JP4785487B2 - Multilayer film - Google Patents

Description

  The present invention relates to a multilayer film that can be used for a packaging bag, and specifically to a multilayer film that can be easily opened after the contents are sealed and packaged in a cylindrical shape by heat-sealing the envelope.

  Widely used as a packaging method for processed products such as livestock and fish, dairy products such as cheese and butter, and confectionery products such as yokan and jelly, and heat-sealing the film on an envelope and packaging the contents in a cylindrical shape Has been. Here, heat-sealing with envelope sticking means that when the contents are wrapped in a film with a film slightly over one round, the excess edge is overlapped with the other edge along the cylindrical side, It refers to heat-sealing the lower surface of the superposed upper film and the upper surface of the lower film. Opening means such as an I notch, a V notch or a scar is often provided on one of the film edges of the heat-sealed portion in order to ensure the opening property. In addition, both ends corresponding to the upper and lower bases of the cylinder are often sealed by ligation with a metal wire, a plastic clip or the like, or heat sealing.

  Conventionally, polyvinylidene chloride films have been used for cylindrical packaging, but heat-sealable polyolefin layers on both sides of the polyamide layer are used to reduce the environmental impact during disposal of packaging materials and to improve the transport strength of the packaging. Has been proposed (see Patent Document 1). However, such a multilayer film has a drawback that the unsealing property of the package is remarkably deteriorated because the strength of the film is stronger than that of the polyvinylidene chloride film.

  As an improvement measure, the multilayer film is a composite film of three or more layers, and the peel strength between the outer layer film that becomes the outer layer and the intermediate layer film that becomes the intermediate layer when it is made into a cylindrical shape is the inner layer film that becomes the inner side when it is made into a cylindrical shape And a package set smaller than the peel strength between the intermediate layer films (see Patent Document 2). According to this, when the opening piece is pulled, the outer layer film breaks at the heat seal portion, the outer layer film peels off from the intermediate layer film, and can be easily opened by peeling to the overlapping non-heat seal portion. I can do it.

However, Patent Document 2 does not specifically disclose a method for setting the peel strength of such a multilayer film to a small value, and the Examples also show a method for controlling the strength of the peel strength as “adhesive adhesive”. “Change selection” (column 0020). The inventors of the present invention have tried to make an additional test of the present invention by using commercially available adhesives having various adhesive strengths. By satisfying the above-mentioned requirements for food packaging films, the selection of the adhesives is possible. Further, it was not possible to find a structure that could be a package that can be opened stably and easily by controlling the strength of the peel strength.
JP-A-5-316933 JP 2002-219777 A

  The present invention provides a multilayer film that can be stably and easily opened while performing the original function of protecting the contents in a multilayer film that heat-seals the envelope and wraps the contents in a cylindrical shape. The issue is to provide.

[1] First heat-sealable polyolefin layer, first strong-adhesive layer, polyamide layer, weak-adhesive layer having weak adhesion to the polyamide layer, second strong-adhesive layer, second heat-sealability Each of the layers is laminated in the order of a polyolefin layer, and the weak adhesive layer is a layer made of a urethane resin or an ethylene-acrylic acid ester copolymer .
[2] The multilayer film is obtained by a dry lamination method or an extrusion lamination method, and a surface of the polyamide layer in contact with the first strong adhesive layer is previously oxidized, and the weak adhesive layer Is a layer made of a urethane resin, the multilayer film as described in [1] above .
[3] The multilayer film is obtained by a dry lamination method, and at least one of the first strong adhesive layer and the second strong adhesive layer is a layer made of a two-component curable urethane adhesive. The multilayer film as described in [1] or [2] above, wherein
[ 4 ] A cylindrical package in which the multilayer film according to any one of [1] to [3] is used, and the contents are packaged by attaching an envelope with the second heat-sealable polyolefin layer on the outside.

  By using the multilayer film of the present invention, the contents are heat-sealed on an envelope and packaged in a cylindrical shape, so that the weak adhesive layer / polyamide layer can be stably and reliably peeled when the package is opened. A cylindrical package that can be easily opened while maintaining the protection of the contents is obtained.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. FIG. 1 is a schematic diagram showing an outline of a cross-sectional configuration of the multilayer film 1. The multilayer film 1 has a weak adhesive strength with respect to the first heat-sealable polyolefin layer 2, the first strong adhesive layer 3, the polyamide layer 4, and the polyamide layer 4 from the inner surface when the package is formed. The adhesive layer 5, the second strong adhesive layer 6, and the second heat-sealable polyolefin layer 7 are laminated in this order.

  In laminating each layer, a) a step of providing the weak adhesive layer 5 on the surface of the polyamide layer 4, b) a step of providing the first strong adhesive layer 3 on the other surface of the polyamide layer 4, and c) on the polyamide layer 4 A step of providing the first heat-sealable polyolefin layer 2 on the first strong adhesion layer 3; d) a step of providing the second strong adhesion layer 6 on the weak adhesion layer 5 on the polyamide layer 4; Each step of providing the second heat-sealable polyolefin layer 7 on the second strong adhesive layer 6 on the layer 5 is performed. Each layer may be laminated by sequentially performing these steps, but the order of performing each step is not particularly limited. Of these, a plurality or all of the steps may be performed simultaneously.

  As a method for laminating each layer, any of known methods, specifically, a dry laminating method, an extrusion laminating method, a coextrusion molding method, or the like can be used. Different methods may be used in combination depending on the layer. Here, a so-called solventless laminating method in which a solventless adhesive is heated and coated on a base film and then bonded to another film is included in the dry laminating method.

  As a lamination method, for example, a polyamide film is used as the polyamide layer 4, and a weak adhesion layer 5 is laminated thereon by a coating method, and then a second strong adhesion layer 6 is applied on the weak adhesion layer 5. A polyolefin film as the second heat-sealable polyolefin layer 7 is bonded by a dry laminating method. Next, the first strong adhesive layer 3 is applied on the opposite surface of the polyamide film of the polyamide layer 4, and a polyolefin film as the first heat-sealable polyolefin layer 2 is bonded by a dry laminating method, The multilayer film 1 can be formed.

  As another lamination method, a polyamide film is used as the polyamide layer 4, and a weak adhesion layer 5 is laminated thereon by a coating method, and then a second strong adhesion layer 6 is applied on the weak adhesion layer 5, A polyolefin resin layer is extruded and bonded onto the second strong adhesive layer 6 as the second heat-sealable polyolefin layer 7 by an extrusion laminating method. Next, the first strong adhesive layer 3 is applied on the opposite side of the polyamide film of the polyamide layer 4, and the polyolefin resin layer is formed as the first heat-sealable polyolefin layer 2 by the extrusion laminating method. The multilayer film 1 can be formed by extruding and bonding onto the adhesive layer 3.

In the laminating method by the above laminating method, the surface of the polyamide layer 4 is subjected to an oxidation treatment before the first strong adhesive layer 3 is applied, and the adhesive strength between the polyamide layer 4 and the first strong adhesive layer 3 is increased. A higher level is preferable because the package can be opened more stably and more easily. As the method of oxidation treatment, any of known methods can be used, and examples thereof include corona treatment, plasma treatment, flame treatment and the like.
As another lamination method, there is a method of simultaneously obtaining a multilayer film by a coextrusion molding method. For example, using a six-layer coextrusion die and four extruders, the second heat-sealable polyolefin layer 7 is a polyolefin resin layer, the second strong adhesion layer 6 is an adhesive resin layer, and the weak adhesion layer 5 is A low-adhesion resin layer, a polyamide resin layer as the polyamide layer 4, an adhesive resin layer as the first strong adhesive layer 3, and a polyolefin resin layer as the first heat-sealable polyolefin layer 2 are coextruded into a film and molded. The multilayer film 1 can be formed.

  Any of the known methods can be used as the method for forming the film, and specific examples of the known method include a casting method and an inflation method as a method for forming an unstretched film, and a stretched film. Examples of the forming method include a tenter biaxial stretching method and a tubular stretching method. Whether it is an unstretched film or a stretched film may be appropriately selected depending on the use conditions such as contents, sterilization method, and storage conditions.

  The polyamide layer 4 is a resin layer mainly composed of a polyamide resin, bears the strength of the multilayer film, and plays a role of imparting functions such as barrier properties and heat shrinkability as required. Here, having a polyamide resin as a main component means containing 50% by mass or more of a polyamide resin. As the polyamide resin, nylon-6 (hereinafter referred to as Ny6), nylon-66, nylon-12, nylon-6 / 12 copolymer, MXD-nylon (hereinafter referred to as MXDNy) or the like is preferably used.

  Further, two or more combinations of the above polyamide resins and other polyamide resins may be blended into a single layer, or a plurality of layers having different compositions may be laminated. Specifically, Ny6 blended with MXDNy or Ny6 / MXDNy / Ny6 laminated is preferably used. Moreover, you may blend other resin other than a polyamide resin, an additive, etc. in the range below 50 mass%, or you may laminate | stack. For example, in order to improve gas barrier properties, a blend of Ny6 with an ethylene-vinyl alcohol copolymer (hereinafter EVOH) or a laminate of Ny6 / EVOH / Ny6 can be used.

  When the laminating method is selected as the laminating method, the polyamide layer 4 uses a polyamide film. Here, the polyamide film means a film mainly composed of a polyamide resin. As described above, the polyamide film may be a single film of a suitable polyamide resin, and different polyamide resins may be blended or laminated in a combination of two or more. Moreover, you may blend with other resin other than a polyamide resin, an additive, etc. in the range below 50 mass%, or you may laminate | stack. The polyamide film may be an unstretched film or a stretched film, and may be appropriately selected depending on the use conditions such as contents, sterilization method, and storage conditions. However, a stretched film is preferable from the viewpoint of laminating suitability and film strength.

  In the laminating method, printing can be performed on the surface of the polyamide film as necessary. The surface to be printed may be an outer surface or an inner surface when it becomes a package, and may be appropriately selected. The printing method may follow a known method for the polyamide film. For example, an intaglio printing method using a gravure roll can be used. Similarly, a known ink may be used for printing.

  The heat-sealable polyolefin layers 2 and 7 are layers mainly composed of a polyolefin resin and having heat-sealability. Polyolefin resins include low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, polypropylene homopolymer, random copolymer or block copolymer, ethylene-vinyl acetate copolymer, and ethylene-acrylic ester copolymer. And ethylene-acrylic acid copolymer. Among the above polyolefin resins and other polyolefin resins, two or more combinations may be blended or laminated.

  The heat-sealable polyolefin layers 2 and 7 may be blended or laminated with other resins or additives other than the polyolefin resin within a range of less than 50% by mass. For example, anti-blocking agents such as synthetic zeolite, siliceous fine particles, spherical polymethylmethacrylate, and slip agents such as erucic acid amide and stearic acid amide may be blended to improve slipperiness when it becomes a multilayer film. it can. The heat-sealable polyolefin layer 2 and the layer 7 may have the same composition or different compositions. If they are different, they must be heat-sealable. Moreover, as long as it is in a range where heat sealing is possible, crosslinking may be performed with an electron beam or the like.

  When the dry lamination method is selected as the lamination method, a polyolefin film is used for the heat-sealable polyolefin layer 2 and the layer 7. Here, the polyolefin film refers to a film mainly composed of a polyolefin resin. As described above, the polyolefin film may be a single film of a suitable polyolefin resin, and may be blended or laminated in a combination of two or more. Moreover, you may blend or laminate | stack other resin, an additive, etc. in the range below 50 mass% with respect to a polyolefin film. The polyolefin film may be an unstretched film or a stretched film, and may be appropriately selected depending on the use conditions such as contents, sterilization method, storage conditions, etc., but from the viewpoint of laminating suitability and film stability, etc. It is preferable to use a film.

  The first strong adhesive layer 3 is a layer for bonding the polyamide layer 4 and the first heat-sealable polyolefin layer 2 with high adhesive strength, and the second strong adhesive layer 6 includes the weak adhesive layer 5 and This is a layer for bonding the second heat-sealable polyolefin layer 7 with high adhesive strength. The strong adhesive layers 3 and 6 have different layer contents depending on the selection of the lamination method of the multilayer film.

  When the dry laminating method is selected, the second strong adhesive layer 6 is formed by applying an adhesive on the weak adhesive layer 5 on the polyamide layer 4, and the first strong adhesive layer 3. Is formed by applying an adhesive on the polyamide layer 4. As the adhesive used here, any of the known adhesives having high adhesive strength can be used. For example, urethane adhesives, acrylic adhesives, epoxy adhesives and the like can be mentioned. Among them, two-component curable urethane adhesives are excellent in adhesive performance, laminating suitability, content resistance, etc. Used.

  The first strong adhesive layer 3 and the second strong adhesive layer 6 may have the same composition or different compositions, but considering the productivity, the same composition is desirable as long as there is no problem. The thickness of the adhesive layer is preferably 1 μm to 5 μm. Sufficient adhesive strength can be obtained when the thickness is 1 μm or more, and the texture of the multilayer film can be maintained in a flexible state when the thickness is 5 μm or less, and the time until the adhesive is cured remains within a relatively short range. Is also good. The first strong adhesive layer 3 and the second strong adhesive layer 6 may have the same thickness or different thicknesses, but considering productivity, the thickness is almost the same unless there is a particular problem. Is desirable.

  When the extrusion laminating method is selected, an anchor coating agent (hereinafter referred to as AC agent) is applied on the weak adhesive layer 5 on the polyamide layer 4 as the second strong adhesive layer 6, and the second heat sealability is applied thereon. The polyolefin layer 7 may be extruded and bonded. Further, an AC agent is applied as the first strong adhesive layer 3 on the polyamide layer 4, and the first heat-sealable polyolefin layer 2 is extruded and bonded thereon. Any known AC agent can be used. For example, there are organic titanium-based AC agents, urethane-based AC agents, polyethyleneimine-based AC agents, polybutadiene-based AC, etc. Among them, the two-component curable urethane-based AC agent has adhesive performance, suitability for laminating, and resistance to physical properties. Since it is excellent, it is preferably used.

  The first strong adhesive layer 3 and the second strong adhesive layer 6 may have the same composition or different compositions. However, considering productivity, the first strong adhesive layer 3 and the second strong adhesive layer 6 have the same composition as long as there is no problem. Is desirable. The thickness of the first strong adhesive layer 3 and the second strong adhesive layer 6 is not particularly limited, and an appropriate thickness may be determined depending on the selected AC agent. In general, the thickness of the AC agent in the extrusion laminating method is often thinner than the thickness of the adhesive in the dry laminating method, and even the thickest two-component curable urethane AC agent is 2 μm or less.

  When the coextrusion molding method is selected, an adhesive resin is used for the first strong adhesive layer 3 and the second strong adhesive layer 6. Here, the adhesive resin is a resin that exhibits adhesiveness to both the polyamide resin and the polyolefin resin by a coextrusion molding method, and any of known resins can be used. A typical example is a maleic acid-modified polyolefin resin, and the polyolefin component is preferably similar to the polyolefin resin to be bonded. The thickness of the adhesive layer is preferably 1 μm to 10 μm. When the thickness is 1 μm or more, sufficient adhesive strength is obtained, and when the thickness is 10 μm or less, sufficient strength as a multilayer film is obtained.

  The weak adhesive layer 5 is set so that the adhesive force to the polyamide layer 4 is weaker than the adhesive force between the first strong adhesive layer 3 and the polyamide layer 4, and the second strong adhesive layer 6 The adhesive strength is a layer set to be equal to the adhesive strength between the first strong adhesive layer 3 and the polyamide layer 4, that is, to be strongly adhered. The weak adhesive layer 5 plays a role of stably and reliably causing peeling at the interface between the weak adhesive layer 5 and the polyamide layer 4 when the package is opened. Thereby, it becomes possible to open the package stably and easily.

  The content of the weak adhesive layer 5 varies depending on the selection of the lamination method of each layer. When the dry laminating method or the extrusion laminating method is selected, a solution that can form the weak adhesive layer 5 is applied to the surface of the polyamide film. The solution that can be used is a solution in which a resin component is dissolved in a volatile solvent, and is a solution that exhibits weak adhesion to a polyamide resin in a state where the resin component is dried and solidified after being coated and laminated. Examples of the resin component contained in the solution include a vinyl chloride-vinyl acetate copolymer and a urethane resin. Among them, the urethane resin is preferable because it exhibits an appropriate weak adhesive strength while being excellent in content resistance. The volatile solvent is not particularly limited as long as it is a volatile solvent capable of dissolving the resin component.

  The solid content concentration of the solution is preferably 5 to 30% by mass, and the viscosity of the solution is preferably in the range of 10 cp to 1000 cp. Examples of such a solution include a vehicle for printing ink, and a vehicle for gravure printing ink is particularly preferable from the viewpoints of adhesive strength and drying properties. The thickness of the weak adhesive layer 5 is preferably 0.5 μm to 2 μm. A minimum adhesive strength of 0.5 μm or more that does not cause trouble as a multilayer film can be secured, and a thickness of 2 μm or less remains within the range where the adhesive strength does not become too large, which is necessary for the weak adhesive layer 5. The condition can be met. Further, the multilayer film may be colored by mixing a pigment or the like as a colorant in the printing vehicle.

  When the coextrusion molding method is selected, a low adhesive resin is used for the weak adhesive layer 5. The low-adhesion resin referred to here is a resin that exhibits adhesion to both polyamide resin and polyolefin resin by co-extrusion molding, but has a weak adhesive force, and uses any known one. be able to. For example, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid ester copolymer, etc. are mentioned. In this case, the thickness of the weak adhesive layer 5 is preferably 1 μm to 10 μm. When the thickness is 1 μm or more, a minimum adhesive strength that does not cause trouble as a multilayer film can be secured, and when the thickness is 10 μm or less, sufficient strength to function as a multilayer film can be obtained.

  In the multilayer film 1, the adhesive strength of weak adhesion between the weak adhesion layer 5 and the polyamide layer 4 is preferably 0.2 N / 15 mm or more and less than 2 N / 15 mm. The adhesive strength between the weak adhesive layer 5 and the polyamide layer 4 is 0.2 N / 15 mm or more, and the integrity as a multilayer film is sufficient, and it peels off during packaging work or storage after becoming a package. This reduces the risk of failure. Moreover, when the adhesive strength between the weak adhesive layer 5 and the polyamide layer 4 is less than 2N / 15 mm, it becomes a state that can be easily and easily peeled when the packaging body is opened, and the opening property of the packaging body becomes good. .

  On the other hand, it is preferable that the adhesive strength between the polyamide layer 4 and the first strong adhesive layer 3, which are strong adhesives, be 2N / 15 mm or more. The adhesive strength between the polyamide layer 4 and the first strong adhesive layer 3 is 2N / 15 mm or more, the strength of the heat seal part of the package is sufficient, and during storage by heat sterilization work or after becoming a package The risk of breaking and becoming defective is reduced. There is no upper limit on the adhesive strength between the polyamide layer 4 and the first strong adhesive layer 3, but it is naturally limited by the strength of each resin layer constituting the multilayer film 1. The same applies to the adhesive strength between the weak adhesive layer 5 and the second strong adhesive layer 6.

  Furthermore, the difference between the adhesive strength between the polyamide layer 4 and the first strong adhesive layer 3 and the adhesive strength between the weak adhesive layer 5 and the polyamide layer 4 is preferably 1.0 N / 15 mm or more. . The difference between the adhesive strength between the polyamide layer 4 and the first strong adhesive layer 3 and the adhesive strength between the weak adhesive layer 5 and the polyamide layer 4 is 1.0 N / 15 mm or more, and when the package is opened Peeling occurs reliably between the weak adhesive layer 5 and the polyamide layer 4, and peeling between the polyamide layer 4 and the first strong adhesive layer 3 is less likely to occur. In addition, when peeling occurs between the polyamide layer 4 and the first strong adhesive layer 3 at the time of opening the package, as described later, the heat seal layer 7 remains in a state where the contents are sealed. Therefore, opening will be hindered. There is no particular upper limit on the difference between the adhesive strength between the polyamide layer 4 and the first strong adhesive layer 3 and the adhesive strength between the weak adhesive layer 5 and the polyamide layer 4. Due to the adhesive strength with the strong adhesive layer 3, an upper limit is naturally generated.

  In addition, the measurement of the adhesive strength between the layers is performed by peeling the multilayer film slightly at the interface between the corresponding layers, and the angle between the peeled layers with the peeling start portion being the boundary between the peeled portion and the non-peeled portion as the center. Is measured by a method in accordance with JIS Z1707, 7.5 “Heat seal strength test” except that the angle is opened at 180 ° and both ends thereof are attached to both grips of a tensile tester. In addition, the interval between the gripping tools at the time of measurement is 50 mm, and the test speed is 300 mm / min.

  Next, FIG. 2 shows a packaging precursor 10 formed by rolling the multilayer film 1 so that the first heat-sealable polyolefin layer 2 is inside the cylinder, and is rounded so as to slightly exceed one circumference. It is the figure which showed the cross section of this. 2, the first heat-sealable polyolefin layer 2 at the end that is the outer side of the overlap part 11 in FIG. It overlaps with a certain width so that it touches. That is, it exceeds the circumference by the width of the overlap portion 11.

  And in the overlap part 11, it heat-seals along the axial direction of a package so that it may become a fixed width | variety at a right angle direction with respect to the axial direction of a cylinder, and the heat seal part 12 is formed. Thereby, the side part of a package is sealed. The heat seal portion 12 is not provided on the entire surface of the overlap portion 11, but the overlap portion 12 is divided into at least two portions along the circumferential direction of the cylinder and is not heat sealed to the end portion of the outer end portion. The unheat-sealed portion 13a is formed so as to be a pinch allowance when opened, leaving the portion 13a. Furthermore, it is preferable to divide the overlap part 11 into three parts and leave a part 13b that is not heat-sealed at the end part of the inner end part. Thereby, even if the position of the heat seal part 12 shifts somewhat, the package can be produced stably.

  FIG. 3 is a perspective view of the package 20 sealed by filling the contents into the cylindrical package precursor 10 and ligating both ends in the axial direction of the package precursor 10 with metal wires 22. The overlap part of the package 20 is also provided with the heat seal part 12 and the non-heat seal part 13a similar to those described in FIG. Furthermore, innumerable scars 21 as opening means are continuously given along the end side along the end side. The shape of the scar 21 and the method of applying it are not limited. For example, so-called magic cut (registered trademark) processing is useful. The scar 21 is not limited to a continuous one, and may be partially provided at one place or a plurality of places. Further, as other opening means, notches such as I notches and V notches may be provided, and the number thereof may be one or plural. There is no limitation on the method of making a scar or notch, and each can be made according to a known method. Moreover, these opening means may be provided in the film processing stage before the packaging stage, and may be inserted before or after the heat sealing in the packaging stage.

  The sealing means at both ends in the axial direction of the package 20 may be other known methods in addition to the method of ligating with the metal wire 22, for example, the method of ligating with a plastic clip or the method of sealing with heat sealing. be able to.

  FIG. 4 is a cross-sectional view schematically showing a state when the package 20 is opened. When the unheat-sealed portion 13a is picked and cut out from the scar 21 and the package 20 is opened, the heat-sealed portion 12 is reached. Here, in the multilayer film 1, since the adhesive strength between the weak adhesive layer 5 and the polyamide layer 4 is weak, the second heat-sealable polyolefin layer 7 and the second strong adhesive layer 6 having relatively low film strength, The weak adhesive layer 5 breaks and the interface between the weak adhesive layer 5 and the polyamide layer 4 having a relatively high film strength begins to peel off. Furthermore, when the unheat-sealed portion 13a is peeled off, the separation between the weak adhesive layer 5 and the polyamide layer 4 reaches from the unheat-sealed portion 13b to the edge of the inner film, and the opening is completed with this. To do.

The first heat-sealable polyolefin layer 2 at the outer end portion does not break after reaching the heat-seal portion 11 because the polyolefin layer 2 is made of the polyamide layer 4 having a high breaking strength and the first strong adhesive layer 3. This is because it is firmly bonded and integrated with the polyamide layer 4 to resist breakage. That is, which of the heat-sealable polyolefin layer 2 and the layer 7 having a weak strength against breakage is uniquely determined by which of the polyamide layer 4 having a strong strength against breakage is peeled off. In the multilayer film 1, by providing the weak adhesive layer 5 as described above, the second polyolefin layer 7 at the inner end always breaks, and the interface between the weak adhesive layer 5 at the inner end and the polyamide layer 4 is surely formed. Can be opened stably and reliably.
[Example]

EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to the specific aspect of the following Example. In addition, the measuring method and evaluation method in an Example are as follows.
(1) Adhesive strength between polyamide layer of multilayer film and heat-sealable polyolefin layer

The polyamide layer of the multilayer film and the heat-sealable polyolefin layer on the corresponding side are peeled off by a certain distance, and the cellophane tape No. 29 was pasted and reinforced. This was cut out to a width of 15 mm to obtain a test piece. In addition, the test piece was cut out so that it might peel in the width direction of a film. Next, the side of the tensile tester RTC-1210A manufactured by Orientec Co., Ltd., on which the polyamide layer and the polyolefin layer were laminated on the lower gripping tool, the polyolefin on the other side which had been peeled off first on the upper gripping tool. The layer part was attached. The test piece was supported so that the angle between each peeled layer was 180 °, and the angle between the unpeeled portion and the peeled portion was 90 °, and the distance between the upper and lower grips was 50 mm. The upper gripping tool was pulled up at a speed of 300 mm / min. The measurement was performed under the conditions of 23 ° C. and 50 RH%, and five test pieces were measured and averaged.
(2) Evaluation of unpacking property of package 1

While slitting the multilayer film to a width of 64 mm, scratches were made on both ends of the film by magic cutting. Using this film, 20 g of fish sausage was filled and packaged with a vertical casing filling and packaging machine, and both ends were ligated with metal wires to form a cylindrical sealed package. This was retort sterilized at 120 ° C. for 30 minutes. The package was cut out by pulling the picking allowance of the unheat-sealed part, and the unsealing property was evaluated. The case where the second polyolefin layer at the inner end portion from the heat seal portion was broken and peeled stably from the polyamide layer and could be easily opened was indicated as “◯”. The case where peeling was not stable and a part of the film remained for a long time was defined as “Δ”. The case where the first polyolefin layer at the outer end portion was broken and peeled from the polyamide layer, or when all of the multilayer film was broken was designated as “x”. 100 packaging bodies were opened and the number of applicable peeling situations was counted.
(3) Evaluation of unpacking property of package 2

  While slitting the multilayer film to a width of 64 mm, scratches were made on both ends of the film by magic cutting. Using this film, 20 g of meat sausage was filled and packaged with a vertical casing filling and packaging machine, and both ends were ligated with metal wires to form a cylindrical sealed package. This was sterilized by retort at 80 ° C. for 30 minutes. This package was cut out from the end of the unheat-sealed part and evaluated for openability. The case where the polyolefin layer outside the heat seal part was broken and stably peeled from the polyamide layer and could be easily opened was indicated as “◯”. The case where peeling was not stable and a part of the film remained for a long time was defined as “Δ”. The case where the inner polyolefin layer was broken and peeled from the polyamide layer, or when all of the multilayer film was broken was designated as “x”. 100 packaging bodies were opened and the number of applicable peeling situations was counted.

  As the polyamide layer 4, heat shrinkable multilayer nylon film “Heptax VPS” (thickness 22 μm) manufactured by Gunze Co., Ltd. is used. On the untreated surface of the corona treatment, the ink vehicle “NB300” manufactured by Dainichi Seika Co., Ltd. is dried by the gravure method. The weak adhesive layer 5 was formed by coating to 1 μm. Next, the second strong adhesive layer 6 is applied on the weak adhesive layer 5 so as to have a dry thickness of 3 μm, and an unstretched polypropylene film (thickness 15 μm) is formed as the heat-sealable polyolefin layer 2 by a dry laminating method. Was pasted together. Next, the first strong adhesive layer 3 is applied on the polyamide layer 4 so as to have a dry thickness of 3 μm, and an unstretched polypropylene film (thickness of 15 μm) is dried as the first heat-sealable polyolefin layer 2. A multilayer film 1 having a thickness of 59 μm was produced by laminating by a laminating method. As the adhesive layer, a mixture of two-component curable urethane adhesive TM-250V manufactured by Toyo Morton Co., Ltd. and CAT-RT86-60 was used on both sides at a specified compounding ratio.

  Next, the adhesive strength between the polyamide layer 4 and the second polyolefin layer 7 of the multilayer film 1 was measured according to the evaluation method (1). Further, the adhesive strength between the polyamide layer 4 and the first polyolefin layer 2 was measured. The results are shown in Table 1. In peeling between the polyamide layer 4 and the second polyolefin layer 7, peeling was made between the polyamide layer 4 and the weak adhesive layer 5, and the adhesive strength was 1.1 N / 15 mm width. In the peeling between the polyamide layer 4 and the first polyolefin layer 2, the peeling was made between the first polyolefin layer 2 and the first strong adhesive layer 3, and the adhesive strength was 4.1 N / 15 mm width. .

  Next, according to the evaluation method of said (2), the package was created so that the 2nd polyolefin layer 7 might become an outer side, and openability was evaluated. The results are shown in Table 1. All 100 packaging bodies were evaluated as “◯”, indicating good openability.

  As the polyamide layer 4, heat shrinkable multilayer nylon film “Heptax VPS” (thickness 22 μm) manufactured by Gunze Co., Ltd. is used. On the untreated surface of the corona treatment, the ink vehicle “NB300” manufactured by Dainichi Seika Co., Ltd. is dried by the gravure method. The weak adhesive layer 5 was formed by coating to 1 μm. Next, a second strong adhesive layer 6 is applied on the weak adhesive layer 5 of this film so as to have a dry thickness of 1 μm, and a heat sealable polyolefin layer 2 is formed on the linear chain made by Prime Polymer Co., Ltd. Low density polyethylene “Ultzex 2081C” was bonded by an extrusion laminating method so as to have a thickness of 20 μm.

  Next, the first strong adhesive layer 3 is applied on the polyamide layer 4 of this film so as to have a dry thickness of 1 μm, and the first heat-sealable polyolefin layer 2 is made of Prime Polymer Co., Ltd. Density polyethylene “Ultzex 2081C” was laminated by an extrusion laminating method so as to have a thickness of 20 μm to produce a multilayer film 1 having a thickness of 65 μm. As the adhesive layer, a mixture of two-component curable urethane anchor coating agent LX-901 and KW40 manufactured by Dainippon Ink & Chemicals, Inc. at a specified blending ratio was used on both sides.

  Next, the adhesive strength between the polyamide layer 4 and the polyolefin layer 2 or 7 of the multilayer film 1 was measured according to the evaluation method (1). The results are shown in Table 1. In peeling between the polyamide layer 4 and the second polyolefin layer 7, peeling was made between the polyamide layer 4 and the weak adhesive layer 5, and the adhesive strength was 0.8 N / 15 mm width. In peeling between the polyamide layer 4 and the first polyolefin layer 2, peeling was made between the first polyolefin layer 2 and the first strong adhesive layer 3, and the adhesive strength was 2.7 N / 15 mm width.

  Next, according to the evaluation method of (3) above, a cylindrical package was prepared so that the second polyolefin layer 7 was on the outside, and the unsealing property was evaluated. The results are shown in Table 1. All 100 packaging bodies were evaluated as “◯”, indicating good openability.

Comparative Example 1

  As the polyamide layer 33, a heat shrinkable multilayer nylon film “Heptax VPS” (thickness 22 μm) manufactured by Gunze Co., Ltd. is used, and the adhesive layer 32 is applied on the surface of one side so as to have a dry thickness of 1 μm. As the polyolefin layer 31, a linear polymer low-density polyethylene wurtzex 2081C manufactured by Prime Polymer Co., Ltd. was bonded by an extrusion laminating method so as to have a thickness of 20 μm. Next, the adhesive layer 34 is coated on the polyamide layer 33 of the film so as to have a dry thickness of 1 μm, and a linear low density polyethylene urgent xex 2081C manufactured by Prime Polymer Co., Ltd. is used as the heat-sealable polyolefin layer 35. The multilayer film 30 having a thickness of 65 μm was manufactured by pasting by an extrusion laminating method so as to have a thickness of 20 μm. As the adhesive layer, a mixture of two-component curable urethane anchor coating agent LX-901 and KW40 manufactured by Dainippon Ink & Chemicals, Inc. at a specified blending ratio was used on both sides.

  Next, the adhesive strength between the polyamide layer 33 and the polyolefin layer 31 or 35 of the multilayer film 30 was measured according to the evaluation method (1). The results are shown in Table 1. In peeling between the polyamide layer 33 and the polyolefin layer 31, peeling was performed between the layer 31 and the adhesive layer 32, and the adhesive strength was 2.6 N / 15 mm width. In peeling between the polyamide layer 33 and the polyolefin layer 35, peeling was performed between the layer 35 and the adhesive layer 34, and the adhesive strength was 2.8 N / 15 mm width.

  Next, according to the evaluation method of (3) above, 100 packages were prepared so that the polyolefin layer 31 was on the outside, and the unsealing property was evaluated. The results are shown in Table 1. Of the 100 packages, 18 “Δ” and 82 “×” were found, there was no “◯”, and the openability was poor.

  FIG. 5 schematically shows a cross-section in a state where opening has begun in one of the packages having an openability evaluation result of “x”. Since there is no weak adhesive layer, the opening force is applied to the first heat-sealable polyolefin layer 35 and a tear is formed, and between the second strong-adhesive layer 34 and the first heat-sealable polyolefin layer 35. Peeling progressed. Even if the unsealing is continued as it is, the polyolefin layer 35 always remains on the contents, so that the unsealing was impossible.

Comparative Example 2

  As the polyamide layer 43, a heat-shrinkable multilayer nylon film “Heptax VPS” (thickness 22 μm) manufactured by Gunze Co., Ltd. is used, and the second strong adhesion layer 42 is applied on the surface of one side so as to have a dry thickness of 3 μm. As the heat-sealable polyolefin layer 41, an unstretched polypropylene film (thickness 15 μm) was bonded by a dry laminating method. Next, the first strong adhesive layer 44 is applied on the polyamide layer 43 of the film so as to have a dry thickness of 3 μm, and an unstretched polypropylene film (thickness of 15 μm) is dried as the heat-sealable polyolefin layer 45. A multilayer film 40 having a thickness of 59 μm was produced by laminating by a laminating method. As the adhesive layer, a mixture of two-component curable urethane adhesive TM-250V and CAT-RT86-60 manufactured by Toyo Morton Co., Ltd. was used on both sides.

  Next, the adhesive strength between the polyamide layer 43 of the multilayer film 40 and the polyolefin layers 41 and 45 was measured according to the evaluation method of (1) above. The results are shown in Table 1. In the peeling between the polyamide layer 43 and the polyolefin layer 41, the peeling was made between the layer 41 and the second strong adhesive layer 42, and the adhesive strength was 4.0 N / 15 mm width. In peeling between the polyamide layer 43 and the polyolefin layer 45, peeling was made between the layer 45 and the first strong adhesive layer 44, and the adhesive strength was 4.2 N / 15 mm width.

  Next, according to the evaluation method of (2) above, 100 packages were prepared so that the polyolefin layer 41 was on the outside, and the unsealing property was evaluated. The results are shown in Table 1. Of 100 packages, “Δ” was 23, “X” was 77, “◯” was absent, and the unsealing property was poor.

  In FIG. 6, the cross section of the state produced with the package whose sealing performance evaluation result was "x" is shown typically. With the openability evaluation, the first polyolefin layer 45 at the outer end portion was broken, and all the other layers of the multilayer film 40 were broken at the same time, and could not be opened.

1 is a schematic diagram showing a schematic cross-sectional configuration of a multilayer film 1. FIG. It is the schematic diagram which showed the cross-sectional structure of the cylindrical packaging precursor formed using the multilayer film 1. FIG. It is the perspective view which showed the package 20 which formed the multilayer film 1 in the cylinder shape, filled the contents, and sealed both ends. It is the schematic diagram which showed the state of the cross section at the time of opening the package which uses the multilayer film 1. FIG. It is the schematic diagram which showed the state of the cross section at the time of opening the package which uses the multilayer film of the comparative example 1. FIG. It is a schematic diagram which shows the cross-sectional structure at the time of opening the package which uses the multilayer film of the comparative example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Multilayer film 2 1st heat-sealable polyolefin layer 3 1st strong-adhesion layer 4 Weak-adhesion layer 5 Polyamide layer 6 2nd strong-adhesion layer 7 2nd heat-sealable polyolefin layer 10 Cylindrical packaging precursor 11 Overlap portion 12 Heat seal portion 13 Non-heat seal portion 20 Tubular package 21 Scar 22 Metal wire 30 Multilayer film 31 Second heat-sealable polyolefin layer 32 Second strong adhesion layer 33 Polyamide layer 34 First strong adhesion Layer 35 First heat-sealable polyolefin layer 36 Packaging 37 Overlap part 38 Heat-seal part 39 Non-heat-seal part 40 Multilayer film 41 Second heat-sealable polyolefin layer 42 Second strong adhesive layer 43 Polyamide layer 44 First 1 strong adhesive layer 45 First heat-sealable polyolefin layer 6 the tubular wrapper 47 overlap portion 48 heat-sealed portion 49 non heat-sealed portion

Claims (4)

A first heat-sealable polyolefin layer, a first strongly-adhesive layer, a polyamide layer, a weakly-adhesive layer that has a weak adhesion to the polyamide layer, a second strongly-adhesive layer, a second heat-sealable polyolefin layer, Each layer is laminated | stacked in order of these , The said weak adhesive layer is a layer which consists of a urethane resin or an ethylene-acrylic acid ester copolymer, The multilayer film characterized by the above-mentioned. The multilayer film is obtained by a dry lamination method or an extrusion lamination method, and a surface of the polyamide layer in contact with the first strong adhesive layer is previously oxidized, and the weak adhesive layer is made of urethane. The multilayer film according to claim 1 , wherein the multilayer film is a layer made of a resin . The multilayer film is obtained by a dry lamination method, and at least one of the first strong adhesive layer and the second strong adhesive layer is a layer made of a two-component curable urethane adhesive. The multilayer film according to claim 1, wherein: A cylindrical package using the multilayer film according to any one of claims 1 to 3 , wherein the second heat-sealable polyolefin layer is placed outside and an envelope is attached and the contents are packaged.

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