JPH07115301B2 - Diamond grindstone manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a synthetic grindstone using diamond abrasive grains.

(Prior art) Diamond abrasive grains have extremely high hardness and excellent grinding power and durability. Especially, those using fine grained diamond abrasive grains are widely used for high precision finishing. .

Generally, abrasives using diamond abrasives include, for example, lathes equipped with diamond points, grindstones in which diamond abrasives are electrodeposited in a single layer on a metal surface, or diamond resin abrasives using synthetic resin as a binder. Tools and whetstones are included.

Finishing polishing of hard and brittle materials such as hard ceramics includes lapping polishing using fine diamond abrasive grains as free abrasive grains, but this method has a problem that a large amount of expensive diamond abrasive grains are consumed. Therefore, it is conceivable to use a diamond grindstone made of a porous body with a synthetic resin as a fine abrasive grain of diamond,
In this case, the adhesion between the diamond abrasive grains and the resin is not very good, so the diamond abrasive grains produced by the conventional method of manufacturing resin grindstones are extremely easy to fall off, and there is a lot of waste in the manufacturing process. Also, when it is used, there is a problem that it falls off immediately and normal polishing cannot be continued, or the grindstone is greatly reduced. This tendency is more remarkable as the diamond grains are finer and the porosity of the grindstone is larger.

On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 62-246474 discloses a method for producing a superabrasive grindstone for mirror finishing. In this method, an abrasive grain holder and a binder are mixed with abrasive grains, pressure molding is performed, and the molded product is solidified to produce a grindstone. Here, diamond abrasive grains are described as the abrasive grains, and copper powder and tin grains are described as the abrasive grain holder. However, in this manufacturing method, since a grindstone is manufactured by pressure molding, a material having a high porosity is weak in strength and cannot be practically used, and the porosity is limited to a low porosity of about 20 to 40%. Further, since the abrasive grains are held by pressure molding, the holding force of the binder on the abrasive grains is weak. To compensate for this, a small abrasive grain size of 30 μm or less is used and the ratio of the abrasive grains is increased. There must be. That is, the manufacturing method of the above publication requires an extremely large amount of diamond abrasive grains,
There is a problem that expensive diamond abrasive grains cannot be effectively used, and that fine scratches such as scratches (scratches) are likely to occur during polishing.

(Problems to be Solved by the Invention) In view of the above-mentioned problems, the present inventors have conducted diligent research, and as a result, reaction-cured a reaction stock solution made of a specific thermosetting resin to produce fine powder of copper or tin. The present invention has been completed by finding that a synthetic whetstone that is dispersed and fixed uniformly and firmly fixes diamond abrasive grains, and the object thereof is excellent polishing durability and good scratch resistance. Another object of the present invention is to provide a method for producing a diamond grindstone having a porous structure, which is suitable for obtaining surface roughness and can effectively use expensive diamond abrasive grains.

(Means for Solving the Problem) An object of the present invention is to provide a resol-type phenolic resin, a melamine-based resin, a curing catalyst for a melamine-based resin, a pore-forming material, and a dispersion liquid in which a fine metal powder of copper or tin is mixed. A method of producing a synthetic whetstone by adding diamond abrasive grains and uniformly mixing to form a reaction stock solution, drying the intermediate obtained by heating and curing this, and further curing by heating, It is achieved by a method for producing a diamond grindstone, which comprises adding a thickening agent to the stock solution so as to adjust the viscosity of the reaction stock solution to 500 to 5000 cps.

The diamond abrasive grain used in the present invention is a fine diamond powder, and its particle size may be appropriately selected according to the purpose, but is usually 1 to 100 μm, and the larger the particle size, the greater the grinding effect. The smaller the particle size, the greater the polishing effect. Since the diamond abrasive grains have a large grinding force and a large grinding force, it is not necessary to add a large amount thereof, and the amount of the diamond abrasive grains added in the present invention is 25% by volume or less, preferably 10% by volume or less of the entire grindstone obtained. Is an amount equivalent to.

The resol type phenolic resin used in the present invention (hereinafter referred to as “resole resin”) is a generally viscous liquid resin obtained by condensing phenols and aldehydes in the presence of a basic catalyst, such as water, alcohol, acetone and the like. It dissolves well in an aqueous solvent, but when it is further heated, the resinification reaction proceeds and it gradually becomes less soluble in the solvent, and it goes through a brittle solid resin (resitol) with no tackiness, and finally an insoluble and infusible cured resin. (Residue).

The melamine-based resin used in the present invention is a liquid resin obtained by reacting raw material melamine and formaldehyde in the presence of a basic catalyst, which is a thermosetting resin that is condensed and cured in the presence of a curing catalyst. .

In the method of the present invention, the mixing ratio of the resole resin and the melamine resin is preferably resole resin / melamine resin = 1/9 to 9/1 (weight ratio), more preferably 2/8.
It is used in an amount of up to 8/2. The higher the proportion of the resole resin, the stronger the toughness, and the higher the proportion of the melamine resin, the stronger the brittleness.

As the curing catalyst for the melamine-based resin used in the present invention, inorganic acids such as sulfuric acid and hydrochloric acid, and organic acids such as formic acid, acetic acid, maleic acid and benzenesulfonic acid can be used.
Preferably, an acid salt such as ferric chloride or zinc nitrate or a hydrochloride salt of an organic amine is used. When salts are used as the curing catalyst, the curing reaction of the melamine-based resin becomes slow, and a more homogeneous porous structure can be stably obtained.

The fine metal powder of copper or tin used in the present invention preferably has a high purity of 99% or more, and these can be used alone or in combination. If there are many impurities such as iron, these impurities react with acids or the like as a curing catalyst of the thermosetting resin to foam, and it becomes difficult to form a homogeneous structure.

The average particle size of the fine powder is not particularly limited, but if the particle size is too small, it tends to fall off from the porous body, and if the particle size is too large, the holding power of the diamond abrasive grains tends to decrease, It is preferably 300 μm or less, more preferably 10 to 150 μm, still more preferably about 50 to 100 μm, and those having a narrow particle size distribution are suitable.

It should be noted that the use of tin fine powder is superior to the use of copper fine powder in holding force for diamond abrasive grains having a smaller particle size. Specifically, when diamond abrasive grains of 10 μm or less are used. In addition, the polishing action is preferably obtained.
In the present invention, it is also effective to use lead fine powder in combination with the above metal fine powder.

The amount of the fine metal powder mixed is likely to be a porous body having a brittle structure if the amount is too large, and the amount is preferably 5 to 25% by volume, more preferably the volume of the obtained diamond grindstone.
The amount is equivalent to 10 to 20% by volume. Further, it is extremely preferable that the fine metal powders are not in a dispersed state in which the fine powders are independent of each other, but the fine powders are connected to each other and are present in a substantially continuous state. By doing so, the dimensional stability against heat, water, solvent, etc. is improved and the effect of holding the diamond abrasive grains is increased.

As the pore-forming material used in the present invention, it is preferable to use a powder having a relatively uniform particle size, for example, starch granules extracted from a plant such as potato starch are suitable. The type of starch used is
It may be appropriately selected depending on the desired pore diameter. In order to form a porous body having continuous pores, the particles of the pore-forming material are preferably adjacent to each other, and when starch is used, it is preferably 0.5 to 5% by weight / volume based on the reaction stock solution. Examples of the pore-forming material include starch granules and water-soluble polymers such as surfactants, polyethylene oxide, polypropylene glycol or derivatives thereof, and these are suitable for forming finer pores.

In order to manufacture a diamond grindstone using the above-mentioned resole resin, melamine-based resin, curing catalyst, pore-forming material, copper or tin metal fine powder, diamond abrasive grains, etc., first, a predetermined amount of resole resin and melamine resin is mixed. After adding the pore-forming material and the curing catalyst to the aqueous solvent solution and stirring and mixing, the fine metal powder is added and uniformly mixed and stirred. Next, diamond abrasive grains are added and further stirred to obtain a mixed solution in which the particles are uniformly dispersed.

In the above mixed solution, the metal fine powder has a high specific gravity, and particularly when a metal fine powder having a large particle size is used, the metal fine powder easily precipitates. Add a substance with (thickener). As such a thickener, there are fine particles having a relatively high bulk density, and in the method of the present invention, a soft substance that does not particularly affect the characteristics as a grindstone is preferable, and examples thereof include butyl cellosolve powder, pulp powder, and fine powder. Examples thereof include glass powder, silica powder, and fine fiber powder. The amount of addition may be appropriately set so that the dispersed state of the mixed solution is stable, and is such an amount that the viscosity of the mixed solution is adjusted to 500 to 5000 cps, preferably 700 to 3000 cps.

Next, the reaction stock solution obtained as described above is cast into a mold and heated to, for example, 40 to 80 ° C. to cause a reaction to obtain an intermediate which is a brittle solidified product. After removing the obtained intermediate from the mold and dropping it off, it is slowly dried by, for example, a ventilation dryer at about 80 ° C., and subsequently preferably heat-treated at 100-200 ° C., more preferably 120-170 ° C. (curing). By doing so, a hardened body having a porous structure can be obtained, and a diamond grindstone according to the method of the present invention can be obtained.

In the above method, it is preferable that the intermediate is dried relatively slowly, and if it is dried too quickly, cracks and cracks easily occur. It is suitable to obtain a uniform cured product by gradually performing curing at a low temperature. The curing time is usually 5 to 50 hours, but it may be appropriately set in consideration of the size of the intermediate and the properties of the resin. In particular, in the thermosetting reaction of the resol resin, deterioration or burning may occur due to local temperature rise, so it is also effective to add a small amount of an antioxidant or to perform curing in a non-oxidizing atmosphere. is there.

The diamond grindstone obtained by the above method is a porous body having continuous pores, and its porosity is usually 30 to 70% by volume, preferably 40 to 70% by volume, and the average pore diameter is 500 μm.
Hereafter, it is preferably 30 to 200 μm, and the diamond abrasive grains are uniformly dispersed throughout the grindstone together with the fine metal powder.

The continuous pores of the diamond grindstone obtained by the method of the present invention prevent clogging due to polishing debris and effectively reduce temperature rise due to accumulation of polishing heat. When the porosity is less than 30% by volume, the above effects are not sufficiently exhibited, scratches are likely to occur, and the polishing rate is also reduced. On the other hand, when the porosity is larger than 70% by volume, the porous body becomes a brittle structure.

(Effect of the Invention) According to the method of the present invention, since the resin as the binder is obtained by reacting and hardening the reaction stock solution, the diamond abrasive grains can be firmly fixed in the binder. Further, since the reaction stock solution is adjusted to have a specific viscosity, each material constituting the grindstone can be uniformly dispersed in the reaction stock solution, and the diamond grindstone having an extremely homogeneous structure can be easily manufactured. Further, since the continuous pores are formed by the pore forming material, it is possible to stably and efficiently manufacture a diamond grindstone having a continuous pore structure with a high porosity.

Since the diamond grindstone obtained by the method of the present invention is a porous body having fine continuous pores with high porosity,
It effectively prevents the accumulation of polishing debris on the working surface of the grindstone and the clogging phenomenon generated in the polishing work, and efficiently dissipates the heat generated by the polishing operation. Further, it is excellent in dimensional stability against water and heat and can be polished with high accuracy.

Moreover, since the diamond abrasive grains are firmly fixed by the action of the fine metal powder, the diamond abrasive grains are unlikely to fall off. Furthermore, the synergistic effect of the fine metal powder and high porosity can prevent the occurrence of deep scratches, which is a defect that easily occurs in diamond grinding stones, and has a good finished surface roughness and good polishing for a long time. The action can be maintained. Therefore, the diamond grindstone obtained by the method of the present invention can be suitably used for polishing hard and brittle materials such as ceramics and silicon wafers.

Hereinafter, the present invention will be described in detail with reference to examples. Before that, the method of the polishing test in this specification will be described.

<Method of polishing test> The obtained diamond grindstone was formed into a disk shape and mounted on the upper and lower plates of a double-sided polishing machine type 5B (manufactured by Speedfam),
Use high-purity alumina ceramics plate with water as polishing liquid.
Polished for minutes.

After polishing, the polished surface was measured for centerline average roughness Ra and maximum roughness Rmax.

(Example 1) Resol resin PR961A (66% aqueous solution, manufactured by Sumitomo Dures)
360 ml and melamine resin Sumitex resin M-3 (7
180 ml of 0% aqueous solution, manufactured by Sumitomo Chemical Co., Ltd., and then a solution of 4 g of ferric chloride dissolved in 20 ml of water as a catalyst and zinc nitrate.
Add 2g of water dissolved in 10ml of water, and add 100g of potato starch.
Was added to 200 ml of water and uniformly dispersed to obtain a mixed solution. Fine metal powder in the mixture has an average particle size of 80 μm.
After adding 1000 g of fine copper powder and stirring and mixing, the average particle size was 54
63 g of diamond abrasive grains having a diameter of μm was added and further stirred. Subsequently, 30 g of Aerosil fine powder (a mixture of silica and aluminum oxide, manufactured by Nippon Aerosil Co., Ltd.) was added as a thickener and sufficiently mixed with stirring to obtain a reaction stock solution in the form of a viscous slurry. The viscosity of this reaction stock solution at 20 ° C. was about 1000 cps.

Next, the obtained reaction stock solution was cast into a rigid vinyl chloride cylindrical mold, and the mold was allowed to stand in a warm water bath at 60 ° C. for 24 hours to solidify the contents to obtain an intermediate. . This intermediate was a solid with some flexibility. The intermediate is taken out of the mold and dried at 80 ° C. for 10 days by a ventilation drier, subsequently placed in a heat treatment furnace and slowly heated from room temperature to 140 ° C., and further heat-treated at this temperature for 10 hours to be cured. It was a diamond grindstone.

The obtained diamond grindstone was a porous structure having continuous pores having a porosity of 44% by volume and an average pore diameter of about 80 μm, and the proportion of diamond abrasive grains was as shown in Table 1. Further, the diamond abrasive grains and the fine copper powder were uniformly dispersed throughout the grindstone and firmly fixed to the binder resin. The hardness as a grindstone was 45 on the Rockwell HR-R scale (1/2 ″ steel ball, measured at 60 kg pressure). Also, the coefficient of thermal expansion was 3.5 × 10 ⁻⁵ / ° C. Swelling rate is 0.1
%, Which was excellent in dimensional stability. The results of the polishing test of the obtained diamond whetstone are as shown in Table 2.

(Example 2) 1000 g of tin fine powder having an average particle size of 80 μm was used as the metal fine powder.
A diamond grindstone was manufactured in the same manner as in Example 1 except that 63 g of diamond abrasive having an average particle diameter of 2 to 3 μm was used.

The obtained diamond grindstone has a porosity of about 41% by volume,
The proportion of diamond abrasive grains in the porous structure having continuous pores with an average pore diameter of about 80 μm was as shown in Table 1. Further, the diamond abrasive grains and the fine tin powder were evenly distributed throughout the grindstone. It was dispersed and firmly fixed to the binder resin. Rockwell hardness as a grindstone is about 48,
The coefficient of thermal expansion is 4.3 × 10 ^-5 / ° C, and the swelling ratio in water is 0.1.
%, The dimensional stability was excellent, and the results of the polishing test were as shown in Table 2.

(Example 3) 1000 g of fine tin powder having an average particle size of 80 μm as fine metal powder
A diamond grindstone was produced in the same manner as in Example 1 except that 125 g of diamond abrasive having an average particle diameter of 2 to 3 μm was used.

The obtained diamond grindstone has a porosity of about 41% by volume,
The proportion of diamond abrasive grains in the porous structure having continuous pores with an average pore diameter of about 80 μm was as shown in Table 1. Further, the diamond abrasive grains and the fine powder of tin were uniformly dispersed in the whole grindstone and firmly fixed to the binder resin. Rockwell hardness as a grindstone is about 48,
The coefficient of thermal expansion is 4.3 × 10 ^-5 / ° C, and the swelling ratio in water is 0.1.
%, The dimensional stability was excellent, and the results of the polishing test were as shown in Table 2.

(Comparative Example) Example 1 is the same as Example 1 except that fine metal powder is not used.
A diamond grindstone was manufactured in the same manner as in. In this method, the diamond abrasive grains were poorly dispersed, and nodules were observed due to the agglomeration of the abrasive grains in the step of mixing and stirring. Further, a phenomenon was observed in which some of the abrasive grains float on the surface of the reaction stock solution.

In the obtained diamond grindstone, an agglomerate of abrasive grains was observed, and a slight difference in the dispersed state of the abrasive grains was observed between the upper layer and the lower layer of the stone. Further, the adhesion between the abrasive grains and the binder resin was poor, and when a polishing test was performed, the grindstone was heavily worn and could not be put to practical use as a grindstone for polishing.

Claims (2)

[Claims] 1. Diamond abrasive grains are added to a dispersion obtained by mixing a resol-type phenolic resin, a melamine-based resin, a curing catalyst for a melamine-based resin, a pore-forming material and a fine metal powder of copper or tin, and uniformly mixed. And a reaction stock solution, after drying the intermediate obtained by heat curing it, a method for producing a synthetic whetstone by further heat curing, the reaction stock solution viscosity of the reaction stock solution 500 ~ A method for producing a diamond whetstone, wherein a thickening agent is added so as to adjust to 5000 cps. 2. A diamond abrasive grain is added to a dispersion obtained by mixing a resol-type phenolic resin, a melamine-based resin, a curing catalyst for a melamine-based resin, a pore-forming material, and copper or tin metal fine powder, and uniformly mixed. And then the reaction stock solution, after drying the intermediate obtained by heating and curing this, a method for producing a synthetic whetstone by further heating and curing, using a salt as a curing catalyst of the melamine resin, A method for producing a diamond grindstone, wherein a thickener is added to the reaction stock solution so as to adjust the viscosity of the reaction stock solution to 500 to 5000 cps.