Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From ketone or ketene reactant
Reexamination Certificate
2002-10-04
2004-06-15
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From ketone or ketene reactant
C528S176000, C528S480000, C528S485000, C524S356000, C524S401000, C524S404000, C524S407000
Reexamination Certificate
active
06750315
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a polyether aromatic ketone-based resin composition having advantageous properties as a resin material for sliding parts such as gears, cams, pulleys, sleeves, bearings, washers, sealing materials, cushion sheets, valve parts, protective covers, etc., used in a variety of machines and apparatus such as electric and electronic apparatus, aircraft instruments, astronautic equipment, automobile instruments, transportation equipment, business machines, and general industrial equipment.
BACKGROUND ART
Polyether aromatic ketone resins have been well known as an engineering plastic having excellent mechanical, chemical and thermal properties as well as high abrasion resistance. It has also been well known that although polyether aromatic ketone resins have a high coefficient of friction in themselves, their sliding characteristics can be remarkably improved to lower the coefficient of friction by incorporating a fluorine resin (JP-A-6-136255). However, although self lubrication is improved, abrasion would rather be increased in use under a high load condition or under a condition of very high frictional contact speed, due to reduction of mechanical strength or loading resistance of the molded product.
It has been known that mechanical strength and sliding characteristics of polyether aromatic ketone resins can be significantly improved to reduce their abrasion by adding glass fiber, aramide fiber, carbon fiber or a solid lubricant such as molybdenum disulfide to said resins (JP-A-1-282252 and JP-A-1-282253). However, in case the sliding partner material is a relatively soft metal such as aluminum alloy or stainless steel, the sliding partner is easily subjected to abrasion by the fibrous reinforcement added and may even suffer abnormal abrasion in some cases.
The main cause of such abnormal abrasion is the abrading action of abraded powders generated as a result of the attack against the soft metal surfaces by the edges of the relatively hard fibrous reinforcing material such as glass fiber or carbon fiber.
Also, use of a fibrous reinforcement tends to induce large anisotropy of shrinkage factor of the resin molding, which causes a reduction of dimensional stability when the ambient temperature is raised in the use environment or by the generation of frictional heat. Therefore, use of a fibrous reinforcement was difficult in applications where high dimensional precision was required. Further, these fibrous reinforcements had the disadvantage of encumbering the working operation, especially in melt extrusion, as the presence of such reinforcements reduces fluidity of the resin.
DISCLOSURE OF THE INVENTION
An object of the present invention is to solve the above problems and provide a resin material for sliding parts having excellent abrasion resistance and a low coefficient of friction and also proof against damage to themselves as well as to their sliding partners even under the use conditions where the sliding partners are made of a soft metal such as an aluminum alloy. It is also intended to provide a resin material for sliding parts which enables use of various molding methods such as injection molding, melt extrusion molding, cast molding, compression molding, sinter molding and powder coating as a means for molding the resin material into a desired shape.
As a result of intensive researches for the solution of the above problems, the present inventor has found that a polyether aromatic ketone resin composition comprising a polyether aromatic ketone resin and 1 to 100 parts by weight per 100 parts by weight of the resin of a high-hardness filler with a Mohs hardness of 6 or higher (this resin composition is hereinafter referred to as “high hardness filler-containing polyether aromatic ketone material”) is capable of providing a resin material for sliding parts with excellent abrasion resistance and a low coefficient of friction.
DETAILED DESCRIPTION OF THE INVENTION
The polyether aromatic ketone resins used in the present invention are the thermoplastic resins represented by the following formula (1) or (2). Among those having the structure of formula (1) there is mentioned, for example, a commercial product PEEK (trade name) available from Victrex Inc.
In the above formulae (1) and (2), n means 2 to 100000.
These resins may have the following recurring units in addition to those of the formulae (1) and (2):
wherein Ar
1
and Ar
2
represent independently
A represents a direct bond, O, S, SO
2
, CO or a divalent hydrocarbon group; Q and Q′ represent independently SO
2
or CO; Ar
1
represents a divalent aromatic group; and m is a number of 0, 1, 2 or 3.
In accordance with the present invention, it is possible to obtain a resin composition for sliding parts having high heat resistance, abrasion resistance and chemical resistance as well as excellent moldability with high productivity and at low cost by incorporating in a polyether aromatic ketone resin a high-hardness filler having a Mohs hardness of 6 or higher, the amount of said filler incorporated being 1 to 100 parts by weight per 100 parts by weight of said ketone resin.
In the present invention, the filler is contained in an amount of 1 to 100 parts by weight, preferably 3 to 50 parts by weight, per 100 parts by weight of the polyether aromatic ketone resin used as a base material.
When the content of the high-hardness filler having a Mohs hardness of 6 or higher is less than 1 part by weight per 100 parts by weight of the polyether aromatic ketone resin in the present invention, the effect of improving abrasion resistance of the resulting resin composition is unsatisfactorily small. When the filler content exceeds 100 parts by weight, molding workability of the resin composition deteriorates.
The polyether aromatic ketone resins excel in heat resistance, abrasion resistance, chemical resistance and mechanical strength and also have favorable melting properties that enable injection molding or melt extrusion molding of these resins.
According to the present invention, a resin composition for sliding parts with excellent heat resistance, abrasion resistance, chemical resistance and moldability can be obtained at low cost by incorporating in a polyether aromatic ketone resin a high-hardness filler having a maximal particle size of not larger than 100 &mgr;m in an amount of 1 to 100 parts by weight per 100 parts by weight of said ketone resin.
In the present invention, in order to produce an outstanding effect, a high-hardness filler having an average particle size of 0.1 to 10 &mgr;m, preferably 1 to 8 &mgr;m, more preferably 2 to 5 &mgr;m, is used.
When the average particle size of the filler used in the present invention is less than 0.1 &mgr;m, the effect of the filler to improve abrasion resistance of the polyether aromatic ketone resin is small, and furthermore fluidity of the composition tends to reduce during its melt working, making it hard to perform desired working.
When the average particle size of the filler is larger than 10 &mgr;m, the molded products of the resin composition tend to prove defective in appearance and it is hard to obtain desired smoothness of the surface. Poor surface smoothness enlarges the coefficient of friction and also makes it unstable. Further, fluidity of the composition tends to deteriorate during its melt working, making it difficult to perform desired working.
When the maximal particle size of the filler is larger than 100 &mgr;m, there arise the similar problems of defective appearance and poor surface smoothness of the molded products.
The spherical or particulate high-hardness filler used in the present invention can attain drastic improvement of sliding characteristics of the resin composition of the present invention. Since this high-hardness filler has the effect of receiving load at the sliding surface as well as the effect of inhibiting softening of the resin by the frictional heat, it contributes to the improvement of abrasion resistance of the composition.
If the spherical or particulate high-hardness filler used in
Smith , Gambrell & Russell, LLP
Sumitomo Bakelite Company Limited
Truong Duc
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