JP2022107167A - Grindstone and manufacturing method of grindstone - Google Patents

Abstract

To provide a grindstone capable of grinding and polishing with high accuracy and high efficiency a workpiece such as a cylindrical metal component, and achieving great process improvement, quality improvement due to polishing accuracy improvement or development to new use, and to provide a manufacturing method of the grindstone.SOLUTION: A grindstone comprising a cured material obtained by curing an abrasive grain composition containing abrasive grains, a resin and a curing catalyst is such that: the resin contains 50 mass% or more of a resol type phenol resin; and a blend amount of the curing catalyst is 5-23 pts.mass based on 100 pts.mass of the phenol resin. A manufacturing method of the grindstone includes steps of: preparing an abrasive grain composition by blending blended liquid containing abrasive grains, a resin and a curing catalyst; pouring the abrasive grain composition into a mold; and curing the abrasive grain composition poured into the mold. The resin in the abrasive grain composition contains 50 mass% or more of a resol type phenol resin. In the step of curing the abrasive grain composition, curing is performed in two heating steps of heating at a second heating temperature higher than a first heating temperature for the predetermined time after heating at the first heating temperature for predetermined time.SELECTED DRAWING: None

Description

The present invention relates to a grindstone and a method for manufacturing the grindstone, and more particularly to a rotary grindstone for finish polishing a work (workpiece) by centerless polishing and cylindrical grinding, and a method for manufacturing the rotary grindstone.

Conventionally, centerless polishing and cylindrical grinding are used for grinding and polishing cylindrical workpieces such as automobile parts and transport rolls. For these grinding and polishing, a rotary grindstone in which abrasive grains are fixed with a resin or the like is used, and the rotary grindstone is rotated and brought into contact with the workpiece to be processed into an arbitrary surface state.

Examples of the abrasive grains to be fixed to the rotary grindstone include diamond, silicon carbide, alumina and the like. Examples of the binder for fixing the abrasive grains include resin bond and vitrified as the general grindstone, and polyvinyl as the elastic grindstone. Examples thereof include acetal resin, polyurethane resin, urea resin, and rubber. Grindstones using resin bond or vitrify as a binder are extremely hard and have excellent grinding power, so they are widely used from rough grinding to semi-finishing. On the other hand, an elastic grindstone that uses an elastic material such as polyvinyl acetal resin or polyurethane resin as a binder is excellent in finely processing the surface roughness of the work piece with high precision due to the effect of elasticity, and is excellent in scratching and the like. It is characterized by the fact that there are few problems.

As the rotary grindstone, a grindstone in which abrasive grains are fixed with a binder as described above is usually used. For example, a resin bond grindstone using a phenol resin as a binder is known as a prior art (for example, Non-Patent Document 1). There are two types of phenol resin, novolak type and resol type, and novolak type phenol resin is used as the main binder of the grindstone. On the other hand, the resole-type phenol resin is used as a wetting agent for abrasive grains.

Further, as an elastic grindstone, the binder of the grindstone is composed of a bisphenol A epoxy resin having a low elastic modulus, and an organic hollow body having a lower elastic modulus than the resin binder is dispersed in the grindstone. Has been reported (for example, Patent Document 1).

As the rotary grindstone, the grindstone to be used is selected according to the purpose. In recent years, the surface of the workpiece has been improved in precision in many polishing applications, and a rotary grindstone that can achieve both grinding force and high precision in the finished surface is required. Was there.

Japanese Unexamined Patent Publication No. 2005-2465669

Ceramic Society of Japan, "Ceramic Engineering Handbook (2nd Edition)", pp. 1322-1325 (2002)

However, since the grindstone using resin bond or vitrify as a binder has a hardness, the surface of the work piece becomes rough in the final finish, and defects such as scratches are likely to occur. Further, in the case of a polished material such as a conventional elastic grindstone that precisely finishes the roughness of the work surface, the grinding force is weak, so that the wear resistance is low, and the actual grinding amount is small with respect to the cutting amount. Therefore, when the work diameter is managed by a machine setting such as a centerless grinding machine or a cylindrical grinding machine, there is a problem that it is difficult to control the grinding amount and handle it. Further, there is a problem that the work efficiency is deteriorated because the grinding time is long, and there is a problem that the replacement frequency is high and the cost is high because the grindstone life is short.

If it is possible to polish with high precision while maintaining machinability, it is possible to solve these problems, greatly improve productivity, and finish workpieces that could not be finished with high precision. There is sex. However, it has been difficult for conventional grindstones to have performance that combines the merits of both general grindstones such as resin bonds and vitrified grindstones and highly elastic grindstones.

The present invention has been made in view of the above circumstances. The purpose is to provide.

As a result of diligent studies to achieve the above object, the present inventors used a molding method in which a curing reaction was carried out with a curing catalyst, and further molded an intermediate (semi-cured product) and then completely molded it in two steps. By molding, the conventional molding time can be significantly shortened, and by allowing a uniform curing reaction, a molded product that does not generate cracks can be obtained, and the workpiece is ground and polished with the product of the present invention. As a result, it has been found that a cylindrical workpiece can be ground and polished with high accuracy and high efficiency, and the present invention has been completed.

That is, the present invention provides the following grindstone and a method for manufacturing the grindstone.
[1] A grindstone made of a cured product obtained by curing an abrasive grain composition containing abrasive grains, a resin, and a curing catalyst.
The resin contains 50% by mass or more of a resole-type phenol resin.
A grindstone characterized in that the blending amount of the curing catalyst is 5 to 23 parts by mass with respect to 100 parts by mass of the phenol resin.
[2] The grindstone according to [1], wherein the blending amount of the resin is 10 to 40 parts by mass with respect to a total of 100 parts by mass of the abrasive grains and the resin.
[3] The grindstone according to [1] or [2], wherein the number average molecular weight (Mn) of the resol type phenol resin is 300 to 600.
[4] The resin contains an elastic resin, and the resin contains an elastic resin.
The elastic resins include isobrene rubber, butadiene rubber, styrene / butadiene rubber, chlorobrene rubber, nitrile rubber, butyl rubber, ethylene / propylene rubber, ethylene / propylene / diene rubber, acrylic rubber, epichlorohydrin rubber, silicone rubber, fluororubber and propylene / butadiene. The grindstone according to any one of [1] to [3], which is at least one resin selected from the group consisting of rubber.
[5] The grindstone according to [4], wherein the ratio of the elastic resin to the resin is 5 to 50% by mass.
[6] The grindstone according to any one of [1] to [5], wherein the abrasive grain composition contains a pore-forming agent.
[7] The grindstone according to [6], wherein the amount of the pore-forming agent blended with respect to 100 parts by mass of the resin is 1 to 40 parts by mass.
[8] Any of [1] to [7], wherein the abrasive grains are at least one type of ceramic abrasive grains selected from the group consisting of silicon carbide, alumina, chromium oxide, cerium oxide, zirconium oxide and zircon sand. The grindstone described in one.
[9] The grindstone according to any one of [1] to [8], wherein the volume average primary particle diameter of the abrasive grains measured by the laser diffraction / scattering method is 5 to 27 μm.
[10] The grindstone according to any one of [1] to [9], which has a Rockwell hardness of −60 to 0 measured on a superficial 15Y scale.
[11] The grindstone according to any one of [1] to [10], which is a grindstone for centerless polishing and cylindrical grinding final finishing.
[12] A step of preparing an abrasive grain composition by mixing a mixed solution containing abrasive grains, a resin and a curing catalyst.
Including a step of pouring the abrasive grain composition into a mold and a step of curing the abrasive grain composition poured into the mold.
The resin in the abrasive grain composition contains 50% by mass or more of a resole-type phenol resin.
The step of curing the abrasive grain composition is curing by two-step heating in which the abrasive grain composition is heated at a first heating temperature for a predetermined time and then heated at a second heating temperature higher than the first heating temperature for a predetermined time. How to manufacture a grindstone.
[13] The method for producing a grindstone according to [12], wherein the first heating temperature is 30 ° C. or higher, and the second heating temperature is 60 ° C. or higher.
[14] The method for producing a grindstone according to [12] or [13], wherein the predetermined heating time is 1 to 10 hours.

By using the grindstone of the present invention, it is possible to grind and polish workpieces such as cylindrical metal parts with high accuracy and high efficiency. Is realized. Further, according to the method for producing a grindstone of the present invention, it is possible to efficiently obtain a grindstone having further improved hardness, elasticity, degree of wear, machinability, finished surface roughness of a work piece, and the like.

Hereinafter, the present invention will be described in detail with reference to embodiments of the present invention as examples, but the present invention is not limited to these embodiments.

<Whetstone>
The grindstone of the present invention comprises a cured product obtained by curing an abrasive grain composition containing abrasive grains, a resin and a curing catalyst. The resin contains 50% by mass or more of a resol type phenol resin.
(Abrasive grain)
Abrasive grains are substances that have the function of scraping off the work piece, and serve as a cutting edge in the grindstone. Abrasive grains are required to have an appropriate particle size, high hardness, chemical durability, and the like.

The volume average primary particle diameter measured by the laser diffraction / scattering method of the abrasive grains is preferably 5 to 27 μm, more preferably 6 to 22 μm from the viewpoint of improving the finish accuracy of centerless polishing or cylindrical grinding.

The abrasive grains are not particularly limited as long as they are abrasive grains used for a resin bond grindstone. Examples of the abrasive grains include silicon carbide, alumina, chromium oxide, cerium oxide, zirconium oxide, zircon sand and the like, and these can be used alone or in combination of two or more. Among them, silicon carbide and alumina are preferable because they have high hardness and excellent cutting ability as compared with other materials.

The amount of abrasive grains blended in the abrasive grain composition from the viewpoints of finish roughness due to the dispersion of the polishing load applied to the abrasive grains, the ease of clogging of the grindstone, the hardness of the grindstone and the ease of self-falling of the abrasive grains. Is preferably 60 to 90 parts by mass, and more preferably 65 to 80 parts by mass with respect to 100 parts by mass of the total amount of the abrasive grains and the resin.

(resin)
As described above, the resin contains 50% by mass or more of the resole-type phenol resin. That is, the grindstone of the present invention uses a resol type phenol resin as a main binder. In the grindstone, the resin serves to hold the abrasive grains. Further, the elastic behavior of the cutting edge, the impact absorption of the grindstone as a whole, and the like are due to the resin. Furthermore, the resin has a great influence on the sharpness and wear of the grindstone.

From the viewpoint of sharpness and wear of the grindstone, the amount of the resin compounded in the abrasive grain composition is preferably 10 to 40 parts by mass, more preferably 20 parts by mass, based on 100 parts by mass of the total amount of the abrasive grains and the resin. It is ~ 35 parts by mass.

(Resol type phenol resin)
The resole-type phenol resin has self-curing property and is cured by heating to become a cured product. In addition, the resole-type phenol resin is resistant to mechanical impact and thermal impact. The resole-type phenol resin is synthesized, for example, by reacting phenols and aldehydes in the presence of a basic catalyst. Generally, after the above reaction, dehydration under reduced pressure is performed.
Examples of the phenols used for the synthesis of the resole-type phenol resin include phenol, o-cresol, m-cresol, p-cresol, xylenol, alkylphenols, catechol, resorcin, etc., and these may be used alone or in combination of two or more. It can be used together.
Examples of aldehydes used for synthesizing the resole-type phenol resin include aldehyde compounds such as formaldehyde, paraformaldehyde, and benzaldehyde, substances that are sources of these aldehyde compounds, and solutions of these aldehyde compounds. These can be used alone or in combination of two or more.
Basic catalysts used in the synthesis of resole-type phenolic resins include, for example, hydroxides of alkali metals such as sodium hydroxide, lithium hydroxide and potassium hydroxide, and oxides of alkaline earth metals such as calcium, magnesium and barium. And amines such as hydroxide, sodium carbonate, aqueous ammonia, triethylamine, hexamethylenetetramine, divalent metal salts such as magnesium acetate and zinc acetate, etc., and these may be used alone or in combination of two or more. can.

When the resole-type phenol resin is heated, the condensation reaction between the hydroxymethyl group and the phenol nucleus proceeds, and the resole-type phenol resin becomes an insoluble and insoluble solid having a three-dimensional network structure.

As described above, in general, the phenol resin used as the main binder of the grindstone is a novolak type. The novolak type phenol resin is a thermoplastic resin by itself, has a wide range of molding conditions, and has good dimensional stability. Further, the novolak type phenol resin has better storage stability than the resol type phenol resin. However, in order to enable high-precision processing of the finished surface roughness of the work piece, it is preferable to impart a certain degree of elastic performance to the grindstone. Further, there is a method of mixing an elastic body with the conventional novolak type phenol, but that does not mean that the grindstone itself has elasticity, and the hardness is partially different, which affects the finished surface roughness. Above all, the viscosity of the raw material composition tends to increase and it is difficult to manufacture. As a result of diligent studies, the present inventors have made stable a grindstone that has both the strength and machinability of a resin grindstone and the high-precision finish of an elastic grindstone by using an elastic resin for the resole-type phenol resin. Found that it can be manufactured.

From the viewpoint that a grindstone can be stably produced even if an elastic resin is used as the resole-type phenol resin, the resole-type phenol resin is preferably liquid at room temperature of 25 ° C.

The number average molecular weight (Mn) of the resole-type phenol resin is preferably 300 to 600, more preferably 350 to 500, from the viewpoint of the strength of the resin related to the wear resistance of the grindstone. The number average molecular weight (Mn) is a value calculated by gel permeation chromatography (GPC) (molecular weight measuring device: manufactured by Showa Denko KK, model number: RI-71) in terms of polystyrene. As the solvent, 50 mM lithium chloride and 2 mM hydrochloric acid (added dimethyl formaldehyde) were used, and the column temperature was 23 ° C.

The blending amount of the resole-type phenol resin in the entire resin of the abrasive grain composition is 50% by mass or more. If the blending amount of the resole-type phenol resin is less than 50% by mass, the grindstone may be vulnerable to mechanical impact and thermal impact. From the viewpoint of the hardness, machinability, and production efficiency of the grindstone, the blending amount of the resole-type phenol resin in the entire resin of the abrasive grain composition is preferably 60% by mass or more, more preferably 70% by mass or more.

(Elastic resin)
As the resin, the grindstone may further contain an elastic resin in addition to the resole-type phenol resin. A grindstone mainly made of phenol resin has high strength and excellent wear resistance and machinability, but is not suitable for high-precision finishing due to its high hardness. Therefore, in order to secure the elasticity of the grindstone and perform a higher-precision grinding finish, the elastic resin is mixed with the resole-type phenol resin. As a result, the shock absorption of the grindstone can be further increased. The elastic resin is a resin in which the cured product exhibits rubber elasticity as compared with the cured product of the resole-type phenol resin. The elasticity of the grindstone can be improved by including the elastic resin in the abrasive grain composition. The elastic resin is preferably fine particles and uniformly dispersed in the cured phenol resin matrix.

The elastic resin is not particularly limited as long as the cured product is a resin that exhibits rubber elasticity as compared with the cured product of the resole-type phenol resin. Specifically, the elastic resin includes, for example, isobrene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), chlorobrene rubber (CR), nitrile rubber (NR), butyl rubber (IIR), and ethylene. -Propylene rubber (EPM), ethylene / propylene / diene rubber (EPDM), acrylic rubber (ACM), epichlorohydrin rubber (CO), silicone rubber (Q), fluororubber (FKM), propylene / butadiene rubber (PBR), etc. Be done. These elastic resins may be used alone or in combination of two or more. Among these, propylene / butadiene rubber is used as the elastic resin from the viewpoints of dispersibility with the resol type phenol resin, hardness of the obtained grindstone, elasticity, degree of wear, machinability, and finished surface roughness of the work piece. Is preferable.

From the viewpoint of uniformly dispersing the elastic resin in the resole-type phenol resin, the elastic resin is preferably blended in a state of being emulsified or dispersed in a solvent.

When the elastic resin is blended, the blending amount of the elastic resin in the entire resin of the abrasive grain composition is preferably 5 to 50% by mass, more preferably from the viewpoint of the elastic behavior of the cutting edge and the impact absorption of the grindstone. Is 10 to 40% by mass.

(Curing catalyst)
The abrasive grain composition further contains a curing catalyst. By containing the curing catalyst, the curing time can be significantly shortened as compared with the prior art, and at the same time, the cured product can be uniformly cured, so that a molded product in which the occurrence of cracks is suppressed can be obtained. Examples of the curing catalyst include an acidic catalyst and a basic catalyst, and an acidic catalyst is preferable. For example, examples of the acidic catalyst include aromatic sulfonic acid, hydrochloric acid, perchloric acid, and sulfuric acid. Of these acidic catalysts, aromatic sulfonic acids are preferred. As specific examples of aromatic sulfonic acid, for example, toluene sulfonic acid hydrate, xylene sulfonic acid, benzene sulfonic acid and the like can be used. Examples of the basic catalyst include sodium hydroxide, potassium hydroxide, ammonia, primary amines, secondary amines and the like. Of these, sodium hydroxide is preferred. The blending amount of the curing catalyst is 5 to 23 parts by mass, preferably 10 to 20 parts by mass, and more preferably 13 to 17 parts by mass with respect to 100 parts by mass of the phenol resin. If the blending amount of the curing catalyst is less than 5 parts by mass, the acceleration of curing is slow and there is a risk that it is not much different from that when no catalyst is added. It is promoted, and there is a risk of molding abnormalities such as expansion.

(Pore-generating agent)
The abrasive grain composition can further contain a pore-forming agent. The pore-generating agent is added to form pores in the grindstone, and having pores enhances the elasticity of the grindstone and promotes the discharge of grinding debris generated during grinding to suppress clogging. The pores also reduce the grinding resistance of the grindstone and prevent grinding burns. As the pore-forming agent, starch powder or a foaming agent is preferable. Examples of starch flour include cornstarch, potato and rice flour, and these can be used alone or in combination of two or more. Hydrocarbons and their derivatives are used as foaming agents. For example, isobutane, normal pentane and the like can be mentioned, and these may be used alone or in combination of two.

The size of the pores formed in the grindstone by the pore-forming agent can be adjusted by the particle size of the pore-forming agent and the diameter of the foamed bubbles. The larger the pore diameter, the higher the elasticity of the grindstone and the discharge of abrasive debris, but if it is too large, the contact area of the grindstone with the work becomes small and the machinability deteriorates. Therefore, the volume average primary particle size measured by the laser diffraction / scattering method of the pore-forming agent is preferably 2 to 100 μm, more preferably 5 to 40 μm.

When the pore-forming agent is blended, the blending amount of the pore-forming agent is preferably 1 to 40 parts by mass, and more preferably 2 with respect to 100 parts by mass of the resin, from the viewpoint of the amount of abrasive grains falling off and grindability. It is about 30 parts by mass, more preferably 2.5 to 10 parts by mass. Even when the pore-forming agent is not added, pores are formed in the grindstone by the voids naturally generated during molding, but it is preferable to add the pore-forming agent in order to stably promote the suppression of clogging.

(Rockwell hardness)
The Rockwell hardness of the grindstone measured on the Superficial 15Y scale is preferably -60 to 0, more preferably -50 to -10. The Rockwell hardness measured on the Superficial 15Y scale is a value measured by a method according to JIS K7202-2 “Rockwell hardness” measurement. For example, using a Rockwell hardness tester manufactured by Matsuzawa Co., Ltd., a steel ball with a diameter of 1/2 inch (about 12.7 mm) is generated when an indenter with a tip is brought into contact with a grindstone and a reference load of 15 kg · f is applied. The Rockwell hardness can be measured on a superficial 15Y scale by converting from the depth of the dent. The larger the Rockwell hardness value on the positive side, the harder the grindstone, and the larger the negative side, the softer the grindstone.

<Manufacturing method of whetstone>
Further, in the present invention, a step of mixing a mixed solution containing abrasive grains, a resin and a curing catalyst to prepare an abrasive grain composition, a step of pouring the abrasive grain composition into a mold, and a step of pouring the abrasive grain composition into a mold are used. Provided is a method for manufacturing a grindstone including a step of curing. Hereinafter, each step will be described in detail.

[Step of producing abrasive grain composition]
In this step, a mixed solution containing abrasive grains, a resin, and a curing catalyst is mixed to prepare an abrasive grain composition. In addition to the abrasive grains, the resin and the curing catalyst, a pore-forming agent may be further mixed to prepare an abrasive grain composition. The resin contains 50% by mass or more of the resol type phenol resin, preferably 60% by mass or more, and more preferably 70% by mass or more. The resole-type phenol resin may be used as it is, may be used in the state of an aqueous solution, or may be used in a state of being dissolved in a solvent other than water such as alcohol.

The abrasive grains and the resin are preferably mixed under a reduced pressure having a gauge pressure of −0.095 MPa or less. In this way, bubbles are generated in the abrasive grain composition when the abrasive grains and the resin are mixed. Then, since the generated bubbles remain in the abrasive grain composition, it is possible to suppress the formation of large pores in the abrasive grain composition, and it is possible to form uniform bubbles in the grindstone.

[Step of pouring the abrasive grain composition into the mold]
In this step, the abrasive grain composition is poured into a mold. It is preferable to pour the abrasive grain composition into the mold so that the bubbles in the abrasive grain composition remain in the abrasive grain composition even after being poured into the mold.

[Step of curing the abrasive grain composition]
In a general molding method of a resole-type phenol resin, the abrasive grain composition poured into the mold is cured. Specifically, the abrasive grain composition poured into the mold is cured by heating. At this time, in order to allow the curing reaction to proceed sufficiently, the heating temperature is preferably 60 ° C. or higher, more preferably 70 to 90 ° C. However, the present invention contains other raw materials and solvents, and if the heating method is the same as that of the conventional molding method, the molded product tends to expand and a normal molded product cannot be obtained. Therefore, an intermediate (semi-cured product) is first produced by low-temperature heating, and then stably molded by heating at a predetermined molding temperature. Specifically, it is a method of obtaining a molded product by two-step heating of a first heating temperature and a second heating temperature which is a temperature higher than the first heating temperature. The first heating temperature is preferably 30 ° C. or higher, more preferably 40 to 50 ° C., and is heated for a predetermined heating time to obtain an intermediate (semi-cured product). After that, the second heating temperature is preferably 60 ° C. or higher, more preferably 70 to 90 ° C., and is heated for a predetermined heating time to obtain a molded product. The predetermined heating time is, for example, 1 hour or more, preferably 1 to 10 hours. As a result, the curing time of the abrasive grain composition can be shortened by 1/2 to 1/3 from the conventional curing time. Further, since a uniform curing reaction product can be obtained, the occurrence of cracks can be improved.

After the step of curing the abrasive grain composition, it is preferably washed and dried to remove unreacted material from the mold or to remove starch powder when used as a pore-forming agent. It is more preferable to perform further heat treatment after drying. Examples of the heat treatment conditions include a heat treatment temperature of 110 ° C. to 200 ° C. and a heat treatment time of 10 to 30 hours. If the heat treatment temperature is 200 ° C. or lower and the heat treatment time is 30 hours or less, there is no risk that the elasticity of the grindstone will decrease.

[Dimensioning process]
A dimensioning step may be performed after the step of curing the abrasive grain composition. After the above heat treatment, a grindstone processed to a desired size can be obtained by sizing processing. The shape of the grindstone may be a disk shape, a board shape, or any other shape, and is arbitrarily selected depending on the conditions of the mounting grinding machine.

<Whetstone for centerless polishing and cylindrical grinding>
The grindstone of the present invention can be used as a grindstone for centerless polishing and final finishing of cylindrical grinding. Specifically, the grindstone of the present invention can be used for final finishing of cylindrical metal parts.

For example, as a specific example, in the case of a shock absorber using such a grindstone of the present invention, the contact surface of the shock absorber can be finished with high accuracy, and the quality is possible. Furthermore, when rough to intermediate finish is conventional grindstone grinding and final finish is buffing or etching. All can be completed by grindstone polishing, which can simplify the process and improve workability.

Further, the grindstone of the present invention may be used as a grindstone for flattening the surface of a rolling roll such as titanium or stainless steel or a gravure plate making roll by vertical grinding.

The present invention is not limited to the above embodiment. The above-described embodiment is an example, and any object having substantially the same structure as the technical idea described in the claims of the present invention and exhibiting the same effect and effect is the present invention. Is included in the technical scope of.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples and Comparative Examples.

<Evaluation method>
(Number average molecular weight of resin (Mn))
The weight average molecular weight (Mn) of the resole-type phenol resin is a value calculated by gel permeation chromatography (GPC) (molecular weight measuring device: Showa Denko KK, model number: RI-71) in terms of polystyrene. .. As the solvent, 50 mM lithium chloride and 2 mM hydrochloric acid (added dimethyl formaldehyde) were used, and the column temperature was 23 ° C.

(Rockwell hardness)
A dent created when a steel ball with a diameter of 1/2 inch (about 12.7 mm) is brought into contact with a grindstone and a reference load of 15 kg · f is applied using a Rockwell hardness tester manufactured by Matsuzawa Co., Ltd. Converted from the depth, the Rockwell hardness was measured on a superficial 15Y scale.

[Example 1]
Resol-type phenolic resin (effective content 70% by weight, number average molecular weight (Mn) 400, balance water, unreacted phenol, formaldehyde) was added to 3.7 kg, and corn starch (volume average primary particle diameter: 16 μm) was added as a pore-forming agent. 1 kg was mixed, and 6 kg of abrasive grains (GC # 1000, volume average primary particle diameter 11 μm) made of silicon carbide were further added and mixed. Finally, toluenesulfonic acid-hydrate (purity 99% or more) was added as a curing catalyst so that the blending amount of the curing catalyst was 15 parts by mass with respect to 100 parts by mass of the phenol resin to make a uniform slurry (abrasive grain composition). The thing) was prepared. The mixing ratio (mass ratio) of the resole-type phenol resin and the abrasive grains was 30:70. The blending amount of the pore-forming agent with respect to 100 parts by mass of the resin was 3.9 parts by mass. Further, these mixed preparations were carried out under a reduced pressure with a gauge pressure of −0.09 MPa.

The prepared slurry was poured into a mold and held at a first heating temperature of 40 ° C. for 1 hour to obtain an intermediate. Further, the thermosetting reaction was allowed to proceed for 1 hour at a second heating temperature of 80 ° C. to cure the abrasive grain composition, and a cured product was obtained. The obtained cured product was taken out from the mold and washed with water to remove the unreacted product. Then, the cured product washed with water was dried at 80 ° C. for 40 hours, and further heat-treated at 150 ° C. for 10 hours. The cured product after the heat treatment was processed into a desired shape to complete a polishing grindstone. Five grindstones were produced under the same conditions using this method.

The produced polishing grindstone was visually inspected and the occurrence of cracks was confirmed. As a result, no individual with cracks was confirmed, and suppression of cracks was confirmed by adding a curing catalyst.

The outer circumference of a φ30 heat-resistant steel shaft was cylindrically ground using the produced single polishing grindstone. The depth of cut is 1.0 mm / sec. The grindstone feed rate is 100 mm / 30 sec. The grindstone rotation speed was 1800 rpm, and the glossiness and surface roughness of the work after polishing were measured. Table 1 shows the results of the visual inspection and the polishing evaluation. As for the polishing performance, excellent mirror surface and surface roughness were obtained as compared with the general-purpose cash register bond grindstone. In addition, no adverse effect on polishing performance was confirmed even when synthesized using a curing catalyst.

[Example 2]
Emulsion-type propylene / butadiene rubber (PBR resin manufactured by Nippon A & L Co., Ltd., effective content 40) in 3 kg of resole-type phenol resin (effective content 70% by mass, number average molecular weight (Mn) 400, balance water, unreacted phenol, formaldehyde) 1.3 kg of mass%, residual water), 0.1 kg of conealdehyde (volume average primary particle diameter: 16 μm) as a pore-forming agent, and abrasive grains made of silicon carbide (GC # 1000, volume average primary particle diameter 11 μm) 6 kg was added and mixed. Finally, toluenesulfonic acid-hydrate (purity 99% or more) was added as a curing catalyst so that the blending amount of the curing catalyst was 15 parts by mass with respect to 100 parts by mass of the phenol resin to make a uniform slurry (abrasive grain composition). The thing) was prepared. The mixing ratio (mass ratio) of the total of the resole-type phenol resin and the propylene / butadiene rubber and the abrasive grains was 30:70. The mixing ratio (mass ratio) of the resole-type phenol resin and the propylene / butadiene rubber was 80:20. The blending amount of the pore-forming agent with respect to 100 parts by mass of the resin was 3.8 parts by mass. Further, these mixed preparations were carried out under a reduced pressure with a gauge pressure of −0.09 MPa.

The prepared slurry was poured into a mold and held at a first heating temperature of 40 ° C. for 1 hour to obtain an intermediate. Further, the thermosetting reaction was allowed to proceed for 1 hour at a second heating temperature of 80 ° C. to cure the coating composition to obtain a cured product. The obtained cured product was taken out from the mold and washed with water to remove the unreacted product. Then, the cured product washed with water was dried at 80 ° C. for 40 hours, and further heat-treated at 150 ° C. for 10 hours. The cured product after the heat treatment was processed into a desired shape to complete a polishing grindstone. Five grindstones were produced under the same conditions using this method.

The produced polishing grindstone was visually inspected and the occurrence of cracks was confirmed. As a result, no individual with cracks was confirmed, and suppression of cracks was confirmed by adding a curing catalyst.

The same visual inspection and polishing test as in Example 1 were carried out using the prepared single polishing grindstone. The results are shown in Table 1. As a result of blending the elastic resin, the glossiness of the work after polishing was increased and the mirror surface accuracy was further improved as compared with Example 1.

[Comparative Example 1]
Emulsion type propylene / butadiene rubber (PBR resin manufactured by Nippon A & L Co., Ltd., effective content 40) in 3 kg of resole type phenol resin (effective content 70% by mass, number average molecular weight (Mn) 400, residual water, unreacted phenol, formaldehyde) 1.3 kg of mass%, residual water), 0.1 kg of corn starch (volume average primary particle diameter: 16 μm) as a pore-forming agent, and abrasive grains made of silicon carbide (GC # 1000, volume average primary particle diameter 11 μm) 6 kg was added and mixed to prepare a uniform slurry (abrasive grain composition). The mixed preparation of these was carried out under a reduced pressure with a gauge pressure of −0.09 MPa.

The prepared slurry is poured into a mold, not heated at the first heating temperature, held at a second heating temperature of 80 ° C. for 24 hours, and the thermosetting reaction is allowed to proceed to cure the abrasive grain composition and cure it. I got something. The obtained cured product was taken out from the mold and washed with water to remove the unreacted product. Then, the cured product washed with water was dried at 80 ° C. for 40 hours, and further heat-treated at 150 ° C. for 10 hours. The cured product after the heat treatment was processed into a desired shape to complete a polishing grindstone. Five grindstones were produced under the same conditions using this method.

The produced polishing grindstone was visually inspected and the occurrence of cracks was confirmed. As a result, fine cracks were confirmed with 2 out of 5 grindstones.

[Comparative Example 2]
In Comparative Example 2, a polishing grindstone was produced in the same manner as in Example 2 except that the amount of the curing catalyst compounded was 25 parts by mass with respect to 100 parts by mass of the phenol resin.

Table 1 shows the evaluation results of the produced polishing grindstone. In Comparative Example 2, the raw material composition expanded while the thermosetting reaction of the abrasive grain composition was proceeding at the second heating temperature of 80 ° C. As a result, the cured state deteriorated, molding became impossible, and a polishing grindstone could not be produced.

[Comparative Example 3]
In Comparative Example 3, a polishing grindstone was produced in the same manner as in Example 2 except that the amount of the curing catalyst compounded was 3 parts by mass with respect to 100 parts by mass of the phenol resin.

Table 1 shows the evaluation results of the produced polishing grindstone. Curing was not completed by the progress of the thermosetting reaction at a second heating temperature of 80 ° C. for 1 hour, and it took 10 hours or more to cure the abrasive grain composition. In addition, as a result of visual inspection of the produced polishing grindstone, cracks were confirmed in 1 out of 5 individuals. The result was that the effect of shortening the curing time and reducing the crack occurrence rate by the catalyst could not be obtained.

[Comparative Example 4]
In Comparative Example 4, a polishing grindstone was produced in the same manner as in Example 2 except that the mixing ratio (mass ratio) of the resole-type phenol resin and the propylene / butadiene rubber was 45:55.

With respect to the produced polishing grindstone, the raw material composition expanded in the process of curing the abrasive grain composition. Therefore, the cured state deteriorated, and a normal molded product could not be obtained. It was confirmed that if the blending ratio of the elastic resin is large, the cured state is adversely affected and a normal molded product cannot be obtained.

Claims (14)

A grindstone made of a cured product obtained by curing an abrasive grain composition containing abrasive grains, a resin, and a curing catalyst.
The resin contains 50% by mass or more of a resole-type phenol resin.
A grindstone characterized in that the blending amount of the curing catalyst is 5 to 23 parts by mass with respect to 100 parts by mass of the phenol resin. The grindstone according to claim 1, wherein the blending amount of the resin is 10 to 40 parts by mass with respect to a total of 100 parts by mass of the abrasive grains and the resin. The grindstone according to claim 1 or 2, wherein the number average molecular weight (Mn) of the resole-type phenol resin is 300 to 600. The resin contains an elastic resin
The elastic resins include isobrene rubber, butadiene rubber, styrene / butadiene rubber, chlorobrene rubber, nitrile rubber, butyl rubber, ethylene / propylene rubber, ethylene / propylene / diene rubber, acrylic rubber, epichlorohydrin rubber, silicone rubber, fluororubber and propylene / butadiene. The grindstone according to any one of claims 1 to 3, which is at least one resin selected from the group consisting of rubber. The grindstone according to claim 4, wherein the ratio of the elastic resin to the resin is 5 to 50% by mass. The grindstone according to any one of claims 1 to 5, wherein the abrasive grain composition contains a pore-forming agent. The grindstone according to claim 6, wherein the amount of the pore-forming agent blended with respect to 100 parts by mass of the resin is 1 to 40 parts by mass. The aspect of any one of claims 1 to 7, wherein the abrasive grains are at least one ceramic abrasive grains selected from the group consisting of silicon carbide, alumina, chromium oxide, cerium oxide, zirconium oxide and zircon sand. Whetstone. The grindstone according to any one of claims 1 to 8, wherein the volume average primary particle diameter of the abrasive grains measured by a laser diffraction / scattering method is 5 to 27 μm. The grindstone according to any one of claims 1 to 9, wherein the Rockwell hardness measured on a superficial 15Y scale is -60 to 0. The grindstone according to any one of claims 1 to 10, which is a grindstone for centerless polishing and cylindrical grinding final finishing. A process of preparing an abrasive grain composition by mixing a mixed solution containing abrasive grains, a resin and a curing catalyst.
Including a step of pouring the abrasive grain composition into a mold and a step of curing the abrasive grain composition poured into the mold.
The resin in the abrasive grain composition contains 50% by mass or more of a resole-type phenol resin.
The step of curing the abrasive grain composition is curing by two-step heating in which the abrasive grain composition is heated at a first heating temperature for a predetermined time and then heated at a second heating temperature higher than the first heating temperature for a predetermined time. How to manufacture a grindstone. The method for producing a grindstone according to claim 12, wherein the first heating temperature is 30 ° C. or higher, and the second heating temperature is 60 ° C. or higher. The method for producing a grindstone according to claim 12 or 13, wherein the predetermined heating time is 1 to 10 hours.