TWI401307B - Preparation of cerium - based abrasive - Google Patents

Description

Regeneration method of lanthanide abrasive

The present invention relates to a method for regenerating an lanthanide-based abrasive, and more particularly to a polishing rate of a cerium-based abrasive which is greatly reduced in polishing rate and which is usually discarded, and is regenerated to a polishing rate close to that of an unused abrasive. method.

In recent years, glass materials have been used in various applications, and are not only used for glass materials for optical applications such as optical lenses, but also widely used in glass substrates for liquid crystal displays, glass substrates for plasma displays, magnetic sheets, and optical disks. The field of electronic circuit manufacturing, such as a glass substrate for recording media, and a glass substrate for LSI photomask.

As an abrasive used for the surface polishing of these glass substrates, an abrasive containing a rare earth oxide (particularly cerium oxide) as a main component (hereinafter referred to as "lanthanum-based abrasive") has been conventionally used. The reason for this is that cerium oxide has an advantage that the polishing efficiency of the glass is several times higher than that of zirconia or cerium oxide as a polishing abrasive.

When various glass substrates are polished by an lanthanum-based abrasive, they are usually dispersed in an aqueous medium to form a slurry (hereinafter referred to as "abrasive slurry"). For example, the abrasive slurry is supplied to a polishing apparatus for performing a polishing operation, and the polishing apparatus includes a polishing head disposed at an upper portion and a rotating polishing pad of a lower portion, the polishing head imparts an abrasive (glass) The substrate) is held and rotated.

The current state of the art is that the polishing slurry is usually recycled, but the polishing force is gradually lowered with use, and from a practical point of view, when the polishing rate is greatly lowered (for example, it is reduced to 50% or less of the initial polishing rate). At the time), it was disposed of as a used abrasive.

However, the used lanthanide abrasive contains a large amount of valuable rare earth elements such as lanthanum, cerium and lanthanum in addition to cerium. From the point of view of the effective use of resources, it is strongly hoped that these will not be disposed of as industrial waste, but will be recycled and reused.

In addition, as reported in the recent newspapers and the like, the glass substrate is also rapidly increasing in size due to the fierce competition for large-scale LCD TVs (panels for liquid crystal displays) or plasma TVs (panels for plasma displays). The demand for the lanthanide abrasive necessary for grinding also increases. From the viewpoint of ensuring the stability of the rare earth raw material, it is also desirable to recycle the used abrasive.

In recent years, several proposals have been made to add an aggregating agent such as aluminum sulfate to a used cerium-based abrasive slurry, to agglomerate the abrasive particles, and to recover the abrasive raw material by solid-liquid separation means.

Specifically, as disclosed in Japanese Laid-Open Patent Publication No. Hei 10 (1998) No. 280060 (Patent Document 1), it is proposed to add an organic coagulant to an abrasive slurry, adjust the pH, and perform solid-liquid separation. In the method of the present invention, it is proposed to add a polyaluminum chloride as a coagulant and adjust the pH to about 7 to carry out agglutination as described in Japanese Laid-Open Patent Publication No. 2004-237163 (Patent Document 2). And a method of using a flocculant containing aluminum oxide, calcium oxide, cerium oxide, or sodium oxide as a coagulant, as described in Japanese Laid-Open Patent Publication No. 2002-28662 (Patent Document 3). A method in which the abrasive component is agglomerated and recovered.

As described above, the used cerium-based abrasive recovered as a solid component has a greatly reduced polishing power, and it is necessary to perform a treatment for recovering the polishing rate for reuse. The reason why the polishing rate is lowered is considered to be due to the fact that the glass component (Si component) in the material to be polished is peeled off or eluted in the abrasive slurry to be adsorbed to the surface of the abrasive particles, or from the glass component or used. The impurity component (such as an Al component or an Fe component) such as a coagulant is adsorbed on the surface of the abrasive particles in the same manner to lower the activity.

In order to restore the activity, as described in Japanese Laid-Open Patent Publication No. Hei 11 (1999)-90825 (Patent Document 4), there is known a method of adding a large excess amount of hydrogen peroxide to the used lanthanide abrasive. The alkali aqueous solution such as sodium is treated to dissolve and remove the Si component and the Al component. In addition, as described in Japanese Laid-Open Patent Publication No. 2003-205460 (Patent Document 5), a method of adding a dispersing agent and a high-concentration alkali component to a used cerium-based abrasive slurry is also known. The glass component (Si component) adhering to the surface of the abrasive particles is dissolved and removed by heating to 50 ° C or higher.

However, a method of treating a used lanthanum-based abrasive by adding a base (hereinafter, sometimes referred to as "alkali treatment") has a problem that a large excess of alkali is required (for example, a dry base is required to be ground). When the alkali is added, the cerium-based abrasive tends to aggregate, and the particle size of the polishing agent becomes large, and further, a dispersing agent or the like needs to be added in order to control these phenomena.

In addition, the inventors of the present invention have studied the regeneration treatment of the lanthanide-based abrasive by actually performing the alkali addition method, and it has been found that a Si component and an alkali component of 27 equivalents of the Al component are added to the lanthanide-based abrasive. The treatment is carried out, but the removal rate of these is only about 60% at best.

In the Japanese Patent Laid-Open Publication No. 2003-211356 (Patent Document 6), there is described a method of treating a used abrasive with an acid, which is used in almost all disposed of waste disposal. Concentrated hydrochloric acid and hydrogen peroxide are added to the aqueous filter cake of the abrasive to convert cerium oxide into cerium chloride (Ce ³⁺ ) and completely dissolved, and then a base is added to the solution to become a hydroxide or carbonate of cerium. The precipitate is recovered as a sputum resource. The recovered ruthenium compound can be used in various applications other than the abrasive to realize efficient use of resources. However, this technique is not a technique for regenerating an abrasive using a used lanthanide abrasive.

An object of the present invention is to provide a method for regenerating an abrasive, which greatly reduces the polishing rate and regenerates the polishing rate of the commonly used cerium-based abrasive to a polishing rate close to that of an unused abrasive.

Further, an object of the present invention is to provide a method for regenerating a used cerium-based abrasive which does not use a base, so that there is no problem of agglomerating the abrasive particles, and the grinding of the cerium-based abrasive is avoided. There is a problem that the removal rate of the Si component or the Al component is low because of the decrease in speed.

According to the present invention, the following method for regenerating a lanthanide abrasive can be provided.

[1] A method for obtaining a regenerated abrasive by treating a used lanthanide abrasive, comprising the steps of: redispersing the used abrasive particles with water, and then using the obtained slurry as The state of the slurry is treated directly with at least acid.

[2] A method of obtaining a regenerated abrasive by treating a used lanthanide abrasive, comprising the steps of: (1) redispersing the used abrasive particles with water to prepare a slurry. a step of (2) treating the redispersed slurry with an acid; (3) a step of subjecting the obtained acid-treated slurry to solid-liquid separation; and (4) a step of drying and pulverizing the obtained filter cake.

[3] A method for obtaining a regenerated abrasive by treating a used lanthanide abrasive, comprising the steps of: (1) redispersing the used abrasive particles with water to prepare a slurry. a step of (2) treating the redispersed slurry with an acid; (3) a step of subjecting the obtained acid-treated slurry to solid-liquid separation; (4) a step of drying the obtained filter cake; and (5) The step of calcining and pulverizing the dried filter cake.

[4] The method for regenerating an anthraquinone-based abrasive according to any one of the above [1], wherein the acid is a mineral acid.

[5] The method for regenerating an anthraquinone-based abrasive according to the above [4], wherein two or more inorganic acids are used in combination.

[6] The method for regenerating a lanthanide abrasive according to the above [5], wherein one of hydrochloric acid, sulfuric acid and nitric acid and hydrofluoric acid are used in combination.

The basic technical idea of the method of the present invention is to obtain a regenerated abrasive by treating a used lanthanide abrasive, which comprises the steps of: redispersing the used abrasive particles with water, and then obtaining The slurry is treated with at least acid. Hereinafter, a more specific embodiment of the present invention will be described with reference to the drawings.

Fig. 1 is a flow chart showing an example of a specific procedure for obtaining a regenerated abrasive by treating a used cerium-based abrasive.

(1) Slurry treatment of used abrasive (first step)

In the present invention, the used abrasive is a wet cake (dewatered cake) which is obtained by adding a coagulant to the cerium-based abrasive slurry having a greatly reduced polishing rate, aggregating the abrasive particles, and recovering by solid-liquid separation means. Or filter the filter cake-like abrasive particles.

The composition of the used abrasive may be changed depending on the composition of the polishing agent before use (before use), the polishing experience, the type or composition of the material to be polished, the type of the aggregating agent, and the like, and as an example, as will be described later. It is shown that the composition (% by mass (dry basis)) is TREO (Total Rare Earth Oxide) (=CeO ₂ +La ₂ O ₃ +Nd ₂ O ₃ +Pr ₆ O ₁₁ ) is 80 to 95%, The mass ratio of each of the above oxides to TREO is approximately: CeO ₂ 60%, La ₂ O ₃ 33%, Nd ₂ O ₃ 1%, Pr ₆ O ₁₁ 6%, and fluorine component (F) 5~ 6%, Si composition 0.6 to 3%, Al composition 0.3 to 0.9%, Fe composition 0.3 to 1.0%, and the like.

In the present invention, water 12 is added to the used abrasive 10 such as a dewatered cake, and the redispersion treatment 14 is carried out to obtain a redispersed slurry 16 thereof. The slurry concentration is not particularly limited, but is usually from 5 to 60%, preferably from about 10 to 40%. When the slurry concentration is too low, the amount of the abrasive particles to be treated in the following acid treatment step is low, and when the concentration is high, the slurry is not sufficiently stirred, and the acid treatment is incomplete, which is not preferable.

As means for performing the slurrying treatment, a container having a stirring means is preferred.

(2) Acid treatment step (second step)

Acid 18 is added to the redispersed slurry 16 of the redispersed used abrasive for treatment. The acid to be used in the acid treatment step 20 is such that the glass component (Si component) or the impurity component (Al component, Fe component, etc.) adhering to the surface of the abrasive can be dissolved by dissolution, decomposition, washing or the like. Alternatively, the acid may be removed from the abrasive particles, and may be an inorganic acid or an organic acid. However, in view of the effect, a stronger inorganic acid is preferred. Examples of the inorganic acid include hydrofluoric acid, hydrochloric acid, bromic acid, sulfuric acid, nitric acid, and phosphoric acid. These acids may be used alone or in combination of two or more. For example, by using hydrofluoric acid, hydrochloric acid, hydrofluoric acid, sulfuric acid or the like in combination, hydrofluoric acid mainly removes a glass component (Si component), and hydrochloric acid or sulfuric acid mainly removes other impurity components (Al component, Fe component, etc.). The various components can be selectively removed to further improve the removal efficiency as a whole.

The apparatus for carrying out the acid treatment step 20 is not particularly limited as long as it can efficiently react with an acid without precipitating the contained abrasive slurry. It is generally preferred to use a stirring tank type reaction vessel including a stirring means, a heating means, a temperature control means, an abrasive slurry, or an acid supply means. Further, it is also possible to use the agitation tank type reaction vessel as a vessel for carrying out the slurrying step (first step).

The acid treatment step 20 is to add an acid 18 to the redispersion slurry 16 contained in the tank type reaction vessel, and to carry out the slurry state. The addition weight of the acid can be greatly reduced as compared with the case of adding a base in the related art, and is 1 to 5 equivalents to the glass component (Si component) or other impurity component (Al component, Fe component, etc.) in the abrasive particles. Preferably, it is 1.1 to 3 times the equivalent.

The reaction temperature can be carried out at room temperature or under heating, and is usually 5 to 90 ° C, preferably 10 to 80 ° C, more preferably about 15 to 70 ° C. Further, the reaction time may be changed depending on the reaction temperature, the type of acid, the concentration, the amount of addition, the glass component (Si component) in the abrasive particles, or other impurity components (Al component, Fe component, etc.), but is usually 0.5. ~30 hours, preferably 1 to 20 hours, more preferably 2 to 10 hours.

When a plurality of acids, such as hydrofluoric acid and hydrochloric acid, hydrofluoric acid, sulfuric acid, etc., are used, the two acids may be simultaneously added to the abrasive slurry, or an acid may be added first, followed by another acid. . In the latter method, the reaction temperature and the reaction time can also be changed depending on the kind of the acid. Further, the acid treatment step may be carried out in a batch operation, or a plurality of tank reactors may be connected in series and carried out in a continuous flow operation. Further, when it is carried out in a continuous flow type operation, the average residence time in the tank type reactor can be taken as the reaction time.

(3) Solid-liquid separation step (third step)

Thus, the acid-treated treatment slurry 22 is treated in the solid-liquid separation step 24, and separated into the abrasive particle filter cake 26 and the filtrate 25. Most of the glass component (Si component) and other impurity components (Al component, Fe component, etc.) in the abrasive particles are solubilized or freed by an acid, and are transferred to the filtrate 25 (mother liquor or supernatant). Thus, the abrasive particles and the impurity components are separated.

The solid-liquid separation step may be carried out by precipitation separation, that is, the acid-treated slurry is allowed to stand in a thickener (settling tank), the abrasive particles are sedimented and separated, and the supernatant is decanted or the supernatant is overflowed from the tank. . Alternatively, solid-liquid separation may be carried out by mechanical centrifugation, centrifugal sedimentation, filtration, or the like. Further, it is possible to carry out a combination of sedimentation separation, filtration, and the like. Further, in the solid-liquid separation, an appropriate filter cloth such as a filter cloth, a ceramic filter, or a filter paper can be used depending on the particle diameter of the abrasive particles.

In addition, in order to sufficiently wash the glass component (Si component) or the like adhering to the surface of the polishing agent or the like, the filter cake may be sufficiently washed, or the separated abrasive particle cake may be further dispersed in water (re-repulp). The slurry is formed, and then subjected to a solid-liquid separation operation, and the operation is repeated.

In the present invention, the final treatment of the filter cake 26 of the abrasive particles obtained above is carried out to obtain a regenerated abrasive. At this time, according to the purpose, as shown in the drawing, a method using the treatment scheme of the flow 1 obtained by drying and pulverizing only the regenerated abrasive, and drying, calcination, and pulverization to obtain the regenerated abrasive can be used. Any of the methods of processing the scheme.

(4) Scheme of Process 1 (drying, pulverizing step)

The abrasive particle filter cake 26 is formed into a final regenerated abrasive by only the drying step 28 and the pulverizing step 30. The apparatus for performing the drying is not particularly limited, and for example, a box dryer, a belt dryer, a vacuum dryer, a gas flow dryer, a spray dryer, a stirring dryer, a vibration dryer, a hot air dryer, or the like can be used. .

The dry ambient temperature can be appropriately set, but it is preferably 40 to 800 ° C, and particularly preferably 100 to 400 ° C. The drying time can also be appropriately set, for example, several seconds to 30 hours. When a normal hot air dryer is used, the drying ambient temperature is preferably from 100 to 400 °C. Further, when a vacuum dryer is used, the drying ambient temperature is preferably 40 to 200 °C. When using a spray dryer, it can be dried for a few seconds.

By subjecting the dried abrasive particle cake to the pulverization treatment 30, the abrasive particles are sufficiently pulverized and unwound to obtain regenerated abrasive particles 32 having good dispersibility. Further, it is preferable to provide a classification step after the pulverization, and to remove fine particles, coarse particles, and the like by an appropriate classifier such as a wind classifier such as a cyclone.

For example, as shown in the later-described embodiment, the composition of the regenerated abrasive 32 produced by the scheme of the scheme 1 (drying, pulverizing step) is TREO (Total Rare Earth Oxide) (=CeO ₂ +La ₂ O ₃ +Nd ₂ O ₃ +Pr ₆ O ₁₁ ) 93 to 95%, and the mass ratio of each of the above oxides to TREO is approximately CeO ₂ 60%, La ₂ O ₃ 33%, Nd ₂ O ₃ 1%, Pr ₆ O ₁₁ 6%. Further, it contains 5 to 6% of other fluorine components (F), 0.1% of Si component, 0.03% or less of Al component, and 0.1 to 0.2% of Fe component.

On the other hand, as shown in the examples below, the composition of the unused abrasive particles is TREO (Total Rare Earth Oxide) (=CeO ₂ +La ₂ O ₃ +Nd ₂ O ₃ +Pr ₆ O ₁₁ ) ( 95% in the following examples) (the mass ratio of each of the above oxides to TREO is approximately CeO ₂ 61%, La ₂ O ₃ 33%, Nd ₂ O ₃ 0.5%, Pr ₆ O ₁₁ 6%), The other fluorine component (F) is 5%, the Si component is 0.04%, the Al component is 0.03% or less, and the Fe component is about 0.14%.

The regenerated abrasive 32 obtained by the process 1 was found to have almost no difference in the composition ratio of CeO ₂ or the like to TREO and the content of impurities as compared with the unused abrasive. When the comparison is made at the polishing rate, it is restored to about 84 to 87% of the unused product as shown in the examples described later.

However, for example, in the examples described later, the specific surface area (10.92 m ² /g) and the crystallite size (169) Physical and unproductive values (3.82m ² /g, 202) Compared with the fact that the specific surface area is increased and the crystallite size is greatly reduced, it is considered that, in the scheme of only performing the drying and pulverizing steps of the first step, the polishing particles themselves are refined. The deterioration did not completely recover due to the regeneration step.

(4) Scheme of Process 2 (drying, calcination, pulverization step)

The solution of Scheme 2 is followed by a calcination step 29 following the drying step 28 of Scheme 1. By carrying out the calcination step, as described in the examples to be described later, it should be particularly mentioned that the specific surface area (3.45 m ² /g) and the crystallite size (198) by the regeneration step. The deteriorated physical properties shown are almost completely recovered.

The calcination environment temperature is preferably 600 to 1200 ° C, and particularly preferably 700 to 1100 ° C. It is preferred to appropriately adjust the calcination time so as to obtain a desired crystal grain size in the calcination temperature range.

The calcination apparatus for performing calcination is not particularly limited, and any apparatus such as an electric furnace, a gas heating furnace, a rotary furnace (continuous rotary furnace), an infrared heating furnace, a tunnel furnace, or a fluidized bed furnace can be used.

Further, it is preferable to pulverize the calcined product after calcination, and to provide a classification step after the pulverization, and to remove fine particles, coarse particles, and the like by a suitable classifier such as a cyclone or a wind classifier, and at this point, and the flow 1 the same.

(Example)

Hereinafter, the present invention will be described by way of examples. However, these are only one example of the embodiment, and the technical scope of the present invention is not limited to these. In addition, unless otherwise indicated, % means mass%.

[Example 1] (Regeneration treatment using Flow 1) (1) (Used abrasive A)

(i) As the used abrasive A used in the regeneration test, a wet cake having a particle size such as lint removed from the glass cullet and the polishing pad and filtering the abrasive slurry (water content: 21.7% by mass) was used. ). The composition of the used abrasive A in the dry base is TREO (Total Rare Earth Oxide) (=CeO ₂ +La ₂ O ₃ +Nd ₂ O ₃ +Pr ₆ O ₁₁ ) (below In the examples, the same was 93.8% (in addition, the mass ratio of each of the above oxides to TREO was 60.3% of CeO ₂ , 33.3% of La ₂ O ₃ , 0.9% of Nd ₂ O ₃ , and 5.7% of Pr ₆ O ₁₁ ), and the like. The fluorine component (F) was 6.1%, the Si component was 0.66%, the Al component was 0.33%, and the Fe component was 0.33%.

(ii) The average particle diameter (D50) of the used abrasive A was 1.088 μm (by laser scattering measuring apparatus (manufactured by Nikkiso Co., Ltd., trade name: Microtrac, model 9320-X100), using laser scattering method Determination. The same as below). Further, the minimum particle diameter Dmin was 0.375 μm, and the maximum particle diameter Dmax was 6.541 μm. In the cumulative particle size distribution, D10 was 0.592 μm and D90 was 2.364 μm for the particle diameter of 10% and 90% from the small particle diameter.

(iii) Other physical properties of the particles of the abrasive A are as follows.

a) The specific surface area measured by the BET method (measured by a device name manufactured by Shimadzu Corporation, Micro Meritics Flow Sorb II 2300. The same applies hereinafter) was 11.34 m ² /g.

b) crystallite size (measured by a powder X-ray diffractometer (manufactured by Rigaku Co., Ltd., CuK α ray, Rint-2000 type), measured by the Scherrer method. The following is the same) .

The physical properties of the above used abrasive A are summarized in Tables 1 to 4. In addition, the physical properties of the unused new abrasives are also shown in Tables 1 to 4. In addition, Table 1 is the composition (% by mass) of the abrasive, Table 2 is the particle size (μm) of the abrasive, Table 3 is the specific surface area (m ² /g) of the abrasive, and Table 4 is the crystal grain size of the abrasive ( ).

(2) (Recycling treatment of used abrasive A)

(i) 2 kg of the used abrasive A in the form of a dewatered cake was weighed in a beaker made of polyethylene, and 3 L of water was added to make the slurry concentration about 30%, and the mixture was stirred to obtain a redispersed slurry. (first step, slurrying step)

(ii) The redispersed slurry was subjected to an acid treatment as follows. Specifically, 35 mL of 35% hydrochloric acid (1.3 equivalents to the Al and Fe components contained in the filter cake) was gradually added, and the mixture was stirred at room temperature for 2 hours to carry out an acid treatment of hydrochloric acid.

Further, 58 g of 46% hydrofluoric acid (1.3 equivalents to the Si component contained in the filter cake) was gradually added to the slurry, and the mixture was heated to 50 ° C and stirred for 5 hours to carry out acid treatment of hydrofluoric acid. (second step, acid treatment step)

(iii) The acid-treated slurry was subjected to solid-liquid separation as follows. That is, the slurry was allowed to stand for 1 hour to precipitate the abrasive particles, and then the supernatant was decanted, and 3 L of water was added to the obtained precipitate, followed by further pressure filtration, and the mixture was thoroughly stirred and allowed to stand for 1 hour to be ground. After the agent particles settled, the supernatant was decanted to obtain a precipitate.

This operation (precipitation re-filtration-sedimentation separation operation) was repeated three times, and the abrasive particle precipitation was sufficiently washed with water to prevent hydrochloric acid, hydrofluoric acid, and dissolved glass components from remaining. Finally, suction filtration was performed using ADVANTEC No. 5A filter paper, and the precipitate of the washed abrasive particles was recovered. (third step, solid-liquid separation step)

(iv) The recovered abrasive particles were precipitated (filter cake) in a box dryer and dried at 110 ° C for 12 hours. The dried filter cake was pulverized by a pulverizer, and classified by an air classifier to recover 1.33 kg of regenerated abrasive A'. (fourth step, drying, pulverizing step)

(3) (physical properties of regenerated abrasive A')

(i) The composition of the regenerated abrasive A' is TREO (=CeO ₂ +La ₂ O ₃ +Nd ₂ O ₃ +Pr ₆ O ₁₁ ),94.8 mass% (in addition, the mass ratio of each of the above oxides to TREO is CeO ₂ 59.4 %, La ₂ O ₃ 33.5%, Nd ₂ O ₃ 0.9%, Pr ₆ O ₁₁ 5.9%), other fluorine component (F) is 6.0%, Si component is 0.09%, Al component is 0.03% or less, and Fe component is 0.09%.

(ii) The average particle diameter (D50) of the regenerated abrasive A' was 1.046 μm. Further, the minimum particle diameter Dmin was 0.375 μm, and the maximum particle diameter Dmax was 5.5 μm. In the cumulative particle size distribution, D10 was 0.582 μm and D90 was 2.098 μm for the particle diameter of 10% and 90% from the small particle diameter.

(iii) Other physical properties of the particles of the abrasive A' are as follows.

a) The specific surface area measured by the BET method was 10.92 m ² /g.

b) crystal grain size is 169 .

The physical properties of the above regenerated abrasive A' are summarized in Tables 1 to 4.

(4) (grinding test using regenerated abrasive A')

(i) The grinding tester used a double-faced grinder 6BF type manufactured by Sakai Industry Co., Ltd. The ground glass used in the test used an alkali-free glass manufactured by Asahi Glass Co., Ltd. (trade name: AN-100, SiO ₂ content in the glass composition was about 60% by mass, and test plate size (square): 100 mm/100 mm/0.7 mm) .

(ii) The polishing pad was made of a non-woven fabric made of foamed polyurethane, and the polishing pressure was 130 g/cm ² , and the double-side polishing test was carried out at a chassis rotation speed of 60 rpm.

(iii) The concentration of the abrasive in the abrasive slurry was 15% by mass (the rest was water), and it was used while circulating at a supply amount of 1.8 L/min.

(iv) The polishing time was 45 minutes per batch, and 6 batches of polishing were performed, and the amount of grinding was calculated from the difference in mass of the glass plate to be polished. When the amount of grinding of the unused abrasive (new abrasive) A ₀ was taken as 100, the relative value of the amount of grinding was 87. The results are shown in Table 5.

(5) (Exploration of results)

(i) In Example 1 in which the regeneration treatment step including the step (drying and pulverization) of the scheme 1 was employed, the regenerated abrasive A' was almost the same as the composition and particle size of the unused new abrasive _A0 . No difference was confirmed, but its specific surface area (10.92 m ² /g), crystallite size (169 The physical property and the value of A ₀ (3.82m ² /g, 202) In comparison with the fact that the specific surface area is increased and the crystallite size is largely lowered, it is considered that the abrasive particles A' do not completely recover the deterioration of the used abrasive due to the procedure of the first step.

(ii) As shown in Table 5, the relative value 87 of the amount of grinding when A' was used was a result of about 10% lower than that of the unused new abrasive A ₀ 100. However, the regenerated abrasive A' having the relative value of 87 can be sufficiently used as an abrasive.

[Example 2] (Regeneration treatment using Flow 2) (1) (Used abrasive A)

The same abrasive as used in Example 1 was used for the used abrasive A used in the regeneration test.

(2) (Recycling treatment of used abrasive A)

(i) 2 kg of the used abrasive A in the form of a dewatered cake was weighed in a beaker made of polyethylene, and 3 L of water was added to make the slurry concentration about 30%, and the mixture was stirred to obtain a redispersed slurry. (first step, slurrying step)

(ii) The redispersed slurry was subjected to an acid treatment as follows. Specifically, 35 mL of 35% hydrochloric acid (1.3 equivalents to the Al and Fe components contained in the filter cake) was gradually added, and the mixture was stirred at room temperature for 2 hours to carry out an acid treatment of hydrochloric acid.

Further, 58 g of 46% hydrofluoric acid (1.3 equivalents to the Si component contained in the filter cake) was gradually added to the slurry, and the mixture was heated to 50 ° C and stirred for 5 hours to carry out acid treatment of hydrofluoric acid. (second step, acid treatment step)

(iii) The acid-treated slurry was subjected to solid-liquid separation as follows. That is, the slurry was allowed to stand for 1 hour to precipitate the abrasive particles, and then the supernatant was decanted, and 3 L of water was added to the obtained precipitate, followed by further pressure filtration, and the mixture was thoroughly stirred and allowed to stand for 1 hour to be ground. After the agent particles settled, the supernatant was decanted to obtain a precipitate.

This operation (precipitation re-filtration-sedimentation separation operation) was repeated three times, and the abrasive particle precipitation was sufficiently washed with water to prevent hydrochloric acid, hydrofluoric acid, and dissolved glass components from remaining. Finally, suction filtration was performed using ADVANTEC No. 5A filter paper, and the precipitate of the washed abrasive particles was recovered. (third step, solid-liquid separation step)

(iv) The recovered abrasive particles were precipitated (filter cake) in a box dryer and dried at 110 ° C for 12 hours. (fourth step, drying step)

(v) The dried filter cake was calcined at 950 ° C for 3 hours in an electric calciner. The calcined cake was pulverized by a pulverizer, and classified by an air classifier to recover 1.07 kg of regenerated abrasive A" (fifth step, calcination, pulverization step)

(3) (physical properties of regenerated abrasive A)

(i) The composition of the regenerated abrasive A" is TREO (=CeO ₂ +La ₂ O ₃ +Nd ₂ O ₃ +Pr ₆ O ₁₁ ) 94.7 mass% (in addition, the mass ratio of each of the above oxides to TREO is CeO ₂ 59.7 %, La ₂ O ₃ 33.2%, Nd ₂ O ₃ 0.9%, Pr ₆ O ₁₁ 5.8%), other fluorine component (F) was 6.0%, Si component was 0.07%, Al component was 0.03% or less, and Fe component was 0.15%.

(ii) The average particle diameter (D50) of the regenerated abrasive A" is 1.074 μm. In addition, the minimum particle diameter Dmin is 0.375 μm, the maximum particle diameter Dmax is 4.625 μm, and in the cumulative particle size distribution, 10 from the small particle diameter %, 90% particle size, D10 is 0.582 μm, and D90 is 2.127 μm.

(iii) Other physical properties of the particles of the abrasive A" are as follows.

a) The specific surface area measured by the BET method was 3.45 m ² /g.

b) The crystallite size is 198 .

The physical properties of the above regenerated abrasive A" are summarized in Tables 1 to 4.

(4) (grinding test using regenerated abrasive A)

(i) Polishing Test The same procedure as in Example 1 was carried out using the same polishing tester as in Example 1.

(ii) In the same manner as in the first embodiment, the amount of grinding was calculated from the difference in mass of the glass plate to be polished. When the amount of grinding of the unused abrasive (new abrasive) A ₀ was taken as 100, the relative value of the amount of the grinding was 98. The results are shown in Table 5.

(5) (Exploration of results)

(i) In the second embodiment in which the regeneration treatment step including the calcination and pulverization step of the second step is employed, the regenerated abrasive A" has almost no component composition and particle size as compared with the unused new abrasive _A0 . Difference, and its specific surface area (3.45m ² /g), crystallite size (198 The physical property and the value of A ₀ (3.82m ² /g, 202) In comparison, the fact that it is almost restored is also confirmed. It is considered that the abrasive particles A" completely recover the deterioration of the used abrasive by the regeneration step.

(ii) As shown in Table 5, the relative value of the amount of grinding when using A" is 98 (relative to the value of the unused new abrasive A ₀ 100), even if compared with the new abrasive A ₀ In other words, it can be judged that the regenerated abrasive A" of the second embodiment can be used again as the same abrasive as the new one.

[Example 3] (Regeneration treatment using Flow 1) (1) (Used abrasive B)

(i) As the used abrasive B used in the regeneration test, a wet cake (water content: 47.5 mass%) using a waste material such as lint from the glass cullet and the polishing pad and filtering the abrasive slurry was used. . The composition of the used abrasive B in the dry state is 81.5% of TREO (=CeO ₂ +La ₂ O ₃ +Nd ₂ O ₃ +Pr ₆ O ₁₁ ) (in addition, the mass ratio of each of the above oxides to TREO is CeO ₂ 60.9%, La ₂ O ₃ 33.0%, Nd ₂ O ₃ 1.0%, and Pr ₆ O ₁₁ 6.0%), and the fluorine component (F) was 5.2%, the Si component was 2.70%, and the Al component was 0.90%. It is 6.88%.

(ii) The used abrasive B had an average particle diameter (D50) of 2.768 μm. Further, the minimum particle diameter Dmin was 0.375 μm, and the maximum particle diameter Dmax was 26.11 μm. In the cumulative particle size distribution, D10 was 0.762 μm and D90 was 8.098 μm for the particle diameter of 10% and 90% from the small particle diameter.

(iii) Other physical properties of the particles of the abrasive B are as follows.

a) The specific surface area measured by the BET method was 18.7 m ² /g.

b) crystal size is 167 .

The physical properties of the above used abrasive B are summarized in Tables 6 to 9. In addition, the physical properties of the unused new abrasive B ₀ are also shown in Tables 6 to 9.

(2) (Recycling treatment of used abrasive B)

(i) 3 kg of the used abrasive B in the form of a dehydrated cake was weighed in a beaker made of polyethylene, and 3 L of water was added to make the slurry concentration about 30%, and the mixture was stirred to obtain a redispersed slurry. (first step, slurrying step)

(ii) The redispersed slurry was subjected to an acid treatment as follows. Specifically, 570 mL of 35% hydrochloric acid (1.3 equivalents to the Al and Fe components contained in the filter cake) was gradually added, and the mixture was stirred at room temperature for 2 hours to carry out an acid treatment of hydrochloric acid.

Further, 240 g of 46% hydrofluoric acid (1.3 equivalents to the Si component contained in the filter cake) was gradually added to the slurry, and the mixture was heated to 50 ° C and stirred for 5 hours to carry out acid treatment of hydrofluoric acid. (second step, acid treatment step)

(iii) The acid-treated slurry was subjected to solid-liquid separation as follows. That is, the slurry was allowed to stand for 1 hour to precipitate the abrasive particles, and then the supernatant was decanted, and 3 L of water was added to the obtained precipitate, followed by further pressure filtration, and the mixture was thoroughly stirred and allowed to stand for 1 hour to be ground. After the agent particles settled, the supernatant was decanted to obtain a precipitate.

This operation (precipitation re-filtration-sedimentation separation operation) was repeated three times, and the abrasive particle precipitation was sufficiently washed with water to prevent hydrochloric acid, hydrofluoric acid, and dissolved glass components from remaining. Finally, suction filtration was performed using ADVANTEC No. 5A filter paper, and the precipitate of the washed abrasive particles was recovered. (third step, solid-liquid separation step)

The second and third steps described above are repeated.

(iv) The recovered abrasive particles were precipitated (filter cake) in a box dryer and dried at 110 ° C for 12 hours. The dried cake was pulverized by a pulverizer, and classified by an air classifier to recover 1.16 kg of regenerated abrasive B'. (fourth step, drying, pulverizing step)

(3) (physical properties of regenerated abrasive B')

(i) The composition of the regenerated abrasive B' is TREO (=CeO ₂ +La ₂ O ₃ +Nd ₂ O ₃ +Pr ₆ O ₁₁ ),93.7 mass% (in addition, the mass ratio of each of the above oxides to TREO is CeO ₂ 60.5%, La ₂ O ₃ 32.1%, Nd ₂ O ₃ 1.0%, Pr ₆ O ₁₁ 6.2%), other fluorine component (F) is 5.2%, Si component is 0.10%, Al component is 0.03% or less, and Fe component It is 0.17%.

(ii) The average particle diameter (D50) of the regenerated abrasive B' was 1.077 μm. Further, the minimum particle diameter Dmin was 0.375 μm, and the maximum particle diameter Dmax was 5.5 μm. In the cumulative particle size distribution, D10 was 0.577 μm and D90 was 2.154 μm for the particle diameter of 10% and 90% from the small particle diameter.

(iii) Further, other physical properties of the particles of the abrasive B' are as follows.

a) The specific surface area measured by the BET method was 19.1 m ² /g.

b) crystal grain size is 176 .

The physical properties of the above regenerated abrasive B' are summarized in Tables 6 to 9. In addition, the physical properties of the unused new abrasive B ₀ are also shown in Tables 6 to 9. In addition, Table 6 is the composition (% by mass) of the abrasive, Table 7 is the particle size (μm) of the abrasive, Table 8 is the specific surface area (m ² /g) of the abrasive, and Table 9 is the crystal grain size of the abrasive ( ).

(Note) indicates the name of the device manufactured by Rigaku Co., Ltd.: powder X-ray diffractometer Rint-2000 type, crystallite size determined by the Scherrer method ( ).

(4) (grinding test using regenerated abrasive B')

(i) Polishing Test The same procedure as in Example 1 was carried out using the same polishing tester as in Example 1.

(ii) In the same manner as in the first embodiment, the amount of grinding was calculated from the difference in mass of the glass plate to be polished. The relative value of the amount of the grinding when the amount of grinding of the unused abrasive (new abrasive) was 100 was 84. The results are shown in Table 10.

(5) (Exploration of results)

(i) a step comprising using the procedure of Example (dried and pulverized) regeneration process of step 1 in 3, for the regeneration of the abrasive B ', compared to the new abrasive B ₀ unused, although the chemical composition, particle size almost No difference was confirmed, but its specific surface area (19.1 m ² /g), crystallite size (176 Physical property and value of B ₀ (3.82m ² /g, 202 In comparison with the fact that the specific surface area is increased and the crystallite size is largely lowered, it is considered that the abrasive particles B' do not completely recover the deterioration of the used abrasive due to the regeneration step.

(ii) As shown in Table 10, the relative value 84 of the amount of grinding when B' was used was a result of about 15% lower than that of the unused new abrasive B ₀ 100. However, it is considered that the regenerated abrasive B' having the relative value of 84 can be sufficiently used as an abrasive. In addition, it is considered that the used polishing agent B has a larger glass component and agglomerating agent component than A, and the aggregation of the particles is strong, and regeneration is more difficult. However, the regeneration method according to the present invention is confirmed by the method of the first embodiment. It can achieve the purpose of complete regeneration.

[Embodiment 4] (Regeneration processing using Flow 2) (1) (Used abrasive B)

The same abrasive as used in Example 3 was used for the used abrasive B used in the regeneration test.

(2) (Recycling treatment of used abrasive B)

(i) 2 kg of the used abrasive B in the form of a dewatered cake was weighed in a beaker made of polyethylene, and 3 L of water was added to make the slurry concentration about 30%, and the mixture was stirred to obtain a redispersed slurry. (first step, slurrying step)

(ii) The redispersed slurry was subjected to an acid treatment as follows. Specifically, 570 mL of 35% hydrochloric acid (1.3 equivalents to the Al and Fe components contained in the filter cake) was gradually added, and the mixture was stirred at room temperature for 2 hours to carry out an acid treatment of hydrochloric acid.

Further, 240 g of 46% hydrofluoric acid (1.3 equivalents to the Si component contained in the filter cake) was gradually added to the slurry, and the mixture was heated to 50 ° C and stirred for 5 hours to carry out acid treatment of hydrofluoric acid. (second step, acid treatment step)

(iii) The acid-treated slurry was subjected to solid-liquid separation as follows. That is, the slurry was allowed to stand for 1 hour to precipitate the abrasive particles, and then the supernatant was decanted, and 3 L of water was added to the obtained precipitate, followed by further pressure filtration, and the mixture was thoroughly stirred and allowed to stand for 1 hour to be ground. After the agent particles settled, the supernatant was decanted to obtain a precipitate.

This operation (precipitation re-filtration-sedimentation separation operation) was repeated three times, and the abrasive particle precipitation was sufficiently washed with water to prevent hydrochloric acid, hydrofluoric acid, and dissolved glass components from remaining. Finally, suction filtration was performed using ADVANTEC No. 5A filter paper, and the precipitate of the washed abrasive particles was recovered. (third step, solid-liquid separation step)

(iv) The recovered abrasive particles were precipitated (filter cake) in a box dryer and dried at 110 ° C for 12 hours. (fourth step, drying step)

(v) The dried filter cake was calcined at 950 ° C for 3 hours in an electric calciner. The calcined cake was pulverized by a pulverizer, and classified by an air classifier to recover 0.94 kg of regenerated abrasive B" (fifth step, calcination, pulverization step)

(3) (physical properties of regenerated abrasive B)

(i) The composition of the regenerated abrasive B" is TREO (=CeO ₂ +La ₂ O ₃ +Nd ₂ O ₃ +Pr ₆ O ₁₁ ) of 94.5 mass% (in addition, the mass ratio of each of the above oxides to TREO is CeO ₂ 60.2%, La ₂ O ₃ 32.8%, Nd ₂ O ₃ 0.9%, Pr ₆ O ₁₁ 5.9%), other fluorine component (F) is 5.1%, Si component is 0.09%, Al component is 0.03% or less, and Fe component It is 0.13%.

(ii) The average particle diameter (D50) of the regenerated abrasive B" is 1.010 μm. Further, the minimum particle diameter Dmin is 0.375 μm, and the maximum particle diameter Dmax is 5.5 μm, in the cumulative particle size distribution, from the small particle diameter 10%, 90% particle size, D10 is 0.564 μm, and D90 is 2.178 μm.

(iii) Other physical properties of the particles of the abrasive B" are as follows.

a) The specific surface area measured by the BET method was 3.26 m ² /g.

b) crystal size is 213 .

The physical properties of the above regenerated abrasive B" are summarized in Tables 6 to 9.

(4) (grinding test using regenerated abrasive B)

(i) Polishing Test The same procedure as in Example 1 was carried out using the same polishing tester as in Example 1.

(ii) In the same manner as in the first embodiment, the amount of grinding was calculated from the difference in mass of the glass plate to be polished. The relative value of the amount of grinding of the unused abrasive (new abrasive) was 100, which was 97. The results are shown in Table 10.

(5) (Exploration of results)

(i) a process comprising calcining using 2, Example 4 step regeneration process of the pulverization step, for the regeneration of the abrasive B ", compared with the new B ₀ unused abrasive, not only hardly confirmed the chemical composition, particle size Difference, and its specific surface area (3.26m ² /g), crystallite size (213 Physical property and value of B ₀ (3.82m ² /g, 202 In comparison, it was confirmed that the recovery was almost equivalent to the use of an unused abrasive. It is considered that the abrasive particles B" completely recover the deterioration of the used abrasive by the regeneration step.

(ii) As shown in Table 10, the relative value of the amount of grinding when using B" is 97 (relative to the value of the unused new abrasive B ₀ 100), even if compared with the new abrasive B ₀ The amount of grinding that is not inferior, that is, it can be judged that the regenerated abrasive B" of the fourth embodiment can be used again as the same abrasive as the new one.

Further, it is considered that the used abrasive B has a larger glass component and agglomerating component than the original A, and the aggregation of the particles is strong, and regeneration is more difficult. However, the regeneration method according to the present invention, particularly the method including the flow 2 It is confirmed that the purpose of complete regeneration can be achieved.

(industrial availability)

According to the present invention, there is provided a method of regenerating a polishing rate of a generally discarded cerium-based abrasive having a greatly reduced polishing rate to a regeneration rate close to that of an unused abrasive.

Further, according to the present invention, there is further provided a method of regenerating a used lanthanide-based abrasive which does not use a base, so that there is no problem of agglomerating the abrasive particles, and the like is avoided. There is a problem that the removal rate of the Si component or the Al component is low because the polishing rate is lowered.

10. . . Used abrasive

12. . . water

14. . . Redispersion step

16. . . Redispersed slurry

18. . . acid

20. . . Acid treatment step

twenty two. . . Treatment slurry

twenty four. . . Solid-liquid separation step

25. . . filtrate

26. . . Abrasive particle filter cake

28. . . dry

29. . . Calcination

30. . . Crushing (grading)

32. . . Regenerated abrasive

Fig. 1 is a flow chart showing an example of a procedure for obtaining a regenerated abrasive by treating a used cerium-based abrasive.

10. . . Used abrasive

12. . . water

14. . . Redispersion step

16. . . Redispersed slurry

18. . . acid

20. . . Acid treatment step

twenty two. . . Treatment slurry

twenty four. . . Solid-liquid separation step

25. . . filtrate

26. . . Abrasive particle filter cake

28. . . dry

29. . . Calcination

30. . . Crushing (grading)

32. . . Regenerated abrasive

Claims (6)

A method for regenerating a lanthanum-based abrasive, which comprises treating a regenerated abrasive with a used lanthanide abrasive, comprising the steps of: redispersing the used abrasive particles with water, and then The obtained slurry is directly neutralized with at least a Si component which is a glass component adhered to the surface of the abrasive particles, and an Al component which is an impurity component and an Fe component are dissolved or freed in a slurry state, thereby removing the acid from the abrasive particles. Process it. A method for regenerating a lanthanum-based abrasive which is obtained by treating a used lanthanide abrasive to obtain a regenerated abrasive, comprising the steps of: (1) redispersing the used abrasive particles with water; a step of forming a slurry, and (2) removing and removing the Si component belonging to the glass component adhered to the surface of the abrasive particle and the Al component and the Fe component which are impurity components, thereby being removed from the abrasive particle. a step of acid-treating the redispersed slurry; (3) a step of subjecting the obtained acid-treated slurry to solid-liquid separation; and (4) a step of drying and pulverizing the obtained filter cake. A method for regenerating a lanthanum-based abrasive which is obtained by treating a used lanthanide abrasive to obtain a regenerated abrasive, comprising the steps of: (1) redispersing the used abrasive particles with water; a step of forming a slurry; (2) treating the redispersed slurry with an acid capable of dissolving or dissolving the Si component belonging to the glass component adhered to the surface of the abrasive particles and the Al component and the impurity component belonging to the impurity component to be removed from the abrasive particles Step; (3) a step of subjecting the obtained acid-treated slurry to solid-liquid separation; (4) a step of drying the obtained filter cake; and (5) a step of further calcining and pulverizing the dried filter cake. The method for regenerating an anthraquinone abrasive according to any one of claims 1 to 3, wherein the acid is a mineral acid. The method for regenerating an abrasive according to the fourth aspect of the patent application, wherein two or more inorganic acids are used in combination. The method for regenerating an abrasive according to the fifth aspect of the patent application, wherein one of hydrochloric acid, sulfuric acid and nitric acid and hydrofluoric acid are used in combination.