JP2018111768A - Fiber material and method for producing fiber material, and composite material and method for producing composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber material that is excellent in workability of a composite material using cellulose nanofiber and a method of producing the same.SOLUTION: A method for producing a fiber material includes: a mixture step (S10) for mixing cellulose nanofiber, metal salt and aqueous solvent to obtain a CNF dispersion liquid; and a drying step (S12) for removing the aqueous solvent from the CNF dispersion liquid obtained in the mixture step (S10) to obtain a fiber material. In the CNF dispersion liquid, a mass ratio of metal salt to cellulose nanofiber is 0.1-2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fiber material using a cellulose nanofiber, a method for producing the fiber material, a composite material, and a method for producing the composite material.

  In recent years, cellulose nanofibers obtained by deflating natural cellulose fibers into nanosizes have attracted attention. Natural cellulose fiber is biomass that uses pulp such as wood as a raw material, and it is expected to reduce the environmental load by effectively using this.

  Cellulose nanofibers are provided in the market as aqueous dispersions, but it has been difficult to process them for compounding with elastomers and synthetic resins. Cellulose nanofibers agglomerate by forming hydrogen bonds in the drying process that removes water from the aqueous dispersion, so that cellulose nanofibers cannot exist in a highly defibrated state in the composite process, and the composite material The cellulose nanofibers could not be sufficiently reinforced.

  Then, the method of mixing a cellulose nanofiber aqueous dispersion and rubber latex or a resin emulsion was proposed (refer patent documents 1, 2).

  However, composite materials produced by these methods may be affected by the properties of rubber latex or resin emulsion. In addition, it could not be applied to rubber and resin not marketed as rubber latex or resin emulsion.

Japanese Patent Laying-Open No. 2015-98576 Japanese Patent Laid-Open No. 2006-29169

  The objective of this invention is providing the fiber material excellent in the workability for complexing a cellulose nanofiber, and its manufacturing method. Moreover, the objective of this invention is providing the composite material using the said fiber material, and its manufacturing method.

[Application Example 1] A manufacturing method of a fiber material according to this application example is as follows:
A mixing step of mixing a cellulose nanofiber, a metal salt, and an aqueous solvent to obtain a CNF dispersion;
A drying step of removing the aqueous solvent from the CNF dispersion obtained in the mixing step to obtain a fiber material;
Including
The mass ratio of the metal salt to the cellulose nanofiber in the CNF dispersion is 0.1 to 2 times.

[Application Example 2]
In the method for manufacturing a fiber material according to the application example,
The metal salt may include at least one of a monovalent metal salt and a divalent metal salt.

[Application Example 3]
In the method for manufacturing a fiber material according to the application example,
The metal salt is a monovalent metal salt;
The mass ratio of the monovalent metal salt to the cellulose nanofibers in the CNF dispersion may be 0.2 to 2 times.

[Application Example 4]
In the method for manufacturing a fiber material according to the application example,
The metal salt is a divalent metal salt;
The mass ratio of the divalent metal salt to the cellulose nanofiber in the CNF dispersion may be 0.1 to 2 times.

[Application Example 5]
The manufacturing method of the composite material according to this application example is as follows:
The fiber material of the application example is a swollen fiber material containing a predetermined amount of moisture,
Further comprising a kneading step of mixing the swollen fiber material with an elastomer to obtain a composite material,
The kneading step includes a step of thinning using an open roll having a roll interval of 0.1 mm to 0.5 mm and a roll temperature of 0 ° C. to 50 ° C.

[Application Example 6]
The manufacturing method of the composite material according to this application example is as follows:
The fiber material of the application example is a swollen fiber material containing a predetermined amount of moisture,
The method further includes a kneading step of mixing the swollen fiber material with a synthetic resin to obtain a composite material.

[Application Example 7]
In the method for manufacturing a composite material according to the application example,
The synthetic resin is a thermoplastic resin,
In the kneading step, the processing region expression temperature in the storage elastic modulus of the thermoplastic resin composition near the melting point (Tm ° C.) of the thermoplastic resin is 1.06 times the flat region expression temperature (T3 ° C.) in the storage elastic modulus. A step of kneading at a kneading temperature in a range up to a temperature of (T3 ° C. × 1.06) can be included.

[Application Example 8]
In the method for manufacturing a composite material according to the application example,
The synthetic resin is a thermosetting resin,
In the kneading step, the swollen fiber material is mixed with the main component of the thermosetting resin and kneaded at a kneading temperature ranging from a temperature 20 ° C. lower than the softening point of the main agent to a temperature 10 ° C. higher than the softening point. Furthermore, the process of mixing a hardening | curing agent can be included.

[Application Example 9]
In the method for manufacturing a composite material according to the application example,
It may further include a dehydration step of dehydrating the composite material obtained in the kneading step.

[Application Example 10]
The fiber material according to this application example is
Cellulose nanofibers to which metal derived from a metal salt is bound are included.

[Application Example 11]
In the fiber material according to the application example,
The metal salt may include at least one of a monovalent metal salt and a divalent metal salt.

[Application Example 12]
The composite material according to this application example is
It includes cellulose nanofibers defibrated from the fiber material of the application example and an elastomer or a synthetic resin.

[Application Example 13]
In the composite material according to the application example,
The composite material may not include cellulose nanofiber aggregates having a maximum width of 50 μm or more.

  ADVANTAGE OF THE INVENTION According to this invention, the fiber material excellent in the workability for complexing a cellulose nanofiber and its manufacturing method can be provided. Moreover, according to this invention, the composite material using the said fiber material and its manufacturing method can be provided.

It is a flowchart which shows the manufacturing method of the fiber material which concerns on one embodiment. It is a flowchart which shows the manufacturing method of the composite material which concerns on one embodiment. It is a figure which shows typically the kneading | mixing process in the manufacturing method of the composite material which concerns on one embodiment. It is a figure which shows typically the kneading | mixing process in the manufacturing method of the composite material which concerns on one embodiment. It is a figure which shows typically the kneading | mixing process in the manufacturing method of the composite material which concerns on one embodiment. 4 is an electron micrograph of a tensile fracture surface of a composite material of Example 2. FIG. It is a figure which shows the electron micrograph of the tensile fracture surface of the composite material of Example 4. FIG. 10 is a diagram showing an electron micrograph of a tensile fracture surface of a composite material of Example 11. FIG. 10 is an electron micrograph of a tensile fracture surface of a composite material of Comparative Example 3. FIG. It is a figure which shows the electron micrograph of the tensile fracture surface of the composite material of the comparative example 6. It is a figure which shows the electron micrograph of the tensile fracture surface of the composite material of the comparative example 14. It is a figure which shows the graph of the stress-strain of the composite material of Example 21,22. It is a figure which shows the graph of the linear expansion coefficient-temperature of the composite material of Example 23. FIG. It is a graph which shows the relationship between the storage elastic modulus and temperature of the sample of Example 24 explaining the method for obtaining the range of 2nd temperature.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unduly limit the contents of the present invention described in the claims. In addition, not all of the configurations described below are essential constituent requirements of the present invention.

1. Manufacturing method of fiber material The manufacturing method of the fiber material which concerns on one Embodiment is demonstrated using FIG. FIG. 1 is a flowchart showing a method for manufacturing a fiber material according to an embodiment.

As shown in FIG. 1, the manufacturing method of the fiber material which concerns on this embodiment is a mixing process (S10) which mixes a cellulose nanofiber, a metal salt, and an aqueous solvent, and obtains a CNF dispersion liquid, and a mixing process (S10). A drying step (S) in which the aqueous solvent is removed from the CNF dispersion obtained in step 1 to obtain a fiber material.
12). Here, the mass ratio of the metal salt to the cellulose nanofibers in the CNF dispersion is 0.1 to 2 times.

1-1. Mixing step The mixing step (S10) is a step of obtaining a CNF dispersion by mixing cellulose nanofibers, a metal salt, and an aqueous solvent.

  In the mixing step (S10), a metal salt is added to the cellulose nanofiber dispersion as a raw material, and mixing can be performed using a known stirrer, for example, a propeller stirrer, a rotary stirrer, or a three roll. A cellulose nanofiber dispersion and a metal salt dispersion in which a metal salt is dissolved or dispersed may be mixed.

1-1-1. Cellulose nanofiber dispersion The cellulose nanofiber dispersion used as a raw material may be a commercially available one from Daiichi Kogyo Seiyaku Co., Ltd. In general, commercially available cellulose nanofibers are provided in a state of being dispersed in an aqueous solution at a concentration of 2%, for example.

  The cellulose nanofiber dispersion used as a raw material can be obtained, for example, by a production method including an oxidation step of oxidizing natural cellulose fibers to obtain oxidized cellulose fibers and a refinement step of refining oxidized cellulose fibers. Here, although the manufacturing method of the cellulose nanofiber dispersion using an oxidation process is demonstrated, what was obtained with the other manufacturing method may be used.

  First, an oxidation process adds water with respect to the natural cellulose fiber used as a raw material, processes with a mixer etc., and prepares the slurry which disperse | distributed the natural cellulose fiber in water.

  Here, natural cellulose fibers include, for example, wood pulp, cotton-based pulp, bacterial cellulose and the like. More specifically, examples of the wood pulp include coniferous pulp, hardwood pulp, and the like. Examples of the cotton pulp include cotton linter and cotton lint. Non-wood pulp includes Mention may be made of straw pulp, bagasse pulp and the like. At least one of these natural cellulose fibers can be used.

  Natural cellulose fibers have a structure composed of cellulose microfibril bundles and lignin and hemicellulose filling them. That is, it is presumed that the cellulose microfibril and / or the cellulose microfibril bundle has a structure in which hemicellulose covers and further this is covered with lignin. Cellulose microfibrils and / or cellulose microfibril bundles are firmly bonded by lignin to form plant fibers. Therefore, it is preferable that lignin in the plant fiber is removed in advance from the viewpoint that aggregation of the cellulose fiber in the plant fiber can be prevented. Specifically, the lignin content in the plant fiber-containing material is usually about 40% by mass or less, preferably about 10% by mass or less. Further, the lower limit of the lignin removal rate is not particularly limited, and it is preferably as close to 0% by mass. The lignin content can be measured by the Klason method.

As the cellulose microfibril, a cellulose microfibril having a width of about 4 nm exists as a minimum unit, and this can be called a single cellulose nanofiber. In the present invention, the “cellulose nanofiber” is a material obtained by unraveling natural cellulose fibers and / or oxidized cellulose fibers to the nanosize level. In particular, the average value of the fiber diameters can be 1 nm to 200 nm, and further 1 nm. Can be ˜150 nm, in particular cellulose microfibrils and / or cellulose microfibril bundles of 1 nm to 100 nm. That is, the cellulose nanofiber can include a single cellulose nanofiber alone or a bundle of a plurality of single cellulose nanofibers.

  The aspect ratio (fiber length / fiber diameter) of the cellulose nanofiber can be an average value of 10 to 1000, more preferably 10 to 500, and particularly preferably 100 to 350.

  In addition, the average value of the fiber diameter and fiber length of a cellulose nanofiber is an arithmetic average value measured about at least 50 or more of the cellulose nanofiber within the visual field of an electron microscope.

  Next, as an oxidation step, natural cellulose fibers are oxidized in water using an N-oxyl compound as an oxidation catalyst to obtain oxidized cellulose fibers. Examples of N-oxyl compounds that can be used as an oxidation catalyst for cellulose include 2,2,6,6-tetramethyl-1-piperidine-N-oxyl (hereinafter also referred to as TEMPO), 4-acetamide-TEMPO, 4-carboxy-TEMPO, 4-phosphonooxy-TEMPO, etc. can be used.

  After the oxidation step, for example, a purification step of repeating washing with water and filtration can be carried out to remove impurities other than oxidized cellulose fibers contained in the slurry, such as unreacted oxidant and various by-products. The solvent containing the oxidized cellulose fiber is, for example, in a state of being impregnated with water. At this stage, the oxidized cellulose fiber is not defibrated up to the unit of cellulose nanofiber. As the solvent, water can be used. For example, in addition to water, organic solvents (alcohols, ethers, ketones, etc.) soluble in water can be used depending on the purpose.

  Oxidized cellulose fiber has a carboxyl group by modifying a part of the hydroxyl group of cellulose nanofiber with a substituent having a carboxyl group. The average value of the fiber diameter of the oxidized cellulose fiber can be 10 μm to 30 μm. In addition, the average value of the fiber diameter of an oxidized cellulose fiber is an arithmetic average value measured about at least 50 or more of the oxidized cellulose fiber in the visual field of an electron microscope. The oxidized cellulose fiber can be a bundle of cellulose microfibrils. Oxidized cellulose fibers can be fibrillated into cellulose nanofibers in the refinement process.

  In the micronization step, the oxidized cellulose fiber can be stirred in a solvent such as water, and cellulose nanofibers can be obtained.

  In the miniaturization step, the solvent as the dispersion medium can be water. Moreover, as a solvent other than water, water-soluble organic solvents such as alcohols, ethers, and ketones can be used alone or in combination.

  The agitation treatment in the miniaturization process includes, for example, a disaggregator, a beater, a low pressure homogenizer, a high pressure homogenizer, a grinder, a cutter mill, a ball mill, a jet mill, a short axis extruder, a twin screw extruder, an ultrasonic agitator, and a home juicer mixer. Etc. can be used.

  Moreover, solid content concentration of the solvent containing the oxidized cellulose fiber in the refining treatment can be, for example, 50% by mass or less. When this solid content concentration exceeds 50% by mass, high energy is required for dispersion.

  A cellulose nanofiber dispersion containing cellulose nanofibers can be obtained by the refinement process. The cellulose nanofiber dispersion can be a colorless, transparent or translucent suspension. In the suspension, cellulose nanofibers, which are fibers oxidized and defibrated and refined, are dispersed in water. That is, in this dispersion, cellulose nanofibers can be obtained by weakening the strong cohesion between microfibrils (hydrogen bonding between surfaces) by introducing carboxyl groups in the oxidation step and further through a refinement step. And by adjusting the conditions of the oxidation step, the carboxyl group content, polarity, average fiber diameter, average fiber length, average aspect ratio, etc. can be controlled.

  Thus, the obtained cellulose nanofiber dispersion liquid can contain 0.1-10 mass% of cellulose nanofibers. Further, for example, it can be a dispersion diluted to 1% by mass of cellulose nanofibers. Further, the dispersion may have a light transmittance of 40% or more, a light transmittance of 60% or more, and particularly 80% or more. The transmittance of the dispersion can be measured as the transmittance at a wavelength of 660 nm using an ultraviolet-visible spectral hardness meter.

1-1-2. Metal salt Metal ions can be ion-bonded to cellulose nanofibers by mixing with a cellulose nanofiber dispersion. The metal salt can include at least one of a monovalent metal salt, a divalent metal salt, and a trivalent metal salt. As the metal salt, a monovalent metal salt and a divalent metal salt are preferable. The monovalent metal salt is a salt containing sodium, potassium, and silver, and examples thereof include unsaturated acid metal salt monomers such as sodium acrylate, potassium acrylate, sodium methacrylate, and potassium methacrylate. Examples of the divalent metal salt include magnesium, calcium, barium, zinc, copper, iron, lead, nickel, manganese, tin, and the like. For example, zinc acrylate, magnesium acrylate, calcium acrylate, zinc methacrylate And unsaturated acid metal salt monomers such as magnesium methacrylate and calcium methacrylate. Examples of the trivalent metal salt include neodymium methacrylate, aluminum chloride (AlCl ₃ ), and iron chloride (FeCl ₃ ). The metal salt may be water-soluble or water-insoluble.

  The mass ratio of the metal salt to the cellulose nanofibers in the CNF dispersion is 0.1 to 2 times. When the metal salt is less than 0.1 times in mass ratio with respect to the cellulose nanofiber, workability in the kneading step described later is lowered. That is, it becomes difficult to fibrillate the aggregate of cellulose nanofibers in the kneading step. Moreover, when a metal salt exceeds 2 times by mass ratio with respect to a cellulose nanofiber, the metal salt which was not couple | bonded with the cellulose nanofiber will precipitate in the stage of a fiber material. The precipitated metal salt may affect the physical properties of the elastomer and the like in the kneading step described later. The metal salt may further have a mass ratio with respect to the cellulose nanofibers of 0.2 times to 1.5 times.

  When the metal salt is a monovalent metal salt, the mass ratio of the monovalent metal salt to the cellulose nanofibers in the CNF dispersion can be 0.2 to 2 times, and further 0.5 to 1 to 1. It can be 5 times. When the metal salt is a divalent metal salt, the mass ratio of the divalent metal salt to the cellulose nanofibers in the CNF dispersion can be 0.1 to 2 times, and further 0.2 to 1 to 1. It can be 5 times. As a result of the experiment, it can be presumed that the workability in the kneading step described later is affected by the blending amount of the monovalent metal salt or divalent metal salt and cellulose nanofiber.

  The aqueous solvent may be water or an aqueous solution containing a water-soluble component.

1-1-3. CNF dispersion The CNF dispersion is a mixture of cellulose nanofibers, metal salts, and aqueous solvents. The water-soluble metal salts are ionized and the metal ions are bonded to the cellulose nanofibers, resulting in a water-insoluble metal. It is considered that the metal ions bind to cellulose nanofibers in the salt. The CNF dispersion is referred to as “CNF dispersion” in order to distinguish it from the cellulose nanofiber dispersion as a raw material not containing a metal salt. The metal ion is ion-bonded by substitution with Na ⁺ that is ion-bonded to the carboxy group of the cellulose nanofiber. In the CNF dispersion, water-soluble metal ions are considered to form an ion cluster by gathering a plurality of metal ions. And it is thought that the cellulose nanofiber has couple | bonded with the ion cluster. In addition, even if a water-insoluble metal salt is used, the physical properties of the composite material are improved in the same way as the water-soluble metal salt, so that metal ions form ion clusters and cellulose nanofibers bind to the ion clusters. it seems to do. The size of the ion cluster is several tens nm to several hundreds nm.

  Water-soluble metal ions are bonded and dispersed throughout the cellulose nanofibers in a defibrated state in the CNF dispersion. The water-insoluble metal ions are bonded to the fibrillated cellulose nanofibers, but are dispersed in the CNF dispersion in a state where a part of the aqueous solvent of the CNF dispersion is separated.

1-2. Drying Step The drying step (S12) is a step of removing the aqueous solvent from the CNF dispersion obtained in the mixing step (S10) to obtain a fiber material. As a method for removing the aqueous solvent from the CNF dispersion, a known method can be used, and for example, drying may be performed by heating.

  For example, the CNF dispersion is poured into a container (such as a vat), and the container is placed in an oven to evaporate the aqueous solvent at 30 ° C. to 100 ° C. When the fiber material is used in the composite material manufacturing method described later, the fiber material may be dried to a state containing a predetermined amount of moisture to obtain a swollen fiber material. The swollen fiber material will be described in the later-described swelling step.

1-3. Fiber material The fiber material obtained in the drying step includes cellulose nanofibers to which a metal derived from a metal salt is bound.

  The fiber material can be pulverized into powder in consideration of processability in the kneading step.

  By removing the aqueous solvent, the cellulose nanofibers in the fiber material are again formed with hydrogen bonds on the surface of the cellulose nanofibers, and thus re-aggregate to form, for example, a sheet-like solid. Even if the fiber material is mixed with the elastomer or the like as it is, it is not defibrated into the cellulose nanofibers, and the pulverized solid is only dispersed in the elastomer.

  In order to obtain the effect of reinforcing cellulose nanofibers, which are nano-sized fibers, by mixing fiber materials with elastomers, etc., the cellulose nanofibers are loosened one by one as in the CNF dispersion. It must be dispersed in the composite material.

2. Manufacturing Method of Composite Material A manufacturing method of a composite material according to an embodiment will be described with reference to FIG. FIG. 2 is a flowchart showing a method for manufacturing a composite material according to an embodiment.

The method for producing a composite material according to this embodiment further includes a kneading step (S16) in which the swollen fiber material is mixed with an elastomer or a synthetic resin to obtain a composite material. The swollen fiber material used in the kneading step (S16) may be a swollen fiber material in which the fiber material obtained in the drying step (S12) contains a predetermined amount of moisture. For example, as shown in FIG. 2, the method for producing a composite material includes a swelling step (S14) of swelling a fiber material with water, and mixing the swollen swollen fiber material with an elastomer or a synthetic resin to produce a composite material. A kneading step (S16) to be obtained and a dehydration step (S18) for removing moisture from the composite material can be included.

2-1. Swelling step The swelling step (S14) is a step of swelling the fiber material with water.

  By including a predetermined amount of water in the fiber material, the peelability between cellulose nanofibers firmly bonded in the fiber material is improved. It is considered that the metal bonded to the cellulose nanofibers is ionized again by the water absorbed by the fiber material and weakens the hydrogen bonds between the cellulose nanofibers and the ionic bonds with the metal ion clusters.

  In the swelling step (S14), the fiber material and a predetermined amount of water are put into a sealed container and heated and held for a predetermined time. For example, it is about 1 hour at 70 ° C. Water that has become saturated water vapor in the sealed container is absorbed by the fiber material, and the fiber material swells. As the sealed container, a glass container can be used, and an autoclave apparatus can be used.

  The predetermined amount of water to be included in the fiber material in the swelling step (S14) can be 0.5 to 4 times by mass ratio with respect to the cellulose nanofibers included in the fiber material. If the mass ratio of water to cellulose nanofibers is less than 0.5 times, the processability in the kneading step (S16) decreases. When the mass ratio of water to cellulose nanofibers exceeds 4 times, it becomes difficult to mix with the elastomer and the like, and the processing time becomes long. The predetermined amount of water to be included in the fiber material in the swelling step (S14) can further have a mass ratio of 1 to 3.5 times with respect to the cellulose nanofibers, and particularly a mass ratio with respect to the cellulose nanofibers of 1 to 3 times. Can be double.

  The swelling step (S14) is for improving the workability and defibration in the kneading step. Therefore, the fiber material used in the kneading step only needs to contain a predetermined amount of water without passing through the swelling step (S14). For example, the water is removed until the predetermined moisture amount is reached in the drying step (S12). May be. A fiber material containing a predetermined amount of water is called a swollen fiber material. The predetermined amount of water in the swollen fiber material is the same as the amount of water contained in the swollen fiber material obtained in the swelling step (S14) even when the swollen fiber material is obtained in the drying step (S14).

2-2. Kneading process The conditions of the kneading process (S16) differ depending on the material to be the matrix of the composite material. A thermoplastic resin and a thermosetting resin will be described as elastomers and synthetic resins, respectively.

2-2-1. Kneading Step Using Elastomer A kneading step (S16) for kneading the fiber material with the elastomer will be described with reference to FIGS. 3-5 is a figure which shows typically the manufacturing method of the composite material which concerns on one Embodiment. The kneading step (S16) includes a thinning step of thinning using an open roll having a roll interval of 0.1 mm to 0.5 mm and a roll temperature of 0 ° C to 50 ° C.

  First, before the thinning process, as shown in FIG. 3, the elastomer 30 wound around the first roll 10 can be masticated, and the molecular chain of the elastomer 30 is appropriately cut to remove free radicals. Generate. The free radicals of the elastomer 30 generated by mastication are in a state where they are easily combined with the cellulose nanofibers. As the elastomer 30, natural rubber, synthetic rubber and thermoplastic elastomer can be used.

  Next, as shown in FIG. 4, the step of gradually adding the swollen fiber material 80 to the bank 34 of the elastomer 30 wound around the first roll 10 and kneading to obtain an intermediate mixture can be performed. Here, the swelling fiber material 80 is, for example, a crosslinking agent, a vulcanizing agent, a vulcanization accelerator, a vulcanization retarding agent, a softening agent, a plasticizer, a curing agent, a reinforcing agent, a filler, an anti-aging agent, in addition to cellulose nanofibers. Agents, colorants, acid acceptors and the like. These compounding agents other than cellulose nanofibers can be added to the elastomer 30 at an appropriate time in the mixing process.

  The step of obtaining the intermediate mixture of FIGS. 3 and 4 is not limited to the open roll method, and for example, a closed kneading method or a multi-screw extrusion kneading method can be used.

  Furthermore, as shown in FIG. 5, a thinning process can be performed. A thinning process can perform the process of performing thinning at 0 degreeC-50 degreeC using the open roll 2 whose roll space | interval is 0.5 mm or less, and obtaining the uncrosslinked composite material 50. FIG. In this step, the roll interval d between the first roll 10 and the second roll 20 is set to, for example, 0.5 mm or less, and more preferably 0.1 mm to 0.5 mm, and obtained in FIG. The intermediate mixture 36 can be put into the open roll 2 and thinning can be performed once to several times. For example, the thinning can be performed about 1 to 10 times. When the surface speed of the first roll 10 is V1 and the surface speed of the second roll 20 is V2, the ratio of the surface speeds (V1 / V2) in thinness is 1.05 to 3.00. And can be 1.05-1.2. By using such a surface velocity ratio, a desired shear force can be obtained.

  Thus, the composite material 50 pushed out between narrow rolls deform | transforms large like FIG. 5 with the restoring force by the elasticity of an elastomer, and a cellulose nanofiber moves large with an elastomer in that case. The composite material 50 obtained through thinning is rolled with a roll and dispensed into a sheet having a predetermined thickness, for example, 100 μm to 500 μm.

  In this thinning process, in order to obtain as high a shearing force as possible, the roll temperature can be set to, for example, 0 ° C. to 50 ° C., and further set to a relatively low temperature of 5 ° C. to 30 ° C. Can do. The actually measured temperature of the composite material 50 can also be adjusted to 0 ° C. to 50 ° C., and further adjusted to 5 ° C. to 30 ° C.

  By adjusting to such a temperature range, cellulose nanofibers can be defibrated using the elasticity of the elastomer, and the defibrated cellulose nanofibers can be dispersed in the composite material 50.

  Due to the high shearing force in this thinning process, a high shearing force acts on the elastomer, so that the cellulose nanofibers in the swollen fiber material are separated from each other so as to be pulled out one by one to the elastomer molecules and dispersed in the elastomer. . This is because the metal bonded to the cellulose nanofibers is ionized by the swelling of the fiber material and weakens the bonding force between the cellulose nanofibers. In particular, since an elastomer has elasticity and viscosity, cellulose nanofibers can be defibrated and dispersed. And the composite material 50 excellent in the dispersibility and dispersion stability of cellulose nanofiber (it is hard to re-aggregate a cellulose nanofiber) can be obtained.

More specifically, when the elastomer and the cellulose nanofiber are mixed with an open roll, the viscous elastomer penetrates into the cellulose nanofiber. When the surface of the cellulose nanofiber is moderately high by, for example, oxidation treatment, it can be easily bonded to an elastomer molecule. Next, when a strong shearing force acts on the elastomer, the cellulose nanofibers move as the elastomer molecules move, and the aggregated cellulose nanofibers are separated by the restoring force of the elastomer due to elasticity after shearing. Will be dispersed in the elastomer. In particular, the open roll method is preferable because it can measure and manage not only the roll temperature but also the actual temperature of the mixture.

  Next, a method for manufacturing a composite material using a synthetic resin will be described.

2-2-2. Kneading process using a thermoplastic resin A kneading process using a thermoplastic resin as a synthetic resin will be described. In the kneading step, the processing region expression temperature in the storage elastic modulus of the thermoplastic resin composition near the melting point (Tm ° C.) of the thermoplastic resin is 1.06 times the flat region expression temperature (T3 ° C.) in the storage elastic modulus (T3). A step of kneading at a kneading temperature in the range up to a temperature of ° C x 1.06).

  In the kneading step, an apparatus for melting and molding a thermoplastic resin, for example, an open roll, a closed kneader, an extruder, an injection molding machine, or the like can be used. For example, it can be performed using an extruder having a conical screw or an open roll 2 as shown in FIGS.

  The kneading step includes, for example, a first temperature mixing step of kneading a thermoplastic resin and a swollen fiber material at a first temperature to obtain a first mixture, and a low temperature step of adjusting the temperature of the first mixture to a second temperature. And a low temperature kneading step of kneading the first mixture at the second temperature. The first temperature is higher than the second temperature, and the second temperature is a flat region expression in the storage elastic modulus from a processing region expression temperature in the storage elastic modulus of the composite material near the melting point (Tm ° C.) of the thermoplastic resin. The range is up to 1.06 times the temperature (T3 ° C.) (T3 ° C. × 1.06).

2-2-1-1. First Temperature Mixing Step In the first temperature mixing step, a thermoplastic resin and a swollen fiber material are kneaded at a first temperature to obtain a first mixture.

  The first temperature mixing step is a step until the amount of the swollen fiber material of a predetermined blending amount is completely added to the thermoplastic resin. Preferably, the cellulose nanofiber is mixed with the entire thermoplastic resin by visual observation by an operator. It can be a process until it is recognized. Similar to the case of the elastomer described above, the present invention can be carried out as shown in FIGS.

  The first temperature is higher than the melting point (Tm) of the thermoplastic resin. The first temperature is higher than the second temperature. The first temperature may be a temperature that is 25 ° C. or more higher than the melting point (Tm) of the thermoplastic resin. The first temperature may be a temperature that is 25 ° C. or more and 70 ° C. or less higher than the melting point (Tm) of the thermoplastic resin, and may be a temperature that is 25 ° C. or more and 60 ° C. or less higher than the melting point (Tm). The first temperature is the actual temperature of the thermoplastic resin during the first temperature mixing step, not the temperature of the processing apparatus. The molding processing temperature of the thermoplastic resin is generally represented by the set temperature of the heating cylinder in the case of, for example, an extruder or an injection molding machine of the processing apparatus. Even the actual resin temperature becomes high. Since the first temperature is the temperature during processing, it is desirable to measure the surface temperature of the actual resin as much as possible. However, if it cannot be measured, the surface temperature of the resin immediately after taking out the first mixture from the processing apparatus is measured. Temperature. The first temperature is not the temperature immediately after the resin is added to the processing apparatus, but the temperature when the swollen fiber material has been added and mixed.

  In the present invention, “melting point (Tm)” refers to a melting peak value measured in accordance with JIS K7121 using differential scanning calorimetry (DSC).

Cellulose nanofibers in the first mixture obtained in the first temperature mixing step are dispersed throughout and remain in the same aggregate as the raw material. Therefore, the first mixture has defects in the material. For example, when a tensile test or the like is performed, the elongation at break is significantly lower than that of the raw material thermoplastic resin alone.

2-2-2-2. Low temperature process The low temperature process adjusts the temperature of the first mixture to the second temperature.

  Here, the second temperature will be described.

  The general processing set temperature in the first temperature mixing step, that is, the set temperature of the processing apparatus, is recommended as the processing set temperature of the thermoplastic resin in order to sufficiently melt the thermoplastic resin in a short time and process it quickly. The temperature is higher than the Therefore, the thermoplastic resin is not processed near its melting point. As described above, the surface temperature of the thermoplastic resin during processing is higher than the processing set temperature.

  In particular, when a filler such as cellulose nanofiber is blended in a thermoplastic resin, the processing set temperature is usually higher than the general processing set temperature. is there. Moreover, if the compounding quantity of a cellulose nanofiber increases, the temperature of the 1st mixture in a 1st temperature mixing process will rise rapidly by the heat_generation | fever by shearing.

  Therefore, in order to carry out the low temperature kneading step, it is necessary to lower the temperature of the first mixture. When kneading is performed, the temperature of the first mixture rises, so it may be difficult to lower the temperature while continuing kneading. Therefore, in the low temperature process, after kneading, the kneader can be stopped for a predetermined time, or the first mixture can be taken out from the kneader and allowed to cool to the second temperature. In addition, the first mixture can be actively cooled using a cooling device including a cooling mechanism such as a fan, a spot cooler, or a chiller. Processing time can be shortened by actively cooling.

  The second temperature is 1.06 of the flat region expression temperature (T3 ° C.) in the storage elastic modulus from the processing region expression temperature in the storage elastic modulus of the composite material in the vicinity of the melting point (Tm ° C.) of the thermoplastic resin used in this production method. It is the range to the temperature of twice (T3 ° C. × 1.06).

  As a result of studies by the inventors, it was found that when a dynamic viscoelasticity test (hereinafter referred to as DMA test) is performed on a composite material, the composite material exhibits a behavior different from that of the raw material thermoplastic resin. The raw thermoplastic resin flows with the storage elastic modulus (E ′) rapidly decreasing near the melting point (Tm). However, a composite material in which cellulose nanofibers are mixed is a flat region in which the storage elastic modulus (E ′) hardly decreases even when the melting point is exceeded by dispersing cellulose nanofibers of a predetermined amount or more, that is, rubber such as elastomer. It was found that an elastic region was developed.

  In the low temperature kneading step, the aggregated cellulose nanofibers are disentangled using a temperature from the vicinity of the melting point to a part of the flat region, and dispersed in the thermoplastic resin. In order to set the range of the second temperature, it is necessary to perform a DMA test in advance on a sample of the composite material having the blend. Specifically, it is as follows.

First, the 1st temperature mixing process of said 2-2-2-1 is implemented with a predetermined | prescribed mixture, and a 1st mixture is obtained. Next, the first mixture is subjected to a step similar to the low-temperature kneading step described later with the temperature near the melting point of the thermoplastic resin serving as the matrix (for example, the processing range of +10 to + 20 ° C. of the melting point). To obtain a composite material sample. In this sample, it is desirable that cellulose nanofibers are defibrated and dispersed, but even if defibration is insufficient, a clear change in characteristics can be confirmed near the inflection point and flat region expression temperature. A DMA test is performed on the composite material sample, and the relationship between the storage elastic modulus (E ′) and temperature (° C.) is graphed, and if a flat region is confirmed, the DMA test result is used. In addition, if a flat region cannot be confirmed in this composite material sample, a new composite material sample is obtained by the above method with the temperature near the inflection point as the second temperature, and a DMA test is performed and graphed in the same manner. . Such an operation is repeated until a flat region is clearly expressed.

  A method for setting the kneading temperature (second temperature) in the low-temperature kneading step will be described using the DMA test result of the composite material sample of Example 24 described later, which was produced using the kneading temperature thus obtained. FIG. 14 is a graph showing DMA measurement results (temperature dependence of storage elastic modulus E ′) of the sample of Example 24. In FIG. 14, the horizontal axis is temperature (° C.), the left vertical axis is the logarithmic value (log (E ′)) of the storage elastic modulus (E ′), and the log (E ′) graph is a solid line. Indicated. In FIG. 14, the vertical axis on the right is the differential value (d (log (E ′)) / dT) of the logarithmic value (log (E ′)) of the storage elastic modulus (E ′), and d (log (E The graph of ')) / dT is indicated by a broken line.

  The thermoplastic resin of Example 24 is a linear short chain branched polyethylene (LLDPE) having a melting point of 115 ° C., and the log (E ′) graph has an inflection point P1 at 121.5 ° C. The inflection point P1 clearly appears in the graph of d (log (E ′)) / dT. The inflection point appears at slightly different temperatures by changing the amount of cellulose nanofibers. Further, the inflection point P1 varies depending on the melting point of the thermoplastic resin.

  Next, the “processing region expression temperature T2” in the storage elastic modulus (E ′) is obtained from the log (E ′) graph of FIG. In the log (E ') graph, the slope of the graph is constant below 78 ° C, and the storage elastic modulus (E') suddenly decreases around 115 ° C, which is the melting point (Tm), and flow begins. If the thermoplastic resin alone, which does not contain cellulose nanofibers, begins to flow, the storage elastic modulus (E ') continues to decrease and flows, but in the composite material, the rapid decrease in the log (E') graph stops Then it becomes a flat region and does not flow. The first region W1 having a constant slope in the region below the melting point before the flow starts clearly appears in the graph of d (log (E ′)) / dT, and is found to be in the range of 62 ° C. to 78 ° C. . The temperature at the first intersection P2 between the extrapolated tangent L2 of the graph of log (E ′) in the first region W1 and the tangent L1 of the graph of log (E ′) at the inflection point P1 is the processing region expression temperature T2. (108 ° C.). The processing region expression temperature T2 is a lower limit temperature at which the kneading process in the low temperature kneading process is possible.

  Further, the “flat region (rubber elastic region) expression temperature T3” in the storage elastic modulus (E ′) is obtained from the log (E ′) graph of FIG. In FIG. 14, the slope is constant in the range of 128 ° C. to 142 ° C. The second region W2 having a constant slope starting from the point where the rapid decrease in the log (E ′) graph ends at a temperature exceeding the melting point clearly appears in the graph of d (log (E ′)) / dT. . The temperature of the second intersection point P3 between the extrapolated tangent line L3 of the graph of log (E ′) in the second region W2 and the tangent line L1 of the graph of log (E ′) at the inflection point P1 is the flat region expression temperature T3. It is.

  In the region (W1, W2) where the slope is constant, the region where the slope of the log (E ′) graph is constant exists in a temperature range of at least 10 ° C. or more. The flat region is the second region W2.

The temperature is higher than the temperature T1 of the inflection point P1 obtained in this way and the viscosity of the composite material sample becomes low and does not flow out, for example, 1 of the flat region expression temperature T3 (125 ° C. in FIG. 14). A temperature T4 (132.5 ° C. in FIG. 14) that is 0.06 times (T3 ° C. × 1.06) is set as the upper limit of the kneading temperature. It is considered that the aggregate of cellulose nanofibers can be defibrated with any thermoplastic resin as long as the temperature reaches T4 which is 1.06 times the flat region expression temperature T3 (T3 ° C. × 1.06).

  In the temperature range from the processing region expression temperature T2 to a temperature T4 that is 1.06 times the flat region expression temperature T3 (T3 ° C. × 1.06), the second mixture has moderate elasticity and moderate viscosity. Therefore, processing is possible and cellulose nanofibers can be defibrated. According to the study by the present inventors, the temperature range from T3 to T4 tends to become wider as the melting point becomes higher.

  The lower limit of the kneading temperature in the low temperature kneading step may be the inflection point temperature T1 or more at the inflection point P1. This is because the processing of the second mixture becomes easier. Note that the temperature T2 and the temperature T4 are slightly different by changing the blending amount of the cellulose nanofibers.

  According to the study by the present inventors, the low temperature kneading step with a kneading temperature in a range from a temperature slightly lower than the inflection point temperature T1 to a temperature T4 that is 1.06 times the flat region onset temperature T3 (T3 ° C. × 1.06). As a result, the cellulose nanofibers that have been agglomerated can be disentangled so as to be loosened and dispersed in the thermoplastic resin.

  The second temperature is a relatively low temperature that is not employed as the processing temperature of the thermoplastic resin, and in particular, is a low temperature range that has not been employed as the processing temperature of the second mixture.

  The first mixture whose temperature has been lowered to the second temperature can be placed, for example, in an oven set to the second temperature and maintained at a predetermined temperature within the second temperature range. The temperature of the first mixture taken out from the kneader is lowered, so that the processing quality is stabilized.

  Moreover, when using the pellet containing a commercially available cellulose nanofiber as a 1st mixture, a reheating process is needed between a 1st temperature mixing process and a low temperature process. The reheating step can be performed by heating to a temperature higher than the melting temperature of the thermoplastic resin.

2-2-2-3. Low temperature kneading step The low temperature kneading step kneads the first mixture at the second temperature.

  As a 1st mixture, what was obtained by the 1st temperature mixing process of said 2-2-2-1 can be used.

  In this step, for example, the roll interval d between the first roll 10 and the second roll 20 is, for example, 0.5 mm or less, more preferably 0 mm, as in FIG. The interval can be set to ˜0.5 mm, and the first mixture obtained in the first temperature mixing step can be charged into the open roll 2 for kneading.

  Since the first mixture extruded from between the narrow rolls in this manner has a temperature range in which the second temperature has an appropriate elasticity and an appropriate viscosity, it depends on the elasticity of the thermoplastic resin. The cellulose nanofibers can be greatly deformed by the restoring force, and the cellulose nanofibers can move greatly with the deformation of the thermoplastic resin at that time.

  The second temperature is the surface temperature of the first mixture in the low-temperature kneading step, not the set temperature of the processing apparatus. As explained for the first temperature, it is desirable to measure the surface temperature of the actual resin as much as possible for the second temperature, but if this is not possible, measure the surface temperature of the resin immediately after taking out the composite material from the processing device. It can be set as the 2nd temperature in process from the temperature.

In the case of the open roll 2, the surface temperature can be measured using a non-contact thermometer, and the arrangement of the non-contact thermometer 40 may be other than the position immediately after passing through the nip, preferably the first roll Above the roll 10. Immediately after passing through the nip, the temperature of the first mixture is an unstable temperature at which the temperature rapidly changes.

  If the surface temperature of the first mixture in the low-temperature kneading process cannot be measured, such as in a closed kneader or an extruder, the surface temperature of the composite material immediately after taking out from the apparatus after kneading is set. It can be measured and confirmed to be within the second temperature range.

  The low temperature kneading step can be, for example, 4 minutes to 20 minutes at the second temperature, and can be further 5 minutes to 12 minutes. By sufficiently taking the kneading time at the second temperature, the cellulose nanofibers can be defibrated more reliably.

  The processability of the first mixture is reduced due to the blending of cellulose nanofibers, and the temperature of the first mixture becomes higher than the set temperature of the apparatus due to shearing heat generated by kneading the cellulose nanofiber. Therefore, in order to maintain the surface temperature of the first mixture in the second temperature range suitable for the low temperature kneading step, if the roll is an open roll, the temperature of the first mixture is not increased by adjusting the temperature of the roll. The temperature must be adjusted so that it is actively cooled. The same applies to a closed kneader, an extruder or an injection molding machine, and the surface temperature of the first mixture is kept constant within the second temperature range by adjusting the processing set temperature of the apparatus so as to be actively cooled. Can be maintained for hours. For example, in the extruder, in the vicinity of supplying the material, the set temperature of the heating cylinder is set to a temperature higher than the general processing temperature, the other zones are set to a temperature lower than the second temperature, and the resin being processed The surface temperature can be adjusted to the second temperature.

  The composite material obtained by the low-temperature kneading step can be put into a mold and pressed, for example, or can be further processed into pellets using an extruder, for example, to form a known thermoplastic resin It can shape | mold into a desired shape using this processing method.

  The shearing force obtained in the low-temperature kneading process causes a high shearing force to act on the thermoplastic resin, and the cellulose nanofibers that have been aggregated are separated from each other so that they are pulled out one by one into the thermoplastic resin molecules, and defibrated. And dispersed in the thermoplastic resin. This is because the metal bonded to the cellulose nanofibers is ionized by the swelling of the fiber material and weakens the bonding force between the cellulose nanofibers. In particular, since the thermoplastic resin has elasticity and viscosity in the second temperature range, cellulose nanofibers can be defibrated and dispersed. And the composite material excellent in the dispersibility and dispersion stability of cellulose nanofiber (it is hard to re-aggregate cellulose nanofiber) can be obtained.

2-2-3. Kneading process using thermosetting resin A kneading process using a thermosetting resin as a synthetic resin will be described. Here, a two-component mixed resin using a main agent and a curing agent such as an epoxy resin, a phenol resin, and a urethane resin as a thermosetting resin will be described, but the present invention is not limited thereto.
In the kneading step, the swollen fiber material is mixed with the main component of the thermosetting resin, kneaded at a kneading temperature ranging from a temperature 20 ° C. lower than the softening point of the main agent to a temperature higher by 10 ° C. than the softening point, and then the curing agent is further added. Mixing may be included. If the temperature is in the vicinity of the softening point of the main agent, it is not completely liquid, and according to the test results, it is appropriate at a kneading temperature ranging from a temperature 20 ° C. lower than the softening point to a temperature 10 ° C. higher than the softening point. Can have elasticity and viscosity.
In the case of an epoxy resin, for example, a bisphenol A type that is solid at room temperature and has a softening point of 100 ° C. or lower can be used as the main agent. The softening point of the main agent can be determined by the ring and ball method. For the ring and ball method, for example, a softening point test method defined in JIS K 7234 can be used. In addition, as a curing agent for the epoxy resin, for example, an amine-based or amidoamine-based liquid can be used at room temperature. The fiber material mixed with the main component of the thermosetting resin can be a swollen fiber material.
In the case of a phenol resin, for example, a novolak resin can be used as the main agent, and hexamethylenetetramine or the like can be used as the curing agent. The softening point of the main agent can be determined by the ring and ball method.
If the main agent is solid at room temperature and has a softening point of 100 ° C. or lower, it is excellent in kneading workability, and in particular, it is easy to process using the restoring force due to the elasticity of the main agent by applying a shearing force during kneading.

  For the kneading step, for example, an open roll, a closed kneader, an extruder, or the like can be used. For example, it can carry out using the open roll 2 as shown in FIGS.

The basic procedure is the same as in the case of an elastomer, but here, in the case of an epoxy resin, a bisphenol A type main agent (solid at room temperature and a softening point of 64 ° C.) will be described as an example. First, the first roll 10 is muffled in FIG. 3 at a temperature of 60 to 70 ° C. and the second roll 20 is a temperature of 50 to 60 ° C. Next, as shown in FIG. 4, the swollen fiber material is gradually added to the main agent and mixed. Thereafter, a thinning process as shown in FIG. 5 can be performed, for example, with the roll interval d set to 0 mm to 0.5 mm. The surface speed ratio of the roll is the same as that of the elastomer. This is because, as in the thinning process using an elastomer, cellulose nanofibers are defibrated by utilizing appropriate elasticity and appropriate viscosity of the main agent.
The roll temperature is controlled in the vicinity of the softening point of the main agent and the roll 10 and the roll 20 have a temperature difference of about 10 ° C. because of the workability of the main agent. When such a main agent is used, it easily adheres to the roll, so when the two rolls 10 and 20 are at the same temperature, the two rolls 10 and 20 are simply separated and attached. Therefore, it is difficult to apply a shearing force to the main agent, and the cellulose nanofibers are not easily defibrated. Therefore, by providing such a temperature difference, the main agent can be wound around the second roll 20 on the low temperature side, and a desired shearing force can be applied to the main agent. As a result, cellulose nanofibers can be effectively used. Can be defibrated.
In this kneading step, the metal bonded to the cellulose nanofibers is ionized by the moisture of the swollen fiber material. Therefore, the shearing force of kneading is added in a state where the bonding force between the cellulose nanofibers is weakened by metal ions, and the spacing between the cellulose nanofibers is expanded by utilizing the restoring force due to the elasticity of the main agent in the thinning process. The cellulose nanofibers are uniformly defibrated and dispersed.
The step of mixing the curing agent is desirably performed after the dehydration step. This is to improve the quality of the processed product.
After kneading the main agent and cellulose nanofiber, a curing agent (for example, polyamidoamine) is further added and kneaded again in the same manner and conditions as in the case of the main agent, so that the curing agent can be mixed uniformly. it can. The mixing method of the curing agent is also performed in the same manner as the kneading method of the main agent, so that the defibrated state of the cellulose nanofibers in the main agent is not deteriorated and the uniform mixing and dispersion state is maintained. Thereafter, molding (press processing, compression molding, extrusion molding, etc.) is performed, and for example, it is left at room temperature for 1 day to cure, and then post-baked (80 ° C., 15 hours) to obtain a composite material.

2-3. Dehydration step The dehydration step (S18) is a step of dehydrating the composite material obtained in the kneading step (S16). In the method for producing a composite material using a thermosetting resin, as described above, a composite material is obtained by mixing a curing agent after a dehydration step (S18) after the kneading step of the main agent and cellulose nanofibers. It is preferable.

  In the dehydration step (S18), the composite material can be heated to evaporate water. For example, the composite material may be placed in an oven and heated, and the inside of the oven may be evacuated.

  Moreover, when the water in a fiber material is removed in the middle of a kneading | mixing process (S16), it is not necessary to provide a spin-drying | dehydration process (S18). For example, when the kneading step (S16) is performed with an open roll, the roll may be heated after thinning to remove water, and when it is a closed kneader, an apparatus having a dehydrating function is used. Also good.

  In the case of a composite material using an elastomer, it is further blended with known rubber chemicals such as a vulcanization accelerator, a vulcanizing agent, an anti-aging agent, a reinforcing agent, and a coupling agent, and vulcanized with a heating press or the like. May be formed into a desired shape. Moreover, in order to obtain the desired physical properties of the rubber product, a known reinforcing agent such as carbon black, silica, or carbon nanotube may be blended with the elastomer in the kneading step (S16).

2-4. Composite Material The composite material is characterized by not containing cellulose nanofiber aggregates having a maximum width of 50 μm or more. Cellulose nanofiber aggregates are scattered in a matrix while a plurality of cellulose nanofibers are gathered and aggregated in the form of particles. The maximum width of the cellulose nanofiber agglomerates is measured by observing the split cross-section of the composite material with a scanning electron microscope to observe the particulate agglomerates scattered in the matrix material.

  The composite material includes cellulose nanofibers to which a metal derived from a metal salt in a CNF dispersion is bonded. Since the composite material has high rigidity, the metal derived from the metal salt in the composite material exists close to each other and forms an ion cluster. It can be inferred that a fiber reinforced structure can be obtained by forming a three-dimensional pseudo network in the composite material of cellulose nanofibers that bind to the metal forming the ion cluster. This is because, in a polymer that does not react with a silane coupling agent, the rigidity of the composite material does not improve even when the composite material is manufactured in a state where the cellulose nanofibers are defibrated with a silane coupling agent that does not form an ion cluster.

  In the composite material, the cellulose nanofibers contained in the fiber material are separated into one by one against the hydrogen bonding between the cellulose nanofibers by a kneading process and dispersed in the composite material.

  The composite material can include cellulose nanofibers deflated from the fiber material and an elastomer or a synthetic resin. The fiber material in the composite material exists as cellulose nanofibers in a defibrated state in an elastomer or synthetic resin matrix. It is preferable that all of the cellulose nanofibers in the composite material are defibrated, but even if at least the tensile fracture surface is observed with an electron microscope, the cellulose nanofiber aggregates having a maximum width of 50 μm or more may not be included. preferable. This is because if such an agglomerate is included, not only the reinforcing effect as a fiber cannot be obtained but also a breakage starting point in a tensile test.

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

(A) Preparation of sample using elastomer (A-1) Preparation of samples of Examples 1 to 20 Mixing process: Cellulose nanofiber dispersion (Daiichi Kogyo Seiyaku Co., Ltd. 2% concentration TEMPO oxidized cellulose nanofiber) is water As a dispersion with 1% concentration of cellulose nanofibers (solvent is water), the metal salts of the types shown in Tables 1 to 5 are mixed into the dispersion by stirring with a propeller-type stirrer, and then CNF A dispersion was obtained.

In Tables 1 to 5,
“CNF”: TEMPO oxidized cellulose nanofibers (average fiber diameter of cellulose nanofibers is 3.3 nm, average aspect ratio is 225),
"Na methacrylate": Asada Chemical Co., Ltd. sodium methacrylate (metal content 19-21%, methacrylic acid content 75-80%),
"Zn methacrylate": Asada Chemical Co., Ltd. zinc methacrylate R-20S (metal content 25-27%, methacrylic acid content 60-64%),
"Zn acrylate": Asada Chemical Co., Ltd. zinc acrylate RSS (metal content 27% or more, acrylic acid content 56% or more),
“Acrylic acid Ca”: calcium acrylate (metal content: 18-22%, acrylic acid content: 60-75%) manufactured by Asada Chemical Industry Co., Ltd.
“CaCl ₂ ”: calcium chloride manufactured by Wako Pure Chemical Industries, Ltd. (special grade reagent, purity 95% or more)
Met.

  “Composition of fiber material” in Tables 1 to 5 is expressed as a ratio of each compounding amount when CNF in the swollen fiber material after the swelling process is 1.

  Drying step: The aqueous solvent was removed from the CNF dispersion to obtain a fiber material. More specifically, the CNF dispersion was poured into a vat and dried in an oven at 80 ° C. for 24 hours to remove the aqueous solvent to obtain a fiber material. The fiber materials used in Examples 1 to 20 could not confirm the deposition of metal salts on the surface by visual observation.

  Swelling step: The fiber material was swollen with water to obtain a swollen fiber material. More specifically, the fibrous material and a predetermined amount of water were placed in a glass sealed container, and kept in the sealed container at 70 ° C. for 1 hour to swell to obtain a swollen fiber material. The amount of water was shown by the ratio of the blending amount when CNF shown in Tables 1 to 5 was 1.

  Kneading step: The swollen fiber material was mixed with the elastomers shown in Tables 1 to 5 to obtain composite materials. More specifically, the swollen fiber material is gradually added to an elastomer kneaded using two rolls, kneaded to obtain an intermediate mixture, and thinned (roll temperature 10 ° C. to 30 ° C., roll interval 0. 3 mm, roll speed ratio 1.1) to obtain a composite material.

  “Composition of composite material” in Tables 1 to 5 represents the amount of cellulose nanofiber and metal salt contained in the swollen fiber material in the kneading step in parts by mass (phr). A sample of the composite material was made using 100 g of elastomer.

In Tables 1 to 5,
"HNBR": Zeonpol 2010 (Zetpol is a registered trademark) manufactured by Nippon Zeon Co., Ltd. (bound acrylonitrile content center value 11 (%), iodine value center value 7 or less (mg / 100 mg), Mooney viscosity (center value) 85),
“EPDM”: JSR EP24 manufactured by JSR (JSR is a registered trademark) (ENB content 4.5 (%), ethylene content 54 (%), Mooney viscosity 42 (ML (1 + 4) 100 ° C.), oil expansion amount 0 (PHR) )),
Met.

  Dehydration step: The composite material obtained in the kneading step was dehydrated. More specifically, it was dried in an oven at 40 ° C. to 90 ° C. for 12 hours, and water added in the swelling process was removed from the composite material.

Pressing process: After blending a dehydrating composite material with a crosslinking agent, an anti-aging agent and the like with two rolls, the composite material was placed in a mold and pressure-molded under vacuum to prepare a sample. In vacuum press molding, the mold is heated to 165 ° C., press-molded for 25 minutes while applying pressure (on the mold), and the mold is moved to the cooling press and pressed (on the mold). While cooling to room temperature, sheet-like samples of Examples 1 to 20 having a thickness of 1 mm were obtained.

(A-2) Preparation of Samples of Comparative Examples 1 to 15 Samples of Comparative Examples 1 to 15 were prepared according to the blending amounts in Tables 6 to 9.

  Samples of Comparative Examples 1 and 15 were obtained by press-molding pure rubber in the same manner as in the Examples. Comparative Example 1 was “HNBR” and Comparative Example 15 was “EPDM”.

  The samples of Comparative Examples 2 and 3 were samples to which no metal salt was added. Samples of Comparative Examples 2 and 3 were obtained in the same manner as in Example 1 except that the mixing step (Comparative Example 2 further includes a swelling step) and a resin material containing no metal salt was used.

  A sample of Comparative Example 4-7 was obtained in the same manner as in Example 1. Comparative Example 4 is a case where the amount of the metal salt is small, and Comparative Example 5-7 is a case where the amount of the metal salt is the same as that of the samples of Examples 3 to 5 and the water in the swelling process is changed. In Comparative Example 5, the swelling process was not performed.

  Samples of Comparative Examples 8 to 14 were obtained in the same manner as in Example 1 except that a silane coupling agent was used instead of the metal salt.

In Table 8 and Table 9,
Coupling agent 1 is “3-methacryloxypropyltrimethoxysilane”: KBM-503 manufactured by Shin-Etsu Chemical Co., Ltd.
Coupling agent 2 is “3-glycidoxypropyltrimethoxysilane”: KBM-403 manufactured by Shin-Etsu Chemical Co., Ltd.
Coupling agent 3 is “N-2- (aminoethyl) -3-aminopropyltrimethoxysilane”: KBM-603 manufactured by Shin-Etsu Chemical Co., Ltd.
Coupling agent 4 is “3-isocyanatopropyltriethoxysilane”: KBE-9007 manufactured by Shin-Etsu Chemical Co., Ltd.
Coupling agent 5 is “3-mercaptopropylmethyldimethoxysilane”: KBM-803 manufactured by Shin-Etsu Chemical Co., Ltd.
Met.

(B) Evaluation method (B-1) Hardness measurement About the sample of an Example and a comparative example, rubber hardness (Hs (JIS A)) was measured based on the JISK6253 test. The measurement results are shown in Tables 1 to 9.

(B-2) Tensile test About the sample of an Example and a comparative example, about the test piece punched in the dumbbell shape of JIS6, 23 ± 2 degreeC using the Shimadzu Corporation autograph AG-X tensile tester, A tensile test was performed based on JIS K6251 at a standard line distance of 20 mm and a tensile speed of 500 mm / min. Tensile strength (TS (MPa)), elongation at break (Eb (%)), and 50% modulus (σ50 (MPa)) ) Was measured. The measurement results are shown in Tables 1 to 9.

(B-3) Processability evaluation About the sample of an Example and a comparative example, the processability in the said kneading | mixing process at the time of the trial manufacture in HNBR100g or EPDM100g was evaluated. Evaluation results (○ is processing time within 30 minutes, roll winding property is good, Δ is processing time more than 30 minutes to 1 hour, roll winding property is good, × is processing time more than 1 hour, roll winding property is bad. Table 1 to Table 9 show the results.

(B-4) Evaluation of defibration and dispersibility The defibration and dispersibility of the composite material were evaluated for the samples of Examples and Comparative Examples. The tensile fracture surface of each sample was observed with a scanning electron microscope. Tables 1 to 9 show the evaluation results (◯: no aggregate having a maximum width of 50 μm or more, Δ: aggregate having a maximum width of 50-100 μm, and x: an aggregate having a width of 100 μm or more). . Moreover, the electron micrograph of Example 2,4,11 is shown in FIGS. 6-8 as a sample of "(circle)", the electron micrograph of the comparative example 3 is shown in FIG. 9 as a sample of "x", and "(triangle | delta)" The electron micrographs of Comparative Examples 6 and 14 are shown in FIGS.

(C) Evaluation results As shown in Tables 1 to 5, in the samples of Examples 1 to 20, the evaluation of “workability” and the evaluation of “definability and dispersibility” in the kneading process were “◯”. It was. As shown in FIGS. 6 to 8, in the sample with “◯” as the evaluation of “definability and dispersibility”, there is no aggregate of fiber material having a maximum width of 50 μm or more, and cellulose nanofibers are undissolved. I found out that it was fine.

  The samples of Examples 1 to 14 using HNBR shown in Tables 1 to 4 have larger values of “σ50” and “TS” than the pure rubber samples of Comparative Example 1 shown in Table 6, and cellulose nanofibers. It was found that there is a reinforcing effect by. In addition, the samples of Examples 1 to 5 and 8 to 14 using HNBR shown in Tables 1 to 4 have a larger “σ50” than the Comparative Examples 2 and 3 having the same CNF amount shown in Table 5, and metal salts. It was found that a reinforcing effect can be obtained by cellulose nanofibers defibrated by. Since the sample of Comparative Example 4 shown in Table 7 has too little Na methacrylate, it is difficult to defibrate cellulose nanofibers, and “processability” is “△” and “definability, dispersibility” is “×”. "Met. Although the samples of Comparative Examples 5 to 7 shown in Table 7 varied the amount of water in the swelling process, there was a problem in “workability” in particular.

  In the samples of Comparative Examples 8 to 14 shown in Table 8 and Table 9, various silane coupling agents were used instead of metal salts, but “workability” was obtained by blending a predetermined amount of the silane coupling agent. However, the “definability and dispersibility” did not reach the samples of Examples 1 to 16 using metal salts.

  The samples of Examples 17 to 20 using EPDM shown in Table 5 have larger values of “σ50” and “TS” than the sample of Comparative Example 15 shown in Table 9, and have a reinforcing effect by cellulose nanofibers. I understood.

(D) Preparation of sample using thermosetting resin The sample of Example 21 was prepared as follows. Two main epoxy resins (Bisphenol A, solid type jER1001 ("jER" is a registered trademark) manufactured by Mitsubishi Chemical Corporation), epoxy equivalent 450-500, softening point (ring and ball method) 64 ° C, specific gravity 1.19, molecular weight 900 Then, the swollen fiber material (CNF1: acrylic acid Ca0.1: water 4.0) prepared by blending the water of Example 15 with 4.0 was gradually added to the main agent. The kneading step was performed in the same manner as in Example 15 except that the temperature of the first roll 10 was set to 60 to 70 ° C., the temperature of the second roll 20 was set to 50 to 60 ° C. Thereafter, the mixture obtained in the kneading step is dried, pulverized, put again into the two rolls, added with a curing agent jER ST12 (polyamidoamine, “jER” is a registered trademark)) and further kneaded, and reduced pressure It was press-molded and cured at room temperature for 1 day, and then cured (post-baked) at 80 ° C. for 15 hours to obtain a sample of a composite material (epoxy resin 100 phr: CNF 20 phr).

  Further, as a sample of Example 22, a composite material sample was obtained in the same manner as in Example 21 with the blending amount of Ca acrylate being 0.5.

  A sample of Example 23 was prepared as follows. The main component (novolak resin, softening point (ring and ball method) 80 ° C. (estimated)) of phenol resin (Asahi Organic Materials Co., Ltd., AV Light (registered trademark)) was put into two rolls, and then the same as in Example 4 above. The swollen fiber material (CNF1: acrylic acid Na1: water 2.5) prepared in the above step was gradually added to the main agent, the roll temperature was set to 60 ° C., and the kneading step was performed in the same manner as in Example 4. It was. Thereafter, a curing agent was added to the mixture obtained in the kneading step, and the mixture was further kneaded. Further, the mixture was put into an extruder, kneaded, extruded, cured, and a composite material (phenol resin 100 phr: CNF 20 phr) sample was obtained.

(E) Evaluation method About the sample of the composite material of Examples 21 and 22, the tensile test was done by the method similar to said (B-2). The result of the tensile test is shown as a stress-strain curve in FIG.

  About the sample of the composite material of Example 23, an expansion coefficient was measured on the conditions of stress 100kPa using the thermal analysis rheology apparatus by SII Nanotechnology, Inc., and the temperature range of -10 degreeC-190 degreeC The change of the linear expansion coefficient in was shown in the graph of FIG.

(F) Evaluation As shown in FIG. 12, in the samples of Examples 21 and 22, the stress at the time of 2% strain increased 1.7 times as compared with the sample of the single epoxy. The composite material was reinforced by the fibrillated cellulose nanofibers.

  As shown in FIG. 13, in the sample of Example 23, the average linear expansion coefficient in the range of 30 ° C. to 120 ° C. was 1/5 or less of the average linear expansion coefficient of the sample of simple phenol. It was found that the thermal expansion deformation of the composite material was suppressed by the defibrated cellulose nanofiber.

(G) Preparation of sample using thermoplastic resin First temperature mixing step: The thermoplastic resin was charged into a desktop twin-screw kneader MC15 manufactured by Xplore Instruments and melted. Next, the swollen fiber material of Example 5 was put into a desktop biaxial kneader and kneaded at a first temperature to obtain a first mixture. The set temperature of the desktop biaxial kneader was 165 ° C., the actually measured resin temperature was 155 ° C., and the kneading time was 3 minutes. In addition, Table 10 shows the blending amounts (units are “wt%” and “phr”) of each Example.

  Low temperature process: The setting temperature of the tabletop kneader was lowered to the setting temperature (137 ° C.) of the low temperature kneading process.

  Low temperature kneading step: The first mixture was kneaded by desktop biaxial kneading at a set temperature of the table kneader of 137 ° C. (measured resin temperature 130 ° C.). The kneading time was 8 minutes.

  Extrusion step: After the set temperature of the table kneader was raised to 165 ° C. (measured resin temperature 155 ° C.), injection molding was performed with a table biaxial kneader to obtain a JIS K7161 1BA dumbbell test piece molded from a composite material. .

  In Comparative Example 16, a similar dumbbell test piece was injection-molded with a single thermoplastic resin (LLDPE), and in Comparative Example 17, a raw material cellulose nanofiber dispersion not containing Na acrylate was used instead of the swollen fiber material. A dumbbell test piece was produced using the powder in the same manner as in Example 24.

In each table,
"LLDPE": Prime Polymer Ultrazex 15150J, melting point 115 ° C,
“CNF”: TEMPO oxidized cellulose nanofibers manufactured by Daiichi Kogyo Seiyaku Co., Ltd. (average fiber diameter of cellulose nanofibers is 3.3 nm, average aspect ratio is 225),
-"Na methacrylate": It was sodium methacrylate (metal content 19-21%, methacrylic acid content 75-80%) by Asada Chemical Industry.

  Since the second temperature in Table 10 must be set within the range of the second temperature of each sample, the second temperature in the low-temperature kneading step is set to 130 ° C. (measured resin temperature) as described above. The second temperature measurement sample of the composite material was obtained. For the second temperature measurement sample of the formulation of each example, DMA measurement was performed in the same manner as in (H) below. From the measurement result, a graph of storage elastic modulus (E ′) and temperature is prepared, and in the case of the sample of Example 24, for example, the inflection point temperature T1 (121.5 ° C.) A temperature onset temperature T2 (108 ° C.) and a temperature T4 (132.5 ° C.) that is 1.06 times (T3 ° C. × 1.06) the flat region onset temperature T3 (125 ° C.) were determined. The method for obtaining the second temperature range of each sample was as described above, and the temperature dependence of the storage elastic modulus measured by DMA in Example 24 was as shown in FIG.

  As a result of the DMA measurement of the second temperature measurement samples of Examples 24-26, the range of the temperature T2 to the temperature T4 of all the samples included the second temperature used in the low-temperature kneading step.

(H) Evaluation method (H-1) Tensile test About samples of Examples 24 to 26 and Comparative Examples 16 and 17, a dumbbell test piece of JIS K7161 1BA was used, and an autograph AG-X tensile tester manufactured by Shimadzu Corporation was used. A tensile test was performed based on JIS K7161 at 23 ± 2 ° C., a standard line distance of 25 mm, and a tensile speed of 25 mm / min. Tensile strength (TS (MPa)), elongation at break (Eb (%))
) And yield point tensile stress (σy (MPa)). The measurement results are shown in Table 10.

(H-2) DMA measurement About the sample of Examples 24-26 and the comparative examples 16 and 17, about the test piece cut out in strip shape (30x5x2mm), the dynamic viscoelasticity tester DMS6100 made from SII company was used. Using a DMA test (dynamic viscoelasticity test) based on JIS K7244 at a distance between chucks of 10 mm, a measurement temperature of 20 to 200 ° C., a temperature rising pace of 1.5 ° C., a dynamic strain of ± 0.05%, and a frequency of 1 Hz. went. The temperature dependence of the storage elastic modulus of the sample of Example 24 is shown in FIG.

(I) Evaluation As compared with Comparative Examples 16 and 17, the samples of Examples 24 to 26 were higher in tensile strength (TS (MPa)), elongation at break (Eb (%)), and yield point tensile stress (σy). (MPa)) was large.

  DESCRIPTION OF SYMBOLS 2 ... Open roll, 10 ... 1st roll, 20 ... 2nd roll, 30 ... Elastomer, 34 ... Bank, 36 ... Intermediate mixture, 50 ... Composite material, 80 ... Swelling fiber material

Claims (13)

A mixing step of mixing a cellulose nanofiber, a metal salt, and an aqueous solvent to obtain a CNF dispersion;
A drying step of removing the aqueous solvent from the CNF dispersion obtained in the mixing step to obtain a fiber material;
Including
The manufacturing method of the fiber material whose mass ratio with respect to the said cellulose nanofiber of the said metal salt in the said CNF dispersion is 0.1 time-2 times. In claim 1,
The method for producing a fiber material, wherein the metal salt includes at least one of a monovalent metal salt and a divalent metal salt. In claim 1,
The metal salt is a monovalent metal salt;
The manufacturing method of the fiber material whose mass ratio with respect to the said cellulose nanofiber of the said monovalent metal salt in the said CNF dispersion is 0.2 times-2 times. In claim 1,
The metal salt is a divalent metal salt;
The manufacturing method of the fiber material whose mass ratio with respect to the said cellulose nanofiber of the said bivalent metal salt in the said CNF dispersion is 0.1 times-2 times. The said fiber material of any one of Claims 1-4 is a swelling fiber material containing a predetermined amount of moisture,
Further comprising a kneading step of mixing the swollen fiber material with an elastomer to obtain a composite material,
The kneading step is a method for producing a composite material including a step of thinning using an open roll having a roll interval of 0.1 mm to 0.5 mm and a roll temperature set to 0 ° C to 50 ° C. The said fiber material of any one of Claims 1-4 is a swelling fiber material containing a predetermined amount of moisture,
The manufacturing method of a composite material further including the kneading | mixing process which mixes the said swelling fiber material with a synthetic resin, and obtains a composite material. In claim 6,
The synthetic resin is a thermoplastic resin,
In the kneading step, the processing region expression temperature in the storage elastic modulus of the thermoplastic resin composition near the melting point (Tm ° C.) of the thermoplastic resin is 1.06 times the flat region expression temperature (T3 ° C.) in the storage elastic modulus. A method for producing a composite material, comprising a step of kneading at a kneading temperature in a range up to a temperature of (T3 ° C. × 1.06). In claim 6,
The synthetic resin is a thermosetting resin,
In the kneading step, the swelling fiber material is mixed with the main component of the thermosetting resin, and then kneaded at a kneading temperature ranging from a temperature 20 ° C. lower than the softening point of the main agent to a temperature 10 ° C. higher than the softening point. Then, the manufacturing method of a composite material including the process of further mixing a hardening | curing agent. In any one of Claims 5-8,
A method for producing a composite material, further comprising a dehydration step of dehydrating the composite material obtained in the kneading step.   A fiber material comprising cellulose nanofibers to which a metal derived from a metal salt is bound. In claim 10,
The metal salt is a fiber material containing at least one of a monovalent metal salt and a divalent metal salt.   A composite material comprising cellulose nanofibers defibrated from the fiber material of claim 10 or 11 and an elastomer or a synthetic resin. In claim 12,
The composite material does not include a cellulose nanofiber aggregate having a maximum width of 50 μm or more.