Adhesive label

Abstract

To provide an adhesive label that does not require physical peeling of the adhesive label from a polyolefin-based container by means of a device.SOLUTION: An adhesive label has, in this order, a release coat layer, a polyolefin-based resin substrate, and an adhesive layer, wherein the release coat layer comprises a propylene-based polymer and an acid-modified ethylene-based copolymer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an adhesive label. [Background technology]

[0002] Polyolefin resins are used in many hollow molded products due to their excellent rigidity and moldability (for example, Patent Document 1).

[0003] In recent years, there has been a strong demand for container recycling due to issues such as environmental pollution and the depletion of petroleum resources. In container material recycling, containers are usually crushed into flakes, then heated and melted to homogenize the entire material, and the resulting recycled resin is used as the container material.

[0004] Typically, containers are affixed with adhesive labels (also referred to as labels) having information sections on their surfaces on which various pieces of information are recorded. When such labeled containers are recycled, if the resin substrate of the label and the resin constituting the container are not compatible, the resin substrate constituting the label acts as a foreign substance, resulting in a problem of reduced mechanical properties of the recycled resin. Therefore, in such cases, it is necessary to physically peel off the label affixed to the polyolefin container using a device, then crush it into flakes and heat-melt it. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2017-179015 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the operation of physically peeling the label from the container using a device or the like is extremely cumbersome and time-consuming, and the recycling cost is high, resulting in problems of being disadvantageous in terms of both work and economy. Furthermore, even when the label is physically peeled from the container using a device or the like, the printed portion printed on the adhesive label becomes an impurity when the resin substrate is recycled, so there is an advantage in that the recyclability is improved by being able to easily peel the printed portion from the resin substrate.

[0007] The present invention has been made to solve the above problems, and an object of the present invention is to provide an adhesive label that does not require physical peeling from a polyolefin-based container. Another object of the present invention is to provide an adhesive label that is highly recyclable. [Means for solving the problem]

[0008] In order to achieve the above object, an adhesive label according to one embodiment of the present invention is an adhesive label having a release coating layer, a polyolefin-based resin substrate, and an adhesive layer in this order, wherein the release coating layer contains a propylene-based polymer and an acid-modified ethylene-based copolymer. [Effects of the Invention]

[0009] According to the adhesive label of the present invention, the release coating layer can be peeled off from the adhesive label by immersing it in an alkaline aqueous solution. Therefore, the printed portion can be easily peeled off from the resin substrate. Furthermore, according to the adhesive label of the present invention, when attached to a polyolefin-based resin molded product, the adhesive label has high recyclability even without peeling. Furthermore, according to the adhesive label of the present invention, adhesion to polyolefin-based resin substrates (e.g., polypropylene-based resin substrates) is high. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view schematically illustrating a pressure-sensitive adhesive label according to one embodiment of the present invention. [Figure 2] FIG. 10 is a cross-sectional view illustrating a pressure-sensitive adhesive label according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicate explanations will be omitted. Furthermore, the dimensional proportions in the drawings are exaggerated for the convenience of explanation, and may differ from the actual proportions.

[0012] In this specification, the range "X to Y" means "X or more and Y or less." Unless otherwise specified, operations and measurements of physical properties are performed at room temperature (20 to 25°C) and a relative humidity of 45 to 55% RH. "(Meth)acrylate" refers to "acrylate" and "methacrylate," and "(meth)acrylic acid" refers to "acrylic acid" and "methacrylic acid."

[0013] The adhesive label is attached to, for example, a polyolefin (e.g., polypropylene) resin molded product (e.g., a container). The shape of the adhesive label is not particularly limited, but is generally rectangular when viewed from the stacking direction. The adhesive label may also be triangular or circular. The adhesive layer is disposed, for example, on the entire surface of the polyolefin resin substrate.

[0014] The structure of the adhesive label will be described below with reference to FIG.

[0015] FIG. 1 is a schematic cross-sectional view of an adhesive label 10 according to an embodiment of the present invention. As shown in FIG. 1, the adhesive label 10 according to an embodiment of the present invention comprises, from top to bottom, a printed portion 13, a release coating layer 14, a polyolefin-based resin substrate (hereinafter also referred to simply as the resin substrate) 16, an adhesive layer 15, and a release liner 30. The release liner 30 comprises a release agent layer 12 and a release substrate 11, arranged in this order. The release coating layer 14 decomposes and dissolves upon contact with an alkaline aqueous solution, causing the printed portion 13 to detach (peel) from the adhesive label 10. That is, the release coating layer 14 can be detached from the resin substrate 16 by the alkaline aqueous solution. Here, the alkaline aqueous solution is, for example, a 70°C, 1.5 mass % sodium hydroxide aqueous solution (pH 13.6). This allows the detached printed portion 13 to float on the surface, making it easy to collect. The adhesive label 10 may have other functional layers, such as a primer layer, between the layers or on the surface.

[0016] Furthermore, a preferred embodiment has no release coating layer between the resin substrate 16 and the adhesive layer 15. In one preferred embodiment, the resin substrate 16 and the adhesive layer 15 are adjacent to each other. Since there is no release coating layer between the resin substrate 16 and the adhesive layer 15 and the release coating layer 14 exists between the resin substrate 16 and the printed portion 13 or between the resin substrate 16 and the alkali-insoluble coating layer 17, the resin substrate 16 does not peel off from the polyolefin-based container (adherend) when contacted with an alkaline aqueous solution, and the adhesive layer 15 and the resin substrate 16 remain attached to the polyolefin-based resin molded product (e.g., a container). Here, the resin substrate 16 is a polyolefin-based resin substrate. Therefore, the resin substrate 16 and the adhesive layer 15 can be recycled as they are while still attached to the polyolefin-based resin molded product (e.g., a container) without removing the label.

[0017] FIG. 2 is a cross-sectional schematic diagram of a pressure-sensitive adhesive label 20 according to another embodiment. The pressure-sensitive adhesive label 20 has an alkali-insoluble coating layer 17 between the printed portion 13 and the release coating layer 14. That is, the alkali-insoluble coating layer 17 is provided on the release coating layer 14 facing the polyolefin resin substrate 16. The alkali-insoluble coating layer 17 does not dissolve during alkali peeling and remains as a resin, so it is released in the form of a film together with the upper printed portion 13. That is, the printed portion does not become small and has a certain size or larger, making it easy to collect. Here, "on the release coating layer" does not only mean that the release coating layer and the alkali-insoluble coating layer are adjacent to each other, but also means that another layer may exist between the release coating layer and the alkali-insoluble coating layer. A preferred embodiment is that the release coating layer and the alkali-insoluble coating layer are adjacent to each other.

[0018] The concept of "label" includes what are called films, sheets, tapes, etc.

[0019] Each component will be described below.

[0020] <Print section 13> The printed portion is a layer for displaying information, and is an optional layer in the present invention. There are no particular limitations on how the printed portion is formed, and it can be formed by, for example, letterpress printing, flexographic printing, offset printing, relief printing, gravure printing, screen printing, etc.

[0021] The information displayed on the printed portion may be, for example, letters, numbers, symbols, illustrations, photographs, graphs, or a combination thereof.

[0022] <Alkali-insoluble coating layer> The alkali-insoluble coating layer is a layer disposed below the printed part, and since it does not dissolve during alkali peeling and remains as a resin, the printed part is detached in the form of a film, making it easy to recover the printed part. For this reason, the alkali-insoluble coating layer is preferably disposed on the printed surface.

[0023] The alkali-insoluble coating layer is mainly composed of a resin. Here, "main component" refers to a resin that accounts for 60% by mass or more (upper limit: 100% by mass) of the alkali-insoluble coating layer. The resin is alkali-insoluble. Here, "alkali-insoluble" refers to a resin whose solubility in a 1.5% by mass aqueous sodium hydroxide solution (pH 13.6) at 70°C is 20% by mass or less (lower limit: 0% by mass), preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 1% by mass or less.

[0024] Examples of resins that form the alkali-insoluble coating layer include urethane-modified polyester resins, acrylic acid ester (co)polymers, epoxy resins, and polyamide resins. Among these, urethane-modified polyester resins are preferred as the resin that forms the alkali-insoluble coating layer, as they provide high print adhesion. Furthermore, the resin that forms the alkali-insoluble coating layer preferably has an acid value of 3 KOHmg / g or less, and more preferably 2 KOHmg / g or less, in order to reduce the solubility in alkaline water.

[0025] Specific examples of urethane-modified polyester resins include polymers (polyester urethanes) obtained by reacting various polyisocyanate compounds with polyester polyols having hydroxyl groups at the terminals of polymers obtained by condensation polymerization of polyols and carboxylic acid components.

[0026] Examples of the polyisocyanate compound include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, and naphthalene diisocyanate.

[0027] The number average molecular weight (Mn) of the urethane-modified polyester resin is preferably 2,000 to 100,000, and more preferably 5,000 to 50,000. Here, the number average molecular weight (Mn) is the number average molecular weight measured by gel permeation chromatography (GPC) and converted into polystyrene.

[0028] The glass transition temperature (Tg) of the urethane-modified polyester resin is, for example, preferably 100°C or lower, and more preferably from -40 to 100°C.

[0029] The urethane-modified polyester resin may be a commercially available product, and examples of commercially available products include the Vylon series (trade name) manufactured by Toyobo MC Co., Ltd., and preferred examples include Vylon UR-1400 (hydroxyl value 2 to 3, acid value less than 1, number average molecular weight 40,000, Tg 83°C), Vylon UR-8300 (hydroxyl value 3 to 4, acid value less than 1, number average molecular weight 30,000, Tg 23°C), and Vylon UR-6100 (hydroxyl value 4 to 6, acid value less than 1, number average molecular weight 25,000, Tg -30°C).

[0030] The content of the resin in the alkali-insoluble coating layer is preferably 80 to 100% by mass, and more preferably 90 to 99% by mass.

[0031] The resin contained in the alkali-insoluble coating layer is preferably a crosslinked product. A crosslinked resin is preferred because it further reduces the solubility in an alkaline aqueous solution. To crosslink the resin, a crosslinking agent may be added to the composition for forming the alkali-insoluble coating layer used to form the alkali-insoluble coating layer. In this case, the crosslinking agent is appropriately selected so as to react with the crosslinkable reactive groups in the resin. In particular, selecting a crosslinking agent that reacts with the crosslinkable reactive groups, hydroxyl groups and / or carboxyl groups, is preferred because it can crosslink the resin and further reduces the solubility in an alkaline aqueous solution.

[0032] Examples of crosslinking agents that can react with crosslinkable reactive groups (preferably hydroxyl groups and / or carboxyl groups) include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, and metal chelate-based crosslinking agents.

[0033] Examples of isocyanate crosslinking agents include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanate methylcaprate, lysine diisocyanate, lysine ester triisocyanate, 1,6,11-undecane triisocyanate, Examples of the polyisocyanate compound include aliphatic diisocyanates such as 1,3,6-hexamethylene triisocyanate, trimethylhexamethylene diisocyanate, and decamethylene diisocyanate; aromatic diisocyanates such as tolylene diisocyanate and xylylene diisocyanate; and alicyclic diisocyanates such as isophorone diisocyanate; as well as isocyanate derivatives such as adducts of polyisocyanate compounds and polyol compounds such as trimethylolpropane, biuret compounds and isocyanurate compounds of polyisocyanate compounds, and bifunctional polyisocyanate compounds.

[0034] Examples of epoxy crosslinking agents include 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidylaniline, and diglycidylamine.

[0035] Examples of the aziridine crosslinking agent include diphenylmethane-4,4'-bis(1-aziridinecarboxamide), trimethylolpropane tri-β-aziridinylpropionate, tetramethylolmethane tri-β-aziridinylpropionate, toluene-2,4-bis(1-aziridinecarboxamide), triethylenemelamine, bisisophthaloyl-1-(2-methylaziridine), tris-1-(2-methylaziridine)phosphine, and trimethylolpropane tri-β-(2-methylaziridine)propionate.

[0036] Metal chelate crosslinking agents include chelate compounds whose metal atoms are aluminum, zirconium, titanium, zinc, iron, tin, etc., but aluminum chelate compounds are preferred from the viewpoint of performance. Examples of aluminum chelate compounds include diisopropoxyaluminum monooleyl acetoacetate, monoisopropoxyaluminum bisoleyl acetoacetate, monoisopropoxyaluminum monooleate monoethyl acetoacetate, diisopropoxyaluminum monolauryl acetoacetate, diisopropoxyaluminum monostearyl acetoacetate, and diisopropoxyaluminum monoisostearyl acetoacetate.

[0037] Among these, it is preferable that the crosslinking agent is an isocyanate-based crosslinking agent, since high print adhesion can be obtained in the coating layer after crosslinking.

[0038] The above crosslinking agents may be used alone or in combination of two or more.

[0039] The amount of crosslinking agent added is appropriately determined taking into consideration the amount of crosslinkable reactive groups in the resin, and is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the resin.

[0040] Considering the ease of recovery of the printed portion and thinness, the thickness of the alkali-insoluble coating layer is preferably 0.05 to 1 μm, and more preferably 0.05 to 0.5 μm.

[0041] The alkali-insoluble coating layer may contain additives such as a catalyst, an ultraviolet absorber, a pigment, and a filler.

[0042] <Detachment Coating Layer 14> The release coating layer enables the printed portion (and the alkali-insoluble coating layer) to be peeled from the substrate by washing and immersion in an alkaline aqueous solution (alkali immersion). In one embodiment, the release coating layer contains a propylene-based polymer and an acid-modified ethylene-based copolymer. By using a combination of a propylene-based polymer and an acid-modified ethylene-based copolymer, it is possible to achieve both improved deinking properties (removal properties of the printed portion from the label) and improved adhesion of the substrate to the polyolefin-based resin substrate.

[0043] The thickness of the release coating layer is preferably 0.01 to 5 μm, and more preferably 0.03 to 3 μm, from the viewpoint of deinking properties (ability to remove printing ink) when immersed in alkali.

[0044] (Acid-modified ethylene copolymer) The acid-modified ethylene copolymer refers to a polymer obtained by acid-modifying a polymer containing ethylene as a monomer component. In the acid-modified ethylene copolymer, ethylene is the main component of the monomers constituting the polymer, and the main component preferably accounts for 50% by mass or more, and more preferably 60% by mass or more, of all the monomers.

[0045] The acid modification can be introduced using an unsaturated carboxylic acid or its acid anhydride. Examples of unsaturated carboxylic acids and their acid anhydrides (hereinafter also referred to as unsaturated carboxylic acid components) include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, crotonic acid, etc., as well as half esters and half amides of unsaturated dicarboxylic acids. Among these, it is preferable to use at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, and maleic anhydride for the acid modification, more preferably acrylic acid and / or maleic anhydride, and even more preferably acrylic acid. Furthermore, the unsaturated carboxylic acid component may be copolymerized in the polyolefin, and the form thereof is not limited, and examples thereof include random copolymerization, block copolymerization, and graft copolymerization.

[0046] The acid-modified ethylene copolymer may be a copolymer of another monomer copolymerizable with ethylene, and a (meth)acrylic acid ester may be used as the monomer. Examples of the (meth)acrylic acid ester include esters of (meth)acrylic acid with alcohols having 1 to 30 carbon atoms (preferably 1 to 20 carbon atoms). Specific examples of such compounds include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, dodecyl (meth)acrylate, and stearyl (meth)acrylate. Mixtures of these may also be used. Examples of copolymerizable components other than acrylic acid esters include alkenes and dienes having more than 6 carbon atoms, such as 1-octene and norbornenes; maleic acid esters, such as dimethyl maleate, diethyl maleate, and dibutyl maleate; (meth)acrylic acid amides; alkyl vinyl ethers, such as methyl vinyl ether and ethyl vinyl ether; vinyl esters, such as vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, and vinyl versatate; and vinyl alcohols obtained by saponifying vinyl esters with basic compounds, etc., 2-hydroxyethyl acrylate, glycidyl (meth)acrylate, (meth)acrylonitrile, styrene, substituted styrenes, carbon monoxide, and sulfur dioxide.

[0047] Examples of acid-modified ethylene copolymers include ethylene-(meth)acrylic acid (salt) copolymers, ethylene-(meth)acrylic acid (salt)-maleic anhydride (salt) copolymers, acid-modified polyethylene, and ethylene-(meth)acrylic acid ester-unsaturated carboxylic acid copolymers obtained by further acrylic-modifying these acid-modified resins with (meth)acrylic acid esters or the like. Among these, the acid-modified ethylene resin is preferably an ethylene-(meth)acrylic acid (salt) copolymer. Here, (meth)acrylic acid (salt) refers to (meth)acrylic acid and / or a (meth)acrylic acid salt, and maleic anhydride (salt) refers to maleic anhydride and / or a maleic anhydride salt.

[0048] In the ethylene-acrylic acid (salt) copolymer, the content of ethylene (structural units derived from) is preferably 70 to 95 mass %, and the content of acrylic acid (salt) (structural units derived from) is preferably 5 to 30 mass %.

[0049] The weight average molecular weight of the ethylene-acrylic acid (salt) copolymer is, for example, 5,000 to 10,000.

[0050] The melting point of the ethylene-acrylic acid (salt) copolymer is, for example, preferably 60 to 160°C, and more preferably 60 to 120°C.

[0051] In the present invention, it is preferable to use an aqueous dispersion of an ethylene-acrylic acid (salt) copolymer, in which the ethylene-acrylic acid copolymer is neutralized, as the acid-modified ethylene-based resin, in terms of substrate adhesion to a polyolefin substrate. That is, in a preferred embodiment of the present invention, the acid-modified ethylene-based copolymer is an aqueous dispersion of an ethylene-acrylic acid (salt) copolymer. The aqueous dispersion is in the form of a solution or dispersion as an emulsion in an aqueous solvent. The use of an aqueous solvent makes it possible to reduce the amount of volatile organic compounds emitted during coating. Here, the aqueous solvent is at least one selected from water and water-soluble organic solvents. Examples of water-soluble organic solvents include methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, dimethylformamide, methyl cellosolve, tetrahydrofuran, and ethylene glycol mono-t-butyl ether (ETB). To obtain the aqueous dispersion, a small amount of an emulsifier, surfactant, etc. may be used within a range that does not impair the effects of the present invention.

[0052] Examples of the neutralizing agent for the ethylene-acrylic acid copolymer include sodium hydroxide, ammonia, alkylamines, alkanolamines, etc., and sodium salts neutralized with sodium hydroxide are preferably used.

[0053] The solids concentration of the aqueous dispersion of ethylene-acrylic acid (salt) copolymer is preferably 5 to 50% by mass, more preferably 10 to 40% by mass. The viscosity of the aqueous dispersion of ethylene-acrylic acid (salt) copolymer at 25°C is, for example, 1 to 5000 mPa·s, and may be 10 to 5000 mPa·s. In this specification, the viscosity is a value measured using a B-type rotational viscometer.

[0054] The aqueous dispersion of the ethylene-acrylic acid (salt) copolymer preferably has an emulsion shape (particulate shape) in which the polymer is dispersed. In this case, the average particle size of the emulsion polymer is, for example, 500 nm or less, 300 nm or less, or 200 nm or less. Here, the average particle size of the ethylene-acrylic acid (salt) copolymer is the volume-based median size measured by a laser diffraction dispersion method.

[0055] The aqueous dispersion of ethylene-acrylic acid copolymer may be a commercially available product, such as ZAIXXEN AC (neutralized by ammonia), ZAIXXEN L (neutralized by dimethylethanolamine), or ZAIXXEN N (neutralized by sodium hydroxide) (all manufactured by Sumitomo Seika Chemicals).

[0056] From the viewpoint of releasability, the content of the acid-modified ethylene copolymer in the release coating layer is preferably 10% by mass or more, 15% by mass or more, 20% by mass or more, or 30% by mass or more. From the viewpoints of substrate adhesion and releasability, the content of the acid-modified ethylene copolymer in the release coating layer may be 10 to 80% by mass, 10 to 70% by mass, 15 to 65% by mass, or 20 to 65% by mass, more preferably 30 to 65% by mass, even more preferably 40 to 65% by mass, even more preferably 45 to 65% by mass, and particularly preferably 45 to 55% by mass.

[0057] (Propylene polymer) Examples of propylene-based polymers include propylene homopolymers, polypropylenes such as propylene-α-olefin copolymers, and acid-modified propylene-based polymers. Among these, acid-modified propylene-based polymers are preferred in terms of compatibility with acid-modified ethylene-based copolymers and deinking properties. In the propylene-based polymers, propylene is the main component of the monomers that make up the polymer, and the main component preferably accounts for, for example, 50% by mass or more, and more preferably 60% by mass or more, of all the monomers.

[0058] The acid modification can be introduced by an unsaturated carboxylic acid or its acid anhydride. Examples of unsaturated carboxylic acids and their acid anhydrides (hereinafter also referred to as unsaturated carboxylic acid components) include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, crotonic acid, etc., as well as half esters and half amides of unsaturated dicarboxylic acids. Among these, it is preferable to use at least one acid selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, and maleic anhydride for the acid modification.

[0059] The unsaturated carboxylic acid or acid anhydride modified polyolefin is preferably obtained by copolymerizing a polyolefin with an unsaturated carboxylic acid or acid anhydride by a method known per se.

[0060] The amount of copolymerization of the unsaturated carboxylic acid or its acid anhydride with respect to the propylene main chain is preferably, for example, 0.5 to 5% by mass with respect to the solid content weight of the propylene main chain.

[0061] The acid-modified propylene polymer may also be a copolymer with other α-olefins such as ethylene and butene.

[0062] The propylene polymer may further contain other monomer components copolymerizable with propylene. Examples of such other monomers include (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, and octyl (meth)acrylate; alkenes and dienes having more than 6 carbon atoms, such as 1-octene and norbornenes; maleic acid esters such as dimethyl maleate, diethyl maleate, and dibutyl maleate; (meth)acrylic acid amides; alkyl vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, and vinyl versatate, as well as vinyl alcohols obtained by saponifying such vinyl esters with a basic compound; (meth)acrylic acid derivatives such as 2-hydroxyethyl acrylate, glycidyl (meth)acrylate, and (meth)acrylonitrile; and substituted or unsubstituted styrenes. These other monomers may be used alone or in combination.

[0063] In addition, some or all of the acid groups may be neutralized (the acid-modified propylene polymer may be a (partially) neutralized product of an acid-modified propylene polymer). The neutralizing agent used may be at least one compound selected from the group consisting of alkali metal salts, organic ammonium compounds, organic amine compounds, and ammonia. The degree of neutralization is, for example, 30 to 100 mol%.

[0064] An aqueous dispersion of an acid-modified ethylene copolymer is a preferred embodiment, and an aqueous dispersion of a propylene polymer is also preferred in terms of compatibility with the aqueous dispersion. In this case, the solids concentration of the aqueous dispersion of the propylene polymer is preferably 5 to 50 mass%, more preferably 10 to 40 mass%. The viscosity of the aqueous dispersion of the propylene polymer at 25°C is, for example, 0.1 to 1000 mPa·s, and may be 0.5 to 500 mPa·s.

[0065] The melting point of the propylene polymer is, for example, preferably 60 to 160°C, and more preferably 60 to 100°C.

[0066] From the viewpoint of substrate adhesion, the content of the propylene polymer in the release coating layer is preferably 20% by mass or more, 25% by mass or more, 30% by mass or more, or 35% by mass or more. From the viewpoint of substrate adhesion and release property, the content of the acid-modified ethylene copolymer in the release coating layer is preferably 20 to 80% by mass, or may be 25 to 75% by mass, 30 to 75% by mass, or 35 to 75% by mass, and is preferably 40 to 70% by mass, 40 to 65% by mass, 40 to 65% by mass, 45 to 65% by mass, 45 to 60% by mass, or 45 to 55% by mass.

[0067] From the viewpoints of substrate adhesion and releasability, the mass ratio of the propylene polymer to the acid-modified ethylene copolymer in the release coating layer is preferably propylene polymer:acid-modified ethylene copolymer=20:80 to 80:20, more preferably 30:70 to 70:30, even more preferably 40:60 to 60:40, and even more preferably 45:55 to 55:45.

[0068] (particle) The release coating layer may contain particles for the purpose of improving the blocking resistance between films when rolled.

[0069] The particles may be either inorganic or organic. Examples of inorganic particles include zirconia, silica, titanium dioxide, kaolin, alumina, titania, zeolite, calcium carbonate, barium sulfate, magnesium hydroxide, calcium phosphate, glass, mica, and talc. Examples of organic particles include acrylic resin particles such as polymethyl methacrylate, polystyrene particles, styrene-acrylic resin particles, and polycarbonate particles. These particles may be used alone or in combination of two or more. Among these, silica particles are preferred.

[0070] The content of the particles in the release coating layer is appropriately set to achieve the desired purpose (e.g., improving blocking resistance), and is, for example, 0.1 to 10 parts by mass per 100 parts by mass of the total of the propylene-based polymer and the acid-modified ethylene-based copolymer.

[0071] The average particle size of the particles is appropriately set taking into consideration the desired purpose, but for example, for the purpose of improving blocking resistance, it is preferably 0.1 μm or more and 1 μm or less, and more preferably 0.3 μm or more and 0.6 μm or less. In this specification, unless otherwise specified, the average particle size refers to the average particle size on a volume basis, and can be determined, for example, by measuring a particle dispersion using a Coulter Counter particle size distribution analyzer with a 50 μm aperture.

[0072] (general-purpose additives, other resin components) The release coating layer used in one embodiment of the present invention may contain, in addition to the resins and particles described above, general-purpose additives such as surfactants; crosslinking agents, etc., within the scope of not impairing the effects of the present invention.

[0073] <Resin substrate 16> The resin substrate is a polyolefin-based resin substrate made of the same material as the polyolefin-based resin molded article (e.g., a container) that is compatible with the adherend. Examples of polyolefin-based resins that are preferably used as the material for the polyolefin-based resin substrate include homopolymers or copolymers of α-olefins such as ethylene and propylene, or cyclic olefins such as norbornene. Specific examples include polyethylene (PE), polypropylene (PP), polybutene (PB), ethylene-propylene copolymers, olefin elastomers (TPO), ethylene-vinyl acetate copolymers (EVA), ethylene-methyl methacrylate copolymers (EMMA), and olefin terpolymers such as ethylene-propylene-(5-ethylidene-2-norbornene). One or more of these materials may be appropriately selected and used. Depending on the type of resin used in the adherend polyolefin-based resin molded article, one or more may be appropriately selected and used to obtain a resin substrate that is compatible with the resin. Here, compatibility means that the resin is melted at the temperature at which the polyolefin resin molded product is heated and melted, and is well mixed with the melted polyolefin resin molded product and the resin substrate, so that the properties of the recycled product are not deteriorated. When the resin constituting the polyolefin resin molded product is a mixture of two or more compatible resins, one of the resins in the mixture constituting the polyolefin resin molded product can be used as the resin of the resin substrate 16.

[0074] The thickness of the resin substrate 16 is not particularly limited and can be appropriately selected depending on the application, but is generally preferably in the range of 25 to 100 μm. When attaching an adhesive label to a container, a labeling process may be performed using a labeling device to attach the adhesive label to the container, from the perspective of production efficiency. By making the thickness of the resin substrate 16 25 μm or more, the adhesive label can be easily released from the release liner 30 during the labeling process. Furthermore, by making the thickness of the resin substrate 16 100 μm or less, the roll length installed in the labeling device can be sufficiently long, reducing the frequency of roll replacement and improving work efficiency. The resin substrate 16 may be obtained by any conventional film-forming method, such as an extrusion method, a calendar method, a solution coating method, or a casting method.

[0075] In the present invention, one or both sides of this resin substrate 16 may be subjected to a surface treatment as desired in order to improve adhesion to a coating layer provided thereon or to the pressure-sensitive adhesive layer 15 provided on the opposite side. Examples of such surface treatment methods include surface roughening treatments such as sandblasting or solvent treatment, or surface oxidation treatments such as corona discharge treatment, chromic acid treatment, flame treatment, hot air treatment, and ozone / ultraviolet irradiation treatment.

[0076] Various additives may be contained as needed in the material that constitutes the resin substrate 16. Examples of additives include stabilizers, colorants, and fillers.

[0077] <Adhesive layer 15> Next, the adhesive layer 15 will be described. The adhesive layer 15 is formed from an adhesive composition containing an adhesive. The adhesive is not particularly limited, and examples of the adhesive that can be used include polyolefin-based adhesives, acrylic-based adhesives, rubber-based adhesives, silicone-based adhesives, urethane-based adhesives, polyester-based adhesives, styrene-diene block copolymer adhesives, and vinyl alkyl ether-based adhesives. The above adhesives may be used alone or in combination of two or more.

[0078] As the adhesive, a polyolefin-based adhesive is preferably used from the viewpoint of compatibility with polyolefin-based resin molded products (e.g., containers). Conventionally known polyolefin-based adhesives can be used. Examples include the polyolefin-based adhesives described in International Publication Nos. 2006 / 026689 and 2014 / 105402.

[0079] Examples of polyolefin-based pressure-sensitive adhesives include modified polyolefin-based pressure-sensitive adhesives, olefin block copolymers, etc. Examples of modified polyolefin-based pressure-sensitive adhesives include pressure-sensitive adhesives whose main component is polyolefin modified with an unsaturated carboxylic acid or its anhydride, or a silane-based coupling agent.

[0080] A polyolefin modified with an unsaturated carboxylic acid or anhydride thereof may have, for example, a graft structure in which an unsaturated carboxylic acid and / or anhydride thereof is bonded to a polyolefin backbone serving as a main chain to form a side chain.

[0081] Examples of unsaturated carboxylic acids or anhydrides thereof include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, citraconic acid, citraconic anhydride, itaconic acid, itaconic anhydride, ester compounds of monoepoxy compounds of these derivatives with the above acids, and reaction products of these acids with polymers having groups in the molecule that can react with these acids. Metal salts of these can also be used. Of these, maleic anhydride is more preferably used.

[0082] Examples of polyolefins include homopolymers of α-olefins having 2 to 10 carbon atoms, such as ethylene, propylene, 1-butene, 1-hexene, 3-methyl-1-butene, 4-methyl-1-pentene, 1-heptene, 1-octene, and 1-decene; random or block polymers of two or more of the above α-olefins; random, block, or graft polymers of the above α-olefins with other monomers; and mixtures thereof. Among these, at least one polyolefin selected from ethylene-based resins such as high-density polyethylene, low-density polyethylene, and ethylene-vinyl acetate copolymer (EVA), and propylene-based resins such as polypropylene, is preferred in terms of low cost and excellent low-temperature adhesion.

[0083] Examples of silane coupling agents for modifying polyolefins include vinyltriethoxysilane, methacryloyloxytrimethoxysilane, and γ-methacryloyloxypropyltriacetyloxysilane.

[0084] The pressure-sensitive adhesive composition may contain conventionally known additives such as crosslinkers, hydrolysis inhibitors, softeners, ultraviolet absorbers, stabilizers, antistatic agents, and tackifiers, as well as other powdery or particulate additives such as inorganic or organic fillers, metal powders, and pigments, within the scope of not impairing the effects of the present invention.

[0085] The thickness of the pressure-sensitive adhesive layer is not particularly limited, but may be, for example, 5 to 100 μm, or 10 to 50 μm.

[0086] <Release liner 30> 1, the release liner 30 has a release substrate 11 and a release agent layer 12. The release liner is peeled off when the label is attached to an adherend, and the pressure-sensitive adhesive label of the present invention also includes a form that does not have a release liner.

[0087] The material of the release substrate 11 is not particularly limited, and known materials can be used. Examples include resin materials and paper. Examples of resin materials include polyester and polyolefin. Examples of paper include kraft paper, high-quality paper, glassine paper, and laminated paper laminated with a thermoplastic resin such as polyethylene.

[0088] The thickness of the release liner 30 is preferably 25 μm or more and 100 μm or less. By making the thickness of the release liner 30 25 μm or more, the adhesive label 10 (20) has excellent suitability for punching. Furthermore, by making the thickness of the release liner 30 100 μm or less, the release liner 30 has excellent releasability from the adhesive layer 15 during the labeling process.

[0089] Examples of the release agent constituting the release agent layer 12 include silicone-based release agents, long-chain alkyl-based release agents, fluorine-based release agents, and rubber-based release agents. Among these, silicone-based release agents are preferred. The thickness of the release agent layer is usually about 0.01 to 5 μm.

[0090] <Manufacturing method> The method for producing the pressure-sensitive adhesive label of the present invention is not particularly limited, and examples thereof include a method in which an adhesive roll or sheet is produced, and then printing, half-punching, and scrap removal are performed as necessary to produce the pressure-sensitive adhesive label. Examples of methods for producing an adhesive roll or sheet include (1) a method in which a (polyolefin-based) pressure-sensitive adhesive composition is applied to a release liner to form a pressure-sensitive adhesive layer, and then this is laminated to a resin substrate, and (2) a method in which a (polyolefin-based) pressure-sensitive adhesive composition is applied directly to a resin substrate to form a pressure-sensitive adhesive layer, and then a release liner is laminated.

[0091] The method for applying the PSA composition to the resin substrate or release liner is not particularly limited, and the composition can be applied using a known application device such as a roll coater, knife coater, air knife coater, bar coater, blade coater, slot die coater, lip coater, or gravure coater.

[0092] Furthermore, a release coating layer and an alkali-insoluble coating layer can be formed in advance on the resin substrate.

[0093] For each coating layer, a coating layer-forming composition (a composition for forming a detachment coating layer or a composition for forming an alkali-insoluble coating layer, hereinafter collectively referred to as a coating layer-forming composition) is prepared by mixing a resin, an additive as needed, and a solvent. The solvent is appropriately selected depending on the form of the resin, and examples thereof include water, alcohols (e.g., ethanol, isopropanol, etc.), toluene, methyl ethyl ketone, and ethyl acetate. The solvent may be used alone or in combination of two or more.

[0094] Thereafter, the coating layer-forming composition is applied to the resin substrate or coating layer to form a coating layer (a release coating layer or an alkali-insoluble coating layer). The coating method is not particularly limited, and a conventionally known method, such as applying the coating layer-forming composition to the resin substrate and drying it to form each coating layer, can be used. The coating method is not particularly limited, and can be, for example, a method of applying the coating layer by appropriately selecting various coating devices such as a blade coater, air knife coater, rod blade coater, bar blade coater, gravure coater, bar coater, multi-stage roll coater, roll coater, reverse roll coater, curtain coater, or spray coater.

[0095] After the coating layer-forming composition is applied, it may be subjected to a drying step. Drying conditions are appropriately set, for example, at 80 to 160° C. for 10 to 60 seconds.

[0096] <Polyolefin resin molded products> The present invention also provides a polyolefin-based resin molded article having the above-mentioned pressure-sensitive adhesive label attached thereto. The polyolefin-based resin molded article refers to a molded article made of a polyolefin-based resin. Examples of polyolefin-based resins include polyethylene and polypropylene. The polyolefin-based resin molded article is, for example, a container.

[0097] The present invention also includes the following aspects.

[0098] (1) A film having a release coating layer, a polyolefin resin substrate, and a pressure-sensitive adhesive layer in this order; An adhesive label, wherein the release coating layer comprises a propylene-based polymer and an acid-modified ethylene-based copolymer.

[0099] (2) The adhesive label according to (1), wherein the mass ratio of the propylene polymer to the acid-modified ethylene copolymer is propylene polymer:acid-modified ethylene copolymer=30:70 to 70:30.

[0100] (3) The adhesive label according to (1) or (2), wherein the adhesive layer contains a polyolefin-based adhesive.

[0101] (4) The pressure-sensitive adhesive label according to any one of (1) to (3), further comprising an alkali-insoluble coating layer on the release coating layer facing the polyolefin resin substrate.

[0102] (5) The pressure-sensitive adhesive label according to any one of (1) to (4), wherein the acid-modified ethylene copolymer is an aqueous dispersion of an ethylene-acrylic acid (salt) copolymer.

[0103] (6) The pressure-sensitive adhesive label according to any one of (1) to (5), wherein the propylene polymer is an acid-modified polymer.

[0104] (7) The pressure-sensitive adhesive label according to any one of (1) to (6), wherein the propylene-based polymer is an aqueous dispersion.

[0105] (8) An adhesive label to be affixed to the surface of a polyolefin-based resin molded product, the adhesive label having a substrate made of a polyolefin-based resin that is compatible with the polyolefin-based resin molded product to be adhered, a release coating layer that can be peeled off from the substrate by an alkaline aqueous solution on one side thereof, and an adhesive layer on the other side thereof.

[0106] (9) A polyolefin resin molded product having the adhesive label according to any one of (1) to (8) attached thereto. [Example]

[0107] Next, the examples will be described. In the examples, the units "parts" or "%" may be used, but unless otherwise specified, they represent "parts by mass" or "% by mass." Furthermore, unless otherwise specified, each operation is carried out at room temperature (25°C).

[0108] (Test Example 1) 50 parts by mass (solid content) of an aqueous dispersion of an acid-modified propylene-based polymer (trade name: Arrowbase (registered trademark) DA-5010N, manufactured by Unitika Ltd., solid content 25.0%, melting point 75°C), 50 parts by mass (solid content) of an aqueous dispersion of a sodium ion-neutralized ethylene-acrylic acid copolymer (trade name: Zaixen N, manufactured by Sumitomo Seika Chemicals Co., Ltd., solid content 25.0%), and water were mixed to a solid content of 20% by mass to obtain a composition for forming a release coating layer.

[0109] The composition for forming a release coating layer was applied to the corona treated surface of a polypropylene film (Torayfan (registered trademark) #50, thickness 50 μm) using a Mayer bar and dried to a dry film thickness of 1 μm to obtain a laminate.

[0110] (Test Example 2) A laminate was obtained in the same manner as in Test Example 1, except that 40 parts by mass (solid content) of an acid-modified propylene-based polymer (trade name: Arrowbase (registered trademark) DA-5010N, manufactured by Unitika Ltd., solid content 25.0%) and 60 parts by mass (solid content) of an aqueous dispersion of a sodium ion-neutralized ethylene-acrylic acid copolymer (trade name: Zaixen N, manufactured by Sumitomo Seika Chemicals Co., Ltd., solid content 25.0%) were mixed.

[0111] (Test Example 3) A laminate was obtained in the same manner as in Test Example 1, except that 60 parts by mass (solid content) of an acid-modified propylene-based polymer (trade name: Arrowbase (registered trademark) DA-5010N, manufactured by Unitika Ltd., solid content 25.0%) and 40 parts by mass (solid content) of an aqueous dispersion of sodium ion-neutralized ethylene-acrylic acid copolymer (trade name: Zaixen N, manufactured by Sumitomo Seika Chemicals Co., Ltd., solid content 23.0%, sodium ion-neutralized) were mixed.

[0112] (Test Example 4) A laminate was obtained in the same manner as in Test Example 1, except that 70 parts by mass (solid content) of an acid-modified propylene-based polymer (trade name: Arrowbase (registered trademark) DA-5010N, manufactured by Unitika Ltd., solid content 25.0%) and 30 parts by mass (solid content) of an aqueous dispersion of sodium ion-neutralized ethylene-acrylic acid copolymer (trade name: Zaixen N, manufactured by Sumitomo Seika Chemicals Co., Ltd., solid content 25.0%, sodium ion-neutralized) were mixed.

[0113] (Test Example 5) In Test Example 1, an acid-modified propylene polymer (trade name: Arrowbase (registered trademark) DA-5010N, manufactured by Unitika Ltd., solid content 25.0%) and water were mixed to a solid content of 20% by mass to obtain a composition for forming a detachment coating layer. A laminate was obtained in the same manner as in Test Example 1, except that in Test Example 1, an acid-modified propylene polymer (trade name: Arrowbase (registered trademark) DA-5010N, manufactured by Unitika Ltd., solid content 25.0%) and water were mixed to a solid content of 20% by mass to obtain a composition for forming a detachment coating layer.

[0114] (Test Example 6) A laminate was obtained in the same manner as in Test Example 1, except that 50 parts by mass (solid content) of an aqueous dispersion of an acid-modified ethylene polymer (trade name: Arrowbase (registered trademark) SB-5230N, manufactured by Unitika Ltd., solid content 25.0%) was used instead of 50 parts by mass (solid content) of an aqueous dispersion of an acid-modified propylene polymer (trade name: Arrowbase (registered trademark) DA-5010N, manufactured by Unitika Ltd., solid content 25.0%).

[0115] [Evaluation method 1: Adhesion to substrate] A total of 100 cross-cuts (10 squares x 10 squares) were made at 1 mm intervals, and the remaining release coating layer after peeling with cellophane tape was evaluated according to the following criteria. The results are shown in Table 1.

[0116] <Evaluation criteria> 5:91-100% remaining, 4:66-90% remaining, 3: 41-65% remaining, 2: 16-40% remaining, 1: 0-15% remaining.

[0117] [Evaluation method 2: Deinking] Printing was performed in the same manner as in the printability test, and the ink was cured by irradiating it with ultraviolet light from a high-pressure mercury lamp. Five samples were then cut into 10 mm x 10 mm pieces and placed in 1 L of a 1.5% by weight sodium hydroxide solution (pH 13.6) at 70°C and stirred. The time it took for all five prints to peel off was recorded (maximum 15 minutes), and the results were evaluated according to the following criteria. The results are shown in Table 1.

[0118] <Evaluation criteria> 5: It all comes off within 15 minutes 4: More than 60% peels off within 15 minutes 3: More than 20% peels off within 15 minutes 2: No peeling after 15 minutes, peeling occurs when the printed surface is rubbed immediately after removal 1: No peeling after 15 minutes, and no peeling even when the printed surface is rubbed immediately after removal.

[0119] [Table 1]

[0120] As shown above, the pressure-sensitive adhesive labels of the examples had excellent adhesion to the substrate and also had excellent deinking properties with alkaline water. [Explanation of symbols]

[0121] 10, 20 adhesive labels, 11 release substrate, 12 release agent layer, 13 Printing Department, 14. Detachable coating layer, 15 adhesive layer, 16 Resin substrate, 17 Alkali-insoluble coating layer, 30 release liners.

Claims

1. The film has a release coating layer, a polyolefin resin substrate, and a pressure-sensitive adhesive layer in this order, An adhesive label, wherein the release coating layer comprises a propylene-based polymer and an acid-modified ethylene-based copolymer.

2. 2. The pressure-sensitive adhesive label according to claim 1, wherein a mass ratio of the propylene polymer to the acid-modified ethylene copolymer (propylene polymer:acid-modified ethylene copolymer) is 30:70 to 70:

30.

3. The adhesive label according to claim 1 or 2, wherein the adhesive layer comprises a polyolefin-based adhesive.

4. 3. The pressure-sensitive adhesive label according to claim 1, further comprising an alkali-insoluble coating layer on the release coating layer facing the polyolefin resin substrate.

5. 3. The pressure-sensitive adhesive label according to claim 1, wherein the acid-modified ethylene copolymer is an aqueous dispersion of an ethylene-acrylic acid (salt) copolymer.

6. The pressure-sensitive adhesive label according to claim 1 or 2, wherein the propylene-based polymer is an acid-modified polymer.

7. The pressure-sensitive adhesive label according to claim 6, wherein the propylene-based polymer is an aqueous dispersion.

8. The adhesive label is to be attached to the surface of a polyolefin resin molded product, and comprises a polyolefin resin as a substrate, a release coating layer on one side of the substrate that can be peeled off from the substrate by an alkaline aqueous solution, and an adhesive layer on the other side.

9. A polyolefin resin molded product having the adhesive label according to claim 1 or 8 attached thereto.

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