JP2023177489A - Nonwoven fabric and manufacturing method thereof and solid electrolyte sheet - Google Patents

Abstract

To provide a nonwoven fabric in which constituting fibers are short fibers and the constituting fibers are bonded to each other and which has low basis weight and high air permeability.SOLUTION: The applicant of the present application provides a nonwoven fabric in which constituting fibers are short fibers and the constituting fibers are bonded to each other by adopting a nonwoven fabric manufacturing method having a step according to the present invention to obtain the nonwoven fabric by bonding the constituent fibers to each other in a fiber layer on a base material and subsequently peeling off the bonded fibers from the base material. The nonwoven fabric having low basis weight less than 5 g/m2 and air permeability exceeding 1000 cm3/cm2/s is provided in an embodiment allowing the nonwoven fabric to be independently treated.SELECTED DRAWING: None

Description

The present invention relates to a nonwoven fabric, a method for manufacturing the same, and a solid electrolyte sheet in which solid electrolyte particles are supported on the nonwoven fabric.

In recent years, nonwoven fabrics have been used in various industrial applications, such as separators and separator support members for electrochemical devices such as capacitors and primary/secondary batteries, particle support materials in sheets that support particles, prepregs, gas filters, and liquid filters. , medical applications such as adhesive medicinal base materials and masks, cushioning materials and sealing materials, liquid absorbing materials, interior skin materials, cell culture substrates and cell separation materials, conductive materials and insulating materials, heat dissipation materials and insulation materials, and cores. As clothing materials such as cloth and batting, or as supports for liquid separation membranes, gas separation membranes, medical materials, ion exchange membranes, dialysis membranes, water electrolyte membranes, polymer electrolyte membranes for fuel cells, solid electrolyte sheets, etc. It is used.

As a specific example of such a nonwoven fabric, Japanese Patent Application Publication No. 2021-028869 (Patent Document 1) discloses a nonwoven fabric formed by paper-making short fibers by a wet method and bonding the constituent fibers to each other. In addition, in the invention of Patent Document 1, the problem was found that the fiber aggregate (nonwoven fabric) with low strength causes large damage during handling and during the manufacturing process of solid-state batteries, and solid electrolyte particles are likely to fall off. In order to solve the problem, an invention characterized in that the value of tensile strength (unit: N/50mm) per area weight (unit: g/m ² ) of the fiber aggregate (nonwoven fabric) is set larger than 0.5. be. Example 1 of Patent Document 1 discloses that a nonwoven fabric having a basis weight (basis weight) of 5 g/m ² and an air permeability of 600 cm ³ /cm ² /s was manufactured.

JP2021-028869

In recent years, in order to provide nonwoven fabrics that can be used in a wider variety of industrial applications, there has been a demand for nonwoven fabrics that have lower basis weight and higher air permeability. For example, all-solid-state batteries are required to have improved energy density and lower resistance. Therefore, as a support for holding the solid electrolyte in an all-solid-state battery, it has a lower basis weight to further lower resistance, and has large pores and a high air permeability so that more solid electrolyte particles can be packed into the space of the support. The use of high-quality nonwoven fabrics is required.

Therefore, in the present invention, the fabric weight is even lower than the nonwoven fabric disclosed in the prior art such as Patent Document 1 (a nonwoven fabric whose constituent fibers are short fibers, and whose constituent fibers are bonded to each other). At the same time, the objective is to provide a nonwoven fabric with high air permeability.

The present invention is
“(Claim 1) A nonwoven fabric whose constituent fibers are short fibers,
The constituent fibers are bonded to each other,
A nonwoven fabric having a basis weight of less than 5 g/m ² and an air permeability of more than 1000 cm ³ /cm ² /s.
(Claim 2)
The nonwoven fabric according to claim 1, having an air permeability of 1440 cm ³ /cm ² /s or more.
(Claim 3)
The nonwoven fabric according to claim 2, wherein the constituent fibers include core-sheath adhesive short fibers having a fiber diameter of 7 μm or more.
(Claim 4)
The nonwoven fabric according to claim 3, wherein the constituent fibers are only core-sheath adhesive short fibers with a fiber diameter of 7 μm or more.
(Claim 5)
The nonwoven fabric according to claim 4, wherein the sheath component of the core-sheath adhesive staple fiber is a polyolefin resin.
(Claim 6)
A solid electrolyte sheet comprising solid electrolyte particles supported on the nonwoven fabric according to any one of claims 1 to 5.
(Claim 7)
A method for manufacturing a nonwoven fabric, the method comprising:
Step (1) preparing a dispersion liquid in which short fibers are dispersed;
Step (2) preparing a base material;
Step (3) forming a laminate having a fiber layer containing the short fibers on the base material by scooping up the dispersion liquid onto the main surface of the base material;
Step (4) removing the dispersion medium contained in the laminate;
Step (5) bonding the constituent fibers of the fiber layer to each other by heating the laminate, and then allowing it to cool and/or cooling it;
Step (6) allowing the fiber layer to cool and/or peeling off the fibrous layer from the cooled laminate and obtaining the peeled fibrous layer as a nonwoven fabric;
A method for manufacturing a nonwoven fabric, comprising: ”
It is.

The applicant of this application has developed a nonwoven fabric whose constituent fibers are short fibers and which are bonded to each other, and which has a light basis weight of less than 5 g/m ² and an air permeability higher than 1000 cm ³ /cm ² /s. , we have succeeded in providing it in a form that can be handled independently. In particular, the applicant has succeeded in providing a nonwoven fabric with an air permeability of 1440 cm ³ /cm ² /s or more in a manner that can be handled alone.

Furthermore, the applicant of the present application has proposed that the constituent fibers include core-sheath type bonded short fibers with a fiber diameter of 7 μm or more, and more preferably, the constituent fibers include only core-sheath type bonded short fibers with a fiber diameter of 7 μm or more. of nonwoven fabrics.

Moreover, the above-mentioned nonwoven fabric could also be provided in a nonwoven fabric in which the sheath component of the core-sheath type adhesive short fibers is a polyolefin resin.

The nonwoven fabric according to the present invention has a structure that has a low basis weight and high air permeability (in other words, a structure that has voids suitable for supporting a sufficient amount of solid electrolyte particles, etc.). There is. Therefore, by using the nonwoven fabric according to the present invention, it is possible to provide a particle-supporting sheet in which particles are supported on the nonwoven fabric in an intended manner, such as being able to support a large amount of particles between the constituent fibers of the nonwoven fabric and on the surface of the constituent fibers. . Therefore, by supporting solid electrolyte particles on the nonwoven fabric according to the present invention, it is possible to provide a solid electrolyte sheet in which solid electrolyte particles are supported on the nonwoven fabric in an intended manner, such as being able to support a large amount of solid electrolyte particles.

The method for manufacturing a nonwoven fabric according to the present invention differs from the method for manufacturing a nonwoven fabric disclosed in Patent Document 1, in that the constituent fibers (short fibers) of the nonwoven fabric are formed on a base material to form a fiber layer on the base material. After that, the fiber layer together with the base material is subjected to a heating process, and then it has a process of allowing it to cool and/or cooling it. Therefore, by going through the heating process, the constituent fibers of the fiber layer are bonded together, and the structure of the paper-made fiber layer can be prevented from collapsing unintentionally, so the strength of the fiber bonding of the constituent fibers on the base material is It is possible to form a fiber layer rich in fibers.

As a result, even if a fiber layer with a low fabric weight and high air permeability is formed, it is possible to peel off the fiber layer from the base material after the heating process, and the peeled fiber layer can be removed with a low fabric weight. It can be obtained as a nonwoven fabric with high air permeability that can be handled independently.

In the present invention, various configurations can be selected as appropriate, for example, the following configurations. The various measurements described in the present invention were performed under atmospheric pressure unless otherwise specified. Further, measurements were conducted under a temperature condition of 25°C. Unless otherwise specified, various measurement results described in the present invention were obtained by measurement to a value one digit smaller than the desired value, and the obtained value was calculated by rounding off the value. As a specific example, if the desired value is to the first decimal place, calculate the value to the first decimal place by determining the value to the second decimal place by measurement, and rounding the obtained value to the second decimal place. This value was used as the value to be determined.

Each upper limit value and each lower limit value described below can be arbitrarily combined as desired to define an employable numerical range.

The nonwoven fabric according to the present invention contains short fibers as its constituent fibers, and the short fibers can serve as the skeleton of the nonwoven fabric. The term "short fiber" as used in the present invention does not refer to a fiber in which a plurality of fibers are generated by splitting the fiber in the middle of the fiber, but rather to a fiber having a specific length that has been cut and prepared. Note that fibril fibers and pulp fibers can be exemplified as fibers in which a plurality of fibers are generated by splitting the fibers in the middle of the fibers. Examples of fibers that do not have a specific length and are prepared by cutting include fibers that have a continuous length and are spun using a direct spinning method such as an electrostatic spinning method, a melt blowing method, or a spunbond method. . Note that the short fibers constituting the nonwoven fabric may have crimps.

Examples of short fibers include polyolefin resins (e.g., polyethylene, polypropylene, polymethylpentene, polyolefin resins with a structure in which part of the hydrocarbon is replaced with a cyano group or a halogen such as fluorine or chlorine), styrene resin, and polyvinyl. Alcohol-based resins, polyether-based resins (e.g., polyetheretherketone, polyacetal, modified polyphenylene ether, aromatic polyetherketone, etc.), polyester-based resins (e.g., polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene terephthalate, etc.) phthalate, polybutylene naphthalate, polycarbonate, polyarylate, fully aromatic polyester resin, etc.), polyimide resin, polyamideimide resin, polyamide resin (e.g. aromatic polyamide resin, aromatic polyetheramide resin, nylon resin, etc.) , resins with nitrile groups (e.g. polyacrylonitrile, etc.), urethane resins, epoxy resins, polysulfone resins (e.g. polysulfone, polyethersulfone, etc.), fluorine resins (e.g. polytetrafluoroethylene, polyfluorinated resins) vinylidene, etc.), cellulose resins, polybenzimidazole resins, acrylic resins (e.g. polyacrylonitrile resins copolymerized with acrylic esters or methacrylic esters, modacrylic resins copolymerized with acrylonitrile and vinyl chloride or vinylidene chloride) etc.), etc., and can be constructed using known resins. In particular, it is preferable that the short fibers be made of polyolefin resin, so that nonwoven fabrics with excellent chemical resistance (acid resistance, alkali resistance, organic solvent resistance, etc.) can be used for various industrial purposes. .

Note that these resins may be made of either a linear polymer or a branched polymer, and the resin may be a block copolymer or a random copolymer. However, there is no particular limitation. Furthermore, a mixture of multi-component resins may be used.

The short fibers may be made of one type of resin or may be made of multiple types of resin. Short fibers composed of multiple types of resins are generally referred to as composite fibers, such as core-sheath type, sea-island type, side-by-side type, orange type, bimetallic type, etc. can.

When the short fibers are heat-fusible fibers, it is preferable to heat-fuse the constituent fibers of the nonwoven fabric to provide a highly strong nonwoven fabric even if it has a structure with a low basis weight and high air permeability. Therefore, it is preferable that the nonwoven fabric contains heat-fusible short fibers as constituent fibers, and more preferably, the constituent fibers of the non-woven fabric are only heat-fusible short fibers. Such thermally fusible short fibers may be of a fully fused type or may be of a partially fused type such as the above-mentioned composite fibers. However, since the fiber shape can be maintained even after heat fusion, and strength and morphological stability can be further imparted to the nonwoven fabric, heat-fusible short fibers are core-sheath type fibers that have a region with a higher melting point than the heat-fusion component. A partially fused type, such as a side-by-side type or a side-by-side type, is preferable. In particular, by adopting core-sheath type heat-fusible short fibers (core-sheath type adhesive short fibers, especially core-sheath type adhesive short fibers whose sheath portion is made of polyolefin resin), the constituent fibers can be bonded by the sheath component. This is preferable because it can provide a nonwoven fabric with high strength that is integrated at the intersection points. Moreover, by employing core-sheath type adhesive short fibers, it is possible to provide a particle-carrying sheet in which particles are supported on the sheath component of the core-sheath type adhesive short fibers constituting the nonwoven fabric. From this point of view, it is preferable that the constituent fibers of the nonwoven fabric are only core-sheath adhesive short fibers (particularly core-sheath adhesive short fibers whose sheath portion is made of a polyolefin resin).

In particular, polyolefin resins are more easily softened than other resins. Therefore, when a nonwoven fabric whose sheath component is a polyolefin resin is composited with solid electrolyte particles, the core-sheath type adhesive short fibers are moderately deformable, so that the solid electrolyte particles This is preferable because it can provide a nonwoven fabric that easily retains particles such as.

Furthermore, the short fibers may be fibers with irregular cross sections, in addition to fibers with substantially circular cross sections or oval fibers. In addition, the irregular cross-section fibers include hollow shapes, polygonal shapes such as triangular shapes, alphabetic character shapes such as Y-shapes, symbol-type shapes such as irregular shapes, multilobed shapes, and asterisk shapes, or multiple shapes of these shapes. It may also be short fibers having a fiber cross section such as a bonded shape.

The fineness, fiber diameter, and fiber length of the short fibers are not particularly limited and can be adjusted as appropriate. The fineness can be 10 dtex or less, 5 dtex or less, and 1 dtex or less. Although the lower limit of the fineness is adjusted as appropriate, it is realistically 0.01 dtex or more. Although the fiber diameter of the short fibers can be adjusted as appropriate, it can be from 0.1 to 30 μm, from 3 to 20 μm, and from 5 to 15 μm. In particular, by using short fibers with a fiber diameter of 7 μm or more (particularly core-sheath adhesive short fibers), it is possible to provide a nonwoven fabric with high strength even if it has a structure with a low basis weight and high air permeability. From this point of view, it is preferable that the constituent fibers of the nonwoven fabric are only core-sheath type adhesive short fibers having a fiber diameter of 7 μm or more (particularly core-sheath type adhesive short fibers made of polyolefin resin).

Further, when the nonwoven fabric contains core-sheath adhesive short fibers having a fiber diameter of 7 μm or more as constituent fibers, the number of constituent fibers can be reduced in the nonwoven fabric with the same basis weight. As a result, the number of portions having small pores is reduced, so that solid electrolyte particles and the like can easily enter the inside, and a nonwoven fabric having a structure with fewer defects and voids after filling can be provided, which is preferable.

The fiber length can be from 0.1 to 20 mm, from 0.5 to 15 mm, from 1 to 10 mm. Note that "fiber length" refers to a value measured according to JIS L1015 (2010), 8.4.1c) direct method (C method).

The Young's modulus of the short fibers can be adjusted as appropriate. However, in order to prevent the fibers from being too crushed during particle filling and making it difficult to provide a low-resistance solid electrolyte membrane, it is preferable to use short fibers with a Young's modulus of 10 cN/dtex (decitex) or more, and 20 cN/dtex (decitex) or more. It is preferable to use short fibers with a diameter of 30 cN/dtex (decitex) or more, and it is preferable to use short fibers with a diameter of 40 cN/dtex (decitex) or more. Although the upper limit of Young's modulus is not particularly limited, 100 cN/dtex or less is realistic, 90 cN/dtex or less is realistic, and 80 cN/dtex or less is realistic.

The tensile strength of the short fibers can be adjusted as appropriate. However, even if the structure has a low basis weight and high air permeability, short fibers with a tensile strength of 4.5 cN/dtex (decitex) or more are used to provide a nonwoven fabric made of short fibers that is strong enough to be handled independently. It is preferable to adopt it. More preferably, the tensile strength is 5.0 cN/dtex or more. Although the upper limit of the tensile strength is not particularly limited, it is realistically 50 cN/dtex or less. "Tensile strength" in the present invention refers to a value measured according to JIS L1015 (chemical fiber short test method, constant speed tension type).

Further, it is preferable that the nonwoven fabric contains, as short fibers, partially fused heat-fusible fibers having the tensile strength (in particular, core-sheath type adhesive short fibers made of polyolefin resin). Because the constituent fibers of the nonwoven fabric are bonded and integrated with each other by the partially fused heat-fusible fibers with the tensile strength, even if the structure has a low basis weight and high air permeability, it can be handled independently. This is preferable because it can provide a nonwoven fabric with high strength. From this point of view, it is preferable that the constituent fibers of the nonwoven fabric are only partially fused heat-fusible fibers (particularly core-sheath adhesive short fibers whose sheath portion is made of polyolefin resin) having the tensile strength. . In particular, it is preferable that the constituent fibers of the nonwoven fabric are only core-sheath adhesive short fibers in which the core and sheath portions having the tensile strength are made of a polyolefin resin.

The nonwoven fabric according to the present invention is composed of short fibers aggregated together. Such nonwoven fabrics can be produced, for example, by a dry method in which fibers containing short fibers are fed to a carding device or an airlay device to entangle the fibers, or by dispersing fibers containing short fibers in a dispersion medium and forming them into a sheet shape. It can be prepared from a fibrous web prepared by a wet raising method or the like.

A nonwoven fabric can be prepared by entangling and/or integrating the fibers of a fibrous web. One method is to subject the fibrous web to heat treatment, thereby bonding and integrating the constituent fibers with a heat-fusible component (for example, a heat-fusible component of heat-fusible fibers) contained in the constituent fibers of the fibrous web. In addition to integrating the constituent fibers with a binder resin, for example, a method of entangling them with a needle or a water stream may be used.

The method of heat treatment can be selected as appropriate, but for example, heating with a roll or heating and pressurizing, heating by applying to a heating device such as an oven dryer, far infrared heater, dry heat dryer, hot air dryer, etc., and heating using infrared rays under no pressure. A method of heating the contained resin by irradiating the resin can be used.

The thickness of the nonwoven fabric can be adjusted as appropriate. The thickness can be from 3 to 60 μm, from 5 to 50 μm, from 7 to 40 μm. In the present invention, the thickness refers to the length in the vertical direction when a compressive load of 160 KPa is applied in the direction perpendicular to the main surface.

The nonwoven fabric according to the present invention is characterized by a basis weight of less than 5 g/m ² . Its basis weight can be 4.4 g/m ² or less, 4.0 g/m ² or less, 3.5 g/m ² or less, 3.0 g/m ² or less It can be less than or equal to 2.5 g/m ² , less than or equal to 2.0 g/m ² , and less than or equal to 1.5 g/m ² . Although the lower limit value is heavier than 0 g/m ² and can be adjusted as appropriate, it is realistic to be 1.0 g/m ² or more. In the present invention, the basis weight refers to the mass per 1 m ² of the surface (principal surface) having the widest area of the object to be measured.

The nonwoven fabric according to the present invention is characterized in that its air permeability is higher than 1000 cm ³ /cm ² /s. The air permeability can be 1100 cm ³ /cm ² /s or more, 1200 cm ³ /cm ² /s or more, 1300 cm ³ /cm ² /s or more, 1400 cm ³ /cm ² /s or more, and 1440 cm ³ /cm ² /s or more. Although the upper limit value can be adjusted as appropriate, it is realistically 10000 cm ³ /cm ² /s or less.

In the present invention, air permeability refers to a value measured by a method specified in JIS L1096:2010 (8.(26).1 A method (Fragir method)). In addition, when measuring the air permeability of the measurement object using this method, if the air permeability is too high and the air permeability cannot be measured, measure the air permeability of a sample made by laminating a specific number of measurement objects, and By integrating the number of laminated sheets of the measurement object constituting the sample to the air permeability value, the air permeability of the measurement object per sheet is obtained. As a specific example, if the air permeability of a stack of four nonwoven fabrics is 360 cm ³ /cm ² /s, the air permeability of one nonwoven fabric is considered to be 1440 cm ³ /cm ² /s.

The porosity of the nonwoven fabric is adjusted as appropriate to realize a nonwoven fabric having the air permeability according to the present invention, but the higher the porosity (unit: %) of the nonwoven fabric, the more the air permeability specified by the present invention is satisfied. Therefore, the porosity thereof is preferably higher than 60%, preferably 70% or more, and preferably 80% or more. Although the upper limit is adjusted as appropriate, it is preferably 98% or less, and preferably 95% or less so that the nonwoven fabric has high strength. Note that "porosity" refers to a value obtained by the following formula.
P=[1-M/(T×d)]×100
Here, M is the basis weight (unit: g/m ² ) of the object to be measured such as nonwoven fabric or fiber web, T is the thickness (unit: μm) of the object to be measured, and d is the average density (unit: μm) of the various organic resins that make up the object to be measured ( Unit: g/cm ³ ).

Further, the apparent density (g/cm ³ ) of the nonwoven fabric can be calculated by dividing the basis weight (g/m ² ) of the nonwoven fabric by the thickness (μm) of the nonwoven fabric. The lower limit of the apparent density (g/cm ³ ) of the nonwoven fabric can be adjusted as appropriate, but it is preferably 0.08 (g/cm ³ ) or more, and 0.09 to provide a highly breathable nonwoven fabric. (g/cm ³ ) or more, preferably 0.1 (g/cm ³ ) or more. Further, the upper limit of the apparent density (g/cm ³ ) of the nonwoven fabric can be adjusted as appropriate, but it is preferably 0.70 (g/cm 3 ) or less, and 0.70 (g/cm ³ ) or less so as to provide a nonwoven fabric with high strength. It is preferably 50 (g/cm ³ ) or less, and preferably 0.40 (g/cm ³ ) or less.

The tensile strength (unit: N/50 mm) and tensile elongation (unit: %) of the nonwoven fabric are preferably adjusted as appropriate so that a nonwoven fabric that can be handled independently can be realized. The tensile strength is preferably 1 N/50 mm or more, and preferably 3 N/50 mm or more. Further, the tensile elongation is preferably 1% or more, preferably 3% or more, preferably 6% or more, and preferably 7% or more.

The "tensile strength" and "tensile elongation" can be measured by subjecting the measurement target to the method described below.
(1) A test piece (shape: rectangular, length: 200 mm, width: 50 mm) was collected from the measurement object so that the machine direction (flow direction during manufacturing, referred to as MD) and the length direction matched. .
(2) The sampled test piece was subjected to a constant speed extension type tensile testing machine (manufactured by Orientec, Tensilon, initial grip interval: 100 mm, tensile speed: 300 mm/min), and the sample piece was pulled until it broke. The tensile strength (N/50mm) in the MD direction was determined from the strength.
(3) By substituting the length of the gripping interval (mm) at the maximum load of the measured specimen when the specimen is pulled until it breaks into the following formula, the tensile elongation of the specimen in the MD direction is calculated. The degree (%) was calculated.
a={(b-c)/c}×100
a: Tensile elongation (%)
b: Grasp interval at maximum load (mm)
c: Initial grip interval (100mm)

In addition, a test piece (shape: rectangular, length: 200 mm, width: 50 mm) was taken from the measurement object so that the direction perpendicular to the machine direction (referred to as CMD) coincides with the length direction, as described above. By subjecting it to the steps (2) and (3), the tensile strength (N/50 mm) and tensile elongation (%) in the CMD direction can be obtained.

In addition to the particles according to the present invention, the nonwoven fabric contains additives such as flame retardants, fragrances, pigments, antibacterial agents, antifungal materials, photocatalyst particles, emulsifiers, dispersants, surfactants, and thickeners. It's okay. The additive may be provided by being kneaded into the constituent fibers of the nonwoven fabric, or may be provided by being provided with a binder containing the additive.

The nonwoven fabric according to the present invention can support particles between the constituent fibers of the nonwoven fabric and on the surface of the constituent fibers. The type of particles and the amount of particles supported are appropriately adjusted depending on the use of the particle-supporting sheet formed by supporting particles on a nonwoven fabric. As the particles, for example, graphite, ion exchange resin, solid electrolyte particles, solid polymer electrolyte, inorganic particles, metal particles, polymer particles, etc. can be employed.
By using the nonwoven fabric according to the present invention, it is possible to provide a particle-supporting sheet in which particles are supported on the nonwoven fabric in an intended manner, such as being able to support a large amount of particles between the constituent fibers of the nonwoven fabric and on the surface of the constituent fibers. In particular, by employing solid electrolyte particles as particles, it is possible to provide a solid electrolyte sheet in which solid electrolyte particles are supported on a nonwoven fabric.

Next, a method for manufacturing a nonwoven fabric according to the present invention will be explained. It should be noted that explanation of the points having the same configuration as the above-mentioned items will be omitted. Although the method for manufacturing the nonwoven fabric according to the present invention can be selected as appropriate, as an example,
Process (1) Core-sheath type adhesive short fibers as short fibers (core part: higher softening temperature or melting point than the resin contained in the sheath part, sheath part: higher softening temperature or melting point than the resin contained in the core part) A process of preparing a dispersion liquid by dispersing it in a dispersion medium,
Step (2) A separately prepared base material is laid on the paper-making mesh, and the core-sheath type adhesive short fibers contained in the dispersion are drawn up on the main surface of the base material. a step of forming a laminate having a fiber layer formed by aggregation of core-sheath adhesive staple fibers on top;
Step (3) removing the dispersion medium contained in the laminate;
Step (4) The laminate is subjected to a heating device to soften or melt the sheath component of the core-sheath adhesive short fibers contained in the fiber layer, and after bonding and integrating the constituent fibers of the fiber layer, the laminate is left to cool. and/or a cooling step;
Step (5) Peeling off the fiber layer formed by the core-sheath type adhesive short fibers bonded to the fibers from the laminate after being subjected to a heating device and cooled, and obtaining the peeled fiber layer as a nonwoven fabric;
It can be a method for manufacturing a nonwoven fabric, comprising:

The applicant of the present application can provide a nonwoven fabric according to the present invention having a basis weight of less than 5 g/m ² and an air permeability higher than 1000 cm ³ /cm ² /s by employing a method for manufacturing a nonwoven fabric comprising the steps described above. This is what we discovered. In addition, as long as the manufacturing method disclosed in Patent Document 1 is adopted, that is, steps (3) to 1 of the present invention, in which the constituent fibers of the fibrous layer are fiber-adhered on the base material and then peeled off from the base material to obtain a nonwoven fabric. As long as a method for manufacturing a nonwoven fabric that does not include step (5) is adopted, even if an attempt is made to manufacture a nonwoven fabric according to the present invention, the nonwoven fabric will be damaged in the manufacturing process, making it impossible to manufacture a nonwoven fabric that can be handled independently.

Step (1) will be explained.
The type of dispersion medium for dispersing short fibers can be adjusted as appropriate, and water etc. can be used.Although the dispersion medium may contain additives such as surfactants and adhesives, In order to manufacture a nonwoven fabric in which short fibers aggregate to form a sheet shape, the dispersion medium can be one that does not contain any additives other than the short fibers, and a surfactant or adhesive is blended. You can use white water. Note that the amount of short fibers to be dispersed in the dispersion medium is adjusted as appropriate.

Step (2) will be explained.
The type of base material to be prepared can be selected as appropriate, such as a papermaking mesh provided in the papermaking apparatus, a separately prepared mesh, a woven fabric, a nonwoven fabric (such as a PET nonwoven fabric), etc. Note that the base material used should preferably have water permeability. It is preferable to use a nonwoven fabric having a pore diameter smaller than the fiber length of short fibers contained in the dispersion medium as the base material so that fibers can be efficiently drawn onto the base material.

Usable resins include, for example, polyolefin resins (e.g., polyethylene, polypropylene, polymethylpentene, polyolefin resins with a structure in which part of the hydrocarbon is replaced with a cyano group or a halogen such as fluorine or chlorine), styrene resins, etc. , polyvinyl alcohol resin, polyether resin (e.g., polyetheretherketone, polyacetal, modified polyphenylene ether, aromatic polyetherketone, etc.), polyester resin (e.g., polyethylene terephthalate (PET), polytrimethylene terephthalate, polyester resin) butylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polycarbonate, polyarylate, fully aromatic polyester resin, etc.), polyimide resin, polyamideimide resin, polyamide resin (e.g. aromatic polyamide resin, aromatic polyetheramide resin) , nylon resin, etc.), resins with nitrile groups (e.g., polyacrylonitrile, etc.), urethane resins, epoxy resins, polysulfone resins (e.g., polysulfone, polyethersulfone, etc.), fluorine resins (e.g., polytetra fluoroethylene, polyvinylidene fluoride, etc.), cellulose resins, polybenzimidazole resins, acrylic resins (for example, polyacrylonitrile resins copolymerized with acrylic esters or methacrylic esters, copolymerized acrylonitrile with vinyl chloride or vinylidene chloride) It can be constructed using a known resin such as a polymerized modacrylic resin.

Regarding the composition of the base material, it is preferable to use a material that has a melting point higher than the heat bonding temperature of the short fibers and is difficult to bond to the heat bonding resin so that the fiber layer made of core-sheath adhesive short fibers can be easily peeled off. In addition, appropriate adjustments are made so that the fiber layer made of core-sheath adhesive short fibers can be easily peeled off from the base material. As an example, by subjecting a fiber web containing undrawn fibers to a thermocompression bonding process, a nonwoven fabric in which the component fibers are thermocompression bonded without melting can be employed. Furthermore, in order to prevent the binder from unintentionally adhering to the fiber layer, instead of using a base material in which the constituent fibers are bonded with a binder, the constituent fibers are bonded to each other by fiber adhesion or thermocompression bonding. Preferably, a base material is used. Then, it is preferable to use a base material with a strength of 5 N/5 cm or more so that the base material is not damaged when peeling off the fiber layer made of core-sheath adhesive short fibers from the base material.

As a specific example of the above-mentioned base material, a PET nonwoven fabric prepared by subjecting a fibrous web containing unstretched PET fibers to a thermocompression bonding process can be employed.

In addition, a wet-laid nonwoven fabric is used as the base material in order to prevent the inability to obtain the nonwoven fabric of the present invention due to nonuniform fiber distribution of the base material, which would result in nonuniform fiber distribution of the fiber layer. is preferable. Further, the air permeability of the nonwoven fabric used as the base material is preferably 200 cm ³ /cm ² /s or less. Wet-type PET nonwoven fabric is preferred as one that satisfies the above-mentioned viewpoints.

In addition, in order to be able to pick up the short fibers contained in the dispersion onto the main surface of a separately prepared base material, on the main surface of the base material opposite to the side from which the short fibers are collected, A suction device may be provided to remove the dispersion medium by suction.
The amount of the dispersion liquid to be scooped onto the main surface of a separately prepared base material is appropriately adjusted so that a nonwoven fabric having a basis weight of less than 5 g/m ² can be manufactured.

Step (3) will be explained.
The method for removing the dispersion medium contained in the laminate can be selected as appropriate. For example, heating the dispersion medium in a heating device such as an oven dryer, far infrared heater, dry heat dryer, or hot air dryer, under a room temperature atmosphere or under a reduced pressure atmosphere. The dispersion medium can be evaporated and removed by allowing it to stand still. The heating temperature when removing the dispersion medium is a temperature at which the dispersion medium can volatilize, and the upper limit of the heating temperature is adjusted (e.g. , the temperature is adjusted to below the softening temperature or melting point of the resin contained in the sheath).

Step (4) will be explained.
As the heating device, the heating device mentioned in step (3) can be employed. The heating temperature is a temperature that softens or melts the sheath component of the core-sheath type adhesive short fibers and allows the constituent fibers of the fiber layer to be bonded and integrated, and also to prevent unintended changes in the shape or function of the members constituting the nonwoven fabric. Adjust the upper limit of heating temperature so that it does not drop. As a specific example, the heating temperature is preferably in a temperature range of 50° C. or lower, and preferably 30° C. or lower, from the softening temperature or melting point of the resin to be softened or melted.

After heating, the laminate is allowed to cool by being left in a room temperature atmosphere, or is cooled by using a cooling device. By cooling, it is possible to produce a nonwoven fabric in which the short fibers are aggregated together and are integrally bonded to each other.

Step (5) will be explained.
By peeling off the fiber layer made of core-sheath type adhesive short fibers from the laminate after being cooled in a heating device, the peeled fiber layer can be made into a nonwoven fabric.

The nonwoven fabric according to the present invention can be manufactured by the above manufacturing method.

In addition, when the nonwoven fabric contains polyolefin resin fibers (such as core-sheath adhesive short fibers whose sheath portion is made of polyolefin resin) as short fibers, the nonwoven fabric can be suitably used as a support for a solid electrolyte. However, in order to efficiently produce a nonwoven fabric comprising short fibers of polyolefin resin, an activator may be added to the white water that is applied to the short fibers and is skimmed onto the base material. At this time, in the method for manufacturing a nonwoven fabric according to the prior art, the surface of the short fibers becomes slippery, making it impossible to manufacture a nonwoven fabric that satisfies the configuration of the present invention. However, by employing the nonwoven fabric manufacturing method according to the present invention, a nonwoven fabric that satisfies the configuration of the present invention can be manufactured even under the above-mentioned conditions.

The method for manufacturing the nonwoven fabric described above involves various secondary processes, such as the process of laminating other structural members such as porous bodies, films, and foams, and the process of processing by punching out shapes according to the purpose and usage mode. You may prepare. The nonwoven fabric may also be subjected to various secondary processes such as a calendering process to adjust various physical properties such as thickness and surface smoothness.

A particle-supporting sheet can be manufactured by supporting particles on the nonwoven fabric manufactured as described above. The method of supporting the particles on the nonwoven fabric can be adjusted as appropriate, but there are several methods: by simply adhering the particles to the nonwoven fabric, by adhering and fixing the particles to the nonwoven fabric with a binder, and by attaching the particles to the constituent fibers of the nonwoven fabric. The resin constituting the surface of the constituent fibers (for example, the resin constituting the sheath portion of core-sheath adhesive short fibers) is heated in a state of contact, and the particles are bonded to the surface of the constituent fibers using the melted resin. A method in which heated particles are brought into contact with the constituent fibers of a nonwoven fabric to melt the resin constituting the surface of the constituent fibers, and a method in which the particles are fixed to the surface of the constituent fibers by the melted resin can be adopted.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but these are not intended to limit the scope of the present invention.

(Short fiber used)
The core is made of polypropylene with a melting point of 168°C, and the sheath is made of high-density polyethylene with a melting point of 135°C, and the ratio of the area of the core to the area of the sheath in the fiber cross section is 60%:40%. Fiber A (fineness: 0.8 dtex, fiber diameter: 11 μm, fiber length: 5 mm, tensile strength: 6 cN/dtex, Young's modulus: 40 cN/dtex) was prepared.
In addition, the core is made of polypropylene with a melting point of 168°C and the sheath is made of high-density polyethylene with a melting point of 135°C, and the core-sheath type has a ratio of core area to sheath area in the fiber cross section of 60%:40%. Adhesive short fibers B (fineness: 0.4 dtex, fiber diameter: 7 μm, fiber length: 5 mm, tensile strength: 6 cN/dtex, Young's modulus: 77 cN/dtex) were prepared.

(Comparative example 1)
A dispersion liquid in which core-sheath type adhesive short fibers A were dispersed in water containing an activator was prepared. Then, the core-sheath adhesive short fibers A contained in the dispersion were directly formed on the main surface of a papermaking mesh of a 200 mm x 250 mm rectangular paper machine. As a result, a laminate including a fiber layer made of core-sheath type adhesive short fibers A was formed on the paper-making mesh. At this time, the amount of papering was adjusted so that the basis weight of the fiber layer was 4.0 g/m ² when dry.
Then, an attempt was made to prepare a nonwoven fabric by peeling the fiber layer from the laminate. However, since the fiber layer was damaged in the process, it was not possible to obtain a single nonwoven fabric.

(Example 1)
A dispersion liquid in which core-sheath type adhesive short fibers A were dispersed in water containing an activator was prepared. A wet PET nonwoven fabric (fabric weight: 6 g/m ² , thickness : 10 μm, air permeability 140 cm ³ /cm ² /s, hereinafter abbreviated as wet PET nonwoven fabric), and the core-sheath type adhesive short fibers A contained in the dispersion were cut out on the main surface of the wet PET nonwoven fabric. Ta. Thereby, a laminate including a fiber layer made of core-sheath type adhesive short fibers A was formed on the wet-processed PET nonwoven fabric. At this time, the amount of papering was adjusted so that the basis weight of the fiber layer was 4.0 g/m ² when dry.
Then, the laminate was taken out from above the papermaking mesh, and the laminate was placed in an oven dryer whose heating temperature was adjusted to 140°C. As a result, the dispersion medium was removed and the sheath component of the core-sheath type adhesive short fibers A was melted, so that the core-sheath type adhesive short fibers A were bonded and integrated. Thereafter, it was cooled by standing to cool.
Then, the fiber layer was peeled off from the top of the wet-processed PET nonwoven fabric to obtain a single nonwoven fabric with a basis weight of 4.0 g/m ² .

(Example 2)
A nonwoven fabric with a basis weight of 2.0 g/m ² was obtained as a single piece in the same manner as in Example 1, except that the amount of papering was adjusted so that the fiber layer had a basis weight of 2.0 g/m ² when dry. .

(Examples 3 to 5)
A dispersion liquid in which core-sheath adhesive short fibers B were dispersed in water containing an activator was prepared. Then, a separately prepared wet PET nonwoven fabric (fabric weight: 6 g/m ² , thickness: 10 μm) was spread on the papermaking mesh of a 200 mm x 250 mm rectangular paper machine, and the dispersion was placed on the main surface of the wet PET nonwoven fabric. The core-sheath type adhesive short fibers B contained in the above were prepared. As a result, a laminate including a fiber layer made of core-sheath adhesive short fibers B was formed on the wet-processed PET nonwoven fabric. At this time, in Example 3, the amount of papering was adjusted so that the basis weight of the fibrous layer was 1.5 g/m ² when dry, and in Example 4, the basis weight of the fibrous layer was 2.0 g/m ² when dry. In Example 5, the amount of papering was adjusted so that the dry weight of the fiber layer was 3.0 g/m ² .
Then, the laminate was taken out from above the papermaking mesh, and the laminate was placed in an oven dryer whose heating temperature was adjusted to 140°C. As a result, the dispersion medium was removed and the sheath component of the core-sheath type adhesive short fibers B was melted, so that the core-sheath type adhesive short fibers B were bonded and integrated. Thereafter, it was cooled by standing to cool.
Then, the fiber layer was peeled off from the wet-processed PET nonwoven fabric. In Example 3, a nonwoven fabric with a fabric weight of 1.5 g/m ² was obtained, in Example 4 a nonwoven fabric with a fabric weight of 2.0 g/m ² was obtained, and in Example 5, a nonwoven fabric with a fabric weight of 3.5 g/m 2 was obtained. A nonwoven fabric of 0 g/m ² was obtained individually.

Table 1 summarizes the physical properties of each nonwoven fabric produced as described above. In addition, "-" is written in the table for items that could not be measured because the nonwoven fabric could not be manufactured.

When the short fibers are directly formed on the main surface of the papermaking mesh using the nonwoven fabric manufacturing method according to Patent Document 1 as in Comparative Example 1, the short fibers are formed directly on the main surface of the papermaking mesh. When the basis weight of the nonwoven fabric was lowered to less than 5 g/m ² , it was impossible to produce a nonwoven fabric in a manner that it could be handled alone.

On the other hand, in Examples 1 to ⁵ , a nonwoven fabric (especially a nonwoven fabric with ^an air permeability of ¹⁴⁴⁰ cm ³ /cm ² /s or more) in a manner that can be handled alone.

The nonwoven fabric according to the present invention can be used in various industrial applications, such as separators and separator support members for electrochemical devices such as capacitors and primary/secondary batteries, particle support materials in sheets on which particles are supported, prepregs, and gas filters. medical applications such as liquid filters, adhesive medicinal base materials and masks, cushioning materials and sealing materials, liquid absorbing materials, interior skin materials, cell culture substrates and cell separation materials, conductive materials and insulating materials, heat dissipation materials and heat retention. It can be used as clothing materials such as interlining and batting, or as liquid separation membranes, gas separation membranes, medical materials, ion exchange membranes, dialysis membranes, water electrolyte membranes, polymer electrolyte membranes for fuel cells, solid electrolyte sheets, etc. Can be used as a support.

Claims (7)

A nonwoven fabric whose constituent fibers are short fibers,
The constituent fibers are bonded to each other,
The basis weight is less than 5 g/m ² and the air permeability is higher than 1000 cm ³ /cm ² /s.
Non-woven fabric. The nonwoven fabric according to claim 1, having an air permeability of 1440 cm ³ /cm ² /s or more. The nonwoven fabric according to claim 2, wherein the constituent fibers include core-sheath adhesive short fibers having a fiber diameter of 7 μm or more. The nonwoven fabric according to claim 3, wherein the constituent fibers are only core-sheath adhesive short fibers with a fiber diameter of 7 μm or more. The nonwoven fabric according to claim 4, wherein the sheath component of the core-sheath adhesive staple fiber is a polyolefin resin. A solid electrolyte sheet comprising solid electrolyte particles supported on the nonwoven fabric according to any one of claims 1 to 5. A method for manufacturing a nonwoven fabric, the method comprising:
Step (1) preparing a dispersion liquid in which short fibers are dispersed;
Step (2) preparing a base material;
Step (3) forming a laminate having a fiber layer containing the short fibers on the base material by scooping up the dispersion liquid onto the main surface of the base material;
Step (4) removing the dispersion medium contained in the laminate;
Step (5) bonding the constituent fibers of the fiber layer to each other by heating the laminate, and then allowing it to cool and/or cooling it;
Step (6) allowing the fiber layer to cool and/or peeling off the fibrous layer from the cooled laminate and obtaining the peeled fibrous layer as a nonwoven fabric;
A method for manufacturing a nonwoven fabric, comprising: