JPH06240138A - Polyimide resin composition for sliding material - Google Patents

Abstract

PURPOSE:To produce the subject composition for sliding material excellent in heat resistance, sliding properties and abrasion resistance, having little shrinkage at crystallization by compounding a mixture of a specific thermoplastic polyimide resin and a graphitization substance of a non-phenol resin with an ethylene tetrafluoride resin. CONSTITUTION:This polyimide resin for sliding material is produced by compounding 100 pts.wt. of a resin composition consisting of 50-90wt.% of a thermoplastic polyimide resin of the formula (X is direct bonding, 1-10C hydrocarbon, isopropylidene hexafluoride, carbonyl, thio or sulfone; R1 to R4 are H, lower alkyl, lower alkoxy, Cl or Br; Y is tetravalent group of aliphatic of >=C2, alicyclic, monocyclic aromatic or condens polycyclic aromatic, etc.) and 50-10wt.% of graphite containing >=97% of fixed carbon produced by graphitization of a raw material for a non-phenolic resin with 5-20 pts.wt. of ethylene tetrafluoride resin. This polyimide resin is excellent in heat resistance, sliding properties and abrasion resistance under sliding conditions of high PV value and having a small shrinkage ratio before and after crystallization treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyimide resin composition for a sliding material which is applied under sliding conditions where a high load is required mechanically and thermally.

[0002]

2. Description of the Related Art Polyimide resins have excellent heat resistance, and their properties have been improved so that they can be used as a sliding agent under severe conditions such as high temperature, high load and high speed sliding. .

For example, as a technique for improving the sliding characteristics of polyimide resin, Japanese Patent Laid-Open No. 63-8455 discloses:
It is described that a tetrafluoroethylene resin is added to a polyimide resin. Further, JP-A-63-314712 discloses that abrasion resistance is improved by adding a phenol resin cured product together with a tetrafluoroethylene resin to a polyimide resin.

[0004]

However, a conventional polyimide-based resin composition for a sliding material obtained by adding a phenol resin cured product together with a tetrafluoroethylene resin to a polyimide resin has a glass transition temperature (Tg = 240
℃), for example, 640 kg / cm ² -m /
There is a problem that the abrasion resistance is extremely low when sliding at a high PV value such as min.

In order to improve the wear resistance under the above-mentioned severe sliding conditions, a method of subjecting a thermoplastic polyimide resin to a heat treatment to obtain a crystallinity of 25% is also known. However, in this case, since the molded product shrinks by 2 to 5% (shrinkage rate) before and after the crystallization treatment, it is not possible to obtain a molded product with good dimensional accuracy.

As a technique for reducing the shrinkage ratio before and after the crystallization treatment, JP-A-4-175373 and JP-A-4-202470 describe adding a thermotropic liquid crystal polymer. ing. The liquid crystalline polymer used in this case is highly oriented to reduce the linear expansion coefficient of the molded product and improve the dimensional accuracy of the molded product.

However, since the composition comprising the thermotropic liquid crystal polymer and the thermoplastic polyimide resin is an incompatible system, the wear resistance can hardly be improved.

Therefore, the present invention solves the above-mentioned problems and provides a polyimide resin composition for a sliding material, which has excellent heat resistance and sliding characteristics, and has an abrasion resistance under sliding conditions of a high PV value. In addition to having excellent properties, it is an object to make the shrinkage rate smaller before and after the crystallization treatment and to easily manage the dimensional accuracy.

[0009]

In order to solve the above-mentioned problems, in the present invention, 50 to 90% by weight of a thermoplastic polyimide resin represented by the following formula and a non-phenolic resin-based raw material are obtained by graphitization. 5 to 20 parts by weight of a tetrafluoroethylene resin was mixed with 100 parts by weight of a resin composition composed of 50 to 10% by weight of graphite having a fixed carbon amount of 97% or more.

[0010]

[Chemical 3]

Alternatively, the composition may be such that 1 to 5 parts by weight of a thermotropic liquid crystal polymer represented by the following formula is further added to the polyimide resin composition for sliding materials having the above composition.

[0012]

[Chemical 4]

The graphite having a fixed carbon content of 97% or more may be flaky natural graphite. The details will be described below.

First, the thermoplastic polyimide resin represented by the above formula 3 used in the present invention is obtained by the reaction of one or more tetracarboxylic dianhydrides with the aromatic ether diamine represented by the following formula 5. It is obtained by dehydration cyclization of polyamic acid.

[0015]

[Chemical 5]

Of such polyimide resins, commercially available products of polyimide resins (R _{1 to} R ₄ in the above formula 3) are used.
Are all hydrogen), manufactured by Mitsui Toatsu Chemicals Inc .:
AURUM is mentioned.

Next, the fixed carbon amount in the present invention is 97%.
The above graphite may be natural flake graphite produced from the ground or artificial graphite. Out of natural graphite
Experiments have shown that scaly graphite having an average particle size of about 10 μm is particularly preferable for achieving the intended purpose of the present invention. The artificial graphite is preferably, for example, one in which coke derived from pitch is solidified with tar or pitch, baked at about 1200 ° C., placed in a graphitizing furnace, and crystals are grown at a high temperature of about 2300 ° C. In addition, as a raw material of artificial graphite, pitch, coal tar, coke, wood raw material, furan resin,
Polyacrylonitrile is used, and phenol resin is not used as a raw material. Because from the experiment described later,
This is because a significant difference is clearly seen in comparison with graphite obtained from other raw materials.

Here, the fixed carbon in the graphite component is the remaining component obtained by quantitatively removing water, ash, and volatile matter in the industrial analysis of the coal test method, and a small amount of hydrogen containing carbon as the main component, It contains oxygen and nitrogen. When the fixed carbon content is less than 97%, satisfactory results cannot be obtained for both wear resistance and shrinkage of the molded product before and after the crystallization treatment.

The blending ratio of the above-mentioned thermoplastic polyimide resin and graphite is 50 to 90% by weight of the thermoplastic polyimide resin and 50 to 10% by weight of graphite having a fixed carbon amount of 97% or more. This is because if the amount of graphite added is more than 50% by weight, the melt viscosity of the composition becomes large and melt molding becomes difficult, and if it is less than 10% by weight, the effect of improving wear resistance cannot be sufficiently obtained. Because.

Next, the tetrafluoroethylene resin used in the present invention is preferably in a powder form so that it can be uniformly mixed in the composition. For example, molding powder, fine powder, or γ rays after molding and firing can be used. It may be pulverized by electron beam irradiation. The blending ratio of the tetrafluoroethylene resin is 5 to 20 parts by weight based on 100 parts by weight of the composition of the thermoplastic polyimide resin and graphite. Because, if the amount is less than 5 parts by weight, the added thermoplastic polyimide resin composition does not have sufficient sliding properties, and if the amount exceeds 20 parts by weight, the mechanical strength inherent to the thermoplastic polyimide resin is impaired. Because.

Next, the thermotropic liquid crystal polymer (hereinafter abbreviated as LCP) used in the present invention has the basic structure of (II) to (IV) of the above chemical formula 4. As such an LCP, commercially available Nippon Petrochemical Co., Ltd .: Zaider, Sumitomo Chemical Co., Ltd .: Econol, etc. can be exemplified.

By blending 1 to 5 parts by weight of the above LCP, which is the above-mentioned predetermined range, the flowability at the time of melt molding and the shrinkage rate at the time of crystallization can be alleviated. However, if the amount is less than 1 part by weight, the effect of improving the flowability and the deformation at the time of crystallization cannot be obtained, and if the amount is more than 5 parts by weight, the abrasion resistance is significantly impaired as described above.

The polyimide resin composition for a sliding material according to the present invention may be mixed with various known additives as listed in the following items within a range not impairing the object of the present invention.

That is, as a reinforcing agent, glass fiber,
Carbon fibers, boron fibers, silicon carbide fibers, carbon whiskers, asbestos, metal fibers, rock wool, etc. Flame retardant improvers such as antimony trioxide, magnesium carbonate, calcium carbonate, etc. Electrical property improvers such as clay, mica, etc. , Asbestos, silica, graphite, etc. as cracking resistance improver, iron, zinc, aluminum, copper and other metal powders as thermal conductivity improver, other fillers such as glass beads, glass balloons, calcium carbonate, alumina, Talc, diatomaceous earth,
Hydrated alumina, shirasu balloon, various metal oxides, inorganic pigments, etc., which are natural or synthetic compounds stable at 300 ° C. or higher.

The means for mixing the raw materials used in the present invention described above is not particularly limited, and the raw materials may be individually supplied to the melt mixer, or a Henschel mixer, a ball mixer, a ribbon blender in advance. Two or more types may be simultaneously mixed using a general-purpose mixer such as. The mixing temperature in that case is usually 250 to 420.
C., preferably 300 to 400.degree. Further, as the molding method, compression molding, sinter molding or the like can be adopted, and injection molding or extrusion molding can be performed by forming a homogeneous melt blend.

[0026]

The polyimide resin composition for sliding materials according to the present invention uses a heat-resistant polyimide resin as a matrix, and a tetrafluoroethylene resin, which is particularly excellent in the effect of reducing the friction coefficient, is added to the matrix. It has excellent abrasion resistance and frictional properties, and by adding a specified amount of graphite with a fixed carbon content of not less than a specified amount, the wear resistance is improved and the shrinkage ratio before and after the crystallization process is small. .

[0027]

[Examples] The raw materials used in Examples and Comparative Examples are summarized below. All the blending ratios were% by weight, and the abbreviations were shown in [].

(1) Thermoplastic polyimide resin [TPI] manufactured by Mitsui Toatsu Chemicals, Inc .: AURUM # 450 (2) Flake-shaped natural graphite [scaly graphite] manufactured by Nippon Graphite Co., Ltd .: ACP (fixed carbon content 99.5%) (3) Artificial graphite [artificial graphite] LONZA: KS10 (fixed carbon content 99.5%) (4) Soil-granular natural graphite [earth-granular graphite] Nippon Graphite: blue P (fixed carbon content 92.5%) (5) Phenolic resin cured product (Ph cured product) manufactured by Kanebo: Bellpearl C2000 (6) Thermotropic liquid crystal polymer [LCP-1] Sumitomo Chemical: Econol E5000 (7) Thermotropic liquid crystal polymer [LCP- 2] Nippon Petrochemical Co., Ltd .: Zaider SRT300 (8) Tetrafluoroethylene resin [PTFE] Kitamura Co., Ltd .: KTL610 [Examples 1-7, Comparative Examples 1-7] Original After mixing dry blended in proportions shown in Table 1 or Table 2 the fee, extruded and granulated under the conditions of 370-400 ° C. using a twin-screw melt extruder,
The pellets obtained are supplied to an injection molding machine, the cylinder temperature is 370 to 400 ° C., the injection pressure is 1000 kg / c.
m ^2, by injection molding at a mold temperature of 150 to 200 ° C.,
A test piece was molded. For the obtained test pieces, (1) friction coefficient, (2) wear coefficient, (3) critical PV value, (4) flexural modulus, (5) dimensional change due to crystallization treatment were measured by the following methods, respectively. The obtained results are shown in Table 3 or Table 4.

(1) Coefficient of friction Using a thrust type friction / wear tester (manufactured by our company), surface pressure 5.0 kg / cm ² , sliding speed 128 m / min, mating material S
UJ2, unlubricated, and dynamic friction coefficient after 60 minutes of operation were determined.

(2) Wear coefficient Using the tester used for measuring the friction coefficient, the surface pressure is 5.0 k
g / cm ² , sliding speed 128 m / min, mating material; SUJ
2. The wear coefficient (× 10 ⁻¹⁰ cm ³ / kgf · m) was obtained from the wear test results in the non-lubricated state, the amorphous state after 100 hours of operation, and the state after the crystallization treatment.

(3) Limit PV value In the above wear test, the sliding speed was 128 m / min, the mating material was SUJ2, no lubrication, and the limit PV value after crystallization treatment for 100 hours of operation (kg / cm ² -m / min) )
I asked. However, the wear coefficient is 100 × 10 ^-10 cm ³
The surface pressure of not less than / kgf · m was defined as the limit PV.

(4) Flexural Modulus The flexural modulus (kgf / cm ² ) at room temperature and 230 ° C. was determined according to ASTM-D790. (5) Dimensional change due to crystallization treatment Thrust washer type test piece (outer diameter 66.5 mm, inner diameter 37 mm, thickness 2 mm)
20 pieces that were formed by disc gate molding with a diameter of 10 mm and the inner diameter was cut.
Crystallization treatment was performed at 2 ° C. for 2 hours. And (a) outside diameter standard deviation before and after treatment, (b) shrinkage ratio (%),
(C) The presence or absence of warpage was examined by visual observation.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

[0036]

[Table 4]

As is clear from the results of Tables 3 and 4, Comparative Example 1 in which PTFE was not compounded had a high wear coefficient, and Comparative Example 2 in which graphite was not compounded exhibited a shrinkage ratio upon crystallization treatment. Was unsuitable, exceeding 4%. Further, Comparative Example 4 in which the amount of graphite having a fixed carbon content of 97% or more exceeded the predetermined range was unmoldable. Furthermore, fixed carbon amount 9
Comparative Example 5 containing less than 7% graphite or Comparative Example 6 containing no graphite had a large dimensional change after the crystallization treatment.

On the other hand, in Examples 1 to 7 which satisfy all the conditions of the compounding ingredients and the compounding ratios, the limit PV value is 1000 or more, which is sufficiently large, and the abrasion coefficient and the mechanical strength of other test items are large. The (bending elastic modulus) and the friction coefficient also showed excellent properties as a sliding material, and the dimensional change after crystallization treatment was 1% or less, which was sufficiently small.

Therefore, the sliding material composition of the above examples is formed into a sheet, a film, a rod or a fibrous molded article, which is used for automobile piston rings, bearings, seal rings, valves, valve guides, Valve seats, seals,
Synchronizer ring, clutch friction plate, gear, bearing,
It can be applied to a viscous coupling plate or the like, or can be expected to have a wide range of applications such as gears, bearings, heat insulating materials, separation claws, other general-purpose sliding members, and structural members for office equipment such as copying machines and printers.

[0040]

[Effect] As described above, the present invention uses a heat-resistant polyimide resin as a matrix, and adds tetrafluoroethylene resin, which is particularly excellent in the effect of reducing the friction coefficient, to the matrix,
Further, the fixed carbon amount is a polyimide resin composition containing a predetermined amount of graphite in a predetermined amount or more, or a polyimide resin composition containing a thermotropic liquid crystal polymer in a predetermined amount, so that heat resistance, sliding properties and An advantage of the polyimide resin composition for a sliding material is that it has excellent abrasion resistance under sliding conditions with a high PV value, and that it has a small shrinkage factor before and after crystallization treatment, and that dimensional accuracy can be easily controlled. is there.

Claims (3)

[Claims] 1. A thermoplastic polyimide resin represented by the following formula: 50 to 90% by weight; and a graphite having a fixed carbon content of 97% or more obtained by graphitizing a raw material of a non-phenolic resin.
A polyimide resin composition for a sliding material, comprising 100 parts by weight of a resin composition consisting of 10% by weight and 5 to 20 parts by weight of a tetrafluoroethylene resin. [Chemical 1] 2. A polyimide resin for a sliding material, which is obtained by adding 1 to 5 parts by weight of a thermotropic liquid crystal polymer represented by the following formula to the polyimide resin composition for a sliding material according to claim 1. Composition. [Chemical 2] 3. The polyimide resin composition for a sliding material according to claim 1, wherein the graphite having a fixed carbon content of 97% or more is flaky natural graphite.