JP2003306668A - Method for producing cerium-based polishing material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a cerium-based polishing material by using an excellent pulverizing means having good pulverizing efficiency and hardly causing fine particles. <P>SOLUTION: A pulverized product (the objective pulverized product) having a prescribed average particle diameter is obtained by using the pulverizing means such as a ball mill in the pulverizing step when producing the cerium- based polishing material. The pulverizing means such as the ball mill pulverizes a raw material to be pulverized by putting the raw material and a pulverizing medium such as a carbon steel ball in a pulverizing container, and imparting kinetic energy to the pulverizing medium by the rotation or the like of the container. The pulverizing medium having an average diameter not less than 0.3 mm and not larger than 8,000 times as large as the average particle diameter of the pulverized product is preferably used. <P>COPYRIGHT: (C)2004,JPO

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 cerium-based abrasive, and more particularly to a method characterized by a crushing step.

[0002]

2. Description of the Related Art Cerium-based abrasives are composed of particles of cerium oxide (CeO ₂ ) as a main component and particles of other rare earth metal oxides. For example, cerium-based rare earth carbonate (rare carbonate). Or a rare earth salt such as a cerium rare earth oxalate, or a raw material such as a cerium rare earth oxide (rare earth oxide) obtained by roasting such a rare earth salt. The manufacturing process is as follows. First, a raw material for a cerium-based abrasive (hereinafter, also simply referred to as a raw material) is crushed, and subsequently, a chemical treatment (wet treatment) is performed if necessary. The chemical treatment is, for example, a fluorination treatment performed for the purpose of ensuring high machinability of the cerium-based abrasive,
This is a mineral acid treatment that removes alkali metals such as sodium that cause abnormal grain growth during subsequent roasting. After this,
Filter and dry as necessary, sinter the raw material particles by heating the raw material at high temperature and roasting, crush the raw material after sintering to an appropriate particle size, and classify In this way, an abrasive having a desired particle size and particle size distribution is manufactured.

By the way, as a means widely used in the crushing process performed in the manufacturing process of the abrasive, there is a crushing means using a crushing medium such as a steel ball. For example, pulverization is performed by using a pulverizing device such as a rotary ball mill, a vibrating ball mill, a planetary ball mill, a bead mill, and an attritor. The crushing methods include dry crushing and wet crushing. In this type of crusher, a large number of crushing media such as stainless balls and the raw material to be crushed are put into a crushing container (shell), and the crushing container is moved (rotated or vibrated) or crushed. The inside of the container is agitated to give kinetic energy to the grinding medium to grind the material to be ground.

The larger the diameter of the grinding medium used in such a grinding means is, the faster the raw material particles having a large particle size can be ground. Therefore, in the past, in order to increase the pulverization efficiency, a pulverization medium having a somewhat large diameter is used.

[0005]

By the way, in recent years, cerium-based abrasives have come to be used also for polishing electronic materials such as glass substrates for liquid crystals, magnetic recording media or semiconductors. In this case, as the performance of the abrasive, excellent smoothness is required for the polished surface,
The use of a cerium-based abrasive having an average particle size of more than about 3 μm manufactured by the conventional manufacturing method cannot sufficiently meet such requirements.

The present invention has been made under the above circumstances, and provides a method for producing a cerium-based abrasive using an excellent pulverization method which has a high pulverization efficiency and suppresses the generation of fine particles. Another object is to provide a cerium-based abrasive which is excellent in smoothness after polishing and suitable for polishing electronic materials.

[0007]

[Means for Solving the Problems] In order to solve such a problem, the inventors examined the crushing process.
First, it was examined to lengthen the grinding time.
However, if the crushing time is simply lengthened, a crushed product (abrasive material) having an average particle diameter smaller than that of the conventional one can be obtained, but the crushing efficiency is certainly lowered. It was also found that when pulverization was carried out for a long time, a large amount of fine particles considered to be caused by excessive pulverization were produced. As the amount of fines in the crushed product increases, the amount of fine abrasive in the abrasive produced also increases. It was also found that when the amount of the fine-grained abrasive increased, the amount of the fine-grained abrasive remaining on the surface after polishing increased, the smoothness rather decreased, and the polishing efficiency decreased.

As a result of such an examination, when a crushed product having a smaller average particle size is obtained, even if the crushing medium is the one used in the conventional crushing process, the crushing time can be adjusted to achieve the target average. Although it may be possible to reach the particle size, in order to secure the grinding efficiency required in the industry, or to improve the physical properties of the abrasive other than the average particle size and the polishing characteristics other than the polishing speed (for example, the above-mentioned smoothness). In order to obtain excellent abrasives,
It has been found that it is necessary to carry out a grinding process using a grinding medium of a suitable size to obtain a ground product. Further, it has been found that the necessity of limiting the size of the grinding medium is further increased in order to obtain a ground product (abrasive) having a small average particle diameter while ensuring excellent grinding efficiency and abrasive characteristics. That is,
When trying to obtain a crushed product with a small average particle size, the use of a relatively small crushing medium suppresses the generation of fine particles, and the obtained crushed product has a sharper particle size distribution than using a larger crushing medium. Moreover, it has become clear that a crushed product having a sharp particle size distribution can be obtained in a relatively short time. The present invention has been completed based on such results.

The present invention uses a crushing step having the following characteristics in a method for producing a cerium-based abrasive having a step of crushing a raw material for a cerium-based abrasive and a roasting step. The crushing step is to crush the raw material by giving kinetic energy to the crushing medium while the raw material and the crushing medium are put into a crushing container to obtain a target crushed product (crushed product) having a predetermined average particle size. In the process, a grinding medium having an average diameter of 0.3 mm or more and not more than 8000 times the average particle size of the target pulverized product is used.

In the pulverizing means using the pulverizing medium, a spherical pulverizing medium is usually used, but even if the average diameter of the pulverizing medium is specified, the range of the diameter of each individual pulverizing medium is not limited. Absent. Therefore, it was thought that the relationship between the average diameter of the grinding medium and the grinding efficiency, and the relationship between the average diameter and the production amount of fine particles could not be found, but as a result of the above-mentioned examination, when the average diameter is within the above range, It has been found that the efficiency can be higher and the amount of fines produced can be reduced.

According to the crushing method using the crushing container as in the present invention, the range of diameters that can be taken by each crushing medium is limited due to the nature of the crushing means. It is considered that the condition of the entire medium is specified, and the average diameter of the crushed product obtained by crushing, the amount of fine particles produced, and the crushing efficiency are specified. Incidentally, the lower limit of the diameter of the grinding medium is basically not particularly limited, but in the case of grinding with the grinding medium, there is a step of separating the raw material as the ground product and the grinding medium. For separation, the grinding medium preferably has a diameter larger than a predetermined diameter (for example, 0.3 mm or more is preferable).

Further, as a result of studying how to specify a suitable average diameter of the grinding medium, it is found that the average diameter of the grinding medium is specified in relation to the average particle diameter of the target pulverized product. It turned out to be preferable. Specifically, it has been found that the grinding medium preferably has an average diameter of 8,000 times or less the average particle size of the target pulverized product, as described above. This is because if it exceeds this range, it becomes difficult to suppress the generation of fine particles and the pulverization efficiency is also poor. The "average particle size of the intended pulverized product" here is the average particle size of the abrasive that is to be obtained by pulverization, but the "average particle size of the abrasive that is actually obtained after pulverization (step)" It is also the diameter. As described above, in the crushing step, by adjusting the crushing time, the average particle size of the abrasive material obtained after crushing can be adjusted in a wide range, and a crushing medium having a suitable size as in the present invention is used. This is because, finally, it is possible to actually obtain an abrasive having a desired average particle size.

In the crushing step, a crushing means using a crushing medium such as the above-mentioned method using the rotary ball mill is used. The raw material to be ground in the grinding step before roasting is a known material containing cerium as a main component, such as bastnasite concentrate, carbonates, hydroxides, oxalates and oxides. is there.

Incidentally, the crushing process includes a crushing process before roasting and a crushing process after roasting. Of these, the crushing step before roasting can be said as a step of producing a raw material for roasting, and the crushing step after roasting can also be said as a finishing (final) crushing step. The kind of raw material to be crushed is specified to some extent by such a difference in the crushing time. Further, the crushing characteristics differ depending on the type of raw material to be crushed. The inventors have found that suitable crushing conditions depend on the difference in the crushing characteristics, and studied the size of the crushing medium.

As a result of studies, it has been found that the suitable size of the grinding medium is preferably relatively small regardless of the kind of the raw material. Specifically, in the crushing step before the roasting step, the average diameter is 0.3 mm or more and 500 of the average particle diameter of the target crushed product.
It has been found that it is more preferable to use a grinding medium that is 0 times or less.

It is considered that a rare earth oxide raw material can be cited as a particularly preferable raw material for a grinding medium having such a size range. Rare earth oxide has a higher hardness than rare earth carbonate. Therefore, in order to secure the pulverization efficiency in pulverizing such a raw material, it is necessary to pulverize with a larger pulverizing medium than in the case of rare earth carbonate. However, when a grinding medium having an average diameter exceeding 5000 times the target grinding particle size is used, the production of fine particles may not be sufficiently suppressed. As a result of comprehensively examining these aspects, it was found that when the raw material is rare earth oxide, a larger grinding medium can be used as a suitable grinding medium than when rare earth carbonate is the raw material. That is, it was found that when the raw material is rare earth oxide, the average diameter of the grinding medium is preferably 5000 times or less the target grinding particle size.

By crushing with a crushing medium of a suitable size in this way, the generation of fine particles is suppressed, so that the particle size distribution of the target crushed product becomes sharper, and the particle size in the roasting step and crushing step is increased. Will be easier to manage. Note that the rare earth oxide raw material is usually already subjected to a roasting step in the raw material production (refining) step before the so-called abrasive production, and in this case, strictly speaking, the abrasive production step There will be multiple roasting steps. Therefore,
For the sake of accuracy, the term "roasting (step)" used in the description of the present invention means the last roasting (step) when there are multiple roasting steps before the abrasive is manufactured. Process).

Further, rare earth carbonate has a hardness lower than that of rare earth oxide, and when such rare earth carbonate is a raw material to be pulverized, a smaller pulverizing force (kinetic energy of the pulverizing medium).
It is considered possible to secure sufficient pulverization efficiency. As a result of the study, it was found that if the grinding medium is 3000 times or less the average particle size of the target crushed product, the amount of fine particles generated by excessive crushing can be suppressed more reliably. If the generation of fine particles is suppressed, the particle size distribution becomes sharper when compared to the conventional crushed product with the same average particle size, and it is easier to control the particle size in the subsequent roasting process and crushing process. become.

Bastnaesite concentrate is also widely used as a raw material for abrasives. This raw material has a relatively high hardness. Further, the bastnasite concentrate has a property that particles are disintegrated at a stage before being sintered by roasting, that is, at an initial stage of roasting. That is, when the bastnasite concentrate is a raw material, crushing proceeds due to the collapse of the raw material in the initial stage of roasting. Therefore, in the pulverizing step before the start of roasting, it is preferable to not only improve the pulverizing efficiency but also suppress the generation of fine particles. As a result of the examination,
The average diameter of the grinding media is 300 times the average particle size of the target grinding product.
It was found that when the amount is 0 times or less, the amount of fine particles produced can be more reliably suppressed, and further, sufficient crushing and crushing efficiency can be secured in combination with the disintegrating effect during roasting. If the generation of fine particles is suppressed, the particle size distribution of the target pulverized product becomes sharper as in the case of rare earth oxide, and it becomes easier to control the particle size in the roasting process and the pulverization process.

On the other hand, when crushing rare earth oxide as a raw material to be crushed in the crushing step after the roasting step, the average diameter is 3,000 times or less the average particle size of the target crushed product (and 0.3 mm).
It has been found that it is preferable to use the grinding medium which is the above).

The crushing process after roasting is directly connected to the final product, the abrasive. Therefore, in the crushing step after roasting, unlike the crushing step before roasting, it is more preferable to consider not only the crushing efficiency but also the suppression of generation of fine particles. In this respect, by using a grinding medium having a size within the above range, it is possible to more reliably suppress the generation of fine particles.

As can be seen from the above description, whether or not the size of the crushing medium is suitable depends on the size (average particle size) of the raw material to be crushed. However, the raw material becomes smaller as it is crushed. Therefore, even if the crushing medium determined to have a suitable size at the start of crushing is continued to be used, the crushing time may cause the crushing medium to lose its suitable size. As a result of diligent study on this point, it was found that as the grinding progresses, if the grinding medium can be replaced with a smaller diameter during the grinding, the size of the grinding medium with respect to the raw material to be ground can be maintained at a suitable size. .

That is, as a crushing step which is carried out at least one of before and after roasting, a crushing step of crushing the raw material stepwise by changing the crushing medium during the crushing step is used. It has been found that it is preferable to use, as the grinding medium used in each of the second and subsequent grinding steps in the process, a grinding medium having an average diameter smaller than that of the grinding medium used in the grinding step immediately before the grinding step. It was

As described above, if the crushing process is stepwise, the crushing medium can be exchanged for each crushing step. That is,
As the average diameter of the raw material to be pulverized becomes smaller by pulverization, the pulverizing medium can be replaced with one having a smaller average diameter. Therefore, the size of the grinding medium for the raw material to be ground is maintained at a suitable size. If the size of the grinding medium is suitable, excessive grinding is prevented, generation of fine particles is suppressed, and grinding efficiency is ensured. Further, if the average particle size to be the crushing target and the average diameter of the crushing medium to be used are determined for each crushing step, the size of the crushing medium with respect to the raw material to be crushed is stable over all crushing steps, and The particle size distribution of the resulting pulverized product, and thus the manufactured abrasive, becomes sharper.

As a result of further study, when the crushing process after roasting is to be performed in stages, the final crushing step among the plurality of crushing steps is the average particle size or the particle size of the abrasive produced. It has been found that it affects distribution and is important. Then, as a result of the examination, in addition to the average diameter of the pulverizing medium in the final pulverizing stage being 0.3 mm or more and 3,000 times or less of the average particle diameter of the objective pulverized product,
It has been found to be more preferable to use a grinding medium that is smaller than the mean diameter of the grinding medium in the grinding stage immediately before that.

That is, by using a pulverizing medium having an average diameter closer to the average particle size of the target pulverized product, it is possible to suppress the generation of fine particles which deteriorate the performance such as the smoothness of the surface to be polished.
The raw material to be crushed in the last crushing step is already crushed in the previous crushing step or crushing step, and not a few particles have already been crushed to the crushing target average particle size or a particle size close to it. It is considered to include. Therefore, it is considered more preferable to suppress the generation of fine particles by using a grinding medium having a smaller diameter. Further, since it has already been crushed in the previous crushing stage, it is considered that there is a relatively low need to attach importance to crushing efficiency in determining the crushing medium to be used in the last crushing stage.

By the way, as a part of the examination of the crushing process,
The movement of the grinding medium in the grinding container was examined.
As a result, it has been found that it is determined that the movement in the crushing container differs depending on the material of the crushing medium. Therefore,
The relationship between the difference in the material of the grinding media and the grinding efficiency was examined. As a result, it has been found that when the raw material of the cerium-based abrasive is crushed, the crushing medium preferably has a density of 3 g / cm ³ or more. This is because if the density of the grinding medium is less than 3 g / cm ³ , the grinding efficiency will be low and the grinding will take a long time. For example, in wet pulverization, as the raw material particles become finer as the pulverization progresses, the viscosity of the pulverized slurry becomes higher. Therefore, with a pulverized medium having a density of 3 g / cm ³ or less, the settling speed of the pulverized medium in the pulverized slurry is significantly reduced However, it is considered that the grinding efficiency is reduced.

A preferable grinding medium is, for example, a stainless steel.
Iron (7.9g / c) such as ballless ball (SUS304)
m³) As a main component, α-alumina (4.0
g / cm³), Zirconium oxide (5.6 g / cm³),
Silicon nitride (3.4 g / cm ³) Etc., the density is
3 g / cm³The above grinding media can be mentioned. Well
Crushed by coating stainless steel spheres with plastic
The density of the whole grinding medium is 3 g / cm even if it is in the medium³that's all
Are preferred. The density is 10 g / cm³Beyond
A grinding medium that is preferable is special in terms of grinding efficiency,
The current quality, supply stability, or cost
Considering the aspect, it is not always preferable.

In examining the movement of the pulverizing medium in the pulverizing container, it was found that the movement in the pulverizing container was different depending on whether the size of the powder medium was uniform or varied. Was issued. Therefore, the relationship between the size variation of the grinding medium and the grinding efficiency was examined. As a result, it was found that the crushing efficiency is higher when the crushing media of various sizes are mixed, as compared with the case where the crushing media have a uniform size.

For example, if the grinding medium has a uniform diameter,
A large number of grinding media tend to be regularly stacked in the grinding container. When kinetic energy is applied to the grinding media in such a state, it is easy for them to move integrally such as translational motion in a state where these grinding media are in contact with each other.
Since there is little collision between the grinding media that move together, the kinetic energy is less likely to be used as the energy for grinding the raw materials. Therefore, it is considered that the pulverization efficiency tends to deteriorate.

On the other hand, when the diameters of the grinding media are non-uniform, that is, when the grinding media of various sizes are mixed, the grinding media are difficult to be regularly arranged and an integral movement is unlikely to occur. Therefore, each grinding medium tends to move randomly. When the movements of the grinding media become random, collision of the grinding media with each other is promoted, and the grinding efficiency is improved. Further, if the collision is frequent, the given kinetic energy is dispersed and used in each collision occurring in the entire grinding medium, so that the entire polishing raw material is ground more uniformly. As a result, it is considered that excessive crushing is prevented and generation of fine particles is suppressed. If the generation of fine particles can be suppressed, the particle size distribution of the obtained crushed product will be sharp (so that the distribution will be concentrated near the average particle size), and by extension, the particle size distribution of the abrasive material that is the target crushed product will be sharper. become.

However, it has been found that if the difference in the diameters of the mixed grinding media is too large, the translational motion of the large grinding media may not be prevented in some cases. In this state, it is considered that the small grinding medium intervenes between the large grinding media, and the large grinding medium behaves in a manner similar to that of the large grinding medium alone. Therefore, in order to suppress the generation of fine particles while ensuring high pulverization efficiency, it is necessary to prevent the difference in diameter between individual pulverization media from being too large.

Therefore, when the grinding media having different diameters are mixed, the inventors examined a preferable range of the diameter of the grinding media. As a result, it has been found that the minimum diameter of the grinding medium to be put into the grinding container is preferably 0.16 times or more the maximum diameter.

The reason why such a range is preferable is considered to be appropriate in view of the following points. For example, a spherical grinding medium of the same size (hereinafter referred to as a large diameter sphere)
Prepare one and arrange each large-diameter sphere so as to contact all three other large-sized spheres (position each large-diameter sphere at the apex of a regular tetrahedron in contact with each other). . In this state, a grinding medium having a diameter that is too large to be placed in a gap formed in the center of the four large-diameter spheres (hereinafter,
It is conceivable that the regular arrangement of the four large-diameter spheres can be disrupted by mixing the small-diameter spheres) and the translational motion of the grinding medium can be prevented. That is, it is preferable that the diameter of the small diameter sphere is larger than the diameter of the large diameter sphere by 2 / √3−1 times (≈0.1547 times) in order to suppress the generation of fine particles and ensure high pulverization efficiency. Conceivable. From the above, the above range is derived. For example, the diameter range of the pulverizing medium to be mixed is 1550 times to 1000 times the average particle size of the objective pulverized product.
A range of 0 times or 1000 times to 6400 times is preferable.

Further, as a result of the examination, for example, when the large diameter sphere and the small diameter sphere are mixed, if the difference in diameter between them is too small, the large diameter sphere and the small diameter sphere are mixed in a pseudo and regular manner. It was found that they were lined up, and the effect of introducing grinding media having different diameters was hardly obtained. For example, when a large diameter sphere and a small diameter sphere are mixed, the diameter of the small diameter sphere is preferably 0.99 times or less the diameter of the large diameter sphere. By doing so, it is possible to prevent the large-diameter spheres and the small-diameter spheres from being regularly arranged in a mixed state, suppress the generation of abrasive fine particles, and ensure a high grinding efficiency.

The method of manufacturing the cerium-based abrasive according to the present invention has been described above. As explained so far,
The manufacturing method according to the present invention is characterized in that the content of fine particles in the abrasive can be suppressed to an extremely low level. Therefore, according to the manufacturing method of the present invention, the fine particle content of the abrasive having an average particle size of 3 μm or less, for example, which is too high if the conventional manufacturing method is used, is suppressed. Can be manufactured in the state. If the abrasive thus obtained is used for polishing optical glass, glass substrates for electronic materials, etc., while ensuring a sufficient and sufficient polishing efficiency, a polished surface having excellent smoothness after polishing is secured. it can. Further, the abrasive having an average particle size of 2 μm or less obtained by the production method according to the present invention is particularly excellent in smoothness, and is used for electronic materials such as liquid crystal, magnetic recording medium or semiconductor glass substrates. It is particularly preferable as an abrasive for use in polishing a glass substrate.

The cerium-based abrasive obtained in this manner was used as C in the total rare earth oxide (TREO) in the abrasive.
The proportion of eO ₂ is 30% by weight or more, and the usual value is in the range of 40% by weight to 99.9% by weight. Therefore, as a raw material, a raw material having a chemical composition containing CeO ₂ in this range after roasting is selected. The roasting temperature in the roasting step of the production method of the present application is usually 500 ° C or higher, preferably 700 ° C to 120 ° C.
It is 0 ° C. And roasting time is usually 30 minutes or more.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the method for producing a cerium-based abrasive according to the present invention will be described below.

First Embodiment : First, the attritor (MA-
1SE, manufactured by Mitsui Miike Seisakusho Co., Ltd., was charged with 10 kg of carbon steel balls (crushing medium) for crushing in a crushing container (capacity 5.4 liters), and subsequently, cerium-based rare earth carbonate as a raw material to be crushed. A slurry consisting of 2.5 kg of salt (rare earth carbonate) and 2.5 kg of pure water was added. The carbon steel balls put in had a diameter of 4.769 mm (hereinafter, 4.7
mm is the nominal diameter). The rare earth carbonate was produced from the complex ore from Baotou, China. In this state, the attritor was operated to perform wet pulverization. In this wet pulverization, a part of the slurry in the pulverization container was sampled every hour from the start of pulverization, and the average particle size was measured. As a result, the average particle diameter D ₅₀ was 1.0 after 5 hours from the start of pulverization.
A slurry (target pulverized product) having a size of μm or less was obtained.

After the completion of the pulverization, the slurry obtained by the pulverization was filtered, dried and then roasted at 900 ° C. for 8 hours. After roasting, the obtained abrasive was subjected to dry classification with the classification point set to 3 μm, and the fine grain side was collected to obtain a cerium-based abrasive.

[0041]Particle size measurement: Grinding of each embodiment and comparative example
Average particle size D of the slurry collected in the process _Fifty(= Small particle size side
The particle size value with a cumulative volume of 50% is measured as follows.
Decided First, a small amount (several drops) of grinding slurry from the grinding container
And extract 0.1% by weight sodium hexametaphosphate
Ultrasonic homogenizer
(Product name: MODEL US-300T, Nihonsei Co., Ltd.
(Manufactured by Kiki Seisakusho) at 300 W for 10 minutes. That
After that, take out a part of the obtained dispersion liquid and use it for measuring the particle size distribution.
Oki (Product name: Microtrac MK-II particle size analyzer
  SPA MODEL 7997-20, manufactured by Nikkiso Co., Ltd.
Measure the particle size distribution by_Fifty) Was asked.

Second Embodiment : This is an embodiment in which carbon steel balls having a diameter different from that of the first embodiment are used for crushing. Specifically, a diameter of 1.558 mm (hereinafter, 1.6 mm is a nominal diameter) was used. The other abrasive manufacturing conditions are the same as those in the first embodiment, and thus the description thereof is omitted. In the pulverization, a slurry having an average particle diameter D ₅₀ of 1.0 μm or less was obtained 3 hours after the start of pulverization.

Third Embodiment : An embodiment in which a raw material different from that of the first embodiment is used. The raw material to be crushed in this embodiment was a cerium-based rare earth oxide (rare earth oxide). Abrasive manufacturing conditions other than raw materials are all the first
It was the same as the embodiment. In the pulverization, a slurry having an average particle diameter D ₅₀ of 1.0 μm or less was obtained 9 hours after the start of pulverization.

Fourth Embodiment : An embodiment in which a raw material different from that of the second embodiment is used. The raw material was rare earth oxide. The manufacturing conditions of the abrasives other than the raw materials were all the same as in the second embodiment. In the pulverization, the average particle diameter D ₅₀ did not become 1.0 μm or less even after 12 hours from the start of the pulverization, and the pulverization was finished here. The average diameter of the slurry obtained by milling for 12 hours was 1.1 μm.

Fifth Embodiment : An embodiment using a raw material different from that of the first embodiment. The raw material was bastnaesite concentrate. Abrasive manufacturing conditions other than raw materials are all the first
It was the same as the embodiment. In the pulverization, a slurry having an average particle diameter D ₅₀ of 1.0 μm or less was obtained 7 hours after the start of pulverization.

Sixth Embodiment : An embodiment using a raw material different from that of the second embodiment. The raw material was bastnaesite concentrate. Abrasive manufacturing conditions other than raw materials are all second
It was the same as the embodiment. In the pulverization, a slurry having an average particle diameter D ₅₀ of 1.0 μm or less was obtained 4 hours after the start of pulverization.

Polishing test : The polishing materials obtained in the respective embodiments and comparative examples were subjected to a polishing test to measure the polishing value and evaluate the state of the polished surface (evaluation of scratches). In the polishing test, a high-speed polishing tester was used as a testing device, and 65 mmφ
The glass for a flat panel of 1 was used as a material to be polished, and this glass was polished using a polishing pad made of polyurethane. In the polishing test, first, the obtained abrasive was further dispersed in water to prepare an abrasive slurry having a slurry concentration of 10% by weight.
The polishing conditions are as follows: the prepared abrasive slurry is supplied at a rate of 5 l / min and the pressure on the polishing surface is 15.7 kg / c.
m ² and the rotation speed of the abrasion tester is 1000 rpm
Was set to. The glass material after polishing was washed with pure water and dried without dust.

Evaluation of scratches : The state of the polished surface of the flat panel glass obtained after the polishing test was evaluated. The scratches on the polished surface were evaluated. Specifically, the glass surface after polishing is irradiated with a halogen lamp of 300,000 lux, and the glass surface is observed by the reflection method, and the degree of scratches (size and number) is determined and scored. The evaluation points were determined by the deduction system from.

Cleaning Test : A cleaning test was conducted on the cerium-based abrasives obtained in the respective embodiments and comparative examples. In the cleaning test, first, a cerium-based abrasive was dispersed in water to obtain an abrasive slurry with a concentration of 10% by weight. The obtained abrasive slurry is immersed in a slide glass made of borosilicate glass for optical microscope observation that has been ultrasonically cleaned and dried in advance,
After this, the test piece was pulled up and sufficiently dried in a dryer to obtain a test piece for a detergency test. The temperature of the preparation atmosphere during drying was 50 ° C. Then, the obtained test piece was immersed in pure water and ultrasonically cleaned for 5 minutes. After ultrasonic cleaning, the preparation was taken out of the beaker and washed with pure water. The surface of the prepared slide after washing with running water was observed with an optical microscope to evaluate the remaining amount of the abrasive particles remaining on the surface.

[0050]

[Table 1]

As can be seen from Table 1, all of the abrasives obtained in the respective embodiments had good qualities such as a scratch evaluation of "95" or more and a cleaning property of "◯" or more. Then, whichever raw material is to be pulverized, the diameter is 1.6 mm (about 1600 of the average particle diameter D ₅₀ of the objective pulverized product).
Times, hereinafter, only magnifications are shown. ) The embodiment using the carbon steel ball of 4) has a diameter of 4.7 mm (about 4700 times).
It was possible to pulverize in a shorter time than in the case of the above embodiment. Judging based on these embodiments, regardless of the type of raw material to be crushed, if the size of the crushing medium is 5000 times or less the average particle size of the target crushed product, the target crushed product can be obtained by crushing in a short time. As a result, it was found that an abrasive having good polishing characteristics could be finally obtained. And the average particle size of the target pulverized product is 30
It has been found that when the amount is 00 times or less, it is possible to pulverize in a shorter time and obtain an abrasive having better polishing characteristics.

Seventh Embodiment : In this embodiment, a bead mill (DINO-MILL (Type K
DL-PILOT A), Willy A .; Boch
made by ofen AG Moschinenfabrik)
And a zirconia ball (a grinding medium made of zirconium oxide) was used as a grinding medium. Then, the crushing target average particle diameter D ₅₀ (average particle diameter of the crushed object) was set to 0.5 μm. The other abrasive production conditions were the same as those in the second embodiment, such as the diameter of the grinding medium being 1.6 mm. In the crushing step, crushing with a bead mill was repeated. In this embodiment, a slurry having an average particle size D ₅₀ of 0.5 μm or less was obtained after the fifth pulverization.

Eighth Embodiment : In this embodiment, a zirconia ball having a diameter different from that of the seventh embodiment is used. Specifically, a diameter of 0.7938 mm (hereinafter, a nominal diameter is 0.8 mm) was used. The other abrasive manufacturing conditions were the same as in the seventh embodiment. Then, in the pulverizing step, a slurry having an average particle diameter D ₅₀ of 0.5 μm or less was obtained after the fourth pulverization.

Ninth Embodiment : In this embodiment, a zirconia ball having a diameter different from that of the seventh embodiment is used. Specifically, a diameter of 0.3969 mm (hereinafter, a nominal diameter is 0.4 mm) was used. The other abrasive manufacturing conditions were the same as in the seventh embodiment. Then, in the pulverizing step, a slurry having an average particle diameter D ₅₀ of 0.5 μm or less was obtained after the third pulverization.

Tenth Embodiment : In this embodiment, unlike the seventh to ninth embodiments, the diameter of the zirconia balls used for crushing was changed during the crushing by the bead mill which was repeatedly performed. Specifically, zirconia balls having a diameter of 0.8 mm were used in the first crushing, and those having a diameter of 0.4 mm were used in the second crushing. The other abrasive manufacturing conditions were the same as in the seventh embodiment. Then, in the crushing step, when the second crushing is completed, the average particle diameter D
A slurry having ₅₀ of 0.5 μm or less was obtained.

Comparative Example 1 : In this comparative example, a zirconia ball having a diameter different from that of the seventh embodiment was used. Specifically, the one having a diameter of 5.0 mm was used. All the other abrasive manufacturing conditions were the same as in the seventh embodiment. And in the crushing process, after finishing the crushing of the eighth time,
A slurry having an average particle size D ₅₀ of 0.5 μm or less was obtained.

Comparative Example 2 : In this comparative example, a zirconia ball having a diameter different from that of the seventh embodiment was used. Specifically, the one having a diameter of 0.2 mm was used. All the other abrasive manufacturing conditions were the same as in the seventh embodiment. Then, in the pulverizing step, a slurry having an average particle diameter D ₅₀ of 0.5 μm or less was obtained after the 10th pulverization.

[0058]

[Table 2]

As can be seen from Table 2, the scratch evaluation results were good for all of the embodiments and the abrasives obtained in Comparative Example 2. Then, among these, the eighth embodiment using a zirconia ball having a diameter of 0.8 mm (about 1600 times) and the ninth embodiment using a zirconia ball having a diameter of 0.4 mm (about 800 times) at the time of crushing. Further, according to the tenth embodiment in which the diameter of the zirconia balls was changed on the way, it was possible to obtain an abrasive excellent in both scratch evaluation and cleanability with a small number of pulverizations (that is, a short time). Further, according to the seventh embodiment using the zirconia balls having a diameter of 1.6 mm (about 3200 times), an excellent abrasive having no practical problem could be obtained with a small grinding number of 5 times. On the other hand, Comparative Example 1 using a zirconia ball having a diameter of 5.0 mm (about 10,000 times) or a diameter of 0.2 mm
The abrasives obtained in Comparative Example 2 using (about 400 times) zirconia balls were all inferior in cleanability. In Comparative Example 2, since the size of the grinding medium is too small, the number of times of grinding until the target particle size is reached increases,
The productivity has dropped significantly. Although not appearing in the table, in Comparative Example 2, it was not easy to separate the pulverizing medium and the raw material as the pulverized product after pulverizing, and it took time and effort.

As described above, the following is found from the results of the first to tenth embodiments and Comparative Examples 1 and 2. That is,
The average diameter of the grinding medium used in the grinding step before roasting is 0.3 from the viewpoint of the ease of separating the raw material and the grinding medium after grinding.
It has been found that it is preferably mm or more, and more preferably 0.3 mm or more for each grinding medium. This is because if the diameter of the grinding medium is less than 0.3 mm, the resulting abrasive will be inferior in cleanability, as shown in Comparative Example 2, and after grinding, it will be troublesome to separate the ground product from the grinding medium. Because it costs. Further, it has been found that the average diameter of the pulverizing medium is preferably 8000 times or less the average particle size of the obtained pulverized product (target pulverized product). This is because when the diameter of the grinding medium exceeds 8,000 times as in Comparative Example 1, the obtained abrasive material is inferior in cleanability. From a comparison between the seventh embodiment and the eighth embodiment, it was found that the average diameter of the grinding medium is more preferably 3000 times or less the average particle diameter of the target ground product.

By the way, the 7th, 8th, 9th and 10th
In the pulverizing step of the embodiment, the particle diameter D ₁₀ of the slurry (raw material) to be pulverized (cumulative 10% average particle size from the small particle diameter side) before the start of pulverization and after each pulverization by the bead mill performed a plurality of times is completed. _{diameter), D 5 0} (average particle diameter), D
₉₀ (cumulative 90% average particle size) was measured. The measurement method is
This is the above-mentioned “particle size measurement” method, and a description thereof will be omitted. The results are shown in FIGS. 1 and 2.

As shown in FIGS. 1 and 2, it was found that in the pulverization of each embodiment, the D ₉₀ of the slurry to be pulverized was drastically reduced. That is, it was found that high grinding efficiency can be secured by using the grinding medium of the size used in these embodiments. On the other hand, D ₁₀ remained almost unchanged. As a result, it was found that fine particles were difficult to be generated by using the grinding medium of the size used in each embodiment. If you can suppress the generation of fine particles,
The particle size distribution of the obtained pulverized product becomes sharper, which in turn results in a sharper particle size distribution of the final abrasive material. If the amount of the fine abrasive is small, the fine abrasive is prevented from remaining on the surface after polishing, and the smoothness of the surface is prevented from being lowered.

If the generation of fine particles can be suppressed, it becomes possible to obtain a crushed product having a smaller average particle size. That is, the crushing time in the crushing process becomes relatively longer as the average particle size of the target crushed product becomes smaller, but if the generation of fine particles that adversely affect the polishing characteristics such as cleaning property is suppressed, the crushing time becomes longer. This is because crushing is possible.

By the way, of the seventh to tenth embodiments,
The tenth embodiment in which the average diameter of the grinding medium is gradually reduced is that the number of times of grinding until obtaining the target ground material is the smallest (highest grinding efficiency). As a result, in order to secure high pulverization efficiency, it is more preferable to gradually reduce the average diameter of the pulverizing medium in accordance with the change in the particle diameter of the raw material to be pulverized, which gradually becomes smaller as it is pulverized. It turned out to be preferable. Then, as shown in FIGS. 1 and 2, D at the end of crushing in the eighth, ninth and tenth embodiments
Comparing No. _10, as compared with the eighth embodiment, the value of D ₁₀ is higher in the ninth and tenth embodiments in which a grinding medium having a diameter of 0.4 mm (about 800 times) is used in the final grinding. Was large and there were few fine particles. As a result, the last crushing step among multiple crushing steps has a great influence on the average particle size and particle size distribution of the crushed product, and by extension, on the average particle size and particle size distribution of the abrasive produced. I understand. Also,
In the seventh embodiment in which a grinding medium having a diameter of 1.6 mm (about 3200 times) is used in the last grinding step, a ground product in which generation of fine particles is sufficiently suppressed was obtained. From this,
The average diameter of the grinding media used in the last grinding step is 0.3 m
It has been found that if the average particle size is at least m and not more than 3000 times the average particle size of the target pulverized product, sufficient polishing performance can be obtained with respect to smoothness required for precise polishing, and this is considered preferable. The average diameter of the grinding medium used in the final grinding step is more preferably 2000 times or less, and even more preferably 1500 times or less, the average particle diameter of the target ground material. Eighth embodiment (diameter 0.8 mm, grinding medium of about 1600 times)
Alternatively, according to the ninth embodiment (milling medium having a diameter of 0.4 mm and about 800 times), the number of milling operations is smaller than that of the seventh embodiment and the production of fine particles is suppressed to the same level as or more than that of the seventh embodiment. This is because the product was obtained.

Further, the use of a grinding medium mixed with grinding media having different diameters was examined.

Eleventh Embodiment : An embodiment using carbon steel balls having a diameter different from that of the fifth embodiment. Specifically, a diameter of 3.175 mm (hereinafter, 3.2 mm is a nominal diameter) was used. All other manufacturing conditions of the abrasive were the same as in the fifth embodiment. In the pulverization, the average particle size D ₅₀ is 1.0 after 6 hours from the start of pulverization.
A slurry having a size of μm or less was obtained.

Twelfth embodiment : Different from the eleventh embodiment, it is an embodiment in which two kinds of carbon steel balls having different diameters are crushed. Specifically, the same number of balls having a diameter of 1.6 mm and those having a diameter of 4.7 mm were put into the ball mill. Therefore, the average diameter of carbon steel balls is
It was 3.2 mm, which is almost the same as the embodiment. All other manufacturing conditions of the abrasive were the same as in the eleventh embodiment. In the pulverization, a slurry having an average particle diameter D ₅₀ of 1.0 μm or less was obtained 5 hours after the start of pulverization.

[0068]

[Table 3]

As can be seen from Table 3, the performance of the abrasives such as the scratch evaluation and the cleaning property were the same as those of the abrasives obtained in both embodiments. On the other hand, although the total weight and the average particle size of the pulverizing medium were the same, the twelfth embodiment in which carbon steel balls having different diameters were mixed was pulverized in a shorter time to the pulverizing target average particle size. did it. As a result, even if the average diameter is the same, it is better to mix grinding media with different diameters.
It turned out that it can be crushed in a shorter time.

Further, the crushing process performed after roasting was also examined.

Thirteenth Embodiment : This embodiment has a crushing step even after roasting. The conditions for crushing before roasting were the same as those for the crushing of the eighth embodiment. In addition, the abrasive manufacturing conditions other than having a crushing step after roasting,
It was the same as the eighth embodiment. By the way, in the crushing after roasting, the same attritor as the crushing means used in the first embodiment is used, and the crushing medium has a diameter of 1.2 mm (about 2400 mm).
2 times) zirconia balls were used. 10 kg of this zirconia ball was put into a crushing container, and subsequently 2.0 kg of the raw material after roasting and 4.0 kg of pure water, which was the object of crushing, were charged and crushed. The raw material after roasting that was the object of pulverization was rare earth oxide, and the average particle size was 0.55 μm. Then, in the pulverization after roasting, a slurry having an average particle diameter D ₅₀ of 0.49 μm was obtained 4 hours after the initiation of pulverization.

Fourteenth Embodiment : In crushing after roasting,
Zirconia balls having a diameter different from that of the thirteenth embodiment were used. Specifically, a diameter of 0.8 mm (about 2000 times) was used. The other abrasive production conditions were the same as in the thirteenth embodiment. In the pulverization after roasting, a slurry having an average particle diameter D ₅₀ of 0.38 μm was obtained 4 hours after the initiation of pulverization.

Fifteenth Embodiment : In grinding after roasting,
Zirconia balls having a diameter different from that of the thirteenth embodiment were used. Specifically, the one having a diameter of 0.4 mm (about 1300 times) was used. The other abrasive production conditions were the same as in the thirteenth embodiment. In the pulverization after roasting, a slurry having an average particle diameter D ₅₀ of 0.33 μm was obtained 4 hours after the initiation of pulverization.

Comparative Example 3 : 13th in crushing after roasting
A zirconia ball having a diameter different from that of the embodiment was used.
Specifically, a diameter of 5.0 mm (about 10,000 times) was used. The other abrasive production conditions were the same as in the thirteenth embodiment. In the pulverization after roasting, a slurry having an average particle diameter D ₅₀ of 0.66 μm was obtained 4 hours after the initiation of pulverization. Although the average particle diameter (0.5 μm) targeted for pulverization was not reached, it was determined that the pulverization would not proceed any further, and the pulverization was terminated at this point.

Comparative Example 4 : In grinding after roasting,
A zirconia ball having a diameter different from that of the embodiment was used.
Specifically, the one having a diameter of 2.0 mm (about 4000 times) was used. The other abrasive production conditions were the same as in the thirteenth embodiment. In the pulverization after roasting, a slurry having an average particle diameter D ₅₀ of 0.51 μm was obtained 7 hours after the initiation of pulverization.

Comparative Example 5 : Abrasive manufacturing conditions were the same as in Comparative Example 4 except for the grinding time after roasting. In this comparative example,
Crushing after roasting was performed for 10 hours. As a result of the pulverization, an abrasive slurry having an average particle diameter D ₅₀ of 0.50 μm was obtained. Although the average particle diameter (0.3 μm) targeted for pulverization was not reached, it was determined that pulverization would not proceed any further, and pulverization was terminated at this point.

[0077]

[Table 4]

As can be seen from Table 4, according to the thirteenth embodiment, the fourteenth embodiment and the fifteenth embodiment, it is possible to obtain a suitable abrasive having excellent scratch evaluation and cleanability by crushing for a short time. I understand. Further, of these embodiments, the most suitable abrasive has the smallest diameter of 0.4 m.
15th using m (about 1300 times) zirconia ball
It was an embodiment. On the other hand, the diameter is 5.0 mm (about 1000
Comparative Example 3 using zirconia balls of 0 times) and Comparative Examples 4 and 5 using zirconia balls having a diameter of 2.0 mm (about 4000 times) are used for each embodiment, despite being crushed for a long time. Only an abrasive having a larger particle size than the average particle size of the abrasive obtained in Example 1 was obtained, and the abrasives obtained by each Comparative Example were obtained by each embodiment in terms of both scratch evaluation and detergency. It was significantly inferior to the obtained abrasive.

As a result, it was found that the crushing medium used in the crushing step after roasting is preferably one having an average diameter of 3000 times or less the average particle size of the crushed product (target crushed product). This is because when the size is more than 3000 times, as shown in Comparative Examples 4 and 5, an abrasive having poor cleanability can be obtained. From the viewpoint of easy separation of the crushed raw material and the crushing medium, the crushing medium preferably has an average diameter of 0.3 mm or more.

Sixteenth Embodiment : In a crushing step before roasting, alumina balls (density 4.0 g) are used as a crushing medium.
/ Cm ³ ) was used. The diameter of the ball used is 1.6 m
It was m. And the input amount was 5.0 kg. This is to make the volumes of the grinding media the same. The other conditions for producing the abrasive were the same as those in the first embodiment.
In the crushing, the average particle size D
A slurry having ₅₀ of 0.5 μm or less was obtained.

Comparative Example 6 Nylon (nylon 88) balls (density 1.1 g / cm ³ ) were used as a grinding medium. The diameter of the balls used was 1.6 mm. And the input amount was 1.4 kg. The other conditions for producing the abrasive were the same as those in the first embodiment. In the pulverization, even if 12 hours have passed from the start of pulverization, the average particle diameter D ₅₀
No slurry of 0.5 μm or less was obtained.

[0082]

[Table 5]

As can be seen from Table 5, in Comparative Example 6 (milling medium is nylon balls), even if milled for 12 hours, it was not possible to obtain an abrasive slurry having an average particle diameter D ₅₀ of 0.5 μm or less. . On the other hand, in the sixteenth embodiment (the crushing medium is an alumina ball), it was possible to crush in a short time of 5 hours. As a result, the density of the grinding medium is 3.0 g /
It was found that if it is lower than cm ³ , the pulverization efficiency is low and sufficient pulverization cannot be performed.

[0084]

As can be seen from the above description, according to the present invention, it is possible to obtain an excellent crushing efficiency in which the crushing efficiency is good and the generation of abrasive fine particles which deteriorates the performance such as the smoothness of the surface to be polished is suppressed. A method for producing a cerium-based abrasive using the method can be provided.

[Brief description of drawings]

FIG. 1 is a graph showing a change in average particle size of a crushed product obtained by crushing with a bead mill in relation to the number of times of crushing.

FIG. 2 is a graph showing a change in average particle diameter of a crushed product obtained by crushing with a bead mill, in relation to the number of times of crushing.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuya Ushiyama             1-11-1 Osaki, Shinagawa-ku, Tokyo Mitsui Kin             Rare Meta, Functional Materials Business Group, Genus Mining Co., Ltd.             Within the business unit (72) Inventor Yuki Nakajima             1-11-1 Osaki, Shinagawa-ku, Tokyo Mitsui Kin             Rare Meta, Functional Materials Business Group, Genus Mining Co., Ltd.             Within the business unit (72) Inventor Hiroyuki Watanabe             1-11-1 Osaki, Shinagawa-ku, Tokyo Mitsui Kin             Rare Meta, Functional Materials Business Group, Genus Mining Co., Ltd.             Within the business unit F term (reference) 3C058 AA07 AC04 CB01 DA17

Claims (5)

[Claims] 1. A method for producing a cerium-based abrasive having a crushing step and a roasting step, wherein the crushing step applies kinetic energy to the crushing medium with the raw material to be crushed and the crushing medium being put into a crushing container. It is a step of pulverizing the raw material to obtain a target pulverized product having a predetermined average particle diameter, and the pulverization medium has an average diameter of 0.3 mm or more and 8,000 times or less of the average particle diameter of the target pulverized product. And a method for producing a cerium-based abrasive. 2. The crushing process after the roasting process is a crushing process in which a cerium-based rare earth oxide is a raw material to be crushed, and the crushing medium has an average diameter of 300 times the average particle size of the target crushed product.
The method for producing a cerium-based abrasive according to claim 1, which is 0 times or less. 3. The pulverizing step performed at least one of before and after roasting is a step of pulverizing the raw material stepwise by changing the pulverizing medium during the pulverizing step. 3. The grinding medium used in each of the second and subsequent grinding steps in step 3, the average diameter of which is smaller than the average diameter of the grinding medium used in the grinding step immediately before the grinding step. Method for producing cerium-based abrasive. 4. The method for producing a cerium-based abrasive according to claim 1, wherein the grinding medium has a density of 3.0 g / cm ³ or more. 5. A cerium-based abrasive having an average particle diameter of 3 μm or less, which is produced by the method for producing a cerium-based abrasive according to any one of claims 1 to 4.