JP2020001940A - Method of manufacturing granulated particle for producing ceramic - Google Patents

Abstract

To provide a method capable of effectively suppressing contamination of impurities to a granulated particle when manufacturing the granulated particle for producing a ceramic using a nonmagnetism inorganic material powder.SOLUTION: The method of manufacturing a granulated particle for producing ceramic includes: a slurry-preparing process of preparing a slurry composed of a mixture containing a nonmagnetism inorganic material powder, and a solvent; and a process of granulating the slurry by introducing a spray-drying device, where there is provided an impurity-removing process of removing magnetic metals contained in the slurry by contacting the slurry to a magnet right before the slurry is introduced into the spray-drying device.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing granules for ceramic production using a nonmagnetic inorganic material powder, for example, a powder of aluminum nitride.

  A nonmagnetic inorganic material represented by aluminum nitride is used for various applications as a sintered body, which is formed into a granule and then solidified by heat treatment (firing), that is, a ceramic. For example, ceramics made of aluminum nitride exhibit high thermal conductivity and high insulation properties, and are widely used as heat dissipation materials and electrical insulation materials in applications such as heat dissipation boards for electronic devices, electronic circuit boards, members for semiconductor manufacturing equipment, and the like. (Patent Document 1).

  By the way, as described above, the granules of the inorganic compound used for the production of ceramics (granules for ceramic production) are generally prepared by mixing the powder with a solvent, and further suitably, a binder (binder) to prepare a slurry, It is manufactured by granulating the slurry by spray drying (Patent Documents 1 and 2).

However, there has been a problem that the granules for ceramic production obtained by the above-described method often contain impurities in an amount exceeding the allowable limit. Such incorporation of impurities causes the ceramic produced using the granules to have a reduced strength due to a reduction in the strength of the sintered body and a change in the color of the surface of the sintered body, and furthermore, a decrease in the electrical characteristics such as electrical insulation. There is a need for improvement because it may lead to a decrease.
In particular, when metal impurities such as stainless steel are mixed, discoloration points such as black spots and white spots are generated on the surface of the sintered body. In the final stage of a product having a relatively large size and a long manufacturing process, such as an insulating plate or a heater for a semiconductor manufacturing apparatus, the occurrence of such a discoloration point on the surface of the sintered body leads to a large loss.

Patent No. 3479160 Patent No. 2525074

  Accordingly, an object of the present invention is to provide a method capable of effectively preventing impurities from being mixed into granules for producing ceramics using the non-magnetic inorganic material powder.

  The present inventor believes that impurities mixed in the ceramic manufacturing granules may cause wear caused by the manufacturing process of the non-magnetic inorganic material powder as a raw material, and the steel conveying pipe used in the manufacturing process of the granules using the same. They have found that they are derived from powder, and have completed the present invention.

That is, according to the present invention, a slurry preparation step of preparing a slurry composed of a mixture containing a nonmagnetic inorganic material powder and a solvent, including a step of granulating the slurry by introducing the slurry into a spray-drying apparatus, comprising: In the manufacturing method,
Immediately before the slurry is introduced into a spray drying apparatus, an impurity removing step of contacting the slurry with a magnet to remove magnetic metal impurities contained in the slurry is provided. A method for producing a granule is provided.

In the production method of the present invention, (1) a filtration step of filtering the slurry with a filter medium having an aperture of 10 to 100 μm is provided prior to the impurity removal step;
(2) the viscosity (20 ° C.) of the slurry introduced into the impurity removing step is 0.02 to 2000 mPa · s;
(3) the non-magnetic inorganic material is aluminum nitride;
Is preferred.

  In the present invention, when a slurry containing a non-magnetic inorganic material powder is introduced into a spray drying apparatus and granulated to produce granules for ceramic production, immediately before being introduced into the spray drying apparatus, impurities that cause the slurry to become magnets An important feature is that a removal step is provided.

That is, the present inventors investigated the state of contamination until the slurry containing the non-magnetic inorganic material powder was introduced into the spray drying apparatus, and found that the slurry was extremely small before being introduced into the spray drying apparatus. Is mixed with abrasion powder of a metal, furthermore, in a sintered body formed using granules obtained by such a small amount of a metal powder, an appearance defect due to generation of a discoloration point occurs, It has been found that when the occurrence of cracks increases, the strength and electrical insulation of the sintered body may vary. Specifically, the inorganic material powder used in the preparation of the slurry, when moving in a transport pipe or the like in the manufacturing process, scrapes the metal material constituting the pipe by contact with the transport pipe, and abrasion powder is mixed. Also, when the slurry prepared using the above-mentioned inorganic material powder passes through a slurry preparation apparatus described later or a subsequent transfer pipe, a metal material constituting the pipe is cut by contact with the transfer pipe. It was found that wear powder was mixed.
The transfer pipe and the like are generally made of steel such as stainless steel, and the used inorganic material powder, particularly aluminum nitride powder, is a substance having a very high hardness, and the above phenomenon is remarkable.
As a result, abrasion powder of a magnetic metal such as steel, which is conductive, is mixed into the granules for ceramic production, which causes a reduction in sinterability, resulting in a decrease in strength and electrical characteristics of the ceramic product obtained from the granules for ceramic production. It causes quality deterioration such as deterioration of quality.

  However, in the present invention, a non-magnetic inorganic material is used, and the slurry containing the powder is brought into contact with the magnet immediately before being introduced into the spray drying apparatus. It is possible to obtain a granule for ceramic production which can be effectively removed and does not contain such metal powder.

  In addition, after granulation by a spray drying apparatus, it is conceivable to remove the magnetic metal powder by bringing the granulated material into contact with a magnet, but in this case, it is necessary to bring the granulated material and the magnet into close contact. Therefore, magnetic metal powder cannot be efficiently removed. As in the present invention, since the material that comes into contact with the magnet is in the form of a slurry, the two materials come into close contact and the magnetic metal powder can be efficiently removed.

Further, by using a transfer pipe having an inner surface coated with an insulating material such as ceramic, it is possible to prevent metal powder from being mixed. However, in the process of industrially producing a large amount of powder for ceramic production and granules using the same, a step of transporting the inorganic material powder or mixing the inorganic material powder with a solvent or the like to prepare a slurry, and further using a spray drying apparatus It is not possible to industrially implement the use of a transfer pipe having an inner surface coated with an insulating material in the process up to the supply to the substrate.
That is, in the present invention, since means for removing metal powder using a magnet is used, an inexpensive steel transfer pipe can be used, and industrial implementation is possible.

3 is a flowchart showing a process of the method for producing granules for ceramic production of the present invention.

  Referring to the flowchart of FIG. 1, the manufacturing method of the present invention generally includes preparing a nonmagnetic inorganic material powder, a solvent, and optionally used optional materials as raw materials, and introducing these raw materials to a slurry preparation step. Then, the slurry obtained in this step is introduced into an impurity removing step using a magnet, and the slurry from which the impurities have been removed is supplied to a spray drying apparatus to be granulated, and the obtained granules are collected as a product. Is what you do.

raw materials;
In the present invention, the inorganic material powder used as a raw material is a component that forms the skeleton of the finally produced ceramic, but must be nonmagnetic as a matter of course. This is because when a magnetic metal such as iron, cobalt, nickel, or manganese or a compound thereof is used, impurities cannot be removed using a magnet.
The non-magnetic inorganic material powder is not particularly limited as long as it is non-magnetic. In principle, powders of various non-magnetic metals or compounds thereof can be used. From the viewpoint that the effects of the present invention are maximized, it is preferable to use aluminum nitride powder or alumina powder, and aluminum nitride powder is most suitable. That is, the aluminum nitride powder has a very high hardness and is most likely to cause abrasion of the steel transfer pipe.

  The non-magnetic metal powder described above generally has an average particle size of 5 μm or less, particularly preferably in the range of about 0.5 to 3 μm, in order to obtain granules having a uniform particle size distribution. The average particle size is measured by, for example, a particle size distribution measuring device using a laser diffraction / scattering method.

The solvent used together with the non-magnetic inorganic material powder is an essential component for slurry preparation and granulation by spray drying, and water, a volatile organic solvent and the like are used. Note that it is preferable to use an organic solvent in which the inorganic material powder is easily dispersed uniformly in the slurry. For those having a problem in water resistance such as aluminum nitride, an organic solvent is preferably used.
Examples of such an organic solvent include, but are not limited to, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; alcohols such as ethanol, propanol and butanol; Aromatic hydrocarbons such as benzene, toluene, and xylene; and halogenated hydrocarbons such as trichloroethylene, tetrachloroethylene, and bromochloromethane; and the like. Can also be used.
Such an organic solvent is preferably used in an amount such that the viscosity of the obtained slurry at 25 ° C. is in the range of 0.02 to 2000 Pa · s. It is used in an amount of 20 to 200 parts by weight per part by weight.

  In addition, as the optional components appropriately used, known compounding agents used for molding a ceramic, for example, a binder, a surfactant, and a sintering aid can be exemplified.

The binder is used for molding a ceramic using the granules, and is used for molding a molded article having a predetermined shape without particles falling apart before sintering, It is a conventionally known compounding agent.
Examples of such binders include, but are not limited to, generally polyvinyl butyral, polymethyl methacrylate, polyethyl methacrylate, poly 2-ethylhexyl methacrylate. , Polybutyl methacrylate, polyacrylate, cellulose acetate butyrate, nitrocellulose, methylcellulose, hydroxymethylcellulose, polyvinyl alcohol, polyoxyethylene oxide and polypropylene oxide Organic polymers; hydrocarbon-based synthetic resins such as petroleum resin, polyethylene, polypropylene, and polystyrene; polyvinyl chloride; organic polymers such as waxes and emulsions thereof; Can also be used as a mixture.
Generally, it is preferable to use the binder in an amount of 0.1 to 30 parts by weight per 100 parts by weight of the nonmagnetic inorganic material in order to effectively perform molding before sintering.

The surfactant is used to uniformly disperse the nonmagnetic inorganic material powder in the slurry, and a surfactant known per se can be used. Generally, the surfactant has an HLB of 4.5 to 18, In particular, a nonionic surfactant in the range of 6.0 to 10.0 is preferably used. Note that HLB in the present invention is a value calculated by the Davis formula.
Examples of such nonionic surfactants include carboxylated trioxyethylene tridecyl ether, digserin monooleate, diglycerin monostearate, carboxylated heptaoxyethylene tridecyl ether, and tetraglycerin monoester. Oleate, hexaglycerin monooleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monooleate and the like can be mentioned, and these can be used in combination of two or more. It is possible.
In general, the amount of the surfactant to be used is preferably in the range of 0.01 to 10 parts by mass, particularly preferably 0.02 to 3.0 parts by mass, per 100 parts by mass of the nonmagnetic inorganic material powder.

  Further, the sintering aid is used for accelerating sintering when producing the ceramic, and any known sintering aid can be used depending on the type of the nonmagnetic inorganic powder. For example, when aluminum nitride powder is used, alkaline earth metal oxides such as calcium oxide and strontium oxide; rare earth oxides such as yttrium oxide and lanthanum oxide; composite oxides such as calcium aluminate; It is suitable as an auxiliary agent, and is used in the range of 0.1 to 10% by mass in the total amount with the aluminum nitride powder.

Slurry preparation;
The above-described various raw materials are appropriately mixed by using a mixing device such as a rotary ball mill to obtain a slurry in which the nonmagnetic inorganic material powder is uniformly distributed.
The obtained slurry is preferably filtered. After removing coarse particles in the slurry, the slurry is temporarily stored in a slurry tank. By this filtration, it is possible to remove impurities of several hundred μm or more which are difficult to be removed in an impurity removing step described later.

In addition, the above-mentioned filtration is generally performed by passing the slurry through a filter medium having an opening of 10 to 100 μm.
Further, such a filtration step can be performed before an impurity removal step described later.
In this way, a slurry having a viscosity at 25 ° C. of preferably 0.02 to 2000 Pa · s is obtained. If the viscosity is too high, the effect of removing impurities in the below-described impurity removing step is reduced.

Removal of impurities;
The slurry temporarily stored in the slurry tank as described above is introduced into an impurity removing step, and is brought into contact with a magnet to remove magnetic impurities in the slurry.
That is, the above-mentioned nonmagnetic inorganic powder, the raw material containing the inorganic powder, and the slurry conveying pipe are made of steel such as stainless steel, and therefore, due to contact with the hard nonmagnetic inorganic powder, steel wear powder is generated. Mixed into the slurry as impurities. Particularly in a pipe for supplying a slurry, a large pressure is applied to the pipe surface, so that a lot of abrasion powder is generated. For this reason, in the present invention, prior to granulation by a spray drying apparatus described below, the slurry is made to flow in contact with a magnet to remove magnetic steel wear powder. According to this method, it is also possible to remove metal impurities mixed in the production process of the nonmagnetic inorganic powder.

The contact between the slurry and the magnet can be easily performed, for example, by passing the slurry through a magnet filter. It has been confirmed that a magnetic metal derived from stainless steel, such as iron, chromium, and nickel, adheres to this magnet filter.
The magnet filter preferably forms a magnetic field having a magnetic flux density of 6000 gauss or more, preferably 6000 gauss or more, for removing stainless steel having weak magnetic properties.
The structure of the magnet filter is not limited at all, and a magnet provided with a magnet bar in a casing is generally used. The slurry introduced into the casing comes into contact with the magnet bar, and metal impurities adhere. Examples of such a magnet filter include a Diasler series manufactured by Daika Co., Ltd. and an HCPB series manufactured by Technoplan Co., Ltd.
The installation of the magnet bar is appropriately determined in consideration of the magnetic force so that the magnet has an interval capable of acting on the magnetic metal component in the slurry.
The flow rate when the slurry comes into contact with the magnet is preferably 0.1 to 50 L / min and 1 to 40 L / min from the viewpoint of high metal removal efficiency and high processing efficiency.

  As described above, in the present invention, since the slurry is brought into contact with the magnet, abrasion powder of the magnetic metal can be removed very effectively. In the following contact with the magnet after granulation by spray drying, the contact between the granular material and the magnet does not become dense, so that it is not possible to effectively remove magnetic wear powder.

  Therefore, in the present invention, the removal of impurities using a magnet should be performed immediately before the slurry is introduced into the spray drying apparatus, and contact between the slurry after the removal of the impurities and the transport pipe should be avoided as much as possible. For example, the length of the piping for supplying the slurry after passing through the magnet filter to the spray drying apparatus is within 2 m, preferably within 1 m, or a non-metallic material such as a Teflon tube is used. preferable. Thus, the amount of new wear powder generated due to the contact of the slurry with the pipe can be effectively suppressed.

Granulation;
The slurry from which the magnetic wear powder has been removed as described above is introduced into a spray drying device.
In a spray drying apparatus into which the slurry is introduced, the slurry is sprayed from above into a suitably heated dry air stream (for example, air or nitrogen gas), whereby the solvent is removed, and a granular material containing an inorganic compound is obtained. The obtained granules are discharged from below.

Fluidization treatment;
The particulate matter mixed with the fine powder as described above is supplied to a step of accumulating the granules in a turbulent gas (fluidization step) to improve the fluidity, the strength of the granular substance, and the renewal of the granular substance and the fine powder. It is preferable to achieve uniformity.
Taking aluminum nitride granules as an example of the granules for ceramic production, the gas used for the fluidization is preferably a gas that does not substantially react with additives such as aluminum nitride powder and a binder, for example, air, Oxygen, nitrogen and the like can be mentioned. Further, the wind speed of the supplied gas may be any wind speed required for fluidizing the granules. The wind speed required for fluidization of the granules is, for example, the value of the value calculated by the formula of the fluidization start speed described on page 176 and the formula of the terminal speed described on page 1056 of “Chemical Engineering Handbook Revised 4th Edition” edited by the Society of Chemical Engineers. Arbitrarily selected from the range. The residence time of the granules is preferably selected from the range of 1 minute to 36 hours. The temperature of the supplied gas may be any temperature, but is preferably selected from the range of 0 to 250 ° C. in order to obtain aluminum nitride granules having an appropriate breaking strength. By this fluidization step, the granules repaired from under the spray dryer and the fine powder collected by the cyclone are uniformly mixed. In addition, the fluidity and strength of the granules can be adjusted.

  The granules obtained through the fluidization step are appropriately sieved, whereby coarse particles are further removed, for example, recovered as the granules for ceramic production of the present invention having a predetermined average particle diameter and fine particle content. You.

  In addition, as a conveyance pipe for the granulated matter discharged from the spray drying apparatus, the interval from the granulation to the fluidization step is short, and a large amount of abrasion powder is not generated unlike contact with the slurry. Although it may be made of stainless steel, the inner surface of the pipe is preferably coated with a ceramic such as alumina in order to minimize mixing of wear powder and obtain high-purity granules.

  The granules for ceramic production obtained as described above are molded into a desired shape by, for example, press molding filled in a predetermined mold, and then heated according to the type of nonmagnetic inorganic material used. (For example, at 1600 ° C. or more in the case of aluminum nitride) to obtain a ceramic as a final object.

In the granules for ceramic production obtained by the production method of the present invention, the mixing of the inorganic material powder and the magnetic metal abrasion powder due to the abrasion of the slurry conveying pipe or the like using the same is effectively suppressed, and the mixing of such impurities Therefore, deterioration of the quality of the ceramic as a final product due to the above is effectively avoided.
For example, when aluminum nitride powder is used as the inorganic powder of the raw material, the final product, ceramic, has extremely high quality, and is widely used as a circuit board or a heat sink of various electronic devices.

  Examples and Comparative Examples will be described below in order to more specifically describe the present invention, but the present invention is not limited to these Examples.

<Example 1>
5 parts by weight of yttria as a sintering aid, 5 parts by weight of polybutyl methacrylate as a binder, and digserin mono as a dispersant are added to 100 parts by weight of aluminum nitride powder (H grade No. 1) produced by the alumina reduction nitriding method. 0.5 parts by weight of oleate and 120 parts of toluene as a solvent were mixed in a nylon ball mill for about overnight using steel balls coated with nylon to obtain about 200 kg of aluminum nitride slurry. The viscosity of this slurry was about 10 mPa · s.

  This slurry is pressure-fed to a viscose rayon thread-wound type filter element having an outer diameter of 60 mm, a length of 250 mm, and a filtration accuracy of 50 μm to obtain a purified slurry. Transferred to.

A magnet filter of 10,000 gauss was set at 0.8 m before being put into the spray dryer and passed therethrough, and then aluminum nitride granules were produced by spray drying. Using the granules, a dry pressing method was used to prepare an aluminum nitride molded body, which was then degreased and sintered to produce 30 sintered bodies having a diameter of 200 mm and a thickness of 2 mm. After polishing the surface of the sintered body, the presence or absence of foreign matter having black spots and white spots was visually confirmed.
Further, when the matter attached to the magnet filter was analyzed with an X-ray microanalyzer, it was confirmed that Fe, Ni, and Cr were contained. Its weight was 0.8 g.

<Comparative Example 1>
Aluminum nitride granules were produced in the same manner as in Example 1 except that the particles were not passed through the magnet filter. Using the granules, a dry pressing method was used to prepare an aluminum nitride molded body, which was then degreased and sintered to produce 30 sintered bodies having a diameter of 200 mm and a thickness of 2 mm. After polishing the surface of the sintered body, the presence or absence of black spots and white spots was visually confirmed. As a result, the presence of the spots was recognized in 2 out of 30 sheets.

Claims (4)

A slurry preparing step of preparing a slurry comprising a mixture containing a non-magnetic inorganic material powder and a solvent, including a step of introducing the slurry into a spray-drying apparatus and granulating the same, in a method for producing granules for ceramic production,
Immediately before the slurry is introduced into a spray drying apparatus, an impurity removing step of contacting the slurry with a magnet to remove magnetic metal impurities contained in the slurry is provided. A method for producing granules.   2. The method for producing granules for ceramic production according to claim 1, wherein a filtration step of filtering the slurry with a filter medium having an aperture of 10 to 100 μm is provided prior to the impurity removing step. 3.   The method for producing granules for ceramic production according to claim 1 or 2, wherein the viscosity (20 ° C) of the slurry introduced into the impurity removal step is 0.02 to 2000 mPa · s.   The method for producing granules for ceramic production according to any one of claims 1 to 3, wherein the nonmagnetic inorganic material is aluminum nitride.