KR20170033096A - Regenaration method of spent abrasives containing ceria - Google Patents
Regenaration method of spent abrasives containing ceria Download PDFInfo
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- KR20170033096A KR20170033096A KR1020150130980A KR20150130980A KR20170033096A KR 20170033096 A KR20170033096 A KR 20170033096A KR 1020150130980 A KR1020150130980 A KR 1020150130980A KR 20150130980 A KR20150130980 A KR 20150130980A KR 20170033096 A KR20170033096 A KR 20170033096A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B57/00—Devices for feeding, applying, grading or recovering grinding, polishing or lapping agents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B57/00—Devices for feeding, applying, grading or recovering grinding, polishing or lapping agents
- B24B57/02—Devices for feeding, applying, grading or recovering grinding, polishing or lapping agents for feeding of fluid, sprayed, pulverised, or liquefied grinding, polishing or lapping agents
Abstract
Description
The present invention relates to a method for regenerating a ceria-containing waste abrasive. More particularly, the present invention relates to a method for regenerating a ceria-containing abrasive material that effectively removes impurities contained in a ceria-containing abrasive material while ensuring stability of a regeneration process and significantly reducing occurrence of fine scratches generated during polishing.
In general, TV cathode ray tubes and TFT-LCD glass substrates used for liquid crystal panels are produced in a state where the flatness and roughness of the surface are poor during the production process, and the disc glass is used as it is for a TV cathode ray tube or a glass substrate for a liquid crystal panel it's difficult. In particular, a variety of methods have been studied to improve the brightness, viewing angle, and contrast difference of a glass panel for a TFT-LCD used as a liquid crystal panel. Such characteristics are also greatly influenced by the surface of a glass substrate for a TFT-LCD It is known to receive. To this end, companies producing glass substrates are making efforts to improve the surface of glass substrates, and various glass substrate abrasives are being used. Among them, abrasives containing ceria (CeO 2 ) as a general abrasive are widely used.
However, such a ceria-containing abrasive has been disposed of as waste sludge due to a reduction in polishing efficiency after a certain period of glass polishing process. This is because the SiO 2 or Al 2 O 3 component as the glass substrate component for the TFT-LCD is polished and contained after the polishing process for a predetermined time, and the back pad for attaching the glass substrate in the polishing step, the polishing pad The polishing efficiency of the abrasive slurry is reduced, and agglomeration of the abrasive particles occurs, thereby increasing the risk of occurrence of a large amount of scratches.
As a result, the abrasive needs to be discarded after being used in the polishing process for a certain period of time, which may reduce the efficiency and economy of the process. Accordingly, several techniques for recycling the abrasive have been studied.
In the case of the recycling and regeneration method of previously known ceria-containing abrasives, a solution of a fluorine-containing or hydrofluoric acid-containing solution is used to dissolve impurities derived from a glass substrate such as silica contained in ceria-containing waste sludge, The impurities are separated from the waste sludge, and then the waste sludge and the waste abrasive are regenerated through a drying process and a firing process. Particularly, in such a conventional regeneration method, impurities dissolved in the solubilizing agent solution are removed by washing the waste sludge by applying a natural sedimentation method, a filtration method, a decanter or a centrifugal separator in the washing step, Liquid separation and removal from waste sludge.
In the case of such a solid-liquid separation and washing method, there is a disadvantage in that the continuous process is impossible and the washing efficiency is lowered and the yield of the whole regeneration process is lowered. Furthermore, in the case of using the decanter or the centrifugal separator, it is necessary to separate the abrasive particles contained in the waste sludge during the process of solid-liquid separation by strong centrifugal force, And there is a fear of occurrence of scratches due to use of the reclaimed abrasive. In addition, even if the redispersion step is carried out separately, it is difficult to sufficiently remove large particles, and it is difficult to obtain a desired particle size distribution. In addition, even when the conventional filtration method or the like is applied, powder derived from impurities or the like easily accumulates in the filter, and it is difficult to remove the powder, shortening the filter life.
Particularly, waste sludge collected for wet recycling of ceria abrasive is present in a state where foreign substances such as glass fragments, back pads and polishing pad pieces generated during glass polishing are mixed and mixed. In the state where such foreign substances are mixed, There is a problem that the efficiency of the regeneration process due to the foreign materials and the contamination problem of the equipment due to the residual foreign matter between the processes.
Therefore, it is continuously required to develop a process capable of ensuring the stability of the regeneration process while effectively removing the impurities contained in the ceria-containing waste abrasive, and capable of remarkably reducing the generation of fine scratches during polishing using the recycle slurry have.
Accordingly, the present invention effectively removes impurities such as glass fragments, back pads, polishing pad pieces, and the like generated during polishing of glass contained in ceria-containing waste abrasive material, and can efficiently perform a recycling process including a washing process in a continuous process. And a method for regenerating a cerium-containing abrasive abrasive which can remarkably reduce occurrence of fine scratches.
The present invention relates to a method for producing waste sludge containing ceria (CeO 2 ) by using a mesh filter of 100 mesh to 200 mesh under a pressure of 0.01 to 2 bar, Removing insoluble impurities of 150 mu m;
Dissolving the ceria-containing waste sludge from which the insoluble impurities have been removed in a solubilizing solution containing a fluorine-based compound;
Washing the ceria-containing waste sludge solution to remove silica (SiO 2 ) -containing impurities;
The washed ceria-containing waste sludge is redispersed in a slurry state using a wet grinding apparatus;
Removing the ceria abrasive grains under a pressure of 0.01 to 10 bar using an absolute filter having a pore size of 10 m or less; And
The regenerated slurry from which the ceria abrasive grains were removed was applied to a regenerated slurry using a mesh filter of 325 mesh or more under a pressure of 0.01 to 2 bar to obtain a flexible impurity ;
Containing abrasive material containing ceria.
Hereinafter, a method for regenerating a ceria-containing abrasive material according to an embodiment of the present invention will be described in detail.
According to one embodiment of the invention, cerium (CeO 2 ) -containing waste sludge is treated with a mesh filter of 100 mesh (pore size 150 μm) to 200 mesh (pore size 75 μm) at a pressure of 0.01 to 2 bar Removing insoluble impurities having a particle size of 75 to 150 mu m contained in the waste sludge under the condition; Dissolving the ceria-containing waste sludge from which the insoluble impurities have been removed in a solubilizing solution containing a fluorine-based compound; Washing the ceria-containing waste sludge solution to remove silica (SiO 2 ) -containing impurities; The washed ceria-containing waste sludge is redispersed in a slurry state using a wet grinding apparatus; Removing the ceria abrasive grains under a pressure of 0.01 to 10 bar using an absolute filter having a pore size of 10 m or less; And the regenerated slurry from which the ceria abrasive grains have been removed is applied to a flexible slurry having a particle size of 45 μm or less contained in the regenerated slurry under a pressure of 0.01 to 2 bar by using a mesh filter of 325 mesh or more, And removing impurities from the ceria-containing waste abrasive.
In the ceria-containing waste abrasive recycling method of one embodiment, the ceria-containing waste sludge derived from the abrasive abrasive is dissolved in a predetermined solvent solution to dissolve the impurities derived from the glass substrate or the like, and these impurities are removed by washing, The ceria-containing waste abrasive can be regenerated as a reclaimed abrasive through a final filtering step.
Particularly, in the regenerating method of one embodiment, glass fragments, back pad scum, polishing pad scum, and large particle size included in the ceria scum collected before starting the process of dissolving ceria-containing waste sludge derived from the abrasive abrasive The insoluble impurities are subjected to a first-order filtering using a mesh filter of 100 to 200 mesh to remove these macromolecule impurities. In addition, in the final process, the ceria-containing reclaimed abrasive can be used as a backing pad scraper, a polishing pad scraper, and a small-diameter flexible scraper using a mesh filter of 325 to 635 mesh or more, ) To remove impurities.
In the regeneration method of the embodiment, the filtering of the specific mesh is performed simultaneously before the start of the process and at the final stage, so that the glass fragments, the back pad and the polishing pad pieces generated during the polishing contained in the collected ceria waste sludge, It is possible to effectively reduce the pollution problem of the equipment due to the deterioration of the regeneration process efficiency and the residual foreign matter between the processes. Particularly, the collected Ceria waste sludge contains glass fragments, back pads and polishing pad pieces generated during polishing. When a conventional commercialized filter system is used, the foreign matter clogs the filter quickly, There is a problem that the inconvenience to be exchanged and the process cost due to the use of the filter increase.
Therefore, in the regeneration method of one embodiment, when a mesh type filter is used, it can be directly connected to the slurry transfer line, and when a mesh type filter is connected from a large size to a small size, The problem can be solved, and when the filter is clogged, the filter can be cleaned and then used again. Particularly, the mesh type filter used for the final filtering is advantageous in that it can effectively remove the flexible back pad and the polishing pad pieces which can not be removed even by using an absolute filter (10 μm absolute filter) Thereby significantly reducing the occurrence of fine scratches during polishing of wet recycled slurries.
A method of regenerating a ceria-containing abrasive material according to an embodiment will be described below.
A schematic process diagram of a wet recycling process of a ceria-containing abrasive material according to an embodiment of the present invention is shown in FIG. The wet-type wet recycling process of FIG. 1 is composed of a primary mesh filter, silica dissolution, cleaning, re-dispersion, an absolute filter process, a secondary mesh filter, and a product package.
First, the ceria-containing abrasive material and the waste sludge derived from the ceria which are objects of the regeneration method of one embodiment may be derived from the ceria-containing abrasive used for glass substrate polishing in the manufacturing process of the TFT-LCD and the like. Accordingly, the ceria-containing waste sludge or the like contains silica (SiO 2 ) and alumina (Al 2 O 3 ) derived from the glass substrate as main impurities. The waste sludge and the waste abrasive may contain, as impurities, iron (Fe), chromium (Cr), and the like, as well as various organic substances derived from the polishing pad on which the polishing has been performed and the back pad used to support the glass substrate to be polished, Or a metal component-containing impurity such as nickel (Ni).
Particularly, ceria-containing waste abrasive materials and waste sludge or waste abrasive materials derived therefrom are used in a variety of applications, such as glass pieces generated by shattering of the abrasive plate, metal impurities derived from polishing equipment, insoluble impurities having large particle diameters such as abrasive pad and back pad giant pieces, , A polishing pad scraper, and other flexible impurities having a small particle diameter. At this time, the insoluble impurities may have a particle diameter of 75 mu m or more or 75 to 150 mu m. Further, the flexible impurity may have a particle diameter of 45 mu m or less or 20 mu m to 45 mu m.
Therefore, in regenerating the ceria-containing waste sludge and the like, the step of removing the insoluble impurities having a large particle size contained in the waste sludge, the step of removing silica and alumina, the step of removing the impurities from the polishing pad, the back pad, It is necessary to carry out a process of removing other impurities and a process of removing flexible impurities having a small particle diameter included in the final reclaimed abrasive.
In the regeneration method of the embodiment, ceria (CeO 2 ) -containing waste sludge is first treated with a predetermined mesh filter to remove insoluble impurities having large particle diameters such as glass fragments, back pad scum, polishing pad scum, It is possible to carry out the process of removing the water. More specifically, the mesh filter of the first filtering may be 100 to 200 mesh, preferably 140 to 200 mesh, more preferably 170 to 200 mesh. The pore size of the mesh filter of the primary filtering may be 75 to 150 mu m, preferably 75 to 100 mu m, more preferably 75 to 90 mu m. At this time, the mesh filter may have a mesh size of 100 meshes or more in terms of process productivity, and may be used at 200 mesh or less in terms of impurity removal efficiency. For reference, the larger the mesh size in the mesh filter, the smaller the sieve size. For example, 100 mesh for 100 mesh, 75 mesh for 200 mesh, 45 mesh for 325 mesh, 38 mesh for 400 mesh, 25 mesh for 500 mesh, and 20 mesh for 635 mesh out of the ready-made mesh filters.
If the recycling process is started with such foreign matter mixed, the efficiency of the regeneration process due to the foreign substance and the foreign matter remaining between the processes may cause the equipment pollution problem. Therefore, in order to prevent this, In order to remove the glass fragments and the pad pieces, a large-scale foreign matter is firstly removed using a mesh filter of 100 to 200 mesh, followed by a wet recycling process. Here, the insoluble impurities may have a particle size of 75 탆 or more, or 75 to 150 탆, and may be a glass piece, a metal impurity, a giant polishing pad, a back pad, or the like. Particularly, in order to remove metal impurities, a process of removing by using a magnetic rod may be added in addition to the mesh filter process. In addition, the pressure applied in the filtering step may be determined by a pump for transferring the slurry. In addition to the pressure corresponding to the hydraulic pressure, the pressure may be applied at normal temperature and normal pressure without applying any additional pressure.
In general, the waste slurry contains a large amount of impurities, so it is impossible to carry out the recycling process without removing it in the first filtering step. Accordingly, in the present invention, the above-described first filtering step is carried out and the dissolving step is performed. In order to remove small puddles which can not be removed by the first filtering, a third mesh filter step is added as described later .
On the other hand, after the insoluble impurities contained in the ceria-containing waste sludge are removed, a step of dissolving the waste sludge in a solution containing a predetermined fluorine compound can be performed. More specifically, the solubilizer solution comprises hydrofluoric acid or hydrogen fluoride compound, a strong base of sodium or potassium hydroxide, or, NaHF 2, (NH 4) a predetermined fluorine-containing compound of the HF 2 or KHF 2, or NaF, (NH 4 ) F or a predetermined fluorine salt of KF and a mixture of acids such as sulfuric acid, nitric acid or hydrochloric acid.
In this solution of the solubilizer, the hydrofluoric acid or hydrogen fluoride compound is mainly used as a glass etching solution, and it is also possible to dissolve impurities such as silica and alumina derived from the glass substrate. In addition, the strong base can also dissolve impurities such as silica derived from a glass substrate.
In another example of the solubilizer solution, a mixture of a fluorine-based compound such as NaHF 2 , (NH 4 ) HF 2 or KHF 2 , or a fluorine salt such as NaF, (NH 4 ) F or KF and an acid is added to the solubilizer solution (SiO 2 ) and alumina (Al 2 O), which are contained in the waste sludge and the waste abrasive, such as silica (SiO 2 ) and alumina 3 ) can be removed almost completely or close to 100%.
Therefore, when the ceria-containing waste sludge is treated by dispersing the ceria-containing waste sludge in a solution solution in an aqueous solution state using the above-described solubilizer solution, impurities derived from the glass substrate contained in the waste sludge, for example, silica and alumina It can be dissolved by the solubilizer solution and separated from the waste sludge.
At this time, the concentration of the fluorine compound, the fluorine salt, the acid or the strong base in the solubilizer solution can be appropriately controlled in consideration of the content of impurities such as silica or alumina contained in the waste sludge. However, in order to effectively remove impurities such as silica and alumina from the waste sludge used for polishing a conventional glass substrate for LCD, the above-mentioned hydrofluoric acid compounds, other compounds such as NaHF 2 , and fluoride salts such as NaF Containing compound is suitably contained in the solubilizer solution at a concentration of about 0.01 to 20 M, or about 0.1 to 15 M, or about 1 to 10 M. The acid or strong base, which may be contained together with the hydrofluoric acid, the hydrogen fluoride compound or the fluorine salt, may be contained in the solution at a concentration of about 0.01 to 20 M, or about 0.1 to 15 M, or about 1 to 10 M. If the concentration of each component in the solution is too low, the removal efficiency of the impurities may be lowered. On the contrary, if the concentrations are too high, the amount of the raw materials may be unnecessarily increased.
On the other hand, after the ceria-containing waste sludge is dissolved in a predetermined solubilizer solution, such waste sludge may be washed to separate and remove the silica-containing impurities from the waste sludge by solid-liquid separation. Particularly, in the regeneration method of one embodiment, the washing process can be performed while continuously passing the waste sludge treated with the solubilizing agent solution into a cross-flow filtration system.
The cross-flow filtration system includes a predetermined filter in the system, and the filtration and solid-liquid separation proceeds with the waste sludge-containing solution continuously passing through the upper space of the filter in a direction perpendicular to the filter. In such a system, the waste sludge-containing solution is continuously in contact with the lower filter while passing through the system, and liquid impurities (for example, silica or alumina) dissolved in the solution of the solvent are passed through the filter, Liquid separation and removal, and the remaining waste sludge-containing highly concentrated solution can be discharged from the system without exiting through the filter. In addition, the above-described process may be repeated while circulating the high-concentration solution and passing the cross-flow filtration system and the filter again a plurality of times, for example, about 2 to 10 times.
Through this process, the cleaning process using the cross flow filtration system is performed, and the cleaning process described above can be continuously processed to proceed more efficiently. Further, as already described above, since the waste sludge-containing solution is in contact with the lower filter in a large surface area while continuously passing through the system, the impurities dissolved in the solution of the dissolving agent are filtered, separated and removed, The efficiency and the yield of the entire regeneration process can be further improved. In addition, agglomeration of abrasive particles and generation of large particles during the cleaning process can be suppressed.
In this cleaning process, the cross-flow filtration system is a system in which a particle size of about 5 占 퐉 or less, or a ceramic such as alumina or zirconia having filter eyes for filtering particles having a particle size of about 0.002 to 5 占 퐉 Filter. By using such a filter, abrasive particles in the waste sludge can be prevented from being filtered and lost by the filter to reduce the regeneration yield, and the impurities dissolved in the solubilizer solution can be completely removed more effectively, Can be improved.
In addition, the cross-flow filtration system can remove the powder on the surface of the filter through a back pulse to the filter, thereby reducing the accumulation of powder in the filter or shortening the life of the filter, The process can be made more efficient as a whole.
When the above-described washing step is carried out, the waste sludge and the glass substrate-containing impurities such as silica or alumina dissolved in the solution of the solubilizer can be separated and removed from the waste sludge by solid-liquid separation. At this time, the cleaning process may be performed while adding a separate cleaning solution such as deionized water, water or other water solvent to the filtration system. In order to more effectively clean and remove the impurities dissolved in the solution, 4 < / RTI > or pH < RTI ID = 0.0 > 10-14. ≪ / RTI > In order to appropriately adjust the pH, an acid or base may be appropriately dissolved in the water or deionized water to use it as a cleaning liquid, and the impurities can be completely removed through the above-described cleaning process.
Meanwhile, as shown in FIG. 1, after the washing process, the washed ceria-containing waste sludge may be redispersed in a slurry state using a wet grinding apparatus. In this re-dispersion process, the ceria abrasive grains and the back pad scum are removed in order to effectively apply the waste sludge, from which impurities such as silica and insoluble impurities having a large particle size are removed, to the subsequent filtering step through the above- And an insoluble solid such as a flexible impurity such as a polishing pad scum can be dispersed in the form of fine particles.
The re-dispersion process may be performed by a wet grinding apparatus such as an APEX mill, a netzsch mill, or a ball mill. Of these, the APEX mill is a type of vertical vertical high-speed ball mill. By using such an APEX mill, the agglomerated ceria abrasive can be dispersed and the efficiency of the filtering process of the dispersed ceria slurry is increased . Therefore, the APEX mill can more suitably be used in the redispersion process.
The redispersion process may also proceed to normal pressure and normal pressure without applying a separate pressure as in the first filtering process.
On the other hand, after the above-mentioned redispersion process is performed, a subsequent filtering process can be performed on the redispersed slurry as shown in FIG. In this filtering process, ceria abrasive grains are removed by using an absolute filter with a redispersed slurry, and then flexible impurities having a small particle size are removed using a mesh filter of 325 mesh or more . Through the progress of the filtering process, a flexible urethane material impurity such as a polishing pad or a back pad piece having a small particle diameter is effectively removed, the polishing rate of the reclaimed abrasive is controlled to be excellent, and the occurrence of scratches Can be suppressed.
In the second filtering step, the ceria abrasive grains aggregated from the waste abrasive material can be removed from the slurry redispersed in a slurry state. It is also possible to remove impurities such as metal impurities, foreign particles, dust, etc. which have not been removed from the mesh filter together with the ceria abrasive large particles. Such ceria abrasive grains and the like may be small impurities having a particle diameter of less than 10 mu m and may be small impurities having a particle diameter of 0.01 mu m to 9.99 mu m, for example.
The ceria abrasive massive particle removal filtering process can be carried out using an absolute filter having a pore size of 10 μm or less. As described above, by using the absolute filter, it is possible to remove small impurities that have not been removed from the mesh filter, which is simply formed of a metal mesh. Therefore, the absolute filter can be more suitably used in the filtering process for removing the agglomerated ceria abrasive grains. The absolute filtering process for removing the ceria abrasive grains may be performed under normal temperature and pressure conditions.
The regenerated slurry from which the ceria abrasive grains are removed through the absolute filtering process is subjected to a final filtering process for removing flexible impurities having a small particle diameter using a mesh filter of 325 mesh or more can do. More specifically, the final filtering mesh filter may have a mesh size of 325 mesh or more, or 325 to 635 mesh, preferably 400 to 635 mesh, more preferably 500 to 635 mesh, ). The pore size of the mesh filter of the final filtering may be 45 탆 or less or 20 to 45 탆, preferably 20 to 38 탆, more preferably 20 to 25 탆.
Particularly, even when filtering is performed using an absolute filter (10 μm Absolute Filter), polishing pads and back pad pieces of 10 μm or more pass through filter pores that are pressured due to the flexible urethane material And thus it may not be removed in such an absolute filtering process.
Accordingly, in the present invention, by using a mesh filter having a mesh size of 325 mesh or more, a final filtering process in which the mesh filter is hooked in a state of no pressure allows flexible impurities such as polishing pads or back pad pieces of urethane material Can be effectively removed. Here, the flexible impurity may have a particle diameter of 45 mu m or less or 20 mu m to 45 mu m, and may be a polishing pad residue, a back pad residue, or the like. The flexible impurities may be rubber-like. In addition, the final filtering process may be carried out at 1 to 10 psi pressure conditions, preferably 1 to 7 psi pressure conditions, and 1 to 5 psi pressure conditions.
According to the present invention, the purified ceria-containing regeneration slurry finally washed in the regeneration step may be used as it is, or the regenerated slurry solution may be further dried and calcined.
Particularly, after the above-mentioned final filtering step is carried out, the ceria-containing regenerated slurry obtained through final filtering can be dried if necessary. In this drying step, the moisture contained in the ceria-containing reclaimed slurry obtained through the wet recycling process described above can be dried and removed, and the ceria-containing reclaimed abrasive material having been subjected to the drying process in this manner can be used in an amount of about 1% % ≪ / RTI > by weight.
Such a drying process may be carried out in an oven dryer or a CD dryer (Compact Disc dryer). The CD dryer is a type of disk type dryer in which the reclaimed slurry is dried on a rotary disk which is heated and supplied. By using such a CD dryer, the coagulation of abrasive particles (for example, ceria particles) So that generation of large particles is suppressed, and occurrence of scratches can be further minimized when using the regenerated ceria-containing abrasive. Therefore, the CD dryer can be more suitably used in the drying process. This is presumably because heat can be uniformly transferred to the reclaim slurry at high efficiency as the CD dryer dries.
The drying step may be carried out in an oven drier at a temperature of about 100 to 200 DEG C for about 1 to 30 seconds or in a CD drier rotating at about 1 to 10 rpm or about 5 to 10 rpm at a temperature of about 100 to 200 DEG C Lt; / RTI > for about 1 to 30 seconds. If the rotational speed of the CD drier is too low or the drying time is too long, there is an increased risk of scratches due to the coagulation of the particles. On the contrary, if the rotational speed is too fast or the drying time is too short , The drying process may not be efficiently performed.
Alternatively, when the drying process is conducted under optimized conditions, the regenerated ceria-containing reclaimed abrasive may have an appropriate average particle size of about 0.5 to 3.0 탆, suppressing the generation of large particles of about 6.0 탆 or more, In addition, it is easy to obtain a reclaimed abrasive having a water content of about 1% by weight or less by efficiently proceeding drying.
On the other hand, after the above-described drying step, the dried reclaimed abrasive is heated to a temperature of about 800 to 1200 ° C, or about 800 ° C to about 800 ° C in the presence of a flux containing an ammonium salt, an alkali metal salt, a metal oxide, a metal oxyacid or an alkaline earth metal salt, To 1000 < 0 > C, or about 800 to 900 < 0 > C. Through the progress of the sintering process, the surface characteristics and crystal properties of the ceria-containing abrasive material can be restored, the polishing rate of the reclaimed abrasive material can be increased, and impurities such as various organic substances derived from the pad can be further removed.
The flux may be used in an amount of about 1 to 3.0% by weight, or about 1 to 2.0% by weight, or about 1 to 1.5% by weight based on the weight of the reclaimed abrasive to be subjected to the sintering process. As the content of the flux and the above-described calcination temperature are appropriately controlled, the particle size distribution and crystal size of the reclaimed abrasive are appropriately adjusted to crystal sizes of about 0.5 to 3.0 mu m and about 60 to 90 nm, respectively, The generation of large particles due to the generation of large particles can be suppressed, the polishing rate of the reclaimed abrasive can be controlled to be excellent, and the occurrence of scratches due to the generation of large particles can be suppressed.
In the above-described firing step, the flux may be an ammonium salt such as ammonium fluoride, ammonium chloride or ammonium sulfate; Alkali metal salts or alkaline earth metal salts such as sodium chloride, sodium fluoride, sodium hydroxide, potassium chloride, sodium borate or barium chloride; Metal oxides such as boron oxide; Boric acid, and the like, and two or more selected from these may be used together. Depending on the use of such a flux, the surface characteristics, crystal characteristics, and the like of the reclaimed abrasive can be adjusted to a desirable range after the above-described firing process.
The flux may be introduced and wet-blended in a previously conducted cleaning step, or dry-blended immediately before the firing step, and may be suitably wet-blended in the cleaning step. Further, the firing step may be carried out at the above-mentioned temperature for about 1 to 4 hours.
Through the progress of the above-mentioned optimized firing process, a ceria-containing reclaimed abrasive having a crystal size of about 60 to 90 nm and an average grain size of about 3 to 10 탆 and inhibiting the formation of macroparticles can be obtained. If the crystal size or the average grain size becomes too small, the polishing rate of the reclaimed abrasive may not be sufficient. On the other hand, if the crystal size or the average grain size becomes too large, scratches may occur in the polishing process using the reclaimed abrasive, The pulverization and classification process proceeding as needed may be unnecessarily inefficient. Moreover, when the pulverization and classification process is excessively advanced in order to reduce an excessively large particle size or crystal size, not only the efficiency of the regeneration process is greatly reduced, but also the surface properties of the reclaimed abrasive are rather impaired during such grinding process The properties of the reclaimed abrasive may be deteriorated.
After the above-described firing step, if necessary, a grinding or classifying step may be further carried out in order to reduce the particle size distribution or crystal size of the reclaimed abrasive or to remove large particles. Can proceed in a manner well known to those skilled in the art. For example, the pulverization process may be performed using a jet-mill or the like, and the classification process may be performed using a wind power classifier such as a cyclone, a dry classifier, a two-pole or three-pole tip EJ-ELBO classifier, or a sieve for sorting.
According to the above-described regeneration method, impurities derived from a glass substrate or the like are substantially completely and effectively removed, the entire regeneration process including the cleaning process is continuously processed and efficiently, and a flexible urethane material such as a polishing pad or a back pad piece Impurities can be effectively removed. Thus, by the above-described regeneration method, a ceria-containing regenerated abrasive material exhibiting excellent properties with excellent efficiency and yield and having a remarkably reduced residual amount of flexible impurities such as polishing pads and back pad pieces, can be obtained. In particular, it is possible to effectively remove large impurities and fine impurities simultaneously, minimize the problem of shortening the exchange period due to clogging of the filter, and improve the overall regeneration process efficiency. Furthermore, such a ceria-containing regenerated abrasive can be used alone or in combination with a new abrasive to be recycled for polishing an LCD glass substrate or the like, which can greatly contribute to economical efficiency and yield of the process.
In the present invention, matters other than those described above can be added or subtracted as required, and therefore, the present invention is not particularly limited thereto.
According to the present invention, large impurities and fine impurities contained in the ceria-containing abrasive, such as polishing pads and back pad pieces, can be easily removed through a primary filtering process before the start of the wet process, ) A method of regenerating a ceria-containing abrasive material capable of efficiently performing a regeneration process including a cleaning process and a filtering process in a continuous process while effectively removing impurities.
1 is a view showing a wet recycling process.
Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited to the following examples.
Example 1
The waste sludge containing ceria (CeO 2 ) was firstly subjected to first-order filtration under a normal temperature and pressure condition using a 200 mesh filter (product name: 200 mesh diameter 300 mm filter manufactured by Cheonggye Sang Construction Co., Ltd.) Glass fragments, back pad scum, abrasive pad scum, and insoluble impurities with large particle size. The pressure applied to the filtering was determined by a pump for conveying the slurry. The pressure was applied by hydraulic pressure, but no pressure was applied. All processes were carried out at room temperature.
4 kg of NaHF 2 was added to the waste sludge aqueous solution containing the ceria-containing waste sludge from which the insoluble impurities were removed at a solid concentration of 15% by weight, followed by dissolution and reaction for 2 hours. Thereafter, the waste sludge-containing solution was passed through a cross-flow filtration system (product name: Membralox, Pall) for eight consecutive times, and the washing process was performed. Concentration was made to 50wt% solid content each time. After the cleaning process, it was confirmed that the ionic conductivity (IC) value dropped from 23 mS / cm to 450 μS / cm, and the residual amount of silica was less than 0.05 wt%.
Apex mill 1 pass was performed to disperse the washed waste sludge. Ceria abrasive giant particles were removed with a 10 탆 absolute depth type filter under normal temperature and normal pressure, and a 635 mesh filter (product name: Final cleaning was carried out under normal temperature and normal pressure conditions using a TESTING SIEVES (registered trademark), thereby removing the back pad residue contained in the wet regenerated abrasive and the flexible impurities having a small particle size.
Comparative Example 1
Ceria (CeO 2) containing liquid recycle (mesh) filter 635 mesh process for waste sludge: The same procedure as in Example 1, but using (product name Cheonggye over Priest TESTING SIEVES) that did not perform the final filter by A regenerated slurry of Comparative Example 1 was obtained.
Control Example 1
A new slurry containing ceria (CeO 2 ) was prepared.
Test Example
Using the slurries of Example 1, Comparative Example 1 and Control Example 1, glass substrate polishing evaluation was carried out in the production line of the LCD glass division of LG Chemical Co., Ltd. as follows.
Glass substrate polishing evaluation method
Twelve generations (2500 mm * 2500 mm) glass substrates of 8 generations (2500 mm * 2500 mm) were polished using the slurry of Example 1 and Comparative Example 1 and the control sample, and then the polishing rate (탆) was measured and the average value was measured. In addition, final inspection defect and OPC (Offline Particle Count) values were visually measured on the glass substrate obtained after polishing.
As shown in Table 1, the polishing rate of Example 1 in which the wet recycling process was carried out according to the present invention was 97.6%, that is, 95% or more as compared with the control as a new abrasive, It can be seen that the final inspection defect and the OPC (Offline Particle Count) values are 81.8% or more, that is, 80% or more of the new abrasive material.
Claims (14)
Dissolving the ceria-containing waste sludge from which the insoluble impurities have been removed in a solubilizing solution containing a fluorine-based compound;
Washing the ceria-containing waste sludge solution to remove silica (SiO 2 ) -containing impurities;
The washed ceria-containing waste sludge is redispersed in a slurry state using a wet grinding apparatus;
Removing the ceria abrasive grains under a pressure of 0.01 to 10 bar using an absolute filter having a pore size of 10 m or less; And
The regenerated slurry from which the ceria abrasive grains were removed was applied to a regenerated slurry using a mesh filter of 325 mesh or more under a pressure of 0.01 to 2 bar to obtain a flexible impurity ;
Containing abrasive material.
Ceria (CeO 2) containing waste sludge recycling method of waste containing ceria abrasive material containing at least one element selected from the group consisting of silica, alumina, a metal component as an impurity.
Wherein the insoluble impurities include at least one selected from the group consisting of glass fragments, back pad scum, and polishing pad scum.
Wherein the solubilizer solution is an aqueous solution containing hydrofluoric acid or a hydrogen fluoride compound and a strong base of sodium hydroxide or potassium hydroxide.
Wherein the washing step is carried out while passing the ceria-containing waste sludge solution through a cross-flow fliltration system.
The cross-flow filtration system is a method of regenerating a ceria-containing abrasive material having a filter of alumina or zirconia that filters particles having a particle diameter of 5 μm or less.
Wherein the rinsing step is carried out with a water solvent adjusted to a pH of 1 to 4 or a pH of 10 to 14.
Wherein the re-dispersing step is carried out by using a wet grinding apparatus using an APEX mill, a Netzsch mill, or a ball mill.
Wherein the flexible impurities include at least one selected from the group consisting of back pad scum and polishing pad scum.
Further comprising the step of drying and firing the regenerated slurry from which the flexible impurities have been removed.
And the drying step is carried out in an oven dryer or a CD dryer (compact disc dreyer).
Wherein the sintering step is carried out by firing the waste sludge at 800 to 900 DEG C in the presence of a flux containing an ammonium salt, an alkali metal salt, a metal oxysane, a metal oxide, or an alkaline earth metal salt.
A reclaimed ceria containing abrasive having a crystal size of 60 to 90 nm and an average particle size of 0.5 to 3.0 mu m is obtained.
Wherein the ceria-containing waste sludge is derived from a ceria-containing abrasive used for polishing glass substrates.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004268215A (en) * | 2003-03-10 | 2004-09-30 | Fujitsu Hitachi Plasma Display Ltd | Regenerating method of abrasive |
| KR101051207B1 (en) * | 2011-02-09 | 2011-07-21 | 윤종훈 | Recycling mineral abrasive for lcd and pdp glass panel based on rare earth metal oxides and method for recycling mineral abrasive using sludge disposal |
| KR101539421B1 (en) * | 2012-09-17 | 2015-07-27 | 주식회사 엘지화학 | Regenaration method of spent abrasives containing ceria |
| KR101539419B1 (en) * | 2012-09-14 | 2015-07-27 | 주식회사 엘지화학 | Regenaration method of spent abrasives containing ceria |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004268215A (en) * | 2003-03-10 | 2004-09-30 | Fujitsu Hitachi Plasma Display Ltd | Regenerating method of abrasive |
| KR101051207B1 (en) * | 2011-02-09 | 2011-07-21 | 윤종훈 | Recycling mineral abrasive for lcd and pdp glass panel based on rare earth metal oxides and method for recycling mineral abrasive using sludge disposal |
| KR101539419B1 (en) * | 2012-09-14 | 2015-07-27 | 주식회사 엘지화학 | Regenaration method of spent abrasives containing ceria |
| KR101539421B1 (en) * | 2012-09-17 | 2015-07-27 | 주식회사 엘지화학 | Regenaration method of spent abrasives containing ceria |
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