JP2017109291A - Manufacturing method of recycled abrasive and manufacturing apparatus of recycled abrasive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a recycled abrasive capable of forming the recycled abrasive which is easy to use as an abrasive.SOLUTION: A manufacturing method of a recycled abrasive includes the steps of: melting gas into aqueous dispersion of a used abrasive; forming a coagulated body by freezing the aqueous dispersion; and melting the coagulated body.SELECTED DRAWING: Figure 1

Description

  The present invention generally relates to a method for manufacturing a recycled abrasive and an apparatus for manufacturing the same, and more particularly to a method for manufacturing a recycled abrasive from a used abrasive and an apparatus for manufacturing the same.

  Conventionally, a polishing material containing rare earth such as cerium and lanthanum is used to polish glass products such as optical lenses and glass substrates, and electronic parts such as silicon wafers. When a glass product or the like is polished using this abrasive, the glass product or the like can be polished by rubbing a polishing pad impregnated with an aqueous dispersion of the abrasive against the glass product or the like. Unused abrasives contain secondary particles with an appropriate particle size and are therefore equipped with a polishing ability. However, secondary particles are crushed in the course of using abrasives, resulting in small primary particles. As a result, the polishing ability decreases. In general, used abrasives having a reduced polishing ability are discarded, but due to the recent rise in the price of rare earths, a method for reusing used abrasives is required.

  For example, in Patent Document 1, after collecting an aqueous dispersion of a used glass abrasive, the aqueous dispersion is frozen to form secondary particles of the glass abrasive between ice crystals. A reusable glass abrasive (recycled abrasive) is obtained by melting ice to form an aqueous dispersion containing secondary particles of glass abrasive and further removing water from the aqueous dispersion. Is disclosed.

  Patent Document 2 includes a refrigerant, water, and a glass abrasive, respectively, after dripping a used slurry of glass abrasive into a refrigerant and freezing it, and then allowing the frozen slurry and refrigerant to stand and melt. It is disclosed that a recycled abrasive is obtained by separating into three layers and further removing refrigerant and water from the glass abrasive layer.

  In the methods of Patent Documents 1 and 2, secondary particles of abrasive particles are formed in the process of freezing the aqueous dispersion of used abrasives. The secondary particles have a larger diameter than the primary particles in the used abrasive. By including these secondary particles in the recycled abrasive, the recycled abrasive can be used for polishing glass products.

JP 2010-214515 A Japanese Patent Application Laid-Open No. 2015-150658

  However, in the method disclosed in Patent Document 1, secondary particles may aggregate to form an aggregate having an excessively large diameter. Such an agglomerate precipitates immediately even when dispersed in water, is trapped by a foreign matter removal filter of the polishing pad, or requires a step of pulverizing the agglomerate. It is difficult to use as a material.

  Further, in the method disclosed in Patent Document 2, since the aqueous dispersion of the used abrasive is frozen more quickly than the method of Patent Document 1, formation of aggregates having a diameter that is too large is suppressed. There is a need to further suppress the formation of complex aggregates.

  This invention is made | formed in view of said point, and it aims at providing the manufacturing method of the reproduction | regeneration abrasive | polishing material which is easy to use as an abrasive | polishing material.

The method for producing a recycled abrasive according to the present invention is as follows:
Dissolving gas in an aqueous dispersion of used abrasive;
Freezing the aqueous dispersion to produce a solidified body;
And a step of melting the solidified body.

An apparatus for producing a recycled abrasive according to the present invention comprises:
A gas introduction part for introducing gas into an aqueous dispersion of used abrasives;
A freezing part for freezing the aqueous dispersion to produce a solidified body,
And a melting part for melting the solidified body.

  The method for producing a recycled abrasive according to the present invention can produce a recycled abrasive that is easy to use as an abrasive.

It is the schematic of the 1st manufacturing apparatus which is an example of the manufacturing apparatus of a recycled abrasive material. It is the schematic of the 2nd manufacturing apparatus which is an example of the manufacturing apparatus of a recycled abrasive material. It is the schematic of the 3rd manufacturing apparatus which is an example of the manufacturing apparatus of a recycled abrasive material. It is a graph which shows the result of having measured the particle size distribution of the aggregate. It is a graph which shows the result of having measured the particle size distribution of the aggregate before and behind applying an ultrasonic vibration to an aggregate.

  Hereinafter, modes for carrying out the present invention will be described.

  The method for producing a recycled abrasive according to this embodiment includes a step of dissolving a gas in an aqueous dispersion of a used abrasive, a step of freezing the aqueous dispersion to produce a solidified body, and a melting of the solidified body. And a step of causing.

  In the method for producing a recycled abrasive according to the present embodiment, when an aqueous dispersion of a used abrasive in which a gas is dissolved is frozen to produce a solidified body, an aggregate in which particles of the used abrasive are aggregated in the solidified body. It is formed. Traces of gas bubbles are formed in the aggregate. When the solidified body is melted, the aggregate precipitates. Aggregates are brittle due to traces of gas bubbles. When this aggregate is recovered and used for polishing, the aggregate is easily crushed by the polishing pressure, and secondary particles suitable for polishing are formed. For this reason, the aggregate can be used as a recycled abrasive as it is. Further, since the aggregate can be easily pulverized by stirring vibration, ultrasonic treatment, etc., secondary particles suitable for polishing can be easily formed. For this reason, a recycled abrasive can also be obtained by pulverizing the aggregate.

  A method for manufacturing a recycled abrasive according to this embodiment will be described for each step.

(Process of preparing an aqueous dispersion of used abrasive)
In this step, an aqueous dispersion of used abrasive (hereinafter also simply referred to as “aqueous dispersion”) is prepared. The used abrasive is an abrasive after being used for polishing an object to be polished. Examples of the object to be polished include optical products such as optical lenses, prisms, and mirrors, and glass products such as glass substrates such as hard disks and liquid crystal panels. The used aqueous dispersion of abrasive is a slurry in which used abrasive is dispersed in water.

  In the present embodiment, the abrasive preferably contains a rare earth element oxide. That is, it is preferable that the used abrasive contains an oxide of a rare earth element, and accordingly, the recycled abrasive also preferably contains an oxide of a rare earth element. In this case, it is possible to polish an object to be polished containing silicon in particular by chemical polishing using the abrasive and the recycled abrasive. Examples of rare earth elements include cerium, lanthanum, neodymium, and the like.

In the present embodiment, it is particularly preferable that the rare earth element oxide contains cerium oxide. Hereinafter, the mechanism of polishing using an abrasive will be described by taking as an example the case of polishing a glass product with an abrasive containing cerium oxide. When polishing a glass product using an abrasive containing cerium oxide, a part of Si forming a Si—O bond in silicon oxide (SiO ₂ ), which is the main component of glass, is oxidized in the abrasive. It is replaced with Ce in cerium (CeO ₂ ), and a Ce—O bond is formed between the abrasive and the glass. Since this Ce—O bond is weaker than the Si—O bond, it is easily dissociated. Therefore, the glass structure around the Ce—O bond is easily peeled off from the glass product surface. When polishing a glass product using an abrasive containing cerium oxide, the surface of the glass product may be smoothed because distortions, protrusions, etc. existing on the surface of the glass product are peeled off due to the characteristics of the above cerium oxide. it can. In addition, since cerium oxide has a lower hardness than glass, when the object to be polished, which is a glass product, is polished, the object to be polished can be prevented from being damaged.

  Many of the used abrasive particles (hereinafter also referred to as abrasive particles) are primary particles having a small particle size. This is because the particles in the unused abrasive are crushed during the polishing process, the particle size is reduced, and primary particles are formed. In addition, components derived from the object to be polished are mixed in the aqueous dispersion of the used abrasive. In particular, when the object to be polished is a glass product, an alkaline component derived from the glass product such as sodium is mixed in the aqueous dispersion. In this case, the aqueous dispersion is alkaline.

  The component derived from the object to be polished may include coarse foreign matters such as a coarse glass structure formed by rough cutting before polishing and a coarse glass structure formed by polishing. These coarse foreign substances are preferably removed from the aqueous dispersion in the step of preparing an aqueous dispersion of the used abrasive.

(Step of dissolving gas in aqueous dispersion)
In this step, gas is dissolved in the aqueous dispersion. The gas is a gas that can be dissolved in the aqueous dispersion.

In particular, in this embodiment, it is preferable that the gas contains an acidic gas. When the aqueous dispersion is alkaline, the gas can be easily dissolved in the aqueous dispersion by including an acidic gas. For example, the acidic gas may include one or more selected from the group consisting of carbon dioxide (CO ₂ ), nitrogen oxide (NO _x ), and sulfur dioxide (SO ₂ ). In the present embodiment, it is particularly preferable that the acidic gas contains carbon dioxide. This is because carbon dioxide is not toxic, has high solubility in water, and has solubility in refrigerants such as silicone oil.

  Examples of the method for dissolving the gas in the aqueous dispersion include a method for directly dissolving the gas in the aqueous dispersion, and a method for moving the gas from the refrigerant to the aqueous dispersion when using the refrigerant.

  The method for directly dissolving the gas in the aqueous dispersion is not particularly limited as long as the gas dissolves in the aqueous dispersion. As this method, for example, bubbling a gas in an aqueous dispersion, filling a gas in a sealed container containing the aqueous dispersion and dissolving the gas in the aqueous dispersion, a solid that generates a gas such as dry ice And the like, and spraying the aqueous dispersion into a container filled with gas. In particular, in this embodiment, it is preferable to dissolve the gas in the aqueous dispersion by bubbling the gas in the aqueous dispersion. In this case, the amount of gas dissolved in the aqueous dispersion can be easily adjusted.

  The method of moving the gas from the refrigerant to the aqueous dispersion is a method of moving the gas from the refrigerant to the aqueous dispersion by bringing the aqueous dispersion into contact with the refrigerant into which the gas has been introduced. Examples of the method of bringing the refrigerant into contact with the aqueous dispersion include dropping the aqueous dispersion into the refrigerant and mixing the refrigerant and the aqueous dispersion. This will be described later.

(Step of freezing the aqueous dispersion to produce a solidified body)
In this step, the aqueous dispersion in which the gas is dissolved is cooled and solidified to produce a solidified body of the aqueous dispersion. In this step, spent abrasive particles and gas are excluded from the crystals as the water freezes to form crystals. For this reason, an aggregate in which abrasive particles are aggregated is formed in the solidified body. Gas bubbles are formed in the solidified body.

  Examples of the method of freezing the aqueous dispersion include a method of cooling a container containing the aqueous dispersion and a method of bringing a refrigerant into contact with the aqueous dispersion.

  In the method of cooling the container containing the aqueous dispersion, the aqueous dispersion in which the gas is dissolved is put in the container, and the aqueous dispersion is cooled together with the container to solidify the aqueous dispersion to produce a solidified body. . The cooling temperature and the cooling time are appropriately set depending on the composition of the aqueous dispersion and the amount of the aqueous dispersion. In the method of bringing the refrigerant into contact with the aqueous dispersion, the aqueous dispersion is solidified by bringing the aqueous dispersion into contact with the cooled refrigerant to produce a solidified body. In particular, in the present embodiment, it is preferable to freeze the aqueous dispersion by dripping the aqueous dispersion into a refrigerant to produce the solidified body. In this case, since the specific surface area of the aqueous dispersion during solidification can be increased, the aqueous dispersion can be solidified quickly.

  This refrigerant is not particularly limited as long as it has a melting point lower than that of water, but preferably has a specific gravity different from that of water. For example, the refrigerant is preferably oil or fat. It is also preferable that the refrigerant is silicone oil. It is preferable that the temperature of a refrigerant | coolant exists in the range of -5 degreeC--30 degreeC, for example. In this case, an aggregate having an appropriate particle size can be formed efficiently.

  When the aqueous dispersion is solidified with the refrigerant, as described above, the gas is introduced into the refrigerant, the aqueous dispersion is dropped into the refrigerant, and the gas is moved from the refrigerant to the aqueous dispersion. May be dissolved. In this case, the introduction of the gas into the aqueous dispersion and the production of the solidified body by freezing the aqueous dispersion can be performed at once. In addition, when the aqueous dispersion is dropped into the refrigerant into which the gas has been introduced / dissolved, the gas in the refrigerant moves to the aqueous dispersion, and the temperature of the refrigerant in the vicinity of the droplets of the aqueous dispersion rises. Saturation solubility decreases. For this reason, part of the gas dissolved in the refrigerant is vaporized, and the heat of vaporization is taken away from the refrigerant, so that the temperature of the refrigerant decreases around the droplets. When the aqueous dispersion is dripped into the refrigerant into which the gas is introduced to solidify the aqueous dispersion, the aqueous dispersion can be solidified faster than when the gas is not introduced into the refrigerant. Note that not only an aqueous dispersion in which gas is not dissolved but also an aqueous dispersion in which gas is dissolved may be introduced into the refrigerant into which the gas has been introduced. The method for introducing and dissolving the gas in the refrigerant is not particularly limited. In particular, in this embodiment, it is preferable to introduce and dissolve the gas in the refrigerant by bubbling the gas into the refrigerant. In this case, the amount of gas dissolved in the refrigerant can be easily adjusted.

  As a method of bringing the refrigerant into contact with the aqueous dispersion, a method of mixing the refrigerant and the aqueous dispersion may be employed. In this method, the cooled refrigerant and the aqueous dispersion are mixed to solidify only the aqueous dispersion to produce a solidified body. In this case, the solidified body can be produced by an easy method of mixing the refrigerant and the aqueous dispersion. In the method of mixing the refrigerant and the aqueous dispersion, gas may be introduced into the aqueous dispersion, gas may be introduced into the refrigerant, or gas is introduced into both the aqueous dispersion and the refrigerant. Also good. In particular, when the gas is moved from the refrigerant to the aqueous dispersion, the gas is preferably carbon dioxide and the refrigerant is preferably silicone oil. Since the carbon dioxide is easily dissolved in the refrigerant and water and more easily dissolved in water than the refrigerant, the carbon dioxide easily moves from the refrigerant to the aqueous dispersion.

(Process of melting the solidified body)
In the step of melting the solidified body, the solidified body prepared by freezing the aqueous dispersion is melted. The method for melting the solidified body is not particularly limited. For example, the solidified body can be melted by allowing the solidified body to stand at room temperature. Of course, the solidified body may be melted by heating the solidified body.

  When a solidified body is prepared by cooling a container containing an aqueous dispersion, when the solidified body melts, a layer mainly containing aggregates (recycled abrasive layer) and a layer mainly containing water Two layers with (water layer) are formed. Aggregates are likely to precipitate in water, so the recycled abrasive layer is the lower layer and the aqueous layer is the upper layer. Aggregates are collected from the recycled abrasive layer.

  When a solidified body is prepared by bringing a refrigerant and an aqueous dispersion into contact with each other and the solidified body is melted in a state where the refrigerant and the solidified body coexist, when the solidified body melts, a layer mainly containing the refrigerant (refrigerant layer) ), Three layers of a layer mainly containing aggregates (recycled abrasive layer) and a layer mainly containing water (water layer) are formed. When the specific gravity of the refrigerant is smaller than that of water, an aqueous layer is disposed on the recycled abrasive layer, and the refrigerant layer is disposed on the aqueous layer. Aggregates are collected from the recycled abrasive layer. Note that the refrigerant may be recovered from the refrigerant layer and reused.

  When the solidified body melts, an aggregate of abrasive particles precipitates. Gas escapes from this aggregate, but it is brittle because traces of gas bubbles are formed.

  When this brittle aggregate is used for polishing, the aggregate is pulverized by the polishing pressure, and secondary particles suitable for polishing are easily formed. For this reason, the collected aggregate can be used as a recycled abrasive. Further, since the aggregate can be easily pulverized by an operation such as stirring vibration, secondary particles suitable for polishing can be easily formed. For this reason, a recycled abrasive may be obtained by pulverizing the collected aggregates with stirring vibration or the like.

  The recycled abrasive may be washed with water. In this case, components derived from the object to be polished contained in the recycled abrasive can be reduced, and the purity of the recycled abrasive can be increased.

  Examples of the method for producing the recycled abrasive material described above (Production Method Example 1 to Production Method Example 3) are shown below. The method for producing the recycled abrasive is not limited to these examples.

(Production Method Example 1)
In Production Method Example 1, first, an aqueous dispersion of a used abrasive containing cerium oxide is prepared.

  Next, the gas is dissolved in the aqueous dispersion. The gas is, for example, carbon dioxide. The gas is dissolved in the aqueous dispersion by bubbling the gas in the aqueous dispersion. In Production Method Example 1, particularly when the gas is carbon dioxide, the amount of carbon dioxide supplied to the aqueous dispersion by bubbling is within a range of 0.5 to 5 L in a standard state with respect to 1 L of the aqueous dispersion. Preferably there is. In this case, sufficient traces of carbon dioxide bubbles can be formed in the aggregate.

  Next, the aqueous dispersion is frozen to produce a solidified body. In Production Method Example 1, as a method of freezing the aqueous dispersion, a method of cooling the container containing the aqueous dispersion can be employed. For example, the temperature during cooling is preferably in the range of −10 ° C. to −25 ° C., and more preferably in the range of −15 ° C. to −20 ° C. In this case, it can suppress that an aggregate becomes large too much. The cooling time is preferably 1 hour or longer, and more preferably 2 hours or longer.

  Next, the solidified body is melted. In Production Method Example 1, the solidified body of the aqueous dispersion in the container can be melted by allowing it to stand at room temperature. When the solidified body is melted, the solidified body forms two layers of a recycled abrasive layer mainly containing an aggregate of abrasive particles and an aqueous layer mainly containing water. Aggregates are collected from the recycled abrasive layer.

(Production Method Example 2)
In Production Method Example 2, as in Production Method Example 1, after preparing an aqueous dispersion of used abrasive, carbon dioxide is dissolved in the aqueous dispersion.

  Next, the aqueous dispersion is dropped into the refrigerant. When the aqueous dispersion is dropped into the refrigerant, the aqueous dispersion is frozen in the refrigerant to produce a solidified body of the aqueous dispersion. In Production Method Example 2, silicone oil is used as the refrigerant. For example, the temperature of the refrigerant is preferably in the range of −5 ° C. to −30 ° C., and more preferably in the range of −10 ° C. to −20 ° C. In this case, a spherical solidified body can be formed, and the size of the aggregate can be made uniform.

  Next, the solidified body is recovered together with a part of the refrigerant, and the solidified body is melted in a state where the refrigerant and the solidified body are mixed. In Production Method Example 2, when the solidified body is melted, a recycled abrasive layer mainly containing aggregates of abrasive particles, an aqueous layer mainly containing water, and a refrigerant layer mainly containing refrigerant The three layers are formed. Aggregates are collected from the recycled abrasive layer.

  In production method example 2, a solid dispersion is prepared by dripping an aqueous dispersion into a refrigerant, and after the coagulated body mixed with the refrigerant is recovered, the solidified body is continuously melted and melted in order to melt the solidified body. Can be done automatically.

(Production Method Example 3)
In Production Method Example 3, first, as in Production Method Example 2, an aqueous dispersion of used abrasive is prepared.

  Next, a refrigerant is prepared and carbon dioxide is dissolved in the refrigerant. In Production Method Example 3, silicon oil is used as the refrigerant, and carbon dioxide is bubbled into the silicone oil to dissolve carbon dioxide in the refrigerant. In Production Method Example 3, the temperature of the refrigerant is, for example, preferably in the range of −5 ° C. to −30 ° C., and more preferably in the range of −10 ° C. to −20 ° C. In this case, a spherical solidified body can be formed, and the size of the aggregate can be made uniform. Further, when the gas is carbon dioxide, it is preferable to continue bubbling to the refrigerant until at least the saturated dissolution amount at the temperature of the refrigerant. In this case, sufficient traces of carbon dioxide bubbles can be formed in the aggregate of abrasive particles.

  Next, an aqueous dispersion is dropped into the refrigerant. When the aqueous dispersion is dropped into the refrigerant, the gas moves from the refrigerant to the aqueous dispersion to dissolve the gas in the aqueous dispersion, and the aqueous dispersion is frozen to produce a solidified body.

  Next, the solidified body is recovered together with a part of the refrigerant, and the solidified body is melted in a state where the refrigerant and the solidified body are mixed. In Production Method Example 3, when the solidified body is melted, a recycled abrasive layer mainly containing aggregates of abrasive particles, an aqueous layer mainly containing water, and a refrigerant layer mainly containing refrigerant The three layers are formed. Aggregates are collected from the recycled abrasive layer.

  In Production Method Example 3, the aqueous dispersion is dropped into the refrigerant into which the gas is introduced to dissolve the gas in the aqueous dispersion, and a solidified body is produced. After the solidified body mixed with the refrigerant is recovered, the solidified body is removed. In order to melt, the gas can be dissolved in the aqueous dispersion, the solidified body can be produced, and the solidified body can be melted continuously.

  Hereinafter, the manufacturing apparatus of the recycled abrasive material which concerns on this embodiment is demonstrated.

  The recycled abrasive manufacturing apparatus according to the present embodiment includes a gas introducing unit that introduces gas into an aqueous dispersion of used abrasive, a freezing unit that freezes the aqueous dispersion to produce a solidified body, and a solidified body. And a melting part for melting.

  Hereinafter, a first manufacturing apparatus, a second manufacturing apparatus, and a third manufacturing apparatus, which are examples of a manufacturing apparatus for a recycle abrasive according to this embodiment, will be described with reference to FIGS. In addition, the manufacturing apparatus of a recycled abrasive is not limited to the structure of a 1st manufacturing apparatus, a 2nd manufacturing apparatus, and a 3rd manufacturing apparatus.

(First manufacturing equipment)
As shown in FIG. 1, the first manufacturing apparatus includes a storage tank 11, a gas introduction device 12, a freezing tank 13, and a melting tank 15.

  The storage tank 11 is a tank for storing an aqueous dispersion. A storage tank will not be specifically limited if an aqueous dispersion can be stored.

  The gas introduction device 12 is a device that introduces gas into the aqueous dispersion stored in the storage tank 11. The gas introduction device 12 includes a gas supply source 120 such as a gas cylinder, and a supply path 121 that connects the gas supply source 120 and the storage tank 11. The gas in the gas supply source 120 is introduced into the aqueous dispersion stored in the storage tank 11 through the supply path 121, whereby the gas is bubbled with respect to the aqueous dispersion. The gas introduction device 12 is not limited as long as gas can be introduced into the aqueous dispersion in the storage tank 11.

  The freezing tank 13 is a tank for storing the aqueous dispersion in the storage tank 11 and freezing the aqueous dispersion to produce a solidified body. The freezing tank 13 is not particularly limited as long as the aqueous dispersion can be stored and the aqueous dispersion can be frozen. The freezing tank 13 may be connected to the storage tank 11 via a transfer path for transferring the aqueous dispersion in the storage tank 11 to the freezing tank 13. This transfer path may include, for example, a pump that sucks up the aqueous dispersion in the storage tank 11, and includes transfer means for transferring the aqueous dispersion using the difference in height between the storage tank 11 and the freezing tank 13. It may be.

  The freezing tank 13 is provided with a cooling device 14. The cooling device 14 is a device that can cool and freeze the aqueous dispersion stored in the freezing tank 13. The cooling type of the cooling device 14 may be a vapor compression type, a vapor absorption type, a Peltier effect type, or a chemical heat pump type. The cooling device 14 can cool the aqueous dispersion to at least −10 to −25 ° C.

  The melting tank 15 is a tank for melting the solidified body produced in the freezing tank 13 and storing the melted solidified body. In the melting tank 15, the solidified body may be allowed to stand and melt at room temperature, or the solidified body may be heated to melt. When the solidified body is heated and melted, the melting tank 15 may include a heater. The melting tank 15 is not particularly limited as long as it can store a solidified body of an aqueous dispersion and a melted solidified body.

  A process of manufacturing the recycled abrasive using the first manufacturing apparatus will be described with reference to FIG. First, gas is bubbled into the aqueous dispersion of used abrasives stored in the storage tank 11 by the gas introducing device 12 to dissolve the gas in the aqueous dispersion. Next, after the aqueous dispersion is transferred from the storage tank 11 to the freezing tank 13, the aqueous dispersion in the freezing tank 13 is cooled by the cooling device 14 and frozen to produce a solidified body. Next, the solidified body produced in the freezing tank 13 is transferred to the melting tank 15, and the solidified body is melted in the melting tank 15. In the first manufacturing apparatus, when the solidified body is melted in the melting tank 15, two layers of a recycled abrasive layer mainly containing an aggregate of abrasive particles and an aqueous layer mainly containing water are formed (FIG. 1). And an aggregate is collect | recovered from this reproduction | regeneration abrasive material layer.

  For this reason, in the first manufacturing apparatus, the storage tank 11 and the gas introduction device 12 are included in the gas introduction unit 1, the freezing tank 13 and the cooling device 14 are included in the freezing unit 2, and the melting tank 15 is included in the melting unit 3. (See FIG. 1).

  In addition, in the 1st manufacturing apparatus, although the storage tank 11, the freezing tank 13, and the melting tank 15 are separate structures, it is not restricted to this. For example, the storage tank 11 may double as the freezing tank 13, the freezing tank 13 may double as the melting tank 15, and the storage tank 11 may double as the freezing tank 13 and the melting tank 15. That is, the aqueous dispersion stored in the storage tank 11 may be cooled and frozen to produce a solidified body. The solidified body prepared in the freezing tank 13 may be thawed in the freezing tank 13, and after the solidified body of the aqueous dispersion is prepared in the storage tank 11, the solidified body may be thawed in the storage tank 11. .

(Second manufacturing equipment)
The second manufacturing apparatus shown in FIG. 2 includes a storage tank 21, a gas introduction apparatus 22, a dropping apparatus 23, a refrigerant tank 24, and a melting tank 26.

  The storage tank 21 and the gas introduction device 22 in the second production apparatus may be the same as the storage tank 11 and the gas introduction apparatus 12 in the first production apparatus, respectively. The gas introduction device 22 includes a gas supply source 220 such as a gas cylinder, and a supply path 221 that connects the gas supply source 220 and the storage tank 21.

  The dropping device 23 is a device that drops the aqueous dispersion stored in the storage tank 21 into the refrigerant tank 24. The dripping device 23 is connected to the storage tank 21 via a transfer path for transferring the aqueous dispersion in the storage tank 21. The dropping device 23 is not particularly limited as long as the aqueous dispersion can be dropped, and examples thereof include a liquid dispensing device (dispenser), a dropping funnel, a burette, and a dropper.

  The refrigerant tank 24 is a tank in which the cooled refrigerant can be stored and the aqueous dispersion dropped from the dropping device 23 is cooled and frozen to produce a solidified body. The refrigerant tank 24 is not particularly limited as long as it can store the refrigerant.

  The refrigerant tank 24 is provided with a cooling device 25. The cooling device 25 is a device that can cool the refrigerant stored in the refrigerant tank 24. The cooling type of the cooling device 25 may be a vapor compression type, a vapor absorption type, a Peltier effect type, or a chemical heat pump type. The cooling device 25 can cool the refrigerant to at least −5 to −30 ° C.

  The melting tank 26 is a tank capable of storing a mixture of the solidified body prepared in the refrigerant tank 24 and the refrigerant and storing a melt of the solidified body and the refrigerant. For this reason, the melting tank 26 may be connected to the refrigerant tank 24 through a transfer path for transferring a mixture of the solidified body and the melt produced in the refrigerant tank 24. For example, the transfer path may include a pump for sucking up the refrigerant and the solidified body in the refrigerant tank 24. In the melting tank 26, the solidified body may be allowed to stand and melt at room temperature, or the solidified body may be heated to melt. When the solidified body is heated and melted, the melting tank 26 may include a heater. The melting tank 26 is not particularly limited as long as it can store a refrigerant, a solidified body, and a melt of the solidified body.

  A process of manufacturing the recycled abrasive using the second manufacturing apparatus will be described with reference to FIG. First, gas is bubbled into the aqueous dispersion of used abrasives stored in the storage tank 21 by the gas introducing device 22 to dissolve the gas in the aqueous dispersion. Next, the aqueous dispersion in the storage tank 21 is dropped into the refrigerant stored in the refrigerant tank 24 by the dropping device 23. The aqueous dispersion is cooled by a refrigerant and frozen to produce a solidified body. Next, the solidified body is transferred to the melting tank 26 while being mixed with a part of the refrigerant. The solidified body melts in the melting tank 26. In the second manufacturing apparatus, when the solidified body is melted in the melting tank 26, a regenerated abrasive layer mainly containing aggregates of abrasive particles, an aqueous layer mainly containing water, and a refrigerant layer mainly containing refrigerant. Three layers are formed. And an aggregate is collect | recovered from this reproduction | regeneration abrasive material layer.

  For this reason, in the 2nd manufacturing apparatus 1, the storage tank 21 and the gas introduction apparatus 22 are contained in the gas introduction part 1, the dripping apparatus 23, the refrigerant tank 24, and the cooling device 25 are contained in the freezing part 2, and the melting tank 26 is included. It is contained in the melting | dissolving part 3 (refer FIG. 2).

(Third manufacturing equipment)
The third manufacturing apparatus shown in FIG. 3 includes a storage tank 31, a dropping device 32, a refrigerant tank 33, a refrigerant gas introduction device 34, and a melting tank 36.

  The storage tank 31 is a tank for storing a used aqueous dispersion. The storage tank 31 will not be specifically limited if an aqueous dispersion can be stored.

  The dropping device 32 is a device that drops the aqueous dispersion stored in the storage tank 31 to the refrigerant tank 33, and the configuration thereof may be the same as that of the dropping apparatus 23 of the second manufacturing apparatus. The dropping device 32 is connected to the storage tank 31 through a transfer path for transferring the aqueous dispersion in the storage tank 31.

  The refrigerant tank 33 is a tank in which the cooled refrigerant can be stored and the water dispersion dropped from the dropping device 32 is cooled and frozen to produce a solidified body. The configuration of the refrigerant tank 33 may be the same as that of the refrigerant tank 24 of the second manufacturing apparatus.

  The refrigerant gas introduction device 34 is a device that introduces gas into the refrigerant stored in the refrigerant tank 33. The refrigerant gas introduction device 34 includes a gas supply source 340 such as a gas cylinder, and a supply path 341 that connects the gas supply source 340 and the refrigerant storage tank 33. The gas in the gas supply source 340 is introduced into the refrigerant stored in the refrigerant tank 33 through the supply path 341, so that the gas is bubbled with respect to the refrigerant. The configuration of the refrigerant gas introducing device 34 is not limited as long as the gas can be bubbled through the refrigerant in the refrigerant tank 33.

  The refrigerant tank 33 is provided with a cooling device 35. The configuration of the cooling device 35 may be the same as that of the cooling device 25 of the second manufacturing apparatus. The cooling device 35 can cool the refrigerant to at least −5 to −30 ° C.

  The melting tank 36 is a tank that can store a mixture of the solidified body and the refrigerant produced in the refrigerant tank 33 and can store a melt of the solidified body and the refrigerant. For this reason, the melting tank 36 may be connected to the refrigerant tank 33 via a transfer path for transferring a mixture of the solidified body and the melt produced in the refrigerant tank 33. This transfer path may include, for example, a pump for sucking up the refrigerant and the solidified body in the refrigerant tank 33. In the melting tank 36, the solidified body may be allowed to stand and melt at room temperature, or the solidified body may be heated and melted. When the solidified body is heated and melted, the melting tank 36 may include a heater. The melting tank 36 is not particularly limited as long as it can store a refrigerant, a solidified body, and a melt of the solidified body.

  A process of manufacturing the recycled abrasive using the third manufacturing apparatus will be described with reference to FIG. First, gas is bubbled into the refrigerant stored in the refrigerant tank 33 by the refrigerant gas introduction device 34 to dissolve the gas in the refrigerant. Next, the aqueous dispersion of used abrasives stored in the storage tank 31 is dropped onto the refrigerant stored in the refrigerant tank 33 by the dropping device 32. At this time, the gas dissolved in the refrigerant moves to the dropped aqueous dispersion, and the aqueous dispersion is cooled and frozen by the refrigerant to produce a solidified body. Next, the solidified body is transferred to the melting tank 36 while being mixed with a part of the refrigerant. The solidified body melts in the melting tank 36. In the third manufacturing apparatus, when the solidified body is melted in the melting tank 36, a recycled abrasive material layer mainly containing aggregates of abrasive particles, an aqueous layer mainly containing water, and a refrigerant layer mainly containing refrigerant. Three layers are formed. And an aggregate is collect | recovered from this reproduction | regeneration abrasive material layer.

  For this reason, in the third manufacturing apparatus, the storage tank 31, the dropping apparatus 32, the refrigerant tank 33, the refrigerant gas introduction apparatus 34, and the cooling apparatus 35 are included in the gas introduction section 1 and the freezing apparatus 2, and the melting tank 36 is the melting section. 3 (see FIG. 3).

  In the second manufacturing apparatus and the third manufacturing apparatus, three layers of a recycled abrasive material layer, an aqueous layer, and a refrigerant layer are formed in the melting part, and the refrigerant is recovered from the refrigerant layer, It may be used again as a refrigerant.

  Hereinafter, the present invention will be specifically described by way of examples.

(Examples 1-6, Comparative Examples 1-3)
A polishing agent was prepared by dispersing 1 kg of an abrasive containing a mixture of cerium oxide and lanthanum oxide in 20 kg of water, and a glass product was polished using this polishing solution. Subsequently, the coarse glass structure was removed from the polishing liquid by passing the polishing liquid through a sieve having an opening of 0.045 mm. As a result, 20 kg of an aqueous dispersion of used abrasive was prepared. After collecting a small amount of this aqueous dispersion and evaporating the water, the composition of the used abrasive was analyzed using a fluorescent X-ray analyzer (trade name: RIX1000, manufactured by Rigaku Corporation). It contained 40 mass%, lanthanum oxide 16 mass%, praseodymium oxide 3 mass%, neodymium oxide 1 mass%, silicon oxide 32 mass%, and aluminum oxide 8 mass%. In addition, trace amounts of iron and sodium were detected.

  Next, carbon dioxide was bubbled into the refrigerant to dissolve the carbon dioxide in the refrigerant. By dripping the aqueous dispersion into the refrigerant, the gas in the refrigerant was moved to the aqueous dispersion and the aqueous dispersion was frozen to produce a solidified body. Pure silicone oil was used as the refrigerant. The bubbling amount of carbon dioxide, the temperature of the refrigerant, and the cooling time of the aqueous dispersion (cooling holding time after completion of the dropping step) are as shown in Table 1 below.

  Next, the solidified body was recovered in a state where it was mixed with some refrigerant. This solidified body was melted by allowing it to stand at room temperature for 2 hours in a state where it was mixed with some refrigerant. As a result, three layers were formed: a refrigerant layer mainly containing a refrigerant, an aqueous layer mainly containing water, and a recycled abrasive material layer mainly containing aggregates of abrasive particles. Aggregates were collected from the recycled abrasive layer.

(Examples 7 to 9)
First, the same thing as the aqueous dispersion of the used abrasive | polishing material used in Examples 1-6 and Comparative Examples 1-3 was prepared.

  Next, carbon dioxide was bubbled into the aqueous dispersion to dissolve the carbon dioxide in the aqueous dispersion. The bubbling amount of carbon dioxide is as shown in Table 1 below.

  Next, the aqueous dispersion was dropped into a refrigerant and frozen to produce a solidified body. Pure silicone oil was used as the refrigerant. The temperature of the refrigerant and the cooling time of the aqueous dispersion (cooling holding time after completion of the dropping step) are as shown in Table 1 below.

  Next, the solidified body was recovered in a state where it was mixed with some refrigerant. This solidified body was melted by allowing it to stand at room temperature for 2 hours in a state where it was mixed with some refrigerant. As a result, three layers were formed: a refrigerant layer mainly containing a refrigerant, an aqueous layer mainly containing water, and a recycled abrasive material layer mainly containing aggregates of abrasive particles. Aggregates were collected from the recycled abrasive layer.

(Examples 10-11, Comparative Example 4)
First, the same thing as the aqueous dispersion of the used abrasive | polishing material used in Examples 1-6 and Comparative Examples 1-3 was prepared.

  Next, carbon dioxide was bubbled into the aqueous dispersion to dissolve the carbon dioxide in the aqueous dispersion. The bubbling amount of carbon dioxide is as shown in Table 1 below.

  Next, the aqueous dispersion was cooled to below the melting point with a freezer to produce a solidified body. The cooling temperature and cooling time of the aqueous dispersion are as shown in Table 1 below.

  Next, the solidified body was melted by standing at room temperature for 2 hours. As a result, two layers of a water layer mainly containing water and a regenerated abrasive layer mainly containing aggregates of abrasive particles were formed. Aggregates were collected from the recycled abrasive layer.

  Using a Microtrac particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., model number: MT3300EX), the particle size distribution of the aggregates of Examples 1 to 11 and Comparative Examples 1 to 4 is measured on a volume basis by the laser diffraction / scattering method. did.

  As a representative, the measurement results of the particle size distribution of the aggregates of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in FIG. As shown in FIG. 4, it was confirmed that aggregates were formed in all of Examples 1 to 3 and Comparative Examples 1 to 3. Then, by dissolving carbon dioxide in the refrigerant, two peaks appear in the particle size distribution of the aggregates of Examples 1 to 3 in which carbon dioxide is dissolved from the refrigerant into the aqueous dispersion. On the other hand, as shown in FIG. 4, only one peak appears in the particle size distribution of the aggregates of Comparative Examples 1 to 3 in which carbon dioxide was not dissolved in the aqueous dispersion.

  Also, Examples 4 to 6 in which the cooling temperature was changed, Examples 7 to 9 in which carbon dioxide was dissolved in the aqueous dispersion, Example 10 in which carbon dioxide was dissolved in the aqueous dispersion and cooled without using a refrigerant, In the particle size distribution of the 11 aggregates, two peaks appeared as in Examples 1-3. In the particle size distribution of the aggregate of Comparative Example 4 in which carbon dioxide was not dissolved in the aqueous dispersion, only one peak appeared as in Comparative Examples 1 to 3.

  Furthermore, 10 g of the aggregates of Examples 1 to 11 and Comparative Examples 1 to 4 were added to 100 mL of water and placed in a container, an ultrasonic vibrator with an ultrasonic output of 40 W was inserted, and ultrasonic vibration was applied. Distribution was measured.

  As a representative, FIG. 5 shows the measurement results of the particle size distribution of the aggregate of Example 7 and the particle size distribution after applying ultrasonic vibration a plurality of times. As shown in FIG. 5, by applying ultrasonic vibration to the aggregate of Example 5 in which carbon dioxide is dissolved in an aqueous dispersion, the large particle size peak is lowered and the small particle size peak is raised. ing.

  Further, by applying ultrasonic vibration to the aggregates of Examples 1 to 6 and Examples 8 to 11 in which carbon dioxide is dissolved in an aqueous dispersion, the large peak of the particle size is lowered and the small peak of the particle size is reduced. Became high. On the other hand, even if ultrasonic vibration was applied to the aggregates of Comparative Examples 1 to 4 in which carbon dioxide was not dissolved in the aqueous dispersion, no significant change was observed in the particle size distribution.

  For this reason, the aggregates of Examples 1 to 11 in which carbon dioxide is dissolved in an aqueous dispersion are very brittle and can be easily pulverized, thereby obtaining an aggregate that is easy to use as an abrasive. On the other hand, the aggregates of Comparative Examples 1 to 4 in which carbon dioxide is dissolved in the aqueous dispersion cannot be easily pulverized.

1 Gas introduction part 2 Freezing part 3 Melting part

Claims (10)

Dissolving gas in an aqueous dispersion of used abrasive;
Freezing the aqueous dispersion to produce a solidified body;
Melting the coagulum.
A method for producing recycled abrasives. The used abrasive comprises a rare earth oxide;
The method for producing a recycled abrasive according to claim 1. The rare earth element oxide comprises cerium oxide,
A method for producing a recycled abrasive according to claim 2. The gas includes an acidic gas;
The manufacturing method of the recycled abrasive | polishing material as described in any one of Claims 1 thru | or 3. The acid gas includes carbon dioxide;
The manufacturing method of the recycled abrasive | polishing material of Claim 4. Dropping the aqueous dispersion into a refrigerant to freeze the aqueous dispersion to produce the solidified body;
The manufacturing method of the recycled abrasive | polishing material as described in any one of Claims 1 thru | or 5. Introducing the gas into the refrigerant, dropping the aqueous dispersion into the refrigerant, and dissolving the gas in the aqueous dispersion;
A method for producing a recycled abrasive according to claim 6. Introducing the gas into the refrigerant by bubbling the gas into the refrigerant;
The method for producing a recycled abrasive according to claim 7. Dissolving the gas in the aqueous dispersion by bubbling the gas in the aqueous dispersion;
The method for producing a recycled abrasive according to any one of claims 1 to 8. A gas introduction part for introducing gas into an aqueous dispersion of used abrasives;
A freezing part for freezing the aqueous dispersion to produce a solidified body,
A melting part for melting the solidified body,
Recycled abrasive manufacturing equipment.

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