JP2006124566A - Cerium-based abrasive and method for producing cerium-based abrasive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cerium-based abrasive containing no fluorine, improved in not only abrasive activity but also grinding accuracy. <P>SOLUTION: The cerium-based abrasive contains ≥30 wt.% cerium oxide based on the total rare earth oxide (TREO) and has ≤0.5 wt.% fluorine content based on TREO, wherein the cerium-based abrasive contains 0.01-3.0 wt.% at lest one alkali metal selected from a group consisting of sodium, potassium and lithium based on TREO as a whole, and has ≤0.3 wt.% chlorine content. The content of at least one alkali metal selected from a group consisting of sodium, potassium and lithium is preferably 0.02-1.0 wt.% (TREO base), and, in that case, the chlorine content is preferably ≤0.1 wt.%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a cerium-based abrasive. Specifically, the present invention relates to a cerium-based abrasive that contains almost no fluorine and has excellent polishing speed and polished surface accuracy.

  Cerium-based abrasives containing cerium-based particles as a main component are rapidly expanding their applications due to their excellent polishing action. Currently, it is used not only for conventional optical glass polishing applications, but also for fields such as glass for liquid crystals, glass polishing for magnetic recording media such as hard disks, and the manufacture of electronic circuits such as glass substrates for photomasks.

  The manufacturing process of the cerium-based abrasive is roughly explained in a step of pulverizing the abrasive raw material and a step of appropriately sintering the raw material particles by heating and baking the pulverized raw material at a high temperature, Further, an abrasive having a desired particle size and particle size distribution is obtained through an appropriate classification process. And as a raw material for abrasives, natural rare earth concentrates such as bastonite ore have been used conventionally, but in recent years, in addition to this, cerium-based rare earth carbonates obtained by processing rare earth concentrates ( Hereinafter, it is often used as a raw material, or a cerium-based rare earth oxide (hereinafter also referred to as rare earth oxide) obtained by pre-calcining the rare earth carbonate at a high temperature.

  By the way, the conventional cerium-based abrasive contains several percent of fluorine (total rare earth oxide standard (hereinafter referred to as TREO)). The reason why fluorine is contained in the cerium-based abrasive is to ensure the polishing power of the cerium-based abrasive. That is, in the conventional cerium-based abrasive, the mechanical polishing action by the abrasive particles made of cerium oxide or the like is mainly, but in addition to this, fluoride is formed on the surface of the abrasive by the contained fluorine. This is to improve the polishing force by simultaneously exerting the chemical polishing action of promoting the erosion of the material to be polished. Fluorine is already contained during the roasting process of the abrasive raw material, and the abrasive is manufactured by roasting in a state containing fluorine. Fluorine causes the abrasive particles to appropriately sinter in this roasting step, whereby abrasive particles having a high abrasive power are obtained.

  And in the conventional cerium type abrasive, what adjusted the fluorine concentration according to the abrasive raw material is used. That is, since the bust nesite concentrate contains about 6% by weight of fluorine, when the bust nesite concentrate is used as an abrasive material, a fluorine-containing abrasive can be produced without any special treatment. . On the other hand, rare earth carbonates or rare earth oxides that have been used recently as raw materials for abrasives have most of the fluorine removed in the production process. For this reason, fluoride is added in the production process for abrasives. The product is manufactured by adjusting the fluorine concentration.

  As described above, the conventional cerium-based abrasive can contain a fluorine so as to ensure a high polishing speed and to produce a polished surface having excellent specularity. However, recently, with the emphasis on environmental issues, the presence of fluorine in the abrasive is regarded as a problem, and establishment of a cerium-based abrasive that does not contain fluorine is required. This takes into account the release of fluorine into the atmosphere during the production of abrasives and the exhaust treatment of used abrasive slurries. In addition, recently, attempts to recycle used abrasives have been considered. In this case, it is also considered that the presence of fluorine is an obstacle.

As a conventional technique for a fluorine-free cerium-based abrasive containing almost no fluorine, Patent Document 1 discloses 40 to 99.5% by weight of cerium oxide and a colorless oxide of at least one other rare earth element. A cerium-based abrasive containing 0.5 to 60% by weight is disclosed. The applicant of the present invention is characterized in that in Patent Document 2, 0.5 wt% or less of fluorine is contained, and alkali metal and / or alkaline earth metal is contained in an element conversion of 0.3 to 5 wt%. A cerium-based abrasive mainly composed of cerium oxide is disclosed.
Japanese Patent Publication No. 63-27389 JP 2002-155269 A

  With respect to these prior arts, the former completely eliminates fluorine as a constituent component, thereby ensuring recyclability for glass. However, according to the inventors of the present invention, no particular consideration has been given to the improvement of the polishing characteristics (polishing speed and polishing surface accuracy). In fact, the polishing speed is low and many polishing scratches are generated. There is a problem that the polished surface accuracy is inferior. On the other hand, the latter is more successful in improving the polishing characteristics than the former prior art, and in particular, the improvement in the polishing speed is clearly seen. However, there is room for improvement in the latter polishing material, and the level of improvement in polishing scratches is required.

  The present invention has been made in view of the above circumstances, and provides a cerium-based abrasive and a method for producing the same, in which the polishing accuracy is further improved in addition to the polishing force in a cerium-based abrasive containing almost no fluorine.

  The inventors of the present invention have studied the latter prior art, and have studied an abrasive that can solve the above-described problems. As a result, in a polishing material that does not contain fluorine, paying attention to the relationship between the alkali metal and chlorine and the polishing characteristics, it has been found that the polishing accuracy can be improved together with the polishing speed by clarifying their preferred range, The present invention has been conceived.

  That is, the present invention relates to a cerium-based abrasive containing 30% by weight or more of cerium oxide with respect to all rare earth oxides (TREO) and having a fluorine concentration of 0.5% by weight or less with respect to TREO. A total of 0.01 to 3.0% by weight of at least one alkali metal selected from the group consisting of TREO and a chlorine concentration with respect to TREO of 0.3% by weight or less. It is a cerium-based abrasive.

  As described above, in a cerium-based abrasive containing no fluorine (substantially not contained), if the constituent component is only a rare earth oxide, the function as an abrasive becomes insufficient. Some additive element is required to impart a polishing force to the rare earth oxide. In the present invention, it is clarified that alkali metals such as sodium, potassium and lithium are useful as the additive element, and the necessity of reducing the chlorine concentration.

  And in this invention, the density | concentration (total density | concentration of sodium, potassium, lithium) of the alkali metal in an abrasive is 0.01-3.0 weight% (TREO standard). If the amount is less than 0.01% by weight, the additive element is not substantially contained, and a sufficient polishing rate cannot be obtained. On the other hand, an increase in the polishing rate is observed due to an increase in the alkali metal concentration. However, if the concentration exceeds 3.0% by weight, the generation of polishing flaws becomes remarkable and the accuracy of the polishing surface is deteriorated. A more preferable range is 0.02 to 1.0% by weight, and 0.03 to 0.5% by weight is more preferable from the viewpoint of the balance between the polishing speed and the polished surface accuracy. In addition, when the cerium oxide content in the abrasive increases, the alkali metal can act more effectively even at a low concentration. For example, when the cerium oxide content is 99% (TREO standard), By setting the alkali metal to 0.3% by weight or less (TREO standard), sufficient polishing characteristics are exhibited. Moreover, as an alkali metal added, sodium is especially preferable.

  On the other hand, regarding the influence of chlorine, even if the alkali metal content is appropriate, an abrasive containing a large amount of chlorine cannot obtain a sufficient polishing rate. According to the present inventors, the chlorine concentration in the abrasive must be 0.5% by weight or less (TREO standard), preferably 0.1% by weight or less.

  In the abrasive according to the present invention, the cerium oxide content needs to be at least 30% by weight (TREO standard). This is because when the cerium oxide content is less than 30% by weight, the polishing rate is low and impractical. Preferably, it is 50% by weight or more (TREO standard). The cerium oxide content is preferably as high as possible from the standpoint of polishing speed, and may be as close as possible to 100%, but from the viewpoint of cost, 99% by weight or less is preferable.

  The fluorine concentration in the abrasive must be 0.5% by weight or less (TREO standard) with respect to TREO. This is because, as already mentioned, fluorine is a component that also has an adverse effect on the environment during the production and use of the abrasive, and is also an obstacle to the recycling of the abrasive. More preferably, the fluorine concentration is preferably 0.1% by weight or less.

In the abrasive according to the present invention, the particle size indicated by D ₅₀ (50% diameter in volume-based cumulative fraction by laser diffraction / scattering particle size distribution measurement) is preferably 0.1 to about the characteristics of the abrasive particles. The thickness is preferably 3.0 μm, more preferably 0.2 to 2.5 μm, and still more preferably 0.3 to 2.0 μm. This is because if the particle size is too small, a sufficient polishing rate cannot be obtained, and conversely if the particle size is too large, the occurrence of polishing scratches becomes significant.

The specific surface area of the abrasive particles is not particularly limited but is preferably 1 to 200 m ² / g. Regarding the relationship between the specific surface area and the polishing characteristics, if the specific surface area is large, the polishing rate tends to decrease, and if the specific surface area is small, the generation of polishing scratches is observed. Therefore, considering the balance between the polishing speed and the polishing scratches, 1 to 30 m ² / g is preferable, and ^{2 to} 25 m ² / g is more preferable. However, for example, polishing materials for finishing polishing may be required to suppress polishing scratches. In such a case, the specific surface area of the abrasive particles may exceed 30 m ² / g, but the present invention is also effective in such an abrasive. That is, even if the polishing material has a large specific surface area, those containing an alkali metal are improved in polishing speed over those containing no alkali metal, and the polishing speed can be improved while maintaining high polishing accuracy.

  Furthermore, the abrasive according to the present invention is preferably an abrasive having a large particle size and a small number of coarse particles. Specifically, it is preferable that coarse particles having a Stokes diameter of 5 μm or more are 1.0% by weight or less (based on the abrasive weight). This is because the presence of coarse particles causes abrasive scratches. The coarse particle content is more preferably 0.5% by weight or less, and more preferably 0.3% by weight or less and 0.1% by weight or less. In the present invention, coarse particles having a Stokes diameter of 5 μm or more are measured by allowing the abrasive slurry to settle for a calculation time in accordance with the Stokes formula and then discarding the supernatant liquid, thereby leaking particles having a Stokes diameter of 5 μm or more. It is preferable to carry out by a method in which the amount is separated and the amount is measured. It is difficult to accurately measure the amount of particles having a size of 5 μm or more, which is contained in the particle size distribution measuring apparatus and contained only about 1% or less by this method, and a large error occurs. This is because a method of separating particles with a particle size of 5 μm or more and measuring the amount is preferable from the viewpoint of accuracy of measurement results. In addition, as a method for separating and measuring particles having a particle size of 5 μm or more, in addition to the above method, the abrasive slurry is passed through an electroformed sieve having an opening of 5 μm or more, and the residual particles on the sieve are dried and the amount thereof is measured. Although there is a method for measuring the above, it is not practical to pass a 5 μm sieve for a long time, regardless of a sieve of 10 μm or more. Therefore, the above method is preferred.

  Next, a method for producing a cerium-based abrasive according to the present invention will be described. The production of the cerium-based abrasive according to the present invention basically conforms to the conventional method of producing a cerium-based abrasive, and the grinding process of the abrasive material, the roasting process of the pulverized abrasive material, necessary And crushing and classifying the roasted product accordingly. However, in the present invention, it is necessary to pay attention firstly in controlling the cerium oxide and fluorine concentrations in the cerium-type abrasive that is the product, and secondly in adjusting the alkali metal concentration. Hereinafter, the manufacturing method of the cerium-based abrasive according to the present invention will be described based on these considerations.

  First, it is preferable that the abrasive material contains 30% by weight or more of cerium oxide with respect to TREO. In particular, it is preferable to use a cerium-based rare earth carbonate whose fluorine concentration with respect to TREO is not higher than the fluorine concentration with respect to TREO of the abrasive for manufacturing by more than 0.1% by weight. In this way, the cerium oxide content relative to TREO in the abrasive raw material is defined because the cerium oxide in the raw material is present in the abrasive that becomes the product without decreasing in the subsequent baking process, etc. It is because it is convenient to control the cerium oxide content in the abrasive to regulate the cerium oxide content from the raw material stage. The cerium oxide content in the raw material is preferably 50% by weight or more (TREO standard), as in the case of the abrasive used as the product. Moreover, the higher the value, the better. It may be as close as possible to 100%, but from the viewpoint of cost, 99% by weight or less is preferable.

  In addition, cerium-based rare earth carbonate is used as an abrasive raw material because the present invention aims to contain almost no fluorine. This is because it is preferable to use a rare earth carbonate. And, the fluorine concentration is regulated because the fluorine in the raw material is somewhat volatilized and removed in the subsequent roasting process, but basically most of it remains in the abrasive that becomes the product. This is because it is preferable to control the fluorine concentration of the abrasive in order to control the fluorine concentration of the abrasive. Furthermore, the fluorine concentration in the raw material exceeds 0.1% by weight (TREO standard) and is not higher than the fluorine concentration of the abrasive for manufacturing purposes. When considering the amount of decrease in concentration, a certain margin can be taken for the fluorine concentration in the raw material, and the margin is 0.1% even when the baking temperature is low and the volatilization of fluorine is small. Is due to. Incidentally, as an example of the relationship between the fluorine concentration of the abrasive material to be manufactured and the fluorine concentration in the raw material, there is the following relationship.

As a method for producing carbonated rare earth, for example, cerium-containing rare earth concentrates such as bastonite concentrate, monazite concentrate, Chinese complex ore concentrate are decomposed by sulfuric acid decomposition method or alkali decomposition method, and fractional precipitation or By performing a treatment such as fractional dissolution, a rare earth solution is obtained by reducing and removing impurities such as fluorine, uranium, thorium, calcium, barium, iron and phosphorus. Then, the obtained rare earth solution is separated and purified by solvent extraction using an organic solvent as necessary to obtain a rare earth solution having an increased cerium content. The CeO ₂ / TREO can be adjusted from 30% by mass to almost 100% by mass depending on the degree of the solvent extraction. In particular, in the case of producing a high-purity product, solvent extraction may be performed after adding an oxidizing agent to the rare earth solution to convert cerium (III) to cerium (IV). Cerium (IV) has a large difference in extraction behavior into an organic solvent as compared with other rare earth elements (III), and separation and purification become easy. These rare earth solutions and ammonium hydrogen carbonate are mixed to precipitate rare earth carbonates, which are filtered and washed with water to obtain cerium-based rare earth carbonates. The rare earth carbonate produced in this way is easily available from China and other countries.

  In the production of the abrasive according to the present invention, the cerium carbonate rare earth as described above may be used as it is, but preferably, the abrasive raw material is reduced to 5% on the basis of drying before roasting. It is preferable to calcine so as to be ˜25% by weight. This is because an improvement in the polishing speed of the resulting abrasive can be expected. The calcination of the abrasive raw material is preferably heated at a temperature of 300 to 800 ° C. for 10 minutes to 24 hours. The calcination may be performed either before or after pulverization of the abrasive raw material, or may be performed either before or after addition of an alkali metal compound described later. Further, the loss on ignition means the weight reduction rate when the object is ignited. As a measuring method of the ignition raw material, an abrasive material sufficiently dried at 105 ° C. was put in a crucible whose weight was measured in advance, and the weight was measured. Then, the material was heated in a furnace at 1000 ° C. for 1 hour, and then in a dry atmosphere. After standing to cool, the weight of the crucible after standing to cool can be measured, and it can obtain | require by following the following formula.

（Ｂ：強熱減量（％）、Ｗ_１：加熱前の研摩材用原料とるつぼの重量（ｇ）、Ｗ_２：加熱後の研摩材用原料とるつぼの重量（ｇ）、Ｗ_３：るつぼの重量）

(B: Loss on ignition (%), W ₁ : Weight of abrasive raw material crucible before heating (g), W ₂ : Weight of abrasive raw material crucible after heating (g), W ₃ : Crucible Weight)

  On the other hand, the alkali metal concentration of the abrasive is determined by adding at least one compound of sodium, potassium, and lithium to the raw material before the roasting step. The amount of the compound added at this time is such that the total concentration of at least one alkali metal selected from the group consisting of sodium, potassium, and lithium in the abrasive raw material to be subjected to the roasting step is 0.01-3. Add an amount to achieve 0% by weight. The reason why the alkali metal compound is added is that the rare earth carbonate does not contain these alkali metals. The alkali metal compound to be added is preferably an inexpensive sodium compound. And, the concentration of 0.01 to 3.0% by weight and the final alkali metal concentration in the abrasive are the same, the concentration of these alkali metals in the abrasive is not reduced by roasting. It is because it will exist. Therefore, the addition amount of the alkali metal compound is such that the concentration of at least one alkali metal selected from the group consisting of sodium, potassium and lithium in the abrasive raw material to be subjected to the roasting step is 0.02 to 0.25. It is preferable to set it as weight%, and it is more preferable to set it as 0.03-0.20 weight. Moreover, when adding an alkali metal compound by mixing an alkali metal compound and an abrasive raw material in an aqueous solution and filtering, if the alkali metal is contained in the filtrate, it remains in the filtrate. It is necessary to adjust the amount of alkali metal compound to be added in consideration of the amount of alkali metal.

The alkali metal compound to be added is preferably one in which the weight ratio of chlorine to alkali metal (chlorine / alkali metal) is 0.2 or less in consideration of the influence of chlorine on the polishing characteristics. What does not contain chlorine in (element contained in chemical formula) is preferable. By using such an alkali metal compound, an abrasive with a low chlorine content can be produced. The timing for adding the alkali metal compound is not particularly limited as long as it is before the roasting step. Therefore, it may be performed either before or after the pulverization step, and may be performed before or after the calcination of the abrasive material. In addition, as an alkali metal compound to add, a water-soluble thing is preferable. This is because mixing with the abrasive raw material can be performed more uniformly in the aqueous solution state. Examples of preferred compounds include alkali metal hydroxides, carbonates and bicarbonates. In particular, a hydroxide is preferable.
When an alkali metal compound is added by mixing an alkali metal compound and an abrasive raw material in an aqueous solution and filtering, if an aqueous solution of hydroxide is applied, no alkali metal remains in the filtrate, This is because there is no fear of adding an excessive amount of metal. Further, by applying a hydroxide, it is possible to produce an abrasive having a good polishing speed.

  As a grinding | pulverization process of the abrasive raw material before a roasting process, it is normally performed with a pulverizer and it is generally performed with a wet pulverizer. In the present invention, pulverization with a pulverizer is useful, but as a pulverization method, the abrasive material may be mixed with a solvent containing water and heated at 60 to 100 ° C. to pulverize the abrasive material. (Hereinafter, such a grinding method is referred to as immersion heating grinding). By performing this immersion heating and pulverization, the manufactured abrasive can form a highly accurate polished surface with few abrasive scratches. The timing of immersion heating pulverization is not particularly limited as long as it is before the roasting step. Therefore, it may be performed either before or after the addition of the alkali metal compound. In addition, when the abrasive raw material is calcined, it may be performed either before or after that, but since the pulverizing effect is higher when the carbonic acid radicals in the raw material are large, the pre-calcination is preferable. In addition, performing immersion heating pulverization does not prevent performing pulverization by a pulverizer. Therefore, both pulverization methods may be appropriately combined.

  In the present invention, the fluorine concentration may be adjusted on condition that the fluorine concentration does not exceed the above range. For example, when using an abrasive raw material having a substantially zero fluorine concentration, the fluorine concentration may be adjusted by adding a fluorine compound before baking. An increase in the fluorine concentration has a problem of occurrence of polishing scratches, but has an effect of increasing the polishing speed. Further, if the fluorine concentration is within the above range, the problem of abrasive scratches is not so great. Therefore, it is also useful to adjust the fluorine concentration with emphasis on the polishing speed. The fluorine concentration is preferably adjusted by adding a fluorine compound. As the fluorine compound, ammonium fluoride, ammonium hydrogen fluoride, hydrogen fluoride. Acid etc. can be applied. The timing of fluorine concentration adjustment is not particularly limited as long as it is before the roasting step.

  After the raw material preparation (calcination) and the pulverization step, the abrasive according to the present invention is manufactured through the roasting step. Here, the roasting temperature in the roasting step is preferably 700 to 1100 ° C, more preferably 750 to 1050 ° C. The roasting time is preferably 0.5 to 48 hours, more preferably 1 to 24 hours. If both conditions are less than the lower limit, the cerium oxide particles are insufficiently sintered, resulting in an abrasive with a low polishing rate, and if the upper limit is exceeded, the abrasive grows with many scratches due to grain growth. . However, when producing a high-purity abrasive that is particularly excellent in polishing accuracy, a roasting temperature lower than the above temperature range may be applied. For example, a cerium-based rare earth carbonate containing 90% by weight or more of cerium oxide (TREO standard) is used as a raw material, which is dipped and heated and pulverized to form monooxycarbonate, and further dried at 130 to 250 ° C. to obtain cerium oxide. Abrasives that are subsequently roasted and manufactured are abrasives with excellent polishing accuracy. In the production of this abrasive, it is preferable that the roasting temperature is 300 to 600 ° C., which is lower than the above range, but also in this abrasive, the polishing rate can be improved by adding an alkali metal. Therefore, it should be considered that there is no particular limitation on the roasting temperature. In addition, when calcining the raw material, the roasting temperature needs to be higher than the calcining temperature. This is because if the roasting temperature is equal to or lower than the calcining temperature, the sintering is difficult to proceed.

  About the abrasive after a roasting process, it is preferable to crush and classify a roasted material. This is because the agglomerated and coarsened abrasive particles are crushed and the abrasive has a suitable particle size distribution.

  As described above, the cerium-based abrasive according to the present invention is an abrasive having excellent polishing power and further improved polishing accuracy, despite containing almost no fluorine.

  Hereinafter, preferred embodiments of the present invention will be described together with comparative examples. In the present embodiment, in the manufacturing process of the abrasive having the raw material crushing process and the roasting process, different types of manufacturing processes are applied depending on the presence or absence of immersion heating pulverization, the presence or absence of calcining, and the presence or absence of fluorine concentration adjustment. Manufactured. Each will be described below.

Manufacturing process 1
In this production process, an abrasive was produced without adjusting the fluorine concentration while performing immersion heating pulverization and calcination on a rare earth carbonate as a raw material. An outline of this manufacturing process is shown in FIG. The abrasives produced by this production process correspond to Examples 1 to 17, Examples 24 to 31, Examples 33 to 49, Comparative Examples 1 to 6, Comparative Examples 8 to 11, and Comparative Examples 15 and 16, which will be described later. To do.

  The abrasive raw material here is 45% by weight of TREO, 61% by weight of cerium oxide, and a rare earth carbonate with a fluorine concentration of less than 0.1% by weight (both are based on TREO). The concentration of alkali metal (sodium, potassium, lithium) in this raw material was less than 0.002% by weight (TREO standard).

  Moreover, in order to examine the difference depending on the cerium oxide content in the abrasive, a carbonated rare earth having different cerium oxide content was prepared, and an abrasive was produced using this as an abrasive material. In this case, the rare earth carbonate material is prepared by adjusting the cerium oxide content to 99.99% by weight (TREO standard), cerium carbonate having a lanthanum oxide content of 99.99% by weight (TREO standard), and praseodymium oxide content of 99. .99 wt% (TREO standard) praseodymium carbonate, neodymium oxide content 99.99 wt% (TREO standard) neodymium carbonate, samarium oxide content 99.99 wt% (TREO standard) samarium carbonate, gadolinium oxide content 99.99 wt% (TREO standard) gadolinium carbonate was mixed at the following TREO mixing ratio to produce a rare earth carbonate raw material having a cerium oxide content of 25 to 99.99 wt% (hereinafter adjusted in this way). The raw material is referred to as the adjusted raw material). The concentration of alkali metal (sodium, potassium, lithium) in this raw material was also less than 0.002% by weight (TREO standard).

  In the production of the abrasive, first, this abrasive raw material was immersed and pulverized. The immersion heating pulverization was performed by mixing 2000 kg of raw material with 5000 L of pure water, blowing the steam while stirring the mixture, and maintaining this temperature for 4 hours after reaching 90 ° C. and then allowing to cool. And the slurry after immersion heating grinding | pulverization was filtered. This immersion heating pulverization is performed twice (2 batches). However, in the case of using the adjusted raw material, 90 kg of the raw material corresponding to TREO was mixed with 400 L of pure water, and this was subjected to immersion heating and pulverization.

  Next, the obtained immersion heating pulverized rare earth carbonate was calcined. In this step, the immersion heating pulverized rare earth carbonate was heated at 600 ° C. for 2 hours. The calcined rare earth after calcining had a loss on ignition (ignition temperature 1000 ° C.) of 15% by weight.

  Then, the calcined rare earth carbonate after calcining was made into a 5000 L slurry using pure water and then wet pulverized. The wet pulverization was performed for 3 passes in a bead mill using zirconia balls having a diameter of 1.0 mm. The 5000 L slurry after pulverization was divided into 100 L units for later sample production (partly, it was used for abrasive production in Step 2 described later). However, when the adjusted raw material was used, the raw material after calcination was made into 200 L slurry using pure water, and then wet crushed in the same manner, and the crushed slurry was divided into two.

  An alkali metal compound was added to the pulverized slurry. As the alkali metal compound to be added, sodium hydroxide, potassium hydroxide, lithium hydroxide, and sodium chloride were used in the examples. Moreover, what changed the addition amount to 0.0005 to 0.5 weight% (TREO standard) was manufactured. And the slurry after alkali metal compound addition was filtered and dried. However, about what added sodium chloride, the whole quantity was dried without filtering and it used for the following process. In Examples 26 and 27 and Comparative Example 28, sodium hydroxide and sodium chloride were mixed so that the Cl / Na weight ratios were 0.1, 0.2, and 0.25, respectively. Was added. In Example 49, three types of sodium hydroxide, potassium hydroxide, and lithium hydroxide were added as alkali metal compounds to be added.

  The raw material for the abrasive after the above-described immersion heating pulverization, calcination, and alkali metal addition was roasted. The roasting conditions here were a roasting temperature of 650 to 1150 ° C. and a time of 12 hours. Finally, the baked product after baking was crushed and classified to obtain a cerium-based abrasive.

Manufacturing process 2
In this production process, a rare earth carbonate as a raw material was subjected to immersion heating and pulverization and calcining, and further the fluorine concentration was adjusted to produce an abrasive. An outline of this manufacturing process is shown in FIG. The abrasives produced by this production process correspond to Examples 18 to 20 and Comparative Example 7 described later.

  In the production process 2, a part of the pulverized calcined rare earth carbonate slurry produced in the production process 1 was used. 1 mol / L of ammonium fluoride was added to 100 L of pulverized calcined carbonated rare earth slurry so that the fluorine concentration was 0.2 to 0.9 wt% (TREO standard), and this was filtered to obtain a fluorine-added raw material. . Then, pure water was added to this raw material to make a slurry of 100 L, and thereafter, an alkali metal compound was added, roasted, crushed and classified in the same manner as in the above-mentioned production step 1 to obtain an abrasive.

Production process 3 (a) to (c)
In this production process, the abrasive was produced for the rare earth carbonate material without performing one or both of immersion heating and pulverization and calcination. The fluorine concentration is not adjusted. An outline of this manufacturing process is shown in FIGS. The abrasive produced by this production process corresponds to Examples 21 to 23 described later.

  In the manufacturing process 3 (a) (FIG. 3 (a)), the raw material that has been subjected to immersion heating and pulverization in the same process as in the manufacturing process 1 is made into a slurry. Three passes of pulverization were performed with the used bead mill, and an alkali metal compound (sodium hydroxide) was added to the slurry. And the subsequent process manufactured the abrasive as the manufacturing process 1.

  In the production process 3 (b) (FIG. 3 (b)), 200 kg of pure water was mixed with 100 kg of a rare earth carbonate raw material similar to the production process 1 to form a slurry, which was pulverized without performing immersion heating and pulverization. The grinding method at this time was performed by operating an attritor using a zirconia ball having a diameter of 3.0 mm for 8 hours in a circulation system. And after filtering the slurry after grinding | pulverization, the raw material was calcined similarly to the manufacturing process 1, Then, it grind | pulverized in a bead mill again, the alkali metal compound was added, and it roasted, and manufactured the abrasive.

  In the production process 3 (c) (FIG. 3 (c)), the abrasive is produced without performing immersion heating and calcination. Here, 200 kg of pure water is mixed with 100 kg of raw material to form a slurry. First, an attritor using a zirconia ball having a diameter of 3.0 mm is pulverized by operating for 8 hours in a circulation system, and further zirconia having a diameter of 1.0 mm. Three passes of pulverization were performed with a bead mill using balls. Then, an alkali metal compound was added to the pulverized rare earth carbonate slurry in the same manner as in the production step 1, and roasted to produce an abrasive.

Manufacturing process 4
This manufacturing process manufactures an abrasive according to the content of the above-mentioned patent document 1 (Example 2). The abrasive produced by this production process corresponds to Comparative Examples 12 and 13 described later.

In this production method, first, the pH is adjusted to 7.6 with pure water and a small amount of ammonia water in a reaction tank with an agitator with an effective volume of 20 L and an aging tank with an agitator with an effective volume of 20 L into which overflow from the reaction tank flows. I put the liquid. While stirring the liquid, 0.16 L of cerium (III) nitrate + lanthanum nitrate (III) aqueous solution (TREO 171 g / L, CeO ₂ / TREO 92 wt%, La ₂ O ₃ / TREO 8%) was added to the reaction layer. Added at a rate of / min. At this time, 3 mol / L of ammonia water was continuously added so that the pH in the reaction vessel was maintained at 7.6. The liquid temperature of the reaction tank and the aging tank was 20 ° C. And the overflow from an aging tank was filtered and the filter cake was obtained.

  And the filter cake was divided | segmented into half, and one side was introduce | transduced into the rotary furnace in which temperature distribution is changing in steps from inlet temperature 100 degreeC to outlet temperature 1090 degreeC, and it dried and roasted. Drying was performed at 100 ° C. to 600 ° C. for 2 hours, and roasting was performed at 600 to 1090 ° C. for 3 hours. The roasted product after roasting was crushed and classified in the same manner as in Production Process 1 to produce an abrasive (Comparative Example 12). The other filter cake was dried, roasted (roasting temperature 1100 ° C.), crushed and classified in the same manner as in production step 1 to obtain an abrasive.

Manufacturing process 5
In this production process, TREO is 45% by weight, cerium oxide content is 99.9% by weight, fluorine concentration is less than 0.1% by weight, and alkali metal concentration is less than 0.002% by weight (both are TREO standards). Using cerium as a raw material, an abrasive was produced by the production method described in the latter half of paragraph 0031. An outline of this manufacturing process is shown in FIG. The abrasive produced by this production process corresponds to Example 32 and Comparative Example 14 described later.

  Here, 200 kg of raw material was prepared, and first, immersion heating and pulverization was performed. The conditions of the immersion heating pulverization were the same as those in the production process 1. Then, this was pulverized in three passes by a bead mill using zirconia balls having a diameter of 1.0 mm to divide the slurry into two parts. One slurry (Comparative Example 14) was immediately dried at 200 ° C. for 48 hours, and the other slurry (Example 32) was dried after adding sodium hydroxide as an alkali metal compound. After drying, it was baked at 500 ° C. for 12 hours, and the baked product was dry-pulverized with an atomizer. The pulverized product was made into 100 L slurry with pure water, and finally, this was subjected to 6-pass wet pulverization with a bead mill using zirconia balls having a diameter of 0.8 mm to obtain a slurry abrasive.

For the cerium-based abrasives manufactured by the above-described manufacturing process, the D50 particle size, BET specific surface area, and coarse particle content were measured, and the fluorine concentration, alkali metal (sodium, potassium, lithium) Concentration was measured. Then, a polishing test was conducted to evaluate the polishing characteristics of these polishing materials.

  The measurement of the specific surface area of the BET method is based on “(3.5) One-point method of 6.2 flow method” of JIS R 1626-1996 (Method of measuring specific surface area of fine ceramic powder by gas adsorption BET method). Measurements were made. At that time, a mixed gas of helium as a carrier gas and nitrogen as an adsorbate gas was used. In the measurement of the slurry abrasive, the BET method specific surface area was measured for a dried product obtained by sufficiently drying (heating to 105 ° C.) the slurry.

D ₅₀ particle size is measured by measuring the particle size distribution using a laser diffraction / scattering particle size distribution measuring device (Horiba, Ltd .: LA-920), so that the cumulative mass from the small particle size side is measured. This was done by determining the particle size at 50% by mass.

  To measure the content of coarse particles (particles having a Stokes diameter of 5 μm or more), first put 200 g of a powdery measurement object into a measurement container, and add 0.1% sodium hexametaphosphate aqueous solution to the upper standard of the container. Mix until well. Next, the container is left to stand and allowed to settle and settle for a specified time. After the specified time has elapsed, the slurry between the upper marked line and the lower marked line is extracted. When the slurry has been extracted, add a new 0.1% aqueous solution of sodium hexametaphosphate to the upper marked line of the container, mix well, let the container stand and settle for a specified time, and then move from the upper marked line to the lower marked line. Remove the slurry between the marked lines. In this way, a series of operations (specifically, a series of operations consisting of injection of a sodium hexametaphosphate aqueous solution, standing and settling, and extraction of the slurry) was repeated (in this embodiment, six more times (eight times for convenience)). After repeating), finally, the particles remaining below the lower marked line of the container are sufficiently dried at 105 ° C. The weight A (g) of the dry residual particles thus obtained was measured with a precision balance. Then, the content S (% by weight) of coarse particles having a Stokes diameter of 5 μm or more was calculated using a calculation formula (S = A ÷ 200 × 100). The specified time (stationary / sedimentation time) is the time required for the particles with a Stokes diameter of 5 μm at the position of the upper marked line (the upper surface of the slurry) to settle to the lower marked line. Is divided by the sedimentation velocity calculated from the Stokes equation. If the above series of operations is performed only once, a large amount of particles having a Stokes diameter of 5 μm or less are mixed in the portion below the lower marked line. When the object to be measured is a slurry abrasive, when the dried product is obtained by measuring the BET specific surface area, the ratio of the weight of the dried product to the slurry weight is measured, and from this ratio, the dried product is measured. A slurry amount corresponding to 200 g is collected and used as a sample.

  The fluorine concentration was measured by melting the abrasive with alkali and extracting it with hot water, and measuring it by the fluoride ion electrode method. The alkali metal concentration was measured by atomic absorption after dissolving the abrasive with acid. The chlorine concentration was measured by the Volhard titration method after the abrasive was dissolved in nitric acid. In addition, TREO serving as a reference is obtained by dissolving an abrasive in acid, adding ammonia water to the solution to form a precipitate, filtering and washing the precipitate to remove alkali metals, After redissolving in, oxalic acid was added to the solution to form a precipitate, which was calcined and measured by a gravimetric method.

For the abrasive material test, a polishing tester (HSP-2I type, manufactured by Taito Seiki Co., Ltd.) was prepared. This polishing tester polishes the polishing target surface with a polishing pad while supplying a slurry-like polishing material to the polishing target surface. In the polishing test, a polishing material and pure water were mixed to prepare 20 L of a slurry-like polishing material of TREO 100 g / L. In the polishing test, a slurry-like abrasive was supplied at a rate of 5 liters / minute, and the abrasive was recycled. The polishing object was a glass for a flat panel having a diameter of 65 mm. A polishing pad made of polyurethane was used. The polishing pad pressure against the polishing surface was 9.8 kPa (100 g / cm ² ), the rotation speed of the polishing tester was set at 100 rpm, and polishing was performed for 30 minutes.

  For the evaluation of the polishing characteristics, first, the glass weight before and after polishing was measured to determine the amount of decrease in glass weight due to polishing, and the polishing value was determined based on this value. In this polishing test, the polishing rate was evaluated using this polishing value. Here, the polishing value when polishing was performed using the sample obtained in Comparative Example 1 (abrasive material not containing alkali metal) was used as the reference (100).

  Then, the polished surface obtained by polishing was washed with pure water and dried in a dust-free state, and then scratch evaluation was performed. Scratch evaluation was performed by observing the glass surface by a reflection method using a 300,000 lux halogen lamp as a light source, scoring the number of large scratches and fine scratches, and evaluating 100 points as a perfect score. In this scratch evaluation, the polishing accuracy required for finish polishing of a glass substrate for hard disk or LCD was used as a criterion.

  Tables 3 to 5 show the analysis results and the polishing test results of the abrasives produced in this example. In the table below, the alkali metal concentration with respect to TREO of the abrasive according to each example is only one of sodium, potassium, and lithium, but the other two types not described are as follows: Except for Example 49 in which three kinds of sodium, potassium, and lithium were added, all were less than 0.002% by weight.

Evaluation 1: Evaluation by Alkali Metal Concentration Table 3 shows the evaluation results of the polishing characteristics by the alkali metal concentration. First, when the polishing materials (Examples 1 to 9 and Comparative Examples 1 to 3) manufactured at a constant roasting temperature of 900 ° C. while changing the alkali metal concentration (sodium concentration) are shown, the alkali metal concentration (sodium) As the (concentration) increases, the D ₅₀ particle size and coarse particle content increase, and the BET surface area decreases. And with a raise of sodium concentration, there exists a tendency for a polishing speed to rise, and when sodium concentration is 0.01 weight% or more, it is rising rapidly. On the other hand, as for abrasive scratch evaluation, the lower the sodium concentration, the better. The reason why the scratch evaluation is not good in Comparative Examples 1 and 2 is that, since the polishing speed is too low, once a scratch occurs, it cannot be erased by polishing, and the scratch remains.

  Moreover, although the result (Example 4, 10-17, Comparative Examples 4-6) of the lower part of Table 3 is a result regarding the abrasives manufactured changing sodium concentration and roasting temperature, it turns out from Table 1. As described above, the roasting temperature set here is adjusted so that the particle size of the abrasive becomes substantially constant. As can be seen from the results, when the sodium concentration is out of the predetermined range, the occurrence of abrasive scratches is observed even if the particle diameters are substantially the same. On the contrary, it turns out that the appropriate range of roasting temperature spreads by making sodium concentration into an appropriate range.

  Furthermore, in Example 49, three types of alkali metal, sodium, potassium, and lithium, are included at the same time. Comparing Example 49 with Examples 1 to 6 and Comparative Example 9 manufactured under the same conditions except for the alkali metal concentration, even if three types of alkali metals are included, the concentration is 3% by weight or less. It can be seen that the polishing characteristics are not significantly inferior.

  From the above results, the alkali metal concentration in the abrasive is preferably 0.01 to 3.0% by weight (TREO standard), more preferably 0.02 to 1.0% by weight (TREO standard), 0.03 It was confirmed that ˜0.5% by weight (TREO basis) is more preferable.

Evaluation 2: Evaluation by Chlorine Concentration The lower part of Example 4 (Example 9, Examples 26 and 27, Comparative Examples 8 and 9) shows the evaluation result by the chlorine concentration in the abrasive. From this result, as the chlorine concentration increases, the polishing rate decreases and the number of scratches increases. Therefore, it was confirmed that the chlorine concentration in the abrasive is preferably 0.3% by weight or less, and more preferably 0.1% by weight or less.

Evaluation 3: Evaluation by Fluorine Concentration The upper part of Table 4 (Examples 4, 18 to 20, Comparative Example 7) shows the evaluation results by the fluorine concentration in the abrasive. From this result, as the fluorine concentration increases, the polishing rate increases, but on the other hand, the number of scratches increases. Therefore, considering the balance between polishing speed and scratches, the fluorine concentration needs to be 0.5 wt% or less (TREO standard), preferably 0.2 wt% or less (TREO standard), It is more preferably 0.1% by weight or less (TREO standard).

Evaluation 4: Evaluation by presence / absence of immersion heating pulverization and calcination The upper middle part of Examples 4 (Examples 4, 21 to 23) evaluates the polishing characteristics depending on the presence / absence of immersion heating pulverization and calcination. From these polishing characteristics, it can be seen that immersion heating pulverization and calcination are not necessarily essential steps. However, the amount of generation of coarse particles is reduced by performing immersion heating and pulverization, and thus the effect of suppressing the generation of abrasive scratches is confirmed, and the effect of improving the polishing rate is confirmed by carrying out calcination. Therefore, it is preferable to perform both.

Evaluation 5: Evaluation by Alkali Metal Type The central part of Examples 4 (Examples 4, 24, and 25) is for evaluating the polishing characteristics of abrasives produced by adding various alkali metal compounds. Looking at these polishing characteristics, the effects of using sodium hydroxide, potassium hydroxide, and lithium hydroxide are almost the same. Therefore, it can be said that there is not much difference depending on the type of alkali metal. In addition, when sodium chloride is added, the elementary particle content in the abrasive is increased, and some scratches are observed.

Evaluation 6: Evaluation by roasting temperature The lower part of Examples 4 (Examples 4, 28 to 31, Comparative Examples 10 and 11) is for evaluating the polishing characteristics of abrasives produced by variously changing the roasting temperature. . From this table, when the roasting temperature is increased, the D50 particle size and the coarse particle content increase, and the BET surface area decreases. As the roasting temperature increases, the polishing speed increases, but the number of scratches increases.

Therefore, within the same alkali metal concentration range, the roasting temperature is preferably 700 to 1100 ° C, more preferably 750 to 1050 ° C. _{Further, D 50} particle size is preferably from 0.1 to 3.0 m, more preferably 0.2 to 2.5 [mu] m. And about a BET specific surface area, 1-30 m < ² > / g is preferable and 2-25 m < ² > / g is more preferable.

Evaluation 7: Evaluation by cerium oxide content The central part of Examples 5 to 35 (Examples 33 to 40, Comparative Example 15) is an evaluation result of abrasives in which the roasting temperature was kept constant at 900 ° C. and the cerium oxide content was changed. Indicates. From this result, with an increase in the cerium oxide content, the D50 particle size and the coarse particle content increased, and the BET surface area decreased. And with the increase in the cerium oxide content, the polishing rate tends to increase, and rapidly increases at 30% by weight or more. On the other hand, with respect to abrasive scratch evaluation, the lower the cerium oxide content and the fewer coarse particles, the better the results. The reason why the scratch evaluation is not good despite the small amount of coarse particles in Comparative Example 14 is that the polishing rate is too low, and once scratches are generated, they cannot be erased by polishing.

  Moreover, although the result (Examples 41-48, comparative example 16) of the lower part of Table 5 is a result regarding the abrasives manufactured changing cerium oxide content and roasting temperature, the roast set here is set. The firing temperature is adjusted so that the grain size of the abrasive becomes substantially constant. As can be seen from this result, when the cerium oxide content is low, an abrasive with many scratches is produced even when the roasting temperature is set high and the particle size is uniform. Considering the above, the cerium oxide content of the abrasive grains is preferably 30% by weight or more (TREO standard).

Evaluation Examples 12 and 13 Comparative Examples 12 and 13 are abrasives manufactured by a method completely different from the method according to the present invention. As can be seen from the evaluation results (the uppermost part of Table 5), polishing is performed. In addition to the occurrence of scratches, it was confirmed that the polishing speed was not so high. In the first place, this manufacturing method is laborious and difficult to say industrial.

Evaluation Example 32 and Comparative Example 14 for Example 32 and Comparative Example 14 are abrasives manufactured by raw materials and processes different from the abrasives according to other examples. As can be seen from the evaluation results (upper part of Table 5), the abrasive of Comparative Example 14 is an abrasive with extremely good polished surface accuracy, but has a problem that the polishing speed is relatively low. Thus, in Example 32, an alkali metal was added to the polishing material, but the polishing rate was clearly improved by the addition of the alkali metal. At this time, good polished surface accuracy is not impaired. Therefore, it was confirmed that inclusion of an alkali metal is effective for improving the polishing characteristics of the abrasive.

The figure which shows the process of the manufacturing process 1 of this embodiment. The figure which shows the process of the manufacturing process 2 of this embodiment. The figure which shows the process of manufacturing process 3 (a)-(b) of this embodiment. The figure which shows the process of the manufacturing process 5 of this embodiment.

Claims (10)

In a cerium-based abrasive containing 30% by weight or more of cerium oxide based on total rare earth oxide (TREO) and having a fluorine concentration of 0.5% by weight or less with respect to TREO,
Containing at least one alkali metal selected from the group consisting of sodium, potassium and lithium in a total amount of 0.01 to 3.0% by weight based on TREO,
Furthermore, the cerium type abrasive | polishing material characterized by the chlorine concentration with respect to TREO being 0.3 weight% or less. The cerium-based abrasive according to claim 1, wherein the fluorine concentration is 0.1% by weight or less based on TREO. A total of 0.02 to 1.0% by weight of at least one alkali metal selected from the group consisting of sodium, potassium and lithium with respect to TREO, and a chlorine concentration with respect to TREO is 0.1% by weight or less Item 3. The cerium-based abrasive according to item 1 or 2. The cerium-based abrasive according to any one of claims 1 to 3, wherein the alkali metal is sodium. In the method for producing a cerium-based abrasive, the method comprises a roasting step of roasting the abrasive raw material, and a raw material grinding step of pulverizing the abrasive raw material before the roasting step.
As the abrasive raw material, a cerium-based rare earth carbonate containing cerium oxide at 30% by weight or more based on TREO is used,
Before the roasting step, sodium, so that the total concentration of at least one alkali metal selected from the group consisting of sodium, potassium, and lithium with respect to TREO is 0.01 to less than 3.0% by weight. Having a step of adding at least one compound of potassium and lithium to an abrasive material;
A method for producing a cerium-based abrasive, wherein a compound having a weight ratio of chlorine to an alkali metal (chlorine / alkali metal) of 0.2 or less is used as the sodium, potassium, or lithium compound to be added. 6. The method for producing a cerium-based abrasive according to claim 5, wherein a compound containing no chlorine as a constituent element is used as the compound of sodium, potassium, and lithium to be added. The method for producing a cerium-based abrasive according to claim 5 or 6, further comprising a step of calcining the raw material of the abrasive before roasting so that the loss on ignition on a dry basis is 5 to 25% by weight. The compound of sodium, potassium and lithium is adjusted so that the total concentration of TREO of at least one alkali metal selected from the group consisting of sodium, potassium and lithium in the raw material is 0.02 to 1.0% by weight. The method for producing a cerium-based abrasive according to any one of claims 5 to 7, wherein at least one kind is added. The method for producing a cerium-based abrasive according to any one of claims 5 to 8, wherein a sodium compound is added before the roasting step. 10. The cerium according to claim 5, wherein the abrasive raw material is mixed with a solvent containing water and heated at 60 to 100 ° C. to grind the abrasive raw material before the roasting step. A manufacturing method for abrasives.

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