Preparation method of regenerated material composition

Abstract

The invention relates to a method for preparing a regenerated raw material composition by utilizing a waste polyester depolymerization method. The preparation method comprises the following steps: (1) pretreating waste polyester with the apparent density of 0.1 kg / L or lower until the apparent density is 0.5 kg / L or higher; (2) depolymerizing the pretreated waste polyester; and (3) purifying a reactant obtained by depolymerization.

Description

Technical Field

[0001] The present invention relates to a method for preparing a recycled raw material composition, which can prepare a high-purity and high-yield recycled raw material composition through a waste polyester recovery process (pretreatment and depolymerization), and the recycled raw material composition prepared thereby. Background Art

[0002] Polyester is a type of polymer that is widely used as a raw material for internal and external materials such as beverage containers, various packaging films, panels, shelves, partitions, etc. due to its excellent mechanical strength, heat resistance, transparency and gas barrier properties.

[0003] As a result, the amount of plastic (such as polyester) waste generated each year has reached an uncontrollable level. Recently, countries around the world have formulated regulations and plans for the recycling of waste plastic resources (including waste polyester).

[0004] Although physical or chemical recycling methods are used to recycle waste polyester, physical recycling methods cannot guarantee purity and are therefore not widely used. Meanwhile, in chemical recycling methods, the ester bonds of waste polyester are cut to depolymerize the waste polyester. The reactions used include glycolysis, hydrolysis, methanolysis, and aminolysis. Glycolysis is the decomposition of waste polyester by adding alcohols such as ethylene glycol or diethylene glycol. Regenerated raw materials such as bis(2-hydroxyethyl) terephthalate (BHET) are obtained.

[0005] However, waste polyester varies in contamination, shape and apparent density due to different collection environments. It may contain heterogeneous components rather than a single component; therefore, the amount that can be depolymerized using chemical recycling methods is limited. Therefore, there is a limit to increasing the yield of recycled raw materials to the required level. Summary of the invention

[0006] Technical issues

[0007] In order to solve the above-mentioned conventional problems, the object of the present invention is to provide a method for preparing a regenerated raw material composition. Preparation method, The method can prepare the regeneration raw material composition economically and in high yield, even if the Waste polyester with different degrees of contamination, shape, apparent density, etc. and with heterogeneous components, as well as single component are used as depolymerization raw materials.

[0008] In addition, another object of the present invention is to provide a high-purity recycled raw material composition prepared by the above preparation method.

[0009] Technical solutions to technical problems

[0010] In order to solve the above problems, the present invention provides a method for preparing a recycled raw material composition, which comprises: (1) pretreating waste polyester with an apparent density of 0.1 kg / L or less to an apparent density of 0.5 kg / L or more; (2) depolymerizing the pretreated waste polyester; and (3) purifying the reactants obtained by depolymerization.

[0011] In addition, the present invention also provides a renewable raw material composition prepared by the above preparation method.

[0012] Advantageous Effects of the Invention

[0013] In the present invention, waste polyester is pretreated to adjust its apparent density to a certain range or higher, and then the waste polyester with adjusted apparent density is depolymerized to prepare a recycled raw material composition. Therefore, even if waste polyesters having different degrees of contamination, shapes, apparent densities, etc. and having heterogeneous components, as well as waste polyesters having a single component, are used as depolymerization raw materials, a high-purity, high-yield recycled raw material composition can be prepared.

[0014] Therefore, the present invention can recycle waste polyester economically and efficiently.

[0015] Best Mode for Carrying Out the Invention

[0016] The present invention will be described in detail below. The present invention is not limited to the contents disclosed below, and can be modified into various forms as long as the gist of the present invention is not changed.

[0017] In this specification, the term "comprising" is used to clarify a particular feature, region, step, process, element and / or component. Unless otherwise expressly stated, the existence or addition of any other feature, region, step, process, element and / or component is not excluded.

[0018] Throughout this specification, the terms first, second and similar terms are used to describe various components. However, these components should not be limited by these terms. These terms are only used to separate one element from another element.

[0019] Unless otherwise indicated, terms used herein relating to amounts of ingredients, reaction conditions and similar terms are All numbers and expressions should be understood as being modified by the term "about".

[0020] In this specification, unless the context otherwise indicates, a singular expression is construed as including the plural.

[0021] Since polyester is widely used in many fields, its commercial forms are also diverse. Articles containing polyester are composed of polyester as a single component, or a heterogeneous composition in which polyester is mixed with other components as necessary. Accordingly, waste polyester extracted from waste products has various shapes, sizes and compositions.

[0022] In order to be recycled, this waste polyester usually goes through steps such as removing foreign matter and crushing. In this case, the difference in the degree of crushing of the waste polyester can be expressed as apparent density (kg / L). The larger the apparent density, the more favorable it is for the chemical recycling process of the waste polyester.

[0023] Specifically, the present inventors have found that when a chemical recovery process is performed using waste polyester as a raw material for depolymerization, and when a waste polyester having a low apparent density is used, the amount of waste polyester and reactants (e.g., ethylene glycol-based compounds) available for the depolymerization step is limited; therefore, the productivity of producing a recycled raw material composition by a chemical recovery process of waste polyester is reduced. In addition, waste polyester having heterogeneous components (e.g., polyester mixed with polyolefin, polyamide, polytetrafluoroethylene, or the like) rather than a single component and having a low apparent density makes it difficult to separate the heterogeneous components and remove impurities during the purification process after the depolymerization process. Therefore, the purity and yield of the recycled raw material composition derived from the waste polyester are also significantly reduced.

[0024] As described above, the inventors have found that the apparent density of waste polyester used as 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. Based on this, the inventors have adopted a pretreatment method to control the apparent density of waste polyester to improve the overall process efficiency and prepare a high-purity, high-yield recycled raw material composition.

[0025] That is, in the present invention, the apparent density of waste polyester is increased to a certain range or higher through a specific pretreatment procedure and then subjected to a chemical recovery process including a depolymerization step, which will be described in detail below.

[0026] Method for preparing recycled raw material composition

[0027] The method for preparing the recycled raw material composition according to the present invention comprises: (1) pretreating waste polyester having an apparent density of 0.1 kg / L or less to an apparent density of 0.5 kg / L or more; (2) depolymerizing the pretreated waste polyester; and (3) purifying the reactant obtained by depolymerization.

[0028] Step (1): Pretreatment to control apparent density

[0029] 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 to an apparent density of 0.5 kg / L or more.

[0030] When the apparent density of the waste polyester is 0.1 kg / L or less, the amount of the waste polyester and the ethylene glycol-based compound that can be used in the depolymerization process is limited, which may reduce the efficiency of the depolymerization step. Therefore, through the pretreatment of step (1), the apparent density of the waste polyester is adjusted to 0.5 kg / L or more. When the apparent density of the waste polyester is adjusted to 0.5 kg / L or more, the surface area of ​​the waste polyester is increased, thereby significantly improving the efficiency of the depolymerization step using the ethylene glycol-based compound, and the insoluble components (foreign matters generated by the heterogeneous components) in the reactants obtained by the depolymerization procedure may exist in the form of uniform small particles, thereby making the purification of the insoluble components easier. Therefore, in the present invention, the overall process efficiency is improved, while the loss of recycled raw materials (e.g., bis(2-hydroxyethyl) terephthalate (BHET)) accompanying the insoluble components is minimized, so that a high-purity, high-yield recycled raw material composition can be prepared.

[0031] Depending on the purity and yield of the recycled raw material composition, the apparent density of the pretreated waste polyester may specifically be 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 kg / L),

[0032] The pretreatment method of the waste polyester is not particularly limited, but can be performed by melt extrusion using an extruder. After the waste polyester is pretreated by melt extrusion, the apparent density of the waste polyester can be easily adjusted to 0.5 kg / L or more, which is the level required by the present invention. In this case, in order to The apparent density of polyester is adjusted to 0.5kg / L or higher. The conditions of melt extrusion need to be optimized and controlled. system.

[0033] Specifically, according to the present invention, melt extrusion may 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 melt extrusion conditions are outside the above ranges, the waste polyester may be decomposed (deformed or lost) due to overheating, or standardization of the controllable apparent density may not be achieved.

[0034] The melt extrusion temperature refers to the barrel temperature of the extruder, and may be, for example, 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.

[0035] The melt extrusion speed refers to the screw speed of the extruder. Specifically, it can 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.

[0036] The melt extrusion time refers to the time that the waste polyester stays in the extruder screw. Specifically, it can be 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.

[0037] The extruder used for melt extrusion is not particularly limited as long as it is a common extruder, and specifically, it can be a single-screw extruder or a twin-screw extruder.

[0038] According to the present invention, no separate additive (organic additive or inorganic additive) shall be added in the melt extrusion. That is, in the present invention, the apparent density of the waste polyester is not adjusted chemically, but adjusted physically by the melt extrusion method.

[0039] According to the present invention, the waste polyester whose apparent density has been adjusted to 0.5 kg / L or more by pretreatment can have various forms. Specifically, the shape of the waste polyester after pretreatment can be spherical, elliptical, cylindrical or prismatic, and is preferably cylindrical. In addition, the size (longest length) of the waste polyester after pretreatment 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 mm to 4.5 mm, 2 to 4 mm, 2.5 to 3.5 mm or 2 to 3 mm). As a result, the efficiency of the depolymerization reaction of the waste polyester can be improved while ensuring the convenience of handling the waste polyester.

[0040] Meanwhile, according to the present invention, the waste polyester to be pretreated is not particularly limited as long as it is a waste material containing polyester. Specifically, it may include waste polyester fabric (fiber), waste polyester film, waste polyester flake, waste polyester powder or a combination thereof.

[0041] Step (2): Depolymerization

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

[0043] Specifically, step (2-1) may include performing a glycolysis reaction to preliminarily cut the polymer chain of the waste polyester using the first ethylene glycol-based compound to obtain a first reactant (first product).

[0044] The first ethylene glycol-based compound used in the depolymerization step of 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-based compound is not particularly limited. Specifically, it can 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) the weight of the pretreated waste polyester.

[0046] The depolymerization temperature in step (2-1) may be 180 to 200° C., 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 in 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. Since the depolymerization in step (2-1) is carried out within the above-mentioned temperature and time range, the first glycolysis reaction of the waste polyester can be smoothly carried out while minimizing the formation of side reactants such as diethylene glycol ester compounds.

[0047] The depolymerization in step (2-1) can be carried out in the presence of a catalyst, which can activate the second glycolysis reaction. The catalyst is not particularly limited as long as it is a known catalyst, but it can specifically include metal acetates, anhydrides thereof or hydrates thereof. More specifically, the catalyst can be selected from at least one of the group consisting of zinc acetate, sodium acetate, cobalt acetate and manganese acetate, hydrates thereof or anhydrides thereof.

[0048] The amount of catalyst fed (used) in step (2-1) is not particularly limited, but is preferably Part by weight of the waste polyester, specifically 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.

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

[0050] Specifically, step (2-2) may include performing a glycolysis reaction to perform a secondary cleavage of the first reactant obtained in step (2-1) using a second glycol-based compound to obtain a second reactant (second product). The second reactant may refer to the reactant obtained by step (2).

[0051] The second glycol-based compound used in the depolymerization of 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-based compound may be derived from the depolymerization process of step (2-1), or may be further added during the depolymerization process of step (2-2).

[0052] The feeding amount of the second ethylene glycol-based compound (the additional amount used in the second depolymerization) is not particularly limited, and can specifically 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 (for example, 1 to 7 times, 2 to 5 times, or 3 to 4 times) the weight of the pretreated waste polyester.

[0053] The depolymerization temperature in step (2-2) may be 150 to 170° C., 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 in 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 second depolymerization is reached. Since the depolymerization in step (2-2) is carried out within the above-mentioned temperature and time range, the second glycolysis reaction of the first reactant can proceed smoothly while minimizing the formation of side reactants such as diethylene glycol ester compounds.

[0054] The depolymerization in step (2-2) can be carried out in the presence of a catalyst, which can activate the second glycolysis reaction. The catalyst can be derived from the depolymerization process in step (2-1) or can be further added during the depolymerization process in step (2-2). The description of the catalyst is the same as that of the catalyst in the above step (2-1), so the detailed description is omitted.

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

[0056] Step (3): Purification

[0057] According to the present invention, step (3) is a step of purifying the reactant (depolymerization reactant) obtained by depolymerization in step (2). The purification of the reactant can be carried out by various steps.

[0058] For example, according to the present invention, the purification in step (3) may include cooling the reactant to a temperature of 100 to 150° C. and pressure filtering the reactant at a pressure of 0.01 to 0.5 MPa. Specifically, in the pressure filtration, the reactant is cooled by flash evaporation under reduced pressure, and then solid-liquid separation is performed by a pressure filtration procedure using a filter aid. As a result, the reactant can be converted into a liquid reactant. When the pressure filtration is performed, solid foreign matter such as particles and insoluble organic matter contained in the reactant is removed, thereby improving the purity and yield of the regenerated raw material composition.

[0059] The temperature of the reactants cooled by reduced pressure flash distillation can be specifically 100° C. to 135° C., 105° C. to 125° C., or 110° C. to 120° C. In addition, the pressure for reduced pressure flash distillation is not particularly limited, and can be specifically 200 Torr or less, 150 Torr or less, 100 Torr or less, 50 Torr or less, or 30 Torr or less and 5 Torr or more, 8 Torr or more, 10 or more Torr, 15 Torr or more (e.g., 5 to 200 Torr, 10 to 100 Torr, 15 to 50 Torr).

[0060] The pressure filtration rate of the reactant cooled by reduced pressure flash evaporation can reach 1.5L / min or more. Specifically, the pressure filtration rate of the reactant can be 2L / min or more, 2.5L / min or more, 3L / min or more, 3.5L / min or more, 4L / min or more, 4.5L / min or more, 5L / min or more or 5.5L / min or more (e.g., 1.5 to 6L / min, 3 to 5.7L / min, 4 to 5.6L / min or 4.5 to 5.5L / min). As described above, since the pressure filtration rate of the reactant is very high in the present invention, the overall process efficiency can be very high. By adjusting the apparent density of the waste polyester to 0.5kg / L or higher, the pressure filtration rate can be increased, thereby ensuring good separation of heterogeneous components in the waste polyester.

[0061] Meanwhile, the filter aid is not particularly limited as long as it is publicly known, but it may specifically include at least one selected from the group consisting of diatomaceous earth, perlite and asbestos powder.

[0062] According to the present invention, the purification in step (3) may include treating the reactants with an ion exchange resin. Land, can By passing the reactants through an ion exchange resin or adding an ion exchange resin to the reactants By carrying out the above process, the ionic impurities contained in the reactants can be removed, thereby obtaining high-purity reactants.

[0063] The ion exchange resin may be a well-known cation exchange resin, anion exchange resin, amphoteric ion exchange resin, chelate resin or a combination thereof.

[0064] The cation exchange resin can specifically include a strongly acidic cation exchange resin with a sulfonic acid group (-SO3H) or a weakly acidic cation exchange resin with a carboxyl group (-COOH). The anion exchange resin can include a strongly basic anion exchange resin in the form of a quaternary ammonium salt or a weakly basic anion exchange resin with a primary amine group to a tertiary amine group. Chelating resins can be polymeric resins with reactive functional groups, such as acetates or phosphates that can chelate metal ions, such as sodium, copper, nickel, zinc and manganese.

[0065] When the treatment is performed by adding an ion exchange resin to the reactants, the amount of the ion exchange resin charged (used amount) is not particularly limited, but may be 1 time or more, 2 times or more, 3 times or more, 5 times or more and 20 times or less, 15 times or less, 10 times or less, 8 times or less (e.g., 1 to 20 times, 2 to 15 times, 3 to 10 times or 5 to 8 times) the weight of the catalyst used for depolymerization in step (2). In addition, the amount of the ion exchange resin charged (used amount) 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) relative to 100 parts by weight of the waste polyester in step (2).

[0066] When the reactant is processed by an ion exchange resin, the ion exchange resin can be in the form of particles of a predetermined size. Specifically, the ion impurities can be removed by passing the reactant (e.g., 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 mm to 1.0 mm.

[0067] According to the present invention, the purification in step (3) may include cooling the reactant and crystallizing it. Specifically, crystallization by cooling may be performed by lowering the temperature of the reactant. The temperature for cooling the reactant to crystallize it is not particularly limited, but may specifically be 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. As crystallization by cooling is performed, impurities such as acetate compounds and diethylene glycol ester compounds may be effectively removed.

[0068] According to the present invention, the purification in step (3) may include distilling the reactants. Specifically, the distillation may be performed by subjecting the reactants to vacuum distillation to obtain the product and subjecting the product thus obtained to thin film evaporation.

[0069] The reactants can be vacuum distilled using a glass distillation apparatus or a rotary evaporator.

[0070] The conditions of vacuum distillation are not particularly limited, but can be carried out at a temperature of 150° C. or less and at a pressure of 0.1 to 200 Torr. More specifically, the pressure for vacuum 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 vacuum distillation can be 90° C. or more, 100° C. or more, 110° C. or more, and 145° C. or less, 140° C. or less, 135° C. or less (e.g., 90 to 150° C., 100 to 145° C., 120 to 135° C., or 100 to 130° C.).

[0071] Unreacted glycol-based compounds (such as ethylene glycol and diethylene glycol) contained in the reactants can be removed and recovered by vacuum distillation, and the recovered glycol-based compounds can be reused in the depolymerization process of step (2).

[0072] The thin film evaporator includes an evaporator, a scraped rotor and a condenser, and can be used for thin film evaporation of reactants.

[0073] The conditions for thin film evaporation are not particularly limited, but can be performed at a temperature of 150 to 200° C. and a pressure of 0.005 to 5 Torr. More specifically, the pressure for thin film evaporation can 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 thin film evaporation (internal film temperature of thin film evaporator) can be 180 to 240° C., 185 to 230° C., 190 to 225° C., 195 to 220° C., or 200 to 220° C.

[0074] Oligomers (such as BHET dimers and BHET trimers) contained in the reactants, such as dimers or higher polymers, can be effectively removed by thin film evaporation.

[0075] At the same time, according to the types of impurities, pressure filtration, ion exchange resin treatment, cooling crystallization, vacuum distillation, thin film evaporation can be carried out to purify the reactants, and the order of each step can be appropriately selected.

[0076] In the present invention, by the purification in step (3), a high-purity regeneration raw material composition can be prepared in high yield. In particular, in the present invention, a regeneration raw material composition in which the content of specific impurities is controlled within a certain range or lower and the content of bis(2-hydroxyethyl) terephthalate (BHET) as a desired component is significantly high can be prepared.

[0077] Specifically, the components of the recycled raw material composition obtained by depolymerizing the waste polyester can be confirmed by measuring the peak area ratio (%) of the analyzed component to the total peak area in the spectrum obtained by analyzing the recycled raw material composition by high performance liquid chromatography (HPLC). In this case, when the peak area ratio of the component regarded as an impurity is small and the peak area ratio of BHET as a desired component is high, the purity of the recycled raw material composition is likely to be high.

[0078] For example, according to the present invention, when the regeneration raw material composition obtained by steps (1) to (3) is analyzed by high performance liquid chromatography (HPLC), the sum (x+y) of the peak area ratio (x) of the diethylene glycol ester (DEG-ester) compound and the peak area ratio (y) of monohydroxyethyl terephthalate (MHET) may be less than 4.0%. Specifically, the sum (x+y) of the peak area ratios 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%). If the diethylene glycol ester (DEG-ester) compound remains in the recycled raw material composition, the melting point of the recycled polyester resin prepared using the recycled raw material composition will be reduced, thereby deteriorating the heat resistance of the recycled polyester resin. However, since the content of the diethylene glycol ester (DEG-ester) compound in the recycled raw material composition of the present invention is controlled to a minimum, it is advantageous to use it as a polymerization raw material for preparing a recycled polyester resin having excellent heat resistance.

[0079] The diethylene glycol ester (DEG-ester) compound 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.

[0080] According to the present invention, when the regeneration raw material composition obtained by steps (1) to (3) is analyzed by high performance liquid chromatography (HPLC), the peak area ratio of the acetate ester (HA-ester) compound may be less than 0.4%. Specifically, the peak area ratio of the acetate ester (HA-ester) compound 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. 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 acetate ester (HA-ester) compound remains in the recycled raw material composition, when the recycled raw material composition is used to prepare a recycled polyester resin, it may act as a terminator that inhibits the growth of the polymer chain, thereby deteriorating the heat resistance of the recycled polyester resin. However, since the content of the acetate ester (HA-ester) compound in the recycled raw material composition of the present invention is controlled to a minimum, it is advantageous to use it as a polymerization raw material for preparing a recycled polyester resin having excellent heat resistance.

[0081] The acetate ester (HA-ester) compound may include 2-hydroxyethyl (2-acetoxyethyl) terephthalate.

[0082] According to the present invention, when the regeneration raw material composition obtained by steps (1) to (3) is analyzed by high performance liquid chromatography (HPLC), the peak area ratio of bis(2-hydroxyethyl) terephthalate (BHET) can be 95% or more. Specifically, the peak area ratio of bis(2-hydroxyethyl) terephthalate (BHET) can 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%). As described above, since the peak area ratio of bis(2-hydroxyethyl) terephthalate (BHET), the desired component, in the regeneration raw material composition of the present invention is significantly higher, high purity and high yield can be achieved.

[0083] According to the present invention, when the regenerative raw material composition is prepared by steps (1) to (3), the process yield (Y) obtained according to the following equation 1 can reach 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%).

[0084] [Equation 1]

[0085] Y(%)=(W1 / W2)×100

[0086] In equation 1, W1 is the weight of the recycled raw material composition obtained through steps (1) to (3) (the actual weight of the recycled raw material composition obtained by the chemical recycling process), and W2 is the theoretical weight of the recycled raw material composition prepared using waste polyester in step (1) (the theoretical weight of the recycled raw material composition that can be obtained by the chemical recycling process of waste polyester).

[0087] Recycled raw material composition

[0088] The recycled raw material composition according to the present invention is prepared by the above-mentioned method for preparing the recycled raw material composition. Specifically, the recycled raw material composition may include a high content of recycled bis(2-hydroxyethyl) terephthalate (r-BHET) formed by depolymerization of waste polyester.

[0089] According to the present invention, since the recycled raw material composition contains a high content of recycled bis(2-hydroxyethyl) terephthalate (r-BHET), and the content of impurities (such as MHET, DEG-ester, HA-ester, BHET dimer, BHET trimer, etc.) is controlled within a certain range or lower, it can be well used to prepare recycled polyester resin. In particular, since the recycled bis(2-hydroxyethyl) terephthalate (r-BHET) contained in the recycled raw material composition has crystallinity and high purity, its physical properties are comparable to those of original bis(2-hydroxyethyl) terephthalate (original BHET). Therefore, when using recycled bis(2-hydroxyethyl) terephthalate (r-BHET) to prepare recycled polyester resin, a recycled polyester resin with excellent properties such as heat resistance, weather resistance, color characteristics, etc. can be provided.

[0090] Invention Mode

[0091] The present invention will be described in detail below with reference to Examples. However, these Examples are only for illustrative purposes and the present invention is not limited thereto.

[0092] [Example 1]

[0093] Step (1): Preprocessing

[0094] The waste polyester fabric with an apparent density of 0.1 kg / L or less is fed into a twin-screw extruder and subjected to melt extrusion pretreatment at a barrel temperature of 250°C and an extrusion speed of 200 rpm for 3 minutes to obtain 1000 g of waste polyester fabric with adjusted apparent density.

[0095] Step (2): Depolymerization

[0096] 1000 g of the above-obtained waste polyester fabric, 2000 g of ethylene glycol and 15.0 g of anhydrous zinc acetate were placed in a first reactor made of stainless steel (SUS). The temperature in the first reactor was raised to 180°C. The first depolymerization (first sugar The first reactant is then reacted with the lysate for 2 hours. The obtained first reactant was transferred to a second reactor and cooled to 150° C. Then, 2000 g of ethylene glycol was further added to the second reactor, and a second depolymerization (second sugar decomposition reaction) was performed for 2 hours while the reactor temperature was maintained at 150° C. to obtain a second reactant.

[0097] Step (3): Purification

[0098] The second reactant is cooled to 120° C. by flash evaporation under reduced pressure, and then filtered under high temperature and pressure (solid-liquid separation) to obtain a liquid reactant.

[0099] The obtained liquid reactant was passed through a column filled with an 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.

[0100] The mixture was transferred to a 10L distillation apparatus and vacuum distilled at 130°C to remove (recover) unreacted ethylene glycol. Subsequently, the third reactant from which ethylene glycol was removed was subjected to thin film evaporation in a thin film evaporator (VTA VKL70-4S) at 220°C and 0.08 Torr to obtain a fourth reactant from which dimers or oligomers above dimers were removed.

[0101] Thereafter, for adsorption-crystallization, the fourth reactant and distilled water were charged into a 20 L glass reactor and dissolved at a temperature of 70° C. Then, activated carbon was added thereto, followed by stirring for 30 minutes and filtering. Next, the filtrate obtained by filtration was cooled to room temperature for crystallization, filtered again, and dried in a vacuum oven, thereby preparing a regenerated raw material composition containing regenerated bis(2-hydroxyethyl) terephthalate.

[0102] [Example 2]

[0103] A recycled raw material composition was prepared by the same process as in Example 1, except that waste polyester banner was used instead of waste polyester fabric, and the pretreatment conditions were adjusted as shown in Table 1 below.

[0104] [Example 3]

[0105] A recycled raw material composition was prepared by the same process as in Example 1, except that waste polyester film waste was used instead of waste polyester fabric, and the pretreatment conditions were adjusted as shown in Table 1 below.

[0106] [Example 4]

[0107] A recycled raw material composition was prepared by the same process as in Example 1, except that the pretreatment conditions of the waste polyester fabric were adjusted as shown in Table 1 below.

[0108] [Example 5]

[0109] A recycled raw material composition was prepared by the same process as in Example 1, except that the pretreatment conditions of the waste polyester fabric were adjusted as shown in Table 1 below.

[0110] [Example 6]

[0111] A recycled raw material composition was prepared by the same process as in Example 1, except that the pretreatment conditions of the waste polyester fabric were adjusted as shown in Table 1 below.

[0112] [Comparative Example 1]

[0113] A recycled raw material composition was prepared by the same process as Example 1, except that the pretreatment of the waste polyester fabric was omitted.

[0114] [Comparative Example 2]

[0115] A recycled raw material composition was prepared by the same process as in Example 2, except that the pretreatment of the waste polyester banner was omitted.

[0116] [Comparative Example 3]

[0117] A recycled raw material composition was prepared by the same process as in Example 3, except that the pretreatment of the waste polyester film waste was omitted.

[0118] [Comparative Example 4]

[0119] A recycled raw material composition was prepared by the same process as in Example 1, except that, instead of pre-treating by melt extrusion, waste polyester fabric having an apparent density of 0.1 kg / L or less was fed into a reactor capable of crushing and crystallization, and pre-treated (heat setting) by heating at 220°C for 60 minutes to obtain waste polyester fabric having adjusted apparent density.

[0120] [Comparative Example 5]

[0121] A recycled raw material composition was prepared by the same procedure as Comparative Example 4, except that waste polyester banner was used instead of waste polyester fabric.

[0122] [Comparative Example 6]

[0123] A recycled raw material composition was prepared by the same procedure as in Comparative Example 4, except that waste polyester film waste was used instead of waste polyester fabric.

[0124] [Test example]

[0125] The materials obtained in Examples 1 to 6 and Comparative Examples 1 to 6 were tested by the following methods, respectively. The results are shown in Tables 1 and 2 below.

[0126] (1) High performance liquid chromatography (HPLC)

[0127] 0.01 g of the sample (regeneration raw material composition) was diluted with 20 mL of methanol and analyzed by high performance liquid chromatography (HPLC) (mode: 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). Then, the peak area percentage (%) of the following components in the total HPLC peak area was determined.

[0128] -MHET: Monohydroxyethyl terephthalate

[0129] -BHET: bis(2-hydroxyethyl) terephthalate,

[0130] -DEG-ester-1: 2-hydroxyethyl[2-(2-hydroxyethoxy)ethyl]terephthalate

[0131] -DEG-ester-2: bis[2-(2-hydroxyethoxy)ethyl]benzene-1,4-dicarboxylate

[0132] -HA-ester: 2-hydroxyethyl (2-acetoxyethyl) terephthalate

[0133] -Dimer BHET dimer

[0134] -Trimer BHET trimer

[0135] (2) Apparent density (kg / L)

[0136] Each waste polyester was filled into a 2L flask of known volume without pressure, the weight was measured, and the apparent density was calculated using the relationship between the measured weight and the volume of the flask. The results are shown in Tables 1 and 2 below.

[0137] (3) Pressurized filtration rate (L / min)

[0138] The pressure filtration rate of the depolymerization reactant (second reactant) was measured under the following conditions. The results are shown in Tables 1 and 2 below.

[0139] - Pressurized filtration area: 700cm 2 ; - Pressure filter size: 1μm; - Pressure: 0.01 to 0.5MPa

[0140] (4) Process yield (%)

[0141] The process yield of the regenerated raw material compound is calculated according to the following equation 1.

[0142] [Equation 1]

[0143] Y(%)=(W1 / W2)×100

[0144] In equation 1, W1 is the weight of the recycled raw material composition obtained through steps (1) to (3), and W2 is the theoretical weight of the recycled raw material composition prepared from the waste polyester used in step (1).

[0145] [Table 1]

[0146]

[0147]

[0148] [Table 2]

[0149]

[0150]

[0151] Referring to Tables 1 and 2 above, the apparent density of the waste polyester used as the depolymerization raw material is adjusted to 0.5 kg / L or higher through a melt extrusion pretreatment process, so that the depolymerization reaction can proceed smoothly. Even if the waste polyester contains heterogeneous components and a single component, the separation efficiency of the insoluble components can be improved, thereby preparing a high-purity recycled raw material composition with a high yield (see Examples 1 to 3).

[0152] However, if the temperature, extrusion speed and time are not optimally controlled during pretreatment and melt extrusion, the waste polyester will be excessively decomposed or not melted, and thus standardization cannot be achieved. Therefore, it is best to optimally control the conditions of melt extrusion (see Examples 4 to 6).

[0153] Meanwhile, when the recycled raw material composition is prepared without the pretreatment process, a recycled raw material composition having a high impurity content is prepared, and the yield is significantly low (see Comparative Examples 1 to 3). In addition, when the pretreatment is performed by a method other than melt extrusion, the apparent density of the waste polyester cannot be adjusted to 0.5 kg / L or more, and therefore, the purity and yield of the recycled raw material composition are reduced (see Comparative Examples 4 to 6).

Claims

1. A method for preparing a renewable raw material composition, comprising: (1) pretreating waste polyester having an apparent density of 0.1 kg / L or less to an apparent density of 0.5 kg / L or more; (2) depolymerizing the pretreated waste polyester; and (3) Purify the reactants obtained by depolymerization.

2. The method for preparing a recycled raw material composition according to claim 1, wherein the pretreatment in step (1) is carried out by melt extrusion.

3. The method for producing a recycled raw material composition according to claim 2, wherein the melt extrusion is performed at a temperature of 250 to 300°C and an extrusion rate of 100 to 350 rpm for 2 to 15 minutes.

4. The method for producing a renewable raw material composition according to claim 2, wherein the melt extrusion is performed without adding additives.

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

6. The method for preparing a recycled raw material composition according to claim 1, wherein the waste polyester to be pretreated in step (1) comprises waste polyester fabric, waste polyester film, waste polyester sheet, waste polyester powder or a combination thereof.

7. The method for preparing a renewable raw material composition according to claim 1, wherein step (2) comprises: (2-1) depolymerizing the waste polyester whose apparent density has been adjusted by a first glycolysis reaction at a temperature of 180 to 200° C. to obtain a first reactant; and (2-2) The first reactant is depolymerized by a second glycolysis reaction at a temperature of 150 to 170° C. to obtain a second reactant.

8. A method for preparing a recycled raw material composition according to claim 1, wherein step (3) comprises cooling the reactants to 100 to 150°C and pressure filtering the reactants at a pressure of 0.01 to 0.5 MPa, and the pressure filtration rate of the cooled reactants is 1.5 L / min or more.

9. The method for preparing a renewable raw material composition according to claim 1, wherein step (3) comprises cooling and crystallizing the reactants.

10. The method for preparing a renewable raw material composition according to claim 1, wherein step (3) comprises distilling the reactants.

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

12. The method for producing a regenerative raw material composition according to claim 1, wherein when the regenerative raw material composition obtained through steps (1) to (3) is analyzed by high performance liquid chromatography (HPLC), the peak area ratio of the acetate ester compound is less than 0.4%.

13. The method for producing a recycled raw material composition according to claim 1, wherein 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 is 95% or more.

14. The method for preparing a renewable raw material composition according to claim 1, wherein the process yield (Y) is 80% or more according to the following equation 1: [Equation 1] Y(%)=(W1 / W2)×100 In equation 1, W1 is the weight of the recycled raw material composition obtained through steps (1) to (3), and W2 is the theoretical weight of the recycled raw material composition prepared from the waste polyester used in step (1).

15. A renewable raw material composition, which is prepared by the preparation method according to any one of claims 1 to 14.

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