JPH0359938B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is an injection-moldable sliding material that has a high limit PV value and has a very low degree of damage to the mating material, which is made by adding oxybenzoyl polyester and natural flaky graphite to an injection-moldable fluororesin. It is about things. Polytetrafluoroethylene (hereinafter abbreviated as PTFE) has a low coefficient of friction, but its wear resistance and compression creep resistance are significantly inferior. Therefore, various fillers have been studied for application as sliding materials for bearings and the like. Among these fillers, those that do not damage soft metals such as aluminum, SUS, and brass, and also significantly improve the wear resistance of PTFE, include polyimide and oxysilane. Heat-resistant organic fillers such as benzoyl polyester are known. In particular, the filling effect of oxybenzoyl polyester is large;
Filled with PTFE at about 20% by weight, the amount of wear is less than 1/1000 of that of PTFE, the compression creep resistance is greatly improved, and the friction coefficient not only maintains the low value of PTFE but also is stable. It has extremely excellent sliding properties. Of course, even if the mating material is a soft metal such as aluminum, there will be almost no damage, and it can be used even under high PV values (product of pressure applied to the bearing and speed) of 800 to 1000 Kg/cm ² m/min. be. Such a composition is described in Japanese Patent Publication No. 49-27415. However, the method for molding this composition is a very special method in which a preform is molded at room temperature and then sintered in a hot air circulation firing furnace at a high temperature (350 to 370°C) with sufficient temperature control. is taken. Furthermore, since further cutting is required to form the bearing shape, there are problems such as poor productivity and very high costs. On the other hand, when injection moldable fluororesins such as ethylene-tetrafluoroethylene copolymer and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer are filled with oxybenzoyl polyester, PTFE is filled with oxybenzoyl polyester. A similar effect can be obtained in this case. These compositions are described in Japanese Patent Application Laid-Open No. 1973
-115263. However, these injection moldable fluororesins have a lower melting point and lower crystallinity than PTFE, so a composition of injection moldable fluororesin and oxybenzoyl polyester is different from a composition of PTFE and oxybenzoyl polyester. The limit PV value was also considerably lower than that of conventional products, and the range of use was also limited. For example, when applied to piston rings with extremely fast reciprocating cycles or oil-free bearings with extremely small heat dissipation areas, the temperature of the sliding surfaces increases significantly, resulting in a melting phenomenon.
These problems have resulted in canceling out the advantage that injection molding is possible. In order to improve these problems, the present inventors added a mixture of oxybezoyl polyester and natural flaky graphite to injection moldable fluororesin, thereby maintaining the property of not damaging the mating material. However, the present inventors have discovered that the critical PV value is about 1.5 to 2 times higher than that of an injection moldable fluororesin containing only oxybenzoyl polyester. That is, the present inventors added 10 to 100 parts of a mixture of oxybenzoyl polyester and natural flaky graphite in a weight ratio of 90:10 to 40:60 to injection moldable fluororesin. As a result, it maintains the property of not damaging the mating material, and the limit PV value is 1.5 to 1.5 compared to injection moldable fluororesin with only oxybenzoyl polyester added.
They discovered that the range of application could be expanded by improving the performance by about twice as much, leading to the present invention. Oxybenzoyl polyesters that can be used in the present invention generally have repeating units of the following formula (). As a synthesis method for these polyesters, Tokkosho
46-6796 and Japanese Patent Publication No. 47-47870, and a method using a high boiling point solvent as a polymerization medium, as in Japanese Patent Publication No. 54-46287, and Japanese Patent Publication No. 54-46291, there is a method in which a high boiling point solvent is used as a polymerization medium. There is a bulk polymerization method that does not use a solvent, and this method is commercially available under the trade name Econol E101 (manufactured by Sumitomo Chemical Industries). Injection moldable fluororesins that can be used in the present invention include ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polytrichloroethylene copolymer, It includes fluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, etc., but especially ethylene-tetrafluoroethylene copolymer (hereinafter referred to as
(abbreviated as ETFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (hereinafter referred to as
(abbreviated as PFA) is preferred. Examples of commercially available ETFEs include Tefzel 200 (manufactured by Mitsui Fluorochemical) and Aflon COP-C88A (manufactured by Asahi Glass).
and so on. Examples of commercially available PFA include Teflon PFA-340J (manufactured by Mitsui Fluorochemical). The natural flaky graphite that can be used in the present invention is a naturally occurring graphite that mostly contains scales, leaves, and needles in external shape, and has a higher fixed carbon content than natural earthy graphite, and contains SiO ₂ and other substances. Low ash content, heat resistance,
It is extremely superior in terms of electricity, resistance, and lubricity. Furthermore, compared to artificial graphite, it has high crystallinity and is far superior in terms of heat resistance and lubricity. especially
It has a particle size of 300 mesh or less and has a fixed carbon content.
When using 95% or more natural flaky graphite, it is excellent in terms of dispersibility, μ stability, and degree of damage to the mating material, and a high PV value can be stably obtained. Commercially available products include CPB-30-, CPB1000, and CPB.
-3000, CPB-5000 (manufactured by Chuetsu Graphite), etc. The filling amount of the mixture of oxybenzoyl polyester and natural flaky graphite per 100 parts of injection moldable fluororesin is 10 to 100 parts, preferably 20 parts.
~60 copies. If these mixtures are less than 10 parts, the wear resistance of injection moldable fluoroplastics,
If the compression creep resistance is insufficiently improved and the amount exceeds 100 parts, injection molding becomes impossible, or even if injection molding is possible, the product becomes mechanically very brittle. The mixing ratio of oxybenzoyl polyester and natural flaky graphite to be filled into the injection moldable fluororesin is 90:10 to 40:60, preferably 85:
15:50-50:50. Beyond this range, the critical PV value of the composition of injection moldable fluororesin and oxybenzoyl polyester cannot be observed. The composition of the present invention is mixed by dry blending the injection moldable fluororesin, oxybenzoyl polyester, and natural flaky graphite in a mixer such as a Henschel mixer or a super mixer, and then passing the mixture through an extruder to form pellets. However, other methods include roll kneading, kneading with a Banbury mixer, and then pelletizing with a sheet pelletizer. The composition of the present invention is hardly damaged even when the counterpart material, which is found in compositions made of PTFE or injection moldable fluororesin and oxybenzoyl polyester, is a soft metal such as aluminum. It is a sliding material that maintains unique properties and has a critical PV value approximately 1.5 to 2 times higher than a composition made of injection moldable fluororesin and oxybenzoyl polyester, so it can be used even under extremely harsh conditions. It is. Furthermore, unlike compositions mainly composed of PTFE, the composition of the present invention can be manufactured using a general injection molding machine.
Since sliding parts such as bearings, piston rings, and seal rings can be easily molded into their final shapes, they are extremely superior in terms of productivity. The invention will be illustrated by the following examples:
Parts and % represent parts by weight and % by weight unless otherwise specified. Further, the Examples are intended to illustrate preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Examples 1 to 5 PFA (Teflon PFA-340J, manufactured by Mitsui Flochemical Co., Ltd.) and oxybenzoyl polyester (Econol E101, manufactured by Sumitomo Chemical Co., Ltd.) having an average particle size of 20μ, and the average particle size of a total of 800 meshes (18μ) pass Natural flaky graphite (CPB-3000, manufactured by Chuetsu Graphite Co., Ltd.) having a diameter of 5 μm was mixed in a Henschel mixer to the composition ratio shown in Table 1, and then mixed at a well-controlled temperature of 360 to 370°C using a 6-inch roll. After kneading the mixture for 10 minutes at a temperature of 100 mL, the mixture was cut using a sheet pelletizer to obtain pellets of 3 to 5 mm square. These were molded using a 1OZ injection molding machine (Neomat 47/28 manufactured by Sumitomo Heavy Industries) to reduce the temperature at the center of the cylinder to 370.
The temperature was set at ~390°C, and a wear ring (outer diameter 25.6 mm, inner diameter 20 mm, height 15 mm) was molded. Using a Suzuki type abrasion tester (manufactured by Toyo Baldwin), pressure P = 10 Kg/cm ² and speed V =
Under the condition of 40m/min, the mating material is aluminum (JIS5052)
The sliding was carried out for two hours. Then P 15Kg/
^cm2 is constant, V is PV=500, 600, 700...Kg/
^cm2 ． m/min at a rate of 100 for 2 hours, the sample will melt, abnormal wear will occur, or the friction coefficient will suddenly become unstable.
When the PV value reached this value, the operation was stopped and the amount of wear on the aluminum material up to this point was measured. These results are summarized in Table 1. As is clear from the table, all of them are 900 to 1200Kg/ ^cm2・m/
It has a high limit PV value of min, and there was almost no wear on the aluminum mating material.

[Table] Regarding the compositions of Example 2 and Example 4,
Under the conditions of P = 15 Kg/cm ² and V = 70 m/min, the mating material was aluminum (JIS5052), and sliding was performed for 20 hours to measure the wear coefficient, the abrasion coefficient, and the amount of wear of the mating material aluminum. These results are shown in Table 2. As is clear from the table, even under such high PV values, good sliding properties were exhibited, and there was almost no wear on the aluminum mating material.

[Table] Examples 6, 7 PFA 100 parts, oxybenzoyl polyester 36
part, natural flaky graphite with a composition ratio of 7 parts, natural flaky graphite with an average particle size of 7μ after 500 meshes (30μ) passes (Chuetsu Graphite Co., Ltd., CPB-1000), and average particle size after 1500 meshes (10μ) passes. The limit PV value was determined in the same manner as in Examples 1 to 5 using two types of 2μ diameter ones (manufactured by Chuetsu Graphite, CPB-5000), and both were 1100 to 1200 Kg/cm ² m/min. There was almost no wear on the aluminum mating material. Furthermore, these were subjected to sliding for 20 hours under the conditions of P=15 Kg/cm ² and V=70 m/min in the same manner as in Examples 1 to 5. These results are shown in Table 3. As is clear from the table, almost the same sliding properties as in Example 4 using CPB-3000 as the natural flaky graphite were obtained. In addition, there was almost no wear on the aluminum mating material.

[Table] Comparative Examples 1 to 4 The compositions shown in Table 4 consisting of PFA and oxybenzoyl polyester, which do not use natural flaky graphite, and PFA alone were tested in the same manner as in Examples 1 to 5 to determine the limit PV. value, and the amount of wear on the mating material aluminum. While PFA alone (Comparative Example 4) suffered significant wear at an initial PV of 400 Kg/cm ² m/min, the limit PV value of all PFA additives with oxybenzoyl polyester improved. However, the value was about 1/2 that of the compositions of Examples 1 to 5 in which natural scaly graphite and oxybenzoyl polyester were added. However, there was almost no wear on the aluminum mating material. These results are summarized in Table 4.

[Table] In addition, sliding was performed on a composition consisting of PFA and oxybenzoyl polyester under the conditions of P = 15 Kg/cm ² and V = 50 m/min in the same manner as in Examples 1 to 5. However, the sample deforms within 2 hours after measurement, causing abnormal wear, and the wear coefficient decreases.
It became unstable at a high value of 0.28 to 0.35. Looking at the sliding surface after measurement, some cracks were seen due to melting.
From these comparative examples, the effect of adding natural flaky graphite is clear. Comparative Example 5 The same procedure as in Examples 1 to 5 was carried out except that the composition was the same as in Example 4, but earthy graphite (AX-600 manufactured by Chuetsu Graphite Co., Ltd.) having a particle size similar to that of CPB-3000 was used instead of natural flaky graphite. The limit PV value and the wear amount of the mating material aluminum were determined, and PV = 600Kg/cm ² . The sample was deformed due to abnormal wear at a speed of m/min. Additionally, the aluminum surface of the mating material was severely damaged. It is thought that SiO ₂ contained in the earthy graphite damaged the mating material. Comparative Example 6 The same procedure as in Examples 1 to 5 was carried out using the same composition as in Example 4, but using artificial graphite (G-10 manufactured by Chuetsu Graphite Co., Ltd.) having the same particle size as CPB-1000 instead of natural flaky graphite. , the limit PV value, and the wear amount of the mating material aluminum were determined. As a result, PV=700Kg/cm ² . The sample deformed at m/min. However, almost no wear was observed on the aluminum surface of the mating material. That is, in the case of artificial graphite, although it did not have an adverse effect like earthy graphite by adding it, the effect was not very noticeable. Examples 8 and 9 ETFE (Tefzel 200, manufactured by Mitsui Fluorochemical Co., Ltd.) and oxybenzoyl polyester (Econol E101, manufactured by Sumitomo Chemical Co., Ltd.) having an average particle size of 20 μm, and a total amount of 800 meshes (18 μ) pass with an average particle size of 5 μm. natural flaky graphite (manufactured by Chuetsu Graphite,
CPB-3000) were mixed using a hexyl mixer to the composition ratio shown in Table 5, and using a twin-screw extruder (PCM-30 manufactured by Ikegu Iron Works), the temperature at the center of the cylinder was adjusted to 300 to 310℃. and extrusion granulation to obtain pellets. Example 1
A wear ring having the same shape as described in 5 to 5 was molded, and the limit PV value,
The amount of wear on the mating material was measured. However, the conditions are that initially the pressure P = 10Kg/cm ² and the speed V = 10m/
Sliding was carried out for 2 hours at min ^.
Assuming that V is constant, PV=200, 300, 400...Kg/cm ²・
The speed was increased by increasing m/min by 100 every 2 hours. These results are shown in Table 5. As is clear from the table, each weighs approximately 700Kg/ ^cm2・m/
It had a limit PV value of min, and there was almost no wear on the aluminum mating material.

[Table] Comparative Examples 7 to 9 For the compositions in Table 6 consisting of ETFE and oxybenzoyl polyester that do not use natural flaky graphite, and ETFE alone, the limit PV value, The limit PV value of ETFE alone (Comparative Example 9), which determined the wear amount of the mating material aluminum, is approximately 200Kg/cm ² m/min.
The limit PV value of ETFE with oxybenzoyl polyester added was improved, but the value was about 1/2 that of the compositions of Examples 8 and 9 in which natural flaky graphite and oxybenzoyl polyester were added. Ta. However, almost no wear on the aluminum material was observed. These results are summarized in Table 6.

[Table] From these comparative examples, the effect of adding natural flaky graphite is clear.

Claims (1)

[Claims] 1. For 100 parts of injection moldable fluororesin,
A mixture of oxybenzoyl polyester and natural flaky graphite in a weight ratio of 90:10 to 40:60
An injection moldable sliding material composition comprising 100 parts. 2. The sliding material composition according to claim 1, which uses natural flaky graphite having a particle size of 300 mesh or less and a fixed carbon content of 95% or more.