JP2002309237A - Method for manufacturing raw material for cerium- containing abrasive, and raw material manufactured thereby - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a raw material for abrasives that can be sintered at a relatively low baking temperature, and does not cause abnormal grain growth when used for manufacturing cerium-containing abrasives. SOLUTION: This is a manufacturing method to produce a raw material for cerium-containing abrasives comprising, as a main component, a mixture of a cerium-containing rare earth carbonate and a cerium-containing rare earth oxide, wherein part of the carbonate is converted into the oxide by calcining at 400-800 deg.C. The baking time is preferably 0.1-48 hours.

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 raw material used for producing a cerium-based abrasive containing cerium oxide as a main component, and further relates to a cerium-based abrasive having excellent polishing characteristics using the raw material.

[0002]

2. Description of the Related Art Cerium-based abrasives have been used for polishing various glass materials. In particular, in recent years, glass for magnetic recording media such as hard disks and liquid crystal displays (LC) have been used.
It is also used for polishing glass materials used in electric and electronic devices such as the glass substrate of D), and its application fields are expanding.

[0003] This cerium-based abrasive comprises abrasive particles composed of cerium oxide (CeO ₂ ) particles as a main component and other rare earth metal oxide particles, and the total rare earth oxide content of cerium oxide ( (Hereinafter referred to as TREO)), but are classified into high cerium abrasives and low cerium abrasives, but there is no significant difference in the production process. That is, any cerium-based abrasive is first subjected to a chemical treatment (wet treatment) after pulverizing the raw material. This is done by adding a fluorine component to the cerium-based abrasive to ensure its high machinability. In some cases, in addition to this, an alkali metal such as sodium which causes abnormal grain growth during the subsequent roasting process In order to remove. Then, the raw material after the wet treatment is filtered, dried, heated to a high temperature and then roasted to sinter the raw material particles, and then crushed and classified again to obtain a desired particle size and polishing having a desired particle size distribution. The material is manufactured.

Here, as a raw material used for the production of a cerium-based abrasive, a natural raw material called bastnaesite concentrate, which is a beneficiated rare earth ore, has conventionally been used in many cases. Recently, however, cerium-based rare earth carbonates (hereafter referred to as rare earth carbonates) that have been enriched in rare earth metal concentration by chemically treating bastnaesite ores and relatively inexpensive complex ores in China, Cerium-based rare earth oxides (hereinafter referred to as rare earth oxides), which are oxides obtained by calcining carbonates at a high temperature prior to the abrasive production process, are often used as raw materials.

[0005]

Incidentally, in order to ensure sufficient machinability as an abrasive, it is important to sinter the raw material particles in the roasting step to produce abrasive particles of an appropriate size. . Therefore, when the rare earth carbonate and the rare earth oxide are used as raw materials, the roasting temperature is set to 1
Usually, the temperature is set to a relatively high temperature range of around 000 ° C. This is because no matter which material is used, it is empirically clarified that the raw material particles cannot be sufficiently sintered unless the temperature is within such a temperature range.

However, raising the roasting temperature has the effect of promoting sintering, but causes abnormal grain growth. Then, coarse particles are generated by the abnormal grain growth, and in some cases, may be mixed in the abrasive as a final product. Since such coarse particles cause scratches, it is necessary to reduce the content as much as possible. In the past, it was performed by preparing a classification process after roasting.However, if the classification conditions were too strict to lower the coarse particle concentration, the production efficiency of the abrasive was reduced and the cost was increased. .

[0007] Therefore, in order to suppress the mixing of coarse particles and secure production efficiency, it can be said that it is desirable to be able to perform roasting at the lowest possible temperature in order to suppress abnormal grain growth in the roasting step. .

Accordingly, the present invention provides a method for producing a raw material for an abrasive, which is capable of sintering even at a relatively low roasting temperature in the production of an abrasive, and which is free from abnormal grain growth. Aim. An object of the present invention is to provide a raw material for an abrasive produced by this method and a cerium-based abrasive produced by the method and capable of forming a high-quality polished surface.

[0009]

Means for Solving the Problems In order to solve such problems, the present inventors have conducted intensive studies and studied the sintering mechanism at the time of roasting using the above-mentioned rare earth carbonate and rare earth oxide. did. According to the present inventors, the reason why roasting of rare earth carbonate and rare earth oxide at a high temperature is necessary is as follows.

First, the rare earth carbonate is as shown in FIG. The rare earth carbonate carried in as a raw material is composed of coarse aggregates in which rare earth carbonate particles are bound. In the process of manufacturing an abrasive using rare earth carbonate as a raw material, first, the raw material is crushed. The aggregate of the rare earth carbonate has a strong binding power. Although wet pulverization of slurrying and pulverization is often applied, since the viscosity of this slurry is higher than the cohesive force of rare earth oxide, the pulverization efficiency is low, and it is difficult to make it into fine particles completely. Coarse particles are partially left in the fine rare earth carbonate.

The raw material after the pulverizing step is subjected to a fluorination treatment. In the fluorination treatment, a part of the carbonic acid component in the rare earth carbonate is exchanged for fluorine, and the rare earth carbonate becomes rare earth fluorocarbonate. Accordingly, the coarse particles are destroyed. But,
Since the amount of fluorine added in the fluorination treatment is limited due to the relationship with the fluorine concentration of the final product, coarse particles are not sufficiently destroyed.

Then, the fluorinated rare earth carbonate is roasted, and most of the carbonate component in the rare earth carbonate is released as CO ₂ during the roasting. And low porous particles. Since the sintering speed of such shaped particles is low, sintering does not proceed unless the temperature is high. In particular, since the rare earth carbonate has a large amount of coarse particles remaining as described above, the coarse particles form coarse shaped body particles, but the coarse shaped body particles have a very low sintering rate. For this reason, when producing an abrasive using rare earth carbonate as a raw material, it is necessary to raise the roasting temperature.

On the other hand, the sintering mechanism for rare earth oxide is illustrated in FIG. As described above, the rare earth oxide is obtained by calcining the rare earth carbonate at a high temperature. Therefore, the rare earth carbonate as the raw material of the rare earth oxide forms coarse particles as in FIG. However, by calcining this rare earth carbonate, the release of the carbonic acid component occurs to form shaped particles, which are brittle and collapse by the impact received during the calcining process,
Form some fine particles of rare earth carbonate. Then, these fine particles of rare earth carbonate are oxidized by the subsequent heating to become rare earth oxide.

However, in the calcining step at this high temperature, the generated rare earth oxide particles sinter together to form an aggregate. This rare earth oxide aggregate has a strong binding force and a part thereof remains in the same shape even in the subsequent pulverization step.
As a result, such an agglomerate is not fluorinated to the inside when the fluorination treatment is performed, and the rare earth oxide particles at the center remain as oxide.

[0015] Such non-uniformity of fluoridation adversely affects the sintering step in the subsequent roasting. That is, the agglomerates in which such fluorination is made nonuniform are collapsed by heating and impact during the roasting step, but are not fluorinated with the rare earth oxide particles that have been sufficiently fluorinated by this, or have a low fluorine concentration. It becomes a state in which rare earth oxide particles are mixed.
The former sinters quickly, but the latter does not have a sufficient sintering rate unless the sintering rate is low and the temperature is considerably high. For this reason, when producing an abrasive using rare earth oxide as a raw material, it is necessary to raise the roasting temperature.

The present inventors have considered the sintering mechanism of rare earth carbonate and rare earth oxide as described above, and can perform the fluorination treatment uniformly without the presence of shaped particles during roasting. As a method of manufacturing the raw material, by calcining the rare earth carbonate before pulverization in the same manner as the rare earth oxide, by causing the change from the rare earth carbonate to the rare earth oxide by the calcination to occur partially, We thought that the above problem could be solved. FIG. 3 shows the process of such partial calcination.

In this partial calcination, the rare earth carbonate is calcined similarly to the method for producing the rare earth oxide. Therefore, the change occurring in the rare earth carbonate particles in the initial stage of the calcination is the same as that of the rare earth oxide. is there. In other words, the carbonic acid component is released as CO ₂ , and the rare earth carbonate particles become skeleton particles, disintegrate, and form fine rare earth carbonate particles. Then, the rare earth carbonate particles are oxidized, and the proportion of the oxide in the particles increases as the heating time elapses. In the partial calcination according to the present invention, the calcination is stopped before the rare earth carbonate is completely turned into a rare earth oxide,
The particles constituting the raw material are mixed rare earths composed of oxide carbonate.

In the mixed rare earth particles formed by the partial calcination, the remaining pulverized particles are broken and further atomized by the subsequent pulverization step and fluorination treatment. In the fluoridation treatment, uniform fluorination is performed because no aggregated particles exist as in the case of rare earth oxide. As a result, in the calcining step, there is no factor that hinders sintering, such as shaped particles or particles with insufficient fluorination, so that sintering proceeds even at a relatively low temperature.

As described above, according to the partial calcination proposed by the present inventors, polishing which does not cause a problem that sintering is difficult to occur unless the high temperature of the rare earth carbonate and the rare earth oxide is present. Raw materials for materials can be manufactured.

On the other hand, in this partial calcination, it is important how the rare earth carbonate is appropriately oxidized into a mixed rare earth. If the heating is excessive, the rare earth carbonate becomes completely a rare earth oxide and is fluorinated non-uniformly as described above, and if the heating is insufficient, sufficient destruction of the skeleton particles does not occur. This is because in any case, the raw material has a problem in sinterability. The present inventors have conducted intensive studies to find out different conditions in producing the raw material for an abrasive by performing such partial calcination, and as a result, have come to the invention described in claim 1 of the present application. Was.

That is, the invention according to claim 1 of the present application is a method for producing a raw material for a cerium-based abrasive mainly comprising a mixed rare-earth salt of a cerium-based rare earth carbonate and a cerium-based rare earth oxide, Rare earth carbonate at 400 ° C ~ 80
This is a method for producing a raw material for a cerium-based abrasive, in which a part of the cerium-based rare earth carbonate is converted into a cerium-based rare earth oxide by calcining at 0 ° C.

The reason for setting the calcination temperature to 400 to 800 ° C. is to release the carbonate component from the rare earth carbonate appropriately by calcination at such a temperature. That is, 800 ° C
If the temperature exceeds 400 ° C., the conversion to rare earth oxide will be rapid and complete rare earth oxide will be obtained, and if the temperature is lower than 400 ° C., sufficient release of carbonic acid component and destruction of coarse particles will not occur. Similarly, in performing the partial calcination in this temperature range from the viewpoint of appropriately releasing the carbonate component from the rare earth carbonate, the calcination time is set to 0.1 to 48 hours as described in claim 2. Is preferred.

The raw material produced according to the present invention is
It can be applied as it is to the conventional cerium-based abrasive production process, and by performing pulverization and fluorination treatment, it is possible to reduce the amount of coarse particles and uniformly fluorinate. Thereby, the roasting temperature in the roasting step can be reduced.

Here, in consideration of the convenience of transporting the raw materials and the productivity of the abrasive as a final product in addition to the sinterability during roasting, more preferable raw materials are as described in claim 4. It contains raw materials for cerium-based abrasives,
Cerium-based abrasive raw materials having a loss on ignition of 1.0 to 20% on a dry weight basis when heated at 000 ° C. for 1 hour are preferred.

Loss on ignition (hereinafter referred to as LOI (Loss On)
Ignition). ) Means the rate of weight loss when the object is ignited. The high ignition loss in the cerium-based abrasive material means that the productivity is poor because the weight of the final product is lower than the weight of the raw material before roasting during roasting. It is known that the value of this ignition loss is as high as about 30% for rare earth carbonate and about 0.5% for rare earth oxide which has been sufficiently calcined at a high temperature. Therefore, in the present invention, the value of LOI can be said to be an index for indirectly indicating the existence ratio of rare earth carbonate and rare earth oxide. In the present invention, the standard for ignition loss is 10
The case of heating at 00 ° C. for 1 hour is because, in the case of rare earth carbonate, it has been experimentally confirmed that the value of loss on ignition starts to stabilize by heating at 500 ° C. or more. It is based on the idea that heating can be applied as the most stable indicator.

In the present invention, the ignition loss is 1.0
According to the test results of the present inventors, within the above range, sintering proceeds sufficiently and uniformly even when roasting at a relatively low temperature. This is because it is possible to obtain an abrasive which scarcely generates scratches. Here, in order to set the range of the loss on ignition to 1.0 to 20%, the rare earth carbonate is adjusted so that the desired loss on ignition is obtained in the above-mentioned range of the calcination temperature and the calcination time by the method according to the present invention. By adjusting the distribution of rare earth carbonate and rare earth oxide by heating. Also, in the raw material produced according to the present invention,
It can also be prepared by appropriately mixing rare earth oxide or rare earth carbonate.

As described above, the raw material for an abrasive according to the present invention can be sintered at a sufficient sintering rate even when roasted at a relatively low temperature. Therefore, the invention according to claim 5 includes a step of pulverizing and fluorinating this raw material, and then roasting the fluorinated cerium-based abrasive raw material in a temperature range of 700 to 1000 ° C. A method for producing abrasives. By roasting at such a low temperature, it is possible to produce a cerium-based abrasive capable of suppressing abnormal grain growth and forming a high-quality polished surface without flaws.

In the method for producing a cerium-based abrasive, a fluorination treatment is performed before the roasting step. This fluorination treatment is preferably performed using ammonium fluoride. Hydrofluoric acid can also be used for the fluoridation treatment, but ammonium fluoride allows the fluorination reaction to proceed slowly, so that fluorine can be more uniformly distributed in the raw material. This is because roasting at a lower temperature becomes possible.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below along with comparative examples.

First Embodiment : Abrasive materials are prepared by calcining 20 kg of rare earth carbonate having a cerium oxide content of 60% in TREO (TREO: 70% (dry weight basis)) in a muffle furnace at 500 ° C. for 2 hours. Raw materials were manufactured. Then, the LOI at this time was measured.

The LOI was measured as follows. The raw material for an abrasive was placed in a crucible whose weight was measured in advance, and the weight thereof was measured. After that, the material was heated in an electric furnace at 1000 ° C. for 1 hour and then allowed to cool in a dry atmosphere. After cooling, the weight of the crucible was measured, and the value of LOI was determined according to the following formula. as a result,
The LOI of the raw material for the abrasive produced according to this embodiment is 5
%Met.

[0032]

(Equation 1)(B: Loss on ignition (%), W₁: Raw material for abrasive before heating
Crucible weight (g), W ₂： Take raw material for abrasive after heating
Pot weight (g), W₃: Crucible weight)

Next, 2 kg of this abrasive material and 2 l of pure water
Were crushed for 5 hours in a wet ball mill (volume: 5 l) filled with 12 kg of a steel crushing medium having a diameter of 5 mm, and the average particle size (microtrack method D50 (cumulative 50% particle size)) 1
The slurry was made of a powder of μm. Then, a 1 mol / l ammonium fluoride solution was added to the pulverized slurry so that the fluorine concentration in the abrasive in the final state became 6%, followed by washing with pure water and filtration to obtain a cake. . Next, after drying this cake, it was roasted at 900 ° C. for 3 hours, pulverized again, and classified to obtain a cerium-based abrasive.

Second to Fourth Embodiments : Cerium-based abrasives were manufactured by changing the roasting temperature using the raw materials manufactured in the first embodiment. The roasting temperature is 850 ° C., 950 ° C., 10
50 ° C. The conditions other than the roasting temperature were the same as in the first embodiment.

Fifth Embodiment : In this embodiment, a raw material for an abrasive is manufactured by changing the calcination temperature and calcination time of rare earth carbonate.
After measuring the LOI, a cerium-based abrasive was manufactured. At this time, the production conditions of the raw material for the abrasive were the same as in the first embodiment except that the calcination temperature was 400 ° C. and the calcination time was 18 hours. The production conditions of the abrasive were the same as in the first embodiment except that the roasting temperature was 900 ° C. The LOI of the raw material for abrasives produced in this embodiment was also 5%.

Sixth to Eighth Embodiments : Cerium-based abrasives were manufactured by changing the roasting temperature using the raw materials manufactured in the fifth embodiment. The roasting temperature is 850 ° C., 950 ° C., 10
50 ° C. The conditions other than the roasting temperature were the same as in the fifth embodiment.

Comparative Example 1 : As a comparative example for the cerium-based abrasives manufactured in the first to eighth embodiments, a rare earth carbonate was calcined to produce an abrasive material consisting of rare earth oxide. A cerium-based abrasive was manufactured from rare earth. Rare earth oxide was produced by calcining 20 kg of the same rare earth carbonate as in the first embodiment at 900 ° C. for 3 hours in a muffle furnace to obtain a rare earth oxide. The production of cerium-based abrasives requires a roasting temperature of 980.
Except that the temperature was set to ° C., the same process as in the first embodiment was performed.

Comparative Examples 2 to 5 : In the step of producing a cerium-based abrasive from the rare earth oxide of Comparative Example 1, the roasting temperature was changed to 850 ° C., 900 ° C., 950 ° C., and 1050 ° C. Abrasives were manufactured.

Comparative Example 6 Next, a cerium-based abrasive was manufactured using rare earth carbonate as a raw material for the abrasive. The same rare earth carbonate as the abrasive material used in the first embodiment was used. The production conditions in the process of producing the cerium-based abrasive from the rare earth carbonate were the same as those in Comparative Example 1 including the roasting temperature.
The same as above.

Comparative Examples 7 to 10 : As in Comparative Example 1, rare earth carbonate was used as a raw material for an abrasive, and the roasting temperature was 850.
The cerium-based abrasive was manufactured by changing the temperature to 900C, 950C, and 1050C.

And among these cerium-based abrasives,
Second to fourth embodiments and sixth to eighth embodiments, and
For the cerium-based abrasives produced by changing the roasting temperature in Comparative Examples 2, 4, 5 and Comparative Examples 7, 9, and 10, the specific surface area was measured in order to examine the size of the abrasive particles after roasting. Was. The specific surface area was measured by the BET method. Table 1 shows the results.

[0042]

[Table 1]

As a result, it was confirmed that the abrasive using the rare earth oxide or the rare earth carbonate as a raw material had a small specific surface area, that is, did not undergo sintering, unless the temperature was as high as 1050 ° C. Was. On the other hand, the cerium-based abrasives according to the second to fourth embodiments and the sixth to eighth embodiments have a small specific surface area even when roasted at about 850 ° C. This indicates that the abrasive raw material that has been calcined at a relatively low temperature as in these embodiments can be easily sintered.

Next, with regard to the cerium-based abrasives according to the first and fifth embodiments and the cerium-based abrasives according to Comparative Examples 1, 3, 6, and 8, coarse particles in the abrasive (polishing having a particle size of 10 μm or more) were used. The cerium-based abrasive was used to polish a glass material, and the polishing value was measured and the state of the polished surface was compared and evaluated.

The measurement of the coarse particle concentration was carried out as follows. 200 g of each cerium-based abrasive was weighed, collected and dispersed in an aqueous solution containing 0.1% sodium hexametaphosphate as a dispersant. The mixture was stirred for minutes to produce a slurry. This slurry was filtered through a micro sieve having a pore size of 10 μm, and the residue on the sieve was recovered. The collected residue was again dispersed in a 0.1% sodium hexametaphosphate solution to form a slurry. At this time, the dispersion was carried out by ultrasonic stirring for 1 minute. Then, the slurry was filtered with a micro sieve having a pore size of 10 μm. Re-slurry and filtration of the collected residue were performed twice to collect coarse particles. Thereafter, the coarse particles were sufficiently dried and weighed, and the coarse particle concentration was determined from the weight of the coarse particles.

For the measurement of the polishing value and the evaluation of the state of the polished surface, first, each abrasive was dispersed in water to obtain an abrasive slurry of 10% by weight. This abrasive slurry was constantly stirred with a stirrer during the polishing test so that the abrasive did not settle. Polishing of glass material is performed with a high-speed polishing machine.
The glass for flat panel of mmφ was polished using a polishing pad made of polyurethane as a material to be polished. The polishing conditions were such that the abrasive slurry was supplied at a rate of 5 ml / min, the pressure on the polished surface was set at 15.7 kg / cm ^2, and the rotation speed of the polisher was 1000 rpm. The polished glass material was washed with pure water and dried in a dust-free state.

The polishing value in this evaluation test was determined by measuring the weight of the glass before and after polishing to determine the weight loss due to polishing, and expressing the polishing value from this weight reduction. Was relatively evaluated as 100.
The surface finish of the polished surface was evaluated based on the presence or absence of scratches on the polished surface and the presence or absence of abrasive particles on the polished surface. Specifically, the surface of the polished glass was irradiated with a halogen lamp of 300,000 lux, and the glass surface was observed by a reflection method. At this time, the evaluation of the flaw was scored according to the degree (size) of the flaw and its size, and evaluated by a deduction system from 100 points. Table 2 shows the evaluation results.

[0048]

[Table 2]

From these results, it was found that the cerium-based abrasives according to the first and fifth embodiments had good polishing values, and could form an excellent polished surface with no scratches on the polished surface. On the other hand, the comparative example is a cerium-based abrasive using rare earth oxide and rare earth carbonate as raw materials. Polishing value is low. When the sintering temperature was increased, the polishing value increased to some extent, but scratches were observed and the evaluation of the polished surface was lowered. This result is, as can be seen from the measurement results of the coarse particle concentration, 400 ppm in the abrasives of Comparative Examples 1 and 6.
It is considered that the above coarse particles are mixed, but since these coarse particles cause sintering by performing roasting at a high temperature for rare earth oxides and rare earth carbonates,
It is considered that abnormal grain growth occurred, and the coarse particles thus generated remained in the final abrasive product.

[0050]

As described above, according to the present invention, the rare earth carbonate is partially calcined, the calcining is stopped before the rare earth carbonate is completely converted to the rare earth oxide, and the particles constituting the raw material are removed. This is used as a raw material for an abrasive as a mixed rare earth composed of an oxide carbonate. ADVANTAGE OF THE INVENTION According to this invention, the raw material for abrasives which can be sintered even if roasting temperature is relatively low in abrasive production can be manufactured. According to this raw material for an abrasive, a cerium-based abrasive capable of forming a high-quality polished surface without mixing of coarse particles due to abnormal grain growth can be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram showing a change in rare earth carbonate particles in an abrasive production process.

FIG. 2 is a view showing a change of rare earth oxide particles in an abrasive production process.

FIG. 3 is a diagram showing a change in raw material particles for an abrasive when partial calcination according to the present invention is performed.

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Yoshitsugu Uchino 1-11-1 Osaki, Shinagawa-ku, Tokyo Rare Metals Division, Materials Business Unit

Claims (7)

[Claims] 1. A method for producing a raw material for a cerium-based abrasive mainly comprising a mixed rare-earth salt of a cerium-based rare-earth carbonate and a cerium-based rare-earth oxide, wherein the cerium-based rare-earth carbonate is heated to 400 ° C. to 800 ° C. A method for producing a raw material for cerium-based abrasives, wherein a part of the cerium-based rare earth carbonate is converted into a cerium-based rare earth oxide by calcining. 2. The method according to claim 1, wherein the calcination time is 0.1 to 48 hours. 3. A raw material for a cerium-based abrasive produced by the method according to claim 1. 4. A cerium-based abrasive material containing the cerium-based abrasive material according to claim 3, wherein a loss on ignition when heated at 1000 ° C. for 1 hour is 1.0 to 20% on a dry weight basis. Raw material for abrasives. 5. The cerium-based abrasive raw material according to claim 3 is pulverized and fluorinated, and then the cerium-based abrasive raw material after fluorination is treated at 700 to 1000 ° C.
A method for producing a cerium-based abrasive, comprising a step of roasting in a temperature range of 1. 6. The method for producing a cerium-based abrasive according to claim 5, wherein the fluorination treatment is performed with ammonium fluoride. 7. A cerium-based abrasive produced by the method according to claim 5.