JPS6023702B2 - Fluororesin composition with improved moldability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fluororesin composition with improved moldability, and more particularly to a tetrafluoroethylene/hexafluoroprobene copolymer-polytetrafluoroethylene composition.

Tetrafluoroethylene (hereinafter referred to as "TFEJ").

) and hexafluoroprobeso (hereinafter referred to as "HFP").
) is a copolymer of polytetrafluoroethylene (hereinafter referred to as "P").
It's called "TFE". ) has heat resistance, chemical resistance, and electrical properties comparable to those of PTFE, as well as melt flowability not found in PTFE, making it suitable for compression molding, extrusion molding, injection molding,
It can be subjected to all types of melt processing, including fluidized immersion painting, and is used in a wide range of applications. However, compared to general thermoplastic resins, the melt flow temperature is significantly higher and the melt viscosity is also higher, so the molding temperature is 330 to 420°C, and in some cases as high as 440 qo is required, and sufficient moldability is required. It cannot be said that it has. Generally, to increase the molding speed, it is sufficient to increase the molding temperature and extrusion pressure, but molding at high temperatures (over 400q0) causes thermal decomposition of the polymer, and increasing the extrusion pressure may cause roughness on the surface of the extrudate or abnormal flow. (melt fracture).

Further, if the molecular weight of the polymer is lowered, the viscosity at the time of melting will be lowered, and the molding speed can be improved, but this is not preferable because lowering the molecular weight is accompanied by deterioration of physical properties such as stress crack resistance. The present invention solves the above-mentioned problems,
TFE with improved formability without deterioration of physical properties/
This was done for the purpose of providing an HFP copolymer composition, and this purpose is achieved by uniformly blending a small amount of PTFE into a TFE/HFP copolymer.

The fluororesin composition according to the present invention contains TFE/HFP copolymer and PTFE in a weight ratio of 99.99:0.0.
1-95:5, preferably 99.9:0.1-95:5
It is a homogeneous composition containing the following:

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, with small amounts of third components, modifiers,
There is no problem even if it contains a filler or the like.

In addition, PTFE is not only a homopolymer of TFE, but also a TFE homopolymer.
It may also be a copolymer of FE and a small amount of hexafluoroprobene, trifluoroethylene, trifluorochloroethylene, or the like.
Low molecular weight materials such as wax-like PTFE have little effect on improving molding speed and tend to cause cracks in molded products.
Generally, those having a molecular weight of 1 million or more are preferred. In addition, T
The use of FE/fluorovinyl ether copolymer, polyvinylidene fluoride, fluorine-containing elastomer, and the like was also investigated, but none of them were found to have an effect on improving the molding speed.
In order to achieve uniform blending, PTFE preferably has a small particle size, usually 100 or less, preferably 10 or less.

If PTFE particles of 100 French or less are blended, white spots will be observed in the extrudate, which is not preferable.

Further, when compounding, PTFE can take any form such as powder, dispersion, suspension, etc. In order to blend PTFE into the TFE/HFP copolymer, any wet or dry mixing method using a mixer, mixing roll, kneader, ball mill, Banbury mixer, blender, etc. can be employed.

In addition, when producing TFE/HFP copolymer, PTFE
may be added before and/or during the polymerization reaction. The TFE/HFP copolymer composition according to the present invention comprises TF
The surface of the molded product is rougher than that of the E/HFP copolymer alone.
In order to minimize phenomena such as abnormal flow, the extrusion speed at which such phenomena begin to occur, that is, the critical extrusion speed, has been greatly improved. If the amount of PTFE blended is too small, there is no effect, and if it is too large, the melt viscosity increases significantly, transparency is lost, the product becomes milky white, and the molded product becomes brittle. Generally, when the PTFE content exceeds 0.1% by weight, abnormal expansion of the extrudate immediately after exiting the die, so-called die swell, increases, and heat shrinkage occurs when the extrudate is reheated. has been recognized, making it useful for new applications such as thermal expansion tubes. Example below
The present invention will be explained in more detail with reference to comparative examples and test examples.

Note that "parts" and "%" mean "parts by weight" and "% by weight" unless otherwise specified. In addition, the HFP content (wt%) of the polymer was measured by infrared absorption spectrum of a film with a thickness of about 40 mm.
It is expressed as a value obtained by dividing the absorbance at a wave number of 2350 arc-1 by the absorbance at a wave number of 2350 arc-1 times 3.2. Furthermore, the specific melt viscosity is based on the Koka formula. - A tester was developed in which the polymer was loaded into a willow cylinder with an inner diameter of 9.5 mm, held at a temperature of 38,000 for 5 minutes, and then passed through an orifice with an inner diameter of 2.1 mm and a length of 8 sails under a piston load of 5 k9 at the same temperature. Extrusion, extrusion speed (t/min) at this time is 531
It is obtained by dividing 50. Example 1 Relative melt viscosity 7
．． Powdered T with 8×1 piboids and HFP content of 12.2%
A mixture of 300 parts of FE/HFP copolymer and 100 parts of water-acetone (weight ratio 1:1) was placed in a ball mill, and the mixture had a melting point of 3370 (measured with a differential calorimeter) and an average particle size of 0.2.
Two parts of an aqueous dispersion containing 2% by weight of 5% PTFE are added and then mixed for 2 hours.

Next, 1 part of 20% nitric acid was added, thoroughly washed with water, and the temperature was increased to 1.
Dry at 40°C for 2 hours. The powdered polymer premixed in this way was extruded at a temperature of 360q0 using a screw extruder with a cylinder diameter of 15 cm, D/L = 20, discharge hole diameter of 2 rows, and discharge hole length of 10, and this extruded product was extruded again in the same manner. It is pelletized to obtain a blended polymer. The specific melt viscosity of this polymer is 8×1 poise, HF
The P content was 12.2%. Example 2 The same procedure as in Example 1 was carried out except that 15 parts of the PTFE aqueous dispersion was used to obtain a blend polymer having a specific melt viscosity of 9×1 piboise and an HFP content of 12.2%.

Example 3 SUS-32 with jacket that can accommodate 300 parts of water
After putting 100 tons of demineralized water into a Nawa Azusa type autoclave, and adding 1 part of the PTFE aqueous dispersion of Example 1, the internal space was sufficiently replaced with pure nitrogen gas.
Press-fit the HFP60 anchor part and TFEIIO part.

The temperature inside the pot was maintained at 20:00, and 2 parts of di(hydrodecafluoroheptanoyl) peroxide as a polymerization initiator and 15 parts of methyl alcohol as a molecular weight regulator were introduced under pressure. The reaction was started immediately, and TFE was added successively as the reaction progressed. After reacting for 3 calm hours, the monomer of the reaction was released, and after adding 3 parts of 20% nitric acid, the polymer was recovered. After thoroughly washing the polymer with water, it was dried at a temperature of 14,000 for 2 hours.
A white powdery blended polymer was obtained. The specific melt viscosity of this polymer is 7.4×1 pipoise, and the HFP content is 1
It was 2.2%. This was melt-extruded under the same conditions as in Example 1 to obtain a pellet-shaped polymer. Example 4 The operation was carried out in the same manner as in Example 1 except that 35 parts of PTFE aqueous dispersion was used, and the specific melt viscosity was 9.6×
A pellet-like polymer having a HFP content of 12.1% was obtained.

Comparative Example 1 The operation was carried out in the same manner as in Example 3 except that PTFE was not added, and the specific melt viscosity was 8.0 × 1 pipoise, and the HFP content was 1.
218 parts of a 2.2% polymer pellet were obtained.

Comparative Example 2 The procedure was carried out in the same manner as in Example 1 except that 10 parts of the PTFE aqueous dispersion was used to obtain a blended polymer having a specific melt viscosity of 1.8×1 pipoise and an HFP content of 12.0%. .

Comparative Example 3 The same procedure as in Example 3 was carried out except that 0.01 part of PTFE aqueous dispersion was used, and the specific melt viscosity was 7.5×
A pellet-shaped polymer with a HFP content of 12.2% was obtained.

Comparative Example 4 Powdered PT with average particle size of 0.5 willow and polymer melting point of 3370
The same operation as in Example 1 was carried out except that 5 parts of FE was used, and the specific melt viscosity was 9.8×1 pipoise and the HFP content was 12.
A 1% blend polymer was obtained.

Comparative Example 5 Wax-like P with average particle size of 30 French and polymer melting point of 320°C
The operation was carried out in the same manner as in Example 1 except that 3 parts of TFE was used, and the specific melt viscosity was 7.0×1 pipoise and the HFP content was 12
．． A 1% blend polymer was obtained.

Test Examples The extrusion speeds of the polymers obtained in Examples and Comparative Examples were measured.

The measurement method is as follows. Cylinder diameter 15 skin, L
/D = 2u Using a screw extruder with an extrusion nozzle diameter of 2 ribs and a length of 1 rib, the temperature of the cylinder part was 360 qo, extrusion /
The pellet-shaped polymers of Examples and Comparative Examples were melt-extruded under conditions of a total temperature of 0°C near the nozzle and a screw rotation speed of 10 to 10 pm. ) was measured.

The results are shown in the table, and the critical extrusion speed of the polymer of the example is clearly higher than that of Comparative Example 1 in which PTFE is not blended, and the effect of the present invention can be understood.

In Comparative Example 2, in which a large amount of PTFE was added, the critical extrusion speed decreased, while in Comparative Example 3, in which the amount was too small, Comparative Example 4, in which PTFE with a large particle size (0.5 feet) was blended, and in waxy PTFE. In Comparative Example 5, no effect was observed in any case. In addition, a significant decrease in tensile strength was observed in Comparative Examples 4 and 5, but almost no change was observed in the polymer of Example compared to Comparative Example 1, and TFE/HFP
The effect of the present invention, which improves moldability without deteriorating the physical properties of the copolymer, can be understood. Table note: *) Measured according to the method described in ASTM, D638.

Claims (1)

[Scope of Claims] 1. A fluororesin composition for extrusion molding comprising a tetrafluoroethylene/hexafluoropropene copolymer blended with polytetrafluoroethylene in a content of 0.01 to 5% by weight. . 2. The fluororesin composition as described in 1 above, wherein the polytetrafluoroethylene has a molecular weight of 1 million or more. 3 The average particle size of polytetrafluoroethylene is 100μ
The fluororesin composition according to 1 or 2 above, which is as follows. 4. The fluororesin composition according to any one of 1 to 3 above, wherein the content of polytetrafluoroethylene is 2 to 5% by weight.