JPH0651820B2 - Composite rubber composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a composite rubber composition. For more details,
The present invention relates to a composite rubber composition capable of giving a vulcanized molded article having excellent gas barrier properties.

[Prior Art] and [Problems to be Solved by the Invention] It is known that rubbers generally have poor gas barrier properties and their gas permeability is about 10 to 100 times higher than that of resin. This is thought to be due to the mobility of the molecular order, and the molecular motion of rubber is more active than that of resin (micro Brownian motion). On the other hand, resins are generally hard and have lower flexibility and extensibility than rubber, and thus the gas barrier property and the flexibility and extensibility are shown as properties contradictory to each other.

Therefore, the present inventors, without substantially impairing the flexibility and extensibility, which are preferable properties inherent in rubbers,
As a result of various investigations for a rubber composition capable of imparting a gas barrier property to the vulcanized molded product, as a result, a fluororubber compound containing a compounding agent generally shown in fluororubber was added to a fibrillated polymer porous material. It has been found that such a problem can be effectively solved by using a complex to which a body is added.

[Means for Solving Problems] and [Action] Accordingly, the present invention relates to a composite rubber composition capable of providing a vulcanized molded article having excellent gas barrier properties. The composite rubber composition comprises a compounding agent. And a fibrillated porous body of polytetrafluoroethylene or polychlorotrifluoroethylene.

The compound of the fluororubber to be modified is a compounding agent generally shown in the fluororubber, for example, a reinforcing agent such as carbon black or white carbon, a filler such as calcium carbonate, a plasticizer such as phthalate ester, and naphthylamine. It is prepared by appropriately compounding an antiaging agent such as a compound, a vulcanizing agent such as sulfur, polyamine and organic peroxide, and a compounding agent such as a vulcanization accelerator such as a guanidine compound and a thiuram compound. .

The fibrillated polymer porous material added to such a fluororubber compound is formed from polytetrafluoroethylene (PTFE) or polychlorotrifluoroethylene. The formation of the fibrillated porous body is generally performed by a stretching method using a polymer fine powder having a particle size of μm order as a raw material, and by applying an appropriate shearing force to the fine powder, a lumped portion usually called a connecting portion is formed. A continuous phase consisting of fibril parts is formed.

The compounding by adding the fibrillated polymer porous material to the fluororubber compound is performed in a form in which the fluororubber is filled in the voids of the fibril portion of the continuous phase formed by the fibrillated polymer porous material. For example, taking a combination of fibrillated PTFE and fluororubber as an example, a few methods of compounding will be described as follows.

(1) First, PTFE fine powder (particle size of about 0.1 to 50 μm) is PT of hydrocarbons, halogenated hydrocarbons, ketones, alcohols, etc.
FE is added to a wetting solvent and mixed using a ball mill or the like. This kneaded product is extruded, molded into a sheet by a molding method under shearing conditions such as rolling, and after leaving the solvent as it is or after drying, about 0.
About 30 to 500% is drawn at a drawing speed of 1 to 1000%. While maintaining this stretched state or after stretching, when heated and baked for about several minutes near the softening point or melting point of PTFE (about 310 to 400 ° C), the proportion of voids to about 50 to 90% by volume depending on the stretching ratio. A fibrillated porous body having a high content can be obtained. When such a fibrillated porous material is impregnated with a ketone solution of a fluororubber compound and the solvent is removed, a composition in which the fluororubber is composited in the voids is obtained.

(2) PTFE fine powder in a solution of fluororubber compound, about 10 to 80% PTFE by volume ratio of solid content, about 90% fluororubber compound.
It is added so that the ratio becomes ˜20%, and this is mixed using a ball mill or the like. Thereafter, when the sheet is formed, stretched, and heated and fired in the same manner as in the above (1), the fibrillated porous body is formed and the fluororubber is compounded.

(3) A method in which the fluororubber compound is wound around a roll, and the PTFE fine powder is gradually added to the roll in the same manner as in a normal roll kneading method to simultaneously form a fibrillated porous body and compound it. This method has the advantage of being easier to operate than the above two methods. However, be careful that if too much shear force is applied when mixing the PTFE fine powder, the PTFE may clump, or even if the volume fraction of the PTFE fine powder becomes approximately 40% or more. Requires.

Among the above methods, in the method (2), the vulcanization of the fluororubber is simultaneously performed at the time of heating and firing, but in the methods (1) and (3), the heat vulcanization of the formed composite composition is performed. Be seen.

(4) To a polyterafluoroethylene or polychlorotrifluoroethylene aqueous suspension or organic solvent dispersion, add a fluororubber formulation while using an organic solvent,
The solvent is removed by, for example, casting the composite rubber composition mixed liquid formed therein, and the obtained composite rubber composition is preformed or extruded and then rolled or stretched to give a fibrillated porous body. Is formed and compounded with fluororubber.

〔The invention's effect〕

The composite rubber composition according to the present invention significantly improves the gas barrier property of the vulcanized molded product without substantially impairing the flexibility and the extensibility, which are desirable properties inherent in the fluororubber, and It is also excellent in its mechanical strength.

Therefore, the composite rubber composition of the present invention cannot be used with fluororubber from the viewpoint of heat resistance, chemical resistance, etc., and is molded into a gasket, packing, etc. used at a place to be sealed with a resin such as polytetrafluoroethylene. Be used effectively. When polytetrafluoroethylene is used as the material for the fibrillated porous material, it can be effectively used for applications requiring thinness and slidability due to its lubricity.

〔Example〕

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

Example 1 500 parts of polytetrafluoroethylene powder (Teflon 6J, a product of Mitsui Fluorochemicals) (weight, hereinafter the same) was mixed with 100 parts of solvent naphtha, and this mixture was mixed with a molding machine at 60 kg /
It was pressurized with a pressure of cm ² for 1 minute and preformed into a square rod shape having a cross section of 50 × 50 mm. Then, using a ram extruder, it was
mm, and a sheet having a thickness of 1 mm was extruded. This sheet, 100
It was cut into a length of 100 mm, 100% stretched at a stretching speed of 1400 mm / min using a stretching machine, and then heat-treated at 340 ° C. for 5 minutes.

The thus obtained polytetrafluoroethylene porous body (porosity 46%) was immersed in a fluororubber solution having the following composition (20 minutes) -drying (using a vacuum dryer, at 50 ° C. for 12 hours. The step of drying) was repeated 3 times to obtain a composite (composition 52/48 by volume ratio) in which fluororubber was impregnated in the polytetrafluoroethylene porous body.

Fluororubber (Viton E60C manufactured by DuPont) 100 parts MgO 4 Ca (OH) ₂ 3 MT Carbon black 15 Methyl ethyl ketone 400 This sheet composite (50 × 100 × 1.3 mm) was vulcanized by heat pressing to obtain Vulcanized sheet (50 x 100 x 1.0 mm)
The attachment to the tensile tester, 20% stress and elongation residual elongation at the initial and 20% elongation of 10 times-performed after a hydrogen gas permeability coefficient P _{H 2} were measured.

Comparative Example 1a A mixture of 500 parts of polytetrafluoroethylene powder (Teflon 6J) and 500 parts of sodium chloride powder was press-molded at 340 ° C. for 5 minutes, and a sheet having a thickness of 1 mm was obtained at 50 ° C.
Sodium chloride was eluted by immersing in water for 12 hours.

The polytetrafluoroethylene porous body thus obtained was impregnated with fluororubber and dried in the same manner as in Example 1 to obtain a sheet-like composite obtained from the composite (volume ratio 53/47). (50 × 100 × 1.4 mm) was heat pressed to be vulcanized and molded. The same measurement as in Example 1 was performed on this vulcanized sheet (50 × 100 × 1.0 mm).

Comparative Example 1b 500 parts of polytetrafluoroethylene powder (Teflon 6J) and 1942 parts of the fluororubber solution used in Example 1 were stirred and mixed at room temperature, and then 3000 parts of ethanol were gradually added to the polytetrafluoroethylene and fluorine. Coprecipitated with rubber.
This precipitate was separated by filtration, washed with 1000 parts of ethanol, and then dried at 50 ° C. for 24 hours using a vacuum dryer.

Polytetrafluoroethylene-obtained in this way
Fluorine rubber (volume ratio 50/50) composite was heat-pressed to be vulcanized and molded, and for this vulcanized sheet (50 × 100 × 1.0 mm),
The same measurement as in Example 1 was performed.

Example 2 500 parts of polytetrafluoroethylene powder (Teflon 6J) and 1235 parts of the fluororubber solution used in Example 1 were stirred and mixed at room temperature, and then 2000 parts of ethanol were gradually added to the polytetrafluoroethylene and fluorine. Coprecipitated with rubber.
The precipitate was separated by filtration, washed with 1000 parts of ethanol, and then dried at 50 ° C. for 24 hours using a vacuum dryer.

Polytetrafluoroethylene-obtained in this way
The fluororubber (volume ratio 61/39) composite was pressed for 1 minute at a pressure of 60 kg / cm ² , and was preformed into a square rod shape having a cross section of 50 × 50 mm.
Then, using a ram extruder, this is 50 mm wide and 2 mm thick.
Was extruded into a sheet form.

This sheet is cut into a length of 100 mm, 100% stretched using a stretching machine at a stretching speed of 1400 mm / min, and then 5% at 340 ° C.
It was press-molded for a minute to obtain this vulcanized sheet (50 × 100 × 1.0 mm). The same measurement as in Example 1 was performed on this vulcanized sheet.

Comparative Example 2a In Comparative Row 1a, the polytetrafluoroethylene porous body was dipped in a fluororubber solution-the drying step was repeated twice, and the obtained composite (volume ratio 62/38) was
A vulcanized sheet was molded and evaluated.

Comparative Example 2b The polytetrafluoroethylene-fluororubber composite used in Example 2 was vulcanized and molded by a heat press, and the obtained vulcanized sheet (50 × 50 × 1.0 mm) was evaluated.

Example 3 In Example 2, using 792 parts of the fluororubber solution, a polytetrafluoroethylene-fluororubber (volume ratio 69/31) composite was obtained, and thereafter, a vulcanized sheet was molded and evaluated in the same manner. It was

Comparative Example 3a In Comparative Example 1a, the polytetrafluoroethylene porous body was immersed in a fluororubber solution (however, changed to 15 minutes).
-The drying step was repeated twice, and the obtained composite (volume ratio 72/28) was molded into a vulcanized sheet and evaluated.

Comparative Example 3b The polytetrafluoroethylene-fluororubber composite used in Example 3 was vulcanized and molded by heat pressing, and the obtained vulcanized sheet (50 × 100 × 1.0 mm) was evaluated.

The results obtained in each of the above Examples and Comparative Examples are shown in Table 1 below.

From the above results, it is understood that the composite rubber composition according to the present invention is flexible and has gas barrier properties even after the elongation test.

Furthermore, the relationship between elongation and stress is shown in the graph of FIG.
The relationship between the gas permeability coefficient and the temperature is shown in the graph of FIG.

Example 4 Polychlorotrifluoroethylene (Molecular weight: about 100 to 1.2 million)
2152 parts of 50% by weight aqueous suspension of Fluorine rubber (Viton GF from Showa Denko / DuPont) at a concentration of 20% by weight in an ethyl acetate solution in which the solution temperature of 9 ° C was maintained. The mixture was added dropwise and mixed with stirring. After thorough mixing, ethanol was added dropwise to precipitate a solid content, which was taken out to obtain a powdery body dried under reduced pressure.

This powdery material was preformed into a columnar shape under the conditions of pressure 20 kg / cm ² and temperature 100 ° C, and this was molded at temperature 120 ° C and extrusion pressure 4ton / c.
Extruded into a sheet with a thickness of 2 mm under the condition of m ² and drawing rate of 100,
Then, using two calenders, roll it to a thickness of 1.1 mm while taking it off at a draft ratio of 4 at 150 ° C, and finally press it at a temperature of 280 ° C and a pressure of 100 kg / cm ² to apply a pressure of 100 × 100 × 1.0 mm. A sulfurized sheet was obtained.

Comparative Example 4 According to Example 4, a vulcanized sheet of fluororubber was produced.

The following items were measured for the vulcanized sheets obtained in Example 4 and Comparative Example 4 described above.

Tensile strength (kg / cm ² ): According to Shimadzu autograph Surface friction coefficient: Bowden Leben type; Sliding speed 0.1 cm / sec, load 20 g, 8
mm-shaped steel ball Gas permeability coefficient [× 10 ^-12 cc (stp) ・ cm / cm ²・ sec ・ cmHg]: Nitrogen gas measured at 20 ℃ by pressure method using Baratron vacuum pressure gauge , As shown in Table 2 below.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the elongation and stress of the vulcanized molded product of the composite composition according to the present invention, and FIG. 2 is a graph showing the relationship between the gas permeation coefficient and temperature.

Claims (1)

[Claims] 1. A composite rubber composition comprising a fluororubber compound containing a compounding agent and a fibrillated porous material of polytetrafluoroethylene or polychlorotrifluoroethylene.