JPS60206615A - Die for controlling film thickness - Google Patents

Abstract

PURPOSE:To regulate precisely the thickness of an extruded film, by combining a heat bolt method by the thermal extension and contraction of a bolt with a lip heater method capable of changing the viscosity of a resin by the adjustment of the temperature of a lip. CONSTITUTION:A heater block 28 having a regulating bolt capable of being thermally extended and contracted by a heater 29 and a cooling apparatus 30 is attached to a die main body 35 via an insulating material 40, and a fixed lip 33 having a lip heater 34 is attached in opposite to a flexible lip 32. By thermally extending or contracting the adjusting bolt 31, a die outlet gap 41 defined between the flexible lip 32 and the fixed lip is regulated, and the viscosity of a melted resin is regulated by a lip heater 34. A film thickness can be precisely regulated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a die for controlling film thickness that can be applied to a die for unstretched films and sheets or biaxially stretched film frames.

Recently, product films such as biaxially stretched films are required to have higher and higher thickness accuracy in the 1 direction. In order to obtain a film of uniform thickness from a thermoplastic polymer, even if the opening of the die is made uniform throughout the gou, it does not necessarily result in a film of uniform thickness. Particularly in the case of biaxially stretched films, it is necessary to make the thickness of the biaxially stretched film uniform; rather, it is necessary to make the thickness of the biaxially stretched film uniform.
must have a specific pattern of thickness distribution.

Several methods for adjusting film thickness distribution have been proposed in the past. Broadly speaking, (1) a method of adjusting the gap in the opening of the die by rotating a bolt using a robot. (2) A method of adjusting the temperature of the bolt and adjusting the gap at the die opening by expanding and contracting the bolt (heat bolt method). (3) A method of adjusting the viscosity of the molten resin by changing the temperature of the goo opening (lip temperature adjustment method) has been proposed. However, none of these methods can be said to be perfect depending on the application. That is, (1)
However, when using low-viscosity resins such as polyester resins, there was a risk that the vibrations caused when the bolts were operated by robots could adversely affect film quality.

Regarding the method (2), Fig. 1 (U.S. Patent No. 39
40221), molten resin enters the die from the die inlet 12 and is discharged from the die outlet gap 14. During this process, the flexible bar 9 is deformed by the bolt 10 to adjust the gap 13. In addition, a voltage is applied to the heater 6 inserted in the heater block 5 to heat the heater 6, and at the same time, the refrigerant can be sent into the refrigerant passage 7.
By expanding and contracting the bolt 3 by heating and cooling the bolt 3 to deform the flexible knob 4 and adjusting the die exit gap 14, the die exit discharge flow rate is changed and the thickness is adjusted.

Further, in the figure, 1.2 is the die body, 11 is the fixed lip, and 8 is the heat insulation +J. Although the method shown in FIG. 1 is effective in finely adjusting the flexible lip 4 using the bolt 3, there is a limit to the amount of expansion and contraction, so it was not possible to adjust the entire thickness using this bolt alone. Therefore, one more adjustment point is required, and the flexible bar 9 is provided. However, it is dangerous to provide such a flexible bar 9 for resins such as polyester resins which tend to generate gel due to retention, and the die having the structure shown in FIG. 1 could not be used.

Next, regarding method (3), see Fig.
As shown in Japanese Patent No. 9050), by using a heater 18 capable of heating and cooling the die lip 17 and changing the temperature of the lip 17 to change the temperature of the molten resin,
A method has been proposed in which the flow rate of the resin at the lip outlet 19 is controlled in the middle direction by changing the viscosity. However, with this method, it was difficult to locally change the temperature due to heat conduction in the width direction.

Further, as shown in Fig. 3, a26 is provided in the width direction of the die,
A method has also been proposed (Japanese Patent Publication No. 56-3171) in which the effect of heat conduction is reduced by dividing the lane into a large number of lanes, but none of these methods can correct locally occurring thickness unevenness. However, it could not be said to be sufficient to meet the requirements for high thickness accuracy.

The present invention was proposed in order to solve the above-mentioned conventional drawbacks, and includes a thermoplastic resin film or a thermoplastic resin film.

In the die that adjusts the sheet thickness, advanced technology is achieved by installing a heat bolt method that utilizes the expansion and contraction of the bolt due to heating and cooling, and a lip heater that adjusts the lip temperature and changes the viscosity of the resin. It is an object of the present invention to provide a film thickness control die capable of manufacturing a film with a high degree of thickness accuracy in response to demands for thickness tolerance.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 4 shows an embodiment of the present invention, in which a flexible lip 32 is fixed to one side of a gooey body 35 with a bolt 37. Further, the flexible knob 32 is provided with an 8JIII adjustment bolt 31 that can be expanded and contracted by heating and cooling the heater block 28. The heater block 28 is heated by a heater 29 such as a heater, and a cooling medium is passed through the fluid passage 30. Furthermore, the heat insulating material 40 prevents the goo body 35 and flexible lip 32 from being affected.

On the other hand, on the other side of the die body 35, a fixed lip 33 heated by a lip 34 is fixed with a bolt 36, and the goo body 35 is heated to a constant temperature by heaters 38 and 39. Also, it is preferable that the pitch in the middle direction of adjustment pole 31 be as small as possible, but realistically it is 15~
It is provided with a 30mm pinch, and the lip heater 34
The pinch is preferably 20 to 4 Qmm.

Next, to explain the operation, the thermoplastic resin is generally melted by an extruder or the like (not shown), passes through a filter or a gear pump, enters the cocoon bold 27 of the die, is extruded from the lip part 38, and is cooled by a cooling roll (not shown) or the like. It is solidified and formed into films and sheets. The formed film or sheet is either slit at both sites and used as a film or sheet (non-stretched film), or it is then stretched in the direction of travel and used as a -axially stretched film. Moreover, after stretching in the direction of travel, the film is stretched in a direction perpendicular to the direction of travel and used as a so-called biaxially stretched film.

By the way, the above-mentioned unstretched film only needs to have a uniform thickness in the middle direction at the exit of the die, and a high-precision film (η) can be obtained relatively easily.

However, the biaxially stretched film is then stretched in the direction of travel and in the direction perpendicular to it, so if you try to make the thickness of the biaxially stretched film uniform, the film or sheet extruded from the die will have a It is no use forming sushi to have a uniform thickness in the middle direction; it is necessary to form it into a specific thickness pattern.

The present invention provides a fully automatic thickness-adjustable die, which is basically a combination of a finely adjustable heat bolt method and a large pattern adjustable knob heater method. The resin that enters the die manifold 27 is not necessarily a uniform resin; for example, the resin temperature is not ideally uniform, but has variations within a certain allowable range.

Furthermore, assuming that the gap between the lip portions 41 is set uniformly, the resin that has entered the die manifold 27 is distributed in the middle direction, and due to the pressure loss within the manifold, the resin enters the lip portions as it goes from the inlet to the end. The amount of resin extruded from 41 decreases, and the thickness becomes thinner. In order to compensate for this, a pattern with a somewhat uniform thickness can be obtained by setting the gap between the lips at the entrance to be as small as possible during assembly.

In such a corrected state, first, the voltage of the lip heater is adjusted so that a product close to the target thickness accuracy in the middle direction can be obtained.

However, as mentioned above, if a singular point occurs due to variations in the resin temperature or stretching and cannot be corrected using the lip heater alone, correction is made to the target thickness accuracy by adjusting the voltage of the heater 1-volt.

In addition, the thickness accuracy requirements for biaxially stretched polyester films used for applications such as magnetic tapes have become increasingly strict in recent years (width direction thickness accuracy 2%), and the present invention has an accuracy that fully satisfies these requirements. It has been found that the present invention can be obtained, and the present invention is useful for these applications. Further, although each control may be performed manually, it is preferable to perform feedback control using a computer.

[Brief explanation of the drawing]

1 and 2 are side sectional views showing different examples of a conventional die, FIG. 3 is a partial perspective view of a further different conventional die, and FIG. 4 is a diagram showing an embodiment of the present invention. FIG. 3 is a side cross-sectional view of the die. Explanation of the main parts of the figure 28- Heater block 29- Heater 31-8 Circumference adjustment bolt 32- Flexible lip 33- Fixing rib 34- Lip heater 35- Die body 36.37- Bolt Patent applicant Mitsubishi Heavy Industries, Ltd. Figure 1 Figure 2/'r Figure 3 Figure 4

Claims (1)

[Claims] The thickness of the thermoplastic resin film or sheet is KM [
Film thickness control features a heat bolt method that utilizes the expansion and contraction of the bolt due to heating and cooling, and a lip heater that changes the viscosity of the resin by adjusting the temperature of the knob. die.