JP7724142B2 - Label for molded product, labeled molded product, and method for manufacturing labeled molded product - Google Patents

Description

The present invention relates to labels for molded articles, labeled molded articles, and methods for manufacturing labeled molded articles.

Traditionally, food products have been sold in containers made of resins such as polyester in the food sections of supermarkets and convenience stores. For example, molded products such as container bodies and lids are used to package boxed lunches, prepared meals, eggs, etc. In particular, in recent years, the use of containers made of amorphous polyethylene terephthalate (A-PET) has been considered, with the aim of meeting required properties by reducing the liquid crystallinity of polyester to make it amorphous (non-crystalline).

For example, Patent Document 1 discloses a heat-resistant, transparent A-PET container for storing food, which is made by dry-laminating a laminated sheet obtained by heating an A-PET sheet, primarily stretching it, and then primarily heat-setting it, together with an unstretched A-PET film or unstretched A-PET sheet, and then heat-forming the laminated sheet in a mold of a thermoforming machine to enhance crystallization through secondary stretch-oriented crystallization caused by molding.

On the other hand, product labels (sometimes called "adhesive labels") are affixed to molded products such as containers to provide information such as place of origin, expiration date, and barcode, as well as decorative features such as decoration.

For example, Patent Document 2 discloses a thermoforming polyester sheet in which a copolymer polyester with a glass transition temperature of 85°C or less, or a blend resin containing such a polyester and other types of polyester, is arranged as a heat-seal layer on the inner surface of an amorphous linear saturated polyester resin base layer, and polybutylene terephthalate is compounded on the outer surface of the opposite layer to the heat-seal layer to prevent blocking.

JP 2009-280218 A Japanese Patent Application Publication No. 07-009645

However, there is still room for improvement in achieving both thermoformability and recyclability when it comes to labels for molded products that are affixed to the above-mentioned resin molded products.

For example, one method for producing labeled molded products in which the above-mentioned labels for molded products are affixed to molded products (e.g., various containers such as container bodies and lids) is to affix the labels for molded products using a labeling device or the like. In this regard, the inventors have also considered methods in which, when producing labeled molded products using a labeling device or the like, the labels for molded products are first affixed to a resin sheet for thermoforming to form a laminate, and then a thermoforming process is carried out to process and form this into the shape of the molded product. However, with conventional labels for molded products, even when such manufacturing methods are devised, it is still not possible to achieve a high level of both thermoformability and recyclability.

The present invention was made in light of the above circumstances, and its purpose is to provide a label for molded products, a labeled molded product, and a method for manufacturing a labeled molded product that can achieve high levels of both thermoformability and recyclability.

As a result of further intensive research to achieve the above-mentioned objective, the inventors discovered that a label for molded products could be made that includes a base layer containing an amorphous polyester film and a polyester-based adhesive layer provided on at least one surface of the base layer, and that has an initial adhesive strength of 1.0 N/25 mm or more, leading to the completion of the present invention.

In other words, the present invention is as follows:

(1)
The label for molded products comprises a base layer containing an amorphous polyester film and a polyester-based pressure-sensitive adhesive layer provided on at least one surface of the base layer, and has an initial adhesive strength of 1.0 N/25 mm or more as described below.
Initial adhesive strength: Adhesion strength measured in accordance with JIS Z0237:2009, in which a test piece of a label for molded products is attached to an amorphous polyester test plate while being pressed with a roller in an environment of 23°C, and the test piece is peeled off at an angle of 180° from the amorphous polyester test plate within 30 seconds of attachment at a peeling rate of 300 mm/min.
(2)
The label for molded products according to (1), wherein the amorphous polyester film has a heat shrinkage rate in the machine direction when treated at 100°C for 5 minutes of 2.0% or more and 5.0% or less.
(3)
The label for molded products according to (1) or (2), wherein the amorphous polyester film is an amorphous polyethylene terephthalate (A-PET) film.
(4)
The label for molded products according to any one of (1) to (3), further comprising a coating layer provided on the surface of the base layer opposite to the polyester-based pressure-sensitive adhesive layer.
(5)
The label for molded products is a label for molded products according to any one of (1) to (4), which is used by being attached to the surface of a molded product made of a resin containing an amorphous polyester resin.
(6)
The label for molded products according to any one of (1) to (5), wherein all of the resin layers constituting the label for molded products are polyester resin layers.
(7)
A labeled molded product includes a resin molded product containing an amorphous polyester resin, and the label for molded products according to any one of (1) to (6) attached to the surface of the molded product.
(8)
A method for producing a labeled molded product in which a label for a molded product is affixed to a molded product, the method comprising: (a) a labeling step in which labels for a molded product are continuously affixed at regular intervals to the surface of a long polyester resin sheet to obtain a labeled sheet for a molded product; (b) a thermoforming step in which a shape corresponding to the shape of the molded product is continuously formed into the labeled sheet for a molded product by thermoforming to obtain a container sheet; and (c) a cutting step in which the container sheet is divided into molded product units, wherein the labeled molded product is continuously produced by continuously performing at least steps (a) and (b), and the label for a molded product comprises a base layer containing an amorphous polyester film and a polyester-based pressure-sensitive adhesive layer provided on at least one surface of the base layer.

The present invention provides labels for molded products, labeled molded products, and methods for manufacturing labeled molded products that achieve high levels of both thermoformability and recyclability.

FIG. 1 is a cross-sectional view of a label with a release liner according to this embodiment. FIG. 2 is a partial cross-sectional view of a labeled molded product in which the label for molded products according to this embodiment is attached to the molded product. FIG. 3 is a partial schematic view illustrating the method for manufacturing a labeled molded product according to this embodiment.

The following describes in detail the form for carrying out the present invention (hereinafter simply referred to as the "present embodiment"). The following present embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be carried out with appropriate modifications within the scope of its gist.

In the drawings, identical elements will be given the same reference numerals, and duplicate explanations will be omitted. Furthermore, unless otherwise specified, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings. Furthermore, the dimensional ratios of the drawings are not limited to those shown.

In addition, in this specification, terms preceded by "abbreviation" indicate the meaning of the term excluding "abbreviation" within the scope of common technical knowledge of a person skilled in the art, and include the meaning itself excluding "abbreviation." Furthermore, in this specification, terms written as "film" may also be referred to as "sheet," etc., and vice versa.

Figure 1 is a cross-sectional view of a label with a release liner according to this embodiment.

The label 1 for molded products according to this embodiment includes a base layer 10 containing an amorphous polyester film and a polyester-based adhesive layer 12 provided on at least one surface of the base layer 10, and has an initial adhesive strength of 1.0 N/25 mm or more.

(Initial adhesive strength)

The initial adhesive strength of the label 1 for molded products in an initial adhesive strength test is 1.0 N/25 mm or more. The lower limit of the initial adhesive strength is preferably 5.0 N/25 mm or more, more preferably 7.0 N/25 mm or more, and even more preferably 8.0 N/25 mm or more. The upper limit of the initial adhesive strength is preferably 20.0 N/25 mm or less. By ensuring that the initial adhesive strength is at or above the above lower limit, problems that may occur when the label is attached to the molded product 30, such as label slippage and unintended peeling, can be prevented. Furthermore, in the manufacturing method for labeled molded product 3 described below, problems that may occur when labeling a polyester resin sheet for thermoforming, such as label slippage and unintended peeling, can be prevented, and subsequent thermoforming can be carried out stably. Furthermore, by ensuring that the initial adhesive strength is at or below the above upper limit, the label can be easily reattached, improving its convenience as a label.

The initial adhesive strength can be measured by the following method.
Initial adhesive strength: Adhesion strength measured in accordance with JIS Z0237:2009, in which a test piece of label 1 for molded products is attached to an amorphous polyester test plate while being pressed by a roller in an environment of 23°C, and the test piece is peeled off at an angle of 180° from the amorphous polyester test plate within 30 seconds of attachment at a peeling rate of 300 mm/min.

The amorphous polyester test plate used in the above measurement of initial adhesive strength is an amorphous polyethylene terephthalate (A-PET) plate. A 2 kg rubber roller is used for roller compression to press the test piece.

<Base material layer>

The substrate layer 10 includes an amorphous polyester film. Polyester is typically obtained by polycondensation of a polycarboxylic acid such as terephthalic acid and a polyol component such as ethylene glycol. However, amorphous (uncrystallized) polyester can also be obtained, for example, by rapidly cooling from a molten state. A specific example of how amorphous polyester film can be produced is by rapidly cooling with a cooling roll during sheet extrusion processing, thereby achieving an amorphous state and producing a film with high transparency, excellent thermoformability, etc.

Amorphous polyester film has high transparency and excellent thermoformability, so the label 1 for molded products according to this embodiment offers advantages such as high transparency, excellent thermoformability, good design, and excellent recyclability. For example, when recycling a resin molded product 30 that has outlived its usefulness, it is possible to recycle the labeled molded product 3 (e.g., various containers with labels) without removing the label 1 for molded products from the molded product 30.

Furthermore, if the molded product 30 is made from amorphous polyester resin, it is possible to further advance mono-materialization, further improving recyclability in particular. For example, if the molded product 30 is a container, polyester resins, especially amorphous polyester resins, are commonly used. However, the combination of materials for the label 1 for molded products and the molded product 30 is a combination of materials that are compatible with each other, further improving thermal processability and recyclability.

Furthermore, because of the good compatibility when the molded product 30 to which the label 1 for molded products is affixed is heated and melted, there is no need to separate the label 1 for molded products from the molded product 30; the label can be collected as a single unit and recycled. Furthermore, the properties of the recycled product are not compromised. These advantages contribute to the development of mono-materials, etc.

Furthermore, as will be described in more detail below, the label 1 for molded products according to this embodiment also offers advantages in terms of manufacturing process. When the label 1 for molded products uses an amorphous polyester film as the base layer 10, as described above, it is expected that molded products (such as labeled molded product 3) incorporating an attractive, transparent, amorphous label can be efficiently manufactured by, for example, first attaching the label 1 for molded products to a resin sheet for thermoforming to form a laminate, and then carrying out a thermoforming process to process and mold this into the shape of the molded product 30.

For example, a label 1 for molded products can be attached to a resin sheet for thermoforming in advance, and then thermoformed into the shape of a molded product 30 (such as a container). This improves productivity, provides high transparency, and provides good design. Furthermore, when recycling labeled molded products 3, it is possible to carry out the regeneration process without removing the label 1 for molded products attached to the molded product 30.

Examples of amorphous polyester films include amorphous polyethylene terephthalate (A-PET) films. Among these, amorphous polyethylene terephthalate (A-PET) films are preferred because they offer the advantages described above. Commercially available A-PET films can also be used, including the "NOACRYSTAL" series manufactured by RP Topla Co., Ltd. and the "Kanelon" series manufactured by Shin-ei Kasei Co., Ltd.

From the perspective of further enhancing the advantages of the mono-material and further improving the various effects described above, it is preferable that all of the resin layers constituting the label 1 for molded products be polyester resin layers, and it is even more preferable that all of them be amorphous polyester films.

The amorphous polyester film of the base layer 10 preferably has a heat shrinkage rate in the MD (machine direction) direction of 2.0% or more and 5.0% or less when treated at 100°C for 5 minutes. The lower limit of the heat shrinkage rate is more preferably 2.5% or more, and even more preferably 3.0% or more. The upper limit of the heat shrinkage rate is more preferably 4.5% or less, and even more preferably 4.0% or less. The heat shrinkage rate can be measured by the following method. First, the film to be measured is cut into a strip measuring 100 mm in the MD direction and 10 mm in the CD (cross direction) direction to prepare a sample piece. This sample piece is left unstrained in a gear oven maintained at 100°C for 5 minutes. It is then removed to room temperature, and the length (B) of the sample piece in the MD direction after heat treatment is determined. The thermal shrinkage rate can then be calculated as the difference ((A-B)/A (%)) between the MD length of the sample piece before treatment (A) and the MD length of the sample piece after treatment (B).

The substrate layer 10 may be any layer that contains at least an amorphous polyester film, and may be, for example, a single layer or a multi-layer structure consisting of two or more types of layers.

Even if the base layer 10 is composed of multiple layers, it is preferable that all of the layers constituting the base layer 10 be polyester films, and it is more preferable that they be amorphous polyester films. Also, it is preferable that all of the layers constituting the base layer 10 be polyethylene terephthalate films, and it is more preferable that they be amorphous polyethylene terephthalate (A-PET) films.

The thickness of the substrate layer 10 is not particularly limited and can be selected appropriately depending on the application, etc., but is preferably in the range of 25 μm to 500 μm, more preferably 30 μm to 200 μm, and even more preferably 40 μm to 150 μm. By making the thickness of the substrate layer 10 equal to or greater than the above lower limit, the releasability from the release material layer 20 (e.g., release liner) during the labeling process, etc., is further improved. Furthermore, by making the thickness of the substrate layer 10 equal to or less than the above upper limit, the wound length when made into a label roll for installation in a labeling device can be sufficiently long, thereby reducing the frequency of roll replacement and further improving work efficiency. The substrate layer 10 may be obtained by a conventional film-forming method, such as extrusion, calendaring, solution coating, or casting.

<Coat layer, etc.>

The label 1 for molded products according to this embodiment preferably further includes a coating layer 14 provided on the surface of the base layer 10 opposite the polyester-based adhesive layer 12. The coating layer 14 can be provided on the surface of the base layer 10. The coating layer 14 is preferably provided on the base layer 10 from the viewpoint of improving the adhesion of printing ink and further improving printability. The coating layer 14 can be printed as desired using a common printing method such as gravure printing, screen printing, letterpress printing, offset printing, or flexographic printing.

The material constituting the coating layer 14 is preferably one that has good adhesion to the material used as the base layer 10 (e.g., an amorphous polyester film such as A-PET film). Furthermore, from the perspective of recyclability, the material is preferably one that can be easily peeled from the base layer 10 by washing and immersing in an alkaline aqueous solution. A preferred configuration for the coating layer 14 includes an anchor layer (not shown) containing a water-based polyester resin and a print-receiving layer (not shown) on the surface of the anchor layer that contains a polyester urethane resin (e.g., a solvent-based polyester urethane). Here, "water-based" refers to any of the following properties: aqueous, water-soluble, water-dispersible, or water-suspendable.

In addition, to improve the adhesion between the base layer 10 and the polyester-based adhesive layer 12, known surface treatments such as corona discharge treatment can be applied as desired. The surface treatment is not limited to the contact surface between the base layer 10 and the polyester-based adhesive layer 12, but can also be applied to the contact surface between the base layer 10 and the coating layer 14. This further improves the printability of the label 1 for molded products according to this embodiment, and also allows it to be easily peeled from the anchor layer (not shown) using an alkaline aqueous solution.

<Polyester adhesive layer>

The polyester-based pressure-sensitive adhesive layer 12 can be formed from a polyester-based pressure-sensitive adhesive composition whose main component is a polyester-based resin. The polyester-based resin used in the polyester-based pressure-sensitive adhesive layer 12 is not particularly limited, and known resins can be used, such as polyester-based resins in the "Nichigo Polyester™" series manufactured by Mitsubishi Chemical Corporation (product names "NP-110S50EO," "SNT," "NP-120S45EO," etc.). The polyester-based resin used in the polyester-based pressure-sensitive adhesive layer 12 is produced, for example, by polycondensation of a polycarboxylic acid component and a polyol component in the presence of a catalyst.

The glass transition temperature (T _g ) of the polyester resin is not particularly limited, but is preferably −70° C. or higher and 0° C. or lower from the viewpoints of room temperature adhesion, initial adhesive strength, etc. This allows the polyester pressure-sensitive adhesive layer 12 to have adhesiveness (pressure-sensitive adhesiveness) at room temperature and to be attached to the surface of a resin molded article containing an amorphous polyester resin at room temperature. The glass transition temperature can be determined by measurement at a temperature rise rate of 10° C./min in accordance with JIS K7121:1987.

The number average molecular weight ( _Mn ) of the polyester resin is not particularly limited, but from the viewpoints of cohesive strength, heat resistance, mechanical strength, adhesiveness, etc., it is preferably from 5,000 to 100,000, more preferably from 10,000 to 100,000, and even more preferably from 15,000 to 80,000. Unless otherwise specified, the number average molecular weight ( _Mn ) referred to here is a value measured by gel permeation chromatography (GPC) and converted into a standard polystyrene molecular weight.

Furthermore, crosslinking the polyester resin with a crosslinking agent can further improve the cohesive strength and performance as an adhesive. Examples of such crosslinking agents include polyisocyanate compounds, polyepoxy compounds, and other compounds that have functional groups that react with the hydroxyl and/or carboxyl groups contained in the polyester resin. Among these, polyisocyanate compounds are preferred, as they can achieve higher levels of initial adhesive strength, mechanical strength, heat resistance, and other properties. The crosslinking agents may be used alone or in combination of two or more.

The amount of crosslinking agent blended can be selected appropriately taking into consideration the molecular weight of the polyester resin, intended use, etc., but it is preferable to blend the crosslinking agent in a ratio such that the reactive groups contained in the crosslinking agent are 0.2 to 10 equivalents per equivalent of hydroxyl and/or carboxyl groups contained in the polyester resin, more preferably 0.5 to 5 equivalents, and even more preferably 0.5 to 3 equivalents. Blending in such an amount further improves cohesion based on the number of equivalents of reactive groups contained in the crosslinking agent, and tends to more effectively prevent label slippage after application. In addition, deterioration in flexibility and initial adhesive strength can be more effectively prevented, which tends to more effectively prevent peeling immediately after application.

The polyester-based pressure-sensitive adhesive composition can contain conventional additives such as hydrolysis inhibitors, softeners, UV absorbers, stabilizers, antistatic agents, and tackifiers, as well as other powdery or particulate additives such as inorganic or organic fillers, metal powders, and pigments, provided that the effects of the present invention are not impaired.

When the polyester-based pressure-sensitive adhesive layer 12 is formed by coating using a polyester-based pressure-sensitive adhesive composition, the solvent may be, for example, alcohols, acetone, ethyl acetate, acetic acid, tetrahydrofuran (THF), diethyl ether (DME), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), toluene, carbon tetrachloride, n-hexane, (water), or a mixture thereof.

Examples of alcohols include monoalcohols such as methanol, ethanol, propanol, isopropanol, n-butanol, isobutanol, and phenethyl alcohol; diols such as ethylene glycol, propylene glycol, and butanediol; triols such as triethylene glycol; and polyols such as polyethylene glycol.

The storage modulus G' of the polyester-based pressure-sensitive adhesive layer 12 is preferably 1 x ¹⁰⁵ Pa or more and 100 x ¹⁰⁵ Pa or less, and more preferably 5 x ¹⁰⁵ Pa or more and 50 x ¹⁰⁵ Pa or less, at 23°C and a frequency of 1 Hz. If the storage modulus G' of the polyester-based pressure-sensitive adhesive layer 12 is not more than the above upper limit, the adhesive strength tends to be more easily ensured. If the storage modulus G' of the polyester-based pressure-sensitive adhesive layer 12 is not less than the above lower limit, the cohesive strength tends to be more easily ensured.

The storage modulus G' of the adhesive layer can be adjusted by appropriately changing the type, molecular weight, and compounding ratio of the monomers constituting the polymer (adhesive) contained in the polyester-based adhesive layer 12, as well as the degree of polymerization of the polymer, and, if a crosslinking agent is included, the amount of crosslinking agent (crosslinking density of the polymer).

The storage modulus G' of the polyester-based pressure-sensitive adhesive layer 12 can be measured using a dynamic viscoelasticity measuring device (manufactured by TA Instruments Japan, device name "ARES"). A laminate having a polyester-based pressure-sensitive adhesive layer 12 with a thickness of 500 μm to 1 mm (e.g., 800 μm) formed between two release liners is punched into a disk with a diameter of 8 mm, and the sample obtained after removing the release liners is used as the measurement sample. The storage modulus G' at 23°C is then measured in a temperature range of -50°C to 150°C, at a heating rate of 5°C/min, and in shear mode at a frequency of 1 Hz.

The thickness of the polyester-based adhesive layer 12 can be selected appropriately depending on the application of the label 1 for molded products. The thickness of the polyester-based adhesive layer 12 is preferably 1 μm or more and 50 μm or less, more preferably 5 μm or more and 50 μm or less, even more preferably 10 μm or more and 40 μm or less, and even more preferably 10 μm or more and 30 μm or less.

<Removal layer>

The molded product label 1 of this embodiment may be formed into a release-attached molded product label 2 by laminating a release material layer 20 (e.g., a release liner) on the surface of the polyester-based adhesive layer 12. The release material layer 20 may be made of any material that can be peeled off from the polyester-based adhesive layer 12, and any known material can be used. Examples include glassine paper, coated paper, laminated paper, and various plastic films coated with a release agent such as silicone resin. One embodiment of the release-attached molded product label 2 of this embodiment has a structure in which a coating layer 14 is provided on one side of a base layer 10, and a polyester-based adhesive layer 12 and a release material layer 20 are sequentially laminated on the opposite side. When attaching a molded product label 1 having such a structure to a molded product 30, the release material layer 20 is peeled off to expose the polyester-based adhesive layer 12, and the polyester-based adhesive layer 12 is brought into contact with the surface of the molded product 30 (adherend) and attached.

The thickness of the release material layer 20 can be selected appropriately depending on the application of the label 1 for molded products, but from the standpoint of handleability, it is preferably 10 μm or more and 200 μm or less, more preferably 20 μm or more and 150 μm or less, and even more preferably 30 μm or more and 100 μm or less.

Furthermore, as long as the effects of this embodiment are achieved, functional layers other than those described above may be provided on the label 1 for molded products as needed.

<Manufacturing method for labels for molded products>

The manufacturing method of the label 1 for molded products according to this embodiment is not particularly limited, but it can be manufactured, for example, by a manufacturing method including a step of laminating a polyester-based adhesive layer 12 on the surface of the base layer 10. Examples of methods for laminating the polyester-based adhesive layer 12 on the surface of the base layer 10 include a method of forming the polyester-based adhesive layer 12 by applying a composition containing a polyester-based adhesive (a polyester-based adhesive composition) to the surface of the base layer 10. Examples of methods for applying the polyester-based adhesive composition include roll coating, spin coating, spray coating, bar coating, knife coating, roll knife coating, blade coating, die coating, and gravure coating.

When producing a label 2 for molded products with a release material, the release material layer 20 described above can be laminated onto the surface of the polyester-based adhesive layer 12.

<Molded product with label>

Figure 2 is a partial cross-sectional view of a labeled molded product in which a label for molded products according to this embodiment has been attached to the molded product.

The label 1 for molded products is used by being affixed to the surface of a molded product 30 made of a resin containing amorphous polyester resin. That is, the labeled molded product 3 is one in which the label 1 for molded products according to this embodiment is affixed to the molded product 30. Specifically, the labeled molded product 3 includes a molded product 30 made of a resin such as amorphous polyester resin, and the label 1 for molded products affixed to the surface of the molded product 30. If the molded product 30 to be affixed is composed of multiple layers, the label 1 for molded products is affixed to the surface layer.

Examples of molded articles 30 include containers such as container bodies and lids. Specific examples include, but are not limited to, blister packs, fruit cups, egg cartons, etc.

As mentioned above, when selecting a material for the molded product 30, it is sometimes preferable to use an amorphous polyester resin, or even amorphous polyethylene terephthalate (A-PET), which has superior physical properties such as thermoformability compared to conventional biaxially oriented polyester resins. Using such a molded product 30 in conjunction with the label 1 for molded products of this embodiment promotes mono-materialization, making it suitable for use as a mono-material packaging material, particularly as a label-integrated container with excellent recyclability.

From this perspective, it is preferable that all of the resin layers constituting the label for molded products 1 are polyester resin layers, and that all of the resin layers constituting the molded product 30 are polyester resin layers. Furthermore, it is preferable that all of the resin layers constituting the label for molded products 1 are amorphous polyethylene terephthalate (A-PET) resin layers, and that all of the resin layers constituting the molded product 30 are amorphous polyethylene terephthalate (A-PET) resin layers. By using A-PET as the material for both the molded product 30 and the label for molded products 1, it is expected that the various physical properties described above will be improved by A-PET for the labeled molded product 3 as a whole.

<Manufacturing method for labeled molded products>

Figure 3 is a partial schematic diagram illustrating the manufacturing method of a labeled molded product according to this embodiment.

The method for manufacturing a labeled molded product 3 according to this embodiment is a method for manufacturing a labeled molded product in which a label for a molded product 1 is attached to a molded product 30,
(a) a labeling step in which labels 1 for molded products are continuously attached at regular intervals to the surface of a long polyester resin sheet 40 to obtain a labeled sheet 4 for molded products;
(b) a thermoforming step of continuously forming a shape corresponding to the shape of the molded product 30 on the label-attached sheet 4 for the molded product by thermoforming to obtain a container sheet;
(c) a cutting step of dividing the container sheet into molded product units;
At least steps (a) and (b) are continuously carried out to continuously produce a labeled molded product 3, and the label 1 for a molded product comprises a base layer 10 containing an amorphous polyester film and a polyester-based pressure-sensitive adhesive layer 12 provided on at least one surface of the base layer 10. One embodiment of the method is described below by way of example.

In the manufacturing method according to this embodiment, at least (a) the labeling step is performed, followed by (b) the thermoforming step. As described above, the material of the label 1 for molded products and the material of the molded product 30 obtained from a polyethylene resin sheet are an ideal combination for mono-material packaging materials. Therefore, even if these are integrated into the label-attached sheet 4 for molded products and then thermoformed to form the shape of a container or the like, problems such as processing defects and peeling between the label 1 for molded products and the molded product 30 can be sufficiently suppressed. Furthermore, the occurrence of defective products is low, yield is high, and continuous production is possible, making it economical.

In process (a), a long polyester resin sheet 40 is used. This will later become a component of the molded product 30. A long, approximately rectangular polyester resin sheet 40 can be used as the polyester resin sheet 40. Labels 1 for molded products are affixed to the surface of the polyester resin sheet 40 at regular intervals in both the vertical and horizontal directions to obtain a labeled sheet 4 for molded products. The labels 1 for molded products can be affixed continuously to the polyester resin sheet 40. For example, in FIG. 3, the labels 1 for molded products are affixed continuously at regular intervals in both the vertical and horizontal directions to the polyester resin sheet 40 as it is conveyed in the conveying direction (arrow F). While FIG. 3 illustrates an example in which the labels 1 for molded products are arranged in three rows (three in the width direction), the spacing and conveying speed are not particularly limited and can be adjusted as appropriate. These conditions can be adjusted by appropriately changing the configuration and conditions of the labeling device used. Furthermore, as mentioned above, since the label 1 for molded products has adhesive properties at room temperature, it is preferable to apply the label 1 for molded products to the polyester resin sheet 40 at room temperature in step (a). This eliminates the need for heat application during the labeling process, improving productivity.

In step (b), the label-attached sheet 4 for molded products obtained in step (a) is heated and softened using a vacuum/pressure molding machine or the like, and then shaped into a shape corresponding to the shape of the molded product 30 (for example, the shape of the container body or lid) using a mold or the like. Shaping can be performed using vacuum/pressure molding or the like. This allows a container sheet with a shaped shape to be obtained.

In this embodiment, the polyester resin sheet 40 and the label 1 for molded products have good material affinity (e.g., compatibility, etc.), so the edges of the label 1 for molded products do not lift or peel, transparency is maintained, and high formability can be achieved. Furthermore, if the coating layer 14 of the label 1 for molded products is printed with ink, etc., ink loss can be suppressed. The molding conditions are not particularly limited, and can be adjusted to achieve suitable conditions by appropriately changing the configuration and conditions of the molding machine used, etc.

In step (c), after steps (a) and (b) have been performed, the sheet is cut into individual molded products. For example, in step (b), the individual containers of the container sheet are transported in the state in which they are formed in the thermoforming process and aligned at regular intervals both vertically and horizontally. These can be cut into individual containers to obtain labeled molded products 3. In this embodiment, it is also possible to perform steps (a) and (b) continuously, and then cut into individual molded products in step (c).

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples in any way. Note that percentages and parts are by weight unless otherwise specified.

<Creating Label 1 for Molded Products>

(Polyester-based adhesive layer 12)

A pressure-sensitive adhesive composition was prepared by adding and mixing 2 parts by mass (solid content) of a crosslinking agent (manufactured by Tosoh Corporation, trade name "Coronate L") and 40 parts by mass of ethyl acetate to 100 parts by mass (solid content) of a polyester resin (manufactured by Mitsubishi Chemical Corporation, trade name " _Nichigo Polyester™ NP-110S50EO"; glass transition temperature (T g ) -50°C or less).

The resulting adhesive composition was applied using a knife coater to the surface of a release liner made of glassine paper coated with a silicone-based release agent, so that the dried film thickness would be 25 μm. After application, the composition was dried at 90°C for 1 minute to form a polyester-based adhesive layer 12.

(Substrate layer 10, coating layer 14)

A 120 μm-thick amorphous polyethylene terephthalate (A-PET) film (manufactured by RP Topla Co., Ltd., product name "NOACRYSTAL-M") was used as the base layer 10. A solvent-based polyester urethane resin was applied to one surface of this film using a Mayer bar, followed by drying to form a 1 μm-thick print-receiving layer (polyester urethane resin layer). In this way, a coating layer 14 consisting of the print-receiving layer was formed on the surface of the base layer 10.

The amorphous polyethylene terephthalate film used as the base layer 10 had a thermal shrinkage rate of 3.5% in the machine direction when treated at 100°C for 5 minutes.

Then, an amorphous polyethylene terephthalate (A-PET) film (manufactured by RP Topla Co., Ltd., product name "NOACRYSTAL-M") was attached to the surface opposite the coating layer 14 on the polyester-based adhesive layer 12, rolled up, and left to stand at 23°C for 7 days to obtain label 1 for molded products. This was then rolled up to obtain the corresponding label roll.

(Initial adhesive strength)
The required amount was cut out from the label roll and formed into a sheet. This was left to stand for 24 hours in a 23°C environment in accordance with JIS Z0237:2009, after which the release liner was peeled off, and the adhesive layer surface was attached to an amorphous polyethylene terephthalate (A-PET) plate while being pressed with a 2 kg rubber roller. The adhesive strength was measured immediately after application and after being left to stand for 24 hours under standard conditions. Specifically, the sheet was peeled off in a 180° direction at a test speed of 0.3 m/min using a tensile tester, and the adhesive strength was measured. The numerical value was converted to the peel force per 25 mm of sheet width (N/25 mm).
The initial adhesive strength of the label 1 for molded products in the above example was 5.5 N/25 mm.

Next, the coating layer 14 of the label 1 for molded products was printed using UV-curable ink.

<Preparation of labeled molded product 3>

((a) Labeling process)

The label roll was cut to a length of 300 m and a width of 60 mm, and punched to a label size of 35 mm x 35 mm with label spacing of 3 mm. This label roll was used to continuously apply labels to a thermoforming A-PET sheet (polyester resin sheet 40) using a labeling device at a labeling speed of 100 m/min, yielding a labeled sheet 4 for molded products (a thermoforming A-PET sheet with a label 1 for molded products attached). The resulting labeled sheet 4 for molded products was visually inspected for any peeling or lifting of the labels at the edges, etc.

((b) Thermoforming process to (c) Cutting process)

The label-attached sheet 4 for molding was heated to a surface temperature of 120°C using a vacuum/pressure forming machine to soften it, and then vacuum/pressure formed using a female aluminum mold under 0.5 MPa of compressed air to obtain a shaped container sheet. After sequentially performing steps (a) and (b) above, a cutting process was performed to divide the container sheet into molded product units, resulting in food tray container lids (heat-resistant transparent A-PET container lids) with openings (172 mm wide x 88 mm long, 22 mm deep). Visual inspection of the resulting food tray container lids confirmed that there was no peeling or lifting of the label edges, they were transparent, free of deformation, and no ink loss from the printed surface of the label.

1: Label for molded product 2: Label for molded product with release material 3: Labeled molded product 4: Labeled sheet for molded product 10: Base material layer 12: Polyester-based adhesive layer 14: Coating layer 20: Release material layer 30: Molded product 40: Polyester resin sheet

Claims (8)

a substrate layer including an amorphous polyester film;
a polyester-based pressure-sensitive adhesive layer provided on at least one surface of the base material layer;
Including,
The initial adhesive strength is 1.0 N/25 mm or more.
Labels for molded products.
Initial adhesive strength: Adhesion strength measured in accordance with JIS Z0237:2009, in which a test piece of a label for molded products is attached to an amorphous polyester test plate while being pressed with a roller in an environment of 23°C, and the test piece is peeled off at an angle of 180° from the amorphous polyester test plate within 30 seconds of attachment at a peeling rate of 300 mm/min. The amorphous polyester film has a heat shrinkage rate in the MD direction of 2.0% or more and 5.0% or less when treated at 100°C for 5 minutes.
The label for molded products according to claim 1. The amorphous polyester film is an amorphous polyethylene terephthalate (A-PET) film.
The label for molded products according to claim 1 or 2. The adhesive sheet further includes a coating layer provided on a surface of the base layer opposite to the polyester-based pressure-sensitive adhesive layer.
The label for molded products according to any one of claims 1 to 3. The label for molded products is used by being attached to the surface of a molded product made of a resin containing an amorphous polyester resin.
The label for molded products according to any one of claims 1 to 4. All of the resin layers constituting the label for molded products are polyester resin layers.
The label for molded products according to any one of claims 1 to 5. a resin molded article containing an amorphous polyester resin;
The label for molded products according to any one of claims 1 to 6 attached to the surface of the molded product;
Labeled articles, including: A method for manufacturing a labeled molded product in which a label for a molded product is attached to a molded product, comprising:
(a) a labeling step of continuously attaching labels for molded products at regular intervals to the surface of a long polyester resin sheet to obtain a labeled sheet for molded products;
(b) a thermoforming step in which a shape corresponding to the shape of the molded product is continuously formed on the label-attached sheet for the molded product by thermoforming to obtain a container sheet;
(c) a cutting step of dividing the container sheet into molded articles;
Including,
The labeled molded article is continuously produced by continuously carrying out at least the steps (a) and (b),
The label for molded products includes a base layer containing an amorphous polyester film and a polyester-based pressure-sensitive adhesive layer provided on at least one surface of the base layer.
A method for manufacturing labeled molded articles.