WO2021153063A1 - Method for manufacturing concentrated/dried cellulose nanofiber article, and decompression belt dryer - Google Patents

Method for manufacturing concentrated/dried cellulose nanofiber article, and decompression belt dryer Download PDF

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WO2021153063A1
WO2021153063A1 PCT/JP2020/046973 JP2020046973W WO2021153063A1 WO 2021153063 A1 WO2021153063 A1 WO 2021153063A1 JP 2020046973 W JP2020046973 W JP 2020046973W WO 2021153063 A1 WO2021153063 A1 WO 2021153063A1
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Prior art keywords
cellulose nanofiber
decompression
concentrated
dispersion liquid
dried
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PCT/JP2020/046973
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French (fr)
Japanese (ja)
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晋一 小野木
利一 村松
啓吾 渡部
加藤　健
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日本製紙株式会社
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Priority to JP2021514446A priority Critical patent/JP6968311B1/en
Publication of WO2021153063A1 publication Critical patent/WO2021153063A1/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
    • C08B15/00—Preparation of other cellulose derivatives or modified cellulose, e.g. complexes
    • C08B15/02—Oxycellulose; Hydrocellulose; Cellulosehydrate, e.g. microcrystalline cellulose
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
    • D21H11/16—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only modified by a particular after-treatment
    • D21H11/18—Highly hydrated, swollen or fibrillatable fibres

Definitions

  • the present invention relates to a method for producing a concentrated / dried product of cellulose nanofibers by drying a dispersion of cellulose nanofibers (hereinafter, also referred to as "CNF"), and a pressure reducing belt dryer used in this production method.
  • CNF dispersion of cellulose nanofibers
  • CNF is produced in a state of being stably dispersed in water, and is usually used for various purposes as an industrial material or an additive material for foods and cosmetics as the produced CNF dispersion liquid having a predetermined concentration.
  • CNF concentration
  • removal drying
  • the CNF redispersion solution in order to use the CNF concentrated / dried product obtained by concentrating / drying the CNF dispersion, it is necessary to redisperse the CNF dispersion in water and prepare the CNF redispersion having a predetermined concentration suitable for use again. If the prepared CNF redispersion solution is significantly lower than the transparency and viscosity characteristics (thixotropy) of the CNF dispersion solution before concentration and drying, the CNF redispersion solution cannot be used for the above-mentioned various uses.
  • Patent Document 1 a technique for increasing the transparency and viscosity characteristics of the CNF redispersion liquid to the same level as the transparency and viscosity characteristics of the CNF dispersion liquid before drying has been studied in Patent Document 1 below.
  • Patent Document 1 discloses a technique for converting a CNF dispersion into a dry solid using a drum dryer.
  • the physical characteristics such as transparency and viscosity of the redispersion liquid obtained by redispersing in water have less change than the CNF dispersion liquid before drying (redispersibility). It is said that a CNF dry solid having the above is obtained.
  • the physical characteristics such as the transparency and viscosity of the redispersion liquid obtained by redispersing the CNF dry solid obtained in Patent Document 1 in water are compared with the physical characteristics such as the transparency and viscosity of the CNF dispersion liquid before drying.
  • the change was large, and the redispersibility was not sufficient. Therefore, the physical properties such as the transparency and viscosity of the CNF dispersion obtained by redispersing the CNF-concentrated / dried product in water have characteristics (redispersability) that are less changed than those of the CNF dispersion before drying.
  • the present invention has been made in view of the above problems, and when a CNF dispersion is concentrated and dried to produce a CNF-concentrated / dried product, and then redispersed to produce a CNF redispersion, the CNF dispersion is concentrated and dried.
  • a method for producing a cellulose nanofiber concentrated / dried product capable of obtaining a CNF concentrated / dried product capable of producing a redispersion liquid having the same degree of transparency and viscosity characteristics as the CNF dispersion liquid before drying.
  • the present inventors have provided a pressure reducing belt dryer capable of drying a CNF dispersion at a low temperature under reduced pressure, which is provided with a nozzle having a specific diameter.
  • a pressure reducing belt dryer capable of drying a CNF dispersion at a low temperature under reduced pressure, which is provided with a nozzle having a specific diameter.
  • the present invention provides: (1) An endless transport belt and a heating region and a cooling region are sequentially arranged in the pressure reducing tank along the moving direction of the endless transport belt, and the cellulose nanofiber dispersion is dried at a low temperature to be concentrated and dried.
  • a method for producing a cellulose nanofiber concentrated / dried product which is carried out using a pressure reducing belt dryer for obtaining the product, wherein the pressure reducing belt dryer is provided on the upstream side of the heating region of the endless transport belt.
  • a nozzle having a diameter of 1 mm or more and 8 mm or less for supplying the cellulose nanofiber dispersion liquid and a decompression device for creating a decompression atmosphere in the decompression tank are provided, and the heating region is provided along the moving direction of the endless transport belt.
  • Cellulous nanofibers including a drying step of drying the cellulose nanofiber dispersion liquid supplied on the belt in the heating region and a cooling step of cooling the concentrated / dried product dried in the drying step in the cooling region.
  • Manufacturing method for concentrated / dried products (2)
  • the cellulose nanofiber dispersion liquid contains 99.9 parts by weight or more of cellulose nanofibers in solid content out of 100 parts by weight of solid content, and in the drying step, the temperature of the heating plate is 80 to 130 ° C.
  • the cellulose nanofiber dispersion liquid includes a step of adjusting the pH of the cellulose nanofiber dispersion liquid supplied in the supply step to 9 to 11, and the cellulose nanofiber dispersion liquid is water-soluble with respect to 100 parts by weight of the solid content of the cellulose nanofibers.
  • the cellulose nano according to (1) which contains 5 to 300 parts by weight of a polymer as a solid content, and in the drying step, the heating plate is heated to a temperature of 80 to 130 ° C. and the cellulose nanofiber dispersion is dried until it becomes a dry solid. Method for manufacturing fiber-concentrated / dried products.
  • An endless transport belt and a heating region and a cooling region are sequentially arranged in the pressure reducing tank along the moving direction of the endless transport belt, and the cellulose nanofiber dispersion is dried at a low temperature to be concentrated and dried.
  • a method for producing a cellulose nanofiber concentrated / dried product which is carried out using a pressure reducing belt dryer for obtaining the product, wherein the pressure reducing belt dryer is provided on the upstream side of the heating region of the endless transport belt.
  • a nozzle having a diameter of 1 mm or more and 8 mm or less for supplying the cellulose nanofiber dispersion liquid and a decompression device for creating a decompression atmosphere in the decompression tank are provided, and the heating region is provided along the moving direction of the endless transport belt.
  • Cellulose including a drying step of drying the cellulose nanofiber dispersion liquid supplied on the endless transport belt in the heating region and a cooling step of cooling the concentrated / dried product dried in the drying step in the cooling region. Manufacturing method for nanofiber concentrated / dried products.
  • An endless transport belt and a heating region and a cooling region are sequentially arranged in the pressure reducing tank along the moving direction of the endless transport belt, and the cellulose nanofiber dispersion is dried at a low temperature to be concentrated and dried.
  • a pressure reducing belt dryer for obtaining the above, provided on the upstream side of the heating region of the endless transport belt, a nozzle having a diameter of 1 mm or more and a diameter of 8 mm or less for supplying the cellulose nanofiber dispersion liquid, and the pressure reducing tank.
  • a pressure reducing belt dryer provided with a pressure reducing device for creating a pressure reducing atmosphere inside, and the heating region is provided with heating means along the moving direction of the endless transport belt.
  • a cellulose nanofiber concentrated / dried product capable of producing a redispersion liquid having the same degree of transparency and viscosity characteristics as the CNF dispersion liquid before concentration / drying can be obtained.
  • a method for manufacturing a product and a pressure reducing belt dryer suitable for this manufacturing method are provided.
  • the pressure reducing belt dryer of the present invention is not limited to the one shown in FIG. Further, in the present invention, "-" includes a fractional value. That is, "X to Y” includes the values X and Y at both ends thereof.
  • the pressure reducing belt dryer 2 shown in FIG. 1 has a pressure reducing tank 4 capable of depressurizing the inside, an endless transport belt 6 installed in the pressure reducing tank 4, and cellulose nanofibers (CNF) installed on the endless transport belt 6.
  • a first heating plate 10a and a second heating plate which are heating means for heating the nozzle 8 for supplying the dispersion liquid 7 and the CNF dispersion liquid 7, and are arranged on the lower surface of the endless transport belt 6 along the moving direction thereof.
  • a collection unit 18 for collecting the concentrated / dried product discharged from the unit 16 is provided.
  • the heating plates 10a, 10b, and 10c use hot water sent from a hot water generator 26 including an expansion tank 20, a pump 22, and a heat exchanger 24 as a heat medium.
  • the inside of the pressure reducing tank 4 is depressurized during operation by a vacuum generator 28 including a cold trap 28a and a vacuum pump 28b.
  • the diameter of the nozzle 8 is 1 mm or more and 8 mm or less, preferably 1 mm or more and 4 mm or less, and more preferably 1 mm or more and 2.5 mm or less in diameter from the viewpoint of uniform and sufficient drying.
  • the CNF dispersion liquid 7 supplied from the nozzle 8 onto the endless transport belt 6 moves with the movement of the endless transport belt 6, and the first heating plate 10a, the second heating plate 10b, and the third heating plate 10c constituting the heating region.
  • the cooling plate 14 constituting the cooling region are sequentially passed and subjected to a predetermined drying treatment.
  • the temperature of the heating plate can be set individually, and the heating plates 10a, 10b, and 10c may all be set to have the same temperature, or the first heating plate 10a, the second heating plate 10b, and the second heating plate 10b may be set to have the same temperature. 3
  • the temperature may be set to decrease in the order of the heating plates 10c.
  • the surface of the endless transport belt 6 may be treated with a fluororesin on the surface in contact with the CNF dispersion liquid 7 from the viewpoint that the concentrated / dried product can be easily peeled off from the belt.
  • the receiving unit 16 may have a mechanism for crushing the obtained concentrated / dried product.
  • the heating means has been described as an example composed of a plurality of heating plates from the first to the third, but even if the heating means is composed of a single heating plate. good.
  • a heating plate is used as the heating means, but the decompression belt dryer of the present invention uses a single or a plurality of microwave generators instead of the heating plate as the heating means. It may be.
  • the method for producing a CNF concentrated / dried product executed by using the pressure reducing belt dryer of the present invention is a CNF dispersion liquid 7 on an endless transport belt 6 moving at a constant speed from a nozzle 8 having a diameter of 1 mm or more and 8 mm or less.
  • the concentrated / dried product dried in the drying step is dried in the heating region, and the CNF dispersion liquid 7 supplied on the endless transport belt 6 is dried in the heating region. Includes a cooling step to cool.
  • the CNF dispersion liquid 7 is supplied in strands or granules from a nozzle 8 having a diameter of 1 mm or more and 8 mm or less onto an endless transport belt 6 installed in the pressure reducing tank 4 and moving at a constant speed.
  • the moving speed of the endless transport belt 6 is not particularly limited, but is 5 to 30 cm / min, more preferably 9 to 24 cm / min from the viewpoint of drying efficiency.
  • the air pressure in the pressure reducing tank 4 is reduced by the vacuum generator 28, for example, preferably from 0 to 20 kPa, more preferably from 1.5 to 10 kPa.
  • the supply form of the CNF dispersion 7 is preferably in the form of strands or granules from the viewpoint of being able to dry evenly, and more preferably in the form of strands from the viewpoint of efficiency.
  • the drying temperature in the drying step is preferably 80 to 130 ° C., more preferably 80 to 100 ° C., and even more preferably 80 to 90 ° C.
  • the drying step when the CNF dispersion 7 contains 99.9% by weight or more of CNF in solid content, it is preferable to dry the CNF dispersion 7 until the solid content concentration is 10 to 20% by weight. More preferably, it is dried to 10 to 15% by weight.
  • the CNF dispersion 7 contains a water-soluble polymer
  • the blending amount of the water-soluble polymer is preferably 5 to 300 parts by weight, preferably 20 to 300 parts by weight, based on 100 parts by weight of the absolute dry solid content of CNF. Parts by weight are more preferred. If the blending amount of the water-soluble polymer is less than 5 parts by weight, the effect of sufficient redispersibility is not exhibited, and if it exceeds 300 parts by weight, the viscosity characteristics such as thixotropy and the dispersion stability, which are the characteristics of CNF, are lowered. Problems such as occur.
  • the blending amount of the water-soluble polymer is 25 parts by weight or more with respect to 100 parts by weight of the absolute dry solid content of CNF, because particularly excellent redispersibility can be obtained. Further, considering the thixotropy property, it is preferably 200 parts by weight or less, and 60 parts by weight or less is particularly preferable.
  • the dry solid substance of CNF means CNF dehydrated and dried so that the water content is 12% by weight or less.
  • Step to adjust pH When the CNF dispersion 7 contains a water-soluble polymer, the step of adjusting the pH of the CNF dispersion 7 supplied in the supply step is preferably 9 to 11, more preferably 9 to 10, from the viewpoint of redispersibility. It is preferable to further include it.
  • the chemicals used to adjust the pH of the CNF dispersion 7 to 9 to 11 are not particularly limited, and sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, magnesium hydroxide, ammonia, and hydroxide are used.
  • Basic inorganic compounds selected from copper, aluminum hydroxide, iron hydroxide, ammonium hydroxide, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate, calcium carbonate, magnesium carbonate, magnesium oxide, or arginine, lysine, histidine and ornithine. Examples thereof include basic organic compounds selected from the above.
  • cellulose nanofibers are fine fibers having a fiber diameter of about 3 to 500 nm and an aspect ratio of 100 or more.
  • the cellulose nanofibers used in the present invention include anion-modified cellulose nanofibers (CNF).
  • the anion-modified CNF can be obtained by defibrating oxidized cellulose, carboxymethylated cellulose and the like.
  • the average fiber length and average fiber diameter of the fine fibers can be adjusted by an oxidation treatment, a carboxymethylation treatment, and a defibration treatment.
  • the average fiber length of the cellulose nanofibers used in the present invention is not particularly limited, but is preferably 100 nm to 1 ⁇ m, and more preferably 100 nm to 400 nm.
  • the average fiber diameter of the cellulose nanofibers used in the present invention is 3 nm to 10 nm, preferably 3 nm to 8 nm.
  • the average fiber length and average fiber diameter of the cellulose nanofibers can be obtained by averaging the fiber length and fiber diameter obtained from the results of observing each fiber using an atomic force microscope (AFM).
  • the average aspect ratio of cellulose nanofibers is usually 50 or more.
  • the upper limit is not particularly limited, but is usually 1000 or less.
  • the origin of the cellulose raw material which is the raw material of the cellulose nanofibers, is not particularly limited, but for example, plants (for example, wood, bamboo, hemp, jute, kenaf, agricultural waste, cloth, pulp (conifer unbleached kraft pulp (NUKP)).
  • plants for example, wood, bamboo, hemp, jute, kenaf, agricultural waste, cloth, pulp (conifer unbleached kraft pulp (NUKP)).
  • NNKP Conifer bleached kraft pulp
  • LKP broadleaf unbleached kraft pulp
  • LKP broadleaf bleached kraft pulp
  • NUSP conifer unbleached sulphite pulp
  • TMP thermomechanical pulp
  • Recycled pulp used paper, etc.
  • animals for example, squirrels
  • algae for example, acetic acid bacteria (acetobacter)
  • microbial products etc.
  • the cellulose raw material used in the present invention is any of these.
  • It may be a combination of two or more kinds, but is preferably a pulp raw material derived from a plant or a microorganism (for example, cellulose fiber), and more preferably a pulp raw material derived from a plant (for example, cellulose fiber). be.
  • the number average fiber diameter of the cellulose raw material is not particularly limited, but it is about 30 to 60 ⁇ m in the case of softwood kraft pulp, which is a general pulp, and about 10 to 30 ⁇ m in the case of hardwood kraft pulp. In the case of other pulp, the one that has undergone general purification is about 50 ⁇ m. For example, when a chip or the like having a size of several cm is purified, it is preferable to perform mechanical treatment with a dissociator such as a refiner or a beater to adjust the size to about 50 ⁇ m.
  • a dissociator such as a refiner or a beater
  • the amount of carboxyl groups based on the absolute dry weight of cellulose oxide or cellulose nanofibers obtained by modifying the cellulose raw material by oxidation is 0.5 mmol / g or more, preferably 0.8 mmol / g or more, more preferably 1.0 mmol / g. It is g or more.
  • the upper limit is 3.0 mmol / g or less, preferably 2.5 mmol / g or less, and more preferably 2.0 mmol / g or less.
  • the cellulose oxide nanofiber used in the present invention has a carboxyl group amount of 0.5 mmol / g to 3.0 mmol / g, preferably 0.8 mmol / g to 2.5 mmol / g, and 1.0 mmol / g. -2.0 mmol / g is more preferable.
  • a cellulose raw material is oxidized in water using an oxidizing agent in the presence of an N-oxyl compound and a substance selected from the group consisting of bromide, iodide or a mixture thereof.
  • the primary hydroxyl group at the C6 position of the glucopyranose ring on the surface of cellulose is selectively oxidized to generate a group selected from the group consisting of an aldehyde group, a carboxyl group, and a carboxylate group.
  • the concentration of the cellulose raw material during the reaction is not particularly limited, but is preferably 5% by weight or less.
  • the N-oxyl compound is a compound capable of generating a nitroxy radical.
  • the nitroxyl radical include 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO).
  • TEMPO 2,2,6,6-tetramethylpiperidine 1-oxyl
  • any compound can be used as long as it is a compound that promotes the desired oxidation reaction.
  • the amount of the N-oxyl compound used is not particularly limited as long as it is a catalytic amount capable of oxidizing cellulose as a raw material. For example, 0.01 mmol or more is preferable, and 0.02 mmol or more is more preferable with respect to 1 g of cellulose that has been completely dried.
  • the upper limit is preferably 10 mmol or less, more preferably 1 mmol or less, and even more preferably 0.5 mmol or less. Therefore, the amount of the N-oxyl compound used is preferably 0.01 to 10 mmol, more preferably 0.01 to 1 mmol, still more preferably 0.02 to 0.5 mmol, based on 1 g of dry cellulose.
  • Bromide is a compound containing bromine, and examples thereof include alkali metals bromide that can be dissociated and ionized in water, such as sodium bromide.
  • the iodide is a compound containing iodine, and examples thereof include an alkali metal iodide.
  • the amount of bromide or iodide to be used may be selected within a range in which the oxidation reaction can be promoted.
  • the total amount of bromide and iodide is preferably 0.1 mmol or more, more preferably 0.5 mmol or more, based on 1 g of dry cellulose.
  • the upper limit is preferably 100 mmol or less, more preferably 10 mmol or less, and even more preferably 5 mmol or less. Therefore, the total amount of bromide and iodide is preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, still more preferably 0.5 to 5 mmol with respect to 1 g of dry cellulose.
  • the oxidizing agent is not particularly limited, and examples thereof include halogen, hypochlorous acid, hypochlorous acid, perhalogenic acid, salts thereof, halogen oxide, and peroxide. Among them, hypochlorous acid or a salt thereof is preferable, hypochlorous acid or a salt thereof is more preferable, and sodium hypochlorite is further preferable because it is inexpensive and has a small environmental load.
  • the amount of the oxidizing agent used is preferably 0.5 mmol or more, more preferably 1 mmol or more, still more preferably 3 mmol or more, based on 1 g of the dry cellulose.
  • the upper limit is preferably 500 mmol or less, more preferably 50 mmol or less, still more preferably 25 mmol or less.
  • the amount of the oxidizing agent used is preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, still more preferably 1 to 25 mmol, and most preferably 3 to 25 mmol with respect to 1 g of the dry cellulose.
  • the amount of the oxidizing agent used is preferably 1 mol or more with respect to 1 mol of the N-oxyl compound.
  • the upper limit is preferably 40 mol. Therefore, the amount of the oxidizing agent used is preferably 1 to 40 mol with respect to 1 mol of the N-oxyl compound.
  • Conditions such as pH and temperature during the oxidation reaction are not particularly limited, and in general, the oxidation reaction proceeds efficiently even under relatively mild conditions.
  • the reaction temperature is preferably 4 ° C. or higher, more preferably 15 ° C. or higher.
  • the upper limit is preferably 40 ° C. or lower, more preferably 30 ° C. or lower. Therefore, the temperature is preferably 4 to 40 ° C, and may be about 15 to 30 ° C, that is, room temperature.
  • the pH of the reaction solution is preferably 8 or more, more preferably 10 or more.
  • the upper limit is preferably 12 or less, more preferably 11 or less. Therefore, the pH of the reaction solution is preferably about 8 to 12, more preferably about 10 to 11.
  • the pH of the reaction solution tends to decrease because a carboxyl group is generated in the cellulose as the oxidation reaction progresses. Therefore, in order to allow the oxidation reaction to proceed efficiently, it is preferable to add an alkaline solution such as an aqueous sodium hydroxide solution to maintain the pH of the reaction solution in the above range. Water is preferable as the reaction medium for oxidation because it is easy to handle and side reactions are unlikely to occur.
  • the reaction time in the oxidation reaction can be appropriately set according to the degree of progress of oxidation, and is usually 0.5 hours or more.
  • the upper limit is usually 6 hours or less, preferably 4 hours or less. Therefore, the reaction time in oxidation is usually about 0.5 to 6 hours, for example, about 0.5 to 4 hours.
  • Oxidation may be carried out in two or more stages of reaction. For example, by oxidizing the oxidized cellulose obtained by filtration after the completion of the first-stage reaction again under the same or different reaction conditions, the efficiency is not affected by the reaction inhibition by the salt produced as a by-product in the first-stage reaction. Can be oxidized well.
  • carboxymethylation of the cellulose raw material can be carried out by using a known method, and the degree of carboxymethyl group substitution per anhydrous glucose unit of cellulose is 0.01 to 0. It is preferable to adjust it to 50.
  • the following production method can be mentioned, but it may be synthesized by a conventionally known method, or a commercially available product may be used.
  • cellulose as the base material 3 to 20 times by weight of water and / or lower alcohol, specifically methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, tertiary butanol, etc. Use alone or a mixed medium of two or more.
  • the mixing ratio of the lower alcohol is 60 to 95% by weight.
  • the mercerizing agent 0.5 to 20 times mol of alkali metal hydroxide, specifically sodium hydroxide and potassium hydroxide, is used per anhydrous glucose residue of the bottoming material.
  • the bottoming material, the solvent, and the mercerizing agent are mixed, and the mercerization treatment is carried out at a reaction temperature of 0 to 70 ° C., preferably 10 to 60 ° C., and a reaction time of 15 minutes to 8 hours, preferably 30 minutes to 7 hours.
  • the reaction temperature is 30 to 90 ° C., preferably 40 to 80 ° C.
  • the reaction time is 30 minutes to 10 hours, preferably 1 hour.
  • the etherification reaction is carried out for about 4 hours.
  • the defibration of the cellulose raw material may be performed before or after the modification treatment of the cellulose raw material. Further, the defibration may be performed at one time or a plurality of times. In the case of multiple times, the time of each defibration may be any time.
  • the device used for defibration is not particularly limited, and examples thereof include high-speed rotary type, colloid mill type, high-pressure type, roll mill type, ultrasonic type, and the like, preferably a high-pressure or ultra-high pressure homogenizer, and a wet high pressure. Alternatively, an ultrahigh pressure homogenizer is more preferable.
  • the apparatus preferably can apply a strong shearing force to the cellulose raw material or the modified cellulose (usually a dispersion).
  • the pressure that can be applied by the device is preferably 9 MPa or more, more preferably 50 MPa or more, further preferably 100 MPa or more, and particularly preferably 140 MPa or more.
  • the solid content concentration of the cellulose raw material in the dispersion is usually 0.1% by weight or more, preferably 0.2% by weight or more, more preferably 0.3. Weight% or more.
  • the upper limit is usually 10% by weight or less, preferably 6% by weight or less. This makes it possible to maintain liquidity.
  • pretreatment may be performed if necessary. The pretreatment may be performed using a mixing, stirring, emulsifying, or dispersing device such as a high-speed shear mixer.
  • water-soluble polymer examples include cellulose derivatives (carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose, ethyl cellulose), xanthan gum, xyloglucane, dextrin, dextran, carrageenan, locust bean gum, alginic acid, alginate, purulan, and the like.
  • starch shavings, scraps, processed starch (cationized starch, phosphorylated starch, phosphoric acid cross-linked starch, phosphoric acid monoesterified phosphoric acid cross-linked starch, hydroxypropyl starch, hydroxypropylated phosphoric acid cross-linked starch, acetylated adipic acid cross-linked starch, acetylation Phosphoric cross-linked starch, acetylated oxidized starch, sodium octenyl succinate, acetate starch, oxidized starch), corn starch, Arabic gum, locust bean gum, gellan gum, polydextrose, pectin, chitin, water-soluble chitin, chitosan, casein, albumin, soybean Protein lysate, peptone, polyvinyl alcohol, polyacrylamide, sodium polyacrylic acid, polyvinylpyrrolidone, vinyl acetate, polyamino acid, polylactic acid, polyapple acid, polyg
  • cellulose derivatives are preferable from the viewpoint of compatibility with cellulose nanofibers, and carboxymethyl cellulose and salts thereof are particularly preferable. It is considered that water-soluble polymers such as carboxymethyl cellulose and salts thereof penetrate between cellulose nanofibers and increase the distance between CNFs to improve redispersibility.
  • carboxymethyl cellulose or a salt thereof is used as the water-soluble polymer
  • the one of 1 is more preferable, and the one of 0.65 to 1.1 is further preferable.
  • a long molecule (high viscosity) is preferable because it has a high effect of widening the distance between CNFs, and the B-type viscosity at 25 ° C. and 600 rpm in a 1 wt% aqueous solution of carboxymethyl cellulose is 3 to 14000 mPa ⁇ s. Is preferable, 7 to 14000 mPa ⁇ s is more preferable, and 1000 to 8000 mPa ⁇ s is further preferable.
  • the decompression belt dryer of the present invention it is possible to perform slow drying as compared with the drum type dryer. Therefore, according to the method for producing a concentrated / dried product of a CNF dispersion using this pressure reducing belt dryer, the obtained concentrated / dried product without excessive heat being applied to the CNF dispersion has a restoration rate of transparency and viscosity. Excellent for. Further, the pressure reducing belt dryer of the present invention can produce a concentrated product and a dried solid product separately.
  • the CNF dispersion liquid containing ink droplets was sandwiched between two glass plates so that the film thickness was 0.15 mm, and an optical microscope (digital microscope KH-8700 (manufactured by Hirox Co., Ltd.)) was used. It was observed at a magnification of 100 times. It was evaluated according to the following criteria. It can be said that the smaller the number of white lumps (gel grains) seen in the obtained image, the better the dispersibility. The results are shown in Tables 1 and 2. A: Almost no gel grains were observed. B: Some gel grains were observed. C: Many gel grains were observed.
  • Viscosity restoration rate (%) (viscosity before drying) / (viscosity after redispersion) x 100
  • the reaction was terminated when sodium hypochlorite was consumed and the pH in the system did not change.
  • the mixture after the reaction was filtered through a glass filter to separate the pulp, and the pulp was thoroughly washed with water to obtain oxidized pulp (carboxylated cellulose).
  • the pulp yield at this time was 90%, the time required for the oxidation reaction was 90 minutes, and the amount of carboxyl groups was 1.6 mmol / g.
  • the oxidized pulp obtained in the above step is adjusted to 3.0% (w / v) with water, treated three times with an ultra-high pressure homogenizer (20 ° C., 150 MPa), and TEMPO oxidized cellulose nanofiber (CNF) water. A dispersion was obtained.
  • the obtained fibers had an average fiber diameter of 40 nm and an aspect ratio of 150.
  • Example 1 (Concentration / drying) 10 g (sample) of an aqueous dispersion of TEMPO oxide CNF having a solid content concentration of 3% obtained in Production Example 1 is superposed on a vat whose surface is lined with Teflon (registered trademark) from a nozzle having a diameter of 2.5 mm. It was placed in a strand shape so that there was no part.
  • the vat on which the sample is placed is placed in a static vacuum dryer (AVO-200V, manufactured by AS ONE Corporation) so that the pressure inside the dryer is 10 kPa or less at a temperature at which the surface of the vat is 80 to 90 ° C.
  • AVO-200V static vacuum dryer
  • Example 2 A concentrated / dried TEMPO-oxidized CNF having a solid content concentration of 15.5% was obtained in the same manner as in Example 1 except that the treatment time was changed to 12 minutes. Further, it was diluted to 1% in the same manner as in Example 1 and redispersed to obtain a CNF redispersion solution.
  • Example 3 A concentrated / dried TEMPO-oxidized CNF having a solid content concentration of 20.4% was obtained in the same manner as in Example 1 except that the treatment time was changed to 14 minutes. Further, it was diluted to 1% in the same manner as in Example 1 and redispersed to obtain a CNF redispersion solution.
  • Example 1 A concentrated / dried TEMPO-oxidized CNF having a solid content concentration of 26.5% was obtained in the same manner as in Example 1 except that the treatment time was changed to 16 minutes. Further, it was diluted to 1% in the same manner as in Example 1 and redispersed to obtain a CNF redispersion solution.
  • Example 2 A concentrated / dried TEMPO-oxidized CNF having a solid content concentration of 33.3% was obtained in the same manner as in Example 1 except that the treatment time was changed to 17 minutes. Further, it was diluted to 1% in the same manner as in Example 1 and redispersed to obtain a CNF redispersion solution.
  • Example 4 (Preparation of dispersion of TEMPO oxidized CNF and CMC) Carboxymethyl cellulose (CMC) (manufactured by Nippon Paper Co., Ltd., trade name: F350HC-4, viscosity (1%, 25 ° C.)) of about 3000 mPa in the TEMPO oxidized CNF aqueous dispersion obtained in Production Example 1 having a solid content concentration of 3%. -S, carboxymethyl substitution degree of about 0.9) is added so as to be 30 parts by weight with respect to 100 parts by weight of the solid content of TEMPO oxide CNF, and the mixture is stirred with a TK homomixer (12,000 rpm) for 60 minutes.
  • CMC Carboxymethyl cellulose
  • Example 3 Water was added to the CMC-containing TEMPO oxidized CNF aqueous dispersion obtained in Example 4 before pH adjustment to obtain an aqueous dispersion having a pH of 6.9 and a solid content concentration of 1.0%. By treating for 75 minutes in the same manner as in Example 4 except that this dispersion was used, a dry solid of CMC-containing TEMPO-oxidized CNF that was almost completely dry (solid content concentration 96%) was obtained. Further, it was diluted to 1% in the same manner as in Example 4 and redispersed to obtain a CNF redispersion solution.

Abstract

This method for manufacturing a concentrated/dried cellulose nanofiber article is executed using a decompression belt dryer which is for obtaining a concentrated/dried article by drying a cellulose nanofiber dispersion at low temperature, the decompression belt dryer comprising, within a decompression tank, an endless conveyor belt and a heating region and a cooling region disposed in sequence in the direction of movement of the endless conveyor belt. The decompression belt dryer is provided with: a nozzle which is disposed on the upstream side of the heating region of the endless conveyor belt, which supplies the cellulose nanofiber dispersion, and which has a diameter of 1–8 mm; and a decompression device which forms a reduced-pressure atmosphere within the decompression tank. The heating region is provided with a heating plate, following the direction of movement of the endless conveyor belt. The method includes: a supply step in which the cellulose nanofiber dispersion is supplied in a strand form or a granular form from the nozzle with a diameter of 1–8 mm onto the endless conveyor belt moving at a constant speed; a drying step in which the cellulose nanofiber dispersion supplied onto the endless conveyor belt is dried in the heating region; and a cooling step in which the compressed/dried article produced by drying in the drying step is cooled in the cooling region.

Description

セルロースナノファイバー濃縮・乾燥品の製造方法及び減圧ベルト乾燥機Cellulose nanofiber concentrated / dried product manufacturing method and decompression belt dryer
　本発明は、セルロースナノファイバー（以下「ＣＮＦ」ともいう）の分散液を乾燥してセルロースナノファイバーの濃縮・乾燥品を製造する方法、及びこの製造方法に使用する減圧ベルト乾燥機に関する。 The present invention relates to a method for producing a concentrated / dried product of cellulose nanofibers by drying a dispersion of cellulose nanofibers (hereinafter, also referred to as "CNF"), and a pressure reducing belt dryer used in this production method.
　一般にＣＮＦは水に安定的に分散させた状態で製造され、通常は製造された所定濃度のＣＮＦ分散液のまま工業材料あるいは食品や化粧品の添加物材料として各種用途に使用されている。
　そして、このＣＮＦの状態を安定的に保つためには、ＣＮＦの数十倍程度の水分が必要になり、この水分の多さがＣＮＦの包装、保管、輸送等のコストアップにつながるため、該水分の減少（濃縮）と除去（乾燥）がＣＮＦの普及を図る上で欠かすことのできない技術とされていた。 Generally, CNF is produced in a state of being stably dispersed in water, and is usually used for various purposes as an industrial material or an additive material for foods and cosmetics as the produced CNF dispersion liquid having a predetermined concentration.
In order to keep the state of CNF stable, about several tens of times as much water as CNF is required, and the large amount of water leads to an increase in the cost of packaging, storage, transportation, etc. of CNF. Moisture reduction (concentration) and removal (drying) have been regarded as indispensable technologies for the spread of CNF.
　一方、ＣＮＦ分散液を濃縮・乾燥して得られたＣＮＦ濃縮・乾燥品を使用するには、水に再分散させて再び使用に適した所定濃度のＣＮＦ再分散液に調製しなければならないが、調製したＣＮＦ再分散液が濃縮・乾燥前のＣＮＦ分散液の透明度や粘度特性（チキソトロピー性）を大きく下回るようでは、上記各種用途にＣＮＦ再分散液を使用できなくなってしまう。 On the other hand, in order to use the CNF concentrated / dried product obtained by concentrating / drying the CNF dispersion, it is necessary to redisperse the CNF dispersion in water and prepare the CNF redispersion having a predetermined concentration suitable for use again. If the prepared CNF redispersion solution is significantly lower than the transparency and viscosity characteristics (thixotropy) of the CNF dispersion solution before concentration and drying, the CNF redispersion solution cannot be used for the above-mentioned various uses.
　そこで、上記ＣＮＦ再分散液の透明度および粘度特性を乾燥前のＣＮＦ分散液の透明度および粘度特性と同等程度まで高めるための技術について、下記の特許文献１で検討がされている。 Therefore, a technique for increasing the transparency and viscosity characteristics of the CNF redispersion liquid to the same level as the transparency and viscosity characteristics of the CNF dispersion liquid before drying has been studied in Patent Document 1 below.
　具体的には、特許文献１にはＣＮＦ分散液を、ドラム乾燥機を用いて乾燥固形物とする技術が開示されている。また、この技術を実行することにより、水に再分散させて得られた再分散液の透明度や粘度などの物性が、乾燥前のＣＮＦ分散液と比較して変化が少ない特性（再分散性）を有するＣＮＦ乾燥固形物が得られたとしている。 Specifically, Patent Document 1 discloses a technique for converting a CNF dispersion into a dry solid using a drum dryer. In addition, by implementing this technology, the physical characteristics such as transparency and viscosity of the redispersion liquid obtained by redispersing in water have less change than the CNF dispersion liquid before drying (redispersibility). It is said that a CNF dry solid having the above is obtained.
特開２０１７－８１７６号公報Japanese Unexamined Patent Publication No. 2017-8176
　しかし、特許文献１で得られたＣＮＦ乾燥固形物を水に再分散して得られた再分散液の透明度や粘度などの物性は、乾燥前のＣＮＦ分散液の透明度や粘度などの物性と比較して変化が大きく、再分散性は十分ではなかった。したがって、ＣＮＦ濃縮・乾燥品を水に再分散したＣＮＦ分散液の透明度や粘度などの物性が、乾燥前のＣＮＦ分散液と比較して、より変化が少ない特性（再分散性）を有するＣＮＦ濃縮・乾燥品を得ることができる乾燥装置および製造方法が求められていた。 However, the physical characteristics such as the transparency and viscosity of the redispersion liquid obtained by redispersing the CNF dry solid obtained in Patent Document 1 in water are compared with the physical characteristics such as the transparency and viscosity of the CNF dispersion liquid before drying. The change was large, and the redispersibility was not sufficient. Therefore, the physical properties such as the transparency and viscosity of the CNF dispersion obtained by redispersing the CNF-concentrated / dried product in water have characteristics (redispersability) that are less changed than those of the CNF dispersion before drying. -There has been a demand for a drying device and a manufacturing method capable of obtaining a dried product.
　本発明は、上記の課題に鑑みてなされたものであり、ＣＮＦ分散液を濃縮・乾燥してＣＮＦ濃縮・乾燥品を製造し、その後再分散させてＣＮＦ再分散液を生成するに際して、濃縮・乾燥前のＣＮＦ分散液と同等程度の透明度および粘度特性を有する再分散液を生成することが可能なＣＮＦ濃縮・乾燥品を得ることができるセルロースナノファイバー濃縮・乾燥品の製造方法を提供すること、及び、この製造方法に適した減圧ベルト乾燥機を提供することを目的とする。 The present invention has been made in view of the above problems, and when a CNF dispersion is concentrated and dried to produce a CNF-concentrated / dried product, and then redispersed to produce a CNF redispersion, the CNF dispersion is concentrated and dried. Provided is a method for producing a cellulose nanofiber concentrated / dried product capable of obtaining a CNF concentrated / dried product capable of producing a redispersion liquid having the same degree of transparency and viscosity characteristics as the CNF dispersion liquid before drying. And, it is an object of the present invention to provide a pressure reducing belt dryer suitable for this manufacturing method.
　本発明者らは、上記の課題を解決するべく鋭意検討した結果、減圧下でＣＮＦ分散液を低温乾燥させることが可能な減圧ベルト乾燥機であって、特定の直径を有するノズルを備えるものを用いることにより上記目的が達成されることを見出し、本発明を完成させた。 As a result of diligent studies to solve the above problems, the present inventors have provided a pressure reducing belt dryer capable of drying a CNF dispersion at a low temperature under reduced pressure, which is provided with a nozzle having a specific diameter. We have found that the above object can be achieved by using the product, and have completed the present invention.
　本発明は、以下を提供する。
（１）　減圧槽内に、無端搬送ベルトと、前記無端搬送ベルトの移動方向に沿って加熱領域および冷却領域を順次配設してなり、セルロースナノファイバー分散液を低温乾燥して濃縮・乾燥品を得るための減圧ベルト乾燥機を用いて実行されるセルロースナノファイバー濃縮・乾燥品の製造方法であって、前記減圧ベルト乾燥機は、前記無端搬送ベルトの前記加熱領域の上流側に設けられた、前記セルロースナノファイバー分散液を供給する直径１ｍｍ以上、８ｍｍ以下のノズルと、前記減圧槽内を減圧雰囲気にする減圧装置とを備え、前記加熱領域は、前記無端搬送ベルトの移動方向に沿って、加熱プレートを備え、直径１ｍｍ以上、８ｍｍ以下の前記ノズルから、定速で移動する前記無端搬送ベルト上に、前記セルロースナノファイバー分散液をストランド状又は粒状に供給する供給工程と、前記無端搬送ベルト上に供給された前記セルロースナノファイバー分散液を、前記加熱領域で乾燥する乾燥工程と、前記乾燥工程で乾燥した濃縮・乾燥品を、前記冷却領域で冷却する冷却工程とを含むセルロースナノファイバー濃縮・乾燥品の製造方法。
（２）　前記セルロースナノファイバー分散液は、固形分１００重量部の内、セルロースナノファイバーを固形分で９９．９重量部以上含み、前記乾燥工程は、前記加熱プレートを温度８０～１３０℃として前記セルロースナノファイバー分散液を固形分濃度１０～２０重量％まで乾燥させる（１）記載のセルロースナノファイバー濃縮・乾燥品の製造方法。
（３）　前記供給工程において供給する前記セルロースナノファイバー分散液のｐＨを９～１１に調整する工程を含み、前記セルロースナノファイバー分散液は、セルロースナノファイバーの固形分１００重量部に対して水溶性高分子を固形分で５～３００重量部含み、前記乾燥工程は、前記加熱プレートを温度８０～１３０℃として前記セルロースナノファイバー分散液を乾燥固形物となるまで乾燥させる（１）記載のセルロースナノファイバー濃縮・乾燥品の製造方法。
（４）　減圧槽内に、無端搬送ベルトと、前記無端搬送ベルトの移動方向に沿って加熱領域および冷却領域を順次配設してなり、セルロースナノファイバー分散液を低温乾燥して濃縮・乾燥品を得るための減圧ベルト乾燥機を用いて実行されるセルロースナノファイバー濃縮・乾燥品の製造方法であって、前記減圧ベルト乾燥機は、前記無端搬送ベルトの前記加熱領域の上流側に設けられた、前記セルロースナノファイバー分散液を供給する直径１ｍｍ以上、８ｍｍ以下のノズルと、前記減圧槽内を減圧雰囲気にする減圧装置とを備え、前記加熱領域は、前記無端搬送ベルトの移動方向に沿って、マイクロ波発生装置を備え、直径１ｍｍ以上、８ｍｍ以下の前記ノズルから、定速で移動する前記無端搬送ベルト上に、前記セルロースナノファイバー分散液をストランド状又は粒状に供給する供給工程と、前記無端搬送ベルト上に供給された前記セルロースナノファイバー分散液を、前記加熱領域で乾燥する乾燥工程と、前記乾燥工程で乾燥した濃縮・乾燥品を、前記冷却領域で冷却する冷却工程とを含むセルロースナノファイバー濃縮・乾燥品の製造方法。
（５）　減圧槽内に、無端搬送ベルトと、前記無端搬送ベルトの移動方向に沿って加熱領域および冷却領域を順次配設してなり、セルロースナノファイバー分散液を低温乾燥して濃縮・乾燥品を得るための減圧ベルト乾燥機であって、前記無端搬送ベルトの前記加熱領域の上流側に設けられた、前記セルロースナノファイバー分散液を供給する直径１ｍｍ以上、８ｍｍ以下のノズルと、前記減圧槽内を減圧雰囲気にする減圧装置とを備え、前記加熱領域は、前記無端搬送ベルトの移動方向に沿って、加熱手段を備える減圧ベルト乾燥機。
（６）　前記加熱手段は、加熱プレートである（５）記載の減圧ベルト乾燥機。
（７）　前記加熱手段は、マイクロ波発生装置である（５）記載の減圧ベルト乾燥機。 The present invention provides:
(1) An endless transport belt and a heating region and a cooling region are sequentially arranged in the pressure reducing tank along the moving direction of the endless transport belt, and the cellulose nanofiber dispersion is dried at a low temperature to be concentrated and dried. A method for producing a cellulose nanofiber concentrated / dried product, which is carried out using a pressure reducing belt dryer for obtaining the product, wherein the pressure reducing belt dryer is provided on the upstream side of the heating region of the endless transport belt. A nozzle having a diameter of 1 mm or more and 8 mm or less for supplying the cellulose nanofiber dispersion liquid and a decompression device for creating a decompression atmosphere in the decompression tank are provided, and the heating region is provided along the moving direction of the endless transport belt. A supply step of supplying the cellulose nanofiber dispersion liquid in strands or granules onto the endless transport belt that is provided with a heating plate and moves at a constant speed from the nozzle having a diameter of 1 mm or more and 8 mm or less, and the endless transport. Cellulous nanofibers including a drying step of drying the cellulose nanofiber dispersion liquid supplied on the belt in the heating region and a cooling step of cooling the concentrated / dried product dried in the drying step in the cooling region. Manufacturing method for concentrated / dried products.
(2) The cellulose nanofiber dispersion liquid contains 99.9 parts by weight or more of cellulose nanofibers in solid content out of 100 parts by weight of solid content, and in the drying step, the temperature of the heating plate is 80 to 130 ° C. The method for producing a cellulose nanofiber concentrated / dried product according to (1), wherein the cellulose nanofiber dispersion is dried to a solid content concentration of 10 to 20% by weight.
(3) The cellulose nanofiber dispersion liquid includes a step of adjusting the pH of the cellulose nanofiber dispersion liquid supplied in the supply step to 9 to 11, and the cellulose nanofiber dispersion liquid is water-soluble with respect to 100 parts by weight of the solid content of the cellulose nanofibers. The cellulose nano according to (1), which contains 5 to 300 parts by weight of a polymer as a solid content, and in the drying step, the heating plate is heated to a temperature of 80 to 130 ° C. and the cellulose nanofiber dispersion is dried until it becomes a dry solid. Method for manufacturing fiber-concentrated / dried products.
(4) An endless transport belt and a heating region and a cooling region are sequentially arranged in the pressure reducing tank along the moving direction of the endless transport belt, and the cellulose nanofiber dispersion is dried at a low temperature to be concentrated and dried. A method for producing a cellulose nanofiber concentrated / dried product, which is carried out using a pressure reducing belt dryer for obtaining the product, wherein the pressure reducing belt dryer is provided on the upstream side of the heating region of the endless transport belt. A nozzle having a diameter of 1 mm or more and 8 mm or less for supplying the cellulose nanofiber dispersion liquid and a decompression device for creating a decompression atmosphere in the decompression tank are provided, and the heating region is provided along the moving direction of the endless transport belt. A supply step of supplying the cellulose nanofiber dispersion liquid in strands or granules from the nozzle having a diameter of 1 mm or more and 8 mm or less onto the endless transport belt moving at a constant speed, which is provided with a microwave generator. Cellulose including a drying step of drying the cellulose nanofiber dispersion liquid supplied on the endless transport belt in the heating region and a cooling step of cooling the concentrated / dried product dried in the drying step in the cooling region. Manufacturing method for nanofiber concentrated / dried products.
(5) An endless transport belt and a heating region and a cooling region are sequentially arranged in the pressure reducing tank along the moving direction of the endless transport belt, and the cellulose nanofiber dispersion is dried at a low temperature to be concentrated and dried. A pressure reducing belt dryer for obtaining the above, provided on the upstream side of the heating region of the endless transport belt, a nozzle having a diameter of 1 mm or more and a diameter of 8 mm or less for supplying the cellulose nanofiber dispersion liquid, and the pressure reducing tank. A pressure reducing belt dryer provided with a pressure reducing device for creating a pressure reducing atmosphere inside, and the heating region is provided with heating means along the moving direction of the endless transport belt.
(6) The decompression belt dryer according to (5), wherein the heating means is a heating plate.
(7) The decompression belt dryer according to (5), wherein the heating means is a microwave generator.
　本発明によれば、濃縮・乾燥前のＣＮＦ分散液と同等程度の透明度および粘度特性を有する再分散液を生成することが可能なＣＮＦ濃縮・乾燥品を得ることができるセルロースナノファイバー濃縮・乾燥品の製造方法、及びこの製造方法に適した減圧ベルト乾燥機が提供される。 According to the present invention, a cellulose nanofiber concentrated / dried product capable of producing a redispersion liquid having the same degree of transparency and viscosity characteristics as the CNF dispersion liquid before concentration / drying can be obtained. A method for manufacturing a product and a pressure reducing belt dryer suitable for this manufacturing method are provided.
本発明の減圧ベルト乾燥機の一例を示す概略図である。It is the schematic which shows an example of the pressure reducing belt dryer of this invention.
　以下、図面を参照して本発明の減圧ベルト乾燥機について説明する。なお、本発明の減圧ベルト乾燥機は、図１に示すものに限られるものではない。また、本発明において「～」は端値を含む。すなわち「Ｘ～Ｙ」はその両端の値ＸおよびＹを含む。 Hereinafter, the pressure reducing belt dryer of the present invention will be described with reference to the drawings. The pressure reducing belt dryer of the present invention is not limited to the one shown in FIG. Further, in the present invention, "-" includes a fractional value. That is, "X to Y" includes the values X and Y at both ends thereof.
　図１に示す減圧ベルト乾燥機２は、内部を減圧することが可能な減圧槽４、減圧槽４内に設置された無端搬送ベルト６、無端搬送ベルト６上に設置されたセルロースナノファイバー（ＣＮＦ）分散液７を供給するノズル８、ＣＮＦ分散液７を加熱する加熱手段であって、無端搬送ベルト６の下面にその移動方向に沿って配設された第１加熱プレート１０ａ、第２加熱プレート１０ｂ、第３加熱プレート１０ｃ、さらにその下流に配設され、チラーユニット１２から供給される冷水によって濃縮・乾燥品を冷却する冷却プレート１４、冷却された濃縮・乾燥品を受け入れる受入部１６、受入部１６から払い出された濃縮・乾燥品を回収する回収部１８を備えている。ここで、加熱プレート１０ａ、１０ｂ、１０ｃは、膨張タンク２０、ポンプ２２、熱交換器２４からなる熱水発生装置２６から送られた熱水を熱媒としている。減圧槽４内は、コールドトラップ２８ａおよび真空ポンプ２８ｂからなる真空発生装置２８によって、運転中は減圧されている。 The pressure reducing belt dryer 2 shown in FIG. 1 has a pressure reducing tank 4 capable of depressurizing the inside, an endless transport belt 6 installed in the pressure reducing tank 4, and cellulose nanofibers (CNF) installed on the endless transport belt 6. ) A first heating plate 10a and a second heating plate, which are heating means for heating the nozzle 8 for supplying the dispersion liquid 7 and the CNF dispersion liquid 7, and are arranged on the lower surface of the endless transport belt 6 along the moving direction thereof. 10b, a third heating plate 10c, a cooling plate 14 arranged further downstream to cool the concentrated / dried product with cold water supplied from the chiller unit 12, a receiving unit 16 for receiving the cooled concentrated / dried product, and receiving. A collection unit 18 for collecting the concentrated / dried product discharged from the unit 16 is provided. Here, the heating plates 10a, 10b, and 10c use hot water sent from a hot water generator 26 including an expansion tank 20, a pump 22, and a heat exchanger 24 as a heat medium. The inside of the pressure reducing tank 4 is depressurized during operation by a vacuum generator 28 including a cold trap 28a and a vacuum pump 28b.
　ノズル８の直径としては、均一に十分に乾燥する観点から、直径１ｍｍ以上８ｍｍ以下、好ましくは直径１ｍｍ以上４ｍｍ以下、より好ましくは直径１ｍｍ以上２．５ｍｍ以下である。 The diameter of the nozzle 8 is 1 mm or more and 8 mm or less, preferably 1 mm or more and 4 mm or less, and more preferably 1 mm or more and 2.5 mm or less in diameter from the viewpoint of uniform and sufficient drying.
　ノズル８から無端搬送ベルト６上に供給されたＣＮＦ分散液７は、無端搬送ベルト６の移動に伴って、加熱領域を構成する第１加熱プレート１０ａ、第２加熱プレート１０ｂ、第３加熱プレート１０ｃ、ならびに冷却領域を構成する冷却プレート１４上を順次通過し、所定の乾燥処理を施される。なお、加熱プレートの温度は、個別に設定可能であり、加熱プレート１０ａ、１０ｂ、１０ｃをすべて同じ温度となるように設定しても良いし、第１加熱プレート１０ａ、第２加熱プレート１０ｂ、第３加熱プレート１０ｃの順に温度を低下させるように設定しても良い。 The CNF dispersion liquid 7 supplied from the nozzle 8 onto the endless transport belt 6 moves with the movement of the endless transport belt 6, and the first heating plate 10a, the second heating plate 10b, and the third heating plate 10c constituting the heating region. , And the cooling plate 14 constituting the cooling region are sequentially passed and subjected to a predetermined drying treatment. The temperature of the heating plate can be set individually, and the heating plates 10a, 10b, and 10c may all be set to have the same temperature, or the first heating plate 10a, the second heating plate 10b, and the second heating plate 10b may be set to have the same temperature. 3 The temperature may be set to decrease in the order of the heating plates 10c.
　所定の乾燥処理を施された結果、得られたＣＮＦ濃縮・乾燥品は、無端搬送ベルト６の下流端まで到達すると、下方に落下し、受入部１６に受け入れられる。受入部１６に受け入れられた濃縮・乾燥品は、ダブルダンパ機構により減圧状態が解除され、回収部１８に払い出される。 When the CNF concentrated / dried product obtained as a result of the predetermined drying treatment reaches the downstream end of the endless transport belt 6, it falls downward and is received by the receiving unit 16. The concentrated / dried product received in the receiving unit 16 is released from the reduced pressure state by the double damper mechanism and is discharged to the collecting unit 18.
　無端搬送ベルト６の表面は、濃縮・乾燥品がベルトから剥離しやすくなる観点から、ＣＮＦ分散液７が接する面に対して、フッ素樹脂加工を施したものであってもよい。 The surface of the endless transport belt 6 may be treated with a fluororesin on the surface in contact with the CNF dispersion liquid 7 from the viewpoint that the concentrated / dried product can be easily peeled off from the belt.
　なお、受入部１６は、得られた濃縮・乾燥品を粉砕する機構を有するものであってもよい。 The receiving unit 16 may have a mechanism for crushing the obtained concentrated / dried product.
　また、上述の実施形態では、加熱手段が第１から第３までの複数個の加熱プレートにより構成される例として説明したが、加熱手段が、単独の加熱プレートにより構成されるものであってもよい。 Further, in the above-described embodiment, the heating means has been described as an example composed of a plurality of heating plates from the first to the third, but even if the heating means is composed of a single heating plate. good.
　さらに、上述の実施形態では、加熱手段として加熱プレートを用いているが、本発明の減圧ベルト乾燥機は、加熱手段として加熱プレートに代えて、単独または複数個のマイクロ波発生装置を用いたものであってもよい。 Further, in the above-described embodiment, a heating plate is used as the heating means, but the decompression belt dryer of the present invention uses a single or a plurality of microwave generators instead of the heating plate as the heating means. It may be.
　次に、本発明の減圧ベルト乾燥機を用いたＣＮＦ濃縮・乾燥品の製造方法について説明する。 Next, a method for producing a CNF concentrated / dried product using the pressure reducing belt dryer of the present invention will be described.
　本発明の減圧ベルト乾燥機を用いて実行されるＣＮＦ濃縮・乾燥品の製造方法は、直径１ｍｍ以上、８ｍｍ以下のノズル８から、定速で移動する無端搬送ベルト６上に、ＣＮＦ分散液７をストランド状又は粒状に供給する供給工程と、無端搬送ベルト６上に供給されたＣＮＦ分散液７を、加熱領域で乾燥する乾燥工程と、乾燥工程で乾燥した濃縮・乾燥品を、冷却領域で冷却する冷却工程とを含む。 The method for producing a CNF concentrated / dried product executed by using the pressure reducing belt dryer of the present invention is a CNF dispersion liquid 7 on an endless transport belt 6 moving at a constant speed from a nozzle 8 having a diameter of 1 mm or more and 8 mm or less. In the cooling region, the concentrated / dried product dried in the drying step is dried in the heating region, and the CNF dispersion liquid 7 supplied on the endless transport belt 6 is dried in the heating region. Includes a cooling step to cool.
（供給工程）
　供給工程では、直径１ｍｍ以上、８ｍｍ以下のノズル８から、減圧槽４内に設置された、定速で移動する無端搬送ベルト６上に、ＣＮＦ分散液７をストランド状又は粒状に供給する。無端搬送ベルト６の移動速度は、特に限定されないが、乾燥効率の観点から５～３０ｃｍ/分、より好ましくは９～２４ｃｍ/分である。また減圧槽４の気圧は、真空発生装置２８により、例えば、好ましくは０～２０ｋＰａ、より好ましくは１．５～１０ｋＰａ減圧されている。ＣＮＦ分散液７の供給形態は、ムラなく乾燥できる観点からストランド状又は粒状が好ましく、効率の観点からストランド状がより好ましい。 (Supply process)
In the supply step, the CNF dispersion liquid 7 is supplied in strands or granules from a nozzle 8 having a diameter of 1 mm or more and 8 mm or less onto an endless transport belt 6 installed in the pressure reducing tank 4 and moving at a constant speed. The moving speed of the endless transport belt 6 is not particularly limited, but is 5 to 30 cm / min, more preferably 9 to 24 cm / min from the viewpoint of drying efficiency. The air pressure in the pressure reducing tank 4 is reduced by the vacuum generator 28, for example, preferably from 0 to 20 kPa, more preferably from 1.5 to 10 kPa. The supply form of the CNF dispersion 7 is preferably in the form of strands or granules from the viewpoint of being able to dry evenly, and more preferably in the form of strands from the viewpoint of efficiency.
（乾燥工程）
　乾燥工程における乾燥温度は、乾燥効率の観点から、加熱プレートの温度を８０～１３０℃とすることが好ましく、８０～１００℃とすることがより好ましく、８０～９０℃とすることがさらに好ましい。また、乾燥工程においては、ＣＮＦ分散液７がＣＮＦを固形分で９９．９重量％以上含む場合は、ＣＮＦ分散液７の固形分濃度が１０～２０重量％となるまで乾燥させることが好ましく、１０～１５重量％となるまで乾燥させることがより好ましい。 (Drying process)
From the viewpoint of drying efficiency, the drying temperature in the drying step is preferably 80 to 130 ° C., more preferably 80 to 100 ° C., and even more preferably 80 to 90 ° C. In the drying step, when the CNF dispersion 7 contains 99.9% by weight or more of CNF in solid content, it is preferable to dry the CNF dispersion 7 until the solid content concentration is 10 to 20% by weight. More preferably, it is dried to 10 to 15% by weight.
　また、ＣＮＦ分散液７が水溶性高分子を含む場合は、乾燥固形物となるまで乾燥させることができる。ＣＮＦ分散液７が水溶性高分子を含む場合は、水溶性高分子の配合量が、ＣＮＦの絶乾固形分１００重量部に対して、５～３００重量部であることが好ましく、２０～３００重量部がより好ましい。水溶性高分子の配合量が５重量部未満であると十分な再分散性の効果が発現せず、３００重量部を超えるとＣＮＦの特徴であるチキソトロピー性などの粘度特性、分散安定性の低下などの問題が生じる。 When the CNF dispersion 7 contains a water-soluble polymer, it can be dried until it becomes a dry solid. When the CNF dispersion 7 contains a water-soluble polymer, the blending amount of the water-soluble polymer is preferably 5 to 300 parts by weight, preferably 20 to 300 parts by weight, based on 100 parts by weight of the absolute dry solid content of CNF. Parts by weight are more preferred. If the blending amount of the water-soluble polymer is less than 5 parts by weight, the effect of sufficient redispersibility is not exhibited, and if it exceeds 300 parts by weight, the viscosity characteristics such as thixotropy and the dispersion stability, which are the characteristics of CNF, are lowered. Problems such as occur.
　水溶性高分子の配合量が、ＣＮＦの絶乾固形分１００重量部に対して、２５重量部以上であると、特に優れた再分散性を得ることができるので好ましい。また、チキソトロピー性を考慮すると２００重量部以下であることが好ましく、６０重量部以下が特に好ましい。 It is preferable that the blending amount of the water-soluble polymer is 25 parts by weight or more with respect to 100 parts by weight of the absolute dry solid content of CNF, because particularly excellent redispersibility can be obtained. Further, considering the thixotropy property, it is preferably 200 parts by weight or less, and 60 parts by weight or less is particularly preferable.
　ここで、本発明においてＣＮＦの乾燥固形物とは、水分量が１２重量％以下になるように脱水・乾燥したＣＮＦを意味する。 Here, in the present invention, the dry solid substance of CNF means CNF dehydrated and dried so that the water content is 12% by weight or less.
（ｐＨを調整する工程）
　ＣＮＦ分散液７が水溶性高分子を含む場合は、再分散性の観点から、供給工程において供給するＣＮＦ分散液７のｐＨを好ましくは９～１１、より好ましくは９～１０に調整する工程をさらに含むことが好ましい。 (Step to adjust pH)
When the CNF dispersion 7 contains a water-soluble polymer, the step of adjusting the pH of the CNF dispersion 7 supplied in the supply step is preferably 9 to 11, more preferably 9 to 10, from the viewpoint of redispersibility. It is preferable to further include it.
　ＣＮＦ分散液７のｐＨを９～１１に調整するために用いる薬品は特に限定されるものではなく、水酸化ナトリウム、水酸化カリウム、水酸化カルシウム、水酸化バリウム、水酸化マグネシウム、アンモニア、水酸化銅、水酸化アルミニウム、水酸化鉄、水酸化アンモニウム、炭酸水素ナトリウム、炭酸水素カリウム、炭酸ナトリウム、炭酸カルシウム、炭酸マグネシウム、酸化マグネシウムから選ばれた塩基性無機化合物、あるいはアルギニン、リジン、ヒスチジン及びオルニチンから選ばれた塩基性有機化合物などを例示することができる。 The chemicals used to adjust the pH of the CNF dispersion 7 to 9 to 11 are not particularly limited, and sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, magnesium hydroxide, ammonia, and hydroxide are used. Basic inorganic compounds selected from copper, aluminum hydroxide, iron hydroxide, ammonium hydroxide, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate, calcium carbonate, magnesium carbonate, magnesium oxide, or arginine, lysine, histidine and ornithine. Examples thereof include basic organic compounds selected from the above.
（冷却工程）
　冷却工程では、濃縮・乾燥品が冷却され、温度が下がり、硬化することにより、無端搬送ベルト６から剥離しやすくなる。 (Cooling process)
In the cooling step, the concentrated / dried product is cooled, the temperature is lowered, and the product is hardened, so that the product is easily peeled off from the endless transport belt 6.
（セルロースナノファイバー）
　本発明においてセルロースナノファイバーとは、繊維径が３～５００ｎｍ程度、アスペクト比が１００以上の微細繊維である。本発明で用いるセルロースナノファイバーとしては、アニオン変性セルロースナノファイバー（ＣＮＦ）が挙げられる。アニオン変性ＣＮＦは、酸化したセルロース、カルボキシメチル化したセルロースなどを解繊することにより得ることができる。微細繊維の平均繊維長と平均繊維径は、酸化処理、カルボキシメチル化処理、解繊処理により調整することができる。
　本発明に用いるセルロースナノファイバーの平均繊維長は、特に限定されないが、好ましくは１００ｎｍ～１μｍ、より好ましくは１００ｎｍ～４００ｎｍである。また、本発明に用いるセルロースナノファイバーの平均繊維径は３ｎｍ～１０ｎｍ、好ましくは３ｎｍ～８ｎｍである。 (Cellulose nanofiber)
In the present invention, cellulose nanofibers are fine fibers having a fiber diameter of about 3 to 500 nm and an aspect ratio of 100 or more. Examples of the cellulose nanofibers used in the present invention include anion-modified cellulose nanofibers (CNF). The anion-modified CNF can be obtained by defibrating oxidized cellulose, carboxymethylated cellulose and the like. The average fiber length and average fiber diameter of the fine fibers can be adjusted by an oxidation treatment, a carboxymethylation treatment, and a defibration treatment.
The average fiber length of the cellulose nanofibers used in the present invention is not particularly limited, but is preferably 100 nm to 1 μm, and more preferably 100 nm to 400 nm. The average fiber diameter of the cellulose nanofibers used in the present invention is 3 nm to 10 nm, preferably 3 nm to 8 nm.
　なお、セルロースナノファイバーの平均繊維長及び平均繊維径は、原子間力顕微鏡（ＡＦＭ）を用いて、各繊維を観察した結果から得られる繊維長及び繊維径を平均することによって得ることができる。
　セルロースナノファイバーの平均アスペクト比は、通常５０以上である。上限は特に限定されないが、通常は１０００以下である。平均アスペクト比は、下記の式により算出することができる：
　アスペクト比＝平均繊維長／平均繊維径 The average fiber length and average fiber diameter of the cellulose nanofibers can be obtained by averaging the fiber length and fiber diameter obtained from the results of observing each fiber using an atomic force microscope (AFM).
The average aspect ratio of cellulose nanofibers is usually 50 or more. The upper limit is not particularly limited, but is usually 1000 or less. The average aspect ratio can be calculated by the following formula:
Aspect ratio = average fiber length / average fiber diameter
（セルロース原料）
　セルロースナノファイバーの原料であるセルロース原料の由来は、特に限定されないが、例えば、植物（例えば、木材、竹、麻、ジュート、ケナフ、農地残廃物、布、パルプ（針葉樹未漂白クラフトパルプ（ＮＵＫＰ）、針葉樹漂白クラフトパルプ（ＮＢＫＰ）、広葉樹未漂白クラフトパルプ（ＬＵＫＰ）、広葉樹漂白クラフトパルプ（ＬＢＫＰ）、針葉樹未漂白サルファイトパルプ（ＮＵＳＰ）、針葉樹漂白サルファイトパルプ（ＮＢＳＰ）、サーモメカニカルパルプ（ＴＭＰ）、再生パルプ、古紙等）、動物（例えばホヤ類）、藻類、微生物（例えば酢酸菌（アセトバクター））、微生物産生物等が挙げられる。本発明で用いるセルロース原料は、これらのいずれかであってもよいし２種類以上の組み合わせであってもよいが、好ましくは植物又は微生物由来のセルロース原料（例えば、セルロース繊維）であり、より好ましくは植物由来のセルロース原料（例えば、セルロース繊維）である。 (Cellulose raw material)
The origin of the cellulose raw material, which is the raw material of the cellulose nanofibers, is not particularly limited, but for example, plants (for example, wood, bamboo, hemp, jute, kenaf, agricultural waste, cloth, pulp (conifer unbleached kraft pulp (NUKP)). , Conifer bleached kraft pulp (NBKP), broadleaf unbleached kraft pulp (LUKP), broadleaf bleached kraft pulp (LBKP), conifer unbleached sulphite pulp (NUSP), conifer bleached sulphite pulp (NBSP), thermomechanical pulp (TMP) ), Recycled pulp, used paper, etc.), animals (for example, squirrels), algae, microorganisms (for example, acetic acid bacteria (acetobacter)), microbial products, etc. The cellulose raw material used in the present invention is any of these. It may be a combination of two or more kinds, but is preferably a pulp raw material derived from a plant or a microorganism (for example, cellulose fiber), and more preferably a pulp raw material derived from a plant (for example, cellulose fiber). be.
　セルロース原料の数平均繊維径は特に制限されないが、一般的なパルプである針葉樹クラフトパルプの場合は３０～６０μｍ程度、広葉樹クラフトパルプの場合は１０～３０μｍ程度である。その他のパルプの場合、一般的な精製を経たものは５０μｍ程度である。例えばチップ等の数ｃｍ大のものを精製したものである場合、リファイナー、ビーター等の離解機で機械的処理を行い、５０μｍ程度に調整することが好ましい。 The number average fiber diameter of the cellulose raw material is not particularly limited, but it is about 30 to 60 μm in the case of softwood kraft pulp, which is a general pulp, and about 10 to 30 μm in the case of hardwood kraft pulp. In the case of other pulp, the one that has undergone general purification is about 50 μm. For example, when a chip or the like having a size of several cm is purified, it is preferable to perform mechanical treatment with a dissociator such as a refiner or a beater to adjust the size to about 50 μm.
（酸化）
　酸化によりセルロース原料を変性して得られる酸化セルロース又はセルロースナノファイバーの絶乾重量に対するカルボキシル基の量は、０．５ｍｍｏｌ／ｇ以上、好ましくは０．８ｍｍｏｌ／ｇ以上、より好ましくは１．０ｍｍｏｌ／ｇ以上である。上限は、３．０ｍｍｏｌ／ｇ以下、好ましくは２．５ｍｍｏｌ／ｇ以下、より好ましくは２．０ｍｍｏｌ／ｇ以下である。すなわち、本発明に用いる酸化セルロースナノファイバーは、カルボキシル基の量が０．５ｍｍｏｌ／ｇ～３．０ｍｍｏｌ／ｇであり、０．８ｍｍｏｌ／ｇ～２．５ｍｍｏｌ／ｇが好ましく、１．０ｍｍｏｌ／ｇ～２．０ｍｍｏｌ／ｇがより好ましい。 (Oxidation)
The amount of carboxyl groups based on the absolute dry weight of cellulose oxide or cellulose nanofibers obtained by modifying the cellulose raw material by oxidation is 0.5 mmol / g or more, preferably 0.8 mmol / g or more, more preferably 1.0 mmol / g. It is g or more. The upper limit is 3.0 mmol / g or less, preferably 2.5 mmol / g or less, and more preferably 2.0 mmol / g or less. That is, the cellulose oxide nanofiber used in the present invention has a carboxyl group amount of 0.5 mmol / g to 3.0 mmol / g, preferably 0.8 mmol / g to 2.5 mmol / g, and 1.0 mmol / g. -2.0 mmol / g is more preferable.
　本発明においては、酸化する方法として、Ｎ－オキシル化合物、及び、臭化物、ヨウ化物若しくはこれらの混合物からなる群より選択される物質の存在下で酸化剤を用いて水中でセルロース原料を酸化する。この方法によれば、セルロース表面のグルコピラノース環のＣ６位の一級水酸基が選択的に酸化され、アルデヒド基、カルボキシル基、及びカルボキシレート基からなる群より選ばれる基が生じる。反応時のセルロース原料の濃度は特に限定されないが、５重量％以下が好ましい。 In the present invention, as a method for oxidizing, a cellulose raw material is oxidized in water using an oxidizing agent in the presence of an N-oxyl compound and a substance selected from the group consisting of bromide, iodide or a mixture thereof. According to this method, the primary hydroxyl group at the C6 position of the glucopyranose ring on the surface of cellulose is selectively oxidized to generate a group selected from the group consisting of an aldehyde group, a carboxyl group, and a carboxylate group. The concentration of the cellulose raw material during the reaction is not particularly limited, but is preferably 5% by weight or less.
　Ｎ－オキシル化合物とは、ニトロキシラジカルを発生しうる化合物をいう。ニトロキシルラジカルとしては例えば、２，２，６，６－テトラメチルピペリジン１－オキシル（ＴＥＭＰＯ）が挙げられる。Ｎ－オキシル化合物としては、目的の酸化反応を促進する化合物であれば、いずれの化合物も使用できる。
　Ｎ－オキシル化合物の使用量は、原料となるセルロースを酸化できる触媒量であれば特に制限されない。例えば、絶乾１ｇのセルロースに対して、０．０１ｍｍｏｌ以上が好ましく、０．０２ｍｍｏｌ以上がより好ましい。上限は、１０ｍｍｏｌ以下が好ましく、１ｍｍｏｌ以下がより好ましく、０．５ｍｍｏｌ以下が更に好ましい。従って、Ｎ－オキシル化合物の使用量は絶乾１ｇのセルロースに対して、０．０１～１０ｍｍｏｌが好ましく、０．０１～１ｍｍｏｌがより好ましく、０．０２～０．５ｍｍｏｌがさらに好ましい。 The N-oxyl compound is a compound capable of generating a nitroxy radical. Examples of the nitroxyl radical include 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO). As the N-oxyl compound, any compound can be used as long as it is a compound that promotes the desired oxidation reaction.
The amount of the N-oxyl compound used is not particularly limited as long as it is a catalytic amount capable of oxidizing cellulose as a raw material. For example, 0.01 mmol or more is preferable, and 0.02 mmol or more is more preferable with respect to 1 g of cellulose that has been completely dried. The upper limit is preferably 10 mmol or less, more preferably 1 mmol or less, and even more preferably 0.5 mmol or less. Therefore, the amount of the N-oxyl compound used is preferably 0.01 to 10 mmol, more preferably 0.01 to 1 mmol, still more preferably 0.02 to 0.5 mmol, based on 1 g of dry cellulose.
　臭化物とは臭素を含む化合物であり、例えば、臭化ナトリウム等の、水中で解離してイオン化可能な臭化アルカリ金属が挙げられる。また、ヨウ化物とはヨウ素を含む化合物であり、例えば、ヨウ化アルカリ金属が挙げられる。臭化物又はヨウ化物の使用量は、酸化反応を促進できる範囲で選択すればよい。臭化物及びヨウ化物の合計量は絶乾１ｇのセルロースに対して、０．１ｍｍｏｌ以上が好ましく、０．５ｍｍｏｌ以上がより好ましい。上限は、１００ｍｍｏｌ以下が好ましく、１０ｍｍｏｌ以下がより好ましく、５ｍｍｏｌ以下が更に好ましい。従って、臭化物及びヨウ化物の合計量は絶乾１ｇのセルロースに対して、０．１～１００ｍｍｏｌが好ましく、０．１～１０ｍｍｏｌがより好ましく、０．５～５ｍｍｏｌがさらに好ましい。 Bromide is a compound containing bromine, and examples thereof include alkali metals bromide that can be dissociated and ionized in water, such as sodium bromide. Further, the iodide is a compound containing iodine, and examples thereof include an alkali metal iodide. The amount of bromide or iodide to be used may be selected within a range in which the oxidation reaction can be promoted. The total amount of bromide and iodide is preferably 0.1 mmol or more, more preferably 0.5 mmol or more, based on 1 g of dry cellulose. The upper limit is preferably 100 mmol or less, more preferably 10 mmol or less, and even more preferably 5 mmol or less. Therefore, the total amount of bromide and iodide is preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, still more preferably 0.5 to 5 mmol with respect to 1 g of dry cellulose.
　酸化剤は、特に限定されないが例えば、ハロゲン、次亜ハロゲン酸、亜ハロゲン酸、過ハロゲン酸、それらの塩、ハロゲン酸化物、過酸化物などが挙げられる。中でも、安価で環境負荷が少ないことから、次亜ハロゲン酸又はその塩が好ましく、次亜塩素酸又はその塩がより好ましく、次亜塩素酸ナトリウムが更に好ましい。酸化剤の使用量は、絶乾１ｇのセルロースに対して、０．５ｍｍｏｌ以上が好ましく、１ｍｍｏｌ以上がより好ましく、３ｍｍｏｌ以上が更に好ましい。上限は、５００ｍｍｏｌ以下が好ましく、５０ｍｍｏｌ以下がより好ましく、２５ｍｍｏｌ以下が更に好ましい。従って、酸化剤の使用量は絶乾１ｇのセルロースに対して、０．５～５００ｍｍｏｌが好ましく、０．５～５０ｍｍｏｌがより好ましく、１～２５ｍｍｏｌがさらに好ましく、３～２５ｍｍｏｌが最も好ましい。Ｎ－オキシル化合物を用いる場合、酸化剤の使用量はＮ－オキシル化合物１ｍｏｌに対して１ｍｏｌ以上が好ましい。上限は、４０ｍｏｌが好ましい。従って、酸化剤の使用量はＮ－オキシル化合物１ｍｏｌに対して１～４０ｍｏｌが好ましい。 The oxidizing agent is not particularly limited, and examples thereof include halogen, hypochlorous acid, hypochlorous acid, perhalogenic acid, salts thereof, halogen oxide, and peroxide. Among them, hypochlorous acid or a salt thereof is preferable, hypochlorous acid or a salt thereof is more preferable, and sodium hypochlorite is further preferable because it is inexpensive and has a small environmental load. The amount of the oxidizing agent used is preferably 0.5 mmol or more, more preferably 1 mmol or more, still more preferably 3 mmol or more, based on 1 g of the dry cellulose. The upper limit is preferably 500 mmol or less, more preferably 50 mmol or less, still more preferably 25 mmol or less. Therefore, the amount of the oxidizing agent used is preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, still more preferably 1 to 25 mmol, and most preferably 3 to 25 mmol with respect to 1 g of the dry cellulose. When an N-oxyl compound is used, the amount of the oxidizing agent used is preferably 1 mol or more with respect to 1 mol of the N-oxyl compound. The upper limit is preferably 40 mol. Therefore, the amount of the oxidizing agent used is preferably 1 to 40 mol with respect to 1 mol of the N-oxyl compound.
　酸化反応時のｐＨ、温度等の条件は特に限定されず、一般に、比較的温和な条件であっても酸化反応は効率よく進行する。反応温度は４℃以上が好ましく、１５℃以上がより好ましい。上限は４０℃以下が好ましく、３０℃以下がより好ましい。従って、温度は４～４０℃が好ましく、１５～３０℃程度、すなわち室温であってもよい。反応液のｐＨは、８以上が好ましく、１０以上がより好ましい。上限は、１２以下が好ましく、１１以下がより好ましい。従って、反応液のｐＨは、好ましくは８～１２、より好ましくは１０～１１程度である。通常、酸化反応の進行に伴ってセルロース中にカルボキシル基が生成するため、反応液のｐＨは低下する傾向にある。そのため、酸化反応を効率よく進行させるためには、水酸化ナトリウム水溶液などのアルカリ性溶液を添加して、反応液のｐＨを上記の範囲に維持することが好ましい。酸化の際の反応媒体は、取扱い性の容易さや、副反応が生じにくいこと等の理由から、水が好ましい。 Conditions such as pH and temperature during the oxidation reaction are not particularly limited, and in general, the oxidation reaction proceeds efficiently even under relatively mild conditions. The reaction temperature is preferably 4 ° C. or higher, more preferably 15 ° C. or higher. The upper limit is preferably 40 ° C. or lower, more preferably 30 ° C. or lower. Therefore, the temperature is preferably 4 to 40 ° C, and may be about 15 to 30 ° C, that is, room temperature. The pH of the reaction solution is preferably 8 or more, more preferably 10 or more. The upper limit is preferably 12 or less, more preferably 11 or less. Therefore, the pH of the reaction solution is preferably about 8 to 12, more preferably about 10 to 11. Usually, the pH of the reaction solution tends to decrease because a carboxyl group is generated in the cellulose as the oxidation reaction progresses. Therefore, in order to allow the oxidation reaction to proceed efficiently, it is preferable to add an alkaline solution such as an aqueous sodium hydroxide solution to maintain the pH of the reaction solution in the above range. Water is preferable as the reaction medium for oxidation because it is easy to handle and side reactions are unlikely to occur.
　酸化反応における反応時間は、酸化の進行の程度に従って適宜設定することができ、通常は０．５時間以上である。上限は通常は６時間以下、好ましくは４時間以下である。従って、酸化における反応時間は通常０．５～６時間、例えば０．５～４時間程度である。 The reaction time in the oxidation reaction can be appropriately set according to the degree of progress of oxidation, and is usually 0.5 hours or more. The upper limit is usually 6 hours or less, preferably 4 hours or less. Therefore, the reaction time in oxidation is usually about 0.5 to 6 hours, for example, about 0.5 to 4 hours.
　酸化は、２段階以上の反応に分けて実施してもよい。例えば、１段目の反応終了後に濾別して得られた酸化セルロースを、再度、同一又は異なる反応条件で酸化させることにより、１段目の反応で副生する食塩による反応阻害を受けることなく、効率よく酸化させることができる。 Oxidation may be carried out in two or more stages of reaction. For example, by oxidizing the oxidized cellulose obtained by filtration after the completion of the first-stage reaction again under the same or different reaction conditions, the efficiency is not affected by the reaction inhibition by the salt produced as a by-product in the first-stage reaction. Can be oxidized well.
（カルボキシメチル化）
　本発明において、セルロース原料のカルボキシメチル化は公知の方法を用いて行うことができ、特に限定されるものではないが、セルロースの無水グルコース単位当たりのカルボキシメチル基置換度が０．０１～０．５０となるように調整することが好ましい。その一例として次のような製造方法を挙げることができるが、従来公知の方法で合成してもよく、市販品を使用してもよい。セルロースを発底原料にし、溶媒に３～２０重量倍の水及び／又は低級アルコール、具体的にはメタノール、エタノール、Ｎ－プロピルアルコール、イソプロピルアルコール、Ｎ－ブタノール、イソブタノール、第３級ブタノール等の単独、又は２種以上の混合媒体を使用する。なお、低級アルコールの混合割合は、６０～９５重量％である。マーセル化剤としては、発底原料の無水グルコース残基当たり０．５～２０倍モルの水酸化アルカリ金属、具体的には水酸化ナトリウム、水酸化カリウムを使用する。発底原料と溶媒、マーセル化剤を混合し、反応温度０～７０℃、好ましくは１０～６０℃、かつ反応時間１５分～８時間、好ましくは３０分～７時間、マーセル化処理を行う。その後、カルボキシメチル化剤をグルコース残基当たり０．０５～１０．０倍モル添加し、反応温度３０～９０℃、好ましくは４０～８０℃、かつ反応時間３０分～１０時間、好ましくは１時間～４時間、エーテル化反応を行う。 (Carboxymethylation)
In the present invention, carboxymethylation of the cellulose raw material can be carried out by using a known method, and the degree of carboxymethyl group substitution per anhydrous glucose unit of cellulose is 0.01 to 0. It is preferable to adjust it to 50. As an example thereof, the following production method can be mentioned, but it may be synthesized by a conventionally known method, or a commercially available product may be used. Using cellulose as the base material, 3 to 20 times by weight of water and / or lower alcohol, specifically methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, tertiary butanol, etc. Use alone or a mixed medium of two or more. The mixing ratio of the lower alcohol is 60 to 95% by weight. As the mercerizing agent, 0.5 to 20 times mol of alkali metal hydroxide, specifically sodium hydroxide and potassium hydroxide, is used per anhydrous glucose residue of the bottoming material. The bottoming material, the solvent, and the mercerizing agent are mixed, and the mercerization treatment is carried out at a reaction temperature of 0 to 70 ° C., preferably 10 to 60 ° C., and a reaction time of 15 minutes to 8 hours, preferably 30 minutes to 7 hours. Then, 0.05 to 10.0 times the molar amount of the carboxymethylating agent is added per glucose residue, the reaction temperature is 30 to 90 ° C., preferably 40 to 80 ° C., and the reaction time is 30 minutes to 10 hours, preferably 1 hour. The etherification reaction is carried out for about 4 hours.
（解繊）
　セルロース原料の解繊は、セルロース原料に変性処理を施す前に行ってもよいし、後に行ってもよい。また、解繊は、一度に行ってもよいし、複数回行ってもよい。複数回の場合それぞれの解繊の時期はいつでもよい。
　解繊に用いる装置は特に限定されないが、例えば、高速回転式、コロイドミル式、高圧式、ロールミル式、超音波式などのタイプの装置が挙げられ、高圧又は超高圧ホモジナイザーが好ましく、湿式の高圧又は超高圧ホモジナイザーがより好ましい。装置は、セルロース原料又は変性セルロース（通常は分散液）に強力なせん断力を印加できることが好ましい。装置が印加できる圧力は、９ＭＰａ以上が好ましく、５０ＭＰａ以上がより好ましく、さらに好ましくは１００ＭＰａ以上であり、特に好ましくは１４０ＭＰａ以上である。これらの圧力を印加することができる湿式の高圧又は超高圧ホモジナイザーを用いることにより、解繊を効率的に行うことができる。 (Defibration)
The defibration of the cellulose raw material may be performed before or after the modification treatment of the cellulose raw material. Further, the defibration may be performed at one time or a plurality of times. In the case of multiple times, the time of each defibration may be any time.
The device used for defibration is not particularly limited, and examples thereof include high-speed rotary type, colloid mill type, high-pressure type, roll mill type, ultrasonic type, and the like, preferably a high-pressure or ultra-high pressure homogenizer, and a wet high pressure. Alternatively, an ultrahigh pressure homogenizer is more preferable. The apparatus preferably can apply a strong shearing force to the cellulose raw material or the modified cellulose (usually a dispersion). The pressure that can be applied by the device is preferably 9 MPa or more, more preferably 50 MPa or more, further preferably 100 MPa or more, and particularly preferably 140 MPa or more. By using a wet high-pressure or ultra-high-pressure homogenizer capable of applying these pressures, defibration can be efficiently performed.
　セルロース原料の分散体に対して解繊を行う場合、分散体中のセルロース原料の固形分濃度は、通常は０．１重量％以上、好ましくは０．２重量％以上、より好ましくは０．３重量％以上である。これにより、セルロース繊維原料の量に対する液量が適量となり効率的である。上限は通常１０重量％以下、好ましくは６重量％以下である。これにより流動性を保持することができる。
　解繊（好ましくは高圧ホモジナイザーでの解繊）、又は必要に応じて解繊前に行う分散処理に先立ち、必要に応じて予備処理を行ってもよい。予備処理は、高速せん断ミキサーなどの混合、撹拌、乳化、分散装置を用いて行えばよい。 When defibrating the dispersion of the cellulose raw material, the solid content concentration of the cellulose raw material in the dispersion is usually 0.1% by weight or more, preferably 0.2% by weight or more, more preferably 0.3. Weight% or more. As a result, the amount of liquid becomes appropriate with respect to the amount of the cellulose fiber raw material, which is efficient. The upper limit is usually 10% by weight or less, preferably 6% by weight or less. This makes it possible to maintain liquidity.
Prior to defibration (preferably defibration with a high-pressure homogenizer) or, if necessary, a dispersion treatment before defibration, pretreatment may be performed if necessary. The pretreatment may be performed using a mixing, stirring, emulsifying, or dispersing device such as a high-speed shear mixer.
（水溶性高分子）
　本発明において、水溶性高分子としては、例えば、セルロース誘導体（カルボキシメチルセルロース、メチルセルロース、ヒドロキシプロピルセルロース、エチルセルロース）、キサンタンガム、キシログルカン、デキストリン、デキストラン、カラギーナン、ローカストビーンガム、アルギン酸、アルギン酸塩、プルラン、澱粉、かたくり粉、クズ粉、加工澱粉（カチオン化澱粉、燐酸化澱粉、燐酸架橋澱粉、燐酸モノエステル化燐酸架橋澱粉、ヒドロキシプロピル澱粉、ヒドロキシプロピル化燐酸架橋澱粉、アセチル化アジピン酸架橋澱粉、アセチル化燐酸架橋澱粉、アセチル化酸化澱粉、オクテニルコハク酸澱粉ナトリウム、酢酸澱粉、酸化澱粉）、コーンスターチ、アラビアガム、ローカストビーンガム、ジェランガム、ポリデキストロース、ペクチン、キチン、水溶性キチン、キトサン、カゼイン、アルブミン、大豆蛋白溶解物、ペプトン、ポリビニルアルコール、ポリアクリルアミド、ポリアクリル酸ソーダ、ポリビニルピロリドン、ポリ酢酸ビニル、ポリアミノ酸、ポリ乳酸、ポリリンゴ酸、ポリグリセリン、ラテックス、ロジン系サイズ剤、石油樹脂系サイズ剤、尿素樹脂、メラミン樹脂、エポキシ樹脂、ポリアミド樹脂、ポリアミド・ポリアミン樹脂、ポリエチレンイミン、ポリアミン、植物ガム、ポリエチレンオキサイド、親水性架橋ポリマー、ポリアクリル酸塩、でんぷんポリアクリル酸共重合体、タマリンドガム、グァーガム及びコロイダルシリカ並びにそれら１つ以上の混合物が挙げられる。この中でも、セルロース誘導体は、セルロースナノファイバーとの相溶性の点から好ましく、カルボキシメチルセルロース及びその塩は特に好ましい。カルボキシメチルセルロース及びその塩のような水溶性高分子は、セルロースナノファイバー同士の間に入りこみ、ＣＮＦ間の距離を広げることで、再分散性を向上させると考えられる。 (Water-soluble polymer)
In the present invention, examples of the water-soluble polymer include cellulose derivatives (carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose, ethyl cellulose), xanthan gum, xyloglucane, dextrin, dextran, carrageenan, locust bean gum, alginic acid, alginate, purulan, and the like. Starch, shavings, scraps, processed starch (cationized starch, phosphorylated starch, phosphoric acid cross-linked starch, phosphoric acid monoesterified phosphoric acid cross-linked starch, hydroxypropyl starch, hydroxypropylated phosphoric acid cross-linked starch, acetylated adipic acid cross-linked starch, acetylation Phosphoric cross-linked starch, acetylated oxidized starch, sodium octenyl succinate, acetate starch, oxidized starch), corn starch, Arabic gum, locust bean gum, gellan gum, polydextrose, pectin, chitin, water-soluble chitin, chitosan, casein, albumin, soybean Protein lysate, peptone, polyvinyl alcohol, polyacrylamide, sodium polyacrylic acid, polyvinylpyrrolidone, vinyl acetate, polyamino acid, polylactic acid, polyapple acid, polyglycerin, latex, rosin-based sizing agent, petroleum resin-based sizing agent, urea Resin, melamine resin, epoxy resin, polyamide resin, polyamide / polyamine resin, polyethyleneimine, polyamine, vegetable gum, polyethylene oxide, hydrophilic crosslinked polymer, polyacrylate, starch polyacrylic acid copolymer, tamarind gum, guar gum and Examples include colloidal silica and one or more mixtures thereof. Among these, cellulose derivatives are preferable from the viewpoint of compatibility with cellulose nanofibers, and carboxymethyl cellulose and salts thereof are particularly preferable. It is considered that water-soluble polymers such as carboxymethyl cellulose and salts thereof penetrate between cellulose nanofibers and increase the distance between CNFs to improve redispersibility.
　水溶性高分子として、カルボキシメチルセルロース又はその塩を用いる場合には、無水グルコース単位当たりのカルボキシメチル基置換度が０．５５～１．６のカルボキシメチルセルロースを用いることが好ましく、０．５５～１．１のものがより好ましく、０．６５～１．１のものがさらに好ましい。また、分子が長い（粘度が高い）ものの方が、ＣＮＦ間の距離を広げる効果が高いので好ましく、カルボキシメチルセルロースの１重量％水溶液における２５℃、６００ｒｐｍでのＢ型粘度は、３～１４０００ｍＰａ・ｓが好ましく、７～１４０００ｍＰａ・ｓがより好ましく、１０００～８０００ｍＰａ・ｓがさらに好ましい。 When carboxymethyl cellulose or a salt thereof is used as the water-soluble polymer, it is preferable to use carboxymethyl cellulose having a carboxymethyl group substitution degree of 0.55 to 1.6 per anhydrous glucose unit, and 0.55 to 1. The one of 1 is more preferable, and the one of 0.65 to 1.1 is further preferable. Further, a long molecule (high viscosity) is preferable because it has a high effect of widening the distance between CNFs, and the B-type viscosity at 25 ° C. and 600 rpm in a 1 wt% aqueous solution of carboxymethyl cellulose is 3 to 14000 mPa · s. Is preferable, 7 to 14000 mPa · s is more preferable, and 1000 to 8000 mPa · s is further preferable.
　本発明の減圧ベルト乾燥機によれば、ドラム型乾燥機と比較して、ゆっくりとした乾燥を行うことができる。したがって、この減圧ベルト乾燥機を用いたＣＮＦ分散液の濃縮・乾燥品の製造方法によれば、過度の熱がＣＮＦ分散液に加わらず、得られる濃縮・乾燥品は、透明度および粘度の復元率に優れる。また、本発明の減圧ベルト乾燥機は、濃縮品と乾燥固形品とを作り分けることができる。 According to the decompression belt dryer of the present invention, it is possible to perform slow drying as compared with the drum type dryer. Therefore, according to the method for producing a concentrated / dried product of a CNF dispersion using this pressure reducing belt dryer, the obtained concentrated / dried product without excessive heat being applied to the CNF dispersion has a restoration rate of transparency and viscosity. Excellent for. Further, the pressure reducing belt dryer of the present invention can produce a concentrated product and a dried solid product separately.
　以下、実施例を挙げて本発明をさらに詳細に説明するが、本発明はこれらに限定されない。 Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.
（分散性）
　実施例、比較例で得られた固形分濃度１％のＣＮＦ再分散液１ｇに墨滴（株式会社呉竹製、固形分１０％）を２適垂らし、ボルテックスミキサー（ＩＵＣＨＩ社製、機器名：Ａｕｔｏｍａｔｉｃ Ｌａｂ－ｍｉｘｅｒ ＨＭ-１０Ｈ）の回転数の目盛りを最大に設定して１分間撹拌した。次に、墨滴を含有するＣＮＦ分散液の膜厚が０．１５ｍｍになるように二枚のガラス板に挟み、光学顕微鏡（デジタルマイクロスコープＫＨ－８７００（株式会社ハイロックス製））を用いて倍率１００倍で観察した。下記の基準で評価した。得られた画像中に見られる白い塊（ゲル粒）が少ないほど、分散性がよいといえる。結果を表１及び２に示した。
Ａ：ゲル粒はほとんど観察されなかった。
Ｂ：ゲル粒が若干観察された。
Ｃ：ゲル粒が多く観察された。 (Dispersity)
Two ink droplets (manufactured by Kuretake Co., Ltd., manufactured by Kuretake Co., Ltd., 10% solid content) were appropriately added to 1 g of the CNF redispersion solution having a solid content concentration of 1% obtained in Examples and Comparative Examples, and a vortex mixer (manufactured by IUCHI, device name: Automatic) was added. The scale of the rotation speed of the Lab-mixer HM-10H) was set to the maximum, and the mixture was stirred for 1 minute. Next, the CNF dispersion liquid containing ink droplets was sandwiched between two glass plates so that the film thickness was 0.15 mm, and an optical microscope (digital microscope KH-8700 (manufactured by Hirox Co., Ltd.)) was used. It was observed at a magnification of 100 times. It was evaluated according to the following criteria. It can be said that the smaller the number of white lumps (gel grains) seen in the obtained image, the better the dispersibility. The results are shown in Tables 1 and 2.
A: Almost no gel grains were observed.
B: Some gel grains were observed.
C: Many gel grains were observed.
（透明度の測定）
　実施例、比較例で得られた固形分濃度１％のＣＮＦ再分散液に対して、可視光光度計ＡＳＶ１１Ｄ（アズワン株式会社製）を用い、透明度（６６０ｎｍ光の透過率）を測定した。なお、透明度復元率は以下の式で算出した。結果を表１及び２に示した。
透明度復元率（％）＝（乾燥前の透明度）／（再分散後の透明度）×１００ (Measurement of transparency)
The transparency (transmittance of 660 nm light) was measured with respect to the CNF redispersion liquid having a solid content concentration of 1% obtained in Examples and Comparative Examples using a visible light photometer ASV11D (manufactured by AS ONE Corporation). The transparency restoration rate was calculated by the following formula. The results are shown in Tables 1 and 2.
Transparency restoration rate (%) = (transparency before drying) / (transparency after redispersion) x 100
（Ｂ型粘度の測定）
　実施例、比較例で得られた固形分濃度１％のＣＮＦ再分散液３００ｍＬをプライミクス社製撹拌機にて３０００ｒｐｍで１分撹拌直後に、Ｂ型粘度計(英弘精機社製)を用いて、２５℃の条件にて、回転数６０ｒｐｍで３分後の粘度を測定した。なお、粘度復元率は以下の式で算出した。結果を表１及び２に示した。
粘度復元率（％）＝（乾燥前の粘度）／（再分散後の粘度）×１００ (Measurement of B-type viscosity)
Immediately after stirring 300 mL of the CNF redispersion solution having a solid content concentration of 1% obtained in Examples and Comparative Examples at 3000 rpm for 1 minute with a stirrer manufactured by Primix Corporation, a B-type viscometer (manufactured by Eiko Seiki Co., Ltd.) was used. The viscosity after 3 minutes was measured at a rotation speed of 60 rpm under the condition of 25 ° C. The viscosity recovery rate was calculated by the following formula. The results are shown in Tables 1 and 2.
Viscosity restoration rate (%) = (viscosity before drying) / (viscosity after redispersion) x 100
（製造例１）
（ＴＥＭＰＯ酸化ＣＮＦの調製）
　針葉樹由来の漂白済み未叩解クラフトパルプ（白色度８５％）５００ｇ（絶乾）をＴＥＭＰＯ（Ｓｉｇｍａ  Ａｌｄｒｉｃｈ社）７８０ｍｇと臭化ナトリウム７５．５ｇを溶解した水溶液５００ｍＬに加え、パルプが均一に分散するまで撹拌した。反応系に次亜塩素酸ナトリウム水溶液を６．０ｍｍｏｌ／ｇになるように添加し、酸化反応を開始した。反応中は系内のｐＨが低下するが、３Ｍ水酸化ナトリウム水溶液を逐次添加し、ｐＨ１０に調整した。次亜塩素酸ナトリウムを消費し、系内のｐＨが変化しなくなった時点で反応を終了した。反応後の混合物をガラスフィルターで濾過してパルプ分離し、パルプを十分に水洗することで酸化されたパルプ（カルボキシル化セルロース）を得た。この時のパルプ収率は９０％であり、酸化反応に要した時間は９０分、カルボキシル基量は１．６ｍｍｏｌ／ｇであった。 (Manufacturing Example 1)
(Preparation of TEMPO Oxidized CNF)
Add 500 g (absolutely dry) of bleached unbeaten kraft pulp (whiteness 85%) derived from softwood to 500 mL of an aqueous solution of 780 mg of TEMPO (Sigma Aldrich) and 75.5 g of sodium bromide until the pulp is uniformly dispersed. Stirred. An aqueous sodium hypochlorite solution was added to the reaction system so as to have a concentration of 6.0 mmol / g, and the oxidation reaction was started. Although the pH in the system decreased during the reaction, a 3M aqueous sodium hydroxide solution was sequentially added to adjust the pH to 10. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system did not change. The mixture after the reaction was filtered through a glass filter to separate the pulp, and the pulp was thoroughly washed with water to obtain oxidized pulp (carboxylated cellulose). The pulp yield at this time was 90%, the time required for the oxidation reaction was 90 minutes, and the amount of carboxyl groups was 1.6 mmol / g.
　上記の工程で得られた酸化パルプを水で３．０％（ｗ／ｖ）に調整し、超高圧ホモジナイザー（２０℃、１５０Ｍｐａ）で３回処理して、ＴＥＭＰＯ酸化セルロースナノファイバー（ＣＮＦ）水分散液を得た。得られた繊維は、平均繊維径が４０ｎｍ、アスペクト比が１５０であった。 The oxidized pulp obtained in the above step is adjusted to 3.0% (w / v) with water, treated three times with an ultra-high pressure homogenizer (20 ° C., 150 MPa), and TEMPO oxidized cellulose nanofiber (CNF) water. A dispersion was obtained. The obtained fibers had an average fiber diameter of 40 nm and an aspect ratio of 150.
 （カルボキシル基量の測定方法）
　カルボキシル化セルロースの０．５重量％スラリー（水分散液）６０ｍＬを調製し、０．１Ｍ塩酸水溶液を加えてｐＨ２．５とした後、０．０５Ｎの水酸化ナトリウム水溶液を滴下してｐＨが１１になるまで電気伝導度を測定し、電気伝導度の変化が緩やかな弱酸の中和段階において消費された水酸化ナトリウム量（ａ）から、下式を用いて算出した：
カルボキシル基量〔ｍｍｏｌ／ｇカルボキシル化セルロース〕＝ａ〔ｍＬ〕×０．０５／カルボキシル化セルロース重量〔ｇ〕。 (Measuring method of carboxyl group amount)
60 mL of a 0.5 wt% slurry (aqueous dispersion) of carboxylated cellulose was prepared, and a 0.1 M hydrochloric acid aqueous solution was added to adjust the pH to 2.5, and then a 0.05 N sodium hydroxide aqueous solution was added dropwise to adjust the pH to 11. The electrical conductivity was measured until
Amount of carboxyl group [mmol / g carboxylated cellulose] = a [mL] × 0.05 / weight of carboxylated cellulose [g].
（実施例１）
（濃縮・乾燥）
　製造例１で得られた固形分濃度３％のＴＥＭＰＯ酸化ＣＮＦの水分散液１０ｇ（サンプル）を、直径２．５ｍｍのノズルから、表面をテフロン（登録商標）でライニングしたバットの上に、重なる部分が無いようストランド状に載置した。
　サンプルが載置されたバットを静置型減圧乾燥機（アズワン株式会社製、ＡＶＯ－２００Ｖ）に投入し、バットの表面が８０～９０℃となる温度で、乾燥機内の気圧が１０ｋＰａ以下になるように減圧し、１０分間処理することにより、固形分濃度が１０．６％の濃縮・乾燥ＴＥＭＰＯ酸化ＣＮＦを得た。 (Example 1)
(Concentration / drying)
10 g (sample) of an aqueous dispersion of TEMPO oxide CNF having a solid content concentration of 3% obtained in Production Example 1 is superposed on a vat whose surface is lined with Teflon (registered trademark) from a nozzle having a diameter of 2.5 mm. It was placed in a strand shape so that there was no part.
The vat on which the sample is placed is placed in a static vacuum dryer (AVO-200V, manufactured by AS ONE Corporation) so that the pressure inside the dryer is 10 kPa or less at a temperature at which the surface of the vat is 80 to 90 ° C. By reducing the pressure to 10.6 and treating for 10 minutes, a concentrated and dried TEMPO oxidized CNF having a solid content concentration of 10.6% was obtained.
（再分散）
　上記で得られた濃縮・乾燥ＴＥＭＰＯ酸化ＣＮＦに水を加え、ホモディスパー（ＰＲＩＭＩＸ社製）を使用して３０００ｒｐｍの条件で３０分間撹拌することにより固形分濃度１％まで希釈した。 (Redispersion)
Water was added to the concentrated / dried TEMPO-oxidized CNF obtained above, and the mixture was diluted to a solid content concentration of 1% by stirring with a homodisper (manufactured by PRIMIX Corporation) at 3000 rpm for 30 minutes.
（実施例２）
　処理時間を１２分間に変更したこと以外は実施例１と同様にして、固形分濃度が１５．５％の濃縮・乾燥ＴＥＭＰＯ酸化ＣＮＦを得た。また、実施例１と同様に１％まで希釈し、再分散させてＣＮＦ再分散液を得た。 (Example 2)
A concentrated / dried TEMPO-oxidized CNF having a solid content concentration of 15.5% was obtained in the same manner as in Example 1 except that the treatment time was changed to 12 minutes. Further, it was diluted to 1% in the same manner as in Example 1 and redispersed to obtain a CNF redispersion solution.
（実施例３）
　処理時間を１４分間に変更したこと以外は実施例１と同様にして、固形分濃度が２０．４％の濃縮・乾燥ＴＥＭＰＯ酸化ＣＮＦを得た。また、実施例１と同様に１％まで希釈し、再分散させてＣＮＦ再分散液を得た。 (Example 3)
A concentrated / dried TEMPO-oxidized CNF having a solid content concentration of 20.4% was obtained in the same manner as in Example 1 except that the treatment time was changed to 14 minutes. Further, it was diluted to 1% in the same manner as in Example 1 and redispersed to obtain a CNF redispersion solution.
（比較例１）
　処理時間を１６分間に変更したこと以外は実施例１と同様にして、固形分濃度が２６．５％の濃縮・乾燥ＴＥＭＰＯ酸化ＣＮＦを得た。また、実施例１と同様に１％まで希釈し、再分散させてＣＮＦ再分散液を得た。 (Comparative Example 1)
A concentrated / dried TEMPO-oxidized CNF having a solid content concentration of 26.5% was obtained in the same manner as in Example 1 except that the treatment time was changed to 16 minutes. Further, it was diluted to 1% in the same manner as in Example 1 and redispersed to obtain a CNF redispersion solution.
（比較例２）
　処理時間を１７分間に変更したこと以外は実施例１と同様にして、固形分濃度が３３．３％の濃縮・乾燥ＴＥＭＰＯ酸化ＣＮＦを得た。また、実施例１と同様に１％まで希釈し、再分散させてＣＮＦ再分散液を得た。 (Comparative Example 2)
A concentrated / dried TEMPO-oxidized CNF having a solid content concentration of 33.3% was obtained in the same manner as in Example 1 except that the treatment time was changed to 17 minutes. Further, it was diluted to 1% in the same manner as in Example 1 and redispersed to obtain a CNF redispersion solution.
Figure JPOXMLDOC01-appb-T000001
  
Figure JPOXMLDOC01-appb-T000001
  
（実施例４）
（ＴＥＭＰＯ酸化ＣＮＦとＣＭＣの分散液の調製）
　製造例１で得られた固形分濃度３％のＴＥＭＰＯ酸化ＣＮＦ水分散液に、カルボキシメチルセルロース（ＣＭＣ）（日本製紙株式会社製、商品名：Ｆ３５０ＨＣ－４、粘度（１％、２５℃）約３０００ｍＰａ・ｓ、カルボキシメチル置換度約０．９）を、ＴＥＭＰＯ酸化ＣＮＦの固形分１００重量部に対して３０重量部となるように添加し、ＴＫホモミキサー（１２，０００ｒｐｍ）で６０分間撹拌することにより、ＣＭＣ含有ＴＥＭＰＯ酸化ＣＮＦ水分散液を得た。この水分散液のｐＨは７～８程度であった。得られた分散液に水酸化ナトリウム水溶液０．５％を加えｐＨを９に調整し、固形分濃度２．３％の水分散液を得た。 (Example 4)
(Preparation of dispersion of TEMPO oxidized CNF and CMC)
Carboxymethyl cellulose (CMC) (manufactured by Nippon Paper Co., Ltd., trade name: F350HC-4, viscosity (1%, 25 ° C.)) of about 3000 mPa in the TEMPO oxidized CNF aqueous dispersion obtained in Production Example 1 having a solid content concentration of 3%. -S, carboxymethyl substitution degree of about 0.9) is added so as to be 30 parts by weight with respect to 100 parts by weight of the solid content of TEMPO oxide CNF, and the mixture is stirred with a TK homomixer (12,000 rpm) for 60 minutes. To obtain a CMC-containing TEMPO oxidized CNF aqueous dispersion. The pH of this aqueous dispersion was about 7-8. 0.5% of an aqueous sodium hydroxide solution was added to the obtained dispersion to adjust the pH to 9, and an aqueous dispersion having a solid content concentration of 2.3% was obtained.
（濃縮・乾燥）
　上記で得られた固形分濃度２．３％のＣＭＣ含有ＴＥＭＰＯ酸化ＣＮＦ水分散液１０ｇ（サンプル）を、直径２．５ｍｍのノズルから、表面をテフロン（登録商標）でライニングしたバットの上に、重なる部分が無いようストランド状に載置した。
　サンプルが載置されたバットを静置型減圧乾燥機（アズワン株式会社製、ＡＶＯ－２００Ｖ）に投入し、バットの表面が８０～９０℃となる温度で、乾燥機内の気圧が１０ｋＰａ以下になるように減圧し、７５分間処理することにより、ほぼ絶乾（固形分濃度９６％）のＣＭＣ含有ＴＥＭＰＯ酸化ＣＮＦの乾燥固形物を得た。 (Concentration / drying)
10 g (sample) of the CMC-containing TEMPO oxidized CNF aqueous dispersion obtained above having a solid content concentration of 2.3% was placed on a vat whose surface was lined with Teflon (registered trademark) from a nozzle having a diameter of 2.5 mm. It was placed in a strand shape so that there was no overlapping part.
The vat on which the sample is placed is placed in a static decompression dryer (AVO-200V, manufactured by AS ONE Corporation) so that the air pressure inside the dryer is 10 kPa or less at a temperature at which the surface of the vat is 80 to 90 ° C. The pressure was reduced to 75 minutes, and the mixture was treated for 75 minutes to obtain a dry solid of CMC-containing TEMPO-oxidized CNF that was almost completely dry (solid content concentration 96%).
（再分散）
　上記で得られたＣＭＣ含有ＴＥＭＰＯ酸化ＣＮＦの乾燥固形物に水を加え、ホモディスパー（ＰＲＩＭＩＸ社製）を使用して３０００ｒｐｍの条件で３０分間撹拌することにより固形分濃度１％まで希釈した。 (Redispersion)
Water was added to the dry solid of the CMC-containing TEMPO oxidized CNF obtained above, and the mixture was diluted to a solid content concentration of 1% by stirring with a homodisper (manufactured by PRIMIX Corporation) at 3000 rpm for 30 minutes.
（比較例３）
　実施例４で得られたｐＨ調整前のＣＭＣ含有ＴＥＭＰＯ酸化ＣＮＦ水分散液に、水を加えることにより、ｐＨ６．９、固形分濃度１．０％の水分散液を得た。この分散液を用いたこと以外は、実施例４と同様にして、７５分間処理することにより、ほぼ絶乾（固形分濃度９６％）のＣＭＣ含有ＴＥＭＰＯ酸化ＣＮＦの乾燥固形物を得た。また、実施例４と同様に１％まで希釈し、再分散させてＣＮＦ再分散液を得た。 (Comparative Example 3)
Water was added to the CMC-containing TEMPO oxidized CNF aqueous dispersion obtained in Example 4 before pH adjustment to obtain an aqueous dispersion having a pH of 6.9 and a solid content concentration of 1.0%. By treating for 75 minutes in the same manner as in Example 4 except that this dispersion was used, a dry solid of CMC-containing TEMPO-oxidized CNF that was almost completely dry (solid content concentration 96%) was obtained. Further, it was diluted to 1% in the same manner as in Example 4 and redispersed to obtain a CNF redispersion solution.
Figure JPOXMLDOC01-appb-T000002
  
 
Figure JPOXMLDOC01-appb-T000002
  
 

Claims (7)

  1. 　減圧槽内に、無端搬送ベルトと、前記無端搬送ベルトの移動方向に沿って加熱領域および冷却領域を順次配設してなり、セルロースナノファイバー分散液を低温乾燥して濃縮・乾燥品を得るための減圧ベルト乾燥機を用いて実行されるセルロースナノファイバー濃縮・乾燥品の製造方法であって、
    　前記減圧ベルト乾燥機は、前記無端搬送ベルトの前記加熱領域の上流側に設けられた、前記セルロースナノファイバー分散液を供給する直径１ｍｍ以上、８ｍｍ以下のノズルと、前記減圧槽内を減圧雰囲気にする減圧装置とを備え、
    　前記加熱領域は、前記無端搬送ベルトの移動方向に沿って、加熱プレートを備え、
    　直径１ｍｍ以上、８ｍｍ以下の前記ノズルから、定速で移動する前記無端搬送ベルト上に、前記セルロースナノファイバー分散液をストランド状又は粒状に供給する供給工程と、
    　前記無端搬送ベルト上に供給された前記セルロースナノファイバー分散液を、前記加熱領域で乾燥する乾燥工程と、
    　前記乾燥工程で乾燥した濃縮・乾燥品を、前記冷却領域で冷却する冷却工程とを含むセルロースナノファイバー濃縮・乾燥品の製造方法。     An endless transport belt and a heating region and a cooling region are sequentially arranged in the pressure reducing tank along the moving direction of the endless transport belt, and the cellulose nanofiber dispersion liquid is dried at a low temperature to obtain a concentrated / dried product. This is a method for producing cellulose nanofiber concentrated and dried products, which is carried out using a vacuum belt dryer.
    The decompression belt dryer has a nozzle having a diameter of 1 mm or more and 8 mm or less for supplying the cellulose nanofiber dispersion liquid provided on the upstream side of the heating region of the endless transport belt, and the inside of the decompression tank has a decompression atmosphere. Equipped with a decompression device
    The heating region includes a heating plate along the moving direction of the endless transport belt.
    A supply step of supplying the cellulose nanofiber dispersion liquid in a strand form or granules from the nozzle having a diameter of 1 mm or more and 8 mm or less onto the endless transport belt moving at a constant speed.
    A drying step of drying the cellulose nanofiber dispersion liquid supplied on the endless transport belt in the heating region, and
    A method for producing a cellulose nanofiber concentrated / dried product, which comprises a cooling step of cooling the concentrated / dried product dried in the drying step in the cooling region.
  2. 　前記セルロースナノファイバー分散液は、固形分１００重量部の内、セルロースナノファイバーを固形分で９９．９重量部以上含み、
    　前記乾燥工程は、前記加熱プレートを温度８０～１３０℃として前記セルロースナノファイバー分散液を固形分濃度１０～２０重量％まで乾燥させる請求項１記載のセルロースナノファイバー濃縮・乾燥品の製造方法。     The cellulose nanofiber dispersion liquid contains 99.9 parts by weight or more of cellulose nanofibers in solid content out of 100 parts by weight of solid content.
    The method for producing a cellulose nanofiber concentrated / dried product according to claim 1, wherein the drying step dries the cellulose nanofiber dispersion liquid to a solid content concentration of 10 to 20% by weight by setting the heating plate at a temperature of 80 to 130 ° C.
  3. 　前記供給工程において供給する前記セルロースナノファイバー分散液のｐＨを９～１１に調整する工程を含み、
    　前記セルロースナノファイバー分散液は、セルロースナノファイバーの固形分１００重量部に対して水溶性高分子を固形分で５～３００重量部含み、
    　前記乾燥工程は、前記加熱プレートを温度８０～１３０℃として前記セルロースナノファイバー分散液を乾燥固形物となるまで乾燥させる請求項１記載のセルロースナノファイバー濃縮・乾燥品の製造方法。     The step of adjusting the pH of the cellulose nanofiber dispersion liquid to be supplied in the supply step to 9 to 11 is included.
    The cellulose nanofiber dispersion liquid contains 5 to 300 parts by weight of a water-soluble polymer in terms of solid content with respect to 100 parts by weight of solid content of cellulose nanofibers.
    The method for producing a cellulose nanofiber concentrated / dried product according to claim 1, wherein the drying step dries the cellulose nanofiber dispersion liquid at a temperature of 80 to 130 ° C. until it becomes a dry solid.
  4. 　減圧槽内に、無端搬送ベルトと、前記無端搬送ベルトの移動方向に沿って加熱領域および冷却領域を順次配設してなり、セルロースナノファイバー分散液を低温乾燥して濃縮・乾燥品を得るための減圧ベルト乾燥機を用いて実行されるセルロースナノファイバー濃縮・乾燥品の製造方法であって、
    　前記減圧ベルト乾燥機は、前記無端搬送ベルトの前記加熱領域の上流側に設けられた、前記セルロースナノファイバー分散液を供給する直径１ｍｍ以上、８ｍｍ以下のノズルと、前記減圧槽内を減圧雰囲気にする減圧装置とを備え、
    　前記加熱領域は、前記無端搬送ベルトの移動方向に沿って、マイクロ波発生装置を備え、
    　直径１ｍｍ以上、８ｍｍ以下の前記ノズルから、定速で移動する前記無端搬送ベルト上に、前記セルロースナノファイバー分散液をストランド状又は粒状に供給する供給工程と、
    　前記無端搬送ベルト上に供給された前記セルロースナノファイバー分散液を、前記加熱領域で乾燥する乾燥工程と、
    　前記乾燥工程で乾燥した濃縮・乾燥品を、前記冷却領域で冷却する冷却工程とを含むセルロースナノファイバー濃縮・乾燥品の製造方法。     An endless transport belt and a heating region and a cooling region are sequentially arranged in the pressure reducing tank along the moving direction of the endless transport belt, and the cellulose nanofiber dispersion liquid is dried at a low temperature to obtain a concentrated / dried product. This is a method for producing cellulose nanofiber concentrated and dried products, which is carried out using a vacuum belt dryer.
    The decompression belt dryer has a nozzle having a diameter of 1 mm or more and 8 mm or less for supplying the cellulose nanofiber dispersion liquid provided on the upstream side of the heating region of the endless transport belt, and the inside of the decompression tank has a decompression atmosphere. Equipped with a decompression device
    The heating region includes a microwave generator along the moving direction of the endless transport belt.
    A supply step of supplying the cellulose nanofiber dispersion liquid in a strand form or granules from the nozzle having a diameter of 1 mm or more and 8 mm or less onto the endless transport belt moving at a constant speed.
    A drying step of drying the cellulose nanofiber dispersion liquid supplied on the endless transport belt in the heating region, and
    A method for producing a cellulose nanofiber concentrated / dried product, which comprises a cooling step of cooling the concentrated / dried product dried in the drying step in the cooling region.
  5. 　減圧槽内に、無端搬送ベルトと、前記無端搬送ベルトの移動方向に沿って加熱領域および冷却領域を順次配設してなり、セルロースナノファイバー分散液を低温乾燥して濃縮・乾燥品を得るための減圧ベルト乾燥機であって、
    　前記無端搬送ベルトの前記加熱領域の上流側に設けられた、前記セルロースナノファイバー分散液を供給する直径１ｍｍ以上、８ｍｍ以下のノズルと、
    　前記減圧槽内を減圧雰囲気にする減圧装置とを備え、
    　前記加熱領域は、前記無端搬送ベルトの移動方向に沿って、加熱手段を備える減圧ベルト乾燥機。     An endless transport belt and a heating region and a cooling region are sequentially arranged in the pressure reducing tank along the moving direction of the endless transport belt, and the cellulose nanofiber dispersion liquid is dried at a low temperature to obtain a concentrated / dried product. Decompression belt dryer
    A nozzle having a diameter of 1 mm or more and a diameter of 8 mm or less for supplying the cellulose nanofiber dispersion liquid provided on the upstream side of the heating region of the endless transport belt.
    A decompression device for creating a decompression atmosphere in the decompression tank is provided.
    The heating region is a pressure reducing belt dryer provided with heating means along the moving direction of the endless transport belt.
  6. 　前記加熱手段は、加熱プレートである請求項５記載の減圧ベルト乾燥機。 The decompression belt dryer according to claim 5, wherein the heating means is a heating plate.
  7. 　前記加熱手段は、マイクロ波発生装置である請求項５記載の減圧ベルト乾燥機。   The decompression belt dryer according to claim 5, wherein the heating means is a microwave generator.
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