JP2004106533A - Manufacturing apparatus and method for inflation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an inflation film in which quality fluctuation of quality can be sufficiently suppressed, and an apparatus therefor. <P>SOLUTION: A raw material resin is extruded from an annular die 2 in a molten state to form an annular film 4 and air is supplied into the inner space of the annular film 4 under cooling to inflate the film. At least one air ring 31, which is provided so as to be concentric to the annular die 2, is provided along with the cooling ring 12 provided in close vicinity to the annular die 2 and air is blown off from the air ring 31 not only to support the annular film 4 in a molten state but also to set the temperature of air blown off from the air ring 31 to a temperature capable of ensuring the inflation of the annular film 4 of a molten state. <P>COPYRIGHT: (C)2004,JPO

Description

{Circle over (1)} The present invention relates to an apparatus and a method for producing an inflation film which suppresses quality variations.

The inflation molding method is widely used in the production of films made of thermoplastic resins such as polyolefin resins such as low-density polyethylene and high-density polyethylene, because the apparatus is simple and inexpensive. In a general inflation molding method, a molten thermoplastic resin is extruded from an annular die of an extruder, and the outer surface of the extruded annular film is taken out while being cooled by air blown from a cooling ring, and at the same time, air is introduced into an inner space of the annular film. Such a gas is supplied and expanded to a predetermined size by the internal pressure, then the annular film is folded into a sheet by a pair of nip rolls, and then both ends of the folded film are cut with a slitter or the like to form a flat sheet. , Or as a bag-like film as it is.

で は In the inflation molding method, the annular film extruded from the annular die is stretched in the longitudinal and transverse directions by taking up and expanding. At the same time, the film changes from an amorphous state molten by cooling to a solid state, and at this time, the physical properties of the film are determined. Thus, the inflation molding method plays an important role in determining the physical properties of the film obtained by the cooling step.

In the inflation method, various proposals have been made for the purpose of suppressing the variation in the quality of the obtained film.
For example, a control means for controlling the amount of air blown from the cooling ring so as to keep the height of the frost line (the line where the film solidifies by cooling and reaches the final diameter) of the cylindrical film extruded from the die constant. There has been proposed an inflation film forming apparatus provided with such an apparatus (see Japanese Patent Application Laid-Open No. Hei 6-182868 (Patent Document 1)).
Further, in addition to the first air ring provided in proximity to the die, a second air ring having a plurality of annular slits is provided at a position where the resin bubble extruded from the die expands rapidly, and the second air ring is provided. (2) An inflation molding method characterized by adjusting the temperature of the resin bubble at the inlet of the air ring to a specific range to form a film, and an apparatus used in the method have been proposed (Japanese Patent Application Laid-Open No. 6-39916). (See Patent Document 2). According to the description of this publication, cooling of the resin bubble is performed by air blown from the first air ring, and cooling conditions are set so that the temperature of the resin bubble at the inlet of the second air ring falls within the above range. Adjusted.

The method described in Japanese Patent Application Laid-Open No. 6-182868 has a certain effect on the control of the frost line. Fluctuation, loosening and wrinkles are likely to occur.
In the method described in Japanese Patent Application Laid-Open No. 6-39916, it is preferable that the second air ring is configured to blow air substantially parallel to the bubble taking-out direction or outward. It is described that "a reduced-pressure atmosphere created by blowing out cooling air affects a molten resin bubble, and a sudden expansion of the bubble starts at this position". This method aims to improve the instability of the resin bubble by molding with a long neck type, even when using a thermoplastic resin having a low melt tension, by controlling the expansion start position of the resin bubble. Is what you do.
However, in the method disclosed in the publication, the temperature of the resin bubble at the inlet of the second air ring is adjusted to a certain range, but the fluctuation of the temperature of the resin bubble is not considered. Further, the air blown out from the second air ring is supposed to create a reduced-pressure atmosphere, but it tends to give a rapid change to the cooling state of the resin bubble. As described above, in the method described in Japanese Patent Application Laid-Open No. 6-39916, delicate adjustment of operating conditions is required to suppress fluctuations in the quality of the obtained film.
JP-A-6-182868 JP-A-6-39916

The present invention has been made in view of the above-described conventional technology, and has as its object to provide an apparatus and a method for producing an inflation film, which can sufficiently suppress variations in the quality of an obtained film.

In the production of a film by the inflation molding method, in order to suppress the variation in the quality of the obtained film, it is necessary to suppress the fluctuation of the film in the molten state and minimize the fluctuation of the cooling state in the cooling process as much as possible. It is desirable to do. The present inventors have conducted intensive studies from such a viewpoint, and as a result, completed the present invention.
That is, the present invention relates to an inflation film manufacturing apparatus comprising: extruding a material resin from an annular die to form an annular film; and supplying a gas to an inner space thereof while cooling the annular film to expand the film. Along with the cooling ring provided in the vicinity of the annular die, at least one air ring provided concentrically with the annular die is disposed, and the temperature of the gas blown out from the air ring is reduced by the molten annular ring. Provided are an apparatus for producing a blown film, which is provided with a means for adjusting a temperature at which film expansion can be ensured, and an inflation molding method using the apparatus.

According to the present invention, it is possible to obtain an inflation film in which variation in quality is sufficiently suppressed.

Examples of the raw material resin usable in the present invention include low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), polypropylene, α-olefin polymer, and ethylene-unsaturated ester. In addition to olefin resins such as polymers, ethylene-vinyl alcohol copolymer, soft polyvinyl chloride, soft polyvinylidene chloride, polyamide, polystyrene, polyarylate, thermoplastic liquid crystal polymer such as thermoplastic liquid crystal polyester, and the like. .

方法 The method of the present invention is particularly useful for producing a film composed of a thermoplastic liquid crystal polymer. When the thermoplastic liquid crystal polymer is discharged from a slit of a die in a film forming apparatus, molecules are oriented in a discharge direction, and a direction of a mechanical axis of the film (hereinafter, may be abbreviated as MD direction) and a direction perpendicular to the direction (hereinafter, abbreviated as MD direction). , In the TD direction), there is a tendency to become a so-called anisotropic film having a difference in physical properties. However, if the inflation molding method is used, the film is stretched also in the TD direction upon expansion and the anisotropy is increased. This is because the film is relaxed and an isotropic film can be easily obtained.

(4) As the thermoplastic liquid crystal polymer, a polymer having a melting point in the range of 200 to 400 ° C., preferably 250 to 350 ° C. in terms of processability and heat resistance of the obtained film is used.

Further, the apparatus for producing a blown film according to the present invention comprises melt-extruding a raw material resin from an annular die to form an annular film, and supplying a gas to an inner space thereof while cooling the annular film to expand the film. In the apparatus for manufacturing a blown film, at least one air ring is disposed concentrically with the annular die together with the cooling ring in the vicinity of the annular die, and further includes means for adjusting the temperature of gas blown from the air ring. I have. Then, a gas adjusted to a temperature at which the expansion of the molten annular film can be ensured is blown from such an air ring to support the molten annular film. For this reason, the fluctuation of the film in the molten state and the fluctuation of the cooling state of the film are sufficiently suppressed, and the variation in the quality of the obtained film can be suppressed.

In such a device, it is preferable that the above-mentioned air ring is provided with a height adjusting mechanism. With such a height adjustment mechanism, the height of the frost line can be set to an arbitrary position according to the type of the raw material resin to be used, the thickness of the target film, and the like, and it is easy to manufacture various films. It is possible to respond.

FIG. 1 is a longitudinal sectional view showing a blown film manufacturing apparatus according to one embodiment of the present invention. In the apparatus shown in the figure, a cooling ring 12 having an outlet 11 is disposed concentrically with the annular die 2 at a position directly above the resin extrusion side of the annular die 2. A tubular member 20 covering the neck 7 of the annular film (bubble) 4 in a state is arranged concentrically with the annular die 2, and air is concentrically provided on the upper end of the tubular member 20 with the annular die 2. The ring 31 is arranged. Although not shown, as in the case of a normal blown film manufacturing apparatus, a gas is supplied to the inner space of the annular film 4 in a molten state extruded from the annular die 2. FIG. 1 shows a case in which a thermoplastic liquid crystal polyester is used as a raw material resin. A molten annular film 4 extruded from an annular die 2 expands by the action of gas supplied to an inner space. To the frost line 10 and solidifies.
At this time, the ratio (expansion coefficient) between the inner diameter (r0) of the film 4 immediately after being extruded by the annular die 2 and the inner diameter (rf) of the solidified film in the frost line 10 depends on the type of the raw material resin and the physical properties of the obtained film. Although it is appropriately set according to the like, it is usually about 2 to 10 times.

The tubular member 20 is desirably installed because it prevents gas blown out from the cooling ring 12 from diffusing around the tubular film 4 and contributes to preventing swinging of the tubular film. The inner diameter L of the tubular member 20 is usually in the range of twice (2 × r0) the inner diameter of the film 4 immediately after being extruded to the inner diameter (rf) of the solidified film in the frost line 10.
Further, the inside of the tubular member 20 may have a funnel shape so that the distance between the inner surface of the tubular member 20 and the annular film 4 in a molten state is kept constant.

Further, in the apparatus shown in FIG. 1, an annular guide member 13 is attached to the outlet 11 of the cooling ring 12, and the cooling air blown from the cooling ring 12 by the guide member 13 is directed to the annular film 4 side. I will guide you.

Further, a first blower 16 is connected to the cooling ring 12 via a first temperature control means 14 such as a heater and a first valve 15. The wind from the blower 16 reaches the first temperature control means 14 via the first valve 15, where it is adjusted to a predetermined temperature, and blows out to the annular film 4 through the outlet 11 of the cooling ring 12. Then, the annular film 4 is cooled. Also, a second blower 34 is connected to the air ring 31 via a second temperature adjusting means 32 and a second valve 33. The air from the blower 34 reaches the second temperature control means 32 via the second valve 33, where it is heated and blown out from the air ring 31 to the molten annular film 4.

The air ring 31 is provided with an adjusting means 50 for adjusting the temperature of the gas blown out of the air ring 31 to a range in which the expansion of the molten annular film 4 can be ensured. Further, a temperature sensor 51 is disposed inside the air ring 31, and is configured to detect the temperature of the gas to be blown out. Reference numeral 52 denotes a CPU, and in the apparatus shown in FIG. 1, the adjusting means 50 is configured to control the second temperature adjusting means 32 such as a heater and the second blower 34. As the adjusting means 50, a CPU is typical. The adjusting unit 50 adjusts the temperature of the gas by the second temperature adjusting unit 32, the air volume of the second blower 34, and the like to a preset value. These are calculated in advance so that the temperature of the gas blown from the air ring 31 becomes a predetermined value in accordance with the film manufacturing conditions. The adjusting means 50 can be configured to adjust the valve 33.

In the production of the blown film according to the present invention, in the steady state, it is not necessary to particularly change such set values. However, when the temperature of the gas blown out by the temperature sensor 51 fluctuates, the adjustment means 50 feeds back. However, adjustments can be made to cancel such fluctuations. Further, a means for detecting the temperature of the annular film 4 in a molten state is provided, and when a change in the temperature of the annular film 4 is observed by the detecting means, feedback is provided by the adjusting means 50, and the gas to be blown out so as to cancel such a change. The temperature can also be adjusted.

As shown in FIG. 1, the adjusting unit 50 may be configured to adjust the first heater 14 and the first blower 16 connected to the cooling ring 12. Further, the temperature of the gas blown out from the cooling ring 12 may be controlled based on the temperature detection result of the temperature sensor 53 disposed inside the cooling ring 12.

The temperature of the gas blown from the cooling ring 12 is appropriately selected in consideration of the type of the raw material resin, the shape of the target film, the physical properties, and the like. However, the temperature is usually 220 times higher than the melting point (Tm) of the raw material resin. The temperature is set to a temperature (Tm-220 to Tm-60) lower by 〜60 ° C., preferably a temperature (Tm-180 to Tm-80) lower by 180 to 80 ° C. than the melting point (Tm). The air velocity of the gas blown from the cooling ring 12 is usually in the range of 1 to 10 m / sec, preferably 2 to 5 m / sec.

(4) The temperature of the gas blown out from the air ring 31 needs to be a temperature at which the expansion of the molten annular film can be ensured. The temperature of the gas blown from the air ring 31 is appropriately determined in consideration of the type of the raw material resin and the shape and physical properties of the target film, the position of the air ring 31 with respect to the frost line 10, the direction of the gas blown from the air ring, and the like. It is usually selected from a temperature (Tm−80) lower than the melting point (Tm) of the raw material resin by 80 ° C. (Tm + 20 ° C.), preferably 60 ° C. higher than the melting point (Tm) of the raw resin. The temperature is set in a range from a low temperature (Tm-60) to a temperature (Tm + 5) 5 ° C. higher than the melting point. The air velocity of the gas blown from the air ring 31 is usually in the range of 1 to 10 m / sec, preferably 3 to 10 m / sec.

方向 The direction of the gas blown out from the air ring 31 is not particularly limited as long as it can support the annular film 4 in a molten state.

The air ring 31 is provided concentrically with the cooling ring 12. The position of the air ring 31 can be provided at any position above the cooling ring 12 and below the frost line 10, but is provided at a height (below) of 5 cm to 15 cm from the frost line 10. Is preferred.
The structure of the air ring 31 is not particularly limited, and a simple structure having one slit as an air outlet can be used, but a structure having a plurality of slits may be used.

The air ring 31 is preferably provided with a height adjustment mechanism 21 for setting and maintaining the height of the air ring 31 at an arbitrary position according to the frost line 10 of the resin used.

FIG. 2 is a partially cutaway front view showing the height adjusting mechanism 21. In the embodiment shown in the figure, a height adjusting mechanism 21 is formed using the tubular member 20. In other words, the height adjusting mechanism 21 is configured such that the cylindrical member 20 is divided into a first cylindrical body 22 to which the air ring 31 is attached, and a second cylindrical body 23 which is movably inserted therein. A screw 26 is screwed into a screw hole 25 provided in the second cylindrical body 23 from an elongated hole 24 formed in the first cylindrical body 22 and extending in the vertical direction. By adjusting the overall length of the second air ring 31, the height of the second air ring 31 is adjusted according to the position of the frost line 10 of the resin to be used.

Although not shown in FIG. 1, the solidified cylindrical film 4 may be folded into a sheet by a pair of nip rolls and wound up as a bag-like film, and then the folded film may be used. May be cut with a slitter or the like and wound up as two planar films.

As the gas blown from the cooling ring 12, the air ring 31, the optional air ring 41, and the gas supplied to the inner space of the annular film 4, a gas that does not adversely affect the material resin is used. However, air, nitrogen, carbon dioxide and the like can be used, and air is preferred in terms of production cost.

FIG. 3 shows a blown film manufacturing apparatus according to another embodiment of the present invention. In the apparatus shown in this figure, in addition to the air ring 31, a second air ring 41 is provided below the frost line. Although not shown, the second air ring 41 is also provided with a third valve, a temperature adjusting means such as a heater, a blower, and an adjusting means 50 for adjusting the temperature of the gas to be blown out. The temperature adjustment of the gas blown out of the second air ring 41 can be performed in the same manner as the temperature adjustment of the gas blown out of the air ring 31 described above. Further, the temperature, the wind speed and the direction of the gas blown from the second air ring 41 are the same as the temperature, the wind speed and the direction of the gas blown from the air ring 31 described above. Other parts are the same as those of the manufacturing apparatus shown in FIG. 1, and therefore, the same parts are denoted by the same reference numerals and description thereof will be omitted.

Hereinafter, an example of producing a thermoplastic liquid crystal polymer film by the method of the present invention will be described. The evaluation of the thermoplastic liquid crystal polymer film (fluctuation in film thickness, appearance) and the stability of the annular film (bubble) were performed by the following methods.

(1) Fluctuation in film thickness The obtained film was sampled for 4 m in the take-off direction (machine axis direction; MD), and the film thickness was taken at 20 points (20 cm interval) in the take-off direction (MD), in the direction perpendicular to the take-off direction TD) was measured at 24 points, for a total of 480 points (20 × 24), and the difference between the thickest film thickness and the thinnest film thickness was defined as the film thickness variation.
(2) Bubble Stability As shown in FIG. 4, a pair of laser displacement sensors 60, 60 each having a laser beam emitting port 61 and a laser beam receiving port 62 opposed thereto, block the annular film 4 above the frost line. In this manner, the laser beam was placed at two opposing positions, and the intensity of the shielded laser beam was measured, and the fluctuation was used to detect the swing width W (unit: mm) of the annular film 4. The standard deviation (σ) of the swing width W of the annular film 4 was determined and used as an index of bubble stability. The smaller the value is, the smaller the sway of the bubble is and the better the stability is.
(3) Appearance of Film The appearance of the obtained film was visually observed at a length of 1000 m, and evaluated according to the following four grades.
：: No wrinkle is observed. ○: 1 to 10 wrinkles are observed. Δ: 11 to 50 wrinkles are observed. X: 51 or more wrinkles are observed.

Production Example 1
Using a manufacturing apparatus shown in FIG. 1, a thermoplastic liquid polyester (Vectra A950 (trade name), manufactured by Polyplastics; melting point: 283 ° C.) was used as a raw material resin, and a blown film was formed under the following conditions. The film was wound up as a bag-like film to obtain a thermoplastic liquid crystal polyester film (average film thickness: 25 μm, average fold width: 314 mm).
As shown in Table 1, the variation of the film thickness in the obtained film was 5 μm, and the value of the standard deviation (σ) of the fluctuation width W of the film, which indicates stability during production, was 1.0 mm. Also, no wrinkles were observed in the obtained film (evaluation: ◎).

Forming conditions of blown film Diameter of annular die 2: 50 mm
Slit width of annular die 2: 250 μm
Diameter of protective cylinder 20: 150 mm
Discharge temperature of raw resin: 283 ° C
Discharge rate of raw resin (molten): 13 kg / hr
Film take-up speed: 9.9 m / min Expansion rate: 4 times Position of cooling ring 12: Temperature of gas blown from cooling ring 12 right above annular die 2: 150 ° C.
Wind velocity of gas blown from cooling ring 12: 5 m / sec
Position of air ring 31: 200 mm above annular die 2
Temperature of gas blown out from air ring 31: 230 ° C
Wind velocity of gas blown out from air ring 31: 5 m / sec
Direction of gas blown from air ring 31: Vertical upward frost line position: 300 mm above annular die

Production Examples 2 and 3
Except that the temperature and the wind speed of the gas blown from the cooling ring 12 and the temperature and the wind speed of the gas blown from the air ring 31 were changed as shown in Table 1, the blown film was molded in the same manner as in Example 1, and the thermoplastic liquid crystal was formed. A polyester film (average thickness: 25 μm, average fold width: 314 mm) was obtained. Table 1 also shows the value of the standard deviation (σ) of the fluctuation width W of the film, which indicates the change in film thickness, the appearance, and the stability during production of the obtained film.

Comparative Example 1
In the manufacturing apparatus shown in FIG. 1, an inflation manufacturing apparatus in which the protective cylinder 20 and the air ring 31 are omitted is used, and a thermoplastic liquid crystal polyester [VECTRA A950 (trade name), manufactured by Polyplastics Co., Ltd .; ° C], and a blown film was formed under the following conditions and wound up as a bag-like film to obtain a thermoplastic liquid crystal polyester film (average film thickness: 25 µm, average folding width: 314 mm). The variation in the film thickness of the obtained film was 13 μm, and the value of the standard deviation (σ) of the fluctuation width W of the film, which indicates the stability during production, was 2.5 mm. Moreover, many wrinkles were observed in the obtained film (Evaluation: X).

Forming conditions of blown film Diameter of annular die 2: 50 mm
Slit width of annular die 2: 250 μm
Discharge temperature of raw resin: 283 ° C
Discharge rate of raw resin (molten): 13 kg / hr
Film take-up speed: 9.9 m / min Expansion rate: 4 times Position of cooling ring 12: Temperature of gas blown from cooling ring 12 right above annular die 2: 150 ° C.
Wind velocity of gas blown from cooling ring 12: 2 m / sec

Comparative Example 2
In the manufacturing apparatus shown in FIG. 1, an inflation manufacturing apparatus in which the air ring 31 is omitted is used, and a thermoplastic liquid crystal polyester [VECTRA A950 (trade name), manufactured by Polyplastics; melting point: 283 ° C.] is used as a raw material resin. Then, an inflation film was formed under the following conditions and wound up as a bag-like film to obtain a thermoplastic liquid crystal polyester film (average film thickness: 25 μm, average folding width: 314 mm). The variation in the film thickness of the obtained film was 11 μm, and the value of the standard deviation (σ) of the fluctuation width W of the film, which indicates the stability during production, was 2.0 mm. Further, the obtained film had noticeable wrinkles (evaluation: Δ).

Forming conditions of blown film Diameter of annular die 2: 50 mm
Slit width of annular die 2: 250 μm
Diameter of protective cylinder 20: 150 mm
Discharge temperature of raw resin: 283 ° C
Discharge rate of raw resin (molten): 13 kg / hr
Film take-up speed: 9.9 m / min Expansion rate: 4 times Position of cooling ring 12: Temperature of gas blown from cooling ring 12 right above annular die 2: 150 ° C.
Wind velocity of gas blown from cooling ring 12: 5 m / sec

Production Example 4
Using the manufacturing apparatus shown in FIG. 1, a thermoplastic liquid crystal polyester [VECTRA C950 (trade name), manufactured by Polyplastics; melting point: 325 ° C.] was used as a raw material resin, and an inflation film was molded under the following conditions. A wound thermoplastic liquid crystal polyester film (average thickness: 50 μm, average folding width: 314 mm) was obtained as a bag-like film. As shown in Table 2, the variation of the film thickness in the obtained film was 6 μm, and the value of the standard deviation (σ) of the fluctuation width W of the film, which indicates stability during production, was 1.2 mm. Also, in the obtained film, generation of wrinkles was hardly recognized.

Forming conditions of blown film Diameter of annular die 2: 40 mm
Slit width of annular die 2: 500 μm
Diameter of protective cylinder 20: 150 mm
Discharge temperature of raw resin (molten): 325 ° C
Discharge rate of raw resin (molten): 26 kg / hr
Film take-up speed: 10 m / min Expansion rate: 5 times Location of cooling ring 12: Temperature of gas blown from cooling ring 12 right above annular die 2: 195 ° C.
Wind velocity of gas blown from cooling ring 12: 5 m / sec
Position of air ring 31: 250 mm above annular die 2
Temperature of gas blown out from air ring 31: 275 ° C
Wind velocity of gas blown from air ring 31: 10 m / sec
Direction of gas blown out from air ring 31: Vertical upward frost line position: 350 mm above annular die

Production Example 5
Using a production apparatus shown in FIG. 1, a thermoplastic liquid crystal polyester (Vectra Ei950 (trade name), manufactured by Boliplastics; melting point: 340 ° C.) was used as a raw material resin, and a blown film was formed under the following conditions. The film was wound up as a bag-like film to obtain a thermoplastic liquid crystal polyester film (average film thickness: 100 μm, average folding width: 314 mm). As shown in Table 2, the variation of the film thickness in the obtained film was 5 μm, and the value of the standard deviation (σ) of the fluctuation width W of the film, which indicates the stability during production, was 1 mm. Also, no wrinkles were observed in the obtained film (evaluation: ◎).

Molding conditions of blown film Diameter of annular die 2: 67 mm
Slit width of annular die 2: 1000 μm
Diameter of protective cylinder 20: 150 mm
Discharge temperature of raw resin: 340 ° C
Discharge rate of raw resin (molten): 39 kg / hr
Film take-up speed: 7.5 m / min Expansion rate: 3 times Location of cooling ring 12: Temperature of gas blown from cooling ring 12 directly above annular die 2: 210 ° C.
Wind velocity of gas blown from cooling ring 12: 5 m / sec
Position of air ring 31: 300 mm above annular die 2
Temperature of gas blown out from air ring 31: 290 ° C.
Wind velocity of gas blown out from air ring 31: 8 m / sec
Direction of gas blown from air ring 31: Vertical upward frost line position: 400 mm above annular die

Production Example 6
Using the production apparatus shown in FIG. 1, high-density polyethylene (Hi-Zex 7000F (trade name), manufactured by Mitsui Chemicals; melting point: 135 ° C.) was used as a raw material resin, and an inflation film was molded under the following conditions to form a bag. And a polyethylene film (average film thickness: 25 μm, average folding width: 314 mm) was obtained. As shown in Table 2, the variation of the film thickness in the obtained film was 7 μm, and the value of the standard deviation (σ) of the fluctuation width W of the film, which indicates the stability during production, was 1.2 mm. Also, no wrinkles were observed in the obtained film (evaluation: ◎).

Molding conditions of blown film Diameter of annular die 2: 50 mm
Slit width of annular die 2: 250 μm
Diameter of protective cylinder 20: 150 mm
Discharge temperature of raw resin: 165 ° C
Discharge rate of raw resin (molten): 12 kg / hr
Film take-up speed: 13.5 m / min Expansion rate: 4 times Location of cooling ring 12: Temperature of gas blown from cooling ring 12 directly above annular die 2: 55 ° C
Wind velocity of gas blown from cooling ring 12: 4 m / sec
Position of air ring 31: 350 mm above annular die 2
Temperature of gas blown out from air ring 31: 130 ° C
Wind velocity of gas blown out from air ring 31: 8 m / sec
Direction of gas blown from air ring 31: Vertical upward frost line position: 450 mm above annular die

Comparative Example 3
In the manufacturing apparatus shown in FIG. 1, an inflation manufacturing apparatus in which the air ring 31 is omitted is used, and high-density polyethylene (Hizex 7000F (trade name), manufactured by Mitsui Chemicals; melting point 135 ° C.) is used as a raw material resin. The blown film was formed under the conditions described above and wound up as a bag-like film to obtain a polyethylene film (average film thickness: 25 μm, average folding width: 314 mm). The variation in the film thickness of the obtained film was 14 μm, and the value of the standard deviation (σ) of the fluctuation width W of the film, which indicates stability during production, was 3.0 mm. In addition, the obtained film had noticeable wrinkles (evaluation: x).

Molding conditions of blown film Diameter of annular die 2: 50 mm
Slit width of annular die 2: 250 μm
Diameter of protective cylinder 20: 150 mm
Discharge temperature of raw resin: 165 ° C
Discharge rate of raw resin (molten): 12 kg / hr
Film take-up speed: 13.5 m / min Expansion rate: 4 times Location of cooling ring 12: Temperature of gas blown from cooling ring 12 directly above annular die 2: 55 ° C
Wind velocity of gas blown from cooling ring 12: 4 m / sec

As is clear from the above, according to Production Examples 1 to 6, a film having excellent stability during production as compared with Comparative Examples 1 to 3 and having a small thickness variation and a small quality variation can be obtained.

It is a longitudinal section showing an apparatus for manufacturing a blown film according to an embodiment of the present invention. It is the front view which partially notched and showed the height adjustment mechanism. It is a longitudinal section showing the manufacturing device of the blown film concerning other embodiments of the present invention. It is a top view which shows the evaluation state of bubble stability.

Explanation of reference numerals

2 annular die 4 annular film 10 frost line 12 cooling ring 31 air ring 50 adjusting means

Claims (4)

An apparatus for producing an inflation film, which comprises melt-extruding a raw material resin from an annular die to form an annular film, and supplying a gas to an inner space thereof while cooling the annular film to expand the film.
Along with the cooling ring provided in proximity to the annular die, at least one air ring provided concentrically with the annular die is disposed, and the temperature of the gas blown from the air ring is adjusted by the temperature of the molten annular film. An apparatus for producing a blown film, which comprises means for adjusting the temperature to a temperature at which expansion can be ensured. 装置 The blown film manufacturing apparatus according to claim 1, wherein the air ring includes a height adjusting mechanism. A method for producing an inflation film, comprising forming a circular film by melt-extruding a raw material resin from a circular die, supplying a gas to an inner space of the circular film while cooling the circular film, and expanding the film.
Along with a cooling ring provided close to the annular die, at least one air ring provided concentrically with the annular die is provided, and the temperature of the air ring is adjusted to a temperature at which expansion of the molten annular film can be ensured. A method for producing an inflation film, comprising blowing out a blown gas. The method according to claim 3, wherein the raw material resin is a thermoplastic liquid crystal polymer.

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