JP2003089581A - Granule for compacting ceramics, compact, sintered compact, electronic parts obtained by using these, and method for producing granule for compacting ceramics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide granules for compacting satisfactory ceramics compact and sintered compact which have high deflective strengths, and have reduced chipping, cracks and breaking, to provide a ceramic compact and a sintered compact obtained by the granules, and to provide a method for producing the granules for compacting ceramics. SOLUTION: The granules for compacting the ceramics consist of 100 pts. mass ceramics raw material powder, 0.4 to 1.4 pts.mass polyvinyl alcohol having a mean polymerization degree of 500 to 1,700 and a mean saponification degree of >=88 mol%, and 0.1 to 1.4 pts.mass water soluble resol type phenol resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic molding granule, a ceramic molding, a ceramic sintered body, an electronic component using the ceramic sintered body, and a method for producing the ceramic molding granule. More specifically, it is possible to provide a high-strength ceramic compact that can be used in the manufacture of a wide range of electronic components and a ceramic sintered body that is excellent in appearance with few defects such as chips, cracks, and breaks, and is of excellent quality. The present invention relates to a molding granule, a ceramic molding, an electronic component using the ceramic sintered body, and a method for manufacturing the ceramic molding granule. Unless otherwise specified, in the present specification, "ceramics molding granules" are simply referred to as "granules", "ceramics moldings" are simply referred to as "molded bodies", and "ceramics sintered bodies" are simply referred to as "fired". Sometimes referred to as "union".

[0002]

Ceramics are widely used in various electronic components. Such ceramics are generally obtained by molding ceramic molding granules composed of ceramic raw material powder and a binder into various shapes according to the purpose as shown in FIGS. 1 and 2, and firing the molded body thus molded. It is obtained by doing. Figure 1 (a)
It is a schematic diagram of a cylindrical core, FIG.1 (b) is a drum type core which cut | disconnected the center part of a cylindrical core by cutting etc., FIG.1 (c) is another typical drum type core. It shows a different shape. 2A is a schematic diagram of a plate-shaped core, and FIG. 2B is a schematic diagram of a box-shaped core manufactured by a dry pressure molding method. The arrows in the figure show the locations where appearance defects are likely to occur in these sintered bodies, and details thereof will be described later. The ceramics sintered body obtained in this way is used for notebook computers, PD
As an electronic component for an electronic device such as an information terminal such as A, a mobile phone, a mobile phone such as PHS, or a peripheral device of these, or for a relatively large home electric appliance such as a television or a stereo. Although it is used as various electronic parts, the ceramics sintered bodies used for these parts tend to be smaller, thinner and lighter. Therefore, there is a demand for a ceramic sintered body that is small or thin and has high strength, which is used as these electronic components.

Conventionally, various methods have been adopted as a method for producing a ceramic molded body from ceramic molding granules, but among them, a dry pressure molding method is generally widely used. For example, an aqueous slurry is prepared from a ceramic raw material powder, a binder and water and spray-dried with a spray dryer to produce granules for ceramics, or a ceramic raw material powder and a binder solution are stirred and mixed, followed by drying and oscillating. A ceramic molded body is manufactured by press-molding granules for ceramic molding which are produced by repeating extrusion granulation. The shaped body produced in this manner is processed as needed, degreased, fired at a predetermined temperature, and optionally subjected to secondary processing to obtain a ceramic sintered body as a final product. In addition, the oscillating extrusion is, for example, a process of crushing particles granulated to a particle diameter of about several mm on a net and dropping the fine particles in a step of several steps in which the stitches are sequentially fined. A method of obtaining particles having a predetermined particle size or less.

Polyvinyl alcohol (P) is used as a binder to be added when producing granules for molding ceramics.
VA), polyacrylic resin, cellulose resin and the like are generally used, and the binder is usually added in an amount of 1 to 10 parts by mass with respect to 100 parts by mass of the raw material powder. PVA
In the ceramic molded body obtained by molding the granules for ceramic molding which are spray-granulated using the binder represented by, the bending strength by ordinary three-point bending is 1.0 to
It is about 2.0 MPa. On the other hand, due to the recent demand for miniaturization of electronic parts, when molding a ceramic molded body into a core mold (FIGS. 1A to 1C), the diameter of the core is set to 2 mm or less, or the ceramic molded body is formed into a plate shape. When molding (FIGS. 2A and 2B), the thickness may be about 1 mm.

When the ceramic compact is made smaller and thinner as described above, the bending strength of the ceramic compact is 1.0.
When it is about 2.0 MPa, it may be damaged or cracked by a slight impact during handling.
Therefore, there is a demand for granules for ceramics molding capable of molding a ceramics compact whose bending strength is 2.0 MPa or more, preferably 2.5 MPa or more, more preferably 3.0 MPa or more.

In order to increase the strength of the molded product, it is effective to increase the amount of binder at the time of granule molding. However, simply increasing the amount of binder degreasing for removing unnecessary binders. Since the time is increased, the density of the sintered body obtained by firing is decreased, or strong firing shrinkage occurs, it becomes difficult to control the dimensions of the sintered body. Naturally, the amount added is also limited.

As another method for improving the strength of the molded body, a method of increasing the water content in the granules for molding ceramics containing the binder more than usual can be considered. The increase in the amount of water in the granules has hitherto been mainly performed in order to improve the moldability of the ceramics molded body, that is, to facilitate the deformation of the ceramics molding granules during pressurization and to remove defects in the molded body due to the deformation. For example, Japanese Patent Publication No. 6-8201 describes that the water content is adjusted to be 1.5 to 1.7 parts by mass with respect to 100 parts by mass of the ceramic molding granules.

However, in general, when the water content in the ceramic molding granules is 1.0% by mass or more, so-called sticking in which the ceramic molding granules adhere to the molding die is liable to occur, and the resulting molded body is It is known to cause poor appearance and trouble during continuous molding. By adjusting the amount of binder and the amount of water in the granules for ceramics molding in this way, methods for improving the flexural strength of the ceramics compact have been tried, but in these methods, in exchange for high flexural strength. However, other problems such as a decrease in density of the sintered body, occurrence of strong firing shrinkage, and increase in sticking occur, so that a ceramic molded body having high bending strength could not be obtained.

Another method for obtaining a ceramic molded body having high bending strength is disclosed in, for example, Japanese Patent Laid-Open No. 10-25.
No. 9060 discloses that granules obtained by spray granulating a ceramic slurry containing a phenol resin as a binder and an organic solvent such as isopropyl alcohol instead of water as a solvent are subjected to heat treatment after CIP molding. Proposed. According to this method, 5
3 to 30% by mass of the binder, which is contained in an amount of 0 parts by mass or more, is added to 100 parts by mass of the ceramic raw material powder. However, when a large amount of such a binder is added, degreasing must be performed for a long time as described above, In this case, the product density decreases, and further, the dimension control becomes difficult, and as a result, the dimensional accuracy of the obtained ceramic molded body deteriorates. Furthermore, since an organic solvent represented by isopropyl alcohol, which is flammable, is used for the ceramic slurry, it is necessary to add explosion-proof equipment to the production equipment, and environmental hygiene problems occur.

[0010]

Therefore, there is a strong demand for granules for ceramics molding which are water-based binders and which can impart high bending strength to the obtained ceramic moldings with a binder and a water content as small as possible. Has been done. In view of such circumstances, the first object of the present invention is to provide a ceramics molding granule capable of imparting high bending strength to the obtained ceramics molding with a relatively small binder and water content. That is. A second object of the present invention is to provide a ceramic molded body having a high bending strength of 2.0 MPa or more. A third object of the present invention is to provide a ceramics sintered body having less appearance defects such as cracks, cracks, and breaks by firing such a ceramics molded body having a high bending strength. A fourth object of the present invention is to provide a method for producing granules for ceramics molding, which can impart high bending strength to the ceramics compact.

[0011]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventor has found that a specific polyvinyl alcohol and a water-soluble resol type binder are used as a binder when granulating ceramic molding granules. The inventors have found that the above problems can be solved by mixing a phenol resin with a predetermined ratio and used the invention.

That is, the invention according to claim 1 is a granule for ceramics molding obtained by granulating a mixture of a ceramic raw material powder and a binder, wherein the average degree of polymerization is 100 parts by mass of the ceramic raw material powder. 500-17
00, 0.4-1.4 parts by mass of polyvinyl alcohol having an average saponification degree of 88 mol% or more, and 0.1-1.4 parts by mass of a water-soluble resol-type phenol resin. Is. With such a constitution, it is possible to obtain ceramic molding granules capable of molding a ceramic molded body having a bending strength of at least 2.0 MPa or more. Moreover, the granules for ceramics molding are granulated from an aqueous slurry composed of ceramic raw material powder, a specific polyvinyl alcohol and a specific water-soluble resol-type phenol resin, and since no organic solvent is used, explosion-proof No additional equipment such as equipment is required, which is preferable in terms of environmental hygiene. In the invention according to claim 2, the polyvinyl alcohol has an average saponification degree of 94.5.
The granules for ceramics molding according to claim 1, wherein the granules are 97.5 mol%. The ceramic molding granules obtained by using polyvinyl alcohol having an average saponification degree in this range as one component of the binder have a high level of low-pressure crushability, disintegration resistance and sticking resistance that are well balanced. By using the granules for molding, it is possible to obtain good ceramic compacts and sintered ceramics that have little dimensional variation and high bending strength.

The term "low-pressure crushability" used in the present invention means the crushability of the granules at low pressure (typically 29 to 147 MPa) when molding the ceramic molding granules. The good low-pressure crushability means that the ceramic molding granules are uniformly crushed. Further, the “disintegration resistance” refers to resistance to disintegration of the ceramic molding granules caused by rolling or mutual collision during storage, transportation, or filling into a mold. Further, the "sticking resistance" means the resistance to adhesion of fine particles in the ceramics molding granules to the surface of the mold or the like.

A third aspect of the present invention is a ceramic compact obtained by heat-treating the granules for ceramics molding according to the first or second aspect of the present invention after dry pressure molding. The ceramic molded body thus obtained is
The heat treatment cures the water-soluble resol-type phenol resin in the ceramic molding granules, so at least 2.0
It exhibits a high bending strength of at least MPa, and shows a bending strength of at least 2.5 MPa, or at least 3.0 MPa depending on the manufacturing conditions. Therefore, the occurrence of breakage and cracks during handling of the ceramic molded body is reduced, and it becomes possible to manufacture a high-density ceramic sintered body as a final product with high dimensional accuracy.

The invention according to claim 4 is a ceramic sintered body obtained by firing the ceramic molded body according to claim 3. The ceramics sintered body obtained in this manner has few appearance defects such as cracks, cracks, and breaks, has high density, and has high dimensional accuracy.

The invention according to claim 5 is the ceramic sintered body according to claim 4, which is formed into a core shape having a diameter of 2 mm or less. The invention according to claim 6 is the ceramic sintered body according to claim 4, which is formed into a plate shape having a thickness of 1 mm or less. Since the ceramic sintered body of the present invention has high density and high dimensional stability, it has a core shape with a diameter of 2 mm or less and a thickness of 1 mm.
Even if it is processed into a plate shape having a size of not more than mm, chips, cracks, breaks, etc. do not occur and it has sufficient mechanical strength. Further, since the ceramic sintered body of the present invention is excellent in dimensional accuracy and mechanical strength, it becomes possible to make a ceramic having a small size and a complicated shape. In addition, such a relatively thin core or a relatively thin core sufficiently meets the demand for reducing the size and weight of electronic components.

The invention according to claim 7 is an electronic component including the ceramics sintered body according to claim 5 or 6. INDUSTRIAL APPLICABILITY The ceramic sintered body of the present invention has a high dimensional accuracy and can be processed into a small size and a complicated shape. Therefore, it can be suitably used for various electronic parts.

The invention according to claim 8 is a method for producing granules for ceramics molding for molding into a ceramics compact having high strength, wherein the ceramic raw material powder 1
Polyvinyl alcohol having an average degree of polymerization of 500 to 1700 and an average degree of saponification of 88 mol% or more with respect to 00 parts by mass of 0.4.
To 1.4 parts by mass, and 0.1 to 1.4 parts by mass of the water-soluble resol type phenol resin and 25 to 100 parts by mass of water are prepared, and the aqueous ceramics slurry prepared in this manner is prepared. A method for producing granules for ceramics molding, which comprises granulating the granules for ceramics molding by a spray drying method. According to the manufacturing method of claim 8, ceramic molding granules capable of molding a ceramic molded body having a high bending strength of 2.0 MPa or more can be easily manufactured by a spray drying method. Also,
Since no organic solvent is used as the solvent for the ceramic slurry, it is not necessary to add explosion-proof equipment to the production equipment, and it is possible to keep the production cost of the granules for forming ceramics low.

The invention according to claim 9 is a method of producing granules for ceramics molding for molding into a ceramics compact having high strength, which comprises a ceramic raw material powder 1
Polyvinyl alcohol having an average degree of polymerization of 500 to 1700 and an average degree of saponification of 88 mol% or more with respect to 00 parts by mass of 0.4.
To 1.4 parts by mass and 0.1 to 1.4 parts by mass of a water-soluble resol type phenol resin are mixed, and the mixture is granulated into ceramic molding granules by an oscillating extrusion method. It is a method for producing granules for molding ceramics. According to the manufacturing method of claim 9, ceramic molding granules capable of molding a ceramic molded body having high bending strength can be easily manufactured by the oscillating extrusion method.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. [Ceramics Powder] The ceramics molding granules of the present invention are composed of a ceramics powder and a binder as in the conventional ceramics molding granules. The ceramic powder used at this time can be appropriately selected according to the application of the finally obtained ceramic sintered body, and is not particularly limited. Typically, ferrite, alumina,
Examples thereof include powders of metal oxide ceramics such as zirconia, non-oxide ceramics such as silicon carbide and silicon nitride, barium titanate, titanium, zirconates, and composite compounds thereof. These ceramic powders may be used alone or as a mixture of two or more kinds. The particle size of these ceramic powders may be in the range conventionally adopted as ceramic powder for ceramics sintered bodies, and is generally 0.5 to 5
μm, preferably 0.7 to 3 μm.

[Polyvinyl Alcohol] In the granules for ceramics molding of the present invention, polyvinyl alcohol, which is the first essential component, functions as a binder (binder) for the primary particles, that is, a binder (binder) for the ceramic powders to form the ceramics. It affects the low-pressure crushability, disintegration resistance, and strength of the molded product. In particular,
The average saponification degree of polyvinyl alcohol affects the moldability of the ceramic molded body. The polyvinyl alcohol used in the present invention has an average saponification degree of 88.
It is essential that the content is at least mol%. That is, when polyvinyl alcohol having an average degree of saponification of less than 88 mol% is used as the binder, the low-pressure crushability of the ceramic molding granules is deteriorated, but the disintegration resistance and the sticking resistance are deteriorated. Further, polyvinyl alcohol having an average degree of saponification of less than 88 mol% is suitable for spray granulation because it has good solubility in water and easy slurry adjustment, but is suitable for wire mesh when granulated by the oscillating extrusion method. Since the material adheres, continuous granulation becomes difficult. Conversely, if the average degree of saponification of polyvinyl alcohol is too high, the disintegration resistance is good,
Since the granulated ceramics molding granules are relatively hard, the low-pressure crushability may deteriorate, and the solubility in water may worsen, making slurry adjustment difficult. Taking these circumstances into consideration, the average degree of saponification of polyvinyl alcohol, which is the first essential component of the present invention, is 94.5 to 9
It is even more preferable if it is 7.5 mol%. Although it is preferable to use polyvinyl alcohol having a single average saponification degree (88 mol% or more) as a binder, a plurality of polyvinyl alcohols having different average saponification degrees are blended to obtain an average saponification degree of 88 as a whole. It is also possible to use it as a mol% or more.

The average degree of polymerization of polyvinyl alcohol used as a binder in the present invention is 500 to
It is essential that it be 1700. That is, when the average degree of polymerization of polyvinyl alcohol is less than 500, the granulated ceramics molding granules have good low-pressure crushability but poor disintegration resistance, and the ceramic compacts obtained from the granules for ceramics molding have a low resistance to collapse. Folding strength is also low, which is not preferable. On the other hand, when the average degree of polymerization of polyvinyl alcohol exceeds 1700, the granules for ceramics molding become hard although the collapse resistance of the granulated ceramics molding and the bending strength of the obtained ceramics molded body are relatively good. If it is too low, the low-pressure crushability will deteriorate, which is not preferable.

Polyvinyl alcohol having the above-mentioned average degree of saponification and average degree of polymerization is ceramic raw material powder 100.
It is desirable to add it in a range of 0.4 to 1.4 parts by mass with respect to parts by mass. If the addition amount of polyvinyl alcohol is less than 0.4 parts by mass, the amount of the binder is too small and it becomes difficult to granulate the granules for forming ceramics, which is not preferable. The molding granules become too hard and the low-pressure crushability deteriorates. As a result, the residual amount of the grain boundaries in the ceramic molded body increases, and molding defects easily occur, which is not preferable.

[Water-soluble resol-type phenol resin] Second
The water-soluble resol-type phenol resin, which is an essential component of, has a molar ratio of formaldehyde to phenol of 1.0 to 3.0, and an alkali metal and / or
Or resolization using an alkaline earth metal compound,
It is a water-soluble phenol resin obtained by neutralizing with an organic acid or an inorganic acid. Such water-soluble phenolic resin,
For example, JP-A-5-262838 and JP-A-6-49.
No. 158, JP 2001-131253 A, etc., for example, a resin sold by Sumitomo Bakelite Co., Ltd. under the trade name of "Sumilite Resin" can be used. Such a water-soluble resol type phenol resin can be mixed with an aqueous solution of polyvinyl alcohol having the above-mentioned average saponification degree and average polymerization degree, and is used without impairing the above-mentioned properties of the polyvinyl alcohol as a binder. It is possible to Moreover, since the water-soluble resol-type phenol resin is cured by heating the ceramic molded body to which the water-soluble resol-type phenol resin is added, it is possible to impart high strength to the ceramic molded body.

In the present invention, the amount of the water-soluble resol type phenol resin added is preferably 0.1 to 1.4 parts by mass with respect to 100 parts by mass of the ceramic raw material powder. If the addition amount is less than 0.1 parts by mass, sufficient strength cannot be imparted to the ceramic molded body, which is not preferable. Conversely, if the addition amount exceeds 1.4 parts by mass, the ceramic molded body and the mold are This is not preferable because the adhesiveness becomes strong and a molding trouble such as sticking of the molded body to the upper mold easily occurs when the ceramic molded body is released from the mold after the pressure molding is completed.

[Arbitrary Ingredients] In the present invention, when granulating the ceramic molding granules, various conventionally known additives can be added, if desired, within a range not impairing the objects and effects of the present invention. . Examples of such additives are:
Dispersants such as polycarboxylic acids and condensed naphthalene sulfonic acids, plasticizers such as glycerin, glycols and triols, waxes, lubricants such as stearic acid (salts), polyether-based, urethane-modified polyether-based, polyacrylic acid-based , An organic polymer flocculant such as a modified acrylic acid polymer,
Inorganic flocculants such as aluminum sulfate, aluminum chloride and aluminum nitrate may be used.

In the present invention, these respective components are mixed and the resulting raw material mixture is granulated by a conventionally known granulation method to obtain granules for ceramics molding. More specifically, the raw material mixture can be granulated by a spray drying method or an oscillating extrusion method to obtain granules for ceramics molding. These granulation methods can be appropriately selected depending on the granulation amount of the ceramic molding granules, the properties of the intended ceramic molded body, and the like.

[Granulation of Granules: Spray Drying] In one embodiment of the present invention, granules for ceramics molding are granulated by a spray drying method. At this time, these components, that is, 100 parts by mass of the ceramic raw material powder, Polyvinyl alcohol having the average degree of saponification and the average degree of polymerization of 0.4 to
1.4 parts by mass, 0.1 to 1.4 parts by mass of the water-soluble resol-type phenolic resin, 25 to 100 parts by mass of water and 25 to 100 parts by mass of optional components are mixed according to a conventionally known method. Then, an aqueous ceramics slurry for granulating ceramics granules is prepared.

The thus-prepared aqueous ceramics slurry can be granulated into ceramics forming granules by a conventionally known spray drying method. In this way, spherical ceramic molding granules are obtained by the spray drying method. The granules for molding ceramics are 40 ~ 250μ
It is desirable to have a particle size of m, preferably 60 to 2
It is desirable that the thickness is 00 μm, more preferably 70 to 150 μm. Granule size for ceramics molding is 40μm
If the amount is less than the above range, the fluidity of the ceramic molding granules and the filling property into the mold may be deteriorated, and variations in the size of the obtained molded body and the mass of the molded body may be large.
On the other hand, if the particle size exceeds 250 μm, a large number of grain boundaries may remain in the molded product to cause defective molding, or the molded product may have large variations in size and mass.

[Granulation of granules: oscillating extrusion]
In another embodiment of the present invention, 100 parts by mass of ceramic raw material powder, polyvinyl alcohol having an average degree of polymerization of 500 to 1700 and an average degree of saponification of 88 mol% or more of 0.4 to 1.
4 parts by mass and 0.1 to 1.4 parts by mass of the water-soluble resol-type phenol resin can be mixed to obtain granules for ceramics molding by an oscillating extrusion method. The ceramic molding granules of the present invention granulated by the oscillating extrusion method in this manner are 80 to 50
It is desirable to have a particle size of 0 μm. The particle size of the ceramic molding granules is preferably 100 to 300 μm, more preferably 125 to 200 μm.
When the particle size of the ceramics forming granules is less than 80 μm, the fluidity of the ceramics forming granules and the filling property into the mold are deteriorated, and variations in the size and mass of the obtained molded body may be large. is there. In addition, the adhesion of fine powder (sticking) to the mold easily occurs, which is not preferable. On the other hand, if the particle size exceeds 500 μm, a large number of grain boundaries may remain in the molded product to cause defective molding, or the size and mass of the molded product may vary greatly.

The ceramic compact of the present invention can be obtained by filling the ceramic granules of the present invention obtained as described above in a mold and molding by a conventionally known dry pressing method.

[Heat Treatment] The ceramic molded body of the present invention thus molded is preferably subjected to a heat treatment for the purpose of imparting high strength to the molded body. The heat treatment temperature at this time is preferably higher than the curing temperature (80 ° C.) of the water-soluble resol-type phenol resin component present in the molded body, preferably 100 to 220 ° C., more preferably 11
The temperature is preferably 0 to 170 ° C. The heat treatment time depends on the shape and size of the molded body, but it is desirable that the water-soluble resol-type phenol resin component present in the molded body be sufficiently cured even inside the molded body. Specifically, it is desirable that the time is about 5 to 90 minutes. Moreover, such heat treatment can be performed in a fluidized bed, a box dryer, a continuous drying furnace, or a rotary kiln. By performing heat treatment in this manner, it becomes possible to impart a high bending strength of at least 2.0 MPa to the ceramic molded body, and depending on the manufacturing conditions, a bending strength of 2.5 MPa or more, or 3.0 MPa or more. It becomes possible to give strength.

[Ceramic Sintered Body] The ceramic molded body of the present invention thus obtained was processed according to a conventional method to obtain 10
By firing at a temperature of 00 to 1450 ° C., it is possible to obtain a ceramics sintered body with less appearance defects such as chipping, cracking, and breaking. In particular, it is possible to reduce the frequency of appearance defects such as cracks, cracks, and breaks that frequently occur in the conventional arrow portions shown in FIGS. 1 and 2, for example.

[0034]

[Examples 1 to 7, Comparative Examples 1 to 6]

[Granulation] Ni-Cu-Zn, which is a ceramic raw material powder
System ferrite powder 100 parts by mass, water 50 parts by mass, and polycarboxylic acid ammonium salt 0.3 as a dispersant.
In parts by weight, polyvinyl alcohol having the average degree of polymerization, average saponification degree, and addition amount changed as shown in Table 1 as a binder, and water-soluble resol-type phenol resin having the addition amount changed as shown in Table 1 Was wet mixed according to a conventional method to prepare an aqueous ceramic slurry. This aqueous ceramics slurry was spray-granulated by a spray dryer to obtain 13 types of spherical shaped granules (Examples 1 to 6) having an average particle size of 90 μm and a water content of 0.3% by mass. .

[0035]

[Table 1]

The amount of polyvinyl alcohol added was 0.
In the granules for ceramics molding of Comparative Examples 1 to 3 having 4 parts by mass or less, the binding amount of the binder was small, so that the bonding property of the ceramic powders was poor at the time of granulation, and the particle size was 40%.
A large amount of fine particles having a size of less than or equal to μm and granules for forming a ceramic having many holes or depressions on the surface were generated, and the yield of the granule for forming a ceramic having a predetermined particle size (about 90 μm) was very poor.

[Preparation of Molded Article] Next, these 13 kinds of granules for molding ceramics are respectively used in an amount of 40 to 150 M.
By pressure-molding with a pressure of Pa by a commonly used dry method, the density of the molded body is 3.0 g / cm ³ , and the rectangular parallelepiped block-shaped ceramic molded body (length 55 mm, width 12 mm, height 3 mm ( Hereinafter, referred to as a first block molded body) and a rectangular parallelepiped block-shaped ceramic molded body having a molded body density of 3.2 g / cm ³ , a length of 55 mm, a width of 12 mm, and a height of 2.8 mm (hereinafter, referred to as a second block molded body). (Referred to as a block molded body). The ceramic molding granules of Comparative Example 4 in which the amount of the water-soluble resol-type phenol resin added was 3.0 parts by mass, which was beyond the range of the present invention, were inferior in mold release property from the mold at the time of dry pressure molding. Problems often occurred in which the molded body stuck to the upper mold of the mold.

[Heat Treatment] Then, the water-soluble resol-type phenol resin in the first block molded body and the second block molded body thus obtained is cured to impart high bending strength to the molded body. Then, heat treatment was performed at 130 ° C. for 30 minutes in a box-type dryer. After that, these block molded bodies were left at room temperature for 1 hour and cooled to room temperature.

[Measurement of flexural strength of molded body] After heat treatment, the flexural strength of the first and second block molded bodies was measured by using a load tester (manufactured by Aiko Engineering Co., Ltd.).
It was measured according to the method specified in IS R1601. Table 2 shows the measurement results of the bending strength of the first and second block molded bodies.

[0040]

[Table 2]

As shown in Table 2, the first and second block compacts produced from the ceramic molding granules of Examples 1 to 7 satisfying the requirements of the present invention are both 2.5 MP.
It can be seen that it shows a high bending strength of a or more (see the column after heat treatment). Further, when the same measurement was performed on the block molded body before heat treatment, the bending strength was 1.1 to
It is in the range of 1.8 MPa, and it can be seen that the first and second block molded bodies of Examples 1 to 7 exhibit relatively high flexural strength even before the heat treatment (see the column before heat treatment).
From this, the first and second block molded bodies obtained from the ceramic molding granules of Examples 1 to 7 were:
Even before the heat treatment, it has some bending strength, and it is presumed that it is unlikely that defective appearance such as cracks, cracks, and breaks will occur during handling.

On the other hand, the first prepared from the ceramic molding granules of Comparative Examples 1 to 4 which do not satisfy the requirements of the present invention.
And the second block molded body has a flexural strength before heat treatment of 0.
It is as low as 4 to 0.5 MPa, and it is suggested that the yield strength is low, and there is a high possibility that defects such as cracks, cracks, and breaks will occur during handling. Comparative Example 5 in which only polyvinyl alcohol was added as a binder
Also, in the first and second block compacts produced from the ceramic molding granules of Comparative Example 6, almost no change in bending strength was observed before and after the heat treatment. This indicates that in Examples 1 to 7, curing of the water-soluble resol-type phenolic resin present in the ceramic molded body by heat treatment increases the mechanical strength (flexural strength) of the ceramic molded body. . Further, among the first and second block molded bodies obtained from the granules for ceramics molding of Comparative Examples 1 to 6, there are also those having a bending strength after heat treatment of 2.0 MPa or more. In the case of 1 to 3, there is a problem that the yield at the time of granulating ceramics granules is poor, and in the case of Comparative Example 4, there is a problem that the moldability of the ceramics molded product from the mold is poor. In the case of Comparative Example 6, since the amount of polyvinyl alcohol added is too large, the resulting ceramic compact has poor low-pressure crushability and contains a large amount of grain boundaries. Have Thus, only in the case of Examples 1 to 7, low-pressure crushability of granules, collapse resistance and sticking resistance, and bending strength of the obtained molded body and sintered body, dimensional accuracy described later, yield and mold. The elements of demolding from were in harmony at a high level.

[Continuous Formability Evaluation 1] Using the ceramic molding granules of Example 1, Example 3, Comparative Example 1 and Comparative Example 5, cylindrical core-shaped ceramic molding having a diameter of 1.8 mm and an L dimension of 2.0 mm. The body (Fig. 1 (a)) is 100,000
Pieces were continuously molded. The ceramic molded body molded in this manner was heated at 130 ° C. for 30 minutes using a box dryer.
Heat treatment was performed for a minute to improve the mechanical strength (flexural strength) of the molded body. After the ceramic molded body thus heat-treated is cooled to room temperature, it is cut with a diamond foil to produce a coil drum core having a core diameter of 0.8 mm shown in FIG. 1 (b). Further, firing was performed at 1050 ° C. to obtain a ceramics sintered body. Table 3 shows the results of the appearance evaluation performed on the ceramic molded body and the sintered body after cutting. The results of appearance evaluation shown in Table 3 are average values of 100,000 continuously formed ceramic compacts and sintered compacts.

[0044]

[Table 3]

From Table 3, the evaluation results of the molded bodies and sintered bodies manufactured from the ceramic molding granules of Comparative Example 1 and Comparative Example 5 which do not satisfy the essential conditions of the present invention are x or Δ. However, in the case of the molded bodies and the sintered bodies manufactured from the ceramic molding granules of Example 1 and Example 3 which satisfy the essential conditions of the present invention, the evaluation result is ○, and there are cracks, cracks, It can be seen that the number of breaks is extremely small. In addition, when investigating the dimensional variation of the final product ceramics sintered body,
All the sintered bodies obtained from the ceramic molding granules of Example 1 and Example 3 had dimensional variation within the allowable tolerance. On the other hand, in the sintered bodies obtained from the granules for molding ceramics of Comparative Example 1 and Comparative Example 5, the dimensional variation exceeded the allowable tolerance in 0.3% of all the sintered bodies. From this, according to the granules for ceramics molding of the present invention, it becomes clear that a ceramics sintered body having excellent dimensional accuracy can be produced, and thereby the yield of the ceramics sintered body can be improved. It was Further, by using the ceramics molding granules of the present invention,
Since many appearance defects such as cracks, chips, and breaks conventionally occur, it has become possible to manufacture a core-shaped ceramics sintered body having a diameter of 2 mm or less, which is inferior in manufacturing yield, with good yield.

[Continuous Formability Evaluation 2] Using the ceramic molding granules of Example 1, Example 3, Comparative Example 1 and Comparative Example 5, a plate-shaped ceramic molding of 10.0 mm × 10.0 mm × 0.9 mm was formed. 1000 bodies (FIG. 2A) were continuously molded. The ceramic molded body thus molded was heat-treated at 130 ° C. for 30 minutes using a box dryer to improve the mechanical strength (flexural strength) of the molded body. The ceramic molded body thus heat-treated was cooled to room temperature and then fired at 1050 ° C. to obtain a ceramic sintered body. Table 4 shows the results for the sintered ceramics. The result of appearance evaluation is shown.

[0047]

[Table 4]

From Table 4, the evaluation results of the molded bodies and sintered bodies manufactured from the ceramic molding granules of Comparative Example 1 and Comparative Example 5 which do not satisfy the essential conditions of the present invention are x or Δ. However, in the case of the molded bodies and the sintered bodies manufactured from the ceramic molding granules of Example 1 and Example 3 which satisfy the essential conditions of the present invention, the evaluation results are all ○, and there are cracks and cracks. It can be seen that the occurrence is extremely low.

Further, in the sintered bodies using the ceramic molding granules of Examples 1 and 3, none of the dimensional variations exceeded the allowable tolerance. Further, by using the ceramics-forming granules of the present invention, many defective appearances such as cracks, chips, and breaks conventionally occur, so that the yield of plate-shaped ceramics sintered bodies having a thickness of 1 mm or less, which is inferior to the production yield, is increased. It has become possible to manufacture well.

[0050]

According to the ceramics forming granules of the present invention constructed as described above, 100 parts by mass of ceramic raw material powder, polyvinyl alcohol having an average degree of polymerization of 500 to 1700 and an average degree of saponification of 88 mol% or more are used. By using 0.4 to 1.4 parts by mass and 0.1 to 1.4 parts by mass of the water-soluble resol type phenol resin, the bending strength is at least 2.0 MPa, and It is possible to provide a ceramics molding granule capable of molding a good ceramics molding with less chipping, cracks and breakage (claim 1). Further, since the ceramic molding granules do not use an organic solvent, they do not require additional equipment such as explosion-proof equipment and are preferable in terms of environmental hygiene.

In the ceramic molding granules of the present invention, the average saponification degree of the polyvinyl alcohol is 94.5.
When it is set to 97.5 mol%, granules having a good balance of low-pressure crushability, collapse resistance and sticking resistance can be obtained, and by using this, good ceramic compacts and ceramic sintered bodies with small dimensional variation can be obtained ( Claim 2).

The ceramic compact obtained by subjecting the granules for ceramics molding of the present invention to dry pressure molding and then heat treatment has a bending strength of at least 2.0 MPa, and 2.5 MPa depending on the manufacturing conditions. It has a high strength of at least 3.0 MPa. Therefore, the occurrence of breakage and cracks during handling of the ceramic molded body is reduced, and a high-density ceramic sintered body as a final product can be manufactured with high dimensional stability (claim 3).

Further, the ceramic sintered body obtained by firing the ceramic molded body according to the present invention has few appearance defects such as cracks and cracks, has a high density and has high dimensional stability. (Claim 4). In particular, a ceramic sintered body having such a high density and high dimensional stability is suitable for a core shape having a diameter of 2 mm or less (Claim 5) and a plate shape having a thickness of 1 mm or less (Claim 6). It can be used, and can be suitably used for various electronic parts that are required to be small, thin, lightweight, etc. (Claim 7).

Further, according to the method for producing granules for ceramics molding of the present invention, granules for ceramics molding capable of molding a ceramics compact having a high bending strength of at least 2.0 MPa are easily manufactured by the spray drying method. It becomes possible to do. Further, since an organic solvent is not used as a solvent for the ceramic slurry, it is not necessary to take explosion-proof measures in the manufacturing apparatus, and the manufacturing cost of the ceramic molding granules can be reduced (claim 8).

Further, according to the method for producing a ceramics molding granule of the present invention, a ceramics molding granule capable of molding a ceramics molding having a high bending strength of at least 2.0 MPa can be easily prepared by the oscillating extrusion method. It becomes possible to manufacture (Claim 9).

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of the shape of a ceramics sintered body.

FIG. 2 is a perspective view showing another example of the shape of a ceramics sintered body.

Claims (9)

[Claims] 1. A granule for ceramics molding obtained by granulating a mixture of a ceramic raw material powder and a binder, wherein the average degree of polymerization is 500 to 1700 and the average degree of saponification is 88 mols per 100 parts by mass of the ceramic raw material powder. % Or more of polyvinyl alcohol 0.4 to 1.4 parts by mass, and water-soluble resol type phenol resin 0.1 to 1.4 parts by mass, a ceramics forming granule. 2. The granules for ceramics molding according to claim 1, wherein the polyvinyl alcohol has an average saponification degree of 94.5 to 97.5 mol%. 3. A ceramic compact obtained by dry-pressing the granules for ceramic molding according to claim 1 or 2 and then heat-treating the granules. 4. A ceramic sintered body obtained by firing the ceramic molded body according to claim 3. 5. The ceramics sintered body according to claim 4, which is formed into a core shape having a diameter of 2 mm or less. 6. The ceramic sintered body according to claim 4, which is formed into a plate shape having a thickness of 1 mm or less. 7. An electronic component including the ceramic sintered body according to claim 5 or 6. 8. A method for producing granules for ceramics molding for molding into a ceramics compact having high strength, wherein the average degree of polymerization is 500 to 1700 and the degree of saponification is 88 mols per 100 parts by mass of the ceramic raw material powder. % Polyvinyl alcohol 0.4 to 1.4 parts by mass, an aqueous ceramics slurry containing 0.1 to 1.4 parts by mass of a water-soluble resol type phenolic resin and 25 to 100 parts by mass of water, and A method for producing ceramics-forming granules, which comprises granulating the aqueous ceramics slurry prepared in step 1 into granules for forming ceramics by a spray drying method. 9. A method for producing granules for ceramics molding for molding into a ceramics compact having high strength, wherein the average degree of polymerization is 500 to 1700 and the degree of saponification is 88 mols per 100 parts by mass of the ceramic raw material powder. % Or more of polyvinyl alcohol 0.4 to 1.4 parts by mass and water-soluble resol type phenol resin 0.1 to 1.4 parts by mass are mixed, and the mixture is made into granules for ceramics molding by an oscillating extrusion method. A method for producing granules for molding ceramics, which comprises granulating.