JP2000318037A - Method and apparatus for producing tubular film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a tubular film uniform in strength in its longitudinal and lateral directions by suppressing the shaking of a film even if a blowup ratio is enhanced when high density polyethylene is used. SOLUTION: In a method for producing a tubular film by emitting a tubular thermoplastic molten resin from an annular resin outlet to inflate the same, pressure of 0.48-5.6 kgf/cm2 is applied to the outside of the tubular film 2 in a region of a temp. range from the m.p. of the molten resin +10 deg.C to the softening point thereof -15 deg.C before starting the inflation of the tubular film and, after pressurization, the tubular film 2 is inflated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a tubular film using a thermoplastic resin and an apparatus for producing the same.

[0002]

2. Description of the Related Art A blown film molding method has been known as one of the methods for producing a tubular film of a thermoplastic resin. FIG. 7 is a schematic configuration diagram showing a conventional blown film manufacturing apparatus. This manufacturing device 81
Includes an extruder 82 for extruding a polymer, an annular die 84 attached to the extruder 82, an air cooling ring 86 for cooling the tubular film 85, a folding plate 87 for folding the tubular film 85, and a take-off device 88.
And a film winding device 89. The take-off device 88 includes a pinch roll 90 and a guide roll 91.

The annular die 84 has an air supply passage 92 through which air is supplied under pressure. From the annular slit 83 of the annular die 84, a molten tubular film 85 heated to a temperature higher than the melting point of the resin by about 100 ° C. is extruded, and while cooling the tubular film 85 by a cooling means such as an air cooling ring 86, the tubular film 85 is cooled. After blowing air from the air supply passage 92 into the film 85 to expand the film 85, the film 85 is pulled in the vertical direction by a take-off device 88 to produce an inflation film.

[0004]

However, the above-mentioned conventional method for producing a thermoplastic resin film has the following problems. (A) Due to the resistance of the tubular film 85 applied to the folding plate 87, the surface of the expanded tubular film 85 fluctuates, and this vibration is amplified at the beginning of the expansion of the film, causing the molten tubular film 85 to fluctuate, thereby producing the tubular film 85. This causes the thickness of the tubular film 85 to vary. In addition, when the surface of the tubular film 85 shakes, a so-called respiration phenomenon occurs in which the film surface expands or contracts, and in a severe case, the tubular film 85 may be cut in the middle. Even if the cutting is not performed as described above, it is difficult to keep the width and the volume of the tubular film constant due to the swing of the tubular film 85. In particular, in the method of folding the film by inserting a folding machine at the end of the tubular film 85, the resistance of the folding machine makes the film surface more liable to shake, making it difficult to accurately maintain the film dimensions.

(B) When HDPE (high-density polyethylene) is to be manufactured by the above-mentioned conventional film manufacturing method, there is a problem that only a film having a high vertical strength and a low horizontal strength can be prepared. This problem will be described in more detail. FIGS. 8A and 8B are diagrams showing a method of manufacturing a tubular film. The film manufacturing apparatus shown in FIG. 8 is provided with a soy-side cooling air discharge device (hereinafter, a die-side air cooling ring 71) close to an annular slit 83 of the annular die 84.
By setting the type of resin and the spray angle of the die-side air cooling ring 71, the position where the tubular film 85 expands is changed. That is, FIG.
As shown in (A), if the angle is adjusted so that the air released by the die-side air-cooling ring 71 is blown as much as possible to the root of the discharged tubular film 85, a low-spread film 72 that expands from the root is obtained. As shown in FIG. 8 (B), the angle is adjusted so as to be sprayed to a high place of the molten tubular film 85, and the cooling air amount is reduced as much as possible to obtain a high place expansion film 73.

The low extension film 72 is a film having a shape in which the resin remains mixed, so that it is easily stretched and has no absolute strength. On the other hand, the high place expansion film 73
Because the resin molecules are arranged in the vertical direction as the altitude expands,
There is a property that the absolute intensity in the vertical direction is 1.5 times or more the absolute intensity in the horizontal direction. Therefore, when the film is pulled in a direction (horizontal direction) perpendicular to the direction in which the film is taken, the film is apt to tear in the vertical direction. In general, it is known that the blow-up ratio should be increased in order to balance the strength balance in the vertical and horizontal directions.
In order to balance the strength balance in the vertical and horizontal directions, the blow-up ratio of the blow-up ratio of the low expansion film is twice, that is, in the case of HDPE, PP (polypropylene),
A blow-up ratio of 5.0 to 7.0 is required.
Here, the blow-up ratio refers to the ratio of the maximum bubble diameter to the outermost annular slit diameter (lip diameter) of the annular die.

In the conventional method of manufacturing a high-altitude expanded film, the blow-up ratio is limited to 4.5 to 5.0 times. If the blow-up ratio exceeds the limit, the tubular film shakes and cannot be operated. Therefore, in the high-density polyethylene film manufactured by the conventional method of manufacturing a high-altitude expanded film, the blow-up ratio is in the range of 4.5 to 5.0, and the relative strength balance in the vertical and horizontal directions is reduced. There is a problem that remains. As described above, in the case of the inflation film manufactured by the conventional method of manufacturing a high-altitude expanded film, there is a problem that it is difficult to form a tubular film having a balanced strength in the vertical and horizontal directions.

Further, in the case of a linear molecular structure resin having a stereoscopic regulation of a thermoplastic resin, a blow-up ratio commensurate with the molecular chain is required even in a low-expansion film, and the strength cannot be balanced in the vertical and horizontal directions. is there. In particular, in the case of HDPE (high-density polyethylene) described above, it appears remarkably. On the other hand, in the conventional method for producing HDPE, the film is rotated at an angle of 60 ° to 40 ° at the time of film formation by rotating a circular die, and the orientation of the film molecules is oblique.
There is a configuration in which the vertical and horizontal intensities are apparently balanced. However, this method does not substantially change the substance of the film, and has a problem that the film is easily torn along the orientation direction of the obliquely arranged molecules.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing a tubular film using a thermoplastic resin and an apparatus for manufacturing the same, which can solve the above problems. is there. An example of a specific purpose is as follows. (a) A film manufacturing method and apparatus capable of maintaining high dimensional accuracy such as film width. (b) In a thermoplastic resin, even if the blow-up ratio is increased, the sway of the film is suppressed, and the production of a tubular film with uniform strength in the vertical and horizontal directions is enabled. (c) To provide a technique capable of producing a double-layered tubular film with higher quality than before. The problems of the invention other than those described above and the means for solving the problems will be described in detail later in the specification.

[0010]

According to the present invention, for example,
The following will describe the embodiment of the present invention with reference to FIGS. 1 to 5. According to the first invention, in a tubular film manufacturing method for discharging a tubular thermoplastic molten resin from an annular resin outlet 10 to produce a tubular film by an inflation method, a temperature from a melting point of the molten resin + 10 ° C. to a softening point of −15 ° C. Before the tubular film 2 starts expanding in the temperature range of 0.48 kg / cm ² , a force in the range of 0.48 kgf / cm ² to 5.6 kgf / cm ^{2 is} applied from the outside of the tubular film 2. 2 is expanded to produce a tubular film. The second invention comprises, for example, as shown in FIG. 1, an annular die 3 for discharging a tubular thermoplastic molten resin from an annular resin outlet 10 and an air supply passage 11 for feeding air into the molten resin. In a tubular film production apparatus for producing a tubular film by
In the region from the temperature of 0 ° C. to the temperature range of −15 ° C. of the softening point, before the tubular film 2 starts expanding, 0.48 kgf / cm ^{2 to} 5.6 kg from the outside of the tubular film 2.
annular film pressing means 5 for applying a force in the range of f / cm ²
Is provided, and after the pressurization, the tubular film 2 is expanded to produce a tubular film.

The third aspect of the present invention includes, as shown in FIGS. 3 and 4, for example, a double annular die 28 having a plurality of annular resin outlets 20 and 27 concentrically. Tubular film 19 and outer annular resin outlet 2
In the film manufacturing method for manufacturing a tubular film by bonding the outer tubular film 24 discharged from the outer tube 7 and the outer tubular film 24 outside the double annular die 28, the inner annular resin outlet 2
The inner tubular film 19 passes through the inside of the tubular body 22, and the outer tubular film 24 passes through the outside of the tubular body 22 by extending the tubular body 22 from between the zero and the outer annular resin outlet 27. The cylindrical body 22 has an annular film pressing portion 23. The annular film pressing portion 23 is provided at a predetermined position before the inner tubular film 19 starts expanding, and has a melting point of + 10 ° C. of the molten resin. 0.48 kgf / cm ^{2 to} 5.6 kgf from the outside of the inner tubular film 19 in the temperature range from the temperature of 50 ° C. to the softening point of −15 ° C.
/ Cm ² , and the space between the inner tubular film 19 and the outer tubular film 24 is formed inside the tubular body 22 by the pressurization of the annular film presser 23. Outer space (in-cylinder space 34)
And a space (inter-film space 25) outside the tubular body 22 and inside the outer tubular film 24. The fourth invention is characterized in that the double annular die 28 is configured such that the inner annular resin outlet 20 and the outer annular resin outlet 27 rotate in directions different from each other.

[0012] The first to fourth aspects of the present invention further include:
explain. As the thermoplastic resin applicable to the present invention,
Examples include polyethylene-based resins such as medium-density polyethylene and high-density polyethylene, ethylene-based polymers, and crystalline polymers such as polypropylene, polyamide, and polyester. The annular film pressing means 5 according to the second invention.
Is an annular contact surface 1 that comes into contact with the outside of the tubular film 2
It can also be constituted by a film pressurizing cylinder 13 (see FIG. 2) provided with 2. In this case, it is preferable that the contact surface 12 is formed by providing a flocked material for reducing the coefficient of friction on the elastic body. Further, it is preferable that the tubular film is pressurized only by the annular contact surface 12 and the tubular film is not brought into contact with other portions. The width of the contact surface 12 in the direction in which the film is pulled out is 1 mm to 15 mm.
mm, preferably 5 mm to 1 mm.
It is more preferable to set the range to 0 mm. The annular film pressing means 5 in the second invention may be configured to include an air knife.

Hereinafter, the basic concept of the first invention and the second invention will be described with reference to FIG. As shown in FIG. 1, the molten tubular film 2 discharged from the annular die 3 has a temperature (for example, 10 ° C.) substantially higher than the melting point of the resin.
(A temperature as high as about 0 ° C.). Here, the process of manufacturing a tubular film as a product from the discharged resin can be roughly classified into: (a) a molten tubular film 7 in a molten state; and (b) a heat-softened tubular film in a process of being solidified by cooling. Film 8 (c) Solid state normal film 9 can be classified into three types. Molten tubular film 7
Is cooled by cooling air from the die-side air cooling ring 4 and is manufactured as a high-altitude expansion film. The inventor of the present invention has a drawback of the above-described high-expansion film by applying a force from the outer periphery of the thermally softened tubular film 8 in the process of solidifying by cooling within a predetermined temperature range in the above-described method of manufacturing the high-expansion film. It has been found that the fluctuation of the tubular film can be eliminated.

Further, from the viewpoint of the viscoelasticity of the resin, a phenomenon in which a heat-softened state is exhibited between the molten tubular film 7 and the normal tubular film 9 has been found. It was referred to as a softened tubular film 8.
When a certain pressure is applied to the heat-softened tubular film 8, the film has a balanced portion that also contracts and expands. If this portion is stabilized, the expanded and solidified normal tubular film 9 is shaken. It has been found that it is possible to suppress, and to solve various problems such as the adverse effect on the molten tubular film 7 caused by the shaking of the normal tubular film 9, that is, the variation of the film thickness and the deformation of the width of the tubular film. did.

As a result of studying the present invention in a number of experiments, the following was found.
It is clear that film shake can be reduced under the conditions
Became. The conditions are as follows: (a) Temperature range of resin The viscous fluid resin melted from the annular die 3 is solidified at room temperature.
During the temperature change to the shape, usually the melting point of the molten resin
Softening point (° C) from temperature (melting point x 1.1) 10% higher than (° C)
Deformation in the range of 15% lower temperature (softening point x 0.85)
Transformation occurs. Therefore, determine the temperature range in this range,
Or from the melting point of the molten resin + 10 ° C to the softening point -15 ° C
Apply the tubular film 2 from outside in the temperature range
You only have to press. The above temperature range is from the melting point to the softening point.
The temperature range is more preferably up to (B) Force applied to the tubular film Regarding the force applied to the tubular film 2 from the outer periphery,
0.48kgf / cm ^Two~ 5.60kgf / cm^TwoSet to
I found out what to do. This range is 0.4
8kgf / cm^Two~ 4.24kgf / cm^TwoSet to
And preferably 0.48 kgf / cm^Two~ 2.
88kgf / cm^TwoIs more preferably set to.

Also, by repeating many experiments,
The force applied to the tubular film 2 is not necessarily limited to the configuration in which the pressurized body contacts the tubular film 2,
It has also been found that a non-contact configuration can provide a braking effect on the tubular film. Speaking the above conditions in terms of air pressure, 47070 Pa to 549 172 Pa
(0.46456 atm to 5.4199 atm), and by applying such a gas pressure (medium pressure), the same effect as the pressurization by the contact can be obtained. (C) Pressing before the film is greatly expanded The pressing of the present invention needs to be performed before the tubular film is expanded. The conditions are, for example, the annular resin outlet 10
In terms of the ratio of the diameter (lip diameter), the viscoelasticity of the resin,
It varies depending on the die, lip diameter, extrusion amount, required blow-up ratio, etc.
It is preferable to pressurize at a position in the range of 1.65 to 1.65. Further, it is more preferably provided at a position in the range of 0.85 to 1.60, and even more preferably provided at a position in the range of 0.85 to 1.2. Then, after the pressurization, it is greatly expanded by the internal pressure of the tubular film.

(D) Pressing according to the present invention is performed without cooling the film. Since the pressing according to the present invention focuses on preventing the film from shaking, the pressing does not lower the temperature of the film. ADVANTAGE OF THE INVENTION According to the manufacturing method and manufacturing apparatus of this invention, the bad influence which the shaking of a tubular film becomes large and expansion of a tubular film becomes unstable can be suppressed. Such a configuration is particularly required for HDPE, which requires a large blow-up ratio to equalize the strength in the vertical and horizontal directions.
It is suitable for a method for producing a tubular film employing a (high-density polyethylene) or a gusset folding machine in which fluctuations easily occur.

In the present invention, assuming an embodiment in which the annular film pressing means 5 and the annular film pressing section 23 are pressurized in a non-contact manner by gas or the like, at a glance, Japanese Patent Publication No. 57-14295. Although it may be considered that the configuration is very similar to the conventional two-stage air cooling method disclosed in the above, the two-stage air cooling method and the configuration of the present invention are completely different in the following points. First, the two-stage air cooling method is shown in FIG.
The first cooling is performed by blowing cooling air from around the molten tubular film 7 immediately after the discharge of the annular die 3, and the tubular film 2 is placed immediately before the frost line position 14 of the tubular film 2. This is a method of performing the second air cooling by blowing cooling air from around. In the position before the film expands, cooling the film has the effect of preventing film crystallization,
The effect of lowering the blow-up ratio and reducing the balance strength in the vertical and horizontal directions works, and the conventional blow-up ratio is 4.5 to 5.0.
However, it is reduced to 3.5 to 4.0. Therefore, the object of the present invention cannot be achieved.

When cooling is performed after the film is expanded, the increase in crystallization of molecules is reduced, which is effective in miniaturizing crystals and improving the transparency of the film. In order to increase the fineness and transparency of the crystal, the amount of cooling air applied to the normal tubular film is a problem, and as the cooling effect is enhanced, the swing of the tubular film is amplified. This is against the balance of the length and width of the tubular film of the present invention. On the other hand, in the present invention, just before the tubular film starts expanding by the first cooling start, the film is held without being cooled by applying pressure while maintaining the temperature of the film without cooling the film. The purpose of the present invention is to prevent the vibration of the film caused by the film folding and folding steps from being propagated to the molten tubular film. Further, the present invention provides a resistance to the upper portion of the molten tubular film, thereby relaxing the resin take-up stress, temporarily relaxing the orientation of the resin molecules generated by extrusion from the annular die, and forming the inside of the molten tubular film. It develops stress and exerts self-shrinkage of the resin. Such a function is 2
There is no such thing in the step air cooling method.

[0020]

According to the first aspect of the invention, since the tubular film is manufactured by applying a force, it is possible to suppress the expansion of the tubular film from becoming unstable due to the large swing of the tubular film and the film width. Accuracy such as dimensions can be improved. Further, even if the blow-up ratio is increased so that the strength in the vertical and horizontal directions is adjusted, the sway of the film surface can be suppressed, so that it is possible to stably produce a tubular film having the uniform strength in the vertical and horizontal directions. According to the second aspect, since the annular film pressurizing means applies the force to produce the tubular film, it is possible to suppress the swing of the tubular film from increasing and the expansion of the tubular film from becoming unstable, Accuracy such as film width dimension can be improved. Further, even if the blow-up ratio is increased so that the strength in the vertical and horizontal directions is adjusted, the sway of the film surface can be suppressed, so that it is possible to stably produce a tubular film having the uniform strength in the vertical and horizontal directions.

According to the third aspect of the present invention, the tubular body is extended from between the inner annular resin outlet and the outer annular resin outlet, and the inner tubular film and the outer tubular film are pressed by the annular film pressing portion. Since the space therebetween is divided into a space outside the inner tubular film inside the cylindrical body and a space inside the outer tubular film outside the cylindrical body, the film is expanded after the discharge of the film. The transmission of undesired effects in the formation of the inner tubular film and the outer tubular film, such as the pressure transfer between the inner tubular film and the outer tubular film, can be interrupted. Can be performed well. Further, the cylindrical body is provided with an annular film pressurizing means, and presses the inner tubular film from the outer peripheral side, so that the sway of the tubular film can be suppressed to improve the dimensional accuracy and, if necessary, in the vertical and horizontal directions. It is also possible to produce a tubular film having a high strength. Therefore, the production of a double-layered tubular film can be performed with higher quality than before.

According to the fourth aspect of the present invention, the die is configured such that the inner annular resin outlet and the outer annular resin outlet rotate in directions different from each other, so that the strength of the joined tubular film is increased. In addition, it is possible to appropriately set the direction in which the resin is to be taken. For example, the molten tubular film can be configured to be evenly crossed by a die rotating in the right and left directions, and to take in the resin in a range of 45 ° ± 15 ° with respect to the flow direction of the resin. By doing so, the orientation of the resin separation of the tubular film becomes oblique so as to cross, so that the overall strength of the joined tubular film of the inner tubular film and the outer tubular film can be significantly increased.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram for explaining a tubular film manufacturing method according to the first embodiment of the present invention. This tubular film manufacturing apparatus 1 is roughly divided into an annular die 3 for extruding molten resin, a die-side air cooling ring 4 for cooling the tubular film 2, and a tubular film 2 in order from the upstream side when viewed from the traveling direction of the tubular film 2. It comprises an annular film pressing means 5 for pressing from the outside. In addition, a post-expansion air-cooling ring 6 for cooling the expanded tubular film 2 as necessary is also provided. Reference numeral 90 denotes a pinch roll for picking up the tubular film 2. The tubular film manufacturing apparatus 1 has a take-up device 88 composed of a pinch roll 90 and a guide roll 91 and a film take-up device 89 as shown in FIG. The molten resin to be the tubular film 2 is extruded from the annular die 3 to become a molten tubular film 7, and is cooled by the die-side air cooling ring 4 to become the normal tubular film 9 via the above-mentioned heat-softened tubular film 8.

The annular die 3 is attached to a resin extruder (not shown). The annular die 3 is provided with an annular slit 10 through which the molten resin is extruded, and an expansion air supply passage 11 for increasing the internal pressure in the tubular film 2. The molten annular film 7 is cooled by the air blown downstream from the die-side air cooling ring 4. Although the internal pressure in the molten tubular film 7 is increased by the air blown into the molten resin from the air supply passage 11, the blowing pressure of the die-side air-cooling ring 4 increases the height from the position exiting the annular slit 10. It is possible to correct that the molecules of the molten resin are strongly vertically aligned between the positions of the extended portions. And the workability of a film extension part can be improved by the correction. As described above, by raising the frost line position 14 as much as possible throughout the film formation and performing inflation, a film having excellent tear strength and impact resistance can be obtained. Annular film pressing means 5 shown in FIG.
Schematically shows a function as a film pressing means, and the annular film pressing means 5 has an annular contact surface 12 which contacts the tubular film 2 from outside.

In this embodiment, the annular film pressing means 5 is provided in a temperature range from the melting point of the resin constituting the tubular film 2 to the softening point, and is 0.1 mm relative to the lip diameter.
It is provided at a position before expansion of 95 to 1.1. That is, it is provided immediately before the film is expanded. Then, 0.48 kgf / cm ² is applied to the tubular film 2 from the outside of the resin.
While applying a force in the range of ５5.6 kgf / cm ² , braking is applied by pressing the tubular film from the outer peripheral side. By applying the above force in this temperature range,
The shaking of the normal tubular film 9 can be blocked from the molten tubular film 7, and the internal stress of the molten tubular film 8 can be developed. In addition, in the case of HDPE, the height H1 of the annular film pressing means 5 from the annular die 3 is usually set to 4.5 to 5.0 times the annular slit diameter. In FIG. 1, if necessary, at a position downstream of the position where the annular film pressurizing means 5 is provided, an enclosure 43 for covering the expanded portion of the tubular film 2 is provided, and an annular heater 44 for increasing the temperature in the enclosure 43 is provided. May be provided. By providing the enclosure 43 and the annular heater 44 in this manner, the temperature of the expanded film is prevented from lowering, the film is self-expanded by the internal pressure, and the blow-up ratio is increased by using the annular film pressing means 5 together. be able to.

In this embodiment, no pressurizing member for pressurizing the tubular film 2 from the inner peripheral side is provided. This is because, when a pressurizing body is installed on the inner surface of the tubular film, the film is likely to be cooled and cut, and it is difficult to work at the start of film processing because the film is entangled with the film at a low position. It depends. On the other hand, by providing the annular film pressing means 5 only on the outside of the tubular film 2 without providing various jigs inside the tubular film 2, it is possible to prevent the occurrence of the above work trouble.

As shown in FIGS. 2A and 2B, the annular film pressing means 5 has a specific construction.
Some use. FIG. 2A is a schematic explanatory view of a cylindrical body, and FIG. 2B is a partial longitudinal sectional view thereof. This cylinder 1
Reference numeral 3 denotes a cylindrical body that can be directly attached to a conventional tubular film manufacturing apparatus. The contact surface 12 of the cylindrical body 13 is formed on an elastic body 38. This cylinder 13 is
A predetermined position of the cylindrical body 13 is narrowed, and the upper part has a substantially alcoholic cup shape opened at a wide angle. The opening angle of the upper part is set so that the tubular film 2 that has passed through the contact surface 12 does not come into contact with the inner peripheral surface of the tubular body 13 during the expansion process. This opening angle is
It differs depending on the blow-up ratio of the film and the type of resin. As shown in FIG. 2B, the contact surface 12 of the cylindrical body 13 is a belt-shaped convex curved surface. This belt-shaped convex curved surface is provided annularly along the inner surface of the cylindrical body 13 and has a width d.
Varies depending on the film width of the tubular film, the type of resin, and the like, but is, for example, about 10 mm.
This contact surface 12 functions as the annular film pressing means 5.

As shown in FIG. 2B, the cross-sectional structure of the cylindrical body 13 is such that a low-density paper 36 is attached to an inner peripheral surface of a steel cylindrical body 35 serving as a base. The structure is such that a felt cloth 37 is attached. The thickness of the steel cylinder 35 serving as the base is about 2.5 mm to 5.0 mm, and the low-density paper 3
6, the thickness is about 2.5 mm to 5.0 mm, and the felt cloth 3
The thickness of 7 is about 5 mm. The low-density paper 36 functions as the elastic body 38 described above. The reason why the low-density paper 36 is used as the elastic body 38 is that it is a material having a small thermal conductivity and a small temperature change, and has excellent heat resistance.
Examples of the low-density paper 36 include foamable paper containing air therein, which is used for a paper pack or the like containing about 10 eggs. The reason why the raised woven cloth (such as the felt cloth 37) is attached to the contact surface where the film comes into contact is to reduce the coefficient of friction by making it smooth.

In addition to the low-density paper 36, a foamed resin, felt paper or the like can be used as the elastic body 38. Also in this case, a configuration in which the elastic body 38 itself is directly exposed to the contact surface 12 can be adopted, but more preferably, the above-mentioned raised woven cloth is used on the elastic body 38. It is possible to make a pressure resistance cylinder which is smooth and has good contact. As another method, a material such as a heat-resistant tube may be coated with low-density paper, felt cloth, or the like. In the case of this configuration, the contact surface may be a ring having a substantially triangular cross section or a ring having a substantially quadrangular cross section. The material forming the cylindrical body may be not only steel but also wood or nonmetal. However, it is preferable to be made of steel in view of workability, cost and stability. Note that FIG.
As shown in (A), in the case where the annular film pressing means 5 is constituted by a part of the cylindrical body 13, the tubular film 2 passing through the cylindrical body 13 is appropriately expanded in order to be a high-altitude expanded film. The configuration of the cooling air passage 45 in the body 13 is selected. Further, a ventilation port 46 is provided in the cylindrical body 13, and an air pressure adjusting pipe 47 is provided in the annular die 3.

The operation and effect of the film manufacturing apparatus shown in FIGS. 1 and 2 will be described. The cylindrical body 13 is connected to the annular die 3
Mount on top of Since the annular film pressing means 5 is constituted by the cylindrical body 13, even when the discharge of the molten tubular film 7 starts, the discharged molten tubular film 7 is pulled up to the pinch roll 90 through the inside of the cylindrical body 13. be able to. Then, when the tubular film 2 expands at the designated blow-up ratio, the heat-softened tubular film 8 comes into contact with the annular contact surface 12 of the tubular body 13, and the contact is made. Starting from the surface 12, the heat-softened tubular film 8 has a core to which it is fixed, and the heat-softened tubular film 8 stably expands radially around this core.

Further, since the height position of the contact surface 12 of the cylindrical body 13 is fixed, the expanding height position of the heat-softened tubular film 8 to be taken out is also fixed at a constant level. The dimensions of the formed tubular film 2 are constant.
Further, the swing generated from the folding plate and the folding board not shown in FIG. 1 is held by the contact surface 12 as the annular film pressing means 5, so that the molten tubular film 7 on the upstream side of the contact surface 12 is held. Never reach.

Further, even when the pulling speed of the expanded tubular film is increased, the portion of the molten tubular film 7 is
By exhibiting the function of alleviating the adverse effect of increasing the take-up speed of the molten tubular film 7 by the resistance of the contact surface 12, the internal stress (shrinking force) of the molten tubular film 7 can be exhibited. . Therefore, the lifting of the tubular film can be achieved in a natural state, and the shaking of the film and the partial disturbance of the internal temperature do not occur.
The dimensional accuracy can be improved. In the configuration of the first embodiment, if necessary, a temperature control device is provided so that the resin performs a predetermined temperature change with respect to the molten tubular film 7 and the heat-softened tubular film 8, and the molten tubular film 7 By controlling the temperature of the heat-softened tubular film 8, the blow-up ratio of the tubular film can be increased more stably. By increasing the blow-up ratio, a tubular film having a balanced strength in the vertical and horizontal directions can be produced. Also, by employing a known method such as water cooling at a predetermined position of the tubular film by means other than that shown in FIG. 1, the longitudinal and transverse strengths of various thermoplastic resins which have been difficult to expand conventionally can be balanced at a high level. It becomes possible.

FIG. 5 is a longitudinal sectional view for explaining a case where the annular film pressing means 5 is constituted by an air knife device for pressing the film surface in a non-contact manner. The air knife device 51 is provided annularly so as to surround the tubular film from the outer periphery. The air knife device 51 has a structure in which an annular gas supply pipe 52 is connected to an annular air knife section 53. A gas having a predetermined pressure from a compressor or the like is sent into the gas supply pipe 52, and the gas pressurized through the communication pipe section 54 of the gas supply pipe 52 is sent out to the first gas reservoir 55 of the air knife section 53. . Air knife part 5
3, an annular upper plate-like body 56 and an annular lower plate-like body 57 are fastened by fastening bolts 59 via a packing 58.
It has an integrated configuration. Recesses are formed in the upper plate-like body 56 and the lower plate-like body 57 at positions facing each other,
By combining these recesses, the first gas reservoir 5
5, a first gas passage 60, a second gas reservoir 61, a second gas passage 62, a third gas reservoir 63, and an outlet passage 64 are respectively formed. Gas outlet 6 of outlet passage 64
5 has a width of about 0.1 mm to 0.3 mm.

By providing a plurality of gas reservoirs between the gas passages as described above, it is possible to reduce the turbulence of the gas flow and to uniformly blow out the substrate. Also, since the width of the gas outlet 65 is about 0.1 mm to 0.3 mm, unlike a cooling air from a so-called air cooling ring that sends air for cooling by a blower, it does not cause gas convection on the film surface,
Only pressure can be applied to the film surface. The air knife device is provided with a heater (not shown) at a predetermined position so as to increase the temperature of the gas exiting from the gas outlet 65 so as not to lower the temperature of the film. The air blowing angle of the air knife device ranges from a minimum installable angle θ at which air strikes from the direction opposite to the traveling direction of the tubular film 2 to a direction perpendicular to the film traveling direction (the state shown in FIG. 5). I do. The distance S between the gas outlet 65 and the tubular film 2 is 40 mm or less, preferably 20 mm
It is set to about 2 mm. The wind speed of the gas and the static pressure in the gas storage chamber are appropriately set to the extent that the film shake is suppressed. The description of the cooling air pressure, which is well described in the prior art using an air cooling ring, describes the value of the static pressure of the air reservoir of the blower, whereas the static pressure of the present invention is applied to the film. It is an indication of the applied force, and obviously has a different content.

[0035]

Second Embodiment FIG. 3 is a schematic view showing a manufacturing apparatus for manufacturing a double-layered tubular film according to a second embodiment of the present invention, and FIG. 4 is a view of a double-ring annular die viewed from a downstream side. It is a top view. The tubular film manufacturing apparatus 16 includes a cylindrical inner die 17 having a rotating shaft (not shown) at the center.
And an annular outer die 18 provided concentrically so as to fit the inner die 17 to the outside. The inner die 17 is rotatable clockwise and counterclockwise, respectively. In the configuration shown in the second embodiment, the inner die 17 is rotated clockwise as shown in FIG.
The outer die 18 is configured to rotate counterclockwise. As shown in FIG. 4, the inner die portion 17 has an inner annular resin outlet 20 for discharging the inner tubular film 19,
And an expansion air supply passage 21. The expansion air supply passage 21 is a double pipe, and supplies air through an inner passage 21a and exhausts air through an outer passage 21b to maintain the internal pressure of the inner tubular film 19 at a predetermined pressure described later. I am trying to do it.

As shown in FIG. 3, a cylindrical body is formed from the upper surface 17a of the inner die 17 so as to surround the discharged inner tubular film 19 from the outside at an outer peripheral position from the inner annular resin outlet 20 of the inner die 17. 22 extends downstream. An annular film pressing unit 23 is provided at the downstream end of the cylindrical body 22.
Is provided so that the pressure can be applied by the abutting surface 12 of the annular film pressing unit 23 within the above-described temperature range and force of the resin. The inner tubular film 19 and the outer tubular film 2 are pressed by the pressure of the annular film pressing section 23.
4 between the inner tubular film 1 inside the tubular body 22.
9 and a space outside the tubular body 22 and inside the outer tubular film 24. In the configuration shown in FIG. 3, the space inside the inner tubular film 19 is referred to as an inner space 30, and the space inside the tubular body 22 and outside the inner tubular film 19 is the in-cylinder space 3.
The space outside the tubular body 22 and inside the outer tubular film 24 is called an inter-film space 25, and the space outside the outer tubular film 24 is called an outer space 31.

An annular cooling air discharge port 40 for turning the inner tubular film 19 into an elevated film is provided immediately inside the cylindrical body 22. Cooling air outlet 4 formed on upper surface 17a
The pressure in the in-cylinder space 34 is maintained at a predetermined pressure by being discharged from 1. The outer die portion 18 has an outer annular resin outlet 27 for discharging the outer tubular film 24 and an auxiliary air supply passage 26. As shown in FIG.
The auxiliary air supply passage 26 is provided inside the outer annular resin outlet 27. The expansion air supply passage 26 is a double tube, and supplies air through an inner passage 26a and exhausts air through an outer passage 26b to reduce the pressure in the inter-film space 25 to a predetermined pressure described later. I keep it. As shown in FIG.
The inner tubular film 19 extruded from the outer tubular resin 24 and the outer tubular film 24 extruded from the outer annular resin outlet 27 are joined at a joining point 32 outside the double annular die 28 to form an integrated tubular film 29. I have.

The pressure in the internal space 30 is increased to 3922.
6 (Pa) to 470712 (Pa), and the pressure of the inter-film space 25 is 23536 (Pa) to 313813 (Pa).
And the pressure of the outer space 31 is set to 27458 (Pa) to 3
72653 (Pa). The pressure in the in-cylinder space 34 is set substantially equal to the pressure in the outer space 31.
The pressure in the internal space 30 is 39226 (Pa) to 3
53039 (Pa), the pressure in the inter-film space 25 is set to 23536 (Pa) to 235356 (Pa), and the pressure in the outer space 31 is 27458 (Pa) to 282432.
(Pa) is preferable, and the pressure of the internal space 30 is set to 39226 (Pa) to 282432 (Pa), and the pressure of the inter-film space 25 is 23536 (Pa).
It is more preferable that the pressure is set to １６０160829 (Pa) and the pressure of the outer space 31 is set to 27458 (Pa) to 191230 (Pa). The material of the resin of the inner tubular film 19 and the material of the resin of the outer tubular film 24 may be different from each other.

The operation and effect of the tubular film manufacturing apparatus 16 having the above configuration will be described. An inner die 17 for rotating the inner tubular film 19 clockwise, and an outer die 18 for rotating the outer tubular film 24 counterclockwise.
In this way, the tubular films 19 and 24 are evenly crossed with each other, and the resin is extruded while adjusting the amount of resin extruded within the range of 45 ° ± 15 ° with respect to the flow direction of the resin in accordance with the take-off direction. Then, the orientation directions of the resin molecules of the tubular film joined at the joining point 32 are obliquely intersecting with each other as indicated by reference numeral 33 in FIG. 3, and are thinner and higher in overall strength than the conventional method. Can be.

In this method, the inner tubular film 19
By setting the pressure of the inner space 30 which is the space inside the uppermost space, and setting the inter-film space 25 lower than the pressure of the inner space 30, the inner tubular film 19 is turned by the innermost high pressure. To achieve an adhesion commonly referred to as blocking. Here, since the space between the inner tubular film 19 and the outer tubular film 24 is pressure-divided by the tubular body 22 into the in-cylinder space 34 and the inter-film space 25, the pressure in the inter-film space 25 causes It is possible to prevent the film surfaces of the tubular film 19 from sticking to each other.
That is, since the in-cylinder space 34 is partitioned from the inter-film space 25, it is possible to set the pressure most suitable for forming the high-altitude expanded film. Also, as the film shakes in the expanded portion of the inner tubular film 19, the joint point 3
At 2, air bubbles are introduced, resulting in a decrease in the quality of the product. Therefore, by providing the annular film pressing portion 23 of the cylindrical body 22 and pulling up the inner tubular film 19 in a state where no shaking occurs, a good tubular film can be produced as described above.

In this embodiment, the joining is performed in the double configuration of the inner tubular film and the outer tubular film. However, a double annular die for discharging three or more layers of the tubular film is provided, and the film surface of the three or more layers is formed. Can be adopted. The present invention is not limited to the first and second embodiments, and various design changes can be made without departing from the scope of the present invention. Hereinafter, such an embodiment will be described. (1) The film manufacturing method and the manufacturing apparatus of the present invention are techniques that can be widely applied to inflation film formation, and for example, can be adopted also in a manufacturing method and a manufacturing apparatus of a biaxially stretched film. (2) In the above-described embodiment, the configuration in which the tubular film is discharged upward from the annular die against gravity is shown. However, a configuration in which the annular resin outlet of the circular die is directed downward and the tubular film is discharged downward can also be adopted. .

[0042]

EXAMPLES Hereinafter, typical examples of the present invention will be described, and comparative examples with the conventional method will be described. (A) Examples 1 to 4 (see FIG. 9) A case where the folding type is flat and the resin is HDPE. In Examples 1 to 4, the error in the take-up dimension was small and the processing condition was good. On the other hand, in Comparative Examples 1 and 2, although the blow-up ratio was small, the error of the take-up dimension was large, and the film surface was shaken, resulting in instability. (B) Examples 3 to 6 (see FIG. 10) A case where the folding type is gusset and the resin is HDPE. FIG.
Is a view showing how to set the folding size of the gusset, L1
Is a front width dimension, and L2 is a folding dimension. The take-off dimension is given by L1 + 2 · L2. Example 3 to Example 6
In this case, the error in the take-up dimension was small and the processing condition was good. On the other hand, in Comparative Examples 3 and 4, although the blow-up ratio was small, the error in the take-up dimension was large. Was.

(C) Examples 7 and 8 (see FIG. 11) Examples 7 and 8 are examples in which the resin is HDPE and the double annular die described in the second embodiment is used. . The processing conditions were good in both Example 7 and Example 8. In addition, when the numerical value of the double-layered film formed according to Example 7 is shown, the average thickness of the film is 50 μm,
Tensile breaking strength (kg / mm ² ) is MD (vertical) / TD (horizontal)
Is 25.48 / 25.61 and the tensile elongation at break (%) is 79.41 in MD (longitudinal) / TD (horizontal).
/70.05, and the tensile strength (kg / mm ² )
The ratio of D (vertical) / TD (horizontal) was 117.6 / 118.2, and a high-strength film having balanced vertical and horizontal strengths could be produced.

(D) Examples 9 to 11 (see FIG. 12) The case where the folding type is flat and the resin is nylon. Even when the blow-up ratio is about 2.0 or more, which makes production difficult in Comparative Examples 5 to 7, it is possible to form a good film while maintaining high dimensional accuracy in Examples 9 to 11. Became. (E) Examples 12 to 14 (see FIG. 13) A case where the folding type is flat and the resin is HDPE. Even in the blow-up ratio of 5.5 or more, in which the production is difficult in Comparative Examples 8 to 9, in Examples 12 to 14, it is possible to form a good film while maintaining high dimensional accuracy. became.

[Brief description of the drawings]

FIG. 1 is a schematic view for explaining a method for producing a tubular film according to a first embodiment of the present invention.

FIGS. 2A and 2B are diagrams for explaining a cylindrical body as an example of an annular film pressing means.

FIG. 3 is a schematic view for explaining a tubular film manufacturing method according to a second embodiment of the present invention.

FIG. 4 is a plan view of a double-layer annular die employed in a second embodiment as viewed from a downstream side.

FIG. 5 is a longitudinal sectional view of an air knife device that can be used for pressurization according to the present invention.

FIG. 6 is a diagram for explaining how to set a folding size of the gusset.

FIG. 7 is a schematic configuration diagram showing a conventional blown film manufacturing apparatus.

FIG. 8A is a view for explaining a method of manufacturing a low-altitude extension film, and FIG. 8B is a view for explaining a method of manufacturing a high-altitude extension film.

FIG. 9 is a table comparing the dimensional accuracy and processing status of the example and the comparative example with HDPE as the resin used.

FIG. 10 is a table comparing the dimensional accuracy and the processing status of the example and the comparative example with HDPE as the resin used.

FIG. 11 is a table showing the dimensional accuracy and processing status of an example in which a resin used is HDPE and a double-layered die is used.

FIG. 12 is a table in which the resin used is nylon and the dimensional accuracy and processing conditions of the example and the comparative example are compared.

FIG. 13 is a table comparing the dimensional accuracy and the processing status of the example and the comparative example with HDPE as the resin used.

[Explanation of symbols]

5 ... annular film pressurizing means, 10 ... annular resin outlet, 19
... inner tubular film, 20 ... inner annular resin outlet, 22 ...
Cylindrical body, 23: annular film pressing section, 24: outer tubular film, 25: inter-film space, 27: outer annular resin outlet, 28: double annular die, 34: inner space of cylinder.

Claims (4)

[Claims] 1. A tubular film production method for producing a tubular film by an inflation method by discharging a tubular thermoplastic molten resin from an annular resin outlet (10), wherein the melting point of the molten resin is + 10 ° C. 15 ℃
In the temperature range of 0.48 kK before the tubular film (2) begins to expand from the outside of the tubular film (2).
gf / cm ^{2 to} 5.6 kgf / cm ² .
A method for producing a tubular film, characterized in that the tubular film (2) is expanded after the pressurization to produce a tubular film. 2. An annular die (3) for discharging a tubular thermoplastic molten resin from an annular resin outlet (10), and an air supply passage (11) for feeding air into the molten resin. In a tubular film manufacturing apparatus for manufacturing a film, a temperature from a melting point of the molten resin + 10 ° C. to a softening point of −15 ° C.
In the temperature range of 0.48 kK before the tubular film (2) begins to expand from the outside of the tubular film (2).
gf / cm ² ~5.6kgf / cm tubular film pressurizing means for applying a force range of ² (5) is provided, by extending the tubular film (2) in its after pressing, characterized in that to produce a tubular film A tubular film manufacturing apparatus. 3. A plurality of annular resin outlets (20 · 2) concentrically.
An inner tubular film (19) having a double annular die (28) having an inner annular resin outlet (20) having an inner annular resin die (7) having
And the outer tubular film (24) discharged from the outer annular resin outlet (27) are joined to each other outside the double annular die (28) to produce a tubular film. ) And the outer annular resin outlet (27), the inner tubular film (19) passes through the inside of the tubular body (22), and the outer tubular film (24) The cylindrical body (22) includes an annular film pressing unit (23), and the annular film pressing unit (23) includes an inner tubular film.
(19) is provided at a predetermined position before the start of expansion, and in the region from the melting point of the molten resin of + 10 ° C. to the softening point of −15 ° C., from the outside of the inner tubular film (19). A force in the range of 48 kgf / cm ^{2 to} 5.6 kgf / cm ² is applied, and the inner tubular film (19) and the outer tubular film (24) are pressed by the annular film pressing section (23). A space (34) inside the tubular body (22) outside the inner tubular film (19), and a space (25) outside the tubular body (22) inside the outer tubular film (24). A method for producing a tubular film, characterized in that: 4. The method of claim 3, wherein the inner annular resin outlet (20) and the outer annular resin outlet.
(27) The method of manufacturing a tubular film, wherein the double annular die (28) is configured to rotate in directions different from each other.