JPH11944A - Apparatus for manufacture of thermoplastic resin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust automatically a discharge electrode in an apparatus for manufacture of a thermoplastic resin film. SOLUTION: A die 1 as a mouthpiece, a cooling rotary drum 3, a discharge electrode 2, an electrode position adjusting means 5, and a distance measuring means 11 are provided. The electrode position adjusting means 5 adjusts a position of the discharge electrode 2 maintaining a height of the discharge electrode 2 from a surface of the rotary drum 3. The distance measuring means 11 measures a distance between a film-like melt 4 before coming in contact with the rotary drum 3 and the discharge electrode 2. Thermoplastic resin under a molten state is made a film-like melt 4 with the die 1, extruded on the rotary drum 3, an electrostatic charge is impressed to the film-like melt 4 with the linear discharge electrode 2 provided parallel to a rotary shaft of the rotary drum 3, and the film-like melt 4 is solidified being transferred by being bonded to the rotary drum 3. In that case, the electrode position adjusting means 5 adjusts the electrode position 2 based on the measured distance between the film-like melt 4 and the discharge electrode 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a die, a rotating drum for cooling and a discharge electrode. The thermoplastic resin in a molten state is extruded into a film-like molten material by the die and extruded onto the rotating drum. The present invention relates to an apparatus for producing a thermoplastic resin film by applying an electrostatic charge to a film-like melt by a linear discharge electrode provided in parallel to an axis, and solidifying the film-like melt while transferring the film-like melt in close contact with a rotating drum. .

[0002]

2. Description of the Related Art A thermoplastic resin film (also referred to as a sheet) is formed by extruding a molten thermoplastic resin into a film from a slit-shaped die and extruding the film onto a cooling drum. Then, if necessary, processing such as stretching is also performed thereafter. At the time of this molding, a wire electrode, which is a discharge electrode to which a high voltage is applied, is placed at a predetermined position of the film information on the cooling rotary drum to electrostatically improve the degree of adhesion of the film to the cooling rotary drum. It is known that a good molding state can be obtained.

[0003] A minute current flows from the wire electrode to the cooling rotary roll side, and the thermoplastic resin is pressed against the cooling rotary roll by the electrostatic force generated at that time, and the air is caught between the film and the cooling rotary roll. Is prevented, the cooling efficiency is improved, and the moldability is improved.

By the way, in order to obtain the above-mentioned good molding state in this method, the position of the wire electrode is an important condition. In other words, of the positional relationship between the wire electrode and the surface of the cooling rotary drum, for the distance to the surface,
If this interval is too large, the potential gradient between the wire electrode and the cooling drum is reduced, and sufficient electric charge is not released from the wire electrode. Sufficient adhesion cannot be obtained. On the other hand,
If this interval is too narrow, the potential gradient becomes excessive, causing dielectric breakdown in the film, and causing defects such as pinholes.

[0005] In addition, the position of the rotating direction of the rotating drum for cooling the wire electrode, that is, the position of the film feeding direction,
When the discharge direction of the film at the ground contact point is grounded on the surface of the cooling drum that rotates at a predetermined speed in a state where the film discharged from the base falls naturally and the wire electrode is installed upstream from this direction, the film becomes Before landing on the surface of the cooling drum in the natural fall state, it is pressed against the cooling drum, so that the film is not stable and tends to vibrate and shake. Occurs.

Conversely, when the film is installed downstream of the radiation direction, the cooling roll side of the film is already cooled to some extent and has elasticity at the point closest to the wire electrode where a large pressing force acts. Air is caught between the drum and the drum, causing bubbles and surface defects.

Therefore, the optimum position of the wire electrode in the film feeding direction is at or immediately before the landing point on the surface of the cooling rotary drum in the state of natural fall without the action of external force such as electrostatic force of the film. In this case, stable landing and a good molding surface can be obtained by being installed at that position.

[0008]

However, this landing point is determined by the relationship between the plasticity of the discharged film and the rotation speed of the cooling rotary drum, and if there is a large change in the manufacturing conditions, the position of the discharge electrode is changed. There is a problem that the above-mentioned drawbacks and the like occur, and the adjustment takes time. Especially,
The change of the product brand is remarkable, and there has been a problem that it takes a lot of time to search for the optimum position of the discharge electrode.

On the other hand, a conventionally proposed automatic positioning method of a wire electrode is disclosed in JP-A-60-120.
No. 028, a method of detecting the maximum value of the current flowing through the wire electrode, a method of adjusting the current fluctuation width to be a minimum as disclosed in Japanese Patent Application Laid-Open No. 4-83627, or As disclosed in Japanese Unexamined Patent Publication No. Hei 4-77230, a method has been proposed in which vibration of a film extruded from a die is detected and adjusted to minimize the vibration.

However, if the desired change cannot be detected in any of the methods, the position of the discharge electrode operates excessively, and the discharge electrode comes into contact with the film extruded from the base or moves too much downstream. Due to the potential, operators had to monitor and adjust in the end, and complete automation was not possible.

An object of the present invention is to solve the above-mentioned problems and to provide a thermoplastic resin film manufacturing apparatus capable of automatically adjusting a discharge electrode, which has not been achieved in the prior art.

[0012]

The apparatus for producing a thermoplastic resin film according to the present invention comprises a die, a rotating drum for cooling, and a discharge electrode, and turns the molten thermoplastic resin into a film-like molten material with the die. The film is extruded onto a drum, and a linear discharge electrode provided in parallel with the rotation axis of the rotating drum applies an electrostatic charge to the film-like molten material. This is an apparatus for producing a thermoplastic resin film. And in the present invention,
Electrode position adjusting means for adjusting the position of the discharge electrode while maintaining the height of the discharge electrode from the surface of the rotating drum, and distance measurement for measuring the distance between the film-shaped melt before contact with the rotating drum and the discharge electrode Means for adjusting the electrode position based on the measured distance between the film-shaped melt and the discharge electrode.

[0013] The thermoplastic resin in the present invention generally includes all resins that can be formed into a film (also referred to as a sheet). Representative examples of these thermoplastic resins include polyesters such as polyethylene terephthalate and polyethylene naphthalate. Further, these copolymer mixtures may contain other additives and the like. Further, the film extruded from the die may be a single-layer film or a multilayer film in which the same or different resin layers are laminated in a plurality of layers.
The discharge electrode only needs to be made of a linear conductive material,
Usually, a wire electrode made of a metal wire is used.

As described above, a feature of the present invention resides in that the position of the discharge electrode is adjusted while detecting the distance between the film-like melt coming out of the die and the discharge electrode. Therefore,
The distance measuring means may be installed at any position as long as the distance between the film-like melt coming out of the die and the discharge electrode can be detected.

The distance measuring means measures the distance between the film-like melt and the discharge electrode. At this time, the position to be measured of the film-like melt is pushed out of the die and comes into contact with the rotating drum. Choose from a range up to. Here, in order to achieve the object of the present invention with higher productivity, as the measurement target position of the film-like melt, it is preferable to select a position where the height from the surface of the rotating drum is the same as the discharge electrode. preferable. That is, it is preferable that the distance measuring means measures the distance between the discharge electrode and the film-like melt whose height from the surface of the rotary drum is the same as the discharge electrode.

Any device can be used as a device for detecting the distance between the film coming out of the base and the discharge electrode, as long as it can make this possible. A measuring instrument for measuring, a laser displacement meter and the like can be mentioned, but a thing using a laser is preferable from the viewpoint of a measuring environment that is narrow and has a high temperature.

[0017]

FIG. 1 is an explanatory view of the structure of a film forming section of an apparatus for producing a thermoplastic resin film using the present invention. A film-like melt 4 made of a thermoplastic resin melt-extruded from a die 1 as a die is cooled and solidified on the surface of a cooling rotary drum 3. Here, the discharge electrode 2 is maintained at a high voltage by a high voltage generating mechanism (not shown). As a result, a high charge is induced in the film-like melt 4, and the film-like melt 4 is cooled by a counter electrode. To the rotating drum 3 for use.

In this embodiment, there is provided a position adjusting device 5 which can move the position of the discharge electrode 2 while maintaining the axis of the discharge electrode 2 in parallel with the rotating drum 3 for cooling and the interval between the rotating electrode and the cooling drum. Discharge electrodes 2 are provided. The position of the discharge electrode is adjusted by the signal of the position detector 12 of the film-like melt 4 and the signal of the distance detector 11 for calculating the distance between the discharge electrode 2 and the film-like melt 4 from the position of the discharge electrode 2, and the discharge is performed. The distance between the electrode 2 and the film-like melt 4 on the trajectory of the discharge electrode 2 is adjusted so that it does not become less than a certain value and does not become larger than a certain value.

A detailed description will be given of a case where a laser is used for the distance detecting device 11 for the film-like melt 4 with reference to FIG. The discharge electrode 2 is moved by the position adjusting device 5 so as to move along the trajectory indicated by the arrow 13 while maintaining the height from the surface of the cooling drum 3. The distance 14 between the discharge electrode 2 and the film-like melt 4 on the locus 13 can be easily calculated if the absolute position on the locus 13 of the film is known because the position of the discharge electrode 2 is known.

In this method, laser light 16 emitted from the He-Ne laser 6 is applied to the mirror 7 and the mirror 7 is rotated so that the reflected light scans the trajectory 13. The reflected light of the film-shaped melt 4 irradiated with the laser light 16 is detected by the light receiving element 8 composed of a photodiode and a lens. When the reflected light is detected, the signal is sent to the film position determination unit 15 via the amplifier 9. On the other hand, the mirror angle detector 10 detects the angle θ of the mirror 7 and sends the signal to the film position determiner 15. The film position determining means 15 determines the angle of the mirror 7 when the reflected light is detected from these signals, and thereby determines the position of the film-like melt 4 on the trajectory 13.

The distance detecting device 11 obtains a distance 14 between the position of the discharge electrode 2 from the position adjusting device 5 and the position of the film-like melt 4 obtained from the film position judging section 15. Based on the data of the distance 14, the position of the discharge electrode 2 is adjusted by the position adjusting device 5 without causing the discharge electrode 2 to be too close to the film-like melt 4 and erroneous operation of the direction for automatic adjustment.

[0022]

According to the present invention, the manpower required for adjusting the position of the discharge electrode can be reduced, and the automatic control of this position can be performed more stably.

[Brief description of the drawings]

FIG. 1 is a configuration of an apparatus for manufacturing a thermoplastic resin film.

FIG. 2 shows a configuration of a distance measuring means using a laser.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Die 2 Discharge electrode 3 Cooling rotating drum 4 Film 5 Position adjusting device 6 Laser light source 7 Mirror 8 Light receiving element 9 Amplifier 10 Mirror angle detecting unit 11 Distance detecting device 12 Film position detecting device 13 Locus of discharge electrode 14 Discharge electrode and film Distance on the trajectory of the discharge electrode 15 Film position determination unit 16 Laser beam

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[Procedure amendment]

[Submission date] July 15, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0002

[Correction method] Change

[Correction contents]

[0002]

2. Description of the Related Art A thermoplastic resin film (also referred to as a sheet) is formed by extruding a molten thermoplastic resin into a film from a slit-shaped die and extruding the film onto a cooling drum. Then, if necessary, processing such as stretching is also performed thereafter. At the time of this molding, the degree of adhesion of the film to the cooling drum is improved electrostatically by installing a wire electrode, which is a discharge electrode to which a high voltage is applied, at a predetermined position of the film information on the cooling drum. It is known that a good molding state can be obtained.

Claims (2)

[Claims] The present invention comprises a die, a rotating drum for cooling, and a discharge electrode. The thermoplastic resin in a molten state is formed into a film-like melt by the die and extruded onto the rotating drum, and is provided in parallel with the rotating shaft of the rotating drum. By a linear discharge electrode, an electrostatic charge is applied to the film-like melt, and the film-like melt is adhered to the rotating drum and solidified while being transferred to produce a thermoplastic resin film. While maintaining the height of the discharge electrode, an electrode position adjusting means for adjusting the position of the discharge electrode, and a distance measuring means for measuring the distance between the film-like melt and the discharge electrode before contacting the rotating drum, An apparatus for producing a thermoplastic resin film, wherein an electrode position adjusting means adjusts an electrode position based on the measured distance between the film-shaped melt and the discharge electrode. 2. A distance measuring means, comprising: a film-like melt whose height from the surface of the rotary drum is the same as the discharge electrode;
2. The method according to claim 1, wherein a distance from the discharge electrode is measured.
The apparatus for producing a thermoplastic resin film according to the above.