JP4992374B2 - Fluoro rubber blend - Google Patents

Description

The present invention relates to a fluororubber blend. More specifically, the present invention relates to a fluororubber blend used as a molding material for a vulcanized molded product that comes into contact with a low-grade fuel oil.

Fluororubber for seal materials such as oil seals used for fuel oil applications include fluorine rubber that can be peroxide-crosslinked with excellent liquid resistance, but high fluorine content that is copolymerized with tetrafluoroethylene. An amount of ternary fluororubber is known to exhibit particularly good fuel oil resistance. However, the following disadvantages are recognized in the fluorine rubber having a high fluorine content, and the functions of an oil seal for fuel oil and the like are deteriorated.
(1) The low temperature characteristic is about -7 ℃ with TR10 value, which is inferior in cold resistance, so the sealing performance of sealing materials such as oil seals used in cold districts is reduced.
(2) The strength drop after soaking in low-grade fuel oil is large, and as a result, the pressure resistance and wear resistance of seal materials such as oil seals are reduced.
(3) Fluororubber that is not copolymerized with tetrafluoroethylene has a large volume change rate after immersion in low-grade fuel oil and a large decrease in strength, so it is used as a sealing material for oil seals for low-grade fuel oil applications. Is difficult.

In Patent Document 1 describing the invention according to the application of the present applicant, perfluoro (methoxymethoxyethyl vinyl ether) having a crosslinking site derived from a bromine-containing and / or iodine-containing compound and having a fluorine content of 64% or more, A fluororubber-based sealing material composition is described in which an acid acceptor metal compound, an organic peroxide and a polyfunctional monomer are added to a fluororubber comprising a copolymer of vinylidene fluoride and tetrafluoroethylene (and hexafluoropropylene). It is said that it is excellent in heat resistance, cold resistance and fuel oil resistance, and is suitably used as a sealing material for automobile fuel. Fuel oil resistance is not limited to gasoline, which is a hydrocarbon fuel, but also fuel efficiency, etc. 60 ° C for fuel oil C-methanol (volume ratio 80:20) mixed fuel, also used for oxygen-containing fuels such as ether and alcohol Changes in hardness and volume change before and after immersion for 70 hours are measured.
JP 2004-217892 A

  The comparative example of Patent Document 1 includes a vinylidene fluoride / tetrafluoroethylene / perfluoro (methyl vinyl ether) having a crosslinking site derived from a brominated and / or iodinated unsaturated fluorohydrocarbon having a fluorine content of 64% or 67%. ) Based copolymer rubber is inferior in cold resistance (TR-10 value) and resistance to oxygenated fuel oil (methanol), and it is described that there is leakage in the low temperature seal test and fuel seal test. In particular, it has been shown that this tendency is observed with a fluorine content of 64%.

  An object of the present invention is to provide a fluororubber using a vinylidene fluoride / tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer rubber, which has excellent fuel oil resistance, particularly low-grade fuel oil property. It is in.

  The object of the present invention is that peroxide crosslinking is possible, vinylidene fluoride / tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer rubber having a fluorine content of 64 to 67% by weight and peroxide crosslinking are possible. And a vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer rubber having a fluorine content of 69 to 72% by weight, and an organic peroxide having a blend fluorine content of 65 to 69%. Is achieved by a fluororubber blend which can be more co-crosslinked. By adding an organic peroxide as a co-crosslinking agent to the fluororubber blend, co-crosslinking between the respective blend rubbers is made possible.

  The fluororubber blend according to the present invention blends a vinylidene fluoride / tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer rubber and a vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer rubber, and By prescribing and using the fluorine content, these co-crosslinked products can be effectively used as vulcanized molded products excellent in fuel oil resistance, particularly low-grade fuel oil properties, particularly as sealing materials.

More specifically, the fuel oil resistance is excellent in terms of the volume change rate and the strength change rate when immersed in a low-grade fuel oil , particularly the stability of the change over time of these change rates. More specifically, the volume change rate after immersion in low-grade fuel oil is stabilized, the rate of change in strength is reduced, and not only a stable strength is ensured even after long-term immersion, but also a high fluorine content. Compared with the vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer rubber, a TR10 value of −15 ° C. or less and a significant improvement in low-temperature characteristics is achieved.

The fluororubber blend of the present invention having such characteristics can be effectively used as a molding material for a fuel oil seal material such as an oil seal for automobile fuel oil, which is easily reduced in quality.

  As the peroxide-crosslinkable vinylidene fluoride / tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer rubber, perfluoro (alkyl vinyl ether) is perfluoro (methyl vinyl ether), perfluoro (ethyl vinyl ether), perfluoro ( Propyl vinyl ether), preferably perfluoro (methyl vinyl ether) and having a fluorine content in the copolymer rubber of 64 to 67% by weight (the former), and vinylidene fluoride / tetra, which can be peroxide-crosslinked. A fluoroethylene / hexafluoropropylene copolymer rubber having a fluorine content in the copolymer rubber of 69 to 72% by weight (the latter) is used as a blend.

  The former copolymer rubber having a lower fluorine content is obtained by copolymerizing more vinylidene fluoride monomer components in the copolymer and is actually a commercial product DuPont Viton LT type (GLT, GBLT GFLT, etc.) can be used as they are. The latter copolymer rubber having a higher fluorine content is obtained by copolymerizing more tetrafluoroethylene, hexafluoropropylene, particularly tetrafluoroethylene monomer components in the copolymer, and is actually a commercially available product. A Daikin product Daiel G-900 series can be used as it is.

  The introduction of the peroxide crosslinkable group into these two kinds of copolymer rubbers can be carried out by a copolymerization reaction in the presence of a bromine and / or iodine-containing saturated or unsaturated compound.

  When the fluorine-containing copolymer side chain contains an iodine atom and / or a bromine atom, for example, perfluoro (2-bromoethyl vinyl ether), 3,3,4,4, -tetrafluoro-4-bromo-1-butene And copolymers of crosslinking point forming monomers such as 2-bromo-1,1-difluoroethylene, bromotrifluoroethylene, perfluoro (2-iodoethyl vinyl ether), and iodotrifluoroethylene.

When an iodine atom and / or a bromine atom are contained at the end of the fluorine-containing copolymer, the general formula X ₁ C _n F _2n X ₂ (X ₁ : F, Br, IX ₂ : Br, I, n: 1 to 12) ) Is used, and from the viewpoint of reactivity and handling balance, n: 1 to 6 1-bromoperfluoroethane, 1-bromoperfluoroethane, 1-bromoper Fluorobutane, 1-bromoperfluoropentane, 1-bromoperfluorohexane, 1-iodoperfluoroethane, 1-iodoperfluoroepropane, 1-iodoperfluorobutane, 1-iodoperfluoropentane, 1-iodoper A copolymer containing iodine atoms and / or bromine atoms derived from fluorohexane or the like is preferably used.

Further, by setting X ₁ and X ₂ to Br and / or I, a crosslinking point can be introduced at the end of the fluorine-containing copolymer. Examples of such compounds include 1-bromo-2-iodotetrafluoroethane, 1-bromo-3-iodoperfluoropropane, 1-bromo-4-iodoperfluorobutane, 2-bromo-3-iodoperfluorobutane, Monobromomonoiodoperfluoropentane, monobromomonoiodoperfluoro-n-hexane, 1,2-dibromoperfluoroethane, 1,3-dibromoperfluoropropane, 1,4-dibromoperfluorobutane, 1,5- Dibromoperfluoropentane, 1,6-dibromoperfluorohexane, 1,2-diiodoperfluoroethane, 1,3-diiodoperfluoropropane, 1,4-diiodoperfluorobutane, 1,5-diiodo Perfluoropentane, 1,6-diiodoperfluorohexane, etc. are used. These compounds can also be used as chain transfer agents. Moreover, methanol, ethanol, isopropanol, ethyl acetate, acetone, etc. can be used as a chain transfer agent.

  These two types of copolymer rubbers having different fluorine contents are blended in a proportion of 50 to 90% by weight, preferably 65 to 80% by weight of the former, and 50 to 90% by weight, preferably 35 to 20% by weight of the latter. Used. If the former is used in a smaller proportion, the change in strength with time gradually increases, the improvement of the low temperature characteristics is not achieved, and the sealing performance at low temperatures is also impaired. On the other hand, when the former is used in a larger proportion, there is no problem in the change over time in the strength reduction rate due to low temperature characteristics and fuel oil resistance, but the volume swelling increases and the sealing material such as an oil seal. As unsuitable.

  In addition, the fluorine content of the fluororubber blend must be 65 to 69% by weight, preferably 66 to 67% by weight. , The volume change rate in fuel oil resistance, that is, the volume swell increases, making it unsuitable as a sealing material. On the other hand, blends with higher fluorine content are inferior in low-temperature characteristics, and the sealing performance at low temperatures is also impaired. . Further, a vinylidene fluoride / tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer rubber or a vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer rubber having a fluorine content as defined above, However, a single type of copolymer rubber cannot achieve the desired object of the present invention, and the two types of copolymer rubbers having different fluorine contents and copolymer compositions must be blended and used. .

  Such fluororubber blends are co-crosslinked with organic peroxides. The organic peroxide can be used without particular limitation as long as it is generally usable for rubber, for example, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, di-tertiary. Butyl peroxide, tertiary butyl cumyl peroxide, dicumyl peroxide, 1,1-di (tertiary butyl peroxy) -3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di ( (Tert-butylperoxy) hexane, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3, 1,3-di (tert-butylperoxyisopropyl) benzene, 2,5-dimethyl -2,5-di (benzoylperoxy) hexane, tertiary butyl peroxybenzoate, tertiary butyl peroxyisopropyl carbonate, n-butyl-4,4-di (tertiary butyl peroxy) valerate and the like are used.

  These organic peroxides are used in a proportion of 0.2 to 8 parts by weight, preferably 1 to 5 parts by weight, per 100 parts by weight of the fluororubber blend. If the ratio is less than this, a sufficient crosslinking density cannot be obtained. On the other hand, if it is used at a ratio greater than this, the foamed vulcanized molded product cannot be obtained, or even if it is obtained, the rubber elasticity and elongation are reduced. become.

  In the fluororubber blend, in addition to the above essential components, reinforcing agents such as carbon black generally used as rubber compounding agents, fillers such as talc, clay, graphite, calcium silicate, stearic acid Further, processing aids such as palmitic acid and paraffin wax, acid acceptors such as zinc oxide and magnesium oxide, anti-aging agents, plasticizers and the like are appropriately added as necessary.

  Preparation of a composition mainly composed of a fluororubber blend is performed by kneading using a kneader such as an intermix, kneader, Banbury mixer, or an open roll, and the vulcanization molding is performed by an injection molding machine, An oven that is heated at about 150-200 ° C. for about 3-60 minutes using a compression molding machine, vulcanizing press, etc., and is heated at about 150-250 ° C. for about 1-24 hours as necessary. Heating (secondary vulcanization) is performed.

  The vulcanized molded product obtained by vulcanization molding is suitably used as a sealing material for fuel oil, particularly for low grade fuel oil. Here, the fuel oil is fuel oil C, fuel oil D, etc. used for applications such as automobiles, and the low grade fuel oil is fuel oil mixed with alcohols such as methanol or the like. Refers to fuel oil mixed with moisture and the like when used for its intended purpose.

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

Examples 1-3
As fluorine-containing rubber, the following three types of vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer rubber (fluorinated rubber A) and vinylidene fluoride / tetrafluoroethylene / perfluoro (methyl vinyl ether) copolymer rubber ( Use 2 or 3 types of fluorine-containing rubber B, C)
Fluorine-containing rubber A: Daikin product G901; Fluorine content 71%
Fluorine-containing rubber B: DuPont GBLT600S; fluorine content 65%
Fluorine-containing rubber C: DuPont GLT600S; fluorine content 64%

100 parts by weight of fluorine-containing rubber blend
FEF carbon black 20 〃
Wollastonite 18 〃
Highly active magnesium oxide 3 〃
Sodium stearate 1 〃
Triallyl isocyanurate 1.2 〃
2,5-dimethyl-2,5-di (tert-butylperoxy) hexane 3 3
(Nippon Oil Products Perhexa 25B40; concentration 40%)
After kneading each of the components using a kneader and a roll, the kneaded product (fluororubber composition) was subjected to press vulcanization at 180 ° C. for 4 minutes, and then oven vulcanized at 200 ° C. for 15 hours (two Next vulcanization) was performed.

About the obtained cross-linked product (sheet-like product), low temperature characteristics (TR-10 value; JIS K6261 compliant) and fuel oil resistance (80% by weight of fuel oil C, 20% by weight of methanol and 2000 ppm of H ₂ O in fuel oil) Further, the volume change rate when immersed for 70 or 168 hours and the intensity change rate when immersed for 70, 168, 500 or 1000 hours at room temperature were measured, respectively.

The obtained results are shown in the following Table 1 together with the fluorine-containing rubber blend composition.
Table 1
Example 1 Example 2 Example 3
[Blend]
Fluorine-containing rubber A (wt%) 20 30 20
Fluorine-containing rubber B (wt%) 80-50
Fluorine-containing rubber C (wt%) − 70 30
F content after blending (wt%) 66.2 66.1 65.9
〔Measurement result〕
Low temperature characteristics
TR-10 (℃) -22 -19 -24
Fuel oil resistance Volume change rate
70 hours (%) +42 +44 +43
168 hours (%) +48 +49 +46
Strength change rate
70 hours (%) -54 -62 -59
168 hours (%) -60 -64 -60
500 hours (%) -61 -65 -62
1000 hours (%) -62 -66 -63

Comparative Example 1
In Example 1, 100 parts by weight of fluorine-containing rubber A (F content: 71%) was used in place of the fluorine-containing rubber blend.

Comparative Example 2
In Example 1, 100 parts by weight of fluorine-containing rubber C (F content: 64%) was used instead of the fluorine-containing rubber blend.

Comparative Example 3
In Example 1, a fluororubber composition comprising the following components was used.
Viton A (DuPont product; 100 parts by weight with 66% F content)
Polyol crosslinkable vinylidene fluoride /
(Hexafluoropropylene copolymer rubber)
FEF carbon black 20 〃
Wollastonite 18 〃
Calcium hydroxide 3 〃
Magnesium oxide 3 〃
Cross-linking agent (DuPont product curative # 30) 2 〃
Crosslinking aid (Corporate product # 20) 1 〃

The results obtained in the above comparative examples are shown in the following Table 2.
Table 2
Measurement Results Comparative Example 1 Comparative Example 2 Comparative Example 3
Low temperature characteristics
TR-10 (℃) -6 -30 -18
Fuel oil resistance Volume change rate
70 hours (%) +31 +53 +76
168 hours (%) +38 +59 +80
Strength change rate
70 hours (%) -54 -60 -71
168 hours (%) -68 -64 -66
500 hours (%) -77 -65 -93
1000 hours (%) -81 -66 Cannot be measured

From the results obtained in Table 1 (each example) and Table 2 (each comparative example), the following can be said.
(1) Each example has excellent low-temperature characteristics and fuel oil resistance. With regard to fuel oil resistance, the volume change rate and the strength change rate over time, particularly the strength change rate over time are small. It is noted that.
(2) Good fuel oil resistance cannot be obtained unless it is a fluorine-containing rubber blend with a high fluorine content. However, as shown in the results of Comparative Example 1, the volume change rate of a fluorine-containing rubber with a high fluorine content is small. However, the change with time in strength change rate (decrease in strength) is large, and the sealing property at low temperature is also poor.
(3) Fluoro rubber alone with a lower fluorine content (64%) is satisfactory in terms of low temperature characteristics and strength change rate, but has a large volume change rate (volume swelling) and is an oil for fuel-resistant oil. It is not suitable as a seal material such as a seal.
(4) In Comparative Example 3, although the fluorine content is 66% and the polyol-crosslinkable vinylidene fluoride / hexafluoropropylene copolymer rubber is used, the strength change rate is used because it is used alone. The change over time is very large and the fuel oil resistance is not satisfied in this respect.

  Even when such low-grade fuel oil is used as a sealing material, the pressure resistance and wear resistance of the sealing material such as an oil seal can be secured over a long period of time due to the decrease in the rate of change in strength after immersion in fuel oil. In addition, the volume change rate after immersion in the fuel oil is less likely to change over time and stabilizes, so it is possible to prevent uneven wear and wear resistance of seal materials such as oil seals, and to maintain low-temperature characteristics. The improvement makes it possible to secure a sealing property at a low temperature and satisfy the use in a cold region.

Claims (5)

Peroxide-crosslinkable, vinylidene fluoride / tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer rubber with fluorine content of 64 to 67% by weight and peroxide crosslinkable with fluorine content of 69- Vulcanized molding that consists of 50% to 10% by weight of 72% by weight vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer rubber, and the fluorine content of the blend is 65 to 69%, and is in contact with low-grade fuel oil A fluororubber blend that can be co-crosslinked with an organic peroxide , used as a molding material for products.   The fluororubber blend according to claim 1, further comprising an organic peroxide added as a co-crosslinking agent. A vulcanized molded product that is vulcanized and molded from the fluororubber blend according to claim 2 and used as a molded product that comes into contact with a low-grade fuel oil . 4. The vulcanized molded article according to claim 3 , wherein the low-grade fuel oil is a fuel oil mixed with alcohols or a fuel oil mixed with water by using it for a purpose .   The vulcanized molded product according to claim 3 or 4, which is used as a sealing material.