JP3093579B2 - Gasket for phosphoric acid type fuel cell and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gasket used for sealing a main body cell of a phosphoric acid type fuel cell and having excellent heat resistance and phosphoric acid resistance, and a method for producing the gasket.

[0002]

2. Description of the Related Art Conventionally, as a gasket for sealing a main body cell of a phosphoric acid type fuel cell, a molded article of a fluororesin molded article and a vinylidene fluoride-based fluororubber (hereinafter referred to as a fluororubber) has been used. However, fluororesin moldings have high sealing properties due to high hardness, and fluororubber moldings have sufficient mechanical strength at high temperatures (compression resistance), electrical insulation and phosphoric acid resistance. There was a problem such as not.

[0003]

SUMMARY OF THE INVENTION The present invention uses a tetrafluoroethylene-propylene copolymer,
An object of the present invention is to provide a gasket for a phosphoric acid type fuel cell having excellent mechanical strength (compression crush resistance) at high temperatures, heat resistance, electrical insulation and phosphoric acid resistance, and having good sealing properties, and a method for producing the same. is there.

[0004]

The first invention relates to the above-mentioned gasket for a phosphoric acid type fuel cell and relates to ethylene tetrafluoride-containing gasket.
The rubber composition of at least one of adding 20 to 70 parts by weight of the propylene copolymer 100 parts by weight per carbon black and fumed silica made by vulcanization molding, the 230 ° C. Formic
Permanent 70 hours compression at 25% compression ratio in oven
Compression permanent distortion when performing a distortion test of 50% or less, 20
0 crack load by hot cracking load test in a high temperature atmosphere in ℃ is 40 kgf / cm or more, a volume resistivity of 10 ¹⁵ [Omega] cm or higher,
Surface resistivity is 10 ¹⁴ Ω or more, concentration 85%, temperature 180
℃ weight change rate by the anti-phosphorus acid test of immersing 30 days phosphate is equal to or less than 1.5%.

The second invention relates to a method for producing the above-mentioned gasket for a phosphoric acid type fuel cell, wherein at least one of carbon black and dry silica is added in an amount of 20 to 70 parts by weight per 100 parts by weight of a tetrafluoroethylene-propylene copolymer. Then, a rubber composition comprising 1 to 3 parts by weight of an organic peroxide crosslinking agent, 2 to 8 parts by weight of a co-crosslinking agent and an appropriate amount of a processing aid is mixed with a metal for producing a gasket for a phosphoric acid type fuel cell. The mold is filled, press-vulcanized at a temperature of 150 to 180 ° C for 10 to 30 minutes, and then heated in an oven at a temperature of 180 to 230 ° C for 5 to 2 minutes.
It is characterized by performing secondary vulcanization for 4 hours.

The above-mentioned tetrafluoroethylene-propylene copolymer is a copolymer in which tetrafluoroethylene and propylene are arranged almost alternately. As the carbon black, MT, SRF, GPF, HAF and the like can be used, but in terms of mechanical strength at high temperature (compression crush resistance), H
AF, particularly high reinforcing carbon having a particle diameter of 20 to 30 nm, is preferable, and MT carbon is preferable in terms of acid resistance and electric insulation. Further, in place of the above carbon black, dry silica having good acid resistance can be used in combination with carbon black.

The amount of the above-mentioned carbon black or fumed silica, when used alone, is 20 to 100 parts by weight per 100 parts by weight of the tetrafluoroethylene-propylene copolymer.
70 parts by weight, and in particular, the mixing amount when MT carbon alone is used is preferably 40 to 60 parts by weight. When both are used in combination, the total amount is 20 to 70 parts by weight. If the amount is less than 20 parts by weight, the mechanical strength at high temperatures is low and the moldability is low.
On the other hand, if it exceeds 70 parts by weight, the hardness becomes too high, the sealing performance is reduced, and molding becomes difficult.

In the present invention, an organic peroxide crosslinking agent and a co-crosslinking agent are used in combination. As the organic peroxide crosslinking agent,
The use of 1,3 bis (t-butyl peroxy-iso-propyl) benzene is preferred. The compounding amount of the organic peroxide crosslinking agent is 1 to 3 parts by weight per 100 parts by weight of the tetrafluoroethylene-propylene copolymer, and when the compounding amount is less than 1 part by weight, the vulcanization rate is reduced. If the molding is slow, the appearance is poor, and the compression set and creep resistance of the molded product are reduced. On the other hand, if it exceeds 3 parts by weight, the vulcanization speed is too fast and scorch (early vulcanization) or poor appearance Occurs, the molded product becomes brittle, and the mechanical strength at high temperatures decreases.

Further, triallyl isocyanurate is preferably used as a co-crosslinking agent. The compounding amount of this co-crosslinking agent is the same as that of the tetrafluoroethylene-propylene copolymer 10
It is 2 to 8 parts by weight per 0 parts by weight. If the amount is less than 2 parts by weight, vulcanization is not sufficiently performed, and the compression set and creep resistance of the molded product are deteriorated. Conversely, if it exceeds 8 parts by weight, the vulcanizate becomes brittle and the mechanical strength at high temperatures decreases.

The above-mentioned ethylene tetrafluoride-propylene copolymer, carbon black (or fumed silica), an organic peroxide crosslinking agent and a co-crosslinking agent are kneaded together with appropriate amounts of usually used processing aids and lubricants. . The obtained rubber composition is molded into a desired shape by primary vulcanization and secondary vulcanization.

The primary vulcanization is carried out by press vulcanization in which a mold is filled with the above rubber composition. Vulcanization temperature is 150
The curing temperature is set to 10 to 30 minutes, and the pressing pressure (surface pressure) is set to ²⁰ to 60 kg / cm ² . If the above vulcanization temperature is less than 150 ° C., since vulcanization is slow, vulcanization takes a long time to reduce productivity or may cause defects on the outer surface of the molded product, On the other hand, when the temperature exceeds 180 ° C., the vulcanization rate is too high, and the outer surface of the molded product is likely to be damaged. The vulcanization time is 10
When the time is less than minutes, the initial physical properties are low and the compression set becomes large. On the other hand, when the time exceeds 30 minutes, the initial physical properties are reduced and the productivity is reduced. The press pressure is 20kg
If it is less than / cm ² , the outer surface of the molded product is likely to be damaged, while if it exceeds 60 kg / cm ² , damage to the mold and press hot plate is accelerated.

The secondary vulcanization is performed by oven vulcanization at a temperature of 1
Performed at 80-230 ° C. for 5-24 hours. This temperature is 1
When the temperature is lower than 80 ° C., the vulcanization is insufficient and the compression set of the product becomes large. On the other hand, when the temperature exceeds 230 ° C., the vulcanization proceeds excessively and the molded product ages. In addition, when the vulcanization time is less than 5 hours, the initial physical properties are low and the compression set becomes large, and when it exceeds 24 hours, heat aging proceeds,
The physical properties are significantly reduced.

[0013]

The gasket for a phosphoric acid type fuel cell of the first invention is
As a main component of the rubber composition, a tetrafluoroethylene-propylene copolymer is used. Since this copolymer has better electric insulation and phosphoric acid resistance than conventional fluororubbers, Are improved in terms of electrical insulation and phosphoric acid resistance. Further, since at least one of carbon black and dry silica is used as the filler, crack load resistance at high temperatures is improved. Moreover, as described above, the compression set is 50% or less, the crack load by the high temperature crack load test is 40 kgf / cm or more, and the volume resistivity is 1%.
0 ¹⁵ Ωcm or more, surface specific resistance is 10 ¹⁴ Ω or more, and the weight change rate by the phosphoric acid resistance test is 1.5% or less. To maintain over.

When MT carbon black is used as carbon black, the MT carbon black is inactive, so that the phosphoric acid resistance and the electrical insulation are further improved. However, when the compounding amount is less than 40 parts by weight, the mechanical strength and the workability decrease, and when it exceeds 60 parts by weight, the hardness increases and the sealability and the workability decrease.

Since the method of the second invention uses a tetrafluoroethylene-propylene copolymer, the electrical insulation and the phosphoric acid resistance are improved as compared with the conventional fluororubber. Further, since at least one of carbon black and dry silica is used as the filler, crack load resistance at high temperatures is improved. In addition, since an organic peroxide and a co-crosslinking agent are used together as a crosslinking agent, heat resistance and acid resistance are improved. Then, the rubber composition having the above composition is filled in a mold for producing a gasket of a phosphoric acid type fuel cell,
Press vulcanization for 10 to 30 minutes at a temperature of
Since it is a method of performing secondary vulcanization for 5 to 24 hours in an oven at 0 to 230 ° C, the hardness (JIS-A) is 75 to 85.
Degree, tensile strength 200 kgf / cm ² or more, elongation at break 180% or more, compression set (230 ° C. × 70 hours gear oven, 25% compression, JISK6301) 50% or less, hot crack load test (at 200 ° C. atmosphere) Cracking load by compression fracture test) 40kgf / cm or more, volume resistivity 10 ¹⁵ Ωcm
As described above, the phosphoric acid-type fuel according to the first invention has a surface specific resistance of 10 ¹⁴ Ω or more and a weight change rate of 1.5% or less in a phosphoric acid resistance test (immersion in phosphoric acid at a concentration of 85% and a temperature of 180 ° C. for 30 days). A gasket for a battery is obtained.

[0016]

Examples: Tetrafluoroethylene propylene polymer (trade name "Afras 100S", manufactured by Nippon Synthetic Rubber Co., Ltd.), sodium stearate, MT carbon, fumed silica, 1,3
Phosphoric acid of Examples 1 to 3 using bis (t-butylperoxy-isopropyl) benzene (organic peroxide cross-linking agent A) and triallyl isocyanurate (co-cross-linking agent) and changing its composition variously A gasket for a fuel cell was manufactured. As shown in FIG. 1, this gasket has a rectangular frame shape (horizontal D: 500 mm, vertical L: 1000 mm).
Each side is formed in a groove shape (width b: 15 mm, height h: 10 mm). The compounding ratio, workability (kneadability and press moldability) and vulcanization conditions are shown in Table 1 below.

Table 1 Example 1 Example 2 Example 3 Afras 100S 100 100 100 Sodium stearate 22 22 MT carbon 45-20 Dry silica-45 20 Organic peroxide crosslinking agent A 222 Co-crosslinking agent 55 5 Total 154 154 149 Workability 〇 〇 〇 Press vulcanization (℃ × min) 170 × 20 170 × 20 170 × 20 Secondary vulcanization (℃ × time) 200 × 7 200 × 7 200 × 7

Instead of the tetrafluoroethylene propylene polymer (trade name "Afras" manufactured by Nippon Synthetic Rubber Co., Ltd.) in the above embodiment, vinylidene fluoride-based fluoro rubber A (trade name "Viton B" manufactured by DuPont) Alternatively, using vinylidene fluoride-based fluororubber B (trade name “Daiel 902” manufactured by Daikin Industries, Ltd.), carnauba wax, magnesium oxide 150, calcium hydroxide, MT carbon,
2,5 ・ dimethyl ・ 2,5 di (t ・ butyl peroxy)
Hexane (organic peroxide crosslinking agent B), amine vulcanizing agent (manufactured by DuPont, trade name "Diac # 3"), the above-mentioned co-crosslinking agent, polyol vulcanizing agent A (manufactured by DuPont, trade name " Curatev # 20 ") and polyol vulcanizing agent B
(Manufactured by DuPont, trade name “Curativ # 30”) was blended to produce gaskets for phosphoric acid type fuel cells of Comparative Examples 1 to 3. The compounding ratio, workability (kneadability and press moldability) and vulcanization conditions are shown in Table 2 below.

Table 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Viton B 100 100-Daiel 902--100 Carnauba wax 111 Magnesium oxide 150 15 3 1 Calcium hydroxide-6-MT carbon 30 30 30 Organic peroxide Crosslinking agent B--3.5 Amine vulcanizing agent 3--Co-crosslinking agent--5 Polyol vulcanizing agent A-3-Polyol vulcanizing agent B-4-Total 149 147 140.5 Workability 〇 〇 △ Press vulcanization (℃ × min) 160 × 20 160 × 20 170 × 20 Secondary vulcanization (℃ × time) 230 × 24 230 × 24 200 × 7

The tetrafluoroethylene propylene polymer of the above embodiment (trade name "AFLAS 1" manufactured by Nippon Synthetic Rubber Co., Ltd.)
00S "), sodium stearate, HA on MT carbon
F carbon, wet silica, dry silica, 1,3 bis (t
-Phosphoric acid type fuel cells of Comparative Examples 4 to 11 using butyl peroxy isopropyl) benzene (organic peroxide crosslinking agent A) and triallyl isocyanurate (co-crosslinking agent) and changing the composition in various ways Gaskets for the manufacture. The compounding ratio, workability (kneadability and press moldability) and vulcanization conditions are described in Tables 3 and 4 below.

Table 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Afras 100S 100 100 100 100 Sodium stearate 222 2 2 MT carbon 580--HAF carbon--20-Wet silica---45 Dry silica − − − − Organic peroxide crosslinking agent A 2 222 Co-crosslinking agent 5 5 5 5 Total 114 189 129 154 Workability × × △ △ Press vulcanization (℃ × min) 170 × 20 170 × 20 170 × 20 170 × 20 Secondary vulcanization (℃ × time) 200 × 7 200 × 7 200 × 7 200 × 7

Table 4 Comparative Example 8 Comparative Example 9 Comparative Example 10 Comparative Example 11 Afras 100S 100 100 100 100 Sodium stearate 222 2 22 MT carbon 45 45 45 45 Organic peroxide crosslinking agent A 0.5 4 2 2 Co-crosslinking agent 5 5 1 9 Total 152.5 156 150 158 Workability △ △ △ △ Press vulcanization (℃ × min) 170 × 20 170 × 20 170 × 20 170 × 20 Secondary vulcanization (℃ × time) 200 × 7 200 × 7 200 × 7 200 × 7

Examples 1 to 3 and Comparative Examples 1 to 11
, Hardness (JIS-A), tensile strength (kgf / cm ² ) and elongation at break (%) were measured as initial physical properties. The rate of change in mechanical properties after heat aging (230 ° C. × 70 hours gear oven, JIS K6301) was measured for hardness (point), tensile strength (%), and elongation at break (%). Further, C-set (%) of compression set (230)
70 ℃ gear oven, 25% compression, JISK6
301) was measured. In addition, the hot crack load test (200
Cracking load (kgf / c)
m) was measured. Further, regarding electrical insulation, a volume resistivity (Ωcm) and a surface resistivity (Ω) were measured. Further, the rate of weight change was measured by a phosphoric acid resistance test (immersion in phosphoric acid at a concentration of 85% and a temperature of 180 ° C. for 30 days). The results are shown in Tables 5 to 8.

Table 5 Example 1 Example 2 Example 3 Initial physical properties Hardness (JIS-A) 80 85 82 Tensile strength (kgf / cm ² ) 233 201 228 Elongation at break (%) 200 190 200 Change after heat aging Hardness (point) +1 -1 +1 Tensile strength (%) -12 -15 -17 Elongation at break (%) +20 +11 +13 Compression set C-set (%) 35 49 41 Hot crack load test Crack load (kgf / cm) 55 47 50 Electrical insulation Volume resistivity (Ωcm) 10 ¹⁶ or more 10 ¹⁶ or more 10 ¹⁶ or more Surface resistivity (Ω) 1.3 × 10 ¹⁵ 5.1 × 10 ¹⁵ 4.3 × 10 ¹⁵ Phosphoric acid resistance test Weight change rate ( %) 0.9 1.3 1.2

Table 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 Initial physical properties Hardness (JIS-A) 78 77 79 Tensile strength (kgf / cm ² ) 158 133 229 Elongation at break (%) 380 230 280 Change after heat aging Hardness (point) +1 ± 0 +1 Tensile strength (%) -10 -8 -12 Elongation at break (%) +13 +9 +23 Compression set C-set (%) 81 33 56 Hot crack load test Crack load ( kgf / cm) 38 37 44 Electrical insulation Volume resistivity (Ωcm) 1.4 × 10 ¹² 1.3 × 10 ¹³ 2.1 × 10 ¹⁰ Surface resistivity (Ω) 1.5 × 10 ¹¹ 1.2 × 10 ¹³ 1.1 × 10 ¹⁰ Phosphoric acid resistance test Weight change rate (%) 5.1 5.9 1.0

Table 7 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Initial Physical Properties Hardness (JIS-A) 61 92 82 84 Tensile Strength (kgf / cm ² ) 121 180 243 189 Elongation at Break (%) 540 120 170 190 Rate of change after thermal aging Hardness (point) +1 ± 0 +2 +1 Tensile strength (%) -8 -17 -16 -14 Elongation at break (%) +10 +11 +5 +13 Compression set C-set (% ) 38 33 35 47 High temperature crack load test Crack load (kgf / cm) 21 57 55 48 Electrical insulation Volume resistivity (Ωcm) 10 ¹⁶ or more 3.1 × 10 ¹² 2.1 × 10 ¹² 2.4 × 10 ¹⁴ Surface resistivity (Ω) 1.1 × 10 ¹⁵ 2.4 × 10 ¹¹ 1.3 × 10 ¹¹ 3.1 × 10 ¹³ Phosphoric acid resistance test Weight change rate (%) 0.8 2.1 3.4 3.8

Table 8 Comparative Example 8 Comparative Example 9 Comparative Example 10 Comparative Example 11 Initial physical properties Hardness (JIS-A) 76 83 78 82 Tensile strength (kgf / cm ² ) 151 193 143 173 173 Elongation at break (%) 340 130 350 170 Rate of change after thermal aging Hardness (point) +2 + 1 + 2 + 1 Tensile strength (%) + 1-5-15-11 Elongation at break (%)-9-8 + 16 + 10 Compression set C-set ( %) 53 32 51 35 High temperature crack load test Crack load (kgf / cm) 31 33 44 43 Electrical insulation Volume resistivity (Ωcm) 10 ¹⁶ or more 10 ¹⁶ or more 10 ¹⁶ or more 1.4 × 10 ¹⁴ Surface resistivity (Ω) 3.3 × 10 ¹⁵ 4.1 × 10 ¹⁵ 1.2 × 10 ¹⁵ 1.3 × 10 ¹³ Phosphoric acid resistance test Weight change rate (%) 1.7 0.8 1.3 0.8

As can be understood from the above Tables 1 to 8, the embodiment of the present invention containing a tetrafluoroethylene-propylene copolymer as a main component is the same as the embodiment 1 using carbon black and the fumed silica. In both Example 2 used and Example 3 using carbon black and fumed silica in combination, the compression set was 50% or less, the crack load by a high temperature crack load test was 47 kgf / cm or more, and the volume resistivity was 50%. Is 10 ¹⁶ Ωcm or more, and the surface resistivity is 1.3 × 10 ¹⁵ Ω
It was excellent in electrical insulation and phosphoric acid resistance, and had a weight change rate of 1.3% or less. On the other hand, Comparative Examples 1 to 3 mainly composed of vinylidene fluoride rubber (FKM) had a low cracking load in a high-temperature cracking load test and were inferior in electrical insulation. In particular, Comparative Example 1 using an amine vulcanizing agent
Had inferior compression set.

In Comparative Examples 4 to 11, the main component was a tetrafluoroethylene-propylene copolymer. In Comparative Example 4, the workability was low and the initial physical properties were low because the amount of carbon black was small. It was inferior and the crack load by the high temperature crack load test was small. In Comparative Example 5, the workability was low, the hardness of the initial physical properties was too high, the sealing property was inferior, and the electric insulation was low because the amount of carbon black was excessive. In Comparative Example 6, since high-activity reinforcing carbon was used, the phosphoric acid resistance was inferior and the electric insulation was low. In Comparative Example 7, phosphoric acid resistance was poor because wet silica was used instead of carbon black and dry silica.

In Comparative Example 8, since the amount of the organic peroxide crosslinking agent was small, the compression set was large and the crack load was small. In Comparative Example 9, the crack load was reduced due to the excessive amount of the organic peroxide crosslinking agent.
In Comparative Example 10, since the amount of the co-crosslinking agent was small,
The compression set increased. Further, Comparative Example 11 was inferior in electric insulating property because the amount of the co-crosslinking agent was large.

[0031]

As described above, according to the first aspect of the present invention, at least one of carbon black and fumed silica is added in an amount of 20 to 70 parts by weight per 100 parts by weight of the tetrafluoroethylene-propylene copolymer. The rubber composition obtained is vulcanized and molded to have a compression set (230 ° C. × 70 hours gear oven, 25% compression, JIS K6301) of 50% or less, a hot crack load test (compressive fracture test in an atmosphere of 200 ° C.) Cracking load of 40 kgf / cm or more, volume resistivity of 10 ¹⁵ Ωcm or more, surface resistivity of 10 ¹⁴ Ω or more, weight change by phosphoric acid resistance test (85% concentration, immersion in phosphoric acid at 180 ° C for 30 days) Since the gasket for a phosphoric acid fuel cell is characterized in that the ratio is 1.5% or less, the mechanical strength at high temperatures (compression fracture resistance), heat resistance, electrical insulation and resistance It is excellent in phosphoric acid, maintains good sealing properties over a long period of time as a gasket for a phosphoric acid type fuel cell, and can be easily produced by the method described in claim 3.

The second aspect of the present invention is the same as the first aspect, except that the carbon black is limited to MT carbon black and the compounding amount is 40 to 60 parts by weight. Particularly excellent in mechanical strength (compression fracture resistance), heat resistance and phosphoric acid resistance.

The invention described in claim 3 is characterized in that at least one of carbon black and fumed silica is used in an amount of 20 to 7 per 100 parts by weight of the tetrafluoroethylene-propylene copolymer.
0 parts by weight of a rubber composition comprising 1 to 3 parts by weight of an organic peroxide crosslinking agent, 2 to 8 parts by weight of a co-crosslinking agent and an appropriate amount of a processing aid are added to a phosphoric acid fuel cell. Fill the mold for gasket production,
The gasket for a phosphoric acid type fuel cell according to claim 1, that is, a method of press vulcanizing for 30 minutes and then performing secondary vulcanization in an oven at a temperature of 180 to 230 ° C for 5 to 24 hours. A gasket for a phosphoric acid type fuel cell having excellent strength (compression resistance), heat resistance, electrical insulation and phosphoric acid resistance and having good sealing properties can be obtained.

According to a fourth aspect of the present invention, in the third aspect of the present invention, MT carbon black is used as the carbon black and the compounding amount is 40 to 60 parts by weight. A gasket for a phosphoric acid type fuel cell having particularly excellent mechanical strength (compression crush resistance), heat resistance and phosphoric acid resistance can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of a gasket for a phosphoric acid type fuel cell.

[Explanation of symbols]

 D: Horizontal length of gasket L: Vertical length of gasket b: Cross-sectional width of side h: Cross-sectional height of side

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Keiichi Suzuki 2-81-1, Kamimaezu, Naka-ku, Nagoya-shi, Aichi Rubber Goinaki Co., Ltd. (56) References JP-A-62-208561 (JP, A) JP-A Sho 60-241657 (JP, A) JP-A-60-148469 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 8/00-8/24

Claims (4)

(57) [Claims] 1. A tetrafluoroethylene-propylene copolymer 1
A rubber composition containing 20 to 70 parts by weight of at least one of carbon black and dry silica per 100 parts by weight is vulcanized and molded in a 230 ° C. gear oven.
70 hours <br/> compression distortion during compression was permanent strain test at a rate 25% 50% or less, in a high temperature atmosphere of 200 ° C.
Cracking load due to the high temperature cracking load test is 40kgf / cm or more,
Volume resistivity is 10 ¹⁵ Ωcm or more, surface resistivity is 10 ¹⁴
Immersed in phosphoric acid of Ω or more, concentration of 85% and temperature of 180 ° C for 30 days
Phosphoric acid fuel cell gaskets, wherein a weight change rate by the anti-phosphorus acid test for pickles is not more than 1.5%. 2. The gasket for a phosphoric acid type fuel cell according to claim 1, wherein the carbon black is MT carbon black, and the compounding amount thereof is 40 to 60 parts by weight. 3. At least one of carbon black and fumed silica is added in an amount of 20 to 70 parts by weight per 100 parts by weight of a tetrafluoroethylene-propylene copolymer.
A rubber composition prepared by mixing 2 parts by weight of an organic peroxide crosslinking agent, 2 to 8 parts by weight of a co-crosslinking agent, and an appropriate amount of a processing aid is charged into a mold for producing a gasket of a phosphoric acid fuel cell,
Press vulcanization at a temperature of 180 to 230C for 10 to 30 minutes, and then secondary vulcanization in an oven at a temperature of 180 to 230C for 5 to 24 hours. . 4. The method for producing a gasket for a phosphoric acid type fuel cell according to claim 3, wherein the carbon black is MT carbon black, and the compounding amount is 40 to 60 parts by weight.