WO2018116661A1

WO2018116661A1 - Acid-type carboxylated cellulose nanofibers

Info

Publication number: WO2018116661A1
Application number: PCT/JP2017/039814
Authority: WO
Inventors: 賢志高市; 丈史中谷; 昌浩森田; 晋一小野木; 健嗣藤井; 健一郎佐々木; 眞松本; 武史中山
Original assignee: 日本製紙株式会社
Priority date: 2016-12-21
Filing date: 2017-11-02
Publication date: 2018-06-28

Abstract

The present invention addresses the problem of providing acid-type carboxylated cellulose nanofibers having a high viscosity in a low shear region, or acid-type carboxylated cellulose nanofibers having extremely short fiber lengths. The carboxylated cellulose nanofibers have a carboxyl group on at least a portion of structural units constituting a cellulose molecule chain, wherein: the viscosity of an aqueous dispersion in which the content rate of the acid-type carboxylated cellulose nanofibers is 0.95-1.05 mass%, is 400 Pa·s or higher at 30ºC and a shear rate of 0.003-0.01 s^-1; or the average fiber length of the acid-type carboxylated cellulose nanofibers is 50-500 nm, and the proportion of the fibers each having a fiber length of 300 nm or less is 50% or more.

Description

Acid-type carboxylated cellulose nanofiber

The present invention relates to an acid-type carboxylated cellulose nanofiber.

When cellulose raw material is treated in the presence of 2,2,6,6-tetramethyl-1-piperidine-N-oxy radical (hereinafter also referred to as “TEMPO”) and an inexpensive oxidizing agent, sodium hypochlorite In addition, carboxyl groups can be efficiently introduced onto the surface of cellulose microfibrils. When cellulose introduced with a carboxyl group is treated in water with a mixer or the like, a highly viscous and transparent aqueous dispersion of cellulose nanofibers is obtained.

As described above, since a carboxyl group is introduced on the surface of the cellulose nanofiber, it can be freely modified starting from the carboxyl group. In addition, since the cellulose nanofiber is in the form of a dispersion, it can be blended with a water-soluble polymer or can be modified by being combined with an organic or inorganic pigment. Furthermore, cellulose nanofibers can be formed into sheets or fibers. Due to such characteristics, development of new high-functional products in which cellulose nanofibers are applied to high-functional packaging materials, transparent organic substrate members, high-functional fibers, separation membranes, regenerative medical materials, and the like has been studied.

As an example of the above-mentioned new highly functional product, Patent Document 1 proposes a spray composition containing carboxylated cellulose fibers and water. Since the carboxylated cellulose fiber contained in the spray composition described in Patent Document 1 has not undergone a desalting step, it is presumed that it is a sodium salt type from the production procedure.

Further, for the purpose of reducing energy required for defibrating cellulose introduced with a carboxyl group, it has been proposed to perform an alkali hydrolysis treatment before the defibrating treatment (for example, see Patent Document 2). For the purpose of further reducing the energy required for defibration, it has been proposed to perform a viscosity reduction treatment in addition to the alkali hydrolysis treatment performed before the defibration treatment (see, for example, Patent Document 3). ).

JP 2010-37200 A International Publication No. 2013/137140 JP 2012-214717 A

Patent Document 1 describes that there is an additive whose function is lowered in the presence of salts. Therefore, when using the carboxylated cellulose fiber for a spray composition, the carboxylated cellulose fiber is preferably desalted and converted into an acid form.
However, acid-type carboxylated cellulose nanofibers obtained by acid-treating carboxylated cellulose fibers with a mineral acid such as hydrochloric acid, in a region where the shear rate is low (hereinafter also referred to as “low shear region”), The viscosity tended to be low. For this reason, when used in a spray composition, a thickener may be added to prevent dripping.
Accordingly, development of acid-type carboxylated cellulose nanofibers having a high viscosity in a low shear region is desired.

Moreover, when the cellulose which introduce | transduced the carboxyl group was alkali-hydrolyzed prior to defibration by the method proposed in Patent Documents 2 and 3, the obtained carboxylated cellulose nanofiber is an alkali metal salt type. When this was desalted by acid treatment, acid-type carboxylated cellulose nanofibers could not be isolated.
The present inventors examined the reason why acid-type carboxylated cellulose nanofibers cannot be isolated. After producing alkali-hydrolyzed carboxylated cellulose nanofibers by defibration, nanofibers having extremely short fiber lengths were obtained. It turns out that the ratio increases. Therefore, even if it filtered after the desalting process by an acid treatment, it could not be isolated as a filtrate and was found to be contained in the filtrate together with NaCl and the like.
Among some new high-performance products, there is a field in which acid-type carboxylated cellulose nanofibers having extremely short fiber lengths are desired, and it is preferable to provide them in isolation.

The first object of the present invention is to provide an acid-type carboxylated cellulose nanofiber having a high viscosity in a low shear region.
A second object of the present invention is to provide an acid-type carboxylated cellulose nanofiber having an extremely short fiber length.

As a result of earnestly examining the first problem, the present inventors have found that an acid-type carboxylated cellulose nanofiber obtained by desalting with a cation exchange resin can solve the first problem, The present invention has been completed.
In addition, as a result of intensive studies on the second problem, the present inventors have conducted cation exchange on a carboxylated cellulose nanofiber salt obtained by dehydrofibrating an oxidized cellulose having a carboxyl group introduced therein after alkaline hydrolysis. It discovered that said 2nd subject could be solved by desalinating with resin, and came to complete this invention.
That is, the present inventors provide the following [1] to [8].
[1] Carboxylated cellulose nanofiber having a carboxyl group in at least a part of the constituent units constituting the cellulose molecular chain, the viscosity of the aqueous dispersion having a content of 0.95 to 1.05 mass% is 30 Acid-type carboxylated cellulose nanofibers (hereinafter also referred to as “nanofiber A”) having a shear rate of 400 Pa · s or more at 0.003 to 0.01 s ⁻¹ at ⁰ ° C.
[2] Carboxylated cellulose nanofibers having carboxyl groups in at least some of the constituent units constituting the cellulose molecular chain, the average fiber length is 50 to 500 nm, and the proportion of fibers having a fiber length of 300 nm or less is Acid-type carboxylated cellulose nanofiber (hereinafter also referred to as “nanofiber B”) that is 50% or more.
[3] The acid-type carboxylated cellulose nanofiber according to the above [2], having an average fiber diameter of 2 to 50 nm.
[4] The acid-type carboxylated cellulose nanofiber according to the above [2], having an average fiber diameter of 2 to 30 nm.
[5] The acid-type carboxylated cellulose nanofiber according to any one of the above [2] to [4], wherein the proportion of fibers having a fiber length of 600 nm or more is less than 20%.
[6] At least a part of the cellulose molecular chain is composed of structural units having a carboxyl group in which a carbon atom having a primary hydroxyl group at the C6 position of a glucopyranose unit is selectively oxidized. 5] The acid-type carboxylated cellulose nanofiber according to any one of 5).
[7] The acid form according to any one of [1] to [6], wherein the carboxyl group amount is 0.6 to 2.0 mmol / g based on the absolute dry mass of the carboxylated cellulose nanofiber. Carboxylated cellulose nanofiber.
[8] The acid form according to any one of [1] to [6], wherein the amount of the carboxyl group is 0.8 to 2.0 mmol / g with respect to the absolute dry mass of the carboxylated cellulose nanofiber. Carboxylated cellulose nanofiber.

According to the present invention, an acid-type carboxylated cellulose nanofiber having a high viscosity in a low shear region can be provided.
In addition, according to the present invention, an acid-type carboxylated cellulose nanofiber having an extremely short fiber length can be provided.

FIG. 1 is a graph showing the fiber length distribution of acid-type carboxylated cellulose nanofibers of Examples 1 and 5.

Hereinafter, the present invention will be described in detail on the basis of preferred embodiments thereof. In the present specification, the “acid-type carboxylated cellulose nanofiber” refers to a carboxylated cellulose nanofiber obtained by desalting a metal salt such as a sodium salt to convert it into an acid form.

[1. Nanofiber A]
Nanofiber A of the present invention is acid-type carboxylated cellulose nanofiber. In addition, the nanofiber A of the present invention has a carboxyl group in at least a part of the constituent units constituting the cellulose molecular chain, and the viscosity of the aqueous dispersion having a content of 0.95 to 1.05% by mass is It is 400 Pa · s or more at a shear rate of 0.003 to 0.01 s ⁻¹ at 30 ° C.
Therefore, when the nanofiber A of the present invention is used in, for example, a spray composition, other thickeners are not used, or even if other thickeners are used, dripping can be prevented in a small amount. it can.

In the nanofiber A of the present invention, the lower limit of the viscosity in an aqueous dispersion having a content of 0.95 to 1.05 mass% is 400 Pa at a shear rate of 30 ° C. and 0.003 to 0.01 s ^−1. · S or more, preferably 500 Pa · s or more, and 925 Pa · s. More preferably, it is more than 930 Pa.s. More preferably, it is s or more, and even more preferably 950 Pa · s or more. The upper limit is 100,000 Pa.s. s or less, preferably 50,000 Pa.s. s or less, more preferably 25,000 Pa.s. More preferably, it is s or less.
For example, the viscosity is 0.95 to 1.05% by weight of an aqueous dispersion prepared by adding water to the nanofiber A, and the aqueous dispersion is obtained from a viscoelastic rheometer (for example, “MCR301”). , Manufactured by Anton Paar) and measured at a predetermined shear rate.

The nanofiber A of the present invention preferably has an average fiber length of 200 to 2000 nm, more preferably 250 to 1500 nm, further preferably 300 to 1000 nm, and further preferably 550 to 1000 nm. More preferred.
Further, the nanofiber A of the present invention preferably has an average fiber diameter of 1.50 to 1000 nm, more preferably 2.00 to 750 nm, and further preferably 2.50 to 500 nm. Even more preferably, it is 2.85 to 500 nm.

[2. Nanofiber B]
Nanofiber B of the present invention is acid-type carboxylated cellulose nanofiber. Further, the nanofiber B of the present invention has a carboxyl group in at least a part of the constituent units constituting the cellulose molecular chain, the average fiber length is 50 to 500 nm, and the ratio of fibers having a fiber length of 300 nm or less Is 50% or more.
After subjecting the oxidized cellulose to an alkali hydrolysis treatment, the nanofiber B satisfying the above two fiber length requirements can be isolated and obtained by desalting using a cation exchange resin.

The nanofiber B of the present invention has an average fiber length of 50 to 500 nm, preferably 100 to 400 nm. Moreover, the ratio of the fiber which has a fiber length of 300 nm or less is 50% or more, and it is preferable that it is 60% or more. Furthermore, the proportion of fibers having a fiber length of 600 nm or more is preferably less than 20%, more preferably less than 15%, and even more preferably less than 10%. The nanofiber B satisfying such a condition converges in a region where the fiber length distribution is short, and can be particularly expected to be used as a composite material with a resin or rubber, or as an additive to a coating material.
The nanofiber B of the present invention preferably has an average fiber diameter of 2.0 to 50 nm, 2.0 to 40 nm, 2.0 to 30 nm, 2.5 to 30 nm, 3.0 to 30 nm, 3.0 More preferably, it is ˜20 nm, and further preferably 3.0˜15 nm.

The average fiber length of carboxylated cellulose nanofibers can be calculated as follows. Carboxylated cellulose nanofibers can be fixed on a mica section, 200 fiber lengths can be measured using an atomic force microscope (AFM), and a length (weighted) average fiber length can be calculated. In addition, the measurement of fiber length is performed in the range of arbitrary length using image analysis software WinROOF (made by Mitani Corporation). The ratio of fibers having a fiber length of 300 nm or less or 600 nm or more can be calculated as the ratio of carboxylated cellulose nanofibers of 300 nm or less or 600 nm or more of all measured fibers.
Moreover, the average fiber diameter of carboxylated cellulose nanofiber can be calculated as follows. An aqueous dispersion of carboxylated cellulose nanofibers diluted to have a concentration of carboxylated cellulose nanofibers of 0.001% by mass is prepared. This diluted dispersion is thinly spread on a mica sample stage and dried by heating at 50 ° C. to prepare an observation sample. The cross-sectional height of the shape image observed with an atomic force microscope (AFM) can be measured to calculate the weighted average fiber diameter.

In the nanofiber A and nanofiber B of the present invention, at least a part of a cellulose molecular chain is composed of a structural unit having a carboxyl group in which a carbon atom having a primary hydroxyl group at the C6 position of a glucopyranose unit is selectively oxidized. It is preferred that In addition, a cellulose molecular chain may be comprised only by the structural unit which has the carboxyl group in which the carbon atom which has C1-position primary hydroxyl group of the glucopyranose unit was selectively oxidized.
Here, the glucopyranose unit refers to a structural unit represented by the following formula (0).

In the nanofiber A and nanofiber B of the present invention, the carboxyl group amount is preferably 0.6 to 2.0 mmol / g with respect to the absolutely dry mass of the carboxylated cellulose nanofiber, and 0.8 to 2 It is more preferably 0.0 mmol / g, further preferably 1.2 to 2.0 mmol / g, and still more preferably 1.4 to 1.8 mmol / g. When the carboxyl group amount is 0.6 mmol / g or more, a carboxyl group is introduced to the surface of the cellulose molecular chain and can have an electrostatic repulsion effect, and nanofibers can be produced by defibration. . In addition, when the carboxyl group amount is 0.8 mmol / g or more, the carboxyl group is sufficiently introduced to the surface of the cellulose molecular chain, and can have an electrostatic repulsion action. Can be produced.
The amount of carboxyl groups can be measured as follows. 60 ml of a 0.5% by weight slurry (aqueous dispersion) of carboxylated cellulose is prepared. A 0.1 M hydrochloric acid aqueous solution is added to the prepared slurry to adjust the pH to 2.5, and then 0.05 N sodium hydroxide aqueous solution is dropped to measure the electric conductivity until the pH becomes 11. The amount of carboxyl groups can be calculated from the amount of sodium hydroxide consumed (a) in the neutralization step of the weak acid with a gradual change in electrical conductivity using the following formula:
Amount of carboxyl group [mmol / g carboxylated cellulose] = a [ml] × 0.05 / carboxylated cellulose mass [g]
In addition, the carboxyl group amount of carboxylated cellulose nanofiber and the carboxyl group amount of carboxylated cellulose are usually the same value.

[3. Production method]
The carboxylated cellulose nanofiber can be produced, for example, as follows. The cellulose raw material is oxidized to prepare oxidized cellulose (hereinafter also referred to as “oxidation treatment”), the prepared oxidized cellulose is defibrated (hereinafter also referred to as “defibration treatment”), and the fibrillated oxidized cellulose is converted into a cation. Nanofiber A can be manufactured by desalting with an exchange resin (hereinafter also referred to as “desalting”). In addition, nanofiber B can be manufactured by using oxidized cellulose obtained by alkaline hydrolysis (hereinafter, also referred to as “alkaline hydrolysis treatment”) of oxidized cellulose after oxidization treatment and before defibration treatment.
The acid-type carboxylated cellulose nanofibers can also be produced by subjecting the prepared oxidized cellulose or hydrolyzed oxidized cellulose to a desalting treatment with a cation exchange resin, followed by a fibrillation treatment. In the following description, a case where acid-type carboxylated cellulose nanofibers are produced by desalting with a cation exchange resin after defibration will be described.

[3-1. Oxidation treatment]
The oxidation treatment is a treatment for preparing oxidized cellulose by oxidizing a cellulose raw material. The oxidation method is not particularly limited, but a method using an oxidizing agent in the presence of an N-oxyl compound and bromide, iodide or a mixture thereof is preferable. When the cellulose raw material is oxidized by this method, a structural unit having a carboxyl group in which a carbon atom having a primary hydroxyl group at the C6 position of a glucopyranose unit constituting a cellulose molecular chain is selectively oxidized can be obtained.
The partial structure of oxidized cellulose obtained by this method is shown in the following general formula (1).

(In general formula (1), M ₁ represents a cation salt.)

In the general formula (1), examples of the cation salt represented as M ₁ include alkali metal salts such as sodium salt and potassium salt, phosphonium salt, imidazolinium salt, ammonium salt and sulfonium salt.

Natural cellulose has a microfibril structure in which a large number of linear cellulose molecular chains are converged by hydrogen bonds. When cellulose is oxidized using an N-oxyl compound, a carbon atom having a primary hydroxyl group at the C6 position of a glucopyranose unit constituting a cellulose molecular chain is selectively oxidized to a carboxyl group via an aldehyde group as described above. . Therefore, carboxyl groups are introduced at a high density on the surface of the microfibril structure. The introduced carboxyl group has a repulsive action, and cellulose nanofibers separated one by one by defibration can be obtained.

The cellulose raw material includes wood-derived kraft pulp or sulfite pulp, powdered cellulose obtained by pulverizing them with a high-pressure homogenizer, a mill, or the like, or microcrystalline cellulose powder obtained by purifying them by chemical treatment such as acid hydrolysis. In addition, plant-derived cellulose raw materials such as kenaf, hemp, rice, bagasse and bamboo can also be used. From the viewpoint of mass production and cost, it is preferable to use powdered cellulose, microcrystalline cellulose powder, or chemical pulp such as kraft pulp or sulfite pulp. When using chemical pulp, it is preferable to perform a known bleaching treatment to remove lignin. As the bleached pulp, for example, bleached kraft pulp or bleached sulfite pulp having a whiteness (ISO 2470) of 80% or more can be used.

Powdered cellulose is rod-like particles made of microcrystalline or crystalline cellulose obtained by removing the non-crystalline portion of wood pulp by acid hydrolysis, and then pulverizing and sieving. In powdered cellulose, the degree of polymerization of cellulose is about 100 to 500, the degree of crystallinity of powdered cellulose by X-ray diffraction is 70 to 90%, and the volume average particle size by a laser diffraction type particle size distribution device is usually 100 μm or less. Preferably, it is 50 μm or less. Such powdered cellulose may be prepared by purifying and drying an undegraded residue obtained after acid hydrolysis of a selected pulp, pulverizing and sieving, or KC Flock (registered trademark) (Nippon Paper Industries Co., Ltd.). Manufactured products), Theolas (registered trademark) (manufactured by Asahi Kasei Chemicals), Avicel (registered trademark) (manufactured by FMC), and the like may be used.

Bleaching methods include chlorination (C), chlorine dioxide bleach (D), alkali extraction (E), hypochlorite bleach (H), hydrogen peroxide bleach (P), alkaline hydrogen peroxide treatment stage ( Ep), alkaline hydrogen peroxide / oxygen treatment stage (Eop), ozone treatment (Z), chelate treatment (Q) and the like can be performed in combination. For example, C / D-EHD, ZEDP, Z / D-Ep-D, Z / D-Ep-DP, D-Ep-D, D-Ep-D- P, D-Ep-PD, Z-Eop-DD, Z / D-Eop-D, Z / D-Eop-DED, etc. can be used. Note that “/” in the sequence means that the processes before and after “/” are continuously performed without cleaning.

In addition, the above cellulose raw material that has been refined by a high-speed rotating type, colloid mill type, high-pressure type, roll mill type, ultrasonic type dispersing device, wet high-pressure or ultra-high pressure homogenizer, etc. should be used as the cellulose raw material. You can also.

An N-oxyl compound is a compound capable of generating a nitroxy radical. As the N-oxyl compound, any compound can be used as long as it is a compound that performs the target oxidation reaction. Examples of the N-oxyl compound include compounds represented by the following general formulas (2) to (5) and (7) and compounds represented by the following formula (6).

(In the general formula (2), R 1 ^- R ⁴ are the same or different optionally 1 carbon atoms even if 1-4 alkyl group, R ⁵ represents a hydrogen atom or a hydroxyl group.)

(In the general formulas (3) to (5), R ⁶ represents a linear or branched hydrocarbon group having 1 to 4 carbon atoms.)

(In the general formula ^{(7), R 7 ~ R} 8 denote the same or may be different, a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms.)

In the general formula (2), examples of the alkyl group having 1 to 4 carbon atoms represented by R ¹ to R ⁴ include a methyl group, an ethyl group, a propyl group, and a butyl group. Of these, a methyl group or an ethyl group is preferable.
In the general formulas (3) to (5), examples of the linear or branched hydrocarbon group having 1 to 4 carbon atoms represented by R ⁶ include a methyl group, an ethyl group, an n-propyl group, Examples include isopropyl group, n-butyl group, s-butyl group, and t-butyl group. Of these, a methyl group or an ethyl group is preferable.
In the general formula (7), examples of the linear or branched alkyl group having 1 to 6 carbon atoms represented by R ⁷ to R ⁸ include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. N-butyl group, s-butyl group, t-butyl group, n-pentyl group and n-hexyl group. Of these, a methyl group or an ethyl group is preferable.

Examples of the compound represented by the general formula (2) include 2,2,6,6-tetramethyl-1-piperidine-N-oxy radical (hereinafter also referred to as “TEMPO”), or 4-hydroxy-2 2,6,6-tetramethyl-1-piperidine-N-oxy radical (hereinafter also referred to as “4-hydroxy TEMPO”).
The N-oxyl compound may be TEMPO or a derivative of 4-hydroxy TEMPO. As a derivative of 4-hydroxy TEMPO, for example, a compound represented by the general formula (3), that is, a hydroxyl group of 4-hydroxy TEMPO has a linear or branched hydrocarbon group having 4 or less carbon atoms. Derivatives obtained by etherification with alcohol and compounds represented by general formula (4) or (5), that is, derivatives obtained by esterification with carboxylic acid or sulfonic acid can be mentioned.
When 4-hydroxy TEMPO is etherified, if an alcohol having 4 or less carbon atoms is used, the resulting derivative becomes water-soluble regardless of the presence or absence of saturated or unsaturated bonds in the alcohol, and is a good oxidation catalyst. To work.

When the N-oxyl compound is a compound represented by the formula (6), that is, a compound in which the amino group of 4-amino TEMPO is acetylated, moderate hydrophobicity is imparted, and it is inexpensive and uniform oxidation. Since cellulose can be obtained, it is preferable. The N-oxyl compound is preferably a compound represented by the general formula (7), that is, an azaadamantane-type nitroxy radical, because uniform oxidized cellulose can be obtained in a short time.

The amount of the N-oxyl compound used is not particularly limited as long as it is a catalytic amount that can oxidize the cellulose raw material sufficiently to make the obtained oxidized cellulose nanofiber. For example, the amount is preferably 0.01 to 10 mmol, more preferably 0.01 to 1 mmol, and still more preferably 0.01 to 0.5 mmol with respect to 1 g of the absolutely dry cellulose raw material.

The bromide used in the oxidation of the cellulose raw material is a compound containing bromine, and examples thereof include an alkali metal bromide that can be dissociated and ionized in water. Further, an iodide is a compound containing iodine, and examples thereof include alkali metal iodide.
The amount of bromide or iodide used can be adjusted as long as the target oxidation reaction can be promoted. The total amount of bromide and iodide is, for example, preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, and still more preferably 0.5 to 5 mmol with respect to 1 g of the absolutely dry cellulose raw material.

As the oxidizing agent, for example, known oxidizing agents such as halogen, hypohalous acid, halous acid, perhalogen acid or salts thereof, halogen oxide, peroxide, and the like can be used. Of these, sodium hypochlorite is preferable because it is inexpensive and has a low environmental impact.
The amount of the oxidizing agent used may be any amount that allows an oxidation reaction. For example, the amount is preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, and still more preferably 2 with respect to 1 g of cellulose raw material. .5-25 mmol.

Since the oxidation reaction of the cellulose raw material proceeds efficiently even under relatively mild conditions, the reaction temperature may be about 15 to 30 ° C. As the reaction proceeds, carboxyl groups are generated in the cellulose, so that the pH value of the reaction solution decreases. In order to allow the oxidation reaction to proceed efficiently, an alkaline solution such as an aqueous sodium hydroxide solution is added to the reaction system in a timely manner so that the pH value of the reaction solution is maintained at 9 to 12, preferably about 10 to 11. preferable. The reaction medium is preferably water because it is easy to handle and hardly causes side reactions.

The reaction time in the oxidation reaction can be appropriately set according to the progress of oxidation, and is usually about 0.5 to 6 hours, preferably about 0.5 to 4 hours.

Moreover, the oxidation reaction may be carried out in two stages. For example, by oxidizing the cationic salt of oxidized cellulose obtained by filtration after completion of the first-stage reaction again under the same or different reaction conditions, the reaction is inhibited by the salt produced as a by-product in the first-stage reaction. And a carboxyl group can be efficiently introduced into the cellulose raw material.

In the oxidized cellulose obtained in the above step, the carboxyl group introduced into the cellulose raw material is usually an alkyl metal salt such as a sodium salt. Prior to the desalting or defibrating treatment described below, the alkali metal salt of oxidized cellulose may be replaced with another cation salt such as a phosphonium salt, an imidazolinium salt, an ammonium salt, or a sulfonium salt. The substitution can be performed by a known method.

As another example of the oxidation method, a method of oxidizing by contacting a gas containing ozone and a cellulose raw material can be mentioned. By this oxidation reaction, the carbon atom having at least the 2-position and 6-position hydroxyl groups of the glucopyranose ring is oxidized and the cellulose chain is decomposed.

The ozone concentration in the gas containing ozone is preferably 50 to 250 g / m ³ , more preferably 50 to 220 g / m ³ . The amount of ozone added to the cellulose raw material is preferably 0.1 to 30 parts by mass, and more preferably 5 to 30 parts by mass, when the solid content of the cellulose raw material is 100 parts by mass. The ozone treatment temperature is preferably 0 to 50 ° C., and more preferably 20 to 50 ° C. The ozone treatment time is not particularly limited, but is usually about 1 to 360 minutes, and preferably about 30 to 360 minutes. When the conditions for the ozone treatment are within these ranges, the cellulose can be prevented from being excessively oxidized and decomposed, and the yield of oxidized cellulose is improved.

After the ozone treatment, an additional oxidation treatment may be performed using an oxidizing agent. The oxidizing agent used for the additional oxidation treatment is not particularly limited, and examples thereof include chlorine compounds such as chlorine dioxide and sodium chlorite, oxygen, hydrogen peroxide, persulfuric acid, peracetic acid and the like. For example, these oxidizing agents can be dissolved in a polar organic solvent such as water or alcohol to prepare an oxidizing agent solution, and a cellulose raw material can be immersed in the solution for additional oxidation treatment.

The oxidized cellulose obtained by the oxidation treatment is preferably washed before being subjected to the following alkaline hydrolysis treatment from the viewpoint of avoiding side reactions. The washing method is not particularly limited, and can be performed by a known method.

[3-2. Defibration treatment]
The defibrating process is a process of defibrating oxidized cellulose or oxidized cellulose subjected to alkali hydrolysis treatment. Since the carboxyl group is introduced into the oxidized cellulose or the oxidized cellulose subjected to the alkali hydrolysis treatment by the oxidation treatment, it can be easily made into nanofibers by the fibrillation treatment.

As the fibrillation treatment, for example, the oxidized cellulose or the oxidized cellulose subjected to the alkali hydrolysis treatment can be sufficiently washed with water and then used using a known apparatus such as a high-speed shear mixer or a high-pressure homogenizer. Examples of the type of defibrating apparatus include a high-speed rotation type, a colloid mill type, a high-pressure type, a roll mill type, and an ultrasonic type. These devices may be used alone or in combination of two or more.

When a high-speed shear mixer is used, the shear rate is preferably 1000 sec ⁻¹ or more. When the shear rate is 1000 sec ⁻¹ or more, there are few aggregated structures, and nanofibers can be formed uniformly.
When using a high-pressure homogenizer, the applied pressure is preferably 50 MPa or more, more preferably 100 MPa or more, and further preferably 140 MPa or more. When treated with a wet high-pressure or ultrahigh-pressure homogenizer at the pressure, nanofibrosis proceeds efficiently, and carboxylated cellulose nanofibers can be obtained efficiently.

The oxidized cellulose or the oxidized cellulose subjected to the alkali hydrolysis treatment is subjected to a defibrating treatment as an aqueous dispersion such as water. If the concentration of oxidized cellulose or oxidized cellulose subjected to alkali hydrolysis treatment in the aqueous dispersion is high, the viscosity may increase excessively during the defibrating process and may not be defibrated uniformly or the device may stop. . Therefore, the concentration of the oxidized cellulose or the oxidized cellulose subjected to the alkali hydrolysis treatment needs to be appropriately set according to the processing conditions of the oxidized cellulose or the oxidized cellulose subjected to the alkali hydrolysis treatment. As an example, the concentration of oxidized cellulose or oxidized cellulose subjected to alkali hydrolysis treatment is preferably 0.3 to 50% (w / v), more preferably 0.5 to 10% (w / v), and 1.0 to 5% (w / v) is more preferable.

[3-3. Alkaline hydrolysis treatment]
The alkali hydrolysis treatment is a treatment for preparing hydrolyzed oxidized cellulose by hydrolyzing the oxidized cellulose obtained by the above-described oxidation treatment in an alkaline solution. The acid-type carboxylation obtained by obtaining the treatment The cellulose nanofiber is Nanofiber B. The reaction medium for the hydrolysis treatment is preferably water from the viewpoint of suppressing side reactions.
By hydrolyzing in an alkaline solution, the nanofiber B is shortened to satisfy the numerical range defined in the present application. The reason is presumed as follows. A carboxyl group is interspersed in an amorphous region of oxidized cellulose oxidized with an N-oxyl compound, and an electron is attracted to the hydrogen atom at the C5 position adjacent to the carboxyl group by the carboxyl group. So it is in a state of lack of charge. Therefore, under alkaline conditions of pH 8 to 14, the hydrogen atom is easily extracted with hydroxide ions, and the glucoside bond is cleaved by β elimination reaction. As a result, oxidized cellulose is shortened, and the proportion of carboxylated cellulose nanofibers having a short fiber length is also increased.

When hydrolyzing in an alkaline solution, the pH value of the reaction solution in the reaction is preferably 8 to 14, more preferably 9 to 13, and further preferably 10 to 12. When the pH value is less than 8, sufficient hydrolysis does not occur, and shortening of oxidized cellulose may be insufficient. On the other hand, when the pH value exceeds 14, hydrolysis proceeds, but the oxidized cellulose after hydrolysis is colored, and the resulting cellulose nanofiber is also colored, so that the transparency is lowered and the application technique is limited. May arise. The alkali used for adjusting the pH value may be water-soluble, and sodium hydroxide is preferable from the viewpoint of production cost.

Hydrolysis of oxidized cellulose in an alkaline solution may cause the oxidized cellulose to be colored yellow due to the formation of double bonds during β elimination. Therefore, the obtained cellulose nanofibers are also colored and the transparency is lowered, and the application technique may be limited. Therefore, it is preferable to perform a hydrolysis process using an oxidizing agent or a reducing agent as an adjuvant, in order to suppress the production | generation of a double bond. When an oxidizing agent or a reducing agent is used in the hydrolysis treatment in an alkaline solution having a pH value of 8 to 14, the oxidized cellulose can be shortened while oxidizing or reducing the double bond. As the oxidizing agent or reducing agent, those having activity in the alkaline region can be used.
From the viewpoint of reaction efficiency, the amount of the auxiliary added is preferably 0.1 to 10% by mass, more preferably 0.3 to 5% by mass, and 0.5 to 2% by mass with respect to the absolutely dry oxidized cellulose. Further preferred.

Examples of the oxidizing agent include oxygen, ozone, hydrogen peroxide, and hypochlorite. Among them, the oxidizing agent is less likely to generate radicals, and oxygen, hydrogen peroxide, and hypochlorite are preferable, and hydrogen peroxide is more preferable.
In addition, an oxidizing agent may be used individually by 1 type, and may be used in combination of 2 or more type.

Examples of the reducing agent include sodium borohydride, hydrosulfite, and sulfite.
In addition, a reducing agent may be used individually by 1 type, and may be used in combination of 2 or more type.

From the viewpoint of reaction efficiency, the hydrolysis reaction temperature is preferably 40 to 120 ° C, more preferably 50 to 100 ° C, and further preferably 60 to 90 ° C. When the temperature is low, sufficient hydrolysis does not occur, and shortening of oxidized cellulose or carboxylated cellulose nanofibers may be insufficient. On the other hand, when the temperature is high, hydrolysis proceeds, but the oxidized cellulose after hydrolysis may be colored.
The reaction time for hydrolysis is preferably 0.5 to 24 hours, more preferably 1 to 10 hours, and further preferably 2 to 6 hours.
From the viewpoint of reaction efficiency, the concentration of oxidized cellulose in the alkaline solution is preferably 1 to 20% by mass, more preferably 3 to 15% by mass, and even more preferably 5 to 10% by mass.

[3-4. Desalination treatment]
The desalting treatment is a treatment for desalting the fibrillated oxidized cellulose or the alkali hydrolyzed oxidized cellulose (carboxylated cellulose nanofiber salt) with a cation exchange resin. The cationic salt of oxidized cellulose that has been fibrillated by the treatment or oxidized cellulose that has been subjected to alkali hydrolysis can be substituted with protons to obtain acid-type carboxylated cellulose nanofibers. Since a cation exchange resin is used, unnecessary by-products such as sodium chloride are not generated, and after desalting with the cation exchange resin, the cation exchange resin is removed by filtration through a metal mesh or the like. As a result, an aqueous dispersion of acid-substituted carboxylated cellulose nanofibers with proton substitution can be obtained as a filtrate.

An object to be removed as a filtrate by a metal mesh or the like is a cation exchange resin, and carboxylated cellulose nanofibers are hardly removed by the diameter of the metal mesh or the like, and almost the entire amount is contained in the filtrate. Therefore, the yield reduction is extremely small.
The filtrate contains a large amount of carboxylated cellulose nanofibers having a short fiber length. Further, since the filtrate does not have to be washed or dehydrated, the acid-type carboxylated cellulose nanofibers are hardly aggregated. Therefore, when the alkali hydrolysis treatment is not obtained, it is presumed that the dispersion of carboxylated cellulose nanofibers has a high viscosity in the low shear region. In addition, when an alkali hydrolysis treatment is obtained, an acid-type carboxylated cellulose nanofiber having an extremely short fiber length can be isolated.

The carboxylated cellulose nanofiber salt can be directly used in the desalting step with the aqueous dispersion obtained in the defibrating step. If necessary, water can be added to lower the concentration.

As the cation exchange resin, any of strong acid ion exchange resin and weak acid ion exchange resin can be used as long as the counter ion is H ⁺ . Among these, it is preferable to use a strongly acidic ion exchange resin. Examples of the strong acid ion exchange resin and the weak acid ion exchange resin include those obtained by introducing a sulfonic acid group or a carboxyl group into a styrene resin or an acrylic resin.
The shape of the cation exchange resin is not particularly limited, and various shapes such as fine particles (particles), membranes, and fibers can be used. Among these, granular is preferable from the viewpoint that the carboxylated cellulose nanofiber salt is efficiently desalted and separation after the desalting is easy. A commercial item can be used as such a cation exchange resin. Commercially available products include, for example, AmberJet 1020, 1024, 1060, 1220 (above, Organo), Amberlite IR-200C, IR-120B (above, Tokyo Organic Chemical Co.), Lebatit SP 112 S100 (manufactured by Bayer), GEL CK08P (manufactured by Mitsubishi Chemical), Dowex 50W-X8 (manufactured by Dow Chemical) and the like.

The desalting treatment is performed, for example, by mixing a granular cation exchange resin and an aqueous dispersion of carboxylated cellulose nanofiber salt, and stirring and shaking as necessary to obtain a carboxylated cellulose nanofiber salt and a cation. After the contact with the exchange resin for a certain time, the cation exchange resin and the aqueous dispersion can be separated.

The concentration of the aqueous dispersion and the ratio with the cation exchange resin are not particularly limited, and those skilled in the art can appropriately set from the viewpoint of efficiently performing proton substitution. As an example, the concentration of the aqueous dispersion is preferably 0.05 to 10% by mass. If the concentration of the aqueous dispersion is less than 0.05% by mass, it may take too much time for proton substitution. If the concentration of the aqueous dispersion is more than 10% by mass, sufficient proton substitution effect may not be obtained.
The contact time is also not particularly limited, and those skilled in the art can appropriately set from the viewpoint of efficiently performing proton substitution. For example, the contact can be performed for 0.2 to 4 hours.

At this time, the carboxylated cellulose nanofiber salt or oxidized cellulose is contacted for a sufficient time using an appropriate amount of the cation exchange resin, and then the cation exchange resin is removed as a filtrate with a metal mesh or the like, thereby removing the cation exchange resin. Salt treatment can be performed.

[3-5. Short fiber treatment]
When manufacturing the nanofiber B of this invention, you may perform a fiber shortening process after an oxidation process or an alkali hydrolysis process and before a fibrillation process. By performing such treatment, nanofiber B having a shorter fiber length can be produced.
The fiber shortening treatment refers to a treatment for appropriately shortening the fiber by appropriately cutting the cellulose chain of oxidized cellulose or oxidized cellulose subjected to alkali hydrolysis treatment. For example, ultraviolet irradiation treatment, oxidative decomposition treatment, acid hydrolysis treatment and the like can be mentioned. Among these, acid hydrolysis treatment is preferable.
In addition, said process may be 1 type of single process, and may combine 2 or more types of processes.

The acid hydrolysis treatment is a treatment for hydrolyzing oxidized cellulose or oxidized cellulose subjected to alkali hydrolysis treatment in an acidic solution.
Carboxylated cellulose nanofibers can be shortened by hydrolysis in an acidic aqueous solution. The reason is presumed as follows. A carboxyl group is localized on the surface of the cellulose raw material oxidized using the N-oxyl compound, and a hydrated layer is formed. For this reason, the oxidized celluloses are close to each other and form a network. When an acid is added to the oxidized cellulose for hydrolysis, the balance of charges in the network is lost, and a strong network of cellulose molecules is lost. As a result, the specific surface area of the oxidized cellulose increases, and shortening of the oxidized cellulose is promoted. Therefore, since oxidized cellulose is shortened, the proportion of carboxylated cellulose nanofibers having a short fiber length also increases.

When hydrolyzing in an acidic solution, it is preferable to use a mineral acid such as sulfuric acid, hydrochloric acid, nitric acid, or phosphoric acid as the acid. In order to carry out the reaction efficiently, it is preferable to use a dispersion liquid in which oxidized cellulose is dispersed in a dispersion medium such as water.
The conditions for the hydrolysis in the acidic solution may be any conditions that allow the acid to act on the amorphous part of cellulose. For example, the amount of acid added is preferably 0.01 to 0.5% by mass, more preferably 0.1 to 0.5% by mass, based on the absolutely dry mass of oxidized cellulose. It is preferable for the amount of acid added to be 0.01% by mass or more, since hydrolysis of cellulose proceeds and the treatment efficiency in the defibrating process is improved. Moreover, the excessive hydrolysis of a cellulose can be prevented as the addition amount is 0.5 mass% or less, and the fall of the yield of a cellulose nanofiber can be prevented.

When hydrolyzing in an acidic solution, the pH value of the reaction solution in the reaction is preferably 2.0 to 4.0, more preferably 2.0 or more and less than 3.0. From the viewpoint of reaction efficiency, the reaction temperature is preferably 70 to 120 ° C. and the reaction time is preferably 1 to 10 hours.

When hydrolyzed in an acidic solution, it is usually neutralized by adding an alkali such as sodium hydroxide in order to efficiently perform the defibration process.

The ultraviolet irradiation treatment is a treatment for irradiating ultraviolet rays to oxidized cellulose or oxidized cellulose subjected to alkali hydrolysis treatment. By irradiating ultraviolet rays, carboxylated cellulose nanofibers can be shortened. The reason is presumed as follows. Ultraviolet rays can directly act on cellulose and hemicellulose to lower the molecular weight, and shorten the cellulose chain in oxidized cellulose. Therefore, the proportion of carboxylated cellulose nanofibers with a short fiber length also increases.

When irradiating ultraviolet rays to oxidized cellulose or oxidized cellulose subjected to alkali hydrolysis treatment, the wavelength of ultraviolet rays used is preferably 100 to 400 nm, more preferably 100 to 300 nm. Among these, ultraviolet rays having a wavelength of 135 to 260 nm are preferable because they can directly act on cellulose and hemicellulose to cause low molecular weight and shorten the cellulose chain in oxidized cellulose.

As a light source for irradiating ultraviolet rays, a light source using light in a wavelength region of 100 to 400 nm can be used. For example, a xenon short arc lamp, an ultra high pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a deuterium lamp, and a metal halide lamp can be used.
In addition, these light sources may be used individually by 1 type, and may be used in combination of 2 or more types arbitrarily. It is preferable to use a combination of a plurality of light sources having different wavelength characteristics, because ultraviolet rays having different wavelengths are simultaneously irradiated to increase the number of cut sites in the cellulose chain and hemicellulose chain, thereby promoting shortening of the fiber.

As the container for containing oxidized cellulose when performing ultraviolet irradiation, for example, when ultraviolet rays of 300 to 400 nm are used, a container made of hard glass can be used. When ultraviolet rays having a wavelength shorter than 300 nm are used, it is preferable to use a quartz glass container that transmits ultraviolet rays more. In addition, what is necessary is just to select appropriately about the material of the part which does not participate in the light transmission reaction of a container from materials with little deterioration with respect to the wavelength of the ultraviolet-ray used.

The concentration of oxidized cellulose upon irradiation with ultraviolet rays is preferably 0.1 to 12% by mass, more preferably 0.5 to 5% by mass, and still more preferably 1 to 3% by mass. It is preferable that the concentration of oxidized cellulose is 0.1% by mass or more because energy efficiency is increased. It is preferable that the concentration of the oxidized cellulose is 12% by mass or less because the flowability of the oxidized cellulose in the ultraviolet irradiation device is good and the reaction efficiency is increased.

The temperature at the time of irradiation with ultraviolet rays is preferably 20 to 95 ° C., more preferably 20 to 80 ° C., and further preferably 20 to 50 ° C. A temperature of 20 ° C. or higher is preferable because the efficiency of the photooxidation reaction is increased. When the temperature is 95 ° C. or lower, there is no possibility of adverse effects such as deterioration of the quality of oxidized cellulose, and there is no possibility that the pressure in the reaction apparatus exceeds atmospheric pressure, and it is necessary to design an apparatus that takes pressure resistance into consideration. Since it disappears, it is preferable.

The pH value when irradiating with ultraviolet rays is not particularly limited, but considering the simplification of the process, the neutral value, for example, the pH value is preferably about 6.0 to 8.0.

The degree of irradiation received by oxidized cellulose during ultraviolet irradiation can be arbitrarily set by adjusting the residence time of oxidized cellulose in the irradiation reaction apparatus, adjusting the amount of energy of the irradiation light source, or the like. In addition, the concentration of oxidized cellulose in the irradiation apparatus can be adjusted by dilution with water, or the concentration of oxidized cellulose can be adjusted by blowing an inert gas such as air or nitrogen into the oxidized cellulose. It is possible to arbitrarily control the irradiation amount of ultraviolet rays received by oxidized cellulose. These conditions such as residence time and concentration can be appropriately set according to the target quality of oxidized cellulose (fiber length, cellulose polymerization degree, etc.) after ultraviolet irradiation.

When the ultraviolet irradiation treatment is performed in the presence of an auxiliary agent such as oxygen, ozone, peroxide (hydrogen peroxide, peracetic acid, sodium percarbonate, sodium perborate, etc.), the efficiency of the photooxidation reaction is increased. preferable.

When irradiating ultraviolet rays in the wavelength region of 135 to 242 nm, ozone is generated from the air present in the gas phase around the light source. While continuously supplying air to the periphery of the light source, the generated ozone is continuously extracted, and this extracted ozone is injected into the oxidized cellulose, so that light can be supplied without supplying ozone from outside the system. Ozone can also be used as an auxiliary for the oxidation reaction. Further, by supplying oxygen to the gas phase around the light source, a larger amount of ozone can be generated in the system, and the generated ozone can also be used as an auxiliary agent for the photooxidation reaction. In this way, ozone generated secondary by the ultraviolet irradiation reactor can also be used.

The ultraviolet irradiation treatment may be repeated a plurality of times. The number of repetitions is not particularly limited, but can be appropriately set according to the relationship such as the target quality of oxidized cellulose. For example, preferably 100 to 400 nm, more preferably 135 to 260 nm, preferably 1 to 10 times, more preferably 2 to 5 times, as an irradiation time per time, preferably 0.5 to 10 hours, More preferably, it can be carried out by irradiating with ultraviolet rays for 0.5 to 3 hours.

When oxidized cellulose is subjected to oxidative decomposition treatment, hydrogen peroxide and ozone are usually used in combination.
The reason why the oxidized cellulose can be efficiently shortened by using hydrogen peroxide and ozone together is presumed as follows. Carboxyl groups are localized on the surface of oxidized cellulose produced by oxidation using an N-oxyl compound, and a hydrated layer is formed. Therefore, it is considered that there is a microscopic gap between the cellulose chains of the oxidized cellulose, which is not found in ordinary cellulose, due to the action of the charge repulsion between the carboxyl groups. When the oxidized cellulose is treated with ozone and hydrogen peroxide, hydroxy radicals with excellent oxidizing power are generated from the ozone and hydrogen peroxide, and the cellulose chains in the oxidized cellulose are efficiently oxidized and decomposed. Short fiber. Therefore, the proportion of carboxylated cellulose nanofibers with a short fiber length also increases.

Ozone can be generated by a known method using an ozone generator using air or oxygen as a raw material. The amount of ozone added (in terms of mass) is preferably 0.1 to 3 times, more preferably 0.3 to 2.5 times, and more preferably 0.5 to 1.5 times the absolute dry mass of oxidized cellulose. Further preferred. When the amount of ozone added is at least 0.1 times the absolute dry mass of oxidized cellulose, the amorphous part of cellulose can be sufficiently decomposed. When the amount of ozone added is 3 times or less of the absolutely dry mass of oxidized cellulose, excessive decomposition of cellulose can be suppressed, and a decrease in the yield of oxidized cellulose can be prevented.

The amount of hydrogen peroxide added (in terms of mass) is preferably 0.001 to 1.5 times, more preferably 0.1 to 1.0 times the absolute dry mass of oxidized cellulose. When the added amount of hydrogen peroxide is 0.001 times or more of the absolutely dry mass of oxidized cellulose, the synergistic effect of ozone and hydrogen peroxide is exhibited. In addition, when the oxidized cellulose is decomposed, it is sufficient that the amount of hydrogen peroxide added is not more than 1.5 times that of oxidized cellulose, and adding more than 1.5 times is not preferable because it leads to an increase in cost.

As conditions for the oxidative decomposition treatment with ozone and hydrogen peroxide, the pH value is preferably 2 to 12, more preferably 4 to 10, more preferably 6 to 8, and the temperature is preferably 10 to 90 ° C. The reaction efficiency is preferably 20 to 70 ° C., more preferably 30 to 50 ° C., and the reaction time is preferably 1 to 20 hours, more preferably 2 to 10 hours, and further preferably 3 to 6 hours. From the viewpoint of

The apparatus for performing the treatment with ozone and hydrogen peroxide is not particularly limited, and a known apparatus can be used. For example, a normal reactor equipped with a reaction chamber, a stirrer, a chemical injection device, a heater, and a pH electrode can be used.

Ozone and hydrogen peroxide remaining in the aqueous solution after the treatment with ozone and hydrogen peroxide act effectively in the defibrating process, and can further promote the lowering of the viscosity of the dispersion of carboxylated cellulose nanofibers.

[4. Application]
The nanofiber A of the present invention can be used for spray compositions, rubber reinforcing materials, resin reinforcing materials, cosmetics, medical products, foods, beverages, paints, and the like. Especially, it is preferable to use for the composition for sprays which utilizes the characteristic that it is a high viscosity in a low shear area | region.

(Spray composition)
The composition for spraying contains the nanofiber A and water. Depending on the application of the spray, the spray composition may contain a functional additive.
Since the nanofiber A has a high viscosity in the low shear region, the spray composition can prevent dripping with no additional thickener or a small amount.

Examples of the functional additive include surfactants, oils, humectants, organic fine particles, inorganic fine particles, preservatives, deodorants, fragrances, organic solvents and the like. These can be selected depending on the application of the spray composition.
In addition, a functional additive may be used individually by 1 type, and may be used in combination of 2 or more type.

Examples of the nonionic surfactant include propylene glycol fatty acid ester, glycerin fatty acid ester, polyoxyethylene glycerin fatty acid ester, polyglycerin fatty acid ester sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbit fatty acid ester, Polyethylene glycol fatty acid ester, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, polyoxyethylene alkyl ether, polyoxyethylene phytosterol, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene lanolin, polyoxy Ethylene lanolin alcohol, polyoxyethylene beeswax derivative, polio Shi polyoxyethylene alkyl amines, polyoxyethylene fatty acid amides, polyoxyethylene alkylphenyl formaldehyde condensates and the like.

Examples of oils include jojoba oil, macadamia nut oil, avocado oil, evening primrose oil, mink oil, rapeseed oil, castor oil, sunflower oil, corn oil, cacao oil, coconut oil, rice bran oil, olive oil, almond oil, sesame oil, safflower oil. Natural animal and vegetable fats and oils such as flower oil, soybean oil, cocoon oil, persic oil, cottonseed oil, molasses, palm oil, palm kernel oil, egg yolk oil, lanolin, squalene; synthetic triglyceride, squalane, liquid paraffin, petrolatum, ceresin, microcrystalline wax , Hydrocarbons such as isoparaffin; waxes such as carnauba wax, paraffin wax, whale wax, beeswax, candelilla wax, lanolin; higher alcohols (cetanol, stearyl alcohol, lauryl alcohol, cetostearyl alcohol, olei Alcohol, behenyl alcohol, lanolin alcohol, hydrogenated lanolin alcohol, hexyl decanol, octyldodecanol, etc.); lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, isostearic acid, oleic acid, linolenic acid, linoleic acid, oxystearic acid Higher fatty acids such as undecylenic acid, lanolin fatty acid, hard lanolin fatty acid, soft lanolin fatty acid; cholesterol and derivatives thereof such as cholesteryl-octyldodecyl-behenyl; isopropyl myristic acid, isopropyl palmitic acid, isopropyl stearic acid, glycerol 2-ethylhexanoate , Esters such as butyl stearic acid; diethylene glycol monopropyl ether, polyoxyethylene polyoxypropylene pentaerythritol Polar oils such as ether ether, polyoxypropylene butyl ether, ethyl linoleate; amino-modified silicone, epoxy-modified silicone, carboxyl-modified silicone, carbinol-modified silicone, methacryl-modified silicone, mercapto-modified silicone, phenol-modified silicone, one-end reactive silicone, Different functional group-modified silicones, polyether-modified silicones, methylstyryl-modified silicones, alkyl-modified silicones, higher fatty acid ester-modified silicones, hydrophilic specially-modified silicones, higher alkoxy-modified silicones, higher fatty acid-containing silicones, silicones such as fluorine-modified silicones, etc. Is given.
The details of silicones are dimethylpolysiloxane, methylphenylpolysiloxane, methylpolysiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexanesiloxane, methylcyclopolysiloxane, octamethyltrisiloxane, decamethyl. Tetrasiloxane, polyoxyethylene / methylpolysiloxane copolymer, polyoxypropylene / methylpolysiloxane copolymer, poly (oxyethylene / oxypropylene) methylpolysiloxane copolymer, methylhydrogenpolysiloxane, tetrahydrotetramethylcyclo Tetrasiloxane, stearoxymethyl polysiloxane, cetoxymethyl polysiloxane, methyl polysiloxane emulsion, highly polymerized methyl poly Rokisan, trimethylsiloxy silicic acid, crosslinked methylpolysiloxane, a crosslinked methylphenyl polysiloxane.

Examples of humectants include polyhydric alcohols such as glyceryl trioctanoate, maltitol, sorbitol, glycerin, propylene glycol, 1,3-butylene glycol, polyethylene glycol, glycol; organic acids such as pyrrolidone carboxylate soda, lactate soda, and sodium citrate And its salts; hyaluronic acid and its salts such as sodium hyaluronate; hydrolyzate of yeast and yeast extract; fermentation metabolites such as yeast culture and lactic acid bacteria culture; water-soluble proteins such as collagen, elastin, keratin and sericin; collagen Peptides such as hydrolysates, casein hydrolysates, silk hydrolysates, sodium polyaspartate and their salts; saccharides / polysaccharides such as trehalose, xylobiose, maltose, sucrose, glucose, vegetable viscous polysaccharides and the like Guidance Glycosaminoglycans and salts thereof such as water-soluble chitin, chitosan, pectin, chondroitin sulfate and salts thereof; amino acids such as glycine, serine, threonine, alanine, aspartic acid, tyrosine, valine, leucine, arginine, glutamine and prophosphoric acid Sugar-amino acid compounds such as aminocarbonyl reaction products; plant extracts such as aloe and maronier, nucleic acid-related substances such as trimethylglycine, urea, uric acid, ammonia, lecithin, lanolin, squalane, squalene, glucosamine, creatinine, DNA, RNA, etc. Can be given.

Examples of the organic fine particles include latex emulsions obtained by emulsion polymerization such as styrene-butadiene copolymer latex and acrylic emulsion, and polyurethane water dispersions.
Examples of the inorganic fine particles include inorganic fine particles such as zeolite, montmorillonite, asbestos, smectite, mica, fumed silica, colloidal silica, and titanium oxide.

Examples of the preservative include methyl paraben and ethyl paraben.

Deodorants and fragrances include D-limonene, decylaldehyde, menthone, pulegone, eugenol, cinnamaldehyde, benzaldehyde, menthol, peppermint oil, lemon oil, orange oil, and a deodorizing active ingredient extracted from each organ of plants (for example, Deodorant active ingredient extracted from each organ of water, hydrophilic, organic solvent, honey beetle, dolphin, moth, ginkgo, black pine, larch, red pine, giraffe, holly mushroom, lilac, beetle, coral, camellia, forsythia ) Etc.

Examples of the organic solvent include water-soluble alcohols (methanol, ethanol, isopropanol, isobutanol, sec-butanol, tert-butanol, methyl cellosolve, ethyl cellosolve, ethylene glycol, glycerin, etc.), ethers (ethylene glycol dimethyl ether, 1,4-dioxane, tetrahydrofuran, etc.), ketones (acetone, methyl ethyl ketone), N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide and the like.

Nanofiber B of the present invention is a composition for spraying; rubber reinforcement such as NR, SBR, EPDM, NBR; resin reinforcement such as polyolefin resin, acrylic resin, urethane resin, PVC resin, polyamide resin, PC resin, etc. Ingredients; creams, lotions, gels, sticks, pump sprays, aerosols, roll-on antiperspirants in the form of epidermis, deodorants, fragrance release gels, lipsticks, lip gloss, liquid cosmetics and other cosmetics; Controlled, sustained or delayed additives, disintegrants for tablets, liquid retainers in wound care products, medical products such as rheology modifiers; rheology modifiers, inhibiting creaming and precipitation in suspensions Stabilizers, foods such as indigestible dietary fiber; beverages; paints; metals unfavorable to the environment contained in soil and wastewater It can be utilized in metal adsorbents.

Hereinafter, the present invention will be described in detail with reference to examples. The following examples are for explaining the present invention preferably and are not intended to limit the present invention. In addition, unless otherwise indicated, the measuring methods, such as a physical-property value, are the measuring methods described above.

[Viscosity (Pa · s)]: Water is added to carboxylated cellulose nanofibers to prepare an aqueous dispersion of 1.95 to 1.05% by mass, and the aqueous dispersion is prepared using a viscoelastic rheometer. And measured at a predetermined shear rate.

[Amount of carboxyl group]: The amount of carboxyl group was measured as follows. Prepare 60 ml of 0.5% by weight slurry (aqueous dispersion) of carboxylated cellulose, add 0.1 M hydrochloric acid aqueous solution to pH 2.5, then add 0.05 N aqueous sodium hydroxide solution dropwise to adjust the pH to 11 The electrical conductivity was measured until The amount of carboxyl groups was calculated from the amount of sodium hydroxide consumed (a) in the weak acid neutralization stage where the change in electrical conductivity was gradual using the following formula:
Amount of carboxyl group [mmol / g carboxylated cellulose] = a [ml] × 0.05 / carboxylated cellulose mass [g]

[Average fiber length (nm)]: Carboxylated cellulose nanofibers are fixed on a mica section, the fiber length of 200 fibers is measured using an atomic force microscope (AFM), and the length (weighted) average fiber is measured. The length was calculated. The fiber length was measured using image analysis software WinROOF (Mitani Corporation).

[Average fiber diameter (nm)]: An aqueous dispersion of carboxylated cellulose nanofibers diluted so that the concentration of carboxylated cellulose nanofibers was 0.001% by mass was prepared. This diluted dispersion was thinly spread on a mica sample stage and heated and dried at 50 ° C. to prepare an observation sample. The cross-sectional height of the shape image observed with an atomic force microscope (AFM) was measured, and the weighted average fiber diameter was calculated.

[Ratio (%) of fibers having a fiber length of 300 nm or less or 600 nm or more]: The ratio of fibers having a fiber length of 300 nm or less or 600 nm or more among carboxylated cellulose nanofibers whose length (weighted) average fiber length was measured. Calculated.

Example 1
5 g (absolutely dried) of bleached softwood unbeaten pulp (Nippon Paper Co., Ltd.) was added to 500 ml of an aqueous solution in which 78 mg (0.5 mmol) of TEMPO (manufactured by Sigma Aldrich) and 754 mg (7.4 mmol) of sodium bromide were dissolved. Stir until the pulp is uniformly dispersed. After adding 14 ml of 2M aqueous sodium hypochlorite solution to the reaction system, the pH was adjusted to 10.3 with 0.5N aqueous hydrochloric acid solution to initiate the oxidation reaction. Since the pH in the system was lowered during the reaction, a 0.5N sodium hydroxide aqueous solution was sequentially added to maintain the pH at 10. After reacting for 2 hours, the mixture was filtered through a glass filter and washed thoroughly with water to obtain oxidized cellulose having a carboxyl group amount of 1.60 mmol / g.

Next, the obtained slurry of oxidized cellulose was adjusted to 1% (w / v) with water, treated with an ultra-high pressure homogenizer (20 ° C., 140 MPa) three times, and a transparent gel-like carboxylated cellulose nanofiber salt was obtained. A dispersion (1% (w / v)) was obtained.

A cation exchange resin (manufactured by Organo Corporation, “Amberjet 1024”) was added to the resulting dispersion of carboxylated cellulose nanofiber salt, and the mixture was stirred at 20 ° C. for 0.3 hours for contact. Thereafter, the cation exchange resin and the aqueous dispersion were separated with a metal mesh (aperture 100 mesh) to obtain an acid-type carboxylated cellulose nanofiber (nanofiber A).

The viscosity of an aqueous dispersion of 1.00% by mass of the obtained acid-type carboxylated cellulose nanofibers was 925 Pa · s under the conditions of shear rate (0.00417 s ⁻¹ , 30 ° C.), and (0.00671 s ⁻¹ , 30 ° C.), it was 920 Pa · s. The results are shown in Table 1.
Moreover, the average fiber length of the obtained acid-type carboxylated cellulose nanofiber is 549 nm, the average fiber diameter is 2.83 nm, and the proportion of fibers having a fiber length of 300 nm or less is 29.3%. The proportion of fibers having a fiber length of 600 nm or more was 23.2%. The results are shown in Table 2, and the fiber length distribution ratio is shown in FIG.

(Comparative Example 1)
Carboxylated cellulose nanofibers were obtained in the same manner as in Example 1 except that the desalting step was changed as follows.
A 10% aqueous hydrochloric acid solution was added to the dispersion of the carboxylated cellulose nanofiber salt until the pH reached 2.4, and the mixture was stirred for 0.4 hours at 20 ° C. and contacted. Thereafter, washing and dehydration were repeated three times, followed by filtration. Water is added to the filtrate to adjust to 1.0% (w / v), treated twice with an ultra-high pressure homogenizer (20 ° C., 140 MPa), and dispersion of transparent gel-like H-type carboxylated cellulose nanofibers A liquid (1% (w / v)) was obtained.

The viscosity of an aqueous dispersion of 1.00% by mass of the obtained carboxylated cellulose nanofiber is 336 Pa · s under the condition of shear rate (0.00417 s ⁻¹ , 30 ° C.), and (0.00671 s ⁻¹ , 30 Pa) under the condition of 30 ° C. The results are shown in Table 1.
Moreover, the average fiber length of the obtained carboxylated cellulose nanofiber was 503 nm, and the average fiber diameter was 2.55 nm.

(Example 2)
5 g (absolutely dried) of bleached softwood unbeaten pulp (Nippon Paper Co., Ltd.) was added to 500 ml of an aqueous solution in which 78 mg (0.5 mmol) of TEMPO (manufactured by Sigma Aldrich) and 754 mg (7.4 mmol) of sodium bromide were dissolved. Stir until the pulp is uniformly dispersed. After adding 11 ml of 2M aqueous sodium hypochlorite solution to the reaction system, the pH was adjusted to 10.3 with 0.5N aqueous hydrochloric acid solution to initiate the oxidation reaction. Since the pH in the system was lowered during the reaction, a 0.5N sodium hydroxide aqueous solution was sequentially added to maintain the pH at 10. After reacting for 1.5 hours, the mixture was filtered through a glass filter and sufficiently washed with water to obtain oxidized cellulose having a carboxyl group amount of 1.23 mmol / g.

Next, the obtained slurry of oxidized cellulose was adjusted to 1% (w / v) with water, treated twice with an ultrahigh pressure homogenizer (20 ° C., 140 MPa), and a transparent gel-like carboxylated cellulose nanofiber salt was obtained. A dispersion (1% (w / v)) was obtained.

A cation exchange resin (manufactured by Organo Corporation, “Amberjet 1024”) was added to the resulting dispersion of carboxylated cellulose nanofiber salt, and the mixture was stirred at 20 ° C. for 0.3 hours for contact. Thereafter, the cation exchange resin and the aqueous dispersion were separated with a metal mesh (aperture 100 mesh) to obtain acid-type carboxylated cellulose nanofibers (nanofibers).

The viscosity of the 1.00 mass% aqueous dispersion of the obtained acid-type carboxylated cellulose nanofibers was 18300 Pa · s under the conditions of the shear rate (0.00417 s ⁻¹ , 30 ° C.), and (0.00671 s ^-1, under the condition of 30 ℃) was 17800Pa · s. The results are shown in Table 1.
Moreover, the average fiber length of the obtained acid-type carboxylated cellulose nanofibers was 624 nm, and the average fiber diameter was 3.11 nm.

(Example 3)
5 g (absolutely dried) of bleached softwood unbeaten pulp (Nippon Paper Co., Ltd.) was added to 500 ml of an aqueous solution in which 78 mg (0.5 mmol) of TEMPO (manufactured by Sigma Aldrich) and 754 mg (7.4 mmol) of sodium bromide were dissolved. Stir until the pulp is uniformly dispersed. After adding 12 ml of a 2M aqueous sodium hypochlorite solution to the reaction system, the pH was adjusted to 10.3 with a 0.5N aqueous hydrochloric acid solution to initiate the oxidation reaction. Since the pH in the system was lowered during the reaction, a 0.5N sodium hydroxide aqueous solution was sequentially added to maintain the pH at 10. After reacting for 2 hours, the mixture was filtered through a glass filter and washed thoroughly with water to obtain oxidized cellulose having a carboxyl group amount of 1.50 mmol / g.

The viscosity of an aqueous dispersion of 1.00% by mass of the obtained acid-type carboxylated cellulose nanofibers is 995 Pa · s under the conditions of shear rate (0.00417 s ⁻¹ , 30 ° C.), and (0.00671 s ^-1, under the condition of 30 ℃) was 970Pa · s. The results are shown in Table 1.
The obtained acid-type carboxylated cellulose nanofibers had an average fiber length of 570 nm and an average fiber diameter of 2.85 nm.

Example 4
5 g (absolutely dried) of bleached softwood unbeaten pulp (Nippon Paper Co., Ltd.) was added to 500 ml of an aqueous solution in which 78 mg (0.5 mmol) of TEMPO (manufactured by Sigma Aldrich) and 754 mg (7.4 mmol) of sodium bromide were dissolved. Stir until the pulp is uniformly dispersed. After adding 6 ml of 2M aqueous sodium hypochlorite solution to the reaction system, the pH was adjusted to 10.3 with 0.5N aqueous hydrochloric acid solution to initiate the oxidation reaction. Since the pH in the system was lowered during the reaction, a 0.5N sodium hydroxide aqueous solution was sequentially added to maintain the pH at 10. After reacting for 0.5 hour, the mixture was filtered through a glass filter and sufficiently washed with water to obtain oxidized cellulose having a carboxyl group amount of 0.60 mmol / g.

The viscosity of an aqueous dispersion of 1.00% by mass of the obtained acid-type carboxylated cellulose nanofibers was 24100 Pa · s under the conditions of shear rate (0.00417 s ⁻¹ , 30 ° C.), and (0.00671 s ⁻¹ , 30 ° C.), it was 23300 Pa · s. The results are shown in Table 1.
Moreover, the average fiber length of the obtained acid-type carboxylated cellulose nanofibers was 840 nm, and the average fiber diameter was 3.22 nm.

As can be seen from Table 1, in an acid-type carboxylated cellulose nanofiber prepared by desalting with a cation exchange resin, when the carboxyl group amount is 1.60 mmol / g, 0.00417 or 0.00671 s ⁻¹ 925 or 920 Pa · s (see Example 1), and when the carboxyl group amount is 1.50 mmol / g, it is 995 or 970 Pa · s (see Example 3), and the carboxyl group amount is In the case of 1.23 mmol / g, it was 18300 or 17800 Pa · s (see Example 2), and when the carboxyl group amount was 0.60 mmol / g, the viscosity was as high as 24100 or 23300 Pa · s (see Example 4). ).

On the other hand, the acid-type carboxylated cellulose nanofibers prepared by desalting with hydrochloric acid had a low ^value of 0.00417 or 0.00671 s ⁻¹ when the amount of carboxyl groups was 1.60 mmol / g as in Example 1. In the shear region, the viscosity was as low as 336 or 350 Pa · s (see Comparative Example 1). From this, it was found that the physical properties of the obtained acid-type carboxylated cellulose nanofibers, particularly the viscosity in the low shear region, differ depending on the process during the desalting treatment. Therefore, acid-type carboxylated cellulose nanofibers can be expected to be widely used by changing the desalting process according to the application.

(Example 5)
5 g (absolutely dried) of bleached softwood unbeaten pulp (Nippon Paper Industries Co., Ltd.) was added to 500 ml of an aqueous solution in which 78 mg (0.5 mmol) of TEMPO (Sigma Aldrich) and 754 mg (7.4 mmol) of sodium bromide were dissolved. Stir until the pulp is uniformly dispersed. After adding 16 ml of 2M aqueous sodium hypochlorite solution to the reaction system, the pH was adjusted to 10.3 with 0.5N aqueous hydrochloric acid solution to initiate the oxidation reaction. During the reaction, the pH in the system was lowered, but a 0.5N aqueous sodium hydroxide solution was successively added to adjust the pH to 10. After reacting for 2 hours, the mixture was filtered through a glass filter and washed thoroughly with water to obtain oxidized cellulose having a carboxyl group amount of 1.60 mmol / g.

Next, 1% (w / v) of hydrogen peroxide was added to 5% (w / v) slurry of oxidized cellulose and the pH was adjusted to 12 with 1M sodium hydroxide. This slurry was hydrolyzed at 80 ° C. for 2 hours. Then, it filtered with the glass filter and washed thoroughly with water.

The hydrolyzed 2% (w / v) oxidized cellulose slurry was treated 5 times with an ultra-high pressure homogenizer (20 ° C., 140 MPa) to obtain a transparent gel-like carboxylated cellulose nanofiber salt dispersion (1% (w / v) v)) was obtained.

A cation exchange resin (manufactured by Organo Corporation, “Amberjet 1024”) was added to the resulting dispersion of carboxylated cellulose nanofiber salt, and the mixture was stirred at 20 ° C. for 0.3 hours for contact. Thereafter, the cation exchange resin and the aqueous dispersion were separated with a metal mesh (aperture 100 mesh) to obtain acid-type carboxylated cellulose nanofiber (nanofiber B) at a high yield of 92%.

The obtained acid-type carboxylated cellulose nanofibers have an average fiber length of 311 nm, an average fiber diameter of 5.73 nm, and a ratio of fibers having a fiber length of 300 nm or less is 79.9%, 600 nm or more. The proportion of fibers having a fiber length of 1.1% was 1.1%. The results are shown in Table 2, and the fiber length distribution ratio is shown in FIG.

As can be seen from Table 2, carboxylated cellulose nanofibers obtained by hydrolysis treatment have a short average fiber length, a large proportion of 300 nm or less, and a very small proportion of 600 nm or more (Example 1). 5). Therefore, the fiber length has converged to a short region, and application to a field where a short fiber cellulose nanofiber is desired is expected.

Claims

A carboxylated cellulose nanofiber having a carboxyl group in at least a part of structural units constituting a cellulose molecular chain,
Acid-type carboxylated cellulose nanofibers having a viscosity in an aqueous dispersion having a content of 0.95 to 1.05% by mass of 400 Pa · s or more at 30 ° C. and a shear rate of 0.003 to 0.01 s −1 .
A carboxylated cellulose nanofiber having a carboxyl group in at least a part of structural units constituting a cellulose molecular chain,
Acid-type carboxylated cellulose nanofibers having an average fiber length of 50 to 500 nm and a ratio of fibers having a fiber length of 300 nm or less being 50% or more.
The acid-type carboxylated cellulose nanofiber according to claim 2, wherein the average fiber diameter is 2 to 50 nm.
The acid-type carboxylated cellulose nanofiber according to claim 2, wherein the average fiber diameter is 2 to 30 nm.
The acid-type carboxylated cellulose nanofiber according to any one of claims 2 to 4, wherein the proportion of fibers having a fiber length of 600 nm or more is less than 20%.
6. The method according to claim 1, wherein at least a part of the cellulose molecular chain is composed of a structural unit having a carboxyl group in which a carbon atom having a primary hydroxyl group at the C6 position of a glucopyranose unit is selectively oxidized. The acid-type carboxylated cellulose nanofiber according to Item.
The acid-type carboxylated cellulose nanoparticle according to any one of claims 1 to 6, wherein the amount of the carboxyl group is 0.6 to 2.0 mmol / g with respect to the absolutely dry mass of the carboxylated cellulose nanofiber. Fiber.
The acid-type carboxylated cellulose nanoparticle according to any one of claims 1 to 6, wherein the amount of the carboxyl group is 0.8 to 2.0 mmol / g with respect to the absolutely dry mass of the carboxylated cellulose nanofiber. Fiber.