KR20120080027A - Method for manufacturing oriented polyolefin film with multi-layer and oriented polyolefin film with multi-layer manufactured by thereof - Google Patents

Abstract

PURPOSE: A method for manufacturing a multilayer polyolefin oriented film and the multilayer polyolefin oriented film by the same are provided to laminate a resin layer through an additional extrusion at a low melting point. CONSTITUTION: A method for manufacturing a multilayer polyolefin oriented film(F) is as follows. The multilayer polyolefin oriented film is extruded. The extruded film is frozen. The film is horizontally elongated. One of more resin layers are laminated on the longitudinally stretched film by being secondly compressed. The film having resin layers is frozen. The secondly frozen film is transversely elongated.

Description

Manufacturing method of multilayer polyolefin-based stretched film and multilayer polyolefin-based stretched film manufactured therefrom

The present invention relates to a method for producing a multilayer polyolefin-based stretched film and a multilayer polyolefin-based stretched film prepared therefrom, and more particularly, including an additional extrusion process after extrusion and longitudinal stretching, wherein the resin layer is formed through the additional extrusion process. By laminating, even a resin having a low melting point can be laminated by continuous extrusion, and thus the manufacturing process is monotonous and takes less time, thereby reducing the production cost of the product. It relates to a multilayer polyolefin-based stretched film produced by.

In general, polyolefin-based stretched films having a multilayer structure such as polypropylene (PP) -based or polyethylene (PE) -based are widely used for packaging materials and lamination coating (lamination). In addition to these PP and PE systems, there are polyvinyl chloride (PVC) films and polyethylene terephthalate (PET) films, but PVC films emit harmful substances such as dioxins when incinerated, and PET films are less economical and difficult to recycle. have.

Accordingly, multilayer polyolefin-based stretched films, particularly biaxially stretched polypropylene films (BOPP films; Biaxially Oriented Polypropylene Films) manufactured by biaxial stretching, which are advantageous in terms of economy and recycling, are frequently used. The BOPP film is not only advantageous to economics and properties, but also excellent in mechanical properties such as tensile strength, rigidity, surface hardness, impact resistance, optical properties such as glossiness, transparency, and food hygiene such as non-toxicity and odorlessness. Etc.) and lamination coating (lamination).

1 is a cross-sectional view of a typical BOPP film, Figure 2 is a block diagram of a manufacturing apparatus for explaining a manufacturing method of the BOPP film according to the prior art.

Referring to FIG. 1, a BOPP film generally includes a PP layer as a core layer 3, a skin outer layer 1 and a skin inner layer 2 laminated on and under the core layer 3. , skin inner layer). At this time, the skin outer layer 1 is composed of a PP layer, the skin inner layer 2 is composed of a PP layer or a PE layer. The functional resin layer 4 is laminated on the skin outer layer 1 and / or the skin inner layer 2.

For example, the above BOPP film is for lamination coating (lamination), specifically for lamination coating (lamination) which is thermally fused after inserting recognition materials such as photographs, ID cards, printed matter or menu plates between two BOPP films. When used as a film for packaging films such as food or food, low-temperature adhesive resin such as ethylene vinyl acetate (EVA) or polyethylene (PE) capable of heat sealing (heat sealing) is used as the functional resin layer 4. do.

In addition, referring to FIG. 2, in manufacturing a BOPP film having a multilayer structure as described above, the skin outer layer 1, the core layer 3, and the skin inner layer 2 are simultaneously extruded through an extruder 5. The three layers (1) (2) (3) are then joined together in an extrusion die and molded into a multilayer film. Then, the extruded multilayer film is cooled by passing through a cooling roll 6, followed by biaxial stretching, that is, longitudinal stretching (MDO; Machine Direction Orientation) and transverse stretching (TDO; Transverse Direction Orientation). That is, as shown in FIG. 2, the longitudinal stretching machine (MDO) is performed in the machine direction (length direction) by passing through the longitudinal stretching machine 7 having a plurality of rolls R combination, and then continuously the transverse stretching machine 8 ) And transverse stretching (TDO) in the width direction by a rail pattern (rail pattern). The longitudinally and laterally stretched film is then wound directly onto a winding roll 9.

Conventionally, in manufacturing a BOPP film having a multi-layer structure, as described above, extrusion-> cooling-> longitudinal stretching-> transverse stretching process is carried out continuously, for example, as shown in Figure 1 PP layer / PP A multilayer film is produced having a layer / PP (or PE) layer.

In addition, after the multilayer film is manufactured through the continuous process as described above, the functional resin layer 4 is laminated on the skin outer layer 1 and / or the skin inner layer 2 as described above. In addition, functional resin layers 4 such as ethylene vinyl acetate (EVA) are laminated and formed through further processes such as lamination (heat fusion). However, these additional processes are costly, time consuming and complex.

In this case, in laminating the functional resin layer 4, a method of co-extrusion may be considered by adding a functional resin to a skin extrusion part during multilayer extrusion coating, but the functional resin and polyolefin (PP, etc.) may be considered. If the physical and chemical properties of the difference is large, co-extrusion is difficult. That is, resins having a low melting point or resins other than polyolefins are difficult to co-extrude. For example, in the case of a resin having a low melting point such as ethylene vinyl acetate (EVA), the interlayer adhesion strength (adhesive force) is lowered due to the difference in melting point with PP. In addition, scratches are generated in the resin layer 4 in the course of passing the roll R of the longitudinal stretching machine 7, resulting in poor appearance of the product, and a phenomenon in which the resin layer 4 sticks to the roll R. Co-extrusion is difficult.

Accordingly, in laminating the conventional functional resin layer 4, as described above, the lamination is performed through additional processes such as separate coating or paper (heat fusion), which require a lot of time and cost, and thus, the production cost of the product is increased. Caused by.

Therefore, in the present invention, in the lamination of the functional resin layer, even a resin having a low melting point can be laminated in a continuous process through extrusion, so that the manufacturing process is monotonous and takes less time, thereby reducing the production cost of the product. It is an object of the present invention to provide a method for producing a stretched film and a multilayer polyolefin-based stretched film prepared therefrom.

The present invention to achieve the above object,

A first extrusion step of extruding the multilayer polyolefin film;

A first cooling step of cooling the extruded film;

A longitudinal stretching step of longitudinally stretching the film that has passed through the first cooling step;

A second extrusion step of extrusion molding such that at least one resin layer is laminated on the longitudinally stretched film;

A second cooling step of cooling the film in which the resin layer is laminated; And

It provides a method for producing a multilayer polyolefin-based stretched film comprising a transverse stretching step of transverse stretching of the film passed through the second cooling step.

According to a preferred embodiment, the second cooling step is to form an air groove in the resin layer using a cooling roll having a concave-convex structure on the surface.

In addition, the present invention provides a multi-layered polyolefin-based stretched film prepared according to the production method of the present invention.

According to the present invention, after the longitudinal stretching, including an additional extrusion / cooling process (second extrusion / second cooling step), the resin layer is laminated through the additional extrusion, even in the case of a resin having a low melting point lamination through extrusion It is possible. Accordingly, in manufacturing the polyolefin-based stretched film having a multi-layered structure, each layer including the resin layer is laminated through continuous extrusion, so that the manufacturing process is monotonous and takes less time, thereby lowering the production cost of the product.

1 is a cross-sectional view of a conventional general polyolefin-based stretched film (BOPP film).
2 is a block diagram of a manufacturing apparatus for explaining a method for producing a polyolefin-based stretched film (BOPP film) according to the prior art.
3 and 4 are exemplary cross-sectional configuration diagrams of a multilayer polyolefin-based stretched film prepared according to the present invention.
5 is an exemplary configuration diagram of a manufacturing apparatus for explaining a method for manufacturing a multilayer polyolefin based stretched film according to the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

First, the multilayer polyolefin-based stretched film produced according to the present invention will be described, and then, the method for manufacturing the multilayer polyolefin-based stretched film according to the present invention will be described.

3 and 4 are exemplary cross-sectional configuration diagrams of a multilayer polyolefin based stretched film (hereinafter, abbreviated as "stretched film") produced according to the present invention.

Referring to FIGS. 3 and 4, the stretched film produced according to the present invention may be formed on at least two or more multilayer polyolefin films (hereinafter referred to as 'multilayer films') on the multilayer film (F). The laminated resin layer 40 is included.

At this time, the multilayer film (F) is formed by laminating two or more layers simultaneously through extrusion, and each layer contains at least polyolefin resin as a base resin (main raw material). The multilayer film F may have a laminated structure of, for example, 2 to 5 layers, and more specifically 3 to 4 layers. According to an exemplary embodiment of the present invention, the multilayer film (F) comprises a core layer (30); A skin outer layer 10 stacked on the core layer 30; And a skin inner layer 20 stacked below the core layer 30.

In the multilayer film F, according to a preferred embodiment, as shown in FIGS. 3 and 4, the three layers described above, specifically, the skin outer layer 10, the core layer 30, and the skin inner layer 20 are sequentially formed. It may have a three-layer structure stacked. In this case, each of the layers 10, 20, 30 may include at least one selected from polypropylene (PP) and polyethylene (PE) as a base resin (main material). For example, the skin outer layer 10 and the core layer 30 may be composed of a PP layer made of polypropylene (PP) as a base resin. The skin inner layer 20 may be composed of a PP layer, a PE layer, or a PP-PE mixed layer having at least one selected from polypropylene (PP) and polyethylene (PE) as a base resin.

In addition, the stretched film includes a resin layer 40 laminated on the multilayer film F, wherein the resin layer 40 is formed from the skin outer layer 10 and the skin inner layer 20 as one or two layers. Laminated to one or more selected. 3 illustrates that the resin layer 20 is laminated on the skin inner layer 20, and FIG. 4 illustrates that the resin layer 40 is laminated on both the skin outer layer 10 and the skin inner layer 20. It is illustrated.

At this time, as described below, the resin layer 40 is not formed by a separate coating process or a lamination process by thermal fusion as in the prior art, but through an additional extrusion process performed after longitudinal stretching according to the present invention. It is laminated on the multilayer film (F). Hereinafter, the manufacturing method according to the present invention in detail.

Figure 5 shows an example of a manufacturing apparatus for implementing the manufacturing method according to the present invention. The manufacturing apparatus shown in FIG. 5 is exemplarily illustrated to help understanding of the present invention, and the manufacturing apparatus may have various forms in addition to those shown in FIG. 5.

Referring to FIG. 5, the manufacturing apparatus includes a first extruder 100-1, a first cooling roll 200, a longitudinal drawing machine 300, a second extruder 100-2, and a second cooling roll 400. , Transverse stretching machine 500 and winding machine 600. Each of these devices is arranged to enable a continuous process. The structure of each device is not particularly limited, and for example, the longitudinal drawing machine 300 may be configured by combining a plurality of rolls R as shown in FIG. 5. In FIG. 5, the drawings R1 and R2 are guide rolls R1 and R2 provided adjacent to the first cooling roll 200 and the second cooling roll 400, respectively.

The production method according to the invention, the first extrusion step of extrusion molding to form a multi-layer film (F); A first cooling step of cooling the extruded multilayer film (F); A longitudinal stretching step of longitudinally stretching the multi-layer film F passed through the first cooling step; A second extrusion step of extrusion molding such that at least one resin layer 40 is laminated on the longitudinally stretched multilayer film F; A second cooling step of cooling the multilayer film F in which the resin layer 40 is laminated; And a transverse stretching step of transverse stretching of the multilayer film F passed through the second cooling step. And each of these steps is continuous.

In the first extrusion step, the multilayer film F is extrusion molded through the first extruder 100-1. Specifically, the multilayer film F is molded by extruding two or more layers to be laminated at the same time. In this case, the first extruder 100-1 has an extrusion part corresponding to the number of layers of the multilayer film F, and the layers are combined in the extrusion die. For example, when the multilayer film F having a three-layer structure including the skin outer layer 10, the core layer 30, and the skin inner layer 20 is to be molded, the first extruder 100-1 corresponds to this. It may have three extrusion parts.

In addition, a polyolefin resin composition is used as a raw material for extrusion molding of the multilayer film F, that is, a raw material introduced into the first extruder 100-1. The polyolefin resin composition contains at least one polyolefin resin as a base resin (main raw material). The polyolefin resin is not particularly limited as long as it is a polyolefin, and preferably at least one selected from polypropylene (PP), polyethylene (PE) and the like can be used. In addition, as the polyolefin resin, as one or more copolymers selected from ethylene and propylene, for example, ethylene-methacrylic acid binary copolymer or ethylene-methacrylic acid-ester terpolymer may be used. It is not limited by these.

In addition, the polyolefin-based resin composition includes at least a polyolefin-based resin, but may further include other resins or other additives, if necessary. At this time, although not particularly limited, the polyolefin resin composition may include 0 to 40 parts by weight, more specifically 5 to 20 parts by weight, of other resins or other additives based on 100 parts by weight of the polyolefin resin. The additive may be used as is commonly used in the art, and preferably include one or more selected from slip agents, antiblocking agents, antistatic agents and the like. Specific types (components) of such additives are as illustrated below.

In forming the multilayer film F through the first extrusion step, the layers may be the same raw material or different raw materials, for example, the skin outer layer 10 and the core as shown in Figs. The layer 30 can be molded so that it becomes a PP layer using polypropylene (PP) as a base resin (main raw material). The skin inner layer 20 may be molded to be a PP layer, a PE layer, or a PP-PE mixed layer using at least one selected from polypropylene (PP) and polyethylene (PE) as a base resin (main material). In this case, as a preferred example, in the case of the skin inner layer 20, it is preferable to mold the PE layer. The PE layer is more compatible with low melting point resins such as ethylene vinyl acetate (EVA) than the PP layer, and may be preferable for preventing layer separation.

In addition, in the first extrusion step, it is preferable that the extrusion molding to include at least one selected from the slip agent and the anti-blocking agent as an additive in the outermost layer of the multilayer film (F), that is, the skin outer layer (10). Specifically, when the outermost layer of the final product (stretched film) is to be the skin outer layer 10 without forming the resin layer 40 on the skin outer layer 10, as shown in FIG. The raw material constituting the outer layer 10 may be blended so as to further include at least one selected from slip agents, antiblocking agents and the like as an additive.

The slip agent may impart slip property (or release property), and for example, one or more selected from silicone, siloxane, silane, wax-based, and oleic acid amide may be used. In addition to those listed above, slip agents can be used as long as they can lubricate the surface of the stretched film and reduce the coefficient of friction. Although this slip agent is not specifically limited, 0.1-20 weight part, More specifically, 2-12 weight part can be used with respect to 100 weight part of polyolefin resins.

The anti-blocking agent may prevent adhesion between the films by forming a small space at the contact surface with an adjacent film when the stretched film is wound, which is selected from inorganic material particles such as silica, diatomaceous earth, kaolin and talc, for example. You can use more than one. The anti-blocking agent is not particularly limited, but the same content range as the slip agent, specifically 0.1 to 20 parts by weight, more specifically 2 to 12 parts by weight based on 100 parts by weight of the polyolefin resin.

In addition, in forming the multilayer film F through the first extrusion step, it is preferable to appropriately adjust the thickness of each layer. For example, referring to FIG. 3, the skin outer layer 10, the core layer 30, and the skin inner layer 20 have a three-layer structure, wherein the thickness T10 of the skin outer layer 10 is 1-10% of the stretched film total thickness T, the thickness T30 of the core layer 30 is 30-70% of the stretched film total thickness T, and the thickness T20 of the skin inner layer 20. It can shape | mold so that it may become 1 to 10% of the stretched film total thickness T. In addition, the extrusion temperature in the first extrusion step may have a variety of temperature range depending on the raw material used, for example, it may be carried out in a temperature range of 140 ~ 320 ℃.

Referring to FIG. 5, the multilayer film F extruded through the first extrusion step as described above passes through the first cooling roll 200 to undergo a first cooling step. In this case, in FIG. 5, one first cooling roll 200 is illustrated in the manufacturing apparatus, but one or two or more plurality of the first cooling rolls 200 may be continuously arranged in the manufacturing apparatus. . The cooling temperature in the first cooling step, that is, the temperature of the first cooling roll 200 may be set, for example, 5 ~ 80 ℃, but is not limited thereto.

The multi-layer film F passed through the first cooling step is transferred to the longitudinal stretching machine 300 along the guide roll R1 and longitudinally stretched (MDO) in the machine direction (length direction). For example, as shown in FIG. 5, it can be longitudinally stretched by a plurality of rolls R. The stretching temperature of the longitudinal stretching step, that is, the temperature of the roll R installed in the longitudinal stretching machine 300 may be set to, for example, 80 to 160 ° C., but is not limited thereto. In addition, in the longitudinal stretching step, it may be longitudinally stretched at 1.5 to 10 times (stretching ratio), for example, 3 to 7 times (stretching ratio), and more specifically, for example, 4 to 5 times (stretching ratio). This longitudinal draw ratio can be realized by the roll (R) speed.

According to the present invention, the multilayer film F subjected to the longitudinal stretching step is subjected to a further extrusion process (second extrusion step) and a cooling process (second cooling step) performed at the same time continuously. In the second extrusion step, the resin layer 40 is laminated on the multilayer film F. Specifically, referring to FIG. 5, the multilayer film F is longitudinally stretched and then supplied to the second extruder 100-2. In this case, the second extruder 100-2 may be provided with a resin supply unit 150 for supplying a raw material for forming the resin layer 40. The multi-layer film F passes through the second extruder 100-2, and at the same time, a raw material is supplied from the resin supply unit 150, and the resin layer 40 is extruded, thereby exposing the resin layer 40 on the multi-layer film F. ) Are combined at the dies.

In the present invention, a raw material of the resin layer 40, that is, a raw material supplied from the resin supply unit 150 to the second extruder 100-2 is not particularly limited. In the second extrusion step, the raw material of the resin layer 40 is, for example, polyolefin resin, silicone resin, urethane resin, acrylic resin, polyamide resin, metallocene resin, nylon resin, ethylene vinyl acetate (EVA). , Raw materials comprising at least one selected from the group consisting of ethylene methyl acetate (EMA), ethylene methyl acrylic acid (EMAA), ethylene glycol (EG), ethylene acid ter-polymer and rubber Can be.

According to the present invention, after longitudinal stretching, the lateral stretching is not performed immediately, but after longitudinal stretching, the resin layer 40 is laminated through a further extrusion process, that is, the second extrusion step described above, so as a raw material of the resin layer 40. It is possible to use a base resin constituting the multilayer film (F) with a difference in physical and chemical properties (for example, a melting point lower than or higher than a polyolefin).

Specifically, according to the present invention, as the raw material of the resin layer 40, it is possible to use resins other than polyolefins, and more specifically, functional resins having a lower melting point or higher than polyolefins. According to a preferred embodiment, in the second extrusion step, a raw material including a resin having a lower melting point than the raw material used in the first extrusion step may be used as the raw material of the resin layer 40. For example, as a low temperature adhesive resin capable of fusion (heat sealing) by low temperature heat, ethylene vinyl acetate (EVA), ethylene methyl acetate (EMA), ethylene methyl acrylic acid (EMAA), low temperature metallocene resin, Resin having a low melting point and excellent sealing properties, such as ethylene acid terpolymer, may be used. In this case, the ethylene acid terpolymer (ethylene acid ter-polymer) is useful when the stretched film is used for the in-mold label, for example, a ternary copolymer of ethylene / propylene / butadiene. And commercially available terpolymers include DuPont appeal 52009. In addition, the low melting point resin as a raw material of the resin layer 40 is not limited to resin as listed above, It can be used also in case of polyethylene (PE). For example, when polypropylene (PP) is used as the base resin of the skin outer layer 10 and / or skin inner layer 20, the resin constituting the resin layer 40 has a lower melting point than polypropylene (PP). The use of polyethylene (PE) is possible.

As described above, according to the present invention, the resin layer 40 is laminated through an additional extrusion process (second extrusion step), the raw material of the resin layer 40 is not limited, so that the resin layer 40 has various functionalities. In this case, according to a preferred embodiment of the present invention, the raw material of the resin layer 40 may use a raw material containing an antistatic agent. At this time, the resin layer 40 becomes an antistatic layer having antistatic ability. The antistatic agent is not particularly limited as long as it has antistatic performance. The antistatic agent, it is preferable to use a permanent antistatic agent that does not change the antistatic performance over time. In addition, the antistatic agent is more preferable if it is possible to realize the surface resistance of the stretched film to 10 ¹⁰ Ω / ㎠ or less.

For example, the antistatic agent may be a polyamide-based resin, ethylene glycol (EG), or the like, and commercialized products may use IRAGASTT P18 manufactured by CIBA, Germany. In addition, the antistatic agent may be selected from conductive polymers. The conductive polymer is polyacetylene, poly (p-phenylene vinylene), poly (p-phenylene), poly (thienylenevinyl) Poly (thienylene vinylene), Polythiophene, Polyaniline, Polyethylene dioxythiophene, Polyisothianaphthene, Polypyrrole and Polypyrrole For example, one or more selected from the group consisting of poly (p-phenylene sulfide).

As the raw material of the resin layer 40, an antistatic agent as described above may be used to have an antistatic performance, or a master batch including the antistatic agent may be used. For example, a master batch obtained by mixing an appropriate amount of the antistatic agent as described above in polypropylene (PP) or polyethylene (PE) can be used as a raw material of the resin layer 40. As such, when the antistatic agent is included in the resin layer 40 to provide antistatic performance, the stretched film may be usefully used as a packaging material such as an electronic product. In this case, the stretched film may have a surface resistance of 10 ¹⁰ Pa / cm 2 or less by the resin layer 40 composed of an antistatic agent, as described above, so that the stretched film can be used more effectively as a packaging material such as an electronic product.

On the other hand, in providing an antistatic performance (antistatic property) to a stretched film, the method of including an antistatic agent in the multilayer film F, for example, it is included in the skin outer layer 10 or the skin inner layer 20 (addition) You can consider how to do this. However, there are the following problems in this case.

Since the antistatic agent is a resin having a low molecular weight and a low melting point, the antistatic agent may bleed to the surface of the film F with time. At this time, when the antistatic agent is included in the multilayer film (F), the antistatic agent is bleed out in the longitudinal stretching (MDO) process to contaminate the surface of the roll (R), which eventually contaminates the surface of the film (F) Problem occurs. In addition, the problem that the antistatic performance is deteriorated due to the loss of the antistatic agent, that is due to the loss on the surface of the roll (R) or the film (F) is pointed out.

However, according to the preferred embodiment of the present invention as described above, when the antistatic agent is included in the resin layer 40 in the second extrusion step (in-line extrusion) that proceeds after longitudinal stretching (MDO), the above problem is solved. . That is, according to the present invention, the antistatic agent is laminated through an additional extrusion process after the longitudinal stretching process, so as not to contaminate the surface of the roll (R) or the film (F) of the longitudinal stretching machine 300, there is no loss and stable static electricity It can have prevention performance.

According to another embodiment of the invention, it is preferable to use a raw material containing a nylon (Nylon) resin as the raw material of the resin layer 40. That is, it is preferable that the said resin layer 40 is comprised from a nylon resin layer including nylon resin as a main raw material. As such, when the resin layer 40 includes a nylon resin, the nylon resin is excellent in gas barrier property (barrier property) and can be usefully used as a packaging material such as food. In addition, nylon resin is excellent in cold resistance and can be preferably used for packaging of frozen foods. In the present invention, the nylon resin is included in the polyamide-based having an amide bond (-CONH-) in the molecule, for example, one or two or more selected from the group consisting of Nylon6, Nylon66, Nylon12, etc. (Nylon6 + Nylon66, Nylon6 + Nylon12, Nylon6 + Nylon66 + Nylon12) can be used.

In addition, as the raw material of the resin layer 40, the resin as described above as a base resin (main raw material), in addition to the resin composition further comprising other additives may be used. According to a specific embodiment, the raw material of the resin layer 40 is ethylene vinyl acetate (EVA), ethylene methyl acetate (EMA), ethylene methyl acrylic acid (EMAA), low temperature metallocene resin and ethylene acid terpolymer ( low melting adhesive resins such as ethylene acid ter-polymer); Antistatic resins (antistatic agents) such as polyamide resins, ethylene glycol (EG) and conductive polymers; A resin composition including at least one base resin selected from a gas barrier property such as nylon resin and a cold resistant resin, and further including at least one additive selected from a slip agent and an antiblocking agent may be used, if necessary.

Specific types (components) of the slip agent and the antiblocking agent are the same as described above. For example, in the case of the slip agent and the antiblocking agent, 0.1 to 20 parts by weight, and more specifically 2 to each of 100 parts by weight of the base resin, respectively. It may be included in 12 parts by weight.

In addition, in the second extrusion step, the thickness T40 of the resin layer 40 may be molded to be 1 to 50% of the total thickness T of the stretched film. In addition, the extrusion temperature in the second extrusion step may be set in various temperature ranges in consideration of the type of raw material, that is, the base resin constituting the resin layer 40 and the melting point of the resin layer 40. For example, it can extrude by setting in the temperature range of 150-330 degreeC. At this time, if the extrusion temperature is too low as less than 150 ℃ may be difficult to extrusion, if it is too high exceeding 330 ℃ may be undesirably high flowability. For example, when using a low melting point resin, it is good to extrude at 180-250 degreeC.

Referring to FIG. 5, the multilayer film F in which the resin layer 40 is laminated through the second extrusion step as described above is continuously passed through the second cooling roll 400 to undergo a second cooling step. At this time, in passing through the second cooling roll 400, it is preferable to position and cool the resin layer 40 in close contact with the roll surface of the second cooling roll 400. In addition, although FIG. 5 illustrates a state in which one second cooling roll 400 is installed in a manufacturing apparatus, one or two or more plurality of second cooling rolls 400 may be continuously arranged in the manufacturing apparatus. . The cooling temperature in the second cooling step, that is, the temperature of the second cooling roll 400 may be set to, for example, 5 ~ 80 ℃, but is not limited thereto.

According to a preferred embodiment of the present invention, in the second cooling step, it is preferable to cool the resin layer 40 and to form an air flow grove in the resin layer 40. According to the present invention, the winding quality of the film is improved by the air groove. As will be described below, the transversely stretched film is wound in the winder 600, at which time it may be wrinkled and not stretched well in the winding process. In forming the resin layer 40, the present invention is not based on the coating process as in the prior art, the present invention is laminated by the resin layer 40 through the continuous further extrusion process (second extrusion step) after longitudinal stretching, It may be wrinkled and difficult to stretch. When using resin with low melting | fusing point as a raw material of the resin layer 40, the said wrinkle phenomenon may be severe.

At this time, the air groove provides an air flow passage to effectively prevent wrinkles during winding. That is, the air existing between the film and the film during the winding is effectively prevented from escaping through the air groove to be wrinkled. The air groove is plural and its shape is not limited. The air grooves may be formed on the surface of the resin layer 40 in the longitudinal direction or the width direction, for example, in a straight or lattice shape, or may be regularly or irregularly formed as an emboss shape.

In addition, the air groove is formed in the second cooling step, wherein the formation of the air groove is implemented by using the second cooling roll 400 having an uneven structure (fragment structure) on the surface. Specifically, as shown in FIG. 5, an air groove is formed in the resin layer 40 using the piece cooling roll having the uneven structure 450 formed on the surface as the second cooling roll 400. That is, in the second extrusion step, the multilayer film F in which the resin layer 40 is formed is passed through the second cooling roll 400 to cool, but the second cooling roll 400 having the uneven structure 450 formed on the surface thereof is cooled. The resin layer 40 is brought into close contact with each other so that an air groove is formed. At this time, if the concave-convex structure 450 formed in the second cooling roll 400 can form an air groove, the shape and structure thereof are not limited and may be variously designed. For example, the uneven structure 450 is formed in a straight or lattice form parallel or orthogonal to the axial direction of the second cooling roll 400, or protrudes regularly or irregularly on the surface of the second cooling roll 400. It can be formed in the form of emboss (emboss).

The air grooves can be easily removed upon commercialization or use of the stretched film. Specifically, the stretched film (product) wound on the winding machine 600 may be cut into a suitable size to be commercialized, wherein the air groove is easily removed by applying artificial heat to the stretched film. That is, when predetermined heat is applied to the stretched film, the air grooves are removed and the stretched film maintains flattening. In addition, the air grooves can be easily removed in the course of using the stretched film. For example, stretched films can be used for packaging materials, labels, and lamination coatings (lamination), where the heat grooves are easily made by the heat if heat is applied for sealing or heat for coating adhesion. Can be removed.

Referring to FIG. 5, the film which has passed through the second cooling step is transferred to the transverse stretching machine 500 along the guide roll R2 and transversely stretched in the width direction (TDO). The transverse stretching machine 500 may be a conventional one. The stretching temperature of the lateral stretching step, that is, the temperature of the lateral stretching machine 400 may be set to, for example, 100 ~ 200 ℃, but is not limited thereto. In addition, in the transverse stretching step, the transverse stretching may be 2 to 15 times (elongation ratio), for example, 5 to 12 times (elongation ratio), and more specifically, for example, 5 to 10 times (elongation ratio), and the transverse stretching ratio may be It may be implemented by a pattern (Rail pattern).

As described above, the stretched stretched film may be wound on the winding machine 600 and then commercialized. In this case, after lateral stretching, the trimming process may be performed as usual, and then may be wound up. Specifically, when both ends of the film by the transverse stretching machine 500 shows a difference in thickness, after the trimming process to remove both ends, it is good to wind the winding machine 600.

According to the present invention described above, as described above, without further performing the transverse stretching immediately after the longitudinal stretching, further extrusion (second extrusion step) and cooling process (second cooling stage) between the longitudinal stretching process and the transverse stretching process. Including, but the resin layer 40 is laminated through the additional extrusion process (second extrusion step), it is possible to laminate through extrusion in the case of a resin having a low melting point. Accordingly, in manufacturing the multilayer stretched film including the resin layer 40, it is possible to implement a multi-layer through the continuous extrusion, the manufacturing process is monotonous and takes less time to reduce the production cost of the product. In addition, in the second cooling step, in the case of using the second cooling roll 400 having the uneven structure 450, air grooves are formed in the resin layer 40 to prevent the wrinkles from being wound. Secured. In addition, the resin layer 40 has an excellent interlayer adhesive strength with the film (F), that is, excellent interlayer adhesive strength equal to or higher than that by the conventional coating process.

In addition, the stretched film produced according to the present invention can be used in various packaging materials, labels, lamination coating (lamination) and the like. For example, it can be variously used for packaging materials such as food, electronic products and pharmaceuticals, lamination coating (paper) such as photographs, ID cards, printed materials and menu boards, and labeling.

On the other hand, the multi-layered polyolefin-based stretched film according to the present invention is prepared according to the production method of the present invention as described above, the layer structure and the configuration of each layer is as described above.

Hereinafter, the Example and comparative example of this invention are illustrated. The following examples illustrate the interlayer adhesion strength (adhesive force) of the conventional coating film and the extruded film of the present invention, that is, the interlayer adhesion strength of the resin layer 40 and the skin inner layer 20 (adhesive force) among various embodiments of the present invention. It is an example to show the evaluation result for).

[Examples 1 and 2]

Using the apparatus shown in FIG. 5, the skin outer layer 10 / core layer 30 / skin inner layer 20 was formed / cooled by extrusion, and then longitudinally stretched at a 4 times longitudinal draw ratio. After longitudinal stretching, the EVA layer was laminated / cooled as the resin layer 40 on the skin inner layer 20 by an in-line process through continuous extrusion, and then transversely stretched at an aspect ratio of 8 times in FIG. 3. The stretched film of the four layer structure was produced as shown. At this time, the skin outer layer 10 and the core layer 30 were composed of a PP layer, and the skin inner layer 20 was composed of a PE layer. (Example 1) Then, thermal lamination of paper was carried out on the EVA layer. Specimen according to Example 2 was used.

[Comparative Examples 1 and 2]

A commercially available EVA thermal lamination product was purchased and used as a specimen of this comparative example. Specifically, the skin outer layer (PP layer) / core layer (PP layer) / skin inner layer (PE layer) is formed / cooled through extrusion, and longitudinal stretching and transverse stretching are continuously performed at a ratio of 4 times the longitudinal stretch ratio and 8 times the transverse stretch ratio. Then, the thermal lamination of the EVA layer on the skin inner layer (PE layer) through OFF-LINE was used as a specimen according to Comparative Example 1. And the lamination of the paper on the EVA layer was used as a specimen according to Comparative Example 2.

For each specimen according to Example 1 and Comparative Example 1, the interlaminar adhesive strength was evaluated as follows, and the results are shown in the following [Table 1].

* Interlayer adhesion strength ( Peel strength )

(1) A sample obtained by cutting each specimen horizontally (15 mm) x vertical (150 mm) using a cutter bar was prepared.

(2) The resin layer (EVA layer) and the skin inner layer (PE layer) of the sample cut to a certain standard were only interlaminarly peeled with a razor.

(3) The sample which was peeled off partly was impregnated into a container with a standard electrolyte solution and then sealed. (Electrolyte: LiPF6 1M solution)

(4) The electrolyte solution containing the sample was stored in an 85 ° C. drying oven for 1 day.

(5) After 1 day, the sample was taken out and the interlaminar adhesive strength (peel strength) was measured at a peel angle of 180 degrees using a tensile strength machine.

In addition, for the specimens according to Example 2 and Comparative Example 2, the interlayer adhesion strength (peel strength) between the resin layer (EVA layer) and the paper was evaluated by the same method as above, and the results are shown in the following [Table 1]. .

<Evaluation result of adhesion strength between layers> Item
Example 1 Comparative Example 1 Example 2 Comparative Example 2 Of stretched film
Laminated structure PP / PP / PE / EVA PP / PP / PE / EVA PP / PP / PE / EVA / Paper PP / PP / PE / EVA / Paper EVA layer
Formation method Inline extrusion OFF-LINE
Thermal lamination Inline extrusion OFF-LINE
Thermal lamination Interlayer Bonding Strength
(In 1 day) 2.0 kgf 1.5 kgf 0.4 kgf 0.4 kgf

As shown in [Table 1], when laminating a resin layer (EVA layer), when laminated through inline extrusion according to the present invention, compared to the conventional thermal lamination films (Comparative Examples 1 and 2) or equivalent It was found that the interlayer adhesion strength was higher. In addition, as a result of visual evaluation, it was found that the surface appearance was also good, and when the folded portion was folded, it was found that the adhesive strength with the paper was also good.

10: skin outer layer 20: skin inner layer
30 core layer 40 resin layer
100-1: first extruder 100-2: second extruder
150: resin supply unit 200: first cooling roll
300: longitudinal drawing machine 400: second cooling roll
500: transverse stretching machine 600: winding machine

Claims (9)

A first extrusion step of extruding the multilayer polyolefin film;
A first cooling step of cooling the extruded film;
A longitudinal stretching step of longitudinally stretching the film that has passed through the first cooling step;
A second extrusion step of extrusion molding such that at least one resin layer is laminated on the longitudinally stretched film;
A second cooling step of cooling the film on which the resin layer is formed; And
Method for producing a multi-layer polyolefin-based stretched film comprising a transverse stretching step of transverse stretching the film passed through the second cooling step.
The method of claim 1,
The second cooling step is a method for producing a multilayer polyolefin-based stretched film, characterized in that to form an air groove in the resin layer using a cooling roll having an uneven structure on the surface.
The method according to claim 1 or 2,
In the first extrusion step, the multilayer polyolefin film is extruded to include a skin outer layer, a core layer and a skin inner layer,
The second extrusion step, the extrusion method for producing a multilayer polyolefin-based stretched film, characterized in that the extrusion molding so that the resin layer is laminated on at least one selected from the skin outer layer and the skin inner layer.
The method according to claim 1 or 2,
The second extrusion step is a polyolefin resin, a silicone resin, a urethane resin, an acrylic resin, a polyamide resin, a metallocene resin, a nylon resin, ethylene vinyl acetate, ethylene methyl acetate, ethylene methyl acrylic liquid as a raw material of the resin layer. A method for producing a multilayered polyolefin-based stretched film, comprising using a raw material comprising at least one selected from the group consisting of a seed, ethylene glycol, ethylene acid terpolymer, and rubber.
The method according to claim 1 or 2,
In the second extrusion step, a raw material containing a resin having a lower melting point than the raw material used in the first extrusion step is used as a raw material of the resin layer.
The method according to claim 1 or 2,
The second extrusion step is a method for producing a multilayer polyolefin-based stretched film, characterized in that a raw material containing an antistatic agent is used as a raw material of the resin layer.
The method according to claim 1 or 2,
The second extrusion step is a method for producing a multilayer polyolefin-based stretched film, characterized in that a raw material containing nylon resin is used as a raw material of the resin layer.
The method of claim 3,
The first extrusion step, a method for producing a multilayer polyolefin-based stretched film, characterized in that the extrusion molding so as to include any one or more selected from the slip agent and the anti-blocking agent in the skin outer layer.
The multilayer polyolefin stretched film produced by the manufacturing method according to claim 1.

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