivity permeable paper 1 between a surface sheet 11 and an absorber 13. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a low-diffusibility permeable paper for absorbent articles such as sanitary napkins, disposable diapers, and incontinence pads, and more particularly, low liquid diffusibility and excellent liquid permeability when used in absorbent articles. The present invention relates to a low-diffusibility transparent paper exhibiting The present invention also relates to an absorbent article using such low diffusion transmission paper.

  With respect to absorbent articles such as sanitary napkins, disposable diapers, and incontinence pads, many techniques for improving the absorbability of body fluids have been proposed and improved. And most of these improvements were to improve the liquid absorption rate, prevent liquid return from the absorber to the surface material, prevent liquid leakage, and reduce stickiness of the absorbent article to the body.

  Patent Document 1 includes bulky cellulose fibers and hydrophilic fine fibers or hydrophilic fine powder as an absorbent paper suitable as a material for absorbent articles, and the hydrophilic fine fibers or the hydrophilic As for the fine powder, there is described an absorbent paper in which the abundance ratio on one side of the absorbent paper is higher than the abundance ratio on the other side.

The absorbent paper described in Patent Document 1 is provided with a gradient in the existence ratio of specific constituent fibers in the thickness direction of the absorbent paper, thereby increasing not only the liquid permeability but also the diffusibility.
However, in absorbent article applications, only materials having high liquid permeability and liquid diffusibility, such as the absorbent paper described in Patent Document 1, are not used. For example, liquid diffusibility is low, A material with high permeability may be required. No material has yet been provided that can meet these requirements.

JP-A-8-232189

  Accordingly, an object of the present invention is to provide a low-diffusibility permeable paper exhibiting low liquid diffusibility and excellent liquid permeability when used in an absorbent article, and an absorbent article using the same.

  The present invention is a low diffusibility transmission paper for absorbent articles obtained by a wet papermaking method, wherein the average pore diameter of the low diffusibility transmission paper in pore diameter distribution measurement is 30 μm or more, and The pore surface area in the region of 0.7 to 1.3 times the average pore diameter is 70% or more of the total pore surface area of the low-diffusibility permeable paper, and the pores in the region having a pore diameter of 20 μm or less. The object is achieved by providing a low-diffusibility transmission paper having a surface area of 10% or less of the total pore surface area of the low-diffusibility transmission paper.

  Further, the present invention provides an absorbent article using the low-diffusibility permeable paper as a surface sheet constituting a skin contact surface, a back sheet constituting a non-skin contact surface, and an absorber disposed between both the sheets. An absorbent article having a low diffusibility permeable paper is provided between the top sheet and the absorbent body.

The low diffusibility permeable paper of the present invention exhibits low liquid diffusibility and excellent liquid permeability when used in an absorbent article, and has a high liquid absorption rate. For this reason, the low diffusibility transmission paper of this invention is suitable for the use as which high liquid absorptivity is requested | required, for example, it is suitable as a raw material of absorbent articles, such as a sanitary napkin, a disposable diaper, and an incontinence pad.
Moreover, since the said low diffusible permeation | transmission paper is distribute | arranged between the surface sheet and an absorber, the absorbent article of this invention has a high absorption speed of a bodily fluid, and it is hard to produce what is called a liquid return.

Hereinafter, the low diffusibility transmission paper of the present invention is explained based on the preferred embodiment.
The low-diffusibility transmission paper of the present invention is a low-diffusibility transmission paper for absorbent articles obtained by a wet papermaking method. In the measurement of pore diameter distribution, (1) the average fineness of the low-diffusibility transmission paper is The pore diameter is 30 μm or more, preferably 30 to 100 μm, more preferably 40 to 80 μm, and (2) the pore surface area in a region 0.7 to 1.3 times the average pore diameter is the low diffusion 70% or more, preferably 75 to 100%, more preferably 80 to 90% of the total pore surface area of the transparent paper, and (3) the pore surface area in the region having a pore diameter of 20 μm or less is the low diffusion 10% or less, preferably 8% or less, more preferably 0% of the total pore surface area of the transparent paper.

In general, a paper mainly composed of fibers has an infinite number of very narrow “pores” (voids) created by intertwining the fibers, and the size of these pores (pore diameter). However, it greatly affects the liquid permeability and liquid diffusibility of paper. In paper, there is a distribution of pore diameters. Mainly, pores with a large pore diameter are responsible for liquid permeation, and pores with a small pore diameter are responsible for liquid diffusibility. In the paper according to the normal distribution, in the pore diameter distribution measurement, the pore surface area in the region 0.7 to 1.3 times the average pore diameter is 56% of the total pore surface area and 0.5% of the average pore diameter. The pore surface area in the region of ~ 1.5 times is 70% of the total pore surface area.
On the other hand, the low-diffusibility permeable paper of the present invention has the above-mentioned characteristics (1) to (3) with respect to the pore diameter distribution, and therefore contributes to liquid diffusibility compared to ordinary paper. The ratio of pores having a pore diameter of 20 μm or less is small, the peak of the pore distribution curve exists in a specific range contributing to liquid permeability, and the pore diameter distribution is narrow. For this reason, the low-diffusibility permeable paper of the present invention has low liquid diffusibility (the liquid is difficult to spread in the paper surface direction) and high liquid permeability (the liquid is easy to pass in the thickness direction orthogonal to the paper surface direction). ), A feature not found in conventional paper.

  When the average pore diameter is less than 30 μm, the proportion of pores having a pore diameter of 20 μm or less increases, and the liquid diffusibility tends to increase more than necessary. In addition, when the pore surface area in the region of 0.7 to 1.3 times the average pore diameter is less than 70% of the total pore surface area, the proportion of pores having a pore diameter of 20 μm or less increases, and the liquid diffusibility is also observed. Tends to be larger than necessary. Moreover, when the pore surface area in the region having a pore diameter of 20 μm or less exceeds 10% of the total pore surface area, the diffusibility tends to be higher than necessary.

The pore diameter distribution according to the present invention is obtained by pore size distribution measurement using a CFP-1200-AEXL porous material automatic pore size measurement system manufactured by Porous Materials, Inc. In this pore size distribution measurement, the flow rate and pressure of the gas passing through the sample (low diffusive transmission paper) are measured, and the pore size (pore diameter) of the pores in the sample and the gas passing through the pores are measured. From the relationship between the flow rate and the pressure, a pore distribution curve is obtained in which the pore diameter (unit: μm) is on the horizontal axis and the proportion of pores having a predetermined pore diameter (unit:%) is on the vertical axis. Based on the obtained pore distribution curve, the average pore diameter and the total pore surface area were calculated, and further, “a fine area of 0.7 to 1.3 times the average pore diameter in the total pore surface area” was calculated. The ratio of the pore surface area and the ratio of the pore surface area in the region having a pore diameter of 20 μm or less in the total pore surface area are calculated. In order to calculate the average pore diameter and the total pore surface area, the thickness of the sample under no load is required, and the thickness is measured in advance.
The measurement conditions for the pore size distribution measurement are as follows. A circular sample (low diffusion transmissible paper) having a diameter of 5 mm is used as a measurement sample. In the porous material automatic pore size measurement system, the adapter opening diameter is 3.3 mm, the sample liquid is Silwick (surface tension 20.1 dyn / cm), and measurement is performed by the measurement flow Capillary Flow Porometry type wet up dry down method. The measurement is performed in an environment with a room temperature of 23 ° C. and a humidity of 50%.

  The low-diffusibility permeable paper of the present invention having the pore diameter distribution as described above preferably contains hydrophilic fibers and has been treated with a sizing agent. The use of the hydrophilic fiber and the treatment with the sizing agent are effective constituent elements for obtaining a paper having the above-described pore diameter distribution and having low liquid diffusibility and high permeability. Hereinafter, these structural requirements will be described.

  As the hydrophilic fiber, not only fibers that are inherently hydrophilic, such as cellulose fibers, but also fibers that are not inherently hydrophilic but whose surface is made hydrophilic by a hydrophilic treatment can be used. Examples of fibers that are inherently hydrophilic include, for example, hardwood bleached kraft pulp, softwood bleached kraft pulp, hardwood unbleached kraft pulp, softwood unbleached kraft pulp, hardwood sulfite pulp, conifer sulfite pulp, and non-wood such as cotton Plant fiber; regenerated cellulose fiber such as rayon and cupra: synthetic fiber such as polyvinyl alcohol (PVA) fiber and polyacrylic acid fiber. In addition, examples of fibers that have no hydrophilicity but can be used in the present invention as hydrophilic fibers by hydrophilization treatment include synthetic fibers such as polyester, polyethylene (PE), and polypropylene. The hydrophilization treatment can be performed, for example, by a method of treating the surface of the fiber with a surface oil agent or a method of kneading a surfactant into the fiber to form a fiber. In the present invention, one kind of these fibers can be used alone or two or more kinds can be mixed and used.

  The ratio of the hydrophilic fiber to the constituent fibers of the low diffusibility transparent paper of the present invention is preferably 80% by weight or more, and more preferably 100% by weight. If the proportion of hydrophilic fibers in the constituent fibers is less than 80% by weight, the strength may be reduced.

In the present invention, bulky hydrophilic fibers are preferably used. The fiber layer mainly composed of bulky hydrophilic fibers is bulky compared to the fiber layer mainly composed of non-bulk hydrophilic fibers, and the peak of the pore distribution curve exists on the large pore diameter side. While the liquid permeability is high, the liquid diffusivity is not so high. By using bulky hydrophilic fibers having such properties as constituent fibers of the paper, a bulky network structure is formed in the paper, and the above-described pore diameter distribution is more easily obtained.
The proportion of bulky hydrophilic fibers in the hydrophilic fibers contained in the low-diffusibility transparent paper of the present invention is preferably 80% by weight or more, more preferably 80 to 98% by weight.

Examples of the bulky hydrophilic fiber include: 1) a hydrophilic fiber having a bulky fiber structure, specifically, a hydrophilic fiber having a crimp structure, bent or branched; 2) A hydrophilic fiber having a cross-sectional area of the fiber of 3.0 × 10 ⁻⁶ cm ² or more and a roundness of the cross-section of the fiber of 0.5 or more; 3) a cross-sectional area of the fiber regardless of the roundness of the cross-section of the fiber May be a hydrophilic fiber of 5.0 × 10 ⁻⁶ cm ² or more.
Examples of the bulky hydrophilic fibers having the characteristics 1) to 3) include cellulose fibers typified by pulp, cotton, rayon and the like, and hydrophilic synthetic fibers such as acrylonitrile and polyvinyl alcohol. Among these, only one type may be used, or several types may be mixed and used. Among them, pulp fibers having a crimp structure and mercerized pulp having a fiber cross-section swelled / increased by a mercerization process can be preferably used because they can be easily obtained at a relatively low cost. The mercerized pulp can be obtained by mercerizing a regenerated cellulose fiber or pulp fiber whose fiber cross-sectional area and cross-sectional shape can be freely controlled.

Preferable examples of the bulky hydrophilic fiber include a bulky cellulose fiber. Inclusion of bulky cellulose fibers in the hydrophilic fiber is particularly effective when the basis weight of the low-diffusibility transparent paper is in a specific range, specifically when the basis weight is 20 to 70 g / m ^2. is there.
The basis weight of the low diffusivity permeability paper of the present invention, from the viewpoint of high permeability having a thickness and a liquid, preferably 20 to 70 g / m ^2, further 30 to 60 g / m ^2.
The thickness of the low diffusibility transparent paper of the present invention under no load is preferably 0.2 to 0.8 mm, more preferably 0.3 to 0.6 mm.

  As the bulky cellulose fiber, any cellulose fiber may be used as long as it is bulky. As the cellulose fiber, for example, natural cellulose such as wood pulp and cotton, and regenerated cellulose such as rayon and cupra can be used. From the viewpoint of cost, wood pulp is preferably used, and conifer kraft pulp is particularly preferably used. These cellulose fibers can use 1 type (s) or 2 or more types.

  The average fiber length of the bulky cellulose fiber is preferably 1 to 20 mm, more preferably 2 to 10 mm, and still more preferably 2 to 5 mm mainly from the viewpoint of liquid permeability. If the average fiber length is less than 1 mm, a bulky network structure cannot be formed, and if the average fiber length exceeds 20 mm, dispersibility in water is deteriorated and a uniform network structure cannot be formed.

  As an example of a preferable bulky cellulose fiber, there is a crosslinked cellulose fiber obtained by crosslinking cellulose molecules within and / or between molecules. Such a crosslinked cellulose fiber is preferable because it can maintain a bulky structure even in a wet state. A more preferred bulky cellulose fiber is a crosslinked pulp, and a more preferred bulky cellulose fiber is a crosslinked pulp obtained by crosslinking a pulp having an average fiber length of 2 to 5 mm.

  Although there is no restriction | limiting in particular in the method for bridge | crosslinking a cellulose fiber, For example, the crosslinking method using a crosslinking agent is mentioned. Examples of such crosslinking agents include N-methylol compounds such as dimethylolethylene urea and dimethylol dihydroxyethylene urea; polycarboxylic acids such as citric acid, tricarballylic acid and butanetetracarboxylic acid; dimethylhydroxyethylene urea and the like. Polyols; Examples include crosslinkers of polyglycidyl ether compounds. In particular, a crosslinking agent of a polycarboxylic acid or a polyglycidyl ether compound that does not generate formalin or the like harmful to the human body during crosslinking is preferable.

  The amount of the crosslinking agent used is preferably 0.2 to 20 parts by weight with respect to 100 parts by weight of the cellulose fiber. If the amount used is less than 0.2 parts by weight, the crosslinking density of the cellulose fibers is low, so the elastic modulus may be greatly reduced when wet. If the amount used exceeds 20 parts by weight, the cellulose fibers become rigid. Since the cellulose fiber may become brittle when stress is applied excessively, the above range is preferable.

  In order to crosslink cellulose fibers using a crosslinking agent, for example, cellulose fiber is impregnated with a cellulose fiber impregnated with an aqueous solution of a crosslinking agent added with a catalyst as necessary, so that the aqueous solution of the crosslinking agent has a designed adhesion amount. The fiber is dehydrated and then heated to the crosslinking temperature, or the aqueous solution of the crosslinking agent is sprayed onto the cellulose fiber by spraying or the like so as to have a designed adhesion amount, and then heated to the crosslinking temperature to cause a crosslinking reaction.

The bulky cellulose fiber preferably has a fiber roughness of 0.3 mg / m or more in addition to the average fiber length of 1 to 20 mm as described above. A more preferable fiber roughness is 0.3-2 mg / m, and a more preferable fiber roughness is 0.32-1 mg / m. Such cellulose fibers are preferable because the cellulose fibers are accumulated in a bulky state and a bulky network structure is easily formed.
Here, the fiber roughness is used as a scale representing the thickness of fibers in fibers having non-uniform fiber thickness, such as wood pulp. For example, a fiber roughness meter (KAJANNI ELECTRONICS LTD. It can measure using FS-200 made by a company.
Examples of cellulose fibers with a fiber roughness of 0.3 mg / m or more include softwood kraft pulp (“ALBACEL” (trade name) from Federal Paper Board Co. and “INDORAYON” (trade name) from PT IntiIndorayon Utama. ] Etc. are mentioned.

  The bulky cellulose fiber preferably has a roundness of the fiber cross section of 0.5 to 1. Cellulose fibers having a fiber cross-section with a roundness of 0.5 to 1 are preferred because they have low liquid movement resistance and high liquid permeation speed. More preferably, the roundness is 0.55 to 1. In addition, the measuring method of the roundness of a fiber cross section is mentioned later.

  As described above, in the present invention, it is preferable to use wood pulp as the cellulose fiber, but in general, the cross section of the wood pulp is flattened by delignification treatment, and most of its roundness is less than 0.5. is there. In order to make the roundness of such wood pulp 0.5 or more, for example, wood pulp having an average fiber length of 1 to 20 mm may be mercerized to swell the cross section of the wood pulp.

  Thus, as the cellulose fiber having a roundness of the fiber cross section of 0.5 to 1, a mercerized pulp having a roundness of 0.5 to 1 obtained by mercerizing wood pulp is preferable. Examples of commercially available mercerized pulp that can be used in the present invention include “FILTRANIER” (trade name) manufactured by ITT Rayonier Inc. and “POROSANIER” (trade name) manufactured by the same company.

In the present invention, it is also preferable to use a crosslinked mercerized pulp obtained by crosslinking mercerized pulp by the above-described method as the bulky cellulose fiber.
In the present invention, as the bulky cellulose fiber, cellulose having an average fiber length of 2 to 5 mm, a fiber roughness of 0.3 mg / m or more, and a roundness of the fiber cross section of 0.5 to 1. Fiber (pulp) is also preferred.

A more preferable bulky cellulose fiber is a pulp having an average fiber length of 2 to 5 mm, a fiber roughness of 0.3 mg / m or more and a roundness of fiber cross section of 0.5 to 1 by the above-mentioned method. Cross-linked.
A particularly preferable bulky cellulose fiber has an average fiber length of 2 to 5 mm and a pulp having a fiber roughness of 0.3 mg / m or more, and after making the roundness of the fiber cross section 0.5 to 1 by mercerization, Cross-linked by the method described above.

  The constituent fibers of the low diffusibility transparent paper of the present invention preferably contain synthetic fibers. The synthetic fiber may have hydrophilicity (may be hydrophilic fiber) or may not have hydrophilicity. Synthetic fibers are blended in the low-diffusibility permeable paper, so that 1) the low-diffusibility permeable paper becomes bulky and the abundance of pores contributing to liquid permeability increases, and 2) the low-diffusible permeable paper. The effect of increasing the paper strength is obtained.

Examples of the synthetic fiber effective in obtaining the effect 1) (bulkness improving effect) include polyester fiber, polyethylene terephthalate (PET) fiber, and the like. These are used alone or in combination of two or more. It can be used by mixing. Among these synthetic fibers, crimpable fibers are particularly preferable in terms of imparting bulkiness.
Moreover, when it aims at obtaining the effect of said 1), the content of the synthetic fiber (polyester fiber, PET fiber, etc.) is preferably 10 to the total weight of the low-diffusibility permeable paper of the present invention. It is 40% by weight, more preferably 15 to 25% by weight. If the content of the synthetic fiber is less than 10% by weight, the effect of improving the bulkiness may not be sufficiently obtained, and if it exceeds 40% by weight, the paper may have low strength.

On the other hand, examples of the synthetic fibers effective in obtaining the effect 2) (paper strength improvement effect) include PVA fibers and PE fibers. These may be used alone or in combination of two or more. Can be used. Among these synthetic fibers, PVA fibers are particularly preferable from the viewpoint of heat-fusibility during processing and from the point that strength is obtained in a small amount.
Moreover, when it aims at acquiring the effect of said 2), content of synthetic fiber (PVA fiber, PE fiber, etc.) is preferably 2 to the total weight of the low-diffusibility permeable paper of the present invention. 5% by weight, more preferably 2 to 4% by weight. If the content of the synthetic fiber is less than 2% by weight, the effect of improving the paper strength may not be sufficiently obtained, and if it exceeds 5% by weight, the strength may be too strong and the paper may be hard.

  The average fiber length of the synthetic fiber used in the present invention is preferably 1 to 20 mm, more preferably 1 to 10 mm. Synthetic fibers having an average fiber length in such a range are preferable in terms of wet papermaking.

  The constituent fibers of the low diffusibility transparent paper of the present invention are preferably bulky cellulose fibers and synthetic fibers. That is, a preferable combination of the constituent fibers in the present invention is a bulky cellulose fiber and a synthetic fiber. As the synthetic fiber, those described above can be used as appropriate according to the effects of 1) and 2), and the synthetic fiber does not have to be hydrophilic. Specific examples of preferable combinations of the constituent fibers in the present invention include bulky cellulose fibers and hydrophilic synthetic fibers (for example, PVA fibers).

The content ratio of the bulky cellulose fiber and the synthetic fiber in the present invention can be appropriately set according to the type of the synthetic fiber.
For example, when it aims at obtaining the effect (bulkness improvement effect) of said 1), the content weight ratio (bulky cellulose fiber: bulky cellulose fiber and synthetic fiber (specifically, polyester fiber, PET fiber, etc.): The synthetic fiber) is preferably 60:40 to 90:10, more preferably 75:25 to 85:15. In addition, when the purpose is to obtain the effect (paper strength improving effect) of 2) above, the bulkiness is high. The content weight ratio (bulky cellulose fiber: synthetic fiber) of cellulose fiber and synthetic fiber (specifically PVA fiber, PE fiber, etc.) is preferably 91: 9 to 98: 2, more preferably 95: 5 to 98. : 2.

One preferred embodiment of the low diffusibility permeable paper of the present invention comprises hydrophilic fibers [preferably a combination of bulky cellulose fibers and hydrophilic synthetic fibers (eg, PVA fibers)] and treated with a sizing agent as described above. Yes. When a fiber layer composed of hydrophilic fibers is treated with a sizing agent, a large number of fine sizing particles enter and adhere to each of the innumerable pores (voids) present in the fiber layer. As a result of deposition, pores having a small pore diameter are substantially blocked, and pores having a large pore diameter become smaller. As a result, the pore diameter distribution of the fiber layer becomes narrower than before the treatment with the sizing agent, and the peak of the pore distribution curve shifts to the larger pore diameter side. That is, in a preferred embodiment of the low-diffusibility permeable paper of the present invention, among the pores that control liquid permeation and the pores that control liquid diffusion, the latter pores are closed by sizing treatment, thereby allowing liquid permeation. The liquid diffusibility (liquid mobility in the paper surface direction) is greatly suppressed while maintaining the properties (liquid mobility in the paper thickness direction). Ordinary paper is excellent in both liquid permeability and liquid diffusibility, so the liquid diffuses in both the thickness direction and the surface direction. By suppressing the diffusion of the liquid in the direction, the mobility of the liquid in the thickness direction is enhanced, and thus, when incorporated in an absorbent article, excellent body fluid absorbability can be exhibited.
Thus, using hydrophilic fibers as constituent fibers and treating the entire fiber layer with a sizing agent provides a paper having the above-described pore diameter distribution and having low liquid diffusibility and high permeability. Above, it is one of the effective means.

FIG. 1 shows the pore distribution curve of a paper containing hydrophilic fibers and treated with a sizing agent (paper within the scope of the present invention), and FIG. 2 shows the fineness of the paper containing hydrophilic fibers but not treated with a sizing agent. The pore distribution curves are shown respectively. Each pore distribution curve is obtained by the above pore distribution measurement. The paper having the pore distribution curve in FIG. 1 has a basis weight of 30 g / m ² , 96% by weight of bulky cellulose fiber, 4% by weight of polyvinyl alcohol fiber, and rosin (sizing agent) with respect to 100 parts by weight of the constituent fibers. 0.4 part by weight and 0.4 part by weight of polyacrylamide (cationic additive) are contained with respect to 100 parts by weight of the constituent fibers. The paper having the pore distribution curve of FIG. 2 contains 96% by weight of bulky cellulose fiber and 4% by weight of polyvinyl alcohol fiber. 1 and 2, the paper containing hydrophilic fibers and treated with sizing (FIG. 1) is compared to the paper containing hydrophilic fibers but not treated with sizing (FIG. 2). It can be seen that the peak of the pore distribution curve is sharp and the pore diameter distribution is narrow.

  As the sizing agent, those used for preventing bleeding of ink in general paper can be used without particular limitation, and examples thereof include rosin, alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA) and the like. It is done. In this invention, these 1 type may be used independently and may use 2 or more types together. Among these sizing agents, rosin can be preferably used in the present invention because it can control the distribution of pore diameters in a small amount and hardly changes with time.

  The content of the sizing agent is based on 100 parts by weight of the constituent fibers of the low-diffusibility permeable paper of the present invention from the viewpoint of the balance between the effect of the sizing agent described above, the reduction in the number of pores, and the water repellency of the fiber surface The amount is preferably 0.2 to 2 parts by weight, more preferably 0.4 to 1 part by weight.

Examples of the treatment method using a sizing agent in the present invention include the following (I) to (III).
(I) After a slurry (fiber dispersion in water) containing fibers (hydrophilic fibers) is dispersed on a papermaking wire and a paper layer is formed on the papermaking wire, before the paper layer is heated and dried, A method of applying a sizing agent to the paper layer (external addition method).
(II) A method of adding a sizing agent to a slurry containing fibers before paper making (internal addition method).
(III) A method of applying a sizing agent to a dried paper containing fibers (size press method).

  Among the above (I) to (III), the external addition method (I) and the internal addition method (II) are preferable, and the external addition method (I) is particularly preferable. The external addition method (I) has various advantages over other methods, such as no need to replace the slurry, and a sufficient effect can be obtained with a relatively small amount of sizing agent. And is preferably used in the present invention.

In the external addition method (I), examples of the method for applying the sizing agent to the paper layer include a method using a contact-type applicator such as an application roll, a method using a non-contact applicator such as a spray, and the like. Any method may be used.
In the external addition method (I), the sizing agent may be applied after a dehydration process such as pressing is performed on the paper layer formed on the papermaking wire and before heat drying. , Which is preferable in that the sizing agent is effectively applied (it is not discharged together with water in the dehydration step). More specifically, the application of the sizing agent is preferably performed when the moisture content of the paper layer (the moisture content after the dehydration treatment before heat drying) is 60 to 40% by weight.

  In the treatment with the sizing agent in the present invention, particularly in the external addition method (I), it is preferable to use a cation additive together from the viewpoint of increasing the fixing amount of the sizing agent to the paper. That is, it is preferable that the low-diffusibility transmission paper of the present invention contains hydrophilic fibers and a cationic additive and is treated with a sizing agent. Examples of the cation additive include polyacrylamide (PAM) and sponge, and one of these can be used alone, or two or more can be used in combination. Among these cationic additives, PAM is particularly effective in a small amount and is preferably used in the present invention.

The cation additive is preferably added to the system in advance before adding the sizing agent.
That is, in the external addition method (I), a cation additive is preferably contained in the paper layer before sizing application. The paper layer containing such a cation additive is, for example, a method of adding a cation additive to a slurry containing hydrophilic fibers, or a method of applying a cation additive to a paper layer formed on a papermaking wire. Can be manufactured.
Moreover, in the internal addition method of said (II), it is preferable to add to a slurry containing a hydrophilic fiber in order of a cation additive and a sizing agent.
In the size pressing method (III), it is preferable that a cation additive is contained in the paper before size pressing.

  The content of the cation additive is preferably 0.2 to 2 parts by weight, more preferably 0.4 to 1 part by weight, with respect to 100 parts by weight of the constituent fibers of the low diffusibility transmission paper of the present invention. If the content of the cation additive is too small, the effect of improving the fixability of the sizing agent cannot be obtained. If the content is too large, the formation of paper may be lowered or unevenness in papermaking may occur.

In addition to the various components described above [hydrophilic fibers (bulky cellulose fibers), synthetic fibers, sizing agents, cation additives], the low-diffusibility permeable paper of the present invention may further contain other components.
Other components include, for example, paper strength enhancers such as polyvinyl alcohol polymer compounds, urea resins, melamine resins and starches; chemical fixing agents such as sulfuric acid bands; water resistance agents such as polyamides, polyamines and epichlorohydrins; Agents; fillers such as talc; dyes; color pigments; antibacterial agents; ultraviolet absorbers; pH adjusters, and the like, and these can be used alone or in admixture of two or more.
The content of other components is preferably 0 to 2% by weight with respect to the total weight of the low-diffusibility transmission paper of the present invention.

  The low-diffusibility transmission paper of the present invention is a paper obtained by a wet papermaking method as described above, and can be produced by wet papermaking according to a conventional method using the various raw materials described above. The wet papermaking method can be performed using a paper machine such as a long paper machine, a twin wire paper machine, an on-top paper machine, a hybrid paper machine, or a round paper machine.

Since the low-diffusibility permeable paper of the present invention has the pore diameter distribution as described above, it exhibits low liquid diffusibility and excellent liquid permeability when used in absorbent articles. Absorption speed is fast. In addition, the low-diffusibility permeable paper of the present invention can exhibit high liquid retention, particularly by including hydrophilic fibers (bulky cellulose fibers). Further, the low-diffusibility transmission paper of the present invention can be designed to have a small thickness mainly due to a decrease in basis weight.
The low-diffusibility permeable paper of the present invention that exhibits such effects is particularly suitable for applications that require high liquid absorbency, for example, absorbent articles such as sanitary napkins, disposable diapers, and incontinence pads. It is suitable as a material.

3 and 4 show a sanitary napkin as an embodiment of the absorbent article of the present invention using the low-diffusibility transmission paper of the present invention.
A sanitary napkin 10 shown in FIGS. 3 and 4 includes a liquid-permeable top sheet 11, a liquid-impermeable back sheet 12, and a liquid-retaining absorbent 13 disposed between the two sheets 11 and 12. Have. The top sheet 11 constitutes a skin contact surface that contacts the wearer's skin when the napkin is worn, and the back sheet 12 constitutes a non-skin contact surface that contacts the underwear when the napkin is worn. The absorbent body 13 is substantially vertically long, and includes a liquid-retaining longitudinal absorbent core 14 containing pulp fibers and an absorbent polymer, and a liquid-permeable covering sheet 15 that covers the absorbent core 14. It is configured.

  The sanitary napkin 10 is substantially vertically long, and has a pair of flap portions 16 and 16 formed to extend outward in the width direction on both left and right edges in the longitudinal direction. Yes. The pair of flap portions 16, 16 are greatly projecting outward in the width direction of the sanitary napkin 10 in the excretion portion facing portion disposed to face the liquid excretion portion of the wearer, and thereby on both the left and right sides, A pair of wing parts 17 and 17 are extended.

Between the surface sheet 11 and the absorber 13 in the thickness direction of the sanitary napkin 10, the low-diffusibility permeable paper of the present invention described above is disposed as the sublayer sheet 1. In the present embodiment, the sublayer sheet 1 is made of a single sheet of low diffusibility transmission paper and covers substantially the entire area of the upper surface (surface on the skin contact surface side) of the absorber 13.
As described above, in the sanitary napkin 10 in which the low-diffusibility permeable paper of the present invention is disposed as the sublayer sheet 1 between the liquid-permeable surface sheet 11 and the liquid-retaining absorbent 13, the low-diffusion is mainly used. Due to the action of the permeable paper, diffusion of the excreted body fluid in the surface direction (direction orthogonal to the thickness direction of the sanitary napkin 10) is suppressed, and the body fluid is quickly moved downward in the thickness direction of the sanitary napkin 10. Can be absorbed by the absorber 13. In addition, the so-called liquid return phenomenon in which the liquid absorbed by the absorber 13 returns to the top sheet 11 can be effectively prevented by the action of the low-diffusibility permeable paper.

As described above, when the low-diffusibility permeable paper of the present invention is disposed between the liquid-permeable surface sheet and the liquid-retaining absorbent, the basis weight of the low-diffusibility permeable paper is preferably 30. ~70g / m ^2, more preferably 40 to 60 g / m ² Yes, the thickness of the no-load of a low diffusion permeable sheet is preferably 0.2 to 0.8 mm, more preferably 0.3 to 0. 6 mm. The basis weight is for one sheet of low-diffusibility transmission paper.

  As a constituent member of the sanitary napkin 10, those normally used in the technical field can be used without particular limitation. For example, as the surface sheet 2, various liquid-permeable sheet materials such as a nonwoven fabric and an apertured film can be used. As the back sheet 3, a resin film having no moisture permeability, a resin film having fine holes and moisture permeability, a nonwoven fabric such as a water-repellent nonwoven fabric, a laminate of these with other sheets, or the like can be used. .

  In addition, although the sanitary napkin was mentioned as one of the application examples of the absorbent article of this invention, it can apply also to a disposable diaper, a medical pad, an incontinence pad, a breast milk pad, etc.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to these Examples.

[Example 1]
Bulky cellulose fiber [hydrophilic fiber; high bulk additive HBA-S (trade name) manufactured by Weyerhauser Paper, average fiber length 2.38 mm, fiber roughness 0.32 mg / m], and PVA fiber [hydrophilic synthetic fiber; A fibril bond (trade name) manufactured by Chang, average fiber length of 3 mm] was uniformly dispersed in water to prepare a slurry. The concentration of the bulky cellulose fiber in the slurry was 3.75% by weight, the concentration of the PVA fiber was 0.156% by weight, and the fiber concentration of the whole slurry was 3.9% by weight.
Furthermore, 0.4% by weight of PAM [cationic additive; MT-Aqua-Polymer's Akofloc C325 (trade name)] is added to the total weight of these fibers, and stirred so as to be sufficiently uniform. did.
The slurry thus obtained was dispersed on a wire mesh paper making wire having a wire opening diameter of 90 μm (166 mesh) to form a paper layer on the wire mesh paper making wire. The paper layer was dehydrated using a suction box at a rate of 6 ml / [cm ² · sec]. Next, an aqueous dispersion of the rosin prepared so that the concentration of rosin [sizing agent: AL1302 (trade name) manufactured by Seiko PMC] is 0.75% by weight is sprayed on the paper layer. Was applied to give a solid content of 0.1 g / m ^2, and then the paper layer was dried with a drier to obtain paper.
The paper of Example 1 has a basis weight of 30 g / m ² , the bulky cellulose fiber is 96% by weight, the PVA fiber is 4% by weight, and the rosin is 0.4 parts by weight with respect to 100 parts by weight of the constituent fiber. 0.4 part by weight of PAM was contained with respect to 100 parts by weight of the constituent fibers.

[Example 2]
In Example 1, except that the amount of rosin added was changed, paper was obtained in the same manner as in Example 1, and this was used as the sample of Example 2.
The paper of Example 2 has a basis weight of 30 g / m ² , 96% by weight of the bulky cellulose fiber, 4% by weight of the PVA fiber, and 0.2 part by weight of the rosin with respect to 100 parts by weight of the constituent fiber, 0.4 part by weight of PAM was contained with respect to 100 parts by weight of the constituent fibers.

[Comparative Example 1]
In Example 1, a paper was obtained in the same manner as in Example 1 except that rosin was not used, and this was used as a sample of Comparative Example 1.
The paper of Comparative Example 1 has a basis weight of 30 g / m ² and contains 96% by weight of the bulky cellulose fiber, 4% by weight of the PVA fiber, and 0.4 part by weight of the PAM with respect to 100 parts by weight of the constituent fiber. It was.

[Comparative Example 2]
In Example 1, a paper was obtained in the same manner as in Example 1 except that the coating amount of the aqueous dispersion of rosin was 0.005 g / m ^2, and this was used as a sample of Comparative Example 2.
The paper of Comparative Example 2 has a basis weight of 30 g / m ² , 96% by weight of the bulky cellulose fiber, 4% by weight of the PVA fiber, 0.02 part by weight of the rosin with respect to 100 parts by weight of the constituent fiber, 0.4 part by weight of PAM was contained with respect to 100 parts by weight of the constituent fibers.

A sanitary napkin as shown in FIGS. 3 and 4 was prepared using the papers of Examples and Comparative Examples. The paper of the examples and comparative examples was used as the sublayer sheet 1. As the top sheet 11, a perforated nonwoven fabric having a basis weight of 25 g / m ² having a core-sheath type composite fiber (core / sheath = PET / PE) as a constituent fiber is used, and as the back sheet 12, a basis weight of 39 g / m ^{2 is used.} As the absorber 13, a thin absorber having a basis weight of 200 g / m ² in which pulp and a water-absorbing polymer were integrated by pressure bonding was used.

[Performance evaluation]
About the paper of an Example and a comparative example, distribution of a pore diameter is measured by the method mentioned above, "0.7 to 1.3 times the average pore diameter which occupies" average pore diameter "and" total pore surface area " The ratio of the pore surface area in the region of "and the ratio of the pore surface area of the area having a pore diameter of 20 µm or less in the total pore surface area" were obtained. For the papers of Examples and Comparative Examples, “Klem absorption height”, “Liquid permeation time”, “Liquid absorption time”, and “Liquid diffusion area” were evaluated by the following methods. These results are shown in Table 1 below.

<Evaluation of Klem absorption height>
A test piece having a width of 15 mm and a length of 200 mm or more is prepared. With one end in the longitudinal direction of the test piece fixed and the test piece suspended vertically, a portion extending 15 mm from the other end (lower end) in the longitudinal direction of the test piece is immersed in physiological saline. For each of 10 minutes and 24 hours after immersing the test piece in physiological saline, the height of the physiological saline is read, and the height is the Klem absorption height (10 minute value, 24 hour value). And The Klem absorption height is a characteristic value indicating the liquid diffusibility of paper (capability of transporting liquid in the direction of the paper surface) mainly due to capillary force, and the 10 minute value indicates the liquid diffusibility in a short time. The time value indicates the height of the limit value of the liquid diffusibility of the paper itself. It means that the higher the Klem absorption height (in particular, the 10 minute value), the easier the liquid moves in the paper surface direction (direction perpendicular to the thickness direction), and the higher the liquid diffusibility. The measurement value of the 24-hour value is mainly to check whether or not the paper has liquid absorbency. If the 24-hour value is not substantially 0, the paper is subjected to sizing treatment. This means that the paper is not paper with completely closed pores and no liquid absorption.

<Evaluation of liquid permeation time>
A test piece having a width of 70 mm and a length of 70 mm is prepared. The test piece is placed on a horizontal table so as not to loosen, and glass tubes are placed on both ends of the test piece in the longitudinal direction. That is, both ends of the test piece are fixed with two glass cylinders so that the test piece does not loosen. A hole having an inner diameter of 35 mmφ is provided at the bottom of the cylinder, and the liquid inside the cylinder flows out from the hole. With the test piece fixed in this manner, 10 ml of 85% aqueous glycerin solution is simultaneously injected into each of the two cylinders. The time from when the aqueous solution is poured into the two cylinders until the aqueous solution completely disappears is measured, and this is defined as the liquid permeation time.

<Evaluation of liquid absorption time>
In the state where the sanitary napkin using the paper of the example and the comparative example is spread in a flat shape and fixed on the horizontal surface with the top sheet facing upward, a cylindrical shape is formed on the top sheet at the center of the absorber. An acrylic plate with an injection part is placed, a weight is placed on the acrylic plate, and a load of 1.6 kPa is applied to the center of the absorber. The injection part provided in the acrylic plate has a cylindrical shape (height 53 mm) with an inner diameter of 36 mm. The acrylic plate has a cylindrical part of the cylindrical injection part at a third portion in the longitudinal direction and the central axis in the width direction. A through hole having an inner diameter of 36 mm is formed so that the central axes coincide with each other and communicates between the inside of the cylindrical injection portion and the surface sheet facing surface of the acrylic plate. Next, the acrylic plate is arranged so that the central axis of the cylindrical injection portion coincides with the central portion in plan view of the absorber,
2 g of equine blood (manufactured by Nippon Biotest) is injected from the cylindrical injection part and absorbed into the sanitary napkin. The time (seconds) from when the horse blood reached the surface of the napkin until the total amount of 2 g was absorbed by the napkin was measured, and this was defined as the first liquid absorption time. In addition, 3 minutes after the first horse blood injection, the above procedure was repeated to further inject 2 g of horse blood (a total of 4 g of horse blood was injected). The time (second) until absorption was measured, and this was taken as the second liquid absorption time. The smaller the value of these liquid absorption times, the higher the liquid permeability as the absorbent article (the faster the absorption speed), and the higher the evaluation.

<Evaluation of liquid diffusion area>
In the state where the sanitary napkin using the paper of the example and the comparative example is spread in a flat shape and the top sheet is fixed on the horizontal surface with the top sheet facing upward, horse blood ( 4 g (manufactured by Nippon Biotest Co., Ltd.) is injected in 2 steps with the same injection amount as 2 g in the same procedure as in the above <Evaluation of liquid absorption time>, and left for 3 minutes. Thereafter, the outline on the absorber is copied and recorded on a transparent sheet. The obtained image was processed using image analysis processing software (Image-Pro plus, Media Cybernetics) to determine the liquid diffusion area (cm ² ). The smaller the value of the liquid diffusion area, the lower the liquid diffusibility as an absorbent article, and the higher the evaluation.

  As shown in Table 1, the sanitary napkins using the papers of Examples 1 and 2 were both “average pore diameter” and “average pore diameter of 0.7% of the total pore surface area of the paper”. Since the ratio of the pore surface area in the region of -1.3 times and the ratio of the pore surface area of the region having a pore diameter of 20 μm or less in the total pore surface area are in the specific ranges described above, at least one of these Compared with the sanitary napkin using the paper of Comparative Examples 1 and 2 whose part was not in the specific range, the liquid diffusion area was small. That is, from the results shown in Table 1, the papers of Examples 1 and 2 are arranged between the top sheet and the absorber, so that the liquid-permeable layer smoothly guides the liquid to the absorber without diffusing the liquid. As compared with the paper of Comparative Examples 1 and 2, the liquid diffusion is more effective while realizing a short liquid absorption time (excellent liquid permeability) substantially the same as Comparative Examples 1 and 2. It turns out that it can suppress. The liquid permeation time is not different between the example and the comparative example, and it can be seen that the paper of the example has excellent liquid permeability equivalent to that of the paper of the comparative example. In particular, since there was no difference in the liquid permeation time between Example 1 and Comparative Example 1 that differed only in the presence or absence of a sizing agent, it was found that the liquid permeability of the paper itself did not change before and after the sizing treatment.

The distribution of the pore diameters of the papers of Examples 1 and 2 is realized by the sizing treatment. By treating the paper with the sizing agent, liquid diffusibility (easy to move in the paper surface direction). It is presumed that the ratio of the region having a pore diameter of 20 μm or less that controls the number of pores significantly decreases, and as a result, the average pore diameter increases. The distribution of such pore diameters in the papers of Examples 1 and 2 is reflected in the 10-minute value of the Klem absorption height indicating the high liquid diffusibility. That is, it is clear that the papers of Examples 1 and 2 have a smaller 10-minute value and lower liquid diffusibility than the papers of Comparative Examples 1 and 2. In addition, since the 24-hour value of the Klem absorption height in Examples 1 and 2 is a constant size and increased compared to the 10-minute value, the papers in Examples 1 and 2 have pores. It is clear that it is not completely occluded and has liquid absorbency.
On the other hand, since the paper of Comparative Example 1 is not subjected to the sizing treatment, the ratio of the region having a pore diameter of 20 μm or less is large. Further, even when the sizing treatment is performed, the pore diameter distribution as in Examples 1 and 2 cannot be obtained when the amount of the sizing agent used is small as in Comparative Example 2, and therefore, the paper has low liquid diffusibility. Cannot be obtained.

FIG. 1 is a diagram showing a pore distribution curve of an embodiment of the low diffusibility transparent paper of the present invention. FIG. 2 is a diagram showing a pore distribution curve of paper not treated with a sizing agent. FIG. 3 is a perspective view of a sanitary napkin as an embodiment of the absorbent article of the present invention using the low-diffusibility transparent paper of the present invention. 4 is a cross-sectional view schematically showing a cross section taken along line XX of FIG.

Explanation of symbols

1 Sublayer sheet (low diffusive transparent paper)
DESCRIPTION OF SYMBOLS 10 Sanitary napkin 11 Top sheet 12 Back sheet 13 Absorber 14 Absorbent core 15 Cover sheet 16 Flap part 17 Wing part

Claims (5)

  A low-diffusibility transmission paper for absorbent articles obtained by a wet papermaking method, wherein the average pore diameter of the low-diffusibility transmission paper in pore diameter distribution measurement is 30 μm or more, and the average pore diameter The pore surface area in a region 0.7 to 1.3 times as large as 70% or more of the total pore surface area of the low-diffusibility permeable paper and the pore surface area in a region having a pore diameter of 20 μm or less is A low-diffusibility transmission paper that is 10% or less of the total pore surface area of the low-diffusibility transmission paper.   The low-diffusibility permeable paper according to claim 1, wherein the low-diffusibility permeable paper contains hydrophilic fibers and is treated with a sizing agent. Wherein the hydrophilic fibers are included bulky cellulose fibers, and low diffusivity permeability paper of the claim 1 or 2 wherein the basis weight of the low diffusion permeable sheet is 20 to 70 g / m ^2.   The low-diffusible permeable paper according to claim 3, wherein the constituent fibers of the low-diffusible permeable paper are the bulky cellulose fiber and the synthetic fiber. An absorbent article having a surface sheet that constitutes a skin contact surface, a back sheet that constitutes a non-skin contact surface, and an absorber disposed between both the sheets,
An absorbent article in which the low-diffusibility permeable paper according to any one of claims 1 to 4 is disposed between the top sheet and the absorber.

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