JP4479451B2 - Method for adjusting moisture content of ceramic granules - Google Patents

Description

  The present invention relates to a method for adjusting moisture content of ceramic granules particularly suitable for molding by a dry pressure molding method, ceramic granules, a ceramic molded body, a ceramic sintered body, and an electronic component.

  Ceramics are widely used in electronic parts, and the ceramics are formed by using a ceramic material and obtained by firing the formed body.

  As one of the methods for forming a ceramic formed body, a dry pressure forming method is widely used because it is relatively simple and low in cost and can be mass-produced. When forming a ceramic compact by dry pressure molding, it is common to granulate ceramic particles into ceramic granules for the purpose of improving the handling and operating characteristics of powder transportation, packaging, and molding. is there.

  As a method for granulating ceramic granules, generally, an aqueous slurry prepared from a ceramic raw material, a binder, and water is spray-dried using a spray dryer or the like to granulate ceramic granules (spray drying method), or ceramic. There is known a method (oscillating extrusion method) or the like in which a raw material and a binder solution are stirred and mixed, and drying and oscillating extrusion granulation are repeated to granulate ceramic granules. The spray drying method is easy to control the particle size distribution and is suitable for producing a large number of ceramic granules with relatively small particle size. The granulation method by oscillating extrusion is easy to handle and has a small scale. Suitable for producing relatively compacted granules. These granulation methods are appropriately selected depending on the molded product to be produced, the mold used, the production scale, and the like.

  By the way, the ceramic granule used for forming into a ceramic molded body needs to contain appropriate moisture. If the water content in the ceramic granule is small, the strength of the ceramic molded body obtained by molding the ceramic granule will not be high, and it may be damaged by a slight impact or a crack may occur during handling. On the other hand, if the amount of moisture is too large, the ceramic granules may stick to the inner surface of the mold during dry pressure molding and may cause sticking.

  Considering the spray drying method as an example, granulation by this method is difficult to take out while leaving moisture in the granule, and the granulated ceramic granule is almost in a dry state. Therefore, conventionally, proposals have been made to impart appropriate moisture to the granulated ceramic granules.

  For example, in Patent Document 1, by spraying relatively large droplets having an average particle diameter D50 of about 40 μm produced using a two-fluid nozzle in a short time of about several minutes on the granulated ceramic granules. The moisture content of the granulated ceramic granules was adjusted. According to this method, a target value (for example, about 0.3 to 0.5% by weight) can be obtained for the average moisture content of the entire ceramic granule. However, when relatively large droplets as in Patent Document 1 are sprayed in a short time, there is a tendency that the variation in the water content of each granule increases. Even if the average moisture content of the whole granule shows the target value, if there is a variation in the moisture content of each granule, sticking may occur on the inner surface of the mold during dry pressure molding, In some cases, the resulting molded product may have poor appearance or troubles during continuous molding.

  Moreover, in patent document 2, the moisture content of a ceramic granule is adjusted by introduce | transducing the air warmed with the steam with respect to the ceramic granule after granulation. However, the technique of Patent Document 2 also has a disadvantage in that the content of water content in each granule increases as in the technique of Patent Document 1, and aggregates are easily generated in the entire ceramic granule.

In particular, in recent years when there has been a demand for further downsizing and thinning of molded products, the average moisture content of the entire ceramic granule can be adjusted to the target value, and the variation in the moisture content of each granule is reduced. In addition, a technique that can suppress the generation of aggregates is strongly desired. Specifically, it is important to adjust the water content of each granule with an accuracy within a target water content of ± 0.1%.
JP 2000-327431 A JP-A-5-275257

  The object of the present invention is to adjust the average moisture content of the whole granule to a target value, reduce variation in the moisture content of each granule, and suppress the generation of aggregates. Moisture adjustment method, ceramic granule whose water content is adjusted by the method, ceramic molded body obtained by dry pressing the ceramic granule, ceramic sintered body obtained by firing the ceramic molded body, and ceramic sintered body An electronic component having a core material to be provided.

  By applying fine droplets (mist) having a fine particle size over a long period of time, the present inventors can adjust the average moisture content of the whole granule to a target value, and the moisture content for each granule. The present inventors have found that the variation in the amount can be reduced and completed the present invention.

According to the present invention, ceramic granules are placed inside a capsule container that is rotatable about an axial axis and that can swing vertically and horizontally with respect to the axial direction.
Moisture of ceramic granules characterized by spraying mist that is fine droplets in the capsule container while rotating and swinging the capsule container, thereby providing moisture to the ceramic granules in the capsule container An adjustment method,
Spraying mist at a feed rate of 0.5-4 liters / hour and a feed time of 5 minutes or more,
By giving moisture to the ceramic granules, the average moisture content of the ceramic granules is 0.2 to 0.8 wt%, and then dried,
Provided is a method for adjusting the moisture content of ceramic granules that is dried for 2 minutes or more at such a rate that the moisture content of the ceramic granules after moisture is removed is removed at 0.005 to 0.08 wt% / min.

  Preferably, a mist having a 50% average particle diameter (D50) of 1 to 30 μm is sprayed.

  Preferably, the mist produced with the ultrasonic humidifier is sprayed.

  Most preferably, a mist having a 50% average particle diameter (D50) of 1 to 30 μm produced by an ultrasonic humidifier is sprayed.

  Preferably, the capsule container is rotated and oscillated at a rotational speed of 20 to 70 Hz and an oscillation speed of 20 to 70 Hz.

  Preferably, mist is sprayed into the capsule container, and at the same time, excess mist that has not adhered to the ceramic granules is discharged to the outside of the capsule container.

  Preferably, the capsule container is dried while sucking.

  Preferably, the capsule container is dried while being heated while sucking the inside of the capsule container.

  Most preferably, after the mist is sprayed at a supply rate of 1 to 3 liters / hour and a supply time of 10 minutes or more, the water content of the ceramic granules after moisture application is 0.005 to 0.02% by weight / minute. Dry for at least 5 minutes at such a speed that it can be removed. In this way, by slowly applying moisture and then slowly drying, the average moisture content of the resulting ceramic granules is adjusted to the target value, and at the same time, the moisture content of each granule varies. Can be effectively reduced.

  In the ceramic granules whose water content is adjusted by the method of the present invention, the average water content of the whole granule is adjusted to a target value, and there is little variation in the water content of each granule. Specifically, the average moisture content of the whole granule is 0.2 to 0.8% by weight, and the variation of the moisture content of each granule is controlled within ± 0.1% of the average moisture content of the whole granule. it can. Moreover, there is little generation | occurrence | production of the aggregate. The exquisite moisture-adjusted ceramic granule has excellent low-pressure crushing properties. For example, when continuous molding is performed by a dry pressure molding method, sufficient sticking resistance can be exhibited, and the resulting molding can be obtained. It is possible to obtain a molded body that is less likely to cause a poor appearance of the body and that has excellent dimensional accuracy.

  By using a ceramic molded body obtained by molding ceramic granules whose moisture has been adjusted by the method of the present invention, it can be expected to realize further miniaturization and thinning, which are demands from the industry.

Embodiments of the present invention will be described below.
1 (A) and 1 (B) are schematic views of a moisture adjusting device for ceramic granules according to an embodiment of the present invention, and FIG. 1 (C) is a cross section taken along line IC-IC in FIG. 1 (A). Figure,
FIG. 2 is a graph showing the relationship between each molding pressure and molded body density in Example 2 and Comparative Example 2.
3 (A) to 3 (C) are SEM photographs showing the collapsed state of the side surface of the ceramic molded body when the molding pressure was changed in Example 2. FIG.
4A to 4C are SEM photographs showing the collapsed state of the side surface of the ceramic molded body when the molding pressure is changed in Comparative Example 2. FIG.
[Ceramic granules]

The ceramic granule according to the present invention is produced by granulating mainly ceramic particles and a binder (including optional components added as necessary), similarly to the conventional ceramic granule.
[Ceramic powder]

  It does not specifically limit as ceramic powder, According to the use of the ceramic molded object shape | molded finally, it selects suitably. Typical examples include metal oxide ceramics such as ferrite, alumina and zirconia, non-oxide ceramics such as silicon carbide and silicon nitride, barium titanate, titanium / zirconate, and composites thereof. . These ceramic powders may be used alone or as a mixture of two or more.

The particle size of the ceramic powder may be appropriately selected within the range conventionally used as a raw material for a ceramic molded body as a final product, and is generally about 0.5 to 5 μm, preferably about 0.7 to 3 μm.
[binder]

In granulating the ceramic granule according to the present invention, a normal binder is used. As this binder, it can select arbitrarily from the well-known thing generally used in the granulation of the conventional ceramic powder, and can use it. Examples of such a binder include partially saponified products of polyvinyl alcohol and polyvinyl acetate, polyacrylic acid, methyl cellulose, acrylamide homopolymers and copolymers, and the like. These binders are generally used in the range of 0.4 to 5 parts by mass, preferably 0.6 to 2 parts by mass with respect to 100 parts by mass of the ceramic powder.
[Optional ingredients]

When granulating the ceramic granule according to the present invention, various conventionally known additives can be added as desired within a range that does not impair the object and effect of the present invention. Examples of such additives include dispersants such as polycarboxylates, condensed naphthalene sulfonic acids, plasticizers such as glycerin, glycols and triols, waxes, lubricants such as stearic acid (salts), polyethers, Examples thereof include organic polymer flocculants such as urethane-modified polyether-based, polyacrylic acid-based, and modified acrylic acid-based polymers, and inorganic flocculants such as aluminum sulfate, aluminum chloride, and aluminum nitrate.
[Granulation]

  In the present invention, each of these components is granulated into ceramic granules by a conventionally known method. The granulation at this time can be performed by a conventionally known spray-drying granulation method or oscillating extrusion granulation method. Specifically, the above-described ceramic particles, binder, and a slurry in which various additives are dispersed in water as necessary are prepared, and the slurry thus prepared is spray-dried with a spray dryer or the like, or ceramics. Particles, binders, and various additives as required are mixed and granulated with a stirring granulator to produce granulated powder, and this granulated powder is repeatedly extruded and granulated with an oscillating granulator and dried. Thereby, the ceramic granule of this invention is produced.

  The shape and particle size of the granules thus granulated are appropriately selected depending on the granulation method, the shape of the target molded product, and the like. In general, the ceramic granules granulated by spray drying are usually 30 to 250 μm, preferably 60 to 200 μm, more preferably 80 to 150 μm spherical. Moreover, the granule granulated by oscillating extrusion is 80-500 micrometers normally, Preferably it is 100-300 micrometers, More preferably, it is 125-200 micrometers.

Thus, the moisture content of the ceramic granule granulated by the conventionally known spray-drying granulation method is approximately 0.2% by weight in the whole granule, which is almost completely dry. In addition, the moisture content of ceramic granules granulated by the oscillating extrusion granulation method may be reduced depending on the storage period and state. When such an absolutely dry or dried ceramic granule is subjected to a molding process without any moisture adjustment, the molded ceramic body is cracked, making subsequent use difficult.
[Moisture adjustment]

Therefore, next, in the present invention, moisture adjustment is performed on the above-described granulated ceramic granules. In this embodiment, the case where the water | moisture content adjustment of a ceramic granule is performed using the apparatus shown in FIG. 1 is illustrated.
[Moisture adjustment device]

  As shown in FIGS. 1 (A) and 1 (B), the moisture adjusting device 2 used in the present embodiment has a cylindrical capsule container 4. The capsule container 4 is arranged so as to be rotatable around its axis with respect to the axial direction X by a driving means (not shown). Moisturization of the granulated ceramic granules 3 is performed inside the capsule container 4. The capsule container 4 is placed on the gantry 6. The gantry 6 can be swung vertically and horizontally with respect to the axial direction X of the capsule container 4 by rocking means 8 and 8. Therefore, in synchronization with the swing of the gantry 6, the capsule container 4 placed thereon can also swing.

  Above the inside of the capsule container 4, a spray port 42 is arranged. From the spray port 42, the mist 11, which is a fine droplet generated by the ultrasonic humidifier 10 as an example of the water spray humidifier, is sprayed through the line 43 into the capsule container 4.

  In the present embodiment, a heater 12 is preferably provided on the outer periphery of the capsule container 4. By operating the heater 12, the inside of the capsule container 4 is warmed, whereby the surface moisture of the ceramic granules 3 inside the capsule container 4 can be removed.

  In the present embodiment, it is preferable that a discharge port 44 for discharging excess mist not attached to the ceramic granules 3 to the outside is provided inside the capsule container 4. The discharge port 44 is connected to the line 43 and discharges the saturated mist out of the container 4 by natural exhaust.

As shown in FIG. 1C, the line 43 used in the present embodiment is a double pipe composed of an in-side pipe passing through the inside and an out-side pipe covering the periphery of the in-side pipe. The ultrasonic humidifier 10 and the spray port 42 are connected by an in-side pipe, and the suction means 14 such as a vacuum pump and the discharge port 44 are connected by an out-side pipe.
[Moisture adjustment method]

  Next, a method for adjusting the moisture content of the ceramic granules using the apparatus 2 will be described.

  (1) First, the granulated ceramic granule 3 is put into the capsule container 4 and the capsule container 4 is swung together with the gantry 6 by operating the swinging means 8 and 8 while rotating the capsule container 4.

  The input amount of the ceramic granules 3 is appropriately determined according to the processing capacity of the capsule container 4.

  The rotational swing condition of the capsule container 4 is a condition in which the ceramic granules 3 in the capsule container 4 are stirred and mixed without being broken. Specifically, the driving means (not shown) is operated so that the rotation speed of the capsule container 4 is, for example, about 20 to 70 Hz, preferably about 20 to 40 Hz. Further, the swinging means 8 and 8 are operated so that the swing number of the capsule container 4 is, for example, about 20 to 70 Hz, preferably about 20 to 40 Hz.

  (2) Next, the ultrasonic humidifier 10 is operated to spray the mist 11 which is a fine droplet into the capsule container 4 from the spray port 42 through the line 43, so that the moisture content of the ceramic granules 3 in the capsule container 4 is given. I do.

  The timing of spraying the mist 11 is preferably performed in a state where the ceramic granules 3 are mixed and mixed to some extent in the capsule container 4 and the aggregation is loosened. Usually, it is preferable to start spraying the mist 11 after about 3 minutes have passed since the capsule container 4 started to rotate.

  In the present invention, the mist 11 is sprayed as fine droplets whose 50% average particle diameter (D50) is controlled to 1 to 30 μm, preferably 5 to 20 μm. If the D50 of the mist 11 to be sprayed is too small, it is difficult to impart moisture to the granules (the granules do not get wet), and conversely if they are too large, agglomerated granules are generated.

  The 50% average particle diameter (D50) of the mist 11 can be measured by, for example, a particle size analyzer using a light scattering method. The particle size analysis using the light scattering method is an analysis method for measuring the particle size distribution by measuring the scattering angle of Franhofer diffraction or My scattering using a laser beam or a halogen lamp as a light source while circulating the mist 11 to be sprayed. D50 can be determined from the particle size distribution obtained by such a particle size analyzer.

  The ultrasonic humidifier 10 is an apparatus of a system in which water stored in a tank (not shown) is humidified by ultrasonic waves and sprayed in a mist form, and a commercially available apparatus can be used.

  The spraying of the mist 11 performed in the present invention is performed under the condition that the ceramic granules 3 in the capsule container 4 do not aggregate. Specifically, the supply speed, supply time, and rotational swing conditions of the sprayed mist 11 are adjusted as appropriate.

  In the case where the amount of the ceramic granules 3 charged into the capsule container 4 is 20 kg, for example, the sprayed mist 11 has a supply rate of preferably 0.5 to 2 liters / hour, more preferably 0.7 to The supply time is 1.5 liters / hour, preferably 5 minutes or more, more preferably 10 to 30 minutes. In the case where the input amount of the ceramic granule 3 is 100 kg, the mist 11 to be sprayed has a supply rate of preferably 0.5 to 4 liters / hour, more preferably 1 to 3 liters / hour, and a supply time of preferably Is 5 minutes or more, more preferably 10 to 60 minutes. That is, in any case, the mist (fine droplets) 11 is sprayed over a long time. Thus, the dispersion | distribution of a moisture content can be made small by giving a water | moisture content slowly.

  By this step, the moisture content is adjusted to an appropriate range such that the average moisture content of the whole granule is preferably 0.2 to 0.8% by weight, more preferably 0.3 to 0.5% by weight. The moisture content variation of each granule here is expected to be about ± 0.02 to 0.1% of the total average moisture content.

  In the present embodiment, together with the above-described spraying of the mist 11 into the capsule container 4, the excess mist 11 not attached to the ceramic granules 3 can be discharged from the discharge port 44 to the outside through the line 43 by natural exhaust. preferable. If the mist 11 is continuously supplied into the capsule container 4, the capsule container 4 may reach saturation with the mist 11 after a predetermined time. At this time, if the saturated mist 11 is not discharged to the outside, water droplets having a particle diameter larger than the planned particle size may adhere to the ceramic granules 3 and the object of the present invention may not be achieved.

  (3) In this embodiment, it is preferable to dry the ceramic granules 3 in the capsule container 4 next. Drying can be performed by operating the heater 12 attached to the outer periphery of the capsule container 4 and heating the inside of the capsule container 4 so as to be preferably 25 to 90 ° C, more preferably 35 to 75 ° C. . At that time, it is preferable to suck the ceramic container 3 by sucking with a suction means 14 such as a vacuum pump while rotating and swinging the capsule container 4. However, it may be dried only by suction with the suction means 14 without heating. This drying step is preferably performed for about 2 to 60 minutes, more preferably for about 10 to 30 minutes.

  In addition, drying of this process may be performed after the said water | moisture-content provision has settled down, or may be performed simultaneously with water | moisture content.

  The ceramic granule 3 is dried at a rate (drying rate) at which the moisture content of the ceramic granule 3 is removed at 0.005 to 0.08% by weight / min, preferably 2 minutes or more, more preferably 10 to 10%. Do for 30 minutes. That is, when drying is performed after moisture application, it is preferable to perform drying slowly over time, as in the case of moisture application. By slowly drying in this way, the variation in the moisture content of the ceramic granules 3 can be reduced.

  By this step, the total average water content is preferably adjusted to a proper range such as 0.2 to 0.8% by weight, more preferably 0.3 to 0.5% by weight. The variation in the moisture content can be suppressed to preferably within ± 0.1%, more preferably within ± 0.05% of the total average moisture content.

The ceramic granule 3 of the present invention thus obtained is taken out from the capsule container 4 and advanced to the next step.
[Ceramic molded body]

In the present embodiment, a ceramic molded body with high dimensional accuracy can be produced by subjecting the ceramic granules obtained as described above to dry pressure molding using a mold according to a conventional method. The pressing pressure at this time is generally 0.5 to 5 ton / cm ² , preferably 1 to 4 ton / cm ² , as in the usual method. The firing temperature depends on the type of ceramic granules to be used, but is generally in the range of 800 to 1500 ° C, preferably 900 to 1300 ° C.
[Ceramic sintered body and electronic parts]

  In this embodiment, a ceramic sintered body can be obtained by firing the obtained ceramic molded body. Firing is performed in order to obtain a dense sintered body by causing sintering in which the powder adheres at a temperature lower than the melting point between the powder particles of the compact including many voids. Examples of the furnace used for firing include a batch type, a pusher type, and a cart type. The firing temperature is preferably 1000 to 1450 ° C. The firing time is preferably about 1 to 3 hours. Firing may be performed in the air or in an atmosphere having a higher oxygen partial pressure than in the air.

The obtained ceramic sintered body is, for example, for information terminals such as notebook personal computers and PDAs, mobile phones, mobile phones such as PHS, or electronic devices on the premise of carrying such peripheral devices, televisions, It is used as a core material for various electronic components for relatively large home appliances such as stereo.
[Operational effects of this embodiment]

  According to the method for adjusting the moisture content of the ceramic granules using the apparatus 2 according to this embodiment, the average moisture content of the entire granule is adjusted to the target value, and the variation in the moisture content of each granule is small and exquisite. Thus, a ceramic granule in which the water content is adjusted and the generation of aggregates is suppressed can be obtained. The ceramic granules obtained according to the present embodiment are excellent in low-pressure crushing property. For example, when continuous molding is performed by a dry pressure molding method, sufficient sticking resistance can be exhibited, and the appearance of the obtained molded body There is less risk of defects, and a molded body with excellent dimensional accuracy can be obtained.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, Of course, in the range which does not deviate from the summary of this invention, it can implement in various aspects. .

  Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.

  In the following Examples and Comparative Examples, moisture adjustment was performed on the following ceramic granules. That is, as ceramic powder, Ni-Cu-Zn ferrite powder (average particle diameter 1 μm) 66 parts by mass, water 33 parts by mass, binder (polyvinyl alcohol) 1.0 part by mass, dispersant (polycarboxylic acid ammonium salt) 0 .3 parts by mass was mixed with a wet pulverizer to prepare a ceramic slurry. Next, this slurry was rotated at 10,000 rpm with a disk atomizer, and spray granulation was performed using a spray dryer to obtain spherical ceramic granules having an average particle size of 100 μm and a water content of 0.16%.

Example 1
1 was prepared, and 20 kg of the obtained ceramic granules were put into the capsule container 4 of the apparatus 2, and then the capsule container 4 was rotated and swung. The rotation and swing conditions of the capsule container 4 were such that the ceramic granules in the container 4 were stirred and mixed without being broken. Specifically, the capsule container 4 was rotationally oscillated under the conditions of a rotational speed of 20 Hz and an oscillation speed of 20 Hz.

  Five minutes after the capsule container 4 starts rotating and swinging, the ultrasonic humidifier 10 is operated to spray mist, which is a fine droplet, from the spray port 42 into the capsule container 4 through the line 43. Water was given to the inner ceramic granules. The mist was sprayed with a mist having a 50% average particle diameter (D50) of 20 μm at a feed rate of 1.5 liters / hour and a feed time of 32 minutes.

  In this example, along with the spraying of the mist into the capsule container 4, excess mist not attached to the ceramic granules was discharged from the discharge port 44 to the outside through the line 43 by natural exhaust.

  After the mist spraying is finished, the ceramic granules are temporarily taken out from the capsule container 4 and the average moisture content of the whole granules is measured to be 0.68% by weight. I couldn't see it.

Next, after temporarily removing the ceramic granules taken out into the capsule container 4, the heater 12 attached to the outer periphery of the capsule container 4 is operated to heat the inside of the capsule container 4 to 40 ° C. Then, the capsule container 4 was sucked with a vacuum pump (suction means 14) while rotating and swinging, and the ceramic granules were dried for 20 minutes.
The rate at which moisture was removed from the ceramic granules by this drying (drying rate) was 0.017 wt% / min.
[Measurement of average moisture content and variation in moisture content]

  Next, the ceramic granules were taken out from the capsule container 4, and the average moisture content of the entire ceramic granules after moisture adjustment and drying was measured. The results are shown in Table 1.

Moreover, the moisture content variation of each granule was calculated. The moisture content variation of each granule is to sample an arbitrary part of the whole granule 10 times (location), measure the average moisture content at each time, compare each value, and calculate the difference between the maximum value and the minimum value It went by. The results are shown in Table 1.
[Measurement of fluidity]

The fluidity of the obtained ceramic granules was measured for the time (seconds / 50 g) during which 50 g of the granules were allowed to flow down from the funnel defined in JIS-Z2502. The results are shown in Table 2.
[Confirmation of presence of aggregates in granules]

  Confirmation of the aggregate in the obtained ceramic granule was performed by the following method. An arbitrary portion of the whole granule was sampled 10 times (location) 10 g each (total 100 g), and the weight of the aggregate on the sieve after sieving with # 50 (aperture 300 μm) was measured.

Comparative Example 1
Without using an ultrasonic humidifier, a droplet having a 50% average particle diameter (D50) of 40 μm is supplied from a two-fluid nozzle attached to the upper part of the capsule container 4 at a supply rate of 2.4 liter / hour. Time: Ceramic granules were obtained in the same manner as in Example 1 except that spraying was performed for 2 minutes. About the obtained ceramic granule, like Example 1, the average moisture content of the whole granule, the moisture content variation of each granule, and the fluidity of the granule were measured. The results are shown in Tables 1 and 2. Furthermore, the presence or absence of aggregates in the granules was confirmed.

  As shown in Table 1, the average moisture content of the entire ceramic granule is 0.34% by weight in Example 1 and 0.35% by weight in Comparative Example 1, and the target values are obtained. However, regarding the variation in the moisture content of each granule, Comparative Example 1 was ± 0.25% of the average moisture content of the whole granule, and the variation was large, whereas in Example 1, the average moisture content of the entire granule was It was confirmed that the amount was suppressed to a very small range of ± 0.04%.

  In other words, the following can be said with respect to the variation in moisture content. In the case of applying moisture in a short time with large droplets as in Comparative Example 1, even if the target average moisture content can be obtained as a whole granule, variation in the moisture content cannot be suppressed for each granule. . On the other hand, in the case of applying moisture for a long time with small droplets as in Example 1, it is possible to obtain a target average moisture content for the entire granule and suppress variation in the moisture content for each granule. You can also

  As shown in Table 2, regarding the fluidity of the granules, Example 1 showed good fluidity at 14.3 seconds, but in Comparative Example 1, it was difficult to flow at 17.1 seconds, and the fluidity deteriorated. It was confirmed that

  Furthermore, regarding the generation of aggregates, in Comparative Example 1, it was confirmed that 5% by mass of aggregates of about 300 to 800 μm were generated in the entire ceramic granule. On the other hand, in Example 1, generation | occurrence | production of the granulated material aggregated in the whole ceramic granule was not seen.

Example 2 and Comparative Example 2
[Relationship between molding pressure and compact density]

  10 g of each ceramic granule obtained in Example 1 and Comparative Example 1 was filled in a mold having a diameter of 17.8 mm, the molding pressure was changed to 98 MPa, 196 MPa, 294 MPa, and 490 MPa, and dry pressure molding was performed. A cylindrical ceramic molded body having a length of 18 mm and a length of 11 mm to 14 mm was produced.

  About the produced ceramic molded body (sample), the molded body density for each molding pressure was calculated, and the relationship between these was shown in FIG.

[Side view photo]

  Moreover, the result of having image | photographed the collapsed state of the granule of the side surface of each molded object (The molding pressure was changed with 98MPa, 294MPa, and 490MPa) with the SEM photograph is shown in FIG. C).

  As shown in Table 3, FIG. 2, FIGS. 3 (A) to (C) and FIGS. 4 (A) to (C), a molded body produced from the ceramic granules obtained in Example 1 (Example 2). Is excellent in low-pressure crushing property at the time of molding, and it can be confirmed that the granule boundary of the molded body is reduced to form a uniform molded body.

  On the other hand, the molded body (Comparative Example 2) produced from the ceramic granules obtained in Comparative Example 1 has a low pressure crushing property at the time of molding, and leaves many grain boundaries in the molded body. It can be confirmed that the molded body is non-homogeneous with variation in the water content.

  The “low-pressure crushability” means the ease of crushing of granules at a low pressure (typically 29 to 147 MPa) when the ceramic forming granules are molded. “Good pressure crushability” means that the ceramic molding granules are uniformly crushed.

Example 3 and Comparative Example 3
[Continuous formability evaluation]

  Each ceramic granule obtained in Example 1 and Comparative Example 1 was continuously formed into 50,000 pieces in a cylindrical core shape having a diameter of 1.5 mm and an L size of 1.8 mm.

  The state (sticking resistance) of adhesion of the ceramic material after continuous molding to the mold was visually observed. The results are shown in Table 3. In Table 3, the case where the ceramic material was not observed to adhere to the mold even after the continuous molding of 50,000 pieces, and the case where the ceramic material was observed to adhere to the mold at the time of continuous molding of 20,000 pieces A case where adhesion of the ceramic material to the mold was observed when 1000 pieces were continuously formed was evaluated as Δ, and a case where adhesion of the ceramic material occurred at about 1,000 pieces and continuous forming was impossible was evaluated as x.

  Furthermore, the lengthwise dimension of the obtained molded body was measured, and the maximum (Max), minimum dimension (Min), and standard deviation (3σ) were obtained. The results are also shown in Table 3.

  As shown in Table 3, the ceramic granules obtained in Example 1 can continuously form 50,000 or more compacts without adhesion of fine particles to the mold, and have very good resistance to resistance. The sticking property was shown (Example 3). On the other hand, when the ceramic granule obtained in Comparative Example 1 was molded, ceramic particles adhered to the mold at the time of molding about 5,000 pieces, and appearance abnormality such as appearance defect occurred (Comparative Example 3). ).

  In addition, the lengthwise dimension distribution (Max-Min) of the obtained molded body is as small as 10 μm in Example 3 and as wide as 22 μm in Comparative Example 3. The 3σ value in the length direction and the 3σ value in the length direction was 9 μm in Example 3, and it was confirmed that a very good dimensional distribution was exhibited as compared with 20 μm in Comparative Example 3.

  From the above, the superiority of Examples 1 to 3 over Comparative Examples 1 to 3 could be confirmed.

  “Sticking resistance” means the adhesion resistance of fine particles in ceramic granules to the surface of a mold or the like.

Example 4
Ceramic granules were obtained in the same manner as in Example 1 except that mist having a D50 of 2 μm was sprayed at a supply rate of 2 liters / hour and a supply time of 45 minutes. About the obtained ceramic granule, the average water content of the whole granule, the water content variation of each granule, and the fluidity of the granule were measured in the same manner as in Example 1, and almost the same result as in Example 1 was obtained. It was.

Example 5
Ceramic granules were obtained in the same manner as in Example 1 except that mist having a D50 of 10 μm was sprayed at a supply rate of 2 liters / hour and a supply time of 40 minutes. About the obtained ceramic granule, when the average moisture content of the whole granule, the moisture content variation of each granule, and the fluidity of the granule were measured in the same manner as in Example 1, almost the same results as in Example 1 were obtained. It was.

Example 6
Ceramic granules were obtained in the same manner as in Example 1 except that mist having a D50 of 30 μm was sprayed at a supply rate of 1.5 liters / hour and a supply time of 25 minutes. About the obtained ceramic granule, the average water content of the whole granule, the water content variation of each granule, and the fluidity of the granule were measured in the same manner as in Example 1. As a result, almost the same results as in Example 1 were obtained. It was.

Example 7
A capsule container 4 having a size capable of treating 100 kg of ceramic granules was prepared, and 100 kg of ceramic granules were added thereto, and water was added under the same conditions as in Example 1. After the mist spraying is finished, the ceramic granules are temporarily taken out from the capsule container 4, and the average moisture content of the whole granules is measured to be 0.67% by weight. I couldn't see it.

  Next, after temporarily taking out the ceramic granules, the heater 12 attached to the outer periphery of the capsule container 4 is operated (heater temperature is 100 ° C.), and the inside of the capsule container 4 is 70 ° C. The ceramic granules were dried for 20 minutes. The rate at which moisture was removed from the ceramic granules by this drying (drying rate) was 0.016% by weight / min.

  Thereafter, in the same manner as in Example 1, with respect to the obtained ceramic granules, the average moisture content of the whole granule and the moisture content variation of each granule were measured. As a result, the average moisture content of the whole granule is 0.35% by weight, and the variation in the moisture content of each granule is suppressed to a very small range of within ± 0.1% of the average moisture content of the whole granule. Was confirmed.

  The following can be understood from Example 7. That is, even when the processing amount of ceramic granules increases (20 kg → 100 kg), not only the average moisture content of the whole granule but also the moisture content variation of each granule can be reduced by appropriately adjusting the drying temperature after moisture application. can do.

1 (A) and 1 (B) are schematic views of a moisture adjusting device for ceramic granules according to an embodiment of the present invention, and FIG. 1 (C) is a cross section taken along line IC-IC in FIG. 1 (A). FIG. FIG. 2 is a graph showing the relationship between each molding pressure and the compact density in Example 2 and Comparative Example 2. 3 (A) to 3 (C) are SEM photographs showing the collapsed state of the side surface of the ceramic molded body when the molding pressure is changed in Example 2. FIG. 4 (A) to 4 (C) are SEM photographs showing the collapsed state of the side surface of the ceramic molded body when the molding pressure is changed in Comparative Example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Moisture adjustment apparatus 3 ... Ceramic granule 4 ... Capsule container 42 ... Spray port 43 ... Line 44 ... Discharge port 6 ... Stand 8 ... Oscillating means 10 ... Ultrasonic humidifier 11 ... Mist (fine droplet)
12 ... Heater 14 ... Suction means

Claims (7)

Putting ceramic granules inside the capsule container that can rotate around the axial axis and can swing up and down and left and right with respect to the axial direction,
Moisture of ceramic granules characterized by spraying mist that is fine droplets in the capsule container while rotating and swinging the capsule container, thereby providing moisture to the ceramic granules in the capsule container An adjustment method,
Spraying mist at a feed rate of 0.5-4 liters / hour and a feed time of 5 minutes or more,
By giving moisture to the ceramic granules, the average moisture content of the ceramic granules is 0.2 to 0.8 wt%, and then dried,
A method for adjusting the moisture content of a ceramic granule, which is dried for 2 minutes or more at such a rate that the moisture content of the ceramic granule after moisture application is removed at 0.005 to 0.08 wt% / min.   The method for adjusting the moisture content of ceramic granules according to claim 1, wherein a mist having a 50% average particle diameter (D50) of 1 to 30 µm is sprayed.   The method for adjusting the moisture content of ceramic granules according to claim 1 or 2, wherein the mist produced by an ultrasonic humidifier is sprayed.   The method for adjusting the moisture content of the ceramic granules according to any one of claims 1 to 3, wherein the capsule container is rotated and oscillated at a rotation speed of 20 to 70 Hz and an oscillation speed of 20 to 70 Hz.   The method for adjusting the moisture content of the ceramic granules according to any one of claims 1 to 4, wherein the mist is sprayed into the capsule container and, at the same time, surplus mist that has not adhered to the ceramic granules is discharged to the outside of the capsule container.   The method for adjusting the moisture content of ceramic granules according to any one of claims 1 to 5, wherein the inside of the capsule container is dried while being sucked.   The method for adjusting the moisture content of the ceramic granules according to claim 1, wherein the capsule container is dried while being heated while sucking the inside of the capsule container.