JPH03241051A - Liquid impermeable sheet for sanitary material - Google Patents

Abstract

PURPOSE:To obtain the title sheet suitable as a sanitary napkin, having specific weight, excellent prevention of humors leakage, air permeability and soft handle by partially bonding polyolefin superfine fibers having a specific average fiber diameter. CONSTITUTION:Polyolefin superfine fibers (preferably comprising polypropylene) having 0.5-2.5mum, preferably 1.0-2.0mum average fiber diameter prepared by melt blow method are partially bonded to give the objective sheet having 10-40g/m<2> weight. A liquid absorbing layer obtained by covering a liquid absorbing material 4 with a liquid absorbing sheet 3 is wrapped with the objective sheet and a liquid permeable sheet 1 is laminated and bonded to the top of the liquid absorbing layer to give a sanitary napkin having excellent prevention of liquid leakage. Lamination of a bulky, liquid impermeable sheet 5 of polyolefin fiber having <=0.12g/cm<3> bulk density to the inside of the sheet 2 improves prevention of liquid leakage.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a liquid-impermeable sheet for sanitary materials.

More specifically, the present invention relates to a liquid-impermeable sheet for sanitary materials that prevents leakage of body fluids such as blood, has breathability, has a soft texture, and is particularly useful as a sanitary napkin.

(Prior Art) Necessary functions of a liquid-impermeable sheet for sanitary materials, for example, a liquid-impermeable sheet (back sheet material) such as a sanitary napkin, include impermeability to liquids and flexibility. Conventionally, polyethylene film or polyethylene laminate paper has often been used as this backsheet material.

Sheets made of ultrafine fibers can be obtained, for example, by a melt blowing method, and the melt blowing method is described by Industrial and Engineering Chemistry (I
industrial and engineering
Chemistry, Volume 48, No. 8, pp. 1342-1346 (published in 1956) discloses a basic method and an apparatus for carrying out the method.
Publication No. 6-33511 and JP-A-55-142757
The publication discloses a method for producing ultrafine fibers such as polyolefin and polyester.

Further, Japanese Utility Model Publication No. 63-44035 discloses a sanitary napkin consisting of a liquid-permeable sheet, a liquid-absorbing layer, and a liquid-impermeable sheet, in which the liquid-impermeable sheet is formed by a spunbond method. It is a water-repellent non-woven sheet constructed by partially bonding single fibers of ~5 deniers, and the long edge of the liquid-resistant sheet extends inside the long edge of the liquid-permeable sheet. A sanitary napkin is disclosed which is characterized in that it is polymerized with the liquid-permeable sheet surface.

Furthermore, JP-A No. 61-92667 discloses that a fluid-impermeable sheet is formed from a multilayer structure of a meltblown web having a basis weight of 13 to 28 g/rd and a spunbond web having a basis weight of 8 g/rrr or more. A sanitary napkin is disclosed in which the spunbond web has an adhesive attached to the garment for fixation.

[Problems to be Solved by the Invention] The polyethylene film and polyethylene laminate used as the liquid-impermeable sheet (back sheet material) satisfy the necessary functions of being flexible and impermeable to liquids, but have poor air permeability. There was no breathability at all, which caused the problem of stuffiness during wear. Further, since it is a film, the surface is slippery, and there is a problem in that it has a poor texture and texture.

In addition, the liquid-impermeable sheet disclosed in Japanese Utility Model Publication No. 63-44035 is made of relatively thick fiber sheets of 0.1 denier (fiber diameter approximately 4 μm) to 5 denier formed by spunbonding, so it has high water pressure resistance. was relatively low, and liquid impermeability was not necessarily sufficient. That is, there has been a problem in that a person wearing this napkin may leak body fluids, especially when exercising, such as when riding a bicycle. Furthermore, since the fiber diameter was thick, the texture was stiff, and the feeling of wearing was average.

Further, the fluid-impermeable sheet described in JP-A No. 61-92667 uses a spunbond web as the outermost layer as in the above-mentioned Japanese Utility Model Publication No. 63-44035, and this spunbond web is composed of constituent fibers. Fiber diameter is generally 10μ
Since it is thick (more than m), it has a hard texture and has a problem of poor texture and feeling when worn.

The present invention is a liquid-impermeable sheet (back sheet material) that satisfies the required functions of being impermeable to body fluids such as blood and urine and being soft, and also has high air permeability and does not get stuffy, something that could not be achieved with conventional film-like materials. It is an object of the present invention to provide a novel liquid-impermeable sheet for sanitary materials, which has high elasticity, high moisture permeability, high strength, and improved surface slippage, texture, and wearing comfort.

[Means to solve the problem]

One of the present invention is a nonwoven sheet formed by partially bonding ultrafine polyolefin fibers having an average fiber diameter of 0.5 to 2.5 μm formed by a melt blowing method, and the basis weight of the nonwoven sheet is Another invention is a liquid-impermeable sheet for sanitary materials having an average fiber diameter of 10 to 40 g/rrf, which is formed by a melt blowing method and has an average fiber diameter of 0.5 to 2.5
A nonwoven sheet (A) with a basis weight of 10 to 40 g/m2 made by partially bonding micron polyolefin ultrafine fibers, and a nonwoven sheet (B) made of bulky polyolefin fibers with a bulk density of 0.12 g/c1i1 or less ), and the bulky nonwoven sheet (B) is laminated on the inner layer side of the ultrafine fiber handwoven sheet (A).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to drawings of a sanitary napkin, which is one of the sanitary materials shown as an example of the present invention.

The sanitary napkin using the liquid-impermeable sheet of the present invention as shown in Fig. 1 includes a liquid-permeable sheet (1) that comes into direct contact with the skin, and a liquid absorbent material (4) on the lower surface of the sheet to absorb liquid from absorbent cotton, tissue, etc. The liquid-absorbing layer is covered with a transparent sheet (3), and a liquid-impermeable sheet (2) is laminated on the lower surface of the liquid-absorbing layer to prevent liquid leakage. The liquid-impermeable sheet (2) is overlapped with the lower surface of the liquid-permeable sheet (1) and bonded (6) so as to wrap around the liquid absorbers N (3) and (4) to prevent horizontal leakage of liquids such as blood. has been done. This portion (6) may be joined using an adhesive such as a hot melt agent, but heat sealing is preferable in terms of strength, texture, and cost.

Figure 2 shows a sanitary napkin using another liquid-impermeable sheet of the present invention, in which a bulky layer is provided between the liquid-absorbing layers (3), (4) and the liquid-impermeable sheet (2). Non-woven sheet (B
) (5) are laminated.

The liquid-impermeable sheet (2) of the present invention has a basis weight of 10 to 40, which is obtained by partially bonding polyolefin fibers with an average fiber diameter of 0.5 to 2.5 μm formed by a melt blowing method.
g/rrf nonwoven sheets are more preferred.

Examples of polyolefins include polypropylene, polyethylene, propylene and ethylene, or alpha-butene such as 1-butene.
Examples include copolymers with olefins, among which polypropylene, which can be spun into ultrafine fibers by melt blowing and has high water repellency, is most preferred.

The polyolefin fiber sheet used for the liquid-impermeable sheet (2) of the present invention has an average fiber diameter of 0.5 to 2.5.
ttm, preferably 1.0 to 2.0 μm, and the basis weight is 10 to 40 g/rd, 15 to 35 g/rl
(It is necessary that the average fiber diameter is 2.5 μm or more and the basis weight is less than Log/m2), the water pressure resistance of the fiber sheet will be low, the liquid impermeability will be insufficient, and body fluids will be absorbed when worn. On the other hand, when the average fiber diameter is 0.5 μm,
Below, the basis weight is 40g/r+? If it is more than that, the air permeability will be insufficient and it will be stuffy. Furthermore, if the average fiber diameter is 0.5 μm or less and the basis weight is 10 g/rrf or less, the tear strength of the fiber sheet decreases and it cannot be used as the outermost layer sheet.

That is, when a sanitary napkin in which a pressure-sensitive adhesive for fixing to clothes is attached to the fiber sheet is removed from the underwear after being worn, it does not come off cleanly and some of the adhesive and the fiber sheet remain on the underwear. occurs.

It is necessary that the ultrafine fibers constituting the liquid-impermeable sheet of the present invention are partially joined.

This partial bonding can be done using adhesives, or by entangling the fibers with a double punch, water jet, etc., but in order to further increase the strength, breathability, and flexibility of the sheet, it is preferable to use partial thermal bonding to form a sheet. is preferable. Partial thermal bonding is carried out by ultrasonic methods or by passing the web between heated embossing rolls. In the ultrasonic method, the web is passed between an engraved roll and an ultrasonic horn, and in the heated embossing roll method, one is an engraved roll and the other is a smooth roll, and the top and bottom are both engraved rolls and then spliced together. etc. will be adopted. The degree of thermal adhesion is
It is determined by setting the temperature and contact pressure of the upper and lower rolls according to the required performance such as strength, texture, or fluffiness of the resulting nonwoven fabric, but the upper texture temperature should be set below the melting point of the fiber used. is preferable, especially 100 to 135
“C is preferred.

In addition, the quality of the obtained nonwoven sheet is affected by the embossed pattern, and among these, the thermal bonding area ratio and pattern spacing are important points.

The thermal bonding area ratio is 3 to 40%, especially 5 to 40%, from the viewpoint of breathability, texture, strength, especially tear strength, and fluffing property of the nonwoven sheet.
30% is preferred. A low adhesion area ratio results in poor strength and fluffing properties, while a high adhesion area ratio results in poor breathability and texture. The depth of the embossed pattern varies depending on the shape of the pattern and the spacing between the patterns, but it is preferably at least 0.05+mn or more, particularly 0.1 mm or more. Furthermore, if the fibers in the patterned portion of the nonwoven sheet are bonded too strongly to the point where they lose their fiber form and become a film, that portion becomes brittle, which is not preferable. The embossed pattern may be a linear continuous pattern or a separate pattern such as a pinpoint shape or a rectangular shape, but a separated pattern is more preferable because it has a soft texture. The minimum interval between the embossed patterns is preferably 0.3 to 10 mm, particularly 1 to 5 Inffi, from the viewpoint of the texture, strength, and fluffiness of the nonwoven sheet.

It is necessary to select a preferred pattern by considering the above points.

The polyolefin ultrafine fiber nonwoven sheet used in the present invention is
As mentioned above, by satisfying all the combinations of having an average fiber diameter of 0.5 to 2.5 μm, a basis weight of 10 to 40 g/rd, and partially joining these ultrafine fibers,
It is possible to improve water pressure resistance, breathability, feel, and strength, particularly tear strength, to a level sufficient for a sanitary napkin. As a result, there is no need to use a conventional reinforcing sheet such as a spunbond hand-woven sheet with a large fiber diameter as the outermost layer, as disclosed in JP-A No. 61-92667, and only an ultra-fine fiber non-woven sheet can be used. It can achieve sufficient liquid resistance and strength, and can be used as the outermost layer for the first time.

The water pressure resistance of the ultrafine fiber non-woven sheet used in the present invention is preferably 450 KlI20 or higher, particularly 500 KlI20 or higher, since there will be no leakage of liquids such as blood. Air permeability is 5 cc/sec/
cn1 or more, especially 10cc/sec/ci or more, and even 1
It is preferable that the flow rate is 5 cc/sec/cff1 or more because the fragrance will be eliminated. Conventional film-type sheet materials have almost no air permeability and tend to get stuffy, but the ultrafine fiber sheet used in the present invention has air permeability and moisture permeability, so it does not feel stuffy when worn. In addition, the tear strength of the ultrafine fiber nonwoven sheet is 20
If the weight is more than 30g, especially 30g or more, when a sanitary napkin with pressure-sensitive fixing adhesive attached to clothing is attached to this ultrafine fiber nonwoven sheet and removed from underwear after wearing, it will not come off cleanly and the adhesive and ultrafine fibers will not come off cleanly. This is preferable because the problem of the fiber nonwoven sheet remaining in the underwear does not occur.

In addition, the present inventors have developed a liquid-impermeable sheet for sanitary materials in which the upper layer (inner layer side) of an ultrafine fiber nonwoven sheet has a bulk density of 0.
Bulky polyolefin non-woven sheet of 12g/cm or less)
It has been found that the presence of (B) further increases the liquid impermeability.

The polyolefin of this hand-woven sheet (B) is selected from the above-mentioned materials, but a dry nonwoven fabric of crimped staple fibers with a sheath-core structure of polyethylene and polypropylene and a nonwoven fabric of crimped polypropylene fibers are preferred. The bulk a of this hand-woven sheet (B) is 0.12 g/cffl or less,
Preferably it is 0.10 g/cffl or less. It has surprisingly been found that liquid impermeability increases significantly when the bulk density falls within this range. The reason for this is not necessarily clear, but it is thought to be related to the large pores (dead air layer) formed inside the nonwoven sheet and the water repellency of the material itself since it is made of polyolefin. .

The date of this hand woven sheet is 10-50g/rrf, especially 1
Preferably, it is 5 to 35 g/rrf. Within this range, both liquid impermeability and thin thickness are satisfied.

The average fiber diameter of the fibers constituting the nonwoven sheet (B) is 10
It is preferable that the thickness is 30 μm, particularly 12 to 20 μm, since this satisfies both the bulkiness and texture of the nonwoven sheet. This nonwoven sheet (B) and the microfiber nonwoven sheet (A) may be simply laminated, or these two layers may be laminated and then partially joined. This joining method is preferably the method described above. In addition, non-woven sheets (
Another liquid-impermeable sheet (such as waterproof paper) may be interposed between B) and the nonwoven sheet (A).

Furthermore, it is not necessarily necessary for the nonwoven sheet (B) to cover the sides of the sanitary napkin, and it is sufficient to cover only the bottom surface where bodily fluids are most likely to leak. Such a structure has the advantage that the thickness of the sanitary napkin can be reduced.

〔Example〕

The present invention will be explained in more detail below with reference to Examples. The definitions and measurement methods of various physical properties shown in Examples and Comparative Examples are shown below.

(1) Average fiber diameter (μm) Ten arbitrary points on the sample were examined using an electron microscope at a magnification of 2000.
Take 10 photos at double magnification. Measure the diameter of 10 arbitrary fibers for each photograph, and do this for each of the 10 photographs. A total of 100 fiber diameter measurements are obtained and the average value is calculated.

(2) Water pressure resistance (mm Hz Q) Measured by JIS-L-1092B method.

(3) Air permeability Measured by JIS-1096 method (Fraziel method).

(4) Thickness (mm) Measured using a peacock type thickness gauge under a constant load of 30 g/C.

(5) Apparent density (g/cffl) This is a value obtained by measuring the thickness under a constant load of 130 g/C111 and calculating with the basis weight.

(6) Tear strength (g) Take a sample 60 mm wide x 65 mm long, stop the sample on a sample stand, and make a cut with a knife.

Read the maximum vibration using an Elmendorf tear tester.

(7) Leakage rate The leak rate was determined by the percentage of leaks occurring out of 100 people.

(8) Feeling of stuffiness The feeling of stuffiness was evaluated as × if 15 Å or more out of 100 people felt stuffy, △ if 5 to 14 people felt stuffy, and ○ if 4 Å or less felt stuffy.

(9) Underwear peelability Underwear peelability was evaluated as "x" if adhesive and fiber waste remained on the underwear when the napkin was removed from the underwear after wearing, and "O" if no adhesive or fiber debris remained on the underwear.

Examples 1 to 6 and Comparative Examples 1 to 4 Polypropylene was melt-blown to obtain fiber webs having various average fiber diameters and basis weights. 130 this web
Heated to 'C (0.57φ pinpoint pattern!
5 mm pitch, staggered arrangement, thermal bonding area ratio 11.4%
A liquid-impermeable sheet (2 mm) of ultra-fine fibers having a pinpoint pattern is formed by passing between an embossing roll and a flat roll (with an embossing depth of 0.6 mm) and partially bonding with heat.
) was obtained. The physical properties of this liquid-impermeable sheet are shown in Table 1.

This sheet was combined with the following sheet to create a sanitary napkin having the structure shown in FIG.

Separately, as a liquid-permeable sheet, a dry sheet of polyethylene and polypropylene sheath-core short fibers with a fiber diameter of 17 μm, trade name ES fiber, was partially thermally bonded with a pinpoint pattern.
A handwoven sheet of 3 g/rrT was obtained.

Separately, we also have a tissue sheet with a basis weight of 90 g/rrr in which particles of super absorbent polymer are dispersed between two sheets of tissue (
4), absorbent cotton sheet with a basis weight of 20 g/rd (3
) to form a liquid absorbing layer. These sheets were cut into rectangles and assembled into the structure shown in FIG. Liquid permeable sheet (
The bonded portion (6) between 1) and the liquid-impermeable sheet (2) was bonded by heat sealing. A pressure-sensitive adhesive for adhering underwear was attached to the outer surface of the liquid-impermeable sheet (2).

Table 1 shows the results of a wearing test of the obtained sanitary napkin by 100 subjects.

The following margins are Examples 6 to 10. The liquid-impermeable ultrafine fiber nonwoven sheet (2), the liquid-permeable sheet (1), and the liquid absorbing layers (3) and (4) are all the same as Examples 1 to 5. The same sheet was used.

Separately, the fiber diameter of polyethylene and polypropylene is 16 μm.
The crimped short fibers with a sheath-core structure of 1.5 m are made into a sheet by a carding method and bonded with hot air, resulting in a fabric weight of 23 g/rri and a bulk density of 0.09.
A bulky fiber sheet (5) of g/cn was obtained.

Using this sheet and the sheets of Examples 1 to 5, five types of sanitary napkins having the structure shown in FIG. 2 were made.

These five types of sanitary napkins are Examples 1 to 5 and Comparative Example 1.
As a result of the wearing test similar to that in 4 to 4, all samples had a leakage rate of 0%, had a soft texture and excellent wearing comfort, and had good stuffiness and peeling properties of underwear.

Although the liquid-impermeable sheet of the present invention is particularly useful for sanitary napkins, a liquid-permeable sheet used in combination with the liquid-impermeable sheet of the present invention will be described below.

The liquid-permeable sheet (1) can be made of any material, such as polyolefin, polyethylene, boria fiber, cellulose fiber, etc., alone or in a mixture thereof.

Preferred examples include polypropylene-based nonwoven sheets, such as polypropylene spunbond sheets, and dry-laid nonwoven fabrics made of sheath-core fibers of polyethylene and polypropylene, as they have good texture, permeability to blood and other liquids, and appropriate strength. It will be done. The basis weight is 15-35g/rr
f is preferred.

The liquid absorbent layers (3) and (4) are liquid absorbent sheets (3).
) and the absorbent body (4) is preferable because of its high absorbency, but it is also possible to use only one of these, or other absorbent bodies may be added. Examples of the absorbent sheet (3) include absorbent cotton, pulp, cellulose fiber sheet, tissue, and the like. The absorbent body (4) may be a super-absorbent polymer, a sheet containing the super-absorbent polymer, or the like. The basis weight of the liquid absorption layers (3) and (4) is 50 to 500 g/
Bo is preferred.

〔Effect of the invention〕

The liquid-impermeable sheet for sanitary materials of the present invention has excellent liquid-proof properties, breathability (stuffy feeling), and peeling of underwear when used for sanitary materials, especially sanitary napkins, diapers, etc. It is flexible and comfortable to wear. In addition, since the ultra-fine fiber sheet is in direct contact with the underwear, it has the effect that it hardly shifts during wear.

Furthermore, by providing a nonwoven sheet made of bulky polyolefin fibers on the upper layer (inner layer side) of this nonwoven sheet made of ultrafine fibers, a liquid-impermeable sheet for sanitary materials with even better liquidproof properties can be obtained.

The liquid-impermeable sheet for sanitary materials of the present invention is particularly useful as a sanitary napkin, and can be used for menstruation, urine leakage, hemorrhoids, etc.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of a sanitary napkin using a liquid-impermeable sheet according to one aspect of the present invention, and FIG. 1 is a sectional view showing an example of a sanitary napkin. ■...Liquid permeable sheet, 2...Superfine fiber liquid impermeable sheet, 3...Liquid absorbing sheet, 4...Liquid absorber, 5...
... Bulky liquid-impermeable sheet, 6... Joint portion.

Claims (1)

[Claims] 1. The average fiber diameter formed by the melt blowing method is 0.
A nonwoven sheet for sanitary materials, which is a nonwoven sheet formed by partially bonding ultrafine polyolefin fibers of 5 to 2.5 μm, and has a basis weight of 10 to 40 g/m^2. Liquid permeable sheet. 2 The average fiber diameter formed by the melt blowing method is 0.
A nonwoven sheet (A
) and a nonwoven sheet (B) made of bulky polyolefin fibers having a bulk density of 0.12 g/cm^3 or less, and the bulky nonwoven sheet (B) is composed of the ultrafine fiber nonwoven sheet ( A liquid-impermeable sheet for sanitary materials, characterized in that it is laminated on the inner layer side of A).