JPS617353A - Aromatic polyamide resin sliding member and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain the titled sliding member of outstanding frictional characteristics with high wear resistance, suitable for multitype-small-scale production, by compression molding of molding compound prepared by incorporating m-phenylene isophthalamide resin with, as lubricating fillers, graphite and tetrafluoroethylene resin. CONSTITUTION:(A) Powder with a bulk density 0.2-0.4g/cm<3> of m-phenylene isophthalamide prepared by polycondensation between m-phenylenediamine and isophthaloyl chloride is homogeneously incorporated with (B) 8-20wt% of graphite powder, pref. 150 mesh-passable flaky natural graphite and (C) 8-20wt% of tetrafluoroethylene resin powder, pref. 100 mesh-passable one to prepare mixed powder. This powder is dried using a hot-air drier followed by packing into a mold kept at a temperature <=250 deg.C pref. >=100 deg.C. After compressing said powder by application of pressure following mold closure, the mold temperature is elevated to 290-360 deg.C to perform compression molding under a pressure >=70kg/ cm<2> for 1-5min per 1mm. thickness of the molding material, followed by cooling the mold to <=250 deg.C keeping the pressurized state, then mold opening to take out the molded product.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an aromatic polyamide resin sliding member and a method for producing the same.

In particular, applications where lubricating oil cannot be used or is inconvenient, or where it is used in a relatively high temperature atmosphere.
It is suitable for sliding members such as bearing bushes, sliding plates, cams, gears, and seals under conditions involving relatively high-speed sliding.

Another aspect of the present invention is to obtain a sliding member by compression molding an aromatic polyamide resin.

Suitable for high-mix, low-volume production.

(Prior art) Conventionally, methods for manufacturing aromatic polyamide resin molded articles are disclosed in Japanese Patent Publication No. 56-2092 and Japanese Patent Application Laid-open No. 55-131024.
.

As disclosed in JP-A-57-164, etc., sintering methods in a neutral or inert atmosphere such as nitrogen gas have been widely used. Metaphenylene iso7
In the case of talamide resin, the melting point is close to the thermal decomposition temperature of the resin, and melting and thermal decomposition occur almost at the same time. This is because it is difficult to obtain molded products that can be put to practical use using melt molding methods that involve melting of resin during molding.

In addition, since this resin is hygroscopic (saturated water content 5.2 cm at 21°C and relative humidity of 65%), the above-mentioned molding method that involves melt flow cannot interact with gas generation due to thermal decomposition. The fact is that the gasification of the contained moisture has a large effect, which tends to cause blisters, cracks, or cavities, and molded products made by these molding methods have not yet been commercially available.

(Problems to be Solved by the Invention) In general, resin fired bodies produced by the sintering method are +1! It has been pointed out that the mechanical strength is lower than that of molded products made by melt molding.

The mechanical strength of the resin fired body produced by the sintering method is determined by the preform (
It is significantly affected by the magnitude of the pressing force used to obtain the green 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 a molded product made by the sintering method approach the same as that of a molded product made by melt molding, the pressure applied during preforming must be significantly increased. , this pressing force is 2.00o#IA'r&
That's all, preferably! A high pressure of +,000 to 000kgS is required.

In addition to these problems, sintering not only requires a sintering furnace capable of controlling the atmosphere with nitrogen gas, but also requires a sintering time of more than 10 hours.

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 resin has particularly remarkable characteristics compared to, for example, aliphatic polyamide resin (nylon).
It has 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 6-6 nylon #1 with self-lubricating properties.
This is due to the high coefficient of friction and large wear.

(Means for Solving the Problems) In Japanese Patent Application No. 59-59779, the present inventors solved these manufacturing problems and established a compression molding method.

The present invention aims to obtain a sliding member by adding a lubricating filler to an aromatic polyamide resin and using the compression molding method described above.

In the present invention, the aromatic polyamide resin refers to meta-phenylene isophthalamide resin, which is a heavy metal condensation of meta-phenylene diamine and inphthalic acid, both of which have a functional group at the meta-position of phenyl diamine and dicarboxylic acid, and which has ortho- and no-bonds. Contains no polyamide consisting of diamine and dicarboxylic acid.

In the present invention, as the aromatic polyamide resin powder, metaphenylene isophthalamide (trade name: Cornex, manufactured by Teijinsha) resin powder obtained by condensation polymerization of metaphenylene diamine and isophthalic acid chloride was used.

This powder has an average particle size of 150 meshier (Japanese Industrial Standards) and a density of α295 to 0.595j! /Crd
According to the same industrial standard, a powder that passes through 48 meshes has a surface area of 4-8 m/Ji'.

Powders with high density significantly impair moldability. According to experiments conducted by the present inventors, when the density is α417/a& or higher, pressure unevenness and poor flow of the resin occur in molded products using such powder, making it difficult to obtain satisfactory molded products. I couldn't do it.

Although it is preferable that the density is low, if the density is too low, the yield during powder preparation will decrease and economic efficiency will be impaired.

In the present invention, 0.2 to 0.4! Resin powders with high i/cd densities have been used with good results.

The lubricating filler used in the present invention is graphite powder and tetrafluoroethylene resin powder, and since it is almost impossible to modify the resin when these are used alone, it is necessary to add a predetermined amount of both. It was possible to significantly improve its friction and wear characteristics.

The graphite is preferably flaky natural graphite that passes through approximately 150 meshes. The present inventors have obtained 1 CB- manufactured by Nippon Graphite Co., Ltd.
Good results have been obtained using 150.

It is preferable that the tetrafluoroethylene resin powder is a powder that passes through approximately 100 mesh.2 The present inventors
PI'FB Pakder TLP- manufactured by Mitsui 70 Rochemical Co., Ltd.
Good results have been obtained using IQF O and Def Oy7A-J (product names).

As a result of various experiments, the effect appeared when adding 8 parts or more of graphite powder and tetrafluoroethylene resin powder, respectively.
As the amount added increases, the friction and wear characteristics improve; however, if the total amount of both exceeds 40% by weight, the mechanical properties of the molded product are impaired, warping increases, and wear increases.

Graphite powder exhibits a synergistic effect with tetrafluoroethylene resin powder and contributes to improving the friction and wear characteristics of aromatic polyamide resin. In addition, graphite powder also contributes to improving the moldability of aromatic polyamide resin. do.

That is, the temperature at which the resin powder is filled into the mold, the temperature, pressure, and holding time during the molding process.

In either case, near the limit values, molding defects are likely to occur depending on how the lead time is set.
The addition of graphite powder has an additional effect in that it acts very significantly to solve these problems.

However, in any case, adding more than 20% by weight of each of graphite and tetrafluoroethylene resin is not preferable for use in sliding parts.2 In the present invention, the upper limit of addition of these lubricating fillers is set at 20% by weight each. And so.

Prior to molding the lubricating filler-containing aromatic polyamide resin powder 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 weight or more, it is almost impossible to obtain a molded product that can be put to practical use. .

Therefore, after mixing the aromatic polyamide resin powder and the lubricating filler, the molding material powder is dried. When drying under normal pressure, hold at 150°C for about 15 minutes.
The powder could be made into a powder that could be molded.

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 is useful for speeding up the molding cycle.

However, if the mold temperature exceeds 250° C., even if the subsequent molding steps are well controlled, uneven molding or blisters are likely to occur in the molded product, making it difficult to obtain a satisfactory molded product.

What is the compaction pressure applied after filling the molding material powder?

The powder compaction pressure may be significantly smaller than that 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. Either method can be adopted in which compression molding is carried out using a compressor, but in either case, a compacting pressure of 500 kg/cd or less is sufficient.

Here, when the mold is heated to 150 to 250°C, the pressing force may be 70 to 200°C.

The mold temperature during compression molding is 290°C or higher and 360°C or higher.
The temperature was set not to exceed ℃. According to the experiments of the present inventors,
If the mold temperature is less than 290° C., the flow of the resin is insufficient and the pressure is not evenly transmitted, which tends to cause uneven molding. Furthermore, if the mold temperature is increased to more than 360° C., discolored areas appear in the molded product, which is thought to be due to thermal decomposition of the resin, and dry cracks are likely to occur.

It has been found that the molding time is preferably 1 to 5 minutes per wall thickness.

Generally, within the forming temperature ranges mentioned above.

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.

A satisfactory molded product can be obtained by applying a molding pressure of at least 70 kgA-Il, usually 150 to 200 μ(μ), within the same pressure range as the compacting pressure mentioned above.

After maintaining the molding time for a predetermined time, the mold temperature was cooled to 250° C. or less while the pressure was maintained, 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 iso'7 with a density of 0.5 fl/Cd
1 for talamide resin powder (Teijinsha, Conex powder)
Graphite powder passing through 50 mesh (Nippon Graphite Co., Ltd.)

CB-150,) 12% by weight, tetrafluoroethylene resin powder that passes through 100 meshes (Mitsui Fluorochemical Co., Ltd.).

12% by weight of Teflon 7A-J) was mixed and stirred to obtain a mixed powder in which these were uniformly dispersed. 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 thus prepared was used as a molding material powder, and filled into a mold heated to 200°C.
The powder was compacted at a pressure of 1 liter.

The mold temperature was raised to 620° C. while the pressure was being applied, and this temperature was maintained for 15 minutes.

Next, the pressurized mold temperature was cooled to 220°C, and the length was 5QIjl and the width was 100711. A plate-shaped molded product with a thickness of 4 mm was obtained.

The density of the molded product obtained in this way is 1.48 Sakakan, and the hardness is 892 on the Rockwell scale, and the bending strength is 6.
ys#Ad, impact strength was 2.474≠(Izod).

In terms of mechanical strength, especially bending strength, compared to unfilled aromatic polyamide resin molded products.

Although there is a considerable decrease in strength, it can be said that the bending strength for sliding members is 675, which is sufficient to withstand the first shift.

The Tatami Yotsukukue M scale table shows the 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. Sample layers 1 to 5 are those of the present invention. Example, sample layer 6
-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.

Mating material Carbon steel for machine structures (S45C) Inner diameter 1
6th grade, outer diameter 28mm, height 1511mm Slip speed W 80Vmin (rpm 1.16mm)
0 strokes) Load 7.3ft ν Deep lubrication Self-lubricating (no lubrication) Test time 5
The results of the 0-hour bearing performance test showed that graphite was 10 to 15% by weight and tetrafluoroethylene resin (PTFE) was 1 to 15% by weight, that is, the total amount added as a lubricating filler was 20 to 30% by weight.
It showed particularly good performance over the entire test period.

None of the comparative examples of sample layers 6 to 8 could withstand the 50-hour test, and the test was discontinued after 1 hour for sample layer 6, 5 hours for sample/167, and 7 hours for sample/168. . In these comparative examples, the amount of wear is shown as the value when the test was discontinued, and the coefficient of friction is shown as the average value of the coefficient in a relatively stable state.

The value of the overall speed 80 tn/rrin under the test conditions is 1,16 when expressed in terms of rotational speed as described above.
0 rotation, it becomes a duty.

9 In sliding members generally made of synthetic resin.

Moreover, it is extremely rare to find something that can withstand such high-speed sliding without lubrication.

Incidentally, 6-6 nylon causes the friction surface to become flat within just a few minutes due to the generated frictional heat, and phenolic resin laminated materials containing lubricant fillers generate a large amount of friction noise within 10 minutes, which is abnormal. Abrasion occurred (Effect of the invention) As explained above, the aromatic polyamide resin sliding member of the present invention has a synergistic effect by adding a predetermined amount of graphite and tetrafluoroethylene resin powder as a lubricating filler. It exhibits excellent friction and wear characteristics without impairing the heat resistance of the resin. In particular, due to improved self-lubricating properties, dry friction properties are also excellent.

Therefore, it can be used particularly in applications where lubricating oil cannot be used or is inconvenient, and it can also be used in relatively high-temperature atmospheres and under conditions that involve relatively high-speed sliding. That is.

Claims (2)

[Claims] (1) 8 to 20% by weight of graphite in aromatic polyamide resin,
An aromatic polyamide resin sliding member made of a compression molded product in which 8 to 20% by weight of tetrafluoroethylene resin is uniformly dispersed. (2) [A] 8 to 20% by weight of graphite powder to aromatic polyamide resin powder with a density of 0.2 to 0.4 g/cm^3,
Filling a mold maintained at a temperature not exceeding 250°C with a mixed powder in which 8 to 20% by weight of tetrafluoroethylene resin powder is uniformly dispersed; [B] Pressing the mixed powder with flat pressure. After powdering, the metal temperature should be 290°C or higher but not higher than 360°C, and the molding pressure should be at least 70kg/min within this temperature range.
cm^2, the molding time should be maintained at 1 to 5 minutes per 1 mm of wall thickness of the molded product. [C] After maintaining the specified molding time, the mold temperature should be increased to 25 minutes.
A method for producing an aromatic polyamide resin sliding member comprising the steps of: cooling to a temperature of 0° C. or lower; [d] then opening the mold and taking out the molded product from the mold.