Recycled PET film made from recycled chips

Abstract

The recycled PET film of the present invention, including the color-complementing agent containing a glycerin-based compound, has significantly lower yellowing and color difference values ​​than conventional recycled PET films, and can satisfy breaking strength and heat shrinkage rates at levels that make it possible to replace virgin PET.

Description

[Technical Field]

[0001] The present invention relates to a recycled PET film produced by incorporating waste PET and a color-recovering agent, and a method for producing the same. [Background technology]

[0002] PET (polyethylene terephthalate) has excellent durability, processability, and thermal stability, and has been used in a variety of areas, including clothing, packaging containers, home appliances, automobiles, and films. However, its high porosity and non-biodegradability make it difficult to process waste PET, causing serious environmental pollution problems during landfill or incineration processes.

[0003] Therefore, technology to recycle waste PET is attracting attention in an effort to solve the problems of rising costs and environmental pollution due to the depletion of petroleum resources.

[0004] In the recycling process for regenerating waste PET, the recycled PET undergoes sorting, removal of foreign matter, washing, and separation of metals, and is then used to manufacture clothing, packaging containers, home appliances, automobiles, films, etc. However, because the physical properties of recycled PET are inferior to those of PET products made from virgin PET, its recycling applications are limited.

[0005] In particular, recycled PET film made from recycled PET has stricter processing conditions than other molded products. It is produced by stretching it 4 to 5 times in the transverse and axial directions, which means there are many restrictions on the physical properties of the PET resin used, the heat treatment process conditions, and the amount of additives it contains. In addition, because various grades of recycled PET are mixed together, the processing conditions for recycling it into film are even more difficult.

[0006] As a result, recycled PET films manufactured using conventional waste PET have the problem of poor film formability, and in particular, have increased color difference values, resulting in very poor appearance.

[0007] In recent years, recycled PET films manufactured using recycled PET have been supplemented with color-complementing agents containing organic or inorganic compounds to solve the problem of increased color difference, but they still have less favorable color difference than virgin PET films, and the addition of the color-complementing agents causes yellowing, where the color difference changes depending on external environments such as temperature, humidity, or heat. Furthermore, conventional recycled PET films to which organic or inorganic compounds are added as color-complementing agents suffer from reduced thermal shrinkage and breaking strength, making it technically difficult to simultaneously satisfy the desired appearance, heat resistance, and mechanical properties of the recycled PET film.

[0008] Therefore, in order to produce recycled PET film including waste PET, a new technology that can provide excellent film processability is required. Furthermore, the current situation is that new technology needs to be developed that can solve the problem of high color difference values ​​that conventional recycled PET film has, and that can provide excellent yellowing resistance and simultaneously satisfy the required heat shrinkage rate and mechanical strength. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Korean Patent Publication No. 10-2013-0035897 [Patent Document 2] Korean Patent Publication No. 10-2022-0003140 Summary of the Invention [Problem to be solved by the invention]

[0010] As one example, in order to solve the problem of the poor film-forming properties of recycled PET films from conventional waste PET, the present invention produces recycled chips containing waste PET and molding improvers, and uses these to provide recycled PET films with lower haze and excellent film-forming properties.

[0011] As one example, recycled PET films produced using conventional waste PET have high color difference values, but the present invention provides recycled PET films with lower color difference values ​​by including a color complementing agent containing a specific organic compound.

[0012] As one example, by incorporating a color-complementing agent containing the specific organic compound and adjusting the content thereof, the problems of high yellowing and low heat shrinkage and breaking strength that are present in conventional recycled PET films containing color-complementing agents can be solved, thereby providing a recycled PET film that has low color difference and excellent yellowing resistance, heat shrinkage, and breaking strength.

[0013] In one embodiment, the recycled PET film has a color difference value L of 70 or less and b of 5 or less, a color difference value L of 65 or less, preferably 62 or less, and a yellowing resistance of 10% or less, preferably 7% or less, when analyzed by the measurement method defined in the present invention.

[0014] In addition, as an example, a recycled PET film manufactured by incorporating waste PET and a specific color complementing agent has a thermal shrinkage rate of 5% or less in the TD direction and 1% or less in the MD direction, and a breaking strength of 10 kgf / mm in both the MD and TD directions, when measured by the analytical method defined in the present invention. 2 The objective is to provide a recycled PET film that satisfies the above requirements. [Means for solving the problem]

[0015] The recycled PET film of the present invention contains waste PET and virgin PET as PET resin components, and contains a color complementing agent containing a glycerin-based compound represented by the following chemical formula 1. The recycled PET film may have a yellowing resistance of 5 to 10% as measured by ASTM D1925, a color difference value L of 59 to 70 as measured by ASTM E313, and b of 5 or less.

[0016] [Chemical formula 1] JPEG2025528472000002.jpg3852 (wherein R1, R2 and R3 are each independently a linear or branched C1-C 20 Alkyl, or straight or branched C1-C 20 It is an unsaturated alkyl.

[0017] In one embodiment, the complementary coloring agent may include the following formula 2, formula 3, or a mixture thereof.

[0018] [Chemical formula 2] JPEG2025528472000003.jpg1628 (wherein R4 and R5 are independently a linear or branched C1-C 20 Alkyl, or straight or branched C1-C 20 It is an unsaturated alkyl.

[0019] [Chemical formula 3] JPEG2025528472000004.jpg2259 (in the above chemical formula 3, R6 and R7 are each independently a linear or branched C1-C 20 Alkyl, or straight or branched C1-C 20 It is an unsaturated alkyl.

[0020] In one embodiment, the recycled PET film may contain 10 to 100 ppm of a color complementing agent.

[0021] In one embodiment, in Formulas 1 to 3, R1, R2, R3, R4, R5, R6, and R7 are each independently a straight or branched C1-C 12 Alkyl, or straight or branched C1-C 12 It may be an unsaturated alkyl.

[0022] As one example, the recycled PET film may contain 10 to 200 ppm of metal ions derived from virgin material chips produced with a molding improver.

[0023] In another embodiment, the recycled PET film may satisfy the following formulas 1 to 3.

[0024] [Formula 1] 10≦[Mg]≦100 [Formula 2] 0.1≦[Na]≦10 [Formula 3] 1≦[P]≦50 (In the formulas 1 to 3, [Mg] is the concentration (ppm) of magnesium ions contained in the recycled PET film, [Na] is the concentration (ppm) of sodium ions contained in the recycled PET film, and [P] is the concentration (ppm) of phosphorus ions contained in the recycled PET film.)

[0025] In one embodiment, the recycled PET film may contain 300 to 1000 ppm of an anti-blocking agent.

[0026] As an example, the recycled PET film has a breaking strength of 10 to 30 kgf / mm in both the MD and TD directions as measured by ASTM D882. 2 It could be.

[0027] In one embodiment, the recycled PET film may have a heat shrinkage rate of MD 5% or less and TD 1% or less at 200°C.

[0028] In one embodiment, the recycled PET film may contain 30-95% by weight of recycled PET and 5-70% by weight of virgin PET. For example, the recycled PET film may contain 50-90% by weight of recycled PET and 10-50% by weight of virgin PET, or 60-90% by weight of recycled PET and 10-40% by weight of virgin PET, or 60-80% by weight of recycled PET and 20-40% by weight of virgin PET.

[0029] The method for producing a recycled PET film of the present invention includes the steps of producing recycled chips by incorporating waste PET, producing virgin chips by incorporating virgin PET, and producing a recycled PET film by incorporating the recycled chips, the virgin chips, and a glycerin-based compound represented by the following chemical formula 1:

[0030] [Chemical formula 1] JPEG2025528472000005.jpg3852 (wherein R1, R2 and R3 are each independently a linear or branched C1-C 20 Alkyl, or straight or branched C1-C 20 It is an unsaturated alkyl.

[0031] In one embodiment, the recycled PET film may contain 30-95% by weight of recycled chips and 5-70% by weight of virgin chips. For example, the recycled PET film may contain 50-90% by weight of recycled PET and 10-50% by weight of virgin PET, or 60-90% by weight of recycled PET and 10-40% by weight of virgin PET, or 60-80% by weight of recycled PET and 20-40% by weight of virgin PET.

[0032] As one example, the virgin material chips may be produced by including 150 to 14,000 ppm of a molding improver.

[0033] In one embodiment, the virgin material chips may be manufactured to contain 150 to 20,000 ppm of an anti-blocking agent. [Effects of the Invention]

[0034] The recycled PET film according to one embodiment of the present invention can be manufactured containing 30% by weight or more, 50% by weight or more, and preferably 80% by weight or more of the recycled chips, and can have outstanding recycled PET film formability and superior transparency, surface performance, and mechanical strength to conventional recycled PET films, and can therefore be used as a substitute in fields where virgin PET films made from virgin PET resins are used.

[0035] The recycled PET film according to one embodiment of the present invention contains the recycled chips and a color-complementing agent containing a specific organic compound, thereby solving the problem of high color difference values ​​that conventional recycled PET films have.

[0036] The recycled PET film according to one embodiment of the present invention contains a color complementing agent containing a specific organic compound, and by adjusting the content of the color complementing agent, it is possible to maintain excellent yellowing resistance, heat shrinkage, and high breaking strength. Therefore, it is possible to simultaneously achieve better haze, film formability, yellowing resistance, color difference value, heat shrinkage, and breaking strength than conventional recycled PET films.

[0037] Therefore, the recycled PET film of the present invention has excellent film-forming properties and can achieve greater transparency and surface performance than conventional recycled PET films, even when containing a large amount of waste PET. Furthermore, the recycled PET film of the present invention contains a color complementing agent containing a specific organic compound, thereby achieving greater yellowing resistance than conventional recycled PET films. Surprisingly, the recycled PET film can maintain excellent heat shrinkage and breaking strength, making it more useful than conventional recycled PET films. [Brief explanation of the drawings]

[0038] [Figure 1] FIG. 1 is a graph showing the results of NMR measurement of Example 4. [Figure 2] FIG. 2 is a graph showing the results of measuring Example 4 by ICP-OES (optical emission spectroscopy). DETAILED DESCRIPTION OF THE INVENTION

[0039] The recycled PET film and its manufacturing method according to the present invention will be described in detail below. In this regard, unless otherwise defined, the technical and scientific terms used have the meanings that are commonly understood by those skilled in the art to which the present invention pertains, and in the following description, explanations of known functions and configurations that may unnecessarily obscure the gist of the present invention will be omitted.

[0040] As used herein, the singular forms "a," "an," and "the" may be intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0041] Furthermore, the numerical ranges used herein include the lower and upper limits and all values ​​within the range, increments logically derived from the form and width of the defined range, all doubly limited values, and all possible combinations of upper and lower limits of numerical ranges limited in different forms. Unless otherwise specified in the specification of the present invention, values ​​outside the numerical range that may result from experimental error or rounding off values ​​are also included in the defined numerical range.

[0042] As used herein, the term "comprising" is an open-ended term having the same meaning as terms such as "comprising," "containing," "having," or "characterized by," and does not exclude additional, unrecited elements, materials, or steps.

[0043] Recycled PET film, which is made from conventional waste PET, is difficult to produce continuously due to its low film formability, and its surface is not smooth, resulting in significantly reduced transparency.In particular, it has a significantly higher color difference value than virgin PET film, making it difficult to apply to fields requiring excellent optical properties.

[0044] To solve this problem, conventional recycled PET films have been made to contain color-complementing agents to lower color difference values, but this has not yet resolved the problem of increased color difference values, nor has it been possible to solve the problems of increased yellowing, increased heat shrinkage, and decreased breaking strength that arise from the inclusion of the color-complementing agents.

[0045] In order to solve the problems of the poor film formability and high color difference value of the conventional recycled PET film, the inventors have produced a recycled PET film with a lower color difference value by incorporating waste PET and a color complementing agent containing a specific organic compound, and surprisingly, the recycled PET film also has remarkable yellowing resistance.

[0046] Furthermore, to solve the problem of not being able to simultaneously achieve excellent optical, thermal, and mechanical properties due to the complementary nature of these properties, we discovered that recycled PET film has a significant color-complementing effect even when a small amount of a color-complementing agent containing a specific organic compound is added, and therefore the problems of reduced heat shrinkage and breaking strength caused by the addition of a color-complementing agent do not occur, leading to the completion of the present invention.

[0047] The recycled PET film of the present invention will be described in detail below. The recycled PET film of the present invention is produced from recycled PET and virgin PET, and by including a color-complementing agent containing a specific organic compound, it can have a significantly lower color difference value than conventional recycled PET films produced from recycled PET, and can simultaneously achieve excellent yellowing resistance, low heat shrinkage, and excellent breaking strength.

[0048] According to one embodiment, the recycled PET film may include waste PET and virgin PET as resin components, and may include a color complementing agent containing a glycerin-based compound represented by the following Chemical Formula 1:

[0049] [Chemical formula 1] JPEG2025528472000006.jpg3852 (wherein R1, R2 and R3 are each independently a linear or branched C1-C 20 Alkyl, or straight or branched C1-C 20 It is an unsaturated alkyl.

[0050] In one embodiment, in the above Chemical Formula 1, R1, R2, and R3 can be each independently a linear or branched C1-C5 alkyl, or a linear or branched C2-C5 unsaturated alkyl.

[0051] For example, the triacylglycerin-based compound represented by Chemical Formula 1 may include, but is not limited to, glyceryl triacetate (triacetin), tripropionin, glyceryl tributyrate (tributyrin), or glycerol trivalerate.

[0052] As an example, the recycled PET film may have a lower color difference value than conventional recycled PET films because the recycled PET film may contain a color complementing agent containing a glycerin-based compound represented by Chemical Formula 1, thereby better dispersing residual grades contained in the waste PET resin and additives added thereto.

[0053] In addition, recycled PET film containing a color complementing agent containing a glycerin-based compound has a stable structure, making it less likely to decompose in external environments such as ultraviolet rays, heat, and humidity. This minimizes deterioration of the waste PET contained in the film, and therefore provides greater yellowing resistance than conventional recycled PET films.

[0054] According to one embodiment, the recycled PET film is manufactured by including the color complementing agent, and may have a yellowing resistance of 5 to 10% as measured by ASTM D1925, a color difference value L of 59 to 70 as measured by ASTM E313, and b of 5 or less.

[0055] In another embodiment, the recycled PET film may have a yellowing resistance of 5 to 8%, preferably 5 to 6%, a color difference value L of 59 to 65, preferably 59 to 62, a of −1.5 or less, and b of 3 or less.

[0056] Specifically, the recycled PET film may have a color difference value a of, but not limited to, a lower limit of -3.0 or more, -2.0 or more, preferably -1.5 or more, and a color difference value b of, but not limited to, a lower limit of 0.3 or more, 0.1 or more, preferably 0.05 or more.

[0057] Recycled PET films having color difference values ​​within this range can solve the problem of the high color difference value of conventional recycled PET films, and have color difference values ​​at a level that can replace virgin PET films, making them applicable to a wider variety of industrial fields.

[0058] Furthermore, recycled PET films having yellowing resistance within the above range are preferred because they have more pronounced yellowing resistance than conventional recycled PET films and can sustainably maintain their initial color difference value even in external environments such as ultraviolet light, humidity, and heat, or in environments exposed to strong energy.

[0059] According to one embodiment, the complementary color agent may further include organic compounds represented by the following Chemical Formula 2 and Chemical Formula 3.

[0060] [Chemical formula 2] JPEG2025528472000007.jpg1628 (in the above chemical formula 2, R4 and R5 are each independently a linear or branched C1-C 20 Alkyl, or straight or branched C1-C 20 It is an unsaturated alkyl.

[0061] [Chemical formula 3] JPEG2025528472000008.jpg2259 (wherein R6 and R7 are independently a linear or branched C1-C 20 Alkyl, or straight or branched C1-C 20 It is an unsaturated alkyl.

[0062] According to another embodiment, the color complementing agent contained in the recycled PET film further contains organic compounds represented by Chemical Formula 2 and Chemical Formula 3 in addition to the glycerin-based compound represented by Chemical Formula 1, which may be preferable because it can disperse residual grades and additives of the waste PET better than recycled PET films containing the glycerin-based compounds.

[0063] In the above formulas 1 to 3 according to one embodiment, R1, R2, R3, R4, R5, R6 and R7 are straight or branched C1-C 12 alkyl, preferably straight chain C-C 12 A complementary coloring agent containing an organic compound that is alkyl may have a more significant color difference value, but is not limited to this.

[0064] According to one embodiment, the recycled PET film may contain 5 to 200 ppm or 10 to 100 ppm of a color complementing agent, preferably 30 to 80 ppm, and more preferably 40 to 60 ppm.

[0065] A recycled PET film containing a complementary coloring agent in the above range of ppm can have a low color difference value and achieve more remarkable yellowing resistance, i.e., the recycled PET film can satisfy a color difference value L of 70 or less and a yellowing resistance of 5 to 10%.

[0066] In addition, recycled PET films containing more than 100 ppm of the color-complementing agent may have lower color difference values ​​and significant yellowing resistance, but may have reduced thermal shrinkage and mechanical strength, so it may be desirable to contain the color-complementing agent in the above ppm range.

[0067] According to one embodiment, the recycled PET film may contain 10 to 200 ppm of metal ions derived from virgin material chips.

[0068] Specifically, the recycled PET film contains metal ions at 10 to 100 ppm or 60 to 130 ppm, and the metal ions may be derived from a molding improver contained in the manufacturing process of virgin material chips.

[0069] The molding improver may, for example, include one or more selected from metal compounds (metal salts) containing metal cations such as magnesium, sodium, potassium, lithium, manganese, and zinc, and phosphorus-based compounds such as trimethyl phosphate, triethyl phosphate, and tributyl phosphate.

[0070] Specifically, the molding improver may include a magnesium compound, a sodium compound, and a phosphorus compound, since the metal ions contained in the recycled PET film are contained with excellent dispersion, and more specifically, may include magnesium acetate, sodium acetate, and trimethyl(ethyl)phosphate.

[0071] The virgin material chips produced by adding the molding improver contain metal ions in the molding improver, and one example is Mg 2+ , Na + , Ca 2+ , P04 3- , or Li + etc., which may be included in recycled PET film.

[0072] Recycled PET films containing metal ions derived from the molding improver can have excellent PET film-forming properties even when containing trace amounts of metal ions, thereby preventing the phenomenon of metal ions agglomerating on the surface and achieving even better film-forming properties.

[0073] In addition, recycled PET films containing metal ions at ppm levels within the above range can overcome the poor film-forming properties of recycled PET films that are inherent in waste PET, and can have a smooth surface and a complementary effect in which the color-complementing agent inhibits the aggregation of the contained metal ions, resulting in more pronounced transparency and lower color difference values.

[0074] As one example, the recycled PET film may satisfy the following formulas 1 to 3.

[0075] [Formula 1] 10≦[Mg]≦100 [Formula 2] 0.1≦[Na]≦10 [Formula 3] 1≦[P]≦10 (In the formulas 1 to 3, [Mg] is the concentration (ppm) of magnesium ions contained in the recycled PET film, [Na] is the concentration (ppm) of sodium ions contained in the recycled PET film, and [P] is the concentration (ppm) of phosphorus ions contained in the recycled PET film.)

[0076] As another example, in the formulas 1 to 3, [Mg] may be 10-80, [Na] may be 0.1-5, and [P] may be 1-5.

[0077] Recycled PET films containing magnesium ions, sodium ions, and phosphorus ions in the above-mentioned ranges of ppm can have more outstanding film-forming properties than conventional recycled PET films, and because they are contained in smaller amounts and do not aggregate, they can have low haze and color difference values ​​and can achieve better heat resistance, making them preferred.

[0078] According to one embodiment, the recycled PET film may contain 300 to 1000 ppm of an antiblocking agent, preferably 400 to 800 ppm, and more preferably 500 to 800 ppm.

[0079] A recycled PET film containing an antiblocking agent in the above range is preferred because the recycled PET film does not stick to each other during the manufacturing process, and defects due to constant processability and scratches can be significantly reduced.

[0080] The antiblocking agent may be inorganic particles, organic particles, or a mixture thereof. An example is one or more selected from NaF, MgF2, CaF2, BaF2, SiO2, BaSO4, CeF3, Al2O3, ZrO2, TiO2, ZnS, ZnSe, and Ta2O5. Specifically, an antiblocking agent containing SiO2 can achieve excellent film-forming properties for recycled PET films, but this is not a limitation as long as it is recognizable to a person skilled in the art.

[0081] According to one embodiment, the recycled PET film may further include one or more additives selected from the group consisting of lubricants, stabilizers, plasticizers, UV stabilizers, heat stabilizers, fillers, pigments, foaming agents, viscosity modifiers, processing aids, flame retardants, reinforcing agents, and dispersants.

[0082] The recycled PET film further containing the additives can have different physical properties depending on the type and content of the additives, and can therefore be applied to a wider range of industrial fields.

[0083] According to one embodiment, the recycled PET film may contain 30-95% by weight of recycled PET and 5-70% by weight of virgin PET, preferably 70-95% by weight of recycled PET, and more preferably 80-95% by weight of recycled PET. For example, the recycled PET film may contain 50-90% by weight of recycled PET and 10-50% by weight of virgin PET, or 60-90% by weight of recycled PET and 10-40% by weight of virgin PET, or 60-80% by weight of recycled PET and 20-40% by weight of virgin PET.

[0084] According to one embodiment of the present invention, recycled PET film can be produced by containing up to 95% by weight of waste PET, thereby solving environmental pollution problems such as air pollution, soil pollution, and water pollution caused by the landfill or incineration of waste PET.

[0085] Furthermore, even when a large amount of waste PET is included, excellent recycled PET film formability can be achieved, making it possible to continuously produce recycled PET film, and it is preferred because it can achieve greater transparency than conventional recycled PET films produced using waste PET.

[0086] In one embodiment, the recycled PET film may have a thickness of 10 to 150 μm, specifically 10 to 100 μm, more specifically 10 to 50 μm, but this is not limited as long as it does not impair the physical properties of the produced recycled PET film.

[0087] A recycled PET film having a thickness within the above range is preferred because it can have minimal surface scratches, pinholes, or break holes, depending on the degree of stretching in the MD and TD directions of the unstretched recycled PET film extracted through a T-die in the recycled PET film manufacturing method described below. Furthermore, the PET film having a thickness within the above range can be a monolayer film or a laminated film, and the thickness can be increased by laminating, but this is not a limitation.

[0088] Specifically, the laminated film may be a film having two or more recycled PET film layers, or may have a laminated structure including a single PET film layer and another layer of a different type (e.g., a layer that does not contain recycled polyester or a layer that contains another type of resin).

[0089] The waste PET has a weight average molecular weight of 40,000 to 200,000 g / mol, preferably 100,000 g / mol or less, and more preferably 40,000 to 80,000, which is excellent in moldability into a recycled PET film, but this is not a limitation.

[0090] The physical properties of the recycled PET film of the present invention will be described below.

[0091] In one embodiment, the recycled PET film contains 30 to 95% by weight of waste PET, and is manufactured by incorporating a molding improver, which allows for more pronounced PET film formability than conventional recycled PET films and can have better haze.

[0092] In addition, the recycled PET film according to one embodiment contains the glycerin-based compound represented by Chemical Formula 1, and thus has a lower color difference value than conventional recycled PET films, achieving more pronounced yellowing resistance. In addition, the recycled PET film contains a small amount of the color complementing agent, which allows it to maintain its thermal shrinkage rate and breaking strength.

[0093] As described above, in one embodiment, the recycled PET film satisfies the yellowing resistance of 5 to 10%, color difference value L of 59 to 70, and b of 5 or less, as measured by the measurement method defined in the present invention, and can also achieve the following physical properties.

[0094] In one embodiment, the recycled PET film has a breaking strength measured by ASTM D882 of 10 to 30 kgf / mm in both the MD and TD directions. 2 and preferably 15 kgf / mm 2 More than 20kgf / mm 2 It could be more than that.

[0095] Recycled PET films having a breaking strength within the above range have outstanding recycled PET film formability by adjusting the content of color complementing agents and including molding improvers, and can satisfy the breaking strength within the above range by preventing a high content of color complementing agents from suppressing the breaking strength of the recycled PET film.

[0096] In another embodiment, the recycled PET film has a thermal shrinkage rate of 5% or less in the MD direction and 1% or less in the TD direction, with the TD direction having a lower limit of 0.1% or more, preferably 2% or less in the MD direction, more preferably 1% or less, and the MD direction having a lower limit of 0.5% or more.

[0097] The recycled PET film having a thermal shrinkage rate within the above range contains a color complementing agent at a concentration of 100 ppm or less, and by containing the color complementing agent containing the glycerin-based compound represented by Chemical Formula 1, it is possible to solve the problem of the reduced thermal properties of conventional recycled PET films due to the inclusion of a color complementing agent.

[0098] The method for producing a recycled PET film of the present invention will be described in detail below.

[0099] The recycled PET film manufacturing method of the present invention is produced from recycled chips made from waste PET and virgin chips made from virgin PET, and by adding a molding improver and an anti-blocking agent to the recycled chips or virgin chips, the recycled PET film can have better metal compound dispersion.

[0100] Furthermore, in one embodiment, the method for producing the recycled PET film further contains a specific color complementing agent to produce the recycled PET film, thereby achieving a more pronounced dispersion of the metal compound, thereby achieving a color difference value L of 59 to 70 and a yellowing resistance of 5 to 10%.

[0101] The method for producing a recycled PET film according to the present invention may include the steps of producing recycled chips from waste PET, producing virgin chips from virgin PET, and producing a recycled PET film from the recycled chips, the virgin chips, and a glycerin-based compound represented by the following Chemical Formula 1:

[0102] [Chemical formula 1] JPEG2025528472000009.jpg3852 (in the above Chemical Formula 1, R1, R2 and R3 are each independently a straight or branched chain C1-C 20 Alkyl, or straight or branched C1-C 20 It is an unsaturated alkyl.

[0103] In another embodiment of the method for producing the recycled PET film, the color complementing agent may be contained in recycled chips or virgin chips, but is not limited thereto.

[0104] The recycled chips are produced by melting, and the temperature is not particularly limited as long as the chips are formed by melting, but for example, the recycled chips are produced by melting waste PET flakes at 240° C. to 260° C. In the recycled chips production step, a molding improver may be added and compounded, or other additives may be added and melted together, but the method is not limited thereto.

[0105] In one embodiment, the film processing step may include 30-95% recycled chips and 5-70% virgin chips by weight, specifically 70-95% recycled chips and 5-30% virgin chips by weight. For example, the recycled PET film may include 50-90% recycled PET and 10-50% virgin PET by weight, or 60-90% recycled PET and 10-40% virgin PET by weight, or 60-80% recycled PET and 20-40% virgin PET by weight.

[0106] In one embodiment, the molding improver may be included in the step of producing recycled chips or virgin material chips, and the recycled chips or virgin material chips may contain metal ions derived from the molding improver.

[0107] Specifically, in the method for producing recycled PET film, a molding improver is included in virgin PET at the stage of producing virgin material chips, and virgin material chips containing metal ions derived from the molding improver are more preferred, and recycled PET film produced using virgin material chips containing the metal ions can contain the molding improver with excellent dispersion, so this can be preferred.

[0108] As one example, the virgin material chips may be produced containing 150 to 14,000 ppm of molding improver, preferably 500 to 10,000 ppm, and more preferably 1,000 to 6,000 ppm.

[0109] Virgin material chips manufactured by incorporating molding improvers at ppm levels within the above range can solve the problem of low miscibility between waste PET and molding improvers, thereby solving the problem of increased haze and color difference caused by aggregation of metal ions derived from molding improvers in conventional recycled PET films.

[0110] Virgin material chips manufactured with the molding improver in the above range may contain different ppm of molding improver depending on the weight percentage of virgin material chips contained in the recycled PET film manufacturing step, but the ppm range of molding improver contained in the virgin material chip manufacturing step can be satisfied.

[0111] That is, the recycled PET film of the present invention may be produced containing 100 to 700 ppm, specifically 100 to 500 ppm, more specifically 100 to 300 ppm of molding improver, but this is not limited as long as the metal ions contained in the produced recycled PET film satisfy the range of 10 to 100 ppm.

[0112] As described above, the molding improver may be, for example, any one or a mixture of two or more selected from magnesium hydroxide, magnesium acetate, sodium acetate, sodium hydroxide, calcium acetate, lithium acetate, calcium phosphate, magnesium oxide, magnesium hydroxide, magnesium alkoxide, manganese acetate, zinc acetate, trimethyl phosphate, and triethyl phosphate.

[0113] The molding improver may preferably contain magnesium acetate, sodium acetate, and trimethyl(ethyl)phosphate in order to achieve excellent recycled PET film formability even when a small amount of the molding improver is contained.

[0114] In one embodiment, the virgin chips contain 140 to 20,000 ppm of antiblocking agent, preferably 1,000 to 20,000 ppm, and more preferably 1,500 to 18,000 ppm, which may vary depending on the weight percentage of the virgin chips contained in the stage of producing the recycled PET film, but is not limited thereto.

[0115] In one embodiment, the recycled chips are produced by melting and kneading waste PET flakes containing waste PET at 240°C to 260°C, and may further include, but are not limited to, a molding improver solution, an anti-blocking agent, and additives.

[0116] In one embodiment, the step of producing the virgin material chips may be the same as the step of producing the recycled chips, and it is preferable to produce the virgin material chips by further including an antiblocking agent, a molding improver, and additives so that the metal compounds contained in the produced recycled PET film have a greater degree of dispersion, but this is not a limitation.

[0117] The recycled chips may be prepared by melting PET flakes containing recycled PET at 240°C to 260°C, adding a molding improver to the molten PET flakes, and vacuum extruding the resulting mixture into beads.

[0118] Surprisingly, the recycled chips produced by the above method can significantly improve the poor film-forming properties of recycled PET or recycled PET flakes, and in particular, the PET film produced can have a high degree of dispersion of the contained metal compounds.

[0119] In one embodiment, the recycled PET film may be stretched 3 to 5 times in both the MD and TD directions, although there is no restriction on the ratio at which the unstretched recycled PET film is stretched.

[0120] Specifically, the temperature in the MD stretching step may be 80°C to 120°C, preferably 100°C to 120°C, and the stretch ratio may be 3.8 to 4.8 times, preferably 4.0 to 4.5 times, but is not limited thereto. Also, the temperature in the TD stretching step may be 200°C to 240°C, preferably 210°C to 240°C, more preferably 220°C to 235°C, and the stretch ratio may be the same as in the MD stretching step.

[0121] (Example) The PET film and its manufacturing method according to the present invention will be described in more detail below with reference to the following examples. The following examples are merely examples for explaining the present invention in detail, and the present invention is not limited thereto and may be realized in various forms. Unless otherwise defined, all technical and scientific terms have the same meanings as commonly understood by those skilled in the art to which the present invention belongs. The terms used in the description of the present invention are merely for the purpose of effectively describing specific examples and are not intended to limit the present invention.

[0122] [Measurement method] 1. Color difference measurement The recycled PET film was measured according to ASTM E313 and cut into a 100mm x 100mm sample, which was placed between two sample holders. The film was then measured five times using a color difference meter (ZE-6000, Nippon Denshoku Co., Ltd.), and the average value was calculated.

[0123] 2. Yellowing resistance measurement The recycled PET film was measured according to ASTM E313, and the initial L value was determined using the color difference measurement method. An accelerated aging test was performed for 168 hours by applying UV, heat, and moisture to the film surface using an accelerated weathering tester (QUV-SE) from Q-Lab, USA, and then the accelerated L value was measured using the color difference measurement method. The measured initial L value and accelerated L value were then calculated using the following formula to determine yellowing resistance. Yellowing resistance (%) = ((L value after acceleration - initial L value) / initial L value) x 100

[0124] 3. Haze Measurement The haze value was measured using a haze measuring instrument (Nippon Denshoku Co., Ltd., NDH5000) based on ASTM D-1003.

[0125] 4. Breaking strength measurement The samples were prepared and measured according to ASTM D882, and the breaking strength of the samples was determined using a measuring device (INSTRON).

[0126] 5. Heat shrinkage measurement The sample was cut into a rectangle measuring 15 mm (MD) x 400 mm (TD) in the machine direction (MD) and transverse direction (TD). Solid lines were drawn in the MD from 50 mm away from both ends of the transverse direction (TD) to prepare a test piece with an effective measurement length of 300 mm. Then, using tweezers or the like, a point within 50 mm from one end of the sample was taken, regardless of left or right, and the entire sample was placed in warm water at 90°C ± 0.5°C under no load and completely immersed in it for 10 seconds to allow it to heat shrink. After leaving it at room temperature for 1 minute, the shrinkage length at 300 mm intervals in the transverse direction (TD) indicated by the initial solid lines was measured, and the heat shrinkage rate was calculated from the measured length using the following formula: [formula] Heat shrinkage rate in the film transverse direction (TD) = (300 mm - length after shrinkage / 300 mm) x 100

[0127] 6. NMR (Nuclear Magnetic Resonance) Measurement The sample was measured using an NMR device (Bruker, AVANCEIII 400) under the conditions of a 1H probe and a resonance frequency of 400 MHz, and the measurement results are shown in FIG.

[0128] 7.Inorganic component analysis The samples were measured using ICP-OES (PerkinElmer, Avio 550 Max), and the inorganic elements contained in the samples were confirmed by EDX analysis of ash. The measurement results are shown in Figure 2.

[0129] [Examples 1 to 6] Recycled PET flakes were compounded using a compounding machine (EREMA) to produce recycled chips, and virgin chips were produced using a compounding machine (EREMA) containing virgin chip PET, 1000 ppm magnesium acetate (MgAc), 150 ppm sodium acetate (NaAc), 200 ppm triethyl phosphate (TEP), and 3000 ppm antiblocking agent.

[0130] Next, 80% by weight of the recycled chips and 20% by weight of virgin chips were fed into a film-making machine and melted and mixed at 260°C. After mixing was completed, a triacylglycerol-based compound (TAG; e.g., glyceryl triacetate) represented by the following formula (1) and at the concentration shown in Table 1 below was added as a color complementing agent. The mixture was then extruded through a T-die at 270°C, and the extruded PET sheet was stretched 4.5 times in both the MD and TD directions to produce a PET film. The NMR and inorganic component analysis of the produced film was performed using the above methods and is shown in Figures 1 and 2. The concentrations of each inorganic substance contained are shown in Table 1 below. Thereafter, the produced recycled PET film was measured by the above-mentioned measuring method, and the results are shown in Table 2 below.

[0131] [Example 7] A recycled PET film was produced in the same manner as in Example 4, except that virgin material chips were produced without adding magnesium acetate, sodium acetate, and triethyl phosphate. Thereafter, the produced recycled PET film was measured by the above-mentioned measuring method, and the results are shown in Table 2 below.

[0132] [Example 8] A recycled PET film was produced in the same manner as in Example 4, except that virgin material chips were produced without adding an antiblocking agent. Thereafter, the produced recycled PET film was measured by the above-mentioned measuring method, and the results are shown in Table 2 below.

[0133] [Example 9] A recycled PET film was produced in the same manner as in Example 4, except that virgin material chips were produced without adding magnesium acetate, sodium acetate, triethyl phosphate, and an antiblocking agent. Thereafter, the produced recycled PET film was measured by the above-mentioned measuring method, and the results are shown in Table 2 below.

[0134] [Comparative Example 1] A recycled PET film was produced in the same manner as in Example 4, except that titanium dioxide was used as the color complementing agent. Thereafter, the produced recycled PET film was measured by the above-mentioned measuring method, and the results are shown in Table 2 below.

[0135] Comparative Example 2 A recycled PET film was produced in the same manner as in Example 4, except that virgin material chips were produced without magnesium acetate, sodium acetate, and triethyl phosphate, and titanium dioxide was used as a color complementing agent. Thereafter, the produced recycled PET film was measured by the above-mentioned measuring method, and the results are shown in Table 2 below.

[0136] Comparative Example 3 A recycled PET film was produced in the same manner as in Example 4, except that the color complementing agent was not added. Thereafter, the produced recycled PET film was measured by the above-mentioned measuring method, and the results are shown in Table 2 below.

[0137] Comparative Example 4 A recycled PET film was produced in the same manner as in Example 4, except that virgin material chips were produced without magnesium acetate, sodium acetate, and triethyl phosphate, and no color complementing agent was added. Thereafter, the produced recycled PET film was measured by the above-mentioned measuring method, and the results are shown in Table 2 below.

[0138] [Table 1]

[0139] [Table 2]

[0140] Looking at Examples 1 to 6 in Table 2, it can be seen that the physical properties depend on the content of the complementary coloring agent. Examples 4 to 6 had a haze of 2 to 3%, and looking at Examples 5 and 6, it was confirmed that the thermal shrinkage rate and breaking strength were reduced.

[0141] This suggests that as the triacylglycerol content increases, the transparency and yellowing resistance of the recycled PET film increase and the color difference value can decrease significantly, but PET film containing excessive color complementing agents decreases in breaking strength and increases in heat shrinkage.

[0142] Looking at Table 2, Example 7 has the same type and content of the complementary coloring agent as Example 4, but does not contain a molding improver. It was confirmed that the haze increased and the breaking strength and breaking elongation decreased compared to Example 4.

[0143] This means that the simultaneous incorporation of triacylglycerol, magnesium acetate, sodium acetate, and triethyl phosphate surprisingly reduces haze and color difference. Furthermore, Example 4 suggests that the incorporation of the molding improver improves film formability, thereby increasing the breaking strength and breaking elongation of the produced PET film.

[0144] Looking at Example 8 in Table 2, it was confirmed that Example 8, which did not contain an antiblocking agent, had an increased haze, significantly decreased breaking strength and breaking elongation, and significantly increased heat shrinkage compared to Example 4. This suggests that PET films containing an antiblocking agent have excellent dimensional stability against high heat and excellent film-forming properties for recycled PET films.

[0145] Furthermore, looking at Example 9 in Table 2, the physical properties of the PET film obtained without the molding improver and antiblocking agent were more clearly confirmed. It was confirmed that Example 9 had significantly reduced haze, color difference, and breaking strength compared to Example 4, and also had a significantly increased heat shrinkage.

[0146] This means that the thermal shrinkage rate decreases significantly as the inorganic content of the produced PET film decreases, and the molding improver and antiblocking agent improve the film formability, thereby affecting the breaking strength and breaking elongation of the produced PET film.

[0147] In Table 2, Comparative Examples 1 and 2 are PET films prepared by incorporating titanium dioxide as a color complementing agent, and it was confirmed that the heat shrinkage rate increased, and the haze and color difference values ​​significantly increased, resulting in a decrease in the transparency of the PET film. Comparative Example 2 was confirmed to have even greater increases in haze and color difference values.

[0148] This suggests that although the thermal shrinkage rate can be reduced by including a color-complementing agent composed of inorganic particles, the color-complementing effect is inferior to that of triacylglycerin.

[0149] In Table 2, Comparative Examples 3 and 4 did not contain a color-complementing agent, and were measured to have a haze of 20% or more and a color difference value L of 80 or more. This indicates that the transparency of the PET film not containing a color-complementing agent was at an unusable level, and Comparative Example 4, which did not contain a molding improver, had even lower transparency.

[0150] As described above, the present invention has been described using specific and limited examples and comparative examples. However, these are provided only to facilitate a more comprehensive understanding of the present invention, and the present invention is not limited to the above examples. Various modifications and variations can be made from such descriptions by a person having ordinary knowledge in the field to which the present invention pertains.

[0151] Therefore, the spirit of the present invention should not be limited to the described embodiments, and all modifications equivalent to or equivalent to the scope of the claims set forth below are considered to fall within the scope of the spirit of the present invention.

Claims

1. A recycled PET film containing waste PET and virgin PET as PET resin components, and containing a color complementing agent containing a glycerin-based compound represented by the following chemical formula 1: The recycled PET film has a yellowing resistance of 5 to 10% as measured by ASTM D1925, a color difference value L of 59 to 70 as measured by ASTM E313, and b of 5 or less. [Chemical formula 1] In the above Chemical Formula 1, R １ , R ２ and R ３ are each independently a straight or branched chain C １ -C ２０ Alkyl, or straight or branched chain C １ -C ２０ It is an unsaturated alkyl.

2. The recycled PET film according to claim 1, wherein the color complementing agent comprises the following chemical formula 2, chemical formula 3, or a mixture thereof: [Chemical formula 2] In the above Chemical Formula 2, R ４ and R ５ are each independently a straight or branched chain C １ -C ２０ Alkyl, or straight or branched chain C １ -C ２０ It is an unsaturated alkyl. [Chemical formula 3] In the above Chemical Formula 3, R ６ and R ７ are each independently a straight or branched chain C １ -C ２０ Alkyl, or straight or branched chain C １ -C ２０ It is an unsaturated alkyl.

3. The recycled PET film according to claim 1, wherein the recycled PET film contains a color complementing agent in an amount of 5 to 200 ppm.

4. In the above chemical formulas 1 to 3, R １ , R ２ , R ３ , R ４ , R ５ , R ６ and R ７ are each independently a straight or branched chain C １ -C １２ Alkyl, or straight or branched chain C １ -C １２ The recycled PET film of claim 1, wherein the unsaturated alkyl group is an unsaturated alkyl group.

5. The recycled PET film according to claim 1, wherein the recycled PET film contains 10 to 200 ppm of metal ions derived from virgin material chips produced with a molding improver.

6. The recycled PET film according to claim 5, which satisfies the following formulas 1 to 3: [Formula 1] 10≦[Mg]≦100 [Formula 2] 0.1≦[Na]≦10 [Formula 3] 1≦[P]≦50 (In the above formulas 1 to 3, [Mg] is the concentration (ppm) of magnesium ions contained in the recycled PET film, [Na] is the concentration (ppm) of sodium ions contained in the recycled PET film, [P] is the concentration (ppm) of phosphorus ions contained in the recycled PET film.

7. The recycled PET film according to claim 1, wherein the recycled PET film contains an antiblocking agent at 300 to 1000 ppm.

8. The recycled PET film has a breaking strength of 10 to 30 kgf / mm in both the MD and TD directions as measured by ASTM D882. ２ The recycled PET film according to claim 1,

9. The recycled PET film according to claim 1, wherein the recycled PET film has a heat shrinkage rate of 5% or less in MD and 1% or less in TD at 200°C.

10. The recycled PET film according to claim 1, wherein the recycled PET film contains 30 to 95% by weight of waste PET and 5 to 70% by weight of virgin PET.

11. A step of producing recycled chips including waste PET; producing virgin chips including virgin PET; and manufacturing a recycled PET film by incorporating the recycled chips, the virgin material chips, and a glycerin-based compound represented by the following Chemical Formula 1: [Chemical formula 1] In the above Chemical Formula 1, R １ , R ２ and R ３ are each independently a straight or branched chain C １ -C ２０ Alkyl, or straight or branched chain C １ -C ２０ It is an unsaturated alkyl.

12. 12. The method of claim 11, wherein the recycled PET film comprises 30 to 95 wt % recycled chips and 5 to 70 wt % virgin PET.

13. The recycled PET film manufacturing method according to claim 11, wherein the virgin material chips are manufactured containing 150 to 14,000 ppm of a molding improver.

14. The recycled PET film manufacturing method according to claim 11, wherein the virgin material chips are manufactured containing an anti-blocking agent at 150 to 20,000 ppm.

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