JP2018150641A - Nonwoven fabric and liquid impregnated nonwoven fabric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonwoven fabric excellent in handleability even in a state where liquid is impregnated.SOLUTION: The nonwoven fabric comprises cellulosic fibers and adhesive fibers. The nonwoven fabric comprises at least 10 mass% of cellulosic fibers and at least 55 mass% of adhesive fibers. The fibers are mutually bonded with the adhesive fibers. The basis weight is at least 200 g/m.SELECTED DRAWING: None

Description

  The present invention relates to a nonwoven fabric and a liquid-impregnated nonwoven fabric obtained by impregnating the nonwoven fabric with a liquid.

  One application of a liquid-impregnated nonwoven fabric obtained by impregnating a nonwoven fabric with a liquid is a filter for humidifying a mask. When a nonwoven fabric impregnated with a liquid is used as a filter for a mask, the filter has a function of humidifying the oral cavity and throat, and prevents, for example, drying of the oral cavity and throat during sleep. For example, the humidifying filter is provided in a non-moisture permeable container. The user of the mask takes out the wet filter from the non-moisture permeable container at the time of use, and uses the filter in a storage portion such as a pocket provided in the mask. A mask provided with such a filter is described in Patent Document 1, for example.

Japanese Patent No. 4832166

  When using a mask with a humidifying filter (hereinafter also referred to as a “humidifying mask”), it is often necessary to attach a wet filter to the mask (this is done by the user). For this reason, the humidifying filter needs not only to retain moisture but also to have good handleability. An object of this indication is to provide the nonwoven fabric excellent in the handleability also in the state impregnated with the liquid.

The present disclosure is a non-woven fabric including cellulosic fibers and adhesive fibers, including at least 10% by mass of the cellulosic fibers, including at least 55% by mass of the adhesive fibers, and the fibers are formed by the adhesive fibers. Provided is a non-woven fabric which is bonded and has a basis weight of at least 200 g / m ² .

  According to the present disclosure, it is possible to obtain a nonwoven fabric having an appropriate hardness and excellent handleability in a state where the liquid is impregnated while maintaining a good liquid. Therefore, when it is necessary to attach the member in which the nonwoven fabric is impregnated with the liquid to, for example, a mask or an instrument, the attaching operation can be easily performed.

It is sectional drawing of an example of the cellulosic fiber used by this embodiment. It is sectional drawing of an example of the cellulosic fiber used by this embodiment. It is sectional drawing of an example of the cellulosic fiber used by this embodiment. It is sectional drawing of an example of the cellulosic fiber used by this embodiment. It is sectional drawing of an example of the cellulosic fiber used by this embodiment. It is sectional drawing of an example of the cellulosic fiber used by this embodiment. (A) And (b) is a schematic diagram which shows the method of evaluating the hardness of a nonwoven fabric. 4 is an electron micrograph of an entire cross section of a nonwoven fabric of Example 2. FIG. 4 is an electron micrograph of a cross section taken near the upper surface of the nonwoven fabric of Example 2. FIG. 4 is an electron micrograph of the inside of a cross section of the nonwoven fabric of Example 2. FIG. 4 is an electron micrograph of a cross section taken near the lower surface of the nonwoven fabric of Example 2. FIG.

(Background to the present embodiment)
When storing non-woven fabric wetted with liquid (that is, in a wet state) in a predetermined place, such as a humidifying filter for a humidifying mask, if the non-woven fabric is too soft, it may be difficult to handle and the storing operation may not proceed smoothly. all right. In particular, many of the nonwoven fabrics that are impregnated with liquid contain cellulosic fibers such as rayon in order to ensure liquid absorbency and liquid retention. In addition, the handleability tends to decrease. Therefore, the present inventors have the property of retaining a relatively large amount of liquid (liquid absorption) and the property of retaining the impregnated liquid for a long period of time (liquid retention), while also being easy to handle. The composition of an excellent nonwoven fabric was examined. As a result, in the nonwoven fabric configured to bond fibers with adhesive fibers, even if the proportion of adhesive fibers is increased to some extent (that is, the proportion of cellulosic fibers is decreased), the liquid absorbency of the nonwoven fabric is not much. It was found that the handleability was remarkably improved and the liquid retention was also improved without lowering.
Hereinafter, the nonwoven fabric of the present embodiment and the liquid-impregnated nonwoven fabric obtained by impregnating the nonwoven fabric with the liquid will be described.

(Cellulose fiber)
First, the cellulosic fiber contained in the nonwoven fabric of this embodiment is demonstrated.
As a cellulosic fiber used in this embodiment,
-Natural fibers derived from plants such as cotton, linen, ramie, jute and hemp-obtained by viscose method, rayon and polynosic; obtained by copper ammonia method, cupra; and obtained by solvent spinning method Examples thereof include semi-synthetic fibers such as cellulose fibers-acetate fibers obtained by a regenerated fiber-melt spinning method such as cellulose fibers (such as Lyocell (registered trademark) and Tencel (registered trademark) of Renzing). In the present embodiment, the cellulosic fibers are not particularly limited, and one or more of these fibers may be arbitrarily selected.

  In this embodiment, rayon (viscose rayon) obtained by the viscose method is used. As will be described later, viscose rayon is preferably used in this embodiment because it is easy to obtain a modified cross-section, easily gives a nonwoven fabric with high liquid absorbency, and is easy to produce a nonwoven fabric.

  The cross section of the cellulosic fiber is not particularly limited, and may be a circular cross section or an irregular cross section other than a circular shape. In this specification, the “cross section” of a fiber refers to a cross section that appears when a fiber is cut perpendicularly to its length.

  The cross section of the cellulosic fiber having an atypical cross section may be, for example, an irregular chrysanthemum flower shape, an jade shape, or a circular, elliptical or jade shape having a slit. The cellulosic fiber having an irregular chrysanthemum-like cross section is, for example, viscose rayon manufactured using a spinneret having a circular extrusion hole. Viscose rayon has an irregular chrysanthemum shape even when manufactured using a die having a circular extrusion hole. Cotton has a flat cross section having a hollow portion, which is also a cellulosic fiber having an atypical cross section.

  Alternatively, the cellulosic fiber having an atypical cross section has a cross section in which one or a plurality of rod-shaped portions abut against or intersect with another one or a plurality of rod-shaped sections (hereinafter also referred to as “branched cross section”). You may have. When the cellulosic fiber has a branch-like cross section, the surface area of the fiber increases, and the abutting part and the crossing part tend to give a minute inter-fiber gap, so that more liquid is absorbed and the absorbed liquid is absorbed. It is thought that it becomes easy to hold. Specifically, the cross section of the cellulosic fiber is, for example, as shown in FIG. 1 and FIG. 2, a cross-sectional shape in which one rod-like portion a abuts on one rod-like portion b, and as shown in FIG. The section a may have a cross-sectional shape that intersects with one bar-shaped part b, and as shown in FIG. 4, the two bar-shaped parts a and b may have a cross-sectional shape that abuts against one bar-shaped part c. In the cellulosic fibers having these cross-sectional shapes, the liquid is easily held at a portion where the rod-shaped portion abuts against another rod-shaped portion or intersects.

  When a plurality of bar-like portions hit or intersect with another bar-like portion, the hitting points or the intersecting points may overlap each other as shown in FIG. Further, the rod-shaped portion does not have to be straight as illustrated, and may be curved. For example, as shown in FIG. 5, a cellulosic fiber having a cross section in which one bar-like part a is in contact with one curved bar-like part b can also be used in this embodiment.

  The cellulosic fibers are particularly shaped as shown in FIG. 1, especially a T-shaped cross section, or as shown in FIG. 2, especially as a substantially y-shaped cross section, or as shown in FIG. It may have a Y-shaped cross section. The cellulosic fibers of these shapes are shapes that can easily hold a liquid, and the number of fibers that exist in a certain region because the rod-shaped portions easily overlap each other in the non-woven fabric when it is deformed or deformed. Easy to make more. Therefore, if the cellulose fiber of these shapes is used, a nonwoven fabric with high liquid absorbency can be provided in a form having a relatively small bulk (that is, a relatively high fiber density). In addition, if cellulosic fibers having these shapes are used, it is easy to obtain a nonwoven fabric in which the fiber density is higher on at least one surface than the inside in a cross section cut along the thickness direction of the nonwoven fabric, which will be described later. Become. More specifically, such a non-woven fabric can be obtained by, for example, pressing as described later, but since the cellulosic fibers of these shapes tend to overlap with each other, even with relatively weak pressing, It is easy to give a high fiber density on the nonwoven fabric surface. On the other hand, according to such a weak pressing process, the fiber density inside the nonwoven fabric can be kept relatively low, and therefore the fiber density inside the nonwoven fabric tends to be lower than that of at least one surface.

  In the present embodiment, the cellulosic fiber has a plurality of protrusions on the outer periphery in the cross section, and a recess formed between the protrusions and the protrusions forms a line extending in the length direction on the outer peripheral surface of the fiber. It may be what you are doing. The viscose rayon having the above irregular chrysanthemum-like cross section is an example, and on the outer peripheral surface thereof, the filaments corresponding to the recesses formed between the chrysanthemum petals (convex parts) and the petals are observed. The A cellulosic fiber having an irregular cross section having such a convex portion (and a concave portion) has a large surface area of the fiber and easily retains the liquid in the concave portion, so that the liquid absorbency of the nonwoven fabric is easily improved.

  Also in the fiber having a branch-like cross section as shown in FIGS. 1 to 5, a plurality of convex portions are formed on the outer periphery of the cross section, that is, on the outer periphery of each rod-like portion, and formed between the convex portions. The formed recessed part may form the filament extended in a length direction in the outer peripheral surface of a fiber. Specifically, the outer periphery of the fiber may have fine convex portions as shown in FIG. Cellulosic fibers having such a fiber cross-section easily retain liquid in the concave portion formed between the convex portions on the outer periphery of the fiber in addition to the portion where the rod-shaped portion abuts. And further improve liquid retention. Since the fiber having a branch-shaped cross section has a larger surface area, it is considered that the liquid absorbency and liquid retention of the nonwoven fabric are further improved if a fine convex portion is formed over the entire outer periphery.

  The cellulosic fiber having the cross section shown in FIGS. 1 to 5 may be, for example, viscose rayon. When producing rayon by the viscose method, fibers as shown in FIGS. 1 to 5 can be obtained by appropriately designing the shape of the extrusion hole of the spinneret. Moreover, a viscose rayon is easy to be obtained as a thing of the cross-sectional shape where the outer periphery (namely, the whole fiber outer periphery) of each rod-shaped part as shown in FIG. 6 has a fine convex part. Alternatively, the cellulosic fibers having the cross sections shown in FIGS. 1 to 5 may be solvent-spun cellulose fibers or melt-spun cellulose fibers. These fibers may have the cross section shown in FIGS. 1 to 5 by appropriately designing the shape of the spinneret.

  In the case where the cellulosic fiber has a branch-like cross section, the ratio of the length to the width of each rod-like portion may be, for example, 1 to 6, particularly 1.5 to 5, and more particularly 2. It may be ~ 4. When the width is not constant in one rod-shaped portion, the largest width is set as the width of the rod-shaped portion. In one fiber cross section, each bar may have a different length / width ratio.

  The fineness of the cellulosic fiber is not particularly limited, and may be, for example, 0.6 dtex to 5.6 dtex, particularly 1.4 dtex to 4.4 dtex, and more particularly 1.7 dtex to 3.3 dtex. If the fineness is too small, the nonwoven fabric may be soft and handleability may be reduced. If it is too large, the number of nonwoven fabric components may be reduced and the liquid absorbency may be reduced. In addition, when it is a natural fiber, the fineness can be calculated according to the method by JIS L 1019 7.4.1 Micro Ney.

  The fiber length of the cellulosic fiber is not particularly limited, and may be appropriately selected according to the method for producing the nonwoven fabric. When producing a card web and manufacturing a nonwoven fabric, the fiber length of a cellulosic fiber may be 25 mm-100 mm, especially 30 mm-70 mm. When producing an air laid web to produce a nonwoven fabric, the fiber length may be, for example, 1 mm to 50 mm, and particularly 5 mm to 30 mm. When producing a wet papermaking web to produce a nonwoven fabric, the fiber length may be, for example, 0.5 mm to 20 mm, particularly 1 mm to 10 mm.

(Adhesive fiber)
The adhesive fiber exhibits adhesiveness by an adhesive treatment (for example, thermal adhesion treatment, electron beam irradiation, ultrasonic welding (ultrasonic welder), etc.) and serves to bond the fibers together.
The adhesive fiber is, for example, a synthetic fiber made of a thermoplastic resin. The thermoplastic resin is not particularly limited. For example, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polylactic acid, polybutylene succinate, and copolymers thereof; polypropylene, polyethylene (high A propylene copolymer (propylene-ethylene copolymer, propylene-butene-1-ethylene copolymer) comprising, as main components, density polyethylene, low density polyethylene, linear low density polyethylene, and the like, polybutene-1, and propylene. And polyolefin resins such as ethylene-vinyl acetate copolymers; polyamide resins such as nylon 6, nylon 12 and nylon 66; acrylic resins; polycarbonate, polyacetal, polystyrene And engineering plastics such as cyclic polyolefin, and is selected arbitrarily from those elastomers.

  The synthetic fiber may be a single fiber composed of one or a plurality of thermoplastic resins selected from the above, or may be a composite fiber composed of two or more components (also referred to as “sections”). In the composite fiber, each component may be composed of one thermoplastic resin, or may be a mixture of two or more thermoplastic resins. The composite fiber may be, for example, a core-sheath composite fiber, a sea-island composite fiber, a split composite fiber, or a side-by-side composite fiber. The core-sheath type composite fiber may be an eccentric core-sheath type composite fiber in which the center of the core component does not coincide with the center of the sheath component in the fiber cross section, and the center of the core component coincides with the center of the sheath component in the fiber cross section. It may be a sheath type composite fiber.

Whether it is a single fiber or a composite fiber, the synthetic fiber may have an atypical cross section. In the case of the core-sheath type composite fiber and the sea-island type composite fiber, the core component and / or the island component may have an atypical cross section in the fiber cross section.
When the synthetic fiber has an atypical cross section, the cross section may be the shape described in connection with the cellulosic fiber, or an ellipse, a polygon, a star, or a shape in which a plurality of convex portions are joined at the base. (For example, clover shape). Even when the synthetic fiber has an atypical cross section, as described above in relation to the cellulosic fiber, the liquid absorbency and liquid of the non-woven fabric can be increased by increasing the surface area and forming concave portions between the convex portions. Retention is easy to improve.
In the present embodiment, two or more synthetic fibers may be used in combination as synthetic fibers.

  When the synthetic fiber is a composite fiber, two or more components may be arranged so that a thermoplastic resin having a lower melting point forms part of the fiber surface. In that case, the thermoplastic resin having a low melting point is melted or softened when heat is applied in the process of producing the nonwoven fabric, and becomes an adhesive component, which contributes to adhesion between fibers or adhesion to other members. Combinations of thermoplastic resins constituting the composite fiber include, for example, combinations of polyolefin resins such as polyethylene / polyethylene terephthalate, polypropylene / polyethylene terephthalate, and propylene copolymer / polyethylene terephthalate, and polyester resins, and polyethylene / polypropylene, A combination of two types of polyolefin-based thermoplastic resins such as propylene copolymer / polypropylene, and a combination of two types of polyester-based resins having different melting points. In addition, the thermoplastic resin illustrated as a structural component of a single fiber or a composite fiber may contain another component as long as it contains 50 mass% or more of the specifically shown thermoplastic resin. For example, in the combination of polyethylene / polyethylene terephthalate, “polyethylene” may contain other thermoplastic resins and additives as long as it contains 50% by mass or more of polyethylene. This also applies in the following examples.

  When the adhesive fiber is a core-sheath type composite fiber in which a thermoplastic resin having a lower melting point constitutes the sheath, the core / sheath combination includes, for example, polyethylene terephthalate / polyethylene, polyethylene terephthalate / polypropylene, and polyethylene terephthalate / propylene. It may be a copolymer, polytrimethylene terephthalate / polyethylene, polybutylene terephthalate / polyethylene, polyethylene terephthalate / copolyester (for example, polyethylene terephthalate copolymerized with isophthalic acid). The core-sheath type composite fiber whose sheath is polyethylene (for example, high density polyethylene, low density polyethylene, or linear low density polyethylene) or copolymer polyester is heat-treated at a temperature equal to or higher than the melting point of the thermoplastic resin constituting the sheath. By doing so, the sheath melts and the fibers are bonded together.

  When the adhesive fiber is a core-sheath type composite fiber, the core / sheath composite ratio (volume ratio, core / sheath) may be, for example, 80/20 to 20/80, and in particular 60/40 to 40/60. It may be. When the ratio of the sheath is too small, the adhesion between the fibers becomes insufficient, and the hardness (koshi) when wet may be insufficient. When the ratio of the sheath is too large, the ratio of the core component that maintains the fiber shape decreases, so that the hardness (koshi) of the nonwoven fabric may be insufficient.

  Synthetic fibers as adhesive fibers impart mechanical strength to the nonwoven fabric by bonding the fibers together, and also impart hardness (koshi) to the nonwoven fabric to improve the handleability of the nonwoven fabric. In addition, the nonwoven fabric containing the synthetic fiber is easy to handle in a wet state because its “stiffness” is not easily lowered even in a wet state.

  The fineness of the adhesive fiber is not particularly limited, and may be, for example, 1.4 dtex to 7.8 dtex, particularly 2.2 dtex to 6.7 dtex, and more particularly 3.3 dtex to 5.6 dtex. If the fineness is too small, the nonwoven fabric may become dense and the liquid absorbency may be reduced. If the fineness is too large, voids of the nonwoven fabric may be increased and the liquid retention may be reduced.

  The fiber length of the adhesive fiber is not particularly limited, and may be appropriately selected according to the method for producing the nonwoven fabric. When producing a card web and manufacturing a nonwoven fabric, the fiber length of an adhesive fiber may be 25 mm-100 mm, especially 30 mm-70 mm. When producing an air laid web to produce a nonwoven fabric, the fiber length may be, for example, 1 mm to 50 mm, and particularly 5 mm to 30 mm. When producing a wet papermaking web to produce a nonwoven fabric, the fiber length may be, for example, 0.5 mm to 20 mm, particularly 1 mm to 10 mm.

(Nonwoven fabric configuration)
Then, the structure of the nonwoven fabric of this embodiment is demonstrated.
The nonwoven fabric of this embodiment contains at least 10% by mass of cellulosic fibers. Cellulosic fibers are contained in the nonwoven fabric in order to ensure the liquid absorbency and liquid retention of the nonwoven fabric. If the proportion of cellulosic fibers is too small, the liquid absorbency and liquid retention of the nonwoven fabric will be reduced. Cellulosic fibers may be contained in an amount of 12% by mass or more, more particularly 15% by mass or more. The upper limit of the ratio of the cellulosic fibers is 45% by mass, particularly 40% by mass, and more particularly 35% by mass.

  The nonwoven fabric of this embodiment contains at least 55% by mass of adhesive fibers. Adhesive fiber gives the nonwoven fabric strength and hardness (koshi) by bonding the fibers together, and plays the role of improving the handleability of the nonwoven fabric. If the proportion of the adhesive fibers is too small, the nonwoven fabric will be insufficiently hard, and handling properties in a wet state may be reduced, and the nonwoven fabric is likely to become fuzzy. May decrease. Adhesive fibers may be contained in particular in an amount of 60% by mass or more, more particularly 65% by mass or more. The upper limit of the ratio of the adhesive fibers is 90% by mass, particularly 85% by mass, and more particularly 80% by mass.

  Cellulosic fibers and adhesive fibers have a cellulosic fiber: adhesive fiber mass ratio of, for example, 10:90 to 45:55, particularly 15:85 to 40:60, and more particularly 20:80 to 35:65. As such, they may be mixed and used. If the ratio of cellulosic fibers to adhesive fibers is too small, sufficient absorbency and liquid retention may not be imparted to the nonwoven fabric, and if too large, the handleability of the nonwoven fabric may decrease. In addition, fluffing is likely to occur.

  The nonwoven fabric of this embodiment may contain fibers other than cellulosic fibers and adhesive fibers (hereinafter “other fibers”). Other fibers include natural fibers that are not cellulosic fibers (for example, wool, silk, etc.), synthetic fibers that are not adhesive fibers (for example, they do not melt or soften when the adhesive component of the adhesive fibers is melted, and exhibit adhesive properties. Not synthetic fibers). Other fibers may be included in a proportion of 35% by mass or less, particularly 25% by mass or less, and more particularly 10% by mass or less. Other fibers are not included, that is, the nonwoven fabric of this embodiment may be composed of cellulosic fibers and adhesive fibers.

  In the nonwoven fabric of this embodiment, the fibers are bonded to each other with adhesive fibers. Thereby, the strength and hardness of the nonwoven fabric are ensured, and the handleability in a wet state is improved. Adhesion with adhesive fibers is achieved by fixing a fiber in which a part of the adhesive fiber is melted or softened or altered to show adhesiveness and cross or contact with it. Specifically, the adhesion between fibers refers to the adhesion between adhesive fibers and adhesive fibers, and the adhesion between adhesive fibers and cellulosic fibers. If other fibers are further included, they are additionally adhered. This refers to the adhesion between the conductive fiber and other fibers. The adhesion may be by thermal adhesion in which heat is applied to melt or soften part of the adhesive fiber, or may be by irradiation with an electron beam or ultrasonic welding.

Nonwoven fabric of the present embodiment has at least a basis weight of 200 g / ^{m 2.} If the basis weight is less than 200 g / m ² , the hardness of the nonwoven fabric is lowered, and it becomes difficult to handle in a wet state. Although the upper limit of the fabric weight of a nonwoven fabric is not specifically limited, For example, it is 600 g / m < ² >, especially 500 g / m < ² >, More specifically, it is 400 g / m < ² >. As the basis weight of the nonwoven fabric increases, the liquid absorbency tends to decrease. If it is too large, sufficient liquid absorbency may not be obtained in the nonwoven fabric. In addition, as the basis weight of the nonwoven fabric increases, the liquid retention tends to improve, but when the basis weight exceeds 500 g / m ² , the liquid retention tends to decrease. In view of these, nonwoven preferred basis weight is ^{300g / m 2 ~400g / m 2} .

Overall nonwoven fabric of the present embodiment, at the time of drying, for ^example, may have a fiber density of ^{0.01g / cm 3 ~0.20g / cm 3} . The fiber density of the whole nonwoven fabric can be determined from the basis weight and thickness (thickness measured by applying a load of 2.94 cN per cm ² ). Fiber density of the entire non-woven fabric, particularly ^{0.02g / cm 3 ~0.15g / cm 3} , and more particularly may be ^{0.04g / cm 3 ~0.10g / cm 3} .

  The nonwoven fabric of this embodiment may have a higher fiber density on at least one surface than the inside when observing a cross section cut along the thickness direction. In this embodiment, it is preferable that the fiber density is higher than the inside on both surfaces. If the fiber density is higher than the inside at least on one surface, the liquid absorbed inside the nonwoven fabric is difficult to be released to the outside, and the liquid is easily held for a longer time. Whether there is a difference in the fiber density between the inside and the surface of the nonwoven fabric can be recognized by observing a cross section of the nonwoven fabric along the thickness direction with an electron microscope (approximately 50 times magnification). More specifically, when observed with an electron microscope, the portion where the fibers are gathered more densely is a region where the fiber density is higher, and the portion where the fibers are gathered more loosely is lower in the fiber density. It can be said that it is an area.

  The height of the fiber density can be confirmed, for example, by counting the number of cross-sections of fibers cut per fixed area with an electron microscope (about 50 times magnification) in a cross-section cut along the thickness direction of the nonwoven fabric. More specifically, when the cross section of the nonwoven fabric is divided into five equal parts along the thickness direction, the upper and lower fifth portions are designated as “nonwoven fabric surface” (“upper surface” and “lower surface, respectively”. )), And when the cross section of the nonwoven fabric is divided into five equal parts along the thickness direction, the upper fifth portion and the lower fifth portion excluding the lower fifth portion are When the ratio of the number of cross-sections of the fibers on the surface of the non-woven fabric to the number of cross-sections of the fibers inside the non-woven fabric is 1.05 or more, the fiber density on the non-woven fabric surface can be regarded as higher than the inside. If it is difficult to confirm the number of cross sections of the adhesive fiber, for example, dye only the cellulose fibers, count only the number of cross sections of the cellulosic fibers using an optical microscope, and calculate the ratio described above based on the number of cross sections of the cellulosic fibers. May be.

The nonwoven fabric of the present embodiment may be laminated with another nonwoven fabric on one or both surfaces of the nonwoven fabric for the purpose of further improving the liquid absorbability and liquid retention. The basis weight of the other nonwoven fabric may be, for example, 10 to 100 g / m ² .

(Nonwoven fabric manufacturing method)
The nonwoven fabric of this embodiment can be manufactured by mixing cellulosic fibers, adhesive fibers, and other fibers, if included, producing a fiber web, and bonding the fibers together with adhesive fibers. . The fiber web can be produced by a known method. The form of the fiber web may be any form of a card web such as a parallel web, a cross web, a semi-random web, and a random web, a long fiber web such as an air lay web, and a wet papermaking web.

  The fiber web is subjected to an adhesive treatment. The adhesion process may be a heat treatment, for example. According to the heat treatment, the component having the lowest melting point (thermoadhesive component) among the resin components constituting the adhesive fiber can be melted or softened by heating during the heat treatment, and the fibers constituting the fiber web can be bonded to each other. . The heat treatment may be, for example, hot air processing for blowing hot air, hot roll processing (for example, hot embossing roll processing), or heat treatment using infrared rays. The hot air processing may be performed using a device that blows hot air having a predetermined temperature onto the fiber web, for example, a hot air through heat treatment machine and a hot air blowing heat treatment machine. The heat treatment is performed by a method of applying pressure to the surface of the fiber web using a hot roll or the like having a smooth surface after the hot air processing is performed under the condition that the adhesive fibers are bonded to the center of the fiber web. Good. By carrying out such a two-stage treatment, it is possible to obtain a non-woven fabric having a fiber density higher on the surface than on the inside in a cross section cut in the thickness direction. In addition, the thickness of a nonwoven fabric can be adjusted simultaneously by applying a pressure to a fiber web during heat processing so that it may mention later.

  The temperature of the heat treatment may be a temperature at which the component having the lowest melting point (thermal bonding component) among the resin components constituting the adhesive fiber is softened or melted, for example, a temperature equal to or higher than the melting point of the component. For example, when the hot air processing is performed when the component having the lowest melting point among the resin components constituting the adhesive fiber is high-density polyethylene, hot air having a temperature of 130 ° C. to 150 ° C. may be blown.

  The adhesion treatment may be performed by irradiation with an electron beam or the like, or ultrasonic welding. Also by these adhesion treatments, the fibers can be bonded to each other with the resin component constituting the adhesive fibers.

  The fiber web (nonwoven fabric) after the adhesion treatment may be subjected to pressing to adjust the thickness and / or increase the smoothness of the surface, if necessary. The pressing process refers to a process of applying pressure to the surface of the fiber web using a member such as a roll, a flat plate, a mesh, or a net. The adjustment of the thickness may be performed in order to obtain the fiber density in the above-described range, or may be performed in order to obtain a desired thickness depending on the application. For example, when producing a humidifying filter for a humidifying mask, the thickness of the nonwoven fabric may be adjusted to be, for example, 1 mm to 15 mm, particularly 3 mm to 7 mm.

  Alternatively, the adhesion process and the pressing process may be performed simultaneously. When the bonding process and the pressing process are performed at the same time, it is easy to obtain a non-woven fabric having a higher fiber density on the surface than on the inside in the cross section cut in the thickness direction. Specifically, when heat treatment is performed while applying pressure to the fiber web, thickness adjustment and / or surface smoothing can be performed simultaneously with thermal bonding. Pressurization and heating can be performed simultaneously by adjusting the roll pressure during hot roll processing, for example. Alternatively, during hot air processing, for example, heating and pressing can be performed simultaneously by applying hot air to the fiber web in a state where a metal plate provided with a large number of ventilation holes is placed on the fiber web. If the nonwoven fabric becomes too thin due to the weight of the metal plate, a stopper that prevents the metal plate from moving below the predetermined position may be used so that the thickness of the nonwoven fabric does not become thinner than the predetermined thickness. .

  The obtained nonwoven fabric may be subjected to a punching process as necessary. The punching process is performed to make the nonwoven fabric into a predetermined shape according to the application. Alternatively, the punching process may be performed when it is desired to provide an opening in the nonwoven fabric.

(Liquid impregnated nonwoven fabric)
The nonwoven fabric of this embodiment may be impregnated with a liquid and used as a liquid-impregnated nonwoven fabric. The type of liquid and the amount of impregnation thereof are appropriately selected according to the application. The liquid may be impregnated with an impregnation amount of, for example, 600 parts by mass or more and 2500 parts by mass or less, particularly with an impregnation amount of 600 parts by mass or more and 1500 parts by mass or less, more particularly 100 parts by mass of the nonwoven fabric. May be impregnated with an impregnation amount of 700 parts by mass or more and 1500 parts by mass or less.

  For example, when a liquid-impregnated non-woven fabric is used as a humidifying filter for a humidifying mask, 100 masses of non-woven fabric containing water or a liquid obtained by adding at least one additive selected from a humectant, preservative, and fragrance to water. The impregnation amount may be 300 parts by mass or more and 1400 parts by mass or less with respect to the part. Examples of the humectant include polyhydric alcohols such as glycerin, dipropylene glycol, and 1,3-butylene glycol. Examples of the preservative include methyl paraben and phenoxyethanol. The humidifying filter is used by being attached to a mask made of a nonwoven fabric or the like.

  Alternatively, the liquid-impregnated nonwoven fabric may be used as a filter for a humidifier. Similar to the humidifying filter of the humidifying mask, the humidifier filter may be preliminarily impregnated with a liquid and gradually discharge the impregnated liquid. Alternatively, the liquid may be impregnated by being immersed in a container or the like containing a liquid such as water and sucking up the liquid, and the sucked liquid may be gradually discharged.

  In the nonwoven fabric of the present embodiment, highly hydrophilic cellulosic fibers are included, and the positional relationship between the fibers is relatively easily maintained by adhesion between the fibers, and the inter-fiber gap is not easily crushed. This non-woven fabric exhibits relatively high liquid absorption and liquid retention. Furthermore, since the nonwoven fabric of this embodiment contains an adhesive fiber in a comparatively large ratio, it is hard and firm even in a wet state, and gives a firm feel to the user. Therefore, the liquid-impregnated nonwoven fabric using the nonwoven fabric of the present embodiment is useful for supplying a liquid (or vapor) to an object while holding a sufficient amount of liquid, and is also handled in a state where the liquid is held. It facilitates the work of receiving or mounting in a predetermined position. Furthermore, since the liquid-impregnated nonwoven fabric of this embodiment exhibits high rigidity even in a wet state and exhibits high shape retention, for example, when used as a humidifying filter for a humidifying mask, the liquid-impregnated nonwoven fabric is unlikely to sag and bend during use.

  Moreover, since the nonwoven fabric of this embodiment has comparatively high fabric weight, it is easy to attach | subject to a punching process combined with the fibers being joined by adhesive fiber. Therefore, the liquid-impregnated nonwoven fabric using the nonwoven fabric of the present embodiment can be provided in various shapes by punching, and can be provided in a form having an opening formed by punching if necessary. it can.

(Other uses)
The non-woven fabric of this embodiment may be applied to a use for absorbing a liquid other than a use for impregnating a liquid in advance. For example, you may use the nonwoven fabric of this embodiment as a drip absorption sheet for foodstuffs for absorbing the liquid (for example, blood of fresh fish) which exudes from foodstuffs. Since the nonwoven fabric of this embodiment can absorb a relatively large amount of liquid and can retain the absorbed liquid, it can be suitably used for applications that absorb excess liquid.

In preparing the nonwoven fabric in this example, the following fibers were prepared.
Cellulose fiber 1: Viscose rayon having a fineness of 2.2 dtex, a fiber length of 38 mm, a fiber cross section of y-shape or Y-shape shown in FIG. 2 and FIG. (Product name RBA, manufactured by Daiwabo Rayon Co., Ltd.)
Cellulose fiber 2: Viscose rayon (trade name CD, manufactured by Daiwabo Rayon Co., Ltd.) having a fineness of 2.2 dtex, a fiber length of 38 mm, and an irregular chrysanthemum flower shape.
Cellulosic fiber 3: Viscose rayon (trade name CD, manufactured by Daiwabo Rayon Co., Ltd.) having a fineness of 1.7 dtex, a fiber length of 51 mm, and an irregular cross section of chrysanthemum.
Cellulosic fiber 4: Solvent-spun cellulose fiber having a fineness of 1.7 dtex, a fiber length of 40 mm, a substantially circular fiber cross section, and no fine protrusions on the outer periphery (trade name Lyocell (registered trademark), manufactured by Renzing)
Cellulose fiber 5: Cotton (trade name MSD, manufactured by Marusan Sangyo Co., Ltd.)

Adhesive fiber 1: core-sheath type composite having a fineness of 2.2 dtex, a fiber length of 51 mm, a core component of polypropylene, a sheath component of high-density polyethylene, and a composite ratio (volume ratio, core / sheath) of 50/50 Fiber (trade name NBF (H), manufactured by Daiwabo Polytech Co., Ltd.)
Adhesive fiber 2: core-sheath type with a fineness of 2.2 dtex, a fiber length of 51 mm, a core component of polyethylene terephthalate, a sheath component of copolymerized polyester, and a composite ratio (volume ratio, core / sheath) of 50/50 Composite fiber (trade name T9611, manufactured by Toray Industries, Inc.)

(Examples 1-9, Comparative Examples 1-2)
From the fibers, as shown in Table 1 and Table 2, cellulosic fibers and adhesive fibers are selected one by one, mixed in the proportions shown in Table 1 and Table 2, and parallel using a parallel card machine. A card web was prepared. The produced parallel card webs were overlapped using a cross layer machine, and the fabric weight webs shown in Table 1 and Table 2 were produced. The cross web was heat-treated for 15 seconds in a hot-air through heat treatment machine set at 110 ° C. for Examples 6 to 8 and at a temperature of 135 ° C. for the other examples and comparative examples, and the fibers were bonded with adhesive fibers. A nonwoven fabric was obtained by heat bonding. During the heat treatment, pressing was simultaneously performed so that the nonwoven fabric had a desired thickness and a nonwoven fabric having a higher fiber density on the surface than the inside was obtained.

  Tables 1 and 2 show the basis weight, thickness when dried and wet, fiber density when dried, water absorption, and hardness of the obtained nonwoven fabric, and Table 3 shows the liquid retention. The evaluation methods of these physical properties are as follows.

[thickness]
Using a thickness measuring machine (trade name: THICKNESS GAUGE model CR-60A, manufactured by Daiei Kagaku Seisakusho Co., Ltd.), the measurement was performed with a load of 2.94 cN per 1 cm ^{2 of} the sample. The wet thickness was measured in a state where 700 parts by mass of distilled water was impregnated when the weight of the sample was 100 parts by mass.

[Water absorption rate (liquid absorption)]
A sample was cut out so that the length × width was 5 cm × 10 cm, and the weight (W) of the sample was measured. Thereafter, the sample was immersed in distilled water for 2 minutes. Then, the sample was taken out, hung with a clothespin, allowed to stand for 10 minutes, the weight (W ₁ ) of the sample was measured, and the water absorption rate was calculated from the following formula (A).
Water absorption (%) = 100 × (W ₁ −W) / W (Formula A)

[Liquid retention]
A sample was cut out so that the length × width was 5 cm × 10 cm, the weight of the sample was measured, and then the sample was impregnated with about 10 g of distilled water. This sample was allowed to stand in a ventilated state (temperature: 27.4 ° C., relative humidity: 64%). The sample was weighed when 0.5 hours passed from the start of standing, and then returned to the dryer. Then, when 1 hour, 2 hours, 3 hours, and 4 hours passed from the start of standing, the weight of the sample was measured in the same manner. From the weight of the sample before impregnation with distilled water and the weight of the sample measured at each elapsed time, how much water was retained at each elapsed time was calculated.

[Hardness]
The sample was cut out so that the length × width was 9 cm × 5 cm, and the sample was fixed so that the sample floated in the air over a length of 4 cm along the length direction (FIG. 7A). The position of the laser thickness measuring device was adjusted so that the laser of the laser thickness measuring device was irradiated to the end of this sample. Next, using a terminal having a diameter of 2 cm, a load of 9.8 cN or 49 cN was slowly applied to the approximate center of the floating area of the sample (FIG. 7B), and 5 seconds after the load was applied. The hanging amount (cm) of the sample was measured with a laser thickness meter. The wet hardness was measured in a state in which 700 parts by mass of distilled water was impregnated when the weight of the sample was 100 parts by mass.

  The nonwoven fabric of Comparative Example 1 in which the proportion of the adhesive fibers was 50% by mass was very soft in a wet state, and the sample drooped too much when a load was applied, and the amount of droop could not be measured. The comparative example 2 which does not contain a cellulosic fiber had a small water absorption rate.

The nonwoven fabrics of Examples 1 to 9 all showed a relatively high water absorption rate and were relatively hard in a wet state. Comparing Example 3 and Comparative Example 1 in which the basis weight and the type of cellulose fiber / adhesive fiber are the same, Example 3 has a smaller proportion of cellulosic fibers, but the liquid absorbency is smaller than that of Comparative Example 1. It did not drop that much. Furthermore, since Examples 1-9 all contained adhesive fibers in a larger proportion, the decrease in the thickness of the nonwoven fabric due to wetting was smaller than in Comparative Example 1.
From the results of Examples 1 to 5 and the results of Examples 6 to 8, it was found that the greater the basis weight, the greater the hardness when wet. It was also found that the liquid absorption rate tends to decrease as the basis weight increases.

When Example 3 and Comparative Examples 1 and 2 having the same basis weight and cellulose fiber / adhesive fiber type were compared, Example 3 showed better liquid retention than any of the Comparative Examples. From the results of Examples 1 to 5, in a range having a basis weight of ^{250g / m 2 ~400g / m 2} , the basis weight becomes larger, there is a tendency that the liquid retaining property is high, the liquid holding the basis weight is 500 g / ^{m 2} It was found that the sex became low. Although the same tendency was seen also about Examples 6-8, there is almost a difference in liquid retainability between a thing with a basis weight of 300 g / m ² (Example 7) and a thing with 400 g / m ² (Example 8). Was not seen.

  When Example 3 and Example 9 were compared, Example 9 showed a higher liquid absorption rate when viewed as a whole sample. However, since the thickness of Example 9 is larger than that of Example 3, when comparing the liquid absorption rate per unit thickness, Example 3 showed a higher liquid absorption rate. Moreover, when the liquid retention of Example 3 and Example 9 was compared, Example 3 showed higher liquid retention. From these facts, the rayon having a fiber cross section that is y-shaped or Y-shaped and having fine protrusions on the entire outer periphery of the fiber has higher liquid absorbency and liquid retention than the chrysanthemum cross-section rayon. It turns out that it can be higher.

When the nonwoven fabric of Example 2 was cut in the thickness direction and observed with an electron microscope at a magnification of 50 times, it was confirmed that the fiber density was higher on the surface and the fiber density was lower inside. The electron micrograph which image | photographed the cross section of Example 2 is shown to FIG. 8a is a photograph of the entire cross section, FIG. 8b is a photograph of the cross section near the upper surface, FIG. 8c is a photograph of the inside of the cross section, and FIG. 8d is a photograph of the cross section near the lower surface.
Moreover, about the nonwoven fabric of Example 2, using FIG. 8a, the inside of the nonwoven fabric (the upper fifth portion and the lower fifth portion when the cross section of the nonwoven fabric is divided into five equal parts along the thickness direction). The surface of the nonwoven fabric with respect to the number of fiber cross-sections in the three-fifth portion excluding the portion (upper and lower fifth portions when the cross-section of the nonwoven fabric is divided into five equal parts along the thickness direction) The ratio of the number of cross sections of the fibers was measured. The ratio of the number of cross sections was 1.33 (upper surface / internal) and 1.10 (lower surface / internal).

(Examples 10 to 12)
As shown in Table 4, cellulosic fibers and adhesive fibers were selected one by one from the above fibers, mixed at a ratio shown in Table 4, and a parallel card web was produced using a parallel card machine. The produced parallel card web was overlapped using a cross layer machine to produce a cross web having a basis weight of 300 g / m ² . The cross web was sandwiched between two metal plates provided with a large number of openings. On one side of the metal plate, stoppers having a height of 5 mm were arranged at the four corners so that the web was not compressed by the weight of the metal plate and the thickness did not become 5 mm or less. Hot air is applied to one surface of the web for 120 seconds and hot air is applied to the other surface of the web for 120 seconds in a hot air through heat treatment machine set at a temperature of 140 ° C., and the fibers are thermally bonded to each other with adhesive fibers. At the same time, the thickness was adjusted to about 5 mm to obtain a nonwoven fabric.

  Table 4 shows the basis weight, thickness at the time of drying, fiber density at the time of drying, water absorption, and hardness of the obtained nonwoven fabric, and Table 5 shows the liquid retention. These physical property evaluation methods are as described above. However, the liquid retention was evaluated by setting the temperature and relative humidity in the dryer to 21 ° C. and 71%, respectively.

  Example 10 using a cellulosic fiber having an irregular chrysanthemum-like cross section has Example 11 using a cellulosic fiber having a smooth outer periphery and no outer periphery. Compared with No. 12 and No. 12, it showed higher liquid absorbency and liquid retention. This is considered to be because the concave portion formed between the convex portion and the convex portion of the fiber cross section easily holds the liquid.

  The nonwoven fabric of the present embodiment is excellent in liquid absorbency and liquid retention, and is relatively hard and easy to handle in a wet state. Therefore, for example, it is suitably used as a humidifying filter for a humidifying mask, a filter for a humidifier, etc. Is done.

  a, b, c

Claims (6)

A non-woven fabric comprising cellulosic fibers and adhesive fibers, comprising at least 10% by mass of the cellulosic fibers and at least 55% by mass of the adhesive fibers, wherein the fibers are bonded to each other by the adhesive fibers. A nonwoven fabric having a basis weight of at least 200 g / m ² .   The nonwoven fabric according to claim 1, wherein the cellulosic fiber has an atypical cross section.   The non-woven fabric according to claim 2, wherein the cross section of the cellulosic fiber has a shape in which one or more rod-shaped portions abut against or intersect with another one or more rod-shaped portions.   The cellulosic fiber has a plurality of convex portions on the outer periphery of the cross section, and a concave portion formed between the convex portions and the convex portions forms a line extending in the length direction on the outer peripheral surface of the fiber. The nonwoven fabric according to claim 2 or 3.   The nonwoven fabric according to any one of claims 1 to 4, wherein in a cross section cut along the thickness direction of the nonwoven fabric, the fiber density is higher on at least one surface than on the inside.   A liquid-impregnated nonwoven fabric obtained by impregnating the nonwoven fabric according to any one of claims 1 to 5 with a liquid.