JPH06193628A - Thrust washer - Google Patents

Abstract

PURPOSE:To obtain the required flexural strength and modulus of bending elasticity and a sufficient fatigue strength by taking polyimide resin as a matrix, adding tetfafluorethylene resin, and further adding a specific amount of graphite wherein the amounts of powdered phenol resin hardening material and fixed carbon are more than specific percents. CONSTITUTION:A thrust washer is formed of polyimide group resin component formed by mixing tetrafluorethylene resin of 5 to 20 parts weight and powdered phenol resin hardening material of 5 to 30 parts weight into resin component of 100 parts weight composed of thermoplastic polyimide resin of 50 to 90 parts weight % and scaly natural graphite of 50 to 10 parts weight %, having fixed carbon amount of 97% or more shown in the formula I. Moreover, in the formula I, the letter X indicates the direct link or hydrocarbon radical whose carbon number is 1 to 10, or a radical selected from the group formed by sulfone radical, and R1 to R4 indicate hydrogen, lower alkyl group, lower grade alkoxyl group, chlorine, or bromine, moreover Y indicates tetravalent radical selected among the group formed by aliphatic radical, etc., whose carbon number is 2 or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thrust washer used for a crank portion of a transmission or an engine of automobiles and construction machines.

[0002]

2. Description of the Related Art Thrust washers used for transmissions of automobiles, construction machinery, etc. and cranks of engines are required not only to have wear resistance but also to have fatigue strength because of repeated bending stress due to vibration during use. It

[0003] As a guideline for the fatigue strength of the case, the flexural less elastic modulus 70000kgf / cm ^2, and bending strength is 800 kgf / cm ² or more.

Conventionally, 66 nylon resin or phenol resin filled with glass fiber has been used as the thrust washer used in such applications.
As the horsepower and speed of automobiles and construction machinery have increased, the demand for thrust washers has also increased, and abrasion resistance cannot be satisfied with 66 nylon resin and fatigue strength cannot be satisfied with phenol resin. It was

In order to solve these problems, a method of adding a tetrafluoroethylene resin and a powdery phenolic resin cured product as a filler to a thermoplastic polyimide resin (Japanese Patent Laid-Open No. 6-58242).
No. 3-314712) was disclosed, and improvements were observed in wear resistance and fatigue strength.

[0006]

However, even a conventional thrust washer obtained by adding a tetrafluoroethylene resin and a cured phenol resin to a thermoplastic polyimide resin as a filler still has a sufficiently improved abrasion resistance. However, as mentioned above, further improvement has been required with the increase in horsepower and speed of the apparatus.

On the other hand, under more severe operating conditions in which the heat generated by sliding reaches the glass transition temperature (Tg = 240 ° C.) of the polyimide resin, even if the above-mentioned improved wear resistance is lowered. There is also a problem.

As a method for solving such a problem of deterioration in wear resistance, it is also known to subject a thermoplastic polyimide resin to a heat treatment to obtain a crystallinity of 25%. However, in this case, the molded product is 2 to 5 due to the crystallization treatment.
% (Shrinkage rate) also contracts, so a large amount of warpage occurs in the thrust washer, and local warpage easily occurs during use, which may cause so-called "uneven wear" in which the sliding surface partially wears abnormally. There is a nature.

In view of the above, the present invention solves the above-mentioned problems, and the thrust washer has heat resistance and sliding characteristics and is sufficiently excellent in wear resistance, and further has excellent wear resistance due to crystallization treatment. Even if you acquire sex,
It is an object of the present invention to have a small shrinkage ratio before and after such treatment and no warp, and to have a required bending strength and bending elastic modulus and sufficiently excellent fatigue strength.

[0010]

In order to solve the above-mentioned problems, in the present invention, it is obtained by graphitizing 50 to 90% by weight of a thermoplastic polyimide resin represented by the following formula and a non-phenol resin raw material. 5 to 20 parts by weight of a tetrafluoroethylene resin and 5 to 30 parts by weight of a powdered phenol resin cured product, to 100 parts by weight of a resin composition consisting of 50 to 10% by weight of graphite having a fixed carbon amount of 97% or more. The thrust washer is made of a polyimide resin composition containing

Note

[0012]

[Chemical 2]

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 2 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 3. It is obtained by dehydration cyclization of polyamic acid.

[0015]

[Chemical 3]

Among such polyimide resins, commercially available polyimide resins (R _{1 to} R ₄ in the above formula 2) 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. This is because it is not preferable to use it together with a phenol resin cured product added separately.

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 when the amount of graphite added exceeds 50% by weight, the melt viscosity of the composition becomes large, making it difficult to perform melt molding, and when the amount added is less than 10% by weight, improvement in wear resistance and hardening 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.

The powdery phenolic resin cured product used in the present invention comprises a novolac type or resol type phenolic resin produced by using a formalin-generating compound for phenols, if necessary, with a known filler, and then as it is. Alternatively, it may be obtained by adding a crosslinking agent such as hexamine and heating it to obtain a cured product, which is then crushed. The manufacturing method is disclosed in JP-A-57-17701 and JP-A-58-1.
As disclosed in Japanese Patent No. 7114 and the like, examples of commercially available products include Bell Pearl manufactured by Kanebo Co., Ltd.

Here, these phenolic resins are heat infusible powdery resins, and specifically have an average particle size of 50 μm.
The particle size is preferably m or less, and 80% by weight or more and 150 μm or less. This is because when the particle size is larger than 150 μm, the mutual adhesion of the powder particles to each other is insufficient at the time of molding, and the mechanical strength such as wear resistance and bending strength of the molded article decreases. This is because it is not preferable. And, the phenol resin cured product used in the present invention is required to be sufficiently cured. For example, when the degree of curing is used as a scale to display the solubility in methanol,
Its solubility is 20% by weight or less, preferably 15% by weight or less, and more preferably 5% by weight or less. This is because when the solubility of methanol exceeds 20% by weight, foaming occurs during molding, resulting in voids and microcracks in the molded body.

The compounding ratio of such a cured phenol resin product is 5 to 30 parts by weight based on 100 parts by weight of the composition comprising the thermoplastic polyimide resin and the graphite. This is because, if the amount is less than 5 parts by weight, the effect of abrasion resistance cannot be obtained, and if the amount is more than 30 parts by weight, not only the melt viscosity of the composition becomes high and melt molding is not possible, but also the friction coefficient cannot be reduced. is there.

The polyimide resin composition for a sliding material according to the present invention may contain various known additives as listed below in the range not impairing the object of the present invention. Of course.

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.

[0027]

The thrust washer of the present invention has 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, so that the required heat resistance and friction characteristics are excellent. In addition, by adding a predetermined amount of powdered phenolic resin cured product and graphite having a fixed carbon amount of not less than a predetermined amount, the bending elastic modulus is 70000 kgf / cm ² or less, and the bending strength is 800 kgf / cm ² As described above, the abrasion resistance is improved, and the shrinkage ratio before and after the crystallization treatment is as small as 1% or less.

[0028]

[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] Mitsui Toatsu Chemical Co., Ltd .: AURUM # 450 (2) Glass Fiber Filled Nylon 66 [GF-PA] Asahi Kasei Corporation: ZYRON G702H (3) Glass Fiber Filled Phenol Resin [GF-PF] Sumitomo Bakelite Co., Ltd .: PM-9600 (4) Scale natural graphite [scaly graphite] Nippon Graphite Co., Ltd .: ACP (fixed carbon content 99.5%) (5) Powdery phenol resin cured product [PF] Kanebo: Bellpearl C2000 (average particle size: 48 μm) (6) Tetrafluoroethylene resin [PTFE] Kitamura: KTL610 [Examples 1 to 4, Comparative Example 1] Raw materials in proportions shown in Table 1. After compounding and dry mixing, 37 using a twin-screw melt extruder
It is extruded and granulated under the condition of 0 to 400 ° C., the obtained pellets are supplied to an injection molding machine, and the cylinder temperature is 370 to 4
00 ° C, injection pressure 1000 kg / cm ² , mold temperature 15
Injection molding was performed under the conditions of 0 to 200 ° C. to mold a test piece.

Regarding the obtained test piece, (1) wear test,
(2) Bending strength, (3) Bending elastic modulus, (4) Fatigue test was conducted, and the obtained results are shown in Table 2. Further, for Example 4 and Comparative Example 1, separate test pieces were prepared, and (5) Dimensional change before and after crystallization treatment (a) Shrinkage rate and (b) Existence of warpage were examined, and the results are shown in Table 3. .

(1) Abrasion coefficient Using a thrust type abrasion tester (made in-house), surface pressure of 20 kg
f / cm ² , sliding speed of 260 m / min, mating material: FC4
5, automatic transmission oil (AT
Wear coefficient of 10 hours in F) × 10 ^-11 (cm
³ / kgf · m) was determined.

(2) Bending strength According to ASTM D790, bending strength (kgf / c
m ² ) was calculated.

(3) Flexural Modulus According to ASTM D790, flexural modulus (kgf / cm
² ) asked.

(4) Fatigue test As shown in FIG. 1, thrust washers having an inner diameter of 55 mm, an outer diameter of 70 mm and a thickness of 2 mm were placed on the pedestal 1 arranged at L = 40 mm intervals, and the central portion of the thrust washer 2 was placed. The load indenter 3 was repeatedly loaded up to 10 ⁷ times so that the deflection amount D was 0.8 mm, and the number of times of loading until failure was counted.

(5) Dimensional change due to crystallization treatment Thrust washer test piece (outer diameter: 66.5 mm, inner diameter: 37 mm, thickness: 2 mm)
Disc gate molding with m and cutting the inner diameter)
Using 20 pieces, step heating to these at 320 ° C,
The crystallization treatment was performed for 2 hours. Then, (a) shrinkage ratio before and after the treatment and (b) presence or absence of warpage by visual observation were examined.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

As is clear from the results in Table 2, Comparative Examples 2 and 3 in which the powdered phenolic resin cured product was not blended had a high wear coefficient and could not achieve the intended purpose. Further, Comparative Example 1 in which graphite having a fixed carbon content of 97% or more is not mixed
Has a relatively small wear coefficient, but as is clear from the results in Table 3, the shrinkage ratio due to the crystallization treatment is large and warpage occurs due to the heat treatment.

On the other hand, Examples 1 to 4, which satisfy all the conditions of the compounding ingredients and the compounding ratios, also show excellent characteristics as a thrust washer in terms of wear coefficient, bending strength, bending elastic modulus, and fatigue test. example 2-4, flexural modulus of 70000kgf / cm ² or less, and flexural strength because it is 800 kgf / cm ² or more, excellent in fatigue strength, it was indicative of excellent characteristics as a thrust washer .

[0041]

As described above, the present invention uses a polyimide resin as a matrix, to which a tetrafluoroethylene resin having a particularly excellent effect of reducing the friction coefficient is added, and a powdered phenol resin cured product and fixed carbon are further added. Since the thrust washer is made of a polyimide resin composition in which a predetermined amount of graphite is added in a predetermined amount or more, this product has heat resistance and sliding properties and is sufficiently excellent in abrasion resistance, and also has a crystal structure. Even when superior wear resistance is obtained by chemical treatment, shrinkage is small before and after such treatment, and there is no warp, and the required bending strength and bending elastic modulus are sufficient to provide sufficient fatigue strength. It has the advantage of being excellent.

[Brief description of drawings]

FIG. 1 is a schematic side view of a test apparatus for explaining a fatigue test.

[Explanation of symbols]

 1 Cradle 2 Thrust washer 3 Load indenter

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Claims (2)

[Claims] 1. A thermoplastic polyimide resin represented by the following formula in an amount of 50 to 90% by weight, and a graphite having a fixed carbon amount of 97% or more obtained by graphitizing a non-phenolic resin raw material.
Molded with a polyimide resin composition in which 5 to 20 parts by weight of a tetrafluoroethylene resin and 5 to 30 parts by weight of a powdered phenol resin cured product are mixed with 100 parts by weight of a resin composition consisting of 0% by weight. Thrust washer. Note: 2. The thrust washer according to claim 1, wherein the graphite having a fixed carbon content of 97% or more is flaky natural graphite.