Labeled molded object

Abstract

The purpose of the present invention is to provide a labeled molded object from which it is possible to separate an adhered label at the time of recycling, yet which still has an adhesive strength to deter easy peeling of the label at the time of use.　The present invention pertains to a labeled molded object comprising a molded object and a label adhered to the molded object, wherein: the label includes a heat seal layer and an adhesive force adjustment region positioned on a molded-object-side main surface of the heat seal layer; the label is in contact with the molded object at a side surface of the heat seal layer and at the adhesive force adjustment region; the molded object contains a polyolefin resin (A); the heat seal layer contains a polyolefin resin (B); and the adhesive force adjustment region contains a self-polymerization reaction product having a polar group (a).

Description

Labeled molded product

[0001] The present invention relates to a labeled molded article.

[0002] A laminate such as a label is attached to the molded product and is used to display the product name, contents, etc. In-mold molding is known as a method for manufacturing a labeled molded product (labeled molded product). In-mold molding involves pouring a parison (resin) molten at high temperature into a mold and cooling it to form a molded product according to the shape of the mold. At this time, a label is placed in the mold, allowing the production of a labeled molded product. Such labeled molded products typically require high adhesion (adhesion strength) of the label to the molded product. For example, Patent Document 1 discusses resin materials to be used in a heat-sealable resin layer in order to obtain good adhesion to polyethylene or polypropylene resin containers (molded products).

[0003] On the other hand, when recycling plastics from the viewpoint of environmental protection, properties opposite to high adhesion between the label and the molded product are also required. For example, when recycling a resin container (molded product) to which a shrink label is attached, the shrink label is mechanically peeled off from the resin container in a process of crushing the used resin container, and the resin container after peeling is recycled. On the other hand, in the case of a molded product to which a label is attached by in-mold molding, the label may be peeled off by immersing the labeled molded product in a high-temperature alkaline aqueous solution (see Patent Document 2).

[0004] JP 2006-69674 A JP 2006-168355 A

[0005] When a label is removed by immersion in a high-temperature alkaline aqueous solution, part of the label (especially the adhesive component) may dissolve and contaminate the resin container to be recycled. In such cases, it is desirable to remove the label during a crushing process. In this regard, with labeled molded products that achieve high adhesive strength between the label and the molded product, as in Patent Document 1, it tends to be difficult to remove the label and recycle them through a crushing process.

[0006] In light of the above background, the present invention aims to provide a labeled molded article that has adhesive strength that makes it difficult to peel off during use, but allows the affixed label to be separated from the molded article when recycled.

[0007] The present inventors have conducted extensive research to solve the above problems and have come up with the following invention.

[0008] That is, the present invention is as follows: [1] A labeled molded product comprising a molded product and a label attached to the molded product, wherein the label includes a heat seal layer and an adhesive force adjustment region located on the molded product-side main surface of the heat seal layer, the label is in contact with the molded product at a side surface of the heat seal layer and the adhesive force adjustment region, the molded product contains a polyolefin resin (A), the heat seal layer contains a polyolefin resin (B), and the adhesive force adjustment region contains a self-polymerization reaction product having a polar group (a). [2] The labeled molded product according to [1], wherein at least a portion of the heat seal layer is attached to the molded product on the molded product-side main surface of the heat seal layer without the adhesive force adjustment region. [3] The labeled molded product according to [1] or [2], wherein the adhesive force adjustment region further contains a polymer having a polar group (b). [4] The labeled molded product according to any of [1] to [3], wherein the self-polymerization reaction product having the polar group (a) is a self-polymerization reaction product of a silane coupling agent having the polar group (a). [5] The labeled molded article according to any one of [1] to [4], wherein the label is in contact with the molded article at a thickness of 55% or more of the thickness of the heat seal layer. [6] The labeled molded article according to any one of [1] to [5], wherein the polyolefin-based resin (A) is a polypropylene-based resin, and the polyolefin-based resin (B) is a polypropylene-based resin.

[0009] The following is an example of a method for producing a labeled molded product: [7] A method for producing a labeled molded product comprising a molded product and a label affixed to the molded product, comprising the steps of: providing an adhesive force adjustment region in a heat seal layer containing a heat seal resin to obtain a label; and an injection molding step of placing the label on the mold so that the adhesive force adjustment region faces the resin injection side of the mold and injecting molding resin into the mold to obtain a labeled molded product with the label affixed to the molded product, wherein the heat seal resin contains a polyolefin resin (B), the adhesive force adjustment region contains a self-polymerization reaction product having a polar group (a), and the molding resin contains a polyolefin resin (A), and in the injection molding step, the molding resin, having a melting point of the heat seal resin of (Mps + 35)°C or higher and (Mps + 150)°C or lower, is injected at a pressure of 20 to 70 MPa, where Mps is the melting point of the heat seal resin. [8] A manufacturing method in which the basis weight of the adhesive force adjustment region is 0.002 to 1 g / m ２ [7] The manufacturing method according to [7],

[0010] An object of the present invention is to provide a labeled molded article that has adhesive strength that makes it difficult to peel off during use, and in which the affixed label can be separated from the molded article when recycled.

[0011] Fig. 1 is a schematic cross-sectional view showing an example of a labeled molded article in an embodiment. Fig. 2 is a schematic cross-sectional view showing another example of a labeled molded article in an embodiment. Fig. 3 is a schematic front view showing a location where a sample is prepared in measuring adhesive strength.

[0012] The present invention will be described in detail below with reference to the following embodiments. Note that the embodiments are merely examples of the present invention, and the present invention is not limited to these embodiments.

[0013] [Labeled Molded Article] The labeled molded article comprises a molded article and a label attached to the molded article. The label includes a heat seal layer and an adhesive force adjustment region located on the main surface of the heat seal layer facing the molded article. The labeled molded article is configured so that at least one side of the heat seal layer and the adhesive force adjustment region of the label come into contact with the molded article.

[0014] In this way, the label has an adhesive strength adjusting region between the heat-seal layer and the molded article, which can adjust the adhesive strength between the heat-seal layer and the molded article. Both the heat-seal layer and the molded article contain polyolefin resins, which enable relatively strong adhesion, while the adhesive strength adjusting region contains a self-polymerization reaction product having a polar group, which can adjust the adhesive strength between the heat-seal layer and the molded article so that the adhesion between the heat-seal layer and the molded article is not too strong or can be reduced.

[0015] Here, conventionally, the adhesion between the label and the molded article has usually been achieved on the main surface of the label on the heat seal layer side. Therefore, providing an adhesive strength adjustment region on the main surface that reduces the adhesive strength may be considered to be contrary to the problem of maintaining adhesive strength during use. However, the labeled molded article according to this embodiment is also adhered to the molded article on the side of the label, so that it is easy to maintain sufficient adhesive strength during use even though it has an adhesive strength adjustment region on the main surface.

[0016] Furthermore, since the side surface of the heat seal layer is in contact with the molded body, the labeled molded body tends to have the label embedded in the molded body. Therefore, when an attempt is made to peel the label from the molded body by hand, peeling that would otherwise cause the label to peel off is unlikely to occur on the side surface. As a result, the labeled molded body is one in which the label is difficult to peel from the molded body during use, but is also easily separated from the molded body along the main surface during a crushing process or the like during recycling.

[0017] The labeled molded product will be described in detail below with reference to FIGS. 1 and 2. FIGS. 1 and 2 are schematic cross-sectional views showing an example of the configuration of a labeled molded product. In the labeled molded product shown in FIGS. 1 and 2, a label 10 is attached to the molded product 1. The label 10 may be in the form of a sheet having any thickness. One of the two main surfaces of the label 10 is attached to the molded product 1. Hereinafter, in the stacking direction (thickness direction) of the label 10, the side where the label 10 and the molded product 1 are attached (the side where the molded product is located) may be referred to as the "attachment side," and the side opposite to the attachment side may be referred to as the "surface side." Herein, in the labeled molded product of this embodiment, the label attached to the molded product may be, for example, a label having a printing layer (not shown) on the surface side of the label 10.

[0018] As shown in Fig. 1, the label 10 includes a heat seal layer 100 and an adhesive force adjusting region 200. As shown in Fig. 2, the label 10 may have other layers in addition to the heat seal layer 100 and the adhesive force adjusting region 200. The label 10 may have only the heat seal layer 100 and the adhesive force adjusting region 200 without having other layers. Fig. 2 shows a label 10 in which a base layer 300, as an example of other layers, is laminated on the main surface on the front side of the heat seal layer 100.

[0019] As shown in FIGS. 1 and 2 , the label 10 contacts the molded body 1 not only at the adhesive force adjusting region 200 but also at the side surface S of the heat-seal layer 100. Having the side surface S of the heat-seal layer 100 in contact with the molded body 1 in this manner makes it less likely for peeling to occur, which could lead to the label 10 being peeled off from the molded body 1. Furthermore, the heat-seal layer 100 contains a polyolefin-based resin (B), which is the same type of resin as the polyolefin-based resin (A) of the molded body. Furthermore, as described above, the heat-seal layer 100 contacts the molded body 1 at the side surface S, allowing the heat-seal layer 100 and the molded body 1 to adhere to each other at the side surface S. This point will be explained in detail with reference to FIGS. 2 and 3 . In the example shown in FIG. 3 , there is a gap between the side surface S of the heat-seal layer 100 and the molded body 1, leaving the side surface of the label 10 exposed. In this labeled molded body, peeling, which could lead to the label being peeled off, can occur from the side surface. In contrast, as shown in FIG. 2 , in the labeled molded product of this embodiment, the side surface S of the heat-seal layer 100 and the molded product 1 are in contact, so there is no gap as shown in FIG. 3 , and the side surface of the label 10 is embedded in the molded product 1. This makes it difficult for peeling to occur, which could lead to label peeling. Furthermore, because the side surface S of the heat-seal layer 100 and the molded product 1 are in contact, the heat-seal layer 100 and the molded product 1 can be bonded at the side surface S. Therefore, the labeled molded product of this embodiment makes it difficult for the label to peel off during use. Note that when the label 10 has multiple side surfaces S, it is sufficient that at least one side surface S of the heat-seal layer 100 is in contact with the molded product 1, and it is preferable that multiple side surfaces S are in contact, and it is particularly preferable that all side surfaces S of the heat-seal layer 100 are in contact with the molded product 1.

[0020] It is preferable that at least a portion of the heat seal layer 100 of the label 10 is attached to the molded product 1 on the molded product-side (adhesion side) main surface of the heat seal layer without the adhesive force adjusting region 200. Having a portion of the heat seal layer 100 attached directly to the molded product 1 without the adhesive force adjusting region 200 in this way makes it easier to improve the adhesive strength between the label 10 and the molded product 1. By appropriately having a portion where the heat seal layer 100 is directly attached to the molded product 1 in this way as a labeled molded product, it is possible to prevent the label 10 from unintentionally peeling off during use and to easily adjust the adhesive strength to an appropriate level.

[0021] Whether the side surface S of the label 10 is "in contact" with the molded article 1 can be confirmed by checking whether the heat seal layer of the label 10 is attached to the molded article 1 when the label 10 is peeled off from the molded article 1. Furthermore, the label 10 preferably contacts the molded article 1 at a thickness of 55% or more of the thickness of the heat seal layer (contact length / thickness of the heat seal layer; this is called the contact ratio). The contact ratio can be calculated from the ratio (b / a x 100) of the thickness (a) of the heat seal layer to the thickness (b) of the portion of the label 10 that was in contact with the molded article 1. The thicknesses used to calculate the contact ratio can be measured by observing a cross-sectional image of the label 10 using an electron microscope or the like. The contact ratio is more preferably 80% or more from the viewpoint of enhancing adhesion between the side surface of the heat seal layer and the molded article. The contact ratio may even be 100%.

[0022] (Heat Seal Layer) The heat seal layer 100 melts when heated during molding and heat-seals to the molded article 1, thereby increasing the adhesive strength between the label 10 and the molded article 1. From the above viewpoints, an appropriate material can be selected as the material for the heat seal layer 100 depending on the molding temperature. For example, when injection molding, which often uses a molding temperature relatively higher than blow molding, is used as the molding method, even a material with a higher melting temperature than blow molding can be used as a material having heat sealability.

[0023] Specifically, the heat-seal layer 100 contains a polyolefin resin (B). The melting point of the polyolefin resin (B) can be selected depending on the molding resin. For example, when the polyolefin resin (A) of the molded article contains a polypropylene resin as a main component, from the viewpoint of exhibiting heat-sealability during molding, the melting point of the polyolefin resin (B) of the heat-seal layer is preferably 200°C or less, more preferably 180°C or less, and even more preferably 170°C or less. Furthermore, when the polyolefin resin (A) contains a polyethylene resin as a main component, from the same viewpoint, the melting point of the polyolefin resin (B) is preferably 160°C or less, more preferably 140°C or less, and even more preferably 130°C or less. On the other hand, when the polyolefin resin (A) contains a polypropylene resin as a main component, from the viewpoints of preventing sticking to a roll during label production and suppressing excessive adhesiveness due to the heat seal layer, the melting point of the polyolefin resin (B) is preferably 110° C. or higher, more preferably 120° C. or higher, and even more preferably 130° C. or higher. Furthermore, when the polyolefin resin (A) contains a polyethylene resin as a main component, from the same viewpoint, the melting point of the polyolefin resin (B) is preferably 60° C. or higher, more preferably 90° C. or higher, and even more preferably 110° C. or higher.

[0024] Note that "resin X contains resin Y as a main component" means that resin X contains 70% by mass or more of resin Y. Similarly, when resin X contains 80% by mass or more of resin Y, when resin X contains 90% by mass or more of resin Y, or when resin X is entirely resin Y, it can be said that resin X contains resin Y as a main component. The melting point can be measured using a differential scanning calorimetry (DSC) in accordance with JIS K 7121. In a graph obtained by a differential scanning calorimetry, the temperature indicated by the melting peak top is taken as the melting point. When there are multiple melting peaks in the graph, the temperature at which the integrated area of ​​the melting peaks is 50% is taken as the melting point.

[0025] Examples of the polyolefin resin (B) include polypropylene resins, polyethylene resins, and polybutylene resins. When the polyolefin resin (A) of the molded article contains a polypropylene resin, the polyolefin resin (B) of the heat-seal layer is preferably a polypropylene resin from the viewpoint of melting at the molding temperature. The polypropylene resin is preferably a propylene homopolymer, a propylene-ethylene copolymer, a maleic acid-modified polypropylene, or a polypropylene-based monomer (e.g., a metal salt of a propylene (meth)acrylic acid copolymer). From the viewpoint of adhesiveness, a propylene homopolymer or a propylene-ethylene copolymer is preferred, and a propylene homopolymer is more preferred. Note that a propylene-ethylene copolymer is a copolymer containing propylene and ethylene polymerized, and contains more than 50 mol% propylene as a copolymerization component.

[0026] When the polyolefin resin (A) of the molded article contains a polyethylene resin, the polyolefin resin (B) of the heat seal layer is preferably a polyethylene resin from the viewpoint of melting at the molding temperature. The polyethylene resin is preferably high-density polyethylene, medium-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, or ethylene-methacrylic acid copolymer, and more preferably high-density polyethylene or medium-density polyethylene. In this specification, high-density polyethylene refers to a polyethylene having a density of 0.94 g / cm. ３ The above polyethylene resins, medium density polyethylene has a density of 0.93 g / cm ３ 0.94g / cm or more ３ Polyethylene resins with a density of less than 0.93 g / cm ３ This refers to polyethylene resins with a molecular weight of less than 1000.

[0027] Examples of polypropylene-based resins include isotactic homopolypropylene and syndiotactic homopolypropylene obtained by homopolymerizing propylene, as well as polypropylene-based copolymers having various stereoregularities obtained by copolymerizing propylene as the main component with α-olefins such as ethylene, 1-butene, 1-hexene, 1-heptene, 1-octene, and 4-methyl-1-pentene. The polypropylene-based copolymers may be binary or ternary or higher multi-component systems, and may be random or block copolymers.

[0028] The heat seal layer 100 may contain a heat seal resin other than the polyolefin resin (B). Examples of such a heat seal resin include polyester resins, polyvinyl chloride resins, polyamide resins, polystyrene resins, and polycarbonate resins, and the resin is selected appropriately depending on the molding temperature, etc.

[0029] From the viewpoint of adhesion to the molded article, the content of polyolefin resin (B) in the heat-seal layer 100 is preferably 35% by mass or more, more preferably 45% by mass or more, and even more preferably 50% by mass or more. The content of polyolefin resin (B) in the label may be 100% by mass, or may be 95% by mass or less, or may be 80% by mass or less. Furthermore, the content of polyolefin resin (B) relative to the entire heat-seal resin in the heat-seal layer 100 is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. The content of polyolefin resin (B) relative to the entire heat-seal resin may be 100% by mass.

[0030] (Filler) The heat seal layer may contain a filler to adjust the rigidity, whiteness, and opacity of the label. Examples of fillers include inorganic fillers and organic fillers, which may be used alone or in combination. When a heat seal layer containing a filler is stretched, a large number of fine pores centered on the filler can be formed in the heat seal layer, resulting in whitening, opacity, and weight reduction. Furthermore, when the heat seal layer is a stretched porous heat seal layer having pores, the heat insulation of the label is improved. Therefore, when a labeled molded article is formed, the heat of the polyolefin resin (A) heated for molding can be utilized to melt the polyolefin resin (B) without losing heat, which tends to improve adhesive strength.

[0031] Examples of inorganic fillers include heavy calcium carbonate, light calcium carbonate, calcined clay, talc, diatomaceous earth, titanium oxide, zinc oxide, barium sulfate, silicon oxide, magnesium oxide, and inorganic particles surface-treated with fatty acids, polymer surfactants, antistatic agents, etc. Among these, heavy calcium carbonate, light calcium carbonate, calcined clay, and talc are preferred because they have good pore formability and are inexpensive. From the viewpoint of improving whiteness and opacity, titanium oxide, zinc oxide, and barium sulfate are preferred.

[0032] The organic filler is not particularly limited, but is preferably an organic particle that is incompatible with the polyolefin resin, has a melting point or glass transition temperature higher than that of the polyolefin resin, and is finely dispersed under the melt-kneading conditions of the polyolefin resin. Examples of organic fillers include organic particles of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polyamide, polycarbonate, polyethylene sulfide, polyphenylene sulfide, polyimide, polyether ketone, polyether ether ketone, polymethyl methacrylate, poly-4-methyl-1-pentene, homopolymers of cyclic olefins, and copolymers of cyclic olefins and ethylene. Furthermore, fine powders of thermosetting resins such as melamine resins may also be used, and it is also preferable to crosslink the polyolefin resin to make it insoluble. The melting point (°C) and glass transition temperature (°C) of the resin can be measured by differential scanning calorimetry (DSC).

[0033] The inorganic filler and the organic filler may be selected from the above and used alone or in combination of two or more thereof. When two or more thereof are combined, the combination may be a combination of an inorganic filler and an organic filler.

[0034] The average particle size of the inorganic filler and the average dispersed particle size of the organic filler are preferably large from the viewpoint of ease of mixing with the polyolefin resin. Furthermore, when voids are generated inside by stretching to improve opacity and printability, the average particle size of the inorganic filler and the average dispersed particle size of the organic filler are preferably small from the viewpoint of preventing problems such as label tearing and a decrease in surface layer strength during stretching. Specifically, the average particle size of the inorganic filler and the average dispersed particle size of the organic filler are preferably 0.01 μm or more, more preferably 0.1 μm or more, and even more preferably 0.5 μm or more. Furthermore, the average particle size of the inorganic filler and the average dispersed particle size of the organic filler are preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less.

[0035] The average particle size of the inorganic filler can be measured as the particle size corresponding to 50% of the total (cumulative 50% particle size) measured using a particle measuring device, for example, a laser diffraction particle measuring device (Microtrac, manufactured by Nikkiso Co., Ltd.) The average dispersed particle size of the organic filler can be determined by observing a cut surface of the label with an electron microscope, measuring the maximum diameters of at least 10 particles, and calculating the average value as the average dispersed particle size when dispersed in a polyolefin-based resin by melt-kneading and dispersion.

[0036] The content of the filler in the heat seal layer is preferably 15% by mass or more, more preferably 25% by mass or more, and even more preferably 30% by mass or more, because this makes it easy to impart opacity to the label. When opacity of the label is unnecessary or when opacity can be ensured by a layer other than the heat seal layer, the content of the filler in the heat seal layer may be less than 15% by mass, or even 0% by mass. From the viewpoint of imparting rigidity to the label and improving its handleability, the content of the filler in the heat seal layer is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less.

[0037] (Other Components) In the present invention, the heat seal layer may optionally contain known additives as needed. Examples of additives include known auxiliaries such as antioxidants, light stabilizers, UV absorbers, crystal nucleating agents, plasticizers, filler dispersants, slip agents such as fatty acid amides, antiblocking agents, dyes, pigments, release agents, and flame retardants. In particular, when durability is required for labeled molded articles, such as for outdoor use, it is preferable to include antioxidants, light stabilizers, and the like. The content of these additives may be, for example, 0.001 to 5% by mass. The content of the additives may be adjusted appropriately as long as it does not impair the functions of the label and the heat seal layer.

[0038] The heat seal layer may have a single-layer structure or a multi-layer structure. The heat seal layer preferably has a multi-layer structure in which each layer has its own unique properties. For example, the heat seal layer may have a two-layer structure of base layer / surface layer, or a three-layer structure of surface layer / base layer / surface layer, in which the base layer can provide the rigidity, opacity, lightness, etc., suitable for labels. When the heat seal layer has the above-mentioned three-layer structure, the two surface layers may be formed from the same or different materials. For example, by making one surface layer suitable for printing and the other surface layer suitable for adhesion to a molded body or separation from the molded body during recycling, a label suitable for use as a label can be obtained. Furthermore, by appropriately designing the composition, thickness, etc. of one surface layer and the other surface layer, curling of the seal can be prevented.

[0039] The thickness of the heat seal layer is preferably 2 μm or more, more preferably 4 μm or more, even more preferably 10 μm or more, even more preferably 30 μm or more, and particularly preferably 50 μm or more, from the viewpoint of easily obtaining the desired mechanical strength and adhesiveness. Furthermore, the thickness of the heat seal layer is preferably 200 μm or less, more preferably 150 μm or less, from the viewpoint of easily reducing the weight of the label and improving handleability.

[0040] (Porosity) When the heat-seal layer has pores inside, the porosity, which represents the proportion of pores in the heat-seal layer, is preferably 15% or more, more preferably 20% or more, even more preferably 30% or more, and particularly preferably 35% or more, from the viewpoint of obtaining opacity. From the viewpoint of maintaining mechanical strength, the porosity is preferably 60% or less, more preferably 50% or less, even more preferably 45% or less, and particularly preferably 40% or less. When opacity is not required for the label, or when opacity can be ensured by a non-heat-seal layer (a layer other than the heat-seal layer) described later, the porosity of the heat-seal layer may be less than 15%, 10% or less, or 0% (i.e., it may not have pores inside).

[0041] The porosity can be measured by determining the area ratio of pores in a certain region of the cross section of the heat seal layer observed with an electron microscope. Specifically, an arbitrary portion of the heat seal layer is cut out, embedded in epoxy resin, and solidified. Then, the heat seal layer is cut perpendicular to the surface direction using a microtome, and the cut surface is attached to an observation sample stage so that the observation surface is the surface. Gold, gold-palladium, or the like is vapor-deposited on the observation surface, and the pores are observed at an arbitrary magnification (e.g., 500x to 3000x) that is easy to observe with an electron microscope. The observed region is captured as image data. The obtained image data is processed using an image analyzer to determine the area ratio (%) of the pores, which can then be used as the porosity (%). In this case, the porosity can be determined by averaging the measured values ​​from observations of 10 or more arbitrary locations.

[0042] (Method for producing heat seal layer) The heat seal layer can usually be obtained by mixing the polyolefin resin and other components to be contained in the heat seal layer and then molding the mixture. The method for molding the heat seal layer is not particularly limited, and various known molding methods can be used alone or in combination to produce the heat seal layer.

[0043] The heat seal layer can be formed into a film by, for example, cast molding in which a molten resin is extruded into a sheet using a single-layer or multi-layer T-die, I-die, etc. connected to a screw-type extruder, calendar molding, roll molding, inflation molding, etc. The heat seal layer may also be formed by cast molding or calendar molding a mixture of a polyolefin resin and an organic solvent or oil, and then removing the solvent or oil.

[0044] Examples of molding methods for forming a heat seal layer into a multilayer structure include a multilayer die method using a feed block or a multi-manifold, and an extrusion lamination method using multiple dies, and these methods can also be combined.

[0045] The heat seal layer may be unstretched or stretched. Examples of stretching methods include longitudinal stretching using the difference in peripheral speed between rolls, transverse stretching using a tenter oven, sequential biaxial stretching using a combination of these, rolling, simultaneous biaxial stretching using a tenter oven and a pantograph, and simultaneous biaxial stretching using a tenter oven and a linear motor. Also usable is simultaneous biaxial stretching (inflation molding) in which a molten resin is extruded into a tubular shape using a circular die connected to a screw extruder, and then air is blown into the extruded tubular shape.

[0046] When the heat seal layer has a multi-layer structure, it is preferable that at least one of the layers is stretched. When stretching multiple layers, each layer may be stretched individually before lamination, or may be stretched collectively after lamination. Furthermore, a stretched layer may be stretched again after lamination.

[0047] When the polyolefin resin used in the heat seal layer is an amorphous resin, the stretching temperature is preferably in the range of not less than the glass transition temperature of the polyolefin resin. When the polyolefin resin is a crystalline resin, the stretching temperature is preferably in the range of not less than the glass transition temperature of the amorphous part of the polyolefin resin and not more than the melting point of the crystalline part of the polyolefin resin, specifically, a temperature 2 to 60°C lower than the melting point of the polyolefin resin is preferred.

[0048] The stretching speed of the heat-sealable layer is not particularly limited, but is preferably within the range of 20 to 350 m / min from the viewpoint of stable stretching. The stretching ratio when stretching the heat-sealable layer can also be appropriately determined taking into account the properties of the polyolefin resin used. For example, when a heat-sealable layer containing a propylene homopolymer or a copolymer thereof is stretched in one direction, the stretching ratio typically has a lower limit of about 1.2 times, preferably 2 times, and an upper limit of 12 times, preferably 10 times. On the other hand, when biaxially stretching, the stretching ratio, in terms of areal stretching ratio, typically has a lower limit of 1.5 times, preferably 10 times, and an upper limit of 60 times, preferably 50 times.

[0049] (Surface Treatment) From the viewpoint of enhancing adhesion to the adhesive force adjusting region, the heat seal layer is preferably subjected to a surface treatment to activate the surface. Examples of the surface treatment include corona discharge treatment, flame treatment, plasma treatment, glow discharge treatment, ozone treatment, etc., and these treatments can be combined. Among these, corona discharge treatment or flame treatment is preferred, and corona treatment is more preferred.

[0050] (Substrate Layer) The substrate layer imparts physical strength, whiteness, opacity, etc. to the label, and can also impart water resistance and durability. Examples of the substrate layer include a pulp paper layer, a nonwoven fabric layer, and a high-melting-point resin layer. Examples of lamination methods for the substrate layer and the heat-sealing layer include dry lamination and melt lamination. The melting point of the high-melting-point resin is assumed to be, for example, 40°C or more higher than the melting point of the resin contained as the main component of the polyolefin resin (A) of the molded article. That is, when the polyolefin resin (A) contains a polypropylene resin as the main component, the melting point of the high-melting-point resin of the substrate layer is preferably above 200°C, more preferably above 220°C. Furthermore, when the polyolefin resin (A) contains a polyethylene resin as the main component, the melting point of the high-melting-point resin is preferably above 160°C, more preferably above 180°C. Examples of such high-melting-point resins include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polypropylene resins, polyimide resins, polyamide resins, polycarbonate resins, etc. The thickness of the substrate layer is designed so that the thickness of the label falls within a suitable range.

[0051] (Adhesion Adjustment Region) The adhesion adjustment region contains a self-polymerization reaction product having a polar group (a) and can adjust the adhesive strength between the heat seal layer and the molded article. A self-polymerization reaction product having a polar group (a) easily reduces the adhesive strength between the heat seal layer and the molded article. The self-polymerization reaction product having a polar group (a) is preferably a self-polymerization reaction product of a silane coupling agent, which is a self-polymerizable compound having a polar group (a). A labeled molded article of this embodiment, which has such an adhesion adjustment region on the adhesive side of the heat seal layer (the side attached to the molded article), facilitates peeling of the label along the main surface during a crushing process or the like during recycling. The adhesion adjustment region may be formed continuously or intermittently in a layer on the molded-side main surface of the heat seal layer. That is, the adhesion adjustment region may be a layer having the same shape as the main surface of the heat seal layer and a predetermined thickness, or may have any number of discontinuous adhesion adjustment regions each having a predetermined area rather than covering the entire main surface of the heat seal layer.

[0052] The adhesive force adjusting region preferably further contains a polymer having a polar group (b). The polar group (b), together with the polar group (a), tends to reduce the adhesive strength between the heat seal layer and the molded article. The polar group (b) is preferably a group capable of reacting with the polar group (a).

[0053] The adhesive force adjustment region can be formed, for example, by applying an aqueous solution of a polymer having a polar group (b) and a self-polymerizing compound containing a polar group (a) to one main surface of the heat seal layer, followed by drying. Here, the reaction rate of the reactive groups in the coating solution does not have to be 100%. That is, the adhesive force adjustment region may contain unreacted substances in addition to the resin reactant (reaction product). The aqueous solution used for the above coating can be obtained by mixing a polymer having a polar group (b), a self-polymerizing compound having a polar group (a), and an aqueous solvent, and then stirring. This aqueous solution may also be obtained by mixing an aqueous solution of a polymer having a polar group (b) with an aqueous solution of a self-polymerizing compound containing a polar group (a). The unreacted components and reactants in the adhesive force adjustment region can be confirmed by time-of-flight secondary ion mass spectrometry (TOF-SIMS).

[0054] (Self-polymerization reaction product containing polar group (a)) In the adhesive strength adjusting region, the self-polymerization reaction product containing polar group (a) is contained as a self-polymerization reaction product of a self-polymerizable compound containing polar group (a). By containing the polar group (a), the adhesive strength between the label and the molded product can be adjusted.

[0055] The self-polymerization reaction product containing the polar group (a) is preferably a self-polymerization reaction product of a silane coupling agent containing the polar group (a). The silane coupling agent has a plurality of silanol groups, which can condense and self-polymerize to form the self-polymerization reaction product. The polar group (a) is preferably capable of reacting with the polar group (b).

[0056] Specifically, the silane coupling agent can be a silane coupling agent having, in the molecule, an alkoxysilyl group or a silanol group formed by hydrolysis of the alkoxysilyl group, and at least one group other than a silanol group, such as an epoxy group, a vinyl group, a (meth)acrylic group, an amino group, a ureido group, a mercapto group, or an isocyanate group, as the polar group (a).From the viewpoint of reactivity with the polar group (b), the polar group (a) is preferably an epoxy group or an amino group.In addition, the term "(meth)acrylic" refers to both acrylic and methacrylic.

[0057] It is also believed that the silane coupling agent undergoes a condensation reaction between the silanol groups and a part of the polyolefin resin (B) in the heat seal layer, while the polar groups (a) other than the silanol groups react with the polar groups (b) to crosslink, thereby enhancing the adhesion between the adhesive force adjusting region and the heat seal layer.

[0058] (Polymer having polar group (b)) The adhesive force adjustment region may further contain a polymer having a polar group (b). The adhesive force adjustment region may contain the polymer having the polar group (b) as a resin that is a reaction product with a self-polymerizing compound having a polar group (a). However, it is preferable that the adhesive force adjustment region contains a portion of the polymer having the polar group (b) as an unreacted product. This makes it even easier to adjust the adhesive force with the molded body.

[0059] Examples of the polar group (b) include an amino group, an ammonium salt structure, a carboxyl group, and a hydroxyl group. The polar group (b) is preferably an amino group or an ammonium salt structure. Examples of polymers having the polar group (b) include cationic water-soluble polymers, anionic water-soluble polymers, and nonionic water-soluble polymers.

[0060] When a cationic water-soluble polymer is used as the polymer having a polar group (b), the water solubility is sufficient to be such that the aqueous medium containing the cationic water-soluble polymer is in a solution state when preparing the coating liquid for the adhesive force adjusting region.

[0061] Examples of the polymer having the polar group (b) include (meth)acrylic polymers, ethyleneimine polymers, polyvinylpyrrolidone, and vinyl polymers, and one of these may be used alone or two or more may be used in combination. Among these, (meth)acrylic polymers or ethyleneimine polymers are preferred from the viewpoints of adhesion to the heat seal layer and wetting and spreading.

[0062] The polymer having the polar group (b) preferably has a tertiary amino group or an ammonium salt structure from the viewpoint of increasing the number of unreacted polar groups (b) and adjusting the adhesive strength with the molded article. Furthermore, from the viewpoint of obtaining a resin with a high degree of crosslinking by the reaction with the silane coupling agent and easily inhibiting physical contact between the heat sealing resin and the molding resin during molding, the polymer having the polar group (b) preferably has a primary or secondary amino group or an ammonium salt structure, more preferably a primary amino group or an ammonium salt structure.

[0063] Examples of ethyleneimine-based polymers include polyethyleneimine, poly(ethyleneimine-urea), ethyleneimine adducts of polyamine polyamides, alkyl-modified products thereof, cycloalkyl-modified products thereof, aryl-modified products thereof, allyl-modified products thereof, aralkyl-modified products thereof, benzyl-modified products thereof, cyclopentyl-modified products thereof, alicyclic hydrocarbon-modified products thereof, glycidol-modified products thereof, and hydroxides thereof. Examples of modifiers for obtaining modified products include methyl chloride, methyl bromide, n-butyl chloride, lauryl chloride, stearyl iodide, oleyl chloride, cyclohexyl chloride, benzyl chloride, allyl chloride, cyclopentyl chloride, and the like.

[0064] From the viewpoint of heat resistance, the (meth)acrylic polymer or ethyleneimine polymer having an amino group or an ammonium salt structure has a weight-average molecular weight of preferably 10,000, more preferably 20,000, and more preferably 1,000,000, and more preferably 20,000. On the other hand, the weight-average molecular weight has an upper limit of preferably 1,000,000, more preferably 500,000. The weight-average molecular weight and number-average molecular weight of the resin can be obtained by converting values ​​measured by Gel Permeation Chromatography (GPC) into polystyrene equivalents.

[0065] The coating liquid forming the adhesive force adjusting region may contain a polymer other than the polymer having the polar group (b) as long as the effects of the present invention are not significantly impaired. For example, the adhesive force adjusting region may contain a polymer that does not have a polar group such as the polar groups (a) and (b) and has heat-sealing properties, such as a melting point. This allows for adjustment to increase the adhesive strength with the molded body. Examples of such resins include ethylene-(meth)acrylic acid copolymers. However, from the viewpoint of maintaining the function of reducing adhesive strength, the content of the above polymer in the adhesive force adjusting region is preferably 10% by mass or less, more preferably 9% by mass or less, and even more preferably 5% by mass or less.

[0066] The amounts of the polymer having a polar group (b) and the self-polymerizing compound containing a polar group (a) in the coating liquid may be such that a coupling reaction between the polymer having a polar group (b) and the self-polymerizing compound containing a polar group (a) proceeds, and it is preferable that the amount of unreacted components of either is small.

[0067] From the above, the coating liquid preferably contains 15 to 35% by mass of the self-polymerizable compound containing the polar group (a) relative to 100% by mass of the polymer having the polar group (b), more preferably 15 to 30% by mass, and even more preferably 17 to 25% by mass. That is, the content of the self-polymerizable compound component (unreacted and reacted) containing the polar group (a) in the adhesive force adjustment region is preferably 15 to 35% by mass, more preferably 15 to 30% by mass, and even more preferably 17 to 25% by mass relative to the polymer component having the polar group (b) in the adhesive force adjustment region. Within this range, the coating liquid does not aggregate due to a crosslinking reaction and become gel-like, making it possible to stably apply the adhesive force adjustment region.

[0068] The coating liquid may contain other auxiliary components such as an antistatic agent, a crosslinking accelerator, an antiblocking agent, a pH adjuster, an antifoaming agent, etc., as needed. That is, the adhesion adjusting region may contain other auxiliary components such as an antistatic agent, a crosslinking accelerator, an antiblocking agent, a pH adjuster, an antifoaming agent, etc., as needed.

[0069] (Method for forming an adhesive force adjustment region) As described above, the adhesive force adjustment region can be produced by applying the above-described coating liquid to one main surface of the heat seal layer and then drying it. The adhesive force adjustment region can also be produced by roll-to-roll production to improve productivity. The adhesive force adjustment region can be produced so that the adhesion between the heat seal layer and the molded product in the labeled molded product falls within a desired range by adjusting the amount and location of application of the coating liquid.

[0070] The coating solution can be prepared by dissolving each component, such as a cationic water-soluble polymer and a silane coupling agent, in an aqueous solvent. The aqueous solvent may be water, or may contain water as the main component and a water-soluble organic solvent, such as methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone, methyl ethyl ketone, ethyl acetate, toluene, or xylene. "Containing water as the main component" means that 50% by mass or more of the total is water. Using an aqueous solvent facilitates process control and is also preferred from the viewpoint of safety.

[0071] The total amount of the self-polymerizable compound having a polar group (a) and the polymer having a polar group (b) contained in the coating solution is preferably 0.5% by mass or more, more preferably 10% by mass or more, based on the total amount of the coating solution. The total amount of the self-polymerizable compound having a polar group (a) and the polymer having a polar group (b) contained in the coating solution is preferably 40% by mass or less, more preferably 25% by mass or less.

[0072] The application of the coating liquid and the drying of the coating film may be carried out inline in accordance with the formation of the heat-seal layer, or may be carried out offline. The coating liquid can be applied using a coating device such as a die coater, bar coater, roll coater, lip coater, gravure coater, spray coater, blade coater, reverse coater, or air knife coater. The amount of the coating liquid to be applied can be appropriately adjusted taking into account the thickness of the adhesive strength adjustment region after drying, the concentration of the contained components, and the like.

[0073] The coating film can be dried using a drying device such as a hot air blower or an infrared dryer. It is presumed that drying the coating film advances a dehydration condensation reaction of the self-polymerizable compound having the polar group (a) in the coating film, producing a self-polymerization reaction product having the polar group (a), and further producing a resin that is a reaction product of the self-polymerizable compound having the polar group (a) and a polymer having the polar group (b).

[0074] The mass per unit area of ​​the component (solid content) contained in the adhesive force adjusting region after drying, i.e., the "basis weight of the adhesive force adjusting region", is 0.002 g / m from the viewpoint of easily adjusting the adhesive force between the heat seal layer and the molded body. ２ More than 0.01 g / m ２ More preferably, 0.02 g / m or more ２ The basis weight of the adhesive force adjusting region is more preferably 0.05 g / m ２ From the viewpoint that the heat seal layer and a part of the molded article are in contact with each other on the main surface of the heat seal layer facing the molded article without the adhesive force adjusting region therebetween, and the adhesive force is easily increased and maintained at an appropriate level, the basis weight of the adhesive force adjusting region may be 1 g / m or more. ２ Preferably, 0.5 g / m or less ２More preferably, 0.2 g / m or less ２ The adhesive force adjusting region has a basis weight of 0.1 g / m ２ It may be the following:

[0075] (Other Layers, etc.) As shown in Figure 2, the label to be attached to the molded product may have a non-heat-sealable layer that does not have heat-sealability, in addition to the heat-sealable layer and adhesive force adjusting region described above. By having the label have a non-heat-sealable layer, the label shape during molding can be stabilized, and a labeled molded product with a better appearance can be obtained. The non-heat-sealable layer may have other layers such as a support layer and an ink-receiving layer. The other layer can be laminated on the main surface of the heat-sealable layer opposite the adhesive force adjusting region.

[0076] The non-heat-sealable layer is preferably a layer that does not melt during molding. Examples of such non-heat-sealable layers include a cured resin layer, a high-melting-point resin layer, and a paper (pulp) layer. The high-melting-point resin layer preferably contains a high-melting-point resin having a melting point 30°C or more higher than that of the polyolefin-based resin (B) contained in the heat-sealable layer. The melting point of the high-melting-point resin may be 40°C or more higher, or even 50°C or more higher than that of the polyolefin-based resin (B). Examples of such high-melting-point resins include fluorine-based resins, polyamide-based resins, polyester-based resins, polycarbonates, and polystyrenes. The lamination method for the non-heat-sealable layer is not particularly limited, and known methods such as dry lamination or wet lamination using an adhesive, hot-melt lamination, and extrusion molding similar to that for the heat-sealable layer can be applied.

[0077] (Label Thickness) From the viewpoint of suppressing wrinkles on the label, the thickness of the label is preferably 25 μm or more, more preferably 45 μm or more, and even more preferably 60 μm or more. Furthermore, from the viewpoint of easily embedding the periphery of the label with the polyolefin resin (A) constituting the molded product during production of the labeled molded product, the thickness of the label is preferably 200 μm or less, more preferably 150 μm or less. When the label has a non-heat-sealable layer, the thickness of the non-heat-sealable layer is appropriately set so that the thickness of the entire label is within the above range.

[0078] (Printed Layer) The label preferably includes a printed layer. The printed layer is a layer provided by printing on the side of the label opposite the adhesive strength adjustment area. Examples of printed information on the printed layer include product names, product indications such as logos, manufacturer names, sales company names, usage instructions, barcodes, etc. Examples of printing methods for forming the printed layer include gravure printing, offset printing, flexographic printing, seal printing, and screen printing.

[0079] (Molded Article) The molded article contains a polyolefin resin (A). When the heat seal layer and the molded article both contain a polyolefin resin as a labeled molded article, high adhesion can be easily achieved at the contact area between the heat seal layer and the molded article. Examples of the polyolefin resin (A) that can be used include the same polyolefin resin (B). From the viewpoint of adhesiveness, the polyolefin resin (A) is preferably the same type of resin as the polyolefin resin (B). For example, when the polyolefin resin (B) contains a polypropylene resin, the polyolefin resin (A) is preferably a polypropylene resin. Furthermore, when the polyolefin resin (B) contains a polyethylene resin, the polyolefin resin (A) is preferably a polyethylene resin. The color and shape of the molded article are not particularly limited, and any suitable shape can be used depending on the molding method.

[0080] [Method for Manufacturing Labeled Molded Articles] Labeled molded articles can be manufactured using a method comprising the steps of: providing an adhesive strength adjustment region in a heat-seal layer containing a heat-seal resin to obtain a label; and placing the label on a mold so that the adhesive strength adjustment region faces the resin injection side of the mold, and injecting molding resin into the mold to obtain a labeled molded article with the label affixed to the molded article. The injection molding step, as in the embodiment, makes it easy to obtain labeled molded articles in which the label is in contact with the molded article even on the side of the heat-seal layer. In the injection molding step, molding resin with a melting point of the heat-seal resin of (Mps + 35)°C or higher and (Mps + 150)°C or lower is injected at a pressure of 20 to 70 MPa, where Mps is the melting point of the heat-seal resin.

[0081] The heat-sealing resin used in the label production process contains a polyolefin resin (B). The polyolefin resin (B) may be any of the resins listed above for the polyolefin resin (B) in the heat-sealing layer. The adhesive strength adjustment region may be formed by the method described above for forming an adhesive strength adjustment region.

[0082] In the injection molding process, before the molding resin is injected, the label is placed in a predetermined position on one of the molds so that the side with the adhesive strength adjustment region faces the side where the resin is injected.Then, the open surface of the other mold is closed, and the molding resin is injected into the mold through a gate to form a labeled molded product.

[0083] The pressure when injecting the molding resin is preferably 20 MPa or more and 70 MPa or less. When the injection pressure of the molding resin is 20 MPa or more, the resin is more likely to be injected along the shape of the label, making it easier for the molded body and the side of the heat seal layer in the labeled molded body to come into contact. From the same perspective, the injection pressure of the molding resin is more preferably 30 MPa or more, and particularly preferably 35 MPa or more. Furthermore, when the injection pressure of the molding resin is 70 MPa or less, excessive stress is less likely to be applied to the label.

[0084] The temperature of the injected resin in the injection molding process is set to be (Mps + 35)°C or higher and (Mps + 150)°C or lower. Mps is the melting point of the heat-seal resin. By setting the temperature of the injected resin at (Mps + 35)°C or higher, the resin is more easily injected along the shape of the label, and the molded body and the side of the heat-seal layer in the labeled molded body are more likely to come into contact with each other. From the same perspective, the temperature of the injected resin is preferably (Mps + 50)°C or higher, and particularly preferably (Mps + 65)°C or higher. By setting the temperature of the injected resin at (Mps + 150)°C or lower, deterioration of the resin can be suppressed.

[0085] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. In the examples, "parts", "%", and the like are based on mass unless otherwise specified.

[0086] Example 1 A label having a heat seal layer and an adhesive strength adjusting region was obtained by the following procedure, and then the label was attached to a molded article by injection molding to obtain a labeled molded article.

[0087] Preparation Example 1 A reactor having an internal volume of 150 L, equipped with a reflux condenser, a nitrogen inlet tube, a stirrer, a thermometer, a dropping funnel, and a heating jacket, was charged with 40 kg of isopropanol (manufactured by Tokuyama Corporation, product name: Tokuso IPA). While stirring, 12.6 kg of N,N-dimethylaminoethyl methacrylate (manufactured by Sanyo Chemical Industries, Ltd., product name: Methacrylate DMA), 12.6 kg of butyl methacrylate (manufactured by Mitsubishi Rayon Co., Ltd., product name: Acrylate B), and 2.8 kg of a higher alcohol methacrylate ester (manufactured by Mitsubishi Rayon Co., Ltd., product name: Acrylate SL, a mixture of lauryl methacrylate and tridecyl methacrylate) were introduced into the reactor. Next, the system was purged with nitrogen, and the temperature inside the reactor was raised to 80°C. Then, 0.3 kg of 2,2'-azobisisobutyronitrile (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product name: V-60 (AIBN)) was introduced into the reactor as a polymerization initiator.

[0088] The copolymerization reaction was carried out by continuing stirring for 4 hours while maintaining the temperature inside the reactor at 80 ° C. Next, after cooling to room temperature, 4.3 kg of glacial acetic acid (manufactured by Fujifilm 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 concentration 35 mass %) of a methacrylic acid-based copolymer (having no melting point, weight average molecular weight 40,000) having a tertiary amino group in the side chain as the polar group (b) was obtained.

[0089] (Preparation of resin composition a1) As a resin composition for forming a base layer, 80 mass% of a propylene homopolymer (trade name: Novatec PP FY4, manufactured by Japan Polypropylene Corporation) and 20 mass% of heavy calcium carbonate (trade name: Softon 1800, manufactured by Bihoku Funka Kogyo Co., Ltd.) were blended and stirred and mixed in a mixer to obtain a resin composition a1.

[0090] (Preparation of resin composition b1) As a resin composition for forming a surface layer, 50% by mass of propylene homopolymer (trade name: Novatec PP MA3, manufactured by Japan Polypropylene Corporation), 5% by mass of high-density polyethylene (trade name: Novatec HD HJ360, manufactured by Japan Polyethylene Corporation), and 45% by mass of heavy calcium carbonate (trade name: Softon 1800, manufactured by Bihoku Funka Kogyo Co., Ltd.) were blended and stirred and mixed in a mixer to obtain resin composition b1.

[0091] (Preparation of Coating Liquid 1) As a coating liquid for forming an adhesion adjusting region, an aqueous solution (Coating Liquid 1) was obtained containing 17.6 mass% of a silane coupling agent having an epoxy group as the polar group (a) (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.), 41.2 mass% (solid content equivalent) of polyethyleneimine having primary to tertiary amino groups as the polar group (b) (trade name: Polymin SK, manufactured by BASF Japan), and 41.2 mass% (solid content equivalent) of a methacrylic acid copolymer (Preparation Example 1) having a tertiary amino group as the polar group (b). The materials used in Coating Liquid 1 are shown in Table 1 below.

[0092]

[0093] (Label Production) Resin composition a1 was melt-kneaded in an extruder set at 250° C., extruded into a sheet through a die, and cooled to 70° C. in a cooling device to obtain a single-layer unstretched sheet. This unstretched sheet was reheated to 145° C. and then stretched 5 times in the longitudinal direction by utilizing the difference in peripheral speed between multiple rolls to obtain a longitudinal uniaxially stretched film.

[0094] Resin composition b1 was melt-kneaded in an extruder set at 250 ° C, extruded into a sheet, and laminated on one side of the longitudinally uniaxially stretched film to obtain a two-layer sheet. The obtained two-layer sheet was reheated to 158 ° C in an oven, then stretched 9 times in the transverse direction using a tenter stretcher and heat-treated at 170 ° C to obtain a laminated resin sheet. The laminated resin sheet had a total thickness of 80 μm, and each layer laminated in the order of base layer / surface layer had a resin composition of a1 / b1, biaxial / uniaxial stretching axis number, thickness of 63 μm / 17 μm, and porosity of 35% / 24%, respectively. The base layer and surface layer are both layers (heat seal layers) that exhibit heat sealability in the following injection molding.

[0095] 30 W·min / m on the surface of the outer layer of the laminated resin sheet ２ After corona discharge treatment under the conditions of ２ The coating liquid 1 was applied by a roll coater so that the thickness of the laminated resin film became as follows: The coated laminated resin film was placed in an oven at 60°C to dry the coating liquid and form an adhesive strength adjustment region, thereby obtaining a label.

[0096] (Injection molding) An injection molding machine (Niigata Iron Works Co., Ltd., model: NV50ST, clamping force: 50 tons, vertical arrangement) and a split mold for injection molding were used, which produced a resin molded body in a flat plate measuring 130 mm wide, 150 mm long, and 1 mm thick. The label obtained above was cut to a size of 55 mm wide and 90 mm long and fixed to the surface of a female mold attached to the lower fixed platen side so that the base layer side was in contact with the mold (with the adhesive strength adjustment region layer facing the cavity). The split mold was then clamped, and a molten propylene homopolymer (Novatec PP MA3, manufactured by Japan Polypropylene Corporation, melting point: 165°C) was injected into the mold through the gate at a pressure of 45 MPa using an injection device set at 240°C. The molten resin was cooled and solidified, and the label was attached, and then the mold was opened to obtain a flat polypropylene injection-molded article with a label attached (labeled molded article of Example 1).

[0097] Example 2 A labeled molded article of Example 2 was obtained in the same manner as in Example 1, except that Coating Liquid 2 was used instead of Coating Liquid 1.

[0098] [Examples 3 and 4] Labeled molded articles of Examples 3 and 4 were obtained in the same manner as in Example 1, except that Coating Liquid 1 was applied so that the basis weight of the adhesive force adjustment region was as shown in Table 2.

[0099] Example 5 A labeled molded article of Example 5 was obtained in the same manner as in Example 1, except that the molding temperature in injection molding was set to the temperature shown in Table 2.

[0100] [Example 6] A labeled molded article of Example 6 was obtained in the same manner as in Example 1, except that the following resin composition b2 was used for the surface layer of the heat seal layer instead of resin composition b1. (Preparation of resin composition b2) Resin composition b2 was obtained by using 100% by mass of metallocene polyethylene (product name: Harmolex NJ744N, manufactured by Japan Polyethylene Corporation) and stirring and mixing it in a mixer.

[0101] [Example 7] A labeled molded article of Example 7 was obtained in the same manner as Example 6, except that an injection machine set to 160°C was used in injection molding instead of an injection machine set to 240°C, and a low-density polyethylene (Novatec LD LJ802, manufactured by Japan Polyethylene Corporation) was used instead of a propylene homopolymer (Novatec LD LJ802, manufactured by Japan Polyethylene Corporation, product name: Novatec PP MA3, melting point: 165°C).

[0102] [Comparative Examples 1 and 2] Labeled molded bodies of Comparative Example 1 and Comparative Example 2 were obtained in the same manner as in Example 1, except that in Comparative Example 1, no adhesive strength adjustment region was provided, and in Comparative Example 2, an adhesive strength adjustment region was provided using a coating liquid 3 that did not contain a self-polymerization reaction product having a polar group (a).

[0103] Comparative Example 3 A labeled molded article of Comparative Example 3 was obtained in the same manner as in Example 1, except that the molding temperature in injection molding was set to the temperature shown in Table 2.

[0104] Comparative Example 4 A labeled molded article of Comparative Example 4 was obtained in the same manner as in Example 1, except that the labeled molded article was obtained by the following blow molding instead of injection molding.

[0105] (Blow Molding) The resulting label was cut into sheets and punched into a rectangle measuring 55 mm wide and 90 mm long. The punched label was placed on one side of a blow molding mold capable of molding a resin container with a capacity of 0.4 L, with the heat seal layer (surface layer) facing the cavity, and fixed to the mold using suction. A propylene homopolymer (trade name: Novatec PP EA9, manufactured by Japan Polypropylene Corporation, MFR (JIS K 7210 (1999)): 0.5 g / 10 min) was melted at 240°C and extruded into a parison between the molds. The temperature of the parison where the label was to be attached was set to 180°C. After clamping the mold, compressed air at 0.4 MPa was supplied into the parison, expanding it for 20 seconds to adhere it to the mold, forming a container shape and attaching the label. The molded product was then cooled in the mold and opened to obtain a labeled molded product of Comparative Example 4.

[0106] [Comparative Example 5] A labeled molded body of Comparative Example 5 was obtained in the same manner as in Comparative Example 4, except that resin composition b2 was used instead of resin composition b1 for the surface layer of the heat seal layer and no adhesive strength adjustment area was provided.

[0107] The labeled molded articles of the above Examples and Comparative Examples were evaluated as follows. The results are shown in Table 2.

[0108] (Contact Ratio) A cross section including the side surface S of the heat seal layer of the labeled molded article was observed using a digital microscope HRX-01 (manufactured by Hirox Co., Ltd.). A total of 16 cross sections were sampled, four from each of the four side surfaces S. The thickness of the heat seal layer in each cross section image and the length of the portion where the heat seal layer was embedded in the molded article and in contact were measured, and the average values ​​of the cross section images at all locations were taken as the thickness (a) of the heat seal layer and the length (b) of the portion where the heat seal layer was embedded in the molded article and in contact, respectively. The contact ratio was calculated as the ratio (b / a × 100) of the length (b) of the portion where the heat seal layer was embedded in the molded article and in contact with the heat seal layer to the thickness (a) of the heat seal layer.

[0109] (Adhesive Strength) Adhesive strength was measured using the following method. The labeled molded article was stored for two days in an environment at a temperature of 23°C and a relative humidity of 50%. Next, the labeled portion of the labeled molded article was cut out with a cutter to prepare a sample measuring 12 cm in the horizontal direction W and 1.5 cm in the height direction H (the horizontal direction W and the height direction H are indicated by arrows in Figure 4). The label and molded article were cut out as a single unit so that the labeled portion in the horizontal direction W was 8 cm and the non-labeled portion (grab margin) was 4 cm, and so that the label was attached across the entire width in the height direction H. A total of six samples were prepared from two molded articles.

[0110] Next, the adhered portion of the label was carefully peeled away from the non-adhered portion of the label, peeling for approximately 1 cm to form a gripping area. A 1.5 cm wide PET film (50 μm thick) was placed over the gripping area and adhered with an adhesive to form a gripping area on the label side. The sample with the gripping area formed was placed in a tensile tester (model: Autograph AGS-5kNJ, manufactured by Shimadzu Corporation). Using this tensile tester, a 180-degree peel test between the molded product and the label was conducted at a peel rate of 300 mm / min in accordance with JIS K6854-2:1999. The average peel force was measured over a peel length of 25 to 75 mm, and the average value obtained by averaging the measurements for six samples was used as the adhesive strength. The adhesive strength was measured in units of gf / 15 mm. Furthermore, if a portion of the heat seal layer remained attached to the molded product after peeling, it was considered to have undergone "cohesive failure."

[0111] FIG. 4 is a schematic diagram showing the measurement location of a sample for measuring adhesive strength, and is a diagram of a molded article 1 with a label 10 attached thereto, viewed from the main surface of the label 10. As shown by A in FIG. 4, the measurement was performed near the center of the label attached to the molded article. As shown by B in FIG. 4, the measurement was also performed so as to include the side surface S of the heat seal layer. Note that in the measurement including the side surface S shown by B in FIG. 4, only whether the peel mode was "cohesive failure" was evaluated. Whether or not "cohesive failure" occurred was determined by whether or not a part of the heat seal layer remained attached to the molded article after peeling.

[0112] (Trigger for Peeling) The labeled molded article was evaluated for trigger for peeling when peeled off by hand according to the following criteria: Evaluation criteria ◯: No trigger for peeling occurred and no peeling occurred. ×: Trigger for peeling occurred easily.

[0113] (Peeling Rate) The labeled portion of each labeled molded article of each Example and Comparative Example was cut out. The mass (Ta) of the cut out labeled molded article was measured. This labeled portion was crushed into flakes using a crusher (manufactured by Morita Seiki Kogyo Co., Ltd., product name: XL-15, mesh screen size 8 mmφ) to prepare a sample for evaluation. Of the evaluation samples, the total mass (Tb) of the molded article and the label remaining on the molded article (that was not peeled off during the crushing process) was measured. Thereafter, the label was completely peeled off from the molded article, and the mass (B) of the remaining molded article was measured. The label peeling rate (%) was calculated from the mass of the label before crushing and the mass of the label peeled off after crushing using the following formula: Label peeling rate (%) = (Ta - Tb) / (Ta - B) × 100

[0114]

[0115] None of the labeled molded articles of Examples 1 to 7 peeled off when tried to be peeled off by hand, showing good adhesion during use, and the peeling rate during the crushing process also showed good results.

[0116] The labeled molded article of Comparative Example 1, which did not have an adhesive force adjustment region, had a low peel rate. The labeled molded article of Comparative Example 2, in which an adhesive force adjustment region was provided using Coating Liquid 3 that did not contain a self-polymerization reaction product having a polar group (a), had a low peel rate. The labeled molded articles of Comparative Example 3, which were molded at a temperature of 180°C, and Comparative Example 4, which were molded by blow molding, did not have the side of the heat seal layer in contact with the molded article, and when trying to peel them off by hand, the trigger for peeling was easily found, and sufficient adhesion during use was not obtained. The labeled molded article of Comparative Example 5 had strong adhesive strength of the label to the container and an extremely low peel rate.

[0117] REFERENCE SIGNS LIST 1 Molded body 10 Label 100 Heat seal layer 200 Adhesion control region 300 Base layer S Side of heat seal layer

Claims

1. A labeled molded product comprising a molded product and a label affixed to the molded product, wherein the label comprises a heat seal layer and an adhesive strength adjustment region located on the main surface of the heat seal layer facing the molded product, the label contacts the molded product at the side of the heat seal layer and the adhesive strength adjustment region, the molded product contains a polyolefin resin (A), the heat seal layer contains a polyolefin resin (B), and the adhesive strength adjustment region contains a self-polymerization reaction product having a polar group (a).

2. The labeled molded article according to claim 1, wherein at least a portion of the heat seal layer is attached to the molded article on the main surface of the heat seal layer facing the molded article without the adhesive strength adjustment region interposed therebetween.

3. The labeled molded article according to claim 1 or 2, wherein the adhesive strength adjusting region further contains a polymer having a polar group (b).

4. A labeled molded article according to claim 1 or 2, wherein the self-polymerization reaction product having the polar group (a) is a self-polymerization reaction product of a silane coupling agent having the polar group (a).

5. A labeled molded article according to claim 1 or 2, wherein the label is in contact with the molded article at a thickness of 55% or more of the thickness of the heat seal layer.

6. A labeled molded article according to claim 1 or 2, wherein the polyolefin resin (A) is a polypropylene resin, and the polyolefin resin (B) is a polypropylene resin.

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