JP3067778B2 - Surface sheet for disposable sanitary materials - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a topsheet for disposable sanitary materials such as disposable diapers.

[Conventional technology]

FIG. 2 (A) shows an example and a plan view of the disposable diaper, and FIG. 2 (B) shows a sectional view. As shown in FIGS. 2 (A) and 2 (B), the disposable diaper 1 has a topsheet 2 on the front side (human body side) and a backsheet 4 on the back side with the absorbent 3 for absorbing excreted liquid interposed therebetween. It is configured by placing. Conventionally, a non-woven fabric made of various fibers is used as the top sheet 2.

[Problems to be solved by the invention]

In recent years, disposable diapers have become very popular, and their production has been rapidly increasing. One of the problems as a disposable diaper in such an environment is that reduction of loss on the production line and stability of quality are important.
In particular, the demand for high productivity accompanying the expansion of production volume has been strongly demanded, and equipment has been devised.However, the material used is not only strong enough to withstand high-speed lines, but also frequently used during low to high speed shifts. It has become necessary to use a material that can withstand the change and has less wrinkling, width deviation, and dimensional change in the width.

As a second problem, there is an improvement in leakage in terms of performance of the disposable diaper. Various proposals have been made so far.

That is, as a method of increasing the form stability of a disposable diaper to prevent leakage, there are known a method of increasing the use amount of a kink preventing net, an absorbent for absorbing excreted liquid, and a method of preventing leakage using a hot melt adhesive. Have been. As a method of improving the form of the disposable diaper to prevent leakage, a method of forming a pants style or providing gathers on the side and waist of the disposable diaper is known. As a method for preventing leakage by increasing the absorbing power, a method using a superabsorbent polymer or a diffusion sheet is known. As a method of preventing the disposable diaper from being loosened and leaking when the disposable diaper is used, a method using an elastic tape and a freely attachable tape is known.

On the other hand, for the topsheet, instantaneous water absorption or several-order water permeability is applied to increase the liquid permeation speed, or a liquid permeable treatment agent is applied only to the portion that comes into contact with the absorber, and the outer portion thereof Uses the hydrophobicity of the nonwoven fabric itself to prevent excreted liquid from transmitting to the outer part, and to prevent leakage that is still insufficient, more specifically, to gather gathers on the outer part to prevent side leakage and vertical leakage Measures have been taken such as providing a hot melt agent or applying a hot melt agent to eliminate voids between fibers of the nonwoven fabric to prevent the excreted liquid from advancing due to capillary action.

By appropriately combining these measures, even in the case of a conventional disposable diaper, leakage prevention during excretion can be substantially prevented as long as there is no mishandling by the user such as improper installation or size mismatch. However, the above-mentioned conventional countermeasures can solve the problem that the excreted liquid once excreted and absorbed oozes out with the passage of time, and leakage that occurs when absorption is concentrated at a specific location, particularly at the sandwiched portion. Can not do. That is, at present, there is no method for preventing the occurrence of leakage caused by excreted liquid after excretion. Also, among the above-mentioned countermeasures, there are those in which the bulk of the disposable diaper becomes too large, the feeling of the topsheet in contact with the human body becomes hard, or the cost becomes high, which is not always practical. .

The present invention has a problem that the diaper line is easily deformed by the tension applied to the line in the production accompanying the speeding up of the conventional diaper line,
In order to solve the problem of the leakage of disposable diapers, especially the bleeding problem, by improving the essential structure of the nonwoven sheet used as the topsheet, it is possible to reduce the feeling of the sheet without special treatment. It is an object of the present invention to provide a topsheet for disposable sanitary materials that can prevent bleeding of the excreted liquid while maintaining the same.

[Means for solving the problem]

The above object of the present invention is a surface sheet in a disposable sanitary material comprising a liquid-permeable top sheet, a liquid-impermeable back sheet and an absorber interposed between the two sheets, wherein the surface sheet is made of a hydrophobic synthetic fiber. It consists of a web of continuous filaments, in which the arrangement of fibers is such that the length / width ratio of the microwave transmission intensity is 1.1, the liquid permeable treatment agent is applied to the center of the web, and the outside of both edges thereof This is achieved by a topsheet for a disposable hygiene material, wherein the topsheet is a non-woven fabric portion.

Normally, the tension applied to a sheet in a diaper production line does not correspond to the breaking strength of the sheet, but depends on the process applied on the line. 1 to 6 kg, and the higher the speed, the higher the tension due to the speed change, but on average about 2 kg / 30
It is estimated to be about cm wide. Therefore, no matter how strong the breaking tension is, the tension applied in the line, if it is easily deformed, it becomes highly dependent on speed, and if it is hard to be deformed to line tension even with low breaking strength,
It can be said that its running stability is excellent. We have:
From the viewpoint of cost, we are studying improvement methods with the same weight (basis weight) and considering the performance such as the surface cover properties and feeling as a diaper surface sheet. By providing a direction difference, especially the direction to which tension is applied (in the case of a normal line, the direction of webbing)
By making the arrangement superior, even for flexible fibers, the width change at low tension is reduced, and the overall soft texture,
It has been found that running stability on a diaper line can be imparted while maintaining surface coverage.

Further, the present inventors have noted that liquids generally tend to advance by capillary action along the better arrangement of the aligned fibers in the web, and as described above, the arrangement of the fibers in the permeable web has The sheet of the present invention can prevent the excretion liquid from bleeding by providing a difference in the horizontal direction and using the sheet of the present invention so that the fibers are arranged in a greater direction across the direction in which the excretion liquid is not likely to bleed.

Further, since the web made of the hydrophobic synthetic fiber constituting the topsheet of the present invention has a performance of repelling liquid, it is necessary to use the property to provide a portion requiring water permeability, that is, at the center of the surface of the sanitary material. If the liquid permeable treatment agent is applied to the corresponding surface sheet portion, the liquid in the portion to which the liquid permeable treatment agent is applied hardly permeates beyond that portion to the portion where the liquid permeable treatment agent is not applied. This makes it possible to more completely prevent the exudation liquid from bleeding.
That is, in the topsheet 2 shown in FIGS. 1 (A) and 1 (B), the central portion 5a in the vertical direction and the central portion in the horizontal direction.
If a liquid permeable treatment agent is applied only to the center portion 5c in the vertical direction 5b or the horizontal direction and the horizontal direction, when the disposable diaper is made using the topsheet 2, it is possible to prevent the excreted liquid from bleeding.

If a web is used in the vertical direction in the topsheet of FIG. 1, the processing area of the liquid-permeable treating agent is as shown in FIG. 1 (a).
If 5a is provided, bleeding of the topsheet in the horizontal direction can be more completely prevented. If the treatment area 5b is provided as shown in FIG. 1 (b), the bleeding in the horizontal direction of the topsheet can be suppressed by the orientation of the fibers, and the bleeding in the vertical direction can be prevented by preventing the permeation outside the treatment area. FIG. 1 (c) has both features.

The nonwoven fabric is partially thermocompression-bonded, for example, with a staggered pinpoint emboss 6 as shown in FIG. This embossing is obtained by using an embossing roll or an embossing plate in which circular projections are arranged in a staggered manner, and the fibers in the web are partially thermocompression-bonded at a portion indicated by 7. In the embossment 6, a fiber layer showing a capillary phenomenon is continuous, and the bleeding of the liquid due to the capillary phenomenon in the fiber layer cannot be suppressed in a specific direction of the web.

Therefore, the vertical line embossing 8 shown in FIG. 4 or the horizontal line embossing 9 shown in FIG. 5 may be appropriately used. These linear embossments are formed by arranging in parallel in the longitudinal or width direction of the web a linear thermal compression bonding portion 8a or 9a of the width W ₂ at a pitch W _1.
If a linear thermocompression part is used as shown in FIG. 4 or FIG.
Since the fiber layer is interrupted, the movement of the liquid between the fibers in the direction perpendicular to the thermocompression bonding line is suppressed, and the bleeding of the liquid can be stopped.

As the hydrophobic synthetic fibers, various synthetic fibers having a low water content can be used. In particular, synthetic fibers made of polyolefin or polyester such as polyethylene polypropylene and composite fibers containing these are preferably used. Other substances may be mixed within a range that does not impair the hydrophobicity of the synthetic fiber.

Further, the continuous filament constituting the web may include a continuous filament crimped in a loop shape or a continuous filament having a non-circular cross-section such as a Y-shaped cross-section, as described in Examples below.

Various methods can be used for producing the web. That is, any web may be used as long as long fibers are used. In particular, a web by a spun bond method or the like can be used. At this time, the web is formed so that the arrangement of the fibers in the web is different in the vertical and horizontal directions.

6 to 8 show various aspects of a method of forming a web by a spun bond method as an example.

Figure 6 (A), the filament group f ₁ is spinning nozzle 11
Extruded from, and towed by the high-speed airflow traction device 12,
It is deposited while being absorbed by the absorber 14 to the net-like endless belt 13 to form a web W _1. At that time, as the filaments were stretched elongated in the running direction of the endless belt 13 around the point P ₁ dropped by the speed difference between the yarn speed and the endless belt was driven as illustrated in FIG. 6 (B) The web is deposited in a pattern and sequentially overlapped to form a web.

Figure 7 (A) is a method of blowing inclined filament group f ₂ for a net-like endless belt 13, the larger the inclination angle, dropping point as shown in FIG. 7 (B)
P ₂ filaments f ₂ is extended elongated from about a to form a web W ₂ is disposed on the net-like endless belt 13. The inclination angle α may be arbitrarily selected. However, if the inclination angle α is too large, it is necessary to pay attention to scattering of the formed web. For example, about 7 ° is used. Naturally, the spraying direction shown in FIG. 7A may be directed to the web traveling direction.

Figure 8 (A) is intended to form a web W ₃ by depositing a filament group f ₃ on the cylindrical wire mesh suction drum 15, the filament by changing the diameter of this cylindrical drum 15 the arrangement on the drum 15 can be elongated by advancing direction of the web W _3. Of course, if the web is inclined and blown to the drum to such an extent that the web does not blow off as shown in FIG.

In the top sheet of the present invention, as shown in FIG.
The nonwoven fabric portion 17 outside 16a is preferably left water-repellent. That is, the liquid that spreads in all directions at the central portion 16 as indicated by 18 does not spread to the water-repellent portion 17 near the both edges 16a as indicated by 18a. Therefore, by appropriately arranging the area treated with the liquid-permeable treatment liquid, bleeding of the liquid can be prevented.

The central portion 16 may be arranged at the central portion 5b in the horizontal direction as shown in FIG. 1 (B) or at the central portion 5c in the vertical direction and horizontal direction as shown in FIG. 1 (C).

As described above, the sheet of the present invention is manufactured by a method in which the arrangement of the fibers in the sheet can be elongated in the longitudinal direction of the sheet. As a result, a vertical / horizontal difference occurs in the arrangement of the fibers in the sheet as described above, and the vertical / horizontal difference reduces the width change on the line of the nonwoven fabric.
The dimensional stability at high speed can be obtained, and the direction of bleeding of the liquid can be controlled. Further, by appropriately providing the liquid permeable treatment agent on the sheet, the direction of the liquid bleeding can be further controlled.

The vertical / horizontal difference in the arrangement of the fibers in the sheet is the vertical / horizontal difference in the tensile speed of the sheet as will be described in detail in Examples below.
It can be proved by the measurement by the horizontal difference and the micro liquid orientation.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to various examples of the topsheet of the present invention.

Prior to the description of each embodiment, the performance evaluation method of the sheet of the present invention will be described.

-Fiber orientation direction Tensile strength-width ratio A sample is taken from a sheet obtained by setting the web traveling direction to the vertical direction and the web width direction to the horizontal direction, and JIS-L-108
Measure the tensile strength according to 5. The strength of the arrangement of the fibers in the sheet can be estimated from the ratio of the obtained vertical strength and horizontal strength.

Fiber orientation by microwave Microwave molecular orientation meter (manufactured by Kanzaki Paper Co., Ltd.) MOA-200
Using 1A, a polarized microwave is applied to the sample, the orientation of the main axis of the fiber molecule is detected by interaction with the dipole of the fiber molecule, and the sample is rotated to anisotropy (orientation). ,
Find the intensity ratio of the transmitted microwaves in the TD and MD directions.

This method is a conventional method used for examining the orientation angle and orientation pattern of the main axis of the molecular chain of a sheet or the like, and the electrical anisotropy of the sheet. FIG. 12 shows the transmission microscopicity of a polyimide film (130 μm thickness). The measurement result of the angle dependence of wave intensity is illustrated. In the case of FIG. 12, the orientation angle of the main axis of the molecular chain is 36 °, and the Max / Min is 3.08, indicating a large difference.

In this application, the orientation of the fibers in the web was confirmed using this method. FIG. 13 (A) is a measurement of the bang state, and the obtained transmitted microwave intensities are equal over 360 °, ie, FIG. 13 (B) shows the transmitted microwave intensity in the case of the second embodiment of the present invention, and FIG. 13 (C) shows the transmitted microwave intensity in the case of the third embodiment of the present invention.

In the case of the sheet of the present invention, the angle difference between the MD direction and the main orientation direction of the sample (INCLINE in the figure) indicates the main arrangement direction of the fibers.
In the case of the sheet of the present invention, the value is extremely small as shown in the examples described later. The transmission TD / MD ratio is a value related to the arrangement ratio of the fibers in the web. As shown in FIG. 13 (A), a value of 1 indicates isotropicity, and a value greater than 1 indicates a vertical direction (MD). ) Indicates that the fibers are arranged, and a larger value indicates a stronger degree of the arrangement. However, since the measurement is based on the transmission intensity, the absolute value of the orientation is not shown.

・ Water permeability As shown in FIG. 10 (A), a liquid absorber 27 such as a tissue, a parf, etc. is placed under the sample 19 and brought into close contact therewith. 15 mm above sample 19
One drop (0.1 cc / piece) of physiological saline was dropped from the dropper 21 of the above, and the liquid that had almost passed through the sample within 2 seconds and was absorbed by the absorber was regarded as having water permeability.

・ Smear spread When you see the spread of the liquid on the sheet itself,
10 As shown in FIG. 10 (B), the sample 19 is directly fixed to the support 20 and held horizontally in the air. Drop a drop of saline,
The spread of the liquid on the surface of the sample when the droplet was transmitted was measured.

・ Bleed length Using the device 22 shown in FIG.
23, and place the sample (15 m wide) on the sample table flush with the liquid surface.
m) 24 is arranged, and one end 2 cm of the sample 24 is immersed in the tank 23. The position of the end 26 of the liquid-penetrated portion 25 in the sample 60 seconds after being immersed in the liquid is measured, and the length is used as the bleeding length to indicate the ease of bleeding when a large amount of liquid is present.

・ With a web width of 3cm, apply a tension of 0.2kg / width at a distance of 20cm between the gripping parts, measure the width of the sample at the center in the longitudinal direction after 10sec, and calculate the shrinkage ratio with respect to the original width (3cm). Width ratio This value indicates whether the running stability of the web when the nonwoven fabric is actually put on a diaper production line is good or bad.

Example 1 Polypropylene (MFR measured under condition K of JIS K7210 =
38) is stretched in the width direction at a temperature of 240 ° C., and the extruded filament group is pulled and dispersed at a speed of 3,500 m / min using a high-speed airflow pulling device, and 45 cm below the spinning port as shown in FIG.
The web was formed while sucking on the net moving in the horizontal direction. This web is transported and the entire surface is
Staggered 0.45Φ protrusions at 1.5mm pitch (See Fig. 3)
It was passed through a partial thermocompression bonding roll obtained by combining the embossed roll and the smooth surface roll to obtain a partially thermocompression bonded spunbonded nonwoven fabric having a basis weight of 20 g / cm ² . The temperature of the upper and lower rolls at that time was 135 ° C., and a pressure of 60 kg / cm was applied. The single yarn denier of the fiber in the obtained nonwoven fabric was 2.3 denier.

When this nonwoven fabric was used for a disposable diaper, the liquid-permeable treatment agent was uniformly applied only to the center of the width (15 cm of the center of the diaper having a width of 30 cm). The treating agent provided an alkylphenol ethylene oxide adduct of 0.5%.

Example 2 In forming a web by blowing a group of polypropylene filaments pulled and dispersed under the same conditions as in Example 1 onto a moving net, the filaments were vertically aligned so that the fibers in the web were arranged in the traveling direction. It was sprayed on the moving net with a 7 ° inclination to the direction (see FIG. 7). The obtained web was subjected to thermocompression bonding of zigzag embossing under the same conditions as in Example 1, and a liquid permeable treatment agent was further applied to obtain a polypropylene spunbond nonwoven fabric of Example 2.

Example 3 Instead of the moving net used in Example 1, a cylindrical wire mesh suction drum having a diameter of 110 cm was prepared. By using this suction drum, the web is formed in a state where the fibers in the web are arranged in the traveling direction (see FIG. 8), and the partial thermocompression bonding portion of the zigzag emboss and the liquid permeation are used under the same conditions as in Example 1. The polypropylene spunbonded nonwoven fabric of Example 3 having a functionally treated portion was obtained.

Table 1 shows the performance evaluation results of Examples 1 to 3 of the nonwoven fabric.

As is clear from comparison of Examples 1 to 3 shown in Table 1, the filaments vertically deposited on the conveyor belt also have a vertical arrangement of the fibers because the traveling speed of the endless belt is high ( (Example 1), it is more inclined to deposit on a conveyor belt (Example 2), or on a cylindrical drum (Example 3).
The alignment of the filaments is better in the longitudinal direction of the web, as indicated by the tensile strength length / width ratio, microwave orientation. That is, the difference in the vertical and horizontal directions of the fiber arrangement is increased. Also, the better the filaments are aligned in the longitudinal direction of the web, the less the width is entered, which indicates that the running stability in the diaper line as a water-repellent nonwoven fabric is improved.

The effect of increasing the vertical / horizontal difference in the arrangement of filaments also appears in the spread value. That is, the bleeding spread is longer in the vertical direction and shorter in the horizontal direction in each of the embodiments, and the tendency is larger in the second and third embodiments than in the first embodiment. Therefore, when the sheet of the present invention is used as a top sheet of a disposable diaper, the direction of the sheet may be appropriately selected in accordance with the direction in which the excreted liquid is prevented from leaking. It can make disposable diapers with low leakage.

When the bleed length was measured for the nonwoven fabric of Example 1, the portion to which the treatment liquid was applied showed a bleed length of 40 mm in 60 seconds, but the test liquid did not penetrate into the untreated portion. Next, when the test liquid was dropped on this nonwoven fabric, the length of the test area 16 was bleeding and spreading 18 in the central processing area 16, but at both edges 16a, the test liquid was outside the edge 16a as shown by 18a, that is, untreated. Part 17 did not extend.

Example 4 When extruding the same polypropylene resin as in Example 1, the spinning nozzle was a modified nozzle having a Y-shaped cross section, and before the extruded filament group entered the high-speed airflow traction device, about 10 cm to 50 cm below the spinning nozzle. During the period, cooling air (20 ° C., 70% RH) is applied at right angles to the running direction of the filament group from 1 to 0.5
The web was formed while pulling and dispersing at about 3,500 m / min while spraying and quenching at m / sec, and further sucking on a cylindrical wire mesh suction drum having a diameter of 110 cm.

This web was conveyed and passed through a staggered pinpoint embossing roll in the same manner as in Example 1 to obtain a nonwoven fabric. When this nonwoven fabric is used for disposable diapers, a liquid permeable treatment agent (alkylphenol ethylene oxide adduct) is applied only to the center of the width (the center of the diaper with a width of 30 cm is 15 cm).
0.7% was granted.

This nonwoven fabric had a Y-shaped fiber cross section (corresponding to 2.3d) and each filament was crimped in a loop. The filament had a crimped helical diameter of 0.8 mm and a number of crimps of 12 cores / inch. Therefore, it had a plump soft and voluminous feel, had a smooth feel, was excellent as a diaper surface sheet, and was also excellent in preventing liquid bleeding.

 Table 2 shows the physical properties of the obtained nonwoven fabric.

[Effect of the Invention] The topsheet for disposable sanitary materials according to the present invention is formed by forming a continuous filament of hydrophobic synthetic fibers on a web such that the arrangement of the fibers is superior in the vertical direction as compared to the horizontal direction. In addition, since the liquid-permeable treatment agent is applied to the center of the web, the excreted liquid can be sufficiently permeated in the portion where the liquid-permeability treatment agent is applied, and the arrangement of the fibers is appropriately utilized. In addition, by utilizing the hydrophobicity of the fibers used, it is possible to prevent the excreted liquid from bleeding while maintaining the feeling of the sheet.

[Brief description of the drawings]

1 (A) to 1 (C) are plan views showing examples of the topsheet for disposable sanitary materials of the present invention, and FIG. 2 (A) is a disposable diaper using the topsheet of the present invention. FIG. 2 (B) is a cross-sectional view taken along line II (B) -II (B) of FIG. 2 (A), and FIG. 3 to FIG. FIGS. 3A and 3B show examples of various patterns of partial thermocompression bonding which are preferably applied to a sheet. FIG. 3 shows a staggered arrangement, FIG. 4 shows a vertical line emboss, FIG. 5 shows a horizontal line emboss, and FIGS. FIG. 8 is a view showing various embodiments of a method of forming a web. FIG. 6 (A) is a method of vertically sucking a filament to an endless belt, and FIG. 7 (A) is a method of inclining the filament to an endless belt. FIG. 8 (A) shows a method of sucking a filament into a cylindrical drum. FIGS. 6 (B), 7 (B) and 8 (B) are views showing a model of the spread state of the filaments in the web obtained by the corresponding method, and FIG. FIG. 10 (A) is a diagram for explaining a method of testing the water permeability of a sheet, with reference to FIG. 10 (A). (B) is a diagram for explaining a method for measuring the spread of the sheet, FIG. 11 is a perspective view for explaining a device for measuring the length of the sheet bleeding,
FIG. 12 is a view showing an example of a printer output of the measurement result of the fiber orientation by the microwave, and FIG. 13 is a diagram showing three examples (FIG.
FIG. 13 (A), FIG. 13 (B), FIG. 13 (C)). DESCRIPTION OF SYMBOLS 1 ... Disposable diaper, 2 ... Top sheet, 3 ... Absorbent, 4 ... Back sheet, 5a, 5b, 5c, 16 ... Part provided with liquid-permeable treatment agent, 6 ... Staggered arrangement Embossing, 8 Vertical embossing, 9 Embossing horizontal wire, 11 Spinning port, 12 High-speed airflow traction device, 13 Endless belt net, 14 Suction device, 15 Wire mesh Suction drum, 16: Liquid bleeding part, 17: Untreated part of liquid permeable treatment agent, 18, 18a ... Liquid bleeding part.

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁷ Identification code FI D04H 3/00 3/16

Claims (4)

(57) [Claims] 1. A surface sheet in a disposable sanitary material comprising a liquid-permeable top sheet, a liquid-impermeable back sheet, and an absorber interposed between the two sheets, wherein the continuous sheet of hydrophobic synthetic fibers comprises The fiber arrangement in the web is such that the length / width ratio of the microwave transmission intensity is 1.1, the liquid permeable treatment agent is applied to the center of the web, and the outside of both edges is not applied. A topsheet for disposable sanitary materials characterized by being a nonwoven fabric part. 2. The web has a tensile strength to transverse strength ratio of 3.6 or more as measured by JIS-L-1085.
The surface sheet for disposable sanitary materials according to the above. 3. The topsheet for a disposable sanitary material according to claim 1, wherein said web contains continuous filaments crimped into a loop. 4. The topsheet for disposable sanitary materials according to claim 1, wherein said web comprises continuous filaments of non-circular cross section.