JPH05286019A - Manufacture of thermoplastic resin film - Google Patents

Abstract

PURPOSE:To prevent sublimate which is sublimed from the surface of a thermoplastic resin from attaching to an electrode in a method for manufacturing thermoplastic resin film wherein electrostatic charge is applied to a film-shaped molten resin from an electrode provided near a contact point between the film- shaped molten resin and a cooling drum to bring said resin close to the drum, thereby rapidly cooling and solidifying it. CONSTITUTION:In manufacture of thermoplastic resin film wherein molten thermoplastic resin is extruded from a die 1 onto a cooling drum 2 in the form of film and electrostatic charge is applied to the film-shaped molten resin from an electrode 4 provided near a contact point between the film-shaped molten resin 3 and the drum 2 so that the resin 3 is brought into close contact with the drum 2 so as to be rapidly cooled and solidified, an exhaust nozzle 5 is provided above the electrode to effect forced ventilation.

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 thermoplastic resin film, and more specifically, a molten thermoplastic resin is extruded from a die into a cooling drum in a film form, and the film-like molten resin is cooled. A method for producing a thermoplastic resin film in which an electrostatic charge is applied to the film-shaped molten resin from an electrode provided in the vicinity of a contact point with the drum to bring the film-shaped molten resin into close contact with a cooling drum and to rapidly solidify the resin. , Of a thermoplastic resin film improved so as to prevent sublimates sublimated from the surface of the thermoplastic resin from adhering to the electrode and to keep the adhesion effect between the film-shaped molten resin and the cooling drum stable for a long time. The present invention relates to a manufacturing method.

[0002]

2. Description of the Related Art When a thermoplastic resin is melt-extruded and rapidly solidified, a wire or knife-shaped electrode is provided between a die and a cooling drum so that an electrostatic charge is applied to the surface of the film-shaped molten resin. A method of causing the film-shaped molten resin to adhere to a cooling drum and rapidly cooling it by deposition (so-called electrostatic contact film-forming method) is described in, for example, JP-B-37-6.
No. 142 publication.

However, in this method, there is a serious problem that the productivity is greatly reduced when the thermoplastic resin is brought into close contact with the cooling drum and cooled.

This serious problem is that the sublimate sublimes from the molten thermoplastic resin and adheres to the metal parts around the die, especially to the above-mentioned electrodes. Then, the sublimate attached to the electrode is oxidatively decomposed by ozone generated by corona discharge around the electrode and becomes water or carbon dioxide gas and scatters, but part of it becomes an oxide insulator on the electrode surface. To remain. This oxide insulator deteriorates the characteristics of the electrode and significantly shortens its life. Such a phenomenon also occurs in a thermoplastic resin to which an inorganic lubricant is added, but it has been found that a thermoplastic resin to which an organic lubricant is added has a larger amount of oxide insulation attached than an inorganic lubricant. This is because when a part of the organic lubricant component, for example, a silicone fine particle lubricant is used, a part of the silicone component sublimes and adheres to the electrode, and becomes an oxide insulator such as SiO ₂ by the oxidative decomposition action of ozone and remains on the electrode. It is thought to be due to doing.

When the sublimate and the oxide insulator adhere to the electrode in this way, the electrostatic application effect is reduced, and the adhesion effect between the film-shaped molten resin and the cooling drum is reduced. Therefore, in order to satisfy the intended purpose, there is no choice but to replace the electrode that has reached the end of its life with a clean one, and the work and production loss required for this replacement were serious problems of the electrostatic contact film formation method. ..

Several methods have been proposed in the past for extending the service life of electrodes.

The first method is to blow hot air to the electrode because the sublimate is a low melting point substance (Japanese Examined Patent Publication No. 45).
-37874), a method of heating the electrode itself by applying a low-voltage current to the electrode (Japanese Patent Publication No. 47-29782), and a method of raising the temperature of the electrode by irradiating infrared rays (JP-A-52).
No. -68262), a method of providing a coating means between the die and the cooling drum to keep the temperature of the electrode at 150 ° C. or higher (Japanese Patent Publication No. 59-41850), or 180 ° C. or higher when the electrode surface material is gold or platinum. The method of controlling to a high temperature (Japanese Patent Laid-Open No. 63-42832) is a means for avoiding adhesion of sublimates.

The second method is a method of moving the electrode wire continuously like a ribbon of a typewriter to avoid a production loss due to replacement of the electrode wire (Japanese Patent Publication No. 40-40904).

The third method is to use an electrode carrying an oxidation catalyst and maintain it at 150 ° C. or higher for oxidative decomposition (JP-A 61-202817), or to use platinum or platinum on the surface of the electrode core material. This is a method of coating with an alloy and catalytically oxidatively decomposing (JP-A-63-81018).

[0010]

However, these methods physically prevent the sublimation of the sublimate sublimated from the surface of the molten thermoplastic resin by cooling and solidification on the electrode by heating or by moving the adhered portion. Different methods,
This is a chemical method utilizing an oxidation catalyst action, and does not fundamentally solve the problem due to the adhesion of an oxide insulator generated by the oxidative decomposition action of ozone, and the effect is not sufficient.

An object of the present invention is to fundamentally solve such problems and to provide an epoch-making method different from the conventional physical and chemical methods.

[0012]

That is, according to the present invention, a molten thermoplastic resin is extruded from a die into a cooling drum in a film shape, and an electrostatic charge is applied from an electrode provided in the vicinity of a contact point between the film-shaped molten resin and the cooling drum. In the method for producing a thermoplastic resin film in which the film-like molten resin is applied to the film-like molten resin so that the film-like molten resin is brought into close contact with the cooling drum, and the film is rapidly cooled, an exhaust nozzle is provided above the electrode to forcefully exhaust the thermoplastic resin. It is a manufacturing method of a resin film.

The present invention will be described with reference to the drawings.

In the present invention, examples of the thermoplastic resin include polyesters such as polyethylene terephthalate and polyethylene naphthalate, but the thermoplastic resin is not particularly limited thereto.

FIG. 1 is a side view showing a conventional casting method, and FIGS. 2 and 3 are side views showing the casting method of the present invention.

As shown in FIG. 1, the molten thermoplastic resin is extruded from the die 1 onto the cooling drum 2 in a film form and cast. At that time, in order to bring the film 3 into close contact with the cooling drum, the electrode 4 is provided in the vicinity of the contact point between the film-shaped molten resin and the cooling drum, and a high-voltage direct current is usually applied. This electrode is preferably linear, but
It may be knife-shaped or rod-shaped, and is usually stretched over the entire width direction of the film-shaped molten resin. The material of the electrode is preferably made of tungsten, stainless steel or the like.

FIG. 2 shows a casting method in which an exhaust nozzle 5 is provided above the electrodes to forcibly exhaust the air.

The exhaust nozzle 5 is provided above the electrode 4 between the die 1 and the cooling drum 2. Sublimates sublimated from the surface of the thermoplastic resin are sucked by the exhaust nozzle 5, and the exhaust duct 6,
It is exhausted to the outside of the system by the exhaust blower 8 via the exhaust hose 7. The exhaust nozzle 5 may be provided between the side edge of the die and the die lip, but preferably between the vertical upper portion of the electrode and the die lip, and more preferably in the vicinity of the die lip. The exhaust amount is preferably adjusted by a method such that the rotation speed of the exhaust blower 8 is made variable by a variable speed device or a method of providing a damper. The larger the exhaust amount, the smaller the amount attached to the electrode and the longer the exchange period, but since it affects the unevenness of the film thickness, the exhaust amount adjusting device converts it to 20 to 20 m per 1 m of the die width. 120 Nm
^It is preferable to adjust to the range of ³ / Hr.

FIG. 3 shows a casting method in which a high temperature air stream is blown from the side surface of the electrode under the die centering on the electrode 4 in addition to the method of forcibly exhausting by providing the exhaust nozzle 5 above the electrode. The forced exhaust device is installed in the same manner as in FIG.

The spray nozzle 9 is provided on the downstream side of the electrode and is installed at a position where the high temperature air flow is sprayed under the die with the electrode 4 as the center. The hot air flow is a heater such as a heater 1
It is heated at 0 ° C. and controlled to 150 ° C. or higher, preferably 200 ° C. or higher, more preferably 250 ° C. or higher, and sprayed uniformly from the spraying nozzle 9 by the spraying blower 11 over the entire width of the film. The blowing amount is preferably adjusted by a method in which the rotation speed of the blowing blower is made variable by a variable speed device or a method in which a damper is provided. The larger the sprayed amount, the smaller the adhered amount to the electrode and the longer its replacement period, but since it affects the thickness unevenness of the film, the sprayed amount adjusting device converts it to 30 to 180 Nm per 1 m of the die width. ^It is preferable to adjust to the range of ³ / Hr.

[0021]

EXAMPLES The present invention will be further described below with reference to examples. The electrode replacement cycle is determined by the time until the current value from the electrode decreases by 1% with respect to the current value immediately after the electrode replacement, and until a defect occurs due to insufficient adhesion to the cooling drum on the surface of the unstretched film. Whichever time was used earlier. In addition, the blowing amount of the high temperature blowing device and the exhaust amount of the forced exhaust device were values converted per 1 m of the die width, and the film thickness unevenness was determined immediately after the electrode replacement.

[0022]

Example 1 Polyethylene terephthalate (PET) added with an inorganic lubricant was melted at 280 ° C. and then heated at 30 ° C. from a die.
It was extruded onto the cooling drum set to, and a stainless steel electrode was attached to the entire width of the film-shaped molten PET at 5 mm above the position where the film-shaped molten PET was in contact with the cooling drum, and a DC voltage of 7 kV was applied. The thickness of the electrode is 0.2m
m, the length is 700 mm.

The casting speed was 50 m / min, the thickness of the cooled and solidified film was 200 μm, the hot air blowing device was not used, and the exhaust amount of the forced exhaust device was 2
When the film was formed by setting it to 0 Nm ³ / Hr, the electrode exchange period was 12 Hr, and there was no unevenness in the film thickness, which was good. The results are shown in Table 1.

[0024]

[Examples 2 and 3] Films were formed in the same manner as in Example 1 except that the exhaust amount was changed to 60 and 100 Nm ³ / Hr. The results are shown in Table 1.

[0025]

Example 4 A film was formed in the same manner as in Example 1 except that the exhaust amount was changed to 120 Nm ³ / Hr. The electrode exchange period was 44 hours, but the unevenness of the film thickness was somewhat defective, which was the upper limit of the exhaust amount. The results are shown in Table 1.

[0026]

Comparative Example 1 A film was formed in the same manner as in Example 1 except that the forced exhaust device was not provided. Electrode replacement cycle is 8H
At r, the film thickness unevenness was good. The results are shown in Table 1.

[0027]

Examples 5 to 7 Films were formed in the same manner as in Example 1 except that a high temperature air blowing device was used and the blowing amount and the forced exhaust device exhaust amount were changed as shown in Table 1. The results are shown in Table 1.

[0028]

[Embodiment 8] The amount of high temperature air blown is 180 Nm ³ / H.
A film was formed in the same manner as in Example 5 except that the r and the exhaust amount were changed to 120 Nm ³ / Hr. Electrode replacement cycle is 80 hours
However, the unevenness in the thickness of the film was slightly defective, and the upper limits of the spraying amount and the exhaust amount were set. The results are shown in Table 1.

[0029]

[Example 9] A film was formed in the same manner as in Example 2 by using PET to which silicone fine particles were added as an organic lubricant.
The electrode exchange period was 16 hours, and the film thickness unevenness was good. The results are shown in Table 1.

[0030]

[Example 10] A film was formed in the same manner as in Example 6 using PET to which silicone fine particles were added as an organic lubricant. The electrode exchange period was 24 hours, and the film thickness unevenness was good. The results are shown in Table 1.

[0031]

[Comparative Example 2] A film was formed in the same manner as in Comparative Example 1 using PET to which silicone particles were added as an organic lubricant.
The electrode exchange period was 4 hours, and the film thickness unevenness was good. The results are shown in Table 1.

[0032]

[Table 1]

[0033]

As described above, according to the method of the present invention, since the exhaust port is provided on the upper part of the electrode to forcibly exhaust the air, it is more preferable to add a high temperature air flow from the side surface of the electrode in addition to the forced exhaust device. Since it is sprayed under the die centering around the electrode, the effect of preventing sublimation of sublimation from the surface of the thermoplastic resin, especially oxide insulation that adheres in large quantities when forming the organic lubricant-containing thermoplastic resin Is large, the electrode replacement cycle is long, the production loss due to electrode replacement or the like can be significantly reduced, and the productivity can be significantly increased.

[Brief description of drawings]

FIG. 1 is a side view showing a conventional casting method.

FIG. 2 is a side view showing a casting method when an exhaust port is provided on an electrode upper part of the present invention to perform forced exhaust.

FIG. 3 is a side view showing a casting method when a high temperature air flow is made to flow from the side surface of the electrode in addition to the forced exhaust device of FIG.

[Explanation of symbols]

 1 Die 2 Cooling Drum 3 Film 4 Electrode 5 Exhaust Nozzle 6 Exhaust Duct 7 Exhaust Hose 8 Exhaust Blower 9 Spray Nozzle 10 Heater 11 Exhaust Blower

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[Procedure amendment]

[Submission date] September 11, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

The casting speed was 50 m / min, the thickness of the cooled and solidified film was 200 μm, the hot air blowing device was not used, and the exhaust amount of the forced exhaust device was 2
When the film was formed by setting it to 0 Nm ³ / Hr, the electrode exchange period was 15 Hr, and there was no unevenness in the film thickness, which was good. The results are shown in Table 1.

Claims (3)

[Claims] 1. A molten thermoplastic resin is extruded from a die onto a cooling drum in a film shape, and an electrostatic charge is applied to the film molten resin from an electrode provided in the vicinity of a contact point between the film molten resin and the cooling drum. A method for producing a thermoplastic resin film, which is brought into close contact with a cooling drum to rapidly solidify the film-like molten resin, wherein an exhaust nozzle is provided above the electrode to forcibly exhaust the thermoplastic resin film. 2. The method for producing a thermoplastic resin film according to claim 1, further comprising blowing a high-temperature air stream from the side surface of the electrode under the die centering on the electrode. 3. The method according to claim 1 or 2, wherein
A method for producing a thermoplastic resin film, wherein the thermoplastic resin contains an organic lubricant.