JPH0636808B2 - Disposable diaper absorber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an absorbent body, which is a liquid absorbing portion of a disposable diaper.

[Conventional technology]

Although various types of disposable diapers have been proposed in the past, their basic structure is generally composed of a liquid-permeable front surface portion, a liquid-impermeable back surface portion, and an absorber interposed therebetween. It is connected. This liquid-permeable surface is generally
It is made of non-woven fabric and perforated polyethylene film. The liquid impermeable back surface is generally made of a synthetic resin film. On the other hand, the absorbent body is generally composed of pulp material called crushed pulp or cotton-like pulp, and this pulp material is encapsulated by a skin material such as Teisyu paper, and the pulp material is stably wrapped. It is supposed to be included. It has been proposed that the absorbent body has a water-absorbent polymer laid under the skin material, and the like.A diaper body composed of such a front surface portion, a rear surface portion and the absorbent body is provided with an adhesive tape for fixing to the body. The diaper is constructed.

FIG. 1 shows an example of the diaper. In the figure, 1 is a diaper body and 2 is an adhesive tape.

For the conventional absorbent body of such a diaper, a pulp material such as crushed pulp is used as described above, but this material has a drawback that it contracts when absorbing a liquid.
There is a problem that a step of wrapping this pulp material with a skin material is necessary.

[Problems to be solved by the invention]

The present invention is intended to provide a disposable diaper absorbent body that overcomes such difficulties.

Other objects and novel features of the present invention will be apparent from the description of the entire specification and the accompanying drawings.

[Means for Solving Problems] and [Action] The present inventors have previously used a film, which is a substitute for the conventional thermoadhesive conjugate fiber by spinning, in Japanese Patent Application No. 59-23506. We proposed a heat-bondable composite fiber consisting of

The method for producing the composite fiber proposed by the present inventors is as follows.

A multilayer film comprising at least two layers, wherein one layer and another layer are made of a thermoplastic resin having different melting points by slit-stretching or stretching after stretching, or the multilayer film is a stretched multilayer film. In some cases, the stretching step is omitted to perform slitting, or when the multilayer film is a tape, the slitting step is omitted to perform stretching, and then splitting and shortening into fibers.

The present inventors first examined the diaper absorber,
As a result of diligent studies on the use of the composite fiber in the absorber, the composite fiber can be well blended with the crushed pulp constituting the diaper absorber, and is solidified by heat treatment of the blend. The resulting absorbent body has little shrinkage even when absorbing liquid, and can be solidified without using a skin material such as tissue paper, which simplifies the process. It has been found that the strength is stronger than that of the absorbent body, and based on this, the present invention has been completed.

That is, the present invention relates to an absorbent body of a disposable diaper, which is composed of the above-mentioned composite fiber and crushed pulp.

Next, the present invention will be described in detail.

As a conventional composite fiber, there is known one in which two kinds of spinning dope are simultaneously spun from two partitioned spinnerets, and both fibers are bonded to each other to form one fiber (conjugate fiber). Has been.

On the other hand, conventionally, as a heat-adhesive conjugate fiber utilizing the difference in melting point, for example, crystalline polypropylene (m.p165 ° C.) is used as the high-melting polymer and polyethylene (m.p125 ° C.) is used as the low-melting polymer. It is also known that each composite component is formed by melt composite spinning.

Examples of these cross-sectional models of composite fibers are shown in FIGS. 5 and 6.
Shown in the figure.

In the models shown in FIGS. 5 and 6, the inside is formed by the high melting point polymer 3, while the outside is formed by the low melting point polymer 4.

Such a conventional thermoadhesive conjugate fiber is usually heat-treated after being formed into a web, that is, the low-melting polymer is melted, but the high-melting polymer is heat-treated at a temperature at which the high-melting polymer is not melted. It can be fused to form a web or the like.

However, in the case of the above-mentioned melt composite spinning, the die and nozzle structure are complicated, and due to this, it is generally impossible to produce a composite fiber of three or more components, and
It is difficult to form a composite fiber composed of polymers having no adhesiveness to each other, and it is practically impossible even for a composite fiber composed of two components because it is difficult to change the color of the raw material. Therefore, despite the excellent performance of the heat-adhesive web, the range of use has been greatly limited.

The present inventors obtained composite fibers by a method different from the conventional composite spinning as described above, and as a result, it is possible to obtain composite fibers that overcome the drawbacks of the above-mentioned conventional techniques, and easy coloring. With this, it is possible to have a wide variety of colors, not only two layers but also three or more layers of multi-layer structure can be realized, and it is also possible to realize a fiber structure composed of polymers without adhesiveness. There are no problems with dies and nozzles (disassembly and cleaning, etc.) that are typical of melt-composite spinning, and by changing the die shape, it is possible to produce webs with a wide variety of textures, voluminous sensations, etc. As a result, it was possible to obtain a safe, low-cost composite fiber, especially a heat-adhesive (heat-fusible) composite fiber.

Furthermore, this composite fiber is a composite fiber having a non-uniform thickness (fiber) and length, and has a branched structure, unlike the conventional composite fiber. The crushed pulp used for diaper absorbents is also generally non-uniform and has a branched structure, which allows it to be well blended with the bicomponent fibers of the present invention.

The above-mentioned multilayer film used in the present invention will be described by taking a multilayer film as an example. The multilayer film can be produced by various molding methods such as a calender method, an extrusion method and a cast method.

Among them, the inflation method and the extrusion method by the T-die method are preferable methods, and the film according to the present invention can be produced by various methods such as co-extrusion with an inflation die or a T-die, and lamination.

For example, a method of simultaneously extruding different thermoplastic resins from two or more extruders to form a multilayer inflation film is adopted, whereby a multilayer film similar to a laminated product can be obtained.

As described above, the multilayer film is made of a thermoplastic resin. As the thermoplastic resin, it is preferable to use a film-moldable resin.

Specific examples include alpha olefin (co) polymers such as polyethylene and polypropylene, polyamides and polyesters.

Such a resin may be a copolymer with a different kind of monomer, and may further contain an antioxidant, a lubricant, an ultraviolet absorber, a matting agent, a stabilizer, a flame retardant, etc., if necessary. .

In the present invention, as described above, it is preferable to use a film-formable thermoplastic resin, but even if it is not possible to form a multilayer film, a single film-formable one is combined with this. By doing so, it is possible to form a multi-layer film and also to manufacture a composite fiber.

The multilayer film comprises at least two layers.

At least a thermoplastic resin constituting the multilayer film,
A thermoplastic resin forming one layer and a thermoplastic resin forming another layer have different melting points.

The melting point difference between the low melting point thermoplastic resin and the high melting point thermoplastic resin, the heat treatment conditions and extrusion conditions of the multilayer film, which will be described later,
Considering the stretching conditions in the subsequent process, the melting point of the resin
When the temperature is Mp ° C, the melting point of the latter resin is preferably Mp + 10 ° C or higher.

Examples of the multilayer film having a two-layer structure include one having a low melting point thermoplastic resin and one layer having a high melting point thermoplastic resin having a higher melting point than the resin.

Specific examples thereof include those using polyethylene (m.p125 ° C.) as the low melting point thermoplastic resin and crystalline polypropylene (m.p165 ° C.) as the high melting point thermoplastic resin.

Examples of the multilayer film having a three-layer structure include a structure in which the same low-melting thermoplastic resin is further laminated on the back surface of the high-melting thermoplastic resin of the above-mentioned two-layer structure.

Further, for the low melting point thermoplastic resin, for example, using linear low density polyethylene, for the high melting point thermoplastic resin, for example,
In the case where these resins do not have adhesiveness as in the case of using polyamide, an adhesive resin may be interposed between these resins to form a composite fiber composed of polymers having no adhesiveness to each other. It will be possible.

As an example of the adhesive resin, a resin composition obtained by modifying polyethylene, polypropylene or the like with an acid anhydride such as maleic anhydride or an acid can be used, and specific examples thereof include a maleic anhydride modified wire. Low density polyethylene.

In the present invention, it goes without saying that not only these two-layer and three-layer structures but also four or more layers may be used,
At that time, the multilayer film is constructed in consideration of heat treatment conditions at a temperature at which the low melting point polymer melts and the high melting point polymer does not melt.

When the multilayer film according to the present invention is formed by the T-die method or the like, the die lip structure may be a flat one, but it is preferable to use a streak die.

As a result, the composite fiber according to the present invention can have a feeling and a feeling of volume.

FIG. 3 shows an example of a cross-sectional model of the conjugate fiber of the present invention when a flat die is used, and FIG. 4 shows an example of a cross-sectional model of the conjugate fiber of the present invention when a streak die is used. .

In FIGS. 3 and 4, reference numerals 5 and 6 respectively indicate a low melting point thermoplastic resin layer, and 7 indicates a high melting point thermoplastic resin layer.

In the present invention, the multilayer film is then slit and stretched. It is also possible to stretch the already slit multi-layer film or tape. Therefore,
The multi-layer films referred to in the present invention include such tape-shaped ones. Also, it may be a sheet.

Further, the multilayer film may be slit after stretching, or the already stretched multilayer film is directly subjected to the slitting step. The thickness of the multilayer film is not particularly limited, but is preferably 30 to 100 μm.

The multi-layer film may be stretched by using any stretching tank such as a hot plate, a hot roll or an oven. The stretching temperature and the stretching ratio are not particularly limited, and may be set to optimum conditions depending on the composition and formation of the multilayer film. However, the strength, feel, volume and the like of webs and non-woven fabrics obtained through the post-process largely depend on the physical properties of the fibrils.

When a preferable example of the stretching temperature and the stretching ratio is shown, for example, when a multilayer film made of polyethylene and crystalline polypropylene is slit in the longitudinal direction and then stretched by a hot roll, the stretching temperature is 100 ° C to 130 ° C, and the stretching ratio is Is 4
It is preferably in the range of 10 times.

Cleavage performed after such a step is performed by, for example, contacting a stretched stretched film (tape-like material) with a roll having a needle on the surface and rotating the roll in the same direction with respect to the traveling direction of the film. This is a step of making the film into a fibrous shape, and the final fiber diameter is determined by the lead or pitch of the splitting needle used in this case.

After forming the split yarn, the continuous fibers are shortened by using a cutter or the like.

The fiber length of the short fibers is preferably about 50 to 100 m / m in consideration of the card processing in the subsequent step and the feel of the heat-contact composite fiber.

Short fibers are blended with crushed pulp by air blowing,
Heat treatment of the blend can form an absorbent body for the diaper. FIG. 2 schematically shows a cross section of the diaper. Second
In the figure, 8 is an absorber, 9 is a liquid permeable front body, and 10 is a liquid impermeable back body.

The short fibers can be formed into a non-woven fabric by preliminarily defibrating or directly subjected to card processing or the like to form a nonwoven fabric, and further, a gauze, a diaper cover, a carpet or the like can be formed.

〔The invention's effect〕

(1) According to the present invention, it was possible to satisfactorily blend with the crushed pulp constituting the diaper absorber.

(2) According to the present invention, by heat-treating the above blend, a solidified sheet (mat) is obtained,
It is possible to fix the crushed pulp, and therefore, the skin material such as Tissue paper, which has been conventionally required, does not require the step of wrapping the crushed pulp, and the process can be significantly simplified when manufacturing the absorber. I was able to. Of course, by utilizing the advantages of the heat-fusible composite fiber, a binder such as an adhesive is unnecessary, and a disposable diaper that is sanitary and harmless can be obtained.

(3) The absorber obtained by the present invention absorbs liquid,
The shrinkage was less than that of the conventional one, and it was possible to prevent the crushed pulp from shrinking.

Others The conjugate fiber according to the present invention has the following advantages over the conjugate fiber produced by conventional spinning.

(4) In the present invention, not only two layers but also a composite fiber having a multilayer structure of three or more layers is possible, and in particular, a composite fiber of three or more components, which has been difficult in melt composite spinning, can be made possible. It was

(5) According to the present invention, it is possible to freely obtain a composite fiber composed of polymers having no adhesive property, from a multilayer film having an adhesive resin interposed.

(6) According to the present invention, a composite having a cross-sectional model as shown in FIG. 1 and FIG. 2 which has a cross-sectional shape different from that of the conventional composite fiber by using a film as a starting material and changing the die shape. Fibers could be obtained, with the use of a creasing die to obtain a composite fiber rich in texture and volume.

(7) According to the present invention, since the fibers are formed from the film, it is possible to eliminate the troubles (disassembly and cleaning) of the die and nozzle, which are common in the conventional melt composite spinning.

[Brief description of drawings]

FIG. 1 is a perspective view of an example of a diaper, FIG. 2 is a schematic sectional view of a diaper showing an embodiment of the present invention, and FIG. 3 is a sectional view showing an example of a composite fiber model according to the present invention. Is a cross-sectional view showing another example of the composite fiber model according to the present invention, FIG. 5 is a cross-sectional view of a conventional example composite fiber, and FIG. 6 is a composite fiber cross-sectional view showing another example of the conventional composite fiber. 5, 6 ... Low melting point thermoplastic resin layer 7 ... High melting point thermoplastic resin layer 8 ... Absorber 9 ... Liquid permeable front body 10 ... Liquid impermeable back body

Claims (1)

[Claims] 1. An absorbent body of a disposable diaper having a liquid-permeable front body, a liquid-impermeable back body, and an absorbent body interposed therebetween, wherein the absorbent body and the heat-bondable conjugate fiber are crushed. A multi-layer film consisting of pulp, wherein the thermoadhesive conjugate fiber is a multi-layer film consisting of at least two layers, and one layer and another layer consisting of a thermoplastic resin having different melting points;
Stretching after slitting or slitting after stretching, or when the multi-layered film is a stretched multi-layered film, the stretching step is omitted, and when the multi-layered film is a tape, the slitting step is omitted. Then, the slitted stretched film or sheet or stretched tape-like material is split into fibrous form and made into short fibers to obtain a disposable diaper absorbent body.