JP2011183326A - Sheet-like material for dehumidification - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet-like material for dehumidification which scarcely drops powder even if containing a moisture adsorbent at a high ratio and is excellent in a water adsorption property and processibility. <P>SOLUTION: The sheet-like material for dehumidification containing a water adsorbent includes at least one kind of fibrillated Lyocell fibers selected from (A) fibrillated Lyocell fibers with a fiber diameter of 1 μm or smaller separated from trunk parts by applying shear force and (B) fibrillated Lyocell fibers having branch parts with a fiber diameter of 1 μm or smaller formed from trunk parts with a fiber diameter of 2 μm or larger by applying shear force as well as organic fibers. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sheet material for dehumidification having moisture absorption / release performance.

  A dehumidifying sheet containing a moisture adsorbent is packaged when storing or transporting artwork, electrical appliances, crafts, clothing, etc. for the purpose of maintaining the surrounding environment at a constant relative humidity. It is used as a material, house interior material, indentation hygroscopic agent, etc. Also in air conditioning equipment and dehumidifying elements that dehumidify and humidify indoor air, and total heat exchange elements that ventilate indoors while exchanging temperature (heat) and humidity (moisture) between exhaust and intake air A sheet-like material having moisture absorption / release properties is used. In air-conditioning equipment, total heat exchange elements, etc., a laminate of corrugated sheet-like materials or a sheet-like material wound in a rotor shape is used as a dehumidifying element or heat exchange element.

  Desiccant air conditioning, one of the fields of application of dehumidifying sheets containing moisture adsorbents, directly removes moisture from the air with moisture adsorbents and adjusts the air supplied to the room to a comfortable temperature and humidity. It is an air conditioning system. In general, humans feel uncomfortable in a hot and humid environment, but when the relative humidity is 50% or less, comfort is greatly improved even in an environment of the same temperature. In a general desiccant air conditioning system, a dehumidification rotor containing a moisture adsorbent is rotated, and high-humidity air such as outside air is passed through the dehumidification rotor in the adsorption zone, and moisture is adsorbed to create low-humidity air. On the other hand, the dehumidification rotor that has adsorbed moisture is regenerated to a state in which moisture can be adsorbed again by passing high-temperature regeneration air in the regeneration zone to release moisture in the dehumidification rotor. Activated carbon is also used as a moisture adsorbent, but porous metal oxides are widely used as a superior material because of its small amount of adsorption.

  In a desiccant air conditioning system, in order to improve moisture absorption / release performance, higher-temperature regeneration air may be passed through a dehumidification rotor. Therefore, the sheet material for dehumidification containing the moisture adsorbent constituting the dehumidification rotor is often required to be incombustible or flame retardant, and therefore, many use inorganic fibers. As a manufacturing method thereof, for example, a method of forming inorganic fiber paper into a honeycomb shape, firing at a high temperature to remove organic substances, impregnating in a coating solution containing a moisture adsorbent, and then drying at a high temperature (for example, patents) Document 1), a method of impregnating ceramic fiber paper with water glass to produce silica gel (for example, see Patent Document 2), and the like have been proposed. Sheet materials using these inorganic fibers have problems that they are hard and brittle, so that they have poor impact resistance and there are many powders of moisture adsorbents. In addition, in a sheet-like material using inorganic fibers, high temperature firing is performed for the purpose of weight loss, so organic water adsorbents cannot be used. There was a restriction on the selection of moisture adsorbents that could not be used if their physical properties change.

  In order to solve restrictions on impact resistance and moisture adsorbent selection, a sheet-like material containing a moisture adsorbent and organic fibers has been proposed. For example, a total heat exchanger paper composed of a moisture adsorbent, a papermaking fiber, and a heat-fusible substance (see, for example, Patent Document 3), a total heat exchanger paper composed of a moisture adsorbent, a papermaking fiber, and microfibrillated cellulose. (See, for example, Patent Document 4), humidity control sheet made of cellulose fiber and moisture adsorbent (see, for example, Patent Document 5), base material made of moisture adsorbent and organic fiber (see, for example, Patent Document 6), flame retardant An adsorbing element (for example, refer to Patent Document 7) containing a water-soluble synthetic pulp, a polyvinyl alcohol-based binder, and a moisture adsorbent has been proposed. Since the sheet-like material using these organic fibers is less likely to be broken by an impact and does not have a high-temperature firing step, restrictions on the selection of the moisture adsorbent are reduced. However, when manufacturing a workpiece by corrugating the sheet material or winding it into a rotor shape, or while using the sheet material in packaging materials, air conditioning equipment, etc. The problem that powder falling occurs cannot be completely solved. In particular, there is much powder falling when the content ratio of the moisture adsorbent is increased to 30% by mass or more in order to increase the moisture absorption amount of the sheet-like material. In order to prevent powder falling, if the content ratio of the moisture adsorbent is reduced, the amount of sheet material used must be increased in order to obtain the target relative humidity, and the air conditioning equipment and the total heat exchange element will become larger. There was a problem of ending up.

JP-A-6-226037 Japanese Patent Laid-Open No. 5-115737 Japanese Patent Laid-Open No. 10-212691 Japanese Patent Laid-Open No. 11-189999 JP 2004-68188 A US Patent Application Publication No. 2002/0070002 JP 2004-268020 A

  An object of the present invention is to provide a sheet material for dehumidification that has little powder falling even when a water adsorbent is contained at a high ratio and is excellent in water adsorption characteristics and processability.

As a result of intensive studies to solve the above problems,
(1) In a dehumidifying sheet containing a moisture adsorbent, (A) a fibrillated lyocell fiber having a fiber diameter of 1 μm or less detached from the trunk by applying a shear force, and (B) a fiber diameter by applying a shear force. A sheet-like material for dehumidification comprising at least one fibrillated lyocell fiber selected from fibrillated lyocell fibers in which branches having a fiber diameter of 1 μm or less are generated from a trunk portion of 2 μm or more, and an organic fiber,
(2) The dehumidifying sheet-like material according to (1), wherein at least a part of the organic fiber is a heat-fusible binder fiber,
I found.

  The dehumidifying sheet-like material of the present invention has little powder falling even when it contains a moisture adsorbent at a high rate, and the moisture adsorbent retention rate (powder yield) is improved even in the production process. Furthermore, since there is little decline in the adsorption | suction performance of the water | moisture-content adsorption agent by sheeting, it becomes a dehumidification sheet-like thing excellent in moisture absorption / release performance. Moreover, since it has moderate flexibility, it is excellent in processability. Therefore, for example, when the sheet material for dehumidification of the present invention is applied to a dehumidifying rotor for desiccant air conditioning, the high-performance desiccant rotor for desiccant air conditioning that has high impact resistance, is easy to handle, and has excellent moisture absorption and desorption performance. It becomes.

  In the present invention, the moisture adsorbent contains an oxide of at least one metal atom selected from silicon, titanium, aluminum, tantalum, vanadium, zirconium, zinc, magnesium, calcium, etc. And granular materials having a large number of pores, composite particles formed by agglomerating a plurality of single particles having a primary particle diameter of several nm, tubular bodies, aggregates of fibrous metal oxides, and the like. More specifically, examples include amorphous aluminum silicate, porous silica, mesoporous silica, zeolite, silica gel, fibrous or tubular aluminum silicate, fibrous or tubular titanium oxide, diatomaceous earth, and the like.

  Although content of the water | moisture-content adsorption agent in the sheet material for dehumidification of this invention is not specifically limited, 10-90 mass% is preferable, 30-80 mass% is more preferable, 50-75 mass% is further more preferable. If the content of the moisture adsorbent is less than 10% by mass, the amount of moisture adsorbed may be too small as a dehumidifying sheet, and if it exceeds 90% by mass, the sheet for dehumidification is produced by the wet papermaking method. Since the amount of fibers forming the skeleton of the product is relatively small, it may be difficult to form a sheet or the processability may be reduced. In addition, the content of fibrillated lyocell fibers may be relatively decreased, which may reduce the powder yield and increase the amount of powder falling.

  In the present invention, “lyocell” is a fiber term defined in ISO standard and JIS standard, and is “cellulose fiber obtained by spinning cellulose directly dissolved in an organic solvent without passing through a derivative”. Features of lyocell fiber include excellent wet strength, easy fibrillation, and easy strength when formed into a sheet by hydrogen bonds derived from cellulose fibers.

  Lyocell fiber is beater, dispersion equipment such as beater, PFI mill, single disc refiner (SDR), double disc refiner (DDR), ball mill, dyno mill, etc. used for dispersing and crushing pigments, etc. Can be fibrillated. Since lyocell fiber is a raw material of cellulose fiber, it has a characteristic that strength improvement by hydrogen bonding can be expected even after fibrillation.

  The fibrillated lyocell fiber contained in the sheet material for dehumidification of the present invention is entangled with water adsorbents or with other fibers constituting the water adsorbent and the sheet material, and plays a role of holding the water adsorbent. Make the most of the characteristics of lyocell fiber, improve the powder yield in the manufacturing process without impairing the adsorption performance of the moisture adsorbent, and produce a dehumidifying sheet that does not easily fall off after being made into a sheet In order to do so, it is important to find optimal fibrillation conditions. (A) A fibrillated lyocell fiber having a fiber diameter of 1 μm or less detached from the trunk by applying a shearing force, (B) A fibrillated lyocell having a fiber diameter of 1 μm or less generated from a trunk having a fiber diameter of 2 μm or more by applying a shearing force It is necessary to contain both or either fibrillated lyocell fiber.

  The lyocell fiber is fibrillated by beating and can be a material suitable for the dehumidifying sheet of the present invention, but it is important to determine the optimum beating conditions. In order to confirm the fibrillation state in which fibrillated lyocell fiber (A) and / or fibrillated lyocell fiber (B) is properly present, the fibrillated fiber is sufficiently diluted with water and then dried. And observed with a microscope, preferably an electron microscope. However, it is not necessary to observe each time after the optimum fibrillation conditions are determined.

  In the dehumidifying sheet of the present invention, in order to retain more moisture adsorbent, (A) the aspect ratio (fiber length / fiber diameter) of the fibrillated lyocell fiber with a fiber diameter of 1 μm or less detached from the trunk is: 10-100,000 are preferable and 100-50000 are more preferable. Moreover, (B) In the fibrillated lyocell fiber in which the branch part is generated from the trunk part, the aspect ratio of the trunk part is preferably 10 to 50000, more preferably 50 to 30000. Moreover, 10-100,000 are preferable and, as for the aspect ratio of a branch part, More preferably, it is 100-50000. These fibrillation states can be confirmed by microscopic observation described above.

  In the sheet material for dehumidification of the present invention, the mixing ratio of the fibrillated lyocell fiber is not particularly limited, but the content with respect to the sheet material for dehumidification is preferably 0.5 to 30% by mass, and more preferably 1 to 20% by mass. . If the content of the fibrillated lyocell fiber is less than 0.5% by mass, it may be insufficient to retain the moisture adsorbent, and the powder yield will be significantly reduced when producing a dehumidifying sheet. Or, powdering may become very large after forming into a sheet. On the other hand, when it exceeds 30% by mass, the fibrillated lyocell fiber covers the periphery of the moisture adsorbent too much, which may reduce the moisture absorption / release performance. In addition, for example, when manufacturing by a wet papermaking method, the drainage is significantly reduced, and the papermaking machine may be limited.

  The organic fibers in the dehumidifying sheet of the present invention are olefin resin, polyester resin, polyvinyl acetate resin, ethylene-vinyl acetate copolymer resin, polyamide resin, acrylic resin, polyvinyl chloride resin. , Polyvinylidene chloride resin, polyvinyl ether resin, polyvinyl ketone resin, polyether resin, polyvinyl alcohol resin, diene resin, polyurethane resin, phenol resin, melamine resin, furan resin, urea resin , Synthetic fibers made of aniline resin, unsaturated polyester resin, alkyd resin, plant fibers such as wood pulp, straw, cocoon, straw, kenaf, bamboo, linter, bagasse, esparto, and sugarcane. Moreover, the fiber which refined | miniaturized these can be used in the range which does not inhibit moisture absorption / release performance. Furthermore, rayon fibers, lyocell fibers, semi-synthetic fibers such as acetate, fluorine resin fibers such as polytetrafluoroethylene (PTFE), silicone resin fibers, and the like, which are cellulose regenerated fibers, can also be used. Further, fibers having an irregular cross section such as a T-shaped, Y-shaped, or triangular cross section can also be used for ensuring air permeability related to moisture absorption / release performance. In addition, metal fibers such as stainless steel and nickel wool, carbon fibers, ceramic fibers, glass fibers, and other flame-retardant or non-flammable inorganic fibers are used within a range that does not impair the performance of the sheet material for dehumidification of the present invention such as processability. You can also.

  The dehumidifying sheet-like material of the present invention is a fibrillated lyocell fiber (A) and a fibrillated lyocell fiber (B), or lyocell fiber fibrillated in either state and a water adsorbent moderately entangled, Aggregates are formed and further entangled with organic fibers that form the skeleton of the sheet-like material to form a three-dimensional network structure having an appropriate space. Thereby, air permeability can be ensured while containing a moisture adsorbent at a high ratio, and high moisture absorption / release performance can be obtained. Preferably, when two or more kinds of organic fibers having different fiber diameters are contained, a further space is created in the network, and the moisture absorption / release performance is improved.

  Although the fiber diameter of the organic fiber in the sheet-like material for dehumidification of the present invention is not particularly limited, 1 to 40 μm is preferable, 1.5 to 30 μm is more preferable, and 2 to 15 μm is further preferable. If the fiber diameter of the organic fiber is less than 1 μm, the air permeability of the dehumidifying sheet may be impaired, and the moisture absorption / release performance may be hindered. Also, the drainage may be lowered, and the papermaking machine may be limited when manufacturing by wet papermaking. On the contrary, when the fiber diameter of the organic fiber exceeds 40 μm, the voids of the fiber network constituting the sheet for dehumidification become too large, and the moisture adsorbent falls off (powder off), or when wet papermaking is performed. In some cases, the moisture adsorbent slips through the constituent fibers and the papermaking net, and the retention rate (powder yield) may decrease.

  Although the fiber length of the organic fiber in the sheet-like material for dehumidification of the present invention is not particularly limited, 1 to 20 mm is preferable, 1.5 to 15 mm is more preferable, and 2 to 10 mm is more preferable. If the fiber length of the organic fiber is less than 1 mm, it may be insufficient for forming the skeleton of the sheet for dehumidification, and the workability may be reduced. In addition, when the fiber length of the organic fiber exceeds 20 mm, the fiber dispersibility is deteriorated when the wet papermaking process is performed, and the formation of the dehumidifying sheet may be deteriorated, and the dehumidifying sheet having stable performance is obtained. It may be difficult to obtain a product.

  Although content of the organic fiber in the sheet material for dehumidification of this invention is not specifically limited, 9-89 mass% is preferable, 19-69 mass% is more preferable, 24-49 mass% is further more preferable. When the content of the organic fiber is less than 9% by mass, the sheet material for dehumidification may be difficult to form a skeleton when manufactured by a wet papermaking method, making it difficult to form a sheet or reducing the processability. there is a possibility. On the other hand, if it exceeds 89% by mass, the content of the moisture adsorbent and / or fibrillated lyocell fiber is relatively reduced, so that the moisture adsorption amount of the dehumidifying sheet-like material is reduced or the amount of powder falling is increased. there's a possibility that.

  In the dehumidifying sheet of the present invention, a heat-fusible binder fiber can be used for some or all of the organic fibers. In the manufacturing process of the dehumidifying sheet, the mechanical strength is improved by raising the temperature of the dehumidifying sheet more than the melting temperature of the heat-fusible binder fiber. For example, when a dehumidifying sheet-like material is produced by a wet papermaking method, a dehumidifying sheet-like material having high strength is obtained by melting the heat-fusible binder fiber in the drying step after papermaking.

  Examples of the heat-fusible binder fiber in the dehumidifying sheet of the present invention include single fibers as well as composite fibers such as core-sheath fibers (core-shell type), parallel fibers (side-by-side type), and radial split fibers. Since the composite fiber hardly forms a film, the mechanical strength can be improved while maintaining the space of the dehumidifying sheet. Examples of heat-fusible binder fibers include polypropylene single fibers, unstretched polyester single fibers, a combination of polypropylene (core) and polyethylene (sheath), a combination of polypropylene (core) and ethylene vinyl alcohol (sheath), and polypropylene. A combination of (core) and polyethylene (sheath), a combination of high melting point polyester (core) and low melting point polyester (sheath), and the like. In addition, a single fiber (fully fused type) composed only of a low-melting resin such as polyethylene or a hot water-soluble binder such as a polyvinyl alcohol-based fiber is easy to form a film but is used within a range that does not impair the properties. be able to.

  The sheet for dehumidification of the present invention can contain a hygroscopic salt for the purpose of improving the hygroscopic performance. Hygroscopic salts include metal halides such as lithium chloride, calcium chloride and magnesium chloride, metal sulfates such as sodium sulfate, calcium sulfate, magnesium sulfate and zinc sulfate, metal acetates such as potassium acetate, dimethylamine hydrochloride and the like Amine salts, phosphoric acid compounds such as orthophosphoric acid, guanidine salts such as guanidine hydrochloride, guanidine phosphate, and guanidine sulfamate, and metal hydroxides such as potassium hydroxide, sodium hydroxide, and magnesium hydroxide. In particular, by using a metal halide salt or a guanidine salt, it is possible to efficiently increase the amount of moisture absorption and the rate of moisture release.

  The sheet material for dehumidification of the present invention can be provided with a flame retardant as long as it does not hinder its properties. Examples of flame retardants include phosphorus flame retardants, bromine flame retardants, chlorine flame retardants, nitrogen flame retardants, silicon flame retardants, and inorganic flame retardants. Can be used. In addition, a polymer-type flame retardant such as vinyl chloride-ethylene copolymer can also be used. Inorganic flame retardants include metal hydroxides such as aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, and metatitanic acid. Examples of the method for imparting the flame retardant include a method of adding a dehumidifying sheet-like material into the raw material by a wet papermaking method, a method of impregnation, spraying, and application after forming into a sheet.

  The sheet material for dehumidification of the present invention is preferably produced by a wet papermaking method from the balance between the moisture adsorbent content and the moisture absorption / release performance. In the production method, a water adsorbent and fibrillated lyocell fiber are dispersed and mixed in water, and a flocculant is added, so that the water adsorbent grows while entraining the fibrillated lyocell fiber to form an aggregate. Furthermore, the dispersion slurry used as a papermaking raw material is produced by disperse-mixing at least 1 type or more of organic fiber there.

  In general, when the content of the moisture adsorbent in the sheet-like material is increased, the moisture adsorbent slips through the constituent fibers and the paper-making net during paper making, and is substantially contained in the sheet-like material (powder). (Body yield) decreases. However, since the sheet material for dehumidification of the present invention contains both or one of the fibrillated lyocell fibers (A) and the fibrillated lyocell fibers (B), the powder yield is increased.

  When the sheet material for dehumidification of the present invention is produced by a wet papermaking method, the agglomerating agent is used to control the agglomerates composed of the moisture adsorbent and the fibrillated lyocell fiber to an appropriate size and stabilize the structure. Used. Flocculants include basic or amphoteric metal hydroxides such as sodium hydroxide, potassium hydroxide, lithium hydroxide, zinc hydroxide, aluminum hydroxide, magnesium hydroxide, alumina, silica, aluminum silicate, magnesium silicate Inorganic water-containing oxides such as, aluminum sulfate, polyaluminum chloride, anion or cation-modified polyacrylamide, polyethylene oxide polymers, water-soluble polymers such as acrylic acid or methacrylic acid-containing copolymers, alginic acid or polyvinyl phosphoric acid and these Alkali salts such as ammonia, alkylamines such as diethylamine and ethylenediamine, alkanolamines such as ethanolamine, pyridine, morpholine, acryloylmorpholine-containing polymer, and the like. In particular, an anion or cation-modified water-soluble polymer flocculant is included. Among these, the amphoteric flocculant having both a cation unit and an anion unit in the polymer exhibits an excellent effect.

  The sheet material for dehumidification of the present invention is, for example, a paper machine for producing general paper or wet nonwoven fabric such as a long paper machine, a circular paper machine, and an inclined wire paper machine, or the same or different kinds of paper machines. Manufactured by a combination paper machine with two or more paper machines installed online. The wet paper formed by these paper machines is dried by a dryer to form a dehumidifying sheet. Thereafter, if necessary, a hygroscopic salt or the like is contained and dried with a dryer. As the dryer, an air dryer, a cylinder dryer, a suction drum dryer, an infrared dryer, or the like is used.

  The sheet material for dehumidification of the present invention can be used after being subjected to secondary processing such as pleating processing, corrugating processing, honeycomb processing, laminating processing, roll core processing, and donut processing, if necessary. Examples of the use include packaging materials, dehumidifying sheets, interior materials, filters, humidity control elements, heat exchange elements, and the like. Humidity adjustment elements and heat exchange elements include dehumidification rotor elements such as desiccant air conditioning systems, total heat exchange elements, building air conditioning vaporization type humidification elements, fuel cell humidification elements, dehumidifier dehumidification elements, and vending machines A transpiration element, a cooling water absorption transpiration element, etc. can be mentioned.

  A dehumidification rotor used in a desiccant air-conditioning system or the like can be produced by forming a sheet-like material for dehumidification of the present invention into a honeycomb structure. The honeycomb-shaped structure is a structure composed of cell walls having openings, and specifically, a corrugated honeycomb-shaped structure composed of single-sided corrugated cardboard produced in accordance with “Exterior Corrugated Cardboard” described in JIS Z1516. Body, hexagonal cell-shaped hexagon honeycomb-shaped structure, square cell-shaped honeycomb-shaped structure, triangular cell-shaped honeycomb-shaped structure, and honeycomb-shaped structure formed by assembling hollow cylindrical cells.

  A method of manufacturing a dehumidification rotor using the sheet material for dehumidification of the present invention is a method of cutting the honeycomb structure into a disk shape by a method such as die cutting, and winding the single-sided cardboard in a spiral shape. And the like.

  A dehumidification rotor having a honeycomb structure not only has a high aperture ratio and excellent air permeability, but also has a large surface area. Therefore, the dehumidification rotor made of the dehumidifying sheet of the present invention has a large capacity. It becomes a high-performance dehumidification rotor having the moisture absorption performance. In addition, problems with conventional dehumidification rotors made of inorganic materials, such as poor impact resistance, many desorption (powder removal) of water adsorbents, and restrictions on the selection of water adsorbents for high-temperature firing Can be solved.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples. In the following Examples and Comparative Examples, the parts and percentages are based on mass unless otherwise specified.

  Table 1 shows the moisture adsorbents and fibers used in the examples and comparative examples.

(Preparation of moisture adsorbent)
The moisture adsorbent (D4) was prepared by the following method. A 20 mol / kg potassium hydroxide aqueous solution is added to the anatase titanium oxide particles obtained by the sol-gel method, and the slurry obtained by heating at a temperature of 120 ° C. for 24 hours is repeatedly washed with water, and further neutralized with acetic acid. After thoroughly washing with water again to remove excess ionic components, a fibrous titanium oxide dispersion liquid aggregated into a network having a concentration of 20% by mass was obtained using a centrifuge. A part of the dispersion was dried, the powder was taken out, and the specific surface area was measured by the BET method. As a result, it was 350 m ² / g.

  The moisture adsorbent (D5) was prepared by the following method. 400 ml of an aqueous sodium orthosilicate solution diluted with pure water was prepared so that the Si concentration was 383 mmol / L. Separately, aluminum chloride was dissolved in pure water to prepare 400 ml of an aqueous solution having an Al concentration of 450 mmol / L. Next, the sodium orthosilicate aqueous solution was mixed with the aluminum chloride aqueous solution and stirred with a magnetic stirrer. The Si / Al ratio at this time was 0.85. Further, 18 ml of 1N aqueous sodium hydroxide solution was added dropwise to the mixed solution to adjust the pH to 7. The precursor was recovered from this solution by centrifugation and dispersed in 4 L of pure water. After stirring for 1 hour at room temperature, it was transferred to a 4 L sealed container and heated at 98 ° C. for 2 days in a thermostatic bath. After cooling, it was washed three times by centrifugation and dried at 60 ° C. to obtain a moisture adsorbent (D5). When the moisture adsorbent (D5) was observed with a transmission electron microscope and a scanning electron microscope, the composite particle having a particle diameter of 2 to 40 nm composed of particles having a primary particle diameter of 2 to 5 nm was 0.1 to 100 μm. 2 to 20 nm pores were found in the aggregated structure.

(Preparation of fibrillated lyocell fiber)
Three types of fibrillated lyocell fibers were prepared by the following method.

  Unfibrillated lyocell monofilament (1.7 dtex × 4 mm, manufactured by Coatles Co., Ltd.) was repeatedly treated 40 times using a double disc refiner, and fibrillated lyocell fiber (L1) having a fiber diameter of 0.9 μm or less detached from the trunk. Was prepared.

  Non-fibrillar lyocell monofilament (1.7 dtex × 4 mm, manufactured by Courtles Co., Ltd.) was repeatedly processed 30 times using a single disc refiner, and fibrillation was generated from a trunk having a fiber diameter of 4 μm or more to a branch having a fiber diameter of 1 μm or less. A lyocell fiber (L2) was prepared.

  Unfibrillated lyocell monofilament (1.7 dtex × 4 mm, manufactured by Coatles Co., Ltd.) was subjected to 40000 rotation treatment using a PFI mill, and a fibrillated lyocell fiber having a fiber diameter of 1 μm or less detached from the trunk and a fiber diameter of 4 μm or more. A mixed fiber (L3) with fibrillated lyocell fiber in which a branch having a fiber diameter of 1 μm or less was generated from the trunk was prepared.

Example 1
Water adsorbent (D1), fibrillated lyocell fiber (L1), and organic fiber (R1) were dispersed and mixed with water in a 2 m ³ tank at a ratio of 50:10:40, respectively, and a flocculant (trade name: Percoll). 57, manufactured by Ciba Specialty Chemicals Co., Ltd.) was added in an amount of 0.2% by mass based on the solid content to obtain a raw material slurry having a solid content concentration of 2% by mass. The raw material slurry was made with a circular paper machine so that the dry mass was 50 g / m ² and dried with a cylinder dryer having a surface temperature of 130 ° C. to obtain a dehumidifying sheet of Example 1. .

(Examples 2 to 18)
Dehumidifying sheet materials of Examples 2 to 18 were obtained in the same manner as in Example 1 except that the moisture adsorbent and the fibrillated lyocell fiber were changed as shown in Table 2.

(Example 19)
Water adsorbent (D1), fibrillated lyocell fiber (L1), organic fiber (R1), and heat-fusible binder fiber (M1) are dispersed in water in a 2 m ³ tank at a ratio of 50: 10: 20: 20, respectively. Furthermore, 0.2% by mass of a flocculant (trade name: Percoll 57, manufactured by Ciba Specialty Chemicals Co., Ltd.) was added to the solid content to obtain a raw material slurry having a solid content concentration of 2% by mass. . The raw slurry was made with a circular paper machine so that the dry mass was 50 g / m ^2, and dried with a cylinder dryer having a surface temperature of 130 ° C. to obtain a dehumidifying sheet of Example 19 .

(Examples 20 to 36)
Dehumidifying sheets of Examples 20 to 36 were obtained in the same manner as in Example 19 except that the moisture adsorbent and the fibrillated lyocell fiber were changed as shown in Table 2.

(Example 37)
Water adsorbent (D1), fibrillated lyocell fiber (L1), organic fiber (R2), and heat-fusible binder fiber (M2) are dispersed in water in a 2 m ³ tank at a ratio of 80: 5: 7: 8, respectively. Furthermore, 0.2% by mass of a flocculant (trade name: Percoll 57, manufactured by Ciba Specialty Chemicals Co., Ltd.) was added to the solid content to obtain a raw material slurry having a solid content concentration of 2% by mass. . The raw material slurry was made with a circular paper machine so that the dry mass was 50 g / m ^2, and dried with a cylinder dryer having a surface temperature of 130 ° C. to obtain a dehumidifying sheet of Example 37. .

(Examples 38 to 54)
Dehumidifying sheets of Examples 38 to 54 were obtained in the same manner as in Example 37 except that the moisture adsorbent and the fibrillated lyocell fiber were changed as shown in Table 3.

(Example 55)
Water adsorbent (D1), fibrillated lyocell fiber (L3), organic fiber (R1), and heat-fusible binder fiber (M1) in a 2 m ³ tank at a ratio of 50: 0.5: 29.5: 20, respectively In addition, 0.2% by mass of a flocculant (trade name: Percoll 57, manufactured by Ciba Specialty Chemicals Co., Ltd.) is added to the solid content, and the raw material has a solid content concentration of 2% by mass. A slurry was obtained. The raw slurry was made with a circular net paper machine so that the dry mass was 50 g / m ² and dried with a cylinder dryer having a surface temperature of 130 ° C. to obtain a dehumidifying sheet of Example 55. .

(Examples 56 to 60)
Dehumidifying sheet materials of Examples 56 to 60 were obtained in the same manner as Example 55 except that the moisture adsorbent was changed as shown in Table 3.

(Example 61)
The water adsorbent (D1), the fibrillated lyocell fiber (L3), and the heat-fusible binder fiber (M2) were dispersed and mixed with water in a 2 m ³ tank at a ratio of 50:30:20, respectively, and a flocculant ( Product name: Percoll 57, manufactured by Ciba Specialty Chemicals Co., Ltd.) was added in an amount of 0.2% by mass based on the solid content to obtain a raw material slurry having a solid content concentration of 2% by mass. The raw material slurry was made with a circular paper machine so that the dry mass was 50 g / m ^2, and dried with a cylinder dryer having a surface temperature of 130 ° C. to obtain a dehumidifying sheet of Example 61. .

(Examples 62 to 66)
Dehumidifying sheets of Examples 62 to 66 were obtained in the same manner as in Example 61 except that the moisture adsorbent was changed as shown in Table 3.

(Example 67)
Water adsorbent (D1), fibrillated lyocell fiber (L3), organic fiber (R1), and heat-fusible binder fiber (M1) in a 2 m ³ tank at a ratio of 50: 0.4: 29.6: 20, respectively In addition, 0.2% by mass of a flocculant (trade name: Percoll 57, manufactured by Ciba Specialty Chemicals Co., Ltd.) is added to the solid content, and the raw material has a solid content concentration of 2% by mass. A slurry was obtained. The raw material slurry was made with a circular net paper machine so that the dry mass was 50 g / m ² and dried with a cylinder dryer having a surface temperature of 130 ° C. to obtain a dehumidifying sheet of Example 67. .

Example 68
The water adsorbent (D1), the fibrillated lyocell fiber (L3), and the heat-fusible binder fiber (M1) were dispersed and mixed with water in a 2 m ³ tank at a ratio of 50:31:19, respectively. Product name: Percoll 57, manufactured by Ciba Specialty Chemicals Co., Ltd.) was added in an amount of 0.2% by mass based on the solid content to obtain a raw material slurry having a solid content concentration of 2% by mass. The raw slurry was made with a circular net paper machine so that the dry mass was 50 g / m ² and dried with a cylinder dryer having a surface temperature of 130 ° C. to obtain a dehumidifying sheet of Example 68. .

(Comparative Example 1)
Water adsorbent (D1), non-fibrillated lyocell monofilament (1.7 dtex × 5 mm, manufactured by Coatles Co., Ltd.), organic fiber (R1), and heat-fusible binder fiber (M1) were respectively 50: 10: 20: 20. The mixture is dispersed and mixed with water in a 2 m ³ tank, and a flocculant (trade name: Percoll 57, manufactured by Ciba Specialty Chemicals Co., Ltd.) is added in an amount of 0.2% by mass with respect to the solid content. A raw material slurry having a partial concentration of 2% by mass was obtained. The raw slurry was made with a circular paper machine so that the dry mass was 50 g / m ^2, and dried with a cylinder dryer having a surface temperature of 130 ° C. to obtain a dehumidifying sheet of Comparative Example 1. .

(Comparative Example 2)
Non-fibrillated lyocell monofilament (1.7 dtex × 5 mm, manufactured by Courtles Co., Ltd.) was placed in a ball mill (paint conditioner) which is a dispersing device for pigments and the like together with beads having a diameter of 2 mm and water, and treated for 11 hours. As a result, the lyocell fiber was beaten excessively, and further chopped in the fiber length direction, so that it was not fibrillated but rather finely pulverized into particles.

The water adsorbent (D1), the lyocell fiber, the organic fiber (R1), and the heat-fusible binder fiber (M1) are dispersed and mixed with water in a 2 m ³ tank at a ratio of 50: 10: 20: 20, A flocculant (trade name: Percoll 57, manufactured by Ciba Specialty Chemicals Co., Ltd.) was added in an amount of 0.2% by mass based on the solid content to obtain a raw material slurry having a solid content concentration of 2% by mass. The raw material slurry was made with a circular paper machine so that the dry mass was 50 g / m ² and dried with a cylinder dryer having a surface temperature of 130 ° C. to obtain a dehumidifying sheet of Comparative Example 2. .

(Comparative Example 3)
Moisture adsorbent (D1), fibrillated cellulose fiber (trade name: Celish KY-100G, manufactured by Daicel Chemical Industries, Ltd.) and heat-fusible binder fiber (M1) are each 2m ^{3 in} a ratio of 50:30:20. In addition, the flocculant (trade name: Percoll 57, manufactured by Ciba Specialty Chemicals Co., Ltd.) is added in an amount of 0.2% by mass to the solid content, and the solid content concentration is 2% by mass. The raw material slurry was obtained. The raw material slurry was made with a circular paper machine so that the dry mass was 50 g / m ² and dried with a cylinder dryer having a surface temperature of 130 ° C. to obtain a dehumidifying sheet of Comparative Example 3. .

(Comparative Example 4)
Water adsorbent (D1), fibrillated lyocell fiber (L1), and glass fiber (fiber diameter 9 μm, fiber length 6 mm, manufactured by Asahi Fiber Glass Co., Ltd.) are each placed in a 2 m ³ tank at a ratio of 50:10:40. Furthermore, 0.2% by mass of a flocculant (trade name: Percoll 57, manufactured by Ciba Specialty Chemicals Co., Ltd.) is added to the solid content, and a raw material slurry having a solid content concentration of 2% by mass is added. Obtained. The raw slurry is made with a circular net paper machine so that the dry mass is 45 g / m ² , and acrylic latex in the state of a wet paper web (trade name: Boncoat SFC54, Dainippon Ink & Chemicals, Inc.) The dry weight was 5 g / m ² and dried with an air dryer having a hot air temperature of 130 ° C. to obtain a dehumidifying sheet of Comparative Example 4.

  About the dehumidification sheet-like material obtained in Examples 1 to 68 and Comparative Examples 1 to 4, adsorption characteristics, powder yield, powder falling, and processability were evaluated by the following methods.

<Adsorption characteristics>
The adsorption characteristics of the dehumidifying sheet were measured by equilibrium adsorption measurement in which the mass change due to moisture adsorption was measured. A 200 mm × 200 mm test piece was collected from the sheet for dehumidification, allowed to stand in a warm air dryer at a temperature of 90 ° C. for at least 120 minutes, and the mass when dried was defined as the absolutely dry mass WD. Thereafter, the dried dehumidified sheet is regarded as an adsorption equilibrium state when it is left in a constant temperature and humidity chamber adjusted to a temperature of 25 ° C. and a relative humidity of 80%, and the mass at that time. Was the adsorption mass WA. The moisture adsorption amount W was calculated from the following formula (1).

Water adsorption amount W = (WA−WD) / WD (1)

<Powder yield>
A test piece of 150 mm × 150 mm was taken from the sheet for dehumidification, left in a hot air dryer at a temperature of 90 ° C. for at least 120 minutes, and the mass when dried was defined as the absolutely dry mass WD. Thereafter, the mass after firing in an electric furnace at a temperature of 600 ° C. for 120 minutes was defined as WB. Similarly, the moisture adsorbent (powder) contained in the dehumidifying sheet was fired to obtain PD and PB, respectively. The powder yield E was calculated from the following formula (2) from the mass value and the mixing ratio C of the moisture adsorbent at the time of making the sheet for dehumidification.

Powder yield E = WB / WD × 1 / C × PD / PB (2)

<Food fall>
A test piece of 50 mm × 200 mm was collected from the sheet for dehumidification. A test piece was placed on the black paper, and a 50 g square 200 g weight was placed on one end in the long side direction of the test piece. Then, the other end of the test piece was drawn at a speed of 100 mm / sec to observe the desorbed moisture adsorbent remaining on the black paper, and the state was evaluated in the following stage. ◎ and ○ are practically satisfactory levels.
A: Level at which almost no moisture adsorbent is observed B: Level at which desorption of water adsorbent is slightly observed Δ: Level at which fibers are slightly desorbed along with desorption of water adsorbent ×: Moisture adsorbent and fibers The level at which both detachments of

<Processability>
The folding strength FE defined in JIS P8115 was measured as one index indicating the processability of the sheet for dehumidification of the present invention. Ten test pieces each having a width of 15 mm and a length of 110 mm were sampled from the dehumidified sheet, and the number of folding times N was measured at a load of 500 g using an MIT tester. The folding strength FE was calculated from the value of the obtained folding resistance N from the following formula (3), and the average values of 10 test pieces were compared.

Folding strength FE = log ₁₀ N (3)

  The evaluation results are shown in Tables 4 and 5.

  From Examples 1 to 68 and Comparative Examples 1 to 3, the sheet material for dehumidification of the present invention is (A) a fibrillated lyocell fiber having a fiber diameter of 1 μm or less detached from the trunk by applying a shearing force, and (B) a shearing force. And at least one kind of fibrillated lyocell fiber selected from fibrillated lyocell fibers in which branches having a fiber diameter of 1 μm or less are generated from a trunk part having a fiber diameter of 2 μm or more, the moisture adsorbent is 50% or more high A high yield of 90% or more is shown despite the blending ratio. Moreover, since there is also little powder fall-off, there is little performance fall by dropping of a water | moisture-content adsorption agent, and it does not stain the periphery.

  From Examples 31, 55, 61 and Examples 67, 68, in the dehumidifying sheet of the present invention, the fibrillated lyocell fiber content is preferably 0.5 to 30% by mass. If the content of the fibrillated lyocell fiber is less than 0.5% by mass, the powder yield decreases and the amount of moisture adsorbent contained in the dehumidifying sheet decreases, so the moisture of the dehumidifying sheet There was a tendency for the amount of adsorption to decrease. On the other hand, if the amount exceeds 30% by mass, the yield of the powder is improved, but the surface of the moisture adsorbent is covered with the fibrillated lyocell fiber, so that the moisture adsorption is inhibited, resulting in the moisture content of the sheet material for dehumidification. There was a tendency for the amount of adsorption to decrease.

  From Examples 1 to 68 and Comparative Example 4, the sheet material for dehumidification of the present invention contains organic fibers, so that the flexibility is improved, the folding strength is strong, and the processability is excellent. Further, from Examples 1 to 18 and 19 to 68, by making a part or all of the organic fiber into a heat-fusible binder fiber, the strength is improved, and the dehumidifying sheet material excellent in processability and Become. Therefore, when the sheet material for dehumidification of the present invention is used for a dehumidifying rotor for desiccant air conditioning, for example, it becomes a dehumidifying rotor for desiccant air conditioning having excellent impact resistance and high moisture adsorption characteristics.

  The sheet material for dehumidification of the present invention can be used for packaging materials, dehumidifying sheets, interior materials, filters, humidity control elements, heat exchange elements, and the like. Humidity adjustment elements and heat exchange elements include dehumidification rotor elements such as desiccant air conditioning systems, total heat exchange elements, building air conditioning vaporization type humidification elements, fuel cell humidification elements, dehumidifier dehumidification elements, and vending machines. A transpiration element, a cooling water absorption transpiration element, etc. can be mentioned.

Claims (2)

  In a dehumidifying sheet containing a moisture adsorbent, (A) a fibrillated lyocell fiber having a fiber diameter of 1 μm or less detached from the trunk by applying a shearing force, and (B) a fiber diameter of 2 μm or more by applying a shearing force. A dehumidified sheet-like material comprising at least one fibrillated lyocell fiber selected from fibrillated lyocell fibers in which branches having a fiber diameter of 1 μm or less are generated from the trunk and organic fibers.   The dehumidifying sheet-like material according to claim 1, wherein at least a part of the organic fibers is a heat-fusible binder fiber.