JP3152972B2 - Internal mandrel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for manufacturing a tubular thin film or sheet from a thermoplastic resin, in which a tubular molten thin film extruded from an annular die of an extruder is brought into direct contact with the inside to cool down very rapidly. A cooling internal mandrel.

[0002]

2. Description of the Related Art Conventionally, various types of apparatuses have been provided for cooling a thin film extruded in a process of forming a tubular thin film from a thermoplastic resin by directly contacting the thin film with a cooling liquid. For example, a method of quenching and solidifying while directly pressing and holding the overflow liquid flowing down the outer wall of the inner overflow pipe (Japanese Patent Publication No. 45-3)
No. 5192), a method for improving the high-speed film forming property by providing a spiral groove through which another coolant flows under the pipe diameter regulating double pipe through which the overflow liquid flows down (Japanese Patent Publication No. 49-31473) and cooling. A method of contacting a liquid, cooling and solidifying the liquid, and removing the adhering liquid by suction (Japanese Patent Publication No. 39-2072) is known.

[0003]

The most important technical point for producing a thin film having excellent stretchability is how to produce a substantially amorphous thin film. There is a need to. Various methods have been proposed in which the thin film is brought into contact with the cooling internal mandrel cooled by the internal cooling liquid, that is, indirect cooling is performed, but the cooling rate by indirect cooling is the cooling rate when directly contacting the cooling liquid. Clearly smaller.

In addition, in the case of direct cooling with a mere internal overflow cooling liquid, a cooling rate is reduced due to boiling of a partially retained cooling liquid, or partial adhesion to a cooling internal mandrel due to uneven flow is generated. It is difficult to obtain a regular thin film. For example, Japanese Patent Publication No. 45-35192 discloses a method of cooling by overflowing from a water tank in an internal mandrel for internal cooling. The overflowing liquid flowing down has a low flow velocity and a thin film moving downward even at high speed. And the same speed. Therefore, the cooling liquid flowing down along with the thin film is heated to a high temperature by the residual heat of the thin film and partially boiled, so that the cooling capacity is reduced and cooling spots are significantly generated. If it is attempted to increase the flow rate to suppress this decrease in cooling capacity, the uniformity of the balance between the head pressure of the water tank and the water pressure of the external coolant will be lost, and the appearance of unevenness such as haze due to reduced circularity or cooling unevenness will occur. It is difficult to obtain a thin film of good quality due to the occurrence of thin spots and the like. Therefore, in order to perform high-speed film formation, the temperature of the cooling liquid must be reduced to a low level, but there is a limit in economical efficiency, and it is inevitable that high-speed film formation is inferior. Japanese Patent Publication No. 46-31473 has a spiral groove at the bottom to enable high-speed film forming.
The lower internal coolant is used to promote cooling.
Cooling of the upper pipe diameter control double pipe section is described in JP-B-45-3
The cooling capacity of the double tube body is almost the same as that of No. 5192 and has the same limitation as described above. Japanese Patent Publication No. 39-2072 is a simple cooling method using an overflow liquid, as in Japanese Patent Publication No. 45-35192, and is inferior in high-speed film forming properties.

[0005]

Means for Solving the Problems In order to solve the above-mentioned drawbacks, the present inventors diligently studied an internal mandrel for cooling,
The high-speed film-forming property was successfully improved by improving the direction of jet of the cooling liquid (Japanese Patent Application No. 3-192682).
However, as a result of intensive studies on further improving the cooling capacity, the present invention has been achieved. That is, the present invention relates to a direct cooling internal mandrel, which is coupled below an annular extrusion die and cools a tubular molten thin film extruded downward from an annular slit of the die from the inside in combination with an external annular cooling liquid tank. The present invention relates to an internal mandrel for direct cooling, wherein two or more stages of annular slit nozzles for jetting coolant are provided, and the annular slit nozzle for jetting uppermost stage coolant is directed upward from the horizontal direction. That is, by providing two or more stages of annular slit nozzles for jetting the upper cooling liquid, the cooling capacity was increased by multi-stage cooling with the laminar internal cooling liquid, and the high-speed film forming property was significantly improved.

Hereinafter, the present invention will be specifically described with reference to the drawings of embodiments. Reference numeral 1 denotes an annular die mounted downwardly on the extruder, and the thermoplastic resin melted by the extruder 1 is extruded into a tubular shape below the annular slit 3 through a resin passage 2 inside the die. Reference numeral 5 denotes a cooling internal mandrel suspended from an annular die. The cooling internal mandrel 5 mainly includes a compressed air ejection nozzle portion 20, an upper coolant ejection annular nozzle 8, a middle coolant ejection annular nozzle 7,
It has a substantially cylindrical shape composed of six parts: a pipe diameter regulating ring portion 6, a lower cooling portion 15, and a seal ring portion 17. A compressed air ejection nozzle 20 for maintaining the bubble shape and an exhaust port 19 for discharging generated gas and the like are provided at the uppermost portion of the inner mandrel 5. The molten tubular thin film 4 is the die 1
The upper bubble portion formed between the cooling air and the cooling internal mandrel 5 is formed by the balance between the compressed air exhausted from the coolant discharge port 18 and the compressed air exhausted from the exhaust port 19 and the compressed air supplied from the ejection nozzle 20. The shape is maintained. An annular nozzle 8 for ejecting an upper coolant and an annular nozzle 7 for ejecting a middle coolant are provided below the nozzle section 20 for ejecting an annular compressed air. Alternatively, as shown in FIG. 3, the upper one-stage cooling liquid jetting annular nozzle 43, the upper two-stage cooling liquid jetting annular nozzle 42 (corresponding to 8 in the case of two stages), and the middle cooling liquid jetting annular nozzle 41. (Equivalent to 7 in the case of two stages)
The three-stage annular nozzle for jetting coolant is provided.
In some cases, four or more stages of annular nozzles for jetting coolant may be provided. By providing the cooling liquid jetting annular nozzle in multiple stages, a fresh cooling liquid (having no rise in temperature) can be sequentially sprayed on the tubular thin film 4.
The cooling effect can be increased. When the outer wall of the cooling internal mandrel is cooled by sliding the tubular thin film 4 together with the cooling liquid, the amount of the cooling liquid is limited, and the cooling capacity is smaller than when immersing in the cooling liquid tank and cooling with a large amount of the cooling liquid. . However, when a tubular thin film is formed, simply immersing it in a cooling liquid bath and cooling it is inferior in uniformity such as roundness of the thin film. Further, if there is no flow of the cooling liquid, a film layer of the cooling liquid is generated between the thin film and the thin film, and the cooling effect is significantly reduced. That is, by providing a multistage annular nozzle for jetting the cooling liquid, it is possible to always supply fresh cooling liquid, and it is possible to reduce the film layer by the forced flow of the cooling liquid, thereby significantly increasing the cooling capacity. . The cooling liquid ejection direction of the annular nozzle for ejecting the cooling liquid having two or more stages can be variously arranged, but the nozzle direction of the lowermost annular slit nozzle 7 is preferably lower than the horizontal direction. When the nozzle direction of the lowermost annular slit nozzle 7 is set to the horizontal line direction or upward, the cooling speed flowing downward is equal to or less than the moving speed of the thin film, and the cooling capacity of the cooling liquid flowing down with the thin film is reduced. By jetting downward, the flow rate of the cooling liquid can be made faster than the flowing rate of the thin film. It can be significantly larger. The nozzle direction of the uppermost annular slit nozzle (8 in FIG. 2 and 43 in FIG. 3) is preferably higher than the horizontal direction in order to perform countercurrent cooling with a high cooling effect. The nozzle direction of the annular slit nozzle 42 located in the middle of the three-stage cooling shown in FIG. 3 may be either upward or downward, but is appropriately selected depending on the characteristics of the resin to be formed. The shape of the uppermost annular slit nozzle is determined by the characteristics of the resin to be formed in the same manner as described above. For example, the height h of the weir 8 ′ above the nozzle may be low for a resin having a high solidification rate due to cooling, and the height h of the weir 8 ′ may be high for a resin having a low solidification rate. It is more effective to do so. In FIGS. 2 and 3, the rectifying plate 1 is provided in the internal circulation grooves 9 to 11 and 50 to 53 of the internal coolant.
2 is provided, whereby the flow of the coolant is rectified, and the coolant can be jetted uniformly in the outer peripheral direction.
The lower side of the annular slit nozzle 7 is a ring 6 for regulating the diameter of the tubular thin film 4 for smoothing the diameter of the tubular thin film 4. The tubular thin film 4 is cooled by the cooling liquid jetted from the upper cooling liquid jet nozzle. The ring 6
And cooled while the pipe diameter is regulated by the diameter of the ring 6. Although the thin film 4 is regulated by the diameter of the ring 6, the cooling liquid ejected from the nozzle 7 at high speed is interposed between the outer periphery of the ring 6 and the tubular thin film 4 as a film. The surface of the thin film 4 does not directly contact with the surface of the thin film 4, and as a result, there is a feature that the inner surface of the thin film 4 is not scratched. Immediately below the upper coolant internal flow groove 9, a lower coolant internal flow groove 11 is provided, from which the lower coolant is supplied to a spiral groove 14 provided inside the pipe diameter regulating ring 6, It flows down along the groove. One or two or more spiral grooves 14 may be arranged in parallel.
4, the liquid flows from the upper end of the cylindrical body 15 to the lower end thereof, and flows out of the lower end of the spiral groove 14 to the drainage port 16 at the lower end of the cylindrical body 15. A seal ring part 17 is provided below the lower cooling part, and prevents the external cooling liquid from leaking downward by pressing against the elastic substance 31 provided at the bottom of the external cooling tank 30 via the thin film 4. In addition, the internal coolant is prevented from leaking. The internal coolant flowing down from the upper portion is smoothly discharged to the drain port 16. Further, the thin film has a braking effect on the thin film being taken by being pressed against the elastic material 31 and has an important function of suppressing a change in the taking speed due to the weight of the thin film. In order to appropriately adjust the braking effect, the material and the surface roughness of the seal ring 17 are selected according to the material used for manufacturing the thin film. Further, an upper compressed air discharge hole 22, an upper bubble formed compressed air introduction hole 23, an upper coolant introduction hole 24, a middle coolant introduction hole 25, and a lower coolant introduction hole 2 penetrating through the center of the die.
6, a compressed air introduction hole 27 for forming a lower bubble, a lower compressed air discharge hole 28 and an internal coolant discharge hole 29 are provided. still,
When there are three or more cooling liquid jetting annular nozzles, corresponding cooling liquid introduction holes are provided. The tubular thin film which has been subjected to the cooling and forming process is gradually folded by the folding roll group 32 by the usual method, and the nip roll 33 is formed.
Picked up at The external cooling tank 30 used in the present invention is usually of a well-known type, and the liquid level in the tank is adjusted to the level of the internal mandrel while being partially renewed by overflow.

[0007]

As described above, the internal mandrel of the present invention can be prevented from abnormal deformation of the molten tubular thin film extruded downward from the slit of the annular die, and can effectively and very rapidly by the multi-stage cooling liquid flow while regulating the pipe diameter. In addition, the quenching effect is enhanced by the lower internal cooling liquid and the external cooling liquid.The combination of a relatively short internal cooling mandrel and an external cooling tank makes it possible to form a film at extremely high speed. It is possible and troubles during stretching can be reduced. In addition, since the tubular thin film is completely cooled and formed to almost the same temperature as the inner and outer cooling liquids while passing through the cooling internal mandrel, there is no risk of shrinkage or abnormal deformation after leaving the cooling internal mandrel. A tubular thin film having an extremely uniform diameter and good flatness can be manufactured. In particular, in the case of forming a thermoplastic resin film which is easily crystallized, the cooling rate is extremely high, so that crystallization is remarkably suppressed. Therefore, a tubular thin film excellent in transparency, impact resistance, stretchability and the like can be produced.

[0008]

The present invention will be described more specifically with reference to the following examples.
The present invention is not limited to these embodiments.
A molten tubular thin film is extruded from polypropylene (MI = 2.3, ethylene content: 4%) at a resin temperature of 260 ° C. from an annular die having an annular slit having an extrusion opening of 300 mmφ,
The outer wall of the cooling internal mandrel 5 having the shape as shown in FIG. The inner coolant that is jetted out and the bottom of the cooling internal mandrel 5 penetrate,
The film was simultaneously cooled from inside and outside by the external cooling liquid in the external cooling liquid tank 30 having the elastic body 31. The cooling internal mandrel used is a pipe diameter regulating ring 6 shown in FIG.
The maximum diameter of the shoulder is 298 mmφ, the length of the trunk is 125 mm,
The length of the body of the cylindrical body 15 is 270 mm, and the seal ring 17 is provided.
Has a maximum diameter of 296 mmφ, and the outer surface of the cooling inner mandrel which is in contact with the resin is mirror-plated with chrome. The compressed air supplied from the compressed air introduction pipes 23 and 27 and the compressed air discharged from the compressed air discharge pipes 22 and 28 were controlled to form upper and lower thin film bubbles, respectively. In addition, ground water of 20 ° C. is supplied to the inner upper coolant introduction hole 24 at 1.1 t / h, and into the inner middle coolant introduction hole 25 at 0.9 t / h.
It was supplied at each flow rate at the time, and was ejected from an annular slit nozzle having a slit gap of 0.8 mm. The upper coolant is jetted upward from the horizontal direction to cool the thin film 4 in a countercurrent manner.
The middle coolant was jetted downward from the horizontal direction to cool while flowing down together with the thin film 4. The internal upper cooling water partially overflows and flows out to the common drain port 13, and further, the common cooling water is discharged from a drain port provided between the upper cooling liquid jetting annular nozzle 8 and the middle cooling liquid jetting annular nozzle 7. It flows out to the outlet 13. The inner middle cooling water flows out from the drainage port between the nozzles to the common drainage port 13 and flows down together with the thin film 4 passing downward to smoothly flow into the lower drainage port 16 for temporary cooling. At the same time, and was discharged to the outside through the internal coolant drain port 18 and the internal coolant drain port 29.

On the other hand, ground water at the same temperature of 20 ° C. is supplied at a flow rate of 1.2 t / h to the internal lower coolant introduction hole 26, and the inclination angle is set to 12 degrees through the lower coolant internal flow passage 11 attached to the current plate 12. The twelve spiral grooves 14 having the following flow down.
Since the lower cooling water flows into the cooling internal mandrel through the drain port 16, it was discharged to the outside through the internal cooling liquid drain hole 29. On the other hand, underground water at the same temperature of 20 ° C. was supplied to the external cooling layer 30 at a flow rate of 3.4 t / h, and the thin film 4 was cooled from the outside. At this time, the external cooling tank 30 is set so that the level of the upper internal cooling water is substantially equal to the level of the external cooling water.
The water level was adjusted.

External cooling water is applied to the elastic body 31 to seal ring 1
Pressing to 7 prevented leakage from below.
At the same time, this pressure is adjusted to control the braking action against the thin film take-off, and the thin film falls under its own weight or the chatter of the thin film in the reverse case (the slip between the film and the seal ring or the elastic body is reduced, and the vibration in the take-up direction is reduced. Phenomenon). The thin film obtained as described above has an average thickness of 300 μm and a range of thick and thin spots of 10 μm,
The transparency was also very good.

Comparative Example When the tubular thin film 4 was cooled in the same manner as in the above example in the internal mandrel from which the annular nozzle 8 for jetting out the upper coolant was removed in the example, the cooling effect was inferior. Also got worse. In order to obtain the same transparency as in the example, it was necessary to reduce the film forming speed (film forming take-off speed by the nip roll 33) to 23 m / min.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating the entire structure of a cooling internal mandrel.

FIG. 2 is a detailed explanatory view of a cooling section of the internal mandrel for cooling in the embodiment.

FIG. 3 is a detailed explanatory view of a cooling section of a cooling internal mandrel when the number of slit nozzles is three.

[Explanation of symbols]

 Reference Signs List 1 annular die downwardly attached to extruder 2 resin passage inside die 3 annular slit 4 molten tubular thin film 5 internal mandrel for cooling 6 pipe diameter regulating ring part 7 annular nozzle for ejecting middle coolant 8 annular for ejecting upper coolant Nozzle 8 ′ Nozzle at upper part of nozzle 9 Middle coolant internal circulation groove 10 Upper coolant internal circulation groove 11 Lower coolant internal circulation groove 12 Coolant rectifying plate 13 Common drainage port 14 Spiral groove 15 Lower cooling section 16 Lower drainage Liquid port 17 Seal ring portion 18 Coolant discharge port 19 Exhaust port for discharging generated gas and the like 20 Compressed air ejection nozzle portion 21 Compressed air ejection rectifying plate 22 Upper compressed air discharge hole 23 Upper compressed air introduction hole for upper bubble formation 24 Upper cooling Liquid introduction hole 25 Middle coolant introduction hole 26 Lower coolant introduction hole 27 Compressed air introduction hole for lower bubble formation 28 Bottom compressed air discharge hole 29 Internal coolant Discharge hole 30 External cooling tank 31 Elastic material 32 Folding roll group 33 Nip roll 41 Annular nozzle for ejecting middle coolant 42 Annular nozzle for ejecting upper two-stage coolant 43 Annular nozzle for ejecting upper one-stage coolant 50 Lower coolant internal circulation groove 51 Middle coolant internal flow groove 52 Upper two-stage coolant internal flow groove 53 Upper one-stage coolant internal flow groove

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B29C 47/00-47/96

Claims (2)

(57) [Claims] An internal mandrel for direct cooling, wherein a tubular molten thin film coupled below an annular extrusion die for thermoplastic resin and extruded downward from an annular slit of the die is used together with an external annular cooling liquid tank to cool from the inside. 2. The internal mandrel for cooling a tubular thin film according to claim 1, wherein two or more annular slit nozzles for ejecting the upper coolant are provided, and the annular slit nozzle for ejecting the upper coolant is directed upward from the horizontal direction. 2. The internal mandrel for cooling a tubular thin film according to claim 1, wherein the annular slit nozzle for ejecting the lowermost cooling liquid is directed downward from the horizontal direction.