JPS5939135B2 - absorbent articles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an absorbent article, and more particularly to an absorbent article using a backsheet composed of a mixed ionomer resin layer and a sheet-like fiber aggregate.

Absorbent articles such as sanitary napkins and disposable diapers consist of a top sheet that is permeable to moisture and menstrual blood that comes in contact with the body, a leak-proof back sheet, and an absorbent layer interposed between them. The absorbent layer made of water-absorbing paper or absorbent cotton has a leak-proof backsort on the bottom (and sides) to prevent moisture and menstrual blood from leaking, and the top (or the whole)
The top sheet is covered with non-woven fabric.

A wet-laid nonwoven fabric or a dry-laid nonwoven fabric is used as the top sheet of such an absorbent article, but the strength and water repellency can be changed by mixing a binder or a polyolefin heat-melt fiber. This basic three-layer structure of the absorbent article is integrated into the absorbent article by wrapping the leak-proof backsheet and the absorbent layer with a nonwoven topsort, or by joining the topsheet and the leak-proof backsheet. How to join the top sheet and leak-proof back sheet [,
Conventionally, the method of heat-sealing a polyethylene film laminated to the binder contained in the top sheet or the waterproof paper used as the back sheet, or the method of transferring a hot melt adhesive in an adhesive pattern to the top sheet and forming the back sheet. Methods such as gluing are used. However, these conventional bonding methods have disadvantages in that high-speed production is not possible because heat fusion is insufficient in high-speed production, and the timing of adhesive transfer in high-speed production is not consistent.
Therefore, as a result of intensive research, the present inventors have conducted extensive research in order to improve the shortcomings of the bonding between the top sheet and pack sheet of conventional absorbent articles. High-speed productivity is achieved by using a leak-proof backsheet, or by applying a thin layer of hot-melt adhesive to the entire backsheet substrate when manufacturing absorbent articles. He discovered an absorbent material with excellent leakage properties and filed a patent application (patent application filed in October 1989).
6980).

In addition, by using a backsheet composed of an outer layer made of a liquid-impermeable sheet and an inner layer made of an ionomer resin layer, the present inventors achieved an absorbent material with better high-speed productivity and excellent leak-proofing properties. He discovered a sex product and filed an application for utility model registration (see Utility Model Application No. 164962/1983).

Further, as a result of repeated research, the present inventors have discovered an absorbent article with further improved leak-proofing properties and higher productivity at higher speeds, and have arrived at the present invention.

That is, the present invention provides an absorbent material comprising a top sheet, a back sheet, and an absorbent layer inserted between the two sheets, the back sheet comprising an outer layer made of a sheet-like fiber aggregate and an inner layer made of an ionomer resin. In the article, the ionomer resin is a mixed ionomer resin having a melt index difference of 2 to 10, and the melt index of the mixed ionomer resin is 1 to 6. It provides goods.

Next, the structure of the absorbent article of the present invention will be explained with reference to the drawings.

1 and 4 are partially cutaway external perspective views showing an embodiment of the absorbent article of the present invention, and FIG. 2 is a
A two-line sectional view, FIG. 3 is a sectional view of the back sheet.

That is, the absorbent article of the present invention consists of a top sheet 1, a back sheet 3, and an absorbent layer 2 inserted between these two sheets, and the back sheet 3 has an outer layer 4 made of a sheet-like fiber aggregate as shown in FIG. It is composed of an inner layer 5 made of a mixed ionomer resin layer. The top sheet 1 used in the present invention may be made of various nonwoven fabrics that are permeable to moisture and menstrual blood, preferably single or mixed nonwoven fabrics containing pulp, rayon, polypropylene, polypropylene-polyethylene, polyester, etc. as main components. , the appropriate basis weight is 15 to 309/i.

Examples of such nonwoven fabrics include acrylic resin-based, polyvinyl alcohol resin-based binder type nonwoven fabrics, spunbond type nonwoven fabrics, etc., but those with a high thermal melting temperature are more preferred. In addition, the absorbent material used as the absorbent layer 2 in the present invention includes cotton pulp, absorbent paper, rayon cotton, highly absorbent polymer absorbent, etc., and these are used in a single layer or in a stacked manner. Highly absorbent polymeric absorbents include acrylic acid copolymers (e.g., crosslinked polyacrylic acid, starch-polyacrylate copolymers), crosslinked polyethylene oxide, crosslinked carboxymethylated cellulose sodium salt or calcium salt. , a copolymer of acrylate and vinyl alcohol, and the like. The water absorption capacity of these highly absorbent polymeric absorbents is desirably one in which the water absorption amount is 30 times or more its own weight in terms of water absorbent performance. The shape of the absorbent layer 2 is not particularly limited, but it is preferable to have a shape in which a recess is formed by cutting out the central part of the long side as disclosed in Japanese Patent Application Laid-Open No. 55-52758 (see Fig. 4). . Further, as the sheet-like fiber aggregate 4, which is the base material constituting the back sheet 3, water-repellent treated waterproof paper, woven fabric, non-woven fabric, etc. are used, and as with the top sheet 1, it is preferable that the non-woven fabric has a high thermal melting temperature.

The ionomer resin is preferably a resin in which the molecules of an ethylene-methacrylic acid copolymer are cross-linked with metal ions.
As the metal ion, metal ions such as sodium and zinc are preferred. The mixed ionomer resin of the present invention is a mixture of resins having a melt index (hereinafter abbreviated as MI) of 2 to 10, and the MI is 1.0 to 6.01, preferably 2.0 to 5.0. It is something.

The mixing ratio is preferably 1/4 to 4/1 (weight ratio). Single or mixed resins with a low MI have poor fluidity and weak adhesion, but have high leak-proof properties; conversely, when the MI is high, they have good fluidity and, for example, if the outer layer is nonwoven fabric, they penetrate well. The adhesive force becomes very strong. However, the leak-proof performance is significantly reduced. Therefore, by mixing these two and controlling M1, it is possible to compensate for each other's shortcomings and take advantage of their advantages. That is, it is possible to improve adhesiveness and leakage prevention. The back sheet 3 of the present invention is obtained by laminating the mixed ionomer resin 5 on the sheet-like fiber aggregate 4 by extrusion lamination or the like.
The mixed ionomer resin is applied to the sorted fiber aggregate 4 to a thickness of 1
The fibers are bonded on the entire surface or partially to a thickness of 0 to 50μ, preferably 15 to 35μ, and laminated to a total thickness of 15 to 200μ, preferably 26 to 100μ with the sheet-like fiber aggregate.

If the thickness of the mixed ionomer resin layer is less than 10 μm, the leak-preventing effect will be low, and if it exceeds 50 μm, the backsheet will become hard and feel undesirable. When waterproof paper, non-woven cloth, etc. are used as a sheet-like fiber aggregate and laminated with a mixed ionomer resin, it becomes quite stiff even at a thickness of 50μ or less, but in order to soften this, the fibers can be laminated with end pressure bonding. A very soft back sheet is obtained without the resin penetrating into the inside. In such a case, by using the ionomer resin layer 5, the heat-sealability (especially adhesiveness during high-speed production) of the top sheet 1 and the back sheet 3 is increased, and the back sheet 3 has an increased waterproof property of the sheet-like fiber aggregate 4. can be obtained.

As a result, the leak-proof properties of absorbent articles manufactured using this backsheet 3 are significantly improved. The top sheet 1 and the back sheet 3 are easily bonded together by pressing the unbonded absorbent laminate between hot rolls.
The bonding pattern at this time may be any of flat pressure bonding, pressure bonding using countless dots, and pressure bonding using a combination of straight lines or curves. Alternatively, the back sheet 3 can be rolled up or folded onto the top sheet 1 and bonded as shown in FIG. The absorbent article of the present invention is particularly effective when used as a sanitary napkin, but it can also be easily applied to a bag by laminating backsheets together, or to various packaging containers, etc. Highly leak-proof and enables high-speed production.

Hereinafter, the present invention will be explained in further detail with reference to Examples.

Example 1 Cotton-like pulp was used as an absorbent layer, and a rayon/polypropylene nonwoven fabric (209/A) was placed on the top surface of the absorbent layer.
Furthermore, on the bottom surface, MI= which is made by cross-linking the molecules of ethylene-methacrylic acid copolymer with zinc ions on a pulp/rayon/polypropylene wet nonwoven fabric (209/I, water repellent treated)
A mixed ionomer resin (MI2 3.0) of an ionomer resin of M=0.5 and an ionomer resin of M=7 was laminated to a thickness of 20μ and thermocompression bonded at 260°C. I got napkins.

This sanitary napkin exhibited sufficient adhesion stability to withstand high-speed production, ie, twice as fast as the conventional heat-sealing method, and its leak-proof properties were significantly improved. Example 2 Disposable diapers and sanitary napkins were manufactured using the following combinations of top sheets, absorbent layers, and back sheets.

All of these have sufficient adhesion stability for high-speed manufacturing.
Demonstrated strength and leak-proof properties. (a) Disposable diaper top sheet: polyester spunpond nonwoven fabric (
209/a) Absorbent layer: Laminated cotton-like pulp and water-absorbing paper (containing water-absorbing polymer) Back sheet: Rouyon 100 (:f) binder nonwoven fabric with 65% by weight of ionomer resin with MI=1 and MI=5 Ionomer resin 3
Mixed ionomer resin (MI=2.5) with 5% by weight was extruded and laminated (unpressed) to a thickness of 30 μm (
b) Sanitary napkin top sheet... Rouyon 10001) non-woven fabric (30
9/Trl) Absorbent layer: Cotton-like pulp back sheet: Polyester, rayon, polypropylene wet-laid nonwoven fabric 209/Trl) Mixed ionomer resin (MI= 5.0) was extruded and laminated (crimped) to a thickness of 18μ.In order to further clarify the effects of the present invention, a comparative example will be shown and compared.

Comparative example top sheet...100 (f) Rayon nonwoven fabric (30
9/Trl) Absorbent layer...cotton-like pulp back sheet...polyester, polypropylene wet-laid nonwoven fabric with 20% of the following single and mixed ionomer resins
Extrusion laminated to a thickness of μ (a) Single ionomer resin (MI = 1.5) (b) Single ionomer resin (MI = 14) (c) Single ionomer resin (MI =
5)(d) Ionomer resin with MI=3 and MI=14
Mixed ionomer resin (MI=
7) The absorbent articles obtained in Examples 1 to 2 and Comparative Examples above were heated at a temperature of 260°C and a pressure of 2.5 kg/(17711 speed 3).
The adhesive strength and leakage rate when thermally bonded at 00 and 350 pieces/min were investigated and are shown in Table 1.

If the M1 of the single or mixed ionomer resin is high, the adhesive strength is very high, but the leakage rate is also high and the quality of the product is low.

When the MI is low, the leakage rate is very low and is good, but there is a drawback that the adhesive strength becomes weak and it peels off easily. However, the mixed ionomer resins with MI of 5.0, 301 and 2.5 have good adhesive strength and a very low leakage rate. Therefore, it is most suitable for high-speed production, and the normal speed of 200 pieces/minute can be increased to 450 pieces/minute, which is 2 to 3 times faster.
Productivity has doubled.

[Brief explanation of drawings]

1 and 4 are partially cutaway external perspective views showing embodiments of the absorbent article of the present invention, FIG. 2 is a sectional view taken along the line X1-X2 of FIG. 1, and FIG. 3 is an absorbent article of the present invention FIG. 3 is a cross-sectional view of a backsheet used in the article. 1... Top sheet, 2... Absorbent layer,
3... Back sheet, 4... Sheet-like fiber aggregate, 5... Mixed ionomer resin layer.

Claims (1)

[Claims] 1. An absorbent article consisting of a top sheet, a back sheet, and an absorbent layer inserted between the two sheets, wherein the back sheet is constituted of an outer layer made of a sheet-like fiber aggregate and an inner layer made of an ionomer resin. , the ionomer resin has a melt index difference of 2 to
10. An absorbent article characterized in that the mixed ionomer resin has a melt index of 1 to 6.