JPH0548260B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing an aromatic polyamide resin sliding member. In particular, bearing bushes, sliding plates, cams, gears,
It is also suitable as a sliding member such as a seal. Further, the present invention provides a sliding member by compression molding an aromatic polyamide resin,
Suitable for high-mix, low-volume production. (Prior art) Conventionally, methods for producing aromatic polyamide resin molded products include Japanese Patent Publication No. 56-2092, Japanese Patent Application Publication No. 55-131024,
As disclosed in Japanese Patent Application Laid-Open No. 57-164, etc., a sintering method in a neutral or inert atmosphere such as nitrogen gas is employed. This is because the melting point of this resin is high (430°C in the case of metaphenylene isophthalamide resin), and this melting point is close to the thermal decomposition temperature of the resin, and melting and thermal decomposition occur almost simultaneously, making it practical. This is because it is difficult to obtain molded products that can be used. In addition, since this resin is hygroscopic (saturated moisture content is 5.2% at 21°C and relative humidity of 65%), the above-mentioned molding method that involves melt flow will reduce the moisture content due to gas generation due to thermal decomposition. The fact is that molded products produced by these molding methods have not yet been commercially available on the market because the gasification of the molding material has a large effect on the molding process, easily causing blisters, cracks, and cavities. (Problems to be Solved by the Invention) Generally, it has been pointed out that a resin fired body produced by a sintering method has lower mechanical strength than a molded product produced by a melt molding method. The mechanical strength of a resin fired body produced by the sintering method is significantly affected by the magnitude of the pressing force applied when obtaining a preform (powder compact). That is, if the pressing force is small, the compression ratio will inevitably be small and the porosity of the green compact will also increase, so the mechanical strength of the sintered body obtained by sintering this green compact will be low. Therefore, in order to make the mechanical strength of the molded product obtained by the sintering method approach the same as that of the molded product obtained by melt molding, it is necessary to significantly increase the pressure applied during preforming. In the case of aromatic polyamide resin (metaphenylene isophthalamide resin), this pressure is 2000Kg/
A high pressure of ³⁰⁰⁰ to 7000 Kg/ ^cm2 is required. In addition to these problems, sintering not only requires a sintering furnace that can control the atmosphere using nitrogen gas, but also requires more than 10 hours of sintering time. As described above, the sintering method is suitable for mass production of a small number of products, but is not suitable for production of a large number of products in small quantities. In addition, aromatic polyamide resins have particularly remarkable properties compared to, for example, aliphatic polyamide resins (nylon), such as a high melting point, little decrease in mechanical strength at high temperatures, and high rigidity. . Despite these features, the friction and wear characteristics in the range from room temperature to the limit temperature of each resin are not comparable to those of 6-6 nylon. Simply put, this is because the self-lubricating property is not as good as that of 6-6 nylon, the coefficient of friction is high, and the wear is also large. (Means for solving the problem) The present inventors have proposed patent application No. 59-59779 (Patent Application No.
-68811), we established a compression molding method that solved these manufacturing problems. The present invention utilizes this compression molding method and aims to provide a method for manufacturing a sliding member made of an aromatic polyamide resin containing a lubricating filler. In the present invention, the aromatic polyamide resin refers to metaphenylene isophthalamide resin, which is a condensation polymer of metaphenylene diamine and isophthalic acid, both of which have a functional group at the meta position, including phenyl diamine and dicarboxylic acid, and Contains no polyamide consisting of bonded diamine and dicarboxylic acid. In the present invention, as the aromatic polyamide resin powder, metaphenylene isophthalamide (Cornetx (trade name) manufactured by Teijinsha Co., Ltd.) resin powder obtained by condensation polymerization of metaphenylene diamine and isophthalic acid chloride was used. This powder has a bulk density of 0.295 to 0.393 g/cm ³ when the average particle size is 150 mesh (Japanese Industrial Standard), and a surface area of 4.8 m ² /g in a powder that passes 48 mesh according to the same industrial standard. It is something. Powders with high bulk density significantly impair moldability. According to the inventors' experiments, the bulk density was 0.4g/
If the particle size exceeds cm ³ , pressure unevenness and poor flow of the resin occur in molded products using such powder, making it impossible to obtain a satisfactory molded product. It is preferable that the bulk density is small, but if it is too small, the yield during powder preparation will decrease and economic efficiency will be impaired. In the present invention, resin powder having a bulk density of 0.2 to 0.4 g/cm ³ has been used and good results have been obtained. The lubricating fillers used in the present invention are graphite powder and tetrafluoroethylene resin powder, and when used alone, it is almost impossible to modify the resin, but by adding a predetermined amount of both. We were able to significantly improve friction and wear characteristics. The graphite is preferably flaky natural graphite that passes through approximately 150 meshes. The present inventors have obtained good results using CB-150 manufactured by Nippon Graphite Co., Ltd. The tetrafluoroethylene resin is preferably a powder that passes approximately 100 meshes, and the present inventors used PTFE powder TLP-10F and Teflon 7A-J (trade name) manufactured by Mitsui Fluorochemical Co., Ltd. We are getting good results. As a result of various experiments, effects appear when graphite powder and tetrafluoroethylene resin powder are added in an amount of 8% by weight or more, and the friction and wear characteristics improve as the amount added increases, but when the total amount of both is 40% by weight or more, the effect appears. If it exceeds this, the mechanical properties of the molded product will be impaired and wear will increase. Graphite powder exhibits a synergistic effect with tetrafluoroethylene resin powder and contributes to improving the friction and wear characteristics of aromatic polyamide resin, but graphite powder also contributes to improving the moldability of aromatic polyamide resin. . In other words, the filling temperature of the resin powder into the mold, the temperature, pressure and holding time during the molding process, etc.
In either case, near the limit values, molding defects are likely to occur depending on how the lead time is taken, but the addition of graphite powder has an extremely significant effect on solving these problems. There is an effect. However, in any case, adding more than 20% by weight of both graphite and tetrafluoroethylene resin is not preferable for use in sliding parts, and in the present invention, the upper limit of addition of these lubricating fillers is set at 20% by weight each.
It was expressed as weight%. Prior to molding the aromatic polyamide resin powder containing a lubricating filler of the present invention, it is essential to remove moisture due to moisture absorption in the molding material powder as much as possible. According to experiments conducted by the present inventors, it has been found that if the aromatic polyamide resin powder contains water of 1% by weight or more, it is almost impossible to obtain a molded article that can be used for practical purposes. Therefore, after mixing the aromatic polyamide resin powder and the lubricating filler, the molding material powder is dried. In the case of drying under normal pressure, it was possible to obtain a powder that could be molded by holding it at 150°C for about 15 minutes. When filling the molding material powder prepared in this way into a mold, the temperature of the mold is heated to a temperature not exceeding 250°C. Although the mold temperature may be room temperature, it is usually preferable to heat the mold to 100° C. or higher to avoid the influence of atmospheric moisture, and this also helps speed up the molding cycle. However, if the mold temperature exceeds 250° C., even if the subsequent molding process is well controlled, uneven molding and blisters are likely to occur in the molded product, making it difficult to obtain a satisfactory molded product. The powder compaction pressure applied after filling the molding material powder may be significantly smaller than the powder compaction pressure in the sintering method. After compacting, the mold is heated as it is to proceed with compression molding, or after compacting, the mold is opened and the compact is taken out of the mold, and it is loaded into a separate compression mold and heated and pressurized. It is possible to adopt either of the methods of proceeding with compression molding, but in either case, a powder compaction pressure of 500 kg/cm ² or less is sufficient. Here, if the mold is heated to 150 to 250°C, the pressing force may be 70 to 200 kg/cm ² . The mold temperature during compression molding must be 290℃ or higher.
The temperature was set not to exceed 360℃. According to experiments conducted by the present inventors, when the mold temperature is lower than 290° C., resin flow is insufficient, and pressing force is not evenly transmitted, which tends to cause uneven molding. Furthermore, if the mold temperature is raised above 360°C, discolored areas appear on the molded product, which is thought to be due to thermal decomposition of the resin, and dry cracks are more likely to occur. It has been found that the molding time is preferably 1 to 5 minutes per 1 mm of wall thickness. Generally, within the above-mentioned molding temperature range,
The higher the mold temperature, the shorter the molding time. When the molded product was thick, good results were obtained by taking a longer molding time in a relatively low temperature range. The compacting pressure is the same as the pressure range of the compacting pressure mentioned above, at least 70Kg/cm ² , usually 150-200Kg/cm ²
A satisfactory molded product can be obtained by applying a molding pressure of . After maintaining the molding time for a predetermined time, the mold temperature was cooled to 250° C. or less while the pressure was being applied, and then the pressure was lowered and the mold was opened to take out the molded product from the mold. Examples will be described below. (Example) Metaphenylene isophthalamide resin (Teijinsha, Cornex powder) with a bulk density of 0.3 g/cm ²
Graphite powder passing through 150 meshes (Nippon Graphite Co., Ltd.,
CB-150) 12% by weight and 12% by weight of tetrafluoroethylene resin powder (Mitsui Fluorochemical Co., Ltd., Teflon 7A-J) that passes through a 100 mesh were mixed and stirred.
A mixed powder in which these were uniformly dispersed was obtained. This mixed powder was dried using a hot air dryer at a temperature of 140° C. for 15 minutes. The residual water content when drying under these conditions was about 0.5% by weight. The powder prepared in this way was used as a molding material powder and was filled into a mold heated to 200℃, producing a molding material of 150Kg/ ^cm2.
The powder was compacted at a pressure of While pressurizing, the mold temperature was raised to 320°C and held at this temperature for 15 minutes. Then, the mold temperature was cooled to 220° C. while the pressure was being applied to obtain a plate-shaped molded product having a length of 50 mm, a width of 100 mm, and a thickness of 4 mm. The density of the molded product thus obtained is 1.48
g/cm ³ , hardness is 89 on Rockwell M scale, bending strength is 673Kg/cm ² , impact strength is 2.4Kg・cm/cm
It was (Izotsu). Regarding mechanical strength, especially bending strength,
Although the strength is considerably lower than that of unfilled aromatic polyamide resin moldings, the bending strength of around 673 kg/cm ² is sufficient for use in sliding parts. I can do it.

[Table] Wear amount is in mm.
The table shows various properties of molded products obtained by compression molding according to the molding conditions of the above-mentioned examples with varying amounts of lubricating filler added. Samples Nos. 1 to 5 are examples of the present invention. Nos. 6 to 8 are comparative examples. Bearing performance was tested under the following conditions by pressing the cylindrical end face of a mating material made of steel against the plate surface of a plate-shaped sample and rotating it in sliding contact. Compatible material: Machine structural carbon steel (S45C) inner diameter 16mm,
Outer diameter 28mm, height 15mm Sliding speed 80m/min (rotation speed 1160rpm) Load 7.3Kg/cm ² Lubrication Self-lubrication (no lubrication) Test time 50 hours Bearing performance test results showed that graphite was 10 to 15% by weight and Tetrafluoroethylene resin (PTFE) 10-15% by weight,
That is, when the total amount added as a lubricating filler was 20 to 30% by weight, particularly excellent performance was exhibited over the entire test time. None of the comparative examples of samples No. 6 to 8 could withstand the 50-hour test; sample No. 6 was tested for 1 hour, sample No. 7 was tested for 5 hours, and sample No. 8 was tested for 7 hours. was discontinued. In these comparative examples, the amount of wear is shown as the average value at the time the test was discontinued. The value of a sliding speed of 80 m/min under the test conditions is 1160 when expressed in terms of rotation speed as described above.
revolutions/minute. Generally, in sliding members made of synthetic resin,
Moreover, it is extremely rare to find something that can withstand such high-speed sliding without lubrication. By the way, 6-6 nylon causes the friction surface to wear out within just a few minutes due to the generated frictional heat, and phenolic resin laminated material containing a lubricant filler produces a large amount of friction noise within 10 minutes, which is abnormal. caused wear. (Effects of the Invention) As explained above, according to the manufacturing method of the present invention, there is little variation in quality and manufacturing is easy, and this method is particularly suitable for high-mix, low-volume production. The sliding member obtained by the manufacturing method of the present invention exhibits a synergistic effect by adding a predetermined amount of graphite and tetrafluoroethylene resin powder as a lubricating filler, and has the heat resistance of the resin. Provides excellent friction and wear properties without sacrificing properties. In particular, by improving self-lubricating properties, dry friction properties are also excellent. Therefore, especially if lubricating oil cannot be used,
Alternatively, it can be applied to applications where it is inconvenient to use it, and it can also be used in relatively high-temperature atmospheres and under conditions involving relatively high-speed sliding.

Claims (1)

[Scope of Claims] 1 (a) 8 to 20% by weight of graphite powder and 8 to 20% by weight of tetrafluoroethylene resin powder are uniformly added to aromatic polyamide resin powder having a bulk density of 0.2 to 0.4 g/cm ³ . (b) After compacting the mixed powder by applying closed mold pressure, the mold temperature is kept at 290°C or higher. The temperature should not exceed 360℃, and within this temperature range, the molding pressure should be at least 70Kg/cm ² and the molding time should be maintained at 1 to 5 minutes per 1 mm of wall thickness of the molded product. (c) The specified molding time was maintained. Later, the mold temperature
A method for manufacturing an aromatic polyamide resin sliding member comprising the steps (a) to (d) above: cooling to a temperature of 250°C or less; (d) then opening the mold and taking out the molded product from the mold. .