JP2009083164A - Multilayer laminated film having easy peelability - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer laminated film with both practicality and good appearance, which is excellent in peelability when used as a lid material for a container, suppresses a break in a substrate and a tear in the film when peeled off, and prevents the appearance from being damaged, and further is prevented from being damaged in appearance due to cobwebbing of a peel part or the like, and a packaging container using the laminated film. <P>SOLUTION: In the multilayer laminated film having a seal layer (A) and a substrate layer (B), on the seal layer (A) made of a mixture comprising 20-60 pts.wt. of high density polyethylene and 40-80 pts.wt. of polypropylene, at least one substrate layer (B) made of an ethylene-propylene copolymer having a density of 0.90-0.91 g/cm<SP>3</SP>which is polymerized by using a metallocene catalyst is laminated. The thickness of the seal layer (A) is 1-20 μ, and the thickness of the substrate layer (B) is 20-100 μm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is a multilayer laminated film mainly used as a lid for packaging containers for foods, chemical products, etc. in the field of soft packaging, and has a sufficient sealing property and an excellent opening property. The present invention relates to a multilayer laminated film having both practicality and aesthetics, and a packaging container using the same as a lid, without causing breakage and tearing of the film, and without impairing the appearance by stringing the peel portion.

  The multilayer laminated film of the present invention can be produced by various methods known to those skilled in the art, and in particular, can be suitably produced by an inflation film forming method.

  In recent years, packaging containers are required to have sufficient hermeticity for protecting and preserving the contents, and also required to be easily opened (easy peel) that can be easily opened when consumed. Various proposals have been made as packaging films having both practical sealing properties and easy opening properties.

For example, as a film for easy opening, a heat-sealable laminated film (see Patent Document 1) consisting of two layers of a blend layer of various acrylic acid copolymers and polyethylene, or a base material layer made of polypropylene A film in which a three-component blend layer of polybutene, polypropylene and polyethylene is laminated (see Patent Document 2), a multilayer film having a layer made of a mixture of a methacrylic acid copolymer and polypropylene and a polyethylene sealant layer (see Patent Document 3) ) Has been developed.
JP-A-5-212835 JP-A-6-328639 JP 2002-283513 A

  However, conventional films intended for easy opening have a high material cost, a low degree of freedom in film forming conditions (blending conditions, etc.), and heat resistance such as polybutene for the purpose of improving low temperature sealing properties. Therefore, the appearance is impaired by stringing the peel part. Furthermore, when polyethylene was used for the base material layer of the film, the base material was easily broken when the lid was peeled off, and when polypropylene was used, the film was easily torn.

Then, as a result of studying to solve the above problems, the present inventors have a sealing layer (A) and a base material layer (B) as a multilayer laminated film for a lid of a packaging container excellent in easy-openability. A multilayer laminated film having a density of 0.90 g / cm ³ polymerized using a metallocene catalyst on a sealing layer (A) comprising a mixture of 20 to 60 parts by weight of high density polyethylene and 40 to 80 parts by weight of polypropylene One or more base layers (B) made of an ethylene / propylene copolymer of 0.91 g / cm ³ are laminated, and the layer thickness of the sealing layer (A) is 1 μm to 20 μm. A multilayer laminated film having a material layer (B) thickness of 20 μm to 100 μm was developed.

  The multilayer laminated film for the lid of the packaging container of the present invention not only has an excellent easy-opening property, but also is less susceptible to substrate breakage and film tearing at the time of peeling, and has less stringing at the peel portion. Is beautiful and excellent in both practicality and aesthetics.

  The sealing layer (A) of the multilayer laminated film of the present invention is composed of incompatible high-density polyethylene and polypropylene, and among these resins, the higher component ratio forms the sea, and the lower component ratio forms the island. Take a sea-island structure.

  In the present invention, a desired cohesive fracture strength can be achieved by controlling the sea-island structure by controlling the MFR (melt mass flow rate) of the resin. Moreover, by taking such a structure, this invention can reduce the cost concerning manufacture compared with the conventional easy-open film.

  The base material layer (B) of the multilayer laminated film of the present invention comprises an ethylene / propylene copolymer. Since this resin has a higher breaking strength than polyethylene, it is difficult for the base material to break when the lid is peeled off. In addition, since the tear strength is greater than that of polypropylene, it is possible to prevent the film from tearing when the lid member is peeled off.

The present invention will be described in detail below.
The multilayer laminated film of the present invention has a seal layer (A) and one or more base material layers (B), and optionally a surface base material layer (C).
<1> Seal layer (A)
Hereinafter, the resin names used in the present invention are those commonly used in the industry. In the present invention, the density was measured according to “JIS K7112”.
(1) High-density polyethylene constituting the seal layer (A) In the present invention, polyethylene includes ethylene homopolymer and ethylene and other α-olefins (for example, propylene, 1-butene, 1-pentene, 1-hexene). , 1-octene and the like) or random copolymers.
The high-density polyethylene constituting the sealing layer (A) uses a resin having a relatively high melt viscosity with a density of 0.945 to 0.965 g / cm ³ and an MFR (190 ° C.) of 1 to 7 g / 10 min. To do.

In the above, if the density is less than 0.945 g / cm ³ , stringing is likely to occur, and if it exceeds 0.965 g / cm ³ , the low-temperature sealing property is lost, which is not preferable.
If the MFR (190 ° C.) is less than 1 g / 10 min, the flowability is lowered, making the production difficult, and in addition, causing a poor compatibility with the high MFR polypropylene. Is not preferable. On the other hand, if it exceeds 7 g / 10 minutes, the difference from the MFR of polypropylene disappears, so that the degree of mutual dispersion increases and the desired easy-openability cannot be obtained, which is not preferable. Here, MFR (190 ° C.) was measured in accordance with “JIS K6922”.
Suitable high-density polyethylene used in the present invention includes, for example, Hi-Zex 3300F manufactured by Prime Polymer Co., Ltd.

(2) Polypropylene constituting the seal layer (A) In the present invention, polypropylene includes a propylene homopolymer and a block or random copolymer of propylene and another α-olefin.
As the polypropylene constituting the sealing layer (A), a resin having a density of 0.9 to 0.91 g / cm ³ and an MFR (230 ° C.) of 5 to 30 g / 10 min is used. In order to obtain an appropriate seal strength, an ethylene / propylene random copolymer is particularly preferable. In the block copolymer, since polypropylene is present in a block shape, the adhesive strength becomes too high and good easy-openability may not be obtained.

In the above, if the MFR (230 ° C.) is less than 5 g / 10 min, it is compatible with the low MFR high-density polyethylene and becomes in a finely dispersed state, so that sufficient easy-openability cannot be obtained. Moreover, when MFR (230 degreeC) exceeds 30 g / 10min, since fluidity | liquidity is too high, it cannot manufacture by an inflation film forming method. Here, MFR (230 ° C.) was measured according to “JIS K6921”.
Examples of suitable polypropylene used in the present invention include J235T manufactured by Prime Polymer Co., Ltd. and FW4BT manufactured by Nippon Polypro Co., Ltd.

(3) Blend ratio It is preferable that the blend ratio of the high-density polyethylene and polypropylene in the seal layer (A) is composed of 20 to 60 parts by weight of high-density polyethylene and 40 to 80 parts by weight of polypropylene. The blend ratio can be changed according to the adhesive strength.
If the ratio of polypropylene is higher than the above range, the adhesive strength becomes too high and good easy-openability cannot be obtained, and if the ratio is low, sufficient adhesive strength cannot be obtained and the sealing performance as a packaging container cannot be satisfied. .

<2> Base material layer (B)
The base material layer (B) of the multilayer laminated film of the present invention, in combination with the sealing layer (A), not only contributes to easy opening, but also provides strength and boil treatment for serving as a lid for packaging containers. Heat resistance that can withstand heat treatment such as, and film formation stability are also required. In the present invention, an ethylene / propylene copolymer is used as a resin that satisfies such various requirements. In particular, an ethylene / propylene copolymer polymerized using a metallocene catalyst is preferable from the viewpoint of film formation stability because the molecular weight distribution is sharp.
As for a base material layer (B), 1 layer or 2 layers or more can be laminated | stacked as needed.

<3> Surface base material layer (C)
When producing by the inflation film-forming method, in order to improve the film-forming stability of the film, a surface base material layer (C) may be further laminated on the base material layer (B) of the multilayer laminated film of the present invention. it can. In the present invention, a high-viscosity ethylene / α-olefin copolymer having a density of 0.91 g / cm ^{3 to} 0.94 g / cm ³ is used as the resin constituting the surface base material layer (C). In particular, those polymerized using a metallocene catalyst are preferred for the same reason as described above. If the density is 0.91 g / cm ³ or less, the heat resistance is inferior, and if it is 0.94 g / cm ³ or more, the adhesive strength with the metallocene substrate layer (B) decreases, and the substrate layers (B) and ( C) is not preferable because it can be peeled off.

<4> Layer thickness The seal layer (A) has a layer thickness of 20 μm or less, preferably 10 μm or less. If it exceeds 20 μm, the release layer (cohesive failure layer) becomes dirty and the release surface is inferior in beauty. Moreover, regarding the base material layer (B), a layer thickness of 20 μm to 100 μm is preferable from the viewpoint of easy cutting.

<5> Physical property Next, the factor at the time of setting the physical property requested | required of the multilayer laminated film for lid | cover materials of the packaging container of this invention is demonstrated.
(1) Cohesive failure strength The easy-opening property or the cohesive failure strength of the multilayer laminated film for lids of the packaging container of the present invention is controlled by changing the blending ratio of high-density polyethylene and polypropylene used in the seal layer (A). Do.

(2) Base material breaking strength In order to prevent base material destruction at the time of peeling, the base material layer (B) of the multilayer laminated film of the present invention must have a breaking strength greater than the cohesive failure strength of the seal layer (A). This is achieved by using a mixture of high density polyethylene and polypropylene as the resin constituting the sealing layer (A) and using an ethylene / propylene copolymer as the resin constituting the base layer (B). .

(3) Tear strength In order to prevent tearing of the film at the time of peeling, it is important to select a resin constituting the base layer (B), and the density of polymerized using a metallocene catalyst is 0.90 g / cm ^{3 to} 0.91 g / cm. By using the ethylene / propylene copolymer of ^3, a preferable film that hardly causes tearing of the film can be obtained.

<6> Configuration of Lid Material Next, the configuration of the lid material of the packaging container using the multilayer laminated film of the present invention will be described with reference to the example shown in FIG. The lid of the packaging container in FIG. 1 is formed by laminating a laminated adhesive layer printed as necessary on a multilayer laminated film composed of a sealing layer (A) and a base material layer (B) according to the present invention. Further, a transparent packaging material base material made of polyester, polyamide or the like is further laminated as a stretched film.

<7> Packaging container The multilayer laminated film of the present invention is used for a sealant film for a lid of a packaging container. Specifically, heat sealing is performed in a state where the seal layer (A) is overlapped with an opening of a container formed of polypropylene, and the seal layer (A) is coherently broken at the time of opening.

The present invention will be described more specifically with reference to examples.
[Example 1]
(1) Seal layer (A)
High-density polyethylene (Hi-Zex 3300F manufactured by Prime Polymer Co., Ltd .: Density = 0.950 g / cm ³ , MFR (190 ° C.) = 1.1 g / 10 min) and 30 parts by weight of ethylene / propylene random copolymer (Prime Polymer Co., Ltd.) ) J235T: Density = 0.9 g / cm ³ , MFR (230 ° C.) = 15 g / 10 min) 70 parts by weight were sufficiently kneaded to prepare a resin composition for the seal layer (A).

(2) Base material layer (B)
Base material layer consisting of 100 parts by weight of an ethylene / propylene copolymer (Wintech WFX4T manufactured by Nippon Polypro Co., Ltd .: density = 0.9 g / cm ³ , MFR = 7.0 g / 10 min) polymerized using a metallocene catalyst (B ) Resin composition was prepared.
A multi-layer laminated film (sealing layer (A) 5 μm / base layer (B) 25 μm) having a total thickness of 30 μm was produced using a top-blown air-cooled inflation coextrusion film forming machine.

Corona treatment is applied to the surface of the base material layer (B) that does not face the seal layer (A), and a two-component curable urethane adhesive (main agent: polyester polyol, curing agent: aliphatic isocyanate) is applied to the surface. Two polyester films were laminated (first biaxially stretched PET film manufactured by Toyobo Co., Ltd. [E5200] (double-sided corona treatment): then 12 μm thick, then biaxially stretched PET film manufactured by Toyobo Co., Ltd. [E5100] (Single-side corona treatment): 12 μm thick was laminated). The obtained multilayer laminated film has a structure of (polyester film layer / DL / polyester film layer / DL / base material layer (B) / seal layer (A)) (DL means an adhesive part).
The multilayer laminated film produced above was used as a lid for cup-shaped containers made of polypropylene (outer dimensions 80 mm x 80 mm, flange width 5 mm), from a flat seal to a seal temperature of 190 ° C, 3 kg / cm ² , 1 second Heat sealed under conditions. As a result, the multilayer laminated film of the present invention was able to be peeled with an appropriate strength, and the peeled surface was also beautiful.

[Example 2]
(1) Seal layer (A)
High-density polyethylene (Hi-Zex 3300F made by Prime Polymer Co., Ltd .: density = 0.950 g / cm ³ , MFR (190 ° C.) = 1.1 g / 10 min) and 30 parts by weight of ethylene / propylene random copolymer (Nippon Polypro Co., Ltd.) FW4BT: density = 0.9 g / cm ³ , MFR (230 ° C.) = 6.5 g / 10 min) 70 parts by weight were sufficiently kneaded to prepare a resin composition for the seal layer (A).

(2) Base material layer (B)
A group comprising 100 parts by weight of an ethylene / propylene copolymer polymerized using a metallocene catalyst (Wintech WFX6 manufactured by Nippon Polypro Co., Ltd .: density = 0.90 g / cm ³ , MFR (230 ° C.) = 2.0 g / 10 min) A resin composition for the material layer (B) was prepared.
A multi-layer laminated film (seal layer (A) 5 μm / base material layer (B) 45 μm) having a total thickness of 50 μm was produced using a top-blown air-cooled inflation coextrusion film forming machine.
The same results were obtained as in Example 1 below.

[Example 3]
Linear low density polyethylene (1) Seal layer (A)
High-density polyethylene (Hi-Zex 3300F made by Prime Polymer Co., Ltd .: density = 0.950 g / cm ³ , MFR (190 ° C.) = 1.1 g / 10 min) and 30 parts by weight of ethylene / propylene random copolymer (Nippon Polypro Co., Ltd.) FA3EB: Density = 0.9 g / cm ³ , MFR (230 ° C.) = 10.5 g / 10 min) 70 parts by weight were sufficiently kneaded to prepare a resin composition for the seal layer (A).

(2) Base material layer (B)
A group comprising 100 parts by weight of an ethylene / propylene copolymer polymerized using a metallocene catalyst (Wintech WFX6 manufactured by Nippon Polypro Co., Ltd .: density = 0.90 g / cm ³ , MFR (230 ° C.) = 2.0 g / 10 min) A resin composition for the material layer (B) was prepared.

(3) Base material layer (C)
Resin composition for base layer (C) consisting of 100 parts by weight of linear low density polyethylene (Evolue SP2020 manufactured by Prime Polymer Co., Ltd .: density = 0.916 g / cm ³ , MFR (190 ° C.) = 2.3 g / 10 min) A product was prepared.
A multi-layer laminated film (sealing layer (A) 5 μm / base material layer (B) 25 μm / base material layer (C) 20 μm) having a total thickness of 50 μm was produced using a top blow air-cooled inflation coextrusion film forming machine.
The same results were obtained as in Example 1 below.

[Comparative Example 1]
(1) Seal layer (A)
High-density polyethylene (Hi-Zex 3300F made by Prime Polymer Co., Ltd .: density = 0.950 g / cm ³ , MFR (190 ° C.) = 1.1 g / 10 min) and 30 parts by weight of ethylene / propylene random copolymer (Nippon Polypro Co., Ltd.) FW4BT: density = 0.9 g / cm ³ , MFR (230 ° C.) = 6.5 g / 10 min) 70 parts by weight were sufficiently kneaded to prepare a resin composition for the seal layer (A).

(2) Base material layer (B)
A group comprising 100 parts by weight of an ethylene / α-olefin copolymer (prime polymer Evolue SP2020: density = 0.913 g / cm ³ , MFR (190 ° C.) = 2.3 g / 10 min) polymerized using a metallocene catalyst A resin composition for the material layer (B) was prepared.
A multi-layer laminated film (seal layer (A) 5 μm / base material layer (B) 45 μm) having a total thickness of 50 μm was produced using a top-blown air-cooled inflation coextrusion film forming machine.
Evaluation was performed in the same manner as in Example 1. However, since the fracture strength of the base material layer (B) was smaller than the cohesive fracture strength of the seal layer (A), the base material was destroyed at the time of peeling.

[result]
Each physical property evaluation in the multilayer laminated films of Examples 1-2 and Comparative Example 1 was carried out as follows.
(1) Layer thickness: Measured with a μ-meter manufactured by SONY Corporation.
(2) Seal strength: Sealed from a flat seal to a polypropylene cup under conditions of a seal temperature of 190 ° C., 1 kg / cm ² , and 1 second. A strip-shaped test piece having a width of 15 mm was cut out from the tensile tester, and a tensile test was performed at 300 mm / min.
(3) Tear strength: Measured by the Elmendorf tear test method (based on JIS K 7128).

  In Examples 1 to 3 of the present invention, the cohesive failure of the seal layer (A) occurred at the time of peeling, and excellent openability was shown. Further, the peeled surface was clean without stringing. On the other hand, in Comparative Example 1, the base material layer (B) was destroyed.

It is sectional drawing which shows the layer structure of the cover material (multilayer laminated film + packaging base material) using the film of this invention.

Claims (7)

A multilayer laminated film having a sealing layer (A) and a base material layer (B), the sealing layer (A) comprising a mixture of 20 to 60 parts by weight of high-density polyethylene and 40 to 80 parts by weight of polypropylene, A base material layer (B) made of an ethylene / propylene copolymer having a density of 0.90 g / cm ^{3 to} 0.91 g / cm ³ polymerized using a metallocene catalyst is laminated, and the sealing layer ( A multilayer laminated film in which the layer thickness of A) is 1 μm to 20 μm, and the layer thickness of the base material layer (B) is 20 μm to 100 μm.   The multilayer laminated film according to claim 1, wherein the polypropylene constituting the seal layer (A) is an ethylene / propylene random copolymer.   The multilayer laminated film of Claim 1 or 2 whose MFR (190 degreeC) of the high density polyethylene which comprises a sealing layer (A) is 1-7 g / 10min.   The multilayer laminated film according to any one of claims 1 to 3, wherein the MFR (230 ° C) of polypropylene constituting the sealing layer (A) is 5 to 30 g / 10 min. A surface base material layer (C) made of an ethylene / α-olefin copolymer having a density of 0.91 g / cm ^{3 to} 0.94 g / cm ³ polymerized using a metallocene catalyst is further laminated on the base material layer (B). The multilayer laminated film according to any one of claims 1 to 4.   The multilayer laminated film according to any one of claims 1 to 5, wherein a stretched film is laminated on the outermost surface of the base material layer (B) on the side opposite to the seal layer (A).   It is a packaging container which uses the multilayer laminated film of any one of Claims 1-6 as a lid | cover material, Comprising: The sealing layer (A) of this lid | cover material touches the opening part of the container formed with the polypropylene. A packaging container that is heat-sealed in a state where it is overlaid and opened when the sealing layer (A) of the lid material is coherently broken when opened.

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