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EP-4481096-B1 - NONWOVEN FABRIC AND METHOD FOR PRODUCING THE SAME, ORGANIC SOLVENT RECOVERY METHOD USING THE SAME, AND ORGANIC SOLVENT RECOVERY APPARATUS

EP4481096B1EP 4481096 B1EP4481096 B1EP 4481096B1EP-4481096-B1

Inventors

  • MURAKAWA, YUKA
  • IMANISHI, Masachiyo

Dates

Publication Date
20260506
Application Date
20230327

Claims (10)

  1. A nonwoven fabric comprising: a carbon fiber or carbon fiber precursor (A) each having an average fiber diameter of 10 µm or more and 30 µm or less, a tensile strength (1) of 40 N/mm 2 or more and 300 N/mm 2 or less, and an elongation percentage of 0% or more and 10% or less; and a fiber (B) having an average fiber diameter of 5 µm or more and 30 µm or less and a tensile strength (2) of 200 N/mm 2 or more and 600 N/mm 2 or less, provided that the tensile strength (2) is higher than the tensile strength (1), wherein a blend ratio between the carbon fiber or carbon fiber precursor (A) and the fiber (B) ((A):(B)) is 50:50 to 99:1 on mass basis, the carbon fiber or carbon fiber precursor (A) is an activated carbon fiber or an infusibilized fiber, and the fiber (B) is a carbon fiber or a carbon fiber precursor.
  2. The nonwoven fabric according to claim 1, wherein the activated carbon fiber is a pitch-based activated carbon fiber, and the activated carbon fiber has a specific surface area of 600 m 2 /g or more and 2000 m 2 /g or less.
  3. The nonwoven fabric according to claim 1 or 2, having a thermal resistance temperature of 200°C or more and 500°C or less.
  4. The nonwoven fabric according to any one of claims 1 to 3, wherein the fiber (B) is an acrylic carbon fiber, a pitch-based carbon fiber, a phenolic-resin-based carbon fiber, an acrylic flame-resistant carbon fiber, a pitch-based flame-resistant carbon fiber, a phenolic-resin-based flame-resistant carbon fiber, an acrylic carbonized carbon fiber, a pitch-based carbonized carbon fiber, or a phenolic-resin-based carbonized carbon fiber.
  5. The nonwoven fabric according to any one of claims 1 to 4, wherein the fiber (B) is a polyacrylonitrile-based flame-resistant carbon fiber or a pitch-based carbon fiber each differing from the carbon fiber or carbon fiber precursor (A).
  6. The nonwoven fabric according to any one of claims 1 to 5, wherein the nonwoven fabric exhibits a deodorization rate of 90% or more for any of odor gasses of ammonia, toluene, acetaldehyde, methyl mercaptan, trimethylamine, and acetic acid as measured in the following odor gas elimination test: (Odor gas elimination test) in a room at 20°C or more and 25°C or less and 30%RH or more and 60%RH or less, 5 g of the nonwoven fabric is put in a gas collection bag having a capacity of 10 L; subsequently, gas collection bag was charged with 3 L of air and sealed, and the gas collection bag was charged with any of the odor gasses in a predetermined initial gas concentration P and sealed, wherein the predetermined initial gas concentration P is 350 ppm for ammonia, 500 ppm for toluene, 100 ppm for acetaldehyde, 40 ppm for methyl mercaptan, 70 ppm for trimethylamine, and 100 ppm for acetic acid; the gas collection bag is left to stand for 30 minutes, and a concentration Q of ammonia, toluene, acetaldehyde, methyl mercaptan, trimethylamine, or acetic acid in the gas collection bag is then measured with a gas-detecting tube; and a deodorization rate for each of ammonia, toluene, acetaldehyde, methyl mercaptan, trimethylamine, and acetic acid is calculated from the following expression (1) with the initial gas concentration P and the concentration Q: Deodorization rate % = P − Q / P × 100
  7. A method for producing the nonwoven fabric according to any one of claims 1 to 6, wherein the carbon fiber (A) is an activated carbon fiber, and the method comprises: a step of defibrating and mixing the activated carbon fiber and the fiber (B) to provide a nonwoven fabric.
  8. A method for producing the nonwoven fabric according to any one of claims 1 to 6, wherein the carbon fiber precursor (A) is an infusibilized fiber, and the method comprises: a step of defibrating and mixing the infusibilized fiber and the fiber (B) to provide a nonwoven fabric precursor; and an activation step of subjecting the nonwoven fabric precursor to activation treatment.
  9. An organic solvent recovery method comprising: an adsorption step of allowing the nonwoven fabric according to any one of claims 1 to 6 to adsorb an organic solvent in an odor gas; a desorption step of desorbing the organic solvent from the nonwoven fabric with a desorbing gas, or a pressure-swing-adsorption-based desorption step of desorbing the organic solvent from the nonwoven fabric by depressurizing; and a recovery step of recovering the desorbed organic solvent.
  10. An organic solvent recovery apparatus comprising: an adsorbing unit that allows the nonwoven fabric according to any one of claims 1 to 6 to adsorb an organic solvent in an odor gas; a desorbing unit that desorbs the organic solvent from the nonwoven fabric with a desorbing gas, or a pressure-swing-adsorption-based desorbing unit that desorbs the organic solvent from the nonwoven fabric by depressurizing; and a recovering unit that recovers the desorbed organic solvent.

Description

Technical Field The present invention relates to a nonwoven fabric and a method for producing the nonwoven fabric, an organic solvent recovery method using the nonwoven fabric, and an organic solvent recovery apparatus. Background Art Nonwoven fabrics with an activated carbon fiber are generally superior in deodorization for various odor gasses. Accordingly, they are useful as a material of deodorants that are used in various scenes, such as industries, household use, automobiles, and daily life materials. In particular, nonwoven fabrics are used for organic solvent recovery apparatuses to recover organic solvents that are generated, for example, in production processes in the printing industry, the electric industry, and the machine industry. To such organic solvent recovery apparatuses, for example, a step is applied in which an odor gas is fed to a packed tower packed with a nonwoven fabric to allow the nonwoven fabric to adsorb an organic solvent contained in the odor gas, and the organic solvent adsorbed on the nonwoven fabric is then desorbed from the nonwoven fabric to recover the organic solvent. As a nonwoven fabric that is used as a deodorizing material, for example, Patent Document 1 discloses an activated carbon sheet formed by mixing activated carbon and a thermally fusible synthetic fiber as main components and partially melting the thermally fusible synthetic fiber to adhere the components. Patent Document 2 discloses a deodorizing material consisting of 10% by mass or more or 30% by mass of an acrylate-based fiber, 5% by mass or more or 30% by mass of an activated carbon fiber, and other fibers. Document 3 discloses a nonwoven fabric comprising carbon fibers with a diameter of 15-120 µm, intended for removing solvents from gases by adsorption. Citation List Patent Document Patent Document 1: Japanese Patent Laid-Open No. 2003-64563Patent Document 2: Japanese Patent Laid-Open No. 2000-93493Patent Document 3: PCT Patent Application WO 2021/256324 A1. Summary of Invention Technical Problem Nonwoven fabric for odor gas adsorption is required to have adsorption performance to odor gasses, durability (tensile strength) as nonwoven fabrics, and thermal resistance. However, if the blended rate of a hot-melt fiber, which is mixed as a reinforcing fiber for an activated carbon fiber in a nonwoven fabric for odor gas adsorption, is high, the blended rate of the activated carbon fiber is relatively small, and the resulting nonwoven fabric for odor gas adsorption fails to have sufficient adsorption performance. If the blended rate of the hot-melt fiber is low, on the other hand, the resulting nonwoven fabric for odor gas adsorption suffers from the lowering of durability (tensile strength) as nonwoven fabrics. The hot-melt fiber has a low melting point, and thus has a problem of poor thermal resistance as well. In Patent Document 1, a thermally fusible synthetic fiber, which is a low-melting-point fiber, is used together with activated carbon, and hence the thermal resistance is insufficient. In Patent Document 2, at most about 30% by mass of an activated carbon fiber is blended, and hence the adsorption performance to odor gasses is disadvantageously insufficient. The present invention has been made in view of such problems, and an object of the present invention is to provide a nonwoven fabric having superior adsorption performance to odor gasses, superior durability (tensile strength), and high thermal resistance and a method for producing the nonwoven fabric, an organic solvent recovery method using the nonwoven fabric, and an organic solvent recovery apparatus. Solution to Problem The present inventor has diligently studied to achieve the object. As a result, the present inventor has found that a nonwoven fabric containing a specific carbon fiber or carbon fiber precursor (A) and a specific fiber (B) at a specific blend ratio has superior adsorption performance to odor gasses, superior durability (tensile strength), and high thermal resistance, and eventually completed the present invention. The present invention includes the following modes of implementation. [1] A nonwoven fabric containing: a carbon fiber or carbon fiber precursor (A) each having an average fiber diameter of 10 µm or more and 30 µm or less, a tensile strength (1) of 40 N/mm2 or more and 300 N/mm2 or less, and an elongation percentage of 0% or more and 10% or less; and a fiber (B) having an average fiber diameter of 5 µm or more and 30 µm or less and a tensile strength (2) of 200 N/mm2 or more and 600 N/mm2 or less, provided that the tensile strength (2) is higher than the tensile strength (1), wherein a blend ratio between the carbon fiber or carbon fiber precursor (A) and the fiber (B) ((A):(B)) is 50:50 to 99:1 on mass basis, the carbon fiber or carbon fiber precursor (A) is an activated carbon fiber or an infusibilized fiber, and the fiber (B) is a carbon fiber or a carbon fiber precursor.[2] The nonwoven fabric according to [