JP7238578B2 - Heat-sealable multilayer film and easy-open package - Google Patents

Description

The present invention relates to a heat-sealable multilayer film and an easy-open package using the same.

BACKGROUND ART In recent years, deep-drawn packages, four-sided bags, pillow packages, and the like made of plastic films have been widely used for packaging foods, daily necessities, miscellaneous goods, medical supplies, and the like. In addition, in response to the demand for universal design of packaging due to recent global environmental problems, declining birthrate and aging population, etc., these packages have features such as easy opening and tearing that are easy for consumers to open. There is a strong demand for such functionality.

However, generally, when the easy-open property is improved, the heat-sealing strength, pinhole resistance, and impact resistance that are originally required for the package are lowered, and the bag is broken during transportation and display at the store, and the contents are damaged. The risk of leakage, etc. increases. In order to solve these contradictory problems, efforts have been made for many years to develop packaging bodies according to their uses.

In particular, there is a risk of contamination of the contents or foreign objects when opening deep-drawn packaging, so it is required to provide easy-openability (easy peelability) as a means that can be opened more easily than tearing open. There are many things. In that case, the plastic film for packaging is generally heat-sealed on the base layer so that it can be given not only heat-sealing properties and easy-opening properties, but also barrier properties, pinhole resistance properties, and appearance design properties at the same time. A layered composite multilayer film is used.

As the heat seal layer of such a composite multilayer film, for example, a blend of two or more incompatible resins such as a polyethylene resin and a polypropylene resin or a polybutene resin is used. A so-called cohesive failure mechanism is generally known in which the is separated by cohesive failure. In such a heat-seal layer, it is desired that the peel strength can be intentionally designed by designing various resin formulations so as to meet various uses.

On the other hand, it has been proposed to use a norbornene-based resin (cyclic polyolefin resin) as a heat seal layer in order to provide higher moisture resistance and transparency than general olefin-based resins and to suppress adsorption of volatile components. ing. However, cyclic polyolefin resins have a low affinity with polypropylene resins, and have the drawback that the mating base material for heat sealing is limited to some polyethylene resins. As a means of increasing affinity with polypropylene resin, a means of adding a styrene elastomer has been proposed (Patent Document 1). There is a problem of spoiling. Furthermore, cyclic polyolefin resins are inferior in mechanical properties to general olefin resins, and are therefore poor in heat sealability, film forming processability, and pinhole resistance, and are not generally used.
An easily tearable film has been proposed (Patent Document 2) that takes advantage of the poor mechanical properties of cyclic polyolefin resins, but it cannot be easily opened.
In addition, although there has been proposed a cohesive failure mechanism heat seal formulation (Patent Document 3) that makes use of the fact that it is incompatible with polypropylene resin, the formulation is limited so as not to impair the heat resistance of polypropylene resin. However, no systematic study has been made to associate the properties of the cyclic polyolefin resin with the ease of opening.

Japanese Unexamined Patent Application Publication No. 2011-93209 JP 2013-75439 A JP 2008-115294 A

The present invention has been made in view of the above circumstances, and the problem to be solved is that it is heat-sealable with a substrate containing polyethylene resin and / or polypropylene resin as a main component, and a polyethylene resin An object of the present invention is to provide a base material containing a resin and/or a polypropylene-based resin as a main component, a heat-sealable multilayer film having easy peelability, and a package using the heat-sealable multilayer film.

Means for Solving the Problems As a result of intensive studies in view of the above problems, the present inventors have found that the above problems can be easily solved by adopting a specific resin formulation, and have completed the present invention.

That is, the gist of the present invention resides in the following [1] to [7].

[1] 50 to 90% by mass of a cyclic block copolymer having at least two hydrogenated aromatic vinyl polymer block units and at least one hydrogenated conjugated diene polymer block unit, and 10 to 50% by mass of a polyethylene resin; A heat-sealable multilayer film having a sealant layer containing a resin component as a main component.

[2] The heat-sealable multilayer film of [1], wherein the sealant layer is a cohesive failure easy peel layer.

[3] The heat-sealable multilayer film according to [1] or [2], wherein the polyethylene-based resin is a low-density polyethylene resin.

[4] The sealant layer is heat-sealable with a substrate containing a polyethylene-based resin and/or polypropylene-based resin as a main component, and is easily peelable from the substrate [1] to [3] ] The heat-sealable multilayer film according to any one of ].

[5] The heat-sealable multilayer film according to any one of [1] to [4], which is a coextruded multilayer film.

[6] The heat-sealable multilayer film according to any one of [1] to [4], which is a laminate film.

[7] Easy-open packaging obtained by heat-sealing the heat-sealable multilayer film according to any one of [1] to [6] and a substrate containing a polyethylene-based resin and/or a polypropylene-based resin as a main component. body.

According to the present invention, a sealant layer containing a specific cyclic block copolymer, which is a cyclic polyolefin resin, and a polyethylene-based resin as main components can be used without impairing the transparency of the film. It is possible to provide a heat-sealable multilayer film that can be heat-sealed with a substrate containing as and has such a substrate and easy peelability.

The heat-sealable multilayer film of the present invention has a base material containing a polyethylene-based resin and/or a polypropylene-based resin as a main component, that is, a polyethylene-based resin base material, a polypropylene-based resin base material, or a mixed resin base material of these. Even if it is, it can be used without changing the sealant layer depending on the base material, and the peel strength can be easily designed according to the application, and it is economical and easy-open packaging at a lower price. Since it becomes possible to provide it, its industrial utility value is high.

The present invention will be described in detail below, but the following description is an example of an embodiment of the present invention, and the present invention is not limited to the following description content as long as it does not exceed the gist of the present invention. Arbitrary modifications can be made without departing from the gist of the invention.

In the present specification, the term "main component" refers to a component that accounts for 50% by mass or more when the total of the components constituting each layer is 100% by mass, and this percentage is preferably 60% by mass or more. , more preferably 70% by mass or more, more preferably 80% by mass or more, particularly preferably 90% by mass or more, and most preferably 95% by mass or more.
In addition, when described as "X to Y" (X and Y are arbitrary numbers), unless otherwise specified, "X or more and Y or less", "preferably larger than X" and "preferably smaller than Y" ” is included.
In addition, the upper limit and lower limit of the numerical range in this specification, even if slightly deviating from the numerical range specified by the present invention, as long as it has the same effect as within the numerical range, the present invention shall be included in the equivalent range of

[Heat-sealable multilayer film]
The heat-sealable multilayer film of the present invention (hereinafter sometimes referred to as "the film of the present invention") comprises at least two hydrogenated aromatic vinyl polymer block units and at least one hydrogenated conjugated diene polymer block. A cyclic block copolymer having a unit (hereinafter sometimes referred to as "the cyclic block copolymer of the present invention") and a resin component composed of 10 to 50% by mass of a polyethylene resin as a main component. It has a sealant layer (hereinafter sometimes referred to as "the sealant of the present invention").

<Cyclic block copolymer>
The cyclic block copolymer (hereinafter sometimes referred to as "CBC") of the present invention has at least two hydrogenated aromatic vinyl polymer block units and at least one hydrogenated conjugated diene polymer block unit. The term "cyclic" in the cyclic block copolymer of the present invention refers to an alicyclic structure produced by hydrogenation of the aromatic ring of the hydrogenated aromatic vinyl polymer block unit.

As used herein, "block" refers to polymerized segments of a copolymer that represent microlayer separation from structurally or compositionally distinct polymerized segments of the copolymer, as described below. Thus, for example, "having at least two block units" means that the cyclic block copolymer has at least two polymerized segments of the copolymer that exhibit microlayer separation from polymerized segments that are structurally or compositionally different. Say.

The aromatic vinyl monomer, which is the raw material of the aromatic vinyl polymer block unit before hydrogenation, is a monomer represented by the following general formula (1).

Here, R represents a hydrogen atom or an alkyl group, and Ar represents an aromatic group such as a phenyl group, halophenyl group, alkylphenyl group, alkylhalophenyl group, naphthyl group, pyridinyl group or anthracenyl group.

The alkyl group of R preferably has 1 to 6 carbon atoms, and the alkyl group is monosubstituted with a functional group such as a halo group, a nitro group, an amino group, a hydroxy group, a cyano group, a carbonyl group, and a carboxyl group. or may be multiply substituted.
Ar is preferably a phenyl group or an alkylphenyl group, more preferably a phenyl group.

Examples of aromatic vinyl monomers include styrene, α-methylstyrene, vinyltoluene (including all isomers, and p-vinyltoluene is particularly preferred), ethylstyrene, propylstyrene, butylstyrene, vinylbiphenyl, and vinylnaphthalene. , vinylanthracene (including all isomers), and mixtures thereof.

The conjugated diene monomer, which is the raw material of the conjugated diene polymer block unit before hydrogenation, is not particularly limited as long as it has two conjugated double bonds.
Conjugated diene monomers include, for example, 1,3-butadiene, 2-methyl-1,3-butadiene, 2-methyl-1,3-pentadiene, isoprene and analogs thereof, and mixtures thereof. Polybutadiene, a polymer of 1,3-butadiene, has either a 1,2 configuration which on hydrogenation gives the equivalent of 1-butene repeating units, or a 1,4 configuration which on hydrogenation gives the equivalent of ethylene repeating units. can include

Hydrogenated polymer blocks composed of the above aromatic vinyl monomers and the above conjugated diene monomers including 1,3-butadiene are included in the cyclic block copolymers used in the present invention. Preferably, the cyclic block copolymers are block copolymers without functional groups.
By "free of functional groups" is meant that there are no functional groups, ie, groups containing atoms other than carbon and hydrogen atoms, in the block copolymer.

A preferred example of the hydrogenated aromatic vinyl polymer block unit is hydrogenated polystyrene, and a preferred example of the hydrogenated conjugated diene polymer block unit is hydrogenated polybutadiene.

A preferred embodiment of the cyclic block copolymers of the present invention may include hydrogenated triblock or pentablock copolymers of styrene and butadiene, preferably without any other functional groups or structural modifiers.

A "block" is defined as a polymerized segment of a copolymer that represents a microlayer separation from structurally or compositionally distinct polymerized segments of the copolymer. Microlayer separation results from the immiscibility of the polymerized segments in the block copolymer.
Microlayer separation and block copolymers are extensively discussed in PHYSICS TODAY, February 1999, pp. 32-38, "Block Copolymers-Designer Soft Materials".

The content of hydrogenated aromatic vinyl polymer block units in the cyclic block copolymer of the present invention is preferably 50 to 99 mol%, more preferably 60 to 90 mol%, and the content of hydrogenated conjugated diene polymer block units is , preferably 1 to 50 mol %, more preferably 10 to 40 mol %.

Cyclic block copolymers of the present invention may be triblock, multiblock, tapered, such as SBS, SBSBS, SIS, SISIS, and SISBS, where S is polystyrene, B is polybutadiene, and I is polyisoprene. It is produced by hydrogenation of block copolymers, including block and star block copolymers.

The cyclic block copolymers of the present invention preferably contain segments of hydrogenated aromatic vinyl polymer at each end. Thus, the cyclic block copolymers of the present invention have at least two hydrogenated aromatic vinyl polymer block units and between the two hydrogenated aromatic vinyl polymer block units is at least one hydrogenated conjugate. It has diene polymer block units.

The pre-hydrogenated block copolymers that make up the cyclic block copolymers of the present invention may contain a number of additional block units other than the hydrogenated aromatic vinyl polymer block units and the hydrogenated conjugated diene polymer block units. block may be attached at any position on the triblock polymer backbone.

Linear blocks suitable for the present invention include, for example, SBS, SBSB, SBSBS, SBBSSB. The copolymer may be branched and the polymer chains may be attached at any position along the backbone of the copolymer.

The lower limit of the weight average molecular weight (Mw) of the cyclic block copolymer of the present invention is preferably 30,000 or more, more preferably 40,000 or more, still more preferably 45,000 or more, particularly preferably 50,000 or more, from the viewpoint of moldability. 000 or more. On the other hand, from the viewpoint of moldability and dispersibility, the upper limit of Mw of the cyclic block copolymer of the present invention is preferably 120,000 or less, more preferably 100,000 or less, still more preferably 95,000 or less, and particularly preferably 90. ,000 or less, most preferably 85,000 or less, and most preferably 80,000 or less.
Here, the Mw of the cyclic block copolymer is a polystyrene-equivalent value determined using gel permeation chromatography (GPC).

The hydrogenation level of the cyclic block copolymer of the present invention is preferably hydrogenated aromatic vinyl polymer block units from the viewpoint of heat-sealability and unsealability with substrates containing polyethylene-based resins and/or polypropylene-based resins as main components. is 90% or more, hydrogenated conjugated diene polymer block units are 95% or more, more preferably hydrogenated aromatic vinyl polymer block units are 95% or more, hydrogenated conjugated diene polymer block units are 99% or more, and further Preferably, the hydrogenated aromatic vinyl polymer block unit is 98% or more, the hydrogenated conjugated diene polymer block unit is 99.5% or more, and particularly preferably the hydrogenated aromatic vinyl polymer block unit is 99.5% or more, hydrogen 99.5% or more of the conjugated diene polymer block units.
The hydrogenation level of the hydrogenated aromatic vinyl polymer block unit indicates the ratio at which the aromatic vinyl polymer block unit is saturated by hydrogenation, and the hydrogenation level of the hydrogenated conjugated diene polymer block unit indicates the Indicates the percentage of polymer block units saturated by hydrogenation.

The hydrogenation level of each block unit is determined using proton NMR.
In addition, the cyclic block copolymer of the present invention is not necessarily limited to those obtained through the hydrogenation step as described above. That is, as long as they have the same chemical structure, they are included in the cyclic block copolymers of the present invention. For example, if it is a hydrogenated aromatic vinyl polymer block, it may be a block obtained from a monomer having a cyclohexane ring structure, and if it is a hydrogenated conjugated diene polymer block, it may be an ethylene or α-olefin polymer block. There may be.

The density (ISO1183) of the cyclic block copolymer of the present invention is preferably 0.92 g/cm ³ or more and 0.96 g/cm ³ or less. When the density is 0.92 g/cm ³ or more, the heat resistance is good, and when it is 0.96 g/cm ³ or less, the impact resistance and flexibility are good.

The melt flow rate (hereinafter sometimes referred to as MFR) of the cyclic block copolymer of the present invention (ISO 1133, measurement temperature 230°C, measurement load 21.17 N) is preferably 0.5 g/10 min or more and 30 g/10 min or less. , more preferably 1.0 g/10 min or more and 25 g/10 min or less. By setting the MFR within the above range, good moldability can be obtained, and when added to the sealant layer, good dispersibility can be obtained, and good easy peelability can be imparted.

The glass transition temperature (Tg) of the cyclic block copolymer of the present invention is preferably 70°C or higher and 140°C or lower, more preferably 115°C or higher and 135°C or lower. If the glass transition temperature is at least the above lower limit, the heat resistance is excellent. On the other hand, if the glass transition temperature is 140° C. or lower, the heat-sealing property to polyethylene-based resins and polypropylene-based resins is excellent.

As the cyclic block copolymer of the present invention, commercially available products can be used, and specific examples thereof include Zelas (registered trademark) manufactured by Mitsubishi Chemical Corporation.

The sealant layer of the present invention may contain only one type of the cyclic block copolymer of the present invention, or may contain two or more types having different block compositions, physical properties, and the like.

<Polyethylene resin>
Examples of the polyethylene-based resin contained in the sealant layer of the present invention include linear low-density polyethylene (LLDPE) resin, low-density polyethylene (LDPE) resin, medium-density polyethylene (MDPE) resin, high-density polyethylene (HDPE) resin, and the like. is mentioned. These may be used alone or in combination of two or more. Among them, low-density polyethylene resin is preferable from the viewpoint of exhibiting sealing properties to both polyethylene-based resin and polypropylene-based resin.

MFR of polyethylene resin (JIS K6922-2, measurement temperature 190°C, measurement load 21.17N) is preferably 0.1 g/10 min or more and 20.0 g/10 min or less, and 0.2 g/10 min or more15. 0 g/10 minutes or less is more preferable. By setting the MFR within the above range, good moldability can be obtained, good dispersion diameter and transparency can be obtained when blended into the sealant layer of the present invention, and good easy peelability can be imparted to the sealant layer.

The melting point (JIS K7121) of the polyethylene resin is preferably 90°C or higher and 130°C or lower, more preferably 95°C or higher and 125°C or lower. If the melting point is 90° C. or higher, heat resistance necessary for sterilization treatment, etc. can be obtained, and if it is 130° C. or lower, the heat-sealing property to both polyethylene-based resin and polypropylene-based resin is excellent.

<Sealant layer>
The sealant layer of the present invention contains a resin component consisting of 50 to 90% by mass of the cyclic block copolymer of the present invention and 10 to 50% by mass of a polyethylene resin (100% by mass of the cyclic block copolymer of the present invention and the polyethylene resin). Contains as a main component. It is preferable that the ratio of the cyclic block copolymer of the present invention in the resin component is 60 to 80% by mass and the ratio of the polyethylene resin is 20 to 40% by mass.

When the ratio of the cyclic block copolymer of the present invention in the resin component is 50% by mass or more, it is possible to exhibit good easy peelability from a substrate containing a polyethylene-based resin and/or a polypropylene-based resin as a main component. . On the other hand, when it is 90% by mass or less, the film formability of the film is improved.
When the ratio of the polyethylene-based resin in the resin component is 10% by mass or more, it is possible to impart good sealability to the substrate containing the polyethylene-based resin and/or the polypropylene-based resin as the main component. On the other hand, when the content is 50% by mass or less, the tensile elongation of the sealant layer can be suppressed, and a good feeling of peeling can be obtained.

In addition, the sealant layer of the present invention may be composed mainly of a resin component consisting of the cyclic block copolymer of the present invention and a polyethylene-based resin. may contain an additive or the like.

The tensile elongation of the sealant layer of the present invention is preferably 200% or less, more preferably 100% or less. When the tensile elongation is 200% or less, good easy peelability can be obtained without causing stringiness and film residue at the time of peeling. Although the lower limit of the tensile elongation is not particularly limited, it is usually 2% or more. The tensile elongation of the sealant layer is measured by the method described in the Examples section below.

The sealant layer of the present invention preferably has an internal haze of 5% or less, more preferably 3% or less at a thickness of 30 μm. When the internal haze is 5% or less, the visibility of the content is improved, and even when combined with other layers to form a multilayer film, the visibility of the multilayer film is not affected, which is preferable.

Since the internal haze depends on the thickness, the internal haze at a thickness of 30 μm can be obtained from the following formula (2).
30 μm thick internal haze
= (measured internal haze) / (measured thickness μm) × 30 μm (2)

The sealant layer of the present invention is preferably an easy-peel layer having easy-peelability when it is peeled off after being heat-sealed with a substrate, and particularly preferably an easy-peelable cohesive failure layer. When the film is peeled off, the sealant layer undergoes cohesive failure and the sealant layer remains on both the film and the base material, which is called "cohesive failure easy peel".

Although the thickness of the sealant layer of the present invention is not particularly limited, it is preferably 3 μm or more from the viewpoint of film formability, and preferably 100 μm or less from the viewpoint of easy peeling. The thickness of the sealant of the invention is preferably in the range of 3-100 μm.

<Layer structure of heat-sealable multilayer film>
In addition to the sealant layer, the film of the present invention includes a layer (PA layer) containing a polyamide resin for the purpose of improving pinhole resistance, and a layer (EVOH) containing an ethylene-vinyl alcohol copolymer resin for the purpose of improving oxygen barrier properties. layer), a layer containing polyethylene resin (PE layer) or a layer containing ethylene-vinyl acetate copolymer (EVA layer) for the purpose of imparting flexibility, polypropylene resin for the purpose of improving sterilization heat resistance and elastic modulus A layer containing these (PP layer) and an adhesive resin layer (AD layer) necessary for co-extrusion film formation of a combination of these can be provided. Moreover, the film of the present invention may have at least one sealant layer of the present invention, and may have two or more sealant layers.

An example of the layer structure of the heat-sealable multilayer film of the present invention is shown below, but the heat-sealable multilayer film of the present invention may have at least one sealant layer of the present invention. is not particularly limited. Also, the thickness of each layer can be arbitrarily designed according to the required properties. For example, when represented by a PA layer (PA), a PE layer (PE), an EVA layer (EVA), a PP layer (PP), and an adhesive resin layer (AD), the layer structure of the heat-sealable multilayer film of the present invention is can be exemplified by the following layer structure.
PA/AD/PE/sealant layer PA/AD/PP/sealant layer PP/AD/PA/AD/PE/sealant layer PP/AD/PA/EVOH/AD/PE/sealant layer PE/AD/EVOH/AD/ PE/sealant layer PA/AD/PA/AD/PE/sealant layer PA/AD/PA/AD/EVA/sealant layer PA/AD/EVOH/AD/EVA/sealant layer

<Additive for heat-sealable multilayer film>
The film of the present invention contains inorganic particles such as silica, talc, kaolin, calcium carbonate, oxidized Additives such as pigments such as titanium and carbon black, flame retardants, weather stabilizers, heat stabilizers, antistatic agents, melt viscosity improvers, cross-linking agents, lubricants, nucleating agents, plasticizers, anti-aging agents, etc. Alternatively, two or more kinds can be added as appropriate.
These additives may be contained in any constituent layer of the film of the present invention.

<Total haze of heat-sealable multilayer film>
The total haze of the film of the invention is preferably 20% or less, more preferably 15% or less. When the total haze is 20% or less, the visibility of the contents is improved. The total haze of the film of the invention is measured by the method described in the Examples section below.

<Method for producing heat-sealable multilayer film>
The film of the present invention can be produced by laminating necessary layers including a sealant layer by known methods such as coextrusion, dry lamination, extrusion lamination and hot melt lamination. Among them, the co-extrusion method and the extrusion lamination method are desirable. That is, the film of the present invention is preferably a coextruded multilayer film or laminate film.

[Easy-open package]
By heat-sealing the film of the present invention and a substrate containing a polyethylene-based resin and/or a polypropylene-based resin as a main component, an easy-open package can be obtained.
The easy-open package of the present invention is useful as an easy-peel package for packaging foods, daily necessities, miscellaneous goods, medical supplies, and various other articles.

EXAMPLES The present invention will be described in more detail with reference to examples and comparative examples below, but the present invention is not limited by the following examples as long as the gist thereof is not exceeded. Various production conditions and values of evaluation results in the following examples have meanings as preferable values of the upper limit or the lower limit in the embodiment of the present invention. It may be a range defined by the value of the example or a combination of the values of the examples.

[material]
Raw materials used in the following examples and comparative examples are as follows.

CBC: Mitsubishi Chemical Corporation cyclic block copolymer "Zerath MC930" (polycyclohexylethylene-ethylene-1-butene-polycyclohexylethylene block copolymer, hydrogenated aromatic vinyl polymer block unit content: 65 mol%, hydrogenated Conjugated diene polymer block unit content: 35 mol%, Mw: 71,600, Tg: 125°C, density: 0.94 g/cm ³ , MFR: 1.3 g/10 minutes (230°C, 21.17N))
COC: Norbornene-based cyclic polyolefin resin "TOPAS" manufactured by Polyplastics
LDPE: Low-density polyethylene "Novatec LDPE" manufactured by Nippon Polyethylene Co., Ltd. (Melting point: 111°C, MFR: 0.25 g/10 minutes (190°C, 21.17N))
hPP: Homopolypropylene "Novatec PP" manufactured by Japan Polypropylene Corporation (melting point 167°C, MFR: 2.4 g/10 min (230°C, 21.17N))
rPP: Random polypropylene "Novatec PP" manufactured by Japan Polypropylene Corporation (melting point 140°C, MFR: 0.8 g/10 min (230°C, 21.17N))
PA: Polyamide-based resin "Novamid" manufactured by Mitsubishi Engineering-Plastics Co., Ltd.

[Evaluation method]
The evaluation method of the obtained film is as follows.

<Tensile elongation>
The sealant film prepared in each example was cut into strips (test piece: width 10 mm, initial length 40 mm), and a tensile tester (Shimadzu universal testing machine AG-XPlus) was used at room temperature at a tensile speed of 200 mm / min. A tensile test was performed to measure the elongation at break in MD (extrusion direction) and TD (extrusion direction and perpendicular direction), respectively.

<Internal haze>
The internal haze of the sealant film produced in each example was measured according to JIS K7105.

<Sealability>
(Preparation of heat seal sample)
A heat-sealed sample was produced by heat-sealing the lid material film and the heat-sealable multilayer film produced in each example with a deep drawing packaging machine (R530 manufactured by Multivac). As the cover material film, a PE base (LLDPE base) and a PP base (random polypropylene base) were used. was heat-sealed under the conditions of 160° C.×2 seconds.

(seal strength)
In the above heat-sealed sample, the sealed portion was cut into strips with a width of 15 mm, and the lid material film and the sample film were peeled off at a speed of 200 mm/min using a tensile tester, and the seal strength was obtained from the average load. rice field. When used as an easy-open package, the seal strength is preferably 100 to 1000 gf/15 mm.

(Evaluation of easy peelability)
In the above heat-sealed sample, the sealed portion was manually peeled off, the state of the peeled surface was observed, and evaluated according to the following criteria.
○: Marks of peeling of the sealant layer on both the heat-sealable multilayer film and the base material, no stringiness of the sealant layer (practical level)
△: Slight traces of peeling of the sealant layer on both the heat-sealable multilayer film and the substrate, stringiness of the sealant layer (unpractical)
×: Completely sealed or incompletely sealed, no traces of peeling of the sealant layer on both the heat-sealable multilayer film and the base material, stringiness of the sealant layer (unpractical)

<Transparency>
(total haze)
The total haze of the heat-sealable multilayer film produced in each example was measured according to JIS K7105.
(Visibility)
The heat-sealable multilayer film was visually observed and evaluated according to the following criteria.
○: Good visibility with no problem with transparency △: Decrease in transparency is observed, but visibility is in the range where there is no problem ×: Transparency, visibility is poor (practical impractical)

[Examples and Comparative Examples]
<Example 1>
A sealant layer having a thickness of 30 μm was formed as a single layer at a molding temperature of 230° C. and a cast roll temperature of 80° C. using a φ25 mm twin-screw extruder. As the material for the sealant layer, 80% by mass of a cyclic block copolymer “Zelath MC930” manufactured by Mitsubishi Chemical Corporation and 20% by mass of “Novatec LDPE” manufactured by Japan Polyethylene Co., Ltd. were mixed and used.
A 40 μm-thick film made of a polyamide-based resin “Novamid” manufactured by Mitsubishi Engineering-Plastics Co., Ltd. was laminated and integrated on the formed sealant film by a dry lamination method to produce a heat-sealable multilayer film of the present invention.
The sealant film and the heat-sealable multilayer film were evaluated respectively. Table 1 shows the results.

<Example 2, Comparative Examples 1 to 5>
A sealant film and a heat-sealable multilayer film were produced in the same manner as in Example 1 by changing the resin composition of the sealant layer as shown in Table 1 and setting the cast roll temperature during the formation of the sealant film to the temperature shown in Table 1. made an evaluation.
Table 1 shows the results.

<Discussion>
In Examples 1 and 2, in which the cyclic block copolymer of the present invention and the polyethylene-based resin were used in the specified formulation of the present invention in the sealant layer, the hand peelability was good for both the PE base material and the PP base material. An easily peelable heat-sealed sample can be obtained, and the seal strength can be adjusted by changing the compounding ratio of the cyclic block copolymer and the polyethylene resin, and the transparency is also excellent.
In Comparative Example 1, which contained a large amount of the polyethylene resin, stringiness and fluffing were slightly conspicuous during manual peeling evaluation, and the transparency was remarkably inferior.
In Comparative Example 2 using only the cyclic block copolymer of the present invention, both the PE base material and the PP base material were completely sealed.
In Comparative Example 3, in which polypropylene-based resin (hPP) was used instead of polyethylene-based resin, it was in a completely sealed state with the PP base material, and due to its low affinity with the PE base material, it was easy to peel without leaving any traces of peeling. It wasn't.
In Comparative Example 4, in which a norbornene-based cyclic polyolefin resin was used instead of the cyclic block copolymer of the present invention, good heat sealability was not exhibited for both the PE base material and the PP base material.
In Comparative Example 5, in which polypropylene resin (rPP) was used instead of polyethylene resin, both the PE base material and the PP base material were in a completely sealed state.
In Comparative Example 6, in which the amount of the cyclic block copolymer of the present invention was particularly small, a completely sealed state was obtained with the PE base material, and an incompletely sealed state with the PP base material was obtained.
In Comparative Examples 7 and 8 using a norbornene-based cyclic polyolefin resin and a polyethylene-based resin, both the PE base material and the PP base material could be heat-sealed, and easy peeling was possible, but stringiness occurred and good easy peeling was not achieved. Moreover, there was no change in peel strength even when the compounding ratio was changed.

As described above, according to the present invention, it is possible to achieve both easy peelability and heat sealability for both PE and PP substrates without impairing transparency, and the seal strength is also improved. It turns out that it is adjustable.

Claims (7)

A resin comprising 50 to 90% by mass of a cyclic block copolymer having at least two hydrogenated aromatic vinyl polymer block units and at least one hydrogenated conjugated diene polymer block unit, and 10 to 50% by mass of a polyethylene resin. A heat-sealable multilayer film having a sealant layer containing a component as a main component, wherein the polyethylene-based resin is selected from a linear low-density polyethylene resin, a low-density polyethylene resin, a medium-density polyethylene resin, and a high-density polyethylene resin. A heat-sealable multilayer film that is at least one of A resin comprising 50 to 90% by mass of a cyclic block copolymer having at least two hydrogenated aromatic vinyl polymer block units and at least one hydrogenated conjugated diene polymer block unit, and 10 to 50% by mass of a polyethylene resin. A heat-sealable multilayer film having a sealant layer containing a component as a main component, wherein the polyethylene-based resin is a low-density polyethylene resin. 3. The heat-sealable multilayer film according to claim 1, wherein the sealant layer is a cohesive failure easy peel layer. Any one of claims 1 to 3, wherein the sealant layer is heat-sealable with a base material containing polyethylene resin and/or polypropylene resin as a main component, and is easily peelable from the base material. 1. The heat-sealable multilayer film according to claim 1. The heat-sealable multilayer film according to any one of claims 1 to 4, which is a coextruded multilayer film. The heat-sealable multilayer film according to any one of claims 1 to 4, which is a laminate film. An easy-to-open package obtained by heat-sealing the heat-sealable multilayer film according to any one of claims 1 to 6 and a substrate containing a polyethylene-based resin and/or a polypropylene-based resin as a main component. .