Reclosable heat-seal laminate and reclosable packaging container

Abstract

To solve the above problems, the present application provides a heat-sealable laminated body and a heat-sealable packaging container. The heat-sealable laminated body is a laminated body in which a base material (A), an adhesive layer (B) and a heat-sealable resin layer (C) are sequentially arranged, the adhesive layer (B) contains an acrylic copolymer (D), and the heat-sealable resin layer (C) contains a polyethylene resin and further contains at least either of a polypropylene resin and a polybutylene resin.

Description

Technical Field

[0001] This invention relates to resealable heat-sealing laminates. It further relates to resealable packaging containers having said resealable heat-sealing laminates. Background Technology

[0002] Traditionally, packaging containers for instant noodles, soups, snacks, chocolates, jellies, and other frozen foods have been made of plastics such as polyethylene, polypropylene, and polystyrene; paper containers coated with polyethylene resin; and metal containers such as iron and aluminum. The lids of these containers are typically laminates that utilize an adhesive resin layer (heat-sealing resin layer) that exhibits adhesion to the container body through heat sealing. Examples of such laminates include paper / polyethylene film / aluminum foil / polyethylene film / heat-sealing resin layer and polyethylene terephthalate (PET) film / aluminum foil / polyethylene film / heat-sealing resin layer. In these examples, the heat-sealing resin layer adheres to the container body through heat sealing (heat fusion), therefore, once peeled off, it cannot be re-adhere to the container body.

[0003] In the market, there is a demand for lid materials and packaging containers with the property of resealing temporarily opened lid materials (hereinafter also referred to as resealability) for the preservation of leftover food, and active research has been conducted on this. A lid material that can be resealed by using a multilayer film with a resealable layer is disclosed.

[0004] Specifically, Patent Document 1 discloses a cover material for a multilayer film composed of a substrate, a hot melt adhesive, and a hot melt bonding agent. A cover material is proposed that achieves sealing by heat-sealing a paper container made by coating the aforementioned multilayer film cover material with a polyethylene resin. When the cover material is peeled off, it does not break or string, exposing the hot melt adhesive layer and allowing for resealing.

[0005] Patent document 2 proposes a cap material with high reopening strength and excellent productivity by co-extruding and laminating a substrate in the order of an adhesive layer composed of styrene monomer, styrene block copolymer, tackifier, and sealant layer.

[0006] However, the cap materials described in Patent Documents 1 and 2 contain liquid components such as mineral oil and styrene monomer, which may cause seepage into the hot melt adhesive layer and sealant layer over time due to the storage environment, resulting in a decrease in the strength upon resealing.

[0007] Patent Document 1: Japanese Patent Application Publication No. 2013-082914

[0008] Patent Document 2: Japanese Patent Application Publication No. 2018-051926 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] The present invention was made in view of the above-mentioned problems, and its object is to provide a resealable heat-sealing laminate and a resealable packaging container. The resealable heat-sealing laminate does not easily leave a portion of the heat-sealing resin layer on the heat-sealed portion of the cap material side or easily form filaments when the cap material is peeled off from the container, thus exhibiting sufficient initial opening strength. Furthermore, even after opening, it can be resealed with practically sufficient strength by pressing the cap material and the container. Moreover, there is no seepage of liquid components on the surface of the laminate over time, and there is no decrease in reopening strength.

[0011] Methods for solving problems

[0012] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that the above-mentioned problems can be solved by manufacturing the following resealing heat-sealing laminate:

[0013] The aforementioned resealing heat-sealing laminate is a laminate composed of a substrate (A), an adhesive layer (B), and a heat-sealing resin layer (C) arranged sequentially. The adhesive layer (B) contains an acrylic copolymer (D).

[0014] The heat-sealing resin layer (C) contains a polyethylene resin and further contains at least one of a polypropylene resin and a polybutene resin.

[0015] That is, the present invention relates to a resealing heat-sealable laminate, which is a laminate composed of a substrate (A), an adhesive layer (B), and a heat-sealable resin layer (C) arranged sequentially.

[0016] The adhesive layer (B) contains an acrylic copolymer (D).

[0017] The heat-sealing resin layer (C) contains a polyethylene resin and further contains at least one of a polypropylene resin and a polybutene resin.

[0018] The present invention relates to a resealing heat-sealable laminate in which the adhesive layer (B) further contains a curing agent (E).

[0019] The present invention relates to a resealing heat-sealing laminate in which the above-mentioned adhesive layer (B) further contains a tackifier (F).

[0020] The present invention relates to a resealing heat-sealing laminate containing rosin-based tackifier (F1) or terpene-based tackifier (F2) of the above-mentioned tackifier (F).

[0021] The present invention relates to a resealable packaging container having the above-described resealable heat-sealing laminate and container body.

[0022] Invention Effects

[0023] Using the laminate of the present invention, a resealable heat-sealing laminate and a resealable packaging container can be obtained. The resealable heat-sealing laminate exhibits sufficient initial opening strength because when the cap material is peeled off from the container, a portion of the heat-sealing resin layer is not easily left on the heat-sealed portion of the cap material side or is not easily pulled into filaments. Furthermore, even after opening, it can be resealed with practically sufficient strength by pressing the cap material and the container. Moreover, there is no leakage of liquid components on the surface of the laminate over time, and there is no decrease in resealing strength. Detailed Implementation

[0024] Before providing a detailed description of the invention, the following terms are defined. Sheets, films, and tapes are synonyms. (Meth)acrylic acid includes acrylic acid and methacrylic acid. (Meth)acrylates include acrylates and methacrylates. Monomers are monomers containing vinyl unsaturated double bonds.

[0025] Furthermore, the numerical range defined by “~” in this specification includes the range of values ​​recorded before and after “~” as the lower and upper limits.

[0026] The resealable heat-sealing laminate of the present invention is composed of a substrate (A), an adhesive layer (B), and a heat-sealing resin layer (C) arranged sequentially. The heat-sealing resin layer (C) exhibits adhesiveness upon heating and bonds to the container body. The laminate of the present invention can then be torn off from the container to open it. At this time, the heat-bonded portion of the heat-sealing resin layer (C) is designed to be transferred to the container side and peeled off between the layers with the adhesive layer (B). Therefore, in the torn laminate, the adhesive layer (B) is exposed (but only in the portion heat-sealed with the container), and the heat-sealing resin layer (C) is transferred to the container. When the container is resealed, the exposed adhesive layer (B) comes into contact with the heat-sealing resin layer (C) transferred to the container, and appropriate adhesive force is exhibited between the adhesive layer (B) and the heat-sealing resin layer (C). The laminate of the present invention achieves resealability through this mechanism.

[0027] <Substrate (A)>

[0028] The substrate (A) of this invention can be any material as long as it can support the adhesive layer (B) and the heat-sealing resin layer (C), and can be paper, plastic film, metal foil, etc. Examples of plastic films include: polyester resin films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; fluorinated films such as polyvinylidene fluoride, polyvinylidene fluoride, polytetrafluoroethylene, and ethylene-tetrafluoroethylene copolymer films; and cellulose films such as acrylic films and triacetyl cellulose films. From the viewpoints of film rigidity, water vapor and oxygen barrier properties, and cost, polyester resin films are preferred, and polyethylene terephthalate (PET) films are more preferred. Examples of metal foils include aluminum foil. These substrates can be used as a single layer or in two or more layers using an adhesive. Furthermore, the substrate can also be composed of an inorganic layer having a metal oxide or non-metallic inorganic oxide deposited or sputtered.

[0029] The thickness of the substrate (A) is not particularly limited as long as it is suitable for use as a cover material, but is preferably 10 to 1000 μm.

[0030] <Adhesive layer (B)>

[0031] The adhesive layer (B) of the present invention can be formed by applying an adhesive containing an acrylic copolymer (D) onto a substrate (A) and drying it with a dissolving medium such as water or solvent as needed. The adhesive and the acrylic copolymer (D) may or may not contain water or solvent as a dissolving medium.

[0032] [Acrylic copolymer (D)]

[0033] Acrylic copolymers (D) can be obtained by polymerizing monomers using a free radical polymerization initiator via conventional methods. There are no particular limitations on the polymerization method; when using a solvent as the dissolving medium, solution polymerization is preferred. When using water as the dissolving medium, emulsion polymerization is preferred because it readily yields resin dispersions with high molecular weight, low viscosity, and high solids content. Examples of monomers include (meth)acrylate monomers, hydroxyl-containing monomers, carboxyl-containing monomers, amide-containing monomers, amino-containing monomers, epoxy-containing monomers, aromatic-ring-containing monomers, alicyclic hydrocarbon-containing monomers, and vinyl esters.

[0034] Examples of (meth)acrylate monomers include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, isobutyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, n-nonyl methacrylate, isononyl methacrylate, n-decyl methacrylate, isodecyl methacrylate, n-dodecyl methacrylate, n-tridecyl methacrylate, and n-tetradecyl methacrylate, which are alkyl (meth)acrylate monomers having straight-chain or branched alkyl groups. Among these, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, and 2-ethylhexyl methacrylate are preferred.

[0035] Examples of monomers containing hydroxyl groups include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and 4-hydroxybutyl methacrylate.

[0036] Monomers containing carboxyl groups include, for example, maleic acid, fumaric acid, itaconic acid, citraconic acid or their alkyl or alkenyl monoesters, acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, etc.

[0037] Monomers containing amide groups include, for example, (meth)acrylamide, N-methyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N,N'-methylenebisacrylamide, N-hydroxymethyl (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, N-methoxyethyl (meth)acrylamide, N-vinylpyrrolidone, diacetone acrylamide, N,N-dimethylaminopropyl (meth)acrylamide, (meth)acryloylmorpholine, etc.

[0038] Examples of amino-containing monomers include N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate.

[0039] Examples of monomers containing epoxy groups include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, and allyl glycidyl ether.

[0040] Monomers containing aromatic rings include, for example, phenyl acrylate, phenoxyethyl acrylate, benzyl acrylate, biphenyl acrylate, styrene, vinyltoluene, α-methylstyrene, etc.

[0041] Examples of monomers containing alicyclic hydrocarbon groups include cyclohexyl methacrylate, dicyclopentyl methacrylate, and isobornyl methacrylate.

[0042] Examples of vinyl esters include vinyl acetate, vinyl propionate, and vinyl laurate.

[0043] The monomers constituting the acrylic copolymer (D) may be one type or two or more types. Preferably, it contains an alkyl (meth)acrylate monomer and further contains at least one of a hydroxyl-containing monomer and a carboxyl-containing monomer. When containing an alkyl (meth)acrylate monomer, it preferably contains 30 to 99 parts by mass out of 100 parts by mass of the total monomers. When containing at least one of a hydroxyl-containing monomer and a carboxyl-containing monomer, the total amount of these monomers is preferably 0.1 to 10 parts by mass out of 100 parts by mass of the total monomers.

[0044] As free radical polymerization initiators used in polymerization reactions, known oil-soluble polymerization initiators and water-soluble polymerization initiators can be used. They can be used alone or in combination of two or more.

[0045] As an oil-soluble polymerization initiator, there are no particular limitations. Examples include: benzoyl peroxide, tert-butyl peroxide, tert-butyl hydroperoxide, tert-butyl peroxide (2-ethylhexanoate), tert-butyl peroxide-3,5,5-trimethylhexanoate, di-tert-butyl peroxide, dilauroyl peroxide, and other organic peroxides.

[0046] Azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylpentanonitrile, 2,2'-azobis(4-methoxy-2,4-dimethylpentanonitrile), 1,1'-azobis-cyclohexane-1-carboxylonitrile, and other azobis compounds.

[0047] In emulsion polymerization, water-soluble polymerization initiators are preferred. For example, conventionally known initiators such as ammonium persulfate (APS), sodium persulfate (NPS), potassium persulfate (KPS), hydrogen peroxide, and 2,2'-azobis(2-methylpropanediamine) dihydrochloride are preferred.

[0048] [reducing agent]

[0049] Furthermore, reducing agents can be used in conjunction with polymerization initiators in emulsion polymerization. By using reducing agents together, the rate of emulsion polymerization is accelerated, and low-temperature emulsion polymerization becomes easier. Examples of reducing agents include: reducing organic compounds such as ascorbic acid, isoascorbic acid, tartaric acid, citric acid, glucose, formaldehyde hyposulfite, sodium thiosulfate, and thiourea dioxide metal salts; and reducing inorganic compounds such as sodium thiosulfate, sodium sulfite, sodium bisulfite, sodium metabisulfite, and ferrous chloride.

[0050] [Basic compounds]

[0051] During monomer polymerization, alkaline compounds can be used as neutralizing agents to improve the stability of acrylic copolymers (D). Examples of alkaline compounds include: ammonia, various organic amines such as dimethylaminoethanol, diethanolamine, and triethanolamine, and inorganic alkaline agents such as alkali metal hydroxides such as sodium hydroxide, lithium hydroxide, and potassium hydroxide; from the viewpoint of water resistance, ammonia is preferred.

[0052] The glass transition temperature (Tg) of the acrylic copolymer (D) is preferably -80 to -10°C, more preferably -75 to -20°C, and even more preferably -70 to -30°C. A glass transition temperature within this range can improve the adhesive's adhesion. There can be two or more glass transition temperatures, preferably at least one within the above range.

[0053] It should be noted that the glass transition temperature in this invention refers to the glass transition temperature measured by differential scanning calorimetry (DSC) for a resin prepared after drying with 100% by mass of non-volatile components.

[0054] For example, the glass transition temperature is determined as follows: An aluminum dish containing approximately 10 mg of sample and an aluminum dish without sample are placed in a DSC apparatus. The mixture is rapidly cooled to -100°C in a nitrogen stream using liquid nitrogen. Then, the temperature is increased to 200°C at a rate of 20°C / min, and the DSC curve is plotted. The extrapolated glass transition onset temperature (Tig) can be determined by extending the baseline of the DSC curve from the low-temperature side (the portion of the DSC curve in the temperature region where no transfer or reaction to the test piece occurs) towards the high-temperature side, and then drawing the tangent line from the point where the slope of the stepped change portion of the glass transition curve is greatest. This extrapolated glass transition onset temperature (Tig) is then used as the glass transition temperature.

[0055] The weight-average molecular weight (Mw) of the acrylic copolymer (D) is preferably 50,000 to 2,000,000, more preferably 100,000 to 1,500,000, and even more preferably 300,000 to 1,000,000. Within this weight-average molecular weight range, the adhesive strength of the adhesive becomes higher.

[0056] It should be noted that the weight-average molecular weight is a polystyrene conversion value obtained through gel permeation chromatography (GPC) of the resin. For example, it can be determined as follows: the temperature of the chromatographic column (Showa Denko KF-805L, KF-803L and KF-802 manufactured by Showa Denko Co., Ltd.) is set to 40°C, THF (tetrahydrofuran) is used as the eluent, the flow rate is set to 0.2 ml / min, the detection is set to RI, the sample concentration is set to 0.02% by mass, and polystyrene is used as the standard sample.

[0057] It should be noted that if the acrylic copolymer (D) has a high weight-average molecular weight, it may sometimes be insoluble in THF used as the eluent. In such cases, the determination cannot be performed, and therefore it is judged to have a weight-average molecular weight greater than 2,000,000.

[0058] When solvents are used in adhesives and acrylic copolymers (D), examples of solvents include: alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol methyl ether, and diethylene glycol methyl ether; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ethers such as tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether; hydrocarbons such as hexane, heptane, and octane; aromatics such as benzene, toluene, xylene, and cumene; and esters such as ethyl acetate and butyl acetate.

[0059] It should be noted that the acrylic copolymer (D) can also be made of a substance that does not contain water or solvents. In this case, the acrylic copolymer (D) is preferably a block copolymer. Examples of block copolymers include acrylic copolymers having polymer blocks containing structural units of alkyl methacrylates with 1 to 3 carbon atoms from alkyl groups and polymer blocks containing structural units of alkyl acrylates with 1 to 8 carbon atoms from alkyl groups. By using such block copolymers, the cohesive force within the acrylic copolymer (D) is increased, and an improved adhesive force is expected.

[0060] Block copolymers include triblock polymers formed by combining hard segments (AH) of alkyl methacrylates with 1 to 3 carbon atoms of the aforementioned alkyl groups with soft segments (AS) of alkyl acrylates with 1 to 8 carbon atoms of the aforementioned alkyl groups in a -AH-AS-AH- configuration, and diblock polymers formed by combining segments in a -AS-AH- configuration. Triblock polymers and diblock polymers can be used together.

[0061] Alkyl methacrylates with 1 to 3 carbon atoms, which are used as hard segments for forming block copolymers, are preferably methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, or isopropyl methacrylate.

[0062] Examples of alkyl acrylates with 1 to 8 carbon atoms in the alkyl group used to form the soft segment of the block copolymer include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, isoamyl acrylate, hexyl acrylate, and 2-ethylhexyl acrylate.

[0063] Specific examples of the block copolymer include KURARITY LA2140E, KURARITY LA2250, KURARITY LA2330, KURARITY LA3320, KURARITY LA3170, KURARITY LA2270, KURARITY LA4285, KURARITY LA1892, KURARITY LK9243, KURARITY KL-LK9333, and the like.

[0064] The adhesive layer (B) contains an acrylic copolymer (D) and may contain a curing agent (E) and / or a tackifier (F) as needed.

[0065] [Curing agent (E)]

[0066] Examples of curing agents (E) include isocyanate curing agents, epoxy curing agents, aziridine curing agents, chelate-type curing agents, etc.

[0067] As an isocyanate curing agent, diisocyanate or polyisocyanate with isocyanate groups and having three or more functions obtained by modifying diisocyanate are preferred.

[0068] Examples of diisocyanates include aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates.

[0069] Examples of aromatic diisocyanates include 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, toluene diisocyanate, etc.

[0070] Examples of aliphatic diisocyanates include butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, phenylenediamine diisocyanate, and m-tetramethylphenylenediamine diisocyanate.

[0071] Alicyclic diisocyanates include, for example, cyclohexane-1,4-diisocyanate, isophorone diisocyanate, lysine diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanate methyl)cyclohexane, methylcyclohexane diisocyanate, norbornane diisocyanate, etc.

[0072] Polyisocyanates are preferably adducts obtained by modifying diisocyanates with trifunctional polyols, biuret forms obtained by reacting diisocyanates with water, and trimers (isocyanurate forms) formed by three molecules of diisocyanate having an isocyanurate ring. Examples of polyisocyanates include trimethylolpropane adducts of dimethyl phthalate diisocyanate, trimethylolpropane adducts of toluene diisocyanate, biuret forms of hexamethylene diisocyanate, urea-formate forms of hexamethylene diisocyanate, and isocyanurate forms of isophorone diisocyanate.

[0073] Examples of epoxy curing agents include 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-phenylenedimethyldiamine, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, and diglycidylamine.

[0074] Examples of aziridine curing agents include diphenylmethane-4,4'-bis(1-aziridine carbamide), trimethylolpropane tri-β-aziridine propionate, tetramethylolpropane tri-β-aziridine propionate, toluene-2,4-bis(1-aziridine carbamide), triethylene melamine, bis(isophthaloyl-1-(2-methylaziridine), tri-1-(2-methylaziridine)phosphine, and trimethylolpropane tri-β-(2-methylaziridine) propionate.

[0075] As chelate-type curing agents, examples include compounds composed of multivalent metals and ligands. Examples of multivalent metals include nickel, aluminum, chromium, iron, titanium, zinc, cobalt, manganese, and zirconium. Examples of ligands include acetylacetone and acetoacetate.

[0076] When using a curing agent, its content relative to 100 parts by weight of the non-volatile components of the adhesive layer is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 7.5 parts by weight, and even more preferably 0.5 to 5 parts by weight. Within these ranges, the curing agent can be expected to provide effects such as improved adhesion and durability.

[0077] [Tackifier (F)]

[0078] Examples of tackifiers (F) include rosin-based tackifiers (F1), terpene-based tackifiers (F2), coumarin-based tackifiers, styrene-based tackifiers, and petroleum-based tackifiers.

[0079] Examples of rosin-based tackifiers (F1) include rosin-based resins, polymerized rosin-based resins, rosin ester-based resins, and polymerized rosin ester-based resins. Examples of terpene-based tackifiers (F2) include terpene-based resins and terpene-phenolic resins. When using tackifiers (F), it is preferable to include either rosin-based tackifier (F1) or terpene-based tackifier (F2), and more preferably, rosin-based tackifier (F1). By using these tackifiers (F), an improvement in adhesion can be expected.

[0080] When using a tackifier (F), its content is preferably 1 to 40 parts by mass relative to 100 parts by mass of the non-volatile components of the adhesive layer, more preferably 5 to 40 parts by mass, and even more preferably 15 to 30 parts by mass. Within these ranges, it is easier to improve adhesion, and a laminate with excellent resealing properties can be produced.

[0081] The adhesive layer of the present invention may further contain flame retardants, heat stabilizers, weather stabilizers, anti-aging agents, ultraviolet absorbers, leveling agents, antistatic agents, slip agents, anti-blocking agents, anti-fogging agents, lubricants, dyes, waxes, etc. as any component.

[0082] <Heat-sealing resin layer (C)>

[0083] The heat-sealing resin layer (C) contains a polyethylene-based resin and further contains at least one of a polypropylene-based resin and a polybutene-based resin. The polyethylene-based resin is incompatible with the polypropylene-based resin and the polybutene-based resin, therefore, incompatible resins coexist in the heat-sealing resin layer (C).

[0084] Furthermore, as described above, after the heat-sealing resin layer (C) is bonded to the container by heat pressing, the heat-sealed portion will transfer to the container after the laminate is opened. That is, upon opening, the heat-sealing resin layer (C) will tear between the heat-sealed portion and the other portions. If the tear resistance of the layer is insufficient, the heat-sealing resin layer (C) will remain on either the laminate side or the container side, or it will become stringy and elongated. By containing polyethylene-based resins and at least one of polypropylene-based resins and polybutene-based resins that are incompatible with polyethylene-based resins, tear resistance is improved, and such a phenomenon is less likely to occur.

[0085] Polyethylene-based resins can be, for example, low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer (EVA), and copolymers composed of monomers mixed in any proportion with at least one monomer selected from the group consisting of propylene, butene, pentene, hexene, or an olefin having a carbon chain thereon. It should be noted that for copolymers of ethylene and propylene and copolymers of ethylene and butene, substances containing less than 50% by mass of propylene or butene in 100% by mass of the total monomers are included in the polyethylene-based resin. From the perspective of extrusion lamination processability, low-density polyethylene and ethylene-vinyl acetate copolymer (EVA) are preferred, and low-density polyethylene is more preferred. Low-density polyethylene manufactured by a high-pressure process is particularly preferred. Furthermore, the ethylene content in 100% by mass of the total monomers of the polyethylene-based resin is preferably 60% or more, and more preferably 70% or more.

[0086] Polypropylene-based resins can be homopolymers of propylene or copolymers composed of monomers mixed with at least one monomer selected from the group consisting of ethylene, butene, pentene, hexene, or olefins with carbon chains thereon. It should be noted that, for copolymers of ethylene and propylene, substances containing 50% or more propylene in 100% by mass of the total monomers are included in the polypropylene-based resin. Polypropylene-ethylene copolymers are preferred from the perspective of coatability based on extrusion lamination. Furthermore, the propylene content in 100% by mass of the total monomers of the polypropylene-based resin is preferably 60% or more, more preferably 70% or more.

[0087] Polybutene-based resins include homopolymers of 1-butene, 2-butene, and isobutene, or polymers obtained through copolymerization. Furthermore, copolymers consisting of these monomers mixed in any proportion with at least one monomer selected from the group consisting of ethylene, propylene, pentene, hexene, or an olefin with a carbon chain thereto. It should be noted that, for copolymers of ethylene and butene, substances containing 50% or more butene in 100% by mass of the total monomers are included in the polybutene-based resin. Of these, 1-butene-ethylene copolymers are preferred from the perspective of coatability based on extrusion lamination. Furthermore, the butene content in 100% by mass of the total monomers of the polybutene-based resin is preferably 60% or more, more preferably 70% or more.

[0088] The melt flow rate (MFR) of the polyethylene resin is preferably 0.1 to 30 g / 10 min, more preferably 0.1 to 20 g / 10 min, and even more preferably 0.1 to 10 g / 10 min. Within this range, coating can be performed more stably using extrusion lamination. It should be noted that the MFR of the polyethylene resin is a value measured according to JIS.K7210 at 190°C and 21.168 N.

[0089] The preferred MFR (Mean Friction Rate) for polypropylene and polybutene resins is 0.1–10 g / 10 min, more preferably 0.5–8 g / 10 min. Within this range, coating can be performed more stably using extrusion lamination. It should be noted that the MFR for polypropylene and polybutene resins is a value measured according to JIS.K7210 at 230°C and 21.168 N.

[0090] The content of polyethylene resin in the heat-sealing resin layer (C) is preferably 35-70% by mass, more preferably 40-65% by mass, and even more preferably 45-60% by mass. With a polyethylene resin content of 35% by mass or more, coating via extrusion lamination can be performed more stably. Furthermore, with a content of 70% by mass or less, the tear resistance and adhesion of the heat-sealing resin layer (C) are easily maintained.

[0091] The total content of polypropylene resin and polybutene resin in the heat-sealing resin layer (C) is preferably 15-40% by mass, more preferably 18-35% by mass, and even more preferably 20-30% by mass. If it is within the above range, it is preferred in terms of the tear resistance of the heat-sealing resin layer (C).

[0092] Without compromising its performance, the heat-sealing resin layer (C) may also contain other resins and tackifiers. Examples of other resins include maleic acid modified compounds, ethylene-acrylic acid copolymers, ethylene-(meth)acrylic acid copolymers and other ethylene-unsaturated monocarboxylic acid copolymers and their metal salts, styrene-butadiene copolymer elastomers and their hydroadductors, and various elastomers. The tackifier may be the same substance as the tackifier (F) that may be contained in the adhesive layer (B). The content of other resins and tackifiers in the heat-sealing resin layer (C) is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0093] In the heat-sealing resin layer (C), wax can be further added to improve adhesion to the adhesive layer (B) and improve stringiness. Examples of waxes include polyethylene wax, polypropylene wax, ethylene-vinyl acetate copolymer wax, Fischer-Tropsch wax, paraffin wax, acidified wax, and maleic acid modified wax. Polyethylene wax is preferred. When wax is present, its content in 100% by mass of the heat-sealing resin layer (C) is preferably 8–40% by mass, more preferably 12–30% by mass, and even more preferably 15–25% by mass. The viscosity of the wax at 140°C is preferably 50–10000 mPa·s, more preferably 60–8000 mPa·s. It should be noted that the viscosity is a value measured using a Type B viscometer (measured under the conditions of 140°C, No. 3 rotor, 12 rpm, and 30 seconds).

[0094] To prevent thermal degradation, thermal decomposition, and adhesion, and to facilitate appropriate film processing and extrusion lamination, additives may be further used in the heat-sealing resin layer (C) without compromising its performance. Examples of additives include organic lubricants such as erucamide, inorganic lubricants such as calcium carbonate, antioxidants such as hindered phenols, other anti-blocking agents, antistatic agents, fillers, and pigments. The additives are formulated, for example, by feeding the components used in the heat-sealing resin layer (C) into a mixing device such as a Henschel mixer or a drum mixer, mixing for 5 to 20 minutes, then feeding the mixture into an extruder, heating and kneading, and finally extruding. The extrudate is typically granular and is used in subsequent processes. Preferred extruders include, for example, twin-screw extruders, but are not limited to these. Furthermore, extrusion is typically carried out at 140–200°C.

[0095] Resealing heat-sealing laminate

[0096] The resealing heat-sealing laminate of the present invention can be obtained, for example, by laminating a heat-sealing resin layer (C) onto the adhesive layer (B) of a substrate (A) to which the adhesive layer (B) is laminated.

[0097] The adhesive layer (B) can be formed by applying the adhesive to the substrate (A) using conventionally known coating methods, and then further drying it in the presence of water and solvent. Examples of coating methods include spin coating, spray coating, bar coating, blade coating, roller coating, roller-scalpel coating, blade coating, mold coating, and gravure coating. The drying process can be performed using known equipment such as hot air ovens, electric ovens, and infrared heaters. If the adhesive does not contain water or solvent, for example, a method can be used where the viscosity of the adhesive is reduced by heating, and then it is applied to the substrate (A) using a coating method such as mold coating, followed by a cooling process to form the adhesive layer (B). After the adhesive layer (B) is formed, it can be directly transferred to the next process on the same production line, or the release paper and release film can be stacked on the adhesive layer (B) and wound up, and then the release paper and release film can be peeled off on another production line to expose the adhesive layer (B) before being transferred to the next process.

[0098] As a method for laminating a heat-sealing resin layer (C) onto an adhesive layer (B), one possible method is as follows: the components used in the heat-sealing resin layer (C) are mixed, heated and extruded using an extruder, then chopped and granulated. Using these granules, a single-layer film is formed by blowing or casting. This single-layer film is then laminated onto the adhesive layer (B). Alternatively, the granules can be melted and directly coated onto the adhesive layer (B) using a T-die extrusion apparatus.

[0099] Resealable Packaging Containers

[0100] The resealable packaging container of the present invention is formed by using the resealable heat-sealing laminate of the present invention as the cap material, cutting it according to the opening shape of the container body, and then heating and pressing it with the opening of the container body to seal it. That is, the heat-sealing resin layer (C) of the resealable heat-sealing laminate of the present invention is brought into contact with the adhesive surface (also called the flange) of the opening of the sealed container and heated (heat-sealed). The bonding conditions are preferably 130–170°C.

[0101] The preferred container body is a container body made of polyethylene resin or a container body whose inner surface is covered with polyethylene resin.

[0102] When the container body is a PET container, it is preferable to heat-bond the container body and the lid material at a heat-bonding temperature of 130-170°C, and the opening strength at room temperature is preferably in the range of 10-20N. The resealable packaging container of the present invention can, for example, package jelly, pudding, yogurt, frozen food, dry snacks, cup noodles, etc.

[0103] Example

[0104] The present invention will be described below based on embodiments, but the present invention is not limited to these embodiments. It should be noted that in the embodiments, "parts" and "%" represent "parts by mass" and "% by mass," respectively.

[0105] The glass transition temperature and weight-average molecular weight of the acrylic copolymer (D) were determined as follows.

[0106] <Determination of Glass Transition Temperature (Tg)>

[0107] The glass transition temperature was determined by the aforementioned differential scanning calorimetry (DSC) method.

[0108] It should be noted that the sample used for Tg determination is a sample obtained by heating the resin solution to be measured at 150°C for about 15 minutes to dry and solidify it.

[0109] <Determination of weight-average molecular weight>

[0110] The weight-average molecular weight was determined by the aforementioned method, using the polystyrene conversion value obtained by gel permeation chromatography (GPC).

[0111] <Synthesis of Acrylic Copolymer (D1)>

[0112] To a mixture of 3.15 parts methyl methacrylate, 32 parts 2-ethylhexyl acrylate, 64 parts butyl acrylate, and 0.85 parts acrylic acid, 1.0 part of "Aqualon KH-10" (polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfate ammonium salt, manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), an anionic reactive emulsifier, and 25.1 parts deionized water were added and stirred to obtain an emulsion. The obtained emulsion was then placed in a dropping funnel.

[0113] In addition, 45.6 parts of deionized water and 1.0 part of the emulsion were added to a four-necked flask equipped with a stirrer, condenser, thermometer, and the aforementioned dropping funnel. The inside of the flask was purged with nitrogen, and the internal temperature was heated to 70°C while stirring. Then, 10% ammonium persulfate was added to initiate the reaction. While maintaining the internal temperature at 70°C, the emulsion was added dropwise over 180 minutes, and the reaction was continued for 1 hour while stirring and maintaining the internal temperature at 70°C. Then, the internal temperature was cooled to 65°C, and 1.0 part of a 10% aqueous solution of the oxidant "PERBUTYL H-69" (manufactured by Nippon Yushi Co., Ltd.) and 1.0 part of a 10% aqueous solution of the reducing agent "Elbit N" (manufactured by Fuso Chemical Co., Ltd.) were added every 10 minutes, three times, and the reaction was continued for another hour. Then, the mixture was cooled and neutralized by adding 25% ammonia at 30°C, resulting in an acrylic copolymer (D1) solution with a non-volatile component concentration of 50% and a Tg of -45°C. The acrylic copolymer (D1) is insoluble in THF, therefore its weight-average molecular weight is determined to be greater than 2,000,000.

[0114] <Synthesis of Acrylic Copolymer (D2)>

[0115] Using 5 parts methyl methacrylate, 90.5 parts 2-ethylhexyl acrylate, and 4.5 parts acrylic acid as monomers, and "HITENOL NF-08" (polyoxyethylene alkyl ether sulfate, manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.) as emulsifier, the acrylic copolymer (D1) was synthesized in the same manner, except that a solution of acrylic copolymer (D1) with a non-volatile component concentration of 50% and a Tg of -46°C was obtained. The acrylic copolymer (D1) is insoluble in THF, therefore its weight-average molecular weight is determined to be greater than 2,000,000.

[0116] <Synthesis of Acrylic Copolymer (D3)>

[0117] Using a polymerization apparatus equipped with a stirrer, thermometer, dropper, and reflux condenser, under a nitrogen atmosphere, half of a raw material mixture comprising 1 part methyl methacrylate, 4 parts isobutyl methacrylate, 4 parts vinyl acetate, 85.3 parts butyl acrylate, 5 parts 2-methoxyethyl acrylate, 0.7 parts 2-hydroxyethyl acrylate, 10 parts methyl ethyl ketone, 60 parts ethyl acetate, and 0.1 parts benzoyl peroxide was added to the reaction vessel. The remaining half of the raw material mixture was added in a dropping layer. Heating of the reaction vessel was then initiated. After confirming the start of polymerization, the raw material mixture was added dropwise over 1 hour. After the dropping was completed, solution polymerization was continued for another 7 hours under reflux. After the reaction was completed, the mixture was cooled to obtain an acrylic copolymer (D3) solution with 58.8% non-volatile components. The obtained acrylic copolymer (D3) had a Tg of -47°C and a weight-average molecular weight of 708,000.

[0118] <Synthesis of Acrylic Copolymers (D4) and (D5)>

[0119] The monomers were changed to the composition shown in Table 1, and the same procedure was followed as for the synthesis of the acrylic copolymer (D3) to obtain solutions of acrylic copolymers (D4) and (D5) with 58.8% non-volatile components. Their Tg and weight-average molecular weights are shown in Table 1.

[0120] <Synthesis of Acrylic Copolymer (D6)>

[0121] The monomers were changed to the composition shown in Table 1, and the amount of methyl ethyl ketone was changed to 7 parts and the amount of ethyl acetate was changed to 63 parts. Otherwise, the same procedure was followed as for the synthesis of the acrylic copolymer (D3) to obtain an acrylic copolymer (D6) solution with 58.8% non-volatile components. Tg and weight-average molecular weight are shown in Table 1.

[0122] <Acrylic copolymers (D7), (D8)>

[0123] The acrylic copolymers (D7) and (D8) use the following substances respectively.

[0124] Acrylic copolymer (D7): KURARITY LK9243 (manufactured by Kuraray, methyl methacrylate-2-ethylhexyl acrylate-methyl methacrylate block copolymer, MFR 93 g / 10 min)

[0125] Acrylic copolymer (D8): KURARITY LA3320 (manufactured by Kuraray, methyl methacrylate-butyl acrylate-methyl methacrylate block copolymer, MFR 6 g / 10 min)

[0126] It should be noted that the MFR values ​​mentioned above are all values ​​at 190℃ and a load of 2.16kg.

[0127] [Table 1]

[0128]

[0129] It should be noted that the abbreviations in Table 1 are as follows.

[0130] MMA: Methyl methacrylate

[0131] EA: Ethyl acrylate

[0132] 2EHA: 2-Ethylhexyl acrylate

[0133] IBMA: Isobutyl methacrylate

[0134] VAc: Vinyl acetate

[0135] BA: n-Butyl acrylate

[0136] 2MTA: 2-Methoxyethyl Acrylate

[0137] AA: Acrylic acid

[0138] 2HEA: 2-Hydroxyethyl acrylate

[0139] [Example 1: Manufacturing of a laminate]

[0140] <Adhesive Manufacturing>

[0141] An adhesive was prepared by combining 79.1 parts of acrylic copolymer D3, 1.1 parts of curing agent E1, and 19.8 parts of tackifier F1-1 as solid components. The ratios in Table 2 represent the solid component ratios.

[0142] <Manufacturing of a single-layer film of heat-sealable resin layer (C)>

[0143] Mix 53 parts of polyethylene resin PE1, 26 parts of polypropylene resin PP1, and 21 parts of additive C1, and premix for 5 minutes using a Henschel mixer. Transfer the premix to a funnel and feed it into an extruder using a screw feeder to produce the resin mixture for the heat-sealing resin layer (C).

[0144] Extruder Conditions

[0145] Extruder: IKG PMT32-40.5 co-rotating twin-screw extruder.

[0146] Barrel temperature: 180℃ (supply port 160℃)

[0147] Screw rotation speed: 200 rpm

[0148] Feeding rate: 10kg / hr

[0149] The mixture was blown into shape using a Labtech blow molding machine (mold diameter: 40 mm φ, molding temperature: 130 °C) to produce a single-layer film with a heat-sealing resin layer (C) of 20 μm thickness.

[0150] Single-layer molding conditions

[0151] Blow molding machine: Made by Labtech

[0152] Resin temperature: 130℃

[0153] Barrel temperature: 180℃ (feed port 170℃)

[0154] Screw rotation speed: 60 rpm

[0155] Stretching speed: 5m / min

[0156] Cooling roller surface temperature: 20℃

[0157] <Manufacturing of Laminated Structures>

[0158] The obtained adhesive was applied to the corona-treated surface of a 12 μm biaxially stretched PET film, which served as the substrate (A), using a roller coater. The solvent was removed using an oven at 100°C, thereby forming an adhesive layer (B) with a thickness of 20 μm. Next, a single-layer film of a heat-sealing resin layer (C) was laminated onto the surface of the adhesive layer (B) to obtain the laminate of Example 1, which is stacked in the order of substrate (A) / adhesive layer (B) / heat-sealing resin layer (C).

[0159] [Table 2]

[0160]

[0161] [Table 3]

[0162]

[0163] <Styrene-based copolymers (S)>

[0164] S1: Kraton G-1657 (manufactured by Kraton Polymers, Japan, styrene-ethylene butadiene-styrene block copolymer, MFR 22g / 10min)

[0165] S2: Kraton G-1652 (manufactured by Kraton Polymers, Japan, styrene-ethylene butadiene-styrene block copolymer, MFR 5g / 10min)

[0166] It should be noted that the above MFR values ​​are all at 230℃ and 5kg load.

[0167] <Curing Agent (E)>

[0168] E1: A substance made by diluting the trimethylolpropane adduct of diphenylmethylene diisocyanate with ethyl acetate to 50% of its non-volatile components: an isocyanate-based curing agent.

[0169] E2: A substance made by diluting the trimethylolpropane adduct of toluene diisocyanate with ethyl acetate to 40% of its non-volatile components: an isocyanate-based curing agent.

[0170] E3: A substance containing TETRAD-X (manufactured by Mitsubishi Gas Chemical Co., Ltd., a multifunctional epoxy resin) diluted with MEK to 10% of its non-volatile components: an epoxy curing agent.

[0171] <Tackifier (F)>

[0172] F1-1: PINECRYSTAL KE-359 (manufactured by Arakawa Chemical Co., Ltd., a rosin derivative).

[0173] F1-2: PENSEL D-125 (manufactured by Arakawa Chemical Co., Ltd., rosin ester)

[0174] F2-1: YS RESIN PX-1000 (manufactured by Yasuhara Chemical Co., Ltd., terpene resin)

[0175] F3: Alcon P-100 (manufactured by Arakawa Chemical Co., Ltd., hydrogenated petroleum resin)

[0176] F4: Kristalex F-100 (manufactured by Eastman Chemical Company, styrene-α-methylstyrene copolymer)

[0177] <Liquid component (L)>

[0178] L1: DIANA PROCESS PW-32 (manufactured by Idemitsu Kosan Co., Ltd., mineral oil)

[0179] L2: Styrene monomer (manufactured by Kanto Chemical Co., Ltd.)

[0180] <Other Additives (P)>

[0181] P1: MS-P (manufactured by Japan Talc Corporation, inorganic material, average particle size 14μm)

[0182] <Polyethylene-based resins>

[0183] PE1: PETROTHENE 213 (manufactured by Tosoh Corporation, low-density polyethylene, MFR 8g / 10min)

[0184] PE2: Urutorasen 526 (manufactured by Tosoh Corporation, ethylene-vinyl acetate copolymer, vinyl acetate content 7%, MFR 25g / 10min)

[0185] It should be noted that the MFR values ​​mentioned above are all values ​​at 190℃ and a load of 2.16kg.

[0186] <Polypropylene-based resins and polybutene-based resins>

[0187] PP1: SB-520 (manufactured by LOTTE, polypropylene-polyethylene copolymer, MFR 1.8 g / 10 min)

[0188] PB1: TAFMER BL-4000 (manufactured by Mitsui Chemicals, butene-ethylene copolymer, MFR 1.8 g / 10 min)

[0189] It should be noted that the MFR values ​​mentioned above are all values ​​at 190℃ and a load of 2.16kg.

[0190] <Additive (C)>

[0191] C1: L-C121N (manufactured by Lionchemtech, polyethylene wax, melting point 109℃)

[0192] [Example 1: Manufacturing of a resealable packaging container]

[0193] After aligning the flange portion (approximately 4 mm wide) around the opening of a cylindrical paper container (outer diameter: 95 mm φ) with an inner layer of polyethylene film, the laminate obtained in Example 1 was heat-sealed using a MODEL2005 (manufactured by Towa Techno) under the conditions of a sealing temperature of 150°C, a sealing pressure of 100 kgf / cup, and a sealing time of 1 second to obtain a resealable packaging container.

[0194] (1) Opening strength

[0195] For resealable packaging containers, the adhesive strength was measured using a tensile testing machine (Autograph AGS-X, manufactured by Shimadzu Corporation) at 23°C and 65% relative humidity (65% RH) when approximately 50% of the laminate was peeled off at an opening angle of 90 degrees and an opening speed of 300 mm / min. The maximum value was then recorded.

[0196] ◎: 12N or higher but less than 20N: Excellent

[0197] ○: 9N or higher but less than 12N, or 20N or higher but less than 23N: Good

[0198] △: 6N or higher but less than 9N, or 23N or higher but less than 26N: can be used

[0199] ×: Less than 6N or more than 26N: Not suitable for use.

[0200] (2) Wire drawing

[0201] By visually observing the peeling of the laminate from the container after the opening strength of the resealable packaging container is measured, the occurrence of stringing is confirmed.

[0202] ◎: No stringing (the area of ​​the peeled portion where stringing occurs is 0%): Excellent

[0203] ○: Of the area of ​​the peeled portion, the area where stringing occurs is greater than 0% and less than 10%: Good

[0204] △: In the area of ​​the peeled portion, the area where stringing occurs is greater than 10% but less than 30%: Suitable for use.

[0205] ×: If the area of ​​the peeled portion where stringing occurs is greater than 30%, it cannot be used.

[0206] (3) Zipping

[0207] Confirm the occurrence of zipping during the opening strength test of resealable packaging containers.

[0208] ◎: No cracking (0% of the area of ​​the peeled portion is cracked): Excellent

[0209] ○: Of the area of ​​the peeled portion, the area of ​​the cracked portion is greater than 0% but less than 10%: Good

[0210] △: If the area of ​​the peeled portion where cracking occurs is greater than 10% but less than 30%, it can be used.

[0211] ×: If more than 30% of the area of ​​the peeled portion is cracked, it is unusable.

[0212] (4) Reseal

[0213] After measuring the opening strength of the resealable packaging container, overlap the laminated portion of the container with the peeled portion, and press the laminate back and forth twice with your fingers to seal it. Then measure the opening strength again. Repeat this operation 5 times and read the maximum value on the 5th time.

[0214] ◎: 4N or higher but less than 7N: Excellent

[0215] ○: 2N or higher but less than 4N, 7N or higher but less than 10N: Good

[0216] △: 1N or higher but less than 2N, 10N or higher but less than 13N: can be used

[0217] ×: Less than 1N, or more than 13N: Not usable

[0218] (5) Exudation to the surface of the heat-sealing resin layer (C) after a period of time

[0219] After the laminate has been heated at 40℃ for 24 hours, the changes in surface condition are confirmed by visual inspection and comparison with the laminate before the heating period.

[0220] ○: No change: Good

[0221] ×: Surface is moist and sticky: Do not use.

[0222] (6) Resealing after a period of time

[0223] Using a laminate that has been heated to 40°C for 24 hours, and otherwise operated in the same manner as described above, a cylindrical paper container with a polyethylene film laminated on the inner side is heat-sealed to obtain a resealable packaging container. For this resealable packaging container, at 23°C and 65% relative humidity (65% RH), approximately 50% of the laminate is peeled off using a tensile testing machine (Autograph AGS-X, Shimadzu Corporation) at an opening angle of 90 degrees and an opening speed of 300 mm / min. Next, the peeled portion of the laminate from the opened resealable packaging container is overlapped with the peeled portion of the container, and the laminate is sealed by pressing it back and forth twice with fingers. The opening strength is then measured again. This operation is repeated 5 times, and the maximum value is recorded on the 5th attempt. Using this value and the resealability evaluation value when using an unsealed laminate, the following relative ratio is calculated and evaluated as follows.

[0224] Relative ratio (%) = 100 × (evaluation value of resealing when using unsealed laminates) / (evaluation value of resealing when using laminates after 40°C for 24 hours)

[0225] ○: Relative ratio of 70% or higher: Usable

[0226] ×: Relative ratio less than 70%: Not usable

[0227] [Examples 2-15]

[0228] In Examples 2-15, the composition and ratio of the adhesive were changed as shown in Tables 2 and 3. Otherwise, the same procedure as in Example 1 was followed to manufacture the laminate and resealable packaging container and to evaluate them.

[0229] [Example 16: Fabrication of a laminate]

[0230] <Adhesive Manufacturing>

[0231] Mix 65 parts of acrylic copolymer D7, 15 parts of tackifier F3, and 20 parts of tackifier F4 using a Henschel mixer and premix for 5 minutes. Transfer the premix to a funnel and feed it into an extruder using a screw feeder to produce the adhesive.

[0232] Extruder Conditions

[0233] Extruder: IKG PMT32-40.5 co-rotating twin-screw extruder.

[0234] Barrel temperature: 180℃ (supply port 160℃)

[0235] Screw rotation speed: 200 rpm

[0236] Feeding rate: 10kg / hr

[0237] <Manufacturing of Laminated Structures>

[0238] On the corona-treated surface of a 12μm biaxially stretched PET film serving as the substrate layer, an adhesive is extruded from a T-die with a thickness of 20μm. Simultaneously, a single-layer film of a heat-sealing resin layer (C) is laminated onto the surface of the adhesive layer (B). Through the sandwich lamination method described above, a laminate is obtained in the order of substrate (A) / adhesive layer (B) / heat-sealing resin layer (C).

[0239] [Example 16: Manufacturing of Resealable Packaging Containers]

[0240] The same procedure as in Example 1 was followed to manufacture resealable packaging containers and evaluate them.

[0241] [Example 17]

[0242] In Example 17, the adhesive was changed to the composition and ratio shown in Table 3. Otherwise, the same procedure as in Example 16 was followed to manufacture the laminate and resealable packaging container for evaluation.

[0243] [Examples 18-20]

[0244] In Examples 18-20, the adhesive and heat-sealing resin layer (C) were changed to the composition and ratio shown in Table 3. Otherwise, the same procedure as in Example 1 was followed to prepare laminates and resealable packaging containers for evaluation.

[0245] [Comparative Example 1: Fabrication of Laminated Materials]

[0246] <Adhesive Manufacturing>

[0247] In a stainless steel beaker equipped with a mixer, 35 parts of liquid component L1 (mineral oil) were added and heated and stirred to 160°C. While stirring, 30 parts of styrene-based elastomer S1 and tackifier F3 were added, and the mixture was stirred for 3 hours to obtain a hot melt adhesive.

[0248] <Fabrication of Adhesive Layer>

[0249] A hot melt adhesive heated to 160°C is applied to the corona-treated surface of a 12μm biaxially stretched PET film (A) as substrate (A) using a manual coating machine to form an adhesive layer (B) with a thickness of 30μm, resulting in a laminate of substrate (A) / adhesive layer (B).

[0250] <Manufacturing of Laminated Structures>

[0251] A single film of heat-sealing resin layer (C) is laminated on the surface of the adhesive layer (B) of the laminate of substrate (A) / adhesive layer (B) to obtain a laminate of substrate (A) / adhesive layer (B) / heat-sealing resin layer (C).

[0252] [Comparative Example 1: Manufacturing of Resealable Packaging Containers]

[0253] The same procedure as in Example 1 was followed to manufacture a cup-shaped seal and evaluate it.

[0254] [Comparative Example 2]

[0255] The adhesive was changed to the composition and ratio in Table 3. Otherwise, the same procedure as in Example 16 was followed to manufacture the laminate and cup-shaped seal, and the results were evaluated.

[0256] [Compare Examples 3 and 4]

[0257] In Comparative Examples 3 and 4, the adhesive and heat-sealing resin layer (C) were changed to the composition and ratio shown in Table 3. Otherwise, the same procedure as in Example 1 was followed to manufacture the laminate and cup-shaped seal, and the results were evaluated.

[0258] As shown in Tables 2 and 3, compared with Comparative Examples 1 to 4, Examples 1 to 20, in which the adhesive layer (B) contains an acrylic copolymer (D) and the heat-sealing resin layer (C) contains a polyethylene resin and further contains at least one of a polypropylene resin and a polybutene resin, exhibited sufficient initial opening strength. When the cap material was peeled off from the container, a portion of the heat-sealing resin layer (C) was not easily left on the heat-sealed portion of the cap material side or was not easily pulled into filaments. Furthermore, even after opening, it could be resealed with practically sufficient strength by pressing the cap material and the container together. Moreover, no liquid components seeped out on the surface of the laminate over time.

Claims

1. A resealing heat-sealable laminate, comprising a substrate (A), an adhesive layer (B), and a heat-sealable resin layer (C) arranged sequentially. The adhesive layer (B) contains an acrylic copolymer (D). The heat-sealing resin layer (C) contains a polyethylene-based resin and further contains at least one of a polypropylene-based resin and a polybutene-based resin. The monomers constituting the acrylic copolymer (D) contain alkyl (meth)acrylate monomers and further contain at least one of hydroxyl-containing monomers and carboxyl-containing monomers. The alkyl methacrylate monomer contains 30-99 parts by mass out of 100 parts by mass of the total monomer. The content of the polyethylene resin in the heat-sealing resin layer (C) is 35-70% by mass in 100% by mass.

2. The resealing heat-sealing laminate according to claim 1, wherein the adhesive layer (B) further contains a curing agent (E).

3. The resealing heat-sealing laminate according to claim 1, wherein the adhesive layer (B) further comprises a tackifier (F).

4. The resealing heat-sealing laminate according to claim 3, wherein the tackifier (F) contains a rosin-based tackifier (F1) or a terpene-based tackifier (F2).

5. The resealing heat-sealing laminate according to claim 1, wherein the substrate (A) is a polyester resin film, metal foil, or paper.

6. A resealable packaging container having a resealable heat-sealing laminate and a container body as described in any one of claims 1 to 5.

Images