JPWO2019181498A1 - Abrasive recycling system and abrasive recovery / regeneration method - Google Patents

Abstract

An object of the present invention is to provide an abrasive recycling treatment system and an abrasive recovery / regeneration method for efficiently recovering an abrasive from a processed abrasive slurry and reusing it as a recycled abrasive slurry. Is. The abrasive recycling processing system of the present invention continues the polishing process while controlling the concentrations of the constituent components of the abrasive and the constituent components of the object to be polished in the abrasive slurry used for polishing, and from the processed abrasive slurry, An abrasive recycling processing system that removes the constituents of the object to be polished and collects and regenerates the abrasive, and has an abrasive slurry recovery process section having a polishing process section and a slurry supply tank for storing the abrasive used for polishing. The feature is that the regenerated abrasive slurry is supplied into the slurry supply tank while controlling the concentration of the constituent components of the abrasive in the slurry supply tank to be equal to or lower than the initial concentration at the start of the polishing process. To do.

Description

The present invention relates to an abrasive recycling processing system and an abrasive recovery / regeneration method. More specifically, polishing for efficiently recovering an abrasive from a processed abrasive slurry and reusing it as a recycled abrasive slurry. Regarding the agent recycling processing system, etc.

Conventionally, diamonds, boron nitride, silicon carbide, alumina, alumina zirconia, zirconium oxide, cerium oxide and the like have been represented as abrasives (also referred to as abrasives) for precision polishing optical glass and crystal oscillators in the finishing process. Fine particles with high hardness are used.

In general, some of the main constituent elements of abrasives are obtained from minerals that are not produced in Japan, and some of them are resources that rely on imports, and many of them are expensive in terms of material price.

Since these abrasives are fine particles with high hardness, they are important resources that are widely used as optical abrasives for electronic components such as optical lenses, semiconductor silicon substrates, and glass plates for liquid crystal screens. It is one of the resources that is strongly desired to be used. In addition, the polishing agent for optical polishing may contain fine particles of transition metal elements such as sodium salt and chromium salt, and rare earth elements such as yttrium and deciprosium, with each of the above compounds as the main component, and is simple. Disposal is strongly prohibited in the environment. Therefore, it is strongly desired to develop a treatment technology for decontaminating the waste liquid after being used for polishing. Therefore, for the waste liquid of optical abrasives containing processed abrasives, it is an important issue to take technical measures to recycle resources or make them pollution-free.

Generally, as a method for treating wastewater containing suspended fine particles generated in various industrial fields, suspended fine particles are coagulated and separated using a neutralizing agent, an inorganic flocculant, a polymer flocculant, etc., and then the treated water is discharged. However, the current situation is that sludge that has been coagulated and separated is disposed of by means such as incineration.

Further, these abrasives are usually used in a large amount in the polishing process, and constituent components of the object to be polished, such as optical glass scraps, coexist in the waste liquid, but usually, the abrasive and the abrasive are to be polished. As mentioned above, since it is difficult to efficiently separate the abrasive from the object, the abrasive waste liquid is often discarded after use, which is an environmental load and a disposal cost. I also have a problem.

Therefore, in recent years, it has become an important problem to efficiently reuse the main constituent elements of abrasives to conserve resources of elements having high rare value.

Regarding the method for regenerating the constituent components of the abrasive, for example, an electrolyte substance is added to the processed abrasive to coagulate and precipitate the abrasive, and the constituent components (components to be polished) derived from the polished object to be polished are dissolved. However, a method for solid-liquid separation is disclosed (see, for example, Patent Document 1). In the method described in Patent Document 1, an alkali metal hydroxide, an alkali metal carbonate, an alkali metal salt, and an ammonium salt are used as the electrolyte material.

Further, a method of regenerating a fine abrasive by mixing a solution of sodium hydroxide and potassium hydroxide with a processed abrasive and sieving a solid substance by solid-liquid separation is disclosed (for example). , Patent Document 2). Further, a method is disclosed in which rare earths and rare metals are dissolved by adding sulfuric acid to a processed abrasive and heat-treating the processed abrasive, and separating and removing the aggregates such as silica in the abrasive slurry (for example). , Patent Document 3).

Further, as a method for recovering a colloidal silica-based abrasive, a coagulation treatment is performed by adding an alkali to the CMP (Chemical Mechanical Polishing) waste liquid in the presence of magnesium ions to adjust the pH value to 10 or more. (See, for example, Patent Document 4). Further, Non-Patent Document 1 provides a review on the metal recovery technique described above.

Generally, "abrasive regeneration amount = abrasive usage amount x recovery rate x regeneration rate", and improvement of the recovery rate and the regeneration rate is important. However, the above-mentioned technique focuses on improving the regeneration rate of the recovered processed abrasive, and studies on the improvement of the recovery rate have not been sufficient in the past. Unless the recovery rate is also improved, the abrasive cannot be efficiently regenerated.

For example, if glass polishing is continued with an abrasive slurry containing a constant concentration of abrasive, the silicon oxide concentration of the object to be polished in the abrasive slurry increases. When the silicon oxide concentration increases, silicon oxide precipitates and solidifies, and becomes a foreign substance in the abrasive slurry. Since this foreign matter causes defects such as scratches, the abrasive slurry cannot be used. Further, as the viscosity of the abrasive slurry increases, scattering or adhesion to the periphery of the polishing apparatus occurs, and there is a problem that the amount of the abrasive component recovered is reduced.

Japanese Unexamined Patent Publication No. 06-254764 Japanese Unexamined Patent Publication No. 11-90825 Japanese Unexamined Patent Publication No. 11-50168 Japanese Unexamined Patent Publication No. 2000-254659

Metal Resources Report Page 45 2010.11.

The present invention has been made in view of the above problems and situations, and the problem to be solved is to efficiently recover the abrasive from the processed abrasive slurry and reuse it as a regenerated abrasive slurry. It is to provide an abrasive recycling processing system and an abrasive recovery / regeneration method.

In order to solve the above problems, the present inventor performs an abrasive recycling process in the process of examining the cause of the above problem, and sets the concentration of the abrasive in the abrasive slurry during processing to be equal to or less than the initial concentration at the start of polishing. It has been found that the precipitation and solidification of the object to be polished can be suppressed and the efficient recovery is possible.

That is, the above-mentioned problem according to the present invention is solved by the following means.

1. 1. Polishing is continued while controlling the concentrations of the constituents of the polishing agent and the constituents of the object to be polished in the abrasive slurry used for polishing, and the constituents of the object to be polished are removed from the processed abrasive slurry. An abrasive recycling processing system that collects and regenerates the abrasive.
It has a polishing process unit for polishing using a polishing machine and an abrasive slurry recovery process unit having a slurry supply tank for storing the polishing agent slurry supplied to the polishing machine.
Polishing characterized in that the regenerated abrasive slurry is supplied into the slurry supply tank while controlling the concentration of the constituent components of the abrasive in the slurry supply tank to be equal to or lower than the initial concentration at the start of the polishing process. Abrasive recycling processing system.

2. The concentration of the constituent components of the abrasive in the slurry supply tank is within the range of 20 to 90% at the end point concentration at the end of the polishing process with respect to the concentration at the start of the polishing process, and during the polishing process. The concentration of the constituent components of the abrasive is always equal to or higher than the end point concentration, and the fluctuation range of the change in the concentration of the constituent components of the abrasive in the next processing batch with respect to the pre-processing batch is controlled within ± 1.0% by mass. The abrasive recycling treatment system according to paragraph 1, wherein the abrasive is characterized by the above.

3. 3. The concentration of the constituent components of the abrasive in the slurry supply tank is within the range of 30 to 80% at the end point concentration at the end of the polishing process with respect to the concentration at the start of the polishing process, and during the polishing process. The concentration of the constituent components of the abrasive is always equal to or higher than the end point concentration, and the fluctuation range of the change in the concentration of the constituent components of the abrasive in the next processing batch with respect to the pre-processing batch is controlled within ± 1.0% by mass. The abrasive recycling treatment system according to paragraph 1, wherein the abrasive is characterized by the above.

4. Any of the items 1 to 3 characterized by having a separation / concentration process unit and a regenerated abrasive slurry preparation process unit in addition to the polishing process unit and the abrasive slurry recovery process unit. The abrasive recycling processing system according to item 1.

5. In the abrasive slurry recovery process section, the slurry supply tank for storing the abrasive slurry to be supplied to the polishing process section and the recovery mixture tank for storing the mixed solution of the processed abrasive slurry and the washing water are stored. With and
The separation / concentration step unit is provided with a separation / concentration tank that separates the mixed liquid into a permeation liquid and a concentrated liquid of an abrasive.
The regenerated abrasive slurry preparation process unit is provided with a regenerated abrasive slurry storage tank for storing a liquid containing the regenerated abrasive from which the constituent components of the object to be polished have been removed, and an abrasive slurry is provided between the process units. The abrasive recycling treatment system according to item 4, further comprising a circulation line for supplying and a control unit for adjusting the supply amount.

6. The abrasive recycling treatment system according to item 4 or 5, further comprising an abrasive particle size adjusting process unit for adjusting the particle size of the abrasive obtained in the separation / concentration process unit.

7. Any one of items 1 to 6, wherein the recycled abrasive slurry contains a maleic acid-acrylic acid copolymer in the range of 0.04 to 1.5 g / L. Abrasive recycling processing system as described in the section.

8. The abrasive recycling treatment system according to any one of items 1 to 7, wherein the abrasive contains a metal oxide and the object to be polished contains silicon (Si). ..

9. The abrasive recycling treatment system according to any one of items 1 to 8, wherein the abrasive contains cerium oxide.

10. The abrasive recycling treatment system according to any one of items 4 to 9, wherein an alkaline earth metal salt is used as an abrasive flocculant in the separation / concentration step unit.

11. The abrasive recycling treatment system according to Item 10, wherein the alkaline earth metal salt is a magnesium salt.

12. Polishing is continued while controlling the concentrations of the constituents of the polishing agent and the constituents of the object to be polished in the abrasive slurry used for polishing, and the constituents of the object to be polished are removed from the processed abrasive slurry. A polishing agent recovery / regeneration method for recovering / regenerating the polishing agent.
The concentration of the constituent components of the abrasive in the slurry supply tank for storing the abrasive slurry used for the polishing supplied to the polishing machine is controlled to be equal to or lower than the initial concentration of the constituent components of the abrasive at the start of the polishing process. A method for recovering and regenerating an abrasive, which comprises supplying a recycled abrasive slurry to a polishing process section and recovering the processed abrasive slurry.

13. The concentration of the constituent components of the abrasive in the slurry supply tank is within the range of 20 to 90% at the end point concentration at the end of the polishing process with respect to the concentration at the start of the polishing process, and during the polishing process. The concentration of the constituent components of the abrasive is always equal to or higher than the end point concentration, and the fluctuation range of the change in the concentration of the constituent components of the abrasive in the next processing batch with respect to the pre-processing batch is controlled within ± 1.0% by mass. The method for recovering and regenerating an abrasive according to Item 12, wherein the polishing agent is recovered and regenerated.

14. The concentration of the constituent components of the abrasive in the slurry supply tank is within the range of 30 to 80% at the end point concentration at the end of the polishing process with respect to the concentration at the start of the polishing process, and during the polishing process. The concentration of the constituent components of the abrasive is always equal to or higher than the end point concentration, and the fluctuation range of the change in the concentration of the constituent components of the abrasive in the next processing batch with respect to the pre-processing batch is controlled within ± 1.0% by mass. The method for recovering and regenerating an abrasive according to Item 12, wherein the polishing agent is recovered and regenerated.

15. Any one of the items 12 to 14, wherein the reclaimed abrasive slurry contains a maleic acid-acrylic acid copolymer in the range of 0.04 to 1.5 g / L. The method for collecting and regenerating the abrasive according to the section.

Provided are an abrasive recycling treatment system and an abrasive recovery / regeneration method for efficiently recovering an abrasive from a processed abrasive slurry and reusing it as a regenerated abrasive slurry by the above means of the present invention. be able to.

Although the mechanism of expression or mechanism of action of the effect of the present invention has not been clarified, it is inferred as follows.

The conventional abrasive recycling system aims to keep the abrasive concentration in the abrasive slurry constant during the polishing process. Therefore, as the polishing progresses, the concentration of the object to be polished increases, the viscosity increases and the temperature becomes locally high, and the precipitation of the object to be polished lowers the recovery rate and adversely affects the polishing processing quality. By lowering the concentration of the abrasive in the abrasive slurry during processing, the concentration of the object to be polished is also reduced, the adhesion of the abrasive slurry to the polishing machine is reduced, and the recovery rate of the processed abrasive slurry is reduced. It seems that it can be improved.

Conceptual diagram showing the relationship between the polishing time, the concentration of the abrasive in the abrasive slurry during processing, and the concentration of the constituent components of the object to be polished Conceptual diagram showing the relationship between the polishing time, the concentration of the abrasive in the abrasive slurry during processing, and the concentration of the constituent components of the object to be polished. Schematic diagram showing an example of the abrasive recycling processing system of the present invention SEM photo of polishing pad after polishing SEM photo of polishing pad after polishing

The abrasive recycling processing system of the present invention continues the polishing process while controlling the concentrations of the constituent components of the abrasive and the constituent components of the object to be polished in the abrasive slurry used for polishing, and from the processed abrasive slurry, An abrasive recycling processing system that removes the constituents of the object to be polished and collects and regenerates the abrasive, and is used for the polishing process unit for polishing using a polishing machine and the polishing supplied to the polishing machine. It has an abrasive slurry recovery process unit having a slurry supply tank for storing the abrasive slurry, and controls the concentration of the constituent components of the abrasive in the slurry supply tank to be equal to or lower than the initial concentration at the start of the polishing process. At the same time, it is characterized in that the regenerated abrasive slurry is supplied into the slurry supply tank. This feature is a technical feature common to or corresponding to each of the following embodiments.

The concentration of the constituent components of the abrasive in the slurry supply tank is within the range of 20 to 90%, more preferably 30 to 80%, at the end point concentration at the end of the polishing process with respect to the concentration at the start of the polishing process. Within the range, the concentration of the constituent components of the abrasive during the polishing process is always equal to or higher than the end point concentration, and the fluctuation range of the change in the concentration of the constituent components of the abrasive in the next processing batch with respect to the preprocessing batch. Is preferably controlled within ± 1.0% by mass.

Further, having a separation / concentration process unit and a regenerated abrasive slurry preparation process unit in addition to the polishing processing process unit and the abrasive slurry recovery process unit has the effect of improving the efficiency of the abrasive recycling processing system. It is preferable because it can be obtained.

Further, in the present invention, in the abrasive slurry recovery process unit, the slurry supply tank for storing the regenerated abrasive slurry to be supplied to the abrasive processing process unit, and a mixed solution of the processed abrasive slurry and cleaning water. The separation / concentration step unit is provided with a separation / concentration tank for separating the mixed solution into a permeate and an abrasive concentrate, and the regenerated abrasive slurry preparation step. The unit is provided with a regenerated abrasive slurry storage tank for storing a liquid containing the regenerated abrasive from which the constituent components of the object to be polished have been removed, and has a circulation line for supplying the abrasive slurry between the process units. , It is preferable to provide a control unit for adjusting the supply amount from the viewpoint of improving the recovery / regeneration rate.

As an embodiment of the present invention, from the viewpoint of exhibiting the effect of the present invention, it is preferable to have an abrasive particle size adjusting step section for adjusting the particle size of the abrasive obtained in the separation / concentration step section.

Further, it is preferable that the regenerated abrasive slurry contains a maleic acid-acrylic acid copolymer in the range of 0.04 to 1.5 g / L.

Further, it is preferable that the abrasive contains a metal oxide and the object to be polished contains silicon (Si) because the effects of the present invention can be easily obtained.

In an embodiment of the present invention, it is preferable that the abrasive contains cerium oxide from the viewpoint of polishing rate.

Further, in the separation / concentration process section, it is preferable to use an alkaline earth metal salt as a flocculant of the abrasive, and it is preferable that the alkaline earth metal salt is a magnesium salt from the viewpoint of efficiency of recovery and regeneration of the abrasive. preferable.

Further, in the present invention, the polishing process is continued while controlling the concentrations of the constituent components of the polishing agent and the constituent components of the object to be polished in the polishing agent slurry used for polishing, and the processed abrasive slurry is used as the object to be polished. It is a polishing agent recovery / regeneration method that removes the constituent components of the above and recovers / regenerates the polishing agent.
The concentration of the constituent components of the abrasive in the slurry supply tank for storing the abrasive slurry used for the polishing supplied to the polishing machine is controlled to be equal to or lower than the initial concentration of the constituent components of the abrasive at the start of the polishing process. However, it can be applied to an abrasive recovery / regeneration method having a step of supplying an abrasive slurry to a polishing process section and recovering the processed abrasive slurry.

Further, the concentration of the constituent components of the polishing agent in the slurry supply tank is within the range of 20 to 90%, more preferably 30 to 80, at the end point concentration at the end of the polishing process with respect to the concentration at the start of the polishing process. %, And the concentration of the constituent component of the polishing agent during the polishing process is always equal to or higher than the end point concentration, and further, the change in the concentration of the component component of the polishing agent in the next processing batch with respect to the preprocessing batch. Controlling the fluctuation range within ± 1.0% by mass is preferable in the polishing agent recovery / regeneration method.

Further, it is preferable that the regenerated abrasive slurry is an abrasive recovery / regeneration method containing a maleic acid-acrylic acid copolymer in the range of 0.04 to 1.5 g / L.

Hereinafter, the present invention, its constituent elements, and modes and modes for carrying out the present invention will be described in detail. In the present application, "~" is used to mean that the numerical values described before and after the value are included as the lower limit value and the upper limit value.

Further, in the present invention, the abrasive slurry refers to a slurry that is generically expressed including the following various abrasive slurries according to the polishing process. From the viewpoint of the polishing process, the "initial polishing agent slurry" refers to a processing liquid at the initial stage of polishing, which contains a polishing agent component and water and does not substantially contain a component to be polished. The “abrasive slurry being processed or processed” refers to an abrasive slurry containing an object component to be polished or an abrasive slurry having an end of the abrasive slurry life. The "regenerated abrasive slurry" refers to an abrasive slurry from which the constituent components of the object to be polished have been removed, or an abrasive slurry in which the constituent components of the object to be polished have been removed and then concentrated.

1 << Overview of the basic configuration of the abrasive recycling system >>
The abrasive recycling processing system of the present invention continues the polishing process while controlling the concentrations of the constituent components of the abrasive and the constituent components of the object to be polished in the abrasive slurry used for polishing, and from the processed abrasive slurry, An abrasive recycling processing system that removes the constituents of the object to be polished and collects and regenerates the abrasive, and is used for the polishing process unit for polishing using a polishing machine and the polishing supplied to the polishing machine. It has an abrasive slurry recovery process unit having a slurry supply tank for storing the abrasive slurry, and controls the concentration of the constituent components of the abrasive in the slurry supply tank to be equal to or lower than the initial concentration at the start of the polishing process. At the same time, it is characterized in that the regenerated abrasive slurry is supplied into the slurry supply tank.

The conventional abrasive recycling system aims to keep the abrasive concentration in the abrasive slurry during the polishing process constant. Therefore, as the polishing progressed, the concentration of the object to be polished increased, the viscosity increased and the temperature became locally high, and the recovery rate decreased due to the precipitation of the object to be polished.

For example, in the conventional polishing process section for polishing an object to be polished, the temperature of the abrasive slurry in the polishing process section may rise to about 40 to 60 ° C. due to the polishing process. When glass is used as the object to be polished, when the concentration of silicon oxide increases due to the polishing process, the viscosity of the abrasive slurry during processing increases and adheres to the processed portion. Further, since the temperature of the polished portion rises due to the processing, the precipitation and solidification of silicon oxide are accelerated. The abrasive component adhering to the polished portion by polishing is washed with washing water and recovered as a rinse slurry containing the abrasive component.

Some of the precipitated solids of silicon oxide are recovered as a rinse slurry, and some remain in the polished portion. Residues in the polished portion are also present inside and outside the polishing pad and affect the processing quality.

Therefore, the frequency of replacement of the polishing pad is increased, so that the number of polishing processes is reduced. Further, in order to reuse and recycle the rinse slurry, it is necessary to remove the precipitated solid substance of silicon oxide which is a foreign substance. Incorporating a process for removing precipitated solids of silicon oxide reduces the abrasive recovery rate.

Further, in the slurry supply tank, the initial abrasive slurry prepared in advance is repeatedly circulated between the slurry supply tank and the polishing machine while being replenished with the regenerated abrasive slurry. By polishing, the silicon component of the object to be polished is in a state of being dissolved in the abrasive slurry. When the silicon concentration in the abrasive slurry increases, silicon oxide precipitates and solidifies, becoming foreign matter in the abrasive slurry. Since the above foreign matter causes defects such as scratches, the abrasive slurry cannot be used. In order to reuse the processed abrasive slurry, it is necessary to remove the precipitated solid of silicon oxide as a foreign substance. Incorporating a process for removing precipitated solids of silicon oxide reduces the abrasive recovery rate.

In response to this problem, in the present invention, the concentration of the constituent components of the abrasive contained in the abrasive slurry during processing is controlled to be equal to or lower than the initial concentration of the abrasive at the start of the polishing process, and is regenerated. This can be solved by supplying the abrasive slurry to the polishing machine.

1A and 1B are conceptual diagrams showing the relationship between the polishing time, the concentration of the abrasive in the abrasive slurry during processing, and the concentration of the constituent components of the object to be polished. FIG. 1A shows the abrasive concentration in the abrasive slurry with respect to the polishing time. In the conventional polishing process, the abrasive concentration was kept constant as shown by the dotted line even as the polishing progressed. Therefore, as shown in the relationship between the polishing process time and the concentration of the constituent components of the object to be polished in FIG. 1B, the concentration of the components of the object to be polished in the abrasive slurry increases as the polishing process time advances. Then, when this concentration reached a, precipitation of the object to be polished occurred, and the abrasive slurry could not be used.

On the other hand, in the present invention, as shown by the solid line in FIG. 1A, the concentration of the abrasive in the abrasive slurry is kept below the concentration at the initial stage of the polishing process with the progress of the polishing process time. As a result, an increase in the concentration of the constituent components of the object to be polished in the abrasive slurry can be suppressed as shown by the solid line in FIG. 1B, and the life of the abrasive slurry can be extended. Further, since the viscosity of the abrasive slurry is unlikely to increase, the recovery rate of the abrasive can be increased.

2 << Configuration example of the embodiment of the abrasive recycling treatment system >>
The polishing agent recycling processing system of the present invention includes at least a polishing processing process unit for polishing using a polishing machine and a polishing agent slurry recovery process unit having a slurry supply tank for storing the polishing agent slurry supplied to the polishing processing process unit. Have. It is preferable that the abrasive slurry recovery process unit further has a recovery mixed liquid tank for storing the mixed liquid of the processed abrasive slurry and the washing water.

Further, a separation / concentration process section for separating the abrasive from the processed abrasive slurry, an abrasive particle size adjustment process section for adjusting the particle size of the collected processed abrasive particles, and a regeneration process for storing the regenerated abrasive slurry. It is preferable to have an abrasive slurry preparation process unit.

Further, in the polishing agent recovery / regeneration method of the present invention, the polishing process is continued while controlling the concentrations of the components of the polishing agent and the components of the object to be polished in the polishing agent slurry used for polishing, and the processed polishing agent is processed. A polishing agent recovery / regeneration method in which the constituent components of the object to be polished are removed from the slurry and the polishing agent is recovered / regenerated.
The concentration of the constituent components of the abrasive in the slurry supply tank for storing the abrasive slurry used for the polishing supplied to the polishing machine is controlled to be equal to or lower than the initial concentration of the constituent components of the abrasive at the start of the polishing process. At the same time, it is characterized by having a step of supplying the abrasive slurry to the polishing process section and collecting the processed abrasive slurry.

The abrasive recovery / regeneration method of the present invention is performed in addition to a polishing process of polishing using a polishing machine, an abrasive slurry recovery step of having a slurry supply tank for storing the abrasive slurry supplied to the polishing process section, and processing. Separation / concentration step to separate the abrasive from the finished abrasive slurry, abrasive particle size adjustment step to adjust the particle size of the recovered processed abrasive particles, and reclaimed abrasive slurry preparation step to store the regenerated abrasive slurry. It is preferable to have.

FIG. 2 is a schematic view showing an example of the abrasive recycling processing system of the present invention. The abrasive recycling processing system shown in FIG. 2 includes an abrasive processing process unit 1, an abrasive slurry recovery process unit 2, a separation / concentration process unit 3, an abrasive particle size adjusting process unit 4, and a regenerated abrasive slurry preparation process unit 5. It is shown. Hereinafter, each process section will be described in detail in sequence.

(1) Polishing process section In the polishing process section 1, the polishing machine 12 has a polishing surface plate to which a polishing cloth composed of a non-woven fabric, a synthetic resin foam, a synthetic leather, etc. is attached. The board is rotatable. At the time of polishing work, the polishing platen is rotated while pressing the object to be polished (for example, optical glass or the like) against the polishing surface plate with a predetermined pressing force N using a holder. Further, the cleaning water for cleaning the polishing machine 12 is stored in the cleaning water tank 11, and is sprayed onto the polishing portion from the cleaning water injection nozzle for cleaning. The polishing process is a process performed by the polishing process unit 1.

(Abrasive)
_{Generally, fine particles such as red iron oxide (αFe 2} O ₃ ), cerium oxide, aluminum oxide, manganese oxide, zirconium oxide, and colloidal silica are dispersed in water or oil as constituent components of an abrasive such as optical glass or a semiconductor substrate. A slurry is used, but as the polishing agent recovery / regeneration method of the present invention, in the polishing process of the surface of a semiconductor substrate or glass, a sufficient processing speed can be achieved while maintaining high accuracy and flatness. Diamond, boron nitride, silicon carbide, alumina, alumina zirconia, zirconium oxide and cerium oxide applicable to chemical mechanical polishing (CMP), which is polished by both physical and chemical action to obtain It is preferable to apply it to the recovery of at least one selected from.

Examples of the constituent components of the abrasive according to the present invention include synthetic diamond (for example, manufactured by Nippon Microcoating Co., Ltd.) and natural diamond as the diamond type, and for example, cubic boron nitride BN as the boron nitride type. (For example, manufactured by Showa Denko KK). Boron nitride type has the hardness next to diamond. Examples of the silicon carbide system include silicon carbide, green silicon carbide, and black silicon carbide (for example, manufactured by Mipox). Further, as the alumina type, in addition to alumina, brown alumina, white alumina, pink alumina, crushed alumina, alumina zirconia type (for example, manufactured by Coralvan Co., Ltd.) and the like can be mentioned. Examples of zirconium oxide include BR series zirconium oxide for abrasives manufactured by Daiichi Rare Element Chemical Industry Co., Ltd. and zirconium oxide manufactured by HZ of China.

In addition, cerium oxide (for example, manufactured by CI Kasei Co., Ltd., Technorise Co., Ltd., Wako Junyaku Co., Ltd., etc.) is used after firing an ore containing a large amount of rare earth elements called bastnäsite rather than pure cerium oxide. , Crushed ones are often used. Although cerium oxide is the main component, it contains rare earth elements such as lanthanum, neodymium, and praseodymium as other components, and may contain fluoride and the like in addition to oxides.

The abrasive used in the present invention is highly effective and preferable when the content of the constituent components of the above-mentioned abrasive is 50% by mass or more. It is more preferably in the range of 95 to 100% by mass, and even more preferably 100% by mass.

Using an abrasive, it can be polished by the polishing machine 12 of the polishing process unit 1 as shown in FIG. The present invention is an abrasive recycling processing system that regenerates an abrasive by using the processed abrasive slurry used in the polishing process unit 1 as a regenerated abrasive slurry.

Taking the polishing of a glass substrate as an example, the polishing process unit 1 constitutes one polishing process unit by polishing and cleaning the polishing unit.

(1-1) Polishing The polishing pad (polishing cloth) and the object to be polished (for example, a glass substrate) are brought into contact with each other, and while the abrasive slurry is supplied to the contact surface, the pad and the glass substrate are relative to each other under pressurized conditions. Exercise.

The polishing pad can be subjected to pad dressing or pad brushing after continuous polishing. Pad dressing is a process of keeping the pad state constant by roughening the surface while physically scraping the pad. On the other hand, pad brushing is a process performed to remove polishing debris and the like contained in the unevenness of the pad without scraping the pad.

Further, polishing may be performed using a plurality of polishing machines in one batch of processing. In such a case, the change width of the processing time per batch of the next batch with respect to the previous batch is preferably within 10%. Within this range, it is possible to suppress variations in polishing processing time among a plurality of polishing machines. Here, one batch means one polishing processing unit, and for example, six glass substrates can be polished in one batch.

In the present invention, the concentration of the abrasive in the slurry supply tank 21 is adjusted for each batch from the viewpoint that the change in the concentration of the constituent components of the abrasive in the abrasive slurry of the next processing batch with respect to the preprocessing batch can be reduced. It is preferable to do this.

(1-2) Cleaning A large amount of abrasive is attached to the glass substrate immediately after polishing and the polishing machine. Therefore, after polishing, water or the like is supplied from the cleaning water tank 11 instead of the abrasive slurry to clean the glass substrate and the abrasive adhering to the polishing machine.

In this cleaning operation, a certain amount of abrasive is discharged to the outside of the system, so that the amount of abrasive in the system is reduced. In order to make up for this decrease, a new reclaimed abrasive slurry is added to the slurry supply tank 21 from the regenerated abrasive slurry storage tank 51. As an additional method, the addition may be made for each batch or several batches, but it is desirable to supply the abrasive in a state of being sufficiently dispersed with respect to the solvent.

(2) Abrasive Slurry Recovery Process Unit The abrasive slurry recovery process unit has a slurry supply tank 21 for storing the abrasive slurry used for polishing, and the polishing machine 12 and cleaning are performed in the abrasive slurry recovery process unit. The processed abrasive slurry discharged from the system consisting of the water tank 11 is collected.

The abrasive slurry recovery process unit 2 preferably has a recovery mixture tank 22 in addition to the slurry supply tank 21. In the slurry supply tank 21, the processed abrasive slurry discharged from the polishing machine, the regenerated abrasive slurry supplied from the regenerated abrasive slurry storage tank 51, and water are used, and the initial polishing agent is used at the start of the polishing process. It is controlled below the concentration. Then, the abrasive slurry in the slurry supply tank 21 is supplied to the polishing machine 12 via a pump.

The processed abrasive slurry in the present invention means an abrasive slurry discharged to the outside of the system of the polishing process unit 1 composed of the polishing machine 12 and the washing water tank 11.

The processed abrasive slurry to be recovered includes two types, an abrasive slurry 1 containing the washing water and an abrasive slurry 2 containing the processed abrasive. The recovered abrasive slurry contains an abrasive in the range of approximately 0.1 to 40% by mass.

Each abrasive slurry may be transferred to a separation step immediately after being recovered, or may be stored until a certain amount is recovered. In either case, the recovered abrasive slurry is constantly stirred. , It is preferable to prevent agglomeration and sedimentation of particles and maintain a stable dispersed state.

In the present invention, the abrasive slurry 1 and the abrasive slurry 2 recovered in the abrasive slurry recovery step 2 are mixed and prepared as a mother liquor in the recovery mixture tank 22, and then processed in the subsequent separation / concentration step 3. The method of

In the present invention, the regenerated abrasive slurry is supplied to the slurry supply tank 21 while controlling the concentration of the constituent components of the abrasive in the slurry supply tank 21 to be equal to or lower than the initial concentration at the start of the polishing process.

(Adjustment of abrasive slurry concentration)
The concentration can be adjusted by controlling the flow rate of water, the regenerated abrasive slurry, and the processed abrasive slurry discharged from the polishing process, which are charged into the slurry supply tank 21, through a pipe. it can. The supply to the polishing machine 12 is performed from the slurry supply tank 21 by a pump (not shown) provided in the piping of the polishing machine 12. The control unit has a flow meter and a pump, and the flow rate is controlled by a circulation line for supplying the abrasive slurry between the process units and a pipe for supplying other additives and the like.

In the present invention, the end point concentration of the constituent components of the abrasive in the slurry supply tank at the end of the polishing process is 20 to 90% of the concentration of the constituent components of the abrasive in the slurry supply tank at the start of the polishing process. It is preferably in the range of, more preferably in the range of 30 to 80%.

By lowering the abrasive concentration in this way, it is possible to suppress the temperature rise and viscosity rise of the abrasive slurry, prevent the precipitation of silicon oxide, prevent scratches on the object to be polished, and improve the recovery rate. ..

If the end point concentration of the constituent components of the abrasive in the slurry supply tank at the end of the polishing process is 20% or more of the initial concentration of the polishing process, the effect of reduction of the polishing lubricant etc. is small and the polishing speed is also high. It does not decrease significantly. Further, if it is 90% or less, the recovery rate can be increased, which is preferable.

Further, since a certain amount of abrasive is discharged to the outside of the system during the cleaning operation, the abrasive concentration in the slurry supply tank 21 fluctuates when a new regenerated abrasive slurry is added. The fluctuation range of the abrasive concentration in the abrasive supply tank 21 controls the fluctuation range of the concentration change of the abrasive components in the abrasive slurry of the next processing batch with respect to the preprocessing batch within ± 1.0% by mass. It is preferable that the concentration of the abrasive does not exceed the concentration of the abrasive at the start of the polishing process.

The abrasive concentration in the slurry supply tank 21 can be measured using, for example, a UCUF-04K small-diameter ultrasonic flowmeter detector (manufactured by Tokyo Instrumentation Co., Ltd.). Specifically, a calibration curve of the abrasive concentration and the flow rate is prepared, and the target abrasive concentration is measured by measuring the flow rate of the abrasive slurry in the slurry supply tank 21, and the regenerated abrasive slurry storage tank. It feeds back to the control unit of 51.

The measurement of the above-mentioned UCUF-04K small-diameter ultrasonic flowmeter detector (manufactured by Tokyo Keiso Co., Ltd.) shall be carried out under the conditions that the temperature of the target abrasive slurry is 30 ° C. and the flow rate pressure is 0.2 MPa. Can be done. The measurement of the abrasive slurry concentration in the slurry supply tank 21 may be carried out online, or the abrasive slurry may be sampled and measured as appropriate.

In order to start polishing first, when preparing the abrasive solution at the start of polishing in the slurry supply tank 21, for example, the concentration range of the abrasive powder with respect to a solvent such as water is 1 to 40% by mass. The initial abrasive slurry can be prepared by adding and dispersing so as to be. This initial abrasive slurry is stored in the slurry supply tank shown in FIG. 2 and circulated and supplied to the polishing machine for use. As the fine particles used as an abrasive, it is preferable that particles having an average particle diameter of several tens of nm to several μm are used.

It is preferable to prevent the abrasive particles from aggregating by adding a dispersant or the like, and to maintain the dispersed state by constantly stirring with a stirrer or the like. Generally, a tank for abrasive slurry is installed next to the grinding machine, a stirrer or the like is used to maintain a dispersed state at all times, and a supply pump is used to circulate and supply the abrasive to the grinding machine. Is preferable.

(3) Separation / Concentration Process Unit Next, in the separation / concentration process unit 3, only the abrasive is separated and concentrated with respect to the mixed solution of the processed abrasive slurry and the cleaning water recovered in the slurry recovery process unit.

The separation / concentration step 3 in the present invention separates the abrasive from the mother liquor and concentrates it. A known method may be used as the method for separating and concentrating, but in particular, an alkaline earth metal salt is added as an inorganic salt to the abrasive slurry recovered in the abrasive slurry recovery step 2, and the polishing agent is used. It is preferable that the abrasive is separated from the mother liquor and concentrated in a state where only the abrasive is aggregated and the component to be polished is not aggregated. As a result, after coagulating and precipitating only the abrasive component, the glass component is mostly present in the supernatant to separate the agglomerates, thereby separating the abrasive component and the glass component and concentrating the abrasive slurry at the same time. be able to.

A known method can be used as the method for separating and concentrating. A membrane separation method or a sedimentation method can be adopted.

(3-1) Separation step For separation, an alkaline earth metal salt is added as an inorganic salt as described above, only the abrasive is aggregated, and the abrasive is used as a mother liquor in a state where the component to be polished is not aggregated. It is preferable to separate them more.

In the solid-liquid separation operation, solid-liquid separation by natural sedimentation may be performed without applying the forced separation means. In this way, the mother liquor is separated into a supernatant liquid containing an object to be polished and a concentrate containing a recovered abrasive precipitated at the bottom, and then a decantation method, for example, tilting the kettle to drain the supernatant liquid. The liquid or the drainage hype is inserted close to the interface between the supernatant liquid and the concentrate in the separated kettle, and only the supernatant liquid is discharged to the outside of the kettle to recover the abrasive.

The recovered processed abrasive slurry is in a state in which glass components and the like derived from the object to be polished are mixed. In addition, the concentration has decreased due to the mixing of cleaning water, and in order to reuse the recovered abrasive for polishing, it is necessary to separate the glass component, etc., which is the object to be polished, and concentrate the abrasive. is there.

(Alkaline earth metal salt)
In the present invention, it is preferable that the inorganic salt used for agglutinating the abrasive is an alkaline earth metal salt.

Examples of the alkaline earth metal salt according to the present invention include calcium salt, strontium salt, and barium salt, but in the present invention, elements belonging to Group 2 of the periodic table are also broadly defined. , Defined as an alkaline earth metal. Therefore, beryllium salt and magnesium salt also belong to the alkaline earth metal salt referred to in the present invention.

Further, the alkaline earth metal salt according to the present invention is preferably in the form of a halide, a sulfate, a carbonate, an acetate or the like.

The inorganic salt according to the present invention is preferably an alkaline earth metal salt, and more preferably a magnesium salt.

The magnesium salt applicable to the present invention is not limited as long as it functions as an electrolyte, but magnesium chloride, magnesium bromide, magnesium iodide, magnesium sulfate, etc. Magnesium chloride and the like are preferable, and magnesium chloride and magnesium sulfate are particularly preferable because the pH change of the solution is small and the precipitated polishing agent and waste liquid can be easily treated.

(Method of adding inorganic salt)
Next, a method for adding the inorganic salt according to the present invention to the abrasive slurry (mother solution) will be described.

a) Concentration of inorganic salt The inorganic salt to be added may be directly supplied to the abrasive slurry (mother solution), or may be dissolved in a solvent such as water and then added to the abrasive slurry (mother solution). Although it is preferable, it is preferable to add it in a state of being dissolved in a solvent so that it becomes a uniform state after being added to the abrasive slurry.

The preferred concentration of the inorganic salt is an aqueous solution in the concentration range of 0.5 to 50% by mass. In order to suppress the pH fluctuation of the system and improve the efficiency of separation from the glass component, the concentration range is more preferably in the range of 10 to 40% by mass.

b) Temperature at which the inorganic salt is added The temperature at which the inorganic salt is added can be appropriately selected as long as it is at least the temperature at which the recovered abrasive slurry freezes and is within the range of 90 ° C. From the viewpoint of efficient separation, the temperature is preferably in the range of 10 to 40 ° C, more preferably in the range of 15 to 35 ° C.

c) Addition rate of inorganic salt The addition rate of the inorganic salt to the abrasive slurry (mother solution) is the concentration of the inorganic salt in the recovered abrasive slurry, which is uniform without locally generating a high concentration region. It is preferable to add as such. The amount added per minute is preferably 20% by mass or less, and more preferably 10% by mass or less of the total amount added.

d) pH value when adding an inorganic salt In the abrasive recovery / regeneration method of the present invention, the pH value of the abrasive slurry recovered in advance should not be adjusted when the inorganic salt is added in the separation / concentration step 3. This is a preferred embodiment. Generally, the pH value of the recovered abrasive slurry is slightly alkaline because it contains a glass component, and is in the range of less than 8 to 10, and it is not necessary to adjust the pH value of the recovered abrasive slurry in advance. Therefore, in the present invention, it is preferable to perform separation and concentration under the condition that the pH value of the mother liquor in terms of 25 ° C. is less than 10.0.

In the present invention, the pH value can be measured at 25 ° C. using a Lacom tester desktop pH meter (pH 1500 manufactured by AS ONE Corporation).

In the present invention, it is preferable to add the inorganic salt and then maintain the pH value at the time of adding the inorganic salt or less until the concentrate is separated. The pH value at the time of adding the inorganic salt here means the pH value immediately after the addition of the inorganic salt is completed.

The pH value at the time of adding the inorganic salt is maintained or lower until the precipitated agglomerates are separated. Preferably, the pH value converted to 25 ° C. is maintained at less than 10. By setting the pH value to less than 10, it is possible to prevent the glass components contained in the waste liquid from agglutinating, so that the purity of cerium oxide at the time of recovery can be increased, which is preferable.

The lower limit of the pH value when the inorganic salt is added is preferably 6.5 or more because of the decrease in purity due to the pH adjuster and operability.

e) Stirring after adding the inorganic salt After adding the inorganic salt, it is preferable to continue stirring for at least 10 minutes, more preferably 30 minutes or more. Aggregation of the abrasive particles is started at the same time as the addition of the inorganic salt, but by maintaining the agitated state, the agglomerated state becomes uniform throughout the system, the particle size distribution of the concentrate becomes narrow, and the subsequent separation becomes easy.

In the separation / concentration step 3, the supernatant is separated into a supernatant containing a glass component and a concentrate containing the recovered abrasive particles, and then the concentrate is recovered.

(3-2) Concentration Step In the present invention, from the viewpoint of obtaining a high-purity reclaimed abrasive without mixing impurities (for example, polished glass coarse particles, etc.) into the concentrate that settles in the lower part as much as possible, As the primary concentration method, it is preferable to apply natural sedimentation.

Due to the addition of the inorganic salt, the recovered abrasive particles are aggregated and separated from the supernatant in this state. Therefore, the concentrated product has a higher specific gravity than the recovered slurry and is concentrated. This concentrate contains a recovered abrasive at a concentration higher than that of the recovered slurry.

As an example of the method of separating the agglomerated abrasive concentrate and the supernatant liquid, after separating into the supernatant liquid containing the object to be polished and the like and the concentrate containing the recovered abrasive precipitated in the lower part by natural sedimentation. , The concentrate can be inserted close to the interface between the supernatant and the concentrate, and only the supernatant can be discharged to the outside of the kettle using a pump to recover the concentrate containing the abrasive.

(4) Regeneration of Abrasive (4-1) Abrasive Particle Size Adjusting Process Unit The abrasive particle size adjusting process unit 4 redistributes the agglomerated abrasive to obtain a desired particle size distribution. For example, the particle size distribution level is adjusted to be close to that of an unused (before polishing) abrasive. In the present invention, it is preferable to apply the particle size control treatment of the abrasive particles to the concentrated / separated abrasive slurry.

In the abrasive slurry concentrated and separated by the above method, since the abrasive particles form aggregates (secondary particles) via inorganic salts, water and a dispersant are used to disperse the particles to a state close to independent primary particles. And disperse to the desired particle size using a disperser.

Examples of the method of redispersing the agglomerated abrasive particles include a) a method of adding water to reduce the concentration of inorganic ions having an aggregating effect on the abrasive in the treatment liquid, and b) a dispersant (also known as a metal separating agent). A method of reducing the concentration of metal ions adhering to the abrasive by adding) c) and a method of forcibly defibrating the agglomerated abrasive particles using a disperser or the like can be mentioned.

These methods may be used individually or in combination, but at least a method of combining b) is preferable, and a method of combining all of a), b) and c) is more preferable. ..

When water is added, the amount to be added is appropriately selected depending on the volume of the concentrated abrasive slurry, and is generally 5 to 50% by volume, preferably 10 to 40% by volume of the concentrated slurry.

(Dispersant)
As the dispersant, a known dispersant can be used. The amount added can be in the range of 0.01 to 5.0 g / L with respect to the recycled abrasive slurry.

In the present invention, a polycarboxylic acid-based polymer dispersant having a carboxy group is preferably mentioned, and in particular, a copolymer of acrylic acid-maleic acid is preferable.

When the polishing process of the glass substrate is continued, the pH of the abrasive slurry being processed increases with the dissolution of the object to be polished such as polysilicic acid, and the pH shifts to the alkaline side. Shifting to the alkaline side tends to cause defects such as discoloration on the surface of the object to be polished (a phenomenon in which the appearance of glass gradually becomes white and cloudy). If an acid is added to adjust the pH in order to prevent this defect, the dissolved polysilicic acid tends to solidify, which may cause a decrease in the non-defective rate of the object to be polished.

Such a phenomenon can be alleviated by using a copolymer of acrylic acid-maleic acid as a dispersant. In addition to its function as a dispersant, the equilibrium state of hydrolysis of maleic acid acts as a buffer against pH fluctuations of the abrasive slurry during processing, and the dissolved polysilicic acid is stably dissolved without solidifying. It is thought that this is because it is possible to maintain.

The maleic acid-acrylic acid copolymer has a buffering effect against pH fluctuations and is useful as an additive having a dispersing function, and is not only used as a dispersant in the abrasive particle size adjusting step 4 but also added. As an agent, it may be separately added to the slurry supply tank 21 or the recycled abrasive storage tank 51.

From the viewpoint of keeping the pH value in the slurry supply tank 21 stable, the reclaimed abrasive slurry in the reclaimed abrasive storage tank 51 in the regenerated abrasive containing liquid preparation process unit 5 contains 0 maleic acid-acrylic acid copolymers. It is preferably contained in the range of .04 to 1.50 g / L.

<Acrylic acid-maleic acid copolymer>
As an additive having a dispersing function, the water solubility of a copolymer in which the molar ratio of (a) acrylic acid to (b) (maleic anhydride) maleic acid is (a) / (b) = 50/50 to 95/5. A copolymer of acrylic acid-maleic acid, which is composed of a salt and has a molecular weight distribution (Mw / Mn) of 3.5 to 10 is preferable.

The molecular weight distribution (Mw / Mn) of the copolymer is preferably 3.5 to 7. The number average molecular weight of the copolymer is in the range of 1000 to 20000, preferably 1000 to 10000. If necessary, other copolymerization monomers may be copolymerized.

As the polymerization initiator, it is preferable to use a persulfate such as ammonium persulfate, potassium persulfate, and sodium persulfate in combination with a reducing agent such as phosphorous acid, hypophosphorous acid, or a salt thereof. Is particularly preferable as sodium hypophosphite. Both the persulfate and the reducing agent are preferably used in an amount of 1 to 6 mol% based on the monomer, and the total amount of the persulfate and the reducing agent is preferably less than 10 mol% based on the monomer. A specific synthesis method is described in JP-A-7-316999 and the like.

Specific examples of the acrylic acid-maleic acid copolymer include Polyty A-550 (manufactured by Lion Corporation) and Mighty 21HP (manufactured by Kao Corporation). Acrylic acid-maleic acid copolymer and a known dispersant can also be used in combination.

Further, as the disperser, a medium stirring type mill such as an ultrasonic disperser, a sand mill or a bead mill can be applied, and it is particularly preferable to use an ultrasonic disperser.

As the ultrasonic disperser, for example, various devices are commercially available from SMT Co., Ltd., Ginsen Co., Ltd., Titec Co., Ltd., BRANSON Co., Ltd., Kinematica Co., Ltd., Nissei Tokyo Office Co., Ltd., etc. ) SMT UDU-1, UH-600MC, Ginsen GSD600CVP, Nissei Tokyo Office RUS-600TCVP, etc. can be used. The frequency of the ultrasonic wave is not particularly limited.

As a circulation type device that performs mechanical stirring and ultrasonic dispersion in parallel, SMT UDU-1, UH-600MC, Ginsen GSD600RCVP, GSD1200RCVP, Nissei Tokyo Office RUS600-TCVP, etc. However, the present invention is not limited to these.

For example, after adding water to store an abrasive dispersion having a reduced inorganic salt concentration, a dispersant (for example, a polymer dispersant) is added from an addition container while stirring with a stirrer. , The ultrasonic disperser 44 performs a dispersion treatment with a pump to loosen the agglomerated abrasive particles. Next, the particle size distribution of the abrasive particles after dispersion can be monitored by a particle size measuring machine 45 provided on the downstream side thereof, and the particle size distribution of the abrasive dispersion liquid can be made into a desired particle size distribution profile. ..

As the particle size distribution obtained in this step, it is desirable that the particle size distribution does not fluctuate with time and the average particle size fluctuates after one day.

(4-2) Regenerative Abrasive Slurry Preparation Process Unit In the regenerative abrasive slurry preparation process unit 5, the necessary additives are added in this way to bring the regenerated abrasive slurry to a predetermined concentration, and the regenerated abrasive slurry storage tank 51 Store in.

In the present invention, the final reclaimed abrasive slurry obtained in the reclaimed abrasive slurry preparation step 5 contains a high-purity abrasive of 98% by mass or more, and the particle size distribution does not fluctuate with time and is recovered. The content of the inorganic salt is preferably in the range of 0.0005 to 0.08% by mass, which is higher than the concentration of.

As described above, a high-quality and high-purity reclaimed abrasive can be obtained as a reclaimed abrasive slurry by a simple method.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. Although the display of "%" is used in the examples, it represents "mass%" unless otherwise specified.

Example 1
<< Preparation of regenerated abrasive >>
First, a regenerated abrasive slurry was prepared using the abrasive recycling treatment system shown in FIG.

1) Abrasive slurry recovery process part 2
After polishing the glass substrate in the polishing process unit 1 shown in FIG. 2, 210 liters of the abrasive slurry 1 containing cleaning water is added to the recovery mixture tank 22, and the polishing has been processed from the slurry supply tank 21. 30 liters of the abrasive slurry 2 containing the agent was recovered, and 240 liters was used as the recovered slurry liquid. This recovered slurry liquid in the recovered mixed liquid tank 22 has a specific gravity of 1.03 and contains 8.5 kg of cerium oxide.

2) Separation / concentration process section 3
Next, the recovered slurry liquid is transferred to the separation / concentration tank 32, the liquid temperature of the recovered slurry liquid is controlled within the range of 20 ± 1 ° C., and 10% by mass of magnesium chloride is stirred while stirring so that cerium oxide does not settle. 2.5 liters of aqueous solution was added over 10 minutes. Immediately after the addition of magnesium chloride, the pH value at 25 ° C. was 8.60, and this condition was maintained.

After continuing stirring for 30 minutes in the above state, the mixture was allowed to stand for 1.5 hours, and the supernatant liquid and agglomerates were settled and separated by a natural sedimentation method. After 1.5 hours, the supernatant was discharged using a drainage pump, and the agglomerates were separated and recovered. The collected agglomerates were 60 liters.

3) Abrasive particle size adjustment process part 4
The separated agglomerates were transferred to the abrasive separation liquid storage tank 42, and 22.5 liters of water was added. Further, 300 g of Polyty A-550 (manufactured by Lion Co., Ltd.), which is an additive having a dispersing function as a dispersant, is added, stirred for 30 minutes, filtered through a 10 micron membrane filter 43, and further ultrasonically dispersed. Using the machine 44, the agglomerates were dispersed and loosened to obtain a regenerated abrasive containing an abrasive having a predetermined particle size.

4) Regenerated abrasive slurry preparation process part 5
The regenerated abrasive was transferred to the regenerated abrasive slurry storage tank 51, and the concentration was adjusted to obtain 80 liters of the regenerated abrasive slurry containing regenerated cerium oxide. The cerium oxide concentration was 10% by mass, the particle size (D90 <2.0 μm), and the magnesium content was 0.01% by mass. The concentration of Polyty A-550, which is an additive having a dispersing function, in the reclaimed abrasive slurry was 0.50 g / L with respect to the reclaimed abrasive slurry.

[Abrasive Recycling System 1]
The slurry supply tank 21 was filled with a regenerated abrasive slurry containing cerium oxide having an initial concentration of 10.0% by mass, and the glass substrate was subjected to 200 batch polishing in the polishing process section as follows. The abrasive slurry recovery process unit 2 cleans and removes the abrasive slurry remaining in the polishing process unit with cleaning water each time the glass substrate is polished. The abrasive slurry 1 containing the washing water was recovered in the recovery mixed liquid tank 22. Further, after the completion of 200 batch processing, the processed abrasive slurry was recovered from the abrasive slurry supply tank 21 into the recovery mixed liquid tank 22. Then, in the separation / concentration step 3, the abrasive particle size adjusting step 4, and the reclaimed abrasive slurry preparation step 5, the reclaimed abrasive was prepared as a reclaimed abrasive slurry in the same manner as in the above-mentioned preparation of the reclaimed abrasive. ..

[Polishing process section]
During polishing, the concentration of the polishing agent in the slurry supply tank 21 for storing the polishing agent slurry used for polishing is controlled to be equal to or less than the initial concentration (10.0% by mass) at the start of the polishing process, and polishing is performed. One batch (one processing) while controlling the concentration of cerium oxide in the slurry supply tank 21 so that the concentration in the slurry supply tank at the end of the processing process is 50% (5.0% by mass) of the initial concentration. After each process, a reclaimed abrasive slurry and, if necessary, water were supplied into the slurry supply tank.

Specifically, first, the slurry supply tank 21 was replenished with a regenerated abrasive slurry containing an abrasive having an initial concentration of 10.0% by mass. Next, polishing is performed, and after each batch of polishing, the abrasive slurry 2 containing the processed abrasive is returned to the slurry supply tank 21, and the polishing machine is washed with water so as to have a predetermined thickness. The polishing process of 200 batches was repeated.

At this time, the concentration of the abrasive (cerium oxide) in the abrasive slurry supply tank 21 is 10.0% by mass or less at the initial concentration, and the concentration of the abrasive in the abrasive slurry supply tank 21 at the end of the polishing process is the initial concentration. In the slurry supply tank 21 so as to be 50% (5% by mass) and within ± 1.0% by mass of the fluctuation range of the change in the concentration of the abrasive in the abrasive slurry of the next processing batch with respect to the preprocessing batch. While controlling the concentration of cerium oxide in the above, each time one batch (one processing) of processing was completed, a regenerated abrasive slurry and, if necessary, water were supplied into the slurry supply tank.

[Abrasive slurry being processed and processed]
After polishing the glass substrate, the abrasive slurry remaining in the polishing process part is washed and removed with washing water. The abrasive slurry 1 containing the washing water was recovered in the recovery mixed liquid tank 22. Further, after the completion of 200 batch processing, the processed abrasive slurry was recovered from the abrasive slurry supply tank 21 into the recovery mixed liquid tank 22.

The concentration of the abrasive in the slurry supply tank 21 supplied to the polishing machine 12 during polishing is determined by using a UCUF-04K small-diameter ultrasonic flowmeter detector (manufactured by Tokyo Instrumentation Co., Ltd.) under the following usage conditions. It was measured.

terms of use:
Slurry temperature: 30 ° C
Slurry fluid pressure: 0.2 MPa
Detection of cerium oxide concentration: The abrasive slurry for which the cerium oxide content and the silicon oxide content are known was measured, and a calibration curve was created so that the cerium oxide content could be grasped.

《Evaluation》
The abrasive recycling treatment system was evaluated based on four items: the recovery rate of the abrasive after polishing, the non-defective rate of the glass substrate, the life of the polishing pad, and the range of change in the polishing time between batches. The life of the polishing pad was evaluated by continuing polishing after 200 batches of polishing were completed.

[Abrasive recovery rate]
The recovery rate was calculated by the following formula and evaluated according to the following evaluation criteria. The recovery rate needs to be at least 50% or more.

Recovery rate = (total mass of abrasive recovered from processed abrasive slurry after 200 batch polishing and abrasive slurry contained in washing water / mass of abrasive used for polishing) × 100 (%)
⊚: Recovery rate 90% or more ○: Recovery rate 70% or more and less than 90% Δ: Recovery rate 50% or more and less than 70% ×: Recovery rate less than 50% [Good product rate of glass substrate]
The glass substrate was visually observed, and those with no scratches were evaluated as non-defective products according to the following evaluation criteria. Evaluation rank △ or higher was regarded as acceptable.

⊚: Non-defective rate 80% or more ○: Non-defective rate 60% or more and less than 80% Δ: Non-defective rate 50% or more and less than 60% ×: Non-defective rate less than 50% [Life of polishing pad]
The polishing pad was removed and SEM (scanning electron microscope) photo observation was performed. When silicon oxide is deposited during polishing, silicon oxide is deposited on the foamed portion of the polishing pad and is observed white by SEM observation. For example, in FIG. 3A, no precipitation is observed, but in FIG. 3B, white silicon oxide precipitation is observed so as to fill the foamed portion of the polishing pad. It was evaluated by the method of removing the precipitate remaining on the polishing pad in 200 processing batches and the degree of recovery of the surface physical properties of the polishing pad. Evaluation rank △ or higher was regarded as acceptable.

⊚: Brushing the polishing pad restores the physical characteristics of the surface of the polishing pad. Precipitation was observed when the number of processing was 300 batches or more. (Precipitates can be removed without shaving the polishing pad.)
○ Brushing the polishing pad restores the physical characteristics of the surface of the polishing pad. Precipitation was observed after 250 batches or more of processing. (Precipitates can be removed without shaving the polishing pad.)
Δ: Dressing the polishing pad restores the physical characteristics of the surface of the polishing pad, but brushing does not. (The polishing pad is machined to remove the precipitate.)
X: The physical characteristics of the surface of the polishing pad are not restored even if the polishing pad is dressed. (A large amount of polishing pad is machined to remove precipitates, and the physical properties of the polishing pad surface change significantly.)
[Change range of processing time]
The change width of the processing time per batch of the next batch with respect to the previous batch was measured, and the maximum change width of the processing time per batch of the next batch with respect to the previous batch was evaluated when 200 batch polishing processing was performed. Evaluation rank △ or higher was regarded as acceptable.

⊚: Change width of machining time per batch of next batch with respect to previous batch is less than ± 5% ○: Change width of machining time per batch of next batch with respect to previous batch is ± 5% or more, less than ± 10% △: Previous The change width of the processing time per batch of the next batch with respect to the batch is ± 10% or more and less than ± 15% ×: The change width of the processing time per batch of the next batch with respect to the previous batch is ± 15% or more [Abrasive Recycling System 2 ~ 5 and 7 ~ 13]
In the abrasive recycling system 1, the abrasive cycle systems 2 to 5 and 7 to 13 include the abrasive concentration at the end point in the slurry supply tank 21 in the abrasive slurry recovery process unit 2 and the abrasive of the next processing batch with respect to the preprocessing batch. Polishing was performed by changing the fluctuation range of the change in concentration, the maximum concentration, the dispersant in the regenerated abrasive slurry and its amount as shown in Table I. The dispersant in the regenerated abrasive slurry and its amount were adjusted by adjusting the dispersant added to the abrasive particle size adjusting step 4 and its amount.

Further, in the abrasive recycling system 12, in the abrasive recycling system 1, the slurry supply tank 21 is filled with the regenerated abrasive slurry containing cerium oxide having an initial concentration of 10% by mass, and then the slurry supply tank 21 is filled with the regenerated abrasive slurry. The powder of cerium oxide and water were supplied, and the polishing agent concentration in the slurry supply tank 21 at the end point of the polishing process was set to 10% by mass or less as the initial concentration, and 200 batch polishing process was performed.

Further, the abrasive recycling system 12 did not control the fluctuation range of the change in the abrasive concentration of the next processing batch with respect to the preprocessing batch.

Therefore, in the abrasive recycling system 12, the maximum concentration of the abrasive in the slurry supply tank exceeds 10.0% by mass.

[Abrasive Recycling System 6]
The abrasive slurry was prepared in the same manner for the abrasive recycling system 1 except that the separation / concentration step unit 3 was changed from the sediment separation method to the membrane separation method. That is, the same procedure as in the Abrasive Recycling System 1 was carried out except that the module was changed to a Microza Lab module using an MF film (Microza: manufactured by Asahi Kasei Co., Ltd.) having an abrasive slurry pore diameter of about 0.5 μm.

≪Evaluation of Abrasive Recycling System 2-13≫
The abrasive recycling systems 2 to 13 were evaluated in the same manner as the evaluation of the abrasive recycling system 1. The results are shown in Table I.

The following abbreviations were used for the dispersant type column in the table.

A: Polity A-550 (maleic acid-acrylic acid copolymer: manufactured by Lion Corporation)
B: Mighty 21HP (maleic acid-acrylic acid copolymer: manufactured by Kao Corporation)
C: Nopco Perth 5600 (manufactured by San Nopco Co., Ltd.)

From Table I, it can be seen that the abrasive recycling treatment system of the present invention has an excellent recovery rate, a high non-defective rate, and a long life of the polishing pad.

The abrasive recycling treatment system of the present invention can efficiently recover the abrasive from the processed abrasive slurry and reuse it as a recycled abrasive slurry. Therefore, it is possible to contribute to resource saving of elements having high rare value such as cerium used as an abrasive.

1 Abrasive processing process 2 Abrasive slurry recovery process 3 Separation / concentration process 4 Abrasive particle size adjustment process 5 Regenerated abrasive slurry preparation process 11 Washing water tank 12 Polishing machine 21 Slurry supply tank 22 Recovery mixture tank 31 Additive tank 32 Separation / concentration tank 41 Additive tank 42 Abrasive separation liquid storage tank 43 Membrane filter 44 Ultrasonic disperser 45 Particle size measuring device 51 Abrasive slurry storage tank

Claims (15)

Polishing is continued while controlling the concentrations of the constituents of the polishing agent and the constituents of the object to be polished in the abrasive slurry used for polishing, and the constituents of the object to be polished are removed from the processed abrasive slurry. An abrasive recycling processing system that collects and regenerates the abrasive.
It has a polishing process unit for polishing using a polishing machine and an abrasive slurry recovery process unit having a slurry supply tank for storing the polishing agent slurry supplied to the polishing machine.
Polishing characterized in that the regenerated abrasive slurry is supplied into the slurry supply tank while controlling the concentration of the constituent components of the abrasive in the slurry supply tank to be equal to or lower than the initial concentration at the start of the polishing process. Abrasive recycling processing system. The concentration of the constituent components of the abrasive in the slurry supply tank is within the range of 20 to 90% at the end point concentration at the end of the polishing process with respect to the concentration at the start of the polishing process, and during the polishing process. The concentration of the constituent components of the abrasive is always equal to or higher than the end point concentration, and the fluctuation range of the change in the concentration of the constituent components of the abrasive in the next processing batch with respect to the pre-processing batch is controlled within ± 1.0% by mass. The abrasive recycling treatment system according to claim 1, wherein the abrasive is recycled. The concentration of the constituent components of the abrasive in the slurry supply tank is within the range of 30 to 80% at the end point concentration at the end of the polishing process with respect to the concentration at the start of the polishing process, and during the polishing process. The concentration of the constituent components of the abrasive is always equal to or higher than the end point concentration, and the fluctuation range of the change in the concentration of the constituent components of the abrasive in the next processing batch with respect to the pre-processing batch is controlled within ± 1.0% by mass. The abrasive recycling treatment system according to claim 1, wherein the abrasive is recycled. Any of claims 1 to 3, characterized in that it has a separation / concentration process section and a regenerated abrasive slurry preparation process section in addition to the polishing process section and the abrasive slurry recovery step section. The abrasive recycling processing system according to item 1. In the abrasive slurry recovery process section, the slurry supply tank for storing the abrasive slurry to be supplied to the polishing process section and the recovery mixture tank for storing the mixed solution of the processed abrasive slurry and the washing water are stored. With and
The separation / concentration step unit is provided with a separation / concentration tank that separates the mixed liquid into a permeation liquid and a concentrated liquid of an abrasive.
The regenerated abrasive slurry preparation process unit is provided with a regenerated abrasive slurry storage tank for storing a liquid containing the regenerated abrasive from which the constituent components of the object to be polished have been removed, and an abrasive slurry is provided between the process units. The abrasive recycling treatment system according to claim 4, further comprising a circulation line for supplying and a control unit for adjusting the supply amount. The abrasive recycling treatment system according to claim 4 or 5, further comprising an abrasive particle size adjusting process section for adjusting the particle size of the abrasive obtained in the separation / concentration step section. Any one of claims 1 to 6, wherein the recycled abrasive slurry contains a maleic acid-acrylic acid copolymer in the range of 0.04 to 1.5 g / L. Abrasive recycling processing system as described in the section. The abrasive recycling treatment system according to any one of claims 1 to 7, wherein the abrasive contains a metal oxide and the object to be polished contains silicon (Si). .. The abrasive recycling treatment system according to any one of claims 1 to 8, wherein the abrasive contains cerium oxide. The abrasive recycling treatment system according to any one of claims 4 to 9, wherein an alkaline earth metal salt is used as an abrasive flocculant in the separation / concentration step unit. The abrasive recycling treatment system according to claim 10, wherein the alkaline earth metal salt is a magnesium salt. Polishing is continued while controlling the concentrations of the constituents of the polishing agent and the constituents of the object to be polished in the abrasive slurry used for polishing, and the constituents of the object to be polished are removed from the processed abrasive slurry. A polishing agent recovery / regeneration method for recovering / regenerating the polishing agent.
The concentration of the constituent components of the abrasive in the slurry supply tank for storing the abrasive slurry used for the polishing supplied to the polishing machine is controlled to be equal to or lower than the initial concentration of the constituent components of the abrasive at the start of the polishing process. A method for recovering and regenerating an abrasive, which comprises supplying a recycled abrasive slurry to a polishing process section and recovering the processed abrasive slurry. The concentration of the constituent components of the abrasive in the slurry supply tank is within the range of 20 to 90% at the end point concentration at the end of the polishing process with respect to the concentration at the start of the polishing process, and during the polishing process. The concentration of the constituent components of the abrasive is always equal to or higher than the end point concentration, and the fluctuation range of the change in the concentration of the constituent components of the abrasive in the next processing batch with respect to the pre-processing batch is controlled within ± 1.0% by mass. The abrasive recovery / regeneration method according to claim 12, wherein the abrasive is recovered and regenerated. The concentration of the constituent components of the abrasive in the slurry supply tank is within the range of 30 to 80% at the end point concentration at the end of the polishing process with respect to the concentration at the start of the polishing process, and during the polishing process. The concentration of the constituent components of the abrasive is always equal to or higher than the end point concentration, and the fluctuation range of the change in the concentration of the constituent components of the abrasive in the next processing batch with respect to the pre-processing batch is controlled within ± 1.0% by mass. The abrasive recovery / regeneration method according to claim 12, wherein the abrasive is recovered and regenerated. Any one of claims 12 to 14, wherein the reclaimed abrasive slurry contains a maleic acid-acrylic acid copolymer in the range of 0.04 to 1.5 g / L. The method for collecting and regenerating the abrasive according to the section.

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