JP4206579B2 - Fluorine-containing copolymer composition - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fluorine-containing copolymer composition. More specifically, the present invention relates to a fluorine-containing copolymer composition that can impart engine oil resistance to a general-purpose fluorine-containing elastomer.
[0002]
[Prior art]
Fluorine-containing elastomers are used in many applications including automotive parts because of their excellent heat resistance, chemical resistance and compression set resistance. Among them, the oil seal for automobiles is one of the largest uses of the fluorine-containing elastomer, but further improvement is required in the following points.
[0003]
In other words, with the recent high performance and low fuel consumption of automobile engines, the performance of engine oils has also been improved. For this reason, amine-based additives tend to be added to engine oils.
[0004]
However, vinylidene fluoride-hexafluoropropene copolymer, a vinylidene fluoride-hexafluoropropene-tetrafluoroethylene terpolymer, which is widely used as a molding material for oil seals, is used. The crosslinked molded product of the copolymer elastomer is deteriorated by the engine oil, causing cracks and elongation, a remarkable decrease in the tensile strength, and the like, and impairs the sealing performance. The cause of such deterioration due to engine oil is considered to be because the vinylidene fluoride-hexafluoropropene chain site in the copolymer elastomer main chain reacts with the amine-based compound in engine oil.
[0005]
Tetrafluoroethylene-perfluoro (methyl vinyl ether) copolymer, vinylidene fluoride-tetrafluoroethylene-perfluoro (methyl vinyl ether) terpolymer, tetrafluoroethylene-propylene copolymer, etc. are excellent in engine oil resistance. Although known as a fluorine-containing elastomer, perfluoro (methyl vinyl ether) is extremely expensive, the copolymer using it lacks cost and performance, and the tetrafluoroethylene-propylene copolymer has a low temperature. It is inferior to the above-mentioned general-purpose fluorine-containing elastomer in terms of characteristics.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a fluorine-containing copolymer composition having improved engine oil resistance without deteriorating the low temperature characteristics, compression set resistance, etc. inherent to the fluorine-containing elastomer.
[0007]
[Means for Solving the Problems]
The object of the present invention is achieved by a fluorine-containing copolymer composition comprising a fluorine-containing elastomer and a tetrafluoroethylene-alkyl vinyl ether-crotonic acid terpolymer.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Tetrafluoroethylene in the terpolymer added to the fluorine-containing elastomer is an indispensable monomer for developing miscibility and engine oil resistance when forming a composition with the fluorine-containing elastomer. It is necessary that about 0.5 to 80 mol%, preferably about 30 to 60 mol% of the terpolymer is copolymerized. If the copolymerization ratio is less than this, not only the dispersion failure tends to occur when preparing a composition with a fluorine-containing elastomer by an open roll or the like, but also the chemical resistance inherent in the fluorine-containing elastomer is lowered. . On the other hand, when the copolymerization ratio is higher than this, solution polymerization, which is a preferred method for producing a fluorinated copolymer, becomes difficult.
[0009]
Examples of the alkyl vinyl ether include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tertiary butyl vinyl ether, n-pentyl vinyl ether, n-hexyl vinyl ether, 2-ethylhexyl vinyl ether, n-octyl vinyl ether, etc. Alicyclic vinyl ethers such as aliphatic alkyl vinyl ethers, cyclohexyl vinyl ethers, 4-methylcyclohexyl vinyl ethers, and the like, preferably methyl vinyl ether, ethyl vinyl ether, n-butyl vinyl ether, or cyclohexyl vinyl ether.
[0010]
These alkyl vinyl ethers are used after being copolymerized in a proportion of about 0.5 to 80 mol%, preferably about 20 to 50 mol%, in the terpolymer. When the copolymerization ratio is less than this, stable solution polymerization becomes difficult. On the other hand, when the copolymerization is performed at a ratio higher than this, the amount of other monomers is relatively reduced, and the engine oil resistance is improved. It will not be done.
[0011]
The crotonic acid is presumed to have its carboxyl group oriented on the surface of the composition with the fluorine-containing elastomer, and traps amines in the engine oil and prevents the fluorine-containing elastomer from deteriorating. Crotonic acid is copolymerized in a proportion of about 0.5 to 50 mol%, preferably about 5 to 30 mol% in the terpolymer. If the copolymerization ratio of crotonic acid is less than this, the effect of improving engine oil resistance is small. On the other hand, copolymerization at a ratio higher than this will not only lower the polymerization rate of the copolymerization reaction, but also The water resistance and steam resistance of the crosslinked product of the composition with the elastomer are also lowered.
[0012]
Incidentally, a crotonic acid copolymer similar to the tetrafluoroethylene-alkyl vinyl ether-crotonic acid terpolymer used in the present invention, for example, hexafluoropropene-ethyl vinyl ether-crotonic acid terpolymer (Japanese Patent Laid-Open No. Hei 10). No. 319,593) shows little improvement in engine resistance because hexafluoroethylene is copolymerized. Also known is a terpolymer of fluoroolefin, crotonic acid and vinyl carboxylate or alkyl vinyl ether (Japanese Patent No. 2,884,819), and chlorotrifluoroethylene specifically described as an example therein. The vinyl pivalate-crotonic acid terpolymer does not have heat resistance as a molding material for the final sealing material of the present invention.
[0013]
Further, from the general description of this patent publication, a combination of tetrafluoroethylene-alkyl vinyl ether-crotonic acid terpolymers can be considered, but there is no general description indicating such a terpolymer. Not seen at all. In addition, methyl vinyl ether is not described as an example of alkyl vinyl ether. In this type of terpolymer, the higher the Tg, the better the normal physical properties and low-temperature properties of the composition with the fluorine-containing elastomer. From this point of view, ternary copolymer obtained by copolymerizing methyl vinyl ether in particular. Coalescence is preferred.
[0014]
In the terpolymer according to the present invention, other olefin compounds or vinyl compounds, such as ethylene, propylene, vinyl chloride, vinylidene chloride, within a range that does not impair the purpose, more specifically, about 10 mol% or less. , Vinyl fluoride, vinylidene fluoride, methyl crotonate, ethyl crotonate and the like may be further copolymerized.
[0015]
The copolymerization reaction is carried out at a pressure of about 0.2 to 2 MPa, preferably about 0.5 to 1.5 MPa (gauge pressure) in the presence of a radical polymerization initiator at about 20 to 100 ° C., preferably about 50 to 80 ° C. Done in Examples of radical polymerization initiators include acetyl peroxide, benzol peroxide, lauroyl peroxide, methyl ethyl peroxide, cyclohexane non-peroxide, tertiary butyl peroxide, cumene hydroperoxide, di-tertiary butyl peroxide, dicumyl Peroxides such as peroxides; azo compounds such as azobisisobutylnitrile and dimethyl-2,2′-azobis (2-methylpropionate) are used.
[0016]
The polymerization reaction is also carried out by an emulsion polymerization method, a suspension polymerization method, a bulk polymerization method or the like. From the viewpoint of the stability of the alkyl vinyl ether, a nonaqueous aqueous solution polymerization method is preferably used. Reaction solvents used during solution polymerization include methyl acetate, ethyl acetate, butyl acetate, propyl acetate, isopropyl acetate, amyl acetate, esters such as ethylene glycol monoethyl ether monoacetate and ethylene glycol monobutyl ether monoacetate; acetone, methyl ethyl ketone , Ketones such as methyl isobutyl ketone, diisobutyl ketone, methyl amyl ketone, cyclohexane and isophorone; aromatic hydrocarbons such as benzene, toluene and xylene; aliphatic carbonization such as n-pentane, n-hexane and n-octane Hydrogen: Alicyclic hydrocarbons such as cyclopentane, cyclohexane, and ethylcyclohexane are used.
[0017]
The reaction mixture obtained by the solution polymerization method can be used to obtain the desired terpolymer by distilling off the unreacted monomer and the reaction solvent under normal pressure or reduced pressure. It is preferable to perform reprecipitation purification because problems such as odor due to unreacted crotonic acid occur.
[0018]
The obtained terpolymer having a number average molecular weight Mn of about 1,000 to 200,000 is used by blending with a fluorine-containing elastomer. Any fluorine-containing elastomer to be blended can be used. For example, the above-mentioned vinylidene fluoride-hexafluoropropene copolymer elastomer, vinylidene fluoride-chlorotrifluoroethylene copolymer elastomer, Vinylidene-perfluoro (alkyl vinyl ether) copolymer elastomer, vinylidene fluoride-tetrafluoroethylene-perfluoro (alkyl vinyl ether) terpolymer elastomer, tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer elastomer, tetra Examples thereof include fluoroethylene-propylene copolymer elastomers and vinylidene fluoride-tetrafluoroethylene-propylene terpolymer elastomers.
[0019]
The terpolymer and fluorine-containing elastomer according to the present invention are used by blending the former at a ratio of about 1 to 100 parts by weight, preferably about 3 to 20 parts by weight with respect to the latter 100 parts by weight. When the blending ratio of the terpolymer is less than this, the effect of improving the engine oil resistance aimed at by the present invention is not achieved. On the other hand, when the blending ratio is higher than this, the fluorine-containing elastomer is inherently preferable. The characteristics will be lost.
[0020]
Preparation of the composition containing the above components as essential components is performed by mixing and kneading using a mixing roll, a kneader, a Banbury mixer, or the like. Crosslinking molding of the prepared composition is performed using a crosslinking agent, and in that case, it is preferable to use a crosslinking accelerator or a co-crosslinking agent in combination.
[0021]
The crosslinking system is not particularly specified, and any method such as amine crosslinking, polyol crosslinking, peroxide crosslinking and the like can be used depending on the type of the fluorine-containing elastomer used, but the peroxide crosslinking method is preferably used. . When peroxide crosslinking is performed, examples of organic peroxides include 2,5-dimethyl-2,5-bis (tertiary butylperoxy) hexane, 2,5-dimethyl-2,5-bis (tertiary butyl). Peroxy) hexyne-3, benzoyl peroxide, bis (2,4-dichlorobenzoyl) peroxide, dicumyl peroxide, di-tert-butyl peroxide, tert-butyl cumyl peroxide, tert-butyl peroxybenzene, 1 , 1-Bis (tert-butylperoxy) -3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroxyperoxide, α, α'-bis (tert-butylperoxy)- p-Diisopropylbenzene, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane and tert-butylperoxyisopropyl carbonate are used.
[0022]
Along with these organic peroxides, for example, tri (meth) allyl isocyanurate, triallyl trimellitate, N, N'-m-phenylenebismaleimide, diallyl phthalate, tris (diallylamine) -s- A polyfunctional unsaturated compound co-crosslinking agent such as triazine, triallyl phosphite, 1,2-polybutadiene, ethylene glycol diacrylate, diethylene glycol diacrylate is preferably used in combination.
[0023]
Each of the above components to be blended in the peroxide crosslinking system comprises about 0.1 to 10 parts by weight of organic peroxide, preferably about 0.5 to 5 parts by weight, and a co-crosslinking agent per 100 parts by weight of the blend. About 0.1 to 10 parts by weight, preferably about 0.5 to 5 parts by weight, respectively.
[0024]
In addition to the cross-linking system comprising the above components, the composition includes acceptors such as oxides or hydroxides of divalent metals such as ZnO, CaO, Ca (OH) ₂ , MgO, PbO, or synthetic hydrotalcite. The acid agent is used in an amount of about 1 to 20 parts by weight, preferably about 3 to 15 parts by weight per 100 parts by weight of the blend.
[0025]
Furthermore, carbon black, silica, graphite, clay, talc, diatomaceous earth, barium sulfate, titanium oxide, wollastonite and other fillers or reinforcing agents, lubricants, processing aids, pigments and the like are appropriately added to the composition. Can also be used.
[0026]
The prepared composition is crosslinked and molded by heating at about 150 to 220 ° C. for about 0.5 to 10 minutes using a press molding machine, injection molding machine, etc., but if necessary, about 150 to 250 ° C. Secondary crosslinking is performed for about 1 to 20 hours.
[0027]
【The invention's effect】
The fluorine-containing copolymer composition according to the present invention has the effect of improving its engine oil resistance without deteriorating the normal physical properties, low temperature characteristics, compression set resistance, etc. inherent to the fluorine-containing elastomer.
[0028]
What is specially noted is that almost no increase in hardness due to the addition of such a fluorinated copolymer (ternary copolymer) is observed, and this does not reduce the degree of freedom in compounding design. There is nothing else.
[0029]
【Example】
Next, the present invention will be described with reference to examples.
[0030]
Reference Example Into an autoclave with an internal volume of 10 L, 10 g of ammonium perfluorooctanoate, 2 g of sodium hydroxide (for pH adjustment) and 5 L of deionized water were charged, and the interior space was sufficiently replaced with nitrogen gas. 15.0 g of diiodoperfluorobutane was injected under pressure. afterwards,
Vinylidene fluoride [VdF] 70 mol%
Hexafluoropropene [HFP] 30 mol%
The mixed monomer gas was injected until the internal pressure became 2.0 MPaG, and the internal temperature was raised to 70 ° C.
[0031]
Thereafter, an aqueous polymerization initiator solution in which 5 g of ammonium persulfate was dissolved in 150 ml of water was pressed into the autoclave to initiate the polymerization reaction. The internal pressure at this time was 3.2 MPaG . When the internal pressure dropped to 2.9MPaG, VdF / HFP (molar ratio 78:22) the mixed gas as a divisional addition gas, the operation of press-fitting until the internal pressure reached 3.0 MPaG, solid concentration 30 wt generated in the latex It repeated until it became%. Immediately after reaching a predetermined solid content concentration, the reaction was stopped by purging the unreacted gas in the autoclave.
[0032]
The resulting copolymer was coagulated by adding 5% by weight potassium alum water to the obtained aqueous latex, washed with water and dried. 2188 g of fluorine-containing elastomer (polymerization rate 85%) was obtained, and the copolymer composition (by ¹⁹ F-NMR) of this copolymer was VdF / HFP = 78/22 (mol%), iodine content (by elemental analysis) 0.030 mmol / g, glass transition temperature (by DSC method) was −15 ° C., and solution viscosity ηsp / c [specific viscosity of 1 wt% methyl ethyl ketone (MEK) solution, 35 ° C.] was 0.65 dl / g. It was.
[0033]
Example 1
In a 3L stainless steel autoclave equipped with a stirrer,
Crotonic acid [CA] 91g
Ethyl vinyl ether [EVE] 234g
Lauroyl peroxide 20g
Methyl isobutyl ketone 1000g
After fully replacing with nitrogen gas,
Tetrafluoroethylene [TFE] 150g
Was introduced, and the temperature was gradually raised.
[0034]
When the temperature in the autoclave reached 70 ° C, a pressure of 0.82 MPaG was shown. Thereafter, 185 g of TFE was added over 2 hours while maintaining the pressure at 0.8 to 0.85 MPaG. The reaction at 70 ° C. was carried out under stirring conditions for 2 hours. When the pressure dropped to 0.53 MPaG, the autoclave was cooled with water to stop the reaction.
[0035]
Unreacted TFE was removed, and the autoclave was opened to obtain 1570 g of a terpolymer solution having a solid content concentration of 33% by weight. The resulting copolymer was purified by reprecipitation from n-hexane and dried under reduced pressure to obtain 470 g of terpolymer A (polymerization rate 71%).
[0036]
The resulting terpolymer A has an acid value (based on JIS K-0070; unit KOHmg / g) of 85, Tg (DSC method) of 25 ° C., number average molecular weight Mn (GPC polystyrene conversion value; solvent tetrahydrofuran) Was 13000 (Mw / Mn = 1.8), and the copolymer composition determined from ¹⁹ F-NMR, elemental analysis and acid value was TFE 47 mol%, EVE 40 mol%, and crotonic acid 13 mol%.
[0037]
Example 2
In the initial charge in Example 1, the amount of crotonic acid was changed to 101 g, the amount of tetrafluoroethylene was changed to 270 g, and 210 g of methyl vinyl ether [MVE] was used instead of ethyl vinyl ether.
[0038]
When the temperature inside the autoclave was raised to 70 ° C., the pressure showed 1.7 MPaG at that time. While maintaining this temperature, the reaction was continued for 7 hours under stirring conditions. When the pressure dropped to 0.53 MPaG, the autoclave was cooled with water to stop the reaction. Thereafter, the same treatment as in Example 1 was performed to obtain 496 g of terpolymer B (polymerization rate: 85%).
[0039]
The acid value of the obtained terpolymer B is 103, Tg is 47 ° C., the number average molecular weight Mn is 15000 (Mw / Mn = 1.8), and the copolymer composition is TFE 45 mol%, MVE 40 mol%, CA 15 Mol%.
[0040]
Example 3
In the initial charge of Example 1, the amount of crotonic acid was changed to 81 g, the amount of tetrafluoroethylene was changed to 170 g, and n-butyl vinyl ether [BVE] 290 g was used instead of ethyl vinyl ether.
[0041]
When the temperature in the autoclave reached 70 ° C, a pressure of 1.3 MPaG was shown. Thereafter, 120 g of TFE was added over 1 hour while maintaining the pressure at 0.8 to 0.85 MPaG. The reaction at 70 ° C. was carried out under stirring conditions for 4 hours. When the pressure dropped to 0.47 MPaG, the autoclave was cooled with water to stop the reaction. Thereafter, the same treatment as in Example 1 was performed to obtain 443 g of terpolymer C (polymerization rate: 67%).
[0042]
The resulting ternary copolymer C has an acid value of 80, Tg of 26 ° C., and a number average molecular weight of 3500 (Mw / Mn = 2.0), and the copolymer composition is TFE 47 mol%, BVE 39 mol%, CA 14 Mol%.
[0043]
Example 4
In the initial charge of Example 1, the tetrafluoroethylene amount was changed to 213 g, and cyclohexyl vinyl ether [CHVE] 234 g was used instead of ethyl vinyl ether.
[0044]
When the temperature in the autoclave was raised to 70 ° C., the pressure showed 1.5 MPaG at that time. While maintaining this temperature, the reaction was continued for 6 hours under stirring conditions. When the pressure dropped to 0.85 MPaG, the autoclave was cooled with water to stop the reaction. Thereafter, the same treatment as in Example 1 was performed to obtain 237 g (polymerization rate: 44%) of terpolymer D.
[0045]
The acid value of the obtained terpolymer D is 87, Tg is 54 ° C., the number average molecular weight Mn is 2500 (Mw / Mn = 2.5), and the copolymer composition is TFE 48 mol%, CHVE 35 mol%, CA. It was 17 mol%.
[0046]
Examples 5-8
100 parts by weight of fluorine-containing elastomer of reference example
MT carbon black 30 〃
2,5-dimethyl-2,5-di (tert-butylperoxy) hexane 0.5 〃
Triallyl isocyanurate 4 〃
Ternary copolymer A 4.5 〃 (Example 5)
〃 B 4.5 実 施 (Example 6)
〃 C 4.5 実 施 (Example 7)
〃 D 4.5 〃 (Example 8)
The above blended components were kneaded with an 8-inch open roll to prepare a fluorinated copolymer composition. This composition was press-crosslinked at 180 ° C. for 5 minutes, and then secondarily crosslinked in an oven at 200 ° C. for 4 hours to cross-link the O-ring and the sheet.
[0047]
About the obtained crosslinked material, the following each item was measured.
Normal physical properties : Hardness (Shore A) ASTM D-2240-81 compliant
100% modulus ASTM D-412-83 compliant tensile strength ASTM D-412-83 compliant Elongation ASTM D-412-83 compliant Low temperature properties: TR test according to ASTM D-1329 Compression set: O-ring with a wire diameter of 3.5 mm Measured for 25% compression at 200 ° C, 70 hours and 150 ° C, 70 hours Engine oil resistance: Normal condition after immersing test pieces in engine oil (TOYOTA Castle Motor Oil Clean SJ 10W-30) at 175 ° C for 70 hours Measure physical properties [0048]
Comparative example
In Examples 5 to 8 , the same kneading, cross-linking molding and measurement were performed without using the terpolymers A to D.
[0049]
The measurement results in the above Examples 5 to 8 and Comparative Example are shown in the following table.
table
Example comparison
Measurement item Five 6 7 8 cases
[Normal physical properties]
Hardness (points) 74 74 75 76 74
100% modulus (MPa) 6.0 6.5 5.9 6.3 5.8
Tensile strength (MPa) 14.7 15.7 14.8 15.2 14.5
Elongation (%) 210 210 200 220 210
[Low temperature characteristics]
TR-10 (℃) -14 -16 -15 -16 -16
TR-70 (℃) -5 -6 -5 -5 -7
[Compression set]
O-ring (℃) 28 26 29 28 26
[Engine oil resistance]
Hardness (points) 75 74 76 76 78
100% modulus (MPa) 3.6 3.7 2.9 3.5-
Tensile strength (MPa) 8.1 9.8 7.9 9.0 5.8
Elongation (%) 150 160 130 160 70

Claims (10)

A fluorine-containing copolymer composition comprising a fluorine-containing elastomer and a tetrafluoroethylene-alkyl vinyl ether-crotonic acid terpolymer. The fluorine-containing copolymer composition according to claim 1, wherein the alkyl vinyl ether is an aliphatic alkyl vinyl ether. The fluorine-containing copolymer composition according to claim 1, wherein the alkyl vinyl ether is an alicyclic alkyl vinyl ether. The fluorine-containing copolymer composition according to claim 1, which is used as a molding material for a sealing material. The fluorine-containing copolymer composition according to claim 1 or 4, which is crosslinked by an organic peroxide crosslinking agent. A tetrafluoroethylene-alkyl vinyl ether-crotonic acid terpolymer having a number average molecular weight Mn of 1,000 to 200,000. The terpolymer according to claim 6, wherein the alkyl vinyl ether is an aliphatic alkyl vinyl ether. The terpolymer according to claim 7, wherein the aliphatic alkyl vinyl ether is methyl vinyl ether. The terpolymer according to claim 6, wherein the alkyl vinyl ether is an alicyclic alkyl vinyl ether. The ternary copolymer according to claim 6, which is produced by a solution polymerization method.