Abrasive slurry

Abstract

To provide an abrasive slurry being inexpensive and having superior dispersion stability, workability, and abrasion performance, and a method for producing the same.SOLUTION: An abrasive slurry contains 3 to 55 mass% of silicon dioxide, 0.5 to 12 mass% of smectite, and 60 to 95 mass% of water.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an abrasive slurry and a method for producing an abrasive slurry. [Background technology]

[0002] Polishing is an important industrial operation that is used for a variety of purposes, including improving the shape and dimensional accuracy of various parts, enhancing aesthetics, improving the sharpness of blades, removing foreign matter from surfaces, and increasing the transparency and reflective properties of objects, as well as extending the service life of machines and other equipment by reducing frictional resistance and improving the sliding properties of machine parts (Non-Patent Document 1).

[0003] Abrasive grains generally used in polishing agents include aluminum oxide, silicon dioxide, calcium carbonate, and the like. In addition to an appropriate hardness, the grain size of the abrasive grains is usually required to be uniform within a certain range (Non-Patent Document 2). Such grains are generally manufactured through a complicated process of melting, crushing, and sieving various materials that are the raw materials for the grains (Non-Patent Document 3). In addition, when used as a paste or slurry, a dispersion process is also required, and in this case, the grains are required to have dispersion stability in a medium such as water.

[0004] Among them, if the abrasive can be made into a slurry, it can be used for a wide range of polishing for industrial and household use (for example, chemical mechanical polishing (CMP), wet blasting, buff polishing, etc.), so it can be said that it has high industrial utility value. On the other hand, in order to make the abrasive into a slurry, it is necessary to stably disperse the abrasive in the dispersion medium or to maintain the dispersed state for at least a certain period of time. In order to increase the dispersion stability of the abrasive in the slurry, a dispersant, a surfactant having a dispersing function, or a thickener is generally used. For example, Patent Document 1 discloses a polishing slurry containing an anionic modified colloidal silica abrasive and an anionic surfactant, having an electrical conductivity value of 100 μS / cm to 350 μS / cm, and a robust value of 0.9 or less. In this slurry, the anionic modified colloidal silica abrasive, which is the abrasive, is considered to be stably dispersed in the slurry by the action of the anionic surfactant. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2022-54445 [Non-patent literature]

[0006] [Non-Patent Document 1] Hiromi Yoshida, "Illustrated Guide to the Basics of Polishing," Nikkan Kogyo Shimbun, January 2012, pp. 24-33 [Non-Patent Document 2] Hiromi Yoshida, "Illustrated Guide to the Basics of Polishing," Nikkan Kogyo Shimbun, January 2012, pp. 55-57 [Non-Patent Document 3] Hiromi Yoshida, "Illustrated Guide to the Basics of Polishing," Nikkan Kogyo Shimbun, January 2012, pp. 58-64 Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, when a surfactant or the like is used as a dispersant to improve the dispersion stability of the abrasive, there is a problem that sufficient washing is required to remove the surfactant or the like after polishing. In addition, since it is necessary to use a dispersant that is compatible with the abrasive, there are restrictions on the type of dispersant, and furthermore, since dispersants and surfactants with dispersion function generally use organic polymer materials, there is a problem that they have low heat resistance / durability, and in addition, there is also a problem that the manufacturing cost of the abrasive slurry (abrasive composition) increases due to the added dispersant.

[0008] An object of the present invention is to provide an abrasive slurry that is excellent in dispersion stability, workability and polishing property while suppressing production costs, and a method for producing the same. [Means for solving the problem]

[0009] The present inventors have conducted extensive research in view of the above problems, and have found that by recovering a precipitated component obtained as a by-product in an elutriation process carried out for purifying a high-purity smectite component from a smectite-containing ore and forming the component into an aqueous dispersion (slurry), the slurry has excellent dispersion stability, good polishing properties, and is also easy to work with. The present invention has been completed based on these findings and through further investigation.

[0010] The above-mentioned object of the present invention has been achieved by the following means. [1] An abrasive slurry comprising 3 to 55 mass % silicon dioxide, 0.5 to 12 mass % smectite, and 60 to 95 mass % water. [2] The abrasive slurry according to [1] above, wherein a content ratio of the silicon dioxide to the smectite is 20:1 to 3:1 on a mass basis. [3] The abrasive slurry according to [1] or [2] above, which is derived from a by-product fraction mainly composed of silicon dioxide, which is produced in the process of obtaining refined smectite by subjecting crushed smectite-containing ore to elutriation. [4] The abrasive slurry according to any one of the above [1] to [3], wherein the smectite is selected from the group consisting of montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite, and stevensite. [5] The abrasive slurry according to any one of [1] to [4] above, wherein the 50% particle size of silicon dioxide contained in the abrasive slurry is 0.1 to 100 μm. [6] A method for producing an abrasive slurry, comprising recovering a by-product fraction mainly composed of silicon dioxide, which is generated in the process of obtaining purified smectite by subjecting pulverized smectite-containing ore to elutriation, and obtaining the abrasive slurry according to any one of the above [1] to [5], using the by-product fraction. [7] The method for producing an abrasive slurry according to [6] above, wherein a content ratio of the silicon dioxide to the smectite in the abrasive slurry is 20:1 to 3:1 on a mass basis. [8] The method for producing an abrasive slurry according to [6] or [7] above, wherein the smectite in the abrasive slurry is selected from the group consisting of montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite, and stevensite. [9] The method for producing an abrasive slurry according to any one of [6] to [8] above, wherein the 50% particle size of silicon dioxide contained in the abrasive slurry is 0.1 to 100 μm. Effect of the Invention

[0011] The present invention makes it possible to obtain an abrasive slurry that is excellent in dispersion stability, workability, and polishing property while suppressing production costs. Also, according to the method for producing an abrasive slurry of the present invention, the above-mentioned abrasive slurry can be obtained from a by-product fraction generated in the refining process of clay minerals. Therefore, the method for producing an abrasive slurry of the present invention contributes to the effective use of resources and enables the inexpensive and stable supply of an abrasive that exhibits excellent polishing properties. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a flow diagram showing an example of a process for producing purified smectite from smectite-containing ore and a process for obtaining a by-product fraction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Preferred embodiments of the present invention will be specifically described below, but the present invention is not limited to these embodiments except as specified in the present invention.

[0014] [Abrasive slurry] The abrasive slurry of the present invention is a slurry-like composition containing specific amounts of silicon dioxide, smectite, and water. The components of the abrasive slurry of the present invention are described below.

[0015] (Silicon dioxide) In the abrasive slurry of the present invention, silicon dioxide functions as an abrasive grain. Silicon dioxide is chemically inactive and generally has high safety. The silicon dioxide used in the present invention may be non-crystalline (amorphous) silicon dioxide or crystalline silicon dioxide. The silicon dioxide used in the present invention may also be a mixture of non-crystalline silicon dioxide and crystalline silicon dioxide. For example, amorphous silicon dioxide has the advantage of being safer to use. Crystalline silicon dioxide (crystalline silica) has high hardness (it has the same Mohs hardness as cerium oxide) and can exhibit good abrasive properties even when polishing hard objects.

[0016] Examples of the crystalline silicon dioxide include quartz, as well as tridymite, cristobalite, coesite, stishovite, keatite, moganite, seifertite, and melanophlogite.

[0017] The silicon dioxide constituting the abrasive slurry of the present invention may be silicon dioxide derived from smectite ore, or may be silicon dioxide derived from a refined product or a commercially available product. Examples of commercially available products include quartz powder (model number: SI008BP, 50% particle size: 4 μm, manufactured by Kojundo Chemical Laboratory) and amorphous silicon dioxide powder (model number: 37049-01, 50% particle size: 8 μm, manufactured by Kanto Chemical Co., Ltd.).

[0018] The abrasive slurry of the present invention can be used for a wide range of applications, from rough polishing to precise polishing. The particle size of the silicon dioxide, which is an abrasive grain, can be appropriately set depending on the purpose. In the abrasive slurry of the present invention, from the viewpoint of preventing the precipitation of silicon dioxide in the slurry, the 50% particle size of the silicon dioxide is preferably larger than the 50% particle size of the smectite contained in the abrasive slurry of the present invention. The 50% particle size of the silicon dioxide is preferably 0.1 to 100 μm, may be 0.5 to 50 μm, or may be 2 to 20 μm. In addition, it is preferable that silicon dioxide having a particle size (when simply referred to as "particle size", it means the particle size of each particle) of 100 μm or more is not contained, and the form may be one that does not contain silicon dioxide having a particle size of 50 μm or more, or one that does not contain silicon dioxide having a particle size of 20 μm or more. In the present invention, the "50% particle size" of the silicon dioxide in the slurry is the volume-based median size (D50). The particle size and particle size distribution can be determined, for example, by a laser diffraction / scattering type particle size distribution measuring device.

[0019] The particle size distribution of the silicon dioxide may have one peak or multiple peaks. From the viewpoint of uniformity of the polishing state, it is preferable that the particle size distribution has one peak. In addition, it is preferable that the particle size distribution of the silicon dioxide is distributed within a certain narrow range. For example, when the abrasive slurry of the present invention is used for mirror finishing, the 50% particle size of the silicon dioxide is preferably 0.1 μm or more and less than 15 μm. When the abrasive slurry of the present invention is used for mirror finishing, the particle size distribution of the silicon dioxide preferably has one or more (preferably one) peaks in the particle size range of less than 15 μm and does not contain coarse particles with a particle size of 15 μm or more. When there are multiple peaks in the particle size distribution and coarse particles with a particle size of 15 μm or more are included, it is preferable that the peaks are at least one in the particle size range of less than 15 μm and no peak exists in the particle size range of 15 μm or more. Alternatively, it is preferable that there is at least one peak in the range of particle diameters less than 15 μm and at least one peak in the range of particle diameters 15 μm or more, and the maximum peak frequency value (%, meaning the peak top value (%)) of the peaks with particle diameters of 15 μm or more is 1 / 5 or less of the maximum peak frequency value (%) of the peaks with particle diameters of less than 15 μm.

[0020] In the abrasive slurry of the present invention, the content of silicon dioxide is 3 to 55% by mass. From the viewpoint of further improving the polishing property, the content of silicon dioxide is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 10% by mass or more. In addition, from the viewpoint of further improving the dispersion stability of silicon dioxide and from the viewpoint of workability (operability) such as liquid delivery stability and fluidity, the content is preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, even more preferably 39% by mass or less, even more preferably 35% by mass or less, even more preferably 30% by mass or less, and even more preferably 25% by mass or less. The preferred range of the silicon dioxide content is preferably 5 to 50 mass%, more preferably 7 to 45 mass%, even more preferably 10 to 40 mass%, even more preferably 10 to 39 mass%, even more preferably 10 to 35 mass%, even more preferably 10 to 30 mass%, and even more preferably 10 to 25 mass%.

[0021] (Smectite) In the abrasive slurry of the present invention, smectite functions as a dispersant for silicon dioxide, an anti-settling agent, a thickener, etc. Smectite can also function as a slipping agent during polishing work and an adsorbent for ions and components having an electric charge, and can also function as abrasive grains with low hardness, etc. In addition, in the abrasive slurry of the present invention, the inclusion of smectite allows the dispersion stability to be maintained at a high level, and furthermore, the aggregation of silicon dioxide particles can be suppressed. Therefore, for example, the 50% particle size of silicon dioxide during dispersion can be maintained within the above-mentioned preferred range, and even if the water content is high and the abrasive grains are likely to settle, the abrasive grains are unlikely to become in a shape that is difficult to redisperse, such as a hard caking state, and can be easily redispersed by stirring.

[0022] In addition, the abrasive slurry of the present invention has excellent dispersion stability in water etc. due to the inclusion of smectite, so it can be in a form that does not contain organic dispersants or solvents, and in this case, the abrasive slurry can be easily removed from the object to be polished by rinsing the object to be polished with water after polishing. Furthermore, smectite has the property of imparting thixotropy to water. As a result, the viscosity is high when left to stand and the abrasive grains can be prevented from settling, but when the liquid is delivered, ejected from the nozzle, or the polishing pad is rotated, the viscosity is reduced and good polishing properties can be exhibited.

[0023] The type of smectite constituting the abrasive slurry of the present invention is not particularly limited, and natural smectite or synthetic smectite can be used as appropriate. Smectite itself is known and commercially available. When the abrasive slurry of the present invention is obtained from a smectite-containing ore through elutriation purification as described below, the smectite contained in the abrasive slurry is natural smectite derived from the smectite-containing ore. In the present invention and this specification, the term "smectite-containing ore" means an ore containing smectite, and usually contains a certain amount of components other than smectite. For example, bentonite raw ore is a smectite-containing ore containing montmorillonite as the smectite. The smectite is preferably one or more selected from montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite, and stevensite. When the smectite is a natural smectite, it is preferably one or more selected from montmorillonite, beidellite, nontronite, hectorite, sauconite, and stevensite.

[0024] The interlayer cation species of the smectite used in the present invention is not particularly limited, but from the viewpoint of easy swelling in water, it is preferably a monovalent metal ion, more preferably a lithium ion and / or a sodium ion. The cation exchange capacity (CEC) of the smectite is preferably 20 meq (milli-equivalent) / 100 g or more, more preferably 25 meq / 100 g or more, and even more preferably 30 meq / 100 g or more, from the viewpoint of improving the swelling property during dispersion in water. The cation exchange capacity of the smectite used in the present invention is usually 250 meq / 100 g or less.

[0025] In the present invention, the term "smectite" refers to fine particle smectite. More specifically, the 50% particle size of the smectite is preferably 20 to 500 nm, more preferably 30 to 400 nm, even more preferably 40 to 380 nm, and particularly preferably 50 to 370 nm. By setting the particle size of the smectite within the above preferred range, for example, the abrasive slurry of the present invention can be provided with good viscosity and lubricity during polishing. In the present invention, the "50% particle size" of the smectite in the slurry is a median size based on volume. This particle size can be determined, for example, by a laser diffraction / scattering type particle size distribution measuring device.

[0026] In the abrasive slurry of the present invention, the content of the smectite is 0.5 to 12 mass%. From the viewpoint of further improving the dispersion stability of silicon dioxide in the abrasive slurry, the content of the smectite is preferably 0.6 mass% or more, more preferably 1.0 mass% or more, and even more preferably 1.5 mass% or more. From the viewpoint of workability (operability) such as liquid delivery stability and fluidity, the content is preferably 10 mass% or less, more preferably 8 mass% or less, and even more preferably 6 mass% or less. The smectite content is preferably in the range of 0.6 to 10 mass %, more preferably 1.0 to 8 mass %, and further preferably 1.5 to 6 mass %.

[0027] (Ratio of silicon dioxide to smectite) In the abrasive slurry of the present invention, the content ratio of the silicon dioxide to the smectite (silicon dioxide content: smectite content) is not particularly limited, but from the viewpoint of the dispersion stability of the silicon dioxide, it is preferably 20:1 to 3:1 by mass, more preferably 18:1 to 3.5:1, and even more preferably 15:1 to 4:1.

[0028] (water) The abrasive slurry of the present invention is a slurry containing water as described above. There is no particular limitation on the water, and it may be tap water or purified water such as distilled water or ion-exchanged water. From the viewpoint of quickly peeling and dispersing smectite and preventing viscosity increase and sedimentation, it is particularly preferable that the water is purified water from which ions have been removed. In this case, the ionic conductivity of the water is preferably 10 μS / m or less, more preferably 5 μS / m or less, and even more preferably 2 μS / m or less.

[0029] The water content (moisture content) in the abrasive slurry of the present invention is 60 to 95% by mass. From the viewpoints of liquid delivery stability, fluidity, etc., the water content is preferably 63% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 70% by mass or more. From the viewpoint of dispersion stability, the content is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less. The preferred range of the water content is preferably 63 to 90% by mass, more preferably 65 to 85% by mass, and even more preferably 70 to 80% by mass. For example, the composition may be produced and stored with a water content of 60 to 70% by mass, and then diluted just before use.

[0030] (Other Ingredients) The abrasive slurry of the present invention may contain other components within the range that does not impair the effects of the present invention. For example, known and commonly used additives such as dispersants, surfactants, antifoaming agents, wetting agents, polymeric materials, binders, lubricants, etc. may be used. Furthermore, in order to increase the wettability of the abrasive slurry, the abrasive slurry may contain an organic solvent having at least a hydrophilic group in at least a part thereof. Furthermore, other abrasive grain components may be included to enhance polishing properties. For example, aluminum oxide compounds such as alundum and white alundum, oxides such as cerium oxide, iron oxide, tantalum oxide, and niobium oxide, carbonate compounds such as calcium carbonate, nitrides such as silicon nitride and boron nitride, carbides such as silicon carbide, and single elements with high hardness such as diamond and tungsten may be added and used in combination.

[0031] When the abrasive slurry of the present invention is produced using a by-product fraction obtained by subjecting smectite-containing ore to elutriation purification as described below, impurity components may include shale, mica, feldspar, calcite, pyrite, zeolite, kaolin, illite, etc. The abrasive slurry of the present invention may contain these impurity components within a range that does not impair the effect of the abrasive slurry of the present invention. In this case, it is preferable that the content of the impurity components is 50 parts by mass or less per 100 parts by mass of silicon dioxide contained in the abrasive slurry of the present invention.

[0032] The object to be polished with the abrasive slurry of the present invention is not particularly limited. For example, metals such as stainless steel, iron, steel, copper, aluminum, and zinc, and oxides, nitrides, and carbides such as glass, silicon, alumina, and silicon carbide can be used as the object to be polished with the abrasive slurry of the present invention.

[0033] [Polishing method using abrasive slurry] The polishing method using the abrasive slurry of the present invention is not particularly limited, and can be used in known wet polishing, such as CMP polishing, polishing (buffing), wet lapping, barrel polishing, wet blast polishing, etc. When the object to be polished is flat, a method such as polishing or wet lapping, in which the object to be polished is pressed against a rotating polishing pad while dropping the abrasive slurry of the present invention onto the polishing pad, can be suitably used. Apparatuses used for such polishing include a double-sided polishing apparatus, a single-sided polishing apparatus, a double-sided lapping apparatus, and a single-sided lapping apparatus.

[0034] The barrel polishing is a method in which an object to be polished and the abrasive slurry of the present invention are placed in a barrel container on a drum, and the barrel container is rotated and vibrated to polish the object. The wet blast polishing is a method in which abrasive grains are dispersed in a liquid mainly made of water, and then sprayed at the object to be polished at high speed using compressed air to polish the object. Unlike flat surface processing, there are no restrictions on the shape of the object to be polished, and in addition to polishing, it can also be used to remove rust and paint.

[0035] [Method of manufacturing abrasive slurry] The abrasive slurry of the present invention can be obtained by mixing the above-mentioned components. In addition, a by-product fraction (elutriation purification by-product fraction, sludge) generated in the process of obtaining refined smectite by subjecting smectite-containing ore such as bentonite raw ore to elutriation purification can be recovered as the abrasive slurry of the present invention or its raw material (precursor), and the abrasive slurry of the present invention can be obtained by diluting and dispersing it in water as necessary.

[0036] (Method for manufacturing abrasive slurry using elutriation by-product fraction) Elutriation is a method of classifying solid particles by utilizing the difference in sedimentation velocity of solid particles in water. The sedimentation velocity at this time is described by Stokes' law. In the present invention, the sedimentation of solid particles in elutriation purification (elutriation step) may be natural sedimentation or sedimentation by centrifugation or the like. When purifying smectite from smectite-containing ore by elutriation, a large amount of water is added to the crushed smectite-containing ore, the mixture is stirred, and the supernatant liquid component is collected and dried, thereby purifying smectite, which has a light specific gravity and is easily swollen by water. On the other hand, in this elutriation purification process, a sedimentary component (by-product fraction) with a higher specific gravity than smectite is generated. This by-product fraction can be collected and diluted with water as necessary to form the abrasive slurry of the present invention or its raw material. The method of obtaining purified smectite from smectite-containing ore by elutriation is known per se. A flow diagram of an example of a process of obtaining purified smectite and a by-product fraction from smectite-containing ore by elutriation is shown in FIG. 1.

[0037] The by-product fraction may be collected after one elutriation purification, or after multiple (preferably two or more, more preferably three or more) elutriation purifications. By multiple elutriation purifications, the particle size and specific gravity of the precipitated components are uniform. As a result, a fraction with a narrow particle size distribution and high purity can be obtained. In addition, the fraction with a relatively large specific gravity that has been precipitated by natural elutriation or by gentle centrifugation can be removed, and the by-product fraction that has been precipitated under more severe centrifugation conditions can be used as the abrasive slurry of the present invention or its raw material. Such a by-product fraction has a relatively small particle size and a narrow particle size distribution. If the by-product fraction satisfies the content of each component specified in the present invention, it can be used as it is to form the abrasive slurry of the present invention, or the abrasive slurry of the present invention can be obtained by appropriately adjusting the amount of each component. The by-product fraction can also be subjected to a desired treatment, such as centrifugation, filtration, or water dispersion treatment, to form the abrasive slurry of the present invention. In the present invention, the abrasive slurry "derived from the by-product fraction" means that it includes both of these forms.

[0038] In the above-mentioned elutriation purification, it is difficult to separate particles with similar specific gravities or components that strongly interact (bond), so the obtained by-product fraction inevitably contains a certain proportion of smectite.

[0039] When the abrasive slurry of the present invention is obtained from the by-product fraction obtained by the above-mentioned elutriation purification, the obtained abrasive slurry has excellent abrasiveness and can effectively suppress the congestion of coarse particles. In addition, since the water dispersion treatment is carried out for a long time in the elutriation purification, it is expected that the interaction between the abrasive component silicon dioxide and smectite will become stronger. As a result of this interaction, the abrasive grain silicon dioxide becomes stably dispersed, and an abrasive slurry with superior polishing properties, storage stability (dispersion stability), and abrasive lubricity can be obtained.

[0040] Thus, in one embodiment, the present invention provides the following method for producing an abrasive slurry.

[0041] The method for producing an abrasive slurry comprises recovering a by-product fraction mainly composed of silicon dioxide, which is generated in the process of obtaining refined smectite by subjecting pulverized smectite-containing ore to elutriation, and using the by-product fraction to obtain an abrasive slurry containing silicon dioxide as an abrasive component.

[0042] According to the above-mentioned manufacturing method, by-product fractions that have conventionally been disposed of as waste can be effectively utilized as an abrasive slurry, which contributes to the effective utilization of resources and enables a stable supply of an abrasive exhibiting excellent abrasive properties at low cost. EXAMPLES

[0043] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0044] Example 1 Bentonite ore from Tsukinuno, Yamagata Prefecture was crushed with a crushing roll, and 27 parts by mass of tap water was added to 3 parts by mass of the obtained coarsely crushed ore and left to stand for 24 hours to swell the bentonite ore. Next, it was stirred for 30 minutes using a stirrer, left to stand for 20 hours, and then the coarse precipitate was removed by decantation. The obtained supernatant was further separated using a centrifuge (conditions: 8000 x g, 15 minutes), and the paste-like precipitated components after removing the supernatant were collected and used as the abrasive slurry precursor. To 100 parts by mass of this paste-like abrasive slurry precursor, 40 parts by mass of distilled water was added, and the mixture was stirred for 15 minutes with a three-one motor to obtain a dispersion liquid. The obtained dispersion liquid was filtered through a stainless steel sieve with an opening of 106 μm to obtain the abrasive slurry of Example 1 (slurry-like abrasive composition).

[0045] Example 2 An abrasive slurry of Example 2 was obtained in the same manner as in Example 1, except that the amount of distilled water added was changed from 40 parts by mass to 100 parts by mass per 100 parts by mass of the abrasive slurry precursor.

[0046] Example 3 An abrasive slurry of Example 3 was obtained in the same manner as in Example 1, except that the amount of distilled water added was changed from 40 parts by mass to 300 parts by mass per 100 parts by mass of the abrasive slurry precursor.

[0047] Example 4 An abrasive slurry of Example 4 was obtained in the same manner as in Example 1, except that the amount of distilled water added was changed from 40 parts by mass to 500 parts by mass per 100 parts by mass of the abrasive slurry precursor.

[0048] Example 5 Except for using bentonite ore from Mikawa, Niigata Prefecture instead of bentonite ore from Tsukinuno, Yamagata Prefecture, the paste-like precipitated components were recovered in the same manner as in Example 1, and a paste-like abrasive slurry precursor having a different composition from that of Example 1 was obtained. An abrasive slurry of Example 5 was obtained in the same manner as in Example 2, except that the abrasive slurry precursor (manufactured by Mikawa) obtained above was used instead of the abrasive slurry precursor (manufactured by Tsukinuno) used in Example 2.

[0049] Example 6 75 parts by mass of distilled water was added to 20 parts by mass of amorphous silicon dioxide powder (model number: 37049-01, 50% particle size: 8 μm, manufactured by Kanto Chemical Co., Ltd.), and the mixture was stirred and mixed for 10 minutes using a planetary mixer (Awatori Rentaro ARE-310, manufactured by Thinky Corporation) at 2000 rpm stirring mode. 5 parts by mass of purified montmorillonite (trade name: Kunipia F, 50% particle size: 300 nm, manufactured by Kunimine Kogyo Co., Ltd.) was then added, and the mixture was further stirred and mixed for 10 minutes using the planetary mixer at 2000 rpm stirring mode to obtain an abrasive slurry of Example 6.

[0050] Comparative Example 1 Except for using a cationic surfactant (product name: Liposocard C / 25, component name: polyoxyethylene coconut alkyl methyl ammonium chloride, manufactured by Lion Corporation) instead of the purified montmorillonite, an abrasive slurry of Comparative Example 1 was obtained in the same manner as in Example 6. In this slurry, the amorphous silicon dioxide powder settled and the supernatant was in a liquid state.

[0051] Comparative Example 2 One part by mass of a cellulose compound (trade name: Metolose (registered trademark) HE, chemical name: hydroxypropyl methylcellulose, viscosity grade: 30000, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 21 parts by mass of distilled water, and the mixture was stirred and mixed for 10 minutes at 2000 rpm stirring mode using a planetary mixer (Thinky Mixer ARE-310, manufactured by Thinky Corporation) to obtain a viscous dispersion. 18 parts by mass of amorphous silicon dioxide powder (model number: 37049-01, 50% particle size: 8 μm, manufactured by Kanto Chemical Co., Ltd.) was added to the obtained dispersion, and the mixture was stirred and mixed again using the planetary mixer under the same conditions as above to obtain an abrasive slurry precursor, which is a slightly viscous dispersion. To 40 parts by mass of this abrasive slurry precursor, 40 parts by mass of distilled water was added, and the mixture was stirred for 10 minutes using a planetary mixer to obtain an abrasive slurry of Comparative Example 2. Note that sedimentation occurred in the abrasive slurry of Comparative Example 2 immediately after production (immediately after completion of stirring), and the mixture did not become a uniform dispersion.

[0052] Comparative Example 3 50 parts by mass of amorphous silicon dioxide powder (model number: 37049-01, 50% particle size: 8 μm, manufactured by Kanto Chemical Co., Ltd.) was mixed with 50 parts by mass of distilled water and stirred with a stirrer for 1 hour. After that, a planetary mixer (Awatori Rentaro ARE-310, manufactured by Thinky Corporation) was used to mix and stir at 2000 rpm for 10 minutes. Note that even with this mixing and stirring, the amorphous silicon dioxide was not stably dispersed, and separated into a supernatant portion and a sediment portion within a short time after mixing. 20 parts by mass of the resulting mixed liquid was sampled in a substantially uniformly dispersed state immediately after stirring, and 20 parts by mass of distilled water was further added and stirred for 10 minutes with a planetary mixer to obtain an abrasive slurry of Comparative Example 3. Note that sedimentation occurred in the abrasive slurry of Comparative Example 3 immediately after production (immediately after stirring was completed), and the slurry did not become a uniformly dispersed liquid.

[0053] [Analysis of component composition] The composition of the abrasive slurry precursor used in Examples 1 to 5 was analyzed by the following method. The component compositions of the abrasive slurry in Examples 1 to 5 were calculated from the composition analysis results of the abrasive slurry precursor and the amount of distilled water added to the precursor. The calculation results are shown in Table 1 below. The component compositions of the abrasive slurries of Example 6 and Comparative Examples 1 to 3 were calculated from the blending amounts of each component. The results are shown in Table 1 below.

[0054] (moisture content) The moisture content (mass%) in the abrasive slurry precursor was measured by the 105°C drying loss method in accordance with Japanese Industrial Standard JIS A 1125:2015.

[0055] (Smectite content) Taking advantage of the property of methylene blue to specifically adsorb between clay layers, the amount of methylene blue adsorbed on the purified smectite powder and the dry powder of the abrasive slurry precursor was measured, and the amount of smectite in the abrasive slurry precursor was calculated as follows. The methylene blue adsorption amount of smectite was measured according to the JBAS-107-77 method (filter paper method) which is the standard of the Japan Bentonite Industry Association. As the standard for smectite, high-purity (purity of 99% by mass or more) purified smectite (product name: Kunipia F, originating from Tsukinuno, Yamagata Prefecture or from Mikawa, Niigata Prefecture, manufactured by Kunimine Co., Ltd.) was used, which had almost disappeared the quartz peak detected around 27° in X-ray diffraction (XRD) measurement by repeating elutriation purification for each of bentonite raw ore from Tsukinuno, Yamagata Prefecture and bentonite raw ore from Mikawa, Niigata Prefecture. The methylene blue adsorption amount (unit: mmol / 100 g-purified smectite) of the purified smectite (powder dried at 105°C for 2 hours) which was the standard product was measured, and this measurement value was used as the methylene blue adsorption amount (standard value) specific to montmorillonite in each bentonite raw ore. The methylene blue adsorption amount (standard value) of refined smectite from Tsukinuno, Yamagata Prefecture was 145 mmol / 100 g, and the methylene blue adsorption amount (standard value) of refined smectite from Mikawa, Niigata Prefecture was 125 mmol / 100 g. Each abrasive slurry precursor was dried at 105°C for 2 hours and pulverized, and the methylene blue adsorption amount (unit: mmol / 100g-purified smectite) was measured for each of the obtained dry powders. The measurement results of the methylene blue adsorption amount of the dry powder of the abrasive slurry precursor of Examples 1 to 4 using bentonite raw ore from Tsukinuno, Yamagata Prefecture were divided by the standard value of 145 mmol / 100g, and the measurement result of the methylene blue adsorption amount of the dry powder of the abrasive slurry precursor of Example 5 using bentonite raw ore from Mikawa, Niigata Prefecture was divided by the standard value of 125 mmol / 100g, and each value was multiplied by 100 to obtain the smectite amount (montmorillonite amount, unit: mass (%)) in the solid content of each abrasive slurry precursor. Furthermore, the smectite content (mass%) in the abrasive slurry precursor was calculated from the amount of smectite in the solid content and the above-mentioned water content.

[0056] (quartz content) Using an XRD device, MiniFlex500 (manufactured by Rigaku Corporation), the X-ray reflection intensity of the above-mentioned dry powder of the abrasive slurry precursor was measured in the measurement range of 2θ=1 to 65°, and X-ray analysis data was obtained. The area of ​​the quartz-derived peak at around 2θ=27° in the X-ray analysis data of the dry powder of the above-mentioned abrasive slurry precursor was calculated. In addition, as a reference value, the area of ​​the quartz-derived peak at around 2θ=27° in a 100% silicon dioxide standard having the same particle size distribution as each of the above-mentioned dry powders was calculated. The value obtained by dividing the obtained peak area by the peak area obtained in each standard was multiplied by 100 to obtain the quartz content (mass%) in the solid content of each abrasive slurry precursor. Furthermore, the quartz content (crystalline silicon dioxide content, mass%) in the abrasive slurry precursor was calculated from the quartz content in the solid content and the above-mentioned water content.

[0057] (Other Ingredients) The content of other components was calculated by subtracting the contents (g) of montmorillonite and quartz from the solid content of the abrasive slurry precursor (the total amount (g) of the abrasive slurry precursor minus the water content (g)). It is to be noted that the X-ray analysis data above indicates that the dry powder of each of the abrasive slurry precursors above contains small amounts of feldspar, calcite, zeolite, etc. as other components.

[0058] [Physical property testing] The following tests were carried out on each of the abrasive slurries of Examples 1 to 6 and Comparative Examples 1 to 3. The results are summarized in Table 1.

[0059] (dispersion stability) After preparing each of the abrasive slurries of Examples 1 to 6 and Comparative Examples 1 to 3, they were placed in a container and left to stand for 30 minutes, and the settling state of the abrasive grain components (quartz, amorphous silicon dioxide) was visually observed. If no settling was observed, it was judged as "Good." If settling was observed but the settling was redispersed by gently shaking the container by hand (also called a soft caking state), it was judged as "Good." If the settling was not redispersed by the same operation (hard caking state), it was judged as "Poor."

[0060] (liquid transfer stability) When each of the abrasive slurries of Examples 1 to 6 and Comparative Examples 1 to 3 was supplied from the abrasive slurry supply port of the polishing test device in the "Polishing Test" described below, the case where it was possible to supply stably (liquid was discharged with no change in the supply amount during the 5-minute test period) was judged as "O", the case where the liquid supply amount fluctuated partially during the 5-minute period was judged as "△", and the case where the liquid supply stopped during the 5-minute period was judged as "X".

[0061] (50% particle size) Each of the abrasive slurries of Examples 1 to 6 and Comparative Examples 1 to 3 was diluted with distilled water to a dispersoid concentration of 0.01% by mass to prepare a sample for particle size measurement. The 50% particle size (volume-based median size) of each of the samples for particle size measurement was measured using a laser diffraction / scattering type particle size distribution measuring device LA-950V2 (manufactured by Horiba, Ltd.).

[0062] (Coarse particle state) In the measurement of the 50% particle size, the peak of the particle size distribution (frequency distribution) and the presence or absence of coarse particles were evaluated according to the following evaluation criteria. -Evaluation criteria- ◯: The particle size distribution has one peak in the range of particle diameters less than 15 μm and does not contain coarse particles with a particle diameter of 15 μm or more, or contains coarse particles with a particle diameter of 15 μm or more but does not have a particle size distribution peak in the range of particle diameters of 15 μm or more. △: There is one or more peaks in the particle size distribution range below 15 μm and one or more peaks in the range of 15 μm or more, and the maximum peak frequency value (%) of the peaks with particle sizes of 15 μm or more is 1 / 5 or less of the maximum peak frequency value (%) of the peaks with particle sizes of less than 15 μm. ×: There is one or more peaks in the particle size distribution range of less than 15 μm and one or more peaks in the particle size range of 15 μm or more, and the maximum peak frequency value (%) of the peaks of particle sizes of 15 μm or more exceeds 1 / 5 of the maximum peak frequency value (%) of the peaks of particle sizes of less than 15 μm.

[0063] (Polishing test) Metal test plates (manufactured by Kenis Co., Ltd.) made of copper and iron with a thickness of 0.5 mm, short side 20 mm, long side 70 mm were used as metal plates for polishing tests. They were placed in a thermo-hygrostat at 40°C and humidity of 90% RH for one month to allow rust to form on the surface of the metal plate. The metal plate was bent at a position about 15 mm from one end in the longitudinal direction to be processed into an L-shaped test piece. As the polishing test device, Doctor Lap ML-180 manufactured by Maruto Co., Ltd. was used. As the polishing pad, a soft polishing cloth made specifically for the device was set on a plastic lapping plate. A container for replenishing the abrasive slurry was connected to the polishing liquid outlet, and the liquid supply valve (needle valve) of the outlet was set to a pre-adjusted opening position so that water could be discharged at a rate of 50 g / min. Next, after the outlet valve was fully closed, 300 ml of the abrasive slurry of each Example and Comparative Example was immediately filled into the tank for replenishing the abrasive slurry after sufficient pre-mixing. Immediately after that, the supply valve of the discharge port was set to the above-mentioned setting position, and the lapping machine was rotated at 100 rpm while supplying the slurry to the soft polishing cloth. In this state, the polishing cloth was rotated at about 100 g / cm by hand within a plane of 20 mm x 15 mm of the L-shaped test piece prepared as a test piece. 2 In this state, lap polishing was performed for 5 minutes. The copper and lead plates were polished and the rust was removed to give a mirror-like appearance, as ◯, the rust was mostly removed but shallow scratches were also observed as △, and the polishing was insufficient and the rust could not be removed and shallow scratches were also observed as ×. If the supply of the abrasive slurry stopped and polishing was not possible, it was judged as "not rated."

[0064] [Table 1]

[0065] As is clear from Table 1, the abrasive slurry of Comparative Example 3, in which only amorphous silicon dioxide was dispersed in water, was inferior in both dispersion stability and liquid transfer stability. In addition, since the particles were in an agglomerated state, the 50% particle size was 54 μm, and the peak frequency value of coarse particles with a particle size of 15 μm or more was large. Furthermore, stable liquid transfer to the polishing test device was not possible, and the polishing test could not be performed. In addition, the abrasive slurry of Comparative Example 1, in which a surfactant was used as a substitute for smectite, was inferior in dispersion stability and liquid transfer stability, as in Comparative Example 3, and since the particles were in an agglomerated state, the 50% particle size was 33 μm, and the peak frequency value of coarse particles with a particle size of 15 μm or more was large. Furthermore, in the polishing test, the removal of rust was insufficient, and scratches caused by coarse particles were observed. In the abrasive slurry of Comparative Example 2, in which a cellulose compound was used instead of smectite, the dispersion stability and liquid delivery stability were restored compared to Comparative Examples 1 and 3, but the particles were in an aggregated state, the 50% particle size was 25 μm, and the peak frequency value of coarse particles with particle sizes of 15 μm or more was high. Furthermore, in the polishing test, rust removal was insufficient, and scratches caused by coarse particles were observed. In contrast, the abrasive slurries of Examples 1 to 5, in which materials derived from bentonite ore were diluted and dispersed in water, had a particle size distribution that was restricted to a narrow range of small particle sizes, and exhibited excellent liquid delivery stability and polishing properties, making them excellent abrasive slurries.The abrasive slurry of Example 6, in which amorphous silicon dioxide and smectite were dispersed in water, also had sufficiently excellent properties as an abrasive slurry.

[0066] From the above, it has been demonstrated that an abrasive slurry having excellent properties as described above can be provided by preparing an abrasive slurry using a by-product fraction, mainly composed of silicon dioxide, which is generated in the process of subjecting crushed smectite-containing ore to elutriation purification to obtain refined smectite, or by forming an abrasive slurry having the same particle size distribution or component composition as this abrasive slurry.

Claims

1. An abrasive slurry comprising 3 to 55% by weight of silicon dioxide, 0.5 to 12% by weight of smectite, and 60 to 95% by weight of water.

2. 2. The abrasive slurry according to claim 1, wherein a content ratio of said silicon dioxide to said smectite is from 20:1 to 3:1 on a mass basis.

3. 3. The abrasive slurry of claim 1, wherein the abrasive slurry is derived from a by-product fraction, mainly composed of silicon dioxide, produced during the process of subjecting crushed smectite-bearing ore to elutriation to obtain refined smectite.

4. 3. The abrasive slurry according to claim 1, wherein the smectite is selected from the group consisting of montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite, and stevensite.

5. 3. The abrasive slurry according to claim 1, wherein the 50% particle size of silicon dioxide contained in the abrasive slurry is 0.1 to 100 μm.

6. A method for producing an abrasive slurry, comprising recovering a by-product fraction mainly composed of silicon dioxide produced in the process of obtaining purified smectite by subjecting pulverized smectite-containing ore to elutriation, and using the by-product fraction to obtain the abrasive slurry described in claim 1.

7. 7. The method for producing an abrasive slurry according to claim 6, wherein a content ratio of said silicon dioxide to said smectite in said abrasive slurry is from 20:1 to 3:1 on a mass basis.

8. 8. The method for producing an abrasive slurry according to claim 6, wherein the smectite in the abrasive slurry is selected from the group consisting of montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite, and stevensite.

9. 8. The method for producing an abrasive slurry according to claim 6, wherein the 50% particle size of silicon dioxide contained in the abrasive slurry is 0.1 to 100 μm.

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