JPS6250288B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an adapter that connects a synthetic resin extruder (hereinafter simply referred to as an extruder) and a die that extrude synthetic resin in different directions to change the flow direction of the synthetic resin.

As shown in FIG. 1, a resin flow path 101 of a commonly used extruder adapter 106 is gradually narrowed toward a die 102 and bent at right angles. In the case of such a resin flow path 101, uneven thickness occurs in the film 103 drawn out from the die 102. This phenomenon occurs even when a rotary or oscillating die is used, and cannot be prevented even in blow molding. This is die 102 or extruder 1
This is not due to the defect 04, but is caused by the unevenness of the amount of molten resin in the bent portion A of the resin flow path 101. In other words, since the molten resin extruded by the screw 105 of the extruder 104 changes the flow direction while being pressed against the front surface at the bent portion, the flow path portion 101
Areas with a coarse amount of resin or areas with a dense amount of resin occur near the walls. And this is die 10
Even in case 2, the problem is not solved and the amount of extruded resin becomes locally uneven.

An object of the present invention is to provide an adapter for a synthetic resin extruder that can prevent the occurrence of uneven resin amounts. , forming two or more resin flow channels that change the flow direction of the synthetic resin, and forming a symmetrical resin outlet chamber directly connected to the die, and merging the plurality of resin flow channels into the resin outlet chamber. It is characterized by

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be explained in detail below based on an embodiment shown in the drawings. Note that this embodiment is applied to an inflation device.

The adapter 6 connects the die 2 and the extruder 4, and is attached to the front end surface of the extruder barrel 7.
Place die 2 above. The adapter 6 is provided with two or more resin channels 1 for guiding the molten resin extruded from the extruder 4 to the die 2. The resin inlet chamber 8 and the extruder barrel 7 are not directly connected, but communicated through a screen pack 9 and a breaker plate 10. However, as shown in FIG. 3, the screen pack 9 may be placed directly in the resin inlet chamber 8 without using the breaker plate 10. On the other hand, a die 2 is screwed into the resin outlet chamber 11 side. This resin outlet chamber 11
is a part where the molten resin that has passed through each resin flow path 1 joins, and has a symmetrical shape in order to force the resin into the die 2 in a uniform state.

With the above structure, the molten resin flows as follows. First, the molten resin in the extruder barrel 7, which is kept at a constant temperature by the heating/cooling device, is pushed into the adapter 6 side while being kneaded by the screw 5. The molten resin passes between the screen pack 9 and the breaker plate 10, flows into the resin inlet chamber 8 of the adapter 6, and then further divides into resin flow paths 1 and heads toward the die 2. The synthetic resin flowing in each resin flow path 1 has a flow path bent portion A.
As a result, uneven resin amounts occur at different locations, but the molten resin that merges in the resin outlet chamber 11 rarely has uneven resin amounts that are accompanied by uneven thickness of the film. Although the amount of resin is uneven in each resin flow path 1, it is dispersed throughout, so in the merged state, small uneven spots unevenly distributed throughout the resin flow path do not pose a problem. In other words, if there is a large uneven part locally as in the conventional case, the amount of molten resin will become uneven even when the flow is divided or ejected in the die 2, causing uneven thickness. As long as there are uneven parts, there is no effect on local thickness unevenness.

This is demonstrated by the experimental results shown in FIGS. 4a and 4b. The experimental results shown in Figure 4a were obtained using the conventional adapter shown in Figure 1.Extruder: 50mmExtruder die: Circular dieResin: Low density polyethyleneExtrusion rate: 35Kg/h Local thickness unevenness occurs at point B. Moreover, the overall thickness deviation is +4 microns and -6.5 microns for a film thickness of 60 microns.

On the other hand, the adapter using the adapter 6 of the present invention shown in FIG. 4b did not exhibit any noticeable uneven thickness. In other words, if the extruder, die, and resin are used under the same conditions and the extrusion rate is 46.2 kg/h, the overall thickness deviation is
+4 microns for a film thickness of 60 microns, -
It is 2 microns. However, the resin flow path is φ6mm x 37
It is individual.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional side view of an example of a conventional adapter for a synthetic resin extruder. FIG. 2 is a partially sectional side view showing an embodiment of the adapter for a synthetic resin extruder of the present invention, and FIG. 3 is a central vertical sectional side view illustrating the state of connection between the extruder and the adapter.
Figure 4a is a thickness unevenness chart showing the thickness unevenness test results when using the conventional adapter shown in Figure 1.
FIG. b is a thickness unevenness chart showing the results of a thickness unevenness test when using the adapter of the present invention. In the drawing, 1 is a resin flow path, 2 is a die, 3 is a film, 4 is an extruder, 6 is an adapter, 8 is a resin inlet chamber, 11 is a resin outlet chamber, A is a bent part of the resin flow path, and B is a local part. This is a spot with uneven thickness.

Claims (1)

[Claims] 1. In an adapter that connects an extruder and a die that extrude synthetic resin in different directions, two or more resin channels are formed to change the flow direction of the synthetic resin, and a symmetrical resin outlet chamber is formed that is directly connected to the die, An adapter for a synthetic resin extruder, characterized in that the plurality of resin channels are merged into the resin outlet chamber.