JPH08132521A - Production of fluoroplastic stretched article - Google Patents

Abstract

PURPOSE: To produce a fluoroplastic stretched article excellent in strength and the modulus of elasticity by extruding fluoroplastic in a solid phase within a temp. range not substantially melting fluoroplastic before stretching the same. CONSTITUTION: Fluoroplastic is extruded or rolled in a solid phase within temp. range not substantially melting fluoroplastic. That is, when fluoroplastic extruded or rolled in a solid phase (processed in a solid phase) is stretched, it is pref. to set the temp. of fluoroplastic lower than solid phase processing temp. As fluoroplastic, polytetrafluoroethylene capable of obtaining a degree of crystallization by stretching is pref. The number average mol.wt of raw material fluoroplastic is pref. 5.0×10<6> to 1.0×10<7> . The temp. range not substantially melting fluoroplastic may be set so that the difference between the max. endothermic temp. after processing and that before processing is within 2 deg.C.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a stretched fluororesin. More specifically, the present invention produces a stretched fluororesin having improved mechanical properties such as strength and elastic modulus by solid-phase extrusion or solid-phase rolling of a fluororesin under specific conditions and then tensile stretching. Regarding the method.

[0002]

2. Description of the Related Art Fluororesin is generally used as one of engineering plastics because it has a very high melting point, good chemical resistance, and a small coefficient of friction on the resin surface. However, since the chemical structure of fluororesin is very similar to that of polyolefin, its molecular chain is sufficiently stretched and uniaxially oriented and crystallized to form a film, tape or yarn of high strength and high elastic modulus. Attempts have also been made to obtain a stretched product. For example, JP-A-1-192812,
JP-A-2-307907, JP-A-5-78908 and the like teach methods for producing fluororesin fibers by applying the technique of stretching polyethylene or polypropylene. One of these conventional techniques requires a complicated process in which a fluororesin that does not dissolve in a general-purpose solvent is solubilized with a special solvent, spun and stretched, and then the solvent is extracted. . The other is to melt the fluororesin at a temperature higher than its melting point, and spin and stretch the resulting high-viscosity melt. However, it is technically extremely difficult to spin a highly viscous solution or melt homogeneously,
In particular, the latter method employs a very high temperature above the melting point, so there is concern about thermal decomposition of the fluororesin and generation of gas harmful to the human body. Therefore, in reality, the above-mentioned two conventional techniques cannot necessarily be prized. As a conventional technique other than the above, for example, J.Polym.Sci.Polym.Phys.E
d., 17 (1979) 73 or Polym.Eng.Sci., 26 (1986) 239
As can be seen from the above, there is a method of solid-phase extrusion of polytetrafluoroethylene, but this method cannot improve the strength of the drawn product to a satisfactory level. In general, when the raw material resin is stretched at the same ratio, by stretching the molecular weight of the raw material resin, and when the molecular weight of the raw material resin is the same, by stretching the stretching ratio, stretching of the stretched product The strength and elastic modulus in the direction can be improved. However, increasing the molecular weight of the fluororesin unnecessarily means that in the above-mentioned conventional technique, the solubility in a solvent is lowered, or the viscosity at the time of melting is increased, which causes troubles in spinning or drawing. In addition to inconveniences, when the stretching ratio is increased, stretching breakage may occur frequently, which is not preferable.

[0003]

Means for Solving the Problems The inventors of the present invention have made extensive studies as to a method for producing a stretched fluororesin without the problems pointed out in the prior art. After solid phase extrusion or solid phase rolling,
It has been found that a stretched fluororesin having excellent mechanical properties such as strength and elastic modulus can be produced by tensile stretching.
That is, the method for producing a stretched fluororesin according to the present invention is characterized in that the fluororesin is subjected to solid phase extrusion or solid phase rolling within a temperature range in which the fluororesin is not substantially melted, and then stretched and stretched. In the present invention, solid phase extrusion or solid phase rolling (hereinafter collectively referred to as solid phase processing)
When the stretched fluororesin is stretch-stretched, the temperature is preferably set to a temperature lower than the solid-phase processing temperature.

As the raw material resin of the present invention, any kind of fluororesin can be used, including a copolymer. Examples of the fluororesin usable in the present invention include polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-ethylene. Copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), chlorotrifluoroethylene-ethylene copolymer (ECTFE),
Tetrafluoroethylene-hexafluoropropylene-
Perfluoroalkyl vinyl ether copolymer (EP
E), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF) and the like. Among them, fluororesins that can obtain high crystallinity by stretching are preferable, and polytetrafluoroethylene is particularly preferable. When the raw material fluororesin is a copolymer, there is no particular limitation on the comonomer ratio of the copolymer, and the polymerization form may be alternating copolymerization, random copolymerization, block copolymerization or the like. . Further, the comonomers may be bonded in any of head-to-head bonding, head-to-tail bonding, or tail-to-tail bonding. The fluororesin exemplified as the raw material used in the present invention may be only one kind or a combination of two or more kinds (for example, a blend). In the case of a combination of two or more kinds, the use ratio (for example, blend ratio) of each resin is not particularly limited as long as the object of the present invention is achieved.

There is no particular limitation on the molecular weight of the raw material fluororesin, but if a material having a small molecular weight is used, it is difficult to obtain a stretched product having a high tensile strength because the stretch ratio at the time of tensile stretching cannot be increased. If a polymer having a large molecular weight is used, it is difficult to increase the deformation ratio during extrusion or rolling because the molecular chain becomes too long. Therefore, the raw material fluororesin used in the present invention has a number average molecular weight of preferably 5.0 × 10 ^{4 to} 5.0 × 10 ⁸ , more preferably 5.0 × 10 ^{5 to} 5.0 × 10 ⁷ , and further It is preferably in the range of 5.0 × 10 ^{6 to} 1.0 × 10 ⁷ . Various molecular weight measurements of fluororesins have been reported in various documents. For example, for PTFE, Pol
As described in ym.Eng.Sci., 28 , 538 (1988), a method for estimating the relaxation time of stress in the molten state, Macr.
As described in Omol., 22 , 831 (1989), it can be measured by a method estimated from the light scattering state of the solution.
Further, for the tetrafluoroethylene-hexafluoropropylene copolymer, as described in Macromol., 18 , 2023 (1985), a method of estimating from the relaxation time of stress in the molten state, tetrafluoroethylene-ethylene copolymer Can be measured by the method estimated from the light scattering state of the solution, as described in Macromol., 20 , 98 (1987). Other fluororesins can be measured by applying a method of estimating from the relaxation time of the response in the molten state, as described in Polym. Eng. Sci., 25 , 122 (1985). The molecular weight distribution of the fluororesin can be determined at the same time when the molecular weight is measured by the above-mentioned method, but the raw material fluororesin used in the present invention is used to obtain a stretched product having excellent mechanical properties. A narrow one is desirable.

The raw material fluororesin of the present invention may be manufactured by any method. Therefore, the raw material fluororesin used in the present invention may be produced by any of suspension polymerization method, emulsion polymerization method, bulk polymerization method, solution polymerization method, gas phase polymerization method, etc. There are no particular restrictions on the type of polymerization catalyst or co-catalyst employed in the polymerization method, and on the polymerization conditions such as temperature, pressure and time. In the polymerization method that requires a solvent, the solvent used is not particularly limited. In the present invention, the powdery or granular fluororesin obtained by removing the solvent after the polymerization can be directly used as the raw material resin, but prior to that, the powdery or granular fluororesin is melted and then cooled, or After dissolving in a suitable solvent, a preliminary treatment of removing the solvent can be performed.
However, it is desirable that the fluororesin after this preliminary treatment is a fluororesin that satisfies the following conditions. That is, about 1 mg each of powdery or granular fluororesin before and after pretreatment
Accurately weigh each, using a differential scanning calorimeter (DSC-220 manufactured by Seiko Denshi Kogyo Co., Ltd.), heating rate 10 ℃
A melting endothermic curve is drawn under the condition of / min, and the temperature at which the curve shows the largest endothermic peak is the peak temperature (so-called melting point). In this case, [peak temperature after pretreatment (° C)> peak temperature before pretreatment (° C) -4 ° C], preferably, [peak temperature after pretreatment (° C)> peak temperature before pretreatment (° C) ) −2 ° C.] The powdery or granular fluororesin is a fluororesin after pretreatment. The particle size of the raw material fluororesin of the present invention is
Usually, it is in the range of about 0.1 μm to 1000 μm, preferably in the range of about 1 μm to 500 μm. The raw material fluororesin of the present invention also contains a reinforcing agent such as milled carbon fiber for improving the physical properties thereof, an ultraviolet absorber, a weather resistance agent, a light resistance agent, an antioxidant, and further, any additive such as a pigment or a dye. The additives can be blended within a range that does not impair the effects of the present invention, but those additives that do not act as a lubricant or a solvent on the fluororesin are selected.

In the method of the present invention, basically, the raw material fluororesin is subjected to solid phase extrusion or solid phase rolling (collectively referred to as solid phase processing) at a temperature at which it does not substantially melt, and then stretched and stretched. Although it is composed of steps, the fluororesin can be pre-compression-molded prior to the above solid-phase processing. This optional pre-compression molding step is also carried out at a temperature at which the fluororesin does not substantially melt, but the upper limit of "the temperature at which the fluororesin does not substantially melt" in the present invention varies depending on the type and properties of the raw fluororesin. Also, it differs depending on the content of the processing applied to the raw material fluororesin, that is, whether the processing is compression molding, solid phase extrusion, solid phase rolling, or tensile drawing. Therefore, first, the “temperature at which the fluororesin does not substantially melt” in the present invention will be described. If you draw a melting endothermic curve of a certain fluororesin using a differential scanning calorimeter, you can determine the maximum endothermic peak temperature (so-called melting point) from that curve, but even for the same type of fluororesin, the maximum The endothermic peak temperature is different between the fluororesin that has been processed and the fluororesin that has not been processed.
If the content of processing is different, the maximum peak temperature before processing and that after processing also differ accordingly. Regarding the difference in the maximum endothermic peak temperature of the fluororesin before and after processing, the present inventor has obtained the following new findings. That is, when the fluororesin is subjected to compression molding, solid-phase extrusion, solid-phase rolling, or tensile stretching, the maximum endothermic peak temperature of the fluororesin after processing, depending on the temperature adopted in the processing,
The maximum endothermic peak temperature before processing may be higher or lower than that, but whether the processing is compression molding, solid phase extrusion, solid phase rolling or tensile stretching, the fluororesin is at any temperature (t ° C). When the maximum endothermic peak temperature of the fluororesin after the processing is higher than the maximum endothermic peak temperature before the processing, the intended stretched product can always be obtained by the method of the present invention. Further, even when the maximum endothermic peak temperature of the fluororesin after processing is lower than the maximum endothermic peak temperature before processing, the present inventor is the same as long as the difference is 4 ° C, preferably 2 ° C or less. The desired stretched product can be obtained. Therefore, in the present invention, the maximum endotherm of each of the samples obtained by processing the raw material fluororesin or the fluororesin processed in the previous step at an arbitrary temperature (t ° C.) and the sample before the processing in the processing step from the melting endothermic curves The peak temperature is determined, and if the difference between the two satisfies the following equation, the processing is defined as "the temperature at which the fluororesin does not substantially melt". P (t)> P0 -4 ° C, preferably P (t)> P
0 −2 ° C. Here, P (t) is the maximum endothermic peak temperature (° C.) of the processed sample that was processed at a temperature of t ° C., that is, compression molded, solid phase extruded, solid phase rolled or stretched. P0 indicates the maximum endothermic peak temperature (° C.) of the sample before the processing in the processing step. In drawing the melting endothermic curve of the fluororesin, a measurement sample was accurately weighed by about 1 mg, and a differential scanning calorimeter (DSC-220 manufactured by Seiko Denshi Kogyo Co., Ltd.) was used to raise the temperature at 10 ° C / Used under the condition of minutes.

Further, using any one of the fluororesin as a raw material in the present invention, the processing temperature (t ° C.) was changed, and the above experiments were conducted for compression molding, solid phase extrusion and solid phase rolling. By repeating it, the upper limit of each processing temperature that satisfies the above expression 1 can be obtained. Then, with respect to the other raw material fluororesins, the upper limit of each processing temperature satisfying the above formula 1 can be obtained by the same procedure as above. In the present invention, for each raw material fluororesin, the upper limit of the processing temperature required for each step is the upper limit of "the temperature at which the fluororesin does not substantially melt", which is hereinafter referred to as the upper processing temperature. In the practice of the present invention, each processing of compression molding, solid phase extrusion and solid phase rolling performed on the fluororesin is required only to be carried out at the processing upper limit temperature or less defined as above for each processing. As long as this requirement is satisfied, compression molding, solid phase extrusion, solid phase rolling and tensile stretching can be performed at any temperature. By the way, the processing lower limit temperature in each processing step of compression molding, solid phase extrusion and solid phase rolling is 150 ° C from the above processing upper limit temperature.
Low temperature, preferably 100 ° C.

Next, the respective steps of compression molding, solid phase extrusion, solid phase rolling and tensile stretching adopted in the present invention will be described. The raw material fluororesin can be directly subjected to the solid phase extrusion step or the solid phase rolling step,
Prior to that, it is preferable that the raw material resin is previously compression-molded. Any compression molding machine can be used for this preliminary compression molding, and the shape of the fluororesin after compression molding may be rod-shaped or sheet (film) -shaped. When a sheet (film) shaped article is obtained by preliminary compression molding, the thickness thereof is usually 0.1 mm to 5 mm.
It is in the range of about mm. This optional pre-compression molding is carried out at the above-mentioned "temperature at which the fluororesin does not substantially melt", and in general, a temperature not higher than the processing upper limit temperature but not lower than room temperature is selected. By the way, in the case of PTFE, it is usually room temperature to 335 ° C., preferably 2
The pre-compression molding temperature is selected from the range of 00 to 330 ° C. Further, there is no particular limitation on the pressure adopted in the pre-compression molding, but it is usually possible to set it in the range of 10 MPa to 2 GPa, preferably 20 MPa to 500 MPa.

According to the present invention, the raw material fluororesin is subjected to the solid phase extrusion step or the solid phase rolling step directly or through the above-mentioned preliminary compression molding step. The solid phase extrusion process of the present invention includes so-called co-extrusion in which other resins are co-extruded in addition to ordinary extrusion in which only a fluororesin is extruded. In any case, there is no special limitation on the extrusion method. For example, the raw material fluororesin or its compression molded product can be supplied to a cylinder of a solid-phase extrusion apparatus having a die attached to its end, and this can be extruded in a usual manner. When the solid-phase coextrusion method is adopted, typically, a method of extruding a fluororesin that has been compression-molded into a sheet shape in advance by sandwiching it between a sheet or billet manufactured from another resin is used. Adopted. In this case, as the sheet or billet manufactured from another resin, a polyolefin such as polyethylene, polypropylene, and poly (methyl 4-pentene), or a fluororesin prepared separately can be used. The shape of the die used for solid phase extrusion can be arbitrarily selected, such as circular, elliptical, rectangular, etc. Normally, a die with a smaller cross-sectional area on the outlet side than the cross-sectional area on the inlet side is used. It
The size of the die is not particularly limited, but the diameter (diagonal line) on the die inlet side is usually selected in the range of 5 to 100 mm, preferably 5 to 50 mm. The extrusion pressure varies depending on the size of the deformation ratio of extrusion, but when the range of the extrusion ratio of the present invention is assumed, it is usually 0.1 MPa.
˜300 MPa, preferably 1 MPa to 100 MPa. The extrusion ratio (drawing ratio) is selected according to the production method, particle size, particle size distribution, molecular weight, molecular weight distribution, etc. of the raw material fluororesin, and according to the shape or size of the die used. Generally, the lower limit of extrusion ratio is 2 times, preferably 5 times. The upper limit is not particularly limited, but if the extrusion ratio is increased, a large extrusion pressure is required. Therefore, solid phase extrusion is usually performed at an extrusion ratio of 100 times, preferably 60 times. The solid phase extrusion temperature is the “temperature at which the fluororesin does not substantially melt” as described above, and specifically, is equal to or lower than the processing upper limit temperature for solid phase extrusion defined according to the description above. Then, solid phase extrusion is performed in a temperature range above the lower processing temperature limit. By the way, PTF
When E is targeted, solid phase extrusion is performed at room temperature to 335
C., preferably in the range of 200 to 330.degree. C. If the solid phase extrusion is carried out at a temperature above the processing upper limit temperature, problems will occur in the extrudability of the fluororesin and the maximum ultimate stretching ratio in the subsequent tensile stretching step, and the object of the present invention cannot be achieved. Further, if solid phase extrusion is performed at a temperature equal to or lower than the processing lower limit temperature, problems will occur in the maximum ultimate stretch ratio and the physical properties of the stretched product in the subsequent tensile stretching step, and the object of the present invention cannot be achieved. In the solid phase extrusion of the present invention, a method of prepressurizing an object to be extruded and then solid phase extrusion is also preferably used. Pre-pressurization pressure in this case is 10 MPa to 1
About 00 MPa is desirable. The extrusion speed can be appropriately selected, but is usually selected in the range of 1 mm / min to 1 m / min, preferably 10 mm / min to 500 mm / min. The shape of the solid-phase extruded resin is determined by the die shape and the coextrusion method,
Usually, its cross-sectional shape is any one of a circle, an ellipse, and a rectangle.

In the solid phase rolling step in the present invention, a fluororesin which has been compression-molded into a rod or sheet shape in advance is usually supplied. For solid-phase rolling, a method in which a fluororesin that is compression-molded into a rod shape or a sheet shape is sandwiched between at least two rolling rolls having different constant speeds or peripheral speeds and rolled is generally adopted. The deformation ratio of the fluororesin due to the rolling operation can be widely selected, and if it is expressed by rolling efficiency (length after rolling / length before rolling), the lower limit is usually 1.2 times,
It is preferably 1.5 times, but it is usually possible to carry out solid phase rolling 30 times, preferably 20 times. The solid phase rolling temperature is the “temperature at which the fluororesin does not substantially melt” as described above, and specifically, is equal to or lower than the processing upper limit temperature for solid phase rolling defined according to the description above. Then, solid phase rolling is performed in a temperature range equal to or higher than the lower working temperature limit. By the way, in the case of performing solid phase rolling of PTFE, it is desirable to set the rolling temperature in the range of room temperature to 335 ° C, preferably 200 to 330 ° C. If the solid phase rolling is performed at a temperature equal to or higher than the processing upper limit temperature, problems occur in the rollability of the fluororesin and the maximum ultimate stretching ratio in the subsequent tensile stretching step, and the object of the present invention cannot be achieved. Further, if solid-phase rolling is performed at a temperature equal to or lower than the processing lower limit temperature, problems will occur in the maximum ultimate stretch ratio and the physical properties of the stretched product in the subsequent tensile stretching process, and the object of the present invention cannot be achieved. The rolling speed can be selected as appropriate,
Usually 0.5 m / min to 100 m / min, preferably 1 m / min
It is selected in the range of minutes to 50 m / min. The shape of the solid-phase rolled resin is generally a tape shape, a film shape or a sheet shape, and its cross section can be any shape such as an elliptical shape or a rectangular shape. Of course, the solid phase rolling operation may be carried out multiple times in multiple stages.

In the tensile drawing step in the present invention, a solid phase extruded fluororesin or a solid phase rolled fluororesin is supplied. In the tensile stretching of the present invention, for example, a batch method in which a solid-phase extrudate or a rolled product is stretch-stretched by a tensile tester in a constant temperature bath can be used, nip stretching,
A continuous method such as hot plate stretching, zone stretching or hot air stretching can also be used. When using the continuous tensile stretching, as heating means, heating roll, hot plate, high frequency heating, microwave heating, infrared or far infrared heating, hot air heating, etc. Can be used. The deformation ratio of the sample due to the tensile stretching can be widely selected, and the lower limit is usually 1.5 times, preferably 5 times as shown by the tensile stretching ratio (length after tensile stretching / length before tensile stretching). Can be selected arbitrarily. However, it is usually possible to carry out the tensile stretching of the present invention at a draw ratio of 20 times, preferably 10 times. The tensile stretching temperature is the "temperature at which the fluororesin does not substantially melt" as described above.
That is, specifically, at or below the processing upper limit temperature for tensile stretching defined according to the description above, preferably the temperature at which the fluororesin was solid-phase extruded or solid-phase rolled before the tensile stretching step. At lower temperatures, the tensile stretching of the present invention is carried out. By the way, when PTFE is stretched and stretched, the upper limit of the tensile stretching temperature is preferably 170 ° C. or lower, more preferably 120 ° C. or lower, and more preferably 1 ° C. or lower.
It is less than 00 ° C, and the lower limit is usually room temperature or higher, preferably 4
0 ° C. or higher. The tensile stretching speed can be appropriately selected depending on the molecular weight of the fluororesin, the molecular weight distribution, the stretching ratio, and the shape of the resin before stretching, but the lower limit of the tensile stretching speed in the case of batchwise stretching is usually 1 mm / min, preferably 5 mm / min. The upper limit is usually 500 mm / min, preferably 100 mm / min, more preferably 50 mm / min. In the case of continuous stretching, the lower limit of the tensile stretching speed is usually 10 mm / min, preferably 50 mm / min, and the upper limit is usually 500 m / min, preferably 300 m / min, more preferably 100 m / min. When performing the tensile stretching of the present invention, it is possible to stretch the extruded product or rolled product in the width as it is,
Prior to stretching, the extrudate or rolled product should be 0.5 to 15
0 mm, preferably 1 to 100 mm, more preferably 1 to 5
You may slit it to a fixed width of 0 mm, and then perform drawing. The operation of the tensile stretching of the present invention may be carried out multiple times in multiple stages. The resin after the tensile stretching can take any shape such as a fibrous shape, a tape shape, a film shape, etc., but its cross-sectional shape is usually an ellipse or a rectangle.
For the resin having a tape shape or a film shape after the tensile stretching, a split treatment may be performed in which mechanical cracks are formed in the stretching direction so that the resin has a net-like shape when laterally spread. . Also, as a post-process of tensile stretching,
The stretched product under tension or in a relaxed state within a temperature range in which the stretched product does not substantially melt may be subjected to heat treatment. In the method of the present invention, the higher the total draw ratio (the product of the deformation ratios of the respective processing steps, specifically the extrusion ratio × the tensile draw ratio or the rolling efficiency × the tensile draw ratio), the higher the strength and the high elastic modulus achieved. Therefore, it is desirable to increase the draw ratio as much as possible. Specifically, 30 to 150 times,
A draw ratio of about 30 to 100 times is preferably selected.
According to the method of the present invention, a stretched product having unprecedented high tensile strength and elastic modulus can be obtained by stretching the molecular chain of the fluororesin to the maximum extent and orienting the molecules in the stretching direction. For example, in the case of PTFE, the tensile strength at room temperature is 300 MPa or more, preferably 350
MPa, tensile modulus 40 GPa, preferably 50 G
A fluororesin stretched product having a high strength of Pa or higher and a high elastic modulus can be obtained.

[0013]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. Melting point measuring method Approximately 1 mg of fluororesin (raw material resin, resin before or after each processing step) is accurately weighed, and a differential scanning calorimeter (DSC-220 manufactured by Seiko Denshi Kogyo Co., Ltd.) [hereinafter,
[Abbreviated as DSC]], a melting endothermic curve was drawn under the condition of a heating rate of 10 ° C./min, and the temperature at which the curve showed the largest endothermic peak (peak temperature) was taken as the melting point. Example 1 Polytetrafluoroethylene powder (PTFE, 6-J manufactured by DuPont Mitsui Fluorochemical Co., Ltd., molecular weight 5.0)
X10 ⁶ , melting point 334 ° C.), weigh about 6 g, diameter 10
It is sandwiched between 0mm disk-shaped iron plates, preheated at a temperature of 320 ° C below the melting point for 10 minutes, and then 100MP at the same temperature.
The pressure of a was applied and compression molding was performed. It was cooled to room temperature while applying pressure to obtain a film having a thickness of 0.5 mm and a diameter of 90 mm. The melting point of this film was 335 ° C. as measured by DSC. This film was cut into strips, sandwiched between separately prepared PTFE billets, and solid phase coextrusion was performed at 330 ° C. At this time, 20 times extrusion was carried out in the length direction, extrusion with a clean appearance was carried out, and when the sample sandwiched between billets was taken out, a tape-shaped extrudate was obtained. The melting point of this extrudate was 336 ° C. as measured by DSC. This extruded product was cut out to a length of about 5 cm and stretched using a tensile tester equipped with a constant temperature layer. At this time, the temperature was 330 ° C., the distance between grips before stretching was 25 mm, and the pulling speed was 25 mm / min. Tensile stretching is up to 1.9
It was achieved up to double, and a stretched product of 38 times in total was obtained. The melting point of this stretched product is 337 ° C., and the tensile strength and tensile modulus at 24 ° C. are 300 MPa and 40 G, respectively.
It was Pa. Example 2 A compression molded film produced in the same manner as in Example 1 was cut into strips, sandwiched between separately prepared PTFE billets, and solid phase coextrusion was performed at 330 ° C. At this time, 20 times extrusion was carried out in the length direction, extrusion with a clean appearance was carried out, and when the sample sandwiched between billets was taken out, a tape-shaped extrudate was obtained. The melting point of this extrudate was 336 as measured by DSC.
° C. This extruded product was cut out to a length of about 5 cm and stretched using a tensile tester equipped with a constant temperature layer. At this time, the temperature is 120 ° C, the distance between the grips before stretching is 25 mm,
The pulling speed was 25 mm / min. Tensile stretching was achieved up to 3.5 times, and a total 70 times stretched product was obtained. The melting point of this stretched product is 341 ° C., and the tensile strength and tensile elastic modulus at 24 ° C. are 450 MPa and 7 respectively.
It was 8 GPa. Example 3 Compression molding was carried out in the same manner as in Example 1, and the vertical and horizontal thickness was 15 cm ×
A 5 cm × 0.1 cm sheet was obtained. The melting point of this sheet is D
It was 334 ° C. when measured using SC. This sheet was sandwiched between rolling rolls having a diameter of 15 cm and a face length of 30 cm and heated to 200 ° C., and rolled 8 times in the length direction. The rolling speed was 0.6 m / min. The melting point of the rolled product was 335 ° C. This rolled product was cut into a piece having a width of 1 cm and a length of about 5 cm and stretched using a tensile tester equipped with a thermostatic layer. At this time, the temperature was 60 ° C., the distance between the grips before stretching was 25 mm, and the pulling speed was 25 mm / min. Tensile stretching was achieved up to 8.2 times, and a total of 65.6 times stretched material was obtained. The melting point of this stretched product is 340 ° C., 2
The tensile strength and tensile elastic modulus at 4 ° C are 42 respectively.
It was 5 MPa and 70 GPa. Comparative Example 1 Polytetrafluoroethylene powder (PTFE, 6-J, manufactured by Mitsui DuPont Fluorochemical Co., Ltd., molecular weight 5.0)
X10 ⁶ , melting point 334 ° C), weigh about 6 g, diameter 100
It was sandwiched by a disc-shaped iron plate of mm, preheated at a temperature of 360 ° C. or higher than the melting point for 10 minutes, and then a pressure of 100 MPa was applied to perform compression molding. It was cooled to room temperature while applying pressure to obtain a film having a thickness of 0.5 mm and a diameter of 90 mm. The melting point of this film was measured by DSC and found to be 326.
° C. After cutting this film into strips, insert it into a separately prepared PTFE billet and heat it at 330 ° C.
Solid phase coextrusion was carried out. At this time, 20 times extrusion was performed in the length direction, and extrusion with a clean appearance was performed, but when the sample sandwiched between the billets was taken out, it was found to be finely torn into small pieces, and it was effective. It was found that there was no extrusion. Comparative Example 2 About 5 g of the polytetrafluoroethylene powder used in Comparative Example 1 was weighed, placed in a cylinder having a diameter of 10 mm, heated to 320 ° C., and a pressure of 100 MPa was applied.
It was compression molded for 30 minutes and cooled to room temperature while applying pressure. The obtained cylindrical sample having a diameter of 10 mm and a length of about 3 cm (melting point was 334 ° C.) was again inserted into the cylinder, and a die having a circular cross section with an extrusion ratio of 60 times was attached to the cylinder outlet. Solid phase extrusion was performed at a temperature of 330 ° C. A linear extrudate having a diameter of about 0.65 mm was obtained. The flexural modulus at 24 ° C. of the obtained extrudate was measured and found to be about 12 GPa. The extrudate had a melting point of 338 ° C.

[0014]

EFFECTS OF THE INVENTION The stretched fluororesin produced by the present invention is a new fluororesin having the unprecedented high strength and high elastic modulus while maintaining the same heat resistance and chemical resistance as conventional fluororesins. It is a resin material. Further, since the production method of the present invention is an economical process as compared with the prior art, it becomes possible to provide a fluororesin stretched product at a price that meets the market needs, and other applications where the fluororesin has been used conventionally In addition, completely new applications can be expected in the field of resin materials that require high strength and high elastic modulus. Specifically, the stretched product of the present invention is used for ropes, fishing nets, seaweed nets, land nets, ball nets, medical sutures, fishing lines, kite yarns, cement reinforcing agents, woven fabrics, non-woven fabrics, softeners, various filters, etc. Not only can it be used, but it can also be used for applications such as reinforcing agents for composite materials, and it can be used not only in industries such as automobiles, electricity, petroleum, chemicals, fisheries, civil engineering, construction, and medical care, but also in everyday clothes, sundries, etc. It is worth using.

Claims (3)

[Claims] 1. A method for producing a stretched fluororesin, which comprises subjecting the fluororesin to solid phase extrusion or solid phase rolling within a temperature range in which the fluororesin does not substantially melt, and then stretching the stretched fluororesin. 2. The temperature at which the fluororesin is stretched and stretched is
The method according to claim 1, wherein the temperature is lower than the temperature during solid phase extrusion or solid phase rolling. 3. The method according to claim 1, wherein the fluororesin is polytetrafluoroethylene.