Laminates and packaging materials using them

Abstract

The present invention provides a heat sealant that has excellent heat sealability for various materials such as paper and various film materials, exhibits excellent heat seal strength at low temperatures of 150°C or below, can achieve sufficient heat seal strength immediately after heat sealing, and has excellent blocking resistance, as well as laminates and packaging materials using the heat sealant. [Solution] An aqueous heat seal composition comprising an aqueous medium and a thermoplastic resin, wherein the thermoplastic resin comprises an ethylene-vinyl acetate copolymer resin and a (meth)acrylic resin, and the glass transition temperature of the thermoplastic resin is 30°C or lower.

Description

[Technical Field]

[0001] The present invention relates to a laminate having a thermoplastic resin layer on a base material and a packaging material using the same. [Background technology]

[0002] Heat sealants are used in packaging materials and containers for food, household goods, pharmaceuticals, and various other industrial applications. There are two types of heat sealants: organic solvent-based and water-based. In recent years, there has been a growing demand for water-based heat sealants due to environmental protection and safety and hygiene concerns.

[0003] Packaging materials used for food and daily necessities typically consist of various resin films such as polyethylene film, polypropylene film, and polyester film. The heat-sealing properties of heat sealants depend on their compatibility with the film material, so a heat sealant suitable for each film material and application is selected.

[0004] Furthermore, with the issue of marine plastic waste, including microplastics, coming into sharp focus, there is a growing demand for paper packaging materials and containers that do not use plastic film. As a result, packaging materials are becoming increasingly diverse, including those using paper in addition to various resin films, and those made by laminating paper and resin films, making the selection of the optimal heat sealant essential.

[0005] Furthermore, heat sealing is typically performed by applying heat at temperatures of 150°C or higher (see Patent Document 1). However, from an energy-saving perspective, a heat sealant that exhibits heat-sealing properties at lower temperatures of 150°C or below is desirable. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 7014345 [Overview of the project] [Problems that the invention aims to solve]

[0007] Given the increasing diversification of packaging materials, it is desirable from a workability standpoint that a single heat sealant can be applied to various substrates. However, sufficient research has not yet been conducted on heat sealants that possess excellent heat-sealing properties for all materials.

[0008] Furthermore, from the perspective of energy conservation, there is a demand for heat sealants that exhibit excellent heat seal strength at low temperatures below 150°C. However, achieving excellent heat seal strength at low temperatures is difficult. Moreover, from the perspective of shortening packaging time, it is necessary to exhibit sufficient heat seal strength immediately after heat sealing, but it is difficult to achieve sufficient strength immediately after processing under low-temperature heat sealing conditions. In addition, the problem of reduced blocking properties is also likely to occur. However, no heat sealant that can solve these problems is known.

[0009] Therefore, the problem that the present invention aims to solve is to provide a heat sealant that has excellent heat sealability for various materials such as paper and various film materials, exhibits excellent heat seal strength at low temperatures of 150°C or below, can exhibit sufficient heat seal strength immediately after heat sealing, and has excellent blocking resistance, as well as laminates and packaging materials using the heat sealant. [Means for solving the problem]

[0010] In other words, the present invention is an aqueous heat seal composition comprising an aqueous medium and a thermoplastic resin, wherein the thermoplastic resin comprises an ethylene-vinyl acetate copolymer resin and a (meth)acrylic resin, and the glass transition temperature of the thermoplastic resin is 30°C or lower.

[0011] Furthermore, the present invention relates to a laminate having a base material and a heat-seal layer provided on the base material, wherein the heat-seal layer is a layer formed from an aqueous heat-seal composition containing an aqueous medium and a thermoplastic resin, wherein the thermoplastic resin contains an ethylene-vinyl acetate copolymer resin and a (meth)acrylic resin, and the glass transition temperature of the thermoplastic resin is 30°C or lower.

[0012] Furthermore, the present invention relates to a packaging material using a laminate having a base material and a heat-seal layer provided on the base material, wherein the heat-seal layer is formed from an aqueous heat-seal composition containing an aqueous medium and a thermoplastic resin, the thermoplastic resin containing an ethylene-vinyl acetate copolymer resin and a (meth)acrylic resin, and the glass transition temperature of the thermoplastic resin is 30°C or lower. [Effects of the Invention]

[0013] The present invention provides a heat sealant that exhibits excellent heat sealability for various materials such as paper and various film materials, has excellent heat seal strength at low temperatures of 150°C or below, can exhibit sufficient heat seal strength immediately after heat sealing, and has excellent blocking resistance, as well as laminates and packaging materials using the heat sealant. The present invention enables energy saving and shortens packaging work time, and also improves workability by providing a heat sealant that can be widely used for packaging materials and containers for various applications. [Modes for carrying out the invention]

[0014] <Water-based heat seal composition> The aqueous heat seal composition of the present invention contains at least an aqueous medium and a thermoplastic resin.

[0015] (thermoplastic resin) The thermoplastic resin contains at least an ethylene-vinyl acetate copolymer resin and a (meth)acrylic resin. In the present invention, the (meth)acrylic resin represents a homopolymer or copolymer of (meth)acrylate, (meth)acrylate represents the general term for acrylate and methacrylate, and (meth)acrylic acid represents the general term for acrylic acid and methacrylic acid.

[0016] ((ethylene-vinyl acetate copolymer resin)) The ethylene-vinyl acetate copolymer resin is a copolymer obtained by copolymerizing ethylene and vinyl acetate, and may be one in which the ester moiety is partially or wholly hydrolyzed in some cases. Further, the ethylene-vinyl acetate copolymer resin may be further copolymerized with other monomers, but the content of the structural units derived from other monomers is preferably 30% by mass or less, more preferably 10% by mass or less, still more preferably 3% by mass or less, and even more preferably 1% by mass or less of the entire copolymer.

[0017] In the present invention, from the viewpoints of the stability of the heat seal strength and blocking resistance in a low temperature range of 80°C to 140°C, preferably about 80°C to 120°C, the proportion of vinyl acetate in the ethylene-vinyl acetate copolymer is preferably such that the proportion of ethylene in the copolymer is 70 mol% or less. Preferably it is 60 mol% or less, more preferably 55 mol% or less. On the other hand, from the viewpoint of blocking resistance, the proportion of vinyl acetate in the copolymer is preferably 5 mol% or more, more preferably 10 mol% or more.

[0018] The weight average molecular weight of the ethylene-vinyl acetate copolymer resin is not particularly limited, but from the viewpoint of blocking resistance, it is preferably 200,000 or more. On the other hand, from the viewpoint of low temperature heat sealability, the weight average molecular weight is preferably 1,000,000 or less.

[0019] Also, since the glass transition temperature of the ethylene-vinyl acetate copolymer results in good heat sealability at low temperatures, it is preferably 30°C or lower, more preferably 20°C or lower, and even more preferably 10°C or lower. On the other hand, from the perspective of blocking resistance, the lower limit of the glass transition temperature is preferably -50°C or higher, more preferably -40°C or higher, and even more preferably -30°C or higher.

[0020] ((Acrylic resin)) As the acrylic resin, there is no particular limitation on the homopolymer or copolymer of (meth)acrylate. Examples of the copolymer include a copolymer obtained by copolymerizing a vinyl monomer that can copolymerize with (meth)acrylate. Also, a copolymer having an acid value is preferably used for the purpose of imparting water dispersibility or water solubility.

[0021] The (meth)acrylate used as a constituent component of the homopolymer or copolymer of (meth)acrylate is not particularly limited. Among them, an acrylate having an alkyl group with 1 to 20 carbon atoms is preferably used. Since a homopolymer having acrylate exhibits a lower glass transition temperature, it is preferably used, and it is preferably mainly composed of an acrylate having an alkyl group with 1 to 20 carbon atoms, and more preferably mainly composed of an acrylate having an alkyl group with 4 to 15 carbon atoms. Examples of such an acrylate having an alkyl group with 1 to <15> carbon atoms include methyl acrylate, ethyl acrylate, iso-propyl acrylate, allyl acrylate, n-butyl acrylate, iso-butyl acrylate, (meth)acrylate sec-butyl, tert-butyl acrylate, n-amyl acrylate, iso-amyl acrylate, n-hexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, (meth)acrylate n-lauryl, (meth)acrylate n-tridecyl, etc.

[0022] Furthermore, examples of vinyl monomers that can copolymerize with other (meth)acrylates include aromatic (meth)acrylates such as benzyl (meth)acrylate; hydroxyl group-containing monomers such as 2-hydrodoxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate; alkyl polyalkylene glycol mono(meth)acrylates such as methoxypolyethylene glycol mono(meth)acrylate and methoxypolypropylene glycol mono(meth)acrylate; and perfluoroalkylethyl (meth)acrylate, etc. Fluorinated (meth)acrylates; styrene, styrene derivatives (p-dimethylsilylstyrene, (p-vinylphenyl)methyl sulfide, p-hexynylstyrene, p-methoxystyrene, p-tert-butyldimethylsiloxystyrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, α-methylstyrene, etc.), vinylnaphthalene, vinylanthracene, 1,1-diphenylethylene, and other aromatic vinyl compounds; glycidyl (meth)acrylate, epoxy (meth)acrylate, ethylene glycol di(meth)acrylate Acrylate, diethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylene glycol tetra(meth)acrylate, 2-hydroxy-1,3-diacroxypropane, 2,2-bis[4-(acryloxymethoxy)phenyl]propane, 2,2-bis[4-(acryloxyethoxy)phenyl]propane, dicyclopentenyl(meth)acrylate, tricyclodecanyl(meth)acrylate, tris(acryloxyethyl)isocyanurate, urethane(meth)acrylate Examples include (meth)acrylate compounds such as: alkylamino group-containing (meth)acrylates such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, and dimethylaminopropyl (meth)acrylate; vinylpyridine compounds such as 2-vinylpyridine, 4-vinylpyridine, and naphthylvinylpyridine; and conjugated dienes such as 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, and 1,3-cyclohexadiene.These monomers can be used individually or in combination of two or more.

[0023] Furthermore, with the aim of introducing one or more acidic groups selected from the group consisting of carboxyl groups and carboxylate groups obtained by neutralizing a carboxyl group with a basic compound, copolymers having an acid value can be obtained by copolymerizing (meth)acrylic monomers having carboxyl groups, such as (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, β-(meth)acryloyloxyethyl hydrogen succinate, and β-(meth)acryloyloxyethyl hydrogen phthalate.

[0024] When introducing an acidic group, it is preferable to appropriately adjust the amount of monomer so that the acid value falls within the desired range.

[0025] The meth(acrylic) resin used in the aqueous heat sealant of the present invention is preferably a copolymer of (meth)acrylic acid and the (meth)acrylate. For example, it is preferably a copolymer of (meth)acrylic acid and an acrylate having an alkyl group with 4 to 15 carbon atoms, such as n-butyl (meth)acrylate, n-dodecyl (meth)acrylate, or n-tridecyl (meth)acrylate, and more preferably a copolymer of (meth)acrylic acid and n-butyl (meth)acrylate.

[0026] (Meth)acrylate homopolymers or copolymers can be produced, for example, by polymerizing one or more monomers in the presence of a polymerization initiator in the temperature range of 50°C to 180°C, with a temperature range of 80°C to 150°C being more preferable. Examples of polymerization methods include bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Examples of polymerization modes include random copolymers, block copolymers, and graft copolymers. The copolymer may also be of the core-shell type.

[0027] (Other resins) The thermoplastic resin layer of the present invention may contain resins other than ethylene-vinyl acetate copolymer resin and (meth)acrylic resin.

[0028] Other resins include, for example, polyolefin resins, vinyl chloride resins, styrene resins, styrene / butadiene copolymers, styrene / unsaturated carboxylic acid copolymers, acrylonitrile / styrene copolymers, acrylonitrile / butadiene copolymers, ABS resins, AAS resins, AES resins, vinylidene chloride resins, polyurethane resins, poly-4-methylpentene-1 resins, polybutene-1 resins, vinylidene fluoride resins, vinyl fluoride resins, fluorine resins, polycarbonate resins, polyamide resins, acetal resins, polyphenylene oxide resins, polyester resins (polyethylene terephthalate, polybutylene terephthalate, etc.), polyphenylene sulfide resins, polyimide resins, polysulfone resins, polyethersulfone resins, polyarylate resins, olefin / unsaturated carboxylic acid copolymers, and modified versions thereof. These may be used individually or in combination of two or more.

[0029] In the heat-seal composition of the present invention, it is preferable that the solid content concentration of the ethylene-vinyl acetate copolymer resin in the entire thermoplastic resin component is 30% by mass or more. Furthermore, in order to obtain the effects of the present invention, the solid content concentration of the ethylene-vinyl acetate copolymer resin and the (meth)acrylic resin in the entire thermoplastic resin component is preferably adjusted to 60% by mass or more, more preferably to 70% by mass or more, even more preferably to 80% by mass or more, and may be 100% by mass.

[0030] Furthermore, the ratio of solid content concentrations between the ethylene-vinyl acetate copolymer resin and the (meth)acrylic resin is preferably (ethylene-vinyl acetate copolymer resin):((meth)acrylic resin) = 30:70 to 90:10, more preferably 40:60 to 80:20, and even more preferably 50:50 to 70:30. In aqueous heat seal compositions, it is preferable to adjust the solid content concentration of the resin component to 20 to 70% by mass.

[0031] The glass transition temperature of the thermoplastic resin of the present invention is 30°C or lower. By setting the glass transition temperature to 30°C or lower, excellent heat seal strength can be achieved even in heat sealing processes at low temperatures of 80°C to 140°C. Furthermore, excellent heat seal strength can be achieved immediately after heat sealing at low temperatures, preventing problems such as the bonded substrates peeling off immediately after heat sealing.

[0032] The glass transition temperature of the thermoplastic resin is preferably 15°C or lower, more preferably 0°C or lower, and even more preferably -10°C or lower. On the other hand, from the viewpoint of blocking resistance, the lower limit of the glass transition temperature is preferably -50°C or higher. The glass transition temperature of the thermoplastic resin of the present invention refers to the value measured as follows. Using a differential scanning calorimetry system (DSC-7000, manufactured by SII Nanotechnology Co., Ltd., hereinafter referred to as DSC), 5 mg of the sample is heated from room temperature to 200°C at a rate of 10°C / min under a nitrogen flow of 30 mL / min, and then cooled to -80°C at a rate of 10°C / min. The sample is heated again to 200°C at a rate of 10°C / min, and the DSC curve is measured. The glass transition point is defined as the intersection of a straight line extending from the low-temperature baseline of the measurement results observed in the second heating step to the high-temperature side, and a tangent line drawn at the point where the slope of the curve of the step-like portion of the glass transition is maximum. The temperature at this point is defined as the glass transition temperature. In addition, the temperature is raised to 200°C in the first heating step, but this is sufficient as long as the thermoplastic resin is sufficiently melted; if 200°C is insufficient, the temperature should be adjusted accordingly. Similarly, if the cooling temperature of -80°C is insufficient (for example, if the glass transition temperature is lower), the temperature should be adjusted accordingly.

[0033] (aqueous medium) As an aqueous medium, water, water-soluble organic solvents that dissolve in water, etc., can be used. As water, pure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, distilled water, or ultrapure water can be used. From the viewpoint of long-term storage, it is preferable to use water that has been sterilized by ultraviolet irradiation or hydrogen peroxide addition, as this can prevent the growth of mold or bacteria.

[0034] Examples of water-soluble organic solvents include glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, polyethylene glycol, and polypropylene glycol; diols such as butanediol, pentanediol, and hexanediol; glycol esters such as propylene glycol laurate; diethylene glycol ethers such as diethylene glycol monoethyl, diethylene glycol monobutyl, diethylene glycol monohexyl, and carbitol; glycol ethers such as cellosolve containing propylene glycol ether, dipropylene glycol ether, and triethylene glycol ether; alcohols such as methanol, ethanol, isopropyl alcohol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, butyl alcohol, and pentyl alcohol; and various other solvents known as aqueous organic solvents, such as sulfolanes, esters, ketones, lactones such as γ-butyrolactone, lactams such as N-(2-hydroxyethyl)pyrrolidone, glycerin, and its polyalkylene oxide adducts. These aqueous organic solvents can be used individually or in combination of two or more. While water is preferred, if water alone does not provide sufficient wettability to the substrate, it is preferable to use water and alcohol together. Ethanol and isopropanol are preferred alcohols. When water and a water-soluble organic solvent are used together, the ratio is preferably such that the proportion of water in the aqueous medium is 70% by mass or more, and more preferably 80% by mass or more.

[0035] The aqueous heat seal composition may contain additives other than the resin component, such as silica, alumina, defoaming agents, viscosity modifiers, leveling agents, tackifiers, preservatives, antibacterial agents, rust inhibitors, antioxidants, and silicone oils, to the extent that they do not impede the purpose of the present invention.

[0036] (Additives) The aqueous heat seal composition of the present invention may contain additives other than the thermoplastic resin, such as antiblocking agents, defoaming agents, viscosity modifiers, leveling agents, tackifiers, preservatives, antibacterial agents, rust inhibitors, antioxidants, silicone oils, lubricants, antistatic agents, ultraviolet absorbers, and crosslinking agents, to the extent that they do not impede the purpose of the present invention.

[0037] Examples of lubricants include fatty acid amide waxes such as oleic acid amide, erucic acid amide, stearic acid amide, behenic acid amide, ethylenebisoleic acid amide, and ethylenebiserucic acid amide; animal and vegetable oil-based waxes such as rice wax, carnauba wax, candelilla wax, lanolin wax, beeswax, whale oil, and beef tallow; petroleum-based waxes such as petrolatum, paraffin wax, microcrystalline wax, polyethylene wax, polypropylene wax, PTFE wax, and linear higher alcohols; and silicon such as dimethylpolysiloxane and modified silicon in which at least one methyl group in the side chain of dimethylpolysiloxane is replaced with an organic group other than a methyl group (such as a carbinol group, polyether group, or alkyl group with 2 or more carbon atoms). The amount of lubricant added is preferably 0.1 to 2% by weight relative to the total heat sealant, as this provides lubricity while maintaining a good balance with other properties such as improved blocking resistance. Furthermore, an amount of 2 to 5% by weight relative to the modified polyolefin is preferable because it facilitates the handling of the heat sealable film coated with the heat sealant.

[0038] (Antifoaming agent) In aqueous heat sealants, it is preferable to include an antifoaming agent to prevent foaming when coating with various coaters. Preferred antifoaming agents include nonionic antifoaming agents, silicone-based antifoaming agents, and fluorine-based antifoaming agents. These antifoaming agents can be of any type, including emulsified dispersion and solubilized forms. Among these, nonionic antifoaming agents are preferred. The amount of antifoaming agent added is preferably in the range of 0.005% to 3% by mass, and more preferably in the range of 0.1% to 1% by mass, relative to the total amount of the aqueous heat sealant.

[0039] (Anti-blocking properties) While the aqueous heat sealant for cables of the present invention exhibits good heat sealability at low temperatures, it tends to have poor blocking properties. Therefore, it is preferable to include a blocking inhibitor.

[0040] It is preferable to use inorganic fine particles, organic fine particles, etc., as the blocking inhibitor.

[0041] Examples of organic fine particles include polystyrene-based and polymethacrylate-based organic polymer fine particles. Among these, polymethacrylate-based organic polymer fine particles are preferred because they can enhance blocking properties while maintaining heat-sealability, and cross-linked polymethyl methacrylate is preferred.

[0042] As the inorganic fine particles, silica is preferred, and synthetic amorphous silica is preferred in particular. The shape of the silica is not particularly limited, and may be, for example, spherical silica consisting of a single particle, or amorphous silica forming secondary and tertiary particles from a plurality of primary particles. Spherical silica is preferred in particular.

[0043] Examples of spherical silica include AdmaFine SO-C4, SO-C5, and SO-E4 from Admatex Corporation, UFP-30 and SFP-30M from Denka Corporation, the Seahostar KE series from Nippon Shokubai Corporation, and the SYLOSPHERE series from Fuji Silicia Corporation. Examples of amorphous silica include AEROSIL200 and R972 from EVONIK Corporation, HDK H15 and H18 from Asahi Kasei Wacker Silicone Corporation, and MT-10 and DM20S from Tokuyama Corporation.

[0044] From the viewpoint of achieving both blocking properties and heat sealability, the average particle size of the blocking inhibitor is preferably 0.1 μm to 20 μm, more preferably 0.5 μm to 15 μm, and even more preferably 1.0 μm to 10 μm.

[0045] The amount of the blocking inhibitor added is preferably in the range of 0.1% by mass or more and 2% by mass or less relative to the total amount of the aqueous heat sealant.

[0046] (Crosslinking agent) Water-based heat sealants preferably contain a crosslinking agent. The inclusion of a crosslinking agent can further enhance heat seal strength, heat resistance, and other properties.

[0047] The crosslinking agent is not particularly limited, but known materials such as polyisocyanate compounds, silane coupling agents, epoxy compounds, carbodiimides, aziridines, oxazoline compounds, and metal chelating agents can be used.

[0048] The polyisocyanate compound is not particularly limited, as long as it is an isocyanate compound having multiple isocyanate groups that can react with the resin in the heat sealant. Examples include polyisocyanates such as tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), lysine diisocyanate, trimethylhexamethylene diisocyanate, 1,3-(isocyanatemethyl)cyclohexane, 1,5-naphthalene diisocyanate, and triphenylmethane triisocyanate; and derivatives (modified products) of polyisocyanates such as adducts of these polyisocyanates, burettes of these polyisocyanates, or isocyanurates of these polyisocyanates.

[0049] Polyisocyanate compounds act as curing agents and can be selected and used as appropriate, and may be aromatic or aliphatic. Preferred polyisocyanate compounds include, for example, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), xylylene diisocyanate (XDI), tolylene diisocyanate (TDI), and diphenylmethane diisocyanate (MDI). Among these, xylylene diisocyanate (XDI) and tolylene diisocyanate (TDI) are preferred.

[0050] The silane coupling agent is a silane compound having one or more hydrolyzable groups and one or more organic polymerizable functional groups in one molecule. Examples of the hydrolyzable groups include alkoxy groups such as methoxy groups and ethoxy groups; acyloxy groups such as acetoxy groups; and halogen groups such as chloro groups. Examples of the organic polymerizable functional groups include vinyl groups, epoxy groups, methacryloxy groups, acryloxy groups, amino groups, mercapto groups, isocyanate groups, ureido groups, and isocyanurate groups. The silane coupling agent may contain one or more of these hydrolyzable groups and one or more of these organic polymerizable functional groups in one or more molecules.

[0051] Examples of the silane coupling agents include vinyl group-containing silane coupling agents (silane compounds having vinyl group and hydrolyzable group), epoxy group-containing silane coupling agents (silane compounds having epoxy group and hydrolyzable group), (meth)acryloxy group-containing silane coupling agents (silane compounds having (meth)acryloxy group and hydrolyzable group), amino group-containing silane coupling agents (silane compounds having amino group and hydrolyzable group), mercapto group-containing silane coupling agents (silane compounds having mercapto group and hydrolyzable group), isocyanate group-containing silane coupling agents (silane compounds having isocyanate group and hydrolyzable group), ureido group-containing silane coupling agents (silane compounds having ureido group and hydrolyzable group), and isocyanurate group-containing silane coupling agents (silane compounds having isocyanurate group and hydrolyzable group).

[0052] Examples of silane coupling agents having a vinyl group include vinyltrimethoxysilane, vinyltriethoxysilane, and p-styryltrimethoxysilane.

[0053] Examples of silane coupling agents having the epoxy group include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane.

[0054] Examples of silane coupling agents having a (meth)acryloxy group include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane.

[0055] Examples of silane coupling agents having an amino group include compounds having one hydrocarbon group with one amino group in the molecule and one or more hydrolyzable groups in the molecule, such as 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, and N-phenyl-3-aminopropyltrimethoxysilane; and compounds having one hydrocarbon group with two amino groups in the molecule and one or more hydrolyzable groups in the molecule, such as N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, and N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane.

[0056] Examples of silane coupling agents having a mercapto group include 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane.

[0057] Examples of silane coupling agents having an isocyanate group include 3-isocyanatetopropyltriethoxysilane.

[0058] Examples of silane coupling agents having a ureido group include 3-ureidopropyltrimethoxysilane and 3-ureidopropyltriethoxysilane.

[0059] Examples of silane coupling agents having an isocyanurate group include tris-(trimethoxysilylpropyl)isocyanurate.

[0060] These crosslinking agents are preferably present in an amount of 0.1 to 30% by mass relative to the solid content of the aqueous heat sealant of the present invention, and more preferably in an amount of 0.5 to 15% by mass.

[0061] The acid value of the aqueous heat seal composition of the present invention is preferably 3 mg KOH / g or more and 30 mg KOH / g or less. If it is 3 mg KOH or more, the solubility in water can be improved. On the other hand, if it is 30 mg KOH / g or less, the dispersion state in water can be stabilized. Preferably, it is in the range of 3 mg KOH or more and 15 mg KOH / g or less, and more preferably in the range of 4 mg KOH / g or more and 12 mg KOH / g or less.

[0062] Furthermore, it is preferable that the minimum film-forming temperature of the aqueous heat seal composition is in the range of 50°C to 100°C. In the present invention, the minimum film-forming temperature is the lowest temperature required for a continuous film to be formed when the moisture in the synthetic rubber latex evaporates and dries, and is obtained by the temperature gradient plate method. Among these, the range of 60°C to 95°C is preferred, and the range of 70°C to 90°C is more preferred.

[0063] <Laminate> The laminate of the present invention comprises at least a substrate and a heat-seal layer provided on the substrate, wherein the heat-seal layer is formed from the aforementioned aqueous heat-seal composition.

[0064] The heat seal layer is formed by applying an aqueous heat seal composition to the substrate and drying it, and can be used as a heat seal layer. In addition, the coated areas other than the sealing (adhesion) areas also function as a coating agent that imparts water resistance and oil resistance to the substrate. The thermoplastic resin layer formed by the aqueous composition can be easily softened by heating with a burner or hot air, allowing the substrates to adhere to each other or to other materials, and then the bonded area solidifies upon cooling, creating a strong seal between the substrates or between the substrates and other materials.

[0065] Known methods can be used for coating the aqueous heat seal composition of the present invention. For example, roll coaters, gravure coaters, flexo coaters, air doctor coaters, blade coaters, air knife coaters, squeeze coaters, impregnation coaters, transfer roll coaters, kiss coaters, curtain coaters, cast coaters, spray coaters, die coaters, offset printing presses, screen printing presses, etc. A drying step in an oven or the like may also be provided after coating.

[0066] The thickness of the solid content of the aqueous heat seal composition after coating, i.e., the thickness of the heat seal layer, is adjusted as appropriate depending on the desired seal strength and substrate. For example, when using paper as the substrate, it is 3 to 12 g / m². 2 It is preferable that the range is 5-10 g / m². 2 It is more preferable that the range is within this range. Also, when using film, vapor-deposited film, metal foil, etc. as the base material, 1 g / m 2 ~5g / m 2 It is preferable that this be the case.

[0067] (base material) Examples of base materials include paper, nonwoven fabric, plastic film, and metal foil.

[0068] The paper used in this invention is manufactured using natural fibers for papermaking, such as wood pulp, in a known papermaking machine, but the papermaking conditions are not particularly specified. Examples of natural fibers for papermaking include wood pulp such as softwood pulp and hardwood pulp, non-wood pulp such as Manila hemp pulp, sisal hemp pulp, and flax pulp, and pulps obtained by chemically modifying these pulps. As for the type of pulp, chemical pulps produced by sulfate pulping, acidic, neutral, and alkaline sulfite pulping, soda salt pulping, etc., as well as gland pulp, chemigland pulp, thermomechanical pulp, etc. can be used.

[0069] More specifically, examples include, but are not limited to, various types of uncoated papers such as printing paper, gravure paper, kraft paper, Bristol board, copy paper, newsprint, and newspaper; lightly coated papers; coated papers such as art paper, single-sided art paper, coated paper, single-sided coated paper, and lightweight coated paper; fine paper; double-sided kraft paper for heavy, general, and special use; unbleached wrapping paper such as ribbed kraft paper and single-sided gloss kraft paper; pure white roll paper; bleached kraft paper such as double-sided bleached kraft paper and single-sided gloss bleached kraft paper; other bleached wrapping papers; resin-impregnated papers such as paraffin paper; cardboard and paperboard; metal-deposited papers on which metals such as aluminum are vapor-deposited; and laminated papers on which these papers are bonded to metal foils such as aluminum foil.

[0070] The aforementioned paper substrate can be selected sequentially according to the purpose, including the type of paper and thickness. For example, for burger wrap, it corresponds to a basis weight of 20 grams / m². 2 For paper cups, this corresponds to a basis weight of 200-300 grams / m². 2 For paper plates, paper spoons, paper stirrers, etc., the basis weight is 50-500 grams / m². 2 Food-grade paper such as cup paper is preferred.

[0071] Various types of plastic films can be used, specifically including polyethylene, polyolefins such as polypropylene, polyesters such as polyethylene terephthalate (hereinafter also referred to as PET), polycarbonate, and polylactic acid, polystyrene, polystyrene-based resins such as AS resin and ABS resin, nylon, polyamide, polyvinyl chloride, polyvinylidene chloride, cellophane, paper, aluminum, or films or sheets made from composite materials thereof. Vapor-deposited films, in which metals or metal oxides are deposited onto the above-mentioned plastic films, can also be used.

[0072] Examples of metal foils include aluminum foil.

[0073] These substrates may have a printed layer. The printed layer is formed using various printing inks such as gravure inks, flexographic inks, offset inks, stencil inks, and inkjet inks, using common printing methods that have been used for printing on polymer films. The printed layer may be provided on the heat-sealing layer side of the substrate, or on other sides.

[0074] Furthermore, other coating layers may be present between the substrate and the heat-seal layer. For example, if the substrate is paper, a sealing layer may be provided. Additionally, an anchor coat layer may be provided to improve the adhesion between the substrate and the heat-seal layer. Known configurations can be applied to the sealing layer and the anchor coat layer.

[0075] (Heat-sealable material) In this specification, "material to be heat-sealed" refers to a substrate that comes into contact with the heat-seal layer when a laminate having a heat-seal layer is heat-sealed via the heat-seal layer.

[0076] The heat-seal layer formed by the aqueous heat-seal composition of the present invention exhibits excellent heat-sealing properties regardless of the material of the material to be heat-sealed. Therefore, the material to be heat-sealed can be any variety of materials, including paper, nonwoven fabric, plastic, and metal.

[0077] Paper, nonwoven fabrics, plastics, metals, etc., can be the same as the substrates having the heat-seal layer described above. Plastics may be plastic films or molded bodies such as plastic containers. Metals may be metal foils, metal vapor-deposited materials, or molded metal bodies.

[0078] As a specific example of a combination of a laminate having a heat-seal layer and a material to be heat-sealed, if it is written as "(laminated material having a heat-seal layer) / / (material to be heat-sealed)", the following configuration can be exemplified.

[0079] (Paper / Heat-sealed layer) / / (Paper) (Paper / Heat-seal layer) / / (Heat-seal layer / Paper) (Paper / Heat-sealed layer) / / (Plastic) (Paper / Heat-sealed layer) / / (Non-woven fabric) (Plastic film / heat-sealed layer) / / (Plastic) (Plastic film / heat seal layer) / / (Heat seal layer / plastic) (Plastic film / heat-sealed layer) / / (Metal) (Plastic film / heat-sealed layer) / / (Non-woven fabric) (Metal foil / heat seal layer) / / (Metal) (Metal foil / heat seal layer) / / (Plastic) (Nonwoven fabric / heat-sealed layer) / / (Nonwoven fabric) In the aforementioned configuration of "(laminated body having a heat-seal layer) / / (material to be heat-sealed)", the laminate having a heat-seal layer or the material to be heat-sealed may have other layers such as a printed layer or a barrier coating layer. Furthermore, it may be a configuration in which it is further bonded to another substrate via an adhesive layer or the like.

[0080] When paper is used as the material to be heat-sealed, it is preferable to have a configuration in which the material to be heat-sealed also has a heat-seal layer, i.e., a (paper / heat-seal layer) / / (heat-seal layer / paper) configuration, in order to improve the heat-seal strength. This is thought to be because the aqueous heat-seal composition easily penetrates paper, and when the heat-seal surfaces of the laminate having the heat-seal layer and the material to be heat-sealed are bonded together, a sufficient amount of heat-seal coating is achieved, and the paper itself becomes stronger due to the heat-seal composition that has penetrated the paper.

[0081] The laminate of the present invention, when heat-sealed under the conditions of 140°C, 0.2 MPa, and 1 second, has a hot tack peel distance of 200 mm or less, more preferably 150 mm or less, and more preferably 120 mm or less, when heat-sealed with heat-sealed layers of a laminate with a paper base material bonded together in a configuration of (paper / heat-seal layer) / / (heat-seal layer / paper).

[0082] The hot tack peel distance is the distance at which the heat seal layers peel off when a force is applied to peel the substrate immediately after heat sealing at 140°C, 0.2 MPa, and 1 second (within 1 second). This value represents the heat sealability immediately after heat sealing. When the hot tack peel distance is 200 mm or less, preferably 150 mm or less, after heat sealing at 140°C, 0.2 MPa, and 1 second, sufficient heat seal strength can be achieved immediately after heat sealing, thus shortening the packaging time.

[0083] In heat sealing processes at low temperatures below 140°C, a shorter hot tack peeling distance results in energy savings at low temperatures and shorter packaging times.

[0084] The laminate of the present invention preferably has a hot tack peel distance of 80 mm or less, more preferably 50 mm or less, and even more preferably 40 mm or less, when heat-sealed under the conditions of 120°C, 0.2 MPa, and 1 second, when heat-sealed with heat-sealed layers of laminates with a paper base material, i.e., in a configuration of (paper / heat-seal layer) / / (heat-seal layer / paper).

[0085] Furthermore, in the laminate of the present invention, when heat-sealed under the conditions of 100°C, 0.2 MPa, and 1 second, the hot tack peel distance is preferably 80 mm or less, more preferably 50 mm or less, and even more preferably 40 mm or less, when heat-sealed with heat-sealed layers of laminates with paper as the base material, i.e., in a configuration of (paper / heat-seal layer) / / (heat-seal layer / paper).

[0086] Furthermore, in the laminate of the present invention, when heat-sealed under the conditions of 80°C, 0.2 MPa, and 1 second, the hot tack peel distance is preferably 80 mm or less, more preferably 50 mm or less, and even more preferably 40 mm or less, when heat-sealed with heat-sealed layers of laminates with paper as the base material, i.e., in a configuration of (paper / heat-seal layer) / / (heat-seal layer / paper).

[0087] Furthermore, when the heat-seal layers of the laminate of the present invention, which uses paper as the base material, are bonded together in a configuration of (paper / heat-seal layer) / / (heat-seal layer / paper), the hot tack peel distance when heat-sealed under the conditions of 80°C to 140°C, 0.2 MPa, and 1 second is preferably 200 mm or less, more preferably 150 mm or less, and more preferably 120 mm or less.

[0088] The laminate of the present invention has excellent heat seal strength at low heat sealing temperatures of 140°C or below. Specifically, when heat seal layers of laminates with paper as the base material are bonded together in a configuration of (paper / heat seal layer) / / (heat seal layer / paper), the heat seal peel strength when heat sealed at a temperature range of 80°C to 140°C under conditions of 0.2 MPa and 1 second is preferably 2 N / 15 mm or more, more preferably 3 N / 15 mm or more, and even more preferably 4 N / 15 mm or more.

[0089] More specifically, when heat-seal layers of a laminate with a paper base material are bonded together in a configuration of (paper / heat-seal layer) / / (heat-seal layer / paper), the heat-seal peel strength when heat-sealed under the conditions of 140°C, 0.2 MPa, and 1 second is preferably 2N / 15mm or more, more preferably 3N / 15mm or more, and even more preferably 5N / 15mm or more.

[0090] Furthermore, the laminate of the present invention preferably has a heat seal peel strength of 2N / 15mm or more, more preferably 3N / 15mm or more, and even more preferably 5N / 15mm or more, when heat-sealed under the conditions of 120°C, 0.2MPa, and 1 second, when heat-sealed together with heat-seal layers of laminates using paper as the base material, i.e., in a configuration of (paper / heat seal layer) / / (heat seal layer / paper).

[0091] Furthermore, the laminate of the present invention preferably has a heat seal peel strength of 2N / 15mm or more, more preferably 3N / 15mm or more, and even more preferably 4N / 15mm or more, when heat-sealed under the conditions of 100°C, 0.2MPa, and 1 second, when heat-sealed together with heat-seal layers of laminates using paper as the base material, i.e., in a configuration of (paper / heat seal layer) / / (heat seal layer / paper).

[0092] Furthermore, the laminate of the present invention preferably has a heat seal peel strength of 2N / 15mm or more, more preferably 3N / 15mm or more, and even more preferably 4N / 15mm or more, when heat-sealed under the conditions of 80°C, 0.2MPa, and 1 second, when heat-sealed together with heat-seal layers of laminates using paper as the base material, i.e., in a configuration of (paper / heat seal layer) / / (heat seal layer / paper).

[0093] Furthermore, the laminate of the present invention has excellent heat seal strength at low heat seal processing temperatures of 140°C or below, regardless of the type of material to be heat sealed. Specifically, in a laminate with a paper base material, whether the material to be heat sealed is paper or a plastic base material such as PET film or OPP film, it is preferable that the heat seal peel strength when heat sealed at a temperature of 100°C to 140°C under conditions of 0.2 MPa and 1 second is 2 N / 15 mm or more, and more preferably 3 N / 15 mm or more. However, in the case of the material to be heat sealed, the heat seal peel strength is when the material to be heat sealed has the same configuration as the laminate with a paper base material, and the heat seal layers are laminated together.

[0094] <Packaging materials or containers> The laminate of the present invention can be used as a packaging material for the purpose of protecting food, household goods, pharmaceuticals, and various other industrial products. When used as a packaging material, the layer structure of the laminate may change depending on the contents, usage environment, and usage method.

[0095] The packaging material of the present invention can be obtained, for example, by using the laminate of the present invention, overlapping the thermoplastic resin layers of the laminate facing each other, and then heat-sealing the peripheral edges. Methods for making the bag include folding or overlapping the laminate of the present invention so that the inner layer surfaces (sealant film surfaces) face each other, and then heat-sealing the peripheral edges in forms such as side seal type, two-side seal type, three-side seal type, four-side seal type, envelope seal type, gusset seal type, pleated seal type, flat-bottom seal type, square-bottom seal type, gusset type, and other heat-seal types. The packaging material of the present invention can take various forms depending on the contents, usage environment, and usage. Self-standing packaging materials (standing pouches) are also possible. As for heat sealing methods, conventionally known means such as a burner or other heat source, hot air, electric heating, infrared rays, and electron beams can be used. Specifically, heating with a burner or hot air, or depending on the molding shape, heat welding sealing, ultrasonic sealing, or high-frequency sealing are preferred.

[0096] In the present invention, a product using the present invention is manufactured by filling the contents into the packaging material through its opening, and then heat-sealing the opening.

[0097] The laminates and containers of the present invention have excellent recyclability. The recycling method for the printed materials, laminates, and packaging materials of the present invention is not particularly limited and can be carried out using known methods and equipment. In particular, it is suitable for recycling methods that use alkaline treatment for the separate collection of laminates. [Examples]

[0098] The present invention will be further described in detail by reference to examples. Hereinafter, "parts" and "%" will be based on mass.

[0099] (Preparation of aqueous composition) Each aqueous composition was prepared according to the formulations shown in Table 1 below.

[0100] [Table 1]

[0101] In the table, for EVA1, a commercially available ethylene-vinyl acetate copolymer resin (vinyl acetate ratio 50%) was used. For EVA2, a commercially available ethylene-vinyl acetate copolymer resin (vinyl acetate ratio 30%) was used. For EVA3, a commercially available ethylene-vinyl acetate copolymer resin (vinyl acetate ratio 10%) was used. For the polyester resin, a commercially available aqueous polyester was used. For the polyolefin resin, a commercially available modified polyolefin was used. For the wax, solid paraffin was used. For methacrylic resin 1, a commercially available methacrylic acid copolymer (polymer of butyl methacrylate and methacrylic acid) was used. For methacrylic resin 2, a commercially available methacrylic acid copolymer (polymer of butyl methacrylate, dodecyl methacrylate, methacrylic acid, and tridecyl methacrylate) was used. For methacrylic resin 3, a commercially available methacrylic acid copolymer (polymer of butyl methacrylate, 2-(dimethylamino)ethyl methacrylate, dodecyl methacrylate, and methacrylic acid) was used. For the wax, commercially available paraffin wax was used. In addition, the components other than water in the table represent the solid content ratio.

[0102] (Example 1) The aqueous composition of Adjustment Example 1 was applied to the rough surface of one-sided coated kraft paper with a basis weight of 70 g / m 2 using a wire bar so that the dry film thickness of the solid content became 6 g / m 2 and dried at 150 °C for 20 seconds using a dryer to produce the laminate of Example 1.

[0103] (Example 2) A laminate of Example 2 was produced in the same manner as in Example 1, except that the aqueous composition of Adjustment Example 2 was used.

[0104] (Comparative Examples 1 to 3) A laminate of Comparative Example 1 was prepared in the same manner as in Example 1, except that the aqueous compositions of Comparative Adjustment Examples 1 to 3 were used.

[0105] The laminates of Examples 1 and 2 and Comparative Examples 1 to 3 were evaluated as follows. The results are shown in Table 2.

[0106] (Heat seal (HS) strength) The heat-sealed coated surface of the fabricated laminate and the material to be heat-sealed were placed on top of each other, and test pieces were created by heat-sealing at temperatures in 20°C increments within the temperature range of 80°C to 140°C using a heat seal tester TP-701 (manufactured by Tester Industry Co., Ltd.) (all at 0.2 MPa for 1 second). For each test piece, the adhesive strength was recorded using a small desktop tester EZ test manufactured by Shimadzu Corporation, with a peeling speed of 200 mm / min, T-shaped peeling, and a test piece width of 15 mm.

[0107] The heat-sealable material used was paper, PET film, OPP film, or PE film. When the heat-sealable material was paper, the heat-sealable coated surfaces of identical laminates were stacked together. When the heat-sealable material was PET film or OPP film, an uncoated heat-sealable film was used, and the heat-sealable coated surface was stacked against the corona-treated surface of the film. When the heat-sealable material was PE film, the heat-sealable coated surface was stacked against the uncorona-treated surface of the film.

[0108] (Blocking resistance) The fabricated laminates are stacked so that the coated surfaces are in contact with each other, and a coating of 5 kgf / cm² is applied. 2 The samples were subjected to a load and left in a 40°C environment for 24 hours. After removal, the adhesion between the coated surfaces was visually evaluated on a five-point scale. The results are shown in the "Surface × Surface" column of the table.

[0109] Furthermore, the fabricated laminates are stacked so that the coated surface and the uncoated surface (back surface of the substrate) are in contact, and a pressure of 5 kgf / cm² is applied. 2The samples were subjected to a load and left in a 40°C environment for 24 hours. After removal, the adhesion between the coated and uncoated surfaces was visually evaluated on a five-point scale. The results are shown in the "Surface × Back" column of the table.

[0110] Furthermore, the fabricated laminate is stacked so that the coated surface and the PET film are in contact, and a pressure of 5 kgf / cm² is applied. 2 The samples were subjected to a load and left in a 40°C environment for 24 hours. After removal, the adhesion between the coated and uncoated surfaces was visually evaluated on a five-point scale. The results are shown in the table under "Surface × PET".

[0111] (Evaluation Criteria) 5: No blocking is observed at all. 4: Slight blocking is observed, but it can be peeled off without any release noise. 3: It is blocking, and a release sound is heard when peeling. 2: The coated surface and the back surface of the substrate are bonded together, and delamination is not possible at the interface between them. 1: The coated surface is strongly adhered, and substrate damage occurs when peeling.

[0112] (Hot tack peeling distance) Two laminates (60 cm long, 4 cm wide) with a heat-sealing layer coated onto paper were placed side by side with the heat-sealing coated surface facing the material to be heat-sealed. The center of the laminates in the longitudinal direction was clipped together, and the ends were passed between pulleys. With the two laminates separated, 30 g weights were hung from the ends of both laminates.

[0113] Subsequently, using a heat seal tester TP-701 (manufactured by Tester Sangyo Co., Ltd.), heat sealing was performed on a 30cm long, 1cm wide sealing bar at temperatures ranging from 80°C to 140°C in 20°C increments (all at 0.2 MPa for 1 second). During heat sealing, the clip was removed, and at the moment the sealing bar separated (i.e., immediately after heat sealing (within 1 second)), a load was applied using a pre-attached weight in the direction that would cause the seal to peel off. The distance the seal peeled off at this time was measured.

[0114] [Table 2]

[0115] As shown in Table 2, the heat seal composition of the present invention was found to exhibit excellent heat seal strength regardless of the type of material to be heat sealed, even in heat sealing processes at low temperatures of 140°C or below. It also showed excellent blocking resistance. Furthermore, the hot tack peeling distance could be reduced in heat sealing processes at low temperatures of 140°C or below. Therefore, using the heat seal composition of the present invention can lead to energy savings and shorter packaging times.

Claims

1. It contains an aqueous medium and a thermoplastic resin. The thermoplastic resin contains an ethylene-vinyl acetate copolymer resin and a (meth)acrylic resin. The glass transition temperature of the thermoplastic resin is 30°C or lower. Aqueous heat seal composition.

2. The acid value of the aqueous heat seal composition is 3 mg / KOH or more and 15 mg / KOH or less. The aqueous heat seal composition according to claim 1.

3. The minimum film-forming temperature of the aqueous heat seal composition is in the range of 50°C to 100°C. The aqueous heat seal composition according to claim 1 or 2.

4. Contains lubricant The aqueous heat seal composition according to claim 1 or 2.

5. The (meth)acrylic resin is a copolymer of (meth)acrylic acid and (meth)acrylate. The laminate according to claim 1 or 2.

6. It has a base material and a heat-seal layer provided on the base material, A laminate in which the heat seal layer is a layer formed from the aqueous heat seal composition described in claim 1 or 2.

7. The substrate is selected from plastic film, metal foil, nonwoven fabric, or paper. The laminate according to claim 6.

8. When heat-seal layers of a laminate with a paper substrate are heat-sealed at 140°C, 0.2 MPa, and 1 second, the hot tack peel distance is 150 mm or less. The laminate according to claim 6.

9. Furthermore, when heat-seal layers of a laminate with a paper substrate are heat-sealed together under the conditions of 140°C, 0.2 MPa, and 1 second, the heat-seal peel strength is 2 N / 15 mm or more. The laminate according to claim 8.

10. The laminate according to claim 5, wherein the heat-seal layer has heat-sealing properties with respect to any of the heat-sealable materials selected from paper, polyester film, and polyolefin film.

11. A packaging material using the laminate described in claim 6.

12. A packaging material heat-sealed via the heat-seal layer using the laminate described in claim 6.

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