JP2023061348A - Regeneration method for abrasive slurry, and regeneration system for abrasive slurry - Google Patents

Abstract

To provide a regeneration method for an abrasive slurry and a regeneration system for an abrasive slurry which are excellent in separability between an abrasive grain component containing cerium oxide and a component (glass component) of a polished object, when abrasive agent regeneration processing of removing the component (glass component) of the polished object from a used abrasive slurry used in glass polishing processing is performed.SOLUTION: A regeneration method for an abrasive slurry includes: a first step including a slurry recovery step of recovering a used abrasive slurry discharged from an abrasive machine, a desalting step of lowering ion concentration of the recovered abrasive slurry, and a dispersing step of adding a pH adjuster and a dispersion agent to the desalted abrasive slurry, and dispersing an abrasive component and a component of the polished object; and a second step of separating the abrasive component and the component of the polished object, and preparing a regeneration abrasive slurry from the abrasive component, after the first step.SELECTED DRAWING: Figure 1

Description

The present invention relates to an abrasive slurry regeneration method and an abrasive slurry regeneration system. More specifically, when carrying out abrasive regeneration treatment for removing constituents (glass components) of the object to be polished from used abrasive slurry used for glass polishing etc., abrasive grain components containing cerium oxide and a method for regenerating an abrasive slurry excellent in separability from constituent components (such as a glass component) of an object to be polished.

Rare earth oxides such as cerium oxide are used as abrasives (also referred to as "abrasives" or "abrasive grains") in precision polishing of glass and chemical mechanical polishing (CMP) in semiconductor manufacturing. ing. Cerium oxide is used as a polishing agent in the finishing process of various products such as optical glass, cover glass for smartphones, and cover glass for in-vehicle displays, and in the CMP processing of semiconductor silicon oxide films. .

In glass polishing or semiconductor CMP processing, cerium oxide is generally supplied to a polishing machine as a slurry in which cerium oxide fine particles are dispersed in water or the like, and a polishing cloth or brush is pressed against the glass to Polishing is performed by applying pressure and making relative movements.

In CMP processing, when abrasive grains containing cerium oxide come into contact with an object to be polished, not only physical force but also chemical action is produced, thereby obtaining excellent polishing performance. Therefore, in performing CMP processing, it is important that the abrasive grains are stably dispersed in the slurry without agglomeration. In addition, if the abrasive grains agglomerate in the abrasive slurry and become coarse particles, the possibility of causing defects such as scratches on the object to be polished increases. It is important to stably disperse them in the slurry.

As described above, cerium oxide is generally used in CMP processing of an object to be polished (glass) containing silicon as a main component. Cerium oxide is produced in ubiquitous regions around the world, and the process of extracting cerium oxide from minerals containing cerium oxide has a high environmental impact. There is a strong desire to make efficient use of precious resources.

As a method of effectively using cerium oxide, a method of recovering and reusing the abrasive from the cerium oxide abrasive slurry that has been subjected to CMP processing is known. For example, Patent Document 1 discloses a method for recovering an abrasive for regenerating a cerium oxide abrasive from a used abrasive slurry containing cerium oxide abrasive obtained by polishing an object to be polished whose main component is silicon. there is Specifically, an inorganic salt is added to the recovered cerium oxide abrasive slurry under the condition that the mother liquor has a pH of 7 to 10 at 25° C. to separate and aggregate the abrasive from the component derived from the object to be polished. , a method of recovering a cerium oxide abrasive by separating the abrasive from the mother liquor and concentrating it, then adding a dispersant or the like to disperse the abrasive components.

Further, Patent Documents 2 and 3 disclose a method of recovering a cerium oxide abrasive from used abrasive slurry. Specifically, it is a method of recovering an abrasive from an abrasive slurry obtained by polishing an object to be polished containing silicon as a main component, wherein a solvent is added under the condition that no pH adjuster is used, and the particles of the object to be polished are is dissolved and then the abrasive slurry is filtered to recover the abrasive.

In recent years, in order to enhance the optical or physical functions and properties of glass, various metals and the like have been added to glass in addition to the base material (for example, silicon). In addition, from the viewpoint of effective utilization of cerium oxide, which is a rare earth resource, in order to increase its utilization efficiency (amount of glass processed per mass of abrasive), cerium oxide abrasive grains are used from the start of use to disposal. Therefore, polishing is often performed for as long a time as possible. For this reason, the content of the component to be polished (glass component) contained in the used abrasive slurry, the content of components such as metals eluted from the object to be polished (glass) (ionic component), and polishing during processing There is an increasing number of cases where the content of ionic components derived from pH adjusters added for the purpose of adjusting the pH of agent slurries increases.

In such a case, the amount of the glass component, the ionic components dissolved from the glass, and the used abrasive slurry containing a large amount of ionic components derived from the pH adjuster, etc., have a structure in which the glass component itself is gelled. In addition, the abrasive particles and the glass component form aggregates, and it is difficult to separate the abrasive particles and the glass component efficiently even if the known technique is applied. I understand.

Japanese Patent No. 6292119 Japanese Patent No. 5850192 Japanese Patent No. 5843036

The present invention has been made in view of the above problems and circumstances, and the problem to be solved is to remove the component (glass component) of the object to be polished from the used abrasive slurry used for glass polishing. Method for regenerating abrasive slurry excellent in separation between abrasive grain component containing cerium oxide and component (glass component, etc.) of object to be polished when performing abrasive regeneration treatment, and regeneration of abrasive slurry It is to provide a system.

In order to solve the above problems, the present inventors, in the process of studying the causes of the above problems, discovered that from a used abrasive slurry containing abrasive components and constituents of the object to be polished, A desalting treatment step for reducing the ion concentration of the recovered used abrasive slurry when removing the abrasive, and adding a pH adjuster and a dispersant to the desalted abrasive slurry to remove the abrasive component and the surface. Separation of the abrasive grain component containing cerium oxide and the component (glass component, etc.) of the object to be polished by a method for regenerating abrasive slurry comprising a specific step including a dispersion treatment step of dispersing the component of the polished object. It has been found that a method for regenerating an abrasive slurry having excellent properties can be obtained.

That is, the above problems related to the present invention are solved by the following means.

1. A method for regenerating abrasive slurry, comprising removing constituents of the object to be polished from used abrasive slurry containing abrasive components and constituents of the object to be polished, and recovering and regenerating the abrasive components. hand,
a slurry recovery step of recovering the used abrasive slurry discharged from the polishing machine;
a desalting step of reducing the ion concentration of the recovered abrasive slurry;
a first step including a dispersion treatment step of adding a pH adjuster and a dispersant to the desalted abrasive slurry to disperse the abrasive component and the component of the object to be polished;
a second step of, after the first step, separating the abrasive component from the constituent components of the object to be polished to prepare a regenerated abrasive slurry from the abrasive component;
A method for regenerating an abrasive slurry, comprising:

2. The second step includes a separating and concentrating step of separating the abrasive component and the constituent component of the object to be polished by natural sedimentation, centrifugation, salt-adding sedimentation, or filter filtration. 2. The method for regenerating abrasive slurry according to claim 1, further comprising: an abrasive regeneration step of preparing a regenerated abrasive slurry from the abrasive component concentrated in the above step.

3. In the desalting step, desalting is performed so that the ion concentration of the used abrasive slurry becomes 5.0 mS/cm or less as an electrical conductivity value converted at 25°C. 3. The method for regenerating the abrasive slurry according to item 1 or 2.

4. The method for regenerating abrasive slurry according to item 3, wherein the desalting treatment is carried out so that the ion concentration becomes 1.0 mS/cm or less as the electric conductivity value.

5. In the dispersing step of the first step, the pH adjuster adjusts the pH value of the used abrasive slurry to 6.0 or higher when converted to 25°C, and the dispersant is added to the 4. The method according to any one of items 1 to 4, wherein the abrasive is added in a range of 0.1 to 5.0% by mass based on the mass of the abrasive contained in the used abrasive slurry. A method of reclaiming the described abrasive slurry.

6. The pH adjuster is an inorganic acid, carboxylic acid, amine base or ammonium hydroxide, and the dispersant is a water-soluble anionic dispersant, a water-soluble cationic dispersant or a water-soluble amphoteric dispersant. 6. The method for regenerating an abrasive slurry according to any one of items 1 to 5, wherein the abrasive slurry is a polishing agent.

7. A method for regenerating an abrasive slurry for removing constituent components of an object to be polished from a used abrasive slurry containing an abrasive component and constituent components of an object to be polished, and recovering and regenerating the abrasive component, comprising:
a slurry recovery step of recovering the used abrasive slurry discharged from the polishing machine;
a desalting step of adjusting the ion concentration of the collected used abrasive slurry to be 0.3 mS/cm or less as an electrical conductivity value converted to 25° C.;
A pH adjuster is added to the desalted abrasive slurry to adjust the pH value of the used abrasive slurry to 8.0 or more at 25° C., and the abrasive component and the object to be polished are combined. a first step comprising a dispersing step of dispersing the constituents;
a second step of, after the first step, separating the abrasive component from the constituent components of the object to be polished to prepare a regenerated abrasive slurry from the abrasive component;
A method for regenerating an abrasive slurry, comprising:

8. In the second step, the abrasive component and the constituent component of the object to be polished are separated by natural sedimentation, centrifugation, sedimentation by adding salt, filter filtration, or coagulation sedimentation by pH value adjustment. 8. The method for regenerating abrasive slurry according to claim 7, comprising a concentration step and an abrasive regeneration step of preparing a regenerated abrasive slurry from the separated and concentrated abrasive component.

9. The method for regenerating abrasive slurry according to item 7 or 8, wherein the desalting treatment is performed so that the ion concentration becomes 0.1 mS/cm or less as the electrical conductivity value. .

10. A seventh characterized in that the second step adjusts the pH value of the used abrasive slurry converted to 25° C. to a range of 6.0 or more and less than 8.0 to perform the coagulation sedimentation. Item 9. The method for regenerating the abrasive slurry according to any one of Items 1 to 9.

11. The method for regenerating abrasive slurry according to any one of items 7 to 10, wherein the pH adjuster is inorganic acid, carboxylic acid, amine base or ammonium hydroxide.

12. By the method for regenerating abrasive slurry according to any one of items 1 to 11, the used abrasive slurry containing the abrasive component and the component of the object to be polished is removed from the object to be polished. An abrasive slurry regeneration system for removing the constituent components of and recovering and regenerating the abrasive components,
a polishing process section having a polishing machine; an abrasive slurry supply process section having a slurry supply tank for supplying abrasive slurry to the polishing process section; and a recovery for recovering the used abrasive slurry discharged from the polishing machine. a slurry recovery process unit having a mixed liquid tank;
a desalting process section having a dilution water supply tank for reducing the ion concentration of the recovered abrasive slurry, a desalting processing tank, a desalting device, and an ion concentration measuring section for measuring the ion concentration;
Dispersion processing comprising: an additive supply tank for supplying a pH adjuster and a dispersant to the desalted abrasive slurry; and a dispersion tank and a dispersion apparatus for dispersing the abrasive component and the component of the object to be polished. the engineering department;
a separation/concentration process unit having a separation/concentration tank for separating and concentrating the abrasive component and the constituent components of the object to be polished;
an abrasive regeneration process section having a regenerated abrasive slurry preparation tank having an additive supply tank for adding a pH adjuster and a dispersant to the separated and concentrated abrasive component;
A polishing slurry regeneration system comprising:

13. In item 12, wherein the separation and concentration process unit has a natural sedimentation means, a centrifugal means, a means for sedimentation separation by adding salt, a filter filtration means, or a coagulation sedimentation means by pH value adjustment. A regeneration system for the described abrasive slurry.

By the means of the present invention, when carrying out an abrasive regeneration treatment for removing constituent components (glass components) of an object to be polished from used abrasive slurry used for polishing of glass or the like, the slurry contains cerium oxide. It is possible to provide a method for recycling abrasive slurry and a system for recycling abrasive slurry in which the abrasive grain component and the constituent component of the object to be polished (glass component, etc.) are excellent in separability.

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

In the used abrasive slurry containing a large amount of the glass component, which is the object to be polished, ionic components derived from glass, ionic components derived from pH adjusters, etc., The glass component itself tends to have a gelled structure, and the abrasive grains and the glass component form agglomerates. It was found that it is difficult to separate the glass component, which is a substance.

In order to solve the above problems, in the process of examining the causes of the above problems, it was found that the components of the object to be polished, the ionic components eluted from the components of the object to be polished, and the ionic components derived from the pH adjuster, etc., contained in the regenerated abrasive. , and components such as metal ions mixed in during the process from use as an abrasive to recovery, the glass component itself contained in the abrasive slurry tends to take a gelled structure. It was speculated that agglomerates would be formed, the dispersion stability of the abrasive grains would be lowered, and the abrasive grain components would be in an agglomerated state.

As a countermeasure, as a method for removing the dissolved ionic components contained in the used abrasive slurry (also referred to as "demineralization treatment" in the present invention), filter filtration or centrifugation is performed to remove cerium oxide and glass. It is conceivable to efficiently remove the dissolved ionic components by solid-liquid separation between the solid content and the solution in which the ionic components are dissolved.

As a method for sufficiently removing the ionic components, the used abrasive slurry is once diluted with water or the like, and then subjected to a stirring treatment or the like to remove the ionic components adhering to the abrasive grains into the slurry. It is conceivable to carry out the above solid-liquid separation operation after elution

Furthermore, regarding the dispersion of the abrasive grain component containing cerium oxide and the glass component aggregates contained in the used abrasive slurry after the separation, the pH value of the slurry with a pH adjuster is used for the aggregated cerium oxide and glass components It is considered that the aggregation state can be eliminated by adjusting the above and performing dispersion treatment by adding a dispersant or the like.

The addition of the pH adjuster and the dispersant is preferably carried out so that the surface potential of the abrasive grain component containing cerium oxide contained in the slurry and the glass component are in the same phase. It is more preferable to apply energy such as sound waves.

In the separation of the abrasive grain component containing cerium oxide and the glass component, the cerium oxide abrasive grain and the glass component are dispersed in the slurry during the regeneration treatment by performing the above-mentioned treatment, and the glass component is As compared with cerium oxide abrasive grains, its size is sufficiently small and its density is also low, so that it can be easily separated by a method such as sedimentation separation or filtration separation.

Therefore, when the average particle diameter (D50) of abrasive grains containing cerium oxide is larger than about 0.5 μm, a sufficient separation speed can be obtained even by a sedimentation separation method such as natural sedimentation. In the case where it is desired to further increase the separation speed of the abrasive grains containing cerium oxide and the glass component, or in the case where the grain diameter of the abrasive grains containing cerium oxide is relatively small and the separation by natural sedimentation takes a long time, the known method is As in the example of , by adding salt, the abrasive grains containing cerium oxide may be selectively agglomerated to increase the sedimentation speed. A classifier or the like may be used, or the separation treatment may be performed using a filtration filter or the like.

By adopting the above-described desalting treatment step and dispersion treatment step as the first step of the method for regenerating the abrasive slurry, the abrasive grain component containing cerium oxide and the glass component, which is a component of the object to be polished, are mixed. It is possible to achieve a method for regenerating abrasive slurry with excellent separability.

On the other hand, the abrasive grain component containing cerium oxide contained in the used abrasive slurry and the glass component constituting the object to be polished aggregated in the slurry under the influence of the ion component contained in the slurry. It is in an easy state.

Therefore, in order to disperse the abrasive grain component containing cerium oxide and the glass component contained in the abrasive slurry, it is necessary to remove the ion component. It is important to control the surface potential of each component in each liquid.

It is known that the surface potential of the particle component present in the liquid changes its value according to the pH value of the liquid. is around pH 7.0, the surface potential is positive on the acidic side of the isoelectric point, and negative on the alkaline side of the isoelectric point.

On the other hand, the isoelectric point of the glass component is around pH 2.0, the surface potential is positive on the acidic side of the isoelectric point, and the surface potential is negative on the alkaline side of the isoelectric point. Are known.

Based on the above relationship, after sufficiently removing the ionic components contained in the used abrasive slurry, the pH value at 25°C is adjusted to alkaline, so that the cerium oxide in an aggregated state is included. It has been found that the abrasive grain component and the glass component can be dispersed without adding a dispersant or the like.

In addition, by returning the 25° C. converted pH value of the used abrasive slurry in the dispersed state to near neutrality, the surface potential of the abrasive grain component containing cerium oxide approaches zero (isoelectric point). A phenomenon was observed in which the electrostatic repulsive force decreased and the abrasive grain component containing the cerium oxide selectively aggregated again.

That is, by adjusting the pH value, the abrasive grain component containing cerium oxide is selectively aggregated again, so that the sedimentation speed is increased, and it is possible to improve the processing speed of the separation and concentration step. be done.

Compared to the case of natural sedimentation, since the glass component enters inside the agglomerate of the abrasive grain component containing cerium oxide, it is somewhat disadvantageous to natural sedimentation from the viewpoint of the removal rate of the glass component. In particular, in abrasive slurries with small cerium oxide particles, the spontaneous sedimentation velocity of the cerium oxide particles is very slow.

Schematic diagram showing an example of a basic process flow of a method for regenerating abrasive slurry Schematic diagram showing an example of the first process flow Schematic diagram showing an example of the second process flow Schematic diagram explaining the second process

The method for regenerating an abrasive slurry of the present invention comprises removing constituents of the object to be polished from a used abrasive slurry containing the constituents of the abrasive and the object to be polished, and recovering and regenerating the constituents of the abrasive. a slurry recovery step of recovering the used abrasive slurry discharged from the polishing machine; a desalting step of reducing the ion concentration of the recovered abrasive slurry; a first step including a dispersion treatment step of adding a pH adjuster and a dispersant to the desalted abrasive slurry to disperse the abrasive component and the constituent components of the object to be polished; After the first step, a second step of separating the abrasive component and the component of the object to be polished to prepare a regenerated abrasive slurry from the abrasive component. This feature is a technical feature common to or corresponding to the following embodiments.

As an embodiment of the present invention, from the viewpoint of manifestation of the effect of the present invention, the second step includes natural sedimentation, centrifugation, and salt addition of the abrasive component and the constituent components of the object to be polished. Efficiently regenerate the abrasive slurry by including a separation and concentration step of separating by sedimentation separation or filter filtration and an abrasive regeneration step of preparing a regenerated abrasive slurry from the separated and concentrated abrasive components. It is preferable from the viewpoint of performing

In the desalting step, desalting is performed so that the ion concentration of the used abrasive slurry becomes 5.0 mS/cm or less, more preferably 1.0 mS/cm or less as an electrical conductivity value at 25°C. Treatment is preferable from the viewpoint of obtaining excellent separation between the abrasive grain component containing cerium oxide and the constituent components of the object to be polished.

In the dispersion treatment step of the first step, the pH value of the used abrasive slurry converted to 25° C. is adjusted to 6.0 or higher with the pH adjuster, and the dispersant is added to the used Addition within the range of 0.1 to 5.0% by mass with respect to the mass of the abrasive contained in the abrasive slurry is excellent in the abrasive grain component containing cerium oxide and the constituent components of the object to be polished. It is preferable from the viewpoint of obtaining good separation.

The pH adjuster is an inorganic acid, carboxylic acid, amine base or ammonium hydroxide, and the dispersant is a water-soluble anionic dispersant, a water-soluble cationic dispersant or a water-soluble amphoteric dispersant. From the viewpoint of facilitating the separation of the abrasive grain component containing cerium oxide and the glass component, which is a constituent component of the object to be polished, it is preferable that there is a

Further, in the method for regenerating abrasive slurry of the present invention, constituent components of the object to be polished are removed from used abrasive slurry containing abrasive components and constituent components of the object to be polished, and the abrasive components are recovered. - A method for regenerating abrasive slurry, comprising: a slurry recovery step of recovering the used abrasive slurry discharged from a polishing machine; A desalting treatment step of adjusting the electrical conductivity to be 0.3 mS/cm or less, and adding a pH adjuster to the desalted abrasive slurry to heat the used abrasive slurry at 25°C. a first step including a dispersion treatment step of adjusting the converted pH value to 8.0 or more and dispersing the abrasive component and the constituent component of the object to be polished; and a second step of separating the abrasive component and the constituent components of the object to be polished, and preparing a regenerated abrasive slurry from the abrasive component.

From the viewpoint of exhibiting the effect of the present invention, the second step is to separate the abrasive component and the component of the object to be polished by natural sedimentation, centrifugation, sedimentation separation by adding salt, filter filtration, or pH The abrasive slurry can be efficiently regenerated by including a separation and concentration step of separating by coagulation sedimentation by value adjustment and an abrasive regeneration step of preparing a recycled abrasive slurry from the separated and concentrated abrasive components. It is preferable from the viewpoint of performance.

Further, in the desalting step, desalting is performed so that the ion concentration of the used abrasive slurry becomes 0.1 mS/cm or less as an electrical conductivity value at 25° C. conversion. It is preferable from the viewpoint of efficiently carrying out a dispersion treatment step in which only the pH adjuster is added to the agent slurry to disperse the abrasive component and the component of the object to be polished.

Furthermore, in the second step, the pH value of the used abrasive slurry converted to 25° C. is adjusted to a range of 6.0 or more and less than 8.0 to perform the coagulation sedimentation. From the viewpoint of improvement, it is preferable. An inorganic acid, a carboxylic acid, an amine base, or ammonium hydroxide can be appropriately used as the pH adjuster.

The abrasive slurry recycling system of the present invention removes the constituents of the object to be polished from the used abrasive slurry containing the constituents of the abrasive and the object to be polished, and recovers and regenerates the abrasive components. an abrasive slurry recycling system comprising: a polishing process section having a polishing machine; an abrasive slurry supply process section having a slurry supply tank for supplying abrasive slurry to the polishing process section; A slurry recovery process unit having a recovered mixed liquid tank for recovering the discharged used abrasive slurry, a diluting water supply tank for reducing the ion concentration of the recovered abrasive slurry, a desalting treatment tank, and a desalting treatment device. and a desalting process unit having an ion concentration measuring unit for measuring the ion concentration, an additive supply tank for supplying a pH adjuster and a dispersant to the desalted abrasive slurry, the abrasive component and the A dispersion processing unit having a dispersion tank for dispersing the constituent components of the object to be polished and a dispersion processing unit, and a separation and concentration tank for separating and concentrating the abrasive component and the constituent components of the object to be polished. and an abrasive regeneration process unit having a regenerated abrasive slurry preparation tank having an additive supply tank for adding a pH adjuster and a dispersant to the separated and concentrated abrasive component. characterized by having

In addition, separation and concentration can be efficiently performed when the separation and concentration process section has a natural sedimentation means, a centrifugal means, a means for sedimentation separation by adding salt, a filter filtration, or a flocculation sedimentation means by pH value adjustment. preferable from this point of view.

DETAILED DESCRIPTION OF THE INVENTION The present invention, its constituent elements, and embodiments and modes for carrying out the present invention will be described in detail below. In the present application, "-" is used to mean that the numerical values before and after it are included as the lower limit and the upper limit.

In the present invention, the "used abrasive slurry" is an abrasive slurry that is the target of the regeneration of abrasive slurry, and is prepared using newly prepared abrasive slurry or regenerated abrasive slurry. Abrasive slurry recovered and regenerated after polishing. Therefore, it is the abrasive slurry that is the target for determining the removal rate of the glass component according to the present invention.
Hereinafter, a method for regenerating abrasive slurry and a system for regenerating abrasive slurry will be described in detail.

<Outline of the method for regenerating abrasive slurry of the present invention>
The method for regenerating an abrasive slurry of the present invention comprises removing constituents of the object to be polished from a used abrasive slurry containing the constituents of the abrasive and the object to be polished, and recovering and regenerating the constituents of the abrasive. a slurry recovery step of recovering the used abrasive slurry discharged from the polishing machine; a desalting step of reducing the ion concentration of the recovered abrasive slurry; a first step including a dispersion treatment step of adding a pH adjuster and a dispersant to the desalted abrasive slurry to disperse the abrasive component and the constituent components of the object to be polished; After the first step, a second step of separating the abrasive component and the component of the object to be polished to prepare a regenerated abrasive slurry from the abrasive component.

As described above, in order to increase the utilization efficiency of abrasive grains containing cerium oxide (the amount of glass processed per mass of abrasive), if the polishing process is carried out as long as possible, the amount of the polished glass component, In addition, the used abrasive slurry contains a large amount of ionic components derived from glass and ionic components derived from pH adjusters, etc., and the glass component itself tends to have a gelled structure. The abrasive particles and the glass component formed aggregates, and it was difficult to separate the abrasive particles and the glass component even by applying known techniques.

An example of such a used abrasive slurry may have a glass component of 3.3 g/L or more and an ion concentration of 5.0 mS/c or more as an electrical conductivity value converted to 25°C. The load applied to the regeneration treatment was significantly different from the used abrasive slurry having a glass component of about 1.0 g/L and an ion concentration of about 1.4 mS/c, and regeneration failure occurred frequently.

However, according to the present invention, the amount of the glass components polished, the ionic components derived from the glass, the pH adjuster, etc., are reduced by the method for regenerating the abrasive slurry having the first step and the second step. When carrying out a polishing agent regeneration treatment for removing the component (glass component) of the object to be polished from the used abrasive slurry containing a large amount of the ion component derived from the abrasive grain component containing cerium oxide, It is possible to provide a method for regenerating abrasive slurry and a system for regenerating abrasive slurry that are excellent in separability from constituent components (glass components, etc.) of an object to be polished.

In addition, even in the used abrasive slurry containing the conventional glass component concentration and ion component concentration, by making use of the characteristics of the recycling method of the present invention, the abrasive grain component containing cerium oxide and the constituent components of the object to be polished ( It is possible to provide a method for regenerating an abrasive slurry that is excellent in separability from the glass component, etc.).

In addition, the abrasive slurry recycling system of the present invention provides a polishing processing section having a polishing machine and supplies abrasive slurry to the polishing processing section from the viewpoint of efficiently performing the polishing slurry recycling method. an abrasive slurry supply process unit having a slurry supply tank; a slurry recovery process unit having a recovery mixture tank for recovering the used abrasive slurry discharged from the polishing machine; and an ion concentration of the recovered abrasive slurry. a desalting process unit having a diluting water supply tank, a desalting processing tank, a desalting device, and an ion concentration measuring unit for measuring the ion concentration, and a pH adjuster added to the desalted abrasive slurry. an additive supply tank for supplying a dispersant; a dispersion processing unit having a dispersion tank and a dispersion processing device for dispersing the abrasive component and the constituent components of the object to be polished; the abrasive component and the object to be polished; and a separation/concentration process section having a separation/concentration tank for separating and concentrating the constituent components of the above, and a reclaim polishing process section having an additive supply tank for adding a pH adjuster and a dispersant to the separated and concentrated abrasive components. and an abrasive regeneration process section having an abrasive slurry preparation tank.

Further, it is preferable that the separation/concentration step section has a natural sedimentation means, a centrifugal means, a means for sedimentation separation by adding salt, or a filter filtration means from the viewpoint of efficiently performing the separation/concentration.

Further, as another method of the method for regenerating abrasive slurry of the present invention, from a used abrasive slurry containing abrasive components and constituents of the object to be polished, the constituents of the object to be polished are removed, and the abrasive A method for regenerating abrasive slurry for recovering and regenerating components, comprising: a slurry recovery step of recovering the used abrasive slurry discharged from a polishing machine; and a desalting step of adjusting the electrical conductivity of the used abrasive slurry to be 0.3 mS/cm or less, and adding a pH adjuster to the desalted abrasive slurry to remove 25% of the used abrasive slurry. a first step comprising a dispersion treatment step of adjusting a pH value converted to °C to 8.0 or higher and dispersing the abrasive component and the constituent component of the object to be polished; and after the first step, and a second step of separating the abrasive component and the constituent components of the object to be polished to prepare a regenerated abrasive slurry from the abrasive component.

Further, the second step includes a process of separating and concentrating the abrasive component and the constituent component of the object to be polished, in addition to natural sedimentation, centrifugation, sedimentation by adding salt, and filter filtration. Adopting coagulation sedimentation by adjustment is preferable from the viewpoint of improving the speed of the separation and concentration process and performing the separation and concentration efficiently.

In the case of this alternative method, in the desalting step, the ion concentration of the used abrasive slurry is dehydrated so that the electrical conductivity value at 25° C. is 0.1 mS/cm or less. The salt treatment is preferable from the viewpoint of efficiently performing the dispersion treatment step of adding only the pH adjuster to the abrasive slurry and dispersing the abrasive component and the constituent components of the object to be polished.

In that case, the pH value adjustment in the second step may be performed by adjusting the pH value of the used abrasive slurry converted to 25° C. to a range of 6.0 or more and less than 8.0. This is a preferred embodiment.

In the following, the method for regenerating abrasive slurry of the present invention will be described mainly along the process flow, but reference will also be made to the method and system for regenerating abrasive slurry according to the alternative methods described above, as appropriate. However, this is an example, and the present invention is not limited to this explanation.

FIG. 1 is a schematic diagram showing an example of a basic process flow relating to the method for regenerating abrasive slurry according to the present embodiment.

[1] Polishing process [Abrasive]
In general, as a polishing agent for optical glass, semiconductor substrates, etc., fine particles such as iron oxide (αFe ₂ O ₃ ), cerium oxide, aluminum oxide, manganese oxide, zirconium oxide, colloidal silica, etc. are dispersed in water or oil to form a slurry. However, in the present invention, in polishing the surface of a semiconductor substrate or glass, in order to maintain flatness with high precision and obtain a sufficient processing speed, physical action and chemical action are used. A polishing agent containing cerium oxide as a main component, which is applicable to chemical mechanical polishing (CMP), is used.

The cerium oxide used as an abrasive (for example, C.I. Kasei Co., Ltd., Technorise Co., Wako Pure Chemical Co., Ltd., etc.) has a cerium oxide content of almost 100%. In addition, there are cases in which not pure cerium oxide but bastnaesite, ore containing rare earth elements other than cerium, is fired and pulverized. Other rare earth components include rare earth elements such as lanthanum, neodymium, and praseodymium, and fluorides and the like may be contained in addition to oxides.
The cerium oxide used in the present invention is not particularly limited in terms of its composition and shape, and generally commercially available abrasives can be used. In some cases, the effect is large and preferable.

[Polishing]
As polishing, there are usage patterns (polishing steps) as shown below.
As the object to be polished, an object to be polished containing silicon as a main component is used. For example, optical glass, glass substrates for information recording media, smartphone cover glasses, car-mounted display cover glasses, silicon wafers, and the like can be used. Taking the polishing of a glass substrate as an example, as explained with reference to FIG. 1, the polishing process generally comprises a series of steps of preparation of an abrasive slurry, polishing and cleaning.

The unused abrasive slurry is prepared by using an abrasive powder containing cerium oxide as a main component and a dispersant so that the content of the abrasive becomes 0.1 to 40% by mass with respect to a solvent such as water. It is preferred to prepare the abrasive slurry as follows. The cerium oxide microparticles used as the abrasive have an average particle diameter (particle diameter (D50)) of several tens of nanometers to several micrometers.

In the present invention, a dispersing agent is added to prevent the cerium oxide particles from aggregating and to prevent sedimentation. In general, a tank for the abrasive slurry is installed next to the polishing machine, a stirrer or the like is used to maintain a constantly dispersed state, and a supply pump is used to circulate and supply the slurry to the polishing machine. is preferred.

The abrasive slurry is preferably unused abrasive slurry, but may be regenerated abrasive slurry. That is, the regenerated abrasive slurry can be newly prepared as unused abrasive slurry depending on the purpose and application, and used as unused abrasive slurry.

For example, used abrasive slurry used for polishing quartz glass is recovered to prepare regenerated abrasive slurry according to the present invention, and this is newly used as unused abrasive slurry for polishing aluminosilicate glass with different additions. It can be used as an unused abrasive slurry for polishing aluminum silicate glass by adding an agent or the like. Using such a regenerated abrasive slurry as an unused abrasive slurry, a regenerated abrasive slurry for polishing aluminum silicate glass can be further prepared according to the present invention.

In this way, when preparing a new abrasive slurry as an unused abrasive slurry, when the object to be polished is different as described above, or when polishing the same product, multiple polishing methods such as rough polishing and fine polishing are used. A case of having a polishing process is mentioned. Additives added to the freshly prepared unused abrasive slurry include a pH adjuster and a dispersant, which will be described later.

In the polishing process shown in FIG. 1, a polishing apparatus 1 (polishing machine) has a polishing surface plate 2 to which a polishing cloth F made of nonwoven fabric, synthetic resin foam, synthetic leather, or the like is attached. The platen 2 is rotatable. During the polishing operation, the polishing surface plate 2 is rotated while pressing the object to be polished (for example, glass) 3 against the polishing surface plate 2 with a predetermined pressing force. At the same time, an abrasive liquid 4 containing cerium oxide is supplied from a slurry nozzle 5 via a pump. A polishing agent liquid 4 containing cerium oxide is stored in a slurry tank T ₁ (slurry supply tank) through a flow path 6 and repeatedly circulated between the polishing apparatus 1 and the slurry tank T ₁ .

The cleaning water 7 for cleaning the polishing apparatus 1 is stored in the cleaning water storage tank _T2 , and is sprayed from the cleaning water injection nozzle 8 to the polishing part for cleaning. , through the flow path 9 and stored in the cleaning liquid storage tank T3. This cleaning liquid storage tank _T3 is a tank for storing the cleaning water used in cleaning (rinsing), and is constantly stirred by stirring blades in order to prevent sedimentation and agglomeration.

Abrasive agent liquid 4 (used abrasive slurry a to be described later) stored in the slurry tank _T1 generated in the above polishing step and circulated and used, and a cleaning liquid containing an abrasive stored in the cleaning liquid storage tank _T3 . 10 (used abrasive slurry b), which will be described later, both contained cerium oxide particles as an abrasive and a non-abrasive scraped from the object to be polished (for example, glass) 3 polished in the polishing step 1. state.

[2] First step The first step in the present invention comprises a slurry recovery step of recovering the used abrasive slurry discharged from the polishing machine, and a desalting step of reducing the ion concentration of the recovered abrasive slurry. and a dispersion treatment step of adding a pH adjuster and a dispersant to the desalted abrasive slurry to disperse the abrasive component and the component of the object to be polished.
In the case of adopting the alternative method, only the pH adjuster is added to the desalted abrasive slurry. Each step will be described below.

[2.1] Slurry Recovery Step Next, the abrasive liquid 4 and the cleaning liquid 10 containing the abrasive are recovered as a mixed liquid or as individual liquids. This step is called a slurry recovery step.

The used abrasive slurry referred to in the present invention is abrasive slurry that is discharged to the outside of a system comprising a polishing machine and an abrasive slurry tank, and there are mainly two types of slurry shown below.

The first is the abrasive slurry a (rinse slurry) containing the cleaning liquid discharged in the cleaning process, and the second is the used slurry stored in the slurry tank _T1 , which is discarded after being used a certain number of times. Abrasive slurry b (end of life). In the present invention, these are referred to as abrasive slurry a and abrasive slurry b, respectively. The present invention is preferably applied to both abrasive slurries a and b, but may be applied to only one of them.

The following two points can be mentioned as characteristics of the abrasive slurry a containing washing water.

1) A large amount of washing water flows in because it is discharged during washing, and the abrasive concentration is lower than that of the slurry in the tank.

2) The glass component adhering to the polishing cloth or the like also flows into this abrasive slurry a during washing.

On the other hand, a feature of the used abrasive slurry b is that it has a higher concentration of components in the object to be polished than the abrasive slurry before use.

A large amount of abrasive adheres to the glass substrate and the polishing machine immediately after being polished. Therefore, as described with reference to FIG. 1, after polishing, water or the like is supplied instead of the abrasive slurry to clean the abrasive adhering to the glass substrate and the polishing machine. At this time, the cleaning liquid containing the abrasive is discharged out of the system.

Generally, the recovered abrasive slurry contains cerium oxide abrasive in the range of 0.01 to 40% by mass. Abrasive amount of is reduced. To compensate for this decrease, new abrasive slurry can be added to slurry tank _T1 . As for the method of addition, addition may be performed for each processing, or addition may be performed for each fixed processing, but it is desirable to supply the abrasive in a state of being sufficiently dispersed in the solvent.

Next, in order to regenerate the abrasive slurry from the used abrasive slurry, a mixed liquid of the abrasive liquid 4 recovered in the slurry recovery step and the cleaning liquid 10 containing the abrasive, or individual liquids of each (hereinafter, these liquids is sometimes referred to as "mother liquor"), a separation and concentration step is required to separate and concentrate only the abrasive from the mother liquor in a state in which the object to be polished (for example, the glass component) is not aggregated. In a used abrasive slurry containing a large amount of glass components, ionic components derived from glass, and ionic components derived from pH adjusters, etc., the glass component itself tends to form a gelled structure. Also, the abrasive particles and the glass component form agglomerates, making it difficult to separate the abrasive particles and the glass component even by applying the known technique.

Therefore, in the present invention, following a slurry recovery step of recovering the used abrasive slurry discharged from the polishing machine, a desalting treatment step of reducing the ion concentration of the recovered abrasive slurry, and a desalting treatment step. It is characterized by adopting a new process of adding a pH adjuster and a dispersant to the abrasive slurry to disperse the abrasive component and the constituent components of the object to be polished. This series of steps is called the first step.

In the first step according to the present invention, the step of preliminarily removing coarse foreign matters (also referred to as "foreign matter removal step") from the recovered abrasive slurry by a filter filtration method using a filtration filter is a desalting treatment. It is preferable to carry out before the process. In this case, in order to remove foreign matter, it is preferable to perform filtration using a single filter having a pore size of 20 to 100 μm or multiple stages of filters having different pore sizes. As an example of multistage filtration, it is preferable to use a combination of a filter with a diameter of 25 μm and a filter with a diameter of 10 μm in succession.

Filtration filters used for filtration are not particularly limited, and examples thereof include membrane filters, hollow fiber filters, metal filters, thread filters, ceramic filters, and roll-type polypropylene filters.

Applicable ceramic filters include, for example, a ceramic filter manufactured by TAMI (France), a ceramic filter manufactured by Noritake, a ceramic filter manufactured by NGK Insulators (eg, CERAREC DPF, SEFIRT, etc.), a ceramic filter manufactured by Pall, and the like.

[2.2] Desalting Treatment Process The filtered and recovered abrasive slurry is first treated in a desalting treatment process.

The desalting step is a step of removing or reducing the concentration of dissolved glass, ionic components derived from the glass, and ionic components derived from pH adjusters and the like.

FIG. 2 is a schematic diagram showing an example of the first process flow.

In step (A-1), used abrasive slurry (also referred to as “mother liquor”) 13 recovered in the preceding slurry recovery step was filtered to remove foreign matter, and then a stirrer 15 was provided. Adjustment kettle 14 (FIGS. 2 and 3 show an example in which the adjustment kettle 14 also serves as a recovered mixed liquid tank, a desalting treatment tank, a dispersion tank, a separation and concentration tank, and a preparation tank for regenerated abrasive slurry.) Then, in step (A-2), while stirring the abrasive slurry (mother liquor) 13, the value of electrical conductivity converted to 25° C. is preferably 5.0 mS/cm or less, more preferably Dilution water 17 is added from the dilution water tank 16a (dilution water supply tank) so that the value becomes 1.0 mS/cm or less. Distilled water, purified water, ion-exchanged water, pure water, or the like can be used as the dilution water, but pure water containing as few ions as possible is preferred. The adjustment pot 14 has an ion concentration measuring section (not shown) to monitor the value of the electrical conductivity.

The step of adding the diluent water may be performed once, and after the diluent water is added and stirred to form a uniform slurry, the slurry is filtered through the above-mentioned filtration filter, and then further diluted water is added to improve the electrical conductivity of the abrasive slurry. You can reduce the rate value.

The amount of diluent water to be added can be appropriately adjusted by setting the ion concentration of the used abrasive slurry, and can range from 2 to 10 times the volume of the used abrasive slurry.

The value of the electrical conductivity can be measured, for example, with an electrical conductivity measuring device. Industrial CM-30G), Lacombe tester handy type conductivity meter CyberScan CON110 (AS ONE Corporation), or compact electrical conductivity meter LAQUAtwin B-771 (manufactured by HORIBA), etc. are used, and the sample liquid is heated to 25 ° C. It can be determined by temperature control and measurement.

In step (A-3), after diluting and adjusting the 25° C. equivalent electrical conductivity value of the abrasive slurry 13 to a desired value or less, cerium oxide Solid-liquid separation is performed by filtering through a filter having a pore size smaller than the particle size of the cerium oxide, and a mixture 18 of the abrasive grain component and the glass component containing cerium oxide is obtained. Moreover, it may be separated into a sediment part containing cerium oxide and a supernatant part in which ionic components are dissolved by natural sedimentation.

When the alternative method is adopted as the method for regenerating the abrasive slurry, in step (A-2), while stirring the abrasive slurry (mother liquor) 13, the electrical conductivity value converted to 25° C. is reduced to 0. Dilution water 17 is added from the dilution water tank 16a (dilution water supply tank) so that the concentration becomes 3 mS/cm or less, more preferably 0.1 mS/cm or less.

The abrasive grain component containing cerium oxide contained in the used abrasive slurry and the glass component constituting the object to be polished tend to aggregate in the slurry due to the influence of the ion components contained in the slurry. Therefore, it is preferable to reduce the ionic components in advance from the viewpoint of efficiently performing the dispersion treatment, which is the next step.

[2.3] Dispersion treatment step The dispersion treatment step is a step of separating the abrasive grains containing cerium oxide and the glass component adhering thereto by adjusting the pH value and adding a dispersant.

In step (A-4), water is added from the dilution water tank 16a to the mixture to disperse it in water, and then the pH adjuster supply tank 16b adjusts the pH value to 6.0 to 10.5 at 25°C. Adjust within range. Then, from the dispersant supply tank 16c, it is preferable to add a dispersant within a range of 0.1 to 5.0% by mass with respect to the mass of the abrasive contained in the used abrasive slurry. . It is possible to adjust the pH value and add a dispersant, and use a dispersion treatment device such as the stirrer 15 to disperse the abrasive grain component containing cerium oxide and the glass component to the extent that they can be easily separated. In -5), an abrasive slurry is obtained which is a dispersion 19 containing an abrasive grain component containing cerium oxide and a glass component.

The addition of the pH adjuster and dispersant is preferably carried out so that the surface potentials of the abrasive grain component containing cerium oxide and the glass component contained in the slurry are in the same phase. It is also more preferable to apply energy by an ultrasonic disperser or the like.

In the case of adopting the above alternative method for regenerating the abrasive slurry, in step (A-4), water is added to the mixture from the dilution water tank 16a to disperse it in water, and then the pH adjuster supply tank 16b is used. , the pH value at 25°C is adjusted within the range of 8.0 to 10.5. In this case, it is necessary to adjust the pH value to 8.0 or higher from the viewpoint of efficient dispersion treatment.

<pH adjuster>
Acids or alkalis added as pH adjusters are not particularly limited, and inorganic acids, organic acids and the like can be used. However, when polishing an object to be polished such as a silicon oxide film used in the field of semiconductors, it is preferable to use a pH adjuster that does not contain a metal element. The pH adjuster is preferably an inorganic acid, a carboxylic acid, an amine base, or ammonium hydroxide, and is preferred from the viewpoint of suppressing contamination with unnecessary excess metal ions in polishing.

As the pH value, a value measured at 25° C. using a Lacombe tester desktop pH meter (pH 1500 manufactured by AS ONE Corporation) can be used.

<Dispersant>
Examples of dispersants include water-soluble anionic dispersants, water-soluble cationic dispersants, and water-soluble amphoteric dispersants. Dispersants such as ammonium polyacrylate, copolymers of acrylic amide and ammonium acrylate, and polyacrylate-maleic acid copolymers are also preferred.

At least one polymer dispersant containing ammonium acrylate salt as a copolymer component, and at least one selected from water-soluble anionic dispersants, water-soluble cationic dispersants, and water-soluble amphoteric dispersants. You may use together two or more types of dispersing agents containing.

Among these, the dispersant used in the present invention is a water-soluble anionic dispersant, a water-soluble cationic dispersant or a water-soluble amphoteric dispersant. is preferable from the viewpoint of measurement and control using the value of electrical conductivity as an index.

In addition, when used for polishing in the manufacture of semiconductor devices, it is preferable to suppress the content of metal electrodes such as sodium ions and potassium ions in the dispersant to 10 ppm or less.

(Water-soluble anionic dispersant)
Examples of anionic dispersants include triethanolamine lauryl sulfate, ammonium lauryl sulfate, triethanolamine polyoxyethylene alkyl ether sulfate, and polycarboxylic acid-type polymer dispersants.

Examples of the polycarboxylic acid-type polymer dispersant include polymers of carboxylic acid monomers having unsaturated double bonds such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid; Copolymers of a carboxylic acid monomer having a bond and another monomer having an unsaturated double bond, and their ammonium salts and amine salts are included.

<Water-soluble cationic dispersant>
Examples of cationic dispersants include primary to tertiary aliphatic amines, quaternary ammonium, tetraalkylammonium, trialkylbenzylammonium alkylpyridinium, 2-alkyl-1-alkyl-1-hydroxyethylimidazolinium, N,N-dialkylmorpholinium, polyethylenepolyamine fatty acid amide, urea condensate of polyethylenepolyamine fatty acid amide, quaternary ammonium of urea condensate of polyethylenepolyamine fatty acid amide and salts thereof.

(Water-soluble amphoteric dispersant)
As the water-soluble amphoteric dispersant, a betaine dispersant is preferred. Examples of betaine dispersants include N,N-dimethyl-N-alkyl-N-carboxymethylammonium betaine, N,N,N-trialkyl-N-sulfoalkylene ammonium betaine, N,N-dialkyl-N, Betaines such as N-bispolyoxyethylene ammonium sulfate betaine and 2-alkyl-1-carboxymethyl-1-hydroxyethylimidazolinium betaine; aminocarboxylic acids such as N,N-dialkylaminoalkylene carboxylate; mentioned.

(Addition amount of dispersant)
The amount of these dispersants added is 0.01 per 100 parts by mass of the cerium oxide particles, considering the dispersibility and sedimentation prevention of the abrasive particles in the abrasive slurry, and the relationship between the polishing scratches and the amount of the dispersant added. A range of up to 5.0 parts by mass is preferred. The molecular weight of the dispersant is preferably in the range of 100-50,000, more preferably 1,000-10,000. If the molecular weight of the dispersant is 100 or more and 50000 or less, it is possible to suppress the increase in viscosity and ensure the dispersion stability of the abrasive grains.

As a method for dispersing these abrasive particles in water, a homogenizer, an ultrasonic disperser, a wet ball mill, or the like can be used in addition to the usual dispersing treatment using a stirrer.

[3] Second step In the second step, the abrasive component and the constituent components of the object to be polished are separated by natural sedimentation, centrifugation, sedimentation by adding salt, filter filtration, or coagulation sedimentation by adjusting the pH value. and a polishing agent regeneration step of preparing a recycled abrasive slurry from the separated and concentrated abrasive components. FIG. 3 is a schematic diagram showing the second process flow. In the separation/concentration step, individual devices for natural sedimentation, centrifugation, salt-adding sedimentation, or filter filtration are not shown.

[3.1] Separation and Concentration Steps Steps (B-1) and (B-2) in FIG. 3 are schematic diagrams for explaining the steps of separating and concentrating the abrasive from the abrasive slurry dispersed in the first step. It is a diagram.

For the separation and concentration step, a natural sedimentation method, a centrifugal method, a coagulation sedimentation method in which a salt is added for sedimentation, a filter filtration method, or a coagulation sedimentation method by adjusting the pH value can be used as appropriate. The natural sedimentation method is preferable, but when the other method is employed, it is also preferable to appropriately use the coagulation sedimentation method by adjusting the pH value.

The abrasive slurry dispersed in the first step is then subjected to the step (B-1) in FIG. After sedimenting the abrasive grain component containing cerium oxide by the natural sedimentation method, the supernatant liquid 21 containing the glass component is discharged by the supernatant discharge pipe 24 and the pump 25, and in step (B-2) , the abrasive grain component 20 containing cerium oxide separated from the glass component is concentrated.

In the case of adopting the above alternative method for regenerating the abrasive slurry, in the step (B-1), water is added to the mixture from the diluent water tank 16a to disperse it in water, and then the pH adjuster supply tank 16b is used. It is preferable that the abrasive grain component containing cerium oxide is aggregated and precipitated by adjusting the pH value in terms of 25° C. to within the range of 6.0 or more and less than 8.0, and the separation and concentration treatment is efficiently performed.

This is because by returning the pH of the used abrasive slurry in a dispersed state to near neutrality, the surface potential of the abrasive grain component containing cerium oxide approaches zero (isoelectric point), so that the electrostatic repulsive force is reduced. The abrasive grain component containing the cerium oxide is selectively aggregated again.

That is, by adjusting the pH, the abrasive grain component containing cerium oxide is selectively aggregated again, thereby increasing the sedimentation rate and making it possible to improve the processing rate of the separation and concentration step.

Compared to the case of natural sedimentation, since the glass component enters inside the agglomerate of the abrasive grain component containing cerium oxide, it is somewhat disadvantageous to natural sedimentation from the viewpoint of the removal rate of the glass component, In particular, in abrasive slurries with small cerium oxide particle sizes, the spontaneous sedimentation velocity of the cerium oxide particles is very slow, so intentionally aggregating them to increase the sedimentation velocity is practically advantageous.

For the separation and concentration step, a coagulation sedimentation method can be used as long as the effects of the present invention are not impaired. The coagulation-sedimentation method will be described below.
〈Coagulation sedimentation method〉
In the coagulation-sedimentation method, a divalent alkaline earth metal salt or a monovalent alkali metal salt is added as an inorganic salt to the abrasive slurry that has undergone the dispersion treatment, and the cerium oxide abrasive is separated from the components derived from the object to be polished. It is a method of concentration.

Specifically, for the abrasive slurry that has been subjected to the dispersion treatment, divalent alkaline earth as an inorganic salt is added to the abrasive slurry that has a pH value of 6.5 or more and less than 10.0 at 25°C. It is preferable to add a metal salt and separate and concentrate the cerium oxide abrasive from the component derived from the object to be polished. As a result, only the abrasive component mainly composed of cerium oxide is coagulated and precipitated, and then the glass component is mostly present in the supernatant to separate the aggregates, thereby separating the cerium oxide component and the glass component and polishing. Concentration of the agent slurry can be done at the same time. The alkaline earth metal salt is used as a flocculating agent for selectively flocculating and precipitating cerium oxide contained in the used abrasive slurry.

The pH adjuster used for adjusting the pH value may be the same as the pH adjuster described above.

(Divalent alkaline earth metal salt)
In the present invention, the inorganic salt used for aggregating cerium oxide is preferably a divalent alkaline earth metal salt.

Examples of the divalent alkaline earth metal salt according to the present invention include calcium salts, barium salts, beryllium salts, magnesium salts, etc. Among them, the effects of the present invention can be exhibited more. From the point of view, the divalent alkaline earth metal salt is preferably a magnesium salt.

The magnesium salt that can be applied to the present invention is not limited as long as it functions as an electrolyte, but from the viewpoint of high solubility in water, magnesium chloride, magnesium bromide, magnesium iodide, magnesium sulfate, and magnesium acetate etc. are preferred, and magnesium chloride and magnesium sulfate are particularly preferred from the viewpoint that the pH change of the solution is small and the precipitated abrasive and waste liquid can be easily treated.

(Addition method of divalent alkaline earth metal salt)
A method for adding a magnesium salt, which is a divalent alkaline earth metal salt, will now be described.

a) Concentration of Magnesium Salt The magnesium salt to be added may be directly supplied as a powder to the recovery slurry, or may be dissolved in a solvent such as water and then added to the abrasive slurry. It is preferable to add it in a state of being dissolved in a solvent so that it will be in a uniform state after addition.

A preferred concentration is an aqueous solution of 0.5 to 50 mass %. It is more preferably 1 to 10% by mass in order to suppress pH fluctuations in the system and to improve the efficiency of separation from the glass component.

b) Magnesium Salt Addition Temperature The temperature at which the magnesium salt is added can be appropriately selected within the range of 90° C. or higher, which is higher than the temperature at which the recovered abrasive slurry freezes. From the viewpoint of efficiently separating from, the temperature is preferably within the range of 10 to 40°C, more preferably within the temperature range of 15 to 35°C.

c) Magnesium Salt Addition Rate The magnesium salt addition rate is preferably such that the concentration of magnesium in the recovered abrasive slurry does not become locally high and is uniform. The amount added per minute is preferably 20% by mass or less, more preferably 10% by mass or less, of the total amount added.

d) pH value when magnesium salt is added In the deconcentration step, it is preferable to add a magnesium salt and perform the separation and concentration under the condition that the pH value of the mother liquor converted to 25°C is 6.5 or more and less than 10.0.

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

Concentration is carried out so that the concentration of the abrasive becomes a desired concentration in the range of 0.1 to 40% by mass.

By setting the concentration of the abrasive to 0.1% by mass or more, an abrasive having high polishing performance can be obtained, and by setting the concentration to 40% by mass or less, an abrasive slurry having an appropriate concentration can be obtained without clogging the filter. can be played.

[3.2] Abrasive Slurry Regeneration Step In step (B-3) of FIG. For example, by adding a pH adjuster from the pH adjuster supply tank 16b and a dispersant from the dispersant supply tank 16c, the components of the reclaimed abrasive slurry are adjusted. The addition of a pH adjuster and a dispersant is not essential and can be omitted, but the component to be polished and the component to be polished mixed in the regenerated abrasive slurry containing the separated and concentrated cerium oxide. By adding the dispersant and the pH adjuster that interacts with the ionic components eluted from the abrasive or metal ions mixed in the process from use as a polishing agent to recovery, the pH value at 25 ° C. is reduced to 6.0 The electrical conductivity value can also be adjusted within the range of ~10.5, and the regenerated abrasive slurry 23 is obtained in step (B-4).

In addition, in the concentrate containing concentrated cerium oxide, if the cerium oxide particles form agglomerates (secondary particles), in order to disentangle them to a state close to independent primary particles, in the abrasive regeneration process, a dispersant It is preferable to control the particle size by dispersing to a desired particle size using a dispersing device after adding the pH adjuster.

By adding the pH adjuster and the dispersant in this manner, the pH value of the regenerated abrasive slurry and the electrical conductivity value of the regenerated abrasive slurry containing the dispersant are equal to or approximate to those of the unused abrasive slurry. Therefore, it is possible to reduce the decrease in the polishing rate and the variation in quality.

In addition, a regenerated abrasive slurry is prepared using an unused abrasive slurry, and after polishing is performed using the regenerated abrasive slurry, a regenerated abrasive slurry is prepared according to the present invention from the recovered abrasive slurry. You can also Although it is possible to regenerate the abrasive slurry a plurality of times in this manner, the adjustment of the pH value and electrical conductivity of the regenerated abrasive slurry prepared each time can be performed on the unused abrasive slurry. preferable.

Specific examples of adjustment of various components are shown below.
<Adjustment of electric conductivity value and pH value>
The addition amount of the dispersant to be replenished to the abrasive slurry containing cerium oxide concentrated in step (B-2) is determined. In the present invention, the replenishment amount of the dispersant is such that the electrical conductivity value is within the range of 0.10 to 10.00 times that of the unused abrasive slurry, and the pH value converted to 25°C is The reclaimed abrasive slurry is adjusted so that it falls within the range of 6.0 to 10.5. More preferably, the pH value is adjusted within the range of 7.0 to 10.0, more preferably within the range of 8.0 to 9.5.

(dispersant)
The dispersant to be added is preferably the same as the dispersant used in the dispersion treatment step. As the content of the dispersant in the abrasive slurry increases, the electrical conductivity increases proportionally. Therefore, the content of the dispersant in the abrasive slurry can be easily grasped by measuring the electrical conductivity. can be done.

The amount of dispersant to be added is adjusted so that the electrical conductivity of the virgin abrasive slurry falls within the above electrical conductivity range.

For example, if the unused abrasive slurry is regenerated abrasive slurry, it may contain substances that affect electrical conductivity, such as metal ions. , the amount of dispersant added must be adjusted accordingly.

The electrical conductivity can be measured by adjusting the temperature of the sample liquid to 25° C. using the above-mentioned electrical conductivity meter or the like.

(pH adjuster)
Acids or alkalis added as pH adjusters are not particularly limited, and inorganic acids, organic acids and the like can be used. However, when polishing an object to be polished such as a silicon oxide film used in the field of semiconductors, it is preferable to use a pH adjuster that does not contain a metal element.

Preferably, the pH adjuster is an inorganic acid, carboxylic acid, amine base or ammonium hydroxide.

As the pH value, similarly, a value measured at 25° C. using a Lacombe tester desktop pH meter (pH 1500 manufactured by AS ONE Corporation) can be used.

(Particle size control)
In the abrasive regeneration step, it is preferable to adjust the particle size distribution of the cerium oxide particles.

In particular, when the cerium oxide particles are agglomerated and collected using a magnesium salt or the like, it is preferable to re-disperse the agglomerated particles to loosen them. The aggregated abrasive component is redispersed to adjust the particle size distribution to be the same as that of the abrasive slurry before treatment.

As a method of redispersing the aggregated abrasive particles, there is a method of crushing the aggregated abrasive particles using a disperser or the like. As the dispersing machine, an ultrasonic dispersing machine, a medium stirring mill such as a sand mill or a bead mill can be applied, and it is particularly preferable to use an ultrasonic dispersing machine.

Further, the ultrasonic dispersing machine is commercially available from, for example, SM T Co., Ltd., Ginsen Co., Ltd., Taitec Co., Ltd., BRANSON, Kinematica, Nippon Seiki Seisakusho Co., Ltd., etc., and SMT UDU Co., Ltd. -1, UH-600MC, Ginseng GSD600CVP, Nippon Seiki Seisakusho RUS600TCVP, etc. can be used. The frequency of ultrasonic waves is not particularly limited.

Examples of circulation-type devices that simultaneously perform mechanical stirring and ultrasonic dispersion include SM T UDU-1 and UH-600MC, Ginsen Co., Ltd. GSD600RCVP, GSD1200RCVP, Nippon Seiki Seisakusho Co., Ltd. RUS600TCVP, and the like. possible, but not limited to this.
As described above, a high-quality regenerated abrasive slurry can be obtained.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these. In the examples, "parts" or "%" are used, but "mass parts" or "mass%" are indicated unless otherwise specified. Unless otherwise specified, the abrasive slurry was basically prepared under conditions of 25° C. and 55% RH. At this time, the temperature of the solution etc. is also 25°C.

Example 1
<Preparation of used abrasive slurry 1>
A used abrasive slurry 1 was prepared according to the following manufacturing process.

[Preparation of unused abrasive slurry 1]
After adding an acrylic acid-maleic acid copolymer as a dispersant to pure water, the mixture was stirred for 5 minutes with a stirrer. Then, while stirring, cerium oxide (E21, manufactured by Mitsui Kinzoku Co., Ltd.) was added, and after stirring with a stirrer for 30 minutes, dispersion treatment was performed with an ultrasonic disperser (manufactured by BRANSON).

The concentration of cerium oxide was added to be 10% by mass, and the dispersant was added so as to be 5% by mass with respect to cerium oxide. The unused abrasive slurry 1 was prepared so as to be 50 L in total.

After that, the pH value of the prepared unused abrasive slurry 1 at 25° C. was adjusted to 8.5 using ammonia water as a pH adjuster. Moreover, the value of electrical conductivity converted to 25° C. was 1.0 mS/cm.

After that, the average particle size (D50) was measured using a particle size distribution analyzer (eg, Horiba LA-950V2), and the average particle size (D50) was 0.96 μm.

The following measuring instruments were used.
pH value: Lacombe Tester desktop pH meter (manufactured by AS ONE Corporation, pH 1500)
Electrical conductivity: Compact electrical conductivity meter LAQUAtwin B-771 (manufactured by HORIBA)

[Polishing process]
〈Polishing〉
The aluminosilicate glass substrate was polished under the following conditions. The aluminosilicate glass substrate contains 60% by mass of silicon oxide, 15% by mass of oxides of alkali metals and alkaline earth metals, and 25% by mass of aluminum oxide and other components.

In the polishing step shown in FIG. 1, the surface to be polished was polished with a polishing cloth while supplying the unused abrasive slurry 1 prepared above using a double-side polishing machine to the surface to be polished. Polishing was performed by circulating and supplying unused abrasive slurry 1 at a flow rate of 5 L/min. An aluminosilicate glass substrate having a diameter of 65 mm and a thickness of 5 mm was used as an object to be polished, and a polishing cloth made of polyurethane was used. The polishing pressure on the polishing surface was set to 9.8 kPa (100 g/cm ² ), and the rotational speed of the polishing tester was set to 100 min ⁻¹ (rpm), and polishing was performed for 30 minutes. In addition, 100 sheets of glass were set in one patch.

During the polishing process, the pH is appropriately measured, and if the pH exceeds 8.5, an aqueous sulfuric acid solution is added to keep the pH from falling below 7.0 so that the pH becomes 8.5 or less. It was adjusted. Polishing was performed until the total polishing amount of the glass reached 10 g/L. After the polishing was completed, the cleaning wastewater containing the abrasive slurry and the abrasive slurry containing the used abrasive were recovered to obtain the used abrasive slurry 1 .

The 25° C. conversion electrical conductivity of the used abrasive slurry 1 was 12.1 mS/cm.

<Preparation of Recycled Abrasive Slurry 1>
[Separation and concentration step]
First, 1.0 L of the collected used abrasive slurry 1 was filtered using a 100 μm mesh filter to remove coarse foreign matter.

Then, a dispersing agent (ammonium polyacrylate: abbreviated as PAA in the table) was added in an amount of 2.5% by mass based on the cerium oxide abrasive particles.

Furthermore, after adding a pH adjuster (aqueous ammonia) to adjust the pH to 8.5, dispersion treatment was performed using an ultrasonic disperser. The pH adjusters listed in the table are NH ₃ : ammonia water, H ₂ SO ₄ : sulfuric acid aqueous solution, TEA: triethanolamine, NaOH: sodium hydroxide aqueous solution, and KOH: sodium hydroxide aqueous solution, respectively.

After the ultrasonic dispersion treatment, the dispersion was allowed to stand still for 1 hour, separated into a supernatant and a sediment by a natural sedimentation method, and the supernatant was discharged to recover 0.1 L of abrasive slurry containing the sediment. . Thus, the glass component was removed and the cerium oxide component was concentrated.

[Abrasive regeneration step]
<Adjustment of pH value and electrical conductivity value>
An acrylate-maleic acid copolymer is added as a dispersant to the abrasive slurry, and an acetic acid aqueous solution is used as a pH adjuster to adjust the pH value of the abrasive slurry to 8.5 at 25°C. bottom.

<Control of particle size>
Then, after stirring for 30 minutes using a disperser stirrer, the precipitate was dispersed and loosened using an ultrasonic disperser (manufactured by BRANSON).

After completion of dispersion, filtration was performed with a 10 μm depth filter to obtain a regenerated abrasive slurry 1 containing cerium oxide.

<Preparation of Recycled Abrasive Slurries 2 to 4>
In the preparation of the regenerated abrasive slurry 1, the regenerated abrasive slurry was prepared under the following conditions.

First, using a 100 μm mesh filter, 1 1.0 L of used abrasive slurry was filtered to remove coarse foreign matter.

Next, the filtrate component containing the cerium oxide abrasive was diluted with pure water to 3-fold (6-fold, 10-fold) volume, and then stirred for 30 minutes using a stirrer. The 25° C. conversion electrical conductivity of the desalted used abrasive slurry was 5.0 (2.4, 1.4) mS/cm.

After the stirring treatment, 2.5% by mass of a dispersant (ammonium polyacrylate: PAA) is added to the cerium oxide abrasive particles, and a pH adjuster (ammonia water) is added to adjust the pH to 8. After adjusting to 0.5, dispersion treatment was performed using an ultrasonic disperser.

After the ultrasonic dispersion treatment, the dispersion was allowed to stand still for 1 hour, separated into a supernatant and a sediment by a natural sedimentation method, the supernatant was discharged, and 0.3 L (0.3 L) of abrasive slurry containing the sediment was obtained. 6L, 1
. 0L) was recovered. Thus, the glass component was removed and the cerium oxide component was concentrated.

The concentration of the cerium oxide abrasive and the concentration of the glass component contained in the recovered abrasive slurry were measured by the ICP emission spectroscopic plasma method (also referred to as "ICP-AES"), and the used abrasive slurry 1 was measured. On the other hand, the removal rate of the glass component was measured.

(Component analysis by ICP emission spectroscopy plasma)
<Preparation of sample solution A>
(a) 1 ml of a sample (recovered abrasive slurry) was sampled while stirring with a stirrer or the like.
(b) 5 mL of hydrofluoric acid for atomic absorption was added;
(c) The silica was eluted by ultrasonic dispersion. (d) The mixture was allowed to stand at room temperature for 30 minutes.
(e) The total amount was made up to 50 mL with ultrapure water.
The sample liquid prepared according to the above procedure is called sample liquid A.

<Quantification of cerium oxide and glass component (Si)>
(a) Each sample liquid A was filtered with a membrane filter (hydrophilic PTFE).
(b) The filtrate was measured with an inductively coupled plasma atomic emission spectrometer (ICP-AES, manufactured by SII Nano Technology Co., Ltd.).
(c) Cerium oxide and Si were quantified by the calibration curve method of the standard addition method.

The removal rate of the glass component is [1-(concentration of glass component in recycled abrasive slurry/concentration of cerium oxide abrasive component)/(concentration of cerium oxide abrasive component in used abrasive slurry/concentration of cerium oxide abrasive component)]. Calculated by ×100 (%).

Next, in the same manner as in the preparation of regenerated abrasive slurry 1, regenerated abrasive slurries 2 to 4 were prepared according to the abrasive regeneration step.

<Preparation of Recycled Abrasive Slurries 5 to 28>
In the preparation of the regenerated abrasive slurry 1, the regenerated abrasive slurry was prepared under the following conditions.

First, using a 100 μm mesh filter, 1 1.0 L of used abrasive slurry was filtered to remove coarse foreign matter.

Next, the filtrate component containing the cerium oxide abrasive was diluted with pure water to double or quadruple the volume, and then stirred for 30 minutes using a stirrer.

The agitated abrasive slurry was filtered through a filter with a pore size of 1.0 μm, and after recovering the solid content remaining on the filter, pure water was added to bring the total volume to 20 L, and the slurry was again dispersed with a stirrer. However, only the regenerated abrasive slurry 7 was again filtered through a 1.0 μm filter to recover the solid content, then pure water was added to make 20 L, and dispersed with a stirrer.
The 25° C. conversion electrical conductivity values (ion concentrations) of the desalted used abrasive slurries are shown in Tables I and II below.

Then, 2.5% by mass of a dispersant (ammonium polyacrylate: PAA) was added to the cerium oxide abrasive particles.

Furthermore, after adding a pH adjuster (aqueous ammonia) to adjust the pH to 8.5, dispersion treatment was performed using an ultrasonic disperser.

After the ultrasonic dispersion treatment, the dispersion was allowed to stand for 1 hour to separate into a supernatant and a sediment, and 1.0 L of abrasive slurry containing the sediment was recovered.

The concentration of the cerium oxide abrasive and the concentration of the glass component contained in the collected abrasive slurry were measured by the methods described above.

Next, in the same manner as the preparation of regenerated abrasive slurry 1, regenerated abrasive slurries 5 to 28 were prepared according to the abrasive regeneration step. The types of dispersants listed in Table II are PANa: sodium polyacrylate, PAMNa: sodium polyacrylate maleate, and PEI: polythyleneimine.

<Preparation of Recycled Abrasive Slurry 29>
First, using a 100 μm mesh filter, 1 1.0 L of used abrasive slurry was filtered to remove coarse foreign matter.

A 0.1 mol/L aqueous solution of magnesium chloride was added to the above abrasive slurry at a feed rate of 10 mL/L while stirring, until the particle size average value (D50) was double that before addition. Diameter measurements were repeated.

After the addition of the aqueous magnesium chloride solution was completed, the dispersion was allowed to stand for 1 hour to separate into a supernatant liquid and a precipitate.

0.1 L of slurry containing precipitates was recovered, and the concentration of the cerium oxide abrasive and the concentration of the glass component contained in the recovered slurry were measured by the methods described above. Component removal rates were similarly measured.

<Preparation of Recycled Abrasive Slurries 30 to 36>
<Preparation of used abrasive slurry 2>
A used abrasive slurry 2 was prepared in the same manner as in the preparation of the used abrasive slurry 1, except that the total polishing amount of the glass was changed to 5 g/L. The 25° C. conversion electrical conductivity value of the used abrasive slurry 2 was 6.8 mS/cm.

<Preparation of Recycled Abrasive Slurry 30>
[Separation and concentration step]
First, 1.0 L of the collected used abrasive slurry 2 was filtered using a 100 μm mesh filter to remove coarse foreign matter.

Then, 2.5% by mass of a dispersant (ammonium polyacrylate: PAA) was added to the cerium oxide abrasive particles.

Furthermore, after adding a pH adjuster (aqueous ammonia) to adjust the pH to 8.5, dispersion treatment was performed using an ultrasonic disperser.

After the ultrasonic dispersion treatment, the dispersion was allowed to stand still for 1 hour, separated into a supernatant and a sediment by a natural sedimentation method, and the supernatant was discharged to recover 0.1 L of abrasive slurry containing the sediment. . Thus, the glass component was removed and the cerium oxide component was concentrated.

The concentration of the cerium oxide abrasive and the concentration of the glass component contained in the collected abrasive slurry were measured by the methods described above.

Next, in the same manner as the preparation of the regenerated abrasive slurry 1, a regenerated abrasive slurry 30 was prepared along the abrasive regeneration process.

<Preparation of Recycled Abrasive Slurries 31 to 33>
A regenerated abrasive slurry was prepared in the same manner as in the preparation of the regenerated abrasive slurry 1, except that the conditions were as follows.

First, using a 100 μm mesh filter, 1.0 L of used abrasive slurry 2 was filtered to remove coarse foreign matters.

Next, the filtrate component containing the cerium oxide abrasive was diluted with pure water to 3-fold (6-fold, 10-fold) volume, and then stirred for 30 minutes using a stirrer.

After the stirring treatment, 2.5% by mass of a dispersant (ammonium polyacrylate: PAA) is added to the cerium oxide abrasive particles, and a pH adjuster (ammonia water) is added to adjust the pH to 8. After adjusting to 0.5, dispersion treatment was performed using an ultrasonic disperser.

After the ultrasonic dispersion treatment, the dispersion was allowed to stand still for 1 hour, separated into a supernatant and a sediment by a natural sedimentation method, the supernatant was discharged, and 0.3 L (0.3 L) of abrasive slurry containing the sediment was removed. 6 L, 1.0 L) were collected. Thus, the glass component was removed and the cerium oxide component was concentrated.

The concentration of the cerium oxide abrasive and the concentration of the glass component contained in the recovered abrasive slurry were measured by the method described above, and the removal rate of the glass component for the used abrasive slurry 2 was similarly measured. .

Next, in the same manner as in the preparation of regenerated abrasive slurry 1, regenerated abrasive slurries 31 to 33 were prepared along the abrasive regeneration step.

<Preparation of Recycled Abrasive Slurries 34 and 35>
A regenerated abrasive slurry was prepared in the same manner as in the preparation of the regenerated abrasive slurry 1, except that the conditions were as follows.

First, using a 100 μm mesh filter, 1.0 L of the used recycled slurry 2 was filtered to remove coarse foreign substances.

Next, the filtrate component containing the cerium oxide abrasive was diluted with pure water to double or quadruple the volume, and then stirred for 30 minutes using a stirrer.

The agitated abrasive slurry was filtered through a 1.0 μm filter, and the solid content remaining on the filter was recovered. However, only the regenerated abrasive slurry 7 was again filtered through a 1.0 μm filter to recover the solid content, then pure water was added to make 20 L, and dispersed with a stirrer.

Then, 2.5% by mass of a dispersant (ammonium polyacrylate: PAA) was added to the cerium oxide abrasive particles.

Furthermore, after adding a pH adjuster (aqueous ammonia) to adjust the pH to 8.5, dispersion treatment was performed using an ultrasonic disperser.

After the ultrasonic dispersion treatment, the dispersion was allowed to stand for 1 hour to separate into a supernatant and a sediment, and 1.0 L of abrasive slurry containing the sediment was recovered.

The concentration of the cerium oxide abrasive and the concentration of the glass component contained in the recovered abrasive slurry were measured by the method described above, and the removal rate of the glass component for the used abrasive slurry 2 was similarly measured.

Next, regenerated abrasive slurries 34 and 35 were prepared in the same manner as in the preparation of regenerated abrasive slurry 1, following the abrasive regeneration step.

<Preparation of Recycled Abrasive Slurry 36>
First, using a 100 μm mesh filter, 1.0 L of used abrasive slurry 2 was filtered to remove coarse foreign matters.

A 0.1 mol/L aqueous solution of magnesium chloride was added to the above abrasive slurry at a feed rate of 10 mL/L while stirring, until the particle size average value (D50) was double that before addition. Diameter measurements were repeated.

After the addition of the aqueous magnesium chloride solution was completed, the dispersion was allowed to stand for 1 hour to separate into a supernatant liquid and a precipitate.

0.1 L of slurry containing precipitates was recovered, and the concentration of the cerium oxide abrasive and the concentration of the glass component contained in the recovered slurry were measured by the methods described above. Component removal rates were similarly measured.

<Preparation of Recycled Abrasive Slurries 37 to 39>
<Preparation of Spent Abrasive Slurry 3>
A used abrasive slurry 3 was prepared in the same manner as in the preparation of the used abrasive slurry 1, except that the total polishing amount of the glass was changed to 2 g/L. The 25° C. conversion electrical conductivity value of the used abrasive slurry 3 was 2.9 mS/cm.

First, using a 100 μm mesh filter, 1.0 L of used abrasive slurry 3 was filtered to remove coarse foreign matters.

Next, the filtrate component containing the cerium oxide abrasive was diluted with pure water to 3-fold (6-fold, 10-fold) volume, and then stirred for 30 minutes using a stirrer.

After the stirring treatment, 2.5% by mass of a dispersant (ammonium polyacrylate: PAA) is added to the cerium oxide abrasive particles, and a pH adjuster (ammonia water) is added to adjust the pH to 8. After adjusting to 0.5, dispersion treatment was performed using an ultrasonic disperser.

After the ultrasonic dispersion treatment, the dispersion was allowed to stand still for 1 hour, separated into a supernatant and a sediment by a natural sedimentation method, the supernatant was discharged, and 0.3 L (0.3 L) of abrasive slurry containing the sediment was removed. 6 L, 1.0 L) were collected. Thus, the glass component was removed and the cerium oxide component was concentrated.

The concentration of the cerium oxide abrasive and the concentration of the glass component contained in the recovered abrasive slurry were measured by the method described above, and the removal rate of the glass component for the used abrasive slurry 3 was similarly measured.

Next, in the same manner as in the preparation of regenerated abrasive slurry 1, regenerated abrasive slurries 37 to 39 were prepared along the abrasive regeneration process.

<Preparation of Recycled Abrasive Slurries 40 and 41>
In the preparation of the regenerated abrasive slurry 1, the regenerated abrasive slurry was prepared under the following conditions.

First, using a 100 μm mesh filter, 1.0 L of used abrasive slurry 3 was filtered to remove coarse foreign matters.

Next, the filtrate component containing the cerium oxide abrasive was diluted with pure water to double or quadruple the volume, and then stirred for 30 minutes using a stirrer.

The agitated abrasive slurry was filtered through a 1.0 μm filter, and the solid content remaining on the filter was recovered.

Then, 2.5% by mass of a dispersant (ammonium polyacrylate: PAA) was added to the cerium oxide abrasive particles.

Furthermore, after adding a pH adjuster (aqueous ammonia) to adjust the pH to 8.5, dispersion treatment was performed using an ultrasonic disperser.

After the ultrasonic dispersion treatment, the dispersion was allowed to stand for 1 hour to separate into a supernatant and a sediment, and 1.0 L of abrasive slurry containing the sediment was recovered.

The concentration of the cerium oxide abrasive and the concentration of the glass component contained in the collected abrasive slurry were measured by the methods described above.

Next, regenerated abrasive slurries 40 and 41 were prepared in the same manner as in the preparation of regenerated abrasive slurry 1, following the abrasive regeneration step.

<Preparation of Recycled Abrasive Slurry 42>
First, using a 100 μm mesh filter, 1.0 L of used abrasive slurry 3 was filtered to remove coarse foreign matter.

A 0.1 mol/L aqueous solution of magnesium chloride was added to the above abrasive slurry at a feed rate of 10 mL/L while stirring, until the particle size average value (D50) was double that before addition. Diameter measurements were repeated.

After the addition of the aqueous magnesium chloride solution was completed, the dispersion was allowed to stand for 1 hour to separate into a supernatant liquid and a precipitate.

0.1 L of the abrasive slurry containing precipitates was recovered, and the concentration of the cerium oxide abrasive and the concentration of the glass component contained in the recovered slurry were measured by the method described above. , the removal rate of the glass component was similarly measured.

Next, in the same manner as in the preparation of the regenerated abrasive slurry 1, a regenerated abrasive slurry 42 was prepared along the abrasive regeneration step.

<<Evaluation of Recycled Abrasive Slurry>>
[Removal rate of glass component]
The concentration of the cerium oxide abrasive and the concentration of the glass component contained in the recovered abrasive slurry were measured by the ICP emission spectroscopic plasma method (ICP-AES). Removal rate was measured.

The removal rate of the glass component is [1-(concentration of the glass component in the recycled abrasive slurry/concentration of the cerium oxide abrasive component)/(concentration of the cerium oxide abrasive component in the used abrasive slurry/concentration of the cerium oxide abrasive component). ]×100(%).

Next, the evaluation rank criteria were as follows.

× Removal rate is less than 50% ○ Removal rate is 50% or more and less than 80% ○○ Removal rate is 80% or more and less than 95% ○○○ Removal rate is 95% or more According to the present invention, the removal rate is 50% or more It is judged to have the effect of Preferably, the removal rate is 80% or more.
Tables I and II show the composition of the recycled abrasive slurries 1 to 42 and the removal rate of the glass component.

From Tables I and II, the dissolved glass components derived from the object to be polished, the components dissolved from the glass, and the ionic components such as the pH adjuster are removed from the used abrasive slurry used for polishing the glass. By performing the first step of performing the desalting treatment step and the dispersion treatment step by adding a pH adjuster and a dispersant, the removal rate of the glass component is significantly improved, and the abrasive grain component containing cerium oxide and the glass It was found that a method for regenerating an abrasive with excellent separability from components can be obtained.

Example 2
In Example 2, an example relating to the dispersion treatment step in which only the pH adjuster is added in the first step, which is the alternative method, and the separation and concentration treatment step will be described.

<Preparation of Recycled Abrasive Slurries 43 to 47>
<Preparation of Spent Abrasive Slurry 3>
A used abrasive slurry 3 was prepared in the same manner as in the preparation of the unused abrasive slurry 1 in the preparation of the used abrasive slurry 1 above, except that the total polishing amount of the glass was changed to 2 g/L. The 25° C. conversion electrical conductivity value of the used abrasive slurry 3 was 2.9 mS/cm.

First, using a 100 μm mesh filter, 1 L of used abrasive slurry was filtered to remove coarse foreign matter.

Next, the filtrate component containing the cerium oxide abrasive was diluted 10 times by volume with pure water, and then stirred for 30 minutes using a stirrer. The 25° C. conversion electrical conductivity of the desalted used abrasive slurry was 0.3 mS/cm.

After the stirring treatment, a pH adjuster (ammonia water) is added to adjust the pH value at 25°C to 7.0 (7.5, 8.0, 8.5, 9.0), Dispersion treatment was performed using an ultrasonic disperser.

After the ultrasonic dispersion treatment, the dispersion was allowed to stand for 1 hour, separated into a supernatant and a sediment by a natural sedimentation method, and the supernatant was discharged to collect 1.0 L of abrasive slurry containing the sediment. . Thus, the glass component was removed and the cerium oxide component was concentrated.

The concentration of the cerium oxide abrasive and the concentration of the glass component contained in the recovered abrasive slurry were measured by the method described above, and the removal rate of the glass component for the used abrasive slurry 3 was similarly measured.

Next, in the same manner as in the preparation of regenerated abrasive slurry 1, regenerated abrasive slurries 43 to 47 were prepared in accordance with the abrasive regeneration step.

<Preparation of Recycled Abrasive Slurries 48 to 52>
First, using a 100 μm mesh filter, 1 L of used abrasive slurry was filtered to remove coarse foreign matter.

Next, the filtrate component containing the cerium oxide abrasive was diluted with pure water to double the volume, and then stirred for 30 minutes using a stirrer.

The agitated abrasive slurry was filtered through a 1.0 μm filter, and the solid content remaining on the filter was recovered. The 25° C. conversion electrical conductivity of the desalted used abrasive slurry was 0.2 mS/cm.

Furthermore, after adding a pH adjuster (ammonia water) to adjust the pH value converted to 25 ° C. to 7.0 (7.5, 8.0, 8.5, 9.0), an ultrasonic disperser was used for distributed processing.

After the ultrasonic dispersion treatment, the dispersion was allowed to stand for 1 hour to separate into a supernatant and a sediment, and 1 L of abrasive slurry containing the sediment was recovered.

The concentration of the cerium oxide abrasive and the concentration of the glass component contained in the collected abrasive slurry were measured by the methods described above.

Next, in the same manner as in the preparation of regenerated abrasive slurry 1, regenerated abrasive slurries 48 to 52 were prepared following the abrasive regeneration step.

<Preparation of Recycled Abrasive Slurries 53 to 57>
First, using a 100 μm mesh filter, 1 L of used abrasive slurry was filtered to remove coarse foreign matter.

Next, the filtrate component containing the cerium oxide abrasive was diluted with pure water to 4 times its volume, and then stirred for 30 minutes using a stirrer.

The agitated abrasive slurry was filtered through a 1.0 μm filter, and the solid content remaining on the filter was recovered. The 25° C. conversion electrical conductivity of the desalted used abrasive slurry was 0.1 mS/cm.

Furthermore, after adding a pH adjuster (ammonia water) to adjust the pH value converted to 25 ° C. to 7.0 (7.5, 8.0, 8.5, 9.0), an ultrasonic disperser was used for distributed processing.

After the ultrasonic dispersion treatment, the dispersion was allowed to stand for 1 hour to separate into a supernatant and a sediment, and 1 L of abrasive slurry containing the sediment was recovered.

The concentration of the cerium oxide abrasive and the concentration of the glass component contained in the collected abrasive slurry were measured by the methods described above.

Next, in the same manner as the preparation of the regenerated abrasive slurry 1, regenerated abrasive slurries 53 to 57 were prepared along the abrasive regeneration process.

<Preparation of Recycled Abrasive Slurry 58>
First, using a 100 μm mesh filter, 1 L of used abrasive slurry was filtered to remove coarse foreign matter.

Next, the filtrate component containing the cerium oxide abrasive was diluted 10 times by volume with pure water, and then stirred for 30 minutes using a stirrer. The 25° C. conversion electrical conductivity of the desalted used abrasive slurry was 0.3 mS/cm.

After the stirring treatment, a pH adjuster (aqueous ammonia) was added to adjust the pH value at 25° C. to 9.0, and then dispersion treatment was performed using an ultrasonic disperser.

After the dispersion treatment, as a second step, a pH adjuster (aqueous sulfuric acid solution) is added to adjust the pH value at 25° C. to 7.0, and then stirred for 10 minutes using a stirrer. , the dispersion was allowed to stand for 1 hour, separated into a supernatant and a sediment by a natural sedimentation method, and the supernatant was discharged to recover 1.0 L of abrasive slurry containing the sediment. Thus, the glass component was removed and the cerium oxide component was concentrated.

The concentration of the cerium oxide abrasive and the concentration of the glass component contained in the recovered abrasive slurry were measured by the method described above, and the removal rate of the glass component for the used abrasive slurry 3 was similarly measured.

Next, in the same manner as the preparation of the regenerated abrasive slurry 1, a regenerated abrasive slurry 58 was prepared along the abrasive regeneration step.

<Preparation of Recycled Abrasive Slurry 59>
First, using a 100 μm mesh filter, 1 L of used abrasive slurry was filtered to remove coarse foreign matter.

Next, the filtrate component containing the cerium oxide abrasive was diluted with pure water to double the volume, and then stirred for 30 minutes using a stirrer.

The agitated abrasive slurry was filtered through a 1.0 μm filter, and the solid content remaining on the filter was recovered. The 25° C. conversion electrical conductivity of the desalted used abrasive slurry was 0.2 mS/cm.

Further, a pH adjuster (aqueous ammonia) was added to adjust the pH value at 25° C. to 9.0, followed by dispersion treatment using an ultrasonic disperser.

After the above dispersion treatment, a pH adjuster (aqueous sulfuric acid solution) is added to adjust the pH value to 7.0 at 25°C, and then stirred for 10 minutes using a stirrer. The mixture was allowed to stand, separated into a supernatant and a sediment by a natural sedimentation method, and the supernatant was discharged to recover 1.0 L of abrasive slurry containing the sediment. Thus, the glass component was removed and the cerium oxide component was concentrated.

The concentration of the cerium oxide abrasive and the concentration of the glass component contained in the recovered abrasive slurry were measured by the method described above, and the removal rate of the glass component for the used abrasive slurry 3 was similarly measured.

Next, in the same manner as the preparation of the regenerated abrasive slurry 1, a regenerated abrasive slurry 59 was prepared in accordance with the abrasive regeneration step.

<Preparation of Recycled Abrasive Slurry 60>
First, using a 100 μm mesh filter, 1 L of used abrasive slurry was filtered to remove coarse foreign matter.

Next, the filtrate component containing the cerium oxide abrasive was diluted with pure water to 4 times its volume, and then stirred for 30 minutes using a stirrer.

The agitated abrasive slurry was filtered through a 1.0 μm filter, and the solid content remaining on the filter was recovered. The 25° C. conversion electrical conductivity of the desalted used abrasive slurry was 0.1 mS/cm.

Further, a pH adjuster (aqueous ammonia) was added to adjust the pH value at 25° C. to 9.0, followed by dispersion treatment using an ultrasonic disperser.

After the above dispersion treatment, a pH adjuster (aqueous sulfuric acid solution) is added to adjust the pH value to 7.0 at 25°C, and then stirred for 10 minutes using a stirrer. The mixture was allowed to stand, separated into a supernatant and a sediment by a natural sedimentation method, and the supernatant was discharged to recover 1.0 L of abrasive slurry containing the sediment. Thus, the glass component was removed and the cerium oxide component was concentrated.

The concentration of the cerium oxide abrasive and the concentration of the glass component contained in the recovered abrasive slurry were measured by the method described above, and the removal rate of the glass component for the used abrasive slurry 3 was similarly measured.

Next, in the same manner as in the preparation of the regenerated abrasive slurry 1, a regenerated abrasive slurry 60 was prepared along the abrasive regeneration process.

<<Evaluation of Recycled Abrasive Slurry>>
[Removal rate of glass component]
The concentration of the cerium oxide abrasive and the concentration of the glass component contained in the recovered abrasive slurry were measured by the ICP emission spectroscopic plasma method (ICP-AES). Removal rate was measured.

The removal rate of the glass component is [1-(concentration of the glass component in the recycled abrasive slurry/concentration of the cerium oxide abrasive component)/(concentration of the cerium oxide abrasive component in the used abrasive slurry/concentration of the cerium oxide abrasive component). ]×100(%).

Next, the evaluation rank criteria were as follows.

× Removal rate is less than 50% ○ Removal rate is 50% or more and less than 80% ○○ Removal rate is 80% or more and less than 95% ○○○ Removal rate is 95% or more According to the present invention, the removal rate is 50% or more It is judged to have the effect of Preferably, the removal rate is 80% or more.

Table III shows the composition of the recycled abrasive slurries 43 to 60 and the removal rate of the glass component.

From Table III, from the used abrasive slurry used for polishing glass, dissolved glass components derived from the object to be polished, components dissolved from the glass itself, and ionic components such as pH adjusters were converted to 25°C. By adopting a dispersion treatment step in which desalting treatment is performed so that the electric conductivity value of is 0.3 mS / cm or less, and then the pH value converted to 25 ° C. is adjusted to a range of 8.0 or more, It was found that the removal rate of the glass component is improved. Therefore, in the first step, the abrasive grain component containing cerium oxide and the glass component are excellently separated from each other without adding a dispersant. was gotten.

Also, the recycled abrasive slurry No. 58 to 60, as a second step, a pH adjuster is added to the dispersion-treated abrasive slurry, and the pH value converted to 25° C. is adjusted from alkaline (9.0) to neutral (6.0). or more and less than 8.0), the abrasive grain component containing cerium oxide is aggregated and precipitated, and the separation and concentration treatment step is performed. It was found that a method for regenerating an abrasive with excellent separability from the glass component can be obtained.

REFERENCE SIGNS LIST 1 polishing apparatus 2 polishing surface plate 3 object to be polished 4 abrasive liquid 5 slurry nozzle 7 cleaning water 8 cleaning water injection nozzle 10 cleaning liquid containing abrasive 13 used abrasive slurry (mother liquor)
14 adjustment kettle 15 agitator 16a dilution water addition tank 16b pH adjuster supply tank 16c dispersant parish hot water tank 17 dilution water 18 mixture of abrasive grain component and glass component containing cerium oxide 19 abrasive grain component and glass component containing cerium oxide 20 Separation concentrate of abrasive grain component containing cerium oxide 21 Supernatant containing glass component 22 Component adjustment liquid 23 Regenerated abrasive slurry

Claims (13)

A method for regenerating an abrasive slurry for removing constituent components of an object to be polished from a used abrasive slurry containing an abrasive component and constituent components of an object to be polished, and recovering and regenerating the abrasive component, comprising:
a slurry recovery step of recovering the used abrasive slurry discharged from the polishing machine;
a desalting step of reducing the ion concentration of the collected used abrasive slurry;
a first step including a dispersion treatment step of adding a pH adjuster and a dispersant to the desalted abrasive slurry to disperse the abrasive component and the component of the object to be polished;
a second step of, after the first step, separating the abrasive component from the constituent components of the object to be polished to prepare a regenerated abrasive slurry from the abrasive component;
A method for regenerating an abrasive slurry, comprising: The second step includes a separating and concentrating step of separating the abrasive component and the constituent component of the object to be polished by natural sedimentation, centrifugation, salt-adding sedimentation, or filter filtration. 2. The method for regenerating abrasive slurry according to claim 1, further comprising an abrasive regeneration step of preparing a regenerated abrasive slurry from the concentrated abrasive component. 2. The desalting process, wherein the desalting process is performed so that the ion concentration of the used abrasive slurry becomes 5.0 mS/cm or less as an electrical conductivity value converted to 25° C. in the desalting process. 3. The method for regenerating abrasive slurry according to claim 1 or claim 2. 4. The method for regenerating abrasive slurry according to claim 3, wherein desalting is performed so that the ion concentration becomes 1.0 mS/cm or less as the value of the electrical conductivity. In the dispersion treatment step of the first step, the pH value of the used abrasive slurry converted to 25° C. is adjusted to 6.0 or higher with the pH adjuster, and the dispersant is added to the used 5. The abrasive according to any one of claims 1 to 4, characterized in that it is added within a range of 0.1 to 5.0% by mass with respect to the mass of the abrasive contained in the abrasive slurry. A method for regenerating an abrasive slurry. The pH adjuster is an inorganic acid, carboxylic acid, amine base or ammonium hydroxide, and the dispersant is a water-soluble anionic dispersant, a water-soluble cationic dispersant or a water-soluble amphoteric dispersant. 6. The method for regenerating abrasive slurry according to any one of claims 1 to 5, characterized in that: A method for regenerating an abrasive slurry for removing constituent components of an object to be polished from a used abrasive slurry containing an abrasive component and constituent components of an object to be polished, and recovering and regenerating the abrasive component, comprising:
a slurry recovery step of recovering the used abrasive slurry discharged from the polishing machine;
a desalting step of adjusting the ion concentration of the recovered used abrasive slurry to be 0.3 mS/cm or less as an electrical conductivity value converted to 25° C.; a dispersion treatment step of adding an adjusting agent to adjust the pH value of the used abrasive slurry to 8.0 or more at 25° C. conversion, and dispersing the abrasive component and the constituent components of the object to be polished; a first step comprising
a second step of, after the first step, separating the abrasive component from the constituent components of the object to be polished to prepare a regenerated abrasive slurry from the abrasive component;
A method for regenerating an abrasive slurry, comprising: In the second step, the abrasive component and the constituent component of the object to be polished are separated by natural sedimentation, centrifugation, sedimentation by adding salt, filter filtration, or coagulation sedimentation by pH value adjustment. 8. The method for regenerating abrasive slurry according to claim 7, comprising a concentration step and an abrasive regeneration step of preparing a regenerated abrasive slurry from the separated and concentrated abrasive component. 9. The method for regenerating abrasive slurry according to claim 7, wherein the desalting treatment is performed so that the ion concentration becomes 0.1 mS/cm or less as the electric conductivity value. 8. The coagulating sedimentation is performed in the second step by adjusting the pH value of the used abrasive slurry converted to 25° C. to a range of 6.0 or more and less than 8.0. A method for regenerating an abrasive slurry according to any one of claims 9 to 9. 11. The method for regenerating abrasive slurry according to any one of claims 7 to 10, wherein the pH adjuster is an inorganic acid, a carboxylic acid, an amine base, or ammonium hydroxide. By the method for regenerating an abrasive slurry according to any one of claims 1 to 11, a used abrasive slurry containing at least an abrasive component and constituent components of an object to be polished is removed from the object to be polished. An abrasive slurry regeneration system for removing the constituent components of and recovering and regenerating the abrasive components,
a polishing process section having a polishing machine; an abrasive slurry supply process section having a slurry supply tank for supplying abrasive slurry to the polishing process section; and a recovery for recovering the used abrasive slurry discharged from the polishing machine. a slurry recovery process unit having a mixed liquid tank;
a desalting process section having a dilution water supply tank for reducing the ion concentration of the recovered abrasive slurry, a desalting processing tank, a desalting device, and an ion concentration measuring section for measuring the ion concentration;
A dispersing step having an additive supply tank for supplying a pH adjuster and a dispersant to the desalted abrasive slurry, and a dispersion tank and a dispersion processing device for dispersing the abrasive component and the constituent components of the object to be polished. Department and
a separation/concentration process unit having a separation/concentration tank for separating and concentrating the abrasive component and the constituent components of the object to be polished;
an abrasive regeneration process section having a regenerated abrasive slurry preparation tank having an additive supply tank for adding a pH adjuster and a dispersant to the separated and concentrated abrasive component;
A polishing slurry regeneration system comprising: 13. The polishing according to claim 12, wherein the separating and concentrating process unit has a natural sedimentation means, a centrifugal means, a means for sedimentation separation by adding salt, a filter filtration means, or a flocculation sedimentation means by pH adjustment. A system for regenerating agent slurry.

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