Nonwoven fabric for absorbent articles and method for producing the same

Abstract

To provide a nonwoven fabric for absorbent articles that is suitable for use as a topsheet of an absorbent article, and exhibits excellent liquid excreta absorption performance, prevents the absorbed liquid excreta from returning to the skin side, and can maintain a dry feel.SOLUTION: The nonwoven fabric for absorbent articles is formed by hydroentangling a web containing 30-90 mass% of lyocell having a sedimentation time of 6-40 seconds as measured by the sedimentation method according to JIS L 1907 7.1.3, and 10-70 mass% of lyocell having a sedimentation time of 10 minutes or longer as measured by the sedimentation method according to JIS L 1907 7.1.3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a nonwoven fabric for absorbent articles, such as incontinence pads and panty liners, and a method for producing the same. Regarding. [Background technology]

[0002] Generally, absorbent articles have, for example, a liquid-permeable top sheet, a liquid-impermeable barrier sheet, and a liquid-absorbent core sandwiched between these two sheets. Since the top sheet comes into contact with the skin when the absorbent article is in use, in order to enhance comfort during use, it is required to have excellent absorbency for liquid excrement, and to prevent the absorbed liquid excrement from returning to the skin, thereby maintaining a dry feeling.

[0003] Conventional nonwoven fabrics used as top sheets of absorbent articles include those made of one type of cellulosic fiber such as cotton or rayon, as disclosed in Patent Document 1. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-028222 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the nonwoven fabrics made of a single type of fiber such as cotton or rayon have good liquid absorption properties, but they tend to resorb liquid and are unable to maintain a dry feeling, so they are not sufficiently comfortable to use.

[0006] The present invention has been made in view of the above-mentioned problems of the prior art. An object of the present invention is to provide a nonwoven fabric for absorbent articles that has excellent absorbency for liquid excrement, prevents absorbed liquid excrement from returning to the skin, and maintains a dry feeling, and is suitable for use as a top sheet of an absorbent article. Means for solving the problem and effects of the invention

[0007] The nonwoven fabric for absorbent articles according to the first aspect of the present invention can be formed by hydroentangling a web containing 30% by mass or more of lyocell having a sedimentation time of 6 to 40 seconds according to the JIS L 1907 7.1.3 sedimentation method.

[0008] Furthermore, the nonwoven fabric for absorbent articles according to the second aspect of the present invention can be formed by hydroentangling a web containing 30 to 90 mass% of lyocell having a settling time of 6 to 40 seconds as determined by the JIS L 1907 7.1.3 settling method and 10 to 70 mass% of lyocell having a settling time of 10 minutes or longer as determined by the JIS L 1907 7.1.3 settling method.

[0009] The nonwoven fabric for absorbent articles according to the third aspect of the present invention can be configured to have a large number of through-holes that penetrate through the fabric in the thickness direction.

[0010] Furthermore, the nonwoven fabric for absorbent articles according to the fourth aspect of the present invention can be configured so that the surface roughness of the nonwoven fabric for absorbent articles has a mean deviation SMD of 8 μm or more as measured with a KES surface tester.

[0011] Furthermore, a method for producing a nonwoven fabric for absorbent articles according to a fifth aspect of the present invention includes using lyocell having a sedimentation time of 6 to 40 seconds according to the JIS L 1907 7.1.3 sedimentation method as a first fiber, and 7.1.3 The method can include a web-forming step of using fibers having a sedimentation time of 10 minutes or more by a sedimentation method as second fibers, mixing the first fibers and the second fibers to form raw fibers containing 30 to 90% by mass of the first fibers and 10 to 70% by mass of the second fibers, and carding the raw fibers in a carding machine to form a web; a hydroentanglement step of supporting the web with a mesh-like support placed on the back side of the web and running the web together with the support, while spraying high-pressure water toward the web from a number of nozzles placed on the front side of the web, thereby hydroentangling the first fibers and the second fibers and obtaining a wet nonwoven fabric having a number of through-holes; and a drying step of heating and drying the wet nonwoven fabric obtained in the hydroentanglement step.

[0012] As described above, the present invention can provide a relatively inexpensive nonwoven fabric for absorbent articles that has excellent absorbency for liquid excrement, does not easily allow absorbed liquid excrement to return to the skin, and maintains a dry feeling, and is suitable for use as a top sheet for absorbent articles. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a photograph showing a plan view of a nonwoven fabric for absorbent articles according to one embodiment of the present invention (Example 2). DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, preferred embodiments of the present invention will be described based on preferred examples, but the present invention is not limited to these. (Nonwoven fabric for absorbent articles)

[0015] A nonwoven fabric for absorbent articles according to one embodiment of the present invention is used as a top sheet (surface material) that comes into contact with the skin of a user when using an absorbent article. The nonwoven fabric is a spunlace nonwoven fabric containing a large number of staple fibers of a first fiber and a large number of staple fibers of a second fiber. This nonwoven fabric for absorbent articles has a large number of through-holes that penetrate through the fabric in its thickness direction, and its surface is formed so that the mean deviation of surface roughness (SMD) measured with a KES surface tester is 8 μm or more. The content of the first fiber in this nonwoven fabric for absorbent articles is 30 to 90 mass% of the total mass of the nonwoven fabric, and the content of the second fiber is 10 to 70 mass% of the total mass of the nonwoven fabric.

[0016] The first fiber is lyocell having a sedimentation time (hereinafter simply referred to as "settling time") of 6 to 40 seconds according to the JIS L 1907 7.1.3 sedimentation method. This lyocell is a type of regenerated cellulose fiber, obtained by spinning a solution of cellulose dissolved in a solvent without going through a process called derivatization. Lyocell has attracted attention as a fiber with excellent environmental performance due to the use of plant-derived raw materials and the high recovery rate of the solvent that dissolves cellulose. By using lyocell with a sedimentation time of 6 to 40 seconds, absorbed liquid excrement is less likely to return to the skin compared to rayon or cotton, allowing for a dry feeling to be maintained.

[0017] The second fiber is a lyocell fiber similar to the first fiber, whose surface has been treated with a water-repellent material, and has a settling time of 10 minutes or more. By blending the second fiber, it becomes even more difficult for liquid excrement to return to the skin compared to when only the first fiber is used, making it possible to maintain a dry feeling. (Method for manufacturing nonwoven fabric for absorbent articles)

[0018] The method for producing a nonwoven fabric for absorbent articles includes a web-forming step of mixing a large number of staple fibers of the first fibers and a large number of staple fibers of the second fibers to form raw fibers containing 30 to 90% by mass of the first fibers and 10 to 70% by mass of the second fibers, and carding the raw fibers in a carding machine to form a web; a hydroentanglement step of supporting the web with a mesh-like support placed on the back side of the web and running the web together with the support, while spraying high-pressure water toward the web from a large number of nozzles placed on the front side of the web, thereby hydroentangling the first fibers and the second fibers and obtaining a wet nonwoven fabric having a large number of through-holes; and a drying step of heating and drying the wet nonwoven fabric obtained in the hydroentanglement step.

[0019] Nonwoven fabrics for absorbent articles have numerous through-holes formed by spraying high-pressure water onto the web, which increases the surface irregularities and roughness of the surface. As the irregularities of nonwoven fabrics for absorbent articles increase, the contact area between the skin and the nonwoven fabric tends to decrease, resulting in a dry feeling. By achieving a mean deviation (SMD) of the surface roughness measured by the KES surface tester of 8 μm or more, nonwoven fabrics for absorbent articles can have a linen-like texture (a texture like hemp) and a dry feel. [Example]

[0020] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples in any way.

[0021] In order to understand the influence of the blending ratio of the first fiber and the second fiber on the liquid absorption time and liquid return amount of the nonwoven fabric for absorbent articles, and the influence of the number of meshes of the support plate that supports the web during hydroentanglement on the surface roughness of the nonwoven fabric for absorbent articles, nonwoven fabrics for absorbent articles of Examples 1 to 6 and Comparative Examples 1 to 3 were prepared by the above-mentioned manufacturing method.

[0022] The settling time of each fiber was measured according to JIS L 1907 7.1.3 (sedimentation method). Five grams of fiber was collected and loosened by hand to prepare a sample. Two liters of water were placed in a plastic container with a diameter of 13 cm and a depth of 18 cm. The sample was dropped from a height of 1 cm above the water surface, and the time from when the sample came into contact with the water surface until the entire sample was submerged in water was measured, which was taken as the settling time. Example 1

[0023] The nonwoven fabric for absorbent articles according to Example 1 was produced by the following method: Lenzing Lyocell (fineness 1.7 dtex, fiber length 38 mm, sedimentation time 8.2 seconds) was used as the first fiber, Lenzing Lyocell (fineness 1.7 dtex, fiber length 38 mm, sedimentation time 10 minutes or more) to which a water repellent agent had been added was used as the second fiber, and the first fiber and the second fiber were loosened and mixed to form raw fiber containing 30% by mass of the first fiber and 70% by mass of the second fiber, and the raw fiber was carded to align the fiber direction and achieve a target basis weight of 30 g / m 2 A single-layer web was formed by combining the above materials. This web was placed on a support made of stainless steel wire mesh (mesh size: 14 mesh) and transported. While the web was being conveyed, high-pressure water was sprayed onto the web at a pressure of 6.0 MPa from nozzles positioned at predetermined positions on the opposite side of the support, thereby hydroentangling the first fibers and the second fibers in the web and forming through-holes. This nonwoven fabric was then dried by heating with hot air at 150°C for 5 minutes to obtain a nonwoven fabric for absorbent articles. The through-holes formed in this nonwoven fabric for absorbent articles had a diameter of approximately 1.3 mm in the MD direction (the web conveying direction) and approximately 0.8 mm in the CD direction (the direction perpendicular to the web conveying direction).

[0024] The high-pressure water was sprayed from two nozzles arranged 300 mm apart in the MD, and each nozzle had a number of nozzles with a diameter of 0.1 mm arranged at a pitch of 0.6 mm in the CD. The support was a plain-woven wire mesh, with the outer diameter of the vertical and horizontal wires 0.5 mm and the pitch of the vertical and horizontal wires 1.81 mm. Example 2

[0025] Fig. 1 shows a photograph of a plan view of the nonwoven fabric of Example 2. Example 2 differs from Example 1 in that, during production, the first fibers and the second fibers were mixed to form raw material fibers containing 50% by mass of the first fibers and 50% by mass of the second fibers. Example 3

[0026] Example 3 differs from Example 1 in that during production, the first fibers and the second fibers were mixed to form raw fibers containing 70% by mass of the first fibers and 30% by mass of the second fibers. Example 4

[0027] Example 4 differs from Example 2 in that instead of the support (mesh size: 14 mesh) used in the production of Examples 1 to 3, a support was used in which the mesh size of the wire mesh was 80 mesh, the pitch of the wire in the wire mesh was 0.32 mm in both the vertical and horizontal directions, and the outer diameter of the wire constituting the wire mesh was 0.14 mm, and the through holes formed in the nonwoven fabric had a diameter of approximately 0.6 mm in the MD direction and approximately 0.4 mm in the CD direction. Example 5

[0028] Example 5 differs from Example 4 in that the web was formed from raw material fibers containing 90% by mass of the first fibers and 10% by mass of the second fibers during production. Example 6

[0029] Example 6 differs from Example 4 in that the web was formed from raw material fibers containing 100% by mass of the first fibers during production. (Comparative Example 1)

[0030] Comparative Example 1 differs from Example 1 in that during production, the first fibers and the second fibers were mixed to form raw fibers containing 20% ​​by mass of the first fibers and 80% by mass of the second fibers. (Comparative Example 2)

[0031] Comparative Example 2 differs from Example 4 in that the web was formed from raw fiber containing 100% by mass of rayon having a fineness of 1.7 dtex and a sedimentation time of 4.4 seconds according to the JIS L 1907 7.1.3 sedimentation method. (Comparative Example 3)

[0032] Comparative Example 3 differs from Example 4 in that rayon having a fineness of 1.7 dtex and a settling time of 4.4 seconds was used as the first fiber instead of the lyocell used as the first fiber in Example 4.

[0033] For the prepared Examples 1 to 6 and Comparative Examples 1 to 3, the basis weight, thickness, density, average deviation of surface roughness, liquid absorption time, and amount of liquid return were determined by the following methods. (Metsuke)

[0034] The basis weight was measured based on JIS L 1913:1998 6.2. Specifically, three 200mm x 200mm test pieces were taken from the nonwoven fabric to be evaluated. The mass of each test piece (three pieces) under standard conditions was measured and divided by the area to determine the basis weight (g / m 2 ) and calculated the average value. (Thickness)

[0035] The thickness was measured based on JIS L1913:1998 6.1.2 Method A. Specifically, five 50mm x 50mm test pieces were taken from the nonwoven fabric to be evaluated. Using a thickness measuring device (Peacock thickness meter manufactured by Daiei Scientific Instruments Co., Ltd., terminal: φ44mm), a pressure of 0.34kPa was applied to the test pieces under standard conditions to measure the thickness (mm). Measurements were taken for each test piece (five pieces), and the average value was calculated. (Liquid absorption time)

[0036] The absorption time was calculated as follows. First, three 100 mm x 100 mm test pieces were collected from the nonwoven fabric to be evaluated. A 0.9% by mass sodium chloride aqueous solution was prepared as artificial urine. A circular qualitative filter paper "No. 1 φ110 mm" manufactured by Advantec Toyo Co., Ltd. was prepared. Five sheets of the filter paper were stacked on a polyethylene film to form an absorbent. The test piece was placed on top of the filter paper. 1.0 g of the artificial urine was dispensed into the center of the test piece from a height of 1 cm. The dispense was performed as quickly as possible without causing side leakage from the top of the test piece. The time from the start of the dispense until the artificial urine was no longer visible on the test piece was measured, and this time was defined as the first absorption time (seconds). Measurements were performed on each test piece (three pieces), and the average value was calculated. (amount of liquid returning)

[0037] The amount of liquid return was measured as follows. First, circular qualitative filter paper "No. 1 φ110 mm" manufactured by Advantec Toyo Co., Ltd. was prepared. Three filter papers were removed and the pre-test filter paper mass (W0) was measured. To measure the liquid absorption time, one minute after the artificial urine was no longer visible on the test piece, the three-ply filter paper was placed on the center of the test piece (the area where the artificial urine was administered), and a stainless steel weight (100 mm × 100 mm, 500 g) was placed on top of the filter paper. Three minutes after the weight was placed, the weight was removed and the post-test filter paper mass (W1) was measured. The first-test liquid return amount (mg) was calculated using the post-test filter paper mass (W1) and the pre-test filter paper mass (W0) according to the formula (first-test liquid return amount = W1 - W0). Measurements were performed on each test piece (three sheets), and the average value was calculated. (Repeated test of absorption time and amount of liquid return)

[0038] A repeat test for absorption time and rewet volume was conducted as follows. However, the step of stacking five sheets of the above-mentioned filter paper on a polyethylene film to calculate the absorption time was only performed the first time, and from then on, the five-ply filter paper prepared in the first operation was used. On the other hand, new filter paper was prepared and used for the three-ply filter paper used to measure the rewet volume from the second time onwards. In this test, the second artificial urine was administered 30 minutes after the administration of the artificial urine for the absorption time, and the second absorption time and second rewet volume were measured in the same way as the calculation of the first absorption time and first rewet volume. Similarly, the third absorption time, third rewet volume, and fourth absorption time and fourth rewet volume were measured. (Surface roughness mean deviation SMD measured by KES surface tester)

[0039] Measurements were performed using a KES surface tester "KES-FB4-A" manufactured by Kato Tech Co., Ltd. First, three 200mm x 200mm test pieces were taken from the nonwoven fabric to be evaluated. The test pieces were placed on the sample stage, and a surface roughness measurement probe (material: φ0.5mm piano wire, contact length: 5mm) with a load of 10gf was used to scan the surface of the test piece to measure the average deviation of the surface irregularities. Measurements were performed at three locations on each measurement sample, for a total of nine locations on three samples. This measurement was performed in both the MD and CD directions of the nonwoven fabric, and the average of the values ​​at a total of 18 locations was taken as the mean deviation of surface roughness SMD (μm).

[0040] For the prepared Examples 1 to 6 and Comparative Examples 1 to 3, the basis weight, thickness, density, average deviation of surface roughness, liquid absorption time, and amount of liquid return were determined. The results are shown in Table 1. [Table 1]

[0041] Table 1 shows that increasing the mesh size of the support reduces the mean deviation of surface roughness SMD, and that the mesh size of the support does not significantly affect the basis weight, thickness, and density.

[0042] It can also be seen that the liquid absorption time was the longest the first time the test was conducted and tended to become shorter with each test, while the amount of liquid returning tended to increase with each test.

[0043] Furthermore, it has been found that when the settling time of the first fibers contained in the nonwoven fabric for absorbent articles is short, the liquid absorption time is short, but the amount of liquid return tends to be large. Furthermore, when the nonwoven fabric for absorbent articles is made only of first fibers with short settling times, the shorter the settling time of the first fibers, the greater the amount of liquid return.

[0044] Furthermore, when the nonwoven fabric for absorbent articles contains the first fiber and the second fiber, it is found that if the blending ratio of the first fiber is 20 mass %, the liquid absorption time becomes extremely long.

[0045] Therefore, if the content (mixing ratio) of the first fiber is 30% by mass to 90% by mass, the balance between the liquid absorption time and the amount of liquid returning is good, the nonwoven fabric for absorbent articles has good absorbency, excrement does not easily return to the skin, and a dry feeling can be maintained.

[0046] According to the present invention, the nonwoven fabric for absorbent articles may be formed by hydroentangling a web containing 100% by mass of lyocell having a settling time of 6 to 40 seconds, or by hydroentangling a web formed from a raw fiber mixture of lyocell having a settling time of 6 to 40 seconds and synthetic resin fibers such as rayon, polyester, polypropylene, polyester / polyethylene sheath / core fibers, or polypropylene / polyethylene sheath / core fibers having a settling time of 10 minutes or longer, to a lyocell content of 30% by mass or greater. However, a combination of lyocell having a settling time of 6 to 40 seconds and lyocell having a settling time of 10 minutes or longer is preferred for its environmental friendliness. Furthermore, the nonwoven fabric for absorbent articles thus formed may have a large number of through-holes penetrating through its thickness, and the surface roughness of the nonwoven fabric for absorbent articles may be 8 μm or greater in terms of the mean deviation (SMD) of the surface roughness measured with a KES surface tester.

Claims

1. A nonwoven fabric for absorbent articles formed by hydroentangling a web containing 30% by mass or more of lyocell having a sedimentation time of 6 to 40 seconds according to the JIS L 1907 7.1.3 sedimentation method.

2. A nonwoven fabric for absorbent articles is formed by hydroentangling a web containing 30 to 90% by mass of lyocell having a sedimentation time of 6 to 40 seconds as measured by the JIS L 1907 7.1.3 sedimentation method and 10 to 70% by mass of lyocell having a sedimentation time of 10 minutes or more as measured by the JIS L 1907 7.1.3 sedimentation method.

3. 3. The nonwoven fabric for absorbent articles according to claim 1 or 2, having a large number of through-holes penetrating in the thickness direction.

4. 4. The nonwoven fabric for absorbent articles according to claim 3, wherein the surface roughness of the nonwoven fabric for absorbent articles has a mean deviation SMD of 8 μm or more as measured by a KES surface tester.

5. Lyocell having a sedimentation time of 6 to 40 seconds according to JIS L 1907 7.1.3 sedimentation method is used as the first fiber, and 7.1.3 A web forming process in which fibers having a sedimentation time of 10 minutes or more by a sedimentation method are used as second fibers, the first fibers and the second fibers are mixed to form raw fibers containing 30 to 90% by mass of the first fibers and 10 to 70% by mass of the second fibers, and the raw fibers are carded using a carding machine to form a web; a hydroentanglement step in which the web is supported by a mesh-like support disposed on the back side of the web and travels together with the support, while high-pressure water is sprayed onto the web from a number of spray nozzles disposed on the front side of the web, thereby hydroentangling the first fibers and the second fibers and obtaining a wet nonwoven fabric having a number of through-holes; a drying step of heating and drying the wet nonwoven fabric obtained in the hydroentanglement step; A method for producing a nonwoven for an absorbent article comprising the steps of:

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