WO2010074207A1 - Non-woven fabric and process for producing same - Google Patents

Abstract

Disclosed is a non-woven fabric (10) which comprises: core-sheath-type composite fibers each composed of a sheath part comprising a polyethylene resin and a core part comprising a resin component having a higher melting point than that of the polyethylene resin; and a hydrophilizing agent adhered on the surfaces of the core-sheath-type composite fibers.  The non-woven fabric has thermally fused parts which are formed by thermally fusing the intersection points of the constituent fibers.  The core-sheath-type composite fibers contain thermally extendable fibers which can extend in the length direction upon heating.  In each of the thermally extendable fibers, a hydrophilicity gradient is formed in the thickness direction and/or the planar direction of the non-woven fabric (10).  The non-woven fabric (10) can be used suitably as a surface sheet for an absorbent article and the like.

Description

Nonwoven fabric and method for producing the same

The present invention relates to a nonwoven fabric obtained using fibers whose hydrophilicity is lowered by heat and a method for producing the same.
The present invention also relates to an improvement of a nonwoven fabric containing heat-extensible fibers whose length is increased by heating.

There is known a method of manufacturing a nonwoven fabric by blowing hot air to a web containing heat-fusible fibers to fuse the intersections of the fibers.
Patent Document 1 discloses an electret nonwoven fabric used for a filter that collects pollen, house dust, and the like by an electrostatic collection function, and an oil agent of 0.2 to 0.6 wt. % Of the polyolefin-based heat-bonding fibers attached to the nonwoven fabric, and the heat treatment after the non-woven fabric and / or after the non-woven fabric heat treatment reduces the oil adhesion amount of the non-woven fabric to 0.0001 to 0.2% by weight, A polyolefin-based heat-bonding fiber for electret non-woven fabric, which can be reduced by 60% or more, and an electret non-woven fabric manufactured using the fiber are described.
Further, in Patent Document 2, in a nonwoven fabric fiber comprising a polyolefin-based composite fiber having thermal adhesiveness and an oil agent attached to the fiber, the oil agent has a specific polyethylene glycol aliphatic ester as a main component. Further, there is described a polyolefin-based composite fiber for a nonwoven fabric to which 0.2 to 0.6% by weight of this is adhered.

In addition, regarding a nonwoven fabric made from a heat-extensible fiber, which is a fiber whose length is increased by heating, the present applicant has a number of pressure-bonding portions to which constituent fibers are pressure-bonded or bonded, and pressure bonding. The intersection of the constituent fibers is joined by means other than pressure bonding in a portion other than the portion, and the concave-convex shape in which the pressure-bonded portion is a concave portion and the concave portion is a convex portion is formed on at least one surface A three-dimensional shaped non-woven fabric has been proposed (see Patent Document 3).

US2002146951A1 JP4-316673A JP2005-350836A

According to the techniques described in Patent Literatures 1 and 2, the oil agent adhered to the fiber surface can prevent the generation of static electricity and troubles in the card process, while the heat treatment thereafter reduces the oil agent from the surface. Therefore, the electret nonwoven fabric which is easy to express an electrostatic collection function can be obtained.
However, in Patent Documents 1 and 2, oil agents that can be used in practice are limited to those mainly composed of an ester of polyethylene glycol and a fatty acid, and the degree of freedom in selecting the oil agent is low. Moreover, in patent document 1, the application other than an electret nonwoven fabric is not assumed. Moreover, in patent document 2, although use as a surface material of a disposable diaper is described, it is limited to the usage method which requires water repellency, and it does not assume that a hydrophilic gradient is expressed.
The non-woven fabric of Patent Document 3 has an advantage that it has a three-dimensional uneven shape, is flexible, and has a low basis weight, without using a special manufacturing method, by using a heat-extensible fiber as a raw material. Have However, for example, when considering use as a surface sheet of an absorbent article, the liquid may easily remain in the nonwoven fabric.

The present invention relates to a core-sheath type composite fiber having a sheath part made of polyethylene resin and a core part made of a resin component having a melting point higher than that of the polyethylene resin, and a hydrophilizing agent attached to the surface of the core-sheath type composite fiber The core-sheath type composite fiber includes a heat-extensible fiber whose length is increased by heating, and the heat-extensible property The fiber provides a nonwoven fabric having a hydrophilicity gradient in the thickness direction and / or plane direction of the nonwoven fabric (this nonwoven fabric is also referred to as nonwoven fabric NW1).

The “heat-stretchable composite fiber whose length is extended by heating” in the nonwoven fabric NW1 is not limited to those whose length is further increased by heating. In the state of the nonwoven fabric, the length has already been extended by heating. It is meant to include things.

Further, the present invention provides a core-sheath type composite fiber having a sheath part made of polyethylene resin and a core part made of a resin component having a melting point higher than that of the polyethylene resin, and hydrophilization attached to the surface of the core-sheath type composite fiber A web or nonwoven fabric containing fibers that have a crystallite size of 100 to 200 mm and whose hydrophilicity is lowered by heat, and the hydrophilicity of a part of the web or nonwoven fabric is reduced. A non-woven fabric (this non-woven fabric is also referred to as non-woven fabric NW2) is obtained.
Nonwoven fabric NW2 is also a preferred embodiment of nonwoven fabric NW1.

The present invention also provides a method for producing a nonwoven fabric, in which a web or nonwoven fabric made of fibers whose hydrophilicity is lowered by heat is subjected to a heat treatment to obtain a nonwoven fabric having a partially reduced hydrophilicity of the web or nonwoven fabric. It is.
In addition, the present invention provides a method of controlling the hydrophilicity of a nonwoven fabric by reducing the hydrophilicity of a part of the web or nonwoven fabric by subjecting the web or nonwoven fabric containing fibers whose hydrophilicity is lowered by heat to a heat treatment. Is.

FIG. 1 is a schematic view showing an apparatus used in the melt spinning method. FIG. 2 is a schematic view showing a process of obtaining a heat-repellent fiber from the core-sheath type composite fiber. Fig.3 (a) is a perspective view which shows one Embodiment of the nonwoven fabric of this invention, FIG.3 (b) is a partially expanded view of the cross section along the thickness direction of the nonwoven fabric shown to Fig.3 (a). . FIG. 4 is a schematic diagram showing a process for producing a partially water-repellent nonwoven fabric using heat-repellent fibers.

Hereinafter, the present invention will be described based on preferred embodiments thereof.
The “fiber whose hydrophilicity is lowered by heat” used in the present invention includes a sheath portion made of polyethylene resin and a core-sheath type composite fiber having a core portion made of a resin component having a melting point higher than that of the polyethylene resin, and the core-sheath type And a hydrophilizing agent attached to the surface of the composite fiber.
The core-sheath type composite fiber in the present invention may be a concentric core-sheath type, an eccentric core-sheath type, a side-by-side type, or a concentric core-sheath type.

The resin component which comprises the sheath part of the core-sheath-type composite fiber in this invention is a polyethylene resin. As the polyethylene resin, low density polyethylene (LDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE) and the like can be used, but the density is 0.935 to 0.965 g / cm ^3. Polyethylene is preferred. The resin component constituting the sheath is preferably a polyethylene resin alone, but other resins can also be blended. Other resins to be blended include polypropylene resin, ethylene-vinyl acetate copolymer (EVA), ethylene-vinyl alcohol copolymer (EVOH), and the like. However, the resin component constituting the sheath part is preferably 50% by mass or more, particularly 70 to 100% by mass of the resin component of the sheath part, preferably polyethylene resin.

The polyethylene resin constituting the sheath part imparts heat-fusibility to the core-sheath type composite fiber and plays a role of incorporating a hydrophilizing agent described later during heat treatment.
The polyethylene resin constituting the sheath part preferably has a crystallite size of 100 to 200 mm.
When the crystallite size is 100 mm or more, the hydrophilizing agent is easily taken into the fiber from the surface during heat treatment, and the selection of the hydrophilizing agent to be used is wide. Thereby, the hydrophilic property of desired parts, such as this fiber and a web obtained using this, a nonwoven fabric, etc. can be reduced easily.

From the viewpoint of reliably causing a change in the hydrophilicity of the fiber surface, the crystallite size is preferably 100 to 200 mm, more preferably 115 to 180 mm.
The upper limit value of 200 mm of the crystallite size is determined from the viewpoint of mechanical properties such as tensile strength and elongation at break. If the crystallite size is within 200 mm, the number of crystals is not reduced and the mechanical properties are not lowered.

[Method for measuring crystallite size of polyethylene resin]
The crystallite size is calculated from the half width measured by the powder X-ray diffraction method by the Serrer equation. As a calculation method, RINT-2500 manufactured by Rigaku Corporation is used, and the peak of the plane index (110) of PE is calculated by the attached crystallite size calculation program JADE 6.0. Specific conditions were a CuKα ray (wavelength 0.154 nm) as a radiation source, a generated voltage and current of 40 kV · 120 mA, and a sweep rate of 10 ° / min. The sample was placed at the time of measurement by attaching a fiber bundle so as to be parallel to the length direction of the slit of the sample holder so that the fiber bundle was perpendicular to the incident direction of X-rays.

A core part is a part which provides intensity | strength to a core-sheath-type composite fiber, As a resin component which comprises a core part, the resin component whose melting | fusing point is higher than a polyethylene resin can be especially used without a restriction | limiting. Examples of the resin component constituting the core include polyolefin resins such as polypropylene (PP) (excluding polyethylene resin), polyester resins such as polyethylene terephthalate (PET), and polybutylene terephthalate (PBT). Furthermore, a polyamide-type polymer, the copolymer of 2 or more types of the resin component mentioned above, etc. can be used.
Of these combinations, it is preferable to use polypropylene (PP) or polyethylene terephthalate (PET). A plurality of types of resins can be blended and used. In this case, the melting point of the core is the melting point of the resin having the highest melting point.
Further, the difference in melting point between the resin component constituting the core part and the resin component constituting the sheath part (the former-the latter) is preferably 20 ° C. or more because the nonwoven fabric can be easily produced. The difference in melting point is preferably within 150 ° C.

The composite fiber having a sheath part made of polyethylene resin having a crystallite size of 100 to 200 mm is designed to promote solidification of the ethylene resin constituting the sheath part when, for example, a core-sheath type composite fiber is produced by a melt spinning method. It can be manufactured by doing.
The spinning device shown in FIG. 1 includes two systems of extrusion devices 1 and 2 including extruders 1A and 2A and gear pumps 1B and 2B, and a spinneret 3. The resin components melted and measured by the extruders 1A and 2A and the gear pumps 1B and 2B are merged in the spinneret 3 and discharged from the nozzle. As the shape of the spinneret 3, an appropriate shape is selected according to the shape of the target composite fiber. In a preferred embodiment, both resin components are discharged from the nozzle in a state in which the resin forming the sheath surrounds the resin forming the core, and such a nozzle is circular. Many are formed in a dispersed state in the region. A take-up device 4 is installed immediately below the spinneret 3 and the molten resin discharged from the nozzle is taken down at a predetermined speed.

As a method for promoting solidification of the ethylene resin in the sheath, for example, as shown in FIG. 1, a method of accelerating solidification of the sheath by applying cold air 5 to the molten resin discharged from the nozzle, or a polyethylene resin Examples thereof include a method of blending a nucleating agent to promote crystallization.
When the cold air 5 is applied, the temperature of the cold air can be, for example, 20 to 40 ° C., and particularly preferably 20 to 25 ° C.
Further, the wind speed is preferably high, and the wind speed is preferably 5 m / sec or more, more preferably 10 m / sec or more, and further preferably 20 m / sec or more.
Further, it is also preferable to spray water or pass through a water bath or oil bath after a relatively short time after melt spinning.

As a nucleating agent for promoting crystallization of a polyethylene resin, a diacetal compound-based nucleating agent such as 1,3: 2,4-dibenzylidenesorbitol, 1,3: 2,4-di (p-methylbenzylidene) sorbitol, Alkyl esters of alicyclic polybasic acids such as tetrahydrophthalic acid and hexahydrophthalic acid (preferably alkyl esters having 8 to 22 carbon atoms), nucleating agents, aliphatic polybasic acids such as adipic acid, sebacic acid and azelaic acid An alkyl ester (preferably an alkyl ester having 8 to 22 carbon atoms) nucleating agent, tris (2-methylcyclohexylamide) of tricarballylic acid and the like can be preferably used.

In addition, a method of applying cold air 5 and a method of blending a nucleating agent can be used in combination. Further, in one or both of these methods, a method of raising the temperature of the resin component of the core part from a general temperature, A method of increasing the take-up speed of the spun yarn from a conventional general speed can be combined.
The take-up speed of the spun yarn is preferably 1000 m / min or more and more preferably 1300 m / min or more from the viewpoint of promoting the solidification of the sheath. Further, in order to make it easy to bundle the fibers discharged from the spinneret 3 and to reduce friction with the take-up device 4, lubricating oil is applied to the fiber surface by the rollers 7.

The core-sheath type composite fiber is preferably a fiber whose length is increased by heating (hereinafter also referred to as a heat-extensible composite fiber). Examples of the heat-extensible fiber include a fiber that spontaneously extends as the crystal state of the resin changes due to heating. The heat-extensible fiber is present in the nonwoven fabric in a state where its length is extended by heating and / or in a state where it can be extended by heating.

A preferable heat-extensible conjugate fiber has a first resin component that constitutes a core portion and a second resin component that comprises a polyethylene resin and constitutes a sheath portion, and the first resin component is a second resin component. Has a higher melting point. A 1st resin component is a component which expresses the heat | fever extensibility of this fiber, and a 2nd resin component is a component which expresses heat-fusibility. The 2nd resin component which comprises a sheath part should just exist at least one part of the fiber surface continuously in a length direction.
The melting points of the first resin component and the second resin component were determined by thermal analysis of a finely cut fiber sample (sample weight 2 mg) using a differential scanning calorimeter (DSC6200 manufactured by Seiko Instruments Inc.) at a heating rate of 10 ° C./min. The melting peak temperature of each resin is measured and defined by the melting peak temperature. When the melting point of the second resin component cannot be clearly measured by this method, the resin is defined as “resin having no melting point”. In this case, the temperature at which the second resin component is fused to such an extent that the strength of the fusion point of the fiber can be measured is used as the temperature at which the molecular flow of the second resin component begins, and this is used instead of the melting point.

The preferred orientation index of the first resin component in the heat-stretchable conjugate fiber is naturally different depending on the resin used. For example, in the case of a polypropylene resin, the orientation index is preferably 60% or less, more preferably 40% or less. More preferably, it is 25% or less. When the first resin component is polyester, the orientation index is preferably 25% or less, more preferably 20% or less, and still more preferably 10% or less. On the other hand, the second resin component preferably has an orientation index of 5% or more, more preferably 15% or more, and still more preferably 30% or more. The orientation index is an index of the degree of orientation of the polymer chain of the resin constituting the fiber. And when the orientation index of a 1st resin component and a 2nd resin component is each said value, a heat | fever extensible composite fiber comes to expand | extend by heating.

The orientation index of the first resin component and the second resin component is expressed by the following formula (1), where A is the birefringence value of the resin in the heat-extensible conjugate fiber, and B is the intrinsic birefringence value of the resin. expressed.
Orientation index (%) = A / B × 100 (1)

Intrinsic birefringence refers to birefringence in the state where the polymer polymer chains are perfectly oriented. The values are, for example, the first edition of “Plastic Materials in Molding”, Appendix, Typical Plastic Materials Used in Molding (Plastics) Edited by the Japan Society for Molding and Processing, Sigma Publishing, published on February 10, 1998).

The birefringence in the heat-extensible composite fiber is measured under polarization in a direction parallel to and perpendicular to the fiber axis by attaching a polarizing plate to an interference microscope. As the immersion liquid, a standard refraction liquid manufactured by Cargille is used. The refractive index of the immersion liquid is measured with an Abbe refractometer. From the interference fringe image of the composite fiber obtained by the interference microscope, the refractive index in the direction parallel and perpendicular to the fiber axis is obtained by the calculation method described in the following document, and the birefringence that is the difference between the two is calculated.
“Fiber structure formation in high-speed spinning of core-sheath type composite fiber”, page 408 (Journal of the Fiber Society, Vol. 51, No. 9, 1995)

The heat stretchable conjugate fiber can be stretched by heat at a temperature lower than the melting point of the first resin component. The heat-extensible composite fiber preferably has a thermal elongation rate of 0.5 to 20% at a temperature 10 ° C. higher than the melting point of the second resin component (softening point in the case of a resin having no melting point), Preferably it is 3 to 20%, more preferably 5.0 to 20%. A nonwoven fabric containing fibers having such a thermal elongation rate becomes bulky due to the elongation of the fibers or has a three-dimensional appearance. For example, the uneven shape on the surface of the nonwoven fabric 10 becomes remarkable.

[Thermal elongation of fiber]
The thermal elongation rate of the fiber is measured by the following method. A thermomechanical analyzer TMA / SS6000 manufactured by Seiko Instruments Inc. is used. As a sample, after preparing a plurality of fibers having a fiber length of 10 mm or more so that the total weight per 10 mm of the fiber length is 0.5 mg, and arranging the plurality of fibers in parallel, Mount on the device with 10mm distance between chucks. The measurement start temperature is 25 ° C., and the temperature is increased at a temperature increase rate of 5 ° C./min with a constant load of 0.73 mN / dtex applied. The amount of elongation of the fiber at that time is measured, and the amount of elongation X (mm) at a temperature 10 ° C. higher than the melting point of the second resin component (softening point in the case of a resin having no melting point) is read. The elongation rate is calculated.
Fiber thermal elongation (%) = (X / 10) × 100
The reason for measuring the thermal elongation rate at the above temperature is that when the nonwoven fabric 10 is produced by thermally fusing the intersections of the fibers, the melting point or the softening point of the second resin component is higher than that and about 10 ° C. higher than them. It is because it is normal to manufacture in the range up to temperature.

[Evaluation of thermal extensibility of fibers taken out from non-woven fabric]
When taking out fiber from a nonwoven fabric and judging the heat | fever extensibility of a fiber, the following methods are used. First, five fibers located at each part of the nonwoven fabric shown in FIG. 3B are collected. The length of the fiber to be collected is 1 mm or more and 5 mm or less. The collected fiber is sandwiched between preparations, and the total length of the sandwiched fiber is measured. The measurement is performed using a microscope VHX-900 and a lens VH-Z20R manufactured by KEYENCE, observing the fibers at a magnification of 50 to 100 times, and using a measurement tool incorporated in the apparatus for the observed image. . The length obtained by the measurement is defined as “the total length of fibers collected from the nonwoven fabric” Y. The fiber whose total length has been measured is put into a DSC6200 sample container (product name: robot container 52-023P, 15 μL, aluminum) manufactured by SII Nano Technology. The container containing the fibers is placed in a sample place in a DSC 6200 heating furnace set in advance at a temperature 10 ° C. lower than the melting point of the first resin component. 60 sec after the temperature (display name in the measurement software: sample temperature) measured with a thermocouple installed directly under the DSC6200 sample storage area falls within the range of ± 1 ° C, which is 10 ° C lower than the melting point of the first resin component Heat briefly and then remove quickly. The heat-treated fiber is taken out from the DSC sample container and sandwiched between preparations, and the total length of the sandwiched fiber is measured. For the measurement, a microscope VHX-900 and a lens VH-Z20R manufactured by KEYENCE were used. The measurement was performed by observing the fiber at a magnification of 50 to 100 times and using a measurement tool incorporated in the apparatus for the observed image. The length obtained by the measurement is referred to as “full length of fiber after heat treatment” Z. The thermal elongation rate (%) is calculated from the following formula.
Thermal elongation (%) = (Z−Y) ÷ Y × 100 [%]
This value is defined as the thermal elongation rate of the fiber taken out from the nonwoven fabric. When this thermal elongation rate is larger than 0, it can be determined that the fiber is a heat-extensible fiber.

In order to achieve the orientation index as described above for each resin component in the thermally stretchable conjugate fiber, for example, the first resin component and the second resin component having different melting points are used, and melt spinning is performed at a low speed of less than 2000 m / min. Then, after obtaining the composite fiber, the composite fiber may be heat-treated and / or crimped. In addition to this, the stretching process may be avoided.

As the crimping process, it is easy to perform mechanical crimping. There are two-dimensional and three-dimensional forms of mechanical crimping. In addition, there are three-dimensional manifested crimps found in the eccentric type core-sheath type composite fiber and side-by-side type composite fiber. Any aspect of crimping may be performed in the present invention. The crimping process may be accompanied by heating. Moreover, you may heat-process after a crimping process. Furthermore, in addition to the heat treatment after the crimping treatment, a separate heat treatment may be performed before the crimping treatment. Or you may perform a heat processing separately, without performing a crimping process.

The fiber may be slightly stretched during the crimping process, but such stretching is not included in the stretching process referred to in the present invention. The drawing treatment referred to in the present invention refers to a drawing operation usually performed on an undrawn yarn at a draw ratio of about 2 to 6 times.

The conditions for the heat treatment are appropriately selected according to the types of the first and second resin components constituting the composite fiber. The heating temperature is lower than the melting point of the second resin component. For example, when the heat-extensible conjugate fiber is a core-sheath type, the core component is polypropylene and / or polyester, and the sheath component is high-density polyethylene, the heating temperature is preferably 50 to 120 ° C., particularly preferably 70 to 115 ° C. The heating time is preferably 10 to 1800 seconds, more preferably 20 to 1200 seconds. Examples of the heating method include hot air blowing and infrared irradiation. As described above, this heat treatment can be performed after the crimping treatment.

The ratio (weight ratio) between the first resin component and the second resin component in the heat-extensible composite fiber is 10:90 to 90: 10%, particularly 20:80 to 80: 20%, especially 50:50 to 70:30. % Is preferred. Within this range, the mechanical properties of the fiber are sufficient, and the fiber can withstand practical use. Further, the amount of the fusion component is sufficient, and the fibers are sufficiently fused. Moreover, it is preferable that the ratio of the 1st resin component used as a core is large from a viewpoint of making the card | curd permeability favorable when it uses as a raw material of the nonwoven fabric manufactured with a card machine, without impairing extensibility.

As the fiber length of the heat-extensible composite fiber, one having an appropriate length is used according to the method for producing the nonwoven fabric. For example, when the nonwoven fabric is manufactured by the card method as described later, the fiber length is preferably about 30 to 70 mm. The same applies to the fiber length of the heat-fusible composite fiber described below.

The fiber diameter of the heat-extensible composite fiber is appropriately selected according to the specific use of the nonwoven fabric. When the nonwoven fabric is used as a constituent member of an absorbent article such as a surface sheet of the absorbent article, it is preferable to use a nonwoven fabric having a thickness of 10 to 35 μm, particularly 15 to 30 μm. The same applies to the fiber diameter of the heat-fusible conjugate fiber described below. In addition, the fiber diameter of the heat-extensible composite fiber is reduced when the fiber diameter is reduced, and the fiber diameter is a fiber diameter when the nonwoven fabric is actually used.

As the heat-extensible composite fiber, in addition to the above-described heat-extensible composite fiber, Japanese Patent No. 4131852, Japanese Patent Application Laid-Open No. 2005-350836, Japanese Patent Application Laid-Open No. 2007-303035, Japanese Patent Application Laid-Open No. 2007-204899, The fibers described in JP 2007-204901 A and JP 2007-204902 A can also be used.

The hydrophilizing agent is attached to the surface of the core-sheath composite fiber, and increases the hydrophilicity of the surface of the fiber as compared with that before attaching the hydrophilizing agent.
As a hydrophilizing agent, the thing similar to what is used in the said technical field can be used. Typical examples of such a hydrophilizing agent include various surfactants.
As the surfactant, anionic, cationic, zwitterionic and nonionic surfactants can be used.
Examples of anionic surfactants include alkyl phosphate sodium salt, alkyl ether phosphate sodium salt, dialkyl phosphate sodium salt, dialkyl sulfosuccinate sodium salt, alkylbenzene sulfonate sodium salt, alkyl sulfonate sodium salt, alkyl sulfate sodium salt, secondary Examples include alkyl sulfate sodium salt (all alkyls preferably have 6 to 22 carbon atoms, particularly 8 to 22 carbon atoms). These may use other alkali metal salts such as potassium salts in place of sodium salts.
Examples of the cationic surfactant include alkyl (or alkenyl) trimethyl ammonium halide, dialkyl (or alkenyl) dimethyl ammonium halide, alkyl (or alkenyl) pyridinium halide, etc., and these compounds have 6 to 6 carbon atoms. Those having 18 alkyl or alkenyl groups are preferred. Examples of the halogen in the halide compound include chlorine and bromine.

Examples of zwitterionic surfactants include alkyl (C1-30) dimethylbetaine, alkyl (C1-30) amidoalkyl (C1-4) dimethylbetaine, alkyl (C1-30). ) Betaine-type zwitterionic surfactants such as dihydroxyalkyl (carbon number 1-30) betaine, sulfobetaine-type amphoteric surfactants, alanine type [alkyl (carbon number 1-30) aminopropionic acid type, alkyl ( Amino acid type amphoteric surfactant such as carbon number 1-30) iminodipropionic acid type amphoteric surfactant, glycine type [alkyl (carbon number 1-30) aminoacetic acid type etc.] amphoteric surfactant, alkyl (carbon (Formula 1-30) Aminosulfonic acid type amphoteric surfactants such as taurine type.

Examples of nonionic surfactants include polyhydric alcohol fatty acid esters such as glycerin fatty acid esters, poly (preferably n = 2 to 10) glycerin fatty acid esters, sorbitan fatty acid esters (preferably those having 8 to 8 carbon atoms of fatty acids). 22), an alkylene oxide adduct of the polyhydric alcohol fatty acid ester (preferably an addition mole number of 2 to 20 moles), a polyoxyalkylene (addition mole number of 2 to 20) alkyl (carbon number of 8 to 22) amide, a polyoxyalkylene (Additional mole number 2 to 20) alkyl (carbon number 8 to 22) ether, polyoxyalkylene-modified silicone, amino-modified silicone and the like.

Of the nonionic surfactants, polyethylene glycol and polyethylene glycol fatty acid esters can be used. For example, the core-sheath composite fiber having these surfactants attached to the surface is used to form a nonwoven fabric. From the viewpoint of preventing static electricity from being generated in the non-woven fabric during storage after manufacture and preventing dust in the air from being used, it is preferable to use other than these, and sanitary napkins, panty liners, disposable When the non-woven fabric is used as a surface material for absorbent articles such as diapers, it is difficult to remove the surfactant from the fiber surface by the excretory liquid, and in terms of increasing the sustainability of the excretory liquid absorbency (absorption rate). It is preferable to use other than these.

For the purpose of increasing the hydrophilicity of the fiber and reducing the hydrophilicity by heat, preferred surfactants or surfactant combinations include alkyl phosphate potassium salts, polyoxyethylene alkylamides and alkylbetaines, Alkyl phosphate potassium salt and alkyl sulfonate sodium salt, polyoxyethylene alkyl amine and polyglycerol monoalkylate, polyoxyethylene alkylamide and stearyl phosphate potassium salt, polyoxyethylene alkylamide and polyglycerol monoalkylate, alkylsulfonate sodium salt Salts and stearyl phosphate potassium salts, alkyl ether phosphate potassium salts and polyglycerol fatty acid esters, polyoxyethylene alcohols Luamide and dialkyl sulfosuccinate sodium salt, polyoxyethylene polyoxypropylene modified silicone and dialkyl sulfosuccinate, polyglycerin fatty acid ester and dialkyl sulfosuccinate sodium salt, sorbitan fatty acid ester and dialkyl sulfosuccinate sodium salt, polyoxyethylene alkyl Amides and polyglycerin fatty acid esters, polyoxyethylene alkylamides and sorbitan fatty acid esters, polyoxyethylene alkylamines and sorbitan fatty acid esters, polyoxyethylene polyoxypropylene modified silicones and polyoxyethylene alkyl ethers, polyoxyethylene polyoxypropylene modified silicones And polyglycerol fatty acid ester Le, polyoxyethylene polyoxypropylene-modified silicone, and sorbitan fatty acid esters, sorbitan fatty acid esters and polyoxyethylene alkyl ethers, polyglycerol fatty acid esters and sorbitan fatty acid esters, polyglycerol fatty acid esters and polyoxyethylene alkyl ethers, and the like. These preferable surfactants and preferable combinations of surfactants only need to contain these surfactants, and may further contain other surfactants and the like.

The adhesion amount of the hydrophilizing agent is preferably 0.1 to 0.6% by mass with respect to the mass of the core-sheath type composite fiber, more preferably from the viewpoint of increasing the hydrophilicity of the non-hydrophobic part. 2 to 0.5% by mass.
As a method for attaching the hydrophilizing agent to the surface of the core-sheath composite fiber, various known methods can be employed without any particular limitation. For example, application by spraying, application by slot coater, application by roll transfer, immersion in a hydrophilic oil, and the like can be mentioned. These treatments may be performed on the core-sheath type composite fiber before being formed into a web, or may be performed after the core-sheath type composite fiber is formed into a web by various methods.

In FIG. 2, the core-sheath type composite fiber tow-like aggregate obtained by the spinning device shown in FIG. 1 is pulled out from the accommodating portion 6 that accommodated it, and the lubricating oil adhered by the roller 7 is washed. A state is schematically shown in which the hydrophilic agent is attached to the surface of the core-sheath-type conjugate fiber through the hydrophilic agent application device 62 after being washed away by the device 61 and removed.
The core-sheath type composite fiber having a hydrophilic agent attached to the surface thereof is dried at a temperature sufficiently lower than the melting point of the ethylene resin (for example, 120 ° C. or less) in a hot air blowing type dryer 63 and then crimped. Then, crimping is performed, and then cut into a predetermined length by the cutting device 65 to obtain a short fiber aggregate.

The “fiber whose hydrophilicity is lowered by heat” used in the present invention is preferably used for the production of sheet materials such as webs and nonwoven fabrics. In addition, a part of the layered body can be formed on the manufactured sheet material. And the hydrophilic property of a desired part can be reduced by heat-processing after the manufacturing process of the sheet material, and manufacture of a sheet material and a laminated body. The decrease in hydrophilicity may decrease the entire hydrophilicity of the sheet material, or may decrease a part of the sheet material. The thickness (fineness) of the fiber is selected in an appropriate range according to the specific application such as a non-woven fabric produced by using the fiber, but from the viewpoint of producing a non-woven fabric that is soft and has a good touch. Is preferably 1.0 to 10.0 dtex, and more preferably 2.0 to 8.0 dtex.

3 (a) and 3 (b) are diagrams showing a nonwoven fabric 10 which is an embodiment of the nonwoven fabric of the present invention. From the “fibers whose hydrophilicity decreases due to heat” obtained as described above, the web is shown. After forming the web, the hydrophilicity of a part of the web is reduced.
As a method for obtaining a web from a fiber whose hydrophilicity is lowered by heat, various known methods such as a card method, an airlaid method, and a spunbond method can be used. As shown in FIG. 4, a card machine 11 is used. The method (card method) is preferred.

As shown in FIG. 4, the nonwoven fabric shown in FIG. 3 (a) and FIG. 3 (b) forms a web 12 by using a card machine 11 using a short fiber aggregate of fibers whose hydrophilicity is lowered by heat as a raw material. Then, the web 12 is introduced into an embossing device 13 having a pair of rolls 14 and 15 for embossing, and the embossed web 16 is heat-treated by a hot-air treatment device 17 using an air-through method. It is a thing.
One of the pair of rolls used for the embossing is an embossing roll 14 in which convex portions for embossing in a lattice pattern are formed on the peripheral surface, and the other has a smooth peripheral surface and faces the embossing roll. The flat roll 15 is arranged. Embossing is performed by pressing and compressing the web between the convex portion of the embossing roll 14 and the smooth peripheral surface of the flat roll 15. Thereby, the nonwoven fabric which has the thin part (embossing part) 18 formed by the embossing, and the thick part 19 other than that is obtained.

In 1st Embodiment of the manufacturing method of the nonwoven fabric of this invention, in the embossing at the time of manufacturing the nonwoven fabric 10 in this way, the temperature applied to the web 12 is the sheath of the fiber whose hydrophilicity is lowered by heat. The temperature is kept below the melting point of the polyethylene resin constituting the part, and at the subsequent hot air treatment, a temperature not lower than the melting point of the polyethylene resin and not higher than the melting point of the resin component of the core part is applied. At the time of this embossing, the air permeability decreases as the compression becomes closer to the embossed portion of the web. On the other hand, the polyethylene resin constituting the embossed portion only needs to be melted by pressure and can be minimized. On the other hand, at the time of hot air treatment, the portion (embossed portion) that has been consolidated by embossing has little or no amount of hot air to pass, and hot air passes through thicker portions other than the embossed portion. , Hydrophilicity decreases.
As a result, the thin portion 18 and / or its peripheral portion formed by embossing becomes a hydrophilic portion, and becomes relatively hydrophobic as it becomes closer to the other thick portion 19, and the thickest portion becomes thicker. A nonwoven fabric in which the vicinity of the portion is a portion exhibiting maximum hydrophobicity is obtained. Moreover, by the said hot air process, melting | fusing of the sheath part of parts other than an embossing part advances, the intersection of a fiber is heat-seal | fused, and a strong nonwoven fabric is obtained.

The nonwoven fabric 10 shown in FIGS. 3A and 3B has a single layer structure. The nonwoven fabric 10 has a concavo-convex surface 10b having one concavo-convex shape, and the other surface is flat or a flat surface 10a having a small degree of concavo-convexity compared to the concavo-convex surface.
The thick portion 19 and the thin portion 18 in the nonwoven fabric 10 form a convex portion 119 and a concave portion 118 on the concave-convex surface 10 b of the nonwoven fabric 10. The concave portion 118 includes a first linear concave portion 118a extending in parallel with each other and a second linear concave portion 118b extending in parallel with each other, and the first linear concave portion 118a and the second linear concave portion 118b. And intersect at a predetermined angle. The convex portion 119 is formed in a rhombus-shaped closed region surrounded by the concave portion 118.

The top part P1 of the thick part is the top part P1 of the convex part 119 formed on the uneven surface 10b of the nonwoven fabric by the thick part 19. Compared with the top portion P1 of the thick portion 19, the thin portion 18 or its neighboring portion P3 has high hydrophilicity. When liquid enters from the uneven surface 10b side, the liquid is introduced to the flat surface 10a side. It is preferable in terms of easy removal and less liquid residue in the nonwoven fabric 10. Further, it is preferable that the hydrophilicity gradually increases from the top portion P1 of the thick portion 19 toward the thin portion (embossed portion) 18 or its vicinity P3.

The concavo-convex surface 10b of the nonwoven fabric 10 is directed to the embossing roll 14 side during embossing, and is directed to the side opposite to the net surface (breathable support) when hot air treatment is performed by an air-through method. It is the surface of the side which sprays directly. Therefore, when a heat-extensible conjugate fiber is used as a constituent fiber of the nonwoven fabric, the heat-extensible conjugate fiber extends more greatly on the uneven surface 10b than on the flat surface 10a. Therefore, the fiber diameter in the surface of the flat surface 10a becomes larger than the fiber diameter in the surface of the uneven surface 10b. Further, the hydrophilicity of the thick portion 19 is lower on the uneven surface 10b side than on the flat surface 10a side.

In the method for manufacturing a nonwoven fabric according to the first embodiment, the temperature applied to the web during embossing is a polyethylene that constitutes the sheath portion from the viewpoint of suppressing changes in hydrophilicity at the embossed portion and / or its vicinity (peripheral portion). It is preferable that the temperature is 20 ° C. or more lower than the melting point of the resin and less than the melting point of the resin component constituting the core. On the other hand, the temperature applied during the hot air treatment is at least 10 ° C. lower than the melting point of the polyethylene resin, in particular, more than the melting point of the polyethylene resin, and more preferably the melting point of the polyethylene resin +5 from the viewpoint of surely causing a change in hydrophilicity. It is preferable that the temperature is at least ° C.
According to the method of this embodiment, a nonwoven fabric having a hydrophilic portion and a hydrophobic portion can be produced without requiring a complicated device or a special device, and the obtained nonwoven fabric is, for example, a sanitary napkin or a panty. When used as a surface material for absorbent articles such as liners and disposable diapers, the skin feels good, liquid residue hardly occurs on the surface, liquid flow hardly occurs on the surface, and good absorption performance is exhibited.

In other embodiment (2nd embodiment) of the manufacturing method of the nonwoven fabric of this invention, arbitrary methods (for example, a card method, an airlaid method, a spun bond method, etc.) from the fiber which hydrophilicity falls by the heat of this invention After the web is formed or after the web is made into a non-woven fabric, heat treatment is performed only on one side of the web or the non-woven fabric, one surface side is relatively hydrophilic, and gradually toward the other surface side, it becomes gradually relatively hydrophobic. A non-woven fabric having a hydrophilicity gradient in a multistage or stepless manner in the thickness direction is obtained.

As a method of performing heat treatment only on one side, a method of contacting a roll heated to a temperature equal to or higher than the melting point of the polyethylene resin of the sheath on only one side of the web or nonwoven fabric being conveyed, or the back side of the web or nonwoven fabric being conveyed And a method of spraying hot air having a temperature equal to or higher than the melting point of the polyethylene resin on the surface side of the web or the nonwoven fabric. The temperature of this heat treatment is also at least 10 degrees lower than the melting point of the polyethylene resin, particularly at least the melting point of the polyethylene resin, and more preferably at the melting point of the polyethylene resin + 5 ° C. Preferably there is.
As a web nonwoven fabric forming method, various known nonwoven fabric forming methods such as spunlace, needle punch, chemical bond, and dot-like embossing can be employed.

According to the nonwoven fabric in which one surface obtained in the present embodiment is relatively hydrophilic and the other surface is relatively hydrophobic, for example, the sanitary napkin, panty liner, disposable diaper with the hydrophobic surface facing the skin side When used as a surface material for absorbent articles, etc., the excretory liquid is unlikely to remain on the hydrophobic surface in contact with the skin. Therefore, when thick fibers are used, the texture is deteriorated and the concealability by reducing the number of fibers In addition, the texture and whiteness are reduced, and the stickiness during use is reduced.

In the fiber or the web containing the fiber whose hydrophilicity is lowered by heat in the present invention, the hydrophilicity is lowered by the heat treatment. The hydrophilic part and the hydrophilic part in the nonwoven fabric of the present invention need only have a high degree of hydrophilicity in comparison with the part whose hydrophilicity has been lowered by heat treatment. In addition, the hydrophobic part or the hydrophobic part may be a part where the hydrophilicity is lowered before the hydrophilicity is lowered by heat treatment or compared with a part where the hydrophilicity is not lowered. The hydrophilicity reduction may be any treatment that reduces the hydrophilicity in comparison with that before the heat treatment. A decrease in hydrophilicity is synonymous with an increase in contact angle. However, the hydrophilicity of the web or non-woven fabric before reducing the hydrophilicity (the same applies to the hydrophilic portion of the completed non-woven fabric, etc.), the water contact angle with respect to the fiber is preferably 40 to 70 degrees, preferably 60 to 70 degrees. More preferably. On the other hand, the water contact angle with the fiber is preferably 60 to 90 degrees, and more preferably 70 to 85 degrees, in the portion where the hydrophilicity is lowered (the same applies to the hydrophobic portion of the finished nonwoven fabric). The term “decreased hydrophilicity” as used herein means that the difference in contact angle is 2 degrees or more, preferably 5 degrees or more, and more preferably 10 degrees or more.

The non-woven fabric partially reduced in hydrophilicity according to the present invention may be three-dimensional by secondary processing, and further, additional processing such as performing a hydrophilization treatment on only a part may be appropriately performed.

[Measurement method of water contact angle to fiber]
The contact angle of water with respect to the fiber is measured by the following method. As a measuring device, an automatic contact angle meter MCA-J manufactured by Kyowa Interface Science Co., Ltd. is used. Distilled water is used for contact angle measurement. The amount of liquid discharged from an ink jet type water droplet discharge part (manufactured by Cluster Technology Co., Ltd., pulse injector CTC-25 having a discharge part hole diameter of 25 μm) is set to 20 picoliters, and a water drop is dropped just above the fiber. The state of dripping is recorded on a high-speed recording device connected to a horizontally installed camera. The recording device is preferably a personal computer incorporating a high-speed capture device from the viewpoint of image analysis or image analysis later. In this measurement, an image is recorded every 17 msec. In the recorded video, the first image of water droplets on the fiber is attached to the attached software FAMAS (software version is 2.6.2, analysis method is droplet method, analysis method is θ / 2 method, image processing algorithm Is non-reflective, the image processing image mode is frame, the threshold level is 200, and the curvature is not corrected). Image analysis is performed to calculate the angle between the surface of the water droplet that touches the air and the fiber, and the contact angle And
In addition, the measurement sample (fiber obtained by taking out from the nonwoven fabric) is the convex portion corresponding part Q on the top portion P1, the middle abdominal portion P2, the concave portion vicinity portion P3 and the rear surface (flat surface) 10a of the convex portion shown in FIG. The fiber located at 1 is cut from the outermost layer with a fiber length of 1 mm, the fiber is placed on a sample table of a contact angle meter and kept horizontal, and two different contact angles are measured for each fiber. In each of the aforementioned parts, N = 5 contact angles are measured to one decimal place, and a value obtained by averaging a total of 10 measured values (rounded to the second decimal place) is defined as each contact angle.

In addition to the above-described heat-extensible composite fiber, the nonwoven fabric 10 'according to another embodiment of the present invention has a non-heat-extensible heat-fusible composite that does not substantially extend its length by heating. The heat-fusible conjugate fiber containing fibers is a non-woven fabric having a hydrophilizing agent attached thereto and having a contact angle with water of 50 to 75 °. The nonwoven fabric 10 ′ is common to the nonwoven fabric 10 described above in that it has the form shown in FIGS. 3 (a) and 3 (b).
The concave portion 118 in the nonwoven fabric 10 ′ includes a joint portion formed by compacting and joining the constituent fibers of the nonwoven fabric. Examples of means for forming the joint include embossing with or without heat, ultrasonic embossing, and the like. On the other hand, the convex part 119 is a non-joining part. The thickness of the concave portion 118 is smaller than the thickness of the convex portion 119. The convex part 119 has a shape protruding toward the surface side of the nonwoven fabric 10 ′ (the upper surface side in FIG. 3B). The inside of the convex part 119 is filled with the constituent fibers of the nonwoven fabric 1′0.

Nonwoven fabric 10 'is excellent in absorption performance and bulk recovery property.
That is, when the present inventors further investigated the nonwoven fabric made from heat-extensible fibers, the heat-extensible fibers have a lower flexural modulus than that of ordinary heat-fusible fibers, which It has been found that when a load is applied to the nonwoven fabric in the thickness direction, the bulk is reduced and the interfiber distance tends to be shortened. When such a nonwoven fabric with reduced bulk is used as, for example, a surface sheet of an absorbent article, the liquid permeability is impaired due to the short interfiber distance, and the excreted liquid remains in the nonwoven fabric, The liquid may be easy to touch the skin that is in contact.

By combining the heat-extensible composite fiber and the non-heat-extensible heat-sealable composite fiber, and controlling the hydrophilicity of the heat-sealable composite fiber, the thickness is increased by the load applied in the thickness direction of the nonwoven fabric. Thus, it is possible to provide a nonwoven fabric having excellent bulk recovery properties when the amount of water decreases. The nonwoven fabric 10 'has a high bulk recoverability by blowing hot air.

Non-heat-extensible heat-fusible conjugate fibers (hereinafter also simply referred to as heat-fusible conjugate fibers) have a contact angle with water of 50 to 75 °, preferably 55 to 75 °, more preferably 65 to 75. It is effective to control the hydrophilicity / hydrophobicity of the heat-fusible conjugate fiber so that the temperature becomes 0 °. When the contact angle with water is less than 50 °, that is, when the fiber is too hydrophilic, for example, when used as a surface sheet of an absorbent article, body fluid may flow down on the surface of the nonwoven fabric. However, the desired fluid permeability cannot be obtained, or once absorbed body fluid flows back to the surface side, and the body fluid tends to remain on the nonwoven fabric. On the contrary, when the contact angle with water is more than 75 °, that is, when the fiber is too hydrophobic, the liquid permeability is good and once absorbed, the body fluid flows back to the surface side. Although it can prevent, a bodily fluid tends to flow down on the nonwoven fabric surface.

The contact angle of water with the heat-fusible conjugate fiber is measured by the method described above by taking out only the heat-fusible conjugate fiber from each part shown in FIG.

In order to control the contact angle of water with the heat-fusible composite fiber, a hydrophilizing agent may be attached to the fiber. Adhesion of the hydrophilizing agent is achieved by a method of applying a hydrophilizing agent to the surface of the fiber or a method of kneading a hydrophilizing agent in advance to a resin constituting the fiber and spinning using the resin. As a hydrophilizing agent, the thing similar to what is used in the said technical field can be used. Typical examples of such a hydrophilizing agent include various surfactants.
The adhesion amount of the hydrophilizing agent to the heat-fusible conjugate fiber is 0.1 to 0.6% by mass with respect to the mass of the heat-fusible conjugate fiber from the viewpoint of increasing the hydrophilicity of the portion that is not hydrophobized. Is more preferable, and 0.2 to 0.5% by mass is more preferable.

As surfactant, the thing similar to what was mentioned above as surfactant used for a heat | fever extensible composite fiber can be used.
In particular, surfactants for obtaining desired hydrophilicity include polyoxyethylene alkylamides, stearyl phosphate potassium salts, glycerin fatty acid esters, polyoxyethylene alkyl ethers, polyglycerin monoalkylates and the like. In addition, preferable combinations thereof include polyoxyethylene alkylamide and stearyl phosphate potassium salt; glycerin fatty acid ester and polyoxyethylene alkyl ether; polyoxyethylene alkylamide and alkylbetaine. These preferable surfactants and preferable combinations of surfactants only need to contain these surfactants, and may further contain other surfactants and the like.

The mixing ratio of the heat-extensible fiber and the heat-fusible composite fiber (the former / the latter) is one of the factors affecting the hydrophilicity / hydrophobicity of the entire nonwoven fabric. It is also one of the factors that facilitate the recovery of bulk when hot air is blown onto the nonwoven fabric. From these viewpoints, the mixing ratio (the former / the latter) of the heat-extensible fibers and the heat-fusible composite fibers contained in the nonwoven fabric is 20/80 to 80/20, particularly 30/70 to 70 / It is preferably set to 30, particularly 40/60 to 60/40.

In the nonwoven fabric 10 ′, it is preferable to control not only the above-described heat-fusible conjugate fiber but also the contact angle of water with the heat-extensible fiber from the viewpoint of making it more difficult for the nonwoven fabric to remain. From this viewpoint, the hydrophilicity / hydrophobicity of the heat-extensible fibers is adjusted so that the contact angle of water with the heat-extensible fibers contained in the nonwoven fabric is 40 to 90 °, particularly 60 to 75 °, particularly 65 to 75 °. It is preferable to control. The method for measuring the contact angle is as described above. In order to obtain the desired hydrophilicity, a hydrophilizing agent composed of a surfactant or the like can be attached to the heat-extensible fiber. As the surfactant, it is preferable to use a combination of two kinds of surfactants from the viewpoint that desired hydrophilicity can be easily obtained.

Regarding the heat-extensible fiber of the nonwoven fabric 10 ′, on the condition that the contact angle is in the above-mentioned range, the convex portion 119 is directed from the top P1 toward the back surface 10a side of the nonwoven fabric, that is, P1 in FIG. From P3 to P3 and from P3 to Q, it is preferable that the contact angle of the heat-extensible fiber with water gradually decreases. This makes it more difficult for the nonwoven fabric to remain liquid. Such a gradient of the contact angle is achieved by adopting a method to be described later as a method for producing the nonwoven fabric.

Regarding the heat-fusible conjugate fiber of the nonwoven fabric 10 ′, on the condition that the contact angle between the heat-fusible conjugate fiber and water is in the range of 50 to 75 °, the convex portion 119 has its top portion back to the back surface of the nonwoven fabric. Even if the contact angle of the heat-fusible conjugate fiber does not change or gradually increases toward the side 10a, that is, from P1 to P3 and from P3 to Q in FIG. Good. This also makes it more difficult for the nonwoven fabric to remain liquid. Such a gradient of the contact angle is achieved by adopting a method described later as a method for producing the nonwoven fabric.

Regarding the contact angles of heat-extensible fibers and heat-fusible composite fibers, when these are compared at the same measurement site in the same nonwoven fabric, the difference between the two is from the viewpoint of making the effect that liquid residue hardly occurs on the nonwoven fabric more remarkable. Is preferably within 25 °, in particular within 20 °, in particular within 15 °. In order to provide such a difference, for example, the type of fiber to be used, the method for producing the nonwoven fabric, the type of hydrophilic agent, the amount of adhesion, and the like may be appropriately controlled.

In the nonwoven fabric 10 ', the non-thermally stretchable heat-fusible conjugate fiber used as a raw material together with the heat-stretchable fiber includes two components having different melting points and is subjected to a stretching treatment. The heat-fusible conjugate fiber does not substantially extend its length even when heat is applied. As a raw material of the nonwoven fabric 10 ', by using a heat-extensible fiber and a heat-fusible conjugate fiber in combination, the bulk recovery when hot air is blown onto the nonwoven fabric 10' is evident from the results of the examples described later. The property becomes very good.

In the nonwoven fabric 10 ′, at least at the convex portion 119, the intersection of the heat-extensible fibers, the intersection of the heat-fusible conjugate fibers, and the intersection of the heat-extensible fibers and the heat-fusible conjugate fibers are respectively air-through. It is heat-sealed. Thereby, the recoverability of the bulk when hot air is blown onto the nonwoven fabric 10 'becomes remarkable. Further, fuzz on the surface of the nonwoven fabric 10 ′ is less likely to occur. Whether or not the intersection of the fibers is thermally fused is determined by observing the nonwoven fabric 10 'with a scanning electron microscope.

The heat-fusible conjugate fiber is a bicomponent conjugate fiber that includes a high-melting component and a low-melting component, and the low-melting component is continuously present in the length direction on at least a part of the fiber surface. There are various forms of the composite fiber such as a core-sheath type and a side-by-side type, and any form can be used. The heat-fusible conjugate fiber is stretched at the raw material stage (that is, before being used for the nonwoven fabric 10 '). The stretching treatment referred to here is a stretching operation at a stretching ratio of about 2 to 6 times as described above.

The fusion temperature of the heat-fusible composite fiber is preferably close to the fusion temperature of the heat-extensible fiber. Thereby, the heat-extensible fibers, the heat-fusible conjugate fibers, and the heat-extensible fibers and the heat-fusible conjugate fibers can be successfully fused. From this viewpoint, when the fusion temperature of the heat-fusible conjugate fiber is T1, and the fusion temperature of the heat-extensible fiber is T2, the temperature difference between T1 and T2 is preferably within 20 ° C. Since it is not easy to strictly measure the fiber fusion temperature, the melting temperature of the resin involved in the fusion (that is, the low melting point resin) is replaced with the fusion temperature. The method for measuring the melting point is as described above.

From the viewpoint of successfully fusing the heat-extensible fiber and the heat-fusible composite fiber, the low melting point component in the heat-fusible fiber and the second resin component in the heat-extensible composite fiber are the same type of resin. In the case of being different or different, it is preferable to have compatibility.

Non-woven fabric 10 'may contain fibers other than the heat-extensible fibers and heat-fusible composite fibers described so far. Examples of such fibers include fibers that are not inherently heat-fusible (for example, natural fibers such as cotton and pulp, rayon and acetate fibers). These fibers are preferably contained in an amount of 5 to 30% by weight or less based on the weight of the nonwoven fabric. These fibers are contained in the nonwoven fabric 10 'for the purpose of improving the drawability of the liquid when the nonwoven fabric 10' is used as, for example, a surface sheet of an absorbent article.

Next, a preferred method for producing the nonwoven fabric 10 'will be described with reference to FIG. First, the web 12 is produced using a predetermined web forming means such as the card machine 11. The web 12 includes a heat-extensible conjugate fiber and a heat-fusible conjugate fiber in a state before elongation. As the web forming means, in addition to the card machine shown in the figure, a known method such as a method of transporting short fibers in an air stream and depositing them on a net (air array method) can be used.

The web 12 is sent to a hot embossing device 13 where it is subjected to hot embossing. The hot embossing device 13 includes a pair of rolls 14 and 15. The roll 14 is a sculpture roll having rhombic lattice-shaped projections formed on the peripheral surface. On the other hand, the roll 15 is a smooth roll (anvil roll) having a smooth peripheral surface. Each roll 14 and 15 can be heated to a predetermined temperature.

The hot embossing is performed at a temperature that is equal to or higher than the melting point of the second resin component −20 ° C. and lower than the melting point of the first resin component in the heat-extensible composite fiber in the web 12. The hot embossing is performed at a temperature of the melting point of the low melting point component of the heat-fusible conjugate fiber in the web 12 which is −20 ° C. or higher and lower than the melting point of the high melting point component. When the melting points of the second component of the heat-extensible conjugate fiber and the heat-fusible conjugate fiber are different, the temperature range is set to the lower melting point. Further, the heat embossing is performed at a temperature lower than the temperature at which the heat-extensible composite fiber exhibits heat elongation. The heat-extensible conjugate fiber and the heat-fusible conjugate fiber in the web 12 are joined by hot embossing. As a result, a large number of joints are formed on the web 12 to form the heat bond nonwoven fabric 16. This joint becomes a recess 118 in the target nonwoven fabric 10 '.

In the joint portion of the heat bond nonwoven fabric 16, the heat-extensible conjugate fiber and the heat-fusible conjugate fiber are consolidated and joined. In the part other than the joint part, both the heat-extensible conjugate fiber and the heat-fusible conjugate fiber are in a non-joined free state. Further, the elongation of the heat-extensible composite fiber has not yet occurred.

Next, the heat bond nonwoven fabric 16 is conveyed to the hot air spraying device 17. In the hot air spraying device 17, the heat bond nonwoven fabric 16 is subjected to air through processing. That is, the hot air blowing device 17 is configured such that hot air heated to a predetermined temperature penetrates the heat bond nonwoven fabric 16. The air-through process is performed at a temperature at which the heat-extensible conjugate fiber in the heat bond nonwoven fabric 16 is elongated by heating. And the intersection of the heat-extensible composite fibers in the free state existing in the part other than the joint portion in the heat bond nonwoven fabric 16, the intersection of the heat-fusible composite fibers, and the heat-extensible composite fiber and the heat-fusible composite fiber It is performed at a temperature at which the intersection with the heat seals. However, such temperature needs to be set to a temperature lower than the melting point of the first resin component of the heat-extensible conjugate fiber and the high melting point component of the heat-fusible conjugate fiber.

¡By such an air-through process, the heat-extensible composite fiber existing in the portion other than the joint portion is extended. Since a part of the thermally stretchable conjugate fiber is fixed by the joint portion, it is the portion between the joint portions that is stretched. And since a part of the thermally stretchable conjugate fiber is fixed by the joint portion, the stretched portion of the stretched thermally stretchable conjugate fiber loses its place in the plane direction of the heat bond nonwoven fabric 16, and the nonwoven fabric 16 Move in the thickness direction. As a result, convex portions 119 are formed between the joint portions, and the nonwoven fabric 10 'becomes bulky. Further, it has a three-dimensional appearance in which a large number of convex portions 119 are formed. Further, by air-through processing, the intersection of the heat-extensible conjugate fibers, the intersection of the heat-fusible conjugate fibers, and the intersection of the heat-extensible conjugate fibers and the heat-fusible conjugate fibers are respectively formed by heat fusion. Join.

By controlling the air-through conditions and ending the air-through process before the heat-extensible composite fiber is not fully extended, a non-woven fabric containing a heat-extensible composite fiber that can be further extended in the subsequent heat treatment step can also be obtained. . Therefore, the nonwoven fabric 10 'is manufactured using a heat-extensible composite fiber that can be stretched by heat as a raw material, and exists in a state that can be stretched by heating. It contains the fibers of the state.

When air-through processing is performed on a web containing a heat-extensible fiber to which a hydrophilizing agent is previously attached, and the heat-stretched composite fiber is stretched, the amount of passing hot air is controlled to be low as shown in FIG. The amount of heat applied toward the tops P1 to P3 and from P3 to Q of the nonwoven fabric 10 ′ shown in FIG. And it became clear as a result of examination of the present inventors that the higher the temperature applied to the fiber, the higher the elongation rate and the lower the hydrophilicity. Therefore, for example, in the manufacturing method shown in FIG. 4, the degree of elongation increases as the heat-extensible composite fiber located on the hot air blowing surface side increases and the decrease in hydrophilicity increases. The hot air blowing surface is a surface on which the convex portion 119 and the concave portion 118 of the nonwoven fabric 10 ′ are formed. Therefore, regarding the obtained nonwoven fabric 10 ′, the lower the hydrophilicity is, the greater the distance is to the top of the convex portion 119. Since the decrease in hydrophilicity is synonymous with the increase in contact angle, in other words, the heat-extensible conjugate fiber is formed at the convex portion 119 from the top P1 toward the back surface 10a side of the nonwoven fabric 10 ′, that is, FIG. In FIG. 1, the contact angle of the heat-extensible conjugate fiber gradually decreases from P1 to P3 and from P3 to Q.

The “fiber whose hydrophilicity is lowered by heat” according to the present invention forms a sheet material such as a web or a non-woven fabric, and heat-treats a part of the sheet material, so that it can be efficiently processed without requiring a complicated apparatus. It is possible to produce a sheet material having a hydrophilic part and a hydrophobic part. Further, the hydrophilizing agent attached to the surface of the core-sheath composite fiber is not limited to polyethylene glycol and polyethylene glycol fatty acid ester, and various hydrophilizing agents can be used.
The nonwoven fabric according to the present invention can be efficiently produced without requiring a complicated device, and the hydrophilicity or hydrophobicity of the heat-extensible conjugate fiber is different between one part of the nonwoven fabric and the other part. Taking advantage of the hydrophilicity gradient in the thickness direction and / or the plane direction, it can be used for various applications such as the surface material of absorbent articles.
According to the method for producing a nonwoven fabric according to the present invention, it is possible to efficiently produce a web or a nonwoven fabric partly hydrophilic and the other part hydrophobic without requiring a complicated apparatus. Moreover, the nonwoven fabric in which the hydrophobic part was formed in the desired pattern can be manufactured by changing the part which heat-processes suitably.

The nonwoven fabric according to the present invention can be applied to various fields by taking advantage of having a hydrophilicity gradient, such as partly hydrophilic and the other part hydrophobic or hydrophilicity-reduced part.
Moreover, the nonwoven fabric 10 ′ described above can be applied to various fields that take advantage of its uneven shape, bulkiness, and ease of liquid permeability.
For example, a surface sheet, a second sheet (between the surface sheet and the absorbent body) in an absorbent article (particularly a disposable hygiene article) used to absorb liquid discharged from the body, such as sanitary napkins, panty liners, disposable diapers, and incontinence pads Sheet), back sheet, leak-proof sheet, or interpersonal wiping sheet, skin care sheet, or objective wiper.

The nonwoven fabric 10 'before being used for these applications is generally stored in a state of being wound in a roll. Due to this, the bulkiness of the nonwoven fabric 10 'is often reduced. Therefore, when the nonwoven fabric 10 'is used, it is preferable to restore the reduced bulk by blowing hot air to the nonwoven fabric 10' by an air-through method. In restoring the bulk, it is preferable to use hot air having a temperature lower than the melting point of the second resin component in the heat-stretchable composite fiber and a temperature equal to or higher than the melting point −50 ° C. as the hot air blown onto the nonwoven fabric 10 ′. As a method for recovering the bulk of such a nonwoven fabric, for example, the techniques described in JP 2004-137655 A, JP 2007-177364 A, JP 2008-231609 A, and the like related to the earlier application of the present applicant are used. Can be used.

The basis weight of the web or nonwoven fabric used for the production of the nonwoven fabric is selected within a suitable range depending on the specific use of the intended nonwoven fabric. The basis weight of the finally obtained nonwoven fabric is preferably 10 to 80 g / m ² , particularly preferably 15 to 60 g / m ² .

When the nonwoven fabric 10, 10 ′ is used as, for example, a surface sheet of an absorbent article, the basis weight is preferably 10 to 80 g / m ² , particularly preferably 15 to 60 g / m ² . When used for the same purpose, the thickness of the convex portion 119 (thick portion 19) in the nonwoven fabric 10, 10 ′ is 0.5 to 3 mm, particularly 0.7 to 3 mm after the bulk recovery by hot air. Is preferred. On the other hand, the thickness of the recess 118 (thin portion 18) is preferably 0.01 to 0.4, particularly 0.02 to 0.2 mm. The thickness of the recess 118 is not substantially changed before and after the hot air is blown. The thickness of the convex part 119 and the recessed part 118 is measured by observing the longitudinal cross-section of the nonwoven fabric 10, 10 '. First, the nonwoven fabric is cut into a size of 100 mm × 100 mm, and a measurement piece is collected. A plate of 12.5 g (diameter 56.4 mm) is placed on the measurement piece, and a load of 49 Pa is applied. Under this condition, the longitudinal section of the nonwoven fabric is observed with a microscope (manufactured by Keyence Corporation, VHX-900), and the thicknesses of the convex portions 119 and the concave portions 118 are measured. In addition, when the convex part (thick part) and the concave part (thin part) are formed in the nonwoven fabric, the “thickness of the nonwoven fabric” refers to the thickness of the convex part (thick part).

The area ratio between the concave portion 118 and the convex portion 119 in the nonwoven fabric 10, 10 ′ is represented by an embossing rate (an embossed area ratio, that is, a ratio of the total area of the concave portion to the entire nonwoven fabric 10, 10 ′). It affects the bulkiness and strength of '. From these viewpoints, the embossing rate in the nonwoven fabric 10, 10 ′ is preferably 5 to 35%, particularly preferably 10 to 25%. The embossing rate is measured by the following method. First, using a microscope (manufactured by Keyence Co., Ltd., VHX-900), obtain a magnified photo of the surface of the nonwoven fabric 10, 10 ', adjust the scale to this magnified photo, and measure the dimensions of the embossed part in the total area T Measure and calculate the embossed area U.
The embossing rate can be calculated by the formula (U / T) × 100.

An absorbent article used for absorbing liquid discharged from the body typically includes a top sheet, a back sheet, and a liquid-retaining absorbent body interposed between both sheets. As the absorbent body and the back sheet when the nonwoven fabric according to the present invention is used as a top sheet, materials usually used in the technical field can be used without particular limitation.
For example, as the absorbent body, a fiber assembly made of a fiber material such as pulp fiber or a fiber assembly in which an absorbent polymer is held can be coated with a covering sheet such as tissue paper or nonwoven fabric. As the back sheet, a liquid-impermeable or water-repellent sheet such as a thermoplastic resin film or a laminate of the film and a nonwoven fabric can be used. The back sheet may have water vapor permeability. The absorbent article may further include various members according to specific uses of the absorbent article. Such members are known to those skilled in the art. For example, when applying an absorbent article to a disposable diaper or a sanitary napkin, a pair or two or more pairs of three-dimensional guards can be disposed on the left and right sides of the topsheet.

As mentioned above, although this invention was demonstrated based on the preferable embodiment, this invention is not restrict | limited to embodiment mentioned above.
For example, when the embossed portion is formed on the nonwoven fabric, the embossed portion forming pattern can be an arbitrary pattern such as a multi-row stripe shape, a dot shape, a checkered shape, or a spiral shape instead of the lattice shape. The shape of each point in the case of a dot shape may be a circle, an ellipse, a triangle, a quadrangle, a hexagon, a heart shape, or an arbitrary shape. Moreover, you may employ | adopt the shape which makes a square or rectangular lattice shape, or a tortoiseshell pattern.
Moreover, in the manufacturing method of the nonwoven fabric shown in FIG. 4, when embossing is performed, an embossing roll and / or a flat roll can be heated, and the nonwoven fabric which the embossing part and / or its periphery hydrophilicity fell can also be manufactured.
In addition, when the nonwoven fabric of the present invention is used for diapers, napkins, wipers, and other products, heat is applied to a desired portion at any time before production, during production, and after product formation. Thus, the hydrophilicity of some or all of the nonwoven fabrics of the present invention can be lowered, or water repellency can be achieved.

In the embodiment, hot embossing is used to form the joint (recessed portion 118), but the joint can be formed by ultrasonic embossing instead. In addition, the nonwoven fabric is not limited to a single-layer structure, and may be a multilayer structure in which one or more other nonwoven fabrics are laminated and integrated with the nonwoven fabric.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples.

[Example 1]
(1) Production of fiber whose hydrophilicity is lowered by heat Melt spinning was performed under the conditions shown in Table 1 to obtain a concentric core-sheath type composite fiber. The obtained composite fiber was not subjected to stretching treatment, and was then immersed in an aqueous solution of a hydrophilizing agent of the type shown in Table 1 to attach the hydrophilizing agent of the type and amount shown in Table 1. The drawing treatment here means a drawing operation of about 2 to 6 times that is usually performed on an undrawn yarn obtained after melt spinning. And after performing mechanical crimping, it cut | disconnected and obtained the fiber of the short fiber (fiber length 51mm). During spinning, cold air of 20 ° C. was blown onto the molten resin discharged from the spinning nozzle in order to accelerate the solidification of the resin constituting the sheath.
About the obtained fiber, the crystallite size of the constituent resin (polyethylene resin) of the sheath portion was measured by the method described above.

(2) Manufacture of a nonwoven fabric Using the obtained fiber, the nonwoven fabric was manufactured by the method shown in FIG. A specific manufacturing method is as follows. First, the web formed using the card machine was embossed. The embossing was performed such that a grid-like embossed part was formed and the area ratio of the embossed part (compressed part) was 22%. The processing temperature for embossing is 110 ° C. as shown in Table 1. Next, air-through processing was performed. In the air-through process, heat treatment was performed once by blowing hot air from the embossed surface side in the embossing process. The heat treatment temperature for air-through processing was set to 136 ° C. as shown in Table 1.
The obtained non-woven fabric has a thin portion (embossed portion) 18 and a thick portion 19 other than that, a rough surface 10b having a large undulation with one side having a convex portion 119 and a concave portion 118, and the other side being The flat surface 10a is almost flat.

[Examples 2 to 24, Comparative Examples 1 to 6]
The fibers shown in Table 1 were used, and the conditions shown in the same table were used. Except this, it carried out similarly to Example 1, and obtained the nonwoven fabric.

In the nonwoven fabrics obtained in Examples 1 to 24, the intersections of the constituent fibers were heat-sealed by the air-through method. Further, regarding the fibers contained in the nonwoven fabrics obtained in Examples 1 to 24, the presence or absence of thermal extensibility was determined by the method described above, and it was confirmed that fibers having thermal extensibility were contained. .

The hydrophilizing agents A to S shown in Table 1 and Table 2 are as follows.
[Hydrophilic agent]
A: Hydrophilizing agent blended with 50% by weight: 50% by weight of polyoxyethylene (addition mole number 2) stearylamide (manufactured by Kawaken Fine Chemical Co., Ltd., Amizole SDE) and stearyl betaine (manufactured by Kao Corporation, Amphital 86B) B: 100 wt% hydrophilizing agent of alkyl phosphate dipotassium salt (Kao Co., Ltd., gripper 4131) C: Alkyl phosphate dipotassium salt (Kao Co., Ltd., neutralized potassium hydroxide of gripper 4131) Compound) and alkylsulfonate sodium salt (Latemul PS, manufactured by Kao Corporation) at 50% by weight: 50% by weight D: polyoxyethylene alkylamine (Ao 302, manufactured by Kao Corporation) and diglycerin laur Rate (Riken Vitamin Co., Ltd. Marl L-71-D) 50% by weight: 50% by weight hydrophilizing agent E: Stearyl ether phosphate dipotassium salt (manufactured by Toho Chemical Co., Ltd., neutralized potassium hydroxide of phosphanol RL-210) and Hydrophilic agent formulated with 50% by weight of diglycerin laurate (Riken Vitamin Co., Ltd., Riquemar L-71-D) F: Polyoxyethylene (2 moles added) Stearylamide (Kawaken Fine Chemical) Hydrophilizing agent containing 50% by weight and 50% by weight of a dialkylsulfosuccinate sodium salt (manufactured by Co., Ltd., Amizole SDE) and dialkyl sulfosuccinate sodium salt (manufactured by Kao Corporation) G: polyoxyethylene polyoxypropylene modified silicone ( Shin-Etsu Chemical Co., Ltd., KF-6012) and dialkylsulfosa Hydrophilizing agent formulated with 50% by weight: 50% by weight of citrate sodium salt (manufactured by Kao Corporation, Perex OT-P) H: diglycerin stearate (Riken Vitamin Co., Ltd., Riquemar S-71-D) And dialkylsulfosuccinate sodium salt (Perex OT-P, manufactured by Kao Corporation), 50% by weight: 50% by weight hydrophilizing agent I: sorbitan monopalmitate (manufactured by Kao Corporation, Rheodor SP-P10) And dialkylsulfosuccinate sodium salt (Perox OT-P, manufactured by Kao Corporation) blended at 50% by weight: 50% by weight J: polyoxyethylene (added mole number 2) stearylamide (Kawaken Fine Chemical Co., Ltd.) Company-made, Amizole SDE) and diglycerin laurate Hydrophilizing agent containing 50% by weight: 50% by weight of Riquemar L-71-D manufactured by Ken Vitamin Co., Ltd. K: Polyoxyethylene (addition mole number 2) stearylamide (Amizole SDE manufactured by Kawaken Fine Chemical Co., Ltd.) ) And sorbitan monolaurate (Reodol SP-L10, manufactured by Kao Corporation) at 50% by weight: 50% by weight L: polyoxyethylene alkylamine (Ao 302, manufactured by Kao Corporation) and sorbitan monolaurin Hydrophilizing agent containing 50 wt%: 50 wt% of acid ester (Kao Co., Ltd., Rhedol SP-L10) M: polyoxyethylene polyoxypropylene modified silicone (Shin-Etsu Chemical Co., Ltd., KF-6004) and Polyoxyethylene lauryl ether (manufactured by Kao Corporation, N: Polyoxyethylene polyoxypropylene-modified silicone (manufactured by Shin-Etsu Chemical Co., Ltd., KF-6004) and diglycerin lauric acid ester (RIKEN Vitamin Co., Ltd.) Manufactured by Riquemar L-71-D) at 50% by weight: 50% by weight O: polyoxyethylene polyoxypropylene-modified silicone (manufactured by Shin-Etsu Chemical Co., Ltd., KF-6004) and sorbitan monolaurate Hydrophilizing agent containing 50% by weight: 50% by weight of Leodol SP-L10, manufactured by Kao Corporation P: Sorbitan monolaurate ester (Reodol SP-L10, manufactured by Kao Corporation) and polyoxyethylene stearyl ether (Kao Corporation) Company made, Emulgen 306P Q: diglycerin stearate ester (Riken Vitamin Co., Ltd., Riquemar S-71-D) and sorbitan monolaurate ester (Kao Co., Ltd., Leodol SP-L10) ) 50% by weight: 50% by weight hydrophilizing agent R: diglycerin stearate (Riken Vitamin Co., Ltd., Riquemar S-71-D) and polyoxyethylene lauryl ether (Kao Co., Ltd., Emulgen 102KG) ) 50% by weight: 50% by weight of hydrophilizing agent compounded at 50% by weight S: distearyldimethylammonium chloride (Kao Co., Ltd., Cotamine D86P) and polyoxyethylene stearyl ether (Kao Co., Ltd., Emulgen 306P) : Hydrophilizing agent formulated at 50% by weight

[Evaluation]
About the nonwoven fabric obtained by the Example and the comparative example, the contact angle of the fiber was measured by the method mentioned above. Further, the remaining liquid amount and the liquid flow distance were measured by the method described later. The results are shown in Tables 1 and 2.

In Tables 1 and 2, the “convex portion top portion P1” in the column of “contact angle” is the top portion P1 (the top portion of the thick portion) of the convex portion 119 of the uneven surface 10b, and the “concave portion vicinity portion P3” is the embossed portion. A part 1 mm inside (near part of the thin part) from the edge of (thin part) toward the top part P1, “middle part P2” is an intermediate part between P1 and P3, and the back surface Q is on the flat surface 10a. It is a measurement result of the contact angle with the distilled water of the fiber in the site | part corresponding to the top part of a convex part.

[Liquid remaining amount]
The surface sheet was removed from a commercially available sanitary napkin (trade name “Laurier Sarah Cushion Skin Clean Absorption”) manufactured by Kao Corporation. Instead, the nonwoven fabrics of Examples and Comparative Examples were laminated and the periphery was fixed and evaluated. A sanitary napkin for use was obtained.
On the surface of the sanitary napkin, an acrylic plate having a transmission hole with an inner diameter of 1 cm is overlapped, and a constant load of 100 Pa is applied to the napkin. Under such a load, 3.0 g of defibrinated horse blood is poured from the permeation hole of the acrylic plate. The acrylic plate is removed 60 seconds after pouring the horse blood, and then the weight (W2) of the nonwoven fabric is measured. The difference from the weight (W1) of the nonwoven fabric before pouring horse blood is measured in advance. (W2-W1) is calculated. The above operation is performed three times, and the average value of the three times is defined as the remaining liquid amount (mg). The liquid remaining amount is an index of how much the wearer's skin gets wet. The smaller the liquid remaining amount, the better the result.

[Liquid flow distance]
A sanitary napkin is obtained in the same manner as in [Liquid remaining amount]. The test apparatus has a mounting portion in which the mounting surface of the napkin is inclined 45 ° with respect to the horizontal plane. A napkin is placed on the placement portion so that the topsheet faces upward. As a test solution, colored distilled water is dropped onto the napkin at a rate of 1 g / 10 sec. First, the distance from the point where the nonwoven fabric gets wet to the point where the test liquid is first absorbed by the absorbent is measured. The above operation is performed three times, and the average of the three times is defined as the liquid flow distance (mm). The liquid flow distance is an index of the amount that the liquid touches the wearer's skin without being absorbed by the sanitary napkin. The shorter the liquid flow distance, the higher the evaluation. Note that the liquid flow distance exceeding 100 mm is expressed as> 100.

From the results shown in Tables 1 and 2, it can be seen that the nonwoven fabric used in the Examples has a large crystallite size of the sheath polyethylene, and the hydrophilicity has decreased due to heat treatment.
In addition, the nonwoven fabrics obtained in the examples have a hydrophilic gradient due to a decrease in hydrophilicity caused by a decrease in the degree of hydrophilicity, a small liquid flow, a small liquid residue, and excellent absorbency. I understand that.

Example 25
Using the apparatus shown in FIG. 4, a single layer nonwoven fabric 10 ′ having the structure shown in FIG. 3 was produced. The embossing roll 14 in the apparatus shown in FIG. 4 had rhombic lattice-shaped convex portions with a line width of 0.5 mm. The embossing rate (bonding rate) in the embossing roll 14 was 14.1%. Non-woven fabrics were obtained under the conditions shown in Table 3 using the heat-extensible conjugate fiber and the heat-fusible conjugate fiber shown in Table 3. In the obtained non-woven fabric, the intersection of the heat-extensible conjugate fibers, the intersection of the heat-fusible conjugate fibers, and the intersection of the heat-extensible conjugate fibers and the heat-fusible conjugate fibers are each heat-sealed by an air-through method. Was. Moreover, about the fiber contained in the obtained nonwoven fabric, when the presence or absence of heat extensibility was judged by the method mentioned above, it was confirmed that the fiber which has heat extensibility is contained. The heat-extensible conjugate fiber is melt-spun at a take-up speed of 1300 m / min. After melt spinning, the heat-extensible conjugate fiber was immersed in an aqueous solution of a hydrophilizing agent to adhere the hydrophilizing agent. Next, after mechanical crimping, the fiber was dried by heat treatment and cut to obtain short fibers (fiber length 51 mm). The adhesion amount of the hydrophilizing agent was 0.4% by weight. In addition, the extending | stretching process is not performed in manufacturing this fiber (it is the same also in a following example and a comparative example). Here, the drawing treatment means a drawing operation of about 2 to 6 times that is usually performed on an undrawn yarn obtained after melt spinning.

[Examples 26 to 28 and Comparative Examples 7 to 12]
The fibers shown in Table 3 were used, and the conditions shown in the same table were used. Except this, it carried out similarly to Example 25, and obtained the nonwoven fabric. In the nonwoven fabric obtained in each example, the intersection between the heat-extensible conjugate fibers, the intersection between the heat-fusible conjugate fibers, and the intersection of the heat-extensible conjugate fibers and the heat-fusible conjugate fibers are air-through methods, respectively. It was heat-sealed. Moreover, about the fiber contained in the nonwoven fabric obtained in each Example, when the presence or absence of heat extensibility was judged by the method mentioned above, it was confirmed that the fiber which has heat extensibility is contained.

The hydrophilizing agents A1 to F1 shown in Table 3 are as follows.
[Hydrophilic agent]
A1: 50% by weight of polyoxyethylene (addition mole number 2) stearylamide (manufactured by Kawaken Fine Chemical Co., Ltd., Amizole SDE) and alkyl phosphate dipotassium salt (manufactured by Kao Corporation, neutralized potassium hydroxide of gripper 4131): Hydrophilizing agent blended at 50% by weight B1: 50% by weight of diglycerin stearate ester (Riken Vitamin Co., Ltd., Riquemar S-71-D) and polyoxyethylene lauryl ether (Kao Co., Ltd., Emulgen 102KG): Hydrophilizing agent blended at 50% by weight C1: Polyoxyethylene (added mole number 2) stearylamide (manufactured by Kawaken Fine Chemicals Co., Ltd., Amizole SDE) and stearyl betaine (manufactured by Kao Co., Ltd., Amphitol 86B) Hydrophilizing agent formulated at 50% by weight 1: Polyoxyethylene (added mole number 2) stearylamide (manufactured by Kawaken Fine Chemical Co., Ltd., Amizole SDE) and diglycerin laurate (manufactured by Riken Vitamin Co., Ltd., Riquemar L-71-D) 50% by weight: 50% E1: Polyoxyethylene (added mole number 2) stearylamide (manufactured by Kawaken Fine Chemical Co., Ltd., Amizole SDE) and lauryl phosphate dipotassium salt (Phosphanol ML- manufactured by Toho Chemical Co., Ltd.) Hydrophilizer formulated with 50% by weight: 50% by weight of potassium hydroxide neutralized product F1: Lauryl phosphate dipotassium salt (Tosho Chemical Co., Ltd. Phosphanol ML-200 potassium hydroxide neutralized ) And dimethyl silicone (Shin-Etsu Chemical Co., Ltd., KF-96L) -0.65CS) at 50% by weight: 50% by weight

[Evaluation]
About the nonwoven fabric obtained by the Example and the comparative example, the contact angle of the fiber was measured by the method described previously. Moreover, the liquid remaining amount and liquid flow distance in a nonwoven fabric were measured with the following method. Furthermore, the bulk recovery property by blowing hot air was evaluated. The results are shown in Table 1 above and Tables 4 and 5 below.

[Liquid remaining amount]
The surface sheet is removed from a commercially available sanitary napkin (trade name “with Laurie Sarasara cushion wing” manufactured by Kao) to obtain a napkin absorbent body. Moreover, the nonwoven fabric of a measuring object is cut | disconnected to MD50mm x CD50mm, and a cut piece is produced. The cut piece is placed at the place where the top sheet in the napkin absorbent body was present (on the skin contact surface of the napkin absorbent body), and the back surface 10a of the nonwoven fabric 10 'in FIG. The sanitary napkin using the non-woven fabric to be measured as a surface sheet is obtained by bonding and fixing with an adhesive so as to be the opposite surface of each other. An acrylic plate having a cylindrical transmission hole is placed on the surface of a sanitary napkin that uses the nonwoven fabric to be measured, and a constant load of 100 Pa is applied to the napkin. Under such a load, 3.0 g of defibrinated horse blood is poured from the permeation hole of the acrylic plate. 120 g after pouring defibrinated horse blood, another 3.0 g of defibrinated horse blood is poured. A total of 6.0 g of defibrinated horse blood was poured, and 60 seconds later, the acrylic plate was removed, and then the weight (W2) of the nonwoven fabric was measured. Then, the difference (W2−W1) from the weight (W1) of the non-woven fabric before pouring defibrillated horse blood, which has been measured in advance, is calculated. The above operation is performed three times, and the average value of the three times is defined as the remaining liquid amount (mg). The liquid remaining amount is an index of how much the wearer's skin gets wet. The smaller the liquid remaining amount, the higher the evaluation.

[Liquid flow distance]
In the same manner as in [Liquid remaining amount], the nonwoven fabric to be measured is cut into MD150 mm × CD50 mm to obtain a sanitary napkin using the nonwoven fabric as a surface sheet. The napkin absorbent was obtained by removing the surface sheet from a commercially available sanitary napkin (manufactured by Kao, trade name “with Laurie Sarasara cushion wing”). Other than that, it measured similarly to the measuring method of the liquid flow distance mentioned above.

[Bulk recovery]
The non-woven fabric 10 is wound around a paper tube having an outer diameter of 85 mm in a roll shape with a length of 2700 m and stored at room temperature for 2 weeks. The non-woven fabric after storage is drawn out at a conveyance speed of 150 m / min in a range outside the diameter of 500 mm and inside the diameter of 600 mm, a treatment temperature of 115 ° C., a treatment time of 0.20 seconds, and a wind speed of 2.8 m / second. The nonwoven fabric thickness is recovered by spraying hot air on the nonwoven fabric. For the bulk recoverability of the nonwoven fabric, the thickness of the convex portion of the nonwoven fabric (thickness before storage) before winding the nonwoven fabric into a roll shape was C, and the thickness of the convex portion of the nonwoven fabric after hot air blowing (thickness after recovery) was D. Is represented by the following equation (2). The thickness of the nonwoven fabric after the hot air is sprayed is measured 1 minute to 1 hour after the hot air is sprayed. The thickness of the nonwoven fabric is measured by the method described above.
Bulk recovery (%) = D / C × 100 (2)
X when the bulk recovery calculated by the formula (2) is less than 60%, Δ when it is 60% or more and less than 70%, ○ when it is 70% or more and less than 80%, and ◎ when it is 80% or more. And evaluate. The higher the bulk recovery value, the higher the evaluation.

As is apparent from the results shown in Table 4, it can be seen that the nonwoven fabrics obtained in Examples 25 to 28 have a small liquid remaining amount, a short liquid flow distance, and a very high absorption performance. Moreover, it turns out that it is excellent in the bulk recovery property of the nonwoven fabric after blowing hot air. On the other hand, as is apparent from the results shown in Table 5, the nonwoven fabric of Comparative Example 7 consisting only of heat-extensible conjugate fibers, the nonwoven fabric of Comparative Examples 8 to 10 consisting only of heat-fusible conjugate fibers, and the heat The nonwoven fabrics of Comparative Examples 11 and 12 composed of an extensible conjugate fiber and a heat-fusible conjugate fiber are liable to remain in the liquid, are liable to flow, or are inferior in bulk recoverability of the nonwoven fabric. I know that there is.

The nonwoven fabric of this invention is easily obtained by heat-processing the web or nonwoven fabric containing the fiber which hydrophilicity falls by heat, and the hydrophilic property of the desired part has fallen.
The nonwoven fabric of the present invention has a part in which the hydrophilicity is partially reduced, and can be utilized for various applications by utilizing the characteristics.
According to the method for producing a nonwoven fabric of the present invention, a nonwoven fabric having a portion with reduced hydrophilicity can be produced efficiently.
According to the method for controlling the hydrophilicity of the nonwoven fabric of the present invention, the part to be subjected to heat treatment can be prepared even if the fibers are purposely mixed, made into two layers, or subjected to a hydrophilic treatment in a separate step after forming the nonwoven fabric. The hydrophilicity of the desired part of a nonwoven fabric can be reduced only by changing or controlling the passage of hot air.
In the present invention, there is a wide range of selection of hydrophilizing agents that can be used.

According to the nonwoven fabric of the present invention, the liquid residue of the nonwoven fabric can be reduced by controlling the hydrophilicity of the nonwoven fabric. For example, when used as a surface sheet of an absorbent article, it is possible to prevent the bodily fluid once absorbed from flowing back to the surface that is in contact with the skin of the wearer, or the bodily fluid from flowing on the nonwoven fabric surface. . Therefore, when the nonwoven fabric of the present invention is used as, for example, a surface sheet of an absorbent article, the nonwoven fabric satisfies the absorption performance required for the surface sheet, such as reduction of the remaining liquid amount and reduction of the liquid flow amount.

Claims (17)

Having a sheath containing a polyethylene resin and a core-sheath composite fiber having a core containing a resin component having a melting point higher than that of the polyethylene resin, and a hydrophilizing agent attached to the surface of the core-sheath composite fiber, A non-woven fabric having a heat-sealed portion where the intersection of the constituent fibers is heat-sealed,
The core-sheath type composite fiber includes a heat-extensible composite fiber whose length is extended by heating,
The nonwoven fabric in which the heat-extensible conjugate fiber has a hydrophilicity gradient in the thickness direction and / or the plane direction of the nonwoven fabric. It has a thin part formed by embossing and a thick part other than that, the thin part or its vicinity is hydrophilic, and the top part of the thick part is the thickness The non-woven fabric according to claim 1, wherein the hydrophilicity is lower than that of the thin portion or the vicinity thereof. The nonwoven fabric according to claim 1 or 2, wherein the hydrophilizing agent comprises polyoxyethylene alkylamide and / or alkylbetaine. The nonwoven fabric according to claim 3, wherein the hydrophilizing agent contains polyoxyethylene alkylamide and alkylbetaine. The nonwoven fabric according to claim 3 or 4, wherein the thick portion has a higher abundance ratio of the polyoxyethylene alkylamide and / or alkylbetaine than the thin portion or the vicinity thereof. . A non-thermally stretchable heat-fusible conjugate fiber comprising two components having different melting points and stretched, the length of which is not substantially extended by heating, the heat-fusible conjugate fiber comprising a hydrophilizing agent The nonwoven fabric according to any one of claims 1 to 5, wherein the contact angle with water is 50 to 75 °. The mixing ratio (the former / the latter) of the heat-extensible conjugate fiber and the heat-fusible conjugate fiber is 20/80 to 80/20 by weight ratio,
The intersection of the heat-extensible conjugate fibers, the intersection of the heat-fusible conjugate fibers, and the intersection of the heat-extensible conjugate fibers and the heat-fusible conjugate fibers are each thermally fused by an air-through method. The nonwoven fabric according to claim 6. The nonwoven fabric according to any one of claims 1 to 7, wherein a contact angle of the heat-extensible conjugate fiber is 40 to 90 °. A large number of convex portions and concave portions are formed on one surface, and the contact angle of the heat-extensible conjugate fiber with water gradually decreases from the top to the other surface side of the nonwoven fabric. The nonwoven fabric according to any one of claims 1 to 8. Having a sheath containing a polyethylene resin and a core-sheath composite fiber having a core containing a resin component having a melting point higher than that of the polyethylene resin, and a hydrophilizing agent attached to the surface of the core-sheath composite fiber, A nonwoven fabric obtained by heat-treating a web or nonwoven fabric containing fibers whose hydrophilicity is lowered by heat, wherein the polyethylene resin has a crystallite size of 100 to 200 mm, and lowering the hydrophilicity of a part of the web or nonwoven fabric. The nonwoven fabric according to claim 10, wherein the hydrophilizing agent is at least one selected from the group consisting of anionic, cationic and zwitterionic surfactants. It has a thin part formed by embossing and a thick part other than that, and the thick part is a hydrophilicity-reduced part, and the thin part and / or its vicinity is a hydrophilic part. The nonwoven fabric according to claim 10 or 11. The nonwoven fabric according to claim 12, wherein one surface is hydrophilic and the other surface is more hydrophobic. Having a sheath part made of polyethylene resin and a core-sheath type composite fiber having a core part made of a resin component having a melting point higher than that of the polyethylene resin, and a hydrophilizing agent attached to the surface of the core-sheath type composite fiber, The polyethylene resin has a crystallite size of 100 to 200 mm, and heat treatment is performed on a web or nonwoven fabric containing fibers whose hydrophilicity is lowered by heat to obtain a nonwoven fabric in which a part of the web or nonwoven fabric has been reduced in hydrophilicity. Nonwoven fabric manufacturing method. The nonwoven fabric production according to claim 14, wherein the temperature of the heat treatment ranges from a temperature 10 ° C lower than the melting point of the polyethylene resin constituting the sheath part to the melting point of the resin component constituting the core part. Method. Having a sheath part made of polyethylene resin and a core-sheath type composite fiber having a core part made of a resin component having a melting point higher than that of the polyethylene resin, and a hydrophilizing agent attached to the surface of the core-sheath type composite fiber, The polyethylene resin has a crystallite size of 100 to 200 mm, and the nonwoven fabric has a hydrophilicity that reduces the hydrophilicity of a part of the web or nonwoven fabric by heat-treating the web or nonwoven fabric containing fibers that are hydrophilically reduced by heat. How to control. An absorbent article using the nonwoven fabric according to any one of claims 1 to 13.

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