JPS62108464A - Porous seal tape - Google Patents

Abstract

PURPOSE:To reduce influence of thermal expansion/contraction so as to improve the cushion performance and the gas seal performance by forming a porous seal tape while laminating and integrating at least two layers of porous fluororesin sheet. CONSTITUTION:Fluororesin such as PTFE, tetra-fluoroethylene-perfluoroalkyl- vinylether copolymer is formed into a porous sheet having the hole diameter of 0.01-10mum, the porosity of 60-95%, the apparent specific gravity lower than 1.5 and the thickness of 0.02-5mm. Then it is laminated at least in two layers, preferably 15-70 layers, to produce a porous seal tape having the porosity of 50-70% and the thickness of 0.3-2mm. It is employed as a seal tape at the position requiring gas seal such as the circumference of an electrode of a fuel cell. Consequently, a good gas seal performance having excellent cushion performance, improved heat-resistance, medicine-resistance, etc. can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a porous sealing tape used for sealing fuel cells and the like.

[Conventional technology and its problems]

In order to increase power generation capacity, fuel cells usually have multiple layers of electrodes stacked together depending on the application. In order to prevent the leakage of hydrogen or oxygen as fuel, it is necessary to seal the area around the stacked electrodes, but since the phosphoric acid is heated to about 200°C inside the fuel cell, it is necessary to seal the area around the stacked electrodes. In order to seal, it is necessary to use a material with good gas sealing properties, cushioning properties, heat resistance, chemical resistance, etc.

Conventionally, as a device having such characteristics, a device sealed with a polytetrafluoroethylene (hereinafter referred to as PTFE) sheet using a foaming agent to provide cushioning properties is known.

However, such foaming agent-added PTF [E sheet] has a limit in expansion ratio, and it is difficult to create something that is very soft (porosity: 40-50%). ), and had the disadvantage that it could not follow the thermal expansion and contraction of each material as the battery started and stopped, and its long-term gas sealing properties were insufficient.

[Means for solving problems]

The present invention relates to a porous sealing tape with improved gas sealing properties, which were insufficient with foaming agent-added PTFE sheets.
Laminated at least two layers of porous fluororesin sheets,
It is characterized by being integrated.

The fluororesin sheet used in the present invention is usually made of fluororesin such as PTFE, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, etc. with a pore size of 0.01 to
It is formed into a porous sheet having a diameter of 100 μm, a porosity of 60 to 95%, an apparent specific gravity of 1.5 or less, and a thickness of 0.02 to 5 mm.

In the present invention, at least two layers, preferably 15 to 70 layers of the above fluororesin sheets are laminated. The porous sealing tape created in this way usually has a porosity of 50 to 70%.
, with a thickness of O13-2 mrn.

In order to create the porous seal tape, it is usually obtained by heating and pressurizing the fluororesin at a temperature below the melting point. Preferably 290~310℃, 1~5kg/
Heated and pressurized at cm2. If the heating temperature exceeds the melting point, the pores will disappear and the sheet will tend to be hard, while if the heating temperature is too low, it will be difficult to bond the fluororesin sheets together. Furthermore, if the pressure is too low, it will be difficult to bond the fluororesin sheets together, and if the pressure is too high, the porosity may become too low or the pressure may collapse.

Although only fuel cells have been described so far, it goes without saying that the porous sealing tape of the present invention can be applied to other uses that require gas sealing properties and the like.

〔Example〕

The present invention will be explained below with reference to Examples.

Example thickness: 0.03 mm, average pore diameter: 0.6 pm, porosity: 85%
60 sheets of fired porous PTFE (melting point 327° C.) were stacked on an aluminum metal plate, and the periphery of the sheet was fixed to the metal plate using a crimping tool. Next, a metal plate was placed on top of the sheet at a temperature of 305°C and a pressure of 3kg/c.
After heating and pressurizing for 10 minutes under the conditions of 1.5 m'', a metal plate at 20 °C was placed on top of the sheet at the same pressure in place of the metal plate.
After cooling for 0 minutes, a porous sealing tape of the present invention having a thickness of 1.0 mm and a porosity of 65% was obtained.

In order to examine the characteristics of the porous seal tape obtained in the above example, gas sealing properties, restoring force, and flexibility were measured. For comparison, a foaming agent-added PTFE sheet having a thickness of 1°Qmm was also measured. The results are shown in Table 1 for gas sealability, FIG. 1 for flexibility, and FIG. 2 for restoring force. In the figure, A indicates an example and B indicates a comparative example.

The methods for measuring gas sealability, restoring force, and flexibility are shown below. The measurement was carried out at 25°C.The first surface pressure was set at 4.5kg/cm2, and this was then set at 200°C.
A heating and cooling cycle of heating for 1 hour and cooling at 25° C. for 1 hour is performed 100 times. Thereafter, gas was added to 5 through the air supply hole 11 having a diameter of 12.5 mm at a pressure of g/cm 2 at 25° C., and the amount of gas leakage at that time was measured using the flow meter 12 .

<Restoring force> Thickness after 10 minutes of applying a load to the sample and 5 minutes after removing the load. However, the thickness before applying the load is 1.

Flexibility> Apply a load to the sample and measure the thickness after 30 seconds. however,
The thickness before applying the load is 1.

〔Effect of the invention〕

As mentioned above, the porous sealing tape of the present invention has at least two layers of porous fluororesin sheets laminated and integrated, so it has excellent cushioning properties compared to conventional foaming agent-added PTFE sheets, and has thermal expansion properties. , it has good gas sealing properties because it is less affected by shrinkage.

[Brief explanation of drawings]

Figures 1 and 2 are graphs showing the characteristics of the porous sealing tape of the present invention and the conventional porous pTf)E sheet, with Figure 1 showing flexibility and Figure 2 showing restoring force. FIG. 3 is a cross-sectional view schematically showing an apparatus used for measuring gas sealability. A...Example B...Comparative example

Claims (2)

[Claims] (1) A porous sealing tape made by laminating and integrating at least two layers of porous fluororesin sheets. (2) The porous sealing tape according to claim 1, wherein the fluororesin is polytetrafluoroethylene or a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer.