JP2011079584A - Packaging material and container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a packaging material and a container which have an appropriate degree of peeling strength, while causing no occurrence of paper peel-off of the container even if it is used for a lid material of a paper-made container, and which shows favorable easy-to-open property. <P>SOLUTION: The packaging material comprises a base material 3 whose one surface side has a heat sealing layer having a resin layer 2B and a resin layer 2A in this sequence, made into a laminated structure while the resin layer 2A and resin layer 2B are mutually laminated by way of a co-extrusion method. The resin layer 2A is constituted in the proportion of a low density polyethylene of 55 to 75 pts.wt. and polybutene-1 of 45 to 25 pts.wt., while MFR of the low density polyethylene is 0.5 to 50 as against MFR of polybutene-1 being 0.2 to 20, whereas the resin layer 2B is made of a resin selected from ethylene-methacrylic acid copolymer or low density polyethylene. If this packaging material is heat-sealed as a lid member of a paper cup container which has polyethylene of melting point 105 to 115°C coated as the innermost layer, the resin layer 2A is subjected to cohesion breakage upon unsealing. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a packaging material and a container.

  Easy-open packaging materials having easy peel properties are roughly classified into an interfacial peel type, an interlayer peel type, and an agglomerated peel type depending on the peel mechanism. Among these, the cohesive peeling type material exhibits easy peel properties by causing internal cohesive failure when the peel layer resin is opened. As cohesive release type materials, EVA-based materials blended with wax and binders, and incompatible polymer alloys such as polyolefin / polystyrene and polyethylene / polypropylene are known, and the seal temperature stability of peel strength is known. , It is characterized by excellent contamination sealing and content resistance. Here, “excellent in sealing property of impurities” means that excellent heat sealing performance is exhibited even when impurities having a relatively large particle size are mixed in the heat sealing material.

  However, the conventional easy-opening material belonging to the cohesive failure type has a problem that the peel layer resin remains on the fiber peeling surface on the seal peeling surface at the time of opening, so that a so-called “stringing phenomenon” is likely to occur. In addition, since it is difficult to control the peel strength, when the polyethylene coated paper is used as an adherend, the peel strength is too strong and the paper on the adherend is easily broken, so-called “paper peeling phenomenon” is likely to occur. There is also a problem.

  Furthermore, when a conventional easy-opening material is laminated on a base material such as paper, film, or metal foil by an extrusion laminating method or the like, the resulting easy-open packaging material is likely to curl, so heat-seal the container as a lid. There is also a problem that troubles often occur in supply and handling.

  An object of the present invention is to use a lid for a paper container having an appropriate peel strength (peeling strength) and having polyethylene coated on the innermost surface in the field of containers that peel and open a heat seal portion of a sealed container. However, it is an object to provide a packaging material and a container that do not cause the container to peel off and show good easy-openability.

  The easy-open packaging material according to the present invention includes at least a base material and a heat seal layer provided on one surface side of the base material, and the heat seal layer is formed from a resin layer (B ) And the resin layer (A) are provided in this order, and the resin layer (A) and the resin layer (B) are laminated together by a coextrusion method, and the resin The layer (A) comprises 55 to 75 parts by weight of low density polyethylene and 45 to 25 parts by weight of polybutene-1, and the MFR of the low density polyethylene is 0.5 to 50. The polybutene-1 has an MFR of 0.2 to 20, and the resin layer (B) is made of a resin selected from ethylene-methacrylic acid copolymer or low-density polyethylene. .

  In the easy-open container according to the present invention, the packaging material is heat-sealed as a cover material of a paper cup container in which polyethylene having a melting point of 105 to 115 ° C. is coated on the innermost layer, and the resin layer (A) is aggregated when opened. It is characterized by destruction.

  The thickness of the resin layer (A) is preferably in the range of 5 to 15 μm, and the thickness of the resin layer (B) is preferably equal to or greater than the thickness of the resin layer (A).

  Moreover, it is preferable that the low density polyethylene of the resin layer (A) is a high pressure method low density polyethylene having a melting point of 110 ° C. or lower, and the polybutene-1 is a homopolymer having a melting point of 120 ° C. or higher. Moreover, it is preferable that melting | fusing point of resin which comprises the said resin layer (B) is below the melting point of the low density polyethylene of the said resin layer (A).

Moreover, it is preferable that the said heat seal layer is laminated | stacked on the said base material by the coextrusion lamination method.

  The packaging material of the present invention has a heat seal layer including a peel layer. When the heat-sealed portion sealed by the heat-sealing method is peeled and opened using this packaging material, cohesive failure occurs in the peel layer, and easy-openability is exhibited. Moreover, no paper peeling occurs at the opening.

  And when this packaging material is used as a cover material for a paper cuff whose inner surface is made of polyethylene, a sealed paper cup having easy opening is obtained. The container thus obtained is extremely usable for consumers.

  FIG. 1 is a schematic cross-sectional view showing an example of the layer structure of the packaging material of the present invention. FIG. 2 is a schematic cross-sectional view showing another example of the layer structure of the packaging material of the present invention. FIG. 3 is a conceptual diagram for explaining a state when the packaging material of the present invention is peeled from the adherend, in which (a) is a heat-sealed state and (b) is a state where the heat-sealed part is peeled off. FIG. 4 shows an embodiment of a container using the packaging material of the present invention as a lid material, (a) is a perspective view of the container, (b) XX section sectional view, (c) seal part. It is sectional drawing, (d) It is a fragmentary sectional view of a peel part when a cover material is peeled.

  As shown in FIG. 1 or FIG. 2, the packaging material 1 of the present invention comprises at least a base material 3 and a heat seal layer 2, and the heat seal layer 2 is formed by laminating different resins from each other. It is composed of two layers (2A, 2B). In the example of FIG. 1, a heat seal layer is directly formed on a substrate 3 such as paper by an extrusion coating method. In the example of FIG. 2, the heat seal layer 2 is formed in advance, and the dry laminating method is performed. The adhesive 4 is used and bonded to a base material such as a plastic film.

  As the substrate, paper, metal foil, a single plastic film, or a laminate of two or more of these can be used. The plastic film may be a deposited film on which an oxide such as silica or alumina or a metal thin film such as aluminum is formed.

  As shown in FIG. 1, the heat seal layer 2 in the packaging material of the present invention has a resin layer 2A in which low density polyethylene is mixed at a ratio of 55 to 75 parts by weight and polybutene-1 at a ratio of 45 to 25 parts by weight; A resin layer 2B made of a resin selected from an ethylene-methacrylic acid copolymer or low-density polyethylene is laminated by a coextrusion method without using an adhesive layer. In the laminate with the base material 3, the heat seal layer 2 is laminated by arranging the resin layer 2B side made of a resin selected from the ethylene-methacrylic acid copolymer or low-density polyethylene on the base material side. In other words, the heat seal layer 2 is laminated with the resin layer 2B side facing the substrate.

  The mixture layer 2A of the low-density polyethylene and polybutene-1 forms a peel layer capable of causing cohesive failure when opened. Polybutene-1 is substantially incompatible with low-density polyethylene, and these mixtures form a so-called “sea-island structure”, thus reducing the cohesive strength of the peel layer and exhibiting an easy peel property of cohesive failure type. Can be made. When the blending ratio of polybutene-1 is less than 25% by weight, the peel strength is too strong, and therefore, when polyethylene coated paper is used as the adherend, paper peeling occurs. When the compounding ratio of polybutene-1 exceeds 45% by weight, the peel strength becomes insufficient, and stringing tends to occur.

  By providing the resin layer 2B made of a resin selected from ethylene-methacrylic acid copolymer or low-density polyethylene adjacent to the peel layer, the cohesive failure of the peel layer at the time of opening is near the boundary between the 2A layer and the 2B layer. It can be concentrated, the peel strength can be stabilized, and the occurrence of stringing can be suppressed. Further, by providing a resin layer 2B made of a resin selected from an ethylene-methacrylic acid copolymer or low-density polyethylene, the lamination strength when the heat seal layer 2 is laminated with the substrate 3 by a coextrusion laminating method, for example. There is an effect to increase.

  By laminating the 2A layer and the 2B layer, the heat seal layer can be easily formed at a predetermined layer ratio. As a method for laminating the heat seal layer 2 formed from the 2A layer and the 2B layer and the substrate 3, a dry laminating method, a sandwich laminating method, a coextrusion laminating method, or the like can be used.

  When the thickness of the 2A layer of the heat seal layer is less than 5 μm, the seal strength tends to be unstable, and the sealing of impurities is insufficient. Further, if the thickness of the 2A layer of the heat seal layer exceeds 15 μm, stringing tends to occur at the time of opening. On the other hand, when the thickness of the 2B layer forming the heat seal layer is thinner than the 2A layer, the curl when the heat seal layer is laminated with the base material is increased, and the 2A layer and 2B layer are laminated by the coextrusion method. It will also be difficult.

  When the melting point of the low density polyethylene contained in the 2A layer of the heat seal layer exceeds 110 ° C., the heat seal strength at a low temperature becomes weak, and stringing tends to occur. In addition, when linear low density polyethylene which is a copolymer of ethylene and α-olefin, so-called LLDPE, is used for the 2A layer, the sealing strength is increased and paper peeling tends to occur. As the low density polyethylene used for the 2A layer of the heat seal layer, a high pressure method low density polyethylene having a density of 0.915 to 0.920 and an MFR of 0.5 to 50, preferably 20 to 50 is suitable.

  When the melting point of polybutene-1 is less than 120 ° C., the sealing strength becomes strong, and paper peeling tends to occur during peeling. When a copolymer comprising butene-1 as a main component and the butene-1 and other olefins are copolymerized is used, the sealing strength is increased and paper peeling tends to occur. It is desirable to use polybutene-1 having a density of 0.905 to 0.917 and an MFR of 0.2 to 20.

  When the melting point of the resin constituting the 2B layer of the heat seal layer is higher than that of the low density polyethylene used for the 2A layer, stringing tends to occur during opening. As the low-density polyethylene of the 2B layer of the heat seal layer, for example, one having a melting point of 105 ° C., a density of 0.92, and an MFR of about 5 to 30 can be used.

  Hereinafter, the opening of the container using the packaging material of the present invention will be described. As shown in FIG. 3A, the heat seal layer of the packaging material 1 of the present invention is opposed to the heat seal layer of the adherend 10 and heat-sealed by a hot plate 30 to form the heat seal portion 13. . When the heat seal portion 13 is peeled off (opened), as shown in FIG. 3B, the cohesive failure 14 occurs in the 2A layer made of the blend resin of the heat seal layer 2 to show easy opening, No release surface is formed.

  When the base material 3 on which the heat seal layer 2 is laminated is a plastic film such as paper, aluminum foil, or polyethylene, the heat seal layer 2 composed of the 2A layer and the 2B layer is a coextrusion laminating method. Can be directly laminated on the base material, which simplifies the manufacturing process.

  The packaging material of the present invention can be suitably used as a lid member 21 that is heat-sealed to a polyethylene-coated paper cup container 22 as shown in FIG. The paper container presses the lip curl portion of the container body 22 to form a smooth flange 23 (see FIG. 5B), and the lid 21 is heat sealed to the flange portion and sealed. At the time of opening, the heat-sealed portion of the lid is peeled off. The packaging material of the present invention is used as a lid, and the peeled state for opening is shown in FIG. The paper container is widely used for foods such as instant noodles, yogurt, snacks, and natto. By using the packaging material of the present invention as a cover material for the paper container, it is possible to give excellent peelability to the peel surface, and to prevent stringing of the peeled surface conventionally observed in paper containers. I was able to.

  Next, the packaging material and container of the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

[Example 1] A mixture of 65 parts by weight of low density polyethylene (melting point 105 ° C) and 35 parts by weight of polybutene-1 (melting point 125 ° C) was used as a peel layer to form a first layer (thickness 10 µm). (Hereinafter referred to as “LDPE”) (melting point 105 ° C., density = 0.92, MFR = 7) is used as the second layer (thickness 20 μm), and the LDPE layer side is subjected to corona treatment while being subjected to ozone treatment. The paper (basis weight 100 g / m ² ) was subjected to coextrusion lamination at an extrusion temperature of 300 ° C. to obtain a packaging material having the following constitution.

Paper (100 g / m ² ) / LDPE (20 μm) / Peel layer (10 μm)

[Example 2] A mixture of 75 parts by weight of LDPE (melting point 106 ° C) and 25 parts by weight of polybutene-1 (melting point 125 ° C) was used as a first layer (thickness 9 µm) as a peel layer, and LDPE (melting point 105 ° C, With density = 0.92, MFR = 7) as the second layer (thickness 50 μm), while applying ozone treatment to the LDPE layer side, paper (basis weight 70 g / m ² ) and aluminum foil (thickness 7 μm) are intermediate Co-extrusion lamination is performed at an extrusion temperature of 280 ° C. on the aluminum foil surface (urethane primer coating treatment) of the base material bonded together by extrusion lamination method (so-called sandwich lamination method) using LDPE (thickness 20 μm) as a layer. A packaging material having the following constitution was obtained.

Paper (70 g / m ² ) / LDPE (20 μm) / Aluminum foil (7 μm) / LDPE (50 μm) / Peel layer (9 μm)

Example 3 A mixture of 70 parts by weight of LDPE (melting point 106 ° C.) and 30 parts by weight of polybutene-1 (melting point 125 ° C.) was used as a first layer (thickness 9 μm) as a peel layer, and LDPE (melting point 105 ° C.). , Density = 0.92, MFR = 20) as the second layer (thickness 50 μm), while applying ozone treatment to the LDPE layer side, paper (basis weight 70 g / m ² ) and aluminum foil (thickness 7 μm) Bonded by a wet laminating method, and further a biaxially stretched polyethylene terephthalate film (hereinafter referred to as a PET film) using a two-component curable polyurethane adhesive by a dry laminating method on the aluminum foil surface (urethane-based primer coated). ) Coextruded laminate at an extrusion temperature of 260 ° C. on the PET film surface (corona discharge treated) of the base material to which (thickness 12 μm) was bonded You have to give the packaging material of the following configuration.

Paper (70 g / m ² ) / Adhesive / Aluminum foil (7 μm) / Adhesive / PET film (12 μm) / LDPE (50 μm) / Peel layer (9 μm)

Comparative Example 1 A mixture of 80 parts by weight of LDPE (melting point 105 ° C.) and 20 parts by weight of polybutene-1 (melting point 125 ° C.) was used as a peel layer as a first layer (thickness 10 μm), and EMAA (ethylene-methacrylic acid) Copolymer) (melting point 98 ° C.) as a second layer (thickness 20 μm), co-extruded at a temperature of 300 ° C. extruded onto paper (100 g / m ² ) subjected to corona treatment while ozone treatment was applied to the EMAA layer side. Lamination was performed to obtain a packaging material having the following configuration.

Paper (100 g / m ² ) / EMAA (20 μm) / Peel layer (10 μm)

[Comparative Example 2] A mixture of 50 parts by weight of LDPE (melting point 105 ° C) and 50 parts by weight of polybutene-1 (melting point 125 ° C) was used as a peel layer as a first layer (10 µm), and EMAA (melting point 98 ° C) was used. As the second layer (20 μm), co-extrusion lamination was performed at a extrusion temperature of 300 ° C. on corona-treated paper (100 g / m ² ) while performing ozone treatment on the EMAA layer side to obtain a packaging material having the following configuration. .

Paper (100 g / m ² ) / EMAA (20 μm) / Peel layer (10 μm)

Comparative Example 3 A mixture of 65 parts by weight of linear low density polyethylene (hereinafter referred to as “LLDPE”) (melting point 110 ° C.) and 35 parts by weight of polybutene-1 (melting point 125 ° C.) as a peel layer The first layer (thickness 10 μm), EMAA (melting point 98 ° C.) as the second layer (thickness 20 μm), and the corona-treated paper (100 g / m ² ) while applying ozone treatment to the EMAA layer side. Coextrusion lamination was performed at an extrusion temperature of 300 ° C. to obtain a packaging material having the following constitution.

Paper (100 g / m ² ) / EMAA (20 μm) / Peel layer (10 μm)

<Test> Cup base paper (280 g / m ² ) obtained by extrusion coating of low-density polyethylene having a melting point of 106 ° C. with a thickness of 20 μm was formed into a cup shape having a flange portion, and the flange portion was prepared in Examples 1, 2, and 3. The packaging material was used as a lid, heat sealed under conditions of 150 ° C. and 0.6 sec, then opened, and the cross section of the peeled surface was observed with a microscope. Since the peel layer of the lid material was observed on both the lid material side and the cup side, it was confirmed that the peel layer was agglomerated and broken at the time of opening.

In addition, the packaging materials prepared in each Example and Comparative Example were subjected to the conditions of 140 ° C., 98 kPa, 1 sec on cup base paper (280 g / m ² ) coated with low-density polyethylene (thickness 20 μm) having a melting point of 106 ° C. The film was heat-sealed, and the peel strength and the presence or absence of paper peeling on the peeled surface were compared and evaluated.

  The easy-openability (peel strength) and the occurrence of paper peeling in Examples and Comparative Examples were as follows.

  The packaging materials of Examples 1, 2, and 3 showed an appropriate peel strength and were good without causing paper peeling on the release surface.

  In the packaging material of Comparative Example 1, since the blending ratio of polybutene-1 was too small, the peel strength was too strong and paper peeling occurred. In the packaging material of Comparative Example 2, since the blending ratio of polybutene-1 was too large, no paper peeling occurred, but the peel strength was too weak, which was not preferable. Since the packaging material of Comparative Example 3 used LLDPE instead of the LDPE of the first layer, the peel strength was too strong and paper peeling occurred.

In addition, the base material which has a layer structure of [Paper (260 g / m ² ) / LDPE (20 μm) / Aluminum foil (7 μm) / EMAA (12 μm) / LDPE (13 μm)] When used as a lid for a paper cup container for snacks molded using, it has an appropriate peel strength, does not cause paper peeling on the peeled surface, and obtains an easy-open container with excellent sealing and heat resistance I was able to.

It is typical sectional drawing which shows an example of the layer structure of the packaging material of wood invention. It is typical sectional drawing which shows another example of the layer structure of the packaging material of this invention. It is a conceptual diagram explaining the state when peeling the packaging material of this invention from a to-be-adhered body, (a) is the state which heat-sealed, (b) is the state which peeled the heat seal part. 1 shows an embodiment of a container using the packaging material of the present invention as a lid, (a) is a perspective view of the container, (b) X-X section sectional view, (c) a seal section partial sectional view, (D) It is a fragmentary sectional view of a peel part when a cover material is peeled.

DESCRIPTION OF SYMBOLS 1 Packaging material 2 Heat seal layer 3 Base material 4 Adhesive layer 10 To-be-adhered body 11 To-be-adhered body heat-sealing layer 13 Heat-sealing part 14 Peeling part 20 Container 21 Lid 22 Container main body 23 Flange part 30 Hot plate

Claims (4)

  It comprises at least a base material and a heat seal layer provided on one surface side of the base material, and the heat seal layer comprises a resin layer (B) and a resin layer (A) from the side close to the base material. The resin layer (A) and the resin layer (B) are laminated together by a co-extrusion method, and the resin layer (A) is made of low-density polyethylene. 55 to 75 parts by weight and 45 to 25 parts by weight of polybutene-1 and the MFR of the low density polyethylene is 0.5 to 50, and the MFR of the polybutene-1 is 0. 0.2 to 20, and the resin layer (B) is made of a resin selected from an ethylene-methacrylic acid copolymer or low-density polyethylene.   The low-density polyethylene constituting the resin layer (A) is a high-pressure method low-density polyethylene having a melting point of 110 ° C. or lower, and the polybutene-1 is a homopolymer having a melting point of 120 ° C. or higher. The easy-open packaging material according to claim 1, wherein the melting point of the resin constituting B) is not more than the melting point of the low-density polyethylene constituting the resin layer (A).   The easy-open packaging material according to claim 1 or 2, wherein the heat seal layer is laminated on the substrate by a coextrusion laminating method.   The easy-open packaging material of any one of Claims 1-3 is heat-sealed as a cover material of the paper cup container which coat | covered polyethylene of melting | fusing point 105-115 degreeC in the innermost layer, and the said resin layer ( An easy-open container characterized in that A) cohesively breaks.

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