KR101014196B1 - Tube type film for package and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A tube type film is provided to ensure excellent tearing simplicity and transparency, thereby being useful for a packing material for medical instrument, food and drug. CONSTITUTION: A tube type film for a packing material is manufactured in a tube form using a polyolefin-based resin under the condition of 0.3~1.5 of expansion rate in an upward air-cooled inflation molding device. The polyolefin-based resin includes polypropylene resin alone or 70 weight% or more of polypropylene resin. The melt index is 0.01~20 g/min(230 °C, 2.16 Kg) and the melt tension is 200~800 mN.

Description

Tube type film for packaging and manufacturing method thereof

The present invention is a tube-like film for packaging material having excellent transparency and easy tearing, more specifically, transparency of easy observation of contents when packaging various contents such as pharmaceuticals, medical supplies, and foods, and easy tearing to easily take out contents when opening the packaging material. A superior tubular film for packaging materials.

Synthetic resins such as polyolefin resins, polyester resins, polyamide resins, and the like are formed into films and are widely used as various industrial packaging materials. In particular, polyolefin resins such as cheap polyethylene and polypropylene are widely used as various industrial packaging materials such as medicines such as sap and antibiotics, medical supplies such as syringes and dialysis machines, processed foods, and foods such as vegetables and fruits.

For example, sap, which is one of the medicines, is usually packaged in a bag formed of a film having a multilayer structure mainly composed of polypropylene resin, and again protects the sap containing bag (hereinafter referred to as sap bag) and supplements physical properties such as blocking property. In order to do so, as a separate packaging material, so-called overlapping packaging is performed. In the past, as an overlap packaging material for an infusion bag, a flat plate film obtained by laminating a flat plate type polypropylene film produced by a tee-die casting method and a biaxially stretched film of such a film by laminating into a rectangular shape having a predetermined size After cutting, fold both sides once and heat seal to make a tube shape, and then heat seal one side of the tube to form an envelope (see Fig. 1), insert the contents of the sap bag, and heat seal the open part again. It was. This type of packaging material has excellent transparency even after sterilization at 121 ° C., and the polypropylene polymer chain is oriented in the machine direction during the stretching process during film production, so that the sap bag can be easily pulled out in the machine direction. However, these packaging materials have a disadvantage of high film manufacturing cost through film forming and laminating process, and high heat sealing manufacturing cost and automatic packaging equipment investment cost due to three heat sealing processes.

Developed in response to consumer demand for cost reduction, a tubular film obtained through an upward air-cooled inflation process of polyolefin-based resin is disclosed, for example, as disclosed in Korean Patent Registration No. 10-0520107 and Japanese Patent Application 1999-185869. . These tubular films are inexpensive to manufacture film compared to conventional packaging materials and are formed in the form of an envelope (see Fig. 2) even if only one side is heat-sealed. Therefore, the heat-sealing manufacturing cost and the investment cost of the automatic packing equipment are very high. It is recognized as a groundbreaking method of lowering and is now widely used. Importantly, as the resin used for such tubular films, high-density polyethylene having good heat resistance and low cost for sterilization treatment is usually used.

However, in the case of drugs that require extremely high safety, serious problems arise when incorporating foreign substances into the packaging, but through several inspection processes, it is necessary to secure transparency to observe the state of foreign substances in the contents. Importantly, tubular films made of high-density polyethylene-based resins, which are widely used as overlap packaging materials for sap bags, are opaque and greatly impair safety. Therefore, there is an urgent need for the emergence of innovative alternatives.

As a method of solving this problem, tubular films using low density polyethylene and linear low density polyethylene resins having excellent transparency have been proposed as alternatives, but serious problems such as sticking of the tubular films to each other due to lack of heat resistance after sterilization have not been solved. As another method, several attempts have been made to produce a tubular film in a water-cooled inflation molding machine using a polypropylene resin having excellent transparency and heat resistance. After sterilization, transparency was secured, but tearability was not obtained. There is a serious problem that is difficult to pull out, and the solution is urgently required.

In order to solve the above problems, the present inventors have led to the present invention as a result of intensive studies.

That is, the present invention is a tube-type film for packaging material having excellent transparency and easy tearing, more specifically transparency for easy observation of contents when packaging various contents such as medicines, medical supplies, foods, and tearability that can be easily taken out when opening the packaging material. It aims at providing this excellent tubular film for packaging materials.

In addition, an object of the present invention is to provide a tubular film for packaging material which is not only excellent in transparency and easy tearing, but also excellent in antiblocking property.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, this invention contains polypropylene resin alone or polypropylene resin at least 70 weight% or more, melt index is 0.01-20g / min (230 degreeC, 2.16Kg), and melt tension is 200 It is to provide a tubular film for high transparency tear-resistant packaging material manufactured in the form of a tube using a polyolefin-based resin of ~ 800mN in an up-air-cooled inflation molding machine under the conditions of expansion ratio 0.3-1.5.

In another aspect, the present invention is to provide a tubular film for a tear-resistant packaging material for tear resistance, characterized in that formed in the inner surface of the tubular film facing each other, the sawtooth-shaped projections having irregularities in the withdrawal direction is formed long.

The present inventors have a polypropylene-based resin having excellent transparency and heat resistance as a main component, and when the used resin has a specific melt index and melt tension, it is excellently formed into a film by an upward air cooling inflation method and at the same time machine direction As a result, the orientation of the polymer chain is well induced, and in particular, under the specific expansion ratio conditions, the tubular film bubble is maintained in a stable state, and the orientation of the polymer chain is further induced in the machine direction, thereby ultimately ensuring tear usability in the machine direction. It has been found that excellent transparency is also completed to complete the present invention.

In the present invention, the polypropylene resin may be a polypropylene homopolymer or a copolymer containing propylene as a main component.

 In addition, in the present invention, the polyolefin resin contains 70% by weight or more of polypropylene resin, and the remaining 30% by weight or less may include the same or different types of polyolefin resin. Specifically, for example, a low-density polyethylene, a linear low-density polyethylene, a medium-density polyethylene, a high-density polyethylene homopolymer or an ethylene-based copolymer, a polypropylene homopolymer or a propylene-based copolymer, polybutene, and the like These can be mentioned, These can be used individually or in mixture. In this case, the polypropylene resin is preferably 70% by weight or more because transparency and heat resistance may be ensured. More specifically, it contains 70 to 100% by weight.

In this invention, the melt index of the said polyolefin resin is 0.01-20 g / min (230 degreeC, 2.16 Kg), Preferably it is 0.05-10 g / min, More preferably, it is 0.1-5 g / min. When the melt index is less than 0.01, the mechanical properties of the film are excellent and tear tearability is excellent due to the orientation effect of the polymer chain in the machine direction. However, the film formability tends to be lowered. Mechanical properties, the orientation effect of the polymer chain, and film formation may be deteriorated at the same time.

In the present invention, the melt tension of the polyolefin resin is preferably 200 to 800 mN, preferably 300 to 600 mN, and more preferably 350 to 500 mN. Melt tension of polyolefin resin can be measured under various methods and conditions, for example, through the capillary flow meter plate (L / D 16) at 200 ° C using a melt tension rheometer as described in Korean Patent Registration No. 10-0762035. The resulting strands can be measured under an acceleration ratio of 1 mm / sec at 140 ° C. chamber temperature. In addition, polyolefin-based resins tend to have a higher melt tension when there are many branches in the polymer chain structure. Polyethylene-based resin has high branching structure and high melt tension, whereas polypropylene-based resin has low branching structure and low melting tension. Korean Patent Registration Nos. 10-0808723, 10-0431637, 10-0511516, USA Through the method described in Patent No. 6323289 B1 or the like, it has many branches and a polypropylene resin having high melt tension can also be obtained. When the melt tension of the polyolefin resin is less than 200 mN, the alignment effect of the polymer chain in the machine direction is excellent, resulting in excellent tearing ease, but the film formation tends to be very bad, such as the bubble formation of the film is not easy. On the other hand, if the melt tension exceeds 800mN film formation is very good, but the orientation effect of the polymer chain is extremely bad, it is difficult to secure the desired tearability.

The expansion ratio during the process of producing a film in the form of a tube in an upward air-cooled inflation molding machine using the polyolefin resin according to the present invention is preferably 0.3 to 1.5, preferably 0.4 to 1.2, more preferably 0.5 to 1.0. . The expansion ratio is defined as the value obtained by dividing the film bubble diameter by the die diameter. When the expansion ratio is less than 0.3, the orientation effect of the polymer chain is excellent in the machine direction, resulting in better tear usability. Film forming tends to be very bad. On the other hand, when the expansion ratio exceeds 1.5, the film formation is very good, but the polymer chain is oriented in the mechanical direction and the width direction at the same time, so that the alignment effect in the mechanical direction is extremely bad, thereby making it difficult to secure desired tearability.

In addition, the anti-blocking between the inner surface of the tubular film and the surface of the contents in order to slide easily into the bag manufactured from the tubular film according to the present invention during the process of automatically inserting the contents, such as the sap bag, and to easily take out the contents when opening the package. I need a surname. As a method of imparting such anti-blocking, it is more preferable that a tooth-shaped projection having unevenness in the withdrawal direction is formed on the inner surface of the tubular film facing each other in the tubular film. Such protrusions eventually reduce the contact surface between the contents and the packaging material, thereby improving antiblocking properties. The range of the region in which the plurality of protrusions formed on the inner surface of the film is elongated is preferably 5 to 70%, preferably 10 to 50%. Less than 5% of the area where a large number of protrusions are formed is excellent in transparency, but it is difficult to secure desired antiblocking property. If it exceeds 70%, antiblocking property is good, but it is difficult to secure desired transparency. There is a need.

In addition, conventional additives such as inorganic particles, antioxidants, sunscreens, lubricants and the like can be prescribed in the polyolefin resin within the scope of not impairing the object of the present invention.

Hereinafter, the method for producing the film according to the present invention will be described in more detail.

First, polyolefin resin composition pellets are obtained by melt blending or dry blending the polyolefin resin pellets according to the present invention containing polypropylene resin as a main component. The obtained resin composition pellets are introduced into an extruder through a hopper, melt-extruded through a cylinder, passed through a circular die and melt-extruded to have an air injection hole in the center, and a gap between the inner die and the outer die in a circular die composed of an inner die and an outer die. When exiting through the air is injected into the inside of the resin through the air injection hole of the inner die by injecting a predetermined amount into the resin exiting from the circular die in this manner is formed after the tubular film is transferred to the expanded state. As described above, the tubular film expanded at the same time as forming is air cooled while passing through the air ring to keep the circular shape, and then reaches the pressing plate (V-shaped pressing plate) of the take-out device, which is pressed in the form of a plate, resulting in two overlapping films. The tubular film of the form is completed. The film thus prepared is transferred to a winder through a roller and finished to be wound.

That is, the manufacturing method of the tube film of this invention is demonstrated, in one aspect.

a) a polyolefin resin containing at least 70% by weight of polypropylene resin, a melt index of 0.01 to 20 g / min (230 ° C., 2.16 Kg) and a melt tension of 200 to 800 mN into the extruder through a hopper; ;

b) melt extruding the resin to pass between the inner die and the outer die of the circular die to form a tubular film;

c) cooling said tubular film in an air-cooled manner;

d) pressing the cooled tubular film through a pressing plate to prepare two layers of film in the form of flat plates stacked on each other;

e) winding the tubular film manufactured in the form of a flat plate in which the two layers of film are overlapped with each other by winding a winder;

It provides a method for producing a tubular film for high transparency tear easy packaging material comprising a.

Hereinafter, a method for manufacturing a tubular film having a plurality of protrusions extending in the machine direction in the machine direction will be described in more detail.

To explain in more detail how the projections are formed on the inner surface of the film, the molten synthetic resin is passed through the gap between the outer die of the circular die and the inner die where the air injection hole is installed. If the process of sawtooth-shaped projections with irregularities over the circumferential side of the inner die exit portion, that is, on the outer edge, is formed as long as there are fine lines in the machine direction along the region where the sawtooth-shaped projections are formed. The area where there were no protrusions or grooves on the circumference of the inner die exit portion is formed into a smooth shape without any fine lines. The shape of the projections on the inner surface of the tubular film such as fine strings by projections or grooves may be any.

The tubular film prepared from the polyolefin resin according to the present invention thus obtained can be usefully used as a packaging material for medicines, medical supplies and foods. In particular, it can be used suitably for pharmaceutical overlap packaging materials, such as infusion.

As described above, the tubular film according to the present invention is a polyolefin resin containing at least 70% by weight or more of polypropylene resin having excellent transparency and heat resistance, and has a melt index of 0.01 to 20 g / min (230 ° C., 2.16 Kg) and is melted. It is manufactured in the form of a tube under the expansion ratio 0.3-1.5 in the up-air-cooled inflation molding machine using a tension of 100-800mN, and the orientation of the polymer chain in the machine direction is maintained while the tubular film bubble remains stable while forming into a film. By inducing, tear ease is expressed in the machine direction, and at the same time, it is a breakthrough that ensures excellent transparency.

The present invention is a polyolefin-based resin containing at least 70% by weight or more of polypropylene-based resin, and has an melt index of 0.01-20 g / min (230 ° C., 2.16 Kg) and an upward air cooling inflation using a melt tension of 200-800 mN. The tubular film according to the present invention is characterized in that it is manufactured in the form of a tube under the expansion ratio of 0.3 to 1.5 in a molding machine. Is viewed.

1 is an envelope made from a flat polypropylene film
Figure 2 is an envelope made from a tubular film of high density polyethylene-based resin
Figure 3 is an envelope made from a tubular film of polyolefin resin according to the present invention
Figure 4 is an example of using a tubular film of a polyolefin resin according to the present invention as a packaging material for sap bag

Through the following examples will be described in more detail the present invention. The following examples are merely examples and are not limited to the examples.

The transparency, tearability, film forming property, anti blocking property, etc. of the tubular films prepared according to the following Examples and Comparative Examples were measured as follows.

(Transparency)

The tubular film specimens (thickness 100㎛, diameter 110mm) were sterilized at 121 ° C for 30 minutes, left at room temperature for 2 days, and then the tubular film specimens were taken to measure the transparency (%) according to ASTM D1004 to evaluate transparency in four steps. (Less than 10% ◎ excellent, more than 10% less than 20% ○ good, more than 20% less than 30% △ moderate, more than 30% poor)

(Tearability)

 According to ASTM D1938, the mechanical direction tear strength [F (MD)] and the width direction tear strength [(F (TD)] of tubular film specimens were measured and the tear strength ratio [= F (TD) / F (TD)] was evaluated for tear usability as a tear strength ratio in four stages (1.5 or more ◎ excellent, 1.25 or more less than 1.5 ○ good, 1.1 or more less than 1.25 △ normal, less than 1.1)

(Film forming)

Pellet-type resin is introduced into the extruder through the hopper of the upward air-cooled inflation molding machine, melt-extruded and passed between the inner die and the outer die of the circular die to form a tubular film, and then the tubular film is cooled by air cooling. During the manufacturing process to obtain the film was evaluated in four stages by observing the degree of the film is formed stably (◎ excellent, ○ good, △ normal, X poor)

(Antiblocking property)

Easily slips in the process of using tubular film specimens as an overlapping packaging material of the sap bag and automatically inserts the sap bag into an envelope made from the tubular film, and the sap bag easily without the inner sap bag and the overlapping packing material not sticking when the packaging material is opened. The anti-blocking property was evaluated in four stages by comprehensively observing the ease of work that can be taken out (◎ excellent, ○ good, △ normal, X poor).

Example 1

A polypropylene resin (resin A) in a pellet state having a melt index (230 ° C., 2.16 Kg) of 0.5 g / 10 minutes and a melt tension of 250 mN was prepared. The obtained resin A pellets were put into a hopper, injected into an extruder having a screw diameter of 40 mm and L / D 30, melt-extruded, and a tube was formed and cooled through a circular die under an expansion ratio of 1.0, and then pressed through a V-shaped pressing plate. The films were made in a flat form superimposed on each other and wound through a winding machine to obtain a final diameter 110 mm tubular film specimen (thickness 100 μm). The film formability in the process of obtaining this tubular film specimen and the transparency, tearability and antiblocking property for this film were evaluated and the results are shown in Table 1.

[Example 2]

Tubing film specimens (thickness) were carried out in the same manner as in Example 1 except that the polypropylene-based resin (resin B) in a pellet state having a melt index (230 ° C., 2.16 kg) of 1.0 g / 10 minutes and a melt tension of 320 mN was used. 100 μm) was obtained. The film formability in the process of obtaining this tubular film specimen and the transparency, tearability and antiblocking property for this film were evaluated and the results are shown in Table 1.

Example 3

Melt index (230 ° C, 2.16Kg) 2.4g / 10min, polypropylene-based resin (resin C) in a pellet state with a melt tension of 640mN, except that the expansion ratio was set to 0.4. It carried out and obtained the tubular film sample (thickness 100 micrometers). The film formability in the process of obtaining this tubular film specimen and the transparency, tearability and antiblocking property for this film were evaluated and the results are shown in Table 1.

Example 4

Only when the expansion ratio was set to 1.4 was carried out in the same manner as in Example 3 to obtain a tubular film specimen (thickness: 100 µm). The film formability in the process of obtaining this tubular film specimen and the transparency, tearability and antiblocking property for this film were evaluated and the results are shown in Table 1.

Example 5

Melt index (230 ° C, 2.16Kg) 15g / 10min, pelletized polypropylene-based resin (resin D) with a melt tension of 480mN, except that it was carried out in the same manner as in Example 1 and the tubular film specimen (thickness 100) Μm). The film formability in the process of obtaining this tubular film specimen and the transparency, tearability and antiblocking property for this film were evaluated and the results are shown in Table 1.

Example 6

A medium density polyethylene resin (Samsung Total, R906U, Resin E) having a melt index (190 ° C., 2.16 Kg) 6 g / 10 min, a density 0.936 g / cm ³ , and a melt tension of 290 mN was prepared. The resin C was mixed at a ratio of 80% by weight and Resin E 20% by weight, and then it was injected into a twin screw extruder having a screw diameter of 120 mm and L / D 32, followed by melt extrusion to melt the melt index (230 ° C., 2.16 Kg) 3.5 g. A resin composition pellet having a melt tension of 580 mN was obtained for 10 minutes. In the up-air-cooled inflation molding machine, an inner die was formed in a circular die, in which a fine sawtooth-shaped 3 mm projection area was machined at regular intervals along the circumference of the outlet side of a 300 mm inner die. The obtained resin composition pellets were put into a hopper, injected into an extruder having a screw diameter of 40 mm, L / D 30, melt extruded, and the tube was formed and cooled under the expansion ratio 1.2 under a sawtooth-shaped circular die, and then V-shaped. Pressed through the pressing plate to produce a flat form with two layers of film superimposed on each other, and wound through a winding machine to obtain a final diameter 110 mm tubular film specimen (thickness 100 μm), which occupies 30% of the area where a plurality of protrusions are formed in the machine direction. . The film formability in the process of obtaining this tubular film specimen and the transparency, tearability and antiblocking property for this film were evaluated and the results are shown in Table 1.

Example 7

After mixing at a ratio of 70% by weight of resin B and 30% by weight of resin D, it was injected into a twin screw extruder having a screw diameter of 120 mm and L / D 32 and melt-extruded to melt index (230 ° C., 2.16 Kg) 5.5 g / A resin composition pellet having a melt tension of 360 mN was obtained for 10 minutes. Using the obtained resin composition pellet, it carried out similarly to Example 6 except having adjusted so that the area | region in which many processus | protrusion was formed long occupied 60%, and obtained the final diameter 110mm tubular film specimen (100 micrometers in thickness). The film formability in the process of obtaining this tubular film specimen and the transparency, tearability and antiblocking property for this film were evaluated and the results are shown in Table 1.

Comparative Example 1

Tubing film specimens (thickness) were carried out in the same manner as in Example 1 except that the polypropylene-based resin (resin F) in a pellet state having a melt index (230 ° C., 2.16 kg) of 1.0 g / 10 minutes and a melt tension of 120 mN was used. 100 μm) was obtained. The film formability in the process of obtaining this tubular film specimen and the transparency, tearability and antiblocking property for this film were evaluated and the results are shown in Table 1.

Comparative Example 2

Tubing film specimens (thickness) were prepared in the same manner as in Example 1, except that the polypropylene-based resin (resin G) in the pellet state having a melt index (230 ° C., 2.16 kg) of 25.0 g / 10 minutes and a melt tension of 90 mN was used. 100 μm) was obtained. The film formability in the process of obtaining this tubular film specimen and the transparency, tearability and antiblocking property for this film were evaluated and the results are shown in Table 1.

Comparative Example 3

Tubing film specimens (thickness) were carried out in the same manner as in Example 1, except that the polypropylene-based resin (resin H) in a pellet state having a melt index (230 ° C., 2.16 kg) of 1.2 g / 10 minutes and a melt tension of 950 mN was used. 100 μm) was obtained. The film formability in the process of obtaining this tubular film specimen and the transparency, tearability and antiblocking property for this film were evaluated and the results are shown in Table 1.

[Comparative Example 4]

The tube-shaped film specimen (thickness 100 µm) was obtained in the same manner as in Example 3 except that only the expansion ratio was 2.5 during the film forming process. The film formability in the process of obtaining this tubular film specimen and the transparency, tearability and antiblocking property for this film were evaluated and the results are shown in Table 1.

[Comparative Example 5]

Melt index (190 ℃, 2.16Kg) 0.044g / 10min, density 0.956g / cm ³ , high density polyethylene resin (Samsung Total, F120A, Resin I) with melt tension of 280mN Only it carried out similarly to Example 1, and obtained the tubular film sample (100 micrometers in thickness). The film formability in the process of obtaining this tubular film specimen and the transparency, tearability and antiblocking property for this film were evaluated and the results are shown in Table 1.

[Table 1] Evaluation results of physical properties and formability of tubular films obtained according to Examples and Comparative Examples

When looking at Examples 1 to 7 polyolefin resin containing 70% by weight or more of polypropylene resin, the melt index is 0.01 ~ 20g / min (230 ℃, 2.16Kg) and the melt tension is 200 ~ 800mN It can be seen that the film obtained by processing under an expansion ratio of 0.3 to 1.5 in an upward air-cooled inflation molding machine has a stable and good film formability and excellent film transparency, tearability and antiblocking property. In addition, when looking at Example 6 and Example 7 it can be seen that the anti-blocking properties can be further improved by having a long tooth-shaped projections having irregularities in the withdrawal direction formed on the inner surface of the tubular film facing each other. On the other hand, when looking at Comparative Examples 1 to 4, even when using a polypropylene resin having excellent transparency, when the melt tension is too low or too high, and if the expansion ratio is too high, it is difficult to secure the desired tearability, the melt index is too high It is difficult to secure film formation. In addition, when using a high-density polyethylene-based resin as can be seen in Comparative Example 5 it can be seen that the film formability and tear tearability is excellent but the transparency is extremely poor.

Claims (9)

The polypropylene-based resin alone or polypropylene-based resin containing at least 70% by weight or more, with a melt index of 0.01 to 20 g / min (230 ° C., 2.16 Kg), and a polyolefin resin having a melt tension of 200 to 800 mN. A tubular film for high transparency tearable packaging material manufactured in the form of a tube in a condition of expansion ratio 0.3 to 1.5 in an air-cooled inflation molding machine. The method of claim 1,
The polypropylene-based resin is a tubular film for high transparency tearable packaging material which is a polypropylene homopolymer or a copolymer based on propylene. The method of claim 1,
The polyolefin-based resin is a group consisting of a homopolymer selected from low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene or a copolymer based on ethylene, a polypropylene homopolymer or a copolymer based on propylene, and a polybutene At least one tubular film for high transparency tearable packaging material selected from. The method of claim 1,
The tubular film is a high-transparent tear-resistant packaging material tubular film formed with a long tooth-shaped projection having an unevenness in the extraction direction on the inner surface of the tubular film facing each other. a) a polyolefin resin containing at least 70% by weight of polypropylene resin, a melt index of 0.01 to 20 g / min (230 ° C., 2.16 Kg) and a melt tension of 200 to 800 mN in an extruder;
b) melt extruding the resin to pass between the inner die and the outer die of the circular die to form a tubular film;
c) cooling said tubular film in an air-cooled manner;
d) pressing the cooled tubular film through a pressing plate to prepare two layers of film in the form of flat plates stacked on each other;
e) winding the tubular film manufactured in the form of a flat plate in which the two layers of film are overlapped with each other by winding a winder;
Method for producing a tubular film for high transparency tear easy packaging material comprising a. 6. The method of claim 5,
Tube type for high transparency tearable packaging material for forming a sawtooth-shaped projection in the extraction direction on the inner surface of the tubular film is formed in the toothed projection formed on the surface with the unevenness on the outer edge side of the outlet side of the inner die in step b) Method for producing a film. A high transparency tearable packaging material using the tubular film according to any one of claims 1 to 4. The method of claim 7, wherein
The packaging material is a packaging material, characterized in that the pharmaceutical, medical supplies or food packaging. The method of claim 8,
The packaging material characterized in that the pharmaceutical packaging material is an overlapping packaging material for sap.

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