JPS6023701B2 - Tetrafluoroethylene/hexafluoropropene copolymer-fluorine-containing elastomer composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides tetrafluoroethylene hexafluoropolymer
The present invention relates to a ben copolymer-fluorine-containing elastomer composition.

A copolymer of tetrafluoroethylene (hereinafter referred to as "TFE") and hexafluoroprobene (hereinafter referred to as "HFP") is polytetrafluoroethylene (hereinafter referred to as "PTF").
It's called E. ), it has heat resistance, chemical resistance, and electrical properties comparable to those of PTFE, and has melt flowability not found in PTFE, so it can be subjected to all kinds of melt processing such as compression molding, extrusion molding, and injection molding. Used in a wide range of applications. T generally used for extrusion molding, injection molding, etc.
The FE/HFP copolymer is required to have a specific melt viscosity, which will be defined later, in the range of 1 to 1 poise from the viewpoint of moldability.

However, TFE with a specific melt viscosity of 1 poise or less
HFP copolymers are relatively prone to stress cracking when exposed to temperatures of 180 pm or higher, which limits their range of use. When the specific melt viscosity becomes 5×1 poise, the stress crack resistance improves and stress cracks do not occur up to near the melting point, but an increase in the specific melt viscosity means a decrease in moldability, which is not preferable. Such TFE/H
Methods for improving the drawbacks of FP copolymers include polymerization methods in which other monomers are copolymerized during production, modifiers are added, or polymerization conditions are changed. There are two methods that can be considered, one is a method of blending materials, and the other is a method of blending materials, and the present invention belongs to the latter category.

That is, the present invention improves the heat stress cracks of the TFE/HFP copolymer described above without sacrificing moldability, and provides a TFE/HFP copolymer composition with excellent heat stress crack resistance. , this purpose is TFE
This is achieved by uniformly blending 99.95 to 90% by weight of the /HFP copolymer with a cloud content of 0.05 to 1% of the fluorine-containing elastomer.

The TFE/HFP copolymer referred to in the present invention is mainly TFE/HFP copolymer.
It is composed of E and HFP, and the HFP content defined later is 5.
~2% by weight, and may contain small amounts of third components, modifiers, etc.

Furthermore, in the present invention, the fluorine-containing elastomer includes, for example, HFP/vinylidene fluoride copolymer, TFE/vinylidene fluoride HFP terpolymer, TFE nopropylene copolymer, TFE/chlorovinyl ether copolymer. , T
FE/ethylenenopropylene terpolymer, ethylene/
Examples include HFP copolymer, TFE/ethylene/HFP terpolymer, TFE/ethylene hexafluoroacetone terpolymer, TFE/hexafluoroacetone copolymer, etc.
These can be used alone or in combination of two or more.

Methods for blending the fluorine-containing elastomer into the TFE/HFP copolymer include, for example, a mixer, mixing roll kneader, ball mill, or mixer.
Any wet or dry mixing method using a blender or the like can be used.

Generally, it is preferable to prepare the fluorine-containing elastomer as an aqueous dispersion and wet-mix it with the TFE/HFP copolymer. In addition, when producing TFE/HFP copolymer,
The fluorine-containing elastomer may be added during the polymerization reaction and/or during the reaction, and this method will not have any adverse effect on the polymerization reaction or product. In order to obtain the above-mentioned effects of the present invention, it is necessary to
It is necessary to uniformly mix (blend) the fluorine-containing elastomer in the FE/HFP copolymer at the molecular level, and for this purpose, all of the above mixing methods are still insufficient and coarse mixing. However, melt mixing must be carried out in the end, but such melt mixing can be achieved naturally by beletizing during product production.

In addition, when the final product is made by directly extruding a pipe without going through beletizing, the purpose of uniform mixing is achieved by melt extrusion. According to the invention, TFE/HF
P copolymer 99.95-9% by weight and fluorine-containing elastomer 0.05-10% by weight, more preferably TFE/
HFP copolymer 99.9-95. By blending 0.1 to 5.0 weight % of a fluorine-containing elastomer to the weight % of the TFE/HFP copolymer, the heat stress crack resistance can be improved without substantially impairing the properties of the TFE/HFP copolymer. If the amount of the fluorine-containing elastomer added is small, no effect will be observed, and if the amount added is too large, discoloration and a decrease in mechanical strength will occur, which is not preferable. If the elastomer to be added is a hydrocarbon elastomer, problems such as insufficient heat resistance may occur.

Furthermore, other fluororesins such as polyvinyridine fluoride, polytetrafluoroethylene, polytetrafluoroethylene wax, and tetrafluoroethylene nofluorovinyl ether copolymers are ineffective. The embodiments of the present invention will be described below with reference to Examples, Comparative Examples, and Test Examples.

In addition, "part" in Examples and Comparative Examples means based on weight unless otherwise specified. In addition, the HFP content (wt%) of the polymer was calculated by dividing the absorbance at a wave number of 980 ka-1 by the absorbance at a wave number of 2350 ka-1, multiplied by 3.2, based on the infrared absorption spectrum of a film with a thickness of about 40 A. Shown numerically. In addition, the t-specific melt viscosity is determined using a Koka-type flow tester, and the polymer is loaded into a cylinder with an inner diameter of 9.5 mm, held at a temperature of 38,000 for 5 minutes, and then heated under a piston load of 5 k9 with an inner diameter of 2 mm. .Extrude through the orifice on the 1st rib and length 8 side at the same temperature, and at the extrusion speed (cc/min)
It is obtained by dividing 3150. Example 1 100 parts of a powdered TFE/HFP copolymer with a specific melt viscosity of 8×1 poise and an HFE content of 12.2% and 50 parts of ion-exchanged water were vigorously concentrated using a tabletop mixer, and TFE/propylene copolymer was mixed. 1 part of an aqueous dispersion containing 10% of a polymeric elastomer (polymer composition TFE/propylene molar ratio=1) is added, and after stirring for 3 minutes, 5 parts of 20% nitric acid are added as a coagulant.

After lighting the lamp for another 30 minutes, it is separated from the oven, thoroughly washed with ion-exchanged water, and dried at a temperature of 120 qo for 24 hours. In addition, during the above-mentioned operations such as furnace separation and washing, almost no detachment of a single TFE/propylene elastomer particle was observed. The premixed polymer was then mixed into a cylinder with a length of 220 mm.
It was extruded at a temperature of 33,000 using a screw extruder with a diameter of 15 mm, a discharge hole length of 2 mm, and a discharge hole length of 10 mm, and the extruded product was extruded again in the same manner to form pellets.
Obtain a blended polymer. This polymer had a specific melt viscosity of 7.6×1 pipoise and an HFP content of 12.2%. Example 2 20 mol% TFE, HFP31 as added elastomer
T having a composition of mol%, vinylidene fluoride 49 mol%
22% FE/HFP/vinylidene fluoride elastomer
The operation was carried out in the same manner as in Example 1 except that 5 parts of the aqueous dispersion containing
A blend polymer with a HFP content of 12.2% was obtained.

Example 3 SUS-32 with jacket that can accommodate 300 ml of water
Deoxidized and demineralized water in Western-style autoclave 10
After charging 20 parts of the TFE/propylene elastomer monoaqueous dispersion of Example 1 and thoroughly purging the internal space with pure nitrogen gas, 600 parts of HFP and 1 part of TFEIIO were introduced under pressure.

The temperature inside the machine was maintained at 20qo, and di(omega hydrodecafluoroheptanoyl) was added as a polymerization initiator.
2 parts of peroxide and 14 parts of methyl alcohol as a molecular weight regulator are introduced under pressure. The reaction was started immediately, and TFE was successively fed as the reaction progressed. After reacting for 2 hours, the unreacted monomer was discharged and the polymer was recovered after adding 3 parts of 20% nitric acid. After thoroughly washing the polymer with water, it was dried at a temperature of 120 pm for two hours to obtain 135 parts of a white powder blend polymer. The specific melt viscosity of this polymer is 7.2×1 pipoise, and the TFP content is 12
．． It was 2%. Example 4 Example 3 except that 5 parts of the TFE/vinylidene fluoride HFP elastomer aqueous dispersion of Example 2 was used as the added elastomer.
Perform the same operation as above to obtain a specific melt viscosity of 8 x 1 poise,
14 $ parts of a blended polymer with a HFP content of 12.0% was obtained.

Comparative Example 1 The same operation as in Example 3 was performed except that no elastomer was added, and the specific melt viscosity was 8 × 1 pipoise, and the HFP content was 1.
A 2.3% portion of Polymer 14 was obtained.

Comparative example 2 No elastomer added, methyl alcohol 1
The operation was carried out in the same manner as in Example 3 except that the polymerization time was 3 feeding hours, and 165 parts of a polymer having a specific melt viscosity of 1.5 x 1 poise and an HFP content of 12.2% was obtained. .

Comparative Example 3 TFP of Example 2 as an added elastomer/
A blend polymer having a specific melt viscosity of 3.2×1 pipoise was obtained by carrying out the same operation as in Example 1, except that vinylidene fluoride/HFP elastomer aqueous dispersion 12 was used. Comparative Example 4 The same procedure as in Example 1 was carried out except that the elastomer aqueous dispersion added was changed to 0.3 parts, and the specific melt viscosity was set to 7.
A blended polymer of 8×1 pipoise and HFP content of 12.2% was obtained.

Test Examples The heat stress crack resistance values of the polymers of Examples and Comparative Examples were measured by the following method.

First, sample 24 was filled into a cylindrical mold with a diameter of 80 m, placed in an electric furnace, and maintained at a temperature of 330 m for two minutes.

Next, the mixture was held at the same temperature for 1 minute under a pressure of 60 k9/cm, and then cooled with water to obtain a sheet with a thickness of 2.3 to 2.4 ribs. After heating this sheet in an electric furnace at 240℃ for 2 hours,
Take a rectangular test piece with the length 39 side and the middle 13 side, and use a razor blade to make a cut with a length of 11 ribs and a depth of 0.5 ribs in the direction of the central long side. The test piece was then subjected to ASTM D1693-? Place the sample in a standard sample holder with the cut side facing out, and place it in an electric furnace with a viewing window at 180°C and 215°C. The time until cracks appear in half of the female measurement test pieces 2 is measured and used as the heat stress crack resistance value. Table 1 shows the measurement results. from this result,
Compared to Comparative Example 1, which does not contain a fluorine-containing elastomer, and Comparative Example 2, which has a high specific melt viscosity, cracks are less likely to occur in both Examples, and the heat stress crack resistance value is reduced by blending a small amount of fluorine-containing elastomer. I can understand the fact that it has been improved. Notes to Table 1: *) Measured according to the method described in ASTM D 638.

Claims (1)

[Claims] 1. A tetrafluoroethylene/hexafluoropropene copolymer characterized in that 99.95 to 90% by weight of a tetrafluoroethylene/hexafluoropropene copolymer is uniformly blended with 0.05 to 10% by weight of a fluorine-containing elastomer. -Fluorine-containing elastomer composition.