JPH0124811B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for surface treatment of molded rubber materials. More specifically, the present invention relates to a method for surface treatment of a fluororubber molding material having improved surface properties. [Prior Art] Various proposals have been made to improve the surface properties of molded rubber materials, such as reducing surface friction resistance, imparting solvent resistance, water repellency or ozone resistance, and reducing tackiness. For individual purposes such as removal, sulfur chloride solution (Japanese Patent Publication No. 26-134,
No. 35-4608), peracetic acid solution (No. 36-190), chlorine gas, bromine gas or sodium sulfonate solution (No. 37-3807), aqueous alkali solution (No. 45-34706), alkyl Hypohalide (Japanese Patent Publication No. 50-27503), bromine or iodine and peroxodisulfuric acid (Japanese Patent Publication No. 53-27751), antimony pentafluoride (Japanese Patent Publication No. 50-23483), polyamine (Japanese Patent Publication No. 51-55379) ), polyorganosiloxane (Publication No. 54-90375) or graphite (Publication No. 54-90375),
Various chemicals such as heat (Publication No. 51-30883) or ultraviolet rays (Publication No. 54-22482),
57576) and other methods have been proposed. However, in many of these methods, the rubber surface becomes hard when treated with various chemicals, so when used for sliding parts, minute cracks occur on the surface, and in the worst case, the rubber surface becomes hard. There are various disadvantages such as the surface loses its rubber elasticity and large cracks occur in the molding material. Moreover, since the depth of the treatment is shallow in the graphite treatment and the ultraviolet treatment, there is a drawback that it cannot withstand long-term use. In the treatment method using antimony pentafluoride, antimony pentafluoride is used as a mixed air stream with an inert carrier gas, and after treatment, the treatment is sequentially washed with an aqueous alkali metal carbonate solution and water.
The surface condition of most rubber materials treated in this way is improved, but in the case of chemically stable rubbers such as fluorocarbon rubber, the surface treatment not only hardly progresses, but Since a compound of antimony, which is a toxic element, is used, it poses undesirable problems such as problems in the preparation of the working environment and wastewater treatment. [Problems to be Solved by the Invention] When a molded rubber material is used as a sliding material for oil seals, O-rings, etc., it is necessary to maintain good rubber elasticity while also having low frictional resistance on the surface and chemical resistance. It is required to have excellent durability and oil resistance. Furthermore, it is also necessary that it does not cause problems such as environmental destruction. As a result of various studies on surface treatment methods for molded rubber materials that meet all of these requirements, the inventors of the present invention have found that in the method using antimony pentafluoride, a more reactive surface treatment method can be used instead of antimony pentafluoride. It has been discovered that these problems can be solved by using elementary gas (Japanese Patent Application Laid-open No. 57641/1983). Fluorine gas used as a surface treatment agent can be used alone or as a mixed gas diluted to about 100 times with an inert carrier gas such as helium, argon, nitrogen, carbon tetrafluoride, or sulfur hexafluoride. , under pressure conditions of normal pressure to increased pressure (~about 20 atmospheres) or reduced pressure (~about 1/100 atmospheres),
Preferably it is used as a circulated air stream. A temperature condition of 10 to 150°C, preferably 20 to 100°C is adopted. However, in the case of fluorine gas treatment of fluorine rubber molding materials, it has been found that surface treatment does not proceed easily at such treatment temperatures, and therefore requires a very long time or the use of high concentration fluorine gas. .
An object of the present invention is to solve this new problem. [Means for solving the problem] Therefore, the present inventor developed a fluoro rubber molding material.
The desired surface treatment of the molded rubber material is carried out by maintaining it in a fluorine gas atmosphere filled in a processing container, preferably in a fluorine gas atmosphere diluted with an inert gas, at a temperature of 155 to 250 °C. conduct,
We were able to achieve our intended purpose. If the treatment temperature is higher than this, the fluorination treatment will proceed excessively and the rubber-like properties of the surface of the molded rubber material will be lost. On the other hand, if the processing temperature is lower than this, the intended purpose of the present invention cannot be achieved. Examples of fluororubber molding materials treated at such temperatures include vinylidene fluoride-hexafluoropropylene copolymer rubber, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene ternary copolymer rubber, and trifluorochloroethylene-tetrafluoroethylene ternary copolymer rubber.
Various fluoro rubbers such as hexafluoropropylene copolymer rubber are blended with vulcanizing agents and other compounding agents, such as fillers, reinforcing agents, softeners, plasticizers, anti-aging agents, processing aids, etc. as necessary. This is a vulcanized molded product of a fluoro rubber compound. Fluorine gas treatment is carried out under the pressure conditions mentioned above.
It is carried out using fluorine gas diluted with an inert gas at a temperature of 155 to 250°C, preferably 155 to 220°C, more preferably 180 to 200°C, and the dilution ratio is about 1% or more, preferably The fluorine gas concentration is preferably about 10 to 50% from the viewpoint of handling and reactivity. Further, at this time, it is preferable that the metal fluoride is present as a hydrogen fluoride adsorbent. The fluorine rubber molding material whose surface has been treated with fluorine gas is immediately immersed in an aqueous alkali metal carbonate solution to be cleaned in order to remove the fluorine gas adhering to its surface. As the alkali metal carbonate, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, etc. are used in the form of an aqueous solution with a concentration of about 5 to 20%. The immersion treatment is carried out at a temperature of about 10 to 100° C. for about 5 to 30 minutes, preferably about 10 to 15 minutes, followed by washing with water for about 10 to 15 minutes and drying under warm air. [Effects of the Invention] The fluororubber molding material treated in this way has surface properties such as tackiness and frictional resistance that are effectively improved without impairing the inherent properties of fluororubber. . Next, the present invention will be explained with reference to examples. [Example] Example 1 In a cylindrical stainless steel reaction vessel with an inner diameter of 80 mm and a length of 300 mm, a fluororubber compound (approximately 75 mol% vinylidene fluoride-approximately 25 mol% hexafluoropropylene copolymer rubber) was added as a filler. 5 relief valves molded from 25 phr MT carbon black) and about 10 g of pelletized sodium fluoride for absorbing hydrogen fluoride gas were added, and fluorine gas diluted to 1/3 concentration with nitrogen gas was added. Fill with a pressure of approximately 1 atmosphere. After treating in this state at 180°C for 4 hours, the relief valve is taken out, washed with a 10% aqueous sodium carbonate solution and running water for 10 minutes each, and dried. The relief valve treated with fluorine gas in this manner had a uniform surface, with no cracks observed in appearance, and a clear decrease in tackiness to the touch. The treated relief valve has a half-cut cross section as shown in Figure 1, where 1 indicates the SUS304 part and 2 indicates the fluoro rubber part, with a diameter of 28 mm.
A hole 3 with a diameter of 4.1 mm is bored in the SUS part, and the fluoro rubber part has an inner diameter of 20 mm and an outer diameter of 29 mm. The fluorine gas treatment relief valve 4 was adjusted using a test device as shown in the schematic diagram in FIG. 2 by using a handle 5 and held down by a spring 6 so as to open at a pressure of 80 mmHg, and then left as it was. Leave it in a constant temperature bath at 150℃ for 50 hours.
When the opening and closing pressures of the valves were measured using a compressed air line 7 equipped with a pressure gauge and a control valve (none of which are shown), all five relief valves opened at 430 mmHg. In addition, since the product without surface treatment opens and closes at 540 mmHg, it can be seen that the fluorine gas treatment improves the adhesion of the surface of the fluorine rubber molded product. Example 2 In Example 1, the treatment temperature with the diluted fluorine gas was varied, and the opening and closing pressures at which all five of the treated relief valves opened were measured. The results obtained are shown in the following table. 【table】

[Brief explanation of drawings]

FIG. 1 shows a half-cut cross-section of the relief valve treated with fluorine gas in Example 1, where the reference numeral 1 indicates
2 indicates the SUS part, and 2 indicates the fluoro rubber part. FIG. 2 is a schematic diagram of a test apparatus for measuring the surface tackiness of these fluorine gas-treated relief valves, in which reference numeral 4 indicates a relief valve, and 5
indicates the handle, 6 indicates the spring, and 7 indicates the compressed air line.

Claims (1)

[Scope of Claims] 1. A method for surface treatment of a molded rubber material, which comprises maintaining the fluorine rubber molding material in a fluorine gas atmosphere filled in a processing container at a temperature of 155 to 250°C. 2. The surface treatment method for a molded rubber material according to claim 1, wherein the molded rubber material is maintained in a fluorine gas atmosphere diluted with an inert gas. 3. A method for surface treatment of a molded rubber material according to claim 1, which is applied to a fluororubber molded material used as a sliding material.