Multilayer film with re-sealing function, multilayer body with re-sealing function, and package with re-sealing function

Abstract

To provide a multilayer film with a re-sealing function which is excellent in initial peeling strength when being opened and re-sealing strength when being re-opened.SOLUTION: There is provided a multilayer film with a re-sealing function in which at least a resin layer (A), an adhesive resin layer (B) and a resin layer (C) are stacked in this order from the outer layer side, wherein the adhesive resin layer (B) contains at least two kinds of styrenic thermoplastic resin elastomers.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a resealable multilayer film, and more particularly to a resealable multilayer film that is suitable for packaging foods, medicines, etc., a resealable multilayer body using the same, and a resealable package. [Background technology]

[0002] BACKGROUND ART Conventionally, various types of resealable packaging have been used as packaging means for cosmetics and sanitary products that are repeatedly opened and resealed each time they are used, or for food and medicines in quantities that cannot be consumed in one go. Such packages can prevent the contents remaining after opening from deteriorating due to oxidation or deterioration due to moisture absorption or drying, and for example, zipper-type packages in which a plastic zipper is laminated are known. Although such packaging can be opened repeatedly and has excellent durability, it requires special equipment to attach accessories such as zippers to the packaging, and the associated processing steps are also required, which results in problems such as increased manufacturing costs and reduced production efficiency.

[0003] On the other hand, multilayer films have also been developed that can impart a resealable function to the packaging itself without the need for attachments such as zippers. For example, Patent Document 1 discloses a multilayer film comprising a surface resin layer, an adhesive resin layer containing a hydrogenated styrene-diene rubber block copolymer and a tackifier, and a heat-sealable resin layer, in which, when the multilayer film is peeled off from a base material, the adhesive resin layer is exposed in an adhesive state at the heat-sealed portion that allows for resealing.

[0004] Furthermore, Patent Document 2 discloses a package using, as a lid material for a container, a multilayer film comprising a surface resin layer, an adhesive resin layer containing a hydrogenated styrene-diene rubber block copolymer and a tackifier, and a heat-sealable resin layer, wherein when the heat-sealable resin layer and a heat-sealable thermoplastic resin layer are heat-sealed together and then peeled apart, the heat-sealable resin layer ruptures and the heat-sealable resin layer and the adhesive resin layer peel apart, exposing the adhesive resin layer in a resealable adhesive state at the heat-sealed portion.

[0005] Furthermore, Patent Document 3 discloses a package using a multilayer film as a base material, characterized in that a peel layer is provided between the heat seal layer and the adhesive resin layer to heat seal the heat seal resin layer and a heat-sealable thermoplastic resin layer, and when the layers are subsequently peeled away, the heat seal resin layer and the peel layer rupture and the peel layer and the adhesive resin layer peel away from each other, exposing the adhesive resin layer in an adhesive state at the heat seal portion that allows for resealing. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-175567 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-75181 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-200960 Summary of the Invention [Problem to be solved by the invention]

[0007] The multilayer films described in Patent Documents 1 to 3 have a resealing function, but the balance between the initial peel strength when opened and the resealing peel strength when resealed is insufficient, and there is room for further improvement.

[0008] The present invention has been made in consideration of the above-mentioned circumstances, and its object is to provide a multilayer film with a resealable function that has excellent initial peel strength when opened and resealable strength when resealed, and a resealable package using the same. [Means for solving the problem]

[0009] As a result of intensive research to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by using at least two types of styrene-based thermoplastic elastomers in the adhesive resin layer of a multilayer film having a resin layer, an adhesive resin layer, and a resin layer laminated in this order, and have completed the present invention.

[0010] That is, the present invention has the following aspects. [1] A resealable multilayer film in which at least a resin layer (A), an adhesive resin layer (B), and a resin layer (C) are laminated in the order (A) / (B) / (C) from the outer layer side, and the adhesive resin layer (B) contains at least two types of styrene-based thermoplastic resin elastomers. [2] The resealable multilayer film according to [1], wherein the styrene-based thermoplastic elastomer of the adhesive resin layer (B) is selected from the following (i) and (ii), and when the total amount of the styrene-based thermoplastic elastomer contained in the adhesive resin layer (B) is taken as 100% by mass, the styrene-based thermoplastic elastomer selected from (i) accounts for 30 to 95% by mass. (i) Hydrogenated styrene-butadiene-styrene block copolymer, hydrogenated styrene-isoprene-styrene block copolymer (ii) Styrene-butadiene-styrene block copolymer, styrene-isobutylene-styrene copolymer [3] The resealable multilayer film according to [1] or [2], wherein the difference in glass transition temperature of the styrene-based thermoplastic elastomer contained in the adhesive resin layer (B) is 7°C or more. [4] The resealable multilayer film according to any one of [1] to [3], wherein the resin layer (A) and the resin layer (C) each contain a polypropylene-based resin. [5] The resealable multilayer film according to any one of [1] to [4], which has a thermoplastic resin layer (D) adjacent to the resin layer (A) and / or the resin layer (C), and the thermoplastic resin layer (D) contains at least one thermoplastic resin selected from the group consisting of polyolefin-based resins, polyamide-based resins, ethylene-vinyl alcohol-based copolymers, polyester-based resins, and polystyrene-based resins. [6] The resealable multilayer film according to any one of [1] to [5], which has a heat-sealable resin layer (E) on the surface side of the resin layer (C). [7] A multilayer film with resealable function according to any one of [1] to [6], wherein when the resealable multilayer film is heat-sealed to an object to be sealed and the resealable multilayer film is peeled off from the object to be sealed, the adhesive resin layer (B) peels off by cohesive failure, and the adhesive resin layer (B) is exposed on both sides of the peeled surface in a resealable state. [8] A multilayer film with resealable function according to any one of [1] to [6], wherein when the resealable multilayer film and an object to be sealed are heat-sealed and the resealable multilayer film is peeled off from the object to be sealed, the adhesive resin layer (B) and the resin layer (A) or the resin layer (C) are exposed in a resealable state. [9] A resealable multilayer body obtained by heat-sealing the resealable multilayer film according to [7] to an object to be sealed.

[10] A multilayer body with resealable function according to [9], wherein when the resealable multilayer film is peeled off from the resealable multilayer body, the adhesive resin layer (B) peels off by cohesive failure, and the adhesive resin layer (B) is exposed on both sides of the peeled surface in a resealable state.

[11] A resealable package using the resealable multilayer body according to [9] or

[10] .

[12] A resealable multilayer body obtained by heat-sealing the resealable multilayer film according to [8] to an object to be sealed.

[13] A resealable package using the resealable multilayer body described in

[12] . [Effects of the Invention]

[0011] The resealable multilayer film of the present invention has excellent initial peel strength when opened and excellent reseal strength when resealed. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a partial cross-sectional view of a package using the resealable multilayer film of the present invention as a lid material. [Figure 2] 2 is a partial cross-sectional view of the package shown in FIG. 1 with a portion of the lid peeled off from the container. [Figure 3] 2 is a partial cross-sectional view showing the state in which the lid and base members of the package shown in FIG. 1 have been resealed. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described below based on examples of embodiments for carrying out the present invention, but the present invention is not limited to the embodiments described below.

[0014] In this specification, "X and / or Y (X and Y are any configurations)" means at least one of X and Y, and means three possibilities: X only, Y only, and X and Y. When expressed as "X to Y" (X and Y are any numbers), unless otherwise specified, it means "X or more and Y or less," as well as "preferably greater than X" or "preferably smaller than Y." When expressed as "X or more" (X is any number) or "Y or less" (Y is any number), it also means that "it is preferably greater than X" or "it is preferably less than Y." In the present specification, when numerical ranges are described in stages, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. In addition, in the numerical ranges described in this specification, the upper or lower limit of the numerical range can also be replaced with the values ​​shown in the examples. In this specification, the term "main component" means a component that has a significant effect on the properties of the target object, and the content of the component is usually 50% by mass or more in the target object, preferably 55% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass, and may be 100% by mass. In this specification, the term "film" encompasses a wide range of materials from thick sheets to thin films.

[0015] A resealable multilayer film according to one embodiment of the present invention (hereinafter sometimes referred to as "the multilayer film") comprises a resin layer (A), an adhesive resin layer (B), and a resin layer (C) laminated in the order (A) / (B) / (C) from the outer layer side, and the adhesive resin layer (B) contains at least two types of styrene-based thermoplastic elastomers. The multilayer film may also have layers other than the resin layer (A), adhesive resin layer (B), and resin layer (C).

[0016] The present multilayer film preferably has a thermoplastic resin layer (D) adjacent to the resin layer (A) and the resin layer (C). The present multilayer film preferably has a heat seal layer (E) on the surface side of the resin layer (C).

[0017] When the present multilayer film is heat-sealed to an object to be sealed and peeled off from the object, the adhesive resin layer (B) undergoes cohesive failure, resulting in peeling, and the adhesive resin layer (B) is exposed on both sides of the peeled surface, or the adhesive resin layer (B) and the resin layer (A) or the resin layer (C) are exposed, making the film resealable. Each layer will be described below.

[0018] <Resin layer (A)> The resin layer (A) in the present embodiment is preferably a layer containing a thermoplastic resin, and more preferably contains a thermoplastic resin as a main component.

[0019] Examples of the thermoplastic resin include polyolefin resins, polyamide resins, polyester resins, etc. These may be used alone or in combination of two or more.

[0020] [Polyolefin resin] Examples of the polyolefin resin include polyethylene resin (PE), polypropylene resin (PP), α-olefin copolymer, cyclic polyolefin resin, and modified polyolefin resin.

[0021] [Polyethylene resin] Examples of the polyethylene resin include resins containing ethylene structural units as a main component, such as very low density polyethylene (VLDPE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), and ethylene-vinyl acetate copolymer (EVA). Among these, LLDPE, LDPE, MDPE, and HDPE are preferred in terms of film-forming properties and heat resistance. Furthermore, when the adhesive resin layer (B) is to undergo cohesive failure, EVA is preferred in terms of adhesion.

[0022] The melting point (JIS K7121) of the polyethylene resin is usually 100°C or higher, preferably 110°C or higher, and more preferably 120°C or higher.

[0023] [Polypropylene resin] Examples of the polypropylene resin include resins containing propylene structural units as the main component, such as propylene homopolymers (homopolypropylenes) and copolymers of propylene with other α-olefins, such as ethylene and butene. Both random and block copolymers can be used as the copolymers. The stereoregularity may be an isotactic structure, a syndiotactic structure, an atactic structure, a stereoblock structure, or the like. These may be used alone or in combination of two or more. Among these, propylene homopolymers (homopolypropylenes) are preferred from the viewpoint of adhesion to the adhesive resin layer (B).

[0024] The melting point (JIS K7121) of the polypropylene resin is usually 120°C or higher, preferably 130°C or higher, and more preferably 140°C or higher.

[0025] [α-olefin copolymer] Examples of the α-olefin copolymer include copolymers of α-olefins having 2 to 10 carbon atoms, such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Specific examples include ethylene-α-olefin copolymers, propylene-α-olefin copolymers, and ethylene-propylene-α-olefin copolymers.

[0026] [Cyclic polyolefin resin] Examples of the cyclic polyolefin resin include random copolymers of ethylene and cyclic olefins such as norbornenes, tetracyclododecenes, and derivatives thereof, cyclic olefin ring-opening polymers, cyclic olefin ring-opening copolymers, hydrogenated cyclic olefin ring-opening polymers and cyclic olefin ring-opening copolymers, and graft-modified products of these polymers or copolymers. Here, in the case of random copolymers of ethylene and cyclic olefins, they may contain an α-olefin other than ethylene, or may contain butadiene, isoprene, or the like as a third component.

[0027] [Modified polyolefin resin] Examples of the modified polyolefin resin include the above-mentioned polyethylene resin, polypropylene resin, and resins obtained by modifying an α-olefin copolymer with an unsaturated carboxylic acid and / or an unsaturated carboxylic acid derivative.

[0028] Examples of the unsaturated carboxylic acid and / or unsaturated carboxylic acid derivative include unsaturated carboxylic acids such as maleic acid, fumaric acid, itaconic acid, acrylic acid, and methacrylic acid, and unsaturated carboxylic acid derivatives such as maleic anhydride, itaconic anhydride, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-hydroxyethyl methacrylate, maleic acid monoethyl ester, maleic acid diethyl ester, fumaric acid monomethyl ester, fumaric acid dimethyl ester, acrylamide, methacrylamide, maleic acid monoamide, maleic acid diamide, fumaric acid monoamide, maleimide, N-butylmaleimide, and sodium methacrylate. Among these, acrylic acid, methacrylic acid, maleic acid, and maleic anhydride are preferred from the viewpoint of excellent adhesiveness.

[0029] Specific examples of modified polyolefin resins include ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), ethylene-methyl acrylate copolymer (EMA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-glycidyl methacrylate copolymer (E-GMA), ethylene-vinyl acetate-glycidyl methacrylate copolymer (E-VA-GMA), ethylene-maleic anhydride copolymer (E-MAH), propylene-maleic anhydride copolymer, ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), metal-neutralized ethylene-acrylic acid copolymer, and metal-neutralized ethylene-methacrylic acid copolymer. These may be used alone or in combination. Among these, EMMA, EEA, and EMA are preferred in terms of adhesion when the adhesive resin layer (B) is to undergo cohesive failure.

[0030] The density of the modified polyolefin resin (JIS K7121) is usually 0.870 g / cm 3 or more, preferably 0.880 to 0.950 g / cm 3 is. The melting point (JIS K7121) of the modified polyolefin resin is usually 100°C or higher, preferably 120°C or higher, and although there are no particular upper limits, it is usually 170°C or lower.

[0031] [Polyamide resin] Examples of the polyamide resin include aliphatic polyamide polymers and aromatic polyamide polymers.

[0032] Examples of the aliphatic polyamide polymer include ring-opening polymerization products of cyclic lactams, polycondensation products of aminocarboxylic acids, polycondensation products of dicarboxylic acids and diamines, etc. Specific examples include a homopolymer of ε-caprolactam called nylon 6, polyhexamethylene adipamide called nylon 66, and a copolymer thereof called nylon 6-66. Furthermore, examples of the aromatic polyamide polymer include resins containing, in the molecular chain, 70 mol% or more of polyamide structural units composed of xylylenediamine and an α,ω-aliphatic dicarboxylic acid having from 6 to 12 carbon atoms. Specific examples include homopolymers such as polymetaxylylene adipamide, polymetaxylylene pimelamide, polymetaxylylene azelamide, polyparaxylylene azelamide, and polyparaxylylene decanamide, and copolymers such as metaxylylene / paraxylylene adipamide copolymer, metaxylylene / paraxylylene pimelamide copolymer, metaxylylene / paraxylylene azelamide copolymer, and metaxylylene / paraxylylene sepacamide copolymer. These polyamide resins may be used singly or in combination of two or more.

[0033] [Polyester Resin] Examples of the polyester resin include polyethylene terephthalate resin, polypropylene terephthalate resin, polybutylene terephthalate resin, polyethylene isophthalate resin, polyethylene naphthalate resin, polybutylene naphthalate resin, polyethylene terephthalate / isophthalate copolymer resin, low-crystalline or amorphous polyethylene terephthalate resin containing 15 mol % to 50 mol % of 1,4-cyclohexanedimethanol structural units in total glycol monomer units, polyethylene / neopentyl terephthalate copolymer resin, and aliphatic polyester resins typified by polylactic acid resin.

[0034] The polyester resin also includes a thermoplastic polyester elastomer having a high melting point, highly crystalline aromatic polyester as a hard segment and an amorphous polyester or amorphous polyether as a soft segment.

[0035] Among these thermoplastic resins, polyolefin-based resins and polyester-based resins are preferred in terms of adhesion to the adhesive resin layer (B), more preferably polyethylene-based resins, polypropylene-based resins, modified polyolefin-based resins, and polyethylene terephthalate-based resins, even more preferably polypropylene-based resins and modified polyolefin-based resins, and particularly preferably homopolypropylene and modified polypropylene-based resins.

[0036] Furthermore, when a thermoplastic resin layer (D) described below is present adjacent to the resin layer (A), in terms of adhesion to the thermoplastic resin layer (D), the thermoplastic resin is preferably a modified polyolefin resin, more preferably an ethylene-maleic anhydride copolymer or a propylene-maleic anhydride copolymer, and particularly preferably a propylene-maleic anhydride copolymer.

[0037] Other resins and components may be added to the resin layer (A) as appropriate within the scope of the present invention, but in order to achieve stable adhesion between the resin layer (A) and the adhesive resin layer (B), it is preferable to avoid mixing additives that tend to bleed onto the surface of the resin layer (A) as much as possible. Examples of the other resins and components include softeners, oils (mineral oils), stabilizers (antioxidants, etc.), liquid paraffin, etc. These may be used alone or in combination of two or more.

[0038] The resin layer (A) is a resin layer having a single layer structure, and its thickness is usually 3 to 100 μm, preferably 5 to 80 μm, and more preferably 10 to 70 μm.

[0039] <Adhesive resin layer (B)> The adhesive resin layer (B) contains at least two kinds of styrene-based thermoplastic elastomers, and preferably contains the styrene-based thermoplastic elastomer as a main component.

[0040] The styrene content of the styrene-based thermoplastic elastomer is usually 5 to 80 mass%, preferably 10 to 70 mass%, more preferably 15 to 60 mass%, and even more preferably 20 to 50 mass%. When the styrene content is within the above range, the resealing strength tends to be excellent.

[0041] The melt flow rate [MFR] (JIS K7210, 230°C, 2160g load) of the styrene-based thermoplastic elastomer is usually 0.1 to 100g / 10min, preferably 0.2 to 50g / 10min. When the MFR of the styrene-based thermoplastic elastomer is within the above range, film formability tends to be stable.

[0042] Examples of the styrene-based thermoplastic elastomer include styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-isobutylene-styrene copolymer (SIBS), and hydrogenated versions of these, such as styrene-ethylene-butadiene-styrene block copolymer (SEBS) and styrene-ethylene-propylene-styrene block copolymer (SEPS). Commercially available products of these styrene-based elastomers include "Tufprene," "Asaprene T," "Tuftec," "SOE," and "Asaflex" manufactured by Asahi Kasei Corporation, "Septon" and "Hybra" manufactured by Kuraray Co., Ltd., "KRATON A," "KRATON D," and "KRATON G" manufactured by KRATON, and "SIBSATR" manufactured by Kaneka Corporation.

[0043] In particular, in the present embodiment, a combination of styrene-based thermoplastic elastomers that allows two or more glass transition temperatures to be measured by differential scanning calorimetry (DSC) is preferred. In other words, it is preferred that the at least two types of styrene-based thermoplastic elastomers are incompatible with each other in order to exhibit resealable function.

[0044] The glass transition temperature of at least one of the styrene-based thermoplastic elastomers contained in the adhesive resin layer (B) is preferably −35° C. or lower from the viewpoint of resealing peel strength, more preferably −40° C. or lower, and particularly preferably −45° C. or lower. The lower limit is not particularly limited, but is usually −90° C., preferably −80° C.

[0045] Moreover, it is preferable from the viewpoint of resealing peel strength that the glass transition temperatures of all styrene-based thermoplastic elastomers contained in the adhesive resin layer (B) are within the above range.

[0046] The difference in glass transition temperatures of the styrene-based thermoplastic elastomers contained in the adhesive resin layer (B) is preferably 7°C or more, more preferably 9°C or more, and particularly preferably 10°C or more. By setting the difference in glass transition temperatures within this range, the adhesive resin layer (B) tends to be more susceptible to cohesive failure upon peeling. When three or more types of styrene-based thermoplastic elastomers are contained, the difference in glass transition temperatures between the two styrene-based thermoplastic elastomers with the greatest difference in glass transition temperatures should be within the above range. Furthermore, when the styrene-based thermoplastic elastomer contains two or more compatible styrene-based thermoplastic elastomers and an incompatible styrene-based thermoplastic elastomer, the difference in glass transition temperature between the compatible styrene-based thermoplastic elastomer and the incompatible styrene-based thermoplastic elastomer should be within the above range. Here, the glass transition temperature of the two or more compatible styrene-based thermoplastic elastomers is the glass transition temperature measured, for example, using a differential scanning calorimeter in accordance with JIS K7121 (2012), by increasing the temperature from -120°C to 200°C at a rate of 10°C / min, decreasing the temperature to -120°C at a rate of 20°C / min, and then increasing the temperature again to 200°C at a rate of 10°C / min.

[0047] In particular, in this embodiment, it is preferable that the styrene-based thermoplastic elastomer is selected from the following (i) and (ii), respectively, since this makes the adhesive resin layer (B) more likely to undergo cohesive failure when peeled off. (i) Hydrogenated styrene-butadiene-styrene block copolymer (SEBS), hydrogenated styrene-isoprene-styrene block copolymer (SEPS) (ii) Styrene-butadiene-styrene block copolymer (SBS), styrene-isobutylene-styrene copolymer (SIBS)

[0048] When the total amount of the styrene-based thermoplastic elastomer contained in the adhesive resin layer (B) is taken as 100% by mass, the amount of the styrene-based thermoplastic elastomer selected from (i) is preferably 30 to 95% by mass, more preferably 35 to 93% by mass, even more preferably 40 to 90% by mass, and particularly preferably 50 to 85% by mass. By setting the lower limit of the content of the styrene-based thermoplastic elastomer selected from (i) to be equal to or greater than the above-mentioned value, adhesion to adjacent layers tends to be improved, and by setting the upper limit of the content to be equal to or less than the above-mentioned value, adhesion and initial peeling tend to be stable, resulting in a good peel surface and improved resealability.

[0049] The mass ratio [(i) / (ii)] of the styrene-based thermoplastic elastomer selected from (i) to the styrene-based thermoplastic elastomer selected from (ii) is usually 99 / 1 to 1 / 99, preferably 90 / 10 to 20 / 80, and more preferably 85 / 15 to 25 / 75. If the mass ratio of the styrene-based thermoplastic elastomer is within the above range, the adhesive resin layer (B) tends to easily undergo cohesive failure when peeled off.

[0050] The adhesive resin layer (B) may contain a tackifier, which tends to improve the resealing strength.

[0051] The tackifier may be any natural or synthetic resin that is tacky at room temperature (25°C), including, for example, rosin-based resins such as natural resin rosin, polymerized rosin, hydrogenated rosin, pentaerythritol esters of rosin, and glycerin esters of rosin; terpene-based resins such as terpene-phenol resins, terpene resins (α-pinene resins, β-pinene resins), aromatic-modified terpene resins, and hydrogenated terpene resins; petroleum-based hydrocarbon resins such as aromatic hydrocarbon resins, aliphatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic-alicyclic petroleum resins, aliphatic-aromatic petroleum resins, unsaturated hydrocarbon copolymers, and hydrogenated hydrocarbon resins; phenol-based resins such as phenol-formaldehyde resins and xylene-formaldehyde resins; and chroman resins such as chroman-indene resins. These may be used alone or in combination of two or more. Among these, from the viewpoint of compatibility with styrene-based thermoplastic elastomers, rosin-based resins, terpene-based resins, and petroleum-based hydrocarbon resins are preferred, and terpene-based resins are more preferred. Commercially available tackifiers include the "Haritack Series" manufactured by Harima Chemical Co., Ltd., the "YS Resin Series" manufactured by Yasuhara Chemical Co., Ltd., and the "Super Ester Series," "Ester Gum Series," "Persene Series," and "Arcon Series" manufactured by Arakawa Chemical Industries, Ltd.

[0052] The softening point (JIS K5902) of the tackifier is usually 20 to 180° C., preferably 50 to 140° C., and more preferably 70 to 110° C. When the softening point of the tackifier is within the above range, the resealing function tends to be more excellent.

[0053] When the adhesive resin layer (B) contains a tackifier, the content thereof is usually less than 40% by mass, preferably 1 to 30% by mass, and more preferably 5 to 25% by mass. When the content of the thermoplastic elastomer is within the above range, the resealability tends to be better.

[0054] Other resins and components may be added to the adhesive resin layer (B) as appropriate within the scope of the present invention. Examples of the other resins and components include low-crystalline or amorphous polyolefin resins, softeners, oils (mineral oils), stabilizers (antioxidants, etc.), liquid paraffin, etc. These may be used alone or in combination of two or more.

[0055] The adhesive resin layer (B) is a resin layer having a single layer configuration, and its thickness is not particularly limited, but is usually 3 to 100 μm, preferably 5 to 80 μm, and more preferably 10 to 70 μm. By setting the thickness of the adhesive resin layer (B) within the above range, film formability is stabilized, cohesive failure upon peeling tends to be stable, and strength is also appropriate.

[0056] <Resin layer (C)> The resin layer (C) in the present embodiment is preferably a layer containing a thermoplastic resin, more preferably containing a thermoplastic resin as a main component. When the resin layer (C) has heat-sealing properties, the resin layer (C) can also be used as a heat-sealing resin layer.

[0057] As the thermoplastic resin, polyolefin resins, polyamide resins, polyester resins, etc., which have been described in the resin layer (A), can be used. Among these thermoplastic resins, polyolefin-based resins are preferred in terms of adhesion to the adhesive resin layer (B), more preferably polyethylene-based resins, polypropylene-based resins, and polyethylene terephthalate-based resins, and particularly preferably polypropylene-based resins.

[0058] Furthermore, other resins and components explained in the resin layer (A) may be added to the resin layer (C) as appropriate, within the scope of the present invention.

[0059] The resin layer (C) is a resin layer having a single layer structure, and its thickness is usually 3 to 100 μm, preferably 5 to 80 μm, and more preferably 10 to 70 μm.

[0060] The resin layer (C) may be the same as or different from the resin layer (A), but from the viewpoint of cohesive failure of the adhesive resin layer (B), it is preferable that the resin layer (C) and the resin layer (A) are the same.

[0061] <Thermoplastic resin layer (D)> The present multilayer film preferably has a thermoplastic resin layer (D) adjacent to the resin layer (A) and / or resin layer (C), and more preferably has a thermoplastic resin layer (D) adjacent to the resin layer (A). The thermoplastic resin layer (D) is a layer containing a thermoplastic resin, and preferably contains the thermoplastic resin as a main component. Furthermore, the thermoplastic resin layer (C) is not particularly limited as long as it has a layer configuration that results in an interlayer peel strength that is higher than the interlayer peel strength between the resin layer (A) and the adhesive resin layer (B), and between the adhesive resin layer (B) and the resin layer (C), and further, the thermoplastic resin layer (D) may be a single layer or multiple layers.

[0062] The thermoplastic resin is preferably a thermoplastic resin that can be melt-extruded within a temperature range of 180 to 300°C.

[0063] Among these, from the viewpoints of moldability, transparency, and production costs, the thermoplastic resin is preferably at least one selected from the group consisting of polyolefin-based resins, polyamide-based resins, ethylene-vinyl alcohol-based copolymers, polyester-based resins, and polystyrene-based resins.

[0064] [Polyolefin resin] As the polyolefin-based resin, the polyolefin-based resins described above in connection with the resin layer (A) can be used.

[0065] [Polyamide resin] As the polyamide-based resin, the polyamide-based resins described above in connection with the resin layer (A) can be used.

[0066] [Ethylene vinyl alcohol copolymer] The ethylene vinyl alcohol copolymer (EVOH) is a resin obtained by saponifying a copolymer of ethylene and a vinyl ester monomer with an alkali catalyst or the like.

[0067] The content of ethylene structural units in the EVOH is not particularly limited, but from the viewpoint of film formation stability, it is usually 29 mol% or more, preferably 32 mol% or more, and from the viewpoint of gas barrier properties, it is usually 47 mol% or less, preferably 44 mol% or less. The saponification degree of EVOH is usually 90% or more, preferably 95% or more. By setting the content of ethylene structural units and the degree of saponification of EVOH within the above ranges, it tends to be possible to improve the gas barrier properties, mechanical strength, etc. These may be used alone or in combination of two or more.

[0068] It should be noted that the EVOH is not limited to those produced by saponification, as long as they have a similar chemical structure.

[0069] [Polyester Resin] As the polyester-based resin, the polyester-based resins described above in relation to the resin layer (A) can be used.

[0070] [Polystyrene resin] Examples of the polystyrene resin include general-purpose polystyrene (GPPS), high-impact polystyrene (HIPS), styrene-(meth)acrylic acid ester copolymer, and resin containing 1 to 20 mass % of a rubber-like elastomer as dispersed particles in a continuous phase of a styrene copolymer consisting of a styrene-based monomer and a (meth)acrylic acid ester.

[0071] In particular, it is preferable to have an EVOH layer (a layer containing EVOH as the main component) and / or a polyamide-based resin layer (a layer containing a polyamide-based resin as the main component) in order to impart functions such as gas barrier properties and pinhole resistance to the present multilayer film.

[0072] In addition, the thermoplastic resin layer (D) may contain an adhesive resin so that the interlayer peel strength between the thermoplastic resin layer (D) and an adjacent layer is higher than the interlayer peel strength between the resin layer (A) and the adhesive resin layer (B) and between the adhesive resin layer (B) and the resin layer (C), or an adhesive resin layer may be disposed between the thermoplastic resin layer (D) and an adjacent layer to increase the interlayer peel strength between the thermoplastic resin layer (D) and an adjacent layer.

[0073] The adhesive resin can be the above-mentioned modified polyolefin resin, and among them, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-maleic anhydride copolymer, and propylene-maleic anhydride copolymer are preferred in terms of excellent adhesiveness. Commercially available modified polyolefin resins that can be used as the adhesive resin include "Admer" manufactured by Mitsui Chemicals, Inc. and "Modic" manufactured by Mitsubishi Chemical Corporation.

[0074] The thickness (total) of the thermoplastic resin layer (D) is usually 1 to 1000 μm, preferably 10 to 600 μm, and more preferably 20 to 500 μm. When the thickness of the thermoplastic resin layer (D) is within the above range, it is easy to arrange a layer that imparts properties such as gas barrier property or pinhole resistance, or an adhesive resin layer, and also, during heat sealing, heat is easily transferred to the heat seal layer (E) described below, which tends to facilitate heat sealing with the sealed portion of the sealed object.

[0075] <Heat seal layer (E)> The present multilayer film preferably has a heat seal layer (E) on the surface side of the resin layer (C) from the viewpoint of heat sealability.

[0076] The heat seal layer (E) is not particularly limited as long as it has a layer configuration that results in an interlayer peel strength higher than the interlayer peel strength between the resin layer (A) and the adhesive resin layer (B), and between the adhesive resin layer (B) and the resin layer (C), and may be a single layer or a multilayer.

[0077] The heat seal layer (E) contains a heat sealable thermoplastic resin, and preferably contains a thermoplastic resin as a main component.

[0078] The thermoplastic resin can be appropriately selected and used so as to provide an appropriate heat seal strength, taking into consideration the material of the sealing surface of the object to be sealed and the types of resins used in the resin layer (A), adhesive resin layer (B), and resin layer (C) of the present multilayer film.

[0079] Specific examples of thermoplastic resins include polyolefin-based resins, polystyrene-based resins, polyester-based resins, and styrene-based thermoplastic elastomers, which are described for the resin layer (A). These may be used alone or in combination of two or more. Among these, polyolefin-based resins are preferred because they are inexpensive, have excellent moldability, and can provide a higher interlayer peel strength than the interlayer peel strength between the resin layer (A) and the adhesive resin layer (B), and between the adhesive resin layer (B) and the resin layer (C) under heat-sealing conditions (temperature: about 120 to 180°C) typically used for various multilayer films. Polypropylene-based resins and modified polyolefin-based resins are more preferred, and random polypropylene and ethylene-maleic anhydride copolymers are particularly preferred.

[0080] In addition, the heat seal layer (E) may contain an adhesive resin so that the interlayer peel strength between the heat seal layer (E) and an adjacent layer is higher than the interlayer peel strength between the resin layer (A) and the adhesive resin layer (B) and between the adhesive resin layer (B) and the resin layer (C), or an adhesive resin layer may be disposed between the heat seal layer (E) and an adjacent layer to increase the interlayer peel strength between the heat seal layer (E) and an adjacent layer. As the adhesive resin, the adhesive resins explained in the thermoplastic resin layer (D) can be used.

[0081] It is preferable to add a lubricant or an anti-blocking agent to the heat seal layer (E) in order to improve processability during extrusion film formation and packaging suitability in a filling machine such as a deep drawing packaging machine.

[0082] Furthermore, other components may be appropriately added to the heat seal layer (E) within the scope of the present invention. Examples of the other components include antifogging agents, antistatic agents, heat stabilizers, nucleating agents, antioxidants, release agents, and ultraviolet absorbers. These may be used alone or in combination of two or more.

[0083] The thickness of the heat seal layer (E) is not particularly limited, but is usually 1 to 30 μm, preferably 3 to 25 μm, and more preferably 5 to 15 μm. If the thickness of the heat seal layer (E) is equal to or greater than the above-mentioned numerical value, problems such as deformation due to pressure from a heat seal hot plate during heat sealing and deterioration of the functions of these layers tend to be prevented. On the other hand, if the thickness of the heat seal layer (E) is equal to or less than the above-mentioned numerical value, it tends to be possible to expose the adhesive resin layer (B) in a resealable state when peeling it off.

[0084] Furthermore, when the resin layer (C) and the heat-sealing layer (E) are adjacent to each other, their total thickness is usually 1 to 130 μm, preferably 3 to 50 μm, and more preferably 4 to 40 μm. If the total thickness is equal to or greater than the above-mentioned numerical value, film formation is stable, and defects such as deformation due to pressure from a heat-sealing hot plate during heat-sealing, which would reduce the functionality of each layer, tend to be prevented. If the thickness is equal to or less than the above-mentioned numerical value, the resin layer (C) and the heat-sealing layer (E) tend to be easily ruptured when opening the package, providing an appropriate initial peel strength.

[0085] Next, a method for producing the present multilayer film will be described. The method for producing the multilayer film in this embodiment is not particularly limited, but a co-extrusion method can be suitably used, which is excellent in protecting the adhesive resin layer (B), productivity, hygiene, etc. For example, the various raw materials forming the resin layer (A), adhesive resin layer (B), resin layer (C), thermoplastic resin layer (D), and heat seal layer (E) described above can be heated and melted in separate extruders, laminated in the molten state by a known method such as a multi-manifold method or a feed block method, and then molded into the multilayer film by a T-die chill roll method, an inflation method, or the like.

[0086] The layer structure of the present multilayer film is not particularly limited as long as the resin layer (A), adhesive resin layer (B), and resin layer (C) are laminated in the order (A) / (B) / (C) from the outer layer side. However, the following layer structure is an example of a preferred layer structure. (1) Resin layer (A) / adhesive resin layer (B) / resin layer (C) (2) Resin layer (A) / adhesive resin layer (B) / resin layer (C) / heat seal layer (E) (3) EVOH layer (D) / polyamide resin layer (D) ( / adhesive resin layer) / resin layer (A) / adhesive resin layer (B) / resin layer (C) / heat seal layer (E) (4) Polyamide resin layer (D) / EVOH layer (D) ( / adhesive resin layer) / resin layer (A) / adhesive resin layer (B) / resin layer (C) / heat seal layer (E)

[0087] In order to improve the printability and lamination suitability of the present multilayer film, it is preferable to subject the surface of the outermost layer of the present multilayer film to a surface treatment. Examples of the surface treatment method include corona treatment, plasma treatment, chromic acid treatment, flame treatment, surface oxidation treatment such as hot air treatment, ozone or ultraviolet treatment, surface roughening treatment such as sandblasting, etc. Among these, corona treatment is preferred from the viewpoints of the effect of the surface treatment, productivity, and production costs.

[0088] Furthermore, the present multilayer film can be made into a laminate film or a laminate sheet by laminating a laminate substrate on the surface of the present multilayer film, if necessary, via an adhesive resin or adhesive, using a known method such as dry lamination or extrusion lamination.

[0089] The laminate substrate is not particularly limited, and examples thereof include biaxially oriented polypropylene film, biaxially oriented nylon film, biaxially oriented polyethylene terephthalate film, unstretched polypropylene sheet, unstretched polyethylene terephthalate sheet, aluminum foil, paper, nonwoven fabric, etc. In the present invention, a dry lamination method is preferably used, and examples of adhesives used in this method include polyester-polyurethane adhesives, polyether-polyurethane adhesives, etc.

[0090] The multilayer film obtained in this manner is heat-sealed to an object to be sealed to form a multilayer body (packaging body), and when the multilayer film is then peeled off from the object to be sealed, the adhesive resin layer (B) undergoes cohesive failure and peels off, exposing the adhesive resin layer (B) in a resealable state on both sides of the peeled surface, or exposing the adhesive resin layer (B) and the resin layer (A) or the resin layer (C) in a resealable state, making it possible to reseal the film by simply applying pressure with hands or fingers.

[0091] For example, as shown in Figure 1, when the present multilayer film, which is composed of a thermoplastic resin layer (D) 3, a resin layer (A) 4, an adhesive resin layer (B) 5, and a resin layer (C) 6 in this order, is used as a lid material 1 and is heat-sealed to a base material 2, which is an object to be sealed and which has a surface resin layer 7 and a heat-sealable resin layer 8 laminated thereon, the resin layer (C) 6 of the lid material 1 is heat-sealed to the heat-sealable resin layer 8 of the base material 2. In other words, the lid material 1 and the base material 2 are bonded together at a heat-sealed portion 9 formed by heat sealing.

[0092] Thereafter, when the tab portion 10 provided on the lid material 1 is pinched and pulled, as shown in Figure 2, at the heat-sealed portion 9, first the adhesive resin layer (B) 5 and resin layer (C) 6 on the tab portion 10 side are broken from the lid material 1, and cohesive failure begins between the layers of the resin layer (A) 4 in the lid material 1. When the cohesive failure of the resin layer (A) 4 reaches the heat-sealed portion 9 on the opposite side to the tab portion 10 side, the adhesive resin layer (B) 5 and resin layer (C) 6 of the lid material 1 are broken. A portion of the broken adhesive resin layer (B) 5 and resin layer (C) 6 of the lid material 1 move to the side of the base material 2, which is the sheet-receiving body, and cohesively failed adhesive resin layer (B) 5 is formed in exposed portions 11 and 12.

[0093] When resealing, as shown in Figure 3, the peeled lid material 1 is placed over the base material 2, and the thermoplastic resin layer (D) 3 is pressed and bonded with hands or fingers, so that the exposed portion 11 of the adhesive resin layer (B) 5 of the lid material 1 overlaps with the exposed portion 12 of the thermoplastic resin layer (B) 5 of the lid material 1 that has transferred to the base material 2, thereby resealing the lid material 1 and the base material 2.

[0094] Furthermore, for example, when the present multilayer film, which is composed of a thermoplastic resin layer (D) 3, a resin layer (A) 4, an adhesive resin layer (B 5), and a resin layer (C 6) in this order as shown in Figure 1, is used as a lid material 1 and heat-sealed to a base material 2 as a sealed object, when the tab portion 10 provided on the lid material 1 is pinched and pulled, at the heat-sealed portion 9, the adhesive resin layer (B) 5 and the resin layer (C) 6 on the tab portion 10 side are first broken from the lid material 1, and peeling occurs between the adhesive resin layer (B) 5 and the resin layer (A) 4 in the lid material 1, or the resin layer (C) 6 is broken from the lid material 1, and peeling begins between the adhesive resin layer (B) 5 and the resin layer (C) 6 in the lid material 1. Thereafter, when the peeling between the adhesive resin layer (B) 5 and the resin layer (A) 4, or the peeling between the adhesive resin layer (B) 5 and the resin layer (C) 6, reaches the heat seal portion 9 on the opposite side to the tab portion 10, the adhesive resin layer (B) 5 and the resin layer (A) 4, or the resin layer (C) 6, of the lid material 1 are ruptured. Then, the adhesive resin layer (B) 5 of the lid material 1 moves in an exposed state to the base material 2 side, which is the sheet-covered body, or is exposed on the surface of the lid material 1, thereby becoming resealable.

[0095] In order to realize such a resealable function, it is necessary to configure the film so that, when peeled off as described above, or when the adhesive resin layer (B) peels off by cohesive failure, the adhesive resin layer (B) is exposed on both sides of the peeled surface in a resealable state, or the adhesive resin layer (B) and the resin layer (A) or the resin layer (C) are exposed in a resealable state. At the same time, it is also important to ensure that the film has a sufficient interlayer peel strength to maintain its function as a package, so that the layers do not easily peel off or are not opened by a slight impact, etc.

[0096] When the multilayer film is heat-sealed to an object to be sealed and then peeled at 23°C or -20°C, the lower limit of the peel strength (initial peel strength) is typically 100 gf / 15 mm width, preferably 300 gf / 15 mm width, and more preferably 1000 gf / 15 mm width. On the other hand, the upper limit of the peel strength (initial peel strength) is not particularly limited, but is equal to or lower than the interlayer peel strength between the resin layer (A) and the adhesive resin layer (B), preferably 5000 gf / 15 mm width, more preferably 4000 gf / 15 mm width, and even more preferably 3500 gf / 15 mm width. If the peel strength (initial peel strength) is equal to or higher than the lower limit, problems such as the package being easily opened by slight impact are unlikely to occur. If the peel strength (initial peel strength) is equal to or lower than the upper limit, the package tends to be easily opened by hand (easy opening).

[0097] Regarding resealability after opening, the lower limit of the peel strength (resealing peel strength) when peeled at 23°C or -20°C is usually 20 gf / 15 mm width, preferably 50 gf / 15 mm width, more preferably 100 gf / 15 mm width, and particularly preferably 200 gf / 15 mm width. The upper limit of the peel strength (resealing peel strength) is not particularly limited, but is equal to or less than the peel strength (initial peel strength), preferably 1000 gf / 15 mm width, and more preferably 800 gf / 15 mm width. If the resealing peel strength is within the above range, practical resealability tends to be obtained.

[0098] The present multilayer film can be suitably used as a lid material for various packages. For example, when the present multilayer film is used as a lid material for a package (container), the heat seal resin layer (E) of the present multilayer film and the heat seal layer of the base material (sealed object) are overlapped and heat sealed to form a package (container) that has airtightness, practical initial peel strength, and resealability.

[0099] As mentioned above, the present multilayer film can be used as a lid material for various containers, and its use is not particularly limited, but it can be used, for example, as a container for packaging several items such as instant noodles, snacks, chocolate confectionery, processed meat products such as sliced ​​ham, wet tissues, sweat blotting paper, air fresheners, disposable diapers, etc., or as a container for packaging cosmetics that are opened and used each time, sanitary products, medicinal patches, first-aid adhesive bandages, throat lozenges, etc. In particular, it can be suitably used as a lid material for packages for storing items in which the remaining contents after opening are susceptible to deterioration due to oxidation, moisture absorption, drying, etc. [Example]

[0100] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. In the examples, "parts" and "%" are by mass.

[0101] Prior to the examples, the following raw materials were prepared. [Polyolefin resin] hPP sheet: 100 μm thick non-oriented polypropylene (CPP) sheet Acid-modified PP (modified polypropylene resin, MFR (230°C) 5.7g / 10min, melting point 135°C) LDPE (low density polyethylene, density 0.924g / cm 3 ) [Styrene-based thermoplastic elastomer] SEBS1 (styrene-based thermoplastic elastomer, styrene content 12%, glass transition temperature -42°C) SEPS1 (styrene-based thermoplastic elastomer, styrene content 12%, glass transition temperature -33°C) SEPS2 (styrene-based thermoplastic elastomer, styrene content 20%, glass transition temperature -17°C) SEPS3 (styrene-based thermoplastic elastomer, styrene content 13%, glass transition temperature -59°C) SIBS1 (styrene-isobutylene-styrene copolymer, styrene content 23%, glass transition temperature -65°C, MFR (230°C) 6g / 10min) SIBS2 (styrene-isobutylene-styrene copolymer, styrene content 24%, glass transition temperature -65°C, MFR (230°C) 20g / 10min) SBS (styrene-butadiene-styrene copolymer, styrene content 35%, glass transition temperature -92°C) [Tackifier] Tackifier 1 (hydrogenated rosin ester, softening temperature 85°C) Tackifier MB (70% petroleum resin, 30% styrene elastomer) [Other materials] Laminated film: A laminated film with a total thickness of 85μm, consisting of an outer layer of unstretched polypropylene film (Toray Advanced Film Co., Ltd.'s "Torayfan" 30μm), a middle layer of biaxially oriented nylon film (Mitsubishi Chemical Corporation's "Superneil" 15μm), and an inner layer of unstretched polypropylene film (Toray Advanced Film Co., Ltd.'s "Torayfan" 40μm), each bonded together using the dry lamination method.

[0102] <Examples 1 to 6 and Comparative Examples 1 to 4> The adhesive resin layer (B) was obtained by kneading the raw materials for the adhesive resin layer (B) shown in Tables 1 and 2 below in a Labo Plastomill (Toyo Seiki Co., Ltd., "4C150") at 200°C x 60 rpm x 5 minutes, and then press-molding at 200°C. The obtained adhesive resin layer (B) was layered in the order of resin layer (A) / adhesive resin layer (B) / resin layer (C) using the raw materials for the resin layer (A) and resin layer (C) shown in Table 1 below, and heat-sealed at 200°C to produce a multilayer film, which was used as an evaluation sample.

[0103] <Examples 7 to 16> The raw materials for each layer shown in Tables 1 and 2 below were co-extruded using a single-screw extruder by the T-die method at a die temperature of 240°C, and then quenched with a cast roll at 90°C to produce a multilayer film.

[0104] The obtained multilayer films of Examples 7 to 16 were heat-sealed using a deep drawing packaging machine ("R-530" manufactured by Multivac) with the resin layer (A) side facing the hot plate in a configuration of laminate film (substrate) / resin layer (A) / adhesive resin layer (B) / resin layer (C) / laminate film (counterpart) at 170°C, a sealing time of 4 seconds, and a sealing pressure of 1.5 MPa to produce a multilayer body with a heat-sealed width of 7 mm, long sides of 170 mm, and short sides of 128 mm, which was used as an evaluation sample.

[0105] In the above examples and comparative examples, the resin layer (C) has heat-sealing properties and therefore also functions as a heat-sealing resin layer.

[0106] The resulting multilayer films and multilayer bodies were evaluated as follows, and the results are shown in Tables 1 and 2 below.

[0107] [Peel test (23°C)] The obtained multilayer films of Examples 1 to 6 and Comparative Examples 1 to 4, and the multilayer bodies of Examples 7 to 16 were cut into strips with a width of 15 mm. The outer resin layers (A) and (C) of the multilayer films of Examples 1 to 6 and Comparative Examples 1 to 4, and the outer laminate film (substrate and mating material) of the multilayer bodies of Examples 7 to 16 were then clamped with a zipper and peeled at room temperature (23°C) at a peel rate of 200 mm / min to measure the initial peel strength, and evaluation was performed according to the following evaluation criteria. The peeled surface was also visually confirmed. Thereafter, the peeled surfaces of the measured samples were resealed by pressing together, and the peel test was conducted again to measure the resealing strength, which was evaluated according to the following evaluation criteria. [Initial strength] ◎: 1000gf / 15mm width or more 〇: 300gf / 15mm width or more, less than 1000gf / 15mm width ×: Less than 300gf / 15mm width or no peeling [Resealing strength] ◎:200gf / 15mm width or more 〇: 50gf / 15mm or more and less than 200gf / 15mm ×: Less than 50gf / 15mm width [Peeling surface] ○: Cohesive failure (the peeled surface turns white and there is an adhesive resin layer on both sides of the peeled surface) △: Interfacial peeling (adhesive resin layer exposed on one side)

[0108] [Peel test (-20°C)] The obtained multilayer bodies of Examples 7 to 12 were cut into strips with a width of 15 mm and stored in a freezer (-20°C) for 5 days. Immediately after taking them out, the outer laminate film (substrate and mating material) was clamped with a zipper and peeled at a peeling speed of 200 mm / min to measure the initial peel strength and evaluate it according to the following evaluation criteria. The peeled surface was also visually confirmed. The peeled surfaces of the measured samples were then resealed by pressing them together at 23°C, and then stored in a freezer (-20°C) for 3 hours. Immediately after removing the samples, the peel test was conducted again, and the resealing strength was measured and evaluated according to the following criteria. [Initial strength] ◎: 1000gf / 15mm width or more 〇: 300gf / 15mm width or more, less than 1000gf / 15mm width ×: Less than 300gf / 15mm width or no peeling [Resealing strength] ◎:200gf / 15mm width or more 〇: 50gf / 15mm or more and less than 200gf / 15mm ×: Less than 50gf / 15mm width [Peeling surface] ○: Cohesive failure (the peeled surface turns white and there is an adhesive resin layer on both sides of the peeled surface) △: Interfacial peeling (adhesive resin layer exposed on one side)

[0109] [Glass transition temperature (Tg) of adhesive resin layer (B)] The raw materials for the adhesive resin layer (B) of each example and comparative example shown in Tables 1 and 2 below were kneaded in a Laboplastomill ("4C150" manufactured by Toyo Seiki Co., Ltd.) at 200°C x 60 rpm x 5 minutes, and then press-molded at 200°C to obtain a single-layer adhesive resin layer (B). The adhesive resin layer (B) obtained in each example and comparative example was measured for glass transition temperature (Tg) using a differential scanning calorimeter (TA Instruments, "DSC2500") at a temperature of -120 to 200°C (10°C / min), and evaluated according to the following evaluation criteria. [Evaluation criteria] ○: Two or more Tg values ​​are measured ×: Only one Tg is measured

[0110] [Table 1]

[0111] [Table 2]

[0112] From the results in Tables 1 and 2, it can be seen that the multilayer films of Examples 1 to 16 had good initial strength, and when peeled, cohesive failure of the adhesive resin layer (B) occurred, exposing the adhesive resin layer (B) on both sides of the peeled surface, thereby exhibiting good resealing strength. In addition, the multilayer films of Examples 15 and 16 had good initial strength, and when peeled, interfacial peeling occurred between the adhesive resin layer (B) and the resin layer (A), exposing the adhesive resin layer (B) on the peeled surface, thereby exhibiting good resealing strength. On the other hand, in the multilayer film of Comparative Example 1, the Tg of the two styrene-based thermoplastic elastomers used was close to each other, and only one Tg was measured, so stable cohesive failure did not occur and the resealable function was not exhibited. Furthermore, the multilayer film of Comparative Example 2 using only SEBS and the multilayer film of Comparative Example 3 using only SEPS had such high initial peel strength that they could not be opened. Furthermore, the multilayer film of Comparative Example 4, which used two styrene-based thermoplastic elastomers, SEBS and SEPS, was unable to be opened because the two styrene-based thermoplastic elastomers were miscible with each other and the initial peel strength was too high. [Industrial Applicability]

[0113] The multilayer film can be suitably used as a lid material for resealable packages. [Explanation of symbols]

[0114] 1 Lid material 2 Bottom material 3. Thermoplastic resin layer of lid material 4. Resin layer of lid material 5. Adhesive resin layer of lid material 6 Resin layer of lid material 7. Surface resin layer of base material 8 Heat-seal resin layer of base material 9 Heat-sealed part of base material 10 Tab of lid 11 Exposed portion of adhesive resin layer when peeled off 12 Exposed portion of adhesive resin layer when peeled off

Claims

1. A resealable multilayer film in which at least a resin layer (A), an adhesive resin layer (B), and a resin layer (C) are laminated in the order (A) / (B) / (C) from the outer layer side, wherein the adhesive resin layer (B) contains at least two types of styrene-based thermoplastic resin elastomers.

2. 2. The resealable multilayer film according to claim 1, wherein the styrene-based thermoplastic elastomer of the adhesive resin layer (B) is selected from the following (i) and (ii), and when the total amount of the styrene-based thermoplastic elastomer contained in the adhesive resin layer (B) is taken as 100% by mass, the styrene-based thermoplastic elastomer selected from (i) accounts for 30 to 95% by mass: (i) Hydrogenated styrene-butadiene-styrene block copolymer, hydrogenated styrene-isoprene-styrene block copolymer (ii) Styrene-butadiene-styrene block copolymer, styrene-isobutylene-styrene copolymer.

3. 2. The resealable multilayer film according to claim 1, wherein the difference in glass transition temperature of the styrene-based thermoplastic elastomer contained in the adhesive resin layer (B) is 7°C or more.

4. The resealable multilayer film according to claim 1 , wherein the resin layer (A) and the resin layer (C) each contain a polypropylene-based resin.

5. 2. The resealable multilayer film according to claim 1, further comprising a thermoplastic resin layer (D) adjacent to the resin layer (A) and / or the resin layer (C), wherein the thermoplastic resin layer (D) contains at least one thermoplastic resin selected from the group consisting of polyolefin-based resins, polyamide-based resins, ethylene-vinyl alcohol-based copolymers, polyester-based resins, and polystyrene-based resins.

6. The resealable multilayer film according to claim 1, further comprising a heat-sealable resin layer (E) on the surface side of the resin layer (C).

7. 7. The resealable multilayer film according to claim 1, wherein, when the resealable multilayer film is heat-sealed to an object to be sealed and the resealable multilayer film is peeled off from the object, the adhesive resin layer (B) peels off by undergoing cohesive failure, and the adhesive resin layer (B) is exposed on both sides of the peeled surface in a resealable state.

8. 7. The resealable multilayer film according to claim 1, wherein when the resealable multilayer film and an object to be sealed are heat-sealed and the resealable multilayer film is peeled off from the object to be sealed, the adhesive resin layer (B) and the resin layer (A) or the resin layer (C) are exposed in a resealable state.

9. A resealable multilayer body obtained by heat-sealing the resealable multilayer film according to claim 7 to an article to be sealed.

10. 10. The resealable multilayer body according to claim 9, wherein, when the resealable multilayer film is peeled off from the resealable multilayer body, the adhesive resin layer (B) undergoes cohesive failure and peels off, exposing the adhesive resin layer (B) in a resealable state on both sides of the peeled surface.

11. A resealable package using the resealable multilayer body according to claim 9.

12. A resealable multilayer body obtained by heat-sealing the resealable multilayer film according to claim 8 to an article to be sealed.

13. A resealable package using the resealable multilayer body according to claim 12.

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