JP2010174202A - Fluororubber composition and molding formed by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluororubber composition which has a gas sealing property, refrigerant resistance, acid resistance, compression set resistance, low temperature characteristics or the like without impairing productivity which fluororubber originally has, and to provide a molding which is formed by using the fluororubber composition. <P>SOLUTION: The fluororubber composition comprises (a) a copolymer, (b) an organic peroxide and (c) a polyfunctional unsaturated compound having two or more double bonds. The copolymer can be obtained by copolymerization of two or more kinds of double bond-having compounds chosen among hexafluoropropene, vinylidene fluoride, tetrafluoroethylene and a perfluoro(alkyl vinyl ether) compound and one or more kinds of double bond-having compounds chosen among perfluoro[(alkyloxy)<SB>n</SB>-alkyl vinyl ether], wherein n is an integer of ≥1, and the copolymer can be vulcanized by the organic peroxide. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fluororubber composition and a molded article such as a gasket, a packing and a sealing material formed using the same, and in particular, is excellent for a medium such as a gas, a refrigerant, and generated water used in a fuel cell. The present invention relates to a fluororubber composition that gives a vulcanizate.

Silicone rubber compositions, ethylene propylene rubber compositions, fluororubber compositions, and the like are used as rubber compositions used for gaskets of solid polymer fuel cells that have been developed in recent years.
In a polymer electrolyte fuel cell, a flat electrode structure in which separators are stacked on both sides is a single cell, that is, a unit cell, and a plurality of unit cells are stacked to form a fuel cell stack. . In the electrode structure, a polymer electrolyte membrane (polymer electrode membrane) is sandwiched between an electrode catalyst layer (cathode) on the positive electrode side and an electrode catalyst layer (anode) on the negative electrode side, and the outside of each electrode catalyst layer. Is a laminate in which a gas diffusion layer is disposed. The separator is made of a material having an electron transfer function. A gas passage is formed on the surface facing the electrode structure, and a refrigerant passage is formed on the surface of at least one of the separators.

  Each of these passages has a groove shape, and hydrogen gas as a fuel gas and an oxidant gas such as oxygen or air are independently flowed through the gas passage, and a coolant such as water or ethylene glycol flows through the coolant passage. Washed away. The separator is laminated on the electrode structure in a state where the protrusions between the gas passages are in contact with the gas diffusion layer. And the gasket for preventing that gas leaks out of a cell is equipped. That is, a plate-like body that is stacked and arranged to constitute a cell, such as a separator or an electrolyte membrane, is sealed by interposing a gasket between the plate-like bodies facing each other around the plate-like body. .

Therefore, the gasket used here requires fuel gas, oxidant gas, gas sealing properties for sealing refrigerant, refrigerant resistance, acid resistance, low temperature resistance, compression set resistance, etc. The product was satisfactory in terms of gas sealability and acid resistance, and the ethylene-propylene rubber composition did not necessarily satisfy the requirements in terms of compression set.
In order to meet these requirements, a fluororubber composition has attracted attention as a suitable material, and among them, a so-called low-temperature fluororubber composition, which has good low-temperature characteristics, is considered suitable.
However, the low-temperature properties (JIS K6261) of this low-temperature fluororubber were about −30 ° C. for TR10, and TR70 was a level that did not even reach −20 ° C. This has the problem that the silicone rubber composition and the ethylene propylene rubber composition do not reach the low temperature property and cannot exhibit sufficient sealing performance at low temperature.

JP 2004-346087 A JP 2007-92076 A JP 2004-51728 A

The above-described Patent Document 1 and Patent Document 2 are fluororubber compositions having a low temperature characteristic of TR-30 of −30 ° C. or lower, but TR70 is −20 ° C., and used as a gasket for a fuel cell. Therefore, it cannot be said that the low temperature property (TR70 is −30 ° C. or lower) considered desirable is satisfied. In addition, it cannot be considered that the distortion of parts due to rapid thermal fluctuation from low temperature to high temperature (-30 ° C to 100 ° C), ensuring gas sealing, refrigerant resistance, and acid resistance as a gasket for fuel cells. It could not be said to have been done. Furthermore, there is a problem in productivity.
Patent Document 3 proposes a fluororubber composition having a main chain with a perfluoroether bond and a rubber called the low-temperature fluororubber. However, even in this case, it cannot be said that the low temperature property (TR70 is −30 ° C. or lower), which is desirable when used as a gasket for a fuel cell, and the physical properties such as low strength and high compression set. Have face issues.

  In view of the above problems, the present invention provides a fluororubber composition having gas sealing properties, refrigerant resistance, acid resistance, compression set resistance, low temperature resistance, and the like, without impairing the productivity inherent to fluororubber, and the same. Provided is a molded article formed using

The fluororubber composition according to the invention of claim 1
(A) a compound having two or more double bonds selected from hexafluoropropene, vinylidene fluoride, tetrafluoroethylene, and perfluoro (alkyl vinyl ether) compounds, and n is an integer of 1 or more. A copolymer vulcanizable with an organic peroxide obtained by copolymerizing a compound having one or more double bonds selected from fluoro [(alkyloxy) n-alkyl vinyl ethers],
(B) an organic peroxide;
(C) a polyfunctional unsaturated compound having two or more double bonds.
In the present invention, the organic peroxide may be a pure product not supported by a carrier.

And the fluororubber composition of this invention can be used as the molded article formed by vulcanization | cure, and can be used for the gasket for fuel cells.
Moreover, the molded product formed by vulcanizing the fluororubber composition of the present invention has a TR70 of −30 ° C. or lower, or a TR70 of −30 ° C. or higher and −20 ° C. or lower in the range of low temperature characteristics (JIS K6261). When the difference between TR70 and TR10 is 10 ° C. or less.

According to the fluororubber composition of the present invention, it is possible to obtain one having gas sealing properties, refrigerant resistance, acid resistance, compression set resistance, low temperature resistance, etc. without impairing productivity. In addition, a molded product formed using the same can be a molded product excellent in various physical properties such as gas sealability, refrigerant resistance, acid resistance, compression set, and low temperature properties.
When a pure product that is not supported by a carrier is used as the organic peroxide contained in the fluororubber composition of the present invention, the fluororubber composition is free from the influence of the carrier. Makes it possible to ensure the above properties.
Further, when the range of the low temperature characteristics (JIS K6261) of the molded article using the fluororubber composition of the present invention is TR70 is −30 ° C. or lower, or TR70 is −30 ° C. or higher and −20 ° C. or lower, TR70 and Since the difference in TR10 is 10 ° C. or less, it is possible to obtain a molded article having excellent low-temperature characteristics, and it is possible to sufficiently ensure sealing performance and durability against a sudden temperature change.

Hereinafter, embodiments of the present invention will be described.
The fluororubber composition of the present invention comprises (a) a compound having two or more double bonds selected from hexafluoropropene, vinylidene fluoride, tetrafluoroethylene, and perfluoro (alkyl vinyl ether) compounds, and n is It is added with an organic peroxide obtained by copolymerizing a compound having one or more double bonds selected from perfluoro [(alkyloxy) n-alkyl vinyl ethers] composed of an integer of 1 or more. A vulcanizable copolymer;
(B) an organic peroxide;
(C) a polyfunctional unsaturated compound having two or more double bonds;
It contains.
For example, one or more kinds selected from vinylidene fluoride, tetrafluoroethylene, perfluoro (methyl vinyl ether), and perfluoro [methoxy- (propyloxy) m-propyl vinyl ether] s (m = n-1) A copolymer obtained by copolymerizing a compound having a double bond of
A compound having vinylidene fluoride, tetrafluoroethylene, and one or more double bonds selected from perfluoro [methoxy- (propyloxy) m-propyl vinyl ether] s (m = n-1). A copolymer obtained by copolymerization,
One or more kinds selected from hexafluoropropene, tetrafluoroethylene, perfluoro (methyl vinyl ether), and perfluoro [methoxy- (propyloxy) m-propyl vinyl ether] s (m = n-1) A copolymer obtained by copolymerizing a compound having a heavy bond;
One or more kinds selected from vinylidene fluoride, tetrafluoroethylene, perfluoro (methyl vinyl ether), and perfluoro [methoxy- (ethoxyoxy) m-ethyl vinyl ether] s (m = n-1) A copolymer obtained by copolymerizing a compound having a heavy bond;
Hexafluoropropene, tetrafluoroethylene, and a compound having one or more double bonds selected from perfluoro [methoxy- (ethoxyoxy) m-ethyl vinyl ether] s (m = n-1). A copolymer obtained by polymerization,
An example is given.

The fluororubber composition vulcanizable with the organic peroxide used in the present invention contains iodine or bromine as a crosslinking point in the copolymer (a), and the content thereof is from 0.01 to It is desirable to include it in an amount of 6% by weight, preferably about 0.1 to 3% by weight.
When the content is less than 0.01% by weight, sufficient strength and compression set cannot be obtained, and workability such as poor releasability cannot be satisfied. On the other hand, when the content is more than 6% by weight, sufficient elongation cannot be obtained, and workability such as poor scorch resistance is not satisfactory.

  The iodine atom and bromine atom in the copolymer (a) are easily separated from the copolymer skeleton by radicals generated from the organic peroxide during vulcanization, and generate highly active radicals in the copolymer. The radical generated in the copolymer can efficiently react with a polyfunctional unsaturated compound having two or more double bonds, and the copolymer can be crosslinked.

Vulcanization with an organic peroxide is also called cross-linking and is interpreted as a synonym in the present invention.
Since the chemical structure of the cross-linking is a C—C bond, it is chemically more stable than a C═N bond formed by vulcanization with a polyamine and a C—O bond formed by vulcanization with a polyol. Therefore, chemical resistance such as acid resistance is good.

The Mooney viscosity ML1 + 10 (121 ° C.) of the copolymer (a) is preferably from 5 to 130 pts, more preferably from 10 to 100 pts in terms of workability during molding and various physical properties. desirable.
When the Mooney viscosity of the copolymer (a) is lower than 5 pts, sufficient strength and compression set cannot be obtained, and workability such as high tackiness cannot be satisfied. Further, when the Mooney viscosity of the copolymer (a) is higher than 130 pts, sufficient elongation cannot be obtained, and the processability cannot be satisfied due to poor flow characteristics.

When the fluororubber composition of the present invention has a low temperature characteristic (JIS K6261) of a molded product formed by vulcanization, TR70 is −30 ° C. or lower, or TR70 is −30 ° C. or higher and −20 ° C. or lower. The difference between TR70 and TR10 is 10 ° C. or lower, preferably TR70 is −30 ° C. or lower.
If it is worse than this low temperature characteristic, it is not possible to secure a sealing property at a low temperature when used as a gasket for a fuel cell, particularly a sealing property in an environment where the temperature changes rapidly from a low temperature to a high temperature.

  The organic peroxide (b) used in the present invention is only required to have a function as a crosslinking agent. For example, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, 2 , 5-dimethyl-2,5-bis (t-butylperoxy) 3-hexyne, benzoyl peroxide, bis (2,4-dichlorobenzoyl) peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, 3-butylperoxybenzene, 1,1-bis (t-butylperoxy) 3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroxyperoxide, Examples thereof include t-butyl peroxyisopropyl carbonate.

From the viewpoint of crosslinking efficiency, these organic peroxides (b) are preferably 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, 2,5-dimethyl-2,5- It is desirable to use di (benzoylperoxy) hexane or dicumyl peroxide. These organic peroxides may be used alone or in combination of two or more.
These organic peroxides (b) are usually carried on a carrier made of silica, calcium carbonate, diatomaceous earth, talc, etc., but the organic peroxide (b) carrier used in the present invention is: If the medium has durability, it is not particularly concerned. However, when using a pure product not supported on a carrier, it is desirable to use a product having a purity of 90% or more, preferably 95% or more. By using a pure product in which the organic peroxide (b) is not supported by the carrier, a fluororubber composition free from the influence of the carrier is obtained. Therefore, a molded product using the composition has gas sealing properties and refrigerant resistance. In addition, various physical properties such as acid resistance, compression set, and low temperature properties can be reliably ensured.

The organic peroxide (b) is used in an amount of 0.1 to 15 parts by weight, more preferably 0.3 to 3 parts by weight, based on 100 parts by weight of the copolymer (a).
When the amount is less than 0.1 parts by weight based on 100 parts by weight of the copolymer (a), sufficient strength and compression set cannot be obtained, and the processability is not satisfactory, such as poor releasability. On the other hand, when the amount is more than 15 parts by weight based on 100 parts by weight of the copolymer (a), sufficient elongation cannot be obtained, and processability such as poor scorch resistance cannot be satisfied.

The fluororubber composition of the present invention using an organic peroxide (b) as a vulcanizing agent is a polyfunctional compound having two or more double bonds for the purpose of improving vulcanization characteristics, mechanical strength, and compression set. The unsaturated compound (c) is used in combination.
Examples of the polyfunctional unsaturated compound (c) having two or more double bonds include tri (meth) allyl isocyanurate, tri (meth) allyl cyanurate, triallyl trimellitate, N, N-m -Phenylene bismaleimide, diallyl phthalate, tris (diallylamine) -s-triazine, triallyl phosphite, 1,2-polybutadiene, ethylene glycol diacrylate, diethylene glycol diacrylate, and the like. Two or more types may be used in combination.

The amount of the polyfunctional unsaturated compound (c) having two or more double bonds is preferably 0.1 to 15 parts by weight, more preferably 100 parts by weight of the copolymer (a). Is preferably used in an amount of 0.3 to 6 parts by weight.
When the amount is less than 0.1 part by weight relative to 100 parts by weight of the copolymer (a), sufficient strength and compression set cannot be obtained, and processability is not satisfactory, such as poor releasability. . Moreover, when it is more than 15 parts by weight with respect to 100 parts by weight of the copolymer (a), sufficient elongation cannot be obtained, and workability such as poor scorch resistance is not satisfactory.

In addition to the above components, the fluororubber composition of the present invention contains compounding agents such as fillers, reinforcing agents, acid acceptors, plasticizers, lubricants, processing aids, and fluorine-based additives typified by perfluoropolyether. May be appropriately blended.
For example, fillers or reinforcing agents include carbon black, bituminous coal-based fillers, inorganic fillers such as titanium oxide, barium sulfate, wollastonite, and talc, and acid acceptors include metal oxides. And hydrotalcite compounds.

What is necessary is just to prepare the fluororubber composition of this invention by a well-known method.
As a kneading method, mixing may be performed using an open roll or a closed kneader such as a kneader or a banbury. Then, a molded product can be obtained by heating and vulcanizing by a method such as compression molding, injection molding, or transfer molding.
For vulcanization, for example, primary vulcanization is performed at a temperature of about 100 to 250 ° C. for about 1 to 60 minutes, and secondary vulcanization (less than 50 hours) is performed at a temperature of about 120 to 330 ° C. as necessary. Alternatively, the temperature may be raised gradually or stepwise until the temperature of secondary vulcanization is reached as necessary.
A molded product formed by vulcanizing the fluororubber composition of the present invention can be used as a gasket for a fuel cell, for example, taking advantage of its characteristics.

Hereinafter, although the example explains the fluororubber composition concerning the present invention still more concretely, these are examples of the implementation of the present invention and are not limited to these.
After kneading with an 8-inch mixing roll with the formulation shown in Table 1, press vulcanization was performed at 160 ° C. for 10 minutes, followed by oven vulcanization at 200 ° C. for 4 hours. Using the vulcanized product (molded product) obtained in this manner as a test piece, each physical property was measured in accordance with JIS standards as follows.

(Normal physical properties)
According to JIS K6253, the hardness of the test piece of a predetermined size was measured.
According to JIS K6251, the tensile strength and elongation of a test piece of a predetermined size were measured. The larger the tensile strength, the more difficult it is to break, indicating that the mechanical strength is high.
(Compression set)
According to JIS B2401, the compression set of a test piece of a predetermined size was measured.
In the table, the test piece was compressed 25%, held in air at 100 ° C. for 1000 hours, then released, and the compression set after 30 minutes was calculated. The test piece was compressed 25%. Then, it was immersed in a sulfuric acid solution of PH1 and a 1000 ppm hydrofluoric acid solution, held for 1000 hours, then released from compression, and the compression set after 30 minutes was calculated. Then, after holding for 1000 hours in hydrogen, the compression is released and the compression set after 30 minutes is calculated. The smaller the value, the higher the force to restore when compressed for a long time.
(Low temperature characteristics)
According to JIS K6261, the low temperature property evaluation of the test piece of a predetermined size was performed. The TR test (low temperature elastic recovery temperature) is a test in which a test piece frozen at a low temperature after stretching is measured for a temperature at which the elasticity recovers as the temperature rises and exhibits a certain shrinkage rate. The temperature when% contracted is TR10, and the temperature when 70% contracted is TR70.
Therefore, it can be said that the lower the temperature at TR70, the better the low temperature property.

[Example 1]
Copolymer obtained by copolymerizing vinylidene fluoride, tetrafluoroethylene, perfluoro (methyl vinyl ether) and perfluoro [methoxy- (propyloxy) m-propyl vinyl ether] as copolymer (a) Having a Mooney viscosity ML1 + 10 (121 ° C.) of 20,
A pure product of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane as the organic peroxide (b),
The above physical properties were measured with a test piece obtained by kneading and vulcanizing triallyl isocyanurate as a polyfunctional unsaturated compound (c) having two or more double bonds. The results are shown in Table 1.

[Example 2]
As copolymer (a), vinylidene fluoride, tetrafluoroethylene, perfluoro (methyl vinyl ether) and perfluoro [methoxy- (propyloxy) m-propyl vinyl ether] are copolymerized, and the Mooney viscosity of the obtained copolymer ML1 + 10 (121 ° C) is 35,
A product containing 60% silica of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane as the organic peroxide (b),
The above physical properties were measured with a test piece obtained by kneading and vulcanizing triallyl isocyanurate as a polyfunctional unsaturated compound (c) having two or more double bonds. The results are shown in Table 1.

[Example 3]
As copolymer (a), vinylidene fluoride, tetrafluoroethylene, perfluoro (methyl vinyl ether) and perfluoro [methoxy- (propyloxy) m-propyl vinyl ether] are copolymerized, and the Mooney viscosity of the obtained copolymer ML1 + 10 (121 ° C) is 60,
A pure product of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane as the organic peroxide (b),
The above physical properties were measured with a test piece obtained by kneading and vulcanizing triallyl isocyanurate as a polyfunctional unsaturated compound (c) having two or more double bonds. The results are shown in Table 1.

[Example 4]
As copolymer (a), hexafluoropropene, tetrafluoroethylene and perfluoro [methoxy- (propyloxy) m-propyl vinyl ether] are copolymerized, and the resulting copolymer has Mooney viscosity ML1 + 10 (121 ° C.). Is 50
A pure product of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane as the organic peroxide (b),
The above physical properties were measured with a test piece obtained by kneading and vulcanizing triallyl isocyanurate as a polyfunctional unsaturated compound (c) having two or more double bonds. The results are shown in Table 1.

[Comparative Example 1]
A copolymer having a Mooney viscosity ML1 + 10 (121 ° C.) of 40 obtained by copolymerizing vinylidene fluoride, tetrafluoroethylene and perfluoro (methyl vinyl ether) instead of the copolymer (a),
A pure product of 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane as the organic peroxide (b),
The above physical properties were measured with a test piece obtained by kneading and vulcanizing triallyl isocyanurate as a polyfunctional unsaturated compound (c) having two or more double bonds. The results are shown in Table 1.

[Comparative Example 2]
The physical properties were measured with a test piece made of perfluoroether rubber. The results are shown in Table 1.

[result]
As can be seen from the measurement results in Table 1, according to those obtained by blending Examples 1 to 4, those having excellent refrigerant resistance, acid resistance, compression set resistance, low temperature resistance, etc. It can be.
Especially what was obtained by the mixing | blending of Example 1 and Example 2 can be made very excellent in low temperature property, since TR70 is -30 degrees C or less. In addition, the one obtained by blending Examples 3 and 4 also has a difference between TR70 and TR10 of 10 ° C. or less when TR70 is −30 ° C. or more and −20 ° C. or less. It can be said that it has stable and excellent low-temperature properties.
Moreover, according to what was obtained by the combination of Examples 1 to 4 from the measurement results regarding compression set, even if immersed in sulfuric acid solution and hydrofluoric acid solution, or placed in hydrogen, It can be seen from the results that the measurement results are the same as those shown in FIG. Furthermore, it can be seen that the calculated value of compression set is smaller than those of Comparative Examples 1 and 2, and the force to restore when compressed for a long time is high, and the compression set is excellent in resistance to compression set.
From the measured values of normal properties (hardness, tensile strength, elongation), it can be seen that the properties are suitable for gaskets.
From the above, the molded products obtained by the blending of Examples 1 to 4 can be excellent in various physical properties such as gas sealing properties, refrigerant resistance, acid resistance, compression set resistance, and low temperature properties, and abruptly. It can be said that it is suitable as a gasket for a fuel cell because it can sufficiently ensure sealing performance and durability against temperature changes.

  On the other hand, when Examples 1 to 4 and Comparative Examples 1 and 2 are compared, Comparative Example 1 is inferior in compression set and cannot satisfy the low temperature property. In Comparative Example 2, the strength and elongation values are small, and the compression set in acid and hydrogen gas is poor. Therefore, it is clear that the molded product obtained by the blending of Comparative Examples 1 and 2 cannot exhibit sufficient performance.

Claims (6)

(A) a compound having two or more double bonds selected from hexafluoropropene, vinylidene fluoride, tetrafluoroethylene, and perfluoro (alkyl vinyl ether) compounds, and n is an integer of 1 or more. A copolymer vulcanizable with an organic peroxide obtained by copolymerizing a compound having one or more double bonds selected from fluoro [(alkyloxy) n-alkyl vinyl ethers],
(B) an organic peroxide;
(C) a polyfunctional unsaturated compound having two or more double bonds;
A fluororubber composition comprising:   2. The fluororubber composition according to claim 1, wherein the organic peroxide is a pure product not supported by a carrier.   A molded article formed by vulcanizing the fluororubber composition according to claim 1 or 2.   4. The molded product according to claim 3, wherein TR70 is −30 ° C. or lower in the range of low temperature characteristics (JIS K6261).   The molded product according to claim 3, wherein, in the range of low temperature characteristics (JIS K6261), when TR70 is -30 ° C or higher and -20 ° C or lower, the difference between TR70 and TR10 is 10 ° C or lower.   The molded article according to any one of claims 3 to 5, wherein the molded article is used for a gasket for a fuel cell.