JPH1135377A - Production of ceramic granulated powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To comminute the whole ceramic granular body into a ceramic powder having an almost uniform grain diameter. SOLUTION: A ceramic granular body 11 having 1-3 mm grain diameters is first crushed by a medium-agitated dry crusher 12, and the crushed ceramic powder 13, a binder and an org. solvent 15 are mixed to prepare a slurry 14 Of specified concn. The slurry 14 is pressurized by a pump 14, and the pressurized slurry 14 is supplied to a spray drier and dried to obtain a ceramic granulated powder. The pressurized slurry 14 is supplied to a medium-agitated wet crusher 18 between the pressurizing and spray-drying of the slurry 14, and the ceramic coarse grain contained in the ceramic powder 13 in the slurry 14 is crushed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a ceramic granulated powder by preparing a slurry from ceramic powder obtained by pulverizing ceramic particles and spray-drying the slurry. is there.

[0002]

2. Description of the Related Art Conventionally, as a method for producing this kind of ceramic granulated powder, first, a ceramic powder having a particle diameter of 1 to 3 mm is pulverized by a media stirring type dry pulverizer. A binder, an organic solvent, a plasticizer, a dispersant, and the like are added to the body, and the mixture is mixed with a stirrer to prepare a slurry. Then, the slurry is pressurized by a pump, supplied to a spray dryer, and further spray-dried with the dryer. A method for producing a ceramic granulated powder is known. The media stirring type dry pulverizer has a tank body,
A rotating shaft inserted into the tank body from above, a motor with a speed reducer driving the rotating shaft, and a plurality of round cross-sections provided at predetermined intervals on the outer peripheral surface of the rotating shaft in the radial direction. A stirring arm.

A predetermined amount of ceramic powder and granules and a predetermined amount of media (ZrO ₂ having a diameter of 5 mm) are placed in a tank body of the pulverizer.
Ball) and the rotating shaft and the stirring arm are driven to rotate by the motor for a predetermined time, and the rotation of the stirring arm imparts a centrifugal force and a rotating force to the media, and the media moves up and down. By repeating this, the ceramic powder is pulverized to obtain finely divided ceramic powder. Further, the ceramic granulated powder produced by the above method is filled in a predetermined mold, formed into a predetermined shape by a press machine, and further fired after removing the binder, thereby obtaining a ceramic sintered body product.

[0004]

However, in the above-mentioned conventional method for producing a ceramic granulated powder, the ceramic powder supplied to the tank body is fluidized by the stirring arm and the medium in the tank body, It is difficult to pulverize the ceramic powder to a desired particle size, and ceramic coarse particles having a small but relatively large particle size remain.
For example, when an electro-fused MgO powder having an average particle diameter of 1 mm is pulverized for about 4 hours by a dry pulverizer of a media stirring type, a finely pulverized MgO powder having an average particle diameter of 1.5 μm is obtained.
However, this MgO powder had a problem that approximately 0.05 to 0.1% of relatively large MgO coarse particles having a particle size of about 100 μm remained. As a result, the strength of the MgO sintered product obtained by molding and firing the MgO powder containing the MgO coarse particles is reduced because the MgO coarse particles are likely to be a starting point of destruction. If the MgO coarse particles are disposed on the surface, only the portion of the MgO coarse particles is darkened and the color tone changes, so that there is a problem that the commercial value of the product is reduced. An object of the present invention is to provide a method for producing a ceramic granulated powder capable of pulverizing all the ceramic powder into a ceramic powder having a substantially uniform particle size.

[0005]

The invention according to claim 1 is
As shown in FIG. 1, a step of pulverizing a ceramic powder 11 having a particle diameter of 1 to 3 mm by a media stirring type dry pulverizer 12, and mixing a pulverized ceramic powder 13, a binder, and an organic solvent 15. Preparing a slurry 14 having a predetermined concentration, pressurizing the slurry 14 by a pump 22, and supplying the pressurized slurry 14 to a spray dryer and spray-drying to obtain ceramic granulated powder. And a method for producing a ceramic granulated powder comprising: The characteristic configuration is that the pressurized slurry 14 is supplied to the media stirring type wet pulverizer 18 between the pressurizing step of the slurry 14 and the spray drying step of the slurry 14 so that the ceramic powder 13 in the slurry 14 is supplied. And a step of pulverizing the ceramic coarse particles contained in the above. In the method for producing a ceramic granulated powder according to the first aspect of the present invention, the ceramic powder 13 obtained by pulverization by a media stirring type dry pulverizer 12 contains ceramic coarse particles. Since the particles are pulverized by the media stirring type wet pulverizer 18, the particle diameter of the ceramic powder 13 becomes uniform.

The invention according to a second aspect is the invention according to the first aspect, further comprising a slurry inlet 18f formed at a lower end and a slurry outlet 18f at an upper end as shown in FIG. 18g is formed, and the slurry 14 adjusted to a predetermined concentration is supplied to the pump 2
After the ceramic coarse particles contained in the ceramic powder 13 in the slurry 14 are pulverized in the case 18a by being continuously supplied from the slurry inlet 18f to the case 18a by the
The slurry 14 is discharged from the slurry outlet 18g. In the method for producing a ceramic granulated powder according to the second aspect, the slurry 14 of the ceramic powder 13 containing the coarse ceramic particles is supplied to the case 1 by the pump 22.
The slurry 14 is supplied to the case 8a and rises inside the case 18a. At this time, the ceramic coarse particles in the slurry 14 settle because they are heavier than the finely-divided ceramic powder 13 and have a lower slurry rising speed.

[0007]

Embodiments of the present invention will now be described with reference to the drawings. As shown in FIG. 1, an apparatus for producing ceramic granulated powder is a media stirring type dry pulverizer 12 for pulverizing ceramic powder 11 having a particle size of 1 to 3 mm.
, A ceramic powder 13 containing ceramic coarse particles, a binder and an organic solvent 15 are mixed to form a slurry 1 having a predetermined concentration.
4, a media stirring type wet pulverizer 18 for pulverizing ceramic coarse particles contained in the ceramic powder 13 in the slurry 14, and a wet pulverizer 1
A spray dryer (not shown) for producing ceramic granulated powder by spray-drying the slurry 14 discharged from 8.

The media-agitation type dry pulverizer 12 includes a tank body 12a, a rotating shaft 12b inserted into the tank body 12a from above, a motor 12c with a speed reducer for driving the rotating shaft 12b, and a rotating shaft 12b. It has a plurality of stirring arms 12d having a circular cross section and extending in the radial direction at predetermined intervals on the outer peripheral surface, and a number of media 12e accommodated in the tank body 12a. Media 12e is Z
It is preferably formed into a sphere having a diameter of 4 to 6 mm by rO ₂ or the like. A discharge pipe 1 is provided at the lower end of the tank body 12a.
The discharge pipe 12f is provided with a valve 12g for opening and closing the discharge pipe 12f. A screen (not shown) is provided integrally with the valve 12g, and the screen is configured to allow the passage of the ceramic powder 11 and prevent the passage of the medium 12e. The cooling water 12i is provided on the outer peripheral surface of the tank body 12a.
Is provided.

[0009] A separating device 19 is provided below the dry mill 12. The separation device 19 includes a vibrator 19a, a housing 19b installed on the vibrator 19a, and a net 19e that partitions the housing 19b into an upper chamber 19c and a lower chamber 19d. At the upper end of the housing 19b, an inlet pipe 19f into which the discharge pipe 12f can be loosely inserted is protruded. The mesh 19e preferably has an opening of 0.05 to 0.1 mm, and this mesh 19e prevents passage of ceramic coarse particles or agglomerated powder having a predetermined particle size or more, and prevents the ceramic powder 13 and the predetermined size. Is configured to allow passage of ceramic coarse particles having a particle size smaller than the particle size. The reason why the mesh size of the net 19e is limited to the above range is that if the mesh size is less than 0.05 mm, the powder is liable to be clogged, and if the mesh size exceeds 0.1 mm, coarse particles having a large diameter pass through and adversely affect the subsequent process. It is. The slurry preparing means 16 includes a container 16a, a rotating shaft 16b inserted into the container 16a from above, a motor 16c with a speed reducer for driving the rotating shaft 16b, and a stirring blade 16d fixed to a lower end of the rotating shaft 16b. Having. Reference numeral 21 in FIG.
Is a measure for measuring the weight of the ceramic powder 13 containing ceramic coarse particles.

The media stirring type wet crusher 18 includes a case 18a, a rotating shaft 18b inserted into the case 18a from above, a motor 18c with a speed reducer for driving the rotating shaft 18b, and an outer peripheral surface of the rotating shaft 18b. It has a plurality of stirring arms 18d having a circular cross-section and extending in the radial direction at predetermined intervals, and a number of media 18e accommodated in a case 18a. The diameter and height of the case 18a depend on the slurry flow rate in the case 18a required for sedimentation of coarse particles in the slurry 14 in the case 18a and the case 1
It is determined by the supply amount of the slurry 14 per time flowing into the 8a. The desired slurry flow rate in this case 18a is about 2 to 5 cm / min. The rotation speed of the rotating shaft 18b is preferably in the range of 30 to 300 rpm, and the medium 18e is made of ZrO ₂ or the like to have a diameter of 4 to 6 mm.
Is preferably formed in a sphere.

The rotation speed of the rotating shaft 18b is usually 250 rpm
m, but when the ceramic coarse particles are extremely small or the slurry flow rate is low, about 30 rpm is sufficient. When it is desired to completely crush the ceramic coarse flow, or when the ceramic powder has an average particle size of about 1.5 μm. When it is desired to further reduce the size of the powder 13, it is preferable to set the pressure to about 300 rpm. This is because the rotation speed of the rotating shaft 18b is 300 rpm
Even if it exceeds m, the degree of pulverization does not change, and the media 18e and the stirring arm 18d may be rather worn.

A slurry inlet 18f and a slurry outlet 18g are formed at a lower end and an upper end of the case 18a, respectively, and screens 18h and 18i are built in the slurry inlet 18f and the slurry outlet 18g, respectively. These screens 18h and 18i are configured to block the passage of the medium 18e and allow the passage of the ceramic powder 13 and the ceramic coarse particles. Reference numeral 22 in FIG. 1 denotes a pump for supplying the slurry 14 prepared by the slurry preparation means 16 to the wet mill 18. This pump 22
It is preferable to use a diaphragm pump, a roller pump, a screw pump, or the like. The spray dryer is a closed type granulator.

A method for producing the ceramic granulated powder thus constituted will be described. First, a ceramic powder 11 having a particle size of 1 to 3 mm is pulverized by a dry pulverizer 12 of a media stirring type. As the ceramic powder 11, electro-fused MgO,
Ceramic powders 11 such as alumina, mullite, spinel, cordierite and the like can be mentioned. In a tank body 12a of the crusher 12, a predetermined amount of ceramic powder 11 and a predetermined amount of media 12e (ZrO ₂ balls having a diameter of 4 to 6 mm) are respectively charged with a valve 12g closed, and a speed reducer is provided. The rotating shaft 12b and the stirring arm 12d are driven to rotate by the motor 12c for 0.5 to 8 hours. The rotation of the stirring arm 12d imparts a centrifugal force and a rotational force to the medium 12e and a vertical movement, and the medium 12e repeats collision and rotation, whereby the ceramic powder 11 is pulverized, and the average particle diameter is 1 to 10 μm. Ceramic powder 1
3 is obtained. Here, in order to obtain the ceramic powder 13 having the target average particle size, the control is usually performed by the pulverization time. For example, in the case of the MgO powder, the average particle diameter becomes about 10 μm when the pulverization time is 30 minutes, and it is completely pulverized in about 4 hours. It is also possible to control the grinding time in combination with the rotation speed of the rotating shaft.

Since the crusher 12 is of a dry type, it is agitated and crushed.
Although frictional heat is generated in the tank body 12a due to friction during mixing and pulverization, the cooling water 12
By flowing i, the tank body 12a is cooled. The ceramic powder 11 supplied to the tank body 12a
Is fluidized by the stirring arm 12d and the medium 12e in the tank body 12a, but it is difficult to pulverize all the ceramic particles 11 to a desired particle size.
The particle size is as small as 0.5 to 0.1% by weight but 100 μm.
A relatively large amount of ceramic grit remains. When the valve 12g is opened after the completion of the pulverization, the ceramic powder 13 containing the ceramic coarse particles is removed from the housing 19a of the separation device 19.
The ceramic powder 13 containing ceramic coarse particles having a particle size smaller than a predetermined particle size is dropped by the vibration of the vibrator 19a.
e and falls into the lower chamber 19d. At this time, the ceramic coarse powder having a predetermined particle size or more remains on the net 19e.

Next, a slurry 14 having a predetermined concentration is prepared by mixing a ceramic powder 13 containing ceramic coarse particles smaller than a predetermined particle size, a binder and an organic solvent 15. The concentration of the slurry 14 is preferably 45 to 75% by weight. The reason why the concentration of the slurry 14 is limited to 45 to 75% by weight is that if it exceeds 75% by weight, the slurry 14 is non-aqueous, so that there is a problem that stable granulation is difficult.
If the content is less than 45% by weight, a dense ceramic sintered product having a uniform structure cannot be obtained. That is, when the concentration of the slurry 14 is limited to the above range, the viscosity of the slurry 14 becomes 200 to 1000 cps, the granulation of the ceramic powder 13 by the spray dryer can be performed stably, and the density of the compact increases. And a dense ceramic sintered product can be manufactured. As the binder, polyethylene glycol or polyvinyl butyral, etc.
It is preferable to use ethanol, propanol, or the like as the organic solvent 15, and the binder is 0.2 to 2.5% by weight.
It is preferred to add. It is also preferable to add a dispersant such as a maleic polyanion, a fatty acid ester or a phosphate anion, or a plasticizer such as stearic acid.

Next, the slurry 14 adjusted to a predetermined concentration
Is pressurized by a pump 22 and supplied to a case 18a from a slurry inlet 18f of the wet crusher 18, and the slurry 14 rises in the case 14 at a relatively slow speed. At this time, the ceramic coarse particles in the slurry 14 settle because they are heavier than the finely divided ceramic powder 13 and the rising speed of the slurry 14 is slow. As a result, the ceramic coarse particles are reliably pulverized by the wet pulverizer 18 and have an average particle diameter of 0.5 to
Since the ceramic powder having a size of 1.5 μm is discharged from the slurry outlet 18g, the ceramic powder 13 in the slurry 14 supplied to the spray dryer does not contain any ceramic coarse particles. The reason why the average particle size of the ceramic powder 13 is limited to the range of 0.5 to 1.5 μm is that
If it is less than μm, the powder 13 is too fine and agglomerates, so that the handling of the powder 13 is deteriorated and it becomes difficult to prepare a high-concentration slurry 14 of 45% by weight or more. It is difficult to control the microstructure,
This is because a dense ceramic sintered body product cannot be obtained.
Further, when the average particle size of the ceramic powder 13 is limited to the above range, there is an advantage that a desired ceramic sintered body product can be obtained without using a sintering aid.

Further, the pressure of the pump 22 causes the case 18 a
The slurry 14 discharged from the slurry outlet 18g is supplied to a spray dryer and then spray-dried by the dryer to obtain a ceramic granulated powder.
A ceramic sintered product is obtained by molding, removing the binder, and firing the ceramic granulated powder. At this time, the particle size of the ceramic powder in the product is substantially uniform, that is, since no ceramic coarse particles are mixed,
The bending strength of the sintered product is high and the color tone of the surface is uniform without change.

[0018]

Next, examples of the present invention will be described together with comparative examples. <Examples 1 to 5> As shown in FIG.
60 kg of commercially available MgO powder and granules 11 to 3 mm, and 300 kg of ZrO ₂ medium 12 e having a diameter of 5 mm are put into the tank main body 12 a of the dry-type crusher 12 of the media stirring type, and the rotating shaft 12 b is rotated at 260 rpm. For 4 hours to pulverize the MgO powder 11 to obtain an MgO powder 13 having an average particle size of about 1.5 μm. The above dry mill 1
The diameter and height of the second tank body 12a are 800
mm and 750 mm.

Next, the MgO powder 13 and the medium 12
e into the separation device 19, the mesh 19e having an opening of 0.1 mm, the MgO powder 13 and MgO coarse particles having a particle size of less than 0.1 mm, and MgO coarse particles having a particle size of 0.1 mm or more. Is separated into The amount of MgO coarse particles having a particle diameter of less than 0.1 mm, that is, relatively large particle diameters of about 100 μm mixed into the MgO powder 13 is small. This Mg
60 kg of MgO powder 13 containing O coarse particles is weighed, 44.4 kg of ethanol 15 (organic solvent), 6 kg of binder,
Along with 750 cc of a phosphate ester-based anion (dispersant) and 160 g of stearic acid (plasticizer), they are charged into the container 16a of the slurry preparation means 16 and stirred for 1 hour to give a concentration of
A weight% slurry 14 was prepared. Here, the stirring time of 1 hour is empirically sufficient for 1 hour, and the concentration of 60% is used to obtain the optimum granulated powder and to prevent the blockage and pulsation of the system. Determined empirically from

Next, the slurry 14 is pressurized by a diaphragm pump 22 so as to be wet by a media stirring type wet pulverizer 18.
The slurry 18 was supplied to the case 18a through the slurry inlet 18f, and the rotating shaft 18b was rotated at a rotation speed of 200 rpm to grind the MgO coarse particles contained in the MgO powder 13 in the slurry 14. The diameter and height of the case 18a are each 250 m.
m and 250 mm, and the slurry 14
Was supplied at a rate of 100 liters / hour. As a result, the slurry flow rate in the case 18a required for sedimentation of the coarse particles in the slurry 14 in the case 18a (3.4 cm)
/ Min). The pressure inside the case 18a is 2 kg.
/ Cm ² . The MgO powder 13 in the slurry 14 discharged from the slurry outlet 18g is spray-dried with a spray dryer (not shown) to produce MgO granulated powder, and then molded, debindered, and fired to obtain a width × thickness. X
Test pieces having a total length of 3 mm × 4 mm × 36 mm were obtained. Five test pieces were prepared, and Examples 1 to 5 were prepared.

<Comparative Examples 1 to 5> The slurry obtained in the same manner as in Examples 1 to 5 was directly supplied to a spray dryer without supplying to a media stirring type wet pulverizer.
Examples 1-5 except that O-granulated powder was produced
In the same manner as described above, five test pieces were obtained. These test pieces were Comparative Examples 1 to 5.

<Comparative Test 1 and Evaluation> Each of the test pieces of Examples 1 to 5 and Comparative Examples 1 to 5 was subjected to a three-point bending test. Table 1 shows the results and average values of Examples and Comparative Examples. The three-point bending test is a breaking strength (bending strength) test based on JIS R1601.

[0023]

[Table 1]

As is clear from Table 1, the three-point bending strength of the test piece of the comparative example was about 1200 kgf / cm ² on average, while the average value of the test piece of the example was about 190 kgf / cm ^2.
It improved by about 35% to 0 kgf / cm ² . As described above, the test piece of the comparative example has a lower flexural strength and a large variation as compared with the test piece of the example.
MgO powder with a relatively large particle size of about 100 μm
This is considered to be because coarse particles are slightly mixed in and the MgO coarse particles serve as starting points of bending fracture. Mg in the slurry
Since the amount of MgO coarse particles contained in the O powder is small,
The ability as a pulverizer necessary for pulverizing the MgO coarse particles is extremely small. As a result, even if the capacity of the case of the wet pulverizer is extremely small, about 1/30 of the capacity of the dry pulverizer, the MgO coarse particles can be reliably pulverized, and the production cost of the wet pulverizer can be relatively small.

<Example 6> The MgO granulated powder obtained in the same manner as in Examples 1 to 5 was placed in a mold having a predetermined shape and placed in a mold.
A ring-shaped molded body is formed by uniaxial pressure molding at a pressure of 00 kg / cm ² , and the molded body is subjected to a binder removal treatment and sintering.
An MgO insulating ring for a fuel cell of mm × 224 mm × 8 mm was obtained. 100 insulating rings were produced. The reason why pressurized MgO granulated powder at 1500 kg / cm ² is because generally raw (raw) of the shaped body at a pressure of 1500 kg / cm ² density is saturated. <Comparative Example 6> MgO obtained in the same manner as in Comparative Examples 1 to 5
An MgO insulating ring was obtained from the granulated powder in the same manner as in Example 6 above. 100 insulating rings were produced.

<Comparative test 2 and evaluation>
The surfaces of each of the 100 MgO insulating rings and the 100 MgO insulating rings of Comparative Example 6 were visually observed to examine the presence or absence of uneven color tone (dark spots). As a result, uneven color tone and crater-like dents caused by MgO coarse particles occurred on the surface of 40 insulating rings of the 100 insulating rings of Comparative Example 6, while 100 No irregular color tone or crater-like dent was generated on the insulating ring.

[0027]

As described above, according to the present invention, between the step of pressing the slurry and the step of spray-drying the slurry,
A step of pulverizing the ceramic coarse particles contained in the ceramic powder in the slurry by supplying the pressurized slurry to a media stirring type wet pulverizer was added. Although the obtained ceramic powder contains ceramic coarse particles, the ceramic coarse particles are pulverized by a media stirring type wet pulverizer. As a result, the particle size of the ceramic powder becomes uniform. The slurry of the ceramic powder is spray-dried with a spray dryer to obtain a ceramic granulated powder, and the ceramic sintered product obtained by molding and firing the ceramic granulated powder is a ceramic powder. Is substantially uniform and does not contain any ceramic coarse particles, so that the bending strength of the sintered product is high and the color tone of its surface is uniform without change.

Further, a media stirring type wet pulverizer has a case in which a slurry inlet is formed at a lower end and a slurry outlet is formed at an upper end, and a slurry adjusted to a predetermined concentration is continuously supplied from the slurry inlet to the case by a pump. Then, after crushing the ceramic coarse particles contained in the ceramic powder in the slurry in the case, and discharging the slurry from the slurry outlet, the slurry of the ceramic powder containing the ceramic coarse particles is supplied to the case by a pump, Rises in the case. At this time, the ceramic coarse particles in the slurry sediment because they are heavier than the finely divided ceramic powder and have a lower slurry rising speed. As a result, the ceramic coarse particles are surely pulverized by the wet pulverizer and then discharged from the slurry outlet, so that the ceramic powder in the slurry supplied to the spray dryer contains no ceramic coarse particles at all.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an apparatus for producing a ceramic granulated powder according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 11 MgO powder (ceramic powder) 12 Dry pulverizer 13 MgO powder (ceramic powder) 14 Slurry 15 Ethanol (organic solvent) 18 Wet pulverizer 18a Case 18f Slurry inlet 18g Slurry outlet 22 Pump

Claims (2)

[Claims] A ceramic powder having a particle size of 1 to 3 mm.
Step 1) pulverizing 1) with a media stirring type dry pulverizer (12), and a slurry (14) having a predetermined concentration by mixing the pulverized ceramic powder (13), a binder and an organic solvent (15). And pressurizing the slurry (14) with a pump (22); and supplying the pressurized slurry (14) to a spray dryer and spray-drying to obtain a ceramic granulated powder. The method for producing a ceramic granulated powder comprising: a step of wet-pulverizing a slurry (14) pressurized between a step of pressurizing the slurry (14) and a step of spray-drying the slurry (14) by a media stirring type. The slurry is supplied to the machine (18).
A method for producing a ceramic granulated powder, comprising a step of crushing ceramic coarse particles contained in the ceramic powder (13) in (14). 2. A media stirring type wet pulverizer (18) has a slurry inlet (18f) formed at a lower end and a slurry outlet (18f) at an upper end.
g) is formed, a slurry (14) adjusted to a predetermined concentration is continuously supplied to the case (18a) from the slurry inlet (18f) by a pump (22), and the case (18a) is formed. The slurry (14) is discharged from the slurry outlet (18g) after the ceramic coarse particles contained in the ceramic powder (13) in the slurry (14) are crushed in (18a). Method for producing ceramic granulated powder.