JP2021195626A - Stretchable sheet - Google Patents

Abstract

To provide a stretchable sheet having improved extensibility with good appearance and high sheet strength.SOLUTION: A stretchable sheet 10 includes an elastomer 13, and a long fiber nonwoven fabric 11 fused to the elastomer 13, with a low-elongation region 21 and a high-elongation region 22 arranged alternately along a stretch direction X. In the low-elongation region 21, the orientation angle of constituent fibers of the long fiber nonwoven fabric 11 relative to an orthogonal direction Y vertical to the stretch direction X is 70° or more, and the orientation strength of the constituent fibers is 1.2 or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to an elastic sheet.

In absorbent articles such as diapers, elastic sheets are used as exterior materials in order to improve adhesion to the skin. Various techniques have been proposed for this telescopic sheet.
For example, Patent Document 1 describes that a large number of elastic filaments are arranged so as to extend in one direction without intersecting each other, from the viewpoint of preventing width shrinkage when the stretchable sheet is stretched.
Further, Patent Document 2 describes a processing apparatus for performing tooth groove stretching processing using a pair of rolls having tooth grooves that mesh with each other. By the tooth groove stretching process performed by such a processing device, it is possible to maintain the elasticity of the sheet according to the stretching ratio depending on the pitch between the teeth, the depth of meshing, and the like.

Japanese Unexamined Patent Publication No. 2008-179128 Japanese Unexamined Patent Publication No. 2007-177384

When the tooth groove stretching process is performed using a pair of rolls, if the stretching ratio is increased too much, holes may be formed in the stretchable sheet, which may lead to deterioration of appearance and sheet strength. Although it has been practiced to use a non-woven fabric having higher extensibility in order to suppress perforation, there is a limit to increasing the extensibility of the non-woven fabric. Further, the stretchable sheet described in Patent Document 1 does not have a fiber structure capable of suppressing the above-mentioned perforation of the nonwoven fabric sandwiching the elastic filament.

In view of the above problems, the present invention relates to an elastic sheet capable of achieving a good appearance, high sheet strength, and improving extensibility.

The present invention is a stretchable sheet having an elastic body and a long-fiber nonwoven fabric fused to the elastic body, in which low-stretch regions and high-stretch regions are alternately arranged along the expansion and contraction direction. A stretchable sheet in which the orientation angle of the constituent fibers of the long-fiber nonwoven fabric in the region is 70 ° or more with respect to the direction perpendicular to the stretching direction, and the orientation strength of the constituent fibers is 1.2 or more.

The elastic sheet of the present invention realizes a good appearance and a high sheet strength, and makes it possible to improve the extensibility.

It is a partially broken perspective view which shows one Embodiment of the telescopic sheet of this invention. It is a top view which shows one Embodiment of the long fiber nonwoven fabric used in this invention.

A preferred embodiment of the elastic sheet of the present invention and an absorbent article having the same will be described with reference to the drawings.

(Expandable sheet)
As shown in FIG. 1, the elastic sheet 10 has two long fiber nonwoven fabrics 11 and 11 and a plurality of elastic bodies 13 sandwiched between the two long fiber nonwoven fabrics 11 and 11. The long fiber nonwoven fabrics 11 and 11 are joined to each elastic body 13 by fusion, and integrally form the elastic sheet 10. The stretchable sheet 10 has elasticity in at least one direction. That is, it has an expansion / contraction direction X and an orthogonal direction Y perpendicular to the expansion / contraction direction X. The terms of the expansion / contraction direction X and the orthogonal direction Y are also used for the constituent members of the expansion / contraction sheet 10.

In the stretchable sheet 10, as shown in FIG. 2, the low stretchable region 21 and the high stretchable region 22 are alternately arranged along the stretchable direction X of the stretchable sheet 10. Since the highly stretchable region 22 expands and contracts mainly in the stretch direction X, the stretchable sheet 10 has high stretchability in the stretch direction X as a whole.
The high elongation region 22 means that when the stretchable sheet 10 is stretched 50% in the stretch direction X (stretched 1.5 times the natural length before stretch), the length of the stretch direction X is larger than that before stretching. An area that increases by 10% or more. On the contrary, the low elongation region 21 refers to a region in which the rate of increase in the length of the expansion / contraction direction X when the expansion / contraction sheet 10 is expanded by 50% in the expansion / contraction direction X is less than 10% as compared with that before expansion. For example, when the portion having a length of 200 μm in the expansion / contraction direction X in the natural length state of the elastic sheet 10 becomes 220 μm or more at the time of 50% elongation, that portion corresponds to the high elongation region 22 and conversely 220 μm. When it is less than, the portion corresponds to the low elongation region 21. In this way, the low elongation region 21 and the high elongation region 22 can be distinguished.

(Long fiber non-woven fabric)
In the present invention, the long fiber nonwoven fabric refers to a nonwoven fabric provided with a fiber assembly layer in which long fibers are intermittently fixed by fusion points. The long fiber means a fiber having a fiber length of 100 mm or more. In particular, a so-called continuous long fiber having a fiber length of 150 mm or more is preferable in that a long fiber non-woven fabric having high breaking strength can be obtained. Examples of such a long fiber nonwoven fabric include a spunbonded nonwoven fabric, a nonwoven fabric composed of a plurality of layers of a spunbond layer and a melt blown layer, a heat roll nonwoven fabric by the card method, and the like. Examples of the non-woven fabric composed of multiple layers include spunbond-spunbond laminated non-woven fabric, spunbond-spunbond-spunbond laminated non-woven fabric, spunbond-melt blown-spunbond laminated non-woven fabric, spunbond-spunbond-meltblown-spunbond laminated fabric. Non-woven fabric and the like can be mentioned. Further, in the case of a single layer, a long fiber nonwoven fabric having fibers (standing fibers) in which one end of the long fibers is not fixed to the fiber assembly layer and stands up on one surface side can be mentioned.
The upper limit of the fiber length in the long fiber is not particularly limited. Further, the long fiber non-woven fabric is not limited to the one composed of only long fibers, and may contain fibers other than long fibers as a part.

(Orientation angle)
In the stretchable sheet 10 of the present invention, in the low stretch region 21, the orientation angle of the constituent fibers of the long fiber nonwoven fabric 11 is 70 ° or more with respect to the orthogonal direction Y (the direction perpendicular to the stretch direction X). The closer the orientation angle is to 90 °, the more the constituent fibers are oriented in the expansion / contraction direction X. When the orientation angle is at least a certain level, it is difficult to make a hole even if the stretchable sheet 10 is stretched at a high stretching ratio, and even if a hole is made, the hole area can be kept small and the sheet strength can be increased.

(Orientation strength)
In the elastic sheet 10 of the present invention, the orientation strength of the constituent fibers of the long-fiber nonwoven fabric 11 is 1.2 or more in the low elongation region 21. The larger the value of the orientation strength, the more the orientation of the constituent fibers is aligned. That is, when the orientation angle is at least a certain level and the orientation strength is at least a certain level, many constituent fibers are aligned in the expansion / contraction direction X, and the expansion / contraction sheet 10 is prevented from being perforated and the sheet strength is reduced. Further contributes to the improvement of.

It is considered that the action of these orientation angles and orientation strengths is due to the fact that the shearing force acting on the constituent fibers can be suppressed to a small value when the tension in the expansion / contraction direction X is applied to the long fiber nonwoven fabric 11.

(Measuring method of orientation angle and orientation strength)
The orientation angle and orientation strength can be found at http: // www. enomae. com / FiberOri / index. It can be measured using the fiber orientation analysis program "Fiber Orientation Analysis 8.13 Single" that can be obtained from http. Specifically, it is as follows.
When the stretchable sheet 10 containing the long-fiber nonwoven fabric 11 to be measured is used in a product such as an absorbent article, the product is sprayed with a cold spray to solidify the adhesive, and the stretchable sheet 10 is carefully peeled off from the product. Hereinafter, in the other measurement method, the elastic sheet 10 is taken out in the same manner.
Using a scanning electron microscope (SEM, trade name: JCM-5100, manufactured by JEOL Ltd.), the surface of the low elongation region 21 of the long fiber non-woven fabric 11 was subjected to an acceleration voltage of 15 kV and an observation magnification of 100 times. Observe. The observation result is imaged so that the expansion / contraction direction X is the vertical direction of the image and the orthogonal direction Y is the horizontal direction of the image, and an image of the surface of the nonwoven fabric is acquired.
The image is read using the above fiber orientation analysis program, the binarization process by the moving average method and the fast Fourier transform are performed in order, and then the orientation angle and the orientation intensity are calculated. Since the calculated orientation angle is expressed as 0 ° or more and less than 180 °, it is converted into the notation of 0 ° or more and 90 ° or less (for example, if the calculation result is 135 °, 180 ° -135 ° = 45). Converted to °).
The above measurement is performed at five arbitrary regions, and the calculated average value of the orientation strength is taken as the orientation strength of the constituent fibers of the long fiber nonwoven fabric 11 in the low elongation region 21. Regarding the orientation angle, the measurement results when the calculated orientation strength was 1.20 or less were excluded, and the average value of the remaining measurement results was taken as the orientation angle of the constituent fibers of the long-fiber nonwoven fabric 11 in the low elongation region 21. And.

The orientation angle of the constituent fibers of the long fiber nonwoven fabric 11 obtained as described above is preferably 70 ° or more with respect to the orthogonal direction Y, preferably 75 °, from the viewpoint of improving the appearance of the elastic sheet 10 and increasing the sheet strength. The above is more preferable, 80 ° or more is further preferable, and 90 ° is most preferable.
The orientation strength of the constituent fibers of the long fiber nonwoven fabric 11 is preferably 1.2 or more, more preferably 1.3 or more, and further preferably 1.4 or more, from the viewpoint of improving the appearance of the elastic sheet 10 and increasing the sheet strength. preferable. Further, the orientation strength of the constituent fibers of the long fiber nonwoven fabric 11 is preferably as large as possible, but is practically 2.0 or less.
When the elastic sheet 10 has a plurality of long-fiber nonwoven fabrics 11, it is preferable that at least one long-fiber nonwoven fabric 11 has the above-mentioned requirements for the orientation angle and the orientation strength, and all the long-fiber nonwoven fabrics 11 have the requirements. It is more preferable to have it.

The constituent fibers of the long fiber nonwoven fabric 11 are not only bonded to the elastic body 13 by fusion, but also the constituent fibers are bonded to each other by fusion. In the present specification, the place where the constituent fibers and the elastic body 13 are fused is referred to as a "fused portion", and the place where the constituent fibers are fused to each other is referred to as the above-mentioned "fusion point". Hereinafter, the fusion point will be described.

(Fusion point)
As shown in FIG. 2, the fusion points 23 formed by fusing the constituent fibers are scattered and arranged on the long fiber nonwoven fabric 11. The fusion point 23 is preferably embossed. That is, it is preferable that the long fiber nonwoven fabric 11 has a fusion point 23 between the constituent fibers by embossing. Since the fusion point 23 is fixed by embossing, the sheet strength can be increased.

The strength of fixing the constituent fibers in the embossed portion can be appropriately adjusted by changing the temperature and pressure during embossing. When the temperature during embossing is raised to a high temperature, the embossing becomes a strong fixation, and conversely, when the temperature is lowered, the embossing becomes a weak fixing. Further, when the pressure during embossing is increased, the embossing is firmly fixed, and when it is lowered, the embossing is weakly fixed.
The fixing strength of the embossed portion can be determined by the density of the fusion point 23 in the long fiber nonwoven fabric 11. The larger the density value of the fusion point 23, the stronger the fixation of the embossed portion. On the contrary, the smaller the density value of the fusion point 23, the weaker the fixation of the embossed portion.

(Density of fusion points by embossing)
When the density of the fusion point 23 by the embossing of the long fiber nonwoven fabric 11 is small, the fusion point 23 is easily loosened because the embossed portion is weakly fixed, and the extensibility of the fusion point 23 itself is maintained. As a result, the constituent fibers are less likely to break during the stretching process, and the appearance of the elastic sheet 10 is improved. From this viewpoint, the density of the bonding spots 23 by embossing, is preferably 1.05 g / cm ³ or less, more preferably 1.00 g / cm ³ or less, 0.95 g / cm ³ or less It is more preferable to have. Further, from the viewpoint of maintaining the sheet strength, the density of the fusion point 23 by embossing ^{is preferably 0.60 g / cm 3} or more, more preferably 0.70 g / cm ³ or more, and 0. It is more preferably 80 g / cm ^{3 or more.}
When the elastic sheet 10 has a plurality of long-fiber nonwoven fabrics 11, it is preferable that at least one long-fiber nonwoven fabric 11 is provided with the density requirement of the fusion point 23 in the above-mentioned specific range, and all the long-fiber nonwoven fabrics 11 are provided. It is more preferable to prepare in.

For good appearance and high sheet strength, the density of fusion points in the above specific range is preferably provided in at least one long fiber nonwoven fabric 11 in combination with the orientation angle and orientation strength in the above specific range. , It is more preferable to provide in all the long fiber non-woven fabrics 11.

(Measuring method of fusion point density)
The long fiber non-woven fabric 11 to be measured is cut into a size of 5 cm × 20 cm and used as a measurement piece. The mass of the measuring piece is measured with a balance, and the measured value is ^{divided by the area of the measuring piece (100 cm 2} ) to calculate the basis weight of the measuring piece.
Next, the measurement piece is cut so that the center of the fusion point in the plan view is cut, and the cut surface is observed using the above-mentioned SEM. The observation results are imaged under the same observation conditions as described above except that the observation magnification is set to 500 times. The length in the thickness direction is measured at any 10 fusion points, and the average value is calculated.
The density of the fusion point is calculated by dividing the basis weight of the measurement piece by the average value of the lengths in the thickness direction.
The above measurement is performed three times, and the average value of the calculated values is taken as the density of the fusion point.

(Distance between fusion points in the orthogonal direction)
When the fusion points 23 are arranged in the orthogonal direction Y, the distance L (see FIG. 2) at which the fusion points 23 are separated from each other in the orthogonal direction Y is preferably 1.1 mm or more, more preferably 1.3 mm or more. , 1.5 mm or more is more preferable. By appropriately separating the fusion points 23 from each other in the orthogonal direction Y, the fixation between the constituent fibers can be appropriately weakened, and the elasticity of the elastic sheet 10 can be increased. Further, the number of fusion points 23 in the entire long fiber nonwoven fabric 11 is reduced, and the breakage of the constituent fibers that tends to occur in the vicinity of the fusion points 23 can be reduced.
Further, from the viewpoint of keeping the sheet strength of the elastic sheet 10 above a certain level, the distance L is preferably 5.0 mm or less, more preferably 4.0 mm or less, and further preferably 3.0 mm or less.
As shown in FIG. 2, the distance L is the length in the orthogonal direction Y from the end of the fusion point 23 to the end of the adjacent fusion point 23. The upper and lower limit values for the distance L apply to both the low elongation region 21 and the high elongation region 22.

(Elastic body)
The elastic body 13 used in the present invention is a member that has elasticity like the long-fiber nonwoven fabric 11 and expands and contracts integrally with the long-fiber nonwoven fabric 11.
As long as the effect of the present invention is exhibited, the shape of the elastic body is not limited to the filament shape shown in FIG. 1, and may be a web shape. However, from the viewpoint of improving the appearance of the elastic sheet 10 and increasing the sheet strength, a filament-like sheet is preferable. Hereinafter, the filament-shaped elastic body is also referred to as an elastic filament.

(Elastic filament)
In the present invention, as shown in FIG. 1, the elastic body 13 is preferably a plurality of elastic filaments extending along the expansion / contraction direction X. Further, it is more preferable that the plurality of elastic filaments are separated from each other without intersecting each other and arranged in parallel. By matching the extension direction of the elastic filament with the expansion / contraction direction X, the elasticity along the expansion / contraction direction X can be enhanced.

Further, it is preferable that the elastic filament is fused to the long fiber nonwoven fabric 11 over the entire length. That is, it is preferable that the fused portion between the long fiber nonwoven fabric 11 and the elastic filament extends in the expansion / contraction direction X. Since all the contact portions between the long fiber nonwoven fabric 11 and the elastic filament are joined by fusion, the long fiber nonwoven fabric can follow the expansion and contraction operation over the entire surface, and the appearance of the entire sheet is improved.

(Manufacturing method of elastic sheet)
The telescopic sheet 10 of the present invention can be manufactured by various methods usually used in this field. For example, the elastic sheet 10 can be manufactured by spinning the elastic body 13 in a molten state, fusing it to the long fiber nonwoven fabric 11 before solidification, and then partially stretching the elastic body 13 by a tooth groove stretching process.
In the case of manufacturing by the tooth groove stretching process, a region where the sheet is largely stretched by the tooth groove and a region where the degree of stretching is smaller than this region or the region where the sheet is hardly stretched appears. The region that is largely stretched by the tooth groove stretching process corresponds to the above-mentioned high stretch region 22 because it is a region that acquires high elasticity by stretching. On the other hand, the region where the degree of stretching is small or hardly stretched corresponds to the above-mentioned low elongation region 21 because the stretchability is not significantly different from that before the tooth groove stretching process.
That is, it can be said that the stretchable sheet 10 of the present invention defines the orientation angle and the orientation strength of the constituent fibers of the long-fiber nonwoven fabric 11 in a region where the influence of stretching due to the tooth groove stretching process is small.

(Use of elastic sheet)
The elastic sheet 10 of the present invention is suitably used as an outer packaging material for pants-type disposable diapers. In addition to this application, it can also be used for various applications such as medical disposable clothing, cleaning sheets, eye patches, masks, bandages, etc. by taking advantage of its good texture, fluff prevention, elasticity, breathability, etc. .. In particular, it is preferably used as a constituent material for absorbent articles such as sanitary napkins and disposable diapers. Examples of the constituent material include a liquid-permeable sheet (including a surface sheet, a sublayer, etc.) located on the skin side of the absorber, a sheet constituting the outer surface of a disposable diaper, a waist circumference, a waist portion, and legs. Examples thereof include a sheet for imparting elastic elasticity to the peripheral portion and the like. Further, it can be used as a sheet or the like for forming a wing of a napkin. Further, even if it is a portion other than that, it can be used for a portion or the like to which elasticity is desired to be imparted. The basis weight and thickness of the telescopic sheet 10 can be appropriately adjusted according to the specific use thereof. For example, when used as a constituent material of an absorbent article, ^{it is desirable that the basis weight is about 20 to 60 g / m 2} and the thickness is about 0.5 to 1.5 mm.

Although the present invention has been described above based on the preferred embodiment thereof, the present invention is not limited to the above embodiment. For example, the elastic sheet 10 of the embodiment shown in FIG. 1 has a structure in which a large number of elastic bodies 13 are sandwiched between two long fiber nonwoven fabrics 11 and 11, but instead of this, one length is used. The elastic body 13 may be fused to the surface of the fibrous nonwoven fabric 11 to form the elastic sheet 10.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

(Example 1)
Styrene-ethylene-propylene-styrene resin (weight average molecular weight 50,000, MFR 40 g / 10 minutes (230 ° C, 2.16 kg) under spinning conditions with a spinning head temperature of 270 ° C, a spinning nozzle diameter of 450 μm, and a spinning nozzle pitch of 1 mm. )) In a molten state, an elastomer (filament-like elastic body) was spun. Before the melted elastomer solidified, the elastic body was sandwiched between two long-fiber non-woven fabrics, and the elastic body was fused with the long-fiber non-woven fabric over the entire length. As the long-fiber non-woven fabric, a continuous fiber (fiber length of more than 100 mm) composed of a polypropylene resin component was used as a constituent fiber, which was previously embossed and provided with a fusion point. This long fiber nonwoven fabric had a basis weight of 18 g / m ² , and the density of the fusion points and the separation distance between the fusion points in the orthogonal direction were as shown in Table 1.
Next, a tooth groove stretching process was performed on the composite of the long fiber nonwoven fabric and the elastic body using a pair of tooth groove rolls in which the teeth and the tooth bottom were alternately formed in the circumferential direction (stretching ratio: 2). .87 times). In this way, the complex was partially stretched to alternately create low-elongation regions and high-elongation regions with respect to the expansion / contraction direction X, and an expansion / contraction sheet sample of Example 1 as shown in FIG. 1 was obtained.

(Example 2)
A stretchable sheet sample of Example 2 was obtained in the same manner as in Example 1 except that a long fiber nonwoven fabric having a density of fusion points as shown in Table 1 was used.

(Comparative Example 1)
In the same manner as in Example 1, Comparative Example 1 was used except that the long fiber non-woven fabric as shown in Table 1 was used in which the orientation of the fibers was different and the density of the fusion points and the separation distance between the fusion points in the orthogonal direction were as shown in Table 1. A stretchable sheet sample was obtained.

(Comparative Example 2)
A stretchable sheet sample of Comparative Example 2 was obtained in the same manner as in Comparative Example 1 except that the stretching ratio in the tooth groove stretching process was 2.30 times.

(Measurement of orientation angle and orientation strength)
For each elastic sheet sample, the orientation angle and orientation strength of the constituent fibers of the long-fiber nonwoven fabric in the low elongation region were measured according to the above-mentioned method.

(Measurement of hole area)
The stretchable sheet samples of Examples 1 and 2 and Comparative Example 1 were stretched by 150% in the stretch direction (stretched 2.5 times with respect to the natural length before stretching). In this state, the holes formed in the stretchable sheet sample were copied onto a transparent OHP sheet. The area was calculated for each hole using image analysis software (trade name: Image-Pro, manufactured by Hakuto Co., Ltd.).
For the top 10 holes with large areas, the calculated area values were averaged and used as the hole area of each elastic sheet sample.
Further, in Comparative Example 2, the hole area was measured in the same manner under the condition of 100% elongation (twice the natural length before elongation).
It is shown that the smaller the hole area is, the more the expansion sheet can be suppressed from being opened, and the appearance is excellent.

(Measurement of strength)
Each stretchable sheet sample was cut out so that the length in the orthogonal direction was 50 mm, and the maximum strength was measured using a tensile tester (trade name: AG-50NIS, manufactured by Shimadzu Corporation). The distance between the chucks was 100 mm, and the tensile speed was 300 mm / min.
The results are shown in Table 1.

As shown in Table 1, in each of the stretchable sheet samples of Examples 1 and 2, the hole area ^{could be suppressed to 2 mm 2} or less, and the appearance was better than that of the stretchable sheet sample of Comparative Example 1. Further, the stretchable sheet samples of Examples 1 and 2 had a strength of 2000 cN / 50 mm or more, which was higher than that of the stretchable sheet sample of Comparative Example 1. In particular, in the stretchable sheet sample of Example 2 in which the density of the fusion point by embossing was 1.05 g / cm ^{3 or less, the hole area was 1 mm 2} or less and the strength was 3000 cN / 50 mm or more, which were further excellent. ..
As described above, the stretchable sheet samples of Examples 1 and 2 have a good appearance even when stretched at a higher elongation rate than the conventional product (stretchable sheet sample of Comparative Example 2), and are torn during use of the absorbent article. It was found that it is possible to maintain the strength (about 1000 cN / 50 mm or more) at which the above is unlikely to occur.

10 Elastic sheet 11 Long fiber non-woven fabric 13 Elastic body 21 Low elongation region 22 High elongation region 23 Fusion point X Expansion direction Y Orthogonal direction L Distance between fusion points in the orthogonal direction

Claims (5)

An elastic sheet having an elastic body and a long-fiber non-woven fabric fused to the elastic body, in which low-elongation regions and high-elongation regions are alternately arranged along the expansion and contraction direction.
In the low elongation region, the stretchable sheet in which the orientation angle of the constituent fibers of the long-fiber nonwoven fabric is 70 ° or more with respect to the orthogonal direction perpendicular to the stretching direction, and the orientation strength of the constituent fibers is 1.2 or more. .. The elastic sheet according to claim 1, wherein the long-fiber nonwoven fabric has a fusion point between constituent fibers by embossing, and the density of the fusion point is 1.05 g / cm ^{3 or less.} The elastic sheet according to claim 1 or 2, wherein the long fiber nonwoven fabric has fusion points between constituent fibers by embossing, and the fusion points are separated from each other by 1.1 mm or more in the orthogonal direction. The one according to any one of claims 1 to 3, wherein the elastic body is a plurality of elastic filaments along the expansion and contraction direction, and the elastic filaments are fused to the long fiber nonwoven fabric over the entire length. The elastic sheet described. An absorbent article having the elastic sheet according to any one of claims 1 to 4.

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