JP3702042B2 - Extrusion die - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an extrusion die applied to a film manufacturing apparatus, a sheet manufacturing apparatus or the like.
[0002]
[Prior art]
A conventional extrusion die will be described with reference to FIG. The molten resin 9 supplied by a conduit from an extruder (not shown) is extruded from the die through the manifold part a and the land part b which are flow paths in the die. The molten resin 9 extruded from the die is extended to a required thickness between the air gaps c. When the expanded molten resin 9 comes into contact with the cooling roll 8, the entrained air pressure e is generated by the entrained air d, and thus the molten resin 9 is prevented from adhering to the cooling roll 8.
[0003]
In the vicinity of the contact point of the molten resin 9 to the cooling roll 8, a pressing force f (air jet, electrostatic force, etc.) is applied to the molten resin 9 by the pressing device 10 so as to be brought into close contact therewith. After the molten resin 9 is brought into close contact with the cooling roll 8, it is cooled and solidified to obtain a sheet or film having a required shape.
[0004]
[Problems to be solved by the invention]
However, at the time of high speed molding, the entrainment air pressure e increases with the increase of the entrainment air d shown in FIG. For this reason, sufficient pressing force f cannot be obtained with the conventional pressing device 10, and problems such as generation of uneven cooling due to insufficient adhesion of the molten resin 9 to the cooling roll 8 and impaired smoothness of the sheet surface arise.
[0005]
The present invention provides an extrusion die capable of improving the adhesion of a molten resin to a cooling roll by eliminating air entrainment even during high-speed molding, and capable of forming a sheet having no cooling unevenness and good sheet surface smoothness. Is an issue.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem in an extrusion die for extruding a molten polymer material from a die and forming a sheet having a required shape with a cooling roll, the present invention has a die tip portion with a surface of the cooling roll. Pressure drop measured by the pressure gauge provided with a pressure gauge to measure the pressure loss between the die lip and the cooling roll. An extrusion die configured to control the gap of the die lip with respect to the cooling roll is provided.
[0007]
In the extrusion molding die according to the present invention, since the resin flow path is formed between the die lip surface and the cooling roll surface in this way, there is no air gap, and the molten resin 9 is generated by the increase of the entrainment air pressure generated during high-speed molding. Insufficient adhesion to the cooling roll 8 is eliminated.
[0008]
FIG. 2 shows the relationship between the pressure loss between the die lip and the cooling roll and the molding state when the resin flow path formed in the gap between the die lip and the cooling roll is changed. Under the positive pressure condition in which the pressure loss in the resin flow path formed between the die lip and the cooling roll is high, resin leakage to the seal portion becomes a problem.
[0009]
Further, when the pressure loss in the resin flow path between the die lip and the cooling roll is a negative pressure, peeling of the molten resin from the die lip surface becomes a problem. For this reason, the pressure loss in the resin flow path between the die lip and the cooling roll in the extrusion die according to the present invention needs to be at a level that can provide a pressing force (positive pressure side) that can eliminate the entrained air near zero. .
[0010]
In the die for extrusion molding according to the present invention, the die lip forming the resin flow path with the surface of the cooling roll is configured to be displaceable, and a pressure gauge is provided for measuring the pressure loss between the die lip and the cooling roll. The gap of the die lip with respect to the cooling roll can be adjusted based on the pressure loss measured by the pressure gauge . By comprising in this way, according to molding conditions, the resin flow path of the clearance gap between a die lip and a cooling roll can be set to an appropriate condition, and the said problem seen by the conventional die for extrusion molding can be eliminated.
[0011]
In the extrusion die according to the present invention, a pressure gauge for measuring the pressure loss between the die lip and the cooling roll is provided, and the gap between the die lip and the cooling roll is controlled based on the pressure loss measured by the pressure gauge. Therefore , it is possible to provide an apparatus capable of automatically controlling the gap between the die lip and the cooling roll to an appropriate value.
[0012]
In the conventional method shown in FIG. 3, the flow rate distribution in the die width direction is controlled by changing the flow channel thickness at the die exit portion by a plurality of flow rate adjusting bolts 11 provided in the die width direction. In the extrusion die according to the present invention, a mechanism for adjusting the flow rate distribution in the die width direction by changing the clearance of the flow path is added to the resin flow path upstream of the die lip surface, so that the upstream of the die lip surface. The flow rate distribution in the die width direction can be adjusted by manipulating the gap between the resin flow paths on the side.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the extrusion die according to the present invention will be described in detail based on the embodiment shown in FIG. In the following embodiments, the same reference numerals are given to the same components as those of the conventional apparatus shown in FIG. 3 for the sake of brevity, and redundant description thereof will be omitted.
[0014]
The extrusion molding die shown in FIG. 1 includes fixed blocks 1 and 2, choke bars 5, a plurality of flow rate adjusting bolts 3 provided in the die width direction, a variable block 6 and a variable block adjustment bolt 4 provided in the die width direction. Become. The fixed block 1 is provided with a pressure gauge 7.
[0015]
While extruding the molten resin 9 under required molding conditions, the pressure loss between the die lip g and the cooling roll 8 is measured by the pressure gauge 7 provided in the fixed block 1. And by the variable block adjusting bolt 4, the pressure loss between the die lip g and the cooling roll 8 gives a pressing force (positive pressure side) that can eliminate the entrained air in the vicinity of zero, and between the die lip g and the cooling roll 8. Set the gap.
[0016]
Under the set conditions, the choke bar 5 is operated by the flow rate adjusting bolt 3 to change the resin flow path gap to make the flow rate distribution in the die width direction uniform. The operation of the choke bar 5 and the variable block 6 can be performed both automatically and manually.
[0017]
【The invention's effect】
As described above in detail, in the die for extrusion molding according to the present invention, the die tip has a die lip that forms a resin flow path with the surface of the cooling roll, and the die lip is configured to be displaceable, A pressure gauge for measuring the pressure loss between the die lip and the cooling roll is provided, and the gap between the die lip and the cooling roll is controlled based on the pressure loss measured by the pressure gauge, and the present invention According to this extrusion molding die, stable sheet molding and film molding can be achieved by eliminating entrainment air, which has conventionally been a bottleneck in speeding up.
[0018]
Compared to conventional dies, the extrusion die of the present invention adjusts the gap between the die lip and the cooling roll , thereby improving the quality such as transparency of the product by improving the adhesion of the molten resin to the roll. Improvement and reduction of ear loss due to elimination of the air gap, improvement of instability such as draw resonance, and the like can be achieved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an extrusion die according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a pressure loss and a molding state between a die lip and a cooling roll in an extrusion die according to the present invention.
FIG. 3 is a cross-sectional view of a conventional extrusion die.
[Explanation of symbols]
1 fixed block 2 fixed block 3 flow rate adjusting bolt 4 variable block adjusting bolt 5 choke bar 6 variable block 7 pressure gauge 8 cooling roll 9 molten resin g die lip

Claims (2)

In an extrusion molding die for extruding a molten polymer material from a die and forming a sheet of a required shape with a cooling roll, a die lip that forms a resin flow path with the surface of the cooling roll is formed at the tip of the die. The die lip is configured to be displaceable, and a pressure gauge for measuring a pressure loss between the die lip and the cooling roll is provided, and the die lip of the die lip with respect to the cooling roll is based on the pressure loss measured by the pressure gauge. An extrusion die characterized in that the gap is controlled . The extrusion die according to claim 1, wherein a mechanism for adjusting a flow rate distribution in a die width direction is provided in the resin flow channel upstream of the die lip surface by changing a gap in the flow channel.

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