JP2019049063A - Composite fiber of metal ferrocyanide compound and fiber and method for producing the same - Google Patents

Abstract

To provide an inorganic-fiber composite fiber in which the fiber surface is coated with a metal ferrocyanide compound such as Prussian blue.SOLUTION: The present invention provides a composite fiber of a metal ferrocyanide compound such as Prussian blue and a fiber. The composite fiber has excellent cesium adsorption ability, and is useful for treating matter contaminated with radioactive material.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a composite fiber of a ferrocyanide metal compound and a fiber and a method for producing the same. In particular, the composite fiber according to the present invention is also useful as a material having a cesium adsorption ability.

  Fibers exhibit various properties based on functional groups on the surface, etc., but depending on the application, the surface may need to be modified. So far, techniques for surface modification of fibers have been developed. Yes.

  For example, regarding a technique for depositing inorganic particles on a fiber such as cellulose fiber, Patent Document 1 describes a composite fiber in which crystalline calcium carbonate is mechanically bonded onto the fiber. Patent Document 2 describes a technique for producing a composite fiber of pulp and calcium carbonate by precipitating calcium carbonate in a pulp suspension by a carbon dioxide method. Patent Document 3 discloses a method for improving the whiteness and cleanliness of waste paper fibers by adding a large amount of filler to the fibers for paper and paperboard, and sending the slurry of waste paper pulp to a gas-liquid contact device. On the other hand, a technique is described in which an alkali salt slurry is contacted in the direction of flow with pulp in the contact zone, and a suitable reactive gas is fed and mixed with the sedimentary filler to adhere the filler to the fiber surface.

  Patent Documents 4 and 5 disclose a technique for manufacturing a fiber web in which calcium carbonate is efficiently incorporated by precipitating calcium carbonate in a step of forming a fiber web (wet paper).

Japanese Patent Laid-Open No. 06-158585 US Pat. No. 5,679,220 US Pat. No. 5,665,205 Special table 2013-521417 gazette US Patent Publication No. 2011/000633

  The subject of this invention is providing the composite fiber which the ferrocyanide compound fixed to the fiber.

The present invention includes, but is not limited to, the following inventions.
(1) A composite fiber in which a metal ferrocyanide compound is fixed to the fiber, and 15% or more of the fiber surface is coated with the metal ferrocyanide compound.
(2) The composite fiber according to (1), wherein the fiber is a cellulose fiber.
(3) The composite fiber according to (1) or (2), wherein the ferrocyanide metal compound is Prussian blue.
(4) The composite fiber according to any one of (1) to (3), wherein the weight ratio of the metal ferrocyanide compound to the fiber is 5/95 to 95/5.
(5) The method for producing a conjugate fiber according to any one of (1) to (4), wherein the fiber, an inorganic salt of hexacyano metal acid, and an inorganic compound containing a transition metal are mixed in a solution, The above method comprising the step of synthesizing the ferrocyanide compound on the fiber.
(6) The step of synthesizing the ferrocyanide metal compound on the fiber comprises (a) mixing an inorganic salt of hexacyanometal acid and the fiber in the solution, (b) the solution obtained in step a, and the transition metal Mixing with the inorganic compound containing an element, The method as described in (5).
(7) The step of synthesizing the ferrocyanide metal compound on the fiber comprises (a) mixing the inorganic compound containing the transition metal element and the fiber in the solution, (b) the solution obtained in step a, and hexacyano The method according to (5), comprising mixing with an inorganic salt of a metal acid.
(8) The method according to any one of (5) to (7), wherein the inorganic salt of hexacyanometal acid is hexacyanoferrate.
(9) The method according to any one of (5) to (8), wherein the inorganic compound containing the transition metal element is an inorganic compound containing iron.
(10) A cesium adsorbent comprising the composite fiber according to any one of (1) to (4).

  ADVANTAGE OF THE INVENTION According to this invention, the fiber by which the surface was coat | covered with the ferrocyanide metal compound can be provided. In particular, according to the present invention, a composite fiber in which 15% or more of the fiber surface is coated with a ferrocyanide compound can be obtained.

  That is, by coating the fiber surface with a ferrocyanide metal compound, a unique composite fiber having the characteristics of both the fiber and the ferrocyanide compound can be obtained. In particular, by covering the fiber surface with Prussian blue, it becomes possible to obtain a composite fiber having cesium adsorption ability. Moreover, since the metal ferrocyanide compound adheres to the fiber, the composite fiber according to the present invention is easy to process and easy to handle.

FIG. 1 is an electron micrograph of Sample 1 synthesized in Experiment 1 (left: 500 times, right: 10,000 times). FIG. 2 shows X-ray diffraction data of a sheet manufactured from Sample 1. Of the two charts, the top is the X-ray diffraction data of sample 1, and the bottom is the X-ray diffraction data of Prussian blue alone (●: peak characteristic of Prussian blue).

  The present invention relates to a fiber whose surface is coated with a metal ferrocyanide such as Prussian blue. In particular, according to the present invention, in a preferred embodiment, a composite fiber in which 15% or more of the fiber surface is coated with a ferrocyanide metal compound such as Prussian blue can be obtained.

  In addition, the composite fiber of the present invention is not simply a mixture of a fiber and a ferrocyanide compound such as Prussian blue, but both are fixed (bound). Such as ferrocyanide compound is less likely to fall off the fiber. The strength of binding can be evaluated by, for example, a numerical value such as ash yield (%, that is, ash content of the sheet ÷ ash content of the composite fiber before disaggregation × 100). Specifically, the composite fiber is dispersed in water, adjusted to a solid content concentration of 0.2%, and disaggregated for 5 minutes with a standard disaggregator specified in JIS P 8220-1: 2012, and in accordance with JIS P 8222: 1998. The ash yield when sheeted using a 150 mesh wire can be used for evaluation. In a preferred embodiment, the ash yield is 20% by mass or more, and in a more preferred embodiment, the ash yield is 50% by mass or more. is there.

Fiber In the present invention, a ferrocyanide metal compound such as Prussian blue is fixed to a fiber such as cellulose fiber or aramid fiber. The fiber constituting the composite fiber is preferably a cellulose fiber. For example, natural fiber, but also regenerated fiber (semi-synthetic fiber) such as rayon and lyocell, and synthetic fiber can be used without limitation. . Examples of cellulose fibers include pulp fibers (wood pulp and non-wood pulp), cellulose nanofibers (CNF), bacterial cellulose, animal-derived cellulose such as sea squirts, and algae. Wood pulp is produced by pulping wood raw materials. do it. Wood raw materials include red pine, black pine, todomatsu, spruce, beech pine, larch, fir, tsuga, cedar, hinoki, larch, shirabe, spruce, hiba, douglas fir, hemlock, white fur, spruce, balsam fur, cedar, pine, Coniferous trees such as Merck pine, Radiata pine, etc., and mixed materials thereof, beech, hippopotamus, alder tree, oak, tab, shii, birch, broadleaf tree, poplar, tamo, dragonfly, eucalyptus, mangrove, lawan, acacia, etc. Examples are materials.

  The method for pulping natural materials such as wood raw materials (woody raw materials) is not particularly limited, and examples thereof include pulping methods generally used in the paper industry. Wood pulp can be classified by pulping method, for example, chemical pulp digested by methods such as kraft method, sulfite method, soda method, polysulfide method; mechanical pulp obtained by pulping by mechanical force such as refiner, grinder; Semi-chemical pulp obtained by carrying out pulping by mechanical force after pretreatment by; waste paper pulp; deinked pulp and the like. Wood pulp may be unbleached (before bleaching) or bleached (after bleaching).

  Examples of the non-wood-derived pulp include cotton, hemp, sisal hemp, manila hemp, flax, straw, bamboo, bagasse, kenaf, sugar cane, corn, rice straw, straw, honey and so on.

The pulp fiber may be either unbeaten or beaten, and may be appropriately selected, but it is preferable to beaten. Thereby, improvement of sheet strength and promotion of fixing of inorganic particles can be expected.
A composite fiber of a synthetic fiber and a cellulose fiber can also be used in the present invention. For example, a composite fiber of a polyester fiber, a polyamide, a polyolefin, an acrylic fiber, a glass fiber, a carbon fiber, various metal fibers, etc. and a cellulose fiber is also used. be able to.

  Further, powdered cellulose obtained by further processing the cellulose raw material, chemically modified cellulose such as oxidized cellulose, and cellulose nanofiber (microfibrillated cellulose: MFC, TEMPO oxidized CNF, phosphate esterified CNF, carboxymethylated CNF, mechanical pulverization CNF etc.) can also be used as the cellulose fiber. As the powdered cellulose used in the present invention, for example, a fixed particle size in the form of a rod shaft produced by a method of purifying and drying an undegraded residue obtained after acid hydrolysis of a selected pulp, pulverizing and sieving. A crystalline cellulose powder having a distribution may be used, or commercially available products such as KC Flock (manufactured by Nippon Paper Industries), Theolas (manufactured by Asahi Kasei Chemicals), and Avicel (manufactured by FMC) may be used. The degree of polymerization of cellulose in powdered cellulose is preferably about 100 to 1500, the degree of crystallinity of powdered cellulose by X-ray diffraction is preferably 70 to 90%, and the volume average particle size by a laser diffraction type particle size distribution analyzer. Is preferably 1 to 100 μm. The oxidized cellulose used in the present invention can be obtained, for example, by oxidizing in water using an oxidizing agent in the presence of a compound selected from the group consisting of N-oxyl compounds and bromides, iodides or mixtures thereof. it can. As the cellulose nanofiber, a method of defibrating the cellulose raw material is used. As the defibrating method, for example, an aqueous suspension of chemically modified cellulose such as cellulose or oxidized cellulose is mechanically ground or beaten with a refiner, a high-pressure homogenizer, a grinder, a single or multi-screw kneader, a bead mill, or the like. A method of defibration can be used. Cellulose nanofibers may be produced by combining one or more of the above methods. The fiber diameter of the produced cellulose nanofiber can be confirmed by observation with an electron microscope, and is, for example, in the range of 5 nm to 1000 nm, preferably 5 nm to 500 nm, more preferably 5 nm to 300 nm. When producing the cellulose nanofiber, before and / or after the cellulose is defibrated and / or refined, an arbitrary compound may be further added and reacted with the cellulose nanofiber to modify the hydroxyl group. it can. Examples of functional groups to be modified include acetyl group, ester group, ether group, ketone group, formyl group, benzoyl group, acetal, hemiacetal, oxime, isonitrile, allene, thiol group, urea group, cyano group, nitro group, azo group , Aryl group, aralkyl group, amino group, amide group, imide group, acryloyl group, methacryloyl group, propionyl group, propioyl group, butyryl group, 2-butyryl group, pentanoyl group, hexanoyl group, heptanoyl group, octanoyl group, nonanoyl group , Decanoyl group, undecanoyl group, dodecanoyl group, myristoyl group, palmitoyl group, stearoyl group, pivaloyl group, benzoyl group, naphthoyl group, nicotinoyl group, isonicotinoyl group, furoyl group, cinnamoyl group, etc., 2-methacryloyl group Isocyanate groups such as oxyethylisocyanoyl group, methyl group, ethyl group, propyl group, 2-propyl group, butyl group, 2-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl Group, decyl group, undecyl group, dodecyl group, myristyl group, palmityl group, stearyl group and other alkyl groups, oxirane group, oxetane group, oxyl group, thiirane group, thietane group and the like. Hydrogen in these substituents may be substituted with a functional group such as a hydroxyl group or a carboxy group. Further, a part of the alkyl group may be an unsaturated bond. The compound used for introducing these functional groups is not particularly limited. For example, a compound having a phosphoric acid-derived group, a compound having a carboxylic acid-derived group, a compound having a sulfuric acid-derived group, or a sulfonic acid-derived compound And the like, compounds having an alkyl group, compounds having an amine-derived group, and the like. Although it does not specifically limit as a compound which has a phosphoric acid group, Lithium dihydrogen phosphate which is phosphoric acid and the lithium salt of phosphoric acid, Dilithium hydrogen phosphate, Trilithium phosphate, Lithium pyrophosphate, Lithium polyphosphate is mentioned. . Furthermore, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate and sodium polyphosphate which are sodium salts of phosphoric acid are mentioned. Furthermore, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, and potassium polyphosphate which are potassium salts of phosphoric acid are mentioned. Further, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, and ammonium polyphosphate which are ammonium salts of phosphoric acid are included. Of these, phosphoric acid, sodium phosphate, phosphoric acid potassium salt, and phosphoric acid ammonium salt are preferred from the viewpoint of high efficiency in introducing a phosphate group and easy industrial application. Sodium dihydrogen phosphate Although disodium hydrogen phosphate is more preferable, it is not particularly limited. The compound having a carboxyl group is not particularly limited, and examples thereof include dicarboxylic acid compounds such as maleic acid, succinic acid, phthalic acid, fumaric acid, glutaric acid, adipic acid and itaconic acid, and tricarboxylic acid compounds such as citric acid and aconitic acid. . The acid anhydride of the compound having a carboxyl group is not particularly limited, but examples thereof include acid anhydrides of dicarboxylic acid compounds such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, and itaconic anhydride. It is done. Although it does not specifically limit as a derivative of the compound which has a carboxyl group, The derivative of the acid anhydride of the compound which has a carboxyl group and the acid anhydride imidation of a compound which has a carboxyl group are mentioned. Although it does not specifically limit as an acid anhydride imidation thing of a compound which has a carboxyl group, Imidation thing of dicarboxylic acid compounds, such as maleimide, succinic acid imide, and phthalic acid imide, is mentioned. The acid anhydride derivative of the compound having a carboxyl group is not particularly limited. For example, at least some of the hydrogen atoms of the acid anhydride of the compound having a carboxyl group, such as dimethylmaleic anhydride, diethylmaleic anhydride, diphenylmaleic anhydride, etc. are substituted (for example, alkyl group, phenyl group, etc. ) Are substituted. Among the compounds having a group derived from a carboxylic acid, maleic anhydride, succinic anhydride, and phthalic anhydride are preferred because they are easily applied industrially and easily gasified, but are not particularly limited. Further, the cellulose nanofiber may be modified in such a manner that the compound to be modified is physically adsorbed on the cellulose nanofiber without being chemically bonded. Examples of the physically adsorbing compound include surfactants, and any of anionic, cationic, and nonionic may be used. When the above-described modification is performed before cellulose is defibrated and / or pulverized, these functional groups can be removed after defibrating and / or pulverization to return to the original hydroxyl group. By performing the modification as described above, it is possible to promote the defibration of the cellulose nanofiber or to easily mix it with various substances when the cellulose nanofiber is used.

  The fibers shown above may be used alone or in combination. Especially, it is preferable that wood pulp is included or the combination of wood pulp, non-wood pulp, and / or synthetic fiber is included, and it is more preferable that it is only wood pulp.

  In a preferred embodiment, the fibers constituting the conjugate fiber of the present invention are pulp fibers. Further, for example, a fibrous material recovered from wastewater of a paper mill may be supplied to the present invention. By supplying such a substance to the reaction tank, various composite fibers can be synthesized.

  In the present invention, in addition to the fiber, a substance that is incorporated into the product inorganic particles to form composite particles can be used. In the present invention, fibers such as pulp fibers are used, but in addition, by synthesizing a ferrocyanide metal compound such as Prussian blue in a solution containing inorganic particles, organic particles, polymers and the like, Furthermore, it is possible to produce composite particles incorporating these substances.

  The fiber length of the fibers to be combined is not particularly limited. For example, the average fiber length may be about 0.1 μm to 15 mm, and may be 1 μm to 12 mm, 100 μm to 10 mm, 500 μm to 8 mm, and the like.

  The fiber to be combined is preferably used in such an amount that 15% or more of the fiber surface is coated with a ferrocyanide metal compound such as Prussian blue, but the coating is 30% or more, 50% or more, 70% or more. It is good also as a rate. Further, for example, the weight ratio of the fiber and the metal ferrocyanide compound such as Prussian blue can be 5/95 to 95/5, 20/80 to 94/6, 40/60 to 93/7, 60. / 40 to 92/8 or 80/20 to 91/9.

  In the composite fiber according to the present invention, 15% or more of the fiber surface is coated with a ferrocyanide metal compound such as Prussian blue, and when the surface of the cellulose fiber is coated with such an area ratio, the fiber such as Prussian blue is coated. While the characteristics resulting from the metallized metal compound become larger, the characteristics resulting from the fiber surface become smaller.

Ferrocyanide metal compound In the present invention, the metal ferrocyanide compounded with fibers such as cellulose fibers is not particularly limited, but can be synthesized by a known method. Synthesis of ferrocyanide metal compounds such as Prussian blue may be carried out in solution, and composite fibers may be used in an aqueous system.

  In the present invention, Prussian blue (PB) is preferable as the metal ferrocyanide compounded with fibers such as cellulose fibers. However, cobalt ferrocyanide, nickel ferrocyanide, copper ferrocyanide, and zinc ferrocyanide are also used. Good.

Prussian blue (Fe ₄ [Fe (CN) ₃ ] ₃ ) is a compound called hexacyanide iron (II) iron (III) ferrate (III) ferrocyanide, ferric ferrocyanide, etc. It is widely used in indigo and scarlet paints, printing inks, and paints. Prussian blue has a Prussian blue complex structure. Specifically, Fe ³⁺ ions form a face-centered cubic lattice, and Fe ²⁺ ions, Fe ³⁺ ions, and Fe ²⁺ ions are formed at the midpoints of the sides of the cube. has a crystal structure ions are located ^- CN between. In the present invention, Prussian blue may contain water of crystallization or may be partially substituted with iron ions, and examples thereof include Li ⁺ , Na ⁺ , K ⁺ , NH ₄ ^{+ and the} like. Is Na ⁺ and / or K ⁺ .

Prussian blue is also used as an adsorbent for cesium. When cesium 137 is ingested due to an accident or the like, it is treated with Prussian blue. Prussian blue is known to bind to cesium, and ingesting it can promote the excretion of cesium out of the body. In addition, Prussian blue is said to be able to suppress contamination of milk and meat when added to the feed of livestock (such as cattle) that are bred and raised based on the redox type ion exchange capacity.
In the present invention, by mixing a fiber, an inorganic salt of hexacyano metal acid, and an inorganic compound containing a transition metal in a solution, the ferrocyanide metal Compound and fiber composite fibers can be produced. For example, (a) fiber and an inorganic salt of hexacyano metal acid are mixed, and (b) the solution obtained in step a is mixed with an inorganic compound containing a transition metal element, or (a) fiber And an inorganic compound containing a transition metal element, and (b) mixing the solution obtained in step a with an inorganic salt of hexacyanometal acid, thereby combining a composite fiber of a ferrocyanide metal compound and a fiber. Can be manufactured.

  In that case, it is preferable to mix the aqueous solution of the inorganic compound containing a transition metal element, or the inorganic salt of hexacyano metal acid with the solution obtained at the process a at 1 ml / min-50 ml / min.

Prussian blue can be synthesized, for example, by reacting an aqueous solution of an iron cyano complex with an aqueous solution of a divalent and / or trivalent iron salt compound. Preferable examples of iron cyano complexes used for Prussian blue synthesis include ferrocyan compounds (M ₄ Fe (II) (CN) ₆ ) and ferricyan compounds (M ₄ Fe (III) (CN) ₆ ). Can do. The concentration of the aqueous solution of iron cyano complex can be, for example, 0.01% to 30%, preferably 0.05% to 10%, and more preferably 0.1% to 5%. The aqueous solution of the divalent and / or trivalent iron salt compound can have a concentration of, for example, 0.01% to 20%, preferably 0.5% to 10%, more preferably 1% to 5%. It is.
The aqueous solution of the iron salt compound may be added gradually, for example, by dropping, or may be added at once.

  In one preferred embodiment, the conjugate fiber of the present invention can be obtained by synthesizing a ferrocyanide metal compound such as Prussian blue in the presence of a fiber such as cellulose fiber. This is because the fiber surface is a suitable place for precipitation of ferrocyanide metal compounds such as Prussian blue, and it is easy to synthesize composite fibers of ferrocyanide metal compounds such as Prussian blue and cellulose fibers.

  As one preferred embodiment, the average primary particle diameter of the ferrocyanide compound such as Prussian blue in the composite fiber of the present invention can be set to, for example, 1.5 μm or less, but the average primary particle diameter is 1200 nm or less or 900 nm. The average primary particle diameter can be 200 nm or less or 150 nm or less. In addition, the average primary particle diameter of the metal ferrocyanide compound such as Prussian blue can be 10 nm or more. The average primary particle diameter can be measured with an electron micrograph.

  Further, the ferrocyanide compound such as Prussian blue in the composite fiber of the present invention may take the form of secondary particles in which fine primary particles are aggregated, and secondary particles corresponding to the application are generated by an aging process. The agglomerates can be made fine by grinding. For grinding, ball mill, sand grinder mill, impact mill, high-pressure homogenizer, low-pressure homogenizer, dyno mill, ultrasonic mill, kanda grinder, attritor, stone mill, vibration mill, cutter mill, jet mill, breaker, beater Short shaft extruder, twin screw extruder, ultrasonic stirrer, household juicer mixer and the like.

  The average particle size and shape of the ferrocyanide metal compound constituting the composite fiber of the present invention can be confirmed by observation with an electron microscope. Furthermore, by adjusting the conditions for synthesizing a metal ferrocyanide compound such as Prussian blue, a metal ferrocyanide compound having various sizes and shapes can be combined with the fiber.

Composite fiber The composite fiber obtained by the present invention can be used in various shapes, for example, powder, pellet, mold, aqueous suspension, paste, sheet, bead, and other shapes. . Moreover, it can also be set as molded objects, such as a mold, particle | grains, and a pellet, with a composite fiber as a main component and other materials. There is no particular limitation on the dryer in the case of drying into a powder, but for example, an air dryer, a band dryer, a spray dryer or the like can be preferably used.

  The composite fiber obtained by the present invention can be used for various applications, for example, paper, fiber, cellulosic composite material, filter material, paint, plastic and other resins, rubber, elastomer, ceramic, glass, tire. , Building materials (asphalt, asbestos, cement, board, concrete, brick, tile, plywood, fiberboard, etc.), various carriers (catalyst carrier, pharmaceutical carrier, agricultural chemical carrier, microbial carrier, etc.), adsorbent (impurity removal, deodorization) , Dehumidifier, etc.), anti-wrinkle agent, clay, abrasive, modifier, repair material, heat insulating material, heat resistant material, heat radiating material, moisture proof material, water repellent material, water resistant material, light shielding material, sealant, shield material, insect repellent , Adhesives, inks, cosmetics, medical materials, paste materials, anti-discoloring agents, food additives, tablet excipients, dispersants, shape retention agents, water retention agents, filter aids, essential oil materials, oil treatment agents Oil modifiers, radio wave absorbers, insulation materials, sound insulation materials, vibration insulation materials, semiconductor sealing materials, radiation shielding materials, cosmetics, fertilizers, feeds, fragrances, additives for paints and adhesives, flame retardant materials, sanitary goods It can be widely used for all uses such as (disposable diapers, sanitary napkins, incontinence pads, breast milk pads, etc.). Moreover, it can be used for various fillers and coating agents in the above applications.

  In particular, the composite fiber according to the present invention is preferably used as a decontamination material such as a cesium adsorbent. For example, according to the conjugate fiber according to the present invention, radioactive cesium can be efficiently and easily removed from contaminated water containing radioactive cesium. In the radioactive cesium adsorbent of the present invention, the type of radioactive cesium that can be adsorbed is not particularly limited. For example, any of radioactive cesium 137, radioactive cesium 134, and combinations thereof can exhibit good adsorption performance. The property of the radioactive cesium adsorbent is not particularly limited, and any of a dispersion, a hydrated product, a dried product, and the like may be used.

  The conjugate fiber of the present invention may be applied to papermaking applications, for example, printing paper, newspaper, inkjet paper, PPC paper, kraft paper, fine paper, coated paper, fine coated paper, wrapping paper, thin paper, and color quality. Paper, cast coated paper, non-carbon paper, label paper, thermal paper, various fancy papers, water-soluble paper, release paper, process paper, base paper for wallpaper, non-combustible paper, flame retardant paper, laminated base paper, printed electronics paper, battery Separator, cushion paper, tracing paper, impregnated paper, ODP paper, building paper, decorative paper, envelope paper, tape paper, heat exchange paper, synthetic fiber paper, sterilized paper, water resistant paper, oil resistant paper, heat resistant paper, photocatalyst Paper, decorative paper (grease paper, etc.), various sanitary paper (toilet paper, tissue paper, wipers, diapers, sanitary products, etc.), tobacco paper, paperboard (liner) Corrugating medium, such as white paperboard), paper plates base paper cup base paper, baking paper, abrasive paper, and synthetic paper. That is, according to the present invention, a composite fiber of inorganic particles and fibers having a small primary particle size and a narrow particle size distribution can be obtained, which is different from the conventional inorganic filler having a particle size of more than 2 μm. Can exhibit its characteristics. Furthermore, unlike the case where the inorganic particles are simply blended with the fibers, if the inorganic particles are combined with the fibers, the inorganic particles are not only easily retained on the sheet, but also a sheet in which the particles are uniformly dispersed without agglomeration. Can be obtained. In the preferred embodiment, the inorganic particles in the present invention are not only fixed on the outer surface of the fiber and the inner side of the lumen, but are also generated on the inner side of the microfibril.

  Moreover, when using the composite fiber obtained by this invention, the particle | grains generally called an inorganic filler and an organic filler, and various fibers can be used together. For example, as inorganic filler, calcium carbonate (light calcium carbonate, heavy calcium carbonate), magnesium carbonate, barium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, clay (kaolin, calcined kaolin, deramikaolin) ), Talc, zinc oxide, zinc stearate, titanium dioxide, silica made from sodium silicate and mineral acid (white carbon, silica / calcium carbonate composite fiber, silica / titanium dioxide composite fiber), white clay, bentonite, diatomaceous earth, Examples thereof include calcium sulfate, zeolite, an inorganic filler that regenerates and uses the ash obtained from the deinking process, and an inorganic filler that forms a composite fiber with silica or calcium carbonate in the process of regeneration. As the calcium carbonate-silica composite, amorphous silica such as white carbon may be used together with calcium carbonate and / or light calcium carbonate-silica composite. Organic fillers include urea-formalin resin, polystyrene resin, phenol resin, fine hollow particles, acrylamide composite fiber, wood-derived materials (fine fiber, microfibril fiber, powder kenaf), modified insolubilized starch, ungelatinized starch, etc. Is mentioned. Fibers include natural fibers such as cellulose, synthetic fibers that are artificially synthesized from raw materials such as petroleum, regenerated fibers (semi-synthetic fibers) such as rayon and lyocell, and inorganic fibers. Can be used. In addition to the above, the natural fibers include protein fibers such as wool, silk thread and collagen fibers, and complex sugar chain fibers such as chitin / chitosan fibers and alginic acid fibers. Examples of the cellulose-based raw material include pulp fibers (wood pulp and non-wood pulp), animal-derived cellulose such as bacterial cellulose and sea squirt, and algae. The wood pulp may be produced by pulping the wood raw material. Wood raw materials include red pine, black pine, todomatsu, spruce, beech pine, larch, fir, tsuga, cedar, hinoki, larch, shirabe, spruce, hiba, douglas fir, hemlock, white fur, spruce, balsam fur, cedar, pine, Coniferous trees such as Merck pine, Radiata pine, etc., and mixed materials thereof, beech, hippopotamus, alder tree, oak, tab, shii, birch, broadleaf tree, poplar, tamo, dragonfly, eucalyptus, mangrove, lawan, acacia, etc. Examples are materials. The method for pulping the wood raw material is not particularly limited, and examples thereof include a pulping method generally used in the paper industry. Wood pulp can be classified by pulping method, for example, chemical pulp digested by methods such as kraft method, sulfite method, soda method, polysulfide method; mechanical pulp obtained by pulping by mechanical force such as refiner, grinder; Semi-chemical pulp obtained by carrying out pulping by mechanical force after pretreatment by; waste paper pulp; deinked pulp and the like. Wood pulp may be unbleached (before bleaching) or bleached (after bleaching). Examples of the non-wood-derived pulp include cotton, hemp, sisal hemp, manila hemp, flax, straw, bamboo, bagasse, kenaf, sugar cane, corn, rice straw, straw, honey and so on. Wood pulp and non-wood pulp may be either unbeaten or beaten. Further, these cellulose raw materials are further processed to give powdery cellulose, chemically modified cellulose such as oxidized cellulose, and cellulose nanofiber: CNF (microfibrillated cellulose: MFC, TEMPO oxidized CNF, phosphate esterified CNF, carboxymethylated). CNF, mechanically pulverized CNF). Synthetic fibers include polyester, polyamide, polyolefin, acrylic fiber, semi-spun fibers include rayon and acetate, and inorganic fibers include glass fiber, carbon fiber, and various metal fibers. About these, these may be used alone or in combination of two or more.

Synthesis of composite fiber In one embodiment of the present invention, a composite fiber can be synthesized by synthesizing a ferrocyanide metal compound such as Prussian blue in a solution containing the fiber. Can be performed by a known method.

  In the present invention, the reaction can be started after promoting the swelling of the fiber by stirring after mixing the raw materials (for example, 15 minutes or more), but the reaction may be started immediately after mixing. There is no particular limitation on the form of the reaction tank and the stirring conditions for obtaining this composite fiber, for example, a solution containing a precursor of a metal ferrocyanide compound such as Prussian blue and the fiber is stirred in an open reaction tank, A composite fiber may be synthesized by mixing, or may be synthesized by spraying an aqueous suspension containing a precursor of a metal ferrocyanide compound such as Prussian blue and the fiber into a reaction vessel. As will be described later, when jetting an aqueous suspension of a precursor of a metal ferrocyanide compound such as Prussian blue into a reaction vessel, cavitation bubbles may be generated and synthesized in the presence thereof.

  In the present invention, water is used for the preparation of the suspension. As this water, normal tap water, industrial water, ground water, well water, etc. can be used, ion-exchanged water, distilled water, Pure water, industrial waste water, and water obtained when separating and dehydrating the reaction liquid can be suitably used.

  Moreover, in this invention, the reaction liquid of a reaction tank can be circulated and used. By circulating the reaction liquid in this way and urging the solution to be stirred, the reaction efficiency is increased and it becomes easy to obtain a desired composite fiber.

  When producing the conjugate fiber of the present invention, various known auxiliary agents can be further added. For example, chelating agents can be added. Specifically, polyhydroxycarboxylic acids such as citric acid, malic acid and tartaric acid, dicarboxylic acids such as oxalic acid, sugar acids such as gluconic acid, iminodiacetic acid, ethylenediaminetetra Aminopolycarboxylic acids such as acetic acid and their alkali metal salts, alkali metal salts of polyphosphoric acid such as hexametaphosphoric acid and tripolyphosphoric acid, amino acids such as glutamic acid and aspartic acid and their alkali metal salts, acetylacetone, methyl acetoacetate, acetoacetic acid Examples include ketones such as allyl, saccharides such as sucrose, and polyols such as sorbitol. In addition, as surface treatment agents, saturated fatty acids such as palmitic acid and stearic acid, unsaturated fatty acids such as oleic acid and linoleic acid, resin acids such as alicyclic carboxylic acid and abietic acid, salts, esters and ethers thereof, alcohols Activators, sorbitan fatty acid esters, amide or amine surfactants, polyoxyalkylene alkyl ethers, polyoxyethylene nonyl phenyl ether, sodium alpha olefin sulfonate, long chain alkyl amino acids, amine oxides, alkyl amines, fourth A quaternary ammonium salt, aminocarboxylic acid, phosphonic acid, polyvalent carboxylic acid, condensed phosphoric acid and the like can be added. Moreover, a dispersing agent can also be used as needed. Examples of the dispersant include sodium polyacrylate, sucrose fatty acid ester, glycerin fatty acid ester, acrylic acid-maleic acid copolymer ammonium salt, methacrylic acid-naphthoxypolyethylene glycol acrylate copolymer, methacrylic acid-polyethylene glycol. Examples include monomethacrylate copolymer ammonium salts and polyethylene glycol monoacrylate. These can be used alone or in combination. The timing of addition may be before or after the synthesis reaction. Such an additive can be added in an amount of preferably 0.001 to 20%, more preferably 0.1 to 10% with respect to the inorganic particles.

  When synthesizing the composite fiber in the present invention, the reaction conditions are not particularly limited, and can be appropriately set according to the application. For example, the temperature of the synthesis reaction can be 0 to 90 ° C, preferably 10 to 70 ° C. The reaction temperature can be controlled by a temperature controller, and if the temperature is low, the reaction efficiency decreases and the cost increases, whereas if it exceeds 90 ° C., coarse inorganic particles tend to increase.

  In the present invention, the reaction can be a batch reaction or a continuous reaction. In general, it is preferable to perform a batch reaction step for the convenience of discharging the residue after the reaction. The scale of the reaction is not particularly limited, but the reaction may be performed on a scale of 100 L or less, or may be performed on a scale of more than 100 L. The size of the reaction vessel can be, for example, about 10 L to 100 L, or about 100 L to 1000 L.

  In addition, the reaction can be controlled by the electric conductivity of the reaction solution and the reaction time. Specifically, the time during which the reaction product stays in the reaction vessel can be adjusted and controlled. In addition, in this invention, reaction can also be controlled by stirring the reaction liquid of a reaction tank or making reaction multistage reaction.

  In the present invention, since the composite fiber as a reaction product is obtained as a suspension, it can be stored in a storage tank or subjected to treatments such as concentration, dehydration, pulverization, classification, aging, and dispersion as necessary. can do. These can be performed by known processes, and may be appropriately determined in consideration of the application and energy efficiency. For example, the concentration / dehydration treatment is performed using a centrifugal dehydrator, a sedimentation concentrator, or the like. Examples of the centrifugal dehydrator include a decanter and a screw decanter. When using a filter or a dehydrator, the type is not particularly limited and a general one can be used. For example, a pressure-type dehydrator such as a filter press, a drum filter, a belt press, a tube press, A calcium carbonate cake can be obtained by suitably using a vacuum drum dehydrator such as an Oliver filter. For grinding, ball mill, sand grinder mill, impact mill, high-pressure homogenizer, low-pressure homogenizer, dyno mill, ultrasonic mill, kanda grinder, attritor, stone mill, vibration mill, cutter mill, jet mill, breaker, beater Short shaft extruder, twin screw extruder, ultrasonic stirrer, household juicer mixer and the like. Examples of the classification method include a sieve such as a mesh, an outward type or inward type slit or round hole screen, a vibrating screen, a heavy foreign matter cleaner, a lightweight foreign matter cleaner, a reverse cleaner, a sieving tester, and the like. Examples of the dispersion method include a high-speed disperser and a low-speed kneader.

  The composite fiber obtained by the present invention can be blended in a filler or pigment in a suspension state without being completely dehydrated, but can also be dried to form a powder. Although there is no restriction | limiting in particular also about the dryer in this case, For example, an airflow dryer, a band dryer, a spray dryer etc. can be used conveniently.

  The composite fiber obtained by the present invention can be modified by a known method. For example, in an embodiment, the surface can be hydrophobized to improve miscibility with a resin or the like.

  In the present invention, the liquid may be ejected under conditions that cause cavitation bubbles in the reaction vessel, or may be ejected under conditions that do not cause cavitation bubbles. The reaction vessel is preferably a pressure vessel in any case. In addition, the pressure vessel in this invention is a container which can apply the pressure of 0.005 Mpa or more. In the condition that does not generate cavitation bubbles, the pressure in the pressure vessel is preferably 0.005 MPa to 0.9 MPa in static pressure.

(Cavitation bubbles)
When the composite fiber according to the present invention is synthesized, Prussian blue can be precipitated in the presence of cavitation bubbles. In the present invention, cavitation is a physical phenomenon in which bubbles are generated and disappear in a short time due to a pressure difference in a fluid flow, and is also referred to as a cavity phenomenon. Bubbles generated by cavitation (cavitation bubbles) are generated with very small “bubble nuclei” of 100 microns or less existing in the liquid as the nucleus when the pressure in the fluid becomes lower than the saturated vapor pressure for a very short time.

  In the present invention, cavitation bubbles can be generated in the reaction vessel by a known method. For example, cavitation bubbles are generated by jetting fluid at high pressure, cavitation is generated by stirring at high speed in the fluid, cavitation is generated by causing explosion in the fluid, ultrasonic vibration It can be considered that cavitation is generated by a child (vibratory cavitation).

  In particular, in the present invention, since cavitation bubbles are easily generated and controlled, it is preferable to generate cavitation bubbles by ejecting a fluid at a high pressure. In this aspect, by compressing the jet liquid using a pump or the like and jetting it through a nozzle or the like at high speed, cavitation bubbles are generated at the same time as the liquid itself expands due to extremely high shearing force near the nozzle and sudden pressure reduction. . The method using a fluid jet has high generation efficiency of cavitation bubbles, and can generate cavitation bubbles having a stronger collapse impact force. In the present invention, the presence of controlled cavitation bubbles when synthesizing Prussian blue is clearly different from cavitation bubbles that cause uncontrollable harm that naturally occurs in fluid machinery.

  In the present invention, cavitation can be generated by using a reaction solution such as a raw material as an injection liquid as it is, or cavitation bubbles can be generated by injecting some fluid into the reaction vessel. The fluid in which the liquid jet forms a jet may be any liquid, gas, solid such as powder or pulp, or a mixture thereof as long as it is in a fluid state. Further, if necessary, another fluid such as carbon dioxide can be added to the above fluid as a new fluid. The fluid and the new fluid may be uniformly mixed and ejected, but may be ejected separately.

  The liquid jet is a jet of a fluid or a fluid in which solid particles or gas are dispersed or mixed in the liquid, and refers to a liquid jet containing raw slurry or bubbles of pulp or inorganic particles. The gas referred to here may include bubbles due to cavitation.

Further, when the cavitation is generated by injecting the injection liquid through the nozzle or the orifice pipe, the pressure of the injection liquid (upstream pressure) is desirably 0.01 MPa or more and 30 MPa or less, and 0.7 MPa or more and 20 MPa or less. It is preferable that it is 2 MPa or more and 15 MPa or less. When the upstream pressure is less than 0.01 MPa, it is difficult to produce a pressure difference with the downstream pressure, and the effect is small. On the other hand, when the pressure is higher than 30 MPa, a special pump and a pressure vessel are required, and energy consumption increases, which is disadvantageous in terms of cost. On the other hand, the pressure in the container (downstream pressure) is preferably 0.005 MPa to 0.9 MPa in static pressure.
Moreover, the ratio of the pressure in the container and the pressure of the jet liquid is preferably in the range of 0.001 to 0.5.

  In the present invention, the inorganic particles can also be synthesized by spraying the spray liquid under conditions that do not generate cavitation bubbles. Specifically, it is more preferable that the pressure of the spray liquid (upstream pressure) is 2 MPa or less, preferably 1 MPa or less, and the pressure of the spray liquid (downstream pressure) is released to 0.05 MPa or less.

  The jet velocity of the jet liquid is desirably in the range of 1 m / second to 200 m / second, and preferably in the range of 20 m / second to 100 m / second. When the jet velocity is less than 1 m / sec, the effect is weak because the pressure drop is low and cavitation hardly occurs. On the other hand, when it is higher than 200 m / sec, a high pressure is required and a special device is required, which is disadvantageous in terms of cost.

  The cavitation generation place in the present invention may be generated in the reaction vessel. Moreover, although it is possible to process by one pass, it can also circulate as many times as necessary. Furthermore, it can be processed in parallel or in permutation using a plurality of generating means.

  The liquid injection for generating cavitation may be performed in a container open to the atmosphere, but is preferably performed in a pressure container in order to control cavitation.

  When cavitation is generated by liquid injection, the solid content concentration of the reaction solution is preferably 30% by weight or less, and more preferably 20% by weight or less. This is because the cavitation bubbles easily act on the reaction system uniformly at such a concentration.

  When synthesizing the composite fiber in the present invention, the reaction can be controlled by monitoring the pH of the reaction solution as long as the pH of the reaction solution changes as the reaction proceeds.

  In the present invention, by increasing the jetting pressure of the liquid, the flow velocity of the jetting liquid is increased, and accordingly, the pressure is lowered, and stronger cavitation can be generated. Further, by pressurizing the pressure in the reaction vessel, the pressure in the region where the cavitation bubbles collapse is increased and the pressure difference between the bubbles and the surroundings increases, so that the bubbles collapse violently and the impact force can be increased. The reaction temperature is preferably 0 ° C. or higher and 90 ° C. or lower, and particularly preferably 10 ° C. or higher and 60 ° C. or lower. In general, the impact force is considered to be the maximum at the midpoint between the melting point and the boiling point. Therefore, in the case of an aqueous solution, a temperature around 50 ° C. is suitable, but even below that temperature is affected by the vapor pressure. Therefore, a high effect can be obtained within the above range.

  In the present invention, the energy necessary for generating cavitation can be reduced by adding a surfactant. As the surfactant to be used, known or novel surfactants, for example, nonionic surfactants such as fatty acid salts, higher alkyl sulfates, alkylbenzene sulfonates, higher alcohols, alkylphenols, alkylene oxide adducts such as fatty acids, etc. , Anionic surfactants, cationic surfactants, amphoteric surfactants and the like. These may consist of a single component or a mixture of two or more components. The addition amount may be an amount necessary for reducing the surface tension of the jet liquid and / or the liquid to be jetted.

Molded product of composite fiber A molded product (body) can be appropriately produced using the composite fiber according to the present invention. For example, when the composite fiber obtained by the present invention is made into a sheet, a high ash content sheet can be easily obtained. Moreover, the obtained sheet | seat can be bonded together and it can also be set as a multilayer sheet. Examples of the paper machine (paper machine) used for sheet production include a long paper machine, a round paper machine, a gap former, a hybrid former, a multilayer paper machine, and a known paper machine that combines the paper making methods of these devices. It is done. The press linear pressure in the paper machine and the calendar linear pressure in the case where the calendar process is performed in the latter stage can be determined within a range that does not hinder the operability and the performance of the composite fiber sheet. In addition, starch, various polymers, pigments, and mixtures thereof may be applied to the formed sheet by impregnation or coating.

  When forming into a sheet, a wet and / or dry paper strength agent (paper strength enhancer) can be added. Thereby, the intensity | strength of a composite fiber sheet can be improved. Examples of paper strength agents include urea formaldehyde resin, melamine formaldehyde resin, polyamide, polyamine, epichlorohydrin resin, vegetable gum, latex, polyethyleneimine, glyoxal, gum, mannogalactan polyethyleneimine, polyacrylamide resin, polyvinylamine. And a resin such as polyvinyl alcohol; a composite polymer or copolymer composed of two or more selected from the above resins; starch and processed starch; carboxymethylcellulose, guar gum, urea resin, and the like. The addition amount of the paper strength agent is not particularly limited.

  Moreover, in order to promote the fixing of the filler to the fiber or to improve the yield of the filler or fiber, a high molecular weight polymer or an inorganic substance can be added. For example, polyethyleneimine and modified polyethyleneimines containing tertiary and / or quaternary ammonium groups, polyalkylenimines, dicyandiamide polymers, polyamines, polyamine / epichlorohydrin polymers, and dialkyldiallyl quaternary ammonium monomers, dialkyls as coagulants Cations such as aminoalkyl acrylate, dialkylaminoalkyl methacrylate, dialkylaminoalkyl acrylamide and polymers of acrylamide and dialkylaminoalkyl methacrylamide, polymers of monoamines and epihalohydrin, polymers with polyvinylamine and vinylamine moieties, and mixtures thereof In addition to the functional polymer, a polymer obtained by copolymerizing an anionic group such as a carboxyl group or a sulfone group in the polymer molecule. Onritchi of zwitterionic polymer, and a mixture of cationic polymer and an anionic or zwitterionic polymers may be used. As a retention agent, a cationic, anionic, or amphoteric polyacrylamide-based material can be used. In addition to these, a retention system called a so-called dual polymer that uses at least one kind of cation or anionic polymer can also be applied, and at least one kind of anionic bentonite, colloidal silica, polysilicic acid, It is a multi-component yield system that uses inorganic fine particles such as polysilicic acid or polysilicate microgels and their modified aluminum products, or one or more organic fine particles having a particle size of 100 μm or less, called so-called micropolymers obtained by crosslinking polymerization of acrylamide. Also good. In particular, when the polyacrylamide material used alone or in combination has a weight average molecular weight of 2 million daltons or more by the intrinsic viscosity method, a good yield can be obtained, preferably 5 million daltons or more, more preferably Can obtain a very high yield in the case of the above-mentioned acrylamide-based material of 10 million daltons or more and less than 30 million daltons. The form of the polyacrylamide-based material may be an emulsion type or a solution type. The specific composition is not particularly limited as long as the substance contains an acrylamide monomer unit as a structural unit. For example, a copolymer of quaternary ammonium salt of acrylate ester and acrylamide, or acrylamide And a quaternized ammonium salt after copolymerization of acrylate and acrylate. The cationic charge density of the cationic polyacrylamide material is not particularly limited.

  In addition, according to the purpose, inorganic particles such as drainage improver, internal sizing agent, pH adjuster, antifoaming agent, pitch control agent, slime control agent, bulking agent, calcium carbonate, kaolin, talc, silica (so-called Etc.). The amount of each additive used is not particularly limited.

The basis weight of the sheet can be appropriately adjusted according to the purpose, but when it is 40 to 1200 g / m ² , the shielding effect is high, and the drying load during production is low, which is favorable. The basis weight of the sheet, also can be a 60~1000g / ^{m 2,} may be a 100 to 600 / ^{m 2.}

  It is also possible to use a molding method other than sheeting, for example, a method of pouring raw materials into a mold and drawing it by suction dehydration and drying as called a pulp mold, or spreading and drying on the surface of a molded product such as resin or metal Thereafter, molded articles having various shapes can be obtained by a method of peeling from the substrate. Further, it can be molded into a plastic like by mixing a resin, or it can be shaped like a ceramic by adding a mineral such as silica or alumina and firing. In the blending / drying / molding described above, only one type of conjugate fiber can be used, or two or more types of conjugate fibers can be mixed and used. When two or more types of composite fibers are used, those obtained by mixing them in advance can be used, or those obtained by blending, drying and molding each can be mixed later.

  Moreover, you may give various inorganic substances, such as various organic substances, such as a polymer, and a pigment, to the molding of a composite fiber later.

  The present invention will be described more specifically with specific experimental examples, but the present invention is not limited to the following specific examples. Unless otherwise specified in the present specification, concentrations and parts are based on weight, and numerical ranges are described as including the end points.

Experiment 1: Synthesis of composite fiber with Prussian blue 2.0% pulp slurry (LBKP / NBKP: 8/2, Canadian standard freeness CSF: about 390 mL, average fiber length: about 1 mm, 4400 g) and potassium ferrocyanide Hydrate (Wako Pure Chemical Industries, 32.4 g) was mixed and stirred at room temperature with a three-one motor for 10 minutes. To this, 540 g of iron (III) chloride hexahydrate aqueous solution (Wako Pure Chemical Industries, 3.1%) was added dropwise at 15 g / min using a peristaltic pump. After completion of dropping, stirring was continued for 5 minutes to obtain a composite fiber (Sample 1) with Prussian blue as a slurry (dark blue, slurry concentration 1.9%).

  The obtained conjugate fiber was washed with ethanol and then observed with a field emission scanning microscope (JEOL Datum, JSM-6700). FIG. 1 shows an electron micrograph showing that the surface of the pulp fiber is covered with an inorganic substance and self-fixed. In the composite fiber according to Sample 1, 95% or more of the fiber surface was covered with Prussian blue (PB), the weight ratio of the fiber to PB was about 85:15, and the average particle size of PB was about 70 nm.

The composite fiber is suction filtered with a filter paper (Advantech, qualitative filter paper No. 2), washed with distilled water, and then dried with a dryer (ISUZU MDN-19SU, 105 ° C.) to obtain a composite fiber sheet. (Sheet basis weight: about 100 g / m ² ). This was analyzed using an X-ray diffractometer (PANallytical, Xpert-PRO). The result of X-ray diffraction is shown in FIG. 2, and the peak of Prussian blue Fe ₄ [Fe (CN) ₆ ] ₃ was confirmed, confirming that a composite fiber with Prussian blue was obtained.

Experiment 2: Evaluation of cesium ion adsorption ability The cesium ion adsorption ability of the composite fiber (sample 1) and pulp fiber (sample 2, control) synthesized in experiment 1 was evaluated.

  Specifically, 50 mL of the following cesium-containing solution and 0.5 g of a test sample were added to a plastic bottle with a lid, and the lid was closed and shaken with a shaker (TAITEC, RECIPRO SHAKER SR-II) for 30 minutes.

After shaking, the mixture was filtered using filter paper (Advantech, quantitative filter paper No. 5B), and the cesium ion concentration of the filtrate was measured with an inductively coupled plasma mass spectrometer (Thermo Fisher SCIENTIFIC, XSERIES-II).
(Cesium-containing solution)
-Simulated Cs contaminated water: A solution in which 12.7 mg of cesium chloride (Wako Pure Chemical Industries) was dissolved in 1 L of distilled water (actual measured value of cesium ion: 8206 ppb).
-Simulated Cs-contaminated seawater: A solution in which 12.7 mg of cesium chloride (Wako Pure Chemical Industries) and 37 g of Daigo artificial seawater SP (Nippon Pharmaceutical Co., Ltd.) were dissolved in 1 L of distilled water (actual measured value of cesium ion: 8682 ppb).
(Test sample)
Sample 1: Composite fiber synthesized in Experiment 1 Sample 2: Kraft pulp (LBKP / NBKP = 8/2, CSF: about 390 mL, average fiber length: about 1 mm)

  From the above results, it was confirmed that the composite fiber of the present invention has high cesium ion adsorption ability. Moreover, since the high cesium ion adsorption ability was shown also on the conditions using simulated Cs contaminated seawater, it was confirmed that the effect of this adsorbent is not reduced even in the presence of various cations and anions.

Claims (10)

  A composite fiber in which a metal ferrocyanide compound is fixed to the fiber, and 15% or more of the fiber surface is coated with the metal ferrocyanide compound.   The composite fiber according to claim 1, wherein the fiber is a cellulose fiber.   The composite fiber according to claim 1 or 2, wherein the ferrocyanide metal compound is Prussian blue.   The composite fiber according to any one of claims 1 to 3, wherein a weight ratio of the ferrocyanide metal compound to the fiber is 5/95 to 95/5. A method for producing a conjugate fiber according to any one of claims 1 to 4,
The method as described above, comprising mixing a fiber, an inorganic salt of hexacyanometal acid, and an inorganic compound containing a transition metal in a solution to synthesize a ferrocyanide metal compound on the fiber. The process of synthesizing the ferrocyanide compound on the fiber,
(A) mixing an inorganic salt of hexacyanometal acid and fiber in solution;
(B) mixing the solution obtained in step a with an inorganic compound containing a transition metal element;
The method of claim 5 comprising: The process of synthesizing the ferrocyanide compound on the fiber,
(A) mixing an inorganic compound containing a transition metal element and a fiber in a solution;
(B) mixing the solution obtained in step a with an inorganic salt of hexacyano metal acid,
The method of claim 5 comprising:   The method according to any one of claims 5 to 7, wherein the inorganic salt of hexacyanometal acid is hexacyanoferrate.   The method according to claim 5, wherein the inorganic compound containing a transition metal element is an inorganic compound containing iron. The cesium adsorbent containing the composite fiber in any one of Claims 1-4.