JP2020079420A - Method for producing cellulose nanofiber - Google Patents

Abstract

To provide a method for producing a cellulose nanofiber capable of obtaining a cellulose nanofiber using a pulp fiber with a simple method and a more excellent collection rate.SOLUTION: A method for producing a cellulose nanofiber includes: a step of pre-treating a pulp fiber by mixed with persulfuric acids; a step of finely grinding the pulp fiber subjected to the pre-treatment in a state of being dispersed in the water, in which the pulp fiber is a hardwood craft pulp or coniferous craft pulp, a preliminary beating step is further provided between the pre-treatment step and the finely grinding step, and the preliminary beating step is a physical method. The preliminary beating step may be a viscous beating method, a cutting beating method or a combined method of them. A step of neutralizing the pulp fiber subjected to the pre-treatment and/or a step of cleaning the pulp fiber subjected to the pre-treatment may be further provided between the pre-treatment step and the preliminary beating step.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing cellulose nanofibers.

  In recent years, attention has been paid to nanotechnology for the purpose of miniaturizing substances to the nanometer level and obtaining new physical properties different from the conventional properties of substances. Cellulose nanofibers produced from cellulosic raw materials by nanotechnology such as chemical treatment and pulverization treatment are excellent in strength, elasticity, thermal stability, etc., and therefore, are filter media, filter aids, base materials for ion exchangers, It is used in industrial applications as a filler for chromatographic analysis equipment, as a filler for compounding resins and rubbers, and as a compounding agent for cosmetics such as lipsticks, powder cosmetics and emulsion cosmetics. In addition, since cellulose nanofibers are excellent in water-based dispersibility, they are viscosity-retaining agents for foods, cosmetics, paints, etc., reinforcing agents for food material dough, moisture-retaining agents, food stabilizers, low-calorie additives, emulsifying agents It is expected to be used in many applications such as a stabilizing aid.

  As a method for producing such cellulose nanofibers, a cellulosic raw material is treated in the coexistence of 2,2,6,6-tetramethyl-1-piperidine-N-oxy radical which is a catalyst and sodium hypochlorite which is an oxidant. A method of doing so has been studied (see Japanese Patent Laid-Open No. 2008-1728). However, when sodium hypochlorite used in this method is mixed with a strongly acidic substance, chlorine gas is generated, so that it is feared that the human body will be adversely affected and the handling thereof will be complicated. Further, as a method for producing cellulose nanofibers, a method of subjecting a cellulosic raw material to ozone treatment, dispersing it in water, and pulverizing an aqueous suspension of the obtained cellulosic raw material has been studied (JP 2010- 254726). However, ozone used in this method is a main component of photochemical oxidants and is feared to have an adverse effect on the environment. Further, when the cellulosic raw material is subjected to ozone treatment, the cellulose molecules are strongly hydrolyzed, so that there is a disadvantage that the recovery rate from the cellulosic raw material becomes low.

JP, 2008-1728, A JP, 2010-254726, A

  The present invention has been made based on the above circumstances, and to provide a method for producing cellulose nanofibers, which can obtain cellulose nanofibers with an excellent recovery rate by a simple method using pulp fibers. With the goal.

  The invention made to solve the above problems comprises a step of pretreating pulp fibers by mixing with persulfates, and a step of refining the pulp fibers subjected to the pretreatment in a state of being dispersed in water. It is a method for producing cellulose nanofibers.

  According to the method for producing cellulose nanofibers, by pretreating pulp fibers with persulfates, it is possible to produce cellulose nanofibers with an excellent recovery rate by a simple method. The reason for this is not clear, but by pretreating the pulp fiber with persulfates, it becomes easier to control the hydrolysis of the cellulose molecules that form the pulp fiber, and the pulp fiber swells in an appropriately hydrolyzed state. There are possible reasons for doing so. By subjecting the pulp fiber in such a state to the micronization step, it is possible to efficiently obtain the cellulose nanofiber having a high recovery rate and good characteristics.

  The pH in the pretreatment step is preferably 1.0 or more and 3.0 or less. By setting the pH in the pretreatment step in the above range, the hydrolysis and swelling of the cellulose molecules constituting the pulp fibers are moderately promoted, and the recovery rate of the cellulose nanofibers from the pulp fibers is further improved, It is possible to produce cellulose nanofibers that are uniform and have excellent moisture retention.

  The pretreatment step is preferably performed in a liquid phase, and the solid content concentration of the pulp fiber in the liquid phase is preferably 1% by mass or more and 20% by mass or less. Pulp fiber is generally produced in a water-dispersed state, and thus, by performing the above-mentioned pretreatment step in the liquid phase, dehydration treatment, drying treatment, and other treatments that require excessive equipment and energy are not required. By using pulp fiber, cellulose nanofiber can be produced by a simple method. Further, by setting the solid content concentration of the pulp fiber in the liquid phase within the above range, the hydrolysis and swelling of the cellulose constituting the pulp fiber is appropriately promoted by persulfates, and the cellulose nanofibers are highly recovered. It can be manufactured efficiently.

  A step of neutralizing the pulp fiber after the pretreatment and/or a step of washing the pulp fiber after the pretreatment may be further provided between the pretreatment step and the refining step. Thus, by further comprising the step of neutralizing the pulp fiber after the pretreatment and/or the step of washing the pulp fiber after the pretreatment, the cellulose nanofibers having better properties can be collected at a high recovery rate. It can be manufactured.

  It is advisable to carry out the above-mentioned miniaturization step using a stone mill, a high-pressure homogenizer, a ball mill, or at least one of these. By subjecting the pulp fibers that have been subjected to the prescribed pretreatment to mechanical refining treatment using these, the defibration of the pulp fibers can be efficiently advanced with low energy. Productivity can be increased.

  Here, the "cellulose nanofiber" refers to a cellulose fiber having an average fiber width of 1,000 nm or less. The “average fiber width” is the average value of the fiber width measured by using an electron microscope or a field emission scanning electron microscope.

  As explained above, according to the method for producing cellulose nanofibers of the present invention, pulp fibers can be used to produce cellulose nanofibers with an excellent recovery rate by a simple method. Therefore, the cellulose nanofibers obtained by the method for producing the cellulose nanofibers are a filtering material, a filter aid, a base material of an ion exchanger, a packing material for a chromatographic analysis instrument, a packing material for blending resin and rubber, and a cosmetic material. It can be suitably used for many purposes such as a compounding agent, a viscosity maintaining agent for foods and paints, a strengthening agent for food material dough, a moisture retaining agent, a food stabilizer, a low calorie additive, and an emulsion stabilizing aid.

<Method for producing cellulose nanofiber>
The method for producing the cellulose nanofibers includes a step of pretreating pulp fibers by mixing with persulfates (hereinafter, also referred to as "pretreatment step"), and the pulp fibers subjected to the pretreatment are dispersed in water. A step of miniaturizing in a state (hereinafter, also referred to as “miniaturizing step”) is provided. The method for producing the cellulose nanofibers is, if necessary, between the pretreatment step and the refining step, a step of pre-beating the pulp fiber subjected to the pre-treatment (hereinafter, "pre-beating step"). Also called), a step of neutralizing the pretreated pulp fibers (hereinafter, also referred to as "neutralization step"), a step of washing the pretreated pulp fibers (hereinafter, "washing step") And/or a step of removing water containing persulfates from the pretreated pulp fiber (hereinafter, also referred to as “dehydration step”). When the method for producing cellulose nanofibers includes a dehydration step, water containing the persulfates removed in the dehydration step may be reused in the pretreatment step. Hereinafter, each step will be described.

(Pretreatment process)
The method for producing the cellulose nanofiber includes a pretreatment step. In this step, pulp fibers are pretreated by mixing with persulfates. In this step, the pulp fibers swell in a hydrolyzed state by being mixed with persulfates.

  Examples of the pulp fibers include wood pulp, pulp mainly composed of fiber raw materials other than wood, waste paper pulp, and the like.

Examples of the wood pulp include hardwood bleached sulfite pulp (LBSP), hardwood unbleached sulfite pulp (LUSP), hardwood bleached kraft pulp (LBKP), hardwood unbleached kraft pulp (LUKP) and other hardwood kraft pulp (LKP), conifer bleached wood. Chemical pulp such as softwood kraft pulp (NKP) such as sulfite pulp (NBSP), unbleached softwood sulfite pulp (NUSP), bleached softwood kraft pulp (NBKP), unbleached softwood kraft pulp (NUKP), soda pulp (AP);
Stone ground pulp (SGP), pressure stone ground pulp (PGW), refiner ground pulp (RGP), chemi ground pulp (CGP), thermo ground pulp (TGP), ground pulp (GP), thermo mechanical pulp (TMP), Mechanical pulp such as chemi-thermo-mechanical pulp (CTMP), bleached thermo-mechanical pulp (BTMP), refiner mechanical pulp (RMP) and the like can be mentioned.

Examples of pulp mainly composed of fiber raw materials other than wood include linter pulp;
Examples include pulp obtained from hemp, bagasse, kenaf, esparto grass, bamboo, chaff, straw and the like.

Used paper pulp is manufactured from tea waste paper, kraft envelope waste paper, magazine waste paper, newspaper waste paper, flyer waste paper, office waste paper, cardboard waste paper, Kamishiro waste paper, Kent waste paper, imitation waste paper, land ticket waste paper, waste paper waste paper, etc. Waste paper pulp;
Examples include deinked pulp (DIP) obtained by deinking used paper pulp.

  Among them, the pulp fiber is preferably a chemical pulp, and more preferably LBKP, from the viewpoint of producing a cellulose nanofiber with an excellent recovery rate by a simple method.

Examples of the persulfates used in the pretreatment step include peroxomonopersulfates such as peroxomonopersulfate, peroxodipersulfate, potassium peroxomonopersulfate;
Examples thereof include peroxodipersulfate such as diammonium peroxodipersulfate, disodium peroxodipersulfate, and dipotassium peroxodipersulfate. Peroxomonopersulfuric acid may be obtained by hydrolyzing peroxydisulfuric acid, or may be obtained by mixing hydrogen peroxide and sulfuric acid at an arbitrary ratio.

  As the above-mentioned persulfates, among these, from the viewpoint of more appropriately hydrolyzing pulp fibers to obtain cellulose nanofibers at an excellent recovery rate, peroxonipersulfate is preferable, and peroxodipersammonium peroxodipersulfate is more preferable. preferable. In addition, as the above-mentioned persulfates, peroxomonopersulfuric acid is preferable from the viewpoint of obtaining pulp fiber without coloration.

  The pretreatment step may be performed in a liquid phase or a gas phase.

  Examples of the method of performing the pretreatment step in the liquid phase include a method of mixing the aqueous solution of persulfate with the pulp fiber to bring the aqueous solution of persulfate into contact with the pulp fiber for treatment.

  Examples of the method of performing the pretreatment step in the gas phase include a method of mixing the vapor phase of persulfate with the pulp fiber to bring the vapor phase of the persulfate into contact with the pulp fiber, and treating. Examples of the method of converting the persulfuric acid into the vapor phase include a method of evaporating the persulfuric acid using an autoclave or the like.

  The pretreatment step is preferably performed in the liquid phase from the viewpoint of producing cellulose nanofibers with a superior recovery rate by a simpler method.

  The lower limit of the concentration of the aqueous solution of the persulfate mixed with the pulp fiber is preferably 1% by mass, more preferably 10% by mass. On the other hand, the upper limit of the concentration of persulfates is preferably 50% by mass, more preferably 30% by mass. If the concentration of the persulfate is less than the lower limit, the hydrolysis and hydrolysis of the cellulose molecules constituting the pulp fiber may not be sufficiently promoted. On the other hand, if the concentration of persulfate exceeds the upper limit, hydrolysis and swelling of the cellulose molecules constituting the pulp fiber may be excessively promoted, and the treated pulp fiber may be discolored.

  The lower limit of the mixing ratio of the persulfates is preferably 0.05% by mass, more preferably 0.3% by mass, based on the absolutely dry mass of pulp fiber. On the other hand, the upper limit of the mixing ratio is preferably 40% by mass, more preferably 10% by mass. If the mixing ratio of the persulfates is less than the above lower limit, hydrolysis and swelling of the cellulose molecules constituting the pulp fibers may not be sufficiently promoted, and the moisture retention of the cellulose nanofibers may be low. On the other hand, when the mixing ratio of the persulfates exceeds the upper limit, hydrolysis and swelling of the cellulose molecules constituting the pulp fibers are excessively promoted, and the recovery rate of the cellulose nanofibers from the pulp fibers may be low. , The treated pulp fiber may be discolored.

  The lower limit of the treatment temperature in the pretreatment step is preferably 45°C, more preferably 55°C, and even more preferably 75°C. On the other hand, the upper limit of the treatment temperature is preferably 120°C, more preferably 100°C, and even more preferably 90°C. If the treatment temperature is lower than the lower limit, the hydrolysis reaction may be significantly reduced. On the other hand, if the treatment temperature exceeds the upper limit, hydrolysis and swelling of the cellulose molecules constituting the pulp fiber are excessively promoted, and the recovery rate of the cellulose nanofibers may be low.

  The lower limit of the treatment time in the pretreatment step is preferably 0.5 hours, more preferably 2 hours. On the other hand, the upper limit of the processing time is preferably 7 hours, more preferably 4 hours. By setting the treatment time within the above range, the cellulose nanofibers can be more appropriately hydrolyzed.

  As a minimum of pH of a mixture in a pretreatment process, 1.0 is preferred and 1.5 is more preferred. The upper limit of the pH is preferably 3.0, more preferably 2.0. By setting the above pH within the above range, hydrolysis of pulp fiber can be made more appropriate.

  When the pretreatment step is performed in the liquid phase, the lower limit of the solid content concentration of the pulp fibers in the liquid phase is preferably 1% by mass. The upper limit of the solid content concentration is preferably 20% by mass. By setting the solid content concentration within the above range, it is possible to produce cellulose nanofibers with a better recovery rate.

(Neutralization process)
The method for producing the cellulose nanofibers may further include a neutralization step between the pretreatment step and the micronization step, if necessary. In this step, the pulp fiber subjected to the above-mentioned pretreatment is neutralized. By including this step, the method for producing cellulose nanofibers can effectively and appropriately refine the pulp fibers.

  As a method of neutralization, for example, sodium hydroxide, magnesium carbonate, barium carbonate, barium sulfate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, alkali such as zinc hydroxide to the pulp fibers subjected to the above pretreatment The method of adding may be mentioned. These alkalis may be used alone or in combination of two or more.

(Washing process)
The method for producing the cellulose nanofibers may further include a washing step between the pretreatment step and the micronization step, if necessary. In this step, the pulp fiber that has been subjected to the above pretreatment is washed. By including this step, the method for producing cellulose nanofibers can effectively and appropriately refine the pulp fibers.

  As a method of washing, for example, the pulp fiber that has been subjected to the above pretreatment is an aqueous solution of alkali such as sodium hydroxide, magnesium carbonate, barium carbonate, barium sulfate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide or the like. And a method of washing with an aqueous solution of an acid such as acetic acid, sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, acetic acid, benzoic acid, metachlorobenzoic acid, formic acid and propionic acid, distilled water, and industrial water. These methods may be used alone or in combination of two or more.

(Dehydration process)
The method for producing the cellulose nanofibers may further include a dehydration step between the pretreatment step and the micronization step, if necessary. In this step, water containing persulfates is removed from the pulp fiber subjected to the pretreatment. By including this step, the method for producing cellulose nanofibers can effectively and appropriately refine the pulp fibers. The method for removing water is not particularly limited, and a known method can be used.

(Preliminary beating process)
The method for producing the cellulose nanofiber may further include a preliminary beating step between the pretreatment step and the refining step, if necessary. When the method for producing cellulose nanofibers further includes a neutralization step, a washing step and/or a dehydration step, a preliminary beating step is provided between the neutralization step, the washing step and/or the dehydration step and the refining step. In this step, the pulp fiber that has been subjected to the pretreatment is pre-beaten. Since the method for producing cellulose nanofibers includes the preliminary beating step, the pulp fibers can be more efficiently refined in the refining step.

  Examples of the pre-beating method include physical methods, chemical methods other than the above-mentioned oxidation treatment and the above-mentioned pretreatment, and the like.

  As the physical method, for example, a viscous beating method using beating equipment such as pulper, beater, disc refiner, conical refiner, cutting beating method using beating equipment such as beater, disc refiner, conical refiner, and a combination thereof. Method etc. are mentioned. The viscous beating method or the cutting beating method is not uniquely determined by the beating equipment, but is determined by the material, shape, gap, etc. of the blade, rotor, disk, etc. used. Examples of the viscous beating method include a method of adjusting the beating blade such as widening the blade width, shortening the blade length, and increasing the contact angle, and a method of lowering the temperature during beating. On the other hand, examples of the beating method for cutting include a method for adjusting the beating blade such as narrowing the blade width, lengthening the blade length, and decreasing the contact angle, and a method for raising the temperature during beating.

  The chemical method other than the pretreatment is not particularly limited, and a known chemical method can be used.

  As the preliminary beating method, a physical method is preferable, a viscous beating method, a cutting beating method and a combination thereof are more preferable, and a method using a beater is further preferable.

  When the preliminary beating step is performed by a viscous beating method using a beater, the lower limit of the solid content concentration of the pulp fiber is preferably 0.5% by mass, more preferably 1.5% by mass. As a maximum of the above-mentioned solid content concentration, 5 mass% is preferred and 3 mass% is more preferred. By setting the solid content concentration within the above range, cellulose nanofibers can be produced more efficiently.

  The lower limit of the treatment time of the beater when performing the viscous beating method is preferably 30 minutes, more preferably 55 minutes. On the other hand, the upper limit of the treatment time of the beater is preferably 5 hours, more preferably 3 hours. If the rotation speed of the beater is less than the above lower limit, the miniaturization may be insufficient. If the rotation speed of the beater exceeds the above upper limit, pulp fibers may deteriorate.

  When the preliminary beating step is carried out by a physical method, the lower limit of the treatment temperature is usually 20°C, preferably 25°C. The upper limit of the treatment temperature is usually 80°C, preferably 65°C. By setting the treatment temperature in the above range, it is possible to obtain cellulose nanofibers having a smaller variation in size with a high recovery rate.

(Miniaturization process)
The method for producing the cellulose nanofiber includes a micronization step. In this step, the pulp fibers subjected to the above-mentioned pretreatment are finely divided in a state of being dispersed in water. The pulp fiber that has been subjected to the above pretreatment is defibrated by a refining process. The miniaturization method may be used alone or in combination of two or more. Further, by repeating this step, the cellulose nanofibers can have a desired average fiber width.

  As the refining method, for example, a grinder method using a stone crusher or the like, an underwater counter collision method in which pulp fibers are dispersed in water to cause a collision under high pressure, a high pressure homogenizer, an ultrahigh pressure homogenizer, a high pressure collision crusher, a ball mill , A disk-type refiner, a conical refiner, a twin-screw kneader, a vibration mill, a homomixer under high-speed rotation, an ultrasonic disperser, a beater and the like to mechanically miniaturize.

  As the micronization method, from the viewpoint that cellulose nanofibers can be more easily and reliably obtained among these, a method using a stone mill type grinder, a high-pressure homogenizer and a ball mill is preferable, and a method using a stone mill type grinder is more preferable. preferable.

  In the grinder method using a stone mill type grinder, concretely, by passing the pulp fiber through the rubbing part of the stone mill type grinder, the pulp fiber is gradually ground by the impact, centrifugal force, shearing force, etc. when passing. Uniform cellulose nanofibers are obtained without being crushed and chemically denatured.

  When carrying out the refining treatment by a method using a stone mill type grinder, the lower limit of the solid content concentration of the pulp fiber is preferably 0.1% by mass, more preferably 0.5% by mass. As a maximum of the above-mentioned solid content concentration, 5 mass% is preferred and 3 mass% is more preferred. By setting the solid content concentration within the above range, cellulose nanofibers can be produced more efficiently.

  As a lower limit of the rotation speed of the stone mill type grinder, 500 rpm is preferable, and 800 rpm is more preferable. On the other hand, the upper limit of the rotation speed of the stone mill type grinder is preferably 2,000 rpm, more preferably 1,400 rpm. If the rotation speed of the stone mill type grinder is less than the above lower limit, the centrifugal force may be insufficient and the micronized cellulose nanofibers may not be discharged. If the rotation speed of the stone mill grinder exceeds the above upper limit, the pulp fibers may be discharged without being finely divided by centrifugal force.

  The lower limit of the temperature in the miniaturization step is preferably 25°C, more preferably 30°C. On the other hand, the upper limit of the temperature for miniaturization is preferably 80°C, more preferably 65°C. If the temperature of the miniaturization step is below the above lower limit, the miniaturization may not be sufficiently promoted. If the temperature in the refining process exceeds the upper limit, pulp fiber may not be supplied due to bumping.

  The cellulose nanofiber obtained by the method for producing the cellulose nanofiber preferably has a single peak in a pseudo particle size distribution curve measured by a laser analysis method in a water dispersion state. Since the cellulose nanofiber has the single peak, it is possible to obtain a cellulose nanofiber having a small variation.

  As a minimum of the recovery rate of the above-mentioned cellulose nanofiber from pulp fiber, 95% is preferred and 98% is more preferred.

  The lower limit of the water retention of the cellulose nanofibers is preferably 310%, more preferably 3200%. When the water retention is within the above range, the cellulose nanofibers have excellent dispersibility in water 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.

(Recovery rate(%))
The percentage of the absolute dry mass of the cellulose nanofibers after the micronization treatment with respect to the absolute dry mass of the pulp fiber before the pretreatment was determined, and this was defined as the recovery rate (%). That is, the recovery rate (%) is the ratio of the yield of the obtained cellulose nanofibers to the feed of the pulp fiber as the raw material.

(Pseudo particle size distribution curve)
According to ISO-13320 (2009), a curve showing a volume-based particle size distribution in a water dispersion state of cellulose nanofibers using a particle size distribution measuring device (“Laser diffraction/scattering type particle size distribution measuring device” manufactured by Seishin Enterprise Co., Ltd.) Was measured and the number of peaks was counted.

(Water retention (%))
The water retention (%) of the cellulose nanofibers is based on JAPAN TAPPI No. It was measured according to 26:2000. The greater the water retention value, the better. When the water retention is 310 or more, it can be judged as “good”, and when it is less than 310, it can be judged as “poor”.

(Average fiber width)
The fiber width of the cellulose nanofiber was measured using a field emission scanning electron microscope, and the average fiber width was determined.

<Example 1>
(Pretreatment process)
At 25° C., 2,500 g of pulp fibers (LBKP, water content 80%), ammonium persulfate (concentration of ammonium persulfate aqueous solution: 30% by mass), and 2 L of fresh water were placed in a container and the mixing ratio of ammonium persulfate was absolutely dry. It mixed so that it might be 30 mass% with respect to the mass, and pH of the mixture was set to 1.0. Next, this mixture was treated for 6 hours in a water bath having a water temperature of 95° C. to obtain pretreated pulp fibers.

(Neutralization process and cleaning process)
The pretreated pulp fiber was neutralized with sodium hydroxide and then washed with industrial water.

(Preliminary beating process)
Using a Niagara beater (“Niyagara beater for test” manufactured by Kumagai Riki Kogyo Co., Ltd.), the pulp fiber after the washing step was treated with 23 L of a solid content concentration of pulp fiber of 2 L for 1 hour.

(Miniaturization process)
Using a stone mill type grinder (“Supermass Colloider” from Masuyuki Sangyo Co., Ltd.), the pre-beaten pulp fiber was treated once at a rotation speed of 1,000 rpm at a solid concentration of 2% by mass of the pulp fiber to obtain cellulose nano. Got fiber.

  The obtained cellulose nanofibers had a recovery rate of 95%, an average fiber width observed by a field emission scanning electron microscope of 1,000 mm or less, and had one peak in the pseudo particle size distribution curve. Yes, the water retention was 374%.

<Examples 2 and 3 and Comparative Examples 1 and 2>
Examples 2 and 3 and Comparative Examples 1 and 2 were performed in the same manner as in Example 1 except that the pretreatment conditions of Example 1 were changed as shown in Table 1.

  Table 1 shows conditions and evaluation results of the pretreatment process and the miniaturization process in Examples and Comparative Examples.

  As shown in Table 1, the cellulose nanofibers obtained in the examples are excellent in recovery rate and water retention, have a single peak in the pseudo-particle size distribution curve, and have an average fiber width of 1,000 nm or less. I understand.

  As described above, according to the method for producing cellulose nanofibers of the present invention, it is possible to produce cellulose nanofibers by a simple method with excellent recovery rate using pulp fibers. Therefore, the cellulose nanofibers obtained by the method for producing the cellulose nanofibers are a filtering material, a filter aid, a base material for an ion exchanger, a packing material for a chromatographic analysis device, a packing material for blending resins and rubbers, and cosmetics. It can be suitably used for many purposes such as a compounding agent, a viscosity maintaining agent for foods and paints, a strengthening agent for food material dough, a water retaining agent, a food stabilizer, a low calorie additive, and an emulsion stabilizing aid.

Claims (3)

A step of pretreating the pulp fiber by mixing with persulfates, and a step of refining the pulp fiber subjected to the pretreatment in a state of being dispersed in water,
The pulp fiber is a hardwood kraft pulp or a softwood kraft pulp,
Further comprising a preliminary beating step between the pretreatment step and the refining step,
A method for producing cellulose nanofiber, wherein the preliminary beating step is a physical method.   The method for producing cellulose nanofibers according to claim 1, wherein the preliminary beating step is a viscous beating method, a cutting beating method, or a combination thereof.   The method further comprising a step of neutralizing the pretreated pulp fibers and/or a step of washing the pretreated pulp fibers between the pretreatment step and the preliminary beating step. Or the manufacturing method of the cellulose nanofiber of Claim 2.