JPH072947A - Cold and alcohol resistant fluorine-containing elastic copolymer - Google Patents

Abstract

(57) [Summary] [Object] To provide a fluororubber having low-temperature resistance and alcohol resistance in addition to the properties of fluororubber such as heat resistance, oil resistance, and chemical resistance. (A) 10 to 35% by weight of a unit based on vinylidene fluoride; (B) 1 to 25% by weight of a unit based on tetrafluoroethylene; (C) a unit based on 5 to 15% by weight of hexafluoropropylene. And (D) 35-60% by weight of the general formula: (In the formula, Rf represents a perfluoroalkyl group having 1 to 3 carbon atoms, and n represents an integer of 2 to 4.), and a unit based on fluorovinyl ether,
Fluorine rubber obtained by vulcanizing a fluorocopolymer having a sum of the components (B) and (C) of 6 to 30% by weight and a sum of the components (C) and (D) of 15 to 25 mol%. To get

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorine-containing copolymer and a fluororubber, and more particularly to a fluorine-containing copolymer containing vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, and a unit based on a specific fluorovinyl ether in specific amounts. The present invention relates to a cold rubber / alcohol resistant fluororubber obtained by vulcanizing a copolymer and the fluorocopolymer.

[0002]

2. Description of the Related Art Various copolymers from resin-like to elastomer-like can be obtained by a copolymerization reaction of a fluoroolefin with another fluoroolefin, or a fluoroolefin with an olefin containing no fluorine. These copolymers can be molded into mechanical parts such as O-rings, flange seals, gaskets, diaphragms and liners, and are particularly useful when special resistance to heat and corrosive fluids is required. Among them, vinylidene fluoride / hexafluoropropylene, tetrafluoroethylene / propylene, tetrafluoroethylene / perfluoroalkyl vinyl ether, vinylidene fluoride / perfluoroalkyl vinyl ether and the like are conventionally known as copolymers which give a fluorine-containing elastomer. And is practically used as a useful elastomer. These elastomers have excellent heat resistance, oil resistance, chemical resistance, and the like that hydrocarbon-based elastomers do not have, but they are not sufficient in terms of low-temperature characteristics. That is, these elastomers lose rubber elasticity at low temperatures and are therefore problematic for use especially in cold regions.

In recent years, from the viewpoint of protecting the global environment,
The use of alcohol fuel or alcohol blended fuel is increasing, and the use of alcohol blended gasoline as automobile fuel is being legally regulated in the United States.
In Japan too, a shift in the near future is expected. Under such circumstances, for example, a material having alcohol resistance in addition to the conventional heat resistance and oil resistance as an elastic material for automobiles is required. Among the above required characteristics, various fluorine-containing elastomers have satisfactory levels of heat resistance and oil resistance, but even those fluorine-containing elastomers having excellent cold resistance have poor alcohol resistance and conversely resistance. There is no known elastic material satisfying all the above-mentioned required properties, such that a material excellent in alcoholic property is unsatisfactory in cold resistance. As a method for solving the low temperature characteristics, a blending method such as co-vulcanization with silicone rubber has been carried out.However, in order to greatly improve the low temperature characteristics, the silicone rubber is the main constituent, and Is sacrificed. Further, it has been attempted to blend a certain kind of plasticizer, but the plasticizer may be separated depending on the use conditions, and an intended elastomer having low temperature resistance has not been obtained yet. On the other hand, by introducing an ether bond into the main chain skeleton of the polymer and attempting to improve the low temperature characteristics, ionic polymerization reaction of hexafluoropropylene oxide, radical polymerization reaction of fluorine-containing ketone, condensation reaction of fluorine-containing polyether Although it has been studied, it has not yet been possible to obtain a practical elastomer.

Attempts have also been made to improve the low temperature characteristics by introducing an ether bond into the side chain. For example, C
An elastic copolymer is obtained by a copolymerization reaction of F ₂ = CFORf (where Rf is CF ₃ , C ₂ F ₅ , or C ₃ F ₇ ) with vinylidene fluoride or tetrafluoroethylene. However, the glass transition temperature of these copolymers is still not sufficiently lowered even if the content of the vinyl ether is increased as much as possible. Among fluorovinyl ethers, fluorovinyl ethers having a plurality of ether bonds are known to be effective in improving low temperature characteristics, and a certain degree of low temperature characteristics can be obtained by a copolymerization reaction with a fluorine-free olefin or a fluoroolefin. Fluoroelastomers having the same have been obtained (see JP-A-57-18710, JP-B-61-50486 and JP-B-61-57324). However, in these fluoroelastomers, expensive fluorovinyl ether must be copolymerized in the copolymer at several tens of mol%.
The low temperature characteristics cannot be improved to the extent necessary for practical use, and the manufacturing cost of the copolymer increases. Further, as a side chain perfluoropolyether structure, it is known that a copolymer having a linear alkylene group has excellent low temperature characteristics (Japanese Patent Laid-Open No. 64-52733), but a fluorovinyl ether having such a structure is known. Takes a complicated synthetic route and is difficult to synthesize.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to economically provide a fluororubber excellent in low temperature characteristics and alcohol resistance in addition to heat resistance, oil resistance and chemical resistance.

[0006]

The first gist of the present invention is (A) a unit based on 10 to 35% by weight of vinylidene fluoride (hereinafter abbreviated as VdF); (B) 1 to 25% by weight of tetra- Fluoroethylene (hereinafter T
A unit based on FE); (C) a unit based on 5 to 15% by weight of hexafluoropropylene (hereinafter abbreviated as HFP); and (D) a general formula of 35 to 60% by weight:

[Chemical 2] (In the formula, Rf represents a perfluoroalkyl group having 1 to 3 carbon atoms, and n is an integer of 2 to 4.) A unit based on a fluorovinyl ether (hereinafter abbreviated as FVE); In addition, the present invention relates to a fluorine-containing copolymer in which the sum of the components (B) and (C) is 6 to 30% by weight and the sum of the components (C) and (D) is 15 to 25 mol%.

The content of vinylidene fluoride (VdF) unit (A) in the copolymer of the present invention is 10 to 35% by weight, preferably 15 to 35% by weight. VdF unit content is 1
If it is less than 0%, the rate of copolymerization becomes low, the polymerization time becomes long, and not only the productivity is poor, but also the low temperature properties of the fluororubber obtained from the copolymer are deteriorated. On the other hand, if it is more than 35% by weight, the resistance to methanol deteriorates. Tetrafluoroethylene (TFE) unit in the copolymer of the present invention
The content of (B) is 1 to 25% by weight, preferably 5 to 20% by weight.

The content of hexafluoropropylene (HFP) unit (C) in the copolymer of the present invention is 5 to 15% by weight, preferably 5 to 10% by weight. When the HFP content is less than 5%, the flexibility of the fluororubber obtained from the copolymer at low temperatures becomes poor (T ₅ -T ₁₀₀ described later becomes large). On the other hand, if it exceeds 15% by weight, the low temperature properties of the fluororubber deteriorate.

Examples of the fluorovinyl ether (FVE) which is the component (D) of the copolymer of the present invention include the following. Perfluoro (2,5-dimethyl-
3,6-dioxanonyl vinyl ether), perfluoro (2,5,8-trimethyl-3,6,9-trioxadecyl vinyl ether), perfluoro (2,5,8-trimethyl-3,6,9- Trioxaundecyl vinyl ether), perfluoro (2,5,8-trimethyl-3,6,9
-Trioxadodecyl vinyl ether), perfluoro (2,5,8,11-tetramethyl-3,6,9,12-tetraoxapentadecyl vinyl ether).

The content of FVE unit in the copolymer of the present invention is 35 to 60% by weight. FVE unit content is 35
If it is less than 60% by weight, the low temperature properties of the fluororubber deteriorate, and if it is more than 60% by weight, the cost is increased because the fluorovinyl ether is relatively expensive, and the strength and elongation of the fluororubber decreases.

Further, the sum of the content of the tetrafluoroethylene (TFE) unit and the content of the hexafluoropropylene (HFP) unit is 6 to 30% by weight, preferably 10 to 25% by weight. If this sum is less than 6% by weight, the resistance to methanol will decrease, and if it exceeds 30% by weight, the low temperature characteristics will deteriorate.

The sum of the content of HFP units and the content of fluorovinyl ether (FVE) units is 15 to 25 mol%,
It is preferably 16 to 23 mol%. When this sum is less than 15 mol%, the flexibility of the obtained fluororubber becomes poor (especially at low temperature), while when it exceeds 25 mol%, HF is exceeded.
The weight fraction of P or FVE becomes high, which causes deterioration of low temperature characteristics and deterioration of strength and elongation. Further, it is difficult to obtain a high molecular weight copolymer.

The copolymer of the present invention is obtained by polymerizing vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene and fluorovinyl ether, which are the components of the copolymer, by a known method such as bulk, solution, suspension and emulsion polymerization. Is obtained by As the solvent used for solution polymerization, dichlorodifluoromethane, trichlorofluoromethane,
Chlorodifluoromethane, 1,1,2-trichloro-1,
2,2-trifluoroethane, 1,2-dichloro-1,1,
A highly fluorinated solvent such as 2,2-tetrafluoroethane, 1,1,2,2-tetrachloro-1,2-difluoroethane, perfluorocyclobutane or perfluorodimethylcyclobutane is preferably used. Blocky,
In suspension and solution polymerization, an oil-soluble initiator is generally used.
Preferred initiators are highly fluorinated peroxides, (Rf-COO) _{2 where} Rf represents a perfluoroalkyl group, an ω-hydroperfluoroalkyl group or a per-chlorofluoroalkyl group. .) Are particularly preferred.

In emulsion polymerization, a monomer is emulsified in water using an emulsifier to carry out polymerization. General formula for emulsifiers:

[Chemical 3] The compound and the like are preferably used. An oil-soluble or water-soluble peroxide is preferably used as a polymerization initiator in emulsion polymerization. Preferred oil-soluble peroxides include those described above, and water-soluble peroxides include persulfates such as ammonium persulfate and potassium persulfate, as well as perphosphates, pernitrates, and percarbonates. Can be mentioned.
A combination of these inorganic peroxides with a water-soluble reducing agent such as sodium sulfite, ammonium sulfite, ferrous sulfate, and ascorbic acid can also be used.

The number average molecular weight of the copolymer is preferably 10,000 to 500,000, more preferably 3
It is 30,000 to 300,000. The molecular weight can be easily adjusted by adding a chain transfer agent. As the chain transfer agent, hydrocarbons having 4 to 6 carbon atoms, alcohols, ethers, organic halides (eg CCl ₄ , CBr)
Cl ₃ , CF ₂ BrCFBrCF ₃ , CF ₂ I ₂ ) and the like can be used advantageously. Fluorocarbon iodide (eg CF ₂ I ₂ , I (CF ₂ ) ₄ I, CF ₂ = CFCF ₂ CF ₂ I)
When used as a chain transfer agent, iodine is bound to the molecular end of the obtained copolymer and still in a radically active state, so that polyfunctional unsaturated compounds such as triallyl isocyanurate and triallyl cyanurate can be used. There is an advantage that peroxide vulcanization using a peroxide as a radical source can be easily performed in the presence of a compound.

In the polymerization of the copolymer of the present invention, a monomer having a vulcanization site can be added. As a monomer having such a vulcanization site, CF ₂ = CF
O (CF ₂ ) mCN, CF ₂ = CFO (CF ₂ ) mBr, CF ₂ =
CFO (CF ₂ ) mI, CH ₂ ═CHOCH ₂ CH ₂ Cl, CF
₂ = CFCF ₂ COOH,

[Chemical 4] (In the formula, m is usually 1 to 8, p is 0 to 1, and q is an integer of 1 to 2.) and the like.

The polymerization temperature varies depending on the decomposition temperature of the polymerization initiator used, but is usually 0 to 100 ° C. The polymerization pressure is determined by the composition of the copolymer, but is preferably 0 to 30 kg / cm ² G.

Next, a method for producing a fluororubber by vulcanizing the fluorocopolymer obtained as described above will be described. Known vulcanizing agents such as peroxides,
A polyamine compound, a polyhydroxy compound or the like can be used, and a peroxide is preferable. As the organic peroxide, in general, one that easily generates a peroxy radical in the presence of heat or a redox system, for example, 1,1-
Bis (t-butylperoxy) -3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butylperoxide,
1-butylcumyl peroxide, dicumyl peroxide, α, α'-bis (t-butylperoxy) -p-diisopropylbenzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane 2,5-dimethyl-2,5-
Di (t-butylperoxy) -hexyne-3, benzoyl peroxide, t-butylperoxybenzene, 2,5
Examples thereof include dimethyl-2,5-di (benzoylperoxy) hexane, t-butyl-oxymaleic acid, t-butylperoxyisopropyl carbonate and the like. Preferred is the dialkyl type.
Generally, the type and amount of the peroxide used are selected in consideration of the amount of active —O—O—, the decomposition temperature and the like. The amount of the organic peroxide used is 0.05 to 1 per 100 parts of the copolymer.
It is 0 part by weight, preferably 1.0 to 5 parts by weight.

When an organic peroxide is used, a remarkable curing can be seen by appropriately using a crosslinking aid or a co-crosslinking agent together. The crosslinking aid or co-crosslinking agent is basically effective as long as it has a reaction activity with respect to a peroxy radical and a polymer radical, and the kind is not particularly limited. Preferred are triallyl cyanurate, triallyl isocyanurate, triallykyl formal, triallyl trimellitate, N, N'-m-
Examples thereof include phenylene bismaleimide, dipropargyl terephthalate, diallyl phthalate, tetraallyl terephthalamide, triallyl phosphate and the like. The amount used is 0.1-10 with respect to 100 parts by weight of the copolymer.
The amount is preferably part by weight, more preferably 0.5 to 5 parts by weight.

The copolymer of the present invention may be blended and crosslinked. Blends that can be cross-linked include silicone oil, silicone rubber, ethylene / vinyl acetate copolymer, 1,2-polybutadiene, fluorosilicone oil, fluorosilicone rubber, fluorophosphazene rubber, vinylidene fluoride / hexafluoropropylene copolymer. Polymer, vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer,
Hexafluoropropylene / ethylene copolymers, tetrafluoroethylene / propylene copolymers, and other radically reactive polymers are used. The amount of these used is not particularly limited, but should not be so large as to essentially impair the properties of the copolymer of the present invention. The fluorocopolymer of the present invention includes a usual rubber compounding agent such as a reinforcing agent, a filler, a plasticizer, a release agent, a softening agent,
You may vulcanize by adding a stabilizer, a bulking agent, etc. as needed.

As a means for mixing these components, an appropriate method is adopted depending on the viscoelasticity and form of the material, and in the case of a solid state, an ordinary open roll or powder mixer is used. In the case of a liquid, a usual mixer is used as appropriate.
Of course, it is also possible to dissolve or disperse the solid components in a solvent and disperse and mix them. The vulcanization can be performed under usual vulcanization conditions of fluororubber. For example, after kneading the fluororubber composition with a roll and putting it in a mold,
Press vulcanization is performed by holding at 200 ° C for 20 to 100 kg / cm ² for 5 to 30 minutes, and then 150 to 250 ° C.
A vulcanized rubber is obtained by carrying out oven vulcanization by holding in an oven for 1 to 24 hours.

The copolymer of the present invention is required as a general molding material, sealant, adhesive, paint, etc., in addition to heat resistance, oil resistance, chemical resistance, solvent resistance, etc., in addition to low temperature resistance and alcohol resistance. It is effectively used in places where it is used. In particular,
It is suitable for a diaphragm in an automobile fuel system, an O-ring for a fuel injection device, and the like.

[0023]

【Example】

Example 1 In a polymerization tank having an internal volume of 1300 ml, 433 ml of pure water and C ₃ F ₇ OCF (CF ₃ ) CF ₂ OCF (CF ₃ ) COONH ₄ as an emulsifier
43.3 g, disodium hydrogen phosphate dodecahydrate 4.3 g
Was charged, and after the system was sufficiently replaced with nitrogen gas, a solution of 200 mg of sodium sulfite in 2 ml of pure water and perfluorovinyl ether CF ₃ CF ₂ CF ₂ [OCF (C
6.2 g of F ₃ ) CF ₂ ] ₃ OCF = CF ₂ (abbreviated as PF ₃ VE) was injected with nitrogen gas. Then, the system is evacuated, HFP is injected at 15 ° C. to an internal pressure of 0 kg / cm ² (gauge pressure), and VdF / TFE / HFP = 68.1 / 18.3 / 13.6.
The pressure was raised to 6.5 kg / cm ² (gauge pressure) with a mol% mixed gas. Then, a solution prepared by dissolving 5 mg of ammonium persulfate in 1 ml of pure water was injected with nitrogen gas to start the reaction. Since the pressure decreases with the progress of the polymerization reaction, it is 5.5 kg / cm ² G
When the pressure drops to 6.5 kg / cm ² G, the mixture gas is repressurized to give perfluoro-1,4-diiodobutane of 0.1.
33 g was injected with nitrogen gas. After that, 6.5 kg / cm ² G
And 5.5 kg / cm ² G between pressure reduction and pressure increase, 5.3 g each of PF ₃ VE was injected with nitrogen gas every 2 times pressure increase, and 2.8 and 5.2 hours from the start of polymerization. After that, 0.43 g of 3-iodo-1,1,2,2-tetrafluoropropyltrifluorovinyl ether each was injected with nitrogen gas under pressure. 7.6 hours after the start of the reaction, unreacted monomer was released to obtain an aqueous emulsion. Coagulate this aqueous emulsion by freezing,
The coagulated product was washed with water and dried in vacuum to obtain 152.6 g of a rubber-like polymer. The composition of this polymer was determined by ¹⁹ F-NMR analysis.
(The same applies hereinafter) VdF / TFE / HFP / PF ₃ VE = 6
It was 3.3 / 18.9 / 11.8 / 5.9 (molar ratio). The Mooney viscosity M _{L1 + 10} (100 ° C.) of this polymer was 55.

Examples 2 to 3 and Comparative Examples 1 to ₃ Polymerization was carried out in the same manner as in Example 1 except that the charged amount of PF ₃ VE and the mixed monomer composition were as shown in Table 1. The results are shown in Table-1.

Comparative Example 4 CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) C instead of PF ₃ VE
Example 1 using F ₂ OCF = CF ₂ (abbreviated as PF ₁ VE)
Polymerization was performed in the same manner as in. The results are shown in Table-1.

[0026]

[Table 1]

Example 4 The copolymers obtained in Examples 1 to 3 and Comparative Examples 1 to 4 were vulcanized and molded as follows. M based on 100 parts by weight of the copolymer
After kneading 20 parts by weight of T carbon black, 4 parts by weight of triallyl isocyanurate and 1.5 parts by weight of 2,5-dimethyl-2,5- (t-butylperoxy) hexane with a rubber roll. Press molding for 10 minutes at 160 ° C, then 180
It was heated in an electric furnace at ℃ for 4 hours to obtain a sheet-shaped molded product having a thickness of 2 mm. The tensile strength, elongation, methanol resistance and low temperature torsion test of this molded product were measured by the following methods. Tensile strength, elongation: According to the method of JIS K6301. Methanol resistance: JIS fuel oil and methanol 20:80
The volume increase rate (ΔV) after immersion in a mixture (volume ratio) at 40 ° C. for 70 hours was determined. Low temperature torsion test: According to the method of JIS K6301. In this test, the torsional modulus at low temperature is room temperature (23 ° C)
The temperature at which the torsional modulus at X is X times is represented by Tx. Poor rubber flexibility at even low glass transition temperature (Tg) of the same, the temperature of the low-temperature torsion test - dull rise of the helix angle curve, for example, T ₅ -T ₁₀₀ takes a large value. A flexible rubber low temperature - sharp rise of the helix angle curve, T ₅ -T ₁₀₀ is small. The results are shown in Table 2.

[0028]

[Table 2]

As is clear from Tables 1 and 2, the copolymer of Comparative Example 1 had too high a vinylidene fluoride content, and the fluororubber obtained from this had poor methanol resistance.
(ΔV is large). In addition, the copolymer of Comparative Example 2 had too large a sum of the contents of tetrafluoroethylene and hexafluoropropylene, and had insufficient low temperature properties (both T ₅ and T ₁₀₀ were high). In the copolymer of Comparative Example 3, the sum of the contents of hexafluoropropylene and fluorovinyl ether is too small and the low temperature characteristics are not good (T ₅ -T ₁₀₀ is large). P in Comparative Example 4
Although PF ₁ VE is used instead of F ₃ VE, the low temperature characteristics are also insufficient in this case (both T ₅ and T ₁₀₀ are high). On the other hand, the copolymers of the present invention (Examples 1 to 3) satisfy methanol resistance and low temperature characteristics.

Front page continued (72) Inventor Masaki Kitaichi 1-1, Nishiichitsuya, Settsu-shi, Osaka Daikin Industries, Ltd. Yodogawa Manufacturing Co., Ltd. Inside the factory

Claims (3)

[Claims] 1. A unit containing (A) 10 to 35% by weight of vinylidene fluoride; (B) a unit containing 1 to 25% by weight of tetrafluoroethylene; (C) containing 5 to 15% by weight of hexafluoropropylene. Based units; and (D) 35-60% by weight of the general formula: (In the formula, Rf represents a perfluoroalkyl group having 1 to 3 carbon atoms, and n is an integer of 2 to 4.) A unit based on a fluorovinyl ether;
The sum of (B) component and (C) component is 6 to 30% by weight, and (C)
A fluorinated copolymer in which the sum of the component and the component (D) is 15 to 25 mol%. 2. A fluorovinyl ether is perfluoro
The copolymer according to claim 1, which is (2,5,8-trimethyl-3,6,9-trioxadodecyl vinyl ether). 3. A fluororubber obtained by crosslinking the copolymer of claim 1 or 2.