JP3032304B2 - Surface material for absorbent articles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface material for absorbent articles such as sanitary napkins, puerperal napkins, disposable diapers, and cosmetic cotton. More specifically, a non-woven fabric which is excellent in absorbing body fluids, especially high-viscosity body fluids such as menstrual blood and diarrhea stool, or highly viscous liquids such as a facial cleansing cream, and has excellent feel and strength to the skin is used. The present invention relates to a surface material of a disposable absorbent article.

[0002]

2. Description of the Related Art Conventional absorbent articles, such as sanitary napkins, disposable diapers and cotton, generally contain an absorbent layer made of cotton-like pulp, absorbent paper, etc. Leak-proof layer arranged on the side,
And it consists of a nonwoven fabric placed on the surface.

[0003] The nonwoven fabric forming the surface layer of such an absorbent article is required to have various performances. In particular, a high-viscosity liquid discharged from a low-viscosity liquid such as ordinary blood or urine over a period of time. For liquids with a wide range of properties, such as menstrual blood, diarrhea stool, and highly viscous liquids in which solids are dispersed, such as cosmetic facial cleansers, the flow of liquid on the surface that leads to leakage (called liquid flow) ), Good feel to the skin, moderate strength, and no fluff are the most desirable performances.

In recent years, due to the rapid spread of synthetic fiber-based dry nonwoven fabrics and the improvement of technology, these requirements have been met with respect to ordinary low-viscosity liquids such as blood, urine, and lotion. It is thought that there is.

By the way, in actual menstruation, highly viscous menstrual blood including mucous membranes in the uterus, bad dew, etc. is often excreted, and also highly excreted fluid such as diarrhea stool is excreted. There is. In addition, it is often necessary in cosmetics to treat highly viscous dispersions, such as facial cleansers.

[0006] Nonwoven fabrics designed to absorb such high-viscosity liquids have not been sufficiently studied. According to reports made so far, the distance between fibers of the nonwoven fabric is increased (JP-A-62-181041), and macroscopic holes are provided in the surface material (JP-A-62-125001, JP-A-62-125001). 62-125061) was typical. However, these surfacing materials are designed with too much emphasis on the absorption function, so that the more basic requirements for surfacing materials are the feel when touching the skin, moderate strength, and no lint. In addition, since there are many points that need to be improved in terms of bulkiness, it cannot be said that it has yet reached a practical level.

That is, it is very difficult for a nonwoven fabric obtained by a conventional manufacturing technique to simultaneously satisfy the absorption performance for a highly viscous liquid and the strength and hand that are practically appropriate.

[0008] The strength of the nonwoven fabric having openings depends on the strength of the region between adjacent holes. Generally, when this type of nonwoven fabric is used as an absorbent article, it passes through the weak portion of the region between the holes. There was a disadvantage that it was easily torn. In order to solve this, a method of increasing the adhesive strength of the fiber, a method of increasing the space between the holes, or a method of reducing the hole diameter, etc., are conceivable.
No satisfactory products in terms of feel and absorption performance have been obtained.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to improve the drawbacks of the nonwoven fabric used as a surface material of such conventional absorbent articles, and as a result, have found that low viscosity materials such as ordinary blood and urine are used. Excellent permeability not only for liquid but also for highly viscous liquids such as high viscosity menstrual blood, diarrhea stool, cosmetic facial cleanser, etc. The present inventor has found a surface material of an absorbent article free of the problem, and has completed the present invention.

That is, according to the present invention, in the surface material of an absorbent article made of a nonwoven fabric, the openings are formed by the distribution of the fibers, and the non-open area is the first area where the holes are closest to each other. And a third region other than the first and second regions, wherein the fiber density of the first region is greater than the second region.
It is intended to provide a surface material of an absorbent article characterized by having a relationship of region> third region.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic plan view showing one embodiment of the surface material of the present invention, and FIG. 2 is a schematic plan view showing another embodiment of the surface material of the present invention. That is, in these surface materials, the opening portions 4 are arranged in a regular pattern, and the non-opening portions are different from the first region 1 and the first region where the holes are closest to each other due to the difference in fiber aggregation density. , And a third region 3 other than the first and second regions. Fibers may be present in the apertures 4, but it is preferable that the fiber density is substantially 0 in consideration of liquid permeability and appearance.

In general, the strength of a nonwoven fabric is exhibited by fusion or entanglement of fibers, and the higher the fiber density, the higher the strength, but on the other hand, the feeling of the high-density portion is reduced.

Particularly in a structure in which regions substantially free of fibers are scattered, such as a perforated non-woven fabric, generally, the non-porous portion must have a high density to maintain strength, and Cannot be obtained.

In the structure of the present invention, since the high-density portion exists only in a part of the non-porous portion, that is, only in the region 1, a decrease in the feeling of the entire nonwoven fabric can be minimized, and the region 1 → 2 → 1 Since a high strength portion such as → 2 → 1... Exists in a net shape, it is possible to disperse and relax the force along the tensile force. Therefore, it exhibits sufficient strength against tensile force.

FIG. 3 is a sectional view taken along line AA 'of FIG.
Since the third region 3 having a low fiber density, that is, having a low rigidity, is located above the first and second regions and the aperture portion 4, the number of contact points with the skin is small and the feeling is excellent. Further, as can be seen from the cross-sectional shape, when the wearer's skin comes into contact, the second region 2 having high rigidity is used as a fulcrum, and the third region 3 moves up and down, thereby exhibiting cushioning and bulkiness.

As described above, the surface material of the present invention is strong,
It has the characteristics of both good feeling and very high permeability of highly viscous liquid. In order to further enhance the flow control of highly viscous liquid and to provide a coating property, it is preferable that a non-perforated nonwoven fabric is laminated and integrated below the surface material of the present invention. As a result, the liquid that has passed through the apertured nonwoven fabric can be quickly guided to the absorption layer, and the flow of the liquid on the surface is suppressed. Such an effect is better as the inter-fiber distance of the non-porous nonwoven fabric is larger.
It is preferably in the range of 300 to 300 μm, and more preferably in the range of 150 to 250 μm, it is possible to hold highly viscous liquids such as loose stool and menstrual blood.

Here, the average inter-fiber distance Δ is defined. As a first approximation of the structure of the nonwoven fabric, a model in which all the fibers are arranged in equidistant equilibrium is considered, and the inter-fiber distance is defined as “average inter-fiber distance”.

[0018]

(Equation 1)

[0019]

(Equation 2)

The thickness was measured by the following method.
Temperature lower than the melting point of the constituent fibers of the nonwoven fabric (50-70 ° C)
For a certain period of time to completely recover the thickness. The total thickness is measured (pressure 2.5 g / cm ² ).

[0021]

(Equation 3)

Non-porous layer thickness = total thickness−porous layer thickness.

Next, the excrement permeation mechanism of the present invention will be described. First, for low viscosity liquids such as urine,
It is possible to pass through the perforated portion or from a third region having a low fiber density which is hydrophilic. On the other hand, for highly viscous substances such as menstrual blood and loose stool, as shown in FIG. 4 (a), the liquid portion 5 is permeated and absorbed from the third region 3, and the remaining solid portion 6 is retained in the third region. However, as shown in FIG. 4 (b), it is introduced into a lower layer such as an absorption layer through the opening 4.

For the method of producing the nonwoven fabric of the present invention, for example, any of the following methods may be used. A. Nonwoven fabric by entanglement (entanglement) of fiber staples (entangled nonwoven fabric): It can be obtained by needling a fiber web formed by a card with a high-speed fluid (water, air, etc.) or a needle. In response to the needling method,
It is called "water jet nonwoven fabric" or "needle punched nonwoven fabric".

B. Non-woven fabric in which fibers are bonded to each other by thermal melting of a resin composition (heat-bonded non-woven fabric): This is further classified as follows. B-1. A type in which fiber filaments having almost no crimp are thermally bonded, and the bonded region is macroscopically discontinuously distributed. Generally, it is called "spunbond nonwoven fabric". B-2. A type in which fiber staples have a large degree of adhesive melting, and the bonding points are tightly and irregularly distributed. It is generally called "heat roll bonded nonwoven fabric". B-3. A type in which only the contact points of the fiber staples are melt-bonded, and the bonding point density is small and irregularly distributed. Generally, it is called "suction heat bond nonwoven fabric".

C. A nonwoven fabric in which fiber staples are adhered by a chemical binder and the adhesion points are tight and irregular, or are regularly and discontinuously distributed:
It is called "binder type nonwoven fabric".

There are many methods for opening the non-woven fabric formed as described above and controlling the fiber density in each region. The production method using the suction heat bonding method will be described as an example.

The hole opening method by the suction heat bonding method is in principle the same as the water jet method.
For example, a fiber web is placed on a perforated plate corresponding to the hole diameter and the opening ratio, and first, hot air slightly lower than the melting point of the fiber is passed, and holes are formed by dividing and heat setting the fiber. Immediately thereafter, hot air having a temperature higher than the melting point of the fiber is passed to simultaneously bond the fibers and stabilize the hole shape.
At this time, if a perforated plate having a shape as shown in FIG. 5 is used, the non-opening portion generates a temperature distribution and a velocity distribution of hot air in the order of the first area> the second area> the third area, and the temperature of the hot air,
A region with a high speed forms a first region with a high fiber density, and a region with a low speed forms a third region with a low fiber density.

Further, when the film is weakly stretched in the longitudinal direction to the extent that the cross-sectional shape is not impaired, the difference in fiber density in each region is further increased, and the strength can be increased.

The nonwoven fabric of the present invention is not limited to a fiber composition.

Here, the details in the case of manufacturing the nonwoven fabric of the present invention by the suction heat bonding method will be described. The basic requirements for the fiber composition of the non-woven fabric are that the surface is melted by hot air, the crimped structure of the whole fiber is hard to change, and the heat-bonding binder (thermoplastic) fiber made of resin with strong heat-bonding strength between the fibers is included. It is. Representative examples of such fibers include polyolefins such as polypropylene and polyethylene, polyesters, nylon 6, and nylon 66.
Sheath-core type, skin-core type (core is a high-melting point resin), side-by-by combining a resin having a relatively high melting point with a resin having a relatively high melting point from a polyamide-based resin such as polyacrylonitrile-based resin and the like. Side-type composite fibers can be used. Among these, more preferred are composite fibers having a low melting point resin made of polyethylene, which has a strong melt adhesion between the resins and is soft in the resin itself. The most preferable is a conjugate fiber composed of a combination of polyethylene-polypropylene and polyethylene-polyester in which the crimp elasticity of the fiber itself is large and stable. In order to further increase the adhesive strength, it is necessary to increase the ratio of the low melting point resin in one fiber. However, if it is too large, the crimped form of the fiber after the heat treatment becomes unstable. It is desirable that In the case of polyethylene-based binder fiber having a low melting point resin, the lower the fluidity of the polyethylene resin at the time of heat melting, the stronger the adhesive force and the smaller the deformation of the bonding point (good texture).
Therefore, it is desirable for the purpose of the present invention to use a polyethylene resin having a melt flow value of 15 or less, preferably 10 or less. Further, in a combination in which the low melting point resin / the high melting point resin has high compatibility, the adhesive strength between the binder fibers is high. For example, when polyethylene resin is used as the low melting point resin, polypropylene is used as the high melting point resin, or polyester is used. It is effective to use a resin obtained by blending a polyethylene resin with such a high elasticity resin.

The mixing ratio of the binder fiber and the non-binder fiber can be set arbitrarily. However, at present, for disposable diapers that require high strength and a high level of lint prevention, the binder fiber content is preferably 70% or more, and most preferably 100%. For sanitary napkins and cosmetic cotton applications where texture is more important, the blending ratio of binder fiber should be at least 50%.

Since the fuzz loss of the nonwoven fabric increases as the mixing ratio of the non-binder fibers increases, the mixing ratio of these fibers is preferably 50% or less in each layer of the nonwoven fabric. Polyethylene binder fiber and polypropylene fiber, and amorphous polyester binder fiber and polyester fiber are highly compatible. Therefore, in a nonwoven fabric layer in which these are mixed, if the mixture ratio of the binder fiber is 30%, the fluff can be prevented from coming off. Can be achieved.

The crimped form of the fibers of the nonwoven fabric is also important. When the above-mentioned binder fiber or non-binder fiber has some bilateral structure and is provided with a three-dimensional crimp, when a web having the same weight is formed, as compared with a case where only a normal mechanical crimp is provided by a stuffing box or the like. Is more preferable in that the inter-fiber voids are large, the web is formed uniformly, and the texture and feel after the opening treatment are good.

The thickness of the fiber is desirably as small as possible in the open nonwoven fabric in view of the strength and hand of the nonwoven fabric. However, considering the fiber density of the region 3, when the above-mentioned fiber is used, 6 denier is used. The following is desirable, and in consideration of manufacturing stability, it is more desirable that the density be 3 denier or less. The non-perforated nonwoven fabric can be freely selected as long as it is sufficiently smaller than the average inter-fiber distance. However, considering the processability in manufacturing, the non-porous nonwoven fabric preferably has a range of 3 denier to 10 denier.

The basis weight is 5 to 50 g / g in consideration of the covering property for the absorbent article and the processability in producing the absorbent article.
It is desirable to set between m ^2.

It is necessary that the formed nonwoven fabric has a proper hydrophilicity. For example, hydrophilicity may be imparted to the nonwoven fabric by using fibers having a hydrophilic surface such as rayon. However, in order to suppress the stickiness of the nonwoven fabric surface and the liquid return from the absorbing layer, the absorption rate is large, and the ratio of the fibers whose surface is hydrophilic and the inside is hydrophobic is preferably large, and the most desirable is The nonwoven fabric is composed of 100% of such fibers. Fibers whose surfaces are hydrophilic and whose interior is hydrophobic are, for example, polyolefin fibers such as polyethylene and polypropylene, polyester fibers, polyamide fibers, and surfaces of hydrophobic synthetic fibers such as polyacrylonitrile fibers. The surface is treated with an activator, chemically modified with a chemical substance having a hydrophilic group such as a monomer with a hydrophilic group or a polymer with a hydrophilic group, or subjected to physical surface modification such as plasma processing. It can be made hydrophilic. In the chemical surface modification, a chemical substance having a hydrophilic group may be bonded to the fiber surface, or a chemical substance having a hydrophilic group may be bonded and crosslinked to cover the fiber surface. More directly, a skin-core type composite fiber in which the skin portion is a hydrophilic fiber and the core portion is a hydrophobic fiber may be used. Further, the surface modification of the above-mentioned hydrophobic synthetic fiber may be performed in a fiber state before forming the nonwoven fabric,
It may be performed during the nonwoven fabric forming step. In these surface hydrophilic states, a suitable hydrophilicity can be set before the liquid permeates, and after the liquid permeates, it falls off with the liquid to expose the hydrophobic surface,
It is most preferable to use a surfactant treatment which reduces the hydrophilicity and is excellent in the effect of suppressing liquid return from the absorption layer in that portion.

The absorbent article using the surface material of the present invention is manufactured by covering the lower surface and side surfaces of the absorbent layer with a leak-proof layer if necessary, and covering the surface with a nonwoven fabric satisfying the above specific conditions. Is done.

The materials of the absorbing layer and the leak-proof layer used here are not particularly limited, and those used in conventionally known absorbent articles can be used.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Absorbent articles using the surface material of the present invention can be used for sanitary napkins, puerperal napkins, disposable diapers, cotton swabs, and the like. Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, with a focus on a disposable diaper.

Examples 1 to 4 and Comparative Examples 1 to 6 Absorbent articles were prepared from the non-woven fabrics manufactured using the various fibers, compositions and manufacturing methods shown in Table 1 by the following method, and the performance thereof was shown below. Tested.

The results are shown in Table 2.

<Measurement Sample> (1) Production of Nonwoven Fabric: In Examples 1 to 4, the nonwoven fabric was produced by the suction-healing method and holes were formed at the same time.
That is, a fiber web is placed on a metal net having irregularities, hot air having a temperature lower than the melting point of the constituent fibers is passed from above, and the web on the convex portion is pressed into the concave portion, and the portion corresponding to the convex portion corresponds to the hole and the concave portion. The fibers were distributed so that the portion to be formed became a non-porous portion, and then hot air having a temperature higher than the melting point of the constituent fibers was passed through the web to heat-bond the fibers together to form a nonwoven fabric.

In Comparative Examples 1 and 2, a non-woven fabric was manufactured by the suction heat bonding method, and holes were formed by punching. In Comparative Examples 3 and 4, nonwoven fabrics were produced by the suction-heal bond method, and no holes were formed. In Comparative Examples 5 and 6, nonwoven fabrics were manufactured by the water needling method.

(2) Manufacture of Absorbent Articles: Using the non-woven fabric prepared as described above, commercially available disposable diapers (trade name: Merize, manufactured by Kao Corporation) and commercially available sanitary napkins (trade name: Laurier, Kao Corporation) )) Was removed, and the nonwoven fabric on which these nonwoven fabrics were placed was used as an absorbent article assuming disposable paper diapers and sanitary napkins.

<Test Method> (1) Thickness: A 50 mm × 50 mm pressure plate is placed on the nonwoven fabric, and the thickness of the nonwoven fabric under a pressure of 2.5 g / cm ² is measured with a dial gauge thickness gauge (manufactured by PEACOCK).

(2) Nonwoven fabric strength: A sample having a width of 50 mm is cut out in a direction perpendicular to the fiber orientation. Using a tensile tester, measure the breaking strength when pulled in the direction perpendicular to the fiber orientation at a distance between the chucks of 100 mm.

(3) Soft stool transmittance: As shown in FIG.
The sample 8 is fixed between two glass cylinders (inner diameter 34 mm) 7, 7 'with scissors clips. 910 g of test solution is injected along the inner wall of the upper cylinder 7 at a speed of 2 g / sec. Sample 8 5 seconds after the end of the injection
, And the amount of liquid collected in the lower cylinder 7 'is weighed.

[0049]

(Equation 4)

(4) Soft stool flow on the surface: disposable diaper assumption: 3 g of test solution from 1 cm above the sample surface inclined at 45 degrees
At a rate of 1 g / sec. The length of the test liquid flowing on the nonwoven fabric surface is measured. As a test liquid, artificial stool having a viscosity of 250 cp, which was prepared by dispersing flour in water, was used. The surface loose stool flow indicates that the shorter the stool flow, the more the flow of the excreted liquid is suppressed, and the higher the leakage prevention force against lateral leakage.

(5) Texture: The sensory evaluation was made on the softness and feel of the nonwoven fabric surface. 3rd grade… Soft, good texture. Grade 2… Slightly hard and rough, but usable. 1st class: Hard and rough, uncomfortable to use.

(6) Fiber density: Measured using an image analyzer. Model name: Image Command 4198 Manufacturer: Nippon Avionics Co., non apertured nonwoven (sheath polyethylene measurement fiber density of the fiber density known (5 to 100 g / m ^2), core is a polyester, 2 denier × 51
The intensity of the reflected light of the nonwoven fabric made of a conjugate fiber having a mm cut length) is measured with an image analyzer, and a calibration curve is created. Next, the intensity of the reflected light of the portion corresponding to the first to third regions of the perforated nonwoven fabric is measured, and the fiber density of each region is obtained from the calibration curve.

(7) Porosity / pore diameter: Measured using an image analyzer. Model name: Image Command 4198 Manufacturer: Nippon Avionics Co., Ltd. Measurement of aperture ratio: Measure the shade area of black mount. When the sample nonwoven fabric is placed on the black mount, the pixel portion indicating the shaded area of the black mount corresponds to the hole. From the number of pixels X in the shaded area corresponding to the hole portion and the number of pixels A in the entire image processing portion of the nonwoven fabric sample, the aperture ratio P was calculated by the following equation. P = 100 × X / A (%) Pore diameter measurement: When image processing is performed to binarize the shading in the shading area corresponding to the hole part and the other shading areas, the holes are distributed in an island shape. You can see the image. The number N of islands (holes) is measured, and an average opening area a is derived by the following calculation. a = c × X / N (c is a known hole area / the number of pixels in the known hole area).

[0054]

[Table 1]

[0055]

[Table 2]

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing one embodiment of a surface material of the present invention.

FIG. 2 is a schematic plan view showing another embodiment of the surface material of the present invention.

FIG. 3 is a sectional view taken along line AA ′ of FIG. 1;

FIG. 4 is a cross-sectional view showing the mechanism by which excrement permeates through the surface material of the present invention, wherein (a) is a state before the permeation of a solid portion,
(b) shows the state after permeation of the solid part.

FIG. 5 is a plan view of a perforated plate used for manufacturing the surface material of the present invention.

FIG. 6 is a cross-sectional view of a measuring apparatus for soft stool transmittance.

[Explanation of symbols]

 1: 1st area 2: 2nd area 3: 3rd area 4: Open part 5: Liquid part 6: Solid part 7, 7 ': Glass cylinder 8: Sample 9: Test liquid

Continuation of the front page (51) Int.Cl. ⁷ identification code FI D04H 1/54 (58) Investigated field (Int.Cl. ⁷ , DB name) A61K 13/15 A61K 5/44

Claims (5)

(57) [Claims] 1. In a surface material of an absorbent article made of a nonwoven fabric, apertures are formed by distribution of fibers, and non-open areas are a first area, a first area where holes are closest to each other, and a first area.
A second region that is a hole surrounding region other than the region, and a first region, a third region other than the second region;
A surface material for an absorbent article, wherein the fiber density of each region is in a relationship of first region> second region> third region. 2. The surface material for an absorbent article according to claim 1, wherein the third region is located above the first and second regions in the cross section of the nonwoven fabric. 3. The surface material of an absorbent article according to claim 1, wherein the surface material of the absorbent article is formed of a thermoplastic fiber. 4. The liquid-permeable non-perforated nonwoven fabric is laminated and integrated on the back surface of the surface material.
The surface material of the absorbent article according to any one of claims 3 to 7. 5. The non-perforated nonwoven fabric having a fiber-to-fiber distance of 100 to 100.
The surface material of an absorbent article according to claim 4, wherein the surface material is in a range of 300 µm.