JP2019060044A - Method of manufacturing wet non-woven fabric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a wet non-woven fabric, which is excellent in uniformity, has no defects, is excellent in coatability, and can obtain a wet non-woven fabric containing fibrillated heat-resistant fibers. To do. SOLUTION: In a method for producing a wet non-woven fabric containing fibrillated heat-resistant fibers, a wet papermaking method using a slurry in which the fibrillated heat-resistant fibers are dispersed in water using a high-speed rotary shear type disperser. It is a method for producing a wet non-woven fabric, which comprises producing a wet non-woven fabric, and more preferably, a high-speed rotary shear type disperser has a ring-shaped blade having fine slits rotating at high speed as a part of the structure. It is a machine. [Selection diagram] None

Description

  The present invention relates to a method for producing a wet non-woven fabric comprising fibrillated heat-resistant fibers.

  As a non-woven fabric having heat resistance, a wet non-woven fabric comprising fibrillated heat-resistant fibers is known. Hereinafter, “wet non-woven fabric containing fibrillated heat-resistant fiber” may be abbreviated as “fibrillated heat-resistant fiber-containing non-woven fabric”. For example, in recent years, applications of lithium ion batteries have been expanded to applications such as electric vehicles in addition to conventional portable devices. In applications such as electric vehicles, large-sized lithium ion batteries are employed as compared to portable devices.

  As a lithium ion battery separator, although the porous film which consists of polyolefins, such as polyethylene or a polypropylene, was used abundantly, the heat resistant separator is used in a large sized lithium ion battery.

  As a heat-resistant separator, an embodiment in which a fibrillated heat-resistant fiber-containing non-woven fabric is used as a separator as it is, a fibrillated heat-resistant fiber-containing non-woven fabric is used as a base material, a porous film comprising the base material, an organic polymer, and porous particles containing inorganic particles. There is known an embodiment in which a film (coated layer) or the like is combined to form a separator.

  In an embodiment in which the fibrillated heat-resistant fiber-containing non-woven fabric is used as a separator as it is, it contains heat-resistant pulp fibers (fibrillated heat-resistant fibers) having a melting point or carbonization temperature of 300 ° C. or more and thermoplastic fibers having a melting point of 200 ° C. or more A separator for a lithium ion secondary battery comprising a non-woven fabric (see, for example, Patent Document 1), containing one or more types of organic fibers (fibrillated heat-resistant fibers) at least partially fibrillated to a fiber diameter of 1 μm or less; A separator for an electrochemical device comprising one or more types of non-fibrillated fibers of 0.5 dtex or less (see, for example, Patent Document 2), melting point or thermal decomposition temperature of 250 ° C. or higher, at least partially A fibrillated polymer having a fiber diameter of 1 μm or less and a weight average fiber length in the range of 0.2 mm to 2 mm (fibrillation A separator for an electrochemical element (see, for example, Patent Document 3) comprising a non-woven fabric containing a heat resistant fiber and an organic fiber having a fineness of 3.3 dtex or less is disclosed.

  A fibrillated heat-resistant fiber-containing non-woven fabric is used as a base material in a mode of combining the base material with a porous film made of an organic polymer, a porous film (painted layer) containing inorganic particles, etc. A wet non-woven fabric (see, for example, Patent Document 4) comprising fibrillated heat-resistant fibers and synthetic short fibers as essential components is disclosed.

  A base material comprising a non-woven fabric containing synthetic resin short fibers and fibrillated lyocell fibers as essential fibers, and the non-woven fabric further comprising fibrillated heat-resistant fibers (see, for example, Patent Document 5), oriented crystallized polyester A non-woven fabric containing 30% by mass or more of fibers and further preferably containing a fibrillated heat-resistant fiber is disclosed (see, for example, Patent Document 6).

  In the substrates disclosed in Patent Documents 1 to 6, fibrillation treatment of fibrillated heat-resistant fibers is disclosed. However, nothing is said about the disaggregation method and dispersion method of the fibrillated heat resistant fiber. In particular, when using as a fibrillated heat-resistant fiber a commercial product in which the medium is removed from a slurry of fibrillated heat-resistant fibers by applying mechanical shear force, the solid content concentration is It has been raised to 20 to 35% by mass, and there has been a problem that powdery unagglomerated matter remains in the ordinary disintegration method and dispersion treatment. When the powdery non-disintegrated material is contained in a wet non-woven fabric, unevenness occurs in thickness, and unevenness in coating layer occurs when it is attempted to provide a coating layer containing inorganic particles, and a separator and an electrode In some cases, there is a problem in that the battery characteristics deteriorate. In addition, in the case of producing a wet non-woven fabric by a wet paper-making method, when wet paper is picked up from a paper-making wire to a wet blanket, there is a problem that powdery unaggregated material is peeled off on the paper-making wire, contact with wet blanket or top blanket In some cases, the problem of peeling off the powdery undegraded material and the problem of peeling off the powdery undegraded material on the surface of the Yankee dryer may occur, and as a result, the micro holes may be opened, resulting in defects. .

JP, 2006-19191, A WO 01/93350 pamphlet Japanese Patent Application Publication No. 2004-146137 JP 2012-3873 A International Publication No. 2011/046066 brochure JP 2012-134024 A

  The subject of the present invention is in view of the above situation, and it is possible to obtain a wet non-woven fabric comprising fibrillated heat-resistant fibers excellent in uniformity, free from defects and excellent in coatability. It is providing a manufacturing method of a wet nonwoven fabric.

  As a result of earnestly researching in order to solve the said subject, the following invention was discovered.

(1) In a method for producing a wet non-woven fabric comprising fibrillated heat-resistant fibers, a wet paper-making method is carried out using a slurry in which the fibrillated heat-resistant fibers are dispersed in water using a high-speed rotary shear type disperser. A method for producing a wet non-woven fabric, comprising producing a wet non-woven fabric.

(2) The method for producing a wet non-woven fabric according to the above (1), wherein the high-speed rotational shear type disperser is a disperser having a ring-shaped blade having fine slits rotating at high speed in a part of its structure.

  According to the method for producing a wet non-woven fabric of the present invention, it is possible to provide a wet non-woven fabric comprising fibrillated heat-resistant fibers excellent in uniformity, free from defects and excellent in coatability.

  The method for producing a wet non-woven fabric according to the present invention is characterized in that a wet non-woven fabric is produced by a wet paper-making method using a slurry in which fibrillated heat-resistant fibers are dispersed in water using a high speed rotary shear type disperser.

  In the present invention, fibrillated heat-resistant fibers are used. As a fibrillated heat-resistant fiber, wholly aromatic polyamide, wholly aromatic polyester, polyimide, polyamide imide, polyetheretherketone, polyphenylene sulfide, polybenzimidazole, poly-p-phenylenebenzobisthiazole, poly-p-phenylenebenzo A fibrillated fiber made of a heat resistant resin such as bisoxazole or polytetrafluoroethylene is used. Among these, wholly aromatic polyamides are preferable because they have high affinity to the electrolyte and are easily fibrillated.

  The fibrillated heat-resistant fiber is a heat-resistant fiber refiner, a beater, a mill, a grinding device, a rotary homogenizer that imparts a shearing force by a high-speed rotary blade, a high-speed rotating cylindrical inner blade and a fixed outer blade. High-speed double-cylindrical high-speed homogenizer that generates shear force, ultrasonic shredder by ultrasonic impact, giving a pressure difference of at least 21MPa to the fiber suspension and passing it through a small-diameter orifice to achieve high speed This can be obtained by processing it using a high pressure homogenizer or the like which applies a shear force and a cutting force to the fibers by making them collide and rapidly decelerate.

  The slurry concentration of the above fibrillated heat-resistant fiber is often 0.001% by mass to 2% by mass, and from the viewpoint of transportation, the medium is removed from the slurry to increase the concentration, and There is something to do. As a method of removing the medium, drainage treatment, for example, filtration, squeezing, centrifugation, etc., drying treatment or a combination thereof can be mentioned.

  When the concentration is increased as described above and a powdery granular composition is prepared, the fibrillated heat-resistant fibers are entangled with each other and heat-hardened into a powdery particulate state. Even if it is in the form of powder, even if it is dispersed in water for a long time, the powder can not be dispersed, and when a wet non-woven fabric is produced by a wet paper machine, it becomes a big disadvantage and impairs the uniformity of the wet non-woven fabric. In the case of combining a wet non-woven fabric, a porous film made of an organic polymer, a porous film (coated layer) containing inorganic particles, etc., coating layer unevenness, uncoated parts, voids, etc. may occur. It may be seriously impaired.

  In the present invention, in the case of producing a wet non-woven fabric, a slurry is used in which fibrillated heat-resistant fibers are dispersed in water using a high-speed rotational shear type disperser. In the present invention, the “high-speed rotational shear type disperser” refers to a slurry containing fibrillated heat-resistant fibers being passed between a rotor having a dispersing blade and rotating with a dispersing blade and a stator having the dispersing blade, The fibrillated heat-resistant fibers are dispersed by applying a shear force to the fibers. As a specific apparatus, a single disc refiner, a double disc refiner, a conical refiner and the like can be mentioned.

  Furthermore, in order to obtain a slurry in which powdery undivided material of fibrillated heat-resistant fibers is dispersed uniformly and efficiently, a high-speed rotary shear type disperser is a ring-shaped cutter having fine slits rotating at high speed. It is effective to be a high-speed rotary shear disperser which has a part of the structure. In a high-speed rotary shear disperser having a ring-shaped blade having a fine slit rotating at a high speed in a part of the structure, a hydrodynamic shock wave generated between the slits is a powdery unagglomerated substance of fibrillated heat-resistant fiber Act effectively. As a specific apparatus, Topfiner (made by Aikawa Iron Works), VF pump (made by Niihama Pump Mfg. Co., Ltd.), Milder (made by Pacific Kiko), etc. may be mentioned.

  When obtaining a slurry in which powdery undivided material of fibrillated heat-resistant fibers is dispersed using the above-mentioned disperser, the slurry concentration, the processing time, the number of revolutions of the disperser rotor, the clearance between the stator and the rotor By adjusting etc., the dispersibility of the fibrillated heat-resistant fiber can be suitably adjusted.

  In the present invention, the wet non-woven fabric may contain fibers other than fibrillated heat-resistant fibers. Examples of fibers other than fibrillated heat-resistant fibers include synthetic resin short fibers, cellulose fibers, pulps and fibrils of cellulose fibers, fibrids made of synthetic resins, pulps made of synthetic resins, and inorganic fibers.

  As synthetic resin short fibers, polyolefin, polyester, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyamide, acrylic, polyvinyl chloride, polyvinylidene chloride, polyvinyl ether, polyvinyl ketone, polyether, polyvinyl alcohol, diene, polyurethane Non-fibrillated staple fibers made of synthetic resins such as phenol, melamine, furan, urea, aniline, unsaturated polyester, fluorine, silicone and their derivatives. Examples of inorganic fibers include glass, alumina, silica, ceramics, rock wool and the like. The cellulose fiber may be either natural cellulose or regenerated cellulose. By containing fibers other than fibrillated heat-resistant fibers, the tensile strength and piercing strength of the wet non-woven fabric are enhanced.

  The synthetic resin staple fiber may be a fiber (single fiber) made of a single resin, or a composite fiber made of two or more resins. The synthetic resin staple fibers contained in the wet-laid nonwoven fabric of the present invention may be used alone or in combination of two or more. As the composite fiber, core-sheath type, eccentric type, side-by-side type, sea-island type, orange type, multiple bimetal type can be mentioned.

  0.01 dtex or more and 0.6 dtex or less are preferable, and, as for the fineness of the fiber used for a wet nonwoven fabric, 0.02 dtex or more and 0.3 dtex or less are more preferable. When the fineness of the fibers used for the wet non-woven fabric exceeds 0.6 dtex, the number of fibers in the thickness direction decreases, so the pore size distribution of the wet non-woven fabric becomes wide. In addition, it becomes difficult to reduce the thickness, and the strength characteristics are easily deteriorated. When the fineness of the fibers used for the wet non-woven fabric is less than 0.01 dtex, the fibers become very expensive, making stable production of the fibers difficult, or when producing a wet non-woven fabric by the wet papermaking method, the dewatering property decreases. There is a case.

  As fiber length of the fiber used for a wet nonwoven fabric, 1 mm or more and 10 mm or less are preferable, and 1 mm or more and 5 mm or less are more preferable. If the fiber length exceeds 10 mm, it may cause formation failure. On the other hand, when the fiber length is less than 1 mm, the mechanical strength of the wet non-woven fabric is lowered, and the wet non-woven fabric may be broken when forming the coated layer.

  The wet nonwoven fabric of the present invention is produced by a wet papermaking method. In the wet papermaking method, first, the fibrillated heat-resistant fiber and, if necessary, the other fibers to be used in combination are uniformly mixed and dispersed in water to form a slurry, and then through steps such as screen (removing foreign matter, lumps, etc.) The final fiber concentration is adjusted to 0.01 to 0.50% by mass to obtain a slurry. The slurry is milled with a paper machine to obtain a wet paper. In order to make the dispersibility of the fibers uniform, chemicals such as dispersants, antifoaming agents, hydrophilic agents, polymeric tackifiers, and mold release agents may be added in the process.

  As the paper making machine, for example, a paper making machine using a single paper making machine such as a long wire, circular wire, inclined wire, etc., a combination paper making machine etc. in which two or more paper making networks of the same or different kinds are installed online be able to. When the wet non-woven fabric has a multi-layered structure of two or more layers, a method of laminating wet paper webs produced by each paper machine, or one of the layers is formed, and then fibers are placed on the layer. A wet non-woven fabric can be produced by a casting method in which the dispersed slurry is cast to form a laminate. When the slurry in which the fibers are dispersed is cast, the layer previously formed may be in a wet paper state or in a dry state. In addition, two or more dried layers can be heat-sealed to form a multi-layer wet nonwoven fabric.

  In the present invention, when the wet nonwoven fabric has a multilayer structure, it may have a multilayer structure in which the fiber composition of each layer is the same, or may have a multilayer structure in which the fiber composition of each layer is different. In the case of a multilayer structure, the fiber concentration of the slurry can be lowered by lowering the basis weight of each layer, so that the formation of the wet nonwoven fabric is improved, and as a result, the uniformity of the formation of the wet nonwoven fabric is improved. Moreover, even if the formation of each layer is uneven, it can be compensated by laminating. Furthermore, the papermaking speed can be increased, and the effect of improving the operability can also be obtained.

  In the wet papermaking method, a sheet-like wet paper non-woven fabric can be obtained by drying a wet paper web produced by a papermaking net by a Yankee dryer, an air dryer, a cylinder dryer, a suction drum dryer, an infrared dryer or the like. When the wet paper is dried, by bringing it into close contact with a heat roll such as a Yankee drier and performing heat and pressure drying, the smoothness of the adhered surface is improved. The heat and pressure drying refers to pressing the wet paper against the heat roll with a touch roll or the like to dry it. 100-180 degreeC is preferable, as for the surface temperature of a heat roll, 100-160 degreeC is more preferable, and 110-160 degreeC is further more preferable. The pressure is preferably 50 to 1000 N / cm, more preferably 100 to 800 N / cm.

  EXAMPLES The present invention will be described by way of examples, which should not be construed as limiting the present invention. In the examples, percentages (%) and parts are all based on mass unless otherwise noted. Moreover, a coating amount is a dry coating amount.

Examples 1 to 6 and Comparative Examples 1 to 4
(Dispersion treatment of fibrillated heat-resistant fiber)
A commercially available fibrillated heat-resistant fiber (made by Daicel Finechem, Tiara (registered trademark) KY-400S and Teijin, twaron (registered trademark) 1094) is dispersed under the conditions described in Table 1 using an apparatus, A slurry of fibrillated heat resistant fibers was obtained.

4.0 parts by mass of fibrillated heat-resistant fiber as a slurry dispersed under the conditions described in Table 1 and 56.0 mass of oriented crystallized polyethylene terephthalate (PET) based synthetic resin short fiber having a fineness of 0.06 dtex and a fiber length of 3 mm Dispersed in water with a pulper, 40.0 parts by mass of an unstretched PET synthetic resin short fiber (softening point 120 ° C., melting point 230 ° C.) for single component type binder, having a denier of 0.2 dtex and a fiber length of 3 mm A uniform papermaking slurry having a concentration of 0.1% by mass was prepared, and a wet paper web was obtained using a gradient paper machine, and was dried by a cylinder drier at a surface temperature of 135 ° C. to obtain a sheet. The resulting sheet was produced using a steel roll with one of the rolls plated with chromium, a resin roll with hardness Shore D 92, and a thermal calender with a surface temperature of 195 ° C and a linear pressure of 100 kN / m for the steel roll. Calender processing was performed, and the basis weight obtained 10 g / m ² of wet nonwoven fabrics of Examples 1 to 6 and Comparative Examples 1 to ² and a thickness of 15 μm.

  The following evaluations were performed on the wet non-woven fabrics manufactured in the examples and comparative examples, and the results are shown in Table 2.

(Evaluation of the number of defects)
A 20 cm × 50 cm wet non-woven fabric was observed by transmitted light, and the number of undigested fibers present in the sample was counted and converted to the number of defects per unit square meter.

(Coating evaluation)
100 parts of boehmite having a D50 particle diameter of 0.9 μm and a specific surface area of 5.5 m ² / g is mixed with 120 parts of a 0.3% aqueous solution of carboxymethylcellulose sodium salt having a viscosity of 200 mPa · s at 25 ° C. Stir sufficiently, then 300 parts of a 0.5% aqueous solution of carboxymethylcellulose sodium salt having a viscosity of 7,000 mPa · s at 25 ° C. and a 1% by mass aqueous solution, a styrene butadiene rubber (SBR) based binder (manufactured by JSR Corporation, trade name: 10 parts of TRD 2001) (solid content concentration 48%) were mixed and stirred to prepare a coating solution. The coating solution was applied and dried on one side of the wet non-woven fabric with a wire bar to a coating amount of 12 g / m ^2, and it was confirmed whether or not there were coating spots.

  A wet non-woven fabric is manufactured by a wet paper making method using a slurry in which fibrillated heat-resistant fibers are dispersed in water using a high-speed rotary shear type disperser by comparing Examples 1 and 2 with Comparative Examples 1 to 4. As a result, it can be seen that it is possible to provide a wet non-woven fabric containing fibrillated heat-resistant fibers having a small number of defects, excellent in uniformity, and excellent in coatability.

  By comparing Examples 1 and 2 with Examples 3 to 6, the high-speed rotational shear type disperser is a disperser having a ring-shaped blade having a fine slit rotating at high speed in a part of the structure. The particulate unagglomerated matter of fibrillated heat-resistant fibers can be dispersed more efficiently and uniformly. And it turns out that the number of defects is smaller, the uniformity is more excellent, and the wet non-woven fabric more excellent in the coating property can be provided.

  By comparing Examples 3 and 4 with Examples 5 and 6, the high-speed rotational shear type disperser is a disperser having a ring-shaped blade having a fine slit rotating at high speed in a part of the structure. Even when the treatment concentration is high, the fibrillated heat-resistant fibers can be dispersed. And it turns out that a wet nonwoven fabric with few defects, excellent uniformity, and excellent coatability can be provided.

  The wet non-woven fabric obtained by the method for producing a wet non-woven fabric of the present invention can be suitably used for battery separators, filter media, wipers, insulating paper and the like.

Claims (2)

  In a method for producing a wet non-woven fabric comprising fibrillated heat-resistant fibers, a wet non-woven fabric is produced by a wet paper making method using a slurry in which the fibrillated heat-resistant fibers are dispersed in water using a high-speed rotational shear type disperser. The manufacturing method of the wet nonwoven fabric characterized by manufacturing.   The method for producing a wet non-woven fabric according to claim 1, wherein the high-speed rotational shear type disperser is a disperser having a ring-shaped blade having fine slits rotating at high speed in a part of the structure.