JPH07266B2 - Whetstone - Google Patents

Description

TECHNICAL FIELD The present invention relates to a grindstone. Particularly suitable for use as a small-grained grindstone for barrel polishing and blasting.

2. Description of the Related Art A grindstone using a phenol resin as a binder is well known. The media used for barrel polishing is spherical, on a cone,
Cylindrical, cubic, amorphous, and other types of granular whetstones are generally used, but inorganic materials are used as binders or thermoplastic synthetic resins are used as binders. Phenolic resin has good adhesion to abrasive grains, heat resistance, and has a toughness that is lower than that of inorganic materials and has a toughness, so it does not scratch the work as sharply as an inorganic material when it collides with the work piece and when it slides .
However, since phenol resin is thermosetting, it is necessary to mold it, and it is practically impossible to mold a small grindstone. Therefore, molding in an open state without using a mold has been desired. When the abrasive particles are mixed with the phenolic resin provided in the form of powder and heated, the phenolic resin softens and melts at the softening point, and then gradually hardens and does not deform. If there are many abrasive grains, for example, if the abrasive grains are 80% by weight phenol resin powder 20% by weight compound, adding a little alcohol makes it a plastic material similar to clay for work and can be spread into a sheet. Divide into cubes and spheres,
A granular grindstone can be obtained by volatilizing alcohol and heating in an oven as it is. However, if the alcohol is difficult to volatilize and remains, a void will be created in the grindstone. Further, when the ratio of the abrasive grains decreases to 70% by weight and 60% by weight, upon heating in an oven, fluidization occurs at the softening point of the phenol resin, and the granular compound processed into a predetermined shape is deformed.

Conventionally, there has been such a problem in heating and hardening a small grindstone using a phenol resin as a binder in an open state.

Means for Solving the Problems The present invention provides a composition in which a binder exceeds 45% by volume in a grindstone, and the binder comprises 75 to 45% by weight of a phenol resin and 25 to 55% by weight of an epoxy compound of glycerin polyglycidyl ether. Characterized by a grindstone characterized by having.

Effects (1) Since the binder has a composition of 75 to 45% by weight of a phenol resin and 25 to 55% by weight of an epoxy compound, the mixture of the abrasive and the binder has a composition of the phenol resin during heating even when the abrasive concentration is low. Does not flow at the softening point.

Therefore, the composition can be heat-cured in an open state while maintaining a predetermined shape, and by overlapping.

(2) Since the epoxy compound is a liquid, it becomes a dispersion medium for the powdery phenolic resin and the abrasive grains, and even if the compound has a high abrasive grain concentration, the compound should be treated with a plastic similar to clay for work without processing. make it easier. Since there are no volatiles, no voids are created in the grindstone due to heating.

(3) Due to the effects of the above (1) and (2), the compound can be processed into small particles having a predetermined shape, and an inexpensive small-sized grindstone can be provided without using a mold.

Detailed Description The grindstone used in the present invention is alumina, silicon carbide, or other abrasive grains, and is not particularly limited. Phenolic resin is a novolak type and is generally provided as a powder, and it is usual that a curing agent such as hexamethylenetetramine has already been added and blended. As the epoxy compound, a liquid compound having 2 or 3 or more glycidyl groups is used. Examples of diepoxy compounds include polyethylene, polypropylene, polytetramethylene, resorcin, neopentyl glycol, 1.6 hexane, diol, bisphenol A, adipic acid, diglycidyl ether formed by phthalic acid, and the like. Examples include polyglycidyl ether having a skeleton of sorbitol, glycerol, diglycerol, polyglycerol, pentaerythritol, and trimethylpropane.

When a binder of 75 to 45% by weight of a phenolic resin and 25 to 55 of an epoxy compound is mixed with abrasive grains, the liquid epoxy compound plays a role of a dispersion medium and becomes plastic. When the plasticized mixture is left at a temperature of 20 to 30 ° C, gelation proceeds and the viscosity increases considerably from several tens of minutes to several hours depending on the type of epoxy compound. For those with a slow progress of gelation, the gelation can be promoted by heating at a temperature lower than the softening point of the phenol resin. While it is plastic, it is rolled into a sheet and appropriately divided into cubic particles or it is further rounded into a spherical shape, or it is extruded into a string shape from an extruder at around 50 ° C, and cut into a cylindrical shape. Process it at will. This is placed in an oven and heated directly to 180 ° C, or the temperature is raised stepwise and heated at 180 ° C to cure. Particles do not deform even if directly heated to 180 ° C if gelled appropriately before putting in the oven. The amount of the epoxy compound with respect to the phenol resin may be a minimum amount that does not cause deformation during heating in the oven, but when the abrasive grain concentration reaches 50 to 55% by volume, it is necessary to increase the amount of the epoxy compound that functions as a dispersion medium. I have something to do. In the oven heating, even if the compound particles are piled up, if the particles in the lowermost layer are piled in such a range that only the load within the deformation load is received, they can be heated all at once.

Examples Example 1 Novolac-type phenol resin powder cash register top PG (A)-
2473 (Gunei Kagaku Kogyo Co., Ltd .. Hexamethylenetetramine as a curing agent. Softening point 84 ° C) and trifunctional epoxy compound SR-GLG (Sakamoto Yakuhin Kogyo Co., Ltd.).
Glycerin polyglycidyl ether) and alumina first
The ingredients were mixed in the proportions shown in the table (unit is part by weight). This is No. 1-3
In Nos. 6 and 6, the sheet was left standing at room temperature for about 30 minutes, rolled into a sheet, disassembled, and rolled into a spherical shape of 3 mm. Since No. 4 and No. 5 are initially sticky, after leaving them at room temperature for 8 hours, make them 3 mm spherical. Even in Nos. 4 to 5, the standing time can be shortened by heating to 40 to 50 ° C. This was kept at 70 ° C. for 30 minutes, then placed in a glass container at a height of 10 cm, and heat-cured in an oven at 180 ° C. for 3 hours. It was good except that slight deformation was observed in No. 1. The abrasive grain concentration of No. 1 to 5 is about 10% by volume, and that of No. 6 is about 50% by volume.

In the case of the comparative example, 8 parts by weight of ethyl alcohol was added to the composition shown in Table 1, similarly rolled into sheets and divided into 3 mm spheres, left at 30 ° C for 48 hours, put in an oven and heated at 70 ° C for 3 hours. After that, the temperature was gradually raised to 180 ° C. and heat-cured at 180 ° C. for 3 hours.

The grindstone of the comparative example was greatly deformed and had many voids inside.

Example 2 SR-NPG (trade name of Sakamoto Yakuhin Kogyo Co., Ltd., neopentyl glycol diglycidyl ether), SR-TPG (previously, polypropylene glycol diglycidyl ether), SR-2EG (previously, diethylene glycol) as an epoxy compound Diglycidyl ether) was prepared, and 33 parts by weight of each was mixed with 66 parts by weight of the same phenol resin as in Example 1, and 90 parts by weight of alumina # 1000 was added and mixed.

Since these epoxy compounds are not sticky enough to be rolled into a sheet, they are left at room temperature for 1 hour and then extruded with an extruder at a nozzle temperature of about 50 ° C into a string with a diameter of 2 mm.
After cutting to a length of mm and holding at 70 ° C. for 1 hour, it was heat-cured in the same manner as in Example 1 to obtain a grindstone without deformation.

Claims (1)

[Claims] 1. A grindstone containing more than 45% by volume of a binder, said binder having a composition of 75-45% by weight of a phenolic resin and 25-55% by weight of an epoxy compound of glycerin polyglycidyl ether. Whetstone.