Rubber grindstone for polishing

Abstract

To provide a rubber grindstone for polishing that efficiently performs polishing to a hard-to-polish material such as ceramics or metal.SOLUTION: A rubber grindstone for polishing includes a polishing part including a binder (A), polishing particles (B), and diatomaceous earth particles (C).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber grindstone for efficiently grinding hard-to-grind materials such as ceramics and metals. [Background technology]

[0002] The materials used in industry are diverse, including metals, ceramics, rubber, and resins. It is well known that grinding wheels are useful for polishing these materials. Among them, rubber grinding wheels, which contain abrasive grains made of alumina (aluminum oxide), silicon carbide, diamond, cubic boron nitride (CBN), etc. dispersed in a rubber-elastic binder, have a good conformity to the surface shape of the workpiece due to their flexibility, and can perform precise polishing in ductile mode (a mode that scrapes away the surface little by little, like a plane).

[0003] In recent years, zirconia has become popular worldwide as a prosthetic device. However, due to its high hardness, zirconia is a difficult material to polish, and diamond is an effective abrasive for polishing it. Therefore, the number of rubber grinding wheels containing diamond is increasing. However, while diamond is useful for polishing high-hardness materials, it is expensive, and increasing the diamond loading rate to improve polishing efficiency increases the unit price of the grinding wheel. Therefore, there is a need to develop an inexpensive rubber grinding wheel with a reduced diamond loading rate that does not reduce polishing efficiency when polishing high-hardness materials like zirconia.

[0004] On the other hand, problems with polishing using rubber grinding wheels include "clogging" and "heat generation." "Clogging" occurs when shavings (grinding debris) from the workpiece accumulate between or cover the exposed abrasive particles, reducing the grinding ability of the rubber grinding wheel even if the abrasive particles are not worn down. Furthermore, continuing polishing with a clogged rubber grinding wheel causes both the workpiece and the rubber grinding wheel to heat up, which generates "heat" and causes the rubber grinding wheel to burn onto the workpiece, impairing the surface quality of the workpiece. Heat generation is particularly pronounced in materials with excellent thermal conductivity, such as metals, which significantly reduce the grinding ability of the rubber grinding wheel and the surface quality of the workpiece.

[0005] Therefore, in the rubber grinding stone industry, a method known to prevent "clogging" and "heat generation" of rubber grinding stones is to add a foaming agent to increase the number of pores contained in the rubber grinding stone. In other words, this method solves the aforementioned problems by allowing the pores to contribute to the discharge of grinding debris and dissipating heat generated during grinding through the pores. However, adding a foaming agent is expected to reduce the abrasive grain and binder compounding ratios in the grinding part that affect the grinding. Furthermore, adding pores to the rubber grinding stone itself is expected to soften it, resulting in faster wear. As a result, the grinding ability and durability of the rubber grinding stone tend to decrease.

[0006] A wide variety of materials are used in the dental industry, and all of them require precise polishing. Generally, when there is a disease such as caries in the oral cavity, it is removed and various materials such as ceramics or metals are used as prosthetic devices to restore the removed area. As with the industrial sector, issues with polishing include clogging and heat generation. When grinding ability decreases due to clogging, the time required for work increases, placing a greater burden on the surgeon. Furthermore, when polishing inside the oral cavity, heat generation causes thermal stimulation, imposing a burden on the patient. There is a need for the development of a rubber grinding wheel that can polish these materials efficiently and without generating heat.

[0007] Technologies to prevent clogging and heat generation in rubber grinding wheels have been studied for some time. Patent Document 1 describes an abrasive in which spherical inorganic beads are contained in a matrix material, in which inorganic long fibers are bound together, in order to solve the problem of clogging in industrial abrasives, particularly rubber abrasives containing inorganic long fibers. However, when this technology is applied to dental abrasives, short grinding times and high heat dissipation are required, so there is still room for improvement. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent Publication No. 2001-225273 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a rubber grindstone that can suppress clogging and heat generation when grinding hard-to-grind materials such as ceramics and metals. [Means for solving the problem]

[0010] The present inventors have conducted extensive research to overcome the above-mentioned problems and have arrived at the present invention, which is a rubber grindstone for polishing, the grinding portion of which contains a binder (A), abrasive particles (B), and diatomaceous earth particles (C). [Effects of the Invention]

[0011] By using the present invention, continuous polishing becomes possible by suppressing clogging and heat generation when polishing hard-to-polish materials such as ceramics or metals. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below. However, the present invention is not particularly limited to the examples shown below. The abrasive part of the rubber grindstone of the present invention is composed of a binder (A), abrasive particles (B), and diatomaceous earth particles (C).

[0013] The abrasive part of the rubber grindstone of the present invention is produced by molding a raw material obtained by uniformly kneading a binder (A), abrasive particles (B), and diatomaceous earth particles (C) using a known method, such as heat processing such as hot pressing. The shape of the abrasive part is not particularly limited, and examples thereof include cylindrical, disk-shaped, bullet-shaped, disc-shaped, and cup-shaped.

[0014] The rubber abrasive grindstone of the present invention is either integrated with a shaft for attachment to a hand grinder or dental handpiece, or has a detachable shaft portion that allows the shaft to be attached and detached. The method for fastening the shaft to the rubber abrasive grindstone of the present invention is not particularly specified, but examples include inserting the shaft into the bottom surface of the abrasive part in advance and fastening it with pressure or adhesive. Furthermore, when the shaft is detachable, a hole of a similar shape to the inserted shaft can be formed inside the abrasive part, allowing the shaft to be attached and detached as needed during use.

[0015] The object to be polished by the rubber abrasive stone of the present invention is not particularly specified, but it is particularly preferably used for ceramics, metals, etc.

[0016] <Binder (A)> The binder contained in the abrasive portion of the rubber grindstone of the present invention may be a solid binder or a liquid binder. In the case of a solid binder, the type of binder is not particularly specified, but it is preferable to select one or more from, for example, silicone rubber, urethane rubber, polyethylene rubber, natural rubber, styrene-butadiene rubber, and acrylic rubber. In the case of a liquid binder, the type of binder is not particularly specified, but it is preferable to select one or more from, for example, silicone rubber, urethane rubber, isoprene rubber, butadiene rubber, and styrene-butadiene rubber. Multiple types can also be used in combination.

[0017] Rubber grinding wheels are made by kneading abrasive grains with a solid or liquid binder and then molding the mixture. A solid binder can uniformly disperse abrasive grains, regardless of their size, without having to worry about settling, resulting in a densely molded product. However, adding a foaming agent or special molding techniques are required to create pores.

[0018] Liquid binders offer the following advantages: (1) They eliminate the need for large machines such as kneaders and rolls for mixing, and machine cleaning is also unnecessary, reducing the burden on workers. (2) They have strong abrasive grain retention in molded products, and the filling rate of filler components such as abrasive grains is high. (3) They are not restricted by molding method; for example, they can be molded using a casting method in addition to heat processing such as hot pressing. Porosity can be easily created using the casting method. A disadvantage of using liquid binders is filler settling. Therefore, when mixing liquid binders with coarse fillers such as abrasive grains, thickeners are generally added to prevent filler settling. However, adding thickeners reduces the abrasive grain content in the polishing area, which is effective for polishing, and is therefore expected to reduce the binder content as well. As a result, the grinding ability and durability of the rubber grinding wheel tend to decrease. However, even when a liquid binder is used, the rubber grindstone of the present invention contains diatomaceous earth particles (C) blended into the liquid binder (A), which acts as a thickener to prevent the abrasive particles from settling.

[0019] <Abrasive particles (B)> The type of abrasive particles (B) used in the rubber grindstone of the present invention is selected depending on the material properties of the object to be polished, and is not particularly specified, but it is preferable to select one or more from, for example, aluminum oxide, silicon carbide, diamond, CBN, and cerium oxide.

[0020] The blending ratio of the abrasive particles (B) used in the rubber grindstone of the present invention is preferably 100 to 250 parts by weight of abrasive particles (B) per 100 parts by weight of the liquid binder (A). If the blending ratio of the abrasive particles (B) is less than 100 parts by weight of the liquid binder (A), the abrasive particle blending ratio in the grinding part that acts on the grinding is low, and grinding performance tends to deteriorate. If the blending ratio exceeds 250 parts by weight, the binder blending ratio in the grinding part is low, and the abrasive particle retention force decreases, tending to increase the amount of abrasive wear. Another disadvantage is that the increased blending ratio of the abrasive particles (B) increases the grindstone unit cost.

[0021] <Diatomaceous earth particles (C)> The rubber grindstone of the present invention contains diatomaceous earth particles (C), which allows for excellent removal of grinding debris, and the abrasive particles can be kept exposed to the binder surface at all times. This allows for the grinding efficiency to be maintained even when the blending ratio of abrasive particles (B) is reduced, and it is also possible to reduce the blending ratio of expensive abrasive particles such as diamond and CBN, thereby lowering the unit price of the grindstone.

[0022] The particle size of the diatomaceous earth particles (C) used in the rubber grindstone of the present invention is preferably an average particle size of 10 to 300 μm, particularly preferably 50 to 150 μm, for the primary particles. If the average particle size is less than 10 μm, the particles tend to be scraped off the surface during polishing, with only a small amount preferentially falling off, and the self-sharpening action of the abrasive particles (B) tends to be insufficient. On the other hand, if the average particle size exceeds 300 μm, a large amount tends to be scraped off the surface, increasing the amount of abrasive wear. Another disadvantage is that the effect as a thickener is reduced. Here, the average particle size refers to the median diameter (d50) and can be determined using a general particle size distribution analyzer. The particle shape of the diatomaceous earth (C) is not particularly limited.

[0023] The blending ratio of diatomaceous earth particles (C) used in the rubber grindstone of the present invention is preferably 5 to 90 parts by weight, and particularly preferably 20 to 60 parts by weight, per 100 parts by weight of liquid binder (A). If the blending ratio of diatomaceous earth particles (C) is less than 5 parts by weight per 100 parts by weight of liquid binder (A), the amount of diatomaceous earth particles (C) scraped off the surface during polishing is small, and the self-sharpening action of the abrasive particles (B) tends to be insufficient. Furthermore, when the binder (A) is used as a liquid binder, there is a disadvantage in that its effectiveness as a thickener is reduced. On the other hand, if the blending ratio exceeds 90 parts by weight, the amount scraped off the surface is large, and the abrasive wear rate tends to increase. Another disadvantage is that the blending ratio of abrasive grains in the polishing portion that is active in polishing is low, resulting in reduced polishing performance.

[0024] In addition to the binder (A), abrasive particles (B), and diatomaceous earth particles (C), the rubber abrasive stone of the present invention may contain any optional components, such as colorants, fillers, plasticizers, and various compounding agents commonly used in elastic rubbers. Furthermore, various vulcanizing agents and vulcanization accelerators may be added as appropriate to crosslink the elastic rubber. Furthermore, a combination of these components may be added.

[0025] For example, colorants are blended to improve the visibility of the remaining dental abrasive and to identify the product. It is desirable to use inorganic pigments such as natural mineral pigments and synthetic inorganic pigments as colorants. Specific examples of such colorants include titanium oxide, iron oxide, cobalt aluminate, and ultramarine.

[0026] Fillers can be blended for the purpose of adjusting the hardness of the dental abrasive and for the purpose of reinforcing the abrasive. Specific examples of fillers include carbon black, thickening silica fine particles, titanium dioxide, diatomaceous earth, aluminum silicate, calcium carbonate, zinc oxide, magnesium oxide, etc. These fillers can be used alone or in combination. [Example]

[0027] Hereinafter, an example of an embodiment of the present invention will be described using examples, but the present invention is not limited to the embodiments described below.

[0028] <Examples and Comparative Examples> The ingredients in Tables 1 to 5 were mixed until homogeneous using a mixer such as a planetary centrifugal mixer to prepare a kneaded mixture. The mixture was then molded into a disk shape (Φ22 mm x thickness 3.2 mm) using a hot press at 100°C for 10 minutes to prepare the rubber grindstones of Examples 1 to 10 and Comparative Examples 1 to 9.

[0029] <Evaluation of thickening properties> After the rubber grindstone was produced, the presence or absence of settling of the abrasive particles (B) was visually confirmed. If settling of the abrasive particles (B) occurred, it means that the abrasive particles (B) will have a different density in the final rubber grindstone, and the grinding properties will be unstable. Evaluation was performed according to the following two-stage criteria, and the results are shown in Tables 1 to 5. a: No sedimentation b: Subsidence

[0030] <Evaluation of polishing durability> 3Y-TZP zirconia plates (15mm x 15mm x 3mm) and metal plates (cobalt chromium alloy, stainless steel, titanium) (15mm x 15mm x 3mm) were polished to a flat surface using waterproof abrasive paper (CC#120 for zirconia and CC#240 (metal) for metal) and then polished using the rubber grindstone. The polishing test was carried out for 30 seconds at a rotation speed of 15,000 min -1The test was conducted under conditions of 1000 kJ / min and a load of 2N. The polishing test was repeated, and the number of polishing runs required to remove scratches on the reference surface of the polished object after the test was confirmed. The number of polishing runs achieved was used as the evaluation standard for polishing durability. If scratches on the reference surface of the polished object could not be removed, it meant that polishing was not successful. In other words, clogging of the rubber grindstone occurred, reducing the efficiency of polishing debris removal and preventing the self-sustaining action of the abrasive grains from being continuously exerted. Evaluation was conducted using the three-level criteria shown below, and the results are shown in Tables 1 to 5. Tables 1 to 4 are tests using a zirconia plate as the polished object, and Table 5 is tests using a metal plate as the polished object. The polishing durability obtained was judged as a good grade, b as average, and c as poor. a: 8 or more times b:4~7 times c: 3 times or less

[0031] <Evaluation of heat dissipation> The polishing test was repeated, and the presence or absence of scorching of the rubber grindstone on the object being polished was visually confirmed. The number of polishing cycles until scorching was not observed was used as the evaluation standard for heat dissipation. If the rubber grindstone is scorched on the object being polished, it means that heat dissipation is not being performed effectively. Evaluation was performed using the four-level criteria shown below, and the results are shown in Tables 1 to 5. Tables 1 to 4 are tests using a zirconia plate as the object being polished, and Table 5 is tests using a metal plate as the object being polished. The heat dissipation obtained was judged as a good grade, b as average, and c as poor. a: 8 or more times b:4~7 times c: 3 times or less <Evaluation Results of Examples and Comparative Examples>

[0032] Table 1 shows Examples 1 and 2 of the present invention, in which diatomaceous earth particles (C) were blended with the liquid binder (A), and Comparative Examples 1 to 3, in which diatomaceous earth particles (C) were not blended. Comparing Example 1 with Comparative Examples 1 and 2, it was confirmed that blending diatomaceous earth particles (C) into the rubber grindstone can suppress the settling of the abrasive particles (B). Even with a low blend ratio of abrasive particles (B), the grindstone exhibits excellent grinding continuity and heat dissipation, thereby enabling cost reduction. This is because the diatomaceous earth particles (C), which are softer than the abrasive particles (B), preferentially fall off during grinding, facilitating the generation of new surfaces on the rubber grindstone. Furthermore, the inclusion of porous diatomaceous earth particles (C) increases the number of pores in the entire rubber grindstone, allowing for more efficient discharge of grinding debris. Furthermore, Examples 1 and 2 confirmed that the effects of the present invention were also achieved when the liquid binder (A) was urethane rubber or silicone rubber.

[0033] Table 2 examines the blending ratio and particle size of abrasive particles (B). Comparing Example 1 in Table 1 with Table 2, it was confirmed that the effects of the present invention can be achieved when the blending ratio of abrasive particles (B) is 100 to 250 parts by weight per 100 parts by weight of liquid binder (A). It was confirmed that if the blending ratio of abrasive particles (B) is less than 100 parts by weight per 100 parts by weight of liquid binder (A), the blending ratio of abrasive particles in the polishing part that acts on the polishing is low, and polishing performance is reduced. On the other hand, if the blending ratio exceeds 250 parts by weight, the blending ratio of the binder in the polishing part is low, and the abrasive grain retention force is reduced, tending to increase the amount of abrasive wear. Another disadvantage is that the increased blending ratio of abrasive particles (B) increases the unit price of the grinding wheel.

[0034] Table 3 examines the particle size of diatomaceous earth particles (C). Comparing Example 1 in Table 1 with Table 3, it was confirmed that an average particle size of diatomaceous earth particles (C) of 50 to 150 μm is particularly preferable for achieving the effects of the present invention. It was confirmed that when the average particle size of diatomaceous earth particles (C) is less than 50 μm, the particles are scraped off the surface during polishing, and the amount that falls off preferentially is small. This prevents the self-sharpening action of abrasive particles (B) from being fully exerted, resulting in a slight decrease in polishing durability. On the other hand, when the average particle size exceeds 150 μm, the effect as a thickener is reduced, and sedimentation of abrasive particles (B) occurs.

[0035] Table 4 examines the blending ratio of diatomaceous earth particles (C). Comparing Example 1 and Comparative Example 2 in Table 1 with Table 4, it was confirmed that the effects of the present invention are achieved when the blending ratio of diatomaceous earth particles (C) is 5 to 90 parts by weight per 100 parts by weight of liquid binder (A). It was confirmed that when the blending ratio of diatomaceous earth particles (C) is less than 5 parts by weight per 100 parts by weight of liquid binder (A), the amount scraped off from the surface during polishing is small, and the self-sharpening action of the abrasive particles (B) is not fully exerted, resulting in a tendency for polishing durability to decrease. On the other hand, when the blending ratio exceeds 90 parts by weight, the amount scraped off from the surface is large, and the amount of abrasive wear tends to increase. It was also confirmed that the blending ratio of abrasive particles (B) in the polishing portion that is active in polishing is low, which tends to reduce polishing performance.

[0036] The types of abrasive particles (B) are examined in Table 5. It was confirmed that the effects of the present invention were also exhibited when the abrasive particles (B) were silicon carbide.

[0037] The examples generally achieved good results in the evaluation of viscosity, polishing continuity, and heat dissipation. Therefore, these examples demonstrated that continuous polishing is possible by suppressing clogging and heat generation when polishing hard-to-polish materials such as ceramics or metals. Furthermore, because the polishing waste discharge efficiency is excellent, the abrasive particles can be kept exposed to the binder surface at all times, so polishing efficiency can be maintained even when the blending ratio of abrasive particles (B) is reduced, and it is also possible to reduce the unit price of the grinding wheel.

[0038]

Table 1

[0039]

Table 2

[0040]

Table 3

[0041]

Table 4

[0042]

Table 5

[0043]

Table 6

Claims

1. A rubber grindstone for polishing, comprising a binder (A), abrasive particles (B), and diatomaceous earth particles (C) in its polishing portion.

2. 2. The rubber grindstone for polishing according to claim 1, wherein the abrasive portion contains 100 to 250 parts by weight of the abrasive particles (B) and 5 to 90 parts by weight of the diatomaceous earth particles (C) relative to 100 parts by weight of the binder (A).

3. 2. The rubber grindstone according to claim 1, wherein the binder (A) is a liquid binder.

4. 2. The rubber grindstone for polishing according to claim 1, which is for dental use.

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