Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B5/00—Preparation of cellulose esters of inorganic acids, e.g. phosphates
  • C08B5/14—Cellulose sulfate
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
  • C08L1/08—Cellulose derivatives
  • C08L1/16—Esters of inorganic acids
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/001—Modification of pulp properties
  • D21C9/002—Modification of pulp properties by chemical means; preparation of dewatered pulp, e.g. in sheet or bulk form, containing special additives
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/001—Modification of pulp properties
  • D21C9/002—Modification of pulp properties by chemical means; preparation of dewatered pulp, e.g. in sheet or bulk form, containing special additives
  • D21C9/005—Modification of pulp properties by chemical means; preparation of dewatered pulp, e.g. in sheet or bulk form, containing special additives organic compounds
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/001—Modification of pulp properties
  • D21C9/007—Modification of pulp properties by mechanical or physical means
• • 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 disclosure relates to a fine cellulose fiber powder and a method for producing a fine cellulose fiber powder.
• biomass-derived materials In the paint, coating, and cosmetics industries, the use of biomass-derived materials is gaining momentum. Furthermore, there is a growing trend to utilize biomass-derived materials in the production of raw materials used in these industries. In addition, in many fields including these fields, from the viewpoint of safety and quality of life, it is required to replace organic solvents that have an adverse effect on the human body with water-based solvents.
• cellulose nanofibers are used or desired to be used in many fields.
• Cellulose nanofiber is a biomass-derived compound obtained by defibrating cellulose fibers to nanosize. It is well dispersed in water, and a transparent nanocellulose film can be easily obtained by drying the dispersion.
• resin or rubber when mixed with resin or rubber, it leads to improvements in various physical properties such as strength, flexibility, and elongation, and is attracting attention as a new environmentally friendly material, and various proposals have been made.
• an N-oxyl compound such as 2,2,6,6-tetramethylpiperidine-N-oxyl (hereinafter referred to as TEMPO) is used as an oxidation catalyst to modify cellulose.
• Fine cellulose fibers are disclosed.
• Patent Document 2 discloses a fine fibrous cellulose aggregate containing fine fibrous cellulose having an average fiber width of 2 to 50 nm and a liquid compound.
• Patent Document 2 discloses, in Example 2-1, fine fibrous cellulose into which a phosphate group is introduced as fine fibrous cellulose.
• Patent Document 3 discloses a method for producing a dry solid containing fine cellulose fibers, which comprises a chemical treatment step of chemically treating pulp, and the pulp after the chemical treatment step is converted into an average fiber A refining treatment process for refining into fine cellulose fibers having a width of 1 nm to 1000 nm is disclosed as an essential process. Further, Patent Document 3 discloses a step of introducing sulfo groups into some of the hydroxyl groups of cellulose constituting pulp fibers as an essential step.
• cellulose nanofibers are fibers with a fiber length of several hundred nm to a maximum of several tens of ⁇ m, and a fiber width of 1 nm to several hundred nm.
• the application of cellulose nanofibers to the industrial world so far has had many problems with the degree of freedom in formulation design, storage, and transportation.
• the cellulose nanofiber aqueous dispersion is dried once and obtained as cellulose nanofiber powder
• the cellulose nanofiber powder is dispersed again in another aqueous composition, and is uniformly distributed in the material such as the resin. It was difficult to disperse. Furthermore, it was difficult to increase the concentration of cellulose nanofibers in the cellulose nanofiber aqueous dispersion.
• conventional cellulose nanofibers have often been sold and used as aqueous dispersions with a low concentration of cellulose nanofibers, for example, about 0.5 to 2 wt %. For this reason, the cellulose nanofiber aqueous dispersion is mostly composed of water, has a large volume and weight, and requires large-scale equipment for transportation and storage.
• the dry solid containing fine cellulose fibers disclosed in Patent Document 3 was able to be redispersed in water. It required a long time for dispersion treatment, required a large-scale apparatus such as a high-pressure homogenizer, etc., and did not have sufficient dispersibility yet.
• an object of the present disclosure is to provide a fine cellulose fiber powder that can be easily dispersed in water or the like.
• the present inventors have conducted intensive research to solve the above problems, and found that the above problems can be solved with a specific fine cellulose fiber powder, leading to the present disclosure.
• the fine cellulose fibers have a sulfate ester group represented by the following general formula (1),
• the fine cellulose fibers have a sulfur introduction amount due to sulfate ester groups of 0.3 mmol/g or more and 3.0 mmol/g or less,
• the median diameter of the powder is 800 ⁇ m or less
• a fine cellulose fiber powder, wherein the powder has a moisture content of 50% by mass or less.
• n is an integer of 1 to 3
• M n+ is an n-valent cation
• the wavy line is a binding site to another atom.
• An aqueous dispersion having a fine cellulose fiber concentration of 0.3% by mass prepared by dispersing the fine cellulose fiber powder in water so that the fine cellulose fiber concentration is 0.3% by mass.
• the fine cellulose fiber powder according to (1) which has a viscosity of 500 mPa ⁇ s or more as measured at 25° C. and 2.6 rpm.
• An aqueous dispersion having a fine cellulose fiber concentration of 0.3% by mass prepared by dispersing the fine cellulose fiber powder in water so that the fine cellulose fiber concentration is 0.3% by mass.
• TI value thixotropic index
• the fine cellulose fiber powder according to any one of (1) to (5) which has a total light transmittance of 96% or more.
• the fine cellulose fiber powder according to any one of (1) to (6) which has a haze value of 20% or less.
• a method for producing an aqueous dispersion of fine cellulose fibers comprising the step of dispersing the fine cellulose fiber powder according to any one of (1) to (9) in water.
• a method for producing a film comprising the step of forming a film from the fine cellulose fiber aqueous dispersion obtained by the production method described in (10).
• This specification includes the disclosure content of Japanese Patent Application No. 2021-177465, which is the basis of priority of this application.
• a fine cellulose fiber powder that can be easily dispersed in water or the like can be provided.
• One aspect of the present embodiment is a fine cellulose fiber powder containing fine cellulose fibers and water, the fine cellulose fibers having an average fiber width of 1 nm to 1000 nm, and the fine cellulose fibers having the following general formula ( 1) having a sulfate ester group represented by , the fine cellulose fibers have a sulfur introduction amount due to the sulfate ester group of 0.3 mmol / g or more and 3.0 mmol / g or less, and the median of the powder
• the fine cellulose fiber powder has a diameter of 800 ⁇ m or less and a moisture content of 50% by mass or less.
• the fine cellulose fiber powder of this embodiment can be easily dispersed in water or the like.
• the stability after being dispersed in water or the like is excellent, and liquid separation is less likely to occur.
• the fine cellulose fiber powder of the present embodiment is easily dispersed in water or the like, it can be blended into the composition as a powder instead of a dispersion liquid. None.
• the powder is not a dispersion containing a large amount of water, it is easy to transport and store, and since it can be stored as a powder with a low water content, there is no need to use preservatives. Therefore, the fine cellulose fiber powder of this embodiment can be used in various fields including the paint, coating, and cosmetics industries.
• the fine cellulose fiber powder of this embodiment contains fine cellulose fibers.
• general cellulose (undenatured cellulose) is a polysaccharide in which glucose is ⁇ -1,4-glycosidicly bonded, and is represented by (C 6 H 10 O 5 ) n .
• the average fiber width of the fine cellulose fibers is 1 nm to 1000 nm, preferably 1 nm to 100 nm, more preferably 2 nm to 10 nm.
• the average fiber length of the fine cellulose fibers is not particularly limited, but is usually 0.1 ⁇ m to 6 ⁇ m, preferably 0.1 ⁇ m to 2 ⁇ m.
• the average fiber width and average fiber length are determined, for example, by using an atomic force microscope (SPM-9700HT, manufactured by Shimadzu Corporation) to determine the fiber width (fiber diameter (equivalent circle diameter)) and It can be measured by measuring the fiber length and taking an addition average value.
• the average fiber width and average fiber length can be set within desired ranges by adjusting the concentration of a reagent such as sulfuric acid, the amount of pulp relative to the reaction solution, and the reaction time.
• a fine cellulose fiber has a sulfate ester group represented by the following general formula (1).
• the fine cellulose fibers are also referred to as sulfate-esterified cellulose nanofibers.
• Fine cellulose fibers usually have sulfate ester groups introduced therein by substituting some of the OH groups in the cellulose constituting the fibers with sulfate ester groups represented by the general formula (1).
• Fine cellulose fibers can be produced, for example, by sulfuric acid esterification and fibrillation of raw material pulp, as shown in the Examples.
• the method of sulfate esterification is not particularly limited.
• sulfuric acid is used, preferably dimethyl sulfoxide (DMSO).
• n is an integer of 1 to 3
• M n+ is an n-valent cation
• the wavy line is a binding site to another atom.
• M n+ examples include hydrogen ions (H + ), metal ions, and ammonium ions. When n is 2 or 3, M n+ forms ionic bonds with two or three -OSO 3 - .
• Metal ions include alkali metal ions, alkaline earth metal ions, transition metal ions, and other metal ions.
• Alkali metal ions include lithium ions (Li + ), sodium ions (Na + ), potassium ions (K + ), rubidium ions (Rb + ), cesium ions (Cs + ), and the like.
• Alkaline earth metal ions include calcium ions (Ca 2+ ), strontium ions (Sr 2+ ), and the like.
• transition metal ions include iron ions, nickel ions, palladium ions, copper ions, and silver ions.
• Other metal ions include beryllium ions, magnesium ions, zinc ions, aluminum ions, and the like.
• Ammonium ions include not only NH 4 + but also ammonium ions derived from various amines formed by replacing one or more hydrogen atoms of NH 4 + with an organic group.
• Ammonium ions include, for example, NH 4 + , quaternary ammonium cations, alkanolamine ions, pyridinium ions, and the like.
• Mn + is preferably a hydrogen ion, a sodium ion, a potassium ion, a calcium ion, or a quaternary ammonium cation from the viewpoint of processability in each application of the fine cellulose fiber powder, and is preferably a sodium ion (Na + ). is particularly preferred.
• Mn + possessed by the sulfate ester group represented by the general formula (1) may be of only one type, or may be of two or more types. When NH 4 + is included as M n + , it is preferred that a portion of M n + is NH 4 + , and 0.1 to 30% of all M n + is NH 4 + . This is one of preferred embodiments.
• the fine cellulose fibers may have other substituents in addition to the sulfate group represented by the general formula (1).
• the fine cellulose fibers have a group other than the sulfate ester group represented by the general formula (1), i.e., other substituents
• the other substituents are usually present in cellulose constituting the fine cellulose fibers. substituted with at least one of the OH groups.
• substituents include, but are not particularly limited to, anionic substituents and salts thereof, ester groups, ether groups, acyl groups, aldehyde groups, alkyl groups, alkylene groups, aryl groups, and combinations of two or more thereof. etc.
• an anionic substituent, a salt thereof, or an acyl group is preferable from the viewpoint of nano-dispersibility.
• an anionic substituent and its salt a carboxy group, a phosphate ester group, a phosphite ester group and a xanthate group are particularly preferred.
• the anionic substituent is in the form of a salt, sodium salt, potassium salt, and calcium salt are particularly preferred from the viewpoint of nano-dispersibility.
• an acetyl group is preferred from the viewpoint of nano-dispersibility.
• the fine cellulose fibers have a sulfur introduction amount of 0.3 mmol/g or more and 3.0 mmol/g or less due to sulfate ester groups.
• the amount of sulfate ester group to be introduced can be set to any appropriate value within the above range depending on the application and the like.
• the amount of sulfur introduced into the fine cellulose fibers due to the sulfate group can be represented by the sulfur content (mmol) per 1 g of the fine cellulose fibers.
• the amount of sulfur introduced is preferably 0.4 mmol/g or more and 2.5 mmol/g or less, more preferably 0.8 mmol/g or more and 2.0 mmol/g or less. It is preferable from the viewpoint of high water dispersibility after drying that the amount of sulfur introduced is within the above range.
• the amount of sulfur introduced can be determined, for example, by the combustion absorption-ion chromatography (IC) method (combustion absorption-IC method, combustion IC method) described in the Examples.
• the amount of sulfur introduced is adjusted, for example, by controlling the concentration of a reagent such as sulfuric acid in the solution (fibrillation solution) used when fibrillating pulp, the amount of pulp relative to the fibrillation solution, the reaction time, the reaction temperature, etc. can do.
• the fine cellulose fiber powder of the present embodiment contains fine cellulose fibers and water.
• the fine cellulose fiber powder may contain components other than fine cellulose fibers and water, but may be formed only from fine cellulose fibers and water. Since fine cellulose fibers usually do not dissolve in water, when the fine cellulose fiber powder is formed only from fine cellulose fibers and water, in the fine cellulose fiber aqueous dispersion prepared from the powder and water
• the solid content means fine cellulose fibers, the solid content concentration and the fine cellulose fiber concentration are substantially synonymous, and the solid content mass and the fine cellulose fiber mass are substantially synonymous.
• the fine cellulose fiber powder may contain a component derived from the manufacturing process of the fine cellulose fiber.
• the fine cellulose fiber powder may contain 10-1000 ppm DMSO. Further, the fine cellulose fiber powder may contain 5000 ppm or less of ammonium ions represented by NH 4 + . Note that "containing 5000 ppm or less” includes not containing (0 ppm or below the detection limit), in other words, means 0 to 5000 ppm.
• the moisture content of the fine cellulose fiber powder is 50% by mass or less, preferably 20% by mass or less, and more preferably 10% by mass or less. Also, the moisture content is preferably 1% by mass or more, more preferably 3% by mass or more. The higher the moisture content, the easier it can be dispersed in water. On the other hand, the lower the water content, the easier the transportation and storage, and the more flexible the formulation design is, which is preferable because it can be blended in a composition or the like without increasing the water content.
• Water in the present invention includes, for example, tap water, ion-exchanged water, distilled water, purified water, and natural water. Tap water, ion-exchanged water, distilled water, and purified water are preferred, and ion-exchanged water, distilled water, Purified water is more preferred.
• the moisture content of the fine cellulose fiber powder can be determined, for example, according to JIS P8203.
• the amount of fine cellulose fibers contained in the fine cellulose fiber powder is usually 50% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more. Also, the amount of fine cellulose fibers is preferably 99% by mass or less, more preferably 97% by mass or less.
• the median diameter of the fine cellulose fiber powder is 800 ⁇ m or less, preferably 200 ⁇ m or less, and more preferably 150 ⁇ m or less. Also, the median diameter is preferably 10 ⁇ m or more, more preferably 20 ⁇ m or more. When the median diameter is within the above range, it is preferable from the viewpoint of high dispersibility in water, prevention of dust explosion and prevention of scattering of powder for handling.
• the median diameter of the fine cellulose fiber powder can be measured, for example, using a dry particle size distribution meter conforming to ISO 13320 and JIS Z 8825 standards for laser diffraction/scattering methods.
• the fine cellulose fiber powder is prepared by dispersing the fine cellulose fiber powder in water so that the concentration of the fine cellulose fibers is 0.3% by mass.
• the viscosity of the liquid measured at 25° C. and 2.6 rpm is preferably 500 mPa ⁇ s or more, more preferably 1000 mPa ⁇ s or more, and particularly preferably 5000 mPa ⁇ s or more.
• the viscosity measured at 2.6 rpm is preferably 50000 mPa ⁇ s or less, more preferably 40000 mPa ⁇ s or less.
• 2.6 rpm means the number of rotations of a viscometer (for example, a Brookfield viscometer) used for viscosity measurement.
• the concentration of fine cellulose fibers is a different concept from the concentration of fine cellulose fiber powder. That is, the concentration of fine cellulose fibers is the concentration when focusing on the fine cellulose contained in the fine cellulose fiber powder. For example, when the fine cellulose fiber powder contains only fine cellulose fibers and water and has a moisture content of 25% by mass, 0.4 g of the fine cellulose fiber powder is weighed and mixed with 99.6 g of water to obtain a fine powder. 100 g of an aqueous dispersion having a cellulose fiber concentration of 0.3% by weight can be prepared.
• the fine cellulose fiber powder is prepared by dispersing the fine cellulose fiber powder in water so that the concentration of the fine cellulose fibers is 0.3% by mass.
• the thixotropic index (TI value) obtained from the viscosity measured at 2.6 rpm and the viscosity measured at 26 rpm of the liquid at 25° C. is preferably 3 to 30, more preferably 4 to 20. , 5 to 15 are particularly preferred.
• 2.6 rpm and 26 rpm respectively mean the number of rotations of a viscometer (for example, a B-type viscometer) used for viscosity measurement.
• the fine cellulose fiber powder is prepared by dispersing the fine cellulose fiber powder in water so that the concentration of the fine cellulose fibers is 0.3% by mass.
• the total light transmittance of the dispersion is preferably 96% or more, more preferably 97% or more. Total light transmission is typically less than 100%.
• the fine cellulose fiber powder is prepared by dispersing the fine cellulose fiber powder in water so that the concentration of the fine cellulose fibers is 0.3% by mass.
• the haze value of the dispersion is preferably 20% or less, more preferably 15% or less, and particularly preferably 10% or less.
• the fine cellulose fiber powder contains components other than fine cellulose fibers and water, it may contain additives, for example.
• the additive may be an inorganic additive or an organic additive.
• inorganic additives include inorganic fine particles.
• inorganic fine particles include silica, mica, talc, clay, carbon, carbonates (e.g. calcium carbonate, magnesium carbonate), oxides (e.g. aluminum oxide, titanium oxide, zinc oxide, iron oxide), ceramics (e.g. ferrite), or fine particles of mixtures thereof.
• the inorganic fine particles may be contained in the fine cellulose fiber powder, for example, in an amount within the range of 0.09 to 5% by weight.
• organic additives include at least one substance selected from the group consisting of resins and rubbers.
• resins and rubbers include phenolic resins, melamine resins, urea resins, alkyd resins, epoxy resins, unsaturated polyester resins, polyurethane resins, polyethylene resins (e.g., high-density polyethylene, medium-density polyethylene, low-density polyethylene), and polypropylene.
• the fine cellulose fiber powder may contain a functional compound as an organic additive. Functional compounds include dyes, UV absorbers, antioxidants, antistatic agents, and surfactants.
• Organic additives may be included in the fine cellulose fiber powder, for example, in amounts ranging from 0.09 to 5% by weight.
• the fine cellulose fiber powder may contain components other than fine cellulose fibers and water, but it is one of preferred embodiments that the fine cellulose fiber powder is formed only from fine cellulose fibers and water.
• formed only from fine cellulose fibers and water means not only the case where the total amount of fine cellulose fibers and water accounts for 100% by mass of the fine cellulose fiber powder, but also the case where the fine cellulose fiber powder is composed of fine cellulose fibers and water. It includes cases where other ingredients are not intentionally added. That is, even when the fine cellulose fiber powder contains components other than fine cellulose fibers and water as impurities, it corresponds to fine cellulose fiber powder formed only from fine cellulose fibers and water.
• the fine cellulose fiber powder formed only from fine cellulose fibers and water is a concept that includes fine cellulose fiber powder formed substantially from only fine cellulose fibers and water.
• the fine cellulose fiber powder formed substantially only from fine cellulose fibers and water is, for example, a mode containing 99% by mass or more of fine cellulose fibers and water in total in 100% by mass of fine cellulose fiber powder. be done.
• the fine cellulose fiber powder of the present embodiment can be used for various purposes, for example, as a fine cellulose fiber aqueous dispersion.
• the fine cellulose fiber aqueous dispersion of the present embodiment include fine cellulose fiber aqueous dispersion in which fine cellulose fiber powder is dispersed in water.
• the present invention includes, as one embodiment, a method for producing an aqueous dispersion of fine cellulose fibers, comprising the step of dispersing fine cellulose fiber powder in water.
• the fine cellulose fiber aqueous dispersion may contain components other than water.
• components other than water for example, various components blended in water-based compositions in the paint, coating, and cosmetics industries can be used. Since fine cellulose fiber powder is easily dispersed in water, a composition in which fine cellulose fibers are uniformly dispersed can be obtained as a fine cellulose fiber aqueous dispersion without using a dispersant.
• conventional fine cellulose fibers are usually distributed as a low-concentration aqueous dispersion, a large amount of water is added to the aqueous composition along with the fine cellulose fibers when mixing with the aqueous composition. Therefore, the degree of freedom in formulation design was low, but the fine cellulose fiber powder can be directly mixed with the water-based composition, so it is preferable because of its high degree of freedom in formulation design.
• the fine cellulose fiber aqueous dispersion can be used as appropriate depending on its application.
• a film can be formed by forming a film.
• the film of the present embodiment include a film produced by forming a film from an aqueous dispersion of fine cellulose fibers.
• the present invention includes, as one embodiment, a method for producing a film, which has a step of forming a fine cellulose fiber aqueous dispersion.
• the thickness of the film (coating film) is not particularly limited, and can be appropriately set according to its use.
• the film of the present embodiment is obtained from an aqueous dispersion of fine cellulose fibers in which the fine cellulose fibers are excellent in dispersibility, aggregation of the fine cellulose fibers is suppressed in the film as well, which is preferable.
• the method for producing the above fine cellulose fiber powder is not particularly limited, but it can be obtained, for example, through a step of drying a dispersion liquid of fine cellulose fibers containing water or a dispersion medium other than water and a powdering step.
• Dispersion media other than water include polar organic solvents such as dimethyl sulfoxide, alcohols and polyols, and ionic liquids such as quaternary ammonium compounds. It is preferable to use water, and it is preferable to use water from the viewpoint of safety and the like.
• the method for preparing a fine cellulose fiber dispersion containing water or a dispersion medium other than water is not particularly limited. It can be obtained by introducing a sulfate ester group, purifying it, and dispersing it in water.
• a dried fine cellulose fiber By removing (drying) the dispersion medium from the fine cellulose fiber dispersion, a dried fine cellulose fiber can be obtained.
• a drying method a known method can be used and is not particularly limited. Examples include freeze-drying, spray-drying, pressing, air-drying, hot-air drying, crystallization, and vacuum drying.
• the drying device is not particularly limited, but may be a conical drying device, a continuous tunnel drying device, a band drying device, a vertical drying device, a vertical turbo drying device, a multi-stage disk drying device, a ventilation drying device, a rotary drying device, or an air stream.
• a drying device, a vacuum box type drying device, a stirring drying device, and the like can be used alone or in combination of two or more. Drying methods include freeze-drying, crystallization, and vacuum drying (a combination of crystallization and vacuum drying), since a porous dried body that is less likely to damage fine cellulose fibers and more easily pulverized can be obtained. It is preferred to carry out spray drying.
• the fine cellulose fiber powder means a powder in which fine cellulose fibers, for example, fine cellulose fibers such as cellulose nanofibers, are agglomerated together with water, and means cellulose particles used in fields such as cosmetics. not something to do.
• the fine cellulose fiber powder can be obtained by pulverizing the dried product as necessary, preferably by pulverizing it with a dry pulverizer.
• the method for producing the aforementioned fine cellulose fiber powder comprises drying an aqueous dispersion of fine cellulose fibers, and drying the aqueous dispersion containing fine cellulose fibers and water.
• a method for producing a fine cellulose fiber powder includes a drying step to obtain a body, and in the drying step, at least one drying selected from freeze-drying, crystallization, vacuum drying, and spray-drying is performed. At least water is used as a dispersion medium for the dispersion liquid, and water or a mixed solvent of water and an organic solvent is preferably used, and water is more preferably used from the viewpoint of safety and the like.
• an aqueous dispersion of fine cellulose fibers is prepared in advance.
• a dried body containing fine cellulose fibers and water can be obtained.
• a fine cellulose fiber powder can be obtained by pulverizing the dried product.
• the concentration of the fine cellulose fibers in the aqueous dispersion of fine cellulose fibers is not particularly limited, but is usually 0.1 to 50% by mass, preferably 0.5 to 10% by mass.
• a dried body containing fine cellulose fibers and water is pulverized with a dry pulverizer to obtain fine particles.
• a method for producing a fine cellulose fiber powder comprising the step of obtaining a cellulose fiber powder.
• a dried body containing fine cellulose fibers and water is prepared in advance.
• the method for preparing the dried product is not particularly limited, but the method for preparing according to Embodiment A described above is preferable. That is, the following embodiment C, which is a combination of the embodiment A and the embodiment B, is one of the preferred embodiments.
• a drying step of drying an aqueous dispersion of fine cellulose fibers to obtain a dried body containing fine cellulose fibers and water is performed.
• at least one drying selected from freeze drying, crystallization, vacuum drying, and spray drying is performed, and the dried body obtained in the drying step is pulverized with a dry pulverizer.
• a method for producing a fine cellulose fiber powder comprising the step of obtaining a fine cellulose fiber powder.
• Example 1 150 g of dimethyl sulfoxide (DMSO), 16.5 g of acetic anhydride (concentration in fibrillation solution: 14% by mass) and 3.35 g of sulfuric acid (concentration in fibrillation solution: 1.87% by mass) were placed in a 300 ml sample bottle, and 23 C. for about 30 seconds using a magnetic stirrer to prepare a fibrillation solution.
• DMSO dimethyl sulfoxide
• acetic anhydride concentration in fibrillation solution: 14% by mass
• sulfuric acid concentration in fibrillation solution: 1.87% by mass
• the mixture was stirred for 3 minutes using a mixer (G5200, manufactured by Biolomix) to obtain 1000 g of an aqueous dispersion of fine cellulose fibers having a uniform sulfate group content of 0.5% by mass.
• a mixer G5200, manufactured by Biolomix
• the resulting aqueous dispersion of fine cellulose fibers was dried for 72 hours using a freeze dryer (FDU-2110, manufactured by Tokyo Rika Kikai Co., Ltd.) to obtain 5 g of dried fine cellulose fibers.
• a total of 15 g of dried fine cellulose fibers was obtained by performing the same operation three times. Subsequently, 15 g of dried fine cellulose fibers were processed for 3 minutes with a dry pulverizer (Wonder Blender WB1, manufactured by Osaka Chemical Co., Ltd.) to give sample No. 1, which is fine cellulose fiber powder. got 1. The experimental instruments were not sterilized before use.
• Example 2 The procedure was carried out in the same manner as in Example 1, except that the treatment time in the dry pulverizer was changed from 3 minutes to 2 minutes. got 2.
• Example 3 The procedure was carried out in the same manner as in Example 1, except that the processing time in the dry pulverizer was changed from 3 minutes to 1.5 minutes. got 3.
• Example 4 The procedure was carried out in the same manner as in Example 1, except that the treatment time in the dry pulverizer was changed from 3 minutes to 1 minute. Got 4.
• Example 5 The procedure was carried out in the same manner as in Example 1 except that the stirring time was changed from 120 minutes to 30 minutes when 5.0 g of softwood kraft pulp NBKP (manufactured by Nippon Paper Industries Co., Ltd.) was added to the fibrillation solution. Got 5.
• Example 6 The procedure was carried out in the same manner as in Example 1, except that the stirring time was changed from 120 minutes to 180 minutes when 5.0 g of softwood kraft pulp NBKP (manufactured by Nippon Paper Industries Co., Ltd.) was added to the fibrillation solution. got 6.
• Example 7 The same procedure as in Example 1 was repeated except that the drying time using the freeze dryer was changed from 72 hours to 48 hours. got 7.
• Example 8 The same procedure as in Example 1 was repeated except that the drying time using the freeze dryer was changed from 72 hours to 24 hours. got 8.
• Example 9 The same procedure as in Example 1 was repeated except that the 5% by mass sodium hydroxide aqueous solution was changed to a 5% by mass potassium hydroxide aqueous solution. got 9.
• Example 10 The procedure was carried out in the same manner as in Example 1, except that the 5% by mass aqueous sodium hydroxide solution was changed to a 5% by mass aqueous calcium hydroxide solution. Got 10.
• Example 11 In the same manner as in Example 1, 1000 g of an aqueous dispersion of fine cellulose fibers having a uniform sulfate group content of 0.5 mass % was obtained. 3000 g of methanol was added to 1000 g of the aqueous dispersion of fine cellulose fibers, and the mixture was stirred for 2 hours to crystallize the fine cellulose fibers.
• the dispersion containing the fine cellulose fiber precipitate obtained in the crystallization step was treated with a centrifuge to remove the supernatant to obtain a fine cellulose fiber precipitate.
• the centrifugation speed was 12000 rpm and the centrifugation time was 50 minutes.
• the fine cellulose fiber sediment was taken out into a beaker and vacuum-dried together with the beaker using a vacuum dryer (AVO-200V, manufactured by AS ONE) at 40°C for 24 hours to obtain 5 g of dried fine cellulose fibers.
• AVO-200V manufactured by AS ONE
• a total of 15 g of dried fine cellulose fibers was obtained by performing the same operation three times. Subsequently, 15 g of dried fine cellulose fibers were processed for 3 minutes with a dry pulverizer (Wonder Blender WB1, manufactured by Osaka Chemical Co., Ltd.) to give sample No. 1, which is fine cellulose fiber powder. 11 was obtained.
• a dry pulverizer Wood Blender WB1, manufactured by Osaka Chemical Co., Ltd.
• Example 12 In the same manner as in Example 1, 1000 g of an aqueous dispersion of fine cellulose fibers having a uniform sulfate group content of 0.5 mass % was obtained. 1000 g of an aqueous dispersion of fine cellulose fibers was dried using a spray dryer (Shibata, Mini Spray Dryers, Model B-290) at an inlet temperature of 160° C. to obtain 5 g of dried fine cellulose fibers.
• a spray dryer Shibata, Mini Spray Dryers, Model B-290
• a total of 15 g of dried fine cellulose fibers was obtained by performing the same operation three times. Subsequently, 15 g of dried fine cellulose fibers were processed for 1 minute with a dry pulverizer (Wonder Blender WB1, manufactured by Osaka Chemical Co., Ltd.) to give sample No. 1, which is fine cellulose fiber powder. 12 was obtained.
• a dry pulverizer Wood Blender WB1, manufactured by Osaka Chemical Co., Ltd.
• Example 1 The procedure was carried out in the same manner as in Example 1, except that the processing time in the dry pulverizer was changed from 3 minutes to 30 seconds. 13 was obtained.
• Example 2 The procedure was carried out in the same manner as in Example 1, except that the processing time in the dry pulverizer was changed from 3 minutes to 10 seconds. 14 was obtained.
• Example 3 In the same manner as in Example 1, 1000 g of an aqueous dispersion of fine cellulose fibers having a uniform sulfate group content of 0.5 mass % was obtained. 1000 g of the aqueous dispersion of fine cellulose fibers was placed in a hot air dryer (LC-114, manufactured by ESPEC Co., Ltd.) in a beaker and dried at 40° C. for 120 hours to obtain sample No. 1, which is a dried fine cellulose fiber film. 15 was obtained.
• LC-114 hot air dryer
• Example 4 The procedure was carried out in the same manner as in Example 1, except that the drying time of the aqueous dispersion of fine cellulose fibers using a freeze dryer was changed from 72 hours to 18 hours. 16 was obtained.
• a phosphorylation reagent was prepared by dissolving 15 g of urea, 8.3 g of sodium dihydrogen phosphate dihydrate, and 6.2 g of disodium hydrogen phosphate in 16.4 g of water.
• a sheet of dried softwood kraft pulp NBKP (manufactured by Nippon Paper Industries) was processed with a cutter mill and a pin mill to obtain cotton-like fibers.
• the phosphorylation reagent was evenly sprayed on cotton-like fibers having an absolute dry weight of 15 g, and kneaded by hand to obtain an impregnated pulp.
• the impregnated pulp was heat-treated for 80 minutes in a blower dryer with a damper heated to 140°C. Phosphorylated pulp was obtained by the above treatment.
• the sheet and 1.5 L of ion-exchanged water were stirred until they were uniformly dispersed, and the dispersion was filtered and dehydrated.
• the resulting sheet was treated in the same way two more times.
• the obtained sheet and ion-exchanged water were mixed to obtain a slurry containing 0.5% by mass of phosphorylated pulp.
• a slurry containing 0.5% by mass of phosphorylated pulp was defibrated for 180 minutes at 6900 rpm using a fibrillation treatment device (Clearmix-11S, manufactured by M Technic Co., Ltd.). Subsequently, ion-exchanged water was added to adjust the solid content concentration of the slurry to 0.5% by mass to obtain an aqueous dispersion of phosphate-esterified fine cellulose fibers.
• aqueous dispersion of fine cellulose fibers was placed in a freeze dryer (FDU-2110, manufactured by Tokyo Rika Kikai Co., Ltd.) and dried for 72 hours to obtain 15 g of dried phosphate-esterified fine cellulose fibers. rice field.
• FDU-2110 manufactured by Tokyo Rika Kikai Co., Ltd.
• Sample No. 15 g of dried phosphate-esterified fine cellulose fibers was treated with a dry pulverizer (Wonder Blender WB1, manufactured by Osaka Chemical Co., Ltd.) for 3 minutes to obtain phosphate-esterified fine cellulose fiber powder. 17 was obtained.
• the experimental instruments were not sterilized before use.
• the temperature of the reaction system was kept at 20° C., and the pH was maintained at 10 by successively adding 3N sodium hydroxide aqueous solution. After reacting for 3 hours, the resulting product was filtered through a glass filter and washed thoroughly with water. Thereby, an oxidized pulp was obtained.
• Ion-exchanged water is added to the oxidized pulp to adjust the solid content concentration of the slurry to 0.5% by mass, and the slurry is treated three times at 140 MPa using an ultrahigh pressure homogenizer, An aqueous dispersion of TEMPO-oxidized fine cellulose fibers was obtained. Subsequently, the resulting aqueous dispersion of fine cellulose fibers was placed in a freeze dryer (FDU-2110, manufactured by Tokyo Rika Kikai Co., Ltd.) and dried for 72 hours to obtain 15 g of dried TEMPO-oxidized fine cellulose fibers. .
• FDU-2110 manufactured by Tokyo Rika Kikai Co., Ltd.
• Example 13 The procedure of Example 11 was repeated except that the number of washings using distilled water and ethanol after the reaction was changed from 3 times to 2 times. 19 was obtained.
• Moisture percentage The moisture content of the samples obtained in Examples and Comparative Examples was obtained by the following method within 24 hours after the completion of sample preparation.
• Moisture content (% by mass) can be represented by the amount of water relative to the mass of the sample in accordance with JIS P8203. That is, the moisture content (% by mass) can be obtained from the following formula.
• Moisture content (mass%) ((mass of sample - mass of solid content of sample) / mass of sample) x 100 (The mass of the sample means the mass (g) of the sample used for measurement.
• the solid content mass of the sample is the same amount of the sample used for measurement in an atmosphere of 105 ° C. for 2 hours. means the mass (g) of solid matter remaining after drying to
• the average fiber width of the fine cellulose fibers in the samples obtained in Examples and Comparative Examples was measured using an atomic force microscope (SPM-9700HT, manufactured by Shimadzu Corporation) to determine the fiber width of 50 arbitrarily selected fibers. was measured and the average value was taken.
• the evaluation sample used was prepared by the following method.
• the sample is weighed so that the fine cellulose fiber is 3 g, the sample is added to distilled water weighed so that the total with the sample is 1000 g, and the mixture is stirred for 3 minutes using a mixer (G5200, manufactured by Biolomix). A 0.3% by mass uniform aqueous dispersion of fine cellulose fibers (aqueous dispersion of fine cellulose fibers) was obtained. Subsequently, a high-pressure homogenizer (M-110EH-30, manufactured by Microfluidics), which is a high-pressure dispersion treatment machine, is equipped with a 200 ⁇ m auxiliary treatment module and an 87 ⁇ m interaction chamber, and three passes are performed under 200 MPa conditions to achieve high dispersion treatment. gone.
• M-110EH-30 manufactured by Microfluidics
• the median diameter of the samples obtained in Examples and Comparative Examples was obtained by the following method.
• the particle size was measured using a dry particle size distribution meter (Microtrac MT-3000, manufactured by Microtrac Bell) conforming to ISO 13320 and JIS Z 8825 standards for laser diffraction/scattering methods.
• the median diameter (X 50 ) which is the value at which the integrated value of the measured particle size distribution becomes 50%, was obtained.
• [Substituent introduction amount] The amount of substituent introduced into the fine cellulose fibers in the samples obtained in Examples and Comparative Examples was determined by the following method. Sample no. 1 to No. 16, and sample no. For Sample No. 19, the amount of sulfur introduced (mmol/g) resulting from the sulfate group was determined as the amount of substituent introduced. For Sample No. 17, the amount of phosphorus introduced (mmol/g) resulting from the phosphoric acid ester group was determined as the amount of substituent introduced. For No. 18, the introduction amount of carboxy groups (mmol/g) resulting from carboxy groups was obtained as the introduction amount of substituent groups.
• the amount of sulfur introduced into the fine cellulose fibers in the sample was quantified by the combustion absorption-IC method using ICS-1500 manufactured by Nippon Dionex Co., Ltd. Dried fine cellulose fibers (0.01 g) are placed on a magnetic board and burned in an oxygen atmosphere (flow rate: 1.5 L/min) in a tubular furnace (1350°C). 20 ml) to obtain an absorption liquid. The resulting absorption liquid was diluted with pure water to 100 ml, and the diluted liquid was subjected to ion chromatography. From the measurement results, the sulfate ion concentration (% by weight) in the fine cellulose fibers was measured, and the sulfur introduction amount (mmol/g) per 1 g of fine cellulose fibers was calculated. The dried fine cellulose fibers were obtained by drying the sample under an atmosphere of 105° C. until it had a constant weight.
• Sample No. 17 The amount of phosphorus introduced into the fine cellulose fibers in No. 17 was measured by alkaline titration. Specifically, it was implemented as follows. As a pretreatment, sample no. 17 was diluted with pure water so that the solid content concentration was 0.2% by mass, then 10% by volume of the strongly acidic ion exchange resin was mixed with the slurry and shaken for 1 hour, and the mesh was 90 ⁇ m mesh. Only the slurry was separated with a wire mesh of .
• Alkaline titration was performed using the slurry separated by the above pretreatment.
• a sodium hydroxide aqueous solution with a concentration of 0.1 N was used for alkaline titration.
• the electric conductivity was measured for each alkali drop, and the titration amount at the inflection point was read from the plot of the alkali titer and the electric conductivity.
• the amount of phosphorus introduced was calculated by dividing by the mass of the fine cellulose fibers in No. 17 (mass of solid content).
• a strong acid group and a weak acid group exist in the phosphate group, and there are two inflection points due to this. Notated.
• DMSO amount measurement method First, 15 g of water was added as an extract to 0.5 g of the samples obtained in Examples and Comparative Examples, and the mixture was treated with an ultrasonic cleaner for 30 minutes. After that, 30 g of acetone was added, and after stirring by hand shaking, the mixture was treated with an ultrasonic cleaner for 5 minutes. The extract was collected, passed through a membrane filter (0.45 ⁇ m), and the amount of DMSO in the extract was measured using GC-MS.
• the atomic percentage of each atom was calculated, and the atomic percentage of nitrogen derived from ammonium ions was determined with the peak of binding energy 4101.9 eV as the peak of nitrogen derived from ammonium ions.
• the weight ratio of ammonium ions was calculated and used as the amount of ammonium ions.
• the bond energies are normalized values with C—C and C—H as 284.6 eV.
• the type of fine cellulose fibers in the samples obtained in Examples and Comparative Examples the average fiber width, the amount of substituents introduced, the type of cation, the median diameter of the sample, the moisture content, the amount of DMSO, the amount of NH 4 + , and the drying method.
• Tables 1 and 2 show.
• the fine cellulose fibers having sulfate ester groups are referred to as sulfate-esterified CNF.
• the phosphate-esterified fine cellulose fibers are referred to as phosphate-esterified CNF
• the TEMPO-oxidized fine cellulose fibers are referred to as TEMPO-oxidized CNF.
• aqueous dispersion of fine cellulose fibers was prepared using the samples obtained in Examples and Comparative Examples. Based on the moisture content, the sample was weighed so that the fine cellulose fiber was 0.3 g, the sample was added to distilled water weighed so that the total with the sample was 100 g, and a mixer (G5200, manufactured by Biolomix) was added. and stirred for 3 minutes to obtain a 0.3% by mass uniform aqueous dispersion of fine cellulose fibers (aqueous dispersion of fine cellulose fibers-1).
• 100 g of the fine cellulose fiber aqueous dispersion was defoamed for 10 seconds with a defoamer (Awatori Mixer ARE-310, manufactured by Thinky) and left to stand for 24 hours. Subsequently, using a Brookfield viscometer (DV-II+, manufactured by Brookfield), the viscosity was measured at a rotation speed of 2.6 rpm, and the viscosity at 10 minutes after the start of measurement (after the start of rotation) was recorded.
• a Brookfield viscometer DV-II+, manufactured by Brookfield
• the measurement was performed in an environment where the temperature of the aqueous dispersion was 25°C.
• a thixotropic index (viscosity of fine cellulose fiber aqueous dispersion at rotation speed 2.6 rpm)/(fine cellulose fiber aqueous dispersion viscosity at rotation speed 26 rpm)
• Haze value (diffused light transmittance/total light transmittance) x 100
• a fine cellulose fiber aqueous dispersion-2 was prepared using the samples obtained in Examples and Comparative Examples. Based on the moisture content, the sample was weighed so that the fine cellulose fiber was 1.0 g, the sample was added to distilled water weighed so that the total with the sample was 100 g, and a mixer (G5200, manufactured by Biolomix) was added. and stirred for 3 minutes to obtain a 1.0% by mass aqueous dispersion of fine cellulose fibers (aqueous dispersion of fine cellulose fibers-2).
• liquid separation stability The liquid separation stability of fine cellulose fiber aqueous dispersion-2 prepared from the samples obtained in Examples and Comparative Examples was measured by the following method.
• the fine cellulose fiber aqueous dispersion is referred to as CNF aqueous dispersion
• the viscosity of the fine cellulose fiber aqueous dispersion at the rotation speed of 2.6 rpm is referred to as viscosity 2.6 rpm
• the viscosity at the rotation speed of 26 rpm The viscosity of the fine cellulose fiber aqueous dispersion is referred to as viscosity 26 rpm
• the fine cellulose fiber aggregates are referred to as CNF aggregates.
• Reference example 1 ⁇ Production of fine cellulose fiber dispersion> Softwood kraft pulp NBKP (manufactured by Nippon Paper Industries) was used. Below, NBKP used in Reference Example 1 is also simply referred to as pulp. The pulp was washed with a large amount of pure water, drained through a 200-mesh sieve, and used after measuring the solid content concentration.
• Step of preparing reaction solution A sulfonating agent and urea and/or a derivative thereof were prepared so as to have the following solid content concentrations.
• Sulfamic acid (purity 98.5%, manufactured by Fuso Chemical Industry Co., Ltd.) was used as the sulfonating agent, and urea solution (purity 99%, manufactured by Wako Pure Chemical Industries, model number; special grade reagent) was used as urea or its derivative. .
• the mixing ratio of both was adjusted to be 1:1.5 in concentration ratio (g/L) to prepare an aqueous solution.
• the method for preparing the reaction solution is shown below. 100 ml of water was added to the vessel. Then, 20 g of sulfamic acid and 30 g of urea were added to this container to prepare a reaction solution having a sulfamic acid/urea ratio ((g/L)/(g/L)) of 200/300 (1:1.5). . That is, urea was added to 150 parts by weight per 100 parts by weight of sulfamic acid.
• the slurry prepared by adding pulp to the reaction solution was stirred for 10 minutes using a stirrer. After stirring, the slurry was suction filtered using filter paper (No. 2). Suction filtration was performed until the solution stopped dripping. After suction filtration, the pulp was peeled off from the filter paper, and the filtered pulp was placed in a drier (LC-114, manufactured by Espec Co., Ltd.) with a constant temperature bath set at 50° C. and dried until the moisture content reached an equilibrium state.
• a drier LC-114, manufactured by Espec Co., Ltd.
• a heating reaction was carried out.
• a dryer (LC-114, manufactured by Espec) was used.
• the reaction conditions are as follows. Thermostatic bath temperature: 160°C, heating time: 1 hour
• the reacted pulp is diluted with pure water so that the solid content is 1% by weight or less, neutralized by adding an excess amount of sodium hydrogen carbonate, and then sufficiently washed with pure water.
• a sulfamic acid/urea treated pulp suspension was prepared.
• a high-pressure homogenizer (M-110EH-30, manufactured by Microfluidics) was used to defibrate the sulfamic acid/urea-treated pulp to prepare a sulfonated fine cellulose fiber dispersion.
• the processing conditions of the high-pressure homogenizer were as follows.
• the sulfamic acid/urea treated pulp was prepared to have a solid content concentration of 0.5% by weight and was supplied to a high-pressure homogenizer. The number of passes was continued until coarse fibers could not be visually observed. In addition, the pressure in that case was 60 MPa.
• the measurement was performed in an environment where the temperature of the aqueous dispersion was 25°C.
• TI value A thixotropic index (TI value) was calculated based on the following formula from the viscosity of the aqueous dispersion of fine cellulose fibers at a rotation speed of 2.6 rpm and the viscosity of the aqueous dispersion of fine cellulose fibers at a rotation speed of 26 rpm.
• TI value (viscosity of fine cellulose fiber aqueous dispersion at rotation speed 2.6 rpm)/(fine cellulose fiber aqueous dispersion viscosity at rotation speed 26 rpm)
• the DMSO content of the fine cellulose fibers produced in Reference Example 1 was below the detection limit, and NH 4 + was 7700 ppm. , 520 mPa ⁇ s and 220 mPa ⁇ s, respectively, and the TI value was 2.4.
• the aqueous dispersion using the sample obtained in the example had excellent liquid separation stability, the generation of fine cellulose fiber aggregates in the film was suppressed, and the sample had excellent mold resistance.
• the fine cellulose fiber powder can be easily dispersed in water, the fine cellulose fiber aqueous dispersion tends to have a high viscosity measured at 2.6 rpm and a large TI value. There was a tendency for higher modulus and lower haze.
• a preferred range can be defined by arbitrarily combining the upper and lower limits of the numerical range
• a preferred range can be defined by arbitrarily combining the upper limits of the numerical range
• the lower limit of the numerical range Any combination of values can be used to define a preferred range.
• a numerical range represented using the symbol " ⁇ " includes the numerical values described before and after the symbol " ⁇ " as lower and upper limits, respectively.

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