Additive removal apparatus and method of removing additives using the apparatus

Abstract

The present invention provides an additive removal device, comprising: a barrel providing an inner space and having a polymer inlet on one side and a polymer outlet on the other side; a screw provided in the inner space of the barrel and rotating axially; and a solvent discharge unit provided at one end of the barrel; wherein the barrel comprises a swelling solvent inlet between the polymer inlet and the polymer outlet and adjacent to the polymer inlet and a shrinking solvent inlet between the polymer inlet and the polymer outlet and adjacent to the polymer outlet.

Description

Technical Field

[0001] Prior cross-reference

[0002] This application claims priority to Korean Patent Application No. 10-2022-0140595, filed on October 27, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0004] This invention relates to an additive removal apparatus for removing additives contained in a polymer to enable polymer recycling, and a method for removing additives using the apparatus. Background Technology

[0005] Recently, with the development of resin materials with the desired physical properties for various uses and purposes, the use of polymer materials such as resins or plastics is increasing. Typically, the extraction and manufacture of resins or plastics from crude oil consumes a large amount of energy and releases significant amounts of carbon in the process. Furthermore, when the resins or plastics contained in products are discarded along with the final product, environmental pollution is caused and the social costs of treating this pollution are incurred. Therefore, the recycling of waste resins is necessary to reduce energy consumption, carbon emissions, and prevent environmental pollution. Plastics prepared in this way by recycling resins discarded after use by end consumers are called post-consumer recycled (PCR) resins, and continuous efforts are being made to obtain PCR resins with the desired purity and physical properties.

[0006] Meanwhile, polyvinyl chloride (PVC) resin possesses both rigid and flexible properties, excellent molding processability, and superior price competitiveness, thus making PVC a versatile material. As a result, PVC is used in a wide range of applications. However, PVC resin can be used not alone, but in combination with plasticizers to achieve various physical properties, such as imparting flexibility and improving physical properties like processability.

[0007] However, phthalate plasticizers, which have been used as plasticizers in the past, are harmful to the environment and human health, and are therefore subject to strict domestic and international regulations. Phthalate plasticizers are difficult to commercialize when they cannot be removed to allow for the recycling of polymers such as conventional polyvinyl chloride resins that use phthalate plasticizers. Therefore, recent attempts have focused on effectively removing phthalate plasticizers remaining in recycled polymers to enable the recycling of polymers using phthalate plasticizers.

[0008] As part of this process, to remove additives such as plasticizers from recycled polymers, the common practice is to dissolve the recycled polymer in a solvent and then recrystallize the dissolved polymer using an antisolvent, a method known as solution recrystallization. However, in this case, the amounts of solvent and antisolvent used for dissolution and recrystallization are excessive, and the physical properties of the recycled polymer are also poor. Furthermore, the cost of equipment and apparatus becomes prohibitively high with the accompanying increase in solvent volume.

[0009] Therefore, there is a need to develop devices that can efficiently remove additives such as plasticizers from recycled polymers while minimizing the amount of solvent used, as well as methods for using such devices to remove additives from polymers. Summary of the Invention

[0010] [Technical Issues]

[0011] To address the problems mentioned in the background section, the present invention provides a continuous processing method capable of efficiently removing plasticizers contained in a polymer to enable polymer recycling, and an additive removal apparatus optimized for this purpose.

[0012] [Technical Solution]

[0013] According to one embodiment of the present invention, an additive removal apparatus is provided, comprising: a barrel providing an internal space and having a polymer inlet on one side and a polymer outlet on the other side; a screw disposed in the internal space of the barrel and rotating axially; and a solvent discharge unit disposed at one end of the barrel, wherein the barrel includes a swelling solvent inlet and a shrinking solvent inlet, the swelling solvent inlet being located between and adjacent to the polymer inlet and the polymer outlet, and the shrinking solvent inlet being located between and adjacent to the polymer outlet.

[0014] According to another embodiment of the present invention, a method for removing additives is provided, the method comprising: preparing an additive removal apparatus; supplying a polymer containing the additive to a polymer inlet; supplying a swelling solvent and a shrinking solvent to a swelling solvent inlet and a shrinking solvent inlet, respectively; transferring the supplied polymer to a polymer outlet by axial rotation of a screw; causing the polymer to swell in a swelling zone from the polymer inlet to the swelling solvent inlet; and causing the polymer to shrink in a shrinking zone from the swelling solvent inlet to the shrinking solvent inlet.

[0015] [Beneficial Effects]

[0016] According to the additive removal apparatus of the present invention, additives in polymers can be continuously extracted even with a small device size and a small amount of solvent, thereby improving the additive removal efficiency.

[0017] Furthermore, the method for removing additives according to the present invention, unlike conventional dissolution-recrystallization methods, removes additives from the polymer by selectively diffusing and extracting them from the polymer by immersing the swollen solvent in the polymer without dissolving the polymer recovered from waste resin in the solvent. As a result, economic efficiency can be improved by reducing the amount of solvent used and simplifying the required equipment.

[0018] Then, when removing the swollen solvent from the swollen polymer through impregnation with the swollen solvent, the swollen polymer can be shrunk by applying a shrinking solvent to the swollen polymer, thereby effectively reducing the amount of residual solvent and additives present in the solvent in the polymer. Attached Figure Description

[0019] Figure 1 This is a longitudinal cross-sectional view showing an additive removal apparatus according to an embodiment of the present invention. Detailed Implementation

[0020] The terms and words used in this specification and claims should not be interpreted in a general or dictionary sense, but rather should be interpreted as meanings and concepts consistent with the technical ideas of the invention, based on the inventors' ability to appropriately define the concepts of the terms in order to best describe their own invention.

[0021] In the following text, reference will be made to Figure 1 The invention will be described in more detail to aid in understanding it.

[0022] An additive removal apparatus 1 according to an embodiment of the present invention may include: a barrel 10, the barrel 10 providing an internal space and having a polymer inlet 20 on one side and a polymer outlet 30 on the other side; a screw 70 disposed in the internal space of the barrel 10 and rotating axially; and a solvent discharge unit 60 disposed at one end of the barrel 10, wherein the barrel 10 includes a swelling solvent inlet 40 and a shrinking solvent inlet 50, the swelling solvent inlet 40 being located between and adjacent to the polymer inlet 20 and the polymer outlet 30, and the shrinking solvent inlet being located between and adjacent to the polymer outlet.

[0023] First, the polymer is a polymer recovered from waste resin, obtained through pretreatment of the waste resin, and may be in granular form. On the other hand, the waste resin can be recovered from various products or applications molded using the resin or its compositions, regardless of whether it is rigid or flexible. Furthermore, the recovered polymer can be a single type of polymer or a resin composition blended with other resins.

[0024] Pretreatment refers to the overall process of treating waste resin with a polymer in a manner suitable for application in the additive removal apparatus of the present invention. For example, pretreatment may involve first washing the waste resin with a solvent such as water to remove relatively large foreign matter such as dust, drying the waste resin, and grinding the waste resin into particles.

[0025] Specifically, the average particle size D50 of the polymer can be greater than 0.1 mm and less than 2 mm. As the average particle size of the recycled polymer decreases, the impregnation rate of the impregnation solvent increases and the additive removal rate increases. However, a drawback is that the processing time increases in order to prepare recycled polymers with small average particle sizes.

[0026] There are no particular limitations on the type of polymer suitable for the additive removal apparatus according to embodiments of the present invention, but when the additive removed by the additive removal apparatus is a plasticizer, the polymer may be polyvinyl chloride (PVC).

[0027] On the other hand, additives such as plasticizers, fillers, flame retardants, stabilizers, foaming agents, viscosity reducers, colorants, and heat stabilizers can be used to impart the desired physical properties to the resin during product manufacturing, such as during polymer polymerization or post-polymerization molding, and the additives used are retained in the resin prepared according to the additives. Therefore, to enable resin recycling, additives can even be included in waste resin recovered from the product.

[0028] The reasons why additives should be appropriately removed when preparing recycled polymers from polymers recovered from waste resins are as follows.

[0029] First, when additives are present in excess, it may be difficult to manufacture recycled polymers with good physical properties. Due to the influence of additives, physical properties may deteriorate, such as deformation or deterioration of surface properties of the recycled polymer, or color properties may deteriorate, such as discoloration.

[0030] Secondly, depending on the additives, there are additives whose use has recently been regulated due to their environmental and human hazards. That is, since there is no regulation during product manufacturing, the manufacture of recycled polymers becomes more common only when the additives to be regulated should be removed from the recycled polymers to below the required levels.

[0031] For the reasons stated above, the additives that need to be removed from recycled polymers containing additives can primarily be plasticizers. Specifically, the plasticizers can be phthalate plasticizers. More specifically, phthalate plasticizers can be at least one of dioctyl phthalate (DOP), dibutyl phthalate (DBP), dioctyl terephthalate (DOTP), diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), di(2-ethylhexyl) terephthalate (DEHTP), and butyl benzyl phthalate (BBP).

[0032] On the other hand, methods for removing additives differ from conventional methods that involve dissolving the polymer itself in a soluble solvent and then recrystallizing it, because only the additives are selectively eluted while the polymer remains in its original form. In such conventional dissolution-recrystallization methods, it is difficult to remove additives with good compatibility with the resin, such as plasticizers. In particular, in this case, the need to use excessive amounts of solvent (anti-solvent) results in high costs not only for the solvent itself but also for purifying it, leading to a low purification efficiency relative to the cost.

[0033] Therefore, the method for removing additives according to the present invention first contacts the polymer containing the additive with a swelling solvent to immerse the polymer in the swelling solvent, causing the polymer to swell, and simultaneously allows the additive in the polymer to diffuse into the swelling solvent for removal from the polymer. Subsequently, by contacting the polymer impregnated with the swelling solvent with a shrinking solvent to shrink the polymer, the solvent content in the polymer can be minimized. That is, when the polymer in a swollen state is shrunk by the shrinking solvent, as much of the swelling solvent containing the internal additives as possible is discharged to the outside of the polymer, thereby ultimately reducing the additive content in the polymer.

[0034] Here, the term "impregnation" refers not only to washing the additives (plasticizers) present on the surface of the recycled polymer with an impregnation solvent, but also to impregnating the recycled polymer with an impregnation solvent through diffusion and washing away the additives (plasticizers) therein.

[0035] Furthermore, the present invention can provide an optimal additive removal apparatus 1 that can continuously perform methods for removing additives to reduce the amount of swelling and shrinking solvents used, thereby improving economic efficiency and simultaneously increasing the removal efficiency of additives, especially plasticizers.

[0036] From this perspective, the barrel 10 according to an embodiment of the present invention is a component constituting the main body of the additive removal device 1, and can be a tubular shape extending in the longitudinal direction and having an internal space. The barrel 10 can be made of a material that will not deform with the solvent as described below, specifically a metallic material or a glass material.

[0037] The internal space is a space in which polymer supplied to polymer inlet 20 is transferred to polymer outlet 30 by screw 70, and solvent supplied to swelling solvent inlet 40 and shrinking solvent inlet 50 is transferred by gravity, and may also refer to the space in which additives contained in the polymer are removed by swelling and shrinking the polymer.

[0038] Specifically, the barrel 10 may have a polymer inlet 20 on one side and a polymer outlet 30 on the other side. The polymer may be a polymer containing additives, and the polymer may be supplied to the polymer inlet 20, whereby the additives may be removed by a process of sequentially contacting the polymer with a swelling solvent and a shrinking solvent, which will be described below, and the polymer from which the additives have been removed may be discharged through the polymer outlet 30.

[0039] On the other hand, the additive removal device 1 may include a screw 70 disposed in the internal space of the barrel 10 and rotating axially, and a rotational force supply device 80 at the other end of the barrel 10 to apply rotational force to the screw 70. Here, the other end may be the end of the barrel 10 adjacent to the polymer outlet 30.

[0040] The rotational force supply device 80 is used to supply the screw 70 with a driving force for axial rotation, and may specifically be an electric motor.

[0041] Specifically, the screw 70 may include a shaft 71 connected to and axially rotating with the rotary force supply device 80, and a plate 72 fixed to the outer peripheral surface of the shaft 71 and extending helically along the longitudinal direction of the shaft 71. The plate 72 can be rotated using the shaft 71 as a rotation axis by the rotational force applied by the rotary force supply device 80. Thus, polymer supplied to the polymer inlet 20 is loaded onto the plate 72 and can be continuously conveyed to the polymer outlet 30 by the axial rotation of the screw 70.

[0042] Meanwhile, the supply flow rate (g / min) of the polymer supplied to the polymer inlet 20 can be determined by the volume (cm³) of the screw with a pitch (p). 3 ), the bulk density of the supplied polymer (g / cm³) 3 ) and the screw's revolutions per minute (RPM, min) -1 The relationship between the two is determined, and can specifically satisfy the following general formula 1.

[0043] [General Formula 1]

[0044] Volume (cm³) of a screw with a pitch (p) 3 ) The bulk density of the supplied polymer (g / cm³) 3 ) screw revolutions per minute (min) -1 ) 0.1 ≤ Supply polymer flow rate (g / min) ≤ Volume of screw with 1 pitch (p) (cm³) 3 ) The bulk density of the supplied polymer (g / cm³) 3 ) screw revolutions per minute (min) -1 ) 0.5

[0045] On the other hand, according to one embodiment of the present invention, in the additive removal device 1, the extension line of the rotation center axis of the screw 70 (specifically, the extension line of the shaft 71) can be set at an angle relative to the ground. That is, the surface height of the polymer outlet 30 can be set higher than the surface height of the polymer inlet 20. As the base supporting the additive removal device 1, the length of the base supporting the polymer outlet 30 side is longer than the length of the base supporting the polymer inlet 20 side, thus achieving an inclination angle z between the extension line of the rotation center axis of the screw 70 and the ground.

[0046] On the other hand, the swollen solvent and shrinking solvent introduced into the internal space of the barrel 10 can be transferred to the solvent discharge unit 60 by gravity through the tilt angle z between the extension line of the rotation center axis of the screw 70 and the ground, and the introduced swollen solvent and shrinking solvent can be prevented from flowing back to the polymer outlet 30 and being lost.

[0047] Furthermore, the retention time of the swelling and shrinking solvents in the device and the contact time between the solvent and the polymer can be determined by controlling the tilt angle z formed between the extension line of the rotation center axis of the screw 70 and the ground. This allows for more efficient removal of additives from the polymer.

[0048] Specifically, the tilt angle z formed between the extension of the rotation center axis of the screw 70 and the ground can be from 5° to 30°. The tilt angle z is also related to the flow rates of the swelling solvent and the shrinking solvent to be supplied. When the tilt angle exceeds 30°, the solvent supplied to the barrel 10 through the swelling solvent inlet 40 or the shrinking solvent inlet 50 is discharged without sufficient retention in the internal space of the barrel. That is, although the solvent has the ability to swell or shrink the polymer, the solvent is discharged in too short a time, so there is a problem of needing to use too much solvent than necessary. In addition, the energy required for solvent reuse during the purification process increases. Conversely, when the tilt angle is less than 5°, the possibility of the solvent supplied to the barrel being discharged to the polymer outlet 30 and lost increases, and the solvent that has reached the vicinity of the solvent outlet (i.e., the solvent in which the additives are concentrated) cannot be smoothly discharged to the solvent outlet, so the removal efficiency of the additives in the polymer may decrease.

[0049] According to one embodiment of the present invention, a swelling solvent may be supplied to a swelling solvent inlet 40, and a shrinking solvent may be supplied to a shrinking solvent inlet 50.

[0050] Furthermore, the internal space of the barrel 10 can be functionally divided into a swelling region 100 from the polymer inlet 20 to the swelling solvent inlet 40 and a shrinkage region from the swelling solvent inlet 40 to the shrinkage solvent inlet 50. Specifically, the swelling region 100 is the cross-section of the barrel 10, and refers to the region from the cross-section including the center of the polymer inlet 20 to the cross-section including the center of the swelling solvent inlet 40, and the shrinkage region 200 refers to the region from the cross-section including the center of the swelling solvent inlet 40 to the cross-section including the center of the shrinkage solvent inlet 50.

[0051] First, the polymer containing additives supplied through polymer inlet 20 passes sequentially through swelling zone 100 and shrinkage zone 200, and is transferred to polymer outlet 30 by the axial rotation of screw 70.

[0052] The distance x from polymer inlet 20 to swelling solvent inlet 40 can be the length of the swelling zone 100, and the distance y from swelling solvent inlet 40 to shrinking solvent inlet 50 can be the length of the shrinking zone 200. The ratio x / y of the distance x from polymer inlet 20 to swelling solvent inlet 40 to the distance y from swelling solvent inlet 40 to shrinking solvent inlet 50 can be from 0.1 to 60, specifically from 1 to 30. When the ratio x / y is less than 0.1, the retention time of the polymer in the shrinking zone becomes longer than required, and the economic efficiency of the method may decrease. When the ratio x / y is greater than 60, the retention time of the polymer in the shrinking zone becomes shorter than required, thus the problem is that the polymer in the swollen state is difficult to shrink sufficiently.

[0053] On the other hand, in the swelling zone 100, the polymer containing the additives comes into contact with the swelling solvent, so that the swelling solvent can impregnate the interior of the polymer, and the polymer can swell while maintaining its unique molecular structure. The additives contained in the polymer diffuse through the impregnation solvent and are eluted from the recovered polymer, and the additives can be removed from the polymer.

[0054] To effectively remove additives from polymers, it is crucial to select a swelling solvent for polymer swelling. First, the swelling solvent should be able to penetrate the polymer particles rapidly and uniformly, and should be able to elute the maximum amount of additives contained in the polymer into the swollen solvent. Therefore, the type of polymer and the type of additive to be removed should be considered when selecting the swelling solvent.

[0055] From this perspective, when the additive is a phthalate plasticizer, the swelling solvent can be at least one of cyclohexanone, cyclopentanone, N,N-dimethylacetamide, tetrahydrofuran, pyridine, 3-pentanone, 2-pentanone, dimethylformamide, methyl ethyl ketone, dichloromethane, 4-methylpentan-2-one, nitrobenzene, 1,4-dioxane, 1,1,2,2-tetrachloroethane, acetone, ethyl acetate, chloroform, and dimethyl sulfoxide, and specifically, methyl ethyl ketone. In the case of said solvent, it can readily impregnate the polymer and is preferred because it has excellent ability to elute additives (e.g., phthalate plasticizers) from the polymer.

[0056] Therefore, in order to fully immerse the polymer in the swelling zone 100 and smoothly elute the internal additives due to the swelling of the polymer, the supply flow rate (cm) of the swelling solvent to the swelling solvent inlet 40 is [specified]. 3 The flow rate ( / min) can be determined based on the supply flow rate of the supplied polymer and the bulk density of the polymer. Specifically, it can satisfy the following general formula 2.

[0057] [General Formula 2]

[0058] Supply flow rate of polymer (g / min) / Bulk density of polymer (g / cm³) 3 ) 0.5 ≤ Flow rate of the supplied swelling solvent (cm) 3 / min) ≤ Supply flow rate of supplied polymer (g / min) / Bulk density of supplied polymer (g / cm³) 3 ) 10

[0059] That is, when the supply volumetric flow rate of the swelling solvent (cm) 3 / min) / polymer supply volumetric flow rate (cm 3 When the flow rate ( / min) is greater than or equal to 0.5, sufficient swelling of the polymer is possible, and residual additives in the polymer can be smoothly removed. On the other hand, because the supply volumetric flow rate (cm² / min) of the swelling solvent is greater than or equal to 0.5, sufficient swelling of the polymer is possible, and residual additives in the polymer can be smoothly removed. 3 / min) / polymer supply volumetric flow rate (cm 3 When the ratio ( / min) is below 10, unnecessary solvent use can be reduced, thus lowering purification costs due to excessive solvent use and improving the economic efficiency of the method.

[0060] Meanwhile, relative to the value expressed by the average particle size D50 (mm) of the polymer, the retention time of the polymer in the swelling zone 100 can satisfy the following general formula 3.

[0061] [Formula 3]

[0062] Average particle size of the polymer (mm) 5 ≤ Retention time in the swollen zone (min) ≤ Average particle size of the polymer (mm) 240

[0063] That is, when the polymer remains in the swelling zone 100 for a period of time [a value expressed by the average particle size of the polymer], the percentage of time the polymer remains in the swelling zone 100 is [the percentage of time the polymer remains in the swelling zone 100 is] ... 5] For longer retention times, the swelling solvent penetrates the polymer, thus allowing the additives to be fully eluted. On the other hand, when the retention time is longer than [a value expressed by the average particle size of the polymer],

[240] In this case, the economic efficiency of the method may decrease. Specifically, when the screw speed (RPM) is excessively reduced to increase the retention time, or the length of the swelling zone 100 is increased to increase the retention time, the yield of the polymer from which the additives have been removed per unit time decreases. In this case, the size of the equipment may increase.

[0064] Meanwhile, a mixture of swelling solvent and shrinking solvent can exist in the swelling zone 100. That is, since the shrinking solvent supplied to the shrinking solvent inlet 50 passes through the shrinking zone 200 and the swelling zone 100 and is discharged to the solvent discharge unit 60, the swelling solvent and the shrinking solvent coexist in the swelling zone 100.

[0065] In the swelling zone 100, when the shrinking solvent is too large compared to the swelling solvent, the swelling of the polymer and solvent impregnation by the swelling solvent can be reduced. Therefore, the flow rates of the swelling solvent and shrinking solvent in the swelling zone 100 should be controlled to an appropriate ratio. On the other hand, since the flow rates of the swelling solvent and the shrinking solvent in the swelling zone 100 are ultimately determined based on the flow rates of the swelling solvent supplied to the swelling solvent inlet 40 and the shrinking solvent supplied to the shrinking solvent inlet 50, it may be important to appropriately control their flow rate ratio for smooth impregnation of the swelling solvent and swelling of the polymer.

[0066] In this regard, the flow rate ratio of the shrink solvent supplied to the shrink solvent inlet to the swelling solvent inlet can be from 30% to 300% by volume. When the shrink solvent is supplied at a flow rate of less than 300% by volume of the swelling solvent, that is, when the swelling solvent is present in the swelling zone 100 at a rate more than three times that of the shrink solvent, the additive elution function may not be reduced due to the swelling of the polymer in the swelling solvent. On the other hand, considering the function of the shrink solvent in the shrink zone 200 and the resulting removal efficiency of additives in the polymer, it is necessary to maintain the shrink solvent supply flow rate above a certain level. Therefore, when the flow rate ratio of the shrink solvent to the swelling solvent is less than 30% by volume, it may be difficult to smoothly implement the polymer shrinkage function in the shrink zone due to insufficient supply of shrink solvent.

[0067] Simultaneously, the polymer swollen by the swelling solvent can be transferred to the shrinkage zone 200 in the barrel 10. In the shrinkage zone 200, the polymer swollen can come into contact with the shrinkage solvent. Specifically, the polymer transferred from the swelling zone 100 to the shrinkage zone 200 is immersed in a swelling solvent in which additives are eluted. However, when drying is performed without removing the swelling solvent from the swollen polymer, the plasticizer removal efficiency is reduced because the eluted plasticizer remains intact within the regenerated polymer. Therefore, it is important to remove the swelling solvent from the swollen polymer. According to the present invention, the ratio of solvent content to plasticizer content present in the swollen polymer can be minimized by using a shrinkage solvent to chemically shrink the swollen polymer.

[0068] Unlike swelling solvents, shrinking solvents are preferably solvents with low polymer swelling degree. Furthermore, when the additive is a phthalate plasticizer, a solvent with high phthalate plasticizer solubility is preferred. In this regard, when the additive is a phthalate plasticizer, the shrinking solvent is at least one of ethanol, toluene, cyclohexanol, isopropanol, benzene, cyclohexane, 1-pentanol, 1-butanol, 1-propanol, hexane, and diethyl ether, and specifically, it can be isopropanol. Such shrinking solvents not only effectively shrink the swollen polymer but also have excellent phthalate plasticizer solubility, thus the plasticizer present inside the polymer can be easily removed from the polymer during the shrinkage of the swollen polymer.

[0069] In order to facilitate the shrinkage of the swollen polymer and thus smoothly remove the swelling solvent (and additives contained therein) from the swollen polymer by means of the shrinkage solvent in the shrinkage zone 200, the supply flow rate of the shrinkage solvent supplied through the shrinkage solvent inlet 50 can be determined according to the supply flow rate of the polymer and the bulk density of the supplied polymer. Specifically, the following general formula 4 can be satisfied.

[0070] [Formula 4]

[0071] Supply flow rate of the supplied polymer (g / min) / Bulk density of the supplied polymer (g / cm³) 3 ) 0.25 ≤ Supply flow rate of shrinkage solvent (cm) 3 / min) ≤ Supply flow rate of supplied polymer (g / min) / Bulk density of supplied polymer (g / cm³) 3 ) 5

[0072] Furthermore, the retention time of the polymer in the shrinkage zone 200 can be from 0.5 to 10 minutes. When the retention time of the polymer in the shrinkage zone 200 is short (less than 0.5 minutes), the shrinkage solvent may not be able to penetrate the polymer sufficiently, so the swollen polymer cannot shrink smoothly, and the removal efficiency of the additives may be reduced. Moreover, when the retention time of the polymer in the shrinkage zone 200 is 10 minutes or longer, the retention time becomes longer than required, thus becoming uneconomical in terms of solvent consumption and equipment size.

[0073] According to one embodiment of the present invention, the polymer shrunk through the shrinkage zone 200 can be discharged to the outside of the additive removal device 1 through the polymer outlet 30. The discharged polymer can be subjected to a drying process to remove residual swelling solvent and shrinkage solvent from the polymer. The dryer for performing the drying process can be, for example, a paddle dryer, a floating bed dryer, a vacuum dryer, or a devolatilization extruder.

[0074] Meanwhile, according to an embodiment of the present invention, the swelling solvent and the shrinking solvent can be discharged through the solvent discharge unit 60.

[0075] The solvent discharge unit 60 may be connected to one end of the barrel 10, and the solvent discharge unit 60 may include a solvent outlet. The solvent discharge unit 60 may be detachable from one end of the barrel 10 for cleaning the interior of the barrel 10, etc.

[0076] The solvent discharged through solvent discharge unit 60 may include swollen solvent, shrinking solvent, and additives dissolved therein. Therefore, the discharged solvent can be purified by separating the swollen solvent, shrinking solvent, and additives, and the solvents and additives can be reused accordingly.

[0077] The invention will be described in more detail below by way of examples. However, the following examples are for illustrative purposes, and those skilled in the art will understand that various changes and modifications can be made within the scope and spirit of the invention, and that the scope of the invention is not limited thereto.

[0078] Example

[0079] Example 1

[0080] First, prepare Figure 1 The additive removal device 1 shown is specifically designed to remove polymers. It includes a barrel 10 with an inner diameter of 6 cm, a polymer inlet 20 on one side of the barrel and a polymer outlet 30 on the other side, a motor 80 at the other end of the barrel, and a screw 70 connected to the motor and disposed within the barrel. The additive removal device includes a swelling solvent inlet 40 and a shrinking solvent inlet 50 between the polymer inlet and the polymer outlet. Here, the ratio x / y of the distance x from the polymer inlet to the swelling solvent inlet to the distance y from the swelling solvent inlet to the shrinking solvent inlet is 4.

[0081] The additive removal device is mounted on the base of the additive removal device, and the inclination formed by the extension line of the rotation center axis of the screw and the ground is adjusted to 15°.

[0082] Subsequently, a polymer powder sample containing 14.3% by weight of phthalate plasticizer of recycled PVC (D50: 200 μm) was prepared, and methyl ethyl ketone (MEK) as a swelling solvent and isopropanol (IPA) as a shrinkage solvent were prepared. Then, the polymer powder was saturated at 15.5 cm⁻¹. 3 MEK was supplied to the swelling solvent inlet 40 at a volumetric flow rate of 0.75 kg / hr (0.75 kg / hr as the mass flow rate) and at a flow rate of 10.6 cm⁻¹. 3 IPA is supplied to the shrink solvent inlet 50 at a volumetric flow rate of 0.5 kg / hr (0.5 kg / hr as the mass flow rate), and after confirming that steady state has been reached, the polymer powder sample is supplied to the polymer inlet 20 at a mass flow rate of 4.2 g / min (=0.25 kg / hr). Simultaneously, the polymer powder sample passes sequentially through the swelling zone 100 and the shrink zone 200 at a screw speed of 1 rpm, and is then discharged through the polymer outlet 30. In this configuration, the polymer is retained for 24 minutes in the swelling zone and 6 minutes in the shrink zone.

[0083] 0.5 g of PVC polymer discharged through polymer outlet 30 was sampled and analyzed by gas chromatography-flame ionization detection (GC-FID) to calculate the residual phthalate plasticizer content in the sample. An Agilent 7890A GC system was used for GC-FID analysis. The result showed a residual plasticizer content of 100 ppm.

[0084] Example 2

[0085] Compared to Example 1, in Example 2, the same apparatus and method were used to remove the plasticizer from the PVC polymer, except that MEK was applied at a rate of 7.5 cm⁻¹. 3 The volumetric flow rate is 0.375 kg / hr (min as mass flow rate) to the swelling solvent inlet 40, and IPA is supplied at a rate of 2.7 cm⁻¹. 3 A volumetric flow rate of 0.125 kg / hr (as a mass flow rate) is supplied to the shrink solvent inlet 50.

[0086] The residual plasticizer concentration of the discharged PVC polymer, measured in the same manner as in Example 1, was 250 ppm.

[0087] Comparative Example 1

[0088] Compared to Example 1, in Comparative Example 1, the same apparatus and method as in Example 1 were used to remove plasticizer from the PVC polymer, except that solvent was not supplied to the swelling solvent inlet 40, but only by shrinking the solvent inlet 50 to 25.9 cm. 3 MEK is supplied as a swelling solvent at a flow rate of 1.25 kg / hr / min (1.25 kg / hr as mass flow rate), and the retention time of the polymer in the device is set to 30 minutes.

[0089] The residual plasticizer concentration of the discharged PVC polymer, measured in the same manner as in Example 1, was 4200 ppm.

[0090] Comparative Example 2

[0091] Compared to Comparative Example 1, in Comparative Example 2, the same apparatus and method as in Comparative Example 1 were used to remove the plasticizer from the PVC polymer; the difference was that only the IPA, which served as a shrinkage solvent, was removed at 26.5 cm⁻¹. 3 A flow rate of 1.25 kg / hr (min as mass flow rate) is supplied to the shrink solvent inlet 50.

[0092] The residual plasticizer concentration of the discharged PVC polymer, measured in the same manner as in Example 1, was 62,000 ppm.

[0093] Comparative Example 3

[0094] Compared to Comparative Example 1, Comparative Example 3 used the same apparatus and method as Comparative Example 1 to remove plasticizer from the PVC polymer. The difference was that only the mixed solvent in which MEK as a swelling solvent and IPA as a shrinkage solvent were mixed in a 1:1 weight ratio was used at 26.0 cm⁻¹. 3 A flow rate of 1.25 kg / hr (min as mass flow rate) is supplied to the shrink solvent inlet 50.

[0095] The residual plasticizer concentration of the discharged PVC polymer, measured in the same manner as in Example 1, was 1400 ppm.

[0096] Based on the above results, the additive removal apparatus of the present invention can be used to remove additives from polymers in a continuous and efficient manner. Referring to Examples 1 and 2, it can be confirmed that high additive removal efficiency can be achieved when the solvent for swelling the polymer and the solvent for shrinking the polymer are respectively introduced into the swelling solvent inlet and the shrinking solvent inlet provided in the additive removal apparatus. On the other hand, when only one of the swelling solvent or the shrinking solvent is used at the same flow rate (Comparative Examples 1 and 2), or when a mixed solvent of these solvents is used, it is difficult to obtain the desired plasticizer removal efficiency even when using the same solvent at the same flow rate (Comparative Example 3).

Claims

1. An additive removal device, the additive removal device comprising: A barrel, the barrel providing an internal space and having a polymer inlet on one side and a polymer outlet on the other side; A screw, which is disposed inside the barrel and rotates axially; as well as A solvent discharge unit is disposed at one end of the barrel. The barrel includes a swelling solvent inlet and a shrinking solvent inlet. The swelling solvent inlet is located between and adjacent to the polymer inlet and the polymer outlet, and the shrinking solvent inlet is located between and adjacent to the polymer outlet.

2. The additive removal device according to claim 1, wherein, The angle of inclination between the extension of the rotation center axis of the screw and the ground is 5° to 30°.

3. The additive removal device according to claim 1, wherein, A rotational force supply device is provided at the other end of the barrel, and The screw includes a shaft connected to the rotational force supply device and rotating axially, and a plate fixed to the outer circumferential surface of the shaft and extending helically along the longitudinal direction of the shaft.

4. The additive removal device according to claim 1, wherein, The polymer introduced into the polymer inlet by the axial rotation of the screw is transferred to the polymer outlet and discharged.

5. The additive removal device according to claim 1, wherein, The internal space of the barrel is divided into a swelling zone from the polymer inlet to the swelling solvent inlet and a shrinkage zone from the swelling solvent inlet to the shrinkage solvent inlet.

6. The additive removal apparatus according to claim 1, wherein, The ratio x / y of the distance x from the polymer inlet to the swelling solvent inlet to the distance y from the swelling solvent inlet to the shrinking solvent inlet is from 0.1 to 60.

7. A method for removing additives, comprising: Prepare the additive removal device according to claim 1. A polymer containing additives is supplied to the polymer inlet, and a swelling solvent and a shrinking solvent are supplied to the swelling solvent inlet and the shrinking solvent inlet, respectively. The supplied polymer is transferred to the polymer outlet by the axial rotation of the screw; The polymer swells in a swelling zone from the polymer inlet to the swelling solvent inlet; as well as The polymer shrinks in the shrinkage zone from the swelling solvent inlet to the shrinkage solvent inlet.

8. The method according to claim 7, wherein, The additive is a phthalate plasticizer, which is at least one selected from dioctyl phthalate (DOP), dibutyl phthalate (DBP), dioctyl terephthalate (DOTP), diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), di(2-ethylhexyl) terephthalate (DEHTP), and butyl benzyl phthalate (BBP).

9. The method according to claim 7, wherein, The polymer is polyvinyl chloride (PVC).

10. The method according to claim 7, wherein, The swelling solvent is at least one selected from cyclohexanone, cyclopentanone, N,N-dimethylacetamide, tetrahydrofuran, pyridine, 3-pentanone, 2-pentanone, dimethylformamide, methyl ethyl ketone, dichloromethane, 4-methylpentan-2-one, nitrobenzene, 1,4-dioxane, 1,1,2,2-tetrachloroethane, acetone, ethyl acetate, chloroform, and dimethyl sulfoxide.

11. The method according to claim 7, wherein, The shrinkage solvent is at least one selected from ethanol, toluene, cyclohexanol, isopropanol, benzene, cyclohexane, 1-pentanol, 1-butanol, 1-propanol, hexane, and diethyl ether.

12. The method according to claim 7, wherein, The retention time of the polymer in the swelling zone and the average particle size D50 of the polymer satisfy the following general formula 3: [Formula 3] Average particle size of polymer in mm 5 ≤ Retention time in the swollen zone in minutes ≤ Average particle size of the polymer in mm 240.

13. The method according to claim 7, wherein, The flow rate ratio of the shrink solvent supplied to the shrink solvent inlet to the swelling solvent inlet is 30% to 300% by volume.

14. The method according to claim 7, wherein, The polymer is retained in the shrinkage zone for 0.5 to 10 minutes.

15. The method according to claim 7, wherein, The supplied swelling and shrinking solvents are transferred by gravity to the solvent discharge unit and discharged.

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