JP2022158281A - Regenerated cellulosic fiber nonwoven fabric and manufacturing method thereof - Google Patents

Abstract

To provide a nonwoven fabric that is gentle to the skin and excellent in abrasion resistance and has a pleasant feel, an absorbent article including the nonwoven fabric as a surface material thereof, and a manufacturing method of the nonwoven fabric.SOLUTION: A regenerated cellulosic fiber nonwoven fabric has the amount of water extract of 1000 ppm or less, tensile strength per unit basis weight in CD direction of 0.20 (N/50 mm)/(g/m2) or more and 1.00 (N/50 mm)/(g/m2) or less, formation index in dry condition of 250 or more and 400 or less, and fiber diameter of constituting fiber is 5.0 μm or more and 20.0 μm or less. The generated cellulosic fiber nonwoven fabric, an absorbent article including the nonwoven fabric as a surface material thereof, and a manufacturing method of the nonwoven fabric are provided.SELECTED DRAWING: None

Description

The present invention relates to a regenerated cellulosic fiber nonwoven fabric, an absorbent article comprising the nonwoven fabric as a surface material, and a method for producing the nonwoven fabric.

In absorbent articles such as light incontinence liners, incontinence pads, sanitary napkins, postpartum pads, and disposable diapers, the body fluid excreted from the human body is absorbed by the surface material and transferred from the top sheet to the absorbent body. The surface material of absorbent articles not only has an absorption performance that quickly transfers discharged or excreted liquids such as menstrual blood and urine to the absorber, but also has a good surface feel that touches the wearer and the handler, and is effective against the skin. It is required to have surface characteristics such that it gives less irritation to the surface and does not cause fluffing or twisting due to abrasion.

The following Patent Documents 1 and 2 disclose a synthetic fiber nonwoven fabric treated with a hydrophilic agent. Although the nonwoven fabrics described in Patent Documents 1 and 2 have the advantage of being difficult to twist, they still have poor hygroscopicity, and when worn under high-temperature and high-humidity conditions, the nonwoven fabrics tend to get stuffy, causing discomfort when worn. In addition, since a processing agent is used and the surface is not sufficiently smooth, there is also the problem that it tends to be a little prone to rashes and the feel of the skin is not preferable.
Further, Patent Document 3 below discloses a nonwoven fabric composed of cellulosic fibers. The nonwoven fabric described in Patent Document 3 has excellent hygroscopicity, but has problems such as poor surface strength, easy twisting, fiber ends, and skin irritation.
Further, Patent Document 4 below discloses a nonwoven fabric composed of cellulose long fibers. Although the nonwoven fabric described in Patent Document 4 is excellent in hygroscopicity, it has not reached a sufficiently satisfactory level from the viewpoint of surface strength and irritation to the skin.
As described above, the conventional nonwoven fabrics have not been able to simultaneously meet high standards of being gentle to the skin, having excellent wear resistance, and being comfortable to the touch.

WO2011/016343 JP-A-11-347062 Japanese Patent No. 3200673 JP 2004-255176 A

In view of the above-described problems of the prior art, the problem to be solved by the present invention is to provide a nonwoven fabric that is gentle on the skin, has excellent abrasion resistance, and has a pleasant touch, an absorbent article containing the nonwoven fabric as a surface material, and An object of the present invention is to provide a method for producing the nonwoven fabric.

As a result of intensive studies and repeated experiments to solve the above problems, the present inventors have found that the regenerated cellulose fiber nonwoven fabric has the amount of water extract of the constituent fibers, the tensile strength per unit basis weight in the CD direction, and the texture in the dry state. The present inventors have unexpectedly found that the above problems can be solved by setting the combination index and the fiber diameter within specific ranges, and have completed the present invention.

That is, the present invention is as follows.
[1] The amount of water extract is 1000 ppm or less, and the tensile strength per unit basis weight in the CD direction is 0.20 (N/50 mm)/(g/m ² ) or more and 1.00 (N/50 mm)/(g /m ² ) or less, a formation index in a dry state of 250 or more and 400 or less, and a fiber diameter of the structural fiber of 5.0 μm or more and 20.0 μm or less. non-woven fabric.
[2] The nonwoven fabric according to [1] above, which has a basis weight of 5 g/m ² or more and 40 g/m ² or less and a thickness of 0.10 mm or more and 0.30 mm or less.
[3] The nonwoven fabric according to [1] or [2], wherein the cellulosic fibers are continuous filaments.
[4] The nonwoven fabric according to any one of [1] to [3], wherein the fiber diameter is 10.0 μm or more and 16.0 μm or less.
[5] The nonwoven fabric according to any one of [1] to [4], wherein the average deviation SMD of surface roughness in the MD direction in a dry state is 1.5 μm or more and 4.5 μm or less.
[6] The nonwoven fabric according to any one of [1] to [5], wherein the number of fallen fibers is 350/g or less.
[7] An absorbent article comprising the nonwoven fabric according to any one of [1] to [6] as a surface material.
[8] A sheet or web of regenerated cellulose fiber, using a lower layer net of 40 mesh or more and 80 mesh or less, a water flow pressure of 5 MPa or more and 7 MPa or less, and a nozzle number of 1.5 holes/cm ² or more and 2.5 holes/ The method for producing a nonwoven fabric according to any one of the above [1] to [6], which comprises a step of drying after applying hydroentanglement of not more than cm ² .

The regenerated cellulose-based fiber nonwoven fabric according to the present invention is a nonwoven fabric that is gentle on the skin, has excellent wear resistance, and has a good texture. It can be suitably used as a surface material for absorbent articles.

Hereinafter, embodiments of the present invention will be described in detail.
The regenerated cellulose fiber nonwoven fabric of the present embodiment has a water extract amount of 1000 ppm or less, and a tensile strength per unit basis weight in the CD direction of 0.20 (N/50 mm)/(g/m ² ) or more and 1.00. (N/50 mm)/(g/m ² ) or less, the formation index in the dry state is 250 or more and 400 or less, and the fiber diameter of the structural fibers is 5.0 μm or more and 20.0 μm or less. Characterized by
In this specification, the dry state means that a cellulose nonwoven fabric with an area of 0.05 m ² or more is dried at 105°C until it reaches a constant mass, and then left in a constant temperature room at 20°C and 65% RH for 16 hours or more. means what was done.

The regenerated cellulose fibers constituting the nonwoven fabric are not particularly limited, and may be regenerated cellulose fibers such as cuprammonium rayon, viscose rayon, Tencel (lyocell), and polynosic. The regenerated cellulosic fiber is preferably cuprammonium rayon. In addition, this fiber may be continuous long fiber or short fiber, but continuous long fiber is more excellent in lint-free property than short fiber, has less fiber ends and fluff, and does not easily fall off from the nonwoven fabric. , Less chemical and physical irritation to the skin, etc. In addition, since it is formed by self-adhesion by hydrogen bonding or by three-dimensional entangling by high-pressure liquid flow, there is a tendency for bonding and entangling between fibers to be strong, which is preferable.
The non-woven fabric is preferably manufactured by a no-binder manufacturing method such as hydroentanglement or needle punching that does not contain a binder. In particular, with hydroentanglement, the fibers are sufficiently entangled with each other, making it easier to produce a nonwoven fabric that is less prone to delamination.

The regenerated cellulose-based fiber nonwoven fabric of the present embodiment has a specific range of water extract amount, tensile strength per unit basis weight, formation index, and fiber diameter by controlling the manufacturing method such as spinning and hydroentanglement conditions. is doing. The inventors have found that by adjusting and combining these in the nonwoven fabric, when used as a surface material for absorbent articles, the nonwoven fabric is gentle to the skin, has excellent wear resistance, and improves the touch. That is, by optimally controlling the amount of water extract, the tensile strength per unit basis weight, and the formation index, nonwoven fabrics that are gentle on the skin, have excellent wear resistance, and satisfy all of the touch requirements, and absorbent articles containing the nonwoven fabrics. A surfacing can be provided.
In this way, by realizing optimally adjusted amounts of water extract, tensile strength per unit basis weight, texture index, and fiber diameter, we provide nonwoven fabrics that are gentle on the skin, have excellent abrasion resistance, and have a pleasant touch. became possible.

The amount of water extract representing the amount of water-soluble impurities such as surfactants in the fibers constituting the regenerated cellulose fiber nonwoven fabric of the present embodiment is 1000 ppm or less, preferably 900 ppm or less, more preferably 800 ppm or less. If the amount of water extract is more than 1000 ppm, there will be chemical irritation when it comes into contact with the skin, causing rashes and the like. In order to adjust the amount of water extract within this range, a no-binder manufacturing method that does not contain a binder is effective. Although the lower limit of the amount of water extract is not particularly limited, it may be 500 ppm or more.

The tensile strength per unit basis weight in the CD direction of the fibers constituting the regenerated cellulose fiber nonwoven fabric of the present embodiment is 0.20 (N/50 mm)/(g/m ² ) or more and 1.00 (N/(50 mm) )/(g/m ² ) or less, preferably 0.30 (N/50 mm)/(g/m ² ) or more and 0.90 (N/50 mm)/(g/m ² ) or less, and more It is preferably 0.40 (N/50 mm)/(g/m ² ) or more and 0.80 (N/50 mm)/(g/m ² ) or less. On the other hand, if the tensile strength is too high, the rigidity is too high, the touch feeling is reduced, and the feeling of wearing is poor.In order to adjust the tensile strength within this range, is effective in increasing the interlayer entangling force by controlling the fiber diameter, increasing the single fiber strength and the number of hydrogen bonds between fibers, and increasing the water pressure (water pressure) during hydroentangling. The pressure is preferably 5 MPa or more and 7 MPa or less It is also effective to use a lower layer net of 40 mesh or more and 80 mesh or less on which the spun sheets or webs are laminated.

As used herein, the term "CD direction of nonwoven fabric" refers to a direction perpendicular to the direction of machine movement (MD direction). However, when the CD direction cannot be determined, the CD direction refers to the direction orthogonal to the tensile direction in which the tensile strength of the nonwoven fabric is measured to maximize the tensile strength.

In the present invention, the tensile strength per unit basis weight in the CD direction is defined because the entanglement is stronger in the MD direction than in the CD direction due to the manufacturing method, and the tensile strength tends to be stronger, and the entanglement is higher. This is because the degree of entanglement between fibers in the nonwoven fabric can be estimated by considering the weak tensile strength in the CD direction.

In the present invention, the tensile strength per unit basis weight is a quotient obtained by dividing the tensile strength by the basis weight. It means that the weight is large and the amount of fiber is large, and if the basis weight is small, it means that the weight is small and the amount of fiber is small, and the tensile strength is affected by the amount of fiber. is.

The formation index of the regenerated cellulose-based fiber nonwoven fabric of the present embodiment in a dry state is 250 or more and 400 or less, preferably 300 or more and 350 or less. If the formation index is less than 250, the nonwoven fabric is too uniform, and the adhesion to the skin becomes too high during liquid retention, resulting in uncomfortable touch. On the other hand, if the formation index is too high, the surface unevenness will increase and the texture will be poor. In order to adjust the formation index within this range, it is effective to set the number of hydroentanglement nozzles to 1.5 hole/cm ² or more and 2.5 hole/cm ² or less, and adjust the number of water streams.

The fiber diameter of the fibers constituting the regenerated cellulose-based continuous filament nonwoven fabric of the present embodiment is preferably 5.0 μm or more and 20.0 μm or less, more preferably 7.0 μm or more and 18.0 μm or less, and even more preferably. is 9.0 μm or more and 16.0 μm or less, more preferably 10.0 μm or more and 16.0 μm or less. If the fiber diameter is 5.0 μm or less, the single fiber strength is low, the tensile strength is low, and the abrasion resistance is poor. In addition, the adhesiveness to the skin also increases, making it easy to feel stuffy and uncomfortable when worn. On the other hand, when the fiber diameter is 20.0 μm or more, the number of fibers is reduced, hydrogen bonding between fibers is reduced, tensile strength is lowered, and wear resistance is poor. In addition, the surface unevenness is increased, and the texture is also inferior.

As described above, in order to adjust the tensile strength within a specific range, it is necessary to control the single fiber strength, the number of hydrogen bonds between fibers, and the number of entanglements. In order to increase the number of bonds, it is effective to increase the number of fibers, that is, to reduce the fiber diameter, but this lowers the single fiber strength and the tensile strength. Furthermore, the surface becomes dense, the formation index becomes extremely small, the adhesion to the skin becomes too high, and the texture becomes uncomfortable. In order to increase the number of entanglements between fibers, it is effective to increase the water pressure during hydroentanglement. is inferior. If you try to bond the fibers with a binder or the like, the chemical stimulus will increase due to the surfactant or the like. Therefore, by setting the fiber diameter in an appropriate range, the number of hydrogen bonds between fibers is increased while maintaining the single fiber strength. Both indexes can be adjusted within a specific range, and both wear resistance and texture can be achieved.

The basis weight of the regenerated cellulose-based fiber nonwoven fabric of the present embodiment is preferably 5 g/m ² or more and 40 g/m ² or less, more preferably 10 g/m ² or more and 35 g/m ² or less, and still more preferably 15 g/m ² . It is more than 30g/m< ² > or less. By setting the basis weight within the range, the liquid absorbency and liquid retention are excellent, and discomfort does not occur, which is more preferable.

The thickness of the regenerated cellulose-based fiber nonwoven fabric of the present embodiment is preferably 0.10 mm or more and 0.30 mm or less, more preferably 0.15 mm or more and 0.25 mm or less. By setting the thickness within the range, the liquid absorbing property and the liquid retaining property are excellent, and discomfort does not occur, which is more preferable.

The average deviation SMD of the surface roughness in the MD direction of the regenerated cellulose fiber nonwoven fabric of the present embodiment in a dry state is preferably 1.5 μm or more and 4.5 μm or less. By setting the surface roughness within the range, the surface has moderate unevenness, exhibits moderate adhesion to the skin, and is excellent in texture, which is more preferable.

The number of dropped fibers, which is the amount of dropped fibers from the nonwoven fabric in pure water of the fibers constituting the regenerated cellulose continuous filament nonwoven fabric of the present embodiment, is preferably 350/g or less. By keeping the number of falling fibers within the range, it is possible to prevent the fibers falling from the nonwoven fabric from adhering to the skin when the garment is worn, so that discomfort does not occur. Although the lower limit of the amount of dropped fibers is not particularly limited, it may be 100/g or more.

The method for producing the regenerated cellulose fiber nonwoven fabric of this embodiment will be described below.
Another embodiment of the present invention uses a regenerated cellulose fiber sheet or web with a lower layer net of 40 mesh or more and 80 mesh or less, a water flow pressure of 5 MPa or more and 7 MPa or less, and a nozzle number of 1.5 holes / cm. The method for producing a nonwoven fabric according to any one of [1] to [6] above, comprising a step of performing hydroentangling at ² or more and 2.5 holes/cm ² or less, followed by drying.

In the production of non-woven fabrics, binder-free production methods such as hydroentanglement and needle punching, which do not contain binders, are effective. In particular, with hydroentanglement, the fibers are sufficiently entangled with each other, making it possible to produce a nonwoven fabric that is less prone to delamination.
In addition, it is possible to change the fiber diameter by adjusting the spinneret used in the process of spinning the fibers, the discharge amount of the stock solution, and the amount of spinning water flowing down through it. By changing the speed, it is possible to change the surface shape, thickness and strength of the nonwoven fabric.
In order to keep the tensile strength per unit basis weight in the CD direction in a dry state within a predetermined range, it is effective to increase the water pressure (water flow pressure) during hydroentangling. The high water pressure increases the entangling force between the fibers and increases the tensile strength. A preferable water pressure is 5 MPa or more and 7 MPa or less. However, when the pressure of the water stream is increased, the fibers bite into the net, increasing the unevenness of the surface of the nonwoven fabric and increasing the physical irritation. Therefore, it is more effective to combine this method with a method of reducing the number of nozzles for hydroentanglement. By reducing the number of hydroentangled nozzles to the range of 1.5 holes/cm ² or more and 2.5 holes/cm ² or less, the number of hydroentangled nozzles is reduced, but the impact force of each water stream can be increased. By reducing the entanglement points, it is possible to secure the entanglement force between the fibers by improving the collision force while suppressing the surface unevenness, and improve the strength.
In the method for producing a regenerated cellulose-based fiber nonwoven fabric of the present embodiment, the above production conditions are employed to adjust the amount of water extract, the tensile strength per unit basis weight, and the formation index within predetermined ranges. As a result, we were able to achieve an excellent standard of skin-friendliness, abrasion resistance, and texture.

EXAMPLES The present invention will be specifically described below based on Examples and Comparative Examples, but the present invention is not limited to these Examples.
First, methods for measuring physical properties used in Examples and the like will be described.

(1) Amount of water extract (ppm)
640 g of distilled water was added to a glass bottle containing 40 g of dry nonwoven fabric, and the bottle was covered and left for 16 hours. The extract was filtered to remove fiber debris. After that, the filtered extract is distilled under reduced pressure, and the amount of solid extracted substance F (g) is measured, and the following formula:
Amount of water extract (ppm) = F/40 x 1000000
The amount of extract was calculated by

(2) Tensile strength per unit basis weight in the CD direction ((N/50 mm)/(g/m ² ))
A nonwoven fabric of MD 5 cm×CD 10 cm was measured at a constant speed of 300 mm/min using a Tensilon tensile tester manufactured by Orientic, and the strength of the nonwoven fabric at 100% elongation in the CD direction was measured. In addition, the measurement was performed 5 times and the average value was made into the tensile strength (N/50mm). This tensile strength was divided by the basis weight described below to calculate the tensile strength per unit basis weight.
In addition, when a sample size suitable for the above measuring method cannot be obtained, a 5 cm×5 cm is used as a substitute, and a comparison can be made by performing conversion according to the sample size.

(3) Formation index in a dry state The formation index of a nonwoven fabric of 5 cm × 5 cm or more is measured using a formation tester FMT-MIII (manufactured by Nomura Shoji), with the basic settings of the tester unchanged from the factory shipment. It was measured.

(4) Fiber diameter (μm)
The nonwoven fabric was observed at a magnification of 10,000 times using a tabletop microscope TM4000II (manufactured by Hitachi High-Tech), 50 fibers were randomly selected, and the measured average value was taken as the fiber diameter.

(5) basis weight (g/m ² )
A cellulose nonwoven fabric with an area of 0.05 m ² or more is dried at 105°C until it reaches a constant weight, left in a constant temperature room at 20°C and 65% RH for 16 hours or more, and then measured for the mass per m ² of the nonwoven fabric. The mass (g) of was obtained. Let this nonwoven fabric state be a dry state.

(6) Thickness (mm)
The dry nonwoven fabric was subjected to a thickness test in accordance with JIS-L1096 under a load of 1.96 kPa.

(7) Mean Deviation SMD of Surface Roughness in Dry State
The average deviation SMD of the surface roughness of the nonwoven fabric of 7 cm × 17 cm or more was measured along the MD direction using KESFB4-AUTO-A manufactured by Kato Tech Co., Ltd. The measurement was performed three times, and the average value was taken as the standard deviation (μm) of the surface roughness.

(8) Dropped fiber amount (pieces/g)
A 5 cm square nonwoven fabric was placed in 300 ml of pure water and subjected to ultrasonic treatment (BRANSON B2210 ultrasonic cleaner) for 15 minutes. A black filter paper was attached to the filter bottle, the reaction solution was filtered, and the amount of fibers adhering to the black filter paper was measured with a camera (pieces/m ² ). This fiber amount was divided by the basis weight to calculate the amount of omission fiber per unit basis weight.

(9) Feeling of wearing Twenty subjects wore the sanitary napkin for one day on the third day after the end of menstruation in the summer, and sensory evaluation was carried out. The contents of the evaluation were graded according to the kindness to the skin, which is chemical irritation, wear resistance, and the touch, which is physical irritation. Based on the following evaluation criteria, the average value of 20 people was used as the sensory evaluation value of the sample.
In addition, in each item, evaluation of less than the average 4th grade was regarded as unfavorable.
・Gentleness to the skin Grade 5: Not bothering me at all. very comfortable.
Grade 4: I don't care. comfortable.
Grade 3: I am a little concerned. I felt a little rash and discomfort.
Grade 2: I'm curious. It caused irritation and discomfort.
Grade 1: Very concerned. very uncomfortable.
· Abrasion resistance Grade 5: No fluff or twist occurs.
Grade 4: No fluff or twist.
Grade 3: Slightly fluffed and twisted.
Grade 2: Conspicuous fluff and twist.
Grade 1: The fluff is very fluffy and twisted.
- Touch level 5: Extremely comfortable.
Grade 4: Comfortable.
Grade 3: Slightly rough. I experienced some pain and discomfort.
Grade 2: Roughness is conspicuous. Caused pain and discomfort.
Grade 1: Very rough. It caused a lot of pain and discomfort.

[Example 1]
A cotton linter is dissolved in a cuprammonium solution, and a spinneret having a diameter of 0.6 mm and 45 undiluted solution discharge holes/cm ² is used, and the discharge rate per hole is 0.096 cc/min. The sheet was continuously spun in five layers on a net, and the sheet was formed with through-holes and recesses while the fibers were entangled with a high-pressure water stream of 6 MPa, and then dried. Further, the hole-opening conditions are a lower layer net of 70 meshes and a number of hydroentanglement nozzles of 2.0 holes/cm ² . The lower layer net speed was 41.7 m/min. The resulting nonwoven fabric had a water extract content of 681 ppm, a tensile strength per unit basis weight of 0.62 (N/50 mm)/(g/m ² ), a formation index in a dry state of 262, and a fiber diameter of 12.4 µm. Met.

[Example 2]
A cotton linter was dissolved in a cuprammonium solution, and a spinneret with a diameter of 0.6 mm and 45/cm ² undiluted solution discharge holes was used, and the discharge rate per hole was 0.13 cc/min. The sheet was continuously spun in four layers on a net at , and the fibers were entangled with a high-pressure water stream of 5.5 MPa to form through holes and recesses in the sheet, followed by drying. Further, the hole-opening conditions are a lower layer net of 40 meshes and a number of hydroentanglement nozzles of 2.0 holes/cm ² . The lower layer net speed was 43.9 m/min. The resulting nonwoven fabric had a water extract content of 548 ppm, a tensile strength per unit basis weight of 0.31 (N/50 mm)/(g/m ₂ ), a formation index in a dry state of 369, and a fiber diameter of 12.8 µm. Met.

[Example 3]
A nonwoven fabric was obtained in the same manner as in Example 2, except that the hydroentanglement pressure was changed to 5 MPa. The resulting nonwoven fabric had a water extract content of 618 ppm, a tensile strength per unit basis weight of 0.21 (N/50 mm)/(g/m ² ), a formation index in a dry state of 320, and a fiber diameter of 13.0 µm. Met.

[Example 4]
A nonwoven fabric was obtained in the same manner as in Example 1, except that the hydroentanglement pressure was changed to 7 MPa. The resulting nonwoven fabric had a water extract content of 649 ppm, a tensile strength per unit basis weight of 0.9 (7 N/50 mm)/(g/m ² ), a formation index in a dry state of 305, and a fiber diameter of 12.2 µm. Met.

[Example 5]
A nonwoven fabric was obtained in the same manner as in Example 1, except that the number of hydroentangling nozzles was changed to 2.5 holes/cm ² . The resulting nonwoven fabric had a water extract content of 588 ppm, a tensile strength per unit basis weight of 0.78 (N/50 mm)/(g/m ² ), a formation index in a dry state of 252, and a fiber diameter of 11.8 µm. Met.

[Example 6]
A nonwoven fabric was obtained in the same manner as in Example 1, except that the number of hydroentanglement nozzles was changed to 1.5 holes/cm ² . The resulting nonwoven fabric had a water extract content of 810 ppm, a tensile strength per unit basis weight of 0.43 (N/50 mm)/(g/m ² ), a formation index in a dry state of 397, and a fiber diameter of 12.3 µm. Met.

[Example 7]
Using Bemberg (registered trademark) staple fibers (material name: Cupra) manufactured by Asahi Kasei Corp., cotton of 1.7 dtex×51 mm, a card web was produced using a spunlace manufacturing facility. Then, after performing a sterilization treatment to remove impurities such as oils, hydroentanglement was performed in the same manner as in Example 1, followed by drying. The resulting nonwoven fabric had a water extract content of 980 ppm, a tensile strength per unit basis weight of 0.31 (N/50 mm)/(g/m ² ), a formation index in a dry state of 271, and a fiber diameter of 12.7 µm. Met.

[Example 8]
A nonwoven fabric was obtained in the same manner as in Example 1, except that the spinning stock solution was changed to a coagulating solution using N-methylmorpholine N-oxide of cotton linter as a solvent. The resulting nonwoven fabric had a water extract content of 855 ppm, a tensile strength per unit basis weight of 0.67 (N/50 mm)/(g/m ² ), a formation index in a dry state of 277, and a fiber diameter of 13.2 µm. Met.

[Example 9]
A nonwoven fabric was obtained in the same manner as in Example 1, except that the diameter of the spinneret was changed so that the fiber diameter was 5.2 μm. The resulting nonwoven fabric had a water extract content of 713 ppm, a tensile strength per unit basis weight of 0.68 (N/50 mm)/(g/m ² ), and a formation index of 254 in a dry state.

[Example 10]
A nonwoven fabric was obtained in the same manner as in Example 1, except that the diameter of the spinneret was changed so that the fiber diameter was 19.6 μm. The resulting nonwoven fabric had a water extract content of 661 ppm, a tensile strength per unit basis weight of 0.57 (N/50 mm)/(g/m ² ), and a formation index of 385 in a dry state.

[Comparative Example 1]
A nonwoven fabric was obtained in the same manner as in Example 1, except that the hydroentanglement pressure was changed to 4 MPa. The resulting nonwoven fabric had a water extract content of 690 ppm, a tensile strength per unit basis weight of 0.18 (N/50 mm)/(g/m ² ), a formation index in a dry state of 255, and a fiber diameter of 12.9 μm. Met. Compared with Example 1, the tensile strength was low, and the wear resistance was hindered.

[Comparative Example 2]
A nonwoven fabric was obtained in the same manner as in Example 1, except that the hydroentanglement pressure was changed to 8 MPa. The obtained nonwoven fabric had a water extract amount of 814 ppm, a tensile strength per unit basis weight of 1.20 (N/50 mm) (g/m ² ), a formation index in a dry state of 380, and a fiber diameter of 12.1 µm. there were. Compared with Example 1, the tensile strength was large and the abrasion resistance was excellent, but the surface unevenness was large and the texture was detrimental.

[Comparative Example 3]
A nonwoven fabric was obtained in the same manner as in Example 1, except that the number of hydroentangling nozzles was changed to 2.9 holes/cm ² . The resulting nonwoven fabric had a water extract content of 751 ppm, a tensile strength per unit basis weight of 0.82 (N/50 mm)/(g/m ² ), a formation index in a dry state of 244, and a fiber diameter of 12.6 µm. Met. As compared with Example 1, the formation index was small and the adhesion was too high, so that the texture was degraded.

[Comparative Example 4]
A nonwoven fabric was obtained in the same manner as in Example 1, except that the number of hydroentangling nozzles was changed to 1.3 holes/cm ² . The resulting nonwoven fabric had a water extract content of 720 ppm, a tensile strength per unit basis weight of 0.67 (N/(50 mm)/(g/m ² ), a formation index in a dry state of 412, and a fiber diameter of 13.5. Compared with Example 1, the texture index was large and the surface unevenness was large, which caused a problem in touchability.

[Comparative Example 5]
Using Bemberg (registered trademark) staple fibers (material name: Cupra) manufactured by Asahi Kasei Corp., cotton of 1.7 dtex×51 mm, a card web was produced using a spunlace manufacturing facility. Thereafter, a nonwoven fabric was obtained in the same manner as in Comparative Example 1 without sterilization. The resulting nonwoven fabric had a water extract content of 1,087 ppm, a tensile strength per unit basis weight of 0.16 (N/(50 mm)/(g/m ² ), a formation index in a dry state of 260, and a fiber diameter of 11.5. The thickness was 5 μm, and the softness to the skin, abrasion resistance, and texture were all compromised.

[Comparative Example 6]
The properties of a commercially available regenerated cellulose fiber nonwoven fabric (Lyocell nonwoven fabric, Sontara (trade name) manufactured by Jakob Holm) were measured and evaluated. The obtained nonwoven fabric had a water extract amount of 2600 ppm, a tensile strength per unit basis weight of 0.95 (N/50 mm)/(g/m ² ), a formation index in a dry state of 302, and a fiber diameter of 12.3 µm. Met. Compared with Example 1, there was no particular problem with abrasion resistance, but the amount of impurities was large, and some subjects had rashes, and prickly irritation due to the ends of the fibers also occurred.

[Comparative Example 7]
A nonwoven fabric was obtained under the conditions described in Example 1 of JP-A-2004-255176. The hole opening conditions were a high-pressure water flow of 3 MPa, a lower layer net of 40 meshes, and the number of hydro-entangled nozzles of 2.9 holes/cm ² . The resulting nonwoven fabric had a water extract content of 823 ppm, a tensile strength per unit basis weight of 0.14 (N/50 mm)/(g/m ² ), a formation index in a dry state of 203, and a fiber diameter of 4.1 µm. Met. Abrasion resistance and texture were impaired.

[Comparative Example 8]
A nonwoven fabric was obtained under the conditions described in Example 2 of JP-A-9-154870. The hole opening conditions were a high-pressure water flow of 3 MPa, a lower layer net of 40 meshes, and the number of hydro-entangled nozzles of 2.9 holes/cm ² . The resulting nonwoven fabric had a water extract content of 769 ppm, a tensile strength per unit basis weight of 0.18 (N/50 mm)/(g/m ² ), a formation index in a dry state of 219, and a fiber diameter of 11.2 µm. Met. Abrasion resistance and texture were impaired.

[Comparative Example 9]
A nonwoven fabric was obtained under the conditions described in Example 2 of Japanese Patent No. 6680950. The hole opening conditions were a high-pressure water flow of 3 MPa, a lower layer net of 40 meshes, and the number of hydro-entangled nozzles of 2.9 holes/cm ² . The obtained nonwoven fabric had a water extract amount of 1368 ppm, a tensile strength per unit basis weight of 0.50 (N/50 mm)/(g/m ² ), a formation index in a dry state of 156, and a fiber diameter of 13.0 µm. Met. There were no particular problems with abrasion resistance, but some subjects had rashes.

[Comparative Example 10]
A nonwoven fabric was obtained in the same manner as in Example 1, except that the diameter of the spinneret was changed so that the fiber diameter was 4.8 μm. The resulting nonwoven fabric had a water extract content of 713 ppm, a tensile strength per unit basis weight of 0.18 (N/50 mm)/(g/m ² ), and a formation index of 250 in a dry state. Abrasion resistance and texture were impaired.

[Comparative Example 11]
A nonwoven fabric was obtained in the same manner as in Example 1, except that the diameter of the spinneret was changed so that the fiber diameter was 21.4 μm. The resulting nonwoven fabric had a water extract content of 681 ppm, a tensile strength per unit basis weight of 0.16 (N/50 mm)/(g/m ² ), and a formation index of 392 in a dry state. Abrasion resistance and texture were impaired.

Various physical properties of the nonwoven fabrics obtained in Examples 1 to 10 and Comparative Examples 1 to 11 are shown in Table 1 below.

The regenerated cellulose-based fiber nonwoven fabric according to the present invention is a nonwoven fabric material that is gentle on the skin, has excellent abrasion resistance, and has a good texture. It can be suitably used as a surface material for absorbent articles such as.

Claims (8)

The amount of water extract is 1000 ppm or less, and the tensile strength per unit basis weight in the CD direction is 0.20 (N/50 mm)/(g/m ² ) or more and 1.00 (N/50 mm)/(g/m ² ). ) or less, a formation index in a dry state of 250 or more and 400 or less, and a fiber diameter of the structural fibers of 5.0 μm or more and 20.0 μm or less. The nonwoven fabric according to claim 1, having a basis weight of 5 g/m ² or more and 40 g/m ² or less and a thickness of 0.10 mm or more and 0.30 mm or less. The nonwoven fabric according to claim 1 or 2, wherein the cellulosic fibers are continuous filaments. The nonwoven fabric according to any one of claims 1 to 3, wherein the fiber diameter is 10.0 µm or more and 16.0 µm or less. The nonwoven fabric according to any one of claims 1 to 4, wherein the average deviation SMD of surface roughness in the MD direction in a dry state is 1.5 µm or more and 4.5 µm or less. The nonwoven fabric according to any one of claims 1 to 5, wherein the number of fallen fibers is 350/g or less. An absorbent article comprising the nonwoven fabric according to any one of claims 1 to 6 as a surface material. A sheet or web of regenerated cellulose fiber, using a lower layer net of 40 mesh or more and 80 mesh or less, a water flow pressure of 5 MPa or more and 7 MPa or less, and a nozzle number of 1.5 holes/cm ² or more and 2.5 holes/cm ² or less. The method for producing the nonwoven fabric according to any one of claims 1 to 6, comprising a step of drying after applying hydroentanglement.