Laminate and packaging material using the same

Abstract

To provide a laminate provided with a thermoplastic resin layer free from a lubricant, the laminate achieving excellent water and oil resistance without deterioration of heat sealability and also having excellent recyclability, and a packaging material using the laminate.SOLUTION: A laminate comprises a substrate and a thermoplastic resin layer provided on the substrate, wherein the thermoplastic resin layer contains an ethylene-vinyl acetate copolymer resin and a (meth)acrylic resin and is free from a lubricant, and the proportion of vinyl acetate in the ethylene-vinyl acetate copolymer resin is 45 mol% or less.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Heat sealing agents are used in packaging materials and containers for food, household goods, pharmaceuticals, and various other industrial applications. There are organic solvent-based and water-based heat sealing agents, but in recent years there has been a growing demand for water-based heat sealing agents for environmental conservation and safety and hygiene reasons.

[0003] Furthermore, as the problem of marine plastic waste, including microplastics, comes to the forefront, there is a demand for paper packaging materials and containers that do not use plastic film. However, paper packaging materials and containers have the problem of being inferior in oil resistance and water resistance compared to plastic. For this reason, it is known that heat sealing agents used in packaging materials and containers can improve not only the heat sealing function but also various other functions such as oil resistance and water resistance (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7014345 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, there has been a demand for packaging materials and containers with improved functions such as heat sealing function, oil resistance, and water resistance, and the functions required of heat sealing agents have become more diverse. Furthermore, there is a demand for packaging materials and containers coated with a heat sealing agent that do not impair recyclability or that have excellent recyclability.

[0006] Furthermore, many heat-sealing agents contain lubricants, but the use of lubricants can cause problems such as clouding of the coated surface due to the phenomenon of bleed-out, where the lubricant bleeds out onto the surface, or the back surface of the substrate and the heat-sealing layer coming into contact when the substrate is wound onto a roll during production, which can easily cause substrate contamination or component migration, affecting the appearance and physical properties. Furthermore, heat-sealing agents are widely used as packaging materials for food and medical products, so eliminating lubricants, which can bleed out, is expected to improve hygiene. Therefore, there is a need for improved functionality, such as strength stability over a wide range of sealing temperatures, blocking resistance, oil resistance, and water resistance, without the use of lubricants.

[0007] Therefore, the problem to be solved by the present invention is to provide a laminate and a packaging material having a thermoplastic resin layer that does not contain a lubricant, which have excellent water resistance and oil resistance and are also highly recyclable without impairing heat sealability, and a packaging material using the same. [Means for solving the problem]

[0008] That is, the present invention provides a laminate having a substrate and a thermoplastic resin layer provided on the substrate, wherein the thermoplastic resin layer contains an ethylene-vinyl acetate copolymer resin and a (meth)acrylic resin, does not contain a lubricant, and the proportion of vinyl acetate in the ethylene-vinyl acetate copolymer resin is 45% mol or less.

[0009] The present invention also provides a packaging material or container using a laminate having a substrate and a thermoplastic resin layer provided on the substrate, the thermoplastic resin layer containing an ethylene-vinyl acetate copolymer resin and a (meth)acrylic resin, not containing a lubricant, and in which the proportion of vinyl acetate in the ethylene-vinyl acetate copolymer resin is 45% mol or less. [Effects of the Invention]

[0010] The laminate and packaging material of the present invention can realize laminates and packaging materials that are excellent in water resistance, oil resistance, and recyclability without impairing heat sealability. Because the laminate and packaging material of the present invention have a thermoplastic resin layer that does not contain a lubricant, the back surface of the substrate and the heat seal layer are less likely to come into contact with each other, which can easily cause substrate contamination or component migration, thereby affecting appearance and physical properties. Therefore, it can be widely used as packaging materials and containers for various purposes. DETAILED DESCRIPTION OF THE INVENTION

[0011] <Laminate> The laminate of the present invention comprises at least a substrate and a thermoplastic resin layer provided on the substrate. In the present invention, the term "(meth)acrylic resin" refers to a homopolymer or copolymer of (meth)acrylate, "(meth)acrylate" refers collectively to acrylate and methacrylate, and "(meth)acrylic acid" refers collectively to acrylic acid and methacrylic acid.

[0012] (thermoplastic resin layer) The thermoplastic resin layer is formed by a layer containing an ethylene-vinyl acetate copolymer resin and a (meth)acrylic resin, but not containing a lubricant, and is formed by a coating layer of an aqueous composition containing an ethylene-vinyl acetate copolymer resin, a (meth)acrylic resin, and an aqueous medium.

[0013] ((Ethylene-vinyl acetate copolymer resin)) The ethylene-vinyl acetate copolymer resin is a copolymer of ethylene and vinyl acetate, and in some cases, the ester moiety may be partially or completely hydrolyzed. The ethylene-vinyl acetate copolymer resin may further contain other monomers copolymerized therein, but the content of structural units derived from other monomers is preferably 30% by mass or less, more preferably 10% by mass or less, even more preferably 3% by mass or less, and even more preferably 1% by mass or less of the entire copolymer.

[0014] In the present invention, the proportion of vinyl acetate in the ethylene-vinyl acetate copolymer is 45 mol% or less from the viewpoint of heat seal strength stability and blocking resistance in the low temperature range of about 80°C to 100°C. The proportion of ethylene in the copolymer is preferably 40 mol% or less, more preferably 35 mol% or less, and even more preferably 30 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.

[0015] 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, and from the viewpoint of low-temperature heat sealability, the weight-average molecular weight is preferably 1,000,000 or less.

[0016] Furthermore, the glass transition temperature of the ethylene-vinyl acetate copolymer is preferably 30° C. or lower, more preferably 20° C. or lower, and even more preferably 10° C. or lower, in order to improve the heat sealability at low temperatures. On the other hand, in terms of blocking resistance, the lower limit of the glass transition temperature is preferably −40° C. or higher, more preferably −30° C. or higher, and even more preferably −20° C. or higher.

[0017] ((Acrylic resin)) The acrylic resin may be a homopolymer or copolymer of (meth)acrylate without any particular limitation, and examples of the copolymer include copolymers obtained by copolymerizing (meth)acrylate with a vinyl monomer copolymerizable therewith. Furthermore, copolymers having an acid value are preferred for the purpose of imparting water dispersibility and water solubility.

[0018] The (meth)acrylate used as a constituent component of the (meth)acrylate homopolymer or copolymer is not particularly limited, but among them, an acrylate having an alkyl group of 1 to 20 carbon atoms is preferred, as homopolymers having an acrylate exhibit a lower glass transition temperature, an acrylate having an alkyl group of 1 to 20 carbon atoms as the main component is preferred, and an acrylate having an alkyl group of 4 to 15 carbon atoms as the main component is preferred. Examples of such acrylates having an alkyl group of 1 to 15 carbon atoms include methyl acrylate, ethyl acrylate, isopropyl acrylate, allyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl (meth)acrylate, tert-butyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, n-lauryl (meth)acrylate, and n-tridecyl (meth)acrylate.

[0019] Examples of other (meth)acrylates and vinyl monomers copolymerizable with (meth)acrylates include aromatic (meth)acrylates such as benzyl (meth)acrylate; hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate; alkyl polyalkylene glycol mono(meth)acrylates such as methoxy polyethylene glycol mono(meth)acrylate and methoxy polypropylene glycol mono(meth)acrylate; perfluoroalkylethyl (meth)acrylate, etc. Fluorine-based (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.), aromatic vinyl compounds such as vinylnaphthalene, vinylanthracene, and 1,1-diphenylethylene; 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-diacryloxypropane, 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 (meth)acrylate compounds such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, and dimethylaminopropyl (meth)acrylate; (meth)acrylates having an alkylamino group 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 alone or in combination of two or more.

[0020] Furthermore, for the purpose of introducing one or more acidic groups selected from the group consisting of carboxyl groups and carboxylate groups in which the carboxyl group has been neutralized with a basic compound, a copolymer having an acid value can be obtained by copolymerizing a (meth)acrylic monomer having a carboxyl group, such as (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, β-(meth)acryloyloxyethyl hydrogen succinate, or β-(meth)acryloyloxyethyl hydrogen phthalate. When an acidic group is introduced, it is preferable to appropriately adjust the amount of the monomer so that the acid value falls within a desired range.

[0021] A (meth)acrylate homopolymer or copolymer can be produced, for example, by polymerizing one or more monomers in the presence of a polymerization initiator at a temperature range of 50°C to 180°C, preferably at a temperature range of 80°C to 150°C. Examples of the polymerization method include bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Examples of the polymerization mode include random copolymerization, block copolymerization, and graft copolymerization. The copolymer may be a core-shell type.

[0022] (Other resins) The thermoplastic resin layer of the present invention may contain a resin other than the ethylene-vinyl acetate copolymer resin and the (meth)acrylic resin.

[0023] Examples of other resins include 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-containing 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 products thereof. These may be used alone or in combination of two or more. Among these, it is preferable to use chlorine-based resins such as chlorinated polyolefin and chlorinated propylene. (aqueous medium) The aqueous medium may be water, a water-soluble organic solvent that dissolves in water, or the like. As the water, pure water or ultrapure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, or distilled water may be used. From the viewpoint of long-term storage, it is preferable to use water that has been sterilized by ultraviolet irradiation or the addition of hydrogen peroxide, for example, in order to prevent the growth of mold or bacteria.

[0024] 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 propylene glycol ether, dipropylene glycol ether, and cellosolves containing triethylene glycol ether; alcohols such as methanol, ethanol, isopropyl alcohol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, butyl alcohol, and pentyl alcohol; lactones such as sulfolane, esters, ketones, and γ-butyrolactone; lactams such as N-(2-hydroxyethyl)pyrrolidone; and various other solvents known as aqueous organic solvents, such as glycerin and its polyalkylene oxide adducts. These aqueous organic solvents can be used alone or in combination. It is preferable to use water, but if the wettability of the substrate with water alone is insufficient, it is preferable to use water in combination with an alcohol, preferably ethanol or isopropanol.

[0025] In addition to the resin component, the aqueous composition may contain additives such as silica, alumina, an antifoaming agent, a viscosity modifier, a leveling agent, a tackifier, a preservative, an antibacterial agent, a rust inhibitor, an antioxidant, and silicone oil, as long as the object of the present invention is not impaired.

[0026] On the other hand, the aqueous composition does not contain a lubricant. In the present invention, a lubricant is an additive added from the viewpoint of suppressing blocking, such as wax, metal soap, fatty acid ester, etc. In the present invention, even if the aqueous composition does not contain a lubricant, the blocking resistance of the thermoplastic resin layer is not reduced, and the stability of the heat seal strength, water resistance, and oil resistance can be improved.

[0027] In the aqueous composition for forming the thermoplastic resin layer of the present invention, the solid content concentration of the resin component is preferably adjusted to 20 to 70% by mass.

[0028] Furthermore, in order to obtain the effects of the present invention, the solids concentration of the ethylene-vinyl acetate copolymer resin and the (meth)acrylic resin in all the resin components contained in the aqueous composition is preferably adjusted to 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more.

[0029] The ratio of the solid content concentration of the ethylene-vinyl acetate copolymer resin to the (meth)acrylic resin is preferably 30:70 to 90:10, more preferably 40:60 to 80:20, and even more preferably 50:50 to 70:30.

[0030] The acid value of the aqueous composition is preferably 5 mg / KOH or more and 15 mg / KOH or less. If it is 5 mg / KOH or more, the solubility in water can be improved. On the other hand, if it is 15 mg / KOH or less, the dispersion state in water can be stabilized. Preferably, it is in the range of 7 mg / KOH or more and 12 mg / KOH or less, and more preferably in the range of 8 mg / KOH or more and 10 mg / KOH or less.

[0031] The minimum film-forming temperature of the aqueous composition is preferably in the range of 50°C to 100°C. In the present invention, the minimum film-forming temperature is the minimum temperature required to form a continuous film when the water content of the synthetic rubber latex evaporates and the composition dries, and is obtained by the temperature gradient plate method. Among these, the range of 60 to 95°C is preferred, and the range of 70 to 90°C is more preferred.

[0032] The thermoplastic resin layer in the laminate of the present invention is formed by applying an aqueous composition to a substrate and drying it, and can be used as a heat-sealing layer. Furthermore, the coated area other than the sealing (adhesion) area functions as a coating agent that imparts water resistance and oil resistance to the substrate. The thermoplastic resin layer formed from the aqueous composition is easily softened by heating with a burner or hot air, allowing it to bond substrates together or the substrate to other materials. Subsequent cooling solidifies the adhesive portion, allowing it to firmly seal the substrates together or the substrate to other materials.

[0033] The aqueous composition of the present invention can be applied by any known method, such as a roll coater, gravure coater, flexo coater, air doctor coater, blade coater, air knife coater, squeeze coater, impregnation coater, transfer roll coater, kiss coater, curtain coater, cast coater, spray coater, die coater, offset printing machine, screen printing machine, etc. After coating, a drying step in an oven or the like can be carried out.

[0034] The thickness of the solid content of the aqueous composition after coating, i.e., the thickness of the thermoplastic resin layer, is appropriately adjusted depending on the target seal strength and the substrate. For example, when paper is used as the substrate, the thickness is 3 to 12 g / m 2 The range of 5 to 10 g / m is preferable. 2 In addition, when a film, a vapor-deposited film, a metal foil, or the like is used as the substrate, it is more preferable that the thickness is in the range of 1 g / m 2 ~5g / m 2 It is preferable that:

[0035] (base material) Examples of the substrate include paper, nonwoven fabric, plastic film, metal foil, etc. Among these, it is preferable to use paper from the viewpoint of being able to exhibit better water resistance and oil resistance.

[0036] The paper used in the present invention is produced using natural fibers for papermaking, such as wood pulp, on a known papermaking machine, but the papermaking conditions are not particularly specified. Examples of natural fibers for papermaking include wood pulps such as softwood pulp and hardwood pulp, non-wood pulps such as Manila hemp pulp, sisal hemp pulp, and flax pulp, and pulps obtained by chemically modifying these pulps. Pulp types that can be used include chemical pulps produced by sulfate cooking, acidic, neutral, or alkaline sulfite cooking, and soda cooking, as well as ground pulp, chemi-ground pulp, and thermomechanical pulp.

[0037] More specifically, examples include uncoated papers such as various types of printing paper, gravure paper, kraft paper, Kent paper, copy paper, wood-burning paper, and newspaper; lightly coated papers; coated papers such as art paper, one-sided art paper, coated paper, one-sided coated paper, and lightweight coated paper; high-quality paper; double-glazed kraft papers for heavy-duty, general-purpose, and special purposes; unbleached wrapping papers such as ribbed kraft paper and one-sided glossy kraft paper; pure white roll paper; bleached kraft papers such as double-glazed bleached kraft paper and one-sided glossy bleached kraft paper; other bleached wrapping papers; resin-impregnated papers such as paraffin paper, cardboard, and paperboard, vapor-deposited papers in which metals such as aluminum are vapor-deposited onto these papers, and laminated papers in which these papers are laminated with metal foil such as aluminum foil.

[0038] The type and thickness of the paper substrate can be selected according to the purpose. For example, for a burger wrap, the paper thickness is 20 grams per square meter. 2 For paper cups, the weight is 200-300g / m². 2 For paper plates, spoons, stirrers, etc., the weight should be 50-500 grams per square meter. 2 Base paper for food such as cup base paper is preferred.

[0039] Various plastic films can be used, specifically films or sheets made of polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate (hereinafter also referred to as PET), polycarbonate, and polylactic acid, polystyrene-based resins such as AS resin and ABS resin, nylon, polyamide, polyvinyl chloride, polyvinylidene chloride, cellophane, paper, aluminum, etc., or composite materials thereof. Vapor-deposited films in which metals or metal oxides are vapor-deposited on the above plastic films can also be used.

[0040] The metal foil may be an aluminum foil.

[0041] These substrates may be provided with a printing layer. The printing layer is formed using various printing inks such as gravure ink, flexographic ink, offset ink, stencil ink, and inkjet ink by a general printing method that has been used for printing on polymer films. The printing layer may be provided on the surface of the substrate on the side of the heat seal layer, or on another surface.

[0042] Further, another coating layer may be provided between the substrate and the thermoplastic resin layer. For example, if the substrate is paper, a sealing layer may be provided. Furthermore, an anchor coating layer may be provided to improve the adhesion between the substrate and the thermoplastic resin layer. Known configurations can be applied to the sealing layer and the anchor coating layer.

[0043] <Packaging materials or containers> The laminate of the present invention can be used as a packaging material for the purpose of protecting food, daily necessities, pharmaceuticals, and various other industrial uses. When used as a packaging material, the layer structure of the laminate can be changed depending on the contents, the environment in which it is used, and the form in which it is used.

[0044] 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 so that their surfaces face each other, and then heat-sealing the peripheral edges. Examples of bag-making methods include folding or overlapping the laminate of the present invention so that the inner layer surfaces (sealant film surfaces) face each other, and heat-sealing the peripheral edges using, for example, a side seal, two-sided seal, three-sided seal, four-sided seal, envelope seal, flared seal, flat-bottom seal, square-bottom seal, gusset seal, or other heat seal methods. The packaging material of the present invention can take various forms depending on the contents, usage environment, and usage pattern. Self-standing packaging materials (standing pouches) are also possible. Heat-sealing methods can be performed using conventional means such as a heat source such as a burner, hot air, electric heat, infrared rays, or electron beams. Specifically, methods using a burner or hot air, or, depending on the molding shape, heat welding, ultrasonic sealing, or high-frequency sealing are preferred.

[0045] After the contents are filled into the packaging material of the present invention through its opening, the opening is heat-sealed to produce a product using the packaging material of the present invention.

[0046] The laminate and container of the present invention have excellent recyclability. The method for recycling the printed matter, laminate, and packaging material of the present invention is not particularly limited, and they can be carried out using known methods and equipment. In particular, they are suitable for recycling methods that use alkali treatment for the separate recovery of the laminate. [Example]

[0047] The present invention will be explained in more detail with reference to the following examples. Hereinafter, "parts" and "%" are all based on mass.

[0048] (Preparation of aqueous composition) Each aqueous composition was prepared according to the formulation shown in Table 1 below.

[0049] [Table 1]

[0050] In the table, EVA1 is a commercially available ethylene-vinyl acetate copolymer resin (vinyl acetate content: 29%). For EVA2, a commercially available ethylene-vinyl acetate copolymer resin (vinyl acetate content: 32%) was used. For EVA3, a commercially available ethylene-vinyl acetate copolymer resin (vinyl acetate content: 50%) was used. As the methacrylic resin 1, a commercially available acrylic emulsion (butyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, and a polymer of methacrylic acid) was used. As the methacrylic resin 2, a commercially available acrylic emulsion (a polymer of butyl methacrylate, dodecyl methacrylate, and tridecyl methacrylate) was used. As the methacrylic resin 3, a commercially available acrylic emulsion (a polymer of butyl methacrylate and methacrylic acid) was used. The wax used was commercially available amide wax. In the table, the components other than water represent the solid content.

[0051] Example 1 The aqueous composition of Preparation Example 1 was applied to a sheet of paper with a basis weight of 70 g / m 2 Using a wire bar, the thickness of the solid film is 5g / m 2 The mixture was dried at 150° C. for 20 seconds using a dryer to prepare a laminate of Example 1.

[0052] Example 2 A laminate of Example 2 was produced in the same manner as in Example 1, except that the aqueous composition of Preparation Example 2 was used.

[0053] (Comparative Example 1) A laminate of Comparative Example 1 was produced in the same manner as in Example 1, except that the aqueous composition of Comparative Preparation Example 1 was used.

[0054] The following evaluations were carried out on the laminates of Examples 1 and 2 and Comparative Example 1. The results are shown in Table 2.

[0055] (Water resistance evaluation) Tap water was collected in a dropper, and 0.3 ml was dropped onto a coated paper test piece for evaluation. After dropping the tap water, the test piece was left at 25°C for 8 hours, after which the tap water was wiped off and the front and back surfaces were visually evaluated according to the following evaluation criteria. ○: There are no drip marks or swelling due to water on the surface, and there is no penetration to the back side. △: There are drip marks on the surface, but no penetration to the back side. ×: There are drip marks or swelling due to water on the surface, and the water has penetrated to the back side.

[0056] (Oil resistance evaluation) The oil resistance of the produced laminate was evaluated using JAPAN TAPPI Paper Pulp Test Kit No. 41. The larger the value, the higher the oil resistance.

[0057] (Recyclability evaluation) A 5 cm piece of the laminate was immersed in 100 g of a 1% sodium hydroxide solution and stirred for 30 minutes, after which the state of decomposition was visually evaluated to evaluate alkali resistance. The stirring was performed using a batch-type three-dimensional composite motion disperser manufactured by Asada Iron Works Co., Ltd. ○: The laminate was completely dissolved and could not be visually confirmed. △: The laminate was dissolved or decomposed, but residues were visible. ×: The laminate is not dissolved.

[0058] (Heat seal strength stability) The coated surfaces of the prepared laminates were placed together, and heat-sealed using a heat seal tester at temperatures ranging from 80°C to 220°C in 10°C increments to create test pieces (all at 0.2 MPa for 1 second). For each test piece, the adhesive strength was recorded using a compact benchtop tester, EZ test, manufactured by Shimadzu Corporation, at a peel speed of 200 mm / min, T-peel, and a test piece width of 15 mm. The smaller the difference between the maximum and minimum heat seal values, the greater the stability of the heat seal strength over a wide temperature range.

[0059] (coefficient of friction) The coated side of the laminate was placed on the uncoated side (back of the substrate) and moved at 100 mm / min with a load of 100 g, and the stress was measured. Note that a lower value indicates a smaller coefficient of friction.

[0060] (blocking resistance) The laminates were then placed one on top of the other so that the coated and uncoated surfaces (back of the substrate) were in contact, a load of 5 kgf / cm2 was applied, and the laminates were left in a 40°C environment for 24 hours. After removal, the adhesion between the coated and uncoated surfaces was visually evaluated using the following five-point scale. (Evaluation criteria) 5: No blocking observed at all. 4: Slight blocking is observed, but the film can be peeled off without any release noise. 3: Blocking occurs, and a release sound is heard when peeling. 2: The coated surface and the back surface of the substrate are bonded together, and peeling is not possible at the interface. 1: The coated surface is firmly adhered, causing damage to the substrate when peeled off.

[0061] [Table 2]

[0062] The evaluation results showed that the laminate of the present invention has stable heat seal strength over a wide temperature range and is excellent in water resistance and oil resistance. Although the laminate of the present invention has a thermoplastic resin layer that does not contain wax, the results obtained are comparable to those of Comparative Example 1, which contains wax, in terms of blocking resistance and friction coefficient.

Claims

1. The thermoplastic resin film has a substrate and a thermoplastic resin layer provided on the substrate, the thermoplastic resin layer contains an ethylene-vinyl acetate copolymer resin and a (meth)acrylic resin, and does not contain a lubricant; The proportion of vinyl acetate in the ethylene-vinyl acetate copolymer resin is 45 mol % or less. Laminate.

2. The substrate is selected from a plastic film, a metal foil, and a paper. The laminate according to claim 1 .

3. The thermoplastic resin layer is a heat seal layer. The laminate according to claim 1 or 2.

4. The thermoplastic resin layer is a coating layer of an aqueous composition containing an ethylene-vinyl acetate copolymer resin, a (meth)acrylic resin, and an aqueous medium. The laminate according to claim 1 or 2.

5. The aqueous composition has an acid value of 5 mg / KOH or more and 15 mg / KOH or less. The laminate according to claim 1 or 2.

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

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

8. A packaging material using the laminate according to claim 1 or 2.

9. A packaging material obtained by heat-sealing the laminate according to claim 1 or 2 via the thermoplastic resin layer.

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