Patent Application
20250145793
The present invention relates to a plasticizer composition including 2-ethylhexyl(2-hydroxyethyl) terephthalate, di(n-butyl) terephthalate, (n-butyl)(2-ethylhexyl) terephthalate, and di(2-ethylhexyl) terephthalate, and a resin composition including the plasticizer composition.
Typically, in a plasticizer, an alcohol reacts with a polycarboxylic acid such as phthalic acid and adipic acid to form a corresponding ester. In addition, in consideration of domestic and international regulations on phthalate-based plasticizers which are harmful to the human body, studies have continued on plasticizer compositions which can replace phthalate-based plasticizers, such as terephthalate-based, adipate-based, and other polymer-based plasticizers.
Meanwhile, in all of the plastisol industry, car-rendering industry, or extrusion/injection compound industry that manufactures finished products such as flooring, wallpaper, soft and hard sheets, gloves, wires, hoses, films, etc., the demand for such eco-friendly products is increasing. In order to enhance the quality characteristics, processability, and productivity of each finished product, appropriate plasticizers should be used in consideration of discoloration, migration, mechanical properties, etc.
In these various areas of use, according to the characteristics required by each industry, such as tensile strength, elongation, light resistance, migration, gelling, or absorption rate, etc., auxiliary raw materials and the like such as a plasticizer, a filler, a stabilizer, a viscosity reducing agent, a dispersant, an anti-foaming agent, a foaming agent, etc. are mixed in a PVC resin.
For example, among plasticizer compositions applicable to PVC, when di(2-ethylhexyl) terephthalate (DEHTP), which is relatively inexpensive and most universally used, is applied, the hardness or sol viscosity is high, the absorption rate of a plasticizer is relatively slow, and the migration and stress degradation are not good.
In order to make an improvement thereon, as a composition containing DEHTP, it is possible to consider applying a product of a trans-esterification reaction with butanol as a plasticizer, but while the plasticization efficiency is improved, the mechanical properties are somewhat lowered, and there is an endemic problem in that the plasticizer is leaked by heat or physical force.
In addition, securing eco-friendliness has become very important recently, and not only securing eco-friendliness of a final product itself, but also securing eco-friendliness in the supply and demand of raw materials and processes are very important in the industry, but due to the conflict of interest with securing cost competitiveness, which is the first task in the industry, there is a need to develop products that are eco-friendly in terms of raw materials, preparation processes, and final products, and also cost-competitive.
The present invention is to provide an eco-friendly plasticizer composition which is not toxic to reproductive development while having performance equal to or higher than that of a typical phthalate-based plasticizer by applying a composition obtained by an trans-esterification reaction between 2-ethylhexyl(2-hydroxyethyl) terephthalate and di(2-ethylhexyl) terephthalate, which are obtainable during a decomposition process of polyethylene terephthalate, and n-butanol, to a plasticizer.
In addition, the present invention is to provide a method for preparing a plasticizer composition, the method capable of preparing a plasticizer composition having excellent physical properties economically and eco-friendly by using discarded polyethylene terephthalate as a raw material.
In order to solve the above problem, the present invention provides a plasticizer composition, a method for preparing the plasticizer composition, and a resin composition including the plasticizer composition.
(1) The present invention provides a plasticizer composition including 2-ethylhexyl(2-hydroxyethyl) terephthalate, di(n-butyl) terephthalate, (n-butyl)(2-ethylhexyl) terephthalate, and di(2-ethylhexyl) terephthalate, wherein the content of the 2-ethylhexyl(2-hydroxyethyl) terephthalate is 20 wt % or less based on the total plasticizer composition.
(2) In (1) above, the present invention provides a plasticizer composition, wherein the content of 2-ethylhexyl(2-hydroxyethyl) terephthalate is 0.01 wt % to 15 wt %.
(3) In (1) or (2) above, the present invention provides a plasticizer composition, wherein the plasticizer composition further includes n-butyl(2-hydroxyethyl) terephthalate.
(4) In any one of (1) to (3) above, the present invention provides a plasticizer composition, wherein the plasticizer composition further includes di(n-butyl) isophthalate, (n-butyl)(2-ethylhexyl) isophthalate, and di(2-ethylhexyl) isophthalate.
(5) In any one of (1) to (4) above, the present invention provides the plasticizer composition further includes a by-product including any one or more among dimer compounds represented by Formulas 1 to 5 below.
(6) In (5) above, the present invention provides a plasticizer composition, wherein the total content of the by-product in the composition is 0.1 wt % to 5.0 wt %.
(7) In (5) or (6) above, the present invention provides a plasticizer composition, wherein the weight ratio between the by-product and the 2-ethylhexyl(2-hydroxyethyl) terephthalate in the composition is 1:1 to 10.
(8) In (5) to (7) above, the present invention provides a plasticizer composition, wherein the weight ratio between the by-product and the total content of di(n-butyl) terephthalate, (n-butyl)(2-ethylhexyl) terephthalate, and di(2-ethylhexyl) terephthalate in the composition is 1:20.0 to 150.0.
(9) The present invention provides a method for preparing a plasticizer composition according to any one among (1) to (8), wherein the method includes a step of mixing polyethylene terephthalate and 2-ethylhexanol in the presence of a catalyst to perform an esterification reaction, wherein a product of the esterification reaction includes 2-ethylhexyl(2-hydroxyethyl) terephthalate and di(2-ethylhexyl) terephthalate.
(10) In (9) above, the present invention provides a method for preparing a plasticizer composition, wherein the polyethylene terephthalate is mixed in an amount of 80 wt % or less, with respect to the sum of contents of polyethylene terephthalate and 2-ethylhexanol.
(11) In (9) or (10) above, the present invention provides a method for preparing a plasticizer composition, wherein the polyethylene terephthalate is mixed in an amount of 60 wt % or less, with respect to the sum of contents of polyethylene terephthalate and 2-ethylhexanol.
(12) In any one of (9) to (11) above, the present invention provides a method for preparing a plasticizer composition, wherein the polyethylene terephthalate includes discarded and recycled polyethylene terephthalate.
(13) The present invention provides a resin composition including 100 parts by weight of a resin and 5 parts by weight to 150 parts by weight of a plasticizer composition according to any one among (1) to (8).
(14) In (13) above, the present invention provides a resin composition, wherein the resin is one or more selected from the group consisting of a straight vinyl chloride polymer, a paste vinyl chloride polymer, an ethylene vinyl acetate copolymer, an ethylene polymer, a propylene polymer, polyketone, polystyrene, polyurethane, polylactic acid, natural rubber, and synthetic rubber.
A plasticizer composition according to the present invention is an eco-friendly material which is not toxic to reproductive development, and may improve mechanical properties, migration resistance, stress migration, and absorption rate when used in a resin composition when compared to a typical plasticizer, and such a top-down preparation method utilizes waste, and thus is an eco-friendly preparation method, and at the same time, may have excellent cost competitiveness.
It will be understood that words or terms used in the specification and claims of the present invention shall not be construed as being limited to having the meaning defined in commonly used dictionaries. It will be further understood that the words or terms should be interpreted as having meanings that are consistent with their meanings in the context of the relevant art and the technical idea of the invention, based on the principle that an inventor may properly define the meaning of the words or terms to best explain the invention.
The term “composition” as used herein includes not only a reaction product and a decomposition product formed from materials of a corresponding composition, but also a mixture of materials including the corresponding composition.
As used herein, a “straight vinyl chloride polymer” is one of the types of vinyl chloride polymers, which is polymerized through suspension polymerization, bulk polymerization, or the like. The polymer is a porous particle with multiple pores, and has a size of tens to hundreds of micrometers, has no cohesiveness, and has excellent flowability.
As used herein, a “paste vinyl chloride polymer” is one of the types of vinyl chloride polymers, which is polymerized through micro-suspension polymerization, micro-seed polymerization, or emulsion polymerization, or the like. The polymer is a fine and dense particle with no pores, and has a size of tens to thousands of nanometers, has cohesiveness, and has poor flowability.
The terms ‘including’ and ‘having,’ and derivatives thereof, whether they are specifically disclosed or not, do not intend to exclude the presence of any additional components, steps or procedures. In order to avoid any uncertainty, all compositions claimed through the use of the term ‘including’ may include any additional additives, supplements, or compounds, whether they are polymers or others, unless otherwise stated. In contrast, the term ‘consisting essentially of’ excludes any other components, steps, or procedures from the scope of any subsequent description, except that it is not essential to operability. The term ‘consisting of’ excludes any components, steps or procedures which are not specifically stated or listed.
In the present specification, the content analysis of components in a composition is performed through gas chromatography measurement, and the analysis is performed using a gas chromatography device of Agilent (product name: Agilent 7890 GC, column: HP-5, carrier gas: helium (flow rate 2.4 mL/min), detector: F.I.D, injection volume: 1 uL, initial value: 70° C./4.2 min, end value: 280° C./7.8 min, program rate: 15° C./min).
In the present specification, a ‘hardness’ means a shore hardness (Shore “A” and/or Shore “D”) at 25° C. measured under a condition of 3 T 10 s using ASTM D2240, which may be an index for evaluating plasticization efficiency, and the lower the hardness, the more excellent plasticization efficiency.
In the present specification, a ‘tensile strength’ is calculated by Equation 1 below after measuring a point at which a specimen is cut after pulling the specimen at a cross head speed of 200 mm/min (1 T) using a U.T.M (manufacturer; Instron, model name; 4466), which is a test device, by the ASTM D638 method.
In the present specification, an ‘elongation rate’ is calculated by Equation 2 below after measuring a point at which a specimen is cut after pulling the specimen at a cross head speed of 200 mm/min (1 T) using the U.T.M by the ASTM D638 method.
In the present specification, a ‘migration loss’ may be measured according to KSM-3156. Specifically, a test piece having a thickness of 1 mm is obtained, and an absorption sheet capable of moving to both sides of the test piece, thereby absorbing an organic material discharged to the surface of the test piece is added, and then a plate which is able to cover the entire test body is attached thereon to apply a load of 1 kgf/cm2. The test piece is left to stand for 72 hours in a hot-air circulation-type oven (80° C.), and then is taken out of the oven and cooled for 4 hours at room temperature. Thereafter, the plate and the absorption sheet attached to both sides of the test piece are removed, and then the weights of the specimen before and after the specimen is left in the oven are measured to calculate a migration loss amount by Equation 3 below.
In the present specification, a ‘volatile loss’ is obtained by working on a specimen at 80° C. for 72 hours, and then measuring the weight of the specimen.
In the case of the above various measurement conditions, detailed conditions such as temperature, rotation speed, time, and the like may be slightly different depending on a case, and when detailed conditions are different, measurement methods and conditions thereof are specified separately.
In the present specification, an ‘absorption rate’ is evaluated, under the conditions of 77° C. and 60 rpm, by measuring the time taken from when a resin and a plasticizer were mixed with each other using a planetary mixer (Brabender, P600) until when the torque of the mixer is stabilized.
In the case of the above various measurement conditions, detailed conditions such as temperature, rotation speed, time, and the like may be slightly different depending on a case, and when detailed conditions are different, measurement methods and conditions thereof are specified separately.
Hereinafter, the present invention will be described in more detail to facilitate understanding of the present invention.
The present invention provides a plasticizer composition including 2-ethylhexyl(2-hydroxyethyl) terephthalate, di(n-butyl) terephthalate, (n-butyl)(2-ethylhexyl) terephthalate, and di(2-ethylhexyl) terephthalate, wherein the content of the 2-ethylhexyl(2-hydroxyethyl) terephthalate is 20 wt % or less, based on the total plasticizer composition.
The plasticizer composition including the 2-ethylhexyl(2-hydroxyethyl) terephthalate and the di(2-ethylhexyl) terephthalate may be obtained by trans-esterifying a product, which has been produced by a transesterification reaction between polyethylene terephthalate (hereinafter, PET) and 2-ethylhexanol, with n-butanol.
In general, as a means for obtaining di(2-ethylhexyl) terephthalate utilized as a typical general-purpose plasticizer, there is a case in that PET and 2-ethylhexanol are reacted with each other, but there are problems in that a large amount of by-products is generated, and it is not easy to separate bis(2-hydroxyethyl) terephthalate or 2-ethylhexyl(2-hydroxyethyl) terephthalate, which is produced during the reaction process, from di(2-ethylhexyl) terephthalate. In addition, bis(2-hydroxyethyl) terephthalate and 2-ethylhexyl(2-hydroxyethyl) terephthalate are alcohol-based compounds including a hydroxyl group in the intra-molecular structure thereof, so that there may be another problem in that a side reaction with di(2-ethylhexyl) terephthalate, which is a target product, may even occur. Therefore, as a method for preparing di(2-ethylhexyl) terephthalate, almost every manufacturer uses a direct esterification reaction of terephthalic acid and 2-ethylhexanol or a trans-esterification reaction of dimethyl terephthalate and 2-ethylhexanol, and does not use a method of utilizing PET as a raw material.
However, in the present invention, it has been confirmed that it is possible to provide a plasticizer composition having improved performance compared to a typical plasticizer product by focusing on a function of 2-ethylhexyl(2-hydroxyethyl) terephthalate, which is typically regarded as an impurity, and thus is a target to be removed, and allowing the 2-ethylhexyl(2-hydroxyethyl) terephthalate to be included in a predetermined amount in the plasticizer composition instead of removing the same. 2-ethylhexyl(2-hydroxyethyl) terephthalate is not easily separated from di(2-ethylhexyl) terephthalate, but serves to solve a problem of compression migration of the di(2-ethylhexyl) terephthalate, that is, the problem in which a plasticizer is discharged due to heat or pressure. Particularly, due to the presence of a hydroxy group in the intra-molecular structure, 2-ethylhexyl(2-hydroxyethyl) terephthalate may bond more firmly with a resin to be mixed, and may perform a role in holding di(2-ethylhexyl) terephthalate, which is a major component in the plasticizer composition, so as not to be discharged to the outside of the resin.
Furthermore, the plasticizer composition of the present invention is obtained by subjecting a product obtained as a result of a reaction between PET and 2-ethylhexanol to another trans-esterification reaction with n-butanol, and includes a compound in which at least one 2-ethylhexyl group of di(2-ethylhexyl) terephthalate is substituted with an n-butyl group, and more specifically, includes di(n-butyl) terephthalate and (n-butyl)(2-ethylhexyl) terephthalate. The two components complement the plasticization efficiency of di(2-ethylhexyl) terephthalate and ethylhexyl(2-hydroxyethyl) terephthalate in the plasticizer composition, and thus may further improve the overall plasticization efficiency of the plasticizer composition.
Based on the combined weight of di(n-butyl) terephthalate, (n-butyl)(2-ethylhexyl) terephthalate, and di(2-ethylhexyl) terephthalate in the plasticizer composition, the di(n-butyl) terephthalate may be included in an amount of 0.1 wt % to 20 wt %, the (n-butyl)(2-ethylhexyl) terephthalate may be included in an amount of 5 wt % to 50 wt %, and di(2-ethylhexyl) terephthalate may be included in an amount of 30 wt % to 90 wt %. When the wt % of each component is within the above range, the overall physical properties may be excellent, and the balance between physical properties may also be excellent.
According to an embodiment of the present invention, the content of the 2-ethylhexyl(2-hydroxyethyl) terephthalate may be 20 wt % or less, based on the total plasticizer composition. Illustratively, based on the total plasticizer composition, the content of the 2-ethylhexyl(2-hydroxyethyl) terephthalate may be 0.01 wt % or greater, 0.05 wt % or greater, 0.06 wt % or greater, 0.08 wt % or greater, 0.10 wt % or greater, 0.50 wt % or greater, 0.90 wt % or greater, 1.0 wt % or greater, 2.0 wt % or greater, 3.0 wt % or greater, 4.0 wt % or greater, 4.5 wt % or greater, 4.9 wt % or greater, 5.0 wt % or greater, 5.5 wt % or greater, 7.5 wt % or greater, 8.0 wt % or greater, 20.0 wt % or less, 19.5 wt % or less, 19.0 wt % or less, 18.0 wt % or less, 17.0 wt % or less, 16.0 wt % or less, 15.0 wt % or less, 14.9 wt % or less, 14.5 wt % or less, 13.0 wt % or less, 12.8 wt % or less, 12.5 wt % or less, 12.4 wt % or less, 12.0 wt % or less, 11.7 wt % or less, 11.5 wt % or less, 11.3 wt % or less, 11.0 wt % or less, 10.5 wt % or less, 10.0 wt % or less, 9.5 wt % or less, 9.3 wt % or less, 8.0 wt % or less, 8.6 wt % or less, 8.5 wt % or less, 8.0 wt % or less, 7.5 wt % or less, 7.2 wt % or less, 7.0 wt % or less, 6.5 wt % or less, 6.0 wt % or less, 5.5 wt % or less, 5.0 wt % or less, 4.5 wt % or less, 4.0 wt % or less, 3.5 wt % or less, 3.0 wt % or less, 2.5 wt % or less, or 2.0 wt % or less. Preferably, the content of terephthalate may be 1.0 wt % to 20 wt % based on the total plasticizer composition. In addition, the weight ratio between the 2-ethylhexyl(2-hydroxyethyl) terephthalate and the di(2-ethylhexyl) terephthalate may be 1:3.5 to 10000, preferably 1:3.5 to 1000, and more preferably 1:3.5 to 100. When the content of 2-ethylhexyl(2-hydroxyethyl) terephthalate in the plasticizer composition is too small, the above-described effect of improving migration resistance of 2-ethylhexyl(2-hydroxyethyl) terephthalate may be insignificant, and on the contrary, when the content of 2-ethylhexyl(2-hydroxyethyl) terephthalate is excessively large, the content of di(2-ethylhexyl) terephthalate becomes relatively small, so that the volatile loss becomes poor, and the absorption rate increases excessively, which may cause blending with the resin and the process conditions for finished products to be unstable, and accordingly, the overall heat resistance of a resin composition or a finished product obtained from the resin composition may be degraded. Particularly, when the 2-ethylhexyl(2-hydroxyethyl) terephthalate is included as a main component in the plasticizer composition, it may be difficult to blend with a resin due to the molecular weight of 2-ethylhexyl(2-hydroxyethyl) terephthalate which is relatively low, and a rolling process or the like after the blending may not be smoothly performed. When the content of 2-ethylhexyl(2-hydroxyethyl) terephthalate satisfies the above-described preferred range, an appropriate volatile loss and an appropriate absorption rate may be implemented, so that it is possible to provide a plasticizer composition which has excellent heat resistance, and which may be stably blended with a resin composition.
The plasticizer composition of the present invention may further include n-butyl(2-hydroxyethyl) terephthalate, in addition to the above-described components. 2-ethylhexyl(2-hydroxyethyl) terephthalate formed as a result of the trans-esterification reaction between PET and 2-ethylhexanol may also react with n-butanol which is added subsequently, like di(2-ethylhexyl) terephthalate, and since a 2-ethylhexyl group of the 2-ethylhexyl(2-hydroxyethyl) terephthalate is substituted with an n-butyl group, n-butyl(2-hydroxyethyl) terephthalate may be included in the plasticizer composition. The n-butyl(2-hydroxyethyl) terephthalate may implement a function similar to that of the above-described 2-ethylhexyl(2-hydroxyethyl) terephthalate, and may be included in an amount of 20 wt % or less, 15 wt % or less, 10 wt % or less, or 5 wt % or less, based on the content of the total plasticizer composition.
In addition, the plasticizer composition of the present invention may further include di(n-butyl) isophthalate, (n-butyl)(2-ethylhexyl) isophthalate, and di(2-ethylhexyl) isophthalate, in addition to the above-described components.
Polyethylene terephthalate includes isophthalate, which is an isomer of terephthalate, in a trace amount in the molecular structure thereof, and such an isophthalate structure may form the di(n-butyl) isophthalate, the (n-butyl)(2-ethylhexyl) isophthalate, and the di(2-ethylhexyl) isophthalate through the above-described series of trans-esterification reaction processes. In a typical reaction process for recovering di(2-ethylhexyl) terephthalate from PET, such isophthalate-based components are regarded as impurities, so that all isophthalate-based components are removed from a final composition, but in the present invention, when the above isophthalate-based components are partially included in the plasticizer composition, it is possible to implement better physical properties than when only terephthalate is used alone, while maintaining a balance of the physical properties. Therefore, plasticizer composition of the present invention may further include di(n-butyl) isophthalate, (n-butyl)(2-ethylhexyl) isophthalate, and di(2-ethylhexyl) isophthalate.
As the isophthalate content in PET, which is a reaction raw material, is low, the content of isophthalate-based components in the plasticizer composition of the present invention obtained from the PET is also low, and specifically, the combined content of the three components based on the total composition may be 5 wt % or less, preferably 0.3 wt % to 3 wt %. It is not easy to increase the content of the isophthalate-based components above the above-described range due to the structure of the PET, which is a reaction raw material, and when the content of the isophthalate-based components is lower than the above-described range, by an improvement effect obtained including the isophthalate-based components is insignificant.
Meanwhile, when the plasticizer composition further includes di(n-butyl) isophthalate, (n-butyl)(2-ethylhexyl) isophthalate, and di(2-ethylhexyl) isophthalate, as the content % therebetween, the content % of di(n-butyl) terephthalate, (n-butyl)(2-ethylhexyl) terephthalate, and di(2-ethylhexyl) terephthalate described above may be equally applied.
According to an embodiment of the present invention, the plasticizer composition of the present invention may further include a by-product including any one or more among dimer compounds represented by Formulas 1 to 5 below.
In the present invention, like the above-described 2-ethylhexyl(2-hydroxyethyl) terephthalate, a dimer compound, which is one of by-products, having a ((terephthalate or isophthalate)-(ethylene glycol)-(terephthalate or isophthalate)) structure is controlled to be included in a predetermined content in the plasticizer composition, it has been confirmed that it is possible to provide a plasticizer composition having improved performance compared to a typical plasticizer product. Polyethylene terephthalate includes isophthalate, which is an isomer of terephthalate, in a trace amount in the molecular structure thereof, and such an isophthalate structure may be generated as a dimer compound including the isophthalate through the above-described series of trans-esterification reaction processes.
The dimer compound included in the by-product may be prepared in various forms and contents depending on the type of alcohol used or reaction conditions in a depolymerization process of PET, and since compounds having such a structure are included together with a terephthalate-based plasticizer in the plasticizer composition, it is possible to complement the compression migration of a typical terephthalate-based plasticizer.
For example, in a process in which di(2-ethylhexyl) terephthalate, which is a monomer, is synthesized by a reaction between 2-ethylhexanol and PET, a dimer compound in which 2-ethylhexanol is bonded to each terminal of two terephthalic acids may be generated, and the dimer compound may be included in a final plasticizer composition.
The process of forming a dimer compound described above may be an example, and in addition to the formation process described above, dimer compounds in various combinations may be formed by various reactions among di(2-hydroxyethyl) terephthalate, 2-ethylhexyl(2-hydroxyethyl) terephthalate, and 2-ethylhexyl(2-hydroxyethyl) isophthalate.
In addition, the contents of the di(2-ethylhexyl) terephthalate, 2-ethylhexyl(2-hydroxyethyl) terephthalate, and the dimer compound may be controlled by intentionally controlling the trans-esterification reaction in the preparation method described above. Meanwhile, the by-product may further include, in addition to the dimer compound, a trimer and/or tetramer compound. When reaction time is controlled during the trans-esterification reaction, a relatively large amount of by-products such as a trimer and/or tetramer compound as well as a dimer compound may be produced depending on the reaction time, and since the by-product maintains performance of final processing physical properties of the entire plasticizer composition of di(2-ethylhexyl) terephthalate and 2-ethylhexyl(2-hydroxyethyl) terephthalate at a usable level without degrading the performance, a reaction product including the above by-product may be used as a plasticizer composition as it is.
In addition, the content of the by-product may be determined according to the amount of a catalyst used in the preparation method, the amounts of 2-ethylhexanol and n-butanol to be added, the reaction pressure and temperature, the reaction progression time, and the like. In particular, as the amount of n-butanol added is increased, the n-butanol decomposes the bond of the dimer compound among the by-products and converts the dimer compound into (n-butyl)(2-ethylhexyl) terephthalate and di(n-butyl) terephthalate, so that the contents of (n-butyl)(2-ethylhexyl) terephthalate and di(n-butyl) terephthalate may be increased, whereas the contents of the dimer compound and the by-product including the same may be decreased. In the plasticizer composition provided by the present invention, the total content of the by-product including the dimer compound in the composition may be 0.1 wt % to 5.0 wt %, and illustratively, the total content of the dimer compound in the composition may be 0.1 wt % or greater, 0.2 wt % or greater, 0.3 wt % or greater, 0.5 wt % or greater, 0.8 wt % or greater, 1.0 wt % or greater, 1.2 wt % or greater, 1.5 wt % or greater, 5.0 wt % or less, 4.5 wt % or less, 4.0 wt % or less, 3.5 wt % or less, 3.2 wt % or less, 3.1 wt % or less, 3.0 wt % or less, 2.7 wt % or less, 2.5 wt % or less, 2.3 wt % or less, 2.0 wt % or less, or 1.7 wt % or less. Preferably, the total content of the by-product in the composition may be 0.5 wt % to 3.5 wt %. When the content of the by-product is controlled within the above-described range, it is possible to provide a plasticizer composition having plasticizer efficiency properties equal to or higher than those of a typical plasticizer product, and having excellent mechanical properties, such as tensile strength and tensile residual rate, migration loss, absorption rate, and stress resistance.
In addition, the weight ratio between the by-product and 2-ethylhexyl(2-hydroxyethyl) terephthalate in the composition may be 1:1 to 10, and illustratively, 1:1.0 or greater, 1.2 or greater, 1.5 or greater, 1.7 or greater, 2.0 or greater, 2.5 or greater, 2.7 or greater, 3.0 or greater, 3.5 or greater, 4.0 or greater, 4.5 or greater, 4.7 or greater, 5.0 or greater, 10.0 or less, 9.7 or less, 9.5 or less, 9.2 or less, 9.0 or less, 8.5 or less, 8.3 or less, 8.0 or less, 7.5 or less, 7.0 or less, 6.5 or less, 6.0 or less, 5.7 or less, or 5.5 or less. Preferably, the weight ratio between the by-product and the 2-ethylhexyl(2-hydroxyethyl) terephthalate in the composition may be 1:5 to 8. When the weight ratio between the by-product and the 2-ethylhexyl(2-hydroxyethyl) terephthalate in the plasticizer composition satisfies the above range, the effect of improving migration resistance may be excellent, and the volatile loss and absorption rate may be excellent to smoothly perform blending with a resin and a rolling process after the blending, so that processing stability may increase.
In addition, the weight ratio between the by-product and the total content of di(n-butyl) terephthalate, (n-butyl)(2-ethylhexyl) terephthalate, and di(2-ethylhexyl) terephthalate in the composition may be 1:20 to 150, and illustratively, 1:20 or greater, 25 or greater, 30 or greater, 35 or greater, 40 or greater, 45 or greater, 50 or greater, 55 or greater, 60 or greater, 65 or greater, 70 or greater, 150 or less, 145 or less, 140 or less, 135 or less, 130 or less, 125 or less, 120 or less, 115 or less, 110 or less, 105 or less, 100 or less, 95 or less, 90 or less, 85 or less, 80 or less, or 75 or less. Preferably, the weight ratio between the by-product and the total content of di(n-butyl) terephthalate, (n-butyl)(2-ethylhexyl) terephthalate, and di(2-ethylhexyl) terephthalate in the composition may be 1:20.0 to 80. When the ratio between the by-product and the total content of di(n-butyl) terephthalate, (n-butyl)(2-ethylhexyl) terephthalate, and di(2-ethylhexyl) terephthalate is within the above range, an effect of improving migration resistance implemented by including a by-product having a dimer compound in the plasticizer composition may be maximized.
A method for hydrogenating the plasticizer composition of the present invention may be applied. The present invention may provide a plasticizer composition including 2-ethylhexyl(2-hydroxyethyl) cyclohexane-1,4-dicarboxylate and di(2-ethylhexyl) cyclohexane-1,4-dicarboxylate, wherein the content of the 2-ethylhexyl(2-hydroxyethyl) cyclohexane-1,4-dicarboxylate is 20 wt % or less, based on the total plasticizer composition. In addition, the plasticizer composition may further include hydrides of dimer compounds represented by Formulas 1 to 5.
The plasticizer composition including 2-ethylhexyl(2-hydroxyethyl) cyclohexane-1,4-dicarboxylate and di(2-ethylhexyl) cyclohexane-1,4-dicarboxylate may be obtained by subjecting a product, which has been produced by a trans-esterification reaction between polyethylene terephthalate (hereinafter, PET) and 2-ethylhexanol, to a hydrogenation reaction, and the order of the trans-esterification reaction and the hydrogenation reaction may be reversed. The product includes 2-ethylhexyl(2-hydroxyethyl) terephthalate and di(n-butyl) terephthalate, (n-butyl)(2-ethylhexyl) terephthalate and di(2-ethylhexyl) terephthalate described above, and may further include dimer compounds of Formulas 1 to 5.
The plasticizer composition may significantly improve migration and loss properties while removing environmental issues, and may implement a product having significantly improved light resistance and heat resistance compared to typical commercial products.
The present invention provides a method for preparing the above-described plasticizer composition.
Specifically, the present invention includes a method for preparing the above-described plasticizer composition, the method including mixing polyethylene terephthalate and 2-ethylhexanol in the presence of a catalyst to perform a trans-esterification reaction, and adding n-butanol to the reactant to perform a trans-esterification reaction. A product produced through a trans-esterification reaction by mixing the polyethylene terephthalate and the 2-ethylhexanol includes 2-ethylhexyl(2-hydroxyethyl) terephthalate and di(2-ethylhexyl) terephthalate, may further include a by-product including any one or more of dimer compounds represented by Formulas 1 to 5 described above.
The PET and the 2-ethylhexanol are converted into a composition including the two components through the trans-esterification reaction. Specifically, PET is represented by Formula (a) below.
In the trans-esterification reaction of the PET and the 2-ethylhexanol, the 2-ethylhexanol reacts with an ester group present in the PET, thereby releasing a polymerization chain of the PET, and depending on how the reaction is controlled, the ratio of two components of the 2-ethylhexyl(2-hydroxyethyl) terephthalate and the di(2-ethylhexyl) terephthalate may be controlled. Further, it is important to control not only the ratio of the two components but also the ratio of a by-product including the dimer compound to be within the above-described ranges.
The PET may be included in an amount of 80 wt % or less, preferably 60 wt % or less, more preferably 50 wt %, 40 wt %, or 35 wt % or less, based on the sum of contents of the PET and the 2-ethylhexanol. When the content of the PET is within the above range, the amount of 2-ethylhexanol added is sufficient, so that side reactions may be minimized, and a desired trans-esterification reaction between the PET and the 2-ethylhexanol may be maximized. Particularly, when the content of the PET is within the above-described range, a composition obtained through the preparation process satisfies the above-described preferred content conditions, so that there is an advantage in that a plasticizer composition with excellent physical properties may be directly prepared while minimizing post-treatment after the preparation process.
Meanwhile, the PET may include 50 wt % or more of waste PET, preferably 60 wt % or more, and more preferably 70 wt % or more. Even if waste PET is used, the component ratio in a final product is not changed, so that it is possible to use waste PET in the entire amount as long as it is possible to control the color or content of impurities of a plasticizer. Since waste PET is used as described above, cost competitiveness is excellent compared to di(2-ethylhexyl) terephthalate produced from terephthalic acid or dimethyl terephthalate, and the consumption of energy used in preparing terephthalic acid or dimethyl terephthalate may be reduced and environmental pollution may be prevented, thereby making a significant contribution to environmental improvement.
In the preparation method according to an embodiment of the present invention, by-products generated during the reaction, for example, ethylene glycol, may be recovered to outside of the system, wherein some thereof may remain in the reaction system. When some of ethylene glycol remains in the reaction system so as to participate in the reaction, an appropriate level of 2-ethylhexyl(2-hydroxyethyl) terephthalate and dimer compounds of Formulas 1 to 5 above may be formed from the ethylene glycol which remains in the reaction system, and since the 2-ethylhexyl(2-hydroxyethyl) terephthalate and the dimer compounds of Formulas 1 to 5 contribute to the improvement in the performance of a plasticizer composition, there is no need to consume separate energy to remove the formed 2-ethylhexyl(2-hydroxyethyl) terephthalate and the dimer compounds of Formulas 1 to 5, so that it is possible to operate the preparation process economically. Particularly, since ethylene glycol is used as a reactant for forming the 2-ethylhexyl(2-hydroxyethyl) terephthalate and the dimer compounds of Formulas 1 to 5, the content of ethylene glycol in a final composition is also naturally extremely lowered, so that there is an advantage in that a separation process may be simplified.
An example of the catalyst may be one or more selected from an acid catalyst such as sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, paratoluenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid, and alkyl sulfuric acid; a metal salt such as aluminum lactate, lithium fluoride, potassium chloride, cesium chloride, calcium chloride, iron chloride, and phosphoric acid, a metal oxide such as heteropoly acid, a natural/synthetic zeolite, cation and anion exchange resins, a catalyst including a choline compound such as choline chloride, choline hydroxide, choline bicarbonate, choline hydrogen stannate, choline dihydrogen citrate, and choline sulfate; an organic metal such as an alkyl titanate such as tetra alkyl titanate or a polymer thereof; and an organic metal including zirconium or tin. Preferably, the catalyst may be tetraalkyl titanate.
The amount of a catalyst to be used may vary depending on the type thereof, and as an example, a homogeneous catalyst may be in an amount range of 0.01 wt % to 5 wt %, 0.01 wt % to 3 wt %, 1 wt % to 5 wt %, or 2 wt % to 4 wt %, based on 100 wt % of a reactant. A heterogeneous catalyst may be present in an amount range of 5 wt % to 200 wt %, 5 wt % to 100 wt %, 20 wt % to 200 wt %, or 20 wt % to 150 wt %, based on the total weight of the reactant.
According to an embodiment of the present invention, it is preferable that the trans-esterification reaction is performed at a reaction temperature of 120° C. to 240° C., preferably 135° C. to 230° C., and more preferably 141° C. to 220° C., for 10 minutes to 12 hours, preferably 30 minutes to 10 hours, and more preferably 1 to 8 hours. The composition ratio of a final plasticizer composition may be efficiently controlled within the above temperature and time ranges. At this time, the reaction time may be calculated from when the temperature of a reactant is raised until when a reaction temperature is reached.
In addition, the method may further include a step of removing unreacted 2-ethylhexanol and ethylene glycol, which is a reaction by-product, after the trans-esterification reaction is completed. Since ethylene glycol has high solubility with respect to water, the ethylene glycol may be removed through neutralization and washing with water processes after the completion of the reaction, and residual 2-ethylhexanol may be removed through extractive distillation after the neutralization and the washing with water. Through the above step, a plasticizer composition satisfying a desired component and composition ratio may be prepared.
After the completion of the above-described trans-esterification reaction between PET and 2-ethylhexanol, a trans-esterification reaction between a reaction product and n-butanol may be performed. As reaction conditions including catalyst, reaction temperature and time in the present step, conditions in the step described above may be equally applied. In the present step, the input amount of n-butanol may be 5 wt % to 40 wt %, preferably 10 wt % to 30 wt %, based on the weight of di(2-ethylhexyl) terephthalate generated in the previous step. When the input amount of the n-butanol is appropriately controlled within the above range, each component in the final plasticizer composition is included in an appropriate so that overall physical property balance may be maintained.
According to another embodiment of the present invention, a resin composition including the aforementioned plasticizer composition is provided.
As the resin, a resin commonly known in the art may be used. For example, a mixture of one or more selected from the group consisting of a straight vinyl chloride polymer, a paste vinyl chloride polymer, an ethylene vinyl acetate copolymer, an ethylene polymer, a propylene polymer, polyketone, polystyrene, polyurethane, polylactic acid, natural rubber, synthetic rubber, and a thermoplastic elastomer, and the like may be used as the resin. However, the present invention is not limited thereto.
The plasticizer composition may be included in an amount of 5 to 150 parts by weight, preferably 5 to 130 parts by weight, or 10 to 120 parts by weight, based on 100 parts by weight of the resin.
In general, a resin in which a plasticizer composition is used may be manufactured as a resin product through melting processing or plastisol processing, and a melting processed resin and a plastisol processed resin may be produced differently depending on each polymerization method.
For example, when the vinyl chloride polymer is used for melt processing, solid resin particles produced by suspension polymerization and the like, thereby having a large average particle diameter are used, and such vinyl chloride polymer is referred to as a straight vinyl chloride polymer. When used for plastisol processing, a sol-like resin having fine resin particles produced by emulsion polymerization, and the like is used, and such vinyl chloride polymer is referred to as a paste vinyl chloride resin.
At this time, in the case of the straight vinyl chloride polymer, a plasticizer is preferably included in the range of 5 to 80 parts by weight, based on 100 parts by weight of the polymer, and in the case of the paste vinyl chloride polymer, a plasticizer is preferably included in the range of 40 to 120 parts by weight, based on 100 parts by weight of the polymer.
The resin composition may further include a filler. The filler may be 0 to 300 parts by weight based on 100 parts by weight of the resin, preferably 50 to 200 parts by weight, and more preferably 100 to 200 parts by weight.
The filler may be a filler known in the art, and is not particularly limited. For example, the filler may be a mixture of one or more selected from silica, magnesium carbonate, calcium carbonate, hard coal, talc, magnesium hydroxide, titanium dioxide, magnesium oxide, calcium hydroxide, aluminum hydroxide, aluminum silicate, magnesium silicate, and barium sulfate.
In addition, the resin composition may further include other additives such as a stabilizer, if necessary. Other additives such as the stabilizer may be 0 to 20 parts by weight, based on 100 parts by weight of the resin, preferably 1 to 15 parts by weight.
The stabilizer may be, for example, a calcium-zinc-based (Ca—Zn-based) stabilizer such as a complex stearic acid salt of calcium-zinc, or a barium-zinc-based (Ba—Zn based) stabilizer, but is not particularly limited thereto.
As described above, the resin composition may be applied to both melting processing and plastisol processing. For example, car-rendering processing, extrusion processing, or injection processing may be applied as the melting processing, and coating processing or the like may be applied as the plastisol processing.
Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention may be modified into other various forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.
1.5 g of a catalyst, which is TnBT, 500 g of discarded polyethylene terephthalate, and 1220 g of 2-ethylhexanol were added to a reactor in which a stirrer, a condenser, and a decanter were installed, and then subjected to a trans-esterification reaction at a reaction temperature of 150° C. to 230° C. under a nitrogen atmosphere for 3 hours to 8 hours. After the completion of the reaction, unreacted 2-ethylhexanol was removed by decompression. Through the above process, a composition including 0.2 wt % of 2-ethylhexyl(2-hydroxyethyl) terephthalate and 97.5 wt % of di(2-ethylhexyl) terephthalate (DEHTP) was obtained. The remaining components excluding the two components above in the composition include by-products and intermediates generated during the reaction process.
Thereafter, 1000 g of a reactant obtained above and 190 g of n-butanol (19 parts by weight based on 100 parts by weight of the reactant) were added, and the mixture was subjected to a trans-esterification reaction at a reaction temperature of 160° C. under a nitrogen atmosphere for 2 hours. Then, through a purification process, an ester-based plasticizer composition including 0.9 wt % of 2-ethylhexyl(2-hydroxyethyl) terephthalate, 5.3 wt % of di(n-butyl) terephthalate, 38.2 wt % of (n-butyl)(2-ethylhexyl) terephthalate, and 53.9 wt % of di(2-ethylhexyl) terephthalate was finally obtained. The remaining components, such as a dimer compound, excluding the four components above in the composition include by-products generated during the reaction process, and the contents of the by-products are shown in Table 1 below.
An ester-based plasticizer composition including 8.6 wt % of 2-ethylhexyl(2-hydroxyethyl) terephthalate, 3.8 wt % of di(n-butyl) terephthalate, 34.1 wt % of (n-butyl)(2-ethylhexyl) terephthalate, and 50.2 wt % of di(2-ethylhexyl) terephthalate was obtained in the same manner as in Example 1, through controlling the input amount and reaction time of 2-ethylhexanol. The remaining components, such as a dimer compound, excluding the four components above in the composition include by-products generated during the reaction process, and the contents of the by-products are shown in Table 1 below.
An ester-based plasticizer composition including 19.4 wt % of 2-ethylhexyl(2-hydroxyethyl) terephthalate, 1.9 wt % of di(n-butyl) terephthalate, 28.7 wt % of (n-butyl)(2-ethylhexyl) terephthalate, and 45.3 wt % of di(2-ethylhexyl) terephthalate was obtained in the same manner as in Example 1, through controlling the input amount and reaction time of 2-ethylhexanol. The remaining components, such as a dimer compound, excluding the four components above in the composition include a by-product generated during the reaction process, and the contents of the by-product are shown in Table 1 below.
1.5 g of a catalyst, which is TnBT, 500 g of discarded polyethylene terephthalate, and 1220 g of 2-ethylhexanol were added to a reactor in which a stirrer, a condenser, and a decanter were installed, and then subjected to a trans-esterification reaction at a reaction temperature of 150° C. to 230° C. under a nitrogen atmosphere for 8 hours. After the completion of the reaction, unreacted 2-ethylhexanol was removed by decompression. Thereafter, 100 g of a 3 wt % sodium hydroxide aqueous solution was added to neutralize the catalyst, and a small amount of unreacted 2-ethylhexanol was removed by distillation. Through the above process, 2-ethylhexyl(2-hydroxyethyl) terephthalate was all removed from the composition, and a composition including 99.9 wt % of di(2-ethylhexyl) terephthalate (DEHTP) was obtained.
An ester-based plasticizer composition with 2-ethylhexyl(2-hydroxyethyl) terephthalate all removed from the composition and including 5.9 wt % of di(n-butyl) terephthalate, 39.2 wt % of (n-butyl)(2-ethylhexyl) terephthalate, and 54.9 wt % of di(2-ethylhexyl) terephthalate was obtained in the same manner as in Example 1, through controlling the input amount and reaction time of 2-ethylhexanol.
An ester-based plasticizer composition including 22.5 wt % of 2-ethylhexyl(2-hydroxyethyl) terephthalate, 1.7 wt % of di(n-butyl) terephthalate, 26.7 wt % of (n-butyl)(2-ethylhexyl) terephthalate, and 41.2 wt % of di(2-ethylhexyl) terephthalate was obtained in the same manner as in Example 1, through controlling the input amount and reaction time of 2-ethylhexanol. The remaining components, such as a dimer compound, excluding the four components above in the composition include a by-product generated during the reaction process, and the contents of the by-product are shown in Table 1 below.
Using the plasticizers from Examples and Comparative Examples, specimens were produced under the following prescription and production conditions in accordance with ASTM D638.
(1) Prescription: 100 parts by weight of a straight vinyl chloride polymer (LS100), 50 parts by weight of a plasticizer, and 3 parts by weight of a stabilizer (BZ-153T)
(2) Blending: Mixing at 700 rpm at 98° C.
(3) Producing specimen: Working with a roll mill at 160° C. for 4 minutes and working with a press at 180° C. for 2.5 minutes (low pressure) and 2 minutes (high pressure) to produce 1 T to 3 T sheets
1) Hardness: Using ASTM D2240, shore hardness (Shore “A” and “D”) at 25° C. was measured for 10 seconds with the 3T specimen. The smaller the numerical value, the better the plasticization efficiency.
2) Tensile strength By the ASTM D638 method, the 1T specimen was pulled at a cross head speed of 200 mm/min using a U.T.M (manufacturer; Instron, model name; 4466), which is a test device, and a point at which the 1T specimen was cut was measured. The tensile strength was calculated as follows.
Tensile strength (kgf/cm2)=load value (kgf)/thickness (cm)×width (cm)
3) Measurement of elongation rate: By the ASTM D638 method, the 1T specimen was pulled at a cross head speed of 200 mm/min using the U.T.M, and a point at which the 1T specimen was cut was measured, and the elongation rate was calculated as follows:
Elongation rate (%)=length after elongation/initial length×100
4) Measurement of tension and elongation residual: The measurement of tensile and the measurement of elongation residual are to measure the tensile strength and the elongation rate remaining in a specimen after applying heat to 100° C. for 168 hours, and the measurement method is the same as the tensile strength and elongation measurement methods.
5) Measurement of migration loss: The measurement was performed in accordance with KSM-3156. Specifically, a test piece having a thickness of 1 mm was obtained, and an absorption sheet capable of moving to both sides of the test piece, thereby absorbing an organic material discharged to the surface of the test piece was added, and then a plate which was able to cover the entire test body was attached thereon to apply a load of 1 kgf/cm2. The test piece was left to stand for 72 hours in a hot-air circulation-type oven (80° C.), and then was taken out of the oven and cooled for 4 hours at room temperature. Thereafter, the plate and the absorption sheet attached to both sides of the test piece were removed, and then the weights of the specimen before and after the specimen was left in the oven were measured to calculate a migration loss amount by Equation 3 below.
Migration loss (%)={(initial weight of test specimen at room temperature−weight of test specimen after being left to stand in oven)/initial weight of test specimen at room temperature}×100
6) Measurement of volatile loss: After working on the produced specimen at 80° C. for 72 hours, the weight of the specimen was measured.
Volatile loss (wt %)=initial specimen weight−(80° C., specimen weight after 72 hours of work)/initial specimen weight×100
7) Stress test (stress resistance): A specimen with a thickness of 2 mm was bent and left to stand at 23° C. for 168 hours, and then the degree of migration (degree of leaking) was observed on the first day, the third day, and the seventh day, and the results were described in numerical values. The closer the numerical value is to 0, the better the stress resistance.
8) Measurement of absorption rate: Under the conditions of 73° C. and 60 rpm, processability was evaluated by measuring the time taken from when a resin and the plasticizer were mixed with each other using a planetary mixer (Brabender, P600) until when the torque of the mixer was stabilized.
The evaluation results of the items are shown in Tables 2 and 3 below.
Referring to Tables 2 and 3 above, compared to Reference Example, which is a di(2-ethylhexyl) terephthalate-based plasticizer composition, a ready-to-use product, Examples 1 to 3 use discarded PET as a raw material, and thus is eco-friendly and reduces production costs, and Examples 1 to 3 exhibited excellent results in terms of mechanical properties, migration loss, absorption rate, and stress resistance even though a by-product were included therein. This means that the plasticizer composition of the present invention applies 2-ethylhexyl(2-hydroxyethyl) terephthalate and a by-product including one or more of Formulas 1 to 5 together, thereby exhibiting an improvement in stress resistance, migration loss, absorption rate, and mechanical properties without degradation in existing physical properties. In general, in the case of a composition in which two components are mixed, the effect of the mixed composition is manifested in the direction of the decrease in the effectiveness of each component, but on the contrary, in the present invention, an improvement in stress resistance and mechanical properties is achieved while maintaining the same level of physical properties as the existing physical properties, from which it can be confirmed that the present invention achieves an effect that cannot be predicted in the existing technologies.
Meanwhile, in Comparative Example 1, 2-ethylhexyl(2-hydroxyethyl) terephthalate in a final composition was completely removed by adjusting the input amount and reaction time of 2-ethylhexanol, wherein the cost of the manufacturing process was higher than that of Examples 1 to 3, but the physical properties of the finally obtained plasticizer composition were similar to those of the plasticizer compositions of Examples 1 to 3, and in particular, the volatile loss, migration resistance, stress resistance, and mechanical properties were rather inferior to those of the Examples. From the above, it can be confirmed that the plasticizer composition of the present invention has a lower manufacturing cost than a typical plasticizer composition including di(n-butyl) terephthalate, (n-butyl)(2-ethylhexyl) terephthalate, and di(2-ethylhexyl) terephthalate recovered from polyethylene terephthalate, and also has an excellent function of a plasticizer as it is.
Meanwhile, Comparative Example 2 was prepared from polyethylene terephthalate in a manner similar to that of Examples of the present invention, and is a plasticizer composition out of the content of a by-product including 2-ethylhexyl(2-hydroxyethyl) terephthalate and/or dimer compound according to the present invention by controlling the input amount and reaction time of 2-ethylhexanol, and although the plasticization efficiency was similar to that of Examples 1 to 3, the result shows that the mechanical properties and stress resistance were inferior to those of the above Examples. Particularly, the result shows that among the mechanical properties, the elongation residual thereof was significantly inferior to that of Examples 1 to 3. From the above, it can be confirmed that the plasticizer composition of the present invention, in which the content of each compound was limited in order to maximize the improvement in various physical properties such as mechanical properties, stress resistance, heat resistance, and migration resistance, has an excellent function of a plasticizer as it is compared to the plasticizer of Comparative Example 2 out of the content of the by-product including 2-ethylhexyl(2-hydroxyethyl) terephthalate and/or a dimer compound.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2022-0024956 | Feb 2022 | KR | national |
| 10-2023-0024776 | Feb 2023 | KR | national |
The present application is a National Phase entry pursuant to 35 U.S.C. § 371 of International Application No. PCT/KR2023/002663 filed on Feb. 24, 2023, and claims priority to and the benefit of Korean Patent Application No. 10-2022-0024956, filed on Feb. 25, 2022, and Korean Patent Application No. 10-2023-0024776, filed on Feb. 24, 2023, both filed in the Korean Intellectual Property Office, the disclosures of which are incorporated herein in their entirety by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2023/002663 | 2/24/2023 | WO |
