WO2011031470A1

WO2011031470A1 - Sintered agglomerate manufacturing method, sintered agglomerate, abrasive composition and abrasive article

Info

Publication number: WO2011031470A1
Application number: PCT/US2010/046598
Authority: WO
Inventors: Mayumi Yoshikawa; Toshihiro Kasai
Original assignee: 3M Innovative Properties Company
Priority date: 2009-08-25
Filing date: 2010-08-25
Publication date: 2011-03-17
Also published as: JP2013503103A; JP2011045938A; JP5676614B2

Abstract

A sintered agglomerate manufacturing method that produces a sintered agglomerate having a structure of densely-filled internal portions and uniformly dispersed abrasive particles, while suppressing the amount of foreign matter mixed into the sintered agglomerate. A manufacturing method for a sintered agglomerate including: causing a slurry containing a glass frit, abrasive particles and water-soluble polysaccharide to contact a metal salt-containing solution to prepare an agglomerate; and sintering the prepared agglomerate.

Description

SINTERED AGGLOMERATE MANUFACTURING METHOD, SINTERED AGGLOMERATE, ABRASIVE COMPOSITION AND ABRASIVE ARTICLE

Technical Field

[0001] The present invention relates to a sintered agglomerate manufacturing method, a sintered agglomerate, an abrasive composition and an abrasive article.

Background

[0002] Spray-dry methods have conventionally been the main method used to manufacture sintered agglomerates containing dispersed abrasive particles such as diamond particles, because such methods enable industrial mass production (See Patent Document 1 , for example)

Summary

[0003] In the spray-dry method, abrasive particles are dispersed in a slurry and the slurry is spray-dried in a large reaction container. The agglomerate of dried gel generated from the droplets of slurry is made to collide with the walls of the container and fall, whereupon it is collected and sintered.

[0004] In order to generate uniform abrasiveness, sintered agglomerates used in abrasive articles preferably have internal portions that are densely filled with abrasive particles and a binder. With the spray-dry method, however, it is difficult to achieve dense filling in the internal portions of the sintered agglomerate, especially when the grain diameter is 200 μηι or more. When the collected agglomerate is then sintered to prepare the sintered agglomerate, problems such as cavities forming in the internal portions and porosity can occur.

[0005] Moreover, in the spray-dry method, it is difficult to fully clean the inside of the reaction container, and so, when an agglomerate with a differing composition is subsequently prepared, there is a risk that matter adhering to the inside of the reaction container will be mixed into the agglomerate as contaminants. If the contaminants in an abrasive material include particles of an unintended large size, there is a risk that a catastrophic scratch mark will be formed in the article that is to be ground or polished. [0006] Hence, an object of the present invention can be to provide a manufacturing method that produces a sintered agglomerate having a structure of densely filled internal portions and uniformly dispersed abrasive particles, while suppressing the amount of foreign matter mixed-into the sintered agglomerate. A further object of the present invention can be to provide the sintered agglomerate manufactured using the above-described manufacturing method, together with an abrasive composition and abrasive article that make use of the sintered agglomerate.

[0007] In one aspect of the present invention, a sintered agglomerate manufacturing method is provided that includes: preparing an agglomerate by bringing a slurry containing a glass frit, abrasive particles and water-soluble polysaccharide into contact with a metal salt- containing solution; and sintering the agglomerate. According to the manufacturing method, it is possible to manufacture a sintered agglomerate having a structure of densely filled internal portions uniformly dispersed abrasive particles efficiently. Further, the sintered agglomerate manufactured using such a manufacturing method has a reduced amount of foreign matter mixed into the internal portions. Moreover, according to the manufacturing method, it is possible to prepare agglomerates with large particle diameters (300 μηι to 5 mm), which were difficult to prepare using the conventional spray-dry method, and it is simple to control the particle diameter distribution.

[0008] In another aspect of the present invention, a sintered agglomerate is provided that can be produced by sintering an agglomerate, the agglomerate having been prepared by bringing a slurry containing a glass frit, abrasive particles and water-soluble polysaccharide into contact with a metal salt-containing solution. The sintered agglomerate has a structure of densely filled internal portions and uniformly dispersed abrasive particles, with a reduced amount of foreign matter mixed into the internal portions. Consequently, abrasive articles that utilize the sintered agglomerate offer a favorable abrasive performance.

[0009] In an additional aspect of the present invention, an abrasive composition is provided that contains the sintered agglomerate manufactured using the above-described manufacturing method and a binder resin. This abrasive composition can be useful in the manufacture of abrasive articles. [0010] In an additional aspect of the present invention, Thus, an abrasive article is provided that has a backing and composites of abrasives, including the above-described abrasive composition, formed on at least one of the main surfaces of the backing.

[0011] In a further aspect of the present invention, a method is provided for manufacturing a sintered agglomerate having a structure of densely filled internal portions and uniformly dispersed abrasive particles, with a reduced amount of mixed-in foreign matter. In another aspect of the present invention, a sintered agglomerate is provided that is manufactured using the above-described manufacturing method, and an abrasive composition and abrasive article are also provided that utilize the sintered agglomerate.

Brief Description of Drawings

[0012]

Figure 1 is a perspective view of a first embodiment of an abrasive article of the present invention;

Figure 2 is a top view of a first embodiment of an abrasive article of the present invention;

Figure 3 is a flowchart showing a first embodiment of the manufacturing method of the present invention;

Figure 4 is a schematic view showing the first embodiment of the manufacturing method of the present invention;

Figure 5 is a schematic view showing the first embodiment of the manufacturing method of the present invention; and

Figure 6 includes schematic cross-sectional views of an agglomerate of hydrogel, an agglomerate of dried gel, and a sintered agglomerate.

Detailed Description

[0013] The sintered agglomerate manufacturing method of the present embodiment includes: preparing an agglomerate by causing a slurry containing a glass frit, abrasive particles and water-soluble polysaccharide to contact with a metal salt-containing solution; and sintering the agglomerate. Note that the slurry is a dispersion. According to the manufacturing method, it is possible to manufacture a sintered agglomerate having a structure of densely filled internal portions and uniformly dispersed abrasive particles efficiently. Further, the sintered agglomerate manufactured using such a manufacturing method has a reduced amount of foreign matter mixed into the internal portions. Further, according to the manufacturing method, it is possible to prepare a sintered agglomerate of larger grain diameter (300 μηι to 5 mm, for example) and densely filled internal portions. When an agglomerate of similarly large grain diameter is prepared using the conventional spray-dry method, it is difficult to avoid problems such as cavities forming in the internal portion and the grains becoming porous. Further, with the sintered agglomerate of the present embodiment, it is simple to control the grain diameter distribution so that, for example, the coefficient of variation does not exceed 0.2.

[0014] A glass frit is glass in powder or flake form, and, when sintered, functions to bind together the abrasive particles. The glass frit may be a silica glass frit, a silicate glass frit, a boron silicate glass frit, a phosphate glass frit, a bismuth-system glass frit or the like, or a combination thereof.

[0015] In the case of the silicate glass frit, the silica content may be 70 to 80 wt% to ensure that the sintered agglomerate has excellent strength. Besides the silica component, the silicate glass frit preferably contains 10 to 20 wt% sodium oxide, 5 to 10 wt% calcium oxide, 0.1 to 1 wt% aluminum oxide, and 2 to 5 wt% magnesium oxide. The silicate glass frit may be a marketed product, such as a silicate glass frit containing 73 wt% silica, 16 wt% sodium oxide, 5 wt% calcium oxide, 1 wt% aluminum oxide, 4 wt% magnesium oxide and 1 wt% potassium oxide, with respect to the total weight of the silicate glass frit.

[0016] In the case of the boron silicate glass frit, the silica content is preferably 50 to 80 wt% to ensure that the sintered agglomerate has favorable strength. Besides the silicate component, the boron silicate glass frit preferably contains 10 to 30 wt% boron oxide, 1 to 2 wt% aluminum oxide, 0 to 10 wt% magnesium oxide, 0 to 3 wt% zinc oxide, 0 to 2 wt% calcium oxide, 1 to 5 wt% sodium oxide, 0 to 2 wt% potassium oxide, and 0 to 2 wt% lithium oxide. The boron silicate glass frit may, for example, contain 52 wt% silica, 27 wt% boron oxide, 9 wt% aluminum oxide, 8 wt% magnesium oxide, 2 wt% zinc oxide, 1 wt% calcium oxide, 1 wt% sodium oxide, 1 wt% potassium oxide, and 1 wt% lithium oxide, with using the total weight of the boron silicate glass frit as a standard.

[0017] In the case of the phosphate glass frit, the phosphate content is preferably 30 to 80 wt% to ensure that the sintered agglomerate has favorable strength and water-resistance. Besides the phosphoric component, the phosphate glass frit preferably contains 0 to 30 wt% lead oxide/lead fluoride, 20 to 70 wt% antimony oxide, 1 to 5 wt% aluminum oxide, 0 to 10 wt% magnesium oxide, 0 to 3 wt% zinc oxide, 0 to 2 wt% calcium oxide, 1 to 5 wt% sodium oxide, 0 to 2 wt% potassium oxide, and 0 to 2 wt% lithium oxide.

[0018] In the case of the bismuth-system glass frit, the bismuth oxide content is preferably 20 to 75 wt% to ensure that the sintered agglomerate has favorable strength and water-resistance. Besides the bismuth oxide component, the bismuth-system glass frit preferably contains 0 to 30 wt% lead oxide/lead fluoride, 0 to 15 wt% silica, 5 to 40 wt% boron oxide, 0 to 5 wt% aluminum oxide, 0 to 10 wt% zirconium oxide, 0 to 15 wt% zinc oxide, 0 to 15 wt% calcium oxide, 0 to 15 wt% sodium oxide, and 0 to 15 wt% potassium oxide.

[0019] To prepare a sintered agglomerate with a uniform distribution of particles in the internal portions and more dense filling, the average particle diameter of the glass frit is preferably 50 μηι or less, more preferably 20 μηι or less, and even more preferably 10 μηι or less. Further, to prevent the slurry from becoming excessively viscous as a result of increasing surface area, the average particle diameter is preferably no less than 100 nm. Note that the average particle diameter of the glass frit can be measured with a particle size analyzer using laser diffraction, a Coulter counter, or the like.

[0020] It is desirable that the glass frit fuses at a temperature at which the abrasive particles do not decompose, melt or soften. A glass frit with these properties can, for example, be formed from so-called low-melting point glass. The softening point of the glass frit is preferably in a 800 to 600°C range, and more preferably in a 750 to 700°C range. When the softening point is at least the above-described lower limit, the water-resistance and mechanical strength of the sintered agglomerate tend to improve. Further when softening point does not exceed the above-described upper limit value, the glass frit and the abrasive particles can be bound using a small amount of heat, and energy consumption can be reduced.

[0021] In the slurry containing the glass flit, the abrasive particles and the water-soluble polysaccharide, the glass frit content can be adjusted appropriately according to the desired properties of the sintered agglomerate, but is preferably 40 to 5 wt% and more preferably 20 to 10 wt% with respect to the total weight of the slurry. When the contents of the glass frit are in either of these ranges, it is possible to prepare a sintered agglomerate with sufficient bonding between the abrasive particles and without reducing the abrasive capability of the abrasive particles.

[0022] The abrasive particles can be changed according to the abrasive properties desired in the sintered agglomerate. If the sintered agglomerate is to be used to grind or polish an object such as glass hard disks, semiconductor devices or optical devices, the abrasive particles preferably include mineral particles with a Mohs hardness of 5 or more.

[0023] The abrasive particles can be any one or more of diamond particles, silicon carbide particles, green silicon carbide particles, aluminum oxide particles(fused aluminum oxide, ceramic aluminum oxide, heat treated aluminum oxide, sintered alpha alumina, white fused aluminum oxide, brown fused aluminum oxide, mono crystalline fused aluminum oxide), zirconia particles, alumina zirconia particle, fused alumina zirconia particle, ceramic- modified aluminum oxide particles, cubic boron nitride particles, titanium carbide particles, titanium nitride particles, cerium oxide particles and silicon dioxide particles, boron carbide particle, boron oxides particle in the form of B. sub.60 and B. sub.100,, garnet particle, Tripoli particle, boron carbonitride particle, boehmite-derived particle. The diamond particles have extremely high hardness compared to the other above-described abrasive particles, and are suitable for sintered agglomerates that are to be used in high-precision grinding and polishing of difficult materials, such as in wafer grinding and the like. Note that, In one embodiment, abrasive grains "CUBITRON"(3M's Trade Mark) are able to be purchased from 3M Company (St. Paul, Minn.). [0024] The average particle diameter of the abrasive particles can be changed according to the average particle diameter of the sintered agglomerate being prepared, but may, for example, be in a 0.01 μηι to 100 μηι range.

[0025] When, as in this case, both the sintered agglomerate and the abrasive particles are particulate in nature, the ratio between the average grain diameter X of the sintered agglomerate and the average particle diameter Y of the abrasive particles (Y x 100/X(%)) is preferably 0.0001% to 20%, more preferably 0.05% to 5%, and even more preferably 0.2% to 3% to improve the uniformity of the internal portions of the sintered agglomerate. Note that the average grain size of the sintered agglomerate can be adjusted by appropriately changing the size of slurry droplets when the slurry is dropped into the metal salt-containing solution. Further, the average grain diameter of the agglomerate can be measured by sieve classification or sedimentation.

[0026] If the abrasive particles have one or more of a softening point, a melting point and a decomposition temperature, the softening point of the glass frit is preferably lower than any of the temperatures. By using a glass frit of this type, it is possible to achieve spherical abrasive members in which the abrasive particles are uniformly dispersed through the sintered agglomerate, and thereby realize excellent abrasive properties. It is also possible to suppress further the formation of cavities in the internal portions of the sintered agglomerate.

[0027] The abrasive particle content of the slurry can be appropriately adjusted according to the desired properties of the sintered agglomerate, but is preferably 50 to 10 wt% and more preferably 30 to 10 wt% of the total slurry weight. When the content is kept in these ranges, the abrasive characteristics of the abrasive particles are more markedly expressed in the abrasive article.

[0028] The water-soluble polysaccharide may be a monovalent cation-containing alginate, an LM-pectinate, or the like. The salt containing the monovalent cation may be an alkali metal salt or an ammonium salt. Of these, it is preferable to use sodium salts, potassium salts and ammonium salts. From the point of view of being able to prepare a sintered agglomerate having abrasive particles uniformly dispersed in the internal portions, and the point of view of being able to form spherical agglomerates easily and thus further reduce the amount of foreign matter mixed in when forming the spherical agglomerate, it is preferable to select at least one of sodium alginate, ammonium alginate and LM-pectin, and it is particularly preferable to select sodium alginate or ammonium alginate from among the above-described water-soluble polysaccharides.

[0029] The concentration of the water-soluble polysaccharide in the slurry is preferably 0.05 to 5 wt%, more preferably 0.1 to 3 wt%, and even more preferably 0.3 to 1 wt%. By setting the concentration of water-soluble polysaccharide within the above-described range, the agglomerate is made to form quickly and reliably when the slurry makes contact with the metal salt-containing solution. As a result, a sintered agglomerate having more densely filled internal portions can be prepared more easily, and the abrasive properties of the abrasive article can be improved.

[0030] The slurry may further contain additives such as an alcohol, an organic binder and a dispersant (surfactant).

[0031] When the slurry contains an alcohol as an additive, the viscosity of the slurry tends to rise. In other words, it is possible to adjust the viscosity of the slurry by changing the added quantity of alcohol. The added quantity of alcohol is preferably set within a range which allows the water-soluble polysaccharide to be sufficiently dissolved.

[0032] The viscosity of the slurry is preferably at least 1 mPa.s, more preferably at least 100 mPa.s, and even more preferably at least 300 mPa.s. When the slurry of this type is caused to contact the metal salt-containing solution, a sintered agglomerate with a uniform shape can be prepared more easily. Further, the viscosity of the slurry is preferably no more than 3000 mPa.s, more preferably no more than 2000 mPa.s, and even more preferably no more than 1000 mPa.s. A slurry of this type is suitable for being continuously dropped, as uniform droplets, into the metal salt-containing solution, and this improves the productivity.

[0033] One example of a slurry with a viscosity in the above-described ranges is a slurry containing 5 to 20 wt% glass frit, 5 to 20 wt% abrasive particles, 0.1 to 1 wt% water-soluble polysaccharide, and 30 to 80 wt% water.

[0034] The metal salt-containing solution is a solution that forms the agglomerate when the slurry is brought into contact with it, and may contain metal ions such as Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Mn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Co³⁺, Ni²⁺, Cu²⁺, Al³⁺, or Cr³⁺. The metal salt-containing solution is preferably a solution containing divalent metal ions, more preferably a solution

• · · 2 2 2 2"!" 2 containing at least one type of metal ion selected from among Mg , Ca^ZT, Sr^ZT, Ba , Mn , Fe , Co , Ni , OT and A1^JT, and even more preferably a solution containing at least one type of metal ion from among Ca , Sr , Ba , Al , Mn , Fe , Co , Ni and Cu . When the solution containing the metal ions is used, the agglomerate forms quickly and reliably when the slurry is caused contact the metal salt-containing solution.

[0035] The above-described metal ions are dissolved in the metal salt-containing solution as the metal salts. For example, suitable metal ions could be formed by dissolving metal salts like a chloride, a bromide, an iodide, a sulfate, a carbonate, a nitrate, a phosphate or the like into solution.

[0036] Since the metal salt-containing solution makes use of normal water as the solvent, it is desirable that the metal salt is water-soluble. Thus, the chlorides, the bromides and the iodides of various metals can be suitably used, with the chlorides being particularly suitable. Examples of chlorides include calcium chloride, manganese chloride, iron chloride, cobalt chloride, nickel chloride and copper chloride.

[0037] To have the agglomerate form quickly and reliably, the metal salt-containing solution preferably has a metal salt concentration of 0.1 to 5 mol/1, and more preferably has a concentration of 0.5 to 2 mol/1.

[0038] The following describes the manufacturing method for the sintered agglomerate according the present embodiment, with reference to the drawings.

[0039] The manufacturing method for the sintered agglomerate of the present embodiment consists of causing the slurry containing the glass frit, the abrasive particles and the water- soluble polysaccharide to contact a metal salt-containing solution to prepare an agglomerate, and sintering the agglomerate. With the manufacturing method of the present embodiment, it is also possible to prepare a spherical sintered agglomerate by, for example, dropping droplets of the slurry into the metal salt-containing solution to prepare a spherical agglomerate and sintering the spherical agglomerate. Alternatively, a sintered agglomerate with predetermined form can be prepared by causing a slurry, which has been introduced to concave portions with predetermined form, to contact the metal salt-containing solution to prepare an agglomerate with predetermined form, and sintering the agglomerate with predetermined form.

[0040] With the manufacturing method in which the agglomerate is prepared by dropping droplets of the slurry into the metal salt-containing solution, it is possible to easily manufacture a sintered agglomerate having densely filled internal portions and an average particle size of 300 μηι to 5 mm, something that was difficult to achieve using conventional manufacturing methods.

[0041] With a manufacturing method of this type, when the slurry containing the glass frit, the abrasive particles and the water-soluble polysaccharide is dispensed as droplets into the metal salt-containing solution, the water-soluble polysaccharide instantaneously undergoes ion exchange with the metal ions from the metal salt-containing solution to form an insoluble salt, and gelation takes place without any change to the spherical form of the droplets. After dispensing the droplets into the metal salt-containing solution, the agglomerate is generally left for several hours to allow gelation to proceed sufficiently. The resulting spherical agglomerate is washed in distilled water or the like and dried, and then sintered by heating to the fusing temperature band of the glass frit, thereby forming the sintered agglomerate.

[0042] Note that, within the agglomerate obtained in the metal salt-containing solution, the insoluble polysaccharide salt forms a hydrogel including the solvent used to adjust the slurry or the solvent (generally water) of the metal salt-containing solution, and the abrasive particles and glass frit can be seen as being held in the hydrogel. In the following, the agglomerate of this type is referred to as an agglomerate of hydrogel. Figure 6(a) is a schematic cross-sectional view showing the agglomerate of hydrogel formed from the abrasive particles 1 1 1 and glass frit 1 12 held in the hydro-polysaccharide 1 13, which is the hydrogel.

[0043] Further, when the above-described agglomerate of hydrogel is dried, the result is called an agglomerate of dried gel. In the agglomerate of dried gel, the abrasive particles and the glass frit can be seen as being held in a dry gel made up of a polysaccharide salt containing very little solvent. Compared to the agglomerate of hydrogel, the agglomerate of dried gel has a smaller grain diameter and is more densely filled with the abrasive particles and glass frit. Figure 6(b) is a schematic cross-sectional view showing the agglomerate of dried gell20 made of the dried polysaccharide 1 14, and the abrasive particles 1 1 1 and glass frit 1 12 held by the dried polysaccharide 1 14.

[0044] Figure 6(c) is a schematic cross-sectional view showing the sintered agglomerate obtained by sintering the agglomerate of dried gel. In the sintered agglomerate, the glass frit 1 12 in the agglomerate of dried gel has fused to produce a glass matrix 1 15 with a dense structure that holds the abrasive particles 1 1 1. The dried polysaccharide 1 14 is burned off at sintering and is largely eliminated from the sintered agglomerate. The glass frit causes the agglomerate to contract. Hence, the particle diameter of the sintered agglomerate is smaller than that of the agglomerate of dried gel. Note also that, although not shown in figure 6, when the dried polysaccharide 1 14 is a metal salt, the sintered agglomerate may contain metal deriving from the dried polysaccharide 1 14. Thus, in certain cases, the metal deriving from the metal ions contained in the above-described metal salt-containing solution may be included in the sintered agglomerate.

[0045] In the above-described manufacturing method, the slurry is generally prepared by uniformly mixing the glass frit and the abrasive particles, and then adding the polysaccharide- containing solution to the mixture. When the slurry is prepared in this way, the glass frit and the abrasive particles are uniformly dispersed in the slurry, and the agglomerate with uniform internal portions can be prepared more easily. Also, if the slurry is prepared using this method, it becomes easier to estimate the viscosity of the slurry when the viscosity of the polysaccharide-containing solution is adjusted. Consequently, the viscosity of the slurry can be easily changed. Note that the agglomerate of hydrogel can be formed in a stable manner by appropriately adjusting the viscosity of the slurry.

[0046] Here, the solvent used in the polysaccharide-containing solution must dissolve the water-soluble polysaccharide, and is preferably water. For the polysaccharide-containing solution, an aqueous sodium alginate solution is optimal because it is easy to obtain and handle, but ammonium alginate can be used when the introduction of sodium is undesirable. In the polysaccharide salt-containing solution, the relative content of the polysaccharide salt with respect to the total weight of the polysaccharide salt-containing solution is preferably 0.1 to 10 wt%, more preferably 0.5 to 8 wt%, and even more preferably 1 to 5 wt%.

[0047] Here, the viscosity of the slurry is preferably adjusted to 1 to 5000 mPa.s but is selected appropriately according to the necessary grain size. If the viscosity of the slurry is in the above-described range, the droplets have favorable stability. Hence, the spheres of agglomerate are formed stably when the slurry is dropped into the metal salt-containing solution. Note that the viscosity of the slurry tends to increase as the concentration of the polysaccharide in the polysaccharide-containing solution increases, and tends to decrease as the concentration of the polysaccharide decreases. Also, the viscosity of the slurry tends to increase as the combined content of the glass frit and the abrasive particles in the slurry increases, and decrease as the combined content of the glass frit and abrasive particles decreases. Alginic acid includes components of marrunonic acid and guluronic acid, and the viscosity increases as a ratio between the number of parts of marrunonic acid and the number of parts guluronic acid, known as the M/G ratio, decreases. Although this phenomenon can be considered to be one of the main factors affecting the slurry viscosity, the range of the M/G ratio is not limited in the present invention.

[0048] The slurry dropping method can be a well-known droplet preparation technique, such as dropping using a nozzle, sprayer or Ink-jet method. However, to obtain a sintered agglomerate with a narrow grain diameter distribution, it preferable to use a method which allows the continuous formation of uniform droplets. Further, dropping the slurry using a dropping method which allows suitable adjustment to the diameter of the droplets makes it easy to obtain a sintered agglomerate having a predetermined average grain diameter. Further, when there is a large difference in the specific gravity of the glass frit and the abrasive particles, a sintered agglomerate with a uniform internal structure can be obtained by dropping the slurry while stirring it thoroughly.

[0049] The metal salt-containing solution forms the polysaccharide salt to generate the insoluble gel, and contains the resulting metals ions. For the metal salt-containing solution, an aqueous calcium chloride solution, an aqueous manganese chloride solution, an aqueous cobalt chloride solution, an aqueous nickel chloride solution, an aqueous copper chloride solution or the like is used. The metal salt-containing solution may include a colorant to color the agglomerate.

[0050] When the slurry is dropped, it is preferable that the spherical agglomerate of hydrogel floating in the metal salt-containing solution is stirred using a stirrer or the like to encourage uniform dispersion of the abrasive particles in the internal portion of the agglomerate of hydrogel by the time gelation reaches completion. Further, the agglomerate of hydrogel prepared by dropping the slurry is preferably immersed for a predetermined period of time in the metal salt-containing solution to allow gelation to advance sufficiently. Here, the period of immersion depends on the relative composition of the slurry, the concentration of the metal salt-containing solution and the like, but is generally 0.1 to 30 hours at room temperature, and preferably 0.1 to 3 hours at room temperature.

[0051] After the agglomerate of hydrogel that has formed in the metal salt-containing solution is removed from the metal salt-containing solution, the agglomerate of hydrogel is preferably washed in distilled water and dried before sintering. When drying, the heat applied is preferably set to a level at which sudden deformations to the agglomerate do not occur, such as 50 to 80°C (for 5 to 12 hours, for example). During drying, the grains of agglomerate of hydrogel may be at rest or rotationally stirred in continuous manner. Further, the sintering is performed at a temperature at which at least a portion of the glass frit contained in the agglomerate will soften. Although the sintering temperature can be appropriately selected according to the softening point of the glass frit, the glass frit preferably made to soften while suppressing softening, melting, decomposition and the like in the abrasive particles. The sintering temperature is thus dependent on the decomposition temperature of the abrasive particles and the softening point of the glass frit, and is generally selected to be 500 to 1500°C. For example, when the abrasive particles are diamond particles, the temperature is preferably from 650 to 750°C. During the sintering also grains of the agglomerate of dried gel may be at rest or rotationally stirred in continuous manner. To prevent the grains of the agglomerate fusing together at sintering, the agglomerate can be covered with a powder, such as alumina, which has a higher melting point than the softening point or melting point of glass. [0052] With the manufacturing method including the above-described steps, the concentration and viscosity of the slurry and the nozzle diameter and dropping speed of the dropping device can be adjusted allow preparation of a sintered agglomerate of a target size with a extremely narrow grain size distribution. Also, it is possible to continuously mass- produce the sintered agglomerate with a uniform shape.

[0053] A flowchart of a first embodiment of the sintered agglomerate manufacturing method is shown in Figure 3. In a first mixing step SI , the water-soluble polysaccharide and the distilled water are mixed. In a second mixing step S2, the mixed solution prepared in SI is mixed with the abrasive particles and the glass frit to prepare the slurry. In a contact step S3, the slurry prepared in step S2 is made to contact the metal salt-containing solution by, for example, dropping the slurry into the metal salt-containing solution. In S3, the agglomerate of hydrogel is generated by causing the slurry prepared in step S2 to contact the metal salt- containing solution. In a gelation step S4, the agglomerate of hydrogel generated in S3 is made to contact the metal salt-containing solution for a predetermined amount of time, allowing gelation to reach the internal portions the agglomerate of hydrogel. In a washing step S5, the agglomerate of hydrogel prepared via S4 is washed in distilled water. Here, the washing method may include dispersing the agglomerate of hydrogel in the distilled water and stirring or the like. In a drying step S6, the agglomerate of hydrogel is dried to prepare the agglomerate of dried gel. There are no particular limits on the drying method, and the agglomerate of dried gel can, for example, be prepared by heating the agglomerate of hydrogel in an oven at 50 to 80 °C. Note that, although the amount of water held by the agglomerate of dried gel is a smaller than the amount held by the agglomerate of hydrogel, it is acceptable for the agglomerate of dried gel to contain a small amount of water. In a sintering step S7, the agglomerate of dried gel is sintered to prepare the sintered agglomerate. The sintering can be performed by, for example, heating the agglomerate of dried gel at 500 to 1500°C in an electric furnace.

[0054] Schematic views of the first embodiment of the sintered agglomerate manufacturing method are shown in Figures 4 and 5. [0055] In this embodiment, a predetermined amount of distilled water is introduced to a container 20 that includes a stirrer 21 , and a water-soluble polysaccharide 102 is added while stirring to prepare an aqueous polysaccharide-containing solution 103. Next, a glass frit 104 and abrasive particles 105 are added to the aqueous polysaccharide-containing solution 103 while stirring. Here, the glass frit 104 and the abrasive particles 105 may be added simultaneously or sequentially. After adding the glass frit 104 and the abrasive particles 105, the mixture is stirred sufficiently to prepare a slurry 106.

[0056] Next, the slurry 106 is transferred to a quantitative dispenser 23 at a constant flow rate by a pump with flow controller 22, and the slurry is dispensed from this quantitative dispenser 23 as droplets into a Metal salt solution 107. Here, the dropping speed for the slurry 106 can be set to a desired value by control of the pump with flow controller 22. Further, the size of the droplets during the dropping of the slurry 106 can be appropriately adjusted using the quantitative dispenser 23. Here, the grain diameter of the sintered agglomerate can be freely adjusted by adjusting the size of the droplets of the slurry 106. The slurry 106 dropped into the Metal salt solution 107 undergoes gelation, and an agglomerate of hydrogel 108 is obtained. Here, a container 24 of the Metal salt solution 107 preferably includes a stirrer 25, and the Metal salt solution 107 is preferably stirred by the stirrer 25 as the slurry 106 is dropped. Stirring prevents the slurry sinking in the gel at a stage when the gelation of the agglomerate of hydrogel is incomplete, and thereby prevents variation in the composition. As a result, it is possible to prepare an agglomerate of hydrogel with a grain diameter and structure of improved uniformity. After dropping the slurry 106, the gelation is allowed to advance sufficiently to the internal portions of the agglomerate of hydrogel 108 in the Metal salt solution.

[0057] Next, the agglomerate of hydrogel 108 is dispersed in the distilled water 109 and washed. After washing, the agglomerate of hydrogel 108 is heated using an electric oven for drying 28, and thereby dried to prepare the agglomerate of dried gel 1 10. Next, the agglomerate of dried gel 1 10 is sintered using the electric furnace 29 for sintering to prepare the sintered agglomerate 120. [0058] The following describes the abrasive composition and abrasive article of the present embodiment.

[0059] The sintered agglomerate of the present embodiment can be used in a number of conventional abrasive products, including coated abrasive products, bonded abrasive products (such as glass-type, resin-type and metal grinding wheels, cutting wheels, point-mounted abrasives, and honing stones), non-woven(weave) abrasive products, and abrasive brushes. The sintered agglomerate can also simply be dispersed in a solution or the like, and used as a free abrasive. In this case, the abrasive compound (polishing compound, for example) can be used as the abrasive in a milling medium, shot-blast medium, vibrating mill medium or the like in a slurry used for grinding.

[0060] Further, an abrasive composition can be provided by including a binder resin with the sintered agglomerate. Such an abrasive composition is useful in the manufacture of abrasive articles. Using the above-described abrasive composition, it is possible to provide an abrasive article including a backing and composites of abrasives, where the composites of abrasives include the abrasive composition and are formed on at least one of the main surfaces of the backing. An abrasive article of this type has excellent abrasive properties due to the densely filled internal structure of the sintered agglomerate. Here, the binder resin bonds and holds together a plurality of sintered agglomerate grains. An abrasive article including the abrasive composition in which the sintered agglomerate is held by the binder resin in the manner described can be used in problematic cases when the sintered agglomerate might otherwise be used in a slurry and be disposed of without providing abrasiveness. The losses of the sintered agglomerate are then reduced and polishing or grinding can be performed efficiently.

[0061] The binder resin is preferably a thermosetting resin and can, for example, be any of phenol resin, aminoplast resin, urethane resin, epoxy resin, unsaturated ethylene resin, acrylic isocyanurate resin, urea-formaldehyde resin, isocyanurate resin, acrylic urethane resin, acrylic epoxy resin, bismaleimide resin, or the like. Alternatively, the binder may be a combination of a plurality of the above-described resins.

[0062] Further, the abrasive composition many include additives such as fibers, lubricants, wetting agents, thixotropic materials, surfactants, pigments, dyes, antistatic agents (such as carbon black, vanadium oxide or graphite), coupling agent (such as a silane, a titanate or a zirco aluminate), plasticizer and suspending agent. These additives can be included as appropriate to give the desired characteristics.

[0063] The abrasive article of the present embodiment includes a backing and composites of abrasives which include the abrasive composition and are formed on at least one main surface of the backing.

[0064] The first embodiment of the above-described abrasive article is shown in Figure 1 and Figure 2. Figure 1 is perspective view of an abrasive article 10 that has a plurality of composites of abrasives 1 1 formed on a backing 14. The composites of abrasives 1 1 contain a plurality of the sintered agglomerate dispersed in binder resin. Figure 2 is a top view of the abrasive article 10. Here, the composites of abrasives 1 1 have a rhomboid shape and are arranged in a regular manner on the backing 14. By arranging the composites of abrasives 1 1 in a regular manner in this way, uniform abrasive properties are achieved for the abrasive article 10.

[0065] Note that the composites of abrasives 1 1 are preferably separate from one another. Separating the composites of abrasives 1 1 in this way allows a fluid medium to flow freely in the gaps. By designing the abrasive article 10 to allow a fluid medium flow freely between the composites of abrasives 1 1 , the abrasive article 10 is given favorable surface-finishing properties. Note also that the space separating the composites of abrasives 1 1 may also be referred to as "land area".

[0066] The abrasive article 10 preferably includes at least 5 composites of abrasives 1 1 per 1 cm² in top view, and more preferably includes at least 100 composites of abrasives 1 1 per 1 cm².

[0067] The height of the composites of abrasives 1 1 is preferably constant, but may vary. The height of the composites of abrasives 1 1 is preferably 10 to 25,000 μηι, more preferably 25 to 15,000 μηι, still more preferably 100-10,000 μηι, and most preferably 1 ,000 to 8,000 μηι.

[0068] The composites of abrasives can have any of various forms, and can be formed on the backing in as cubes, blocks, cylinders, prisms, cuboids, pyramids, pyramid sections, cones, conic sections, crosses, columns having a fiat upper surface, semi-spheres or the like. The abrasive article may have a plurality of composites of abrasives of different forms.

[0069] The backing functions to support the composites of abrasives. The backing is preferably a material with favorable toughness and durability to give the resulting abrasive article a long lifetime, and may be a polymer film, paper, vulcanized fiber, formed or injection molded elastomer, treated non-fibrous backing, treated fiber, or the like. The polymer film may, for example, be polyester film, co-polyester film, polyimide film, or polyamide film.

[0070] The backing can include additives such as filler, fiber, dye, pigment, wetting agent, a coupling agent, a plasticizing agent, or the like, and may include a reinforcing scrim or fiber such as NOMEXTMTM obtainable from the DuPont Company (Wilmington, Delaware).

[0071] In certain cases, a backing formed in an integrated way with the composite of abrasives is preferable. Instead of attaching the composite of abrasives to the fiber or other backing, the backing is formed directly onto the composite of abrasives. After forming the composites of abrasives, the backing may be formed or molded on the rear side of the composites of abrasives. Alternatively, the composites and the backing may be formed or injection molded simultaneously. This type of backing is generally formed from a thermoplastic or thermosetting resin, which is cured with heat or radiation. Here, preferable thermosetting resins include phenol resin, aminoplast resin, urethane resin, epoxy resin, unsaturated ethylene resin, acrylic isocyanurate resin, urea-formaldehyde resin, isocyanurate resin, acrylic urethane resin, acrylic epoxy resin, bismaleimide resin, or some mixture of these. Further, preferable thermoplastic resins include polyamide resin (such as nylon), polyester resin, and polyurethane resin (including polyurethane-urea resin). Of the above described resins, polyester polyol and the polyurethane induced from the reaction product of polyether polyol and isocyanate are particularly suitable due to their favorable durability.

Examples

[0072] (Examples 1 to 6) A glass frit of BA351 (Bi system low-melting point glass, softening point 598°C, made by Nihon Yamamura Glass), LFZ80 (Zn-B system low-melting point glass, softening point 580°C, made by Nihon Yamamura Glass), 4724(S) and 4724(30 μηι) (boric silicate system low-melting point glass, softening point 620°C, made by Nihon Houru Yuyaku), PCS (phosphate-system low-melting point glass, softening point 680°C, made by Nihon Houru Yuyaku), abrasive particles (diamond particles) of LS6BXT 1/2-1 , LS6BXT 6-1 1 , LS6BXT 22-36 (made by LANDS PRODUCTS) and RJK-1C3M (made by GE Micron PRODUCTS) were mixed in the ratios shown in table 1 , and dispersed in 8g of 1 wt% aqueous sodium alginate solution. The slurry dispersion was dropped into 10 wt% aqueous calcium chloride solution using a dropping device with a nozzle diameter of 500 μηι, and the naturally forming spherical gel agglomerate was dried overnight at 80°C. The dried spherical gel agglomerate was then heated to temperatures (700 to 750°C) around the respective softening points of the glass frits, to prepare the sintered agglomerates of Examples 1 to 16. The colors and forms of the resulting sintered agglomerates are as described in Table 1.

[0073] (Examples 17 to 24)

The glass frit and the abrasive particles were mixed in the ratios described Table 1 and a method similar to that of Example 1 , except in that the mixture was dispersed in 3g of 1 wt% aqueous sodium alginate solution, was used to prepare the sintered agglomerate of Examples 17 to 24. The colors and shapes of the resulting sintered agglomerates are as described in Table 1.

[0074] (Example 25)

The glass frit and the abrasive particles were mixed in the ratios described Table 1 , and a method similar to that of Example 1 , except in that the mixture was dispersed in 8g of 1 wt% aqueous ammonium alginate solution, was used to prepare the sintered agglomerate of Example 25.

The colors and forms of the resulting sintered agglomerates are described in Table 1.

[0075] Load experiments were performed on the sintered agglomerate of Examples 1 to 25. In the simple load experiments, a single grain of the sintered agglomerate was placed on a set of scales, a load was gradually applied, and a reading was taken when the grain fractured. The results of the loading experiments are as described in Table 1.

[0076]

[Table 1]

[0077] In each of Examples 1 to 25, spherical agglomerate of hydrogel, agglomerate of dried gel, and sintered agglomerate were favorably formed. On observing the surface and cross- section using an electron microscope, it was found that the diamond particles were uniformly dispersed in the inner portions of the agglomerate and that the structure was fine. Optimal conditions differ depending on the combination of factors such as the diameters of the particles of the glass frit and the diamond particles and the sintering temperature of the glass frit. However, it was possible to confirm that the above-described spherical sintered agglomerate manufacturing method is widely applicable and effective as a method for manufacturing a sintered agglomerate having a uniform and dense internal structure.

[0078] Load experiments were performed on the sintered agglomerate of Examples 1 to 25. In the simple load experiments, a single grain of the sintered agglomerate was placed on a set of scales, a load was gradually applied, and a reading was taken when the grain fractured. The results of the loading experiments are as described in Table 1.

Claims

What is claimed is:

1. A manufacturing method for a sintered agglomerate comprising:

preparing an agglomerate by causing a slurry containing a glass frit, abrasive particles and water-soluble polysaccharide to contact a metal salt-containing solution; and

sintering the agglomerate.

2. The manufacturing method according to claim 1 , wherein the slurry is caused to contact the metal salt-containing solution by dispensing droplets of the slurry into the metal salt-containing solution.

3. The manufacturing method according to either claim 1 or 2, wherein the water-soluble polysaccharide is a polysaccharide salt.

4. The manufacturing method according to claim 3, wherein the polysaccharide salt is a salt containing a monovalent cation.

5. The manufacturing method according to any of claims 1 to 4, wherein a concentration of the water-soluble polysaccharide in the slurry is from 0.3 to 5 wt%.

6. The manufacturing method according to any of claims 1 to 4, wherein the slurry contains 5 to 20 wt% glass frit, 5 to 20 wt% abrasive particles, 0.1 to 1 wt% water-soluble polysaccharide, and 30 to 80 wt% water.

7. The manufacturing method according to any of claims 1 to 6, wherein the water- soluble polysaccharide is one of an aliginic acid or an alginate.

8. The manufacturing method of any of claims 1 to 7, wherein the metal salt-containing solution contains at least one type of metal ion selected from among Mg , Ca , Sr , Ba ,

Mn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Co³⁺, Ni²⁺, Cu²⁺, Al³⁺ and Cr³⁺.

9. The manufacturing method according to any of claims 1 to 8, wherein the metal salt- containing solution contains 1 to 20 wt% metal salt.

10. The manufacturing method according to any of claims 1 to 9, wherein the abrasive particles are diamond particles.

1 1. The manufacturing method of any of claims 1 to 10, wherein the glass frit is a low- melting point glass frit.

12. A sintered agglomerate produced by sintering an agglomerate, the agglomerate being prepared by causing a slurry containing a glass frit, abrasive particles and a polysaccharide salt to contact a metal salt-containing solution.

13. An abrasive composition comprising:

the sintered agglomerate manufactured by any of the manufacturing method of claims

1 to 11;

and a binder resin.

14. An abrasive article comprising: backing; and a plurality of composites of abrasives that include the abrasive composition of claim 13, formed on at least one main surface of the backing.