JPH0440156B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of the Invention] The present invention relates to a flexible polishing sheet containing dispersed abrasive grains. The above polishing sheet can be attached to various polishing tool bases and used to polish the surface of a material to be polished. [Background of the Invention] Flexible polishing sheets are known in which polishing abrasive grains are coated with polyurethane resin or the like as a binder and adhered to the surface of a base material such as polyester resin or paper. Such abrasive sheets are intended for use in polishing materials with shapes that are difficult to polish with ordinary abrasives, such as surfaces with small curvature, but the base material or binder Due to the insufficient mechanical properties of the material, the tensile strength, heat resistance, abrasion resistance, etc. were insufficient when used as an industrial polishing tool for a long period of time. On the other hand, grinding materials made by uniformly dispersing abrasive grains in a base material include aromatic polyimide powder (abrasive grain binder) obtained from pyromellitic dianhydride and aromatic diamine, and diamond, etc. A powder mixture with abrasive grains is filled into a mold, and the filled material is molded at high temperature and pressure to produce an annular abrasive grain molded body, and this abrasive grain molded body is placed on a wheel-shaped grindstone base. Grinding tools for cemented carbide manufactured by bonding grain layers are well known from US Pat. No. 3,385,684 and US Pat. No. 3,650,715. However, in the powder molding method using aromatic polyimide described in each of the above specifications, although it is possible to process the abrasive grain molding into a sheet, the sheet is essentially a rigid body and is not flexible. It does not result in a strong abrasive sheet. [Object of the invention] An object of the present invention is to provide a flexible abrasive sheet in which abrasive grains are uniformly dispersed in an aromatic polyimide, and which has excellent durability and abrasion resistance. do. [Summary of the Invention] The present invention provides that abrasive grains having an average particle diameter of 0.1 to 60 μm are
A flexible film with a thickness of 5 to 200 μm that is uniformly dispersed in an aromatic polyimide coating obtained from an aromatic tetracarboxylic acid component and an aromatic diamine component at a blending ratio of 0.5 to 50% by volume. It's on the polishing sheet. [Detailed Description of the Invention] The abrasive sheet of the present invention has abrasive grains having a specific average particle diameter uniformly dispersed within a heat-resistant aromatic polyimide coating film, and has a thickness of 5. ~
Flexible thin film (including both film and sheet materials) with a thickness of 200 μm, preferably 20 to 150 μm
This is an abrasive sheet made of The abrasive grains that can be used in the polishing sheet of the present invention have an average particle diameter of 0.1 to 60 μm, preferably 0.5 to 60 μm.
Any abrasive grains for polishing or grinding with a diameter of about 40 μm may be used, such as natural or artificial diamond,
Examples include abrasive grains made of cubic boron nitride and the like having the above average particle diameter. The above-mentioned abrasive grain may be an abrasive grain whose entire surface is coated with an inorganic substance. Examples of the aromatic polyimide that can be used to form the coating film of the polishing sheet of the present invention include an aromatic tetracarboxylic acid component mainly containing pyromellitic acid or its acid dianhydride, and an aromatic diamine component. It is a heat-resistant aromatic polyimide obtained by polymerizing and imidizing equimolar amounts. The aromatic tetracarboxylic acid component mainly containing pyromellitic acid or its acid dianhydride is a mixture of pyromellitic acid or its acid dianhydride and other aromatic tetracarboxylic acids or its acid dianhydride. It may be hot. Aromatic tetracarboxylic acid components that can be used in combination with the above-mentioned pyromellitic acid or its acid dianhydride include 2,3,3',4'-biphenyltetracarboxylic acid, 3,3',4 , 4'-biphenyltetracarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 2,2-bis(3,4
-dicarboxyphenyl)propane, bis(3,
4-dicarboxyphenyl)methane, bis(3,
Preferred examples include 4-dicarboxyphenyl) ether, bis(3,4-dicarboxyphenyl)phosphine, and acid dianhydrides thereof. It is also possible to use aromatic tetracarboxylic acid components other than these pyromellitic acid components alone. The aromatic diamine component mentioned above includes 4,4'-
Diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl thioether, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminobenzophenone, 4,
Preferred examples include 4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)propane, and o-, m- or p-phenylenediamine. Examples of aromatic polyimides that can be used in the present invention include pyromellitic acid or its acid dianhydride.
An aromatic tetracarboxylic acid component containing mol% or more, preferably 60 mol% or more, more preferably 80 to 100 mol%, and 50 mol% or more, preferably 60 mol% or more of 4,4'-diaminodiphenyl ether. , more preferably a high molecular weight aromatic polyimide obtained from an aromatic diamine component containing 80 to 100 mol %. The above-mentioned aromatic polyimide has a logarithmic viscosity (measurement temperature: 50°C, concentration: 0.5 g/100 ml solvent, solvent: p-
Chlorphenol) is preferably from 0.1 to 7, especially from 0.3 to 5. In the present invention, the above-mentioned aromatic polyimide is
5% by weight of the sample when the sample is heated at 10℃/min
The heat resistance indicated by the temperature at which it loses weight on heating is
It is preferable that the temperature is 450℃ or higher, especially 500℃ or higher, and the equilibrium moisture absorption rate shown by the moisture absorption rate reached when maintained in an environmental condition of 50% humidity and 50℃ is preferable.
A content of 2.0% or less, particularly 1.5% or less is preferable in terms of durability after being formed into an abrasive sheet. The polishing sheet of the present invention has excellent polishing performance (abrasive removal grinding ratio, grinding ratio, etc.). In the polishing sheet of the present invention, in addition to the above-mentioned abrasive grains and aromatic polyimide, a filler made of, for example, graphite, SiO ₂ , SiC, Al ₂ O ₃ , Fe ₂ O ₃ , Cu, Sn, etc. One type or two or more types may be blended. The above fillers have an average particle size of
The powder is preferably 0.1 to 100 μm, particularly 0.5 to 50 μm. The polishing sheet of the present invention can be produced by forming a liquid thin film using, for example, an aromatic polyamic acid (aromatic polyimide precursor) solution in which the above-mentioned abrasive grains are uniformly dispersed as a film-forming dope liquid, and then drying the liquid thin film. It can be produced by solidifying to form a solidified film (coating film), imidizing the aromatic polyamic acid, and further heat-treating if necessary. The above-mentioned aromatic polyamic acid in which abrasive grains are uniformly dispersed is obtained by uniformly dispersing the above-mentioned abrasive grains in an organic polar solvent, and then adding the above-mentioned aromatic tetracarboxylic acid component and aromatic A method in which the diamine component is added and dissolved, and both components are polymerized; Alternatively, the above-mentioned aromatic tetracarboxylic acid component and aromatic diamine component are added and dissolved in an organic polar solvent, and both components are polymerized. It can be prepared by a method of forming a polyamic acid solution, adding the above-mentioned abrasive grains to the polyamic acid, and stirring at high speed. Examples of the above organic polar solvent include amide solvents such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, and N,N-diethylacetamide. , phenolic solvents such as phenol, cresol, and halogenated phenol. The aromatic polyamic acid produced in the preparation of the above polyamic acid solution has a logarithmic viscosity (measurement temperature: 30°C, concentration: 0.5 g/100 ml solvent, solvent:
N,N-dimethylacetamide) is from 0.1 to 7, especially from 0.3 to 5, and the polymer concentration of polyamic acid in the solution is from 3 to 50% by weight, especially from 5 to 30%.
% by weight and that the rotational viscosity (25° C.) of the solution is preferably 1 to 50,000 poise for the moldability of the liquid thin film in the present invention. In order to form a liquid thin film from the polyamic acid solution in which the abrasive grains are uniformly dispersed, the polyamic acid solution is applied to a suitable smooth substrate (glass substrate, cast onto a metal drum, metal belt, etc.) to a uniform thickness (approx.
Film formation can be carried out intermittently or continuously by a known film forming method such as a solution casting method that forms a liquid thin film (1000 μm). The abrasive sheet of the present invention has a folding strength of 500 to 50,000.
It is practically preferred that the number of times is 800 to 30,000 times. The abrasive sheet of the present invention is suitably used for applications such as processing it into a belt shape to finish free-form surfaces of products with different diameters, and attaching it to base materials such as Bakelite and plastics to perform honing of various materials. be able to. [Effects of the Invention] The polishing sheet of the present invention is an integrated polishing sheet in which abrasive grains are uniformly dispersed in aromatic polyimide, so it is suitable for polishing materials to be polished that have a surface with a small curvature. It has flexibility. Furthermore, the abrasive sheet of the present invention has strong holding power for abrasive grains and is also excellent in tensile strength, heat resistance, moisture resistance, and chemical resistance, so it has sufficient wear resistance as an industrial abrasive tool. It is durable and durable. In particular, the abrasive sheet of the present invention has excellent bending strength within the above range, so it can be repeatedly used in any form for a long period of time, and is advantageous in practice. Next, Examples and Comparative Examples of the present invention will be shown. [Example 1] (Preparation of aromatic polyamic acid solution) 240 g of N,N-dimethylacetamide was placed in a cylindrical polymerization tank with an internal volume of 500 ml, and while stirring,
20.0 g of diamond powder with an average particle size of 5 μm was added, and stirring was continued for about 30 minutes to prepare an abrasive grain dispersion. Subsequently, 28.72 g of 4,4'-diaminodiphenyl ether was added to the abrasive grain dispersion and dissolved by stirring at 30°C for 30 minutes, and then 28.15 g of pyromellitic dianhydride was gradually added. The mixture was stirred at .degree. C. for 2 hours to dissolve and polymerize both components. Finally, 3.13 g of pyromellitic dianhydride was gradually added to the polymerization solution and stirred at 30°C for 3 hours.
Aromatic polyamic acid was produced to prepare an aromatic polyamic acid solution in which abrasive grains were uniformly dispersed. The above aromatic polyamic acid solution has a polymer concentration of 20% by weight, and a rotational viscosity of the solution (30% by weight).
℃) was 1500 poise. (Film Formation) Using the above aromatic polyamic acid solution as a dope for film formation, a liquid thin film with a uniform thickness is formed on a glass plate by a hand coating method (solution casting method) using an applicator. Formed. Next, a portion of the solution was removed from the liquid thin film by supplying hot air at about 120° C. to form a solidified film in which about 30% by weight of the solvent remained. Then, this solidified film is peeled off from the glass plate,
The solidified film was held with a pin tenter and placed in a heating furnace, and the solidified film was heated with hot air at about 300 to 450°C to remove the solvent and completely imidize the polymer. By the method described above, 26.7% by weight (12.9% by weight) of diamond abrasive grains was added to the aromatic polyimide coating film.
Thickness 90μ, evenly distributed in the proportion of (volume%)
m flexible abrasive sheets were manufactured. Using the above polishing sheet, φ60mm×φ30mm×20
Honing was performed on a silicon nitride material having a diameter of 1.0 mm at a circumferential speed of 15 m/min and a reciprocating speed of 3 m/min, and the durability and abrasion resistance were tested. The results are shown in Figures 1 to 3 of the attached drawings. Furthermore, the tensile strength, bending strength, thermal loss (heat resistance), and equilibrium moisture absorption rate of the polishing sheet were measured. The results are shown in Table 1. [Comparative Example 1] Honing was performed under the same conditions as in Example 1 using an abrasive sheet manufactured by coating a polyester base material with a urethane resin containing diamond abrasive grains at the same volume ratio as the abrasive sheet used in Example 1. The durability and abrasion resistance were tested. The results are shown in Figures 1 to 3 of the attached drawings. [Comparative Example 2] Honing was performed under the same conditions as in Comparative Example 1, except that a polishing sheet in which the diamond abrasive grains in Comparative Example 1 were replaced with silicon carbide abrasive grains, and durability and wear resistance were tested. The results are shown in Figures 1 to 3 of the attached drawings. [Example 2] (Preparation of aromatic polyamic acid solution) 480 g of N,N-dimethylamide was placed in a cylindrical polymerization tank with an internal volume of 1, and 57.44 g of 4,4'-diaminodiphenyl ether was added. The mixture was stirred at ℃ for 30 minutes to dissolve. Then, pyromellitic dianhydride was added to the above solution.
56.30g was gradually added and dissolved by stirring at 30°C for 2 hours, and at the same time, 4,4'-diaminodiphenyl ether and pyromellitic dianhydride were polymerized, and pyromellitic dianhydride was further added to the polymerization liquid. 6.26g
was gradually added and stirred at 30°C for 3 hours to produce aromatic polyamic acid. The above aromatic polyamic acid solution has a polymer concentration of 20% by weight and a rotational viscosity (30℃) of 400%.
It was poise. Add diamond powder (average particle size) to the above solution.
Add 40g of 5μm) and stir at high speed (5000rpm) for 2
By heating for a certain period of time, an aromatic polyamic acid solution in which abrasive grains were uniformly dispersed was prepared. (Film Formation) A film was formed in the same manner as in Example 1 except that the above aromatic polyamic acid solution was used as a dope for film formation. An abrasive sheet with a thickness of 80 μm was produced, which was uniformly dispersed at a ratio of 12.9% (12.9% by volume). The above polishing sheet was measured for tensile strength, bending strength, thermal loss (heat resistance), and equilibrium moisture absorption rate. The results are shown in Table 1.

[Table] [Evaluation of durability and wear resistance] Figure 1 of the attached drawings compares the relationship between polishing time and cumulative removal amount for the polishing sheets of Example 1 and Comparative Examples 1 and 2. It is. In the coated polishing sheets of Comparative Examples 1 and 2, the amount removed by polishing decreased as the polishing time became longer;
It is clear that the polishing sheet of Example 1 maintains a constant polishing removal amount and has excellent durability. FIG. 2 compares the relationship between polishing time and finished surface accuracy for the polishing sheets of Example 1 and Comparative Examples 1 and 2. In the polishing sheets of Comparative Examples 1 and 2, the finished surface accuracy gradually became rough in the initial stage of polishing, and then became finer, which indicates that the polishing ability has decreased. On the other hand, it can be seen that the polishing sheet of Example 1 maintains the finished surface accuracy constant and performs constant polishing. It is clear from FIGS. 1 and 2 that the abrasive sheet of the present invention has excellent durability. FIG. 3 shows the relationship between polishing time and grinding ratio for the polishing sheets of Example 1 and Comparative Examples 1 and 2.
This is a comparison. The grinding ratio is a quantity expressed by the amount of polishing of the material to be polished relative to the amount of wear of the polishing material itself (the amount of polishing of the material to be polished/the amount of self-wear of the polishing material). It is clear that the polishing sheet of the present invention performs a large amount of polishing with a small amount of self-wear, and has superior wear resistance compared to the two comparative examples.

[Brief explanation of drawings]

FIG. 1 shows the relationship between the polishing time and the cumulative amount removed by honing when the polishing sheets of Example 1 and Comparative Examples 1 and 2 were honed. FIG. 2 shows the relationship between polishing time and finished surface accuracy when honing was performed using the polishing sheets of Example 1 and Comparative Examples 1 and 2. Figure 3 shows Example 1 and Comparative Examples 1-
2 shows the relationship between polishing time and grinding ratio when honing is performed using the polishing sheet No. 2.

Claims (1)

[Claims] 1. Abrasive grains with an average particle diameter of 0.1 to 60 μm are 0.5 to 50 μm.
The aromatic polyimide coating film obtained from the aromatic tetracarboxylic acid component and the aromatic diamine component is uniformly dispersed at a blending ratio of % by volume, and has a thickness of 5%.
~200μm flexible abrasive sheet. 2. The polishing sheet according to claim 1, wherein the aromatic tetracarboxylic acid component contains 50 to 100% of pyromellitic acid or its acid dianhydride. 3. The polishing sheet according to claim 1, wherein the abrasive grains are made of natural or artificial diamond or cubic boron nitride.