JPH0885151A - Method for producing inflation resin film - Google Patents

Abstract

(57) [Summary] [Structure] The outer peripheral surface of the molten resin bubble extruded from the annular molding die is cooled by the air blown from the air cooling ring, and the inner surface of the bubble is blown from the inner cooling tube. Cooled by 15 to 50 from the melting point of the bubble resin.
After cooling to a temperature lower by ℃, the bubble is heated by hot air blown from a hot air ring connected to the air cooling ring by a circumferential wall surrounding the bubble, and the heated bubble is crystallized from a thermoplastic resin. When the bubble diameter at temperature is a and the final diameter of the expanded bubble is b, b
A method for producing an inflation resin film, which comprises expanding the bubbles so that / a becomes 1.5 to 15. [Effect] An oriented resin film having excellent transparency, gloss, tensile properties, and heat shrinkage balance can be obtained.

Description

Detailed Description of the Invention

[0001]

The present invention relates to polyethylene, polypropylene, linear low density polyethylene, ethylene / vinyl acetate copolymer, polybutene-1, ethylene / acrylic acid copolymer, ethylene / methacrylic acid alkyl ester copolymer. The present invention relates to a method for producing an oriented inflation resin film in which each thermoplastic resin bubble such as is stretched and oriented at a temperature lower than the crystallization temperature of the resin.

[0002]

2. Description of the Related Art A method for producing an inflation film of a thermoplastic resin film is carried out by using, for example, an inflation film molding machine 1 shown in FIG. In the blown film molding machine 1, the raw material thermoplastic resin c is stored in the supply hopper 2 and supplied. The extruder 3 has a built-in screw 5 that is driven to rotate by a screw motor 4, and the feed hopper 2
The thermoplastic resin c supplied from the above is extruded upward from the tip as a molten resin. In the vertical direction of the tip of the extruder 3,
A blow head 7 incorporating an annular molding die d is attached via a direct connection pipe 6, and in order to blow air into the extruded molten resin to form a cylindrical bubble e, an electromagnetic valve 8 is attached to the blow head 7. An intake / exhaust pump 10 is connected through a valve pipe 9 having An air cooling ring 11 is arranged above the blow head 7, and the cylindrical bubble e is cooled by the air supplied from the cooling blower 12. The cylindrical bubble e is guided by the guide plates 13 and 13, and the take-up roll 1 is driven to rotate by a take-up motor.
An inflation resin film f is formed by folding the sheet 4 and 14 into a two-layer sheet.

The inflation resin film f has its width measured by the width sensor 16 of the film width measuring device 15 and then guided by the guide rolls 17, 18, 18 and inserted into the holding cup 20 of the film winder 19. It is wound around the retained paper tube g. Here, when the bag forming film is manufactured, the inflation resin film f
Is wound around a paper tube g in a state of being folded into a two-layer sheet, but in the case of manufacturing a flat film or the like, the inflation resin film f is divided into a required number of widthwise sections by a cutter and then wound into a film. It is wound around the several paper tubes g inserted and held in the holding cup 20 of the machine.

In blown film molding,
The ratio of the diameter of the expanded cylindrical bubble to the diameter of the annular forming die is called the blow ratio (BUR) and is generally 1.2.
The resin film is molded by 4 times. In the inflation film molding method, generally, the bubbles extruded from the annular molding die are cooled by the air supplied from the cooling blower 12 and blown out from the air cooling ring 11. At this time, the bubbles e are cooled and solidified ( freezi
ng) is expanded in a region up to (frost line: F), and thereafter, further expansion does not occur on the downstream side, so that an inflation resin film is manufactured with a constant diameter without being oriented and stretched. That is, JP-A-5-15491
No. 0 publication describes that the expansion of bubbles in blown film formation ends at the frost line. In addition, Japanese Examined Patent Publication No. 62-6489 and Japanese Patent Publication No. 2-4
No. 6376, No. 2-46377, and Japanese Patent Publication No. 63
-47608, Japanese Patent Publication No. 2-47337, Japanese Patent Publication No. 56-93519, Japanese Patent Publication No. 3-40689, Japanese Patent Laid-Open No. 62-21521, and Japanese Patent Laid-Open No. 62-1.
49417, JP-A-62-284726,
As shown in the drawings of Japanese Patent Publication No. 1-54182 and Japanese Patent Laid-Open No. 4-8529, the bubble diameter at the position of the frost line appearing at the crystallization temperature of the resin of the bubble and the final diameter of the inflation bubble are almost the same. Is the diameter.

Therefore, in the conventional inflation film molding method, the orientation of the bubbles is imparted only to the orientation of the molten region, so that the inflation resin film has a sufficient stretch orientation (stretching at a temperature below the crystallization temperature of the resin).
However, the physical properties such as film strength, appearance, and heat shrinkage properties are not sufficient because of not being provided, and it was practically limited depending on the application. Further, in Japanese Patent Laid-Open No. 6-122150,
The inner surface of the bubble is cooled by a cooling device having a first air-cooling ring on the outer peripheral surface of the bubble, a second air-cooling ring, a cylindrical wall connecting the two, and an annular rectifying cylinder provided on the second air-cooling ring. Although a method of molding an inflation resin film with a blow ratio of 8 to 22 times is proposed by using an inner cooling cylinder, the glossiness is not sufficient as compared with a shrink film or the like. Further, there has been proposed a stretch inflation molding method in which stretch crystal orientation is performed by an internal mandrel method, but in this method, when the resin film passes through the mandrel portion, it is difficult to slip, so that the surface of the resin film is easily scratched. Further, a stretching method (Japanese Patent Laid-Open No. 61-34372) in which a bubble is folded after the blown film is formed and the take-up speed between the nip rolls is changed to crystallize the film is also proposed. It has the drawback of being offset in the direction (vertical direction). Further, a method in which a film is once formed by inflation molding, then the cooled film is reheated to a temperature lower than the crystallization temperature, and air is blown into the bubbles of the film to expand / stretch the bubbles to cause crystal orientation. (Japanese Patent Publication Sho 53-5
No. 340) is also proposed. However, this method is extremely complicated in process, and the product is extremely expensive.

[0006]

SUMMARY OF THE INVENTION The present invention provides a method for producing a stretched resin film having excellent stretch orientation and molding stability.

[0007]

The invention according to claim 1 of the present application is as follows.
The outer peripheral surface of the molten resin bubble extruded from the annular molding die is cooled by the air blown out from the air cooling ring, and the inner surface of the bubble is cooled by the air blown out from the inner cooling tube to obtain the melting point of the bubble resin. It is cooled to a temperature 15 to 50 ° C. lower than that, and then the bubble is heated by hot air blown from a hot air ring connected to the air cooling ring by a circumferential wall surrounding the bubble, and the heated bubble is heated. An inflation resin characterized by expanding the bubbles so that b / a is 1.5 to 15 where a is the bubble diameter at the crystallization temperature of the plastic resin and b is the final diameter of the expanded bubbles. It provides a film.

According to a second aspect of the present invention, in the first aspect of the present invention, a plurality of annular rectifying cylinders having different diameters are arranged on the downstream side of the hot air ring on the same axis as the discharge port with radial intervals. An annular air chamber with a downstream side opening is formed between the adjacent flow regulating cylinders, and between the lower end of the outermost flow regulating cylinder of these flow regulating cylinders and the upper surface of the hot air ring, the outside air intake and exhaust for communicating the air chambers with each other is formed. Each of the mouths is bored, and the height of these several straightening cylinders becomes higher toward the outside, and the shape connecting these downstream ends forms a tapered bubble guide surface that expands to the outside. The present invention provides a method for producing an inflation resin film in which the expansion and orientation of the bubbles is ensured by using the apparatus described above.

[0009]

According to the method of the present invention, the molten resin bubble extruded from the annular molding die is cooled to the crystallization temperature of the resin by the air supplied from the air cooling ring and the inner cooling tube. Even in the temperature region lower than the crystallization temperature on the downstream side, the hot air blown from the hot air ring heats the bubbles to a temperature suitable for expansion / stretching, and expansion / stretching can be stably performed. Further, a device provided with a group of annular rectifying cylinders reduces the pressure between the bubbles and the downstream ends of the respective annular rectifying cylinders, sucks the bubbles toward the rectifying cylinders, and gives the bubbles further forced stretching orientation [the above b / a Is 1.5 to 15
Double] It is possible to obtain an inflation resin film having excellent film strength, appearance, heat shrinkage characteristics, and the like. That is, in the present invention, the airflow blown from the air-cooling ring and the hot-air ring flows along the outer peripheral surface of the bubble, and the velocity of the airflow increases when passing through the bubble and the upper edge of the straightening cylinder group. Since the bubble and the downstream end of each of the annular rectifying cylinders are depressurized by the Venturi action, outside air is introduced into the outside air intake port,
It is sucked into these air chambers through the outside air intake and exhaust,
The air flow from the air cooling ring and the hot air ring flows along the outer peripheral surface of the bubble, so that the bubble can be stably supported, and the inflation resin film can be stably manufactured.

Using the device provided with the air-cooling ring, the hot-air ring, the inner cooling cylinder, and the straightening tube group having a constant tapered bubble guide surface at the downstream end of each annular straightening tube, the same take-up speed,
When molding a resin film of the same thickness, the larger the final bubble diameter, the more outlets of the hot air ring, and by increasing the number of air chambers supporting the bubbles as necessary, regardless of the final bubble diameter, An inflation resin film can be manufactured while stably supporting bubbles.

[Detailed Description of the Invention] Film Material As the material of the thermoplastic resin film, high density polyethylene, low density polyethylene, ethylene 75 to 99% by weight
And linear low-density polyethylene, which is a copolymer of 25 to 1% by weight of α-olefin having 3 to 8 carbon atoms, vinyl acetate content of 5 to 25% by weight, and MFR of 0.3 to 10 g / 10 min ethylene. -Vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, propylene co-polymer, propylene 60-99.5 wt% and ethylene and / Or an α-olefin having 4 to 8 carbon atoms 40 to 0.
Copolymer with 5% by weight, poly (4-methylpentene-
1), a crystalline thermoplastic resin such as polybutene is used,
These may be used alone or in combination of two or more.

As the above α-olefin, ethylene,
Propylene, butene-1, heptene-1, hexene-
1, octene-1, 4-methylpentene-1 and the like. Hydrogenated petroleum resin, hydrogenated styrene-butadiene-styrene copolymer, ethylene
Propylene copolymer, ethylene-butene-1 copolymer,
Impact modifiers such as 1,2-polybutadiene and ethylene / propylene / ethylidene norbornene copolymers may be added to such an extent that the transparency of the film is not impaired (0.5 to 20% by weight). Further, 0.1 to 2% by weight of a lubricant or a tackifier for improving the slipperiness of the film, a nucleating agent or an antioxidant for improving the transparency of the film, a flame retardant or an ultraviolet absorber may be added.

As the lubricant, an aliphatic alcohol having 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms, and 10 to 10 carbon atoms are used.
22, preferably an aliphatic alcohol fatty acid ester which is a compound with 12 to 18 aliphatic compounds, specifically, monoglycerin oleate, polyglycerin ricinoleate, glycerin triricinoleate, glycerin acetylricinoleate, methylacetylricinoleate. , Ethyl acetyl ricinoleate, butyl acetyl ricinoleate, propylene glycol oleate, propylene glycol laurate, pentaerythritol oleate, polyethylene glycol oleate, polypropylene glycol oleate, polyoxyethylene glycerin, polyoxypropylene glycerin, sorbitan oleate, Sorbitan laurate, polyethylene glycerin bitan oleate, polyethylene glycol sorbitan laurate, etc.
In addition, polyalkylene ether polyol, specifically, polyethylene glycol, polypropylene glycol, etc., sugar fatty acid ester, epoxidized soybean oil, polyoxyethylene alkylamine fatty acid ester, polyoxyethylene alkyl phenyl ether, arylic acid amide, stearic acid amide , Higher fatty acid amides having 12 to 22 carbon atoms such as erucic acid amide, ethylenebisstearic acid amide, ethylenebisoleic acid amide, polyethylene wax, polypropylene wax,
Liquid paraffin can be used. Also, as a nucleating agent,
As an inorganic substance such as talc and silica, and as an adhesive, a castor oil derivative, a low molecular adhesive substance of polybutene, a sorbitan higher fatty acid ester, a terpene resin, a petroleum resin and the like can be used.

The resin film may have a single-layer structure or a laminated structure, and can be appropriately selected depending on the purpose. As an example of such a resin film having a laminated structure, for example, the following laminated structures of (1) to (11) can be considered.

(1) On one or both sides of the low-density polyethylene resin layer, 60 to 95% by weight of ethylene and 40 monomers selected from vinyl acetate, aliphatic unsaturated carboxylic acid, and aliphatic monocarboxylic acid alkyl ester A resin film in which a copolymer resin layer containing about 5% by weight is laminated. (2) On one or both sides of the high-density polyethylene resin layer, 60 to 95% by weight of ethylene and 40 to 5% by weight of a monomer selected from vinyl acetate, aliphatic unsaturated carboxylic acid, and aliphatic monocarboxylic acid alkyl ester. % Resin film laminated with a copolymer resin layer. (3) 60 to 95% by weight of ethylene and vinyl acetate, on one or both sides of the linear low-density polyethylene resin layer,
A resin film in which a copolymer resin layer with 40 to 5% by weight of a monomer selected from an aliphatic unsaturated carboxylic acid and an aliphatic monocarboxylic acid alkyl ester is laminated. (4) 60 to 95% by weight of ethylene and 40 to 5% by weight of a monomer selected from vinyl acetate, aliphatic unsaturated carboxylic acid, and aliphatic monocarboxylic acid alkyl ester on one or both sides of the propylene resin layer. A resin film obtained by laminating a copolymer resin layer with.

(5) Ethylene 6 on one or both sides of the resin base material layer selected from polycarbonate, polyamide, polyethylene terephthalate and polyethylene terephthalate
Copolymer resin of 0 to 95% by weight and 40 to 5% by weight of a monomer selected from vinyl acetate, aliphatic unsaturated carboxylic acid, and aliphatic monocarboxylic acid alkyl ester, low density polyethylene, high density polyethylene, A resin film in which a resin layer selected from linear low density polyethylene and propylene resin is laminated. (6) 60 to 95% by weight of ethylene on both surfaces of a resin substrate layer comprising 10 to 90% by weight of a crystalline olefin resin selected from ethylene resin and propylene resin and 90 to 10% by weight of an olefin thermoplastic elastomer. % And 40 to 5% by weight of a monomer selected from vinyl acetate, an aliphatic unsaturated carboxylic acid, and an aliphatic monocarboxylic acid alkyl ester, a resin film laminated. (7) 80 to 95% by weight of linear low-density polyethylene, 60 to 95% by weight of ethylene, and a monomer 40 selected from vinyl acetate, aliphatic unsaturated carboxylic acid, and aliphatic unsaturated monocarboxylic acid alkyl ester To 5 wt% of the copolymer resin and 20 to 5 wt% of the resin base material layer on both sides, 60 to 95 wt% of ethylene and vinyl acetate,
Copolymer resin with 40 to 5% by weight of a monomer selected from aliphatic unsaturated carboxylic acid and alkyl ester of unsaturated unsaturated monocarboxylic acid, resin having 20% to 5% by weight of a copolymer surface layer laminated thereon the film.

(8) 10 to 90% by weight of butene-1 resin
And 60 to 95 ethylene on both sides of a resin base material layer consisting of 90 to 10% by weight of an olefin resin (excluding butene-1 resin) or / and an olefin thermoplastic elastomer.
Copolymer resin 20% by weight of 40% to 5% by weight of a monomer selected from vinyl acetate, aliphatic unsaturated carboxylic acid, and aliphatic unsaturated monocarboxylic acid alkyl ester
A resin film obtained by laminating a copolymer surface layer with 5% by weight. (9) A resin film in which a linear low-density polyethylene resin layer is laminated on one side or both sides of the low-density polyethylene resin layer. (10) A resin film in which a low density polyethylene or a linear low density polyethylene resin layer is laminated on one side or both sides of a high density polyethylene resin layer. Alternatively, a resin film in which a propylene resin layer is laminated. (11) A resin film in which a linear low-density polyethylene resin layer is laminated on one side or both sides of a propylene-based resin layer.

The crystallization temperature of bubbles in the method for producing an inflation resin film according to the present invention is 5-8 mg of the crystalline thermoplastic resin powder used, which is raised to a temperature above the melting temperature at a heating rate of 10 ° C./minute, and then, , The peak temperature of the differential thermal scanning curve (DSC curve) obtained by lowering the temperature at the same rate. Also, when there are two or more peaks,
It is at least the peak temperature on the highest temperature side. It is presumed that this temperature is the temperature at which the frost line (F) in which the solid phase and the molten phase of the bubbles coexist appears. The crystallization temperature when using two or more kinds of the different crystalline thermoplastic resins as a laminated structure or when they are used in combination is the temperature of the peak showing the maximum temperature in the DSC curve of the resin film. .

Film Manufacturing Apparatus As shown in FIG. 2, for example, an apparatus used for manufacturing the inflation resin film of the present invention includes an air-cooling ring 11 provided in the vicinity of the resin discharge port h of the annular molding die d and the inside of the bubble. In order to cool the inside of the annular molding die d, the inner cooling cylinder 2 is erected in a cylindrical shape on the axis o of the annular molding die d and has a plurality of air outlets 22a, 22b, 22c, 22d on its cylindrical peripheral wall.
2, and the air-cooling ring and the circumferential wall 25 that surrounds the bubble are connected, and the temperature of the air blown from the hot-air outlet 21a can be appropriately adjusted so that the temperature is suitable for expanding and stretching the bubble. It consists of a hot air ring 21. On the downstream side of the hot air ring 21, a plurality of annular rectifying cylinders 26 having different diameters are arranged on the same axis as the air outlet at radial intervals, and a downstream opening is formed between adjacent rectifying cylinders. A plurality of outside air intakes 28 are radially formed near the hot air ring on the outermost rectifying cylinder peripheral wall of the rectifying cylinders, and the remaining lower end of the rectifying cylinder and the hot air are formed. Outside air intake / exhaust ports 29 that communicate the air chambers are formed between the upper surfaces of the rings 21. In the hot air ring 21, as shown in FIG. 4, the auxiliary air outlet 21 is suitable for expanding and stretching the film.
A device may be provided in which one or two or more b'are provided and the air temperature, air velocity, and air volume of the air blown out from this air outlet can be adjusted.

As shown in FIGS. 2 and 3, the inner cooling cylinder 22 has a double pipe structure, and the cooling air supplied from the pump 10 passes through the air suction port 23 to form a double pipe structure. The air outlets 22 are passed through the chamber 23a, and in places of the inner pipe and the outer pipe, for example, at intervals of 40 to 200 mm.
a, 22a ', 22b, 22b' ... 22d, 22d 'are provided to cool the bubble e from the inside so that the cooling of the bubble outer peripheral surface from the air cooling ring 11 makes the cooling of the bubble inner and outer surfaces uniform. I have to. The air discharged from the inner cooling cylinder 22 is used for cooling the bubble from the inside and expanding the bubble. The upper surface of the outer tube is opened at the center, and the chamber formed by the inner tube and the outer tube is used as a passage for discharging air, and is discharged from the bubble through the air discharge port 24.

The heights of the several annular flow straightening cylinders 26 become higher as they are located on the outer side, and the shape connecting these downstream ends is a tapered shape [the discharge port (h) of this guide surface]. The angle is 45 to 70 ° C. with respect to the axis (o) of the bubble guide surface. The generatrix of the guide surface of these tapered bubbles e is not limited to a straight line, and may be a quadratic curve depending on the purpose. In addition, the rectifying cylinders 26 having the same diameter are prepared in such a manner that at least two kinds of rectifying cylinders having different heights can be used for both small and large final bubble systems. Needless to say, even when using a short one, the straightening tube group 26 has a higher height as the outer one, as a whole.

The temperature of the hot air blown out from the hot air ring 21 is adjusted so that the bubble surface temperature is equal to or lower than the crystallization temperature of the resin used and is a temperature suitable for expansion / stretching of the bubbles. It is preferably 80 to 160 ° C. In the inflation film molding method of the present invention, the position where the frost line appears, the air cooling ring so as to be located on the upstream side of the hot air ring, and adjusting the wind speed / air volume of the air blown from the inner cooling cylinder, and the hot air ring. The temperature, speed, and volume of the air blown from Further, on the downstream side, the air from the hot air ring heats the bubble to a temperature equal to or lower than the crystallization temperature suitable for expansion / stretching, and reduces the pressure between the bubble and the downstream end of each annular flow straightening cylinder due to the Venturi action. In this state, the bubble is sucked toward the rectifying cylinder to force the stretch orientation, whereby an inflation resin film having excellent film strength, appearance, heat shrinkage characteristics, etc. can be manufactured.

The ratio b / a of the bubble diameter a to the final bubble diameter b at the crystallization temperature is 1.5 to 15 times, preferably 2 to 13 times. When the ratio b / a is less than 1.5, the forced stretch orientation is insufficient and the expected physical properties such as film strength and heat shrinkage properties of the resin film are deteriorated. Also, the ratio b / a
Is greater than 13, the amount of air blown out from the hot air ring must be increased in order to perform the forced stretching orientation, and the molding must be performed, but the large amount of air blown reduces the stability of the bubbles. Furthermore, at this time, the air cooling ring,
By adjusting the amount of air supplied from the inner cooling cylinder and the temperature and amount of air supplied from the hot air ring, the bubble diameter a at the crystallization temperature can be adjusted to the upstream side of the hot air ring.
Alternatively, it is positioned upstream of the position of the outermost annular rectifying cylinder, and on the downstream side of the bubble diameter a, is forcedly stretched and oriented by the Venturi action to form an inflation resin film having excellent film strength, appearance, heat shrinkage characteristics, and the like. To manufacture.

(Example 1) Diameter of molding die d: 120 mmφ Lip width: 1.5 mm Air outlet of air cooling ring Height: Same height as upper surface of die head d, air volume 38 m ³ /
Minute, wind speed 26 m / s Hot air ring outlet: As shown in Table 1.

[0025]

[Table 1] * Height from the upper surface of the die head d.

Outer diameter of circumferential wall: 380 mm Height of circumferential wall: 210 mm Straightening cylinder (upper end taper 60 °): As shown in Table 2.

[0027]

[Table 2] * Height from the upper surface of the die head d.

Inner cooling cylinder Outer tube diameter: 90 mmφ, inner tube diameter: 60 mmφ, outlet: As shown in Table 3

[0029]

[Table 3] * Height from the upper surface of the die head d.

The following inflation resin film was molded by using the apparatus shown in FIG. 4 instead of the air cooling ring 11 of the inflation molding machine 1 shown in FIG. That is, 95.6% by weight of propylene and 4.4% of ethylene as a resin composition.
Random copolymer with wt% (density 0.89 g / cm
³ , MFR at 230 ° C. was 6.0 g / 10 minutes, crystallization temperature was 103 ° C., and the DSC chart is shown in FIG. ) Having a diameter of 50 mm and an L / D of 25 is kneaded at 230 ° C. and supplied to an annular forming die so that the thickness becomes 20 μm, the annular forming die temperature is 230 ° C., and the final bubble diameter is A resin film was produced by inflation-molding b at 960 mm and a take-up speed of 20 m / min. At that time, the bubble diameter a at the crystallization temperature of the bubble is as shown in FIG.
As shown in FIG. 5, the die head is positioned at a height of 150 mm from the upper surface [bubble diameter a = 120 mm], and on the downstream side thereof, heating of bubbles with hot air from the hot air ring, bubbles due to the venturi action and each annular flow straightening cylinder Forced stretch orientation was performed by setting a reduced pressure state between them. [B / a =
8] Table 8 shows film physical properties such as film strength, appearance and heat shrinkage characteristics. Table 4 shows the height from the upper surface of the annular molding die to the downstream end of the outermost annular flow straightening cylinder, the bubble diameter, and the bubble surface temperature.

[0031]

[Table 4] * Height from the upper surface of the die head d.

(Example 2) The same apparatus as in Example 1 was used, and as a resin composition, 85.8% by weight of propylene, 1.7% by weight of ethylene, and 12.5% by weight of butene-1 were co-weighted. Coalescence (density 0.898 g / cm ³ , M at 230 ° C
FR is 5.5 g / 10 minutes, crystallization temperature is 102 ° C.), and the amount of air blown from the hot air ring, the air velocity, and the air temperature are changed as shown in Table 5, and the molding is performed in the same manner, and shown in Table 8. A resin film having a final bubble diameter b of physical properties of 960 mm was obtained [b / a = 8].

[0033]

[Table 5] * Height from the upper surface of the die head d.

Example 3 Using the same apparatus as in Example 1, ethylene 4-methylpentene-1 copolymer resin (density 0.910 g / cm ³ , MFR at 190 ° C. 3.6 g) was used. / 10 minutes, crystallization temperature is 100 ° C.) (A) is 175 ° C. using an extruder having a diameter of 65 mm and L / D of 25.
97.1% by weight of eretin / vinyl acetate copolymer resin (vinyl acetate content: 15% by weight, MFR at 190 ° C .: 2.0 g / 10 minutes, crystallization temperature: 76 ° C.) Kneading a resin composition (B) consisting of 2.9% by weight of glycerin oleate ("Rikemar O-71-D" manufactured by Riken Vitamin Co., Ltd.) at 160 ° C using an extruder having a diameter of 50 mm and an L / D of 25. Then, both of them are supplied to one annular three-layer molding die to have a thickness of the resin composition (A) of 6.
3.8 μm of each thickness of the composition (B) containing an ethylene / vinyl acetate copolymer resin as a main component on both sides of the 4 μm intermediate layer.
Except that the air flow rate, the air velocity, and the air temperature blown out of the three-layer inflation resin film from the hot air ring were changed under the condition that the annular molding die temperature was 175 ° C. Molded in the same manner, a resin film having a physical thickness shown in Table 8 and a final bubble diameter b of 960 mm and having a total thickness of 14 μm was obtained [b / a = 8].

[0035]

[Table 6] * Height from the upper surface of the die head d.

Example 4 The resin composition used in Example 3 was used, except that the hot air ring was molded in the same manner except that the apparatus shown in FIG. 5 was used, and the final bubble diameter of the physical properties shown in Table 8 was obtained. A resin film having b of 1800 mm was obtained [b / a =
15]. Rectifying cylinder (upper end taper 60 degrees): As shown in Table 7.

[0037]

[Table 7] * Height from the upper surface of the die head d.

(Comparative Example 1) In Example 2, the temperature of the air blown from the hot air ring was set to 30 ° C., and inflation molding with a final bubble diameter b of 960 mm was carried out in the same manner to obtain a resin film having the physical properties shown in Table 8. Obtained.

(Comparative Example 2) In Example 3, the temperature of the air blown out from the hot air ring was set to 30 ° C. and the bubbles were not heated.
Inflation molding of 60 mm was performed to obtain a resin film having the physical properties shown in Table 8. (Comparative Example 3) In Example 4, the temperature of the air blown from the hot air ring was set to 30 ° C, and the final bubble diameter b was similarly set.
However, when it was attempted to carry out inflation molding of 1800 mm, the bubble which was trying to expand to a bubble diameter of 1500 mm or more was torn and could not be manufactured.

Table 8 shows the physical properties of the films obtained in Examples 1 to 4 and Comparative Examples 1 to 3. The film evaluation is based on the following method. Tensile Breaking Strength and Tensile Breaking Elongation: JIS Z-1702 Haze Degree: JIS K-6714 Glossiness: JIS Z-8471 (20 degrees) Heat Shrinkage Property: The direction is clarified by using the device shown in FIG. A resin film sampled in a size of 100 mm × 100 mm was dipped in a heat medium (silicon oil (100 c / s) was standard) adjusted to each measurement temperature for 3 minutes, and then taken out, and the shrinkage rate was calculated by the following formula.

[0041]

## EQU1 ## Shrinkage (%) = (L ₀ −L) / L ₀ × 100 L ₀ : Original length of test piece (100 mm) L: Length after treatment (mm)

[0042]

[Table 8]

[0043]

EFFECTS OF THE INVENTION It is possible to obtain an oriented film having excellent transparency and gloss and excellent mechanical strength and physical properties.

[Brief description of drawings]

FIG. 1 is a half sectional view of a conventional inflation molding apparatus.

FIG. 2 is a partial cross-sectional view of an inflation molding device of the present invention.

FIG. 3 is a cross-sectional view of an inner cooling cylinder.

FIG. 4 is a partial cross-sectional view of an inflation molding device showing another embodiment of the present invention.

FIG. 5 is a partial cross-sectional view of an inflation molding device showing another embodiment of the present invention.

FIG. 6 shows the bubble diameter a at the crystallization temperature of the resin in Example 1.

FIG. 7 is a measuring device for heat shrinkage characteristics of a resin film.

FIG. 8 shows a crystallization temperature in a DSC measurement chart.

[Explanation of symbols]

 a Bubble diameter at bubble crystallization temperature b Final bubble diameter c Thermoplastic resin d Annular molding die e Bubble f Resin film h Resin discharge port 1 Inflation molding machine 2 Feed hopper 3 Extruder 7 Blow bed 10 Pump 11 Air cooling ring 12 Cooling blower 15 Film width control device 17, 18 Guide roll 19 Winder 21 Hot air ring 21a, 21a ', 21b' Hot air blowout port 22 Inner cooling tube 22a, 22b, 22c, 22d Air blowout port 23 Air intake port 24 Air exhaust Outlet 25 Cylindrical wall 26 Straightening cylinder 27 Air chamber 28 Outside air intake 29 Outside air intake / exhaust port

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noriyuki Kobayashi 1 Toho-cho, Yokkaichi-shi, Mie Prefecture Yokkaichi Research Institute, Mitsubishi Petrochemical Co., Ltd. (72) Inventor Osamu Akaike 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Oil Chemical Company Yokkaichi Research Institute

Claims (2)

[Claims] 1. An outer peripheral surface of a molten resin bubble extruded from an annular molding die is cooled by air blown from an air cooling ring, and an inner surface of the bubble is cooled by air blown from an inner cooling cylinder. , 15 ~ from the melting point of bubble resin
After cooling to a temperature lower by 50 ° C., the bubbles are heated by hot air blown from a hot air ring connected to the air cooling ring by a circumferential wall surrounding the bubbles, and the heated bubbles are crystallized by a thermoplastic resin. The bubble diameter at the liquefaction temperature is (a), and the final diameter of the expanded bubble is (b).
And the bubble is expanded so that (b) / (a) is 1.5 to 15, the method for producing an inflation resin film. 2. The method according to claim 1, wherein a plurality of annular flow straightening cylinders having different diameters are arranged on the downstream side of the hot air ring on the same axis as the discharge port and at radial intervals. , An annular air chamber having a downstream opening is formed between the adjacent straightening cylinders, and outside air sucking / discharging ports communicating the air chambers are respectively provided between the lower end of the outermost straightening cylinder of these straightening cylinders and the upper surface of the hot air ring. A device in which the height of these several flow straightening cylinders is higher toward the outside, and the shape connecting these downstream ends forms a tapered bubble guide surface that expands to the outside. A method for producing an inflation resin film, which comprises expanding a bubble by using.