JP2013237730A - Method for producing fluororesin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a fluororesin film, which can produce a fluororesin film having high optical transparency by a simple method.SOLUTION: A method for producing a fluororesin film can produce a film that has characteristics such as weather resistance, etc., originated from a fluororesin and high optical transparency in a wide wavelength range at a low cost by a simple operation in which a fluororesin in a molten state is quenched at a cooling rate of 50-1,000°C/s and then stretched into a film. The obtained film has a scattering peak originated from a β phase and the fluororesin film is provided with ferroelectricity such as piezoelectricity, etc., by a polling treatment.

Description

  The present invention relates to a method for producing a fluororesin film. More specifically, the present invention relates to a method for producing a fluororesin film capable of obtaining a highly light-transmitting film.

  In recent years, the production of a fluororesin film exhibiting high transparency or high light transmittance has been studied. For example, by modifying a bulky substituent at a site of the fluororesin, so as not to cause crystallization. A method for synthesizing a transparent amorphous fluororesin has been provided (see, for example, Patent Document 1). However, the fluorine-based resin is expensive, and the complicated method for synthesizing the amorphous fluorine-based resin has caused a further increase in price, which has prevented the spread of the fluorine-based resin.

  In addition, by stretching uniaxially stretching ethyl trifluoroacetate (EFA), which is known as a fluorine-based copolymer resin, at high temperatures, the lamellar crystal structure changes, reducing the difference in electron density between crystals and amorphous materials, and a transparent stretched sample. Is provided (see, for example, Patent Document 2 and Non-Patent Document 1). However, due to heat stretching at a high temperature, there is a problem that the energy consumption necessary for processing is large and the load on the environment is large.

  Fluorine resin by blending crystalline fluoropolymer with acrylic resin, etc., and rapidly cooling to near 0 ° C after melting, inhibiting crystallization by acrylic resin, and suppressing crystal growth by rapid cooling to near 0 ° C A method for obtaining a transparent fluoropolymer solid in which crystallization of the polymer is suppressed has been studied (see, for example, Patent Document 3 and Patent Document 4). However, since materials other than fluororesins such as acrylic resins are used as blending materials, the material cost is increased, and the extra steps and costs such as melt kneading have increased. In addition, since the acrylic resin is weaker in environmental resistance and corrosion resistance than the fluorine resin, there is a problem that the environmental resistance is lowered when blended and used.

  Furthermore, a method of obtaining a thin fluorine-based polymer thin film by a solvent casting method, a vapor deposition method, a plasma method, or the like has been studied (see, for example, Patent Document 5). However, the fluororesin film obtained by these methods has a problem that it is difficult to use as an exterior film or the like because it does not have a sufficient thickness, and that processing and molding are complicated and difficult.

JP 2001-264857 A JP 2002-240144 A JP 2009-13418 A JP 2010-265396 A JP 2010-205485 A

Macromolecules, 41 (20): p. 7606-7615 (2008)

  As described above, various means have been studied as means for producing a fluororesin film having high transparency or high light transmittance. However, operations for production are complicated and costly. In addition, there is a problem that a highly permeable fluorine-based resin film cannot be obtained, and improvement has been demanded.

  The object of the present invention has been made in view of the above problems, and is to provide a method for producing a fluororesin film capable of producing a highly transparent fluororesin film by a simple method. is there.

  In order to solve the above-described problems, the method for producing a fluororesin film according to the present invention is a method of rapidly cooling a crystalline fluororesin in a molten state at a cooling rate of 50 to 1000 ° C./sec. It is made into a film.

  The method for producing a fluororesin film according to the present invention is characterized in that, in the configuration of the present invention described above, a draw ratio in the drawing is 50 to 500%.

  The method for producing a fluororesin film according to the present invention is characterized in that, in the configuration of the present invention described above, a poling treatment is further performed after stretching.

  The method for producing a fluororesin film according to the present invention is characterized in that, in the configuration of the present invention described above, the cooling rate is 100 to 600 ° C./second.

  In the method for producing a fluororesin film according to the present invention, in the configuration of the present invention described above, the fluororesin is composed of polyvinylidene fluoride (polyvinylidene fluoride) (PVDF), polytetrafluoroethylene (PTFE), polyvinyl fluoride. Ride (PVF), polychlorotrifluoroethylene (PCTFE), ethyl trifluoroacetate (EFA), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP) , Chlorotrifluoroethylene / ethylene copolymer (ETFE), chlorotrifluoroethylene / ethylene copolymer (ECTFE), poly (vinylidene fluoride / hexafluoropropylene) copolymer (PVDF-HFP), poly (fluoride) Characterized in that at least one selected from vinylidene / trifluoroethylene) the group consisting of.

  The method for producing a fluororesin film according to the present invention is a simple operation in which a melted fluororesin is rapidly cooled and then stretched to form a film. A film showing high light transmittance in the wavelength range can be manufactured at low cost. Moreover, the obtained film has a scattering peak derived from a β phase, and can impart ferroelectricity such as piezoelectricity to the fluororesin film by performing a poling treatment.

It is the figure which showed the one-dimensional data obtained from the SAXS (small angle X-ray scattering) pattern of a fluorine resin film. It is the figure which showed the one-dimensional data obtained from the SAXS (small angle X-ray scattering) pattern of a fluorine resin film. It is the figure which showed the result of having confirmed the molecular mobility of the polymer chain in a lamellar crystal by a dielectric relaxation measurement about a fluororesin type film. It is the figure which showed the cooling time-temperature curve in operation of Example 1 (2). It is the figure which showed the Hv light scattering result of the film sample. It is the figure which showed the observation result (SEM image) by SEM (scanning electron microscope). It is the figure which showed the external appearance photograph of the fluorine resin film obtained by extending | stretching operation. It is the figure which showed the result of having performed the transmittance | permeability measurement of the light of wavelength 200-900 nm about the fluorine resin film obtained by extending | stretching operation. It is the figure which showed the wide angle X-ray-scattering measurement result before and behind extending | stretching of a fluororesin film. It is the figure which showed the result of having performed the transmittance | permeability measurement of the light of wavelength 200-900 nm about the fluorine resin film obtained by extending | stretching operation.

  Hereinafter, one embodiment of the present invention will be described. The method for producing a fluororesin film of the present invention (hereinafter sometimes referred to simply as “the production method of the present invention”) is a rapid cooling of a molten fluororesin at a cooling rate of 50 to 1000 ° C./sec. Then, it is stretched to form a film. In the present invention, “film” includes “sheet”.

  Examples of the fluororesin that can be used in the production method of the present invention include crystalline fluororesins and copolymers thereof, such as polyvinylidene fluoride (polyvinylidene fluoride) (PVDF), polytetrafluoroethylene (PTFE). ), Polyvinyl fluoride (PVF), polychlorotrifluoroethylene (PCTFE), ethyl trifluoroacetate (EFA), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer Examples thereof include coalescence (FEP), chlorotrifluoroethylene / ethylene copolymer (ETFE), and chlorotrifluoroethylene / ethylene copolymer (ECTFE). Further, a poly (vinylidene fluoride / hexafluoropropylene) copolymer (PVDF-HFP), poly (vinylidene fluoride / trifluoroethylene), or the like, which is a copolymer of polyvinylidene fluoride, may be used. One of these materials may be used alone, or two or more thereof may be used in combination.

  The weight average molecular weight of the fluororesin used is preferably, for example, 50,000 to 1500,000 g / mol, particularly preferably 100,000 to 1300000 g / mol.

  Moreover, you may make it add a conventionally well-known additive to a fluororesin in the range which does not prevent the objective and effect of this invention. Examples of usable additives include UV absorbers, stabilizers, dispersants, antioxidants, matting agents, surfactants, antistatic agents, fillers such as silica and alumina, and fluorine-based surface modifiers. In addition, various additives such as processing aids can be mentioned, and they can be added within a range in which their dispersibility is not impaired.

  In the production method according to the present invention, the above-mentioned fluororesin is rapidly cooled after being brought into a molten state. To make the fluororesin into a molten state, the melting temperature of the fluororesin used (for example, 170 to 350 ° C.) Then, it should be heated for several seconds to several minutes.

  In addition, since the fluororesin is stretched in a subsequent process, it is heated in advance at 170 to 350 ° C. with a hot press or the like to be previously melted into a film or sheet having an appropriate thickness (for example, 10 to 450 μm). You may do it.

  The molten fluororesin is rapidly cooled. The cooling rate is 50 to 1000 ° C./second, preferably 100 to 600 ° C./second, and particularly preferably 200 to 500 ° C./second. The temperature is the actual temperature of the fluororesin. An infinite number of rod-like crystal structures are formed by rapidly cooling the molten fluororesin. Further, the cooling time in the rapid cooling is preferably 0.1 to 4 seconds, and more preferably 0.3 to 2 seconds. As a guide, the molten fluororesin may be cooled from the molten state to the room temperature level in 0.4 to 2 seconds (preferably 0.5 to 1 second).

  Since the cooling rate is not always controlled at a constant value, the cooling rate always changes during the cooling process. Therefore, a typical cooling rate may be, for example, a rate when the temperature of the sample is 100 ° C. in the cooling process. In this case, for example, a temperature curve in the vicinity of 100 ° C. is approximated by a secondary number or the like, an inclination at 100 ° C. is obtained for the obtained curve, and the value is set as a cooling rate at 100 ° C.

  The means for rapidly cooling the fluororesin is not particularly limited as long as the molten fluororesin can be cooled at the above cooling rate. For example, a known cooling method such as water cooling or passing a cooling roll is used. Can be used.

  The rapidly cooled fluororesin is formed into a film by being stretched. For the stretching, a known stretching process such as uniaxial, biaxial, simultaneous, and sequential can be used. The draw ratio is preferably in the range of 50 to 500% where void formation does not become dominant. If the draw ratio is less than 50%, the yield strain may not be exceeded, so that the film may not be remarkably oriented. If the draw ratio exceeds 500%, voids may occur and the film may become clouded. The draw ratio is more preferably in the range of 50 to 450%, particularly preferably in the range of 100 to 400%. Moreover, what is necessary is just to make it the thickness of the fluororesin film obtained become about 60-350 micrometers, for example.

  In the case of uniaxial stretching, the stretching ratio is preferably in the range of 50 to 500%. On the other hand, in the case of biaxial stretching, in the range, for example, longitudinal It is preferable to set it to 50 to 200% in the direction and 50 to 200% in the horizontal direction, and it is particularly preferable to set it to 50 to 150% in the vertical direction and 50 to 150% in the horizontal direction.

  The fluororesin film obtained by stretching becomes a film having a high light transmittance in the wavelength region of 200 to 900 nm and from the ultraviolet region to the infrared region. For example, the fluororesin film obtained by the production method of the present invention has a transmittance of about 90% or more at a wavelength of 900 nm and is equivalent to polymethyl methacrylate (PMMA) even when the film thickness after stretching is about 100 μm. Not only a high value but also a transmittance as high as 80% or higher, especially at a low wavelength of 300 nm, shows a significantly superior light transmittance as compared to a versatile optical film such as PMMA.

  1 and 2 show one-dimensional data obtained from a SAXS (small angle X-ray scattering) pattern of a fluororesin (PVDF) film stretched to 300%. FIGS. 1 and 2 show one-dimensional data obtained by cutting a two-dimensional SAXS pattern of a stretched fluororesin (PVDF) film perpendicular to the stretching direction at the crystal lamella position. Of these, FIG. 1 shows a conventional process in which a molten fluororesin is placed on a temperature control means such as a hot plate, cooled to a predetermined temperature and crystallized (melt crystallization). FIG. 2 shows a stretched fluororesin film, and FIG. 2 shows the process according to the present invention in which a melted fluororesin is rapidly cooled and crystallized (hereinafter sometimes referred to as “rapidly cool crystallization”). It is a result of the obtained fluororesin film. As shown in FIG. 1, in a sample prepared by melt crystallization, lamellar crystals are aligned in the stretching direction. On the other hand, as shown in FIG. 2, it can be confirmed that in the sample prepared by rapid cooling, the lamella crystals are greatly deformed and are arranged obliquely with respect to the stretching direction.

  Moreover, FIG. 3 is the figure which showed the result of having confirmed the molecular mobility of the polymer chain in a lamellar crystal by dielectric relaxation measurement about these two types of fluororesin-type films. As shown in FIG. 3, it was found that the sample prepared by rapid cooling has a higher molecular mobility than the sample prepared by melt crystallization. This indicates that in the fluororesin (PVDF) produced by melt crystallization, the fluororesin chains are densely packed in the lamellar crystal and the movement of the fluororesin chain is suppressed. . In addition, due to the decrease in molecular mobility, stress concentration worked during deformation due to stretching, and voids appeared between lamellae. On the other hand, in the fluororesin produced by rapid cooling, the packing of the fluororesin chain in the lamellar crystal is sparse, and the motion of the fluororesin chain is relatively easy. For this reason, it is considered that the lamellar crystal easily deformed during the stretching process, and void formation or the like did not occur.

  The stretched fluororesin film is heat-fixed so that it hardly heat shrinks even when overheated, has excellent dimensional stability, and improved various properties such as water resistance and wear resistance. To do. What is necessary is just to hold | maintain heat setting at about 100-150 degreeC for about 5 to 15 minutes. The film obtained by the production method of the present invention exhibits high transparency with a transmittance of 90% or more at a wavelength of 900 nm even after heat setting. The heat setting may be performed when the fluororesin is stretched to form a film.

  The method for producing a fluorine-based resin film according to the present invention described above is a simple operation in which a molten fluorine-based resin is rapidly cooled and then stretched to form a film, and weather resistance, chemical resistance, water repellency, difficulty A film having various properties derived from a fluorine-based resin such as flammability and antifouling property and having high light transmittance in a wide wavelength range can be produced at low cost.

  Note that the stretched film not only exhibits high light transmittance in a wide wavelength range, but also exhibits a scattering peak derived from the β phase. Therefore, the obtained fluororesin film is preferably subjected to poling treatment in order to align the direction of polarization. By applying the poling treatment, ferroelectricity such as piezoelectricity can be imparted to the fluororesin film. For the polling treatment, a conventionally known method can be used. For example, the obtained film is sandwiched between electrodes, and a DC high electric field of about 100 to 200 MV / m, for example, may be applied.

  The fluorine-based resin film obtained by the production method according to the present invention can be widely used as a functional material, an electronic material, or the like that exhibits the above-described characteristics in addition to a general packaging material. For example, in addition to the use of commonly used fluorine resin films, taking advantage of the low refractive index peculiar to fluorine materials and transparency in a wide wavelength region, optical component constituent materials and packaging materials in electrical equipment, solar cell protective films In addition to excellent transparency and high transparency, especially high light transmission in the low-wavelength region with high energy, it can be used as a dust-proof film in the lithography process of LSI manufacturing. Taking advantage of the piezoelectricity derived from the above and high dielectric properties, it can be used for sensors and actuators.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example and a reference example, this invention is not limited to this Example at all.

[Example 1]
Production of fluorinated resin film (1):
A fluororesin film was produced using the following operations (1) to (3).

(1) Production of film sample:
Polyvinylidene fluoride (PVDF) (weight average molecular weight 220,000 g / mol) (KF1000: manufactured by Kureha Co., Ltd.), which is a fluorine-based resin, is sandwiched between hot press top plates with a set temperature of 200 ° C., and heated and pressed. A film sample having a thickness of 20 to 500 μm was used.

(2) Rapid cooling operation:
The film sample obtained in (1) was heated on a hot plate near 190 to 230 ° C. for 5 minutes to obtain a molten state, and then rapidly cooled in a water bath set at 30 ° C. The cooling rate was about 200 ° C./second.

  FIG. 4 is a diagram showing a cooling time-temperature curve in this operation. As Reference Example 1, polyvinylidene fluoride (PVDF) melted in the same manner as in Example 1 (1) and (2) was placed on a hot plate (temperature control means) at 30 ° C. instead of being rapidly cooled. A cooling operation (hereinafter, sometimes referred to as “normal cooling operation”) is also performed. FIG. 4 also shows the cooling time-temperature curve in Reference Example 1. The cooling rate of Reference Example 1 was about 20 ° C./second.

  FIG. 5 is a diagram showing the Hv light scattering results of the film samples obtained in the cooling operation of Example 1 and Reference Example 1 (normal cooling operation). The crystallization temperature is 30 ° C. As shown in FIG. 5, in the film sample of Reference Example 1 produced by melt crystallization by a normal cooling operation, a four-leaf-like scattering pattern is observed and a spherulite structure is formed. On the other hand, in the film sample prepared by rapid crystallization by the rapid cooling (cooling) operation of Example 1 (2), a cross-shaped scattering pattern was observed at the center, and it was confirmed that a rod-shaped crystal structure was formed. .

  Next, the observation result (SEM image) by SEM (scanning electron microscope) about a film sample is shown in FIG. It was confirmed that a large spherulite structure was formed in the sample film of Reference Example 1 produced by melt crystallization by a normal cooling operation. On the other hand, it was confirmed that innumerable rod-like crystals appeared in the film sample produced by rapid crystallization by the rapid cooling operation of Example 1 (2).

  In addition, in order to evaluate the thermal stability of a film sample, the fluororesin film after cooling (both Example 1 and Comparative Example 1) was held at a temperature of 120 ° C. for 24 hours. Not observed.

(3) Drawing operation:
The film sample obtained in (2) was cut into a size of 30 mm × 10 mm including that of Reference Example 1. The cut film sample was uniaxially stretched so that the stretch ratio was 300% to obtain a fluororesin film having a thickness of 93 μm.

  FIG. 7 is a view showing an external appearance photograph of the fluororesin film obtained by the stretching operation. As shown in FIG. 7, the fluororesin film of Reference Example 1 produced by melt crystallization by a normal cooling operation did not become a cloudy and transparent film but was shown in Example 1 (2). The fluororesin film obtained by the method prepared by quenching and crystallizing by the quenching operation was made transparent by stretching beyond the yield point.

  Moreover, the result of having measured the transmittance | permeability of light with a wavelength of 200-900 nm using visible and ultraviolet spectroscopy with respect to the obtained fluororesin film is shown in FIG. The transmittance results are obtained by standardizing the thickness of the fluorine-based resin films obtained in Example 1 and Reference Example 1 to 95 μm using the Lambert-Beer equation. For reference, the results of PMMA (polymethyl methacrylate resin) (not stretched) are also listed. As shown in FIG. 8, in the fluororesin film produced in Reference Example 1 melted and crystallized by a normal cooling operation, the transmittance is reduced by 20% or more in the entire wavelength range due to stretching. On the other hand, the fluororesin film produced in Example 1 has increased transmittance in all wavelength regions due to stretching, and in particular, not only has a high transmittance of 93% at a wavelength of 900 nm. Even at a low wavelength of 300 nm, the transmittance was 80%, and it was confirmed that the transmittance was high in a wide wavelength region.

  Further, for the fluororesin film obtained in Example 1, when the fluororesin film was held at 140 ° C. for 10 minutes for heat fixation, the transmittance was 91% in the high wavelength region (wavelength 900 nm), Still high. Even in the low wavelength region, the transmittance of 80% or more was maintained up to a wavelength of 360 nm.

  FIG. 9 is a diagram showing wide-angle X-ray scattering measurement results before and after stretching of the obtained fluororesin film. As shown in FIG. 9, in the fluororesin film produced in the process including the rapid cooling operation of Example 1 (2), a scattering peak derived from the β phase could be observed. Therefore, it was confirmed that the film produced in Example 1 not only showed high light transmittance in a wide wavelength range as shown in FIG. 9, but also had ferroelectricity by poling treatment.

[Example 2]
Production of fluorinated resin film (2):
Instead of polyvinylidene fluoride (PVDF) as the fluororesin used, the mass ratio of poly (vinylidene fluoride / trifluoroethylene) copolymer (PVDF / TrFE: vinylidene fluoride) was 80% of the total copolymer, A fluororesin film was produced in the same manner as in Example 1 except that vinylidene chloride / trifluoroethylene = 80/20) (VT-100, manufactured by Daikin Industries, Ltd.) was used. The draw ratio was 275% in Example 2 and 150% in Reference Example 2 described later.

  In addition, as Reference Example 2, using the above-described poly (vinylidene fluoride / trifluoroethylene) copolymer as a fluororesin, poly (melted in the same manner as in the operations of Example 1 (1) (2), The vinylidene fluoride / trifluoroethylene copolymer is placed on a hot plate (temperature control means) instead of being rapidly cooled and cooled to 30 ° C. (cooling rate is the same as in Reference Example 1 above). After performing a cooling operation (normal cooling operation), a fluororesin film obtained by performing 300% uniaxial stretching was produced.

  FIG. 10 is a diagram showing the results of measuring the transmittance of light having a wavelength of 200 to 900 nm using visible / ultraviolet spectroscopy for the obtained fluororesin film. In addition, the transmittance | permeability result unified the thickness to 95 micrometers using the Lambert-Beer type | formula as the result of the transmittance | permeability similarly to Example 1. FIG. As shown in FIG. 10, as in Example 1, it was confirmed that the transmittance of the film sample of Example 2 produced by rapid cooling was increased by stretching. On the other hand, the transmittance of the film sample of Reference Example 2 produced by melt crystallization by a normal cooling operation was reduced by stretching.

  The present invention can be advantageously used as a method for producing a fluororesin film used as a functional material or an electronic material in addition to a general packaging material.

Claims (5)

  A method for producing a fluororesin film, characterized in that a crystalline fluororesin in a molten state is rapidly cooled at a cooling rate of 50 to 1000 ° C./second, and then stretched to form a film.   The method for producing a fluororesin film according to claim 1, wherein a draw ratio in the drawing is 50 to 500%.   The method for producing a fluororesin film according to claim 1 or 2, further comprising performing a poling treatment after the stretching.   The said cooling rate is 100-600 degreeC / sec, The manufacturing method of the fluorine resin film in any one of Claim 1 thru | or 3 characterized by the above-mentioned. The fluororesin is polyvinylidene fluoride (polyvinylidene fluoride) (PVDF), polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), polychlorotrifluoroethylene (PCTFE), ethyl trifluoroacetate (EFA). , Tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), chlorotrifluoroethylene / ethylene copolymer (ETFE), chlorotrifluoroethylene / ethylene copolymer It is at least one selected from the group consisting of a polymer (ECTFE), a poly (vinylidene fluoride / hexafluoropropylene) copolymer (PVDF-HFP), and poly (vinylidene fluoride / trifluoroethylene). Method for producing a fluorine-based resin film according to any one of claims 1 to 4, characterized in that.