JPS6222746B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved method of manufacturing spherical abrasive material. Free abrasive abrasives are used to polish workpieces with abrasive grains in a free state.The workpiece, free abrasive abrasives, water, and compound are charged into a barrel, and the barrel is rotated, centrifuged, swiveled, and vibrated back and forth. It applies motion to remove scale, burrs, etc. using the relative motion difference between the free abrasive abrasive and the workpiece, and can be used for corner radiusing, plating base, smooth finishing, coarse/medium fine finishing, gloss finishing, etc. It is used in the barrel polishing method, which is often used as a secondary processing method for matte finishes and paint bases. The shapes of free abrasive abrasives are conventionally prismatic, straight,
They are pyramids, cones, etc., and these shapes have been used singly or in combination. However, when an abrasive material with such a shape is used, the polishing effect on the workpiece is significantly uneven, and defects such as deep scratches on the corners and convex parts of the workpiece result from the abrasive material. Ta. Spherical free abrasive abrasives are ideal for improving these drawbacks, but until now it has been difficult to economically manufacture such abrasives for the following reasons, and they have not been put to practical use. . In other words, the conventional manufacturing method for spherical free abrasive abrasives involves making an injection hole at the end of the combined surface of a combination mold, drilling a hemispherical hole in the plane of the mold, and injecting a mixture of a liquid hardenable polymer compound and abrasive grains through the injection hole. It is necessary to form an injection groove that can be injected into the spherical part, and when the mixture is injected and hardened, the cured material remaining in the injection groove is connected to the sphere, so it is impossible to obtain a high-precision sphere from the removed spherical molded product. It was difficult to polish, and it was not put to practical use because it lacked uniform polishing of the material to be polished and caused impressions. The present invention is a spherical free abrasive abrasive that can obtain a top-quality surface finish in a short polishing time without giving an excessive impact to the workpiece, without causing scratches, and without making dents on soft metals. The purpose is to provide a manufacturing method. The method for producing a free abrasive abrasive of the present invention involves curing a mixture consisting of abrasive grains A and a liquid curable polymer binder B using a mold to produce a spherical free abrasive abrasive. A mixture made of unsaturated polyester with an A/B weight ratio of (10 to 100)/100 and a thixotropic agent added to adjust the thixotropic index to 2 to 50 is applied to the symmetrical position of the symmetry plane of the combination mold. This method is characterized by filling a sagging hemispherical portion with a predetermined diameter, and then combining molds and pressing together to harden the mixture within the hemispherical portion. In the present invention, the mixture consisting of abrasive grains and liquid curable polymer binder must have a thixotropic index of 2 to 50. Here, the thixotropic index is 6 revolutions and 60 revolutions using a Bruckfield viscometer.
It represents the viscosity ratio indicated by the rotating rotor. When combining the upper and lower molds of a combination mold, use the vertical combination method in which the upper and lower molds are rotated 90 degrees each, or the lower mold is placed horizontally and the upper mold, which is also placed horizontally, is rotated 180 degrees. There is a method of placing the symmetrical surfaces of the upper mold on top of the upper mold and assembling them, but with either method, if the thixotropic index is less than 2, the uncured mixture will form a hemisphere when the mold is rotated. It flows out from the shaped part, making it difficult to manufacture a perfect sphere. Furthermore, if the thixotropic index is less than 2, the abrasive grains in the mixture consisting of the abrasive grains and the liquid hardenable polymer binder will separate and settle before being left to harden, so the hardness of the hardened spherical abrasive material will be uneven. This is not practical because the abrasive material is unevenly worn during contact with the material to be polished, causing scratches, scratches, embedding, etc. If the thixotropic index exceeds 50, failure to fill the mixture into the mold will occur. As the abrasive grains, alumina, molybdenum disulfide, silica sand, quartz, corundum, graphite, metal powder, etc. may be used alone or in a mixture of two or more. The size of the abrasive grains is appropriately determined depending on the shape and material of the material to be polished, but generally a grain size of 60 mesh or less is used. As the liquid curable polymer binder, unsaturated polyester is used because of its high elasticity and abrasiveness of the product. The above-mentioned unsaturated polyester can be prepared using, for example, a known α,β-unsaturated dibasic acid and, if necessary, a saturated dibasic acid and a polyhydric alcohol at a molar ratio of alcohol component to acid component in the range of 0.8 to 1.3, and carbon dioxide gas. , 140-250℃ in an inert gas such as nitrogen gas
It has a molecular weight in the range of about 600 to 5,000 and an acid value in the range of 5 to 100, obtained by condensation reaction at a temperature in the range of . In addition to the above-mentioned properties, the liquid curable polymer binder used in the present invention has strong adhesion to abrasive grains, impact resistance, water resistance, and has an adhesive surface that does not impart corrosion products to the material to be polished. Characteristics such as no gender are preferable. The mixture of abrasive grains and liquid curable polymeric binder is 2
It is necessary to have a thixotropic index of -50, but the following method can be used to adjust the thixotropic index of the mixture to this range. That is, a thixotropic agent such as silicic anhydride, short fiber asbestos, hydrogenated castor oil, etc. with a particle size of 10 to 20 millimicrons is added to the above mixture alone or in combination of two or more, based on 100 parts by weight of the above mixture. Preferably, the thixotropic agent is added in an amount of 0.5 to 5 parts by weight to adjust the thixotropic index to 2 to 50. The mixing ratio of the abrasive grains and the liquid hardenable polymer binder is in the range of 10-100:100 by weight. The mixing ratio
When the abrasive grains are less than 10:100, the ratio of binder is high, which reduces the polishing efficiency, and when the abrasive grains are more than 100:100, the elasticity of the abrasive material decreases, and the abrasive material is It is unsuitable for the present invention because it has a high probability of breaking and losing its shape. The size of the spherical abrasive material of the present invention is a minimum diameter of 1 mm,
A maximum diameter of 50 mm is preferred, and a diameter of 2 mm to 30 mm is particularly practical. The combination mold is preferably made of meehanite cast steel, cast steel, carbon tool steel, chromium molybdenum steel, etc. from the viewpoint of molded product accuracy. On the symmetry plane of each of the upper and lower molds, a hemispherical portion having a predetermined diameter suitably in the range of 1 mm to 50 mm is carved. If the surface of the mold is subjected to mold release treatment such as plating or baking with silicone resin, the molded product can be easily released from the mold. Since the free abrasive abrasive obtained by the method of the present invention is spherical, it does not apply excessive impact to the workpiece, does not cause scratches, and does not leave dents even on soft metals, resulting in a very high-quality finished surface. Obtained in a considerable amount of sanding time. In addition, since the cured product of liquid curable polymer compound is elastic, even if the height of the abrasive cutting edge is uneven, when it comes into contact with the machined surface of the workpiece, the height of the large cutting edge remains constant. Since the height is adjusted, the polishing marks are uniform and a smooth finished surface is obtained. Furthermore, it is possible to use fine abrasive grains, and the mixing ratio of abrasive grains can be increased. In addition, the cured material of the bonding material produces a self-sharpening effect when worn appropriately, and a constant amount of polishing can be obtained without causing clogging or spillage, and the worn bonding material is constantly removed. Since there are no scratches, scratches, or embeddings, it can produce finishing effects that cannot be obtained with fired abrasives. Furthermore, the degree of bonding and elasticity of the abrasive can be freely adjusted depending on the purpose. Next, the method of the present invention will be explained with reference to the drawings. In FIGS. 1 and 2, a hemispherical portion 3 having a predetermined diameter in the range of 1 to 50 mm is previously drilled in the upper mold 1 and the lower mold 2. Needless to say, this hemispherical portion 3 is constructed so that when the upper and lower molds are combined, the hemispherical portions of the upper and lower molds are combined to form a complete sphere. A resin accelerator and a catalyst are added to the mixture of the liquid curable polymer binder and the abrasive at the appropriate mixing ratio, and the mixture is adjusted to have a thixotropic index of 2 to 50 by the addition of a thixotropic agent. Fill the hemisphere of each mold. After filling, as shown in Figure 2, the upper mold is rotated 180° and combined with the symmetrical surface of the lower mold, and then pushed into a pressing device such as a press 5 and pressed with a pressure of 0.1 kg/cm ² or more. As a result, the upper and lower combination molds are brought into complete contact with each other, and excess mixture other than the spherical part leaks out and is removed. i.e.
Pressing with a pressure of 0.1 Kg/cm ² or less is not preferable because the cured product of the mixture will be integrated with the spheres and adhere as burrs between the upper and lower dies. The pressing time may be set until the mixture loses its fluidity. It is preferable to provide a guide pin 6 in the combination mold in order to completely match the positions of the hemispherical parts of the upper and lower molds of the symmetrical surface filled with the mixture. In addition, in order to improve the molding cycle, it is also possible to incorporate steam piping, electric heating wiring, etc. inside the mold. Alternatively, the entire mold may be placed in a curing chamber to accelerate curing. In order to remove the mold after the mixture has hardened or to demold the upper and lower combination mold, it is easy to install a knockout pin 7 in the combination mold. To release a cured spherical molded product, the hardness should be 50 A at shore A after it is completely cured.
It is preferable that it has some elasticity of about 90A. In the spherical free abrasive abrasive obtained by the manufacturing method of the present invention, excess mixture other than the hemispherical part of the combination mold is leaked and removed during molding, so a highly accurate molded product with almost no burrs attached during mold release can be obtained. can get. The manufacturing method of the present invention can be carried out either batchwise or continuously. The spherical free abrasive abrasive obtained by the method of the present invention can be used in any of the rotating barrel polishing methods, vibrating barrel polishing methods, centrifugal rotating barrel polishing methods, gyroscope finishing methods, reciprocating finishing methods, etc. .
This abrasive can also be used in many applications such as automobile parts, electrical and electronic equipment parts, mechanical parts, watches, camera parts, plastic parts, ceramic products, aircraft parts, workers, toys, household goods, jewelry, glass products, etc. Can be used in various fields. Examples of the present invention are shown below. Example 1 60 parts by weight of unsaturated polyester resin "Estar RG22" (manufactured by Mitsui Toatsu Chemicals), 40 parts by weight of 1000 mesh alumina abrasive grains, 1 part by weight of 6% cobalt naphthenate, 1 part by weight of 55% methyl ethyl ketone peroxide. After mixing and stirring, a thixotropic agent Aerosil (anhydrous silicic acid manufactured by Nippon Aerosil Co., Ltd.) was further added and mixed by the weight shown in Table 1 to obtain a mixture with an adjusted thixotropic index. This mixture was filled into the upper and lower molds of a 300 mm x 300 mm mold with 900 holes made using a 6 mm hemisphere, then the molds were assembled, compressed with a pressure of 2 kg/cm ² , and cured at room temperature for 20 minutes.
After a few minutes, the mold was removed and left at room temperature (23°C) for one week to obtain an abrasive. Next, the above abrasive material and a 50 mm x 30 mm piece of material to be polished were placed in a centrifugal polisher with a barrel capacity of 1.
(thickness: 2 mm) plate aluminum in the amounts shown in the weight before polishing column in Table 1, and then added 3 g of aluminum compound and 0.4 g of water.
After adding , the polishing machine was operated for 30 minutes at a rotational speed of 300 rpm, and the results shown in Table 1 were obtained regarding the weight loss of the material to be polished and the filling state. From these results, the thixotropic index of the mixture is 2~
It is clear that the use of abrasives with a diameter of 50% causes no outflow from the mold or poor filling into the mold, and the resulting abrasive has excellent properties.

[Table] Example 2 Add 100 mesh of quartz powder to 100 parts by weight of unsaturated polyester "Estar G20" (B) manufactured by Mitsui Toatsu Chemical Co., Ltd.
Add 10, 20, 40, 60, 80, and 120 parts by weight of (A), respectively, and add 6 parts by weight to each of these seven mixtures.
% cobalt naphthenate and 1 part by weight of 55% methyl ethyl ketone peroxide were sequentially added and mixed with stirring. To each of these mixtures, 3 parts by weight of Aerosil (manufactured by Nippon Aerosil Co., Ltd.) as a thixotropic agent was further added and thoroughly mixed. The seven kinds of mixtures thus obtained were filled into upper and lower molds in which 625 holes were drilled using a 10 mm hemisphere in a 300 mm x 300 mm mold. Obtained. The obtained abrasive material was left for one week at room temperature. Add the above abrasive to a centrifugal sander with a barrel capacity of 1.
Charge 50g, and the material to be polished is 40mm x 35mm x 3mm.
Table 2 shows the results of examining the fracture state of the abrasive material when the abrasive machine was loaded with sheet aluminum, added with 3 g of aluminum compound and 0.4 g of water, and rotated and rotated for 30 minutes at a rotation speed of 300 rpm. It was as follows.

[Table] From these results, the amount of abrasive grains added is (A)/(B) (10
-100)/100, it is clear that the fracture rate of the abrasive is significantly lower.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of the upper and lower molds of a combination mold used in carrying out the present invention, and FIG. 2 is a cross-sectional view showing an example of the combination mold inserted into a clamping device. DESCRIPTION OF SYMBOLS 1... Upper die, 2... Lower die, 3... Hemispherical part for filling mixture, 4... Filling mixture, 5... Pressing press, 6... Guide pin, 7... Knockout pin.

Claims (1)

[Claims] 1. When producing a spherical free abrasive abrasive by curing a mixture consisting of abrasive grains A and liquid curable polymer compound binder B using a mold, a mixture of abrasive grains A and liquid curable polymer compound binder B is used to produce a spherical free abrasive abrasive material. A mixture made of saturated polyester with a weight ratio of A/B of (10 to 100)/100 and a thixotropic index adjusted to 2 to 50 by adding a thixotropic agent is applied to the symmetrical position of the symmetry plane of the combination mold. 1. A method for producing a free abrasive abrasive material, which comprises filling a hemispherical part with a predetermined diameter that has sagged, and hardening the mixture in the hemispherical part by combining and pressing molds.