JPH10180868A - Method of molding inflation film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily alter a film size without lowering tear strength or impact strength or deteriorating optical characteristics such as transparency (haze) or gloss (clarity) even if high speed molding is performed and without bringing about the lowering of productivity or product loss up to replacing work of an internal stabilizer or an air ring or steady operation. SOLUTION: This film is obtained by expanding a molten bubble formed by extruding a resin compsn. containing polyethylene with density of 0.86-0.94g/cm<3> and 50wt.% or less of other polyolefin so that a ratio of max. diameter (D2 )/min. diameter (D1 ) of the bubble becomes 2.0-5.0. Thereafter, this film is reduced in diameter so that a ratio of product diameter (D3 )/max. diameter (D2 ) of the bubble becomes 0.9-0.5 to be taken over.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a linear low-density polyethylene and / or an ethylene (co) polymer obtained by high-pressure radical polymerization (hereinafter referred to as polyethylene), or 50% by weight or less of these polyethylenes. A resin composition containing other polyolefins (hereinafter collectively referred to as a polyethylene composition), an inflation film obtained by molding at least one kind of thermoplastic resin of the same or different kind from polyethylene or its composition. The present invention relates to a method for forming an inflation film having excellent operability in which the film size can be easily adjusted without lowering the optical properties of a thin film, an ultrathin film, a multilayer film, etc., the mechanical properties of longitudinal tear strength, and the heat seal strength.

[0002]

2. Description of the Related Art Films formed from polyethylene such as low-density polyethylene and linear low-density polyethylene or a composition thereof are used in standard bags (supermarkets, convenience stores, retail stores, etc.) for general business packaging, cleaning, etc. It is widely used in large quantities as packaging materials for foods, medicine, clothing, etc., such as heavy packaging bags, semi-heavy packaging bags, etc. for packaging heavy materials such as grains, fertilizers, earth and stones such as rice. These films are generally formed by extruding polyethylene or a composition thereof in a molten state from an annular die into a cylindrical shape, and a fluid such as air is injected into the cylindrical bubble to expand the molten resin bubble from the outside. It is manufactured by an air-cooled inflation method in which it is cooled and solidified by cooling air such as an air ring, and is continuously wound. In recent years, there has been a demand for the development of a higher-speed molding method in order to further improve the productivity of these blown film molding methods.

[0003] However, as described above, in order to increase productivity and produce ultra-thin films, mechanical strength such as tear strength and impact strength is increased by a faster air-cooled inflation method.
In order to form a film having excellent optical properties (haze, gloss, clarity, etc.), there is a problem that the amount of cooling air for the molten resin bubbles must be increased and the molten resin bubbles must be prevented from swaying. In addition, futon bag, BI
B (bag-in-box), high-density polyethylene, polyamide resin, polyester resin, gas-barrier resin such as saponified ethylene-vinyl acetate copolymer, etc. used for food packaging bags, etc. In the case of a multilayer film in which chain low-density polyethylenes are laminated, similarly to a single-layer film made of the above-mentioned polyethylene or a composition thereof, improvement in productivity is required, and higher speed molding is desired. In other words, in high-speed molding, wrinkles and sagging occur in the raw film of the film due to prevention of deterioration of optical properties due to insufficient cooling of the molten resin bubble and instability of the molten resin bubble due to an increase in cooling air flow. There have been various problems such as a decrease in printability in the next processing step, a decrease in bag making speed during bag making, and a defective heat seal. In addition, as the film forming speed (drawing speed) increases (high speed), the molecular orientation advances in the film taking direction (hereinafter referred to as the MD direction), and the tear strength and heat seal strength in the MD direction decrease. Have.

[0004] As a molding method for improving the longitudinal cracking property in the MD direction, there have been proposed various molding methods in which an internal stabilizer is provided and the blow-up ratio is relatively large, as disclosed in Japanese Patent Publication No. 3-61575. When high-speed molding is performed, the longitudinal crack strength also decreases, and the molding conditions are relatively narrow, and the switching work associated with changes in product specifications, that is, the replacement work of internal stabilizers, air rings, etc. There are problems such as a decrease in productivity. In addition, in these inflation molding methods, a switching operation cannot be continuously performed in accordance with a change in product specifications, and a small-diameter film cannot be continuously manufactured from a large-diameter film.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the tear strength, impact strength, etc., and to improve the transparency (even if the molding is carried out at a higher speed in order to increase the productivity and produce an ultrathin film, etc.). An object of the present invention is to provide a method for forming an inflation film which does not deteriorate optical characteristics such as haze and gloss (gloss, clarity). Another object of the present invention is to change the film from a large-diameter film to a small-diameter film without causing a decrease in productivity or product loss until the internal stabilizer, replacement work of the air ring or the like, or steady operation. An object of the present invention is to provide a method for forming an inflation film, in which a film size can be easily changed and which can be manufactured continuously.

[0006]

The first object of the present invention is to provide a linear low-density polyethylene having a density of 0.86 to 0.94 g / cm ³ and / or an ethylene (co) polymer obtained by high-pressure radical polymerization, or A molten bubble formed by extruding a resin composition containing polyethylene and 50% by weight or less of another polyolefin from a die is subjected to a ratio of a maximum bubble diameter (D ₂ ) / minimum bubble diameter (D ₁ ) of 2.0. ~ 5.
A method for forming an inflation film, characterized in that after inflation to 0, the ratio of product diameter (D ₃ ) / maximum diameter of bubble (D ₂ ) is reduced to 0.9 to 0.5 and taken off. .

The second aspect of the present invention is that the density is 0.86 to 0.94.
g / cm ³ of a linear low-density polyethylene and / or an ethylene (co) polymer obtained by high-pressure radical polymerization, or a resin composition containing these polyethylenes and 50% by weight or less of another polyolefin-based resin, After the molten bubble formed by simultaneously extruding from the multilayer die together with the thermoplastic resin of the above, the ratio of the maximum diameter of the bubble (D ₂ ) / the minimum diameter of the bubble (D ₁ ) is expanded to 2.0 to 5.0,
The ratio of product diameter (D ₃₎ / the maximum diameter of the bubble (D ₂₎ 0.9
A method for forming an inflation film, characterized in that the diameter of the film is reduced to 0.5 and then taken up.

A third aspect of the present invention is that the ratio of the maximum diameter of the bubble (D ₂ ) / the minimum diameter of the bubble (D ₁ ) according to the first or second aspect of the present invention is in the range of 2.0 to 4.5. After inflating with
The ratio of product diameter (D ₃₎ / the maximum diameter of the bubble (D ₂₎ 0.9
This is a method for forming an inflation film which is reduced in diameter to 0.5 and taken up.

A fourth aspect of the present invention is that the polyethylene according to any one of the first to third aspects of the present invention has a density of 0.88 to 0.8.
98 to 2% by weight of a linear low-density polyethylene of 94 g / cm ³ and an ethylene (co) polymer 2 by high-pressure radical polymerization
The method for forming a blown film according to any one of claims 1 and 2, wherein the blown film is made up to 98% by weight.

A fifth aspect of the present invention is that the same or different thermoplastic resin as described in the second aspect of the present invention is a polyolefin resin, a polyamide resin, a polyester resin, a saponified ethylene-vinyl acetate copolymer, This is a method for forming an inflation film, which is at least one resin selected from the group of vinylidene-based resins.

According to a sixth aspect of the present invention, there is provided a blown film according to any one of the first and second aspects of the present invention, wherein a means for supplying a cylindrical molten resin, a cooling means for cooling the molten resin, This is a method for forming an inflation film, which is formed by an inflation film forming apparatus having at least a bubble diameter adjusting means for reducing the diameter of an expanded bubble from the bubble diameter and a winding means for taking up and pinching and winding the bubble.

According to a seventh aspect of the present invention, the cooling means for cooling the molten resin according to the sixth aspect of the present invention includes a first cooling means provided near a die outlet and a cooling means provided with a space from the die surface. 2 is a method for forming an inflation film, which is formed by an apparatus having at least a cooling means.

In the blown film forming method of the present invention, the ratio of the maximum diameter of bubble (D ₂ ) / the minimum diameter of bubble (D ₁ ) is 2.0 to 2.0, specifically using a polyethylene composition.
5.0, preferably 2.2 to 4.5, after inflating more preferably 2.3 to 4.0, the ratio of product diameter (D ₃₎ / the maximum diameter of the bubble (D ₂₎ 0. By reducing the diameter to 9 to 0.5 and taking it off, a film having improved longitudinal tearability, transparency and the like can be obtained regardless of the film formed at a high speed. Further, the product size of the blown film can be freely adjusted.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the molding method of the present invention will be specifically described. As the most preferable embodiment of the blown film forming method of the present invention, (1) a tubular molten resin supply means from a tubular die, (2) a cooling means for cooling the molten resin, and (3) an expansion bubble diameter is determined by the bubble diameter It is desirable that the molding be performed by a molding device having at least a bubble diameter adjusting means for reducing the diameter, and (4) a winding means for pinching and winding the bubble to obtain a product. (1) The cylindrical shape from the annular die The supply means of the molten resin,
An extruder equipped with a raw resin supply port and an annular die is provided with an air hole at the center of the annular die to introduce air into the bubble, and the molten resin extruded from the annular die expands into a cylinder. At least a mechanism for forming bubbles. (2) The cooling means for cooling the molten resin is generally such that air / refrigerant, which is cooled by a refrigerant such as an air blower or water and cooled to a room temperature or less by a chiller or the like, is placed on a die surface as necessary. And a mechanism for cooling by blowing the bubbles from the cooling ring. In some cases, an air circulation mechanism may be provided inside the bubble to cool and circulate the bubble from the inner and outer surfaces. If the neck of the bubble is long, the cooling ring may be provided with a plurality of cooling rings. At this time, it is desirable to provide an internal stabilizer or the like inside the bubble in order to ensure the stability of the bubble. Further, a part of a plurality of cooling rings may be suction-cooled for stabilizing bubbles. The material of the internal stabilizer is rubber, sponge, elastic body such as spring, net-like body, synthetic resin, non-woven fabric, woven fabric, cloth, metal,
It is not particularly limited, such as pottery. (3) The bubble diameter adjusting means capable of adjusting the diameter of the expansion bubble diameter is a mechanism for expanding and contracting the expansion bubble diameter (D ₂ ). One means is preferably larger than the cooling port on the cooling ring. Install an air chamber with an inner diameter,
The bubble diameter can be adjusted with a plurality of iris plates whose opening can be freely adjusted in the air chamber. Other methods include bubble adjusting means combining the cooling ring and a plurality of iris plates, and bubble adjusting means combining a plurality of air chambers and a cooling ring. Also,
A mechanism for automatically adjusting these by correlating the bubble automatic measurement mechanism with these iris plate adjustment mechanisms may be used. (4) The winding means of the present invention introduces the regulated bubble into a guide plate, pinches the bubble between pinch rolls,
It includes a process of flattening and winding by a winder to produce a product, and includes a device required for the process, and in some cases, a device that performs a surface treatment such as a corona discharge treatment.

Hereinafter, the molding method of the present invention will be specifically described with reference to the drawings. FIG. 1 is a schematic enlarged view of the vicinity of a die outlet of an embodiment of the blown film forming method (one-stage cooling method) of the present invention, wherein polyethylene or a composition thereof supplied to an extruder (not shown) is annular. The bubble 1 is extruded from the die 3 as a cylindrical molten resin. The bubble 1 is expanded by the air pressure in the bubble 1 while being cooled by the air ring 2, and is introduced into the air chamber 4 installed on the surface of the air ring 2. The bubble 1 extruded from the die outlet has a ratio of the maximum bubble diameter (D ₂ ) / the minimum bubble diameter (D ₁ ) in the range of 2.0 to 5.0, preferably 2.
After greatly expanding the bubble 1 in the range of 2 to 4.5, more preferably in the range of 2.3 to 4.0, the iris plate 5 reduces the diameter (D ₃ ) of the bubble 1 to a value smaller than the maximum diameter (D ₂ ), Product diameter (D
₃ ) / the maximum bubble diameter (D ₂ ) ratio is 0.9 to 0.5;
Preferably 0.89-0.5, more preferably 0.85
It is adjusted to a range of about 0.5, is taken out, is then guided by a guide plate, is nipped between nip rolls, flattened and wound up to be a product.

In the above forming process, the annular die 3
The extruded cylindrical molten resin was constricted so as to have a smaller diameter than the die diameter (D ₁ ) while sufficiently keeping the distance (the neck portion of the bubble) from the die surface to the bubble expansion start point. Later, by performing a large expansion, the molecular orientation in the lateral direction (CD direction) can be further advanced, and the effect of improving the strength can be enhanced. In addition, if the distance from the die surface to the bubble expansion start point is sufficiently set, the stability of the bubble is impaired. Therefore, it is preferable to provide the internal stabilizer on the inner surface of the bubble.

FIG. 2 is a schematic enlarged view of the vicinity of the die outlet of another example (two-stage cooling method) of the blown film forming method of the present invention. This shows a two-stage cooling method in which a second air ring 9 is provided with a space from the die surface, and an air chamber 4 is installed on the second air ring 9. By taking a sufficient spatial distance from the second air ring 9, the molecular orientation in the vertical direction (MD direction) can be increased, and the mechanical strength in the vertical and horizontal directions can be improved. The space distance is desirably selected in the range of 400 to 1500 mm, preferably 450 to 1000 mm. However, it is desirable to provide the internal stabilizer 10 in this space and mold it as described above, since the sufficient space distance lacks the stability of the bubble. In the above two-stage cooling method, the cooling efficiency of the molten resin bubble can be remarkably increased, and it is the most suitable molding method not only for high-speed molding but also for molding a transparent ultrathin film.

FIGS. 3 to 5 schematically show another modification of the expansion / diameter reduction method which is a feature of the present invention. FIG. 3 shows that an air chamber 4 having an inner diameter larger than the inner diameter of the cooling ring 2 is provided downstream of the cooling ring 2 provided at the die outlet (film taking side), and at least one air chamber 4 is provided in the air chamber 4. The cooling ring also has a function of blowing air into the air chamber 4 in the extrusion direction to cool the molten resin bubble 1 by providing a plurality of suction ports and allowing air to be suctioned from the suction port by a blower, a blower, or the like. Provide a cooling ring that has
A method of reducing the diameter, or providing a plurality of cooling rings at the die outlet, having one or more air chambers having an inner diameter larger than the inner diameter of the most downstream cooling ring 8, and having At least one air inlet is provided, and air can be sucked from the air inlet by a blower, a blower, or the like. The cooling ring blows air into the air chamber 4 in the extrusion direction to cool the molten resin bubble 1. It is also possible to provide a cooling ring that also has a function to perform expansion and contraction.

FIG. 4 shows a state in which a suction ring 11 is provided downstream of one or multiple cooling rings provided at the die outlet, and the molten resin bubble 1 is sucked through a suction ring 11 by a blower, a blower or the like. This is a method of expanding and reducing the diameter.

FIG. 5 shows that at least one cooling ring provided at the die outlet is located downstream (the side where the film is taken off).
An air chamber 4 having an inner diameter larger than the inner diameter of the cooling ring is provided, and at least one energizing plate 12 is provided in the air chamber 4 to charge the energizing plate. This is a method of expanding and reducing the diameter by providing a cooling ring which also has a function of blowing air into the air chamber 4 in the extrusion direction to cool the air.

As in the method shown in FIGS. 3 to 5, the upper portion of the air chamber outlet is closed, a hole is formed therein, and when the bubble is drawn out, the hole is adjusted to a required size to adjust the product diameter. Although it is possible to adjust (D ₃ ), adjusting only with the upper hole of the air chamber has a narrow adjustment range in operation and the product diameter (D) during molding.
Since it is difficult to change ₃ ), the product diameter (D ₃ ) can be freely adjusted by using a combination of air chambers having a plurality of iris plates as shown in FIGS. Further, in any of the molding methods, bubble heating is performed on the inflation molding shaft immediately before the molten resin bubble expands, and the elongation viscosity of the molten bubble is reduced, so that the expansion and diameter reduction can be easily secured. .

In the present invention, when molding using a bubble stabilizer, a stabilizer smaller than the die diameter is used, and in the case of a bubble whose outer diameter expands immediately from the die diameter, the diameter of the die is reduced. The minimum diameter (D ₁ ) of the bubble may be used. Although not shown in the drawings, a second stabilizer having a diameter slightly larger than the die diameter is provided at the die outlet, as shown in FIG. 2, or as shown in FIG. It is also possible to provide a first stabilizer between the first cooling ring 8 and the second cooling ring 9 for operation.

The polyethylene composition of the present invention generally has a lower resin viscosity than high-density polyethylene and is easy to suck a bubble in a molten state, but has a problem that the molding is not stable unless the bubble is sufficiently sucked. The ring preferably has a structure for exerting the Venturi effect as described above.

In order to adjust the shape of the expanded molten bubble, the inner edge of the iris plate 5 whose opening can be freely adjusted is brought close to or away from the bubble to obtain a desired shape. In this case, the physical property of the product film is mainly controlled by the maximum diameter of the bubble (D ₂ ) / the minimum diameter of the bubble (D ₁ ),
The present invention was derived because it was found that changing the product diameter (D ₃ ) / the maximum bubble diameter (D ₂ ), which determines the size of the product, had little effect on the physical properties of the product film even if it was changed.

Until now, by increasing the product diameter (D ₃ ) / minimum bubble diameter (D ₁ ), the molecular orientation is hindered when the take-up speed is increased, and the effect of the take-up speed on the physical properties of the film. It was known that it was possible to reduce the product size, but in this case the product size was determined by the diameter of the die, and it was thought that changing the product without stopping the operation would be extremely difficult . However, it was found that even if the product diameter (D ₃ ) / maximum bubble diameter (D ₂ ) was smaller than 0.9, the influence on the physical properties of the product film was small, so that the once expanded molten resin bubbles were shrunk. By changing the diameter, the product size can be adjusted while maintaining the physical properties without changing the maximum diameter of the bubble (D ₂ ) / the minimum diameter of the bubble (D ₁ ).

For this reason, the problem of a decrease in film physical properties due to an increase in the take-up speed, which has been a problem when forming a small-sized film using a large-diameter die, is caused by a problem that the bubble diameter of the molten bubble is temporarily reduced. (D ₂ ) / Minimum bubble diameter (D ₁ ) is increased to improve mechanical strength such as longitudinal crack strength and heat seal strength, and then product diameter (D
₃ ) / By setting the maximum bubble diameter (D ₂ ) small, a small-sized film can be formed without exchanging parts such as dies while maintaining high productivity.

When the ratio of the maximum diameter of the bubble (D ₂ ) / the minimum diameter of the bubble (D ₁ ) of the present invention is less than 2 times, the mechanical strength in the transverse direction is not sufficient. Loses the strength balance in the vertical and horizontal directions, and the impact strength is reduced. In the present invention, the expanded bubble is then reduced to a diameter smaller than the maximum diameter (D ₂ ) of the bubble, and the product diameter (D ₃ ) /
It is required to adjust the bubble diameter so that the ratio to the maximum bubble diameter (D ₂ ) is in the range of 0.5 to 0.9. When the product diameter is 0.9 or more, the longitudinal tearing property is not improved, and
Below, molding becomes difficult.

In the present invention, the maximum diameter of the bubble (D ₂ )
After the ratio of the minimum diameter of the bubble (D ₁ ) is greatly expanded to 2.0 to 5.0, the ratio of the product diameter (D ₃ ) to the maximum diameter of the bubble (D ₂ ) is 0.9 to 0. Since it is possible to improve the longitudinal tearing property of the film by reducing the diameter to 0.5, it is possible to produce a large-diameter film using a large-diameter die and also to produce a small-diameter film with the same die. It becomes possible. These merits are that there is no need to replace dies or air rings, or to replace internal stabilizers.
It will make a great contribution to the economic effect.

The thickness of the product film of the present invention varies depending on the intended use of the product film.
Preferably it is in the range of 7 to 120 μm. The standard bags considered to be the most in demand are generally 10 to 25 μm,
The ultrathin film which seems to be the thinnest is 5 to 10 μm, and the film which is considered to be the thickest is generally 60 to 150 μm.
m are used, and the molding method of the present invention can be applied to any of them.

The polyethylene of the present invention or its composition is a linear low-density polyethylene having a density of 0.86 to 0.94 g / cm ³ and / or an ethylene (co) polymer obtained by high-pressure radical polymerization, or these polyethylenes And 5
It is a resin composition containing 0% by weight or less of another polyolefin.

The linear low-density polyethylene has a density of 0.86 to 0.94 g / cm ³ , preferably a density of 0.8 to 0.94 g / cm ³ .
8 to 0.94 g / cm ³ , more preferably a density of 0.89
In the range of ~ 0.94 g / cm ³ , with a Ziegler-based catalyst, a Phillips-based catalyst, a metallocene-based catalyst, etc.
It can be obtained by copolymerizing ethylene and an α-olefin having 3 to 12 carbon atoms in one or more stages under a medium or high pressure condition by a usual method such as a gas phase method, a slurry method, and a solution method. it can. As the α-olefin having 3 to 12 carbon atoms, propylene, 1-butene, 4-methyl-1
-Pentene, 1-hexene, 1-octene and the like, and the content thereof is generally in the range of about 3 to 40 mol%.

The ethylene (co) polymer obtained by high-pressure radical polymerization is a polymer which is polymerized under a pressure of 500 to 3500 kg / cm ² G in the presence of a radical generator such as an organic peroxide or oxygen. 0.91 to 0.94 g / cm ³
Low-density polyethylene, a copolymer of ethylene and a functional group-containing monomer, for example, an ethylene-vinyl ester copolymer such as an ethylene-vinyl acetate copolymer, and an ethylene such as an ethylene-ethyl (meth) acrylate copolymer. Copolymers with α, β unsaturated carboxylic acids or derivatives thereof, and the like, and mixtures thereof, and the like.

The above-mentioned linear polyethylene or ethylene (co) polymer obtained by high-pressure radical polymerization may be used alone, but may be arbitrarily compounded with each other according to the purpose and application. From the viewpoint of the balance of properties and the like, the range of 98 to 2% by weight of the linear polyethylene and the range of 2 to 98% by weight of the ethylene (co) polymer obtained by high-pressure radical polymerization, particularly while maintaining the properties of the linear polyethylene,
In order to improve the performance such as processability and melt tension, it is desirable to incorporate an ethylene (co) polymer by high-pressure radical polymerization up to 40% by weight.

The melt flow rate (MFR) of the above linear polyethylene or ethylene (co) polymer obtained by high-pressure radical polymerization and their composition is 0.01 to 50 g / m
It is desirably selected in the range of 10 minutes, preferably 0.05 to 30 g / 10 minutes, more preferably 0.1 to 10 g / 10 minutes. The linear polyethylene or its composition has a melt tension (MT) of 10 to 30 g,
It is preferable that the thickness is in the range of 15 to 25 g from the viewpoint of bubble stability at the time of forming the blown film.

The polyolefin of the present invention includes the above polyethylene or polyethylene excluding its composition, and includes high-density polyethylene, propylene homopolymer,
Random or block copolymers of propylene and α-olefin, poly 1-butene polymer, poly 4-methylpentene-1 polymer, ethylene-propylene copolymer rubber, ethylene-propylene-diene copolymer rubber, and these And the like.

A polyethylene resin composition having a compounding amount of these polyolefins of 50% by weight or less, more preferably 45% by weight or less is preferably used because of a good balance of physical properties such as strength, heat resistance and transparency.

The linear polyethylene or the composition of the linear polyethylene and the ethylene (co) polymer varies depending on the purpose and application, but generally has a molding temperature in the range of 150 to 250 ° C. The take-off speed is 40 to 120 m / min. In the one-stage cooling method. 40 to 1 in the two-stage cooling method
50 m / min. A certain degree of molding becomes possible. The die gap is 1.5 to 6.0 mm, preferably 2.0 to 6.0 mm.
It is selected in the range of 5.0 mm.

The method for forming a blown film of the present invention is not limited to a single-layer film of the above-mentioned polyethylene composition, but may be a multilayer film comprising at least two layers of a polyethylene composition layer and another thermoplastic resin layer. The same can be applied to molding.

Examples of the other thermoplastic resins include polyolefin resins, polyamide resins, polyester resins, saponified ethylene-vinyl acetate copolymers, polyvinylidene chloride resins, and polycarbonate resins. These can be selected in combination depending on the purpose and use. For example, multilayer films used for bag-in-boxes, futon bags and the like made of polyolefin resin include LL / HD / LL and LL + LD / HD / LL + L.
D, LL + VL / HD + VL / LL + VL, LL + EP
It is composed of a multilayer film such as R / HD / LL + EPR. Further, as a packaging material using a gas barrier resin, LL / adhesive layer / EVOH / adhesive layer / LL, LL + L
D / adhesive layer / EVOH / adhesive layer / LL + LD, LL / adhesive layer / PA / adhesive layer / LL, LL / adhesive layer / PET / adhesive layer / LL, LL + LD / adhesive layer / PA / adhesive layer / LL
+ LD, LL + LD / adhesive layer / PET / adhesive layer / LL +
LD and the like. (However, LL: linear polyethylene, VL: ultra low density polyethylene, LD: high pressure radical polymerization low density polyethylene, HD: high density polyethylene, EVOH: saponified ethylene-vinyl acetate copolymer,
PA: polyamide resin, PET: polyester resin, adhesive layer: acid-modified polyolefin, random copolymer of acid and ethylene, etc. )

In the present invention, if necessary, conventional additives such as an antioxidant, a lubricant, an antistatic agent, an ultraviolet ray inhibitor, a light stabilizer, an anti-blocking agent, a coloring pigment, a filler and the like may be added. Good.

[0041]

【Example】

(Examples 1 and 2) Using an apparatus as shown in FIG. 1, three iris plates composed of 32 wings were provided in an air chamber perpendicularly to an inflation molding axis, and the inner diameter was changed. The minimum diameter (D ₁ ) of the resin bubble, the maximum diameter (D ₂ ) of the bubble, and the product diameter (D ₃ ) were adjusted. Density is 0.
A linear low-density polyethylene (manufactured by Nippon Polyolefin Co., Ltd., trade name: JALEX A208FS: high-pressure method low-density polyethylene 20% blend) using 922 g / cm ³ and an MFR of 0.8 g / 10 min.
φ, frost line height 1100mm, product folding width 450
mm (product diameter: D ₃ = 287 mm) and a molding temperature of 19
0 ° C., bubble maximum diameter (D ₂ ) / bubble minimum diameter (D
₁ ) 2.8, product diameter (D ₃ ) / maximum bubble diameter (D ₂ )
0.85, take-off speeds of 40 m / min and 60 m / min,
Molding was performed under the condition of a film thickness of 30 μm. The amount of air blown out of the cooling ring is controlled by a blower (motor capacity: 5.
The air from 5 kW) was blown out by controlling with an inverter, and the air volume was adjusted by the frequency of the inverter motor and formed. The molding could be performed smoothly and the film could be formed stably. Table 1 shows the molding conditions and the physical properties of the obtained film.

Comparative Example 1 Using the same resin as in Example 1,
Without using an air chamber provided with an iris plate, a normal one-step cooling blown film was formed.
The molding could be performed smoothly and the film could be formed stably. Table 1 shows the molding conditions and the physical properties of the obtained film.
Shown in

(Examples 3 to 8)
Consists of 32 wings perpendicular to the flation molding axis
Using an apparatus as shown in FIG. 2 provided with three iris plates,
By changing the inner diameter of the iris plate, the minimum diameter of the molten resin bubble
(D₁ ), Bubble maximum diameter (D_Two ), Product diameter (D _Three )
Molding was performed with adjustment. Resin and film thickness used
The same as in Example 1, the take-up speed, the first cooling ring air volume,
Second cooling ring air volume, maximum bubble diameter (D_Two )/bubble
Minimum diameter (D₁ ), Product diameter (D_Three ) / Maximum diameter of bubble
(D_Two ) Was changed to form a film. Molding goes smoothly
The film could be formed stably. Forming strip
Table 1 shows the properties and physical properties of the obtained film.

Comparative Example 2 Using the same resin as in Example 1,
Without using an air chamber provided with an iris plate, a normal two-stage cooling blown film was formed.
The molding could be performed smoothly and the film could be formed stably. Table 1 shows the molding conditions and the physical properties of the obtained film.
Shown in

[0045]

[Table 1]

(Examples 9 to 10) The density was 0.920 g /
Linear low-density polyethylene (manufactured by Japan Polyolefin Co., Ltd., trade name: JELEX A604HL: high-pressure low-density polyethylene 20 cm ³ , MFR 0.4 g / 10 min)
% Blend), a die diameter of 100 mmφ, a frost line height of 1100 mm, and a device folding width of 450 mm (product diameter: D ₃ = 287 mm) using a device used in Example 1 and Example 3, and a molding temperature of 200 ° C. , The maximum bubble diameter (D ₂ ) / the minimum bubble diameter (D ₁ ) is 2.3.
And 3.8, and take-off speeds of 20 m / min and 30 m / min.
The molding was performed under the conditions of a film thickness of 100 μm. The amount of air blown out from the cooling ring was controlled by an inverter to blow out air from a blower (motor capacity: 5.5 kW), and the amount of air was adjusted by adjusting the frequency of the inverter motor. The molding could be performed smoothly and the film could be formed stably. Table 2 shows the molding conditions and the physical properties of the obtained film.

(Comparative Examples 3 and 4) Using the same resin as in Example 9 and using the apparatus used in Comparative Examples 1 and 2, a 100 μm-thick film was formed into a normal blown film. . The molding could be performed smoothly and the film could be formed stably. Table 2 shows the molding conditions and the physical properties of the obtained film.

[0048]

[Table 2]

(Examples 11 to 12) 0.904 g in density
/ Cm ³ , MFR of 1.2 g / 10 min linear low density polyethylene (manufactured by Nippon Polyolefin Co., Ltd., trade name:
Using a Jerex ULD0410-9) with a die diameter of 100 mmφ and a frost line height of 1100 mm, using the apparatus used in Example 1 and Example 3, a product folding width of 450 mm (product diameter: D ₃ = 287 mm),
Molding at 160 ° C, bubble maximum diameter (D ₂ ) / bubble minimum diameter (D ₁ ) of 3.4 and 3.6, take-off speeds of 35 m / min and 40 m / min, and film thickness of 80 μm. Was done. The amount of air blown out from the cooling ring was controlled by an inverter to blow out air from a blower (motor capacity: 5.5 kW), and the amount of air was adjusted by adjusting the frequency of the inverter motor.
The molding could be performed smoothly and the film could be formed stably. Table 3 shows the molding conditions and the physical properties of the obtained film.
Shown in

(Comparative Example 5) Using the same resin as in Example 11, using the apparatus used in Comparative Example 1, a thickness of 80 μm
Was formed into a normal blown film. The molding could be performed smoothly and the film could be formed stably. Table 3 shows the molding conditions and the physical properties of the obtained film.

[0051]

[Table 3]

(Examples 13-1 to 6 and 14) A linear low-density polyethylene alone having a density of 0.922 g / cm ³ and an MFR of 0.8 g / 10 min, and a resin having a density of 0.928 g / cm ^3, MFR is a low density polyethylene 1.2 g / 10 min, 20 parts, 40 parts, 60 parts and 8
0 parts by blending to make a total of 100 parts, a blend composition,
The low-density polyethylene alone and the high-density polyethylene 1
Example 1 After melt-kneading a resin obtained by blending 90 parts of the low-density polyethylene with 0 parts, respectively, using a twin-screw extruder.
Molding was carried out using the same apparatus and molding conditions as in the above. The molding could be performed smoothly and the film could be formed stably.
Table 4 shows the molding conditions and the physical properties of the obtained film.

[0053]

[Table 4]

Example 15 Using a multilayer die, a saponified ethylene-vinyl acetate copolymer was used as an intermediate layer (C).
Adhesive layer (B: maleic anhydride-modified ethylene-1-butene copolymer / acid addition amount = 0.15% by weight, MFR = 1.3
g / 10 min) through the linear polyethylene (A: d = 0.922 g / cm ³ , MF) used in Example 13-1.
R = 0.8 g / 10 min) on both outer layers (A / B / C / B / A, where total A layer:
(50 μm, B layer: 10 μm, C layer: 20 μm) were molded under the same conditions as in Example 13-1, and could be molded without any problem.

[0055]

According to the present invention, in a method for inflation molding of a thermoplastic resin, the molten resin extruded from a die is expanded to at least twice the minimum diameter (D ₁ ) of the bubble, and then the maximum diameter of the bubble is increased. (D ₂ ) smaller folding diameter (D
₃ ) By taking off as above, even if the molding is performed at a higher speed to increase the productivity and produce an ultra-thin film, the mechanical strength such as the tear strength and the impact strength decreases, and the transparency (haze), gloss ( A blown film that does not deteriorate optical properties such as gloss and clarity) can be formed. In addition, there is no reduction in productivity and no loss of product until the operation of replacing the internal stabilizer, the air ring, or the like, or the steady operation. Further, since films of any size from large-diameter film to small-diameter film can be easily and continuously produced, operability is excellent with no product loss.

[Brief description of the drawings]

FIG. 1 is a schematic enlarged view of the vicinity of a die outlet in one embodiment (one-stage cooling method) of the blown film forming method of the present invention.

FIG. 2 is a schematic enlarged view of the vicinity of a die outlet in another embodiment (two-stage cooling method) of the blown film forming method of the present invention.

FIG. 3 is a partially enlarged view of the expansion / reduction method of the present invention.

FIG. 4 is a partially enlarged view of an expansion / reduction method according to the present invention.

FIG. 5 is a partially enlarged view of the expansion / diameter reduction method of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 molten resin bubble 2 cooling ring (ring) first cooling ring 3 dice 4 air chamber 5 iris plate 6 iris plate adjustment knob 7 air supply chamber 8 second cooling ring 9 internal stabilizer D ₁ die diameter D ₂ bubble diameter D ₃ Product diameter (folding diameter)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 77/00 C08L 77/00 B29K 23:00 27:00 55:00 67:00 77:00 B29L 7:00 9:00

Claims (7)

[Claims] 1. A linear low-density polyethylene having a density of 0.86 to 0.94 g / cm ³ and / or an ethylene (co) polymer obtained by high-pressure radical polymerization, or other polyolefins containing up to 50% by weight of these polyethylenes The molten bubble formed by extruding the resin composition containing the resin from the die is converted into a maximum bubble diameter (D ₂ ) / a minimum bubble diameter (D ₁ ).
Of the product (D ₃ ) after expanding the ratio of
Molding method of inflation film, characterized in that pick up and reduced in diameter from 0.9 to 0.5 the ratio of / the maximum diameter of the bubble (D _2). 2. A linear low-density polyethylene having a density of 0.86 to 0.94 g / cm ³ and / or an ethylene (co) polymer obtained by high-pressure radical polymerization, or other polyethylene and not more than 50% by weight of these polyethylenes A molten bubble formed by simultaneously extruding a resin composition containing a base resin together with the same or different thermoplastic resin from a multilayer die is converted into a maximum bubble diameter (D ₂ ) / a minimum bubble diameter (D ₁ ).
Of the product (D ₃ ) after expanding the ratio of
Molding method of inflation film, characterized in that pick up and reduced in diameter from 0.9 to 0.5 the ratio of / the maximum diameter of the bubble (D _2). 3. After expanding the ratio of the maximum diameter (D ₂ ) of the bubble / the minimum diameter (D ₁ ) of the bubble in the range of 2.2 to 4.5, the product diameter (D ₃ ) / the ratio of the bubble pick up reduced in diameter the ratio of the maximum diameter (D ₂₎ to 0.9 to 0.50 claim 1 or 2
The method for forming a blown film according to any one of the above. 4. The method according to claim 1, wherein the polyethylene has a density of 0.88 or less.
0.94 g / cm ³ linear low density polyethylene 98 to
3. An ethylene (co) polymer obtained by 2% by weight and 2 to 98% by weight of an ethylene (co) polymer obtained by high-pressure radical polymerization.
The method for forming a blown film according to any one of the above. 5. The same or different thermoplastic resin is at least one selected from the group consisting of a polyolefin resin, a polyamide resin, a polyester resin, a saponified ethylene-vinyl acetate copolymer, and a vinylidene chloride resin. The method for forming a blown film according to claim 2, which is a resin. 6. A means for supplying a cylindrical molten resin, a cooling means for cooling the molten resin, a bubble diameter adjusting means for reducing the diameter of the expanded bubble from the bubble diameter, and a step of picking and pinching the bubble. 2. An inflation film forming apparatus having at least a winding means for winding.
3. The method for forming a blown film according to any one of claims 1 to 2. 7. A molding method in which the cooling means for cooling the molten resin is formed by an apparatus having at least a first cooling means provided near a die outlet and a second cooling means provided with a space from the die surface. Item 7. A method for forming a blown film according to Item 6.