JP6626641B2 - Dried body containing cellulose nanofiber, method for producing the same, and method for producing cellulose nanofiber dispersion - Google Patents

Description

  The present invention relates to a dried product containing cellulose nanofibers, a method for producing the same, and a method for producing a cellulose nanofiber dispersion.

  2. Description of the Related Art In recent years, attention has been paid to nanotechnology aimed at miniaturizing a substance to a nanometer level and obtaining new physical properties different from conventional properties possessed by the substance. Cellulose nanofibers produced from pulp which is a cellulosic raw material by chemical treatment, pulverization treatment, etc. are excellent in strength, elasticity, heat stability, etc., so filter media, filter aids, base materials for ion exchangers, It is used for industrial purposes as a filler for chromatography analysis equipment, a filler for compounding resins and rubbers, and a compounding agent for cosmetics such as lipstick, powder cosmetics, and emulsified cosmetics. In addition, since cellulose nanofibers are excellent in aqueous dispersibility, they can be used as a preservative for viscosity of foods, cosmetics, paints, etc., a reinforcing agent for food material dough, a water preservative, a food stabilizer, a low calorie additive, an emulsifier It is expected to be used in many applications such as stabilizing aids.

  Cellulose nanofibers are usually obtained by pulverizing pulp or the like in a water-dispersed state. Accordingly, the obtained cellulose nanofibers are in a water-dispersed state, and such a dispersion of cellulose nanofibers requires a large amount of energy during transportation. Further, cellulose nanofibers containing water can induce steam explosion during melt-kneading with a resin. Therefore, in view of commercialization, it is important to dry the dispersion liquid of the cellulose nanofiber. However, when the cellulose nanofibers are dried, the cellulose nanofibers are strongly aggregated by hydrogen bonding between the cellulose nanofibers. For this reason, when the dried cellulose nanofiber is dispersed again in water, there is a disadvantage that the dispersibility is not sufficiently restored to the state before drying.

  On the other hand, as a technique for improving the redispersibility of cellulose nanofibers in a dispersion medium, a step of mixing a cellulose nanofiber with a redispersion promoter to obtain a gel, and the step of mixing the gel with an organic liquid A method for producing a cellulose nanofiber dispersion including a step of redispersing the cellulose nanofiber by mixing with a dispersant has been developed (see JP-A-2014-118521). However, in this technique, the cellulose nanofiber is not dried to a dry state, but is made into a gel, and is dispersed in an organic liquid compound as a dispersion medium.

  Further, as a technique for obtaining a dried bacterial cellulose having a high redispersibility, a method of adding a hydrophilic liquid or solid such as glycerin to an aqueous suspension containing bacterial cellulose and then dehydrating the aqueous suspension has been developed. See JP-A-9-165402). However, bacterial cellulose is cellulose produced by microorganisms, and has different physical properties and the like from cellulose nanofibers obtained by fibrillating pulp. Therefore, even if this technology for drying bacterial cellulose is diverted to cellulose nanofibers, the same effect is not necessarily produced.

JP 2014-118521 A JP-A-9-165402

  The present invention has been made based on the above circumstances, and an object of the present invention is to provide a dried product containing cellulose nanofibers having excellent dispersibility in water, and a method for producing the same. Another object is to provide a method for producing a cellulose nanofiber dispersion using such a dried product containing cellulose nanofibers.

  The invention made to solve the above-mentioned problem is a cellulose nanofiber-containing dried product containing cellulose nanofibers obtained by fibrillating a plant material, wherein the cellulose nanofiber-containing dried product further comprises hydroxy acids. It is a dried body.

  Since the dried cellulose nanofiber-containing product contains hydroxy acids together with the cellulose nanofiber, it is excellent in dispersibility in water. The reasons for this are not clear, but (1) the hydroxy acids attached to the surface of the cellulose nanofiber weaken the hydrogen bonds between the cellulose nanofibers, and (2) the carboxy contained in the hydroxyacids attached to the cellulose nanofiber surface. It is considered that when the group is anionized in water, the electrostatic repulsion of these groups promotes the dispersion between the cellulose nanofibers.

  The content of the hydroxy acids with respect to 100 parts by mass of the cellulose nanofiber is preferably from 0.1 part by mass to 200 parts by mass. By setting the content of the hydroxy acids in the above range, it is possible to further increase the dispersibility while suppressing an increase in cost.

  Preferably, the hydroxy acids are hydroxy acid salts. Further, the hydroxy acids are preferably citric acid, tartaric acid, malic acid and salts thereof. By using these compounds as hydroxy acids, better dispersibility can be exhibited.

  The moisture content of the dried body containing cellulose nanofibers is preferably less than 50% by mass. Such a dried product containing cellulose nanofibers having a low moisture content is excellent in transportability, handling properties, storage properties, and the like.

  Another invention made to solve the above problem is a step of obtaining a mixed solution by mixing a dispersion containing cellulose nanofibers obtained by fibrillating pulp and hydroxy acids, and drying the mixed solution. This is a method for producing a dried body containing cellulose nanofibers, the method including a step of causing a drying process. According to the production method, a dried product containing cellulose nanofibers having excellent dispersibility in water can be obtained by a simple method.

  Yet another invention made to solve the above-mentioned problem is a method for producing a cellulose nanofiber dispersion, comprising a step of mixing the dried cellulose nanofiber-containing dried product with water. According to the method for producing a cellulose nanofiber dispersion, a cellulose nanofiber dispersion having a high dispersibility and a high concentration can be easily obtained.

  In addition, "hydroxy acids" refers to hydroxy acids, hydroxy acid salts and mixtures thereof, and some of hydroxy acids and hydroxy acid salts are chemically or physically bonded to cellulose nanofibers or the like. Including.

  The dried product containing cellulose nanofibers of the present invention is excellent in dispersibility in water. According to the method for producing a dried product containing cellulose nanofibers of the present invention, a dried product containing cellulose nanofibers having excellent dispersibility in water can be obtained. According to the method for producing a cellulose nanofiber dispersion of the present invention, a cellulose nanofiber dispersion having high dispersibility and high concentration can be easily obtained.

  Hereinafter, a method for producing a dried cellulose nanofiber-containing product according to an embodiment of the present invention (hereinafter sometimes simply referred to as a “dry product” or “a dried cellulose nanofiber product”), a dried cellulose nanofiber-containing product, And a method for producing a cellulose nanofiber dispersion will be described in detail.

<Production method of dried body containing cellulose nanofiber>
The method for producing a dried body containing cellulose nanofibers according to the embodiment of the present invention includes:
Step (A) of obtaining a mixed liquid by mixing a dispersion liquid containing cellulose nanofibers obtained by fibrillating pulp with hydroxy acids, and drying the mixed liquid (B)
Is provided.

(Cellulose nanofiber)
First, the cellulose nanofibers contained in the dispersion used in the step (A) will be described. Cellulose nanofibers are fine cellulose fibers obtained by fibrillating plant materials such as pulp (pulp fibers), and generally include cellulose containing nanofiber cellulose fibers having a nanometer width (1 nm or more and 1000 nm or less). Refers to fiber. Cellulose nanofiber can be usually obtained by defibrating a plant material (fiber material) by a known method.

Examples of the pulp used as a raw material for cellulose nanofibers include hardwood bleached kraft pulp (LBKP), hardwood unbleached kraft pulp (LUKP), and other hardwood kraft pulp (LKP), softwood bleached kraft pulp (NBKP), and softwood bleached kraft pulp. Chemical pulp such as softwood kraft pulp (NKP) such as (NUKP);
Stone ground pulp (SGP), pressurized stone ground pulp (PGW), refiner ground pulp (RGP), chemi ground pulp (CGP), thermo ground pulp (TGP), ground pulp (GP), thermomechanical pulp (TMP), Mechanical pulp such as chemi-thermomechanical pulp (CTMP), bleached thermomechanical pulp (BTMP);
Waste paper pulp produced from tea waste paper, kraft envelope waste paper, magazine waste paper, newspaper waste paper, flyer waste paper, office waste paper, cardboard waste paper, Kamishira waste paper, Kent waste paper, imitation waste paper, ground ticket waste paper, waste paper waste paper, etc .;
Deinked pulp (DIP) obtained by deinking waste paper pulp may be used. These may be used alone or in combination of two or more as long as the effects of the present invention are not impaired.

  Among these, chemical pulp is preferable and hardwood kraft pulp (LKP) is more preferable from the viewpoint of easy drying. Such pulp also has the advantage of having less impurities.

  Other plant raw materials include pulp obtained from linter pulp, hemp, bagasse, kenaf, esparto grass, bamboo, chaff, straw and the like. In addition, wood, hemp, bagasse, kenaf, esparto grass, bamboo, rice husk, straw, etc., which are pulp raw materials, can also be used directly as plant raw materials. Hereinafter, a method for producing cellulose nanofibers in the case where pulp is used as a plant material will be described. However, cellulose nanofibers can be obtained in the same manner also in the case of a plant material other than pulp.

  The method for producing the cellulose nanofiber is not particularly limited as long as the effects of the present invention are not impaired, and a known method can be used. For example, pulp in a water-dispersed state may be subjected to defibration by mechanical treatment, may be subjected to defibration by chemical treatment such as enzyme treatment or acid treatment, but is preferably defibrated by mechanical treatment. . By fibrillating the pulp by mechanical treatment, cellulose nanofibers can be more easily and reliably obtained, and the dispersibility of the dried body obtained using hydroxy acids can be further improved.

  Examples of the defibration method by mechanical treatment include a grinder method for grinding pulp between rotating grindstones, a facing collision method using a high-pressure homogenizer, a crushing method using a ball mill, a roll mill, a cutter mill, and the like.

  The pulp may be subjected to preliminary beating before defibration. Preliminary beating (mechanical pretreatment) is not particularly limited, and a known method can be used. As an example of a specific method, it is preferable to carry out defibration stepwise. In particular, a grinder method in which unbeaten raw pulp is preliminarily beaten to a freeness of 30% or less of the starting material by a so-called viscous beater such as a Niagara beater, and then ground between rotating wheels. It is preferable to perform a defibration treatment until a cellulose nanofiber is obtained.

  Further, the pulp may be subjected to a chemical pretreatment before defibration. Examples of the chemical pretreatment include a hydrolysis treatment using an acid such as sulfuric acid, an enzyme, or the like, and an oxidation treatment using an oxidizing agent such as ozone. By performing such chemical pretreatment, cellulose nanofibers can be efficiently obtained by mechanical or chemical fibrillation treatment.

  As the cellulose nanofiber used in the method for producing the dried body containing cellulose nanofibers, pulp that has not been substantially subjected to oxidation treatment or other functional group modification treatment is subjected to defibration treatment. Is preferably obtained. When the pulp is subjected to an oxidation treatment as a pretreatment, a carboxy group is modified, and a large number of carboxy groups are present in the obtained cellulose nanofiber. Such a functional group such as a carboxy group present in the cellulose nanofiber may affect the dispersibility of the dried cellulose nanofiber-containing product obtained by mixing with the hydroxy acid.

  The water retention of the cellulose nanofiber is preferably, for example, 300% or more and 500% or less. When the water retention is less than the lower limit, the cellulose nanofiber may not be sufficiently fine. On the other hand, when the water retention exceeds the above upper limit, the redispersibility of the obtained dried body containing cellulose nanofibers may be reduced. The water retention (%) of the cellulose nanofibers was determined by JAPAN TAPPI No. It is measured according to No. 26.

  The cellulose nanofiber preferably has a single peak in a pseudo particle size distribution curve measured by a laser diffraction method in an aqueous dispersion state. As described above, the cellulose nanofiber having one peak is sufficiently refined, and can exhibit good physical properties as the cellulose nanofiber. Further, the particle size (mode value) of the cellulose nanofiber which becomes the peak is preferably, for example, 5 μm or more and 25 μm or less. When the cellulose nanofiber has the above-mentioned size, various characteristics unique to the cellulose nanofiber can be exhibited more favorably. The “pseudo particle size distribution curve” means a curve showing a volume-based particle size distribution measured using a particle size distribution measuring device (for example, a laser diffraction / scattering type particle size distribution measuring device manufactured by Seisin Corporation).

(Step (A))
In the step (A), a mixed solution is obtained by mixing a dispersion containing cellulose nanofibers and hydroxy acids.

  The dispersion contains cellulose nanofibers and water as a dispersion medium. However, other components may be further contained as long as the effects of the present invention are not impaired. The content of the cellulose nanofibers in this dispersion is not particularly limited, but may be, for example, 0.1% by mass or more and 5% by mass or less.

  Hydroxy acids refer to hydroxy acids and salts thereof, and may be used as a mixture of two or more. The hydroxy acid is also called a hydroxycarboxylic acid, an oxyacid, or the like, and refers to a carboxylic acid having a hydroxy group (—OH). Examples of the hydroxy acid include glycolic acid, lactic acid, tartronic acid, glyceric acid, hydroxybutyric acid, malic acid, tartaric acid, citric acid, isocitric acid, mevalonic acid, pantoic acid, ricinoleic acid, and other aliphatic hydroxy acids, salicylic acid, vanillic acid, Aromatic hydroxy acids such as gallic acid can be mentioned.

  Examples of the hydroxy acid salt include alkali metal salts such as sodium salt and potassium salt, alkaline earth metal salts such as calcium salt, and other copper salts and ammonium salts. Of these, alkali metal salts are preferred, and sodium salts are more preferred. By using such a hydroxy acid salt, the dispersing performance due to the electrostatic action in water can be more suitably exhibited.

  As the hydroxy acids, a hydroxy acid salt is preferable since the obtained dried product can exhibit good dispersibility. Similarly, from the viewpoint that the obtained dried product can exhibit good dispersibility, aliphatic hydroxy acids and salts thereof are preferable, and citric acid, isocitric acid, tartaric acid, malic acid, and salts thereof are more preferable. , Citric acid, tartaric acid, malic acid or salts thereof are more preferred, citric acid and its salts are even more preferred, and citrate is particularly preferred. In addition, it is preferable to include citric acid, monosodium citrate, disodium citrate, trisodium citrate, and a combination thereof from the viewpoint of exhibiting good dispersibility.

  The number of hydroxy groups contained in the hydroxy acid or a salt thereof is preferably one or more and three or less, more preferably one. The number of carboxy groups contained in the hydroxy acid is preferably 2 or more and 4 or less, more preferably 3 or more. When the hydroxy acid has the number of hydroxy groups and carboxy groups in the above range, adhesion to the cellulose nanofiber surface and resilience in a water-dispersed state can be exhibited favorably, and the redispersion of salulose nanofibers Can be enhanced.

  The method of mixing the dispersion containing the cellulose nanofibers and the hydroxy acids is not particularly limited. Hydroxy acids may be added directly to the dispersion, or the dispersion and an aqueous solution of hydroxy acids may be mixed. However, from the viewpoint of uniformly mixing the cellulose nanofibers and the hydroxy acids, it is preferable to mix the above dispersion and an aqueous solution of hydroxy acids. At this time, the content (concentration) of the hydroxy acids in the aqueous solution of the hydroxy acids can be, for example, 0.1% by mass or more and 10% by mass or less. After the dispersion containing the cellulose nanofibers and the hydroxy acids are mixed, it is preferable to stir the mixture using a known stirrer or the like as necessary.

  In the mixed solution obtained by mixing, the mixing ratio between the cellulose nanofibers and the hydroxy acids is not particularly limited. As a minimum of content of hydroxy acids to 100 mass parts of cellulose nanofibers in a mixture, 0.1 mass part is preferred, 1 mass part is more preferred, 5 mass parts is still more preferred, and 10 mass parts is especially preferred. On the other hand, the upper limit is preferably 200 parts by mass, more preferably 150 parts by mass, and still more preferably 100 parts by mass. The upper limit may be 60 parts by mass or 25 parts by mass. When the content of the hydroxy acids is less than the above lower limit, the obtained dried product containing cellulose nanofibers may not exhibit good dispersibility. Conversely, when the content of the hydroxy acids exceeds the above upper limit, the amount of the hydroxy acids used increases, and the cost may be increased.

  The mixture contains water, cellulose nanofibers and hydroxy acids, but may further contain other components other than water, cellulose nanofibers and hydroxy acids as long as the effects of the present invention are not impaired. However, the content of other components in the mixture is preferably 10% by mass or less, more preferably 1% by mass or less.

  The solid content concentration in the mixed solution is not particularly limited, but the lower limit is preferably 0.1% by mass, more preferably 0.5% by mass. On the other hand, the upper limit is preferably 5% by mass, and more preferably 3% by mass. If the solid content is less than the above lower limit, the drying efficiency tends to decrease. On the other hand, if the solid content exceeds the upper limit, it may be difficult to prepare a mixed solution.

(Step (B))
In the step (B), the mixed solution obtained in the step (A) is dried. Thereby, a dried product containing cellulose nanofibers can be obtained. In such a drying step, it is presumed that hydroxy acids are precipitated on the surface of the cellulose nanofiber, and a cellulose nanofiber-containing dried product in which each cellulose nanofiber is coated with the hydroxy acid can be obtained. The thus-obtained dried body containing cellulose nanofibers can exhibit high redispersibility, in which hydrogen bonds between the cellulose nanofibers are inhibited by hydroxy acids.

  The method for drying the mixed liquid is not particularly limited, and the drying can be performed by a known method such as natural drying, heat drying, vacuum drying, freeze drying, or spray drying. In addition, the spray-drying can obtain a dried product containing cellulose nanofibers in the form of particles having particularly excellent redispersibility.

  The lower limit of the drying temperature in the step (B) is preferably 80 ° C, more preferably 90 ° C. On the other hand, the upper limit is preferably 150 ° C., more preferably 120 ° C. If the drying temperature is lower than the lower limit, it may be difficult to obtain a sufficiently dried cellulose nanofiber-containing dried product. Conversely, when the drying temperature exceeds the upper limit, the cellulose nanofibers may be colored by heat.

<Dried body containing cellulose nanofiber>
A dried product containing cellulose nanofibers according to an embodiment of the present invention is a dried product containing cellulose nanofibers containing cellulose nanofibers obtained by fibrillating pulp, and further includes a hydroxy acid. The cellulose nanofiber-containing dried product can be used as a redispersed liquid by mixing with water, as described later in detail. The dried body containing cellulose nanofibers can be suitably obtained by the above-described method for producing a dried body containing cellulose nanofibers.

  Specific examples and preferred examples of the cellulose nanofibers contained in the dried cellulose nanofiber-containing body and the method for producing the same are the same as those exemplified in the description of the method for producing the cellulose nanofiber-containing dried body. Further, specific examples and preferred examples of the hydroxy acids contained in the dried cellulose nanofiber-containing product are the same as those exemplified in the description of the method for producing the dried cellulose nanofiber-containing product.

  As a minimum of content of a hydroxy acid to 100 mass parts of cellulose nanofibers in the dried cellulose nanofiber content, 0.1 mass part is preferred, 1 mass part is more preferred, 5 mass parts is still more preferred, and 10 mass parts. Is particularly preferred. On the other hand, the upper limit is preferably 200 parts by mass, more preferably 150 parts by mass, and still more preferably 100 parts by mass. The upper limit may be 60 parts by mass or 25 parts by mass. When the content of the hydroxy acids is less than the above lower limit, good dispersibility may not be exhibited. Conversely, when the content of the hydroxy acids exceeds the above upper limit, the content of the cellulose nanofiber relatively decreases, and the use or function may be limited.

  The moisture content (water content) of the dried body containing cellulose nanofibers is, for example, less than 50% by mass, preferably 20% by mass or less, and more preferably 10% by mass or less. When the water content is equal to or less than the upper limit, energy consumption in transportation or the like can be further reduced, and handling properties and storage properties are also improved. Further, the risk of steam explosion during melt-kneading with a resin can be reduced. The lower limit of the moisture content of the dried cellulose nanofiber-containing product may be substantially 0% by mass, but may be 0.1% by mass, 1% by mass, or 3% by mass.

  The shape of the dried body containing cellulose nanofibers is not particularly limited, but is preferably a particle shape or a film shape. When the dried product containing cellulose nanofibers is in the form of particles or a film, the dispersibility in water can be further increased. When the dried body containing cellulose nanofibers is in the form of particles, the average particle diameter can be, for example, 1 μm or more and 5 mm or less. “Average particle size” is calculated based on JIS-Z-8819-2 (2001) based on the particle size distribution measured by the laser diffraction / scattering method based on JIS-Z-8815 (2013). Volume-based integrated distribution is 50%. When the dried body containing cellulose nanofibers is in the form of a film, the average thickness can be, for example, 0.1 μm or more and 1 mm or less.

  The dried body containing cellulose nanofibers is substantially composed of cellulose nanofibers and hydroxy acids. The dried cellulose nanofiber-containing product may contain components (solid content) other than the cellulose nanofiber and the hydroxy acids as long as the effects of the present invention are not impaired. The content of the other components (solid content) other than the cellulose nanofibers and the hydroxy acids in the dried cellulose nanofiber-containing product is 10 parts by mass when the total amount of the cellulose nanofibers and the hydroxy acids is 100 parts by mass. Or less, more preferably 5 parts by mass or less. When the content of other components exceeds the above lower limit, these components may affect the dispersibility of the cellulose nanofiber.

<Production method of cellulose nanofiber dispersion>
The method for producing a cellulose nanofiber dispersion according to an embodiment of the present invention includes a step of mixing the dried cellulose nanofiber-containing product with water. According to the method for producing a cellulose nanofiber dispersion, a high-dispersion, high-concentration cellulose nanofiber dispersion can be easily obtained because a dried cellulose nanofiber-containing product having high dispersibility is used. In addition, when mixing the dried body containing cellulose nanofibers and water, it is preferable to stir as necessary.

  The stirring method is not particularly limited, and a known method such as stirring using a stirring blade or a rotor or stirring by ultrasonic waves can be used. Examples of the stirrer used in the stirring include an automatic or manual shaker, a magnetic stirrer, an ultrasonic vibrator, a stirrer having various other stirrers, a media mill such as a bead mill, a static stirrer such as a static mixer, and the like. Can be mentioned.

  The concentration of the cellulose nanofiber in the obtained cellulose nanofiber dispersion is not particularly limited, but the lower limit is, for example, 0.1% by mass, and preferably 0.5% by mass. On the other hand, the upper limit is, for example, 5% by mass, and can be 3% by mass.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

<Evaluation method>
Various physical properties of Examples and Comparative Examples were measured according to the following evaluation methods.

(Pseudo particle size distribution curve)
In accordance with ISO-13320 (2009), a curve showing a volume-based particle size distribution was measured using a particle size distribution measuring device ("Laser diffraction / scattering type particle size distribution measuring device" manufactured by Seishin Enterprise Co., Ltd.), and the number of peaks was measured. I counted.

(Water retention (%))
The water retention (%) of the cellulose nanofibers was measured according to JAPAN TAPPI No. 26: 2000.

[Example 1]
The raw pulp (LBKP: water content: 98% by mass) was preliminarily beaten for 2 hours and 30 minutes using a Niagara beater. Next, fibrillation treatment was performed twice using a stone mill type dispersing machine (“Super Mass Colloider” of Masuko Sangyo Co., Ltd.) to obtain an aqueous dispersion of cellulose nanofibers (concentration: 2% by mass). The cellulose nanofibers contained in this aqueous dispersion had one peak in the pseudo particle size distribution in the particle size distribution measurement using laser diffraction, and the water retention was 350% or more.

  25 g of the obtained aqueous dispersion of cellulose nanofibers having a concentration of 2% by mass and an aqueous solution of sodium citrate having a concentration of 2% by mass were mixed and stirred at 1200 rpm for 60 minutes using a magnetic stirrer to obtain a mixed solution. The mixing ratio (mass ratio) between cellulose nanofiber (CNF) and sodium citrate is 50:50. This mixed solution was dried at 105 ° C. for 6 hours to obtain a dried film containing cellulose nanofibers. The water content of the obtained cellulose nanofiber was 9.8% by mass.

[Examples 2 to 12, Comparative Example 1]
The compounds of Examples 2 to 12 and Comparative Example 1 were used in the same manner as in Example 1 except that the compounds shown in Table 1 were used as the hydroxy acids and the mixing ratio with the cellulose nanofiber was set to the ratio shown in Table 1. A dried product containing cellulose nanofibers was obtained. In Comparative Example 1, an aqueous dispersion of cellulose nanofibers was dried as it was without mixing hydroxy acids, to obtain a dried product containing cellulose nanofibers.

<Evaluation>
Each dried cellulose nanofiber-containing product obtained was added to water so that the solid content concentration was 2% by mass, and then stirred at 800 rpm for 60 minutes using a magnetic stirrer to redisperse each cellulose nanofiber. A liquid was obtained. After allowing the obtained redispersion liquid to stand for 10 minutes, the concentration of the supernatant was measured by the following method. Table 1 shows the measurement results.

(concentration(%))
1 g of a redispersion liquid of cellulose nanofibers (a supernatant liquid when a precipitate is present) is collected and transferred to a container. After drying at 105 ° C. for 2 hours, the mass was measured with an electronic balance to calculate the concentration. This was performed twice, and the average value was determined.

  As shown in Table 1, the concentration of the supernatant of the redispersion liquid obtained from the dried cellulose nanofiber-containing products of Examples 1 to 12 is higher than that of Comparative Example 1, indicating that the redispersibility is excellent. . In particular, in Examples 1 to 3 using sodium citrate, the concentration was very close to 2% by mass or 2% by mass, and it was found that the cellulose nanofibers were almost completely redispersed.

  INDUSTRIAL APPLICABILITY The dried cellulose nanofiber-containing product of the present invention can be used as a cellulose nanofiber having excellent dispersibility in water and excellent in handleability for use of conventional cellulose nanofibers. Specifically, the dried body containing cellulose nanofibers of the present invention includes a filter material, a filter aid, a base material of an ion exchanger, a filler for a chromatographic analyzer, a filler for blending a resin and rubber, and a blend of cosmetics. It can be suitably used in many applications such as agents, viscosity retainers for foods and paints, tougheners for food raw materials, moisture retainers, food stabilizers, low-calorie additives, and emulsion stabilization aids.

Claims (7)

Cellulose nanofiber-containing dried body containing cellulose nanofiber obtained by defibrating plant material,
Further containing hydroxy acids,
A said hydroxy acids are hydroxy acids, salts or mixtures thereof arsenide Dorokishi acid,
Is at least one said hydroxy acid is glycolic acid, lactic acid, tartronic acid, glyceric acid, hydroxybutyric acid, malic acid, tartaric acid, citric acid, isocitric acid, mevalonic acid is selected from either Ranaru group pantoic acid and ricinoleic acid A dried product containing cellulose nanofibers, characterized in that:   2. The dried cellulose nanofiber-containing product according to claim 1, wherein the content of the hydroxy acid is 0.1 to 200 parts by mass based on 100 parts by mass of the cellulose nanofiber. 3.   The dried product containing cellulose nanofibers according to claim 1 or 2, wherein the hydroxy acids are hydroxy acid salts.   The cellulose nanofiber-containing dried product according to claim 1 or 2, wherein the hydroxy acids are citric acid, tartaric acid, malic acid, or a salt thereof.   The cellulose nanofiber-containing dried product according to any one of claims 1 to 4, wherein the moisture content is less than 50% by mass. A step of obtaining a mixed liquid by mixing a dispersion liquid containing cellulose nanofibers obtained by defibrating pulp and hydroxy acids, and a step of drying the mixed liquid,
A said hydroxy acids are hydroxy acids, salts or mixtures thereof arsenide Dorokishi acid,
Is at least one said hydroxy acid is glycolic acid, lactic acid, tartronic acid, glyceric acid, hydroxybutyric acid, malic acid, tartaric acid, citric acid, isocitric acid, mevalonic acid is selected from either Ranaru group pantoic acid and ricinoleic acid A method for producing a dried body containing cellulose nanofibers. A method for producing a cellulose nanofiber dispersion, comprising a step of mixing the dried cellulose nanofiber-containing dried product according to any one of claims 1 to 5 with water.