JPH0160177B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for surface treatment of molded rubber materials. More specifically, the present invention relates to a method for treating the surface of a molded rubber material, which comprises treating the surface of the molded rubber material with fluorine gas.

Conventionally, many proposals have been made for improving the surface properties, particularly the adhesion and friction properties, of molded rubber materials used for various purposes. One of the present inventors previously proposed that the surface of a molded rubber material be treated with fluorine gas as a method for improving the durability of the anti-adhesive and friction-reducing effects on the surface of such materials. It has been proposed that
−131829, No. 55-133542, No. 55-156577,
No. 55-163971, No. 56-23507, No. 56-40576
issue).

In these fluorine gas treatment methods, although the desired effects can be obtained by limiting the treatment conditions, it has been recognized that the following problems generally still exist.

(1) Although the fluorinated layer on the surface of the molded rubber material satisfactorily achieves the objectives of low adhesion and low friction,
The tackiness and friction resistance of the semi-treated layer inside the treated layer are actually increased compared to those of the untreated rubber material (2). Therefore, the durability of the fluorine gas surface treated rubber material is increased. If the material is used, problems of high adhesion and high friction will occur after a certain period of time.The present inventors have investigated various causes of such phenomena by using the fluorine gas in the model rubber material. Surface analysis of the semi-treated layer by X-ray electron spectroscopy confirmed that the oxygen content of this layer was low compared to that of the fluorine gas treated layer.

Based on these facts, apart from theoretical elucidation of how oxygen content affects surface properties, we investigated countermeasures and found that when treating the surface of molded rubber materials with fluorine gas, It has been found that treatment in the coexistence of generated compounds or oxygen-containing compounds having a vapor pressure of 1 torr or more at 200°C is extremely effective. In other words, in the molded rubber material treated with fluorine gas in this way, when observed under an electron microscope, the layer equivalent to the semi-treated layer has almost completely disappeared, increasing the pass rate in the durability test. This was confirmed.

As the oxygen gas, air or the like can be used in addition to pure oxygen gas, and generally oxygen gas (or equivalent) is used at a ratio of about 5 to 50% to fluorine gas. Oxygen generating compounds include metal fluorides, water, Fe ₂ O ₃ , NiO, CaO,
The oxygen gas generated by compounds such as MgO is generally about 5 to 50% compared to fluorine gas.
used at a rate of These oxygen generating compounds react with fluorine gas to generate oxygen gas as follows.

H ₂ O+2F ₂ →2HF+F ₂ O Δ→2HF+F ₂ +1/2O ₂ MO+F ₂ →MF ₂ +O ₂ (MO: Metal oxide) Among these oxygen-generating compounds, metal fluoride consumes fluorine gas in the system. Particularly preferred because it does not. This is because the degree of surface treatment of rubber materials is
This is because it is often controlled by the total amount of fluorine.

Examples of oxygen-containing compounds that have a vapor pressure of 1 torr or more at 200°C include CO ₂ , COF ₂ , CF ₃ COF, trioxane, etc., and these are generally more sensitive to the oxygen gas generated from these compounds than fluorine gas. is used at a ratio of about 5 to 50%.

As described above, oxygen gas, an oxygen-generating compound, or a specific oxygen-containing compound is used in the proportions described above with respect to fluorine gas, but if the proportion is lower than this, the effects aimed at by the present invention cannot be obtained. On the other hand, fluorination treatment cannot be performed if the amount exceeds this limit.

In the coexistence of these, fluorine gas or a mixed gas of fluorine gas diluted with helium, argon, nitrogen, carbon tetrafluoride, sulfur hexafluoride, etc. is used under normal pressure to increased pressure (~20 atmospheres) or reduced pressure. Lower (~about 1/
The molded rubber material is processed under pressure conditions (100 atmospheres).

The treatment temperature range used is generally from about -20 to 250°C, preferably from about 20 to 250°C. Even within this temperature range, in the case of rubber materials that are particularly susceptible to fluorination, such as natural rubber, isobutylene rubber, and isobrene rubber, which tend to undergo excessive reaction even at room temperature, the temperature range is lower, for example, +5°C to - It is desirable to process at a temperature range of about 20°C.

Molded rubber materials subjected to fluorinated surface treatment include natural rubber, conjugated diene rubbers such as acrylonitrile-butadiene copolymer rubber, styrene-butadiene copolymer rubber, chloroprene rubber, and isoprene rubber, acrylic rubber, and ethylene-propylene rubber.
Various synthetic rubbers such as (diene) copolymer rubber, butyl rubber, epichlorohydrin rubber, chlorosulfonated polyethylene (Hypalon), and fluorocarbon rubber are added with vulcanizing agents and other compounds, such as reinforcing agents, fillers, softeners, and plasticizers. It is a vulcanized molded product of a rubber compound blended with anti-aging agents, processing aids, etc. as necessary, and may be pretreated before surface treatment. In pretreatment, mold release agents, plasticizers, etc. adhering to the surface of the molded product are cleaned with a cleaning agent appropriate for the type of rubber. As the cleaning agent, organic solvents such as tricrene, perchloroethylene, alcohol, and carbon tetrachloride are used, and after cleaning, these organic solvents are thoroughly dried and removed.

Molded rubber materials treated with fluorine gas or a mixture of fluorine gas and an inert gas are immediately immersed in an aqueous solution of alkali metal carbonate and cleaned in order to remove the fluorine gas adhering to the surface. Ru. Examples of aqueous alkali metal carbonate solutions include sodium carbonate, potassium carbonate, sodium hydrogen carbonate,
Potassium hydrogen carbonate is used as an aqueous solution with a hidden degree of about 5 to 20%. The soaking process takes about 10~
At a temperature of 100℃ for about 5-30 minutes, preferably about 10-30 minutes
It is done for 15 minutes, then washed with water for about 10-15 minutes and dried under warm air.

Next, the present invention will be explained with reference to examples.

Example 1 Approximately 350 pieces of fluorine rubber pulp 7 having a centerline cross-sectional shape as shown in FIG.
27.1% by volume, 3.3% by volume of oxygen gas and nitrogen gas
Filled with about 40% mixed gas consisting of 69.6% by volume,
It was treated at 190-200°C for about 4 hours. After treatment, wash the valve with 5% sodium carbonate aqueous solution and water,
Dry.

When the four fluororubber valves were subjected to a durability test (vibration valve opening test) as shown below, 4 valves opened and 0 valves did not open.

[Durability test method]

The interior of the vibrator, which is assembled as shown in the figure and is composed of a metal fitting 1, a case nut 2, a spring guide 3, a poppet seat 4, a coil spring 5, and a poppet holder 6, is pulled to a reduced pressure from the case nut side, and is brought to a certain degree of reduced pressure. When this happens, the pressing force of the coil spring is overcome by atmospheric pressure, and the poppet seat opens, allowing air to flow into it. The valve 7 is fitted into the opening on the poppet seat side of such a vibrator, and with air flowing at 200 rpm, the vibration frequency is 20G in the axial direction of the vibrator, 20G in the radial direction of the vibrator, and 20G in the radial direction of the vibrator. After ¹⁰⁷ vibrations at 200 Hz, activate the valve and check whether it opens or not.

Example 2 In Example 1, the same amount of a mixed gas consisting of 25.0% by volume of fluorine gas, 10.0% by volume of oxygen gas and 65.0% by volume of nitrogen gas was used. As a result of the durability test, 4 valves opened and 0 valves did not open.

Example 3 In Example 1, the same amount of a mixed gas consisting of 31.3% by volume of fluorine gas and 68.7% by volume of nitrogen gas was used, and 6g of Fe ₂ O ₃ was evenly deposited on the wall of the reaction vessel. Gas treatment was performed. As a result of the durability test, 4 valves opened and 0 valves did not open.

Example 4 In Example 1, the same amount of a gas mixture consisting of 29.2% by volume of fluorine gas, 64.2% by volume of nitrogen gas and 6.6% by volume of COF ₂ gas was used. As a result of the durability test, 4 valves opened and 0 valves did not open.

Comparative Example In Example 1, the same amount of a gas mixture consisting of 31.3% by volume of fluorine gas and 68.7% by volume of nitrogen gas was used. As a result of the durability test, two valves opened and two valves did not open.

Electron micrographs showing the surface and cross-sectional structures of the bulbs treated with fluorine gas in Example 1 and Comparative Example are shown in FIGS. 2 to 15.

Figure 2: Valve surface treated with comparative example (500x) Figure 3: Valve surface treated with comparative example (2000x
Figure 4: Cross section of the bulb treated with the comparative example (500x) Figure 5: (2000x) From the bottom left to the top right of Figure 5, it consists of the surface, sticky layer, adhesive layer, and untreated layer. .

Figure 6: Valve surface treated in Example 1 (500
Figure 7: Valve surface treated in Example 1 (2000
Figure 8: Cross section of the valve treated in Example 1 (500
Figure 9: Cross section of the valve treated in Example 1 (2000
From the lower right to the upper left in Figure 9, the surface, mucilage layer, and untreated layer are comprised.

From the comparison between Figures 2 to 5 and Figures 6 to 9, it can be seen that there are more particulate matter on the bulb surface in Example 1 than in Example 1. No adhesive layer was observed.

Figures 10 to 12: Surface or cross section of the bulb corresponding to Figures 3 to 5 after the durability test The upper left part of Figure 12 is the surface, and the other parts are made of adhesive layers.

Figures 13 to 15: Surface or cross section of the bulb corresponding to Figures 7 to 9 after the durability test. From the bottom to the top of Figure 15, it consists of the surface, the sticky layer, and the untreated layer.

From the comparison between Figures 10 to 12 and Figures 13 to 15, it can be seen that after the durability test, the valve surface of the comparative example has almost no undulations, while the valve surface of Example 1 still has particulate matter. I know what's left,
Regarding the cross section of the bulb, it was also observed that the comparative example had no particle layer and was entirely made up of adhesive layers, whereas the one of Example 1 had no adhesive layer and the particle layer had good durability. be done.

[Brief explanation of drawings]

FIG. 1 is a centerline sectional view of the vibrator used in the durability test. In this drawing, 4 is a poppet seat, 5 is a coil spring, and 7 is a poppet seat.
indicates the rubber valve respectively. 2-3 and 4-5 are electron micrographs showing the surface and cross-sectional structure of the bulb treated in the comparative example, respectively. 6-7 and 8-9 are electron micrographs showing the surface and cross-sectional structure of the bulb treated in Example 1, respectively. 10 to 12 are electron micrographs showing the structure of the surface or cross section of the bulb corresponding to FIGS. 3 to 5 after the durability test. Figures 13 to 15 are
9 is an electron micrograph showing the structure of the surface or cross section of the bulb corresponding to FIGS. 7 to 9 after the durability test.

Claims (1)

[Claims] 1 When treating the surface of molded rubber materials with fluorine gas, oxygen gas, oxygen generating compounds or 200℃
A surface treatment method for a molded rubber material, characterized in that the treatment is carried out in the coexistence of an oxygen-containing compound having a vapor pressure of 1 torr or more.