JPH05185506A - Production of moisture-proof film - Google Patents

Abstract

PURPOSE:To enhance moisture-proof properties without impairing flexibility by stretching a specified extruded film in one direction in the specified atmospheric humidity and heat-treating the stretched film at the temperature below melting point and above stretching temperature and laminating the stretched film. CONSTITUTION:A copolymerized copolymer such as, e.g. vinylidene fluoride is used as a raw material in a range wherein moisture-proof properties are not impaired without limiting the raw material to the homopolymer of chlorotrifluoroethylene. The extruded film is stretched at >=1.05 times or more at least in one direction in the conditions of >=80% especially >=90% atmospheric humidity. Stretching is performed in uniaxial stretching, biaxial stretching and simultaneous biaxial stretching or the like at the temperature below melting point and above glass transition point. Heat treatment after stretching is necessarily performed in the conditions of >=80% especially >=90% atmospheric humidity. After the heat treatment, the stretched film is laminated into two layers e.g. by pressure heat fusion sticking by rolls or a press.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a moisture-proof film composed of a laminated film of polychlorotolufluoroethylene (hereinafter referred to as PCTFE).

[0002]

2. Description of the Related Art PCTFE has the smallest water vapor transmission coefficient among various plastics, and its film is EL
It is widely used in applications such as moisture-proof coatings for devices and moisture-proof packaging for various pharmaceutical products. By the way, the phosphors used in EL elements (mainly containing zinc sulfide, cadmium sulfide, etc.) easily absorb moisture in the air, and the technical problem that the luminous efficiency significantly decreases when moisture is absorbed. Therefore, a film having further improved moisture resistance is required.

It is generally known that the specific gravity should be increased in order to improve the moisture resistance of plastics.
For example, regarding PCTFE, it has been attempted to increase the specific gravity and improve the moisture resistance by heat-treating a film obtained by melt extrusion molding.

[0004]

However, although the above method certainly increases the specific gravity and improves the moisture resistance, the flexibility of the film is lost, and cracking occurs when stress such as bending is applied to the film. Practical problems occur. Therefore, an object of the present invention is to provide a method for producing a PCTFE moisture-proof film capable of improving moisture-proof property without impairing flexibility.

[0005]

According to the present invention, a polychlorotolufluoroethylene extruded film is stretched 1.05 times or more in at least one direction under the condition that the atmospheric humidity is 80% or more, and the atmospheric humidity is 80% or more. Provided is a method for producing a moisture-proof film, which comprises heat-treating the film under the conditions and at a temperature not lower than the stretching temperature and lower than the melting point, and laminating at least two heat-treated films obtained.

According to the present invention, further, a polychlorotolufluoroethylene extruded film is stretched 1.05 times or more in at least one direction under the condition that the atmospheric humidity is 80% or more, and at least two layers of the obtained stretched film are laminated, Next, there is provided a method for producing a moisture-proof film, which is characterized in that heat treatment is carried out under the condition that the atmospheric humidity is 80% or more and at a temperature not lower than the stretching temperature and lower than the melting point.

In the present invention, PCTFE used as a film-forming material is not limited to a homopolymer of chlorotrifluoroethylene, and other comonomers such as chlorotrifluoroethylene such as chlorotrifluoroethylene can be used as long as its excellent moisture resistance is not impaired. Copolymers of vinylidene fluoride, etc. can also be used. Incidentally, as a typical commercial product of a homopolymer of chlorotrifluoroethylene, there is "Neoflon CTFE" (trade name) manufactured by Daikin Co., Ltd., "Kel-F" (trade name) manufactured by 3M Co., Ltd. A typical commercial product is Allied Fibers &
There is "Aclon CTFE" (brand name) manufactured by Plastics.

The PCTFE extruded film to be stretched and heat treated can be obtained by methods known per se,
For example, PCTFE resin is melt extruded at a temperature about 100 to 130 ° C. higher than its melting point (about 215 ° C.) and formed into a film by using a cooling roll whose surface temperature is controlled to 60 ° C. or less. Manufactured.

Stretch Treatment According to the present invention, the PCTFE extruded film is stretched
It is important to carry out stretching of 1.05 times or more under the condition that the atmospheric humidity is 80% or more, especially 90% or more. That is, the draw ratio is 1.05
If it is less than twice, the obtained film has poor flexibility and cracks due to bending or the like. Further, when the stretching is carried out under the condition that the atmospheric humidity is less than 80%, if the stretching ratio is 1.05 times or more in order to impart flexibility, the thickness unevenness is large and the commercial value of the film is significantly impaired.

In the present invention, the stretching may be carried out in at least one direction, and may be any stretching treatment such as uniaxial stretching, biaxial stretching, simultaneous biaxial stretching and the like. Except for performing under the conditions described above, the stretching is carried out at a temperature not lower than the glass transition point and lower than the melting point, as in ordinary stretching.
For example, in the case of uniaxial stretching in the machine direction, the surface temperature of the stretching roll is set in the range of 60 to 160 ° C, preferably 80 to 130 ° C. When the temperature is 60 ° C or lower, the film does not stretch, and when the temperature is 160 ° C or higher, the film melts, which makes stretching difficult. The uniaxial stretching in the transverse direction is generally carried out by a tenter clip type transverse stretching. In this case as well, the stretching temperature is 130 to 210 ° C, preferably 150 to 19 ° C for the same reason as above.
It is set in the range of 0 ℃. The biaxial stretching may be performed in the machine direction or the transverse direction first regardless of the stretching order. Simultaneous biaxial stretching is usually carried out by pantograph type tenter clip type simultaneous biaxial stretching, and this stretching temperature is the same temperature condition as in tenter clip type transverse stretching, that is, 130 to 210 ° C, preferably 150 to 210 ° C. It is set in the range of 190 ℃.

In the method of the present invention, the stretched film obtained above is heat-treated and then laminated.
Alternatively, heat treatment is performed after laminating the stretched films.

Heat Treatment After the stretching treatment carried out in the present invention, heat treatment is carried out. This heat treatment also needs to be performed under the condition that the atmospheric humidity is 80% or more, especially 90% or more. That is, when the heat treatment is performed at a humidity of less than 80%, the flexibility of the film is also impaired. This heat treatment is performed at a temperature not lower than the stretching temperature and not higher than the melting point, for example, a temperature of 130 to 210 ° C, preferably 160 to 210 ° C. The heat treatment time is set to such an extent that the specific gravity increases and the satisfactory improvement in moisture resistance is recognized. Generally 0.3
About 5 minutes is sufficient. For example, the physical properties of the CTFE homopolymer monolayer film before the stretching treatment and after the heat treatment are compared are as follows.

[0013]

[Table 1]

Lamination According to the present invention, as described above, at least two layers of the CTFE stretched film are laminated after the above-mentioned heat treatment or prior to the heat treatment. This lamination can be performed by a general method, for example, pressure heat fusion with a roll or pressure heat fusion with a press. The temperature of such pressure heat fusion may be a temperature of about the melting point of the film, and is usually about 220 to 250 ° C. Further, the pressurizing pressure may be sufficient to eliminate air between the films to be laminated, and application of an unnecessarily high pressure should be avoided because it may cause wrinkles and the like in the film. Generally, in the roll method, the width per unit film is 2 to
A pressure in the range of 5 kg / cm is preferable, and in the pressing method, a pressure in the range of 5 to 20 kg / cm ² per unit area of the film is preferable.

Further, when laminating by a roll method, continuous laminating treatment using a long film can be carried out, which is extremely preferable as a production means. Further, in this case, the productivity can be further improved by providing a preheating device before the pressure heat fusion roll and preheating the film to be laminated. As this preheating device, a device in which a plurality of preheating rolls are in contact with the film for preheating, a device in which the film runs in a box-shaped furnace, and the film is preheated by hot air in the meantime are suitable. ,
A plurality of these preheating devices can be used in combination, if necessary. The preheating conditions are set so that the temperature of the film to be preheated is equal to or higher than the heat distortion temperature and lower than the melting point.For example, in the roll contact type, the roll surface temperature is 100 to 200 ° C, and in the box hot air type. It is preferable that the hot air atmosphere temperature is set in the range of 150 to 230 ° C.

Moisture-Proof Laminated Film The PCTFE moisture-proof laminate film thus obtained is
As is clear from the examples described below, stretching under the same conditions
The moisture resistance is remarkably improved as compared with the heat-treated single layer film.

[0017]

EXAMPLES The excellent effects of the present invention will be described in the following examples. Example 1 PCTFE pellets (manufactured by 3M, trade name: Kel-F 6050)
Was extruded using a 40φ extruder and a 300-width T-die at an extruder tip temperature of 330 ° C and a T-die temperature of 340 ° C, and the thickness of 115 μm was passed through a cooling roll whose surface temperature was adjusted to 50 ° C. I wound it up. Roll the film at a surface temperature of 80
With a roll type longitudinal stretching machine adjusted to ℃ and atmospheric humidity 90% 1.
After stretching 15 times, heat treatment is performed for 30 seconds in a box-type hot air heat treatment furnace where the temperature is controlled to 190 ° C and humidity is 90%.
A uniaxially stretched heat-treated film having a thickness of 100 μm was obtained. next,
Two sheets are stacked and passed through a pressure heat fusion roll with the surface temperature of the roll adjusted to 230 ° C, and laminated at a pressing force of 2 kg / cm and a film feed speed of 6 m / min to produce a laminated film with a thickness of about 200 μm. Obtained. The specific gravity, moisture permeability and flexibility of the obtained film were measured. The results are shown in Table 2.

The measuring method is as follows. Specific gravity: Measured according to JIS K 7112. Water vapor transmission rate: The film was cut into 11 cm in length and 11 cm in width, two pieces were superposed, and the entire circumference of the edge was heat-sealed within a width of 5 mm to form a bag. About 20g in this bag
After encapsulating dry silica gel of, the temperature is 50 ° C and the relative humidity is 90.
%, The silica gel was taken out after 1000 hours, and the amount of moisture absorption was measured. Flexibility: Bent to 40 ° and left at 40 ° C for 24 hours. Next, the bending was returned and the crackability was confirmed.

Example 2 In Example 1, a pressing machine was used instead of the lamination using the pressure heat fusion roll, and the pressure was 10 kg / cm ² , the press temperature was 220 ° C., and the press time was 2 minutes. A laminated film having a thickness of about 200 μm was obtained in the same manner as in Example 1 except that the above was carried out, and the specific gravity, moisture permeability and flexibility of the obtained film were measured. The results are shown in Table 2.

Comparative Example 1 A uniaxially stretched heat-treated monolayer film having a thickness of about 200 μm was obtained in the same manner as in Example 1 except that a PCTFE extruded film having a thickness of 230 μm was used. Is not done). The specific gravity, moisture permeability and flexibility of the obtained film were measured, and the results are shown in Table 2.

Example 3 In Example 1, after the longitudinal stretching, a clip type transverse stretching machine was used to stretch at a temperature of 180 ° C. and an atmospheric humidity of 90%.
The thickness was the same as in Example 1 except that transverse stretching was performed 15 times.
A heat-treated biaxially stretched film having a thickness of 100 μm was obtained, and a laminated film having a thickness of about 200 μm was obtained in the same manner as in Example 1. The specific gravity, moisture permeability and flexibility of the obtained film were measured. The results are shown in Table 2.

Example 4 In Example 3, a press was used instead of the lamination using the pressure heat fusion roll, and the pressure was 10 kg / cm ² , the press temperature was 220 ° C., and the press time was 2 minutes. A laminated film having a thickness of about 200 μm was obtained in the same manner as in Example 1 except that the above was carried out, and the specific gravity, moisture permeability and flexibility of the obtained film were measured. The results are shown in Table 2. A film was prepared without any heat treatment, and each physical property was measured. The results are shown in Table 2.

Comparative Example 2 A biaxially stretched heat-treated monolayer film having a thickness of about 200 μm was obtained in the same manner as in Example 3 except that the PCTFE extruded film having a thickness of 265 μm was used in Example 3. Not laminated). The specific gravity, moisture permeability and flexibility of the obtained film were measured, and the results are shown in Table 2.

[0024]

[Table 2]

[0025]

According to the present invention, a PCTFE laminated moisture-proof film having significantly improved moisture-proof property can be easily produced with high productivity.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI technical display location C08L 27/12 LFT 9166-4J // B29K 27:12 B29L 9:00 4F (72) Inventor Sugitani Atsushi 2668-22 Sunayama, Hasaki-cho, Kashima-gun, Ibaraki Prefecture Shin-Etsu Chemical Co., Ltd.

Claims (2)

[Claims] 1. A polychlorotolufluoroethylene extruded film is stretched by 1.05 times or more in at least one direction under the condition that the atmospheric humidity is 80% or more, and the temperature is under the condition that the atmospheric humidity is 80% or more and the stretching temperature is higher than the melting point. A method for producing a moisture-proof film, which comprises heat-treating at 1, and laminating at least two heat-treated films obtained. 2. A polychlorotolufluoroethylene extruded film is stretched 1.05 times or more in at least one direction under the condition that the atmospheric humidity is 80% or more, at least two layers of the obtained stretched film are laminated, and then the atmospheric humidity is 80%. A method for producing a moisture-proof film, which comprises performing a heat treatment at a temperature equal to or higher than a stretching temperature and lower than a melting point under a condition of 10% or more.