Preparation method of recycled plastic

Abstract

The present invention relates to a preparation method of recycled plastic, the preparation method being for recycling waste plastic into a high-quality plastic in an environmentally-friendly manner.

Description

Method of manufacturing recycled plastic

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0120448, filed September 11, 2023, and Korean Patent Application No. 10-2024-0123330, filed September 10, 2024, the entire contents of which are incorporated herein by reference.

[0003]

[0004] The present invention relates to a method for producing recycled plastic.

[0005]

[0006] As the massive use and disposal of plastic products exacerbates environmental problems and resource depletion, policies and regulations on environmental issues such as climate change and carbon neutrality are being strengthened worldwide. Consequently, the development of eco-friendly materials is demanded, and research is underway on ways to recycle waste plastic.

[0007]

[0008] Currently, most waste plastics are disposed of through landfills or incineration. Landfills do not biodegrade, and incineration releases hazardous substances and carbon dioxide, negatively impacting the environment. Therefore, interest is growing in PCR (Post-Consumer Recycled Materials), which recycle waste plastics discarded by consumers into new products.

[0009]

[0010] Generally, the following methods exist for recycling waste plastics: First, reusing waste plastics for the same purpose as before disposal without a separate heat treatment process; recycling waste plastics through processes such as re-extrusion / reprocessing without altering their chemical composition; chemically decomposing the original polymer components of waste plastics to recover them as raw materials; or using waste plastics as a heat source.

[0011]

[0012] Among these, the method of re-extruding / reprocessing the waste plastic has the advantage of significantly reducing carbon emissions due to low thermal energy consumption. However, it is difficult to remove foreign substances during recycling, which reduces quality compared to virgin materials and makes it difficult to ensure quality uniformity. In particular, if these foreign substances are present in the waste plastic, the color of the recycled plastic is inferior, which reduces the utility value of the recycled waste plastic.

[0013]

[0014] Accordingly, to solve the above problems, research is needed on a method for recycling waste plastics with high quality, low energy consumption, and without chemical composition modification.

[0015]

[0016] The present invention provides a method for manufacturing recycled plastic that is environmentally friendly and of high quality.

[0017]

[0018] In order to solve the above problem, the present invention comprises the steps of preparing waste plastic containing 50 wt% or more of LLDPE (linear low density poly ethylene) (step 1);

[0019] A step of preparing a dissolved substance by dissolving the above waste plastic in a solvent (step 2);

[0020] A step of filtering the above-mentioned solution through a filter to prepare a filtrate (step 3);

[0021] A step of crystallizing the above filtrate to separate the solvent and the polymer component including LLDPE (step 4); and

[0022] Including a step of drying the above polymer component (step 5),

[0023] The solvent comprises at least one selected from the group consisting of anisole, ethyl benzoate and butyl benzoate.

[0024] Provides a method for manufacturing recycled plastic.

[0025]

[0026] In addition, the present invention provides a recycled plastic manufactured according to the manufacturing method of the present invention.

[0027]

[0028] In the present invention, terms such as first, second, etc. are used to describe various components, and the terms are used only for the purpose of distinguishing one component from another.

[0029] Additionally, the terms used herein are merely used to describe exemplary embodiments and are not intended to limit the present invention.

[0030] Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0031] In this specification, the terms “comprise,” “include,” or “have” are intended to describe a feature, number, step, component, or combination thereof implemented, but do not exclude the possibility of one or more other features, numbers, steps, components, combinations, or additions thereof.

[0032] Additionally, in this specification, when each layer or element is referred to as being formed “on” or “over” each layer or element, it means that each layer or element is formed directly on each layer or element, or that other layers or elements may be additionally formed between each layer, on the object, or on the substrate.

[0033] The present invention is susceptible to various modifications and takes various forms. Specific embodiments are illustrated and described in detail below. However, this does not limit the invention to a specific disclosed form, but rather encompasses all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention.

[0034]

[0035] In this specification, recycled plastic means PCR (Post consumer recycled).

[0036]

[0037] Hereinafter, the present invention will be described in detail.

[0038]

[0039] The method for producing recycled plastic of the present invention comprises the steps of: preparing waste plastic containing 50 wt% or more of LLDPE (linear low density polyethylene) (step 1); preparing a melt by dissolving the waste plastic in a solvent (step 2); filtering the melt through a filter to prepare a filtrate (step 3); crystallizing the filtrate to separate a polymer component containing the solvent and LLDPE (step 4); and drying the polymer component (step 5), wherein the solvent comprises at least one selected from the group consisting of anisole, ethyl benzoate, and butyl benzoate.

[0040]

[0041] LLDPE is flexible and possesses suitable impact resistance and processability, making it widely used, alone or in combination with other resins, in applications such as packaging materials, shrink films, and agricultural films. Conventionally, solvents such as toltuene, xylene, and heptane were used to dissolve waste plastics containing LLDPE. However, the high viscosity of waste plastics necessitates the use of excessive amounts of organic solvents during processing. However, excessive use of these solvents can be harmful to humans and the environment, making them unsuitable for the development of recycled plastics. Therefore, a solution was needed.

[0042]

[0043] The inventors of the present invention have conducted research to develop an environmentally friendly recycling method for manufacturing recycled plastics through the regeneration of waste plastics without deterioration in quality, and have continued to search for an environmentally friendly solvent that is harmless to the human body. As a result of the toxicity assessment of various organic solvents, representatively, in relation to the toxicity of xylene, n-heptane and toluene, in addition to anisole, ethyl benzoate and butyl benzoate, which are the solvents used in the present invention, anisole, etc. are not compounds harmful to the human body under the Occupational Safety and Health Act or the Chemical Substances Control Act, whereas solvents such as xylene, n-heptane and toluene are classified as hazardous substances subject to management, substances subject to work environment measurement, and substances subject to special health examination under the Occupational Safety and Health Act, and are classified as toxic substances and / or accident preparation substances under the Chemical Substances Control Act. Unlike the above xylene, n-heptane and toluene, anisole, ethyl benzoate and butyl benzoate are not substances that generate separate work environment exposure standards according to domestic regulations and are not substances that generate standards according to the US ACGIH regulations, and thus have the advantage of being environmentally friendly and having low toxicity to the human body.

[0044]

[0045] Meanwhile, the method of manufacturing recycled plastics by regenerating waste plastics through melting has been noted to be difficult to remove residual foreign substances. Residual foreign substances in recycled plastics can degrade their quality, particularly their color, limiting their utility. Therefore, ongoing research is being conducted to effectively and environmentally friendly remove these foreign substances and improve the color of recycled plastics.

[0046]

[0047] At the end of these studies, the inventors of the present invention have completed the present invention by confirming that, in the case of waste plastics, especially waste plastics including LLDPE, the solubility is excellent when dissolved using anisole, ethyl benzoate and butyl benzoate as a solvent, and the process of filtering the dissolved substance through a filter and then separating it through crystallization of anisole is environmentally friendly with relatively low energy consumption, the color of the recycled plastic is significantly improved after regeneration, and the solvent used can be reused.

[0048]

[0049] Below, each step is explained in detail.

[0050]

[0051] (Step 1)

[0052] Step 1 of the present invention is a step of preparing waste plastic feed containing LLDPE.

[0053] LLDPE stands for linear low density polyethylene, and the typical density range of LLDPE is 0.912 to 0.925 g / cm. 3It has a density of , and may be a copolymer of ethylene and an alpha olefin having 3 or more carbon atoms, such as a copolymer of ethylene and 1-hexene. In the present invention, a recycled plastic (PCR) containing 50 wt% or more of the LLDPE is used as a recycled plastic.

[0054]

[0055] Waste plastics are typically manufactured into recycled plastics through a series of processes including crushing, washing, drying, and extrusion. The waste plastic containing LLDPE, the raw material used in the present invention, refers to waste plastic that has undergone the crushing, washing, and drying steps, but before extrusion. For example, waste plastic applicable to the present invention includes SS0618, an LLDPE product procured and recycled by SS Recyclia.

[0056]

[0057] Meanwhile, according to one embodiment of the present invention, in step 1, the waste plastic may contain LLDPE in an amount of 80 wt% or more, 90 wt% or more, or 95 wt% or more. Including LLDPE in the above range facilitates the removal of foreign substances when applying the dissolution, filtration, and crystallization processes described below, and thus the desired color enhancement effect can be expected.

[0058]

[0059] (Step 2)

[0060] Step 2 of the present invention is a step of preparing a dissolved product by dissolving waste plastic feed in a solvent. At this time, the solvent includes at least one selected from the group consisting of anisole, ethyl benzoate, and butyl benzoate.

[0061]

[0062] It can be confirmed that the waste plastic containing the LLDPE of the present invention has high solubility in solvents such as anisole, ethyl benzoate, and butyl benzoate. This is expected to be due to the fact that the intermolecular interaction of the waste plastic containing the LLDPE and the intermolecular interaction of the solvent are similar.

[0063] Based on the characteristics of the waste plastic and the solvent as described above, the waste plastic containing LLDPE prepared in step 1 of the present invention can be completely dissolved in the solvent to produce a melt.

[0064]

[0065] According to one embodiment of the present invention, in step 2, the solvent may be used in an amount of 100 to 10,000 parts by weight based on 100 parts by weight of the waste plastic. Using anisole in the above range can completely dissolve the waste plastic while maintaining an appropriate concentration of the waste plastic, thereby reducing the load in the filtration process described later. Preferably, the solvent may be used in an amount of 300 parts by weight or more, 500 parts by weight or more, 700 parts by weight or more, or 1,000 parts by weight or more, but 95,000 parts by weight or less, or 90,000 parts by weight or less, based on 100 parts by weight of the waste plastic.

[0066]

[0067] According to one embodiment of the present invention, step 2 may be carried out at a temperature of 90 to 153°C. The temperature range may be appropriately adjusted in consideration of the increase in solubility of waste plastic and the boiling point of anisole depending on the temperature. Preferably, step 2 may be carried out at a temperature of 95°C or higher, 100°C or higher, 110°C or higher, 120°C or higher, 125°C or higher, 130°C or higher, 135°C or higher, or 140°C or higher, but not more than 150°C.

[0068]

[0069] Meanwhile, there is no particular limitation on the means for dissolving the waste plastic containing the LLDPE in the solvent, and for example, it can be carried out in a batch reactor equipped with a stirrer.

[0070]

[0071] (Step 3)

[0072] Step 3 of the present invention is a step of producing a filtrate by filtering a solution obtained by dissolving waste plastic containing the LLDPE in a solvent.

[0073] As described above, the present invention can easily remove foreign substances not dissolved in the solvent by simultaneously including the steps of dissolving a waste plastic solution containing LLDPE in a solvent and the steps of filtering the same. Specifically, LLDPE is solid at room temperature and melts at high temperatures, but has a high viscosity, so when passing through a filter with a small pore size, problems such as filter damage due to increased pressure and deterioration of process stability may occur. Therefore, by dissolving LLDPE in an environmentally friendly solvent to reduce the viscosity, the above-mentioned problems do not occur even when passing through a filter with a small pore size, and foreign substances remaining in the waste plastic can be efficiently removed.

[0074]

[0075] According to one embodiment of the present invention, the filter of step 3 may have a pore size of 1 μm to 150 μm. Using a filter within the above range facilitates filtration of the dissolved material, thereby reducing the load on the filtration step, which is advantageous in terms of process speed, and balances the quality of the recycled plastic. Preferably, the filter of step 3 may have a pore size of 2 μm or more, 3 μm or more, 4 μm or more, or 5 μm or more, and 120 μm or less, 100 μm or less, or 80 μm or less.

[0076]

[0077] For example, the filter of step 3 may be any one of a metal filter of 100 mesh to 800 mesh according to the KS-A-5101 standard and a filter paper having a pore size of 1 μm to 30 μm. In general, a metal filter (Mesh Filter) is a two-dimensional woven structure made of a metal material, and has excellent durability and can withstand high pressure, but there is a limit to reducing the size of the filter pores for filtering fine particles. A filter paper is generally a three-dimensional woven structure in which cellulose is randomly arranged, and although durability may be reduced depending on the material applied, the size of the pores can be further reduced compared to a metal filter (Mesh Filter), so it is advantageous in removing fine foreign substances and has an excellent color improvement effect. Considering the color improvement effect and process speed as described above, the metal filter may be a metal filter of 150 mesh to 600 mesh, or 170 mesh to 550 mesh, or 200 mesh to 500 mesh according to the KS-A-5101 standard, and the filter paper may be a filter paper having a pore size of 3 ㎛ to 27 ㎛, or 5 ㎛ to 25 ㎛.

[0078]

[0079] Meanwhile, the filtration step may be performed at atmospheric pressure, or a filtration device equipped with or connected to a vacuum pump may be used to enhance the filtration rate. When using a vacuum pump, the filtration step may be performed under a pressure of approximately 120 to 200 mmbar, 140 to 180 mmbar, or 160 mmbar.

[0080]

[0081] (Step 4)

[0082] Step 4 of the present invention is a step of crystallizing the filtrate prepared through the above filtration step to separate the polymer component including the solvent anisole and LLDPE.

[0083] The present invention can efficiently remove foreign substances while reducing energy consumption by introducing a crystallization step instead of a purification process such as distillation.

[0084]

[0085] According to one embodiment of the present invention, the crystallization in step 4 may be carried out at a temperature of 15 to 70°C. Considering the solubility of the solvent used in step 2 and the waste plastic containing LLDPE, crystallization is carried out by cooling to a temperature within the above range. Preferably, the crystallization step may be carried out at a temperature of 15°C or higher, 35°C or higher, or 50°C or higher, and 65°C or lower, 60°C or lower, or 55°C or lower.

[0086]

[0087] (Step 5)

[0088] The polymer component containing LLDPE obtained after going through the above step 4 is mixed with a solvent and exists in the form of a gel. For example, the solvent may be included in an amount of 500 to 2,000 parts by weight based on 100 parts by weight of the polymer component. Accordingly, step 5 of the present invention is a step of drying the polymer component containing LLDPE obtained through the above crystallization, and through this step, the solvent remaining in the polymer component can be removed.

[0089]

[0090] According to one embodiment of the present invention, the drying in step 5 may be performed at a temperature of 50 to 100°C. Performing the drying step at a temperature within the above range can prevent thermal deformation of the polymer component and appropriately remove the used solvent. Preferably, the drying temperature may be 55°C or higher, 60°C or higher, 65°C or higher, or 70°C or higher, and 95°C or lower, 90°C or lower, or 85°C or lower.

[0091]

[0092] In addition, the drying step can be appropriately controlled by measuring the amount of solvent used or the amount of solvent remaining in the polymer component after crystallization, and can be performed for, for example, 5 to 50 hours, 10 to 30 hours, or 15 to 20 hours.

[0093]

[0094] The method for manufacturing recycled plastic of the present invention described above can provide recycled plastic that is environmentally friendly and has excellent color quality.

[0095]

[0096] According to one embodiment of the present invention, the color difference (△E) calculated based on L, a, and b measured by a spectrophotometer before and after reproduction may be 1 to 20. The color difference (△E) may be calculated according to the following equation 1.

[0097] [Formula 1]

[0098] △E = {(L1-L2) 2 +(a1-a2) 2 +(b1-b2) 2} 1 / 2

[0099] In the above equation 1,

[0100] L1, a1 and b1 represent the L, a and b values ​​in the CIELAB color coordinates of waste plastic containing LLDPE before recycling, respectively.

[0101] L2, a2 ​​and b2 represent the L, a and b values ​​in the CIELAB color coordinates of recycled plastics containing LLDPE after recycling, respectively.

[0102] Specifically, in the CIELAB color coordinates, L represents lightness, a represents the degree of red and green, and b represents the degree of yellow and blue.

[0103] That is, in the above formula 1, L1, a1 and b1 are values ​​measured from recycled plastic containing LLDPE before regeneration, and L2, a2 ​​and b2 are values ​​measured from recycled plastic containing LLDPE obtained after undergoing the regeneration steps of steps 1 to 5 of the present invention.

[0104] When the color difference (△E) above is 1 or less, it is generally considered that there is no color difference, and the higher the color difference (△E) value, the more likely a color difference exists. When the color difference (△E) value increases compared to the existing color value, for example, when the L value increases and the a / b value converges to 0, it can be confirmed that the recycled plastic becomes closer to the color of virgin plastic, that is, white, and it can be confirmed that the color quality is excellent because foreign substances are effectively removed according to the method for manufacturing recycled plastic of the present invention.

[0105]

[0106] Preferably, the color difference (△E) may be 1.5 or more, 2 or more, or 3 or more, and 19.5 or less, 19 or less, or 18.5 or less. When the color difference is in the above range, it can be confirmed that foreign substances are effectively removed and the color quality is excellent according to the method for manufacturing recycled plastic of the present invention. Specifically, the recycled plastic manufactured according to the method for manufacturing recycled plastic of the present invention has an L value that increases compared to the waste plastic before recycling, making the color brighter, and the a and b values ​​each show values ​​close to 0 after recycling compared to before recycling, indicating excellent color quality. Compared to the waste plastic, the recycled plastic manufactured according to the method for manufacturing recycled plastic of the present invention has, for example, an L value that increases by about 1% or more, about 2% or more, about 3% or more, about 5% or more, about 10% or more, about 15% or more, or about 20% or more. In addition, the absolute value reduction rate of the a value of the recycled plastic manufactured according to the manufacturing method of the present invention compared to the waste plastic was 5% or more, 9% or more, 12% or more, or 60% or more, and the absolute value reduction rate of the b value was 5% or more, 7% or more, 10% or more, 15% or more, or 45% or more. At this time, the absolute value reduction rate of the a value is calculated by the following calculation formula A, and the absolute value reduction rate of the b value is calculated by the following calculation formula B.

[0107] [Formula A]

[0108] The absolute value of a decrease rate = [(|a1|-|a2|) / (|a1|)] * 100

[0109] In the above calculation formula A,

[0110] a1 represents the a value in the CIELAB color coordinates of waste plastic containing LLDPE before recycling,

[0111] a2 represents the a value in the CIELAB color coordinates of recycled plastic containing LLDPE after regeneration,

[0112] [Formula B]

[0113] Absolute value of b decrease rate = [(|b1|-|b2|) / (|b1|)] * 100

[0114] b1 represents the b value in the CIELAB color coordinates of waste plastic containing LLDPE before recycling,

[0115] b2 represents the b value in the CIELAB color coordinates of recycled plastic containing LLDPE after recycling.

[0116]

[0117] In addition, the present invention provides a recycled plastic manufactured according to the manufacturing method of the present invention described above.

[0118]

[0119] According to one embodiment of the present invention, the recycled plastic may have a color difference (△E) of 1 to 20 calculated based on L, a, and b measured by a spectrophotometer before and after recycling. The meaning of the L, a, and b values, the calculation method of the color difference (△E), and the preferred range are described above.

[0120]

[0121] According to one embodiment of the present invention, the recycled plastic may have a residual solvent content of 200 ppm or less. Preferably, the recycled plastic according to the present invention may have a residual solvent content of 170 ppm or less, 150 ppm or less, 130 ppm or less, 100 ppm or less, 90 ppm or less, 80 ppm or less, or 70 ppm or less. Meanwhile, the lower limit of the residual solvent content may theoretically be 0, but may be, for example, 1 ppm or more, 2 ppm or more, 5 ppm or more, 7 ppm or more, or 10 ppm or more.

[0122]

[0123] The recycled plastics described above can be used for purposes such as packaging materials, shrink films, and agricultural films, similar to virgin plastics.

[0124]

[0125] As described above, according to the method for producing recycled plastic of the present invention, it is possible to provide recycled plastic that is environmentally friendly and has excellent color quality.

[0126]

[0127] Hereinafter, preferred embodiments are presented to aid understanding of the invention. However, the following examples are intended only to illustrate the invention and are not intended to limit the invention to these embodiments.

[0128]

[0129] [Example]

[0130] Comparative Example 1

[0131] After drying the waste plastic raw material consisting of 100 wt% LLDPE, an extrusion front end (SS0618, manufactured by SS Recyclia) was used.

[0132]

[0133] Comparative Example 2

[0134] 10 g of waste plastic (after drying of raw materials, before extrusion, manufactured by SS Recyclia, SS0618) composed of 100 wt% LLDPE and 900 g of anisole were placed in a 1 L reactor and stirred at 150 ℃ and 200 RPM for approximately 10 minutes.

[0135] After confirming that LLDPE was completely dissolved in anisole, the temperature was lowered to 50°C, and the polymer component containing LLDPE was separated from the anisole through recrystallization. After recrystallization, the polymer component containing LLDPE in a gel state was dried in an oven at 80°C for 17 hours to produce a regenerated recycled plastic.

[0136]

[0137] Example 1

[0138] 10 g of waste plastic (after drying of raw materials, before extrusion, manufactured by SS Recyclia, SS0618) consisting of 100 wt% LLDPE and 900 g of anisole were placed in a 1 L reactor and stirred at 200 RPM at 150 °C for approximately 10 minutes. After confirming that the LLDPE was completely dissolved in the anisole and a dissolved product was produced, it was filtered using a 200 mesh metal filter (filter size: 74 ㎛). During the filtering process, a vacuum pump (160 mmbar, abs) was used to facilitate filtering.

[0139] After filtering, the filtrate was cooled to 50°C, and the polymer component containing LLDPE was separated from the anisole through recrystallization. After recrystallization, the polymer component containing LLDPE in a gel state was dried in an oven at 80°C for 17 hours to produce recycled plastic.

[0140]

[0141] Example 2

[0142] In the filtering process of Example 1, recycled plastic was manufactured in the same manner as in Example 1, except that a 325 mesh filter (filter size: 43 ㎛) was used instead of a 200 mesh metal filter.

[0143]

[0144] Example 3

[0145] In the filtering process of Example 1, recycled plastic was manufactured in the same manner as in Example 1, except that a 500 mesh filter (filter size: 28 ㎛) was used instead of a 200 mesh metal filter.

[0146]

[0147] Example 4

[0148] In the filtering process of Example 1, recycled plastic was manufactured in the same manner as in Example 1, except that filter paper having a pore size of 20 to 25 μm was used instead of a 200 mesh metal filter.

[0149]

[0150] Example 5

[0151] In the filtering process of Example 1, recycled plastic was manufactured in the same manner as in Example 1, except that filter paper having a pore size of 5 μm was used instead of a 200 mesh metal filter.

[0152]

[0153] Example 6

[0154] In Example 5, recycled plastic was manufactured in the same manner as in Example 5, except that 700 g of anisole was used instead of 900 g of anisole.

[0155]

[0156] Example 7

[0157] In Example 5, recycled plastic was manufactured in the same manner as in Example 5, except that 500 g of anisole was used instead of 900 g of anisole.

[0158]

[0159] Example 8

[0160] In Example 3, recycled plastic was manufactured in the same manner as in Example 3, except that 200 g of anisole was used instead of 900 g of anisole.

[0161]

[0162] Example 9

[0163] A recycled plastic was manufactured in the same manner as in Example 5, except that the anisole obtained after separating the polymer component including LLDPE from anisole through recrystallization in Example 5 was used as a solvent (a single-recycled solvent).

[0164]

[0165] Example 10

[0166] A recycled plastic was manufactured in the same manner as in Example 6, except that the anisole obtained after separating the polymer component including LLDPE from anisole through recrystallization in Example 9 was used as a solvent (twice recycled solvent).

[0167]

[0168] Example 11

[0169] In Example 5, recycled plastic was manufactured in the same manner as in Example 5, except that 300 g of ethyl benzoate was used instead of 900 g of anisole.

[0170]

[0171] [Experimental Example]

[0172] (1) Color value measurement

[0173] Manufacturing of the Psalms

[0174] The recycled plastics manufactured in the above examples and comparative examples were pressed using a hot press at 200°C, 0 bar for 1.5 minutes, 10 bar for 0.5 minutes, and 40 bar for 3 minutes to produce a 2T thick specimen.

[0175]

[0176] Color index measurement

[0177] The specimens produced within the device were photographed using the X-rite CCM (Computer Color Matching) System, and the corresponding L / a / b values ​​were measured.

[0178] Specifically, the L1, L2, a1, a2, b1, and b2 values ​​were measured at room temperature using a spectrophotometer from X-rite from the above-mentioned manufactured specimen, and the △E value was calculated according to the following equation 1.

[0179] [Formula 1]

[0180] △E = {(L1-L2) 2 +(a1-a2) 2 +(b1-b2) 2} 1 / 2

[0181] In the above equation 1,

[0182] L1, a1 and b1 represent the L, a and b values ​​in the CIELAB color coordinates of recycled plastics containing LLDPE before recycling, respectively.

[0183] L2, a2 ​​and b2 represent the L, a and b values ​​in the CIELAB color coordinates of recycled plastics containing LLDPE after recycling, respectively.

[0184] Specifically, the L, a, and b values ​​of the recycled plastic before regeneration were measured as L1 57.8, a1 2.1, and b1 12.2, respectively, and based on these, the L, a, and b values ​​of the recycled plastic specimens of the examples and manufacturing examples, L2, a2, and b2, were measured, and the color difference was calculated according to the above equation 1.

[0185]

[0186] (2) Measurement of residual solvent content

[0187] The residual solvent content of the samples taken in the above examples and comparative examples was measured using GC / MS analysis. Specifically, ionic substances separated through gas chromatography were ionized using electron ionization (EI) and then captured in an orbitrap analyzer. The captured ions rotate around the central electrode at different speeds depending on their molecular weight and move along the axis. The mass-to-charge (m / z) was obtained from the frequency obtained from the orbiting motion of the ions, and the presence and content of the target substance were determined by comparing the m / z values ​​of the substances.

[0188] <Target 물질 m / z>

[0189] - Anisole: 108

[0190] - Ethyl benzoate: 105

[0191]

[0192] Classification Color Value Lab△E Comparative Example 157.8 2.1 12.2 Ref Comparative Example 258.0 2.2 11.7 0.5 Example 160.7 1.9 10.13.6 Example 260.0 1.9 9.9 3.2 Example 362.6 1.8 9.7 5.4 Example 470.9 0.76.5 14.4 Example 574.0 0.35.7 17.5 Example 673.7 0.25.2 17.5 Example 774.7 0.15.5 18.0 Example 861.6 1.7 11.33.9 Example 971.7 0.6 6.9 15.0 Example 1073.7 0.25.2 17.5 Example 1170.9-0.812.213.4

[0193]

[0194] Residual solvent content (ppm) Comparative example 1 - Example 540 (anisole) Example 1030 (anisole) Example 1110 (ethyl benzoate)

[0195]

[0196] As can be seen from Tables 1 and 2 above, the method for manufacturing recycled plastic according to the present invention was confirmed to be recyclable with low harmfulness to the human body by using an environmentally friendly solvent, have excellent color characteristics compared to the manufactured waste plastic, and have low residual solvent content.

Claims

1. A step for preparing waste plastic containing 50 wt% or more of LLDPE (linear low density polyethylene) (step 1); A step of preparing a dissolved substance by dissolving the above waste plastic in a solvent (step 2); A step of filtering the above-mentioned solution through a filter to prepare a filtrate (step 3); A step of crystallizing the above filtrate to separate the solvent and the polymer component including LLDPE (step 4); and Including a step of drying the above polymer component (step 5), The solvent comprises at least one selected from the group consisting of anisole, ethyl benzoate and butyl benzoate. Method of manufacturing recycled plastic.

2. In paragraph 1, In the above step 1, the waste plastic contains LLPDE in an amount of 80 wt% or more. Method of manufacturing recycled plastic.

3. In paragraph 1, In the above step 2, the solvent is used in an amount of 100 to 10,000 parts by weight per 100 parts by weight of waste plastic. Method of manufacturing recycled plastic.

4. In paragraph 1, The above step 2 is carried out under temperature conditions of 90 to 153 ℃. Method of manufacturing recycled plastic.

5. In paragraph 1, The filter of step 3 above has a pore size of 1 ㎛ to 150 ㎛. Method of manufacturing recycled plastic.

6. In paragraph 1, The crystallization in step 4 above is carried out under temperature conditions of 15 to 70 ℃. Method of manufacturing recycled plastic.

7. In paragraph 1, The drying in step 5 above is carried out under temperature conditions of 50 to 100 ℃. Method of manufacturing recycled plastic.

8. In paragraph 1, Before and after reproduction, the color difference (△E) calculated based on L, a and b measured by a spectrophotometer is 1 to 20, Method of manufacturing recycled plastic.

9. Manufactured by a manufacturing method according to any one of Articles 1 to 8, Recycled plastic.

10. In paragraph 9, Before and after reproduction, the color difference (△E) calculated based on L, a and b measured by a spectrophotometer is 1 to 20, Recycled plastic.

11. In paragraph 9, With a residual solvent content of 200 ppm or less, Recycled plastic.