Recycled PET film made from recycled chips

Abstract

In order to solve the problems of conventional recycled PET films, such as low breaking strength, breaking elongation, and high heat shrinkage, the present invention provides recycled chips that have a specific range of intrinsic viscosity and DEG unit content, thereby achieving outstanding film formability, and recycled PET films produced from these chips that have excellent breaking strength, breaking elongation, and significantly low heat shrinkage.

Description

[Technical Field]

[0001] The present invention relates to recycled chips manufactured using waste PET and having an adjusted intrinsic viscosity and DEG (Diethylene Glycol) unit content, and to recycled PET films manufactured using the same. [Background technology]

[0002] The problem of disposing of waste plastic is that it is difficult to biodegrade and has a high porosity, which causes various problems such as water pollution, ecosystem destruction, and soil contamination when it is buried. In addition, even if it is incinerated, it emits carbon dioxide and toxic gases, which causes air pollution, making it extremely difficult to dispose of.

[0003] Therefore, currently, in order to treat waste plastics, plastics made from biomass or biodegradable plastics are produced, but commercialization is difficult due to the high cost and complicated manufacturing process, making it difficult to achieve the fundamental purpose of treating waste plastics.

[0004] Among the waste plastic processing processes, the technology that can recover large amounts of waste plastic is waste plastic recycling technology. PET accounts for a large proportion of waste plastic, and since 2000, there has been a trend toward technological development and an increase in the market size for recycling. Recently, due to China's restrictions on waste plastic imports, the recycled PET industry has been growing rapidly.

[0005] In the recycling process of waste PET (recycled PET), the recycled PET goes through processes such as sorting, removal of foreign matter, washing, and separation of metals, and is then used to produce clothing, packaging containers, home appliances, automobiles, and film. However, because the physical properties of recycled PET are inferior to those of PET products made from virgin PET, the main purpose is to minimize the burden on the environment rather than to completely recycle it.

[0006] In particular, waste PET is produced by crushing used products that have undergone primary processing and distributing them as recycled PET flakes, which significantly reduces film processability. In addition, the PET film produced from this process generally has lower mechanical properties and thermal stability than virgin PET film.

[0007] For this reason, it is necessary to introduce new technology that enables recycled PET film to have excellent film processability even when it contains a large amount of waste PET. The reality is that there is a need for technology to manufacture PET film that has physical properties equivalent to or superior to those of virgin PET film made from virgin PET, and that has commercially viable physical properties. [Prior art documents] [Patent documents]

[0008] [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]

[0009] One example of this is to provide a recycled PET film with an intrinsic viscosity (IV) of 0.55 dL / g or more, thereby solving the problem of poor mechanical properties of conventional recycled PET films, and thereby providing a recycled PET film that achieves greater breaking strength.

[0010] As an example, we provide recycled PET film with an intrinsic viscosity of 0.62 dL / g or less to solve the problem of irregular running of unstretched recycled PET film in the conventional process of producing film from waste PET.

[0011] Another example of realization is to provide a recycled PET film that can solve the irregular running problem of the recycled PET film in the film manufacturing process of the conventional recycled PET film by incorporating a molding improver.

[0012] As an example, in order to solve the poor thermal properties of conventional recycled PET films, a recycled PET film with a DEG unit content of 3 mol% or less is provided, thereby providing a recycled PET film that achieves a significantly lower thermal shrinkage rate than recycled PET films made from conventional waste PET.

[0013] As an example, the recycled PET film has a breaking strength of 20 kgf / mm in both the TD and MD directions. 2 Above, 25kgf / mm 2 More than 27kgf / mm 2 The goal is to achieve the above.

[0014] As one example, the recycled PET film has a heat shrinkage rate of MD 5% or less and TD 1% or less at 200°C. [Means for solving the problem]

[0015] The recycled PET film of the present invention is produced from recycled chips produced including waste PET and virgin chips produced including virgin PET, and the recycled PET film may have an intrinsic viscosity (IV) of 0.55 to 0.62 dL / g and a DEG unit content of 3 mol% or less.

[0016] In one embodiment, the recycled chips may have an intrinsic viscosity (IV) of 0.60 to 0.65 dL / g.

[0017] In one embodiment, the waste PET may have a weight average molecular weight of 40,000 to 70,000 g / mol.

[0018] In one embodiment, the recycled PET film may have a DEG unit content of 0.5 to 2 mol %.

[0019] As an example, the recycled PET film has a breaking strength of 20 to 30 kgf / mm in both the MD and TD directions as measured by ASTM D882. 2 It could be.

[0020] 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.

[0021] In one embodiment, the recycled PET film may have a melting temperature of 245°C to 255°C.

[0022] In one embodiment, the recycled PET film may have an acid value (COOH value) of 25 to 45 eq / ton.

[0023] As one example, the recycled PET film may contain 30 to 95% by weight of waste PET and 5 to 70% by weight of virgin PET.

[0024] 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.

[0025] As one example, the recycled PET film may satisfy the following formulas 1 to 3.

[0026] [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.)

[0027] In one embodiment, the recycled PET film may contain 100 to 1000 ppm of an anti-blocking agent.

[0028] The recycled PET film manufacturing method of the present invention includes a step of manufacturing recycled chips including waste PET, a step of manufacturing virgin chips including virgin PET, and a step of manufacturing recycled PET film including the recycled chips and the virgin chips.

[0029] In one embodiment, the recycled PET film may be produced using recycled chips and virgin chips in a weight ratio of 30:70 to 95:5. For example, the weight ratio of recycled chips to virgin chips may be 50:50 to 90:10, 55:45 to 90:10, or 60:40 to 80:20.

[0030] As one example, the virgin material chips may be produced by including 150 to 14,000 ppm of a molding improver.

[0031] 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]

[0032] In one embodiment, the recycled PET film satisfies an intrinsic viscosity of 0.55 to 0.62 dL / g, thereby having excellent breaking strength and breaking elongation, and achieving a more consistent running force of unstretched recycled PET film, allowing it to be produced with a high content of waste PET.

[0033] The recycled PET film according to one embodiment satisfies the DEG unit content of 3 mol% or less, and can have better heat resistance and a significantly lower heat shrinkage rate than conventional recycled PET films.

[0034] In one embodiment, the recycled PET film has a DEG unit content of 0.5 mol% or more, thereby achieving a glass transition temperature of 81°C or less and a melting temperature of 255°C or less, which enables the recycled PET film manufacturing method to produce recycled PET film with more outstanding film-forming properties and with less thermal energy.

[0035] Therefore, the recycled PET film according to one embodiment can have environmentally friendly effects by reusing waste PET, and by adjusting the intrinsic viscosity to have better mechanical strength and heat resistance, it can be used in places where virgin PET is used and can satisfy consumers, so it can be used more usefully than conventional recycled PET. DETAILED DESCRIPTION OF THE INVENTION

[0036] 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.

[0037] 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.

[0038] 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.

[0039] As used herein, the term "comprising" is an open-ended term having the same meaning as terms such as "comprising," "containing," "having," or "featuring," and does not exclude additional, unrecited elements, materials, or steps.

[0040] As used herein, the term "acidity" may refer to the equivalent number of carboxyl groups (-COOH) at the ends of PET contained in recycled PET, recycled chips, or PET film.

[0041] As used herein, the term "unstretched recycled PET film" can refer to a molten recycled PET sheet drawn through a T-die in the production of PET film, or a recycled PET sheet in an unstretched state.

[0042] Conventional waste PET has been produced through processes such as compressing fibers, containers, labels, pipes, bottles, or films, separating and washing inorganic particles, color sorting, drying, crushing, washing with a non-solvent solution, drying, and separating metal particles, and recycled PET molded products have been produced from these processes.

[0043] However, waste PET has been through more than one molding process and has different PDI, crystallinity, physical properties, glass transition temperature, and melting temperature. Due to residual grades, the physical properties of the recycled PET are not as good as those of molded products made from virgin PET.

[0044] In particular, the manufacturing process for recycled PET film from waste PET involves various steps such as heat treatment, cooling, stretching, and drying, all of which are carried out in a short period of time. Therefore, even when a high content of virgin PET, i.e., 50% by weight or more, is used, the recycled PET film produced still has poor physical properties, particularly in terms of mechanical and thermal properties that make it unusable.

[0045] As a result of extensive research aimed at solving the problems of conventional recycled PET films, we discovered that the intrinsic viscosity (IV) of recycled chips made from recycled PET, including waste PET, not only achieves more outstanding film-forming properties for recycled PET films, but also surprisingly, the recycled PET films produced achieve excellent mechanical properties.

[0046] Furthermore, we discovered that a more significant thermal shrinkage rate can be achieved depending on the DEG unit content of the PET resin (waste PET and virgin PET) contained in the recycled PET film, and that this can be adjusted to maintain mechanical properties, leading to the completion of the present invention.

[0047] Therefore, the recycled PET film according to one embodiment has greater mechanical strength and lower thermal shrinkage, which allows it to reuse waste PET and achieve the goal of being environmentally friendly, and can also replace virgin PET film used in fields such as display substrates and protective films for electronic substrates.

[0048] 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 chips containing waste PET and virgin chips containing virgin PET.

[0049] In one embodiment, the recycled PET film may have an intrinsic viscosity (IV) of 0.55 to 0.62 dL / g and a DEG unit content of 3 mol % or less.

[0050] In another embodiment, the recycled PET film has an intrinsic viscosity of 0.57 to 0.59 dL / g. A recycled PET film satisfying the intrinsic viscosity in this range may be preferred because it has a better breaking elongation and a usable breaking strength.

[0051] The intrinsic viscosity of the recycled PET film is a result of the weight average molecular weight or crystallinity of the waste PET and virgin PET contained in the recycled PET film. A recycled PET film having an intrinsic viscosity within the range may have a lower crystallinity than a virgin PET film, and therefore the film produced therefrom may have an excellent breaking elongation.

[0052] The recycled PET film having an intrinsic viscosity of less than 0.55 dL / g may have a significantly reduced crystallinity and an increased breaking elongation, but may also have a significantly reduced breaking strength.

[0053] Furthermore, recycled PET films with an intrinsic viscosity exceeding 0.62 dL / g have poor film formability and may therefore have poor mechanical properties. Therefore, it is more preferable that the recycled PET film has an intrinsic viscosity within the above range.

[0054] According to one embodiment, the recycled chips may have an intrinsic viscosity of 0.60 to 0.65 dL / g.

[0055] Recycled chips having an intrinsic viscosity within the above range are preferred because they achieve a lower intrinsic viscosity than virgin PET resin, allowing the unstretched recycled PET film to run at a constant speed in the recycled PET film production process, and the PET film produced thereby to satisfy an intrinsic viscosity of 0.62 dL / g or less.

[0056] The intrinsic viscosity of the recycled chips is a result of the molecular weight, polymer structure, and repeating unit content of the waste PET and virgin PET contained therein, and in particular, the intrinsic viscosity value can vary depending on the weight average molecular weight of the waste PET contained in the recycled chips.

[0057] According to one embodiment, the waste PET may have a weight average molecular weight of 40,000 to 70,000 g / mol, 45,000 to 65,000 g / mol, and preferably 50,000 to 60,000 g / mol.

[0058] Recycled chips containing waste PET with a weight average molecular weight within the above range can have an intrinsic viscosity within the above range, which can result in better processability for PET films, and the PET films produced therefrom can have excellent breaking elongation and breaking strength, and are therefore preferred.

[0059] In one embodiment, the waste PET has a PDI (Poly Dispersity Index) of 1.0 to 3.0, preferably 1.5 to 2.5. The waste PET is produced by crushing waste PETs having different weight average molecular weights, which may increase the PDI value. However, these are kneaded to produce recycled chips, which can prevent the deterioration of the physical properties of the recycled PET film due to the high PDI of the waste PET.

[0060] As an example, the waste PET and virgin PET contained in the recycled PET film may contain copolymer units that do not only contain ethylene and terephthalate, but also diethylene glycol (DEG).

[0061] As an example, the DEG unit content of the waste PET contained in the recycled PET film may be 0.5 mol % to 3.0 mol %. For example, the DEG unit content of the waste PET contained in the recycled PET film can be 0.5 mol% to 2.9 mol%, 0.5 mol% to 2.8 mol%, 0.5 mol% to 2.7 mol%, 0.5 mol% to 2.6 mol%, 0.5 mol% to 2.5 mol%, 0.6 mol% to 2.4 mol%, 0.6 mol% to 2.3 mol%, 0.6 mol% to 2.2 mol%, 0.6 mol% to 2.1 mol%, 0.6 mol% to 2.0 mol%, 0.7 mol% to 1.9 mol%, 0.7 mol% to 1.8 mol%, 0.7 mol% to 1.7 mol%, 0.8 mol% to 1.6 mol%, 0.8 mol% to 1.5 mol%, 0.8 mol% to 1.4 mol%, 0.9 mol% to 1.3 mol%, 1.0 mol% to 1.3 mol%, or 1.1 mol% to 1.3 mol%.

[0062] The recycled PET film has different crystallinity, glass transition temperature, cooling temperature, heat shrinkage, elongation, and tensile strength depending on the DEG unit content of the waste PET and virgin PET contained therein. As the DEG unit content increases, the crystallinity decreases, which can lead to lower glass transition temperature and melting temperature, and lower breaking strength.

[0063] According to one embodiment, the recycled PET film may have a DEG unit content of 0.5 to 2 mol %, preferably 1 to 2 mol %.

[0064] Recycled PET films that satisfy the above-mentioned range of DEG unit content can achieve a lower thermal shrinkage rate than recycled PET films produced using conventional waste PET, and can also achieve glass transition temperatures and melting temperatures that are excellent for film-forming properties of recycled PET films, making them preferred.

[0065] In other words, recycled PET film containing more than 3 mol% DEG units from recycled PET (waste PET and virgin PET) may have an increased breaking elongation, but may have a significantly reduced breaking strength, making it unable to replace virgin PET film.

[0066] Furthermore, recycled PET films containing PET (waste PET and virgin PET) with a DEG unit content of 0.5 mol% or less have a significantly reduced elongation and an increased melting temperature, which can reduce the film-forming properties of the recycled PET film. Therefore, it is more preferable that the recycled PET film have a DEG unit content of 0.5 to 3 mol%.

[0067] According to one embodiment, the recycled PET film may have an acid value (COOH value) of 25 to 45 eq / ton, specifically 32 to 39 eq / ton.

[0068] Surprisingly, recycled PET films having an acid value in the above range can achieve even more remarkable film formability due to the interaction with the intrinsic viscosity in the above range, and can have better transparency, lower heat shrinkage, and excellent breaking strength and breaking elongation, so they can be preferred.

[0069] In one embodiment, the recycled PET film contains 40 to 95% by weight of recycled PET and 5 to 60% by weight of virgin PET, and preferably contains 60 to 95% by weight of recycled PET and 5 to 40% by weight of virgin PET.

[0070] The recycled PET film contains the above weight percent of waste PET and virgin PET as its PET resin components, and thus contains a larger amount of waste PET than conventional recycled PET films, making it more environmentally friendly. At the same time, the intrinsic viscosity and DEG unit content can be adjusted within the above ranges from recycled chips containing waste PET.

[0071] As a result, the recycled PET film has excellent breaking elongation and breaking strength, and also has a low heat shrinkage rate, so it can achieve physical properties at a level that makes it possible to replace virgin PET film.

[0072] In one embodiment, the recycled PET film may have a thickness of 10 to 200 μm, specifically 10 to 125 μm, more specifically 10 to 100 μm, but this can be adjusted depending on the field of use, and there is no limitation thereto as long as it does not impair physical properties.

[0073] Recycled PET films having a thickness within the above range may be preferred because they may have minimal surface scratches, pinholes, or break holes, depending on the degree to which the unstretched recycled PET film drawn out through a T-die is stretched in the MD and TD directions in the PET film manufacturing method described below.

[0074] In addition, the PET film having the thickness in the above range may be a single layer film or a laminated film, and the thickness may be increased by laminating, but this is not a limitation.

[0075] 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).

[0076] In one embodiment, the recycled PET film contains 10 to 200 ppm of metal ions derived from virgin material chips produced with molding improvers, specifically 10 to 100 ppm, and more specifically 30 to 80 ppm.

[0077] 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.

[0078] 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.

[0079] In one embodiment, the molding improver may include a magnesium compound, a sodium compound, and a phosphorus-based compound, and specifically may include magnesium acetate, sodium acetate, and trimethyl(ethyl)phosphate.

[0080] According to one embodiment, the recycled PET film may satisfy the following formulas 1 to 3.

[0081] [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.)

[0082] As another example, in the formulas 1 to 3, [Mg] may be 10-80, [Na] may be 0.1-5, and [P] may be 1-10.

[0083] A recycled PET film containing magnesium ions, sodium ions, and phosphorus ions in the ppm ranges of the formulas 1 to 3 can achieve outstanding film formability even with a minimum metal ion content, and can prevent the problem of metal ions agglomerating with each other, so that a PET film produced with the recycled PET film can simultaneously achieve outstanding transparency, low color difference, and low surface properties.

[0084] Furthermore, the recycled PET film can achieve excellent processability because it is produced from recycled chips with adjusted intrinsic viscosity, DEG unit content, and acidity. The additional inclusion of the molding improver allows for even better film formability. Surprisingly, the excellent compatibility with recycled chips having an intrinsic viscosity within the above range can further improve the effectiveness of the molding improver.

[0085] According to one embodiment, the recycled PET film contains an antiblocking agent in an amount of 100 to 1000 ppm, specifically 300 to 1000 ppm, and more specifically 500 to 900 ppm.

[0086] Recycled PET films containing an antiblocking agent within the above range are preferred because they can have better recycled PET film formability during the manufacturing process, the produced recycled PET films do not stick to each other during the winding process, and defects due to consistent processability and scratches can be significantly reduced.

[0087] In one embodiment, the antiblocking agent may be inorganic particles, organic particles, or a mixture thereof. For example, the antiblocking agent may be 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 may provide excellent film formability, but this is not a limitation as long as it is recognizable to a person skilled in the art.

[0088] The recycled PET film may further contain 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, but is not limited thereto as long as it is recognizable to a person skilled in the art.

[0089] The physical properties of the recycled PET film according to one embodiment will be described in detail below.

[0090] The recycled PET film according to one embodiment has an intrinsic viscosity and DEG unit content within the aforementioned ranges, which allows it to have excellent elongation at break and strength at break, and from a thermal perspective, the heat shrinkage rate can be significantly reduced.

[0091] Furthermore, the recycled PET film surprisingly further contains a molding improver, which realizes better film formability and is technically significant in providing a recycled PET film with excellent transparency, pinhole defects, and low deviation in height of surface irregularities.

[0092] 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 , preferably 20 to 30 kgf / mm 2 It could be.

[0093] A recycled PET film having a breaking strength within the above range may have a breaking strength superior to that of conventional recycled PET films and may have a breaking strength similar to that of virgin PET films, and therefore may be able to replace virgin PET films in fields where high breaking strength is required.

[0094] In another embodiment, the recycled PET film has a breaking elongation measured by ASTM D882 of 130 to 170% in MD and 100 to 140% in TD, preferably 150 to 170% in MD and 110 to 140% in TD.

[0095] A recycled PET film having a breaking elongation within the above range is an effect that is exhibited by satisfying the aforementioned intrinsic viscosity range of 0.55 to 0.62 dL / g, and can have a breaking elongation superior to that of virgin PET. Because it has a breaking elongation that is more significant than that of conventional recycled PET, it can be more usefully used as a flexible material.

[0096] According to one embodiment, the recycled PET film has a heat shrinkage rate of 5% or less in MD and 1% or less in TD at 200°C, preferably 3% or less in MD, more preferably 2% or less, and 0.1 to 0.5% in TD.

[0097] The recycled PET film having a heat shrinkage rate within this range has excellent dimensional stability even in high-temperature environments, and can be used in a variety of fields such as display substrates, protective films for electronic products, and food containers.

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

[0099] The present invention provides a method for producing a PET film, which includes the steps of producing recycled chips including waste PET, producing virgin chips including virgin PET, and producing a recycled PET film including the recycled chips and virgin chips.

[0100] According to one embodiment, the recycled chips may have an intrinsic viscosity of 0.60 to 0.65 dL / g.

[0101] Recycled chips having an intrinsic viscosity within the above range can have excellent film-forming properties as described above, and the recycled PET film produced from them can have an intrinsic viscosity (IV) of 0.55 to 0.61 dL / g, thereby simultaneously achieving excellent breaking strength and breaking elongation.

[0102] The waste PET can be any waste polyester polymer, and as an example, one or more selected from polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), and polyethylene naphthalate (PEN) can be used.

[0103] The recycled PET may also be a polyester copolymer, for example, terephthalate and C1-C 12 The alkyl diol may be produced by polymerizing one or more alkyl diols, but is not limited thereto as long as it is recognizable to a person skilled in the art.

[0104] In one embodiment, in the step of producing the recycled PET film, the recycled chips and virgin chips are contained in a weight ratio of 30:70 to 95:5, and may be 50:50 to 95:5, 70:30 to 95:5, or 80:20 to 90:10.

[0105] The method for producing recycled PET film, which is produced by mixing recycled chips and virgin chips in a weight ratio within the above range, can recover and reuse large amounts of waste PET, making it extremely environmentally friendly.It can also achieve physical properties that can replace virgin PET film, and can even be used as a substitute in the field of virgin PET film, making it even more environmentally friendly.

[0106] In one embodiment, the method for producing the recycled PET film may further include a molding improver and an anti-blocking agent, and the molding improver may be included in the step of producing recycled chips, and recycled chips may be produced containing metal ions derived from the molding improver, or may be included in the step of producing virgin material chips, and metal ions derived from the molding improver may be contained in the virgin material chips.

[0107] Specifically, it may be preferable to include this step in the production of virgin material chips, since the produced recycled PET film may have better metal ion dispersion.

[0108] 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.

[0109] 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.

[0110] As one example, the virgin material chips may contain 150 to 14,000 ppm of molding improver, preferably 150 to 10,000 ppm, and more preferably 1,000 to 6,000 ppm.

[0111] Specifically, the molding improver may be included in the step of producing virgin material chips, and the virgin material chips thus produced, which contain metal ions derived from the molding improver, may be preferred because they can contain metal ions with an excellent degree of dispersion.

[0112] Virgin material chips produced containing molding improvers in the above ranges may contain different ppm of molding improvers depending on the weight percentage of virgin material chips contained in the recycled PET film production step, but can satisfy the ppm range of molding improvers contained in the virgin material chip production step.

[0113] 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 ion content of the produced recycled PET film satisfies 10 to 200 ppm.

[0114] As one example, the antiblocking agent may be added in the stage of producing recycled chips, virgin chips, or the recycled PET film, similar to the molding improver in the above-mentioned recycled PET production method; however, recycled chips and virgin chips are better contained in virgin chips, and the produced recycled PET film may contain the antiblocking agent with excellent dispersibility.

[0115] In one embodiment, the virgin material chips contain 150 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 material chips contained in the stage of producing the recycled PET film, but is not limited thereto.

[0116] In one implementation example, the step of producing the recycled PET film may involve stretching an unstretched recycled PET film 3 to 5 times in both the TD and MD directions.

[0117] Specifically, unstretched PET film melt-extruded through a T-die (260°C to 280°C) is run in close contact with a casting roll, cooled to 80°C, and stretched 3 to 5 times in the MD (machine direction stretcher) direction. The recycled PET film stretched in the MD direction can then be stretched 4 to 5 times in the TD (transverse direction stretcher) direction at 100°C to 130°C to produce a recycled PET film with a thickness of 10 to 100 μm.

[0118] More specifically, the temperature in the MD stretching step may be 80 to 120°C, preferably 100 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 to 240°C, preferably 210 to 240°C, more preferably 220 to 235°C, and the stretch ratio may be the same as in the MD stretching step.

[0119] (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.

[0120] (Manufacturing recycled chips) [Measurement method] 1. Intrinsic viscosity (IV) measurement A 2.0 g sample was weighed using an electronic balance and placed in a 100 mL glass-stoppered Erlenmeyer flask. 25 mL of OCP (o-chlorophenol) was added using a pipette. The Erlenmeyer flask was then placed in a dissolution bath at 100 °C and dissolved at 150 rpm for 1 hour. The Erlenmeyer flask containing the dissolved sample solution was removed and allowed to cool at room temperature. After cooling in a thermostatic bath at 25 °C, 7.5 mL of the sample solution was then transferred using a volumetric pipette to a Cannon-Fenske viscometer and allowed to cool for 20 minutes. The sample solution in the Cannon-Fenske viscometer was then allowed to drip once, and then allowed to drip naturally from the second time onward. The time it took for the solution to pass from the upper to lower scale on the viscometer was measured and recorded. The intrinsic viscosity was calculated using the Huggins equation.

[0121] 2. Measurement of DEG content 0.0015 g of HD and 0.037 g of DEG were placed in a 100 mL round flask and dissolved in methanol. 1 μL of the resulting solution was analyzed by gas chromatography (AGILENT, 6890N) to obtain a chromatogram. Next, 0.15 g of HD and 0.06 g of zinc acetate were dissolved in methanol in a beaker. 30.0 mL of the resulting reaction solution was placed in a Teflon container, and the Teflon container containing the reaction solution was placed in a pressure tube and sealed. The sealed pressure tube was then placed in a 210 °C oven for 30 minutes. After the reaction was complete, the tube was cooled to room temperature, opened, and the Teflon container was removed. The decomposition reaction solution contained in the Teflon container was separated using a 0.45 μm separation membrane, and 1 μL of the separated reaction solution was placed in a gas chromatograph for chromatography. The measured DEG chromatogram was then compared with the chromatogram of the reaction solution to determine the DEG content of the reaction solution.

[0122] 3. Measurement of glass transition temperature and melting temperature 0.1 mg of the sample was placed in a DSC (Differential Scanning Calorimeter) device (Perkin Elmer, DSC7, heating rate: 0.8°C / s) to measure the glass transition temperature (T g ) and melting temperature (T m ) was calculated.

[0123] [Manufacturing Examples 1 to 7] Recycled chips were produced from waste PET having the physical properties shown in Table 1 below using a compounding device (EREMA).

[0124] The regenerated chips were then measured by the above-mentioned method, and the intrinsic viscosity and DEG unit content are shown in Table 1 below.

[0125] [Table 1]

[0126] In Table 1, in Production Examples 1 to 5, recycled chips were produced from waste PET with different intrinsic viscosities, and it was confirmed that the produced recycled chips had the intrinsic viscosities and DEG unit contents shown in Table 1. The intrinsic viscosity of the recycled chips becomes lower than the intrinsic viscosity of the waste PET by processing the waste PET into recycled chips using a compounding device, but it was confirmed that the initial intrinsic viscosity of the waste PET is the most important factor.

[0127] In Table 1, it was confirmed that Preparation Examples 6 and 7 had the same intrinsic viscosity as Preparation Example 3. These are recycled chips produced using recycled PET with different melting temperatures. It was confirmed that the lower the melting temperature of the recycled PET, the higher the DEG unit content of the recycled PET copolymer contained therein.

[0128] This may be a phenomenon that manifests as decreased crystallinity due to increased irregularity in the waste PET as the DEG unit content of the waste PET increases.

[0129] (Manufacturing recycled PET film) [Measurement method] 4. Breaking elongation and breaking strength measurement Measurement was carried out according to the ASTM D882 standard, and the sample was stretched at a spin head speed of 500 mm / min, and the maximum tensile strength and maximum elongation percentage when the sample broke were measured to determine the breaking tensile strength and breaking elongation percentage.

[0130] 5. Heat shrinkage measurement Measurements were made in accordance with the ASTM D2305 standard, with each sample heated in an oven at 150°C and 200°C for 15 minutes, and the heat shrinkage at 150°C and 200°C of the heated samples was calculated using the dimensional change method based on ASTM D2305.

[0131] [Examples 1 to 4 and Comparative Examples 1 to 5] Virgin PET was fed into a compounding machine (EREMA), and a molding improver containing magnesium acetate (MgAc), sodium acetate (NaAc), and triethyl phosphate (TEP) was added to the virgin PET in accordance with the concentrations of the metal compounds shown in Table 2 below. SiO2 was then added to the virgin PET in the concentrations shown in Table 2 below to produce virgin chips.

[0132] Next, 80% by weight of recycled chips and 20% by weight of virgin chips from the manufacturing example shown in Table 2 below were melted and mixed at a temperature of 260°C, and after mixing was completed, the mixture was extruded through a T-die maintained at a temperature of 275°C (temperature error range: ±15°C), and the extruded unstretched recycled PET film was stretched 4.5 times in the MD and TD directions to produce a recycled PET film with a thickness of 12 μm.

[0133] Thereafter, the produced recycled PET film was measured by the above-mentioned measuring method, and the results are shown in Table 3 below.

[0134] [Table 2]

[0135] [Table 3]

[0136] Looking at Examples 1 to 3 in Table 3, it was confirmed that an increase in intrinsic viscosity increases the breaking strength and decreases the breaking elongation. This suggests that the increase in intrinsic viscosity is a phenomenon that occurs when the crystallinity of the recycled PET film increases, resulting in increased brittleness of the PET film. For the above reasons, looking at Comparative Examples 1 and 2 in Table 3, it was confirmed that a decrease in intrinsic viscosity significantly reduces the breaking strength. In Comparative Example 3, an increase in intrinsic viscosity increases the breaking strength but significantly reduces the breaking elongation, confirming that Comparative Examples 1 to 3 cannot be used in fields where excellent flexibility is required.

[0137] It has also been confirmed that the crystallinity of recycled PET film is related to the DEG unit content of the waste PET and virgin PET contained therein, which can be seen by looking at Comparative Examples 4 and 5 in Table 3 above.

[0138] The recycled PET film of Comparative Example 4 had a DEG unit content of 0.3 mol%, and therefore, it was confirmed that the breaking elongation was significantly lower than that of Example 3. Looking at Comparative Example 5, it was confirmed that the breaking strength was significantly lower and the heat shrinkage rate was significantly higher.

[0139] Therefore, the mechanical properties of the recycled PET film according to the present invention, such as breaking strength and breaking elongation, are adjusted depending on the intrinsic viscosity and DEG unit content of the waste PET and virgin PET contained therein, suggesting that the recycled PET film produced can have excellent breaking strength and breaking elongation simultaneously only when the intrinsic viscosity is in the range of 0.55 to 0.62 dL / g.

[0140] In addition, as the DEG unit content of the PET film according to the present invention increases, the breaking strength can be significantly reduced and the breaking elongation can be increased.

[0141] In particular, as the DEG unit content of recycled PET film increases, the thermal shrinkage rate increases significantly and the dimensional stability of the recycled PET film can be significantly reduced. Therefore, it is suggested that recycled PET film with a DEG unit content in the range of 0.5 to 3 mol% can simultaneously possess excellent mechanical strength and thermal properties.

[0142] 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.

[0143] 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. The recycled PET film is manufactured from recycled chips including waste PET and virgin chips including virgin PET, The recycled PET film has an intrinsic viscosity (IV) of 0.55 to 0.62 dL / g and a DEG unit content of 3 mol% or less.

2. The recycled PET film according to claim 1, wherein the recycled chips have an intrinsic viscosity (IV) of 0.60 to 0.65 dL / g.

3. The recycled PET film according to claim 1, wherein the waste PET has a weight average molecular weight of 40,000 to 70,000 g / mol.

4. The recycled PET film according to claim 1, wherein the recycled PET film has a DEG unit content of 0.5 to 2 mol%.

5. The recycled PET film has a breaking strength of 20 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,

6. 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.

7. The recycled PET film according to claim 1, wherein the recycled PET film has a melting temperature of 245°C to 255°C.

8. The recycled PET film according to claim 1, wherein the recycled PET film has an acid value (COOH value) of 25 to 45 eq / ton.

9. 2. 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.

10. 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.

11. The recycled PET film according to claim 10, which satisfies the following formulas 1 to 3: [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.)

12. The recycled PET film according to claim 1, wherein the recycled PET film contains an antiblocking agent at 100 to 1000 ppm.

13. A step of producing recycled chips including waste PET; producing virgin chips including virgin PET; and manufacturing a recycled PET film including the recycled chips and the virgin material chips.

14. 14. The method of claim 13, wherein the recycled PET film is produced by using recycled chips and virgin chips in a weight ratio of 30:70 to 95:

5.

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

16. The recycled PET film manufacturing method according to claim 13, wherein the virgin material chips are manufactured containing an anti-blocking agent at 150 to 20,000 ppm.

Images