JPH0446147B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to disposable sanitary materials, particularly sanitary materials such as disposable diapers, sanitary napkins, and postpartum napkins. More specifically, the present invention relates to an improved disposable sanitary material comprising a bulky nonwoven fabric as a top sheet. [Prior art and problems to be solved by the invention] Conventional disposable sanitary materials, such as disposable diapers and sanitary napkins, have a surface that comes into contact with the skin by sandwiching an absorbent material made of cotton pulp, absorbent paper, superabsorbent resin, etc. It has a structure with a liquid-permeable sheet and a liquid-impermeable sheet on the back side, and the drained liquid passes through the liquid-permeable sheet (hereinafter referred to as the top sheet) and is absorbed and retained by the absorbent body. The liquid-impermeable sheet on the back prevents liquid from leaking to the outside. A nonwoven fabric is generally used for this top sheet. The nonwoven fabric used as such a top sheet is required to have various properties, and the most important ones are excellent bulkiness, especially bulkiness with cushioning properties, since it comes into direct contact with the skin. The strength and dimensional stability of the disposable sanitary material during manufacture and use must be practically satisfactory. Various nonwoven fabrics have been researched to meet the above requirements and have been proposed. BACKGROUND OF THE INVENTION Currently, there are nonwoven fabrics widely used as surface sheets for sanitary materials that are made of hydrophobic fibers, such as polypropylene fibers, produced by the spunpond method.
This nonwoven fabric has an excellent dry feel and is strong ^, so it is difficult to break during use and has excellent dimensional stability during the production of sanitary materials ^. It has the advantage that it can be used in However, this nonwoven fabric has a problem in that its bulkiness is poor because the fiber arrangement in the nonwoven fabric is planar. On the other hand, a nonwoven fabric is known in which synthetic short fibers are made into a web using a card and the constituent short fibers are joined using an adhesive. Since this nonwoven fabric uses an adhesive, the texture of the fibers is destroyed and the fabric becomes hard, making it undesirable as a topsheet. Therefore, by using partial heat compression bonding or fused fibers to join short fibers, we try to avoid destroying the texture of the fibers.
In addition, mechanical crimping is applied for carding, but if short fibers that are crimped after being made into a web are used, the texture of the fibers is utilized and a nonwoven fabric with good bulk can be obtained. A nonwoven fabric is preferably used as the topsheet. However, since this nonwoven fabric uses short fibers, it has a problem of being inferior in strength and dimensional stability. Naturally, if the bond is strengthened to increase strength, the nonwoven fabric will become harder. Therefore, various proposals have been made to use long fibers to obtain high strength and to obtain bulky nonwoven fabrics. For example, methods are known in which bulkiness is imparted by forming a web using latent crimped long fibers, or by performing pressing, rolling, molding, etc. in post-processing. However, this method has the problem that the dimensions of the nonwoven fabric change during the production of the nonwoven fabric, and additional steps of post-processing are required, and as a result, this method cannot be said to be practical. On the other hand, Japanese Patent Publication No. 62-1026 or Japanese Patent Publication No. 48-1491
As disclosed in the above publication, a method of making a nonwoven fabric by dispersing crimped fibers is known.
With this method, it is impossible to produce a uniform nonwoven fabric with a low basis weight (15 to 25 g/m ² ) suitable for use as a topsheet. The present invention solves the problems of the surface sheets of conventionally known disposable sanitary materials, and has sufficient performance in terms of strength, dimensional stability, and liquid permeability to withstand use, and is bulky, soft, and The purpose of the present invention is to provide a disposable sanitary material with a uniform nonwoven fabric. [Means for Solving the Problems] The above-mentioned object of the present invention is to provide a top sheet that is permeable to liquid discharged from the human body, a liquid-impermeable back sheet, and an absorbent sheet located between the front and back sheets. A disposable sanitary material comprising a body, wherein the top sheet is a web consisting of a continuous filament of a crystalline thermoplastic composite fiber having a helical crimp with a crimp diameter of 1 mm or less, and the constituent filaments in the web are This is achieved by a disposable sanitary material characterized in that at least a portion of the above is a nonwoven fabric bonded to each other by heat fusion or heat compression bonding. The present invention will now be described in detail with reference to the accompanying drawings, which illustrate an example of the disposable sanitary material and nonwoven fabric of the present invention. FIG. 2 shows a plan view of an example of a disposable disposable diaper, which is a type of disposable sanitary material of the present invention, and FIG. 3 shows a sectional view thereof. As shown in FIGS. 2 and 3, the disposable diaper 1 includes a top sheet (top sheet) 2 on the front side, a liquid-impermeable back sheet (back sheet) 4 on the back side, and the top sheet 2.
The disposable diaper 1 consists of an absorbent body 3 disposed between a back sheet 4, and gatherers 5 are provided on both sides of the disposable diaper 1, and tape fasteners 6 are attached to both upper sides. When in use, the top sheet 2 is placed on the human body side, and liquid discharged from the human body is absorbed and retained by the absorbent body 3 through the top sheet 2.
The discharged liquid is prevented from leaking to the outside by the liquid-impermeable back sheet 4. Since the structure of such a disposable diaper itself is well known, description of each component other than the topsheet 2 will be omitted below. The nonwoven fabric used in the disposable diaper of the present invention (hereinafter abbreviated as the nonwoven fabric of the present invention) is made using a web consisting of continuous filaments of crystalline thermoplastic composite fibers having helical crimps with a crimped helix diameter of 1 mm or less. . The crystalline thermoplastic composite fibers used here include polyolefin fibers such as polypropylene fibers, polyester fibers such as polyethylene terephthalate fibers, and polyamide fibers such as nylon 6 or nylon 66. Composite fibers are generally crimped by a translation type or an eccentric sheath-core type in which component fibers are bonded together. Note that it is more preferable to use hydrophobic polyolefin fibers. The filament constituting the nonwoven fabric of the present invention has helical crimps, and the number of crimps is preferably 2 to 30/25 mm, and the helical diameter of the crimps is 1 mmφ or less. Preferably, the diameter of the crimp spiral is 1.0 to 0.3 mm. If the crimped helix diameter exceeds 1.0 mm, the number of crimps per unit length will be small, resulting in poor bulkiness.
If it is less than 0.3 mm, the space obtained by the spiral shape will be extremely small, resulting in poor bulkiness, and the entanglement between the filaments will become too strong, making streaks likely to occur during web production. . Such spiral crimp uses the bimetallic effect of composite fibers. The bimetallic effect can be obtained, for example, by heating and cooling translational composite fibers, and can be obtained by using an asymmetric cooling method. In order to make a continuous filament web from the filaments obtained in this way, it is preferable to use the so-called spunpond method in which the filaments are formed into a web immediately after spinning. In the nonwoven fabric of the present invention, the constituent filaments are substantially interconnected. The term "substantially bonded to each other" here does not mean that all of the intersection points of the plurality of filaments constituting the nonwoven fabric are bonded, but that some of the intersection points are bonded at a rate that depends on the manufacturing conditions. Indicates that there is a Preferred bonding methods for low surface weight products as the topsheet include a method using an adhesive, a heat fusion method using composite fibers having a heat fusion component, or a partial thermocompression bonding method using an embossed member. However, from the standpoint of safety and texture before use, it is preferable to use a heat fusion method that joins the fibers themselves or a partial thermocompression bonding method, and a partial thermocompression bonding method that takes advantage of the texture of the fibers themselves. is particularly preferred. The heat-sealing method mentioned here involves forming a long fiber web from a composite crimped filament in which one component is polyethylene terephthalate and the other component is high-density polyethylene, and then blowing hot air at, for example, 160°C onto these webs. This is a method of joining webs by melting the polyethylene component at the intersections of the filaments.
FIG. 4 is a microscopic photograph showing the surface of the nonwoven fabric obtained by the heat fusion method. As clearly shown in FIG. 4, the filaments are fused together at the intersection points. Next, a partial thermocompression bonding method will be explained. Partial thermocompression bonding can be carried out by pressing a engraved roll or a flat plate against each other, but the roll method is preferable from a production standpoint. A combination in which one is an engraving roll and the other is a smooth metal roll, or a method in which both the upper and lower engraving rolls are butted together is adopted. The degree of thermocompression bonding is determined by setting the temperature and contact pressure of the upper and lower rolls according to the required performance such as strength or fluffiness of the nonwoven fabric to be obtained, but the upper hand temperature is below the melting point of the fiber used. It is preferable to set it to . In addition, the texture of the finished nonwoven fabric is greatly influenced by the embossed pattern of the sculpture, especially the thermocompression area ratio,
The important points are the engraving interval and engraving depth. FIG. 5 shows examples of emboss patterns preferably used to produce the nonwoven fabric of the present invention, and Table 1 shows the corresponding dimensions of each emboss pattern. In FIG. 5, t indicates the minimum interval between each embossing.

〔Example〕

The invention is further illustrated by the following examples. Prior to the description of Examples, the definitions and measurement methods of physical property values used in the present invention will be summarized below. ◎ Fabric weight: Expressed in weight (g) per 1 m ² of nonwoven fabric. ◎ Helix diameter: Measure the diameter of the loop under a micrograph of the nonwoven fabric, and use the average value (mm). ◎ Thickness change due to compressive load Compressive elasticity tester E-2 manufactured by Nakayama Electric Industry Co., Ltd.
Using a mold, the compressive load was set to 0, under a measurement area of 4 cm ² .
The load is changed to 10, 20, 50, 100, and 150 g, and the thickness T (μ) of the nonwoven fabric at each load is measured. ◎ Tensile strength, elongation at break, and 5% modulus in the vertical direction Take a 3 cm wide sample of the nonwoven fabric in both the vertical and horizontal directions and pull it with a Tensilon manufactured by Toyo Baldwin Co., Ltd. at a gripping interval of 10 cm and a tension speed of 30 cm/min. Tested, tensile strength (Kg/3cm width),
The elongation at break (%) and the stress at 5% elongation in the vertical direction are expressed as the vertical 5% modulus (Kg/3cm width). ◎ Flexibility The stiffness of JIS L1096 was measured using the E method (6, 19, 5 handle-o-meter method). ◎ Permeation rate (sec/5 c.c.) and rewetting amount (g) As an absorber, in order to keep the characteristics of the absorber constant, we used a specified filter paper (manufactured by Eaton Dikeman, 939, 10 cm).
Place the square x 3 pieces stacked at the bottom of the measuring device (approximately 800 g, 10 cm square with a 25 mm diameter hole in the center).
A test cloth (10 cm square) is placed on top of this absorbent material, and 5 c.c. of artificial urine is dripped from 25 mm above the cloth.
Artificial urine is made by adding a nonionic activator to physiological saline25
4.5±3dyne/cm at °C (equivalent to infant urine)
Adjusted to. The dropping speed was 3.5 sec/25 c.c. This was defined as the transmission rate (sec/5 c.c.). Next, artificial urine is added as is, so that the total liquid volume is four times the absorbent weight so that the liquid volume contained in the absorbent body is constant. From above the test cloth
A load of 800 g/10 cm square was applied for 3 minutes to stabilize the liquid distribution in the absorber, and then a pre-weighed filter paper (manufactured by Eaton Dikeman, 631, 12.5
A load of 3,600 g/10 cm square (equivalent to the load applied to an infant's diaper) was immediately applied to the filter paper for 2 minutes, and the increase in weight of the filter paper was measured and determined as the amount of wetness (g). Example 1 Polypropylene [specific gravity 0.910, MFR38 (JIS K7210, Table 1
(measured under condition 4)], extruder (B) quantitatively extrudes polyethylene [specific gravity 0.963, MFR40 (JIS7210, measured under condition 4 in Table 1)] at 100 g/min each,
A group of translational composite filaments can be spun by using a spinneret for translational composite filaments with a length of 80 cm and a width of 4 cm, which has Hall spinning nozzles (equally spaced in 100 rows in the longitudinal direction and 2 rows in the width direction). The filaments were pulled at a speed of 3500 m/min using a rectangular high-speed airflow traction device while applying cooling air (0.8 m/sec) from one side, and then the filament group was made into an alloy plate consisting of 20% copper and 80% lead. After colliding and triboelectrically charging, it was deposited on a moving web conveyor. In order to cool the filament group between the spinneret and the rectangular high-speed air traction device, there is a first cooling device 12 having a length of 50 cm in the filament traveling direction, and a long cooling device 12 located closer to the spinneret surface than the first cooling device 12. A second cooling device 13 with a diameter of 5 cm is installed, and cooling air (70% RH 20°C) is applied perpendicular to the running direction of the filament group.
I sprayed it with The upper end of the cold air blowing position of the first cooling device 12 is 15 cm from the spindle surface, and the cooling air is
1.0m/sec, 5cm and
It was 0.5m/sec. Also, the blowing direction of cold air from the first cooling device and the second cooling device is 10° in the horizontal plane.
The company gained traction by making a difference in cooling and strengthening its cooling system. The obtained web was a uniform and bulky web with good filament spreadability and no streaks, and the average number of filament crimps was 7/25 mm. This web was sandwiched between two wire meshes and heated at 150°C for 50 seconds in a circulating air oven to obtain a bulky and uniform long-fiber nonwoven fabric with a basis weight of 22 g/m ² and a thickness of 1560 μ/10 g/4 cm ² load. . The crimp helix diameter of the loop-shaped crimp was 1.0 mm, and the flexibility was 21.5 g in the vertical direction and 11.6 g in the horizontal direction.
When 0.5% of a nonionic liquid permeable agent (octylphenol ethylene oxide (8 to 10 mol) adduct) was added to this nonwoven fabric as a treatment agent, the permeation rate of artificial urine was 2.1 sec, and the amount of rewetting was 95 mg/
(3600g/10cm square load). A disposable diaper using this nonwoven fabric as a top sheet was bulky and soft with cushioning properties, and the diaper did not allow the user to feel the feel of the absorbent material underneath. On the other hand, this web was passed through a thermocompression roll that was a combination of an engraving roll and a smooth roll with a pinpoint pattern (0.45φ, minimum interval 1.0mm, thermocompression area ratio 7.1%, depth 0.8nm) as shown in Fig. 5, and the engraving ( Top) Roll 100℃,
The smooth (lower) roll was partially thermocompressed by applying a pressure of 65 kg/cm at 105°C. As shown by curve h in Figure 1,
Although the initial bulkiness was inferior to that bonded with hot air (curve g), it had a soft and bulky feel with a softness of 12.8g and a horizontal direction of 4.5g.The permeation rate of artificial urine was 2.2sec, wetness return amount 87
mg/3600g/10cm square load. Example 2 From one of the two extruders (A), polyethylene terephthalate (ηnp/c = 0.75, (measured at 25°C using orthochlorophenol as a solvent)) was added at 120 g/min.
From the other extruder (B), high-density polyethylene [specific gravity 0.966, MFR35 (measured under the conditions of JIS K7210 Table 1)] was extruded quantitatively at 80 g/min, and a 200-hole spinning nozzle (with 100 lines in the longitudinal direction and a width A group of translational composite filaments is spun by using a spinneret for translational composite filaments measuring 80 cm in the longitudinal direction and 4 cm in width, and has cooling air (0.8 m/sec) from one side. ) by using a rectangular high-speed airflow traction device while applying
After being towed at a speed of 4000 m/min and charged with a corona charging device, a receiving web is created on a wire mesh web conveyor equipped with a moving suction device. The obtained web was a uniform, bulky, long fiber web without streaks. The filament pulling the web had an average number of crimps of 8/25 mm. This web was sandwiched between two wire meshes and heated at 160° C. for 90 seconds in a circulating air oven to obtain a uniform long-fiber nonwoven fabric with a basis weight of 25 g/m ² and a thickness of 1710 μ/10 g/4 cm ² load. The crimp helix diameter of the loop-shaped crimp was 1.0 mm, and the flexibility was 23.1 g in the vertical direction and 12.5 g in the horizontal direction. When 0.5% of a non-ionic liquid permeable agent (octylphenol ethylene oxide (8 to 10 mol) adduct) was added to this nonwoven fabric as a treatment agent, the permeation rate of artificial urine was 2.2 seconds, and the amount of wetness was 93 mg/(3600 g/10 cm square). load). A disposable diaper using this nonwoven fabric as a top sheet had a soft surface feel and cushioning properties, and did not feel wet. On the other hand, this web was engraved with a transverse line pattern (2.6 m/m width x 0.4 nm length, minimum interval 1.2 mm, thermocompression area ratio 11.4%, depth 0.6 m/n) as shown in Fig. 5 and a smooth roll. A spunbond nonwoven fabric was obtained by partially thermocompressing the upper and lower rolls using the combined thermocompression roll 17 at a temperature of 105° C. and a pressure of 60 kg/cm. The filaments of this non-woven fabric also have crimps, and the thickness at a load of 10 g/4 cm ² is 610 μm, and in this respect, the bulkiness at the initial load is inferior to that of the non-woven fabric produced by the heat-sealing method using hot air. Yes, but the flexibility is vertical
It was more flexible at 13.1g and 4.3g in the horizontal direction. The permeation rate of artificial urine was 2.2 sec, and the amount of rewetting was 89 mg/(3600 g/10 cm square load) in the liquid treated material. [Effects of the Invention] Since the disposable sanitary material according to the present invention is configured as described above, it has excellent dimensional stability when manufacturing sanitary materials such as disposable diapers and sanitary napkins using the nonwoven fabric of the present invention, resulting in high speed production. A disposable diaper that is compatible with production machines, has sufficient practical characteristics during use, is bulky, soft, and has a uniform nonwoven fabric is obtained, and is useful as an unprecedented and excellent disposable sanitary material. used for.

[Brief explanation of drawings]

FIG. 1 is a graph showing the change in thickness of the nonwoven fabric used as the top sheet of the disposable diaper of the present invention (hereinafter referred to as the nonwoven fabric of the present invention) with respect to compressive load, and FIG. 2 is a plan view showing an example of the structure of the disposable diaper. 3 is a cross-sectional view of the disposable diaper shown in FIG. 2, and FIG. 4 is a microscopic photograph showing the shape of fibers on the surface of the nonwoven fabric of the present invention obtained by a heat fusion method, FIG. 5 is a diagram showing the embossed pattern used in manufacturing the nonwoven fabric of the present invention from FIG. 5 1 to FIG. 5 6, and FIG. It is a diagram. 1...Disposable diaper, 2...Top sheet, 3
...Absorbent body, 4...Liquid-impermeable back sheet, 5...
... Gears, 6 ... Tape fastener, 7 ... Thermocompression bonding part, 8 ... Fiber, 11 ... Base, 12 ... First cooling device, 13 ... Second cooling device, 14 ... High-speed traction device, 15... Charging device, 16... Wire mesh conveyor, 17... Partial thermocompression roll, 18
... Liquid permeable agent processing device, 19 ... Winding machine, 20 ...
Web, 21...Nonwoven fabric.

Claims (1)

[Scope of Claims] 1. A disposable sanitary material comprising a top sheet through which fluids discharged from a human body can pass, a liquid-impermeable back sheet, and an absorbent body located between the front and back sheets, comprising: The sheet is made of a continuous filament of a crystalline thermoplastic composite fiber having a helical crimp with a crimp diameter of 1 mm or less, and at least a part of the filaments constituting the web is heat-sealed or thermo-compressed. A disposable sanitary material characterized in that it is a nonwoven fabric that is bonded to each other.