Regenerated PET films made using regenerated sheets

Abstract

Compared with the traditional regenerated PET film, the regenerated PET film disclosed by the invention contains the color complementing agent containing the glyceryl compound, so that the regenerated PET film has obviously lower yellowing value and color difference value, and simultaneously meets the levels of breaking strength and hot shrinkage rate so as to replace a new PET material.

Description

Technical Field

[0001] The present invention relates to a recycled polyethylene terephthalate (PET) film prepared from waste PET and a color correcting agent and a preparation method thereof. Background Art

[0002] PET (polyethylene terephthalate) has excellent durability, processability and thermal stability, so it is widely used in clothing, packaging containers, home appliances, automobiles, films, etc. However, PET has a high porosity and is non-biodegradable, making it very difficult to handle waste PET, which will cause serious environmental pollution during landfill or incineration.

[0003] Therefore, in order to solve the problems of environmental pollution and rising costs caused by the depletion of petroleum resources, the technology of recycling waste PET has attracted much attention.

[0004] In the recycling process of waste PET, waste PET is used to make clothes, packaging containers, home appliances, cars and films after going through screening processes, foreign matter removal processes, washing processes, metal separation processes, etc. However, the physical properties of clothes, packaging containers, home appliances, cars and films are lower than those of PET products made from virgin PET, and there are restrictions on recycling.

[0005] In particular, the processing conditions of the recycled PET film prepared from waste PET are more stringent than other molded products, and it is prepared by stretching 4 to 5 times the original length in the transverse / axial direction, so there are many restrictions on the physical properties of the waste PET resin, heat treatment process conditions and additive content. In addition, since various grades of waste PET are mixed together, the processing conditions for recycling waste PET into films are more stringent.

[0006] Therefore, according to the related art, the film-forming performance of the recycled PET film prepared by including waste PET is low, and in particular, the appearance performance is extremely poor due to the increase in color difference value.

[0007] In recent years, in order to solve the problem of increased color difference value in recycled PET film prepared from waste PET, color correctors containing organic / inorganic compounds have been added, but the color difference value of recycled PET film is still higher than that of original PET film, and the addition of color correctors will cause yellowing phenomenon in which the color difference value changes due to external environment such as temperature, humidity, heat, etc. In addition, according to the relevant technology, the thermal shrinkage rate of recycled PET film added with organic / inorganic compounds as color correctors increases and the breaking strength decreases, which makes it technically difficult to simultaneously meet the appearance performance, heat resistance and mechanical properties of recycled PET film.

[0008] Therefore, in order to utilize waste PET to prepare recycled PET film, a new technology that can provide excellent film processing performance is needed. In addition, a new technology needs to be developed that can solve the problem of large color difference values ​​of recycled PET film in related technologies and can also provide a fairly high yellowing resistance to meet both thermal shrinkage and mechanical strength.

[0009] [Related technical literature]

[0010] [Patent Document]

[0011] (Patent Document 1) Korean Patent Publication No. 10-2013-0035897A

[0012] (Patent Document 2) Korean Patent Publication No. 10-2013-0035897A. Summary of the invention

[0013] Technical issues

[0014] As an embodiment, in order to solve the problem of low film-forming performance of recycled polyethylene terephthalate (PET) from waste PET existing in the related art, the present disclosure aims to provide a recycled PET film, wherein a recycled sheet is prepared by including waste PET and a molding modifier, and low haze and excellent film-forming performance are achieved using the recycled sheet.

[0015] As an embodiment, according to the related art, a recycled PET film prepared by including waste PET has a high color difference value, but the present disclosure aims to provide a recycled PET film including a color correcting agent containing a specific organic compound to have a lower color difference value.

[0016] As an embodiment, the present disclosure aims to provide a recycled PET film, which includes a color corrector containing a specific organic compound, and adjusts its content to solve the problems of high yellowing phenomenon, high thermal shrinkage rate and reduced breaking strength of the recycled PET film containing the color corrector according to the related art, thereby achieving low color difference value, low yellowing resistance, low thermal shrinkage rate and excellent breaking strength at the same time.

[0017] As an embodiment, the present disclosure is intended to provide a recycled PET film, wherein, when the recycled PET film is analyzed by the measurement method defined in the present disclosure, the color difference value L is 70 or less, the color difference value b is 5 or less, the color difference value L is 65 or less, preferably 62 or less, and the yellowing resistance is 10% or less or 7% or less.

[0018] In addition, as an embodiment, the present disclosure is intended to provide a recycled PET film, wherein when the recycled PET film comprising waste PET and a specific color-correcting agent is measured by the analysis method defined in the present disclosure, the heat shrinkage rate is 5% or less in the transverse direction (TD), 1% or less in the longitudinal direction (MD), and the breaking strength is 10 kgf / mm in both MD and TD. 2 or above.

[0019] Technical Solution

[0020] The recycled polyethylene terephthalate (PET) film of the present invention comprises waste PET, virgin PET as PET resin components, and a color corrector, wherein the yellowing resistance of the recycled PET film measured according to ASTM D1925 is in the range of 5% to 10%, and the color difference value L and the color difference value b measured according to ASTM E313 are in the range of 59 to 70 and 5 or less, respectively, and the color corrector contains a glyceryl compound as shown in Formula 1 below:

[0021] [Formula 1]

[0022]

[0023] (Wherein, in Formula 1, R 1 , R 2 and R 3 Each independently is a linear or branched C 1 -C 20 Alkyl or linear or branched C 1 -C 20 Unsaturated alkyl.

[0024] As an embodiment, the color-correcting agent may include an organic compound as shown in Formula 2, an organic compound as shown in Formula 3, or a mixture thereof:

[0025] [Formula 2]

[0026]

[0027] (In Formula 2, R 4 and R 5 Each independently is a linear or branched C 1 -C 20 Alkyl or linear or branched C 1 -C 20 Unsaturated alkyl. ) and

[0028] [Formula 3]

[0029]

[0030] (Wherein, in Formula 3, R6 and R 7 Each independently is a linear or branched C 1 -C 20 Alkyl or linear or branched C 1 -C 20 Unsaturated alkyl.

[0031] As an embodiment, the recycled PET film may contain the color correcting agent in a range of 10 ppm to 100 ppm.

[0032] As an embodiment, in Formula 1-3, R 1 , R 2 , R 3 , R 4 , R 5 , R 6 and R 7 Each independently is a linear or branched C 1 -C 12 Alkyl or linear or branched C 1 -C 12 Unsaturated alkyl.

[0033] As an embodiment, the recycled PET film may include metal ions in a range of 10 ppm to 200 ppm, wherein the metal ions originate from virgin sheets prepared by including the forming modifier.

[0034] As another embodiment, the recycled PET film may meet the requirements of the following expressions 1 to 3:

[0035] [Expression 1]

[0036] 10≤[Mg]≤100

[0037] [Expression 2]

[0038] 0.1≤[Na]≤10

[0039] [Expression 3]

[0040] 1≤[P]≤50

[0041] (Wherein, in Expressions 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).

[0042] As an embodiment, the recycled PET film may include the anti-blocking agent in a range of 300 ppm to 1,000 ppm.

[0043] As an embodiment, in the recycled PET film, the breaking strength measured according to ASTM D882 may be 10 kgf / mm in both the machine direction (MD) and the transverse direction (TD). 2 Up to 30 kgf / mm 2 within the range.

[0044] As an embodiment, the recycled PET film may have a heat shrinkage rate of 5% or less in MD and 1% or less in TD at a temperature of 200°C.

[0045] As an embodiment, the recycled PET film may include waste PET in the range of 30wt% to 95wt% and virgin PET in the range of 5wt% to 70wt%. For example, the recycled PET film may include waste PET in the range of 50wt% to 90wt% and virgin PET in the range of 10wt% to 50wt%, may include waste PET in the range of 60wt% to 90wt% and virgin PET in the range of 10wt% to 40wt%, or may include waste PET in the range of 60wt% to 80wt% and virgin PET in the range of 20wt% to 40wt%.

[0046] According to the method for preparing a recycled PET film of the present invention, it comprises: preparing a recycled sheet by including waste PET, preparing a virgin sheet by including virgin PET, and preparing a recycled PET film by including the recycled sheet, the virgin sheet and a glycerol-based compound shown in Formula 1:

[0047] [Formula 1]

[0048]

[0049] (Wherein, in Formula 1, R 1 , R 2 and R 3 Each independently is a linear or branched C 1 -C 20 Alkyl or linear or branched C 1 -C 20 Unsaturated alkyl.

[0050] As an embodiment, in the preparation of the recycled PET film, the recycled PET film may include waste PET in the range of 30wt% to 95wt% and virgin PET in the range of 5wt% to 70wt%. For example, the recycled PET film may include waste PET in the range of 50wt% to 90wt% and virgin PET in the range of 10wt% to 50wt%, may include waste PET in the range of 60wt% to 90wt% and virgin PET in the range of 10wt% to 40wt%, or may include waste PET in the range of 60wt% to 80wt% and virgin PET in the range of 20wt% to 40wt%.

[0051] As an embodiment, a virgin sheet may be prepared by including a molding modifier in a range of 150 ppm to 14,000 ppm.

[0052] As an embodiment, the raw sheet may be prepared by including the anti-blocking agent in the range of 150 ppm to 20,000 ppm.

[0053] Effects and advantages of the invention

[0054] Even according to an embodiment of the present invention, when a recycled polyethylene terephthalate (PET) film is prepared by including a recycled sheet in a range of 30 wt % or more, 50 wt % or more, and preferably 80 wt % or more, the recycled PET film can also have significantly high film-forming properties as well as significantly high transparency, surface properties, and mechanical strength compared to the recycled PET film according to the related art, thereby enabling the recycled PET film to replace the virgin PET film in the field of using the virgin PET film prepared from the virgin PET resin.

[0055] According to one embodiment of the present invention, a recycled PET film may include a recycled sheet and a color-correcting agent containing a specific organic compound, thereby solving the problem of high color difference value of the recycled PET film in the related art.

[0056] According to one embodiment of the present invention, the recycled PET film may include a color corrector containing a specific organic compound. By adjusting the content of the color corrector, excellent yellowing resistance, high thermal shrinkage rate, and high breaking strength can be maintained, thereby achieving excellent haze, film-forming performance, yellowing resistance, color difference value, thermal shrinkage rate, and breaking strength at the same time.

[0057] Therefore, in the recycled PET film of the present invention, the film-forming properties of the recycled PET film can be achieved, and therefore, even if a large amount of waste PET is included, significant transparency and surface properties can be achieved compared to the recycled PET film of the related art. In addition, the recycled PET film of the present invention can include a color-correcting agent containing a specific organic compound, thereby achieving significantly higher yellowing resistance compared to the recycled PET film of the related art, and can significantly maintain heat shrinkage and breaking strength, so the recycled PET film according to the present invention can be more useful than the recycled PET film of the related art. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 : is a graph showing the nuclear magnetic resonance (NMR) measurement results of Example 4.

[0059] Figure 2 is a graph showing the ICP-OES measurement results of Example 4. DETAILED DESCRIPTION

[0060] Hereinafter, the recycled polyethylene terephthalate (PET) film and the preparation method thereof according to the present invention will be described in detail. In this case, unless otherwise defined, the technical terms and scientific terms used in this specification have the general meanings understood by those skilled in the art to which the present invention belongs, and the description of known functions and configurations that may unnecessarily obscure the gist of the present invention will be omitted in the following description.

[0061] Unless the context indicates otherwise, singular forms used in this specification may also include plural forms.

[0062] In addition, the numerical range used in this specification includes all values ​​within the range, including the lower limit and the upper limit, the increment derived in some form of logic and the span within the defined range, all double limits, and all possible combinations of the upper and lower limits within the numerical range defined in different forms. Unless otherwise defined in the specification of the present invention, values ​​that may exceed the numerical range due to experimental errors or rounding are also included in the defined numerical range.

[0063] The term "comprising" in this specification is an open description, which is equivalent to terms such as "providing", "including", "having" or "characterized by", and does not exclude elements, materials or processes that are not further listed.

[0064] In the related art, the recycled PET film prepared by including waste PET has poor film-forming properties and is difficult to prepare continuously, so the transparency is significantly lower. In particular, the color difference value of the recycled PET film is significantly higher than that of the original PET film, so it is difficult to apply to fields requiring excellent optical properties.

[0065] In order to solve these problems, the related art attempts to add color-correcting agents to the recycled PET film to reduce the color difference value. However, it cannot solve the problem of increased color difference value, nor can it solve the problem of increased yellowing resistance, increased heat shrinkage and reduced breaking strength caused by adding color-correcting agents.

[0066] In order to solve the problems of low film-forming performance and high color difference of recycled PET film in the related art, the inventors prepared a recycled PET film, including waste PET and a color-correcting agent containing a specific organic compound, so that it has a lower color difference value. It is worth noting that the recycled PET film also has significant yellowing resistance.

[0067] In addition, in order to solve the problem in the related art that there is a complementary relationship between optical properties, thermal properties, and mechanical properties, which leads to the inability to achieve excellent performance at the same time, the inventors found that even if a small amount of color corrector containing specific organic compounds is added, the recycled PET film still has an obvious color corrector effect, and the addition of the color corrector will not cause the problem of increased thermal shrinkage and reduced breaking strength, thereby completing the present invention.

[0068] The recycled PET film of the present invention will be described in detail below.

[0069] The recycled PET film of the present invention can be prepared by including waste PET and virgin PET, and can include a color-correcting agent containing a specific organic compound, so that its color difference value is significantly lower than that of the recycled PET film prepared by including waste PET according to the related art. In addition, excellent yellowing resistance, low heat shrinkage rate and excellent breaking strength can also be achieved at the same time.

[0070] According to one embodiment, the recycled PET film may include waste PET and virgin PET as resin components, and may further include a color correcting agent including a glycerol-based compound as shown in Formula 1 below.

[0071] [Formula 1]

[0072]

[0073] (Wherein, in Formula 1, R 1 , R 2 and R 3 Each independently is a linear or branched C 1 -C 20 Alkyl or linear or branched C 1 -C 20 Unsaturated alkyl.

[0074] As an embodiment, in Formula 1, R 1 , R 2 and R 3 Each independently is a linear or branched C 1-C 5 Alkyl or linear or branched C 2 -C 5 Unsaturated alkyl.

[0075] For example, the triacylglycerol compound represented by Formula 1 may include triacetin (glyceryl triacetate), tripropionin, tributyrin (glyceryl tributyrate), or tripalanin, but the present invention is not limited thereto.

[0076] As an embodiment, the recycled PET film may include a color corrector containing a glycerol-based compound as shown in Formula 1 to better disperse the residual fractions in the waste PET resin and the added additives, so it may have a lower color difference value than the recycled PET film in the related art.

[0077] In addition, the recycled PET film including the color correcting agent containing the glycerol-based compound may have a stable structure and thus is not easily decomposed in external environments such as ultraviolet rays, heat, humidity, etc. Therefore, the deterioration of the contained waste PET may be minimized, thereby achieving significantly high yellowing resistance compared to the PET film of the related art.

[0078] According to one embodiment, a recycled PET film may be prepared by including a color-correcting agent. The yellowing resistance of the recycled PET film measured according to ASTM D1925 may be in the range of 5% to 10%, and the color difference value L and the color difference value b measured according to ASTM E313 may be in the range of 59 to 70 and 5 or less, respectively.

[0079] As another embodiment, in the recycled PET film, the yellowing resistance may be in the range of 5% to 8%, preferably 5% to 6%, the color difference value L may be in the range of 59 to 65, preferably 59 to 62, the color difference value a may be -1.5 or less, and the color difference value b may be 3 or less.

[0080] Specifically, the recycled PET film is not limited thereto, and the lower limit of the color difference value a may be -3.0 or above, -2.0 or above, preferably -1.5 or above, and the lower limit of the color difference value b may be 0.3 or above, 0.1 or above, preferably 0.05 or above.

[0081] The recycled PET film with a color difference value within this range can not only solve the problem of high color difference value of the recycled PET film in the related art, but also make the color difference value reach a level sufficient to replace the original PET film, so that the recycled PET film can be applied to a wider range of industrial fields.

[0082] In addition, compared with the recycled PET film of the related art, the recycled PET film having yellowing resistance within this range may have significantly high yellowing resistance, and therefore, the initial color difference value can be continuously maintained even when exposed to strong energy or external environment such as ultraviolet rays, humidity, heat, etc., and therefore the recycled PET film may be preferred.

[0083] According to one embodiment, the color-correcting agent may further include at least one organic compound represented by the following Formula 2 and Formula 3:

[0084] [Formula 2]

[0085]

[0086] (In Formula 2, R 4 and R 5 Each independently is a linear or branched C 1 -C 20 Alkyl or linear or branched C 1 -C 20 Unsaturated alkyl. ) and

[0087] [Formula 3]

[0088]

[0089] (In Formula 3, R 6 and R 7 Each independently is a linear or branched C 1 -C 20 Alkyl or linear or branched C 1 -C 20 unsaturated alkyl).

[0090] According to another embodiment, since the color-correcting agent contained in the recycled PET film may include not only the glycerol-based compound as shown in Formula 1 but also at least one organic compound as shown in Formula 2 and Formula 3, the recycled PET film may be preferred because it can better disperse the residual fraction of waste PET and additives compared to the recycled PET film containing the glycerol-based compound.

[0091] According to one embodiment, the color correction agent comprises an organic compound, wherein in Formulas 1 to 3, R 1 , R 2、 R 3、 R 4 , R 5 , R 6 and R 7 Straight or branched chain C 1 -C 12 Alkyl, preferably straight chain C 1 -C 12Alkyl groups may have significantly lower color difference values, but the present invention is not limited thereto.

[0092] The recycled PET film according to one embodiment may contain the color correcting agent in the range of 5 ppm to 200 ppm, 10 ppm to 100 ppm, preferably 30 ppm to 80 ppm, more preferably 40 ppm to 60 ppm.

[0093] The recycled PET film containing the color correcting agent in this ppm range can have a lower color difference value and a more significantly high yellowing resistance. That is, the recycled PET film can satisfy a color difference value L of 70 or less and a yellowing resistance of 5% to 10%.

[0094] However, the recycled PET film including the color correcting agent in an amount exceeding 100 ppm may have a lower color difference value, significantly high yellowing resistance, but may have an increased heat shrinkage rate and reduced mechanical strength. Therefore, the color correcting agent is preferably contained in such a ppm range.

[0095] According to one embodiment, the recycled PET film may contain metal ions in the range of 10 ppm to 200 ppm from the virgin sheet.

[0096] Specifically, the recycled PET film may contain metal ions in the range of 10 ppm to 100 ppm or 60 ppm to 130 ppm, and the metal ions may come from a molding modifier included in the virgin sheet preparation process.

[0097] Examples of the molding modifier may include at least one selected from metal compounds (metal salts) containing metal cations of magnesium, sodium, potassium, lithium, manganese, zinc, etc.; and phosphorus-based compounds such as trimethyl phosphate, triethyl phosphate, and tributyl phosphate.

[0098] Specifically, from the perspective of making the metal ions contained in the recycled PET film well dispersible, the molding modifier may include at least one of a magnesium compound, a sodium compound and a phosphorus compound, and more specifically, may include at least one of magnesium acetate, sodium acetate and trimethyl (ethyl) phosphate.

[0099] The raw sheet prepared by including a forming modifier may include metal ions in the forming modifier. For example, the metal ions may include Mg 2+ 、Na + , Ca 2+ 、P0 4 3- or Li + , these ions can be contained in recycled PET film.

[0100] Even if containing a small amount of metal ions, the recycled PET film including the metal ions from the molding modifier can have excellent PET film-forming properties, thereby preventing the metal ions from aggregating on the surface and achieving excellent film-forming properties.

[0101] In addition, the recycled PET film containing such metal ions in the ppm range can solve the problem of poor film-forming properties of waste PET, and at the same time can have a smooth surface, as well as a color-correcting effect of the color-correcting agent inhibiting the agglomeration of the metal ions contained therein. Therefore, the recycled PET film can have significantly higher transparency and low color difference values.

[0102] As an embodiment, the recycled PET film may satisfy Expressions 1 to 3 below.

[0103] [Expression 1]

[0104] 10≤[Mg]≤100

[0105] [Expression 2]

[0106] 0.1≤[Na]≤10

[0107] [Expression 3]

[0108] 1≤[P]≤10

[0109] (Wherein, in Expressions 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.)

[0110] As another embodiment, in Expressions 1 to 3, [Mg] may be in the range of 10 to 80, [Na] may be in the range of 0.1 to 5, and [P] may be in the range of 1 to 5.

[0111] Compared with the recycled PET film of the related art, the recycled PET film containing magnesium ions, sodium ions and phosphorus ions in such a ppm range has significantly high film-forming properties, and the magnesium ions, sodium ions and phosphorus ions can be contained in a smaller content and may not aggregate, so the recycled PET film can have low haze and low color difference value, and can have better heat resistance, which is preferred.

[0112] The recycled PET film according to one embodiment may include the anti-blocking agent in an amount ranging from 300 ppm to 1,000 ppm, preferably from 400 ppm to 800 ppm, and more preferably from 500 ppm to 800 ppm.

[0113] Since the recycled PET films do not stick to each other during the manufacturing process, stable processability can be ensured and defects due to scratches can be significantly reduced, so the recycled PET film including the anti-blocking agent within this range may be preferred.

[0114] The anti-adhesion agent may include inorganic particles, organic particles or a mixture thereof. As an example, the anti-adhesion agent may include a selected from NaF, MgF 2 , CaF 2 , BaF 2 、SiO 2 ,BaSO 4 , CeF 3 、Al 2 O 3 、ZrO 2 、TiO 2 , ZnS, ZnSe and Ta 2 O 5 Specifically, when the anti-adhesive agent includes SiO 2 When the recycled PET is used, excellent film-forming properties of the recycled PET can be achieved, but the material of the anti-blocking agent is not limited as long as the material can be recognized by those skilled in the art.

[0115] According to one embodiment, the recycled PET film may further include at least one additive 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.

[0116] The recycled PET film further including the above-mentioned additives may have different physical properties according to the types and contents of the additives, and thus can be applied to a wider range of industrial fields.

[0117] According to one embodiment of the recycled PET film, it can also include 30wt% to 95wt% of waste PET and 5wt% to 70wt% of virgin PET, preferably 70wt% to 95wt% of waste PET, or more preferably 80wt% to 95wt% of waste PET. For example, the recycled PET film can include 50wt% to 90wt% of waste PET and 10wt% to 50wt% of virgin PET, can include 60wt% to 90wt% of waste PET and 10wt% to 40wt% of virgin PET, or can include 60wt% to 80wt% of waste PET and 20wt% to 40wt% of virgin PET.

[0118] According to a recycled PET film of one embodiment of the present invention, the recycled PET film can be prepared by containing up to 95wt% of waste PET, thereby solving environmental pollution problems such as air pollution, geological pollution and underwater pollution caused by landfill or incineration of waste PET.

[0119] In addition, even if a large amount of waste PET is included, excellent film-forming properties of recycled PET can be achieved, thereby continuously preparing recycled PET films, and achieving significantly high transparency compared to recycled PET films prepared by including waste PET according to the related art. Therefore, the recycled PET film according to one embodiment may be preferred.

[0120] The thickness of the recycled PET film according to one embodiment may be 10 μm to 150 μm, specifically 10 μm to 100 μm, more specifically 10 μm to 50 μm, but the thickness of the recycled PET film is not limited as long as the thickness of the recycled PET film does not deteriorate the physical properties of the prepared recycled PET film.

[0121] The recycled PET film having such a thickness range may vary according to the degree of stretching of the unstretched PET film output from the T-die in the longitudinal direction (MD) and the transverse direction (TD) in the method for preparing the recycled PET film to be described below, but may preferably have the least surface scratches, pinholes or broken holes. In addition, the PET film having such a thickness range may be a single-layer film or a laminated film. As the PET films are stacked, their thickness may increase, but the present invention is not limited thereto.

[0122] Specifically, the laminated film may be a film comprising two or more layers of recycled PET films, or may be a laminated structure comprising a single layer of PET film and a different type of layer (eg, a layer not comprising recycled polyester or a layer comprising other types of resins).

[0123] The weight average molecular weight of waste PET may be 40,000 g / mol to 200,000 g / mol, preferably 100,000 g / mol or less, more preferably 40,000 g / mol to 80,000 g / mol, wherein the recycled PET film has excellent formability, but the present invention is not limited thereto.

[0124] The physical properties of the recycled PET film of the present invention are described below.

[0125] According to one embodiment, a recycled PET film may include waste PET in a range of 30 wt % to 95 wt % and may be prepared by including a molding modifier, thereby achieving significantly high PET film molding performance to have a haze that is superior to that of a recycled PET film according to the related art.

[0126] In addition, according to one embodiment, the recycled PET film may include a glycerol-based compound as shown in Formula 1 to have a lower color difference value and significantly higher yellowing resistance than the recycled PET film according to the related art, and may also include a small amount of a color corrector to maintain thermal shrinkage and breaking strength.

[0127] As described above, according to one embodiment, the recycled PET film can satisfy yellowing resistance of 5% to 10%, a color difference value L of 59 to 70, and a color difference value b of 5 or less as measured by the measuring method defined in the present invention, and can achieve the following physical properties.

[0128] According to one embodiment, the breaking strength of the recycled PET film can be 10 kgf / mm in MD and TD as measured according to ASTM D882. 2 Up to 30 kgf / mm 2 In the range of 15 kgf / mm 2 or more, more preferably 20 kgf / mm 2 or above.

[0129] In the recycled PET film having a breaking strength within this range, the content of the color corrector can be adjusted, and a molding modifier can be included to achieve significantly high moldability of the recycled PET film, and the inhibition of the breaking strength of the recycled PET film due to an excessively high content of the color corrector can be avoided, thereby satisfying the breaking strength within this range.

[0130] According to another embodiment, the heat shrinkage of the recycled PET film may be 5% or less in MD and 1% or less in TD. The lower limit of the heat shrinkage may be 0.1% or more in TD, preferably 2% or less in MD, and more preferably 1% or less in MD. The lower limit may be 0.5% or more in MD.

[0131] The recycled PET film having such a range of heat shrinkage may include a color correcting agent in the range of 100 ppm or less, and may include a color correcting agent including a glycerol compound as shown in Formula 1, thereby solving the problem of reduced thermal characteristics caused by the recycled PET film according to the related art including the color correcting agent.

[0132] The preparation method of the recycled PET film of the present invention will be described in detail below.

[0133] According to the present invention, in the method for preparing a recycled PET film, the recycled PET film can be prepared by a recycled sheet prepared by including waste PET and a virgin sheet prepared by including virgin PET. The recycled sheet or the virgin sheet may include a molding modifier and an anti-blocking agent, so the recycled PET film may have a better dispersion degree of the metal compound.

[0134] In addition, according to another embodiment, in the method for preparing a recycled PET film, the preparation of the recycled PET film may further include a specific color correcting agent, so that a more significant degree of dispersion of the metal compound can be achieved, so that the color difference value L can satisfy the range of 59 to 70, and the yellowing resistance can satisfy the range of 5% to 10%.

[0135] The method for preparing a recycled PET film according to the present invention may include: preparing a recycled sheet by including waste PET, preparing a virgin sheet by including virgin PET, and preparing a recycled PET film by including the recycled sheet, the virgin sheet and a glycerol-based compound shown in Formula 1.

[0136] [Formula 1]

[0137]

[0138] (Wherein, in Formula 1, R 1 , R 2 and R 3 Each independently is a linear or branched C 1 -C 20 Alkyl or linear or branched C 1 -C 20 unsaturated alkyl).

[0139] According to another embodiment, in the method for preparing a recycled PET film, the color correcting agent may be contained in a recycled sheet or a virgin sheet, but the present invention is not limited thereto.

[0140] In the preparation of the recycled PET film, the recycled sheet is prepared by melting, and the temperature is not limited as long as the sheet is formed by melting. For example, the waste PET flakes are melted at a temperature of 240° C. to 260° C. to prepare the recycled sheet. In the preparation of the recycled PET film, a molding modifier may be added and mixed, or other additives may be added and melted together to prepare the recycled sheet, but the present invention is not limited thereto.

[0141] According to one embodiment, in the preparation of the recycled PET film, the recycled PET film may include recycled sheets in the range of 30wt% to 95wt% and virgin sheets in the range of 5wt% to 70wt%. Specifically, the recycled PET film may include recycled sheets in the range of 70wt% to 95wt% and virgin sheets in the range of 5wt% to 30wt%. For example, the recycled PET film may include waste PET in the range of 50wt% to 90wt% and virgin PET in the range of 10wt% to 50wt%, may include waste PET in the range of 60wt% to 90wt% and virgin PET in the range of 10wt% to 40wt%, or may include waste PET in the range of 60wt% to 80wt% and virgin PET in the range of 20wt% to 40wt%.

[0142] In one embodiment, the shaping modifier may be included in the preparation of the recycled sheet or in the preparation of the virgin sheet and may include metal ions from the shaping modifier in the recycled sheet or the virgin sheet.

[0143] Specifically, in the preparation of recycled PET film, the molding modifier may be included together with the virgin PET in the process of preparing the virgin sheet, and thus the virgin sheet including the metal ions from the molding modifier may be more preferred. The recycled PET film prepared by including the virgin sheet containing the metal ions may contain the molding modifier having an excellent degree of dispersion, and thus may be preferred.

[0144] As an embodiment, the raw sheet may be prepared by including the molding modifier in a range of 150 ppm to 14,000 ppm, preferably 500 ppm to 10,000 ppm, and more preferably 1,000 ppm to 6,000 ppm.

[0145] According to the virgin sheet prepared by containing a molding modifier in this ppm range, the problem of low miscibility between waste PET and the molding modifier can be solved, thereby solving the problem of increased haze and color difference values ​​caused by aggregation of metal ions derived from the molding modifier in the recycled PET film according to the related art.

[0146] In the virgin sheet prepared by including the molding modifier in this range, the ppm of the molding modifier included may vary according to the wt% of the virgin sheet included when preparing the recycled PET film, but may satisfy the ppm range of the molding modifier included when preparing the virgin sheet.

[0147] That is, the recycled PET film of the present invention can be prepared by including a molding modifier in the range of 100 ppm to 700 ppm, specifically 100 ppm to 500 ppm, and more specifically 100 ppm to 300 ppm. However, there is no limitation as long as the metal ions contained in the prepared recycled PET film meet the range of 10 ppm to 100 ppm.

[0148] As described above, examples of the molding modifier may include one 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 a mixture of triethyl phosphate.

[0149] In order to achieve excellent recycled PET film forming properties with a smaller amount of the forming modifier, the forming modifier preferably includes magnesium acetate, sodium acetate and trimethyl (ethyl) phosphate.

[0150] In one embodiment, the virgin sheet may include an anti-blocking agent in the range of 140 ppm to 20,000 ppm, preferably 1,000 ppm to 20,000 ppm, more preferably 1,500 ppm to 18,000 ppm, but the range may vary depending on the wt% of the virgin sheet included in the preparation of the recycled PET film. The present invention is not limited thereto.

[0151] As an embodiment, in the preparation of the recycled sheet, the recycled sheet can be prepared by melting and kneading waste PET flakes containing waste PET at a temperature of 240°C to 260°C, and may further include a molding modifier solution, an anti-blocking agent and an additive, but the present invention is not limited thereto.

[0152] As an embodiment, the steps of preparing the virgin sheet can be the same as the steps of preparing the recycled sheet. In order to make the metal compound contained in the prepared recycled PET film have a relatively high dispersion, the virgin sheet can preferably also include an anti-blocking agent, a molding modifier and an additive for preparation, but the present invention is not limited thereto.

[0153] In the preparation of the recycled sheet, a PET sheet including recycled PET may be melted at a temperature of 240° C. to 260° C., and a molding modifier may be added to the melted PET sheet and vacuum extruded to prepare a beaded recycled sheet.

[0154] It is noteworthy that the recycled sheet prepared by the above method can significantly improve the low film-forming properties of recycled PET or recycled PET flakes, especially the metal compounds contained in the prepared PET film can have a higher dispersion.

[0155] In the recycled PET film according to one embodiment, there is no limitation on the stretching ratio of the unstretched recycled PET film, but the unstretched recycled PET film may be preferably stretched to 3 to 5 times the original length in MD and TD.

[0156] Specifically, during the stretching process on MD, the temperature may be in the range of 80°C to 120°C, preferably 100°C to 120°C, and the stretching ratio may be in the range of 3.8 to 4.8 times, preferably 4.0 to 4.5 times. However, the present invention is not limited thereto. In addition, during the stretching process on TD, the temperature may be in the range of 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 the stretching ratio on MD.

[0157] Below, the PET film and the preparation method thereof according to the present invention will be described in more detail by way of examples. However, the following examples are only used as references for describing the present invention in detail, and the present invention is not limited thereto, but can be implemented in various forms. In addition, unless otherwise defined, all technical and scientific terms have the same meanings as those generally understood by those skilled in the art. The terms used in the description herein are only for the purpose of effectively describing a certain example and are not intended to limit the present invention.

[0158] [Measurement method]

[0159] 1. Color difference measurement

[0160] The measurement was performed according to ASTM E313. The obtained recycled PET film was prepared into a sample with a size of 100 mm × 100 mm, and the sample was placed between two sample stages. Then, the color difference value was measured using a colorimeter (ZE-6000 manufactured by NIPPONDENSHOKU INDUSTRIES CO., LTD.), and the average value was calculated by measuring 5 times.

[0161] 2. Yellowing resistance measurement

[0162] The initial L value of the prepared recycled PET film was measured according to ASTM E313 by measuring the color difference value. Ultraviolet rays, heat and moisture were applied to the surface of the film using an accelerated test device (QUV-SE, manufactured by Qpanel Inc., USA), and after 168 hours of accelerated testing, the film was accelerated by measuring the color difference value, and then the L value was measured. Then, the measured initial L value and the accelerated L value were calculated by the following formula to obtain yellowing resistance.

[0163] Yellowing resistance (%) = ((L value after acceleration - initial L value) / initial L value) × 100

[0164] 3. Haze measurement

[0165] The haze value was measured using a haze meter (NDH 5000, manufactured by NIPPONDENSHOKU INDUSTRIES CO., LTD.) in accordance with ASTM D-1003.

[0166] 4. Breaking strength measurement

[0167] The samples were prepared and measured according to ASTM D882, and the breaking strength of the samples was obtained using a measuring device (Instron Corporation).

[0168] 5. Thermal shrinkage measurement

[0169] The sample is cut into a rectangle of 15mm (MD) × 400mm (TD) in MD and TD, and a sample with an effective measurement distance of 300mm is prepared by drawing solid lines in MD at points 50mm apart from both ends in the TD direction. Then, a point within 50mm from either end of the sample is grasped with a tool such as tweezers, regardless of left or right, and the entire sample is completely immersed in hot water at a temperature of 90°C±0.5°C under no load, and the sample is heat shrunk for 10 seconds. After that, the sample is left at room temperature for 1 minute, and then the length of the initial 300mm reduction represented by the straight line in TD is measured, and the measured length is calculated by the following formula to calculate the heat shrinkage rate.

[0170] [equation]

[0171] Film TD thermal shrinkage rate = ((300mm-length after shrinkage / 300mm)) × 100

[0172] 6. Nuclear Magnetic Resonance (NMR) Measurement

[0173] The samples were measured using a nuclear magnetic resonance device (AVANCE III 400 manufactured by Bruker Corporation) with a 1H probe and a resonance frequency of 400 MHz. The measurement results are as follows: Figure 1 shown.

[0174] 7. Inorganic component analysis

[0175] The samples were measured using ICP-OES (Avio 550 Max manufactured by PerkinElmer, Inc.), and the inorganic elements contained in the samples were determined by energy dispersive X-ray (EDX) analysis of the ash. The measurement results are as follows: Figure 2 shown.

[0176] [Examples 1-6]

[0177] Recycled PET flakes were made into recycled sheets using a compounding device (manufactured by Erema), and virgin sheet PET, 1000 ppm of magnesium acetate (MgAc), 150 ppm of sodium acetate (NaAc), 200 ppm of triethyl phosphate (TEP), and 3000 ppm of an anti-blocking agent were made into virgin sheets using a compounding device (manufactured by Erema).

[0178] Then, 80 wt% of the prepared recycled sheet and 20 wt% of the virgin sheet were input into a film making machine, melted and mixed at a temperature of 260°C, and after the mixing was completed, a triacylglycerol compound (TAG, such as triacetin) represented by Formula 1 was added as a color corrector at a concentration shown in Table 1. Then, the PET sheet was discharged from the T-Die at a temperature of 270°C, and the discharged PET sheet was stretched to 4.5 times the original length in MD and TD to prepare a recycled PET film. The recycled PET film prepared by this method was subjected to NMR measurement and inorganic component measurement. The measurement results are as follows Figure 1 and 2 As shown, the concentration of each inorganic material included is shown in Table 1 below.

[0179] Afterwards, the prepared recycled PET film was measured by this measurement method. The measurement results are shown in Table 2 below.

[0180] Embodiment 7:

[0181] The preparation method of the recycled PET film is the same as that of Example 4, except that magnesium acetate, sodium acetate and triethyl phosphate are not used in the preparation of the original sheet.

[0182] Afterwards, the prepared recycled PET film was measured by this measurement method. The measurement results are shown in Table 2 below.

[0183] Embodiment 8:

[0184] The preparation method of the recycled PET film is the same as that of Example 4, except that no anti-blocking agent is used when preparing the virgin sheet.

[0185] Afterwards, the prepared recycled PET film was measured by this measurement method. The measurement results are shown in Table 2 below.

[0186] Embodiment 9:

[0187] The preparation method of the recycled PET film is the same as that of Example 4, except that magnesium acetate, sodium acetate, triethyl phosphate and anti-blocking agent are not used in the preparation of the original sheet.

[0188] Afterwards, the prepared recycled PET film was measured by this measurement method. The measurement results are shown in Table 2 below.

[0189] Comparative Example 1:

[0190] The preparation method of the recycled PET film is the same as that of Example 4 except that titanium dioxide is used as the color-correcting agent.

[0191] Afterwards, the prepared recycled PET film was measured by this measurement method. The measurement results are shown in Table 2 below.

[0192] Comparative Example 2:

[0193] The preparation method of the recycled PET film is the same as that of Example 4, except that magnesium acetate, sodium acetate and triethyl phosphate are not used in the preparation of the original sheet and titanium dioxide is used as a color correcting agent.

[0194] Afterwards, the prepared recycled PET film was measured by this measurement method. The measurement results are shown in Table 2 below.

[0195] Comparative Example 3:

[0196] The preparation method of the recycled PET film is the same as that of Example 4 except that no color correcting agent is added.

[0197] Afterwards, the prepared recycled PET film was measured by this measurement method. The measurement results are shown in Table 2 below.

[0198] Comparative Example 4:

[0199] The preparation method of the recycled PET film is the same as that of Example 4, except that magnesium acetate, sodium acetate and triethyl phosphate are not used in the preparation of the original sheet, and no color correcting agent is added.

[0200] Afterwards, the prepared recycled PET film was measured by this measurement method. The measurement results are shown in Table 2 below.

[0201] Table 1:

[0202]

[0203] [Table 2]

[0204]

[0205] For Examples 1 to 6 in Table 2, physical properties can be confirmed according to the content of the color correcting agent. Although the haze of Examples 4 to 6 is in the range of 2% to 3%, it is confirmed that the heat shrinkage and breaking strength in Examples 5 and 6 are decreased.

[0206] This means that with the increase of TAG content, the transparency and yellowing resistance of recycled PET film may increase, and the color difference value may be significantly reduced, but the breaking strength of recycled PET film containing excessive color corrector will decrease and the thermal shrinkage rate will increase.

[0207] For Example 7 in Table 2, the type and content of the color correcting agent are the same as those of Example 4, but no molding modifier is included. The results confirm that, compared with Example 4, the haze increases, and the breaking strength and breaking elongation decrease.

[0208] This means that when TAG, magnesium acetate, sodium acetate and triethyl phosphate are added at the same time, the haze and color difference values ​​are significantly reduced. In addition, this means that the recycled PET film prepared in Example 4 contains a forming modifier, and the film-forming property is increased, so the breaking strength and elongation at break of the prepared recycled PET film are increased.

[0209] Regarding Example 8 in Table 2, in Example 8, no anti-blocking agent was included, and the results confirmed that the haze increased, the breaking strength and the breaking elongation were significantly reduced, and the thermal shrinkage was significantly increased compared with Example 4. This means that the recycled PET film containing the anti-blocking agent has excellent high temperature resistant dimensional stability and excellent recycled PET film molding properties.

[0210] In addition, for Example 9 in Table 2, the physical property behavior of the PET film without the molding modifier and the anti-blocking agent can be more clearly confirmed, and it can be confirmed that compared with Example 4, the haze, color difference value and breaking strength of Example 9 are significantly reduced, and the heat shrinkage rate is significantly increased.

[0211] This means that as the inorganic content in the prepared recycled PET film decreases, the thermal shrinkage rate is significantly reduced. At the same time, the molding modifier and anti-blocking agent will also improve the film-forming properties, thereby affecting the breaking strength and breaking elongation of the prepared recycled PET film.

[0212] In Table 2, the recycled PET films of Comparative Examples 1 and 2 are PET films prepared by containing titanium dioxide as a color correcting agent, and it is confirmed that their thermal shrinkage rate is increased, but the haze and color difference values ​​are significantly increased, thereby reducing the transparency of the recycled PET film, and it is confirmed that in Comparative Example 2, the haze and color difference values ​​are further increased.

[0213] This means that, although the heat shrinkage rate can be reduced by including the color-correcting agent composed of inorganic particles, the color-correcting effect is low compared with TAG.

[0214] In Table 2, in Comparative Examples 3 and 4, which do not contain a color correcting agent, the haze is measured to be 20% or more, and the color difference value L is measured to be 80 or more, which means that the transparency of the recycled PET film not containing a color correcting agent is at a level that is not commercially available, and it is confirmed that the transparency of the recycled PET film of Comparative Example 4 which does not contain a molding modifier is further reduced.

[0215] As mentioned above, the present invention has been described by specific details and limited embodiments and comparative examples, but these are provided only to facilitate a more general understanding of the present invention, and the present invention is not limited to the above embodiments. Those skilled in the art may make various modifications and changes to this specification.

[0216] Therefore, the spirit of the present invention should not be limited to the described embodiments, and the scope of the patent claims described below and all modifications that are equivalent or equivalent to the scope of the patent claims should fall within the scope of the spirit of the present invention.

Claims

1. A recycled polyethylene terephthalate (PET) film comprising Waste PET and virgin PET as PET resin components; and A color correcting agent containing a glyceryl compound as shown in the following formula 1, in, The yellowing resistance of the recycled PET film is in the range of 5% to 10%, the color difference value L is in the range of 59 to 70, and the color difference value b is 5 or less, wherein the yellowing resistance is measured according to ASTM D1925 and the color difference is measured according to ASTM E313: [Formula 1] In formula 1, R 1 , R 2 and R 3 Each independently is a linear or branched C 1 -C 20 Alkyl or linear or branched C 1 -C 20 Unsaturated alkyl.

2. The recycled PET film according to claim 1, in, The color-correcting agent includes an organic compound as shown in Formula 2, an organic compound as shown in Formula 3, or a mixture thereof: [Formula 2] In formula 2, R 4 and R 5 Each independently is a linear or branched C 1 -C 20 Alkyl or linear or branched C 1 -C 20 unsaturated alkyl, and [Formula 3] In formula 3, R 6 and R 7 Each independently is a linear or branched C 1 -C 20 Alkyl or linear or branched C 1 -C 20 Unsaturated alkyl.

3. The recycled PET film according to claim 1, in, The recycled PET film contains a color correcting agent in a range of 5 ppm to 200 ppm.

4. The recycled PET film according to claim 1, in, In formula 1-3, R 1 , R 2 , R 3 , R 4 , R 5 , R 6 and R 7 Each independently is a linear or branched C 1 -C 12 Alkyl or linear or branched C 1 -C 12 Unsaturated alkyl.

5. The recycled PET film according to claim 1, in, The recycled PET film contains metal ions in the range of 10 ppm to 200 ppm, wherein the metal ions are derived from the molding modifiers included in the preparation of the virgin sheet.

6. The recycled PET film according to claim 5, in, The recycled PET film satisfies the following expressions 1 to 3: [Expression 1] 10≤[Mg]≤100 [Expression 2] 0.1≤[Na]≤10 [Expression 3] 1≤[P]≤50 (Wherein, the expression 1 to 3, [Mg] is the concentration of magnesium ions contained in the recycled PET film (ppm), [Na] is the concentration (ppm) of sodium ions contained in the recycled PET film, and [P] is the concentration of phosphorus ions contained in the recycled PET film (ppm).

7. The recycled PET film according to claim 1, in, The recycled PET film includes an anti-blocking agent in a range of 300 ppm to 1,000 ppm.

8. The recycled PET film according to claim 1, in, The recycled PET film has a mechanical strength of 10 kgf / mm in both the machine direction (MD) and the transverse direction (TD) measured according to ASTM D882. 2 Up to 30 kgf / mm 2 The breaking strength is within the range of .

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

10. The recycled PET film according to claim 1, in, The recycled PET film includes 30 wt % to 95 wt % of waste PET and 5 wt % to 70 wt % of virgin PET.

11. A method for preparing a recycled polyethylene terephthalate (PET) film, the method comprising: include: Recycled sheets are prepared by including waste PET; Prepare virgin sheets by including virgin PET; A recycled PET film is prepared by including the recycled sheet, the virgin sheet and a glyceryl compound as shown in Formula 1: [Formula 1] In formula 1, R 1 , R 2 and R 3 Each independently is a linear or branched C 1 -C 20 Alkyl or linear or branched C 1 -C 20 Unsaturated alkyl.

12. The method according to claim 11, in, In the preparation of the recycled PET film, the recycled PET film includes 30 wt % to 95 wt % of recycled sheets and 5 wt % to 70 wt % of virgin sheets.

13. The method according to claim 11, in, The virgin sheet is prepared by including a molding modifier in a range of 150 ppm to 14,000 ppm.

14. The method according to claim 11, in, The raw sheet was prepared by adding an anti-blocking agent in the range of 150 ppm to 20,000 ppm.

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