JPH11293076A - Resin composition for sliding member and sliding member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition exhibiting low friction and excellent resistance to abrasion and to creep under lubrication with an oil by mixing a polytetrafluoroethylene resin, a metallic powder having a specific particle size and a powder obtained by crushing a molded article made of a polytetrafluoroethylene resin composition each in a specific amount. SOLUTION: The titled resin composition comprises 25-90 pts.vol. of a polytetrafluoroethylene resin, 5-40 pts.vol. of metallic powder having an average particle size of 2-150 μm and a Mohs' hardness of 3-4 such as powder of copper or a copper alloy, 5-35 pts.vol. of powder having a particle size of 250 μm or less obtained by crushing a molded article made of a resin composition comprising a polytetrafluoroethylene resin only or a polytetrafluoroethylene resin containing a non-thermoplastic polyimide resin, and, if necessary, a pigment such as titanium oxide, iron oxide or the like. The powder of this composition is put into a specified metal mold and subjected to a pressure of 40-100 MPa to carry out preforming. And the compression molded body is taken out and burned at 360-380 deg.C to give a molded body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition for a sliding member and a sliding member, and more particularly to a sliding member used for a sliding surface such as a bed of a machine tool which reciprocates under oil lubrication. The present invention relates to a resin composition and a sliding member.

[0002]

2. Description of the Related Art If stick slip occurs on a sliding surface such as a bed portion of a machine tool such as a surface grinding machine or a cylindrical grinding machine, the machining accuracy of a product is reduced. Polytetrafluoroethylene (hereinafter abbreviated as PTFE) for the purpose of preventing galling and seizure
The sheet material of the resin composition is adhered. Further, the sheet material is required to have excellent wear and creep properties. PTFE resin is widely used as a resin component of a sheet material because it has excellent heat resistance and chemical resistance, and has a smaller coefficient of kinetic friction at the start of sliding than other resin materials.
For sliding parts of PTFE resin, inorganic fillers such as glass fiber and bronze, and organic fillers such as aromatic polyester and thermoplastic polyimide are added to improve relatively poor abrasion resistance and creep resistance. Materials are also conventionally used.

[0003] When a fibrous filler such as glass fiber is mixed with PTFE resin, abrasion resistance and creep resistance are improved by a reinforcing effect, but the friction coefficient is increased. Further, the elastic modulus is increased, and the workability when bonding the sheet material to a bed portion of a machine tool or the like is deteriorated. The same applies to flaky fillers such as graphite and mica. Therefore, a material for a sliding part of a machine tool comprising 10 to 30% by weight of polyoxybenzoyl or polyphenylene sulfide alone or in a mixture having a relatively spherical shape and 90 to 70% by weight of a PTFE resin having an average particle diameter of 100 to 1000 μm. Is known (Japanese Patent Application Laid-Open
-127933).

On the other hand, there is known a PTFE resin sliding portion material which is filled with an inorganic filler such as bronze which improves the creep resistance and sufficiently fulfills the role of bearing the load on the sliding surface. For example, it is known to use porous bronze to reduce friction (Japanese Patent Application Laid-Open
-391).

[0005] As a method of reducing friction, a porosity of 5 to 30 is used.
% PTFE resin and bronze are known, and it is known to add PTFE resin powder which has been previously heat-treated at a temperature equal to or higher than the melting point and then finely pulverized as means for forming pores. (Japanese Patent Laid-Open No. 52-85246)
issue).

[0006]

However, sliding surfaces such as bed portions of machine tools such as surface grinders and cylindrical grinders reciprocate at low speed under oil lubrication, and have stable low friction characteristics. In order to obtain it, it is necessary to form a stable oil film, but there is a problem that the compounding of the fibrous filler is not sufficient. A PTFE resin composition containing polyoxybenzoyl or polyphenylene sulfide alone or in a mixture having a relatively spherical shape can form a stable oil film, but bears a load because the organic filler is a viscoelastic material. The role is insufficient, the effect on creep resistance is small, and if the amount is too large, there is a problem that the sheet material cracks. In addition, when porous bronze is used, the role of bearing the load is sufficient and the wear resistance is improved.However, if the amount of bronze is increased to obtain low friction characteristics, the elasticity of the sheet material increases. is there. When holes are formed by adding PTFE resin powder that has been heat-treated and finely pulverized, the elasticity of the sheet material decreases, but the holes increase the mechanical strength and elongation, and the sheet material has a thickness of 1 mm or less. Then, there is a problem such as breaking due to insufficient strength. In addition, there is a problem that creep resistance and wear resistance are also reduced.

[0007] In recent years, the properties required for sheet materials include:
There is a need for a sheet material that has good workability when bonding the sheet material to the bed portion of the machine tool and is soft and has good cutting properties. When a molded article of the PTFE resin composition is processed into a sheet by machining such as cutting, the sheet material more or less undulates. Therefore, if the sheet material is hard, it is difficult to handle at the time of bonding and it is difficult to correct the undulation, so that uneven bonding is caused and unevenness is formed on the sliding surface. Sometimes, problems such as peeling off occur. In addition, if the cutting property is poor, it is difficult to cut the sheet material after bonding and to perform the work for fitting to the end surface of the bed.

SUMMARY OF THE INVENTION The present invention has been made to address such a problem, and a resin for a sliding member excellent in low friction, abrasion resistance, creep resistance, low elasticity and bonding workability under oil lubrication. An object is to provide a composition and a sliding member.

[0009]

Means for Solving the Problems The resin composition for a sliding member of the present invention comprises 25 to 90 parts by volume of a PTFE resin and 2 to 150 μm.
It is characterized by comprising 5 to 40 parts by volume of the following metal powder and 5 to 35 parts by volume of a powder obtained by pulverizing a molded article of the PTFE resin composition.

Further, the PTFE resin composition is composed of a PTFE resin alone or a PTFE resin containing a non-thermoplastic polyimide resin, and a powder obtained by pulverizing a molded article of the PTFE resin composition has a particle diameter of 250 μm or less. .

The sliding member of the present invention is a sheet-like sliding member used on a sliding surface of a machine tool under oil lubrication. It is characterized by being processed into a shape.

In the resin composition for a sliding member of the present invention,
The metal powder bears the load, improves abrasion resistance and creep resistance, easily falls off when processed into a sheet material, and tends to form a fine hole for retaining lubricating oil. Further, since the powder obtained by pulverizing the molded body of the PTFE resin composition is pressurized and heated at the time of molding, it is dense and does not generate gas at the time of sintering.
The binding property with the E resin is also relatively excellent. Also, PTFE
It is considered that fine voids are formed between the resin and the resin, and the elastic modulus of the sheet material is appropriately reduced, and the variation in mechanical strength and elongation is reduced even when the amount of the material is increased. Further, the creep resistance is improved. Further, since it is relatively spherical and hard, it easily falls off when processed into a sheet material, and a fine hole for holding lubricating oil is easily formed. Combined use with metal powder results in lower friction. As the powder obtained by pulverizing the molded body of the PTFE resin composition, so-called scrap powder or the like can be reused, so that resources can be effectively used and a low-cost resin composition for a sliding member can be obtained.

[0013]

DETAILED DESCRIPTION OF THE INVENTION The PTFE resin according to the present invention
A fluorine resin comprising a homopolymer of TFE,
Any resin can be used as long as it can be softened at 390 ° C. and compression molding and extrusion molding are possible but ordinary injection molding is not possible. For example, fluorine resins commercially available under trade names such as Algoflon (manufactured by Montegisson Incorporated), Teflon (manufactured by Dupont, USA), Fluon (manufactured by ICI of the United Kingdom), and Polyflon (manufactured by Daikin Industries, Ltd.) Can be mentioned. Further, in the present invention, powdery ones are preferable because they are easily mixed homogeneously.

The metal powder according to the present invention is preferably a metal powder having a hardness equal to or less than that of cast iron (Mohs hardness: 4) in a machine tool or the like. This is preferred because it is less likely to cause damage. On the other hand, the lower the hardness, the lower the wear resistance.
Metal powder having a hardness of about 3 to 4 is preferred. Examples of such metal powder include copper (Mohs hardness: 3.0) and copper alloy powder, nickel (Mohs hardness: 3.5) and nickel alloy powder. Preferred metal powders are
Copper and copper alloy powder. In particular, bronze, which is a copper alloy of a copper-tin type, a copper-aluminum type, a copper-silicon type, or the like, is most preferable in terms of hardness and spheroidization. The content of copper in bronze is not particularly limited. Further, as a method for producing the bronze powder, a method such as an atomizing method, an electrolytic method, and a mechanical pulverizing method can be adopted.
Metal powder such as bronze powder preferably has a spherical shape. In the case of an irregular shape other than a spherical shape, a square shape, or the like, it is difficult to form a hole for retaining oil, and the filler is oriented in various directions and a stable oil film cannot be formed. Further, the elastic modulus of the sheet material increases.

The particle size of the metal powder is 2 to 150 μm, preferably
2 to 75 μm. Metal powders, especially bronze powders, have a high specific gravity.
Uniform dispersion in the E composition becomes difficult, and improvement in properties such as abrasion resistance and creep resistance cannot be expected. Also, 2μm
Even if it is less than that, uniform dispersion becomes difficult.

The powder obtained by pulverizing the molded article of the PTFE resin composition according to the present invention is a powder obtained by pulverizing the molded article which has been pressed and heated at least once. The pressure and heating conditions are substantially the same as the conditions for compression molding the PTFE resin composition, and are not particularly limited. The powder obtained by pulverizing the molded body is used for cutting off the molded body by machining such as turning.
Either a waste material obtained by processing the formed body into a sheet material or a residual material obtained by punching a product from the sheet material may be used. These materials may be used after being crushed using a jet crusher or the like. A commercially available product can be used as a powder obtained by pulverizing the molded body. Commercially available products include recycled Teflon KT300H, KT300M, KT400M and the like (all manufactured by Kitamura Co., Ltd.).

The PTFE resin composition may be PTFE resin alone or PTFE containing non-thermoplastic polyimide resin.
Resin. Here, the non-thermoplastic polyimide resin is
An aromatic polyimide resin that can be compression-molded but cannot be injection-molded normally. Specific examples include P84 manufactured by Ranging Co., UIP-S and UIP-R manufactured by Ube Industries, and TI-3000 manufactured by Toray Industries, Inc. The compounding ratio of the non-thermoplastic polyimide resin can be used as long as it can be molded as a PTFE resin composition. The preferred range of moldability is PTFE resin 100
The volume is 3 to 50 parts by volume. A PTFE resin containing a non-thermoplastic polyimide resin is preferable because it has better creep resistance than a PTFE resin alone.

The particle size of the powder obtained by grinding the compact is 250 μm
Hereafter, it is preferable to pulverize so as to have a size of 100 μm or less. For sizes over 250 μm, PTFE
It is not preferable because it is difficult to uniformly disperse in the inside and the density of the molded body is reduced due to the formation of seat holes, so that mechanical strength and elongation are largely dispersed, and abrasion resistance and creep resistance are also reduced. If the particle size is less than 5 μm, the effect of lowering the elastic modulus of the sheet material and the effect of lowering the friction are poor, so the particle size is preferably 5 μm or more.

The mixing ratio in the resin composition for a sliding member of the present invention will be described. The volume part can be easily converted to the weight part by multiplying by the specific gravity. The PTFE resin is 25 to 90 parts by volume, preferably 40 to 80 parts by volume. The metal powder is 5 to 40 parts by volume, preferably 10 to 30 parts by volume. The powder obtained by pulverizing the molded body of the PTFE resin composition is 5 to 35 parts by volume, preferably 10 to 30 parts by volume. If the metal powder is less than 5 parts by volume, it is difficult to improve the wear resistance and creep resistance of the resin composition for sliding members. Workability at the time may be reduced. Also, if the powder obtained by pulverizing the compact is less than 5 parts by volume, the desired predetermined frictional characteristics and a soft sheet material cannot be obtained. Variations in strength and elongation are large, and wear resistance, creep resistance and the like are also reduced.

It is to be noted that pigments such as titanium oxide, carbon, iron oxide, chromium oxide and cobalt blue can be added within a range not to impair the object of the present invention.

The sliding member of the present invention can be obtained by molding the above resin composition for a sliding member and then processing the resin composition into a sheet. The means for mixing the raw materials in the resin composition is not particularly limited, and for example, dry mixing can be performed using a mixer such as a Henschel mixer, a ball mixer, a Loedige mixer or the like. The molding method is generally PTFE
The method used for the resin composition can be used. For example, a free baking method, a hot molding method in which a batch type compression molding is performed while applying heat and pressure, a ram extrusion molding method, and the like can be given. The atmosphere during molding is
Any of air, nitrogen, or an inert gas such as argon or helium may be used. Explaining the free baking method, the PTFE resin composition powder is put into a mold, pre-molded by applying a pressure of 40 to 100 MPa, and then the compression molded body taken out from the mold is fired at 360 to 380 ° C. Thus, a molded product is obtained. As a method of processing into a sheet shape, it is possible to directly form a sheet material, but it is preferable to cut the formed body obtained by the above method.

The sliding member of the present invention can be suitably used for a sliding surface of a machine tool used under oil lubrication. Machine tools include lathes, grinders, milling machines, boring machines, NC lathes, NC grinding machines, NC boring machines, NC milling machines, MC, dedicated machine tools (machine tools for processing specific products), drilling machines , Planing machine, shaping machine, standing machine, broaching machine, surface finishing machine, gear grinding machine, gear finishing machine and the like. Among these, lathes, grinding machines, milling machines, boring machines, NC lathes, NC grinding machines, NC boring machines, NC milling machines, MCs with dedicated sliding surfaces such as beds, special machine tools (special products Machine tool).

[0023]

EXAMPLES Raw materials used in Examples and Comparative Examples are collectively shown below. The numbers in parentheses for the raw materials correspond to the raw materials in the table. (1) PTFE resin (PTFE): manufactured by Mitsui-Dupont Fluorochemicals Co .; specific gravity of 7-J, 7-J is 2.15. (2) Bronze (BRO1): manufactured by Fukuda Metal Foil & Powder Co., Ltd .;
Bro-At100 and BRO1 have a spherical shape, a copper-tin composition, a particle size of 149 μm or less, and a specific gravity of 8.76. (3) Bronze (BRO2): manufactured by Fukuda Metal Foil & Powder Industry;
Bro-At350 and BRO2 have a spherical shape, a copper-tin composition, a particle size of 44 μm or less, and a specific gravity of 8.76. (4) Bronze (BRO3): manufactured by Fukuda Metal Foil & Powder Co., Ltd .;
Bro-At-W350 and BRO4 are irregular in shape, the composition is copper-tin, the particle size is 44 μm or less, and the specific gravity is
8.76. (5) A powder obtained by pulverizing a molded article of the PTFE resin composition (P
TFE-S1): PTFE resin scrap powder containing 25 parts by volume of non-thermoplastic polyimide resin, particle size: 246 μm
Below, the specific gravity is 1.98. (6) A powder obtained by pulverizing a molded article of the PTFE resin composition (P
TFE-S2): manufactured by Kitamura Corporation; KT300M, PTFE
-S2 is PTFE resin scrap powder with a particle size of 1
Below 00 μm, the specific gravity is 2.15. (7) Aromatic polyester resin (OBP): manufactured by Sumitomo Chemical Co., Ltd .; Sumika Super 101S, Sumika Super 101
The specific gravity of S is 1.45.

Examples 1 to 7 and Comparative Examples 1 to 7 Raw materials were dry-blended in a Henschel mixer dry mixer at the mixing ratios shown in Tables 1 and 2, and the pressure was reduced to 50 MPa using a press machine. With an outer diameter of 122 mm and an inner diameter of 64
mm, 100 mm height cylindrical preform, and φ30 mm, 100 mm height cylindrical preform are preformed at 370 ° C.
Fired for 4 hours. A sheet material having a thickness of 1 mm was obtained by skiving using the fired cylindrical element material. From this sheet material, a friction and wear test piece having a length of 30 mm and a width of 30 mm and a tensile test piece were punched out with a punch. In addition, using the calcined cylindrical material, cutting 12.7mm long, 12.7mm wide
A 12.7 mm high test piece for compression creep was prepared.

Using the test pieces described above, the dynamic friction coefficient, specific wear, compression creep, tensile strength, elongation, and sheet softness were measured and evaluated by the following methods. The results are shown in Tables 1 and 2, respectively. The coefficient of kinetic friction and the specific abrasion were measured using a reciprocating test machine under the lubrication of oil (tona oil manufactured by Showa Shell Sekiyu KK) under lubrication with an induction-hardened mehanite cast iron (FC35) at a sliding speed of 30 / mi.
n, a load of 0.5 MPa and a stroke of ± 100 mm were used for 100 hours. Then, the dynamic friction coefficient immediately before the end of the test and the specific wear amount (× 10 ⁻⁸ mm ³ / (N · m)) of the resin test piece were measured.

The compression creep test was performed according to ASTM-D621.
In accordance with, compression was performed at room temperature at a surface pressure of 13.7 MPa, and the compression creep deformation rate (%) after 24 hours was measured. Tensile strength and elongation were measured in accordance with ASTM-D1708. The softness of the sheet material is as follows: When the sheet material is bonded to the bed part of the machine tool, the softness that does not cause uneven bonding is good (O). Was evaluated as normal (△), and the case where the sheet material was hard and there was a strong possibility that uneven adhesion was generated was evaluated as poor (×).

Comparative Examples 8 and 9 PTFE powder was heat-treated in an electric furnace at 370 ° C. for 4 hours, and then pulverized. A test piece was prepared using this heat-treated and pulverized PTFE powder under the same conditions as in Example 1 except for the mixing ratio shown in Table 2, and the same measurement and evaluation as in Example 1 were performed. Table 2 shows the results.

[0028]

[Table 1]

[Table 2]

Each of the examples shown in Table 1 was excellent in the softness of the sheet material, and exhibited low friction characteristics and abrasion resistance which were stable in oil, as compared with the comparative examples shown in Table 2. Further, the sheet material had no problem in tensile strength and elongation, and exhibited excellent creep resistance. On the other hand, each comparative example shown in Table 2 was inferior as the resin composition for a sliding member and the sliding member as compared with each of the examples. For example, Comparative Example 3, which contains a powder obtained by pulverizing a molded article of the PTFE resin composition but does not contain a predetermined spherical metal powder, has a high coefficient of kinetic friction and a hard sheet material. Further, Comparative Examples 6 and 7 in which a powder obtained by pulverizing a compact of the spherical metal powder and the PTFE resin composition were inferior in wear resistance, tensile strength and elongation.
Comparative Examples 8 and 9 in which PTFE powder heat-treated and ground were mixed instead of powder obtained by pulverizing the molded body of the PTFE resin composition, were soft sheet materials, but were inferior in wear resistance and creep resistance. Was. Comparative Example 2 in which a powder obtained by pulverizing a molded body of the PTFE resin composition was not blended, and only spherical metal powder was blended, and Comparative Example 1 in which irregular-shaped metal powder was blended, were soft sheet materials. Was not obtained, and the wear resistance was poor. Comparative Examples 4 and 5, in which an aromatic polyester resin was blended in place of the powder obtained by pulverizing a molded article of the PTFE resin composition, were inferior in creep resistance, tensile strength, and elongation.

[0030]

The resin composition for a sliding member according to the present invention comprises PT
FE resin 25 to 90 parts by volume, 2 to 150 μm metal powder 5 to
40 volume parts, 5 to 35 volume parts of powder obtained by pulverizing a molded article of the PTFE resin composition, when used on the sliding surface of a machine tool that reciprocates under oil lubrication, has low friction characteristics.
Excellent in abrasion resistance and creep resistance, and a very soft molded product can be obtained when processed into a sheet.

Further, since the PTFE resin composition is composed of a PTFE resin alone or a PTFE resin containing a non-thermoplastic polyimide resin and has a particle diameter of 250 μm or less, the above-mentioned characteristics are further improved. Also, resources can be reused.

The sliding member of the present invention is a sheet-shaped sliding member used under oil lubrication on a sliding surface of a machine tool. The above-described resin composition for a sliding member is processed into a sheet shape. Therefore, it is easy to handle when bonding to the bed surface of the machine tool, and uneven bonding cannot be achieved. As a result, the occurrence of stick slip or the like is suppressed, and the processing accuracy of the product is improved.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 79:08)

Claims (3)

[Claims] 1. Polytetrafluoroethylene resin 25
A resin composition for a sliding member comprising 90 parts by volume, 5 to 40 parts by volume of a metal powder of 2 to 150 μm, and 5 to 35 parts by volume of a powder obtained by pulverizing a molded article of a polytetrafluoroethylene resin composition. 2. The polytetrafluoroethylene resin composition is composed of a polytetrafluoroethylene resin alone or a polytetrafluoroethylene resin containing a non-thermoplastic polyimide resin.
The resin composition for a sliding member according to claim 1, wherein the thickness is 250 µm or less. 3. A sheet-like sliding member used under oil lubrication on a sliding surface of a machine tool, wherein said sliding member is provided.
A sliding member obtained by processing the resin composition for a sliding member according to claim 2 into a sheet.