Method of suppressing plugging in manufacturing process of ethylene-acrylic acid copolymer

Abstract

To provide a method of manufacturing an ethylene-acrylic acid copolymer, which may improve process efficiency by suppressing corrosion and plugging in an ethylene-acrylic acid copolymer manufacturing equipment.SOLUTION: There is provided a method of manufacturing an ethylene-acrylic acid copolymer including the steps of: (S1) supplying an ethylene monomer and an acrylic acid comonomer to a polymerization reactor to manufacture an ethylene-acrylic acid copolymer; (S2) supplying an acrylic acid comonomer-containing mixture discharged from a front or rear end of the polymerization reactor and a cleaning solvent to a cleaning unit; and (S3) dissolving a polyacrylic acid derived from the acrylic acid comonomer contained in the mixture in the cleaning solvent. The cleaning solvent includes a polyhydric alcohol-based solvent.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a method for suppressing the plugging phenomenon that occurs during the manufacturing step of an ethylene-acrylic acid copolymer. [Background technology]

[0002] In the process of preparing ethylene-acrylic acid copolymer, in the downstream of the polymerization reactor where the copolymerization reaction of ethylene monomer and acrylic acid is carried out, the unreacted acrylic acid comonomer is polymerized and converted into polyacrylic acid, and the acrylic acid polymer accumulates in the reactor and piping, which is called plugging. In particular, acrylic acid (AA) comonomer forms acrylic acid polymers such as polyacrylic acid (PAA) due to its high reactivity and self-polymerization, which causes frequent interruptions of the process and reduces the process efficiency.

[0003] To solve this problem, polymerization inhibitors such as hydroquinone (HQ) and phenothiazine (PTZ) have been used to inhibit the polymerization reaction of acrylic acid comonomer. However, under oxygen-free conditions, the polymerization reaction inhibition efficiency is extremely low, and there is a risk of the polymerization inhibitor flowing into the final product, ethylene-acrylic acid copolymer, through the circulation process, reducing process stability. In addition, due to the crystallinity of the polymerization inhibitor, the polymerization inhibitor precipitates in the reactor, which actually promotes the plugging phenomenon. Summary of the Invention [Problem to be solved by the invention]

[0004] One aspect of the present disclosure is to provide a method for producing an ethylene-acrylic acid copolymer, which can suppress corrosion and plugging of an ethylene-acrylic acid copolymer production facility and improve process efficiency. [Means for solving the problem]

[0005] The method for producing an ethylene-acrylic acid copolymer according to the present disclosure includes the steps of: (S1) supplying an ethylene monomer and an acrylic acid comonomer to a polymerization reactor to produce an ethylene-acrylic acid copolymer; (S2) supplying an acrylic acid comonomer-containing mixture and a washing solvent discharged from a front or rear stage of the polymerization reactor to a washing section; and (S3) dissolving an acrylic acid polymer derived from the acrylic acid comonomer contained in the mixture with the washing solvent, wherein the washing solvent includes a polyhydric alcohol solvent.

[0006] In one embodiment, the boiling point of the washing solvent may be from 100°C to 400°C.

[0007] In one embodiment, the polyhydric alcohol solvent may be a dihydric to tetrahydric alcohol solvent.

[0008] In one embodiment, the step (S1) may include a step of secondarily compressing the ethylene monomer and acrylic acid comonomer primarily compressed through a primary compressor with a high-pressure compressor, a step of supplying the compressed ethylene monomer and acrylic acid comonomer to a polymerization reactor to polymerize them, and a step of filtering a portion of the ethylene monomer separated from an effluent discharged from the polymerization reactor and supplying the filtered portion to the primary compressor or a front stage of the high-pressure compressor.

[0009] In one embodiment, the mixture in the (S2) step may include a first mixture containing an acrylic acid comonomer leaking from the high-pressure compressor and a second mixture containing an acrylic acid comonomer discharged from the polymerization reactor.

[0010] In one embodiment, the first mixture may be transferred to the washing section via a first supply line connecting the high-pressure compressor and the washing section, and the second mixture may be transferred to the washing section via a second supply line connecting the polymerization reactor and the washing section.

[0011] In one embodiment, the method may further include, after the step (S3), a step (S4) of discharging the cleaning solution in which the acrylic acid polymer has been dissolved.

[0012] In one embodiment, in the step (S2), the mass ratio of the acrylic acid comonomer to the washing solvent supplied to the washing section may be 1:0.1-1.

[0013] In one embodiment, the steps (S1) to (S4) can be carried out in a continuous process.

[0014] In one embodiment, the first and second supply lines may include a heat exchanger.

[0015] In one embodiment, the washing solvent may be supplied to the washing section by passing through a heat exchanger included in the first supply line and the second supply line.

[0016] In one embodiment, the temperature of the washing section may be 0°C to 50°C. Effect of the Invention

[0017] The method for producing an ethylene-acrylic acid copolymer according to the present disclosure can prevent corrosion of a reactor and piping.

[0018] In addition, the present invention provides a method for producing an ethylene-acrylic acid copolymer that does not require interruption of the process due to plugging, improves process efficiency, and is economical and productive. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a process diagram for producing an ethylene-acrylic acid copolymer according to one embodiment. [Diagram 2] FIG. 1 is a process diagram for producing an ethylene-acrylic acid copolymer according to one embodiment. [Diagram 3] 7 is a photograph showing the plugging suppression effect of a cleaning solvent when cleaning an acrylic acid polymer using the methods according to Examples 1 to FIG. 6, respectively. [Figure 4] 7 is a photograph showing the plugging suppression effect of a cleaning solvent when cleaning an acrylic acid polymer using the methods according to Examples 1 to FIG. 6, respectively. [Diagram 5] 7 is a photograph showing the plugging suppression effect of a cleaning solvent when cleaning an acrylic acid polymer using the methods according to Examples 1 to FIG. 6, respectively. [Figure 6] 7 is a photograph showing the plugging suppression effect of a cleaning solvent when cleaning an acrylic acid polymer using the methods according to Examples 1 to 6, respectively. [Figure 7] 7 is a photograph showing the plugging suppression effect of a cleaning solvent when cleaning an acrylic acid polymer using the methods according to Examples 1 to 6, respectively. [Figure 8] 7 is a photograph showing the plugging suppression effect of a cleaning solvent when cleaning an acrylic acid polymer using the methods according to Examples 1 to FIG. 6, respectively. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The present disclosure provides a detailed description of a method for suppressing plugging in a manufacturing process of an ethylene-acrylic acid copolymer. The terms used in this specification are currently commonly used and general terms that are selected as much as possible while taking into consideration the functions of the present disclosure, but these terms may differ depending on the intentions or precedents of engineers engaged in related fields, the emergence of new technologies, etc. Unless otherwise defined, the technical and scientific terms used may have the meanings that are commonly understood by those having ordinary knowledge in the technical field to which this invention belongs.

[0021] In this specification and the appended claims, the terms "comprise" and "have" mean the presence of features or components described in the specification, and do not preclude the possibility that one or more other features or components may be added, unless specifically limited.

[0022] As used in this specification and the appended claims, the singular term includes the plural term unless the context clearly dictates otherwise, and the plural term includes the singular term unless the context clearly dictates otherwise.

[0023] Additionally, numerical ranges used herein include lower and upper limits and all values ​​within that range, increments logically derived from the shape and width of the defined range, all doubly limited values, and all possible combinations of upper and lower limits of differently limited numerical ranges. Unless otherwise specified in the specification of the present invention, values ​​outside the numerical ranges that may occur due to experimental error or rounding of values ​​are also included in the defined numerical ranges.

[0024] As used in this specification and the appended claims, the term "about" or the like is intended to encompass the tolerance, if any.

[0025] In the process of producing ethylene-acrylic acid copolymer, in the downstream of the polymerization reactor where the copolymerization reaction of ethylene monomer and acrylic acid comonomer is carried out, the unreacted acrylic acid comonomer is polymerized and converted into polyacrylic acid, and the acrylic acid polymer accumulates in the reactor and piping, which is called plugging. In particular, acrylic acid (AA) comonomer forms acrylic acid polymers such as polyacrylic acid (PAA) due to its high reactivity and self-polymerization, which causes frequent process interruptions and reduces process efficiency.

[0026] To solve this problem, polymerization inhibitors such as hydroquinone (HQ) and phenothiazine (PTZ) have been used to suppress the polymerization reaction of acrylic acid comonomer. However, due to the crystallinity of the polymerization inhibitors, the polymerization inhibitors tend to precipitate in the reactor, which leads to the plugging phenomenon.

[0027] Therefore, as a result of thorough research, the applicant has developed a method for producing an ethylene-acrylic acid copolymer, which is economical and productive, by using a washing solvent containing a polyhydric alcohol solvent to rapidly remove the acrylic acid polymer even when the acrylic acid comonomer is polymerized, thereby suppressing plugging of a reactor and piping, and improving process efficiency.

[0028] The present disclosure will now be described with reference to the accompanying drawings.

[0029] The method for producing an ethylene-acrylic acid copolymer according to the present disclosure includes: (S1) a step of producing an ethylene-acrylic acid copolymer by supplying an ethylene monomer and an acrylic acid comonomer to a polymerization reactor; (S2) a step of supplying an acrylic acid comonomer-containing mixture discharged from a front stage or a rear stage of the polymerization reactor and a washing solvent to a washing section; (S3) a washing step in which the washing solvent dissolves an acrylic acid polymer derived from an unreacted acrylic acid comonomer contained in the mixture; and (S3) a washing step in which the washing solvent dissolves an acrylic acid polymer derived from an unreacted acrylic acid comonomer contained in the mixture, wherein the washing solvent includes a polyhydric alcohol solvent.

[0030] When preparing an ethylene-acrylic acid copolymer by the method according to the present disclosure, the acrylic acid polymer formed by polymerization of the acrylic acid comonomer can be quickly and easily removed by using a washing solvent, thereby effectively suppressing the plugging phenomenon occurring in the upstream or downstream of the polymerization reactor. In addition, the process from the polymerization process of the ethylene monomer and the acrylic acid comonomer to the washing process is continuously carried out without interruption, thereby improving the process efficiency.

[0031] 1 and 2 are schematic diagrams showing an ethylene-acrylic acid copolymer production apparatus according to one embodiment. Referring to FIG. 1 and FIG. 2, in step (S1), ethylene monomer is supplied from an ethylene supply unit (10) and is primarily compressed through a primary compressor (20). The primarily compressed ethylene monomer and the acrylic acid comonomer and solvent supplied from the acrylic acid and solvent supply unit (15) are supplied to a high-pressure compressor (25) for secondary compression, and the compressed product containing the compressed ethylene monomer, acrylic acid comonomer and solvent may be supplied to a polymerization reactor (30). At this time, the first mixture containing the acrylic acid comonomer leaking during compression in the high-pressure compressor is transferred to a cleaning unit, thereby significantly reducing the risk of plugging occurring in the upstream stage of the polymerization reactor.

[0032] An ethylene-acrylic acid copolymer may be produced as the final product (A) by the polymerization reaction in the polymerization reactor (30), and a second mixture containing the ethylene-acrylic acid copolymer may be discharged from the polymerization reactor (30). The second mixture discharged from the polymerization reactor (30) may pass through a high-pressure separator (40) and a low-pressure separator (60) to separate the ethylene-acrylic acid copolymer from the second mixture, thereby obtaining the final product (A).

[0033] The second mixture from which the ethylene-acrylic acid copolymer has been separated may be supplied to a washing section 90. The second mixture may contain unreacted ethylene monomer, acrylic acid polymer, a solvent, other additives, an initiator, and the like.

[0034] In one embodiment, the solvent may be any medium in which a copolymerization reaction between an ethylene monomer and an acrylic acid comonomer can occur, for example, a low boiling polar solvent. Exemplarily, the solvent may include any one or more selected from the group including methyl alcohol, ethyl alcohol, isopropyl alcohol, methyl ethyl ketone, tetrahydrofuran, acetone, ethyl acetate, propyl acetate, butyl acetate, 2-methoxyethanol, and 2-ethoxyethanol, but the present disclosure is not limited thereto.

[0035] In one embodiment, in the step (S1), the mixing ratio of the ethylene monomer, the acrylic acid comonomer, and the solvent may be 1 to 20 parts by weight of the acrylic acid comonomer and 1 to 20 parts by weight of the solvent, or 3 to 10 parts by weight of the acrylic acid comonomer and 3 to 10 parts by weight of the solvent, relative to 100 parts by weight of the ethylene monomer, but the present disclosure should not be construed as being limited thereto.

[0036] In the step (S1), the polymerization may be polymerization by an initiator, for example, free radical polymerization, so that the compressed material supplied to the polymerization reactor (30) may further contain an initiator, specifically, a radical initiator, and each monomer may react under the radical initiator to perform polymerization. For example, the polymerization may be performed by using an initiator mixed solution containing a radical initiator and a diluting solvent.

[0037] The amount of the initiator used may be sufficient to initiate a radical polymerization reaction, and may be, for example, 0.001 to 1 part by weight based on 100 parts by weight of the total monomers. The amount of the dilution solvent used may also be appropriately adjusted, and may be, for example, 5 to 1,000 parts by weight of the dilution solvent per 1 part by weight of the initiator. However, this is merely a specific example, and the present disclosure should not be interpreted as being limited thereto.

[0038] As an example, the type of the radical initiator may be any type that can radically polymerize an ethylene monomer and an acrylic acid comonomer, and may be, for example, a peroxy-based organic peroxide including at least one selected from peroxycarbonate, peroxydicarbonate, peroxyester, and peroxyketal, but this is merely a specific example, and the present disclosure should not be construed as being limited thereto.

[0039] The dilution solvent may be a known initiator dilution solvent. For example, by using a paraffin-based solvent containing Isopar-H as the dilution solvent, a uniform copolymer can be produced and deterioration in quality such as a decrease in molecular weight can be prevented.

[0040] In one embodiment of the present disclosure, the compressed material supplied to the polymerization reactor (30) may further include a chain transfer agent. As a non-limiting example, the chain transfer agent may be aliphatic and olefinic hydrocarbons, for example, saturated hydrocarbons having 6 or more carbon atoms, for example, compounds such as hexane, cyclohexane, and octane, ketone compounds such as acetone, diethyl ketone, and diamyl ketone, aldehyde compounds such as formaldehyde and acetaldehyde, and alcohol compounds such as methanol, ethanol, propanol, and butanol. When a chain transfer agent is used, the amount of the chain transfer agent is not particularly limited, and may be, for example, 0.1 to 20 parts by weight based on 100 parts by weight of the total monomers, but the present disclosure is not limited thereto.

[0041] As described above, the (S1) step may be carried out under high temperature and high pressure conditions by controlling the pressure and temperature. For example, the polymerization temperature and pressure may be 100° C. to 400° C., 150° C. to 350° C., or 200° C. to 300° C., respectively, and the polymerization may be carried out under pressure conditions of 1000 bar to 5000 bar, 1100 bar to 4000 bar, or 1200 bar to 3000 bar, but the present disclosure is not limited thereto. The polymerization reactor (30) may be any of various known polymerization reactors, including, for example, a batch reactor such as an autoclave, a continuous stirred tank reactor (CSTR), and a tubular reactor.

[0042] In addition, in one example, the primary compressor (20), the high-pressure compressor (25), the high-pressure separator (40) (HPS), and the low-pressure separator (60) (LPS) may be conventionally known ethylene polymer production equipment.

[0043] As a non-limiting example, in the high-pressure separator (40), a portion of the second mixture may move to a filter section (50), pass through a filtering step, and be supplied to a stage preceding the first compressor (20) or the high-pressure compressor (25). A portion of the second mixture may contain unreacted ethylene monomer. By recovering the unreacted ethylene monomer in the polymerization reactor (30) and reusing it in the polymerization reaction, an ethylene-acrylic acid copolymer can be produced with high efficiency.

[0044] The (S2) step is to supply an acrylic acid comonomer-containing mixture, including a first mixture discharged from a high-pressure compressor (25) upstream of the polymerization reactor (30) and a second mixture discharged from a downstream of the polymerization reactor (30), to a washing section (90). The first mixture may be supplied through a first supply line (81) connecting the high-pressure compressor (25) and the washing section (90), and the second mixture may be supplied to the washing section (90) through a second supply line (82) connecting the polymerization reactor (30) and the washing section (90) after passing through a high-pressure separator (40) and a low-pressure separator (60).

[0045] In one embodiment, the first supply line (81) and the second supply line (82) may include a heat exchanger (85). The temperature (T1) of the mixture containing the unreacted acrylic acid comonomer before passing through the heat exchanger (85) and the temperature (T2) of the mixture containing the unreacted acrylic acid comonomer after passing through the heat exchanger (85) can satisfy the following formula 1.

[0046] [Formula 1] 3 <T2 / T1<20 The T2 / T1 may be 3 to 20, 6 to 19, or 10 to 18. In the above temperature range, the mixture containing the unreacted acrylic acid comonomer in a gaseous state is cooled and condensed through a heat exchanger (85) and then supplied to the washing section (90), thereby achieving excellent washing efficiency and easily removing the washing solution (B) containing the acrylic acid polymer dissolved by the washing solvent in the step (S3) described below.

[0047] In step (S2), the washing solvent may be supplied simultaneously with the first mixture and the second mixture, or the washing solvent may be supplied sequentially after the mixtures are supplied. As shown in Fig. 2, the washing solvent may be directly supplied to the washing section (90) by a washing solvent supplying device (70), or more preferably, as shown in Fig. 1, the washing solvent supplying device (70) is disposed in the first supply line (81) and the second supply line (82), and the washing solvent is supplied to the washing section (90) while passing through a heat exchanger (85), thereby dissolving even the acrylic acid polymer accumulated in the heat exchanger (85) and the piping of the first supply line (81) and the second supply line (82), and preventing clogging of the piping.

[0048] In one embodiment, in the step (S2), the mass ratio of the acrylic acid comonomer to the washing solvent supplied to the washing section (90) may be 1:0.1-1, 1:0.3-1, or 1:0.5-1. At the mass ratio, the washing solvent can effectively dissolve the acrylic acid polymer derived from the acrylic acid comonomer. Outside the range, the dissolving effect of the acrylic acid polymer may be reduced. If the content of the washing solvent is less than the range, the dissolving effect of the acrylic acid polymer may be reduced, and if the washing solvent is supplied beyond the range, not only the dissolving effect of the acrylic acid polymer may be reduced, but also the amount of the washing solvent used may be excessively increased, which may reduce the economic efficiency.

[0049] In addition, in one example, the pressure of the cleaning section (90) may be 1 bar to 20 bar, 5 bar to 15 bar, or 7 bar to 12 bar, but the present disclosure is not limited thereto.

[0050] When the mixture containing the acrylic acid comonomer and the washing solvent are supplied to the washing section (90), the washing solvent can dissolve the acrylic acid comonomer and the acrylic acid polymer. In the conventional process for producing ethylene-acrylic acid copolymer, the unreacted acrylic acid comonomer is rapidly polymerized due to its high reactivity and self-polymerization to form a large amount of acrylic acid polymer. The acrylic acid polymer accumulates in piping, reactors, etc., contaminating the process equipment and reducing the process efficiency.

[0051] Therefore, when the cleaning solvent of the present disclosure is used, even if an acrylic acid polymer produced by polymerization of an acrylic acid comonomer adheres to the piping and the reactor, the acrylic acid comonomer and the acrylic acid polymer are quickly dissolved and removed by the cleaning solvent, so that the plugging phenomenon can be effectively suppressed.

[0052] In one embodiment, the boiling point of the washing solvent may be 100°C to 400°C, 100°C to 350°C, or 150°C to 300°C. By using a washing solvent having a boiling point in the above range, it is possible to provide an excellent washing effect without affecting other processes including the polymerization reaction. When a washing solvent having a boiling point below the above range is used, not only is the washing solvent vaporized inside the washing section (90) to reduce the washing effect, but there is also a risk that the gaseous washing solvent will flow into other processes except for the (S2) step, adversely affecting the ethylene-acrylic acid copolymer production process.

[0053] In one example, the density of the cleaning solvent is 0.5 g / cm 3 ~2g / cm 3 , 0.6g / cm 3 ~1.8g / cm 3 or 0.8g / cm 3 ~1.5g / cm 3 In the above density range, the acrylic acid polymer can dissolve at a high rate, and if the density is higher than the above range, the fluidity may decrease, and the time it takes for the acrylic acid polymer to dissolve may be delayed.

[0054] In one embodiment, the cleaning solvent may include a polyhydric alcohol solvent, which may be an alcohol solvent containing a dihydric to tetrahydric or dihydric to trihydric alcohol group.

[0055] The washing solvent may include one or more dihydric alcohols selected from the group including ethylene glycol (EG), propylene glycol (PG) and diethylene glycol (DEG) or trihydric alcohols including glycerol.

[0056] In one non-limiting example, the temperature of the cleaning section may be 0°C to 50°C, 5°C to 45°C, or 10°C to 40°C, and the pressure of the cleaning section may be 1 bar to 20 bar, 3 bar to 17 bar, or 5 bar to 15 bar.

[0057] In one embodiment, plugging can be suppressed by further comprising a step (S4) of discharging the washing solution (B) in which the unreacted acrylic acid comonomer and the acrylic acid polymer are dissolved, after the step (S3). By performing the steps from the step (S1) of producing the ethylene-acrylic acid copolymer to the step (S4) of washing the acrylic acid polymer and discharging the washing solution in a continuous process without interruption, the process efficiency is improved, and a method for producing an ethylene-acrylic acid copolymer with excellent economy and productivity can be provided.

[0058] In one embodiment, the cleaning section (90) may be a vapor-liquid separator. By using a vapor-liquid separator in the cleaning section (90), the cleaning solution (B) in a liquid state in which the acrylic acid comonomer and the acrylic acid polymer are dissolved is discharged to the outside in step (S4), and at the same time, the unreacted residue in the gas phase is resupplied to the upstream of the polymerization reactor (30) or the upstream of the primary compressor (20), thereby further improving the efficiency of the ethylene-acrylic acid copolymer production process.

[0059] The present disclosure will now be described in further detail with reference to examples.

[0060] Example 1 The mixture containing acrylic acid discharged during the ethylene-acrylic acid copolymer manufacturing process and ethylene glycol (EG) containing 5 wt% acrylic acid polymer were fed to the washing section, and the acrylic acid polymer was washed under normal temperature and pressure conditions. At this time, the mass ratio of acrylic acid, initiator dilution solvent (Exxonmobil, Isopar-H) and washing solvent fed to the washing section was 1:1:1.

[0061] Example 2 The acrylic acid polymer was washed in the same manner as in Example 1, except that propylene glycol (PG) was used instead of ethylene glycol (EG) as the washing solvent.

[0062] Example 3 The acrylic acid polymer was washed in the same manner as in Example 1, except that diethylene glycol (DEG) was used instead of ethylene glycol (EG) as the washing solvent.

[0063] Example 4 The acrylic acid polymer was washed in the same manner as in Example 1, except that glycerol was used instead of ethylene glycol (EG) as the washing solvent.

[0064] Example 5 The acrylic acid-containing mixture and ethylene glycol (EG) discharged during the ethylene-acrylic acid copolymer manufacturing process were fed to the washing section, and the acrylic acid polymer was washed under normal temperature and pressure conditions. At this time, the mass ratio of acrylic acid, initiator dilution solvent (Exxonmobil, Isopar-H) and washing solvent fed to the washing section was 2:1:1.

[0065] Example 6 The acrylic acid polymer was washed in the same manner as in Example 5, except that propylene glycol (PG) was used instead of ethylene glycol (EG) as the washing solvent.

[0066] Example 7 The acrylic acid polymer was washed in the same manner as in Example 1, except that the mass ratio of acrylic acid, initiator dilution solvent (Exxonmobil, Isopar-H) and washing solvent supplied to the washing section was 1:1:0.1.

[0067] Comparative Example 1 The acrylic acid polymer was washed in the same manner as in Example 1, except that ethanol was used instead of ethylene glycol (EG) as the washing solvent.

[0068] Comparative Example 2 The acrylic acid polymer was washed in the same manner as in Example 1, except that methanol was used instead of ethylene glycol (EG) as the washing solvent.

[0069] Comparative Example 3 The acrylic acid polymer was washed in the same manner as in Example 1, except that methyl ethyl ketone (MEK) was used instead of ethylene glycol (EG) as the washing solvent.

[0070] Comparative Example 4 The acrylic acid polymer was washed in the same manner as in Example 1, except that no washing solvent was added.

[0071] Comparative Example 5 The acrylic acid polymer was washed in the same manner as in Example 1, except that the mass ratio of acrylic acid, initiator dilution solvent (Exxonmobil, Isopar-H) and washing solvent fed to the washing section was 1:1:1:1.5.

[0072] The presence or absence of dissolution of the acrylic acid polymer during washing of the acrylic acid polymer was evaluated according to the methods of Examples 1 to 7 and Comparative Examples 1 to 5. In Table 1 below, the case where there was no color change in the washing solution during washing of the acrylic acid polymer and no polyacrylic acid precipitate was observed with the naked eye is represented by ◎, the case where no polyacrylic acid precipitate was observed with the naked eye but the washing solution became opaque is represented by ○, and the case where a polyacrylic acid precipitate was observed is represented by X.

[0073] [Table 1]

[0074] As shown in FIGS. 3 to 8 and Table 1, in the cases of Examples 1 to 7, it was confirmed that acrylic acid and polyacrylic acid were quickly dissolved in the cleaning solvent.

[0075] Specifically, Figs. 3 to 6 are photographs showing cleaning solutions containing a mixture of acrylic acid, Isopar-H, and a cleaning solvent when an acrylic acid polymer is cleaned by the methods of Examples 1 to 4, respectively, and the dissolving effect of the cleaning solvent on the acrylic acid polymer was evaluated.

[0076] As shown in Figures 3 to 6, in Examples 1 to 4 in which ethylene glycol, propylene glycol, diethylene glycol, diethylene glycol and glycerol were used as cleaning solvents, respectively, no phase separation or acrylic acid polymer precipitates were generated from the cleaning solution despite the presence of the dilution solvent isopar-H. This confirmed that the cleaning solvent can effectively suppress plugging of process reactors and piping, regardless of the presence or absence of a dilution solvent.

[0077] FIG. 7 is a photograph showing the results of observing whether or not the acrylic acid polymer is dissolved after 96 hours of mixing ethylene glycol and acrylic acid comonomer as a cleaning solution in the method of Example 5, and FIG. 8 is a photograph showing the results of observing whether or not the acrylic acid polymer is dissolved after 96 hours of mixing propylene glycol and acrylic acid comonomer as a cleaning solution in the method of Example 6.

[0078] In Examples 5 and 6, the cleaning effect was confirmed when a cleaning solvent to which no acrylic acid polymer was added was mixed with a mixture containing acrylic acid and isopar-H discharged from a polymerization reactor. As shown in Figures 7 and 8, even after 96 hours, the acrylic acid dissolved in the cleaning solution was not converted to polyacrylic acid, and polyacrylic acid was not precipitated, demonstrating excellent long-term stability.

[0079] In the case of Example 7, the mass ratio of acrylic acid to washing solvent was 1:0.1, and the amount of washing solvent was significantly reduced compared to Example 1, but the dissolving effect of the acrylic acid polymer was excellent, which reduced the amount of washing solvent used and was economically advantageous.

[0080] As a result, the acrylic acid polymer generated during the ethylene-acrylic acid production process can be rapidly removed, improving process efficiency.

[0081] On the other hand, in Comparative Examples 1 to 3 in which a monohydric alcohol and a ketone-based solvent having a low boiling point of 80° C. or less were used as the cleaning solvent, the ketone-based solvent of Comparative Example 3 could not dissolve the acrylic acid polymer, as shown in Table 1. In Comparative Examples 1 and 2 in which a monohydric alcohol was used as the cleaning solvent, the solubility of the acrylic acid polymer was high, but the cleaning solvent was highly volatile, and the cleaning solvent vaporized during the production of an ethylene-acrylic acid copolymer flowed into the circulation process, causing a problem of adversely affecting other processes. Therefore, it was confirmed that the solvent is unsuitable for use in suppressing plugging in the ethylene-acrylic acid copolymer production process.

[0082] In Comparative Example 4, which did not contain a washing solvent, an acrylic acid polymer was formed and precipitated. In Comparative Example 5, in which the mass ratio of acrylic acid to washing solvent was 1:1.5, no noticeable acrylic acid polymer precipitate was observed with the naked eye, but the transparency of the washing solution decreased over time, and it tended to become slightly opaque. Therefore, the higher the content of the washing solvent relative to acrylic acid, the lower the washing effect, and the greater the amount of washing solvent used, which was not economical.

[0083] Therefore, when the ethylene-acrylic acid copolymer is produced by the method of the present disclosure, the washing solvent can quickly dissolve the acrylic acid polymer derived from the unreacted acrylic acid comonomer, and can suppress plugging caused by the acrylic acid polymer. At the same time, the washing solvent of the present disclosure has the advantage that it does not adversely affect other processes including the polymerization step of the ethylene monomer and the acrylic acid comonomer, and can maintain a high production amount of the ethylene-acrylic acid copolymer. This improves the efficiency of the ethylene-acrylic acid copolymer production process, and prevents breakdowns and corrosion of process equipment such as reactors and piping due to plugging, which advantageously reduces the maintenance costs of the process equipment.

[0084] As described above, the present disclosure has been described using specific and limited examples and drawings, but these are provided to facilitate a more comprehensive understanding of the present disclosure, and the present disclosure is not limited to the above examples. A person having ordinary knowledge in the field to which the present disclosure pertains can make various modifications and variations from these descriptions.

[0085] Therefore, the idea of ​​the present disclosure is not limited to the described embodiments, and all modifications equivalent to or equivalent to the scope of the claims below, as well as the scope of the claims, should be considered to fall within the scope of the idea of ​​the present disclosure. [Explanation of symbols]

[0086] 10: Ethylene supply section 15: Acrylic acid and solvent supply section 20: Primary compressor 25: High pressure compressor 30: Polymerization reactor 40: High pressure separator 50: Filter section 60: Low pressure separator 70: cleaning solvent supply section 81: first supply line 82: Second supply line 85: Heat exchanger 90: Cleaning section A: Final product B: Cleaning solution

Claims

1. (S1) supplying ethylene monomer and acrylic acid comonomer to a polymerization reactor to produce an ethylene-acrylic acid copolymer; (S2) supplying the acrylic acid comonomer-containing mixture and the washing solvent discharged from the upstream or downstream of the polymerization reactor to a washing section; (S3) the washing solvent dissolves an acrylic acid polymer derived from the acrylic acid comonomer contained in the mixture; The method for producing an ethylene-acrylic acid copolymer, wherein the washing solvent contains a polyhydric alcohol solvent.

2. The method for producing an ethylene-acrylic acid copolymer according to claim 1, wherein the boiling point of the washing solvent is from 100°C to 400°C.

3. The method for producing an ethylene-acrylic acid copolymer according to claim 1, wherein the polyhydric alcohol solvent is a dihydric to tetrahydric alcohol solvent.

4. The step (S1) includes: secondarily compressing the ethylene monomer and acrylic acid comonomer primarily compressed by a primary compressor by a high-pressure compressor; feeding compressed ethylene monomer and acrylic acid comonomer into a polymerization reactor for polymerization; and filtering a portion of the ethylene monomer separated from the discharged product discharged from the polymerization reactor, and supplying the filtered portion to the primary compressor or a front stage of the high-pressure compressor.

5. The mixture of the (S2) step is The method for producing an ethylene-acrylic acid copolymer according to claim 4, comprising: a first mixture containing an acrylic acid comonomer leaking from the high-pressure compressor; and a second mixture containing an acrylic acid comonomer discharged from the polymerization reactor.

6. The first mixture is transported to a cleaning section via a first supply line connecting the high-pressure compressor and the cleaning section; The method for producing an ethylene-acrylic acid copolymer according to claim 5, wherein the second mixture is transported to the washing section via a second supply line connecting the polymerization reactor and the washing section.

7. 2. The method for producing an ethylene-acrylic acid copolymer according to claim 1, further comprising, after the step (S3), a step (S4) of discharging the washing solution in which the acrylic acid polymer is dissolved.

8. 2. The method for producing an ethylene-acrylic acid copolymer according to claim 1, wherein in the step (S2), a mass ratio of the acrylic acid comonomer to the washing solvent supplied to the washing section is 1:0.1 to 1.

9. The method for producing an ethylene-acrylic acid copolymer according to claim 7, wherein steps (S1) to (S4) are carried out in a continuous process.

10. The method for producing an ethylene-acrylic acid copolymer according to claim 6, wherein the first supply line and the second supply line include a heat exchanger.

11. The method for producing an ethylene-acrylic acid copolymer according to claim 10, wherein the washing solvent is supplied to the washing section through heat exchangers included in the first supply line and the second supply line.

12. The method for producing an ethylene-acrylic acid copolymer according to claim 1, wherein the temperature of the washing section is 0°C to 50°C.

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