JP2000117812A - T-die for extrusion molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a T-die for extrusion molding which enables a widthwise accurate thickness control by a method wherein the widthwise temperature of the T-die is made uniform by absorbing (or dissipation) the heat directly transferred from die-bolts and heaters and the heat transferred from the heaters through radiation with heat transferring bodies and then releasing (or absorbing) the above-mentioned heats to/from the width direction of the T-die. SOLUTION: In a T-die for strusion molding, a die lip gap 16 is adjusted by pushing and pulling a flexible die lip 12 through the thermal displacement of a die bolt 21, the basic end part of which is fixed to an upper side die main body 11. In the upper side die main body 11, continuous heat transferring bodies 31 and 32, each of which is made of a high pressure liquid sealed in a metal case, are installed so as to direct the longitudinal directions of the heat transferring bodies 31 and 32 toward the width direction of the T-die 1. At the same time, the thermal conductivity of the heat transferring bodies 31 and 32 is 10-100 times as much as that of the metal cases, of which the heat transferring bodies 31 and 32 are constituted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a T-die for extrusion molding for extruding a sheet of thermoplastic resin, rubber or the like, a film or a foam for foam containing a foaming agent.

[0002]

2. Description of the Related Art Conventionally, a T-die is often used to extrude a molten resin into a sheet. In order to adjust the thickness of the sheet, a die bolt provided at a die lip at the tip of a T-die mold is thermally displaced. Then, by pushing and pulling the flexible die lip, the die lip gap is changed to adjust the widthwise flow rate distribution of the molten resin from the T-die. There are two types of a method of pushing and pulling the flexible die lip portion by thermally displacing the die bolt, a "direct-acting type" and a "differential type".

FIG. 3 shows a “direct-acting” unit, and FIG. 4 shows a “differential-type” unit. Die bolts 41 and 61 have die bodies 5 and 7 having flexible die lip portions 51 and 71, respectively. Are fixed to projecting ridges 52 and 72, and heaters 42 and 62 are wound around the die bolts 41 and 61. In addition, 43 and 63 are nuts.

[0004] In the direct acting unit of FIG.
Is heated, the die bolt 41 expands due to thermal expansion, and pressing the flexible die lip portion 51 narrows the die lip gap 53, so that the flow rate is reduced. When the heater 42 is not heated, the die bolt 41 shrinks and the die lip gap 53
To increase the flow rate.

On the other hand, in the differential unit shown in FIG. 4, a core material 611 having a small thermal displacement is provided at the center of the die bolt 61, and the core material 611 is fixed to the nut 63. When the heater 62 is heated, the die bolt 61 is expanded by thermal expansion, and the core material 611 is pulled to expand the die lip gap 73, so that the flow rate is increased. Further, when the heater 62 is not heated, the die bolt 61 shrinks, and the core material 611 is pressed to narrow the die lip gap 73, so that the flow rate is reduced.
However, in any case, the above-described temperature change is transmitted to the flexible die lip portion by the direct transmission of the die bolt and the heater and the transmission of the radiant heat of the heater. Also, the temperature change occurs, and the melt viscosity of the resin changes as shown in Table 1.

[0006]

[Table 1]

For this reason, the melt viscosity of the resin in the width direction varies depending on the heating state of the die bolt, which makes it difficult to adjust the flow rate of the resin and deteriorates the accuracy of thickness adjustment.

As shown in FIG. 5, an aluminum plate 83 is sandwiched between each die bolt to prevent heat transfer from the heater 81 to the flexible die lip portion 82 and to make the temperature distribution uniform in the width direction. There are cases, but there was a problem that the thermal conductivity of the aluminum plate was insufficient, and it took time until the temperature distribution in the width direction became uniform. (Japanese Patent Laid-Open No. 62
(See Japanese Patent No. 220317)

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and it is intended to reduce the direct heat transfer from die bolts and heaters and the heat transfer of heat radiation from heaters. Extrusion for heat absorption (heat dissipation) by the heat transfer body and heat dissipation (heat absorption) in the width direction of the T-die to make the temperature in the width direction of the T-die uniform and to enable accurate thickness adjustment in the width direction. The purpose is to provide a T-die.

[0010]

SUMMARY OF THE INVENTION An extrusion-forming T-die according to the present invention comprises an upper die body having a flexible die lip at the tip and a lower die body having a fixed die lip at the tip. A die lip gap for extruding the resin is provided between the fixed die lip portions, and the die lip gap is adjusted by pushing and pulling the flexible die lip by thermal displacement of a die bolt having a base end fixed to the upper die body. In the T-die for extrusion molding, a long heat transfer member formed by sealing a liquid at a high pressure in a metal case is disposed in the upper die body around the die bolt, and the longitudinal direction of the heat transfer member is oriented in the width direction of the T die. And the thermal conductivity of the heat transfer body is 10 to 100 times the thermal conductivity of the metal case forming the heat transfer body.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a partial front view showing an example of an extrusion T die according to the present invention, and FIG. 2 is a sectional view taken along line AA 'of FIG.

As shown in FIG. 1 and FIG.
The die 1 has a die lip gap 16 for extruding molten resin between a flexible die lip portion 12 provided on an upper die body 11 and a fixed die lip portion 15 provided on a lower die body 14. I have.

A projecting ridge 13 is provided along the width direction at a portion of the die body 11 close to the flexible die lip portion 12, and a plurality of direct-acting die bolts 21 are provided on the projecting ridge 13 at predetermined intervals. Are fixed by the nut 23 and are juxtaposed. A heater 22 is wound around the die bolt 21.

With the above configuration, when the heater 22 is in the heating state, the die bolt 21 is thermally displaced so as to expand due to thermal expansion and presses the flexible die lip portion 12, so that the die lip gap 16 is narrowed and the resin flow rate in that portion is reduced. It can be automatically adjusted to decrease. In addition, heater 2
When 2 is not heated, the die bolt 21 is cooled,
Since the flexible die lip portion 12 is thermally displaced so as to shrink and pull the flexible die lip portion 12, the die lip gap 16 is widened, and the resin flow is automatically adjusted so as to increase the resin flow rate in that portion.

In the die body 11, long heat transfer members 31, 32 in which a liquid is sealed in a metal case at a high pressure are arranged such that the longitudinal direction of the heat transfer members 31, 32 is oriented in the width direction of the T die 1. Attached to. The shape of the heat transfer body is not particularly limited, and examples thereof include a pipe shape and a plate shape. The place where the heat transfer body is mounted is not particularly limited, and the heat transfer body is appropriately provided at the flexible die lip portion 12 to which the heat from the die bolt 21 and the heater 22 is directly transmitted, the portion to which the radiant heat of the heater 22 is transmitted, and the like.
The heat conductivity of the heat transfer bodies 31 and 32 is
Is 10 to 100 times the thermal conductivity of the metal case constituting the above.

In the heat transfer body, the liquid sealed in the metal case evaporates in the high temperature part to form a vapor flow, becomes liquid in the low temperature part, passes through the wick part provided in the metal case, and returns to the high temperature part. With such a configuration, the heat conductivity is 10 to 100 times that of the case of only the metal case, and the heat transfer speed is greatly improved.
Further, as described above, since the sealed liquid repeatedly evaporates and liquefies, the temperature distribution of the entire heat transfer body is kept uniform.

By this effect, the direct heat conduction from the die bolt 21 and the heater 22 to the flexible die lip portion 12 and the heat conduction of the radiant heat from the heater 22 to the upper die body 11 are absorbed (dissipated) and the width of the flexible die lip is increased. The temperature of the part 12 is kept uniform.

The metal constituting the metal case includes:
For example, copper, aluminum, stainless steel, brass and the like, and as the liquid to be sealed in the metal case, for example,
Examples include water, ammonia, methanol, acetone and the like. These are appropriately selected depending on the compatibility between the metal case and the liquid to be sealed, the desired thermal conductivity, the strength, the operating temperature, and the like.

The operating temperature range of the liquid to be sealed depends on the operating conditions and the like, but, for example, 30 to 200 ° C. for water, −60 to 100 ° C. for ammonia, 10 to 130 ° C. for methanol, In the case of acetone, 0 to 120 ° C is appropriate.

[0020]

The present invention will be described below with reference to examples. Example In the T-die for extrusion molding shown in FIGS. 1 and 2, the width is 910 mm, and 25 die bolts are provided at regular intervals (in order from one end, die bolts 1, 2,..., 25), A heat transfer body (heat conductivity of about 10,000 W / m) in which water is sealed in a copper case (heat conductivity of 372 W / mk).
The temperature of the flexible die lip portion immediately below each die bolt when the temperature of the initial die lip portion was set to 125 ° C. using the T-die having k) was measured, and is shown in the initial temperature of FIG. Next, after setting the temperature of the initial die bolt to 250 ° C., the die bolt was further heated. When the temperature of the die bolt reached 350 ° C., the temperature of the flexible die lip immediately below the die bolt was measured, and the results are shown in FIG. Indicated.

COMPARATIVE EXAMPLE As a comparative example, a conventional direct-acting T-die shown in FIG. 4 was used.
, The temperature of the flexible die lip immediately below the die bolt was measured, and the results are shown in FIG.

[0022]

As described above, the T-die for extrusion molding of the present invention absorbs (dissipates) the heat transferred from the die bolt by the heat transfer body, and dissipates the heat in the width direction of the flexible die lip portion. By performing the heat absorption, the temperature in the width direction of the T-die is made uniform, so that the thickness adjustment in the width direction can be accurately performed.

[Brief description of the drawings]

FIG. 1 is a partial front view showing one example of a T-die for extrusion molding of the present invention.

FIG. 2 is a sectional view taken along the line AA ′ of FIG. 1;

FIG. 3 is a cross-sectional view of a conventional direct-acting T-die.

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

FIG. 5 is a cross-sectional view of a conventional T-die using a heat transfer preventing aluminum plate.

FIG. 6 is a diagram illustrating a temperature distribution in a width direction of a flexible die lip portion of an example and a comparative example.

[Description of Symbols] 1 T-die for extrusion molding 11 Upper die body 12 Flexible die lip 14 Lower die body 15 Fixed die lip 16 Dip gap 21 Die bolt 31, 32 Heat transfer body

Claims (1)

[Claims] 1. A die lip for extruding resin between a flexible die lip and a fixed die lip, comprising an upper die body having a flexible die lip at a tip and a lower die body having a fixed die lip at a tip. A gap is provided, and the die lip gap is adjusted by pushing and pulling a flexible die lip by thermal displacement of a die bolt having a base end fixed to an upper die body. A long heat transfer body in which a liquid is sealed in a metal case at high pressure is mounted on the main body so that the longitudinal direction of the heat transfer body is oriented in the width direction of the T-die, and heat conduction of the heat transfer body is performed. A T-die for extrusion molding, wherein the rate is 10 to 100 times that of a metal case constituting a heat transfer body.