JPH0223574B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a fluororubber composition. More specifically, the present invention relates to a fluororubber composition containing a quaternary ammonium salt compound as a vulcanization accelerator component. [Prior art] Fluororubber vulcanizates have useful properties in terms of heat resistance, chemical resistance, oil resistance, weather resistance, etc. at high temperatures, so they are used as sealing materials for gaskets, O-rings, packings, etc. Demand for hoses, sheets, etc. is rapidly increasing in fields such as the automobile industry, hydraulic industry, general machinery industry, and aircraft industry. In other words, in addition to the demand for more efficient molding processes, various demands regarding fluororubber vulcanizates are becoming more diverse and stricter. Vulcanization of fluorocarbon rubber 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, it had disadvantages in terms of 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
Phosphonium salt compound (JP-A-47-191),
Quaternary ammonium salt compound (Japanese Patent Publication No. 52-38072, Japanese Patent Publication No. 47-3831), 8-alkyl (or aralkyl)-1,8-diazabicyclo[5,4,0]-undec-7-ene quaternary ammonium salt compound (Japanese Patent Publication No. 52-8863, JP-A-48-55231, JP-A-63-51441) or 1, in an amount that does not substantially vulcanize the fluororubber. Combination with 8-diazabicyclo[5,4,0]-undec-7-ene (Japanese Patent Publication No. 57-20333), 5-alkyl (or aralkyl)-1,
Quaternary ammonium salt compound of 5-diazabicyclo[4,3,0]-5-nonene (JP-A-59-206451
Publication No. 59-232137, Publication No. 63-51441), etc. are used. However, these quaternary ammonium salt compounds used as vulcanization accelerators, especially 5-alkyl (or aralkyl)-1,5-diazabicyclo[4,3,0]-5-nonene quaternary ammonium salt compounds, Generally, it has the following drawbacks. (1) It is highly hygroscopic and hygroscopic, making it difficult to handle during storage, kneading, etc. (2) It is difficult to prepare masterbatch dispersions with fluoro rubber due to poor kneading processability and dispersibility. Even if it can be adjusted, care must be taken when storing it.(3) Poor moldability due to insufficient mold releasability.(4) Vulcanized physical properties such as elongation and tensile strength, compression set, etc. [Problem to be solved by the invention] The object of the present invention is to use 5-alkyl (or aralkyl)-1,5-diazabicyclo[4] as a vulcanization accelerator. The object of the present invention is to provide a vulcanizable fluororubber composition that does not exhibit these drawbacks when a quaternary ammonium salt compound of ,3,0]-5-nonene is used. [Means for Solving the Problems] The object of the present invention is to provide (a) fluororubber, (b) divalent metal oxide and/or hydroxide, (c) polyhydroxy aromatic compound, and ( d) General formula (wherein, R is an alkyl group having 1 to 24 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, and X ^- is a tetrafluoroborate group or hexafluorophosphate group) This is achieved by a fluororubber composition containing. The fluororubber to be vulcanized is a highly fluorinated elastomeric copolymer; for example, a copolymer of vinylidene fluoride and another fluorine-containing olefin can be used. Specifically, for example, vinylidene fluoride, hexafluoropropene, pentafluoropropene, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, vinyl fluoride, perfluoroacrylate, perfluoroalkyl acrylate, perfluoromethyl Examples include one or more copolymers such as vinyl ether and perfluoropropyl vinyl ether, preferably vinylidene fluoride-hexafluoropropene binary copolymers and vinylidene fluoride-tetrafluoroethylene-hexafluoropropene ternary copolymers. Examples include copolymers. Divalent metal oxides used as acid acceptors,
Hydroxides include magnesium, calcium,
One or more types of oxides and hydroxides of divalent metals such as barium, lead, and zinc are
It is generally used in a proportion of about 1 to 40 parts by weight, preferably about 3 to 15 parts by weight. 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 amounts of about 0.5 to 100 parts by weight of fluorocarbon rubber.
It is used in a proportion of 10 parts by weight, preferably about 0.5 to 6 parts by weight. 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. As the quaternary ammonium salt compound represented by the above general formula, preferably a compound in which R is a benzyl group is used. Such 5-benzyl-1,
5-Diazabicyclo[4,3,0]-5-nonenium tetrafluoroborate (abbreviation: DBN-
F) or hexafluorophosphate (abbreviation:
DBN-P) is an aqueous solution of 5-benzyl-1,5-diazabicyclo[4,3,0]-5-nonenium halide with a tetrafluoroborate salt compound or hexafluorophosphate salt compound, generally the sodium salt thereof. When the compound is added, it quickly precipitates out, and can be easily separated from the solvent and by-product salts by simply filtering it. A typical 5-benzyl-1,5-diazabicyclo[4,3,0]-5-nonenium salt conventionally used is chloride (abbreviation: DBN-C).
or halide such as bromide (abbreviation: DBN-B), which is synthesized by combining 1,5-diazabicyclo[4,3,0]-5-nonene with benzyl chloride or benzyl bromide in a solvent such as toluene. The crystals formed are deliquescent, so there is a restriction that removal and filtration must be carried out in substantially moisture-free air (dry air) or under a nitrogen atmosphere. Of course, similar considerations are required during storage and formulation. In the synthesis of tetrafluoroborate or hexafluorophosphate used in the present invention, such deliquescence of the halide can be utilized in the form of an aqueous solution, and the product can be easily obtained as a crystal. By the way, other anions,
For example, NO ₃ ^- , SO ₄ ^-- , PO ₄ ^--- , RCOO ^- ,
CO ₃ ^-- , BO ₂ ^- , SCN ^- , SiF ₆ ^-- , RSO ₃ ^- ,
With anions such as TiF ₆ ^--, crystals do not precipitate through an anion exchange reaction with halides, and the target product can only be separated by applying means such as concentration and separation of by-product salts, whereas with BF ₄ ^-- In the case of , PF ₆ ^- , it is extremely easy to separate the crystals produced by the anion exchange reaction by simply filtering them. Moreover, the obtained 5-benzyl-1,5-diazabicyclo[4,3,0]-5-nonenium tetrafluoroborate or hexafluorophosphate has extremely low hygroscopicity, and therefore it is difficult to absorb dry air during filtration separation. A nitrogen gas atmosphere is not required, and the same applies during storage and compounding. Incidentally, these quaternary ammonium salt compounds were placed in a shear dish and left in a constant temperature and humidity chamber at 25°C and 100% humidity for 2 days, and then the moisture content (increased weight/initial weight x 100) was measured. 5-benzyl-1,
When compared with 5-diazabicyclo[4,3,0]-5-nonenium salt or 8-benzyl-1,8-diazabicyclo[5,4,0]-undec-7-enium chloride (abbreviation: DBU-C) , the following results were obtained. Moisture content of salt compound at 100℃ (%) DBN-F Liquid 6.5 DBN-P 〃 4.8 DBN-C Solid 42.5 DBN-B 〃 46.3 DBU-C 〃 27.4 Furthermore, these tetrafluoroborates and hexafluorophosphates , have melting points of approximately 80°C and 100°C, respectively, and are easily melted during heat kneading (100°C) using rolls, kneaders, banburys, etc., so that a significant improvement in dispersibility can be achieved. One or two of these quaternary ammonium salt compounds are used in a proportion of about 0.1 to 5 parts by weight, preferably about 0.1 to 2 parts by weight, per 100 parts by weight of fluororubber. If the proportion used is less than this, the crosslinking properties will be poor, and if the proportion is greater than this, the properties of the vulcanizate will be significantly adversely affected. At this time, the quaternary ammonium salt compound can be used as a masterbatch with the fluororubber. Generally, the vulcanization accelerator component of fluororubber tends to cause poor dispersion due to its small blending ratio, and therefore it is often used as a masterbatch as a means to prevent this. The concentration of the vulcanization accelerator in the masterbatch is generally about 20 to 50%, and if it is less than this, the amount to be blended becomes too large, which is not preferable. The quaternary ammonium salt compound used in the present invention, unlike the corresponding halide, can be easily made into master batches. Specifically, when the kneading properties of 500 g of master batches with various vulcanization accelerator concentrations were evaluated, the following results were obtained. The results were obtained.

〔Effect of the invention〕

The fluororubber composition according to the present invention is similar to the conventional
Ammonium salt compounds, especially the known 5-benzyl-1,5-diazabicyclo[4,3,0]-5-
The hygroscopicity, which is a drawback of nonenium salts, has been improved, and as a result, the ease of handling and stability have also been significantly improved. In addition, kneading operability, dispersibility, and processability have been improved by lowering the melting point and creating a masterbatch, and furthermore, excellent improvements have been achieved in terms of vulcanization physical properties, shaping properties, and mold contamination. . [Example] Next, the present invention will be explained with reference to an example. Reference examples 1-2 Capacity with stirring device and Dimroth cooler
26.05g of 1,5-diazabicyclo[4,3,0]-5-nonene in a 300ml separable flask
(0.21 mol), 100 g of toluene and benzyl chloride
27.8g (0.22 mole) or 37.6g benzyl bromide
(0.22 mol) was added one by one, and while stirring, 100~
After reacting at 110°C for about 1.5 hours, white crystals of 5-benzyl-1,5-diazabicyclo[4,3,0]-
5-nonenium chloride (DBN-C) or bromide (DBN-B) was formed. After the reaction is complete, add approximately 50 ml of water to the reaction mixture in the separable flask, and add DBN-C or DBN-B.
The mixture was separated into an aqueous solution layer and a toluene layer containing unreacted benzyl chloride or benzyl bromide dissolved therein. When 23 g (0.21 mol) of sodium tetrafluoroborate NaBF ₄ is added to each of these aqueous solutions with stirring, water-insoluble white crystals will gradually precipitate, and after about 5 minutes, they should be filtered, washed with water, and dried. 5-benzyl-1,5-diazabicyclo[4,3,0]-5-nonenium tetrafluoroborate (DBN-F) is converted into DBN-C
57.3g (90% yield) or from DBN-B
56.7g (yield 89%) was obtained. Reference Example 3 In Reference Examples 1 and 2, when 35.3 g (0.21 mol) of sodium hexafluorophosphate NaPF ₆ is used instead of sodium tetrafluoroborate, 5-benzyl-1,5-diazabicyclo[4,3 ,0]-5-nonenium hexafluorophosphate (DBN-P) (68.4 g (yield 90
%) obtained. DBN-F obtained in each of the above reference examples or
DBN-P is 35% by weight and 65% by weight of fluoro rubber.
They were each used as a masterbatch (the blending amounts in Tables 1 and 3 below are the masterbatch amounts). Examples 1-2, Comparative Examples 1-3 Copolymerization of 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 Copolymer [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); Fluororubber A], a fluororubber composition was prepared by kneading the formulation shown in Table 1 below using an 8-inch mixing roll. Note that all amounts below are in parts by weight.

[Table] Mooney viscosity and scorch time (the time required for the Mooney viscosity to reach the minimum value + 5, which is a guideline for the storage stability and processing safety of the dough) for the various fluororubber compositions obtained. ) was measured at a measurement temperature of 121°C. Furthermore, the composition was press-vulcanized at 180°C for 5 minutes,
Next, secondary vulcanization was performed in an oven at 230°C for 22 hours, and various physical properties of each vulcanized product were measured according to JIS K-6301. Measurement of compression set is performed using O of P-24.
- Manufactured by vulcanizing the ring under the same conditions, and 25
% compression and measurement. The results of these measurements are shown in Table 2 below.

【table】

[Table] Examples 3 to 4, Comparative Example 4 The formulations shown in Table 3 below were kneaded using an 8-inch mixing roll to prepare a fluororubber composition.

[Table] Regarding the obtained fluororubber composition, Example 1
- In the same manner as in 2, various physical properties and characteristics were measured. However, vulcanization was performed by press vulcanization at 170°C for 8 minutes, followed by secondary vulcanization in an oven at 200°C for 22 hours. Furthermore, a valve stem seal having a shape as described in Japanese Utility Model Publication No. 53-33206 was continuously molded from this composition without using a mold release agent, and during vulcanization molding (170°C, 8 minutes). The formability of press vulcanization) and the contamination of the mold (which was initially observed as cloudiness on the mold surface, and when molding continued, scum formed on the mold) were evaluated. The above results are shown in Table 4 below.

【table】

【table】

Claims (1)

[Claims] 1 (a) 100 parts by weight of fluororubber, (b) about 1 to 40 parts by weight of divalent metal oxide and/or hydroxide, (c)
About 0.5 to 10 parts by weight of a polyhydroxy aromatic compound and (d) general formula (wherein, R is an alkyl group having 1 to 24 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, and X ^- is a tetrafluoroborate group or hexafluorophosphate group) A fluororubber composition containing about 0.1 to 5 parts by weight. 2. The fluororubber composition according to claim 1, wherein the quaternary ammonium salt compound (d) is used as a masterbatch with the fluororubber (a). 3. A masterbatch of the quaternary ammonium salt compound (d) according to claim 1 and the fluororubber (a).