JPH07118349A - Fluoroelastomer - Google Patents

Abstract

PURPOSE: To obtain a fluorine-containing elastomer excellent in heat resistance, solvent resistance, chemical resistance, tensile-strength and compression set resistance, small in gasoline permeability and difficult in solvent extraction of low molecular weight components by bonding iodine to a predetermined fluorine-containing elastomer.

CONSTITUTION: A desired fluorine-containing elasomer is obtained by bonding iodine to a fluorine-containing elasomer having a weight ratio of vinylidene fluoride units to hexafluoropropylene units of 40:60-80:20, an intrinsic viscosity of 60-100 ml/g, a multi-peak type of molecular weights formed of 2 or more peaks and a ratio of weight average molecular weight to number average molecular weight of 20-25 at the polymer chain terminal of the polymer derived from the peak of the lower molecular weight side in the molecular weight distribution in an amount of 0.6-2.0 wt.% based on 100 wt.% elastomer.

COPYRIGHT: (C)1995,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel fluorine-containing elastomer. More specifically, it has the same excellent heat resistance, solvent resistance, and chemical resistance as conventionally known fluorine-containing elastomers, but also has high tensile strength, excellent compression set resistance, and low gasoline permeability. The present invention relates to a fluoroelastomer which is difficult to extract low molecular weight components into a solvent and has excellent extrusion moldability. Therefore, the fluorine-containing elastomer of the present invention is suitable as a material for, for example, a fuel hose, a filler hose, an in-tank hose of an automobile.

[0002]

Fluorine-containing elastomers are extremely excellent in heat resistance, solvent resistance, and chemical resistance as compared with other general-purpose elastomers, so that various industrial fields such as general machinery industry, pollution-related departments, automobiles, ships, It is used in aircraft, hydraulic equipment, etc. as O-rings, gaskets, oil seals, diaphragms, valves, hoses, rolls, sheet materials, and the like.

However, fluorine-containing elastomers generally have the drawback of being difficult to process, and various proposals have been made to solve this problem. For example, a method for producing a vinylidene fluoride copolymer containing a low molecular weight polymer and a high molecular weight polymer and having a wide molecular weight distribution by a continuous emulsion polymerization method in which a chain transfer agent is periodically added (Japanese Patent Publication No. 51-24554). Gazette), a vinylidene fluoride-based copolymer having a bimodal molecular weight distribution,
A method of producing by a cascade type two-tank continuous emulsion polymerization method (Japanese Patent Publication No. 51-25279) is disclosed, but the fluorine-containing elastomer obtained by such a continuous production method has a remarkably wide molecular weight distribution. Too much,
When a hose or the like is molded by extrusion molding, the die swell is large and a polymer having an extremely low molecular weight is also contained, so that physical properties of the vulcanized product such as tensile strength are not satisfactory.

Therefore, in order to solve the problems in extrusion molding, a fluorine-containing elastomer having a specific multi-peak molecular weight distribution has been proposed (JP-A-4-209643).
Japanese Patent Laid-Open No. 4-258614). Further, a fluorine-containing elastomer having a specific multi-peak molecular weight distribution and containing bound iodine is vulcanized in combination with polyol vulcanization and / or polyamine vulcanization and peroxide vulcanization to improve mechanical strength and compression set, Studies have been conducted to reduce the solvent extractability (Japanese Patent Laid-Open No. 2-160810).

However, in any case, in the present situation, none of the extrusion molding and the physical properties of the vulcanized product are sufficiently satisfied. The present inventors have previously proposed a fluorine-containing elastomer (JP-A-2-160810). Based on this invention, processability, especially extrusion processability, was improved.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to have high heat resistance, solvent resistance, and chemical resistance equivalent to those of conventionally known fluorine-containing elastomers, while having high tensile strength and compression resistance. The present invention relates to a fluoroelastomer having excellent strainability, low gasoline permeability, difficulty in extracting low molecular weight components into a solvent, and excellent extrusion moldability.

[0007]

That is, the present invention is
(A) (a) Vinylidene fluoride unit (hereinafter VdF
Unit) and (b) a hexafluoropropylene unit (hereinafter abbreviated as HFP unit) in a weight ratio of 40:60 to 80:20 and (b) an intrinsic viscosity [η] of 60.
Is 100 ml / g, (c) is a multi-peak type in which the molecular weight distribution is formed from two or more peaks, and (d) the ratio Mw of the weight average molecular weight (Mw) and the number average molecular weight (Mn).
Fluorine-containing elastomer having a Mn of 20 to 25,
(E) With respect to 100% by weight of the fluorine-containing elastomer,
A fluorine-containing elastomer, wherein 0.6 to 2.0% by weight of iodine is bonded to the polymer chain terminal of the polymer derived from the peak on the low molecular weight side of the molecular weight distribution.

The present invention will be described in detail below. The fluorine-containing elastomer of the present invention comprises (a) VdF units and (b) HFP.
It is necessary that the weight ratio of the units is 40:60 to 80:20. If the VdF unit is less than this, the polymerization rate will be extremely slow, and if it is more than this, the resulting polymer will become a resin and the elastomer elasticity will decrease.

Further, if necessary, (c) tetrafluoroethylene units (hereinafter abbreviated as TFE units) are contained in an amount of 35% by weight based on the total weight of the monomer units (a), (b) and (c).
It is effective within the range not exceeding. More preferred ranges are (a) VdF units and (b) HFP units and monomer units.
10 to 30% by weight based on the total weight of (a), (b) and (c)
Of (c) TFE units, and (a) VdF units and (b)
The weight ratio of HFP units is 42:58 to 65:35.

In the fluorine-containing elastomer of the present invention, the intrinsic viscosity [η], which is an index of the molecular weight, is 60 to 10
It should be 0 ml / g. This [η] is 60
If it is less than ml / g, the tackiness during roll kneading becomes large,
When it exceeds 100 ml / g, the fluidity is lowered and it is difficult to obtain good extrusion molding. Particularly preferable intrinsic viscosity [η] is 70 to 90 ml / g.

The fluorine-containing elastomer of the present invention must have a multi-peak type in which the molecular weight distribution is formed from two or more peaks. When the molecular weight distribution is a single peak type, it is extremely difficult to control the ratio of the amount of the low molecular weight polymer and the amount of the high molecular weight polymer, and it is difficult to obtain good extrusion moldability which is the object of the present invention. The molecular weight distribution of the fluorine-containing elastomer of the present invention is mostly composed of a low molecular weight peak having a molecular weight of 50,000 or less and a high molecular weight peak having a molecular weight of 50,000 or more. Polymers on the low molecular weight side are required to improve flowability, and polymers on the high molecular weight side are required to maintain the green strength of the fluoroelastomer blend.

Further, in the present invention, in order to carry out the combined vulcanization, it is necessary to bond 0.6 to 2.0% by weight of iodine to the polymer chain end of the polymer on the low molecular weight side. . The bound iodine is easily released during peroxide vulcanization to form a radical at the end of the polymer chain, and this radical serves as a crosslinking point. On the other hand, there is no regulation regarding the polymer chain end of the polymer on the high molecular weight side, and polyol vulcanization and / or polyamine vulcanization are performed.

As described above, the polymer on the high molecular weight side is crosslinked by the vulcanization of the polyol and / or the polyamine, and the polymer on the low molecular weight side is simultaneously crosslinked by the vulcanization of the peroxide, so that a uniform crosslinking reaction proceeds. However, a molded product having a high tensile strength, an excellent compression set resistance, a low gasoline permeability, and a low molecular weight component that is difficult to extract into a solvent can be obtained.

A method using an iodine compound as a chain transfer agent (Japanese Patent Publication No. 63-41928, Japanese Patent Application Laid-Open No. 60-221409, etc.) is effective as a method for introducing iodine, which can serve as a crosslinking point, to the polymer chain terminal. is there. Iodine bonded to the polymer chain end of the polymer on the low molecular weight side is 0.6 to 100% by weight of the fluoroelastomer.
The range of 2.0% by weight is that if less than 0.6% by weight, the performance improvement due to combined vulcanization is insufficient,
This is because there is no effect of substantially increasing iodine even if it exceeds. A particularly preferable range of iodine is 0.8 to 1.6% by weight.

In the fluorine-containing elastomer of the present invention, it is necessary that the ratio Mw / Mn of the weight average molecular weight (Mw) and the number average molecular weight (Mn) is 20 to 25.
If the Mw / Mn is less than 20, the spread of the molecular weight distribution is small, and the extrusion moldability such as the extrusion speed and the extruded surface is poor.
If it exceeds 5, the ultra high molecular weight polymer and the extremely low molecular weight polymer increase, so that the die swell at the time of extrusion molding becomes worse. A particularly preferred Mw / Mn is in the range of 21-23.

The fluorine-containing elastomer of the present invention can be produced, for example, by blending a high-molecular weight polymer and a low-molecular weight polymer, which are separately produced, or an emulsion polymerization method, a suspension polymerization method, It can also be produced by a solution polymerization method by adding an iodine compound such as diiodomethane or 1,4-diiodoperfluorobutane, which is a chain transfer agent, during the polymerization.

Next, the method for producing the fluorine-containing elastomer of the present invention will be described by taking the suspension polymerization method as an example. First, a predetermined mixed monomer (charged monomer) is dispersed in an aqueous medium, the pressure is preferably set in the range of 5 to 30 kg / cm ² · G, and a suspension stabilizer and an oil-soluble catalyst dissolved in an inert organic solvent. Is added and the temperature is maintained preferably at 50 to 80 ° C. with mechanical stirring to start the polymerization. Since the pressure decreases as the polymerization proceeds, it is preferably 5 to 30 kg /
Polymerization proceeds by adding a new mixed monomer (additional monomer) so as to be constant within the range of cm ² · G. The composition of the monomer unit in the resulting fluorine-containing elastomer is determined by the relationship between the charged monomer composition and the additive monomer composition. The composition of the charged monomer and the composition of the added monomer are measured by gas chromatography, and the composition of the monomer unit in the fluorine-containing elastomer is measured by ¹⁹ F-NMR after dissolving the elastomer in acetone. In addition, during the polymerization, the iodine compound agent is added to adjust the molecular weight distribution and introduce bound iodine into the polymer chain terminal.

Methyl cellulose is preferred as the suspension stabilizer used in this suspension polymerization method. As the oil-soluble catalyst, dialkyl peroxydicarbonate such as diisopropyl peroxydicarbonate (hereinafter abbreviated as IPP) is preferable because it has a high decomposition temperature. Examples of the inert organic solvent include 1,1,2-trichloro-1,2,2-trifluoroethane, 1,1-dichloro-1-fluoroethane (hereinafter abbreviated as R-141b), 1,3- Dichloro-1,1,2,2,3-pentafluoropropane (hereinafter abbreviated as R-225cb) may be mentioned, and R-141b, R having a small ozone depletion coefficient.
-225cb is more preferable.

The fluorine-containing elastomer of the present invention can be vulcanized with a polyol, vulcanized with a polyamine and vulcanized with a peroxide, but in order to achieve the object of the present application, vulcanization in combination is desirable. Examples of the vulcanization method using both polyol vulcanization and peroxide vulcanization include fluorine-containing elastomer, (d) polyhydroxy aromatic compound, (e) vulcanization accelerator, (f) divalent metal hydroxide and / Alternatively, a method of kneading a divalent metal oxide, (g) an organic peroxide, (h) a polyfunctional unsaturated compound, and optionally other compounding agents, extrusion-molding, and then heating to vulcanize To be

Examples of the polyhydroxy aromatic compound as the component (d) include bisphenol AF, bisphenol A, bisphenol S, dihydroxybenzophenone, hydroquinone, 4,4'-thiodiphenol and metal salts thereof. Especially preferred is bisphenol AF. The mixing ratio is usually 0.1 to 10 parts by weight, preferably 0.6 to 5 parts by weight, based on 100 parts by weight of the fluoroelastomer. The component (d) is in this range because a vulcanized molded product cannot be obtained when the amount is less than 0.1 parts by weight, and the elastomer elasticity is lost when the amount exceeds 10 parts by weight. These polyhydroxy aromatic compounds may be used alone or in combination of two or more.

As the vulcanization accelerator of the component (e), a phosphonium salt, an ammonium salt, an iminium salt, a sulfonium salt, an aminophosphine derivative or the like is used. For example, benzyltriphenylphosphonium chloride (hereinafter abbreviated as BTPPC). , Methyltriphenylphosphonium methylmethanephosphonate, tetrabutylammonium fluoride, tetrabutylammonium bromide, 8-benzyl-1,8-diazabicyclo (5,
4,0) -undecenonium chloride, bis (benzyldiphenylphosphine) iminium chloride and the like, particularly BTPPC, 8-benzyl-1,8-diazabicyclo (5,4,0) -undecenonium chloride, bis. (Benzyldiphenylphosphine) iminium chloride is preferred. The compounding ratio is usually 0.05 to 2 parts by weight, preferably 0.1 to 1 part by weight, based on 100 parts by weight of the fluoroelastomer. The component (e) is in this range because the vulcanization rate is extremely slow when it is less than 0.05 parts by weight, and the compression set resistance is significantly deteriorated when it exceeds 2 parts by weight. These vulcanization accelerators may be used alone or in combination of two or more.

As the divalent metal hydroxide and / or the divalent metal oxide of the component (f), for example, oxides or hydroxides of magnesium, calcium, zinc, lead and the like are used, and particularly magnesium, Calcium oxides and hydroxides are preferred. Mixing ratio is 100% fluorinated elastomer
Usually 1 to 30 parts by weight, preferably 2 to parts by weight.
20 parts by weight. The component (f) is in this range because
This is because if the amount is less than 1 part by weight, the vulcanization does not proceed sufficiently, and if it exceeds 30 parts by weight, the compression set resistance deteriorates. Further, these may be used alone or in combination of two or more.

As the organic peroxide as the component (g), an organic peroxide which generates a peroxide radical under vulcanization conditions is used, and for example, 1,1-bis (tert-butylperoxy) -3, 5,5-trimethylcyclohexane,
1,1-bis (tert-butylperoxy) cyclohexane, 2,2-bis (tert-butylperoxy) octane, n-butyl 4,4-bis (tert-butylperoxy) valerate, 2,2-bis (Tert-butylperoxy) butane, 2,5-dimethylhexane-2,5-dihydroxyperoxide, di-tert-butylperoxide, tert-butylcumylperoxide, dicumylperoxide, α, α′-bis (Tert-butylperoxy-m
-Isopropyl) benzene, 2,5-dimethyl-2,5
-Di (tert-butylperoxy) hexane, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3, benzoyl peroxide, tert-butylperoxybenzene, 2,5-dimethyl- 2,5-di (benzoylperoxy) hexane, tert-butylperoxymaleic acid, tert-butyl-oxyisopropyl carbonate and the like can be mentioned, and particularly preferred (g) component is 2,
5-dimethyl-2,5-di (tert-butylperoxy)
Hexane, dicumyl peroxide, α, α'-bis (te
rt-butylperoxy-m-isopropyl) benzene, particularly preferred is 2,5-dimethyl-2,5-
Di (tert-butylperoxy) hexane, dicumyl peroxide, α, α'-bis (tert-butylperoxy-
m-isopropyl) benzene. The compounding ratio is usually 0.05 with respect to 100 parts by weight of the fluoroelastomer.
To 5 parts by weight, and the preferred range is 0.1 to 3 parts by weight. If the component (g) is within this range, if it is less than 0.05, a sufficient vulcanization rate cannot be obtained and the mold releasability deteriorates.
This is because if it exceeds 5 parts by weight, the compression set resistance is significantly deteriorated. Further, the organic peroxide may be used alone or in combination of two or more kinds.

The polyfunctional unsaturated compound as the component (h) is, for example, triallyl cyanurate, trimethallyl isocyanurate, triallyl isocyanurate, triacryl formal, triallyl trimellitate, N, N'-m-.
Examples thereof include phenylene bismaleimide, diallyl phthalate, tetraallyl terephthalamide, tris (diallylamine) -s-triazine, triallyl phosphite, and N, N-diallyl acrylamide. Particularly preferred is triallyl isocyanurate. The compounding ratio is usually 0.1 with respect to 100 parts by weight of the fluorine-containing elastomer.
10 to 10 parts by weight. If the amount of the component (h) is within this range, sufficient crosslinking density cannot be obtained if the amount is less than 0.1 parts by weight.
This is because if the amount is more than parts by weight, the component (h) bleeds onto the elastomer surface during molding, causing defective molding.
The particularly preferable range of the component (h) is 0.2 to 6 parts by weight. Further, the polyfunctional unsaturated compound may be used alone or in combination of two or more kinds.

Further, in the fluorine-containing elastomer vulcanizing composition of the present invention, if necessary, other components such as carbon black, Austin black, graphite,
Fillers such as silica, clay, diatomaceous earth, talc, wollastonite, calcium carbonate, calcium silicate, calcium fluoride, barium sulfate, sulfone compounds, phosphate esters, fatty amines, higher fatty acid esters, fatty acid calcium, fatty acid amides, low Molecular weight polyethylene, silicone oil, silicone grease, stearic acid,
Processing aids such as sodium stearate, calcium stearate, magnesium stearate, aluminum stearate and zinc stearate, and coloring agents such as titanium white and red iron oxide can be added. The mixing ratio of the filler is preferably in the range of 0.1 to 100 parts by weight, and particularly preferably in the range of 1 to 60 parts by weight, based on 100 parts by weight of the fluorine-containing elastomer. The blending ratio of the filler is in this range because if it is less than 0.1 part by weight, the effect of blending is ineffective, and if it exceeds 100 parts by weight, the elastomer elasticity is lost. The mixing ratio of the processing aid is usually 10 parts or less, and particularly preferably 5 parts or less, relative to 100 parts by weight of the fluorine-containing elastomer. If the blending ratio of the processing aid exceeds this range, the heat resistance is adversely affected. The mixing ratio of the coloring agent is 10% by weight of the fluorine-containing elastomer.
50 parts by weight or less is preferable with respect to 0 parts by weight, and a particularly preferable range is 30 parts by weight or less. The mixing ratio of the colorant is within this range because the compression set resistance is deteriorated when the content exceeds 50 parts by weight.

When vulcanization is carried out in combination with polyamine vulcanization and peroxide vulcanization, instead of the (d) polyhydroxy aromatic compound and (e) vulcanization accelerator, (h)
Polyamine compounds such as hexamethylenediamine, hexamethylenediamine carbamate, ethylenediamine carbamate, N, N-dicinnamylidene-1,6-hexamethylenediamine, 4,4′-bis (aminocyclohexyl) methane carbamate are preferably used. The blending ratio is usually 0.1 to 10 parts by weight, preferably 0.5 to 100 parts by weight with respect to 100 parts by weight of the fluoroelastomer.
5 parts by weight. The component (h) is in this range because
This is because if it is less than 0.1 part by weight, a vulcanized molded product cannot be obtained, and if it exceeds 10 parts by weight, elastomer elasticity is lost.
These polyamine compounds may be used alone or in combination of two or more.

As the method for molding the fluorine-containing elastomer of the present invention, for example, after kneading with an open-type kneading roll or a closed-type kneading roll (Banbury mixer, pressure kneader, etc.), it is cut into strips and subjected to an extrusion molding machine. As a result, a tube or an atypical rod-shaped material can be obtained. It is also possible to perform molding processing by injection molding, press molding, calendar molding, or the like. Next, if desired, secondary vulcanization is performed to obtain a desired vulcanized product.

[0028]

EXAMPLES The properties of the fluorine-containing elastomer were determined by the methods described below. (1) The intrinsic viscosity [η] is 0.1 of methyl ethyl ketone.
35 g / 100 ml of the concentrated solution using a capillary viscometer
Measure at ° C. (2) The molecular weight distribution is measured by liquid chromatography [HLC-8
020 (manufactured by Tosoh Corporation)], column [KF-80M
(2) + KF-800P (pre-column)] (Showa Denko KK) and integrator [AS-8010 (Tosoh KK)], using tetrahydrofuran as a developing solvent and a concentration of 0.1% by weight. Temperature 35 ℃
It was measured at. As the standard polymer for the molecular weight calibration curve, various monodisperse polystyrene [Mw / Mn to 1.2 (max)] (manufactured by Toyo Soda Co., Ltd.) was used. Mn and Mw are measured under the above-mentioned molecular weight distribution measurement conditions. (3) The hardness of the vulcanized product is 10 according to [JIS-A].
The 0% tensile stress, tensile strength, and elongation were measured according to JIS-K6301. (4) The compression set was measured according to JIS-K6301 under the conditions of a temperature of 150 ° C. and 70 hours. (5) In the extrusion test, an extruder 10DW (D = 19.1 mm, L / D = 10) manufactured by Brabender was used, a tube die (outer diameter 9 mm, inner diameter 8 mm) was used, and a screw temperature was 80 ° C. , Head temperature 100 ℃,
It carried out on the conditions of screw rotation speed 50 rpm. The extruded skin was shown in 5 grades (from 5 to 1 in excellent order) by visually observing the fineness of the surface skin. The extrusion rate was calculated from the discharge rate per unit time.

[0029]

Example 1 Inner volume of about 5 equipped with an electromagnetic induction type stirrer
A 0 l autoclave was sufficiently scavenged with nitrogen gas, vacuum-filling with nitrogen was repeated three times, and after nitrogen substitution, 23.7 kg of deoxygenated pure water and methylcellulose as a suspension stabilizer (viscosity 50 cp) 17.7 g was charged and the temperature was maintained at 50 ° C. while stirring at 476 rpm. Then VdF unit 12.7% by weight, HFP unit 7
A mixed monomer composed of 9.7% by weight and 7.6% by weight of TFE is charged to 17 kg / cm ² · G.

Next, 475 g of an R-141b solution containing 78.3 g of IPP as a catalyst was charged to start polymerization. When the pressure was lowered to 16.5 kg / cm ² · G by the polymerization, VdF unit was 44.1% by weight, HFP unit was 28.
A mixed monomer consisting of 2% by weight and 27.7% by weight of TFE is added, and the pressure is returned to 17 kg / cm ² · G.
Such an operation is repeated to carry out the polymerization reaction.

After 5 hours from the start of the polymerization, 533 g of diiodomethane was added, and the pressure was adjusted to 16.5 to 1 in the same manner.
The polymerization reaction was further continued at 7 kg / cm ² · G, and the total was 1
The polymerization reaction is performed for 2.5 hours. After the completion of the polymerization reaction, the remaining mixed monomer is scavenged, the obtained suspension is dehydrated with a centrifuge, thoroughly washed with water, and then vacuum dried at 100 ° C. to obtain 31.9 kg of a fluorine-containing elastomer. The fluorine-containing elastomer had an [η] of 89 ml / g, a VdF unit of 43.5% by weight, an HFP unit of 27.8% by weight, and TFE.
The unit is 27.3% by weight and contains 1.4% by weight of iodine. The molecular weight distribution is formed from two peaks, Mw
/ Mn is 23.0.

100 parts by weight of the fluorine-containing elastomer is wound around an open type kneading roll, and the product S manufactured by Tokai Carbon Co., Ltd.
13 parts by weight of RF carbon black "Cast S", calcium hydroxide "Calbit" manufactured by Omi Chemical Industry Co., Ltd.
6 parts by weight, 3 parts by weight of highly active magnesium oxide "Kyowamag 150" manufactured by Kyowa Chemical Industry Co., Ltd., 1.25 parts by weight of bisphenol AF and 0.7 part by weight of BTPPC are kneaded. Next, Nippon Oil & Fats Co., Ltd. product organic peroxide "Perhexa 25B-40 (contains 40% by weight of 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane 40% by weight)" 0.7 parts by weight Japan K.K. Co., Ltd. Knead 0.6 parts by weight of triallyl isocyanurate "TAIC",
Let stand overnight to mature.

Then, after re-kneading, an extrusion test was performed, and the mixture was placed in a mold and press-vulcanized at a temperature of 160 ° C. for 45 minutes to form a 2 mm-thick sheet and a test piece for measuring compression set, and various tests were conducted. I do. Table 1 shows the extrusion characteristics of the compound thus obtained and the physical properties of the vulcanized molded product.

[0034]

[Example 2] Instead of "Perhexa 25B-40", organic peroxide "Parkmill D-40" manufactured by NOF CORPORATION
Various tests are carried out in the same manner as in Example 1 except that (containing 40% by weight of dicumyl peroxide). The results are shown in Table 1.
Shown in.

[0035]

COMPARATIVE EXAMPLE 1 Instead of the fluorine-containing elastomer of Example 1, 42.2% by weight of VdF unit, 30.7% by weight of HFP unit and 26.2% by weight of TFE unit were used, and the iodine content was 0.9% by weight. %, [Η] is 124 ml / g, the molecular weight distribution is formed from two peaks, and Mw / Mn is 18.
Various tests are conducted in the same manner as in Example 1 except that the fluorine-containing elastomer of No. 8 is used. The results are shown in Table 1.

[0036]

COMPARATIVE EXAMPLE 2 Instead of the fluorine-containing elastomer of Example 1, VdF unit was 43.7% by weight, HFP unit was 29.2% by weight and TFE unit was 26.6% by weight, and the iodine content was 0.5% by weight. %, [Η] is 81 ml / g, the molecular weight distribution is formed from two peaks, and Mw / Mn is 22.7.
Various tests are carried out in the same manner as in Example 1 except that the fluorine-containing elastomer is used. The results are shown in Table 1.

[0037]

[Table 1]

[0038]

The fluoroelastomer of the present invention has high tensile strength, excellent compression set resistance, and extrusion moldability (even if the extrusion speed is increased, the fluoroelastomer of the present invention is It has excellent extruded skin condition) and is suitable as a material for automobile fuel hoses, filler hoses, in-tank hoses, etc., and has an extremely large industrial value.

Front page continued (72) Inventor Hiro Saito 1-3-1 Yoko, Kawasaki-ku, Kawasaki-shi, Kanagawa Asahi Kasei Kogyo Co., Ltd. (72) Inventor Kenichi Hayashi 6-4100 Asahi-cho, Nobeoka-shi, Miyazaki Asahi Kasei Kogyo Within

Claims (1)

[Claims] 1. A weight ratio of (a) vinylidene fluoride unit (a) to hexafluoropropylene unit (b) is 40:
60 to 80:20 and (b) intrinsic viscosity [η]
Is 60 to 100 ml / g, and (c) the molecular weight distribution is 2
It is a multi-peak type formed from two or more peaks,
(D) Weight average molecular weight (Mw) and number average molecular weight (Mn)
In the fluorine-containing elastomer having a ratio Mw / Mn of 20 to 25, (e) 0.6 to 2.0% by weight of iodine per 100% by weight of the fluorine-containing elastomer becomes a peak on the low molecular weight side of the molecular weight distribution. A fluoroelastomer characterized in that it is bonded to the polymer chain end of a polymer derived from it.