JPH04221556A - Surface material for absorbable article - Google Patents

Abstract

PURPOSE:To provide a thrown-away surface material for an absorbable article using an woven fabric which is excellent in absorbing ability for a highly viscous body liquid or highly viscous liquid and which is also excellent in feeling to the skin and in strength. CONSTITUTION:A surface material for an absorbable article made of an unwoven fabric is formed therein with holes by distributing fibers, having a non-hole area section which is composed of a first area in which a distance between holes is shortest, a second area around a hole range other than the first area, and a third area other than the first and second areas, the relationship among the first to third areas is such as the first area > the second area > the fourth area.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to disposable absorbent articles, particularly surface materials for absorbent articles such as sanitary napkins, postpartum napkins, disposable diapers, and cosmetic cotton. More specifically, we use a nonwoven fabric that has excellent absorbency for body fluids, particularly high viscosity body fluids such as high viscosity menstrual blood and diarrheal stool, or high viscosity liquids such as cosmetic facial cleansing cream, and has excellent feel and strength against the skin. The present invention relates to surface materials for disposable absorbent articles.

0002

[Prior Art and Problems to be Solved by the Invention] Conventional absorbent articles, such as sanitary napkins, disposable diapers, and cosmetic cotton, generally have an absorbent layer made of cotton pulp, absorbent paper, etc. It consists of a leak-proof layer placed on the sides and a nonwoven fabric placed on the surface.

[0003] The nonwoven fabric forming the surface layer of such absorbent articles is required to have various performances, but in particular, it can handle everything from low viscosity liquids such as normal blood and urine to high viscosity liquids excreted during menstruation. For liquids with a wide range of properties, including menstrual blood, diarrheal stool, and highly viscous liquids with solids dispersed in them, such as cosmetic facial cleansing creams, fluid flow on the surface (called liquid flow) that can lead to leakage occurs. ), feel good on the skin, have appropriate strength, and do not become fluffy.

[0004] In recent years, with the rapid spread of synthetic fiber-based dry-laid non-woven fabrics and improvements in technology, these required performances have been considerably satisfied for ordinary blood, urine, and low-viscosity liquids such as lotions. It is thought that there are.

By the way, during actual menstruation, highly viscous menstrual blood containing intrauterine mucous membranes, lochia, etc. is often excreted, and during excretion, highly viscous liquid such as diarrhea stool is also excreted. There is. Furthermore, even in cosmetics, it is often necessary to process highly viscous dispersion systems, such as facial cleansing creams.

Nonwoven fabrics designed to absorb such highly viscous liquids have not yet been sufficiently studied. In the reports that have been made so far, the distance between the fibers of nonwoven fabric is increased (Japanese Patent Laid-Open No. 62-181041), and macroscopic holes are installed in the surface material (Japanese Patent Laid-Open No. 62-125001,
JP-A No. 62-125061) was a typical idea. However, these surface materials are designed with too much emphasis on their absorption function, and therefore do not meet the more basic requirements of a surface material: feel when in contact with the skin, appropriate strength, and no fluff. In particular, there are many points that need to be improved in terms of bulkiness, so it cannot be said that it has yet reached a practical level.

[0007] That is, with nonwoven fabrics obtained by conventional manufacturing techniques, it has been extremely difficult to simultaneously satisfy absorbency against highly viscous liquids and practically appropriate strength and texture.

Furthermore, the strength of a nonwoven fabric with openings depends on the strength of the area between adjacent pores, but generally when this type of nonwoven fabric is used as an absorbent article, the strength of the area between the pores is weak. It had the drawback of being easy to tear. To solve this problem, methods such as increasing the adhesive strength of the fibers, widening the distance between the holes, or reducing the hole diameter can be considered.
No material has been obtained that is fully satisfactory in terms of feel and absorption performance.

[0009]

[Means for Solving the Problems] As a result of intensive research to improve the drawbacks of nonwoven fabrics used as surface materials for conventional absorbent articles, the present inventors have found that they can be used for low-viscosity materials such as ordinary blood and urine. It has excellent permeability not only for liquids, but also for highly viscous liquids such as highly viscous menstrual blood, diarrheal stool, and cosmetic facial cleansing cream.It also feels good when it comes in contact with the skin, has moderate strength, and is fluffy. The present inventors have discovered a surface material for absorbent articles that is free of surface oxides, and have completed the present invention.

That is, the present invention provides that in the surface material of an absorbent article made of a nonwoven fabric, the pores are formed by distributing the fibers, and the non-porous area is the first region where the pores are closest to each other. The structure consists of three regions: a region, a second region which is a pore surrounding region other than the first region, and a third region other than the first and second regions, and the fiber density of each region is such that the fiber density of the first region>the second region
The present invention provides a surface material for an absorbent article characterized by a relationship of region>third region.

The present invention will be explained in detail below 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. In other words, in these surface materials, the perforated parts 4 are arranged in a regular pattern, and the non-perforated parts are arranged in the first region 1 where the pores are closest to each other and in the non-first region due to the difference in fiber aggregation density. The second region 2, which is the part around the hole, and the first region
, and a third area 3 other than the second area. Although fibers may exist in the open hole portion 4,
Considering liquid permeability and appearance, fiber density is practically 0.
It is desirable that

[0012] In general, the strength of a nonwoven fabric is developed by the fusion or entanglement of fibers, and the higher the fiber density, the higher the strength, but on the other hand, the feel of the high-density portion deteriorates.

In particular, in structures such as perforated nonwoven fabrics, which are dotted with areas where there are virtually no fibers, it is generally necessary to have a high density in the non-porous areas in order to maintain strength, so it is necessary to have a good texture. 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, in region 1, deterioration in the texture of the entire nonwoven fabric can be minimized, and the area 1→2→1 Since there is a net-like portion of high strength as shown in →2→1, etc., it is possible to disperse and relieve the tensile force along this line. Therefore, it exhibits sufficient strength against tensile force.

FIG. 3 is a sectional view taken along line AA' in FIG. The third region 3 with low fiber density, that is, low stiffness is the first region 3.
, 2 is located above the aperture 4, so there are fewer points of contact with the skin and the feel is excellent. In addition, as can be seen from the cross-sectional shape, when the wearer's skin comes into contact with it, the second region 2 with high rigidity is used as a fulcrum, and the third region 3 moves up and down.
Demonstrates cushioning properties and bulkiness.

As described above, the surface material of the present invention is strong,
It has a good texture and very high permeability to highly viscous liquids. In order to further suppress the flow of a highly viscous liquid and provide better coverage, it is desirable to laminate and integrate a non-porous nonwoven fabric under the surface material of the present invention. This allows the liquid that has passed through the perforated nonwoven fabric to be quickly guided to the absorbent layer, thereby suppressing the flow of liquid on the surface. This effect is better as the distance between the fibers of the non-porous nonwoven fabric increases, and the distance between the fibers is 1.
It is preferably in the range of 00 to 300 μm, more preferably in the range of 150 to 250 μm, so that it is possible to retain high viscosity liquids such as soft stool and menstrual blood.

[0017] Here, the average interfiber distance Δ is defined. As a first approximation of the structure of a nonwoven fabric, consider a model in which all fibers are arranged equidistantly and equidistantly, and the distance between the fibers is defined as the "average interfiber distance."

[0018]

[Math 1]

[0019]

[Math 2]

The thickness was measured by the following method. ■
The nonwoven fabric is heated at a temperature lower than the melting point of the constituent fibers (50 to 7
0℃) for a certain period of time to completely recover the thickness. ■
Measure the overall thickness (pressure 2.5 g/cm2).

[0021]

[Math 3]

[0022] Non-porous layer thickness = total thickness - porous layer thickness.

Next, the excrement permeation mechanism of the present invention will be explained. First, for low viscosity liquids such as urine,
It is possible to pass through through the open pores or through the third region, which is hydrophilic and has a low fiber density. On the other hand, for highly viscous substances such as menstrual blood or loose stool, the liquid portion 5 is permeated and absorbed from the third region 3, as shown in FIG. 4(a).
The remaining solid portion 6 is retained in the third region, but is introduced through the aperture 4 into an underlying layer, such as an absorbent layer, as shown in FIG. 4(b).

[0024] For example, any of the following methods may be used to produce the nonwoven fabric of the present invention. A. Nonwoven fabric created by entanglement of fiber staples (entangled nonwoven fabric): Can be obtained by needling a fibrous web formed by a card with a high-speed fluid (water, air, etc.) or a needle. Depending on the needling method, they are called "water jet nonwoven fabric", "needle punch nonwoven fabric", etc.

B. Nonwoven fabric in which fibers are bonded together by thermal melting of a constituent resin (thermally bonded nonwoven fabric): This is further classified as follows. B-1. A type in which fiber filaments with almost no crimp are thermally bonded, and the bonded area is macroscopically discontinuously distributed. Generally called "spunbond nonwoven fabric." B-2. A type in which the degree of adhesive melting between fiber staples is large, and the adhesive points are tightly and irregularly distributed. Generally called "heat roll bonded nonwoven fabric." B-3. A type in which only the contact points of fiber staples are melted and 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 bonded to each other by a chemical binder, and the bonding points are tightly and irregularly distributed, or are regularly and discontinuously distributed: generally referred to as a "binder-type nonwoven fabric."

Although there are many methods of opening holes in the nonwoven fabric formed as described above and controlling the fiber density in each region, a manufacturing method using a suction heat bond method will be explained as an example.

The hole opening method using the suction heat bond method is basically the same as the water jet method. For example, a fibrous web is placed on a perforated plate corresponding to the pore size and porosity, and hot air slightly lower than the melting point of the fibers is passed through the web to form pores by twisting and heat setting the fibers. Immediately after that, hot air at a temperature higher than the melting point of the fibers is passed through to simultaneously bond the fibers together and stabilize the pore shape. At that time, if a perforated plate having a shape as shown in FIG. 5 is used, the temperature distribution and velocity distribution of the hot air will occur in the order of the first area>second area>third area in the non-perforated area, and the temperature and velocity distribution of the hot air will change in the order of the first area>second area>third area.
The high speed region forms a first region with high fiber density, and conversely the low speed region forms a third region with low fiber density, making it possible to obtain the truly desired apertured nonwoven fabric.

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

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

[0031] Here, details will be particularly given of the case where the nonwoven fabric of the present invention is produced by the suction heat bonding method. The basic requirements for the fiber composition of nonwoven fabrics are that the surface is melted by hot air, the crimped structure of the entire fiber is difficult to change, and that it contains thermobonding binder (thermoplastic) fibers made of resin that has strong thermal adhesion between fibers. It is. Typical examples of such fibers include polyolefins such as polypropylene and polyethylene, polyesters, nylon 6, and nylon 6.
Sheath-core type, skin-core type (the core is made of high-melting point resin), and side-by-side type are made by combining resins with relatively high and low melting points from polyamide-based resins such as No. 6, polyacrylonitrile-based resins, etc. - Examples include side-type composite fibers. More preferred among these is a composite fiber in which polyethylene, which has a strong melt adhesion between resins and is soft in itself, is used as a low melting point resin. Most preferred are composite fibers made of combinations of polyethylene-polypropylene and polyethylene-polyester, which have a highly stable crimp elasticity. In addition, to further increase the adhesive strength, it is possible to increase the proportion of low melting point resin in each fiber, but if it is too large, the crimped form of the fiber after heat treatment will become unstable, so it should not exceed 80%. It is desirable that In addition, in the case of binder fibers whose low melting point resin is polyethylene, the lower the fluidity of the polyethylene resin when it is hot melted, the stronger the adhesive force will be and the less deformation of the bonding point (good texture), so the melt flow value should preferably be 15 or less. 10
It is desirable for the purposes of this invention to use the following polyethylene resins: Furthermore, in a highly compatible combination of low melting point resin/high melting point resin, the adhesion 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, It is effective to use a resin obtained by blending a polyethylene resin with a high elastic resin such as the above.

[0032] The blending ratio of binder fibers and non-binder fibers can be set arbitrarily. However, at present, for disposable diaper applications that require high strength and high anti-lint properties, the blending ratio of binder fibers 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 fibers should be at least 50%.

Since the nonwoven fabric becomes more fluffy as the blending ratio of non-binder fibers increases, it is preferable that the blending ratio of these fibers is 50% or less in each layer of the nonwoven fabric. Polyethylene binder fibers and polypropylene fibers, and amorphous polyester binder fibers and polyester fibers are highly compatible, so in a nonwoven fabric layer in which these are mixed,
If the blending ratio of binder fiber is 30%, prevention of fluffing can be achieved.

[0034] The crimp form of the fibers of the nonwoven fabric is also important. When the above-mentioned binder fibers or non-binder fibers have some kind of bilateral structure and are given three-dimensional crimps, they have a higher web weight when formed into a web of the same weight than those that are given only normal mechanical crimps using a stuffing box or the like. It is more preferable in that the inter-fiber voids are large, the web is formed uniformly, and therefore the texture and feel after hole-opening treatment are good.

[0035] It is desirable that the thickness of the fibers be as thin as possible in view of the strength and texture of the nonwoven fabric, but considering the fiber density in region 3, when using the above-mentioned fibers, the thickness of the fibers should be as thin as possible. The following is desirable, and in consideration of manufacturing stability, it is more desirable to be 3 denier or less. The non-porous nonwoven fabric can be freely selected as long as it is sufficiently small compared to the average interfiber distance, but in consideration of manufacturing process efficiency, it is preferably in the range of 3 deniers or more and 10 deniers or less.

[0036] The basis weight is 5 to 50, considering the ability to coat the absorbent article and the process efficiency in manufacturing the absorbent article.
It is desirable to set it between g/m2.

[0037] Furthermore, it is necessary that the formed nonwoven fabric has appropriate hydrophilicity. For example, hydrophilic properties may be imparted to the nonwoven fabric through the use of fibers with hydrophilic surfaces, such as rayon. However, in order to increase the absorption rate and suppress the sticky feeling on the surface of the nonwoven fabric and liquid return from the absorbent layer, it is better to have a higher proportion of fibers that have a hydrophilic surface and a hydrophobic interior. The nonwoven fabric is made up of 100% such fibers. Fibers with a hydrophilic surface and a hydrophobic interior include, for example, the surface of hydrophobic synthetic fibers such as polyolefin fibers such as polyethylene and polypropylene, polyester fibers, polyamide fibers, and polyacrylonitrile fibers.
The surface can be improved by treatment with surfactants, chemical surface modification by chemically bonding chemical substances with hydrophilic groups such as monomers with hydrophilic groups or polymers with hydrophilic groups, or physical surface modification such as plasma processing. can be obtained by making it 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 to each other and crosslinked to cover the fiber surface. More directly, a skin-core composite fiber may be used in which the skin portion is made of hydrophilic fibers and the core portion is made of hydrophobic fibers. Further, the above-mentioned surface modification of the hydrophobic synthetic fiber may be carried out in the fibrous state before forming the nonwoven fabric, or may be carried out during the process of forming the nonwoven fabric. In these surface hydrophilic states, appropriate hydrophilicity can be set before the liquid permeates, and after the liquid permeates, it falls off with the liquid and the hydrophobic surface is exposed, or the hydrophilicity decreases and the absorption layer from that part is removed. It is most preferable to use a surfactant treatment, which has an excellent effect of suppressing liquid return.

Absorbent articles using the surface material of the present invention are manufactured by covering the lower and side surfaces of the absorbent layer with a leak-proof layer if necessary, and covering the surface with a nonwoven fabric that satisfies the specific conditions described above. be done.

[0039] The materials for the absorbent layer and the leak-proof layer used here are not particularly limited, and those used in conventionally known absorbent articles can be used.

[0040]

[Example] Absorbent articles using the surface material of the present invention can be used for sanitary napkins, puerperal napkins, disposable diapers, cosmetic cotton, etc., but here we will focus on excrement whose volume and viscosity are much larger than those of other products. The present invention will be described in more detail below with reference to Examples and Comparative Examples, focusing on paper diapers.

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

The results are shown in Table 2.

<Sample for measurement> (1) Production of nonwoven fabric: In Examples 1 to 4, holes were formed at the same time as the nonwoven fabric was produced by the suction heat bond method. That is, a fiber web is placed on a metal net with unevenness, hot air with a temperature lower than the melting point of the constituent fibers is passed from above, and the web on the protrusions is pushed into the recesses, and the parts corresponding to the protrusions correspond to the holes and the recesses. The fibers were distributed so that the portions with pores were non-porous, and then hot air at a temperature higher than the melting point of the constituent fibers was passed through the web to thermally fuse the fibers together to form a nonwoven fabric.

[0044] In Comparative Examples 1 and 2, a nonwoven fabric was produced by a suction heat bonding method, and then holes were made by punching. In Comparative Examples 3 and 4, nonwoven fabrics were manufactured by a suction heat bonding method, and no holes were formed. In Comparative Examples 5 and 6, nonwoven fabrics were manufactured by a water needling method.

(2) Manufacture of absorbent articles: Using the nonwoven fabric prototyped above, commercially available disposable diapers (product name: Merries, manufactured by Kao Corporation) and commercially available sanitary napkins (product name: Laurier, manufactured by Kao Corporation) were prepared. The non-woven fabrics (manufactured by )) were removed, and articles covered with these non-woven fabrics were used instead as absorbent articles intended for disposable diapers and sanitary napkins, respectively.

<Test method> (1) Thickness: 50mm x 5
Place a 0mm pressure plate on the nonwoven fabric and apply 2.5g/cm
The thickness of the nonwoven fabric under two pressures is measured using a dial gauge type thickness meter (
(manufactured by PEACOCK).

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

(3) Soft stool transmittance: ■ As shown in Figure 6, two glass cylinders (inner diameter 34 mm) 7,
Sample 8 is placed between 7' and fixed with a scissor clip. ■ 2 g/se along the inner wall of the upper cylinder 7
Inject 10 g of test solution 9 at a rate of c. (5) Weigh the amount of liquid that has passed through the sample 8 and accumulated in the lower cylinder 7' 5 seconds after the injection is completed.

[0049]

[Math 4]

(4) Surface soft stool flow: Assumed paper diaper: 4
3 g of test liquid is discharged at 1 g/sec onto the sample surface inclined at 5 degrees from 1 cm above. Measure the length of flow of the test liquid on the surface of the nonwoven fabric. The test liquid was prepared by dispersing wheat flour in water and had a viscosity of 250 c. p. artificial soft stool was used. The shorter the flow of loose stool on the surface, the more it suppresses the flow of excretory fluid and the higher the ability to prevent side leakage.

(5) Texture: The softness and feel of the surface of the nonwoven fabric were sensory evaluated. Grade 3: Soft and nice to the touch. Grade 2: Slightly hard and rough, but usable. Grade 1: Hard, rough, and unusable.

(6) Fiber density: Measured using an image analysis device. ■ Model name: Image Command 4198
■ Manufacturer: Nippon Avionics Co., Ltd. ■ Measurement of fiber density Non-porous non-woven fabric with known fiber density (5 to 100 g/m2) (sheath part is polyethylene, core part is polyester, made of composite fiber of 2 denier x 51 mm cut length) The intensity of reflected light is measured using an image analyzer and a calibration curve is created. Next, the intensity of the reflected light in the portions corresponding to the first to third regions of the perforated nonwoven fabric is measured, and the fiber density of each region is determined from a calibration curve.

(7) Porosity ratio/pore diameter: Measured using an image analysis device. ■ Model name: Image Command 4198
■ Manufacturer: Nippon Avionics Co., Ltd. ■ Measurement of porosity: Measure the dark and light areas of the black mount. When the sample nonwoven fabric is placed on the black mount, the pixel portions of the black mount that indicate the shading areas correspond to the holes. The open area ratio P was calculated using the following formula from the number of pixels X in the light and shade region corresponding to the hole portion and the number A of pixels in the entire image processing area of the nonwoven fabric sample. P = 100 x You can see the image. The number N of islands (pores) is measured, and the average open pore area a is derived by the following calculation. a=c·X/N (c is known hole area/number of pixels within known hole area).

[0054]

[Table 1]

[0055]

[Table 2]

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view showing an embodiment of the 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 A-A' in FIG. 1;

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

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

FIG. 6 is a sectional view of a soft stool permeability measuring device.

[Explanation of symbols]

1: First area 2: Second area 3: Third area 4: Opening part 5: Liquid part 6: Solid part 7, 7’: Glass cylinder 8: Sample 9: Test liquid

Claims (5)

[Claims] Claim 1: In a surface material of an absorbent article made of a nonwoven fabric, pores are formed by distributing fibers,
The non-opening area includes a first area where the holes are closest to each other, a second area that is an area around the hole other than the first area, and a first area.
A surface material for an absorbent article having a structure consisting of three regions, a third region other than the second region, and in which the fiber density of each region is in the relationship of the first region > the second region > the 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 a cross section of the nonwoven fabric. 3. The surface material of the absorbent article according to claim 1, wherein the surface material of the absorbent article is made of thermoplastic fiber. 4. A liquid-permeable non-porous 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 -3. 5. The non-porous nonwoven fabric has an inter-fiber distance of 1
5. The surface material for an absorbent article according to claim 4, wherein the surface material has a diameter in the range of 00 to 300 μm.