JP2017048293A - Cellulose nanofiber dispersion, method for producing the same and cellulose nanofiber film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dispersion having cellulose nanofibers favorably dispersed therein, to provide a method for producing the dispersion and to provide a cellulose nanofiber film.SOLUTION: The cellulose nanofiber dispersion having high reinforcement property and high dispersibility can be provided even at a low concentration by adding carboxymethyl cellulose (hereinafter referred to as CMC) to a dispersion having cellulose nanofibers dispersed therein and mixing the same; and the method for producing the dispersion and the cellulose nanofiber film are provided. The dispersion of nanofibers excellent in biocompatibility can be produced without using an acid.SELECTED DRAWING: Figure 2

Description

The present invention relates to a cellulose nanofiber dispersion, a method for producing the same, and a cellulose nanofiber film.

Cellulose, chitin, and chitosan, which are natural biomass, function as a tough structure, with nanofibers converging to take a fiber structure. These fibers of cellulose, chitin, and chitosan have a higher-order structure, and are strongly focused mainly by bonding through hydrogen bonds between the surfaces. difficult.

As described in Patent Document 1, biomass nanofibers can be produced by converting cellulose, chitin, chitosan, or these chemically modified raw materials into nanofibers using a water jet. Biomass nanofibers are ultrafine fibers with a width of 20 to 100 nm and a length of several μm, and it is possible to produce a large amount of nanofibers that are difficult to produce artificially by defibrating the higher-order structure of biomass. it can. Cellulose, chitin, and chitosan, which are raw materials for nanofibers, are used as food additives and cosmetic additive raw materials, and nanofibers defibrated by our water jet technology are manufactured only from water and raw materials. It can also be used for medicine, cosmetics and food applications.

Moreover, when adding biomass nanofiber to a target object, the dispersibility is very important. In order to maximize the effects of nanofibers, it is important how uniformly they are dispersed in the object. If the dispersibility is poor, its function is difficult to exert.

Furthermore, chemical treatments such as TEMPO oxidation (see Non-Patent Document 1), carboxymethylation (see Non-Patent Document 2), and cationization (see Patent Document 2) are applied to cellulose to unify nanofibers and improve dispersibility. Many methods have been reported to improve the dispersibility and functionality by applying this method in advance.

Japanese Patent No. 5333455 Japanese Patent No. 5150792

SAITO, T. ET AL. CELLULOSE COMMUN. Vol. 14, no. 2, 2007, 62 Wangberg, L., ET AL., Langmuir, 2008, 24 (3), 784-795

However, when biomass nanofibers are added to a water-soluble polymer such as PVA, the reinforcing effect gradually increases in proportion to the amount added, but considering the physical properties of biomass nanofibers, the reinforcing effect and dispersibility include: There is room for improvement.

In addition, when biomass nanofibers are added to water-based materials that are relatively easy to disperse, although there is a temporary effect due to the addition, especially for addition at low concentrations, aggregation and precipitation are seen over time, It cannot be said that sufficient dispersibility and functionality are provided, and there is room for improvement.

In addition, when only biomass nanofibers are added, the entanglement of the three-dimensional structure, which is the characteristic of nanofibers, is weak when added at low concentrations, making it difficult to form a network. There was room for.

In addition, when chemical treatments such as TEMPO oxidation, carboxymethylation, and cationization are performed in advance, nanofiber unitization and dispersibility are improved, but physical properties such as a conventional reinforcing effect of cellulose are lost. There was a problem.

In view of the above-described problems, an object of the present invention is to provide a cellulose nanofiber dispersion having high reinforcing properties and dispersibility, a production method thereof, and a cellulose nanofiber film even at a low concentration. .

The cellulose nanofiber dispersion of the present invention is a dispersion in which cellulose nanofibers are dispersed, and is characterized by containing carboxymethylcellulose in the dispersion.

The cellulose nanofiber dispersion of the present invention is a nanofiber in which carboxymethylcellulose is defibrated by a high-pressure jet treatment of 100 to 245 MPa, and is any one of a paste, a gel, a slurry, a dispersion, a suspension, or an emulsion. It is characterized by one form.

The cellulose nanofiber dispersion of the present invention is characterized in that the carboxymethyl cellulose has a fiber diameter of 4 to 100 nm.

The cellulose nanofiber dispersion of the present invention contains 0.01 to 10% by weight of cellulose nanofibers and 0.1 to 50% by weight of carboxymethylcellulose with respect to the cellulose nanofibers.

The method for producing a cellulose nanofiber dispersion according to the present invention is characterized by subjecting a dispersion fluid containing cellulose fibers and carboxymethyl cellulose to a high-pressure jet treatment.

The cellulose nanofiber film of the present invention is formed by adding oily components to cellulose nanofibers to which carboxymethylcellulose or carboxymethylcellulose nanofibers have been added, stirring with a mixer and / or stirring deaerator, and then drying. It is characterized by.

According to the present invention, by performing a high-pressure injection treatment of 100 MPa to 245 MPa using water as a solvent without using an acid, the fine pulverization force enables sufficient miniaturization, and nano-materials excellent in biocompatibility. A dispersion of fibers can be obtained.

Moreover, even if it is a low density | concentration by adding and mixing carboxymethylcellulose (henceforth CMC), a cellulose nanofiber with high reinforcement and dispersibility, its manufacturing method, and a cellulose nanofiber film can be provided.

It is a schematic diagram which shows schematic structure of the chamber of the high-pressure-injection processing apparatus used by this invention. It is a field emission type scanning electron microscope image which shows the cellulose nanofiber obtained by this invention. It is a field emission type scanning electron microscope image which shows the CMC nanofiber obtained by this invention. It is a figure which shows the external appearance of the thin film which consists of CMC nanofiber addition cellulose nanofiber which concerns on this invention. It is a figure which shows the result of the tension test of various cellulose nanofiber.

The form for implementing this invention is demonstrated below.

Biomass raw material is a bio-derived polymer and means cellulose, chitin, chitosan, or derivatives thereof. When the biomass raw material is subjected to high-pressure injection processing with the high-pressure injection device according to the present invention, the fibers are entangled and thinned while maintaining the fiber length to some extent. And it is possible to reduce the fiber cutting or the molecular weight by changing the processing conditions such as the injection pressure of the high-pressure injection device and the number of times of processing.

Nanofiber means a fiber diameter (width) that is nanosized. For example, when the fibers of the cellulose are separated from each other by carrying out the method of the present invention to become one minimum unit fiber, the fiber diameter (diameter) is about 10 to 50 nm. The fiber diameter (width) of the nanofiber can be measured based on an electron microscope image (photograph). Such a fiber is not nano-sized in length, but has a diameter (width) of nano-size, and is therefore referred to as nanofiber in this specification.

Cellulose can be made into nanofibers by high-pressure injection treatment, and the resulting nanofibers become a fluid dispersion when the cellulose concentration used in the high-pressure injection treatment is low, but the cellulose is fine. Viscosity increases with increasing the concentration (nanofiber), and when the concentration is increased, it becomes a property close to a paste. Therefore, not only fluid dispersions but also such paste-like cellulose nanofiber dispersions are included.

Examples of the dispersion medium include water, lower alcohols (methanol, ethanol, propanol, isopropanol), glycols (ethylene glycol, propylene glycol, diethylene glycol), glycerin, acetone, dioxane, tetrahydrofuran, acetonitrile, dimethylformamide, dimethylsulfoxide, acetamide, and the like. These may be used alone or in combination of two or more. A preferable dispersion medium is water or a water-containing solvent, and water is particularly preferable.

A dispersing agent may be used independently and may be used in mixture of 2 or more types. Examples of the CMC salt include alkali metal salts such as sodium, potassium and lithium, salts of group 2 elements such as calcium and magnesium, and ammonium salts, and sodium salts and potassium salts from the viewpoint of solubility in water. Ammonium salt and potassium salt are preferred, but sodium salt is most preferred.

Examples of the dispersant include CMC, and preferably CMC nanofibers that have been subjected to nanofiber formation treatment similar to cellulose. The CMC nanofiber can be used in any one of a paste, a gel, a slurry, a dispersion, a suspension, or an emulsion.

In the cellulose nanofiber dispersion, the cellulose nanofiber is contained in an amount of 0.01 to 10% by weight, preferably 0.5 to 5.0% by weight, more preferably 1.0 to 3.0% by weight. It is contained in an amount of 0.1 to 50% by weight, preferably 1 to 20% by weight, more preferably 5 to 20% by weight, based on cellulose nanofiber (solid content weight). Furthermore, the content of the dispersion medium is 50 to 99.9% by weight, preferably 60 to 99.5% by weight, and more preferably 70 to 99% by weight.

The cellulose nanofiber dispersion is 0.01 to 0.4 parts by mass, preferably 0.02 to 0.3 parts by mass, and more preferably 0.03 to 0.3 parts by mass with respect to 1 part by mass of cellulose nanofibers. The amount is about 25 parts by mass, most preferably about 0.05 to 0.2 parts by mass.

The cellulose nanofiber dispersion is produced by subjecting a cellulose dispersion fluid containing cellulose and a dispersant to high-pressure jet treatment one to several times. Or it can manufacture by adding a dispersing agent to the cellulose nanofiber after nanofiber formation, and stirring with a mixer and / or a stirring deaerator.

In the case of producing a cellulose nanofiber dispersion, the concentration of the cellulose dispersion fluid as a raw material is preferable because the treatment efficiency increases as the concentration increases. However, especially in the case of fibers refined to the nano level, the viscosity becomes too high, and high-pressure jetting becomes difficult when it becomes a paste. In the present invention, an apparatus capable of high-pressure jetting even when the concentration of cellulose fiber or cellulose nanofiber is high has been developed, and the cellulose concentration in the dispersion fluid is, for example, about 1 to 20% by weight, preferably 5 to 20% by weight. %, More preferably about 10 to 20% by weight, and still more preferably about 11 to 20% by weight.

The cellulose used for the production of the cellulose nanofiber dispersion may be in any form such as fibrous or granular. As the cellulose, cellulose purified by removing lignin and hemicellulose is preferable. Commercially available raw materials may be used. When cellulose is subjected to high-pressure jet treatment with a high-pressure jet device, the cellulose is untangled and thinned while maintaining the length of the fiber, but by changing the treatment conditions such as the jet pressure and the number of treatments, the fiber can be cut or It is also possible to reduce the molecular weight.

The average diameter of the cellulose nanofibers obtained by the treatment by the method of this embodiment is about 4 to 100 nm, preferably about 10 to 40 nm, and most preferably about 15 to 25 nm. Since the nanofibers of this embodiment have a large fiber length / fiber diameter (aspect ratio) and a good dispersion state, the nanofibers can be molded into a film or sheet in which nanofibers are entangled like a nonwoven fabric while maintaining strength. It is easy and can be suitably used as various materials. A nonwoven fabric obtained by forming a cellulose nanofiber dispersion into a film / sheet can ensure high transparency.

The cellulose-dispersed fluid can be sprayed at a high pressure from the nozzle using an ultrafine device using high-pressure spray developed by Sugino Machine. The pressure of the high pressure injection is about 100 to 245 MPa. The injection speed is about 440 to 700 m / s.

The cellulose-dispersed fluid that has collided with the collision hard body by high-pressure injection is collected and again injected with high pressure from the nozzle toward the collision hard body, and this operation is performed a required number of times, for example, about 1 to 50 times, preferably Repeat about 1 to 40 times, more preferably about 1 to 30 times, still more preferably about 1 to 20 times, and particularly preferably about 1 to 10 times. When the cellulose collides with the collision-use hard body, the fibers are entangled, the fiber diameter is reduced, and the nano size is reduced. In addition, since a specific dispersing agent is contained in the cellulose dispersion fluid to be subjected to the high-pressure spraying process, recombination of the dispersed nanofibers is suppressed, and a well-dispersed nanofiber dispersion can be obtained with a small number of treatments. . In addition, as a hard body for collision, shapes, such as ball shape and flat plate shape, are mentioned.

A mortar (disc mill) or electrospinning method is used to make cellulose nanofibers, but the production efficiency is low, and there is a problem in the uniformity of refinement.

The present invention provides a low-environmental low-load cellulose degradation and nanofibrosis technology using only water or a water-miscible solvent without using any catalyst or harmful chemicals. Moreover, nanofibration can be achieved almost completely, micro-sized cellulose is not included, and the uniformity of the average fiber diameter is excellent.

The nanofiber of the present embodiment has a fiber diameter of 4 to 100 nm or less, more preferably 80 nm or less, still more preferably 60 nm or less, particularly 40 nm or less. The nanofiber of the present embodiment has a fiber diameter that is very thin and substantially free of cellulose that is insufficiently opened, has an appearance close to a transparent solution when dispersed in water, It is not visually recognized that the nanofibers are dispersed, and a transparent dispersion liquid (when the concentration is low) or a transparent gel or an opaque gel (when the concentration is high) can be obtained. The dispersion of this embodiment includes various forms such as an aqueous dispersion, an aqueous dispersion gel, and an aqueous dispersion paste. An opaque gel can be changed to a transparent gel by increasing the number of high-pressure jets. The fiber diameter is measured by direct observation using a scanning electron microscope (SEM) method.

The elastic modulus and strength of cellulose nanofibers composed of extended chain crystals reach 140 GPa and 3 GPa, respectively, which are equal to typical high-strength fibers and aramid fibers, and are known to have higher elasticity than glass fibers. Moreover, the coefficient of linear thermal expansion is 1.0 × 10 ⁻⁷ / ° C., which is as low as quartz glass. Since the cellulose nanofiber dispersion of the present invention is excellent in nanofiber dispersibility, it is also useful as a composite reinforcing fiber.

In addition, the cellulose nanofiber dispersion of the present embodiment includes acids such as phosphoric acid, citric acid, acetic acid and malic acid, alkalis such as sodium hydroxide and potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate and hydrogen carbonate. A small amount of alkali such as potassium may be added.

Hereinafter, although this embodiment is described in detail by examples, it is needless to say that this embodiment is not limited to these examples.

Example 1
A slurry-like dispersion fluid in which cellulose, CMC, or a mixture of cellulose and CMC is mixed with ion-exchanged water is pressurized to an ultra-high pressure of 100 to 245 MPa, and sprayed at a high pressure from a small-diameter orifice nozzle (φ0.1 to 0.8 mm). Get nanofibers.

The discharge flow from the orifice nozzle is a high-speed jet of 440 to 700 m / s, but a high shear force is generated in the orifice accelerated to that speed. Since the thickness of the orifice nozzle used here is extremely thin at 0.4 mm, almost 100% of the pressure energy can be converted into the velocity energy of injection. That is, inside the orifice, a narrow gap of 0.1 to 0.8 mm and an ultrahigh speed of 440 to 700 m / s are obtained, and the conditions for obtaining a high shearing force are satisfied.
Regarding the shearing force = viscosity of slurry × speed / viscosity of the crevice slurry, by improving each part of this processing circuit (high pressure injection device), it becomes possible to process a slurry having a higher concentration, that is, a higher viscosity, It is also a factor that increases the shearing force (shear stress) of the slurry itself.

In a high-speed jet flow (high pressure injection state) of 440 to 700 m / s, bubbles are generated, and a strong impact force is generated by the disappearance of the bubbles. Cavitation can be efficiently generated by providing an impact enhancement region downstream of the orifice nozzle.

In addition, a ball-shaped or flat ceramic hard body is provided as a structural high-speed jet receiver. In order to further reduce the crystallinity, a region where the jet pressure is increased and the jet velocity is high is used, and the impact force against the hard body is also used for pulverization. (See Figure 1)

(Example 2)
The cellulose treated with nanofibers in Example 1 and the CMC dispersion were replaced with t-butanol and lyophilized. A mixture of platinum and palladium was deposited on the dried sample with a film thickness of about 3 nm. The electron microscope was observed under the condition of an acceleration voltage of 2.0 kV using JSM-6700 of JEOL. FIG. 2 shows an FE-SEM image of cellulose nanofibers made into nanofibers by the water jet treatment of the present invention, and FIG. 3 shows an FE-SEM image of CMC nanofibers. According to the present invention, biomass nanofibers are obtained by performing high-pressure injection treatment of 100 to 245 MPa using water as a medium without using an acid, so that the original shape of the fibers was maintained in detail. It turns out that it is miniaturized in the state.

(Example 3)
The mixed dispersion that was subjected to nanofiber treatment in Example 1 was formed into a film. The nanofiber film is obtained by pouring the miniaturized nanofiber into a petri dish (casting) and drying. There is no restriction | limiting in particular in the method of film-forming, A film can be produced by making it dry after operations, such as a film applicator generally used for film production, and suction filtration. Drying can be performed by heating or room temperature drying.

(Experimental example 1)
CMC is added to three types of cellulose having relatively different fiber lengths: (1) IMa-10002 (very long fiber), (2) WMa-10002 (standard), (3) FMa-10002 (very short fiber) Thus, the influence on dilution dispersibility was examined. The CMCs used were (a) Wako Pure Chemicals, (b) BiNFi-s CMC (before nanofiberization), and (c) BiNFi-s CMC (after nanofiberization).

As an experimental method, a dispersion liquid blended as shown in the following table was stirred (3,400 rpm, 5 min) with a mixer (WARING BLENDER 7012S type, WARING), and the dispersion state was observed. The dispersion state is shown by A to D in Table 1.

Table 2 shows the results regarding the dilution dispersibility of the ultra-long fiber cellulose nanofibers.
Precipitation begins to occur when diluted to a concentration of 0.1% by weight or less, but it can be seen that by adding various CMCs, precipitation does not occur and dispersibility is improved. The effects were observed in the order of CMC (after nanofiber formation), CMC, and CMC (before nanofiber formation).

Table 3 shows the results regarding the dilution dispersibility of the standard type cellulose nanofiber. Precipitation begins to occur when diluted to a concentration of 0.05% by weight or less, but it can be seen that by adding various CMCs, precipitation does not occur and dispersibility is improved. The effects were observed in the order of CMC (after nanofiber formation), CMC, and CMC (before nanofiber formation).

Table 4 shows the results regarding the dilution dispersibility of the ultra-short fiber type cellulose nanofiber. Precipitation begins to occur when diluted to a concentration of 0.1% by weight or less, but it can be seen that by adding various CMCs, precipitation does not occur and dispersibility is improved. The effects were observed in the order of CMC (after nanofiber formation), CMC (before nanofiber formation), and CMC.

(Experimental example 2)
Next, three types of cellulose having relatively different fiber lengths (1) IMa-10002 (very long fiber), (2) WMa-10002 (standard), (3) FMa-10002 (very short fiber) and CMC Experiments were conducted to determine the effect of adding to the tensile strength. The CMCs used were (a) Wako Pure Chemicals, (b) BiNFi-s CMC (before nanofiberization), and (c) BiNFi-s CMC (after nanofiberization). Table 5 shows the blending amounts.

As an experimental method, the dispersion liquid blended as shown in Table 5 was stirred (8,400 rpm, 5 minutes) with a mixer (Warring Blender 7012S type), and 50 g of the dispersion liquid was stirred and degassed (Kyoritsu Seiki Co., Ltd.). Under the conditions of rotation: revolution = 9: 9, the mixture was defoamed with stirring, added to a petri dish, dried at 30 ° C., a film was formed, and a tensile test was performed. For the tensile test, the method of Biomacromolecules 2008.9.15799-1585 was used.

In this experimental example, glycerin was blended in the dispersion as an oil component. In the present embodiment, glycerin is used, but glycols (ethylene glycol, propylene glycol, diethylene glycol, butadiol) and the like can also be used as the oil component.

The results are shown in FIG. By adding CMC, the tensile stress of the film is 2 to 2.4 times in IMa (very long fiber), 2.7 to 3.4 times in WMa (standard), and 2.7 to 2.5 in FMa (very short fiber). Increased by a factor of 2. Moreover, the stress at the time of addition of CMC made into nanofiber was the highest, and the reinforcing effect was high.

DESCRIPTION OF SYMBOLS 1 Cellulose nanofiber 2 CMC nanofiber 10 Chamber 11 of a high pressure injection processing apparatus Pressurization part,
12 nozzles (orifice nozzles),
13 Through hole,
14 Impact enhancement area,
15 Hard body for collision

Claims (6)

A cellulose nanofiber dispersion comprising cellulose nanofibers dispersed therein, wherein the dispersion contains carboxymethylcellulose. The carboxymethyl cellulose is a nanofiber defibrated by a high-pressure jet treatment of 100 to 245 MPa, and is in any one form of a paste, a gel, a slurry, a dispersion, a suspension, or an emulsion. The cellulose nanofiber dispersion according to claim 1. The cellulose nanofiber dispersion according to claim 1 or 2, wherein a fiber diameter of the carboxymethylcellulose is 4 to 100 nm. The cellulose nanofiber according to any one of claims 1 to 3, comprising 0.01 to 10 wt% of the cellulose nanofiber and 0.1 to 50 wt% of the carboxymethylcellulose with respect to the cellulose nanofiber. Fiber dispersion. A method for producing a cellulose nanofiber dispersion, comprising subjecting a dispersion fluid containing cellulose fiber and carboxymethylcellulose to high-pressure jet treatment. A cellulose nanofiber film formed by adding oily components to cellulose nanofibers to which carboxymethylcellulose or carboxymethylcellulose nanofibers have been added, stirring the mixture with a mixer and / or stirring deaerator, and then drying.