Method for preparing recycled raw material composition

Abstract

The present invention relates to a method for preparing a recycled raw material composition using depolymerization of waste polyester, the method comprising (1) a step of pretreating waste polyester having an apparent density of 0.1 kg / L or lower so that the apparent density reaches 0.5 kg / L or higher, (2) a step of depolymerizing the pretreated waste polyester, and (3) a step of purifying a reactant obtained through the depolymerization.

Description

Method for producing a regenerative raw material composition

[0001] The present invention relates to a method for producing a recycled raw material composition capable of producing a recycled raw material composition having high purity at a high yield through a regeneration process (pretreatment and depolymerization) of waste polyester, and to a recycled raw material composition produced thereby.

[0002] Among polymers, polyester has excellent mechanical strength, heat resistance, transparency, and gas barrier properties, and is therefore widely used as a material for beverage containers; various packaging films; and various interior and exterior materials such as panels, shelves, and partitions.

[0003] Due to the widespread use of these materials, waste from plastics such as polyester is generated annually at a rate that is difficult to manage, and countries around the world are recently establishing regulations and measures for recycling waste plastic resources, including waste polyester.

[0004] There are physical and chemical methods for recycling the waste polyester, but physical recycling methods are not widely used because they cannot guarantee purity. Meanwhile, chemical recycling methods depolymerize waste polyester by breaking the ester bonds in the waste polyester. These methods utilize reactions such as glycolysis, hydrolysis, methanolysis, and aminolysis. Among these, glycolysis decomposes waste polyester by adding a glycol, such as ethylene glycol or diethylene glycol, primarily producing recycled raw materials such as bis(2-hydroxyethyl) terephthalate (BHET).

[0005] However, the above-mentioned waste polyester has various contamination levels, shapes, apparent densities, etc. depending on the environment in which it is collected, and in some cases has heterogeneous components rather than a single component, so the amount that can be depolymerized when depolymerized using a chemical recycling method is limited, and this limits the ability to increase the yield of recycled raw materials to the required level.

[0006] In order to solve the above-mentioned conventional problems, the object of the present invention is to provide a method for producing a recycled raw material composition that can economically and with high yield produce a recycled raw material composition even when waste polyester having not only a single component but also heterogeneous components and having various contamination levels, shapes, apparent densities, etc. is used as a depolymerization raw material.

[0007] In addition, another object of the present invention is to provide a high-purity recycled raw material composition manufactured using the above manufacturing method.

[0008] In order to solve the above problem, the present invention provides a method for producing a recycled raw material composition, comprising the steps of (1) pretreating waste polyester having an apparent density of 0.1 kg / L or less so that the apparent density becomes 0.5 kg / L or more; (2) depolymerizing the pretreated waste polyester; and (3) purifying the reactant obtained through the depolymerization.

[0009] In addition, the present invention provides a regenerative raw material composition manufactured from the above manufacturing method.

[0010] The present invention manufactures a recycled raw material composition by depolymerizing waste polyester having a controlled apparent density after a pretreatment process of controlling the apparent density of waste polyester to a specific range or higher, so that even if waste polyester having a variety of contamination levels, shapes, apparent densities, etc. and having not only a single component but also different components is used as a depolymerization raw material, a recycled raw material composition having high purity can be manufactured at a high yield.

[0011] Therefore, the present invention can recycle waste polyester economically and efficiently.

[0012] Hereinafter, the present invention will be described in detail. Herein, the present invention is not limited to the contents described below, and may be modified in various forms as long as the gist of the invention is not changed.

[0013] The word "comprising" or "including" in this specification is intended to specify particular features, regions, steps, processes, elements and / or components, and does not exclude the presence or addition of other features, regions, steps, processes, elements and / or components, unless specifically stated to the contrary.

[0014] In this specification, terms such as first, second, etc. are used to describe various components, and the components are not limited to these terms. These terms are used to distinguish one component from another.

[0015] All numbers and expressions indicating the amounts of components, reaction conditions, etc. described in this specification can be understood to be modified by the term “about” in all cases unless otherwise specified.

[0016] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0017]

[0018] Polyester is used in a variety of ways, leading to its diverse product forms. Products containing polyester can be made solely of polyester or, as needed, mixed with other components to form heterogeneous products. Consequently, waste polyester derived from used products comes in a variety of shapes, sizes, and compositions.

[0019] These waste polyesters usually go through processes such as removing foreign substances and crushing for recycling. At this time, the difference in crushing degree of waste polyesters can be expressed as apparent density (kg / L), and the higher the apparent density, the more advantageous the chemical recycling process of waste polyester can be.

[0020] Specifically, the inventors of the present invention have found that when carrying out a chemical recycling process using waste polyester as a depolymerization raw material, if waste polyester with a low apparent density is introduced, the amount of waste polyester and reactants (e.g., glycol compounds) that can be introduced into the depolymerization process is limited, and this reduces the production capacity of the recycled raw material composition that can be produced through the chemical recycling process of waste polyester. In addition, the inventors have found that in the case of waste polyester that has different components rather than a single component (e.g., a component in which polyolefin, polyamide, polytetrafluoroethylene, etc. are mixed with polyester), the lower the apparent density, the more difficult it is to separate the different components and remove impurities during the purification process performed after the depolymerization process, and thus the purity and yield of the recycled raw material composition derived from the waste polyester are also significantly reduced.

[0021] In this way, the inventors of the present invention confirmed that the apparent density of waste polyester, which is a depolymerization raw material, is a factor that greatly affects the efficiency of the chemical recycling process and the purity and yield of the recycled raw material composition, and based on this, by introducing a pretreatment process for controlling the apparent density of waste polyester, the overall process efficiency was improved, while enabling the production of a recycled raw material composition with high purity and high yield.

[0022] That is, the present invention increases the apparent density of waste polyester to a specific range or higher through a specific pretreatment process, and then carries out a chemical recycling process including a depolymerization process, which is specifically described as follows.

[0023]

[0024] Method for producing a regenerative raw material composition

[0025] A method for producing a recycled raw material composition according to the present invention comprises: (1) a step of pretreating waste polyester having an apparent density of 0.1 kg / L or less so that the apparent density becomes 0.5 kg / L or more; (2) a step of depolymerizing the pretreated waste polyester; and (3) a step of purifying a reactant obtained through the depolymerization.

[0026]

[0027] Step (1): Pretreatment for apparent density control

[0028] According to the present invention, step (1) is a step of pretreating waste polyester having an apparent density of 0.1 kg / L or less so that the apparent density becomes 0.5 kg / L or more.

[0029] When the apparent density of the waste polyester is 0.1 kg / L or less, the amount of waste polyester and glycol-based compound that can be introduced into the depolymerization process of step (2) is limited, and the depolymerization reaction efficiency may decrease. Accordingly, the present invention adjusts the apparent density of the waste polyester to 0.5 kg / L or more through the pretreatment of step (1). When the apparent density of the waste polyester is adjusted to 0.5 kg / L or more, the surface area of ​​the waste polyester increases, and the efficiency of the depolymerization reaction with the glycol-based compound is significantly increased, and insoluble components (foreign substances derived from different components) in the reactant obtained through the depolymerization process exist in the form of uniform small particles, so that the purification of the insoluble components can be facilitated. Accordingly, the present invention can manufacture a high-purity recycled raw material composition with high yield by minimizing the loss of recycled raw materials (e.g., bis(2-hydroxyethyl)terephthalate (BHET)) together with insoluble components while increasing the overall process efficiency.

[0030] The apparent density of the waste polyester that has undergone the above pretreatment is, when considering the purity and yield of the recycled raw material composition, specifically, 0.53 kg / L or more, 0.55 kg / L or more, 0.58 kg / L or more, 0.6 kg / L or more, 0.63 kg / L or more, 0.65 kg / L or more, 0.67 kg / L or more, 0.69 kg / L or more, 0.7 kg / L or more, 0.72 kg / L or more, 0.73 kg / L or more, 0.75 kg / L or more, 0.77 kg / L or more, or 0.8 kg / L or more (e.g., 0.52 to 0.8 kg / L, 0.56 to 0.79 kg / L, 0.61 to 0.78 kg / L, 0.64 to 0.78 kg / L, or 0.68 to 0.77 It can be kg / L).

[0031] The pretreatment of the above waste polyester is not particularly limited, but may be performed through melt extrusion using an extruder. By pretreating the waste polyester through the melt extrusion, the apparent density of the waste polyester can be easily controlled to 0.5 kg / L or more, which is the level targeted by the present invention. At this time, in order to control the apparent density of the waste polyester to 0.5 kg / L or more, it is preferable to optimally control the melt extrusion conditions.

[0032] Specifically, according to the present invention, the melt extrusion can be performed at a temperature of 250 to 300°C and an extrusion speed of 100 to 350 rpm for 2 to 15 minutes. If the conditions of the melt extrusion are outside the above range, the waste polyester may be decomposed (deformed or lost) due to overheating, or the shaping operation capable of controlling the apparent density may become impossible.

[0033] The above melt extrusion temperature refers to the barrel temperature of the extruder, and specifically may be 250 to 295°C, 250 to 290°C, 250 to 285°C, 250 to 280°C, 250 to 275°C, 255 to 275°C, or 260 to 270°C.

[0034] The above melt extrusion speed refers to the screw rotation speed of the extruder, and specifically may be 110 to 330 rpm, 115 to 300 rpm, 120 to 280 rpm, 125 to 250 rpm, 130 to 230 rpm, 135 to 220 rpm, 140 to 210 rpm, or 145 to 205 rpm.

[0035] The above melt extrusion time refers to the time that the waste polyester remains in the screw of the extruder, and may be specifically 2 to 13 minutes, 2 to 10 minutes, 2.5 to 8 minutes, 2.5 to 7 minutes, 3 to 6 minutes, 3 to 5 minutes, or 2 to 5 minutes.

[0036] The extruder used for the above melt extrusion is not particularly limited as long as it is a commonly known extruder, and specifically, it may be a single-screw extruder or a twin-screw extruder.

[0037] According to the present invention, no separate additive (organic additive or inorganic additive) may be added to the melt extrusion. That is, the present invention physically controls the apparent density of waste polyester through melt extrusion, rather than chemically controlling it.

[0038] According to the present invention, the waste polyester, whose apparent density is adjusted to 0.5 kg / L or more through the above pretreatment, can have various shapes. Specifically, the shape of the pretreated waste polyester can be spherical, oval, cylindrical, or prismatic, and preferably cylindrical. In addition, the size (longest length) of the pretreated waste polyester is not particularly limited, but specifically can be 5 mm or less, 4 mm or less, 3 mm or less, 2 mm or less, or 1 mm or less (e.g., 0.5 to 5 mm, 1.5 to 4.5 mm, 2 to 4 mm, 2.5 to 3.5 mm, or 2 to 3 mm). Accordingly, the handleability of the waste polyester can be secured while the depolymerization reaction efficiency of the waste polyester can be increased.

[0039] Meanwhile, according to the present invention, the pretreated waste polyester is not particularly limited as long as it is waste containing polyester, but specifically may include waste polyester fabric (fiber), waste polyester film, waste polyester flake, waste polyester powder, or a combination thereof.

[0040]

[0041] Step (2): Depolymerization

[0042] According to the present invention, step (2) is a step of depolymerizing waste polyester, the apparent density of which has been adjusted to 0.5 kg / L or more through the pretreatment of step (1). The depolymerization step may include: (2-1) a step of depolymerizing waste polyester, the apparent density of which has been adjusted through the pretreatment, at a temperature of 180 to 200°C through a first glycolysis reaction to obtain a first reactant; and (2-2) a step of depolymerizing the first reactant at a temperature of 150 to 170°C through a second glycolysis reaction to obtain a second reactant.

[0043] Specifically, the above step (2-1) may include a process of obtaining the first reactant by performing a glycolysis reaction in which the polymer chain of the waste polyester is first decomposed by a first glycol compound.

[0044] The first glycol compound used for depolymerization in the above step (2-1) is not particularly limited, but may specifically include at least one selected from the group consisting of ethylene glycol, propylene glycol, and diethylene glycol.

[0045] The amount of the first glycol compound to be added is not particularly limited, but may be 1 time or more, 2 times or more, or 3 times or more, and 7 times or less, 5 times or less, or 4 times or less (e.g., 1 to 7 times, 2 to 5 times, or 3 to 4 times) relative to the weight of the pretreated waste polyester.

[0046] The depolymerization temperature of the above step (2-1) may be 180 to 200°C, and specifically, 180 to 195°C, 180 to 193°C, 180 to 190°C, 180 to 188°C, or 180 to 185°C. In addition, the depolymerization time of the above step (2-1) is not particularly limited, but may be 1 to 4 hours, 1 to 3 hours, or 1 to 2 hours from the time when the temperature required for the first depolymerization is reached. As the depolymerization of the above step (2-1) is performed at the above temperature and time, the first glycolysis reaction of the waste polyester can be smoothly performed, and the production of by-products such as diethylene glycol ester compounds can be minimized.

[0047] The depolymerization of the above step (2-1) can be carried out in the presence of a catalyst that activates the first glycolysis reaction. The catalyst is not particularly limited as long as it is a commonly known catalyst, but may specifically include a metal acetate, an anhydride thereof, or a hydrate thereof. More specifically, the catalyst may be at least one selected from the group consisting of zinc acetate, sodium acetate, cobalt acetate, and manganese acetate, a hydrate thereof, or an anhydride thereof.

[0048] In the above step (2-1), the amount of the catalyst input (amount used) is not particularly limited, but specifically, it may be 0.01 to 5 parts by weight, 0.05 to 3 parts by weight, 0.1 to 2 parts by weight, 0.15 to 1 part by weight, 0.2 to 0.6 parts by weight, or 0.2 to 0.4 parts by weight, based on 100 parts by weight of the waste polyester.

[0049] For example, the first glycolysis reaction of the above step (2-1) may be a reaction of waste polyester and ethylene glycol in the presence of zinc acetate anhydride.

[0050] The above step (2-2) may include a process of obtaining a second reactant by performing a glycolysis reaction in which the first reactant obtained in the above step (2-1) is secondarily decomposed by a second glycol compound. The above second reactant may refer to a reactant obtained through the above step (2).

[0051] The second glycol compound used for the depolymerization in the above step (2-2) is not particularly limited, but may specifically include at least one selected from the group consisting of ethylene glycol, propylene glycol, and diethylene glycol. The second glycol compound may be derived from the depolymerization process in the above step (2-1) or may be additionally added during the depolymerization process in the above step (2-2).

[0052] The amount of the second glycol compound (additional amount used in the secondary depolymerization) is not particularly limited, but may be 1 or more times, 2 or more times, or 3 or more times, and 7 or less times, 5 or less times, or 4 or less times (e.g., 1 to 7 times, 2 to 5 times, or 3 to 4 times) relative to the weight of the pretreated waste polyester.

[0053] The depolymerization temperature of the above step (2-2) may be 150 to 170°C, and specifically, 150 to 165°C, 150 to 163°C, 150 to 160°C, 150 to 158°C, or 150 to 155°C. In addition, the depolymerization time of the above step (2-2) is not particularly limited, but may be 1 to 4 hours, 1 to 3 hours, or 1 to 2 hours from the time when the temperature required for the secondary depolymerization is reached. As the depolymerization of the above step (2-2) is performed at the above temperature and time, the second glycolysis reaction of the first reactant can be performed smoothly, and the production of impurities such as diethylene glycol ester compounds can be minimized.

[0054] The depolymerization in step (2-2) may be carried out in the presence of a catalyst that activates the second glycolysis reaction. The catalyst may be derived from the depolymerization process in step (2-1) or may be additionally added in the depolymerization process in step (2-2). The description of this catalyst is the same as that of the catalyst in step (2-1), and thus a detailed description thereof will be omitted.

[0055] As depolymerization proceeds through steps (2-1) and (2-2), a reactant containing crude bis(2-hydroxyethyl) terephthalate (crude-BHET) can be obtained in high yield.

[0056]

[0057] Step (3): Purification

[0058] According to the present invention, step (3) is a step of purifying the reactant (depolymerization reactant) obtained through the depolymerization of step (2). The purification of the reactant can be performed through various steps.

[0059] For example, according to the present invention, the purification of step (3) may include a step of cooling the reactant to a temperature of 100 to 150°C and pressurizing and filtering the reactant at a pressure of 0.01 to 0.5 MPa. Specifically, the pressurized filtering may be performed by cooling the reactant through a reduced pressure flash and then performing a pressurized filtering process using a filter aid to separate solid and liquid, whereby the reactant may be converted into a liquid reactant. By performing the pressurized filtering, solid impurities such as fine particles and insoluble organic substances contained in the reactant may be removed, thereby increasing the purity and yield of the renewable raw material composition.

[0060] The temperature at which the reactant is cooled through the depressurization flash may be specifically 100 to 135° C., 105 to 125° C., or 110 to 120° C. In addition, the pressure conditions at which the depressurization flash is performed are not particularly limited, but may specifically be 200 Torr or less, 150 or less, 100 Torr or less, 50 Torr or less, or 30 Torr or less, and may be 5 Torr or more, 8 Torr or more, 10 Torr or more, or 15 Torr or more (e.g., 5 to 200 Torr, 10 to 100 Torr, or 15 to 50 Torr).

[0061] The reactant cooled through the above-described pressure flash may have a pressure filtering speed of 1.5 L / min or more. Specifically, the pressure filtering speed of the reactant may be 2 L / min or more, 2.5 L / min or more, 3 L / min or more, 3.5 L / min or more, 4 L / min or more, 4.5 L / min or more, 5 L / min or more, or 5.5 L / min or more (e.g., 1.5 to 6 L / min, 3 to 5.7 L / min, 4 to 5.6 L / min, or 4.5 to 5.5 L / min). As such, the present invention has a high pressure filtering speed of the reactant, so that the overall process efficiency may be high. This improvement in the pressure filtering speed is possible by controlling the apparent density of the waste polyester to 0.5 kg / L or more so that separation between different components within the waste polyester is well achieved.

[0062] Meanwhile, the filter aid is not particularly limited as long as it is commonly known, but may specifically include at least one selected from the group consisting of diatomaceous earth, perlite, and asbestos powder.

[0063] According to the present invention, the purification in step (3) may include treating the reactant with an ion exchange resin. Specifically, the treatment may be performed by passing the reactant through an ion exchange resin or by introducing an ion exchange resin into the reactant. Through this process, ionic impurities contained in the reactant are removed, thereby obtaining a reactant with increased purity.

[0064] The ion-exchange resin may be a commonly known cation exchange resin, anion exchange resin, amphoteric ion exchange resin, chelating resin, or a combination thereof.

[0065] The cation exchange resin may specifically include a strongly acidic cation exchange resin having a sulfonic acid group (-SO3H), or a weakly acidic cation exchange resin having a carboxyl group (-COOH). The anion exchange resin may include a strongly basic anion exchange resin in the form of a quaternary ammonium salt, or a weakly basic anion exchange resin having a primary to tertiary amino group. The chelating resin may be a polymer resin having a reactive functional group such as acetate or phosphate that chelates metal ions such as sodium, copper, nickel, zinc, and manganese.

[0066] When the above treatment is performed by introducing the ion exchange resin into the reactant, the amount of the ion exchange resin introduced (usage) is not particularly limited, but may be 1 time or more, 2 times or more, 3 times or more, or 5 times or more, and 20 times or less, 15 times or less, 10 times or less, or 8 times or less (e.g., 1 to 20 times, 2 to 15 times, 3 to 10 times, or 5 to 8 times) relative to the weight of the catalyst used in the depolymerization of step (2). In addition, the amount of the ion exchange resin input (usage) may be 1 part by weight or more, 2 parts by weight or more, 3 parts by weight or more, or 5 parts by weight or more, and 50 parts by weight or less, 20 parts by weight or less, 15 parts by weight or less, 10 parts by weight or less, or 7 parts by weight or less (e.g., 1 to 50 parts by weight, 3 to 20 parts by weight, or 5 to 10 parts by weight) based on 100 parts by weight of the waste polyester in the step (2).

[0067] When the above treatment is performed by passing the reactant through the ion exchange resin, the ion exchange resin may be in the form of particles having a predetermined size. Specifically, the treatment for removing ionic impurities may be performed by passing the reactant (e.g., the liquid reactant) through a column filled with ion exchange resin particles having a particle size of 0.3 to 1.5 mm, 0.5 to 1.3 mm, or 0.7 to 1.0 mm.

[0068] According to the present invention, the purification of step (3) may include a step of cooling and crystallizing the reactant. Specifically, the cooling and crystallization may be performed by lowering the temperature of the reactant. The temperature at which the reactant is cooled for crystallization of the reactant is not particularly limited, but may be specifically, 70°C or lower, 60°C or lower, 50°C or lower, 40°C or lower, 30°C or lower, or 25°C or lower, and may be 0°C or higher, 5°C or higher, 10°C or higher, 15°C or higher, or 20°C or higher. By performing this cooling and crystallization process, impurities such as acetate-based ester compounds and diethylene glycol ester compounds can be efficiently removed.

[0069] According to the present invention, the purification of step (3) may include a step of distilling the reactant. Specifically, the distillation may be performed by subjecting the reactant to reduced pressure distillation to obtain a product, and then subjecting the obtained product to thin film distillation.

[0070] A glass distillation apparatus or a rotary evaporator can be used for the reduced pressure distillation of the above reactant.

[0071] The conditions for performing the above-described reduced pressure distillation are not particularly limited, but specifically, it can be performed at 150°C or lower under a pressure of 0.1 to 200 Torr. More specifically, the pressure for performing the above-described reduced pressure distillation can be 0.1 to 150 Torr, 0.2 to 100 Torr, 0.3 to 50 Torr, or 0.5 to 30 Torr. In addition, the temperature for performing the above-described reduced pressure distillation can be 90°C or higher, 100°C or higher, or 110°C or higher, and 145°C or lower, 140°C or lower, or 135°C or lower (e.g., 90 to 150°C, 100 to 145°C, 120 to 135°C, or 100 to 130°C).

[0072] Through this reduced pressure distillation, unreacted glycol compounds (e.g., ethylene glycol, diethylene glycol) contained in the reactant can be removed and recovered, and the recovered glycol compounds can be reused in the depolymerization process of step (2).

[0073] For the thin film distillation of the above reactant, a thin film distillation device including an evaporator, a wiper rotor, and a condenser can be used.

[0074] The conditions for performing the above thin film distillation are not particularly limited, but specifically, it can be performed at 150 to 250°C under a pressure of 0.005 to 5 Torr. More specifically, the pressure for performing the thin film distillation may be 0.005 to 4.5 Torr, 0.01 to 4 Torr, 0.05 to 3 Torr, or 0.07 to 1.5 Torr. In addition, the temperature for performing the thin film distillation (the temperature of the thin film inside the thin film distillation apparatus) may be 180 to 240°C, 185 to 230°C, 190 to 225°C, 195 to 220°C, or 200 to 220°C.

[0075] Through this thin film distillation, oligomers higher than dimers (e.g., BHET dimer, BHET trimer) contained in the above reactant can be efficiently removed.

[0076] Meanwhile, the pressure filtering, ion exchange resin treatment, cooling crystallization, reduced pressure distillation, and thin film distillation for purifying the reactant may be performed at each step depending on the type of impurity, and the order in which each step is performed may also be appropriately controlled.

[0077] By performing the purification in step (3) above, the present invention can produce a high-purity recycled raw material composition at a high yield. In particular, the present invention can produce a recycled raw material composition in which the content of specific impurities is controlled to be below a specific range and the content of the effective ingredient, bis(2-hydroxyethyl)terephthalate (BHET), is significantly high.

[0078] Specifically, the composition of a recycled raw material composition obtained by depolymerizing waste polyester can be confirmed by measuring the peak area ratio (%) of the analyzed component among the total peak area in a spectrum obtained by analyzing the recycled raw material composition using high-performance liquid chromatography (HPLC). At this time, if the peak area ratio of the component considered as an impurity is low and the peak area ratio of the effective ingredient, BHET, is high, the purity of the recycled raw material composition can be considered high.

[0079] For example, according to the present invention, when the recycled raw material composition obtained through steps (1) to (3) is analyzed by high-performance liquid chromatography (HPLC), the total sum (x+y) of the peak area ratio (x) of the diethylene glycol ester compound (DEG-ester) and the peak area ratio (y) of the monohydroxyethyl terephthalate (MHET) may be less than 4.0%. Specifically, the total sum of the peak area ratios (x+y) may be 3.8% or less, 3.5% or less, 3.3% or less, 3.0% or less, 2.8% or less, 2.5% or less, 2.3% or less, 2.0% or less, 1.9% or less, 1.5% or less, 1.3% or less, 1.0% or less, or 0.8% or less (e.g., 0 to 3.5%, 0.3 to 3.0%, 0.5 to 2.5%, or 0.8 to 2.0%). When the diethylene glycol ester compound (DEG-ester) remains in the recycled raw material composition, it may reduce the melting point of a recycled polyester resin manufactured using the recycled raw material composition, thereby lowering the heat resistance of the recycled polyester resin. However, since the content of the diethylene glycol ester compound (DEG-ester) in the recycled raw material composition of the present invention is controlled to a minimum, it can be usefully used as a polymerization raw material for producing a recycled polyester resin having excellent heat resistance.

[0080] The above diethylene glycol ester compound (DEG-ester) may specifically include 2-hydroxyethyl[2-(2-hydroxyethoxy)ethyl]terephthalate (DEG-ester-1), bis[2-(2-hydroxyethoxy)ethyl]benzene-1,4-dicarboxylate (DEG-ester-2), or a combination thereof.

[0081] According to the present invention, when the raw material composition obtained through the above steps (1) to (3) is analyzed by high-performance liquid chromatography (HPLC), the peak area ratio of the acetate-based ester compound (HA-ester) may be less than 0.4%. Specifically, the peak area ratio of the acetate-based ester compound (HA-ester) may be 0.35% or less, 0.3% or less, 0.25% or less, 0.23% or less, 0.2% or less, 0.18% or less, 0.15% or less, 0.13% or less, 0.1% or less, 0.09% or less, 0.07% or less, 0.05% or less, or 0.03% or less (e.g., 0 to 0.35%, greater than 0 to 0.3%, 0.01 to 0.25%, 0.03 to 0.2%, or 0.05 to 0.15%). If the above acetate-based ester compound (HA-ester) remains in the recycled raw material composition, it may act as a terminator that inhibits the growth of polymer chains when producing a recycled polyester resin using the recycled raw material composition, thereby reducing the heat resistance of the recycled polyester resin. However, since the recycled raw material composition of the present invention has the content of the acetate-based ester compound (HA-ester) controlled to a minimum, it can be usefully used as a polymerization raw material for producing a recycled polyester resin having excellent heat resistance.

[0082] The above acetate ester compound (HA-ester) may include 2-hydroxyethyl (2-acetoxyethyl) terephthalate.

[0083] According to the present invention, when the recycled raw material composition obtained through steps (1) to (3) is analyzed by high-performance liquid chromatography (HPLC), the peak area ratio of bis(2-hydroxyethyl)terephthalate (BHET) may be 95% or more. Specifically, the peak area ratio of bis(2-hydroxyethyl)terephthalate (BHET) may be 95.5% or more, 96% or more, 96.5% or more, 97% or more, 97.5% or more, 98% or more, 98.5% or more, 99% or more, 99.5% or more, or 100% (e.g., 95 to 100%, 96 to 99%, 96 to 98%, or 96.5 to 98%). In this way, the regenerative raw material composition of the present invention can achieve high yield while exhibiting high purity by having a significantly high peak area ratio of the active ingredient, bis(2-hydroxyethyl)terephthalate (BHET).

[0084] According to the present invention, when a renewable raw material composition is manufactured through steps (1) to (3), the process yield (Y) according to the following formula 1 may be 80% or more. Specifically, the process yield (Y) may be 81% or more, 81.5% or more, 82% or more, 82.5% or more, 83% or more, 83.5% or more, 84% or more, 84.5% or more, 85% or more, 85.5% or more, 86% or more, 86.5% or more, 87% or more, 88% or more, or 90% or more (e.g., 80 to 99%, 81 to 95%, 82 to 90%, or 84 to 88%).

[0085] [Formula 1] Y (%) = (W1 / W2) × 100

[0086] In the above equation 1,

[0087] W1 is the weight of the recycled raw material composition obtained through the above steps (1) to (3) (actual weight of the recycled raw material composition obtained through the chemical recycling process),

[0088] W2 is the theoretical weight of the recycled raw material composition manufactured from the waste polyester used in the above step (1) (the theoretical weight of the recycled raw material composition that can be obtained through the chemical recycling process of the waste polyester).

[0089]

[0090] Regenerated raw material composition

[0091] The recycled raw material composition according to the present invention is prepared using the method for preparing the recycled raw material composition described above. Specifically, the recycled raw material composition may contain a high content of recycled bis(2-hydroxyethyl) terephthalate (r-BHET) formed by depolymerization of waste polyester.

[0092] According to the present invention, the recycled raw material composition can be usefully used in the production of a recycled polyester resin because it contains a high content of recycled bis(2-hydroxyethyl)terephthalate (r-BHET) while controlling the content of impurities (e.g., MHET, DEG-ester, HA-ester, BHET dimer, BHET trimer, etc.) to below a specific range. In particular, the recycled bis(2-hydroxyethyl)terephthalate (r-BHET) contained in the recycled raw material composition has crystallinity and high purity, and thus can have properties equivalent to those of virgin bis(2-hydroxyethyl)terephthalate (virgin BHET). Therefore, when the recycled polyester resin is produced using the recycled bis(2-hydroxyethyl)terephthalate (r-BHET), a recycled polyester resin having excellent heat resistance, weather resistance, color characteristics, etc. can be provided.

[0093] The present invention is described in more detail through the following examples. However, the following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention.

[0094]

[0095] [Example 1]

[0096] Step (1): Preprocessing

[0097] A waste polyester fabric having an apparent density of 0.1 kg / L or less was fed into a biaxial stretching extruder, and a pretreatment process of melt extrusion was performed at a barrel temperature of 250°C and an extrusion speed of 200 rpm for 3 minutes, thereby obtaining 1000 g of waste polyester fabric having an adjusted apparent density.

[0098] Step (2): Depolymerization

[0099] 1000 g of the above-obtained waste polyester fabric, 2000 g of ethylene glycol, and 15.0 g of zinc acetate anhydride were charged into a first stainless steel (SUS) reactor, the internal temperature of the first reactor was raised to 180°C, and a first depolymerization (first glycolysis reaction) was performed for 2 hours to obtain a first reactant. Subsequently, the obtained first reactant was transferred to a second reactor and cooled to 150°C, and then 2000 g of ethylene glycol was additionally charged into the second reactor, and depolymerization (second glycolysis reaction) was performed for 2 hours while maintaining the internal temperature of the second reactor at 150°C to obtain a second reactant.

[0100] Step (3): Purification

[0101] The second reactant obtained above was cooled to 120°C through a reduced pressure flash, and then high temperature / pressure filtering (solid-liquid separation) was performed to obtain a liquid reactant.

[0102] The liquid reactant obtained above was passed through a column filled with ion exchange resin (BC107(H) from Bonlite) to remove ionic impurities, thereby obtaining a mixture containing regenerated bis(2-hydroxyethyl) terephthalate (r-BHET) and ethylene glycol.

[0103] The above mixture was transferred to a 10 L distillation device, and then distilled under reduced pressure at 130°C to remove (recover) unreacted ethylene glycol. Subsequently, the third reactant from which the ethylene glycol was removed was subjected to thin-film distillation at 220°C and 0.08 Torr in a thin-film distiller (VKL70-4S from VTA) to obtain a fourth reactant from which oligomers higher than dimers were removed.

[0104] Thereafter, the fourth reactant and distilled water were added to a 20 L glass reactor for adsorption-crystallization, dissolved at a temperature of 70°C, activated carbon was added, stirred for 30 minutes, and filtered. Next, the filtrate obtained through the filtration was cooled to room temperature to crystallize, filtered again, and dried in a vacuum oven to prepare a recycled raw material composition including recycled bis(2-hydroxyethyl)terephthalate.

[0105]

[0106] [Example 2]

[0107] A recycled raw material composition was manufactured through the same process as Example 1, except that a waste polyester banner was used instead of the waste polyester fabric and the pretreatment conditions were adjusted as shown in Table 1 below.

[0108]

[0109] [Example 3]

[0110] A recycled raw material composition was manufactured through the same process as Example 1, except that scrap waste polyester film was used instead of waste polyester fabric and the pretreatment conditions were adjusted as shown in Table 1 below.

[0111]

[0112] [Example 4]

[0113] A recycled raw material composition was prepared through the same process as Example 1, except that the pretreatment conditions of the waste polyester fabric were adjusted as shown in Table 1 below.

[0114]

[0115] [Example 5]

[0116] A recycled raw material composition was prepared through the same process as Example 1, except that the pretreatment conditions of the waste polyester fabric were adjusted as shown in Table 1 below.

[0117]

[0118] [Example 6]

[0119] A recycled raw material composition was prepared through the same process as Example 1, except that the pretreatment conditions of the waste polyester fabric were adjusted as shown in Table 1 below.

[0120]

[0121] [Comparative Example 1]

[0122] A recycled raw material composition was prepared through the same process as Example 1, except that the pretreatment step of the waste polyester fabric was omitted.

[0123]

[0124] [Comparative Example 2]

[0125] A recycled raw material composition was prepared through the same process as Example 2, except that the pretreatment step of the waste polyester banner was omitted.

[0126]

[0127] [Comparative Example 3]

[0128] A recycled raw material composition was prepared through the same process as Example 3, except that the pretreatment step of the waste polyester film scrap was omitted.

[0129]

[0130] [Comparative Example 4]

[0131] A recycled raw material composition was manufactured through the same process as Example 1, except that instead of the pretreatment of melt-extruding waste polyester fabric having an apparent density of 0.1 kg / L or less, waste polyester fabric was fed into a reactor capable of crushing and crystallization, and a pretreatment process (heat set) was performed in which the waste polyester fabric was heated at 220°C for 60 minutes to control the apparent density.

[0132]

[0133] [Comparative Example 5]

[0134] A recycled raw material composition was manufactured through the same process as Comparative Example 4, except that a waste polyester banner was used instead of the waste polyester fabric.

[0135]

[0136] [Comparative Example 6]

[0137] A recycled raw material composition was prepared through the same process as in Comparative Example 4, except that waste polyester film scrap was used instead of waste polyester fabric.

[0138]

[0139] [Example Exam]

[0140] The following tests were conducted on the materials obtained in Examples 1 to 6 and Comparative Examples 1 to 6, respectively, and the results are shown in Tables 1 and 2 below.

[0141]

[0142] (1) High-performance liquid chromatography (HPLC)

[0143] 0.01 g of sample (recycled raw material composition) was diluted in 20 ml of methanol and analyzed by high-performance liquid chromatography (HPLC) (Model: Waters e2695, Column: C18 (4.6 × 250 mm), 5 μm, UV Detector: 242 nm, Injection volume: 10 μL, Eluent (Gradient) A: H2O+H3PO4, B: Acetonitrile). Afterwards, the peak area ratio (%) of the following components among the total peak area of ​​HPLC was confirmed.

[0144] - MHET: Monohydroxyethyl terephthalate

[0145] - BHET: bis(2-hydroxyethyl) terephthalate

[0146] - DEG-ester-1: 2-hydroxyethyl[2-(2-hydroxyethoxy)ethyl]terephthalate

[0147] - DEG-ester-2: Bis[2-(2-hydroxyethoxy)ethyl]benzene-1,4-dicarboxylate

[0148] - HA-ester: 2-hydroxyethyl (2-acetoxyethyl) terephthalate

[0149] - Dimer: BHET dimer

[0150] - Trimer: BHET trimer

[0151]

[0152] (2) Apparent density (kg / L)

[0153] A 2 L flask of known volume was filled with waste polyester without pressure, the confirmed weight was measured, and the apparent density was measured using the relationship between the measured weight and the flask volume, and the results are shown in Tables 1 and 2 below.

[0154]

[0155] (3) Pressurized filtering speed (L / min)

[0156] The pressure filtering speed of the depolymerization reactant (second reactant) was measured under the following conditions, and the results are shown in Tables 1 and 2 below.

[0157] - Pressurized filter area: 700 ㎠ / - Pressurized filter mesh size: 1 ㎛ / - Pressurized pressure: 0.01 to 0.5 MPa

[0158]

[0159] (4) Process yield (%)

[0160] The process yield of the regenerative raw material composition was calculated according to the following equation 1.

[0161] [Formula 1] Y (%) = (W1 / W2) × 100

[0162] In the above equation 1,

[0163] W1 is the weight of the raw material composition obtained through steps (1) to (3),

[0164] W2 is the theoretical weight of the recycled raw material composition manufactured from the waste polyester used in step (1).

[0165]

[0166] ClassificationExample 1Example 2Example 3Example 4Example 5Example 6Waste polyester depolymerization Raw material typeWaste fabricWaste bannerWaste film scrapWaste fabricWaste fabricPretreatment methodExtrusionExtrusionExtrusionExtrusionExtrusionExtrusionExtrusionMeltExtrusion temperature / Heat Set temperature (℃)250250270250250320MeltExtrusion speed (rpm)20015015050400200MeltExtrusion time (min)3552013Apparent density (kg / L)Before pretreatment0.050.030.090.050.050.05After pretreatment0.740.770.69Apparent density cannot be measured due to excessive decomposition or non-meltingRecycled raw material compositionHPLC(Aear %)MHET0.391.721.10-BHET97.9896.5897.64DEG-ester-10.360.610.62DEG-ester-20.100.090.16HA-ester0.050.080.12Dimer0.230.900.22Trimer0.020.000.02Other0.90.00.1Pressure filtration speed (L / min)5.405.504.70Process yield (%)87.185.182.8

[0167] ClassificationComparative Example 1Comparative Example 2Comparative Example 3Comparative Example 4Comparative Example 5Comparative Example 6Waste polyester depolymerization raw material typeWaste fabricWaste bannerWaste film scrapWaste fabricWaste bannerWaste film scrapPretreatment methodNot implementedNot implementedNot implementedheat setheat setheat setMelt extrusion temperature / Heat Set Temperature (℃)---220220220Melt extrusion speed (rpm)------Melt extrusion time (min)---606060Apparent density (kg / L)Before pretreatment0.050.030.090.050.030.09After pretreatment---0.450.440.42Recycled raw material compositionHPLC(Aear %)MHET3.622.201.631.201.400.22BHET92.8093.1294.3097.8096.8897.90DEG-ester-12.382.522.170.300.400.70DEG-ester-20.340.540.210.020.000.00HA-ester0.560.700.620.430.440.55Dimer0.270.840.790.160.680.24Trimer0.020.010.020.000.000.00Other0.00.10.30.10.20.4Pressure filtering Speed ​​(L / min) 0.40 0.24 0.15 1.70 1.85 1.55 Process yield (%) 53.85 6.34 3.07 9.27 7.47 5.3

[0168] Referring to Tables 1 and 2 above, it can be confirmed that by adjusting the apparent density of the waste polyester, which is a raw material for depolymerization, to 0.5 kg / L or more through a pretreatment process using melt extrusion, the depolymerization reaction is smoothly performed even if the waste polyester has not only a single component but also different components, and the separation efficiency of insoluble components is improved, so that a high-purity recycled raw material composition is manufactured in high yield (see Examples 1 to 3).

[0169] However, if pretreatment is performed in a state where the temperature, extrusion speed, and time at which melt extrusion is performed are not optimally controlled, the waste polyester may be over-decomposed or not melted, making shaping impossible. Therefore, it may be desirable to optimally control the conditions under which melt extrusion is performed (see Examples 4 to 6).

[0170] Meanwhile, when a recycled raw material composition is manufactured without going through a pretreatment process, it can be confirmed that a recycled raw material composition is manufactured with a high content of impurities and a significantly low yield (see Comparative Examples 1 to 3). In addition, when a pretreatment process is performed by a method other than melt extrusion, it can be confirmed that the apparent density of the waste polyester cannot be controlled to 0.5 kg / L or more, which also reduces the purity and yield of the recycled raw material composition (see Comparative Examples 4 to 6).

Claims

1. (1) A step of pretreating waste polyester having an apparent density of 0.1 kg / L or less so that the apparent density becomes 0.5 kg / L or more; (2) a step of depolymerizing the pretreated waste polyester; and (3) A method for producing a regenerated raw material composition, comprising a step of purifying a reactant obtained through the above depolymerization.

2. In paragraph 1, A method for producing a regenerative raw material composition, wherein the pretreatment of the above step (1) is performed through melt extrusion.

3. In paragraph 2, A method for producing a renewable raw material composition, wherein the above melt extrusion is performed at a temperature of 250 to 300°C and an extrusion speed of 100 to 350 rpm for 2 to 15 minutes.

4. In paragraph 2, A method for producing a recycled raw material composition, wherein the above melt extrusion is performed without adding any additives.

5. In paragraph 1, A method for producing a recycled raw material composition, wherein the waste polyester, whose apparent density is adjusted to 0.5 kg / L or more in the above step (1), has a size of 5 mm or less and a cylindrical shape.

6. In paragraph 1, A method for producing a recycled raw material composition, wherein the waste polyester pretreated in the above step (1) includes waste polyester fabric, waste polyester film, waste polyester flake, waste polyester powder, or a combination thereof.

7. In paragraph 1, The above step (2) is, (2-1) A step of obtaining a first reactant by depolymerizing the waste polyester whose apparent density has been adjusted through the above pretreatment through a first glycolysis reaction at a temperature of 180 to 200°C; and (2-2) A method for producing a renewable raw material composition, comprising a step of depolymerizing the first reactant by a second glycolysis reaction at a temperature of 150 to 170°C to obtain a second reactant.

8. In paragraph 1, The above step (3) includes a step of cooling the reactant to a temperature of 100 to 150°C and pressurizing and filtering at a pressure of 0.01 to 0.5 MPa, A method for producing a regenerative raw material composition, wherein the pressurized filtering speed of the cooled reactant is 1.5 L / min or more.

9. In paragraph 1, The above step (3) is a method for producing a regenerative raw material composition, which includes a step of cooling and crystallizing the reactant.

10. In paragraph 1, The above step (3) is a method for producing a regenerative raw material composition, including a step of distilling the reactant.

11. In paragraph 1, A method for producing a recycled raw material composition, wherein when the recycled raw material composition obtained through the above steps (1) to (3) is analyzed by high-performance liquid chromatography (HPLC), the total sum of the peak area ratio of the diethylene glycol ester compound and the peak area ratio of the monohydroxyethyl terephthalate is less than 4.0%.

12. In paragraph 1, A method for producing a recycled raw material composition, wherein when the recycled raw material composition obtained through the above steps (1) to (3) is analyzed by high-performance liquid chromatography (HPLC), the peak area ratio of the acetate-based ester compound is less than 0.4%.

13. In paragraph 1, A method for producing a recycled raw material composition, wherein when the recycled raw material composition obtained through the above steps (1) to (3) is analyzed by high-performance liquid chromatography (HPLC), the peak area ratio of bis(2-hydroxyethyl)terephthalate is 95% or more.

14. In paragraph 1, A method for producing a renewable raw material composition having a process yield (Y) of 80% or more according to the following formula 1: [Formula 1] Y (%) = (W1 / W2) × 100 In the above equation 1, W1 is the weight of the regenerated raw material composition obtained through the above steps (1) to (3), W2 is the theoretical weight of the recycled raw material composition manufactured from the waste polyester used in the above step (1).

15. A composition of regenerative raw materials manufactured from a manufacturing method according to any one of claims 1 to 14.