Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B21/00—Arrangements for supplying or controlling air or other gases for drying solid materials or objects
  • F26B21/30—Controlling, e.g. regulating, parameters of gas supply
  • F26B21/35—Temperature; Pressure
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
  • B29C71/02—Thermal after-treatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C67/00—Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00
  • B29C67/20—Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00 for porous or cellular articles, e.g. of foam plastics, coarse-pored
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/28—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B21/00—Arrangements for supplying or controlling air or other gases for drying solid materials or objects
  • F26B21/30—Controlling, e.g. regulating, parameters of gas supply
  • F26B21/33—Humidity
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B3/00—Drying solid materials or objects by processes involving the application of heat
  • F26B3/32—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action
  • F26B3/34—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action by using electrical effects
  • F26B3/347—Electromagnetic heating, e.g. induction heating or heating using microwave energy

Definitions

• the present invention relates to a method for producing a porous body and a porous body.
• Porous materials obtained by drying a dispersion of structures with three-dimensional mesh structures such as cellulose nanofibers have high porosity and therefore have insulating properties equivalent to air, making them promising for a variety of applications.
• Patent Document 1 describes a method for producing a porous body in which a hydrogel containing a structure having a three-dimensional mesh structure is subjected to supercritical drying or the like ([Claim 1], [Claim 3], [Claim 8], [Claim 11], [Claim 12]).
• Patent Document 1 The inventors found that the method utilizing supercritical drying described in Patent Document 1 was not suitable for manufacturing, and when they attempted drying at a pressure of 102 Pa or more and 106 Pa or less, volume shrinkage occurred, resulting in a significant decrease in porosity.
• an object of the present invention is to provide a method for producing a porous body that can suppress volume shrinkage during drying at a pressure of 10 2 Pa or more and 10 6 Pa or less and obtain a porous body with high porosity, and to provide the porous body.
• the inventors have discovered that by subjecting a gel having a water-containing solvent and a structure having a three-dimensional mesh structure to a specific drying treatment at a pressure of 102 Pa or more and 106 Pa or less, it is possible to suppress volume shrinkage and obtain a porous body with a high porosity, and have completed the present invention. That is, the present inventors have found that the above problems can be solved by the following configuration.
• a method for producing a porous body comprising the steps of: subjecting a gel having a water-containing solvent and a structure having a three-dimensional network structure to a drying treatment to produce a porous body, A method for producing a porous body, wherein the drying treatment is carried out at a pressure of 10 2 Pa or more and 10 6 Pa or less, at a temperature equal to or higher than the boiling point of the solvent, so that the internal temperature of the gel is equal to or higher than the external temperature of the gel.
• the structure having a three-dimensional mesh structure is a cellulose nanofiber.
• a method for producing a porous body comprising the steps of: subjecting a gel having a water-containing solvent and a structure having a three-dimensional network structure to a drying treatment to produce a porous body, A method for producing a porous body, wherein the drying treatment is a treatment of performing at least one of superheated steam drying and microwave drying at a pressure of 10 2 Pa or more and 10 6 Pa or less and at a temperature equal to or higher than the boiling point of the solvent.
• the method for producing a porous body according to [6] wherein the structure having a three-dimensional mesh structure is a cellulose nanofiber.
• the porous body according to [8] having an indentation fracture stress of 0.5 MPa or more.
• the present invention it is possible to provide a method for producing a porous body, which can suppress volume shrinkage during drying at a pressure of 10 2 Pa or more and 10 6 Pa or less and obtain a porous body with high porosity, and the porous body.
• a numerical range expressed using "to” means a range that includes the numerical values before and after "to” as the lower and upper limits.
• the upper or lower limit value of a certain numerical range in a stepwise described numerical range may be replaced with the upper or lower limit value of another stepwise described numerical range.
• the upper or lower limit value of a certain numerical range in a numerical range described in the present specification may be replaced with a value shown in the examples.
• each component may be used alone or in combination of two or more substances corresponding to each component. When two or more substances are used in combination for each component, the content of the component refers to the total content of the substances used in combination, unless otherwise specified.
• the manufacturing method of the porous body according to the first and second aspects of the present invention (hereinafter, also abbreviated as "the manufacturing method of the present invention” when no particular distinction is required) is a manufacturing method of the porous body in which a gel having a solvent containing water and a structure having a three-dimensional network structure (hereinafter, also abbreviated as "structure hydrogel”) is subjected to a drying treatment to produce a porous body.
• the drying treatment is carried out at a pressure of 102 Pa or more and 106 Pa or less, at a temperature equal to or higher than the boiling point of the solvent, so that the internal temperature of the gel is equal to or higher than the external temperature of the gel.
• the drying treatment is carried out by at least one of superheated steam drying and microwave drying at a pressure of 102 Pa or more and 106 Pa or less, and at a temperature equal to or higher than the boiling point of the solvent.
• the boiling point of the solvent in the production method of the present invention refers to the boiling point of the solvent at normal pressure.
• the drying treatment is carried out at a pressure of 102 Pa or more and 106 Pa or less and at a temperature above the boiling point of the solvent, so that the internal temperature of the gel is equal to or higher than the external temperature of the gel, and in a second aspect, the drying treatment is carried out at a pressure of 102 Pa or more and 106 Pa or less and at a temperature above the boiling point of the solvent, by at least one of superheated steam drying and microwave drying, thereby suppressing volume shrinkage during drying at a pressure of 102 Pa or more and 106 Pa or less, and obtaining a porous body with a high porosity.
• the structure hydrogel used in the manufacturing method of the present invention is a gel having a solvent containing water and a structure having a three-dimensional network structure, and is the object to be subjected to the drying treatment described below.
• the solvent in the structure hydrogel is not particularly limited as long as it contains at least water, and may be water alone or a mixed solvent of water and an organic solvent.
• the organic solvent may be, for example, Ester-based solvents such as ethyl acetate, butyl acetate, isopropyl acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate; Ether solvents such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, ethylene glycol isopropyl ether, ethylene glycol t-butyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether (butyl cellosolve), and propylene glycol monobutyl ether; Alcohol-based solvents such as methanol, ethanol, ethoxypropanol, butanol, me
• a structure having a three-dimensional mesh structure possessed by a structural hydrogel is a structure in which the materials constituting the structure are three-dimensionally interconnected to form an integrated, continuous network.
• examples of structures having a three-dimensional mesh structure that the structural hydrogel has include at least one selected from the group consisting of cellulose nanofibers, cellulose derivatives, chitosan, chitin nanofibers, alginic acid, hyaluronic acid, pectin, carrageenan, gellan gum, xanthan gum, nanoporous ceramics (e.g., silica, zinc oxide, etc.), derivatives thereof, and combinations thereof.
• cellulose nanofibers are preferred.
• the cellulose nanofiber is not particularly limited as long as it is a material obtained from a cellulosic raw material.
• the cellulosic raw material is not particularly limited as long as it is a material mainly composed of cellulose, and examples thereof include pulp, natural cellulose, regenerated cellulose, and fine cellulose obtained by depolymerizing a cellulose raw material through mechanical processing.
• the cellulosic raw material commercially available products such as crystalline cellulose made from pulp can be used as they are.
• the cellulosic raw material may be subjected to chemical treatment such as alkali treatment to facilitate the penetration of an oxidizing agent.
• the fiber length of the cellulose nanofibers is not particularly limited, but is preferably 100 nm to 5000 nm, more preferably 50 nm to 2000 nm, and even more preferably 100 nm to 700 nm.
• the fiber diameter of the cellulose nanofibers is not particularly limited, but is preferably 1 nm to 100 nm, and more preferably 2 nm to 10 nm.
• cellulose nanofibers can be produced by a method in which the cellulosic raw materials are oxidized with sodium hypochlorite, an oxidizing agent, in the presence of a compound having a piperidine skeleton, such as 2,2,6,6-tetramethyl-1-piperidine-N-oxy radical (hereinafter abbreviated as "TEMPO"), as a catalyst.
• TEMPO 2,2,6,6-tetramethyl-1-piperidine-N-oxy radical
• the method for producing the structure hydrogel is not particularly limited, and examples thereof include a method in which a gelling agent is added to a solution containing the above-mentioned solvent and a structure having a three-dimensional network structure.
• the solution may also be concentrated, if necessary, before the addition of the gelling agent.
• an acidic solution for example, an acidic solution, a basic solution, a metal salt solution, or the like can be used.
• the acidic solution include solutions containing phosphoric acid, sulfuric acid, hydrochloric acid, acetic acid, citric acid, lactic acid, etc., with a concentration in the range of 0.1M to 1M.
• the basic solution include solutions containing sodium hydroxide, ammonia, urea, tetramethylammonium hydroxide, etc., and having a concentration in the range of 0.1M to 1M.
• the metal salt solution may be, for example, a solution containing a polyvalent metal salt, preferably a divalent metal salt. Specific examples of such metal salts include Al salts, Fe salts, Ca salts, and Mg salts.
• the concentration of the metal salt may be appropriately set, but is typically in the range of 0.1M to 1M.
• the method of concentration is not particularly limited, but it is preferable to include a step of concentrating under conditions of a temperature of 20 to 80°C and a humidity of 50 to 90%.
• the shape of the structure hydrogel is a three-dimensional shape that may have a curved surface, and that the surface area of a certain face X is a shape that is equal to or greater than the sum of the surface areas of the faces adjacent to face X.
• the structure hydrogel has a polyhedral shape including a top surface, a bottom surface, and a side surface, and the top surface corresponds to surface X
• the top surface corresponds to surface X
• the inventors of the present invention presume that when the structure hydrogel has a polyhedral shape including a top surface, a bottom surface, and a side surface, and the top surface corresponds to surface X, the capillary force of water will be parallel to the bottom surface and will be weakened by the anchor effect of the gel itself, so that the volume shrinkage during drying at a pressure of 10 2 Pa or more and 10 6 Pa or less can be further suppressed, and a porous body with a higher porosity can be obtained.
• the pressure of the drying treatment is preferably 10 3 Pa or more and 10 5 Pa or less, and more preferably 10 4 Pa or more and 10 5 Pa or less, because a porous body having a higher porosity can be obtained.
• the temperature difference between the internal temperature of the gel and the external temperature of the gel during the drying process is preferably within 50°C, more preferably 10 to 50°C, and even more preferably 20 to 40°C, in order to prevent the structural hydrogel from expanding and bursting.
• the drying process is preferably a process that performs at least one of superheated steam drying and microwave drying, and is more preferably a process that performs superheated steam drying.
• superheated steam drying is a method of drying using steam of a solvent superheated to a saturation temperature or higher. Since the solvent in the structure hydrogel contains at least water, a method of drying using a superheated steam dryer set at a temperature of 100 to 180° C. and a humidity of 10 to 50%, for example, is preferred.
• Microwave drying is a drying method in which the molecules of a solvent are vibrated by microwaves to generate heat and evaporate the solvent. From the viewpoint of suppressing the expansion and rupture of the structure hydrogel, it is preferable to carry out the drying method under conditions of, for example, a wavelength of 1 mm to 10 cm and an output of 1 to 5 kW.
• the drying treatment in the second manufacturing method of the present invention is a treatment that performs at least one of superheated steam drying and microwave drying at a pressure of 102 Pa or more and 106 Pa or less and at a temperature equal to or higher than the boiling point of the solvent, and is preferably a treatment that performs superheated steam drying.
• the temperature condition of the above-mentioned drying treatment is not particularly limited as long as it is a temperature equal to or higher than the boiling point of the above-mentioned solvent, but is preferably 100 to 200°C, and more preferably 100 to 180°C.
• the pressure in the drying treatment in the second production method of the present invention, and the superheated steam drying or microwave drying used in the drying treatment are the same as those explained as the preferred embodiment of the first production method of the present invention.
• the porous body of the present invention is a porous body having a porosity of 80% or more and a layered structure in the planar direction.
• porosity refers to a value measured by the following procedure. First, the volume V and mass W of the porous body are measured. Next, the density D of the structure having a three-dimensional network structure constituting the porous body is set to 1.5 g/ cm3 . Next, the porosity is calculated from the following formula.
• Porosity 100 ⁇ volume V ⁇ (mass W/density D) ⁇ /volume V
• “having a layered structure in the planar direction” means having a structure in which a plurality of structures oriented parallel to the surface of the porous body are stacked.
• the porous body of the present invention preferably has an indentation fracture stress of 0.5 MPa or more, and more preferably 1 MPa or more and 5000 MPa or less.
• the indentation breaking stress refers to a value measured under the following conditions: The measurement is performed under the following conditions, and the breaking stress is calculated as the point at which the stress does not increase or decreases with respect to the applied strain. Apparatus: Shimadzu Micro Autograph MST Load cell: 2N Max. Indenter: 15 mm ⁇ plastic homemade indenter Sample size: 10 mm square Compression speed: 100%/min (10 mm/min) Number of n: 3 Compressive elastic modulus: Calculated from strain 0-1%
• the interlayer distance of the porous body of the present invention is preferably at least 1 nm to 10 ⁇ m, more preferably 5 nm to 5 ⁇ m, and even more preferably 5 nm to 1 ⁇ m. If the distance is 10 ⁇ m or less, the porous body is durable against pressure from fingers and the like during processing, and if the distance is 1 nm or more, it is easy to adjust the porosity to 80% or more.
• the porous body produced by the production method of the present invention or the porous body of the present invention can be used for various applications, for example, it can be suitably used for applications such as windows or components thereof, and specifically, it can be suitably used for applications such as an interlayer film for laminated glass or an interlayer film for insulating glass.
• an interlayer film for laminated glass or an interlayer film for insulating glass for laminated glass and insulating glass, the number and type of glass plates, layers other than the glass plates and the interlayer film (e.g., a light-shielding layer, a heat-shielding layer, a flame-retardant layer, etc.), and sealing structure and other configurations may be those publicly known.
• Example 1 [Preparation of cellulose nanofibers] 10 g of softwood kraft pulp was suspended in 1000 g of pure water in which 0.16 g of TEMPO and 1 g of sodium bromide were dissolved. 25 g of an aqueous solution of sodium hypochlorite with an effective chlorine content of 2 M was added thereto to initiate the oxidation reaction. The temperature in the reaction system was kept at 25° C., and the pH in the system was kept at 10 during the reaction by adding an aqueous solution of 0.5 M sodium hydroxide. After 2 hours, the oxidation reaction was stopped by adding about 100 mL of ethanol to the reaction system. Then, filtration and washing were repeated using a glass filter with pure water to obtain oxidized cellulose.
• the obtained oxidized cellulose was passed through a high-pressure homogenizer three times to prepare a dispersion containing 1% by mass of cellulose nanofibers.
• the obtained cellulose nanofibers had a carboxyl group content of 1.5 mmol/g, a fiber diameter of 3 nm, and a fiber length of 500 nm.
• the cellulose nanofiber (CNF) aqueous dispersion obtained above was kept in a thermo-hygrostat dryer at a temperature of 40°C and a humidity of 80% for 8 to 10 days to prepare a concentrated dispersion with a CNF concentration of 4% by weight. It was confirmed that the concentrated dispersion had an orientation degree of 78 to 83% and had structural anisotropy.
• CNF cellulose nanofiber
• Example 2 A porous body was produced in the same manner as in Example 1, except that the size of the hexahedron cut out after gelation was changed to 36 mm length ⁇ 45 mm width ⁇ 10 mm thickness.
• Example 3 A porous body was produced in the same manner as in Example 1, except that the size of the hexahedron cut out after gelation was changed to 100 mm length x 100 mm width x 10 mm thickness.
• Example 4 A porous body was produced in the same manner as in Example 3, except that the drying temperature, the internal temperature of the gel, and the external temperature of the gel were changed to the values shown in Table 1 below.
• Example 5 A porous body was prepared in the same manner as in Example 3, except that the solvent was changed from water to "water containing 10% ethanol.”
• Example 6 A porous body was produced in the same manner as in Example 3, except that microwave drying was carried out as described below instead of the drying treatment using a superheated steam dryer. That is, the structural hydrogel prepared in the same manner as in Example 3 was placed in a microwave dryer. The microwave output was set to the output value at which a predetermined temperature was reached while measuring the internal temperature of the gel, and an aerogel was obtained by leaving it for a predetermined drying time. The drying time was estimated from a graph of the drying time and weight change.
• Example 7 A porous body was produced in the same manner as in Example 6, except that the drying temperature, the internal temperature of the gel, and the external temperature of the gel were changed to the values shown in Table 1 below.
• Example 8 A porous body was prepared in the same manner as in Example 1, except that the pressure in the drying treatment was changed to the value shown in Table 1 below.
• Example 9 A porous body was prepared in the same manner as in Example 6, except that the pressure in the drying treatment was changed to the value shown in Table 1 below.
• Example 1 A porous body was produced in the same manner as in Example 1, except that the drying temperature, the internal temperature of the gel, and the external temperature of the gel were changed to the values shown in Table 1 below by leaving the gel at room temperature (23° C.) instead of using a superheated steam dryer for drying treatment.
• Example 2 A porous body was produced in the same manner as in Example 1, except that the drying temperature, the internal temperature of the gel, and the external temperature of the gel were changed to the values shown in Table 1 below by drying with hot air instead of using a superheated steam dryer.
• Porosity The volume of the porous body was measured with a vernier caliper, the mass was measured with an electronic balance, and the porosity was calculated by the method described above.
• Thickness The thickness of the porous body was measured with a vernier caliper.
• Transmittance The porous body was set in a spectrophotometer (V-670, manufactured by JASCO Corporation) and the transmittance with respect to wavelength was calculated.
• Examples 1 to 3 revealed that when the shape of the structural hydrogel is a polyhedron including a top surface, a bottom surface, and a side surface, and the surface area of the top surface is equal to or greater than the total surface area of the side surfaces, the thickness of the resulting porous body is increased and the porosity is also increased, thereby further suppressing the volumetric shrinkage during drying at a pressure of 10 2 Pa or more and 10 6 Pa or less.

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• 2024
  • 2024-04-02 WO PCT/JP2024/013584 patent/WO2024219216A1/ja not_active Ceased
  • 2024-04-02 JP JP2025515142A patent/JPWO2024219216A1/ja active Pending
• 2025
  • 2025-10-15 US US19/358,470 patent/US20260036369A1/en active Pending

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