JP2000062019A - Method and apparatus for preparing stretched film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stretched film with uniform physical properties by suppressing fluctuation of temp. just before stretching and suppressing fluctuation of stretching when a resin film is to be stretched in the width direction. SOLUTION: In a method and an apparatus for preparing a stretched film having a process for stretching in the width direction after a film is preheated, temp. in the width direction of a film is measured after preheating process and before stretching process, and the information is fed back to the preheating process while temp. distribution in the width direction of a film before stretching process is controlled within a definite range and the film is stretched, is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for producing a stretched film, and more particularly to a method for producing a stretched film capable of producing a stretched resin film having uniform physical properties by uniformly stretching in the width direction. Manufacturing equipment

[0002]

2. Description of the Related Art In the production of a stretched film, particularly a biaxially stretched resin film, a stretching process in the width direction is usually provided. In the widthwise stretching step, the film is usually heated (preheated) to a temperature necessary for stretching, and immediately after that, the film is stretched in the widthwise direction.

In such a width-direction stretching process,
If there is unevenness in the properties of the film immediately before stretching, especially uneven heating, uneven drawing occurs in the stretching process, which causes unevenness in the thickness and physical properties such as heat shrinkage and Young's modulus in the finally obtained film. . Further, if the thickness unevenness becomes too large, it may cause deterioration of the slitting property when slitting into a predetermined film product width and deterioration of the winding appearance of the wound product.

[0004]

The object of the present invention is to pay attention to such problems, and particularly when stretching the resin film in the width direction, the temperature unevenness immediately before the stretching is suppressed to a small level, and the stretching unevenness is suppressed to achieve uniform uniformity. An object of the present invention is to provide a method and an apparatus for producing a stretched film capable of obtaining a stretched film having various physical properties.

[0005]

In order to solve the above problems, a method for producing a stretched film of the present invention is a method for producing a stretched film, which comprises a step of preheating the film and then stretching in the width direction. It is characterized by measuring the temperature in the width direction of the film before the stretching step and feeding back the information to the preheating step to control the width direction temperature distribution of the film before the stretching step within a certain range. Consist of way.

[0006] In this method, it is preferable to control the temperature distribution in the width direction of the film before the stretching step to a temperature not lower than the glass transition point of the resin constituting the film and within the range of ± 5 ° C. If the temperature is less than the glass transition point, stretching is not performed properly, and if the temperature distribution exceeds the range of ± 5 ° C, it becomes difficult to suppress the unevenness of physical properties of the finally obtained film product.

Further, the stretched film manufacturing apparatus according to the present invention is a stretched film manufacturing apparatus having a film preheating means and a film width direction stretching means positioned downstream of the preheating means and the stretching means. Provided between, means for measuring the widthwise temperature distribution of the film, and based on information from the temperature distribution measuring means, so that the temperature of the film at the position of the temperature distribution measuring means is within a certain range, And a means for controlling heating in the preheating means.

In this apparatus, it is preferable that the temperature measuring unit is a unit capable of measuring the temperature distribution in the width direction of the film, and the heating control unit is a unit capable of controlling heating of each portion in the width direction of the film.

In such a method and an apparatus for producing a stretched film according to the present invention, the temperature distribution in the width direction of the film immediately before the stretching in the width direction is measured, and the temperature distribution is small enough to reach a state necessary for stretching. It is judged whether or not the temperature is suppressed, and if the temperature unevenness is too large, the heating in the preheating step is controlled and corrected by the control so that it can be suppressed to a predetermined small temperature unevenness, and then stretching is performed. It Therefore, in the film actually subjected to the stretching step, the temperature of the film is controlled to be within a predetermined small fixed range,
Stretching is performed uniformly, and unevenness in the physical properties of the finally obtained film can be suppressed to a small level.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described in detail below. The type of the stretched film targeted by the present invention is not particularly limited as long as it can be stretched in the width direction, but is typically a biaxially stretched resin film. The type of resin of the film is not particularly limited, and examples thereof include thermoplastic resin films such as polyester film, polypropylene film, polyamide film, nylon film and the like. Further, a film in which a coating agent is applied to these films is also included.

The form of the stretching process of the film is not particularly limited, but typically it can be constituted by the process schematically shown in FIG. 1, for example.

In FIG. 1, 1 is a die for discharging a molten resin 2 in a sheet form, 3 is a cooling roll, and a sheet 4 cooled, solidified and molded by the cooling roll 3 is a longitudinal stretching device 5 ( The film is preheated by a longitudinal stretching device), stretched at a predetermined ratio in the longitudinal direction, and cooled by a cooling roll 6 to obtain a uniaxially stretched film 7.

The uniaxially stretched film 7 is sent to a transverse stretching device 12 (width direction stretching device) which is, for example, a hot air oven (stenter).

The hot air oven of the transverse stretching device 12 is roughly divided into a preheating chamber 13, a stretching chamber 14, and a heat fixing and cooling chamber 15, and upper and lower hot air blowing nozzles 16a and 16b are provided in each chamber. , 17a, 17b, 18a,
Air (hot air) controlled to a predetermined temperature is blown from 18b to preheat, stretch in the width direction, heat set,
Cooling is performed. The biaxially stretched film 19 is wound up as a product roll or an intermediate product roll 20.

A thermometer 21 for measuring the temperature of the film is provided between the preheating step and the stretching step. As the thermometer 21, for example, a non-contact type radiation thermometer is used.

The temperature of the uniaxially stretched film 7 preheated by the nozzles 16a and 16b is measured by the thermometer 21 before the widthwise stretching, as shown in FIG. When measuring the film temperature, use a thermometer 2
1 may be fixed at a fixed position in the film width direction for measurement, but it is possible to measure the temperature distribution in the film width direction by swinging the thermometer or scanning in the film width direction. preferable. Further, a method of arranging a plurality of thermometers in the film width direction may be used.

By measuring the film temperature with the thermometer 21, whether or not the temperature of the film, especially the temperature distribution in the width direction, has reached the temperature required for stretching the film,
It is determined whether the temperature distribution is within a certain small range. That is, a detection value signal from the thermometer 21 is sent to the arithmetic unit 22 and compared with a preset temperature to determine whether or not the film temperature has reached a predetermined temperature, and the temperature distribution is within a preset range. It is determined whether or not it is in. Information based on this determination is the control device 23.
And the heating in the preheating step is controlled based on the output from the control device 23.

If the temperature measured by the thermometer 21 is lower than a predetermined value, the heating in the preheating step is strengthened so as to reach the predetermined value, and if the measured temperature is too high, the temperature becomes within the predetermined value or within the predetermined range. The heating is weakened. If the temperature distribution is not within the preset range, the heating in the preheating step is controlled in the width direction so that the temperature distribution is within the predetermined range.

Control of heating in this preheating step may be performed either by controlling the temperature of the hot air blown from the nozzles 16a, 16b or by controlling the amount of hot air blown.

When controlling the distribution of the temperature of the blowing hot air in the film width direction in the preheating step, for example, the heaters are arranged at predetermined intervals inside the nozzle or at the nozzle outlet to control the ON rate of each heater. Can be achieved by Further, in the case of controlling the distribution of the air volume of the blowing hot air in the film width direction, it can be achieved by, for example, arranging an air volume adjusting damper, a throttle, or the like inside the nozzle or the nozzle outlet and controlling the opening of these. .

As described above, by controlling the temperature and the amount of hot air in the preheating process on the basis of the film temperature information measured by the thermometer 21, the film temperature at the position of the thermometer 21 can be set to a desired temperature, or even a desired temperature. It is possible to control the temperature distribution in the width direction, and the film can be uniformly heated (preheated) in the width direction and then sent to the stretching step.
As a result, the stretching is carried out uniformly, and the physical properties of the stretched film are made uniform especially in the width direction.

[0022]

EXAMPLES The present invention will be described below based on examples. Example 1 Polyethylene terephthalate containing 2% by weight of silica was melt extruded at 280 ° C. and discharged from a T die, and a casting speed was 50 m / by a static drum cast method by a cooling drum.
Cast in minutes, this sheet is 120 ℃ without preheating control
And was stretched 4 times in the longitudinal direction. This uniaxially stretched film was fed into a stenter, and the temperature distribution in the width direction of the film was controlled to 110 ° C. ± 3 ° C. in a preheating chamber in the stenter, and after heating, the film was stretched 3.8 times in the width direction and subsequently 230 ° C.
Was subjected to 4% relaxation treatment to obtain a biaxially stretched film having a film thickness of 4.5 μm. The thickness unevenness in the longitudinal direction of the obtained biaxially stretched film is 5.5%, and the thickness unevenness in the width direction is 3.
It was 0%, and the slitability and the winding shape were good. The heat shrinkage unevenness was 9% and the Young's modulus unevenness was 13%.

In controlling the temperature distribution in the width direction of the preheating film, the ON rate of the heaters arranged at 50 mm intervals inside the hot air blowing nozzle was changed to dynamically change the temperature of the blowing hot air. At this time, the thermometer used for measuring the temperature distribution was a radiation thermometer IT-2 manufactured by KEYENCE CORPORATION,
The emissivity was set to 0.95.

Example 2 The film forming conditions were the same as in Example 1, and the temperature distribution was controlled to 110 ° C. ± 4 ° C. by the method of changing the air flow rate in the widthwise temperature distribution control. The thickness unevenness in the longitudinal direction was 7.0% and the thickness unevenness in the width direction was 3.0%, and the slitability and the winding shape were good. The heat shrinkage unevenness was 10% and the Young's modulus unevenness was 15%.
In addition, to change the air flow, 1 at the nozzle outlet in the nozzle width direction.
Shutters were arranged at 0 cm intervals, and the shutter intervals were dynamically changed based on information from a thermometer.

Example 3 Polyethylene terephthalate containing 2% by weight of silica was melt extruded at 280 ° C. and discharged from a T die, and a casting speed of 40 m / was applied by a static drum cast method using a cooling drum.
Min cast, this sheet is 110 ℃ without preheating control
And was stretched 4 times in the longitudinal direction. This uniaxially stretched film was fed into a stenter, and the widthwise temperature distribution of the film was controlled to 90 ° C. ± 3 ° C. in a preheating chamber in the stenter, and after heating, the film was stretched 3.5 times in the width direction and then 225 ° C. Was subjected to a 5% relaxation treatment to obtain a biaxially stretched film having a film thickness of 12 μm. The thickness unevenness in the longitudinal direction of the obtained biaxially stretched film is 6.0%, and the thickness unevenness in the width direction is 2.5%.
The slitability and winding appearance were good. Also,
The heat shrinkage unevenness was 9% and the Young's modulus unevenness was 13%.

In order to control the temperature distribution in the width direction of the preheating film, the ON rate of the heaters arranged at 50 mm intervals inside the hot air blowing nozzle was changed to dynamically change the temperature of the blowing hot air. At this time, the thermometer used for measuring the temperature distribution was a radiation thermometer IT-2 manufactured by KEYENCE CORPORATION,
The emissivity was set to 0.95.

Comparative Example 1 The thickness unevenness in the longitudinal direction of the film obtained without controlling the temperature distribution under the conditions of Example 1 was 8.5%, the thickness unevenness in the width direction was 5.0%, and the heat shrinkage occurred. The unevenness was 11% and the Young's unevenness was 17%.

Comparative Example 2 The thickness unevenness in the longitudinal direction of the film obtained without controlling the temperature distribution under the conditions of Example 3 was 8.0%, the thickness unevenness in the width direction was 4.0%, and the heat shrinkage occurred. The unevenness was 12% and the Young's unevenness was 17%.

[0029]

As described above, according to the method and apparatus for producing a stretched film of the present invention, the film temperature before the widthwise stretching step can be measured and the information can be fed back to the heating control in the preheating step. As a result, the film temperature immediately before the stretching step can be controlled to the optimum temperature and temperature distribution state at all times, the stretching can be performed uniformly, and the unevenness of the physical properties of the finally obtained film can be reduced. Further, as a result of uniform stretching, it is possible to reduce process troubles such as breakage.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a resin film manufacturing apparatus according to an embodiment of the present invention.

FIG. 2 is a partial schematic configuration diagram of the apparatus of FIG.

[Explanation of symbols]

1 mouthpiece 2 molten resin 3 cooling rolls 4 seats 5 Vertical stretching device 7 Uniaxially stretched film 12 Horizontal stretching device (hot air oven) 13 Preheating room 14 Drawing room 15 Heat fixing and cooling chamber 16a, 16b Hot air blowing nozzle 19 Biaxially stretched film 21 Thermometer 22 Arithmetic device 23 Control device

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kimio Sato             Gifu Prefecture Kobe Town, Anpachi-gun               Gifu factory of Toray Industries, Inc. F-term (reference) 4F210 AA24 AE01 AG01 AP05 AQ01                       AR06 QA02 QA03 QC06 QD25                       QD32 QD34 QG01 QG18 QL16                       QL17 QW12

Claims (10)

[Claims] 1. A method for producing a stretched film having a step of preheating a film and then stretching it in the width direction, measuring the temperature in the width direction of the film after the preheating step and before the stretching step, and feeding back the information to the preheating step. A method for producing a stretched film, which comprises stretching the film while controlling the widthwise temperature distribution of the film before the stretching step within a certain range. 2. The stretched film according to claim 1, wherein the temperature distribution in the width direction of the film before the stretching step is controlled to be equal to or higher than the glass transition point of the resin constituting the film and within a range of ± 5 ° C. Manufacturing method. 3. The method for producing a stretched film according to claim 1, wherein a non-contact radiation thermometer is used as a thermometer for measuring the film temperature. 4. A film is preheated by blowing hot air, the temperature distribution in the width direction of the film before the stretching step is measured, and the temperature distribution in the width direction of the blowing hot air is controlled based on the temperature data so that the temperature before the stretching step is increased. The method for producing a stretched film according to any one of claims 1 to 3, wherein the temperature distribution in the width direction of the film is controlled to fall within the certain range. 5. The film is preheated by blowing hot air, the temperature distribution in the width direction of the film before the stretching step is measured, and the air flow distribution in the width direction of the blowing hot air is controlled based on the temperature data. The method for producing a stretched film according to any one of claims 1 to 3, wherein the temperature distribution in the width direction of the film is controlled to fall within the certain range. 6. The method for producing a stretched film according to claim 1, wherein the film is a thermoplastic resin film. 7. An apparatus for producing a stretched film, comprising a film preheating means and a film widthwise stretching means located downstream thereof, the film widthwise temperature being provided between the preheating means and the stretching means. A means for measuring the distribution and a means for controlling the heating in the preheating means based on the information from the temperature distribution measuring means so that the temperature of the film at the position of the temperature distribution measuring means falls within a certain range. An apparatus for producing a stretched film, characterized in that 8. The apparatus for producing a stretched film according to claim 7, wherein the means for measuring the temperature distribution in the width direction of the film comprises a non-contact radiation thermometer. 9. The film preheating means comprises means for blowing hot air, and the means for controlling heating in the preheating means comprises means for controlling temperature distribution in the film width direction of the blowing hot air. Device for producing stretched film. 10. The film preheating means comprises means for blowing hot air, and the means for controlling heating in the preheating means comprises means for controlling the film width direction air volume distribution of the blowing hot air. Device for producing stretched film.