Abrasive composition and method for producing the abrasive composition

Abstract

To provide an abrasive composition that has superior dispersion stability in water, superior workability, and superior polishing properties, and a method for producing the same.SOLUTION: An abrasive composition includes silicon dioxide and smectite. In the solid content of the abrasive composition, the content of the silicon dioxide is 50-98 mass%, and the content of the smectite is 2-50 mass%.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Polishing is an important industrial process that is used for various purposes, such as improving the shape and dimensional accuracy of various parts, enhancing aesthetics, improving the sharpness of blades, and removing foreign matter from surfaces, in addition to extending the service life of machines by reducing frictional resistance and improving the sliding of machine parts (Non-Patent Document 1).

[0003] Abrasive grains in abrasives are required to have an appropriate hardness and also to have a uniform grain size within a certain range (Non-Patent Document 2). Such abrasive grains are generally produced through a complex process that involves melting, pulverizing, and sieving the various raw materials used to make the abrasive grains (Non-Patent Document 3). Furthermore, when used in paste or liquid form, a dispersion process is also required, and in this case, the abrasive grains are required to have dispersion stability in a medium such as water.

[0004] Commonly used abrasive grains in polishing agents include aluminum oxide, silicon dioxide, calcium carbonate, etc. These abrasive grains are used as sandpaper by fixing them as powder on paper, or as a slurry by mixing them with a dispersant or organic solvent. Depending on the object to be polished, rare metals such as cerium oxide, tantalum oxide, and niobium oxide may be used as the abrasive material. However, these rare metals are produced in limited countries, which poses a supply risk issue. In addition, due to the recent rise in the price of rare metals, development of abrasives that do not contain rare metals as their main component is underway. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Hiromi Yoshida, "Illustrated Basics of Polishing," Nikkan Kogyo Shimbun, January 2012, pp. 24-33 [Non-patent document 2] Hiromi Yoshida, "Illustrated Basics of Polishing," Nikkan Kogyo Shimbun, January 2012, pp. 55-57 [Non-patent document 3] Hiromi Yoshida, "Illustrated Basics of Polishing," Nikkan Kogyo Shimbun, January 2012, pp. 58-64 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide an abrasive composition that has excellent dispersion stability in water, excellent workability, and excellent polishing properties, and a method for producing the same. [Means for solving the problem]

[0007] The present inventors have conducted extensive research in light of the above-mentioned problems, and as a result have found that the precipitated components obtained as a by-product in the elutriation process carried out to purify high-purity smectite components from smectite-containing ores have excellent dispersion stability in water, adhere well to the object to be polished (workpiece to be polished) during polishing work, exhibit appropriate slip properties, and also have excellent polishing properties. The present invention was completed based on these findings and through further investigation.

[0008] The above-mentioned problems of the present invention have been solved by the following means. [1] 1. A polishing compound composition comprising silicon dioxide and smectite, wherein the content of said silicon dioxide is 50 to 98 mass % and the content of said smectite is 2 to 50 mass % in the solid content of said polishing compound composition. [2] A polishing compound composition comprising 20 to 60 mass % of silicon dioxide, 1 to 20 mass % of smectite, and 30 to 70 mass % of water. [3] The abrasive composition according to [1] or [2] above, which is derived from a by-product fraction containing silicon dioxide as a main component, which is produced in the process of obtaining purified smectite by subjecting crushed smectite-containing ore to elutriation. [4] The polishing compound composition according to any one of [1] to [3] above, wherein the smectite is selected from the group consisting of montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite, and stevensite. [5] The polishing compound according to any one of [1] to [4] above, wherein the average particle size of the silicon dioxide contained in the polishing compound is 0.1 to 100 μm. [6] A method for producing an abrasive composition includes recovering a by-product fraction containing silicon dioxide as a main component, which is generated in the process of obtaining purified smectite by subjecting crushed smectite-containing ore to elutriation, and using the by-product fraction to obtain an abrasive composition containing silicon dioxide in the by-product fraction as an abrasive component. [7] The method for producing an abrasive composition according to [6] above, wherein the smectite is selected from the group consisting of montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite, and stevensite. [8] The method for producing an abrasive composition according to [6] or [7] above, wherein the average particle size of the silicon dioxide contained in the abrasive composition is 0.1 to 100 μm. [9] The method for producing an abrasive composition according to any one of [6] to [8] above, wherein the content of the silicon dioxide is 50 to 98 mass % and the content of the smectite is 2 to 50 mass % in the solid content of the abrasive composition.

[10] The method for producing an abrasive composition according to any one of [6] to [8] above, wherein the content of the silicon dioxide in the abrasive composition is 20 to 60 mass %, the content of the smectite is 1 to 20 mass %, and the content of the water is 30 to 70 mass %. [Effects of the Invention]

[0009] The abrasive composition of the present invention has excellent dispersion stability in water, excellent workability, and excellent polishing properties. Furthermore, according to the method for producing an abrasive composition of the present invention, an abrasive composition can be obtained from a by-product fraction generated in the purification process of clay minerals. Therefore, the method for producing an abrasive composition of the present invention contributes to the effective use of resources and enables the inexpensive and stable supply of abrasives that exhibit excellent polishing properties. [Brief explanation of the drawings]

[0010] [Figure 1] Figure 1 is a photograph showing the state of a stainless steel sink being polished with the polishing compound of the present invention. In Figure 1, the area surrounded by the dashed line is the area that was polished. [Figure 2] FIG. 2 is a photograph, substituted for a drawing, showing the state of silver accessories when polished with the polishing compound of the present invention. [Figure 3] FIG. 3 is a flow diagram showing an example of a process for producing purified smectite from smectite ore and a process for obtaining a by-product fraction. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present invention will be specifically described below, but the present invention is not limited to these embodiments except as defined in the present invention.

[0012] [Abrasive composition] The polishing composition of the present invention is a composition containing specific amounts of silicon dioxide and smectite. The polishing composition of the present invention may be a dry product or may contain a medium such as water. The components of the polishing composition of the present invention are described below.

[0013] (silicon dioxide) In the abrasive composition of the present invention, silicon dioxide functions as an abrasive. The silicon dioxide is chemically inert and generally highly safe. The silicon dioxide used in the present invention may be amorphous silicon dioxide or crystalline silicon dioxide. The silicon dioxide used in the present invention may also be a mixture of amorphous silicon dioxide and crystalline silicon dioxide. For example, amorphous silicon dioxide has the advantage of being safer to use, while crystalline silicon dioxide (crystalline silica) has high hardness (its Mohs hardness is similar to that of cerium oxide) and exhibits good abrasive properties even when polishing hard objects.

[0014] Examples of the crystalline silicon dioxide include quartz, as well as tridymite, cristobalite, coesite, stishovite, keatite, moganite, seiffertite, and melanophlogopite.

[0015] The silicon dioxide constituting the polishing compound of the present invention may be silicon dioxide derived from smectite-containing ores, or silicon dioxide derived from refined products or commercially available products. Examples of commercially available products include quartz powder (model number: SI008BP, average particle size: 4 μm, manufactured by Kojundo Chemical Laboratory) and amorphous silicon dioxide powder (model number: 37049-01, average particle size: 8 μm, manufactured by Kanto Chemical Co., Ltd.).

[0016] The polishing compound of the present invention can be used for a wide range of applications, from rough polishing to precision polishing. The particle size of the silicon dioxide abrasive grains can be appropriately set depending on the purpose. Considering factors such as preventing sedimentation when the polishing compound is used as an aqueous dispersion or paste, the average particle size (average primary particle size) of the silicon dioxide is preferably larger than the average particle size of the smectite contained in the polishing compound of the present invention. The average particle size of the silicon dioxide is preferably 0.1 to 100 μm, but can also be 0.5 to 50 μm, or 2 to 30 μm. Furthermore, it is preferable that the polishing compound does not contain silicon dioxide having a particle size of 100 μm or more. The polishing compound may also be a form that does not contain silicon dioxide having a particle size of 50 μm or more, or a form that does not contain silicon dioxide having a particle size of 30 μm or more. The particle size distribution of the silicon dioxide may have one peak or multiple peaks. From the viewpoint of uniformity of the polishing state, the particle size distribution preferably has one peak. Furthermore, the particle size distribution of the silicon dioxide is preferably distributed within a certain narrow range. For example, when the abrasive composition of the present invention is used for mirror finishing, it is preferable that the average particle size of the silicon dioxide is 0.1 μm or more and less than 15 μm. Furthermore, when the abrasive composition of the present invention is used for mirror finishing, it is preferable that the particle size distribution of the silicon dioxide has one or more (preferably one) peaks in the range of particle sizes less than 15 μm and does not contain coarse particles with a particle size of 15 μm or more. When the particle size distribution has multiple peaks and contains coarse particles with a particle size of 15 μm or more, it is preferable that one or more peaks are in the range of particle sizes less than 15 μm and that no peaks exist in the range of particle sizes of 15 μm or more. Alternatively, it is preferable that there is one or more peaks in the particle size 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 (%, meaning the peak top 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. In the present invention, the "average particle size" of the silicon dioxide in the aqueous dispersion refers to the volume-based median size. This average particle size or particle size can be determined, for example, by a laser diffraction / scattering particle size distribution analyzer.

[0017] (Smectite) When the polishing compound of the present invention is in the form of a paste, slurry, or the like containing water, smectite functions as a dispersant for silicon dioxide, an anti-settling agent, a thickener, etc. In addition, smectite functions as a slipping agent during polishing work, an adsorbent for ions and components having an electric charge, and also functions as a low-hardness abrasive grain, etc. When the abrasive composition of the present invention is a dried product and used for polishing in a dry state, the smectite functions as a binder between abrasive grains and between the abrasive grains and the sandpaper substrate. When the abrasive composition is used in the form of a grinding wheel, the smectite functions as a binder, etc.

[0018] The type of smectite constituting the abrasive composition 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 composition of the present invention is obtained from a smectite-containing ore through elutriation purification, as described below, the smectite contained in the abrasive composition is natural smectite derived from the smectite-containing ore. In the present invention and this specification, the term "smectite-containing ore" refers to an ore containing smectite, and typically contains a certain amount of components other than smectite. For example, bentonite 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.

[0019] The interlayer cation species of the smectite used in the present invention is not particularly limited. From the viewpoint of easy swelling in water when used as an aqueous dispersion or aqueous dispersion paste, it is preferably a monovalent metal ion, and more preferably a lithium ion and / or a sodium ion. The cation exchange capacity (CEC) of the smectite is preferably 20 meq (milliequivalent) / 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 swelling properties during dispersion in water. The cation exchange capacity of the smectite used in the present invention is usually 250 meq / 100 g or less.

[0020] In the present invention, the term "smectite" refers to fine particle smectite. More specifically, the smectite preferably has an average particle size (average primary particle size) of 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 adjusting the average particle size of the smectite to fall within the above-mentioned preferred range, for example, when the polishing compound composition of the present invention is used as an aqueous dispersion, it is possible to impart good viscosity, adhesion to the workpiece, and lubricity during polishing. In the present invention, the "average particle size" of the smectite in the aqueous dispersion refers to the volume-based median size. This average particle size can be determined, for example, by a laser diffraction / scattering particle size distribution analyzer.

[0021] (water) The polishing compound of the present invention may contain water as described above. The polishing compound of the present invention may also be a dispersion (slurry) in which the silicon dioxide and smectite are dispersed in water. There are no particular limitations on the water used, and it may be tap water or purified water such as distilled water or ion-exchanged water. From the viewpoints of rapidly exfoliating and swelling the smectite and preventing an increase in viscosity or sedimentation, it is particularly preferable that the water be 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.

[0022] (Other ingredients) The abrasive composition of the present invention may contain other components as long as the effects of the present invention are not impaired. For example, known and commonly used additives such as dispersants, surfactants, antifoaming agents, wetting agents, polymeric materials, binders, and lubricants may be used. Furthermore, other abrasive grain components may be added to enhance abrasiveness. For example, aluminum oxide compounds such as alundum and white alundum, oxides such as cerium oxide, iron oxide, tantalum oxide, and niobium oxide, nitrides such as silicon nitride and boron nitride, carbides such as silicon carbide, and simple elements with high hardness such as diamond and tungsten may be added. The abrasive composition of the present invention contains smectite, which gives it excellent dispersion stability in water, etc. Therefore, it can be formulated without blending an organic dispersant or solvent, and in this case, the abrasive composition can be easily removed from the object to be polished by simply rinsing the object with water after polishing.

[0023] When the polishing composition of the present invention is produced using a by-product fraction obtained by subjecting a smectite-containing ore to elutriation, as described below, impurities such as shale, mica, feldspar, calcite, pyrite, zeolite, kaolin, and illite may be contained. The polishing composition of the present invention may contain these impurities within a range that does not impair the effects of the polishing composition of the present invention. In this case, the content of the impurities is preferably 50 parts by mass or less per 100 parts by mass of silicon dioxide contained in the polishing composition of the present invention.

[0024] (Content of each ingredient) The content of silicon dioxide in the solid content (components other than the liquid medium) of the polishing compound of the present invention is 50 to 98 mass %. From the viewpoint of improving polishing properties, the content of silicon dioxide is preferably 70 to 97 mass %, more preferably 80 to 95 mass %. The smectite content of the solid content of the polishing compound of the present invention is 2 to 50 mass %. From the viewpoints of improving polishing properties, preventing precipitation of silicon dioxide when dispersed in water to improve dispersion stability, improving adhesion to the workpiece to be polished, and improving the lubricity of the polishing liquid, the smectite content is preferably 3 to 30 mass %, and more preferably 5 to 20 mass %.

[0025] When the polishing compound of the present invention contains water, the content of water in the polishing compound is 30 to 70 mass %. From the viewpoints of dispersion stability, workability, and adhesion to the object to be polished, the content of water is preferably 35 to 65 mass %, more preferably 40 to 60 mass %. When the polishing composition of the present invention contains water, the silicon dioxide content in the polishing composition is 20 to 60 mass%, preferably 25 to 55 mass%, and more preferably 30 to 50 mass%.When the polishing composition of the present invention contains water, the smectite content in the polishing composition is 1 to 20 mass%, preferably 1.5 to 15 mass%, and more preferably 2 to 10 mass%.

[0026] The object to be polished with the abrasive composition of the present invention is not particularly limited. For example, metals such as stainless steel, iron, steel, copper, and aluminum, as well as glass, silicon, and stone can be polished in a polishing treatment using the abrasive composition of the present invention. For example, when a stainless steel sink is polished with the abrasive composition of the present invention soaked in water, rust and water stains on the sink can be effectively removed and the luster of the stainless steel can be restored, as shown in Figure 1. Furthermore, when silver accessories are polished with the abrasive composition of the present invention soaked in water, blackening on the surface of the accessories can be effectively removed, as shown in Figure 2.

[0027] [Type of polishing process] The polishing method using the abrasive composition of the present invention is not particularly limited, and it can be used for applications such as coated abrasive processing, grindstone polishing, lapping polishing, polishing polishing, and barrel polishing.

[0028] [Method of manufacturing abrasive composition] The polishing compound of the present invention can be obtained by mixing the above-mentioned components. Furthermore, the by-product fraction (elutriation purification by-product fraction, sludge) generated in the process of obtaining purified smectite by subjecting smectite-containing ore such as bentonite ore to elutriation purification can be recovered as the abrasive composition of the present invention or as a raw material thereof, thereby obtaining the abrasive composition of the present invention.

[0029] (Method for producing an abrasive composition using an elutriation purification 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 is described by Stokes' equation. 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 ore by elutriation, a large amount of water is added to the smectite-containing ore, the mixture is stirred, and the supernatant liquid is recovered and dried, thereby purifying smectite, which has a low specific gravity and easily swells in water. However, this elutriation purification process generates a sedimentary component (by-product fraction) with a higher specific gravity than smectite. This by-product fraction can be recovered and used as the abrasive composition of the present invention or as a raw material therefor. The method of obtaining purified smectite from smectite-containing ore by elutriation is known per se. Figure 3 shows a flow diagram of an example of a process for obtaining purified smectite and a by-product fraction from smectite ore by elutriation.

[0030] The by-product fraction may be recovered after one elutriation purification, or after multiple (preferably two or more, more preferably three or more) elutriation purifications. By performing elutriation purification multiple times, the particle size and specific gravity of the resulting precipitated components become uniform. As a result, a fraction with a narrow particle size distribution and high purity can be obtained. Alternatively, a fraction with a relatively high specific gravity that has settled by natural sedimentation or gentle centrifugation can be removed, and the by-product fraction that has subsequently settled under more severe centrifugation conditions can be used as the abrasive composition 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. The by-product fraction can be used as the abrasive composition of the present invention as is. Alternatively, the by-product fraction can be subjected to a desired treatment, such as drying, classification, or centrifugation, to obtain the abrasive composition of the present invention. In the present invention, the abrasive composition "derived from the by-product fraction" means that both of these forms are encompassed.

[0031] The above-mentioned elutriation purification method has difficulty in separating particles with similar specific gravities or components that strongly interact (bond), and therefore the obtained by-product fraction inevitably contains a certain proportion of smectite.

[0032] When the polishing composition of the present invention is obtained from the by-product fraction obtained by the above-mentioned elutriation purification, the resulting polishing composition has excellent polishing properties and can effectively suppress the inclusion of coarse particles. Furthermore, since the water dispersion treatment is carried out for a long period of time in the elutriation purification, it is expected that the interaction between the silicon dioxide (abrasive component) and smectite will be strong. As a result of this interaction, the silicon dioxide (abrasive grain) will be stably dispersed, and an abrasive composition with superior abrasive properties, storage stability (dispersion stability), abrasive lubricity, etc. can be obtained.

[0033] Thus, in one embodiment, the present invention provides the following method for producing an abrasive composition.

[0034] A method for producing an abrasive composition includes recovering a by-product fraction containing silicon dioxide as a main component, which is generated in the process of obtaining purified smectite by subjecting crushed smectite-containing ore to elutriation, and using the by-product fraction to obtain an abrasive composition containing silicon dioxide in the by-product fraction as an abrasive component.

[0035] According to the above-mentioned production method, by-product fractions that have conventionally been discarded can be effectively utilized as abrasive compositions, thereby contributing to the effective utilization of resources and enabling the inexpensive and stable supply of abrasives that exhibit excellent abrasive properties. [Example]

[0036] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0037] Example 1 Bentonite ore from Tsukinuno, Yamagata Prefecture, was crushed using a crushing roll. 3 parts by mass of the resulting coarsely crushed ore was mixed with 27 parts by mass of tap water and allowed to stand for 24 hours to swell the bentonite ore. The mixture was then stirred for 30 minutes using a stirrer, allowed to stand for 20 hours, and then the coarse precipitate was removed by decantation. The resulting supernatant was further separated using a centrifuge (conditions: 8000 × g, 15 minutes). The supernatant was removed, and the paste-like sediment was recovered to form the abrasive composition. The resulting abrasive composition was analyzed for its component composition and subjected to physical property tests as described below.

[0038] Example 2 The paste-like precipitated component was recovered in the same manner as in Example 1, except that bentonite raw ore from Mikawa, Niigata Prefecture was used instead of bentonite raw ore from Tsukinuno, Yamagata Prefecture, and used as an abrasive composition. The resulting abrasive composition was analyzed for its component composition and subjected to physical property tests as described below.

[0039] Example 3 20 parts by mass of distilled water was added to 18 parts by mass of quartz powder (model number: SI008BP, average particle size: 4 μm, manufactured by Kojundo Chemical Laboratory; hereinafter, this quartz powder will also be referred to as "quartz (reagent)") and stirred with a stirrer for 1 hour. Furthermore, 2 parts by mass of purified montmorillonite (trade name: Kunipia F, average particle size: 300 nm, manufactured by Kunimine Industries Co., Ltd.) was added, 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. The resulting paste-like dispersion was used as an abrasive composition. The resulting abrasive composition was subjected to the following physical property tests.

[0040] Example 4 A paste-like dispersion was obtained in the same manner as in Example 3, except that amorphous silicon dioxide powder (model number: 37049-01, average particle size: 8 μm, manufactured by Kanto Chemical Co., Ltd.) was used instead of the quartz powder, and this was used as an abrasive composition. The resulting abrasive composition was subjected to the following physical property tests.

[0041] (Comparative Example 1) A liquid dispersion was obtained in the same manner as in Example 3, except that a cationic surfactant (trade name: Liposocard C / 25, component name: polyoxyethylene palm alkylmethyl ammonium chloride, manufactured by Lion Corporation) was used instead of purified montmorillonite, and this was used as an abrasive composition. The resulting abrasive composition was subjected to the following physical property tests.

[0042] (Comparative Example 2) One part by mass of a cellulose-based compound (trade name: Metrose (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 using a planetary mixer (Thinky Mixer ARE-310) at 2000 rpm in stirring mode to obtain a viscous dispersion. 18 parts by mass of quartz powder (model number: SI008BP, average particle size: 4 μm, manufactured by Kojundo Chemical Laboratory Co., Ltd.) was added to the resulting dispersion, and the mixture was stirred and mixed again using the planetary mixer under the same conditions as above to obtain a viscous dispersion, which was used as an abrasive composition. The resulting abrasive composition was subjected to the following physical property tests.

[0043] (Comparative Example 3) 20 parts by mass of quartz powder (model number: SI008BP, average particle size: 4 μm, manufactured by Kojundo Chemical Laboratory) was added to 20 parts by mass of distilled water and stirred for 1 hour using a stirrer. Thereafter, the mixture was further stirred and mixed for 10 minutes using a planetary mixer (Awatori Rentaro ARE-310, manufactured by Thinky Corporation) at 2000 rpm in stirring mode. The resulting liquid dispersion was used as an abrasive composition. The resulting abrasive composition was subjected to the following physical property tests.

[0044] Comparative Example 4 A liquid dispersion was obtained in the same manner as in Comparative Example 3, except that amorphous silicon dioxide powder (model number: 37049-01, average particle size: 8 μm, manufactured by Kanto Chemical Co., Ltd.) was used instead of quartz powder, and this was used as an abrasive composition. The resulting abrasive composition was subjected to the following physical property tests.

[0045] [Analysis of component composition] The composition of the polishing compound compositions of Examples 1 and 2 was analyzed by the following method. The results are shown in Table 1. The component compositions of the polishing compound compositions of Examples 3 and 4 and Comparative Examples 1 to 4 were calculated from the blending amounts. These are also shown in Table 1.

[0046] (moisture content) The water content (mass%) in the abrasive composition was measured by the loss on drying at 105°C method in accordance with Japanese Industrial Standard JIS A 1125:2015.

[0047] (Smectite content) Taking advantage of the property of methylene blue to specifically adsorb between clay layers, the amount of methylene blue adsorbed to the purified smectite powder and the dry powder of the abrasive compositions of Examples 1 and 2 was measured, and the amount of smectite in the abrasive compositions of Examples 1 and 2 was calculated as follows. The methylene blue adsorption capacity of smectite was measured according to the Japan Bentonite Industry Association standard, JBAS-107-77 (filter paper method). As a reference smectite, we used high-purity (99% by mass or higher) purified smectite (product name: Kunipia F, derived from Tsukinuno, Yamagata Prefecture, or Mikawa, Niigata Prefecture, manufactured by Kunimine Co., Ltd.) obtained by repeated elutriation purification of bentonite ore from Tsukinuno, Yamagata Prefecture, or Mikawa, Niigata Prefecture, where the quartz peak detected around 27°C in X-ray diffraction (XRD) analysis had almost completely disappeared. The methylene blue adsorption capacity (unit: mmol / 100 g of purified smectite) of the reference purified smectite (powder dried at 105 °C for 2 hours) was measured, and this measurement was used as the methylene blue adsorption capacity (reference value) specific to montmorillonite in each bentonite 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. The abrasive compositions of Examples 1 and 2 were dried at 105°C for 2 hours and pulverized, and the methylene blue adsorption amount (unit: mmol / 100 g - purified smectite) of each resulting dry powder was measured. The methylene blue adsorption amount of the dry powder of the abrasive composition of Example 1, which used bentonite raw ore from Tsukinuno, Yamagata Prefecture, was divided by the standard value of 145 mmol / 100 g. The methylene blue adsorption amount of the dry powder of the abrasive composition of Example 2, which used bentonite raw ore from Mikawa, Niigata Prefecture, was divided by the standard value of 125 mmol / 100 g. Each value was then multiplied by 100 to obtain the smectite amount (montmorillonite amount, unit: mass (%)) in the solid content of each abrasive composition.

[0048] (quartz content) Using an XRD device, MiniFlex500 (manufactured by Rigaku Corporation), the X-ray reflection intensity was measured for the dry powders of the abrasive compositions of Examples 1 and 2 above in the measurement range of 2θ = 1 to 65°, and X-ray analysis data was obtained. The area of ​​the peak at around 2θ=27° derived from quartz was calculated from the X-ray analysis data of the dry powders of the abrasive compositions of Examples 1 and 2. Furthermore, as a reference value, the area of ​​the peak at around 2θ=27° derived from quartz in a 100% silicon dioxide standard having the same particle size distribution as each of the dry powders was calculated. The peak area obtained in Examples 1 and 2 was divided by the peak area obtained in each standard, and the resulting value was multiplied by 100 to obtain the quartz content (% by mass) in the solid content of each abrasive composition.

[0049] (Other ingredients) The content of other components was determined by subtracting the content (g) of montmorillonite and quartz from the solid content of the abrasive composition (the total amount (g) of the abrasive composition minus the content (g) of water). The X-ray analysis data above revealed that the dry powders of the abrasive compositions of Examples 1 and 2 contained traces of feldspar, calcite, and the like as other components.

[0050] [Physical property testing] The following tests were carried out on the polishing compound compositions of Examples 1 to 4 and Comparative Examples 1 to 4. The results are summarized in Table 1.

[0051] (dispersion stability) The polishing compound compositions of Examples 1 to 4 and Comparative Examples 1 to 4 were allowed to stand for 30 minutes after preparation, and the state of settling of the abrasive grain components (quartz, amorphous silicon dioxide) was visually observed. Cases where no settling was observed were rated "Good", and cases where settling was observed were rated "Poor".

[0052] (Dispersed particle size) The polishing compound compositions of Examples 1 to 4 and Comparative Examples 1 to 4 were diluted with distilled water to a dispersoid concentration of 0.01% by mass to prepare samples for particle size measurement. The average dispersed particle size (volume-based median diameter) of each of these samples for particle size measurement was measured using a laser diffraction / scattering particle size distribution analyzer LA-950V2 (manufactured by Horiba, Ltd.).

[0053] (particle size distribution) In the measurement of the average dispersed particle diameter, 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- Good: 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. △: The particle size distribution has one or more peaks in the particle size 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 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 in the range of particle diameters less than 15 μm and one or more peaks in the range of particle diameters 15 μm or more, and the maximum peak frequency value (%) of the peaks with particle diameters 15 μm or more exceeds 1 / 5 of the maximum peak frequency value (%) of the peaks with particle diameters less than 15 μm.

[0054] (Polishing test) Copper and lead plates (experimental metal plate set, manufactured by Kenis Co., Ltd.) measuring 15 mm wide x 45 mm long were prepared as polishing targets. Approximately 0.3 g of the abrasive compositions of Examples 1 to 4 and Comparative Examples 1 to 4 was dropped onto the copper and lead plates, and polished by manually sliding the abrasive composition back and forth vertically 20 times using paper (Kimwipe, manufactured by Nippon Paper Crecia Co., Ltd.) while applying a constant force, and the polishing state was visually observed. Note that the abrasive compositions of Comparative Examples 1, 2, and 4, in which sedimentation of abrasive grain components was observed in the sedimentation state observation, were stirred with a spatula immediately before use. The case where the surfaces of the copper plate and lead plate were mirror-finished by the polishing was judged as "Good", the case where the surfaces were almost mirror-finished but shallow scratches were also observed was judged as "Good", and the case where deep scratches were observed on the surface was judged as "Poor".

[0055] (Slipperiness test) In the above polishing test, the sliding property during polishing was evaluated. When the sample slid back and forth 20 times, there was little resistance and it slid very smoothly, it was judged as "Good." When there was more resistance than "Good" but the sample slid smoothly, it was judged as "Good." When there was much resistance (it felt like something was stuck) and the sample could not slide smoothly, it was judged as "Poor."

[0056] (Adhesion test) The copper plate and lead plate were placed vertically, and about 1 g of each of the abrasive compositions of Examples 1 to 4 and Comparative Examples 1 to 4 was attached to the surface of the copper plate and lead plate. The abrasive composition was left in this state for 1 minute, and a case where it did not move from the attached position was evaluated as "Good", and a case where it moved due to dripping or the like was evaluated as "Poor". The abrasive compositions of Comparative Examples 1, 2, and 4, in which sedimentation of abrasive grain components was observed in the observation of the sedimentation state, were stirred with a spatula immediately before use.

[0057] [Table 1]

[0058] As is clear from Table 1, the abrasive compositions of Comparative Examples 3 and 4, in which only quartz or amorphous silicon dioxide was dispersed in water, and the abrasive composition of Comparative Example 1, in which a surfactant was used as a substitute for smectite, exhibited poor dispersion stability of silicon dioxide, resulting in sedimentation of silicon dioxide. Furthermore, the peak frequency value of coarse particles with a particle size of 15 μm or more was high, resulting in poor polishing properties, as well as poor slip properties and adhesion. The abrasive composition of Comparative Example 2, in which a cellulose-based compound was used instead of smectite, exhibited improved dispersion stability of quartz and improved adhesion to the metal plate, but the other physical properties were similar to those of the abrasive compositions of Comparative Examples 1, 3, and 4.

[0059] In contrast, the abrasive compositions of Examples 1 and 2 derived from bentonite ore, and the abrasive compositions of Examples 3 and 4 in which silicon dioxide and smectite were dispersed in water, all had excellent dispersion stability, the particle size distribution was kept within a narrow range of smaller particle sizes, and they were excellent in polishing properties, slip properties, and adhesion. This shows that abrasive compositions excellent in each of the above-mentioned properties can be provided by preparing abrasive compositions using a by-product fraction containing silicon dioxide as the main component, which is generated in the process of obtaining purified smectite by subjecting pulverized smectite-containing ore to elutriation, or by forming abrasive compositions with the same particle size distribution or component composition as this abrasive composition.

[0060] Example 5 The abrasive composition of Example 1 was dried at 105°C for 24 hours to remove moisture. Thereafter, the resulting dried product was pulverized for 1 minute using a pulverizer (product name: NEW Yomekkosan, model number: Y-308B, manufactured by Yamamoto Electric Co., Ltd.) to pulverize it into fine particles, thereby obtaining the abrasive composition of Example 5. The resulting abrasive composition was subjected to the following analysis of the component composition and physical property tests.

[0061] Example 6 The abrasive composition of Example 2 was dried and pulverized in the same manner as in Example 5 to obtain the abrasive composition of Example 6. The resulting abrasive composition was subjected to the following analysis of its component composition and physical property tests.

[0062] (Comparative Example 5) Quartz powder (model number: SI008BP, average particle size: 4 μm, manufactured by Kojundo Chemical Laboratory Co., Ltd.) was used as the abrasive of Comparative Example 3. The resulting abrasive was subjected to the following physical property tests.

[0063] (Comparative Example 6) Amorphous silicon dioxide powder (model number: 37049-01, average particle size: 8 μm, manufactured by Kanto Chemical Co., Inc.) was used as the abrasive of Comparative Example 4. The resulting abrasive was subjected to the following physical property tests.

[0064] [Analysis of component composition] The compositions of the polishing compositions of Examples 5 and 6 were calculated by subtracting the water content from the compositions of the polishing compositions of Examples 1 and 2. The calculation results are shown in Table 2 below.

[0065] [Physical property testing] The following tests were carried out on the abrasives of Examples 5 and 6 and Comparative Examples 5 and 6. The results are summarized in Table 2.

[0066] (Polishing test) A copper plate and a lead plate (experimental metal plate set, manufactured by Kenis Co., Ltd.) measuring 15 mm wide x 45 mm long were prepared as the object to be polished. Approximately 0.15 g of the abrasives of Examples 5 and 6 and Comparative Examples 5 and 6 and the same amount of distilled water were dropped onto the metal plate and mixed, and then polished by manually sliding paper (Kimwipe, manufactured by Nippon Paper Crecia Co., Ltd.) back and forth in the vertical direction 20 times while applying a constant force, and the polished state was visually observed. The case where the surfaces of the copper plate and the lead plate were almost mirror-finished by the polishing was judged as "good", and the case where deep scratches were generated on the surface was judged as "poor".

[0067] (Slipperiness test) In the above polishing test, the sliding property during polishing was evaluated. If the sample slid smoothly over the 20 reciprocating strokes, it was evaluated as "Good." If the sample resisted too much (feeling stuck) and could not slide smoothly, it was evaluated as "Poor."

[0068] [Table 2]

[0069] As is clear from Table 2, the abrasives of Comparative Examples 5 and 6 were inferior in both abrasiveness and slipperiness even when suspended in water. In contrast, the polishing compound compositions of Examples 5 and 6 were redispersed well in water when suspended in water and had excellent polishing properties and slipperiness.

Claims

1. A method for producing an abrasive composition includes recovering a by-product fraction containing silicon dioxide as a main component, which is generated in the process of obtaining purified smectite by subjecting crushed smectite-containing ore to elutriation, and using the by-product fraction to obtain an abrasive composition containing silicon dioxide in the by-product fraction as an abrasive component.

2. 2. The method for producing a polishing composition according to claim 1, wherein the smectite is selected from the group consisting of montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite, and stevensite.

3. 2. The method for producing an abrasive composition according to claim 1, wherein the average particle size of the silicon dioxide contained in the abrasive composition is 0.1 to 100 μm.

4. 4. The method for producing an abrasive composition according to claim 1, wherein the content of the silicon dioxide is 50 to 98 mass % and the content of the smectite is 2 to 50 mass % in the solid content of the abrasive composition.

5. 4. The method for producing an abrasive composition according to claim 1, wherein the content of the silicon dioxide in the abrasive composition is 20 to 60 mass %, the content of the smectite is 1 to 20 mass %, and the content of the water is 30 to 70 mass %.

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