Sealant film, laminating film and packaging materials

Abstract

SOLUTION: Provided is a sealant film, comprising a surface resin layer (A), an adhesive resin layer (B), a release resin layer (C), and a heat sealable resin layer (D) laminated, wherein the adhesive resin layer (B) comprises a thermoplastic elastomer (b1) and a tackifier resin (b2), the release resin layer (C) comprises an ethylenic ionomer (c1) having a polar group concentration exceeding 5.5 mole% in an amount of 40 mass% or more of resin components contained in the release resin layer (C) and, further, the release resin layer (C) comprises an ethylenic ionomer (c2) having a polar group concentration equal to 5.5 mole% or less in an amount of 0 to 60 mass% of resin components contained in the release resin layer (C), and the heat sealable resin layer (D) comprises an ethylenic resin (d1).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a sealant film, a laminate film, and a packaging material that have good adhesion to an adherend such as a heat-sealed portion of a packaging container, can be suitably peeled off, and can be resealed after peeling. [Background technology]

[0002] Packaging materials using easy-peel films that can be easily opened are widely used as packaging materials for various foods and medical products. Packaging materials using easy-peel films are required to have resealability, that is, to be able to easily reseal the film after opening it, for the purpose of preserving the remaining contents, etc.

[0003] Examples of resealable films that have been disclosed include a multilayer film in which an adhesive resin layer containing an amorphous olefin-based resin and a heat-sealable resin layer containing a thermoplastic resin are laminated together (see Patent Document 1), and a multilayer film in which an adhesive resin layer containing a styrene-based elastomer as a main component is laminated onto a release resin layer using an amide-based resin or the like (see Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-119075 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-043964 Summary of the Invention [Problem to be solved by the invention]

[0005] The multilayer film has resealability, which allows it to be resealed even after being opened, by using a specific configuration of the laminated resin layers. However, if the seal strength after resealing is insufficient, the remaining contents may not be preserved sufficiently or the contents may fall out, and therefore, it is desired to further improve the seal strength after resealing.

[0006] Furthermore, when the film composition is adjusted to improve the seal strength after resealing, the initial peel strength may increase, impairing the ease of opening, or the seal surface may not be exposed well, making it impossible to achieve the desired resealability.

[0007] The problem to be solved by the present invention is to provide a laminate film that has suitable heat sealability to other films and to an adherend, and is easy to open, and that can be suitably resealed even after being opened once. [Means for solving the problem]

[0008] The present invention provides a sealant film comprising a surface resin layer (A), an adhesive resin layer (B), a release resin layer (C), and a heat-sealable resin layer (D), the adhesive resin layer (B) contains a thermoplastic elastomer (b1) and a tackifying resin (b2), the release resin layer (C) contains an ethylene-based ionomer (c1) having a polar group concentration of more than 5.5 mol% in an amount of 40 mass% or more of the resin component contained in the release resin layer (C); further, the release resin layer (C) contains an ethylene-based ionomer (c2) having a polar group concentration of 5.5 mol% or less in an amount of 0 to 60 mass% of the resin component contained in the release resin layer (C), The above-mentioned problems are solved by a sealant film characterized in that the heat-sealable resin layer (D) contains an ethylene-based resin (d1).

[0009] The present invention also solves the above problems by providing a laminate film containing the above-described sealant film.

[0010] The present invention also solves the above problems by providing a packaging material containing the above-described sealant film. [Effects of the Invention]

[0011] The sealant film of the present invention has favorable heat sealing properties and easy opening properties, and can be resealed with excellent sealing strength even after being opened. It can also protect the remaining contents even after being opened, making it suitable for use in packaging various foods, medical products, etc. DETAILED DESCRIPTION OF THE INVENTION

[0012] The sealant film of the present invention is a laminated sealant film comprising a surface resin layer (A), an adhesive resin layer (B), a release resin layer (C), and a heat-sealing resin layer (D). The adhesive resin layer (B) contains a thermoplastic elastomer (b1) and a tackifier resin (b2). The release resin layer (C) contains an ethylene-based ionomer (c1) having a polar group concentration of more than 5.5 mol% in a resin component contained in the release resin layer (C) at a content of 40 mass% or more and an ethylene-based ionomer (c2) having a polar group concentration of 5.5 mol% or less in a resin component contained in the release resin layer (C) at a content of 0 to 60 mass%. The heat-sealing resin layer (D) contains an ethylene-based resin (d1).

[0013] Furthermore, the heat-sealable resin layer (D) contains a thermoplastic elastomer (d2) in an amount of 0 to 80 mass% of the resin components contained in the heat-sealable resin layer (D), and the content of the ethylene-based ionomer (c2) and the thermoplastic elastomer (d2) in the sealant film is 10 to 60% as represented by the following formula: [((Wc2 / Wct)×100)+((Wd2 / Wdt)×100)] / 2 Wct: Total amount (mass) of resin components contained in the peelable resin layer (C) Wc2: Content (by mass) of ethylene-based ionomer (c2) having a polar group concentration of 5.5 mol% or less in the resin component contained in the release resin layer (C) Wdt: Total amount (mass) of resin components contained in the heat seal resin layer (D) Wd2: Content (by mass) of thermoplastic elastomer (d2) in the resin component contained in the heat seal resin layer (D)

[0014] [Surface resin layer (A)] The surface resin layer (A) used in the present invention is a layer that forms the surface opposite to the heat seal resin layer (D) of the sealant film. Various resins used in sealant films can be used as the resin for the surface resin layer (A), but an olefin-based resin is preferably used as the main resin component because it is easy to obtain adhesion to other layers. When an olefin-based resin is used for the surface resin layer (A), the content of the olefin-based resin is preferably 80% by mass or more, and more preferably 90% by mass or more, of the resin components contained in the surface resin layer (A). It is also preferable that the resin component used is solely an olefin-based resin.

[0015] The olefin-based resin used in the surface resin layer (A) used in the present invention can be an ethylene-based resin, a propylene-based resin, a butylene-based resin, etc., and it is preferable to use an ethylene-based resin as the main resin component. When an ethylene-based resin is used as the main resin component, the content of the ethylene-based resin in the olefin-based resin used in the surface resin layer (A) is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. It is also preferable that the olefin-based resin used is only an ethylene-based resin.

[0016] Examples of the ethylene-based resin include polyethylene resins such as very low density polyethylene (VLDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), linear medium density polyethylene (LMDPE), and medium density polyethylene (MDPE); ethylene-based copolymers such as ethylene-vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate (EMA) copolymer, ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), ethylene-acrylic acid copolymer (EAA), and ethylene-methacrylic acid copolymer (EMAA); and further, ionomers of ethylene-acrylic acid copolymers, ionomers of ethylene-methacrylic acid copolymers, and polyethylene-based elastomers. The ethylene-based resin may be used alone or in combination of two or more. Among the ethylene-based resins, ultra-low density polyethylene, low density polyethylene, linear low density polyethylene, and linear medium density polyethylene are preferably used, with linear low density polyethylene being particularly preferred, as they are likely to provide suitable impact resistance.

[0017] The density of the ethylene resin is preferably 0.950 g / cm because good impact resistance can be easily obtained. 3 or less, more preferably 0.940 g / cm 3 Also, it is 0.900 g / cm 3 It is preferable that the density is 0.910 g / cm or more. 3 More preferably, it is equal to or greater than this.

[0018] The melt flow rate (MFR) of the ethylene resin is 0.5 to 50 g / 10 min (190°C, 21.18 N), preferably 1 to 30 g / 10 min (190°C, 21.18 N), and more preferably 2 to 20 g / 10 min (190°C, 21.18 N). An MFR in this range is preferred in terms of obtaining good film-forming properties.

[0019] Examples of the propylene-based resin that can be used include propylene homopolymers, propylene-α-olefin random copolymers such as propylene-ethylene copolymers, propylene-butene-1 copolymers, and propylene-ethylene-butene-1 copolymers, and propylene-α-olefin block copolymers. When using an olefin-based resin other than an ethylene-based resin such as these propylene-based resins, the content of the propylene-based resin or the like is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 10% by mass or less, of the olefin-based resin used in the surface resin layer (A).

[0020] The surface resin layer (A) used in the present invention may contain other resins in addition to those mentioned above, such as thermoplastic elastomers such as polypropylene elastomers, butene elastomers, and styrene elastomers.

[0021] When the other resins are used, the content thereof is preferably 20% by mass or less, more preferably 10% by mass or less, of the resin components contained in the surface resin layer (A).

[0022] In addition to the resin components described above, various additives may be appropriately used in the surface resin layer (A) used in the present invention. Examples of such additives include lubricants, antiblocking agents, ultraviolet absorbers, light stabilizers, antistatic agents, antifogging agents, and colorants. When such additives are used, they are preferably used in an amount of 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably about 0.01 to 3 parts by mass, per 100 parts by mass of the resin components used in the surface resin layer (A).

[0023] In particular, in order to impart processability during film formation and packaging suitability in filling machines, the friction coefficient of the surface resin layer (A) used in the present invention is preferably 0.9 or less, and more preferably 0.8 or less, and therefore it is also preferable to add a lubricant or anti-blocking agent to the surface resin layer (A) as appropriate.

[0024] The thickness ratio of the surface resin layer (A) used in the present invention to the total thickness of the sealant film is preferably in the range of 20 to 70%, more preferably in the range of 30 to 60%, since suitable impact resistance can be easily obtained.

[0025] [Adhesive resin layer (B)] The adhesive resin layer (B) used in the present invention is a resin layer containing a thermoplastic elastomer (b1) and a tackifying resin (b2), and contributes to resealing by adhesion when the sealant film of the present invention or a film containing the sealant film is peeled (unsealed) after heat sealing. A preferred mode of peeling and resealing is peeling at the interface between the adhesive resin layer (B) and the release resin layer (C) used in the present invention, then re-contacting the peeled adhesive resin layer (B) with the release resin layer (C) and, if necessary, pressing them together to reseal. During peeling at the adhesive resin layer (B) / release resin layer (C) interface, a portion of the adhesive resin layer (B) may remain on the surface of the release resin layer (C), or a portion of the release resin layer (C) may remain on the surface of the adhesive resin layer (B). However, after peeling, the exposed portion of the adhesive resin layer (B) on the surface of the adhesive resin layer (B) preferably accounts for 60% or more of the area of ​​the peeled portion, more preferably 70% or more, and even more preferably 80% or more. By setting the ratio of the exposed portion of the adhesive resin layer (B) on the release surface to within this range, it becomes easier to obtain favorable resealability.

[0026] The thermoplastic elastomer (b1) used in the adhesive resin layer (B) used in the present invention may be a thermoplastic elastomer such as an ethylene-based elastomer, a propylene-based elastomer, or a butene-based elastomer, or a styrene-based elastomer. Among these, an ethylene-based elastomer is preferred because it is inexpensive and easily provides favorable releasability and resealability. Furthermore, a styrene-based elastomer is preferred because it easily provides particularly excellent releasability and resealability.

[0027] The ethylene-based elastomer is a thermoplastic elastomer containing ethylene as a monomer component, and is an elastomer containing ethylene as a monomer component in an amount of 50 mol% or more, preferably 50 to 90 mol%, and more preferably about 60 to 85 mol%, based on the total amount of the monomer components. Examples of monomers copolymerizable with ethylene include α-olefins other than ethylene, such as propylene, butene-1, hexene-1, 4-methylpentene-1, octene-1, (meth)acrylic acid esters, and vinyl acetate. Among these, random copolymerization with α-olefins is preferred, and copolymers with α-olefins having 3 to 8 carbon atoms are particularly preferred.

[0028] The density of the ethylene elastomer is 0.870 to 0.943 g / cm 3 The range of 0.870 to 0.910 g / cm is preferable because good adhesion can be obtained when resealing. 3 It is more preferable that:

[0029] The melt flow rate (MFR) of the ethylene elastomer is preferably 0.5 to 20 g / 10 min (190°C, 21.18 N), and more preferably 2 to 15 g / 10 min (190°C, 21.18 N) to facilitate matching of the fluidity with other resin layers.

[0030] Examples of the styrene elastomer include ABA block polymers such as styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), styrene-ethylene-butylene copolymer-styrene (SEBS), styrene-ethylene-propylene-styrene (SEPS), and styrene-butadiene-butylene-styrene (SBBS); AB block polymers such as styrene-butadiene (SB), styrene-isoprene (SI), styrene-ethylene-butylene copolymer (SEB), and styrene-ethylene-propylene copolymer (SEP); styrene random copolymers such as styrene-butadiene rubber (SBR); ABC styrene-olefin crystalline block polymers such as styrene-ethylene-butylene copolymer-olefin crystalline (SEBC), and hydrogenated versions of these. Among these, styrene-butadiene-butylene-styrene (SBBS) is preferred because it provides particularly favorable releasability and resealability.

[0031] The density of the styrene elastomer is 0.92 to 1.1 g / cm 3 The range of 0.92 to 1.0 g / cm is preferable because it contributes to improving the adhesion with the release resin layer. 3 It is more preferable that:

[0032] The melt flow rate (MFR) of the styrene elastomer is preferably 0.5 to 20 g / 10 min (190°C, 21.18 N), and more preferably 2 to 15 g / 10 min (190°C, 21.18 N) to facilitate matching of the fluidity with other resin layers.

[0033] The content of the thermoplastic elastomer (b1) in the adhesive resin layer (B) used in the present invention is preferably 10 to 60 mass %, more preferably 15 to 55 mass %, and even more preferably 20 to 50 mass %, of the resin components contained in the adhesive resin layer (B). By setting the content of the thermoplastic elastomer (b1) within this range, it becomes easier to obtain suitable cohesive strength and easy releasability during peeling, as well as good adhesion during resealing.

[0034] Examples of the tackifying resin (b2) used in the adhesive resin layer (B) used in the present invention include resins made of natural resins or synthetic resins that are adhesive at room temperature, such as rosin-based resins such as natural resin rosin, polymerized rosin, hydrogenated rosin, glycerin ester rosin, and pentaerythritol; terpene-based resins such as terpene, aromatic-modified terpene, terpene phenol, and hydrogenated terpene; petroleum resins such as aliphatic petroleum resins, aromatic petroleum resins, and hydrogenated alicyclic petroleum resins; polybutadiene that is liquid at room temperature, polyisoprene that is liquid at room temperature, and polyisobutylene that is liquid at room temperature. Of these, rosin-based resins, terpene-based resins, and petroleum resins are preferred because they allow for easy adjustment of peelability and resealability.

[0035] The content of the tackifier resin (b2) in the adhesive resin layer (B) used in the present invention is preferably 40 to 90 mass %, more preferably 45 to 85 mass %, and even more preferably 50 to 80 mass %, of the resin components contained in the adhesive resin layer (B). By setting the content of the tackifier resin (b2) within this range, it becomes easier to obtain suitable cohesive strength and easy releasability during peeling, as well as good adhesion during resealing.

[0036] The adhesive resin layer (B) used in the present invention may contain other resins in addition to the thermoplastic elastomer (b1) and tackifier resin (b2). As such other resins, the olefin-based resins exemplified for the surface resin layer (A) can be suitably used.

[0037] The content of the other resin in the adhesive resin layer (B) used in the present invention is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 5 to 15% by mass, of the resin components contained in the adhesive resin layer (B).Within this range, it becomes easier to impart the properties of the added resin while maintaining suitable peelability and resealability.

[0038] The adhesive resin layer (B) may also contain additives such as those exemplified for the surface resin layer (A), and the preferred amounts are the same as those for the surface resin layer (A).

[0039] The thickness ratio of the adhesive resin layer (B) used in the present invention to the total thickness of the sealant film is preferably 10 to 60%, more preferably 20 to 50%, since this makes it easier to obtain suitable seal strength after resealing.

[0040] [Release resin layer (C)] The release resin layer (C) used in the present invention is a layer containing 40 mass% or more of an ethylene-based ionomer (c1) having a polar group concentration exceeding 5.5 mol% of the resin components contained in the release resin layer (C). When the sealant film or a film containing the sealant film of the present invention is heat-sealed and then peeled off (opened), the release resin layer (C) separates the adhesive resin layer (B) from the release resin layer (C), exposing the adhesive resin layer (B). Therefore, the release resin layer (C) is required to have not only releasability from the adhesive resin layer (B) but also adhesion to the heat-seal layer (D). Furthermore, the release resin layer (C) adheres to the adhesive resin layer (B) upon resealing.

[0041] The ethylene-based ionomer (c1) having a polar group concentration of more than 5.5 mol% (hereinafter, this ionomer may be referred to as a high-polarity ionomer) used in the release resin layer (C) of the present invention preferably has a polar group concentration of 5.8 mol% or more, more preferably 6 mol% or more, and even more preferably 6.5 mol% or more. Also, it is preferably 15 mol% or less, more preferably 12 mol% or less, and even more preferably 10 mol% or less. By achieving this polar group concentration, it becomes easier to achieve effects such as favorable seal strength after resealing.

[0042] The polar group concentration is calculated based on the signal intensities of the ethylene chain and the methyl group of methacrylic acid by placing resin pellets (0.025 g) in an NMR tube, adding 0.5 cc of a 1 / 3 (V / V) mixed solution of dibenzofuran (CD6) and orthodichlorobenzene (ODCB), heating the pellets in a dryer at 125°C for 2 days to dissolve them, and then performing H-NMR measurement at 130°C.

[0043] Examples of the polar group include acrylic acid, methacrylic acid, 2-ethylacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride, fumaric anhydride, itaconic anhydride, monomethyl maleate, and monoethyl maleate, with acrylic acid or methacrylic acid being particularly preferred.

[0044] Examples of the highly polar ionomer (c1) that can be used include ethylene-acrylic acid copolymer (EAA) and ethylene-methacrylic acid copolymer (EMAA), and metal-neutralized ethylene-acrylic acid copolymer and metal-neutralized ethylene-methacrylic acid copolymer are preferably used.

[0045] The melt flow rate (MFR) of the high polarity ionomer (c1) is preferably 0.5 to 20 g / 10 min (190°C, 21.18 N), and more preferably 2 to 17 g / 10 min (190°C, 21.18 N) to facilitate matching of the fluidity with other resin layers.

[0046] By setting the content of the high-polarity ionomer (c1) in the release resin layer (C) used in the present invention to 40% by mass or more of the resin components contained in the release resin layer (C), it is possible to suppress the peeling of the release resin layer (C) and peeling at the interface between the release resin layer (C) and the heat-seal layer (D) during peeling, and to achieve suitable easy peelability at the interface between the adhesive resin layer (B) and the release resin layer (C). The content is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, and even more preferably 60 to 85% by mass.

[0047] In the release resin layer (C) used in the present invention, it is also preferable to use an ethylene-based ionomer (c2) having a polar group concentration of 5.5 mol% or less (hereinafter, this ionomer may be referred to as a low-polarity ionomer) in combination with the high-polarity ionomer (c1). By using this low-polarity ionomer (c2) in combination, it becomes easier to obtain effects such as improved adhesion between the release resin layer (C) and the heat-sealable resin layer (D).

[0048] The polar group concentration of the low-polarity ionomer (c2) is preferably 5.5 mol% or less, more preferably 5.2 mol% or less, and even more preferably 5 mol% or less. It is also preferably 1 mol% or more, more preferably 2 mol% or more, and even more preferably 3 mol% or more. By achieving this polar group concentration, it becomes easier to achieve effects such as the development of favorable seal strength after resealing. The method for measuring the polar group concentration is the same as the method for measuring the polar group concentration of the high-polarity ionomer.

[0049] Examples of the low-polarity ionomer (c2) that can be used include ethylene-acrylic acid copolymer (EAA) and ethylene-methacrylic acid copolymer (EMAA), and metal-neutralized ethylene-acrylic acid copolymer and metal-neutralized ethylene-methacrylic acid copolymer are preferably used.

[0050] The melt flow rate (MFR) of the low polarity ionomer is preferably 0.5 to 20 g / 10 min (190°C, 21.18 N), and more preferably 2 to 17 g / 10 min (190°C, 21.18 N) to facilitate matching of fluidity with other resin layers.

[0051] When the low-polarity ionomer (c2) is used, the content of the low-polarity ionomer (c2) in the release resin layer (C) is set to 60% by mass or less of the resin components contained in the release resin layer (C), which makes it easier to achieve a suitable seal strength after resealing. The content is preferably 55% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less.

[0052] The release resin layer (C) used in the present invention may contain, as a resin other than the high-polarity ionomer (c1) and low-polarity ionomer (c2), the olefin-based resins exemplified for the surface resin layer (A). When using such other resins, the content of such other resins is preferably 20% by mass or less, more preferably 10% by mass, and even more preferably 5 to 10% by mass, of the resin components contained in the release resin layer (C). Within this range, it becomes easier to impart the properties of the added resin while maintaining suitable releasability and resealability.

[0053] The release resin layer (C) may also contain additives such as those exemplified for the surface resin layer (A), and the preferred amounts are the same as those for the surface resin layer (A).

[0054] The thickness ratio of the release resin layer (C) used in the present invention to the total thickness of the sealant film is preferably 20% or less, more preferably in the range of 5 to 15%, since this makes it easier to obtain suitable releasability.

[0055] [Heat seal resin layer (D)] The heat-sealable resin layer (D) used in the present invention is a resin layer containing an ethylene-based resin (d1). The use of this heat-sealable resin layer (D) can achieve suitable heat-sealability to an adherend, while also achieving suitable interlayer adhesion that makes it difficult for the peelable resin layer (C) to fall off during peeling.

[0056] Examples of the ethylene-based resin (d1) used in the heat-sealable resin layer (D) of the present invention include polyethylene resins such as very low-density polyethylene (VLDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), linear medium-density polyethylene (LMDPE), and medium-density polyethylene (MDPE), as well as ethylene-vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate (EMA) copolymer, ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), ethylene-acrylic acid copolymer (EAA), and ethylene-methacrylic acid copolymer (EMAA). These ethylene-based resins may be used alone or in combination of two or more. Among these ethylene-based resins, very low-density polyethylene, low-density polyethylene, linear low-density polyethylene, and linear medium-density polyethylene are preferred because they provide favorable impact resistance, with low-density polyethylene being particularly preferred.

[0057] The ethylene-based resin preferably has a melt flow rate of 0.5 to 45 g / 10 min, more preferably 2 to 40 g / 10 min at 190° C. By setting the melt flow rate within this range, it becomes easier to obtain stable adhesion between the container and the lid and stable seal strength.

[0058] The content of the ethylene resin (d1) is preferably 10 to 100% by mass or more, more preferably 20 to 100% by mass, of the resin components contained in the heat-sealable resin layer (D). When a plurality of ethylene resins (d1) are used in combination, the total content thereof is preferably within the above range.

[0059] In the heat-sealable resin layer (D) used in the present invention, it is also preferable to use a thermoplastic elastomer (d2) in combination with the ethylene-based resin (d1). Examples of the thermoplastic elastomer (d2) include the same thermoplastic elastomers (b1) exemplified for the adhesive resin layer (B). Among these, ethylene-based elastomers are preferably used.

[0060] When the content of the thermoplastic elastomer (d2) is 0 to 80% by mass of the resin components contained in the heat-sealable resin layer (D), favorable resealability can be easily achieved. The content is preferably 0 to 70% by mass, more preferably 0 to 60% by mass.

[0061] The heat-sealable resin layer (D) used in the present invention may contain, as a resin other than the ethylene-based resin (d1) and thermoplastic elastomer (d2), the resins exemplified as other resins in the surface resin layer (A). When such other resins are used, the content of such other resins is preferably 20% by mass or less, more preferably 10% by mass, and even more preferably 5 to 10% by mass, of the resin components contained in the heat-sealable resin layer (D). Within this range, it becomes easier to impart the properties of the added resin while maintaining suitable sealability and easy peelability.

[0062] In order to prevent deterioration of slipperiness or blocking due to bleeding of low-molecular-weight components from other layers, it is also preferable to emboss the heat-seal surface of the heat-seal resin layer (D) or to add a filler to the heat-seal resin layer (D). Inorganic materials such as calcium carbonate and talc are preferred as fillers because they are inexpensive, easily form surface irregularities, and easily maintain a good coefficient of friction.

[0063] The content of the filler is preferably 0.1 to 15 parts by mass, more preferably 1 to 10 parts by mass, relative to 100 parts by mass of the resin component contained in the heat seal resin layer (D).

[0064] In addition to the filler, additives such as those exemplified for the surface resin layer (A) may be used as appropriate. The preferred amounts of use are also the same as for the surface resin layer (A).

[0065] In the configuration of the present invention, peeling after heat sealing occurs between the adhesive resin layer (B) and the release resin layer (C). Therefore, even when additives such as the filler, lubricant, and antiblocking agent are added to the heat-sealable resin layer (D), adhesion at the time of resealing can be easily ensured, and a multilayer film with stable resealing strength can be obtained.

[0066] The thickness ratio of the heat seal resin layer (D) to the total thickness of the sealant film is preferably 20% or less, more preferably in the range of 5 to 15%, since suitable seal strength and peelability can be easily obtained.

[0067] [Sealant film] The sealant film of the present invention has the surface resin layer (A), adhesive resin layer (B), release resin layer (C), and heat-sealable resin layer (D). In the sealant film of the present invention, the release resin layer (C) may contain 60% by mass or less of a low-polarity ionomer (c2), and the heat-sealable resin layer (D) may contain 80% by mass or less of a thermoplastic elastomer (d2), but the low-polarity ionomer (c2) and / or the thermoplastic elastomer (d2) are contained in each layer so that the content of the low-polarity ionomer (c2) and the thermoplastic elastomer (d2) represented by the following formula is 10 to 60%:

[0068] [((Wc2 / Wct)×100)+((Wd2 / Wdt)×100)] / 2 Wct: Total amount (mass) of resin components contained in the peelable resin layer (C) Wc2: Content (by mass) of ethylene-based ionomer (c2) having a polar group concentration of 5.5 mol% or less in the resin component contained in the release resin layer (C) Wdt: Total amount (mass) of resin components contained in the heat seal resin layer (D) Wd2: Content (by mass) of thermoplastic elastomer (d2) in the resin component contained in the heat seal resin layer (D)

[0069] By adjusting the content ratio of the low-polarity ionomer (c2) and the thermoplastic elastomer (d2) represented by the above formula within the above range, the interlayer strength between the release resin layer (C) and the heat-sealable resin layer (D) can be increased without impairing the heat-sealability. As a result, the exposure of the adhesive layer can be suitably adjusted, and good heat-sealability, easy opening, and resealability can be achieved. The content ratio of the low-polarity ionomer (c2) and the thermoplastic elastomer (d2) is preferably 10 to 50%, more preferably 10 to 40%. By setting the content ratio of the low-polarity ionomer (c2) and the thermoplastic elastomer (d2) within this range, particularly favorable peelability and resealability can be easily obtained.

[0070] The sealant film of the present invention preferably has a total thickness of 10 to 100 μm, more preferably 20 to 60 μm, and even more preferably 30 to 50 μm. If the total thickness of the film is within this range, stable seal strength, suitability for packaging machines, excellent pinhole resistance, easy opening, etc. can be easily obtained.

[0071] The thickness of each layer may be adjusted appropriately within the range of the thickness ratio of each layer exemplified above, but for example, the thickness of the surface resin layer (A) is preferably 6 to 70 μm, more preferably 9 to 60 μm. The thickness of the adhesive resin layer (B) is preferably 3 to 60 μm, more preferably 6 to 50 μm. The thickness of the release resin layer (C) is preferably 1 to 15 μm, more preferably 2 to 10 μm. The thickness of the heat-sealable resin layer (D) is preferably 1 to 15 μm, more preferably 2 to 10 μm.

[0072] From the viewpoint of protecting the contents, when the sealant film of the present invention is heat-sealed to a polyethylene sheet, the initial seal strength when the sealant film is first peeled from the polyethylene sheet is preferably 5 N / 15 mm or more, more preferably 7 N / 15 mm or more. The seal strength is the maximum strength when the sealant film is heat-sealed at a seal width of 1 cm under conditions of 180°C, 0.2 MPa, and 1 second, and then peeled off in a 180° direction at a rate of 300 mm / min.

[0073] Furthermore, the sealant film of the present invention preferably has an initial seal strength of 20 N / 15 mm or less, more preferably 15 N / 15 mm or less, in order to easily achieve suitable easy-open properties.

[0074] It is preferable that the seal strength be within the above range when heat-sealed at a temperature of 120 to 150° C., since this makes it easier to obtain seal stability during heat-sealing.

[0075] The sealant film of the present invention can be resealed after being peeled off under the above conditions. The seal strength after resealing is preferably 2 N / 15 mm or more, more preferably 3 N / 15 mm or more. When the seal strength after resealing is within this range, good adhesion can be obtained and peeling when an impact is applied after resealing can be suitably suppressed. The seal strength after resealing is the maximum strength measured when the peeled surfaces, once peeled after heat sealing, are brought together, pressed under conditions of 23°C, 0.2 MPa, and 1 second, left in that state for 5 minutes in a thermostatic chamber at 23°C and 50% RH, and then peeled in a 180° direction at a rate of 300 mm / min. There is no particular upper limit, but the seal strength after resealing is preferably 9 N / 15 mm or less, and more preferably 7 N / 15 mm or less.

[0076] In the sealant film of the present invention, the exposed state of the adhesive resin layer (B) on the release surface after peeling is preferably 50% or more, more preferably 80% or more. When the proportion of the exposed surface of the adhesive resin layer (B) on the release surface is within this range, adhesion stability during resealing is easily achieved, and peeling or opening due to external impact after resealing can be suitably suppressed. The exposed proportion can be evaluated, for example, by photographically observing the peel surface and observing the proportion of the exposed surface at approximately five points within any 1 cm square area.

[0077] The haze of the sealant film of the present invention is preferably 30% or less, more preferably 25% or less, and even more preferably 20% or less, so that the packaged contents can be easily viewed.

[0078] The method for producing the sealant film of the present invention is not particularly limited, but examples include a coextrusion method in which the resins or resin mixtures used for the surface resin layer (A), adhesive resin layer (B), release resin layer (C), and heat-seal resin layer (D) are heated and melted in separate extruders, laminated in the molten state in the order (A) / (B) / (C) / (D) by a method such as a coextrusion multilayer die method or a feed block method, and then formed into a film by an inflation method or a T-die / chill roll method. The coextrusion method is preferred because it allows relatively free adjustment of the thickness ratio of each layer and produces a multilayer film that is hygienic and cost-effective. The T-die / chill roll method is preferred because it allows melt extrusion at a relatively high temperature, which makes it easy to suppress phase separation and gel formation of the resins used. The inflation method is preferred because it allows for inexpensive and easy production of sealant films.

[0079] The sealant film of the present invention is preferably produced as an unstretched film without undergoing a special stretching step during production, since this makes it easier to obtain suitable secondary formability.

[0080] Furthermore, in order to improve adhesion to printing inks and lamination suitability when used as a sealant film for lamination, the surface resin layer (A) may be subjected to a surface treatment. Examples of such surface treatments include surface oxidation treatments such as corona treatment, plasma treatment, chromic acid treatment, flame treatment, hot air treatment, and ozone / ultraviolet treatment, and surface roughening treatments such as sandblasting, with corona treatment being preferred.

[0081] [Laminating film] The sealant film of the present invention is preferably laminated with a stretched substrate film, since this generally ensures strength without breakage, ensures heat resistance during heat sealing, and improves the design of printing. Examples of stretched substrate films to be laminated include biaxially oriented polyester films, biaxially oriented nylon films, and biaxially oriented polypropylene films, with biaxially oriented polyester films being more preferred in terms of breaking strength, transparency, and the like. Furthermore, the stretched substrate film may be subjected to an easy-tear treatment or an antistatic treatment as needed. The method for laminating the sealant film and the stretched substrate film is not particularly limited, and a combination technique such as dry lamination, extrusion lamination, thermal lamination, or multilayer extrusion coating may be used. Examples of adhesives used when laminating the sealant film and the stretched substrate film using the dry lamination method include polyether-polyurethane adhesives and polyester-polyurethane adhesives.

[0082] [Packaging material] The sealant film or laminate film of the present invention can be formed into a bag with the heat-sealable resin layer (D) on the inside and heat-sealed to form a packaging material. The packaging material can be in the form of a three-sided sealed bag, a four-sided sealed bag, a gusseted packaging bag, a pillow packaging bag, a Goebel-top type container with a bottom, a Tetra Classic, a Brueck type, a tube container, a paper cup, or the like. Furthermore, the sealant film or laminate film of the present invention can be used as a lid to seal the opening of a container having an opening, thereby producing a packaging container. Examples of such containers include cups and trays made from styrene-based resins, expanded styrene-based resins, propylene-based resins, ester-based resins, etc., by molding methods such as injection molding, vacuum molding, and pressure molding, as well as paper cups and paper trays made by laminating an olefin-based resin such as polyethylene onto paper. The sealant film of the present invention and the laminate film of the present invention are particularly suitable as lid materials for sealing the openings of packaging containers having openings for food, sanitary products, medical products, and the like. Furthermore, when the sealant film of the present invention is used as a lid material, the adhesion surface of the opening of a packaging container to which the sealant film is heat-sealed is preferably made primarily of an olefin-based resin such as an ethylene-based resin. If the heat-seal surface is made primarily of an ethylene-based resin, the seal strength between the opening of the packaging container and the lid material becomes appropriate, achieving both airtightness suitable for protecting the contents and easy opening, and also allowing the formation of a release layer on the opening that adheres closely to the adhesive resin layer when resealing.

[0083] Examples of ethylene-based resins used in the packaging container include polyethylene resins such as very low-density polyethylene (VLDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), linear medium-density polyethylene (LMDPE), and medium-density polyethylene (MDPE), as well as ethylene-vinyl acetate copolymers (EVA), ethylene-methyl methacrylate copolymers (EMMA), ethylene-ethyl acrylate copolymers (EEA), ethylene-methyl acrylate (EMA) copolymers, ethylene-ethyl acrylate-maleic anhydride copolymers (E-EA-MAH), ethylene-acrylic acid copolymers (EAA), and ethylene-methacrylic acid copolymers (EMAA). Furthermore, the packaging container may be a paper packaging material such as a paper cup coated with the ethylene-based resin, or a resin container formed by deep drawing or the like.

[0084] The heat-sealed surface of the opening of the packaging container preferably contains the ethylene-based resin as a main component, and the content of the ethylene-based resin in the resin constituting the heat-sealed surface is more preferably 60% by mass or more, and even more preferably 80% by mass or more. If the content of the ethylene-based resin in the heat-sealed surface is within this range, sufficient seal strength can be obtained, which is preferable. Furthermore, resins that may be used in combination with the ethylene-based resin on the heat-sealing surface are not particularly limited as long as they are compatible with the ethylene-based resin and do not inhibit heat sealing. Examples include propylene-based resins such as propylene homopolymers, propylene-ethylene copolymers, propylene-butene-1 copolymers, and propylene-ethylene-butene-1 copolymers, or copolymers of propylene and an α-olefin. [Example]

[0085] The present invention will now be described in more detail with reference to examples and comparative examples. Unless otherwise specified, "parts" and "%" are based on mass.

[0086] Example 1 The resin compositions for the surface resin layer (A), adhesive resin layer (B), release resin layer (C), and heat-seal resin layer (D) were prepared using the following resins. These resin compositions were fed into extruders for each layer and coextruded using the T-die / chill roll method at a T-die temperature of 250°C. The resulting extruded film was cooled on a water-cooled metal cooling roll at 40°C to obtain a four-layer laminate film: surface resin layer (A), adhesive resin layer (B), release resin layer (C), and heat-seal resin layer (D). The individual layer thicknesses were 12 μm / 12 μm / 3 μm / 3 μm, for a total film thickness of 30 μm. The surface resin layer (A) of the resulting laminate film was subjected to corona discharge treatment to achieve a wetting tension of 40 mN / m. Surface resin layer (A): Linear low-density polyethylene (density: 0.93 g / cm 3 , MFR:4.0g / 10min) (hereinafter referred to as LLDPE(1)) 100 parts by mass Adhesive resin layer (B): 50 parts by mass of styrene-based elastomer (MFR: 8.0 g / 10 min) (hereinafter referred to as styrene-based elastomer (1)), 50 parts by mass of tackifier resin (softening temperature: 110 ° C.) (hereinafter referred to as tackifier resin (1)) Release resin layer (C): 75 parts of a metal-neutralized ethylene-methacrylic acid copolymer having a methacrylic acid-derived component content of 6.8 mol% (MFR: 16.0 g / 10 min) (hereinafter referred to as EMAA (1)), 25 parts of a metal-neutralized ethylene-methacrylic acid copolymer (EMAA) having a methacrylic acid-derived component content of 4.8 mol% (MFR: 6.0 g / 10 min) (hereinafter referred to as EMAA (2)) Heat seal layer (D): Low density polyethylene (density: 0.92 g / cm 3 , MFR: 35 g / 10 min) (hereinafter referred to as polyethylene resin (1)) 100 parts by mass

[0087] Example 2 A multilayer film was obtained in the same manner as in Example 1, except that the resin components used in the heat-sealable resin layer (D) were as follows. Heat seal resin layer (D): Low density polyethylene (density: 0.92 g / cm 3 , MFR: 7 g / 10 min) (hereinafter, polyethylene resin (2)) 100 parts by mass

[0088] Example 3 A multilayer film was obtained in the same manner as in Example 1, except that the resin components used in the heat-sealable resin layer (D) were as follows. Heat seal resin layer (D): 80 parts by mass of polyethylene resin (1), ethylene-butadiene rubber (density: 0.89 g / cm 3 , MFR: 18.0 g / 10 min) (hereinafter, ethylene-based elastomer (1)) 20 parts by mass

[0089] Example 4 A multilayer film was obtained in the same manner as in Example 1, except that the resin components used in the heat-sealable resin layer (D) were as follows. Heat seal resin layer (D): 50 parts by mass of polyethylene resin (1), 50 parts by mass of ethylene elastomer (1)

[0090] Example 5 A multilayer film was obtained in the same manner as in Example 1, except that the resin components used in the heat-sealable resin layer (D) were as follows. Heat seal resin layer (D): 35 parts by mass of polyethylene resin (1), 65 parts by mass of ethylene elastomer (1)

[0091] Example 6 A multilayer film was obtained in the same manner as in Example 1, except that the resin components used in the heat-sealable resin layer (D) were as follows. Heat seal resin layer (D): 20 parts by mass of polyethylene resin (1), 80 parts by mass of ethylene elastomer (1)

[0092] Example 7 A multilayer film was obtained in the same manner as in Example 1, except that the resin component used in the release resin layer (C) was as follows. Release resin layer (C): EMAA (1) 100 parts by mass

[0093] Example 8 A multilayer film was obtained in the same manner as in Example 1, except that the resin components used in the release resin layer (C) were as follows. Peeling resin layer (C): 50 parts by mass of EMAA (1), 50 parts by mass of EMAA (2)

[0094] Example 9 A multilayer film was obtained in the same manner as in Example 1, except that the resin components used in the heat-sealable resin layer (D) were as follows. Heat seal resin layer (D): 50 parts by mass of polyethylene resin (1), 50 parts by mass of polyethylene resin (2)

[0095] (Comparative Example 1) A multilayer film was obtained in the same manner as in Example 1, except that the resin component used in the release resin layer (C) was as follows. Release resin layer (C): EMAA (2) 100 parts by mass

[0096] (Comparative Example 2) A multilayer film was obtained in the same manner as in Example 1, except that the resin component used in the release resin layer (C) was as follows. Peeling resin layer (C): 25 parts by mass of EMAA (1), 75 parts by mass of EMAA (2)

[0097] (Comparative Example 3) A multilayer film was obtained in the same manner as in Example 1, except that the resin components used in the heat-sealable resin layer (D) were as follows. Heat seal resin layer (D): Polypropylene homopolymer using a metallocene catalyst (density: 0.9 g / cm 3 , MFR: 7.0 g / 10 min) (hereinafter, polypropylene resin (1)) 100 parts by mass

[0098] Comparative Example 4 A multilayer film was obtained in the same manner as in Example 1, except that the resin component used in the release resin layer (C) was as follows. Release resin layer (C): Amorphous polyester resin (PETG6763 manufactured by Eastman Chemical, density 1.27 g / cm 3 )100 parts by mass

[0099] The multilayer films obtained in the above Examples and Comparative Examples were evaluated as follows. The results are shown in Tables 1 and 2.

[0100] <Preparation of laminate film> A biaxially oriented polyethylene terephthalate (PET) film (thickness: 12 μm) was attached by dry lamination to the surface of the surface resin layer (A) of the multilayer film obtained in the above Examples and Comparative Examples, and aged for 36 hours at 40° C. to obtain a laminate film for evaluation. In this case, a two-component curing adhesive (polyester adhesive "DIC Dry LX500" and curing agent "DIC Dry KR-90S") manufactured by DIC Corporation was used as the dry lamination adhesive.

[0101] <Haze> The haze of the films obtained in the examples and comparative examples was measured (unit: %) using a haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd.) in accordance with JIS K7105.

[0102] <Initial seal strength> The surface of the heat-sealable resin layer (D) of the resulting laminate film was placed on a polyethylene-laminated paper and heat-sealed at a temperature of 140°C, a pressure of 0.2 MPa, and a sealing time of 1 second. The heat-sealed film was then naturally cooled at 23°C for 24 hours and cut into 15 mm strips to prepare test pieces. These test pieces were then subjected to 180° peeling at a rate of 300 mm / min using a tensile tester (manufactured by A&D Co., Ltd.) in a thermostatic chamber at 23°C and 50% RH to measure the heat-seal strength (initial seal strength).

[0103] <Evaluation of the exposed state of the adhesive resin layer after peeling> The appearance of the laminate film after peeling from the test piece on which the heat seal strength was measured was checked and evaluated according to the following criteria. ◎: The exposed ratio of the adhesive resin layer on the peeling surface is 80% or more ○: The exposed ratio of the adhesive resin layer on the peeled surface is 50% or more and less than 80% △: The exposed ratio of the adhesive resin layer on the peeled surface is 30% or more and less than 50% ×: The exposed ratio of the adhesive resin layer on the peeled surface is less than 30%

[0104] <Resealability> The test pieces whose heat seal strengths had been measured above were re-pressed under conditions of 23°C, 0.2 MPa, and 1 second, and then left to stand in a thermostatic chamber at 23°C and 50% RH for 5 minutes. After that, a 180° peel test was performed at a speed of 300 mm / min using a tensile tester (manufactured by A&D Co., Ltd.) to measure the seal strength (i.e., the seal strength after resealing) and evaluate it according to the following criteria. ◎: Seal strength after resealing is 3N / 15mm or more ○: Seal strength after resealing is 2N / 15mm or more and less than 3N / 15mm ×: Seal strength after resealing is less than 2N / 15mm

[0105] [Table 1]

[0106] [Table 2]

[0107] As is clear from the above table, the laminated films of the present invention in Examples 1 to 11 had suitable initial heat sealability to the adherend and easy opening properties, and the adhesive surface was well exposed when peeled off, allowing for stable resealability. On the other hand, Comparative Example 1 did not contain a high-polarity ionomer, resulting in poor resealability. Comparative Example 2 contained a small amount of high-polarity ionomer, resulting in poor resealability. Comparative Example 3 did not contain a polyethylene-based resin (d1) in the heat-sealable layer (D), resulting in failure to seal to the substrate. Comparative Example 4 did not contain an ethylene-based ionomer (c1) in the release resin layer, resulting in failure to peel between the adhesive resin layer (B) and the release resin layer (C), resulting in failure to reseal.

Claims

1. A sealant film comprising a surface resin layer (A), an adhesive resin layer (B), a release resin layer (C), and a heat-sealable resin layer (D), the adhesive resin layer (B) contains a thermoplastic elastomer (b1) and a tackifier resin (b2), the release resin layer (C) contains an ethylene-based ionomer (c1) having a polar group concentration of more than 5.5 mol% in an amount of 40 mass% or more of a resin component contained in the release resin layer (C); further, the release resin layer (C) contains an ethylene-based ionomer (c2) having a polar group concentration of 5.5 mol% or less in an amount of 0 to 60 mass% of the resin component contained in the release resin layer (C); A sealant film, characterized in that the heat seal resin layer (D) contains an ethylene-based resin (d1).

2. the heat-sealable resin layer (D) contains a thermoplastic elastomer (d2) in an amount of 0 to 80% by mass of a resin component contained in the heat-sealable resin layer (D); The sealant film according to claim 1, wherein the content of the ethylene-based ionomer (c2) represented by the following formula and the thermoplastic elastomer (d2) is 10 to 60%: [((Wc2 / Wct)×100)+((Wd2 / Wdt)×100)] / 2 Wct: total amount (mass) of resin components contained in the release resin layer (C) Wc2: the content (by mass) of the ethylene-based ionomer (c2) in the resin component contained in the release resin layer (C) Wdt: total amount (mass) of resin components contained in the heat seal resin layer (D) Wd2: the content (by mass) of the thermoplastic elastomer (d2) in the resin component contained in the heat seal resin layer (D)

3. The sealant film according to claim 1 or 2, wherein the thermoplastic elastomer (b1) contained in the adhesive resin layer (B) is at least one selected from a styrene-based elastomer, an ethylene-based elastomer, and a propylene-based elastomer.

4. 4. The sealant film according to claim 1, wherein the surface resin layer (A) is a resin layer containing an olefin-based resin as a main resin component.

5. The sealant film according to any one of claims 1 to 4, which can be resealed after being peeled off at the interface between the adhesive resin layer (B) and the release resin layer (C).

6. The sealant film according to any one of claims 1 to 5, which is heat-sealed, peeled off, re-pressed under conditions of 23°C, 0.2 MPa, and a sealing time of 1 second, and then left to stand for 5 minutes under conditions of 23°C and 50% RH, and has a seal strength after resealing measured after measurement of 2 N / 15 mm or more.

7. The sealant film according to any one of claims 1 to 6, wherein the total thickness of the film is 10 to 100 µm.

8. A laminate film comprising the sealant film according to any one of claims 1 to 7.

9. A packaging material comprising the sealant film according to any one of claims 1 to 7.

10. 10. The packaging material according to claim 9, which is used to seal the opening of a container having an opening whose main component is an ethylene-based resin.

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