JP2018066098A - Cellulose nanofiber molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molded article having a cellulose fiber as a principal component, excellent strength, and low temperature dependency of strength thereof.SOLUTION: A cellulose nanofiber molded article is provided that has, as a principal component, a cellulose fiber including a cellulose nanofiber and has an elastic modulus (E) at 25°C of 3,000 MPa or more and 20,000 MPa or less, calculated by a nanoindentation method, and a ratio (E/E) of an elastic modulus (E) at 90°C calculated by a nanoindentation method to the elastic modulus (E) at 25°C of 0.5 or more. The cellulose fiber preferably includes pulp. The pulp is preferably beaten pulp. The content of the pulp in the cellulose fiber is preferably 0.1 mass% or more and 70 mass% or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cellulose nanofiber molded body.

  In recent years, nanotechnology that aims to refine materials to the nanometer level and obtain new physical properties that are different from conventional properties of materials has attracted attention. Cellulose nanofibers (hereinafter sometimes abbreviated as “CNF”) produced from pulp that is a cellulosic material by chemical treatment, pulverization treatment, etc. are excellent in strength, elasticity, thermal stability, and the like. The CNF compact is expected to be used in various applications as a biomass-derived high-strength material.

  Under such circumstances, as a composite material utilizing the strength of CNF, a fiber reinforced composite material obtained by mixing CNF with an organic polymer or the like as a matrix material has been proposed (see Japanese Patent Application Laid-Open No. 2005-60680). However, such a composite material has an inconvenience such as softening in a high temperature environment because an organic polymer or the like is used for a matrix that is a main component. Therefore, in this case, sufficient strength may not be exhibited in a high temperature environment.

JP 2005-60680 A

  The present invention has been made based on the circumstances as described above, and an object thereof is to provide a molded article having cellulose fiber as a main component, excellent strength, and low temperature dependence of the strength. That is.

The invention made in order to solve the above-mentioned problems is mainly composed of cellulose fibers including cellulose nanofibers, and has an elastic modulus (E ₂₅ ) at 25 ° C. calculated by the nanoindentation method of 3,000 MPa or more and 20,000 MPa or less. And the ratio of the elastic modulus (E ₉₀ ) at 90 ° C. calculated by the nanoindentation method to the elastic modulus (E ₂₅ ) at 25 ° C. (E ₉₀ / E ₂₅ ) is 0.5 or more. It is a molded body.

The CNF compacts, on a high modulus of elasticity (E ₂₅₎ at 25 ° C. which is calculated by the nanoindentation method, the elastic modulus in the elastic modulus and (E ₂₅₎ 90 ° C. calculated by the nano-indentation method ( E ₉₀ ) is close to 1 and has a low temperature dependence of strength. Therefore, the CNF compact can exhibit high strength in a wide temperature range.

  It is preferable that the said cellulose fiber further contains a pulp. By containing pulp together with CNF, production cost can be suppressed while maintaining sufficient strength. Further, by adding pulp, efficient dehydration becomes possible, so that productivity can be increased.

  The pulp is preferably beating pulp. By using beating pulp as the pulp, the number of hydrogen bonding points between the CNF and the pulp is increased, and the strength can be relatively increased while using the pulp.

  It is preferable that content of the pulp which occupies for the said cellulose fiber is 0.1 to 70 mass%. By setting the pulp content in the above range, the production cost can be more sufficiently suppressed and the productivity can be further sufficiently enhanced while maintaining sufficient strength.

  It is also preferable that the content of cellulose nanofibers in the cellulose fiber is 50% by mass or more. Since each CNF has high strength and high elasticity and is nano-sized, increasing the content of such CNF increases the number of hydrogen bonding points per unit volume, further increasing the strength. Can be increased.

The density of the CNF molded body is preferably 0.95 g / cm ³ or more and 1.5 g / cm ³ or less. Thus, the intensity | strength of the said CNF molded object can be raised more by being high density.

  Here, the “cellulose nanofiber” refers to a fine cellulose fiber obtained by defibrating a plant raw material such as pulp and having a fiber width of nanosize (1 nm to 1000 nm). “Main component” means a component having the highest content on a mass basis. Further, the elastic modulus at 25 ° C. or 90 ° C. calculated by the nanoindentation method means a value measured and calculated according to ISO14577, specifically, the value obtained by the method described in the examples. Say.

  ADVANTAGE OF THE INVENTION According to this invention, a molded object which has a cellulose fiber as a main component, has the outstanding intensity | strength, and has low temperature dependence of the intensity | strength can be provided.

FIG. 1 is a flowchart showing an exemplary method for producing a cellulose nanofiber molded article of the present invention. FIG. 2 is an explanatory view showing an apparatus and the like used in the preliminary dehydration step of the method of FIG. FIG. 3 is an explanatory view showing a pressurizing step in the method of FIG.

  Hereinafter, the CNF molded body according to an embodiment of the present invention will be described in detail with reference to the drawings as appropriate.

<CNF compact>
The said CNF molded object is a molded object which has as a main component the cellulose fiber containing CNF.

(CNF)
CNF can be usually obtained by fibrillating plant raw materials (fiber raw materials) by a known method. Although the raw material of this CNF will not be specifically limited if it is a plant raw material, A pulp is preferable.

Examples of pulp used as a raw material for CNF include hardwood kraft pulp (LKP) such as hardwood bleached kraft pulp (LBKP), hardwood unbleached kraft pulp (LUKP), softwood bleached kraft pulp (NBKP), and softwood unbleached kraft pulp (NUKP). ) Chemical pulp such as conifer kraft pulp (NKP);
Stone Grand Pulp (SGP), Pressurized Stone Grand Pulp (PGW), Refiner Grand Pulp (RGP), Chemi Grand Pulp (CGP), Thermo Grand Pulp (TGP), Grand Pulp (GP), Thermo Mechanical Pulp (TMP), Mechanical pulp such as chemi-thermomechanical pulp (CTMP) and bleached thermomechanical pulp (BTMP);
Waste paper pulp made from tea waste paper, craft envelope waste paper, magazine waste paper, newspaper waste paper, leaflet waste paper, office waste paper, corrugated waste paper, Kami white waste paper, Kent waste paper, imitation waste paper, lottery waste paper, waste paper waste paper, etc .;
Examples include deinked pulp (DIP) obtained by deinking waste paper pulp. These may be used singly or may be used in combination of plural kinds as long as the effects of the present invention are not impaired.

  Among these, as the pulp used as a raw material for CNF, chemical pulp is preferable, and LKP and NKP are more preferable from the viewpoint that a high-strength molded body can be obtained.

  The method for producing CNF is not particularly limited as long as the effects of the present invention are not impaired, and a known method can be used. For example, water-dispersed pulp may be subjected to defibration by mechanical treatment, or may be subjected to defibration after chemical treatment such as enzyme treatment, acid treatment, TEMPO catalytic oxidation, and phosphoric acid esterification. .

  Examples of the defibrating method by mechanical treatment include a grinder method in which pulp is ground between rotating grindstones, an opposing collision method using a high-pressure homogenizer, a grinding method using a ball mill, a roll mill, a cutter mill, and the like.

  In addition, you may attach | subject the pulp used as the raw material of CNF to pre-beating before defibration. Pre-beating (mechanical pretreatment) is not particularly limited, and a known method can be used. Specific examples of the method include a method using a refiner.

  Moreover, you may perform a chemical pre-process before the fiber opening to the pulp used as the raw material of CNF. Examples of the chemical pretreatment include hydrolysis treatment using an acid such as sulfuric acid, an enzyme, etc., and an oxidation treatment using an oxidizing agent such as ozone. Thus, CNF can be obtained efficiently by performing the defibrating treatment after the chemical pretreatment. In addition, as pretreatment, treatment using a TEMPO catalyst or the like, or phosphoric esterification may be performed.

  The water retention of CNF is, for example, 250% or more and 500% or less. Since CNF having a high water retention rate is inefficient in dehydration, there is a great advantage in using a pre-dehydration step described later that can effectively perform dehydration. The water retention degree (%) of CNF is JAPAN TAPPI No. 26 is measured.

  CNF preferably has a single peak in a pseudo particle size distribution curve measured by laser diffraction in a water dispersion state. As described above, the CNF having one peak has been sufficiently refined, can exhibit good physical properties as CNF, and can further increase the strength of the obtained molded body. In addition, as a particle size (mode) of CNF used as the said single peak, 5 micrometers or more and 25 micrometers or less are preferable, for example. When CNF is the said size, various characteristics peculiar to CNF can be exhibited more favorably. The “pseudo particle size distribution curve” means a curve indicating a volume-based particle size distribution measured using a particle size distribution measuring device (for example, a particle size distribution measuring device “LA-960S” manufactured by Horiba, Ltd.).

  The lower limit of the content of CNF in the cellulose fibers in the CNF molded body may be, for example, 30% by mass, preferably 50% by mass, 70% by mass, or 90% by mass. It may be 95% by mass or 99% by mass. By setting the content of CNF in the cellulose fiber to the above lower limit or more, the strength and the like can be increased by increasing the number of hydrogen bonding points per unit volume. On the other hand, the upper limit of the CNF content may be 99.9% by mass, 90% by mass, 70% by mass, or 50% by mass.

(pulp)
It is preferable that the cellulose fiber in the CNF molded body further includes pulp. While pulp has a lower production cost than CNF, it does not significantly reduce strength even when used in combination with CNF. Therefore, by including pulp together with CNF, production cost can be suppressed while maintaining sufficient strength. Further, by adding pulp, efficient dehydration becomes possible, so that productivity can be increased. In addition, the fiber diameter of a pulp is usually more than 1 micrometer, Preferably it is 10 micrometers or more.

  As said pulp, LKP and NKP are preferable. In addition, it is also preferable to use the pulp which is the raw material of CNF as the said fiber. For example, using a combination of CNF and LKP using LKP as raw materials, or using a combination of CNF and NKP using NKP as raw materials increases the affinity between the two, thereby increasing the dehydration. CNF outflow is suppressed at the time of pressurization, leading to shortening of the total dehydration time, and preferable for obtaining a molded body having a desired shape. Thus, by using the pulp used as the raw material of CNF, the affinity between CNF and pulp is further increased, and the outflow of CNF can be further suppressed. However, the raw material pulp of CNF and the pulp mixed with CNF may be different types.

  The pulp may be beaten pulp or unbeaten pulp. By using beaten pulp, CNF can be easily entangled and the outflow of CNF can be further suppressed, and the strength of the molded product obtained by increasing the hydrogen bonding point can be increased. On the other hand, the dewatering efficiency can be increased by using unbeaten pulp. The freeness of the beaten pulp can be 700 mL or less, for example, 650 mL or less, 600 mL or less, or 500 mL or less. The lower limit of the freeness of the beaten pulp is not particularly limited, but can be 200 mL, for example. On the other hand, the freeness of unbeaten pulp can be, for example, 550 mL or more, or 700 mL or more. Although the upper limit of the freeness of this unbeaten pulp is not specifically limited, For example, it can be set to 800 mL and can also be set to 750 mL.

  The lower limit of the pulp content in the cellulose fibers in the CNF molded body is preferably 0.1% by mass, more preferably 1% by mass, even 3% by mass or 5% by mass. 10 mass% may be sufficient and 20 mass% may be sufficient. By setting the pulp content to the above lower limit or more, the production cost can be suppressed and the productivity can be sufficiently enhanced. On the other hand, the upper limit of the pulp content is preferably 70% by mass, more preferably 50% by mass, still more preferably 30% by mass, and may be 10% by mass. By setting the pulp content to the upper limit or less, the strength and the like of the molded body can be further increased.

(Other ingredients)
The CNF molded body may contain other cellulose fibers other than CNF and pulp, and other components other than cellulose fibers. However, the lower limit of the content of the cellulose fiber in the solid content of the CNF compact is preferably 90% by mass, more preferably 99% by mass, and further preferably 99.9% by mass. Moreover, 90 mass% is preferable, as for the minimum of total content of CNF and a pulp in a cellulose fiber, 99 mass% is more preferable, and 99.9 mass% is further more preferable. Thus, since the said CNF molded object is formed only from CNF or only CNF and a pulp, intensity | strength can be raised more according to the strong hydrogen bond between cellulose fibers, etc. Moreover, since it is formed substantially only from CNF or only from CNF and pulp, the thermal stability is also high, and the load on the environment can be reduced.

(Physical properties)
The CNF compact has an elastic modulus (E ₂₅ ) at 25 ° C. calculated by the nanoindentation method of 3,000 MPa to 20,000 MPa, and the nanoindentation method for the elastic modulus (E ₂₅ ) at 25 ° C. The ratio of elastic modulus (E ₉₀ ) at 90 ° C. calculated by (E ₉₀ / E ₂₅ ) is 0.5 or more.

The lower limit of the elastic modulus (E ₂₅ ) is preferably 5,000 MPa, more preferably 7,000 MPa, and further preferably 9,000 MPa. On the other hand, this upper limit may be 15,000 MPa or 12,000 MPa. When the elastic modulus (E ₂₅ ) is less than the above lower limit, the elastic modulus is insufficient and the use as a high-strength material may be restricted. On the other hand, there are also production conditions that result in a higher density and homogeneous CNF molded body, and there is a possibility that an elastic modulus exceeding the above upper limit may be achieved, but this is preferable because problems such as a decrease in productivity may occur. Absent.

The lower limit of the ratio (E ₉₀ / E ₂₅ ) is preferably 0.6, more preferably 0.7, and still more preferably 0.8. When the ratio (E ₉₀ / E ₂₅ ) is equal to or higher than the lower limit, the temperature dependence of strength can be further reduced. On the other hand, the upper limit of this ratio (E ₉₀ / E ₂₅ ) may be 1, for example, or 0.9.

  The lower limit of the hardness of the CNF compact is preferably 80 MPa, more preferably 100 MPa, further preferably 150 MPa, still more preferably 200 MPa, still more preferably 300 MPa, and particularly preferably 400 MPa. On the other hand, this upper limit may be 1,000 MPa or 500 MPa. The hardness refers to the nanoindentation hardness at 25 ° C. measured and calculated according to ISO14577, and specifically refers to the value obtained by the method described in the examples.

The lower limit of the tensile elastic modulus (T ₂₃ ) at 23 ° C. of the CNF molded body is preferably 5,000 MPa, more preferably 7,000 MPa, further preferably 9,000 MPa, still more preferably 10,000 MPa, and 12,000 MPa. Is more preferable, and 15,000 MPa is particularly preferable. On the other hand, this upper limit may be 20,000 MPa or 18,000 MPa. When the tensile elastic modulus (T ₂₃ ) is less than the lower limit, the tensile elastic modulus is insufficient and may not be used as a high-strength material. On the other hand, there are production conditions that result in a denser and more uniform CNF molded body, and there is a possibility that a tensile elastic modulus exceeding the above upper limit may be achieved, but problems such as reduced productivity may occur. It is not preferable.

The lower limit of the ratio (T ₉₀ / T ₂₃ ) of the tensile elastic modulus (T ₉₀ ) at 90 ° C. to the tensile elastic modulus (T ₂₃ ) at 23 ° C. of the CNF compact is preferably 0.5, 0.6 Is preferred, 0.65 is more preferred, and 0.7 is even more preferred. When the ratio (T ₉₀ / T ₂₃ ) is equal to or higher than the lower limit, the temperature dependency of strength can be further reduced. On the other hand, the upper limit of this ratio (T ₉₀ / T ₂₃ ) may be 1, for example, 0.9, or 0.8.

The tensile elastic modulus (T ₂₃ ) and the tensile elastic modulus (T ₉₀ ) are based on JIS K7127: 1999, respectively, and the tensile test No. 2 type dumbbell in which the test piece is defined by JIS-K6251 in an environment at a temperature of 23 ° C. or 90 ° C. And measured at a test speed of 10 mm / min.

  The lower limit of the tensile strength of the CNF compact is preferably 70 MPa, more preferably 100 MPa, and even more preferably 110 MPa. On the other hand, the upper limit may be 250 MPa, 220 MPa, or 200 MPa depending on the application. If it is less than the above lower limit, the tensile strength may be insufficient and may not be used as a high-strength material. On the other hand, there are also production conditions that result in a denser and more uniform CNF molded body, and there is a possibility that a tensile strength exceeding the above upper limit may be achieved, but there are cases where problems such as reduced productivity may occur. Absent.

  The upper limit of tensile fracture strain in the CNF compact is preferably 10%, more preferably 5%, still more preferably 4%, and even more preferably 3%. On the other hand, the lower limit is preferably 0%, but may be 1%.

  The above-mentioned “tensile strength” and “tensile fracture strain” are in accordance with JIS K7127: 1999, and in a temperature 23 ° C. environment, the test piece is a tensile type 2 dumbbell defined by JIS-K6251 and the test speed is 10 mm. The value measured as / min.

As a minimum of the density of the said CNF compact, 0.95 g / cm ³ is preferred, 1 g / cm ³ is more preferred, and 1.15 g / cm ³ is still more preferred. On the other hand, the upper limit of the density is preferably 1.5 g / cm ³ , 1.4 g / cm ³ , or 1.3 g / cm ³ . When the density of the CNF compact is less than the above lower limit, the number of hydrogen bonding points may decrease, and sufficient strength may not be obtained. On the other hand, when the density exceeds the upper limit, problems such as a decrease in productivity may occur for the same reason as described above, which is not preferable.

  The CNF compact has such high strength and density and low temperature dependence of strength, and can be used as a material that replaces a metal compact, a resin compact, wood, or the like. The shape of the CNF compact is not particularly limited, and may be a rod shape, a plate shape, or any other shape.

<Method for producing CNF compact>
Although the manufacturing method of the said CNF molded object is not specifically limited, It can manufacture suitably with the following method.

  An example of the manufacturing method of the said CNF molded object is equipped with the process (pressurization process) which pressurizes the plate-shaped body containing CNF and water to thickness direction, heating. It is preferable that the manufacturing method of the said CNF molded object is equipped with the preliminary | backup dehydration process for obtaining the said plate-shaped object before this pressurization process. The preliminary dehydration step can employ a step of dehydrating a slurry containing CNF via a mesh member. That is, as shown in FIG. 1, it is preferable that the CNF slurry is made into a CNF plate-like body by a preliminary dehydration step, and this plate-like body is made a CNF molded body by a pressurizing step. In addition, the said manufacturing method may further be provided with other processes other than these processes. Hereinafter, the manufacturing method will be described in detail in the order of the steps.

(Equipment, raw materials, etc. in preliminary dehydration process)
FIG. 2 is a schematic explanatory view showing an example of the preliminary dehydration step. First, the apparatus and raw materials used in the preliminary dehydration step will be described with reference to FIG.

  2 has a rectangular parallelepiped inner surface shape. Moreover, the formwork 11 is a frame body without a bottom. The material of the mold 11 is not particularly limited, and examples thereof include metals, resins, and woods, but metals are preferable from the viewpoint of durability against high pressure.

  For example, the mold 11 is placed on a horizontal base (not shown) having a flat upper surface. The platform on which the mold 11 is placed is not particularly limited as long as it can withstand the pressure applied during the dehydration process, and a general metal, wooden, resin, or the like may be used. it can. In addition, at least the upper surface side of the table may be in a net shape, a mesh shape, a porous shape, or the like so as to efficiently drain water.

  Paper 13 is laid on the bottom of the mold 11 (that is, the upper surface of a table (not shown) in the mold 11). By laminating the paper 13 in this manner, the cushioning property is enhanced, the rapid pressure change is relieved, and the pressure can be gradually increased, so that the outflow of CNF during dehydration can be suppressed. The paper 13 is not particularly limited, such as Japanese paper, western paper, paperboard, and the like, and a paper having a known water permeability can be used. Further, the paper 13 may be a single sheet or a stack of two or more sheets.

  The lower limit of the thickness of the paper 13 is, for example, 0.05 mm, and preferably 0.1 mm. By setting the thickness of the paper 13 to be equal to or more than the above lower limit, more sufficient cushioning properties can be ensured, and the CNF outflow suppression function can be enhanced by alleviating the rapid pressure increase in the preliminary dehydration step. On the other hand, the upper limit of the thickness is 2 mm, for example. It should be noted that the thickness of the paper 13 refers to the thickness of the entire plurality of sheets in a stacked state when a plurality of sheets are stacked.

  Further, since the paper 13 is laid, moisture in the filled slurry 15 to be described later moves to the paper 13 through the mesh-like sheet 14, so that the dewatering efficiency can be improved. In addition, when the thickness of the paper 13 is equal to or more than the above upper limit, the amount of moisture transferred to the paper 13 returns to the formed body (plate-shaped body) after releasing the pressure, and thus the efficiency of dehydration is reduced. . In addition, it is preferable that the paper 13 has a low density from the viewpoints of both cushioning properties and dehydrating properties. Further, from the viewpoint of dewaterability, the paper 13 preferably has a low size. From this point of view, filter paper can be suitably used as the paper 13.

  A mesh sheet 14, which is an example of a mesh member, is laminated on the upper surface of the paper 13. The material of the mesh sheet 14 is not particularly limited, and may be metal, resin, other fibrous materials, or the like. That is, the mesh-like sheet 14 may be a wire mesh, a plastic wire, a filter cloth (woven cloth, non-woven cloth, etc.) and the like. The shape of the mesh of the mesh sheet 14 is not particularly limited, and may be any of plain weave, twill weave, tatami mat, twill weave, and the like.

  As a minimum of the mesh number of the mesh-like sheet | seat 14, 100 mesh is preferable and 200 mesh is more preferable. By setting it to the above lower limit or more, it is possible to suppress the outflow of CNF at the time of filling before pressurization. Moreover, since the speed | rate which pressurizes in steps will become slow if the number of eyes is large even if it is more than the said minimum, 200 mesh or more is more efficient. On the other hand, the upper limit of the number of meshes is preferably 500 mesh, more preferably 400 mesh. By setting it to the upper limit or less, a sufficient opening can be secured and the efficiency of dehydration can be improved. However, 400 mesh or less is more preferable because dehydration becomes slow even if the upper limit is not reached, and stepwise pressurization control becomes difficult.

  The lower limit of the wire diameter of the mesh sheet 14 is preferably 25 μm, and more preferably 30 μm. On the other hand, the upper limit of the wire diameter is preferably 100 μm, and more preferably 50 μm. By setting the wire diameter of the mesh-like sheet 14 to be equal to or more than the above lower limit, it is possible to secure an appropriately small opening size and further suppress the outflow of CNF in the preliminary dehydration step. On the other hand, by making the wire diameter of the mesh-like sheet 14 equal to or less than the above upper limit, it is possible to suppress the opening size from becoming too small and perform more efficient dehydration.

  Thus, the CNF slurry 15 is filled in the mold 11 in which the paper 13 and the mesh-like sheet 14 are sequentially laminated on the bottom. The slurry 15 contains CNF and water as a dispersion medium, and may further contain other components.

  The content of CNF in the slurry 15 subjected to the preliminary dehydration step is preferably more than 0.8% by mass, more preferably 1% by mass or more, and further preferably 1.5% by mass or more. By making CNF content in a slurry more than 0.8 mass%, the outflow of CNF in a pre-dehydration process can be suppressed more fully. In addition, the time for the preliminary dehydration process can be shortened. Further, when the CNF content is 0.8% by mass or less, the fluidity is high even without pressure, and CNF may flow out from the mesh sheet at the time of filling, but the content is more than 0.8% by mass. Thus, such inconvenience can be solved. On the other hand, the upper limit of the CNF content is, for example, 10% by mass, 5% by mass, 4% by mass, or 3% by mass. By setting the content of CNF in the slurry 15 to be equal to or less than the above upper limit, good fluidity can be ensured, and the filling property to the mold 11 can be enhanced. Moreover, by making the content of CNF not more than the above upper limit, unevenness in thickness and density can be suppressed, and a molded product with high uniformity can be obtained.

  A plate-like lid body 16 is laminated on the slurry 15 filled in the mold 11. The length and width of the lid 16 are substantially the same as the inner dimensions of the mold 11 or slightly smaller. The slurry 15 is substantially sealed in a space formed by a lid (not shown) on which the lid 16, the mold 11 and the mold 11 are placed. That is, it becomes the outer surface shape of the molded body (plate body) from which the upper surface of the table and the inner surface shapes of the mold 11 and the lid body 16 are obtained.

  The material of the lid body 16 is not particularly limited, and examples thereof include metals, resins, and woods, but metals are preferable from the viewpoint of durability against high pressure. Note that the material of the lid 16 may be the same as or different from the material of the mold 11.

(Preparation process)
The manufacturing method may include a preparation step for preparing the state of FIG. 2 before performing the preliminary dehydration step. This preparation process is a process of laminating the paper 13 and the mesh-like sheet 14 in order on the bottom of the mold 11 placed on the table so as to be in the state of FIG. . Further, a lid 16 is disposed on the slurry 15 after filling. As will be described later, when dehydration starts when the slurry 15 is filled, the lid 16 need not be placed on the slurry 15 at this timing.

  Moreover, the said manufacturing method may have the preparation process of the slurry containing CNF as a preparatory process, and may have the mixing process of CNF and the said fiber.

(Preliminary dehydration process)
Hereinafter, the procedure of the preliminary dehydration step will be described in detail. In this preliminary dewatering step, it is preferable to increase the pressure applied to the slurry 15 stepwise or continuously. In this dehydration step, the water in the slurry 15 flows out from the bottom of the mold 11 (the lower side in FIG. 2) via the mesh sheet 14 and the paper 13. In this case, since the initial pressure is very weak, the slurry 15 is kept at a high viscosity, and the outflow of CNF can be suppressed. On the other hand, as the dehydration proceeds, the concentration of the slurry 15 increases and the fluidity decreases, so that CNF hardly flows out even if the pressure is increased to some extent. Thus, by gradually increasing the pressure, dehydration can be performed efficiently while suppressing the outflow of CNF.

  The preliminary dehydration step preferably has an initial step of applying pressure at 2.5 kPa or less. When a pressure exceeding 2.5 kPa is applied initially, CNF tends to flow out through the mesh sheet 14. In addition, if the mesh-like sheet | seat 14 with a fine mesh is used, even if it applies the pressure over 2.5 kPa initially, the outflow of CNF can be suppressed, However, In this case, the whole dehydration efficiency may fall. The pressurization in this initial step may be substantially 0 kPa or atmospheric pressure. Moreover, the pressurization by only the dead weight of the cover body 16 may be sufficient. For example, when CNF 15 is charged (filled) into the mold 11 through the paper 13 and the mesh sheet 14, water flows out through the mesh sheet 14 (when dehydration is started). The lid 16 can be placed on the slurry 15 at the time when the outflow of water has been allowed to stand for a while.

  It is preferable to increase the pressure after dehydration has progressed to some extent by the pressurization in the initial step. The method for controlling the pressing force is not particularly limited, and may be controlled by a known press, or may be performed by placing a weight on the lid 16. Further, the pressurizing force may be increased according to the progress of dehydration (dehydration amount), or the relationship between the composition of the slurry 15 and the pressurizing force may be stored in a database, and the pressurizing force may be controlled by time. Good.

  In the preliminary dehydration step, the pressure is increased in this way, and as a final step, pressurization is preferably performed at 20 MPa or more, more preferably 30 MPa or more, and further preferably 40 MPa or more. By passing through this final process, a sufficiently dehydrated plate-like body can be obtained. In addition, as an upper limit of the applied pressure of this final process, it can be 200 Mpa, for example, and 100 Mpa may be sufficient.

  Unlike FIG. 2, a second mesh sheet is laminated on the upper surface of the slurry 15, a second paper is laminated on the upper surface of the second mesh sheet, and a lid is placed on the upper surface of the second paper. The body 16 may be placed. In this way, by laminating paper on the upper surface side with respect to the slurry 15 (the slurry 15 is sandwiched between a pair of papers), the cushioning property is further improved, and the outflow of CNF accompanying pressurization. Can be further suppressed. Further, paper may be laminated only on the upper surface side of the slurry 15. The second mesh sheet laminated on the upper side plays a role of preventing the slurry 15 and the second paper from coming into direct contact. That is, since the CNF plate and paper have high affinity, when the slurry and paper are pressed and dehydrated in direct contact, the paper sticks to the obtained CNF plate, and this paper It becomes difficult to peel off. Therefore, by laminating a mesh sheet between the slurry and paper, the paper or the like can be easily peeled off from the obtained CNF plate. Moreover, since the water | moisture content in a slurry transfers to paper through a mesh-like sheet | seat, dehydration efficiency can also be improved.

  In the preliminary dehydration step of FIG. 2, dehydration is performed only by pressurization without heating, but the preliminary dehydration step may be performed while heating.

(Pressure process)
In the pressurization step, the plate-like body containing CNF and water obtained in the preliminary dehydration step is pressurized in the thickness direction while being heated. The pressurizing step includes a first pressurizing step of pressurizing the plate-like body in a range that does not deform in a direction perpendicular to the thickness direction (horizontal direction in the case of pressurizing in the vertical direction), and the first pressurizing step. A second pressurizing step for compressing the plate-like body in the thickness direction with higher pressure is provided in this order. The pressurization process has at least two stages, and the first pressurization process may be made into a plurality of stages or the second pressurization process may be made into a plurality of stages so that the degree of pressurization increases stepwise. Is also possible. Moreover, you may perform a 3rd pressurization process. A preferred embodiment performed in two stages (a first pressurizing process in one stage and a second pressurizing process in one stage) will be described below.

  In the pressurizing step, as shown in FIG. 3, a plate-like body 27 containing CNF and water is disposed between a pair of upper and lower heating plates 21 and 22. Note that mesh sheets 25 and 26 are laminated on both surfaces of the plate-like body 27, and porous sheets 23 and 24 are laminated on the outer surfaces of the mesh sheets 25 and 26. That is, the first porous sheet 23, the first mesh-like sheet 25, the plate-like body 27, and the second mesh-like sheet 26 are disposed between the pair of horizontally arranged heating plates 21 and 22 in order from the lower side. And the 2nd porous sheet 24 is laminated | stacked. Further, the entire side surface of the plate-like body 27 is exposed.

  The heating plates 21 and 22 are arranged horizontally and parallel to each other. The heating plates 21 and 22 are heating plates (hot plates) provided in a general hot press machine (heating press machine). That is, this heating process can be performed using a conventionally known hot press. While the heating plates 21 and 22 are heated, a force acts in a direction in which the distance between the pair of heating plates 21 and 22 is narrowed, whereby the plate-like body 27 is heated and the thickness direction (vertical direction in FIG. 3) is reached. Pressure. The hot press machine can control the heating temperature and the pressurizing pressure. The temperature control and pressure control by the hot press machine may be automatic control or manual control. Moreover, this heat press machine is not particularly limited, such as a hydraulic heat press machine, a pneumatic heat press machine, and a vise heat press machine.

  The pair of porous sheets 23 and 24 are arranged in a state where the plate-like body 27 is sandwiched between the mesh-like sheets 25 and 26, respectively.

  The mesh sheets 25 and 26 may be of the same type and shape as the mesh sheet 14 used in the preliminary dehydration step. The mesh sheet used in the preliminary dehydration step may be used as it is, or may be replaced with another one. From the viewpoint of workability, it is preferable to use the mesh sheet used in the preliminary dehydration step as it is. .

  The porous sheets 23 and 24 are not particularly limited as long as they are porous sheets, and are inorganic porous sheets made of inorganic particles such as zeolite, fiber porous sheets, and sponge porous. Various porous sheets such as a sheet can be used. Among these, a fiber porous sheet is preferable from the viewpoint of cushioning properties and the like. Fibers constituting the fiber porous sheet include pulp, cotton fibers, silk fibers, hemp and other plant fibers; wool, animal hair and other animal fibers; nylon fibers, polyester fibers, acrylic fibers and other synthetic fibers; glass Examples of fibers include carbon fibers. Further, the fiber porous sheet may be a woven fabric, a nonwoven fabric or the like.

  Among these, as the porous sheets 23 and 24, the nonwoven fabric formed from a vegetable fiber is preferable from points, such as heat resistance, The nonwoven fabric formed from a pulp, specifically, paper is more preferable. When paper is used as the porous sheets 23 and 24, the same type and shape as the paper used in the preliminary dehydration step can be used. However, in order to proceed with the dehydration of the plate-like body 27, it is preferable to replace the paper used in the preliminary dehydration step and use new dried paper as the porous sheets 23 and 24.

  As a minimum of each thickness of porous sheet 23 and porous sheet 24, it is 0.05 mm, for example, and 0.1 mm is preferred. By setting the thickness of the porous sheets 23 and 24 to be equal to or more than the above lower limit, it is possible to secure a particularly sufficient water vapor discharge route during heating and perform effective drying. On the other hand, the upper limit of the thickness is 2 mm, for example. Note that the thickness of each of the porous sheet 23 and the porous sheet 24 is such that when a plurality of porous sheets are used as the porous sheet 23 or the porous sheet 24, a plurality of porous sheets in a stacked state are used. This refers to the thickness of the porous sheet 23 or the entire porous sheet 24.

  Further, by laminating the porous sheets 23 and 24, the moisture in the plate-like body 27 is transferred to the porous sheets 23 and 24, so that the dehydration efficiency can be increased. In addition, when the thickness of the porous sheets 23 and 24 is equal to or more than the above upper limit, the amount of moisture transferred to the porous sheets 23 and 24 returns to the plate-like body 27 after releasing the pressure, so that the efficiency of dehydration is increased. Will be reduced. In addition, it is preferable that the porous sheets 23 and 24 are low density also from any viewpoint of air permeability, cushioning property, and dehydrating property. From the viewpoint of dewaterability, the porous sheets 23 and 24 are preferably low in size. From such a viewpoint, filter paper can be suitably used as the porous sheets 23 and 24.

(First pressurization process)
The first pressurizing step is a step of applying pressure in a range in which the plate-like body 27 is not deformed in a direction perpendicular to the thickness direction (left and right direction in FIG. 3, usually, horizontal direction).

  As an upper limit of the moisture content of the plate-like body of the plate-like body 27 subjected to the first pressurizing step, 90% by mass is preferable, 80% by mass is more preferable, 70% by mass may be sufficient, and 60% by mass. It may be. By making the moisture content of the plate-like body 27 used in the first pressurizing step, that is, the plate-like body 27 before the pressurizing step equal to or less than the above upper limit, the spread in the surface direction of the plate-like body 27 during the pressurization is more sure It can be highly controlled. On the other hand, as a minimum of this moisture content, 40 mass% is preferable and 50 mass% is more preferable. When the water content of the plate-like body 27 subjected to the first pressurizing step is below the lower limit, the dehydration in the preliminary dehydration step is particularly sufficiently performed. The preliminary dehydration step may be performed while heating, but heating may be uneconomical due to the time and energy loss required for heat conduction of the mold. Therefore, it is preferable to dehydrate above the lower limit above which can be relatively easily dehydrated mechanically only by pressurization without heating.

  The lower limit of the applied pressure in the first pressurizing step is preferably 1 MPa, and more preferably 3 MPa. By setting the applied pressure in the first pressurizing step to be equal to or higher than the above lower limit, dehydration can be promoted while maintaining the smoothness and homogeneity of the plate-like body 27, and the deformation in the thickness direction accompanying CNF aggregation is also suppressed. it can. On the other hand, the applied pressure in the first pressurizing step is preferably less than 10 MPa, more preferably 5 MPa or less. By setting the applied pressure in the first pressurizing step to the upper limit or less, it is possible to suppress the spread in the surface direction of the plate-like body 27 during pressurization with higher certainty. Moreover, a certain amount of moisture can be left after the first pressurizing step by setting the pressure in the first pressurizing step to be equal to or lower than the upper limit. By performing the 2nd pressurization process which is a post process in such a state, effective compression arises in the 2nd pressurization process, and a higher-density molded object can be obtained. In other words, if the pressurizing force in the first pressurizing step is too high, the remaining moisture may be too small and sufficient compression may not occur in the second pressurizing step.

  As a minimum of processing temperature in the 1st pressurization process, 100 ° C is preferred and 110 ° C is more preferred. On the other hand, the upper limit of the treatment temperature is preferably 150 ° C, more preferably 140 ° C, and still more preferably 130 ° C. Moreover, as a minimum of the processing time in a 1st pressurization process, 10 minutes are preferable. On the other hand, the upper limit of this treatment time is preferably 30 minutes, more preferably 20 minutes. By performing the first pressurizing step at the above processing temperature and processing time, sufficient drying is performed to such an extent that the spread in the surface direction is unlikely to occur even when the applied pressure is increased in the second pressurizing step which is a subsequent step. Can do. Moreover, a certain amount of moisture can be left in the plate-like body 27 by using such a treatment temperature and treatment time. Due to the presence of the remaining water, hydrogen bonding between CNFs effectively occurs in the second pressurizing step, and the number of hydrogen bonding points per unit volume increases, resulting in a higher density of the CNF molded body. And strength can be increased.

(Second pressure process)
The second pressurizing step is a step of compressing the plate-like body 27 in the thickness direction with a pressure higher than that of the first pressurizing step. The spread in the surface direction of the plate-like body 27 in the second pressurizing step is sufficiently suppressed. Although a 1st pressurization process and a 2nd pressurization process can be performed continuously, it is preferable to provide a stepwise pressure difference with a 1st pressurization process and a 2nd pressurization process. By performing stepwise continuously while providing a pressure difference, for example, the second pressurizing step can be performed while maintaining the heated state, and the drying efficiency is high and the density can be increased. .

  The lower limit of the applied pressure in the second pressurizing step is preferably 10 MPa, and more preferably 12 MPa. By setting the applied pressure in the second pressurizing step to be equal to or higher than the above lower limit, the plate-shaped body 27 is sufficiently compressed in the thickness direction, and a CNF molded body having particularly excellent strength can be obtained. On the other hand, the upper limit of the pressing force in the second pressurizing step may be, for example, 50 MPa, 30 MPa, or 20 MPa. By setting the applied pressure in the second pressurizing step to be equal to or lower than the above upper limit, it is possible to more reliably suppress the spread in the surface direction of the plate-like body 27 during pressurization.

  The processing temperature in the second pressurizing step may be the same as in the first pressurizing step. In addition, the processing time in the second pressurizing step is not particularly limited, and may be terminated when the further compression does not proceed or the further drying does not proceed.

(Post-process)
A CNF molded object can be obtained by passing through the said pressurization process. In addition, you may provide additional processes, such as a cooling process and a humidity control process, after a pressurization process.

(Advantages of the manufacturing method)
In the manufacturing method, moisture in the plate-like body 27 is released from the side surface of the plate-like body 27 as water or water vapor during the pressurizing step. Further, since the plate-like body 27 is sandwiched between the mesh-like sheets 25 and 26 and the porous sheets 23 and 24, moisture is also released from the upper and lower surfaces of the plate-like body 27. According to the manufacturing method, in the first pressurizing step, the plate-like body 27 is pressurized so weakly that it is not deformed in the direction (plane direction) perpendicular to the thickness direction while being heated. Drying can be promoted while suppressing the deformation. Moreover, after a certain amount of drying is advanced in the first pressurizing step, the second pressurizing step is compressed in the thickness direction with a high pressure, so that the direction is perpendicular to the thickness direction (plane direction). Can be obtained, and a high-strength CNF molded body with a high density can be obtained.

  Further, by performing the pressurizing step in a state where the plate-like body 27 is sandwiched between the pair of porous sheets 23, 24, water vapor generated during heating is discharged through the porous sheets 23, 24, and is effectively dried. It can be performed. Furthermore, when pulp is contained in the plate-like body 27, the cohesiveness is reduced as compared with the case of CNF alone, so that the high strength molded body can be obtained by pressurizing in two stages. The benefits can be enjoyed more effectively.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

<Evaluation method>
The following various physical properties were measured according to the following evaluation methods.

(Pseudo particle size distribution curve)
Based on ISO-13320 (2009), the curve which shows a volume reference | standard particle size distribution was measured using the particle size distribution measuring apparatus (The particle size distribution measuring apparatus "LA-960S" of Horiba Seisakusho).

(Water retention (%))
The water retention (%) of the cellulose nanofiber is determined by JAPAN TAPPI No. 26: 2000.

(Elastic modulus (MPa))
The elastic modulus of the CNF compact was measured and calculated under the following conditions (25 ° C. or 90 ° C.) by a nanoindentation method based on ISO14577.

(Hardness (MPa))
The hardness of the CNF compact was measured and calculated under the following conditions (25 ° C.) by a nanoindentation method based on ISO14577.

[Nanoindentation method measurement conditions]
Apparatus: Hysitron Inc. Triboindenter
Indenter: Berkovich (triangular pyramid type)
Temperature: 25 ° C or 90 ° C
Indentation load: 100 mN (Example)
Indentation depth: 500 nm (comparative example)
Indentation speed: 20 mN / sec. (Example)
Indentation speed: 100 nm / sec. (Comparative example)

(Tensile modulus (MPa))
The tensile elastic modulus of the CNF compact was measured according to JIS K7127: 1999. The test piece was a tensile No. 2 type dumbbell defined by JIS-K6251. The test speed was 10 mm / min. Moreover, it measured in the environment of temperature 23 degreeC or 90 degreeC.

(Tensile strength (MPa))
The tensile strength of the CNF compact was measured according to JIS K7127: 1999. The test piece was a tensile No. 2 type dumbbell defined by JIS-K6251. The test speed was 10 mm / min. Moreover, it measured in the environment of temperature 23 degreeC.

(Tensile fracture strain (MPa))
The tensile fracture strain of the CNF compact was measured according to JIS K7127: 1999. The test piece was a tensile No. 2 type dumbbell defined by JIS-K6251. The test speed was 10 mm / min. Moreover, it measured in the environment of temperature 23 degreeC.

(density)
The density of the CNF compact was measured according to JIS-P-8118 (1998).

[Production example]
The raw pulp (LBKP) was subjected to a refiner treatment as a preliminary beating, followed by a defibration (miniaturization) treatment with a high-pressure homogenizer to obtain a CNF slurry (aqueous dispersion: concentration 2.2 mass%). The refiner treatment and the high-pressure homogenizer treatment were both circulated a plurality of times. CNF contained in the obtained slurry had one peak in the pseudo particle size distribution of particle size distribution measurement using laser diffraction (mode value 45 μm), and the water retention was 343%.

[Example 1]
(Preparation process)
A slurry having a solid content concentration of 2.3% by mass was prepared by mixing CNF and pulp (LBKP: unbeaten pulp) obtained from LBKP obtained in Production Example at a mass ratio of 80:20. The pulp used was unbeaten pulp (LBKP) having a concentration of 21.6% by mass and a freeness of 580 mL.

Paper 13 was laid on the bottom of a rectangular metal mold 11 shown in FIG. 2, and then a mesh sheet 14 was laid. Both the paper 13 and the mesh sheet 14 were used with the same size as the bottom surface of the mold 11. As the paper 13, a 0.28 mm thick filter paper was used. The mesh sheet used was made of SUS316 having a mesh size of 300 mesh and a wire diameter of 40 μm. Next, the obtained mixed slurry of CNF and pulp was filled into the mold 11, and a mesh-like sheet, paper, and a metal plate-like lid body 16 (bottom area 0.067 m ² , mass) 8.0 kg) was placed in this order. The mesh-like sheet and paper stacked on the slurry are the same as the mesh-like sheet and paper laid on the top.

(Preliminary dehydration process)
Due to the weight of the lid body 16 placed, the slurry 15 was pressurized at 1.2 kPa, and water began to flow out from the bottom (dehydration was started). In addition, this water was transparent and it confirmed visually that CNF did not flow out. Pressurization by the dead weight of the lid body 16 was set as an initial step.

  Thereafter, at the timing when the outflow of water was weakened, a pressure was applied on the lid body 16 to increase the pressure. Finally, the slurry 15 was pressurized at 50.0 MPa to obtain the final step. The total dehydration time from the initial process to the final process was 60 minutes. As a result, a plate-like body dehydrated to a moisture content of 54.2% was obtained. It was visually confirmed that CNF did not flow out from the initial process to the final process.

(Pressure process)
The obtained plate-like body and a general-purpose hot press were used and set in the state shown in FIG. As the porous sheets 23 and 24, new dry paper similar to the paper used in the preliminary dehydration step was used. As the mesh sheets 25 and 26, those used in the preliminary dehydration step were used as they were.

As the first pressurizing step, pressurization was performed at a pressure of 50 kgf / cm ² (4.9 MPa) and a temperature of 120 ° C. for 15 minutes. Next, as a second pressurizing step, pressurization was performed at a pressure of 150 kgf / cm ² (14.7 MPa) and a temperature of 120 ° C. Thereby, the plate-shaped body was compressed in the thickness direction, and the CNF molded body of Example 1 was obtained. The obtained CNF molded object did not spread in the surface direction and maintained a rectangular shape in plan view.

The elastic modulus (E ₂₅ ) at 25 ° C. calculated by the nanoindentation method of the obtained CNF compact was 9.0 × 10 ³ MPa, and the elastic modulus at 90 ° C. (E) calculated by the nanoindentation method (E ₉₀ ) was 7.6 × 10 ³ MPa, and the nanoindentation hardness was 4.6 × 10 ² MPa. The ratio (E ₉₀ / E ₂₅ ) was 0.84. Moreover, the density of the obtained CNF compact was 1.29 g / cm ³ .

[Example 2]
A CNF molded body was obtained by the same method as in Example 1, and a tensile test was performed. The obtained CNF compact has a tensile modulus (T ₂₃ ) at 23 ° C. of 16.3 × 10 ³ MPa, a tensile modulus at 90 ° C. (T ₉₀ ) of 12.0 × 10 ³ MPa, The strength was 1.1 × 10 ² MPa and the tensile fracture strain was 1.8%. The ratio _(T 90 _/ T ₂₃₎ was 0.74. Moreover, the density of the obtained CNF compact was 1.19 g / cm ³ .

[Example 3]
A CNF compact was obtained in the same manner as in Example 1 using only CNF using LBKP obtained in the production example as a raw material. The elastic modulus (E ₂₅ ) at 25 ° C. calculated by the nanoindentation method of the obtained CNF compact was 9.4 × 10 ³ MPa, and the elastic modulus at 90 ° C. (E ₉₀ ) was 8.4 × 10 ³ MPa, and the nanoindentation hardness was 3.7 × 10 ² MPa. The ratio _(E 90 _/ E ₂₅₎ was 0.90. The tensile modulus at 23 ° C. The resulting CNF moldings _{(T 23)} is 18.4 × ¹⁰ 3 MPa, tensile modulus at ₉₀ ℃ _(T 90) is at 12.6 × ¹⁰ 3 MPa The tensile strength was 1.5 × 10 ² MPa, and the tensile fracture strain was 1.9%. The ratio _(T 90 _/ T ₂₃₎ was 0.68. Moreover, the density of the obtained CNF compact was 1.33 g / cm ³ .

[Example 4]
A CNF compact was obtained in the same manner as in Example 1 except that CNF and pulp (LBKP: beaten pulp) obtained from Production Example LBKP as a raw material were mixed at a mass ratio of 30:70. The elastic modulus (E ₂₅ ) at 25 ° C. calculated by the nanoindentation method of the obtained CNF compact was 3.3 × 10 ³ MPa, and the elastic modulus at 90 ° C. (E) calculated by the nanoindentation method (E ₉₀ ) was 2.3 × 10 ³ MPa, and the nanoindentation hardness was 0.9 × 10 ² MPa. The ratio _(E 90 _/ E ₂₅₎ was 0.70. The tensile modulus at 23 ° C. The resulting CNF moldings _{(T 23)} is 9.6 × ¹⁰ 3 MPa, tensile modulus at ₉₀ ℃ _(T 90) is at 7.8 × ¹⁰ 3 MPa The tensile strength was 0.7 × 10 ² MPa, and the tensile fracture strain was 1.0%. The ratio (T ₉₀ / T ₂₃ ) was 0.81. Moreover, the density of the obtained CNF molded object was 1.07 g / cm < ³ >.

[Example 5]
CNF and pulp (LBKP: unbeaten pulp) obtained from LBKP obtained in Production Example are mixed at a mass ratio of 80:20, and the production conditions are changed from Example 1 to obtain molded bodies having different densities. It was. The elastic modulus (E ₂₅ ) at 25 ° C. calculated by the nanoindentation method of the obtained CNF compact was 4.2 × 10 ³ MPa, and the elastic modulus at 90 ° C. calculated by the nanoindentation method (E ₉₀ ) was 3.8 × 10 ³ MPa, and the nanoindentation hardness was 1.7 × 10 ² MPa. The ratio _(E 90 _/ E ₂₅₎ was 0.92. The tensile modulus at 23 ° C. The resulting CNF moldings _{(T 23)} is 14.5 × ¹⁰ 3 MPa, tensile modulus at ₉₀ ℃ _(T 90) is at 10.6 × ¹⁰ 3 MPa The tensile strength was 1.0 × 10 ² MPa and the tensile fracture strain was 1.1%. The ratio _(T 90 _/ T ₂₃₎ was 0.73. Moreover, the density of the obtained CNF compact was 0.95 g / cm ³ .

[Comparative Examples 1-3]
For the polypropylene (PP) film (Comparative Example 1), PP dumbbell specimen (Comparative Example 2) and aluminum foil (Comparative Example 3), the elastic modulus (E ₂₅ ) calculated by the nanoindentation method was also measured. . The measured values are shown in Table 1. "-" In the table indicates that no measurement is performed.

  As shown in Table 1, it can be seen that the CNF molded body of Example 1 has a high elastic modulus, and this temperature dependency is small. Furthermore, it can be seen that these CNF compacts have high hardness, tensile elastic modulus and tensile strength, and have a small tensile fracture strain.

  The CNF molded body of the present invention is excellent in strength, thermal stability, etc., and can be used as a material that replaces a metal molded body, a resin molded body, wood, or the like.

DESCRIPTION OF SYMBOLS 11 Form 13 Paper 14 Mesh-like sheet 15 Slurry 16 Lid 21, 22 Heating plate 23, 24 Porous sheet 25, 26 Mesh-like sheet 27 Plate-like body

[Nanoindentation method measurement conditions]
Apparatus: Hysitron Inc. Triboindenter
Indenter: Berkovich (triangular pyramid type)
Temperature: 25 ° C or 90 ° C
Indentation load: 100 mN (Examples and Reference Examples)
Indentation depth: 500 nm (comparative example)
Indentation speed: 20 mN / sec. (Examples and Reference Examples)
Indentation speed: 100 nm / sec. (Comparative example)

[Reference Example 1]
A CNF compact was obtained in the same manner as in Example 1 using only CNF using LBKP obtained in the production example as a raw material. The elastic modulus (E ₂₅ ) at 25 ° C. calculated by the nanoindentation method of the obtained CNF compact was 9.4 × 10 ³ MPa, and the elastic modulus at 90 ° C. (E ₉₀ ) was 8.4 × 10 ³ MPa, and the nanoindentation hardness was 3.7 × 10 ² MPa. The ratio _(E 90 _/ E ₂₅₎ was 0.90. The tensile modulus at 23 ° C. The resulting CNF moldings _{(T 23)} is 18.4 × ¹⁰ 3 MPa, tensile modulus at ₉₀ ℃ _(T 90) is at 12.6 × ¹⁰ 3 MPa The tensile strength was 1.5 × 10 ² MPa, and the tensile fracture strain was 1.9%. The ratio _(T 90 _/ T ₂₃₎ was 0.68. Moreover, the density of the obtained CNF compact was 1.33 g / cm ³ .

Claims (6)

Based on cellulose fibers including cellulose nanofibers,
The elastic modulus (E ₂₅ ) at 25 ° C. calculated by the nanoindentation method is 3,000 MPa or more and 20,000 MPa or less,
A cellulose nanofiber molded article having a ratio (E ₉₀ / E ₂₅ ) of an elastic modulus (E ₉₀ ) at 90 ° C. calculated by a nanoindentation method to an elastic modulus (E ₂₅ ) at 25 ° C. of 0.5 or more.   The cellulose nanofiber molded product according to claim 1, wherein the cellulose fiber further comprises pulp.   The cellulose nanofiber molded product according to claim 2, wherein the pulp is beaten pulp.   The cellulose nanofiber molded article according to claim 2 or 3, wherein a content of the pulp in the cellulose fibers is 0.1 mass% or more and 70 mass% or less.   The cellulose nanofiber molded article according to any one of claims 1 to 4, wherein a content of the cellulose nanofibers in the cellulose fibers is 50% by mass or more. The cellulose nanofiber molded article according to any one of claims 1 to 5, wherein the density is 0.95 g / cm ³ or more and 1.5 g / cm ³ or less.

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