JPS6392701A - Disposable diaper - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a disposable diaper. More specifically, the present invention relates to disposable diapers that do not lose their shape.

(Prior art and its problems) As is well known, disposable diapers are liquid-impermeable diapers made of a non-woven fabric made of fiber materials such as polyester, polypropylene, or rayon, and made of a liquid-permeable surface film such as diluted polyethylene. It consists of an absorbent layer made of water-absorbing paper, cotton-like pulp, superabsorbent polymer, etc. placed between a transparent back sheet, and is widely used for reasons such as ease of carrying. It's starting to look like this.

On the other hand, superabsorbent polymers that absorb several tens of times their own weight in urine have come into use, and the amount of cotton pulp used as an absorbent material has decreased, making diapers thinner and more compact. However, the strength of the absorbent layer decreases due to the decrease in cotton-like pulp, and when the absorbent layer gets wet with urine, it loses its shape, or it rips and leaks, which is a problem.

In order to solve these problems, a method is also known in which thermoplastic fibers, synthetic pulp, etc. are mixed with flocculent pulp, and the mixture is heat-treated to melt and bond to increase the strength. For example, JP-A-55-17455 discloses a method in which 5 to 5 OB (by weight) of polyolefin, polyvinyl, or polyester fibers are added to flocculent pulp as thermoplastic fibers to pulverized pulp. The thermoplastic fibers used in this method are single-component fibers, and thermal adhesion occurs by heat treatment at a temperature above the melting point, but the thermoplastic fibers are cut, and in order to increase their strength, However, thermoplastic fibers are inherently hydrophobic, so if a large amount is added, the water absorption performance of urine (e.g. water absorption rate) will deteriorate. There was a point. In addition, Japanese Patent Application Laid-Open No. 55-26495 also proposes a method for improving the integrity and elasticity of the absorber by mixing plastics into the bulb and heat-treating the mixture. This method has the same problems as the method described in the publication. Furthermore, Japanese Patent Application Laid-open No. 59-112005 discloses that polyethylene-based synthetic pulp has a ratio of 7.5 to
A proposal has been made to increase the strength by adding 20 tin and heat treating it. In the case of this method as well, the fiber length of the synthetic pulp is as short as n, s ~ 2.011111, and since it is a single component fiber, the fibers are cut during heat treatment, and a considerable amount of fiber is required to increase the strength. It is necessary to blend a synthetic pulp of 1,000 ml, and when a large amount is blended, there are problems in that it has a negative effect on water absorption performance, texture, etc., and also increases cost.

(Object of the Invention) The present invention solves the above-mentioned problems and provides a disposable diaper that does not cause the absorbent layer to twist or lose its shape and tear.

(Structure of the Invention) The present invention provides a valve having an absorbent layer between a liquid-permeable top sheet and a liquid-impermeable back sheet, and in which thermoplastic fibers are mixed with cotton-like pulp as one of the absorbent layers. In disposable diapers having an absorbent layer, two or more types of thermoplastic fibers having different melting points are used as the thermoplastic material at α5 to 1
This invention relates to a disposable diaper characterized by having a pulp absorbent layer containing α0 weight fmm% and heat-treated at a temperature higher than the melting point of low-melting point fibers.

As a result of intensive studies to solve the above problems, the inventors of the present invention found that two or more types of thermoplastic fibers with different melting points are mixed into cotton pulp, and the mixture is heat-treated at a temperature higher than the melting point of the low-melting point fibers. The high melting point fibers remain as a skeleton, and the low melting point fibers melt and bond between the cotton pulp and the high melting point fibers, so you can increase the strength with a small amount of blending. The present inventors have discovered that not only does it have no adverse effect on the water absorption performance and feel of the skin, but it is also advantageous in terms of cost.

Various types of thermoplastic fibers are known, such as polyethylene, polyethylene, ester, nylon, vinyl chloride, and aramid fibers, and any of them can be used. The blending ratio should be in the range of α5 to 1Q, 0% by weight, but from the standpoint of increasing strength and urine water absorption properties, it should be 2.0 to 4.
．． It is desirable to add about 0.

A mixture of two or more types of single component fibers with different melting points may be used, or a composite fiber in which fibers with different melting points are combined into a single fiber may be used. The ratio of low melting point fibers to high melting point fibers may be about 50 cm to 50 cm. The fiber length of the thermoplastic fibers used in the present invention is preferably as long as possible from the viewpoint of strength, but in order to disperse them well in flocculent pulp with a short average fiber length of 1.0 to 50 gourds, may be in the range of 5 to 20 ■. In terms of dispersibility and strength, it is 7~15w! IA
degree is desirable. Regarding the thickness of the fibers, it is desirable that they be as thin as possible from the viewpoint of strength, but from the viewpoint of dispersibility in flocculent pulp, any denier between 1.0 and 0 denier is sufficient. It is preferably 1.5 to 50 deniers. The heat treatment temperature requires a higher temperature than low melting point fibers,
For example, when using composite fibers of polyethylene and polypropylene, it is possible to sufficiently increase the strength by treating the fibers at a temperature of 140 to 160° C. for several seconds. In order to improve thermal adhesion, it is also possible to use pressure treatment in combination with heat treatment.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

Figure 1 shows one embodiment of the present invention, and is a developed view of the surface with a part of the top sheet cut away.
- A cross-sectional view along the wire. In FIGS. 1 and 2, 1 is a top sheet, 2 is a back sheet, S is a first pulp absorbent layer, 4 is a second pulp absorbent layer, 5 is a super absorbent polymer,
Reference numeral 6 indicates water-absorbing paper, 7 indicates an elastic member, and 8 indicates a fastening tape.

The first pulp absorption layer and the second pulp absorption layer are made by adding 0.5 to 1 [10% by weight (based on the pulp) of two or more types of thermoplastic fibers with different melting points to sheet pulp, and then pulverizing and laminating them. After that, press treatment if necessary, and heat at a temperature higher than the melting point of the low-melting point fiber (for example, if polyethylene or polypropylene fibers are used, a temperature of 150 to 140°C or higher is required). It can be manufactured by heat treatment for several seconds. The heat treatment device may be either a flat dryer or a cylindrical hot air circulation type dryer.

The super absorbent polymer 5 is sprinkled on the first pulp absorbent layer 5 made in this way, and the second pulp absorbent layer 4 is further layered.
Furthermore, the disposable diaper of the present invention can be assembled by covering the upper and lower sides of these pulp absorbent layers with absorbent paper 6, top sheet 1, and back sheet 2, and by integrally attaching elastic member 7 and fastening tape 8. .

The pulp absorbent layer of the present invention maintains high strength even when wet, and disposable diapers using this layer do not lose their shape during use, and because the amount of thermoplastic fiber used is small, they have a good texture. Alternatively, it is advantageous in terms of cost since it requires less amount of expensive thermoplastic fibers, which have a good effect on urine water absorption rate.

A more detailed explanation will be given below based on examples.

Example-1 Thermoplastic fibers were added to sheet pulp at 50, &0, and 9.0 inches per pulp, and subjected to pulverization, lamination, and pressing, and the basis weight was 550 t/-1 and the tension was CLO551/?
Make a flocculent pulp with a diameter of 55mm and heat it at 140℃ for 5cm.
After heat treatment for 1 minute, the wet strength of this product was measured. Except when synthetic pulp was used, the thermoplastic fibers were 3 denier and 10 m long.

Wet strength was determined by soaking the above cotton-like pulp in artificial urine, dehydrating it for 1 minute under a pressure of 2.5 Kpa, fixing the periphery of this mat, and placing a rod with a diameter of 101Ell in the center. When the rod was lowered at a rate of 200 gH/miH, it was expressed as the load when the rod broke through the flocculent pulp.

The test results are shown in Table-1.

Table 1 Test Results Comparative Example 1 is a case in which no thermoplastic fibers are added, and the wet strength is weak.

Comparative Example-2 is a synthetic pulp whose main component is polyethylene (
This is the case in which UL-415 (Mitsui Petrochemical Co., Ltd.), melting point 125° C.) was added. It can be seen that a large amount of addition is necessary in order to increase the strength.

Comparative Example 5 uses polyethylene fibers (melting point 121° C., Daiwabo BP), but as in Comparative Example 2, even if a considerable amount is added, the strength does not improve much.

Invention-1 uses a composite fiber (melting point 150°C, Daiwabo WBF) containing polyethylene as a core component and polypropylene as a sheath component, but the strength is improved compared to Comparative Examples-2 and Comparative Examples-3. It turns out that something is remarkable.

Invention-2 is a case in which polyethylene fibers (melting point 121°C, Daiwabo BIF) and polypropylene fibers (Daiwabo Polypro, melting point 160°C or higher) are mixed in advance, and a predetermined amount of polyethylene 50ts, polypropylene 50%) is added. However, compared to the present invention-1,
Although it is somewhat inferior, it can be seen that the strength is significantly improved compared to Comparative Example-2 and Comparative Example-3.

Example 2 A cotton-like pulp with a weight of 150 f/- was produced under the same conditions as in Example 1, and a disposable diaper having the structure shown in FIGS. 1 and 2 was manufactured as a prototype. The super absorbent polymer is the first pulp absorbent layer and the second pulp absorbent layer.
5 f/sheet was spread between the pulp absorbent layers. The addition rate of thermoplastic fiber was 9 in Comparative Example-5 in order to maintain almost the same strength.
．． In the present invention-3 and present invention-4, 50 g was added.

Ten babies between 6 and 12 months old were asked to use 20 of the prototype disposable diapers, and they were compared for mold breakage and leakage.

We also investigated the hardness of Makyu disposable diapers.

The results are shown in Table-2.

Table 2 Wearing test results Mold breakage occurrence rate - Number of sheets with mold breakage/Number of sheets used x 100 Incidence of leakage - Number of sheets that leaked/Number of sheets used x 100 Comparative example-4 that does not use thermoplastic fibers has a high moldable seam height It was found that mold part cracking occurred at a high rate, and the leakage rate was also high. In addition, in Comparative Example 5, although the mold part was considerably improved, it was found that there was a lot of leakage, which was thought to be caused by poor water absorption. On the other hand, in the disposable diapers of the present invention-5 and the present invention-4, the mold part was greatly improved, and the leakage rate was also low.
It turned out that the diaper itself was not very hard and was good.

[Brief explanation of the drawing]

FIG. 1 shows a partially cut away surface development view of a top sheet of a disposable diaper having an absorbent layer according to the present invention, and FIG. 2 shows a cross-sectional view taken along the line xx' in FIG. 1.

Claims (3)

[Claims] 1. In a disposable diaper that has a cotton-like bulb absorption layer in which thermoplastic fibers are mixed between a liquid-permeable top sheet and a liquid-impermeable back sheet, two or more types of thermoplastic fibers with different melting points are used as the thermoplastic fibers. 0 plastic fibers for cotton pulp
．． A disposable diaper having a cotton-like bulb absorption layer containing 5 to 10.0% by weight and heat-treated at a temperature higher than the melting point of low-melting point fibers. 2. The disposable diaper according to claim 1, wherein the thermoplastic fibers have a fiber length of 5 to 20 mm and a fiber thickness of 1 to 5 deniers. 3. The disposable diaper according to claim 1 or 2, wherein the two or more types of thermoplastic fibers having different melting points are composite fibers.