Recycled PET film made using recycled chips

Abstract

The present invention can provide recycled chips having extremely low melt resistivity and excellent metal compound dispersion, and recycled PET films produced using these chips alone or containing 95% by weight or more can achieve extremely high transparency, low color difference, and a low number of pinholes, or can eliminate the occurrence of breakage holes, due to the effects of the recycled chips.

Description

[Technical Field]

[0001] The present disclosure relates to recycled chips produced by including waste PET and a molding improver, a recycled PET film produced by including the recycled chips, 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, in order to solve the rising costs and environmental pollution problems that come with the depletion of petroleum resources, technology to recycle waste PET is attracting attention.

[0004] In the recycling process for recycling waste PET, recycled PET undergoes sorting, removal of foreign matter, washing, and separation of metals, etc., and is then manufactured into clothing, packaging containers, home appliances, automobiles, films, etc. However, recycled PET is still inferior to virgin PET in processability and physical properties, limiting its use.

[0005] In particular, recycled PET film made from recycled PET has stricter processing conditions than other molded products. It is produced by stretching it 3 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 conditions of the heat treatment process, and the amount of additives. In addition, since recycled PET is a mixture of various grades, the processing conditions for recycling it into film are even more difficult.

[0006] As a result, recycled PET film made from waste PET has significantly lower physical properties such as transparency, color, and gloss than virgin PET film made from virgin PET, and also causes a problem of a significantly increased reject rate during the manufacturing process, so there is a technical limit to the production of PET film containing a large amount of waste PET.

[0007] In recent years, attempts have been made to solve the problem of low processability of recycled PET by adding various metal compounds to recycled PET. However, this method has problems such as low dispersibility of recycled PET and metal compounds, and the aggregation of metal compounds on the surface of recycled PET film due to the addition of excessive amounts of metal compounds.

[0008] Therefore, in order to produce recycled PET film, including waste PET, it is still necessary to develop new technologies that can provide excellent film processability, and ultimately, it is necessary to develop technologies that can provide physical properties that are the same as or superior to those of PET film produced from virgin PET. Summary of the Invention [Problem to be solved by the invention]

[0009] One example of the present invention is to solve the problem of the extremely poor film-forming properties of conventional waste PET by producing recycled chips containing waste PET and molding improvers, and using these to provide a recycled PET film that has low color difference, a low number of pinholes, low haze, and excellent film-forming properties.

[0010] As an example, metal compounds contained in conventional recycled PET film aggregate during the processing process, causing problems with surface properties and processing characteristics. In the present invention, recycled PET film is produced using recycled chips that suppress this, thereby solving the problem of metal compounds agglomerating in the recycled PET film.

[0011] As one example of realization, we aim to provide new recycled chips and recycled PET films manufactured using them that have significantly improved film surface properties and processability due to the improved dispersion power of the recycled chips of the present invention using additives.

[0012] As one example, the present invention solves the problem that conventional recycled PET films must contain a large amount of virgin PET to improve dispersibility, surface properties, and processability, and provides recycled chips and recycled PET films using the same that solve the problem even when a small amount of virgin PET is added.

[0013] As one example, it is possible to provide a recycled PET film that, when analyzed by the measurement method defined in the present invention, has a haze of 5 or less, 4 or less, preferably 3 or less, the number of pinholes of 2 or less, 1.5 or less, 1 or less, preferably 0.7 or less or 0.5 or less, and a color difference value of 70 or less, 65 or less, preferably 63 or less.

[0014] In addition, as one example, the recycled PET film of the present invention can provide a recycled PET film that is excellent in continuous film-forming properties when measured by the analytical method defined in the present invention.

[0015] Furthermore, as one example, the recycled chips used to produce the recycled PET film of the present invention can provide an excellent recycled PET film that achieves the above physical properties, unlike conventional technology, even if virgin PET resin is not used or virgin PET is mixed in at a content of 5% by weight or less. [Means for solving the problem]

[0016] The present disclosure provides a recycled PET film manufactured using 95% by weight or more of recycled chips manufactured using waste PET and a molding improver, and the recycled PET film may contain 10 to 130 ppm of metal ions derived from the molding improver.

[0017] In one implementation example, the recycled PET film may be produced solely from recycled chips.

[0018] In one implementation example, the molding improver may include a magnesium compound, a sodium compound, and a phosphorus-based compound.

[0019] As one example, the recycled PET film may satisfy the following formulas 1 to 3.

[0020] [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.)

[0021] In one embodiment, the recycled PET film may contain 100 to 2000 ppm of an anti-blocking agent.

[0022] In one embodiment, the recycled PET film may further include one or more selected from the group consisting of lubricants, stabilizers, plasticizers, UV stabilizers, heat stabilizers, fillers, pigment blowing agents, viscosity modifiers, processing aids, flame retardants, reinforcing agents, and dispersants.

[0023] In one embodiment, the recycled PET film is 100 cm 2 For an area of ​​10 times, the average number of pinholes may be 2 or less.

[0024] In one implementation, the recycled PET film can have a haze of 5% or less as measured by ASTM D1003.

[0025] In one implementation example, the recycled PET film may have a melt resistivity of 8.0 MΩ or less at 285°C.

[0026] As one embodiment of the present invention, there may be provided a method for producing recycled PET film, including the steps of producing recycled chips containing waste PET and a molding improver, and producing recycled PET film containing 95% by weight or more of the recycled chips.

[0027] In one embodiment, the step of producing the recycled PET film may further include an anti-blocking agent.

[0028] In one implementation example, the step of producing the recycled PET film may involve stretching the film 3 to 5 times in both MD and TD.

[0029] As an example of realization of the present invention, there can be provided recycled chips produced by containing waste PET and 50 to 500 ppm of a molding improver.

[0030] In one implementation example, the recycled chips may contain 10 to 130 ppm of metal ions derived from a molding improver.

[0031] As an example of implementation, the regenerative chip may satisfy the following equations 4, 5, and 6.

[0032] [Formula 4] 10≦[Mg]≦100 [Formula 5] 0.1≦[Na]≦10 [Formula 6] 1≦[P]≦10 (In the formulas 4 to 6, [Mg] is the concentration (ppm) of magnesium ions contained in the regenerated chip, [Na] is the concentration (ppm) of sodium ions contained in the regenerated chip, and [P] is the concentration (ppm) of phosphorus ions contained in the regenerated chip.)

[0033] In one implementation example, the recycled PET film may have a haze of 5 or less, a number of pinholes of 2 or less, and a color difference value L of 70 or less.

[0034] In one embodiment, the recycled PET film may contain 95% or more by weight of waste PET resin and 5% or less by weight of virgin PET resin.

[0035] In one implementation example, the recycled PET film may have a haze of 4 or less, a pinhole count of 1 or less, and a color difference value L of 63 or less. [Effects of the Invention]

[0036] In one embodiment of the present invention, the recycled chips contain a molding improver, so even if 95% by weight or more of the recycled chips or even if only recycled chips are used, a recycled PET film having better physical properties than conventional recycled PET films can be produced. This allows for a significantly higher recycling rate of waste PET and minimizes environmental pollution caused by waste PET.

[0037] In one embodiment, the recycled chips are produced containing waste PET and a molding improver. Since the waste PET and the molding improver can have excellent miscibility, the recycled chips produced can contain metal ions derived from the molding improver with excellent dispersion.

[0038] As one example, recycled PET film manufactured using the recycled chips can simultaneously achieve excellent surface and optical properties even when it contains 95% by weight of the recycled chips (i.e., when virgin PET resin is used at 5% by weight or less).

[0039] Therefore, since the recycled PET film according to the present invention is manufactured using recycled chips that have excellent processability, it is possible to manufacture a recycled PET film with better physical properties even if it is manufactured using a larger amount of waste PET than conventional recycled PET films.

[0040] Furthermore, the recycled PET film can have better transparency than conventional recycled PET films by preventing the contained metal particles or metal ions from agglomerating with each other, and can have significantly fewer pinholes, less color difference, and significantly improved processability, making it more useful than conventional recycled PET films. DETAILED DESCRIPTION OF THE INVENTION

[0041] The recycled chips according to the present invention and the recycled PET film produced therefrom will be described in detail below.

[0042] Unless otherwise defined, the technical and scientific terms used have the meanings that are commonly understood by a person of ordinary skill in the technical field to which this invention belongs, and in the following description, explanations of well-known functions and configurations that may unnecessarily obscure the gist of this invention will be omitted.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] As used herein, the term recycled PET may refer to PET derived from waste PET and produced by combining the components of the present invention.

[0047] As used herein, the term "virgin PET" may refer to PET produced by polymerizing petroleum-derived monomers or compounds.

[0048] As used herein, the term "recycled PET film" may refer to a film made using recycled PET.

[0049] As used herein, the term "virgin PET film" may refer to a PET film made solely from virgin PET, without using recycled PET as a resin component.

[0050] The term "metal ions" used in this specification refers to metal ions derived from the metal compound of the molding improver, and may refer to metal ions contained in the recycled chips or recycled PET film measured by the IPC measurement method.

[0051] Conventional recycled PET film cannot be produced if it contains an excessive amount of waste PET; unless it contains at least 10% by weight, 20% by weight, or even 50% by weight or more of virgin PET, it cannot be produced to a level that can be processed into a film and is usable.

[0052] To solve the above problems, conventional recycled PET films contain a large amount of additives to overcome the poor film-forming properties of waste PET and minimize the amount of virgin PET contained. However, the large amount of various additives causes the additives to aggregate on the surface of the recycled PET film, which results in poor film-forming properties related to high color difference and pinholes, and it has not been possible to solve these problems.

[0053] The present inventors have conducted extensive research to solve the problems of conventional recycled PET films, and as a result, have developed recycled chips manufactured by mixing waste PET and a molding improver solution, thereby solving the problems.

[0054] As a result, as one example, it was discovered that recycled PET film made from the recycled chips can be produced without the above-mentioned problems even when it contains more than 95% by weight of waste PET resin, and that the recycled PET film produced has better physical properties than conventional recycled PET, leading to the completion of the present invention.

[0055] In one implementation of the present invention, recycled chips may be produced containing waste PET and molding modifiers.

[0056] The recycled chips are produced by incorporating waste PET resin and a molding improver in order to solve the problem of conventional recycled PET films, which must be produced containing 10% by weight or more, 20% by weight or more, or even 50% by weight or more of virgin PET due to the poor film processability of waste PET.By adjusting the content of the molding improver, it is possible to provide a recycled PET film with a low pinhole count, low color difference value, and low haze, even if it contains 5% by weight or less of virgin PET.

[0057] In one embodiment, the molding improver may 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.

[0058] In another embodiment, the molding improver is not particularly limited as long as it contains the metal cation and a phosphorus-based compound, and may be composed of a magnesium compound, a sodium compound, and a phosphorus-based compound.

[0059] The magnesium compound and sodium compound may be metal salts containing magnesium cations or sodium cations, respectively, such as magnesium acetate or sodium acetate, and the phosphorus-based compound may be trimethyl phosphate.

[0060] Even when the molding improver containing the three metal compounds is used in smaller amounts than molding improvers containing other metal compounds, recycled chips produced using this agent can achieve outstanding recycled PET film formability. Not only that, recycled PET films produced using the recycled chips can further suppress the phenomenon of metal ions derived from the molding improver agglomerating with each other, thereby achieving better transparency and lower color difference values ​​than conventional recycled PET films.

[0061] Furthermore, recycled chips manufactured with the molding improver are preferred because they contain only trace amounts of residual anions (acetate anions) and can contain metal ions derived from the molding improver with a high degree of dispersion.

[0062] In one embodiment, the recycled chips are produced containing 50 to 500 ppm of molding improver, and in another embodiment, they may be produced containing 50 to 300 ppm or 100 to 300 ppm, but this is not necessarily limited to this as long as recycled PET film can be produced containing 95% by weight of the recycled chips.

[0063] Recycled chips containing molding improvers at ppm levels within this range prevent the aggregation of metal ions derived from the molding improvers and have significantly low melt resistivity, resulting in excellent film formability that allows for continuous production of recycled PET film. Therefore, recycled PET film produced using 95% by weight or more of the recycled chips, or all of the recycled chips, is preferred because it can have excellent surface properties and significantly increased transparency due to excellent metal ion dispersion.

[0064] If the recycled chips are produced with more than 500 ppm of molding improver, the metal ions derived from the molding improver cannot be dispersed evenly and tend to aggregate with each other, which can increase the haze of the recycled PET film produced with these chips, resulting in the formation of numerous pinholes and, in severe cases, breakage holes.

[0065] Furthermore, if the recycled chips are manufactured containing less than 50 ppm of molding improver, the melt resistivity increases and film formability decreases, which not only increases the surface roughness of the recycled PET film manufactured containing this and increases the number of pinholes, but also requires more virgin PET than the content targeted by the present invention, which can reduce environmental friendliness.Therefore, recycled chips manufactured containing molding improver at a content within the above range are preferred, but this is not necessarily a limitation.

[0066] In another embodiment, the recycled chip may be manufactured by including a molding improver solution containing a molding improver, as long as the content of metal ions derived from the molding improver contained therein is satisfied.

[0067] The molding improver solution is more miscible with recycled PET, so recycled chips produced using it can contain metal ions derived from the molding improver at a higher degree of dispersion. The molding improver solution can be one in which the molding improver is dissolved at 5 to 50 wt %, 5 to 30 wt %, or 5 to 15 wt %, but is not particularly limited as long as it does not impair the physical properties of the recycled PET film produced using it.

[0068] As one example, the waste PET may refer to waste PET flakes (waste PET resin) that have been removed from discarded fibers, packaging materials, containers, and beverage bottles by compressing, washing, sorting, crushing, immersion washing, drying, and metal separation in this order, without undergoing a repolymerization process, and only impurities have been removed.

[0069] It is preferable to use the most usable waste PET as the waste PET. However, as a non-limiting example, one or more polyester polymers selected from polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), or copolymers thereof may be used without limitation.

[0070] In one embodiment, the weight average molecular weight of the waste PET is 40,000 to 200,000 g / mol, and in another embodiment, it may be 100,000 g / mol or less or 40,000 to 80,000 g / mol, but this is not necessarily limited as long as the physical properties of the recycled PET film produced including it are not reduced.

[0071] In one embodiment, the recycled chips are produced using waste PET and the molding improver in the above range, and contain 10 to 130 ppm of metal ions derived from the molding improver. In another embodiment, the recycled chips may contain 10 to 120 ppm, 10 to 90 ppm, or 10 to 70 ppm.

[0072] As mentioned above, recycled chips containing metal ions in the above range are preferred because they have excellent film-forming properties and contain metal ions with high dispersibility, and recycled PET films produced using them can have low haze, low pinhole counts, and low color difference values.

[0073] As an example of implementation, the regenerative chip may satisfy the following equations 4, 5, and 6.

[0074] [Formula 4] 10≦[Mg]≦100 [Formula 5] 0.1≦[Na]≦10 [Formula 6] 1≦[P]≦10 (In the formulas 4 to 6, [Mg] is the concentration (ppm) of magnesium ions contained in the regenerated chip, [Na] is the concentration (ppm) of sodium ions contained in the regenerated chip, and [P] is the concentration (ppm) of phosphorus ions contained in the regenerated chip.)

[0075] As another example, since the recycled chips maintain excellent film-forming properties and contain low amounts of metal ions, [Mg] can be 10 to 70 or 30 to 60, [Na] can be 0.1 to 5 or 0.5 to 3, and [P] can be 1 to 8 or 1 to 5, but this is not limited as long as it does not impair the physical properties of the recycled PET film produced.

[0076] The magnesium ions, sodium ions, and phosphorus ions contained in the recycled chips are derived from metal compounds contained in the molding improver, and may be magnesium ions, sodium ions, and phosphorus ions (phosphates) measured by ICP analysis of the recycled chips.

[0077] Recycled chips that satisfy the above formulas 4 to 6 contain magnesium ions, sodium ions, and phosphorus ions in an optimal combination, and can have low melt resistivity even when containing trace amounts, so recycled PET film can be produced using more recycled PET or only recycled PET.

[0078] In one embodiment, the recycled chips have an average particle size of 1 to 10 mm, and in another embodiment, 5 to 10 mm, although this is not a particular limitation.

[0079] As an example of realizing the present invention, there can be provided a recycled PET film manufactured containing 95% by weight of the recycled chips.

[0080] The recycled PET film contains the recycled chips and is continuously produced even when containing 95% by weight of recycled chips, and therefore can have significantly improved physical properties compared to conventional recycled PET films.

[0081] In another embodiment, the recycled PET film may be produced solely from recycled chips.

[0082] The recycled PET film is manufactured using recycled chips, which provide excellent PET film forming properties, so even if it is manufactured using only recycled chips, it can have excellent surface properties, and this can solve the problem of low carbon neutrality that arises when conventional recycled PET films are required to contain 80% or more virgin chips.

[0083] Furthermore, since the recycled PET film is produced using recycled chips containing a trace amount of molding improver, it can have significantly lower haze and color difference values ​​than conventional recycled PET films by preventing the aggregation of metal particles derived from the molding improver.

[0084] In one embodiment of the present invention, the recycled PET film may contain 10 to 130 ppm of metal ions derived from the molding improver, and in another embodiment, 10 to 90 ppm or 10 to 70 ppm.

[0085] The metal ions contained in the recycled PET film are derived from the metal ions contained in the recycled chips, and the recycled chips have excellent film-forming properties.The content of the metal ions contained in the PET film satisfies the above range, and the film can have low surface roughness, few pinholes, low haze, and low color difference.

[0086] In one embodiment, the recycled PET film has a haze of 5% or less, 4% or less, and preferably 3% or less, a pinhole count of 2 or less, 1.5 or less, 1 or less, and preferably 0.7 or less, 0.5 or less, when analyzed by the measurement method defined in the present invention, and a color difference value of 70 or less, 65 or less, and preferably 63 or less.

[0087] The recycled PET film can be produced using 95% by weight or more of recycled chips or only recycled chips, and therefore can have significantly higher carbon neutrality, as well as better surface properties, better transparency, and lower color difference values ​​than conventional recycled PET films, and therefore can be preferred.

[0088] As one example, the recycled PET film may satisfy the following formulas 1 to 3.

[0089] [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.)

[0090] As mentioned above, recycled PET film is produced using recycled chips containing three types of metal ions, which not only provides the excellent film-forming properties of the recycled chips, but also contains a lower content of metal ions, resulting in low haze, low color difference, and a low number of pinholes.

[0091] In another example, the recycled PET film contains a smaller amount of metal ions, so [Mg] can be 10 to 70 or 30 to 60, [Na] can be 0.1 to 5 or 0.5 to 3, and [P] can be 1 to 8 or 1 to 5, but this is not limited as long as the physical properties of the recycled PET film produced are not impaired.

[0092] In one embodiment, the recycled PET film may further include an anti-blocking agent.

[0093] The antiblocking agent may be, for example, one or more selected from NaF, MgF2, CaF2, BaF2, SiO2, BaSO4, CeF3, Al2O3, ZrO2, TiO2, ZnS, ZnSe, and Ta2O5, and specifically, an antiblocking agent containing SiO2 can achieve excellent PET film formability, but is not limited thereto as long as it is recognizable to a person skilled in the art.

[0094] In one embodiment, the recycled PET film contains 100 to 2000 ppm of an antiblocking agent, and in another embodiment, the recycled PET film may contain 200 to 1500 ppm or 500 to 1000 ppm of an antiblocking agent.

[0095] A recycled PET film containing an antiblocking agent in a concentration within the above range is preferred because it can prevent the recycled PET film from sticking to or rubbing against each other during the winding process of the manufacturing process, thereby significantly reducing defects due to scratches in the recycled PET film. However, this is not necessarily a limitation as long as the physical properties of the recycled PET film are not deteriorated.

[0096] In 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, pigment blowing agents, viscosity modifiers, processing aids, flame retardants, reinforcing agents, and dispersants.

[0097] 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.

[0098] As an example, the recycled PET film is not particularly limited as long as it does not impair the physical properties, but the thickness may be 10 to 100 μm, specifically 10 to 50 μm.

[0099] A recycled PET film having a thickness within this range is preferred because it can have minimal surface scratches, pinholes, or breakage holes, depending on the degree of MD and TD stretching of the unstretched PET film extracted from the T-die in the recycled PET film manufacturing method described below. Furthermore, the PET film having a thickness within this range can be a single film or a laminated film, and the thickness can increase with lamination.

[0100] The recycled PET film is produced solely or in a proportion of 95% by weight or more of recycled chips, which are produced by incorporating waste PET and trace amounts of molding improvers. This allows the recycled chips to have excellent film processability, and the contained metal ions do not aggregate with each other, resulting in outstanding transparency, a low number of pinholes, and a low color difference.

[0101] In one implementation example, the recycled PET film may have a haze of 5% or less, preferably 4% or less, and more preferably 3% or less, as measured by ASTM D1003.

[0102] The haze of the film can be mainly caused by the content and particle size of impurities contained in the recycled PET film and the surface roughness of the film. However, the recycled PET film has excellent film-forming properties of recycled chips, has low surface roughness, and contains trace amounts of metal ions derived from molding improvers at 130 ppm or less, 100 ppm or less, preferably 70 ppm or less, and more preferably 50 ppm or less, so it can have a haze within the above range.

[0103] In one embodiment, the recycled PET film has a melt resistivity of 8 MΩ or less, preferably 6 MΩ or less, 5 MΩ or less, more preferably 4 MΩ or less or 3 MΩ or less, and may be, without limiting the upper limit, 1 MΩ or more or 2 MΩ or more.

[0104] Recycled PET films or chips having a melt resistivity within this range have excellent film processability, so the surface properties of the recycled PET film produced are excellent, and defects and even breakage of the recycled PET film produced can be prevented.

[0105] In one embodiment, the recycled PET film has a color difference value L measured by the measurement method defined in the present invention of 70 or less, 69 or less, or 67 or less, preferably 65 or less, 64 or less, or 63 or less, more preferably 61 or less, 60.8 or less, or 60.5 or less, and although there is no upper limit, it may be 60 or more.

[0106] The recycled PET film can have a color difference value in the above range because it has a very low content of metal ions derived from the molding improver contained therein.

[0107] In one embodiment, the recycled PET film may have a pinhole count of 2 or less, preferably 1.5 or less or 1 or less, and more preferably 0.8 or less or 0.5 or less, as measured by the measurement method defined in the present invention.

[0108] The number of pinholes in the recycled PET film is 100 cm 2 The pinhole count is an average of 10 measurements over an area of ​​10 mm. The recycled PET film has a maximum of 2 pinholes, and therefore has excellent surface properties and can have a haze within the above range.

[0109] That is, as one embodiment of the present invention, the recycled PET film, even if it contains waste PET, can have any of the following physical properties: haze of 5% or less, number of pinholes of 2 or less, and color difference value L of 70 or less; as another embodiment, it can have physical properties: haze of 4 or less, number of pinholes of 1 or less, and color difference value L of 63 or less.

[0110] The method for producing the recycled PET film of the present invention will be described below.

[0111] A method for producing a recycled PET film according to one embodiment of the present invention includes the steps of producing recycled chips containing waste PET and a molding improver, and producing a recycled PET film containing 95% by weight or more of the recycled chips.

[0112] In one implementation, the step of producing the recycled PET film may include no more than 5% by weight, no more than 2% by weight, or no virgin chips.

[0113] In one embodiment, the recycled chips may be produced by melting and compounding waste PET flakes and a modifier or molding modifier solution at 240°C to 260°C.

[0114] In one embodiment, the step of producing the recycled PET film further includes adding an antiblocking agent, which may be contained in the virgin chips or recycled chips, or may be added separately to the Banbury mixer.

[0115] The antiblocking agent may be contained in the virgin material chips or added separately, which is preferred because the antiblocking agent contained in the recycled PET film to be produced may have better dispersion, but there are no particular limitations as long as it does not impair the physical properties of the recycled PET film to be produced.

[0116] As an example, in the method for producing the recycled PET film, the content of the antiblocking agent added can be any amount as long as the content of the antiblocking agent in the produced recycled PET film satisfies 100 to 2000 ppm.

[0117] As an example, the step of producing the recycled PET film can be performed using any process recognizable by a person skilled in the art, but an unstretched recycled PET film melt-extruded through a T-die (260°C to 280°C) can be cooled to 80°C by running it in close contact with a casting roll.

[0118] The cooled unstretched recycled PET film may be stretched in the MD (machine direction stretcher) and TD (transverse direction stretcher) directions at 100°C to 150°C to produce a recycled PET film having a thickness of 10 to 100 μm.

[0119] In one embodiment, the recycled PET film is not limited to a stretching ratio of the unstretched recycled PET film, but may be preferably stretched 3 to 5 times in both MD and TD.

[0120] In another embodiment, the temperature in the MD stretching step may be 80°C to 120°C, preferably 100°C to 120°C, and the stretching ratio may be 3.8 to 4.8 times, preferably 4.0 to 4.5 times, but is not limited thereto.

[0121] In the step of stretching in the TD direction, the temperature may be 200° C. to 240° C., preferably 210° C. to 240° C., more preferably 220° C. to 235° C., and the stretching ratio may be the same as in the MD direction.

[0122] (Example) The recycled PET film and its manufacturing method will be described in more detail below with reference to the following examples. However, the following examples are merely reference examples for explaining the present invention in detail, and the present invention is not limited thereto and may be realized in various forms. Furthermore, 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. Furthermore, 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.

[0123] [Measurement method] 1.Melt resistivity measurement The produced regenerated chips were placed in a vacuum oven and vacuum dried at 150°C for 4 hours. 0.5 g of the dried regenerated chips were placed in a groove in a Teflon frame, and aluminum electrodes were connected to both the top and bottom ends of the groove in the Teflon frame. The Teflon frame was then placed over the chips to complete the measurement sample.

[0124] The measurement sample was then placed in a hot press at 285°C, and the chip was melted for 5 minutes. The pressure was maintained at 1.0 MPa, and the electrical resistance was measured after 3, 5, 7, 9, 11, and 13 minutes. The resistance value at which the measured resistance converged (e.g., the resistance value measured at 11 or 13 minutes) was confirmed. The same sample was measured twice using the above method, and the average value was calculated.

[0125] 2. Measuring the number of pinholes The produced PET film is cut into 100cm 2 Samples with an area of ​​100 mm were prepared and photographed using a microscope (Olympus, DSX-CB) in bright filter mode at wavelengths of 400 to 700 nm, and then in dark filter mode. Voids found in the photographs were defined as pinholes, and the number of pinholes was counted. A total of 10 samples were counted in the same manner as above, and the average value was calculated.

[0126] 3. Haze Measurement The haze measurement method was based on ASTM D1003. Seven sections were randomly extracted from two sides and one center section of the manufactured recycled PET film, and each was cut into 5cm x 5cm pieces, which were then placed in a haze meter (Nippon Denshoku Co., Ltd., NDH 300A). Light with a wavelength of 555nm was transmitted through the haze, and the haze was calculated using the following formula, after which the average value excluding the maximum and minimum values ​​was calculated. Haze (%) = (total scattered light / total transmitted light) x 100

[0127] 4. Measurement of color difference value L The recycled PET film was cut into a 100mm x 100mm sample and placed between two sample bases. The color difference was measured five times using a color difference meter (Nippon Denshoku Co., Ltd., SE-6000) and the average value was calculated.

[0128] 5.Film forming properties During the continuous PET film production process for one hour using a film forming machine, film defects and equipment errors were observed.

[0129] If the film was formed normally within one hour, it was marked with ◎; if a part of the film broke two or less times, it was marked with ○; if a part of the film broke three to five times, it was marked with △; if it broke six or more times or the film was cut, it was marked with ×.

[0130] 6.IPC analysis A 2g sample was weighed from the recycled PET film and placed in a 100mL Erlenmeyer flask. 6mL of sulfuric acid was then added to the Erlenmeyer flask with a measuring pipette to create a sample. The sample was then placed on a heating plate and heated at 220°C until the sample was completely carbonized, which took approximately 2-3 hours. The temperature was then raised to 450°C and heated until the sulfuric acid was circulating.

[0131] The Erlenmeyer flask containing the carbonized sample was then allowed to cool, after which 2 mL of nitric acid and 2 mL of perchloric acid were gradually added and the flask was again heated to 380°C. The cooling, addition of nitric acid and perchloric acid, and heating were repeated until the sample solution became transparent, and the transparent sample solution was further heated at 380°C until white smoke from sulfuric acid began to emerge, and the flask was allowed to cool for 30 minutes. Approximately 10 mL of distilled water was added to the cooled sample, mixed, and allowed to cool for 20 minutes to prepare the measurement sample solution.

[0132] Then, 50 mL of the prepared measurement sample solution was placed in a flask, distilled water was added, and the mixture was left for 1 hour. A standard solution of the carbonization sequence was placed in a 100 mL volumetric flask, and the concentration of the standard solution was adjusted to match the concentration of the sample to be measured, and purified water was used.

[0133] The pretreated sample and the standard solution (1000 ppm) were then measured using an ICP-OES (PerkinElmer, Avio-550Max), and the results were calculated using the following formula. JPEG2025530876000001.jpg16128

[0134] [Examples 1 to 8] A molding improver solution was prepared in advance by stirring 10 wt % of a molding improver consisting of the three metal compounds and 90 wt % of acetonitrile so that the magnesium acetate (MgAc), sodium acetate (NaAc), and trimethyl phosphate (TMP) contained in the recycled chips satisfied the ppm limits shown in Table 1 below.

[0135] Then, recycled chips were produced by feeding waste PET flakes with a weight average molecular weight of 56,000 g / mol and the molding improver solution into a compounding device (Rema Co., Ltd.), and the recycled chips and 700 ppm of SiO2 were fed into a film manufacturing machine to produce a recycled PET film with a thickness of 12 μm.

[0136] Thereafter, the produced recycled chips and recycled PET film were measured by the above-mentioned measuring methods, and the results are shown in Table 2 below.

[0137] [Comparative Example 1] A recycled PET film was produced in the same manner as in Example 1, except that recycled chips were produced without containing a molding improver. Thereafter, the produced recycled PET film was measured by the above-mentioned measuring method, and the results are shown in Table 2 below.

[0138] Comparative Example 2 A recycled PET film was produced in the same manner as in Example 1, except that the recycled chips were produced by adding 40 ppm of a molding improver. Thereafter, the produced recycled PET film was measured by the above-mentioned measuring method, and the results are shown in Table 2 below.

[0139] Comparative Example 3 A recycled PET film was produced in the same manner as in Example 1, except that the recycled chips were produced by adding 600 ppm of a molding improver. Thereafter, the produced recycled PET film was measured by the above-mentioned measuring method, and the results are shown in Table 2 below.

[0140] Comparative Example 4 Virgin material chips (masterbatch chips) and 700 ppm of SiO2 were fed into a film molding machine to produce a virgin material PET film with a thickness of 12 μm. Thereafter, the virgin material chips and the virgin material PET film were measured by the above-mentioned measuring method, and the results are shown in Table 2 below.

[0141] Comparative Example 5 A virgin material PET film was produced in the same manner as in Example 1, except that virgin material chips were fed into the film forming machine instead of the recycled chips. Thereafter, the virgin material chips and the virgin material PET film were measured by the above-mentioned measuring method, and the results are shown in Table 2 below.

[0142] [Table 1]

[0143] [Table 2]

[0144] From Table 2, it was confirmed that Examples 1 to 8 had a melt resistivity of 8 MΩ or less, all of which had excellent continuous film-forming properties, and the recycled PET films produced had a haze of 5% or less, a pinhole count of 2 or less, and a color difference value of 70 or less.

[0145] In contrast, in Table 2, Comparative Examples 1 and 2 had melt resistivity much higher than that of the Examples, making continuous film formation impossible, and the recycled PET films produced had very high haze, pinhole counts, and color difference values. Comparative Example 3 also had low melt resistivity, but higher haze and color difference values ​​than the Examples.

[0146] Furthermore, in Table 2, Comparative Examples 4 and 5 are PET films produced using virgin material chips, and it was confirmed that Comparative Example 5 had lower continuous film-forming properties and higher color difference values ​​than the Examples.

[0147] To explain the results in Table 2 in more detail, IPC analysis of the Examples and Comparative Examples confirmed that the Examples contained 10 to 130 ppm of metal ions derived from the molding improver, while Comparative Examples 1 to 3 did not contain the metal ions at 10 to 130 ppm. This suggests that only by containing metal ions in the above ranges can the recycled PET film have excellent film formability and satisfy the physical properties of haze of 5% or less, color difference of 70 or less, and pinhole count of 2 or less.

[0148] Furthermore, looking at Comparative Example 5, it can be seen that the PET film produced using virgin material chips and a molding improver exhibited an increased color difference and decreased continuous film-forming properties. This suggests that the various additives contained in the virgin material chips in Comparative Example 5 have low miscibility with the molding improver, resulting in a greater aggregation of metal ions than in the recycled PET film of the Example produced using the recycled chips.

[0149] 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.

[0150] 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 manufactured using 95% by weight or more of recycled chips manufactured using waste PET and a molding improver, The recycled PET film contains 10 to 130 ppm of metal ions derived from the molding improver.

2. The recycled PET film according to claim 1 , wherein the recycled PET film is produced solely from recycled chips.

3. The recycled PET film according to claim 1 , wherein the molding improver comprises a magnesium compound, a sodium compound, and a phosphorus compound.

4. The recycled PET film according to claim 1, wherein the recycled PET film 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 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.

5. The recycled PET film according to claim 1, wherein the recycled PET film contains an antiblocking agent in an amount of 100 to 2000 ppm.

6. 2. The recycled PET film according to claim 1, further comprising one or more selected from the group consisting of lubricants, stabilizers, plasticizers, UV stabilizers, heat stabilizers, fillers, pigment foaming agents, viscosity modifiers, processing aids, flame retardants, reinforcing agents, and dispersants.

7. The recycled PET film is 100 cm ２ 2. The recycled PET film according to claim 1, wherein the average number of pinholes per area measured 10 times is 2 or less.

8. 2. The recycled PET film of claim 1, wherein the recycled PET film has a haze of 5% or less as measured by ASTM D1003.

9. The recycled PET film according to claim 1, wherein the recycled PET film has a melt resistivity of 8.0 MΩ or less at 285°C.

10. A step of producing recycled chips including waste PET and a molding improver; and producing a recycled PET film containing 95% by weight or more of the recycled chips.

11. The method of claim 10 , wherein the step of producing the recycled PET film further comprises adding an anti-blocking agent.

12. The method for producing a recycled PET film according to claim 10, wherein the step of producing the recycled PET film comprises stretching the film 3 to 5 times in both MD and TD.

13. Recycled chips made from recycled PET and containing 50-500 ppm of molding modifiers.

14. The regenerated chip according to claim 13, wherein the regenerated chip contains 10 to 130 ppm of metal ions derived from a molding improver.

15. The regenerated chip according to claim 13, which satisfies the following formulas 4, 5, and 6: [Formula 4] 10≦[Mg]≦100 [Formula 5] 0.1≦[Na]≦10 [Formula 6] 1≦[P]≦10 (In the above formulas 4 to 6, [Mg] is the concentration (ppm) of magnesium ions contained in the regenerated chips, [Na] is the concentration (ppm) of sodium ions contained in the regenerated chips, [P] is the concentration (ppm) of phosphorus ions contained in the regenerated chip.

16. A recycled PET film containing waste PET, the recycled PET film having a haze of 5 or less, a number of pinholes of 2 or less, and a color difference value L of 70 or less.

17. The recycled PET film according to claim 16, wherein the recycled PET film contains 95% by weight or more of waste PET resin and 5% by weight or less of virgin PET resin.

18. The recycled PET film according to claim 16, wherein the recycled PET film has a haze of 4 or less, a number of pinholes of 1 or less, and a color difference value L of 63 or less.

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