JPS63280618A - Manufacture of chlorotrifluoroethylene polymer film with small water vapor permeability - Google Patents

Abstract

PURPOSE:To manufacture a film of small water vapor permeability without damaging transparency by rolling a chlorotrifluoroethylene polymer film by means of pressure rolls of given temperature. CONSTITUTION:A chlorotrifluoroethylene polymer film is passed between pressure rolls of 120-200 deg.C surface temperature. The crystallinity of the film is increased by pressure rolling and the water vapor permeability of the same is reduced by approximately 20% smaller than that of the films heretofore available. Said pressure rolled film has a small dimensional change ratio at a high temperature and a superior dimensional stability at a high temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a film of chlorotrifluoroethylene polymer having low water vapor permeability.

[Conventional technology]

It has been known that chlorotrifluoroethylene polymer films have low water vapor permeability. For this reason, chlorotrifluoroethylene polymer films are used in applications that require moisture resistance.For example, in electroluminescent devices (EL devices), which have recently been attracting attention as planar light emitting devices, phosphors are exposed to moisture. It is used as a sealing film to prevent deterioration.

[Problem that the invention seeks to solve]

However, when EL elements are used in backlights of liquid crystal displays for automobiles, more moisture resistance is required than ever, and in particular, sufficient moisture resistance at high temperatures is required. Therefore, there has been a demand for films of chlorotrifluoroethylene polymers used as sealing films to have better moisture resistance than ever before, that is, to have low water vapor permeability. In order to reduce the water vapor permeability of a chlorotrifluoroethylene polymer film, it is possible to increase the thickness of the film, but increasing the thickness of the film results in poor transparency and poor visible light transmission. There is a problem in that it cannot be used in applications that require transparency. Also,
As a method of reducing the water vapor permeability of a film, a method of stretching the film (see Japanese Patent Application Laid-Open No. 60-96626) and a method of heat treating the film are known. However, the method using stretching has the problem that the dimensional stability of the stretched film at high temperatures is poor, and the method using heat treatment does not sufficiently reduce water vapor permeability.

An object of the present invention is to provide a method for producing a chlorotrifluoroethylene polymer film that has lower water vapor permeability than conventional films and excellent dimensional stability at high temperatures without impairing transparency. .

[Means for solving problems]

The gist of the present invention is to provide a method for producing a chlorotrifluoroethylene polymer film with low water vapor permeability, which comprises rolling the chlorotrifluoroethylene polymer film with a roll having a surface temperature of 120 to 200°C. Exists.

The chlorotrifluoroethylene polymer film used as a raw material in the present invention is usually obtained by extrusion molding. Here, the chlorotrifluoroethylene polymer refers to a monopolymer of chlorotrifluoroethylene or a copolymer of chlorotrifluoroethylene and 30% by weight or less of a copolymerizable monomer. Examples of the monomer include vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene.

The thickness of the film used in the present invention is not particularly limited, but is usually 25 to 1000 μm, preferably 50 to 200 Im.

The rolling treatment is performed by passing the material between two or more rolls heated to 120 to 200°C. The roll temperature is important; if the temperature is too low, it will be difficult to roll the film sufficiently and uniformly, and if it is too high, the peelability between the roll surface and the film will be poor. Therefore, the roll temperature is 120~
It is necessary that the temperature is within the range of 200°C, particularly preferably within the range of 160 to 290°C.

The rolls used in the rolling process are not particularly limited as long as the temperature can be adjusted.The number of rolls may be 2 or more, and is usually 2 to 5 rolls. The arrangement of the rolls is not particularly limited, and for example, a serial type, a horizontal type, an inclined type, an L type, an inverted type, a Z type, etc. can be adopted.

The roll interval and roll rotation speed in the rolling process vary depending on the thickness of the film to be rolled, but the thickness of the film after rolling is 80% of the thickness of the film before rolling.
It is preferable to set the thickness to ~98%, preferably 85 to 95%. If the thickness of the film after rolling is less than 80% of the thickness before rolling, the film will crack and become transparent. This is because rolling is insufficient if it exceeds 98%.

The chlorotrifluoroethylene polymer film produced by the production method of the present invention has a water vapor permeability of about 20% compared to conventional chlorotrifluoroethylene polymer films.
This is thought to be due to the fact that the rolling treatment increases the crystallinity of the film. Furthermore, the chlorotrifluoroethylene polymer film produced by the production method of the present invention is characterized by a small dimensional change rate at high temperatures.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. 6 Example Manufactured by extrusion molding Thickness: 200 μm, Width: 300 m
m of chlorotrifluoroethylene polymer film (hereinafter referred to as PCTFE film) was rolled under the following conditions using an upright roll calender in which two rolls with a diameter of 200 mm and a width of 500 mm were arranged in series. did.

Roll surface temperature: 190°C Roll rotation speed: 2 rpm Roll gap: 30 to 40 μm (The roll gap is a value measured in advance with a thickness gauge, and as the film is inserted into the roll, the roll moves up and down and the gap changes.) Film take-up speed 1.3 m/min After partial pressure PCT
The results of measuring the UNW degree, visible light transmittance, and dimensional change rate of the FE film are shown in Table 1 together with the measurement results of the PCTFE film before rolling. In addition,
・Moisture permeability is based on JIS-Z0208 at a temperature of 60℃
(JIS-Z 0208 is 25°C or 40°C). Further, the dimensional change rate was determined by heat-treating the PCTFE film at 150° C. for 30 minutes and measuring the dimensional change rate. In addition, in the dimensional change rate in the table, RD
TD represents the dimensional change rate in the rolling direction, and TD represents the dimensional change rate in the direction perpendicular to the rolling direction.

Comparative Example For comparison, (1) uniaxially stretched or (2) heat-treated P
A CTFE film was prepared and measured in the same manner as in the example. The conditions for preparing the film are as follows.

(1) Uniaxial stretching Stretching temperature: 150°C Stretching ratio: 4 times (2) Heat treatment Heat treatment temperature: 150°C Heat treatment time: 24 hours The measurement results are shown in Table 1. However, since visible light transmittance and moisture permeability depend on the thickness of the film, (a) absorbance of visible light is proportional to the thickness of the film (b) i3 humidity is inversely proportional to the thickness of the film. The converted value is shown when the thickness is 200 IIm.

(Blank below) From the results shown in Table 1, the PCTFE film after rolling treatment has a moisture permeability of about 20% compared to the PCTFE film before rolling treatment, even though the thickness of the film is reduced. You can see that it is getting smaller. The visible light transmittance remains at 89% or more even after rolling treatment.
It can be seen that the transparency of the film is virtually unparalleled. It can be seen that the dimensional change rate is clearly smaller after the rolling treatment than before the rolling treatment. On the contrary,
It can be seen that the stretched film of the comparative example has a large dimensional change rate, and the heat-treated film has a small decrease in moisture permeability.

〔Effect of the invention〕

According to the present invention, a chlorotrifluoroethylene polymer film with low water vapor permeability can be obtained without impairing the transparency of the film.

that's all Patent applicant: Daikin Industries, Ltd. Procedural amendment

Claims (1)

[Claims] 1. A film of chlorotrifluoroethylene polymer,
A method for producing a chlorotrifluoroethylene polymer film with low water vapor permeability, which comprises rolling with rolls having a surface temperature of 120 to 200°C. 2. The chlorotrifluoroethylene polymer with low water vapor permeability according to claim 1, which is rolled so that the thickness of the film after rolling is 80 to 98% of the thickness of the film before rolling. film manufacturing method.