JPH0797458A - Method for vulcanizing fluororubber composition - Google Patents

Abstract

(57) [Summary] [Structure] A fluororubber composition comprising a fluororubber and a melt-moldable thermoplastic fluororesin having a melting point of 300 ° C. or less,
A vulcanization method in which an effective amount of a vulcanizing agent for fluororubber is vulcanized at a temperature higher than the above melting point. [Effect] A vulcanized fluororubber having excellent mechanical properties can be obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for vulcanizing a fluororubber composition.

[0002]

2. Description of the Related Art Fluoropolymers have heat resistance, chemical resistance,
It has excellent mechanical and electrical properties and is used in various fields. Among them, fluororubber has been used in a field requiring flexibility. However,
Fluorine rubber has low mechanical properties, and usually a reinforcing material such as carbon must be blended. Although the mechanical strength is improved by the blending, it cannot be said that the physical properties are sufficient as compared with fluororesin, and carbon etc. It has been difficult to say that the compounding of the inorganic filler increases the apparent viscosity of the polymer and that the moldability is excellent.

Japanese Patent Publication No. 56-34018 describes a method in which a thermoplastic fluororesin and fluororubber are uniformly kneaded at the melting temperature of the thermoplastic fluororesin, and then crosslinked at 60 to 65 ° C. There is. However, in this method, since the crosslinking treatment is carried out at a low temperature, the compatibility between the thermoplastic fluororesin and the fluororubber is lowered, and the heterogeneous dispersion state is brought about. Therefore, the elongation and 100% tensile stress of the crosslinked fluororubber are low. there were.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to eliminate the above-mentioned problems and to provide a vulcanized fluororubber having sufficient mechanical properties. A method of vulcanizing a composition is provided.

[0005]

As a result of intensive studies to solve the above problems, the inventors have found that a composition of fluororubber and a thermoplastic fluororesin is vulcanized at a temperature not lower than the melting point of the thermoplastic fluororesin. By doing so, it was found that a vulcanized fluororubber having desired mechanical properties was obtained, and the present invention was accomplished.

That is, the present invention provides an effective amount of a fluororubber composition comprising 100 parts by weight of fluororubber and 10 to 100 parts by weight of a melt-moldable thermoplastic fluororesin having a melting point of 300 ° C. or less. It is intended to provide a vulcanization method characterized by vulcanizing with a vulcanizing agent for fluororubber at a temperature not lower than the melting point of a thermoplastic fluororesin.

In the present invention, the thermoplastic fluororesin is
It is important to use 10 to 100 parts by weight to 100 parts by weight of fluororubber. 10 thermoplastic fluororesins
When it exceeds 0 parts by weight, mechanical properties are excellent, but flexibility inherent in rubber, that is, increase in hardness and increase in tensile stress, is not preferable, and therefore it is not preferable. If the amount of the thermoplastic fluororesin is less than 10 parts by weight, the mechanical properties, especially the strength will be low.

The fluororubber useful in the present invention is
Tetrafluoroethylene, hexafluoropropylene,
Ethylenic containing at least one fluoroolefin selected from trifluoroethylene, vinylidene fluoride, vinyl fluoride, trifluorochloroethylene, and perfluoroalkyl vinyl ether (where the alkyl group has 1 to 12 carbon atoms). It is obtained by polymerizing an unsaturated compound. Examples of the ethylenically unsaturated compound include ethylene, propylene, alkyl vinyl ethers, and perfluoroalkylethylenes, in addition to the above fluoroolefins.

In such fluororubber, vinylidene fluoride / hexafluoropropylene type copolymer, tetrafluoroethylene / propylene type copolymer,
Examples thereof include tetrafluoroethylene / perfluoroalkyl vinyl ether-based copolymers and vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene-based copolymers. These copolymers may be further copolymerized with other copolymerizable components. A copolymer in which tetrafluoroethylene / propylene / copolymerizable unsaturated compound is 30 to 80 mol% / 20 to 55 mol% / 0 to 40 mol% is preferably used.

Further, it is preferable that the fluororubber of the present invention substantially has a vulcanization site for vulcanizing the fluororubber. The vulcanization site, iodine, halogen such as bromine, epoxy group, carboxylic acid group or a derivative group thereof, sulfonic acid group or a derivative group thereof, a hydroxyl group,
Examples thereof include functional groups such as nitrile groups and unsaturated bonds such as vinyl groups and allyl groups. Such a vulcanization site can be introduced by copolymerizing a copolymerizable monomer having the vulcanization site during fluororubber production. Further, it may be introduced into the fluororubber by a polymer reaction.

Further, in the case where the chain of fluororubber itself participates in the vulcanization reaction, the chain unit can be regarded as the vulcanization site, and the above functional group is not necessary.

By using such a vulcanization site, peroxide vulcanization, polyol vulcanization, amine vulcanization, which are generally used for vulcanization of fluororubber, and chemical crosslinking such as ionic vulcanization are possible. is there.

Of the fluororubbers, those having a vulcanization site selected from an epoxy group, a carboxylic acid group or a derivative group thereof, and a sulfonic acid group or a derivative group thereof are particularly preferable because vulcanization proceeds easily. Used.

The vulcanizing agent is appropriately selected depending on the vulcanizing site of the fluororubber used, and is not limited as long as it can vulcanize the fluororubber. The vulcanizing agent is not limited to one kind of compound, and may be a combination of compounds necessary for vulcanization. For example, a fluororubber having vulcanization sites of bromine and iodine can be vulcanized by adding a combination of an organic peroxide and a polyfunctional compound such as triallyl isocyanurate as a vulcanizing agent. A fluororubber having an epoxy group as a vulcanization site undergoes vulcanization by adding ammonium benzoate, tetracarboxylic acid anhydride or the like as a vulcanizing agent. Further, the fluororubber having a vulcanization site such as a carboxylic acid group or a sulfonic acid group can be vulcanized with a polyfunctional epoxy compound, a polyfunctional amine compound, a metal oxide or the like.

The thermoplastic fluororesin in the present invention is required to be melt-moldable. 300 ° C., which is a temperature at which deterioration of the fluororubber used does not matter
A thermoplastic fluororesin having the following melting point is preferable. Of the usual fluororesins, all thermoplastic fluororesins except polytetrafluoroethylene resin can be adopted.

The thermoplastic fluororesin in the present invention is tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, vinylidene fluoride, vinyl fluoride, trifluorochloroethylene, perfluoroalkyl vinyl ether (provided that the alkyl group has a carbon number. It is obtained by polymerizing an ethylenically unsaturated compound containing at least one fluoroolefin selected from the group consisting of 1 to 8). Examples of the ethylenically unsaturated compound include ethylene, propylene, alkyl vinyl ethers, and perfluoroalkylethylenes, in addition to the above fluoroolefins.

Of these polymers, preferred are tetrafluoroethylene / ethylene copolymers, tetrafluoroethylene / hexafluoropropylene copolymers, tetrafluoroethylene / perfluoropropyl vinyl ether copolymers, and trifluoroethylene. A modified ethylene chloride / ethylene copolymer or a vinylidene fluoride polymer is used. In particular, a tetrafluoroethylene / ethylene / perfluoroalkylethylene copolymer is most suitable. Perfluoroalkyl ethylene of the formula CH ₂ = CH-C _n F
_{2n + 1} (where n in the formula is an integer of 2 to 10). Also, a plurality of thermoplastic fluororesins may be used.

The method for producing the fluororubber composition is not particularly limited, and the fluororubber and the thermoplastic fluororesin may be mixed by a general blending method. For example, a method of dry mixing thermoplastic fluororesin powder with fluororubber by a two-roll or Banbury mixer, a method of melt mixing by an extruder or the like, or a method of blending polymerized latex and then coaggregating,
Examples include a method of dissolving the fluororubber in a solvent, mixing the thermoplastic fluororesin, and then removing the solvent. Preferably, a melt mixing method is used, which is considered to melt the thermoplastic fluororesin and make the mixing most uniform.

The vulcanizing agent can be added at the time of producing the above-mentioned fluororubber composition. Further, after the composition is produced, a vulcanizing agent may be added and mixed again.

In molding the composition of the present invention,
It is necessary to carry out molding at a temperature above the melting temperature of the thermoplastic fluororesin used. The thermoplastic fluororesin is in a molten state during the vulcanization reaction of fluororubber, resulting in the entanglement of molecules, and the reinforcing effect is exhibited even if the thermoplastic fluororesin itself is not involved in the vulcanization reaction. Physical properties are improved. In addition, by using a molding machine such as an extruder to advance the vulcanization reaction simultaneously with molding at the melting temperature of the thermoplastic fluororesin or higher, more excellent mechanical properties can be obtained due to the effect of shear mixing.

According to the method of the present invention, a vulcanized fluororubber molded product having excellent mechanical strength can be obtained, and therefore it is useful in fields requiring strength such as soft electric wires, soft tubes, hoses, films, sheets and belts. .

[0022]

EXAMPLES The present invention will be specifically described with reference to examples. The fluororubber and thermoplastic fluororesin used are shown below. In Table 1, fluororesin 1 is Aflon LM-720 (melting point 230 ° C., tetrafluoroethylene / ethylene copolymer) manufactured by Asahi Glass Co., Ltd., and fluororesin 2 is Aflon COP-88A (melting point 270 ° C., tetrafluoroethylene manufactured by Asahi Glass Co., Ltd.). / Ethylene-based copolymer), fluororesin 3 is Kureha Chemical Co., Ltd., Kynar-740 (melting point 170 ° C., vinylidene fluoride polymer), and fluororubber 1 is Asahi Glass Co., Ltd. Aflas #
170 (tetrafluoroethylene / propylene-based copolymer), fluororubber 2 is #Aflas 150 (tetrafluoroethylene / propylene-based copolymer) manufactured by Asahi Glass Co., Ltd., and fluororubber 3 is Daiel G-901 (vinylidene fluoride manufactured by Daikin). / Tetrafluoroethylene / hexafluoropropylene copolymer).

[Examples 1 to 5] Powders obtained by pulverizing a fluororesin, fluororubber and a vulcanizing agent were blended at a ratio shown in Table 1 on a two-roll mill at room temperature to obtain a fluororubber composition.
As shown in Table 1, this composition was subjected to press vulcanization at a temperature not lower than the melting point of the fluororesin for 3 minutes after preheating 100 kgf / c.
A sheet was formed by pressing under a condition of pressing m ^{2 for} 10 minutes. Using this as a sample, the tensile strength, elongation, 100% tensile stress and hardness were measured according to JIS-K6301 and shown in Table 1. The vulcanizates obtained by the examples are the following comparative examples 1
While having the same flexibility as that of a normal fluororubber as shown in (1), that is, 100% tensile stress and hardness, it was excellent in mechanical properties such as tensile strength and elongation.

[Comparative Example 1] MT carbon was used as a usual fluororubber vulcanizate without using thermoplastic fluororesin.
The physical properties of the product obtained by press vulcanization molding at 170 ° C. were measured in the same manner and are shown in Table 1.

Comparative Examples 2 to 3 Vulcanization molding was carried out in the same manner as in Example 1 except that the mixing ratio of the fluororesin was changed to 5 parts by weight and 120 parts by weight, and the physical properties were measured. As shown in Table 1, those having a low proportion of fluororesin have low tensile strength. Further, those having a high content of fluororesin had excellent tensile strength, but had high 100% tensile stress and high hardness.

[Comparative Example 4] Example 1 except that the temperature during molding and vulcanization was 170 ° C., which is lower than the melting point of the fluororesin.
The physical properties of those obtained in the same manner as in Table 1 are shown in Table 1. Since the fluororesin was not vulcanized in the molten state, sufficient tensile strength could not be obtained.

[0027]

[Table 1]

[0028]

The present invention has a melting point of 300 ° C. with fluororubber.
A vulcanized fluororubber having sufficient mechanical properties is obtained by vulcanizing a fluororubber composition having good moldability, which comprises the following melt-moldable thermoplastic fluororesin, at a temperature higher than the melting point of the fluororesin. .

Claims (4)

[Claims] 1. A melting point of 3 relative to 100 parts by weight of fluororubber.
Melt-moldable thermoplastic fluororesin of 00 ° C or less 10
A vulcanization method characterized in that 100 parts by weight of a fluororubber composition is vulcanized with an effective amount of a vulcanizing agent for fluororubber at a temperature equal to or higher than the melting point of the thermoplastic fluororesin. 2. The vulcanization method according to claim 1, wherein the fluororubber has a vulcanization site selected from an epoxy group, a carboxylic acid group or a derivative group thereof, and a sulfonic acid group or a derivative group thereof. 3. A fluororubber is tetrafluoroethylene /
The vulcanization method according to claim 1 or 2, comprising a propylene-based copolymer. 4. The vulcanization method according to claim 1, wherein the thermoplastic fluororesin is a tetrafluoroethylene / ethylene copolymer.