Laminated nonwoven fabric and method for producing the same

Abstract

To provide a nonwoven fabric made by entangling fibers, in which the orientation of fibers is more random due to minute irregularities, and which can be easily stretched in the lateral direction with a relatively small force when impregnated with a liquid. [Solution] A laminated nonwoven fabric in which a fiber layer B containing staple fibers with a fiber length of 20 mm or more and 100 mm or less is positioned on both surfaces of a fiber layer A containing short fibers with a fiber length of less than 20 mm, and fiber layer A and fiber layer B are integrated by entanglement, both surfaces of the laminated nonwoven fabric have irregularities, and the average needle ratio of the recesses of the irregularities on both surfaces of the laminated nonwoven fabric is 2.94 or less.

Description

[Technical Field]

[0001] The present disclosure relates to a laminated nonwoven fabric having specific irregularities formed on its surface, and a method for producing the same. [Background technology]

[0002] Liquid-impregnated nonwoven fabrics are widely used, for example, to cover human or animal skin and deliver a specific substance to the skin, or as wipers for wiping dirt off the human body or objects. Various configurations of nonwoven fabrics for liquid impregnation have been proposed and put to practical use. For example, Japanese Patent Publication No. 4592516 proposes a liquid-impregnated skin covering sheet comprising an upper fiber layer and a lower fiber layer each containing more than 90% by mass of fibers having a fineness of more than 0.5 dtex, and a cellulosic staple fiber layer containing 50% by mass or more of cellulosic staple fibers positioned between them, the three fiber layers being integrated by entangling the fibers with a hydroentanglement treatment, and the cellulosic staple fibers being pulp fibers produced from softwood and / or hardwood.

[0003] Furthermore, Japanese Patent No. 4721788 proposes a laminated nonwoven fabric suitable for specific applications, in which a cotton fiber layer containing 50% by mass or more of cotton is positioned on at least one surface of a cellulosic staple fiber layer containing 50% by mass or more of cellulosic staple fibers, with the surface of this layer being the skin-contacting surface; the cellulosic staple fiber layer and the cotton fiber layer have portions where the cellulosic staple fibers are absent or thin due to entanglement of the fibers by hydroentangling treatment, and the fibers of the cotton fiber layer are entangled and integrated in these portions; the cellulosic staple fiber layer is made of pulp fibers produced using softwood and / or hardwood; and the 10% elongation modulus in the transverse direction is 1.5 N / 5cm or more and 10 N / 5cm or less. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4592516 [Patent Document 2] Japanese Patent Application Laid-Open No. 4721788 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure provides a nonwoven fabric made by entangling fibers, in which the orientation of the fibers is more random due to minute irregularities, and which can be easily stretched in the lateral direction with a relatively small force when impregnated with a liquid. [Means for solving the problem]

[0006] The present disclosure provides a laminated nonwoven fabric in which a fiber layer A containing short fibers with a fiber length of less than 20 mm and a fiber layer B containing staple fibers with a fiber length of 20 mm or more and 100 mm or less are positioned on both surfaces of the fiber layer A, and the fiber layer A and the fiber layer B are integrated by entanglement, Both surfaces of the laminated nonwoven fabric have irregularities, On both surfaces of the laminated nonwoven fabric, the average needle ratio of the recesses of the unevenness is 2.94 or less. A laminated nonwoven fabric is provided.

[0007] The present disclosure also provides a method for producing a laminated web by laminating a fibrous web B containing staple fibers having a fiber length of 20 mm or more and 100 mm or less on both surfaces of a fibrous web A containing short fibers having a fiber length of less than 20 mm; A columnar water stream having a pressure of 1 MPa or more and 10 MPa or less is sprayed onto one or both surfaces of the laminated web 1 to 5 times, At least one of the columnar water jets is a suction water jet, which is performed while placing the laminate web on a support made of a punched metal and sucking the water jet sprayed onto the laminate web. A method for producing a laminated nonwoven fabric is provided. [Effects of the Invention]

[0008] The laminated nonwoven fabric of the present disclosure has relatively random fiber orientation due to the fine irregularities on the surface, and therefore can be easily stretched with a relatively small force when impregnated with a liquid. Therefore, for example, when the fabric is impregnated with a liquid and slightly stretched laterally, it can be easily attached to the skin or attached to a jig for use, providing a product that is easy to attach or attach. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a micrograph showing the surface of the laminated nonwoven fabric of Example 1. [Figure 2] 1 is a photomicrograph showing the surface of the laminated nonwoven fabric of Comparative Example 1. [Figure 3] FIG. 2 is a plan view showing measurement points on a sample when measuring bending resistance with a handle-o-meter. [Figure 4] FIG. 1 is a plan view corresponding to a binarized image for determining the acicular ratio of each concave portion of the unevenness of the surface of a nonwoven fabric sample. [Figure 5] FIG. 1 is a plan view corresponding to a processed image for determining the absolute maximum length and diagonal width of each recess of the unevenness of the surface of a nonwoven fabric sample. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Background to the present embodiment) The laminated nonwoven fabrics for liquid impregnation proposed in Patent Documents 1 and 2 have a structure in which a pulp-containing fibrous layer is flanked on either side by other fibrous layers. This structure allows the pulp-containing fibrous layer to improve the texture of the nonwoven fabric, resulting in a nonwoven fabric with a flat surface. However, these patent documents require the use of specific fibers in the fibrous layers flanked on either side of the pulp-containing fibrous layer, and utilize the properties of these fibers to achieve the desired tactile feel and mechanical properties.

[0011] The present inventors focused on the fiber orientation in a laminated nonwoven fabric with an internal fiber layer containing short fibers, and investigated the effect this has on the user when the fabric is impregnated with a liquid. As a result, they found that by using the average acicular ratio as a parameter indicating the fiber orientation and configuring it to have a specific value, a nonwoven fabric with properties not found in conventional nonwoven fabrics can be obtained. The fibers constituting the nonwoven fabric of this embodiment will be first described below.

[0012] [Short fiber] The fiber layer A of this embodiment contains short fibers having a fiber length of less than 20 mm. When the short fibers are chemical fibers such as rayon or synthetic fibers, the fiber length of the short fibers is measured according to JIS L 1015:2010 (method C). The fiber length of the short fibers may be, for example, 0.7 mm or more and 20 mm or less, particularly 0.8 mm or more and 15 mm or less, and more particularly 0.9 mm or more and 10 mm or less.

[0013] The short fibers may be any of synthetic fibers, cellulosic fibers, natural fibers other than cellulosic fibers, and inorganic fibers.

[0014] Examples of cellulosic fibers include the following: (1) Natural fibers derived from plants such as cotton, flax, flax, ramie, jute, banana, bamboo, kenaf, shell ginger, hemp, and kapok; (2) solvent-spun cellulose fibers such as viscose-derived rayon and polynosic, cupra obtained by the cuprammonium process, and solvent-spun Tencel® and Lyocell, as well as other regenerated fibers; (3) Cellulose fibers obtained by melt spinning; (4) Semi-synthetic fibers such as acetate fibers; and (5) Pulp such as mechanical pulp, recycled pulp, and chemical pulp

[0015] The fineness of the cellulose-based fiber is not particularly limited. The fineness of the cellulose-based fiber may be 0.2 dtex or more and 22.0 dtex or less. The fineness of the cellulose-based fiber may be 0.3 dtex or more, 0.8 dtex or more, or 1.0 dtex or more. The fineness of the cellulose-based fiber may be 14.0 dtex or less, 10.0 dtex or less, 6.7 dtex or less, or 4.4 dtex or less. In one embodiment, the fineness of the cellulose-based fiber is 0.6 dtex or more and 4.4 dtex or less. Since it is difficult to adjust the fineness of natural fibers, cellulose-based fibers with finenesses outside the above range may be used. In the case of natural fibers, the fineness may be measured by a method based on the Micronaire method described in JIS L 1019:2006 7.4.1 "Measurement of Fineness by ISO Method." In addition, in the case of recycled fibers, measurement may be performed using a method conforming to the vibration method described in JIS L 1015:2010 8.5 ISO method (reference method) for measuring fineness.

[0016] The cellulose-based fiber may have a fiber diameter of 5.0 μm or more and 23.0 μm or less. The cellulose-based fiber may have a fiber diameter of 6.0 μm or more, 7.0 μm or more, or 8.0 μm or more. The cellulose-based fiber may have a fiber diameter of 22.0 μm or less, 21.0 μm or less, or 20.0 μm or less. The fiber diameter of the cellulose-based fiber is determined, for example, by observing the fabric with an electron microscope at approximately 400x magnification, and determining the diameter of the fiber cross section. Furthermore, when the fiber cross section is noncircular, the fiber diameter is the average of the length of the major axis of the fiber cross section and the longest distance between two points on the fiber cross section perpendicular to the major axis.

[0017] Synthetic fibers are usually made of a thermoplastic resin. There are no particular limitations on the thermoplastic resin. Examples of the thermoplastic resin include aromatic polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and polyethylene naphthalate; aliphatic polyester resins such as polylactic acid, polyglycolic acid, poly(β-hydroxybutyric acid), poly(β-hydroxyacetic acid-co-β-hydroxyvaleric acid), poly-β-propiolactone, poly-ε-caprolactone, polyethylene succinate, and copolymers thereof; and aliphatic-aromatic polyester resins in which an aromatic polyester and an aliphatic polyester are copolymerized (for example, butylene adipate-co- Polyolefin resins such as polypropylene, polyethylene (including high-density polyethylene, low-density polyethylene, linear low-density polyethylene, etc.), polybutene-1, propylene copolymers with propylene as the main component (including propylene-ethylene copolymer and propylene-butene-1-ethylene copolymer), ethylene-vinyl alcohol copolymer, and ethylene-vinyl acetate copolymer; polyamide resins such as nylon 6, nylon 12, and nylon 66; acrylic resins; polyurethane resins; engineering plastics such as polycarbonate, polyacetal, polystyrene, and cyclic polyolefins, and their elastomers.

[0018] Synthetic fibers may be monofilaments, in which the fiber cross section is composed of a single component (also referred to as a "single section"), and / or conjugate fibers, in which the fiber cross section is composed of multiple components (also referred to as "sections"). Conjugate fibers may be, for example, concentric or eccentric sheath-core conjugate fibers, islands-in-the-sea conjugate fibers, side-by-side conjugate fibers, or splittable conjugate fibers. The cross section of the fiber may be circular or noncircular. Noncircular shapes include elliptical, Y-shaped, X-shaped, I-shaped, multilobal, polygonal, and star-shaped. Synthetic fibers may also have a hollow cross section. In both monofilaments and conjugate fibers, each section constituting the fiber may be composed of a single resin, or a mixture of two or more resins.

[0019] The fineness of the synthetic fibers is, for example, 0.4 dtex or more and 4.0 dtex or less. The fineness of the synthetic fibers may be 0.5 dtex or more, 0.6 dtex or more, 0.9 dtex or more, or 1.1 dtex or more. The fineness of the synthetic fibers may be 4.0 dtex or less, 2.6 dtex or less, 2.4 dtex or less, or 2.2 dtex or less. The method for measuring the fineness is as described above in relation to cellulosic fibers.

[0020] The synthetic fibers may have a fiber diameter of 6.0 μm or more and 20.0 μm or less. The fiber diameter of the synthetic fibers may be 6.5 μm or more, 7.5 μm or more, 9.0 μm or more, or 10.0 μm or more. The fiber diameter of the synthetic fibers may be 19.0 μm or less, 16.0 μm or less, or 15.0 μm or less. The method for determining the fiber diameter of synthetic fibers is as described above in relation to cellulosic fibers.

[0021] Examples of natural fibers that are not cellulosic fibers include silk, wool, animal hair, etc. Examples of inorganic fibers include glass fibers, metal fibers, and carbon fibers.

[0022] In this embodiment, pulp may be used as the short fibers. Pulp is hydrophilic and tends to be well entangled with the fibers of the fiber layers B located on both sides of the fiber layer A when a laminated nonwoven fabric is produced by the hydroentangling method described below. The pulp-containing fiber layer A can also be provided in the form of a wet-laid nonwoven fabric known as tissue paper before being entangled with the fiber layer B, as described below, facilitating the production of the nonwoven fabric. Furthermore, pulp itself is hydrophilic, making it easy to impregnate the nonwoven fabric with liquid and to retain the liquid. Furthermore, pulp tends to exist in a fibrillated state, making it easy to entangle the fibers when entangling them using the method described below. Pulp also has a flat shape, and when dry, hydrogen bonds are formed between the flat surfaces, resulting in relatively high strength and improving runnability during product processing. However, when wet, the hydrogen bonds are released, allowing the nonwoven fabric to be flexible.

[0023] Pulp may be produced by conventional methods using, for example, softwood or hardwood, specifically, mechanical pulp, chemical pulp, or recycled pulp. Alternatively, non-wood pulp made from plant fibers, including straw, bamboo, bagasse, esparto, other reeds and grasses, cotton linters, Manila hemp, flax, hemp, ramie, kenaf, rags, and other textile waste, may be used. When pulp is used as short fibers, the pulp fineness may be, for example, about 1.0 to 4.0 dtex, particularly about 1.3 to 3.5 dtex, and the fiber length may be, for example, 0.8 mm to 4.0 mm, particularly 1.0 mm to 3.0 mm, and more particularly 1.2 mm to 2.0 mm, although pulp with a fineness and / or fiber length outside these ranges may also be used. When the short fibers are pulp, the fiber length of the pulp is measured by the length-weighted average fiber length according to JIS P 8226-2 (2011 edition) Pulp - Optical Automatic Analysis Method.

[0024] [Staple fiber] The fiber layer B of this embodiment contains staple fibers having a fiber length of 20 mm or more and 100 mm or less. The fiber length of the staple fibers is measured according to JIS L 1015:2010 (method C) in the case of synthetic fibers, and is measured as a length-weighted average fiber length using a fiber length measurement system manufactured by REMIER (https: / / www.berthold-jp.com / fibershape / ) in the case of natural fibers such as cotton. The staple fibers may have a fiber length of, for example, 20 mm or more and 100 mm or less, particularly 22 mm or more and 70 mm or less, and more particularly 30 mm or more and 64 mm or less.

[0025] Staple fibers may be synthetic fibers, cellulosic fibers, natural fibers other than cellulosic fibers, or inorganic fibers, examples of which are as described above in connection with staple fibers.

[0026] In this embodiment, cellulosic fibers may be used as staple fibers. Cellulosic fibers are generally hydrophilic, and therefore tend to be well entangled with the fiber layer A when a laminated nonwoven fabric is produced by the hydroentanglement method described below. Hydrophilic cellulosic fibers also facilitate impregnation of the nonwoven fabric with liquid and facilitate retention of liquid. Furthermore, since many cellulosic fibers are natural fibers or fibers made from natural materials, they have a good feel to the touch. In addition, cellulosic fibers have the advantage of being readily accepted by environmentally conscious consumers and / or consumers who are highly interested in natural materials.

[0027] As the cellulosic fiber, for example, regenerated fibers, particularly rayon, and cotton can be used. Regenerated fibers are preferably used because the fineness can be easily adjusted and there is little variation. Among the regenerated fibers, rayon can make the nonwoven fabric soft. Cotton is a natural fiber that has a proven track record of being widely used in products that come into contact with the skin, such as underwear, and is therefore preferably used in applications where the fabric comes into contact with the skin.

[0028] When cellulosic fibers are used as staple fibers, synthetic fibers may be used in combination. The combined use of synthetic fibers improves the strength of the nonwoven fabric and allows the strength of the nonwoven fabric to be adjusted according to the application. Furthermore, the combined use of synthetic fibers increases the bending resistance of the nonwoven fabric in the wet state compared to when only cellulosic fibers are used, and allows the bending resistance to be adjusted according to the application. Furthermore, synthetic fibers have mechanical or three-dimensional crimps, and these crimps are firm, which facilitates good entanglement of fibers in the CD. Therefore, by using synthetic fibers together with staple fibers, the breaking elongation of the nonwoven fabric in the CD can be increased, making it easier to obtain a nonwoven fabric that is resistant to tearing.

[0029] As synthetic fibers, for example, polyester monofilaments such as polyethylene terephthalate can be used. Compared to other synthetic fibers, polyester fibers tend to produce bulkier nonwoven fabrics. Furthermore, because polyester fibers are flexible and strong, their use in combination with cellulose fibers facilitates the production of strong, flexible, and tear-resistant nonwoven fabrics. Polyolefin monofilaments such as polypropylene can also be used as synthetic fibers. Because polyolefin monofilaments themselves have water-repellent properties, they can reduce entanglement during hydroentanglement. This prevents overentanglement and allows the nonwoven fabric to be flexible. As staple synthetic fibers, splittable conjugate fibers whose cross section is composed of multiple sections may also be used. When splittable conjugate fibers are used to produce nonwoven fabrics using the water jet production method described below, some or all of the sections split to form smaller fibers, thereby making the nonwoven fabric denser and smoother to the touch. The splittable conjugate fiber may be made of, for example, a combination of polyethylene terephthalate / polyethylene, polypropylene / polyethylene, or polyethylene terephthalate / polypropylene. Of these, a combination of polyester and polyethylene has good splitting properties during hydroentanglement and tends to provide a nonwoven fabric with a good texture.

[0030] [Fiber layer A] Next, the fiber layer A constituting the nonwoven fabric of this embodiment will be described. The fiber layer A is a fiber layer containing short fibers with a fiber length of less than 20 mm. The fiber layer A contains, for example, 50% by mass or more of short fibers, particularly 60% by mass or more, and more particularly 70% by mass or more of short fibers. The fiber layer A may be composed only of short fibers. When the fiber layer A is composed only of short fibers, entanglement with the fiber layer B is improved, and the fiber orientation due to the fine irregularities on the surface of the nonwoven fabric is made more random, making it easier to obtain a nonwoven fabric with an average needle ratio of 2.94 or less.

[0031] Before being integrated with fibrous layer B, fibrous layer A may be in the form of a wetlaid web, wetlaid nonwoven fabric, airlaid web, or airlaid nonwoven fabric. A wetlaid nonwoven fabric in which fibrous layer A is made only of pulp is also called tissue. In these webs or nonwoven fabrics, the fiber orientation is relatively random, and therefore the fiber orientation resulting from the fine irregularities in the nonwoven fabric after lamination can be made even more random, making it easier to obtain a nonwoven fabric with an average needle ratio of 2.94 or less. However, the form of fibrous layer A before being integrated with fibrous layer B is not limited to these and may be, for example, a carded web or other nonwoven fabric form.

[0032] Fiber layer A may be, for example, composed solely of pulp, and may be provided in the form of a wetlaid paper web or wetlaid nonwoven fabric before being integrated with fiber layer B. A fiber layer composed of pulp facilitates dispersion of short fibers when a nonwoven fabric is produced using the manufacturing method described below for integrating fibers by hydroentanglement, making it easier to form more distinct irregularities on the nonwoven fabric. The wetlaid nonwoven fabric composed of pulp may be crepe paper. Crepe paper has wrinkles that allow it to stretch in the MD direction. Therefore, when a nonwoven fabric is produced using the manufacturing method described below, the crepe paper is dispersed while stretching in the MD during hydroentanglement. While the detailed reason for this dispersion is unknown, it is believed that this dispersion mode facilitates achieving the characteristic needle ratio of this embodiment.

[0033] [Fiber layer B] Next, the fiber layer B constituting the nonwoven fabric of this embodiment will be described. The fiber layer B is a fiber layer containing staple fibers with a fiber length of 20 mm to 100 mm. The fiber layer B contains, for example, 50% by mass or more, particularly 70% by mass or more, and more particularly 80% by mass or more of staple fibers. The fiber layer B may be composed solely of staple fibers. When the fiber layer B is composed solely of staple fibers and does not contain fibers with a fiber length of less than 20 mm and / or fibers with a fiber length of more than 100 mm, the fiber orientation due to the fine irregularities on the surface of the nonwoven fabric becomes more random, making it easier to obtain a nonwoven fabric with an average needle ratio of 2.94 or less. Furthermore, when the fiber layer B does not contain short fibers, fiber ends are less likely to protrude from the surface of the nonwoven fabric, making it easier to improve the texture of the nonwoven fabric. Furthermore, short fiber waste (paper dust) is less likely to be generated during slitting and punching, improving processability.

[0034] The fibrous layer B may be in any form such as a carded web, air-laid web, or wet-laid web, such as a parallel web, cross web, semi-random web, or random web, before being integrated with the fibrous layer A. The fibrous web is preferably in the form of a parallel web or semi-random web, since this results in a smoother surface of the nonwoven fabric.

[0035] As described above, the fibrous layer B may contain cellulosic fibers. The cellulose fibers may comprise, for example, 40% by mass or more, particularly 60% by mass or more, and more particularly 70% by mass or more, based on 100% by mass of the staple fibers contained in the fibrous layer B. The fibrous layer B may be composed solely of cellulose fibers.

[0036] Alternatively, fiber layer B may contain 40% by mass or more and 100% by mass or less, particularly 70% by mass or more and 100% by mass or less, of cellulosic fibers, with the remaining staple fibers being synthetic fibers, assuming the total amount of staple fibers in fiber layer B to be 100% by mass. The significance of using cellulosic fibers and synthetic fibers in combination is as explained above in the section on staple fibers. Examples of cellulosic fiber / synthetic fiber combinations include rayon / polyethylene terephthalate fiber, rayon / polypropylene fiber, rayon / splittable composite fiber (e.g., polyethylene terephthalate / polyethylene), lyocell / polyethylene terephthalate fiber, lyocell / polypropylene fiber, lyocell / splittable composite fiber, cotton / polyethylene terephthalate fiber, and cotton / splittable composite fiber.

[0037] [Laminated nonwoven fabric] The nonwoven fabric of this embodiment is a laminated nonwoven fabric in which fiber layer B is located on both surfaces of fiber layer A, and fiber layer A and fiber layer B are integrated by entanglement. In the nonwoven fabric of this embodiment, it is preferable that the fibers are not integrated by bonding. A nonwoven fabric in which the fibers are not bonded to each other has a better feel and is softer. The fiber layers B located on both surfaces of the fiber layer A may be the same fiber layer or different fiber layers. The two fiber layers B may, for example, differ from each other in the type and / or proportion of cellulosic fiber and / or may have different basis weights from each other.

[0038] The basis weights of the fiber layer A and the fiber layer B are appropriately selected depending on the desired basis weight of the laminated nonwoven fabric. The basis weight of the fiber layer A may be selected, for example, so as not to exceed 60 mass% of the basis weight of the entire laminated nonwoven fabric, particularly so as not to exceed 50 mass%, more particularly 10 to 45 mass%, and even more particularly 10 to 35 mass%. If the proportion of the fiber layer A exceeds 60 mass% (i.e., if the proportion of the fiber layer B is 40 mass% or less in total), the entire sheet becomes paper-like and the texture becomes hard, resulting in poor adhesion to the skin when the laminated nonwoven fabric is used as a liquid-impregnated skin dressing sheet. On the other hand, if the proportion of the fiber layer A is small (i.e., if the proportion of the fiber layer B is large), the laminated nonwoven fabric may have poor formation. For example, if the proportion of the fiber layer A is 60 to 100 g / m 2 In order to obtain a laminated nonwoven fabric of this size, the basis weight of the fiber layer A is 10 to 40 g / m 2 degree, especially 15-30g / m 2 The weight of the fiber layer B is preferably about 10 to 50 g / m 2 The basis weight of the fiber layers B may be the same as that of the other fiber layer B, as described above, or may be different from each other. For example, the basis weight of one fiber layer B may be about 2 to 3 times that of the other fiber layer B.

[0039] The basis weight of the nonwoven fabric of this embodiment is, for example, 40 to 150 g / m 2 In particular, 50 to 120 g / m 2 and more particularly 60 to 100 g / m 2 The weight of the nonwoven fabric is 40 g / m 2 If the density is less than 150 g / m, the absolute amount of liquid will be small when the liquid is impregnated, and the fabric may not feel firm when held in the hand. 2 If it exceeds this, it will become too thick and difficult to handle.

[0040] The nonwoven fabric of this embodiment may have a configuration in which the fibers are entangled by a hydroentanglement treatment, and the fibrous layer A and the fibrous layers B located on both surfaces thereof are integrated together. A nonwoven fabric in which the fibers are entangled by a hydroentanglement treatment has better texture.

[0041] The nonwoven fabric of this embodiment has irregularities on both surfaces, and the average acicular ratio of the concave portions of the irregularities on both surfaces is 2.94 or less. In this embodiment, the average acicular ratio of the concave portions of the irregularities can be determined by performing the following image processing on a 25 mm x 25 mm area of ​​the nonwoven fabric surface: gray imaging → median → automatic binarization → shrinkage → deletion → exclusive expansion → shape feature image processing using image analysis software "WinROOF2018" manufactured by Mitani Corporation.

[0042] When carrying out the above image processing, the median filter size is set to 3x3 and is carried out to remove white speckled noise in the gray image. For automatic binarization, a discriminant analysis method is used to determine the threshold. As shown in Figure 4, automatic binarization distinguishes between recessed and non-recessed areas, and an image can be obtained in which the recessed areas are colored. Next, a contraction process is carried out to correct the obtained binarized image. The contraction process is carried out three times. Next, of the binarized and colored areas, areas with an area of ​​0.01 mm are removed. 2 Anything less than this is deleted. Then, exclusive expansion is performed to restore the contracted image to its original size. Exclusive expansion is performed the same number of times as the contraction process, i.e., three times. The image after exclusive expansion is subjected to shape feature processing, i.e., measurement processing, to measure the acicular ratio. The acicular ratio is calculated by calculating the absolute maximum length and the diagonal width, which is the shortest distance between two lines parallel to the absolute maximum length when the depression is sandwiched between the two lines, for each colored portion (depression) of the binarized image, and then dividing the absolute maximum length by the diagonal width. More specifically, as shown in Figure 5, a rectangle is set circumscribing each depression, and the acicular ratio is calculated by taking the long side as the absolute maximum length and the short side as the diagonal width.

[0043] In this embodiment, 60 cm 2 The acicular ratio of each recess is measured in two areas, and the average of the acicular ratios of each recess determined in the two areas is taken as the average acicular ratio of that surface of the nonwoven fabric. The measurement of the average acicular ratio is carried out on both sides of the nonwoven fabric. When the nonwoven fabric or a product using the nonwoven fabric is measured over a 60 cm 2In the case of a nonwoven fabric having an area capable of having two or more independent areas, the average acicular ratio for each area is calculated, and the average of the calculated average values ​​is further calculated to obtain the average acicular ratio of the nonwoven fabric, etc.

[0044] Alternatively, the nonwoven fabric may have a very large area, e.g., 0.5 m 2 If the nonwoven fabric can have 100 or more independent areas (for example, if a long raw fabric is provided wound on a roll), the needle ratio is measured near the center of the CD direction of the nonwoven fabric, dividing the entire length into 100 equal parts and dividing the area by 0.5 m. 2 Test areas are set up and the test is carried out. For each test area, the average value of the needle ratio of five areas is calculated, and if this average value is 2.94 or less in 90% or more of the area, the needle ratio of the nonwoven fabric is determined to be 2.94 or less, taking into account manufacturing errors, etc. The value of the needle ratio of the nonwoven fabric is the average value of the needle ratios calculated in the test areas where the needle ratio is 2.94 or less.

[0045] The nonwoven fabric of this embodiment is produced by a hydroentanglement method using a specific support, which will be described later. This method makes it difficult for the recesses to have a continuous, elongated shape in the longitudinal direction, and the acicular ratio of the recesses tends to be relatively small on both sides. Furthermore, the direction of the absolute maximum length of the recesses tends to be not parallel to the MD direction of the nonwoven fabric but tilted from the MD direction, which also tends to reduce the acicular ratio.

[0046] The nonwoven fabric of this embodiment has an average acicular ratio of 2.94 or less in the concave portions of the unevenness on both sides. The average acicular ratio may be different on one side and the other side as long as it is 2.94 or less. An average acicular ratio of 2.94 or less results in a smaller stress during elongation and easier elongation than a nonwoven fabric of the same configuration with an average acicular ratio exceeding 2.94. This is thought to be due to the relatively random orientation of the fibers resulting from the fine concave and convex portions of the nonwoven fabric. The average acicular ratio may in particular be 1.80 or greater and 2.94 or less, more in particular 1.90 or greater and 2.90 or less, and even more in particular 2.00 or greater and 2.84 or less.

[0047] In the nonwoven fabric of this embodiment, the irregularities are formed by the water jet marks when the fiber layers are integrated by the hydroentanglement method described below, and are formed by the movement of fibers around the openings of the support on which the fiber web is placed when the water jet is jetted. Therefore, the irregularities are minute, and the area per depression is, for example, 0.05 mm 2 More than 0.35mm 2 Below, especially 0.10 mm 2 More than 0.32mm 2 Below, more particularly 0.15 mm 2 More than 0.30mm 2 Here, the area per recess is the average value of the areas of the recesses measured for the average acicular ratio. 2 The recesses may not have any recesses with an area exceeding 100 mm, may form a uniform flat portion as a whole, and may not have any patterns or designs that exert a design effect. Note that some of the recesses may form openings that penetrate part or all of one recess.

[0048] The nonwoven fabric of this embodiment has a bending resistance of, for example, 0.0010 N m in the machine direction (MD) (the direction in which the machine on the nonwoven fabric production line is arranged (the direction in which the nonwoven fabric travels)), calculated by dividing the sum of the bending resistances measured on the front and back surfaces of the nonwoven fabric when wet using a handle-ometer by the basis weight. 2 / g~0.0044N·m 2 / g, especially 0.0015 N·m 2 / g~0.0035N·m 2 / g, and in the cross direction (CD) (direction perpendicular to the MD), for example, 0.0035 N m 2 / g~0.0090N·m 2 / g, especially 0.0045 N·m 2 / g~0.0078N·m 2 / g. The bending resistance measured with a handle-ometer is an index showing the stiffness (or rigidity) of a nonwoven fabric, and if the value obtained by dividing the bending resistance by the basis weight exceeds the above-mentioned preferable upper limit in each of the longitudinal and transverse directions, the nonwoven fabric becomes too hard and tends to be difficult to use. On the other hand, if the value obtained by dividing the bending resistance by the basis weight is less than the above-mentioned preferable lower limit in each of the longitudinal and transverse directions, the nonwoven fabric lacks stiffness, making it difficult to use, and it is difficult to obtain a firm feel when held in the hand. Furthermore, when used as a skin application sheet, a nonwoven fabric with a small value obtained by dividing the bending resistance measured with a handle-ometer by the basis weight does not provide a feeling of the skin being firmly covered when worn on the skin.

[0049] The nonwoven fabric of this embodiment has a value obtained by dividing the stress at 10% elongation in the cross direction (CD direction) by the basis weight when wet, of, for example, 0.005 N / 5 cm m 2 / g or more 0.0165N / 5cm m 2 / g or less, and in particular 0.008 N / 5 cm m 2 / g or more 0.0150N / 5cm m 2 The nonwoven fabric of this embodiment may have a value of, for example, 0.010 N / 5 cm m / s when wet, calculated by dividing the stress at 20% elongation in the cross direction (CD direction) by the basis weight. 2 / g or more 0.029N / 5cm m 2 / g or less, in particular 0.015 N / 5 cm m 2 / g or more 0.025N / 5cm m 2 / g or less. The value obtained by dividing the stress at 10% elongation by the basis weight is 0.005N / 5cm m 2 / g or the stress at 20% elongation divided by the basis weight is 0.010N / 5cm m 2 If the elongation is less than 0.0165 N / 5 cm m, the sheet will stretch with even a small force, making it difficult to handle. 2 / g or more, or the stress at 20% elongation is 0.029N / 5cm m 2 If the wt. / g is exceeded, the sheet becomes difficult to stretch, which may make it difficult to adhere well to the skin or to attach to a jig.

[0050] [Manufacturing method of laminated nonwoven fabric] The nonwoven fabric of this embodiment is A laminated web is produced by laminating a fibrous web B containing staple fibers having a fiber length of 20 mm or more and 100 mm or less on both surfaces of a fibrous web A containing short fibers having a fiber length of less than 20 mm; and A columnar water stream having a pressure of 1 MPa or more and 10 MPa or less is sprayed onto one or both surfaces of the laminated web 1 to 5 times, At least one of the columnar water jets is a suction water jet, which is performed while placing the laminated web on a support made of a punched metal and sucking the water jet jetted onto the laminated web. It can be produced by a production method.

[0051] Fiber web A is the web that will become fiber layer A, and fiber web B is the web that will become fiber layer B. The types and proportions of fibers contained in fiber webs A and B are as described above in relation to fiber layers A and B. The basis weights of fiber webs A and B are also as described above in relation to fiber layers A and B. The forms of fiber webs A and B are also as described above in relation to fiber layers A and B.

[0052] The hydroentanglement treatment is carried out by placing the laminated fiber web on a support and spraying a columnar water stream onto it. The hydroentanglement treatment may be carried out by spraying water streams at a water pressure of 1 MPa to 10 MPa onto each of the front and back surfaces of the laminated fiber web 1 to 5 times from nozzles having orifices with a hole diameter of 0.05 mm or more and 0.5 mm or less, spaced 0.2 mm or more and 1.5 mm or less. The water pressure is preferably 1 MPa to 10 MPa, more preferably 2 MPa to 7 MPa.

[0053] In the manufacturing method of this embodiment, at least one of the columnar water jets is performed as a suction water jet, in which the laminated web is placed on a support made of perforated metal and the water jetted onto the laminated web is sucked. The perforated metal support is a metal plate with openings formed therein, and the areas between the openings that do not allow the water flow (non-opening areas) are wider than those of, for example, a mesh-like support made of monofilaments woven in a plain weave. This non-opening area, in combination with the suction of the water jet, is thought to relatively randomize the fiber orientation, increasing the proportion of fibers oriented obliquely rather than parallel to the MD direction, resulting in a relatively small average acicular ratio of the concave and convex portions of the nonwoven fabric on both sides.

[0054] The manufacturing method of this embodiment includes drafting the fibrous web at a draft ratio of 1.03 to 1.30 between the preparation of the fibrous web and the spraying of the columnar water stream. Drafting the fibrous web refers to applying tension to the fibrous web between the preparation of the fibrous web and the spraying of the columnar water stream, for example, by increasing the speed of the support conveying the fibrous web when the columnar water stream is sprayed on it compared to the feed speed of the fibrous web. The tension increases with the draft ratio (corresponding to the ratio of the web conveying speed immediately after the web is discharged from the carding machine to the speed immediately after the water stream is sprayed on it). In this embodiment, the draft ratio may be particularly preferably 1.05 to 1.27, more particularly preferably 1.07 to 1.24. For example, in the case of chemical or synthetic fibers with a relatively long fiber length (35 mm or longer), the draft ratio may be particularly preferably 1.05 to 1.25, more particularly preferably 1.07 to 1.16. In the case of natural fibers having a relatively short or variable fiber length, the draft ratio may be particularly from 1.07 to 1.25, more particularly from 1.10 to 1.24. Furthermore, for example, when the fibers constituting fibrous web B are chemical or synthetic fibers having a relatively long fiber length (35 mm or longer), the draft ratio may be particularly from 1.05 to 1.25, more particularly from 1.07 to 1.16. In the case of fibers constituting fibrous web B having a relatively short or variable fiber length (for example, in the case of natural fibers), the draft ratio may be particularly from 1.07 to 1.25, more particularly from 1.10 to 1.24.

[0055] The draft ratio can be adjusted, for example, by creating a difference between the delivery speed of the fibrous web on the production line (e.g., the outlet speed immediately after the web is discharged from the carding machine) and the line speed immediately before the water stream is sprayed, or by pulling the web using a drafter. Drafting of the fibrous web may be carried out throughout the entire process from the production of the fibrous web until the spraying of the columnar water stream, or may be carried out only in some of the processes. When drafting is carried out in some of the processes, the draft ratio is defined as the ratio of the transport speed of the fibrous web at the start of the process to the transport speed of the fibrous web at the end of the process.

[0056] By setting the draft ratio within the above range, the water jet can be sprayed while applying an appropriate tension to the laminated fiber web, improving the adhesion of the fiber web to the support and achieving a uniform nonwoven fabric texture. Drafting tends to align (orient) the fibers in fiber web B in the MD, but fiber web A is less susceptible to drafting because it contains short fibers. In particular, wetlaid papermaking webs or wetlaid papermaking nonwoven fabrics made of pulp fibers are less susceptible to drafting because the pulp fibers are believed to be substantially bonded together by hydrogen bonding. Furthermore, when fiber web A is crepe paper, the wrinkled portions tend to stretch in the MD, and it is believed that only the wrinkled portions stretch during drafting, resulting in little change in fiber orientation. Therefore, in the manufacturing method of this embodiment, even when the draft ratio is within the above range, a nonwoven fabric with a relatively small average needle ratio and good texture can be obtained without excessively orienting the fibers in the MD.

[0057] The suction water jetting may be performed one or more times with one surface of the laminate web in contact with a support made of perforated metal, and one or more times with the other surface of the laminate web in contact with a support made of perforated metal, thereby more reliably randomizing the orientation of the fibers on both surfaces of the nonwoven fabric and more reliably reducing the average acicular ratio of the concaves and convexes on both surfaces.

[0058] The support made of punched metal has an area of ​​0.05 mm 2 Over 3.0mm 2 The openings, each having a diameter of 0.05 mm or less, may be regularly arranged so that the opening ratio of the surface of the support is 7% to 26%. With such a support, the fiber orientation on the surface of the nonwoven fabric can be made random and uniform across the entire surface of the nonwoven fabric. The area per opening is particularly preferably 0.05 mm or less. 2 Over 3.0mm 2 Below, more particularly 0.07 mm 2 Over 1.50mm 2The opening ratio may be particularly 7% or more and 26% or less, more particularly 9% or more and 25% or less. The shape of the opening may be circular, elliptical, triangular, square, rectangular, regular hexagonal, etc., and may be particularly circular.

[0059] For example, a support made of perforated metal may have openings of the same shape and size arranged in a staggered pattern at 45° or 60°. The angle of the staggered arrangement corresponds to the base angle of an isosceles triangle formed by connecting the openings. Such a support can more uniformly spray the suction water flow, making the entire surface of the nonwoven fabric more uniform. Such a support may have, for example, circular openings with a diameter of 0.13 mm to 1.96 mm, arranged in a staggered pattern with a diagonal pitch (the distance between the centers of the openings) of 0.90 mm to 1.50 mm and a horizontal pitch of 0.9 mm to 1.5 mm. Alternatively, a support made of perforated metal may have openings of the same shape and size arranged in a lattice pattern (i.e., the openings are arranged at the intersections of the lattice).

[0060] The water flow is sucked by applying negative pressure to the side of the support made of punched metal opposite to the side on which the nonwoven fabric is placed. The negative pressure may be applied so that the pressure (air pressure) on the side of the support opposite to the side on which the nonwoven fabric is placed is, for example, 2 kPa or more and 20 kPa or less. It is believed that by applying negative pressure to suck the water flow, the water that hits the non-openings flows toward the openings, which randomizes the orientation of the fibers in the non-openings.

[0061] The support made of punched metal may be cylindrical. In this case, the suction of the water flow is performed from the inside of the cylinder. By using a cylindrical support and performing the suction water flow injection from the inside of the cylinder, the device can be simplified, and the fiber web can be easily attached to the support, allowing the fibers to be efficiently entangled.

[0062] In the manufacturing method of this embodiment, before the suction water jetting is performed, a water jet flowing down in a film form may be applied to the laminated web placed on the punched metal. By applying the water jet flowing down in a film form, the adhesion of the laminated web to the punched metal support can be improved during the suction water jetting, and the suction water jetting can be performed more efficiently. The water jet flowing down in a film form may be applied to the laminated web using a flow coater. Furthermore, the water jet flowing down in a film form may be sucked by negative pressure, which further improves the adhesion of the laminated web to the punched metal support. The negative pressure may be, for example, 2 kPa or more and 20 kPa or less.

[0063] In addition to suction water jetting, the hydroentanglement treatment may include placing the laminated web on a support other than a punched metal support, such as a plain weave support with a warp diameter of 0.05 mm to 0.2 mm, a weft diameter of 0.05 mm to 0.2 mm, and a mesh count of 70 to 110 (for example, a plain weave support with a mesh count of 80 to 100 mesh formed by weaving monofilaments in a plain weave), and spraying a columnar water jet onto the support (hereinafter referred to as "non-punched metal water jetting" for convenience). Non-punched metal water jetting may be performed to further entangle the fibers and / or to improve the texture of the nonwoven fabric. During non-punched metal water jetting, the water jet may be suctioned as necessary.

[0064] In the manufacturing method of this embodiment, non-punched metal water jetting may be performed on one side of the laminate web, and suction water jetting may be performed on the other side. Alternatively, non-punched metal water jetting and suction water jetting may be performed on one side of the laminate web. In either case, non-punched metal water jetting may be performed either before or after suction water jetting. By performing suction water jetting first, it is possible to randomize the fiber orientation in a web state where the fibers are loosely bound to each other, making it easier to produce a nonwoven fabric with an needle ratio within the above range. If suction water jetting is performed later, the laminate web is more likely to adhere to each other during suction water jetting, the water flow is more efficiently sucked in, and the random fiber orientation due to the suction of the water flow is more likely to be obtained. Alternatively, in the manufacturing method of this embodiment, only the suction water jetting may be performed.

[0065] In both suction water jetting and non-punched metal water jetting, the water jet may be jetted from a nozzle having orifices with a hole diameter of 0.05 mm or more and 0.5 mm or less, spaced at intervals of 0.2 mm or more and 1.5 mm or less. The distance between the nozzle and the web may be, for example, 3 mm to 100 mm, and particularly 5 mm to 50 mm.

[0066] The nonwoven fabric of this embodiment described above or a nonwoven fabric produced by the production method of this embodiment is particularly suitable for applications in which it is impregnated with a liquid, such as skin application sheets, wet wipes, disposable hand towels, and patches.

[0067] When the nonwoven fabric of this embodiment is impregnated with a liquid to be used as a liquid-impregnated skin-covering sheet for personal use, such as a face mask, an exfoliating sheet, or a décolleté sheet, the nonwoven fabric may be impregnated with a liquid containing an active ingredient (e.g., a cosmetic) in an amount of 500 to 2000 parts by mass, particularly 600 to 1800 parts by mass, and more particularly 700 to 1500 parts by mass, per 100 parts by mass of the nonwoven fabric. Examples of active ingredients include, but are not limited to, moisturizing ingredients, exfoliating ingredients, antiperspirant ingredients, fragrance ingredients, whitening ingredients, blood circulation-promoting ingredients, UV protection ingredients, and slimming ingredients.

[0068] The face mask is provided in a shape suitable for covering the face, and further has openings or cutouts formed by punching, for example, in areas corresponding to the eyes, nose, and mouth, as needed. Alternatively, the face mask may be shaped to cover only a portion of the face (for example, the eyes, mouth, nose, or cheeks). Alternatively, the face mask may be provided as a set consisting of a sheet that covers the area around the eyes and a sheet that covers the area around the mouth, or as a set of sheets that separately cover three or more areas.

[0069] The exfoliating sheet is a skin covering sheet used on areas such as the heels, elbows, and knees where the keratin is thick and prone to hardening. By impregnating it with a liquid containing a keratin softening component and a moisturizing component, it exhibits the effect of promoting moisturizing and softening of the keratin, or the effect of promoting the removal of excess keratin. The nonwoven fabric of this embodiment can be used as a substrate for exfoliating sheets that exhibit either of these effects and efficacy. Exfoliating sheets, for example, exfoliating sheets for the heel, are provided in a form with slits and / or notches and / or openings punched out in parts of the sheet so that the sheet can easily conform to the curve of the heel when applied.

[0070] The liquid-impregnated skin covering sheet may be a moisturizing sheet impregnated with a liquid containing a moisturizing ingredient or other active ingredient, which is used to moisturize or otherwise care for any part of the body (for example, the neck, the back of the hands, or the area from the neck to the chest (also known as the décolleté)). Alternatively, the liquid-impregnated skin covering sheet may be a slimming sheet impregnated with a liquid containing a slimming ingredient. The slimming sheet is used by being attached to the thighs or abdomen, for example.

[0071] When the nonwoven fabric of this embodiment is used as a wet wiper, a disposable hand towel, or the like, it may be impregnated with water or an aqueous solution containing a cleaning component in an amount of 100 to 1,000 parts by mass per 100 parts by mass of the nonwoven fabric. The amount of impregnation may be 150 parts by mass or more, 700 parts by mass or less, or 500 parts by mass or less per 100 parts by mass of the nonwoven fabric.

[0072] Wet wipers may be for either personal use or for object use. When used for personal use, they can be used as wet tissues or baby wipes. When used for object use, they may be used to wipe floors, kitchens, toilets, bathtubs, furniture, vehicles, walls, screen doors, window glass, etc. Object wipers may be used by attaching them to a jig having a wiper attachment part at the end of a rod-shaped object. [Example]

[0073] The present embodiment will be described below with reference to examples. [Fiber layer A (fiber web A)] As a constituent of the fiber layer A, the following wetlaid nonwoven fabric was prepared. Wetlaid nonwoven fabric 1: A mixture of chemical pulp made from softwood and hardwood, with a basis weight of 17 g / m and 100% pulp by mass. 2 A wet-laid nonwoven fabric was prepared. The pulp had a length-weighted average fiber width of 29.1 μm and a length-weighted average fiber length of 1.43 mm. The mechanical properties of the wetlaid nonwoven fabric 1 are as follows: [Table 1]

[0074] [Staple fiber] As staple fibers constituting the fiber layer B, the following fibers were prepared. Rayon 1: Rayon with a fineness of 1.7 dtex and a fiber length of 40 mm (manufactured by Lenzing, product name SPV) Cotton: Length-weighted average fiber length of 23 mm (Marusan Sangyo Co., Ltd., product name: MSD Cotton) PET fiber: Single fiber made of polyethylene terephthalate with a fineness of 1.45 dtex and a fiber length of 38 mm (manufactured by Toray Industries, Inc., product name: T403D)

[0075] Example 1 A blend of 80% rayon and 20% PET fiber, with a target weight of 21.5 g / m 2Fiber web B was produced using a semi-random carding machine. This fiber web B was placed on both surfaces of wetlaid nonwoven fabric 1, which was fiber web A, to produce a laminated web, and this laminated web was subjected to a hydroentanglement treatment. The hydroentanglement treatment was carried out by transporting the laminated fiber web on a cylindrical support made of a punched metal with an opening ratio of 10% and circular openings with a hole diameter of 0.35 mm arranged in a 60° staggered pattern at a pitch of 1.05 mm. First, a columnar water stream at a water pressure of 3.5 MPa was sprayed once onto one side of the laminated fiber web from a nozzle with 0.12 mm orifices spaced 1.0 mm apart, and a columnar water stream at a water pressure of 5.0 MPa was sprayed once onto the other side from a nozzle with 0.13 mm orifices spaced 1.0 mm apart, and a columnar water stream at a water pressure of 4.5 MPa was sprayed once onto the other side from a nozzle with 0.10 mm orifices spaced 0.6 mm apart. The water streams were sprayed from the inside of a cylindrical support while suctioning at a negative pressure of 11 kPa when spraying onto one side, and while suctioning at a negative pressure of 5.0 kPa when spraying onto the other side. The hydroentanglement treatment was carried out while rotating the cylindrical support so that the conveying speed of the laminated web was 58 m / min, and the draft ratio, which is the ratio of the conveying speed of the laminated web during the hydroentanglement treatment to the supply speed of the laminated web, was set to 1.12.

[0076] Example 2 Using only rayon 1, basis weight 21.5g / m 2Fiber web B was produced using a semi-random carding machine. This fiber web B was placed on both surfaces of wetlaid nonwoven fabric 1, which was fiber web A, to produce a laminated web, and this laminated web was subjected to a hydroentanglement treatment. The hydroentanglement treatment was carried out by conveying the laminated fiber web on a cylindrical support made of the same punched metal as used in Example 1, and spraying a columnar water stream at a water pressure of 4.0 MPa once from a nozzle having 0.10 mm orifices spaced 0.6 mm apart on one side, and a columnar water stream at a water pressure of 3.5 MPa once from a nozzle having 0.12 mm orifices spaced 0.6 mm apart on the other side. Then, spraying a columnar water stream at a water pressure of 3.5 MPa once from a nozzle having 0.13 mm orifices spaced 1.0 mm apart on the other side, and a columnar water stream at a water pressure of 4.0 MPa once from a nozzle having 0.10 mm orifices spaced 0.6 mm apart on the other side. The water jet was sprayed from inside the cylindrical support while suctioning at a negative pressure of 11 kPa when spraying onto one surface, and while suctioning at a negative pressure of 5.0 kPa when spraying onto the other surface. The hydroentanglement treatment was carried out while rotating the cylindrical support so that the transport speed of the laminated web was 51.8 m / min, and the draft ratio, which is the ratio of the transport speed of the laminated web during the hydroentanglement treatment to the feed speed of the laminated web, was set to 1.12.

[0077] (Comparative Example 1) A blend of 80% rayon and 20% PET fiber, with a target weight of 21.5 g / m 2 Fiber web B was produced using a parallel carding machine. This fiber web B was placed on both surfaces of wetlaid nonwoven fabric 1, which was fiber web A, to produce a laminated web, and this laminated web was subjected to a hydroentanglement treatment. The hydroentanglement treatment was carried out by placing the laminated web on a 90-mesh plain weave support and transporting it at a speed of 4 m / min, spraying a water stream at a water pressure of 3 MPa once on one side of the web and once on the other side, followed by a drying treatment to obtain a laminated nonwoven fabric. The water stream was sprayed from a nozzle equipped with orifices with a hole diameter of 0.12 mm spaced 0.6 mm apart. No draft was applied to the fiber web during the water stream spraying.

[0078] (Comparative Example 2) Using only rayon 1, basis weight 21.5g / m 2 A laminated nonwoven fabric was produced in the same manner as in Comparative Example 1, except that the fiber web B was produced using a parallel carding machine.

[0079] (Comparative Example 3) Using only cotton, the target weight is 21.5g / m 2 A laminated nonwoven fabric was produced in the same manner as in Comparative Example 1, except that the fiber web B was produced using a parallel carding machine.

[0080] The evaluation of the nonwoven fabrics was carried out as follows. In each example and comparative example, samples for measuring the standard and wet physical properties and the wet bending resistance were produced separately using the above-mentioned methods. Therefore, the nonwoven fabrics used for each measurement were from different production lots, which resulted in some variation. Therefore, the basis weight and other properties of the nonwoven fabrics used for each evaluation are listed in the columns for each measurement. <Thickness and bulk density of nonwoven fabric> The thickness of the nonwoven fabric was measured using a thickness gauge (THICKNESS GAUGE Model CR-60A (trade name) manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd.) with a load of 0.3 kPa applied to the nonwoven fabric. The bulk density was calculated from the thickness and basis weight when a load of 0.3 kPa was applied.

[0081] <Tensile strength, elongation> Tensile strength was measured in accordance with JIS L 1913:2010 6.3 using a constant-speed tension tensile tester with dry samples under conditions of 5 cm sample width, 10 cm grip spacing, and a tensile speed of 30±2 cm / min. The load at break (tensile strength), elongation, and stress at 10% elongation (the force required to elongate by 10%) and 20% elongation were measured. Tensile tests were conducted in both the machine direction (MD) and cross direction (CD) of the nonwoven fabric. Evaluation results are shown as the average of values ​​measured for three samples. The wet measurement was carried out by impregnating 100 parts by mass of the sample with 250 parts by mass of distilled water.

[0082] <Bending resistance> The bending resistance of the nonwoven fabric was measured in accordance with JIS L 1096:2010 8.21.5 E method (handle-o-meter method). Specifically, the measurement was performed according to the following procedure. A sample piece measuring 20 cm in length and 20 cm in width is placed on the sample stage so that the measurement direction of the sample piece is perpendicular to the slot (gap width 10 mm). Next, the blade of the penetrator, adjusted to be 8 mm below the surface of the sample stage, is lowered, and the specimen is pressed into it. The resistance to the pressing is read at different locations on the front and back of the specimen in the MD and CD directions in the numerical order shown in Figure 3 (the dotted lines in Figure 3 indicate the back). The maximum value (cN) indicated by the microammeter is read as the resistance value. The resistance reading is taken three times for each position, and the average of these readings is used as the bending resistance (N) of the surface in the MD direction, the bending resistance of the back surface in the CD direction, and the bending resistance of the back surface in the MD direction when the specimen is dry. In this example, the wet bending resistance was measured by impregnating 100 parts by mass of nonwoven fabric with 500 parts by mass of distilled water, placing a polyethylene sheet (23 cm long, 23 cm wide, 0.06 mm thick) under the nonwoven fabric, and subtracting the bending resistance of the polyethylene sheet alone from the measured value. In this example, 1) the value obtained by dividing the sum (total) of all the surface stiffnesses obtained as described above by the basis weight, 2) the value obtained by dividing the sum of the surface stiffnesses in the MD direction and the back surface stiffnesses in the MD direction obtained as described above by the basis weight, and 3) the value obtained by dividing the sum of the surface stiffnesses in the CD direction and the back surface stiffnesses in the CD direction by the basis weight were calculated.

[0083] <Average acicular ratio of recesses> Using the image analysis software "WinROOF2018" manufactured by Mitani Shoji Co., Ltd., the following steps were carried out for each of the two sides of the nonwoven fabric: gray imaging → median → automatic binarization → shrinkage → deletion → exclusive expansion → image processing of shape features. Measurements were carried out on a 60 cm section of nonwoven fabric.2 Two 25 mm × 25 mm regions were selected for each test, and the test was performed on the two regions. The average value of the acicular ratios of the recesses measured in all regions was taken as the average acicular ratio.

[0084] The evaluation results of each example and each comparative example are shown in Table 2. Micrographs of the surface of the nonwoven fabric obtained in Example 1 and the surface of the nonwoven fabric obtained in Comparative Example 1 are shown in Figs.

[0085] [Table 2]

[0086] The nonwoven fabrics of Examples 1 and 2 had an average acicular ratio of 2.94 or less on both surfaces. In contrast, the nonwoven fabrics of Comparative Examples 1 to 3 had an average acicular ratio exceeding 2.94 on both surfaces or on one of the surfaces. Furthermore, when Example 1 and Comparative Example 1, and Example 2 and Comparative Example 2, which had the same fiber layer configuration, were compared, the values ​​of the stress at 10% and 20% elongation in the wet state divided by the basis weight were all smaller in the Examples. This difference is thought to be due to the fact that all Examples were produced by a method involving suction water jet injection using a punched metal support, which resulted in a different fiber entanglement state and a different average acicular ratio compared to Comparative Examples produced without such a support. Example 1, which contains synthetic fibers in fiber layer B, exhibited a higher bending resistance than Example 2. However, when Comparative Example 1, which contains synthetic fibers, was compared with Comparative Example 2, which does not contain synthetic fibers, little difference in bending resistance was observed, suggesting that the characteristics of synthetic fibers are more readily apparent in the Examples. Example 2 exhibited a smaller bending resistance and was softer than Comparative Example 2 having the same fiber layer structure.

[0087] The present embodiment includes the following aspects. (Aspect 1) A laminated nonwoven fabric in which a fiber layer A containing short fibers with a fiber length of less than 20 mm and a fiber layer B containing staple fibers with a fiber length of 20 mm or more and 100 mm or less are positioned on both surfaces of the fiber layer A, and the fiber layer A and the fiber layer B are integrated by entanglement, Both surfaces of the laminated nonwoven fabric have irregularities, On both surfaces of the laminated nonwoven fabric, the average needle ratio of the recesses of the unevenness is 2.94 or less. Laminated nonwoven fabric. (Aspect 2) The laminated nonwoven fabric of aspect 1, wherein the fiber layer A contains 50% by mass or more of the short fibers, and the fiber layer B contains 50% by mass or more of the staple fibers. (Aspect 3) 3. The laminated nonwoven fabric of aspect 1 or 2, wherein the fiber layer A contains pulp as the short fibers. (Aspect 4) The laminated nonwoven fabric of any one of Aspects 1 to 3, wherein the fibrous layer A is a wetlaid nonwoven fabric. (Aspect 5) 5. The laminated nonwoven fabric of any one of Aspects 1 to 4, wherein the staple fibers are cellulosic fibers. (Aspect 6) The fiber layer A has a basis weight of 10 g / m 2 More than 40g / m 2 the fiber layer B has a basis weight of 10 g / m or less 2 More than 50g / m 2 A laminated nonwoven fabric according to any one of Aspects 1 to 5, which is as follows: (Aspect 7) A wet laminated nonwoven fabric, in which the laminated nonwoven fabric according to any one of aspects 1 to 6 is impregnated with a liquid. (Aspect 8) A face mask, comprising the laminated nonwoven fabric according to any one of Aspects 1 to 6 impregnated with a liquid. (Aspect 9) A laminated web is produced by laminating a fibrous web B containing staple fibers having a fiber length of 20 mm or more and 100 mm or less on both surfaces of a fibrous web A containing short fibers having a fiber length of less than 20 mm; and A columnar water stream having a pressure of 1 MPa or more and 10 MPa or less is sprayed onto one or both surfaces of the laminated web 1 to 5 times, At least one of the columnar water jets is a suction water jet, which is performed while placing the laminate web on a support made of a punched metal and sucking the water jet sprayed onto the laminate web. A method for manufacturing a laminated nonwoven fabric. (Aspect 10) A method for producing a laminated nonwoven fabric according to aspect 9, wherein the suction water stream spraying is performed one or more times with one surface of the laminate web in contact with the support made of the perforated metal, and the suction water stream spraying is performed one or more times with the other surface of the laminate web in contact with the support made of the perforated metal. (Aspect 11) The support made of the punched metal has an area of ​​0.05 mm 2 Over 3.00mm 2 The method for producing a laminated nonwoven fabric according to aspect 9 or 10, wherein the openings having the following properties are regularly arranged so that the open area ratio of the surface of the support is 7% or more and 26% or less. (Aspect 12) 12. The method for producing a laminated nonwoven fabric according to any one of aspects 9 to 11, wherein the support made of punched metal has openings of the same shape and size arranged in a staggered pattern. (Aspect 13) 13. The method for producing a laminated nonwoven fabric according to any one of Aspects 9 to 12, wherein in the suction water jetting, the support made of the punched metal has a cylindrical shape, and the water jet is sucked from inside the cylinder. [Industrial Applicability]

[0088] The laminated nonwoven fabric of the present disclosure has a laminated structure in which a staple fiber-containing fiber layer A is flanked on both surfaces by a staple fiber-containing fiber layer B, and the average needle ratio of the concave portions of the uneven surface of the nonwoven fabric is 2.94 or less, and the fabric has a relatively high bending resistance in a wet state and can be stretched with a relatively small force. Therefore, the laminated nonwoven fabric of the present disclosure can provide a user-friendly product when used as a liquid-impregnated skin application sheet or wet wipes, which are used by impregnating with a liquid.

Claims

1. A laminated web is produced by laminating a fibrous web B containing staple fibers having a fiber length of 20 mm or more and 100 mm or less on both surfaces of a fibrous web A containing short fibers having a fiber length of less than 20 mm; and A water column having a pressure of 1 MPa or more and 10 MPa or less is sprayed onto one or both surfaces of the laminated web 1 to 5 times, At least one of the columnar water jets is a suction water jet that is performed while the laminate web is placed on a support made of a punched metal and the water jet that has been jetted onto the laminate web is sucked, The support made of the punched metal has openings, each having an area of ​​0.05 mm 2 or more and 3.00 mm 2 or less, regularly arranged so that the opening ratio of the support surface is 7% or more and 26% or less. A method for manufacturing a laminated nonwoven fabric.

2. 2. The method for producing a laminated nonwoven fabric according to claim 1, wherein the suction water stream spraying is carried out one or more times with one surface of the laminated web in contact with the support made of the punched metal, and one or more times with the other surface of the laminated web in contact with the support made of the punched metal.

3. The method for producing a laminated nonwoven fabric according to claim 1, wherein the support made of the perforated metal has openings of the same shape and size arranged in a staggered pattern.

4. 2. The method for producing a laminated nonwoven fabric according to claim 1, wherein in the suction water jetting, the support made of the punched metal is cylindrical, and the water jet is sucked from the inside of the cylinder.

5. A method for manufacturing a laminated nonwoven fabric as described in claim 1, wherein the fiber web A contains 50% by mass or more of the short fibers, and the fiber web B contains 50% by mass or more of the staple fibers.

6. A method for manufacturing a laminated nonwoven fabric as described in claim 1, wherein the fiber web A contains pulp as the short fibers.

7. A method for manufacturing a laminated nonwoven fabric as described in claim 1, wherein the fiber web A is a wet-laid nonwoven fabric.

8. A method for producing a laminated nonwoven fabric as described in claim 1, wherein the staple fibers are cellulosic fibers.

9. A method for manufacturing a laminated nonwoven fabric as described in claim 1, wherein the fiber web A has a basis weight of 10 g / m 2 or more and 40 g / m 2 or less, and the fiber web B has a basis weight of 10 g / m 2 or more and 50 g / m 2 or less.

10. A method for manufacturing a laminated nonwoven fabric as described in claim 1, comprising a step of creating a difference between the feed speed of the fiber web and the line speed until just before the water flow is sprayed, or a step of pulling the web using a drafter.

11. A method for manufacturing a laminated nonwoven fabric as described in claim 1, wherein the fiber web A is crepe paper made of pulp.

12. A method for manufacturing a laminated nonwoven fabric as described in claim 1, comprising a step of directing a water flow flowing down in a film-like manner onto a laminated web placed on the punching metal before performing the suction water flow injection.

13. A method for manufacturing a laminated nonwoven fabric as described in claim 1, which includes, in addition to the suction water flow injection, a step of placing the laminated web on a support other than the punched metal and spraying a columnar water flow onto it.

14. A method for manufacturing a laminated nonwoven fabric as described in Claim 13, wherein the support other than the punched metal is a plain weave support having a warp thread diameter of 0.05 mm to 0.2 mm, a weft thread diameter of 0.05 mm to 0.2 mm, and a mesh number of 70 to 110 meshes.

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