JP2019131918A - Nonwoven fabric - Google Patents

Abstract

To provide a nonwoven fabric excellent in bulkiness and softness, and excellent in drape satisfying favorable usage as a sanitary material.SOLUTION: The nonwoven fabric comprises a conjugated fiber (F1) composed of 2 or more constituents of thermoplastic resins where the specific volume of the nonwoven fabric is 10 cm/g or more, and according to a bending resistance obtained by measuring in conformity to a JIS L 1913 (2010 year version) handle-o-meter method, when the value of a first face of the nonwoven fabric is A (mN/200 mm), and the value of a back face thereof is B (mN/200 mm), the value of a ratio of both bending resistances (A/B, provided that A>B) is 1.05 or more.SELECTED DRAWING: None

Description

  The present invention relates to a nonwoven fabric having excellent bulkiness and excellent flexibility.

  In general, non-woven fabrics for sanitary materials such as paper diapers and sanitary napkins are required to have excellent texture for comfort when worn. In particular, a good texture is required for a top sheet that directly touches the skin with the buttocks of the wearer and a back sheet that often touches the skin during clothing.

  The non-woven fabric for sanitary materials is a so-called air-through non-woven fabric in which short fibers represented by a composite fiber composed of polyethylene terephthalate (PET) and polyethylene (PE) are formed into a sheet by carding and then self-fused by hot air treatment, A polypropylene spunbonded nonwoven fabric is preferably used. Among them, the air-through nonwoven fabric has a feature that it is excellent in bulkiness, and is therefore mainly used for sanitary materials as top sheets.

  On the other hand, for the purpose of softening the air-through nonwoven fabric, it has been proposed to use split fibers as the constituent fibers (see Patent Document 1). According to this proposal, a technique for obtaining a flexible nonwoven fabric by dividing a fiber by an external force is disclosed.

Japanese Patent Laid-Open No. 2006-102286

  However, while the conventional air-through nonwoven fabric is characterized by being excellent in bulkiness, it is inferior in flexibility to bending of the nonwoven fabric, and when it is processed into a sanitary material such as a disposable diaper, there is a problem that it is wrinkled. there were. On the other hand, the method disclosed in Patent Document 1 has a problem that it is inevitable that the thickness of the nonwoven fabric becomes thin due to the application of an external force, resulting in poor bulkiness.

  That is, the flexibility with respect to bending and the thickness of the nonwoven fabric are in a trade-off relationship, and it is difficult to achieve both bulkiness and flexibility with respect to bending.

  Therefore, in view of the above-described problems, the object of the present invention is to achieve both excellent bulkiness and flexibility that are preferably required for a nonwoven fabric for sanitary materials, and to generate creases and wrinkles when used as a sanitary material. It is difficult to provide a non-woven fabric excellent in quality and texture.

The present invention is to solve the above-mentioned problems, and the nonwoven fabric of the present invention is a nonwoven fabric containing a composite fiber (F1) made of a thermoplastic resin having two or more components, and the specific volume of the nonwoven fabric is The value of the first surface of the nonwoven fabric is A (mN / 200 mm) for the bending resistance obtained by measuring in accordance with JIS L 1913 (2010 edition) handle ohm method, which is 10 cm ³ / g or more. And the value of the back surface thereof is B (mN / 200 mm), the ratio of the bending resistance of both surfaces (A / B, where A> B) is 1.05 or more. Consists of things.

  According to a preferred aspect of the nonwoven fabric of the present invention, the thermoplastic resin includes a high melting point component resin (P1) and a low melting point component resin (P2), and a difference in melting point between the resin (P1) and the resin (P2). Is a nonwoven fabric having a temperature of 10 ° C. or higher.

  According to the preferable aspect of the nonwoven fabric of this invention, the fiber which comprises the said nonwoven fabric is a nonwoven fabric containing at least 1 type of fiber (F2) other than the said composite fiber (F1).

  According to the preferable aspect of the nonwoven fabric of this invention, it is a nonwoven fabric containing the 2nd composite fiber (F2a) which consists of a 2 or more component thermoplastic resin as fibers (F2) other than the said composite fiber.

  According to a preferred aspect of the nonwoven fabric of the present invention, the composite fiber (F1) and fibers other than the composite fiber (F2, F2a) are unevenly distributed in the thickness direction.

  According to the preferable aspect of the nonwoven fabric of this invention, the fiber web 1 which consists of said composite fiber (F1), and the fiber web 2 which consists of fibers (F2, F2a) other than this composite fiber are laminated | stacked two or more layers. It is a nonwoven fabric.

  According to the present invention, both the bulkiness and flexibility required for a nonwoven fabric for sanitary materials can be achieved, and when used as a sanitary material, it is difficult to generate creases and a nonwoven fabric excellent in quality and texture can be obtained. . In particular, the nonwoven fabric of the present invention is bulky and has excellent bending flexibility due to the difference in flexibility between the front and back surfaces. More specifically, when the flexible layer is bent, the flexible layer follows the other layers to increase the thickness. Bending flexibility is excellent. For this reason, the quality of a product molded as a sanitary material is particularly good due to the feature that folding creases are less likely to occur when folded, so that it can be suitably used as a sanitary material non-woven fabric.

FIG. 1 is a schematic cross-sectional view illustrating a cross section of a composite fiber constituting the nonwoven fabric of the present invention. FIG. 2 is a schematic cross-sectional view illustrating a cross section of another conjugate fiber constituting the nonwoven fabric of the present invention. FIG. 3 is a schematic cross-sectional view illustrating a cross section of another conjugate fiber constituting the nonwoven fabric of the present invention.

The nonwoven fabric of the present invention is a nonwoven fabric including a composite fiber (F1) made of a thermoplastic resin having two or more components, and the specific volume of the nonwoven fabric is 10 cm ³ / g or more, and JIS L 1913 (2010 edition). For the bending resistance obtained by measuring according to the handle ohm method, when the value of the first surface of the nonwoven fabric is A (mN / 200 mm) and the value of the back surface is B (mN / 200 mm), The nonwoven fabric has a ratio of bending resistance on both sides (A / B, where A> B) of 1.05 or more.

Details of these will be described below.
[Composite fiber]
The fiber which comprises the nonwoven fabric of this invention is a composite fiber which consists of a 2 or more component thermoplastic resin. In particular, from the viewpoint of thermal adhesiveness, composite fibers composed of two component raw materials having different melting points are preferably used. Furthermore, it is more preferable that the high melting point component resin (P1) and the low melting point component resin (P2) are included, and the difference in melting point between the resin (P1) and the resin (P2) is 10 ° C. or more. However, it is preferable that the difference in the melting points is within 150 ° C. from the viewpoint of handling properties when made into a nonwoven fabric and processability to sanitary materials.

  Examples of the high melting point component resin (P1) include polyester, polyamide, and polyolefin. Specific examples of the polyester include polyethylene terephthalate, polybutylene terephthalate, and polytrimethylene terephthalate. Specific examples of the polyamide include nylon 6, nylon 66, nylon 12, and the like. Examples of polyolefins include polyethylene, polypropylene, and propylene / ethylene copolymers. Among these, nylon 6, polybutylene terephthalate, and polypropylene are preferably used from the viewpoint of flexibility.

  In addition, this high melting point component resin (P1) may be copolymerized with other components, and it is allowed to contain additives such as particles, flame retardants and antistatic agents.

  Examples of the copolymer component include sodium 5-sulfoisophthalate and 3-hydroxybutanoic acid, and examples of the particles include titanium oxide. Examples of the flame retardant include an organic flame retardant and an inorganic flame retardant, and examples of the antistatic agent include an alcohol-based antistatic agent.

  And as said low melting-point component resin (P2), polyethylene and a polypropylene can be used, and especially polyethylene is preferably used from an adhesive viewpoint. Polyethylene is classified according to the production method and physical properties, and includes high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and the like, each of which has been studied for fibers. In the present invention, any polyethylene is used, but from the viewpoint of spinning stability, LLDPE is a preferred embodiment.

  The polyethylene used as the low-melting-point component resin (P2) is allowed to be blended with a small amount of other component polymers. Examples of the other component polymer include low melting point polyesters and low melting point polyamides in addition to polyolefin polymers such as polypropylene and poly 4 methyl 1 pentene having a melting point close to that of polyethylene. Moreover, in order to fully express the characteristics of polyethylene, the mass ratio of the blend is preferably 5% by mass or less, more preferably 2% by mass or less.

  The polyethylene has a melt flow rate (hereinafter sometimes referred to as MFR) of preferably 10 to 100 g / 10 minutes, and more preferably 20 to 40 g / 10 minutes. The melt flow rate here refers to a value measured at a temperature of 190 ° C. and a load of 2.16 kg in accordance with ASTM D1238 (A method).

  Furthermore, the raw materials for the fibers used in the present invention are generally used antioxidants, weathering stabilizers, light stabilizers, antistatic agents, antifogging agents, and antiblocking agents as long as the effects of the present invention are not impaired. Agents, lubricants such as polyethylene wax, nucleating agents, additives such as pigments, or other polymers can be added as necessary.

  As described above, the cross section of the conjugate fiber of the present invention is preferably composed of two components having different melting points, and the mass ratio is preferably 90/10 to 10/90, and 70/30 to 30/70. It is more preferable that 60/40 to 40/60 is a more preferable embodiment. By setting the mass ratio of the high melting point component resin (P1) to preferably 10% by mass or more, more preferably 30% by mass or more, and further preferably 40% by mass or more, sufficient physical properties can be imparted to the nonwoven fabric. . Further, when the mass ratio of the low melting point component resin (P2) is preferably 10% by mass or more, more preferably 30% by mass or more, and further preferably 40% by mass or more, sufficient thermal adhesiveness can be obtained.

  In the cross-sectional shape of the conjugate fiber of the present invention, the low melting point component preferably forms at least a part of the fiber surface. Examples of the cross-sectional shape may be a concentric core-sheath structure, an eccentric core-sheath structure, and a side-by-side structure.

  1 to 3 are schematic cross-sectional views illustrating the cross-section of fibers constituting the nonwoven fabric of the present invention.

  FIG. 1 is a schematic cross-sectional view showing a cross section of a concentric core-sheath composite fiber. In FIG. 1, the centers of the core (a) and the sheath (b) are the same. Specifically, the concentric core-sheath type composite fiber comprises a core part (a) and a sheath part (b), and the core part (a) is surrounded by a polymer different from the core part (a) in the cross section of the fiber. The portion is arranged in such a way as to extend in the longitudinal direction of the fiber. Moreover, a sheath part (b) says that the part arrange | positioned so that the core part (a) may be surrounded in the cross section of a fiber, and it extends in the length direction of a fiber.

  FIG. 2 is a schematic cross-sectional view showing a cross section of an eccentric core-sheath composite fiber. In FIG. 2, the centers of the core (a) and the sheath (b) are different. Specifically, the eccentric core-sheath type composite fiber comprises a core part (a) and a sheath part (b), and the core part (a) is at least a polymer different from the core part (a) in the cross section of the fiber. A portion arranged so as to be partially surrounded and extending in the length direction of the fiber. Moreover, a sheath part (b) says the part arrange | positioned so that at least one part of a core part (a) may be surrounded in the cross section of a fiber, and extended in the length direction of a fiber. The eccentric core-sheath type composite fiber includes an exposed type in which the side surface of the core part (a) is exposed and an unexposed type in which the side surface of the core part (a) is not exposed. In the present invention, when an eccentric core-sheath type composite fiber is used, the unexposed type is more preferably used from the viewpoint of spinning stability.

  FIG. 3 is a schematic cross-sectional view showing a cross section of a side-by-side type composite fiber. The side-by-side type composite fiber has a structure in which the first component (c) and the second component (d) are bonded together. The two-component bonding surface may be either a straight line or a curved line, and differs depending on the two-component viscosity characteristics and the discharge rate ratio. The cross section of the fiber may be circular or may be an irregular cross section such as an ellipse.

  The average single fiber diameter of the composite fiber used in the nonwoven fabric of the present invention is preferably 7 μm or more and 22 μm or less, more preferably 8 μm or more and 21 μm or less, and further preferably 10 μm or more and 20 μm or less. The average single fiber diameter of the composite fiber is preferably 7 μm or more from the viewpoint of spinning stability. The thinner the average single fiber diameter, the more the bonding points of the fibers as a nonwoven fabric, so the strength is high and the flexibility is good. It becomes. Moreover, since it is used for a sanitary material, it is a preferable aspect that an average single fiber diameter is 22 micrometers or less from a strong viewpoint of the nonwoven fabric for sanitary materials.

Furthermore, the initial tensile resistance of the fiber used in the nonwoven fabric of the present invention is preferably 2000 N / mm ² or less. By setting the initial tensile resistance of the fiber to preferably 2000 N / mm ² or less, more preferably 1500 N / mm ² or less, and even more preferably 1000 N / mm ² or less, it is possible to obtain a non-woven fabric having good bending flexibility. . Furthermore, even when the thickness of the nonwoven fabric is increased, the nonwoven fabric is less likely to be wrinkled, and both bulkiness and flexibility can be achieved. Further, the initial tensile resistance is preferably 500 N / mm ² or more from the viewpoint of processability to a nonwoven fabric, handling properties when formed into a nonwoven fabric, and processability to sanitary materials.
[Nonwoven fabric]
Moreover, it is important that the specific volume of the nonwoven fabric of this invention is 10 cm < ³ > / g or more. Here, the specific volume indicates the volume per unit mass of the nonwoven fabric, and it can be determined that the higher the value, the better the bulkiness of the nonwoven fabric. The specific volume of the nonwoven fabric can be calculated by dividing the thickness by the basis weight. The higher the specific volume of the nonwoven fabric and the higher the bulkiness, the more preferable it is because cushioning can be imparted when used for sanitary materials such as disposable diapers. The specific volume is preferably 100 cm ³ / g or less in view of use as a sanitary material nonwoven fabric.

From the same point of view, the apparent density of the nonwoven fabric of the present invention is preferably 0.100 g / cm ³ or less. The apparent density can be calculated by dividing the basis weight by the thickness. Apparent density is more preferably 0.09 g / cm ³ or less, more preferably 0.080 g / cm ³ or less. By setting the apparent density within the above range, sufficient bulkiness can be obtained when used as a nonwoven fabric. The apparent density is preferably 0.01 g / cm ³ or more in view of the use as a non-woven fabric for sanitary materials.

In the present invention, the nonwoven fabric thickness (mm), is intended to be measured in accordance with JIS L 1908 (2010 year edition), preparing a presser foot having an area of 2500 mm ^2, the presser foot diameter About the test piece of 1.75 times or more magnitude | size, after applying the pressure of 0.2 kPa for a fixed time, thickness is measured and it is an average value for 10 test pieces.

The basis weight (g / m ² ) is measured on the basis of 6.2 “mass per unit area” of JIS L 1913 (2010 edition). Three pieces are collected per 1 m width, each mass (g) in the standard state is measured, and the average value is expressed by the mass per 1 m ² (g / m ² ).

  The thickness of the nonwoven fabric of the present invention is preferably 0.20 mm or more. By setting the thickness of the non-woven fabric to 0.20 mm or more, the non-woven fabric does not become too hard, and when used for a sanitary material such as a paper diaper, an appropriate texture can be obtained. The thickness of the nonwoven fabric is preferably as high as possible, but is preferably 2 mm or less from the viewpoint of use in sanitary materials such as disposable diapers.

Moreover, it is a preferable aspect that the fabric weight of the nonwoven fabric of this invention is 3-200 g / m < ² >. Wherein the basis weight is more preferably from 5 to 150 g / ^{m 2,} more preferably from 10 to 100 g / ^{m 2.} By setting the basis weight within the above range, sufficient flexibility can be imparted to the nonwoven fabric.

  Furthermore, the nonwoven fabric of the present invention has A (mN / 200 mm) as the value of the first surface of the nonwoven fabric for the bending resistance obtained by measuring according to the JIS L 1913 (2010 edition) handle ohm method. When the value of the back surface is B (mN / 200 mm), it is important that the value of the ratio of bending resistance of both surfaces (A / B, where A> B) is 1.05 or more.

Specifically, the bending resistance is measured by the following procedure.
(1) Collect three samples of size 200 mm × 200 mm.
(2) Place the sample on the sample stage so that the measurement direction of the sample is perpendicular to the slot (20 mm), lower the blade adjusted to 8 mm from the sample table surface, and press the sample. Read the number.
(3) About each sample, it measures about the place where front and back differ from each other in the position of 67 mm (one third of sample width) from either side.
(4) For each sample, measure 4 places in the vertical direction and 4 places in the horizontal direction, and calculate the average value of the values measured in total 3 samples.

  By setting the above ratio (A / B) to 1.05 or more, preferably 1.08 or more, more preferably 1.1 or more, the level of bulkiness and bending required for the nonwoven fabric for sanitary materials is improved. Can be made compatible, and when processed into a sanitary material such as a paper diaper, wrinkles generated by bending of the nonwoven fabric can be reduced, and a sanitary material having excellent quality can be obtained. The value of A / B is preferably 1.2 or less from the viewpoint of handling properties when processed into a nonwoven fabric and processability to sanitary materials.

  In order to set the ratio (A / B) to 1.05 or more, it is preferable that at least one type of fiber (F2) is included in addition to the composite fiber (F1). By being configured in this way, it is possible to achieve both the level of bulkiness required for sanitary material nonwoven fabrics and the flexibility to bend, and when processed into sanitary materials such as paper diapers, the nonwoven fabric is bent. The generated wrinkles can be reduced, and a sanitary material having excellent quality can be obtained.

  Examples of the fibers (F2) include natural fibers such as cotton, silk and wool, viscose rayon, cupra, and solvent-spun cellulose fibers (for example, lentung lyocell (registered trademark) and tencel (registered trademark)). Recycled fibers, polyolefin fibers, polyester fibers and polyamide fibers, (poly) acrylic single fibers made of acrylonitrile, fibers made of engineering plastics such as polycarbonate, polyacetal, polystyrene, cyclic polyolefin, etc. .

  Further, as the fiber (F2), not only a single fiber made of one kind of thermoplastic resin but also a composite fiber (F2a) (for example, concentric) other than a split-type composite fiber made of two or more kinds of thermoplastic resins. It is more preferable to use an eccentric core-sheath type composite fiber, sea-island type composite fiber, or side-by-side type composite fiber).

  This composite fiber (F2a) may be a heat-adhesive fiber in which a thermoplastic resin having a melting point equal to or lower than that of one constituent component is exposed on the fiber surface. In this case, when the bonded portion by one component of the composite fiber (F2a) is formed by heating (that is, the heat bonded portion by one component of the composite fiber is formed), the composite fiber (F2a) is the composite fiber (F1). A thermal adhesive part is formed in a nonwoven fabric with 1 component of).

  Furthermore, as a combination of the fibers constituting the nonwoven fabric of the present invention, it is a preferable embodiment that the nonwoven fabric is composed of fibers that impart bulkiness and fibers that impart flexibility.

  As the fiber imparting bulkiness, a composite fiber in which the resin (P1) having a high melting point component is polyethylene terephthalate is preferably used. On the other hand, from the viewpoint of flexibility, a combination with a composite fiber in which the resin (P1) having a high melting point component is nylon 6, polybutylene terephthalate, or polypropylene is preferably used.

  As a mass ratio of the composite fiber which comprises the nonwoven fabric of this invention, it is preferable that it is 10 / 90-90 / 10 in the case of two types, for example, it is more preferable that it is 30 / 70-70 / 30, and 40 / It is a more preferable aspect that it is 60-60 / 40. The composite fiber imparting bulkiness is preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, whereby sufficient bulkiness can be imparted to the nonwoven fabric. Sufficient flexibility can be imparted to the nonwoven fabric by making the composite fiber imparting flexibility preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more.

  In the nonwoven fabric of the present invention, the composite fiber (F1) and the other fibers (F2, F2a) are preferably unevenly distributed in the thickness direction of the nonwoven fabric. By doing so, there is a difference in flexibility between the front and back of the nonwoven fabric, and when processed into sanitary materials such as paper diapers, wrinkles generated by bending the nonwoven fabric can be reduced, and the sanitary material having excellent quality can be obtained. it can.

  In particular, the form formed by laminating two or more layers of the fiber web 1 made of the composite fiber (F1) and the fiber web 2 made of the other fibers (F2, F2a) is a workability when making a nonwoven fabric. It is more preferable from the viewpoint of handling properties.

  When two or more fiber webs are laminated, a combination including a layer containing fibers that impart bulkiness to a nonwoven fabric and a layer containing fibers that impart flexibility is a preferred embodiment.

  As the layer imparting bulkiness, a layer containing fibers in which the resin (P1) as the high melting point component of the composite fiber is polyethylene terephthalate is preferably used. On the other hand, as the layer for imparting flexibility, a layer containing a fiber in which the resin (P1) of the high melting point component of the composite fiber is combined with nylon 6, polybutylene terephthalate, and polypropylene is preferably used.

  In this case, the mass ratio of the fiber web constituting the nonwoven fabric of the present invention is preferably 10/90 to 90/10, more preferably 30/70 to 70/30, for example, in the case of two layers. 40/60 to 60/40 is a more preferred embodiment.

It is possible to impart sufficient bulkiness to the nonwoven fabric by making the layer imparting bulkiness preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more. Moreover, sufficient flexibility can be imparted to the nonwoven fabric by making the layer imparting flexibility preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more.
[Method for producing nonwoven fabric]
Next, an example of a method for producing the nonwoven fabric of the present invention will be described.

  As the non-woven fabric of the present invention, a long-fiber non-woven fabric obtained by a spunbond method or a melt blow method, an air-through non-woven fabric obtained by applying a hot air treatment after forming a fiber web using short cards with a card, etc. Can do. Among these, an air-through nonwoven fabric is preferably used because it has a good bulkiness. Therefore, as a method for producing the nonwoven fabric of the present invention, an air-through nonwoven fabric production method can be preferably applied.

  The air-through method is a manufacturing method in which short fibers, which are raw cotton, are passed through a card machine, the short fibers are opened, formed into a fiber web state, and then made into a nonwoven fabric by heat treatment.

  As for the heat treatment method, for example, heat bonding by hot air treatment or fusion by ultrasonic waves, a heat embossing roll in which engravings (uneven portions) are respectively formed on a pair of upper and lower roll surfaces, and one roll surface is flat (smooth) ) Roll and a heat embossing roll consisting of a combination of the surface of the other roll with a sculpture (uneven portion) and a thermocalendering roll consisting of a combination of a pair of upper and lower flat (smooth) rolls. In addition, each combination can be applied.

  Especially, since the heat bonding by a hot air process can maintain the thickness of a nonwoven fabric, it is used especially preferable.

  In the present invention, in the case of thermal bonding by hot air treatment, the hot air temperature is preferably in the range of the melting point of the low melting point component + 1 ° C to + 30 ° C, more preferably in the range of + 1 ° C to + 15 ° C, and further preferably. Is in the range of + 1 ° C to + 10 ° C. Sufficient thermal adhesiveness can be obtained by setting the hot air temperature to the melting point of the low melting point component + 1 ° C. or higher. Further, by setting the hot air temperature to preferably the melting point of the low melting point resin + 30 ° C. or less, more preferably + 15 ° C. or less, and even more preferably 10 ° C. or less, curing of the nonwoven fabric due to heat can be suppressed, and disposable diapers, etc. As a sanitary material non-woven fabric, a soft texture can be maintained.

  In the present invention, the hot air flow rate is preferably 1.0 to 5.0 m / sec. By setting the hot air flow rate to 1.0 m / second or more, hot air can be passed through the nonwoven fabric for sanitary material, and sufficient adhesiveness can be obtained. On the other hand, the web turbulence at the time of heat processing can be suppressed by setting the hot air flow rate to 5.0 m / second or less.

  Subsequently, heat treatment such as calendering or embossing can be preferably employed for the purpose of setting the nonwoven fabric to a predetermined thickness.

  The embossed adhesion area ratio in embossing is preferably 5 to 30%. When the adhesion area is preferably 5% or more, more preferably 10% or more, a practically usable strength can be obtained. On the other hand, when the embossed adhesion area ratio is preferably 30% or less, more preferably 20% or less, a soft texture can be maintained.

  The embossed adhesion area ratio here refers to the entire nonwoven fabric in the portion where the convex portion of the upper roll and the convex portion of the lower roll overlap and contact the fiber web when heat bonding is performed with a pair of concave and convex rolls. It means the ratio. Moreover, when heat-processing with the roll which has an unevenness | corrugation, and a flat roll, it means the ratio for which the convex part of the roll which has an unevenness | corrugation accounts for the whole nonwoven fabric of the part contact | abutted to a fiber web.

  As the shape of the engraving applied to the hot embossing roll, shapes such as a circle, an ellipse, a square, a rectangle, a parallelogram, a rhombus, a regular hexagon, and a regular octagon can be used.

  The surface temperature of the hot embossing roll is preferably -50 ° C or higher and -1 ° C or lower with respect to the melting point of the resin having the lowest melting point among the resins used. By sufficiently setting the surface temperature of the hot embossing roll to the melting point of the resin having the lowest melting point, preferably −50 ° C. or more, more preferably −30 ° C. or more, and further preferably −10 ° C. or more. It is possible to make it easy to suppress the occurrence of fluff by heat bonding to give strength. On the other hand, among the resins used, the melting point of the resin having the lowest melting point is preferably -1 ° C. or less, thereby facilitating prevention of separation between the resins due to fiber melting. it can.

  On the other hand, the temperature of the calender roll during the heat treatment by calendering is preferably set to −1 ° C. or lower with respect to the melting point of the resin which is the lowest melting point component. By setting the calender roll temperature to −1 ° C. or lower with respect to the melting point of the low melting point component, the surface of the nonwoven fabric after the heat treatment can be prevented from curing. The calender roll temperature can be appropriately adjusted depending on the thickness of the target nonwoven fabric.

  Moreover, it is preferable that the linear pressure of the roll at the time of the heat processing by a calendar | calender or embossing is 10-500 N / cm. When the linear pressure is preferably 10 N / cm or more, more preferably 15 N / cm or more, and still more preferably 20 N / cm or more, sufficient heat treatment can be performed and the thickness can be controlled. On the other hand, the above-mentioned linear pressure is preferably 500 N / cm or less, more preferably 400 N / cm or less, and even more preferably 300 N / cm or less, thereby maintaining the texture of the nonwoven fabric so that the roll is not stressed excessively. can do. The linear pressure of the roll can be appropriately adjusted depending on the thickness of the target nonwoven fabric.

  Since the nonwoven fabric of the present invention is very excellent in texture, it can be suitably used particularly for top sheets and back sheets such as disposable paper diapers and napkins.

Next, based on an Example, the nonwoven fabric of this invention and its manufacturing method are demonstrated concretely.
[Measuring method]
(1) Average fiber diameter (μm) of single fiber:
The nonwoven fabric was observed with a scanning electron microscope (VE-7800, manufactured by SEM Keyence Co., Ltd.) at a magnification of 500 times, and the diameter of 50 randomly extracted single fibers was measured. This was performed at three locations, the diameters of a total of 150 single fibers were measured, and the average value was calculated by rounding off the numbers after the decimal point. When the fiber cross section was an irregular cross section, first, the cross-sectional area of the single fiber was measured, and the average fiber diameter of the single fiber was determined by calculating the diameter when the cross section was regarded as a circle.

(2) Specific volume of non-woven fabric (cm ³ / g);
The specific volume of the nonwoven fabric was calculated from the basis weight and thickness of the nonwoven fabric measured by the above method. The higher this value, the better the bulkiness.

(3) Softness of the nonwoven fabric (handle ohmmeter method);
By the above method, the measurement was performed according to the JIS L 1913 (2010 edition) handle ohmmeter method.
(4) Evaluation of bending wrinkle In the above-mentioned evaluation of the flexibility of the nonwoven fabric, the wrinkle of the sample surface at the lowest point of the blade of the handle ohmmeter (the point lowered from the surface of the sample table to 8 mm) on the surface where the numerical value of the maximum press is low The situation was confirmed visually. The evaluation criteria were the following three-level evaluation (indicated by the symbols of ○, Δ, and × in order from the best evaluation). The most applicable evaluation was adopted with the number of samples (N) being 30.
○: No wrinkles at all Δ: Slight wrinkles on the surface are visible.
X: Wrinkles are observed.

(5) A sample having a texture size of 100 mm × 100 mm was collected, 20 panelists touched the nonwoven fabric, and the texture was judged by the following five-step evaluation. The texture of the nonwoven fabric was evaluated based on the total score determined by each panel. Therefore, the total score was from a minimum of 0 points to a maximum of 100 points, and 85 points or more were judged to be acceptable. Further, the total score is preferably 90 points or more.
5 points Very good (when touching the non-woven fabric, the entire non-woven fabric or part of the non-woven fabric feels comfortable and comfortable in both cushioning and flexibility.)
4 points good (between 5 and 3 points)
3 normal
(When the nonwoven fabric is touched, the cushioning properties and flexibility of the nonwoven fabric are felt in all or part of the nonwoven fabric.)
2 points bad (between 3 points and 1 point)
1 point Very bad (When touching the non-woven fabric, the whole or a part of the non-woven fabric feels that either the cushioning property or the softness of the non-woven fabric is lacking.)
[Raw material]
The following fibers were prepared as fibers used in the present examples and comparative examples.

(Core-sheath type composite fiber)
[Core-sheath type composite fiber (I)]
The core component is made of nylon 6 having a melting point of 220 ° C. and ηr of 2.7, and the sheath component is made of high-density polyethylene having a melting point of 130 ° C. and an MFR of 18 g / 10 min. Using a composite die, an undrawn yarn was obtained under the conditions of a core / sheath composite mass ratio of 50/50, a single hole discharge rate of 0.7 g / min, and a spinning speed of 1100 m / min. Then, after extending | stretching 3.2 times on the conditions whose liquid bath temperature is 90 degreeC, it cut to 51 mm and obtained core-sheath-type composite fiber (I). The average single fiber diameter of the obtained core-sheath type composite fiber (I) was 18.2 μm.

[Core-sheath type composite fiber (II)]
A core-sheath type composite fiber (II) was obtained by the same production method as the core-sheath type composite fiber (I) except that polybutylene terephthalate having a melting point of 227 ° C. and an intrinsic viscosity of 0.85 dl / g was used as the core component. . At this time, the average single fiber diameter of the core-sheath type composite fiber (II) was 19.4 μm.

[Core-sheath type composite fiber (III)]
A core-sheath composite fiber (III) was obtained by the same production method as the core-sheath composite fiber (I) except that polyethylene terephthalate having a melting point of 260 ° C. and an intrinsic viscosity of 0.65 dl / g was used as the core component. At this time, the average single fiber diameter of the core-sheath type composite fiber (III) was 17.8 μm.
[Core-sheath type composite fiber (IV)]
The core component was polyethylene terephthalate having a melting point of 260 ° C. and an intrinsic viscosity of 0.65 dl / g, and the core was obtained except that the obtained unstretched yarn was stretched 3.3 times under the condition of a liquid bath temperature of 90 ° C. The core-sheath type composite fiber (IV) was obtained by the same production method as the sheath type composite fiber (I). The average single fiber diameter of the obtained core-sheath type composite fiber (IV) was 16.3 μm.
Example 1
The fiber web 1 was formed through the card process using only the core-sheath type composite fiber (I). Subsequently, only the core-sheath type composite fiber (IV) was used, the card | curd process was obtained, and the fiber web 2 was formed. After laminating the obtained fiber web 1 and fiber web 2 and using a heat treatment machine, heat treatment was carried out for 12 seconds under conditions of hot air temperature of 160 ° C. and hot air flow rate of 3.3 m / min. It was heat-treated under the conditions of a temperature of 30 ° C. and a linear pressure of 160 N / cm to obtain a nonwoven fabric. The basis weight of the obtained nonwoven fabric is 25 g / m ² , the thickness is 1.5 mm, the specific volume is 60 cm ³ / g, and the measured value of the handle ohmmeter is 150 mN / 200 mm in the vertical direction of the first surface and 80 mN / 200 mm in the horizontal direction. The vertical direction of the back surface was 133 mN / 200 mm, and the horizontal direction was 71 mN / 200 mm. The value calculated from the measurement results and ordered by the value of the first surface of the nonwoven fabric and the value of the back surface thereof was 1.13. The evaluation results are shown in Table 1.

(Example 2)
A nonwoven fabric was obtained in the same manner as in Example 1 except that the core-sheath type composite fiber (II) was used to form the fiber web 1 through the card process. The basis weight of the obtained nonwoven fabric is 25 g / m ² , the thickness is 1.4 mm, the specific volume is 56 cm ³ / g, and the measured value of the handle ohmmeter is 173 mN / 200 mm in the vertical direction of the first surface and 85 mN / 200 mm in the horizontal direction. The vertical direction of the back surface was 149 mN / 200 mm, and the horizontal direction was 77 mN / 200 mm. The value calculated from the measurement result and ordered by the value of the first surface of the nonwoven fabric and the value of the back surface thereof was 1.14. The evaluation results are shown in Table 1.

Example 3
Using the core-sheath type composite fiber (I) and the core-sheath type composite fiber (III) so that the fiber composition ratio of the core-sheath type composite fiber (I) and the core-sheath type composite fiber (III) is 50/50. The nonwoven fabric was obtained by the same method as Example 1 except having formed the fiber web 1 through the card process. The basis weight of the obtained nonwoven fabric is 25 g / m ² , the thickness is 1.5 mm, the specific volume is 60 cm ³ / g, and the measured value of the handle ohmmeter is 157 mN / 200 mm in the vertical direction of the first surface and 82 mN / 200 mm in the horizontal direction. The vertical direction of the back surface was 145 mN / 200 mm, and the horizontal direction was 79 mN / 200 mm. The value calculated from the measurement result and ordered by the value of the first surface of the nonwoven fabric and the value of the back surface thereof was 1.07. The evaluation results are shown in Table 1.

Example 4
Using the core-sheath type composite fiber (II) and the core-sheath type composite fiber (III) so that the fiber composition ratio of the core-sheath type composite fiber (II) and the core-sheath type composite fiber (III) is 50/50. The nonwoven fabric was obtained by the same method as Example 1 except having formed the fiber web 1 through the card process. The basis weight of the obtained nonwoven fabric is 25 g / m ² , the thickness is 1.5 mm, the specific volume is 60 cm ³ / g, and the measured value of the handle ohmmeter is 166 mN / 200 mm in the vertical direction of the first surface and 85 mN / 200 mm in the horizontal direction. The vertical direction of the back surface was 154 mN / 200 mm, and the horizontal direction was 82 mN / 200 mm. The value calculated from the measurement result and ordered by the value of the first surface of the nonwoven fabric and the value of the back surface thereof was 1.06. The evaluation results are shown in Table 1.

(Comparative Example 1)
A nonwoven fabric was obtained in the same manner as in Example 1 except that the core-sheath type composite fiber (III) was used to form the fiber web 1 through the card process. The basis weight of the obtained nonwoven fabric is 25 g / m ² , the thickness is 1.9 mm, the specific volume is 85 cm ³ / g, and the measured value of the handle ohmmeter is 170 mN / 200 mm in the vertical direction of the first surface and 84 mN / 200 mm in the horizontal direction. The vertical direction of the back surface was 165 mN / 200 mm, and the horizontal direction was 85 mN / 200 mm. The value calculated from the measurement result and ordered by the value of the first surface of the nonwoven fabric and the value of the back surface thereof was 1.02. The evaluation results are shown in Table 1.

  Examples 1 to 4 of the present invention are nonwoven fabrics excellent in bulkiness and flexibility for bending because the value starting from the value of the first surface of the nonwoven fabric and the value of the back surface thereof is 1.05 or more. there were. In particular, Example 1 was a non-woven fabric having very good flexibility with respect to the bending of the surface on one side by being unevenly distributed in the thickness direction of two types of fibers constituting the non-woven fabric. Since these nonwoven fabrics are less likely to bend and wrinkle when processed into sanitary materials such as disposable diapers, they can be used as sanitary materials of good quality and can be used very suitably.

  On the other hand, although Comparative Example 1 is excellent in bulkiness, the value of the handle ohmmeter is high on both the first surface and the back surface thereof, and the flexibility for bending is inferior, and both sides are folded and wrinkled when the nonwoven fabric is folded. It was easy to occur, and it was a level where wrinkles were noticeably generated when processed into sanitary materials such as paper diapers.

(A): Core (b): Sheath (c): First component (d): Second component

Claims (6)

A non-woven fabric comprising a composite fiber (F1) made of two or more components of thermoplastic resin, wherein the non-woven fabric has a specific volume of 10 cm ³ / g or more, and conforms to JIS L 1913 (2010 edition) handle ohm method. As for the bending resistance obtained by measurement, the ratio of the bending resistance of both surfaces is defined by assuming that the value of the first surface of the nonwoven fabric is A (mN / 200 mm) and the value of the back surface thereof is B (mN / 200 mm). A nonwoven fabric characterized in that the value of (A / B, where A> B) is 1.05 or more.   The thermoplastic resin includes a high melting point component resin (P1) and a low melting point component resin (P2), and a difference in melting point between the resin (P1) and the resin (P2) is 10 ° C. or more. The nonwoven fabric described.   The nonwoven fabric according to claim 1 or 2, wherein the fibers constituting the nonwoven fabric include at least one type of fiber (F2) in addition to the composite fiber (F1).   The non-woven fabric according to claim 3, comprising a second composite fiber (F2a) made of a thermoplastic resin having two or more components as the fiber (F2) other than the composite fiber.   The nonwoven fabric according to claim 3 or 4, wherein the composite fiber (F1) and fibers other than the composite fiber (F2, F2a) are unevenly distributed in the thickness direction.   The nonwoven fabric according to claim 5, wherein two or more layers of a fiber web 1 made of the composite fiber (F1) and a fiber web 2 made of fibers (F2, F2a) other than the composite fiber are laminated.

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