JPH06860A - T dice - Google Patents

Abstract

(57) [Summary] [Object] To provide a T-die having a structure capable of easily and quickly controlling the temperature of a manifold and capable of stably obtaining a sheet with a small thickness difference in the width direction from the start of operation. A straight pipe portion 9 communicating with a heating portion of an extruder and a branch pipe 10 branched from the straight pipe portion 9 so as to form a substantially T-shape.
A choke bar 12 and a lip bar for adjusting the thickness of the extruded product are provided below the manifold consisting of. In the upper part of the branch pipe 10, a plurality of heating elements 17 are arranged close to the branch tube 10 and the distance between each heating element 17 and the branch tube 10 is set to the branch tube 10.
They are arranged so as to be substantially equal in the longitudinal direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved structure of a T-die used for extruding thin products such as sheets and films in an extruder for extruding a thermoplastic resin.

[0002]

2. Description of the Related Art As an extruder equipped with a T-die, there is, for example, a structure as shown in FIG. In the figure, 1 is a hopper for charging resin powder or the like, 2 is an extrusion mechanism such as ram extrusion or screw extrusion equipped with a heating device, 3 is a drive mechanism connected to the extrusion mechanism 2, and the extrusion mechanism 2 is an adapter 4
It is connected to the T-die 5 via. A chill roll unit 6 is a resin sheet 7 extruded from a T-die.
Is first passed through a pair of cooling rolls R ₁ and R ₂ in a substantially S-shape to cool both the front and back surfaces of the sheet 7 in the same manner, and then wound through a plurality of subsequent rolls (R _{3 to} R ₆ etc.) and wound. It is taken up by a take-up device (not shown). A sheet thickness control mechanism 8 controls the sheet thickness, and can control the opening and closing of a lip bar described later so that the sheet thickness falls within a predetermined range.

FIG. 4 is a side sectional view of the T-die 5, and FIG.
5 is a sectional view taken along line VV of FIG. As shown in FIG. 5, the T-die is divided into two parts on the left and right (divided pieces 5a and 5b), and the left divided piece 5b is divided into a triangular cross section at the lower part (divided piece 5c). That is, the T-die 5 has three divided pieces 5.
It consists of a, 5b and 5c. Then, the T having such a configuration
The solid portion of the die is hollowed out, and branch pipes 10 and 10 are formed in a substantially T-shape with respect to the straight pipe portion 9 communicating with the heating portion of the extruder, and the lower portion of the branch pipe 10 communicates with the slit 11. .
Below the branch pipe 10, a choke bar 12 and a lip bar 13 for adjusting the sheet thickness are provided. The lip bar means the lip (lips) of the lower end of the divided piece 5a. The choke bar 12 and the lip bar 13 are, as shown in FIG.
4 and the lip bolt 15 are integrally connected. A plurality of choke bolts 14 are attached in the T-die width direction as shown in FIG. 4, and although not shown in the figure, a plurality of choke bolts 14 are also attached in the T-die width direction. There is. Therefore, by moving the choke bolt 14 and the lip bolt 15 in the direction of the arrow, the gap between the slits 11 is slightly changed and the resin sheet extruded from the lower end opening 16 of the slit 11 in the width direction (the direction perpendicular to the paper surface of FIG. 3). ) Can be adjusted. Reference numeral 17 denotes a heating element, and a plurality of heating elements are arranged in two rows above the branch pipe 10 at substantially equal intervals. 18 is a temperature sensor.

By the way, as shown in FIG. 4, since the branch pipe 10 is formed so as to be slightly inclined downward so that the material can easily flow, the branch pipes 10 are separated from each other. The distance gradually increases as the distance from the straight pipe portion 9 increases, and the branch pipe 10 has a structure in which it is difficult to uniformly heat the branch pipe 10 in the longitudinal direction. Therefore, it takes some time (about 30 to 60 minutes) from the start of operation of the apparatus until the material stably flows from the straight pipe portion 9 in the manifold to the slit 11 via the branch pipe 10, and during that time. The widthwise thickness of the sheet extruded from the T-die constantly changes.
That is, the sheet thickness at the center is thin immediately after the start of operation of the extruder, and until the die temperature stabilizes, the sheet pressure at the center is due to the relationship of the pressure distribution inside the manifold that the end pressure is slightly lower than the center. There is a tendency that the thickness tends to be slightly thick, and the choke bolt 14 and the lip bolt 15 must be constantly adjusted in order to keep the width-direction sheet thickness constant.

The present invention has been made in view of the above problems of the prior art, and its object is to provide a structure in which the temperature of the manifold can be easily and quickly controlled, and the width of the manifold from the start of operation can be increased. An object of the present invention is to provide a T-die that can stably obtain a sheet with a small difference in thickness between directions.

[0006]

In order to achieve the above object, the gist of the present invention is to provide a straight pipe portion communicating with the heating portion of an extruder and a straight pipe portion branched to form a substantially T-shape. In a T-die having a manifold composed of a branch pipe, a choke bar and a lip bar for adjusting the thickness of an extruded product below the manifold, and a plurality of heating elements arranged on the upper part of the branch tube, the heating element is branched. In the T-die, the heating element and the branch pipe are arranged so as to be close to each other and the distance between them is substantially equal in the longitudinal direction of the branch pipe.

[0007]

The distance between the plurality of heating elements arranged above the branch tube and the branch tube is substantially equal in the longitudinal direction of the branch tube, and the heating elements are close to the branch tube. The temperature of the branch pipe can be easily adjusted by controlling. Therefore, the material flow downward from the branch pipe becomes substantially uniform in the longitudinal direction of the branch pipe, and a sheet having a small thickness difference can be stably obtained.

[0008]

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a side sectional view of the T-die of the present invention, and FIG. 2 is II- of FIG.
It is a II sectional view. As shown in FIG. 1, each heating element 17 is arranged close to the branch pipe 10 and is arranged such that the distance from the branch pipe 10 is substantially equal in the branch pipe longitudinal direction (corresponding to the seat width direction). 19 is the wiring 2 of the heating element 17
It is a heat insulating material that covers 0.

Next, the sheet extruding operation by the T die having such a structure will be described with reference to FIGS. 1, 2 and 3. First, before the extrusion work of the extruder, a plurality of heating elements 17 are provided.
And is preheated until the temperature of the entire die reaches a temperature almost suitable for the extrusion operation of the resin sheet. At this time, the heating section in the extrusion mechanism 2 is also preheated to an appropriate temperature.

Then, a resin material having a predetermined composition is put into the extruder from the hopper 1, and the resin viscous body having an appropriate viscosity by being heated and mixed in the extrusion mechanism 2 is supplied to the T die 5. The resin viscous material passes through the straight pipe portion 9 of the manifold, the branch pipe 10, the slit 11, and the lower opening 1
It is discharged from 6. During this extrusion operation, while the temperature in the vicinity of the branch pipe 10 is detected by the plurality of temperature sensors 18 in order to control the sheet thickness, the sheet thickness control mechanism 8 controls the energization amount of each heating element 17, so that the opening 16
The widthwise thickness of the sheets discharged from the sheet is substantially the same. Therefore, the yield loss of the sheet due to the uneven thickness at the start of operation is small. Thus, the sheet 7 having a small thickness difference in the width direction is cooled by the rolls R ₁ and R ₂ , and then the rolls R ₃ and R ₄ ,
It is taken up by a take-up device via R ₅ and R ₆ . Next, Table 1 below shows main points that the extrusion work by the T-die of the present invention is superior to the extrusion work by the conventional T-die.

[0011]

[Table 1]

As is clear from Table 1, in the T-die of the present invention, since the heating element is installed close to the branch pipe, the die temperature setup time is shortened to about 60% of the conventional one, and Since the temperature in the longitudinal direction of the branch pipe can be delicately controlled,
It is possible to obtain a sheet having a small thickness difference in the width direction from the start of operation, and therefore, it is possible to stably obtain a sheet having a substantially constant thickness with little yield loss.

According to the present invention, the temperature of the manifold can be skillfully controlled in this way to adjust the sheet thickness, so that it is not necessary to use lip bolts or choke bolts, and the number of times these bolts are replaced is reduced. Decrease. As a result, equipment downtime for setup change is reduced.

[0014]

Since the T-die according to the present invention is constructed as described above, it has the following effects. The temperature of the die can be raised in a short time. Since a sheet having a small thickness difference in the width direction can be obtained from the start of operation of the apparatus, the yield is improved. It is possible to stably obtain a sheet having a substantially constant thickness in the width direction and the longitudinal direction from the start of operation.

As the number of bolt replacements decreases, the equipment downtime for setup replacement decreases, and the equipment availability improves.

[Brief description of drawings]

FIG. 1 is a side sectional view of a T-die according to the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a side view of the extruder.

FIG. 4 is a side sectional view of a conventional T-die.

5 is a sectional view taken along line VV of FIG.

[Explanation of symbols]

 1 ... Hopper 2 ... Extrusion mechanism 3 ... Driving mechanism 4 ... Adapter 5 ... T die 6 ... Chill roll unit 7 ... Sheet 8 ... Sheet thickness control mechanism 9 ... Straight pipe part 10 ... Branch pipe 11 ... Slit 12 ... Choke bar 13 ... Lip bar 14 ... Choke bolt 15 ... Lip bolt 16 ... Opening 17 ... Heating element 18 ... Temperature sensor 19 ... Insulation material 20 ... Wiring

Claims (1)

[Claims] 1. A manifold comprising a straight pipe part communicating with a heating part of an extruder and a branch pipe branched from the straight pipe part so as to form a substantially T-shape, and an extrusion molded product is provided below the manifold. In a T-die having a choke bar and a lip bar for adjusting the thickness and having a plurality of heating elements arranged above the branch tube, the heating elements are brought close to the branch tube, and the distance between each heating element and the branch tube is long. A T-die which is arranged so as to be substantially equal in direction.