Powdered composition for ceramic molding, and method for manufacturing electrical and electronic components or ceramics with fine shapes.

Abstract

The present invention provides a powdered composition for ceramic molding that can be prepared simply and with low energy, and that can be densely packed even at low pressure when manufacturing molded products. [Solution] The ceramic molding powder composition according to the embodiment is used to manufacture ceramic electrical and electronic components or ceramics with a fine shape, and contains cellulose nanofibers and inorganic particles with an average particle diameter of 0.005 μm or more and 2 μm or less, and has a moisture content of 20% by mass or less.

Description

Technical Field

[0001] The present invention relates to a powdery composition for ceramic molding, and also to a method for manufacturing an electric and electronic component or a ceramic having a fine shape using the powdery composition for ceramic molding.

Background Art

[0002] There is a press molding method for ceramic molding. In press molding, inorganic particles as ceramic raw materials are generally prepared and used as granules of several tens of μm in order to control fluidity, specific gravity, uniformity, etc. At that time, the granules are prepared by making the inorganic particles into a slurry with a solvent such as water together with a binder and a dispersant, and then spray-drying the slurry (see, for example, Patent Document 1 and Non-Patent Document 1).

[0003] A large amount of energy is required for spray drying by spray drying. For simple and low-energy production, it is required to manufacture a composition for ceramic molding without granulation by spray drying. However, when not granulated, since the fluidity of the composition is low, it is not easy to fill it at a low pressure and with high density in press molding.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

[0006] In view of the above, the embodiments of the present invention aim to provide a powdered composition for ceramic molding that can be filled to high density even at low pressure when manufacturing molded products. [Means for solving the problem]

[0007] The present invention includes embodiments shown below. [1] A powdered composition for ceramic molding used in the manufacture of electrical and electronic components containing ceramics, comprising cellulose nanofibers and inorganic particles with an average particle diameter of 0.005 μm or more and 2 μm or less, and having a moisture content of 20% by mass or less. [2] The powdered composition for ceramic molding according to [1], wherein the content of cellulose nanofibers is 0.001% by mass or more and 1.0% by mass or less. [3] The powdered composition for ceramic molding according to [1] or [2], wherein the inorganic particles mainly consist of at least one selected from the group consisting of metal oxides, silicon compounds, nitrides, and calcium compounds. A method for manufacturing an electrical and electronic component containing ceramic, comprising press molding a ceramic molding powder composition described in any one of items [1] to [3], and firing the resulting molded product.

[0008] [5] A powdered composition for ceramic molding used to manufacture ceramics having a fine shape, comprising cellulose nanofibers and inorganic particles with an average particle diameter of 0.005 μm or more and 2 μm or less, and having a moisture content of 20% by mass or less. [6] The powdered composition for ceramic molding according to [5], wherein the content of cellulose nanofibers is 0.001% by mass or more and 1.0% by mass or less. [7] The powdered composition for ceramic molding according to [5] or [6], wherein the inorganic particles mainly consist of at least one selected from the group consisting of metal oxides, silicon compounds, nitrides, and calcium compounds. A method for producing a ceramic having a fine shape, comprising press molding a powdered composition for ceramic molding described in any one of items [8] [5] to [7], and firing the resulting molded product. [Effects of the Invention]

[0009] The powdered composition for ceramic molding according to this embodiment has excellent fluidity and can be densely packed even at low pressure during the manufacture of molded products. Therefore, it is suitable for the manufacture of electrical and electronic components containing ceramics and ceramics with fine shapes. [Modes for carrying out the invention]

[0010] The powdered composition for ceramic molding according to the embodiment contains cellulose nanofibers and inorganic particles having an average particle size of 0.005 to 2 μm.

[0011] Cellulose nanofibers are fine fibrous cellulose obtained by refining cellulose fibers to the nanoscale (i.e., less than 1 μm). The number-average fiber width of cellulose nanofibers is preferably 500 nm or less, more preferably 1 to 200 nm, even more preferably 1 to 100 nm, even more preferably 2 to 30 nm, and even more preferably 2 to 10 nm.

[0012] The number-average fiber length of cellulose nanofibers is not particularly limited and may be, for example, 100 nm to 10 μm, 300 to 7000 nm, 500 to 5000 nm, 600 to 3000 nm, or 700 to 2000 nm.

[0013] The average aspect ratio (number-average fiber length / number-average fiber width) of cellulose nanofibers is not particularly limited and may be, for example, 10 to 1000, 20 to 500, or 100 to 300.

[0014] Cellulose nanofibers possess a type I cellulose crystal structure. This type I structure is the crystalline form of natural cellulose. Having a type I crystal structure allows cellulose nanofibers to be water-insoluble and maintain their fibrous form in water. The presence of a type I cellulose crystal structure can be identified by the presence of typical peaks in the diffraction profile obtained from wide-angle X-ray diffraction measurements, specifically around 2θ = 14° to 17° and around 2θ = 22° to 23°.

[0015] The cellulose nanofibers may be unmodified and lack anionic functional groups, but those with anionic functional groups are preferred. The presence of anionic functional groups allows for further refinement of the cellulose nanofibers, resulting in even higher density and strength of the molded product.

[0016] Examples of anionic functional groups include at least one selected from the group consisting of carboxyl groups, phosphate groups, sulfonic acid groups, nitrate groups, boric acid groups, and sulfate groups. These anionic functional groups may be directly bonded to glucose units, which are the constituent units of the cellulose molecule, or they may be bonded indirectly. In the case of indirect bonding, for example, an alkylene group having 1 to 4 carbon atoms may be present between the glucose unit and the anionic functional group. One or more anionic functional groups may be bonded to all glucose units constituting the cellulose molecule, or one or more may be bonded to some of the glucose units constituting the cellulose molecule.

[0017] The carboxyl group, as an anionic functional group, is a concept that includes not only the acidic form (-COOH) but also the salt form, i.e., a carboxylic acid base (-COOX, where X is a cation that forms a salt with a carboxylic acid), and both acidic and salt forms may coexist. Similarly, the phosphate group, sulfonic acid group, nitrate group, boric acid group, and sulfate group are also concepts that include not only the acidic form but also the salt form, and both acidic and salt forms may coexist.

[0018] The salts of the anionic functional groups are not particularly limited, and examples thereof include alkali metal salts such as sodium salts and potassium salts, alkaline earth metal salts such as magnesium salts and calcium salts, onium salts such as ammonium salts and phosphonium salts, and amine salts such as primary amines, secondary amines, and tertiary amines. The salt is preferably an alkali metal salt.

[0019] When the cellulose nanofiber has an anionic functional group, the amount of the anionic functional group (preferably a carboxy group) is not particularly limited, and for example, it is preferably 1.0 mmol / g or more per dry mass of the cellulose nanofiber. The amount of the anionic functional group is more preferably 1.0 to 3.0 mmol / g, still more preferably 1.2 to 2.8 mmol / g, and still more preferably 1.5 to 2.5 mmol / g.

[0020] The amount of the anionic functional group is measured as follows. For example, in the case of a carboxy group, after adjusting the pH of 60 mL of a cellulose nanofiber aqueous dispersion prepared to a concentration of 0.1 to 1% by mass to about 2.5 with a 0.1 mol / L hydrochloric acid aqueous solution, a 0.05 mol / L sodium hydroxide aqueous solution is dropped, and the electric conductivity is measured, and the measurement is continued until the pH reaches about 11. From the amount of sodium hydroxide (V) consumed in the neutralization stage of the weak acid where the change in electric conductivity is gentle, it can be determined according to the following formula. For a phosphate group, it can also be measured by the same electric conductivity measurement. Other anionic functional groups may be measured by known methods. In this specification, the "dry mass" refers to the mass after drying at 140°C until the mass change rate per minute becomes 0.05% or less. Amount of anionic functional group (mmol / g) = V (mL) × [0.05 / mass of cellulose nanofiber (g)]

[0021] In one embodiment, the cellulose nanofiber preferably has a carboxy group as an anionic functional group. Examples of the cellulose nanofiber containing a carboxy group include an oxidized cellulose nanofiber obtained by oxidizing the hydroxyl group of a glucose unit in a cellulose molecule, and a carboxymethylated cellulose nanofiber obtained by carboxymethylating the hydroxyl group of a glucose unit in a cellulose molecule.

[0022] Examples of the oxidized cellulose nanofiber include those in which the hydroxyl group at the C6 position of the glucose unit in the cellulose molecule is selectively oxidized and modified to a carboxy group. The oxidized cellulose nanofiber can be obtained by oxidizing natural cellulose such as wood pulp using a co-oxidizing agent in the presence of an N-oxyl compound and subjecting it to fibrillation (miniaturization) treatment.

[0023] As the N-oxyl compound, a compound having a nitroxyl radical generally used as an oxidation catalyst is used. For example, it is a piperidine nitroxyl radical, and particularly 2,2,6,6-tetramethylpiperidinooxyl radical (TEMPO) or 4-acetamido-TEMPO is preferable. The cellulose nanofiber oxidized and miniaturized with TEMPO is generally referred to as TEMPO-oxidized cellulose nanofiber (TOCN). Note that the oxidized cellulose nanofiber may have an aldehyde group or a ketone group together with the carboxy group.

[0024] When obtaining the cellulose nanofiber by fibrillation treatment, the fibrillation treatment may be carried out after introducing an anionic functional group or before the introduction. The fibrillation treatment can be carried out, for example, by treating an aqueous dispersion of cellulose fibers using a homomixer under high-speed rotation, a high-pressure homogenizer, an ultrasonic dispersion processor, a beater, a disk-type refiner, a conical-type refiner, a double-disk-type refiner, a grinder, etc., to obtain an aqueous dispersion of cellulose nanofibers.

[0025] Inorganic particles with an average particle size of 0.005 to 2 μm are used as the inorganic particles blended into the powdered composition for ceramic molding. By using inorganic particles with such a small average particle size, the molded product can be densely packed during manufacturing, and the generation of voids during sintering can be suppressed. The average particle size of the inorganic particles is more preferably 0.05 to 1.8 μm, even more preferably 0.1 to 1.5 μm, and even more preferably 0.3 to 1.2 μm.

[0026] Here, the average particle diameter of the inorganic particles is the average particle diameter of the inorganic particles in a state where cellulose nanofibers are not attached. The average particle diameter of the inorganic particles is the mass-based average diameter (D50) calculated from the particle size distribution, which is measured dry by laser diffraction and scattering using a particle size distribution analyzer (MT3000II, Microtrac-Bel).

[0027] Examples of inorganic particles include metal oxides, silicon compounds, nitrides, and calcium compounds, and it is preferable that at least one of these be the main component. Here, the main component means that it is more than 50% by mass relative to 100% by mass of the total amount of inorganic particles, preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, and may be 100% by mass.

[0028] Examples of the above metal oxides include alumina (Al2O3), titanium oxide (TiO2), copper oxide (CuO), iron oxide (Fe2O3), cobalt oxide (Co2O3), zinc oxide (ZnO), zirconia (ZrO2), cerium oxide (CeO2), magnesium oxide (MgO), calcium oxide (CaO), beryllium oxide (BeO), strontium oxide (SrO), barium oxide (BaO), lithium oxide (Li2O), and sodium oxide (Na2O). Examples include 0), potassium oxide (K2O), yttrium oxide (Y2O3), manganese oxide (Mn2O3), indium oxide (In2O3), tin oxide (SnO2), lanthanum oxide (La2O3), praseodymium oxide (Pr2O3), neodymium oxide (Nd2O3), samarium oxide (Sm2O3), europium oxide (Eu2O3), gadolinium oxide (Gd2O3), terbium oxide (Tb2O3), dysprosium oxide (Dy2O3), etc. These may be used individually or in combination of two or more.

[0029] Examples of the silicon compounds mentioned above include silicon carbide (SiC) and silicon nitride (Si3N4). These may be used individually or in combination of two or more.

[0030] Examples of the above nitrides include aluminum nitride (AlN), boron nitride (BN), titanium nitride (TiN), and zirconium nitride (ZrN). These may be used individually or in combination of two or more.

[0031] Examples of the calcium compounds mentioned above include lime, calcium phosphate, hydroxyapatite, tricalcium silicate, dicalcium silicate, aluminate, ferrite, and calcium sulfate. These may be used individually or in combination of two or more.

[0032] The powdered composition for ceramic molding according to the embodiment contains water along with the cellulose nanofibers and inorganic particles, and the moisture content is adjusted to 20% by mass or less. That is, the moisture content is 20% by mass or less relative to the total mass of the composition. By having such a low moisture content, the composition can be made into a powder form rather than a slurry form, and the aggregation of inorganic particles can be suppressed. In addition, the low moisture content can suppress the generation of voids during sintering, and the strength of the sintered body can be improved. The moisture content of the powdered composition for ceramic molding is preferably 3 to 20% by mass, more preferably 5 to 15% by mass, and even more preferably 7 to 12% by mass.

[0033] In the powdered composition for ceramic molding, the content of cellulose nanofibers is preferably 0.001 to 1.0% by mass relative to the total mass of the composition. Because the amount of cellulose nanofibers added is small, the generation of voids during sintering can be suppressed, and the strength of the sintered body can be improved. The content of cellulose nanofibers is more preferably 0.005 to 0.5% by mass, more preferably 0.01 to 0.3% by mass, even more preferably 0.02 to 0.2% by mass, and even more preferably 0.03 to 0.1% by mass.

[0034] In the ceramic molding powder composition, the content of inorganic particles is not particularly limited, but is preferably 70 to 98% by mass, more preferably 75 to 95% by mass, even more preferably 80 to 93% by mass, and even more preferably 82 to 90% by mass, based on the total mass of the composition.

[0035] The ceramic molding powder composition may consist only of the cellulose nanofibers, inorganic particles, and water mentioned above, but may also contain other components as long as their effectiveness is not impaired. Examples of such other components include binders, dispersants, and lubricants.

[0036] The powdered composition for ceramic molding according to this embodiment can be produced by spraying or sprinkling a cellulose nanofiber aqueous dispersion onto inorganic particles with an average particle size of 0.005 to 2 μm. That is, the cellulose nanofibers and inorganic particles are mixed by spraying or sprinkling the cellulose nanofiber aqueous dispersion onto the inorganic particles. In this case, the cellulose nanofiber aqueous dispersion may be sprayed or sprinkled while stirring the inorganic particles. The powdered composition for ceramic molding can be produced by such a simple process, and spray drying is unnecessary. Therefore, the powdered composition for ceramic molding can be produced simply and with low energy consumption.

[0037] Furthermore, since it is manufactured by spraying or sprinkling a cellulose nanofiber aqueous dispersion onto inorganic particles, the ceramic molding powder composition according to the embodiment is not granulated. In other words, the ceramic molding powder composition of the above embodiment is a non-granulated powder composition and is distinguished from a granulated one. Here, granulation refers to solidifying inorganic particles and forming them into particles larger than the inorganic particles themselves (granulation), and in ceramic press molding applications, they are generally formed into spherical particles by spray drying.

[0038] The amount of cellulose nanofiber aqueous dispersion used for the spraying or sprinkling described above is preferably set so that the moisture content of the ceramic molding powder composition falls within the above range, without requiring a drying step after spraying or sprinkling. That is, it is preferable to spray or sprinkle an amount of cellulose nanofiber aqueous dispersion onto the inorganic particles such that the moisture content of the resulting ceramic molding powder composition is 20% by mass or less. Since the powder form is obtained by lightly moistening with such a small amount of cellulose nanofiber aqueous dispersion, the drying step after the aqueous dispersion treatment can be omitted, further simplifying the process and reducing energy consumption.

[0039] Specifically, the amount of cellulose nanofiber aqueous dispersion to be processed is preferably 3 to 25 parts by mass, and more preferably 5 to 20 parts by mass, per 100 parts by mass of inorganic particles.

[0040] The concentration of the cellulose nanofiber aqueous dispersion (the concentration of cellulose nanofibers, which are the solid component) is not particularly limited and can be set in relation to the processing amount so that the cellulose nanofiber content in the ceramic molding powder composition is within a predetermined range. The concentration of the cellulose nanofiber aqueous dispersion may be, for example, 0.1 to 5% by mass, or 0.2 to 2% by mass.

[0041] In the resulting powdered composition for ceramic molding, cellulose nanofibers are adsorbed onto the surface of inorganic particles. This powdered composition exhibits excellent fluidity due to the effect of the cellulose nanofibers adsorbed onto the inorganic particles, allowing for high-density packing even at low pressure. As a result, high-density molded products can be formed even with low-pressure press molding. Furthermore, because only a small amount of cellulose nanofibers are added, it does not cause adverse effects such as void formation during sintering. These effects make it particularly suitable for the production of ceramic sintered bodies with complex shapes.

[0042] In the powdered composition for ceramic molding obtained by the simple processing described above, the inorganic particles maintain their original particle size at the individual particle level, but some particles are loosely aggregated by cellulose nanofibers and water adsorbed on their surface. Such loosely aggregated particles can be broken up by sieving. Therefore, sieving may be performed after spraying or sprinkling. However, it is not necessary to completely break down each individual inorganic particle, and some aggregated particles may be present.

[0043] The sieve used after spraying or sprinkling may, for example, have a nominal mesh size of 1.4 mm or less, 1 mm or less, or 500 μm or less, in accordance with JIS Z8801-1:2019.

[0044] Cellulose nanofibers are adsorbed onto the surface of the inorganic particles, and some inorganic particles are partially aggregated. Therefore, the average particle size of the powdered composition for ceramic molding does not necessarily have to be the same as the average particle size of the inorganic particles described above. The average particle size of the powdered composition for ceramic molding is not particularly limited, but is preferably 0.1 to 50 μm, more preferably 0.2 to 30 μm, even more preferably 0.5 to 20 μm, and may also be 3 to 15 μm.

[0045] The above-mentioned powdered ceramic molding composition can be used for press molding. Press molding can be carried out according to conventional methods, for example, by filling a mold such as a metal mold or rubber mold with the powdered ceramic molding composition and applying pressure. This yields a molded product made of the powdered ceramic molding composition.

[0046] The pressure used during press forming is not particularly limited and may be, for example, 5 to 200 MPa or 10 to 100 MPa. Furthermore, a molded product of a predetermined shape may be obtained by machining after press forming.

[0047] The resulting molded product is then fired according to a conventional method to obtain a ceramic sintered body. That is, in one embodiment, the method for manufacturing a ceramic sintered body involves press-molding the above-mentioned powdered composition for ceramic molding and firing the resulting molded product. Furthermore, the ceramic sintered body in one embodiment is obtained by firing the above-mentioned molded product. During firing, the inorganic particles fuse together and sinter, and the cellulose nanofibers and moisture are removed.

[0048] The temperature at which the molded product is fired is not particularly limited; for example, it may be 600-2000°C or 800-1800°C. Furthermore, the final product shape may be achieved by grinding and / or polishing after firing.

[0049] The powdered ceramic molding compositions according to the embodiments are suitable for electrical and electronic components and microfabrication because they can be filled to high density by low-pressure pressing as described above. Therefore, the composition according to the first embodiment is a powdered ceramic molding composition used for manufacturing electrical and electronic components containing ceramics. The composition according to the second embodiment is a powdered ceramic molding composition used for manufacturing ceramics with fine shapes, and is a microfabrication composition.

[0050] In the first embodiment, specific examples of electrical and electronic components include, but are not limited to, multilayer ceramic capacitors (MLCCs), low-temperature co-fired ceramics (LTCCs), piezoelectric devices, thermistors, zinc oxide elements, ceramic capacitors, and ceramic packages. The ceramic portion included in such electrical and electronic components can be formed using the ceramic molding powder composition according to the above embodiment.

[0051] For example, a multilayer ceramic capacitor (MLCC) is a capacitor having a structure in which multiple ceramic insulating layers and electrode layers are stacked alternately, and the above-mentioned ceramic molding powder composition is used as the material for forming the ceramic insulating layers.

[0052] Furthermore, for example, low-temperature co-fired ceramics (LTCC) are ceramic multilayer substrates in which low-resistance conductors such as Ag and Cu are integrally formed with a ceramic substrate, and the above-mentioned ceramic molding powder composition is used as the material for forming the ceramic substrate.

[0053] In the first embodiment, when manufacturing an electrical and electronic component containing ceramic, a ceramic molding powder composition is press-molded, and the resulting molded product is fired to obtain an electrical and electronic component containing ceramic, which is the sintered body.

[0054] For example, in the case of MLCCs, a ceramic molding powder composition may be press-molded to obtain a sheet-like molded product, electrodes and wiring may be printed on the molded product, multiple printed molded products may be stacked and pressed together, the resulting laminate may be fired, and then external electrodes may be formed, plating may be performed, etc., to manufacture the product.

[0055] In the second embodiment, the ceramic having a microstructure may (1) have its microstructure formed by press molding, or (2) have its microstructure formed by cutting or grinding after press molding and firing.

[0056] A ceramic with microstructure may have microstructures only in a part of it, or the entire ceramic may have microstructures. Furthermore, a ceramic with microstructure may be part of a product with other components (i.e., a composite in which ceramic is part), or it may be a ceramic alone that constitutes a product. Specific products include, but are not limited to, electrical and electronic components, medical device components, and automotive parts.

[0057] Examples of micro-shapes include protrusions, ridges, depressions, or grooves on the surface of the ceramic, holes penetrating the ceramic, and shapes of the ceramic itself such as tubular, sheet-like, or rod-like shapes, where the dimensions such as width, thickness, diameter, or thickness are, for example, 1 mm or less, more preferably 500 μm or less, and even more preferably 100 μm.

[0058] The powdered composition for ceramic molding according to the above embodiment has excellent fluidity and can be filled to high density by low-pressure pressing. Therefore, whether the fine shape is formed by press molding as in (1) above, or by cutting or grinding after firing as in (2) above, the fine shape can be formed with high precision, and the strength of the fine shape can be improved. In addition, the occurrence of defects such as material loss in the fine shape can be suppressed, and the yield can be improved.

[0059] In the second embodiment, when manufacturing a ceramic having a fine shape, a ceramic molding powder composition is press-molded to produce a molded body having a fine shape by the press-molding, and the resulting molded body is fired to obtain a ceramic having a fine shape as a sintered body. Alternatively, the ceramic molding powder composition is press-molded, the resulting molded body is fired, and the fine shape may be formed on the resulting sintered body by cutting and / or grinding.

[0060] In the first and second embodiments, the pressure during press molding and the temperature during firing of the molded product are not particularly limited, and the above-described pressure and temperature may be used. [Examples]

[0061] Examples are described in detail below, along with comparative examples. However, the present invention is not limited to these examples.

[0062] [Example 1] To 2 g of coniferous pulp, 150 mL of water, 0.25 g of sodium bromide, and 0.025 g of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) were added and thoroughly stirred to disperse the mixture. Then, a 13% by mass sodium hypochlorite aqueous solution (co-oxidant) was added so that the amount of sodium hypochlorite was 6 mmol / g per 1.0 g of the pulp, and the reaction was started. The temperature was maintained at 20°C during the reaction. As the reaction progressed, the pH decreased, so a 0.5 N sodium hydroxide aqueous solution was added dropwise to maintain the pH at 10-11, and the reaction was continued until no further change in pH was observed (reaction time: 120 minutes). After the reaction was complete, 0.1 N hydrochloric acid was added to adjust the pH to 2 or less, and then the mixture was purified by repeated filtration and washing with water. Pure water was added to adjust the solid content to 4%.

[0063] Subsequently, the pH of the slurry was adjusted to 10 with a 24% by mass sodium hydroxide aqueous solution. The slurry was then heated to 30°C, and sodium borohydride was added at a rate of 0.2 mmol / g relative to the cellulose fibers and the mixture was reduced by reacting for 2 hours. After the reaction, 0.1N hydrochloric acid was added to adjust the pH to 2 or less, and the slurry was purified by repeated filtration and washing with water.

[0064] Purified cellulose fibers were mixed with pure water to prepare a final concentration of 0.2% by mass of cellulose fibers. A 24% by mass sodium hydroxide aqueous solution was then added to adjust the pH to 7. This solution was then subjected twice at a pressure of 100 MPa using a high-pressure homogenizer (Sanwa Engineering, H11) to prepare a cellulose nanofiber aqueous dispersion.

[0065] Alumina (N-92, average particle size 0.5 μm, manufactured by Nishimura Ceramics Co., Ltd.) was subjected to a spray spray of the above-mentioned cellulose nanofiber aqueous dispersion at a concentration of 6% by mass relative to the mass of alumina, while the alumina was appropriately stirred. The mixture was then sieved through a 1.4 mm mesh to prepare a powdered composition for ceramic molding. The moisture content and average particle size of the obtained powdered composition for ceramic molding were measured.

[0066] A molded product was produced by placing a powdered ceramic molding composition into a mold and press-molding it at a pressure of 29.4 MPa. A ceramic sintered body was then produced by firing the resulting molded product at 1600°C for 16 hours. The density and compressive strength of the resulting ceramic sintered body were measured.

[0067] [Example 2] A powdered composition for ceramic molding was prepared in the same manner as in Example 1, with a concentration of 0.4% by mass of the cellulose nanofiber aqueous dispersion and an amount of the cellulose nanofiber aqueous dispersion sprayed onto alumina being 12% by mass relative to the mass of alumina. The moisture content and average particle size were measured, molded products and ceramic sintered bodies were produced, and the density and compressive strength were measured.

[0068] [Example 3] A powdered composition for ceramic molding was prepared in the same manner as in Example 1, with the concentration of the cellulose nanofiber aqueous dispersion set to 1.0% by mass, and the amount of the cellulose nanofiber aqueous dispersion sprayed onto alumina set to 25% by mass relative to the mass of alumina. The moisture content and average particle size were measured, molded products and ceramic sintered bodies were produced, and the density and compressive strength were measured.

[0069] [Examples 4, 5] In Example 4, titanium oxide (3YI-R, manufactured by Toray Industries, Inc., average particle size 0.5 μm) was used instead of alumina. In Example 5, silicon nitride (SN2400, manufactured by Kyocera Corporation, average particle size 1.0 μm) was used instead of alumina. Otherwise, the powdered composition for ceramic molding was prepared in the same manner as in Example 2, and the moisture content and average particle size were measured, molded products and ceramic sintered bodies were fabricated, and the density and compressive strength were measured.

[0070] [Example 6] The high-pressure homogenizer treatment conditions for preparing the cellulose nanofiber aqueous dispersion were changed to a single treatment at a pressure of 50 MPa, and otherwise the procedure was the same as in Example 2 to prepare a powdered composition for ceramic molding. The moisture content and average particle size were measured, molded products and ceramic sintered bodies were fabricated, and the density and compressive strength were measured.

[0071] [Example 7] A powdered composition for ceramic molding was prepared in the same manner as in Example 2, except that the amount of sodium hypochlorite added during the preparation of the cellulose nanofiber aqueous dispersion was 3 mmol / g. The moisture content and average particle size were measured, molded products and ceramic sintered bodies were produced, and the density and compressive strength were measured.

[0072] [Example 8] A powdered composition for ceramic molding was prepared in the same manner as in Example 2, except that WFo-1002 (mechanically defibrillated cellulose nanofiber, manufactured by Sugino Machine Co., Ltd.) was used as the aqueous dispersion of cellulose nanofibers and its concentration was set to 0.2% by mass. The moisture content and average particle size were measured, molded products and ceramic sintered bodies were produced, and the density and compressive strength were measured.

[0073] [Example 9] A powdered composition for ceramic molding was prepared in the same manner as in Example 1, with a concentration of 0.2% by mass of the cellulose nanofiber aqueous dispersion and an amount of the cellulose nanofiber aqueous dispersion sprayed onto alumina being 3% by mass relative to the mass of alumina. The moisture content and average particle size were measured, molded products and ceramic sintered bodies were produced, and the density and compressive strength were measured.

[0074] [Example 10] In Example 1, the pH was adjusted to 7 using a 25% by mass aqueous ammonia solution instead of a 24% by mass aqueous sodium hydroxide solution in the neutralization step before treatment with a high-pressure homogenizer, and the rest of the procedure was the same as in Example 1 to prepare a powdered composition for ceramic molding. The moisture content and average particle size were measured, molded products and ceramic sintered bodies were produced, and the density and compressive strength were measured.

[0075] [Example 11] In Example 1, a powdered composition for ceramic molding was prepared in the same manner as in Example 1, except that the high-pressure homogenizer treatment was performed 20 times at a pressure of 100 MPa. The moisture content and average particle size were measured, molded products and ceramic sintered bodies were produced, and the density and compressive strength were measured.

[0076] [Comparative Example 1] A powdered composition for ceramic molding was prepared in the same manner as in Example 2, with the amount of cellulose nanofiber aqueous dispersion sprayed onto alumina being 30% by mass relative to the mass of alumina. The moisture content and average particle size were measured, molded products and ceramic sintered bodies were produced, and the density and compressive strength were measured.

[0077] [Comparative Example 2] A powdered composition for ceramic molding was prepared in the same manner as in Example 2, except that a 0.2% by mass aqueous solution of sodium polycarboxylate was used instead of the cellulose nanofiber aqueous dispersion. The moisture content and average particle size were measured, and molded products were fabricated.

[0078] [Comparative Example 3] A powdered composition for ceramic molding was prepared in the same manner as in Example 2, except that a 0.4% by mass aqueous solution of polyvinyl alcohol was used instead of a cellulose nanofiber aqueous dispersion. The moisture content and average particle size were measured, molded products and ceramic sintered bodies were produced, and the density and compressive strength were measured.

[0079] The measurement methods are as follows, and the results are shown in Tables 1 and 2 below. In Tables 1 and 2, "CNF" refers to cellulose nanofiber.

[0080] [Measurement of number-average fiber width, number-average fiber length, and average aspect ratio] The number-average fiber width and number-average fiber length of cellulose nanofibers were observed using an atomic force microscope (AFM, Hitachi High-Tech Corporation). Specifically, after casting each cellulose nanofiber aqueous dispersion onto a mica substrate, 10 AFM images were taken. From these, 25 cellulose nanofibers were selected, and their fiber width and fiber length were measured. The arithmetic mean of the obtained fiber width and fiber length data was calculated to determine the number-average fiber width [nm] and number-average fiber length [nm]. Furthermore, the average aspect ratio was calculated according to the following formula. Average aspect ratio = Number-average fiber length [nm] / Number-average fiber width [nm]

[0081] [Measurement of carboxyl group content] 60 mL of a cellulose nanofiber aqueous dispersion prepared to a concentration of 0.1% by mass was prepared, and its pH was adjusted to approximately 2.5 with a 0.1 mol / L hydrochloric acid aqueous solution. Then, a 0.05 mol / L sodium hydroxide aqueous solution was added dropwise, and the electrical conductivity was measured. The measurement was continued until the pH reached approximately 11. The amount of sodium hydroxide V [mL] consumed during the neutralization stage of the weak acid, where the change in electrical conductivity was gradual, was used to calculate the amount of carboxyl groups according to the following formula. Carboxylate group content (mmol / g) = V (mL) × [0.05 / cellulose nanofiber mass (g)]

[0082] [Measuring moisture content] The moisture content of the powdered composition for ceramic molding was measured using an infrared heating moisture meter (A&D MX-50, 120°C, 60 minutes).

[0083] [Measurement of average particle size of powdered composition] The average particle size of the powdered composition for ceramic molding was measured dry using the laser diffraction / scattering method with a particle size distribution analyzer (MT3000II, Microtrac-Bel). The average particle size was defined as the mass-based average diameter (D50) calculated from the particle size distribution.

[0084] [Density measurement] The bulk density of the ceramic sintered body was measured in accordance with JIS R 1634:1998.

[0085] [Measurement of compressive strength] The compressive strength of the ceramic sintered body was measured in accordance with JIS R 1608:2003.

[0086] [Table 1]

[0087] [Table 2]

[0088] As shown in Table 1, the ceramic molding powder compositions according to Examples 1 to 11 were densely packed even when press molding was performed at low pressure, resulting in ceramic sintered bodies with high density and high strength. Therefore, they were suitable for electrical and electronic components and microfabrication.

[0089] In contrast, in Comparative Example 1, where the powdered composition for ceramic molding had a high moisture content, the moisture caused voids to form in the ceramic sintered body, resulting in a low density and low compressive strength.

[0090] Furthermore, in Comparative Example 2, which used sodium polycarboxylate instead of cellulose nanofibers, the low fluidity of the powdered composition for ceramic molding prevented high-density filling during low-pressure press molding. As a result, cracks occurred during compression by press molding, making it impossible to perform firing and subsequent evaluation. In Comparative Example 3, which used polyvinyl alcohol instead of cellulose nanofibers, a high-density ceramic sintered body was obtained, but its compressive strength was lower than that of the examples.

[0091] Furthermore, the various numerical ranges described in the specification can be any combination of their upper and lower limits, and all such combinations are described herein as preferred numerical ranges. Also, the description of a numerical range as "X~Y" means X or greater and Y or less.

[0092] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their omissions, substitutions, and modifications are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

Claims

1. A ceramic molding powder composition used for manufacturing electrical and electronic components containing ceramics, A powdered composition for ceramic molding, comprising cellulose nanofibers and inorganic particles with an average particle diameter of 0.005 μm or more and 2 μm or less, and having a moisture content of 20% by mass or less.

2. The powdered composition for ceramic molding according to claim 1, wherein the content of the cellulose nanofibers is 0.01% by mass or more and 1.0% by mass or less.

3. The powdered composition for ceramic molding according to claim 1, wherein the inorganic particles mainly consist of at least one selected from the group consisting of metal oxides, silicon compounds, nitrides, and calcium compounds.

4. A method for manufacturing an electrical and electronic component containing ceramic, comprising press-molding a ceramic molding powder composition according to any one of claims 1 to 3, and firing the resulting molded product.

5. A powdered composition for ceramic molding used to manufacture ceramics with fine shapes, A powdered composition for ceramic molding, comprising cellulose nanofibers and inorganic particles with an average particle diameter of 0.005 μm or more and 2 μm or less, and having a moisture content of 20% by mass or less.

6. The powdered composition for ceramic molding according to claim 5, wherein the content of the cellulose nanofibers is 0.01% by mass or more and 1.0% by mass or less.

7. The powdered composition for ceramic molding according to claim 5, wherein the inorganic particles mainly consist of at least one selected from the group consisting of metal oxides, silicon compounds, nitrides, and calcium compounds.

8. A method for producing a ceramic having a fine shape, comprising press-molding a powdered composition for ceramic molding according to any one of claims 5 to 7, and firing the resulting molded product.

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