Cellulose nanofiber powder and its manufacturing method

Abstract

To provide a highly diffusible cellulose nanofiber powder suitable for pelletizing resin master batches. [Solution] The cellulose nanofiber powder contains 75 to 90 weight % cellulose nanofiber, 10 to 20 weight % polyethylene glycol, 0.05 to 2.0 weight % ester-type dialkylammonium salt, 0.8 to 2.0 weight % silicone oil, and 0.2 to 0.8 weight % carnauba wax.

Description

[Technical field]

[0001] The present invention relates to a cellulose nanofiber powder and a method for producing the same. In particular, the present invention relates to a cellulose nanofiber powder with high diffusivity that is suitable for pelletizing a resin master batch, and a method for producing such a cellulose nanofiber powder. [Background technology]

[0002] Cellulose nanofiber (also known as "Cellulose Nano Fiber"; hereafter sometimes referred to simply as "CNF") is a next-generation plant-derived material that is said to be five times stronger than steel with one-fifth the weight. The use of cellulose nanofiber in automobiles, home appliances, etc. is expected to reduce weight, improve energy efficiency, and make a significant contribution to global warming countermeasures. Toward the social implementation of CNF, the Ministry of Economy, Trade and Industry and the Ministry of Agriculture, Forestry and Fisheries are carrying out model projects in the fields of automobiles, home appliances, housing and building materials, etc. as a collaborative project, and are working to reduce CO 2 We are promoting the evaluation and verification of reduction effects and demonstration of solutions to related issues.

[0003] As one application example of cellulose nanofibers, Patent Document 1 (JP 2022-044861 A) discloses a hot melt adhesive containing cellulose nanofiber fibers, which comprises a resin that melts in the range of 70°C to 160°C and a powder of cellulose nanofiber fibers. It is disclosed that such a hot melt adhesive can instantly solidify the bonded portion, has excellent adhesiveness even at low temperatures, and can firmly hold the bonded surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-044861 A Summary of the Invention [Problem to be solved by the invention]

[0005] When adding CNF to resin products, the use of masterbatches containing CNF has been increasing in recent years. Since it is inconvenient to handle fine powders, there is an increasing demand for pelletizing masterbatches. In this case, it is possible to use a powder made by drying a water-dispersed slurry with a solid content of 1 to 8% by weight of CNF. However, the dried CNF powder remains hydrophobic and hygroscopic. If the CNF is hydrophobic, it will not diffuse well into the resin when directly added to a resin product compound or when combined with resin to make a masterbatch, and it will absorb moisture even in the input device such as a hopper feeder before processing, causing aggregation in the molten resin and causing problems.

[0006] The general method of manufacturing CNF masterbatch is to mix CNF powder with dispersants and additives, knead them into resin, and then manufacture pellets. However, if the CNF masterbatch itself has been treated to be water repellent, it is not hygroscopic and CNF is expected to disperse, but if the CNF itself has not been treated to give it diffusibility, fine fiber aggregates are often scattered in the resin matrix of the masterbatch. Therefore, when a CNF masterbatch manufactured in this way is added to the resin matrix compound during product molding, the CNF will aggregate again and not diffuse, which often affects the product, such as poor dispersion.

[0007] When the masterbatch is melted into the resin compound, the fine fiber aggregates do not break apart, but turn into larger fiber aggregates in the resin of the compound. The reason is that when the compound is molded into a product, it is always made with a focus on productivity, kneaded with mild shear force and high extrusion. Unlike the process of making a masterbatch, which is made by kneading with strong shear force, there is no molding process that disperses the small fiber aggregates remaining in the masterbatch.

[0008] The present invention has been completed in view of the above problems, and aims to provide a cellulose nanofiber powder with high diffusivity suitable for pelletizing a resin master batch in one embodiment. In another embodiment, the present invention aims to provide a method for producing such a cellulose nanofiber powder. [Means for solving the problem]

[0009] As a result of intensive research, the present inventors have found that the above problems can be solved by modifying the CNF. That is, in order to reliably diffuse the CNF of the masterbatch into the molten resin during molding of the resin compound, a CNF filler that is less likely to absorb moisture, is less likely to form fiber aggregates, and is easily loosened is required before the masterbatch is made. Therefore, by making the CNF hydrophobic, the hygroscopicity and tendency to easily bond with hydroxyl groups of the CNF added to the masterbatch are suppressed, and the CNF is less likely to aggregate in the resin matrix during the masterbatch processing, and further, the masterbatch is well diffused even when melted in the base compound of the product.

[0010] The present invention has been completed based on the above findings, and is exemplified below. [Aspect 1] A cellulose nanofiber powder comprising: A cellulose nanofiber powder comprising 75 to 90% by weight of cellulose nanofibers, 10 to 20% by weight of polyethylene glycol, 0.05 to 2.0% by weight of an ester-type dialkylammonium salt, 0.8 to 2.0% by weight of silicone oil, and 0.2 to 0.8% by weight of carnauba wax. [Aspect 2] 2. The cellulose nanofiber powder according to aspect 1, wherein the cellulose nanofibers have an average fiber length within the range of 0.1 μm to 3.0 μm. [Aspect 3] 3. The cellulose nanofiber powder according to aspect 1 or 2, wherein the average fiber diameter of the cellulose nanofibers is within a range of 0.5 nm to 10 nm. [Aspect 4] A method for producing cellulose nanofiber powder, comprising: a first process of supplying a cellulose nanofiber dispersion to a two-roll mill and rotating the two-roll mill to dry the cellulose nanofiber dispersion and obtain dried cellulose nanofibers; A second process of mixing the dried cellulose nanofibers with a melt containing silicone oil and carnauba wax to obtain a cellulose nanofiber powder. Including, The cellulose nanofiber dispersion is prepared so as to contain, relative to the total weight of the cellulose nanofiber powder, 75 to 90% by weight of cellulose nanofibers, 10 to 20% by weight of polyethylene glycol, 0.05 to 2.0% by weight of an ester-type dialkylammonium salt, and 10 to 20% by weight of isopropyl alcohol; The method, wherein the melt is prepared to contain 0.8 to 2.0% by weight of silicone oil and 0.2 to 0.8% by weight of carnauba wax relative to the total weight of the cellulose nanofiber powder. [Aspect 5] The method according to aspect 4, wherein the first treatment comprises heating the surface temperature of the two-roll mill to 100°C to 120°C. Effect of the Invention

[0011] According to one embodiment of the present invention, a cellulose nanofiber powder having high diffusivity suitable for pelletizing a resin master batch can be provided. According to another embodiment of the present invention, a method for producing such a cellulose nanofiber powder can be provided. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram for explaining the structure and operation principle of a two-roll mill in one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Next, the embodiments of the present invention will be described in detail. It should be understood that the present invention is not limited to the following embodiments, and that appropriate changes and improvements in the design may be made based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.

[0014] (1. Raw materials for cellulose nanofiber) Cellulose nanofibers are made by finely grinding cellulose, the main component of plant fibers, to nano size, and the main raw material is wood pulp (the raw material of paper). They are used primarily to reinforce resin materials and to prevent the shrinkage of resins at low temperatures. In the present invention, the raw material of the cellulose nanofibers is not particularly limited.

[0015] Since cellulose nanofibers are usually plant-derived materials, they are in the form of a slurry dispersed in water when extracted from the plant. The solid content is usually 1 to 8% by weight. For example, when producing a dispersant as a powder from a dispersion of cellulose nanofibers, it is necessary to first remove only the water from the aqueous dispersion of cellulose nanofibers dispersed in water to extract the cellulose nanofibers alone. It is also possible to extract the cellulose nanofibers alone again from a re-dispersion in which the cellulose nanofibers alone are re-dispersed in water or a dispersion medium other than water. Therefore, in the present invention, the dispersion medium in the cellulose nanofiber dispersion is not limited to water. However, the dispersion medium in the cellulose nanofiber dispersion is preferably water.

[0016] As mentioned above, the solid content in the cellulose nanofiber dispersion is usually 1 to 8% by weight, but may be further diluted to less than 1% by weight. Therefore, the cellulose nanofiber dispersion may be pre-dried before the above pretreatment. There is no particular limitation on the pre-drying method, and any conventional method may be used. The cellulose nanofiber dispersion may be pre-dried, for example, to a maximum solid content of 12% by weight, and then the drying method of the present invention described below may be carried out.

[0017] As described below, when the cellulose nanofiber dispersion is dried under specific conditions, a cellulose nanofiber powder is obtained. The average fiber length of the cellulose nanofiber powder is preferably 0.1 μm or more. This is expected to improve the dispersion stability. From this viewpoint, the average fiber length of the cellulose nanofiber powder is more preferably 0.2 μm or more, even more preferably 0.3 μm or more, and even more preferably 0.5 μm or more. If the average fiber length of the cellulose nanofiber powder is 0.1 μm or more, it has a high aspect ratio with respect to the average fiber diameter.

[0018] In addition, the average fiber length of the cellulose nanofiber powder is preferably 3.0 μm or less. This makes it possible to prevent the cellulose nanofibers from becoming rounded into a spherical shape during processing. From this perspective, the average fiber length of the cellulose nanofiber powder is more preferably 2.5 μm or less, even more preferably 1.5 μm or less, and even more preferably 1.0 μm or less.

[0019] The average fiber length of the cellulose nanofiber powder refers to the D50 (median diameter) of the fibers in the cellulose nanofiber powder measured according to the laser diffraction / scattering method of JIS Z8825:2022.

[0020] The average fiber diameter of the cellulose nanofiber powder is preferably 0.5 nm or more. This is expected to improve the dispersion stability. From this viewpoint, the average fiber diameter of the cellulose nanofiber powder is more preferably 0.7 nm or more, even more preferably 1 nm or more, and even more preferably 3 nm or more.

[0021] In addition, the average fiber diameter of the cellulose nanofiber powder is preferably 10 nm or less. If the cellulose nanofibers are too thick, the aspect ratio decreases, and the interparticle distance may not be maintained due to steric hindrance. From this viewpoint, the average fiber diameter of the cellulose nanofiber powder is more preferably 8 nm or less, even more preferably 7 nm or less, and even more preferably 5 nm or less.

[0022] The average fiber diameter of the cellulose nanofiber powder means the average particle diameter of the fibers of the cellulose nanofiber powder measured according to the dynamic light scattering method of JIS Z8828:2019.

[0023] (2. Hydrophobization of cellulose nanofibers) In order to obtain the diffusibility of CNF, it is necessary that the dried fiber aggregates are easily loosened. To achieve this, the inventor came up with the idea of ​​applying the fiber softening effect of laundry softener. When water is removed from CNF slurry, fiber aggregates are always formed and are scattered as strong aggregates. Therefore, as a first treatment, a dry powder that is flexible and easy to loosen without strong aggregates is prepared by approaching the formulation of a softener. Furthermore, as a second treatment, the CNF is moistened with silicone to prevent moisture absorption during storage and to give diffusibility and heat resistance from the beginning of resin kneading. By treating CNF in these two stages, it is possible to finish it into a granular powder that is easy to loosen in molten resin, has good diffusibility, and has an ideal resin matrix without aggregates.

[0024] (2-1. First Processing) In the first process, the cellulose nanofiber dispersion is supplied to a two-roll mill, and the two-roll mill is rotated to dry the cellulose nanofiber dispersion and obtain dried cellulose nanofibers. The raw materials used for the cellulose nanofiber dispersion are as follows:

[0025] Cellulose nanofiber (CNF) Cellulose nanofibers are the main raw material of cellulose nanofiber powder, and are usually dispersed in water in a slurry with a solid content of 1 to 8% by weight. In addition, any treatment can be applied to CNF as long as it does not impair the effects of the present invention. For example, carboxymethyl CNF (CM-CNF), TEMPO-oxidized CNF, mechanically dispersed CNF, etc. can be suitably used.

[0026] If the amount of cellulose nanofibers is less than 0.2% by weight relative to the total weight of the cellulose nanofiber dispersion, the workability is poor. From this viewpoint, the amount of cellulose nanofibers in the cellulose nanofiber dispersion is preferably 0.3% by weight or more, more preferably 0.5% by weight or more, even more preferably 0.7% by weight or more, even more preferably 1.0% by weight or more, and even more preferably 1.5% by weight or more. On the other hand, if the amount of cellulose nanofibers exceeds 12% by weight, processing becomes difficult. From this viewpoint, the amount of cellulose nanofibers in the cellulose nanofiber dispersion is preferably 10% by weight or less, more preferably 9% by weight or less, and even more preferably 8% by weight or less.

[0027] In addition, it is necessary to adjust the amount and concentration of the cellulose nanofiber dispersion so that the amount of cellulose nanofiber in the finished cellulose nanofiber powder is 75 to 90% by weight. If the amount of cellulose nanofiber is less than 75% by weight, the reinforcing effect of the cellulose nanofiber as a filler is weakened. From this viewpoint, the amount of cellulose nanofiber in the cellulose nanofiber powder is preferably 76% by weight or more, more preferably 77% by weight or more, even more preferably 78% by weight or more, even more preferably 79% by weight or more, and even more preferably 80% by weight or more. On the other hand, if the amount of cellulose nanofiber exceeds 90% by weight, the effect of other components is weakened, and the diffusion effect is reduced. From this viewpoint, the amount of cellulose nanofiber in the cellulose nanofiber powder is preferably 88% by weight or less, more preferably 86% by weight or less, and even more preferably 84% by weight or less.

[0028] Polyethylene glycol Polyethylene glycol is hydrophilic and highly compatible with water, so it dissolves easily in water. Polyethylene glycol has high adsorption properties to plant fibers, so by mixing it with CNF slurry, it is easy to impregnate the fibers in the slurry.

[0029] The amount of polyethylene glycol added is 10 to 20% by weight based on the total weight of the finished cellulose nanofiber powder. If the amount of polyethylene glycol added is less than 10% by weight, the effect cannot be fully exerted. From this viewpoint, the amount of polyethylene glycol added is preferably 12% by weight or more, more preferably 14% by weight or more. On the other hand, if the amount of polyethylene glycol added exceeds 20% by weight, the product becomes sticky and the processability becomes poor. From this viewpoint, the amount of polyethylene glycol added is preferably 19% by weight or less, more preferably 18% by weight or less. Although polyethylene glycol is usually added in the form of an aqueous solution, it may be added as a single substance.

[0030] Ester-type dialkyl ammonium salt Alkyl ammonium salts belonging to quaternary ammonium salts, which are also used in fabric softeners, include ester-type dialkyl ammonium salts and amide-type alkyl amine salts. Ester-type dialkyl ammonium salts increase the flexibility of fibers, but are poor in water absorption, such as not absorbing sweat. On the other hand, amide-type alkyl amine salts are poor in flexibility but are water absorbent, and are considered to be suitable for washing underwear and other items that come into direct contact with the skin. In the present invention, ester-type dialkyl ammonium salts, which are highly hydrophobic, are selected. When ester-type dialkyl ammonium salts are combined with polyethylene glycol, there is an advantage that although no chemical bond is formed, extreme liquid interlayer separation does not occur.

[0031] When ester-type dialkylammonium salt is mixed into CNF slurry, the ester-type dialkylammonium salt penetrates the fibers in the CNF slurry and is adsorbed onto the fibers. As a result, the ester-type dialkylammonium salt acts as a lubricant between the fiber bundles, eliminating friction and making them less likely to tangle, and even if the fibers are aggregates, they become soft. The ester-type dialkylammonium salt also gives the fibers flexibility and an antistatic effect.

[0032] The amount of the ester-type dialkylammonium salt added is 0.05 to 2.0% by weight based on the total weight of the finished cellulose nanofiber powder. If the amount of the ester-type dialkylammonium salt added is less than 0.05% by weight, the effect cannot be fully exerted. From this viewpoint, the amount of the ester-type dialkylammonium salt added is preferably 0.5% by weight or more, more preferably 1.0% by weight or more. On the other hand, if the amount of the ester-type dialkylammonium salt added exceeds 2.0% by weight, the effect will plateau. From this viewpoint, the amount of the ester-type dialkylammonium salt added is preferably 1.5% by weight or less. The ester-type dialkylammonium salt is usually added in the form of an aqueous solution, but may be added as a single substance.

[0033] Isopropyl alcohol (IPA) IPA lowers the boiling point of the water in the slurry solvent and promotes evaporation. This accelerates the removal of water, which increases the adsorption of other chemicals to the cellulose nanofibers. Note that IPA disappears during the first process due to evaporation, so it does not remain in the second process.

[0034] The amount of IPA added is 10 to 20% by weight based on the total weight of the finished cellulose nanofiber powder. If the amount of IPA added is less than 10% by weight, the effect cannot be fully exerted. From this viewpoint, the amount of IPA added is preferably 12% by weight or more. On the other hand, if the amount of IPA added exceeds 20% by weight, the effect plateaus. From this viewpoint, the amount of IPA added is preferably 17% by weight or less. However, as mentioned above, it should be noted that IPA disappears due to evaporation during the first treatment, and is not contained in the finished cellulose nanofiber powder. Note that IPA is usually added in the form of an aqueous solution, but it may be added alone.

[0035] In one embodiment of the present invention, the above-mentioned additives are added to an aqueous dispersion of cellulose nanofibers and then dried to obtain a first-treatment cellulose nanofiber dispersion. Stirring is preferable for mixing. In the pretreatment stirring, it is desirable to knead the cellulose nanofibers in a spiral manner while maintaining their orientation in the liquid or sol. There are no particular limitations on the stirring method and device, but a Super Mixer (manufactured by Kawata Co., Ltd.), a Henschel Mixer (manufactured by Nippon Coke and Engineering Co., Ltd.), a high-speed mixer (manufactured by Earth Technica Co., Ltd.), etc. can be suitably used.

[0036] The cellulose nanofiber dispersion is fed to the middle of the two-roll mill, so that it penetrates into the gap between the rolls (nip) (Fig. 1). As a characteristic of the two-roll mill, the raw material rotates in the same direction as the rolls in the roll bank above the gap between the rolls before entering the nip. At this time, the cellulose nanofibers maintain their orientation, and when they enter the nip, the fibers enter in the same direction. This causes shear shear in the nip while maintaining the orientation of the cellulose nanofibers. The raw material, whose boiling point has been lowered by self-heating due to shear shear and the heating temperature of the two-roll mill, is easily vaporized, and the drying time is shortened. The distance between the rolls (clearance) is not particularly limited, but in the present embodiment, it is preferably 0.3 to 1.5 mm.

[0037] The greater the rotation ratio (i.e., the difference in rotation speed) between the front roll and the rear roll in the two-roll mill, the faster the speed at which the fibers penetrate into the nip. On the other hand, if the rotation ratio between the front roll and the rear roll is too large, the shear generated by the rotation ratio becomes small and the time it takes for water to evaporate becomes short, so it is preferable that the rotation ratio be 1 to 3. Furthermore, if there is no rotation ratio, the aqueous dispersion of cellulose nanofibers cannot penetrate into the nip and tends to stagnate on the roll bank.

[0038] Self-heating in the nip and heat transfer from the heated two-roll mill causes the water molecules to attract each other in liquid form and interact with other nearby molecules due to the intermolecular attraction and thermal energy of the water molecules. Under the sudden high temperature, the water molecules gain enough energy to overcome the intermolecular attraction with the fibers, and the water and alcohol instantly transition from liquid to gas. As mentioned above, the cellulose nanofibers enter the nip while retaining their orientation, so they undergo vaporization by steam explosion in the same direction, and there is little random stress on the cellulose nanofibers, allowing them to dry in a state close to their original form (a state in which the double helix structure is almost unraveled).

[0039] Here, kneaders other than the two-roll mill can be considered, such as a pressure kneader, a Banbury kneader, and an extruder. However, since these knead randomly, even if the water evaporates instantly, the cellulose nanofibers tend to entangle with each other and form lumps. In addition, conventional techniques such as freeze drying, drying ovens, and spray drying do not provide a means for giving orientation to the cellulose nanofibers, and since drying takes time, the double helix structure tends to loosen and form lumps. Therefore, the treatment using a two-roll mill has advantages that cannot be obtained by conventional techniques. The two-roll mill may be any device that can knead the raw materials between the two rolls, and may have a third or subsequent roll.

[0040] Furthermore, a desired drying effect can be obtained if the surface temperature of the two-roll mill is 100°C or higher, but if the surface temperature of the two-roll mill is too high, there is a risk that the cellulose nanofibers will be altered, and the surface will harden during powderization, making it difficult to produce fine particles, so it is preferably 120°C or lower, and more preferably 115°C or lower. Therefore, in one embodiment of the present invention, the surface temperature of the two-roll mill is 100°C to 120°C, and preferably 105°C to 110°C.

[0041] (2-2. Second Processing) In the second process, the dried cellulose nanofibers are mixed with a melt containing silicone oil and carnauba wax to obtain the finished cellulose nanofiber powder. The raw materials used in the second process are as follows:

[0042] Silicone oil Silicone oil forms a coating on the fibers, giving them water repellency and greatly reducing the coefficient of friction between fibers. On the other hand, silicone oil does not impair the ease of disintegration of fiber aggregates. In addition, since the main structure of silicone oil is a siloxane bond (Si-O-Si), the bond energy between atoms is large, and it can impart weather resistance and heat resistance. The melting point of silicone oil is about 90°C, and although its heat resistance depends on the combination with resin, it is not easily altered even when melt-processed with resin at around 280°C. Silicone oil gives water repellency to the finished CNF powder, so it has the advantage of being less likely to absorb moisture even during storage and processing.

[0043] The amount of silicone oil added is 0.8 to 2.0% by weight based on the total weight of the finished cellulose nanofiber powder. If the amount of silicone oil added is less than 0.8% by weight, the effect cannot be fully exerted. From this viewpoint, the amount of silicone oil added is preferably 1.0% by weight or more. On the other hand, if the amount of silicone oil added exceeds 2.0% by weight, the effect will plateau. From this viewpoint, the amount of silicone oil added is preferably 1.5% by weight or less.

[0044] In addition, from the viewpoint of improving the flexibility of CNF fibers, a low-viscosity oil-type silicone base material to which silicone containing a metal catalyst such as tin has been added can be used.

[0045] Carnauba Wax Carnauba wax contains hydrophobic aliphatic esters and hydrophilic hydroxycarboxylic acids. Silicone oil can be heated to a temperature above the melting point of carnauba wax (such as 88°C), and then carnauba wax can be added and mixed. Carnauba wax has the lowest melting point of all raw materials (usually 80°C to 86°C), so it has the effect of triggering the initial stage of CNF diffusion into the resin. It can also be added to a wide range of resins, is less likely to bleed, and has the same moisture absorption prevention properties as silicone.

[0046] The amount of carnauba wax added is 0.2 to 0.8% by weight relative to the total weight of the cellulose nanofiber powder. If the amount of carnauba wax added is less than 0.2% by weight, the effect cannot be fully exerted. From this viewpoint, the amount of carnauba wax added is preferably 0.3% by weight or more. On the other hand, if the amount of carnauba wax added exceeds 0.8% by weight, the effect will plateau. From this viewpoint, the amount of carnauba wax added is preferably 0.7% by weight or less.

[0047] In addition, before mixing the dried cellulose nanofibers with the molten material containing silicone oil and carnauba wax, it is preferable to further stir the dried cellulose nanofibers with a stirrer or the like and dry them by processing heat.

[0048] The CNF powder obtained by the above method has high diffusibility in molten resin and is less likely to form agglomerates.

[0049] (3. Cellulose nanofiber powder) In another aspect, the present invention provides a CNF powder comprising 75 to 90% by weight of cellulose nanofibers, 10 to 20% by weight of polyethylene glycol, 0.05 to 2.0% by weight of an ester-type dialkylammonium salt, 0.8 to 2.0% by weight of silicone oil, and 0.2 to 0.8% by weight of carnauba wax.

[0050] The manufacturing method of CNF powder and detailed explanation of each component have been described above, so they will not be repeated here. EXAMPLES

[0051] The following examples of the present invention are provided for a better understanding of the present invention and its advantages, and are not intended to limit the invention.

[0052] (raw materials) The raw materials used in each test example are as follows. CNF: Mechanically dispersed 8% CNF aqueous solution, manufactured by Sappi IPA: General-purpose isopropyl alcohol manufactured by ENEOS Corporation Polyethylene glycol: PEG-300 (liquid low molecular weight polyethylene glycol) manufactured by Sanyo Chemical Industries, Ltd. Ester type dialkyl ammonium salt: Catiogen (registered trademark) ES-O manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Silicone oil A: Shin-Etsu Chemical Co., Ltd. KF-96ADF (low viscosity oil type silicone) Silicone oil B: Shin-Etsu Chemical Co., Ltd. KM-2002-T-2 (silicone fabric softener containing tin catalyst) Carnauba wax: Carnauba wax No. 1 manufactured by Kato Yoko Co., Ltd. (melting point approx. 82°C)

[0053] (1. Test Examples 1 to 4) First, in the first process, the raw materials were weighed according to the composition listed in Table 1, and mixed for 5 minutes at 400 rpm with a mixer (Henschel mixer manufactured by Nippon Coke & Engineering Co., Ltd.). The mixed raw materials were dried using a thermal mixing two-roll mill (8-inch roll mill manufactured by Inoue Seisakusho Co., Ltd.), which has a high water vaporization rate and shear shear. The roll surface temperature was 105 to 110°C, the front and rear rotation speeds were front:rear = 7:10, and the roll clearance was 0.5 to 0.7 mm. At this time, it is desirable to sequentially place the raw materials on the rolls, and the raw materials are inserted into the gaps while repeatedly rotating on their own in the roll bank. After 3 to 4 revolutions of the rolls, the raw materials naturally peeled off. The peeled off material became semi-wet scale flakes. If the water vaporization and drying were completely performed by the rolls, hard fiber aggregates would also be mixed in, making it difficult to loosen the whole when silicone oil was added in the next process, so this was the end point. The flakes peeled off from the roll were checked for their flexibility when touched with the hand and for their tendency to crumble. Test example 1 had a moderate flexibility and tendency to crumble, making it suitable for subsequent processing. Test examples 2 to 4 did not contain any of the ingredients, and therefore were not suitable for subsequent processing. (See comments in Table 1.)

[0054] [Table 1]

[0055] (2. Test Examples 5 to 10) Next, the first and second treatments were carried out according to the composition in Table 2. The conditions of the first treatment were the same as those of Test Examples 1 to 4. In the second treatment, a jacketed oil-heated mixer with a pulverizing blade (FM mixer manufactured by Nippon Coke & Engineering Co., Ltd.) was used as the agitator. The flakes produced in the first treatment were added, the jacket temperature was set to 110°C, and stirring was started at 600 rpm. At this time, an exhaust blower with an air filter was operated to discharge the water vapor coming out of the raw material. Stirring was continued until the moisture content was about 5% by weight, and then the mixture was temporarily stopped. At this time, the material was in a fine powder state. Next, the jacket temperature was set to 110°C, the stirring speed was increased to 800 rpm, and stirring was continued again, and silicone oil containing carnauba wax was added while stirring.

[0056] If the additive is added while stirring, it will form lumps, so it is preferable to add the additive while stirring. After stirring for 5 minutes, there were no more water droplets in the mixer tank, and the mixture was stirred in a beautiful vortex with reduced powder scattering. The stirring was stopped after about 7 minutes, and the finished CNF powder was obtained.

[0057] (Evaluation of Diffusion) Regarding the diffusibility into the molten resin, in order to visually confirm the diffusion state, the molten resin was wrapped around an open thermal mixing triple roll, a roll bank was made, and the CNF powder was directly added thereto to confirm the state of the particles diffusing onto the roll surface. The results are shown in Table 2.

[0058] [Table 2]

Claims

1. A cellulose nanofiber powder comprising: A cellulose nanofiber powder comprising 75 to 88% by weight of cellulose nanofibers, 10 to 20% by weight of polyethylene glycol, 0.05 to 2.0% by weight of an ester-type dialkylammonium salt, 0.8 to 2.0% by weight of silicone oil, and 0.2 to 0.8% by weight of carnauba wax, based on the total weight of the cellulose nanofiber powder.

2. The cellulose nanofiber powder according to claim 1, wherein the average fiber length of the cellulose nanofibers is within the range of 0.1 μm to 3.0 μm.

3. The cellulose nanofiber powder according to claim 1 or 2, wherein the average fiber diameter of the cellulose nanofibers is within the range of 0.5 nm to 10 nm.

4. A method for producing cellulose nanofiber powder, comprising: a first process of supplying a cellulose nanofiber dispersion to a two-roll mill and rotating the two-roll mill to dry the cellulose nanofiber dispersion and obtain dried cellulose nanofibers; A second process of mixing the dried cellulose nanofibers with a molten material containing silicone oil and carnauba wax to obtain a cellulose nanofiber powder. Including, The cellulose nanofiber dispersion is prepared to contain 75 to 88% by weight of cellulose nanofibers, 10 to 20% by weight of polyethylene glycol, 0.05 to 2.0% by weight of an ester-type dialkylammonium salt, and 10 to 20% by weight of isopropyl alcohol, based on the total weight of the cellulose nanofiber powder after the second treatment; The method, wherein the melt is prepared to contain 0.8 to 2.0% by weight of silicone oil and 0.2 to 0.8% by weight of carnauba wax, based on the total weight of the cellulose nanofiber powder after the second treatment.

5. 5. The method of claim 4, wherein the first treatment comprises heating the surface temperature of the two-roll mill to 100°C to 120°C.

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