JPS6332881B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for manufacturing disposable diapers, and more specifically, a method for manufacturing disposable diapers, and more specifically, a nonwoven fiber sheet that is continuously supplied to the diaper manufacturing process while manufacturing a nonwoven fiber sheet to be used as a material for a water permeable top sheet of a diaper. The present invention relates to a method for manufacturing a disposable diaper.

Disposable diapers are generally composed of a water-permeable top sheet, a water-impermeable back sheet, and an absorbent body interposed between these two sheets.The top sheet is a nonwoven fiber sheet, the back sheet is a plastic sheet, A carrier sheet and defibrated pulp are used as materials for the absorbent body. In the manufacturing of diapers, each of these materials, in addition to the defibrated pulp itself, is manufactured in advance and supplied as a roll, so that each winding has a separate material for subsequent unwinding after unwinding. However, this will lead to the production of defective products and a decrease in productivity, so it is preferable to minimize the number of locations that require such joints. In particular, the nonwoven fiber sheet used as the material for the top sheet forms the surface of the diaper, so it is preferably supplied continuously and stably.

It is theoretically possible to directly connect the diaper manufacturing process and the nonwoven fiber sheet manufacturing process, and to continuously supply the nonwoven fiber sheet as a material for the top sheet to the diaper manufacturing process while manufacturing the nonwoven fiber sheet. . However, in general, in order to manufacture conventional nonwoven fiber sheets, the scale of manufacturing equipment becomes large, it is difficult to follow and adjust the manufacturing speed of nonwoven fiber sheets to the manufacturing speed of diapers, and nonwoven fiber sheets are constantly It is difficult to achieve stable production of sheets and supply them continuously and stably as the material for the top sheet of diapers, and in order to manufacture nonwoven fiber sheets, it is necessary to make the width as wide as possible economically. However, there are many difficult problems such as the fact that it is not suitable for immediate use as a material for the top sheet of diapers, and it is by no means practical.

An object of the present invention is to directly connect the manufacturing process of diapers and the manufacturing process of special non-woven fiber sheets, and while continuously manufacturing the non-woven fiber sheets, they can be stably used in the diaper manufacturing process as a material for the top sheet. It is an object of the present invention to provide a method for manufacturing diapers that can reduce the occurrence of defective products as much as possible and improve productivity by supplying diapers.

The method of the present invention for achieving the above object will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of a conventionally commonly used device for producing disposable diapers consisting of a water-permeable top sheet, a water-impermeable back sheet, and an absorbent body interposed between the two sheets. is shown as an example. In this device, the sheet is unwound from a winding 2 of a pulp sheet 1 and made into powdered defibrated pulp 4 by a hammer mill 3, and the sheet is unwound from a winding 6 of a water-absorbing carrier sheet 5 onto a conveyor 7. The defibrated pulp 4 is passed through the lower surface of the unwinding hammer mill 3 onto the upper surface of the sheet, and is laminated to an appropriate thickness. By unwinding and stacking them, a continuous absorbent body 10 is formed, and the conveyor 1
1 and 12 for transport. Next, in order to prevent the continuous absorbent body 10 from losing its shape, the absorbent body is pressed in the thickness direction with a press roll 13,
Cutting the absorbent body into the length of one diaper with a cutter 14 to form an individual absorbent body 15,
By providing a difference between the cutting speed of the cutter and the moving speed of the conveyors 16 and 17, the individual absorbent bodies are transported while being separated from each other for a certain period of time. Next, on the upper surface of each individual absorbent body 15, a sheet wider than each individual absorbent body 15 is unwound from a winding 19 of a plastic sheet 18, which is to be used as the material for the water-impermeable back sheet of the diaper, and is stacked on top of the other sheet. In this step, a sheet wider than each individual absorbent body 15 is unwound from a winding 21 of a nonwoven fiber sheet 20 to be used as a material for the water-permeable top sheet of the diaper, and the sheet is conveyed by stacking conveyors 16 and 17, and each individual absorbent body is body 1
Both side edges of the plastic sheet 18 and the nonwoven fiber sheet 20 protruding from both side edges of the individual absorbent bodies 15 are joined by a pressure roll (not shown), and the plastic sheet 18 is bonded between the longitudinal edges of each individual absorbent body 15. By cutting the diaper 18 and the nonwoven fiber sheet 20 with a cutter (not shown) and joining them together, diapers can be manufactured continuously.

FIG. 2 shows a method for carrying out the method of the present invention which utilizes the diaper manufacturing apparatus and continuously manufactures and supplies a special nonwoven fiber sheet instead of the winding 21 of the nonwoven fiber sheet 20. A schematic diagram of the device is shown. In this device, extruder 2
A raw material that is a blend of thermoplastic synthetic resin pellets such as polypropylene or ethylene and a foaming agent that foams when heated is put into the hopper 23 of No. 2, melted in the heating cylinder 24, and formed into a circular shape with a ring-shaped slit by the screw inside the cylinder. A hydrophobic net-like sheet 26 is formed by foaming while being extruded into a tube shape from the die 25, and the sheet is passed through a ring 27 having a diameter larger than that of the die 25.
The sheet is widened and air-cooled to stabilize the sheet, and the sheet is bonded in two layers using a pressure roll 28 to form the sheet. In this case, the basis weight of the net-like sheet 26 can be adjusted by the amount of extrusion of the screw, the slit interval of the die, and the size of the ring 27. Further, in order to narrow the width of the two-layered net-like sheet 26, it is sufficient to reduce the amount of extrusion of the screw and set the diameter of the ring 27 corresponding to the required width.

As shown in FIG. 3, which is an enlarged schematic diagram of the structure, the net-like sheet 26 produced in this way has a continuous filament-like structure in which each fiber 29 is partially connected without overlapping vertically, resulting in innumerable fibers. It has 30 meshes and is thin and lightweight like tissue paper made of pulp. However, since this net sheet 26 is hydrophobic, it alone has no water absorption properties and is therefore unsuitable as a material for the top sheet of a diaper. Therefore, as shown in FIG. 2, a sheet 31 whose main component is a cellulose-based hydrophilic material such as pulp, rayon, cotton, etc.
The sheet is placed on one side of the net-like sheet 26 and then heated with a hot embossing roll 33.
a and a rubber or paper roll 33b and embossing them to form a composite nonwoven fiber sheet 34, and replace the sheet with the nonwoven fiber sheet 20, and The absorbent sheet 31 is continuously supplied with its surface facing the absorbent body 15. As shown in an enlarged schematic diagram in FIG. 4, the nonwoven fiber sheet 34 has a part 35 of the hydrophilic sheet 31 biting into the net-like sheet 26, and the fibers 29 of the net-like sheet having a shape. The bonded state is maintained by melting and adhering to the hydrophilic sheet to the extent that the hydrophilic sheet is not lost. However, in the method of the present invention, the nonwoven fiber sheet 34 prohibits or excludes a state in which a portion of the net-like sheet 26 bites into the hydrophilic sheet 31 or partially bites into each other. isn't it. Furthermore, the emboss shape of the nonwoven fiber sheet 34 applied by the hot embossing roll 33a may be scattered dots, interrupted lines, continuous lines, or the like. Incidentally, as is obvious to those skilled in the art, if the positions of the hot embossing roll 33a and the rubber or paper roll 33b are reversed and the net-like sheet 26 is brought into direct contact with the hot embossing roll, the heat It is necessary to particularly control the temperature of the embus roll. That is, if the temperature of the hot embossing roll is too high, the net-like sheet 26 will melt more than necessary and adhere to the hot-embossing roll, causing trouble in the embossing operation and damaging the shape of the web-like sheet. become.
For example, when polypropylene/polyethylene=50/50% by weight is used as the material for the net-like sheet 26, a temperature of 80 to 130°C is appropriate.

In order to stabilize the bond between the net-like sheet 26 and the hydrophilic sheet 31 and to improve the strength of the nonwoven fiber sheet 34, the hydrophilic sheet contains thermoplastic fibers such as polypropylene or polyester in an amount of 30% by weight or less, preferably 20% by weight. % or less may be added.

Examples of the blowing agent include dinitrolibentametherenetetramine, azodicarbonamide, azobisisobutyronitrile, P-toluenesulfonylhydrazide, 44-oxybis(benzenesulfonylhydrazide), diazoaminobenzene, diphenylsulfone-3, 3-disulfonyl hydrazide and the like are used.

In addition, when the diaper manufacturing process is performed in multiple rows, the nonwoven fiber sheet 34 having a constant width is divided into required widths and supplied to each row of processes.

According to the method of the present invention, as described above, a composite nonwoven fiber sheet, that is, a fiber nonwoven fabric to be used as a material for the top sheet of a diaper, is formed into a hydrophobic net-like sheet, and a hydrophilic sheet is heat-embossed on this sheet. While being joined and formed, it is continuously supplied to the diaper manufacturing process, that is, the lamination process of the front and back sheets and the absorbent body. Therefore, a topsheet is formed in advance and rolled up, and this is unrolled in the diaper manufacturing process, and when the unwinding is finished, it is switched to a topsheet that has been formed and rolled up separately and unrolled. The disadvantages of the conventional diaper manufacturing process are that seams occur in the topsheet used in diapers, the switching takes time, and the unwinding speed of the topsheet cannot be adjusted quickly when switching. Accordingly, the disadvantage that the top sheet cannot be stably supplied can be solved.

In addition, by joining a hydrophobic net-like sheet and a hydrophilic sheet, we can create a relatively small composite fiber sheet (nonwoven fabric) that has the same or better effectiveness than the nonwoven fabric conventionally used as the top sheet of diapers. Since it can be manufactured easily and stably in a large-scale process, it can be directly connected to the diaper manufacturing process. In addition, such direct connection is possible because the hydrophobic net-like sheet is simply made by heating and melting a resin raw material mixed with a foaming agent using an extruder, extruding it into a tube shape, foaming it, expanding it with a ring, and then forming two layers. Not only can it be formed continuously by simply joining in layers, but it can also be formed to have the same width as the top sheet by setting the desired extrusion amount and ring diameter. This is because they are completely different.

The composite nonwoven fiber sheet as a top sheet manufactured by the method of the present invention is composed of an embossed bond of a hydrophobic net-like sheet and a hydrophilic sheet, and therefore has good water permeability, absorbency, and good properties as a top sheet of a diaper. It has strength, especially wet tensile and tear strength.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of equipment commonly used in the manufacture of disposable diapers. FIG. 2 is a schematic diagram of a diaper manufacturing apparatus for carrying out the method of the present invention. FIG. 3 is an enlarged plan view of the structure of the net-like sheet. FIG. 4 is an enlarged schematic cross-sectional view of a composite nonwoven fiber sheet. 22...Extruder, 25...Dice, 26...Net-like sheet, 27...Ring, 28...Crimping roll, 31...Hydrophilic sheet, 33a...Hot embossing roll, 34...Composite nonwoven fiber sheet.

Claims (1)

[Claims] 1. In a diaper manufacturing method in which an absorbent material is interposed between a water-permeable top sheet and a water-impermeable back sheet and these are continuously supplied and laminated in a lamination process, thermoplastic resin pellets are foamed by heating. A step of heating and melting a raw material blended with a blowing agent using an extruder, foaming it while extruding it into a tube shape, expanding the width with a ring, and then bonding it in two layers to continuously form a hydrophobic net-like sheet;
a step of continuously forming a composite nonwoven fiber sheet by stacking a hydrophilic sheet on one side of the net-like sheet and applying embossing and bonding under heating; A method for producing a disposable diaper, characterized in that the surface sheet of the hydrophilic sheet is continuously supplied to the lamination step with the surface of the hydrophilic sheet facing the absorbent body.