JPH10272691A - Information film forming device and forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To steadily form, on an extended period, a resin film which satisfies reguired properties or transparency, glossiness, length and width strength balance, and deformation recovery properties under low cooling efficiency conditions caused by increase of extruding resin. SOLUTION: A tube B extruded from an extruding opening 10A of a molding die 10 is cooled by a first air-cooling ring 23, a second air-cooling ring 24, and ring-shaped rectifiers 27 for inflation forming. A ratio D2 /D1 of a minimum inside diameter D1 of a blow-off port 23A of the first air/cooling ring 23 to a minimum diameter D2 of a blow-off port 24B of the second air-cooling ring 24 is set to 0.6-1.0. Both D1 and D2 are larger than a bore D0 of the extruding opening 10A. A distance L between the first air-cooling ring 23 and the second air-cooling ring 24 is set to 100-700 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin film for stretch packaging of food, a resin film for pallet stretch packaging, and a resin film for bag making and molding, which are suitable for transparency, glossiness, strength balance in vertical and horizontal directions, deformation distortion. The present invention relates to an apparatus and a method for forming an inflation film having excellent recovery properties.

[0002]

2. Description of the Related Art Conventionally, this type of blown film is formed using, for example, an inflation film forming machine 1 shown in FIG.

In the blown film forming machine 1, a thermoplastic resin A as a raw material is stored in a supply hopper 2.

The extruder 3 incorporates a screw 5 driven to rotate by a screw motor 4, and extrudes the thermoplastic resin A supplied from the supply hopper 2 as a molten resin upward from the tip. A blow head 9 having a built-in annular forming die 10 is mounted vertically above the tip of the extruder 3 via a connecting pipe 6, and air is blown into the extruded molten resin to form a cylindrical tube B. To this end, a supply / exhaust pump 12 is connected to the blow head 9 via a bubble pipe 11.

An air cooling ring 13 is provided above the blow head 9.
Is arranged, and the cylindrical tube B is cooled by the air supplied from the cooling blower 14.

[0006] The cylindrical tube B is guided by the guide plates 15 and 15 and is folded into a two-layer sheet by the take-off rolls 17 and 17 which are driven to rotate by a take-up motor (not shown) to form an inflation film C.

[0007] The blown film C is guided by guide rolls 18, 19 and 19, and is wound on a film winder 20.
Is wound around a paper tube 22 inserted into a take-up shaft 21.

Here, when manufacturing a bag-forming film, the inflation film C is wound around the paper tube 22 in a state of being folded into a two-layer sheet. However, when manufacturing a stretch film or the like, the inflation film is used. The film C is divided into a required number of sections in the width direction by a cutter, and then wound around several paper tubes 22, 22, 22 inserted into a winding shaft 21 of a film winding machine 20. In FIG.
F is a frost line of the tube B.

In the ordinary blown film forming method of cooling the annular tube B only with the air cooling ring 13 shown in FIG. 2, when the film material is a crystalline resin such as low-density polyethylene, linear low-density polyethylene, or polypropylene, Due to its crystallization characteristics, sufficient transparency cannot be obtained, and the orientation is strong in the tube advancing direction. There is a problem that it is easy to tear.

When a low-density polyethylene resin film such as a low-density polyethylene resin or an ethylene-butene-1 copolymer resin, which is already known for stretch packaging, is formed by this method, it is hard and difficult to stretch, and it is difficult to form the film. If the product is stretched, it will break or show only uneven growth, and furthermore, the tray on which the packaged food is placed will be deformed or broken, causing wrinkles, and the necessary tightening force for packaging will not be obtained. There is a problem that valuable packaging cannot be performed.

When an ethylene-vinyl acetate copolymer resin film is formed, if the vinyl acetate content, melt flow rate and the like are appropriately selected and used, the above-mentioned low-density polyethylene resin film can be used. Although such problems can be solved, if the packaged food has sharp corners, or if the corner of the tray on which the packaged food is placed is sharp, wrapping the film while stretching it will result in the film becoming these sharp corners. In the physical distribution process as a stretch package, if a small tear occurs in the film by touching various objects, the tear propagates and expands, causing a large tear. There is a problem that it is unwrapped due to this.

Further, a film obtained by laminating the aforementioned low-density polyethylene or linear low-density polyethylene film and an ethylene-vinyl acetate copolymer resin film (Japanese Patent Publication No. 2-1)
In this case, the problem of being hard and difficult to stretch is solved, but the above-mentioned problem that the film is easily torn in packaging and in the physical distribution process is sufficiently solved especially when the film thickness is reduced. Not yet.

As a method for solving such a problem and forming an inflation film excellent in transparency, glossiness, strength balance in the vertical and horizontal directions, and recovery from deformation distortion, the present inventors have proposed a molding method as shown in FIG. In the method, the outer periphery of the molten resin tube extruded from the molding die is surrounded by a first air-cooling ring, a second air-cooling ring downstream of the first air-cooling ring, and an annular rectifying cylinder provided above the second air-cooling ring. A method of forming an inflation film that cools and cools the inner surface of the tube with an inner cooling cylinder has been proposed (JP-A-6-122150).

FIG. 1 is a sectional view showing a tube cooling mechanism of a molding apparatus employed in this Japanese Patent Laid-Open Publication No. 6-122150.
A first air-cooling ring 23 having a cooling gas outlet 23A surrounding (B ′) is provided. The first air-cooling ring 23 is further away from the forming die 10 than the first air-cooling ring 23 and located on the downstream side in the tube feeding direction (hereinafter, referred to as “B”). The second air cooling ring 2 having the cooling gas outlets 24A and 24B surrounding the tube B is simply referred to as “downstream” and the opposite direction is referred to as “upstream”.
4 is further provided, and a group of annular rectifying cylinders 27 surrounding the tube B is provided downstream of the second air-cooling ring 24 at a distance from the forming die 10.

A first air cooling ring 23 and a second air cooling ring 24
Are connected by a cylindrical wall 25 surrounding the tube B. The first air cooling ring 23 and the second air cooling ring 2
As shown in FIG. 2, the supply of air to
4 may be performed, or each may be performed independently,
In this case, a plurality of blowers are used independently.

The annular rectifying cylinder group 27 is coaxially arranged,
Annular air chambers 28a, 28b, 28c,
A plurality of cylinders 27A, 27 forming 28d, 28e
B, 27C, 27D, 27E, and 27F. The downstream end portions 27a of the cylinders 27A to 27F are located in the downstream direction as the outer cylinders are located.
The surface connecting the downstream end portions of the tubes B to 27F forms a tapered surface, and the tube B is inflated along the tapered surface.

A plurality of air inlets 29 are provided at radial positions on the wall surface of the outermost cylindrical body 27A of the annular rectifying cylinder group 27, and the second air cooling rings of the other cylindrical bodies 27B to 27F are provided. Air chambers 28a to 28
A circulation port 30 for circulating air between the e is provided.

On the other hand, inside the tube B, an inner cooling cylinder 26 having a double tube structure of an inner tube 26A and an outer tube 26B is provided. The inner cooling cylinder 26 receives a cooling gas supplied from a blower or a pump (for example, the pump 12 shown in FIG.
6A is taken in from a suction port 26a at the base end, and is blown out from a plurality of air outlets 26b provided to connect the side walls of the inner pipe 26A and the outer pipe 26B to each other (in some cases, suction at the tip of the outer pipe 26B). The inside of the tube B is exhausted from the port 26c, and may be exhausted from the outlet 26d at the base end.)

By using such a cooling mechanism,
The tube B can be efficiently cooled from the outside and the inside, and a good blown film can be formed.

The first air cooling ring 23 and the second air cooling ring 24
Are connected by a circular wall cylinder 25 having an inner diameter larger than the outer diameter of the tube B, so that the cooling air blown out from the outlet 13A can be used efficiently. That is, the first air cooling ring 2
The tube (fused tubular body) extruded from the extrusion port 10A of the forming die 10 by the air discharged from the third air port 23A and the upstream air port 24B of the second air cooling ring 24.
Since B 'is pre-cooled, the amount of air discharged from the downstream air outlet 24A of the second air cooling ring 24 can be reduced (or there is no need to increase the blowing speed). Next, the airflow blown out from the downstream side outlet 24A toward the tube B and slightly heated, then flows into the tube B and the annular rectifying cylinder group 27.
Venturi action generated when flowing between the tapered portion at the downstream end of the tube B, the annular air chamber 28a between the plurality of cylindrical bodies 27A to 27F corresponding to the blow ratio of the tube B.
28e is in a reduced pressure state, and the air intake 29 and the circulation port 30 are provided in the annular air chambers 28a to 28e in the reduced pressure state.
The outside air flow can be taken in through the
The air chambers 28a
A portion of the air in the tubes 28e moves along the tube B from the downstream end of the annular rectifying cylinder group 27 so as to accompany the tube B, and cools the tube B rapidly.

Further, the tube B is stably supported from the outer peripheral surface thereof by the plurality of annular air chambers 28a to 28e in the reduced pressure state. Moreover, these several cylinders 2
Since the downstream ends of 7A to 27F are located on the downstream side toward the outside, and the surface connecting these downstream ends is a tapered guide surface that spreads outward, even in the formation of a high blow ratio, the extrusion port 10A is used. The discharged tube B can be expanded and formed to a desired diameter at a stretch without contacting the downstream ends of the cylindrical bodies 27A to 27F.

Since the air flows in the adjacent air chambers 27a to 27e through the flow ports 30 in accordance with the pressure, the pressure in each of the air chambers 27a to 27e can always be maintained at a pressure suitable for inflation molding. .

Further, the tube B is cooled so that the inner and outer surfaces of the tube are uniformly cooled in response to the cooling from the outside.
The air is also cooled from the inside by the air discharged from the inner cooling cylinder 26.

The air discharged from the inner cooling cylinder 26 is used for cooling the tube B and expanding the tube B.

As described above, by using the first air cooling ring 23, the second air cooling ring 24, the annular rectifying cylinder group 27 and the inner cooling cylinder 26 together, the position of the frost line F of the tube B is separated from the annular forming die 10. It can be set at any position, and a film having excellent transparency can be formed stably. Furthermore, by using a plurality of air-cooling rings 23 and 24 and the annular rectifying cylinder group 27 together, a blown film having a high blow ratio of 5 to 20 times can be formed, and the strength in the vertical direction and the horizontal direction is balanced. A film having excellent strain recovery can be obtained.

Since the film obtained by this method has a balanced stress in the extrusion direction (longitudinal direction) and width (horizontal direction) of the film, the film does not break at the time of packaging, the tray does not deform, and the film does not deform. Stretch packaging can be easily performed without causing wrinkles.

[0027]

SUMMARY OF THE INVENTION The above-mentioned JP-A-6-122
In the method described in Japanese Patent Publication No. 150, the annular rectifying cylinder group 27
High blow ratio molding is possible due to the air chamber effect of
Although a good blown film can be formed,
The cooling efficiency is reduced due to an increase in the resin extrusion amount, and breathing and vibration are generated at the outlet 24 </ b> B on the upstream side of the second air-cooling ring 24. Therefore, there is a problem that the obtained tube lacks stability. In addition, when the air volume of the upstream air outlet 24B of the second air cooling ring is increased to improve the cooling efficiency, the appearance of the obtained film is deteriorated, and the thickness of the film tends to be uneven due to the vibration of the tube. is there.

According to the present invention, when a blown film is formed by the method described in the above-mentioned JP-A-6-122150, the transparency, glossiness, length and breadth are reduced even under the condition that the cooling efficiency is lowered by increasing the amount of extruded resin. Intensity balance,
An object of the present invention is to provide an apparatus and a method for forming an inflation film, which can stably form a resin film satisfying required characteristics such as deformation distortion recovery properties over a long period of time.

[0029]

According to the present invention, there is provided an apparatus for forming a blown film, comprising: a forming die having an extrusion opening for extruding a molten resin into a tube; and a cooling gas surrounding the tube extruded from the forming die. A first air-cooling ring having an air outlet, a second air-cooling ring that is arranged more distant from the forming die than the first air-cooling ring, and has an air outlet for cooling gas surrounding the tube; 2
An annular rectifying cylinder group arranged around the tube at a position more distant from the forming die than the air-cooling ring, and air supply means for supplying gas into the tube to inflate the tube. The annular rectifying cylinder group includes a plurality of cylinders arranged coaxially and forming an annular air chamber therebetween, and the downstream ends of these cylinders in the tube feed direction are provided on the outer side. As the cylindrical body is located in the downstream direction, the surface connecting the downstream ends of these cylindrical bodies forms a tapered surface, and the tube is an inflation film forming apparatus that is inflated along the tapered surface. in, the smallest inner diameter of the outlet of the first air cooling ring and D _1, if the smallest inner diameter of the outlet of the second air cooling ring was D _2, both the ratio of D ₂
/ D ₁ is less than 1 0.6 or more, and, D _1, D ₂ is greater both than the diameter of the extrusion port, outlet of the second air cooling ring 100 than the air outlet of the first air cooling ring 70
0 mm in the downstream direction.

According to the present invention, the smallest inside diameter (hereinafter, referred to as "minimum inside diameter") D of the outlet of the first air cooling ring.
₁ and the ratio D ₂ / D ₁ of the minimum inner diameter D ₂ of the second air cooling ring is set to 0.6 or more and less than 1, and D ₁ and D ₂ are made larger than the diameter D _{0 of the} extrusion port. First ring outlet
By setting the distance L between the outlet of the second air-cooling ring and the outlet of the first air-cooling ring at 100 to 700 mm downstream from the outlet of the air-cooling ring by 100 to 700 mm, the extruded resin amount is reduced. Even under the condition that the cooling efficiency decreases due to the increase, a resin film satisfying required characteristics such as transparency, glossiness, strength balance in vertical and horizontal directions, and recovery from deformation strain can be formed stably for a long period of time.

In the present invention, the minimum inside diameter of the first and second air cooling rings is the inside diameter of the smallest inside diameter of the ring constituting the outlet, and for example, FIG.
When the outlet of the second air-cooling ring 24 is divided into two, upstream and downstream, as shown in (2), it refers to the inside diameter of the portion of the smaller one of the smaller rings having the smallest inside diameter. When the outlet of the second air cooling ring 24 is divided into two, the outlet having the minimum inner diameter is located on the upstream side, that is, the molten resin extrusion port 10A of the molding die 10 and the first air cooling ring 2.
It is desirable that the outlet 24B is located on the side closer to the outlet 3.

The distance L between the outlet of the second air-cooling ring and the outlet of the first air-cooling ring is the shortest distance between the minimum inner diameter of the second air-cooling ring and the minimum inner diameter of the first air-cooling ring. Show.

In the present invention, in particular, the ratio D of the diameter D ₀ of the extrusion port of the forming die to the minimum inner diameter D ₁ of the first air cooling ring is determined.
The ₀ / D ₁ preferably set to 0.5 to 0.8.

The method for forming a blown film of the present invention uses the above-described forming apparatus of the present invention so that the frost line of the tube is positioned near the downstream end of the outermost cylindrical body of the annular straightening cylinder group. Preferably, the molding is performed so that the blow ratio of the tube (blow-up ratio: the ratio of the diameter of the tube to the diameter of the extrusion port of the molding die) is 5 to 20 times. Even under the condition that the cooling efficiency is reduced by the increase in the amount, a resin film satisfying required characteristics such as transparency, glossiness, strength balance in the vertical and horizontal directions, and recovery from deformation distortion can be formed stably for a long period of time.

[0035]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view of a main part of a molding apparatus for explaining an embodiment of the present invention.

The molding apparatus of the present invention comprises the following [I], [II], [II]
The configuration is basically the same as that of the molding apparatus described in JP-A-6-122150 except that the condition [I], preferably further the condition [IV], is satisfied.

[I] Outlet 23A of first air cooling ring 23
Minimum inner diameter D ₁ and the ratio D ₂ / D ₁ is less than 1 0.6 or more and a minimum inner diameter D ₂ of the air outlet 24B of the second air cooling ring 24 [II] of the D _1, D ₂ are both the forming die 10 of the Extrusion port 10
Greater than diameter D ₀ of the A [III] a distance L between the outlet 23A of the air outlet 24B and the first air cooling ring 23 of the second air cooling ring 24 100~700m
m [IV] Minimum inner diameter D of outlet 23A of first air cooling ring 23
The ratio D ₀ between ₁ and the diameter D ₀ of the extrusion port 10A of the molding die 10.
/ D ₁ is between 0.5 to 0.8 minimum inner diameter D ₁ of the outlet 23A of the first air cooling ring 23,
If the ratio D ₂ / D ₁ with respect to the minimum inner diameter D ₂ of the outlet 24B of the second air cooling ring 24 is less than 0.6, the tube comes into contact with the outlet 24B of the second air cooling ring 24 at start-up, and the workability is improved. When the output decreases and the throughput increases, the second
The tube comes into contact with the air outlet 24B of the air cooling ring 24, and the film cannot be formed. If the ratio D ₂ / D ₁ is 1 or more, the cooling efficiency in the second air cooling ring 24 decreases, and stable molding cannot be performed when the extrusion rate increases. Therefore,
0.6 ≦ D ₂ / D ₁ <1.

The outlet 23A of the first air cooling ring 23
Inner diameter D ₁ and the outlet 24B of the second air cooling ring 24
Minimum inner diameter D ₂ is smaller than the diameter D ₀ of the extrusion port 10A of the forming die 10, the air outlet 23A into the tube, 24B of
Contact, making stable molding impossible. Therefore, D ₁ > D ₀ ,
It is assumed that D ₂ > D ₀ .

The air outlet 24B of the second air cooling ring 24 and the first
The distance L between the air cooling ring 23 and the outlet 23A is 700 mm.
If it is larger, the tube is excessively cooled, so that high blow ratio molding cannot be performed. If it is less than 100 mm, the precooling effect is small, and stable molding cannot be performed when the extrusion amount is increased. Therefore, L = 100 to 700 mm, preferably 300 to 60
0 mm.

Further, the air outlet 23A of the first air cooling ring 23
Diameter D of the extrusion port 10A of the minimum inner diameter D ₁ and the forming die 10 of the
_When the ratio D ₀ / D ₁ to ₀ exceeds 0.8, the workability tends to be extremely lowered, and when it is less than 0.5, the cooling efficiency decreases, and when the extrusion amount is increased, stable molding tends to be impossible. There is. Therefore, it is preferable that D ₀ / D ₁ = 0.5 to 0.8.

In the illustrated molding apparatus, two air outlets are provided in the second air cooling ring, but the number of air outlets may be one. That is, in the present invention, the first air cooling ring and the second
At least one air outlet is provided in each of the air cooling rings,
It is sufficient that cooling can be performed with two or more outlets. Preferably,
It is desirable that two air outlets are provided in the second air cooling ring, and that cooling air is blown out by the three air outlets to cool the air. In this case, as shown in FIG.
It is preferable that the 3A is provided in the extrusion port 10A of the forming die 10 so that the minimum inner diameter of the outlet port 24B on the upstream side of the second air cooling ring 24 is smaller than the minimum inner diameter of the outlet port 24A on the downstream side.

In this case, it is preferable from the viewpoints of cooling efficiency and molding stability that the amount and speed of the cooling gas blown out from each outlet be in the following ranges.

Outlet 23A of first air cooling ring 23 Air volume: 2 to 20 m ³ / min, preferably 4 to 15 m ³ / min Wind speed: 2 to 20 m / sec, preferably 4 to 15 m / sec Upstream outlet 24B Air volume: 2 to 20 m ³ / min, preferably ³ to 15 m ³ / min Wind speed: 4 to 40 m / sec, preferably 10 to 30 m / sec Downstream outlet 24A of the second air cooling ring 24 10~80m ³ / min, preferably 15~60m ³
/ Min Wind speed: 5 to 50 m / sec, preferably 8 to 40 m / sec In the present invention, in the cooling by the second air cooling ring 24,
In order to facilitate the diameter expansion of the tube B, as described above, the air volume and the air velocity from the upstream outlet 24B are set smaller than those of the downstream outlet 24A.

In the present invention, the angle θ between the tapered surface formed by the surface connecting the downstream ends 27a of the cylindrical bodies 27A to 27F of the annular rectifying cylinder group 27 and the feeding direction of the tube B is 4
Preferably it is 5 to 70 degrees. If the angle is less than 45 degrees, high blow ratio molding cannot be performed, and if it exceeds 70 degrees, stable molding may be difficult.

There is no particular limitation on the number of cylinders in the annular rectification cylinder group 27, but the difference between the diameters of adjacent cylinders is 50 to 300.
It is preferable that an annular air chamber having a width of 25 mm to 150 mm is formed.

The downstream end 27a of the outermost cylindrical body 27A of the annular rectifying cylinder group 27 is preferably located at a distance of 800 to 2000 mm from the upper surface of the forming die 10.

On the other hand, the outer diameter of the inner cooling cylinder 26 is about 1/2 to 1 / 1.1 of the diameter D ₀ of the extrusion port 10A of the forming die 10, and its tip is 1000 mm from the upper surface of the forming die 10.
It is preferable to set the position at a distance of ２2500 mm. The stat width of the cooling gas outlet 26b of the inner cooling cylinder 26 is set to 0.1.
5 to 2 mm, and the outlet 26b is 40 mm
It is preferable to provide about 3 to 8 air gaps at an interval of about 500 mm. The air volume and the air velocity of each outlet 26b vary depending on the blow ratio, but the air volume is 0.05 to ⁵ m3 / min, preferably 0.1 to 0. The range is preferably 3 m ³ / min and the wind speed is 1 to 15 m / sec, preferably 2 to 10 m / sec.

The cooling gas introduced into the tube B through the inner cooling cylinder 26 is used for cooling the tube B and expanding the tube B.

Therefore, the amount of the cooling gas introduced into the tube B through the inner cooling cylinder 26 is controlled by the blower into the tube B while controlling the width of the tube B and the position of the frost line F to be constant. The blower is blown, and in some cases, the rotation of the blower motor is
And between the inner pipe 26A and the outside.

In the molding method of the present invention, using such a molding apparatus, as shown in FIG. 2, the molten resin of the extruder 3 is extruded from the extrusion port of the annular molding die 10 in a single layer or a laminated structure. The outer peripheral surface of the tube B 'is pre-cooled by the cooling gas blown from the annular outlet 23A of the first air cooling ring 23, and then the second air cooling ring 24 on the downstream side thereof is cooled.
Is further pre-cooled by the cooling gas blown from the upstream annular outlet 24B, and is further cooled in earnest by the cooling gas blown from the downstream annular outlet 24A. On the other hand, the inside of the tube B is cooled by the air blown out from the inner cooling cylinder 26.

As described above, the distance from the annular forming die 10 to the frost line F of the tube B can be increased by cooling from the inside and outside of the tube B, so that the obtained blown film has good transparency. Becomes

The tube B is provided with a cooling gas blown from the inner cooling cylinder 26 near the second air cooling ring 24, the outer peripheral surface of the tube B and the air chambers 27 a to 27 b of the annular rectifying cylinder group 27.
The air passing through 27e is expanded (expanded in diameter) by the Venturi effect.

In the present invention, the frost line F of the tube B is connected to the outermost cylindrical body 2 of the annular rectifying cylinder group 27.
Molding is performed so as to be located near the downstream end 27a of 7A, and by doing so, stable molding at a high blow ratio becomes possible.

The expanded tube B is guided by guide plates 15 and 15, as shown in FIG.
7 and rolled up.

The take-off speed of this film is 20 to 150 m
/ Min.

In the method of the present invention, the blow ratio is 5 to 20 times,
Preferably, molding is performed at a ratio of 8 to 16 times. This blow ratio is 5
If the ratio is less than twice, the blow ratio is too small to obtain an inflation film excellent in various properties, especially in the recovery from deformation strain. When the blow ratio exceeds 20 times, the elongation of the film is extremely reduced, and the film performance is hindered.

Hereinafter, the material of the blown film formed by the present invention will be described.

As a material for the packaging film, an ethylene-vinyl acetate copolymer having an ethylene content of 5 to 25% by weight and an MFR (melt flow rate) of 0.3 to 5 g / 10 min; % And carbon number is 3-8
Low-density polyethylene, high-density polyethylene, low-density polyethylene which is a copolymer with 20 to 1% by weight of α-olefin of the formula: ethylene-acrylic acid copolymer; ethylene-methyl acrylate copolymer; ethylene-meta Methyl acrylate copolymer; Propylene homopolymer; Propylene C 88 to 99.5% by weight, ethylene or carbon number 4 to
Copolymer with 12 to 0.5% by weight of an α-olefin of 8;
Olefinic resins such as poly (4-methylpentene-1); polybutene are preferred, and these may be used alone or in combination of two or more.
Used as a mixture of more than one species. The α-olefin includes butene-1, heptene-1, hexene-1, octene-1, 4-methylpentene-1 and the like.

These olefin resins include hydrogenated petroleum resin, hydrogenated styrene-butadiene-styrene copolymer, ethylene-propylene copolymer rubber, 1,2-polybutadiene, ethylene-propylene-ethylidene norbornene copolymer rubber. May be added to such an extent that the transparency of the film is not impaired (usually about 0.5 to 20% by weight). Further, a lubricant and a tackifier for improving the slipperiness of the film, a nucleating agent for improving the transparency of the film of 0.5 to
You may mix | blend about 2 weight%.

Examples of the lubricant include fatty acid amides such as oleic acid amide, stearic acid amide and erucic acid amide, fatty acid glycerin ester compounds such as stearic acid monoglyceride and stearic acid diglyceride, and polyethylene glycol adducts thereof.
As a nucleating agent, an inorganic substance such as talc or silica can be used, and as an adhesive, a castor oil derivative, a low molecular adhesive substance of polybutene, a higher sorbitan fatty acid ester, or the like can be used.

The blown film to be formed may have a single layer structure or a laminated structure, and preferably has a multilayer structure from the viewpoint of balance between moldability and physical properties of the film.

Examples of such a film having a multilayer structure include:
The following laminated structures are mentioned.

On both surfaces of an intermediate layer of a linear low-density polyethylene resin having an MFR of 0.1 to 5 g / 10 min and a Q value of 1 to 6, 60 to 95% by weight of ethylene and vinyl acetate
A three-layer film in which a surface layer of a copolymer resin with 5 to 40% by weight of a monomer selected from aliphatic unsaturated carboxylic acids and alkyl esters of aliphatic unsaturated monocarboxylic acids is laminated.

On both surfaces of an intermediate layer of a resin composed of 10 to 90% by weight of a crystalline olefin resin of an ethylene resin or a propylene resin and 90 to 10% by weight of an olefinic thermoplastic elastomer, 60 to 95% by weight of ethylene and 3 laminated with a surface layer of a copolymer resin with 5 to 40% by weight of a monomer selected from vinyl esters, aliphatic unsaturated carboxylic acids and aliphatic unsaturated monocarboxylic acid alkyl esters
Layered film.

A monomer 5 selected from 80 to 95% by weight of linear low-density polyethylene, 60 to 95% by weight of ethylene and vinyl acetate, aliphatic unsaturated carboxylic acid, or alkyl ester of aliphatic unsaturated monocarboxylic acid. 60 to 95% by weight of ethylene, vinyl acetate ester, aliphatic unsaturated carboxylic acid, aliphatic unsaturated monocarboxylic acid on both surfaces of an intermediate layer of a resin consisting of 20 to 5% by weight of a copolymer resin of 20 to 5% by weight. 5-4 monomers selected from acid alkyl esters
A three-layer film in which a surface layer of a copolymer resin of 0% by weight is laminated.

10-90% by weight of butene-1 resin
And an olefin resin (excluding butene-1 resin) and / or an intermediate layer of a resin comprising 90 to 10% by weight of an olefin thermoplastic elastomer.
Three layers in which a surface layer of a copolymer resin of 95% by weight and 5 to 40% by weight of a monomer selected from vinyl acetate, aliphatic unsaturated carboxylic acid and aliphatic unsaturated monocarboxylic acid alkyl ester is laminated. Structure film.

A two-layer or three-layer film in which a linear low-density polyethylene resin layer is laminated on one or both sides of a low-density polyethylene resin layer.

A two-layer or three-layer film in which a low-density polyethylene or a linear low-density polyethylene resin layer is laminated on one or both sides of a high-density polyethylene resin layer.

A two-layer or three-layer film in which a low-density polyethylene or propylene-based resin layer is laminated on one or both sides of a linear low-density polyethylene resin layer.

A two-layer or three-layer film in which a linear low-density polyethylene resin layer is laminated on one or both sides of a propylene-based resin layer.

The film formed according to the present invention is excellent in transparency, glossiness and strength balance in the vertical and horizontal directions. Particularly, a film having a high blow ratio of 7 to 15 times has remarkably excellent deformation distortion recovery.

The recovery from deformation strain of this film is, for example, as follows.
As shown in FIG. 3, a circular sample film C having a diameter of 100 mm
After the film C is deformed by pushing a piston rod 34 having a hemisphere with a diameter of 20 mm at the tip at the center thereof to deform the film C, 100% recoverable maximum when the piston rod 34 is raised to remove the hemisphere is removed. According to the present invention, the amount of strain recovery can be obtained by measuring the strain amount H, which is 15 mm or more, particularly 18 mm or more, and especially 2 mm.
A film of 0 to 30 mm can be formed. In the drawing, reference numeral 33 denotes a load cell.

The packaging film is preferably as transparent as possible (has less than 30% haze) so that the contents can be seen through. However, transparency is not important for applications where transparency is not required, such as bag making. In this case, 3 to 40 inorganic fine powders such as carbon black, calcined clay, calcium carbonate, and talc are added to the film material. 3% or more, preferably 40%
A translucent to opaque film of about 100% can be used.

In the present invention, the thickness of the blown film is preferably from 6 to 100 μm, particularly from 8 to 30 μm in the case of a film for stretch wrapping of food and a film for bag making from the viewpoint of economy and transparency. Preferably, the thickness of the intermediate layer is 2 to 10 in the case of a laminated film, for example, a three-layer laminated film.
It is preferable that the thickness of both surface layers is 3 to 10 microns, and the total thickness is 8 to 30 microns. Also,
In the case of a pallet stretch packaging resin film, the thickness is preferably 20 to 50 microns.

[0076]

The present invention will be described more specifically below with reference to examples and comparative examples.

Example 1 In the forming apparatus shown in FIG. 2, the cooling mechanism shown in FIG. 1 was provided, and a blown film having a three-layer structure was formed according to the present invention.

The dimensions and conditions of each part of the molding apparatus are as follows.

Resin extrusion port 10A of forming die 10 Diameter D ₀ : 120 mm Rip width: 2.0 mm Blow-out port 23A of first air cooling ring 23 Minimum inner diameter D ₁ : 180 mm Air volume: 10 m ³ / min Air velocity: 7 m / sec Second Upstream outlet 24B of air cooling ring 24 Minimum inner diameter D ₂ : 160 mm Distance L from outlet 23A of first air cooling ring 23: 30
0 mm Air volume: 4 m ³ / min Wind speed: 15 m / sec Downstream outlet 24A of the second air cooling ring 24 Minimum inner diameter: 200 mm Air volume: 30 m ³ / min Wind speed: 25 m / sec The first air cooling ring 23 and the second air cooling ring 24 Outer diameter: 1
300mm The angle of the taper θ of the current rectification cylinder group 27: 60 degrees The dimensions of each cylinder of the current rectification cylinder group 27 are as follows:

[0080]

[Table 1]

Inner cooling cylinder 26 Outer tube diameter: 90 mm Inner tube diameter: 60 mm Height of the tip from the upper surface of the forming die 10: 2200 mm The stat width of each outlet 26 b is 40 to 250 mm. As follows

[0082]

[Table 2]

Polybutene-1 (trade name “MO200” manufactured by Shell Chemical Co .; density: 0.915 g / cm ³ , 190)
70% by weight of MFR at 1.8 ° C./10 minutes), propylene-ethylene-butene-1 random copolymer resin (ethylene content 2.0% by weight, butene-1 content 13.0% by weight, density 0. 896 g / cm ³ , MFR at 230 ° C.
5.0 / 10 minutes) 15% by weight of an ethylene-vinyl acetate copolymer resin (vinyl acetate content 15% by weight, MFR at 190 ° C. 2.0 g / 10 minutes) 15% by weight (A) Is kneaded at 185 ° C. using an extruder having a caliber of 50 mm and L / D25, and separately, an ethylene-vinyl acetate copolymer resin (vinyl acetate content 15% by weight, MFR 2.0 g / 10 min at 190 ° C.) A resin composition (B) consisting of 98.5% by weight and 1.5% by weight of monoglycerin oleate (trade name "Liquemar OL100" manufactured by Riken Vitamin Co., Ltd.) was prepared using an extruder having a diameter of 65 mm and an L / D25 of 160. C. and kneaded at a temperature of 300.degree. C., and the two were supplied to a single annular three-layer die, and an ethylene-vinyl acetate copolymer resin was used as a main component on both surfaces of a 3 .mu.m thick intermediate layer made of the resin composition of (A). (B) resin As the surface layer of the thickness 5μm composed of Narubutsu is laminated, die temperature 185 ° C., a blow ratio 8.0 times, extrusion rate 110 kg / time, take-up speed of 50
A stretch packaging film having a total thickness of 13 μm (5 μm / 3 μm / 5 μm) was produced by inflation molding at m / min.

Using this film, a tray made of extruded expanded polystyrene (length 210 mm, width 140 mm, depth 2
0mm, meat thickness 2mm), and put the meat, fish and vegetables on the stretch automatic wrapping machine (trade name "A-
18X ").

The results are shown in Table 4 together with the film properties such as haze, gloss, deformation distortion recovery, and the like.

The film was evaluated by the following method.

Molding stability: The variation in the fold diameter of the tube was measured in the direction of travel of the tube for 30 minutes, and the variation width of the fold diameter was measured. Film thickness: Measured at 2 cm intervals in the width direction using a 1/1000 mm dial gauge. Deformation strain recovery: 20 m in diameter using the apparatus shown in FIG.
After the piston rod of m was pushed into the center of the film at a speed of 500 mm / min, the piston rod was retracted, and the amount of strain at which the scar caused by the piston rod on the film disappeared after 3 minutes was defined as the deformation distortion recovery amount. Tensile breaking strength, tensile breaking elongation: Measured according to JIS Z-1702. Haze: Measured according to JIS K-6714. Gloss: Measured according to JIS Z-8741 (20 degrees). Tensile extensibility: Using an “A-18X” packaging machine manufactured by Fujiki Kai Co., Ltd., each of the trays was loaded with meat, fish, and vegetables, and stretch-packaged. At that time, the stretched state of the film was visually observed. Breakage occurrence status: Using a “A-18X” packaging machine manufactured by Fujiki Kai Co., Ltd., each of the trays was loaded with meat, fish, and vegetables, and stretch-wrapped, and the state of the film at that time was observed with the naked eye. Wrinkling occurrence: The stretch-wrapped film was visually observed for wrinkles.

Embodiment 2 In Embodiment 1, the upstream side air outlet 24 of the second air cooling ring is used.
B has a minimum inner diameter D ₂ of 170 mm, a downstream side outlet 24A has a minimum inner diameter of 240 mm, and the first and second air cooling rings 2
The blown film was blown at 8.0 times in the same manner except that the blowing conditions of the cold air from 3, 24 were changed as follows, and the obtained films were evaluated. The results are shown in Table 4.

The air outlet 23A of the first air cooling ring 23 Air volume: 11 m ³ / min Air velocity: 7.7 m / sec The upstream air outlet 24B of the second air cooling ring 24 Air volume: 4.4 m ³ / min Air velocity: 17.0 m / min Second Downstream outlet 24A of second air cooling ring 24 Air volume: 33.0 m ³ / min Air velocity: 27.0 m / sec Example 3 In Example 1, the extrusion rate was 140 kg / hour, and the air supplied into the tube was Change the amount, blow ratio 10.0
And the first and second air cooling rings 23,
Inflation molding was carried out in exactly the same manner except that the conditions for blowing cold air from No. 24 were changed as described below, and the obtained films were evaluated. The results are shown in Table 4.

The air outlet 23A of the first air cooling ring 23 Air volume: 13 m ³ / min Air velocity: 9.5 m / sec The upstream air outlet 24B of the second air cooling ring 24 Air volume: 4.8 m ³ / min Air velocity: 18.0 m / min Seconds Downstream outlet 24A of second air cooling ring 24 Air volume: 36.0 m ³ / min Wind speed: 30.0 m / sec Example 4 In Example 1, the extrusion rate was set to 70 kg / hour, and The amount is changed so that the blow ratio becomes 5.0 times, and the first and second air cooling rings 23 and 24 are changed.
The inflation molding was carried out in exactly the same manner except that the conditions for blowing cold air from were changed as follows, and the obtained films were evaluated. The results are shown in Table 4.

The air outlet 23A of the first air cooling ring 23 Air volume: 7 m ³ / min Air velocity: 5.0 m / sec The upstream air outlet 24B of the second air cooling ring 24 Air volume: 3.2 m ³ / min Air velocity: 12.0 m / min Second Downstream outlet 24A of second air cooling ring 24 Air volume: 30.0 m ³ / min Wind velocity: 24.0 m / sec Example 5 In Example 1, the resin composition (A) of the intermediate layer was replaced with ethylene-4- Methylpentene-1 copolymer resin (4-methylpentene-1 content 15% by weight, density 0.910 g /
cm ^3, and was changed to MFR3.6g / 10 min) at 190 ° C. in the same manner to inflation molding, evaluates the obtained film, the results are shown in Table 4.

Example 6 In Example 1, the extrusion rate was set to 55 kg / hour, the amount of air supplied into the tube was changed so that the blow ratio became 4.5 times, and the first and second air cooling was performed. Rings 23, 24
The inflation molding was carried out in exactly the same manner except that the conditions for blowing cold air from were changed as follows, and the obtained films were evaluated. The results are shown in Table 4.

Outlet 23A of first air-cooling ring 23 Air volume: 7.0 m ³ / min Wind speed: 5.0 m / sec Upstream outlet 24B of second air-cooling ring 24 Air volume: 3.2 m ³ / min Wind speed: 12. 0 m / sec Downstream outlet 24A of second air-cooling ring 24 Air volume: 20.0 m ³ / min Wind speed: 24.0 m / sec Comparative Example 1 In Example 1, minimum of upstream-side outlet 24B of second air-cooling ring 24 Although the inner diameter D ₂ was attempted inflation molding at a blow ratio of 5.0 times in the same manner except that the 120 mm, the second air cooling ring 24 upstream outlet 24B
The tube came into contact with, and the blown film could not be formed.

Comparative Example 2 In Example 1, the upstream outlet 2 of the second air cooling ring 24
The minimum inner diameter D ₂ of 4B and 190 mm, the minimum inner diameter of the downstream outlet and 240 mm, and exactly the same except for changing the first, the cold air blowing conditions from the second air cooling ring 23, 24 as follows Inflation molding was performed at a blow ratio of 8.0 times, and the evaluation was performed. As shown in Table 4, the haze at a place where the film thickness deviation was as large as 13 μm ± 6 μm and the film thickness was thin (8 μm) was obtained. Is 7.0%
And both the uneven thickness and the transparency were not sufficient.

The air outlet 23A of the first air cooling ring 23 Air volume: 11 m ³ / min Air velocity: 7.7 m / sec The upstream air outlet 24B of the second air cooling ring 24 Air volume: 4.4 m ³ / min Air velocity: 17.0 m / min Seconds Downstream outlet 24A of second air cooling ring 24 Air volume: 33.0 m ³ / min Wind speed: 27.0 m / sec Examples 7 to 9, Comparative Examples 3 to 5 In Example 1, the molding conditions are shown in Table 3. Inflation molding is performed in exactly the same way except that it has been changed,
The obtained film was evaluated, and the results are shown in Table 4.
Note that D ₂ / D ₁ in Example 7 and Comparative Example 3 is D ₁ / D _1.
The constant was changed by changing the D _2.

[0096]

[Table 3]

[0097]

[Table 4]

[0098]

As described in detail above, according to the blown film forming apparatus and method of the present invention, a film excellent in deformation strain recovery, transparency, glossiness, and longitudinal and lateral strength balance even at a high extrusion rate. Can be continuously and reliably formed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part of a molding apparatus for explaining an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a conventional blown film forming apparatus.

FIG. 3 is a cross-sectional view showing a method for measuring the amount of deformation recovery strain of a film.

[Explanation of symbols]

Reference Signs List A Thermoplastic resin B Tube C Inflation film 1 Inflation film molding machine 2 Supply hopper 3 Extruder 4 Motor 5 Screw 6 Connecting pipe 9 Blow head 10 Molding die 10A Extrusion port 11 Bubble pipe 12 Pump 13 Air cooling ring 14 Blower 15 Guide plate 17 Take-up roll 18, 19 Guide roll 20 Winding machine 21 Winding shaft 22 Paper tube 23 First air cooling ring 23A Air outlet 24 Second air cooling ring 24A Downstream air outlet 24B Upstream air outlet 25 Same wall 26 Internal cooling cylinder 26A Inner pipe 26B Outer pipe 27 Annular rectifying cylinder group 27A, 27B, 27C, 27D, 27E, 27F Cylindrical bodies 28a, 28b, 28c, 28d, 28e Air chamber

Claims (4)

[Claims] A molding die having an extrusion opening for extruding the molten resin into a tube; a first air cooling ring having a cooling gas outlet surrounding the tube extruded from the molding die; A second air-cooling ring, which is arranged more distant from the forming die than the air-cooling ring, and has a cooling gas outlet surrounding the tube; and a second air-cooling ring which is more distant from the forming die than the second air-cooling ring. An annular rectifying cylinder group arranged around the tube; and an air supply means for supplying gas into the tube to inflate the tube, and the annular rectifying cylinder group is coaxially arranged. ,
A plurality of cylinders forming an annular air chamber between each other are provided, and the ends of these cylinders on the downstream side in the tube feed direction are located closer to the downstream as the outer cylinders are located. A surface connecting a downstream end portion of the cylindrical body forms a tapered surface, and the tube is an inflation film forming apparatus in which the tube is blown along the tapered surface. It was a D _1, the smallest inner diameter of the outlet of the second air cooling ring D
_When the ratio is ₂ , the ratio D ₂ / D ₁ is 0.6 or more and less than 1, and both D ₁ and D ₂ are larger than the diameter of the extrusion port. (1) An inflation film forming apparatus, which is located 100 to 700 mm downstream from an air outlet of an air cooling ring. 2. The method of claim 1, if the diameter of the extrusion port of the molding die set to D _0, the ratio D ₀ / D ₁ of the smallest inside diameter D ₁ of the outlet of the first air cooling ring 0. 5-
A blown film forming apparatus, wherein the ratio is 0.8. 3. A method for forming an inflation film using the forming apparatus according to claim 1 or 2, wherein a frost line of the inflated tube is located near a downstream end of an outermost cylinder of the annular rectification cylinder group. A method for forming an inflation film, comprising forming the film so as to be positioned. 4. The method according to claim 3, wherein the blow ratio of the tube is 5 to 20 times.