JPH02202525A - Synthetic grinding stone - Google Patents

Abstract

PURPOSE:To provide a synthetic grinding stone composed of a mixture of a matrix composed of a polyvinyl acetal resin, etc., and fine abrasive particles existing in the matrix in continuous state, having three-dimensional network texture containing continuous fine pores and having excellent water-resistance and grinding performance. CONSTITUTION:The objective synthetic grinding stone useful for polishing a soft metal plate such as aluminum disk to impart excellent flatness and high surface accuracy to the plate is composed of a three-dimensional network texture containing continuous fine pores and containing fine abrasive particles dispersed in a matrix in continuous state. The grinding stone can be produced by mixing (A) fine abrasive particles (preferably particles finer than grain No.800 and composed of silicon carbide, etc.) into (B) a matrix consisting of a homogeneous polymer composed of a polyvinyl acetal resin, one or more kinds of thermosetting resins (e.g. melamine resin), an amorphous silicate and a polyhydric alcohol, its derivative or its polymer. The amount of the abrasive particle is preferably >=50wt.% based on the total weight of the mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is a metal plate having a flat surface, such as a soft metal such as an aluminum alloy master disk (hereinafter referred to as an aluminum disk) that is a material for a magnetic disk base. It relates to a synthetic whetstone used for surface grinding and polishing, that is, polishing.

(Prior art) Conventionally, a relatively soft metal plate with a flat surface,
For example, surface polishing of aluminum disks, etc. can be done by machining using a precision lathe, so-called lapping using a slurry of fine powder such as silicon carbide, or processing using a synthetic grindstone such as a resinoid grindstone or a urethane grindstone. was common.

However, machining using precision lathes, etc. has different finishing accuracy and work efficiency depending on the skill level of the worker, and is generally poor in workability. The efficiency was noticeably low.

In addition, in the case of lapping processing using a slurry of low-grain fine powder such as silicon carbide, it is economically disadvantageous due to the loss of slurry and the amount used, and it also contaminates the surrounding working environment and workers, and furthermore, Processing using synthetic grindstones has been rapidly becoming popular in recent years, instead of the lapping process using a slurry of fine abrasive grains, which had the problem of requiring a great deal of time and money to process high-concentration waste liquid. . However, synthetic whetstones, such as vitrified or resinoid hard whetstones, have insufficient polishing performance and cannot obtain sufficient finishing precision, lack search power, or cause undesirable phenomena such as clogging. However, there were problems such as not being able to achieve a certain level of performance with high efficiency. In other words, when polishing flat surfaces, especially aluminum disks, etc., which require both flatness and surface precision, the surface of the object to be polished and the surface of the abrasive material are brought into contact with each other. It is necessary to advance the
For example, when using a resinoid-based or urethane-based synthetic whetstone with an independent pore structure, abrasive debris, fallen abrasive grains, etc. due to the polishing action can easily enter the pores, causing clogging, which may affect the sustainability of the polishing effect. This results in chipping and frequent dressing (surface renewal) work.

On the other hand, those using polyvinyl acetal resin with continuous pores as a bonding material are easy to discharge polishing debris, fallen abrasive grains, etc. to the outside of the pores, and are less likely to cause clogging, making them excellent synthetic grindstones. Although it is generally known, it has relatively poor water resistance and is not suitable for such precision polishing applications.

In addition, products containing a cured thermosetting resin for the purpose of imparting water resistance are also available in Japanese Patent Publications No. 39-1898 and No. 53-
It was proposed in various publications such as No. 6752, and is known as a water-resistant synthetic whetstone. In particular, in the latter invention, by changing the blending ratio of the thermosetting resin, an abrasive material with properties ranging from elastic to rigid can be obtained.
In particular, fine-grained whetstones were said to be useful for polishing soft, hard, and difficult-to-cut materials, but their grinding power was still insufficient, and they were particularly useful for polishing soft metal plates with flat surfaces. It was not suitable for flat surface polishing of aluminum disks, etc.

Furthermore, it compensates for the lack of chemical resistance and anti-pressure of polyvinyl acetal grinding wheels, and also serves as an adhesion for abrasive materials.

In order to increase the bonding force, a method of adding silicic acid gel to the matrix has been proposed in Japanese Patent Publication No. 36-22443, but conventional synthetic grindstones manufactured by this method also have the same effect on the precision of soft metal plates. It could not be said that it was suitable for polishing.

In order to solve these problems,
Publication No. 80 proposes a synthetic grinding wheel in which the relationship between the surface hardness of a polyvinyl acetal grinding wheel and the abrasive grain count is limited, and silicic acid gel is added to the matrix. It simultaneously satisfies excellent flatness and high surface precision for surface polishing.

This synthetic whetstone is usually placed in water before being installed in a polishing machine, left for more than 12 hours, and allowed to reach a completely wet state, allowing it to swell by up to 2% and become stable before being disposed of.

However, when this synthetic whetstone is placed in water during the winter, there is a problem in that as the water permeates inside the whetstone, the whetstone cracks and breaks due to distortion due to swelling. Therefore, in the winter, it is necessary to store the whetstone at room temperature and then put it into water before use, making it impossible to use the whetstone immediately, and an improvement has been desired.

(Problems to be Solved by the Invention) The present inventors have completed the present invention as a result of intensive research in view of the above-mentioned technical current situation and problems. These include soft metal plates that have been finished to simultaneously satisfy both excellent flatness and high surface accuracy, especially aluminum disks, and especially annular disks made of special aluminum alloys that can be used for extremely precise applications. To provide a synthetic whetstone which can be used for various purposes and does not cause cracks even when put into water in winter.

(Means for Solving the Problems) The above object is to provide a structure having a three-dimensional network structure with continuous fine pores, which structure is formed by curing polyvinyl acetal resin and at least one thermosetting resin. A matrix consisting of a homogeneous mixture of an amorphous body, a silicate, and a polyhydric alcohol or its derivative or polymer, and abrasive fine particles that are interconnected and exist in a substantially continuous state in the matrix. This is achieved by a synthetic grindstone characterized by being made of a mixture.

The fine three-dimensional network structure of the grindstone of the present invention is completely different from the closed cell structure of resinoid-based or urethane-based artificial grindstones; there are no closed cells, and branches extend three-dimensionally into the voids. The structure is like that, and the pores are infinitely connected. Therefore, abrasive particles and polishing debris caused by polishing work are easily discharged out of the system through these gaps, and even if they are captured, they are deposited in the air bubbles, as seen in other closed-cell whetstones. , it is difficult to cause undesirable phenomena such as clogging.In the case of a closed cell structure, the polishing effect lacks sustainability due to clogging, and frequent dressing operations (surface renewal) are required.

The above-mentioned effects can be sufficiently obtained within the range of average pore diameter of 10 to 100 μm; below this range, the pores are too dense and phenomena such as clogging tend to occur. Moreover, if it exceeds this, the structure will be too rough and there will be some difficulty in terms of uniformity of physical properties.

Further, the porosity is preferably in the range of 60 to 85 volume'kk%. If the capacity is less than 60%, closed cells will be present, and if it exceeds 85% capacity, the strength will be insufficient.

A synthetic whetstone using a hardened polyvinyl acecool resin, a thermosetting resin, and an amorphous silicate as a binder for abrasive grains is known from JP-A-61-192480. Because it contains a hardened thermosetting resin, it is water resistant, and because it also contains an amorphous silicate, it has extremely favorable grinding power as a grindstone for polishing soft metals, and it especially reduces wear on the grindstone itself. This provides performance that reduces the amount of water and causes less undesirable phenomena such as clogging. As mentioned above, the toughness (stickiness) characteristic of polyvinyl acetal synthetic grinding wheels is reduced by using polyvinyl acetal resin, a cured thermosetting resin, and an amorphous silicate as the matrix, which is a binding material. This is a synthetic whetstone with appropriate coldness (brittleness), and the amorphous silicate has the excellent effect of imparting appropriate brittleness to the whetstone and improving its grinding power.

In the present invention, the thermosetting resin includes melamine resin,
Examples include phenolic resins, urea resins, thermosetting urethane resins, and epoxy resins, but melamine resins and phenol resins are usually used.

In the present invention, the amorphous form of dosilicate refers to a gel-like substance produced by the action of acid on various silicates made of silicon dioxide and various bases. In the case of NazO・x8i0z
” It is represented by the chemical formula yHtO, and Nax
It is preferable to use those having a molar ratio of O/5iOt of 2 and 4. In this case, the general formula of the gel-like substance is an inorganic polymer represented by intermolecular crosslinking to form an amorphous three-dimensional compound. In addition to this, aluminum hydroxide or the like may be used as the base.

The above-mentioned binder matrix plays the role of effectively holding fine abrasive particles, which are the main material of polishing. During polishing work, one abrasive grain polishes the surface and is eliminated from the system. At the same time, the grinding wheel generates new low-grade grains and continues the polishing work. In other words, the grindstone itself performs the polishing process while wearing itself. However, by using the silicate amorphous material mentioned above, the matrix itself also undergoes some grinding. The grinding force can be improved significantly, and at the same time, the wear of the button grindstone itself can be reduced.

The polyhydric alcohol, which is another component mixed into the matrix, is added not as a binding material for abrasive grains but as a water penetrating agent, and the matrix itself 5 can also be hydrophilic, making it difficult to absorb water. rapidly penetrates into the inside,
Strain due to moisture does not occur, and cracks can be prevented.

Here, polyhydric alcohol refers to polyhydric alcohol or
It refers to its derivatives or its polymers,
Usually glycerin or glycols.

Vetriol (for example, trade name "Kurarayobrenken Chemical"), ethanolamine, etc. are used. Among these, those that are non-volatile (very low vapor pressure), have low toxicity, have a plasticizing effect and are highly hygroscopic are particularly preferred.

In addition, in the present invention, 85 abrasive fine particles include diamond,
Boron nitride, silicon carbide, fused alumina.

Refers to grinding materials made from compounds or single substances with grinding power, such as garnet, emery, cerium oxide, and chromium oxide, which are then classified using an appropriate method to the particle size specified in JIS Standard R6001. Yes, but
Silicon carbide, fused alumina.

It is desirable to select at least one type of cemented carbide ceramic abrasive grains selected from the group consisting of chromium oxide and cerium oxide.

Furthermore, the key point of the present invention is the coordination and distribution state of abrasive grains having polishing performance. In other words, in this type of synthetic whetstone, the abrasive grains existing on the polishing surface are rubbed off, fall off, and are discharged from the system. It polishes the surface of the body, but if the ratio of abrasive grains is small, each abrasive grain will exist independently, and after that abrasive grain falls off, from a microscopic point of view, it will not bond. Rub the surface with only the wood. In other words, since the rubbing is performed in areas with low abrasive force, the sharpness (grinding force) is poor. Especially when the purpose is to polish the surface of a soft metal such as an aluminum disk, as in the present invention,
Such a phenomenon is undesirable and tends to lead to problems such as surface unevenness and polishing unevenness.

In the present invention, in order to avoid such undesirable phenomena, individual abrasive grains do not exist independently in the matrix, but are interconnected with adjacent abrasive grains, forming a substantially continuous state. It needs to be distributed. The state of such abrasive grains is such that the matrix of the grinding wheel has a continuous pore structure with an average pore diameter of 10 to 100 μm, which is uniformly connected three-dimensionally with a high porosity of 60 to 85 μm,
This is due to the fact that fine abrasive grains of appropriate particle size are arranged in the fine skeleton of such a matrix with sufficient agitation, so to speak, and are uniformly distributed. Also,
In order to ensure such coordination and distribution, a suitable abrasive grain count is at least 800, and the content is 25 or more times the weight of the mixture, more preferably 50 times the weight of the mixture. It's more than enough.

Further, it is preferable that the lower the abrasive grain count, that is, the larger the diameter of the abrasive grains, the higher the hardness.

The grindstone according to the present invention is manufactured by the following method.

That is, the average degree of polymerization is 300 to 2000. Mixing one or more plates of polyvinyl alcohol with a degree of saponification of 80 mol% or more, its derivatives or modified products to form an aqueous solution,
To this, an aqueous solution, nonaqueous solvent solution, emulsion, etc. of a precursor consisting of a thermosetting resin monomer, oligomer or polymer, etc., and an aqueous solution or colloid of a silicate are added and stirred uniformly. aldehydes, acids as a filtration medium, and starch as a pore-forming agent.

etc. to prepare a uniformly viscous slurry, which is poured into a predetermined mold. After that, reaction solidification is carried out in an intestinal bath or other bath at a temperature of 40 to 100°C day and night, and then taken out and washed with water to remove excess aldehydes, acids, and pore-forming agents. Get a body.

Next, a solution is prepared by adding an aqueous solution, a non-aqueous solvent solution, an emulsion, etc. of a precursor consisting of a monomer, oligomer, or polymer of a thermosetting resin, and a polyhydric alcohol, its derivative, or its polymer, and stirring uniformly. , impregnated with the intermediate, squeezed to a predetermined amount, and then heated at 100°
Heat at a temperature of about C to evaporate moisture and dry. After that, heat treatment (curing) f for curing the resin,
However, the temperature and time required for curing will vary slightly depending on the type and amount of resin used. -20℃ at 100 to 250℃ for boat fishing
If curing is performed for 100 hours, the curing reaction is almost completed.

If the curing is insufficient, the toughness will be high, and if the cocuring conditions are harsh and the curing progresses too much, thermal decomposition will occur at the same time, which is likely to cause undesirable phenomena, so conditions must be selected carefully. .

In order to avoid rapid temperature rise during curing, it is also effective to raise the temperature in stages or to perform it in an inert gas atmosphere to suppress local oxidation and deterioration. Furthermore, it is also effective to use a catalyst to promote thermal curing.

The liquid resin may be an aqueous solution, a solution dissolved in an organic solvent, an emulsion, or a resin stock solution.
From the viewpoint of workability and ease of controlling the mixing ratio,
The method using an aqueous solution is most preferred.

(Function) After the whetstone obtained as described above was molded into the desired shape, it was placed in water and left for 12 hours or more to reach a completely wet state, swell by about 2 inches at most, and become stable. It is used for surface polishing of soft metals, but especially when it is used for very precise purposes such as surface polishing of special aluminum alloy annular discs such as aluminum disks, the thickness before and after polishing, that is, the grinding debris, will affect the accuracy. Because the flatness and thickness variations are extremely suppressed, it is difficult to apply it to polishing equipment used on boats; for example, it cannot be installed in extremely precise equipment such as double-sided lapping polishing machines. It is preferable to use it. Here, a double-sided lapping type polishing machine is equipped with circular or ring-shaped metal surface plates on both the upper and lower surfaces, and one or more objects to be polished are sandwiched between them and crimped, and both the upper and lower surface plates are rotated in opposite directions. When applying the grindstone of the present invention, it is first placed in water and left for at least 12 hours to completely wet the surface of the object to be polished. This is achieved by allowing the material to swell by a maximum of 2% and stabilize. At that time, polyhydric alcohols (derivatives,
Since the polyhydric alcohol acts as a penetrant and water quickly penetrates into the matrix, distortion due to swelling does not occur, and therefore cracks do not occur.

Next, the grindstone is attached to both surface plates so that it forms a uniform surface. During operation, polishing is performed by flowing an appropriate amount of a polishing aid liquid to wet the polishing surface, but the liquid used here, the so-called polishing liquid, is water,
This may be water containing a surfactant in a dish, or an organic solvent.

Thus, when the grinding wheel of the present invention is installed in a double-sided lapping type grinding machine to polish, for example, an aluminum disk, the grinding wheel is evenly and densely packed into the matrix resin, which has excellent water resistance and abrasive grain retention, and mutually The abrasive fine particles connected to the abrasive grain count and matrix have appropriate hardness, elasticity,
Combined with the hardness of the surface of the whetstone, which is derived from brittleness, it exhibits sharp cutting ability, that is, abrasive power, and even if the abrasive grains fall off one by one due to the abrasive action, new abrasive grains connected to the back appear on the surface. The abrasive surface is immediately refreshed and regenerated.
Abrasives, fallen abrasive grains, etc. are easily discharged from the continuous fine pores and are less likely to cause clogging, so high polishing power is maintained over a long period of time. In addition, due to the above-mentioned special coordination self-distribution state of the ultrafine abrasive grains of the grinding wheel of the present invention, during polishing work, the entire surface of the flat object to be polished can be coated without any rubbing phenomenon caused only by the matrix resin. The abrasive particles come into contact and rub against each other, and a uniform polishing action is performed at all times. Therefore, the grindstone of the present invention efficiently provides a soft metal plate having a flat surface with high smoothness without polishing spots and excellent finished surface accuracy.

(Example) Embodiments of the present invention will be described below with reference to Examples.

As the abrasive grains, silicon carbide powder No. 3000 was selected. No. 3000 has an average particle size of 5.5 to 4.5 pm. Completely saponified polyvinyl alcohol with a degree of polymerization of 1700 is made into an aqueous solution, and a predetermined amount of P-961A manufactured by Jurez ■ is added as a water-soluble phenol resin, sulfuric acid is used as a catalyst, formaldehyde is used as a crosslinking agent, and formaldehyde is used as a pore forming agent. After adding cornstarch and a predetermined amount of a silicate aqueous solution containing silicon dioxide and soda ash,
A uniform slurry liquid was prepared by mixing with the abrasive grains described above. This slurry liquid was cast into a predetermined mold and allowed to react and solidify at 8°C for one day and night. Thereafter, it was washed with water to remove excess acid, formaldehyde, cornstarch, etc., and dried to obtain an intermediate for a synthetic grindstone. In addition, a solution was prepared by uniformly stirring a predetermined amount of an aqueous solution of 8M-700 manufactured by Showa Kobunshi ■ as an aqueous solution of melamine resin and a predetermined amount of DG manufactured by Daiichi Kogyo Seiyaku ■ as glycerin, and the intermediate was impregnated into this solution. death,
After squeezing it to a specified amount, dry it and heat it at a temperature of 130°C for about 50 minutes.
Heat treatment was performed for 0 hours to obtain a cured product.

The thus obtained cured product has a thickness of 5 as shown in FIG.
It was cut and formed into a substantially fan-shaped shape (1) of 0 mm to obtain a synthetic grindstone of an example of the present invention.

The composition of the grindstone used in this example is shown in Table 1.

After leaving the thus obtained whetstone in the atmosphere at 10°C for 24 hours, the hardness of the whetstone surface was measured, and the bottom surface of the whetstone was bent at an angle of 18°.
The grindstone was immersed in water and the time required for the water to penetrate to the top surface of the grindstone was measured. However, the hardness was measured under the following conditions.

Hardness meter Rockwell hardness meter manufactured by Matsuzawa Seiki Co., Ltd. Model E[A
RDNE88 TE8TERRXT-2 type surface hardness measurement conditions Rockwell Sparphy results are shown in Table 1 below.

(Hereinafter, below, abutment) As is clear from Table 1, in order to uniformly and quickly impregnate water, judging from the water penetration time, the effect cannot be obtained unless 1wt or more of glycerin is included. It turns out that there isn't. Furthermore, as described in JP-A-61-192480 and JP-A-61-182774, when the abrasive grain count is 3000, the Rockwell hardness is -180 to -
A grindstone within the range of 210 can be considered as a standard for polishing an aluminum disk master to excellent flatness and high surface precision. As stated in the above publication,
Generally, when an aluminum disk is polished with a highly hard whetstone, the finished surface of the aluminum disk will have rough surface precision (Ra is large). On the other hand, if the grinding wheel becomes soft, the grinding wheel will become clogged, making it difficult to grind and the flatness of the finished surface will also deteriorate. Considering these points, it is considered that a grindstone with a glycerin adhesion amount of 10 wt% or more is hard and unsuitable for polishing an aluminum disk. Therefore, the content of glycerin is 1 in weight ratio.
-10%.

(Effects of the Invention) As detailed above, the synthetic whetstone according to the present invention does not require storing the whetstone at room temperature (usage atmosphere) during the winter and then putting it into water, so it can be used immediately when needed. This improves work efficiency.

In addition, the synthetic whetstone according to the present invention makes it possible to efficiently and economically obtain soft metal plates, such as aluminum disks, which have both excellent flatness and high surface precision, and is used in the electronic industry, office equipment, etc. It is possible to fully cope with the quality improvement and rapid increase in demand for high-precision finished aluminum disks as information storage media accompanying the development of industry, etc., and the increase in polishing work efficiency makes it possible to lower production and processing costs wt. The contribution to industry is enormous.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a lapping machine of a lapping type polishing machine for explaining the usage of the grindstone of the present invention. (1)...Whetstone, (2)...Mounting plate,
(3)...wrapping disc.

Claims (2)

[Claims] (1) A structure having a three-dimensional network structure with continuous fine pores, which structure consists of a polyvinyl acetal resin, a cured product of at least one thermosetting resin, an amorphous silicate, and a polyhydric alcohol. A synthetic whetstone characterized by comprising a matrix consisting of a homogeneous mixture with a derivative thereof or a polymer thereof, and a mixture of fine abrasive grains that are interconnected and exist in a substantially continuous state in the matrix. . (2) The synthetic whetstone according to claim 1, wherein the content of the polyhydric alcohol, its derivative, or its polymer is in the range of 1 to 10% by weight.