JP2711906B2 - Fluorine-containing elastic copolymer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fluorine-containing elastic copolymer. More specifically, the present invention relates to a fluorine-containing elastic copolymer comprising a tetrafluoroethylene-vinylidene fluoride-perfluoro (methyl vinyl ether) terpolymer excellent in low-temperature properties and solvent resistance.

[Prior Art] A terpolymer of tetrafluoroethylene-vinylidene fluoride-perfluoro (methyl vinyl ether) is already commercially available as a fluororubber having excellent low-temperature properties (for example, Viton GLT manufactured by DuPont).

However, since the terpolymer has a large part of its composition, specifically about 70 mol%, of vinylidene fluoride having poor chemical resistance, the acetone swelling degree which is a measure of chemical resistance is used. (Immersion at 25 ° C for 70 hours) is very bad with about 200% swelling.

In addition, a tetrafluoroethylene-perfluoro (methyl vinyl ether) copolymer is commercially available as a perfluoro-type fluororubber (for example, DuPont product Carrelet). This fluororubber is a perfluoro type, and all of the polymer chains are composed of CF bonds showing strong resistance to various solvents, so that the acetone swelling degree is very excellent, about 1 to 2%. I have. However, since it is a binary copolymer, it is necessary to copolymerize a relatively large amount of expensive monomer perfluoro (methyl vinyl ether), thereby avoiding a very high price of the product. Can not.

In addition, an increase in the fluorine content in the copolymer is generally due to Tg
(Glass transition point) tends to increase and low-temperature properties tend to deteriorate. This perfluoro-type fluororubber also has a high fluorine content of 72%, which is a measure of low-temperature properties and crystallization tendency.
When -10 was measured, it was -1 ° C, which was inferior in low-temperature properties.

[Problems to be solved by the invention]

An object of the present invention is to provide a tetrafluoroethylene-vinylidene fluoride-perfluoro (methyl vinyl ether) terpolymer which is superior to a tetrafluoroethylene-perfluoro (methyl vinyl ether) copolymer in terms of economy and low-temperature characteristics. To provide a well-balanced fluorinated elastic copolymer which has excellent solvent resistance and a low TR-10 value as a measure of low-temperature properties of -5 to -10 ° C, and does not lose flexibility even at low temperatures. It is in.

[Means for solving the problem]

The fluorine-containing elastic copolymer of the present invention for achieving the above object comprises (a) 40 to 55 mol% of tetrafluoroethylene, (b) 15 to 35 mol% of vinylidene fluoride and (c)
A copolymer of 20 to 35 mol% of perfluoro (methyl vinyl ether) having a Mooney viscosity ML _{1 + 10} (121 ° C.) of about 1
Consists of a copolymer having a TR-10 value of -5 to -10C at 0 to 100 pts.

The range of the copolymerization molar ratio is determined by the low-temperature characteristics (TR-10
Value) and solvent resistance (acetone swelling degree: 80% or less). As shown in the following data, tetrafluoroethylene [TFE], vinylidene fluoride [VdF], and If any of the fluoro (methyl vinyl ether) [VE] deviates from this range, the intended purpose of the present invention cannot be achieved.

Japanese Patent Application Laid-Open No. 24803/1990 discloses that vinylidene fluoride monomer units in vinylidene fluoride-hexafluoropropene copolymer or vinylidene fluoride-hexafluoropropene-tetrafluoroethylene terpolymer are 42 units. It is described that by limiting the content to ~ 52 mol%, the alcohol resistance of these fluororubbers is improved.

However, such a fluoroelastomer is not resistant to ketones and esters which are used in large quantities in the paint and automotive industries, but the fluoroelastomer-like copolymer obtained by copolymerizing the perfluoro (methyl vinyl ether) according to the present invention. In the above, by further reducing the vinylidene fluoride monomer unit, resistance to ketones and esters is shown.

During the copolymerization reaction of each component of the comonomer used, if an iodine-containing bromine compound is allowed to coexist in the reaction system, iodine and bromine will be bonded to the molecular terminals of the produced copolymer in a radically active state, The obtained copolymer can be subjected to peroxide vulcanization using peroxide as a radical source in the presence of a polyfunctional compound such as triallyl isocyanurate or triallyl cyanurate.

Examples of such an iodine-containing bromine compound include 1-bromo-2-iodoperfluoroethane and 1-bromo-3-
Chain compounds represented by iodoperfluoropropane, 1-bromo-4-iodoperfluorobutane, 1-bromo-2-iodo-1-chloroperfluoroethane, or o-, m- or p-iodobromobenzene , 3,5-dibromo-1-iodobenzene, aromatic compounds typified by 3,5-diiodo-1-bromobenzene, etc. are used as iodine and bromine in amounts of about 0.01
-5% by weight, preferably about 0.05-3% by weight.

The copolymerization reaction between each monomer component is a random copolymerization method,
With a block copolymer or the like, bulk polymerization, suspension polymerization, solution polymerization, or the like may be used, but preferably emulsion polymerization is used. The polymerization initiator is preferably used by forming a redox system, and the polymerization reaction is carried out at a temperature of about 20 to 80 ° C, preferably about 40 to 60 ° C, while protecting the terminal of the produced copolymer.

In the case of suspension polymerization, for example, an organic peroxide, a fluorinated organic peroxide, an organic azo compound, a fluorinated organic azo compound, or the like as a polymerization initiator, this as it is or trifluorotrichloroethane, methyl chloroform,
It is used as a solution dissolved in a solvent such as dichlorotetrafluoroethane or difluorotetrachloroethane, and the polymerization reaction is carried out in a state where the monomers are dispersed in water.

In the case of solution polymerization, perfluoro (1,2-dimethylcyclobutane), perfluoro (1,2-dimethylcyclobutane), perfluoro (1,2-dimethylcyclobutane), and the like are used as polymerization initiators such as organic peroxides, fluorine-containing organic peroxides, organic azo compounds, and fluorine-containing organic azo compounds. 1,2-dichloroethane), perfluoro (1,2,2-trichloroethane),
Polymerization reaction in a polymerization solvent with low chain transfer such as perfluorocyclohexane, perfluorotributylamine, α, ω-dihydroperfluoropolymethylene, perfluoro (methoxypolyethoxyethane), perfluorocyclobutane, and tert-butanol Done.

In the case of emulsion polymerization, for example, persulfate, hydrogen peroxide,
When a water-soluble polymerization initiator such as an inorganic peroxide such as perchlorate, an organic peroxide such as tertiary butyl hydroperoxide or disuccinyl peroxide is used, and an inorganic peroxide is used, It is also used as a redox system in combination with reducing agents such as sulfites, hyposulfites and ascorbic acid. Further, an emulsifier such as a fluorine-containing carboxylate or a fluorine-containing sulfonate may be used for the purpose of stably dispersing the polymer particles in the polymerization solution, increasing the polymer concentration, and preventing the polymer from adhering to the polymerization tank.

The fluorine-containing elastomer obtained by the method of the present invention can be obtained by various conventionally known vulcanization methods such as a peroxide vulcanization method using an organic peroxide, a polyamine vulcanization method using a polyamine compound, and a polyol vulcanization method using a polyhydroxy compound. Curing can be performed by a method or irradiation method such as radiation or electron beam. Among them, peroxide vulcanization method is a method in which the cured elastomer has excellent mechanical strength and a stable structure of the cross-linking point. This is a particularly preferred method because it forms a bond and gives a vulcanizate having excellent chemical resistance and solvent resistance.

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 (third
Butylperoxy) hexine-3, benzoyl peroxide, bis (2,4-dichlorobenzoyl) peroxide, dicumyl peroxide, di-tert-butyl peroxide, tert-butylcumyl peroxide, tert-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 5,5-di (benzoylperoxy) hexane, tertiary butylperoxyisopropyl carbonate and the like are used.

In the peroxide vulcanization method in which these organic peroxides are used, a polyfunctional unsaturated compound is usually used as a co-crosslinking agent,
For example, tri (meth) allyl isocyanurate, tri (meth) allyl cyanurate, tri (meth) allyl trimellitate, N, N'-m-phenylenebismaleimide, diallyl phthalate, tris (diallylamine) -s-triazine, Triallyl phosphate, 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, and compression set.

Further, depending on the purpose, as a crosslinking aid, a hydroxide, oxide or carbonate of a metal, for example, calcium, magnesium, barium, sodium, lithium, potassium, zinc, hydroxide such as iron (III), calcium, Oxides such as magnesium, copper, zinc, lead, sodium, potassium, and barium; carbonates such as calcium, magnesium, zinc, sodium, potassium, and lithium; and basic lead phosphite are also used.

Each of the above components blended into the peroxide vulcanization system,
Generally, the organic peroxide 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 co-crosslinking agent is used in an amount of about 0.1 to 10 parts by weight, preferably about 100 parts by weight, per 100 parts by weight of the fluorinated elastic copolymer. 0.5
-5 parts by weight, and the crosslinking aid is used in a proportion of about 15 parts by weight or less.

Each of the above vulcanization components may be directly blended with the fluorine-containing elastic copolymer and kneaded, or may be diluted with carbon black, silica, clay, talc, diatomaceous earth, barium sulfate, or the like, It is used as a masterbatch dispersion with a fluorine-containing elastic copolymer. In the composition, in addition to the above components, a conventionally known filling method, reinforcing agent,
A plasticizer, a lubricant, a processing aid, a pigment, and the like can be appropriately blended.

Vulcanization is carried out by mixing the above components by a generally used mixing method such as roll mixing, kneader mixing, Banbury mixing, and solution mixing, and then heating. Heating is generally performed by primary vulcanization performed at about 100 to 250 ° C. for about 1 to 120 minutes and secondary vulcanization performed at about 150 to 300 ° C. for about 0 to 30 hours.

〔The invention's effect〕

The fluorinated elastic copolymer obtained by the method of the present invention is not only excellent in solvent resistance, particularly in terms of resistance to ketones and esters, but also has a T-10 value, which is a measure of low-temperature characteristics, of -5 to-. As low as 10 ° C, it shows well-balanced properties without losing flexibility even at low temperatures.

Fluorine-containing elastic copolymer having such properties,
Aircraft requiring high resistance to solvents, chemicals, etc.,
It is effectively used as a molding material for oil seals for fuel tanks, petrochemical plants, automobiles and machines, packings, gaskets and the like.

〔Example〕

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

Example 1 In a pressure-resistant container with a stirrer having a capacity of 3, 1000 g of deoxygenated and demineralized water, 4.2 g of ammonium perfluorooctanoate as a surfactant, 0.8 g of ammonium persulfate as a polymerization initiator, and ICF ₂ CF ₂ BR
1.63 g, 12 g of a 5% by weight aqueous sodium hydroxide solution as a buffer and 3 g of Na ₂ HPO ₄ .12H ₂ O were charged, and the whole container was subjected to −
Cool to 30 ° C.

Next, the internal space was sufficiently purged with pure nitrogen, and then purged, and then pressurized into the vessel in the order of 295 g of VE, 155 g of TFE, and 71 g of VdF. Thereafter, the temperature was raised in the system to 50 ° C., the reaction and stirring is begun after confirming the deicing proceeds, a pressure of 25 kg / cm ² was lowered to after 19 hours 6 kg / cm ^2. After confirming that no further pressure drop was observed, the unreacted mixed gas was purged to stop the polymerization reaction.

A 5% aqueous sodium chloride solution was added to the obtained aqueous emulsion to coagulate the resulting copolymer, which was washed with water and dried to obtain 392 g (yield: 75%) of a rubber-like random copolymer.

Example 2 In Example 1, the TFE amount was set to 178 g and the VdF amount was set to 57 g.
The polymerization reaction was carried out for 16 hours, and 389 g (yield 73%) of a rubber-like random copolymer was obtained.

Example 3 In Example 1, the TFE amount was set to 200 g, the VdF amount was set to 43 g,
The polymerization reaction was carried out by changing the amount of ammonium persulfate to 0.4 g, and 353 g of a rubber-like random copolymer (yield 65
%).

Example 4 In Example 1, after the amount of ICF ₂ CF ₂ Br was changed to 2.45 g and each raw material was charged, the internal space was sufficiently purged with pure nitrogen and then purged, and VE 295 g and TFE 118 g were removed. They were pressed into the container in order. Thereafter, raise the temperature of the system inside 50 ° C., at the time of reaction and stirring is begun after confirming the deicing proceeds, a pressure of 17 kg / cm ² was reduced after 14.5 kg / cm ² 6 hours, in advance 117 g of the prepared TFE-VdF (molar ratio: 40:60) mixed gas was injected, and the pressure was reduced to 25 kg / cm ^{2 and the} reaction was continued. After 15 hours, the pressure was reduced to 6 kg / cm ^2. Then, it was confirmed that no further pressure drop was observed, and the unreacted mixed gas was purged to stop the polymerization reaction.

A 5% aqueous sodium chloride solution was added to the obtained aqueous emulsion to coagulate the resulting copolymer, which was washed with water and dried to obtain 420 g of a rubbery segment copolymer (yield 79%).

Rubbery copolymer 10 obtained in each of the above Examples
0 parts (weight, same hereafter), MT carbon black 5 parts,
2 parts of 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 5 parts of triallyl isocyanurate (concentration: 60% by weight, diatomaceous earth added) and 3 parts of lead oxide are added, and roll-mixed The kneaded material was subjected to primary vulcanization at 180 ° C. for 10 minutes and secondary vulcanization at 200 ° C. for 22 hours to obtain a sheet and a P.
-24 O-rings were vulcanized.

Regarding the vulcanized sheet, the physical properties in normal state, the degree of swelling in acetone and the degree of swelling in ethyl acetate (volume change after immersion at 25 ° C for 70 hours), and TR-10 and TR-70, which are indicative of cold resistance
Measure the O-ring and set the compression set (200
° C, 70 hours, 25% compression). The results obtained are shown in the table below together with the copolymer composition of the rubbery copolymer used and the Mooney viscosity ML _{1 + 10} (JIS K-6300, 121 ° C.).

Comparative Example 1 In Example 1, the VE amount was set to 166 g, the TFE amount was set to 50 g, and Vd
The amount of F was changed to 224 g, and the polymerization reaction was performed for 16 hours by changing the amount of ICF ₂ CF ₂ Br to 2.0 g, and 423 g of a rubber-like random copolymer was obtained.
(96% yield).

MT carbon black 30 was added to 100 parts of this rubbery copolymer.
Part, 2,5-dimethyl-2,5-di (tert-butylperoxy)
Hexane (2 parts), triallyl isocyanurate (concentration: 60% by weight, diatomaceous earth added) (10 parts) and lead oxide (6 parts) were added, and roll kneading, vulcanization and measurement were performed in the same manner as described above. The results obtained are shown in the table below.

Comparative Example 2 MT was added to 100 parts of fluoro rubber (Viton GLT manufactured by DuPont)
30 parts of carbon black, 2,5-dimethyl-2,5-di (third
4 parts of (butylperoxy) hexane, 7 parts of triallyl isocyanurate (concentration: 60% by weight, diatomaceous earth added) and 4 parts of calcium hydroxide were added, and roll kneading, vulcanization and measurement were performed in the same manner as described above. . The results obtained are shown in the following table.

Claims (1)

(57) [Claims] (1) 40-55 mol% of tetrafluoroethylene, (b) 15-35 mol% of vinylidene fluoride and (c)
A copolymer of 20 to 35 mol% of perfluoro (methyl vinyl ether) having a Mooney viscosity ML _{1 + 10} (121 ° C.) of about 1
An elastic fluorine-containing copolymer having a TR-10 value of -5 to -10C at 0 to 100 pts.