Recycled film

Abstract

We provide recycled films with a multilayer structure that have high interlayer strength. [Solution] The recycled film comprises a first resin layer and a second resin layer laminated on one side of the first resin layer. The first resin layer contains recycled resin raw material made from a resin molded product having a printed layer. The total light transmittance of the recycled film at a measurement wavelength of 400 nm, as measured by spectrophotometric measurement in accordance with JIS K0115, is less than 85%. The average interlaminar strength between the first resin layer and the second resin layer is 0.55 N / 10 mm or more.

Description

Technical Field

[0001] The present invention relates to a recycled film.

Background Art

[0002] In recent years, marine pollution caused by the disposal of plastics has become a global problem. Therefore, resource recycling, such as recycling plastic products that were previously discarded as resources, has attracted attention. For example, Patent Document 1 discloses a method for producing a heat-shrinkable film using fluff and pellets obtained from a packaging material having a printing layer as starting materials. Patent Document 2 discloses a method for producing recycled plastic (pellets) with less coloring, foreign matter, and bubbles after detaching the printing layer from a packaging material having a printing layer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when the present inventors produce a recycled film having a multilayer structure using a recycled resin raw material such as fluff or pellets produced from a plastic product, they noticed a phenomenon that the adhesive strength (interlayer strength) between the layer containing the recycled resin raw material included in the recycled film and the layer adjacent thereto decreases. When the interlayer strength decreases, peeling is likely to occur between the layers. According to further studies by the present inventors, this phenomenon is considered to be caused by components derived from the printing layer contained in the recycled resin raw material.

[0005] An object of the present invention is to provide a recycled film having a multilayer structure with high interlayer strength. [Means for solving the problem]

[0006] Item 1. The first resin layer and, A second resin layer laminated on one side of the first resin layer and Equipped with, The first resin layer includes a recycled resin raw material made from a resin molded product having a printed layer, The total light transmittance at a measurement wavelength of 400 nm, as measured by spectrophotometric measurement in accordance with JIS K0115, is less than 85%. The average interlaminar strength between the first resin layer and the second resin layer is 0.55 N / 10 mm or more. Recycled film.

[0007] Item 2. The first resin layer contains 0.05% or more by weight of an ultraviolet absorber. Recycled film as described in item 1.

[0008] Item 3. The resin molded product includes at least one of the following: polystyrene resin, polyester resin, polyolefin resin, and polyamide resin. Recycled film as described in item 1 or 2.

[0009] Item 4. It is a heat-shrinkable film. Recycled film as described in any of items 1 to 3.

[0010] Item 5. Packaging labels manufactured from recycled films as described in any of items 1 through 4. [Effects of the Invention]

[0011] According to the present invention, a recycled film with a multilayer structure and high interlayer strength is provided. [Brief explanation of the drawing]

[0012] [Figure 1] A cross-sectional view of a recycled film according to one embodiment. [Figure 2]Plan view of a product film before the film ears according to an embodiment are cut out. [Figure 3] Cross-sectional view of a product film according to an embodiment. [Figure 4] Block diagram schematically showing a resource recycling system according to an embodiment. [Figure 5] Diagram showing the configuration of a film manufacturing apparatus according to an embodiment.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, a recycled film according to an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and their descriptions will not be repeated. Also, each drawing is schematically drawn with appropriate omissions or exaggerations of the subject for ease of understanding.

[0014] [1. Configuration of Recycled Film] The recycled film 1 according to the present embodiment is a packaging material in the form of a film or label that can be used in various fields such as food, beverages, pharmaceuticals, medical products, chemicals, cosmetics, toiletries, industrial supplies, and agricultural supplies. The recycled film 1 is used, for example, for packaging various containers such as plastic containers, glass containers, and paper containers.

[0015] When assuming the above uses, from the viewpoint of strength, the thickness of the recycled film 1 is preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more. From the viewpoints of economy and environmental friendliness, the thickness of the recycled film 1 is preferably 60 μm or less, more preferably 50 μm or less, even more preferably 40 μm or less, even more preferably 35 μm or less, and even more preferably 30 μm or less.

[0016] Furthermore, when assuming the above uses, the haze value of the recycled film 1 is preferably 14% or less, more preferably 12% or less, still more preferably 10% or less, still more preferably 8% or less, and still more preferably 7% or less from the viewpoint of ensuring the transparency of the recycled film 1. The haze value can be measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., NDH5000) under the temperature condition of 23°C by a method conforming to JIS Z7136. The haze value can be the average value when measuring a plurality of samples a plurality of times by the above method, and it is preferably the average value when measuring at least 4 times.

[0017] The recycled film 1 is, for example, a heat-shrinkable film. In this case, the recycled film 1 thermally shrinks when heated and is attached to the container by adhering to the outer surface of the container along the outer shape of the container. The recycled film 1 is, for example, formed into a tubular shape, covered on the container so as to cover the container from the outside, and then thermally shrunk to be attached to the container. The recycled film 1 is, for example, formed into a tubular shape by overlapping both ends in the TD (Transverse Direction) and sealing the overlapped portion in the MD (Machine Direction). In this case, when the recycled film 1 is attached to the container as a label, typically, the TD of the recycled film 1 corresponds to the lateral direction of the container, and the MD of the recycled film 1 corresponds to the longitudinal direction of the container.

[0018] When considering the above applications, the recycled film 1 is preferably a uniaxially oriented film with TD as the main shrinkage direction. The stretching ratio of the recycled film 1 in the main shrinkage direction is preferably 300% or more, more preferably 400% or more, and even more preferably 500% or more. The stretching ratio in the same direction is preferably 700% or less, more preferably 650% or less, and even more preferably 600% or less. On the other hand, the stretching ratio of the recycled film 1 in the direction perpendicular to the main shrinkage direction is preferably 120% or more, more preferably 125% or more, and even more preferably 130% or more. The stretching ratio in the same direction is preferably 180% or less, more preferably 170% or less, even more preferably 160% or less, even more preferably 150% or less, and even more preferably 140% or less.

[0019] The heat shrinkage rate of recycled film 1 in the main shrinkage direction is preferably 60% or more, more preferably 65% ​​or more, and even more preferably 70% or more when immersed in 98°C hot water for 10 seconds. The heat shrinkage rate in the same direction is preferably 30% or more, more preferably 35% or more, and even more preferably 40% or more when immersed in 80°C warm water for 10 seconds. The heat shrinkage rate in the same direction is preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more when immersed in 70°C warm water for 10 seconds. On the other hand, the heat shrinkage rate of recycled film 1 in the direction perpendicular to the main shrinkage direction is preferably 5% or more, more preferably 10% or more, and even more preferably 15% or more when immersed in 98°C hot water for 10 seconds. The heat shrinkage rate in the same direction is preferably -5% or more, more preferably 0% or more, and even more preferably 2% or more when immersed in 80°C warm water for 10 seconds.

[0020] Figure 1 is a cross-sectional view of the recycled film 1. In this example, the recycled film 1 has a three-layer structure and includes a first resin layer 11, a second resin layer 12, and a third resin layer 13. The first resin layer 11 is an intermediate layer and is formed between the second resin layer 12 and the third resin layer 13 in the thickness direction of the recycled film 1. In other words, the second resin layer 12 is laminated on one side of the first resin layer 11, and the third resin layer 13 is laminated on the other side of the first resin layer 11. The second resin layer 12 and the third resin layer 13 are each surface layers. In other words, one of the second resin layer 12 and the third resin layer 13 forms one surface (outermost surface) of the recycled film 1, and the other forms the other surface (outermost surface) of the recycled film 1. The first resin layer 11 and the adjacent second resin layer 12 may be bonded together via an adhesive layer. The first resin layer 11 and the adjacent third resin layer 13 may also be bonded together via an adhesive layer. The recycled film 1 is manufactured, for example, by feeding the raw materials for each layer contained in the recycled film 1 (the first resin layer 11, the second resin layer 12, and the third resin layer 13, and the adhesive layer, if any) into an extruder and co-extruding them.

[0021] The first resin layer 11, the second resin layer 12, and the third resin layer 13 each contain a resin. The resin contained in the first resin layer 11, which is an intermediate layer, may be of one type or multiple types. The resin contained in the second resin layer 12 and the third resin layer 13, which are surface layers, may also be of one type or multiple types. The amount of resin contained in each of the first resin layer 11, the second resin layer 12, and the third resin layer 13 is preferably 50 wt% or more, more preferably 60 wt% or more, even more preferably 70 wt% or more, even more preferably 80 wt% or more, even more preferably 90 wt% or more, and even more preferably 95 wt% or more. Each of the first resin layer 11, the second resin layer 12, and the third resin layer 13 may contain additives. Examples of additives include ultraviolet absorbers, antiblocking agents, heat stabilizers, antioxidants, light stabilizers, lubricants, antistatic agents, flame retardants, antibacterial agents, fluorescent whitening agents, etc.

[0022] The first resin layer 11, the second resin layer 12, and the third resin layer 13 may each contain a specific type of resin as their main component. In this specification, "main component" means the component that accounts for the largest weight relative to the total weight. The amount of the main component resin contained in each of the first resin layer 11, the second resin layer 12, and the third resin layer 13 is preferably 50 wt% or more, more preferably 60 wt% or more, even more preferably 70 wt% or more, even more preferably 80 wt% or more, even more preferably 90 wt% or more, and even more preferably 95 wt% or more.

[0023] Examples of the types of resins contained in the first resin layer 11, the second resin layer 12, and the third resin layer 13 include polystyrene resins, polyester resins, polyolefin resins, and polyamide resins.

[0024] Examples of polystyrene resins include homopolymers of styrene monomers and copolymers consisting of styrene monomers and other monomers (conjugated dienes, aliphatic unsaturated carboxylic acid esters, etc.), and any resin containing a styrene monomer may be used. The styrene monomers referred to here are styrene, α-methylstyrene, p-methylstyrene, o-methylstyrene, m-methylstyrene, ethylstyrene, pt-butylstyrene, etc., and styrene is preferred. Only one type of styrene monomer may be used, or two or more types may be used in combination. Specifically, examples include aromatic vinyl hydrocarbon-conjugated diene copolymers, mixed resins of aromatic vinyl hydrocarbon-conjugated diene copolymers and aromatic vinyl hydrocarbon-aliphatic unsaturated carboxylic acid ester copolymers, and rubber-modified impact-resistant polystyrene. More specifically, examples include styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-isoprene-butadiene copolymers, styrene-acrylic copolymers, acrylonitrile-butadiene-styrene copolymers, acrylonitrile-styrene copolymers, general-purpose polystyrene (GPPS), and highly branched polystyrene.

[0025] Examples of polyester resins include those obtained by condensation polymerization of a dicarboxylic acid component and a diol component. The type of dicarboxylic acid component is not particularly limited, and examples include terephthalic acid, o-phthalic acid, isophthalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, octyl succinic acid, cyclohexanedicarboxylic acid, naphthalenedicarboxylic acid, fumaric acid, maleic acid, itaconic acid, decamethylenecarboxylic acid, their anhydrides, and lower alkyl esters. The types of diol components listed above are not particularly limited, and include ethylene glycol, 1,3-propanediol, 1,4-butanediol, diethylene glycol, 1,5-pentanediol, 1,6-hexanediol, dipropylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-butanediol, 2,3-butanediol, neopentyl glycol (2,2-dimethylpropane-1,3-diol), 1,2-hexanediol, 2,5- Examples include aliphatic diols such as hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, and polytetramethylene ether glycol; 2,2-bis(4-hydroxycyclohexyl)propane; alkylene oxide adducts of 2,2-bis(4-hydroxycyclohexyl)propane; and alicyclic diols such as 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol.

[0026] Examples of polyolefin resins include polypropylene, polyethylene, and cyclic polyolefin resins. Examples of polypropylene resins include binary or ternary random copolymers with propylene as the main component and ethylene, butene, and α-olefin as copolymer components. Preferred α-olefins include ethylene, 1-butene, 1-hexene, and 1-octene, and may contain two or more types of α-olefins. Furthermore, the polypropylene resin may be a mixture of different propylene-α-olefin random copolymers. Examples of polyethylene resins include branched low-density polyethylene resins, linear low-density polyethylene resins, high-density polyethylene resins, ethylene-vinyl acetate copolymers, ionomer resins, or mixtures thereof. Also, copolymers of ethylene and α-olefins are included. Examples of α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene. The above copolymers may be random copolymers or block copolymers. Examples of cyclic polyolefin resins include (a) copolymers of ethylene or propylene with cyclic olefins (e.g., norbornene and its derivatives, or tetracyclododecene and its derivatives), (b) ring-opening polymers of the cyclic olefin or copolymers with α-olefins, (c) hydrogenated polymers of the polymers in (b), and (d) graft-modified products of (a) to (c) using unsaturated carboxylic acids and their derivatives. Examples of the cyclic olefins include norbornene, 6-methylnorbornene, 6-ethylnorbornene, 5-propylnorbornene, 6-n-butylnorbornene, 1-methylnorbornene, 7-methylnorbornene, 5,6-dimethylnorbornene, 5-phenylnorbornene, and 5-benzylnorbornene.

[0027] Examples of polyamide resins include aliphatic polyamides, aromatic polyamides, amorphous polyamides, and polyamide elastomers. Examples of the above aliphatic polyamides include aliphatic nylon and its copolymers, specifically polycapramide (nylon-6), poly-ω-aminoheptanoic acid (nylon-7), poly-ω-aminononanoic acid (nylon-9), polyundecanamide (nylon-11), polylauryl lactam (nylon-12), polyethylenediamine adipamide (nylon-2,6), polytetramethylene adipamide (nylon-4,6), polyhexamethylene adipamide (nylon-6,6), polyhexamethylene sevacamide (nylon-6,10), polyhexamethylene dodecamide (nylon-6,12), polyoctamethylene adipamide (nylon-8,6), polydecamethylene adipamide (nylon-10,8), etc.

[0028] The types of resins contained in the first resin layer 11, the second resin layer 12, and the third resin layer 13 may be the same or different. Furthermore, the first resin layer 11, the second resin layer 12, and the third resin layer 13 may contain the same type of resin in different weight ratios. It is preferable that the first resin layer 11, which is an intermediate layer, and the second and third resin layers 12 and 13, which are surface layers, use different types of resins as their main components, as they have different roles to fulfill.

[0029] Preferred examples of the main component resin contained in the first resin layer 11 include polystyrene resins and polyester resins such as PET (Poly-Ethylene-Terephthalate). Furthermore, preferred examples of the main component resins contained in the second resin layer 12 and the third resin layer 13 include polyester resins such as PET.

[0030] The thickness of the first resin layer 11 is preferably 2 μm or more, and especially when the recycled film 1 is a heat-shrinkable film, it is preferably 10 μm or more, more preferably 12 μm or more, and even more preferably 15 μm or more. The thickness of the first resin layer 11 is preferably 40 μm or less, more preferably 30 μm or less, even more preferably 25 μm or less, and even more preferably 20 μm or less.

[0031] The thickness of the second resin layer 12 and the third resin layer 13 is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 5 μm or more. The thickness of the second resin layer 12 and the third resin layer 13 is preferably 15 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less. The thicknesses of the second resin layer 12 and the third resin layer 13 may be the same or different.

[0032] The first resin layer 11 includes recycled resin raw material 3, which is made from a resin molded product 2 having a printed layer. The recycled resin raw material 3 is a recycled resin raw material containing printing-derived components, and may be a mechanically recycled raw material or a materially recycled raw material. Printing-derived components include, for example, various pigments (colorants). Printing-derived components may include, for example, inorganic pigments such as titanium dioxide (white pigment) and aluminum (silver pigment), and organic pigments such as carbon black (black pigment). The first resin layer 11 may further contain biomass raw materials. The resin molded product 2 can be a product that has been used, an unused product, an intermediate processed product, leftovers, scraps, defective products, prototypes, discarded products, etc. In other words, the resin molded product 2 may be post-consumer material that has been collected after being distributed in the market and used by consumers, or it may be pre-consumer material that has not yet reached consumers. The resin molded product 2 is typically packaging material in the form of a film or label, but its form is not limited as long as it is a resin molded product having a printed layer. For example, the resin molded product 2 may be a container such as a tray, bottle, pouch, or bag for holding articles, or it may be an accessory for a container such as a cap. If the resin molded product 2 is a film or a label, it may be, for example, a printed film roll, a film formed into a long tube by bonding both ends of a printed film, a lead film for test printing, a film edge cut from a printed film, or a label collected after being distributed to the market. The printed layer is formed, for example, by printing with oil-based ink or water-based ink using an intaglio plate (gravure plate, etc.), a relief plate (flexographic plate, etc.), a planar plate (offset plate, etc.), or a stencil plate, or by digital printing such as an inkjet method. The thickness of the printed layer is appropriately selected depending on the application, but for example, it can be about 0.1 to 20 μm. In the case of a film for packaging materials, the thickness of the printed layer is preferably 0.5 to 10 μm, more preferably 1 to 8 μm, and even more preferably 2 to 6 μm. The recycled resin raw material 3 may contain only one type of resin molded product 2 as a starting material, or it may contain multiple types of resin molded products 2.

[0033] The resin contained in the main body portion of the resin molded product 2, excluding the printed layer, may be of one type or multiple types. Preferably, the main body portion of the resin molded product 2, excluding the printed layer, contains at least one of the following: polystyrene resin, polyester resin, polyolefin resin, and polyamide resin. Details of the polystyrene resin, polyester resin, polyolefin resin, and polyamide resin in the resin molded product 2 are the same as those described for the resins contained in the first resin layer 11, the second resin layer 12, and the third resin layer 13. In addition, the main body portion of the resin molded product 2, excluding the printed layer, may contain additives. Examples of additives include ultraviolet absorbers, antiblocking agents, heat stabilizers, antioxidants, light stabilizers, lubricants, antistatic agents, flame retardants, antibacterial agents, and fluorescent whitening agents.

[0034] As an example of the resin molded product 2 described above, the following film selvage can be exemplified. Hereafter, the film selvage will also be denoted by reference numeral 2. The film selvage 2 is a narrow, elongated waste film, cut from the wide, elongated product film 5 shown in Figure 2. As shown in Figure 2, the product film 5 includes a product section 50 and film selvages 2,2 adjacent to both ends of the product section 50 in the width direction. Figure 2 shows the product film 5 in an unfolded state, but the product film 5 is wound up for storage and handling purposes and managed in the form of a roll. The product section 50 is used, for example, for packaging various containers such as plastic containers, glass containers, and paper containers. The film selvages 2,2 are separated from the product section 50 by cutting the product film 5 along the boundary line between the product section 50 and the film selvages 2,2 before the product section 50 is shipped. The product section 50 and the film selvages 2,2 are also wound up for storage and handling purposes and managed in the form of a roll.

[0035] Figure 3 shows a cross-sectional view of the product film 5. As shown in the figure, the product film 5, and the product portions 50 and film edges 2,2 cut from it, each have a resin film body 51 and a printed layer 52 laminated on the film body 51. In Figure 3, the printed layer 52 is laminated on only one side of the film body 51, but it may be laminated on both sides. The product portion 50 includes a printed layer 52 on which information such as the target product to be packaged by the product portion 50 is printed. The film edges 2,2 include a printed layer 52 on which information such as the printing status of the product portion 50 is printed.

[0036] Although not limited thereto, the product film 5, and the product portion 50 and film edges 2,2 cut therefrom, are, for example, heat-shrinkable films in their pre-heat-shrink state. The product film 5, product portion 50, and film edges 2 are uniaxially oriented films that shrink mainly in the TD (width direction) for use as a tubular label for the product portion 50. The heat shrinkage rate in the main shrinkage direction of the product film 5, product portion 50, and film edges 2 is appropriately selected considering the ease of attachment of the product portion 50 to containers, etc., when used as a label, but is preferably 30% or more, and more preferably 50% or more, when immersed in 90°C hot water for 10 seconds.

[0037] The first resin layer 11 may contain virgin resin raw materials and / or chemically recycled raw materials in addition to recycled resin raw materials 3. The types of resins in the recycled resin raw materials 3 and virgin resin raw materials contained in the first resin layer 11 are preferably the same, but may be different. Similarly, the types of resins in the recycled resin raw materials 3 and chemically recycled raw materials contained in the first resin layer 11 are preferably the same, but may be different. The ratio of recycled resin raw materials 3 to the total amount of virgin resin raw materials and chemically recycled raw materials contained in the first resin layer 11 (or the total amount of one of the raw materials if only one is included) is preferably 30 wt% or less, more preferably 15 wt% or less, even more preferably 10 wt% or less, and even more preferably 5 wt% or less. However, when the resin molded product 2 is subjected to a deinking treatment during the production of the recycled resin raw material 3 to remove a certain amount of the printed layer, the ratio is preferably 5 wt% or more, more preferably 10 wt% or more, even more preferably 30 wt% or more, and even more preferably 50 wt% or more. The ratio is adjusted depending on the degree of removal of the printed layer due to the deinking treatment method or conditions.

[0038] The second resin layer 12 and the third resin layer 13 each preferably contain at least one of virgin resin raw materials and recycled resin raw materials, and may further contain biomass raw materials. The recycled resin raw materials contained in the second resin layer 12 and / or the third resin layer 13 may be derived from a resin molded product 2 having a printed layer, or from a resin molded product without a printed layer, and may or may not contain printing-derived components. The recycled resin raw materials contained in the second resin layer 12 and / or the third resin layer 13 may be mechanically recycled products or material recycled products, but are preferably chemically recycled products. Furthermore, when the second resin layer 12 and / or the third resin layer 13 contains both virgin resin raw materials and recycled resin raw materials, the types of resins of both raw materials are preferably the same, but may be different.

[0039] Through experiments relating to the embodiments described later, the inventors have discovered that when a multilayer recycled film is manufactured using recycled resin raw materials, the adhesive strength (interlaminar strength) between the layer containing the recycled resin raw materials and the adjacent layer may decrease. When interlaminar strength decreases, delamination between layers may occur more easily. Further investigation by the inventors suggests that this phenomenon occurs because printing-derived components present at the interlayer interface weaken the interlayer adhesion and cause interfacial fracture. In other words, the decrease in interlaminar strength is thought to be due to printing-derived components contained in the recycled resin raw materials. Furthermore, the inventors have also discovered that even within the same recycled film, variations in interlaminar strength are observed depending on the location. This is thought to be because printing-derived components are scattered at the interlayer interface, and while interlaminar strength is maintained in areas where there are few printing-derived components, it becomes lower in areas where there are many printing-derived components.

[0040] A decrease in the interlaminar strength of recycled film 1 is undesirable because it can easily lead to delamination between layers. Therefore, the average interlaminar strength between the first resin layer 11 and the second resin layer 12 is preferably 0.55 N / 10 mm or more, and more preferably 0.6 N / 10 mm or more. Similarly, the average interlaminar strength between the first resin layer 11 and the third resin layer 13 is preferably 0.55 N / 10 mm or more, and more preferably 0.6 N / 10 mm or more. Note that the average interlaminar strength may differ between the principal shrinkage direction and the direction perpendicular to it. Therefore, the smaller of the average interlaminar strength in the principal shrinkage direction and the average interlaminar strength in the direction perpendicular to it is preferably 0.55 N / 10 mm or more, and more preferably 0.6 N / 10 mm or more.

[0041] The interlaminar strength of the film can be measured by the method described in the following examples. The average interlaminar strength is the average value of measurements taken when the interlaminar strength is measured multiple times using multiple samples cut from the same film. Although the interlaminar strength value varies depending on where the sample is cut, the average value converges to a single value as the number of measurements increases. The average interlaminar strength referred to here means this converged value and can be the average value of at least 4, preferably 10 or more, measurements of interlaminar strength.

[0042] Furthermore, through experiments relating to the embodiments described later, the inventors have discovered that a decrease in total light transmittance at a measurement wavelength of 400 nm improves the interlayer strength of the recycled film. From this viewpoint, it is preferable that the total light transmittance of recycled film 1 at a measurement wavelength of 400 nm is less than 85%. The total light transmittance referred to here can be measured by spectrophotometric measurement in accordance with JIS K0115. The measurement wavelength of 400 nm is the wavelength at the boundary between the visible light region and the ultraviolet region. Therefore, even if the total light transmittance at a measurement wavelength of 400 nm is less than 85%, the apparent transparency of recycled film 1 is not particularly impaired.

[0043] From the viewpoint of reducing the total light transmittance at a measurement wavelength of 400 nm, it is preferable that the recycled film 1 contains an ultraviolet absorber. Furthermore, it is preferable to add the ultraviolet absorber to the layer containing the recycled resin raw material 3 containing printing-derived components (in this embodiment, the first resin layer 11). The layer containing the recycled resin raw material 3 containing printing-derived components (in this embodiment, the first resin layer 11) preferably contains 0.05% or more of the ultraviolet absorber by weight, more preferably 0.08% or more, even more preferably 0.10% or more, and even more preferably 0.20% or more.

[0044] Preferred examples of UV absorbers included in recycled film 1 include at least one UV absorber selected from the group consisting of benzotriazole-based UV absorbers, triazine-based UV absorbers, benzoxazinon-based UV absorbers, and benzophenone-based UV absorbers.

[0045] Preferably, the benzotriazole-based UV absorbers are 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3,5-bis(α,α'-dimethylbenzyl)phenyl]benzotriazole, 2-(2H-benzotriazole-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, 2-(2H-benzotriazole-2-yl)-4-(1,1,3,3,-tetramethylbutyl)phenol, 2-(2H-benzotriazole-2-yl)-4-methylphenol, and 2-(2H-benzotriazole-2-yl) -4,6-di-t-butylphenol, 2-(2H-benzotriazol-2-yl)-4,6-di-t-amylphenol, 2-(2H-benzotriazol-2-yl)-4-t-butylphenol, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole (UV326), 2-(2'-hydroxy-3',5-di-t-butylphenyl)-5-chlorobenzotriazole, 6-(2-benzotriazolyl)-4-t-octyl-6'-t-butyl-4'-methyl-2,3-methylenebisphenol, etc. can be used. Commercially available benzotriazole-based UV absorbers can be used, such as ADEKA LA-36, Tinuvin 329, BASF Japan, Tinuvin 234, Tinuvin P, BASF Japan, Tinuvin 360, BASF Japan, Tinuvin 326, BASF Japan, Tinuvin 970, KEMISORB 71, KEMISORB 73, and KEMISORB 279, among others. Tinuvin 326 and Tinuvin 970, which have absorption capabilities in the long-wavelength region, are particularly preferred.

[0046] As a triazine-based UV absorber, 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-(hexyl)oxyphenol can be used, for example. Commercially available triazine-based UV absorbers can be used, such as KEMISORB 102 (manufactured by Chemipro Chemical Co., Ltd.) and Tinosorb S (manufactured by BASF Japan).

[0047] Preferably, 2,2'-p-phenylenebis(3,1-oxazin-4-one), 2-p-nitrophenyl-3,1-benzoxazin-4-one, 2-(2-naphthyl)-3,1-benzoxazin-4-one, 2,2'-p-phenylenebis(3,1-benzoxazin-4-one), 2,2'-(2,6-naphthylene)bis(3,1-benzoxazin-4-one), etc. can be used as benzoxazinon-based UV absorbers. Commercially available benzoxazinon-based UV absorbers can be used, such as KEMISORB 500 (manufactured by Chemipro Chemical).

[0048] Preferably, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 3,5-di-t-butyl-4-hydroxybenzoyl acid, n-hexadecyl ester, bis(5-benzoyl-4-hydroxy-2-methoxyphenyl)methane, 1,4-bis(4-benzoyl-3-hydroxyphenoxy)butane, 1,6-bis(4-benzoyl-3-hydroxyphenoxy)hexane, etc. can be used as benzophenone-based ultraviolet absorbers. Commercially available benzophenone-based UV absorbers can be used, such as KEMISORB 11 (manufactured by Chemipro Chemical), KEMISORB 12 (manufactured by Chemipro Chemical), KEMISORB 111 (manufactured by Chemipro Chemical), and KEMISORB 11S (manufactured by Chemipro Chemical).

[0049] Furthermore, it is possible to use hindered amine light stabilizers in combination with the various UV absorbers mentioned above. Representative commercially available hindered amine light stabilizers include, for example, Tinuvin 123, Tinuvin 152, Tinuvin NOR 371 FF, Tinuvin XT850 FF, Tinuvin XT855 FF, TINUVIN 5100, TINUVIN 622SF, Flamestab NOR 116 FF from BASF Japan, and ADEKA's ADEKA LA-81. These can be used individually or in combination of two or more.

[0050] [2. Method for manufacturing recycled film] Figure 4 is a schematic diagram of the resource recycling system S1 for manufacturing recycled film 1. As shown in Figure 4, in the resource recycling system S1, the resin molded product 2 is recycled and recycled film 1 is manufactured as a new film.

[0051] The resource recycling system S1 comprises a manufacturing apparatus 20 for recycled resin raw material 3 and a film manufacturing apparatus 30. In the resource recycling system S1, recycled resin raw material 3 is manufactured from resin molded products 2 using the manufacturing apparatus 20. The manufacturing apparatus 20 is a device that manufactures recycled resin raw material 3 using resin molded products 2 as the starting material. Recycled resin raw material 3 is a resin raw material obtained by processing the resin molded products 2 into a shape that is easy to handle when manufacturing recycled film 1 from the resin molded products 2. Specifically, recycled resin raw material 3 can be in the form of fluff 3a, pellets 3b, powder 3c, granules 3d, etc. There is a type of pellet 3b that is manufactured by heating and melting the raw material and then solidifying it, but granules 3d are different from such types of pellets 3b; they are lumps that are compressed and solidified without heating and melting powdered raw material. Granules 3d are typically opaque lumps. Furthermore, recycled resin raw materials 3, such as fluff 3a, powder 3c, or granules 3d, which are manufactured without heating and melting the raw materials, may be more susceptible to thermal degradation than recycled resin raw materials 3, such as the pellets 3b described above, which are manufactured by heating and melting the raw materials and then solidifying them, because they do not undergo excessive thermal history such as heating and melting during processing.

[0052] The resin molded product 2 can be processed into fluff 3a by, for example, using a known crusher, shredder, cutter, etc., to break the resin molded product 2 into small pieces. The size (area) of the fluff 3a is 500 mm². 2 The following is preferable: 300mm 2 The following is more preferable: 200 mm 2 The following is even more preferable: 100 mm 2 The following are particularly preferable.

[0053] The resin molded product 2 can be processed into pellets 3b using, for example, a known resin pellet manufacturing machine. For example, the fluff 3a can be supplied to an extruder, heated and melted in the extruder, then extruded through a die, and the extruded material can be cut into an appropriate shape to produce pellets 3b. Note that pellets 3b may be manufactured not only from the resin molded product 2 (fluff 3a) but also from virgin resin raw materials and / or chemically recycled raw materials. In this case, in addition to the fluff 3a, virgin resin raw materials and / or chemically recycled raw materials are supplied to the extruder. This method yields pellets 3b of a type created by heating, melting, and then solidifying the raw materials.

[0054] Another method for processing into pellets 3b is as follows: Film selvages 2 are unwound from a roll, and a single film selvage 2 or a bundle of multiple film selvages 2 is twisted by rotating it parallel to the conveying direction. After the twisted film selvages 2 are compressed, they are cut to a predetermined size. In this method, pellets 3b are produced without heating and melting the raw material.

[0055] The resin molded product 2 can be processed into powder 3c by, for example, the following method. First, the fluff 3a is immersed in a suitable solvent to dissolve the resin components contained in the fluff 3a in the solvent, thereby generating a solution containing the resin components. Then, the resin components are precipitated by cooling the solution, mixing a poor solvent into the solution, and / or heating the solution to evaporate the solvent. After that, the precipitated resin components is dried to produce powder 3c.

[0056] The resin molded product 2 can be processed into granules 3d, for example, by drying the resin component precipitates described above while stirring them under vacuum. Alternatively, the granules 3d can also be manufactured using a known granulator. In this case, the resin component precipitates or powder 3c described above can be fed into the granulator. In this case, it is preferable to dry the resin component precipitates or powder 3c before or during granulation, or to dry the granules 3d after granulation.

[0057] Furthermore, when manufacturing the recycled resin raw material 3, the printed layer contained in the resin molded product 2 may be removed to some extent by a known deinking method. That is, the recycled resin raw material 3 may be manufactured from a resin molded product 2 in which part of the printed layer has been removed and part of it remains. As a deinking method, for example, the resin molded product 2 may be immersed in a cleaning solution containing a solvent that can dissolve the printed layer. Alternatively, the printed layer may be physically removed from the resin molded product 2 using a blade, polishing roller, file, metal rotating brush, rotating blade, scraper, belt sander, blasting device (including wet blasting device), etc.

[0058] In the resource recycling system S1, recycled film 1 is further manufactured from recycled resin raw material 3 using film manufacturing equipment 30. Film manufacturing equipment 30 is a device that manufactures recycled film 1 using recycled resin raw material 3 manufactured using manufacturing equipment 20. Known film formation methods can be used as processing methods for recycled film 1.

[0059] Figure 5 shows an example of the configuration of the film manufacturing apparatus 30. In the example in Figure 5, the film manufacturing apparatus 30 comprises a T-die 300, cast rolls 310 and 320, a longitudinal stretcher 41, and a transverse stretcher 42. The T-die 300 comprises a T-die body 301 and raw material input sections 330, 331, and 332. Raw material for the second resin layer 12, which is one of the surface layers, is fed into the raw material input section 330. Raw material for the third resin layer 13, which is the other surface layer, is fed into the raw material input section 332. Recycled resin raw material 3, which is the raw material for the first resin layer 11, which is the intermediate layer, and other raw materials such as virgin resin raw material or chemically recycled raw material, if available, are fed into the raw material input section 331. Furthermore, if an adhesive layer is inserted between the first resin layer 11 and the second resin layer 12, and / or between the first resin layer 11 and the third resin layer 13, a separate raw material input section for the adhesive layer is provided, and the raw material for the adhesive layer is fed into it. The T-die body 301 heats and melts the raw materials supplied through the raw material input sections 330, 331, 332 (and, if applicable, the raw material input section for the adhesive layer), and then co-extrudes them to fuse the molten materials of the raw materials fed into each raw material input section together, thereby forming a single, integrated recycled film 1 (molten material). The cast rolls 310 and 320 cool the extruded molten material while sending it downstream.

[0060] Subsequently, the recycled film 1 is processed into a heat-shrinkable film by being stretched as appropriate to impart heat shrinkability. The longitudinal stretcher 41 stretches the recycled film 1, which has been cooled by the cast rolls 310 and 320, in the MD (medium-density) direction at a predetermined stretching ratio. The transverse stretcher 42 stretches the recycled film 1, which has been stretched in the MD (medium-density) direction, in the TD (two-stage) direction at a predetermined stretching ratio. The recycled film 1, which has undergone various stretching processes, is wound into a film roll.

[0061] Subsequently, functional layers may be appropriately laminated onto the recycled film 1. Functional layers include, for example, a printing layer, a matte layer, a protective layer (e.g., an overcoat layer, a hardcoat layer, etc.), a smoothing layer (e.g., an innercoat layer, an antiblocking layer, etc.), a barrier layer, a light-shielding layer, an ultraviolet-absorbing layer, a metal film, an easy-adhesion layer, a release layer, an antistatic layer, a conductive layer, and the like.

[0062] Packaging labels can be manufactured from recycled film 1, which has functional layers appropriately laminated on it (typically, at least a printed layer with a design laminated on it). For example, an adhesive layer for attaching to the item to be packaged may be laminated on the recycled film 1. Alternatively, the recycled film 1 may be formed into a tubular shape so that it can cover the container to be packaged. In this case, for example, the recycled film 1 is formed into a tubular shape by overlapping both ends of the TD and sealing the overlapped portion to the MD. For example, the tubular recycled film 1 is placed over the container so as to cover the container from the outside, and then attached to the container. In this case, if the recycled film 1 is a heat-shrinkable film, it is attached to the container by being heat-shrinkable.

[0063] [3. Features] Since recycled film 1 is manufactured using recycled resin raw materials 3, it can contribute to resource recycling. Furthermore, although recycled film 1 contains printing-derived components that cause a decrease in interlayer strength, the total light transmittance at a measurement wavelength of 400 nm is adjusted to less than 85%. As a result, a certain level of interlayer strength is ensured, and recycled film 1 that is resistant to delamination is provided.

[0064] [4. Variant] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the invention. For example, the following modifications are possible. Furthermore, the gist of the following modifications can be combined as appropriate.

[0065] [4-1] In the above embodiment, the first resin layer 11 is configured to contain recycled resin raw material 3. However, the intermediate layer, the first resin layer 11, may not contain recycled resin raw material 3, while at least one of the surface layers, the second resin layer 12 and the third resin layer 13, may contain recycled resin raw material 3. Alternatively, all layers, the first resin layer 11, the second resin layer 12, and the third resin layer 13, may contain recycled resin raw material 3.

[0066] [4-2] In the above embodiment, the recycled film 1 has a three-layer structure, but it may also have a two-layer structure or a multilayer structure of four or more layers. In this case as well, at least one of the layers contains the recycled resin raw material 3. [Examples]

[0067] The following describes embodiments of the present invention. However, the present invention is not limited to the embodiments described below.

[0068] Films relating to the reference examples shown in Tables 1 and 2, and recycled films relating to Examples 1 to 5 and the comparative examples were manufactured. All of these films had a three-layer structure, with surface layers (second and third resin layers) formed on both sides of the intermediate layer (first resin layer). However, the intermediate layer and the surface layers on both sides were bonded together with an adhesive layer mainly consisting of polyester elastomer. The thickness of all of these films was approximately 30 μm. More specifically, the thickness of the intermediate layer was approximately 18 μm, the thickness of each surface layer was approximately 6 μm, and the thickness of each adhesive layer was approximately 0.5 μm. All of these films were uniaxially oriented heat-shrinkable films with TD as the main shrinkage direction. All of these films were manufactured by feeding the raw materials for each layer shown in Tables 1 and 2, in the weight ratios shown in Tables 1 and 2, into an extruder at a barrel temperature of 160°C to 200°C, co-extruding from a multilayer die at 200°C, and cooling and solidifying on a cast roll at 50°C. Next, the film was produced by stretching the material to MD at a stretching ratio of 1.4 times in a longitudinal stretcher with the preheating roll set to 85°C and the stretching roll set to 90°C, then stretching it to TD at a stretching ratio of 4 times in a tenter stretcher (horizontal stretcher) which includes a preheating zone of 102°C, a stretching zone of 89°C to 91°C, and a heat-setting zone of 86°C, and finally winding it up with a winding machine.

[0069] [Table 1]

[0070] [Table 2]

[0071] In Tables 1 and 2, "polyester resin" refers to virgin polyethylene terephthalate raw material, and "polystyrene resin" refers to virgin styrene-butadiene copolymer raw material. In addition, "recycled resin raw material" in Tables 1 and 2 refers to pellets produced from film selvages similar to film selvage 2 described in the above embodiment. These pellets were produced by crushing the film selvage without deinking treatment to obtain fluff, and then mixing this fluff with virgin styrene-butadiene copolymer raw material in a 1:9 ratio and heating and melting it. The film body of this film selvage was a three-layer film having an intermediate layer made of polystyrene resin and surface layers made of polyester resin placed on both sides of the intermediate layer. More specifically, the polyester resin contained in both surface layers was a polyester resin consisting of dicarboxylic acid and diol components, and the polystyrene resin contained in the intermediate layer was a styrene-butadiene copolymer. The printing area of ​​this film selvage was 10%, and the thickness of the printed layer on the film selvage was approximately 5 μm. In this film ear, the ratio of surface layer thickness:intermediate layer thickness:surface layer thickness was 1:3:1.

[0072] In the films for the Reference Example, Examples 1-5, and Comparative Examples, the types of ultraviolet absorbers shown in Tables 1 and 2 were mixed into the intermediate layer in the amounts (by weight) shown in Tables 1 and 2. The amounts here refer to the amounts (by weight) added to the entire intermediate layer.

[0073] For each film relating to the Reference Example, Examples 1-5, and Comparative Example, the total light transmittance at a measurement wavelength of 400 nm, the thermal shrinkage rates of MD and TD, and the average interlaminar strength of MD and TD were measured. The results are shown in Tables 1 and 2. The measurement methods for these indicators are described later.

[0074] <Method for measuring total light transmittance at a measurement wavelength of 400 nm> The total light transmittance was measured by spectrophotometric measurement in accordance with JIS K0115. More specifically, a UV-Vis-Near-Infrared spectrophotometer (JASCO Corporation, model V-670) was used to measure the light transmittance by changing the measurement wavelength from 800 nm to 300 nm at a scan speed of 100 nm / min in 1 nm intervals.

[0075] <Method for measuring thermal shrinkage rate> Samples measuring 100 mm in length (MD) x 100 mm in width (TD) were cut from each film relating to the Reference Example, Examples 1-5, and Comparative Example. Each sample was immersed in warm water at 70°C, 80°C, and hot water at 98°C for 10 seconds. After removing the sample, the thermal shrinkage rate of MD was determined according to equation (1), and the thermal shrinkage rate of TD was determined according to equation (2). In equation (1), LMD is the length of MD of the sample after thermal shrinkage (mm), and in equation (2), LTD is the length of TD of the sample after thermal shrinkage (mm). The thermal shrinkage rate was measured using three samples, and the average value was calculated. Thermal shrinkage rate (%) = {(100-LMD) / 100} × 100···(1) Thermal shrinkage rate (%) = {(100-LTD) / 100} × 100···(2)

[0076] <Method for measuring average interlaminar strength> The interlaminar strength in the principal shrinkage direction (TD) and the direction perpendicular to it (MD) was measured according to a method conforming to JIS K6854. First, samples with a length (MD) of 100 mm and a width (TD) of 10 mm ± 0.5 mm were cut from each film relating to the Reference Example, Examples 1-5, and Comparative Example. A portion of the edge of each sample was delaminated in the MD direction between the intermediate layer and one of the surface layers. Then, using a peel tester (Shinto Kagaku Co., Ltd., model number HEIDON TYPE:17 delamination strength tester), the sample was pulled in the MD direction at a tensile speed of 200 mm / min and delaminated in the 180° direction. The strength (N / 10 mm) at room temperature (23°C) was measured and defined as the MD interlaminar strength. The same measurement was performed 10 times for 10 samples, and the average value was defined as the average MD interlaminar strength. Furthermore, samples measuring 100 mm in width (TD) and 10 mm ± 0.5 mm in length (MD) were cut from each film related to the Reference Example, Examples 1-5, and Comparative Example, and the average interlaminar strength of TD was determined using the same method as for MD. The evaluation criteria were "Good (〇)" for an average interlaminar strength of 0.55 N / 10 mm or higher, and "Poor (×)" for an average interlaminar strength of less than 0.55 N / 10 mm.

[0077] <Consideration> As can be seen by comparing the reference example and the comparative example, when a multilayer film is manufactured using recycled resin raw materials (i.e., when the film contains printing-derived components), the interlaminar strength of the film decreases (the only difference between the reference example and the comparative example is the recycled resin raw material content, but the average interlaminar strength of the MD in the reference example is 0.6 N / 10 mm, while the average interlaminar strength of the MD in the comparative example is 0.5 N / 10 mm, showing a decrease. A similar trend is observed for the average interlaminar strength of the TD as well). The fact that the inclusion of recycled resin raw materials can reduce interlaminar strength can also be understood by comparing Examples 1 and 2, which have the same manufacturing conditions except for the recycled resin raw material content.

[0078] However, as can be seen by further comparing the Comparative Example with Example 1, adding an ultraviolet absorber and reducing the total light transmittance at 400 nm improves the interlaminar strength of the film (the Comparative Example and Example 1 differ only in the amount of ultraviolet absorber added and the total light transmittance at 400 nm, but the average interlaminar strength of the MD in Example 1 is 0.7 N / 10 mm compared to 0.5 N / 10 mm in the Comparative Example. A similar trend is observed for the average interlaminar strength of the TD as well). The fact that reducing the total light transmittance improves interlaminar strength can also be generally understood by comparing Examples 2 to 4, which have the same manufacturing conditions except for differences in the amount of ultraviolet absorber added and the total light transmittance at 400 nm.

[0079] Furthermore, comparing Example 2 and Example 5, which had the same manufacturing conditions (same amount of UV absorber added) except for the type of UV absorber, Example 5, which had a lower total light transmittance at 400 nm than Example 2, showed improved interlayer strength (MD). This also indicates that reducing the total light transmittance improves the interlayer strength of the film.

[0080] Furthermore, it was confirmed that the recycled resin raw material content, the amount of UV absorber added, and the total light transmittance at 400 nm did not particularly affect the thermal shrinkage behavior of the film. [Explanation of Symbols]

[0081] 1. Recycled film 11 First resin layer 12 Second resin layer 13 Third resin layer 2. Resin molded product (film edge) 5 Product Film 50 Product Department 51 Film body 52 Printing layer 3 Recycled resin raw materials 3a Fluff 3b Pellet 3c powder 3d granules 20. Manufacturing equipment for recycled resin raw materials 30 Film manufacturing equipment 300 T-die 301 T-die body 310,320 Cast Roll 330,331,332 Raw material input section 41. Longitudinal extension machine 42 Lateral stretching machine S1 Resource Recycling System

Claims

1. The first resin layer and A second resin layer laminated on one side of the first resin layer and Equipped with, The first resin layer includes a recycled resin raw material made from a resin molded product having a printed layer, The total light transmittance at a measurement wavelength of 400 nm, as measured by spectrophotometric measurement in accordance with JIS K0115, is less than 85%. The average interlaminar strength between the first resin layer and the second resin layer is 0.55 N / 10 mm or more. Recycled film.

2. The first resin layer contains 0.05% or more by weight of an ultraviolet absorber. The recycled film according to claim 1.

3. The aforementioned resin molded product includes at least one of polystyrene resin, polyester resin, polyolefin resin, and polyamide resin. The recycled film according to claim 1 or 2.

4. A packaging label manufactured from the recycled film described in claim 1 or 2.

Images