In-mold label and labeled container

Abstract

Provided is an in-mold label which can be easily peeled off from a resin container for recycling.　The in-mold label has an absolute value of area dimensional change rate at 80°C of 1% or less and a tack force at 80°C of 0.8 N / cm2 or less. The in-mold label can be adhered to a resin container which is a stretch-blow molded product.

Description

Technical Field

[0001] The present invention relates to in-mold labels and labeled containers.

Background Art

[0002] As a label for a resin container molded using a mold, an in-mold label that adheres to the surface of the resin container by heat during molding is known. In order to increase the adhesion strength to the resin container, it is usually necessary to design the heat-sealing layer of the in-mold label according to the physical properties of the material of the resin container (see, for example, Patent Document 1).

[0003] On the other hand, from the viewpoint of environmental protection, recycling of used resin containers is actively carried out. At the time of recycling, labels that do not adhere to the surface of the resin container, such as wrap labels and shrink labels, are mechanically peeled off, and only the resin container is recovered. However, generally, in-mold labels have a strong adhesion strength to resin containers and are not easily peeled off by manual or mechanical impact during recycling. Therefore, the recovered labeled container may be immersed in a hot alkaline aqueous solution for a certain period of time during the recycling process to peel off the label (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] If the in-mold label can be mechanically peeled off, recycling becomes easier. However, if the adhesion strength is such that peeling is easy, the label is likely to peel off even during normal use such as storage or transportation of the labeled container.

[0006] When immersed in a hot alkaline aqueous solution during recycling, even if the adhesion strength of the label is strong, there is no problem, so it is possible to achieve both peel resistance and recyclability. However, since the alkaline aqueous solution requires neutralization treatment, the process management becomes complicated and the cost required for recycling increases. In addition, if the label components dissolve in the alkaline solution, the resin container may be contaminated during immersion in the alkaline solution, which may increase the impurities in the recycled product.

[0007] An object of the present invention is to provide an in-mold label that can be easily peeled from a resin container during recycling.

Means for Solving the Problems

[0008] As a result of intensive studies by the present inventors to solve the above problems, it has been found that the above problems can be solved by adjusting the absolute value of the tack force and the area dimension change rate of the in-mold label at high temperature to be below specific values, and the present invention has been completed. That is, the present invention is as follows.

[0009] [1] An in-mold label for adhering to a resin container which is a stretch blow molded body, The absolute value of the area dimension change rate at 80 °C is 1% or less, The tack force at 80 °C is 0.8 N / cm 2 or less In-mold label.

[0010] [2] The tack force at 90 °C is 1 N / cm 2 or less The in-mold label according to [1] above.

[0011] [3] It is provided with a heat seal layer for adhering to the resin container, The heat seal layer contains a thermoplastic resin having a melting point of 90 to 110 °C The in-mold label according to [1] or [2] above.

[0012] [4] It is provided with a heat seal layer that adheres to the resin container, the melting rate of the heat seal layer at 80 °C is 75% or less, and the melting rate at 100 °C is 70% or more, The in-mold label according to the above [1] or [2].

[0013] [5] The heat seal layer includes a first heat seal layer and a second heat seal layer that adheres to the resin container, The first heat seal layer contains a non-polar resin having a melting point of 90 to 110 °C The in-mold label according to the above [3].

[0014] [6] The heat seal layer includes a first heat seal layer and a second heat seal layer that adheres to the resin container, The second heat seal layer contains a polar resin having a melting point of 90 to 110 °C The in-mold label according to the above [3].

[0015] [7] It includes a resin container that is a stretch blow molded body and an in-mold label that adheres to the surface of the resin container, the absolute value of the area dimension change rate of the in-mold label at 80 °C is 1% or less, the tack force of the in-mold label at 80 °C is 0.8 N / cm 2 or less A labeled container.

[0016] [8] The absolute value of the area dimension change rate of the resin container at 80 °C is 4% or more The labeled container according to the above [7].

Advantages of the Invention

[0017] According to the present invention, it is possible to provide an in-mold label that can be easily peeled off from a resin container during recycling.

Brief Description of the Drawings

[0018]

Fig. 1A

Fig. 1B

Fig. 2A

Fig. 2B

Embodiments for Carrying Out the Invention

[0019] Hereinafter, the in-mold label and the labeled container of the present invention will be described in detail. The following description is an example (representative example) of the present invention, and the present invention is not limited thereto. In the following description, the description of "(meth)acrylic" indicates both acrylic and methacrylic.

[0020] (In-mold label) The in-mold label of the present invention has an absolute value of the area dimensional change rate at 80 °C of 1% or less, and a tack force at 80 °C of 0.8 N / cm 2 as follows. The above area dimensional change rate is obtained as the change rate (%) of the product of the dimensions in the TD (Transverse Direction) and MD (Machine Direction) directions of the in-mold label when the temperature changes from 0 °C to 80 °C. The detailed measurement method will be described later.

[0021] Generally, an in-mold label is installed in a mold used for in-mold molding of a resin container, and melts by the heat during the molding and adheres to the surface of the resin container. Therefore, the in-mold label adheres to the resin container over its entire surface, and it is not easy to peel it off by mechanical means. Therefore, in order to peel the label from the resin container, a high-temperature immersion treatment in which the labeled container is immersed in high-temperature water or an alkaline aqueous solution may be used in the recycling process. The treatment temperature at this time is usually 80 to 90 °C.

[0022] The in-mold label of the present invention has a tack force at 80°C of 0.8 N / cm 2 or lower, and thus is likely to peel off from the resin container during high-temperature dipping treatment at 80 to 90°C. Further, the absolute value of the area dimension change rate of the in-mold label of the present invention at 80°C is 1% or less, and it hardly shrinks. Therefore, for a resin container that shrinks with the absolute value of the area dimension change rate at 80°C exceeding 1%, stress due to the shrinkage difference occurs between the label and the container, and this stress makes the label likely to peel off. Thus, the in-mold label of the present invention designed to enhance the peelability during high-temperature dipping treatment can improve the recyclability of the resin container.

[0023] Examples of in-mold molding methods include blow molding and injection molding. Blow molding is a method of forming a resin container by placing a molten cylindrical mass of raw material resin between split molds and applying air pressure from the inside to expand the mass of raw material resin. Further, the injection molding method is a method of forming a resin container by injecting raw material resin between a concave mold and a convex mold. The blow molding method further includes a direct blow method and a stretch blow method. The direct blow method is a method of forming a resin container by heating the raw material resin above its melting point to melt it to form a parison and applying air pressure to the parison in the mold to expand it. The stretch blow method is a method of forming a resin container by placing a preform pre-formed from the raw material resin in the mold, stretching the preform with a rod near the softening point of the raw material resin, and applying air pressure to expand it.

[0024] In the injection molding method and the direct blow method, since the molten resin is molded, stress due to stretching is less likely to be applied. On the other hand, in the stretch blow method, since the semi-molten preform is expanded by a strong blow pressure for molding, stress due to stretching is applied.

[0025] Therefore, when the stretch blow molded article is heated again to near the temperature during molding, stress is generated and it tends to shrink in the direction opposite to the inflated direction. Further, when an ester resin, particularly polyethylene terephthalate (PET), is used as the raw material resin and molded by the stretch blow method, the temperature of the preform and the temperature of the stretch blow molding are, for example, 70 to 150°C, and can be 80 to 120°C or 90 to 115°C. Thus, particularly, resin containers molded by the stretch blow method are likely to shrink during high-temperature immersion treatment, and particularly ester resin containers are likely to shrink during high-temperature immersion treatment at 80 to 90°C. Therefore, the difference in the area dimensional change rate from the in-mold label of the present invention tends to widen. Thus, the in-mold label of the present invention is likely to peel off from resin containers molded by the stretch blow method, and is even more likely to peel off from ester resin containers. For this reason, the in-mold label of the present invention can be preferably used as a label for stretch blow molded articles or as a label for ester resin molded articles that are stretch blow molded articles.

[0026] The in-mold label of the present invention is preferably a laminated film having a base material layer and a heat seal layer on the base material layer. The heat seal layer that adheres to the resin container facilitates adjustment of the tack force of the in-mold label and the adhesion strength with the resin container, and the base material layer facilitates adjustment of the area dimensional change rate. If the adhesion strength of the in-mold label is low, it is likely to peel off and the recycling of the resin container becomes easy, but sufficient adhesion strength is required so that it does not peel off under normal use conditions such as during storage or transportation of the labeled container. In the present invention, the adhesion strength can be adjusted by the heat seal layer so that it can be sufficiently adhered even under normal use conditions.

[0027] From the viewpoint of facilitating adjustment of not only the tack force but also the adhesion strength under normal use conditions, the heat seal layer preferably includes a first heat seal layer and a second heat seal layer.

[0028] FIG. 1A and FIG. 1B are cross-sectional views showing the configuration of an in-mold label 10 according to an embodiment of the present invention. As shown in FIG. 1A, the in-mold label 10 includes a base material layer 1 and a heat-sealing layer 2 provided on the base material layer 1. A printing layer may be provided by printing on the surface of the base material layer 1 opposite to the heat-sealing layer 2. The heat-sealing layer 2 includes a first heat-sealing layer 21 and a second heat-sealing layer 22 in order from the base material layer 1 side.

[0029] As shown in FIG. 1B, the heat-sealing layer 2, particularly the second heat-sealing layer 22, adheres to the resin container 30 when the in-mold label 10 is attached to the resin container 30. Hereinafter, each layer will be described.

[0030] <Base material layer> The base material layer is not particularly limited as long as it can impart strength to the in-mold label, but from the viewpoints of water resistance or in-mold moldability, it is preferably a thermoplastic resin film.

[0031] <<Thermoplastic resin>> Examples of the thermoplastic resin that can be used for the base material layer include olefin resins, ester resins, vinyl chloride resins, amide resins, styrene resins, and polycarbonate resins. The thermoplastic resin constituting the base material layer preferably contains an olefin resin or an ester resin as a main component, and more preferably contains an olefin resin as a main component from the viewpoints of cost or mechanical strength. In this specification, the main component refers to a component that occupies 50% by mass or more of the total of each resin.

[0032] Examples of the olefin resin that can be used for the base material layer include propylene resins and ethylene resins. Among them, from the viewpoints of moldability and mechanical strength, propylene resins are preferred. From the viewpoint of the formation of pores described later, it is preferable to use an ethylene resin in combination with the propylene resin.

[0033] Examples of propylene-based resins include propylene homopolymers such as isotactic homopolypropylene and syndiotactic homopolypropylene obtained by homopolymerizing propylene alone, and propylene copolymers mainly composed of propylene and copolymerized with α-olefins such as ethylene, 1-butene, 1-hexene, 1-heptene, 1-octene, and 4-methyl-1-pentene. The propylene copolymer may be a binary system, a ternary or higher multi-component system, and may be a random copolymer or a block copolymer.

[0034] Examples of ethylene-based resins include high-density polyethylene having a density of 0.940 to 0.965 g / cm 3 , medium-density polyethylene having a density of 0.920 to 0.935 g / cm 3 , linear low-density polyethylene having a density of 0.900 to 0.920 g / cm 3 , copolymers mainly composed of ethylene and copolymerized with α-olefins such as propylene, butene, hexene, heptene, octene, or 4-methylpentene-1, maleic acid-modified ethylene-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-alkyl acrylate copolymer, ethylene-alkyl methacrylate copolymer, metal salts of ethylene-methacrylic acid copolymer (the metal is, for example, zinc, aluminum, lithium, sodium, potassium, etc.), ethylene-cyclic olefin copolymer, or maleic acid-modified polyethylene. Among the above olefin-based resins, one kind can be used alone or in combination of two or more kinds.

[0035] Examples of ester-based resins include polyethylene terephthalate resin, polybutylene terephthalate resin, or polyethylene naphthalate. Examples of amide-based resins that can be used for the base material layer include nylon-6, nylon-6,6, nylon-6,10, or nylon-6,12.

[0036] The thermoplastic resin used for the base material layer preferably has a melting point of 110°C or higher, more preferably 130°C or higher, and even more preferably 150°C or higher. Thereby, melting of the base material layer at the temperature of the high-temperature dipping treatment is prevented, and it is easy to maintain the rigidity of the base material layer during the high-temperature dipping treatment. Also, the stretching temperature when stretched is likely to be set at 90°C or higher, and thermal shrinkage of the base material layer hardly occurs at the temperature of the high-temperature dipping treatment. Therefore, it becomes easy to adjust the absolute value of the area dimensional change rate of the in-mold label to 1% or less.

[0037] In this specification, the melting point and glass transition point of the resin are measured by a differential scanning calorimeter (DSC: Differential Scanning Calorimetry).

[0038] <<Filler>> The base material layer can contain a filler. By stretching a thermoplastic resin film containing a filler, pores nucleated by the filler are likely to be formed inside the film, and a porous film with high whiteness or opacity is likely to be obtained. The whiteness or opacity of the in-mold label can be adjusted according to the type of filler, the content of the filler, the particle diameter of the filler, the stretching conditions of the film, and the like. Examples of the filler that can be used for the base material layer include inorganic fillers or organic fillers. From the viewpoints of cost and heat resistance, etc., the filler is preferably an inorganic filler.

[0039] Examples of the inorganic filler include calcium carbonate (heavy), calcium carbonate (light), calcined clay, silica, diatomaceous earth, clay, talc, titanium oxide such as rutile type titanium dioxide, barium sulfate, aluminum sulfate, zinc oxide, magnesium oxide, mica, sericite, bentonite, sepiolite, vermiculite, dolomite, wollastonite, and glass fiber. Among them, calcium carbonate (heavy), clay, or diatomaceous earth is preferable because of good pore formability and low cost, and calcium carbonate (heavy) is more preferable. Note that, for the purpose of improving dispersibility, etc., the surface of the inorganic filler may be surface-treated with a surface treatment agent such as a fatty acid.

[0040] When the thermoplastic resin constituting the base material layer is mainly composed of an olefin resin, examples of the organic filler include particles of polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyamide, polycarbonate, polystyrene, cyclic olefin homopolymer, ethylene-cyclic olefin copolymer, polyethylene sulfide, polyimide, polymethacrylate, polyethyl ether ketone, polyphenylene sulfide, and melamine resin, which are incompatible with the olefin resin. The filler contained in the base material layer may be one kind of the above inorganic filler or organic filler, or a combination of two or more kinds.

[0041] From the viewpoint of increasing the whiteness or opacity of the base material layer, the content of the filler in the base material layer is preferably 10% by mass or more, more preferably 15% by mass or more. Further, from the viewpoint of enhancing the molding uniformity of the base material layer, the content of the filler in the base material layer is preferably 70% by mass or less, more preferably 60% by mass or less, and still more preferably 50% by mass or less. Therefore, the content of the filler in the base material layer is preferably 10 to 70% by mass, more preferably 10 to 60% by mass, and still more preferably 15 to 50% by mass.

[0042] From the viewpoint of the ease of forming pores, the average particle diameter of the inorganic filler or organic filler is preferably 0.01 μm or more, more preferably 0.05 μm or more, and still more preferably 0.1 μm or more. From the viewpoint of imparting mechanical strength such as tear resistance, the average particle diameter of the inorganic filler or organic filler is preferably 15 μm or less, more preferably 5 μm or less, and still more preferably 2 μm or less. Therefore, the average particle diameter of the inorganic filler or organic filler is preferably 0.01 to 15 μm, more preferably 0.05 to 5 μm, and still more preferably 0.1 to 2 μm.

[0043] The average particle diameter of the inorganic filler is the volume average particle diameter (cumulative 50% particle diameter) corresponding to 50% in volume cumulative measured by a particle measuring device, for example, a laser diffraction particle size distribution measuring device (Microtrac, manufactured by Nikkiso Co., Ltd.). The average particle diameter of the organic filler is the average dispersed particle diameter when dispersed in the thermoplastic resin by melt kneading and dispersion. The average dispersed particle diameter can be determined by observing the cut surface of the thermoplastic resin film containing the organic filler with an electron microscope, measuring the maximum diameters of at least 10 particles, and taking the average value thereof.

[0044] <<Other Additives>> Depending on the purpose, the base material layer can contain additives such as hindered phenol-based, phosphorus-based, amine-based, sulfur-based antioxidants; hindered amine-based, benzotriazole-based, benzophenone-based light stabilizers; dispersants; lubricants; antistatic agents, etc. From the viewpoint of suppressing the decrease in printing suitability while obtaining a sufficient effect of the additive, the content of the additive in the base material layer can usually be 0.001 to 3% by mass independently for each type of additive.

[0045] <<Thickness>> From the viewpoint of suppressing the generation of wrinkles during printing and facilitating fixation at the target position when inserted into the mold, the thickness of the base material layer is preferably 20 μm or more, more preferably 40 μm or more. Also, from the viewpoint of suppressing the strength reduction due to the thinning of the resin container at the label boundary part when the in-mold label is provided on the resin container, the thickness of the base material layer is preferably 200 μm or less, more preferably 150 μm or less. Therefore, the thickness of the base material layer is preferably 20 to 200 μm, more preferably 40 to 150 μm.

[0046] <<Structure>> The base material layer may have a single-layer structure or a multi-layer structure. In the case of a multi-layer structure, each layer can impart various functions such as white opacity, adhesion to the ink used for the printing layer, heat insulation property, and easy peelability.

[0047] From the perspective of the area dimension change rate, the base material layer is preferably an unstretched film. When it is a stretched film, it is preferably a stretched film stretched at a stretching temperature of 90°C or higher. Whether stretching is performed during the formation of the base material layer or not, when stretching is performed, stretching at 90°C or higher, which is higher than the treatment temperature of the high-temperature dipping treatment, makes it easier to control the absolute value of the area dimension change rate of the in-mold label during the high-temperature dipping treatment to 1% or less.

[0048] On the other hand, the base material layer is preferably a biaxially stretched film and is relatively thick. When the base material layer is a biaxially stretched film, it is easy to enhance the rigidity of the in-mold label. High rigidity is likely to generate a repulsive force against the resin container that tends to thermally contract during the high-temperature dipping treatment, and facilitates peeling from the resin container. Further, it is preferable that the biaxially stretched film contains a thermoplastic resin having a melting point of 110°C or higher. Since the thermoplastic resin has a melting point of 110°C or higher, it becomes easier to reduce the shrinkage during the high-temperature dipping treatment by setting the stretching temperature of the biaxially stretched film to 90°C or higher. Furthermore, from the perspective of the rigidity of the base material layer, the thickness of the base material layer is preferably 20 μm or more, and more preferably 40 μm or more.

[0049] In addition, commercially available products can also be used for the base material layer. In this case, suitable transparent base material layers include unstretched polypropylene-based films (CPP films), biaxially stretched polypropylene-based films (BOPP films), unstretched polyethylene terephthalate-based films (CPET films), and biaxially stretched polyethylene terephthalate-based films (BOPET films), etc., which do not contain fillers. Also, suitable opaque base material layers include CPP films, BOPP films, CPET films, BOPET films, unstretched polyethylene-based films (CPE films), and biaxially stretched polyethylene-based films (BOPE films), etc., which contain fillers.

[0050] <Heat-sealing layer> The heat-sealing layer imparts adhesiveness to the in-mold label with the resin container. During the in-mold molding of the resin container, the in-mold label is provided inside the mold such that the resin container and the heat-sealing layer face each other. The heat-sealing layer melts due to the heat during in-mold molding, and the in-mold label adheres to the surface of the resin container.

[0051] The heat-sealing layer may have a single-layer structure or a multilayer structure including a first heat-sealing layer and a second heat-sealing layer. In the case of a multilayer structure, it is easy to adjust the tack force and adhesive strength of the in-mold label so that each layer is difficult to peel off under normal use conditions but is easy to peel off during high-temperature immersion treatment, which is preferable.

[0052] <<Heat-sealing layer with a single-layer structure>> The heat-sealing layer with a single-layer structure can preferably contain a thermoplastic resin having a melting point of 90 °C or higher, more preferably 95 °C or higher, and even more preferably 100 °C or higher. If the melting point of the thermoplastic resin used is 90 °C or higher, it is easy to keep the tack force of the in-mold label low at 80 to 90 °C, which is the treatment temperature of the high-temperature immersion treatment. On the other hand, the heat-sealing layer can preferably contain a thermoplastic resin having a melting point of 110 °C or lower. If the melting point is 110 °C or lower, it becomes easy to melt sufficiently by the heat during molding. It is easy to obtain sufficient adhesive strength with the resin container and suppress peeling of the in-mold label under normal use conditions.

[0053] Examples of the thermoplastic resin that can be used for the heat-sealing layer include low-density or medium-density polyethylene having a density of 0.900 to 0.935 g / cm 3 and a density of 0.880 to 0.940 g / cm 3Preferred polyethylene-based resins having a melting point of 60 to 130°C include linear low-density polyethylene, ethylene-vinyl ester copolymers, ethylene-α,β-unsaturated carboxylic acid (ester) copolymers, and metal salts thereof such as Zn, Al, Li, K, and Na. Among them, low-density or medium-density polyethylene or linear low-density polyethylene having a crystallinity of 10 to 60% and a number-average molecular weight of 10,000 to 40,000 as measured by the X-ray method is preferred.

[0054] As the thermoplastic resin of the heat-sealing layer, a polar resin is preferably used from the viewpoint of enhancing the adhesiveness to a resin container, particularly a resin container which is an ester-based resin molded body, and a non-polar resin is preferably used from the viewpoint of suppressing the tack force during the high-temperature dipping treatment. The polar resin refers to a thermoplastic resin containing a polar structural unit, and examples thereof include a polymer composed of a polar structural unit or a copolymer containing a polar structural unit and a non-polar structural unit. Among these, a copolymer containing a polar structural unit and a non-polar structural unit is preferred from the viewpoint of adjusting the adhesive strength and the tack force to the resin container. The non-polar resin refers to a thermoplastic resin composed of a non-polar structural unit.

[0055] Examples of the polar structural unit include a vinyl acetate structural unit, a (meth)acrylic acid structural unit, a (meth)acrylic acid ester structural unit (the number of carbon atoms of the alkyl group is preferably 1 to 8), a maleic anhydride structural unit, a urethane structural unit, an amide structural unit, or a structural unit containing a chlorine atom. Among these, a vinyl acetate structural unit, a (meth)acrylic acid structural unit, a (meth)acrylic acid ester structural unit, or a maleic anhydride structural unit is preferred. Examples of the non-polar structural unit include an ethylene structural unit or an olefin structural unit having 2 to 8 carbon atoms such as propylene, and among them, an ethylene structural unit is preferred. When the above polar structural unit is copolymerized with polyethylene, the adhesive strength to an ester-based resin container tends to be improved.

[0056] The polar structural unit in the copolymer may be a unit in which the non-polar structural unit is modified with a carboxylic acid. As a modification method, a method of blending a radical generator such as an organic peroxide and a modifier such as maleic anhydride with a polyolefin resin as a main skeleton and kneading in a molten state in an extruder can be mentioned. Examples of the copolymer obtained by this method include maleic acid-modified polyolefin resins.

[0057] Preferred examples of the copolymer containing a non-polar structural unit and a polar structural unit include ethylene-vinyl ester copolymers or ethylene-α,β-unsaturated carboxylic acid ester copolymers.

[0058] Preferred examples of the ethylene-vinyl ester copolymer include ethylene-vinyl acetate copolymer (EVA). From the viewpoint of moldability, the melt mass flow rate (JIS K 6924-1:1997) of EVA is preferably 1 to 30 g / 10 min. From the viewpoint of improving adhesion, the vinyl acetate content (JIS K 6924-1:1997) of EVA is preferably 5 to 40% by mass, more preferably 8 to 30% by mass. The higher the vinyl acetate content of EVA, the easier it is to obtain sufficient polarity and the easier it is to improve adhesion. The lower the vinyl acetate content, the easier it is to obtain flexibility and the easier it is to improve adhesion. From the viewpoint of improving adhesion, the density (JIS K 6924-2:1997) of EVA is preferably 9.30 to 9.50.

[0059] Preferred examples of the ethylene-α,β-unsaturated carboxylic acid (ester) copolymer include ethylene-methyl methacrylate copolymer (EMMA) and ethylene-methacrylic acid copolymer (EMAA).

[0060] For the heat seal layer, one of the above-mentioned thermoplastic resins may be used alone, or two or more kinds may be mixed and used. In the latter case, from the viewpoint of suppressing peeling, it is preferable that the two or more kinds of resins to be mixed have high compatibility.

[0061] From the perspective of adjusting tackiness and adhesive strength, the content of the thermoplastic resin having a melting point of 90 to 110°C in the heat-sealing layer is preferably 30% by mass or more, more preferably 50% by mass or more, still more preferably 70% by mass or more, and particularly preferably 90% by mass or more. The content may be 100% by mass, but it may also be less than 100% by mass due to the content of other thermoplastic resins or additives described later.

[0062] From the perspective of improving the adhesiveness with an ester-based resin container, particularly a polar resin container typified by a polyethylene terephthalate resin container, the heat-sealing layer preferably contains a tackifier or a plasticizer. Examples of the tackifier include hydrogenated petroleum resins, aromatic hydrocarbon resins, or aliphatic hydrocarbon resins. Examples of the hydrogenated petroleum resin include partially hydrogenated petroleum resins. Examples of the aromatic hydrocarbon resin include terpene-based resins, rosin-based resins, or styrene-based resins. The tackifier or plasticizer may be used alone or in combination of two or more. From the perspective of suppressing peeling, it is preferably highly compatible with the thermoplastic resin used in the heat-sealing layer.

[0063] If necessary, the heat-sealing layer can contain additives commonly used in the polymer field, such as anti-fogging agents, lubricants, anti-blocking agents, antistatic agents, antioxidants, heat stabilizers, light stabilizers, weather stabilizers, and ultraviolet absorbers. The content of these additives in the heat-sealing layer is usually 0.01 to 5% by mass independently for each type of additive.

[0064] In the case of a single-layer structure, the thickness of the heat-sealing layer is preferably 0.5 μm or more, more preferably 0.7 μm or more, and even more preferably 1 μm or more from the viewpoint of enhancing adhesiveness. Further, the thickness of the heat-sealing layer is preferably 10 μm or less, more preferably 3 μm or less, and even more preferably 2 μm or less from the viewpoints of suppressing tackiness and suppressing cohesive failure within the heat-sealing layer. Therefore, the thickness of the heat-sealing layer is preferably 0.5 to 10 μm, more preferably 0.7 to 3 μm, and even more preferably 1 to 2 μm.

[0065] <<Heat-sealing layer of multilayer structure>> When the heat-sealing layer has a multilayer structure, the second heat-sealing layer is the outermost layer of the in-mold label. The first heat-sealing layer is located between the second heat-sealing layer and the base material layer and is preferably adjacent to the second heat-sealing layer.

[0066] <<<First heat-sealing layer>>> The first heat-sealing layer can preferably contain a non-polar resin having a melting point of 90°C or higher, more preferably 95°C or higher, and even more preferably 100°C or higher. If the melting point of the non-polar resin used is 90°C or higher, it is easy to keep the tackiness of the in-mold label low at 80 to 90°C. Further, the heat-sealing layer can preferably contain a non-polar resin having a melting point of 110°C or lower. If the melting point is 110°C or lower, sufficient adhesive strength with the resin container can be easily obtained, and peeling of the in-mold label in a normal use state can be suppressed. Particularly when the second heat-sealing layer is thin, since the first heat-sealing layer greatly affects the adhesive strength of the entire heat-sealing layer, setting the melting point of the non-polar resin to 110°C or lower makes it easy to obtain sufficient adhesiveness with the resin container in a normal use state, which is preferable.

[0067] As the non-polar resin, among the thermoplastic resins composed of the non-polar structural units described above, those having a melting point of 90 to 110°C can be used. From the viewpoint of adhesive strength, the thermoplastic resin used as the non-polar resin is preferably an ethylene-based resin, and among them, the density is 0.9200 g / cm 3Among the following, low-density polyethylene, linear low-density polyethylene, and ethylene-propylene copolymer are more preferred, and linear low-density polyethylene is most preferred. These ethylene-based resins may be used alone or in combination of two or more.

[0068] Examples of linear low-density polyethylene include those synthesized by multi-site catalysts typified by Ziegler-type catalysts and those synthesized by single-site catalysts typified by metallocene catalysts. From the viewpoint of more accurately controlling the melting behavior of the resin with respect to the ambient temperature, those synthesized by single-site catalysts are preferred, and among them, so-called metallocene catalysts composed of transition metals such as Zr, Ti, Hf, etc. and unsaturated rings such as cyclopentadienyl rings or indenyl rings are preferred.

[0069] The first heat-sealing layer may be a film composed of 100% by mass of a non-polar resin as long as it is a film mainly composed of a non-polar resin, or it may contain an adhesion promoter or a plasticizer, etc. listed in the item of << heat-sealing layer with a single-layer structure >>, and the content of the non-polar resin in the film may be less than 100% by mass.

[0070] <<<Second heat-sealing layer>>> The second heat-sealing layer preferably contains a polar resin having a melting point of 90 to 110 °C. If the melting point of the polar resin used is 90 °C or higher, it is easier to keep the tack force of the in-mold label low at 80 to 90 °C compared to the case where the polar resin has a melting point of less than 90 °C or no melting point. Also, if the melting point is 110 °C or lower, it is easy to obtain sufficient adhesive strength with the resin container, and peeling of the in-mold label can be suppressed under normal use conditions.

[0071] As the polar resin, among the thermoplastic resins composed of the above-described polar structural units or the copolymers having polar structural units and non-polar structural units, those having a melting point of 90 to 110 °C can be used. Since the polar resin has a melting point of 90 °C or higher, the tack force at 80 °C can be adjusted to be low. Among them, from the viewpoint of adjusting the tack force and the adhesive strength with the resin container, a (meth)acrylic acid-based copolymer is preferable, and an ethylene-methacrylic acid copolymer (EMAA) is more preferable. If the polar resin to be used is water-soluble, a coating liquid using an aqueous solvent is prepared and the coating liquid is applied, whereby the formation of the second heat-sealing layer becomes easy.

[0072] The second heat-sealing layer can contain other auxiliary components such as an antistatic agent, a crosslinking accelerator, an antiblocking agent, a pH adjuster, and an antifoaming agent, if necessary.

[0073] <<Thickness>> From the viewpoint of obtaining sufficient adhesiveness, the thickness of the first heat-sealing layer is preferably 1 μm or more, more preferably 2 μm or more. From the viewpoint of suppressing cohesive failure inside the layer, the thickness of the first heat-sealing layer is preferably 5 μm or less, more preferably 3 μm or less.

[0074] From the viewpoint of obtaining sufficient adhesiveness, the thickness of the second heat-sealing layer is preferably 0.01 μm or more, more preferably 0.05 μm or more, and still more preferably 0.1 μm or more. On the other hand, the thickness of the second heat-sealing layer may be thin from the viewpoint of suppressing the tack force during high-temperature dipping treatment and making the label easy to peel off. Specifically, it is preferably 2 μm or less, more preferably 1.6 μm or less, still more preferably 1.2 μm or less, and particularly preferably 1 μm or less.

[0075] From the viewpoint of improving adhesiveness, the total thickness of the first heat-sealing layer and the second heat-sealing layer is preferably 1.5 μm or more, more preferably 1.6 μm or more, and still more preferably 1.7 μm or more. On the other hand, from the viewpoint of peelability from the resin container, the total thickness of the first heat-sealing layer and the second heat-sealing layer is preferably 8 μm or less, more preferably 6 μm or less, and still more preferably 4 μm or less.

[0076] The content of the polar resin in the heat-sealing layer is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and still more preferably 10 parts by mass or less with respect to 100 parts by mass of the non-polar resin. If the content of the polar resin is below the above upper limit value, it is easy to suppress the tack force at the temperature during the high-temperature dipping treatment.

[0077] (Physical properties of in-mold label) <Tack force> The tack force of the in-mold label of the present invention at 80 °C is 0.8 N / cm 2 or less, preferably 0.75 N / cm 2 or less, more preferably 0.7 N / cm 2 or less. The lower the tack force at 80 °C, the easier it is for the in-mold label to peel off from the resin container during the high-temperature dipping treatment, and the easier it is to recycle the resin container. The same tack force is, for example, 0.01 N / cm 2 or more.

[0078] Similarly, from the viewpoint of making it easier to peel off the in-mold label during recycling, the tack force of the in-mold label of the present invention at 90 °C is 1.2 N / cm 2 less is preferred, 1 N / cm 2 or less is more preferred. The same tack force is, for example, 0.6 N / cm 2 or more. On the other hand, from the viewpoint of sufficiently adhering the in-mold label to the resin container during in-mold molding, the tack force of the in-mold label of the present invention at 100 °C is 1.2 N / cm 2 or more is preferred, for example, 8 N / cm 2 or less.

[0079] The above tack force can be measured, for example, by a tacking tester TAC-II (manufactured by REHSCA).

[0080] <Rate of change in area dimension> The absolute value of the area dimension change rate of the in-mold label of the present invention at 80°C is 1% or less. The smaller the area dimension change rate, the easier it is to generate stress with a resin container that is prone to shrinkage, and the easier it is for the label to peel off from the resin container during high-temperature immersion treatment.

[0081] Similarly, from the perspective of facilitating the peeling of the in-mold label during recycling, the absolute value of the area dimension change rate of the in-mold label of the present invention at 90°C is preferably also 1% or less.

[0082] The above area dimension change rate is measured as follows. The in-mold label is cut into a strip shape of 50 mm × 5 mm, placed in a thermomechanical analyzer (TMA: Thermal Mechanical Analysis), cooled to near 0°C, and then heated to 120°C at a rate of 10°C / min. Measure the dimension in the TD direction before heating and the dimension in the TD direction at the temperature to be measured after heating, for example, 80°C. Similarly, measure the dimension in the MD direction, and calculate the ratio of the change amount of the product of the dimensions in the TD direction and the MD direction before and after heating to the product of the dimensions in the TD direction and the MD direction before heating. This ratio has a positive sign when it shrinks after heating and a negative sign when it expands. By changing the temperature after heating from 80°C to 90°C, the area dimension change rate at 90°C can be obtained in the same way.

[0083] <Melting rate> In the in-mold label of the present invention, the melting rate of the heat-sealing layer at 80°C is preferably 75% or less, more preferably 70% or less, and even more preferably 65% or less. If the melting rate is 75% or less, it is easy to keep the tack force low under the temperature during high-temperature immersion treatment. The melting rate at 80°C is, for example, 1% or more.

[0084] Similarly, from the perspective of keeping the tack force low, the melting rate of the heat-sealing layer at 90°C is preferably 80% or less, more preferably 75% or less. The melting rate is, for example, 60% or more.

[0085] On the other hand, from the viewpoint of sufficiently adhering the in-mold label, the melting rate at 100 °C of the heat-sealing layer is preferably 70% or more, more preferably 75% or more, still more preferably 80% or more, even more preferably 85% or more, and particularly preferably 90% or more. The melting rate is, for example, 100% or less. The above melting rate is measured by DSC.

[0086] <Adhesion strength> From the viewpoint of suppressing peeling from the resin container in the normal use state, the adhesion strength of the in-mold label of the present invention to the resin container is preferably 100 gf / 15 mm or more, more preferably 150 gf / 15 mm or more, and still more preferably 250 gf / 15 mm or more. From the viewpoint of being easily peeled from the resin container in the high-temperature immersion treatment, the above adhesion strength is preferably 600 gf / 15 mm or less, more preferably 450 gf / 15 mm or less, and still more preferably 350 gf / 15 mm or less.

[0087] The above adhesion strength is measured in accordance with JIS K6854-2:1999 "Adhesives - Peel adhesion strength test method - Part 2: 180-degree peel". The measurement is performed under the condition that no blisters (air bubbles) are generated between the resin container and the label.

[0088] (Method for manufacturing in-mold label) The method for manufacturing the in-mold label is not particularly limited, but it can be manufactured by molding and laminating the films of each layer.

[0089] <Film molding> Examples of the film molding method include extrusion molding (cast molding) using a T-die, inflation molding using an O-die, and calender molding using a rolling roll.

[0090] Examples of the film lamination method include coextrusion method, extrusion lamination method, coating method, and film bonding method, and these can also be combined. The co-extrusion method supplies a thermoplastic composition for a base material layer and a thermoplastic composition for a heat-sealing layer (there may be a plurality of each) to a multi-layer die, laminates them in the multi-layer die, and extrudes them. Therefore, lamination is performed simultaneously with molding. The extrusion lamination method first forms a base material layer, extrudes and laminates a molten thermoplastic composition for a heat-sealing layer thereon, and nips it with a roll while cooling. Therefore, molding and lamination are performed in separate steps. The coating method prepares a coating liquid such as a dispersion of a resin composition of a heat-sealing layer, and forms and laminates a film by coating this on a base material layer. The film laminating method separately forms a base material layer and a heat-sealing layer into films, and bonds the two via a pressure-sensitive adhesive. Therefore, molding and lamination are performed in separate steps. Among these methods, from the viewpoint of being able to firmly bond each layer, the co-extrusion method is preferred.

[0091] When the heat-sealing layer has a multi-layer structure, for example, a first heat-sealing layer can be laminated on a base material layer by the co-extrusion method, and a second heat-sealing layer can be further laminated by the coating method. Examples of the coating method include a solvent coating method or an aqueous coating method. However, an aqueous coating method using an aqueous solvent in the coating liquid is preferable because process management is easy.

[0092] <Stretching> Examples of stretching methods include a longitudinal stretching method using the peripheral speed difference of a roll group, a transverse stretching method using a tenter oven, a sequential biaxial stretching method combining these, a rolling method, a simultaneous biaxial stretching method using a combination of a tenter oven and a pantograph, and a simultaneous biaxial stretching method using a combination of a tenter oven and a linear motor. Further, after extruding and molding a molten resin into a tube shape using a circular die connected to a screw-type extruder, a simultaneous biaxial stretching (inflation molding) method of blowing air into this can also be used.

[0093] The base material layer and the heat-sealing layer may be individually stretched before laminating each layer, or may be stretched together after laminating. Further, the stretched layers may be stretched again after lamination.

[0094] When performing stretching, the stretching temperature is preferably in a range not lower than the glass transition point of the thermoplastic resin used for each layer in the case of an amorphous resin. Further, when the thermoplastic resin is a crystalline resin, the stretching temperature is preferably not lower than the glass transition point of the amorphous portion of the thermoplastic resin and within a range not higher than the melting point of the crystalline portion of the thermoplastic resin. Specifically, a temperature 2 to 60 °C lower than the melting point of the thermoplastic resin is preferable.

[0095] The stretching speed of the film is not particularly limited, but from the viewpoint of stable stretch molding, it is preferably in the range of 20 to 350 m / min. Also, the stretching ratio of the film can be appropriately determined in consideration of the properties of the thermoplastic resin used, etc. For example, when stretching a thermoplastic resin film containing a homopolymer of propylene or a copolymer thereof in one direction, the stretching ratio is usually about 1.2 times or more, preferably 2 times or more, while usually 12 times or less, preferably 10 times or less. Further, when biaxially stretching, the stretching ratio in terms of area stretching ratio is usually 1.5 times or more, preferably 10 times or more, while usually 60 times or less, preferably 50 times or less. Within the above range of the stretching ratio, the target porosity can be obtained and the opacity is likely to be improved. Also, the film is less likely to break and tends to enable stable stretch molding.

[0096] Each film may be activated by an activation treatment from the viewpoint of enhancing the adhesion with an adjacent layer. Examples of the activation treatment include corona discharge treatment, flame treatment, plasma treatment, glow discharge treatment, or ozone treatment, etc. Among them, corona discharge treatment or flame treatment is preferable, and corona treatment is more preferable.

[0097] On the surface of the base material layer of the in-mold label, opposite to the heat-sealing layer, a printing layer can be provided by printing. Examples of printing information include product displays such as product names, logos, etc., manufacturers, sales company names, usage methods, and barcodes. Examples of printing methods include gravure printing, offset printing, flexographic printing, seal printing, and screen printing.

[0098] <Label processing> The in-mold label of the present invention is processed into a required shape and dimensions by cutting or punching. Cutting or punching can be performed before printing, but it is preferably performed after printing for ease of operation.

[0099] (Container with label) The container with label of the present invention has the above-described in-mold label of the present invention adhered to the surface of a resin container that is a stretch blow molded body. As described above, the in-mold label of the present invention is particularly likely to peel off from the stretch blow molded body at the temperature of the high-temperature immersion treatment during recycling, enhancing the recyclability of the resin container. Therefore, it can be particularly suitably used as a label for stretch blow molded bodies.

[0100] A stretch blow molded body is formed into a predetermined shape by heating a preform of a raw material resin to a softening point lower than its melting point and then stretching it under a strong blow pressure. When the molded body stretched during molding is placed again at a temperature near the molding temperature (stretching temperature), it tends to contract in the stretched direction. Although it depends on the type of raw material resin, the molding temperature is often about 70 to 150°C, for example. Therefore, at the high temperature of 80 to 90°C of the high-temperature immersion treatment, the stretch blow molded body tends to contract. When the in-mold label of the present invention, which hardly contracts and has a small tack force, is used at the same temperature, the label is easily peeled off and removed, making the recycling of the resin container very easy.

[0101] As the raw material resin for which the stretch blow method is selected, for example, ester resins such as polyethylene terephthalate can be mentioned. The in-mold label of the present invention can preferably use an olefin resin film, which is low-cost and excellent in moldability and mechanical strength, as a base material layer. However, olefin resins usually have low adhesion strength to ester resins. In the present invention, for example, by using a polar resin for the heat-sealing layer, the adhesiveness to an ester resin, which is the same polar resin, becomes good, and sufficient adhesion strength can be easily obtained in a normal use state.

[0102] <Resin container> The absolute value of the area dimension change rate of the resin container at 80°C is preferably 4% or more, and more preferably 6% or more. The larger the absolute value of the area dimension change rate of the resin container and the wider the difference from the area dimension change rate of the in-mold label, the easier it is for the label to peel off during the high-temperature immersion treatment.

[0103] The area dimension change rate (%) of the above resin container is measured as follows. The resin container is cut into a strip shape of 50 mm × 5 mm and placed in a TMA. After cooling to near 0°C, the temperature is raised to 120°C at 10°C / min. Measure the horizontal dimension before the temperature rise and the horizontal dimension at the temperature to be measured after the temperature rise, for example, 80°C. Similarly, measure the dimension in the height direction, and calculate the ratio of the change amount of the product of the horizontal dimension and the height dimension before and after the temperature rise to the product of the horizontal dimension and the height dimension before the temperature rise. This ratio has a positive sign when it shrinks after the temperature rise and a negative sign when it expands.

[0104] The resin container is not particularly limited as long as it can be formed by the stretch blow method. Among others, the in-mold label according to the present invention can be suitably used for resin containers such as ester resins such as polyethylene terephthalate (PET), polybutylene terephthalate, polybutylene succinate, or polylactic acid. Also, as resin containers that can be used, since they have the same adhesion mechanism as ester resins, other resin containers such as polycarbonate resin, acrylonitrile-styrene (AS) resin, acrylonitrile-butadiene-styrene (ABS) resin, and methyl methacrylate-styrene (MS) resin can also be mentioned.

[0105] The color of the resin container may be transparent or a natural color that does not contain color materials such as pigments and dyes, or may be an opaque color due to color materials or coloring. The cross-sectional shape of the body of the resin container may be a perfect circle, or may be an ellipse or a rectangle. When the cross-sectional shape of the body is a rectangle, it is preferable that the corners have a curvature. From the viewpoint of strength, the cross-section of the body is preferably a perfect circle or an ellipse close to a perfect circle, and more preferably a perfect circle.

[0106] (Method for manufacturing a labeled container) The labeled container of the present invention can be manufactured by in-mold molding a resin container by the stretch blow method and attaching an in-mold label to the surface of the resin container during this molding.

[0107] In the stretch blow method, a preform of the raw material resin is formed by injection molding or the like. The preform is heated to near the softening point of the raw material resin, stretched by a rod in a mold, and stretched by a blow pressure to form a resin container.

[0108] The absolute value of the area dimension change rate of the stretch blow molded body can be adjusted by molding conditions such as molding temperature, blow pressure, or blow time. The larger the absolute value of the area dimension change rate, the more likely a shrinkage difference from the label will occur, and the easier it is to peel off. Although the optimal molding conditions vary depending on the raw material resin, for example, in the case of polyethylene terephthalate, from the viewpoint of label peeling, the molding temperature is preferably 95°C or higher and usually 110°C or lower. Also, the blow pressure is preferably 2.3 MPa or higher and usually 3.5 MPa or lower. The blow time is preferably 3 seconds or longer and usually 9 seconds or shorter.

Examples

[0109] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples. In addition, descriptions such as "parts" and "%" in the examples mean descriptions based on mass unless otherwise specified.

[0110] (Example 1) <Manufacture of In-Mold Label> As a material for the base material layer, 60% by mass of a thermoplastic resin (propylene homopolymer, trade name: Novatec PP FY4, manufactured by Nippon Polypropylene Co., Ltd., MFR (230°C, 2.16 kg load): 5 g / 10 min, melting point: 167°C), 10% by mass of a thermoplastic resin (high-density polyethylene (trade name: Novatec HD HJ360, manufactured by Nippon Polyethylene Co., Ltd., MFR (190°C, 2.16 kg load): 5 g / 10 min, melting point 131°C)), and 30% by mass of a filler (fine powder of heavy calcium carbonate, trade name: Softon #1800, manufactured by Bihoku Powder Chemical Industry Co., Ltd., volume average particle diameter: 1.8 μm) were mixed to prepare a resin composition (a1).

[0111] Also, as a material for the first heat seal layer, a resin composition (b1) consisting of 100% by mass of a non-polar resin (ethylene α-olefin copolymer which is ultra-low density polyethylene (VLDPE), trade name: Exxelen EUL830, manufactured by Sumitomo Chemical Co., Ltd., MFR (190°C, 2.16 kg load): 22 g / 10 min, melting points: 78°C and 109°C, density: 0.895 g / cm 3 ) was prepared.

[0112] The resin composition (a1) for the base material layer was melt-kneaded with an extruder set at 230°C, then supplied to an extrusion die set at 250°C and extruded into a sheet. Next, it was cooled by a cooling device, and the obtained unstretched sheet was heated to 140°C and stretched 4 times in the MD direction. After melting and kneading the resin composition (b1) for the first heat-sealing layer with another extruder set at 230°C, it was extruded into a sheet to form the first heat-sealing layer and laminated on the above 4-fold stretched film. Thereby, a laminated film having a two-layer structure of a base material layer / first heat-sealing layer was obtained. The above laminated film was cooled to 60°C, heated again to about 140°C using a tenter oven, and stretched 10 times in the TD direction. After heat treatment with a heat-set zone adjusted to 160°C, it was cooled to 60°C and the ears were slit.

[0113] On the other hand, as the coating liquid (c1) for forming the second heat-sealing layer, a dispersion of a polar resin (a dispersion of an ethylene-methacrylic acid copolymer (trade name: AC-3100, manufactured by Japan Coating Resin Co., melting point: 90°C)) was prepared. This coating liquid (c1) was coated on the first heat-sealing layer of the above laminated film with a bar coater. Next, it was dried in an oven with a length of 10 m at a drying temperature set at 80°C to form a second heat-sealing layer having a solid content of the polar resin of 100% by mass.

[0114] Thereby, a laminated film having a three-layer structure in which a base material layer / first heat-sealing layer / second heat-sealing layer were laminated in this order (total thickness: 78.65 μm, each layer thickness: 75.5 μm / 3 μm / 0.15 μm, number of stretching axes: 2 axes / 1 axis / -) was obtained as an in-mold label.

[0115] <In-mold molding of resin container> The in-mold label was cut into single sheets and punched into a rectangle of 8 cm × 6 cm to prepare a sample for evaluation. This sample was charged using an electrostatic charging device and placed inside the molding die of a stretch blow molding machine (manufactured by Nissei ASB Co., Ltd., equipment name: ASB-12M) and clamped. At this time, the in-mold label was placed so that the base material layer was in contact with the die (so that the second heat seal layer faced the cavity side). Also, the in-mold label was placed so that the long side of the label was parallel to the circumferential direction of the body of the resin container inside the die. The die was controlled so that the surface temperature on the cavity side was within the range of 20 to 45°C.

[0116] Thereafter, a resin container was molded under the following molding conditions (Sb1). <Molding conditions (Sb1)> A preform of polyethylene terephthalate resin was preheated to 98°C and introduced into the die, and stretch blow molded for 6 seconds under a blow pressure of 3.2 MPa. After cooling to 50°C in 5.5 seconds, the die was opened, and as shown in FIGS. 2A and 2B, a labeled container 30 having a square body portion 31 was obtained. The dimension 30W of the body portion in the horizontal direction W was 145 mm, the dimension 30L in the depth direction L was 72.5 mm, and the dimension 30H in the vertical direction H was 130 cm. The dimension 30H was from the bottom surface to the lower side of the cap opening 32.

[0117] The draw ratios of the labeled container 30 were 1.2 times in the horizontal direction W, 2.6 times in the depth direction L, and 1.8 times in the vertical direction H. The draw ratio was determined as the ratio of the dimensions 30W, 30L, and 30H of the labeled container 30 to the respective dimensions of the preform in the horizontal direction W, depth direction L, and vertical direction H. Since the body portion 31 of the labeled container bulges from the bottom surface, the dimensions 30W and 30L were measured by changing the position in the vertical direction H, and the average value of each measured value was adopted.

[0118] (Example 2) A labeled container of Example 2 was manufactured in the same manner as in Example 1, except that the thickness of the first heat seal layer was changed to 5 μm.

[0119] (Example 3) The non-polar resin used for the first heat-sealing layer was changed to metallocene-catalyzed polyethylene (trade name: Evolue SP0540, manufactured by Prime Polymer Co., Ltd., MFR (190 °C, 2.16 kg load): 3.8 g / 10 min, melting points: 90 °C and 113 °C, density: 0.903 g / cm 3 ) Except for changing it to 100% by mass, a labeled container of Example 3 was manufactured in the same manner as in Example 1.

[0120] (Example 4) The non-polar resin used for the first heat-sealing layer was changed to metallocene-catalyzed polyethylene (trade name: Engage 8402, manufactured by Dow Chemical Co., Ltd., MFR (190 °C, 2.16 kg load): 30 g / 10 min, melting point: 97 °C, density: 0.902 g / cm 3 ) Except for changing it to 100% by mass, a labeled container of Example 4 was manufactured in the same manner as in Example 1.

[0121] (Example 5) The non-polar resin used for the first heat-sealing layer was changed to metallocene-catalyzed polyethylene (trade name: Kernel KS571, manufactured by Japan Polyethylene Corporation, MFR (190 °C, 2.16 kg load): 12 g / 10 min, melting point: 100 °C, density: 0.907 g / cm 3 ) Except for changing it to 100% by mass, a labeled container of Example 5 was manufactured in the same manner as in Example 1.

[0122] (Example 6) Except for changing the thickness of the second heat-sealing layer to 1 μm, a labeled container of Example 6 was manufactured in the same manner as in Example 1.

[0123] (Example 7) The non-polar resin used for the first heat-sealing layer was changed to a mixture of 70% by mass of the above ethylene-α-olefin copolymer (trade name: Exceed EUL830) and 30% by mass of metallocene-catalyzed polyethylene (trade name: Engage 8401, manufactured by Dow Chemical Co., Ltd., MFR (190 °C, 2.16 kg load): 31 g / 10 min, melting point: 79 °C, density: 0.885 g / cm 3 ) Except for changing it to the mixture, a labeled container of Example 7 was manufactured in the same manner as in Example 1.

[0124] (Example 8) A labeled container of Example 8 was produced in the same manner as in Example 1, except that the in-mold label was produced as follows.

[0125] As the material of the base material layer, a resin composition (a2) consisting of 70 mass% of a thermoplastic resin (high-density polyethylene (trade name: Novatec HD HJ360, manufactured by Japan Polyethylene Corporation, MFR: 5 g / 10 min, melting point 131 °C) Quantity % and 30 mass% of a filler (trade name Softon #1800) was prepared. The obtained resin composition (a2) was melt-kneaded with an extruder set at 200 °C, then supplied to an extrusion die set at 230 °C, and extruded into a sheet shape. Next, it was cooled by a cooling device, and the obtained unstretched sheet was heated to 110 °C and stretched 4 times in the MD direction. Quality

[0126] A first heat-sealing layer was formed on the 4-fold stretched film in the same manner as in Example 1. The obtained laminated film was cooled to 60 °C, reheated to about 120 °C again using a tenter oven, and stretched 10 times in the TD direction. After heat treatment was performed by a heat-set zone adjusted to 130 °C, it was cooled to 60 °C and the ears were slit. Then, a second heat-sealing layer was formed in the same manner as in Example 1. As a result, a laminated film having a three-layer structure in which the base material layer / first heat-sealing layer / second heat-sealing layer were laminated in this order (total thickness: 78.65 μm, each layer thickness: 75.5 μm / 3 μm / 0.15 μm, number of stretching axes: 2 axes / 1 axis / -) was obtained as an in-mold label.

[0127] (Example 9) A labeled container of Example 9 was produced in the same manner as in Example 1, except that the molding conditions (Sb1) of the resin container were changed to the following molding conditions (Sb2). <Molding conditions (Sb2)> The preform of polyethylene terephthalate resin was preheated to 112 °C and introduced into the mold, and stretch blow molding was performed for 6 seconds under a blow pressure of 3.2 MPa. Then, it was cooled to 50 °C in 3.5 seconds. The mold was opened to obtain a labeled container having a rectangular body portion with the same dimensions as in Example 1. The dimensions and draw ratio of the labeled container were the same as in Example 1.

[0128] (Example 10) A labeled container of Example 10 was produced in the same manner as in Example 1, except that the molding conditions (Sb1) of the resin container were changed to the following molding conditions (Sb3). <Molding conditions (Sb3)> The preform of polyethylene terephthalate resin was preheated to 99 °C and introduced into the mold, and stretch blow molding was performed for 6 seconds under a blow pressure of 2.8 MPa. Then, it was cooled to 50 °C in 5.5 seconds. The mold was opened to obtain a labeled container having a rectangular body portion with the same dimensions as in Example 1. The dimensions and draw ratio of the labeled container were the same as in Example 1.

[0129] (Example 11) A labeled container of Example 11 was produced in the same manner as in Example 1, except that the molding conditions (Sb1) of the resin container were changed to the following molding conditions (Sb4).

[0130] (Example 12) 75% by mass of a thermoplastic resin (propylene homopolymer, trade name: Novatec PP FY4, manufactured by Japan Polypropylene Corporation, MFR (230 °C, 2.16 kg load): 5 g / 10 min, melting point: 167 °C) and 25% by mass of a thermoplastic resin (high-density polyethylene (trade name: Novatec HD HJ360, manufactured by Japan Polyethylene Corporation, MFR (190 °C, 2.16 kg load): 5 g / 10 min, melting point 131 °C)) were mixed to prepare a resin composition (a3). A labeled container of Example 12 was produced in the same manner as in Example 4, except that the resin composition (a3) was used as the material for the base layer.

[0131] (Example 13) The resin composition (a1) for the base material layer prepared in Example 4 was melt-kneaded with an extruder set at 230°C, then supplied to an extrusion die set at 250°C, and extruded into a sheet. Another extruder set at 230°C was used to melt-knead the resin composition (b1) for the first heat-sealing layer prepared in Example 4, then extruded into a sheet to form the first heat-sealing layer, which was laminated on the above extruded sheet. Thereby, a laminated film having a two-layer structure of a base material layer / first heat-sealing layer was obtained. The obtained laminated film was cooled to 60°C and the ears were slit.

[0132] On the other hand, the coating liquid for forming the second heat-sealing layer prepared in Example 4 was coated on the first heat-sealing layer of the above laminated film with a bar coater. Next, it was dried in an oven with a length of 10 m at a drying temperature set at 80°C to form a second heat-sealing layer with a solid content of the polar resin of 100% by mass.

[0133] Thereby, a laminated film having a three-layer structure in which a base material layer / first heat-sealing layer / second heat-sealing layer were laminated in this order (total thickness: 78.65 μm, each layer thickness: 68.5 μm / 10 μm / 0.15 μm, number of stretching axes: biaxial / uniaxial / -) was obtained as an in-mold label. Using the obtained in-mold label, a labeled container of Example 13 was manufactured in the same manner as in Example 4.

[0134] (Example 14) The non-polar resin used for the first heat-sealing layer was changed to 100% by mass of metallocene-catalyzed polyethylene (trade name: Kernel KC577T, manufactured by Dow Chemical Company, MFR (190°C, 2.16 kg load): 15 g / 10 min, melting point: 102°C, density: 0.910 g / cm 3 ) Except for this change, a labeled container of Example 14 was manufactured in the same manner as in Example 1.

[0135] <Molding conditions (Sb4)> A sample of the in-mold label prepared in the same manner as in Example 1 was placed in a mold set at 25°C of a stretch blow molding machine (trade name: PET-2W type, manufactured by Yoki Sangyo Co., Ltd.). At this time, the in-mold label was placed so that the base material layer was in contact with the inner wall of the mold, and vacuum suction was performed through the vacuum suction holes to attach and fix it to the mold. Then, polyethylene terephthalate (trade name: Unipet RT543, manufactured by Nippon Unipet Co., Ltd.) previously formed into a preform by an injection molding machine was heated to 100°C with an infrared heater and introduced into the mold. This was stretch blow molded for 6 seconds under a blow pressure of 2.5 MPa to obtain a container with a cylindrical label having a dimension of 200 mm in the height direction H and a length of 210 mm around the body. The draw ratios of this labeled container were 3.0 times in the horizontal direction W, 2.6 times in the depth direction L, and 2.4 times in the vertical direction H.

[0136] (Comparative Example 1) A labeled container of Comparative Example 1 was produced in the same manner as in Example 5, except that the second heat seal layer was formed using the following coating liquid (c2).

[0137] <Preparation of Coating Liquid (c2)> 40 kg of isopropanol (manufactured by Tokuyama Corporation, trade name: Tokso IPA) was charged into a reactor with an internal volume of 150 L equipped with a reflux condenser, a nitrogen inlet tube, a lift pump, a thermometer, a dropping funnel, and a heating jacket. While stirring this, 12.6 kg of N,N-dimethylaminoethyl methacrylate (manufactured by Sanyo Chemical Industries, Ltd., trade name: Methacrylate DMA), 12.6 kg of butyl methacrylate (manufactured by Mitsubishi Rayon Co., Ltd., trade name: Acryester B), and 2.8 kg of higher alcohol methacrylic acid ester (manufactured by Mitsubishi Rayon Co., Ltd., trade name: Acryester SL, a mixture of lauryl methacrylate and tridecyl methacrylate) were introduced into the reactor. Next, the system was purged with nitrogen, and after raising the temperature inside the reactor to 80°C, 0.3 kg of 2,2′-azobisisobutyronitrile (manufactured by Wako Pure Chemical Industries, Ltd., trade name: V-60 (AIBN)) was introduced into the reactor as a polymerization initiator.

[0138] The copolymerization reaction was carried out while maintaining the temperature in the reactor at 80 °C and continuing stirring for 4 hours. Then, after cooling to room temperature, 4.3 kg of glacial acetic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was introduced into the reactor to neutralize the obtained copolymer. Next, while introducing 48.3 kg of ion-exchanged water into the reactor, isopropanol was distilled off to replace the system with an aqueous system, and a viscous aqueous solution (solid content concentration: 35% by mass) of a methacrylic acid copolymer having a tertiary amino group as a polar group in the side chain (having no melting point, weight average molecular weight: 40,000) was obtained. Since the obtained methacrylic acid copolymer was bonded to a proton in an aqueous solution and bonded to an acetate ion as a cation, it was confirmed that the above polar group was a cationic group. The methacrylic acid copolymer having this polar group was diluted to a solid content concentration of 10% by mass with ion-exchanged water to prepare a coating solution (c2).

[0139] (Comparative Example 2) A labeled container of Comparative Example 2 was produced in the same manner as in Example 1, except that the non-polar resin used for the first heat-sealing layer was changed to 100% by mass of the above metallocene catalyst polyethylene (trade name: Engage8401).

[0140] (Comparative Example 3) A labeled container of Comparative Example 3 was produced in the same manner as in Example 1, except that the second heat-sealing layer having a thickness of 4 μm was formed by directly coating the following coating solution (c3) on the base material layer without forming the first heat-sealing layer.

[0141] <Preparation of Coating Solution (c3)> A dispersion of a polar resin (dispersion of the above ethylene-methacrylic acid copolymer (trade name: AC-3100)) and an aqueous binder solution (polyethyleneimine which is a cationic water-soluble binder (trade name: Epomin P-1000, manufactured by Nippon Shokubai Co., Ltd., solid content concentration: 30% by mass)) were mixed to prepare a coating solution (c 3 ). The blending amounts of each liquid in the coating solution (c 3 ) were adjusted so that the solid content of the polar resin in the second heat-sealing layer was 80% by mass and the solid content of the water-soluble binder was 20% by mass.

[0142] (Comparative Example 4) A labeled container of Comparative Example 4 was produced in the same manner as in Example 1, except that the polar resin of the second heat-sealing layer was changed to ethylene-vinyl acetate copolymer (EMA) (trade name: Adcoat THS4884, manufactured by Toyo Morton Co., Ltd., melting point: 75°C).

[0143] (Comparative Example 5) A labeled container of Comparative Example 5 was produced in the same manner as in Example 1, except that the molding conditions (Sb1) of the resin container were changed to the following molding conditions (Db). <Molding Conditions (Db)> A sample of the in-mold label was placed so that the base material layer was in contact with the inner wall of the mold set at 15°C of the hollow container manufacturing molding machine. The in-mold label was fixed to the inner wall of the mold by vacuum suction through the vacuum suction holes of the molding machine. Next, a parison of high-density polyethylene (manufactured by Nippon Polyethylene Co., Ltd.: trade name "HB330") was heated to 180°C, and a blow pressure of 0.5 MPa was applied for 20 seconds to directly blow mold the resin container. Thereby, a labeled container in which the in-mold label was adhered to the surface of the resin container was obtained.

[0144] (Raw Materials) Table 1 shows a list of raw materials used in each example and comparative example.

Table 1

[0145] (Molding Conditions) Table 2 shows a list of molding conditions of the resin containers in each example and comparative example.

Table 2

[0146] (Evaluation Method) <Thickness> The thickness (total thickness) of the in-mold label was measured in accordance with JIS K7130:1999 using a constant-pressure thickness measuring instrument (product name: PG-01J, manufactured by Techlock Co., Ltd.). Also, the thickness of each layer in the in-mold label was determined as follows. The sample to be measured was cooled to a temperature of -60°C or lower with liquid nitrogen, and a razor blade (product name: Proline Blade, manufactured by Chic Japan Co., Ltd.) was applied perpendicularly to the sample placed on a glass plate to cut it, thereby preparing a sample for cross-sectional observation. The cross-section of the obtained sample was observed using a scanning electron microscope (product name: JSM-6490, manufactured by JEOL Ltd.), the boundary lines for each thermoplastic resin composition of each layer were discriminated from the appearance, and the thickness was determined by multiplying the thickness ratio of each layer observed in the total thickness of the in-mold label.

[0147] <Areal dimension change rate of in-mold label> The in-mold label was cut out so that the length in the MD direction was 50 mm and the length in the TD direction was 5 mm to create a sample. The created sample was placed in a thermomechanical analyzer TMA7100 (manufactured by Hitachi High-Tech Science Corporation), the sample was gripped with a fixture so that the measurement piece was 15 mm in the TMA7100, and while applying a load of 49 N, the temperature was raised under the conditions of a temperature range of 0 to 120°C and a heating rate of 10°C / min. The dimension in the MD direction (D M 0) at a temperature of 0°C before heating and the dimension in the MD direction (D M 1) after heating were measured. After heating, the dimensions at each temperature of 75°C, 80°C, and 90°C were measured. Similarly, using a sample cut out from the in-mold label so that the length in the TD direction was 50 mm and the length in the MD direction was 5 mm, the dimensions in the TD direction (D T 0 and D T 1) before and after heating were measured.

[0148] From the measured values of each dimension, the areal dimension change rate K 10 (%) at each temperature of 75°C, 80°C, and 90°C was determined by the following formula. The areal dimension change rate K 10 (%) has a negative sign when it contracts after heating and a positive sign when it expands. Areal dimension change rate K 10 (%) = (DM 0×D T 0 - D M 1×D T 1) / (D M 0×D T 0)×100

[0149] <Melting rate of the heat - seal layer> A 5 - mg sample of the heat - seal layer was set in a differential scanning calorimeter DSC7000X (manufactured by Hitachi High - Technologies Corporation). In this differential scanning calorimeter, by performing a heating / cooling / heating cycle at a scanning rate of 10 m / min in the temperature range of - 60°C to 200°C, a DSC curve was obtained. From the DSC curve of the second heating process, the heat of fusion of the entire heating process and the heats of fusion at each of the temperatures 80°C, 90°C, and 100°C were determined, and the melting rate was obtained by dividing the heat of fusion at each temperature by the heat of fusion of the entire heating process.

[0150] <Tack force> A sample of the in - mold label was set in a tacking tester (TAC - II) (manufactured by REHSCA). With this tester, a stainless - steel probe with a diameter of φ5 mm heated to a predetermined temperature was pressed against the surface of the in - mold label in contact with the resin container of the in - mold label with a load of 10 N for 30 seconds, and after 1 minute, the tack force (N / cm 2 ) was measured when peeling at a peeling speed of 30 m / min.

[0151] <Adhesive strength between the resin container and the in - mold label> The obtained labeled container was stored in an environment of 23°C and 50% relative humidity for 2 days. Next, the portion of the labeled container where the label was provided was cut off with a cutter to prepare a sample with a dimension of 12 cm in the horizontal direction W and 1.5 cm in the height direction. The label and the resin container were cut out integrally such that the adhered portion of the label was 8 cm and the non - adhered portion was 4 cm in the horizontal direction W, and the label adhered over the entire width in the height direction H. A total of 6 samples were prepared from 2 resin containers.

[0152] Next, the adhered portion of the label was carefully peeled off from the non-adhered portion of the label, peeled off by about 1 cm, and a gripping margin was formed. The gripping margin and a PET film (thickness 50 μm) with a width of 1.5 cm were overlapped and adhered with an adhesive to form a gripping margin portion on the label side.

[0153] The sample with the above-mentioned gripping margin portion was set in a tensile testing machine (model name: Autograph AGS-5kNJ, manufactured by Shimadzu Corporation). Using this tensile testing machine, based on JIS K6854-2:1999, a 180-degree peel test of the resin container and the label was carried out under the condition of a peel speed of 300 mm / min. The average value of the peel force between 25 and 75 mm of the peel length was measured, and the value obtained by further averaging the measured values of 6 samples was taken as the adhesive strength. The unit of the adhesive strength was gf / 15 mm.

[0154] <Rate of change in the area dimension of the resin container> As shown in FIGS. 2A and 2B, among the surfaces on the opposite side of the surface of the body portion 31 of the labeled container 30 to which the label 10 is attached, a sample was prepared by cutting out 50 mm in the horizontal direction W and 5 mm in the vertical direction H from the region where the positions in the horizontal direction W and the height direction H are the same as the region to which the label 10 is attached. Using this sample, the rate of change in the area dimension K of the in-mold label 10 was measured in the same manner as the dimension (D W 0) in the horizontal direction W at a temperature of 0 °C before the temperature rise and the dimension (D W 1) in the horizontal direction W after the temperature rise. After the temperature rise, the dimensions at each temperature of 75 °C, 80 °C, and 90 °C were measured. Similarly, using a sample cut out from the labeled container 30 so that the length in the vertical direction H is 50 mm and the length in the horizontal direction W is 5 mm, the dimensions (D H 0 and D H 1) in the vertical direction H before and after the temperature rise were measured.

[0155] From the measured values of each dimension, the rate of change in the area dimension K 30 (%) at each temperature of 75 °C, 80 °C, and 90 °C was determined by the following formula. The rate of change in the area dimension K 30 (%) has a negative sign when it contracts after the temperature rise and a positive sign when it expands. Area dimension change rate K 30 (%) = (D W 0 × D H 0 - D W 1 × D H 1) / (D W 0 × D H 0) × 100

[0156] <Label separation rate> The label parts of the labeled containers in each example and comparative example were cut off. This label part was crushed into flakes about 8 mm square to prepare a sample for evaluation. The sample was put into each constant temperature water bath maintaining water temperatures of 75 °C, 80 °C, and 90 °C, and immersed for 10 minutes while stirring. The sample was lifted from the hot water and dried sufficiently. Similarly, the sample was put into a constant temperature water bath maintaining the temperature of an alkaline solution (sodium hydroxide solution) at 80 °C and 90 °C, and immersed for 10 minutes while stirring. After the sample was lifted from the hot alkaline solution, neutralized, washed with water, and dried sufficiently. After drying, the number of peeled labels was measured.

[0157] The separation rate (%) of the label was calculated from the number of samples before immersion and the number of peeled labels after immersion by the following formula. Label separation rate (%) = Number of peeled labels / Number of samples before immersion × 100

[0158] Tables 3 and 4 show the evaluation results. In Tables 3 and 4, the water-soluble binder is described as "binder" for convenience.

Table 3

[0159]

Table 4

[0160] As shown in Tables 3 and 4, the tack force at 80 °C is 0.8 N / cm 2Examples 1 to 14, in which the absolute value of the area dimension change rate at 80°C is 1%, can peel off the label completely not only in an alkaline aqueous solution at 80 to 90°C but also in high-temperature water at the same temperature. It is presumed that this is because the tack force at 80°C is low, and a strong stress acts between these labels and a resin container to which they adhere, and the absolute value of the area dimension change rate of the resin container at 80°C is 6% or more, and the label hardly shrinks, making it easy to peel off.

[0161] In addition, Example 13 is a labeled container manufactured using an in-mold label obtained without stretching the base material layer and the first heat seal layer. The non-stretched film has lower rigidity than the stretched film. When the resin container shrinks during the high-temperature dipping process and curls to wrap the in-mold label, peeling due to repulsion is less likely to occur, and the label separation rate at a higher temperature tends to decrease.

[0162] Moreover, when comparing Examples 4, 5, and 14 that used resins with equivalent melting points in the first heat seal layer, in Example 4, an excellent label separation rate was obtained because the melting rate at 80°C was somewhat low and the tack force was low, and an excellent adhesive strength was obtained because the melting rate at 100°C was high. In contrast, in Examples 5 and 14, although an excellent label separation rate was obtained because the melting rate at 80°C was low and the tack force was low, the melting rate at 100°C was lower than that in Example 4, and the resulting adhesive strength was low.

[0163] On the other hand, the thermoplastic resins used in the heat seal layers of Comparative Examples 1 to 4 have a temperature at which the tack force begins to increase lower than that of Examples 1 to 14, and the tack force exceeds 0.8 N / cm at 80°C 2 and exceeds 1.3 N / cm at 90°C 2 Comparative Examples 2 to 4 also have high adhesive strength. Therefore, the label separation rate is lower than that of Examples 1 to 14. Comparative Example 5 uses a resin container obtained by direct blow molding. For this reason, it is presumed that there is no shrinkage of the resin container even during heating, no stress acts between the label and the container, and the label does not peel off.

[0164] This application claims priority based on Japanese Patent Application No. 2021-139343, filed on August 27, 2021, and Japanese Patent Application No. 2022-17934, filed on February 8, 2022, and incorporates by reference all the descriptions of the said Japanese patent applications.

Description of Reference Numerals

[0165] 10 In-mold label 1 Substrate layer 2 Heat-seal layer 21 First heat-seal layer 22 Second heat-seal layer 30 Resin container

Claims

1. An in-mold label for adhering to a resin container that is a stretch blow molded body, wherein the absolute value of the area dimensional change rate at 80 °C is 1% or less, The tack force at 80 °C is 0.8 N / cm ２ or less the in-mold label.

2. The tack force at 90 °C is 1 N / cm ２ or less The in-mold label according to claim 1.

3. The tack force at 100 °C is 1.2 N / cm2 or more The in-mold label according to claim 1 or 2.

4. Comprising a heat seal layer for adhering to the resin container, wherein the heat seal layer contains a thermoplastic resin having a melting point of 90 to 110 °C The in-mold label according to claim 1 or 2.

5. Comprising a heat seal layer for adhering to the resin container, wherein the melting rate of the heat seal layer at 80 °C is 75% or less and the melting rate at 100 °C is 70% or more, The in-mold label according to claim 1 or 2.

6. The heat seal layer includes a first heat seal layer and a second heat seal layer for adhering to the resin container, wherein the first heat seal layer contains a non-polar resin having a melting point of 90 to 110 °C The in-mold label according to claim 4.

7. The heat seal layer includes a first heat seal layer and a second heat seal layer for adhering to the resin container, wherein the second heat seal layer contains a polar resin having a melting point of 90 to 110 °C The in-mold label according to claim 4.

8. Comprising a resin container that is a stretch blow molded body and an in-mold label adhered to the surface of the resin container, wherein the absolute value of the area dimensional change rate of the in-mold label at 80 °C is 1% or less, The tack force of the in-mold label at 80°C is 0.8 N / cm ２ or less a labeled container.

9. The absolute value of the area dimensional change rate of the resin container at 80 °C is 4% or more The labeled container according to claim 8.

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