JP7560414B2 - Nonwoven fabric for liquid-impregnated skin covering sheet and manufacturing method thereof, liquid-impregnated skin covering sheet, and face mask - Google Patents

Description

This disclosure relates to a nonwoven fabric that serves as the base material for a liquid-impregnated skin covering sheet that is impregnated with a liquid, particularly a cosmetic product, and a method for producing the same, as well as a liquid-impregnated skin covering sheet and a face mask that use the nonwoven fabric.

A variety of liquid-impregnated sheets have been proposed and put into practical use for covering the skin of humans or animals and applying a specific substance to the skin of humans or animals. Specific examples include liquid-impregnated skin covering sheets (face masks and keratin care sheets used on heels, elbows, knees, etc.) that are impregnated with a liquid (e.g., cosmetics) containing active ingredients. Nonwoven fabrics are generally used as the substrate for liquid-impregnated skin covering sheets. Since liquid-impregnated skin covering sheets are often used in contact with the skin for a relatively long period of time, various nonwoven fabrics have been proposed as the substrate from the viewpoints of adhesion, liquid release, tactile feel, convenience, transparency when in contact with the skin, etc.

For example, Patent Document 1 proposes a sheet using transparent fibers as a liquid-retaining sheet with high transparency in a wet state, and discloses examples using regenerated cellulose fibers and solvent-spun cellulose fibers, as well as polyester fibers, that do not contain titanium oxide or contain titanium oxide at a ratio of 0.1 mass% or less. Patent Document 2 proposes the use of a nonwoven fabric containing two types of cellulose fibers with a degree of polymerization within a specific range as a nonwoven fabric that has high liquid retention and excellent visibility of stains after use, and shows a combination of rayon and lyocell as a combination of the two types of cellulose fibers. Patent Document 3 proposes a nonwoven fabric containing a cellulose-based mixed fiber in which cellulose-based fibers that meet specific conditions are thermally bonded by a thermally adhesive fiber, with the aim of improving high transparency and handleability.

International Publication No. 2013/187404 JP 2016-69762 A Patent No. 6587608 Patent No. 6093487

The present disclosure aims to provide a nonwoven fabric that can provide a liquid-impregnated skin application sheet that exhibits good adhesion to the skin when impregnated with liquid.

According to one aspect of the present disclosure, a first cellulosic fiber having a wet strength of 1.5 cN/dtex or more and/or a wet apparent Young's modulus of 1000 N/mm2 ^{or more} ;
and a second cellulosic fiber having a wet strength of 1.2 cN/dtex or less and/or a wet apparent Young's modulus of 930 N/mm2 ^or less;
The cellulosic fiber layer contains the first cellulosic fibers in a ratio of 5% by mass or more and 50% by mass or less,
The cellulosic fiber layer contains the second cellulosic fibers in a proportion of 30% by mass or more and 95% by mass or less,
In the cellulosic fiber layer, a combined ratio of the first cellulosic fiber and the second cellulosic fiber is 80 mass% or more of the total fibers constituting the cellulosic fiber layer,
The cellulosic fiber layer has a basis weight of 40 g/m2 ^or more.
A nonwoven fabric for a liquid-impregnated skin covering sheet is provided.

According to another aspect of the present disclosure, a fabrication method includes providing a fabrication method for a fabrication method comprising: ...
The first cellulosic fiber is a solvent-spun cellulosic fiber having an ash content of 0.5% by mass or less;
The second cellulosic fiber is selected from the group consisting of the following (1) to (3):
(1) A viscose rayon having a single cross section and a degree of irregularity of the cross section calculated by the following formula of 2.0 or less.
Roughness = L ² / (4π・S)
(In the formula, L is the perimeter of the cross section, and S is the area of the cross section.)
(2) Viscose rayon having a single cross section and a cross-sectional outline that is circular, elliptical, or spherical, or a circular, elliptical, or spherical shape with a slit;
(3) The cross section has a single structure, and the flatness of the cross section calculated by the following formula is 1.80 or more, and the unevenness of the cross section calculated by the following formula is 2.50 or less. Viscose rayon flatness = a/b
(In the formula, a is the length of the longest line segment A connecting any two points on the cross section, and b is the length of a line segment that is perpendicular to line segment A and, together with a line segment parallel to line segment A, constitutes a rectangle or square circumscribing the cross section.)
Roughness = L ² / (4π・S)
(In the formula, L is the perimeter of the cross section, and S is the area of the cross section.)
One or more viscose rayons selected from
The cellulosic fiber layer contains the first cellulosic fibers in a ratio of 5% by mass or more and 50% by mass or less,
The cellulosic fiber layer contains the second cellulosic fibers in a proportion of 30% by mass or more and 95% by mass or less,
In the cellulosic fiber layer, a combined ratio of the first cellulosic fiber and the second cellulosic fiber is 80 mass% or more of the total fibers constituting the cellulosic fiber layer,
The cellulosic fiber layer has a basis weight of 40 g/m2 ^or more.
A nonwoven fabric for a liquid-impregnated skin covering sheet is provided.

According to yet another aspect of the present invention, there is provided a method for producing a sheet-like laminate comprising the steps of: providing a sheet-like laminate made of a first cellulosic fiber; and providing a sheet-like laminate made of a second cellulosic fiber having a lower wet strength and/or wet apparent Young's modulus than the first cellulosic fiber;
The cellulosic fiber layer contains the first cellulosic fibers in a ratio of 5% by mass or more and 50% by mass or less,
The cellulosic fiber layer contains the second cellulosic fibers in a proportion of 30% by mass or more and 95% by mass or less,
In the cellulosic fiber layer, a combined ratio of the first cellulosic fiber and the second cellulosic fiber is 80% by mass or more of the total fibers constituting the cellulosic fiber layer,
The present invention provides a nonwoven fabric for a liquid-impregnated skin application sheet, in which the variation in average friction coefficient in the CD direction of the surface of the cellulosic fiber layer in a wet state is 0.013 or less, and the adhesion force after 15 minutes measured on the surface of the cellulosic fiber layer is 180 gf or more .

The nonwoven fabric for liquid-impregnated skin application sheets disclosed herein can provide a liquid-impregnated skin application sheet that has excellent adhesion in a wet state, is smooth to the touch, and is easy to handle.

1 is an electron microscope photograph showing a cross section of cellulosic fiber A used in the examples and comparative examples. 1 is an electron microscope photograph showing a cross section of cellulosic fiber B used in the examples and comparative examples. 1 is an electron microscope photograph showing a cross section of cellulosic fiber C used in the examples or comparative examples. 1 is an electron microscope photograph showing a cross section of cellulosic fiber D used in the examples or comparative examples. 1 is an electron microscope photograph showing a cross section of cellulosic fiber E used in the examples and comparative examples.

(How the present embodiment was arrived at)
As described above, various structures of the substrate and the fibers constituting the substrate of the liquid-impregnated skin-covering sheet (hereinafter also simply referred to as "sheet") have been proposed. The sheet often contains hydrophilic fibers so that the sheet can be impregnated with liquid, and the hydrophilic fibers generally used are industrially mass-produced cellulosic fibers (e.g., rayon, lyocell, etc.) and natural cellulosic fibers such as cotton.

There are various types of cellulose fibers due to differences in their manufacturing methods, and the above-mentioned Patent Documents 1 to 3 attempt to obtain the desired nonwoven fabric by using specific cellulose fibers. For example, Patent Document 4 proposes a viscose rayon having a specific cross-sectional shape, and describes that the use of this viscose rayon can provide a liquid-impregnated sheet that provides a higher level of transparency in a wet state.
Thus, attempts have been made to obtain nonwoven fabrics that exhibit desired performance using particular cellulosic fibers, or by combining one cellulosic fiber with another or other fiber, or by creating particular configurations of layers that include cellulosic fibers.

The present inventors have conducted extensive research to obtain a nonwoven fabric that has high adhesion in a wet state without adopting a laminated structure, can be provided as a relatively thick sheet, and has a high proportion of cellulosic fibers. Improved adhesion is always required by consumers to prevent the sheet from peeling off from the skin. In addition, thickening the sheet has the following advantages: 1) it can hold a larger amount of liquid, and 2) it feels firm when held in the hand, making it easy to handle even in a wet state.
The above-mentioned Patent Documents 1 to 4 propose configurations from the viewpoint of improving transparency and visibility of dirt, but no particular consideration has been given to adhesion.

The inventors have found that adhesion is related to the wet physical properties of cellulosic fibers, particularly strength and/or apparent Young's modulus, and that by using cellulosic fibers with smaller wet strength and/or smaller wet apparent Young's modulus, a sheet exhibiting high adhesion can be obtained, especially in a state where the liquid content is reduced compared to when the product is opened. On the other hand, when cellulosic fibers with small wet strength are used, the nonwoven fabric tends to become extremely soft and difficult to handle, and the strength also tends to decrease. Therefore, when cellulosic fibers with small wet strength are combined with cellulosic fibers with higher wet strength and/or wet apparent Young's modulus, it was found that the nonwoven fabric can obtain high adhesion without becoming excessively soft, even when it contains a relatively high proportion of cellulosic fibers with small wet strength, and this has led to the present embodiment.

The nonwoven fabric of this embodiment contains a specific first cellulosic fiber and a specific second cellulosic fiber. These fibers will be described first below.

(First cellulosic fiber)
The first cellulose fiber has a higher wet strength than the second cellulose fiber, and may be a cellulose fiber having a wet strength of 1.5 cN/dtex or more. The wet strength is measured according to JIS L 1015 8.7 (tensile strength and elongation): 2010. The first cellulose fiber plays a role of an "aggregate" due to its high strength. The first cellulose fiber can impart strength and stiffness to the nonwoven fabric without impairing the improvement in adhesion by the second cellulose fiber by preventing the nonwoven fabric from becoming excessively soft and losing its strength due to the use of the low-strength, soft second cellulose fiber.

Alternatively, the first cellulosic fiber may be a cellulosic fiber having a wet apparent Young's modulus greater than that of the second cellulosic fiber, for example, a wet apparent Young's modulus of 1000 N/mm2 or ^more . By using a cellulosic fiber having a large wet apparent Young's modulus as the first cellulosic fiber, strength and stiffness can be imparted to the nonwoven fabric, as in the case of a cellulosic fiber having a large wet strength. The wet apparent Young's modulus is measured according to JIS L 1015 8.11 (initial tensile resistance): 2010.

The wet strength of the first cellulosic fiber may be, in particular, 2.1 cN/dtex or more, more particularly 2.2 cN/dtex or more, and the upper limit may be, for example, 5.0 cN/dtex, in particular 4.0 cN/dtex, more particularly 2.9 cN/dtex. If the wet strength is less than 1.5 cN/dtex, the strength of the nonwoven fabric may not be improved.

The wet apparent Young's modulus of the first cellulosic fiber may be particularly 1500 N/mm ² or more, more particularly 2000 N/mm ² or more, and the upper limit may be, for example, 5000 N/mm ² , particularly 4000 N/mm ² , more particularly 3200 N/mm ^2. If the wet apparent Young's modulus strength is less than 1000 N/mm ² , the strength of the nonwoven fabric may not be improved.

The first cellulose fiber has a larger apparent Young's modulus in dry state than the second cellulose fiber described later, and the apparent Young's modulus in dry state may be, for example, 8000 N/mm ² or more. By using a cellulose fiber having a large apparent Young's modulus in dry state as the first cellulose fiber, strength and stiffness can be imparted to the nonwoven fabric, as in the case of a fiber having a large wet strength. The apparent Young's modulus in dry state of the first cellulose fiber may be, in particular, 8200 N/mm ² or more, more particularly, 8300 N/mm ² or more. The upper limit of the apparent Young's modulus in dry state is, for example, 12000 N/mm ² , in particular 11000 N/mm ² , and more particularly 10000 N/mm ² .

The first cellulosic fiber has a higher dry strength than the second cellulosic fiber described below, and the dry strength may be, for example, 2.5 cN/dtex or more, particularly 2.6 cN/dtex or more, and more particularly 2.7 cN/dtex or more, with the upper limit being, for example, 4.8 cN/dtex, particularly 4.5 cN/dtex, and more particularly 4.0 cN/dtex. If the dry strength is less than 2.5 cN/dtex, the strength of the nonwoven fabric may not be improved.

The first cellulose fiber may have an ash content of 0.5% by mass or less, and may be substantially free of inorganic substances such as colorants (pigments), such as titanium oxide. Titanium oxide is a matting agent used to suppress the luster of fibers, and not including titanium oxide can increase the transparency of the nonwoven fabric. Furthermore, if the ash content, i.e., the content of inorganic compounds, of the first cellulose fiber is low, the transparency of the nonwoven fabric can be increased. Furthermore, cellulose fibers with low ash content tend to be highly hydrophilic, and can further improve the liquid retention of the nonwoven fabric. The ash content of the first cellulose fiber may be particularly 0.35% by mass or less, more particularly 0.3% by mass or less. The ash content is measured in accordance with JIS L 1015 8.20 (ash content): 2010.

The first cellulose fiber may be, for example, a solvent-spun cellulose such as lyocell. Solvent-spun cellulose fibers are commercially available under the names TencelSkin (trade name) and Lentin Glyocell (trade name). Of these, TencelSkin (trade name) does not contain titanium oxide and has an ash content of 0.2% by mass or less, and therefore, when used, it is possible to improve the transparency of the nonwoven fabric in both dry and wet states.

The fineness of the first cellulosic fiber may be, for example, 0.6 dtex or more and 3.3 dtex or less, particularly 1.0 dtex or more and 2.5 dtex or less, and more particularly 1.4 dtex or more and 2.2 dtex or less. If the fineness of the first cellulosic fiber is too small, the voids in the cellulosic fiber layer will be small, making it difficult for the nonwoven fabric to retain liquid, and if it is too large, the feel of the nonwoven fabric may be reduced. The fineness of the first cellulosic fiber is not limited to these ranges.

The fiber length of the first cellulose fiber is not particularly limited and may be appropriately selected depending on the manufacturing method of the nonwoven fabric. For example, when the cellulose fiber layer is manufactured by preparing a card web in the manufacturing of the nonwoven fabric, the first cellulose fiber may be a short fiber. The fiber length of this short fiber may be, for example, 20 mm or more and 100 mm or less, particularly 28 mm or more and 75 mm or less, and more particularly 30 mm or more and 65 mm or less. Alternatively, when the first fiber layer is manufactured by an air-laying method, the fiber length may be, for example, 2 mm or more and 20 mm or less.
In this embodiment, a plurality of types of cellulosic fibers differing in one or more of material, fiber length, and fineness may be used as the first cellulosic fibers.

(Second Cellulosic Fiber)
The second cellulosic fiber may be a cellulosic fiber having a wet strength less than that of the first cellulosic fiber, for example, a wet strength of 1.2 cN/dtex or less. The second cellulosic fiber, which has low strength and is therefore soft, can improve the adhesion of the nonwoven fabric and make the surface of the nonwoven fabric smooth.
The adhesion of a nonwoven fabric corresponds to the property of the nonwoven fabric tending to remain on an object to which it is attached when a shear force is applied between the nonwoven fabric and the object to which it is attached. If the second cellulosic fiber has low strength and is flexible, it is likely to be deformed and stretched when an external force is applied, and therefore it is possible for the nonwoven fabric to remain on the object to which it is attached while deforming even when a shear force is applied, thereby improving the adhesion.

The wet strength of the second cellulosic fiber may in particular be 1.1 cN/dtex or less, more in particular 1.0 cN/dtex or less, with a lower limit of, for example, 0.4 cN/dtex, in particular 0.5 cN/dtex, more in particular 0.6 cN/dtex. If the wet strength exceeds 1.2 cN/dtex, the adhesion or surface smoothness may be insufficient.

Alternatively, the second cellulose fiber may have a smaller wet apparent Young's modulus than the first cellulose fiber, for example, a wet apparent Young's modulus of 930 N/mm2 ^or less. By using a cellulose fiber with a small wet apparent Young's modulus as the second cellulose fiber, the adhesion of the nonwoven fabric can be improved and the surface of the nonwoven fabric can be made smooth, due to its ease of deformation/stretching, as in the case of a low wet strength. Therefore, if the wet apparent Young's modulus exceeds 930 N/ ^mm2 , the adhesion or surface smoothness may be insufficient. The wet apparent Young's modulus of the second cellulose fiber may be particularly 900 N/mm2 or ^less , more particularly 850 N/mm2 ^or less, and the lower limit may be, for example, 650 N/ ^mm2 , particularly 750 N/ ^mm2 .

The second cellulosic fiber may have a dry strength of, for example, 2.5 cN/dtex or less, particularly 2.2 cN/dtex or less. The lower limit may be, for example, 1.2 cN/dtex, particularly 1.3 cN/dtex, and more particularly 1.4 cN/dtex. By using a cellulosic fiber with low dry strength as the second cellulosic fiber, the adhesion of the nonwoven fabric can be improved and the surface of the nonwoven fabric can be made smooth, due to its ease of deformation/stretching, just as in the case of a cellulosic fiber with low wet strength. If the dry strength exceeds 2.5 cN/dtex, the adhesion or surface smoothness may be insufficient.

Alternatively, the second cellulose fiber may be a cellulose fiber having a smaller dry apparent Young's modulus than the first cellulose fiber, for example, a dry apparent Young's modulus of 7800 N/mm2 ^or less. By using a cellulose fiber having a small dry apparent Young's modulus as the second cellulose fiber, the adhesion of the nonwoven fabric can be improved and the surface of the nonwoven fabric can be made smooth due to its ease of deformation/stretching, as in the case of a fiber having a small wet strength. The dry apparent Young's modulus of the second cellulose fiber may be particularly 7500 N/ ^mm2 or less, more particularly 7000 N/mm2 ^{or less} . The upper limit may be, for example, 4000 N/ ^mm2 , particularly 5000 N/ ^mm2 .

The second cellulose fiber may be one or more fibers selected from viscose rayon, cuprammonium rayon, diacetate, and triacetate. In this embodiment, viscose rayon may be used in particular. Viscose rayon has a lower crystallinity than other regenerated cellulose fibers and therefore tends to have lower strength, but has high water absorption and is therefore preferred. More particularly, the following (1) to (3):
(1) A viscose rayon having a single cross section and a degree of irregularity of the cross section calculated by the following formula of 2.0 or less.
Roughness = L ² / (4π・S)
(In the formula, L is the perimeter of the cross section, and S is the area of the cross section.)
(2) Viscose rayon having a single cross section and a cross-sectional outline that is circular, elliptical, or spherical, or a circular, elliptical, or spherical shape with a slit;
(3) The cross section has a single structure, and the flatness of the cross section calculated by the following formula is 1.80 or more, and the unevenness of the cross section calculated by the following formula is 2.50 or less. Viscose rayon flatness = a/b
(In the formula, a is the length of the longest line segment A connecting any two points on the cross section, and b is the length of a line segment that is perpendicular to line segment A and, together with a line segment parallel to line segment A, constitutes a rectangle or square circumscribing the cross section.)
Roughness = L ² / (4π・S)
(In the formula, L is the perimeter of the cross section, and S is the area of the cross section.)
One or more viscose rayons selected from the following may be used.

The above viscose rayon (1) to (3) corresponds to the viscose rayon disclosed in Patent Document 4 (hereinafter, "single-structure rayon"). When the single-structure rayon is skin-core dyed, no significant difference in dyeability (shade of color after dyeing) is observed between the inner and outer periphery in the cross section (cross section obtained by cutting perpendicularly to the length of the fiber). In addition, the single-structure rayon is a viscose rayon whose cross-sectional shape is different from that of ordinary viscose rayon, and whose cross-sectional outline has no unevenness or has small unevenness. In order to obtain such a cross section, the single-structure viscose rayon is produced by adding a component (particularly polyethylene glycol) that reduces the regeneration rate of viscose. Therefore, the single-structure viscose is easily obtained as a relatively low-strength viscose whose wet strength is within the above range.

In addition, the cross-sectional contour of the monostructure rayon is free of irregularities or has only small irregularities, so that the surface is smoother than that of ordinary viscose rayon. Therefore, when monostructure rayon is used to produce a nonwoven fabric by entangling treatment using a high-pressure fluid flow, the degree of entanglement between the fibers tends to be smaller than that of ordinary viscose rayon. As a result, the degree of freedom of the fibers in the nonwoven fabric is increased, and the adhesion of the nonwoven fabric is easily improved.
In addition, since the single-structure rayon has a smooth cross-sectional contour, it has high transparency itself and is easy to impart transparency to a nonwoven fabric. Therefore, by using the single-structure rayon, a nonwoven fabric having higher transparency in both the dry and wet states can be obtained.

Details of the single-structure rayon are as described in Patent Document 4.
Incidentally, commercially available monostructure rayon may contain fibers having different cross-sectional shapes. As long as the cross-section of each fiber is as described in any one of (1) to (3) above, a product containing fibers having various different cross-sectional shapes may be used in this embodiment.

The second cellulosic fiber may have an ash content of 0.5% by mass or less, and in particular may be substantially free of titanium oxide. As explained above for the first cellulosic fiber having a low ash content, the use of the second cellulosic fiber having a low ash content can increase the transparency of the nonwoven fabric or improve the liquid retention of the nonwoven fabric. The ash content of the second cellulosic fiber may in particular be 0.35% by mass or less, more in particular 0.3% by mass or less. The ash content is measured in accordance with JIS L 1015 8.20 (ash content): 2010.

The second cellulosic fiber may be, for example, 0.6 dtex or more and 3.3 dtex or less, particularly 1.0 dtex or more and 2.5 dtex or less, and more particularly 1.4 dtex or more and 2.0 dtex or less. If the fineness of the second cellulosic fiber is too small, the voids in the cellulosic fiber layer will be small, making it difficult for the nonwoven fabric to retain liquid, and if it is too large, the feel of the nonwoven fabric may be reduced. The fineness of the second cellulosic fiber is not limited to these ranges.

The fiber length of the second cellulose fiber is not particularly limited and may be appropriately selected depending on the manufacturing method of the nonwoven fabric, etc. For example, when the cellulose fiber layer is manufactured by preparing a card web in the manufacturing of the nonwoven fabric, the second cellulose fiber may be a short fiber. The fiber length of this short fiber may be, for example, 20 mm or more and 100 mm or less, particularly 28 mm or more and 75 mm or less, and more particularly 30 mm or more and 65 mm or less. Alternatively, when the first fiber layer is manufactured by an air-laying method, the fiber length may be, for example, 2 mm or more and 20 mm or less.
In this embodiment, a plurality of types of cellulosic fibers differing in one or more of material, fiber length, and fineness may be used as the second cellulosic fibers.

(Adhesive Fiber)
In the nonwoven fabric of this embodiment, the cellulosic fiber layer may contain adhesive fibers. The adhesive fibers bond fibers together in the nonwoven fabric to improve the strength of the nonwoven fabric, suppress excessive stretching of the nonwoven fabric, and suppress fluffing and fluffing on the surface of the nonwoven fabric. The adhesive fibers are generally synthetic fibers made of thermoplastic resins and are thermally adhesive fibers that exhibit adhesiveness when heated, but as long as they have adhesiveness, they do not need to be thermally adhesive and may be fibers other than synthetic fibers.

When the adhesive fiber is a synthetic fiber, the synthetic fiber may be made of one or more thermoplastic resins selected from the following: polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polylactic acid, polybutylene succinate, and copolymers thereof; polyolefin-based resins such as polypropylene, polyethylene (including high-density polyethylene, low-density polyethylene, linear low-density polyethylene, and the like), polybutene-1, propylene copolymers mainly composed of propylene (including propylene-ethylene copolymers and propylene-butene-1-ethylene copolymers), ethylene-vinyl alcohol copolymers, and ethylene-vinyl acetate copolymers; polyamide-based resins such as nylon 6, nylon 12, and nylon 66; acrylic-based resins; engineering plastics such as polycarbonate, polyacetal, polystyrene, and cyclic polyolefins, and elastomers thereof.

The synthetic fibers may be single fibers made of a single component (also called "single section") and/or composite fibers made of multiple components (also called "sections"). The composite fibers may be, for example, concentric or eccentric core-sheath composite fibers, islands-in-the-sea composite fibers, side-by-side composite fibers, or split composite fibers. The cross section of the fiber (transverse section; hereafter, all fiber cross sections are transverse sections) may be circular or noncircular, and noncircular shapes include elliptical, Y-shaped, X-shaped, well-shaped, multi-lobed, polygonal, star-shaped, etc. The synthetic fibers may also have a hollow cross section. In both the case of single fibers and composite fibers, each section constituting the fiber may be made of one type of resin, or may be a mixture of two or more types of resin.

When the synthetic fiber is a monofilament, the monofilament may be made of one or more resins selected from the group consisting of the polyolefin resin, the polyester resin, the polyamide resin, and the acrylic resin. More specifically, a monofilament of polyethylene, a monofilament of polypropylene, a monofilament of polyethylene terephthalate, etc. may be used.

When the synthetic fiber is a composite fiber, two or more components may be arranged so that the thermoplastic resin with the lowest melting point constitutes part of the fiber surface. In that case, when heat is applied under conditions in which the component consisting of the thermoplastic resin with the lowest melting point (hereinafter referred to as the "low melting point component") melts or softens in the process of producing a nonwoven fabric, the low melting point component becomes the adhesive component. The combination of resins (first/second) constituting the composite fiber consisting of a first component which is a thermoplastic resin with a higher melting point and a second component which is a thermoplastic resin with a lower melting point is, for example, a combination of a polyester-based resin and a polyolefin-based resin such as polyethylene terephthalate/polyethylene, polyethylene terephthalate/polypropylene, and polyethylene terephthalate/propylene copolymer, a combination of two types of polyolefin-based thermoplastic resins such as polypropylene/polyethylene, and polypropylene/propylene copolymer, and a combination of two types of polyester-based resins with different melting points.

Alternatively, the combination of the first and second components may be a combination of biodegradable resins, and such a combination can increase the proportion of biodegradable fibers in the laminated nonwoven fabric. Specifically, the adhesive fiber can be made biodegradable by using polylactic acid as the first component and polybutylene succinate as the second component.

The thermoplastic resins exemplified as components of the single fiber or composite fiber may contain other components as long as they contain 50% by mass or more of the specifically indicated thermoplastic resin. The specifically indicated thermoplastic resin may be contained in an amount of 80% by mass or more, or 90% by mass or more, or the components may consist essentially of the specifically indicated thermoplastic resin. The term "substantially" is used here in consideration of the fact that thermoplastic resins usually contain various additives, etc. For example, in the combination of polyethylene terephthalate/polyethylene, as long as the "polyethylene" contains 50% by mass or more of polyethylene, it may contain other thermoplastic resins and additives, etc. This also applies to the following examples.

When the synthetic fibers are concentric or eccentric core-sheath composite fibers in which a thermoplastic resin with a higher melting point constitutes the core component as the first component and a thermoplastic resin with a lower melting point constitutes the sheath component as the second component, the core/sheath combination may be, for example, polypropylene/polyethylene, polypropylene/propylene-ethylene copolymer, polypropylene/propylene-butene-1-ethylene copolymer, polyethylene terephthalate/polyethylene, polyethylene terephthalate/polypropylene, polyethylene terephthalate/propylene copolymer, polytrimethylene terephthalate/polyethylene, polybutylene terephthalate/polyethylene, polyethylene terephthalate/copolyester (for example, polyethylene terephthalate copolymerized with isophthalic acid). These resin combinations may also be used in splittable composite fibers.

In the case of core-sheath composite fibers, the volume ratio of the core component to the sheath component (core component:sheath component) is preferably 80:20 to 20:80, more preferably 70:30 to 30:70, and even more preferably 60:40 to 40:60.

In the case of splittable composite fibers, the ratio of the two components (first:second) is preferably 80:20 to 20:80 by volume, more preferably 70:30 to 30:70, and even more preferably 60:40 to 40:60. In the case of splittable composite fibers, the number of divisions (i.e., the number of sections in the composite fiber) may be, for example, 4 or more and 32 or less, particularly 4 or more and 20 or less, and more particularly 6 or more and 10 or less.

In this embodiment, the adhesive fiber can preferably be a core-sheath type composite fiber (concentric or eccentric) in which the combination of the first component/second component is polyethylene terephthalate/copolymer polyester, polypropylene/polyethylene, or polyethylene terephthalate/polyethylene. These fibers are preferably used because they exhibit adhesiveness at relatively low temperatures (110°C or higher and 130°C or lower) and make the texture of the nonwoven fabric soft after bonding.

The fineness of the adhesive fiber may be, for example, 0.5 dtex or more and 4.0 dtex or less, particularly 1.0 dtex or more and 3.0 dtex or less, more particularly 1.5 dtex or more and 2.5 dtex or less, and even more particularly 1.6 dtex or more and 2.2 dtex or less. If the fineness of the adhesive fiber is too small, the strength of the nonwoven fabric may be low and the nonwoven fabric may be prone to stretching, while if the fineness is too large, the nonwoven fabric may feel hard to the touch. If the nonwoven fabric is prone to stretching, for example, when the nonwoven fabric is used as a face mask, the position of the openings provided at the position of the eyes and mouth may become misaligned.

In particular, when the adhesive fiber is a splittable composite fiber, the splittable composite fiber may have a fineness of 1.0 dtex or more and 4.0 dtex or less before splitting, and may give adhesive fibers of 0.1 dtex or more and less than 1.0 dtex after splitting.

The fiber length of the adhesive fiber is not particularly limited and may be appropriately selected depending on the manufacturing method of the nonwoven fabric, etc. For example, when the cellulosic fiber layer is manufactured by preparing a card web in the manufacture of the nonwoven fabric, the adhesive fiber may be a short fiber. The fiber length of this short fiber may be, for example, 10 mm or more and 100 mm or less, particularly 20 mm or more and 75 mm or less, and more particularly 30 mm or more and 65 mm or less. Alternatively, when the second fiber layer is manufactured by the air laying method, the fiber length may be, for example, 2 mm or more and 20 mm or less.

(Other fibers)
In the nonwoven fabric of this embodiment, the cellulosic fiber layer may include fibers other than the first and second cellulosic fibers, and fibers other than the adhesive fibers. For example, the first fiber layer may include a third cellulosic fiber as a fiber other than the first and second cellulosic fibers. When a single-structure rayon is used as the second cellulosic fiber and a cellulosic fiber having a relatively high wet strength (e.g., a solvent-spun cellulose fiber) is used as the first cellulosic fiber, the third cellulosic fiber may be a cellulosic fiber (e.g., a normal viscose rayon) having a wet strength smaller than that of the first cellulosic fiber and larger than that of the second cellulosic fiber.

Alternatively, the other fibers may be, for example, synthetic fibers that do not function as adhesive fibers. Specifically, when a synthetic fiber that exhibits adhesiveness when heated at T°C is used as the adhesive fiber, a synthetic fiber that has a melting point higher than T°C and does not exhibit adhesiveness when heated at T°C may be included as the other fiber. Therefore, whether a synthetic fiber is included as an adhesive fiber or as another fiber is determined by the synthetic fibers also included in the nonwoven fabric, and a synthetic fiber may be included as an adhesive fiber or as another fiber. Alternatively, if heat treatment at a temperature equal to or higher than the temperature at which the synthetic fiber exhibits adhesiveness is not performed during the manufacturing process of the nonwoven fabric, the synthetic fiber will be included as a other fiber rather than as an adhesive fiber.

For example, when a core-sheath type composite fiber made of polyester (core)/polypropylene (sheath) is used together with a core-sheath type composite fiber made of a combination of polypropylene (core)/polyethylene (sheath), polyethylene is included as another fiber because it exhibits thermal adhesion at the lowest temperature. On the other hand, when this is used together with a split type composite fiber made of a combination of polyethylene terephthalate/nylon 6, polypropylene is included as an adhesive fiber because it exhibits thermal adhesion at the lowest temperature.

The fineness of the other fibers may be, for example, 0.5 dtex or more and 4.0 dtex or less, particularly 1.3 dtex or more and 2.5 dtex or less, and more particularly 1.4 dtex or more and 2.2 dtex or less. If the fineness of the other fibers is too small, it may cause neps in the nonwoven fabric, affecting the texture, and if it is too large, the surface of the nonwoven fabric may become rough, reducing the feel to the touch.

The fiber length of the other fibers is not particularly limited and may be appropriately selected depending on the manufacturing method of the nonwoven fabric, etc. The relationship between the manufacturing method of the nonwoven fabric (the method of producing the cellulosic fiber layer) and the fiber length is as explained in relation to the first and second cellulosic fibers and the adhesive fiber.

(Configuration of nonwoven fabric)
The nonwoven fabric of this embodiment includes a cellulosic fiber layer including a first cellulosic fiber and a second cellulosic fiber. In the cellulosic fiber layer, the first cellulosic fiber is contained in a proportion of 5% by mass or more and 50% by mass or less, based on the total mass of the cellulosic fiber layer, and the second cellulosic fiber is contained in a proportion of 30% by mass or more and 95% by mass or less. In the cellulosic fiber layer, the combined proportion of the first cellulosic fiber and the second cellulosic fiber is 80% by mass or more of the total fibers constituting the cellulosic fiber layer. Here, the proportion of the fibers contained in the cellulosic fiber layer is the proportion of the fibers contained in the cellulosic fiber layer before integration when integrated with another layer. Therefore, even if a part of the fibers constituting the other layer is mixed into the cellulosic fiber layer due to integration with the other layer, the mixed fibers are not included in the cellulosic fiber layer.

The first cellulosic fiber has a higher wet strength and/or wet apparent Young's modulus, and acts as an aggregate in the cellulosic fiber layer, improving the strength of the nonwoven fabric and imparting stiffness. Therefore, if the proportion of the first cellulosic fiber is too small, the nonwoven fabric may become excessively soft and difficult to handle. On the other hand, if the proportion of the first cellulosic fiber is too large, the nonwoven fabric may become hard to the touch, the nonwoven fabric may become difficult to stretch, or the nonwoven fabric may "squeak," which causes discomfort to the user of the sheet.
The proportion of the first cellulosic fibers contained in the cellulosic fiber layer may particularly be 7% by mass or more and 45% by mass or less, and more particularly 10% by mass or more and 35% by mass or less.

The second cellulose fiber has a lower wet strength and/or wet apparent Young's modulus, and improves the adhesion and smoothness of the surface of the cellulose fiber layer (i.e., the surface of the nonwoven fabric). In particular, when the second cellulose fiber is a single-structure rayon, in addition to the adhesion and smoothness, the transparency of the nonwoven fabric is improved, and the transparency can be imparted to a nonwoven fabric having a higher basis weight (particularly, greater than 48 g/ ^m2 and less than 100 g/m2) than the nonwoven fabric proposed in Patent Document ³ .

If the proportion of the second cellulose fiber is too small, the nonwoven fabric may have insufficient adhesion and/or smoothness. On the other hand, if the proportion of the second cellulose fiber is too large, the nonwoven fabric may become too soft and difficult to handle during sheet production, processing, and use. In addition, when the second cellulose fiber is a single-structure rayon, the transparency of the nonwoven fabric tends to improve as the proportion of the second cellulose fiber increases.
The proportion of the second cellulosic fibers contained in the cellulosic fiber layer may particularly be 40% by mass or more and 85% by mass or less, and more particularly may be 45% by mass or more and 80% by mass or less.

When the cellulosic fiber layer contains adhesive fibers, the adhesive fibers may be contained in a proportion of 20% by mass or less, particularly 2% by mass or more and 18% by mass or less, and more particularly 4% by mass or more and 16% by mass or less, based on the total mass of the cellulosic fiber layer. The adhesive fibers bond the cellulosic fibers together to improve the strength of the nonwoven fabric and suppress fluffing. If the proportion of adhesive fibers is too small, these effects may not be obtained. If the proportion of adhesive fibers is too large, the nonwoven fabric may become hard and the touch may deteriorate, and the proportion of cellulosic fibers may become small, which may reduce the liquid retention of the entire nonwoven fabric. The cellulosic fiber layer may not contain adhesive fibers.

In the nonwoven fabric of this embodiment, the first cellulosic fiber and the second cellulosic fiber contained in the cellulosic fiber layer may together account for 80% by mass or more, particularly 82% by mass or more, more particularly 85% by mass or more, and even more particularly 90% by mass or more, based on the total mass of the cellulosic fiber layer. With this configuration, a nonwoven fabric can be obtained in which the effects of the two types of cellulosic fibers are fully exerted, and the liquid retention of the nonwoven fabric can be made relatively high.

The nonwoven fabric of this embodiment may be an all-cellulose nonwoven fabric composed only of the first cellulosic fiber and the second cellulosic fiber, or composed only of these cellulosic fibers and other cellulosic fibers. Sheets using such nonwoven fabrics can be marketed as biodegradable, environmentally friendly products.

When the cellulosic fiber layer contains other fibers, the other fibers may be contained in a proportion of 20% by mass or less, particularly 18% by mass or less, and more particularly 16% by mass or less, based on the total mass of the cellulosic fiber layer. If the proportion of other fibers is too large, the proportions of the first and second cellulosic fibers will be small, and the adhesion, smoothness and/or liquid retention of the nonwoven fabric may decrease.

The nonwoven fabric of this embodiment may be a single-layer nonwoven fabric composed only of the cellulosic fiber layer. Such a nonwoven fabric has a simple structure and can be easily manufactured. Furthermore, a sheet using a single-layer nonwoven fabric does not have a significant difference in adhesion or feel when either side is in contact with the skin, which eliminates the need to distinguish between the front and back when using the sheet, making it easy to use. Furthermore, a single-layer nonwoven fabric can be efficiently manufactured because it does not require marking or marking to distinguish between the front and back when manufacturing the sheet.

Alternatively, the nonwoven fabric of this embodiment may be made of only the cellulosic fiber layer, but may be made of two cellulosic fiber layers having different fiber mixing ratios, etc., laminated together, or may be laminated with another fiber layer.

In this embodiment, the fibers in the cellulosic fiber layer, and the fibers in and between layers when the cellulosic fiber layer is laminated with other fiber layers, are integrated by entangling the fibers. The entanglement of the fibers may be achieved, for example, by needle punching or high-pressure fluid flow (particularly water flow) entanglement. In this embodiment, it is preferable that the fibers are integrated by high-pressure fluid flow (particularly water flow) entanglement. The entanglement process using a high-pressure fluid flow can make the surface of the nonwoven fabric smooth. In addition, when the high-pressure fluid flow is a high-pressure water flow, entanglement of the cellulosic fibers, which are hydrophilic fibers, proceeds smoothly, making production easier.

In the nonwoven fabric of this embodiment, when the cellulosic fiber layer contains adhesive fibers, the fibers may be bonded to each other by the adhesive fibers. By bonding the fibers in addition to entangling them, the mechanical strength of the nonwoven fabric can be further improved.

In the nonwoven fabric of this embodiment, the basis weight of the cellulosic fiber layer is not particularly limited, and may be, for example, 40 g/m ² or more, particularly 45 g/m ² or more, more particularly more than 48 g/m ² , and more particularly 50 g/m ² or more. The upper limit of the basis weight of the cellulosic fiber layer may be, for example, 100 g/m ² , particularly 90 g/m ² , and more particularly 70 g/m ² .

When the nonwoven fabric of this embodiment is composed of only a cellulosic fiber layer, the basis weight of the cellulosic fiber layer is the basis weight of the nonwoven fabric. In the case of a laminated nonwoven fabric in which a cellulosic fiber layer and another fiber layer are laminated, the basis weight of the other fiber layer may be selected according to the application of the nonwoven fabric, etc., so that the basis weight of the cellulosic fiber layer falls within the above range.

The basis weight of the nonwoven fabric is determined according to the application, the amount of liquid to be impregnated, and/or, if there is another fiber layer laminated on the cellulosic fiber layer, the configuration of the other fiber layer. For example, when the sheet is a face mask, the basis weight of the nonwoven fabric may be 40 g/m ² or more and 120 g/m ² or less, particularly 45 g/m ² or more and 100 g/m ² or less. When the sheet is an eye sheet (also called an eye pack), the basis weight of the nonwoven fabric may be 40 g/m ² or more and 120 g/m ² or less, particularly 45 g/m ² or more and 100 g/m ² or less. If the basis weight of the nonwoven fabric is too large, the mass of the sheet becomes large and may be easily peeled off by the weight when applied to the skin. If the basis weight of the nonwoven fabric is too small, it may not be able to hold a sufficient amount of liquid.

When the nonwoven fabric of this embodiment is composed of a single cellulosic fiber layer, the basis weight of the nonwoven fabric is the basis weight of the cellulosic fiber layer. When the nonwoven fabric is composed of two or more cellulosic fiber layers, or a cellulosic fiber layer and another fiber layer, the basis weight of each layer may be appropriately determined according to the application and desired function. In either case, the basis weight of the cellulosic fiber layer may be, for example, 40 g/m ² or more, particularly 45 g/m ² or more, and may be 120 g/m ² or less, particularly 100 g/m ² or less.

The thickness of the nonwoven fabric of this embodiment may be, for example, 0.3 mm or more, particularly 0.4 mm or more, more particularly 0.5 mm or more when a load of 294 Pa is applied when dry. The thickness of the nonwoven fabric may be, for example, 1.5 mm or less, particularly 1.3 mm or less, more particularly 1.2 mm or less. The thickness of the entire nonwoven fabric may be, for example, 0.3 mm or more, particularly 0.4 mm or more, more particularly 0.5 mm or more when a load of 1.96 kPa is applied when dry. The thickness of the nonwoven fabric when the load is applied may be, for example, 1.3 mm or less, particularly 1.1 mm or less, more particularly 0.9 mm or less. If the thickness of the nonwoven fabric is too small, the amount of liquid that can be impregnated into the nonwoven fabric may be reduced, and a predetermined amount of liquid may not be supplied to the skin. If the thickness of the entire nonwoven fabric is too large, it may be difficult to fit the sheet to the curved surface of the skin, and the sheet may partially float, making it difficult to evenly cover the skin with the entire sheet.

The nonwoven fabric of this embodiment may exhibit a water retention rate of, for example, 1300% or less when the water retention rate is measured by the method described in the Examples below. The water retention rate of the nonwoven fabric of this embodiment may in particular be 1200% or less, more in particular 1100% or less, and even more in particular 1000% or less. The lower limit of the water retention rate of this embodiment may be, for example, 700%, in particular 750%, and more in particular 800%.

The water retention rate may vary depending on the type and ratio of fibers constituting the nonwoven fabric, and the basis weight of the nonwoven fabric. Therefore, in the nonwoven fabric of this embodiment, these may be adjusted so that the above water retention rate is obtained.

In the nonwoven fabric of this embodiment, the variation in the average coefficient of friction in the CD direction of the cellulosic fiber layer surface when dry may be, for example, 0.010 or less, particularly 0.0098 or less, and more particularly 0.0097 or less. If the variation in the average coefficient of friction in the CD direction of the cellulosic fiber layer surface when dry is too high, the nonwoven fabric surface may not be smooth and adhesion to the skin may decrease when used as a sheet, whereas if it is too low, handling may be poor when applied to the skin, making it difficult to adjust the position of the sheet.

In the nonwoven fabric of this embodiment, the variation in the average friction coefficient in the CD direction at the moisture content after 15 minutes on the surface of the cellulosic fiber layer may be, for example, 0.013 or less, particularly 0.01 or less, more particularly 0.0097 or less. The variation in the average friction coefficient in the CD direction at the moisture content after 15 minutes is the variation in the average friction coefficient in the CD direction of the nonwoven fabric measured in a state in which the nonwoven fabric is moistened to have the moisture content after 15 minutes, as described below. If the variation in the average friction coefficient in the CD direction at the moisture content after 15 minutes on the surface of the cellulosic fiber layer is too high, the nonwoven fabric surface may not be smooth, and the adhesion may decrease when used as a sheet, and if it is too low, the handling when applied to the skin may be poor, making it difficult to adjust the position of the sheet.

In the nonwoven fabric of this embodiment, the average coefficient of friction in the MD direction of the cellulosic fiber layer surface may be, for example, 0.2 or more and 0.5 or less, particularly 0.25 or more and 0.4 or less, more particularly 0.28 or more and 0.38 or less, and the average coefficient of friction in the CD direction may be, for example, 0.2 or more and 0.4 or less, particularly 0.25 or more and 0.39 or less, more particularly 0.3 or more and 0.38 or less. When the average coefficient of friction is within the above range, it feels smooth to the touch.

The variation in the average coefficient of friction of the nonwoven fabric of this embodiment can be measured and evaluated based on the Kawabata Evaluation System (KES) method, which is one of the methods for measuring and objectively evaluating the texture of a fabric. Specifically, the surface of the cellulosic fiber layer of the nonwoven fabric of this embodiment is used as the measurement surface, and the average coefficient of friction (hereinafter also referred to as MIU) and the variation in the average coefficient of friction (sometimes referred to as the mean deviation of the coefficient of friction μ, hereinafter also referred to as MMD) are measured based on the KES method. MIU indicates the degree of friction, i.e., slipperiness, and a large value indicates high friction and low slipperiness. Within the above range, MMD indicates the variation in friction, and the larger the value, the rougher the surface. The device for measuring the variation in the average coefficient of friction is not particularly limited as long as it is a device that can measure surface friction based on the KES method. For example, a friction tester ("KES-SE", manufactured by Kato Tech Co., Ltd.) or an automated surface tester ("KES-FB4-AUTO-A", manufactured by Kato Tech Co., Ltd.) can be used.

In the nonwoven fabric of this embodiment, the adhesion strength of the cellulosic fiber layer surface after 15 minutes (per 5 cm x 12 cm area) may be, for example, 180 gf or more, particularly 190 gf or more, more particularly 200 gf or more. The upper limit of the adhesion strength of the cellulosic fiber layer surface after 15 minutes is not particularly limited, but may be, for example, 300 gf, particularly 280 gf, more particularly 260 gf. The adhesion strength after 15 minutes is measured in a state where the nonwoven fabric is wetted so as to have a moisture content after 15 minutes, as described below. If the adhesion strength of the cellulosic fiber layer surface after 15 minutes is too low, the sheet may partially lift off the skin during use, or the sheet may shift from a predetermined position.
Considering that a sheet is generally used by being applied to the skin for a relatively long time, the adhesion strength after 15 minutes is an index for evaluating whether the sheet can still adhere to the skin even when the liquid in the sheet is transferred to the skin or evaporated during use and the amount of liquid in the sheet is reduced. Another reason for adopting the adhesion strength after 15 minutes is that the sheet is soaked with a large amount of liquid immediately after the start of use, making it difficult to accurately evaluate the adhesion of the sheet itself.

The nonwoven fabric of this embodiment may have a bending softness when dry of, for example, 340 mN or more, particularly 390 mN or more, more particularly 440 mN or more. The upper limit of the bending softness when dry is, for example, 930 mN, particularly 880, more particularly 785 mN. The nonwoven fabric of this embodiment may have a bending softness when wet of, for example, 440 mN or more, particularly 470 mN or more, more particularly 490 mN or more. The upper limit of the bending softness when wet is, for example, 880 mN, particularly 835 mN, more particularly 735 mN.
As described later, the bending resistance is measured according to the handle-o-meter method, and in this embodiment, the sum of the values measured on the four sides of the sample is taken as the bending resistance of the sample, and this is used as an index of the flexibility of the nonwoven fabric. The larger the handle-o-meter value, the more rigid the nonwoven fabric is.
If the bending resistance is too low, the sheet is difficult to handle, whereas if the bending resistance is too high, the sheet does not easily conform to the skin when applied to the skin, and may float up.

The nonwoven fabric of this embodiment may have a tensile strength in the MD direction when dry of, for example, 50 N/5 cm or more and 160 N/5 cm or less, particularly 55 N/5 cm or more and 150 N/5 cm or less, and more particularly 70 N/5 cm or more and 140 N/5 cm or less. If the tensile strength in the MD direction when dry is too low, the nonwoven fabric may break during product processing. If the tensile strength in the MD direction when dry is too high, the texture of the nonwoven fabric may not be good.

The nonwoven fabric of this embodiment may have a tensile strength in the CD direction when dry of, for example, 4.5 N/5 cm or more and 30 N/5 cm or less, particularly 6.0 N/5 cm or more and 25 N/5 cm or less, and more particularly 8.0 N/5 cm or more and 20 N/5 cm or less. If the tensile strength in the CD direction when dry is too low, vertical streaks are likely to appear in the nonwoven fabric. If the tensile strength in the CD direction when dry is too high, the texture of the nonwoven fabric may not be good.

The nonwoven fabric of this embodiment may have an elongation rate in the MD direction when dry of, for example, 15% or more and 65% or less, particularly 18% or more and 60% or less, and more particularly 20% or more and 55% or less. The nonwoven fabric of this embodiment may have an elongation rate in the CD direction when dry of, for example, 40% or more and 150% or less, particularly 50% or more and 140% or less, and more particularly 55% or more and 130% or less. If the elongation rate in the MD direction or CD direction when dry is too low, the texture of the nonwoven fabric may not be good. If the elongation rate in the MD direction or CD direction when dry is too high, defects are likely to occur during punching during product processing.

The nonwoven fabric of this embodiment may have a stress at 10% elongation in the MD direction when dry of, for example, 7.0 N/5 cm or more and 70 N/5 cm or less, particularly 8.0 N/5 cm or more and 65 N/5 cm or less, and more particularly 9.0 N/5 cm or more and 60 N/5 cm or less. The nonwoven fabric of this embodiment may have a stress at 10% elongation in the CD direction when dry of, for example, 0.4 N/5 cm or more and 3.0 N/5 cm or less, particularly 0.45 N/5 cm or more and 2.5 N/5 cm or less, and more particularly 0.5 N/5 cm or more and 2.3 N/5 cm or less. If the stress at 10% elongation in the MD direction or CD direction when dry is too low, defects are likely to occur during punching during product processing. If the stress at 10% elongation in the MD direction or CD direction when dry is too high, the texture of the nonwoven fabric may not be good.

The nonwoven fabric of this embodiment may have a tensile strength in the MD direction when wet of, for example, 30 N/5 cm or more and 150 N/5 cm or less, particularly 45 N/5 cm or more and 120 N/5 cm or less, and more particularly 55 N/5 cm or more and 100 N/5 cm or less. The nonwoven fabric of this embodiment may have a tensile strength in the CD direction when wet of, for example, 7.0 N/5 cm or more and 35 N/5 cm or less, particularly 10 N/5 cm or more and 25 N/5 cm or less, and more particularly 11.0 N/5 cm or more and 20 N/5 cm or less. If the tensile strength in the MD direction or CD direction when wet is too low, the liquid-impregnated skin application sheet that has been produced as a product may break when removed. If the tensile strength in the MD direction or CD direction when wet is too high, the nonwoven fabric may be difficult to bend, and its ability to conform to uneven skin may decrease.

The nonwoven fabric of this embodiment may have an elongation rate in the MD direction when wet of, for example, 15% to 55%, particularly 20% to 50%, and more particularly 22% to 48%. The nonwoven fabric of this embodiment may have an elongation rate in the CD direction when wet of, for example, 60% to 160%, particularly 65% to 155%, and more particularly 70% to 150%. If the elongation rate in the MD or CD direction when wet is too low, it becomes difficult to attach the nonwoven fabric to the skin. If the elongation rate in the MD or CD direction when wet is too high, the finished liquid-impregnated skin dressing sheet may stretch significantly when removed.

The nonwoven fabric of this embodiment may have a 10% elongation stress in the MD direction when wet of, for example, 2.0 N/5 cm or more and 45 N/5 cm or less, particularly 2.5 N/5 cm or more and 40 N/5 cm or less, more particularly 3.0 N/5 cm or more and 35 N/5 cm or less. The nonwoven fabric of this embodiment may have a 10% elongation stress in the CD direction when wet of, for example, 0.20 N/5 cm or more and 2.5 N/5 cm or less, particularly 0.28 N/5 cm or more and 2.0 N/5 cm or less, more particularly 0.30 N/5 cm or more and 1.8 N/5 cm or less. If the 10% elongation stress in the MD direction or CD direction when wet is too high , it becomes difficult to attach the nonwoven fabric to the skin. If the stress at 10% elongation in the MD or CD when wet is too low , when the liquid-impregnated skin application sheet has eyes, a mouth, etc. punched out, the positions of the eyes, mouth, etc. may stretch and shift when applied, making it difficult to use.

(Method of manufacturing nonwoven fabric)
The nonwoven fabric of this embodiment is, for example,
A first cellulosic fiber is used in a ratio of 5% by mass or more and 50% by mass or less.
A fiber web comprising 30% by mass or more and 95% by mass or less of a second cellulosic fiber having a lower wet strength and/or wet apparent Young's modulus than that of a first cellulosic fiber,
The cellulosic fiber web can be produced by a production method including: producing a cellulosic fiber web in which the combined proportion of the first cellulosic fiber and the second cellulosic fiber is 80 mass% or more of the total fibers constituting the fiber web; and subjecting the cellulosic fiber web to an entanglement treatment using a high-pressure water flow to entangle the fibers.

The cellulosic fiber web can be produced by a known method using the first and second cellulosic fibers described above. The form of the cellulosic fiber web may be any form selected from, for example, a parallel web, a cross web, a carded web such as a semi-random web or a random web, an air-laid web, and a wet-laid paper web. When the cellulosic fiber web is a carded web, the nonwoven fabric is easily stretched, and a sheet with good wearability to the skin can be easily obtained.

Making the cellulosic fibrous web may involve laminating two or more of the same or different cellulosic fibrous webs.
After the cellulosic fiber web is produced, another fiber web is laminated to produce a laminated fiber web, thereby obtaining a laminated nonwoven fabric. The other fiber web may be one produced by the above-mentioned known method, or may be a sheet-like material in which the fibers are integrated to a certain extent, such as a nonwoven fabric (e.g., a long fiber nonwoven fabric, a meltblown nonwoven fabric), a knitted fabric, or a woven fabric.

The cellulosic fiber web, or a laminated fiber web formed by laminating the cellulosic fiber web with another fiber web, is subjected to a process for entangling the fibers. The process for entangling the fibers may be, for example, an entanglement process using a high-pressure fluid flow.

In high-pressure fluid flow processing, the high-pressure fluid is, for example, a high-pressure gas such as compressed air, or a high-pressure liquid such as high-pressure water. In the manufacture of nonwoven fabrics, hydroentanglement processing using high-pressure water as the high-pressure fluid is often used, and in this embodiment, hydroentanglement processing is preferably used in terms of ease of implementation. Below, a manufacturing method in which high-pressure water (hereinafter also simply referred to as "water flow") is used as the high-pressure fluid will be described.

The hydroentanglement treatment is carried out by placing the cellulosic fiber web on a support and spraying a columnar water stream. For example, the support is preferably a plain weave support of 80 mesh or more and 100 mesh or less. The hydroentanglement treatment may be carried out by spraying a water stream with a water pressure of 1 MPa to 15 MPa from a nozzle having orifices with a hole diameter of 0.05 mm or more and 0.5 mm or less, spaced 0.3 mm or more and 1.5 mm or less, 1 to 5 times on each of the front and back surfaces of the cellulosic fiber web. The water pressure is, for example, 1 MPa to 10 MPa, particularly 2.0 MPa to 7.0 MPa, more particularly 3.0 MPa to 6.0 MPa.

The hydroentanglement process may be carried out so that the total energy (E) applied to the cellulosic fiber web is 0.6 kWh/kg/m or less.

The energy (E) applied to the fiber web by the jetted water stream can be calculated using the following formula. When jetting multiple times under different conditions, such as the number of nozzle orifices or water pressure, calculate E for each jet and add them all together.

E=W×N×T/(M/1000×U×60)/1000
E: Energy applied per 1 m width per 1 kg of fiber web per hour (kWh/kg/m)
W: Power (W) of the fluid (water in this embodiment) per one orifice of the nozzle
N: number of orifices per 1 m width in the nozzle; T: number of sprays; M: basis weight (g/m ² ) of the subject of hydroentanglement treatment;
U: conveying speed (m/min)

In the above formula, W (the power of the fluid per one orifice of the nozzle) can be calculated by the following formula.
W=P1×(F/100)×0.163
W: Power of the fluid per nozzle orifice (W)
P1: Water pressure (kgf/ ^cm2 )
F: flow rate of water discharged from one orifice of the nozzle (cm ³ /min)

In the above formula, F (the flow rate of water discharged from one orifice of the nozzle) is calculated by the following formula.
F = S x V
F: flow rate of water discharged from one orifice of the nozzle (cm ³ /min)
S: Area of fluid discharged from one orifice of the nozzle (mm ² )
V: flow velocity of the fluid discharged from the nozzle (m/min)

In the above formula, V (the flow velocity of the fluid discharged from the nozzle) is calculated by the following formula.
V=(20×g×(P1-P2)/ρ) ^1/2 ×60
V: flow velocity of the fluid discharged from the nozzle (m/min)
g: Gravitational acceleration, 9.8 m/s ²
P1: Water pressure (kgf/ ^cm2 )
P2: Atmospheric pressure (kgf/ ^cm2 )
ρ: density of fluid (g/cm ³ )
Details of the method for determining E etc. are described in Japanese Patent No. 4,893,256.

By setting the total energy (E) applied to the cellulosic fiber web to 0.6 kWh/kg/m or less, excessive entanglement of the cellulosic fibers is prevented and the degree of freedom of the fibers is adequately ensured, making it easier to obtain a nonwoven fabric with a soft feel and high adhesion. The total E may be particularly 0.5 kWh/kg/m or less, more particularly 0.45 kWh/kg/m or less.

When the cellulosic fiber web contains adhesive fibers, the cellulosic fiber web after the entanglement treatment may be subjected to a bonding treatment so that the fibers are bonded to each other in the resulting nonwoven fabric. The bonding treatment may be a thermal bonding treatment, or bonding by electron beam irradiation or ultrasonic welding. By the heat treatment, the adhesive fibers (e.g., the low melting point component of the composite fiber) melt or soften by heating during the heat treatment, and can bond the fibers that make up the cellulosic fiber web to each other.

The heat treatment is, for example, a hot air processing treatment in which hot air is blown, a heat roll processing (heat embossing roll processing), or a heat treatment using infrared rays. The hot air processing treatment may be carried out using a device that blows hot air at a predetermined temperature onto the cellulosic fiber web, for example, a hot air penetration type heat treatment machine or a hot air blowing type heat treatment machine.

The heat treatment temperature (e.g., the temperature of the hot air) may be the temperature at which the component that functions as an adhesive component among the components that make up the adhesive fiber softens or melts. For example, the heat treatment temperature may be a temperature equal to or higher than the melting point of the component. If the adhesive fiber contains, for example, polyethylene as a constituent component and polyethylene is the adhesive component, the heat treatment temperature may be 130°C to 150°C, and if polybutylene succinate is the adhesive component, the heat treatment temperature may be 115°C to 133°C.

(Liquid-impregnated skin covering sheet)
By impregnating the nonwoven fabric of this embodiment with a liquid, a liquid-impregnated skin covering sheet for covering the skin of a human or animal can be obtained. The liquid to be impregnated and the amount of impregnation are appropriately selected depending on the application. When the sheet is provided as a liquid-impregnated skin covering sheet for humans, such as a face mask for humans, a keratin care sheet, and a décolleté sheet, the liquid (e.g., a cosmetic) containing an active ingredient may be impregnated in an amount of 500 parts by mass or more and 2000 parts by mass or less, particularly 600 parts by mass or more and 1800 parts by mass or less, and more particularly 700 parts by mass or more and 1500 parts by mass or less, relative to 100 parts by mass of the nonwoven fabric. The active ingredient may be, for example, a moisturizing ingredient, a keratin softening ingredient, an antiperspirant ingredient, a fragrance ingredient, a whitening ingredient, a blood circulation promoting ingredient, an ultraviolet ray prevention ingredient, and a slimming ingredient, but is not limited thereto.

The face mask is provided in a shape suitable for covering the face, and further in a form in which, for example, openings or cutouts are provided by punching as necessary in areas corresponding to the eyes, nose, and mouth. Alternatively, the face mask may be shaped to cover only a portion of the face (e.g., the eyes, mouth, nose, or cheeks). Alternatively, the face mask may be provided as a set consisting of a sheet covering the area around the eyes and a sheet covering the area around the mouth, or as a set of sheets separately covering three or more areas.

The keratin care sheet is a skin covering sheet used on the heels, elbows, knees, etc., where the keratin is thick and prone to hardening. By impregnating it with a liquid containing a keratin softening component and a moisturizing component, etc., it exerts an effect of promoting moisturizing and softening of the keratin, or an effect of promoting the removal of excess keratin. The nonwoven fabric of this embodiment can be used as a substrate in a keratin care sheet that exerts either effect or efficacy. A keratin care sheet, for example a keratin care sheet for the heel, is provided in a form having a cut and/or notch and/or an opening punched out of a part of the sheet so that the sheet can easily be fitted to the curve of the heel when applied.

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 (e.g., the neck, the back of the hand, or the area from the neck to the chest (also called 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.

The liquid-impregnated skin covering sheet using the nonwoven fabric of this embodiment uses the surface of the cellulosic fiber layer as the skin contact surface, and the action of the second cellulosic fiber ensures good adhesion to the skin. In addition, in the sheet of this embodiment, the surface of the cellulosic fiber layer has a relatively small variation in the average coefficient of friction, so the sheet provides the user with a smooth feel.

When the second cellulose fiber is single-structure rayon, a highly transparent sheet is obtained. When the highly transparent sheet is applied to the skin, the color of the skin can be seen through the sheet, which can reduce the psychological feeling of the user when wearing the sheet (e.g., a feeling of pressure). In addition, the highly transparent sheet makes it easy to distinguish between the parts that are in contact with the skin and the parts that are not, and allows the user to quickly and uniformly apply the sheet to the target area by pressing only the parts that are not in contact with the skin with their hands while checking with the naked eye. Furthermore, if a change occurs in the skin while the sheet is applied, the skin can be seen through the sheet, making it easier for the user to notice the change, and providing a sense of security to users with sensitive skin.

A nonwoven fabric in which single-structure rayon is used as the second cellulosic fiber exhibits high transparency not only when wet but also when dry. Therefore, when this nonwoven fabric is used as a sheet that the user impregnates with liquid immediately before use, the sheet, which is transparent before being impregnated with liquid, can give the user a sense of luxury, a refreshing feeling, and a feeling of low irritation to the skin, depending on its appearance.

The present embodiment will now be described with reference to examples.
The following fibers were prepared for use in this example.
Cellulosic fiber A: a solvent-spun cellulose fiber (trade name Tencel Skin, manufactured by Lenzing) containing no titanium oxide and having an ash content of 0.11 mass % having a fineness of 1.7 dtex and a fiber length of 38 mm.
Cellulosic fiber B: Solvent-spun cellulose fiber containing titanium oxide and having an ash content of 0.67% by mass (product name Lenting Glyocell, manufactured by Lenzing) having a fineness of 1.7 dtex and a fiber length of 38 mm.
Cellulosic fiber C: a titanium oxide-free, single-structure rayon having a fineness of 1.7 dtex and a fiber length of 40 mm and an ash content of 0.14% by mass (product name: Bailey Beads, manufactured by Daiwabo Rayon Co., Ltd.).
Cellulosic fiber D: viscose rayon containing no titanium oxide and having an ash content of 0.14% by mass (product name: Corona BH, manufactured by Daiwabo Rayon Co., Ltd.), having a fineness of 1.7 dtex and a fiber length of 44 mm.
Cellulosic fiber E: Viscose rayon containing titanium oxide, having a fineness of 1.7 dtex and a fiber length of 40 mm, and having an ash content of 0.56% by mass (product name: Corona CD, manufactured by Daiwabo Rayon Co., Ltd.)
Adhesive fiber A: a concentric core-sheath type composite fiber (product name: NBF(H)P, manufactured by Yamatobo Co., Ltd.) having a fineness of 1.7 dtex, a fiber length of 51 mm, a core of polypropylene, and a sheath of high-density polyethylene (melting point: about 133°C).

The fiber properties of the above cellulose-based fibers A to E are shown in Table 1. In Table 1, each property was evaluated according to the method specified in JIS L 1015:2010.

Electron microscope photographs of the fiber cross sections (transverse sections) of cellulosic fibers A to E are shown in Figures 1 to 5.

Example 1
A cellulose fiber web was prepared by mixing 15% by mass of cellulose fiber A, 70% by mass of cellulose fiber B, and 15% by mass of adhesive fiber A, using a parallel carding machine, with a target weight of 50 g/ ^m2 . The fibrous web was placed on a 90 mesh plain weave support, and while conveying at a speed of 4 m/min, a water stream with a water pressure of 2.0 MPa was sprayed once on one surface of the fibrous web, and then a water stream with a water pressure of 2.0 MPa was sprayed once on the other surface of the first fibrous web. The nozzle used in the water stream entanglement treatment was a nozzle with orifices with a hole diameter of 0.12 mm provided at intervals of 0.6 mm, and the interval between the nozzle and the fibrous web during the treatment was 20 mm. The sum of the energy (E) applied to the web by the high-pressure water stream was 0.38 kWh/kg/m.

Next, the fiber web after the hydroentanglement treatment was dried using a hot air-penetrating heat treatment machine set at 80°C, and then the fibers were thermally bonded to each other using the adhesive component of adhesive fiber A (high-density polyethylene, sheath component) using a hot air-penetrating heat treatment machine set at 135°C to obtain the nonwoven fabric of Example 1.

(Examples 2 to 5, Comparative Examples 1 to 4 and 9)
A nonwoven fabric was obtained in the same manner as in Example 1, except that the types and ratios of the fibers constituting the cellulosic fiber web and the target weight of the fiber web were as shown in Tables 2 to 4.

(Comparative Examples 5 to 8)
The types and ratios of the fibers constituting the cellulosic fiber web, and the target weight of the fiber web were as shown in Tables 2 and 3.
The fibrous web was placed on a 90 mesh plain weave support and transported at a speed of 10 m/min. A water stream with a water pressure of 2.0 MPa was sprayed once on one surface of the fibrous web, followed by a water stream with a water pressure of 3.0 MPa once and a water stream with a water pressure of 4.0 MPa twice on the other surface of the first fibrous web. The nozzle used in the water stream entanglement treatment was a nozzle with orifices with a hole diameter of 0.12 mm spaced at 0.6 mm intervals, and the interval between the nozzle and the fibrous web during treatment was 20 mm. The sum of the energy (E) applied to the web by the high-pressure water stream was 0.66 kWh/kg/m.
Next, the fiber web after the hydroentanglement treatment was dried using a hot air-penetrating heat treatment machine set at 80°C, and then the fibers were thermally bonded to each other using the adhesive component of adhesive fiber A (high-density polyethylene, sheath component) using a hot air-penetrating heat treatment machine set at 135°C, thereby obtaining nonwoven fabrics of Comparative Examples 5 to 8.

The nonwoven fabric was evaluated as follows.
<Thickness of nonwoven fabric>
The thickness of the nonwoven fabric was measured using a thickness gauge (THICKNESS GAUGE Model CR-60A (product name) manufactured by Daiei Scientific Instruments Co., Ltd.) while a load of 294 Pa or 1.96 kPa was applied to the nonwoven fabric.

<Strength and elongation>
The strength and elongation were measured by a tensile test using a constant-speed tension type tensile tester in accordance with JIS L 1913:2010 6.3 under the conditions of a sample width of 5 cm, a grip distance of 10 cm, and a tensile speed of 30±2 cm/min, and the load value at break (tensile strength), elongation percentage, and stress at 10% elongation (force required for 10% elongation) were measured. The tensile test was performed in the longitudinal direction (MD direction) and transverse direction (CD direction) of the nonwoven fabric as the tensile direction. The evaluation results are all shown as the average of the values measured for three samples.
The tensile strength and the like in a dry state (standard state, DRY) and in a wet state (WET) were measured. The wet state measurement was carried out by impregnating 100 parts by mass of the sample with 250 parts by mass of distilled water.

<Bending resistance>
The bending resistance of the nonwoven fabric was measured in accordance with JIS L 1913:2010 6.7.5 Handle-O-Meter Method. Specifically, the measurement was performed according to the following procedure.
A sample piece 15 cm long and 15 cm wide (100 parts by mass of the sample piece are impregnated with 500 parts by mass of distilled water) 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 so that it is 8 mm below the surface of the sample stage, is lowered to press the sample piece into place. Measurements are taken at different points on both the front and back of the sample in the longitudinal and transverse directions, 6.7 cm (1/3 of the width of the sample piece) from one of the sides, and the resistance to pressing is read. The maximum value (cN) indicated by the microammeter is read as the resistance value. The resistance values read for each of the four sides are calculated to be the sum of the resistance values. This operation of calculating the sum is carried out for three sample pieces taken from the same nonwoven fabric, and the average of the sums is calculated to be the bending resistance (cN) of the sample.
The bending resistance of the wet sample was measured by impregnating the sample with distilled water equivalent to 500% of the mass of the sample. When measuring the wet sample, a polyethylene sheet (length: 23 cm, width: 23 cm, thickness: 0.06 mm) was placed on the sample stage, and the sample was placed on the polyethylene sheet. The bending resistance of the polyethylene sheet alone was measured, and the value measured for the sheet alone was subtracted from the value measured for the sample to obtain the bending resistance of the wet sample.

<Variation of average friction coefficient>
The variation of the average friction coefficient was measured based on the KES (Kawabata Evaluation System) method. Specifically, a friction sensation tester "KES-SE" manufactured by Kato Tech Co., Ltd. was used. The measurement surface was the surface of the cellulose fiber layer, and a static load of 25 gf (245 N) was applied to the friction probe, which was moved in a direction parallel to the MD and CD directions of the nonwoven fabric at a moving speed of 1 mm/sec to measure the average friction coefficient (MIU) and the variation of the average friction coefficient (MMD) of the nonwoven fabric in each direction. Six measurements were performed in each direction for one sample, and the average value of the four values excluding the minimum and maximum values was taken as the MMD of the sample in that direction.

The variation in the average coefficient of friction in a wet state was determined by determining the moisture content after 15 minutes using the method described below, and measuring 100 parts by mass of a specimen taken from the same sample as the specimen for which the moisture content after 15 minutes was determined, impregnated with distilled water to have the same moisture content as the moisture content after 15 minutes.

[Moisture content after 15 minutes]
A 5 cm x 6 cm sample piece (MD x CD) was prepared, the mass of the sample piece was measured, and then 1000 parts by mass of distilled water was impregnated with 100 parts by mass of the sample piece. The sample piece impregnated with distilled water was placed on a metal plate adjusted to 32°C, and the mass was measured after 15 minutes, and the moisture content after 15 minutes was calculated according to the following formula.
Moisture content after 15 minutes (%) = [(m2-m1)/m1] x 100
m1: Mass (g) of the nonwoven fabric before being impregnated with distilled water
m2: Mass (g) of the nonwoven fabric after being placed on a metal plate at 32 ° C for 15 minutes

<Adhesion strength>
The adhesion was measured using a static and dynamic friction measuring instrument (Tribomaster TL201Ts, manufactured by Trinity Labs, Inc.). As the sample piece, a 12 cm x 5 cm sample piece was prepared, which was taken from the same sample as the sample piece for which the moisture content was determined after 15 minutes. The sample pieces were prepared with the long sides in the MD direction and the CD direction of the nonwoven fabric. An artificial skin (24 cm long x 12 cm wide, product name: BIO SKIN PLATE, manufactured and sold by: Viewlux Co., Ltd.) was attached to the measurement table of the measuring instrument (table sliding type).

Based on the moisture content of each sample piece after 15 minutes, 100 parts by mass of the sample piece was impregnated with distilled water so that the moisture content was the same as the moisture content after 15 minutes, and the end of the short side of the sample piece (this part is called the "clip end") was clamped with the clip of the measuring machine to hold it horizontally. The measurement table was moved so that only the area of the sample with a long side of 8 cm and a short side of 5 cm from the end opposite the clip end (this part is called the "non-clipped end") overlapped horizontally with the artificial skin. The maximum resistance force (N) was read when the measurement table was moved parallel to the long side direction of the sample and away from the clip end at a speed of 10 mm/sec along the long side direction of the sample piece. Five sample pieces were measured in each of the MD and CD directions for one example, and the average value of the maximum resistance force (N) was calculated for each direction except for the minimum and maximum values, and this was taken as the adhesion force.

<Water retention rate>
The nonwoven fabric was cut into a size of 100 mm x 100 mm (machine direction x cross direction), the mass of the nonwoven fabric was measured, and the fabric was then immersed in distilled water for 2 minutes. The nonwoven fabric soaked in distilled water was then hung with clothespins at three corners, and the mass was measured after 10 minutes, and the water retention was calculated according to the following formula. The measurements were performed at a temperature of 23±5°C and a relative humidity of 50±20%.
Water retention rate (%) = [(M2-M1)/M1] x 100
M1: Mass (g) of the nonwoven fabric before being impregnated with distilled water
M2: Mass (g) of the nonwoven fabric after it is soaked in distilled water and then hung for 10 minutes

<Transparency>
According to the method described in Patent Document 1, the whiteness (WI value) of the nonwoven fabric when dry and when wet was measured by the SCI method to evaluate it. Specifically, a sample piece of 10 cm x 10 cm (MD x CD) was prepared, placed on a black acrylic plate, and the whiteness of the sample was measured with a color difference meter (manufactured by Konica Minolta, product name CM-700d). The whiteness of the nonwoven fabric when wet was measured by preparing a sample piece impregnated with 350 parts by mass and 700 parts by mass of distilled water per 100 parts by mass of the sample piece, and placing the sample on a black acrylic plate in this state.
In both the dry and wet measurements, the nonwoven fabric was pressed down with a roller (width 7.5 cm, mass 190 g, linear pressure 25.3 gf/cm) to adhere closely to the black acrylic plate.
The smaller the whiteness measured by this method, the higher the transparency.

The evaluation results for Examples 1 to 5 and Comparative Examples 1 to 9 are shown in Tables 2 to 4.

All of Examples 1 to 5 had an adhesion strength of 180 gf or more after 15 minutes, demonstrating high adhesion in a wet state. Furthermore, the variation in the average friction coefficient in the CD direction in a wet state was 0.013 or less, providing a smooth feel or a uniform feel with little localized change in feel. Furthermore, all of Examples 1 to 5 had low whiteness and relatively high transparency in a wet state, and in addition, Examples 1 to 3 and 5 had significantly higher transparency when dry than Comparative Example 1.

In Comparative Examples 1 and 2, regular viscose rayon was used instead of single-structure rayon. As a result, the adhesion after 15 minutes was below 180 gf, and the adhesion was inferior to that of the Examples. The transparency was also lower than that of the Examples. This is thought to be due to the low transparency of regular viscose rayon itself.

In Comparative Example 3, viscose rayon containing no titanium oxide and having a relatively small ash content was used instead of single-structure rayon. Therefore, the transparency was equivalent to that of the Examples, but the adhesion after 15 minutes was less than 180 gf, and the adhesion was inferior to that of the Examples.
Comparative Example 4 has a smaller basis weight than Example 2, and compared to Example 2, the adhesion force is smaller and the variation of the average friction coefficient in the CD direction in a wet state is higher. This is presumably due to the decrease in thickness and the decrease in cushioning property as the basis weight decreases. It is considered that the decrease in thickness reduces the moisture content after 15 minutes, and the amount of liquid between the nonwoven fabric and the skin decreases, which reduces the adhesion force caused by the liquid. In addition, it is presumed that the decrease in cushioning property makes it easier for the friction element to detect small irregularities on the nonwoven fabric surface, which increases the variation of the average friction coefficient.

Comparative Examples 5 to 8 have a configuration similar to that of the examples of Patent Document 1, and were produced by carrying out hydroentanglement treatment under conditions similar to those used in the examples of Patent Document 1. All of these comparative examples showed high transparency in both dry and wet states, but because the wet strength of cellulose fiber D used in combination with cellulose fiber A (corresponding to the first cellulose fiber) exceeded 1.2 cN/dtex, the adhesion after 15 minutes was below 180 gf, and the adhesion was inferior to that of the examples. A similar tendency was also seen in Comparative Example 9, in which the same fibers as in Comparative Example 6 were used to produce a cellulose fiber web with the same target weight, and the hydroentanglement treatment conditions were the same as those used in Examples 1 to 5.

This embodiment includes the following aspects.
(Aspect 1)
A first cellulosic fiber having a wet strength of 1.5 cN/dtex or more and/or a wet apparent Young's modulus of 1000 N/mm2 or ^more ;
and a second cellulosic fiber having a wet strength of 1.2 cN/dtex or less and/or a wet apparent Young's modulus of 930 N/mm2 ^or less;
The cellulosic fiber layer contains the first cellulosic fibers in a ratio of 5% by mass or more and 50% by mass or less,
The cellulosic fiber layer contains the second cellulosic fibers in a proportion of 30% by mass or more and 95% by mass or less,
In the cellulosic fiber layer, a combined ratio of the first cellulosic fiber and the second cellulosic fiber is 80 mass% or more of the total fibers constituting the cellulosic fiber layer,
The cellulosic fiber layer has a basis weight of 40 g/m2 ^or more.
Nonwoven fabric for liquid-impregnated skin covering sheets.
(Aspect 2)
The nonwoven fabric for a liquid-impregnated skin-covering sheet according to claim 1, wherein the first cellulosic fiber has a wet strength of 2.9 cN/dtex or less and/or a wet apparent Young's modulus of 3200 N/mm2 or ^less .
(Aspect 3)
a cellulosic fiber layer including first cellulosic fibers and second cellulosic fibers;
The first cellulosic fiber is a solvent-spun cellulosic fiber having an ash content of 0.5% by mass or less;
The second cellulosic fiber is selected from the group consisting of the following (1) to (3):
(1) A viscose rayon having a single cross section and a degree of irregularity of the cross section calculated by the following formula of 2.0 or less.
Roughness = L ² / (4π・S)
(In the formula, L is the perimeter of the cross section, and S is the area of the cross section.)
(2) Viscose rayon having a single cross section and a cross-sectional outline that is circular, elliptical, or spherical, or a circular, elliptical, or spherical shape with a slit;
(3) The cross section has a single structure, and the flatness of the cross section calculated by the following formula is 1.80 or more, and the unevenness of the cross section calculated by the following formula is 2.50 or less. Viscose rayon flatness = a/b
(In the formula, a is the length of the longest line segment A connecting any two points on the cross section, and b is the length of a line segment that is perpendicular to line segment A and, together with a line segment parallel to line segment A, constitutes a rectangle or square circumscribing the cross section.)
Roughness = L ² / (4π・S)
(In the formula, L is the perimeter of the cross section, and S is the area of the cross section.)
One or more viscose rayons selected from
The cellulosic fiber layer contains the first cellulosic fibers in a ratio of 5% by mass or more and 50% by mass or less,
The cellulosic fiber layer contains the second cellulosic fibers in a proportion of 30% by mass or more and 95% by mass or less,
In the cellulosic fiber layer, a combined ratio of the first cellulosic fiber and the second cellulosic fiber is 80 mass% or more of the total fibers constituting the cellulosic fiber layer,
The cellulosic fiber layer has a basis weight of 40 g/m2 ^or more.
Nonwoven fabric for liquid-impregnated skin covering sheets.
(Aspect 4)
3. The nonwoven fabric for a liquid-impregnated skin-covering sheet according to aspect 2, wherein the second cellulosic fiber has an ash content of 0.5% by mass or less.
(Aspect 5)
a cellulosic fiber layer including a first cellulosic fiber and a second cellulosic fiber having a lower wet strength and/or wet apparent Young's modulus than that of the first cellulosic fiber;
The cellulosic fiber layer contains the first cellulosic fibers in a ratio of 5% by mass or more and 50% by mass or less,
The cellulosic fiber layer contains the second cellulosic fibers in a proportion of 30% by mass or more and 95% by mass or less,
In the cellulosic fiber layer, a combined ratio of the first cellulosic fiber and the second cellulosic fiber is 80% by mass or more of the total fibers constituting the cellulosic fiber layer,
A nonwoven fabric for a liquid-impregnated skin application sheet, wherein the variation in average friction coefficient in the CD direction of the surface of the cellulose fiber layer in a wet state is 0.013 or less, and the adhesion force after 15 minutes measured on the surface of the cellulose fiber layer is 180 gf or more .
(Aspect 6)
6. The nonwoven fabric for a liquid-impregnated skin-covering sheet according to claim 1, 2 or 5, wherein one or both of the first cellulosic fibers and the second cellulosic fibers have an ash content of 0.5% by mass or less.
(Aspect 7)
Aspects 5. The liquid-impregnated nonwoven fabric for skin application sheets according to any one of aspects 1 to 4, wherein the variation in average friction coefficient in the CD direction of the surface of the cellulosic fiber layer in a wet state is 0.013 or less, and the adhesion strength after 15 minutes measured on the surface of the cellulosic fiber layer is 180 gf or more .
(Aspect 8)
Aspect 8. The nonwoven fabric for a liquid-impregnated skin application sheet according to any one of Aspects 1 to 7, wherein the cellulosic fiber layer contains adhesive fibers, and fibers constituting the cellulosic fiber layer are adhered by the adhesive fibers.
(Aspect 9)
The nonwoven fabric for liquid-impregnated skin application sheets according to any one of Aspects 1 to 8, having a basis weight of 40 g/m2 or ^more and 70 g/ ^m2 or less.
(Aspect 10)
10. The nonwoven fabric for a liquid-impregnated skin-applying sheet according to any one of Aspects 1 to 9, which is a single-layer nonwoven fabric consisting of only the cellulosic fiber layer.
(Aspect 11)
The present invention relates to a method for producing a cellulose-based fiber web having a basis weight of 40 g/m2 or ^more , the method comprising the steps of: preparing a cellulose-based fiber web comprising: a first cellulose-based fiber having a wet strength of 1.5 cN/dtex or more and/or a wet apparent Young's modulus of 1000 N/mm2 or more in a proportion of 5% by mass to 50% by ^mass ; and a second cellulose-based fiber having a wet strength of 1.2 cN/dtex or less and/or a wet apparent Young's modulus of 930 N/ ^mm2 or less in a proportion of 30% by mass to 95% by mass; the combined proportion of the first cellulose-based fiber and the second cellulose-based fiber is 80% by mass or more of the total fibers constituting the cellulose-based fiber web; and subjecting the cellulose-based fiber web to an entanglement treatment using a high-pressure fluid flow to entangle the fibers.
A method for producing a nonwoven fabric for liquid-impregnated skin covering sheets.
(Aspect 12)
the high pressure fluid stream being a high pressure water stream;
The method for producing a nonwoven fabric for a liquid-impregnated skin application sheet according to claim 11, wherein a total energy (E) applied to the cellulosic fiber web by the high-pressure water stream is 0.6 kWh/kg/m or less.
(Aspect 13)
A liquid-impregnated skin application sheet, comprising: 100 parts by mass of the nonwoven fabric for liquid-impregnated skin application sheets according to any one of Aspects 1 to 10; and 500 parts by mass or more and 2,000 parts by mass or less of liquid impregnated therein.
(Aspect 14)
A face mask obtained by impregnating 500 parts by mass or more and 2,000 parts by mass or less of liquid with respect to 100 parts by mass of the liquid-impregnated nonwoven fabric for skin application sheet according to any one of Aspects 1 to 10.

The nonwoven fabric of the present disclosure includes a cellulosic fiber layer containing specific first and second cellulosic fibers in specific proportions, and exhibits good adhesion to the skin in a wet state. Therefore, the nonwoven fabric of the present disclosure is useful as a substrate for covering the skin in a liquid-impregnated state, such as a face mask.

Claims (12)

A first cellulosic fiber having a wet strength of 1.5 cN/dtex or more and/or a wet apparent Young's modulus of 1000 N/mm2 or ^more ;
and a second cellulosic fiber having a wet strength of 1.2 cN/dtex or less and/or a wet apparent Young's modulus of 930 N/mm2 ^or less;
The cellulosic fiber layer contains the first cellulosic fibers in a ratio of 5% by mass or more and 50% by mass or less,
The cellulosic fiber layer contains the second cellulosic fibers in a proportion of 30% by mass or more and 95% by mass or less,
In the cellulosic fiber layer, a combined ratio of the first cellulosic fiber and the second cellulosic fiber is 80 mass% or more of the total fibers constituting the cellulosic fiber layer,
The cellulosic fiber layer has a basis weight of 40 g/m2 ^or more.
Nonwoven fabric for liquid-impregnated skin covering sheets. The second cellulosic fiber is selected from the group consisting of the following (1) to (3):
(1) A viscose rayon having a single cross section and a degree of irregularity of the cross section calculated by the following formula of 2.0 or less.
Roughness = L ² / (4π・S)
(In the formula, L is the perimeter of the cross section, and S is the area of the cross section.)
(2) Viscose rayon having a single cross section and a cross-sectional outline that is circular, elliptical, or spherical, or a circular, elliptical, or spherical shape with a slit;
(3) The cross section has a single structure, and the flatness of the cross section calculated by the following formula is 1.80 or more, and the unevenness of the cross section calculated by the following formula is 2.50 or less. Viscose rayon flatness = a/b
(In the formula, a is the length of the longest line segment A connecting any two points on the cross section, and b is the length of a line segment that is perpendicular to line segment A and, together with a line segment parallel to line segment A, constitutes a rectangle or square circumscribing the cross section.)
Roughness = L ² / (4π・S)
(In the formula, L is the perimeter of the cross section, and S is the area of the cross section.)
The nonwoven fabric for liquid-impregnated skin application sheets according to claim 1 , which is one or more viscose rayons selected from the following: 3. The nonwoven fabric for liquid-impregnated skin application sheets according to claim 1 or 2, wherein the variation in average friction coefficient in the CD direction of the surface of the cellulose-based fiber layer in a wet state is 0.013 or less, and the adhesion strength after 15 minutes measured on the surface of the cellulose-based fiber layer is 180 gf or more. The nonwoven fabric for liquid-impregnated skin application sheets according to claim 1 , wherein the first cellulosic fibers have a wet strength of 2.9 cN/dtex or less and/or a wet apparent Young's modulus of 3200 N/mm ² or less. The nonwoven fabric for liquid-impregnated skin application sheets according to claim 1 , wherein one or both of the first cellulosic fibers and the second cellulosic fibers have an ash content of 0.5% by mass or less. 6. The nonwoven fabric for liquid-impregnated skin application sheets according to claim 1 , wherein the cellulosic fiber layer comprises an adhesive fiber, and fibers constituting the cellulosic fiber layer are adhered by the adhesive fiber. The nonwoven fabric for liquid-impregnated skin application sheets according to any one of claims 1 to 6 , having a basis weight of 40 g/m2 or ^more and 100 g/m2 or ^less . The nonwoven fabric for liquid-impregnated skin application sheets according to any one of claims 1 to 7 , which is a single-layer nonwoven fabric consisting of the cellulosic fiber layer alone. A fiber web containing first cellulose fibers having a wet strength of 1.5 cN/dtex or more and/or a wet apparent Young's modulus of 1000 N/mm2 ^{or more} in a proportion of 5% to 50% by mass, and second cellulose fibers having a wet strength of 1.2 cN/dtex or less and/or a wet apparent Young's modulus of 930 N/mm2 or ^less in a proportion of 30% to 95% by mass, wherein the combined proportion of the first cellulose fibers and the second cellulose fibers is 80% by mass or more of the total fibers constituting the fiber web, and the fiber web has a basis weight of 40 g/m2 or ^more ; and the method includes subjecting the cellulosic fiber web to an entanglement treatment using a high-pressure fluid flow to entangle the fibers.
A method for producing a nonwoven fabric for use as a liquid-impregnated skin covering sheet. the high pressure fluid stream being a high pressure water stream;
10. The method for producing a nonwoven fabric for a liquid-impregnated skin application sheet according to claim 9 , wherein a total energy (E) applied to the cellulosic fiber web by the high-pressure water stream is 0.6 kWh/kg/m or less. A liquid-impregnated skin application sheet, comprising 100 parts by mass of the nonwoven fabric for liquid-impregnated skin application sheets according to any one of claims 1 to 8 , and 500 parts by mass or more and 2000 parts by mass or less of liquid impregnated therein. A face mask obtained by impregnating 500 parts by mass or more and 2000 parts by mass or less of liquid with respect to 100 parts by mass of the nonwoven fabric for liquid-impregnated skin application sheet according to any one of claims 1 to 8 .