JP6775296B2 - Cellulose nanofiber-containing dried product and its production method, and cellulose nanofiber dispersion liquid production method - Google Patents

Description

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

In recent years, nanotechnology has been attracting attention for the purpose of refining substances to the nanometer level and obtaining new physical properties different from the conventional properties of substances. Cellulose nanofibers produced from pulp, which is a cellulosic raw material, by chemical treatment, crushing treatment, etc. are excellent in strength, elasticity, thermal stability, etc. It is expected to be used for industrial applications such as fillers for chromatographic analysis equipment, fillers for blending resins and rubbers, and blending agents for cosmetics such as lipsticks, powder cosmetics, and emulsified cosmetics. There is. In addition, since cellulose nanofibers have excellent water-based dispersibility, they are viscosity-retaining agents for foods, cosmetics, paints, etc., fortifiers for food raw material fabrics, water-retaining agents, food stabilizers, low-calorie additives, and emulsification. It is expected to be used in many applications such as stabilizing aids.

Cellulose nanofibers are usually obtained by refining pulp or the like in an aqueous dispersion state. Therefore, the obtained cellulose nanofibers are in a water-dispersed state, and such a dispersion liquid of cellulose nanofibers requires a large amount of energy during transportation. In addition, moisture-containing cellulose nanofibers can induce a steam explosion during melt-kneading with a resin. Therefore, considering commercialization, it is important to dry the dispersion of cellulose nanofibers. However, when the cellulose nanofibers are dried, the cellulose nanofibers strongly aggregate due to hydrogen bonds between the cellulose nanofibers. Therefore, when the dried cellulose nanofibers are redispersed in water, there is an inconvenience that the dispersibility does not sufficiently return to the state before drying. Further, when the cellulose nanofibers are simply dried, the obtained dried product may be discolored (colored). A dried product of cellulose nanofibers that has been discolored is not preferable because it causes unwanted coloring when used as an additive.

On the other hand, as a technique for improving the redispersibility of the cellulose nanofibers with respect to the dispersion medium, a step of mixing the cellulose nanofibers having a carboxy group and a redispersion accelerator to obtain a gel-like body, and the gel-like body and organic A method for producing a cellulose nanofiber dispersion liquid, which comprises a step of mixing a sex liquid and a dispersant to redisperse the cellulose nanofibers, has been proposed (see JP-A-2014-118521). However, this technique does not allow the cellulose nanofibers to dry sufficiently to form a gel. In addition, cellulose nanofibers having a carboxy group generated by oxidation treatment are used, and such cellulose nanofibers have disadvantages such as long drying time, low heat resistance, and uneconomical properties. .. Further, it is known that cellulose nanofibers having a carboxy group generate a very small amount of aldehyde groups and ketone groups as a side reaction in the production process, and the aldehyde groups and ketone groups are colored yellow by heating. However, in the above technique, the presence or absence of coloring of the obtained dried product is not considered at all.

Further, as a technique for obtaining a dried product of bacterial cellulose having high redispersibility, a method has been proposed in which a hydrophilic liquid or solid such as glycerin is added to an aqueous suspension containing bacterial cellulose and then dehydrated and dried. See JP-A-9-165402). However, bacterial cellulose is cellulose produced by microorganisms and has different physical properties from cellulose nanofibers obtained by defibrating pulp. Therefore, even if this technique for drying bacterial cellulose is diverted to cellulose nanofibers, the same effect may not always occur.

In addition, as a method for drying cellulose nanofibers, a freeze-drying method, a critical point drying method, a method of drying after substitution treatment with an organic solvent, and the like have been proposed (see JP-A-6-233691). However, the freeze-drying method and the critical point drying method require a large amount of energy. Further, the method of substituting with an organic solvent also requires the use of a non-polar solvent in order to weaken the hydrogen bond, and is not preferable from the viewpoint of efficiency and economy.

Japanese Unexamined Patent Publication No. 2014-118521 JP-A-9-165402 Japanese Unexamined Patent Publication No. 6-233691

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

The invention made to solve the above problems is a cellulose nanofiber-containing dry product containing cellulose nanofibers having a carboxy group content of 0.1 mmol / g or less and glycerin or a glycerin derivative.

Since the cellulose nanofiber-containing dried product contains glycerin or a glycerin derivative (hereinafter, also referred to as "glycerin") together with the cellulose nanofiber, it is excellent in dispersibility in water. The reason for this is not clear, but it is conceivable that the adhesion of glycerins to the surface of the cellulose nanofibers weakens the hydrogen bonds between the cellulose nanofibers. Further, by using cellulose nanofibers having a small amount of carboxy groups and glycerins, discoloration is less likely to occur during drying, and a dried product with less discoloration can be obtained. Furthermore, since the combination of cellulose nanofibers having a small amount of carboxy groups and glycerins is not an ionic compound with each other, they can be uniformly mixed, and as a result, the redispersibility is enhanced.

The content of glycerin or a glycerin derivative with respect to 100 parts by mass of the cellulose nanofibers is preferably 0.1 parts by mass or more and 200 parts by mass or less. By setting the content of glycerins in the above range, it is possible to further improve the dispersibility while suppressing the high cost.

Another invention made to solve the above problems is a step of obtaining a mixed solution by mixing a dispersion of cellulose nanofibers having a carboxy group content of 0.1 mmol / g or less with an aqueous solution of glycerin or a glycerin derivative. , And a method for producing a cellulose nanofiber-containing dried product, which comprises a step of drying the mixed solution. According to the production method, a cellulose nanofiber-containing dried product having excellent dispersibility in water and less discoloration can be obtained by a simple method. In the production method, since the dispersion liquid of cellulose nanofibers and the aqueous solution of glycerins are mixed, a dried product in which the cellulose nanofibers and glycerins are uniformly mixed can be obtained.

Yet another invention made to solve the above problems is a method for producing a cellulose nanofiber dispersion liquid, which comprises a step of mixing the cellulose nanofiber-containing dry matter and water. According to the method for producing the cellulose nanofiber dispersion liquid, a cellulose nanofiber dispersion liquid having high dispersibility, high concentration and less discoloration can be easily obtained.

The cellulose nanofiber-containing dried product of the present invention has excellent dispersibility in water and is less discolored. According to the method for producing a cellulose nanofiber-containing dried product of the present invention, a cellulose nanofiber-containing dried product having excellent dispersibility in water and having no discoloration can be obtained. According to the method for producing a cellulose nanofiber dispersion liquid of the present invention, a cellulose nanofiber dispersion liquid having high dispersibility, high concentration and less discoloration can be easily obtained.

Hereinafter, a method for producing a cellulose nanofiber-containing dry matter, a cellulose nanofiber-containing dry matter, and a method for producing a cellulose nanofiber dispersion liquid according to an embodiment of the present invention will be described in detail in order.

<Manufacturing method of dry body containing cellulose nanofibers>
The method for producing a cellulose nanofiber-containing dried product according to an embodiment of the present invention is
A step (A) of obtaining a mixed solution by mixing a dispersion of cellulose nanofibers having a carboxy group content of 0.1 mmol / g or less with an aqueous solution of glycerin or a glycerin derivative, and a step of drying the mixed solution (B). )
To be equipped.

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

Examples of pulp used as a raw material for cellulose nanofibers include broadleaf kraft pulp (LKP) such as broadleaf bleached kraft pulp (LBKP) and broadleaf bleached kraft pulp (LUKP), coniferous bleached kraft pulp (NBKP), and conifer unbleached kraft pulp. (NUKP) and other coniferous kraft pulp (NKP) and other chemical pulp;
Stone Grand Pulp (SGP), Pressurized Stone Grand Pulp (PGW), Refiner Grand Pulp (RGP), Chemi Grand Pulp (CGP), Thermo Grand Pulp (TGP), Grand Pulp (GP), Thermo Mechanical Pulp (TMP), Mechanical pulp such as Chemithermo Mechanical Pulp (CTMP), Bleached Thermomechanical Pulp (BTMP);
Waste paper pulp manufactured from used tea paper, used kraft envelopes, used magazines, used newspapers, used leaflets, used office paper, used corrugated paper, used white paper, Kent used paper, imitation used paper, ground ticket used paper, used paper, etc.;
Examples thereof include deinked pulp (DIP) obtained by deinking used paper pulp. These may be used alone or in combination of a plurality of types 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 being low in impurities.

Other plant raw materials include pulp obtained from linter pulp, hemp, bagasse, kenaf, stipa tenacissima, bamboo, rice husks, straw and the like. In addition, wood, hemp, bagasse, kenaf, esparto grass, bamboo, rice husk, straw, etc., which are raw materials for pulp, can be directly used as raw materials for plants. Hereinafter, a method for producing cellulose nanofibers when pulp is used as a plant raw material will be described, but cellulose nanofibers can also be obtained by the same method when using a plant raw material other than pulp.

The method for producing cellulose nanofibers is not particularly limited as long as the effects of the present invention are not impaired, and known methods can be used. For example, the pulp in an aqueous dispersion state may be subjected to defibration by mechanical treatment, or may be subjected to defibration by chemical treatment such as enzyme treatment or acid treatment, but defibration by mechanical treatment is preferable. .. By defibrating the pulp by mechanical treatment, cellulose nanofibers can be obtained more easily and surely, and the dispersibility of the dried product obtained by using glycerins can be further enhanced, resulting in discoloration. It is also possible to obtain less dried material.

Examples of the defibration method by mechanical treatment include a grinder method for grinding pulp between rotating grindstones, an opposed collision method using a high-pressure homogenizer, and a pulverization method using a ball mill, a roll mill, a cutter mill, and the like. Usually, the defibration treatment is repeated until the cellulose nanofibers obtained by defibrating the pulp have a desired size.

The pulp may be subjected to preliminary beating before defibration. The pre-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 proceed with defibration step by step. In particular, a grinder that pre-beats unbeaten raw material pulp to 30% or less of the starting material in advance using a so-called viscous beating facility such as Naiyagara beater, and then grinds it between rotating grindstones. It is preferable to carry out the defibration treatment until cellulose nanofibers are obtained by the method.

In addition, the pulp may be chemically pretreated before defibration. Examples of this chemical pretreatment include hydrolysis treatment using an acid such as sulfuric acid or an enzyme. By applying the chemical pretreatment in this way, cellulose nanofibers can be efficiently obtained by mechanical or chemical defibration treatment.

The cellulose nanofibers used in the method for producing the cellol nanofiber-containing dried product have a carboxy group content of 0.1 mmol / g or less. As described above, by using cellulose nanofibers having low ionicity in which the carboxy group is substantially not modified, it is possible to enhance uniform mixing with nonionic or low ionic glycerins. Further, the discoloration of the obtained dried body can be reduced or the discoloration can be completely eliminated. Furthermore, by using cellulose nanofibers in which the carboxy group is substantially unmodified, drying can be performed relatively easily, the heat resistance of the molded product using the cellulose nanofibers is increased, and the economy is excellent. There are advantages such as.

The carboxy group is introduced into the raw material pulp by using surface oxidation by an N-oxyl compound or the like and various oxidizing agents. Therefore, cellulose nanofibers having a carboxy group content of 0.1 mmol / g or less can be obtained by controlling surface oxidation with an N-oxyl compound or the like as a pretreatment or oxidation treatment with an oxidizing agent. The upper limit of the carboxy group content of the cellulose nanofibers is preferably 0.05 mmol / g. On the other hand, the lower limit may be 0 mmol / g, but may be 0.0001 mmol / g. The carboxy group content of the cellulose nanofibers can be determined by neutralization titration. When the amount of carboxy groups does not substantially change before and after the defibration treatment, such as when the pulp defibration treatment is performed only by mechanical treatment, the carboxy group content of the cellulose nanofibers is the value before the defibration treatment. It is substantially the same as the carboxy group content of pulp. That is, in this case, the carboxy group content of the cellulose nanofibers can be determined by neutralization titration or the like on the pulp before the defibration treatment.

The water retention of the cellulose nanofibers is preferably 250% or more and 500% or less, for example. If the water retention level is less than the above lower limit, the cellulose nanofibers may not be sufficiently finely divided. On the other hand, if the water retention level exceeds the above upper limit, the redispersibility of the obtained cellulose nanofiber-containing dried product may decrease. The water retention rate (%) of the cellulose nanofibers is based on JAPAN TAPPI No. Measured according to 26.

The cellulose nanofibers preferably have a single peak in the pseudo-particle size distribution curve measured by laser diffraction in an aqueous dispersion. As described above, the cellulose nanofiber having one peak has been sufficiently miniaturized, and can exhibit good physical properties as the cellulose nanofiber. Further, the particle size (mode) of the cellulose nanofibers having this peak is preferably, for example, 5 μm or more and 25 μm or less. When the cellulose nanofibers have the above size, various characteristics peculiar to the cellulose nanofibers can be exhibited better. 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 Seishin Enterprise Co., Ltd.).

(Step (A))
In the step (A), a mixed solution is obtained by mixing a dispersion of cellulose nanofibers and an aqueous solution of glycerins.

The dispersion liquid contains cellulose nanofibers and a dispersion medium for cellulose nanofibers. The dispersion medium is usually water. The dispersion may further contain other components 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 can be, for example, 0.1% by mass or more and 5% by mass or less.

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

The glycerin derivative among glycerins refers to a compound obtained from glycerin. Examples of the glycerin derivative include glycerin esters such as glycerol monoacetate, glycerol diacetate, glycerol triacetate, glycerol tributyrate, and glycerol ether acetate, and polyglycerin obtained by polymerizing glycerin.

As the glycerins, glycerin is preferable because the obtained dried product can exhibit good dispersibility.

By mixing the dispersion liquid of cellulose nanofibers and the aqueous solution of glycerins, the cellulose nanofibers and glycerins can be uniformly mixed. After mixing, it is preferable to stir the mixed solution using a known stirrer or the like, if necessary.

In the mixed solution obtained by mixing, the mixing ratio of the cellulose nanofibers and the glycerins is not particularly limited. The lower limit of the content of glycerins with respect to 100 parts by mass of the cellulose nanofibers in the mixed solution is preferably 0.1 parts by mass, more preferably 1 part by mass, further preferably 10 parts by mass, further preferably 50 parts by mass, and 80 parts by mass. Parts by mass are particularly preferred. On the other hand, as the upper limit, 200 parts by mass is preferable, 150 parts by mass is more preferable, and 120 parts by mass is further preferable. When the content of glycerins is less than the above lower limit, the obtained cellulose nanofiber-containing dried product may not exhibit good dispersibility. On the contrary, when the content of glycerins exceeds the above upper limit, the amount of glycerins used may increase and the cost may increase.

The mixed solution contains water, cellulose nanofibers and glycerins, but may further contain other components other than water, cellulose nanofibers and glycerins as long as the effects of the present invention are not impaired. However, the content of other components in the mixed solution 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, as the upper limit, 5% by mass is preferable, and 3% by mass is more preferable. When the solid content concentration is less than the above lower limit, the drying efficiency tends to decrease. On the other hand, if the solid content concentration exceeds the above upper limit, it may be difficult to prepare the mixed solution.

(Step (B))
In the step (B), the mixed solution obtained in the above step (A) is dried. Thereby, a cellulose nanofiber-containing dried product can be obtained. In such a drying step, it is presumed that glycerins are precipitated on the surface of the cellulose nanofibers, and a cellulose nanofiber-containing dried product in which each cellulose nanofiber is coated with the glycerins can be obtained. The cellulose nanofiber-containing dried product thus obtained can exhibit high redispersibility by inhibiting hydrogen bonds between the cellulose nanofibers by glycerins. Further, the cellulose nanofiber-containing dried product thus obtained is a dried product having little discoloration, preferably substantially no discoloration.

The drying method of the mixed solution is not particularly limited, and can be carried out by known methods such as natural drying, heat drying, vacuum drying, freeze drying, and spray drying. By spray drying, a particulate cellulose nanofiber-containing dried product having particularly excellent redispersibility can be obtained.

As the lower limit of the drying temperature in the step (B), 80 ° C. is preferable, and 90 ° C. is more preferable. On the other hand, as the upper limit, 160 ° C. is preferable, and 120 ° C. is more preferable. If the drying temperature is less than the above lower limit, it may be difficult to obtain a sufficiently dried cellulose nanofiber-containing dried product. On the contrary, when the drying temperature exceeds the above upper limit, the cellulose nanofibers may be discolored by heat.

The drying time in the step (B) varies depending on the drying temperature and the like, but can be, for example, 1 hour or more and 24 hours or less.

<Dry body containing cellulose nanofibers>
The cellulose nanofiber-containing dry matter according to the embodiment of the present invention is a cellulose nanofiber-containing dry matter containing cellulose nanofibers having a carboxy group content of 0.1 mmol / g or less and glycerin or a glycerin derivative. The cellulose nanofiber-containing dried product can be used as a dispersion liquid that is mixed with water and redispersed, as will be described in detail later. The cellulose nanofiber-containing dried product can be preferably obtained by the above-mentioned method for producing a cellulose nanofiber-containing dried product.

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

The lower limit of the content of glycerins with respect to 100 parts by mass of the cellulose nanofibers in the cellulose nanofiber-containing dried product is preferably 0.1 parts by mass, more preferably 1 part by mass, further preferably 10 parts by mass, and 50 parts by mass. Is more preferable, and 80 parts by mass is particularly preferable. On the other hand, as the upper limit, 200 parts by mass is preferable, 150 parts by mass is more preferable, and 120 parts by mass is further preferable. If the content of glycerins is less than the above lower limit, good dispersibility may not be exhibited. On the contrary, when the content of glycerins exceeds the above upper limit, the content of cellulose nanofibers may be relatively lowered, and the use and function may be limited.

The water content (water content) of the cellulose nanofiber-containing dried product is, for example, less than 80% by mass, preferably 50% by mass or less, more preferably 20% by mass or less, still more preferably 15% by mass or less. 10% by mass or less is particularly preferable. When the water content is not more than the above upper limit, energy consumption in transportation and the like can be further reduced, and handleability and storability are also improved. In addition, the risk of steam explosion during melt kneading with resin can be reduced. The lower limit of the water content of the cellulose nanofiber-containing dried 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 cellulose nanofiber-containing dried product is not particularly limited, but it is preferably in the form of particles or a film. When the cellulose nanofiber-containing dried product is in the form of particles or a film, the dispersibility in water can be further enhanced. When the cellulose nanofiber-containing dried product is in the form of particles, the average particle size can be, for example, 1 μm or more and 5 mm or less. The "average particle size" is calculated in accordance with JIS-Z-8819-2 (2001) based on the particle size distribution measured by the laser diffraction / scattering method in accordance with JIS-Z-8815 (2013). Refers to the value at which the volume-based integrated distribution is 50%. When the cellulose nanofiber-containing dried product is in the form of a film, the average thickness thereof can be, for example, 0.1 μm or more and 1 mm or less.

The cellulose nanofiber-containing dried product is substantially composed of cellulose nanofibers and glycerins. The cellulose nanofiber-containing dried product may contain components (solid content) other than cellulose nanofibers and glycerins as long as the effects of the present invention are not impaired. The content of the components (solid content) other than the cellulose nanofibers and glycerins in the cellulose nanofiber-containing dried product is 10 mass by mass when the total amount of the cellulose nanofibers and glycerins is 100 parts by mass. It is preferably parts or less, and 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 nanofibers.

<Manufacturing method of cellulose nanofiber dispersion>
The method for producing a cellulose nanofiber dispersion liquid according to an embodiment of the present invention includes a step of mixing the cellulose nanofiber-containing dry matter and water. According to the method for producing the cellulose nanofiber dispersion liquid, since the cellulose nanofiber-containing dried product having high dispersibility is used, the cellulose nanofiber dispersion liquid having high dispersibility and high concentration can be easily obtained. In addition, a non-colored cellulose nanofiber dispersion can be obtained. The water to be mixed with the cellulose nanofiber-containing dried product may be pure water, an aqueous solution containing other components, or an aqueous dispersion. When mixing the cellulose nanofiber-containing dried product with water, it is preferable to stir as necessary.

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

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

The cellulose nanofiber-containing dried product of the present invention, a method for producing the same, and a method for producing a cellulose nanofiber dispersion are not limited to the above-described embodiment. For example, the cellulose nanofiber-containing dried product can be used by being redispersed in a dispersion medium other than water. Further, it may be redispersed in a mixed solvent of water and another dispersion medium. Examples of the dispersion medium other than water include alcohols, ethers, ketones, esters, hydrocarbons and the like. Further, the cellulose nanofiber-containing dried product can also be used by mixing it with, for example, a resin or the like.

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), measure the curve showing the volume-based particle size distribution using a particle size distribution measuring device (“Laser diffraction / scattering type particle size distribution measuring device” manufactured by Seishin Enterprise Co., Ltd.), and determine the number of peaks. I counted.

(Water retention (%))
The water retention rate (%) of the cellulose nanofibers is determined by JAPAN TAPPI No. Measured according to 26: 2000.

(Carboxylic acid group content (mmol / g))
The pulp before defibration (raw material pulp or oxidation-treated pulp) was precisely weighed, adjusted to pH 2.5 to 3.0, and automatically titrated with 0.05 mol / L sodium hydroxide. Conductivity measurement (measurement at room temperature using a conductivity device "pH / ion / EC / DO meter MN-60R" manufactured by Toa DKK Corporation) was performed, and the range in which the conductivity did not change was defined as the amount of carboxy groups.

[Example 1]
The raw material pulp (LBKP: 98% by mass of water content) was pre-beaten over 2 hours and 30 minutes using a Niagara beater. Next, defibration treatment using a stone mill type disperser (“Super Mascoroider” manufactured by Masuyuki Sangyo Co., Ltd.) was performed twice 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 of the particle size distribution measurement using laser diffraction, and the water retention degree was 350% or more. The content of the carboxy group was 0.05 mmol / g.

98 g of water and 2 g of glycerin were mixed and stirred for 60 minutes at 600 rpm using a magnetic stirrer to obtain an aqueous glycerin solution.

25 g of the obtained aqueous dispersion of cellulose nanofibers having a concentration of 2% by mass and 25 g of an aqueous solution of glycerin having a concentration of 2% by mass were mixed and stirred for 60 minutes at 1200 rpm using a magnetic stirrer to obtain a mixed solution. The mixing ratio (mass ratio) of cellulose nanofibers (CNF) and glycerin is 100: 100. This mixed solution was dried at 105 ° C. for 6 hours to obtain a film-shaped dried product containing cellulose nanofibers. The water content of the obtained cellulose nanofibers was 5.0% by mass.

[Examples 2 to 3, Comparative Examples 1 to 9, 11]
The same procedure as in Example 1 was carried out except that the compounds shown in Table 1 were used as the redispersant (glycerins or alternative components thereof) and the mixing ratio with the cellulose nanofibers was the ratio shown in Table 1. Cellulose nanofiber-containing dried compounds of Examples 2 to 3 and Comparative Examples 1 to 9 and 11 were obtained. In Comparative Example 11, a dry product containing cellulose nanofibers was obtained by drying the aqueous dispersion of cellulose nanofibers as it was without mixing glycerins or their alternative components.

[Comparative Example 10]
After mixing 10 g of raw material pulp (LBKP: 98% by mass of water), 0.16 g of TEMPO and 1.0 g of sodium bromide in 500 ml of water by dry mass, 25 ml of 12 mass% sodium hypochlorite aqueous solution is added. It was reacted. A 0.5 M (molar concentration) sodium hydroxide aqueous solution was added so that the pH did not drop below 10 during the reaction. The reaction was terminated when there was no change in pH, washed with water and filtered to obtain oxidized pulp. At this time, the amount of carboxy group introduced was 1.29 mmol / g. The obtained oxidized pulp was diluted to a solid content concentration of 2% by mass and dispersed at 12,000 rpm for 6 hours with a homomixer to obtain an aqueous dispersion of cellulose nanofibers (concentration: 2% by mass). The same as in Example 1 except that the aqueous dispersion of cellulose nanofibers having a carboxy group content of 1.29 mmol / g was used and the mixing ratio of the cellulose nanofibers and the redispersant was set to the ratio shown in Table 1. A dried cellulose nanofiber of Comparative Example 10 was obtained.

<Evaluation>
(concentration(%))
0.2 g of each obtained dried cellulose nanofiber-containing product was added to 9.8 g of water, and then the mixture was stirred with a magnetic stirrer for 60 minutes at 800 rpm to obtain a redispersion solution of each cellulose nanofiber. After allowing the obtained redispersion liquid to stand for 10 minutes, the concentration of the supernatant liquid was measured by the following method. The measurement results are shown in Table 1. In the completely redispersed state, the concentration is 2.0% by mass.

Collect 1 g of the redispersion liquid of cellulose nanofibers (the supernatant liquid if there is a precipitate) and transfer it to a container. After drying at 105 ° C. for 2 hours, the mass was measured with an electronic balance and the concentration was calculated. This was done twice and the average value was calculated.

(Presence or absence of discoloration)
Each of the obtained dried cellulose nanofiber-containing bodies was visually observed, and those that were colorless, transparent or white were evaluated as having no discoloration (coloring). On the other hand, those with yellow, brown, etc. were evaluated as having discoloration (coloring). The evaluation results are shown in Table 1.

As shown in Table 1, in Examples 1 to 3, cellulose nanofiber-containing dried products without discoloration were obtained. Further, the concentration of the supernatant of the redispersion liquid obtained from the cellulose nanofiber-containing dry matter of Examples 1 to 3 is higher than that of Comparative Examples 1 to 11, and it can be seen that the redispersibility is excellent.

The cellulose nanofiber-containing dried product of the present invention can be used as a conventional cellulose nanofiber for use as a cellulose nanofiber having excellent dispersibility in water, less discoloration, and excellent handleability. Specifically, the cellulose nanofiber-containing dry matter of the present invention contains a filter medium, a filter aid, a base material of an ion exchanger, a filler for a chromatography analysis device, a filler for blending resin and rubber, and a blending of cosmetics. It can be suitably used for many applications such as a viscosity preserving agent for foods and paints, a toughening agent for food raw material dough, a water preserving agent, a food stabilizer, a low calorie additive, and an emulsion stabilization aid.

Claims (4)

Cellulose nanofibers having a carboxy group content of 0.0001 mmol / g or more and 0.05 mmol / g or less ,
Containing with glycerin or glycerin derivatives,
The above cellulose nanofibers are made from hardwood bleached kraft pulp.
The cellulose nanofibers have a single peak in the pseudo particle size distribution curve measured by a laser diffraction method in an aqueous dispersion state, and the particle size (most frequent value) of the cellulose nanofibers at the peak is 5 μm or more and 25 μm or less. A dry product containing cellulose nanofibers. The cellulose nanofiber-containing dried product according to claim 1, wherein the content of glycerin or glycerin derivative with respect to 100 parts by mass of the cellulose nanofibers is 0.1 parts by mass or more and 200 parts by mass or less. A step of obtaining a mixed solution by mixing a dispersion of cellulose nanofibers having a carboxy group content of 0.0001 mmol / g or more and 0.05 mmol / g or less with an aqueous solution of glycerin or a glycerin derivative, and drying the mixed solution. Equipped with a process
The above cellulose nanofibers are made from hardwood bleached kraft pulp.
The cellulose nanofibers have a single peak in the pseudo particle size distribution curve measured by a laser diffraction method in an aqueous dispersion state, and the particle size (most frequent value) of the cellulose nanofibers at the peak is 5 μm or more and 25 μm or less. A method for producing a dry product containing cellulose nanofibers. A method for producing a cellulose nanofiber dispersion liquid, which comprises a step of mixing the cellulose nanofiber-containing dry matter according to claim 1 or claim 2 with water.