JPH09169880A - Fluororesin powder composition for sliding member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluororesin powder composition for a sliding member which has a low frictional coefficient and an excellent wear resistance in sliding in the presence of a lubricating oil, resists to filler separation, and does not attack the mating sliding member. SOLUTION: This composition contains a fluororesin component comprising a polytetrafluoethylene molding powder having a mean particle diameter of 1-100μm and a fine tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer powder having a mean primary particle diameter of 0.1-0.5μm and a filler comprising an amorphous almina powder having a mean particle diameter of 5μm and a coke powder having a mean particle diameter of 10μm or below. The volume ratio of the amorphous alumina powder to the coke powder is in the range of 0.5-2.0, and the total amount of these powders is in the range of 10-50 pts.wt. per 100 pts.wt. fluororesin component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is excellent in low friction and wear resistance in sliding in the presence of lubricating oil, and is excellent in molding that does not damage a sliding mating material made of a soft alloy or a soft metal. TECHNICAL FIELD The present invention relates to a fluororesin powder composition for a sliding member capable of molding a product.

[0002]

2. Description of the Related Art Filler-containing fluororesins are widely used as sliding materials and sealing materials. In particular, in applications such as sliding materials, it is required to have many characteristics such as a low friction coefficient, excellent wear resistance, excellent heat resistance and chemical resistance, and not damaging a sliding partner material. The fluororesin used here is polytetrafluoroethylene (hereinafter referred to as PTFE) molding powder, which is a powder for compression molding, while the filler is an inorganic material such as glass fiber, carbon fiber, graphite, molybdenum disulfide, and bronze powder. Fillers or organic fillers such as aromatic polyesters, polyimides and pophenylene sulfide are known (Japanese Patent Publication No. 49-36081 and JP-A-57).
-105442, JP-A-58-19397, etc.).

[0003]

However, in the conventional sliding material molded from the filler-containing PTFE molding powder, since PTFE itself has a non-adhesive property, the PTFE and the filler are not adhered to each other. Since the adhesiveness is poor, the filler easily separates from PTFE on the sliding surface or is exposed to the sliding surface, damaging the mating material in sliding contact and causing an increase in sliding resistance. However, there are problems such as insufficient mechanical strength such as tensile elasticity. Further, in recent years, the material of the mating material with which the sliding material slides is often changed to a soft alloy and a soft metal, particularly an aluminum alloy, from the viewpoint of energy saving, weight saving, and maintenance-free. Conventionally, a filler-containing PTFE for sliding members has been selected and used so that PTFE itself does not wear. However, for soft and sticky materials such as aluminum, PTFE is used.
There is a problem that the resin itself and the sliding counterpart material are largely worn. The present invention relates to a fluororesin powder composition for a sliding member, which has a low friction coefficient and is excellent in wear resistance when sliding in the presence of a lubricating oil, a filler is hard to be removed, and a sliding partner is not damaged. The purpose is to provide.

[0004]

The fluororesin powder composition for a sliding member according to the present invention comprises a polytetrafluoroethylene molding powder having an average particle size of 1 to 100 μm and an average primary particle size of 0.1 to 0.5 μm. Fluorine resin component consisting of tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer fine powder, amorphous alumina powder with an average particle size of 5 μm or less and coke powder with an average particle size of 10 μm or less as fillers, and the volume of both powders The ratio (amorphous alumina powder / coke powder) is 0.5 to 2.
0 and the total amount of both powders is 100
It is in the range of 10 to 50 parts by weight with respect to parts by weight.

A molded product obtained by compression-molding such a powder composition and then firing it has high mechanical strength and less detachment of the filler on the sliding surface during sliding, resulting in molding. The wear of the product itself and the wear of the sliding counterpart material are small, and the coefficient of friction is extremely small.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The amorphous alumina powder used in the present invention has an average particle size of 5 μm or less, preferably 0.5 to 1
μm. When the average particle size exceeds 5 μm, the alumina powder in the molded product is easily detached on the sliding surface, and this detached alumina powder damages the sliding mating material, which is not preferable. Amorphous alumina powder is a powder whose true specific gravity is in the range of 3.65 to 3.85 and which does not complete the transition to α-alumina by X-ray diffraction. Is 3.92, which is distinguished from the powder whose conversion to α-alumina has been completed by X-ray diffraction. The amorphous alumina powder can keep the tensile elastic modulus of the molded product higher than that when the crystalline alumina powder is used. That is, in addition to being able to maintain sufficient rigidity, the amount of wear of the sliding mating material is also small.

The coke powder used in the present invention has an average particle size of 10 μm or less. If the average particle size exceeds 10 μm, the dynamic friction coefficient of the molded product increases and sliding resistance increases, which is not preferable.

In the present invention, the amorphous alumina powder having an average particle size of 5 μm or less and the coke powder having an average particle size of 10 μm or less are used in a volume ratio of 0.5 to 2.0. Within the above range, the alumina powder can be uniformly mixed with the fluororesin powder in a dry state without requiring any special surface treatment on the alumina powder, although the fluororesin powder is easily charged. If the amount of alumina powder outside this range is large, the molded product tends to crack during sliding, and if the amount of alumina powder is small, the amount of wear of the sliding mating material tends to increase. There is. The amount of the filler added to the fluororesin powder is in the range of 10 to 50 parts by weight, preferably 20 to 30 parts by weight, based on 100 parts by weight of the resin. If the addition amount is less than 10 parts by weight, the elongation value of the molded product is large and easily deformed, and a sufficient tensile elastic modulus of the molded product, that is, sufficient rigidity cannot be obtained.
When the addition amount is 50 parts by weight or more, the elongation value of the molded product becomes small and becomes brittle, which is not preferable.

In addition to the above filler powder, an average particle size of 10 μm
1 to 100 parts by weight of the following graphite powder
It is preferable to add it in the range of 10 weights because the exothermic temperature during sliding can be lowered.

The fluororesin component used in the present invention includes a PTFE molding powder having an average particle size of 1 to 100 μm and a tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer having an average primary particle size of 0.1 to 0.5 μm. A mixture of fine powders (hereinafter referred to as PFA) is used. The PFA fine powder having an average primary particle size of 0.1 to 0.5 μm melts during firing, sufficiently covers the surface of the filler and the PTFE molding powder, and surely fills the voids between the filler and the PTFE molding powder. It improves the adhesion between the filler and the PTFE molding powder, and improves the mechanical strength of the molded product.

The PTFE molding powder used in the present invention is a homopolymer of tetrafluoroethylene (TFE) obtained by suspension polymerization (hereinafter referred to as unmodified PT).
TFE modified with 1.0% by weight or less of perfluoro (alkyl vinyl ether)
The polymer (hereinafter, referred to as modified PTFE) may be pulverized for compression molding alone, or may be a mixture of both, but the ratio of unmodified PTFE and modified PTFE is 6 / by weight. In the case of a mixture of 4 to 4/6, unmodified PT
Compared with FE alone or modified PTFE alone,
It is particularly preferable because the molded product has improved elongation, tensile strength, mechanical strength such as tensile elastic modulus, and the amount of wear of the sliding counterpart material made of a soft alloy or a soft metal is reduced. The non-denatured PTFE is a non-denatured PTFE containing a large proportion of fibrous particles as described in Japanese Patent Publication No. 34-10177, which has good entanglement with the filler and prevents desorption of the filler. Since it can be used, it is preferably used. Further, it is considered that the modified PTFE has an intermediate role between the PFA and the non-modified PTFE. The particle size of PTFE molding powder is unmodified PTFE and modified PT.
Both FE are 1 to 100 μm, preferably 10 to 50 μm. The PTFE molding powder thus pulverized is advantageous for uniformly mixing with the filler and the PFA fine powder. The amount of PTFE molding powder added is 70 to 95% by weight, preferably 85 to 95% by weight in the fluororesin.
95% by weight. When the addition amount is less than 70% by weight, the moldability is deteriorated and the mechanical properties of the molded product are deteriorated. When the addition amount exceeds 95% by weight, the sliding properties such as abrasion resistance are remarkably improved. I will not be able to.

The average particle size used in the present invention is 0.1 to 0.
The 5 μm PFA fine powder is obtained by drying copolymer fine particles having an average particle diameter of 0.05 to 0.5 μm obtained by emulsion polymerization of tetrafluoroethylene and perfluoroalkyl vinyl ether at a temperature lower than the melting point of the fine particles. .
Alternatively, it may be a powder of secondary particles having an average particle diameter of 1 to 1000 μm obtained by aggregating the fine particles and then drying at a temperature lower than the melting point. This is because the powder of secondary particles having an average particle size of 1 to 1000 μm dried at a temperature lower than the melting point easily has an average particle size of 0.1 to 0.5 μm when stirring the powder composition of the present invention.
This is because it is crushed into fine powder of m.

The effect of the present invention is obtained only when PFA is a fine powder, that is, the mechanical strength is improved by improving the adhesion between the PTFE molding powder and the filler, and the filler is prevented from being exposed and separated during sliding. It is possible to obtain the effects of significantly reducing the wear of the molded product itself, the wear of the mating material, and the friction coefficient. Therefore, when dried at a temperature equal to or higher than the melting point, the fine particles or the particles are fused and do not become fine powder having an average particle diameter of 0.1 to 0.5 μm even when the powder composition is stirred, which is not preferable.

The perfluoro (alkyl vinyl ether) of PFA used in the present invention is CF ₂ ═CFOR _f
(R _f represents a perfluoroalkyl group having 1 to 10 carbon atoms), and perfluoro (ethyl vinyl ether) and perfluoro (propyl vinyl ether) are particularly preferable. Also, PFA has a viscosity at 372 ° C. of 1 × 10.
It is preferably in the range of ⁴ to 1 × 10 ⁶ boaz, and is preferably a copolymer composed of 97.5 to 95% by weight of tetrafluoroethylene and 2.5 to 5.0% by weight of perfluoro (alkyl vinyl ether).

The average particle size in the present invention is 0.1 to 0.5 μ.
The amount of the PFA fine powder of m added is 5 to 30% by weight, preferably 5 to 15% by weight in the fluororesin. When the addition amount is less than 1% by weight, even if the PFA fine powder is melted during firing, the surface of the filler and the PTFE molding powder cannot be sufficiently covered, and the gap between the filler and the PTFE molding powder is also present. Can not be filled reliably. If the addition amount is 30% by weight or more, not only the effect is improved but also the cost is increased, which is economically disadvantageous, and the deformation rate of the molded product becomes large during firing, which is not preferable.

In mixing the powder composition of the present invention, an ordinary known mixing method is adopted. For example, each component is mixed with a mixer such as a V-type blender, a tumbler, a Henschel mixer. Further, the molding method of the powder composition of the present invention,
There is no limitation, and a known compression molding method of PTFE powder may be applied.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. The following materials were used as raw materials. a) PTFE molding powder with an average particle size of 35 μm (Mitsui-DuPont Fluorochemicals: Teflon® ⁾
7-J) b) Modified PTFE molding powder with an average particle diameter of 35 μm (Mitsui DuPont Fluorochemical Co., Ltd .: Teflon)
^(R) 70-J) c) PFA fine powder having an average particle size of 0.2 μm (manufactured by Mitsui-DuPont Fluorochemicals) d) PFA powder having an average particle size of 30 μm (MP-10, manufactured by Mitsui-DuPont Fluorochemicals) e) Amorphous alumina powder (manufactured by Nippon Light Metal Co., Ltd .: average particle size 0.7 μm, true specific gravity 3.8) f) Crystalline alumina powder (manufactured by Nippon Light Metal Co., Ltd .: average particle size 0.
6 μm) g) Coke powder (manufactured by Nippon Carbon Co., Ltd .: average particle size 7 μm)
m, true specific gravity 1.99) h) Graphite powder (manufactured by SES Co., Ltd .: average particle size 1 μ)
m)

[0018]

Examples 1 to 3 and Comparative Examples 1 to 5 The above raw materials were uniformly mixed with a Henschel mixer in the proportions shown in Table 1 to prepare a fluororesin powder composition for sliding members. The amounts of the amorphous alumina powder, the crystalline alumina powder, the coke powder and the graphite powder, which are the fillers shown in Table 1, are the same as those of Resin 1
It is the weight part of the filler (hereinafter referred to as PPh) relative to 00 weight parts. With respect to this fluororesin powder composition, the elongation value, tensile strength, tensile elastic modulus, dynamic friction coefficient, and wear amount were measured by the following methods.

[0019]

[Elongation Value, Tensile Strength, Tensile Elastic Modulus] The fluororesin powder composition shown in Table 1 was preformed at 1500 kg / cm ² and fired at 380 ° C. for 1 hour to obtain a disk having an outer diameter of 50 mm and a thickness of 2 mm. It was The test piece was punched out with a micro dumbbell according to ASTM-1457, and the elongation value,
The tensile strength and tensile elastic modulus were measured. Table 1 shows the results
Shown in

[0020]

[Dynamic friction coefficient, wear amount] The fluororesin powder composition shown in Table 1 was preformed at 1500 kg / cm ² and 380 ° C.
Baking for 1 hour, outer diameter 65mm, inner diameter 48mm, height 3
A cylindrical molded product of 0 mm was obtained. From now on, the outer diameter is 52 mm,
A ring having an inner diameter of 48 mm and a height of 2 mm was cut into a test piece. The dynamic friction coefficient and the amount of wear of this test piece were measured by the following friction and wear test method. Uses a RIK-type automatic pressurization type high-pressure friction and wear tester and uses AL as a sliding mating material.
Alloy die casting (AD described in JIS 1976 2118)
C12: surface roughness Ra = 2 to 3 μm) was used. The dynamic friction coefficient is that the oil for auto transmission at a temperature of 80 ° C is supplied at a flow rate of 150 cc / min, and the load is 25 k.
The measurement was performed by sliding at g / cm ² , a speed of 11 m / sec, and a time of 5 hours. The amount of wear was measured by measuring the amount of wear of the AL alloy die casting after the completion of sliding. Table 1 shows the results.

Molded articles obtained by subjecting the fluororesin powder compositions of Examples 1 to 3 to compression molding and then firing are:
Elongation value, tensile strength, tensile elastic modulus, dynamic friction coefficient,
It is also excellent in terms of wear amount.

As is clear from Table 1, in the case of Comparative Example 1 in which the amorphous alumina powder was not added, the amount of wear of the AL alloy die casting, which is a sliding counterpart, was large, and the tensile modulus of elasticity of the molded product was large. It is understood that the value is low, the rigidity is low, and it is easily deformed.

Comparative Example 2 in which no coke powder was added
In the case of, the elongation value is remarkably small and the alumina powder and PT
It can be seen that the FE molding powder was not uniformly mixed. Further, in Comparative Example 2, it is understood that the molded product itself also cracks during sliding, and the dynamic friction coefficient is large as compared with Examples 1 to 3, and the soft material cannot be used as the sliding mating material.

[0024]

[Table 1]

In the case of Comparative Example 3 in which PFA fine powder was not added, the dynamic friction coefficient was large and heat was generated, and sliding was stopped after 2 hours. Therefore, the measured value (marked with *) in Comparative Example 3 is the value at this point. Further, since the elongation value of Comparative Example 3 is smaller than that of Examples 1 to 3, it can be seen that the PTFE molding powder and the filler are not well compatible with each other.

Further, in the case of Comparative Example 4 in which PFA powder having an average particle size of 30 μm, which is not PFA fine powder having an average particle size of 0.2 μm, was added, the wear amount of the AL alloy die casting, which is a sliding mating material, was measured. It can be seen that a soft material cannot be used as a sliding mating material because it is very large as compared with Examples 1 to 3. Further, since the elongation value is smaller than that in Comparative Example 3, it is understood that the PTFE molding powder and the filler are not so well compatible with each other.

In Comparative Example 5 in which crystalline alumina powder was used instead of amorphous alumina powder, both the dynamic friction coefficient and the amount of wear were large.

[0028]

Examples 4 to 6 Here, the effect of graphite powder as a filler will be described. The above raw materials were uniformly mixed with a Henschel mixer in the proportions shown in Table 2 to prepare a fluororesin powder composition for sliding members. With respect to this fluororesin powder composition, a ring-shaped test piece for frictional wear test was prepared in the same manner as in Examples 1 to 3, and the AL alloy die-casting which is a sliding mating material when the frictional wear test was performed on this test piece Table 2 shows the results of measuring the heat generation temperature during sliding. Compared with the case where no graphite powder is included (Example 4),
When the graphite powder is included (Examples 5 and 6), the exothermic temperature is low.

[0029]

[Table 2]

[0030]

EFFECTS OF THE INVENTION The resin composition for a sliding member of the present invention has a particularly high abrasion resistance even when a soft metal such as an aluminum alloy or a soft alloy is used as a sliding mating material and both the wear of itself and the mating sliding member are small. Severe usage conditions that require sliding characteristics, that is, high temperature, high speed, not only exhibit excellent sliding characteristics when used under high load, but also the heat resistance required as a resin composition for sliding members, It also has chemical resistance, dimensional stability, and excellent mechanical properties.

Claims (4)

[Claims] 1. A fluororesin comprising a polytetrafluoroethylene molding powder having an average particle size of 1 to 100 μm and a tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer fine powder having an average primary particle size of 0.1 to 0.5 μm. Average particle size of 5μ as a component and filler
m or less amorphous alumina powder and coke powder with an average particle size of 10 μm or less, the volume ratio of both powders (amorphous alumina powder / coke powder) is in the range of 0.5 to 2.0, and the total of both powders. A fluororesin powder composition for sliding members, wherein the amount is in the range of 10 to 50 parts by weight based on 100 parts by weight of the fluororesin component. 2. The composition according to claim 1, wherein the graphite powder having an average particle diameter of 10 μm or less is contained in an amount of 1 to 10 parts by weight based on 100 parts by weight of the fluororesin component. 3. The polytetrafluoroethylene molding powder is a mixture of polytetrafluoroethylene homopolymer and polytetrafluoroethylene modified with perfluoro (alkyl vinyl ether), and the weight ratio of both is 4/6 to 6 /. 4. The composition according to claim 1 or 2, which is 4. 4. The fluororesin according to claim 1, 2 or 3, wherein the tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer fine powder is in the range of 5 to 30% by weight in the fluororesin component. Powder composition.