JPH0655407B2 - Sheet-shaped material extrusion die - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION {Industrial field} The present invention relates to a die for obtaining a sheet-like material from a melt, for example,
The present invention relates to a die for extruding a sheet material for producing a thermoplastic resin film.

More specifically, in a plurality of push-pull transmission devices provided in the vicinity of the die opening, the auxiliary heating device makes use of the thermal expansion of the push-pull transmission device to locally reduce the gap between the die openings in the die width direction. The present invention relates to an improvement of an extrusion die in which the discharge amount of the melt is changed to be uniform over the entire width of the die, and the thickness of the discharged sheet-like material is kept constant.

{Prior Art} In a device for discharging a melt from an extrusion die to mold a sheet, for example, a thermoplastic resin film, it is a basic required function to make the thickness of the discharged film uniform. It is no exaggeration to say that the entire device is configured for this purpose.

Several methods have been already known as means for making the thickness uniform, but as a film forming method for making the obtained film thickness uniform by utilizing thermal expansion of the push-pull transmission device, for example, US Pat. No. 3,940,221. There is a proposal example shown in the specification.

In this proposed example, a block provided with auxiliary heating means and cooling means is provided corresponding to each of the bolts of the bolt portion, which is a push-pull transmission mechanism for adjusting the die opening, and each bolt is a block. Is pierced through. In this method, an embedded electric heater is used as an auxiliary heating means for each block, and an air cooling method using compressed air is used as a cooling means. The input of the embedded electric heater is increased or decreased while cooling the block at all times. The temperature of each adjustment bolt, which is a push-pull transmission device, is indirectly raised and lowered by this, and the die expansion is changed by drawing out the push-pull force by utilizing the difference in thermal expansion generated in each bolt. Is.

That is, in this method, compressed air is constantly and substantially uniformly supplied to a plurality of blocks, and while increasing the heat radiation efficiency of the blocks, the input of electric heaters, which are a plurality of auxiliary heating means, is increased / decreased to discharge the film. It is intended to achieve uniform thickness.

{Problems to be Solved by the Invention} The system described in the above-mentioned US Pat. No. 3,940,221 uses compressed air as a cooling means to improve the quick response of a plurality of push-pull transmission devices. Although it is to be obtained, the necessity of using the cooling means is due to the large heat capacity of each block.

On the other hand, in the invention described in Japanese Patent Application Laid-Open No. 59-127, which has been previously proposed by the present inventors, the auxiliary heating device is embedded inside the push-pull transmission device, and the direct heating method is adopted. It is possible to obtain a quick response of the push-pull transmission device without using such a cooling means, which makes it possible to adjust the lip opening with high accuracy in a short time. That is, the cooling means in the method described in the above-mentioned U.S. Pat. No. 3,940,221 is a push / pull transmission device that raises and lowers the temperature of a block provided with an auxiliary heating device and a cooling device, and penetrates the block. This is effective only in the structure that indirectly raises and lowers the temperature of the bolt, and in actual production, it is not preferable because it is complicated in terms of operability and maintenance.

However, both of the above-described proposals are inventions intended to improve the responsiveness of the push-pull transmission device in the first place in the method utilizing the thermal expansion of the push-pull transmission device.

However, as a result of further diligent examination in an actual film forming test, the gap of the lip opening was adjusted to, for example, 50 μm
When film homogenization is achieved with the following fine adjustment amount, the invention of the above-mentioned JP-A-59-127 worked extremely effectively, but the film formation start immediately after the start of film discharge. It has been found that the following problems are newly caused when the adjustment amount of the gap of the lip opening is required to be 50 μm or more like the unevenness of the film thickness.

That is, in the method of adjusting the gap between the die openings by utilizing the difference in thermal expansion between the push and pull transmission devices, the adjustment amount of the gap between the die openings is determined by the difference in thermal expansion between the push and pull transmission devices. More specifically, it is determined by the temperature difference between the temperature of the push-pull transmission device heated by the thermal energy input from the auxiliary heating device and the temperature of the die body including the other push-pull transmission device. Is.

However, the push-pull transmission device has no choice but to adopt a structure in which the push-pull transmission device is joined to the die body. Therefore, the thermal energy input by using the auxiliary heating device is transferred to the die body through the push-pull transmission device. Therefore, the temperature of the die body forms a new temperature unevenness different from the temperature set by the main heating device.

That is, in the invention described in the above-mentioned Japanese Patent Laid-Open No. 59-127, the adjustment amount of the gap of the lip opening is, for example, 50.
When the thickness is less than or equal to μm, the heat energy input by the auxiliary heating device to thermally expand the push-pull transmission device is small, so the amount of heat conducted to the die body is small, and the temperature rise of the die body is not a substantial problem. Although a film having a uniform thickness was obtained by the quick response of the push-pull transmission device, the amount of adjustment of the gap of the lip opening is required to be 50 μm or more, as when starting film formation immediately after the start of film discharge. In this case, the heat energy to be input must be increased by the auxiliary heating device for increasing the difference in thermal expansion of the push-pull transmission device. Due to the thermal energy conducted, new unevenness in the thickness of the die body is generated.

Furthermore, since the temperature difference between the die main body and the push-pull transmission means is small, the gap adjustment amount of the lip opening cannot be obtained in a desired amount. In order to obtain this, an excessive temperature rise of the push-pull transmission device is caused, and by extension, the heat resistance limit of the material forming the push-pull transmission device is exceeded, and thermal distortion occurs in the push-pull transmission device itself.

In view of the above points, an object of the present invention is to extrude a sheet material, which is extremely useful in actual production, in which the temperature of the die body is substantially uniform and the controllability of the film thickness can be improved by maintaining the desired temperature. Is to provide a die for.

{Means for Solving Problems} A die for extruding a sheet material of the present invention which achieves the above object has the following constitution. That is, a die opening and a main heating device for heating the melt discharged from the opening are provided, and the thermal expansion of the melt from the auxiliary heating means is used to discharge the melt discharged from the die opening. In a die for extruding a sheet material having a push-pull transmission device for controlling the thickness, a heat transfer temperature from the auxiliary heating means is adjusted in a heat transfer path between the push-pull transmission device and the die opening. A die for extruding a sheet-like material, characterized in that cooling means is provided.

In a preferred embodiment of the die for extruding a sheet material of the present invention, the cooling means uses a heat medium passing through a flow path provided inside the die in the width direction of the die in the vicinity of the push-pull transmission device. Further, in this aspect, the cooling means further has a temperature equalizing unit embedded in parallel with the heat medium passage in the vicinity of the push-pull transmission device. In another preferred embodiment, the cooling means uses a temperature equalizing unit of a type provided inside the die in the width direction of the die near the push-pull transmission device and radiating heat outside the die or dies. It is a thing.

Hereinafter, the die for extruding a sheet material of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic side sectional view showing an embodiment of a die for extruding a sheet material of the present invention, wherein 1 is an extrusion die main body, 2 is a temperature of the extrusion die main body 1 and a thermoplastic resin 7. A main heating device to be set, 3 is a push-pull transmission device for locally adjusting the die opening 6 in the die width direction, 4 is an auxiliary heating device for thermally expanding the push-pull transmission device 3, and 5 is a heat medium passage for cooling means. Is.

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

Extrusion die body 1 and thermoplastic resin 7 inside the die
Is maintained at a predetermined temperature by the main heating device 2. Then, according to the thickness unevenness of the discharged thermoplastic resin film, the heat energy input from the auxiliary heating device 4 is manipulated to thermally expand the push-pull transmission device 3 in order to adjust the gap of the die opening 6. .

Since the push-pull transmission device 3 is joined to the extrusion die body 1, when the auxiliary heating device 4 is heated as described above,
The heat energy of the auxiliary heating device 4 is not a little transmitted to the vicinity of the lip opening 6 via the push-pull transmission device 3 and the like, but is thermally conducted, but the adjustment amount of the lip opening is, for example, 50.
With a fine adjustment amount of μm or less, the heat energy input from the auxiliary heating device is small, so the heat transfer heat energy to the lip opening is also small, and there is no substantial problem. However, when the adjustment amount of the lip gap is required to be 50 μm or more, such as when the film is formed immediately after the film is discharged, the auxiliary heating device 4 for increasing the thermal expansion amount of the push-pull transmission device 3 is used. There is no choice but to increase the thermal energy, and in that case, the temperature in the vicinity of the die opening increases due to the thermal energy that is thermally conducted through the push-pull transmission device 3 and the like.

In view of the above points, the present invention is characterized in that cooling means is provided near the push-pull transmission device 3. That is,
The action of the cooling means in the present invention is to cause the heat transfer heating amount and the cooling amount to substantially cancel each other by causing the heat medium set at a predetermined temperature to flow through the heat medium flow path 5, thereby making it possible to reduce the temperature in the vicinity of the die opening. Is to be kept almost the same as the temperature of the main heating device.

Without such a cooling device, due to the heat transfer heat amount, temperature unevenness is formed in the extrusion die along the flow path near the die opening, the local viscosity change of the thermoplastic resin, and the lip opening. A new thickness unevenness is formed due to thermal strain in the vicinity.

Further, when the temperature of the die main body near the push-pull transmission device rises, the temperature difference from the push-pull transmission device becomes small, so that the amount of adjustment of the gap of the lip opening cannot be obtained as desired, and therefore the push-pull transmission device 3 Causes excessive temperature rise,
As a result, the heat resistance limit of the material forming the push-pull transmission device is exceeded, and thermal strain occurs in the push-pull transmission device 3 itself.

In the present invention, the purpose of the cooling means is to substantially uniformly cool the vicinity of the die opening in the width direction of the die. Of the amount of heat applied to the push / pull transmission device 3 by the heating device 4, it is sufficient that the cooling capacity is approximately balanced with the amount of heat transmission to the vicinity of the lip opening via the push / pull transmission device 3 or the like. That is, it is basically to prevent temperature unevenness between the temperature of the extrusion die and the temperature of the thermoplastic resin set by the main heating device and the temperature in the vicinity of the die opening.

In the extrusion die of the present invention, the position of the cooling device is near the push-pull transmission device, and it is more effective if it is as close as possible to the thermoplastic resin, but it does not necessarily have to be particularly close to the thermoplastic resin. For example, as shown in FIG. 3, the heat medium passage 51 may be provided in the vicinity of the joint portion of the push / pull transmission device 3 and the die body 1 on the side away from the die opening 6. It is effective. Further, when the cooling means is installed in the vicinity of the die opening, there are problems in arrangement on the apparatus and problems in strength, and there is generally a limit. This also applies to the die according to the prior art. In the present invention, the cooling device is mainly intended to uniformly cool the die. Therefore, for example, as shown in the heat medium flow passage 52 in FIG. They may be separated from each other within a range that does not impair the gist of the present invention. Also, a plurality of heat medium flow paths may be arranged in parallel.

In the present invention, as the heat medium used for cooling, from the heat medium such as air, water, gas such as oil or liquid, etc., in accordance with the width of the extrusion die, the kind of the molten resin, the film forming conditions, etc. It may be selected appropriately. The temperature setting of the cooling medium is also to be determined according to the extrusion die, the type of molten resin to be discharged, the film forming conditions, etc., but as a typical example, to the knowledge of the present inventors, According to, 15 ℃ ~ 2
It is preferably about 80 ° C. If the set temperature of the cooling medium is too low, the temperature in the vicinity of the die opening in the vicinity of the supply portion of the heat medium flow path tends to be lowered too much, so caution is required.

Another embodiment of the die for extruding a sheet material of the present invention is shown in FIG.

That is, in a mode in which the width of the extrusion die is wide and the temperature is too high while the cooling heat medium is passing through the fluid passage in the mode as schematically shown in FIG. Is, for example, the heat medium channel 5 shown in FIG.
In No. 1 or 52, as in the example shown in the schematic front view in FIG. 4, the heat medium flow path is divided into two, and one end of the die is moved to the center, or vice versa. It is preferable to make it flow to one end.

In such a mode, it is possible to further increase the number of divisions, but the device becomes complicated, which is not preferable. According to the knowledge of the present inventors, most of the dies that are normally used can be sufficiently dealt with by appropriately setting the heat medium flow path in the apparatus configuration of the aspect shown in FIG. It seems

Further, FIG. 5 shows a schematic cross-sectional view of another embodiment of the die for extruding a sheet material of the present invention.

That is, FIG. 5 shows a case where a temperature equalizing unit 8 is additionally provided as a cooling means in parallel with the heat transfer medium passage 5 for cooling in the vicinity of the push-pull transmission device.
Here, the temperature homogenizing unit means a heat transfer element in which a liquid substance such as sodium, mercury, and methanol is appropriately selected according to the operating temperature and sealed inside the pipe-shaped structure, It is generally called a heat pipe.

In the case of such an embodiment, even if the temperature of the heat medium in the heat medium flow path 5 rises while passing through the extrusion die, the temperature equalizing unit 8 for cooling is used together to keep the vicinity of the die opening. It enables uniform cooling, which is particularly effective in the case of a wide extrusion die.

Further, FIG. 6 shows a schematic front view of another embodiment of the die for extruding a sheet material of the present invention.

That is, FIG. 6 shows that, in place of the cooling heat medium flow passage shown in FIGS. 1 and 2, the same temperature equalizing unit 9 as described above is provided in the width direction of the die. The set temperature is controlled by the heat exchange section 10 provided outside the extrusion die. Even in the case of such a mode, it is possible to surely cool the die in the width direction in a wide die, which is preferable. Further, even in the case of such a mode, as shown in FIG. 4, the temperature uniformizing unit may be appropriately divided and provided. Further, depending on the physical properties of the melt and the shape of the die, a suitable number of temperature equalizing units may be used in parallel or the like, which is also the case with the embodiment shown in FIG. .

Further, in FIG. 6, when a problem such as deterioration of the thermoplastic resin does not occur due to a small temperature rise in the lip opening heated by heat transfer from the auxiliary heating device, it is provided outside the extrusion die. It is effective without the heat exchange section 10 provided.

Further, in the sheet material extrusion die of the present invention, it is also effective to provide a plurality of cooling means in a pair so as to sandwich the melt flow path.

{Effect} According to the die for extruding the sheet material of the present invention as described above, since the cooling means for cooling the die in the width direction thereof is used substantially uniformly, the auxiliary heating device is operated to thermally expand the push-pull transmission device. Even if it is made possible, the temperature unevenness of the die body caused by the heat transfer from the auxiliary heating device can be suppressed, and a sheet-shaped material extruding die which is extremely useful in the actual production that a high-quality sheet-shaped material can be obtained was realized.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of one embodiment of a die for extruding a sheet material according to the present invention. FIG. 2 is a schematic front view of the die shown in FIG. FIG. 3 is a schematic cross-sectional view showing another embodiment example of the die for extruding a sheet material according to the present invention. FIG. 4 is a schematic front view showing another embodiment example of the die for extruding a sheet material according to the present invention. FIG. 5 is a schematic cross-sectional view showing another embodiment of the die for extruding a sheet material according to the present invention. FIG. 6 is a schematic front view showing another embodiment example of the die for extruding a sheet material according to the present invention. DESCRIPTION OF SYMBOLS IN THE DRAWINGS 1: Extrusion die main body 2: Main heating device 3: Push-pull transmission device 4: Auxiliary heating device 5, 51, 52: Heat medium flow path for cooling means 5: Extrusion die opening 7: Thermoplastic resin 8, 9: Temperature equalizing unit 10: Heat exchange section

Claims (1)

[Claims] 1. A main heating device for heating a die opening and a melt discharged from the opening, and discharging from the die opening by utilizing thermal expansion by heat energy from an auxiliary heating means. In a die for extruding a sheet-like material provided with a push-pull transmission device for controlling the thickness of a melt, in a heat-transfer path between the push-pull transmission device and the die opening, a heat transfer temperature from the auxiliary heating means. A die for extruding a sheet material, characterized in that a cooling means for adjusting the temperature is provided.