Polyester-based film and regeneration method of polyester-based container using the same

Abstract

To provide a polyester-based film which can improve recyclability and quality while preventing environmental contamination in a container regeneration step, and a regeneration method of a polyester-based container using the same.SOLUTION: A polyester-based film includes a base material layer containing a polyester-based resin, and a printing layer positioned on one surface of the base material layer, wherein the printing layer is formed of a composition for a printing layer containing a first solvent, a first binder and a first pigment, a weight ratio of the first solvent to the first binder is 1:0.5 to 2.5, the polyester-based resin contains a diol component and a dicarboxylic acid component, the diol component contains one or more selected form the group consisting of ethylene glycol, diethylene glycol, and neopentyl glycol, and the polyester-based resin contains 1 mol% to 35 mol% of the neopentyl glycol based on the total molar number of the diol component.SELECTED DRAWING: None

Description

[Technical field]

[0001] The embodiment relates to a polyester film that can improve the recyclability of polyester containers and solve environmental problems, as well as to improve quality, yield and productivity, and a method for recycling polyester containers using the same. [Background technology]

[0002] In recent years, as concerns about environmental issues have increased, there has been a demand for a response to the problem of recycling products made from thermoplastic polymers. In particular, polyethylene terephthalate (PET), a thermoplastic resin with excellent properties such as heat resistance, processability, transparency, and non-toxicity, is widely used to manufacture a wide range of products such as films, fibers, bottles, and containers, and research is being conducted to improve the recycling rate.

[0003] Generally, polyolefin-based stretch films are attached to containers made of PET as labels. Therefore, PET containers collected from general consumers are washed and crushed, and then subjected to liquid specific gravity separation, dehydration drying, and / or air specific gravity separation in order to remove a large amount of film contained in the crushed material, and then additional processes such as pelletization are performed to produce recycled polyester chips. However, even after the above processes, it is difficult to completely remove the film, and there are problems in that the recycled polyester chips are colored by the ink contained in the film, and clumping occurs in which the recycled polyester chips are irregularly aggregated during the heat treatment process due to the thermal properties of the film.

[0004] In response to this, a gravity separation method was proposed in which films of low-density polymers such as polystyrene, polyethylene, and polypropylene were used as labels to facilitate gravity separation. However, this method was unable to solve the problem of residual ink discoloring recycled polyester chips because the ink layer prevented effective low-density processing and made it difficult to completely separate and remove the film. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, the realization example provides a polyester film that can improve recyclability and quality while preventing environmental pollution during the container recycling process, and a method for recycling polyester containers using the same. [Means for solving the problem]

[0006] In one embodiment, the polyester-based film includes a base layer containing a polyester-based resin and a printed layer located on one side of the base layer. The polyester-based film is cut into pieces 1 cm long and 1 cm wide, immersed in a 1% aqueous sodium hydroxide (NaOH) solution, and stirred at 85°C at a speed of 240 m / min for 15 minutes. After this, the average particle size of the printed layer components detached from the base layer is 15 μm or more.

[0007] Another embodiment of the polyester-based film includes a base layer containing a polyester-based resin, a printed layer facing the base layer, and a peel-promoting layer interposed between the base layer and the printed layer, and is cut into a size of 1 cm in length and 1 cm in width, immersed in a 1% aqueous sodium hydroxide (NaOH) solution, and stirred at 85°C at a speed of 240 m / min for 15 minutes, after which the average particle size of the printed layer components detached from the base layer is 15 μm or more.

[0008] Another embodiment of a method for recycling polyester containers includes the steps of preparing a polyester container at least partially surrounded by the polyester film, crushing the polyester container with the film to obtain flakes, immersing the crushed flakes in a 1% aqueous sodium hydroxide (NaOH) solution at 85°C, and heat-treating the immersed flakes to produce recycled polyester chips, and the clumping fraction is 5% or less when the flakes are heat-treated at a temperature of 200°C to 220°C for 60 to 120 minutes.

[0009] In another embodiment, recycled polyester chips are produced by the method for recycling polyester containers. Effect of the Invention

[0010] When the polyester-based film according to the embodiment is immersed in an aqueous sodium hydroxide solution under specific temperature, concentration, and stirring speed conditions, the printed layer does not dissolve completely in the aqueous sodium hydroxide solution, and the average particle size of the printed layer components detached from the base layer is adjusted within a specific range. Therefore, during the recycling process of a polyester-based container containing the film, the printed layer components are easily separated, thereby preventing environmental pollution.

[0011] In addition, the polyester film according to the embodiment can improve the recyclability of polyester containers containing the same, and can improve the quality, yield, and productivity of recycled polyester chips produced by a method for recycling polyester containers using the same.

[0012] Furthermore, the method for recycling polyester-based containers according to the embodiment does not require a separate process for separating the polyester-based container from the film, so time and cost are reduced and it is economical. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention will be described in detail below with reference to the following examples. The implementation examples are not limited to the contents disclosed below, and may be modified in various forms without departing from the spirit of the invention.

[0014] In this specification, when a part is said to "comprise" a certain component, this does not mean that it excludes other components, but that it may further include other components, unless specifically stated to the contrary.

[0015] All numbers and expressions expressing quantities of components, reaction conditions, and the like described herein should be understood to be modified in all instances by the term "about," unless otherwise specifically indicated.

[0016] In this specification, terms such as first, second, primary, and secondary are used to describe various components, and the components are not limited by the terms. The terms are used only to distinguish one component from another.

[0017] In the recycling process of containers equipped with a film as a label, it is important to effectively separate and remove the printed layer components, especially the ink, in order to improve the recyclability and quality of the container. As a method for removing the printed layer components, a washing process using an aqueous sodium hydroxide solution can be performed, but there is a problem that the printed layer components are almost dissolved in the aqueous sodium hydroxide solution during the washing process, or have a very small average particle size, making separation difficult.

[0018] Specifically, if most of the printed layer components are dissolved in the aqueous sodium hydroxide solution during the cleaning process, it may be difficult to separate the printed layer components dissolved in the aqueous sodium hydroxide solution, which may result in environmental pollution.

[0019] Furthermore, if the average particle size of the printed layer components is very small, less than 15 μm, this can reduce the recyclability and quality of the container, and can result in additional costs during the process of separating the container from the aqueous sodium hydroxide solution.

[0020] In the embodiment, the polyester film is cut into pieces 1 cm long and 1 cm wide, immersed in a 1% aqueous solution of sodium hydroxide (NaOH), and stirred at 85°C and a speed of 240 m / min for 15 minutes, after which the average particle size of the printing layer components detached from the base layer is adjusted to 15 μm or more.

[0021] Therefore, in the recycling process of a container equipped with the film, the printed layer components are not dissolved in an aqueous sodium hydroxide solution and can be effectively separated, thereby improving the recyclability and quality of the container and providing excellent effects in preventing environmental pollution.

[0022] [Polyester film] A polyester-based film according to one embodiment includes a base layer containing a polyester-based resin and a printed layer located on one side of the base layer, and is cut into a size of 1 cm in length and 1 cm in width, immersed in a 1% aqueous sodium hydroxide (NaOH) solution, and stirred at 85°C at a speed of 240 m / min for 15 minutes.The average particle size of the printed layer components detached from the base layer is 15 μm or more.

[0023] Another embodiment of the polyester-based film includes a base layer containing a polyester-based resin, a printed layer facing the base layer, and a peel-promoting layer interposed between the base layer and the printed layer, and is cut into a size of 1 cm in length and 1 cm in width, immersed in a 1% aqueous sodium hydroxide (NaOH) solution, and stirred at 85°C at a speed of 240 m / min for 15 minutes, after which the average particle size of the printed layer components detached from the base layer is 15 μm or more.

[0024] [Base material layer] The polyester resin may contain a diol component and a dicarboxylic acid component.

[0025] Specifically, the diol component may include at least one selected from the group consisting of ethylene glycol, diethylene glycol, alkyl group-substituted or unsubstituted propanediol, alkyl group-substituted or unsubstituted butanediol, alkyl group-substituted or unsubstituted pentanediol, alkyl group-substituted or unsubstituted hexanediol, alkyl group-substituted or unsubstituted octanediol, and combinations thereof.

[0026] For example, the diol component may include one or more selected from the group consisting of ethylene glycol, diethylene glycol, 1,3-propanediol, 1,2-octanediol, 1,3-octanediol, 2,3-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, and 1,1-dimethyl-1,5-pentanediol.

[0027] More specifically, the diol component may include one or more selected from the group consisting of ethylene glycol, diethylene glycol, and neopentyl glycol.

[0028] The polyester resin may contain 1 mol% to 35 mol% of neopentyl glycol based on the total number of moles of the diol component. For example, the polyester resin may contain 3 mol% to 35 mol%, 5 mol% to 35 mol%, 7 mol% to 35 mol%, 7 mol% to 33 mol%, 10 mol% to 33 mol%, 15 mol% to 33 mol%, or 17 mol% to 30 mol%, 20 mol% to 35 mol%, 20 mol% to 33 mol%, 21 mol% to 33 mol%, or 22 mol% to 30 mol% of neopentyl glycol based on the total number of moles of the diol component.

[0029] When the content of neopentyl glycol satisfies the above range, the heat shrinkage rate in a first direction or a second direction perpendicular to the first direction can be easily controlled during heat shrinkage of the film, and wrinkles or deformation can be prevented when the film is applied to a container.

[0030] In this specification, the first direction is the transverse direction (TD) or the machine direction (MD), and the second direction perpendicular to the first direction can be the machine direction (MD) or the transverse direction (TD). For example, the first direction can be the machine direction (MD), and the second direction can be the transverse direction (TD) as the main shrinkage direction.

[0031] The polyester resin may contain 55 mol % to 90 mol % of ethylene glycol and 1 mol % to 15 mol % of diethylene glycol based on the total number of moles of the diol component. For example, the polyester resin may contain 60 mol% to 90 mol%, 55 mol% to 85 mol%, 58 mol% to 80 mol%, 60 mol% to 78 mol%, 63 mol% to 78 mol%, 63 mol% to 75 mol%, or 65 mol% to 73 mol% of the ethylene glycol based on the total number of moles of the diol component, and 1 mol% to 13 mol%, 1 mol% to 10 mol%, 3 mol% to 15 mol%, 3 mol% to 13 mol%, 4 mol% to 10 mol%, 4 mol% to 8 mol%, 5 mol% to 7 mol%, 1 mol% to 7 mol%, 2 mol% to 6 mol%, 3 mol% to 5.5 mol%, 3.5 mol% to 5.5 mol%, or 4 mol% to 5.5 mol% of the diethylene glycol.

[0032] The molar ratio of the ethylene glycol and the diethylene glycol may be 5 to 60: 1. For example, the molar ratio of the ethylene glycol and the diethylene glycol may be 7 to 55: 1, 10 to 50: 1, 13 to 46: 1, 12 to 15: 1, 13 to 14.7: 1, 7.8 to 26: 1, 7.8 to 23: 1, 7.8 to 20: 1, 8 to 18: 1, 8 to 16: 1, or 9 to 16: 1. By satisfying the above range of the molar ratio of ethylene glycol and diethylene glycol, there is an advantageous effect on the shrinkage uniformity and shrinkage stress, so that the printed layer components can be more easily removed in the subsequent recycling process.

[0033] The polyester resin may further include a monohydric alcohol other than the diol component. For example, the monohydric alcohol may be methanol, ethanol, isopropyl alcohol, allyl alcohol, or benzyl alcohol. Specifically, the polyester resin may include the monohydric alcohol in an amount of 10 mol% to 30 mol%, 13 mol% to 25 mol%, or 15 mol% to 22 mol% based on the total number of moles of the diol component and the monohydric alcohol, but is not limited thereto.

[0034] The dicarboxylic acid component may be selected from the group consisting of aromatic dicarboxylic acids such as terephthalic acid, dimethyl terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid; aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid; alicyclic dicarboxylic acids; esters thereof; and combinations thereof.

[0035] Specifically, the dicarboxylic acid component may include an aromatic dicarboxylic acid. For example, the dicarboxylic acid component may include 80 mol% or more, 90 mol% or more, 95 mol% or more, 99 mol% or more, or 100 mol% of terephthalic acid or dimethyl terephthalic acid based on the total moles of the dicarboxylic acid component.

[0036] The diol component and the dicarboxylic acid component can undergo an ester exchange reaction and then be polymerized to form a polyester resin.

[0037] Specifically, the transesterification catalyst may be at least one selected from the group consisting of manganese acetate tetrahydrate, calcium, and zinc, and the content of the catalyst may be 0.02 wt% to 0.2 wt%, 0.02 wt% to 0.1 wt%, or 0.03 wt% to 0.08 wt% based on the total weight of the dicarboxylic acid component.

[0038] After the ester exchange reaction is completed, one or more additives selected from the group consisting of silica, potassium and magnesium; a stabilizer such as trimethyl phosphate; and a polymerization catalyst such as antimony trioxide or tetrabutyl ethoxylate may be selectively added.

[0039] The thickness of the substrate layer may be 10 μm to 100 μm. For example, the thickness of the substrate layer may be 20 μm to 80 μm, 30 μm to 70 μm, 35 μm to 65 μm, 35 μm to 55 μm, 40 μm to 60 μm, or 35 μm to 45 μm. When the thickness of the substrate layer satisfies the above range, deterioration of the physical properties of the film and deformation of the appearance such as curling and wrinkling can be effectively prevented when a printing layer is formed on one side of the substrate layer.

[0040] The haze of the substrate layer may be 10% or less, for example, 9% or less, 8.5% or less, 8% or less, 7% or less, or 6.5% or less, and may be 3% to 10%, 4% to 9%, 4.5% to 8%, 4.5% to 7%, or 4.8% to 6.5%.

[0041] When the haze of the substrate layer satisfies the above range, the film including the substrate layer can be easily used as a label. Specifically, if the haze is too low, the transparency is too high, and the film may be unsuitable for use as a label for a container.

[0042] [Print layer] The polyester-based film according to the embodiment includes a printing layer on one side of the base layer.

[0043] Specifically, the print layer may be formed from a print layer composition including a first solvent, a first binder, and a first pigment.

[0044] The first solvent may include at least one selected from the group consisting of benzene, xylene, toluene, tetramethylbenzene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methanol, ethanol, propanol, isopropyl alcohol, butyl alcohol, 2-methyl-2-propanol, octanol, allyl alcohol, benzyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, tetramethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, hexylene glycol, and neopentyl glycol. Specifically, at least one selected from the group consisting of methanol, ethanol, propanol, isopropyl alcohol, butyl alcohol, 2-methyl-2-propanol, octanol, allyl alcohol, benzyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, tetramethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, hexylene glycol, and neopentyl glycol is preferred.

[0045] In addition, the printing layer composition may contain the first solvent in an amount of 1 wt% to 35 wt% based on the total weight of the printing layer composition. For example, the content of the first solvent may be 3 wt% to 35 wt%, 5 wt% to 35 wt%, 10 wt% to 33 wt%, 15 wt% to 32 wt%, 18 wt% to 32 wt%, 25 wt% to 32 wt%, 28 wt% to 32 wt%, 20 wt% to 35 wt%, or 20 wt% to 30 wt% based on the total weight of the printing layer composition. When the content of the first solvent satisfies the above range, the film is cut into a size of 1 cm in length and 1 cm in width, immersed in a 1% concentration sodium hydroxide (NaOH) aqueous solution, and stirred at 85°C at a speed of 240 m / min for 15 minutes, and the average particle size of the printing layer component detached from the base layer can be adjusted to 15 μm or more.

[0046] The first binder may include at least one selected from the group consisting of polyester-based resins, acrylic-based resins, urethane-based resins, nitrocellulose-based resins, chlorinated polypropylene-based resins, and polyester urethane-based resins.

[0047] In addition, the composition for printing layer may contain the first binder in an amount of 25% by weight to 60% by weight based on the total weight of the composition for printing layer. For example, the content of the first binder may be 27% by weight to 60% by weight, 25% by weight to 55% by weight, 25% by weight to 50% by weight, 28% by weight to 45% by weight, 28% by weight to 42% by weight, or 30% by weight to 40% by weight based on the total weight of the composition for printing layer. When the content of the first binder satisfies the above range, the film is cut into pieces measuring 1 cm in length and 1 cm in width, immersed in a 1% concentration aqueous sodium hydroxide (NaOH) solution, and stirred at 85° C. at a speed of 240 m / min for 15 minutes, and the average particle size of the printing layer components detached from the base layer can be adjusted to 15 μm or more.

[0048] The weight ratio of the first solvent and the first binder may be 1:0.5 to 2.5. For example, the weight ratio of the first solvent and the first binder may be 1:0.7 to 2.3, 1:0.9 to 2.2, 1:0.9 to 2.1, 1:1 to 2, 1:0.7 to 1.5, 1:0.7 to 1.3, or 1:0.9 to 1.2. When the weight ratio of the first solvent and the first binder satisfies the above range, the film is cut into a size of 1 cm in length and 1 cm in width, immersed in a 1% sodium hydroxide (NaOH) aqueous solution, and stirred at 85° C. at a speed of 240 m / min for 15 minutes, and the printed layer can be more effectively detached from the base layer, and the average particle size of the printed layer components detached from the base layer can be adjusted to 15 μm or more.

[0049] The first pigment may be an insoluble azo pigment such as barium sulfate, calcium carbonate, titanium oxide, yellow iron oxide, iron black, chrome yellow, chrome vermilion, cadmium yellow, cadmium red, Prussian blue, ultramarine, or organic pigment; a soluble azo pigment; a phthalocyanine pigment; a quinacridone pigment; a polyazo pigment; or a mixture thereof. Specifically, the first pigment may be at least one pigment selected from the group consisting of carbon black, titanium oxide, an insoluble azo pigment, a phthalocyanine pigment, and a polyazo pigment.

[0050] The printing layer composition may contain the pigment in an amount of 5% by weight to 50% by weight based on the total weight of the printing layer composition. For example, the content of the pigment may be 10% by weight to 50% by weight, 20% by weight to 45% by weight, 25% by weight to 45% by weight, 30% by weight to 45% by weight, or 35% by weight to 45% by weight based on the total weight of the printing layer composition.

[0051] The thickness of the printed layer may be 0.1 μm to 100 μm. For example, the thickness of the printed layer may be 0.1 μm to 80 μm, 0.3 μm to 60 μm, 0.5 μm to 40 μm, 0.5 μm to 30 μm, 0.7 μm to 20 μm, 1 μm to 15 μm, 1.5 μm to 10 μm, 1.5 μm to 7 μm, 1.5 μm to 5 μm, or 1.5 μm to 3 μm. When the thickness of the printed layer satisfies the above range, the color development of the printed layer is not reduced and scratch resistance can be improved.

[0052] According to another embodiment, the polyester-based film includes a printing layer facing the base layer. Specifically, the polyester-based film according to another embodiment includes a release promoting layer, the printing layer may be formed on one side of the release promoting layer, and the printing layer, the release promoting layer, and the base layer may be positioned in the above order.

[0053] The printing layer formed on one side of the release-promoting layer can also be formed from a printing layer composition including a first solvent, a first binder, and a first pigment.

[0054] The first solvent for the printing layer formed on one side of the release-promoting layer may be one or more selected from the group consisting of benzene, xylene, toluene, tetramethylbenzene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methanol, ethanol, propanol, isopropyl alcohol, butyl alcohol, 2-methyl-2-propanol, octanol, allyl alcohol, benzyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, tetramethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, hexylene glycol, and neopentyl glycol.

[0055] Specifically, in the case of benzene, xylene, toluene, tetramethylbenzene, acetone, methyl ethyl ketone, methyl isobutyl ketone, or cyclohexanone, which have been conventionally used in printing layers, separation has been difficult during a cleaning process using an aqueous sodium hydroxide solution because they are almost completely dissolved in the aqueous sodium hydroxide solution or have a very small average particle size.

[0056] However, in the case of a polyester-based film including a release-promoting layer according to an embodiment, even if the printing layer contains benzene, xylene, toluene, tetramethylbenzene, acetone, methyl ethyl ketone, methyl isobutyl ketone, or cyclohexanone, the printing layer components are not dissolved in an aqueous sodium hydroxide solution and the printing layer components can be effectively separated.

[0057] [Release-promoting layer] According to another embodiment, the film includes a release-promoting layer on one side of the substrate layer. Specifically, the film includes a release-promoting layer interposed between the substrate layer and the printing layer.

[0058] By including a peel-promoting layer between the base layer and the printed layer, the film is cut into pieces 1 cm long and 1 cm wide, immersed in a 1% sodium hydroxide (NaOH) aqueous solution, and stirred at 85° C. for 15 minutes at a speed of 240 m / min, and the average particle size of the printed layer components detached from the base layer can be adjusted to 15 μm or more. Also, the detachment of the printed layer components can be made easier.

[0059] The release-promoting layer may be formed from a composition for the release-promoting layer, the composition including a second solvent and a second binder.

[0060] The second solvent may include one or more selected from the group consisting of methanol, ethanol, propanol, isopropyl alcohol, butyl alcohol, 2-methyl-2-propanol, octanol, allyl alcohol, benzyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, tetramethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, hexylene glycol, and neopentyl glycol.

[0061] In addition, the composition for the peel-promoting layer may contain the second solvent in an amount of 15% by weight to 40% by weight based on the total weight of the composition for the peel-promoting layer. For example, the content of the second solvent may be 17% by weight to 40% by weight, 15% by weight to 38% by weight, 17% by weight to 38% by weight, or 20% by weight to 35% by weight based on the total weight of the composition for the peel-promoting layer. When the content of the second solvent satisfies the above range, the film is cut into a size of 1 cm in length and 1 cm in width, immersed in a 1% concentration aqueous sodium hydroxide (NaOH) solution, and stirred at 85° C. for 15 minutes at a speed of 240 m / min, and then the printed layer components can be more easily detached from the base layer, and the average particle size of the printed layer components detached from the base layer can be adjusted to 15 μm or more.

[0062] The second binder may include at least one selected from the group consisting of polyester-based resins, acrylic-based resins, polyurethane-based resins, acrylic urethane-based resins, nitrocellulose-based resins, chlorinated polypropylene-based resins, and polyester urethane-based resins.

[0063] In addition, the composition for the peel-promoting layer may contain the second binder in an amount of 10% by weight to 55% by weight based on the total weight of the composition for the peel-promoting layer. For example, the content of the second binder may be 15% by weight to 50% by weight, 15% by weight to 45% by weight, 20% by weight to 43% by weight, or 25% by weight to 40% by weight based on the total weight of the composition for the peel-promoting layer. When the content of the second binder satisfies the above range, the film is cut into a size of 1 cm in length and 1 cm in width, immersed in a 1% sodium hydroxide (NaOH) aqueous solution, and stirred at 85° C. for 15 minutes at a speed of 240 m / min, and the printed layer components can be more easily detached from the base layer, and the average particle size of the printed layer components detached from the base layer can be adjusted to 15 μm or more.

[0064] The weight ratio of the second solvent to the second binder may be 1:0.5 to 3. For example, the weight ratio of the second solvent to the second binder may be 1:0.5 to 2.7, 1:0.5 to 2.5, 1:0.6 to 2.3, or 1:0.7 to 2. When the weight ratio of the second solvent to the second binder satisfies the above range, the film is cut into a size of 1 cm in length and 1 cm in width, immersed in a 1% sodium hydroxide (NaOH) aqueous solution, and stirred at 85° C. at a speed of 240 m / min for 15 minutes, and then the printed layer components can be more easily detached from the base layer, and the average particle size of the printed layer components detached from the base layer can be adjusted to 15 μm or more.

[0065] The composition for the peeling-promoting layer may further include a second pigment. Specifically, the second pigment may be an insoluble azo-based pigment such as barium sulfate, calcium carbonate, titanium oxide, yellow iron oxide, iron black, chrome yellow, chrome vermilion, cadmium yellow, cadmium red, Prussian blue, ultramarine blue, or an organic pigment; a soluble azo-based pigment; a phthalocyanine-based pigment; a quinacridone-based pigment; a polyazo-based pigment; or a mixture thereof. Specifically, the pigment may be at least one selected from the group consisting of carbon black, titanium oxide, an insoluble azo-based pigment, a phthalocyanine-based pigment, and a polyazo-based pigment.

[0066] The composition for the peel-promoting layer may contain the second pigment in an amount of 5 wt% to 50 wt% based on the total weight of the composition for the peel-promoting layer. For example, the content of the second pigment may be 3 wt% to 50 wt%, 5 wt% to 50 wt%, 10 wt% to 50 wt%, 20 wt% to 45 wt%, 25 wt% to 45 wt%, 30 wt% to 45 wt%, or 35 wt% to 45 wt% based on the total weight of the composition for the peel-promoting layer.

[0067] The thickness of the release-promoting layer may be 10 nm to 200 nm. For example, the thickness of the release-promoting layer may be 15 nm to 180 nm, 20 nm to 150 nm, 40 nm to 120 nm, 60 nm to 110 nm, 80 nm to 110 nm, 20 nm to 80 nm, 30 nm to 60 nm, or 40 nm to 50 nm. When the thickness of the release-promoting layer satisfies the above range, the film is cut into a size of 1 cm in length and 1 cm in width, immersed in a 1% sodium hydroxide (NaOH) aqueous solution, and stirred at 85° C. at a speed of 240 m / min for 15 minutes, and then the printed layer components can be more easily detached from the base layer.

[0068] The film is cut into pieces 1 cm long and 1 cm wide, immersed in a 1% aqueous solution of sodium hydroxide (NaOH), and stirred at 85°C for 15 minutes at a speed of 240 m / min. After that, the average particle size of the printing layer components detached from the base layer can be 15 μm or more. For example, the average particle size of the printing layer components detached from the base layer may be 20 μm or more, 23 μm or more, or 25 μm or more, and may be 15 μm to 1000 μm, 15 μm to 100 μm, 15 μm to 80 μm, 20 μm to 100 μm, 20 μm to 80 μm, 25 μm to 75 μm, 20 μm to 1000 μm, 20 μm to 900 μm, 25 μm to 800 μm, 25 μm to 750 μm, 50 μm to 1000 μm, 65 μm to 800 μm, 500 μm to 1000 μm, or 600 μm to 800 μm.

[0069] When the average particle size of the printed layer components detached from the base layer satisfies the above range, the printed layer components can be effectively separated and there is an effect of reducing costs. Specifically, if the average particle size of the printed layer components detached from the base layer is less than the above range, it is not easy to separate the fine particles, which may increase the cost of replacing the filter, and if the average particle size of the printed layer components detached from the base layer exceeds the above range, the quality of the recycled polyester chips produced in the container recycling process may be reduced.

[0070] The total thickness of the film may be 10 μm to 200 μm. For example, the total thickness of the film may be 10 μm to 150 μm, 30 μm to 160 μm, 60 μm to 120 μm, 60 μm to 140 μm, 90 μm to 110 μm, 80 μm to 90 μm, 20 μm to 130 μm, 25 μm to 100 μm, 30 μm to 80 μm, 35 μm to 60 μm, or 35 μm to 45 μm.

[0071] The film may have a light transmittance of 90% or more at a wavelength of 550 nm. Specifically, the light transmittance of the film measured at a wavelength of 550 nm before and after immersion in a 1% sodium hydroxide (NaOH) aqueous solution at a temperature of 85° C. may be 90.5% or more, 91% or more, 92% or more, or 93% or more, respectively.

[0072] The change in light transmittance of the film before and after immersion in a 1% aqueous sodium hydroxide (NaOH) solution at a temperature of 85° C. may be 0.7% or less. For example, the change in light transmittance of the film before and after the immersion may be 0.6% or less or 0.5% or less.

[0073] The change in light transmittance means the absolute value of the difference between the light transmittance of the film measured at a wavelength of 550 nm before the immersion and the light transmittance of the film measured at a wavelength of 550 nm after the immersion.

[0074] Also, the change in Col-L (ΔL) before and after immersion of the film in a 1% aqueous sodium hydroxide (NaOH) solution at a temperature of 85° C. may be 0.7 or less, the change in Col-a (Δa) may be 0.5 or less, and the change in Col-b (Δb) may be 0.5 or less. For example, the change in Col-L (ΔL) before and after immersion may be 0.65 or less, 0.6 or less, 0.55 or less, or 0.5 or less, the change in Col-a (Δa) may be 0.3 or less, 0.1 or less, 0.08 or less, 0.06 or less, or 0.05 or less, and the change in Col-b (Δb) may be 0.3 or less, 0.1 or less, 0.08 or less, or 0.07 or less.

[0075] The change in Col-L (ΔL) means the absolute value of the difference between the Col-L value before the immersion and the Col-L value after the immersion, the change in Col-a (Δa) means the absolute value of the difference between the Col-a value before the immersion and the Col-a value after the immersion, and the change in Col-b (Δb) means the absolute value of the difference between the Col-a value before the immersion and the Col-a value after the immersion.

[0076] In the film according to the embodiment, the change in light transmittance, the change in Col-L (ΔL), the change in Col-a (Δa), and the change in Col-b (Δb) before and after the immersion satisfy the above ranges, so that the average particle size of the printed layer components detached from the base layer satisfies 15 μm or more, and there is almost no change in physical properties such as light transmittance and color before and after the immersion, so that the quality is excellent. Specifically, when a container equipped with the film is recycled, a high-quality recycled polyester chip can be provided.

[0077] The Col-L, Col-a, and Col-b are color systems established by the International Commission on Illumination (CIE (Commission International d'Eclairage)), in which color is expressed as L (lightness), a (complementary color of green to red), and b (complementary color of yellow to blue) to express hue, and can be measured using an UltraScan PRO (Hunterlab), but are not limited thereto.

[0078] Also, the haze change amount before and after immersion of the film in a 1% sodium hydroxide (NaOH) aqueous solution may be 0.5% or less. Specifically, the haze of the film is the haze of the base layer, and since the printed layer components of the film are removed after the immersion, the haze can be measured, and the haze change amount may be 0.4% or less, 0.35% or less, or 0.3% or less. The haze change amount means the absolute value of the difference between the haze value before the immersion and the haze value after the immersion. If the printed layer components are not removed, the haze value of the film including the printed layer cannot be measured.

[0079] Since the haze change amount satisfies the above range, there is almost no change in physical properties such as haze before and after immersion, so the film according to the embodiment satisfies the average particle size of the printed layer components detached from the base layer of 15 μm or more, and there is almost no change in physical properties such as haze before and after immersion, so it is excellent in quality. Specifically, when a container equipped with the film is recycled, a high-quality recycled polyester chip can be provided.

[0080] Furthermore, when the film is heat-treated for 10 seconds at a temperature of 70° C., the heat shrinkage rate in the first direction or the second direction may be 1% to 55%. For example, when the film is heat-treated for 10 seconds at a temperature of 70° C., the heat shrinkage rate in the first direction or the second direction may be 1% to 50%, 3% to 50%, 5% to 50%, 10% to 50%, 20% to 45%, or 25% to 40%.

[0081] The heat shrinkage rate in the first direction or the second direction may be 30% or more when the film is heat-treated for 10 seconds at a temperature of 80° C. For example, when the film is heat-treated for 10 seconds at a temperature of 80° C., the heat shrinkage rate in the first direction or the second direction may be 35% or more, 40% or more, 45% or more, 50% or more, 30% to 85%, 40% to 80%, or 50% to 80%.

[0082] Furthermore, the heat shrinkage rate in the first direction or the second direction may be 50% or more when the film is heat-treated for 10 seconds at a temperature of 90° C. For example, when the film is heat-treated for 10 seconds at a temperature of 90° C., the heat shrinkage rate in the first direction or the second direction may be 55% or more, 60% or more, 70% or more, 50% to 90%, 60% to 85%, 70% to 85%, or 70% to 80%.

[0083] The heat shrinkage rate in the first direction or the second direction may be 30% or more when the film is heat-treated for 10 seconds at a temperature of 100° C. For example, when the film is heat-treated for 10 seconds at a temperature of 100° C., the heat shrinkage rate in the first direction or the second direction may be 35% or more, 40% or more, 50% or more, 30% to 90%, 30% to 80%, 40% to 80%, 45% to 80%, or 50% to 80%.

[0084] When the heat shrinkage rates at 70°C, 80°C, 90°C, and 100°C are within the above ranges, the film can be easily labeled during the process of surrounding at least a portion of a container.

[0085] The glass transition temperature (Tg) of the film measured by a differential scanning calorimetry may be 60° C. or higher. For example, the glass transition temperature (Tg) of the film measured by a differential scanning calorimetry may be 60° C. or higher, 65° C. or higher, 70° C. or higher but lower than 80° C., or 70° C. to 75° C.

[0086] The melting point (Tm) of the film measured by a differential scanning calorimeter may be 170° C. or higher. For example, the melting point of the film measured by a differential scanning calorimeter may be 170° C. or higher, 175° C. or higher, specifically, 170° C. to 230° C., 170° C. to 200° C., or 175° C. to 200° C.

[0087] When the glass transition temperature and melting point of the film are within the above ranges, clumping that may occur during the container recycling process can be reduced. Specifically, during heat treatment in the container recycling process, flakes may adhere to each other to form aggregates. This clumping phenomenon can reduce the quality of the recycled polyester chips produced, thereby reducing the recyclability of the containers.

[0088] However, since the glass transition temperature and melting point of the film according to the embodiment satisfy the above ranges, the clumping phenomenon that can occur during the container recycling process can be reduced, thereby improving the recyclability of the container and maximizing the quality and productivity of the recycled polyester chips produced.

[0089] Furthermore, the crystallization temperature (Tc) of the film measured by a differential scanning calorimeter may not be measured or may be from 70° C. to 130° C. For example, the crystallization temperature (Tc) of the film measured by a differential scanning calorimeter may be not measured or may be from 70° C. to 120° C., 75° C. to 110° C., or 80° C. to 110° C.

[0090] The heat of crystallization of the film measured at the crystallization temperature (Tc) may be 0.01 J / g to 50 J / g. For example, the heat of crystallization of the film measured at the crystallization temperature (Tc) may be 0.01 J / g to 40 J / g, 0.05 J / g to 30 J / g, 0.1 J / g to 20 J / g, 0.1 J / g to 10 J / g, 0.1 J / g to 8 J / g, or 0.1 J / g to 5 J / g.

[0091] By satisfying the above ranges for the crystallization temperature and heat of crystallization, it is possible to reduce the clumping phenomenon that may occur during the container recycling process, thereby improving the recyclability of the container and maximizing the quality and productivity of the recycled polyester chips produced.

[0092] Specifically, when the melting point (Tm) of the film measured by a differential scanning calorimeter is 170° C. or higher and the crystallization temperature (Tc) is 70° C. to 130° C., the effect of preventing the clumping phenomenon can be maximized.

[0093] [Method of manufacturing polyester film] A method for producing a polyester-based film according to an embodiment includes forming a base layer using a composition for a base layer containing a polyester-based resin, and forming a printing layer on one side of the base layer using a composition for a printing layer.

[0094] A method for producing a polyester-based film according to another embodiment includes the steps of forming a base layer using a composition for a base layer containing a polyester-based resin, forming a release promotion layer on one side of the base layer using a composition for a release promotion layer, and forming a printing layer on one side of the base layer using a composition for a printing layer.

[0095] <Base material layer> The base layer may be formed from a base layer composition containing a polyester-based resin, as described above.

[0096] Specifically, the polyester resin is melt-extruded at 260°C to 300°C or 270°C to 290°C using a T-die, and then cooled to obtain an unstretched sheet. The unstretched sheet is preheated while passing through a chamber while being transported at a speed of 10 m / min to 110 m / min or 20 m / min to 90 m / min, and the sheet obtained by stretching is then heat-set to produce a base layer.

[0097] The preheating may be performed for 0.01 to 1 minute at 90° C. to 120° C. For example, the preheating temperature (T1) may be 95° C. to 115° C. or 97° C. to 113° C., and the preheating time may be 0.05 to 0.5 minutes, or 0.08 to 0.2 minutes.

[0098] The stretching may be uniaxial or biaxial. Specifically, the stretching may be uniaxial in a second direction, or biaxial in a first direction and then a second direction perpendicular to the first direction. For example, when the stretching is uniaxial, the second direction may be a transverse direction (TD).

[0099] Specifically, when the stretching is uniaxial stretching, the stretching may be performed in the second direction at an elongation ratio of 3 to 5.5 times at a temperature that is 20° C. or more lower than the preheating temperature (T1). For example, the stretching may be performed in the second direction at an elongation ratio of 2.5 to 5.5 times, 2.5 to 5 times, or 3.5 to 5 times at a stretching temperature of 60° C. to 90° C., 70° C. to 90° C., or 70° C. to 85° C.

[0100] Alternatively, when the stretching is biaxial stretching, the stretching may be performed in a first direction at an elongation rate of 2.5 to 5 times at a temperature 20°C or more lower than the preheating temperature (T1), and then in a second direction at an elongation rate of 3 to 5 times. For example, the stretching may be performed in a first direction at an elongation rate of 2.5 to 5 times, 2.5 to 4 times, or 3.5 to 5 times at a stretching temperature of 60°C to 90°C, 70°C to 90°C, or 70°C to 85°C, and then in a second direction at an elongation rate of 2.5 to 5 times, 2.5 to 4 times, or 3.5 to 5 times.

[0101] In addition, a coating process may be further performed before uniaxially stretching in the second direction, or after stretching in the first direction and before stretching in the second direction. Specifically, a coating process may be further performed to form an accelerating layer that can impart functionality such as antistatic properties to the film. The coating process may be performed by spin coating or in-line coating, but is not limited thereto.

[0102] The heat fixing may be annealing, and may be performed for 0.01 to 1 minute at 70° C. to 95° C. For example, the heat fixing temperature (T2) may be 75° C. to 95° C., 75° C. to 93° C., 80° C. to 93° C., or 85° C. to 93° C., and the heat fixing time may be 0.05 to 0.5 minutes, or 0.08 to 0.2 minutes.

[0103] The preheating temperature (T1)-heat setting temperature (T2) may be 10° C. to 40° C. Specifically, the stretching temperature may be lower than the preheating temperature (T1) by 10° C. or more, 15° C. or more, or 20° C. or more, and the heat setting temperature (T2) may be higher than the stretching temperature by 5° C. or more, or 10° C. or more. When the preheating temperature, stretching temperature, and heat setting temperature satisfy the above ranges, the heat shrinkage rate in the first direction or the second direction can be effectively controlled.

[0104] <Release-promoting layer> The release promoting layer may be formed by coating one surface of the substrate layer with a composition for a release promoting layer, specifically, by in-line or off-line coating of the composition for a release promoting layer on one surface of the substrate layer, but is not limited thereto. The composition for the peel-promoting layer is as described above.

[0105] <Print layer> The printing layer may be formed by using a printing layer composition and a printer. Specifically, the base layer or a base layer having a release-promoting layer formed on one side thereof is placed in a printer, and the printing layer composition is printed on one side of the release-promoting layer to form a printing layer. The composition for the printing layer is as described above.

[0106] <How to recycle polyester containers> Another embodiment of a method for recycling polyester containers includes the steps of preparing a polyester container at least partially surrounded by the polyester film, crushing the polyester container with the film to obtain flakes, immersing the crushed flakes in a 1% aqueous sodium hydroxide (NaOH) solution at 85°C, and heat-treating the immersed flakes to produce recycled polyester chips, wherein the clumping rate is 5% or less when the flakes are heat-treated at a temperature of 200°C to 220°C for 60 to 120 minutes.

[0107] To regenerate a polyester-based container according to one implementation, first provide a polyester-based container having at least a portion surrounded by the polyester-based film.

[0108] Conventionally, collected waste products, which may contain a mixture of containers, metals, glass, plastics, etc., are washed and polyester-based containers are sorted, and a process of removing the films encasing the containers is carried out to improve the recyclability and quality of the containers. The removal process has been carried out by mechanically breaking or cutting the films, or by additional processes such as liquid specific gravity separation, dehydration drying, air specific gravity separation, or pelletization.

[0109] However, it is difficult to completely remove the film using the removal process, and in particular, it is difficult to improve the quality of the recycled polyester chips produced due to residual ink remaining on the film.

[0110] The method for recycling polyester containers according to the embodiment can produce recycled polyester chips without a separate process for removing the film surrounding the polyester container, which has the effect of reducing costs. In addition, the film according to the embodiment has excellent environmental pollution prevention effects because the printed layer components are easily separated and the film is not completely dissolved in the sodium hydroxide solution during the cleaning process.

[0111] The polyester-based container has the polyester-based film on its outer surface. Specifically, after the polyester-based film surrounds the outer surface of the polyester-based container, the film may be shrunk by steam or hot air to enclose at least a portion of the outer surface of the polyester-based container. For example, the polyester-based film may be a heat-shrinkable film that serves as a label for the polyester-based container, but is not limited thereto. The polyester film is as described above.

[0112] The polyester-based container may contain 90% by weight or more of a polyester-based resin based on the total weight of the polyester-based container. For example, the polyester-based container may be a container containing polyethylene terephthalate (PET), and the polyester-based container may contain, but is not limited to, 90% by weight or more, 95% by weight or more, or 99% by weight or more of polyethylene terephthalate based on the total weight of the polyester-based container.

[0113] The polyester container with the film thereon is then crushed to obtain flakes.

[0114] Specifically, at least a portion of the outer surface of the polyester-based container is surrounded by the film, and the container and the film are ground together to obtain flakes without a step of separating the container and the film.

[0115] That is, the flakes include first flakes obtained by pulverizing the polyester container and second flakes obtained by pulverizing the film.

[0116] The particle size of the first flakes may be 0.1 mm to 25 mm, and the particle size of the second flakes may be 0.1 mm to 25 mm. For example, the particle size of the first flakes may be 0.3 mm to 23 mm, 0.5 mm to 20 mm, 1 mm to 20 mm, 0.5 mm to 15 mm, 0.5 mm to 13 mm, 1 mm to 18 mm, 1 mm to 15 mm, 1 mm to 13 mm, or 2 mm to 10 mm, and the particle size of the second flakes may be 0.3 mm to 23 mm, 0.5 mm to 20 mm, 1 mm to 20 mm, 0.5 mm to 15 mm, 0.5 mm to 13 mm, 1 mm to 18 mm, 1 mm to 15 mm, 1 mm to 13 mm, or 2 mm to 10 mm, but is not limited thereto.

[0117] The crushed flakes are then immersed in a 1% aqueous solution of sodium hydroxide (NaOH) at 85°C.

[0118] Specifically, the crushed flakes may be washed by immersing them in a 1% sodium hydroxide aqueous solution at 85° C. for 5 to 30 minutes. For example, the first and second flakes may be washed by immersing them in a 1% sodium hydroxide aqueous solution at 85° C. for 5 to 25 minutes or 10 to 20 minutes.

[0119] By carrying out the washing step, impurities that may remain in the crushed flakes can be removed and printed layer components can be effectively removed, thereby improving the quality and purity of the recycled polyester chips produced and maximizing the recyclability of the containers.

[0120] As described above, the film is cut into pieces measuring 1 cm in length and 1 cm in width, immersed in a 1% aqueous sodium hydroxide solution, and stirred at 85°C and a speed of 240 m / min for 15 minutes, after which the average particle size of the printing layer components detached from the writing layer is 15 μm or more.

[0121] Therefore, the washing step can effectively separate and remove the printed layer components remaining in the crushed flakes, particularly the second flakes, from the second flakes. In addition, since the printed layer components are not dissolved in the sodium hydroxide aqueous solution and have an average particle size of 15 μm or more, the printed layer components, particularly the ink components, can be effectively removed to improve the quality and purity of the recycled polyester chips produced, and the environmental protection effect is also excellent.

[0122] Specifically, the printing layer components having an average particle size of 15 μm or more can be separated and removed from the aqueous sodium hydroxide solution by using a filter having a pore size of 15 μm or a filter having a pore size of 0.1 mm or more and less than 25 mm, which is smaller than the size of the flakes, but is not limited to this.

[0123] In addition, when the cleaning step of immersing the substrate in a 1% sodium hydroxide aqueous solution at 85° C. for 5 to 30 minutes is the first cleaning step, a second cleaning step can be further carried out after the first cleaning step.

[0124] Specifically, the second washing step may be performed with room temperature water and / or a 0.5% to 3% sodium hydroxide aqueous solution at 80° C. to 97° C. for 5 to 30 minutes.

[0125] More specifically, if the second washing step is performed with a sodium hydroxide solution having a concentration of 0.5% to 3%, impurities remaining in the pulverized flakes can be more effectively removed, and if the second washing step is performed with water at room temperature, residual sodium hydroxide solution can be removed. For example, after the first washing step, the second washing step can be performed with water at room temperature, or after the first washing step, washing with a sodium hydroxide solution having a concentration of 0.5% to 3% can be performed, followed by a second washing step with water at room temperature.

[0126] In addition, after the washing step, a step of drying the washed flakes for 10 to 90 minutes at 60° C. to 175° C. can be further performed. For example, the drying step can be performed at 65° C. to 175° C., 70° C. to 170° C., 90° C. to 165° C., 100° C. to 165° C., or 120° C. to 165° C. for 15 to 85 minutes, 20 to 70 minutes, 15 to 30 minutes, or 50 to 70 minutes.

[0127] The washing and drying steps may be repeated 1 to 5 times. For example, the washing and drying steps may be repeated 2 to 5 times or 3 to 5 times in sequence to effectively remove impurities remaining in the flakes.

[0128] Finally, the soaked flakes are heat treated to produce recycled polyester-based chips.

[0129] The heat treatment may be performed for 60 to 120 minutes at 200° C. to 220° C. For example, the heat treatment may be performed for 70 to 120 minutes at 200° C. to 215° C. or 205° C. to 220° C. or for 80 to 120 minutes.

[0130] Furthermore, when the flakes are heat-treated for 60 to 120 minutes at a temperature of 200° C. to 220° C., the clumping fraction may be 5% or less. For example, when the flakes are heat-treated for 60 minutes at 220° C. or for 90 minutes at a temperature of 210° C., the clumping fraction may be 4% or less, 3% or less, 2.5% or less, 2% or less, 1% or less, or 0.8% or less.

[0131] The clumping refers to an aggregate that may be formed from the flakes, and the size of the aggregate may be, for example, three times or more of the flake particle size. The clumping fraction refers to the weight ratio of the aggregate based on the total weight of the flakes. For example, the flakes may be sieved and then heat-treated, during which the flakes may adhere to each other to form an aggregate. The aggregate may be filtered by passing it through a sieve again, and the clumping fraction can be obtained by measuring the weight of the aggregate obtained in this manner and calculating the weight ratio of the aggregate based on the total weight of the heat-treated flakes.

[0132] Therefore, the higher the clumping fraction value, the lower the quality of the recycled polyester chips may be due to the first and second flakes adhering to each other. However, since the second flakes are obtained by crushing the polyester film according to the embodiment, the formation of agglomerates can be effectively reduced or prevented, thereby improving the quality of the recycled polyester chips produced.

[0133] After the heat treatment process, recycled polyester chips are obtained. Specifically, after the heat treatment process, recycled polyester chips including the first flakes and the second flakes are obtained. For example, the flakes are melt-extruded and then cut to obtain recycled polyester chips, but the present invention is not limited thereto.

[0134] <Recycled polyester chips> In another embodiment, recycled polyester chips are produced by the method for recycling polyester containers.

[0135] Specifically, the recycled polyester-based chips may include first flakes containing polyethylene terephthalate and second flakes containing a polyester-based resin.

[0136] The intrinsic viscosity (IV) of the recycled polyester chips may be 0.60 dl / g or more. For example, the intrinsic viscosity of the recycled polyester chips may be 0.63 dl / g or more, 0.65 dl / g or more, 0.70 dl / g or more, 0.75 dl / g or more, 0.60 dl / g to 3.00 dl / g, 0.60 dl / g to 2.0 dl / g, or 0.65 dl / g to 1.0 dl / g.

[0137] The recycled polyester chips may contain 70% to 99% by weight of polyethylene terephthalate and 1% to 30% by weight of polyester resin, based on the total weight of the recycled polyester chips. For example, the recycled polyester chips may contain 80% to 99% by weight, 90% to 99% by weight, or 95% to 99% by weight of polyethylene terephthalate and 1% to 20% by weight, 1% to 10% by weight, or 1% to 5% by weight of polyester resin, based on the total weight of the recycled polyester chips.

[0138] (Example) The above contents will be described in more detail with reference to the following examples, however, the following examples are only for illustrating the present invention and the scope of the present invention is not limited to these examples.

[0139] Example A -Preparation of polyester resin- [Production Example 1-1] In a stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser, 100 mol% terephthalic acid (TPA) as a dicarboxylic acid component, and 78 mol% ethylene glycol (EG), 17 mol% neopentyl glycol (NPG), and 5 mol% diethylene glycol (DEG) as diol components were mixed. Then, 0.05 mol% (relative to the acid component) of zinc acetate was added as an ester exchange catalyst, and an ester exchange reaction was carried out while distilling off the methanol produced. Then, 0.025 mol% (relative to the acid component) of antimony trioxide was added as a polycondensation catalyst, and a polycondensation reaction was carried out at 280°C under reduced pressure of 26.6 Pa (0.2 Torr) to prepare a polyester resin.

[0140] [Manufacturing Examples 1-2 to 1-6] A polyester resin was prepared in the same manner as in Production Example 1-1, except that the components and contents were changed as shown in Table 1 below.

[0141] [Table 1]

[0142] -Preparation of composition for printing layer- [Production Example 2-1] A composition for the printing layer was prepared by mixing and stirring 25% by weight of ethanol, 35% by weight of a polyester binder (BNPE-100, BN Chemical Co.), and 40% by weight of a blue pigment (First Blue 1530, First Color Co.).

[0143] [Manufacturing Examples 2-2 to 2-6] A printing layer composition was prepared in the same manner as in Preparation Example 2-1, except that the components and contents were changed as shown in Table 2 below.

[0144] [Table 2]

[0145] -Production of polyester films- [Production Example 3-1] The polyester resin of Production Example 1-1 was put into an extruder, melt-extruded at 280°C using a T-die, and then cooled to obtain an unstretched sheet. The unstretched sheet was then preheated at 105°C for 0.1 minutes while being transported at a speed of 30 m / min. It was then stretched in the transverse direction at an elongation rate of 4.0 to 4.7 times at 85°C. It was then heat-set at 90°C for 0.1 minutes to produce a base layer having a thickness of 40 μm.

[0146] The base layer was then placed in a printing machine, and one side of the base layer was printed with the printing layer composition of Production Example 2-1 to produce a polyester film with a total thickness of 42 μm on which a printing layer with a thickness of 2 μm was formed.

[0147] [Manufacturing Examples 3-2 to 3-6] As shown in Table 3 below, polyester-based films were produced in the same manner as in Production Example 3-1, except that the polyester-based resins of Production Examples 1-2 to 1-6 were used instead of the polyester-based resin of Production Example 1-1, and the printing layer compositions of Production Examples 2-2 to 2-6 were used instead of the printing layer composition of Production Example 2-1.

[0148] -Manufacturing recycled polyester chips- [Example 1] A portion of the outer surface of a polyethylene terephthalate container (PET container, 30 g) was wrapped with the polyester film (1 g) of Preparation Example 3-1, and then the film was shrunk at a temperature of 90°C under hot air conditions to produce a polyester terephthalate container in which the film surrounded a portion of the outer surface.

[0149] The container containing the film was then crushed in a crusher to obtain flakes, which were then immersed in a 1% aqueous solution of sodium hydroxide (NaOH) at 85° C. and washed for 15 minutes at a stirring speed of 240 m / min.

[0150] The flakes were then washed again with room temperature water to remove residual sodium hydroxide solution, filtered using a sieve with a pore size of 15 μm, dried at 160° C. for 1 hour, and then heat-treated at 210° C. for 90 minutes to produce recycled polyester chips.

[0151] [Examples 2 and 3, and Comparative Examples 1 to 3] Recycled polyester chips were produced in the same manner as in Example 1, except that the polyester films of Production Examples 3-2 to 3-6 were used instead of the polyester film of Production Example 3-1.

[0152] (Evaluation example) [Evaluation Example 1-1: Average particle size] A 1% concentration aqueous sodium hydroxide (NaOH) solution was placed in a stirrer and heated to 85°C, after which the film was cut into pieces of 1 cm length and 1 cm width and placed in the stirrer. After stirring for 15 minutes at a stirring speed of 240 m / min, the average particle size of the detached printing layer components was measured using a MICROTRAC S-3500 (Dream Co., Ltd.).

[0153] [Evaluation example 1-2: Light transmittance and color] The film was cut into a length of 1 cm and a width of 1 cm, and the light transmittance at 550 nm, Col-L, Col-a and Col-b were measured using an UltraScan PRO (Hunterlab) before and after immersion in a 1% aqueous sodium hydroxide solution at 85°C.

[0154] [Evaluation Example 1-3:Clamping Fraction] The flakes produced above were sieved through a 0.625'' sieve, and 1 kg of the flakes that had passed through were exposed to an oven at 210°C for 90 minutes. After cooling to room temperature, the weight of the agglomerates filtered through the 0.625'' sieve was measured, and the clumping fraction was calculated as a percentage of the total weight of the flakes.

[0155] [Table 3]

[0156] As shown in Table 3, the polyester films of Production Examples 3-1 to 3-3 and the recycled polyester chips of Examples 1 to 3 produced by the method for recycling polyester containers using the polyester films were superior in quality to those of Comparative Examples 1 to 3.

[0157] Specifically, the polyester films of Production Examples 3-1 to 3-3, which contain the printed layers of Production Examples 2-1 to 2-3, show almost no change in light transmittance or color before and after immersion in a 1% sodium hydroxide aqueous solution at a temperature of 85° C., and the average particle size of the printed layer components separated in the recycling process is 15 μm or more, so the recycled polyester chips produced by the method for recycling polyester containers containing the same are of excellent quality. In addition, since the printed layer components are not dissolved in the sodium hydroxide aqueous solution, it can be seen that the effect of preventing environmental pollution is also excellent.

[0158] On the other hand, the recycled polyester chips of Comparative Examples 1 to 3 have a high clumping fraction and therefore are of poor quality, making them less recyclable.In addition, the printed layer components are all dissolved in the sodium hydroxide aqueous solution or have an average particle size of less than 15 μm, making them difficult to separate, which can lead to environmental pollution problems.

[0159] Example B -Preparation of polyester resin- [Production Example 4-1] In a stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser, 100 mol% terephthalic acid (TPA) as a dicarboxylic acid component, and 65 mol% ethylene glycol (EG), 30 mol% neopentyl glycol (CHDM), and 5 mol% diethylene glycol (DEG) as diol components were mixed. 0.05 mol% (relative to the acid component) of zinc acetate was added as an ester exchange catalyst, and an ester exchange reaction was carried out while distilling off the methanol produced. Then, 0.025 mol% (relative to the acid component) of antimony trioxide was added as a polycondensation catalyst, and a polycondensation reaction was carried out at 280°C under reduced pressure of 26.6 Pa (0.2 Torr) to prepare a polyester resin.

[0160] [Manufacturing Examples 4-2 to 4-6] Polyester resins were prepared in the same manner as in Production Example 4-1, except that the components and contents were changed as shown in Table 4 below.

[0161] [Table 4]

[0162] -Preparation of Composition for Release-Promoting Layer- [Production Example 5-1] A composition for a release promoting layer was prepared by mixing and stirring 25% by weight of ethanol, 35% by weight of a polyester binder (BNPE-100, BN Chemical Co., Ltd.) and 40% by weight of a blue pigment (FR, Toyo Kagaku Co., Ltd.).

[0163] [Manufacturing Examples 5-2 to 5-4] A composition for a peel-promoting layer was prepared in the same manner as in Preparation Example 5-1, except that the components and contents were changed as shown in Table 5 below.

[0164] [Table 5]

[0165] -Preparation of composition for printing layer- [Production Example 6-1] A composition for the printing layer was prepared by mixing and stirring 30% by weight of toluene, 30% by weight of a polypropylene-based binder (BINDER-I, Hyundai Chemical Co., Ltd.), and 40% by weight of a blue pigment (First Blue 1530, First Color Co., Ltd.).

[0166] [Production Example 6-2] A printing layer composition was prepared in the same manner as in Preparation Example 6-1, except that a yellow pigment was used instead of the blue pigment.

[0167] [Table 6]

[0168] -Production of polyester films- [Production Example 7-1] The polyester resin of Production Example 4-1 was put into an extruder, melt-extruded at 280°C using a T-die, and then cooled to obtain an unstretched sheet. The unstretched sheet was then preheated at 105°C for 0.1 minutes while being transported at a speed of 30 m / min. It was then stretched in the transverse direction at 85°C with an elongation ratio of 4.0 to 4.7 times, and heat-set at 90°C for 0.1 minutes to produce a base layer having a thickness of 40 μm.

[0169] Then, the composition for the release promoting layer of Preparation Example 5-1 was in-line or off-line coated on one side of the base layer to form a release promoting layer having a thickness of 100 nm.Then, the base layer having the release promoting layer formed on one side was placed in a printer, and one side of the release promoting layer was printed with the composition for the printing layer of Preparation Example 6-1 to produce a polyester film having a total thickness of 42.1 μm and a printing layer having a thickness of 2 μm.

[0170] [Manufacturing Examples 7-2 to 7-6] As shown in Table 7 below, polyester-based films were produced in the same manner as in Production Example 7-1, except that the polyester-based resins of Production Examples 4-2 to 4-6 were used instead of the polyester-based resin of Production Example 4-1, the compositions for the release-promoting layer of Production Examples 5-2 to 5-4 were used instead of the composition for the release-promoting layer of Production Example 5-1, and Production Example 6-1 or Production Example 6-2 was used as the composition for the printing layer. However, the polyester-based films of Production Examples 7-5 and 7-6 did not form a release-promoting layer.

[0171] -Manufacturing recycled polyester chips- [Example 4] A portion of the outer surface of a polyethylene terephthalate container (PET container, 30 g) was wrapped with the polyester film (1 g) of Preparation Example 7-1, and then the film was shrunk at a temperature of 90°C and exposed to hot air to produce a polyester terephthalate container in which the film surrounded a portion of the outer surface.

[0172] The container containing the film was then crushed in a crusher to obtain flakes, which were then immersed in a 1% aqueous solution of sodium hydroxide (NaOH) at 85° C. and washed for 15 minutes at a stirring speed of 240 m / min.

[0173] The flakes were then washed again with room temperature water to remove residual sodium hydroxide solution, filtered through a sieve with a pore size of 15 μm, dried at 160° C. for 1 hour, and then heat-treated at 210° C. for 90 minutes to produce recycled polyester chips.

[0174] [Examples 5 and 6, and Comparative Examples 4 to 6] Recycled polyester chips were produced in the same manner as in Example 4, except that the polyester films of Production Examples 7-2 to 7-6 were used instead of the polyester film of Production Example 7-1.

[0175] (Evaluation example) [Evaluation Example 2-1: Average particle size] A 1% concentration aqueous sodium hydroxide (NaOH) solution was placed in a stirrer and heated to 85°C, after which the film was cut into pieces of 1 cm length and 1 cm width and placed in the stirrer. After stirring for 15 minutes at a stirring speed of 240 m / min, the average particle size of the detached printing layer components was measured using a MICROTRAC S3500 (Dream Co., Ltd.).

[0176] [Evaluation Example 2-2: Haze] The film was cut into a length of 1 cm and a width of 1 cm, and the haze was measured before and after immersion in a 1% aqueous sodium hydroxide solution at 85° C. using a haze meter NDH-5000W manufactured by Nippon Denshoku Industries Co., Ltd.

[0177] [Evaluation Example 2-3:Clamping Fraction] The flakes produced above were passed through a 0.625" sieve and 1 kg of the flakes was exposed to an oven at 210°C for 90 minutes. After cooling to room temperature, the weight of the agglomerates filtered through a 0.625" sieve was measured, and the clumping fraction was calculated as a percentage of the total weight of the flakes.

[0178] [Table 7]

[0179] As can be seen from Table 7, the polyester films of Production Examples 4-1 to 4-3 and the recycled polyester chips of Examples 4 to 6 produced by the method for recycling polyester containers using the same are superior in quality to those of Comparative Examples 4 to 6.

[0180] Specifically, the polyester films of Production Examples 7-1 to 7-3 contain a peel-promoting layer, so there is almost no change in haze before and after immersion in a 1% sodium hydroxide aqueous solution at a temperature of 85°C, and the average particle size of the printed layer components that are detached during the recycling process is 15μm or more, so the recycled polyester chips produced by the polyester container recycling method containing this are of excellent quality.In addition, since the printed layer components are not dissolved in the sodium hydroxide aqueous solution, it is also found to be excellent in preventing environmental pollution.

[0181] On the other hand, the recycled polyester chips of Comparative Examples 4 to 6 have environmental pollution problems because all of the printed layer components are dissolved in the sodium hydroxide aqueous solution. Specifically, the recycled polyester chips of Comparative Examples 4 and 5 have a relatively low clumping fraction, but the printed layer components are not removed because the haze cannot be measured, and the recycled polyester chip of Comparative Example 6 has a very high clumping fraction, so the quality is poor and the recyclability is low.

Claims

1. A polyester film, comprising: a base material layer containing a polyester resin; and a printing layer located on one surface of the base material layer, wherein the printing layer is formed of a printing layer composition containing a first solvent, a first binder, and a first pigment, wherein a weight ratio of the first solvent to the first binder is 1:0.5 to 2.5, wherein the first solvent contains ethanol, wherein the polyester resin contains a diol component and a dicarboxylic acid component, wherein the diol component contains one or more selected from the group consisting of ethylene glycol, diethylene glycol, and neopentyl glycol, wherein the polyester resin contains neopentyl glycol in an amount of 1 mol% to 35 mol% based on the total number of moles of the diol component, after cutting into a size of 1 cm in length and 1 cm in width, immersing in a 1% concentration aqueous sodium hydroxide (NaOH) solution, stirring at a rate of 240 m / min for 15 minutes at 85°C, an average particle size of the printing layer component detached from the base material layer is 15 µm or more, a polyester film, wherein when flakes obtained by pulverizing a polyethylene terephthalate container provided with the polyester film are heat-treated at a temperature of 200°C to 220°C for 60 minutes to 120 minutes, a clamping fraction is 5% or less.

2. The polyester film according to claim 1, wherein the printing layer composition contains 1 wt% to 35 wt% of the first solvent, 25 wt% to 60 wt% of the first binder, and 5 wt% to 50 wt% of the first pigment based on the total weight of the printing layer composition.

3. The polyester film according to claim 1, wherein the polyester resin contains 55 mol% to 90 mol% of ethylene glycol and 1 mol% to 15 mol% of diethylene glycol based on the total number of moles of the diol component, and a molar ratio of the ethylene glycol to the diethylene glycol is 5 to 60:

1.

4. The polyester film according to claim 1, wherein in the base material layer, a light transmittance at 550 nm is 90% or more, a change amount of the light transmittance before and after the immersion is 0.7% or less, a change amount (ΔL) of Col-L before and after the immersion is 0.7 or less, a change amount (Δa) of Col-a is 0.5 or less, and a change amount (Δb) of Col-b is 0.5 or less.

5. A polyester film, comprising: a base material layer containing a polyester resin; and A printing layer facing the base material layer, and a peeling promotion layer interposed between the base material layer and the printing layer, wherein the printing layer is formed of a printing layer composition containing a first solvent, a first binder, and a first pigment, wherein the weight ratio of the first solvent and the first binder is 1:0.5 to 2.5, wherein the polyester resin contains a diol component and a dicarboxylic acid component, wherein the diol component contains one or more selected from the group consisting of ethylene glycol, diethylene glycol, and neopentyl glycol, wherein the polyester resin contains neopentyl glycol in an amount of 1 mol% to 35 mol% based on the total number of moles of the diol component, wherein the peeling promotion layer is formed of a peeling promotion layer composition containing a second solvent, a second binder, and a second pigment, wherein the weight ratio of the second solvent and the second binder is 1:0.5 to 3, wherein the first solvent contains toluene and the second solvent contains ethanol, after cutting into a size of 1 cm in length and 1 cm in width and immersing in a 1% concentration aqueous sodium hydroxide (NaOH) solution, stirring at a rate of 240 m / min at 85°C for 15 minutes, the average particle size of the printing layer component detached from the base material layer is 15 µm or more, A polyester film having a clamping fraction of 5% or less when flakes obtained by pulverizing a polyethylene terephthalate container provided with the polyester film are heat-treated at a temperature of 200°C to 220°C for 60 minutes to 120 minutes.

6. The polyester film according to claim 5, wherein the peeling promotion layer composition contains 15% by weight to 40% by weight of a second solvent, 10% by weight to 55% by weight of a second binder, and 5% by weight to 50% by weight of a second pigment based on the total weight of the peeling promotion layer composition.

7. The polyester film according to claim 5, wherein the thickness of the base material layer is 10 µm to 100 µm, the thickness of the peeling promotion layer is 10 nm to 200 nm, and the thickness of the printing layer is 0.1 µm to 100 µm.

8. The polyester film according to claim 5, wherein in the base material layer, the amount of change in haze before and after immersion in a 1% concentration aqueous sodium hydroxide (NaOH) solution is 0.5% or less.

9. A step of preparing a polyester container surrounding at least a part of the polyester film according to claim 1, The step of pulverizing the polyester-based container provided with the film to obtain flakes; The step of immersing the pulverized flakes in an aqueous sodium hydroxide (NaOH) solution at 85 °C and a concentration of 1%; A method for recycling a polyester-based container, comprising the step of heat-treating the immersed flakes to produce recycled polyester-based chips.