JPS61132320A - Extrusion die for extrusion of sheet - Google Patents

Abstract

PURPOSE:To simplify the structure of a die itself and the piping and wiring around the die, and to simplify a system of controlling the thickness, by providing cooling means for cooling the die approximately uniformly in the direction of the width thereof so that cooling by using a cooling medium under predetermined conditions may be effected. CONSTITUTION:An extrusion die 1 and a thermoplastic resin 6 are kept at a prescribed temperature by a main heater 2. Local auxiliary heaters 4 are operated according to the ununiformity of the thickness of the discharged thermoplastic resin film thereby controlling locally the temperature near the die opening. The cooling amount of cooling means with a passage 3 through which a heating medium set to a prescribed temperature is passed can approximately cancel the whole heating amount of the local auxiliary heaters 4, so that the temperature of the die opening 5 is kept approximately equal to the temperature of the main heater 2. It is enough if the cooling capacity of the cooling apparatus is approximately balanced with the heating amount exerted by the auxiliary heaters.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a die for producing a sheet-like product from a melt, for example, an extrusion die for producing a thermoplastic resin film.

More specifically, by locally changing the temperature of the melt in the width direction of the die opening, and correspondingly causing a subtle change in the viscosity of the melt in the said direction, over the entire width of the die, The present invention relates to an improvement of an extrusion die that aims to uniformize the discharge stirrup of the melt and to make the thickness of the discharged sheet material constant.

(Prior art) In an apparatus that expels a melt from an extrusion die to form a sheet-like object, such as a thermoplastic resin film, it is a basic required function to make the thickness of the extruded film uniform. It is no exaggeration to say that the entire device is configured for this purpose.

Several methods are already known as means for making the thickness uniform, but as a film forming method that makes good use of the local viscosity change phenomenon of thermoplastic resin to make the obtained film thickness uniform. , for example, Special Publication 57-590
As proposed in Japanese Patent No. 51, a device is known in which a plurality of auxiliary heating means and a plurality of auxiliary cooling means are provided near the die opening. That is, this method attempts to achieve uniform thickness of the discharged film by skillfully operating a plurality of auxiliary heating devices and a plurality of auxiliary MJ devices.

(Problems to be Solved by the Invention) The method described in the above-mentioned Japanese Patent Publication No. 57-59051 uses a plurality of auxiliary heating devices and a plurality of auxiliary Each cooling device is provided as a bare device, and therefore, when the width of the die is wide, such as a general film manufacturing device with a width of several meters, several tens of auxiliary heating,
An auxiliary cooling device is required, and if these auxiliary heating wiring, auxiliary cooling piping, etc. are also included, the structure of the extrusion die main body must become extremely complicated. Of course, complicated wiring, piping, etc. are also required around the die, which is also undesirable from the viewpoint of operability, maintainability, etc. On the other hand, if an electric heater is used as an auxiliary heating device, there will be relatively little problem with controllability.
Regarding the auxiliary cooling device, it is necessary to maintain a fairly uniform flow rate of the cooling mass heat medium (for example, air) in the dozens of devices, and furthermore, depending on the unevenness of the thickness of the discharged film, Fine flow control or temperature control is required. Although such technology is not impossible, in practice it is
There are many important factors to be considered during control, such as flow rate, temperature, cooling mjl, total heating mjl, etc., and a complex control system is required, which is a big disadvantage from the equipment and control points of view. . Furthermore, for example, even if we take a single flow rate, it is difficult to maintain it uniformly as mentioned above, and this makes it difficult to control other elements. ! This is complicated, and it becomes even more complicated because there is a trade-off with the amount of heating in the auxiliary heating device.

In the first place, the method of controlling each of the dozens of heating devices and cooling devices in bare form to obtain a uniform film is itself a complex control method. It is undesirable and
In other words, since such thickness control is a prerequisite for controlling the thickness after the film has been discharged,
Rapid processing is required to proceed with production, and complicated control systems should be avoided as much as possible.

In actual production, it is required to be able to quickly and efficiently discharge a high-quality film that has the desired thickness uniformly in both the width and length directions in order to minimize product loss. Of course.

In view of the above-mentioned points, an object of the present invention is to simplify the structure of the die itself for extruding sheet-like products, simplify the piping, wiring, etc. around the die, and also simplify the thickness control method. The object of the present invention is to provide a die for extruding sheet-like materials which is extremely useful in actual production.

(Means for Solving the Problems) The die for extruding a sheet-like material of the present invention that achieves the above object has the following configuration.

That is, it is a die for extruding a sheet-like material, and includes: (a) a main heating device installed at a position away from the die opening to heat the melt almost uniformly; and (b) a main heating device installed near the die opening.
c. a plurality of local auxiliary heating devices capable of locally increasing the temperature of the melt in the width direction of the die and locally controlling the thickness of the discharged melt in that direction; A gouer for extruding a sheet-like material, characterized in that it has a cooling means that is provided near the opening and cools the temperature of the melt substantially uniformly in the width direction of the die.

In a preferred embodiment of the goo for extruding sheet-like materials of the present invention, the cooling means uses a heat medium passing through a flow path provided in the width direction of the die near the die opening, Furthermore, in this embodiment, a temperature equalization unit is further embedded in the vicinity of the die opening in parallel to the heat medium flow path as the cooling means. Further, in another preferred embodiment, the cooling means is formed by using one or more temperature equalization units of a type that dissipates heat outside the die, which are provided in the width direction of the die near the die opening. .

(Function and Examples) The goo for extruding sheet-like materials of the present invention will be explained in more detail with reference to the drawings.

FIG. 1 is a schematic side sectional view showing an embodiment of the goo for extruding sheet-like materials of the present invention, and 1 is a goo for extrusion;
2 is a main heating device that sets the temperature of the extrusion goo and thermoplastic resin, 3 is a heat medium flow path for cooling means, and 4 is a main heating device 2
5 is an extrusion die opening, and 6 is a thermoplastic resin.

FIG. 2 is a schematic front view of the die shown in FIG. 1.

The extrusion gooey 1 and the thermoplastic resin 6 are maintained at a predetermined temperature by the main heating device 2. Here, the local auxiliary heating device 4 is operated to locally adjust the temperature near the die opening depending on the thickness unevenness of the thermoplastic resin film to be discharged. In other words, increasing the amount of heating increases the thickness of the discharged film near the position of the auxiliary heating device where the amount of heating is increased, while decreasing the amount of heating increases the thickness of the discharged film near the position of the auxiliary heating device where the amount of heating is decreased. The thickness of the film is reduced.

The action of the cooling means is, for example, by flowing a heat medium set at a predetermined temperature into the flow path 3, the heating amount of the entire local auxiliary heating device and the cooling amount are almost offset, and the temperature of the die opening is reduced. The temperature of the main heating device is kept almost the same as that of the main heating device. Without such a cold W device, the heating effect applied by the local auxiliary heating device would increase the temperature near the die opening, creating temperature unevenness within the extrusion die along the flow path of the thermoplastic resin. be. Similarly, if there is no cooling means and only a local auxiliary heating device is used, the cooling effect relies solely on natural cooling, and in this case, the response characteristics of heating and cooling are completely different, making adjustment extremely difficult. becomes.

In the present invention, the purpose of the cooling means is to cool the vicinity of the die opening almost uniformly in the width direction of the die. It is sufficient that the cooling capacity is approximately balanced with the amount of heating to be applied. The basic idea is to ensure that there is no temperature difference between the temperature of the extrusion goo and thermoplastic resin set by the main heating device and the temperature near the die opening. The basic idea is to make the response time characteristic of the temperature near the die opening during heating by the auxiliary heating device and the response time characteristic during cooling by the cold W device as close as possible to almost the same degree.

As mentioned above, if only natural cooling is relied upon, the cooling response characteristics will be slower than the heating response characteristics. In other words, the response characteristics that reduce the thickness of the sheet-like material become slow, making fine adjustment difficult, and achieving uniform thickness without uneven thickness.
The accuracy also deteriorates.

Therefore, when producing a sheet-like product using the goo for extruding sheet-like products of the present invention, only the local auxiliary heating device is required to adjust the thickness of the sheet-like product to obtain uniformity. The cooling device in the prior art and the cooling means of the present invention have different technical ideas, and in the present invention, basically, the set temperature of the cooling device, the heat medium flow m
etc., there is no need to adjust them during film production, and in normal cases, these conditions can be adjusted before production once the specifications of the desired sheet material or the operating conditions of the main heating device are determined. It is something that can be determined by itself.

In the die of the present invention, the installation position of the local auxiliary heating device and the cold W device is near the die opening, and the closer to the thermoplastic resin as possible, the greater the effect, but there are problems with the placement on the device, strength, etc. Generally speaking, there are limitations due to the problems described above, and this point also applies to dies according to the prior art. However, in the present invention, since the main objective of the cold W device is uniform cooling, it is not necessarily necessary to be particularly close to the thermoplastic resin, and it may be provided within a range that does not impair the spirit of the present invention. It does not matter if the local auxiliary heating device is located a little far away, which increases the degree of freedom in the design of the heating system, and also brings about the advantage that the installation position and manner of installation of the local auxiliary heating device can be made more effective. be.

In the present invention, the heat medium used for immediate cold use is selected from gases such as air, steam, and oil, or liquids, depending on the width of the extrusion die, type of molten resin, film forming conditions, etc. You can select it as appropriate. The set temperature of the cooling medium should also be determined depending on the extrusion die, the type of molten resin to be discharged, film forming conditions, etc. According to 15 to 280, when manufacturing ordinary polyvarnish door film,
It is preferable to set it in the range of about ℃. If the set temperature of the cooling medium is too low, the temperature near the die opening in the vicinity of the heat medium flow path supply section tends to drop too much, so care must be taken.

Another embodiment of the die for extruding sheet-like materials of the present invention is shown in FIG.

In other words, if the width of the extrusion die is wide and the configuration shown in Fig. 2 is schematically shown in Fig. 2, the temperature of the cooling heat medium increases too much while passing through the fluid passage, and the temperature setting on the outlet side of the passage cannot be done properly. In this case, the heat medium flow path is divided into two parts, as shown in the schematic front view in Fig. 3, and the heat medium flow is made to flow from one end of the die to the center, or conversely from the center of the die to one end of the die. It is best to configure it as follows. In such an embodiment, it is possible to roughly increase the number of divisions, but
The device becomes complicated, which is not preferable, and according to the findings of the present inventors, in the case of most commonly used dies, the heat medium flow rate can be appropriately set in the device configuration shown in FIG. 2. This seems to be a sufficient solution.

Further, FIG. 4 shows a schematic cross-sectional view of another embodiment of the die for extruding a sheet-like material of the present invention.

That is, the figure shows a case in which a temperature equalization unit 7 is further provided as a cooling means in parallel with the heat medium flow path 3 for cold W near the die opening, and here, A temperature equalization unit is a heat transfer element in which a liquid substance such as sodium, mercury, or methanol is sealed inside a pipe-like structure, selected as appropriate depending on the operating temperature, and is generally referred to as a heat pipe. It is what it is called.

In such an embodiment, even if the temperature of the heat medium rises while passing through the extrusion die, by using the temperature equalization unit 7 for cooling, it is possible to uniformly cool the vicinity of the die opening. This is particularly effective in the case of wide extrusion dies.

Furthermore, FIG. 5 shows a schematic front view of another embodiment of the die for extruding sheet-like materials of the present invention.

That is, in this figure, a temperature equalization unit 8 similar to that described above is provided in the width direction of the die in place of the cooling heat medium flow path shown in FIGS. 1 and 2, and the temperature equalization unit 8 is The set temperature is controlled by a heat exchange section 9 provided outside the extrusion die.

Even in the case of such an embodiment, it is possible to reliably cool a wide die almost uniformly in the width direction of the die, which is preferable. In addition, even in the case of such an embodiment, the temperature equalization unit may be appropriately divided and provided as shown in FIG. Further, depending on the physical properties of the melt and the shape of the die, an appropriate number of temperature equalization units may be used in parallel, and this also applies to the embodiment shown in Fig. 4. .

Further, in the die for extruding a sheet-shaped material of the present invention, it is also effective to provide a plurality of cooling means in pairs with the flow path of the melt interposed therebetween.

(Effects of the Invention) According to the die for extruding sheet-like materials of the present invention as described above, since a cooling means for cooling almost uniformly in the width direction of the die is adopted, preset conditions are not met. Cooling may be performed using a cooling medium or the like, and this allows the structure of the die itself to be significantly mired, and at the same time, the piping around the die,
Wiring and the like can be simplified, and the method for controlling the thickness of the ejected sheet is also simple, making it possible to realize a die for extruding sheet-like materials that is extremely useful in actual production.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of a die for extruding a sheet-like material according to the present invention. FIG. 2 is a schematic front view of the die shown in FIG. 1. FIG. 3 is a schematic front view showing another embodiment of the sheet extrusion die of the present invention. FIG. 4 is a schematic cross-sectional view showing another embodiment of the die for extruding sheet-like materials according to the present invention. FIG. 5 shows another example of the die for extruding sheet-like materials according to the present invention. ' It is a schematic front view showing an example of an embodiment. Brief description of the drawings 1 Die for extruding a piece-like object 2: Main heating device 3: Heat medium flow path for cooling means 4: Local auxiliary heating device 5: Extrusion die opening 6: Thermoplastic resin 7.8: Temperature equalization unit 9: Heat exchange unit Patent applicant Toshi Co., Ltd. Figure 1 Figure 2 Figure 3

Claims (4)

[Claims] (1) A die for extruding sheet-like materials, which includes: (a) a main heating device that is provided at a position away from the die opening and heats the melt almost uniformly; (b) that is provided near the die opening; a plurality of local auxiliary heating devices capable of locally increasing the temperature of the melt in the width direction of the die and locally controlling the thickness of the discharged melt in that direction; c. near the die opening; 1. A die for extruding a sheet-shaped material, comprising: a cooling means provided in the die for cooling the temperature of the melt substantially uniformly in the width direction of the die. (2) Claim (1) characterized in that the cooling means uses a heat medium that passes through a flow path provided in the width direction of the die near the die opening. The described die for extruding sheet-like materials. (3) As a cooling means, further near the die opening,
Claim 2, characterized in that a temperature equalization unit is embedded in parallel to the heat medium flow path.
) A die for extruding sheet-like materials as described in item 2. (4) A patent characterized in that the cooling means is formed by using one or more temperature equalization units of a type that radiates heat outside the die, which are provided in the width direction of the die near the die opening. A die for extruding a sheet-like material according to claim (1).