JPS6365705B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a fluorine-containing elastomer composition. More specifically, we aim to create a vulcanizate that has excellent vulcanization properties, dispersibility during kneading processing, shaping properties during vulcanization molding, storage stability of dough, and processing safety, as well as greatly improved vulcanized physical properties. The present invention relates to a fluorine-containing elastomer composition. Fluorine-containing elastomer vulcanizates have useful properties in terms of heat resistance, chemical resistance, oil resistance, weather resistance, etc. at high temperatures, so they are used in sealing materials such as gaskets, O-rings, packing, hoses, sheets, etc. Demand is rapidly increasing in fields such as the automobile industry, hydraulic industry, general machinery industry, and aircraft industry. In other words, this means that
In addition to the demand for more efficient molding processes, various demands regarding fluorine-containing elastomer vulcanizates have become more diverse and stricter. Vulcanization of fluorine-containing elastomers was initially carried out using polyamine derivatives such as hexamethylene diamine carbamate and methylene bis(cyclohexyl) amine carbamate, but these vulcanization systems had poor scorch resistance (processing safety). However, the vulcanizate had disadvantages in terms of hardness, storage stability) and compression set of the vulcanizate. Subsequently, as a vulcanization system capable of improving these drawbacks, a method of crosslinking with a polyhydroxy aromatic compound in the presence of a vulcanization accelerator and an acid acceptor was proposed, and has been put into practical use to this day. As a vulcanization accelerator in this vulcanization system, quaternary
class phosphonium compounds (Japanese Unexamined Patent Application Publication No. 1983-191),
Quaternary ammonium compounds (Special Publication No. 52-38072)
No. 47-3831), quaternary ammonium compounds of 8-alkyl (or aralkyl)-1,8-diazabicyclo[5,4,0]-undec-7-ene (Japanese Patent Publication No. 1987-3831), No. 8863), JP-A-48-55231) or a combination thereof with 1,8-diazabicyclo[5,4,0]-undec-7-ene in an amount that does not substantially vulcanize the fluorine-containing elastomer. A combination (Japanese Unexamined Patent Publication No. 131239/1983) is used. However, even when these vulcanization systems are used, the compression set of the vulcanizate is still not at a fully satisfactory level, especially at high temperatures, and the drawback of low mechanical strength of the vulcanizate still remains. I haven't. Furthermore, in terms of formability during vulcanization molding, the above-mentioned known vulcanization systems have problems in that cracks, defects, and fine foaming occur, especially when manufacturing molded products with complex shapes. Therefore, although there are demands for the various uses mentioned above, the current situation is that it is not possible to satisfy all of them. In addition, as a vulcanization accelerator, an 8-alkyl (or 8-aralkyl)-1,8-diazabicyclo[5,4,0]undec-7-enium quaternary ammonium compound, or a substantially fluorine-containing When a combination of 1,8-diazabicyclo[5,4,0]undec-7-ene is used in an amount that does not vulcanize the elastomer, in addition to the drawbacks mentioned above, it is extremely susceptible to moisture absorption and water leakage during storage. Therefore, special consideration is required for storage, which not only may cause problems in handling, but also has the drawback of deteriorating vulcanization characteristics and vulcanized physical properties. Furthermore, when a quaternary phosphonium compound is used as a vulcanization accelerator, in addition to the above-mentioned drawbacks, the melting point of this compound is generally high and is often over 200°C, so it is difficult to incorporate it during kneading processing. The drawback is that poor dispersion tends to occur in the composition. As a method of improving the poor dispersibility of the quaternary phosphonium compound in such a fluorine-containing elastomer composition, a molecular compound having an equimolar amount of an active hydrogen-containing aromatic compound and a quaternary phosphonium compound having a melting point lower than that of the quaternary phosphonium compound is used. It has been proposed that
−108884), although some results have been seen,
Even with this, I still haven't reached a level where I can be fully satisfied. The present inventor has developed the vulcanization system of the fluorine-containing elastomer described in JP-A No. 55-108884, namely (b) below,
By further adding component (e) or both components (e) and (f) to the vulcanization system consisting of components (c) and (d), the storage stability, processing safety, and vulcanization of the fabric can be improved. It not only has excellent curable properties (vulcanization fluidity, vulcanization speed, etc.), but also improves dispersibility during kneading and vulcanization, which were problems that should be improved in many of the known vulcanization systems mentioned above. The present inventors discovered that it is possible to simultaneously significantly improve the formability during sulfur molding, moisture absorption and moisture during storage, and the mechanical strength and compression set of vulcanizates, leading to the completion of the present invention. . Therefore, the present invention relates to a fluorine-containing elastomer composition, which comprises (a) a fluorine-containing elastomer, (b) a divalent metal oxide and/or hydroxide, and (c) a polyhydroxy Aromatic compound, (a) polyhydroxy aromatic compound - quaternary phosphonium compound equimolar molecular compound, and (e) compound selected from the following compound group (a) 1,5-diazabicyclo[4,3,0] 4-dialkylaminopyridine having non-5-ene or an alkyl group having 1 to 4 carbon atoms (b) N-alkyl-substituted amide compound (c) alkylene glycol, polyalkylene glycol or their mono- or dialkyl ether or the above (e) (f) for compounds of group (b) or (c) of component ).
It contains a combination of 1,8-diazabicyclo[5,4,0]undec-7-ene. Prior to the present invention, the present inventor discovered that a quaternary phosphonium compound and substantially no fluorine-containing elastomer were not vulcanized as a vulcanization accelerator component in a vulcanization system using a polyhydroxy aromatic compound as a crosslinking agent. amount of 1,5-diazabicyclo[4,3,0]non-5
We have proposed a method using a combination of -ene or 4-dialkylaminopyridine having an alkyl group of 1 to 4 carbon atoms (see JP-A-55-73979), which improves the storage stability and processing safety of dough. sex,
It not only has excellent vulcanization properties (vulcanization fluidity, vulcanization speed, etc.) and resistance to moisture absorption and tide moisture during storage, but also improves formability during vulcanization molding, mechanical strength of vulcanizate, and compression durability. We have obtained knowledge that distortion can be significantly improved. In the present invention, in place of the quaternary phosphonium compound used in this vulcanization system, a polyhydroxy aromatic compound which has a lower melting point and is advantageous in terms of dispersibility - equimolar molecules of a quaternary phosphonium compound is used. using a compound, and further combining this with the component (e) above.
Compounds of group (a), (b) or (c) or this (b) or
(c)
By using a combination of the group compound and the component compound (f), the synergistic effect between these compounds further improves the dispersibility during kneading and shaping properties during vulcanization molding. It is possible to further improve the vulcanization rate and compression set of the vulcanizate without adversely affecting scorch resistance (fabric storage stability, processing safety), etc. It is extremely useful as a strain vulcanization system. The fluorine-containing elastomer vulcanized in this vulcanization system is a highly fluorinated elastomer-like copolymer, for example, a copolymer of vinylidene fluoride and another fluorine-containing olefin is used. be able to. Specifically, vinylidene fluoride, hexafluoropropene, pentafluoropropene, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, vinyl fluoride, perfluoroacrylate, perfluoroalkyl acrylate, perfluoromethyl vinyl ether Examples thereof include one or more copolymers such as perfluoropropyl vinyl ether, and preferably vinylidene fluoride-hexafluoropropene binary copolymers and vinylidene fluoride-tetrafluoroethylene-hexafluoropropene. Tertiary copolymers may be mentioned. Divalent metal oxides used as acid acceptors,
Hydroxides include magnesium, calcium,
One or more oxides or hydroxides of divalent metals such as barium, lead, zinc, etc. are generally about 1 to 40 parts by weight, preferably about 3 to 15 parts by weight, per 100 parts by weight of the fluorine-containing elastomer. used at a rate of Examples of the polyhydroxy aromatic compound as a crosslinking agent include 2,2-bis(4-hydroxyphenyl)propane [bisphenol A], 2,2-
Bis(4-hydroxyphenyl) perfluoropropane [bisphenol AF], hydroquinone, catechol, resorcinol, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenyl sulfone,
Examples include 2,2-bis(4-hydroxyphenyl)butane, preferably bisphenol A,
Bisphenol AF, hydroquinone, etc. are used. They may also be in the form of alkali metal or alkaline earth metal salts. These crosslinking agents are used in an amount of about 0.5 to 10 parts by weight, preferably about 0.5 to 6 parts by weight, per 100 parts by weight of the fluorine-containing elastomer. If the usage ratio is less than this, the crosslinking density will be insufficient, while if it is more than this, the crosslinking density will become too high and there will be a tendency to lose rubber-like elasticity. Examples of polyhydroxy aromatic compounds that form molecular compounds with quaternary phosphonium compounds include hydroquinone, catechol, resorcinol, bisphenol A, bisphenol AF, 4,4'-dihydroxydiphenyl, and 4,4'-dihydroxydiphenyl. Enylmethane, 4,4'-dihydroxydiphenylsulfone, etc. are used. As a quaternary phosphonium compound, the general formula (Here, R ₁ to _{R 4} are an alkyl group, an aralkyl group, an aryl group, an alkenyl group, a polyoxyalkylene group, a fluoroalkyl group, etc.,
X ^- is an anion such as halide, hydroxylate, alkoxylate, carboxylate, phenoxide, sulfonate, sulfate, sulfite, carbonate or nitrate), for example tetraphenylphosphonium chloride, tetraphenylphosphonium bromide , tetraoctylphosphonium chloride, tetra-n-butylphosphonium chloride, tetraethylphosphonium chloride, tetramethylphosphonium chloride, tetramethylphosphonium bromide, triphenylbenzylphosphonium chloride, triphenylbenzylphosphonium bromide, triphenylbenzylphosphonium stearate, triphenylbenzyl Phosphonium benzoate, triphenylisobutylphosphonium bromide, trioctyl-n-butylphosphonium chloride, trioctylbenzylphosphonium chloride, trioctylbenzylphosphonium acetate, triphenyl-2,4-dichlorobenzylphosphonium chloride, trioctylmethoxyethoxyethylphosphonium chloride, triphenyl Examples include enylethoxycarbonylmethylphosphonium chloride and triphenylallylphosphonium chloride. These polyhydroxy aromatic compounds and quaternary phosphonium compounds generally have a molar ratio of about 0.5 to
2, preferably at a ratio of about 0.8 to 1.1, in a polar organic solvent or a carbonyl group-containing organic solvent. As the polar organic solvent, alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, and isobutyl alcohol are preferably used, but in addition, dimethyl sulfoxide, dimethyl formamide, dimethyl Acetamide and the like can also be used. These polar solvents can also be used in combination with non-polar organic solvents as long as they do not interfere with the reaction. The reaction is carried out at a temperature of -30° to 100°C, preferably 20° to 80°C, and a temperature of 0.1 to
The reaction proceeds sufficiently under the reaction conditions for 10 hours, preferably 1 to 4 hours, and equimolar molecular compounds are precipitated as crystals in a good yield of 90% or more. As the carbonyl group-containing organic solvent, ketones such as methyl ethyl ketone and acetone, and esters such as acetic acid ester are used. Polyhydroxy aromatic compounds generally dissolve in these carbonyl group-containing organic solvents, but quaternary phosphonium compounds, on the other hand, often do not dissolve in these types of solvents, so polar organic solvents such as alcohols are used as reaction solvents. Preference is given to using a solvent. The polyhydroxy aromatic compound-quaternary phosphonium compound equimolar molecular compound obtained as a result of such a reaction has a crystalline melting point that is significantly lower than that of the corresponding quaternary phosphonium compound, as shown in the following table. Therefore, a remarkable improvement in dispersibility during kneading processing is achieved. Table 1 Bisphenol A Melting point 153-156℃ Bisphenol AF 161℃ Triphenylbenzyl phosphonium chloride
>300℃ Bisphenol A molecular compound 157℃ Bisphenol AF molecular compound 184℃ One or more of these equimolar molecular compounds used as a component of the vulcanization system are approximately It is used in a proportion of 0.1 to 10 parts by weight, preferably about 0.2 to 3 parts by weight.
If the usage ratio is less than this, the vulcanization speed will be slow,
It also has poor crosslinking properties; on the other hand, if the amount exceeds this range, it not only adversely affects various properties of the vulcanizate, such as heat aging resistance and compression set, but also affects the storage stability and processing safety of the fabric. Inconvenience will arise. In the vulcanization system of the present invention, in addition to the above-mentioned components, a compound selected from the following compound groups (a), (b), and (c) is further blended into the fluorine-containing elastomer composition. It is an essential requirement to do so. (a) 4-dimethylaminopyridine, 4-diethylaminopyridine, 4-di(n-butyl) having 1,5-diazabicyclo[4,3,0]non-5-ene or an alkyl group having 1 to 4 carbon atoms 4-dialkylaminopyridine (b) such as aminopyridine; N-alkyl substituted carboxylic acid amide such as dimethylformamide and dimethylacetamide;
N-alkyl substituted amide compounds such as N-alkyl substituted heterocyclic amide such as N-methyl-2-pyrrolidone, N-alkyl substituted phosphoric acid amide such as hexamethylphosphoramide (iii) N-alkyl substituted amide compounds such as ethylene glycol, propylene glycol, etc. Polyalkylene glycols such as alkylene glycol and polyethylene glycol, or their mono- or dialkyl ethers such as monomethyl ether, dimethyl ether, and diethyl ether By blending and containing these compounds in the vulcanization system, the crosslinking reaction is significantly accelerated, resulting in crosslinking. In addition to improving the mechanical strength, the shapeability during vulcanization molding is also improved. Furthermore, since the accelerating effect of the crosslinking reaction is very large, the amount of the equimolar molecular compound compounded can be reduced, and therefore the compression set of the vulcanizate can be effectively improved.
Although the causes of this cross-linking reaction promotion effect have not yet been fully elucidated, at least the above-mentioned (b)
Regarding the compounds of group (c), there are reasons such as contributing to the promotion of crosslinking reaction as a result of improving compatibility or dispersibility between polyhydroxy aromatic compounds, equimolar molecular compounds and fluorine-containing elastomers. It will be done. The compound of group (a) or the component compound (f) may be used in an amount that does not substantially vulcanize the fluorine-containing elastomer, generally not more than about 0.1 part by weight per 100 parts by weight of the fluorine-containing elastomer. Preferably, it is used in a proportion of about 10% or less based on equimolar molecular compounds. If the proportion used is higher than this, generally not only the storage stability and processing safety of the composition dough are adversely affected, but also the vulcanizate tends to lose its rubber-like elasticity. The compound of group (b) or (c) is used in an amount of about 5 parts by weight or less, preferably about 3 parts by weight or less, per 100 parts by weight of the fluorine-containing elastomer. The reason why an upper limit is set on the usage ratio is that if the amount is more than this, the vulcanization rate becomes extremely high, but at the same time, the scorch resistance of the fabric and the compression set of the vulcanizate are adversely affected. Each component of the vulcanization system including these compounds is
It may be blended and kneaded as is, or it may be diluted and dispersed with carbon plaque, silica, clay, talc, diatomaceous earth, barium sulfate, etc., or used as a masterbatch dispersion with a fluorine-containing elastomer. . In addition, in the composition of the present invention,
In addition to the above formulations, conventionally known fillers, reinforcing agents, plasticizers, lubricants, processing aids, pigments, etc. can be appropriately incorporated into the composition. Vulcanization is generally carried out after mixing the fluorine-containing elastomer with each of these vulcanization system components and the various additives mentioned above by a commonly used mixing method such as roll mixing, kneader mixing, Banbury mixing, or solution mixing. , by heating.
Generally, primary vulcanization is performed at a temperature of about 140 to 200°C for about 2
For about 120 minutes, secondary vulcanization is carried out by heating at a temperature of about 150 to 250°C for about 0 to 30 hours. The fluorine-containing elastomer composition according to the present invention is
As shown in the results of the following examples, the vulcanization properties,
It has excellent shapeability during vulcanization molding, dispersibility during kneading processing, storage stability, and processing safety, and there is no concern about moisture absorption or tide moisture during storage, and the vulcanizate has low compression set and mechanical strength. Since it has been greatly improved in this respect, it can be effectively used in all of the above-mentioned applications. Next, the effects of the present invention will be explained with reference to Examples. Example 1 Copolymer obtained by copolymerizing vinylidene fluoride and hexafluoropropene in an aqueous medium using acetone as a chain transfer agent and in the presence of ammonium persulfate as a polymerization initiator Body component molar ratio 78:22, solution viscosity ηsp/c 0.90 (35°C, in acetone, c=1.0), polymer Mooney viscosity
ML ₁₊₁₀ 49 (120℃); Fluorine-containing elastomer A], formulations 1 to 8 shown in Table 2 below (those with bracketed numbers are comparative examples; the same applies below) were kneaded using an 8-inch mixing roll to prepare a fluorine-containing elastomer composition.
Note that all amounts below are in parts by weight.

【table】

[Table] Regarding the various fluorine-containing elastomer compositions obtained, Mooney viscosity and scorch time (the time required for Mooney viscosity to reach the minimum value + 5) are used to determine the storage stability and processing safety of the fabric. ) was measured at a measurement temperature of 121°C. Further, the vulcanization properties were measured using an oscillating disk rheometer (ODR) manufactured by Toyo Seiki Co., Ltd. Furthermore, the composition was press-vulcanized at 180°C for 5 minutes,
Next, secondary vulcanization was performed in an open environment at 230°C for 22 hours, and various physical properties of each vulcanized product were measured according to JIS K-6301. To measure compression set, a 5.2 mm diameter O-ring was vulcanized under the same conditions and then
The measurement was performed under 25% compression. In addition, Jikko Sho 53-33206
A valve stem seal having the shape described in the above publication was molded from this composition, and its formability during vulcanization molding was also evaluated. The results of these measurements are shown in Table 3 below.

【table】

[Table] From the comparison of the results of the inventive examples and comparative examples shown in Table 3, the vulcanization system according to the present invention has particularly good scorch resistance (storage stability, It can be seen that the composition is not only excellent in terms of processing safety) and vulcanization properties (acceleration rate), but also significantly improves the tensile strength and compression set of the vulcanizate. Furthermore, it can be seen that the shapeability during vulcanization molding is also very good. Example 2 Fluorine-containing elastomer A used in Example 1
The compositions of formulations 9 to 16 shown in Table 4 below were kneaded using an 8-inch mixing roll to prepare fluorine-containing elastomer compositions.

【table】

[Table] Physical properties and characteristics of each of the obtained fluorine-containing elastomer compositions were measured in the same manner as in Example 1. However, vulcanization was performed by press vulcanization at 170°C for 8 minutes, followed by secondary vulcanization in an open environment at 200°C for 22 hours. The results obtained are shown in Table 5 below.

[Table] A comparison of the results of the examples of the present invention and the comparative examples shown in Table 5 shows the following facts. 9-10/(11)-(16) Equimolar molecular compound and N-methyl- as a vulcanizing agent
The vulcanization system of the present invention that uses 2-pyrrolidone (and 1,8-diazabicyclo[5,4,0]undec-7-ene) in combination with 2-pyrrolidone (and 1,8-diazabicyclo[5,4,0]undec-7-ene) has higher
Even in vulcanization systems containing fillers such as barium sulfate, they are excellent in vulcanization properties (vulcanization rate), tensile strength and compression set of the vulcanizate, and are also excellent in shaping during vulcanization molding. It can be seen that the properties are also very good. Example 3 Vinylidene fluoride-tetrafluoroethylene-
Hexafluoropropene (molar ratio 42:40:18) 3
Original copolymer [Polymer Mooney viscosity ML ₁₊₁₀ 87 (121
℃) ; Fluorine-containing elastomer B], the formulations shown in Table 6 below were kneaded using an 8-inch mixing roll to prepare a fluorine-containing elastomer composition.

[Table] Physical properties and characteristics of each of the obtained fluorine-containing elastomer compositions were measured in the same manner as in Example 1. The results obtained are shown in Table 7 below.
is shown.

[Table] From the comparison of the results of the examples of the present invention and the comparative examples of known vulcanization systems shown in Table 7, 1,5-diazabicyclo[4,3,0]non-5-ene, 4-dimethylaminopyridine , N-methyl-2-pyrrolidone or a combination of two or more thereof can effectively improve the vulcanization properties and the tensile strength of the vulcanizate. Furthermore, in terms of formability during heat molding,
It turns out that it is very good.

Claims (1)

[Scope of Claims] 1 (a) Fluorine-containing elastomer, (b) divalent metal oxide and/or hydroxide, (c) polyhydroxy aromatic compound, (d) polyhydroxy aromatic compound -
Quaternary phosphonium compound equimolar molecular compound and (e) compound selected from the following compound group (a) 1,5-diazabicyclo[4,3,0]non-5-ene or alkyl having 1 to 4 carbon atoms A fluorine-containing elastomer composition containing a 4-dialkylaminopyridine (b) N-alkyl-substituted amide compound (c) an alkylene glycol, a polyalkylene glycol, or a mono- or dialkyl ether thereof. 2 (a) Fluorine-containing elastomer, (b) divalent metal oxide and/or hydroxide, (c) polyhydroxy aromatic compound, (d) polyhydroxy aromatic compound -
Quaternary phosphonium compound (e) Compound selected from the following compound group (b) N-alkyl substituted amide compound (c) Alkylene glycol, polyalkylene glycol or their mono- or dialkyl ether, and (f) )1,8-diazabicyclo[5,4,0]
A fluorine-containing elastomer composition containing undec-7-ene. 3. The fluorine-containing elastomer composition according to claim 2, which contains component (f) in an amount that does not substantially vulcanize the fluorine-containing elastomer.