JPH0623286B2 - Fluorine-containing elastomer composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fluorine-containing elastomer composition. More specifically, it relates to a fluoroelastomer composition capable of providing a vulcanized product having excellent shapeability during vulcanization molding and improved compression set.

[Conventional technology]

The fluorinated elastomer vulcanizate has heat resistance at high temperatures,
Since it has useful properties in terms of chemical resistance, oil resistance, weather resistance, etc., it is used in the form of gaskets, O-rings, packings and other sealing materials, hoses, sheets, etc. for the automobile industry, hydraulic industry, general machinery industry, and aircraft. Demand is rapidly increasing in fields such as industry. In other words, in addition to the demand for efficiency in the molding process, various demands for fluoroelastomer vulcanizates have diversified.
It can also be said that it has become stricter.

Vulcanization of fluorine-containing elastomers was initially carried out using polyamine derivatives such as hexamethylenediamine carbamate and methylenebis (cyclohexyl) amine carbamate, but with these vulcanization systems scorch resistance (processing safety, It had the disadvantages of poor storage stability) and compression set of the vulcanizate. After that, as a vulcanization system capable of improving these drawbacks, a method of cross-linking with a polyhydroxy aromatic compound in the presence of a vulcanization accelerator and an acid acceptor has been proposed and put into practical use.

As a vulcanization accelerator in this vulcanization system, a quaternary phosphonium salt compound (JP-A-47-191), a quaternary ammonium salt compound (JP-B-52-38072, JP-A-47-3831). ), 8-alkyl (or aralkyl) -1,8-diazabicyclo [5,4,0] -undec-7-ene quaternary ammonium salt compounds (Japanese Patent Publication No. 52-8863, JP-A No. 48-
55231) or an amount of 1,8-diazabicyclo [5,4,0] -which does not substantially vulcanize the fluoroelastomer.
A combination with Undec-7-ene (Japanese Patent Publication No. 57-20333) is used.

However, even when these vulcanization systems are used, the compression set of the vulcanizate is not yet at a sufficiently satisfactory level, especially at high temperatures. Further, in the vulcanization system using the fourth phosphonium salt compound, the vulcanization torque is high, and the tear strength of the primary vulcanizate (press vulcanizate) is low, so that the formability during vulcanization molding is inferior. is there.

[Problems to be solved by the invention]

The present inventor has conducted various studies to obtain a fluorine-containing elastomer composition which is excellent in shapeability at the time of vulcanization molding and is also improved in terms of compression set of the vulcanized product. As a result, the following general formula [I ] It was found that such a problem can be effectively solved by using the fourth phosphonium salt compound represented by the formula [1] as one component of the composition.

[Means for Solving Problems] and [Operation] Therefore, the present invention relates to a fluorine-containing elastomer composition,
This fluorine-containing elastomer composition comprises (a) a fluorine-containing elastomer, (b) a divalent metal oxide and / or hydroxide, (c) a polyhydroxy aromatic compound and (d) a general formula. (Here, R _{1 to} R ₃ are aryl groups, aralkyl groups, alkyl groups or alkoxy groups having 1 to 20 carbon atoms, X ⁻ is an anionic group, and n is 1 to 4, m is 2 or 3)), or (4) a phosphonium salt compound represented by the formula (3) above, or (e) a substantial amount of 1,8-diazabicyclo [5,4,0] which does not vulcanize the fluorine-containing elastomer. -Undec-7-ene, 1,5-diazabicyclo [4,3,0] -non-5-ene or 4-dialkylaminopyridine having an alkyl group having 1 to 4 carbon atoms is additionally contained.

The fluorine-containing elastomer to be vulcanized is a highly fluorinated elastic copolymer, and for example, a copolymer of vinylidene fluoride and another fluorine-containing olefin can be used. Specifically, for example, vinylidene fluoride and hexafluoropropene, pentafluoropropene, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, vinyl fluoride, perfluoroacrylic acid ester, perfluoroalkyl acrylate,
Examples thereof include one or more copolymers such as perfluoromethyl vinyl ether and perfluoropropyl vinyl ether, preferably vinylidene fluoride-hexafluoropropene binary copolymer and vinylidene fluoride-
Tetrafluoroethylene-hexafluoropropene terpolymer may be mentioned.

Divalent metal oxides and hydroxides used as acid acceptors include magnesium, calcium, barium, lead,
One or two oxides or hydroxides of divalent metals such as zinc
One or more kinds are generally used in a ratio of about 1 to 40 parts by weight, preferably about 3 to 15 parts by weight, based on 100 parts by weight of the fluoroelastomer.

Examples of the polyhydroxy aromatic compound as a cross-linking agent include 2,2-bis (4-hydroxyphenyl) propane [bisphenol A], 2,2-bis (4-hydroxyphenyl) perfluoropropane [bisphenol AF],
Hydroquinone, catechol, resorcin, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenylsulfone, 2,2
-Bis (4-hydroxyphenyl) butane, and the like, preferably bisphenol A, bisphenol AF,
Hydroquinone or the like is used. They may also be in the form of alkali metal salts or alkaline earth metal salts. These cross-linking agents are fluorine-containing elastomer 100
It is used in a proportion of about 0.5 to 10 parts by weight, preferably about 0.5 to 6 parts by weight, per part by weight. If the amount used is less than this range, the crosslink density will be insufficient, while if it is more than this range, the crosslink density will become too high and the rubbery elasticity will tend to be lost.

Examples of the fourth phosphonium salt compound represented by the above general formula [I] include [2- (1,3-dioxane-2-
Il) ethyl] triphenylphosphonium bromide,
[2- (1,3-dioxan-2-yl) ethyl] trioctylphosphonium bromide, [4- (1,3-dioxan-2-yl) butyl] triphenylphosphonium
Chloride, [2- (1,3-dioxan-2-yl) ethyl] triphenylphosphonium stearate, (1,3
-Dioxolan-2-ylmethyl) triphenylphosphonium bromide, [2- (1,3-dioxolane-2-
Il) ethyl] triphenylphosphonium bromide,
(1,3-Dioxolan-2-ylmethyl) trioctylphosphonium bromide, [2- (1,3-dioxolan-2-yl) ethyl] tribenzylphosphonium bromide, (1,3-dioxolan-2-ylmethyl) triphenyl Specific examples thereof include phosphonium benzoate and the like, and examples of the anionic group include halides, hydroxylates, alkoxylates,
It can be a carboxylate, phenoxide, sulphonate, sulphate, sulphite, carbonate or nitrate group and the like.

These fourth phosphonium salt compounds are novel substances,
General formula (Wherein n is 1 to 4 and m is 2 or 3) and is represented by 2- (ω-anion group-substituted alkyl) -1,3-dioxane or -1,3-dioxolane and the general formula PR ₁ It is produced by addition reaction with a tri-substituted phosphine represented by R ₂ R ₃ [III] (wherein R _{1 to} R ₃ are as defined above).

Examples of the tri-substituted phosphine represented by the general formula [II] include triphenylphosphine, tribenzylphosphine, trioctylphosphine, tributylphosphine, trimethylphosphine, triethylphosphite, tributylphosphite, tridecylphosphite, and the like. Among these, triphenylphosphine is a solid at room temperature and normal pressure, and thus is easy to handle and can be said to be the most practical.

The addition reaction is carried out by heating at a reflux temperature of the solvent used for about 8 to 24 hours in the presence of a hydrocarbon solvent such as benzene, toluene, xylene, hexane or an alcohol solvent such as isopropanol, preferably toluene or isopropanol. Done. In the case of a toluene solvent, the generated fourth phosphonium salt compound is precipitated, so that it can be separated simply by filtration. In the case of an isopropanol solvent, the product may not be precipitated in some cases. After isopropanol was distilled off from the reaction mixture, the crystals were obtained by washing with n-hexane.

One kind or two or more kinds of these fourth phosphonium salt compounds are used in a ratio of about 0.1 to 10 parts by weight, preferably about 0.1 to 2 parts by weight, based on 100 parts by weight of the fluoroelastomer. If the proportion used is less than this range, the crosslinkability will be poor, and if it is greater than this range, various properties of the vulcanizate will be significantly adversely affected.

When 1,8-diazabicyclo [5,4,0] -undec-7-ene or 1,5-diazabicyclo [4,3,0] -non-5-ene is further blended, the vulcanizate is compressed permanently. It has a remarkable effect on the improvement of strain and has an alkyl group having 1 to 4 carbon atoms.
Even if 4-dialkylaminopyridines such as dimethylaminopyridine, 4-diethylaminopyridine and 4-di (n-butyl) aminopyridine are further blended, the effect of promoting the crosslinking reaction is remarkable, and the amount of the fourth phosphonium salt compound is blended. As a result, the compression set can be effectively improved. These additional components may be added in an amount such that one kind or two or more kinds do not substantially vulcanize the fluoroelastomer, generally, the fluoroelastomer 10
It is preferably used in a ratio of about 0.1 parts by weight or less per 0 parts by weight, and particularly preferably used in a ratio of about 10% or less with respect to the fourth phosphonium salt compound. If the use ratio is higher than this range, generally the scorch resistance of the dough is adversely affected, and the crosslink density of the vulcanized product becomes too high and the elongation becomes small.

The vulcanized components may be blended as they are and kneaded,
Further, it may be diluted and dispersed with carbon black, silica, clay, talc, diatomaceous earth, barium sulfate or the like, or may be used as a masterbatch dispersion with a fluorine-containing elastomer. In the composition of the present invention, conventionally known fillers, reinforcing agents, plasticizers, lubricants, processing aids, pigments and the like can be appropriately added to the composition in addition to the above-mentioned composition.

The vulcanization is generally carried out by mixing the fluorinated elastomer with each of these vulcanized components and the various additives as described above by a commonly used mixing method such as roll mixing, kneader mixing, Banbury mixing, and solution mixing. Done by. Generally, primary vulcanization is about 140-200 ℃
About 2 to 120 minutes at the temperature of about 150 to 25 for secondary vulcanization
The heating is performed at a temperature of 0 ° C. for about 0 to 30 hours.

〔The invention's effect〕

The fluorine-containing elastomer composition according to the present invention has a low ODR torque of primary vulcanization (press vulcanization) and a good tear strength of the primary vulcanizate, and therefore has excellent shapeability during vulcanization molding. There is. That is, in the case of a complicated shape such as the valve stem seal or the oil seal of the embodiment, cracks and cracks are likely to occur, but if the tear strength is high, there are few cracks and cracks when taking out the vulcanized molded product from the mold. Become. Further, the low vulcanization torque also reduces the force at the time of mold release, and thus reduces cracks and defects. For this reason, the shapeability is improved. Further, excellent improvements have been achieved in terms of vulcanized physical properties and compression set.

〔Example〕

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

Reference Example 1 Synthesis of [2- (1,3-dioxan-2-yl) ethyl] triphenylphosphonium bromide 2- (2-bromoethyl) -1,3-dioxane 19.5 g
(0.1 mol) and triphenylphosphine 26.2 g (0.1
(Mol) is refluxed in 150 ml of toluene for 15 hours, and crystals gradually precipitate. After completion of the reaction, the mixture was cooled, filtered, and dried to obtain 41.0 g of the desired product (melting point 193-195 ° C) (yield 8
9.7%) was obtained.

Reference Example 2 Synthesis of (1,3-dioxolan-2-ylmethyl) triphenylphosphonium bromide In Reference Example 1, 2- (2-bromoethyl) -1,3-
2-6.7 g (0.1 mol) of 2-bromomethyl-1,3-dioxolane was used in place of dioxane, melting point 193-195 ° C.
39.5 g (yield 92.1%) of the target compound of was obtained. Example 1
4, Comparative Examples 1-2 A copolymer obtained by copolymerizing vinylidene fluoride and hexafluoropropene in the presence of ammonium persulfate as a polymerization initiator in an aqueous medium using acetone as a chain transfer agent [ Comonomer component molar ratio 78:22, solution viscosity ηsp
/ c 0.98 (35 ° C., in acetone, c = 1.0), polymer Mooney viscosity ML _{1 + 10} 53 (121 ° C.); fluorine-containing elastomer A], the formulation of the formulation shown in Table 1 below was used. The mixture was kneaded with an inch mixing roll to prepare a fluorine-containing elastomer composition. In addition, the compounding amounts are all parts by weight below.

Regarding the various fluorine-containing elastomer compositions obtained,
The Mooney viscosity and scorch time (the time required for the Mooney viscosity to reach the minimum value of +5, which is a measure of the storage stability and processing safety of the dough) are 121 respectively.
It was measured at a measurement temperature of ° C.

Further, the composition was press vulcanized at 180 ° C. for 5 minutes and then 230
Secondary vulcanization was carried out in an oven at ℃ for 22 hours, and various physical properties of each vulcanizate were measured according to JIS K-6301. The compression set was measured by vulcanizing the O-ring of P-24 under the same conditions and compressing it by 25%. The results of these measurements are shown in Table 2 below.

Examples 5 to 6 and Comparative Example 3 With respect to the fluorine-containing elastomer A used in Example 1, the compounds having the compounding formulations shown in the following Table 3 were kneaded with an 8-inch mixing roll to obtain fluorine-containing elastomer compositions. Prepared.

With respect to each of the obtained fluorine-containing elastomer compositions, various physical properties and various characteristics were measured in the same manner as in Example 1. However, vulcanization was performed after press vulcanization at 170 ° C for 8 minutes and then 2
It was carried out by secondary vulcanization in an oven at 00 ° C for 22 hours. Further, a valve stem seal having a shape as described in JP-B-53-33206 was molded from this composition, and the shapeability during vulcanization molding was also evaluated. The results obtained are shown in Table 4 below.

Examples 7 to 8 and Comparative Example 4 Vinylidene fluoride-tetrafluoroethylene-hexafluoropropene (molar ratio 41:41:18) terpolymer [polymer Mooney viscosity ML _{1 + 10} 96 (121 ° C); Regarding the fluoroelastomer B], a compound having a formulation shown in the following Table 5 was kneaded with an 8-inch mixing roll to prepare a fluoroelastomer composition.

The same measurement as in Example 1 was performed on the obtained fluorine-containing elastomer composition, and the results are shown in Table 6.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C08K 5/50 KJM 7242-4J

Claims (4)

[Claims] 1. (a) 100 parts by weight of a fluorine-containing elastomer,
(B) Bivalent metal oxide and / or hydroxide 1 to
40 parts by weight, (c) polyhydroxy aromatic compound 0.5 to 10
Parts by weight and (d) general formula (Here, R _{1 to} R ₃ are aryl groups, aralkyl groups, alkyl groups or alkoxy groups having 1 to 20 carbon atoms, X ⁻ is an anionic group, and n is 1 to 4, m is 2 or The fourth phosphonium salt compound represented by 3) 0.1 to 10
A fluoroelastomer composition containing parts by weight. 2. The fluorine-containing elastomer composition according to claim 1, wherein a quaternary phosphonium salt compound in which all of R _{1 to} R ₃ in the general formula [I] are phenyl groups is used. 3. (a) 100 parts by weight of a fluorine-containing elastomer,
(B) Bivalent metal oxide and / or hydroxide 1 to
40 parts by weight, (c) polyhydroxy aromatic compound 0.5 to 10
Parts by weight, (d) general formula (Here, R _{1 to} R ₃ are aryl groups, aralkyl groups, alkyl groups or alkoxy groups having 1 to 20 carbon atoms, X ⁻ is an anionic group, and n is 1 to 4, m is 2 or The fourth phosphonium salt compound represented by 3) 0.1 to 10
Parts by weight and (e) an amount of 1,8-diazabicyclo [5,4,0] -undec-7-ene, 1,5-diazabicyclo [4,3,0] -that does not substantially vulcanize the fluoroelastomer. Non-5
-A fluorinated elastomer composition containing an ene or a 4-dialkylaminopyridine having an alkyl group having 1 to 4 carbon atoms. 4. The fluorine-containing elastomer composition according to claim 3, wherein a quaternary phosphonium salt compound of the general formula [I] in which all of R _{1 to} R ₃ are phenyl groups is used.