Blockage inhibition method of preparation process of ethylene-acrylic acid copolymer

Abstract

The present disclosure relates to a method for preparing an ethylene-acrylic acid copolymer, comprising: (S1) a step of preparing an ethylene-acrylic acid copolymer by supplying an ethylene monomer and an acrylic acid comonomer to a polymerization reactor; (S2) supplying the mixture containing the acrylic acid comonomer discharged from the front end or the rear end of the polymerization reactor and a cleaning solvent to a cleaning part; and (S3) dissolving the acrylic polymer from the acrylic comonomer contained in the mixture by using the cleaning solvent, wherein the cleaning solvent comprises a polyol-based solvent.

Description

Technical Field

[0001] The present disclosure relates to a method for suppressing a clogging phenomenon generated in a process for preparing an ethylene-acrylic acid copolymer. Background Art

[0002] In the process of preparing ethylene-acrylic acid copolymer, at the rear end of the polymerization reactor where the ethylene monomer and the acrylic acid comonomer undergo polymerization reaction, the unreacted acrylic acid comonomer undergoes polymerization and is converted into polyacrylic acid, and the acrylic acid polymer accumulates in the reactor and the pipe, causing a plugging problem. In particular, the acrylic acid (AA) comonomer forms an acrylic acid polymer such as polyacrylic acid (PAA) due to its high reactivity and self-polymerization, which frequently causes process interruptions and reduces process efficiency.

[0003] In order to solve this problem, conventionally, polymerization inhibitors such as hydroquinone (HQ) and phenothiazine (PTZ) are used to inhibit the polymerization reaction of the acrylic acid comonomer. However, under anaerobic conditions, the polymerization reaction inhibition efficiency is significantly low, and there is a risk of reducing process stability due to the influx of the polymerization inhibitor into the ethylene-acrylic acid copolymer as the final product through the circulation process. In addition, the above-mentioned polymerization inhibitor precipitates into the reactor due to its crystallinity, which in turn promotes clogging. Summary of the invention

[0004] According to an embodiment of the present disclosure, there is provided a method for preparing an ethylene-acrylic acid copolymer capable of suppressing corrosion and plugging of an ethylene-acrylic acid copolymer preparation device, thereby improving process efficiency.

[0005] According to the method for preparing an ethylene-acrylic acid copolymer disclosed in the present invention, it includes: (S1) a step of supplying an ethylene monomer and an acrylic acid comonomer to a polymerization reactor to prepare an ethylene-acrylic acid copolymer; (S2) a step of supplying a mixture containing an acrylic acid comonomer discharged from the front end or the rear end of the polymerization reactor and a cleaning solvent to a cleaning section; and (S3) a step of dissolving an acrylic acid polymer from the acrylic acid comonomer contained in the mixture with the cleaning solvent, wherein the cleaning solvent includes a polyol solvent.

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

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

[0008] In one embodiment, the (S1) step may include: a step of secondary compressing the ethylene monomer and acrylic acid comonomer compressed once by a primary compressor using a high-pressure compressor; a step of supplying the compressed ethylene monomer and acrylic acid comonomer to a polymerization reactor for polymerization; and a step of filtering a portion of the ethylene monomer separated from the emissions discharged from the polymerization reactor and supplying the portion to the primary compressor or the front end of the high-pressure compressor.

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

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

[0011] In one embodiment, after the step (S3), the method further includes: (S4) discharging the cleaning solution in which the acrylic polymer is dissolved.

[0012] In one embodiment, in the step (S2), the mass ratio of the acrylic acid copolymer monomer supplied to the cleaning part to the cleaning solvent is 1:0.1 to 1.

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

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

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

[0016] In one embodiment, the temperature of the cleaning part may be 0°C to 50°C.

[0017] The method for preparing the ethylene-acrylic acid copolymer according to the present disclosure can prevent corrosion of the reactor and the calandria.

[0018] In addition, there is no need to interrupt the process due to blockage, thereby providing a method for producing an ethylene-acrylic acid copolymer with improved process efficiency and excellent economy and productivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 and Figure 21 is a process diagram for preparing ethylene-acrylic acid copolymer according to one embodiment.

[0020] Figures 3 to 8 Each is a photograph in which the clogging suppressing effect of a washing solvent was observed when an acrylic polymer was washed by the method according to Examples 1 to 6.

[0021] Explanation of symbols:

[0022] 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: Filtration 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 DETAILED DESCRIPTION

[0023] The clogging suppression method of the preparation process of the ethylene-acrylic acid copolymer disclosed in the present invention is described in detail. The terms used in this specification are selected as much as possible from the commonly used terms that are currently widely used in consideration of the functions of the present invention, but these terms may be different according to the intentions or precedents of technicians engaged in related fields, the emergence of new technologies, etc. If not otherwise defined, the technical terms and scientific terms used may have the meanings that are generally understood by people with ordinary knowledge in the technical field to which the present invention belongs.

[0024] In this specification and the appended patent claims, terms such as "including" or "having" refer to the existence of features or constituent elements recorded in the specification, and do not exclude in advance the possibility of adding one or more other features or constituent elements unless otherwise specified.

[0025] When the context does not clearly specify a specific singular number, the singular expression used in this specification and the attached patent claims includes the plural expression. In addition, when the context does not clearly specify a specific plural number, the plural expression includes the singular expression.

[0026] In addition, the numerical range used in this specification includes the lower limit, the upper limit and all values ​​in the range, the increments logically derived from the form and width of the defined range, all values ​​defined therein, and all possible combinations of the upper and lower limits of the numerical range defined in different forms. When not specifically defined in the specification of the present invention, values ​​outside the numerical range that may occur due to experimental errors or rounding of values ​​are also included in the defined numerical range.

[0027] The degree terms "about" and the like used in this specification and the appended claims are used as meanings including a permissible error when there is a permissible error.

[0028] In the process of preparing ethylene-acrylic acid copolymer, at the rear end of the polymerization reactor where the ethylene monomer and the acrylic acid comonomer undergo polymerization reaction, the unreacted acrylic acid comonomer undergoes polymerization and is converted into polyacrylic acid, and the acrylic acid polymer accumulates in the reactor and the pipe, causing a plugging problem. In particular, the acrylic acid (AA) comonomer forms an acrylic acid polymer such as polyacrylic acid (PAA) due to its high reactivity and self-polymerization, which frequently causes process interruptions and reduces process efficiency.

[0029] In order to solve this problem, conventionally, polymerization inhibitors such as hydroquinone (HQ) and phenothiazine (PTZ) are used to inhibit the polymerization reaction of acrylic acid comonomers. However, the above-mentioned polymerization inhibitors precipitate into the reactor due to their crystallinity, which causes clogging.

[0030] To this end, the applicant has devoted himself to in-depth research and finally developed a method for preparing ethylene-acrylic acid copolymers using a cleaning solvent including a polyol solvent, so that even if the acrylic acid comonomer is polymerized, the acrylic acid polymer can be quickly removed, thereby suppressing the blockage of the reactor and the drain pipe, improving the process efficiency, and having excellent economy and productivity.

[0031] Hereinafter, the present disclosure will be described with reference to the accompanying drawings.

[0032] The method for preparing an ethylene-acrylic acid copolymer according to the present disclosure includes: (S1) supplying an ethylene monomer and an acrylic acid comonomer to a polymerization reactor to prepare an ethylene-acrylic acid copolymer; (S2) supplying a mixture containing an acrylic acid comonomer discharged from the front end or the rear end of the polymerization reactor and a cleaning solvent to a cleaning section; and (S3) dissolving an acrylic acid polymer from the acrylic acid comonomer contained in the mixture with the cleaning solvent, wherein the cleaning solvent includes a polyol solvent.

[0033] When preparing 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 simply removed by the cleaning solvent, thereby effectively suppressing the plugging phenomenon generated at the front end or rear end of the polymerization reactor. In addition, the polymerization process of ethylene monomer and acrylic acid comonomer to the cleaning process can be continuously performed without interruption, thereby improving the process efficiency.

[0034] Figure 1 and Figure 2 1 is a schematic diagram of a device for preparing an ethylene-acrylic acid copolymer according to an embodiment. Figure 1 and Figure 2 In step (S1), ethylene monomer may be supplied from the ethylene supply unit 10 and compressed once by the primary compressor 20. The ethylene monomer and acrylic acid compressed once and the acrylic acid comonomer and solvent supplied from the solvent supply unit 15 may be supplied to the high-pressure compressor 25 for secondary compression, and then the compressed product including the compressed ethylene monomer, acrylic acid comonomer and solvent may be supplied to the polymerization reactor 30. At this time, the first mixture containing the acrylic acid comonomer leaked during compression by the high-pressure compressor may be transferred to the cleaning unit, thereby significantly reducing the risk of blockage at the front end of the polymerization reactor.

[0035] An ethylene-acrylic acid copolymer as a final product A may be prepared by a polymerization reaction in the polymerization reactor 30, thereby discharging a second mixture including the ethylene-acrylic acid copolymer from the polymerization reactor. The second mixture discharged from the polymerization reactor 30 may pass through a high-pressure separator 40 and a low-pressure separator 60, thereby separating the ethylene-acrylic acid copolymer from the second mixture, thereby harvesting the final product A.

[0036] The second mixture from which the ethylene-acrylic acid copolymer is separated may be supplied to the cleaning part 90. The second mixture may include unreacted ethylene monomer, acrylic acid polymer, solvent, other additives, initiator, and the like.

[0037] In one embodiment, as long as it is a medium that can cause the ethylene monomer and the acrylic acid comonomer to copolymerize, the solvent is not limited, for example, it can be a low boiling point polar solvent. As an example, the solvent can include any one or more selected from the group consisting of methanol, ethyl alcohol, isopropyl alcohol, methyl ethyl ketone, tetrahydrofuran, acetone, ethylacetate, propyl acetate, butyl acetate, 2-methoxyethanol and 2-ethoxyethanol, but the present disclosure is not limited thereto.

[0038] In one embodiment, in the (S1) step, the mixing ratio of ethylene monomer, acrylic acid comonomer and solvent can be 1 to 20 parts by weight of acrylic acid comonomer, 1 to 20 parts by weight of solvent, or 3 to 10 parts by weight of acrylic acid comonomer, 3 to 10 parts by weight of solvent relative to 100 parts by weight of ethylene monomer, but the present disclosure is not limited thereto.

[0039] In the step (S1), the polymerization may be polymerization by an initiator, such as free radical polymerization, and thus the compressed material supplied to the polymerization reactor 30 may also include an initiator, specifically a free radical initiator, under which each monomer may react to polymerize. As an example, the polymerization may be performed by an initiator mixed solution including a free radical initiator and a diluent solvent.

[0040] As long as it is capable of initiating a free radical polymerization reaction, the content of the initiator is not limited, for example, 0.001 to 1 part by weight can be used based on 100 parts by weight of the entire monomer. In addition, the content of the diluent solvent can also be appropriately adjusted, for example, the diluent solvent can be diluted to 5 to 1000 parts by weight relative to 1 part by weight of the initiator. However, this is described as a specific example, and the present disclosure is not limited thereto.

[0041] As an example, as long as the free radical polymerization of ethylene monomer and acrylic acid comonomer can be carried out, the type of the free radical initiator is not limited, and any one or more peroxide organic peroxides selected from peroxycarbonate, peroxydicarbonate, peroxyester and peroxyketal can be cited. However, it is described as a specific example, and the present disclosure is not limited thereto.

[0042] The dilution solvent is not limited as long as it is a known initiator dilution solvent. For example, the use of a paraffin-based solvent including Isopar-H as the dilution solvent enables the preparation of a uniform polymer and prevents quality degradation such as a decrease in molecular weight.

[0043] In one example 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 use aliphatic and olefin hydrocarbons, such as saturated hydrocarbons having more than 6 carbon atoms, such as 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 the chain transfer agent is used, the content of the chain transfer agent is not greatly limited, for example, 0.1 to 20 parts by weight can be used relative to 100 parts by weight of the total monomer, but the present disclosure is not limited thereto.

[0044] As mentioned above, the (S1) step can be performed under high temperature and high pressure conditions by pressure and temperature control. As an example, the polymerization temperature and the polymerization pressure can be performed under temperature conditions of 100°C to 400°C, 150°C to 350°C or 200°C to 300°C, and under pressure conditions of 1000bar to 5000bar, 1100bar to 4000bar or 1200bar to 3000bar, respectively, but this announcement is not limited to this.

[0045] The polymerization reactor 30 is not limited as long as a known polymerization reactor is used. For example, various reactors such as a batch reactor such as an autoclave, a continuous stirred tank reactor (CSTR), and a tubular reactor can be used.

[0046] In one example, as long as a conventionally known ethylene polymer production apparatus is used, the primary compressor 20, the high pressure compressor 25, the high pressure separator (HPS) 40 and the low pressure separator (LPS) are not limited.

[0047] As a non-limiting example, in the high-pressure separator 40, a portion of the second mixture can be moved to the filter unit 50, undergo a filtering process, and be supplied to the primary compressor 20 or the front end of the high-pressure compressor 25. A portion of the second mixture may include unreacted ethylene monomer. By recovering the unreacted ethylene monomer to the polymerization reactor 30 and reusing it in the polymerization reaction, the ethylene-acrylic acid copolymer can be prepared with high efficiency.

[0048] The step (S2) is used to supply a mixture containing acrylic acid comonomers, including a first mixture discharged from the high-pressure compressor 25 at the front end of the polymerization reactor 30 and a second mixture discharged at the rear end of the polymerization reactor 30, to the cleaning section 90. The first mixture can be supplied through a first supply line 81 connecting the high-pressure compressor 25 and the cleaning section 90, and the second mixture can be supplied to the cleaning section 90 after passing through the high-pressure separator 40 and the low-pressure separator 60 through a second supply line 82 connecting the polymerization reactor 30 and the cleaning section 90.

[0049] In one embodiment, the first supply line 81 and the second supply line 82 may include a heat exchanger 85. The temperature T of the mixture containing the unreacted acrylic acid comonomer before passing through the heat exchanger 85 is 1and the temperature T of the mixture containing unreacted acrylic acid comonomer passing through heat exchanger 85 2 The following formula 1 can be satisfied:

[0050] [Formula 1]

[0051] 3 <T 2 / T 1 <20

[0052] The T 2 / T 1 It may be 3 to 20, 6 to 19, or 10 to 18. In the temperature range, the mixture including the unreacted acrylic acid copolymer monomer in a gaseous state is cooled and condensed by the heat exchanger 85 and then supplied to the cleaning part 90, thereby achieving excellent cleaning efficiency and being able to easily remove the cleaning solution B including the acrylic acid polymer dissolved by the cleaning solvent in the later-described step (S3).

[0053] In step (S2), the cleaning solvent may be supplied simultaneously with the first mixture and the second mixture, or the cleaning solvent may be supplied sequentially after the first mixture is supplied. Figure 2 As shown, the cleaning solvent can also be directly supplied to the cleaning portion 90 through the cleaning solvent supplier 70, which is more advantageous. Figure 1 As shown, the cleaning solvent supplier 70 is arranged on the first supply line 81 and the second supply line 82, so that the cleaning solvent passes through the heat exchanger 85 and is supplied to the cleaning part 90, thereby even the acrylic polymer accumulated in the drain pipes of the heat exchanger 85, the first supply line 81 and the second supply line 82 is dissolved, thereby preventing the drain pipes from being blocked.

[0054] In one embodiment, in the step (S2), the mass ratio of the acrylic acid comonomer: the cleaning solvent supplied to the cleaning unit 90 may be 1:0.1 to 1, 1:0.3 to 1, or 1:0.5. In the mass ratio, the cleaning solvent can effectively dissolve the acrylic polymer from the acrylic acid comonomer. When it is out of the range, the dissolution effect of the acrylic polymer may be reduced. When the content of the cleaning solvent is less than the range, the dissolution efficiency of the acrylic polymer becomes low. When the cleaning solvent is supplied above the range, not only the dissolution effect of the acrylic polymer is reduced, but also the use of the cleaning solvent is excessively increased, which may reduce the economic efficiency.

[0055] In addition, in one example, the pressure of the cleaning part 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.

[0056] When the mixture containing acrylic acid comonomer and the cleaning solvent are supplied to the cleaning part 90, the cleaning solvent can dissolve the acrylic acid comonomer and the acrylic acid polymer. In the existing preparation process of ethylene-acrylic acid copolymer, the unreacted acrylic acid comonomer is rapidly polymerized due to its high reactivity and self-polymerization, thereby forming a large amount of acrylic acid polymer. The acrylic acid polymer is accumulated in the pipe, reactor, etc., which has the problem of polluting process equipment and reducing process efficiency.

[0057] Therefore, when the cleaning solvent of the present disclosure is used, even if the acrylic acid polymer generated by the polymerization of the acrylic acid comonomer is stuck in the pipe and the reactor, the cleaning solvent can quickly dissolve the acrylic acid comonomer and the acrylic acid polymer and remove them, thereby effectively suppressing the clogging phenomenon.

[0058] In one embodiment, the boiling point of the cleaning solvent may be 100° C. to 400° C., 100° C. to 350° C., or 150° C. to 300° C. Using a cleaning solvent having a boiling point in the above range can provide an excellent cleaning effect without affecting other processes including the polymerization reaction. When a cleaning solvent having a boiling point below the above range is used, the cleaning solvent is vaporized inside the cleaning part 90, which not only reduces the cleaning effect, but also the cleaning solvent in a gaseous state flows into other processes except step (S2), thereby having a risk of adversely affecting the preparation process of the ethylene-acrylic acid copolymer.

[0059] In one example, the density of the cleaning solvent may be 0.5 g / cm 3 Up to 2g / cm 3 , 0.6g / cm 3 Up to 1.8g / cm 3 or 0.8g / cm 3 Up to 1.5g / cm 3 In the density range, the acrylic polymer can be quickly dissolved, and when having a density higher than the range, the fluidity is reduced and there is a problem of delaying the time for dissolving the acrylic polymer.

[0060] In one embodiment, the cleaning solvent may include a polyol solvent, which may be an alcohol solvent including a divalent to a tetravalent or a divalent to a trivalent alcohol group.

[0061] The cleaning solvent may include one or more divalent alcohols selected from the group consisting of ethylene glycol (EG), propylene glycol (PG), and diethylene glycol (DEG), or a trivalent alcohol including glycerol.

[0062] In a 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.

[0063] In one embodiment, after the step (S3), the method further includes the step (S4): discharging the washing solution B in which the unreacted acrylic acid comonomer and the acrylic acid polymer are dissolved, thereby preventing clogging. The steps from the step (S1) of preparing the ethylene-acrylic acid copolymer to the step (S4) of washing the acrylic acid polymer and discharging the washing solution are continuously performed without interrupting the process, thereby providing a method for preparing an ethylene-acrylic acid copolymer with improved process efficiency and excellent economy and productivity.

[0064] In one embodiment, the cleaning section 90 may be a vapor-liquid separator. By using a vapor-liquid separator as the cleaning section 90, in step (S4), the liquid cleaning solution B in which the acrylic acid comonomer and the acrylic acid polymer are dissolved is discharged to the outside, and the unreacted residue in the gas phase is supplied to the front end of the polymerization reactor 30 or the front end of the primary compressor 20 again, thereby further improving the efficiency of the preparation process of the ethylene-acrylic acid copolymer.

[0065] Hereinafter, the present disclosure is further described in detail through examples.

[0066] (Example 1)

[0067] After the mixture containing acrylic acid discharged from the preparation process of ethylene-acrylic acid copolymer and ethylene glycol (EG) added with 5 wt% of acrylic acid polymer is supplied to the cleaning part, the acrylic acid polymer is cleaned under normal temperature and pressure. At this time, the mass ratio of acrylic acid, initiator dilution solvent (Exxonmobil (Isopar-H)) and cleaning solvent supplied to the cleaning part is 1:1:1.

[0068] (Example 2)

[0069] The acrylic polymer was washed by the same method as in Example 1 except that propylene glycol (PG) was used as the washing solvent instead of ethylene glycol (EG).

[0070] (Example 3)

[0071] The acrylic polymer was washed by the same method as in Example 1 except that diethylene glycol (DEG) was used as the washing solvent instead of ethylene glycol (EG).

[0072] (Example 4)

[0073] The acrylic polymer was washed by the same method as in Example 1 except that glycerol was used as the washing solvent instead of ethylene glycol (EG).

[0074] (Example 5)

[0075] After the mixture containing acrylic acid discharged in the preparation process of ethylene-acrylic acid copolymer and ethylene glycol (EG) are supplied to the cleaning part, the acrylic acid polymer is cleaned under normal temperature and pressure. At this time, the mass ratio of acrylic acid, initiator dilution solvent (Exxonmobil (Isopar-H)) and cleaning solvent supplied to the cleaning part is 2:1:1.

[0076] (Example 6)

[0077] The acrylic polymer was washed by the same method as in Example 5 except that propylene glycol (PG) was used as the washing solvent instead of ethylene glycol (EG).

[0078] (Example 7)

[0079] The acrylic polymer was washed by the same method as in Example 1, except that the mass ratio of acrylic acid, initiator diluting solvent (Exxonmobil, Isopar-H) and washing solvent supplied to the washing section was 1:1:0.1.

[0080] (Comparative Example 1)

[0081] The acrylic polymer was washed by the same method as in Example 1 except that ethanol was used as the washing solvent instead of ethylene glycol (EG).

[0082] (Comparative Example 2)

[0083] The acrylic polymer was washed by the same method as in Example 1 except that methanol was used as the washing solvent instead of ethylene glycol (EG).

[0084] (Comparative Example 3)

[0085] The acrylic polymer was washed by the same method as in Example 1 except that methyl ethyl ketone (MEK) was used as the washing solvent instead of ethylene glycol (EG).

[0086] (Comparative Example 4)

[0087] The acrylic polymer was washed by the same method as in Example 1 except that no washing solvent was added.

[0088] (Comparative Example 5)

[0089] The acrylic polymer was washed by the same method as in Example 1, except that the mass ratio of acrylic acid, initiator diluting solvent (Exxonmobil, Isopar-H) and washing solvent supplied to the washing section was 1:1:1.5.

[0090] When the acrylic polymer was washed by the method according to Examples 1 to 7 and Comparative Examples 1 to 5, it was evaluated whether the acrylic polymer was dissolved. In the following Table 1, when the acrylic polymer was washed, the color of the washing solution did not change and the polyacrylic acid precipitate was not observed with the naked eye, and the polyacrylic acid precipitate was indicated by ◎, but when the washing solution became opaque, it was indicated by ○, and when the polyacrylic acid precipitate was observed, it was indicated by X.

[0091]

Table 1

[0092]

[0093]

[0094] like Figures 3 to 8 As shown in Table 1, it was confirmed that in Examples 1 to 7, acrylic acid and polyacrylic acid were rapidly dissolved in the cleaning solution.

[0095] Specifically, Figures 3 to 6 When the acrylic polymer was cleaned by the methods of Examples 1 to 4, photographs of cleaning solutions containing a mixture of acrylic acid, Isopar-H and a cleaning solvent were observed, and the dissolving effect of the cleaning solvent on the acrylic polymer was evaluated.

[0096] like Figures 3 to 6 As shown, in Examples 1 to 4 in which ethylene glycol, propylene glycol, diethylene glycol and glycerol were used as cleaning solvents, respectively, no phase separation or acrylic acid polymer precipitation was generated in the cleaning solution even in the presence of isopar-H as a diluent, thereby confirming that the cleaning solvent can effectively suppress the clogging of the process reactor and the drain pipe regardless of the presence or absence of the diluent.

[0097] Figure 7 This is a photograph of whether the acrylic acid polymer is dissolved during 96 hours after mixing ethylene glycol and acrylic acid comonomer as a cleaning solution by the method of Example 5. Figure 8 This is a photograph showing whether or not the acrylic acid polymer was dissolved after mixing propylene glycol and an acrylic acid comonomer as a cleaning solution by the method of Example 6 during 96 hours.

[0098] Examples 5 and 6 confirm the cleaning effect when a cleaning solvent without any added acrylic acid polymer is mixed with a mixture containing acrylic acid and isopar-H discharged from a polymerization reactor, as shown in FIG. Figure 7 and Figure 8 As shown, it was confirmed that the acrylic acid dissolved in the cleaning solution was not converted into polyacrylic acid or precipitated even after 96 hours, and that the long-term stability was excellent.

[0099] In Example 7, the mass ratio of acrylic acid to cleaning solvent is 1:0.1, and the content of cleaning solvent is significantly reduced compared with Example 1, but the acrylic acid polymer dissolving effect is excellent. This can save the amount of cleaning solvent used, which has an economic advantage.

[0100] This can confirm that the acrylic acid polymer produced in the ethylene-acrylic acid production process can be quickly removed, thereby improving the process efficiency.

[0101] On the contrary, in Comparative Examples 1 to 3 in which low-boiling monovalent alcohols and ketone solvents with a boiling point of 80°C or less were used as the washing solvents, as shown in Table 1, the ketone solvent of Comparative Example 3 did not dissolve the acrylic polymer. In Comparative Examples 1 and 2 in which monovalent alcohols were used as washing solvents, although the solubility in the acrylic polymer was high, the washing solvents were highly volatile, and when preparing ethylene-acrylic acid copolymers, the vaporized washing solvents flowed into the circulation process, causing adverse effects on other processes. Therefore, it was confirmed that the washing solvents were not suitable for use in suppressing clogging in the production process of ethylene-acrylic acid copolymers.

[0102] Comparative Example 4, which does not include a cleaning solvent, also forms and precipitates an acrylic polymer. In Comparative Example 5, in which the mass ratio of acrylic acid to the cleaning solvent is 1:1.5, no significant acrylic polymer precipitate is observed with the naked eye, but the transparency of the cleaning solution decreases over time and tends to become slightly opaque. Therefore, the greater the content of the cleaning solvent compared to acrylic acid, not only does it reduce the cleaning effect, but it also increases the amount of cleaning solvent used, which is not conducive to economic efficiency.

[0103] Therefore, when preparing ethylene-acrylic acid copolymer by the method disclosed in the present invention, the acrylic acid polymer from the unreacted acrylic acid comonomer is quickly dissolved by the cleaning solvent, thereby suppressing the blockage caused by the acrylic acid polymer. At the same time, the cleaning solvent disclosed in the present invention does not have a bad effect on other processes including the polymerization steps of ethylene monomer and acrylic acid comonomer, so it has the advantage of being able to increase the production of ethylene-acrylic acid comonomer. As a result, the efficiency of the preparation process of ethylene-acrylic acid copolymer is improved, and the failure and corrosion of process equipment such as reactors and pipes caused by blockage can be prevented, thereby saving the cost of repairing process equipment, which is beneficial.

[0104] As described above, the present disclosure is explained through specific matters, limited embodiments and drawings, but these are provided to help facilitate a more comprehensive understanding of the present disclosure. The present disclosure is not limited to the embodiments, and anyone with ordinary knowledge in the field to which the present disclosure belongs can make various modifications and variations from these records.

[0105] Therefore, the concept of the present disclosure is not limited to the described embodiments, and not only the attached patent claims, but also variations that are equal or equivalent to the patent claims all fall within the scope of the concept of the present disclosure.

Claims

1. A method for preparing an ethylene-acrylic acid copolymer, comprising: (S1) a step of supplying ethylene monomer and acrylic acid comonomer to a polymerization reactor to prepare an ethylene-acrylic acid copolymer; (S2) a step of supplying a mixture containing an acrylic acid comonomer discharged from a front end or a rear end of the polymerization reactor and a cleaning solvent to a cleaning part; and (S3) the step of dissolving the acrylic acid polymer from the acrylic acid comonomer contained in the mixture with the washing solvent, The cleaning solvent includes a polyol solvent.

2. The method for preparing the ethylene-acrylic acid copolymer according to claim 1, wherein: The boiling point of the cleaning solvent is 100°C to 400°C.

3. The method for preparing the ethylene-acrylic acid copolymer according to claim 1, wherein: The polyol solvent is a dihydric to tetrahydric alcohol solvent.

4. The method for preparing the ethylene-acrylic acid copolymer according to claim 1, wherein: The (S1) step comprises: The step of performing secondary compression of the ethylene monomer and the acrylic acid comonomer compressed once by the primary compressor by using a high-pressure compressor; supplying the compressed ethylene monomer and acrylic acid comonomer to a polymerization reactor for polymerization; and A step of filtering a portion of the ethylene monomer separated from the effluent discharged from the polymerization reactor and supplying the portion to the front end of the primary compressor or the high-pressure compressor.

5. The method for preparing the ethylene-acrylic acid copolymer according to claim 4, wherein: The mixture of step (S2) comprises: a first mixture containing acrylic acid comonomer leaked from the high-pressure compressor and a second mixture containing acrylic acid comonomer discharged from the polymerization reactor.

6. The method for preparing the ethylene-acrylic acid copolymer according to claim 5, wherein: The first mixture is transferred to the cleaning section through a first supply line connecting the high-pressure compressor and the cleaning section, The second mixture is transferred to the cleaning section through a second supply line connecting the polymerization reactor and the cleaning section.

7. The method for preparing the ethylene-acrylic acid copolymer according to claim 1, wherein: After the step (S3), the method further includes: (S4) discharging the cleaning solution in which the acrylic polymer is dissolved.

8. The method for preparing the ethylene-acrylic acid copolymer according to claim 1, wherein: In the step (S2), the mass ratio of the acrylic acid copolymer monomer to the cleaning solvent supplied to the cleaning part is 1:0.1 to 1.

9. The method for preparing the ethylene-acrylic acid copolymer according to claim 7, wherein: The steps (S1) to (S4) are performed in a continuous process.

10. The method for preparing 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 preparing an ethylene-acrylic acid copolymer according to claim 10, wherein: The cleaning solvent is supplied to the cleaning part through a heat exchanger included in the first and second supply lines.

12. The method for preparing an ethylene-acrylic acid copolymer according to claim 1, wherein: The temperature of the cleaning part is 0°C to 50°C.

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