JPH0583343B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a solid grindstone using a synthetic resin as a binder;
This article relates to a so-called resinoid grindstone that is suitable for relatively precision polishing, and a method for manufacturing the same.

(Prior art) Conventionally, solid grinding wheels for polishing have generally been made by holding and fixing fine particles of abrasive grains using some kind of binding material.Vitrified grinding wheels using ceramics as the binding material , resinoid-based grindstones using phenolic thermosetting resin, and PVA-based elastic grindstones using polyvinyl acetal resin, each of which has different fields of use depending on its characteristics.

In particular, resinoid grindstones can be diversified depending on the type of resin, manufacturing conditions, grain size of the grindstone used, etc., and have a wide range of applications from heavy grinding to final polishing. is between rigid whetstones, such as vitrified whetstones, and polyvinyl acetal-based elastic whetstones.
Referred to as a semi-elastic whetstone, it received high praise as a high-performance whetstone that had both grinding and polishing power. The thermosetting resin used as a binding material for resinoid grinding wheels is generally a phenolic resin.
Its production is usually done by mixing abrasive grain powder and phenolic resin powder, kneading with liquid phenolic resin to form a viscous paste, placing this in a predetermined mold, press-molding, and then solidifying with heat press. A method was used in which the material was further cured by curing.

(Problems to be Solved by the Invention) Resinoid-based grindstones manufactured by the method described above are heavy and difficult to use due to their relatively low void ratio, which is an important element of grindstones, and high bulk specific gravity. Since a method of mechanically mixing resin and abrasive grains is used, it is extremely difficult to uniformly disperse fine abrasive grains, and the manufacturing limit is at most 1000 grit (average grain size of approximately 16 μm). However, it had the disadvantage that it was very difficult to obtain a higher count. Moreover, the low void ratio is extremely disadvantageous in terms of escape of polishing debris and dissipation of polishing heat, and therefore, it is not suitable for surface polishing, which involves contacting and polishing the object over a wide area. There were some things that were a little unsuitable. Furthermore, it is difficult to apply precision polishing to surfaces plated with relatively hard metals such as chromium and nickel, and polishing that requires high precision remains inefficient and costly. It has relied on lapping methods using loose abrasive grains and buffing methods, which have many environmental problems.

The present inventors have completed the present invention through intensive research in view of the above-mentioned drawbacks and current problems found in conventional resinoid grinding wheels. The object of the present invention is to obtain metal surfaces with smoothness and high surface precision, especially relatively hard metal surfaces, economically and without environmental pollution problems. Another object is to provide a resinoid-based synthetic grindstone that has a relatively high void ratio and excellent polishing performance.

(Means for Solving the Problems) The above object is to provide a structure having a three-dimensional network structure with a porosity of 40 to 90% by volume, in which the structure is composed of a phenolic resin (P) and a melamine resin. Achieved by a custom-made synthetic whetstone consisting of a matrix whose main component is a two-component thermosetting resin (M) and abrasive grains that are densely embedded and fixed in the matrix. be done.

The method of the present invention for obtaining such a synthetic abrasive stone involves adding abrasive grains, a pore-forming agent, and a catalyst to a liquid mixture mainly consisting of a liquid phenolic resin (P) and a liquid melamine resin (M), and stirring the mixture uniformly. The method is characterized in that an intermediate obtained by reacting and solidifying the slurry-like stock solution is dried to remove moisture, and then heat-treated to harden it.

In other words, while the bonding material of conventional resinoid grinding wheels is mostly composed of hardened phenol resin, the present invention uses melamine resin to suppress the toughness and give brittleness. It is a product that uses a hardened material in combination, and its porosity is further increased to improve the sustainability of polishing performance, and the main focus is to provide resinoid-based grindstones with physical properties suitable for precision polishing. .

The present inventors have found that performance suitable for precision polishing, in other words, excellent performance for self-sharpening of the cutting edge, is achieved by using a two-component hardened product of phenolic resin and melamine resin as the main components of the grinding wheel matrix. The toughness (stickiness) of the cured phenolic resin is used as a binder.
The inventors have discovered that this can be achieved by suppressing this and imparting appropriate (brittleness) to the matrix. In other words, the cured product of phenolic resin has relatively high toughness, so conventional resinoid-based grindstones cannot fully demonstrate their performance unless they are bonded under high pressure and polished. They discovered that by using a cured product of the same, it is possible to exhibit its performance at low pressure.

The composition ratio of phenolic resin (P) and melamine resin (M) is P/M = 1/2 to 3/1 on a weight basis.
Set to . If it exceeds this value, the effect of using melamine resin in combination will be weak, and it will be almost the same as a conventional resinoid-based synthetic whetstone, and if it is less than this, it will become too brittle and will not be able to perform as a resinoid-based grindstone. I also don't like it. Furthermore, it is necessary to set the vacancy rate of the matrix within the range of 40 to 90% by volume. That is, if it is less than 40% by volume, it lacks the ability to capture polishing debris and fallen abrasive grains, and tends to cause clogging phenomena. In addition, those with a volume of more than 90% lack structural strength and are difficult to perform as a grindstone.

Next, the method for manufacturing the synthetic grindstone will be described in detail.

The conventional manufacturing method for resinoid grinding wheels is to mix abrasive grains and hardened phenolic novolac resin powder at a predetermined ratio, add liquid phenolic resin to this, knead it, and prepare a paste-like stock solution. A common method was to mold the paste-like stock solution in a predetermined mold and then harden it using a hot press. In this method, it is undesirable to have a high porosity, and the limit is 30% by volume at most.In addition, since the method involves mixing powdered raw materials, it is difficult to mix uniformly in the case of fine particles, resulting in uneven distribution. It is easy to form abrasive grains, so-called "mamako" or non-uniform layers, and the limit of abrasive grain size is at most 1000 grit, and higher grits cannot be obtained.

The present inventors did not seek powder raw materials for the resins, but instead used phenolic and melamine liquid resins, that is, resin stock solutions or resins, or their monomers.
By using an aqueous solution, solution, or emulsion of a precursor such as an oligomer or a low polymer as its raw material, and adding abrasive particles into the solution and stirring uniformly, abrasive particles of any particle size can be produced extremely easily. They discovered that it can be uniformly dispersed in the stock solution. In addition, by using the phenolic resin and melamine resin liquids, the resin liquids can be mixed completely, and the problem of one resin being unevenly distributed in lumps, stripes, or layers, for example, can be avoided. It is possible. More preferably, the above-mentioned disadvantages can be completely avoided by using both resin liquids with substantially the same viscosity. Regarding the mixing ratio of both resin solutions, the phenol resin (P) and melamine resin (M) in the obtained synthetic grindstone have a composition ratio of P/M = 1/2 to 3/1 on a weight basis. Do it like this.

Next, the use of a pore-forming agent in the method of the present invention is also an important feature. That is, since conventional resinoid grindstones are manufactured by the method described above, the voids are formed by gaps between particles that occur when resin powder and abrasive powder are mixed. However, the vacancy rate varied depending on the mixing method, and at the same time it was unstable. In contrast, in the method of the present invention, the porosity and pore diameter can be controlled by using a pore-forming agent, so that the desired structure can be obtained extremely stably.

In other words, a liquid resin liquid undergoes a condensation crosslinking reaction at a relatively low temperature in the presence of a catalyst to gel and solidify, and as it solidifies, it separates from the medium water or solvent and shrinks in volume. In order to prevent volumetric contraction during the solidification reaction process and form stable pores, which can easily occur, a pore-forming agent is used in the method of the present invention.

As the pore-forming agent, one that is easily dispersible in water is used, and specific examples thereof include starch, modified starch, modified cellulose, and the like. In the case of water-dispersed pore-forming agents such as starches and modified celluloses, the parts where they existed become pores, so by varying the particle size of the pore-forming agent, the pore size can be controlled as appropriate. . The amount of these pore-forming agents used is
It is preferably about 0.5 to 5.0% by weight/volume. If it is too small, the curing will be thin, and if it is too large, it will be difficult to knead and it will not be possible to form a uniform structure.

The liquid phenolic resin used in the present invention is a resin stock solution or an aqueous solution of a precursor consisting of monomers, oligomers, polymers, etc., which can be crosslinked and solidified in the presence of a catalyst such as an acid. Particularly preferred are aqueous solutions of initial products of resol resins produced by reaction in the presence of basic catalysts.

In addition, liquid melamine is an aqueous solution of a precursor consisting of a resin or its monomer, oligomer, polymer, etc., which can undergo intermolecular condensation, that is, cross-linking and hardening, in the presence of a catalyst such as an acid. This is suitable for carrying out the method of the present invention.

The phenolic resins and melamine resins mentioned here can be used at relatively low temperatures (30~30°C) in the presence of a catalyst.
Although it undergoes condensation and solidification reactions even at 100°C, it becomes solid, but at this stage it is soft and not hard enough, so it is an intermediate, so to speak, without the performance as a grindstone.

After drying this intermediate to remove moisture or solvent, heat treatment curing is performed to accelerate the crosslinking reaction caused by the aforementioned condensation and harden it, thereby obtaining the physical properties necessary for the desired grindstone, but it is suitable for curing. The temperature is 100~200℃, the time is 3
~50 hours.

The catalyst used here refers to acids, specifically mineral acids such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid, oxalic acid, butyric acid, maleic acid, adipic acid,
Organic acids such as lactic acid, benzenesulfonic acid, and paratoluenesulfonic acid, or salts consisting of a strong acid and a weak base, i.e. those that show acidity in aqueous solution, and those that generate acid when heated, such as hydrochloride of organic amines. etc.

In the method of the present invention, as mentioned above, solidification proceeds at a relatively low temperature in the pre-process, and heat curing proceeds at a slightly high temperature in the post-process. It is better to keep it at a level. It is preferable to use a mild metal salt catalyst consisting of a strong acid and a weak base in order to proceed with a homogeneous reaction.

It is preferable to add the amount to an extent that does not change the performance of the grindstone of the present invention, specifically, about 0.1 to 5% by weight based on the total weight.

The synthetic whetstone of the present invention is manufactured by the method described above and has extremely excellent performance as a semi-elastic whetstone, and its performance also depends on the mixing ratio of both resins, the void ratio, and even heat treatment (curing). ) It is possible to obtain a variety of products by appropriately changing the conditions.

In addition, the type of abrasive grains is not particularly limited, and diamond, boron nitride, silicon carbide, fused alumina,
Although fine powders such as chromium oxide and cerium oxide can be used, those made of at least one abrasive material selected from the group consisting of silicon carbide, fused alumina, chromium oxide, and cerium oxide are particularly preferred.

(Function) In general, the polishing action of a solid grindstone can be roughly explained as follows.

The abrasive grains on the surface of the whetstone in contact with the object to be polished play the role of cutting blades by sliding, rotating, or being rubbed relative to each other, grinding the surface of the object to be polished, and falling off due to the frictional force. At the same time, new abrasive grains appear on the surface and the same action, the so-called self-growth action, is repeated, and the overall grinding and polishing actions are performed in parallel. In other words, the whetstone polishes the other object while abrading itself, and the matrix, which is the binding material, holds the abrasive grains appropriately.
It must be something that can be shed and worn away. That is, the matrix needs to have hardness, toughness, and brittleness depending on the material of the material to be polished. What is also important is that grinding debris and fallen abrasive grains caused by the polishing action are smoothly discharged from the polishing surface. If this action is insufficient, the abrasive surface will become clogged, the polishing performance will be extremely degraded over time, and undesirable results such as polishing spots and streaks will occur.

The synthetic whetstone of the present invention is extremely suitable for the above-mentioned polishing action, has an appropriate level of brittleness, has excellent self-growth action, and has the ability to trap polishing debris and fallen abrasive grains through its hollow space. It is. Furthermore, since it is possible to manufacture high-grid products that are difficult to produce with conventional resinoid grindstones, this could only be achieved by lapping or buffing methods using loose abrasive grains. Precision polishing (finish polishing) of relatively hard metals has also become possible with the synthetic grindstone of the present invention.

Hereinafter, the present invention will be specifically explained in detail with reference to Examples.

Example 1 250 ml of a 66% aqueous solution of PR-961A manufactured by Sumitomo Bakelite Co., Ltd. as a water-soluble phenolic resin and 150 ml of a 60% aqueous solution of M-3 manufactured by Sumitomo Chemical Co., Ltd. as a water-soluble melamine resin were mixed together, and a catalyst was prepared. Add a small amount of zinc nitrate and ferrous chloride as a mixture, then add a solution prepared by dispersing 40 g of cornstarch in 250 ml of water and 1 kg of fine powder of silicon carbide No. 1500 as abrasive grains, stir evenly, and pour into a specified mold. The reaction mixture was solidified in water at 50°C for 50 hours to obtain an intermediate. After drying this, 145
A synthetic grindstone was obtained by curing at ℃ for 20 hours. The grindstone obtained here has a phenol content of 15.2
%, melamine content 8.3%, P/M=1.8/1, abrasive ratio
The hardness was 76.5 wt%, the vacancy rate was 43 vol%, and the hardness was 55 as measured on a Rockwell hardness tester Superphysical 15-Y scale.

When this was molded into a disk shape and subjected to grinding of a chrome-plated cylinder, good surface accuracy was obtained.
Moreover, phenomena such as clogging did not occur.

(Comparative example) The phenolic resin aqueous solution and melamine resin aqueous solution used in Example 1 were used as resin raw materials, zinc nitrate and ferrous chloride were used as catalysts, silicon carbide No. 1500 fine powder was used as abrasive grains, and as a pore-forming agent. A synthetic grindstone having the following composition was obtained using corn starch and according to the method shown in Example 1.

(B) Phenol content 20.1wt% Melamine content 5.9wt%}P/M=3.4/1 Abrasive grain rate 75.0wt% Vacancy rate 44.1vol% (B) Phenol content 8.6wt% Melamine content 18.1wt%}P/M = 1/2.1 Abrasive grain ratio 72.5wt% Void ratio 43.8vol% (c) Phenol content 29.0wt% Melamine content 17.1wt%｝P/M=1.7/1 Abrasive grain ratio 53.9wt% Void ratio 29.0vol% ( d) Phenol content 22.0wt% Melamine content 12.9wt%}P/M=1.7/1 Abrasive grain rate 65.1wt% Vacancy rate 90.1vol% These samples were subjected to cylindrical grinding with chromium plating in the same manner as in Example 1. , the following results were obtained.

(a) It was too hard and chrome plating was not compatible with the surface, making it impossible to polish it.

(b) It was too fragile, causing severe wear on the grinding wheel, and could not withstand high-speed rotation.

(c) The clogging phenomenon was severe and frequent dressing operations were required.

(d) The grinding wheel was severely worn and could not keep up with the precision of the machine, resulting in significant polishing spots.

(Effect of the invention) With the appearance of the synthetic grinding wheel of the present invention, the clogging phenomenon caused by the low porosity, which was considered to be a drawback of conventional resinoid grinding wheels, has been significantly reduced, and it has been difficult to compare until now. It has also become possible to apply resinoid grinding wheels in the field of precision polishing of flat surfaces. It is also noteworthy that products that are lightweight and easy to handle are now available.

Furthermore, the method of the present invention makes it possible to manufacture high-count products, which has been difficult in the past, and can cover the fields of lapping methods using loose abrasive grains and buff finishing methods. Furthermore, in the method of the present invention, there are no quantitative difficulties in producing the stock solution, and the method of casting into molds is adopted, so it is possible to produce even quite large products, and the shapes can also be changed to plate-like, plate-like, etc.
It can be formed into a disk shape, a cylinder shape, a block shape, etc., and it can be formed into any complicated shape, especially if it is processed at the intermediate stage. In other words, it becomes possible to diversify both performance and shape, and the range of applications far exceeds that of conventional resinoid grindstones.

As described above, the effect of the synthetic whetstone of the present invention is extremely large, and it is difficult to use conventional synthetic whetstones by plating with hard metals such as chromium, nickel, etc., which relied on lapping and buffing methods using loose abrasive grains. Precise polishing of polished surfaces has become possible with the use of high-precision products. The consumption of this expensive granulation material is significantly reduced, which not only brings about economic effects, but also reduces environmental and worker pollution problems, and also reduces the burden of processing high-concentration waste liquid. Its influence is extremely large. In addition, even with conventional grits, the void ratio is higher and the sustainability of polishing performance is improved, specifically, the polishing work can be continued without dressing (surface renewal) work, and the specific gravity is improved. This greatly contributes to improving work efficiency, such as the reduction in labor costs for replacement work, transportation work, etc.

Claims (1)

[Scope of Claims] 1. A structure having a three-dimensional network structure with a porosity of 40 to 90% by volume obtained by eluting starch as a pore-forming agent, wherein the structure has a composition ratio on a weight basis. 1/2
A matrix whose main component is a homogeneous two-component thermosetting resin cured product of phenolic resin (P) and melamine resin (M) in a ratio of ~3/1, and which is densely contained within the matrix. , a synthetic whetstone characterized by comprising fixed abrasive grains. 2. The synthetic whetstone according to claim 1, wherein the abrasive grains are made of at least one abrasive material selected from the group consisting of silicon carbide, fused alumina, cerium oxide, and chromium oxide. 3 Add abrasive grains to a mixed solution consisting of an aqueous solution of water-soluble phenolic resin and an aqueous solution of water-soluble melamine resin.
A slurry-like stock solution containing starch and a catalyst and stirring uniformly is poured into a mold, and the resulting intermediate is solidified by reaction. After drying to remove moisture, it is heat-treated to harden. A synthetic whetstone having a void ratio of 40 to 90% by volume and a composition ratio of phenolic resin (P) and melamine resin (M) of P/M = 1/2 to 3/1 on a weight basis. Production method. 4. The method for producing a synthetic grindstone according to claim 3, wherein the water-soluble phenolic resin is an aqueous solution of a water-soluble resol resin. 5. The method for producing a synthetic grindstone according to claims 3 to 4, wherein the catalyst is a salt consisting of a strong acid and a weak base.