JP5934355B2 - Method for producing polyolefin-based stretched film and polyolefin-based stretched film produced by the method - Google Patents

Description

  The disclosure in the present specification relates to a method for producing a polyolefin-based stretched film used for various packaging materials and the like, and a polyolefin-based stretched film produced by the method. More specifically, when laminating a heat-laminated resin layer on a polyolefin-based stretched film having a multilayer structure, an additional extrusion step is included after the extrusion step and the longitudinal stretching step, and the heat-laminate resin layer is laminated through the additional extrusion step. Thus, even in the case of a resin having a low melting point, lamination by continuous extrusion is possible, so that the production process is monotonous and the time required for production is shortened, so that the production cost of the product can be reduced. The disclosure in the present specification also relates to a method for producing a polyolefin-based stretched film having excellent interlayer adhesion strength, and a polyolefin-based stretched film produced by the method.

  In general, as a film used for a packaging material (food, etc.), a stretched film having a heat laminating resin layer formed on the surface is often used. Polyvinyl chloride (PVC) film and polyethylene terephthalate (PET) film are available as this type of heat laminating film. PVC film discharges harmful substances such as dioxin during incineration, and PET film is economical. Are difficult to recycle.

  For this reason, polyolefin-based stretched films that are advantageous in terms of economy and recycling, in particular, biaxially oriented polypropylene films (BOPP films) produced by biaxial stretching are often used. Polypropylene (PP) is not only advantageous for economic efficiency and recycling, but also has mechanical properties such as tensile strength, rigidity, surface hardness, impact strength, optical properties such as glossiness, transparency, and nontoxicity. It is also excellent in food sanitation such as odorlessness, and is useful for packaging materials (foods, etc.) and laminates / coating (sheet lamination).

  FIG. 1 is a diagram showing a cross-sectional configuration of a conventional general BOPP film, and FIG. 2 is a diagram showing a schematic configuration of a manufacturing apparatus for explaining a method for manufacturing a BOPP film according to the prior art. .

  Referring to FIG. 1, generally, a BOPP film includes a PP layer as a core layer 3, a first skin layer 1 (first skin layer) laminated on the top and bottom of the core layer 3, and a first skin layer 1. 2 skin layer 2 (second skin layer). At this time, the first skin layer 1 and the second skin layer 2 are composed of PP layers. On the first skin layer 1, a resin layer 4 for heat lamination, that is, heat fusion is laminated.

  For example, a BOPP film as described above is used for laminate coating (interleaf), specifically, a photo, identification card, printed matter, or a recognized item such as a menu is sandwiched between two BOPP films and then heat-sealed. When used as a film for laminating coating (interleaf paper) or a packaging film for foods, the resin layers 4 are thermally laminated (heat-sealed) to achieve sealing properties. At this time, the resin layer 4 is made of a low-temperature adhesive resin such as ethylene-vinyl acetate (EVA) capable of low-temperature heat sealing (heat sealing).

  Further, referring to FIG. 2, conventionally, when the BOPP film having the multilayer structure as described above is manufactured, the first skin 1, the core layer 3, and the second skin layer are formed by the extruder 5. The two layers 1, 2, and 3 were laminated with an extrusion die while extruding 2 simultaneously. Then, after the extruded multilayer film is cooled by passing through a cooling roll 6, biaxial stretching, that is, longitudinal stretching (MDO; Machine Direction Orientation) and transverse stretching (TDO; Transverse Direction Orientation) are continuously performed. Applied and manufactured.

  That is, as shown in FIG. 2, after performing longitudinal stretching (MDO) in the machine direction (longitudinal direction) through a longitudinal stretching machine 7 having a combination of a large number of rolls R, the transverse stretching machine 8 continuously Then, transverse stretching (TDO) in the width direction is performed by a rail pattern. Next, the longitudinally and laterally stretched film is immediately wound on a winding roll 9 (winding roll).

  Conventionally, when manufacturing a BOPP film having a multilayer structure, the extrusion, cooling, longitudinal stretching, and transverse stretching processes are continuously performed as described above, and three layers of PP layer / PP layer / PP layer as shown in FIG. A multilayer film having a structure was manufactured.

  In addition, after the multilayer film is manufactured through the above-described continuous process, the resin layer 4 such as ethylene-vinyl acetate (EVA) for thermal lamination is laminated on the first skin layer 1 as described above. Need to form. At this time, in the prior art, after the anchor layer 5 is coated on the first skin layer 1 as shown in FIG. 1, a T-die is formed on the anchor layer 5. The resin layer 4 was formed by extrusion coating.

  At this time, when the resin layer 4 is formed, the anchor layer 5 is not formed, and a low temperature adhesive resin is introduced into the skin extrusion portion during multilayer extrusion coating, and the first skin layer 1 is formed by simultaneous coextrusion. A method in which the resin layer 4 is directly formed thereon can be considered. However, in this case, since the difference in physicochemical properties between the low temperature adhesive resin and the first skin layer 1 made of PP is large, simultaneous coextrusion is difficult and the interlayer adhesion is low. That is, low-temperature adhesive resins such as ethylene-vinyl acetate (EVA) are difficult to co-extrusion due to the difference in melting point with PP, and the difference in properties between the two substances is large. In addition, the interlayer adhesion (adhesion strength) is low.

  Further, when the low-temperature adhesive resin is coextruded as described above, the low-temperature adhesive resin is thermally decomposed by an extrusion die, which may cause corrosion of the equipment. Further, due to the low melting point characteristics, the appearance of the product is inferior due to the generation of scratches in the resin layer 4 in the process of passing through the roll R of the longitudinal stretching machine 7. In addition, the simultaneous coextrusion is difficult due to the phenomenon that the resin layer 4 sticks to the roll R.

  Therefore, in the prior art, as described above, when the heat laminating resin layer 4 is formed, the anchor layer 5 is previously coated on the first skin layer 1, and a separate T-die is formed thereon. The resin layer 4 was formed by extrusion coating. However, in this case, an additional process of coating the anchor layer 5 and the extrusion coating process of the resin layer 4 is involved, which increases cost and time, and complicates the process. This increases the production cost of the product. Further, the anchor layer 5 is not desirable in terms of environment.

  Therefore, in the embodiment of the present invention (embodiments), when forming the heat laminating resin layer, even in the case of a resin having a low melting point, it is possible to form a laminate in a continuous process by extrusion, Providing a method for producing a stretched polyolefin film that can reduce the production cost of the product because the production process is monotonous and the production time is shortened, and has excellent interlayer adhesion, and a polyolefin stretched film produced by the method To do.

To achieve the above object, in an aspect of the present invention, a first extrusion step of extruding a polyolefin film including a first skin layer, a core layer, and a second skin layer;
A first cooling step for cooling the extruded film;
A longitudinal stretching step of longitudinally stretching the film that has undergone the first cooling step;
A second extrusion step of extruding so that a resin layer is formed on the first skin layer of the longitudinally stretched film;
There is provided a method for producing a polyolefin-based stretched film, comprising: a second cooling step for cooling the film on which the resin layer is formed; and a transverse stretching step for transversely stretching the film that has undergone the second cooling step.

  In this case, in the first extrusion step, it is preferable to use a raw material containing a polyethylene resin as a raw material for the first skin layer.

  Furthermore, in the second cooling step, it is preferable that the cooling channel having a concavo-convex structure on the surface is used for cooling and at the same time an air channel is formed in the resin layer.

  Moreover, in the aspect of this invention, the polyolefin-type stretched film manufactured by this manufacturing method is provided.

  According to the aspect of the present invention, an additional extrusion / cooling step (second extrusion / second cooling step) after the longitudinal stretching is included, and the resin layer is formed through the additional extrusion to form a resin having a low melting point. Even in this case, it is possible to form a laminate by an in-line process by extrusion.

  As a result, according to the aspect of the present invention, when the multilayered polyolefin-based stretched film is manufactured, each layer including the resin layer is laminated through a continuous extrusion process, so that the manufacturing process is simple, and Since the manufacturing time is shortened, the production cost of the product can be reduced. In addition, there is an effect that the adhesive strength between the first skin layer and the resin layer is excellent as well as the adhesive strength between layers, that is, the adhesive strength between the resin layer and the adherend.

It is a cross-sectional block diagram of the conventional general polyolefin-type stretched film (BOPP film). It is a block diagram of the manufacturing apparatus for demonstrating the manufacturing method of the polyolefin-type stretched film (BOPP film) which concerns on a prior art. It is a cross-sectional block diagram of the polyolefin-type stretched film manufactured according to the aspect of this invention. It is an exemplary block diagram of the manufacturing apparatus for demonstrating the manufacturing method of the polyolefin-type stretched film which concerns on the aspect of this invention. It is sectional drawing which shows the other aspect of the cooling roll which comprises the said manufacturing apparatus.

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

  First, a stretched polyolefin film produced according to the embodiment of the present invention will be described, and then a method for producing a stretched polyolefin film according to the embodiment of the present invention will be described.

  FIG. 3 is a cross-sectional configuration diagram showing an example of a polyolefin-based stretched film (hereinafter abbreviated as “stretched film”) manufactured according to an embodiment of the present invention.

  Referring to FIG. 3, the stretched film manufactured according to the embodiment of the present invention was formed by laminating at least three layers of polyolefin film F (hereinafter abbreviated as “multilayer film”) and multilayer film F. Resin layer 40.

  At this time, the multilayer film F is formed by simultaneously laminating three or more layers through co-extrusion (through), and each layer contains at least a polyolefin resin as a base resin (main raw material). As shown in FIG. 3, the multilayer film F includes a core layer 30, a first skin layer 10 stacked on the core layer 30, and a second layer stacked on the lower portion of the core layer 30. And the skin layer 20. The multilayer film F includes the above-described three layers, that is, a three-layer structure in which the first skin layer 10, the core layer 30, and the second skin layer 20 are sequentially laminated. In addition to the three layers, one or more other layers may be further included.

  At this time, each of the layers 10, 20, and 30 includes a polyolefin-based resin as a base resin (main raw material). In a preferred embodiment, the core layer 30 includes a polypropylene (PP) resin as a base resin (main raw material), and the first skin layer 10 includes a polyethylene (PE) resin as a base resin (main raw material). The second skin layer 20 may include one or more selected from a polypropylene (PP) resin and a polyethylene (PE) resin as a base resin (main raw material).

  Further, the stretched film according to an aspect of the present invention includes a resin layer 40 laminated on the multilayer film F, and the resin layer 40 includes one layer or two layers, and is formed on the first skin layer 10. Stacked. At this time, as described later, the resin layer 40 is not formed by a separate extrusion coating process after coating the anchor layer 5 (see FIG. 1) as in the prior art. It is laminated on the multilayer film F by an additional extrusion process performed after longitudinal stretching. Hereinafter, the production method according to the embodiment of the present invention will be specifically described as follows.

  FIG. 4 is a diagram showing an example of a manufacturing apparatus for embodying the manufacturing method according to the aspect of the present invention. The manufacturing apparatus shown in FIG. 4 is exemplarily shown to help understanding of the present invention, and the manufacturing apparatus can be realized in various forms other than the form shown in FIG.

  Referring to FIG. 4, the manufacturing apparatus includes a first extruder 100-1, a first cooling roll 200, a longitudinal stretching machine 300, a second extruder 100-2, a second cooling roll 400, and lateral stretching. Machine 500 and take-up roll 600. Each of these devices is sequentially arranged so that a continuous process is possible. The structure of each apparatus is not particularly limited. For example, the longitudinal stretching machine 300 may be a combination of a number of rolls R as shown in FIG. R1 and R2 in FIG. 4 indicate guide rolls installed adjacent to the first cooling roll 200 and the second cooling roll 400, respectively.

  The manufacturing method according to the aspect of the present invention includes the first extrusion step of extruding so as to form the multilayer film F including at least three layers 10, 20, and 30, as described above, and the extrusion molding. A first cooling step for cooling the multilayer film F, a longitudinal stretching step for longitudinally stretching the multilayer film F that has undergone the first cooling step, and one or more resin layers 40 on the longitudinally stretched multilayer film F A second extrusion step in which extrusion is performed so that the resin layer 40 is laminated, a second cooling step in which the multilayer film F in which the resin layer 40 is laminated, and a multilayer film F that has undergone the second cooling step. A transverse stretching step of transverse stretching. Each of these steps is continuous.

  First, in the first extrusion step, a multilayer film F including at least three layers 10, 20, and 30 is extruded by the first extruder 100-1. Specifically, the multilayer film F is formed by co-extrusion so that at least three layers including the first skin layer 10, the core layer 30, and the second skin layer 20 are laminated. At this time, the said 1st extruder 100-1 has an extrusion part corresponding to the number of layers of the multilayer film F, and each layer 10, 20, 30 is laminated with an extrusion die. For example, when it is desired to form a multilayer film F having a three-layer structure including the first skin layer 10, the core layer 30, and the second skin layer 20, the first extruder 100-1 corresponds to this. You may have three extrusion parts.

  A polyolefin resin composition is used as a raw material for extrusion molding of the multilayer film F, that is, as a raw material charged 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-based resin is not particularly limited as long as it is a polyolefin, and preferably one or more selected from polypropylene (PP) -based, polyethylene (PE) -based, copolymers thereof, and the like may be used. The polyolefin resin may be one or more copolymers selected from ethylene and propylene, such as a binary copolymer such as propylene-ethylene copolymer, propylene-butene copolymer, and ethylene-methacrylic acid. Polymers and ethylene-methacrylic acid-ester terpolymers may be used, but are not necessarily limited thereto.

  Furthermore, the polyolefin-based resin composition includes at least a polyolefin-based resin, and may further include other resins and other additives as necessary. At this time, although not particularly limited, the polyolefin resin composition is used in an amount of 0 to 40 parts by weight, more specifically 5 to 40 parts by weight of other resins and other additives with respect to 100 parts by weight of the polyolefin resin. You may include in 20 weight part. As the additive, those commonly used in the art may be used, and preferably one or more selected from an antistatic agent, a slip agent, an antiblocking agent, and the like.

  When the multilayer film F is formed by the first extrusion step, each layer may use the same raw material or different raw materials. For example, the core layer 30 may be formed to be a PP layer using polypropylene (PP) as a base resin (main raw material). The second skin layer 20 may 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 raw material). It may be molded. At this time, the second skin layer 20 can be realized to be glossy by using polypropylene (PP) as a base resin (main raw material), or appropriately mixed polypropylene (PP) and polyethylene (PE). For example, it is possible to realize a glossless mixture by mixing at a weight ratio of 1: 0.5 to 2 (PP: PE). Further, when the second skin layer 20 is constituted by mixing polypropylene (PP) and polyethylene (PE) in this way, the mixture of the two kinds of resins is converted into a master batch, for example, a pellet. ) And then put into the first extruder 100-1.

  In a preferred embodiment, the raw material for the first skin layer 10 may include a polyethylene (PE) resin. Thus, when the 1st skin layer 10 contains polyethylene (PE) type-resin, compatibility with low temperature adhesive resins (low melting point resin), such as ethylene-vinyl acetate (EVA) which comprises the resin layer 40, is sufficient. Therefore, the interlayer adhesion (adhesion strength), that is, the interlayer adhesion (adhesion strength) between the first skin layer 10 and the resin layer 40 is improved. The raw material for the first skin layer 10 may be specifically selected from homopolyethylene (PE) as a polyethylene (PE) -based resin, ethylene polymer, and the like. Density polyethylene (LDPE), more specifically, one selected from linear low density polyethylene (LLDPE) is advantageous in terms of interlayer adhesion.

  Further, in the first extrusion step, as a raw material for each layer 10, 20, and 30, in addition to the base resin (polyolefin resin), as described above, one or more additives selected from an antistatic agent and an antiblocking agent are added. A raw material further containing an agent may be used, and in this case, in the case of the core layer 30, a raw material containing an antistatic agent such as a sulfonate or an ammonium salt may be used. In the case, a raw material containing an anti-blocking agent such as silica, diatomaceous earth, and talc may be used.

  Further, when the multilayer film F is formed by the first extrusion step, the thickness of each layer may be appropriately adjusted. For example, referring to FIG. 3, it has a three-layer structure including a first skin layer 10, a core layer 30, and a second skin layer 20, and a thickness T10 of the first skin layer 10 is described. Is 1 to 10% of the total thickness T of the stretched film, the thickness T30 of the core layer 30 is 30 to 70% of the total thickness T of the stretched film, and the thickness T20 of the second skin layer 20 is the stretched film. You may shape | mold so that it may become 1 to 10% of the total thickness T. Furthermore, the extrusion temperature in the first extrusion step may have various temperature ranges depending on the raw material used, and may be performed in a temperature range of 140 to 320 ° C., for example.

  Referring to FIG. 4, the multilayer film F extruded by the first extruding step described above passes through the first cooling roll 200 and passes through the first cooling step. At this time, FIG. 4 illustrates an embodiment in which one first cooling roll 200 is installed in the manufacturing apparatus. However, one or two or more first cooling rolls 200 are provided in the manufacturing apparatus. A plurality may be arranged continuously. The cooling temperature in the first cooling step, that is, the temperature of the first cooling roll 200 may be set in a range of 5 to 80 ° C., for example, but is not necessarily limited to the temperature range. .

  The multilayer film F that has undergone the first cooling step is conveyed along the guide roll R1 to the longitudinal stretching machine 300 and longitudinally stretched (MDO) in the machine direction (longitudinal direction). For example, as shown in FIG. 4, it may be longitudinally stretched by a plurality of rolls R. The stretching temperature of these longitudinal stretching steps, that is, the temperature of the roll R installed in the longitudinal stretching machine 300 may be set in the range of 80 to 160 ° C., for example, but is not necessarily limited to the temperature range. is not. Further, in the longitudinal stretching step, longitudinal stretching to 2 to 10 times (stretching ratio), 3 to 7 times (stretching ratio) as a specific example, and 4 to 5 times (stretching ratio) as a more specific example. May be. Such a longitudinal stretching ratio can be realized by the speed of the roll R.

  In the aspect of the present invention, the multilayer film F that has undergone the longitudinal stretching step continuously undergoes an additional extrusion step (second extrusion step) and a cooling step (second cooling step) performed simultaneously therewith.

  In the second extrusion step, the resin layer 40 is laminated on the multilayer film F. Specifically, referring to FIG. 4, multilayer film F is longitudinally stretched and then sent to second extruder 100-2. At this time, a resin supply unit 150 that supplies a raw material for forming the resin layer 40 may be installed in the second extruder 100-2. The multilayer extruder F is passed through the second extruder 100-2, and at the same time, the resin layer 40 is extruded by the raw material being supplied from the resin supply unit 150, and the die film (Dies) is used. Lamination of the resin layer 40 is performed.

  The raw material of the resin layer 40 in the embodiment of the present invention, that is, the raw material supplied from the resin supply unit 150 to the second extruder 100-2 is not particularly limited. The raw material of the resin layer 40 is not limited as long as it is a low-temperature adhesive resin (low melting point resin) and can be heat laminated (heat fusion). The raw material of the resin layer 40 is, for example, polyolefin resin, silicon resin, urethane resin, acrylic resin, polyamide resin, metallocene resin, nylon resin, ethylene-vinyl acetate (EVA), ethylene methyl acetate (EMA). Or a raw material containing one or more selected from the group consisting of ethylene methacrylic acid (EMAA), ethylene glycol (EG), ethylene acid ter-polymer and ethylene / propylene / butadiene terpolymer. Good.

  According to the aspect of the present invention, the continuous extrusion is performed by laminating the resin layer 40 in the additional extrusion step after the longitudinal stretching, that is, the second extrusion step without performing the transverse stretching immediately after the longitudinal stretching as in the prior art. Since the resin layer 40 is formed by the in-line process, the process is simple. Further, as a raw material of the resin layer 40, the base resin constituting the multilayer film F, that is, the base resin constituting the first skin layer 10, has a different physicochemical property, that is, has a melting point lower than that of the polyolefin. Alternatively, a high resin can be used. In particular, it is possible to use a resin having a lower melting point than that of the polyolefin resin.

  That is, according to the aspect of the present invention, in the second extrusion step, a raw material containing a resin having a melting point lower than that of the raw material used in the first extrusion step can be used as the raw material for the resin layer 40. For example, low-temperature adhesive resins that can be heat-laminated by low-temperature heat include ethylene-vinyl acetate (EVA), ethylene methyl acetate (EMA), ethylene methacrylic acid (EMAA), low-temperature metallocene resin, ethylene glycol (EG), ethylene acid terpolymer, ethylene / propylene / butadiene terpolymer, etc., can be used for resins having a low melting point and excellent sealing properties, and these resins are laminated by an in-line process by continuous extrusion. be able to. Furthermore, since the first skin layer 10 and the resin layer 40 have an excellent adhesive force without forming the anchor layer 5 (see FIG. 1) as in the prior art, the interlayer adhesive force is improved.

  In addition, according to the aspect of the present invention, the resin layer 40 is laminated by the additional extrusion process (second extrusion step) as described above, and the raw material of the resin layer 40 is not limited. Functionality. For example, in a preferred embodiment of the present invention, a raw material containing an antistatic agent can be used as the raw material for the resin layer 40. At this time, the resin layer 40 has an antistatic ability as well as a heat laminating (heat fusion) function. The kind of the antistatic agent is as described above. For example, the antistatic agent may be contained in an amount of 0.01 to 10.0 parts by weight with respect to 100 parts by weight of the low-temperature adhesive resin constituting the resin layer 40.

  In the second extrusion step, the resin layer 40 can be formed such that the thickness T40 is in the range of 10 to 68% of the total thickness T of the stretched film. Furthermore, the extrusion temperature in the second extrusion step may be set in various temperature ranges in consideration of the raw material used for the resin layer 40, that is, the type and melting point of the low-temperature adhesive resin constituting the resin layer 40. . For example, it can set and extrude to the temperature range of 150-330 degreeC. At this time, if the extrusion temperature is too low as less than 150 ° C, extrusion becomes difficult, and if it exceeds 330 ° C, the flowability is high, which is not preferable. For example, when using a low melting point resin such as ethylene-vinyl acetate (EVA), it may be extruded in a temperature range of 180 to 250 ° C.

  Referring to FIG. 4, the multilayer film F in which the resin layer 40 is formed by the second extrusion step as described above is continuously passed through the second cooling roll 400 to perform the second cooling step. It passes. At this time, when passing through the second cooling roll 400, it is preferable to cool the resin layer 40 so that the resin layer 40 is in close contact with the roll surface of the second cooling roll 400. Moreover, in FIG. 4, although the said 2nd cooling roll 400 illustrated the aspect installed in the manufacturing apparatus, the said 2nd cooling roll 400 was one or two or more in the manufacturing apparatus. May be continuously arranged. The cooling temperature in the second cooling step, that is, the temperature of the second cooling roll 400 may be set in a range of 5 to 80 ° C., for example, but is not necessarily limited to the temperature range. .

  In a preferred aspect of the present invention, in the second cooling step, an air channel may be formed in the resin layer 40 simultaneously with the cooling of the resin layer 40. According to the aspect of the present invention, the air channel improves the winding quality of the film. As will be described later, the laterally stretched film is wound on the winding roll 600, and at this time, wrinkles may be offset in the winding process, making it difficult to remove the wrinkles. When the resin layer 40 is formed, the resin layer 40 is laminated by a continuous additional extrusion process (second extrusion step) after longitudinal stretching, instead of a coating process or the like as in the prior art. Wrinkles may be offset, making it difficult to remove the wrinkles. When a resin having a low melting point is used as a raw material for the resin layer 40, the wrinkling phenomenon may tend to be severe.

  At this time, the air channel effectively prevents wrinkling during winding by providing an air flow passage. That is, it is possible to effectively prevent wrinkles from coming out of the air that has existed between the films at the time of winding. There are a plurality of air channels, and the shape thereof is not limited. The air channel may be formed on the surface of the resin layer 40 in the longitudinal direction or the width direction, for example, in a letter shape or a lattice shape, or may be regularly or irregularly formed.

  In addition, the air channel is formed in a second cooling step, and at this time, the formation of the air channel can be realized by using a second cooling roll 400 having an uneven structure on the surface. Specifically, as shown in FIG. 4, an air channel is formed in the resin layer 40 by using a cooling roll having a concavo-convex structure 450 formed on the surface thereof as the second cooling roll 400. That is, the multilayer film F on which the resin layer 40 is formed in the second extrusion step is allowed to pass through the second cooling roll 400 to be cooled, and the second cooling roll 400 having the concavo-convex structure 450 formed on the surface thereof. The resin layer 40 is passed in close contact to form an air channel.

  At this time, the concavo-convex structure 450 formed on the second cooling roll 400 is not limited in its shape and structure as long as it can form an air channel, and may be formed in various shapes and structures.

  For example, the concavo-convex structure 450 may be formed in a single shape or a lattice shape in parallel or perpendicular to the axial direction of the second cooling roll 400, and the concavo-convex structure 450 is further formed on the surface of the second cooling roll 400. It may be formed regularly or irregularly. The concavo-convex structure 450 may include a protrusion 452 and a groove 454 as shown in FIG. 5, and the number and depth (height) of the protrusion 452 and the groove 454 are limited. Not.

  The second cooling roll 400 may have any surface uneven structure 450 capable of forming an air channel. For example, a mat type roll or an emboss type roll may be used. However, a mat type roll is preferable.

  The mat type roll has a surface that has been subjected to a sanding process, and for example, a mat type roll having a size of 50 to 150 (preferably, a uniformity of 80 to 120) by sanding. Also good. More specifically, a structure in which lattice-shaped protrusions 452 are regularly or irregularly formed by sand having a size of 50 to 150 mesh (mesh) may be used.

The mat type roll may have a groove 454 formed by sanding, and the groove 454 may have a depth D _{454 of 5} to 30 μm. At this time, if the depth D ₄₅₄ of the groove portion 454 by sanding is less than 5 μm, the size of the air channel tends to be too small, or the air channel distribution rate (formation rate) tends to be low. On the other hand, if it is more than the depth D ₄₅₄ of the groove 454 is 30 [mu] m, adhesion of the adhesion is lowered and the resin layer 40 and the adherend tends to be slightly lower. In consideration of such points, the groove 454 may have a depth D ₄₅₄ of 10 μm to 20 μm. When the air channel is formed by a mat type roll having a depth D ₄₅₄ in this range, a good adhesion to the adherend is obtained by effectively preventing the wrinkling phenomenon during winding. be able to.

  On the other hand, the air channel formed by the second cooling roll 400 can be easily removed when the stretched film is commercialized or used. Specifically, the stretched film (product) taken up by the take-up roll 600 can be cut into an appropriate size to produce a product. At this time, if artificial heat is applied to the stretched film, The air channel can be easily removed. That is, when a predetermined heat is applied to the stretched film, the air channel is removed and the stretched film is kept flat. In addition, the air channel can be easily removed during the process of using the stretched film. For example, the stretched film is used for packaging materials, labels, and laminate coatings (interleaf paper). At this time, when heat is applied for sealing or heat is applied for coating adhesion, The air channel can be easily removed by heat.

  In addition, referring to FIG. 4, the film that has undergone the second cooling step is conveyed along the guide roll R2 to the transverse stretching machine 500 and is transversely stretched (TDO) in the width direction. The transverse stretching machine 500 may be a normal one. The stretching temperature of these transverse stretching steps, that is, the temperature of the transverse stretching machine 500 may be set in the range of 100 to 200 ° C., for example, but is not limited to this temperature range. In the transverse stretching step, transverse stretching is performed at 2 to 15 times (stretching ratio), 5 to 12 times (stretching ratio) as a specific example, and 8 to 10 times (stretching ratio) as a more specific example. Such a lateral stretch ratio can be realized by a rail pattern.

  As described above, the transversely stretched stretched film may be commercialized after being wound on the take-up roll 600. At this time, after transverse stretching, the film may be wound after being subjected to a trimming process as usual. Specifically, when both ends of the film show a difference in thickness by the transverse stretching machine 500, the film may be wound on the winding roll 600 after performing a trimming step for removing both ends.

  According to the aspect of the present invention described above, additional extrusion (second extrusion step) and cooling are performed between the longitudinal stretching step and the lateral stretching step without performing lateral stretching immediately after the longitudinal stretching as described above. Including the process (second cooling step), the resin layer 40 is laminated by the additional extrusion process (second extrusion step), and even when the resin has a low melting point, lamination by extrusion becomes possible. As a result, when a multilayer stretched film including the resin layer 40 is manufactured, the multilayer can be realized by an in-line process by continuous extrusion, and the manufacturing process is simple and the manufacturing time is shortened. Can be lowered. Furthermore, since the stretched film can be manufactured with a long width, the price competitiveness is high, and the resin layer 40 has an excellent adhesion to the adherend.

  Further, when the first skin layer 10 includes a polyethylene resin, the adhesive strength with a low-melting-point resin such as ethylene-vinyl acetate (EVA) constituting the resin layer 40 is improved and excellent. The first skin layer 10 and the resin layer 40 have an interlayer adhesive force (adhesive strength).

  Furthermore, in the second cooling step, when the second cooling roll 400 having the concavo-convex structure 450 is used, an air channel is formed in the resin layer 40 to prevent wrinkling at the time of winding, and the appearance. Sex is secured.

  In the aspect of the present invention described above, the produced stretched film can be used in various ways for various packaging materials, labels, laminate coating (interleaf paper) and the like. For example, it can be used in various ways for packaging materials such as foods, electronic products, and pharmaceuticals, for laminating coatings (interleaf paper) such as photographs, identification cards, printed materials and menus, and for labels for blow-in molding. it can.

  On the other hand, the multilayer polyolefin-based stretched film according to the embodiment of the present invention is manufactured by the manufacturing method according to the embodiment of the present invention as described above, and the layer structure and the configuration of each layer are as described above.

  Hereinafter, embodiments of the present invention will be described in detail with reference to Examples and Comparative Examples. The following examples are provided only to help understanding of the present invention, and are not intended to limit the technical scope of the present invention.

[Examples 1 and 2]
Using the apparatus shown in FIG. 4, first, after producing a film in which the first skin layer 10 / core layer 30 / second skin layer 20 are laminated by coextrusion, first cooling is performed, Subsequently, longitudinal stretching was performed at a longitudinal stretching ratio of 4 times. After the longitudinal stretching, an EVA layer as the resin layer 40 is extruded and laminated on the first skin layer 10 by an in-line process by continuous extrusion, and then passed through a cooling roll for second cooling. Then, the film was stretched laterally at a lateral stretching ratio of 8 times to prepare a stretched film having a four-layer structure as shown in FIG. At this time, each of the core layer 30 and the second skin layer 20 was composed of a PP layer, and in the case of the first skin layer 10, it was composed of an LLDPE layer.

  Moreover, when cooling after extrusion of the resin layer 40, in the case of Example 1, cooling was performed by passing through a cooling roll (general roll) having no uneven structure. On the other hand, in the case of Example 2, it was cooled by passing it through a mat type roll subjected to sanding treatment.

[Comparative Examples 1 and 2]
An EVA thermal laminate product currently on the market was purchased and used as a specimen for this comparative example. Specifically, the first skin layer (PP layer) / core layer (PP layer) / second skin layer (PP layer) are formed / cooled by coextrusion, the longitudinal stretching ratio is 4 times, and the lateral stretching ratio is 8 A sample obtained by continuously performing longitudinal stretching and lateral stretching by doubling was used as a specimen according to this comparative example.

  At this time, an adhesive (glue) coated and applied as usual on the first skin layer (PP layer) was used as a specimen according to Comparative Example 1. Then, after an anchor layer is formed on the first skin layer (PP layer) by an OFF-LINE process as usual, an EVA layer is T-die extrusion coated on the anchor layer. 2 was used as a test piece.

  Interlaminar adhesive strength was evaluated as follows for the thermal laminate film specimens according to the respective Examples and Comparative Examples, and the results are shown in Table 1 below. At this time, the evaluation of the interlayer adhesive strength was performed on the first skin layer 10 and the resin layer 40 and on the resin layer 40 and the adherend.

* Interlayer adhesion strength (peel strength)
(1) After using the laminating machine to interleave the produced thermal laminate film specimen with the adherend (printed paper) surface, each interleaving specimen using a cutter bar. The sample which cut | disconnected horizontal (15m) x vertical (15cm) was prepared.
(2) The side surface of the sample cut to the predetermined size was delaminated by a predetermined length with a razor. (Between the first skin layer 10 and the resin layer 40, between the resin layer 40 and the adherend)
(3) Interlaminar bond strength (peel strength) was measured at a peel angle of 180 degrees using a tensile strength tester for the sample from which the predetermined portion was delaminated.

  As shown in [Table 1], as a result of forming a resin layer (EVA layer) by in-line continuous extrusion on the first skin layer 10 in the examples of the present invention, excellent adhesive strength (non-peelable) was obtained. And has been found to be easily formed.

  Further, as shown in [Table 1] above, in the interlayer adhesive strength between the resin layer 40 and the adherend (paper), in the embodiment of the present invention, the first skin layer 10 is constituted by a PE layer (LLDPE). And it became clear that the film (Examples 1 and 2) formed by laminating the resin layer 40 by in-line extrusion shows the same or better evaluation result than the conventional films (Comparative Examples 1 and 2).

  Furthermore, in the case of the film according to the example of the present invention, it can be seen that the appearance after winding is also good, and in particular, the specimen of Example 2 is very excellent in winding quality such as appearance. Turned out to be.

  Provided are a method for producing a stretched polyolefin film used for various packaging materials and the like, and a stretched polyolefin film produced by the method.

DESCRIPTION OF SYMBOLS 10 1st skin layer 20 2nd skin layer 30 Core layer 40 Resin layer 100-1 1st extruder 100-2 2nd extruder 150 Resin supply part 200 1st cooling roll 300 Longitudinal stretching machine 400 1st 2 cooling roll 500 transverse stretching machine 600 winding roll 450 uneven structure 452 protrusion 454 groove

Claims (8)

A first extrusion step of extruding a polyolefin film comprising a first skin layer, a core layer, and a second skin layer;
A first cooling step for cooling the extruded film;
A longitudinal stretching step of longitudinally stretching the film that has undergone the first cooling step;
A second extrusion step of extruding so that a heat sealing resin layer is formed on the first skin layer of the longitudinally stretched film;
A second cooling step for cooling the film on which the heat sealing resin layer is formed; and a transverse stretching step for transversely stretching the film that has undergone the second cooling step;
A method for producing a stretched polyolefin-based film.   The heat sealing resin layer is selected from the group consisting of ethylene vinyl acetate, ethylene methyl acetate, ethylene methacrylic acid, ethylene glycol, ethylene acid terpolymer, and ethylene / propylene / butadiene terpolymer as a raw material of the heat sealing resin layer. The method for producing a stretched polyolefin-based film according to claim 1, comprising at least one of the above. The first skin layer includes a polyethylene resin as a base resin,
The core layer includes a polypropylene resin as a base resin,
The second skin layer includes at least one selected from a polypropylene resin and a polyethylene resin as a base resin,
The heat sealing resin layer is selected from the group consisting of ethylene vinyl acetate, ethylene methyl acetate, ethylene methacrylic acid, ethylene glycol, ethylene acid terpolymer, and ethylene / propylene / butadiene terpolymer as a raw material of the heat sealing resin layer. The method for producing a stretched polyolefin-based film according to claim 1, comprising at least one of the above.   The method for producing a stretched polyolefin-based film according to any one of claims 1 to 3, wherein the first extrusion step uses a raw material containing an antiblocking agent as a raw material for the second skin layer.    5. The polyolefin-based stretched film according to claim 1, wherein in the second cooling step, an air channel is formed in the resin layer using a cooling roll having a concavo-convex structure on a surface thereof. Production method.    6. The method for producing a stretched polyolefin film according to claim 5, wherein the uneven structure formed on the cooling roll has a depth of 5 to 30 [mu] m. A polyolefin stretched film in which a heat sealing resin layer is further formed on a first skin outer layer of a polyolefin film comprising a first skin outer layer, a core layer, and a second skin inner layer,
The first skin outer layer, the core layer and the second skin inner layer are all stretched longitudinally,
A stretched polyolefin film characterized in that the first skin outer layer, the core layer, the second skin inner layer and the heat sealing resin layer are all stretched horizontally, and the heat sealing resin layer is not stretched longitudinally. . It said first skin outer layer comprises a polyethylene resin as the base resin,
The core layer includes a polypropylene resin as a base resin,
The second skin in the layer comprises one or more selected from polypropylene resin and polyethylene resin as the base resin,
The heat sealing resin layer is selected from the group consisting of ethylene vinyl acetate, ethylene methyl acetate, ethylene methacrylic acid, ethylene glycol, ethylene acid terpolymer, and ethylene / propylene / butadiene terpolymer as a raw material of the heat sealing resin layer. The polyolefin stretched film according to claim 7, comprising at least one of the above.

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