JPH10279635A - Fluoroelastomer and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluoroelastomer improved in cold resistance without detriment to the excellent resistances to heat and oil inherent in a fluoroelastomer. SOLUTION: This fluoroelastomer is obtd. by copolymerizing tetrafluoroethylene, methyl vinyl ether, and vinylidene fluoride at about 0-70 deg.C under a pH of 7-11 and comprises about 30-70 mol.% tetrafluoroethylene units, about 5-40 mol.% methyl vinyl ether units, and about 5-65 mol.% vinylidene fluoride units.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fluorine-containing elastomer and a method for producing the same. More particularly, it relates to a fluorine-containing elastomer having excellent low-temperature properties and a method for producing the same.

[0002]

2. Description of the Related Art Compared with vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene
-It is known that a propylene-based copolymer is a fluorine-containing elastomer having better heat resistance and chemical resistance. In addition, in the copolymerization reaction of tetrafluoroethylene and propylene, a water-soluble persulfate-thio (sulfite) -sulfate-iron salt redox catalyst is used in an aqueous medium, and a low temperature of about 0 to 50 ° C is used. It is also known that a high molecular weight copolymer can be obtained when the reaction is carried out as follows. However, such copolymers, especially tetrafluoroethylene, are 55-
The low-temperature properties of the copolymer in which 50 mol% and propylene account for 45 to 50 mol% are determined by the glass transition temperature (DSC method).
As a result, there is a problem that the temperature is around 0 ° C., which is not suitable for applications requiring cold resistance.

[0003] Further, the vinylidene fluoride-propylene-tetrafluoroethylene copolymer has excellent heat resistance as a fluoroelastomer while maintaining excellent heat resistance as compared with the tetrafluoroethylene-propylene copolymer. It is also known to improve lubricating oil properties, fuel oil resistance, etc. (JP-A-52-44895, JP-B-60-19325, U.S. Pat.No. 3,859,259), but this vinylidene fluoride- Even in the propylene-tetrafluoroethylene-based copolymer, its glass transition temperature is around -9 ℃,
The fact is that the application to applications requiring severe cold resistance is hampered. By increasing the copolymerization ratio of vinylidene fluoride, it is possible to improve the cold resistance of this copolymer, but in this case, the decrease in chemical resistance cannot be avoided.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fluoroelastomer which maintains the excellent heat resistance and oil resistance inherently possessed by the fluoroelastomer and which is improved in cold resistance.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
About 30-70 mol% of tetrafluoroethylene, about 5-40 mol% of methyl vinyl ether and about 5-65 mol of vinylidene fluoride
This is achieved by a fluoroelastomer having a mole% copolymer composition.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The copolymer composition is preferably about 30 to 70 tetrafluoroethylene in consideration of the mechanical properties, heat resistance, cold resistance, chemical resistance, oil resistance and the like of the copolymer. Mole%, preferably about 30-50 mole%, methyl vinyl ether about 5-40 mole%, preferably about 20-35 mole%, and vinylidene fluoride about 5-65 mole%, preferably about 20- 60
The ranges that respectively occupy mol% are selected, and it is preferable to increase the amount of tetrafluoroethylene among these, from the viewpoint of the polymerization reaction rate, and to produce a high molecular weight copolymer with superiority. Also, when the proportion of vinylidene fluoride is higher than this, lack of rubber elasticity, reduction in chemical resistance (particularly alkali resistance), etc. are observed, while when used in less than this, cold resistance and vulcanization resistance Is not sufficiently improved. The obtained copolymer has ηsp / c (in tetrahydrofuran (THF) at 35 ° C) of about 0.1 to 3 dl / g, preferably about 0.5 to 2 dl / g, and has a Mooney viscosity ML _{1 + 10} (121 ° C) of about 0.1 to 3 dl / g. 20
It has a value of ~ 150, preferably about 30-120.

[0007] A part of each of these comonomers is replaced with other monomers copolymerizable therewith, such as olefins such as ethylene, propylene and butene, vinyl acetate, ethyl vinyl ether and n-butyl vinyl ether. Vinyl compounds,
Hexafluoropropylene, pentafluoropropylene, chlorotrifluoroethylene, methyl perfluorovinyl ether, ethyl perfluorovinyl ether,
n- or iso-propyl perfluorovinyl ether, n
-, Iso- or tert-butyl perfluorovinyl ether, n- or iso-amyl perfluorovinyl ether, perfluoro (methyl vinyl ether), perfluoro (ethyl vinyl ether), perfluoro (n- or iso-propyl vinyl ether), per Fluoro (n-, iso-
Or tert-butyl vinyl ether), perfluoro (n- or iso-amyl vinyl ether), perfluoro (propoxypropyl vinyl ether), vinyl fluoride, trifluoroethylene, perfluorocyclobutene, perfluoro (methylcyclopropylene), hexa It can also be used after substituting with a fluorine-containing olefin such as fluoroisobutene, 1,2,2-trifluorostyrene, perfluorostyrene or a vinyl compound. The substitution ratio is within a range that does not impair the properties required for the obtained fluoroelastomer, and is generally about 30 mol% or less in all monomers.

[0008] The copolymerization reaction is carried out in an aqueous medium using a water-soluble peroxide catalyst, preferably a redox catalyst thereof.
Generally, it is carried out by an emulsion polymerization method. As the water-soluble peroxide catalyst, for example, persulfates such as ammonium persulfate, potassium persulfate, and sodium persulfate are preferably used. Along with these water-soluble persulfates, for example, a water-soluble sulfite such as sodium sulfite, potassium sulfite, ammonium sulfite, calcium sulfite or the like is used in combination to form a redox-based redox catalyst there. The use ratio is generally about 0.01 to about 0.01 to the aqueous medium.
5% by weight, preferably about 0.1-1% by weight.

Examples of the emulsifier include fluorinated emulsifiers such as fluorinated aliphatic carboxylate, phosphate ester or sulfate of fluorinated alcohol, and normal emulsifier such as sulfate or aromatic sulfonate of higher aliphatic alcohol. , Preferably sodium lauryl sulfate. When sodium lauryl sulfate is used, the polymerization rate does not decrease, and the aqueous latex obtained as a result of the copolymerization reaction is excellent in emulsifiability. These water-soluble emulsifiers may be used alone or in combination in an amount of about 0.001 to 1 based on the aqueous medium.
0% by weight, preferably about 0.01-1% by weight.

[0010] The copolymerization reaction using these catalysts and emulsifiers is carried out at about 0 to 70 ° C, preferably about 10 to 55 ° C. At a reaction temperature higher than this, the molecular weight of the produced copolymer decreases, and the decomposition rate of the polymerization catalyst becomes too high, resulting in a decrease in efficiency.On the other hand, at a temperature lower than this, the polymerization rate decreases, and in practice, Absent. In this copolymerization reaction,
The characteristic that the polymerization rate is highly pH-dependent is recognized.
The pH range is set between 7 and 11, preferably between 7 and 9. In other pH ranges, a decrease in the polymerization rate is observed, and particularly when the pH is tilted toward the acidic side, it is difficult to obtain a fluorine-containing elastomer of the desired property due to the formation of formaldehyde accompanying the decomposition of methyl vinyl ether. .

Adjustment of such a pH range includes sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, sodium tetraborate, Potassium citrate, potassium dihydrogen citrate, etc.
This is performed by adding a pH adjuster.

Further, if necessary, the molecular weight of the fluorine-containing elastomer can be adjusted by using a chain transfer agent such as methanol, ethanol, isopentane, diethyl malonate, carbon tetrachloride or the like.

In the emulsion polymerization method, the resulting copolymer is obtained as a dispersion which is well emulsified in an aqueous medium, and from this dispersion, a known molecular weight such as coagulation can be used to obtain a high molecular weight and not be colored. A copolymer can be easily obtained.

Fluorine-containing elastomers made of such copolymers can be obtained by various conventionally known vulcanization methods, for example, peroxide vulcanization method using organic peroxide, polyamine vulcanization method using polyamine compound, and polyhydroxy compound. It can be cured by polyol vulcanization method or radiation, irradiation method such as electron beam, etc. Among them, peroxide vulcanization method has a cured elastomer with excellent mechanical strength and stable cross-linking point structure. It is a particularly preferred method because it forms a carbon-carbon bond and gives a vulcanizate having excellent chemical resistance, abrasion resistance, solvent resistance and the like.

As the organic peroxide used in the peroxide vulcanization method, for example, 2,5-dimethyl-2,5-bis (tert-butylperoxy) hexane, 2,5-dimethyl-2,5-bis (number 3
(Butylperoxy) hexine-3, benzoyl peroxide, bis (2,4-dichlorobenzoyl) peroxide, dicumyl peroxide, ditertiary butyl peroxide, tertiary butylcumyl peroxide, tertiary butylperoxybenzene, 1 , 1-bis (tert-butylperoxy) -3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroxy peroxide, α, α′-bis (tert-butylperoxy)- p-diisopropylbenzene, 2,5-dimethyl-2,5-di
(Benzoylperoxy) hexane, tertiary butylperoxyisopropyl carbonate and the like are used.

In the peroxide vulcanization method using these organic peroxides, a polyfunctional unsaturated compound, for example, tri (meth) allyl isocyanurate, is usually used as a co-crosslinking agent.
Tri (meth) allyl cyanurate, triallyl trimellitate, N, N'-m-phenylenebismaleimide, diallyl phthalate, tris (diallylamine) -s-triazine, triallyl phosphite, 1,2-polybutadiene, ethylene glycol Diacrylate, diethylene glycol diacrylate, and the like are used in combination for the purpose of obtaining better vulcanization characteristics, mechanical strength, compression set characteristics, and the like.

Further, depending on the purpose, 2
Oxides or hydroxides of valent metals, for example, oxides or hydroxides of calcium, magnesium, lead, zinc and the like can also be used. These compounds also act as acid acceptors.

The above components to be added to the peroxide vulcanization system generally contain about 0.1 to 10 parts by weight, preferably about 0.5 to 5 parts by weight, of an organic peroxide per 100 parts by weight of the fluorine-containing elastomer.
The co-crosslinking agent is used in an amount of about 0.1 to 10 parts by weight, preferably about 0.5 to 5 parts by weight, and the crosslinking aid is used in an amount of about 15 parts by weight or less.

Each of the above vulcanizing components may be directly blended and kneaded with a fluorine-containing elastomer, or may be diluted with carbon black, silica, clay, talc, diatomaceous earth, barium sulfate, or the like. Used as masterbatch dispersion with fluoroelastomer. In the composition, in addition to the above components, conventionally known fillers, reinforcing agents, plasticizers, lubricants, processing aids, pigments, and the like can be appropriately compounded. Carbon black as a filler or reinforcing agent is used in an amount of about 10 per 100 parts by weight of the fluorine-containing elastomer.
It is used in a proportion of ~ 50 parts by weight.

Vulcanization is carried out by mixing the above-mentioned components by a generally used mixing method such as roll mixing, kneader mixing, Banbury mixing, solution mixing and the like, and then heating. Heating is generally at about 100-250 ° C for about 1-120.
Primary vulcanization performed for about 1 minute and 0-30 at about 150-300 ° C
It is performed by secondary vulcanization performed for about an hour.

[0021]

The non-colored, high-molecular-weight fluorine-containing elastomer according to the present invention has a glass transition temperature of the conventional vinylidene fluoride-propylene-tetrafluoroethylene-based copolymer of about -9 ° C, It has excellent low temperature characteristics of about -11.5 to -12.5 ° C, and has no inferiority in oil resistance and heat resistance. Furthermore, an improvement in cold resistance has been achieved in comparison with a tetrafluoroethylene-propylene-based copolymer or a tetrafluoroethylene-methylvinylether-based copolymer, and in comparison with these copolymers,
Improvements in roll workability and formability in the processing step have been achieved without impairing the vulcanization properties.

Accordingly, the fluoroelastomer can be effectively used for applications requiring these various properties, for example, tubes, hoses, oil seals, O-rings, packings, electric wire materials and the like for automobiles.

[0023]

Next, the present invention will be described by way of examples.

Example 1 A stainless steel autoclave having a capacity of 500 ml was charged with ammonium perfluorooctanoate 3.0 g potassium dihydrogen phosphate 2.0 g sodium hydroxide 0.6 g sodium sulfite 0.03 g ion-exchanged water 300 ml, and the aqueous phase was adjusted to pH 9 Kept. After introducing nitrogen gas there, replacing the gaseous air and degassing, while stirring the inside of the autoclave, cooling the internal temperature to −30 ° C., 50 g of tetrafluoroethylene (TFE), 28 g of methyl vinyl ether (MVE) and 44 g of vinylidene fluoride (VdF) were charged.

After the temperature in the reactor was raised to 50 ° C., 0.92 g of ammonium persulfate was charged using a pump to start a polymerization reaction, and the reaction was continued for 7 hours. After completion of the reaction, the remaining monomers were purged to extract the latex (pH about 7, solid content concentration 19.3% by weight), aggregated with a 1% by weight aqueous solution of calcium chloride, washed with water, dried, and 71 g of a rubbery ternary copolymer. A coalescence was obtained. Copolymer composition (elemental analysis, NMR): TFE / MVE / VdF molar ratio = 31.2 / 30.3 / 38.5 ηsp / c (THF, 35 ° C.): 1.87 dl / g Mooney viscosity ML _{1 + 10} (121 ° C.): 84.6 glass Transition temperature (DSC method): -12.47 ° C

Example 2 A stainless steel autoclave having a capacity of 500 ml was charged with sodium lauryl sulfate 2.3 g sodium dihydrogen phosphate 1.2 g sodium tetraborate 0.8 g sodium sulfite 0.06 g ion-exchanged water 280 ml, and the aqueous phase was adjusted to pH 9 Kept. After introducing nitrogen gas there, replacing the gaseous phase air and degassing, while stirring the inside of the autoclave, while cooling the internal temperature to -30 ° C, 34 g of tetrafluoroethylene (TFE), 30 g of methyl vinyl ether (MVE) and 18 g of vinylidene fluoride (VdF) were charged.

After the temperature in the reactor was raised to 50 ° C., 1.8 g of ammonium persulfate was charged using a pump to start the polymerization reaction, and the reaction was continued for 7 hours. After the reaction,
Purify the remaining monomers and remove latex (pH about 7, solid content concentration
21.9% by weight) was extracted, aggregated with a 1% by weight aqueous solution of calcium chloride, washed with water and dried to obtain 53.2 g of a rubbery terpolymer. Copolymer composition (elemental analysis, NMR): TFE / MVE / VdF molar ratio = 31.4 / 33.9 / 34.7 ηsp / c (THF, 35 ° C.): 1.49 dl / g Mooney viscosity ML _{1 + 10} (121 ° C.): 102.1 glass Transition temperature (DSC method): -11.6 ° C

Example 3 100 parts by weight of the rubbery terpolymer of Example 1 MT carbon black 30 〃triallyl isocyanurate 10 鉛 lead oxide (PbO) 5 〃organic peroxide (Nippon Oil & Fat Products PH25B40) 3.5 〃 Sodium stearate 1 〃 Each component above is kneaded with a roll, and
Press vulcanization (primary vulcanization) at 20 ° C. for 20 minutes and oven vulcanization (secondary vulcanization) at 230 ° C. for 22 hours were vulcanized and formed into a sheet or ring (P-24).

The obtained secondary vulcanizate has physical properties in a normal state.
(According to DIN53 505 and DIN53 504), compression set (ASTM D-395
Method-B, 25% compression), heat aging resistance (175 ℃ or 200 ℃, 7
0 hours) and oil resistance (volume change after 70 hours immersion in JIS No. 3 oil at 150 ° C, TOYOTA SG10W30 or Shell ATF). Permanent set was measured. Furthermore, evaluation of roll workability using an 8-inch open roll was also performed. Regarding the surface state of the dispensing sheet, ○: smooth and uniform in thickness △: rough and less sticky ×: many irregularities, poor dispersion, powder remaining on the surface as granules, sometimes failing to dispens properly Regarding the roll wrapping property, ◎: 10 to 100 seconds before winding on the roll, no peeling by adding filler ○: 100 to 200 seconds after winding on the roll, No peeling △: 200 to 400 seconds before winding on a roll, partly peeling by filling filler (separates into two rolls) ×: 400 to 600 seconds before winding on a roll Then, an evaluation method was taken in which the filler was partially peeled off (separated into two rolls) when the filler was charged.

Example 4 In Example 3, the same amount of the rubbery terpolymer of Example 2 was used instead of the rubbery terpolymer of Example 1.

Comparative Example 1 100 parts by weight of TFE-propylene copolymer (Afras 150E from Asahi Glass Co., Ltd.) MF carbon black 25 ナ ト リ ウ ム sodium stearate 1 ト リ triallyl isocyanurate 5 〃 organic peroxide (Nippon Oil and Fat Product Peroximon) 1 〃 or more Knead each component of the roll, 170
Press vulcanization at 20 ° C for 20 minutes and oven vulcanization at 200 ° C for 4 hours were performed to vulcanize and form into a sheet or ring (P-24).

The same measurement as in Example 3 was performed on the obtained secondary vulcanizates and primary vulcanizates.

Comparative Example 2 100 parts by weight of TFE-methyl vinyl ether (molar ratio 55/45) copolymer [ηsp / c (THF, 35 ° C.): 1.79, Tg (DSC method): -44 ° C.] MT carbon black 30 〃 Organic peroxide (PH25B40) 1.34 亜 鉛 Zinc oxide 6 ト リ Triallyl isocyanurate 5 〃 Knead each of the above components with a roll.
Press vulcanization at 20 ° C. for 20 minutes and oven vulcanization at 230 ° C. for 22 hours were performed and vulcanized into a sheet or ring (P-24).

The secondary vulcanizate and primary vulcanizate obtained were measured in the same manner as in Example 3.

Comparative Example 3 100 parts by weight of TFE-ethyl vinyl ether-VdF (molar ratio 50/32/18) copolymer [ηsp / c (THF, 35 ° C.): 0.80, ML _{1 + 4} (100 ° C.): 41 , Tg (DSC method: -13.1 ° C) MT carbon black 35 〃 organic peroxide (PH25B40) 2 マ グ ネ シ ウ ム magnesium oxide 8 ト リ triallyl isocyanurate 5 〃
Press vulcanization at 20 ° C. for 20 minutes and oven vulcanization at 200 ° C. for 22 hours were carried out and vulcanized into a sheet or ring (P-24).

The same measurement as in Example 3 was performed on the obtained secondary vulcanizates and primary vulcanizates.

The measurement results in Examples 3 to 4 and Comparative Examples 1 to 3 are shown in Tables 1 and 2 below.

Table 1 Measurement Items Example 3 Example 4 [Physical Properties] Hardness (Shore A) 69 71 100% Modulus (MPa) 9.2 9.5 Tensile Strength (MPa) 16.8 17.6 Elongation (%) 180 190 Specific Gravity 1.661 1.659 TR ₁₀ -7.8 -7.4 [Heat aging resistance, 175 ℃] Hardness change (pts) +1 +1 100% modulus change rate (%) +2 +5 Tensile strength change rate (%) +3 +4 Elongation change rate (%) -5 -8 [Heat aging resistance, 200 ℃] Hardness change (pts) +2 +3 100% modulus change (%) +3 +6 Tensile strength change (%) +5 +9 Elongation Rate of change (%) -13 -17 [Compression set] 150 ° C, 70 hours (%) 52 50 [Oil resistance] JIS No.3 (%) +11.4 +10.9 SG10W30 (%) +4.9 +5.3 Shell ATF ( %) +7.1 +6.4 [Roll processability] Time required for charging filler (minutes) 87 Kneading time (minutes) up to 18 minutes min. 18 16 Surface condition of mining sheet ○ ○ Roll winding property ◎ ◎

Table 2 Measurement items Comparative example 1 Comparative example 2 Comparative example 3 [Physical properties] Hardness (Shore A) 63 75 68 100% modulus (MPa) 3.2 10.8 6.2 Tensile strength (MPa) 10.1 19.5 12.8 Elongation (%) 310 170 170 Specific gravity 1.612 1.656 1.640 TR ₁₀ 2.7 -1.6 -8.1 [Heat aging resistance, 175 ℃] Hardness change (pts) +1 +3 +1 100% modulus change rate (%) -5 +7 +3 Tensile strength Elongation change rate (%) -1 -9 -5 Elongation change rate (%) -5 -6 -10 [Heat aging resistance, 200 ℃] Hardness change (pts) +1 +1 +3 100% modulus change rate ( %) -6 +7 +5 Change in tensile strength (%) +4 -14 -8 Change in elongation (%) -11 -18 -21 [Compression set] 150 ° C, 70 hours (%) 42 56 47 [Oil resistance] JIS No.3 (%) +12.1 +10.5 +13.4 SG10W30 (%) +5.7 +4.8 +5.8 Shell ATF (%) +5.4 +16.4 +10.7 [Roll workability] Time required for filling with filler ( Minutes) 10 12 10 Kneading time until dispensing (min) 22 23 20 Surface condition of dispensing sheet × △ △ Roll windability × △ ○

Claims (2)

[Claims] 1. About 30 to 70 moles of tetrafluoroethylene
%, About 5 to 40 mol% of methyl vinyl ether and about 5 to 65 mol% of vinylidene fluoride. 2. The fluoroelastomer according to claim 1, wherein tetrafluoroethylene, methyl vinyl ether and vinylidene fluoride are copolymerized under a reaction condition of pH 7 to 11 and a temperature of about 0 to 70 ° C. Production method.