JPH065146Y2 - T-die for plastic sheet molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention belongs] The present invention relates to a flexible lip type (also referred to as a bending lip type) of a plastic molding T die.

[Prior Art] An example of a conventional flexible lip type T die for molding a plastic sheet or film (hereinafter, referred to as a sheet) will be described with reference to FIGS. 3 and 4. The lower left side of the die body 11 is formed as a fixed lip 12 and the upper left side is formed as a flexible lip 13 and is connected to the body side of the die body 11 by a thin neck 14. Molten resin (not shown) enters from the right side of the die body 11, passes from the manifold 15 to the flow path 16, and is molded into a sheet (not shown) from the outlets of the fixed lip 12 and the flexible lip 13. At this time, the flexible lip 13 is attached to the die bolt 17 to determine the thickness of the sheet.
The position is adjusted by. Although this adjustment is shown only when it is manual, it may be electric or automatic due to thermal displacement, and although there are multiple die bolts 17, only one is shown.

Side plates 18 are attached to both sides (in FIG. 3) of the die body 11 by bolts (not shown),
As a result, a contact pressure is generated between the end surface of the fixed lip 12, the end surface of the flexible lip 13 and the end surface of the neck 14. In addition, fixed lip 12 and flexible lip 13
A seal plate 19 is provided at a portion contacting with a narrow width (height direction) interval including and, and the molten resin leaks from the side surface of the die body 11 by pressing the seal plate 19 via the seal plate holding screw 20. Is preventing. A soft metal is preferably provided on the die body 11 side of the seal plate 19.

In such a configuration, the side plate 18 and the seal plate 19 generate contact surface loads, that is, frictional resistance forces as Q ₁ and Q ₂ that try to prevent the movement of the end surface of the flexible lip 13. Flexible lip 13
Since the end faces are required to be deformed more than the central portion due to the following (1) and (2), the flexible lip 13 is bent along with the operation of the die bolt 17, and as a result, it is shown by an arrow Q ₁ in FIG. The upper end face is likely to bite into the side plate 18, and a large contact load exceeding the contact pressure described above is generated. Therefore, the flexible lip 13
The friction resistance when moving is large.

(1) A so-called neck-in occurs at the end of the sheet formed by the T-die, and the sheet thickness at that end becomes thick due to the neck-in. To correct this, deform the flexible lip 13 by a considerable amount. I have to.

(2) In the case of a biaxially stretched raw sheet, it may be necessary to form the sheet end portion into a special pattern. In this case as well, the flexible lip 13 must be deformed by a considerable amount.

Focusing on this problem, the inventors of the present invention comparatively measured the displacement characteristics of the flexible lip of the conventional T die with and without the side plate. found. The fifth
The figure shows the displacement pattern of the flexible lip 13 when the first die bolt 17 is operated from the side plate 18, and FIG. 6 shows the displacement pattern of the flexible lip 13 when the second die bolt 17 from the side plate 18 is operated. Shows. Die bolt 1 in both figures
The load of 7 was 400 kg, which was measured by a load cell. The ◯ mark indicates that there is no side plate 18 ●
The mark indicates the case where the side plate 18 is provided, and each curve is an analysis value by the finite element method.

Due to the large friction in the presence of the side plate, there is the following problem.

(1) Manual operation is difficult. In particular, it is not possible to modify the profile as much as a double-sided die bolt.

(2) Automatic type In particular, the so-called thermal displacement type automatic T-die, which has a restriction on the amount of operation, is similar to the above (1).

[Object of the Invention] The present invention has been made from such a point of view, and its object is to reduce the deformation of the flexible lip, especially at the end, by reducing the contact surface load, that is, the frictional resistance force, whether manual or automatic. Easy plastic molding T
To provide the die.

As a result of pursuing a means for reducing the contact surface load in order to achieve the above-mentioned object, the following idea has been reached.

(1) Although it is difficult to estimate the contact surface load Q ₁ , it is clear that the contact surface width y (see FIG. 3) is related and the larger the contact surface width y is, the more disadvantageous the contact surface load is. Therefore, it is necessary to reduce y.

(2) Considering the distribution of resin pressure that causes leakage, the diagram shown in the lower part of FIG. 4 is obtained. As a result, the flexible lip is clearly more advantageous at low pressure than the neck. Therefore, it is considered that the width v of the contact portion for sealing the end surface of the flexible lip need not be larger than the neck portion.

(3) In order to prevent leakage of the molten resin, it is important that the sealing surfaces of the die body 11 and the seal plate 19 are in close contact with the die body 11, but the target is a high-viscosity molten polymer. Considering this, it is not necessary to increase the contact surface load.

[Points of the Invention] The T-die for molding a plastic sheet of the present invention includes a fixed lip, a flexible lip that adjusts a gap between the fixed lip and a resin flow path, and a resin from the resin flow path to a side surface of the die. In a plastic sheet molding T-die comprising a side plate provided on the side end surface of the die body for preventing the leakage of water, the side end surface of the flexible lip contacting the side plate is a surface substantially parallel to the resin flow path on the side surface of the die. It is characterized by the fact that part of it is retained and the other is slightly removed.

[Embodiment of the Invention] Referring to FIGS. 1 and 2 showing an embodiment of the present invention. The same members as those shown in FIGS. 3 and 4 which are conventional examples are designated by the same reference numerals, detailed description thereof will be omitted, and different portions will be described. On the upper side of the die body 26, that is, on the side of the flexible lip 27, the contact surface formed between the end surface of the flexible lip 27 and the seal plate 19 is in contact with the seal plate 19 below the upper surface of the neck 28 along the flow path. By removing about 1 mm as the distance C from the end surface above the upper surface of 28, the seal plate 1
9 and the side plate 18 are separated.

As a result of such a configuration, among the contact surface loads generated due to the bending of the end surface of the flexible lip 27, Q ₁ is eliminated and only Q ₂ is left, so that the contact surface load is greatly reduced. Therefore, the frictional resistance force at the end face of the flexible lip was greatly reduced as compared with the conventional example. However, even if the contact surface load is reduced, there is no problem with respect to leakage of the molten resin because the molten resin has a high viscosity.

In the embodiment described above, the width of the effective contact portion at the end of the flexible lip 27 is the same as the width of the neck portion 28, but the width is not limited to this and the width thereof is not limited.
The width may be slightly wider or narrower than the width of the part, and includes the case of decreasing the width toward the tip.

[Advantages of the Invention] As described above, in the T die for molding a plastic sheet of the present invention, the side end surface of the flexible lip that comes into contact with the side plate leaves a part of the surface substantially parallel to the resin flow path on the side surface of the die. Has slightly removed the face. As a result, the frictional resistance when moving the flexible lip was reduced, and the operability of the die bolt was greatly improved. And since the effective displacement amount of the flexible lip end can be made large, it becomes easy to correct the thickness of the end part of the sheet caused by neck-in and to finely adjust the edge profile of the original sheet for biaxially stretched film. Particularly, in the case of an automatic die, the present invention has many advantages such as precise control becomes possible.

[Brief description of drawings]

1 and 2 show an embodiment of the present invention. FIG. 1 is a front view of an essential part, FIG. 2 is a side view of an essential part with a side plate removed, and FIGS. 3 and 4 are conventional examples. FIG. 3 is a front view of a main part, FIG. 4 is a side view with a side plate removed from above, and below is a diagram showing the distribution of resin pressure, and FIGS. 5 and 6 operate die bolts in different states. It is a diagram which shows the displacement pattern of a flexible lip when it does. 17 ... Die bolt, 18 ... Side plate, 27 ...
… Flexible lip.

Claims (1)

[Scope of utility model registration request] 1. A fixed lip, a flexible lip for adjusting a gap between the fixed lip and a resin flow path, and a die body for preventing resin from leaking from the resin flow path to a side surface of the die. In a plastic sheet molding T-die including side plates provided on side end faces, a side end face of a flexible lip contacting the side plate leaves a part of a face substantially parallel to the resin flow path on the side face of the die, and the other face. The T die for plastic sheet molding that has been slightly removed.