JPS6315725A - Manufacture of thermoplastic resin film - Google Patents

Abstract

PURPOSE:To permit the stable molding of homogeneous films with uniform section, by a method wherein a heater, capable of setting a temperature profile different widthwisely, is provided near the lip of a die while the amount of resin, extruded out of the lip, is regulated widthwise. CONSTITUTION:A heater 9 for regulating biased thickness is provided widthwise near a die lip 3 and the heater 9 is connected to a controller 11 electrically while the controller 11 is connected electrically to a temperature sensor 10, such as an infrared ray sensor or the like for example, arranged near the die lip 3. Objective temperature profile is inputted into the controller 11 with respect to each blocks of the heater 9. The controller 11 conducts the heater 9 in accordance with said objective temperatures to set the temperature of the heater 9. When the thickness of a film is thin locally, the temperature setting of the heater 9, corresponding to the thin part, is increased to increase the temperature of that part. Then, the flow rate of resin in the die lip 3 near the heater is increased and, as a result, the thickness of the film is increased whereby the film, in which the difference of thickness is small, may be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention involves extruding a molten thermoplastic resin from a die onto a cooling roll surface to produce films (in the present invention, this includes not only films but also sheets). The present invention relates to a method for producing thermoplastic resin films that can stably form homogeneous films with little thickness deviation.

[Conventional technology]

Traditionally, T-
A method is known in which a molten thermoplastic resin is extruded into a film through a die, and then cooled and solidified using a cooling roll.

However, this method has the disadvantage that uneven thickness tends to occur in the width direction of the film because there is a difference in the flow rate of the melted resin per unit length in the width direction of the die.

Therefore, methods using a choker, a movable lip, and a flexible lip (mechanically bending the ring part to change the lip opening degree) are known as methods for reducing the thickness unevenness in the width direction of the film. ing.

In other words, it is a method to adjust the uneven thickness of the film (t-114) by changing the gap in the resin flow path near the die lip during film molding. In other words, the thickness unevenness adjustment accuracy is determined by the pitch and play of the screws, etc., so the accuracy is not fully satisfactory.

Another known technique is a method of mechanically changing the entire gap of the resin flow path by thermal expansion of the metal, but this method utilizes the expansion and contraction of the metal and the distortion of the lip. A sufficient effect was not obtained in terms of thickness unevenness adjustment accuracy.

[Problems to be Solved by the Invention] It is an object of the present invention to solve the above problems and to provide a heat treatment method that can stably produce homogeneous films with little thickness deviation with high thickness adjustment adjustment accuracy. An object of the present invention is to provide a method for producing plastic resin films.

[Means and effects for solving the problems] The present invention has the following features:
In a method of manufacturing films by extruding molten thermoplastic resin from a die onto the surface of a cooling roll, a heater that can set different temperature profiles in the middle direction is installed near the litz of the die, and the resin is extruded near the lip exit. It is characterized in that the amount of resin extruded from the lip is adjusted in the width direction using a temperature sensor that detects a temperature profile.

Hereinafter, the present invention will be described in detail with reference to the drawings.

In FIG. 1, a thermoplastic resin melt-kneaded in an extruder (not shown) flows into a die 2 through a joint 1,
It is extruded from the die lip 3 to the outside of the die, and is passed through the cooling roll 4.
5 and then taken as a film 6. A heater 8 is attached to the die 2 in order to keep the temperature of the entire die constant, and the heating temperature is detected with a thermocouple (not shown) or the like.
The temperature is adjusted by a temperature controller (not shown). 7 is a die rig adjustment bolt, by rotating it, the amount of resin is adjusted.
Roughly adjust the uneven thickness of the film. Furthermore, as is clear from FIG. 2, a heater 9 for adjusting thickness unevenness in the width direction is provided near the die lip f3, and the heater 9 is connected to the controller 1.
1&-, and a temperature sensor 10, such as an infrared sensor, disposed near the die ridge 3 is electrically connected to the controller 11.

It is preferable that the heater 9 adopts an electric heating method as a heat source and is divided into a plurality of blocks (for example, 18 blocks in the drawing) as shown in the figure, and the temperature can be set for each block.

A target temperature profile is input to the controller 11 for each block of the heater 9.

The controller 11 energizes the heater 9 according to the target temperature and sets the temperature. The energization method can be carried out using a triac or the like, and the amount of heat generated by the heater 90 is controlled by changing the voltage value or current value, or the amount of heat generated by the heater 9 is controlled by turning ON and OFF the energization. methods will be adopted. After the temperature of the heater 9 is set, the temperature of the molten resin extruded from the lip 3 changes according to the target temperature of each block of the heater 9. However, because the molten resin temperature profile often differs from the target temperature profile due to the outside temperature, mutual interference between blocks, etc., the controller 11 corrects the difference from the target profile after a certain period of time. In order to do so, a corrected temperature is set for the heater 9.

By repeating the above operations, the temperature of the molten resin will be close to the target profile, making it possible to control the temperature with high precision. For example, if the film is thin in some areas,
The temperature setting of the corresponding heater 9 is increased to raise the temperature. Then, the resin flow rate in the die lip 3 in the vicinity increases, the thickness of the film increases, the thickness deviation in the inside direction of the film decreases, and a film with less difference in thickness can be obtained.

In the present invention, the heater 9 for adjusting J thickness unevenness is provided over the entire die width in the drawing, but since the edge of the film is not substantially used as a product, it may be provided only in the middle of the die width. .

It is necessary for the heater 9 to have a block width of 50 mm or less, and it is particularly preferable that the heater 9 has a structure in which the temperature can be adjusted at 5 f1 or more and 300 m or less, and is divided into a plurality of blocks so as to have independent temperatures.

If the block width of the heater 9 exceeds 50 cm, the accuracy of adjusting the uneven thickness of the film is not sufficient.

The structure of the heater 9 uses electric heat as a heat source, and in order to maintain a uniform temperature within each block, the structural material is preferably a metal with good thermal conductivity, particularly aluminum. A typical example of the heater 9 is a known aluminum cast heater in which the heater is surrounded by aluminum having good thermal conductivity.

The distance from the die lip 3 at which the heater 9 is installed does not affect the film thickness unevenness adjustment accuracy and is a factor; if the distance is long, the thickness unevenness adjustment accuracy will decrease. In the present invention, the distance from the die lip 3 to the heater 9 is 20
The length is 0 meters or less, preferably 150 meters or less, and more preferably 5 meters or more and 100 meters. It does not matter if even a portion of the heater 9 falls within the above range, so even if the other end of the heater 9 exceeds 200 -, it is included in the present invention. Incidentally, some known techniques provide a lip heater or a cartridge heater in the die lip portion, but this is intended to keep the ring temperature constant and is essentially completely different from the present invention.

Furthermore, the thermoplastic resin used in the present invention may be any of those known for forming films. Typical examples include polyolefins such as polyethylene and polypropylene, and polyethylene terephthalate. polyester, polyvinyl such as polystyrene, polyamide such as nylon 66 or nylon 6,
There are polycars, etc.

Note that the die 2 used in the present invention may be used in combination with a choke bar, a movable lip, a flexible lip, etc. used in conventional thickness unevenness adjustment methods, and when used in combination, rough adjustment is performed using the conventional method, and fine adjustment is performed. It is preferable to use the method of the present invention.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Examples 1 to 4 and Comparative Examples 1 to 3 Films of polypropylene and low density r4e polyethylene were molded according to the steps shown in FIG. 1 under the conditions shown below. In addition, the die 20 base is a flexible type in both the example and the comparative example, with a lip width of 1500 m and a lip gear two! Temperature sensor 1 used in the example at 0.5 h
An infrared non-contact thermometer was used for the heater 9, and an electric cast aluminum heater was used for the heater 9.

Example-1 Molding conditions: extruder temperature 180°C to 240°C, joint temperature 240°C, die temperature 240°C 1st place (4th line temperature profile 240+4°C-〇Example-2 Example-1 and heater 90 division number Comparative Example-1 Molding conditions: Extruder temperature 180°C to 240°C, joint temperature 240°C, die temperature 24.0°C Examples 3 and 4 Molding conditions: Extruder temperature 180°C to 200°C ℃3 joint temperature 200℃, die temperature 200℃.

Resin temperature profile 200°C + 4°C - Comparative example-2 Molding conditions: Extruder temperature 180°C to 200°C, no-point temperature 00°C, die temperature 200'r 2 Comparative example-3 Molding conditions: Extruder temperature 180°C to 200°C 200℃, joint temperature 200℃, die temperature 200℃.

Lip heater 204°C [Effects of the invention] As is clear from the above, the present invention is effective in producing films by extruding a molten thermoplastic resin from a die onto a cooling surface.
A heater that can set different temperature profiles in the width direction is installed near the die glue lug, and a temperature sensor that detects the resin temperature profile near the lip exit is used to control the amount of resin extruded from the lip in the middle direction. Since the adjustment is made, it is possible to stably supply films with less uneven thickness under high thickness unevenness adjustment accuracy. Films formed in this manner can exhibit high commercial value when applied to post-processes such as lamination and coating methods.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a thermoplastic resin film manufacturing apparatus used in an embodiment of the present invention, and FIG. 2 is a block diagram of a die portion of the same apparatus. 2...Die, 3...Die lip, 4.5...Cooling roll, 8...Heater, 9...Heater for adjusting uneven thickness, 10...Temperature sensor, 11...Controller .

Claims (4)

[Claims] (1) In a method of manufacturing films by extruding molten thermoplastic resin from a die onto the surface of a cooling roll, a heater capable of setting different temperature profiles in the width direction is installed near the lip of the die, and the lip exit A method for producing thermoplastic resin films, characterized in that the amount of resin extruded from the lip is adjusted in the width direction using a temperature sensor that detects the resin temperature profile in the vicinity; (2) A method for producing thermoplastic resin films according to claim (1), characterized in that part or the whole of the heater is divided into pieces having a width of 50 mm or less along the die width direction; (3) A method for producing thermoplastic resin films according to claim (1) or (2), characterized in that the heater is installed within a distance of 200 mm from the lip outlet; (4) A method for producing thermoplastic resin films according to claims (1) to (3), characterized in that aluminum is used as a heat conductor of the heater;