JPH0791399B2 - Method for producing film made of polyvinylidene fluoride or vinylidene fluoride copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a film made of polyvinylidene fluoride or a vinylidene fluoride copolymer having excellent piezoelectricity, pyroelectricity, and proper sliding property as an electronic material. It relates to the manufacturing method.

(Prior Art) Polyvinylidene fluoride or a vinylidene fluoride copolymer (hereinafter simply referred to as PVDF) has a large relative dielectric constant and
A β-type crystal obtained by stretching DF is excellent in piezoelectricity and pyroelectricity, so it is promising as a capacitor element, a piezoelectric element, and a pyroelectric element. For the reasons such as the increase, the piezoelectric element can be applied to higher frequency ultrasonic waves, and the pyroelectric element can be expected to improve sensitivity, response speed and resolution by reducing the film thickness. PVDF stretched film is widely desired.

In response to such a demand, Japanese Patent Publication No. 60-6220 discloses that a laminated film of a polypropylene resin film or the like and a PVDF film is stretched, and then the polypropylene resin film is peeled to obtain a PVDF stretched ultrathin film. There is.

However, since the surface of the PVDF stretched ultrathin film obtained by this method is very smooth, for example, when manufacturing a metal vapor deposition film capacitor element, a metal vapor deposition step, a narrow slit step, a step of winding around the capacitor element, etc. In the above, since there is too much slip between the film and the member in contact with the film, winding becomes difficult, and wrinkles occur in the processing step, or the film is cut. Occurs, and the production yield of the capacitor element is significantly reduced.

In general, as a method for imparting appropriate slipperiness to the film, a method of adding an inorganic filler to the film raw material resin to impart appropriate irregularities to the film surface, a method of imparting irregularities to the surface of the film with sandplast, etc. is there.

However, the former method is such that a trace amount of metals and dispersants contained in the inorganic filler adversely affects the electrical characteristics, and when a film for a capacitor element is used,
When the film is wound around a capacitor, the film stretches due to tensile force acting in the longitudinal direction of the film, causing wrinkles, and voids around the inorganic filler, which may cause the breakdown voltage of the film to decrease. Become.

In the latter method, a large amount of foreign matter adheres to the surface of the film, which requires washing and the like, resulting in poor workability.

On the other hand, as disclosed in JP-A-61-123520, a film-like molten resin made of a resin containing an inorganic filler is laminated on a film-like molten resin made of a required raw material resin, and stretched and laminated. There has been proposed a method for producing a film having appropriate slidability by forming a film, peeling off a film portion having unevenness formed by one inorganic filler, and transferring the unevenness on the surface of the other film.

The film obtained by this method is superior in dielectric breakdown voltage and the like as compared with the conventional method of adding an inorganic filler and the method of imparting unevenness to the surface with sand plast etc., but the thickness of the film is several. It has been found that the dielectric breakdown voltage is significantly reduced as the thickness becomes extremely thin such as μ or less.

(Problems to be solved by the invention) In the conventional means for imparting appropriate slipperiness to the film, the performance as an electronic material is inconvenienced, and in particular, it has excellent characteristics in dielectric breakdown voltage, and is several μ or less. There was a problem that it was not possible to obtain an ultra-thin film.

(Means for Solving the Problems) The present invention provides a PVDF film which is suitable as an electronic material and can be formed into an ultrathin film, and has suitable slipperiness, and is made of polyvinylidene fluoride or fluorine. One film-like molten resin made of vinylidene chloride copolymer,
The other film-like molten resin composed of a mixture of two or more kinds of thermoplastic resins forming a matrix and a domain is extruded into a close-contact layered form while being crystallized at different temperatures, cooled and solidified, and then stretched. Is a method for producing a film made of a polyvinylidene fluoride or a vinylidene fluoride copolymer obtained by peeling off a film portion made of a film-like molten resin.

(Example) An example of the method of the present invention will be described with reference to an example of an apparatus shown in the drawings.

As shown in FIGS. 1 and 2, a polyvinylidene fluoride or a vinylidene fluoride copolymer is plasticized and kneaded in an extruder 1, and a mixture of polyolefin resins having different crystallization temperatures is used in the extruder 2. The film-like molten resin 4 supplied from the extruder 1 and the film-shaped molten resin 4 supplied from the extruder 1 were supplied from the three-layer structure multi-manifold type T die 3 which was plasticized and kneaded in The other film-like molten resin 5 is extruded into a contact layered form, and the contact layered product 6 is cooled and solidified by rotating a cooling roll 7 and then drawn rolls 8,8,
After being uniaxially stretched by 8 ', 8'and then heat treated,
By peeling off the film portions 9, 9 made of the other film-shaped molten resin 5 made of a polyolefin resin, one film-shaped molten resin 4, that is, made of polyvinylidene fluoride or vinylidene fluoride copolymer, is used as an electric material. It was possible to obtain a film 10 having a suitable dielectric breakdown voltage and a dynamic friction coefficient and having a thickness of several μ.

As the polyvinylidene fluoride in the present invention, a vinylidene fluoride homopolymer or a vinylidene fluoride monomer,
Copolymers with other monomers copolymerizable with vinylidene fluoride, such as vinyl fluoride, trifluoroethylene, tetrafluoroethylene, vinylidene fluorochloride, trifluoroethylene chloride, propylene hexafluoride, etc. The vinylidene fluoride content in the copolymer is preferably 70 mol% or more.

Further, a polymer blend of these polymers and another polymer such as polymethylmethacrylate may also be used.

Further, in the present invention, two or more kinds of thermoplastic resin components which do not show the same crystallization temperature are commonly used, when the crystalline thermoplastic resin components are used in combination, and the crystalline thermoplastic resin component and the crystallization are used together. And the case of using together with a non-crystalline thermoplastic resin component having no temperature.

By varying the crystallization temperature in this way, the irregularities formed in the thermoplastic resin layer are transferred to the surface of the PVDF stretched film, and a film having a proper dielectric breakdown voltage and a dynamic friction coefficient and having a thickness of several μ can be obtained.

The crystallization temperature referred to in the present invention is 320 ° C./m until the temperature at which a sample amount of 5 mg in Perkin Elmer DSC is completely melted.
After the temperature is raised at in and held for 3 minutes, the temperature is lowered at 10 ° C./min, and the starting temperature of the crystallization curve obtained is adopted.

Further, the compatibility between the thermoplastic resin components used together is preferably small.

Furthermore, it is preferable that at least one component of the thermoplastic resin component is a polyolefin resin, and particularly in a mixture of the thermoplastic resin components, a matrix (sea),
In the present invention in which domains (islands) are formed, the component constituting the matrix is preferably polyolefin.

This is because the stretching behavior of the polyolefin and PVDF is close to each other when the mixture is closely laminated in the molten state on the surface of the PVDF film and then stretched, so that the stretched film can be formed homogeneously.

Whether or not the matrix and the domain are formed can be determined by a phase contrast microscope, a differential interference microscope, a polarization microscope, a scanning electron microscope or a transmission electron microscope. The sample may be subjected to surface etching and dyeing as needed.

The blending ratio of the present invention is preferably 95 to 55% by weight of a polyolefin as a thermoplastic resin having a crystallization temperature and 5 to 45% by weight of a thermoplastic resin different from the polyolefin.
It is 10-40% by weight of a thermoplastic resin different from 60% by weight.

When the blending ratio of the polyolefin is more than 95% by weight, the uneven density becomes coarse and the effect of imparting the slip property to the stretched thin film is lost, and the blending ratio of the polyolefin is
If it is less than 55% by weight, uniform unevenness cannot be obtained and the effect of imparting slipperiness is lost, which is not preferable.

The polyolefin-based resin is a polymer or copolymer such as low-density polyethylene, high-density polyethylene, or polypropylene, and has a crystallization temperature, and high-density polyethylene or polypropylene is particularly preferable.

As a desirable high density polyethylene, MFR (melt flow rate) measured by JIS K6760 is 6 to 0.01 g / 10 minutes,
It is preferably 2 to 0.05 g / 10 minutes.

As a desirable polypropylene, MFR measured by JIS K6758 is 12 to 0.5 g / 10 minutes, preferably 8 to 1 g / 10 minutes.

If the MFR of high-density polyethylene exceeds 6 g / 10 minutes and the MFR of polypropylene exceeds 12 g / 10 minutes, the stretched film in the laminated state will easily tear, reducing productivity and reducing the PVDF stretched electrode. The degree of unevenness transferred to the thin film is not preferable, and the coefficient of dynamic friction is also not preferable.

If the MFR is less than 0.01 g / 10 minutes or 0.5 g / 10 minutes, a film having a uniform thickness cannot be obtained.

In the present invention, an aspect of another thermoplastic resin component mixed with the thermoplastic resin component having a desired crystallization temperature will be described.

There is polypropylene as a component of the other film-like molten resin that is adhered and laminated on at least one surface of the film-like molten resin composed of PVDF, and as the other thermoplastic resin that does not have the same crystallization temperature as this polypropylene, high-density polyethylene, There are polymers and copolymers such as low density polyethylene and polypropylene, or polymers and copolymers such as polystyrene and polyester polyamide, or polymers and copolymers of fluororesins other than PVDF, and other thermoplastic resin components. It may be either a crystalline thermoplastic resin or a non-crystalline thermoplastic resin.

A desirable combination of resin components is polypropylene and high-density polyethylene, and the MFR of each is preferably in the above-mentioned range of high-density polyethylene and polypropylene.

Further, in the case of such a combination, it is desirable that the MFR of the polyolefin resin having a large mixing ratio is larger than the MFR of the polyolefin resin having a small mixing ratio.

As a mixing method, each resin may be charged into an extruder at a predetermined ratio and melt-mixed, or a dry blend in which each resin is mixed at a predetermined ratio with a super mixer or the like.

Adhesion lamination in the present invention, before and after the vapor deposition step, part of the PVDF film part is peeled off by the thermoplastic resin film part in peeling after the slitting process, or the like, or conversely a part of the thermoplastic resin film part is PVDF film. It means the state that it does not remain in the part.

At least one film-like molten state consisting of a thermoplastic resin component must have PVDF laminated on one side of the film-like molten resin, but unevenness can be transferred by laminating on both sides of the film-like molten resin consisting of PVDF. When it is laminated on both sides, the mixed thermoplastic resins on both sides may be the same or different, and if different, different concavo-convex states can be transferred to both sides. .

Furthermore, by forming multiple layers such as thermoplastic resin / PVDF / thermoplastic resin / PVDF / thermoplastic resin, a large number of PVDF ultra-thin stretched films can be manufactured at one time.

Stretching in the present invention is at least 3 to 7 times in the uniaxial direction,
It is preferable to draw in a range of 4 to 6 times the draw ratio. In the range where the draw ratio is less than 3 times, the thickness accuracy of the drawn ultrathin film is poor, and when the draw ratio is 7 times or more, the elongation of the film is extremely high. It becomes small and easy to tear, and the unevenness is rough, and the effect of improving the slipperiness is lost.

The stretching temperature is lower than the melting point of polyolefin and is 50 ° C or more, preferably 5 ° C or more lower than the melting point of polyolefin.
The temperature is 60 ° C or higher, and the stretched film is generally thermally unstable and shrinks over time. Therefore, heat treatment is usually performed. Has the effect of increasing the heat resistance and pyroelectricity, and the heat treatment temperature is
It is desirable to carry out at a temperature not lower than 70 ° C below the melting point of PVDF.

The PVDF stretched ultrathin film may be peeled off after the heat treatment, may be peeled off after the vapor deposition step or after slitting, or may be peeled off when the consumer uses it.

In the following, examples of the present invention will be given. In this case, the slidability was measured as a dynamic friction coefficient according to ASTM D1894, and the dielectric breakdown voltage was measured according to JIS C2319.

Polypropylene (Mitsubishi Polypro, MFR = 5.5g / 10min, density
0.90g / cm ³ , melting point 168 ℃, crystallization temperature 114 ℃, and high density polyethylene (Mitsubishi Polyethylene, MFR = 0.8g / 10min, density 0.95)
2g / cm ³ , melting point 136 ° C, crystallization temperature 124 ° C) were mixed in the proportions shown in Table 1, and were plasticized in a 50φ extruder at 230 ° C and PVDF.
(KYNAR made by Pen Walt Co., MFR = 5.5g / 10min [JIS K6758
The density is 1.78 g / 10 min, melting point 171 ° C.) is plasticized by a 20φ extruder at 230 ° C. and extruded in a three-layer mixture / PVDF / mixture form from a three-layer multi-manifold type T die at 70 ° C.
After contacting with the cooling roll and cooling and solidifying, the film was uniaxially stretched 5 times in the longitudinal direction at 120 ° C, and subsequently heat treated at 140 ° C, the film part consisting of the mixture was peeled off, and 0.9μ PVDF
The case of producing a stretched ultrathin film is shown as Example 1, Example 2 and Example 3, and the evaluation results are shown in Table 1.

In addition, using the polypropylene used in this example,
Stretched and heat treated under the same conditions as this example except extruded as polypropylene / PVDF / polypropylene to give 0.9μ PVD
The case of F-stretched ultra-thin film is shown in Table 1 as Comparative Example 1, and 3% by weight of calcium carbonate whiten SSB made of calcium carbonate Shiraishi with an average particle number of 1.2 μ was added as the polypropylene used in this example. Comparative Example 2 shows a case in which polypropylene is extruded like added polypropylene / PVDF / added polypropylene, stretched and heat treated under the same conditions as in this example to obtain a PVDF stretched ultrathin film of 0.9 μm, as Comparative Example 2. .

(Effects of the Invention) The present invention makes a film-like molten resin composed of a thermoplastic resin mixture having different crystallization temperatures adhere to a film-like molten resin of polyvinylidene fluoride or vinylidene fluoride copolymer, and cools it. After solidification, the film part consisting of a mixture of thermoplastic resins with different crystallization temperatures is peeled off and fine irregularities can be transferred to a polyvinylidene fluoride film or a vinylidene fluoride copolymer film to obtain an appropriate sliding property. And has excellent piezoelectricity, pyroelectricity, and performance as an electronic material having a large dielectric breakdown voltage, and an extremely thin film can be efficiently manufactured.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of an apparatus to which the present invention is applied, and FIG. 2 is an explanatory view showing a state in which a thermoplastic resin mixture having different crystallization temperatures is peeled from a contact laminated state. 1,2 ... Extruder, 3 ... T die, 4,5 ... Film-like molten resin,
6 ... Adhesive laminate, 7 ... Cooling roll, 8, 8 ... Stretching roll,
9 ... film part, 10 ... film.

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Claims (1)

[Claims] 1. A film-like molten resin composed of polyvinylidene fluoride or a vinylidene fluoride copolymer, which comprises two or more kinds of thermoplastic resins having different crystallization temperatures and forming a matrix and a domain. The other film-like molten resin consisting of a mixture is extruded in a contact laminated state,
A method for producing a film made of polyvinylidene fluoride or a vinylidene fluoride copolymer, which is obtained by cooling and solidifying, stretching, and then peeling off the film portion made of the other film-like molten resin.