JP7291367B2 - Intermediate and method for producing intermediate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a porous intermediate containing cellulose nanofibers and a method for producing the same.

In recent years, attention has been focused on cellulose nanofibers, which are obtained by defibrating natural cellulose fibers into nanosizes. Natural cellulose fibers are biomass made from pulp such as wood, and are expected to reduce the burden on the environment by effectively using them.

For example, an emulsion containing cellulose nanofibers obtained by reacting natural cellulose fibers with an N-oxyl compound and/or a derivative of the cellulose nanofibers, resin particles, and a liquid medium is prepared, and then dried from the emulsion. A method for producing a cellulose nanofiber composite molded article has been proposed in which a resin-modifying additive is produced by removing a liquid medium, and the resin-modifying additive and a thermoplastic resin are melt-kneaded and melt-molded. (See, for example, Patent Document 1).

In addition, a cationic surfactant is adsorbed on fine cellulose fibers to obtain a solid after dehydration and drying, and the solid is further treated with N,N-dimethylformamide (DMF), N,N-dimethylacetamide, or tetrahydrofuran (THF). A method for producing a composite material has been proposed in which a dispersion is prepared by re-dispersing it in a polar solvent such as a polar solvent, and the dispersion and a resin are combined (see Patent Document 2).

JP 2013-14741 A JP 2016-188375 A

However, according to the technique of Patent Document 1, the cellulose nanofibers aggregate by forming hydrogen bonds in the drying process in which part of the water is removed. remains. Therefore, since the cellulose nanofibers cannot exist in a highly defibrated state in the cellulose nanofiber composite molded article, the thermoplastic resin cannot be sufficiently reinforced by the cellulose nanofibers.

In addition, in the method of Patent Document 2, reaggregation of the fine cellulose fibers tends to occur in the drying process, and even in the process of redispersion with a polar solvent, it is not easy to defibrate the reaggregated fine cellulose fibers again. . In addition, when kneading with a thermoplastic resin, it is necessary to process (knead) at a temperature above the boiling point of the solvent used, so the solvent easily volatilizes, causing reaggregation of the fine cellulose fibers, resulting in It is difficult to obtain a composite material in which the fibers are defibrated. As the cellulose fiber diameter becomes smaller, it tends to aggregate more easily, making it difficult to defibrate again. Therefore, it is expected that it will be difficult to simply apply the method of Patent Document 2.

Accordingly, the present invention provides an intermediate that is excellent in handleability and processability when combining cellulose nanofibers, and a method for producing the same.

[1] One aspect of the intermediate according to the present invention is
A porous intermediate comprising cellulose nanofibers having anionic groups,
The intermediate is directly mixed into a matrix of polymeric material,
The intermediate comprises the cellulose nanofibers, a cationic surfactant and a polyhydric alcohol,
The cellulose nanofibers have an average fiber diameter of 3 nm to 10 nm and an average aspect ratio of 20 to 350,
The mass ratio of the cationic surfactant to the cellulose nanofibers in the intermediate is 0.1 to 2.0 times,
The mass ratio of the polyhydric alcohol to the cellulose nanofibers in the intermediate is 2.0 to 20.0 times.

[2] In one aspect of the intermediate,
The intermediate is a dry body,
The dry body may have a density of 300 kg/m ³ to 600 kg/m ³ .

[3] In one aspect of the intermediate,
The cationic surfactant may be any one or more of primary to tertiary amine salts and quaternary ammonium salts.

[4] In one aspect of the intermediate,
The cationic surfactant may be a quaternary ammonium salt having a long-chain alkyl group of 10-18 carbon atoms.

[5] In one aspect of the intermediate according to the present invention,
The polyhydric alcohol may be one or more of dihydric alcohol and trihydric alcohol.

[6] One aspect of the method for producing an intermediate according to the present invention is
A step of mixing an aqueous cellulose nanofiber dispersion in which cellulose nanofibers having an anionic group are dispersed in an aqueous solvent, a cationic surfactant, and a polyhydric alcohol to obtain a CNF dispersion containing polyfoam;
A step of removing the aqueous solvent from the CNF dispersion to obtain a porous intermediate;
including
The cellulose nanofibers have an average fiber diameter of 3 nm to 10 nm and an average aspect ratio of 20 to 350,
The mass ratio of the cationic surfactant to the cellulose nanofibers in the intermediate is 0.1 to 2.0 times,
The mass ratio of the polyhydric alcohol to the cellulose nanofibers in the intermediate is 2.0 to 20.0 times,
The polyfoam contains the cellulose nanofibers, the cationic surfactant and the polyhydric alcohol,
The intermediate is obtained by removing the aqueous solvent from the multifoam.

[7] In one aspect of the method for producing the intermediate,
In the step of obtaining the CNF dispersion, the dispersion containing the cellulose nanofibers and the cationic surfactant can be stirred at 500 rpm or more and 30000 rpm or less using a stirring blade.

[8] In one aspect of the method for producing the intermediate,
the density of the multifoam is 400 kg/m ³ to 900 kg/m ³ ;
The intermediate may have a density of 300 kg/m ³ to 600 kg/m ³ .

The porous intermediate according to the present invention is excellent in handleability and workability when cellulose nanofibers are combined. The porous intermediate obtained by the method for producing an intermediate according to the present invention is excellent in handleability and workability when cellulose nanofibers are combined.

3 is a flow chart of a method for manufacturing an intermediate according to the present embodiment; 4 is a photograph of the dried intermediate of Example 2. FIG. 3 is a photograph of the dried intermediate of Comparative Example 3. FIG. 2 is an electron micrograph of the dried intermediate of Example 2. FIG. 2 is an electron micrograph of the dried intermediate of Example 2. FIG. 2 is an electron micrograph of the dried intermediate of Example 2. FIG. 4 is an electron micrograph of the dried intermediate of Comparative Example 2. FIG. 4 is an electron micrograph of the composite material of Example 2. FIG. 3 is an electron micrograph of the composite material of Comparative Example 3. FIG. 10 is an electron micrograph of the composite material of Comparative Example 5. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail.

1. The intermediate according to the present embodiment is a porous intermediate containing cellulose nanofibers having an anionic group, the intermediate containing the cellulose nanofibers, a cationic surfactant and a polyhydric alcohol, The cellulose nanofibers have an average fiber diameter of 3 nm to 10 nm and an average aspect ratio of 20 to 350, and the mass ratio of the cationic surfactant to the cellulose nanofibers in the intermediate is 0. .1 to 2.0 times, and the mass ratio of the polyhydric alcohol to the cellulose nanofibers in the intermediate is 2.0 to 20.0 times. In this specification, the numerical range indicated by "-" includes an upper limit and a lower limit.

1-1. Cellulose Nanofiber Cellulose nanofiber has an average fiber diameter of 3 nm to 10 nm and an average aspect ratio of 20 to 350. The average values of the fiber diameter and aspect ratio of the cellulose nanofibers are the arithmetic average values measured for at least 50 or more cellulose nanofibers within the field of view of the electron microscope. Cellulose nanofibers are provided as a cellulose nanofiber aqueous dispersion. The aqueous dispersion may contain oxidized cellulose fibers. Cellulose nanofibers obtained by various known methods can also be used.

The cellulose nanofiber aqueous dispersion may have a cellulose nanofiber solid content of 0.01% to 5% by mass, preferably 0.1% to 2% by mass. If the cellulose nanofiber solid content in the aqueous dispersion is less than 0.01% by mass, the drying process described later will take time, and if it exceeds 5% by mass, the cationic surfactant cannot be uniformly treated and the cellulose nanofibers agglomeration is likely to occur. Further, the aqueous dispersion may be, for example, an aqueous dispersion in which the solid content of cellulose nanofibers is diluted to 1% by mass. Furthermore, the aqueous dispersion can have a light transmittance of 40% or more, and further can have a light transmittance of 60% or more, and in particular can have a light transmittance of 80% or more. The light transmittance of the aqueous dispersion can be measured as light transmittance at a wavelength of 660 nm using an ultraviolet-visible spectrophotometer.

Raw materials for known cellulose nanofibers can be those derived from plant materials such as wood. As a method for producing cellulose nanofibers using a raw material of plant origin, for example, the raw material is chemically treated to make it easy to defibrate, and then the raw material is defibrated by subjecting the raw material to a physical treatment using a mechanical shearing force. Manufactured by physically disentangling raw materials by known methods using high mechanical shear force such as high-pressure homogenizer method, grinder grinding method, freeze grinding method, strong shear force kneading method, ball mill grinding method, etc. can be used.

Cellulose nanofibers have anionic groups. Cellulose nanofibers with anionic groups can be obtained by chemically treating raw materials or by introducing anionic groups into a material that has been physically defibrated and further refining (fibrillation). be done. In the refining process, the fibers are easily fibrillated due to the repulsive action of the anionic groups. The anionic group includes, for example, any one or more of carboxylic acid group, phosphoric acid group, sulfonic acid group, sulfate group, phosphorous acid group, xanthate group ( ^-OCSS- ) and salts thereof. Cellulose nanofibers having anionic groups include, for example, oxidized cellulose nanofibers having a carboxyl group or a salt of a carboxyl group, phosphate-esterified cellulose nanofibers having a phosphate group or a salt of a phosphate group, a sulfate group or a sulfuric acid group. a sulfate-esterified cellulose nanofiber having a group salt, a phosphite-esterified cellulose nanofiber having a phosphite group or a salt of a phosphite group, a xanthate group or a salt of a xanthate group, and the like. be. Oxidized cellulose nanofibers include, for example, TEMPO oxidized cellulose nanofibers and carboxymethylated cellulose nanofibers.

1-1-1. Oxidized Cellulose Nanofibers An aqueous dispersion containing TEMPO oxidized cellulose nanofibers as oxidized cellulose nanofibers is prepared through, for example, an oxidation step of oxidizing natural cellulose fibers to obtain oxidized cellulose fibers, and a refining step of refining the oxidized cellulose fibers. It can be obtained by a manufacturing method including

In the oxidation step, water is added to natural cellulose fibers as a raw material, and the mixture is treated with a mixer or the like to prepare a slurry in which natural cellulose fibers are dispersed in water. Here, the natural cellulose fibers include, for example, wood pulp, cotton pulp, bacterial cellulose, and the like. More specifically, examples of wood pulp include softwood pulp and hardwood pulp, examples of cotton pulp include cotton linter and cotton lint, and examples of non-wood pulp include: Straw pulp, bagasse pulp and the like can be mentioned. At least one of these can be used as the natural cellulose fiber.

As the oxidation step, in the case of TEMPO oxidation, natural cellulose fibers are oxidized in water using an N-oxyl compound as an oxidation catalyst to obtain oxidized cellulose fibers. As the oxidation step, a known method for oxidizing cellulose can be employed. Examples of N-oxyl compounds that can be used as cellulose oxidation catalysts include 2,2,6,6-tetramethyl-1-piperidine-N-oxyl (hereinafter also referred to as TEMPO), 4-acetamido-TEMPO, 4-carboxy-TEMPO, 4-phosphonooxy-TEMPO and the like can be used. Oxidized cellulose fibers can be bundles of cellulose microfibrils. Oxidized cellulose fibers can be defibrated into cellulose nanofibers in a refining process.

In the refining step, the oxidized cellulose fibers can be stirred in a solvent such as water to obtain cellulose nanofibers. Stirring treatment in the miniaturization step includes, for example, a disintegrator, a beater, a low-pressure homogenizer, a high-pressure homogenizer, a grinder, a cutter mill, a ball mill, a jet mill, a short-screw extruder, a twin-screw extruder, an ultrasonic agitator, and a household juicer mixer. etc. can be used. The average fiber diameter of the cellulose nanofibers in the aqueous dispersion thus obtained can be 3 nm to 10 nm, and can be 3 nm to 4 nm. The average aspect ratio of the cellulose nanofibers in the aqueous dispersion can be 20-350, more preferably 20-250, and particularly 50-200.

Aqueous dispersions containing carboxymethylated cellulose as oxidized cellulose nanofibers can be produced, for example, by a mercerization process, an etherification process, and a micronization process.

In the mercerizing step, natural cellulose fibers, a dispersion medium, and a mercerizing agent are mixed and mercerized. As the dispersion medium, for example, a lower alcohol alone or a mixture of two or more lower alcohols and water is used. Lower alcohols are, for example, methanol, ethanol, n-propyl alcohol, isopropyl alcohol and the like. Mercerizing agents are, for example, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide.

In the etherification step, after the mercerization treatment, a carboxymethylating agent is added to carry out an etherification reaction. Carboxymethylating agents include, for example, sodium monochloroacetate.

After the etherification reaction, the micronization step can be performed in the same manner as the micronization step described above. For example, carboxymethylated cellulose nanofibers can be obtained by micronization treatment using a high-pressure homogenizer or the like. The carboxymethylated cellulose nanofibers thus obtained can have the same fiber diameter and aspect ratio as TEMPO-oxidized cellulose nanofibers.

1-1-2. An aqueous dispersion containing phosphorylated cellulose nanofibers can be prepared, for example, by mixing a dry or wet cellulose fiber raw material with a powder or aqueous solution of phosphoric acid or a phosphoric acid derivative, or by mixing cellulose. It can be obtained, for example, by adding an aqueous solution of phosphoric acid or a phosphoric acid derivative to a dispersion of fiber raw materials. In these methods, usually, after mixing or adding a powder or aqueous solution of phosphoric acid or a phosphoric acid derivative, dehydration treatment, heat treatment, or the like is performed. Here, the phosphoric acid or phosphoric acid derivative includes at least one compound selected from oxoacids containing phosphorus atoms, polyoxoacids, and derivatives thereof. As a result, a compound containing a phosphate group in the hydroxyl group of a glucose unit constituting cellulose or a salt thereof undergoes a dehydration reaction to form a phosphate ester, and a phosphate group or a salt thereof is introduced. Phosphate-esterified cellulose nanofibers can be obtained from the cellulose fibers into which a phosphate group or a salt thereof has been introduced by performing the above-described refining process. The phosphate-esterified cellulose nanofibers thus obtained can have the same fiber diameter and aspect ratio as the TEMPO-oxidized cellulose nanofibers.

1-2. Cationic Surfactant A cationic surfactant can suppress aggregation due to hydrogen bonding between cellulose nanofibers. The cationic surfactant has the effect of suppressing aggregation of cellulose nanofibers in the intermediate after removing the aqueous solvent from the multifoam. Cationic surfactants can be any one or more of primary to tertiary amine salts and quaternary ammonium salts. In particular, the cationic surfactant can be a quaternary ammonium salt having a long chain alkyl group of 1 to 40 carbon atoms (C number), preferably 2 to 20 carbon atoms, more preferably 8 to 18 carbon atoms. It can be assumed that the larger the number of carbon atoms, the higher the effect of suppressing the aggregation of adjacent cellulose nanofibers due to hydrogen bonding. Salts can be chlorides, bromides, and the like.

Examples of quaternary ammonium salts having a long-chain alkyl group having 1 to 40 carbon atoms include octyltrimethylammonium chloride, decyltrimethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, and chloride. trimethylammonium salts such as octadecyltrimethylammonium; pyridinium salts such as octylpyridinium chloride, decylpyridinium chloride, dodecylpyridinium chloride, tetradecylpyridinium chloride, hexadecylpyridinium chloride, octadecylpyridinium chloride; benzalkonium chloride, benzethonium chloride, benzyltrichloride alkylammonium, dialkyldimethylammonium chloride, trimethylstearylammonium chloride, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide and the like.

The mass ratio of cationic surfactant to cellulose nanofibers in the CNF dispersion is 0.1 to 2.0 times. If the mass ratio of the cationic surfactant to the cellulose nanofibers is 0.1 times or more, by acting on the carboxyl groups on the surface of the cellulose nanofibers, reaggregation of the cellulose nanofibers is suppressed, and in the matrix component of the composite material. A good defibration state can be obtained. When the mass ratio of the cationic surfactant to the cellulose nanofibers in the CNF dispersion exceeds 2.0 times, the amount of surfactant in the composite material increases, the workability decreases, and the physical properties of the composite material decrease. do. Furthermore, the mass ratio of cationic surfactant to cellulose nanofibers can be 0.1 to 1.5 times. If the mass ratio is 1.5 times or less, the workability in the mixing step described later can be excellent.

1-3. Polyhydric alcohol Polyhydric alcohol prevents reaggregation of cellulose nanofibers after dehydration and drying by preventing hydrogen bonding between cellulose nanofibers even after the aqueous solvent is removed in the step of obtaining the intermediate described later. can. Therefore, the polyhydric alcohol exhibits a function as a substitute material for the aqueous solvent of the CNF dispersion. Moreover, the disentanglement of the cellulose nanofibers in the mixing step can be facilitated. Polyhydric alcohols are alcohols excluding monohydric alcohols. A monohydric alcohol cannot be used because its boiling point is lower than that of water.

Polyhydric alcohols have higher boiling points than water. By having a boiling point higher than that of water, the polyhydric alcohol can remain in the intermediate even if water evaporates through the step of obtaining the intermediate described later. Moreover, since the surfactant is adsorbed to the cellulose nanofibers, the cellulose nanofibers can maintain a stable dispersed state without aggregating. The polyhydric alcohol desirably has a boiling point higher than the kneading temperature in the later-described mixing step. This is to prevent the polyhydric alcohol from rapidly evaporating in the mixing step and causing reaggregation of the cellulose nanofibers.

Polyhydric alcohols can be any one or more of dihydric alcohols and trihydric alcohols. Examples of dihydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol and neopentyl glycol. Examples of trihydric alcohols include glycerin, trimethylolethane, trimethylolpropane, cyclohexanedimethanol and the like. Polyhydric alcohols other than dihydric and trihydric alcohols, such as pentaerythritol, diglycerin, and polyglycerin, may also be included.

The mass ratio of polyhydric alcohol to cellulose nanofibers in the CNF dispersion is 2.0 to 20.0 times. If the mass ratio of the polyhydric alcohol to the cellulose nanofibers is 2.0 times or more, the cellulose nanofibers can be defibrated when the intermediate after the drying step is combined with the rubber component. If it is more than double, it will be difficult to process when forming a composite. In addition, the mass ratio of the polyhydric alcohol to the cellulose nanofibers can be 2.5 to 15.0 times, and the mass ratio of the polyhydric alcohol to the cellulose nanofibers is 2.5 times or more and less than 15.0 times. can be

1-4. Porous Intermediate The intermediate is porous comprising cellulose nanofibers with anionic groups. Since the intermediate is porous, it is excellent in workability when combining cellulose nanofibers. That is, in the case of a dry non-porous plate, it is necessary to crush and mix it with the matrix material, but if it is a porous intermediate, the step of crushing can be omitted, and the processing at the time of compositing can be omitted. Excellent in nature. In addition, in the case of a dried non-porous plate, many aggregates of cellulose nanofibers are present in the composite material even if they are pulverized and mixed with the matrix material. A composite material containing no aggregates of cellulose nanofibers as described above can be easily produced. In the case of a dry non-porous plate, the cellulose nanofibers form aggregates in the polyhydric alcohol. On the other hand, in the case of a porous intermediate, it is speculated that the cellulose nanofiber surface is uniformly covered with a cationic surfactant to suppress aggregation, and that the polyhydric alcohol covers the cellulose nanofiber surface. .

Since the intermediate is porous and has a lower density than a plate-like one, it has a large volume when it is compounded, and is therefore easy to handle. For example, if the intermediate is porous during kneading, it tends to crumble and is easily incorporated into the matrix polymer.

The intermediate can be a dry body. Here, the term "dry matter" refers to one having a moisture content of 0% by mass to 20% by mass in thermogravimetric measurement (TG: Thermo Gravimetry measurement). The intermediate, which is a dry body, may have a density of 300 kg/m ³ to 600 kg/m ³ . The density of the polyfoam was determined by placing the polyfoam in a weighing container (measuring cup, beaker, etc.) and measuring the weight and volume.

The porous intermediate is formed such that a cell structure composed of cellulose nanofibers, a cationic surfactant, and a polyhydric alcohol surrounds the hollow portion. Adjacent hollow portions in the intermediate may be continuous or may be independent of each other. Adjacent cell structures in the intermediate body are continuous, and the thickness of the connection portion is, for example, 4.0 μm to 5 μm, and the thickness of the portion other than the connection portion is, for example, 0.8 μm to 2.0 μm. The thickness of each part in the cell structure is a value measured by observing with a scanning electron microscope in a state where the polyhydric alcohol is evaporated from the intermediate.

Since the cationic surfactant is in a state of being adsorbed to the cellulose nanofibers, the cellulose nanofibers adjacent to each other in the intermediate do not aggregate due to hydrogen bonding, and a stable dispersed state of the cellulose nanofibers can be maintained. In addition, the presence of the polyhydric alcohol between adjacent cellulose nanofibers in the intermediate suppresses reaggregation of the cellulose nanofibers. If the amount of polyhydric alcohol in the intermediate is small, the cellulose nanofibers will come closer to each other, making aggregation more likely to occur.

The cationic surfactant in the intermediate prevents aggregation due to hydrogen bonding between cellulose nanofibers, and the polyhydric alcohol can facilitate defibration of the cellulose nanofibers in the step of mixing with the matrix of the composite material. Therefore, by using the intermediate, the processability for combining the cellulose nanofibers with the matrix material is excellent.

2. Method for Producing Intermediate A method for producing an intermediate will be described with reference to FIG. FIG. 1 is a flow chart of the method for producing an intermediate according to this embodiment.

In the method for producing an intermediate according to the present embodiment, an aqueous cellulose nanofiber dispersion in which cellulose nanofibers having an anionic group are dispersed in an aqueous solvent, a cationic surfactant, and a polyhydric alcohol are mixed to form a multifoam. and a step (S20) of obtaining a porous intermediate by removing the aqueous solvent from the CNF dispersion, wherein the cellulose nanofibers have an average fiber diameter of value is 3 nm to 10 nm, the average aspect ratio is 20 to 350, and the mass ratio of the cationic surfactant to the cellulose nanofiber in the intermediate is 0.1 to 2.0 times. , the mass ratio of the polyhydric alcohol to the cellulose nanofibers in the intermediate is 2.0 to 20.0 times, and the polyfoam is composed of the cellulose nanofibers, the cationic surfactant, and the polyhydric Including alcohol, the intermediate is obtained by removing the aqueous solvent from the foam.

2-1. Step of obtaining a CNF dispersion (S10)
The step of obtaining a CNF dispersion (S10) includes mixing a cellulose nanofiber aqueous dispersion in which cellulose nanofibers are dispersed in an aqueous solvent, a cationic surfactant, and a polyhydric alcohol to obtain a CNF dispersion containing polyfoam. It is a process. As for the cellulose nanofibers, the cationic surfactant, and the polyhydric alcohol, those described above can be used, and overlapping descriptions are omitted here.

In the step of obtaining a CNF dispersion (S10), a predetermined amount of cationic surfactant and polyhydric alcohol can be added to a cellulose nanofiber aqueous dispersion and mixed by a known stirring means. In the step of obtaining a CNF dispersion (S10), cellulose nanofibers and a cationic surfactant are stirred to foam, and then a polyhydric alcohol is added to obtain a CNF dispersion containing polyfoam. In order to obtain foams by stirring the dispersion, the dispersion contains at least a cationic surfactant in the aqueous dispersion of cellulose nanofibers. As the stirring means, the stirring method is not limited as long as the CNF dispersion can be foamed.

In the step of obtaining the CNF dispersion (S10), for example, the dispersion containing the cationic surfactant in at least the cellulose nanofiber aqueous dispersion can be stirred at 500 rpm or more and 30000 rpm or less using a stirring blade. "rpm" is an abbreviation for "rotations per minute" and indicates the number of times the rotation is repeated in one minute. By using a stirring blade, the dispersion liquid can be efficiently foamed. In addition, it is preferable to use a stirring blade because the other drug can be homogeneously mixed with the thixotropic cellulose nanofiber aqueous dispersion. The type of the stirring blade is not particularly limited, and for example, it can be a known stirring blade such as propeller type, paddle type, and turbine type. By stirring at 500 rpm or more using a stirring blade, the cationic surfactant can be uniformly dispersed in the solvent, and the cationic surfactant can be uniformly acted on the cellulose nanofiber surface. A commercially available stirrer can be used for stirring at 30,000 rpm or less.

The density of the multifoam obtained by stirring can be 400 kg/m ³ to 900 kg/m ³ . A foam having a density of 400 kg/m ³ or more is preferable because foaming is possible. In addition, it is preferable that the density of the multi-foam is 900 kg/m ³ or less because the surface area of the multi-foam becomes large and the drying time in the dehydration drying process becomes short. The density of the polyfoam was determined by placing the polyfoam in a weighing container (measuring cup, beaker, etc.) and measuring the weight and volume. The density of the foam is measured after it has been allowed to stand for 10 minutes after stirring. The CNF dispersion separates into two layers, the foam and the liquid underneath the foam, when left to stand for 10 minutes after stirring. The multifoam concentrates the cellulose nanofibers contained throughout the CNF dispersion. Since the polyfoam is in a relatively stable form, it can be transferred to a weighing container, and the stability of the polyfoam can be confirmed visually for a period of, for example, 10 minutes after stirring for 7 days. could not.

2-2. Step of obtaining an intermediate (S20)
The step of obtaining an intermediate (S20) is a step of obtaining a porous intermediate by removing the aqueous solvent from the CNF dispersion obtained in the step of obtaining a CNF dispersion (S10). The porous intermediate obtained in this step is obtained by removing the aqueous solvent from the foam. As a method for removing the aqueous solvent from the foam, a known method can be used. For example, the foam may be dried by heating or may be dried by a spray drying method. For example, about half of the CNF dispersion is multifoam, which increases the surface area and shortens the drying time.

The intermediate obtained by the step of obtaining the intermediate (S20) may have a density of 300 kg/m ³ to 600 kg/m ³ . The density of the intermediate was measured by placing the intermediate in a measuring container (measuring cup, beaker, etc.) and measuring the weight and volume. The porous intermediate described above is thus obtained. Since the cellulose nanofibers were concentrated in the multifoam portion, it can be assumed that the skeleton portion of the cell structure constituting the porous intermediate was formed of cellulose nanofibers. Since the intermediates have been described above, redundant description will be omitted.

3. Method for Producing Composite Material In the method for producing a composite material according to the present embodiment, a composite material can be produced by mixing a porous intermediate with a polymer substance as a matrix material. The polymeric material can be one or more of thermoplastics, thermosets, thermoplastic elastomers, and rubbers.

Mixing of the intermediate and the polymer substance can be performed using various known mixing methods. It is preferable to use a so-called elastic kneading method that applies a force and utilizes the restoring force due to the elasticity of the polymeric substance.

The composite material can be free of aggregates of cellulose nanofibers having a maximum width of 10 µm or more, and further can be free of aggregates of cellulose nanofibers having a maximum width of 5 µm or more, particularly 1 µm or more. It may contain no agglomerates with the widest width. Cellulose nanofiber aggregates are scattered in a matrix while a plurality of cellulose nanofibers are gathered together and aggregated into particles. The maximum width of the cellulose nanofiber agglomerates can be determined by observing the composite sheet with a transmission optical microscope and the fracture surface of the composite material with a scanning electron microscope to observe particulate agglomerates scattered in the matrix material. Measure the maximum width.

The present invention may omit a part of the configuration or combine each embodiment and modifications as long as the features and effects described in the present application are provided.

The present invention includes substantially the same configuration as the configuration described in the embodiment. Here, the same configuration means a configuration with the same function, method and result, or a configuration with the same purpose and effect. Moreover, the present invention includes configurations in which non-essential portions of the configurations described in the embodiments are replaced. In addition, the present invention includes a configuration that achieves the same effects or achieves the same purpose as the configurations described in the embodiments. In addition, the present invention includes configurations obtained by adding known techniques to the configurations described in the embodiments.

Examples of the present invention will be described below, but the present invention is not limited to these.

(A) Preparation of samples of Examples 1 to 8 Step of obtaining CNF dispersion: Cellulose nanofiber aqueous dispersion (CNF1: Daiichi Kogyo Seiyaku Co., Ltd. 2% concentration TEMPO oxidized cellulose nanofiber diluted with water An aqueous dispersion of cellulose nanofibers (solvent is water) having the concentration shown in the table was prepared, polyhydric alcohol was added to the dispersion, and a juicer mixer (Blender MX1200XTX manufactured by Waring) was used at a rotation speed of 20,000 rpm. Further, a cationic surfactant was added to this mixture and mixed by stirring for 15 seconds at the number of rotations described as "stirring speed" in the table using the same juicer mixer. A CNF dispersion was obtained, and the "concentration" of CNF in the table is the concentration of cellulose nanofibers in the aqueous dispersion of cellulose nanofibers, and the unit is % by mass.

In Tables 1 to 8,
"CNF1": TEMPO oxidized cellulose nanofibers (cellulose nanofibers have an average fiber diameter of 3.3 nm and an average aspect ratio of 160);
"K1": manufactured by ACROS ORGANICS, dodecyltrimethylammonium chloride, 98% concentration,
"K2": manufactured by Kanto Chemical Co., Ltd., hexadecyltrimethylammonium chloride: 95% concentration,
"DEG": manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., diethylene glycol, special grade,
Met.

In Tables 1 to 8, the blending amounts of the cationic surfactant and the polyhydric alcohol are shown when the blending amount of the cellulose nanofiber in each example is set to "1". Therefore, for example, if the CNF compounding amount is 1 part by mass (phr) and the DEG is "10", the DEG compounding amount in the CNF dispersion is 10 parts by mass. It should be noted that the blending amount of the polyhydric alcohol in Tables 5 to 8, the blending amount in the CNF dispersion was shown as a reference.

Step of obtaining an intermediate: The aqueous solvent was removed from the CNF dispersion to obtain a porous intermediate. More specifically, the CNF dispersion containing the foam was poured into a vat and dried in an oven at the drying temperature and drying time shown in the table to remove the aqueous solvent and obtain a porous intermediate. The intermediate was a dry body with a moisture content of 20% by mass or less in thermogravimetry (TG: Thermo Gravimetry measurement).

(B) Preparation of Samples of Comparative Examples 2 to 7 In Comparative Example 2, samples were obtained in the same manner as in Example 2, except that the stirring speed was 300 rpm. The sample of Comparative Example 2 did not foam. For Comparative Example 3, a sample was obtained in the same manner as in Example 2, except that no cationic surfactant was added. The sample of Comparative Example 3 did not foam.

For Comparative Example 4, a sample was obtained in the same manner as in Example 2, except that the cationic surfactant was 0.05 times that of CNF. The sample of Comparative Example 4 foamed poorly. For Comparative Example 5, a sample was obtained in the same manner as in Example 2, except that no polyhydric alcohol was added.

For Comparative Example 6, a sample was obtained in the same manner as in Example 2, except that the cationic surfactant was not added and the polyhydric alcohol was 50 times the CNF. The sample of Comparative Example 6 did not foam. Comparative Example 7 was carried out in the same manner as in Example 2, except that the cationic surfactant was three times that of CNF.

(C) Measurement of Density of Multifoam The multifoam was taken out from the CNF dispersions of Examples 1 to 8, and the density (kg/m ³ ) of only the multifoam portion was measured. The density of the polyfoam was calculated by placing the polyfoam in a weighing container and measuring the weight and volume. The density of the multifoam is reported in the table as "Foam Density". The specific volume, which is the reciprocal of the density of the multifoam, was also calculated and reported in the table as "foam specific volume".

(D) Measurement of Density of Intermediates The densities of the intermediates of Examples 1-8 were measured. The density of the intermediate was calculated by putting the intermediate in a weighing container and measuring the weight and volume. The density of the intermediate is listed in the table as "Dry Body Density".

The drying times of Examples 2 and 4 to 8 were shorter than the drying times of Comparative Examples 2 to 6 at the same drying temperature. In Example 3, by setting the drying temperature to 90° C., the drying time was shortened to 4 hours compared to Example 2.

Example 1 had a longer drying time than Example 2 due to the higher water content in the CNF dispersion, but showed values close to those of Example 2 for the densities of the multifoam and intermediates. Since the viscosity of the CNF dispersion is low, the CNF and each compounding agent are easily mixed, and the stirring time is shortened.

The densities of the foams of Examples 1-8 ranged from 484 (kg/m ³ ) to 701 (kg/m ³ ). The specific volumes of the multifoams of Examples 1-8 ranged from 1.4 (cm ³ /g) to 2.1 (cm ³ /g). The densities of the multifoams of Examples 1-8 were lower than that of Comparative Example 4, and the specific volumes of the multifoams of Examples 1-8 were higher than that of Comparative Example 4.

The densities of the intermediates of Examples 1-8 ranged from 338 (kg/m ³ ) to 489 (kg/m ³ ). The densities of the intermediates of Examples 1-8 were lower than those of Comparative Examples 2-4,6.

2 is a photograph of the appearance of the intermediate of Example 2, and FIG. 3 is a photograph of the appearance of the intermediate of Comparative Example 3. FIG. As shown in FIG. 2, the intermediate of Example 2 has a floc-like form like solidified foam, whereas the intermediate of Comparative Example 3 has a plate-like form having a large number of irregularities on the surface. rice field. Although not shown, the appearance of the intermediates of Examples 1 and 3 to 8 was similar to that of the cotton-like intermediate of Example 2.

(E) Microscopic Observation The intermediates of Example 2 and Comparative Example 2 were further dried under reduced pressure at 90° C. for 12 hours to evaporate the polyhydric alcohol, and then observed with a scanning electron microscope. 4 to 6 are electron micrographs of the intermediate of Example 2, and FIG. 7 is an electron micrograph of the intermediate of Comparative Example 2. FIG. A large number of continuous cell structures forming a large number of hollows were observed in FIGS. The wall thickness of the cell structure was about 0.9 μm, and the thickness of the junction of adjacent cell structures was about 4.5 μm. The intermediate of Comparative Example 2 had wavy unevenness on the surface and was not porous.

(F) Production of Composite Material Using the intermediate obtained in (A) above, a low-temperature kneading step, a removal step, and a molding step were performed to produce a composite material sample.

Low temperature kneading step: The thermoplastic resin (modified LLDPE) in Tables 5 and 6 is wound around an open roll (two rolls), and the intermediates of Examples 2 to 5 are gradually added and kneaded to obtain an intermediate mixture. Then, the kneading temperature was set to 130° C., and the mixture was thinly passed (roll gap of 0.3 mm, roll speed ratio of 1.1) to obtain a mixture to be a masterbatch. Then, the masterbatches of Examples 2 to 5 were further put into a thermoplastic resin (mixture of modified LLDPE and LLDPE) and thinly passed. For the intermediates of Examples 7 and 8, composite materials were obtained in the same manner as in Example 2, etc., using "LLDPE" as the thermoplastic resin.

The kneading temperature in the low-temperature kneading step was determined by a DMA test (dynamic viscoelasticity test). .06) was obtained to set the kneading temperature.

By setting the kneading temperature in the low-temperature kneading step of Examples 2 to 5, 7, and 8 to 130 ° C., it was found that any formulation falls within the range of the processing region manifestation temperature T2 to temperature T4. The kneading temperature in the low-temperature kneading step in 5, 7 and 8 was 130°C.

Removal step: The composite material was heated in a vacuum oven at 160°C for 30 minutes to evaporate the polyhydric alcohol. Further, instead of the vacuum oven, the polyhydric alcohol was evaporated by kneading with an open roll for 5 minutes at 160° C. after the low-temperature kneading step as a removal step. The content of polyhydric alcohol in the composite material after the removal step was 1% by mass or less.

Molding process: The composite material that had undergone the removal process was hot-pressed at 140° C. and molded into a sheet. Specimens were cut from the molded sheet.

In Tables 5 to 8, the amount of CNF blended is the mass% (mass%) of CNF in the composite material, and the mass of CNF when the thermoplastic resin (LLDPE, modified LLDPE) is 100 parts by mass (phr). showed the part. In Tables 1 to 8, the column of CNF filling amount (mass%) in the composite material is the blending amount of the thermoplastic resin and CNF, and the residual amount of the cationic surfactant in the composite material is taken into consideration. do not have.

In Tables 5 to 8,
"LLDPE": manufactured by Eastern Petrochemical Company, linear low density polyethylene QAMAR FC21HS, melting point 122°C;
"Modified LLDPE": manufactured by BYK (Bik-Chemie), linear low-density polyethylene modified with maleic anhydride, SCONA TSPE 1112GALL, melting point 115°C,
Met.

(G) Preparation of samples of Comparative Examples 1 and 3 to Comparative Example 7 In Comparative Example 1, LLDPE pellets, which are the raw materials used in Example 2 and the like, were kneaded at 130 ° C. with an open roll heated, and then kneaded at 140 ° C. to obtain a test piece. In Comparative Example 3, the intermediate to which no cationic surfactant was added was pulverized with a pulverizer, and the low-temperature kneading step, removal step, and molding step were carried out in the same manner as in Example 2 to obtain a test piece. In Comparative Example 4, a test piece was obtained in the same manner as in Example 2 using an intermediate in which the cationic surfactant was 0.05 times the mass of CNF. In Comparative Example 5, a test piece was obtained by performing the low-temperature kneading step, removal step, and molding step in the same manner as in Example 2, using an intermediate to which no polyhydric alcohol was added. Comparative Example 6 was carried out in the same manner as in Example 2 using an intermediate in which the amount of polyhydric alcohol was 50 times the mass of CNF, but the mixture slipped on the rolls in the low temperature kneading process and could not be processed. . In Comparative Example 7, a test piece was obtained in the same manner as in Example 2 using an intermediate in which the cationic surfactant was three times the mass of CNF.

(H) Evaluation method (H-1) Processability evaluation The samples of Examples and Comparative Examples were evaluated for processability in a low-temperature kneading process. Evaluation results (○: processing time within 30 minutes, roll winding property is good, △ processing time: over 30 minutes to 1 hour, roll winding property is good, ×: processing time is over 1 hour, roll winding property is poor ) are shown in Tables 5 to 8.

(H-2) Evaluation of defibration property and dispersibility Evaluation of fibrillation property and dispersibility in the composite material was performed on the sheet-shaped samples of Examples and Comparative Examples molded to a thickness of 0.5 mm to 0.8 mm. gone. Each sample was observed with an optical microscope and a scanning electron microscope. Tables 5 to 8 show the evaluation results (○ indicates no agglomerates with a maximum width of 1 μm or more, and × indicates agglomerates with a maximum width of 10 μm or more). Also, an electron micrograph of Example 2 is shown in FIG. 9 and 10 show an electron micrograph of Comparative Example 3 and an electron micrograph of Comparative Example 5, respectively, as "X" samples.

(I) Evaluation Examples 2-5, 7 and 8 were superior to Comparative Examples 1, 3-7 in workability in the low-temperature kneading step. Comparative Example 4 foams, but since the cationic surfactant is small, many carboxyl groups that have not been bound to the cationic surfactant remain on the CNF surface, which makes it easier for the CNF to aggregate, resulting in a longer time for the low-temperature kneading process. rice field. And the composite of Comparative Example 4 had agglomerates. Since Comparative Example 7 contained a large amount of cationic surfactant, the thermoplastic resin was likely to be plasticized, and kneading was difficult in the low-temperature kneading step.

The composite materials of Examples 2-5, 7 and 8 did not have agglomerates of 10 µm or more. As shown in FIG. 8, no lumps exceeding 10 μm were observed in the electron micrograph. The samples of Comparative Examples 3-6 had aggregates of 10 μm or more. When the samples of Comparative Examples 3 to 6 were observed with an electron microscope, many large CNF lumps exceeding 10 μm as shown in FIGS. 9 and 10 were found.

Claims (8)

A porous intermediate comprising cellulose nanofibers having anionic groups,
The intermediate is directly mixed into a matrix of polymeric material,
The intermediate comprises the cellulose nanofibers, a cationic surfactant and a polyhydric alcohol,
The cellulose nanofibers have an average fiber diameter of 3 nm to 10 nm and an average aspect ratio of 20 to 350,
The mass ratio of the cationic surfactant to the cellulose nanofibers in the intermediate is 0.1 to 2.0 times,
An intermediate, wherein the mass ratio of the polyhydric alcohol to the cellulose nanofiber in the intermediate is 2.0 to 20.0 times. In claim 1,
The intermediate is a dry body,
The intermediate, wherein the dry matter has a density of 300 kg/m ³ to 600 kg/m ³ . In claim 1 or 2,
The intermediate, wherein the cationic surfactant is any one or more of primary to tertiary amine salts and quaternary ammonium salts. In claim 1 or 2,
The intermediate, wherein the cationic surfactant is a quaternary ammonium salt having a long-chain alkyl group with 10 to 18 carbon atoms. In any one of claims 1 to 4,
The intermediate, wherein the polyhydric alcohol is at least one of dihydric alcohol and trihydric alcohol. A step of mixing an aqueous cellulose nanofiber dispersion in which cellulose nanofibers having an anionic group are dispersed in an aqueous solvent, a cationic surfactant, and a polyhydric alcohol to obtain a CNF dispersion containing polyfoam;
A step of removing the aqueous solvent from the CNF dispersion to obtain a porous intermediate;
including
The cellulose nanofibers have an average fiber diameter of 3 nm to 10 nm and an average aspect ratio of 20 to 350,
The mass ratio of the cationic surfactant to the cellulose nanofibers in the intermediate is 0.1 to 2.0 times,
The mass ratio of the polyhydric alcohol to the cellulose nanofibers in the intermediate is 2.0 to 20.0 times,
The polyfoam contains the cellulose nanofibers, the cationic surfactant and the polyhydric alcohol,
A method for producing an intermediate, wherein the intermediate is obtained by removing the aqueous solvent from the foam. In claim 6,
The step of obtaining the CNF dispersion is a method for producing an intermediate, wherein the dispersion containing the cellulose nanofibers and the cationic surfactant is stirred using a stirring blade at 500 rpm or more and 30000 rpm or less. In claim 6 or claim 7,
the density of the multifoam is 400 kg/m ³ to 900 kg/m ³ ;
A method for producing an intermediate, wherein the intermediate has a density of 300 kg/m ³ to 600 kg/m ³ .

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