JP3509564B2 - Lubricating rubber composition - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a lubricating rubber composition.

[0002]

2. Description of the Related Art Acrylonitrile butadiene rubber (hereinafter referred to as NBR) is one of those often used as a material for general rubber parts. And especially famous as oil resistant rubber, for general industry, military, space,
It is used for sealing applications and vibration absorption applications in fields such as consumer and medical fields. There are many applications that also function as sliding, and most of them are used in combination with oil or grease.

For example, in the case of sealing parts, conventionally, the material has been selected only to the extent that the elasticity is selected by the amount of nitrile or the hardness is selected by the filler ratio, considering only the sealing property. Therefore, heat is generated by the shearing force generated in the seal / sliding part, oil and grease are discharged, stick slip occurs, and normal operation is not stabilized, or abnormal noise occurs, which is a problem. ing. Worst of all, wear progresses and tears
Some were damaged and had to be replaced in a short period of time.

For example, general oil seals around automobile / motorcycle oil, oil supply system oil seals, air supply / exhaust system seals, air conditioner system coolant seals, wiper blades, glass runs, toner peripheral seals of electronic copying machines for office equipment, Toner blade, seal for switching valve of cup juice vending machine, seal for household water purifier / mixing tap, seal for switching valve of general production line, seal for bread / mochi kneading machine, butterfly valve for tap water / sewage There are many such as seals and medical syringe piston seals.

As a measure for lowering friction and imparting wear resistance, a diene-based synthetic rubber having a Teflon sheet attached to the seal / sliding surface of the seal portion has been adopted (Japanese Patent Publication No. 46-23681). Description). However, since it is exposed to a high pressure for a long period of time, peeling of the adhesive portion is a problem. Further, since the sliding surface is not an elastic body, the sealing property is not sufficiently satisfied.

[0006] To provide the sealing property and the low friction property,
A type in which a diene rubber base material was impregnated with oil was also examined, but the oil was discharged over time, and the sliding resistance gradually increased, causing problems such as stick-slip and damage. Teflon coating on the surface of the seal part was also tried, but there was a problem of heat resistance of the rubber base material against the baking conditions of the coating film, and the wear resistance was not sufficient in the usable class. In addition, the film does not have sufficient followability to the base rubber substrate, and the film peels off due to stretching and movement during attachment of parts. Further, a chemical solution treatment or a plasma treatment with a chlorine-based solvent, which is carried out with a wiper blade or the like, has been devised, but none of them is sufficient.

Fusion of an olefinic polymer to the seal portion as in the invention described in Japanese Patent Publication No. 57-32950 was also investigated, but the sealing property was lost and it could not be used. Many commonly known solid lubricants such as Teflon and silicone are added to diene rubber to give low friction properties, and many have been invented. Low friction was achieved,
The addition of these materials resulted in high hardness and insufficient sealing properties, and they were not usable. Further, since the wettability with the rubber substrate is poor, the tensile strength and the tear strength are extremely lowered, and the abrasion resistance is inferior to that of the conventional product. Silicone rubber and fluororubber were also targeted, but no significant significance was observed.

[0008]

Therefore, in any of the applications, there is a demand for a lubricating rubber material which has excellent static and dynamic friction characteristics, excellent wear resistance characteristics and a long service life and can be used reliably. An object is to provide a lubricating rubber composition that can meet this demand.

[0009]

In order to solve the above-mentioned problems, the present invention adopts a constitution in which NBR and tetrafluoroethylene resin powder having a carbon material stuck on the surface thereof are mixed. The details will be described below.

First, NBR in the present invention can be exemplified by a wide range of compounds as long as they are synthesized by various organic synthesis methods and have rubber-like elasticity at room temperature. This NB
The molecular weight of R is usually preferably 50,000 or more, and as high a molecular weight as possible gives good results. Therefore, the molecular weight of R is more preferably 70,000 or more, particularly preferably 100,000 to 500,000. . As a typical example corresponding to the above conditions,
Japan Synthetic Rubber Co., Ltd .: JSR-N, Nippon Zeon Co., Ltd .: NI
POL, manufactured by Goodyear Co., Ltd .: CHEMIGUM can be exemplified.

The tetrafluoroethylene resin having the carbon material stuck to the surface is, for example, a tetrafluoroethylene resin having the carbon material stuck to the surface after coprecipitation with the carbon material at the end of emulsion polymerization, coagulation, washing and drying. is there.

A carbon material may be mixed with the tetrafluoroethylene resin powder by dry mixing and the surface may be pierced with the carbon material. It should be noted that this carbon material is a powdered material from general carbon powder to graphite, particularly graphite is preferable, and HAF carbon, SAF carbon, MT having a large structure which is generally used for a rubber substrate. You may use together with carbon etc.

As shown in FIG. 1, since graphite 2 is pierced in all directions in tetrafluoroethylene resin (indicated as PTFE in the figure) 1, a physical pile effect in rubber base material 3 is obtained. Therefore, it is considered that a material having higher strength than that obtained by simply kneading the rubber base material and the tetrafluoroethylene resin is obtained due to the affinity of the rubber base material and graphite.

In the present invention, the weight ratio of NBR to tetrafluoroethylene resin is preferably 10 parts by weight or more and less than 140 parts by weight with respect to 100 parts by weight of NBR. If the amount of the tetrafluoroethylene resin is less than 10 parts by weight, the NBR cannot be provided with sufficient friction characteristics. On the contrary, when it exceeds 140 parts by weight, the rubber hardness becomes high, the rubber characteristic is lost, and the mechanical strength is extremely lowered, so that it cannot be used in actual use.

Known additives as listed below may be added within the range not impairing the object of the present invention. (1) Reinforcing agent For example, carbon black, silica, clay, calcium carbonate, magnesium hydroxide, aluminum hydroxide, aluminum oxide, talc, mica, kaolin, bentonite, shirasu, wollastonite, silicon carbide, glass powder, carbon powder , Boron fiber, aramid fiber, etc. (2) Vulcanization aid, for example, zinc white, fatty acid, magnesium oxide, etc. (3) Vulcanization accelerator, for example, guanidines, sulfurs, aldehyde-amines, zinc salts, etc. (4) Plasticizers, for example, dimethyl phthalate, dioctyl phthalate, etc. (5) Anti-aging agents, for example, amines, phenols, etc. (6) Vulcanizing agents, for example, sulfur, sulfur compounds, peroxides, etc. (7) Softeners, for example, mineral oil , Vegetable oil, etc. (8) Flame retardant (9) Colorant The method of kneading the above various raw materials is not particularly limited, and is generally widely used. For example, NBR as a main raw material and other fillers may be individually or sequentially or simultaneously mixed with a roll mixer, a propeller mixer, a kneader mixer, a twin-screw melt mixer, or another mixer. Also,
At this time, it is desirable to install a temperature controller to prevent heat generation due to friction. Further, when a roll mixer is used, it is preferable to carry out thin-threading as finishing mixing.

[0016]

The lubricating rubber composition according to the present invention comprises the acrylonitrile butadiene rubber constituting the rubber base material and the tetrafluoroethylene resin powder having the carbon material pierced on the surface thereof mixed therein. The mixed state of the base material and the tetrafluoroethylene resin is maintained.

[0017]

EXAMPLES The present invention will now be described in more detail by way of examples. First, the basic composition of acrylonitrile butadiene rubber (first essential component) and other materials used in Examples and Comparative Examples are shown below. (1) Acrylonitrile butadiene rubber (NBR: 1st essential component) Pure NBR (Nitrile amount 31-35%) JSR 230S 100 parts by weight Japan Synthetic Rubber Co., Ltd. Stearic acid General industrial material 1 part by weight Carbon HAF 30 parts by weight Vulcanization acceleration Agent (1) Ouchi Shinko Chemical Co., Ltd. TT 2 parts by weight Vulcanization accelerator (2) Ouchi Shinko Chemical Co., Ltd. M 2 parts by weight Plasticizer DOP 10 parts by weight Zinc oxide General industrial materials 1 part by weight Vulcanizing agent Sulfur 0.5 parts by weight (2) PTFE powder (PTFE / GR) with carbon material pierced It is obtained by co-precipitation with graphite having an average particle size of 6 μm, coagulation and washing after completion of polymerization by emulsion polymerization. is there.

(3) PTFE PTFE Lubricant L169 manufactured by Asahi Glass Co., Ltd.
.

Example 1 First, the roll interval is 5 to 10 m.
Wrap pure NBR around a roll mixer adjusted to about m,
Various compounding materials were mixed in the composition of the first essential component described above, and finally the PTFE powder with the carbon material pierced was kneaded at the compounding ratio shown in Table 1.

The mixing ratios shown in Table 1 are the filling ratios (parts by weight) with respect to 100 parts by weight of NBR of the basic composition which is the first essential component.

After that, the roll interval was adjusted to 1 mm and thin threading was performed 10 times. For the purpose of preventing frictional heat at this time, cooling water was constantly passed through the roll to keep the roll temperature at 60 degrees or less.

Next, the cooling water was stopped and steam was passed through the roll to adjust the rubber temperature to 70 ° C. or higher and 90 ° C. or lower, and then the roll interval was narrowed to 1 mm to perform thin threading 1
This was repeated 0 times to obtain a compound of 10 kg each.

300m in height for this compound
m, width 300 mm, thickness 1 mm, using press molding, primary vulcanization (150 ° C., 10 minutes, press pressure 35
kgf / cm ² ) and secondary vulcanization (free heating, 180
(5 ° C., 5 hours) was performed, and the friction / wear characteristics and elastic body characteristics of each vulcanized sheet were determined. Each test method is as follows.

(1) Friction / Abrasion Characteristic Test The obtained sheet was punched into a ring shape of φ17 × φ21 (mm) and bonded to an aluminum alloy ring of φ17 × φ21 × 10 (mm) to obtain a friction test piece. . The mating material was a bearing steel (SUJ2) polished product, and evaluated by a thrust type friction wear test. The test conditions are a peripheral speed of 1.0 m / min and a surface pressure of 3.
It is 0 kgf / cm ² and time is 100 h. The obtained results are shown in Table 1.

(2) Non-adhesion Property Test The contact angle of water of the obtained test piece was measured by a goniometer type contact angle measuring device, and it was judged that the larger the contact angle, the better the non-adhesion property. The obtained results are shown in Table 1.

(3) Elastic body characteristic test The obtained test piece is compliant with JIS-K6301,
The tensile strength, elongation and hardness (JIS-A) were investigated.
The obtained results are shown in Table 1.

[0027]

[Table 1]

[Comparative Examples 1 and 2] PTFE / G in Example 1
R was not compounded (Comparative Example 1), or PTFE
In the same manner as in Example 1 except that PTFE powder was blended in the ratio shown in Table 1 in place of / GR (Comparative Example 2),
A test piece was prepared by performing mixing, sheet forming and vulcanization.
Then, the test method was performed in the same manner as in Example 1 to evaluate the friction / wear characteristics and the elastic body characteristics, and the results are also shown in Table 1.

As is clear from the results shown in Table 1, NBR
Comparative Example 2 in which the PTFE powder was added to Example 1 had a lower friction coefficient than Comparative Example 1 in which the PTFE powder was not added, but the wear characteristics deteriorated.

On the other hand, Example 1 in which NBR was compounded with PTFE / GR in which the carbon material was pierced on the surface of PTFE powder had a low friction comparable to the case of compounding PTFE powder (Comparative Example 2). The coefficient is retained and the friction characteristics are excellent, and the abrasion characteristics are almost the same as those of Comparative Example 1 in which the PTFE powder is not mixed, and the abrasion resistance is sufficient as well as the general physical properties of NBR. Was confirmed.

[0031]

As described above, the lubricating rubber composition according to the present invention has sufficient rubber properties as an NBR material, but is excellent in low friction coefficient and wear resistance.
Therefore, there is an advantage that it can be grease-less as a sealing component and the like and is excellent in stability and reliability for a long period of time.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an example.

[Explanation of symbols]

1 PTFE 2 graphite 3 rubber base material

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Claims (2)

(57) [Claims] 1. A first essential component is acrylonitrile butadiene rubber, a second essential component is a tetrafluoroethylene resin powder having a carbon material pierced on its surface, and the second essential component is 100 parts by weight of the first essential component. The lubricating rubber composition has a blending ratio of 10 parts by weight or more and less than 140 parts by weight. 2. The second essential component is a tetrafluoroethylene resin powder in which the carbon material is pierced on the surface by coprecipitating the tetrafluoroethylene resin after the completion of emulsion polymerization with the carbon material. The lubricating rubber composition according to 1.