JPH0671703B2 - Method for manufacturing flexible PVAc grindstone - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a polyvinyl acetal resin grinding wheel having flexibility (hereinafter abbreviated as PVAc grinding wheel).

Conventional technology Polyvinyl acetal resin grindstone that uses acetalized polyvinyl alcohol resin as a binder, so-called PVAc
The grindstone is suitable for use as a polishing tool for soft members, non-ferrous metal members, etc., because a good mirror-like finished surface is obtained due to the buffering effect of the binder itself.

Problems to be Solved by the Invention By the way, the outer peripheral edge portion of a PVAc grindstone formed in a disk shape having a relatively thin thickness is inserted into an elongated cut or a gap formed in a member to be ground made of a plate metal, for example. When polishing the inner edge or inner wall surface of the
There is a disadvantage that the lateral pressure applied to the grindstone increases and the deformation due to the lateral pressure increases, so that the breaking strength of the PVAc grindstone cannot be sufficiently obtained.

Means for Solving Problems The present invention has been made against the above circumstances.
The gist thereof is a method of manufacturing a PVAc grindstone having flexibility, which is (1) a sheet which is preformed into a sheet-shaped semi-finished product by bonding abrasive grains with a polyvinyl acetal resin as a binder. Molding step, and (2) a pair of the above-mentioned sheet-like semi-finished products sandwiching glass fibers having a phenol resin adhered to the surface by a pretreatment, the polyvinyl acetal-based resin having a glass transition point higher than the glass transition point of the polyacetal-based resin. And a fixing step of fixing each other by heating and pressing at a temperature lower than the temperature at which the resin decomposes.

By doing so, a pair of sheet-shaped semi-finished products preformed by the polyvinyl acetal resin, which originally has a buffering effect, is a glass fiber having a phenol resin adhered to the surface by pretreatment. In the sandwiched state, the polyacetal-based resin is heated and pressed at a temperature higher than the glass transition point of the polyacetal-based resin and lower than the decomposition temperature of the polyvinyl acetal-based resin to be fixed to each other, so that the polyacetal-based resin has excellent flexibility and deformation. It is possible to obtain a PVAc grindstone that is not easily destroyed by. That is, since the glass fiber is pretreated with the phenol resin attached to the surface and a pair of sheet-shaped semi-finished products sandwiching the glass fiber are pressed in a heated state,
While a pair of sheet-shaped semi-finished products are bonded to each other with the glass fiber sandwiched therebetween, the glass fiber is reinforced by the glass fiber by firmly bonding with the abrasive grains by the curing of the phenol resin which is a thermosetting resin, The PVAc grindstone as a whole has excellent flexibility and the fracture strength against deformation related to lateral pressure is significantly increased.

In the fixing step of the present invention, the pair of the sheet-shaped semi-finished products is pressed at a temperature higher than the glass transition point of the polyvinyl acetal resin when the glass fibers having the phenol resin adhered to the surface by the pretreatment are pressed in a sandwiched state. And since it is heated at a temperature lower than the temperature at which the polyvinyl acetal-based resin decomposes, the polyvinyl acetal-based resin that is amorphous at room temperature is crystallized, and further flexibility and high breaking strength can be obtained. There is.

In addition, the above glass fibers usually use a glass fiber mesh in processing work. Further, the number of sheets is sufficient to be one, but a plurality of sheets may be stacked and fixed.

Example 1 First, black silicon carbide (JISR6213) C # 80 (JISR6001)
The sheet-shaped semi-finished product 10 having an outer diameter of 205 mm, a hole diameter of 27 mm and a thickness of 3 mm is molded by bonding the abrasive grains of (1) with a polyvinyl acetal resin. A well-known method for producing a PVAc grindstone is used for this forming method. This manufacturing method is described in, for example, Japanese Patent Publication No. 30-1548 and Japanese Patent Publication No. 39-13290. The sheet-shaped semi-finished product 10 is porous like a normal PVAc grindstone.

A pair of sheet-shaped semi-finished products 10 formed as described above, impregnated by passing through a phenol resin liquid and dried to attach the phenol resin to the surface of the pretreated glass fiber net 12 80 ° C when sandwiched
It is heated at a temperature of up to 150 ° C., sandwiched in a mold (not shown) and subjected to a pressure press. This heating temperature range is determined to be a temperature above the glass transition point at which the polyvinyl acetal resin, which is amorphous at room temperature, crystallizes, and lower than the temperature at which the resin decomposes. The polyvinyl acetal resin, which is a thermoplastic resin, is softened by the above-mentioned heating, and the pair of sheet-shaped semi-finished products 10 are bonded to each other with the glass fiber net 12 sandwiched therebetween, while the phenol resin, which is a thermosetting resin, is cured by reaction. Since the glass fiber net 12 is reinforced by the glass fiber net 12 by firmly adhering to the abrasive grains, PV
The Ac grindstone 14 as a whole has excellent flexibility, and the fracture strength against deformation related to lateral pressure is significantly increased. Further, since the polyvinyl acetal resin is heated at a temperature higher than the glass transition point of the polyvinyl acetal resin and lower than the temperature at which the polyvinyl acetal resin is decomposed, by crystallization of the polyvinyl acetal resin which is amorphous at room temperature, The breaking strength is further enhanced. Incidentally, when the above-mentioned pair of sheet-shaped semi-finished products 10 are pressure-pressed at room temperature, mutual adhesiveness cannot be obtained well due to the springback action. Note that the glass fiber net 12 has, for example, EP specified in JIS R3414.
The equivalent of 35B is used.

Through the above steps, as shown in FIG. 1 and FIG. 2, the pair of sheet-shaped semi-finished products 10 are fixed to each other, and the outer diameter 20
A flexible PVAc grindstone 14 having a diameter of 5 mm, a hole diameter of 27 mm and a thickness of 6 mm is manufactured. The flexible PVAc grindstone 14 manufactured in this manner is a pair of sheet-shaped semi-finished products 10 preformed on the polyvinyl acetal resin which originally has a buffering effect, and a phenol resin is attached to the surface by pretreatment. Since they are fixed to each other by being heated and pressed at a temperature higher than the glass transition point of the polyvinyl acetal-based resin and lower than the decomposition temperature of the polyvinyl acetal-based resin while sandwiching the glass fiber network 12, It has excellent flexibility and is not easily destroyed by deformation. Experimental examples described below clarify this property.

Examples First, the flexible PV except that the glass fiber net 12 was removed
With comparative grindstone No. 1 manufactured by the same manufacturing method as Ac grindstone 14,
The same grindstone number as the glass fiber net 12, the number of fibers, except that the carbon fiber net of the knitted shape is replaced with the glass fiber net 12, the comparative grindstone No. 2 manufactured by the same manufacturing method as the flexible PVAc grindstone 14.
Were prepared and the physical properties of them and the flexible PVAc grindstone 14 were measured, and the physical property values shown in Table 1 were obtained. In addition, the above comparative whetstone No. 1, comparative whetstone No. 2, flexible PVAc whetstone
As shown in FIG. 3, a bifurcated test tool 16 having a notch for receiving the outer peripheral edge of the grindstone while rotating at a peripheral speed of 2000 m / min was rotated from the neutral position where the lateral pressure was zero in a direction parallel to the rotation axis. When the lateral pressure was applied by moving to, the results shown in Table 2 were obtained.

As is clear from Table 2, the flexible PVAc grindstone 14 produced by the manufacturing method of the present invention is superior in flexibility as compared with the comparative grindstones No. 1 and No. 2, and is resistant to deformation due to lateral pressure. It has extremely high breaking strength. Therefore, if the flexible PVAc grindstone 14 is used, it is possible to extremely efficiently polish the inner edge and the inner wall surface of the gap or the notch formed in the tip of the fork of tableware, for example.

Second Embodiment Next, another embodiment of the present invention will be described. In this embodiment,
By bonding C # 80 abrasive grains with a polyvinyl acetal resin, a sheet-shaped semi-finished product having an outer diameter of 205 mm, a hole diameter of 27 mm, and a thickness of 3 mm is molded in the same manner as in the above-mentioned embodiment. Then, a sheet-shaped semi-finished product is impregnated with a 20% melamine resin aqueous solution containing about 0.5% dibasic ammonium phosphate which functions as a catalyst, and dried at a temperature of about 80 ° C. Using the sheet-like semi-finished product thus obtained, a PVAc grindstone is manufactured by sandwiching and fixing the glass fiber nets in the same process as in the above-mentioned embodiment. This PVAc grindstone is rich in rigidity as compared with the flexible PVAc grindstone 14 of the above-mentioned embodiment,
The rotational fracture peripheral speed was improved by 10% and the fracture strength against lateral pressure was also improved. In addition to the melamine resin, epoxy resin, phenol resin, urethane resin, diallyl phthalate resin, or a mixed resin thereof may be used as the resin to be impregnated into the above-mentioned sheet-shaped semi-finished product, and the impregnation amount is determined depending on the purpose. Can be changed as appropriate.

It should be noted that the above is merely an application example of the present invention, and the present invention can be variously modified without departing from the spirit thereof.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view showing a PVAc grindstone according to an application example of the present invention. FIG. 2 is a partial sectional view of FIG. FIG. 3 is a perspective view for explaining a breaking strength test state. 10: Semi-finished sheet 12: Glass fiber net 14: Flexible PVAc grindstone

Claims (2)

[Claims] 1. A method of manufacturing a PVAc grindstone having flexibility, comprising a sheet forming step of preforming a sheet-like semi-finished product by binding abrasive grains with a polyvinyl acetal resin as a binder, Of the sheet-shaped semi-finished product, with glass fibers having a phenol resin adhered to the surface by a pretreatment, is sandwiched, the temperature is higher than the glass transition point of the polyvinyl acetal resin and lower than the decomposition temperature of the polyvinyl acetal resin. A method of manufacturing a PVAc grindstone having flexibility, which comprises a fixing step of fixing each other by heating at a temperature and pressing. 2. The method for manufacturing a flexible PVAc grindstone according to claim 1, wherein in the fixing step, heating is performed at a temperature of 80 ° C. to 150 ° C.