RU2500844C2 - Non-woven fabric and method of its production - Google Patents

Abstract

FIELD: textiles, paper.

SUBSTANCE: non-woven fabric (10) according to the present invention comprises a conjugated fiber of core/shell having a shell composed of a polyethylene resin, and a core composed of a resin component having a melting temperature which is higher than that of polyethylene resin; and a hydrophilising agent, adhering to the surface of the conjugated fiber of core/shell. The non-woven fabric has points connected by the thermal fusion, formed by intersections bound by thermal fusion of constituent fibers. The conjugated fiber of core/shell comprises a heat extensible fiber which length is increased by heating, and the heat extensible fiber has a hydrophilicity gradient in the thickness direction and/or in the planar direction of the non-woven fabric (10).

EFFECT: considered non-woven fabric which is convenient when used as a cover sheet of the absorbent article.

17 cl, 5 dwg

Description

FIELD OF THE INVENTION

The present invention relates to non-woven fabric obtained using fibers, the hydrophilicity of which decreases under the influence of heat, and to a method for its production.

The present invention also relates to the improvement of non-woven fabric containing thermally extensible fiber, the length of which increases with heating.

BACKGROUND

There are known methods for producing non-woven fabrics by blowing hot air onto a mesh containing thermally fusible fibers to fuse the intersections between the fibers.

Patent Literature 1 describes an electret non-woven fabric used as a filter for electrostatically collecting particles such as pollen and house dust, a thermally bonded polyolefin-based fiber used to produce an electret non-woven fabric that consists of a thermally bonded polyolefin-based fiber having from 0.2% to 0.6 wt.% Of the oil agent adhering to it, and in this case, the amount of oil agent adhering to the nonwoven fabric is reduced to 0.0001-0.2 wt.%, And the proportion of its reduction can be attained 60% or higher due to heat treatment during the conversion of fibers into a nonwoven fabric by heating and / or heat treatment step after producing a nonwoven fabric and an electret nonwoven fabric obtained using the fiber.

Patent literature 2 describes a conjugated fiber based on polyolefins for a nonwoven fabric, which consists of a thermally bonded polyolefin conjugated fiber and an oil agent adhering to it, where the oil agent contains as its main component some specific type of aliphatic polyethylene glycol ester, and its amount, adhering to the fiber, is from 0.2% to 0.6 wt.%.

Moreover, the applicant previously proposed, as a non-woven fabric made of thermally expandable fiber, the length of which increases when heated, a non-woven fabric of a three-dimensional shape having a plurality of connected thermocompression / glued sections obtained by thermocompression bonding or bonding of the component fibers, while intersecting the component fibers in sections other than thermocompressed / glued sections, are connected by means other than thermocompressed connection or Ivanov. At least one side of the nonwoven fabric has a shape with protrusions and recesses, where the thermocompressed / glued sections form the recesses and the sections between the recesses comprise the protrusions (see Patent Literature 3).

Citation List

Patent Literature

Patent Literature 1: US 2002146951 A1

Patent Literature 2: JP-A-4-316673

Patent Literature 3: JP-A-2005-350836

SUMMARY OF THE INVENTION

The technologies described in Patent Literatures 1 and 2 can prevent the generation of static electricity, as well as the problems caused by this, during the carding process, due to the oil agent adhering to the surface of the fiber, and can also create an electret non-woven fabric that can easily demonstrate functions electrostatic collection, since the oil agent can be removed from the surface of the fiber by subsequent heat treatment.

However, in Patent Literatures 1 and 2, oil agents that can be used are practically limited to agents containing a polyethylene glycol ester of a fatty acid as their main component, making the number of degrees of freedom when choosing an oil agent low. In addition, Patent Literature 1 is not intended for applications other than electret non-woven fabrics. Moreover, patent literature 2 describes their use in surface materials for disposable diapers, but such use is limited to applications requiring water repulsion, and the hydrophilicity gradient condition is not provided in patent literature 2.

The non-woven fabric from Patent Literature 3 is advantageous in that by manufacturing the non-woven fabric from thermally expandable fiber, the non-woven fabric can be made soft and provided with a low bulk and a three-dimensional profile with protrusions and recesses without using any special manufacturing method. However, when it is intended to use a non-woven fabric as, for example, a coating sheet of an absorbent article, there are cases where there is a tendency for fluids to remain inside the non-woven fabric.

The present invention provides a non-woven fabric (also referred to as “NW1 non-woven fabric”), comprising: a conjugated fiber core / sheath having a sheath containing a polyethylene resin, and a core containing a resin component having a melting point that is higher than that of the polyethylene resin ; and a hydrophilizing agent adhering to the surface of the conjugated fiber core / sheath, fusion bonded points formed by fusion bonded intersections of the constituent fibers; where: the conjugated fiber core / sheath contains a thermally expandable conjugated fiber, the length of which increases when heated; and the thermally extensible conjugated fiber has a hydrophilicity gradient in the thickness direction and / or in the planar direction of the nonwoven fabric.

The “thermally extensible conjugated fiber whose length increases when heated” in the nonwoven fabric NW1 is not limited to a fiber whose length is further increased by heating, but also encompasses a fiber whose length is already increased by heating, in a state where the fiber is converted into a nonwoven fabric.

The present invention also provides a non-woven fabric (also referred to as “NW2 non-woven fabric”) obtained by heat treating a mesh or non-woven fabric containing a fiber whose hydrophilicity decreases due to heat, while reducing hydrophilicity in some parts of the mesh or non-woven fabric. , the fiber contains: a conjugated fiber core / sheath having a sheath containing a polyethylene resin, and a core containing a resin component having a melting temperature which is higher than that of the polyethylene resin; and a hydrophilizing agent adhering to the surface of the conjugated fiber core / sheath; where the polyethylene resin has a crystal size of from 100 to 200 Å.

Nonwoven fabric NW2 is also a preferred embodiment of the nonwoven fabric NW1.

The present invention also provides a method for producing a non-woven fabric, comprising: the effect of heat treatment on a mesh or non-woven fabric containing the above-described fiber, the hydrophilicity of which decreases under the influence of heat, while obtaining a non-woven fabric in which hydrophilicity is reduced in some parts of the mesh or non-woven fabric .

The present invention also provides a method for controlling the hydrophilicity of a nonwoven fabric, the method comprising: applying heat treatment to a mesh or nonwoven fabric containing the above-described fiber, the hydrophilicity of which decreases under the influence of heat, while reducing the hydrophilicity of some parts of the mesh or nonwoven fabric.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a diagram illustrating a device used for spinning from a melt.

FIG. 2 is a diagram illustrating a step of producing a core / fiber sheath from a conjugated fiber that becomes water repellent by heat.

FIG. 3 (a) is a perspective view illustrating an embodiment of the nonwoven fabric of the present invention, and FIG. 3 (b) is a partially enlarged cross-sectional diagram taken in the thickness direction of the nonwoven fabric illustrated in FIG. 3 (a) )

4 is a diagram illustrating a step for producing a non-woven fabric that is partially water repellent using fiber that becomes water repellent under the influence of heat.

DESCRIPTION OF EMBODIMENTS

The present invention will be described below in accordance with its preferred options for implementation.

“A fiber whose hydrophilicity decreases by heat” as used in the present invention includes: a conjugated fiber core / sheath having a sheath consisting of a polyethylene resin and a core consisting of a resin component having a melting point that is higher than that of polyethylene resin; and a hydrophilizing agent adhering to the surface of the conjugated fiber core / sheath.

The conjugated fiber core / sheath of the present invention may be a concentric type of core / sheath, an eccentric type of core / sheath, or a type where the core and sheath are layered; a concentric core / shell type is preferred.

The resin component constituting the core conjugate / sheath of the present invention is a polyethylene resin. For the polyethylene resin, polyethylene such as low density polyethylene (LDPE), high density polyethylene (HDPE), or linear low density polyethylene (LLDPE) can be used; among them, high density polyethylene having a density of from 0.935 to 0.965 g / cm ³ is preferred. Preferably, the resin component constituting the shell consists only of a polyethylene resin, but other types of resins can be mixed. Examples of other miscible resins include polypropylene resin, ethylene vinyl acetate copolymer (EVA) and ethylene vinyl alcohol copolymer (EVOH). However, it is preferable that the resin components constituting the shell at least 50 wt.%, More preferably from 70% to 100 wt.%, The resin components constituting the shell are a polyethylene resin.

The polyethylene resin constituting the sheath serves to provide thermal meltability of the conjugated fiber core / sheath, as well as to receive the hydrophilizing agent described below during heat treatment.

The polyethylene resin constituting the shell preferably has a crystal size of from 100 to 200 Å.

A crystal size of 100 Å or higher makes it easy to take a hydrophilizing agent from the surface of the fiber into it during heat treatment and also expands the range of hydrophilizing agents that can be used. Therefore, this can facilitate a decrease in hydrophilicity at the desired locations of the fiber and in products made from it, such as nets and non-woven fabrics.

From the point of view of a reliable change in hydrophilicity on the surface of the fiber, the crystal size is preferably from 100 to 200 Å, more preferably from 115 to 180 Å.

The upper limit of crystal size, 200 Å, is determined in terms of mechanical properties such as tensile strength and elongation at break. When the crystal size is within 200 Å, the number of crystals will not become too small, thereby deteriorating the mechanical properties.

The method of measuring the size of the crystals of polyethylene resin:

The crystal size is calculated using the Scherrer equation from the half peak width measured by X-ray powder diffraction. Use RINT-2500 from Rigaku Co., Ltd., and perform a peak calculation for the (110) PE plane (polyethylene) using JADE 6.0, the included crystal size calculator. Specific conditions are as follows: radiation source: CuKα radiation (wavelength: 0.154 nm); generated voltage and current: 40 kV, 120 mA; and sweep speed: 10 ° / min. When measuring, the sample in the form of a fiber bundle is attached, in its stretched state, in the sample holder so that the fiber bundle is parallel to the direction along the length of the slit in the sample holder, so that the fiber bundle is installed perpendicular to the direction of incidence of the x-ray radiation.

The core / sheath core of the conjugated fiber is a part that provides strength and any type of resin component having a melting point that is higher than that of the polyethylene resin can be used for the core component of the resin without specific restrictions. Examples of a core constituent resin component include: polyolefin-based resins (excluding polyethylene resins) such as polypropylene (PP); and polyester resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). It is also possible to use polymers and polyamide-based copolymers obtained from two or more types of resin components described above.

Among the above combinations, it is preferable to use polypropylene (PP) or polyethylene terephthalate (PET). Several types of resins can be used as a mixture, in which case, the melting point of the resin having the highest melting point is considered the melting point of the core.

The difference between the melting temperature of the core component of the resin and the melting temperature of the shell component of the resin (the latter is subtracted from the first) is preferably at least 20 ° C., from the point of view of obtaining a non-woven fabric. Preferably, the difference in melting points is within 150 ° C.

A conjugated fiber having a sheath consisting of a polyethylene resin with a crystal size of 100 to 200 Å can be obtained, for example, by using some kind of special measures to accelerate the curing of the ethylene resin constituting the sheath during the preparation of the conjugated fiber core / sheath by spinning from the melt.

The spinning device illustrated in FIG. 1 comprises: two extruding devices 1 and 2, respectively, consisting of extruders 1A, 2A and gear pumps 1B, 2B; and the mouthpiece 3. Each of the resin components is melted and measured using the respective extruders 1A, 2A and gear pumps 1B, 2B, they are combined inside the mouthpiece 3 and ejected together from the nozzles. The shape of the mouthpiece 3 may be selected according to need, depending on the shape / profile of the conjugated fiber to be obtained. In a preferred embodiment, two resin components are ejected from each nozzle in such a configuration that the sheath forming resin surrounds the periphery of the core forming resin, and a plurality of such nozzles are formed distributed in a circular region. Directly under the mouthpiece 3 is a receiving device 4, which receives molten resins ejected from the nozzles at a given speed in a downward direction.

The curing of the ethylene resin of the shell can be accelerated, for example, by the method of accelerating the curing of the shell illustrated in FIG. 1 by blowing cold air 5 onto molten resins ejected from the nozzles, or by the method of accelerating crystallization by mixing a nucleating agent with a polyethylene resin.

In the case of pressurization of cold air 5, the temperature of the cold air can be, for example, from 20 ° C to 40 ° C, more preferably from 20 ° C to 25 ° C.

A higher air velocity is preferred, and the air velocity is preferably 5 m / s or higher, more preferably 10 m / s or higher, even more preferably 20 m / s or higher.

It is also preferred to blow water onto the resins or pass them through a water bath or an oil bath within a relatively short time after melt spinning.

Examples of preferred nucleating agents to accelerate crystallization of the polyethylene resin include: nucleating agents consisting of diacetals based compounds such as 1,3: 2,4-dibenzylidene sorbitol and 1,3: 2,4-di (p-methylbenzylidene) sorbitol; alkyl ester-based nucleating agents (preferably C _8-22 alkyl esters) of alicyclic polybasic acids such as terahydrophthalic acid or hexahydrophthalic acid; alkyl ester nucleating agents (preferably C _8-22 alkyl esters) of aliphatic polybasic acids such as adipic acid, sebacic acid or azelaic acid; and tris (2-methylcyclohexylamide) tricarballylic acid.

In addition, the method of pressurizing cold air 5 and the method of mixing the nucleating agent can be used in combination. In addition, one or both of these methods can be combined with a method of increasing the temperature of the core resin component to temperatures that are higher than normal temperatures, and / or a method of increasing the rate of selection of spun yarn to a speed that is higher than normal speed.

Note that the selection rate of spun yarn is preferably 1000 m / min or higher, more preferably 1300 m / min or higher, from the point of view of accelerating the curing of the sheath. Also, a lubricating oil is applied on the surface of the fibers with the help of rollers 7 to facilitate the collection of fibers ejected from the mouthpiece 3 into bundles and to reduce friction in the receiving device 4.

The core / sheath conjugated fiber is preferably a fiber whose length increases when heated (also referred to below as “thermally extensible conjugated fiber”). An example of a thermally extensible fiber includes a fiber in which the crystalline state of the resin changes with heating and the length of which thus increases spontaneously. A thermally expandable fiber exists in a nonwoven fabric in a state where its length has already been increased by heating, and / or in a state where its length can be increased by heating.

A preferred thermally expandable conjugated fiber comprises a first resin component constituting a core and a second sheath resin component comprising a polyethylene resin, wherein the first resin component has a higher melting point than the second resin component. The first resin component is a component that makes the fiber thermally extensible, and the second resin component is a component that makes the fiber thermally fusible. It will be sufficient if the second resin component that makes up the sheath exists as a unit in the length direction, at least on some parts of the fiber surface.

The melting point of each of the first and second resin components is defined as the peak melting point; the peak melting temperature of each resin is measured using a differential scanning calorimeter (DSC6200 from Seiko Instruments Inc.) by performing thermal analysis of a finely chopped fiber sample (sample weight: 2 mg) at a temperature increase rate of 10 ° C / min. In cases where the melting temperature of the second component of the resin cannot be clearly found using this method, such a resin is defined as “a resin having no melting point”. In this case, the temperature at which the second resin component is bonded by fusion to such an extent that the bond strength obtained by fiber fusion can be measured is defined as the “softening temperature”, which is considered the temperature at which the molecules of the second resin component begin to flow, and this softening point is used instead of melting point.

The preferred orientation coefficient of the first resin component in the thermally expansible conjugated fiber varies depending on the resin that is used; for example, for a polypropylene resin, the orientation coefficient is preferably 60% or lower, more preferably 40% or lower, even more preferably 25% or lower. In cases where the first resin component is a polyester, the orientation coefficient is preferably 25% or lower, more preferably 20% or lower, even more preferably 10% or lower. On the other hand, the orientation coefficient of the second resin component is preferably 5% or higher, more preferably 15% or higher, even more preferably 30% or higher. The orientation coefficient is an indicator of the degree of orientation of the polymer chains in the resin constituting the fiber. By setting the orientation coefficients of the first and second resin components in the above range, the thermally extensible conjugated fiber can be made extensible by heating.

The orientation coefficient of each of the first and second components of the resin can be represented by equation (1) shown below, where A is the birefringence value for the resin in a thermally expandable conjugated fiber, and B is the eigenvalue of the birefringence of this resin.

(1)Orientation Coefficient (%) = A / B × 100 $$\begin{array}{ccc}& & \end{array}$$

(one)

The intrinsic birefringence is the birefringence of a resin when its polymer chains are in an absolutely oriented state. The intrinsic birefringence values of typical plastic materials are described, for example, in “Appendix Table: Tipical Plastic Materials used for Mold Processing,” Plastic Materials in Mold Processing, 1st ed., Edited by Japan Society of Polymer Processing, (Sigma Publishing Co., Ltd. February 10, 1998).

The birefringence of resins in a thermally expandable conjugated fiber is determined using an interference microscope equipped with a polarizer under light polarized in directions parallel and perpendicular to the fiber axis. The standard refractive index fluid available from Cargille Lab. Is used as an immersion fluid. The refractive index of an immersion fluid is measured using an Abbe refractometer. The refractive indices in the directions parallel and perpendicular to the fiber axis are obtained from the pattern of conjugated fiber interference bands obtained using an interference microscope in accordance with the calculation method described in the article entitled “Fiber Structure Formation in High-Speed Melt Spinning of Sheath-Core Conjugate Fibers, ”Journal of Society of the Fiber Science and Technology, Japan, vol. 51, No.9, p408, 1995. The birefringence value is then found as the spirit difference of the refractive indices.

The thermally extensible conjugated fiber is made extensible by heat at a temperature that is lower than the melting temperature of the first resin component. In addition, in a thermally expandable conjugated fiber, the proportion of thermal elongation at a temperature that is 10 ° C higher than the melting temperature of the second resin component (or the softening temperature for a resin without a melting temperature) is preferably 0.5% -20% more preferably 3% -20%, even more preferably 5.0% -20%. A non-woven fabric containing fibers having such a fraction of thermal elongation becomes bulky or exhibits a three-dimensional appearance due to elongation of the fibers. For example, the surface shape of the nonwoven fabric 10 with protrusions and indentations becomes noticeable.

The proportion of thermal tensile fiber:

The proportion of thermal stretching of the fiber is measured as follows. Use a TMA / SS6000 thermomechanical analyzer from Seiko Instruments Inc. A sample is prepared by preparing a plurality of fiber pieces in which the fiber length is 10 mm or higher, so that the total weight per 10 mm fiber length is 0.5 mg, and these fiber pieces are arranged parallel to each other. Then the sample is installed in the analyzer with a distance between the holders of 10 mm The measurement starts at 25 ° C, the temperature rises at a rate of temperature increase of 5 ° C / min, while applying a constant load of 0.73 mN / dtex, and measure the elongation of the fiber during this process. The elongation value X (mm) is recorded at a temperature that is 10 ° C higher than the melting temperature of the second resin component (or the softening temperature for a resin without a melting point), and the proportion of thermal stretching of the fiber is calculated from the following equation:

The proportion of thermal stretching of the fiber (%) = (X / 10) × 100

The reason that the proportion of thermal elongation is measured at the temperature described above is due to the fact that the nonwoven fabric 10 is usually produced by fusion bonding of fiber intersections in a temperature range starting from the melting point or softening temperature of the second resin component and continuing to a temperature that about 10 ° C above it.

Assessment of the thermal elongation of a fiber taken from non-woven fabric:

The thermal elongation of a fiber taken from non-woven fabric is evaluated in accordance with the following method. First, five pieces of fiber are selected from each portion of the nonwoven fabric, as illustrated in FIG. 3 (b). The piece of fiber to be selected must have a length equal to or greater than 1-5 mm. Selected fiber pieces are placed between microscopic glasses to measure the total length of fiber pieces enclosed between them. For measurement, a VHX-900 microscope from Keyence Corporation equipped with a VH-Z20R lens is used. Pieces of fiber are observed at a magnification of from 50x to 100x, and a measuring tool pre-installed in the microscope is used to perform measurements on the observed image. The length found using this measurement is referred to as “the total length Y of the fiber pieces selected from the non-woven fabric”. After measuring the total length, the same fiber pieces are placed in a sample container (product name: 52-023P (robot container); 15 μl; made of aluminum), available from SII NanoTechnology Inc., for the DSC6200 differential scanning calorimeter. A container containing fiber pieces is placed in a sample holder inside the DSC6200 oven, which is pre-set to a temperature that is 10 ° C lower than the melting temperature of the first resin component. The temperature of the sample is measured using a thermocouple provided directly below the DSC6200 sample holder (measurement software designation: “Sample Temperature”) and when the measured temperature falls within a range of ± 1 ° C from a temperature that is 10 ° C lower than the melting temperature of the first resin component, the sample is heated for 60 seconds, and then the sample container is quickly removed from the device. Heat-treated fiber pieces are removed from the DSC sample container and placed between microscopic glasses to measure the total length of the fiber pieces enclosed between them. For measurement, a VHX-900 microscope from Keyence Corporation equipped with a VH-Z20R lens is used. Pieces of fiber are observed at a magnification of from 50x to 100x, and a measuring tool pre-installed in the microscope is used to perform measurements on the observed image. The length found using this measurement is referred to as “the total length Z of the fiber pieces after heat treatment”. The fraction of thermal elongation (%) can be calculated from the following equation:

The proportion of thermal elongation (%) = (Z-Y) ÷ Y × 100 [%]

This value is defined as the fraction of thermal elongation of a fiber taken from non-woven fabric. A fiber can be considered thermally extensible in cases where the fraction of thermal elongation is greater than zero (0).

To give the resin components in the thermally expandable conjugated fiber their respective orientation coefficients as described above, for example, you can use the first resin component and the second resin component with different melting points, melt two resin components from the melt at a low sampling speed below 2000 m / min to obtain a conjugated fiber and subject the conjugated fiber to heat treatment and / or crimping. In addition to this, pulling processing should not be carried out.

Corrugating processing is conveniently carried out by mechanical corrugation. Mechanical corrugations include two-dimensional corrugations and three-dimensional corrugations. Other examples include three-dimensional shaped corrugations visible in conjugated core / sheath fibers of the eccentric type and in layered conjugated fibers. Any of these corrugations may be used in the present invention. The corrugating treatment may be accompanied by heating. After corrugating, heat treatment may follow. In addition, in addition to the heat treatment carried out after the corrugating treatment, a separate heat treatment can be carried out before the corrugating treatment. Alternatively, heating can be carried out without corrugating treatment.

The corrugating treatment may stretch the fibers somewhat, but such stretching does not fall within the designation “stretching treatment” as used herein. The term “pulling treatment”, as used herein, means a pulling operation, usually carried out on an unextracted yarn, in which the stretch ratio is about 2-6 times.

The conditions for heat treatment are selected according to need, depending on the types of the first and second components of the resin constituting the conjugated fiber. The heating temperature is lower than the melting temperature of the second resin component. For example, in the case where the thermally expandable conjugated fiber is of the core / cladding type comprising polypropylene and / or polyester as a core component and high density polyethylene as a sheath component, the heating temperature is preferably from 50 ° C to 120 ° C, more preferably from 70 ° C to 115 ° C, and the heating time is preferably from 10 to 1800 seconds, more preferably from 20 to 1200 seconds. Heating can be carried out, for example, by boosting hot air or using infrared radiation. As described above, heat treatment can be carried out after corrugating treatment.

The ratio (mass ratio) of the first resin component and the second resin component in the thermally expandable conjugated fiber is preferably 10%: 90% -90%: 10%, more preferably 20%: 80% -80%: 20%, even more preferably 50%: 50% -70%: 30%. Relations in the above range will provide the fibers with sufficient mechanical properties and make the fibers sufficiently durable for practical use. Also, the amount of fusion bonded components will be sufficient, allowing the fibers to melt together sufficiently. In addition, it is preferable that the proportion of the first resin component, which makes up the core, be greater, in terms of providing favorable carding properties, without weakening the extensibility, in cases where the fibers are used as a material for non-woven fabric obtained using a carding machine .

The fiber length for the thermally expandable conjugated fiber can be selected according to need depending on how the non-woven fabric is obtained. For example, in cases where a non-woven fabric is obtained by carding, as in the following example, the fiber length is preferably about 30-70 mm. The same applies to the fiber length for a thermally fusion conjugated fiber, further described below.

The fiber diameter for the thermally expandable conjugated fiber can be selected according to need, depending on the specific use of the non-woven fabric. In cases where a nonwoven fabric is to be used as a component of an absorbent article, such as a coating sheet of an absorbent article, it is preferable to use fibers having a diameter in the range of 10 to 35 μm, more preferably 15 to 30 μm. The same applies to fiber diameter for thermally fusible conjugated fiber, further described below. Note that the fiber diameter for a thermally expandable conjugated fiber decreases when the fiber is stretched; the above “fiber diameter” refers to the diameter of the fiber when the nonwoven fabric is in actual use.

In addition to the thermally expandable conjugated fiber described above, other types of fibers, such as those described in Japanese Patent Nos. 4,131,852, JP-A-2005-350836, JP-A-2007-303035, JP-A-2007-204899, JP -A-2007-204901 and JP-A-2007-204902 can be used as the subject thermally expandable conjugated fiber.

The hydrophilizing agent adheres to the surface of the conjugated fiber core / sheath and serves to increase the hydrophilicity of the fiber surface compared to hydrophilicity before applying the hydrophilizing agent.

Hydrophilizing agents such as those used in the art can be used as the hydrophilizing agent in question. Typical examples of such hydrophilizing agents include various surfactants.

Examples of suitable surfactants include anionic, cationic, zwitterionic and nonionic surfactants.

Examples of anionic surfactants include sodium alkyl phosphates, sodium phosphates and alkyl ethers, sodium dialkyl phosphates, sodium dialkyl sulfosuccinates, sodium alkyl benzene sulfonates, sodium alkyl sulfonates, sodium alkyl sulfates and sodium sec-alkyl sulfates (where the alkyl groups preferably have 6-22, more preferably 8 -22 carbon atoms). Other alkali metal salts, such as potassium salts, may be used in place of sodium salts.

Examples of cationic surfactants include alkyl (or alkenyl) trimethylammonium halides, dialkyl (or alkenyl) dimethylammonium halides and alkyl (or alkenyl) pyridinium halides. These compounds preferably have C _6-18 alkyl groups or alkenyl groups. Examples of halogens in the above halide compounds include chlorine and bromine.

Examples of zwitterionic surfactants include: zwitterionic surfactants of the betaine type, such as alkyl (C _1-30 ) dimethyl betaine, alkyl (C _1-30 ) amidoalkyl (C _1-4 ) dimethyl betaine, alkyl (C _1-30 ) dihydroxyalkyl (C _1-30 ) betaine and zwitterionic surfactants such as sulfobetaine; zwitterionic surfactants such as amino acids, such as zwitterionic surfactants such as alanine (e.g., alkyl (C _1-30 ) aminopropionic acid and alkyl (C _1-30 ) iminodipropionic acid) and zwitterionic surfactants such as glycine (for example, type alkyl (C _1-30 ) aminoacetic acid); and zwitterionic surfactants of the aminosulfonic acid type, such as taurine alkyl (C _1-30 ) surfactants.

Examples of non-ionic surfactants include polyol fatty acid esters (fatty acids preferably have 8-22 carbon atoms), such as glycerol fatty acid esters, polyglycerol complex (preferably n = 2-10) fatty acid esters and sorbitan esters fatty acids, alkylene oxide adducts (preferred added moles: 2-20 mol) and the above polyol fatty acid esters, polyoxyalkylene (added moles: 2-20) alkyl (C _8-22 ) amides, alkyl simple high (C _8-22 ) esters of polyoxyalkylene (number of moles added: 2-20), polyoxyalkylene-modified silicone and amino-modified silicone.

Note that with respect to non-ionic surfactants, polyethylene glycol and polyethylene glycol esters of fatty acids can be used; however, in cases where, for example, a non-woven fabric is obtained using a core / shell conjugated fiber having a surfactant adhering to the surface of the fiber, it is preferable to use other surfactants along with polyethylene glycol and polyethylene glycol and fatty esters acids, from the point of view of preventing the generation of static electricity in the non-woven fabric during storage after receipt and, thus, preventing the attraction of frequent q dust from the air in the nonwoven fabric. Also, in cases where a nonwoven fabric is to be used as the surface material of an absorbent article, such as a sanitary napkin, a panty liner, or disposable diapers, it is preferable to use other surfactants along with polyethylene glycol and polyethylene glycol esters and fatty acids, from the point of view of inhibiting the surfactant from falling off the surface of the fiber due to the release of fluid and thereby improved I have long-term maintenance of the absorption properties of the body fluid (absorption thereof).

Examples of surfactants or combinations thereof, preferred to increase the hydrophilicity of the fiber, as well as to be able to reduce the hydrophilicity under the influence of heat, include: potassium alkyl phosphate; polyoxyethylene alkylamide and alkyl betaine; potassium alkyl phosphate and sodium alkyl sulfonate; polyoxyethylene alkylamine and polyglycerol monoalkylate; polyoxyethylene alkylamide and potassium stearyl phosphate; polyoxyethylene alkylamide and polyglycerol monoalkylate; sodium alkyl sulfonate and potassium stearyl phosphate; potassium phosphate and alkyl ether and polyglycerol fatty acid ester; polyoxyethylene alkylamide and sodium dialkyl sulfosuccinate; polyoxyethylene-polyoxypropylene-modified silicone and dialkyl sulfosuccinate; polyglycerol fatty acid ester and sodium dialkyl sulfosuccinate; fatty acid sorbitan ester and sodium dialkyl sulfosuccinate; polyoxyethylene alkylamide and polyglycerol fatty acid ester; polyoxyethylene alkylamide and sorbitan fatty acid ester; polyoxyethylene alkylamine and sorbitan fatty acid ester; polyoxyethylene-polyoxypropylene-modified silicone and polyoxyethylene alkyl ether; polyoxyethylene-polyoxypropylene-modified silicone and polyglycerol fatty acid ester; polyoxyethylene-polyoxypropylene-modified silicone and sorbitan fatty acid ester; fatty acid sorbitan ester and polyoxyethylene alkyl ether; polyglycerol fatty acid ester and sorbitan fatty acid ester; and polyglycerol fatty acid ester and polyoxyethylene alkyl ether. These preferred surfactants and the preferred combinations of surfactants listed above should not include only these surfactants, and other surfactants and agents may be included additionally.

The amount of hydrophilizing agent adhering to the fiber is preferably 0.1% -0.6 wt.%, More preferably 0.2% -0.5 wt.%, Relative to the weight of the core / sheath conjugated fiber, in terms of increasing hydrophilicity in sections that will not hydrophobize.

Various known methods can be used without any limitation to obtain adhesion of the hydrophilizing agent to the surface of the conjugated fiber core / sheath, examples include spray coating, coating using a slot coating device, coating using a moving roller and immersion in a hydrophilic oil agent. The processing may be carried out on a conjugated fiber core / sheath before preparing the mesh, or it may be carried out after the fabrication of the conjugated fiber core / sheath using any of a variety of methods.

FIG. 2 schematically illustrates a method: drawing an aggregate in the form of a bundle of conjugated core / sheath fibers obtained in the spinning device of FIG. 1 from a holding section 6 containing the aggregate; washing and removing lubricating oil, which is applied using rollers 7, using a flushing device 61; and passing the unit through the device 62 for applying a hydrophilizing agent, with the implementation of the adhesion of the hydrophilizing agent to the surface of the conjugated fibers of the core / sheath.

The conjugated core / sheath fibers, now having a hydrophilizing agent adhering to their surface, are dried at a temperature that is significantly lower than the melting point of ethylene resin (at, for example, 120 ° C or lower), in a type 63 dryer with hot air pressurization, then subjected to corrugating processing in the corrugating device 64, and then cut at a given length in the cutting device 65, thus obtaining an aggregate of short fibers.

“Fiber whose hydrophilicity decreases under the influence of heat”, as used in the present invention, can preferably be used, for example, to produce sheet materials such as nets or non-woven fabrics. Thus obtained sheet material may comprise one or more layers of the laminate. By performing heat treatment during the step of producing the sheet material or after receiving the sheet material or the laminate, the hydrophilicity in the desired sections can be reduced. Hydrophilicity may decrease throughout the sheet material or decrease in some parts of the sheet material. The thickness (fineness) of the fibers can be selected according to need, depending on which sheet material they are to be used in, that is, on its specific application, such as non-woven fabric. From the point of view of obtaining, for example, a soft non-woven fabric giving a pleasant feeling on the skin, the fiber thickness is preferably 1.0-10.0 decitex, more preferably 2.0-8.0 decitex.

Figure 3 (a) and Figure 3 (b) are figures illustrating nonwoven fabric 10, as one embodiment of the nonwoven fabric of the present invention, which is obtained by first forming a mesh using “fiber, the hydrophilicity of which decreases under the action of heat ”, obtained as described above, and then a decrease in hydrophilicity in some parts of the grid.

Various known methods, such as carding methods, an aerodynamic method, and a method for producing a nonwoven fabric, can be used to produce a mesh of fiber, the hydrophilicity of which decreases under the influence of heat; however, it is preferable to use a method (carding) using a card 11, as illustrated in FIG. 4.

The nonwoven fabric illustrated in FIGS. 3 (a) and FIG. 3 (b) is obtained as illustrated in FIG. 4: using a carding machine 11 to form a mesh 12, using aggregates of short fibers containing fibers whose hydrophilicity is reduced by heat as a material for the mesh; introducing the mesh 12 into the device 13 for extruding the relief, having a pair of rollers 14, 15 for extruding the relief on the grid; and acting on the mesh 16 with an extruded relief by heat treatment by means of a hot air treatment device 17 using an air purge method.

One of the pair of rollers used to extrude the relief is a relief extrusion roller 14 having relief extrusions having lattice structures formed on its cylindrical surface, and the other roller is a smooth roller 15 having a flat, smooth cylindrical surface and located opposite the roller for extruding the relief. Relief extrusion is carried out by applying pressure and compressing the mesh between the protrusions of the relief roller 14 and the flat, smooth cylindrical surface of the smooth roller 15. In this way, a non-woven fabric having thin sections (sections with extruded relief) 18 formed by extruding the relief and thick sections 19 next to the thin sections 18.

In a first embodiment of the method for producing a nonwoven fabric of the present invention, the temperature applied to the mesh 12 during extrusion of the relief to obtain the nonwoven fabric 10 is maintained equal to or lower than the melting temperature of the polyethylene resin constituting the fiber sheath, the hydrophilicity of which decreases under the influence of heat; then a temperature equal to or higher than the melting temperature of the polyethylene resin, but equal to or lower than the melting temperature of the core resin component, is applied during the subsequent treatment with hot air. In the method of extruding the relief, the areas closer to the sections with the extruded relief in the mesh have reduced air permeability due to compression, while the polyethylene resin in the sections with the extruded relief only melts due to pressure and their melting is kept to a minimum . On the other hand, during hot air treatment, mainly sections that are compressed due to extrusion of the relief (i.e., sections with extruded relief) barely allow hot air to pass through them or allow only a limited amount of air to pass through, even if the passage hot air is possible; however, in thick sections adjacent to sections with an extruded relief, the larger the thickness, the easier hot air can pass through them, which leads to a decrease in hydrophilicity in these sections.

In this way, a non-woven fabric can be obtained in which the thin sections 18 formed by extruding the relief and / or their peripheral sections become hydrophilic sections, and the non-woven fabric becomes relatively hydrophobic when the thickness increases in the direction of the thick sections 19 adjacent to the thin sections while the middle part of the thickest section demonstrates maximum hydrophobicity. In addition, the hot air treatment accelerates the melting of the fiber shells in sections other than sections with an extruded relief, and thereby causes thermal fusion at the intersections between the fibers, thus obtaining a non-woven fabric having considerable strength.

The nonwoven fabric 10 illustrated in FIG. 3 (a) and FIG. 3 (b) has a single layer structure. One side of the nonwoven fabric 10 has a face 10b with protrusions and recesses having a shape with protrusions and recesses, and the other side has a flat front side 10a that is flat or has smaller protrusions and recesses compared to the front side with protrusions and recesses.

Thick sections 19 and thin sections 18 of nonwoven fabric 10, respectively, form protrusions 119 and recesses 118 on the front side 10b with protrusions and recesses of nonwoven fabric 10. The recesses 118 include first linear recesses 118a extending parallel to each other, and second linear recesses 118b, extending parallel to each other, the first and second linear recesses 118a and 118b intersect with each other at a given angle. The protrusions 119 are formed in closed rhombic areas surrounded by recesses 118.

The upper section P1 of each thick section is the upper section P1 of each protrusion 119 formed by the thick section 19 on the front side 10b with the protrusions and recesses of the nonwoven fabric 10. It is preferable that the thin sections 18 or their middle parts P3 have a higher hydrophilicity than the upper sections P1 of the respective thick sections 19, from the point of view that when a fluid enters from the front side 10b with protrusions and recesses, this fluid can easily go in the direction of the flat front sides 10a, which results in less residual fluid inside the non-woven fabric 10. In addition, it is preferable that the hydrophilicity gradually increases from the upper sections P1 of the thick sections 19 towards the thin sections (embossed sections) 18 or their surroundings P3.

The front side 10b with the protrusions and recesses of the non-woven fabric 10 is located opposite the roller 14 for extruding the relief, while extruding the relief, and is located on the other side of the mesh surface (air-permeable support element), and thus serves as the front side onto which hot air is directly blown during the hot air treatment in accordance with a method of blowing air. For this reason, in cases where thermally expandable conjugated fibers are used as constituent fibers of a non-woven fabric, the thermally expandable conjugate fibers will be elongated on the front side 10b with protrusions and recesses more than on the flat front side 10a. As a result, the thermally expandable conjugated fiber will have a larger fiber diameter on the surface of the flat face 10a than on the surface of the face 10b with protrusions and recesses. In addition, the hydrophilicity in the thick section 19 on the side of the front side 10b with protrusions and recesses will become lower than on the side of the flat front side 10a.

In the method for producing a nonwoven fabric for the first embodiment, the temperature applied to the mesh during the extrusion of the relief is preferably equal to or higher than a temperature that is 20 ° C lower than the melting temperature of the polyethylene resin constituting the sheath and lower than the melting temperature of the resin component constituting the core, from the point of view of inhibiting changes in hydrophilicity in sections with extruded relief and / or in their vicinity (in peripheral sections). On the other hand, the temperature applied during the hot air treatment is preferably equal to or higher than a temperature that is 10 ° C lower than the melting temperature of the polyethylene resin, more preferably equal to or higher than the melting temperature of the polyethylene resin, even more preferably equal to or higher than the temperature, which is 5 ° C higher than the melting temperature of the polyethylene resin, from the point of view of reliable implementation of the change in hydrophilicity.

According to the method of the present embodiment, a non-woven fabric having hydrophilic sections and hydrophobic sections can be obtained without requiring any complex or special device, and in cases where the obtained non-woven fabric is used as the surface material of an absorbent article, such as a sanitary napkin, a pad attached to underwear, or disposable diapers, a non-woven fabric will provide a pleasant feeling for the skin and will leave less fluid, leaving surface and cause less liquid to flow on the surface, thus demonstrating excellent absorption characteristics.

In another embodiment (second embodiment) of the method for producing a nonwoven fabric of the present invention, a grid of the fibers in question is first obtained, the hydrophilicity of which decreases under the influence of heat, in accordance with any of numerous methods (e.g., carding, aerodynamic method or method for producing nonwoven fabric ), or the net is subsequently converted into a non-woven fabric, and then only one side of the net or non-woven fabric is heat treated to obtain a non-woven fabric having a stepped or a smooth hydrophilicity gradient in the thickness direction, wherein the nonwoven fabric is relatively hydrophilic on one side and gradually becomes hydrophobic in a direction relative to the other.

Examples of methods for treating only one side of the net or non-woven fabric by heat treatment include: contacting only one side of the net or non-woven fabric that is transferred into contact with a roller heated to a temperature that is equal to or higher than the melting temperature of the polyethylene resin constituting the sheath; and pressurizing hot air at a temperature that is equal to or higher than the melting point of the polyethylene resin onto the upper side of the mesh or non-woven fabric that is transferred using some special measure to prevent the penetration of hot air to the back of the mesh or non-woven fabric. The temperature for the heat treatment is preferably equal to or higher than the temperature, which is 10 ° C lower than the melting point of the polyethylene resin, more preferably equal to or higher than the melting temperature of the polyethylene resin, even more preferably equal to or higher than the temperature, which 5 ° C higher than the melting point of the polyethylene resin, from the point of view of reliable implementation of the change in hydrophilicity.

Any of a variety of known methods for producing non-woven fabric, such as a method of hydroweaving, needle-piercing, chemical bonding and point structured extrusion of relief, can be used to convert the mesh into a non-woven fabric.

In the case where the non-woven fabric obtained in accordance with the present embodiment, which is relatively hydrophilic on one side and relatively hydrophobic on the other side, is used, for example, as the surface material of an absorbent article, such as a sanitary napkin, a pad attached to the bottom linen, or disposable diapers, with the hydrophobic side facing the skin of the user, the stickiness during use can be reduced, and the absorbent article can be A favorable texture and whiteness can be obtained, since the fluid being released is less likely to remain on the hydrophobic side that comes in contact with the skin and thick fibers, which would otherwise impair texture, and wearing secrecy, need not be used, due to a decrease in the number of constituent fibers.

A fiber whose hydrophilicity decreases under the influence of heat, or a network, and the like containing it, used in the present invention, shows a decrease in hydrophilicity by heat treatment. The hydrophilic sections or sections with hydrophilicity in the nonwoven fabric of the present invention should only have a higher hydrophilicity compared to sections in which hydrophilicity is reduced by heat treatment. In addition, hydrophobic sections or sections with hydrophobicity, should only be sections in which hydrophilicity is reduced compared to sections before reducing their hydrophilicity by heat treatment, or with sections in which hydrophilicity should not decrease. A decrease in hydrophilicity can be achieved by any treatment with which hydrophilicity can be reduced, compared with hydrophilicity before heat treatment. The expression “decrease in hydrophilicity” is synonymous with “increase in contact angle”. Note, however, that regarding the hydrophilicity of the mesh or non-woven fabric before the hydrophilicity decreases (as well as the relatively hydrophilic sections, and the like, of the finished non-woven fabric), the contact angle of the water on the fiber is preferably in the range of 40 to 70 degrees, more preferably from 60 to 70 degrees. On the other hand, in sections with reduced hydrophilicity (as well as in hydrophobic sections, and the like, of a finished nonwoven fabric), the contact angle of the water on the fiber is preferably in the range of 60 to 90 degrees, more preferably 70 to 85 degrees. The expression “with reduced hydrophilicity,” as used herein, refers to a difference in contact angles that is equal to or higher than 2 degrees, preferably equal to or higher than 5 degrees, more preferably equal to or higher than 10 degrees.

The non-woven fabric of the present invention, the hydrophilicity of which is partially reduced, can be subjected, if necessary, to an additional treatment, such as secondary processing, to make the non-woven fabric three-dimensional, or an additional treatment for the purpose of hydrophilization in its limited parts.

The method of measuring the contact angle of water on the fiber:

The contact angle of water on the fiber is measured in accordance with the following method. An automatic contact angle meter, MCA-J from Kyowa Interface Science Co., Ltd., is used as a measuring device. Distilled water is used to measure the contact angle. The amount of fluid injected from the ink jet water droplet injector (CTC-25 pulse injector with an injection nozzle with a diameter of 25 μm from Cluster Technology Co., Ltd.) is adjusted to 20 pl, and a drop of water is dripped precisely onto the fiber. The way a drop is dripped is recorded on a high-speed recording device connected to a horizontally configured camera. The recording device is preferably a personal computer having a high-speed capture device, taking into account that the recorded images will be analyzed later. In the measurement in question, images are recorded every 17 ms. The first image in the recorded film, which shows a drop of water landing on a fiber, is analyzed using the supplied FAMAS software (software version: 2.6.2; analysis method: fixed drop method; analysis method: θ / 2 method; image processing algorithm : non-reflective; image processing mode: frame; threshold level: 200; curvature correction: none), to find the angle formed between the fiber and the drop of water / air, which is considered the contact angle.

Regarding the samples to be measured (fibers taken from nonwoven fabric), a piece of fiber located in each section from the upper section P1 of the protrusion illustrated in FIG. 3 (b), the middle section P2, the vicinity of the recess P3 and section Q on the back (flat face) 10a corresponding to the protrusion is cut from the top layer of each section with a fiber length of 1 mm. The fiber is placed in the sample holder in the contact angle meter and held thereon horizontally, and the contact angle is measured at two different points for each fiber piece. For each of the sections described above, the contact angles for five fiber pieces are calculated before the first decimal place, and the average value (rounded to the first decimal place) for the measured values found for ten points in total is defined as the contact angle for each section.

The nonwoven fabric 10 'in accordance with another embodiment of the present invention includes, as its constituent fiber, in addition to the thermally extensible conjugated fiber described above, a thermally inextensible thermally fusion conjugate fiber, the length of which does not substantially increase when heated, a thermally fusion conjugate the fiber has a hydrophilizing agent adhering to it and having a contact angle with water from 50 ° to 75 °. The non-woven fabric 10 'is similar to the non-woven fabric 10 described above in that it has the shape illustrated in FIG. 3 (a) and FIG. 3 (b).

The recesses 118 in the non-woven fabric 10 'include connected sections formed by constituent fibers of the non-woven fabric, which are sealed and joined together. Examples of means for forming the connected sections include extruding the relief, with or without heating, and ultrasonic extrusion of the relief. On the other hand, the protrusions 119 are unconnected sections. The thickness of the recess 118 is less than that of the protrusion 119. Each protrusion 119 is formed as rising in the direction of the upper side (upper side in FIG. 3 (b)) of the non-woven fabric 10 '. The interior of each protrusion 119 is packed with constituent fibers of the nonwoven fabric 10 '.

Non-woven fabric 10 'has excellent absorption and recoverability characteristics.

More specifically, the authors performed additional studies on nonwoven fabrics made from thermally extensible fibers and found that thermally extensible fibers have a lower bending modulus than conventional thermally fused fibers and tend to decrease more when the nonwoven fabric is exposed. load in the direction of thickness, and thus, the distance between the fibers is reduced. In cases where such a reduced-volume non-woven fabric is used, for example, as a coating sheet of an absorbent article, liquid permeability may deteriorate due to the short distance between the fibers, and this may cause the fluid to remain inside the non-woven fabric and makes contact more likely fluid with skin that is in contact with non-woven fabric.

By combining the use of the thermally expandable conjugated fiber described above with a thermally inextensible thermally fusion conjugate fiber, as well as controlling the hydrophilicity of the thermally fusion conjugate fiber, it is possible to obtain a non-woven fabric having excellent bulk recovery even in cases where the thickness decreases due to the load applied to non-woven fabric in the direction of thickness. The non-woven fabric 10 'has good volume recoverability achieved by boosting hot air.

It is effective to control the hydrophilicity / hydrophobicity of a thermally inextensible thermally fused conjugated fiber (also referred to hereinafter simply as “thermally fused conjugated fiber”) such that the contact angle of the thermally fused conjugated fiber with water is from 50 ° to 75 °, preferably from 55 ° up to 75 °, more preferably 65 ° to 75 °. In cases where the fiber has a contact angle with water below 50 °, i.e. in cases where the hydrophilicity of the fiber is too high, bodily fluid can be prevented from flowing onto the surface of the nonwoven fabric in cases where the nonwoven fabric is used, for example, as a coating sheet of an absorbent article, but, in turn, it may be difficult to achieve the desired liquid permeability, or a bodily fluid that is already absorbed can flow back towards the upper side, which makes it possible that the bodily fluid will remain in the non-woven fabric. On the other hand, in cases where the fiber has a contact angle with water in excess of 75 °, that is, in cases where the hydrophobicity of the fiber is too high, the liquid permeability can be good, and the body fluid, which is already absorbed, flows back in the direction the upper side may be prevented, but it is likely that bodily fluid will leak onto the surface of the nonwoven fabric.

The contact angle of water on a thermally fused conjugated fiber is measured in accordance with the method described above, by selecting only the thermally fused conjugated fiber from each of the nonwoven fabric sections illustrated in FIG. 3 (b).

The control of the contact angle of water on a thermally fused conjugated fiber can be achieved simply by adhering the hydrophilizing agent to the fiber. Adhesion of the hydrophilizing agent can be achieved by applying a pre-hydrophilizing agent to the surface of the fiber or mixing the hydrophilizing agent into the resin used to make the fiber and using this resin for spinning. Hydrophilizing agents similar to those used in the art can be used as the hydrophilizing agent in question. Typical examples of such hydrophilizing agents include various surfactants.

The amount of hydrophilizing agent adhering to the thermally fused conjugated fiber is preferably 0.1-0.6 wt.%, More preferably 0.2-0.5 wt.%, Relative to the weight of the thermally fused conjugated fiber, from the point of view increased hydrophilicity in sections that are not hydrophobized.

Examples of suitable surfactants include surfactants similar to the surfactants described above, suitable for thermally expandable conjugated fiber.

In particular, examples of surfactants to achieve the desired hydrophilicity include polyoxyethylene alkylamides, potassium stearyl phosphate, fatty acid glycerol esters, polyoxyethylene alkyl ethers and polyglycerol monoalkylates. Preferred combinations thereof include: polyoxyethylene alkylamide and potassium stearyl phosphate; fatty acid glycerol ester and polyoxyethylene alkyl ether; and polyoxyethylene alkylamide and alkyl betaine. These preferred surfactants and preferred combinations of the surfactants listed above should not include only these surfactants, and other surfactants and agents may be included additionally.

The mixing ratio of the thermally extensible fiber and the thermally fusible conjugated fiber (first / last ratio) is a factor that has an effect on the hydrophilicity / hydrophobicity of the non-woven fabric as a whole. It is also a factor associated with the recoverability of the volume achieved when hot air is blown onto the non-woven fabric. From this point of view, it is preferable that the mass ratio of mixing the thermally extensible fiber and the thermally fusible conjugated fiber contained in the non-woven fabric (first / last ratio) is from 20/80 to 80/20, more preferably from 30/70 to 70/30, even more preferably 40/60 to 60/40.

In the non-woven fabric 10 ', it is preferable to control the contact angle of the water on the thermally expandable fiber, in addition to controlling the contact angle on the thermally fused conjugated fiber described above, from the point of view of further inhibiting that the liquid remains in the non-woven fabric. From this point of view, it is preferable to control the hydrophilicity / hydrophobicity of the thermally extensible fiber so that the contact angle of the water on the thermally extensible fiber in the nonwoven fabric is 40 ° -90 °, more preferably 60 ° -75 °, even more preferably 65 ° - 75 °. The method of measuring the contact angle is as described above. To achieve the desired hydrophilicity, a hydrophilizing agent consisting of agents such as surfactants can adhere to a thermally extensible fiber. As the surfactant in question, it is preferable to use a combination of two types of surfactants since the desired hydrophilicity can be achieved easily.

Regarding the thermally expandable fiber of the nonwoven fabric 10 ', it is preferable that in each protrusion 119 the contact angle with water for the thermally expandable fiber gradually decreases from the upper section P1 of the protrusion towards the back side 10a of the nonwoven fabric, that is, from P1 in the direction P3, and also from P3 in the Q direction, in FIG. 3 (b) - provided that the contact angle is in the range described above. This makes the non-woven fabric even more prone to fluid remaining in it. Such a contact angle gradient can be achieved by using the method described above as a method for producing a non-woven fabric.

Regarding the thermally fusible conjugated fiber of the nonwoven fabric 10 ′, the contact angle of the thermally fused conjugated fiber in each protrusion 119 may be the same or may even gradually increase from the upper section of the protrusion in the direction of the back side 10a of the nonwoven fabric, that is, from P1 in the direction P3, and also from P3 in the Q direction in FIG. 3 (b), provided that the contact angle between the thermally fused conjugated fiber and water is in the range of 50 ° to 75 °. Even so, the non-woven fabric will still be less prone to keep fluid in it. Such a contact angle gradient can be achieved by using the method described below as a method for producing a non-woven fabric.

It is preferable that the difference between the contact angles of the thermally expandable fiber and the thermally fusible conjugated fiber, when comparison is made at the same measurement point and at the same non-woven fabric, is within 25 °, more preferably within 20 °, even more preferably, within 15 °, from the point of view of further enhancing the effect of inhibiting the fact that the liquid will remain in the non-woven fabric. Such a difference can be achieved by appropriate selection, for example, the type of fiber used, the method for producing the nonwoven fabric, the type and amount of adhesion of the hydrophilizing agent, and the like.

In the nonwoven fabric 10 ', a thermally inextensible thermally fusible conjugated fiber, which is used as a material in combination with a thermally expandable fiber, contains two components with different melting points and is subjected to a stretch treatment. This thermally fusible conjugated fiber is substantially inextensible in length, even when heated. Through the use of thermally extensible fiber and thermally fusible conjugated fiber in combination as materials for non-woven fabric 10 ', the recoverability of the volume achieved when hot air is inflated onto non-woven fabric 10' becomes extremely favorable, as will be shown in the results of the presented Examples, further described below .

At least in the protrusions 119 of the nonwoven fabric 10 ', the intersections between the thermally fusible fibers, the intersections between the thermally fused conjugated fibers and the intersections between the thermally fusible fibers and the thermally fused conjugated fibers are bonded by heat fusion using an air purge method. This makes significant the recoverability of the volume achieved when hot air is blown onto the non-woven fabric 10 '. Also, it inhibits the fluffing of the surface of the non-woven fabric 10 '. Whether intersections between the fibers are bonded by thermal fusion or not can be determined by observing the nonwoven fabric 10 'using a scanning electron microscope.

A thermally fusible conjugated fiber is a two-component conjugated fiber containing a high melting point component and a low melting point component, where the low melting point component exists as a continuous medium in a direction along the length of at least some parts of the surface of the fiber. Conjugated fibers can take various forms, such as a sheath / core and a layered form, and any form can be used. The thermally fusible conjugated fiber is subjected to a stretch treatment in the material stage (i.e., in the stage before it is used in the non-woven fabric 10 ′). “Pulling processing,” as used herein, refers to a drawing operation in which the drawing ratio is about 2-6 times as described above.

Preferably, the fusion temperature of the thermally fusion conjugated fiber is close to the fusion temperature of the thermally extensible fiber. This makes it possible for fusion bonding of thermally extensible fibers to be successful, fusion bonding of thermally fusion conjugated fibers, and fusion bonding of thermally extensible fibers and thermally fusion conjugate fibers. From this point of view, assuming that the fusion temperature of the thermally fusion conjugated fiber is T1 and the fusion temperature of the thermally extensible fiber is T2, the temperature difference T1 and T2 is preferably within 20 ° C. Note that accurate measurement of the thermal melting temperature for a fiber is not easy, and for this reason, the melting temperature of the resin involved in fusion bonding (i.e., low melting resin) is used instead of the thermal fusion temperature. The method for measuring the melting point is as described above.

From the point of view of successful fusion bonding of the thermally extensible fiber and the thermally fusible conjugated fiber, it is preferable that the low melting point component in the thermally fusible fiber and the second resin component in the thermally expandable conjugated fiber be the same type of resin, or, when are different so that the two resins are compatible.

In addition to the thermally extensible fiber and the thermally fusible conjugated fiber described above, the nonwoven fabric 10 ′ may contain other fibers. Examples of such fibers include fibers that are not thermally fusible by nature (for example, natural fibers such as cotton or wood pulp, rayon, and acetate fibers). These fibers are preferably added in amounts of from 5 wt.% To 30 wt.%, At most, with respect to the weight of the non-woven fabric. These fibers are incorporated into the non-woven fabric 10 'in order to improve the ability to be drawn in the liquid in cases where the non-woven fabric 10' is used, for example, as a coating sheet of an absorbent article.

Next, preferred methods for producing nonwoven fabric 10 ′ will be described with reference to FIG. 4. First, a net 12 is prepared using predetermined net forming means, such as a carding machine 11. The net 12 contains a thermally extensible conjugated fiber prior to stretching and a thermally fusible conjugated fiber. Along with the carding machine illustrated in the figure, other known methods, such as the method of transferring short fibers in an air stream and allowing them to settle on a mesh (aerodynamic method), can be used as a means of forming a mesh.

The grid 12 is transferred to the device 13 for thermal extrusion of the relief, where it is subjected to thermal extrusion of the relief. The device 13 for thermal extrusion of relief has a pair of rollers 14, 15. The roller 14 is an engraved roller having protrusions in the form of a rhombic lattice structure on its cylindrical surface. On the other hand, the roller 15 is a smooth roller (support roller) in which the cylindrical surface is flat and smooth. These rollers 14, 15 can be heated to predetermined temperatures.

Thermal extrusion of the relief is carried out in a temperature range that is equal to or higher than the temperature, which is 20 ° C lower than the melting temperature of the second resin component in the thermally expandable conjugated fiber of the mesh 12 and below the melting temperature of the first resin component in it, and is in the range temperatures that are equal to or higher than a temperature that is 20 ° C lower than the melting temperature of a component with a low melting point in a thermally fusible conjugated fiber of a mesh 12 and lower than temperatures s melting component with a high melting point in it. In cases where the melting temperature of the second component in the thermally expandable conjugated fiber is different from the melting temperature of the component with the low melting temperature of the thermally fusion conjugated fiber, a temperature range is used for a lower melting temperature. In addition, thermal extrusion of the relief is carried out at a temperature that is lower than the temperature at which the thermally expandable conjugated fiber begins to thermally expand. This relief extrusion treatment binds together thermally expandable conjugated fibers and thermally fusible conjugated fibers in mesh 12, thereby forming a plurality of joined sections in mesh 12, to produce a thermally fused non-woven fabric 16. These connected sections become recesses 118 in the final non-woven fabric 10 ' .

In the connected sections of the thermally fused nonwoven fabric 16, the thermally extensible conjugated fibers and the thermally fusible conjugated fibers are densified and joined together. In sections other than connected sections, both thermally expandable conjugated fibers and thermally fusible conjugated fibers are in their free, unconnected state. Thermally expandable conjugated fibers are still unstretched.

The thermally fused nonwoven fabric 16 is then transferred to a hot air pressurizer 17. In the hot air pressurization device 17, a thermally fused nonwoven fabric 16 is subjected to an air purge treatment. More specifically, the hot air pressurization device 17 has a structure such that hot air heated to a predetermined temperature passes through a thermally fused nonwoven fabric 16. The temperature at which the air purge treatment is performed is the temperature that causes the thermally expandable conjugated fibers in a thermally fused non-woven fabric 16 expand upon heating, and is the temperature that causes the thermal fusion of the intersections between the thermally stretched with conjugated fibers, which are in their free state, in sections other than the connected sections of thermally fused nonwoven fabric 16, intersections between thermally fused conjugated fibers, which are also in the state described above, and intersections between thermally expandable conjugated fibers and thermally fused conjugated fibers. This temperature, however, should be set at a temperature that is lower than the melting temperature of the first resin component in the thermally expandable conjugated fiber and the melting temperature of the high melting component in the thermally fusion conjugated fiber.

This air purge treatment causes the thermally expandable conjugated fibers in sections other than the connected sections to expand. Some parts of the thermally extensible conjugated fibers are fixed by means of connected sections, and for this reason, sections that are stretched are sections between the connected sections. And since some parts of the thermally extensible conjugated fibers are fixed using connected sections, the stretched parts of the stretched thermally expandable conjugated fibers cannot stretch in the planar direction of the thermally fused non-woven fabric 16 and, thus, move in the direction along the thickness of the non-woven fabric 16. This creates protrusions 119 between the connected sections, thereby making the non-woven fabric 10 ′ three-dimensional and providing a three-dimensional appearance having a plurality of protrusions 119 formed in m. An air purge treatment also connects, at protrusions 119, the intersections between the thermally extensible conjugated fibers, the intersections between the thermally fusion conjugate fibers and the intersections between the thermally expandable conjugate fibers and the thermally fusion conjugate fibers by thermal fusion.

By controlling the conditions of the air purge and completing the treatment with the air purge before the thermally extensible conjugated fibers are fully stretched, it is also possible to obtain non-woven fabrics containing thermally extensible conjugated fibers that can be further stretched in subsequent heat treatment steps. Such non-woven fabric 10 'is thus obtained from a thermally extensible conjugated fiber, which is stretchable by heat, and it contains fibers that are in a state in which they can be further stretched by heating, as well as in a state where their length already stretched (to some extent) by heating.

In the process of blowing air on a grid that contains thermally extensible fibers having a hydrophilizing agent that adheres to them in advance, and thereby causing the thermally extensible conjugated fibers to stretch, controlling the amount of hot air passing through at a low value will change the amount of heat applied from the upper section P1 in the direction of the point P3, as well as from P3 in the Q direction, for the nonwoven fabric 10 ′ illustrated in FIG. 3 (b). At the same time, the authors' studies show that in areas where the temperature applied to the fibers is high, the tensile fraction is large, and the hydrophilicity also decreases. For this reason, in the production method illustrated in FIG. 4, for example, the closer the thermally extensible conjugated fibers are located to the face on which hot air is blown, the greater the degree of stretching and the greater the decrease in hydrophilicity. “The front side onto which hot air is blown” is that side of the nonwoven fabric 10 ′ on which protrusions 119 and recesses 118 are formed; for this reason, with respect to the non-woven fabric 10 ′ thus obtained, the degree of hydrophilicity decrease becomes greater in the direction of the upper section of the protrusion 119. The expression “hydrophilicity reduction” is synonymous with the expression “increase in the contact angle”; so that, in other words, with respect to the thermally extensible conjugated fibers in the protrusions 119, the contact angle for the thermally extensible conjugated fibers gradually decreases from the upper section P1 of the protrusion in the direction of the back side 10a of the non-woven fabric 10 ', that is, from P1 in the direction P3, as well as from P3 in the Q direction in FIG. 3 (b).

“Fibers whose hydrophilicity decreases under the influence of heat” in accordance with this document can be used to form a sheet material, such as a mesh or non-woven fabric, which, partially subjected to heat treatment, can be effectively obtained in the form of a partially hydrophilic, partially hydrophobic sheet material or what anything like that without requiring a complicated device. The hydrophilizing agent adhering to the surface of the core / sheath conjugated fiber is not limited to compounds such as polyethylene glycol and polyethylene glycol fatty acid esters, and various other hydrophilizing agents may be used.

The non-woven fabric in accordance with the present invention can be obtained efficiently without the need for a complex device and can be used in various applications, such as surface materials of absorbent articles, taking advantage of its characteristics such that the hydrophilicity / hydrophobicity of the thermally tensile conjugated fiber varies in some sections and other sections of nonwoven fabric, and that thus, the thermally extensible conjugated fiber has a hydrophilic gradient in the direction and in thickness and / or in the planar direction of the nonwoven fabric.

Using the non-woven fabric production method in accordance with this document, a partially hydrophilic, partially hydrophobic mesh or non-woven fabric can be obtained efficiently without the need for a complex device. In addition, by appropriately changing the sections subjected to heat treatment, it is possible to obtain a non-woven fabric in which hydrophobic sections are formed as the desired structure.

The non-woven fabric in accordance with this document can be used in various fields by taking advantage of its advantages, for example, hydrophilicity in some parts and hydrophobicity or by reducing hydrophilicity in other parts, as well as the hydrophilicity gradient.

The non-woven fabric 10 'described above can also be used in a variety of areas by taking advantage of its shape with protrusions and recesses, bulkiness and good liquid permeability.

The nonwoven fabric can be used appropriately, for example, as a coating sheet, a second sheet (a sheet located between the coating sheet and the absorbent core), a backing sheet, or as a sheet to prevent leakage of the absorbent article (in particular, a disposable sanitary product), used to absorb fluid released from the body, such as a sanitary napkin, a panty liner, disposable diapers, or urological products lining, or as a sheet for wet sanitary napkins, a sheet for skin care or blotting material for products.

Non-woven fabric 10 ', before use in these applications, is usually stored rolled up. This often reduces the volume of non-woven fabric 10 '. Accordingly, when using the non-woven fabric 10 ′, it is preferable to blow hot air onto the non-woven fabric 10 ′ by means of a method of blowing air to recover a reduced volume. When recovering the volume, the hot air used to pressurize the non-woven fabric 10 'preferably has a temperature that is lower than the melting temperature of the second resin component in the thermally expandable conjugated fiber and equal to or higher than the temperature, which is 50 ° C lower than this melting temperature. Examples of technologies that can be used for this method of restoring the volume of non-woven fabric are described, for example, in JP-A-2004-137655, JP-A-2007-177364 and JP-A-2008-231609, filed by the applicant earlier.

The range of the main masses of the mesh or non-woven fabric used to obtain the non-woven fabric can be selected according to need depending on the specific use of the finished non-woven fabric. The bulk of the non-woven fabric obtained at the end is preferably from 10 to 80 g / m ² , more preferably from 15 to 60 g / m ² .

In cases where a nonwoven fabric 10 or 10 'is used, for example, as a coating sheet of an absorbent article, the bulk of the nonwoven fabric is preferably from 10 to 80 g / m ² , more preferably from 15 to 60 g / m ² . In cases where a non-woven fabric 10 or 10 'is used for the same application, its thickness on the protrusion 119 (thick section 19) is preferably from 0.5 to 3 mm, more preferably from 0.7 to 3 mm, after volume recovery using hot air. On the other hand, the thickness of the recess 118 (thin section 18) is preferably from 0.01 to 0.4 mm, more preferably from 0.02 to 0.2 mm. Note that there is essentially no change in thickness of recess 118 before and after boosting hot air. The thickness of the protrusion 119 and the recess 118 is measured by observing a vertical cross section of the nonwoven fabric 10, 10 '. First, the nonwoven fabric is cut into samples for measurements in the form of pieces 100 mm long and 100 mm wide. A 12.5 g plate (56.4 mm in diameter) is placed on a piece for measurement, and a load of 49 Pa is applied to it. A vertical cross section of the nonwoven fabric is observed in this state with a microscope (VHX-900 from Keyence Corporation) to measure the thickness of the protrusion 119 and the recess 118. Note that in cases where the nonwoven fabric has protrusions (thick sections) and recesses (thin sections) , the term “non-woven fabric thickness” refers to the thickness of a protrusion (thick section).

The ratio of the areas of the recesses 118 and the protrusions 119 in the non-woven fabric 10, 10 'is expressed as the percentage of extruded relief (the percentage of the area with the extruded relief or the percentage of the total area of the recesses from the entire area of the non-woven fabric 10, 10'), which affects the volume and strength of the non-woven fabric 10 , 10'. From this point of view, the proportion of extruded relief in the non-woven fabric 10, 10 'is preferably from 5% to 35%, more preferably from 10% to 25%. The proportion of extruded relief is measured as follows. First, an enlarged photograph of the surface of the non-woven fabric 10, 10 'is obtained using a microscope (VHX-900 from Keyence Corporation). Then, a scale for measuring the sizes of sections with an extruded relief of the section over the entire area U of the measured section is placed on the enlarged photograph of the surface and thereby to calculate the area U of the sections with extruded relief.

The proportion of extruded relief can be calculated using the following formula: (U / T) × 100.

An absorbent article used to absorb fluid excreted from the body typically comprises a coating sheet, a backing sheet and a liquid-retaining absorbent core located between the two sheets. In the case where the nonwoven fabric of the present invention is used as a coating sheet, materials commonly used in the art can be used for an absorbent core and backing sheet without any limitation.

For example, with respect to the absorbent core, an aggregate of fibers consisting of fibrous materials such as wood pulp fiber or a material carrying particles of an absorbent polymer coated with a sheet such as a sheet of cosmetic paper or non-woven fabric can be used. With respect to the backing sheet, a liquid-impervious or water-repellent sheet such as a thermoplastic resin film or a laminate consisting of this film and non-woven fabric can be used. The backing sheet may have vapor permeability. The absorbent article may also contain various other components, depending on the particular use of the absorbent article. Such components are known to those skilled in the art; for example, one or two or more pairs of three-dimensional safety elements may be located on the coating sheet on the right and left sides of the product in cases where the absorbent product should be used as a disposable diaper or sanitary towel.

The present invention is described above in accordance with its preferred embodiments, but the present invention should not be limited to the above embodiments.

For example, when forming sections with an embossed relief on a non-woven fabric, various other structures, such as many stripes, dots, a checkerboard pattern and spirals, can be used, instead of a lattice structure, as a structure in which sections with an extruded relief are formed. For a dot structure, each dot can take any shape, such as a circle, ellipse, triangle, square, hexagon, or heart shape. A square or rectangular lattice structure or hexagonal structure can also be used.

In the non-woven fabric production method illustrated in FIG. 4, the embossing roller and / or the smooth roller may be heated during embossing to produce a non-woven fabric having reduced hydrophilicity in sections with extruded relief and / or in their vicinity.

In cases where the non-woven fabric of the present invention is to be used in diapers, pads, wipes and other products, some or all parts of the non-woven fabric of the present invention may have reduced hydrophilicity or may even be made water-repellent by applying heat to these desired parts, or before receipt, either at the time of receipt, or after finishing the product.

In the above embodiments, the thermal extrusion of the relief is used to form the connected sections (recesses 118), but instead the connected sections can be obtained using ultrasonic extrusion of the relief. In addition, the nonwoven fabric is not limited to a single layer structure and may have a multilayer structure in which one or more layers of other nonwoven fabrics are laminated and combined with the nonwoven fabric in question.

EXAMPLES

The present invention will be described in more detail below in accordance with its Examples. The scope of the present invention, however, should not be limited to the following Examples.

Example 1

(1) Production of a fiber whose hydrophilicity decreases under the influence of heat.

Spinning from the melt is carried out in accordance with the conditions shown in Table 1, with obtaining a conjugated fiber core / sheath of a concentric type. The obtained conjugated fiber does not carry out a pulling treatment. The fiber is then immersed in an aqueous solution of a hydrophilizing agent of the type shown in Table 1 to obtain a hydrophilizing agent of the type and amount shown in Table 1 adhered to the fiber. Note that “pulling processing”, as used herein, refers to a pulling operation, usually carried out on unextracted yarn obtained after melt spinning, for which the pull ratio is about 2-6 times. The fiber is then mechanically corrugated and then cut into short fibers (fiber length: 51 mm). When spinning, cold air at 20 ° C is blown onto the molten resin ejected from the spinning nozzles to accelerate the curing of the sheathing resin.

The crystal size of the resin constituting the shell (polyethylene resin) in the resin thus obtained is measured in accordance with the method described above.

(2) Obtaining non-woven fabric.

A nonwoven fabric is obtained using fibers thus obtained in accordance with the method illustrated in FIG. 4. A specific production method is as follows. First get a grid using a carding machine, and the grid is subjected to extrusion of the relief. Relief extrusion is carried out in such a way that sections with an extruded relief are formed in the form of a lattice structure and that the percentage of the area of sections with an extruded relief (compressed sections) is 22%. The extrusion extrusion temperature is 110 ° C, as shown in Table 1. Then, the mesh is subjected to an air purge treatment. Regarding this treatment with air purging, the heat treatment is carried out once, while hot air is blown from the extruded surface of the mesh with the relief extruded using the method of extruding the relief. The heat treatment temperature during air purge treatment is set at 136 ° C, as shown in Table 1.

The non-woven fabric thus obtained has thin sections (sections with an extruded relief) 18 and thick sections 19, next to the thin sections, and has, on the one hand, a mostly wavy front side 10b with protrusions and recesses, with protrusions 119 and recesses 118 , and a flat face 10a, on the other hand, which is substantially flat.

Examples 2-24 and Comparative Examples 1-6.

Appropriate non-woven fabrics are obtained as in Example 1, except that they use the appropriate fibers and conditions shown in Table 1.

In the nonwoven fabrics obtained in Examples 1-24, intersections between constituent fibers are bonded together by thermal fusion using an air purge method. Then, the fibers contained in the respective non-woven fabrics obtained in Examples 1-24 are checked for thermal elongation in accordance with the method described above, and it is confirmed that each non-woven fabric contains fibers having thermal elongation.

The hydrophilizing agents A-S shown in Tables 1 and 2 are as follows.

Hydrophilizing agents.

A: A hydrophilizing agent containing 50 wt.%: 50 wt.% Polyoxyethylene stearamide (number of moles added: 2) (Amisol SDE, product of Kawaken Fine Chemicals Co., Ltd.) and stearyl betaine (Amphitol 86B, product of Kao Corporation)

B: A hydrophilizing agent containing 100% by weight of dipotassium alkyl phosphate (neutralized KOH product Gripper 4131, product Kao Corporation)

C: Hydrophilizing agent containing 50 wt.%: 50 wt.% Dipotassium alkyl phosphate (neutralized KOH product Gripper 4131, product Kao Corporation) and sodium alkyl sulfonate (Latemul PS, product Kao Corporation)

D: A hydrophilizing agent containing 50 wt.%: 50 wt.% Polyoxyethylene alkylamine (Amiet 302, product of Kao Corporation) and diglycerol laurate (Rikemal L-71-D, product of Riken Vitamin Co., Ltd.)

E: A hydrophilizing agent containing 50 wt.%: 50 wt.% Dipotassium phosphate and stearyl ether (neutralized KOH product Phosphanol RL-210, product Toho Chemical Industry Co., Ltd.) and diglycerol laurate (Rikemal L-71-D , product of Rinken Vitamin Co., Ltd.)

F: Hydrophilizing agent containing 50 wt.%: 50 wt.% Polyoxyethylene stearamide (number of moles added: 2) (Amisol SDE, product of Kawaken Fine Chemicals Co., Ltd.) and sodium dialkyl sulfosuccinate (Pelex OT-P, product of Kao Corporation )

G: A hydrophilizing agent containing 50 wt.%: 50 wt.% Polyoxyethylene-polyoxypropylene-modified silicone (KF-6012, product of Shin-Etsu Chemical Co., Ltd.) and sodium dialkyl sulfosuccinate (Pelex OT-P, product of Kao Corporation)

H: A hydrophilizing agent containing 50 wt.%: 50 wt.% Diglycerol stearate (Rikemal S-71-D, product of Riken Vitamin Co., Ltd.) and sodium dialkyl sulfosuccinate (Pelex OT-P, product of Kao Corporation)

I: A hydrophilizing agent containing 50 wt.%: 50 wt.% Sorbitan monopalmitate (Rheodol SP-P10, product of Kao Corporation) and sodium dialkyl sulfosuccinate (Pelex OT-P, product of Kao Corporation)

J: A hydrophilizing agent containing 50 wt.%: 50 wt.% Polyoxyethylene stearamide (number of moles added: 2) (Amisol SDE, product of Kawaken Fine Chemicals Co., Ltd.) and diglycerol laurate (Rikemal L-71-D, product Rinken Vitamin Co., Ltd.)

K: Hydrophilizing agent containing 50 wt.%: 50 wt.% Polyoxyethylene stearamide (number of moles added: 2) (Amisol SDE, product of Kawaken Fine Chemicals Co., Ltd.) and sorbitan monolaurate (Rheodol SP-L10, product of Kao Corporation )

L: A hydrophilizing agent containing 50 wt.%: 50 wt.% Polyoxyethylene alkylamine (Amiet 302, product of Kao Corporation) and sorbitan monolaurate (Rheodol SP-L10, product of Kao Corporation)

M: Hydrophilizing agent containing 50 wt.%: 50 wt.% Polyoxyethylene-polyoxypropylene-modified silicone (KF-6004, product of Shin-Etsu Chemical Co., Ltd.) and polyoxyethylene lauryl ether (Emulgen 102KG, product of Kao Corporation)

N: Hydrophilizing agent containing 50 wt.%: 50 wt.% Polyoxyethylene-polyoxypropylene-modified silicone (KF-6004, product of Shin-Etsu Chemical Co., Ltd.) and diglycerol laurate (Rikemal L-71-D, product of Rinken Vitamin Co., Ltd.)

O: Hydrophilizing agent containing 50 wt.%: 50 wt.% Polyoxyethylene-polyoxypropylene-modified silicone (KF-6004, product of Shin-Etsu Chemical Co., Ltd.) and sorbitan monolaurate (Rheodol SP-L10, product of Kao Corporation )

P: Hydrophilizing agent containing 50 wt.%: 50 wt.% Sorbitan monolaurate (Rheodol SP-L10, product of Kao Corporation) and stearyl ether polyoxyethylene (Emulgen 306P, product of Kao Corporation)

Q: A hydrophilizing agent containing 50 wt.%: 50 wt.% Diglycerol stearate (Rikemal S-71-D, product of Rinken Vitamin Co., Ltd.) and sorbitan monolaurate (Rheodol SP-L10, product of Kao Corporation)

R: A hydrophilizing agent containing 50 wt.%: 50 wt.% Diglycerol stearate (Rikemal S-71-D, product of Rinken Vitamin Co., Ltd.) and polyoxyethylene lauryl ether (Emulgen 102KG, product of Kao Corporation)

S: A hydrophilizing agent containing 50 wt.%: 50 wt.% Distearyldimethylammonium chloride (Quartamin D86P, a product of Kao Corporation) and polyoxyethylene stearyl ether (Emulgen 306P, a product of Kao Corporation)

Rating.

For the respective nonwoven fabrics obtained in the Examples and Comparative Examples, the contact angle of the fiber is measured in accordance with the method described above. Also, the amount of remaining liquid and the distance of the fluid flow are measured in accordance with the methods described below. The results are shown in Tables 1 and 2.

In the “contact angle” section in Tables 1 and 2, the line entitled “upper section of the protrusion P1” shows the results of measuring the contact angle of the fiber with distilled water on the upper section P1 of the protrusion 119, on the front side 10b with protrusions and recesses (i.e., on the upper section of the thick section), the line entitled “neighborhood of the recess P3” shows the contact angle measurements measured on the section 1 mm inward towards the upper section P1 from the edge of the embossed section (thin section) (i.e., in the vicinity thin section), the line entitled “middle section P2” shows the results of measuring the contact angle measured in the section in the middle of P1 and P3, and the line entitled “the back side Q” shows the results of measuring the contact angle measured in the section on a flat the front side 10a corresponding to the upper section of the protrusion.

The remaining amount of fluid.

A sample for assessing the sanitary napkin is obtained by: removing the coating sheet from the sanitary napkin commercially available from Kao Corporation (product name: “Laurier Sarasara Cushion Hada Kirei Kyushu (comfortable dry pad, absorption reaching clean skin)”); placing one of the nonwoven fabrics obtained in the Examples and Comparative Examples on a pad instead of a coating sheet; and fixing the outer edge of the nonwoven fabric.

An acrylic plate having a through hole with an inner diameter of 1 cm is placed on the surface of the gasket, and a constant load of 100 Pa is applied to the gasket. When a constant load is applied, 3.0 g of defibrinated horse blood is supplied through a through hole in the acrylic plate. The acrylic plate is removed 60 seconds after feeding the horse blood, then the mass (W2) of the non-woven fabric is measured, and the difference (W2-W1) of the mass (W2) and the mass (W1) of the non-woven fabric previously measured before horse blood is calculated. The above procedure is repeated three times, and the average value for the three measured values is considered the amount of remaining liquid (mg). The amount of remaining liquid serves as an indicator showing how wet the user's skin will become; the smaller the amount of liquid remaining, the better the results.

The distance of the fluid.

Prepare a gasket sample, as in the section, Remaining liquid, above. The research device has a mount with the front side of the fixed gasket, inclined at an angle of 45 ° to the horizontal. The gasket is placed in the mounting section so that the side with the coating sheet is facing up. The colored distilled water serving as the research fluid is dripped onto the diaper at a speed of 1 g / 10 seconds. Measure the distance from the point where the non-woven fabric first becomes wet, to the point where the test fluid is first absorbed into the absorbent core. The above procedure is repeated three times, and the average of the three measured values is considered the distance of the fluid flow (mm). The liquid flow distance serves as an indicator showing the amount of fluid that will come into contact with the skin of the user without being absorbed by the diaper; the smaller the distance the fluid flows, the higher the evaluation results. Note that fluid flow distances greater than 100 mm are marked with “> 100”.

The results in Tables 1 and 2 show that, in the non-woven fabrics used in these Examples, the polyethylene sheaths are large in crystal size and that hydrophilicity is reduced by heat treatment.

In addition, the results show that the non-woven fabrics obtained in these Examples exhibit small flow rates of liquid and remaining liquid, and thus have excellent absorption properties due to sections with reduced hydrophilicity, which are created by reducing hydrophilicity in some parts of the non-woven fabric. creating a hydrophilicity gradient.

Example 25

A single layer non-woven fabric 10 'having the structure illustrated in FIG. 3 is obtained using the apparatus of FIG. 4. The roller 14 for extruding the relief in the device of FIG. 4 has projections with a rhombic lattice structure, each projection has a line width of 0.5 mm. The proportion of extruded relief (percentage of connected sections) of the roller 14 for extruding the relief is 14.1%. The non-woven fabric is obtained in accordance with the conditions shown in Table 3, using the thermally expandable conjugated fiber and the heat-fusion conjugated fiber shown in Table 3. In the resulting non-woven fabric, the intersection between the thermally extensible conjugated fibers, the intersection between the thermally fused conjugated fibers, and the intersections between the thermally expandable conjugated fibers and the thermally fusion conjugate fibers are connected by t fusion by means of a method with air purging. Then, the fibers contained in the thus obtained non-woven fabric are checked for thermal elongation in accordance with the method described above, and it is shown that the non-woven fabric contains fibers having thermal elongation. A thermally expandable conjugated fiber is obtained by melt spinning at a sampling speed of 1300 m / min. After the melt spinning step, the thermally expandable conjugated fiber is immersed in an aqueous solution of a hydrophilizing agent to obtain a hydrophilizing agent adhering to the fiber. The fiber is then mechanically crimped, dried by heat treatment, and then cut into short fibers (fiber length: 51 mm). The amount of adhesion of the hydrophilizing agent is 0.4 wt.%. Note that upon receipt of the fiber, pulling processing is not carried out (this is also true for the following Examples and Comparative Examples). Note that “pulling processing”, as used herein, refers to a pulling operation, usually carried out on an unextracted yarn obtained after spinning from a melt, with the draw ratio being approximately 2-6 times.

Examples 26-28 and Comparative Examples 7-12:

Appropriate non-woven fabrics are obtained as in Example 25, except that they use the appropriate fibers and conditions shown in Table 3. In the non-woven fabrics obtained in these Examples, the intersections between the thermally extensible conjugated fibers, the intersections between the thermally fused conjugated fibers and the intersections Between thermally expandable conjugated fibers and thermally fusible conjugated fibers are bonded by heat fusion using a method with Air duvkoy. Then, the fibers contained in the corresponding non-woven fabrics obtained in these Examples are checked for thermal elongation in accordance with the method described above, and it is shown that each non-woven fabric contains fibers having thermal elongation.

The hydrophilizing agents A1-F1 shown in Table 3 are as follows.

Hydrophilizing agents.

A1: Hydrophilizing agent containing 50 wt.%: 50 wt.% Polyoxyethylene stearamide (number of moles added: 2) (Amisol SDE, product Kawaken Fine Chemicals Co., Ltd.) and dipotassium alkyl phosphate (neutralized KOH product Gripper 4131, product Kao Corporation)

B1: A hydrophilizing agent containing 50 wt.%: 50 wt.% Diglycerol stearate (Rikemal S-71-D, product of Rinken Vitamin Co., Ltd.) and polyoxyethylene lauryl ether (Emulgen 102KG, product of Kao Corporation)

C1: A hydrophilizing agent containing 50 wt.%: 50 wt.% Polyoxyethylene stearamide (number of moles added: 2) (Amisol SDE, product of Kawaken Fine Chemicals Co., Ltd.) and stearyl betaine (Amphitol 86B, product of Kao Corporation)

D1: A hydrophilizing agent containing 50 wt.%: 50 wt.% Polyoxyethylene stearamide (number of moles added: 2) (Amisol SDE, product of Kawaken Fine Chemicals Co., Ltd.) and diglycerol laurate (Rikemal L-71-D, product Rinken Vitamin Co., Ltd.)

E1: A hydrophilizing agent containing 50 wt.%: 50 wt.% Polyoxyethylene stearamide (number of moles added: 2) (Amisol SDE, product of Kawaken Fine Chemicals Co., Ltd.) and dipotassium lauryl phosphate (neutralized KOH product of Phosphanol ML-200, product Toho Chemical Industry Co., Ltd.)

F1: A hydrophilizing agent containing 50 wt.%: 50 wt.% Dipotassium lauryl phosphate (neutralized KOH product Phosphanol ML-200, product Toho Chemical Industry Co., Ltd.) and dimethyl silicone (KF-96L-0.65CS, product Shin- Etsu Chemical Co., Ltd.)

Rating.

The contact angle of the fiber is measured in accordance with the method described above for the corresponding non-woven fabrics obtained in the Examples and Comparative examples. Also, the amount of remaining fluid and the distance of the fluid in each non-woven fabric is measured in accordance with the methods described below. They also assess the recoverability of the volume achieved by boosting hot air. The results are shown in Table 1, above, and in Tables 4 and 5, below.

The amount of fluid remaining.

The absorbent core of the pad is obtained by removing the coating sheet from a commercially available pad (product of Kao Corporation; product name: “Laurier Sarasara Cushion Wing Tsuki (Comfortable Dry Pad with Wings)”). The nonwoven fabric to be measured is cut into a piece 50 mm long in the machine direction (MD) and 50 mm wide in the transverse direction (CD). The cut-out piece is attached and fixed with adhesive to the sections of the absorbent core of the pad, where there is a coating sheet (on the front side in contact with the skin, the absorbent core of the pad), so that the back side 10a of the non-woven fabric 10 'illustrated in Fig. 3 (b) , becomes the opposite side of the absorbent core of the pad, thereby producing a pad in which the nonwoven fabric to be measured is used as a coating sheet. An acrylic plate having a cylindrical through hole is placed on the surface of the gasket having a nonwoven fabric to be measured, and a constant load of 100 Pa is applied to the gasket. At the same time, when a load is applied, 3.0 g of defibrinated horse blood is supplied through a through hole in the acrylic plate. Then, 120 seconds after the delivery of the defibrinated horse blood, another 3.0 g of the defibrinated horse blood is fed. The acrylic plate is removed 60 seconds after a total of 6.0 g of defibrinated horse blood is dispensed, and then the mass (W2) of the non-woven fabric is measured. Then, the difference (W2-W1) of the mass (W2) and the mass (W1) of the non-woven fabric measured before feeding the defibrinated horse blood is calculated. The above procedure is repeated three times, and the average value for the three measured values is considered the amount of remaining liquid (mg). The amount of remaining liquid serves as an indicator showing how wet the user's skin will become; the smaller the amount of remaining liquid, the higher the evaluation results.

The distance of the fluid.

The distance of the fluid flow is measured as in the above method of measuring the distance of the fluid flow, except that: the nonwoven fabric to be measured is cut into pieces 150 mm long in the machine direction (MD) and 50 mm wide in the transverse direction (CD) , and a piece of non-woven fabric is used as a coating sheet to obtain a spacer, as in the section, Remaining liquid, above; and the absorbent core of the pad is obtained by removing the coating sheet from a commercially available pad (product of Kao Corporation; product name: “Laurier Sarasara Cushion Wing Tsuki (Comfortable Dry Pad with Wings)”).

Volume recoverability.

Non-woven fabric 10 with a length of 2700 m is wrapped around a cardboard tube with an outer diameter of 85 mm to form a roll, and stored for 2 weeks at normal temperature. After storage, the non-woven fabric in the range from the point where the roll is 500 mm in diameter to the point where the roll is 600 mm in diameter moves with a transfer speed of 150 m / min and hot air is blown onto the non-woven fabric at a processing temperature of 115 ° C for a treatment time of 0.20 seconds at a flow rate of 2.8 m / s, to restore the thickness of the non-woven fabric. The volume recovery of a non-woven fabric is expressed using the following equation (2), where C is the thickness on the protrusion of the non-woven fabric before folding the non-woven fabric into a roll (“storage thickness”), and D is the thickness on the protrusion of the non-woven fabric after hot air pressurization (“Thickness after recovery”). The thickness of the nonwoven fabric after boosting hot air is measured after 1 minute - 1 hour after the start of boosting hot air onto it. The thickness of the nonwoven fabric is measured in accordance with the method described above.

Volume recoverability (%) = D / C × 100 (2)

The volume recoverability value, which is found from equation (2), which is lower than 60%, is estimated as “bad”; a value equal to or greater than 60% and below 70% is assessed as “moderate”; a value equal to or greater than 70% and below 80% is assessed as “good”; and a value equal to or greater than 80% is rated as “excellent”. The higher the volume recoverability, the higher the evaluation results.

The results in Table 4 show that the nonwoven fabrics obtained in Examples 25-28 have a small amount of remaining liquid and a short flow distance, which indicates that their absorption characteristics are exceptionally high. The results also show that non-woven fabrics have excellent volume recovery after boosting hot air. In contrast, the results in Table 5 show that the non-woven fabric of Comparative Example 7, consisting only of thermally extensible conjugated fibers, the non-woven fabrics of Comparative Examples 8-10, consisting of only fusible conjugated fibers, and the non-woven fabrics of Comparative Examples 11 and 12, consisting of both thermally extensible conjugated fibers and thermally fused conjugated fibers, are either prone to liquid remaining or are prone to post-limiting liquid or are poor recoverability of the nonwoven fabric.

INDUSTRIAL APPLICABILITY

The non-woven fabric of the present invention can easily be obtained by subjecting the heat treatment to a mesh or non-woven fabric containing a fiber whose hydrophilicity is reduced by heat and therefore has a reduced hydrophilicity in its desired parts.

The nonwoven fabric of the present invention partially has sections with reduced hydrophilicity, and for this reason, it can be used in various applications, benefiting from this characteristic.

According to the non-woven fabric production method of the present invention, a non-woven fabric having sections with reduced hydrophilicity can be effectively obtained.

According to the hydrophilicity control method of the nonwoven fabric of the present invention, the hydrophilicity of the desired sections of the nonwoven fabric can be reduced simply by changing the areas to be heat treated or by controlling the amount of hot air passing through it without having to mix the fibers together, laminate two layers together or carry out a separate treatment for hydrophilization after receiving non-woven fabric.

The present invention provides ample opportunity when choosing hydrophilizing agents that can be used.

According to the nonwoven fabric of the present invention, the amount of liquid remaining in the nonwoven fabric can be reduced by controlling the hydrophilicity of the nonwoven fabric. For example, in cases where a non-woven fabric is used as a coating sheet of an absorbent article, back wetting in the direction of the upper side in contact with the skin of the user absorbed by the body fluid can be prevented, and the flow of the body fluid to the surface of the non-woven fabric is prevented. For this reason, when it is used, for example, as a coating sheet of an absorbent article, the nonwoven fabric of the present invention will satisfy the necessary absorption characteristics required of the coating sheet, such as a reduced amount of remaining liquid and a reduced amount of liquid flow.

Claims (17)

1. Non-woven fabric, including: conjugated fiber core / sheath having a sheath containing a polyethylene resin, and a core containing a resin component having a melting point that is higher than that of a polyethylene resin; and a hydrophilizing agent adhering to the surface of the conjugated fiber core / sheath, and points associated with thermal fusion, are formed through associated thermal fusion intersections of the component fibers; where the conjugated fiber core / sheath contains a thermally expandable conjugated fiber, the length of which increases with heating; and the thermally extensible conjugated fiber has a hydrophilicity gradient in the thickness direction and / or in the planar direction of the nonwoven fabric. 2. The non-woven fabric according to claim 1, where having thin sections formed by extruding the relief, and thick sections next to the thin sections; thin sections or their surroundings are hydrophilic; and the upper sections of the corresponding thick sections are less hydrophilic than the thin sections or their surroundings. 3. The non-woven fabric according to claim 1 or 2, in which the hydrophilizing agent contains polyoxyethylene alkylamide and / or alkyl betaine. 4. The non-woven fabric according to claim 3, in which the hydrophilizing agent contains polyoxyethylene alkylamide and alkyl betaine. 5. The nonwoven fabric according to claim 3, in which thick sections have a higher ratio of the presence of polyoxyethylene alkylamide and / or alkyl betaine than thin sections or their surroundings. 6. The nonwoven fabric according to claim 1, additionally containing a thermally inextensible thermally fusible conjugated fiber, the length of which does not substantially increase when heated, the thermally fusible conjugated fiber contains two components with different melting points that are subjected to a stretch treatment that have a hydrophilizing agent that adheres to them, and they have a contact angle with water from 50 ° to 75 °. 7. The nonwoven fabric according to claim 6, in which: the mass mixing ratio between the thermally expandable conjugated fiber and the thermally fused conjugated fiber (first / last ratio) is from 20/80 to 80/20; and intersections between thermally expandable conjugated fibers, intersections between thermally fusion conjugate fibers and intersections between thermally expandable conjugate fibers are bonded by heat fusion using an air purge method. 8. Non-woven fabric according to any one of claims 6 or 7, in which the thermally expandable conjugated fiber has a contact angle of from 40 ° to 90 °. 9. Non-woven fabric according to any one of paragraphs.6 or 7, in which: one side of the non-woven fabric has many protrusions and recesses; and in each protrusion, the contact angle with water for the thermally expandable conjugated fiber gradually decreases from the upper section of the protrusion towards the other side of the non-woven fabric. 10. A non-woven fabric obtained by subjecting a heat treatment to a fabric or non-woven fabric containing a fiber whose hydrophilicity is reduced by heat to thereby reduce hydrophilicity in some parts of the fabric or non-woven fabric, the fiber comprising: a core / sheath conjugated fiber having a shell containing a polyethylene resin, and a core containing a resin component having a melting point that is higher than that of a polyethylene resin; and a hydrophilizing agent adhering to the surface of the conjugated fiber core / sheath; where the polyethylene resin has a crystal size of from 100 to 200 Å. 11. The nonwoven fabric of claim 10, in which the hydrophilizing agent is at least one type of surfactant selected from the group consisting of anionic, cationic and zwitterionic surfactants. 12. The nonwoven fabric of claim 10 or 11, in which: the nonwoven fabric has thin sections formed by extruding the relief, and thick sections next to the thin sections; thick sections are sections with reduced hydrophilicity; and thin sections and / or their surroundings are hydrophilic sections. 13. The nonwoven fabric of claim 12, wherein the first side of the nonwoven fabric is hydrophilic and the other side is more hydrophobic than the first side. 14. A method of producing a non-woven fabric, including: the effect of heat treatment on a fabric or non-woven fabric containing fiber, the hydrophilicity of which decreases under the influence of heat, while obtaining a non-woven fabric in which hydrophilicity decreases in some parts of the fabric or non-woven fabric, and the fiber contains : a conjugated fiber core / sheath having a sheath consisting of a polyethylene resin and a core consisting of a resin component having a melting point that is higher than that of polyethylene new resin; and a hydrophilizing agent adhering to the surface of the conjugated fiber core / sheath; where the polyethylene resin has a crystal size of from 100 to 200 Å. 15. The method of producing a non-woven fabric according to 14, in which the heat treatment is carried out at a temperature ranging from a temperature that is 10 ° C lower than the melting temperature of the polyethylene resin constituting the shell to the melting temperature of the resin component constituting the core. 16. A method of controlling the hydrophilicity of a non-woven fabric, including: the effect of heat treatment on a fabric or non-woven fabric containing fiber, the hydrophilicity of which decreases under the influence of heat, while reducing hydrophilicity in some parts of the mesh or non-woven fabric, and the fiber contains: conjugated fiber core / a shell having a shell consisting of a polyethylene resin and a core consisting of a resin component having a melting point that is higher than that of a polyethylene resin; and a hydrophilizing agent adhering to the surface of the conjugated fiber core / sheath; where the polyethylene resin has a crystal size of from 100 to 200 Å. 17. An absorbent article made using non-woven fabric according to any one of claims 1 to 13.

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