Method for producing ethylene-carboxylic acid copolymer

Abstract

In a method for producing an ethylene-carboxylic acid copolymer according to an embodiment of the present invention, a carboxylic acid monomer and a polar cosolvent are introduced separately into a mixing section or stored together in a supply section to form a mixture. The mixture and ethylene are then injected into a reactor to undergo copolymerization. The production of by-products can be suppressed by adjusting the reaction kinetics of the carboxylic acid monomer and the polar cosolvent.

Description

[Technical field]

[0001] The present invention relates to a method for producing an ethylene-carboxylic acid copolymer. [Background technology]

[0002] For example, ethylene-carboxylic acid copolymers such as ethylene-acrylic acid copolymers are used in a variety of applications, including sealing materials, adhesives, packing materials, and optical films.

[0003] The ethylene-carboxylic acid copolymer can be produced by polymerizing ethylene and a carboxylic acid compound (eg, acrylic acid, methacrylic acid, etc.) as a comonomer in a continuous reactor.

[0004] Carboxylic acid compounds have a higher self-reactivity than ethylene, and therefore may self-polymerize when exposed to high temperatures during the process of being supplied from lines, pumps, compressors, etc. This may cause blockage of the lines and damage to the polymerization equipment. If the operating temperature of the equipment is lowered to prevent this self-polymerization, crystallization of the carboxylic acid compounds may occur.

[0005] When a carboxylic acid compound is supplied, a co-solvent can be used to prevent crystallization and suppress fouling in the equipment. However, if a polar solvent is used as the co-solvent, it may react with the carboxylic acid compound to produce by-products.

[0006] Furthermore, when a continuous process is carried out under severe polymerization conditions such as high temperature and high pressure, detailed component analysis and reaction analysis of by-products in the flow path may become substantially difficult.

[0007] Therefore, there is a need for adjustment of the polymerization process and process variables that can prevent the self-polymerization of the carboxylic acid compound while suppressing the production of additional by-products.

[0008] For example, US Pat. No. 6,852,792 discloses an aqueous dispersion for sealing containing an ethylene-acrylic acid copolymer, but does not recognize the design requirements of the polymerization process discussed above. Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a method for producing an ethylene-carboxylic acid copolymer having improved process reliability and polymerization efficiency. [Means for solving the problem]

[0010] In the method for producing an ethylene-carboxylic acid copolymer according to the exemplary embodiment, a mixture of a carboxylic acid monomer and an organic solvent-based polar co-solvent is formed. The mixture and ethylene are injected into a reactor and copolymerized. When the mixture of the carboxylic acid monomer and the organic solvent-based polar co-solvent is formed, a reaction progress index (RPI) defined by the following formula 1 is set to 1.5 to 1.3 × 10 7 By adjusting the range of sec·K, the amount of side reaction products of the carboxylic acid monomer and the polar co-solvent can be controlled.

[0011]

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[0012]

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[0013] In some embodiments, the reaction progress index is 14.9 to 1.3 × 10 5It may be in the range of sec·K.

[0014] In some embodiments, the mixture can be expelled.

[0015] In some embodiments, the discharge pressure of the mixture may be greater than the mixing pressure of the carboxylic acid monomer and the polar co-solvent.

[0016] In some embodiments, the discharge pressure may be greater than the pressure within the reactor.

[0017] In some embodiments, the carboxylic acid monomer and the polar co-solvent may each be introduced into a mixing section to form the mixture, the mixture may be transferred from the mixing section to a discharge section via a transfer flow path, and the mixture may be discharged from the discharge section via a discharge flow path.

[0018] In some embodiments, the temperature of the mixture can be maintained at or above the crystallization temperature of the carboxylic acid monomer and below the self-polymerization temperature of the carboxylic acid monomer.

[0019] In some embodiments, the mixture can be contacted with ethylene prior to being injected into the reactor.

[0020] In some embodiments, the mixture can be infused with an inhibitor of the reaction between the carboxylic acid monomer and the polar co-solvent.

[0021] In some embodiments, the reaction inhibitor may include an amine-based compound.

[0022] In some embodiments, a chain transfer agent can be injected into the mixture via a pre-stream of the reactor.

[0023] In some embodiments, the chain transfer agent can include a non-polar organic compound.

[0024] In some embodiments, the chain transfer agent can include methyl ethyl ketone or isobutane.

[0025] In some embodiments, the following formula 2 can be satisfied:

[0026]

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[0027]

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[0028] In some embodiments, the carboxylic acid monomer can include acrylic acid and the polar co-solvent can include ethanol. Effect of the Invention

[0029] In the method for producing an ethylene-carboxylic acid copolymer according to the exemplary embodiment, a polar co-solvent can be used as a carrier fluid for the carboxylic acid monomer. The crystallization temperature of the mixture of the polar co-solvent and the carboxylic acid monomer can be lower than the crystallization temperature of the pure carboxylic acid monomer. This can prevent a decrease in process yield or process efficiency due to crystallization or self-polymerization due to crystallization.

[0030] According to an exemplary embodiment, the parameters of the carboxylic acid monomer and the polar co-solvent can be adjusted to appropriately control the reaction performance while suppressing the side reaction between the carboxylic acid monomer and the polar co-solvent. This can prevent the deterioration of the physical properties of the polymer product by suppressing the side reaction products generated from the carboxylic acid monomer, and can prevent the by-reaction products from remaining in the product. In addition, the copolymerization yield, conversion rate, molecular weight and molecular weight distribution of the product can be appropriately controlled.

[0031] According to exemplary embodiments, without the need for additional analytical equipment to identify side reaction products in, for example, high temperature and pressure flow paths, side reaction products can be effectively suppressed without reducing process efficiency by adjusting process conditions. [Brief description of the drawings]

[0032] [Figure 1] FIG. 1 is a schematic process flow diagram illustrating a method for producing an ethylene-carboxylic acid copolymer according to an exemplary embodiment. [Diagram 2] FIG. 2 is a schematic process flow diagram illustrating a method for producing an ethylene-carboxylic acid copolymer according to some exemplary embodiments. [Diagram 3] 3 to 11 are graphs showing the amount of ethyl acrylate generated over time. [Figure 4] 3 to 11 are graphs showing the amount of ethyl acrylate generated over time. [Diagram 5] 3 to 11 are graphs showing the amount of ethyl acrylate generated over time. [Figure 6] 3 to 11 are graphs showing the amount of ethyl acrylate generated over time. [Figure 7] 3 to 11 are graphs showing the amount of ethyl acrylate generated over time. [Figure 8] 3 to 11 are graphs showing the amount of ethyl acrylate generated over time. [Figure 9]3 to 11 are graphs showing the amount of ethyl acrylate generated over time. [Figure 10] 3 to 11 are graphs showing the amount of ethyl acrylate generated over time. [Figure 11] 3 to 11 are graphs showing the amount of ethyl acrylate generated over time. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] An embodiment of the present invention provides a method for producing an ethylene-carboxylic acid copolymer, in which a carboxylic acid monomer is supplied together with a polar cosolvent to induce copolymerization with ethylene, thereby suppressing side reactions caused by the polar cosolvent.

[0034] In the following, preferred examples are presented to aid in understanding the present invention, but these examples are merely illustrative of the present invention and do not limit the scope of the appended claims. It is clear to those skilled in the art that various changes and modifications can be made to these examples within the scope of the scope and technical ideas of the present invention, and it is natural that these changes and modifications fall within the scope of the appended claims.

[0035] FIG. 1 is a schematic process flow diagram illustrating a method for producing an ethylene-carboxylic acid copolymer according to an exemplary embodiment.

[0036] 1, the carboxylic acid monomer and the polar co-solvent can be supplied to the introduction section. For example, the carboxylic acid monomer and the polar co-solvent can be supplied to the mixing section 30 from the carboxylic acid monomer supply section 10 and the co-solvent supply section 20, respectively.

[0037] The carboxylic acid monomer may include an unsaturated carboxylic acid capable of undergoing a chain polymerization reaction. According to an exemplary embodiment, the carboxylic acid monomer may be (meth)acrylic acid or an ester thereof (e.g., (meth)acrylate). In the present application, (meth)acrylic acid is used as a general term including methacrylic acid and acrylic acid.

[0038] The polar co-solvent can be mixed with the carboxylic acid monomer and delivered to the reactor to inhibit crystallization and self-polymerization of the carboxylic acid monomer.

[0039] For example, the crystallization temperature of a mixture of a polar co-solvent and a carboxylic acid monomer can be lower than that of the pure carboxylic acid monomer, which allows for a wider range of process temperatures at which crystallization can be prevented, and therefore allows for lower operating temperatures of equipment without causing crystallization, thereby reducing the self-polymerization of the carboxylic acid monomer.

[0040] According to an exemplary embodiment, the polar co-solvent may be a polar organic solvent such as an alcohol-based solvent, an ether-based solvent, a ketone-based solvent, etc. For example, the alcohol-based solvent may be ethanol, methanol, propanol, butanol, etc.

[0041] In a preferred embodiment, ethanol, acetone and / or ethyl acetate may be used as polar co-solvents.

[0042] According to an exemplary embodiment, water can be excluded from the polar co-solvent. When water is used as a polar co-solvent, it may accelerate the self-polymerization of the carboxylic acid monomer. Therefore, according to an embodiment of the present invention, the crystallization temperature can be lowered without promoting the self-polymerization by using the organic solvent-based polar co-solvent described above.

[0043] However, when a polar co-solvent is used, it may react with the carboxylic acid monomer to produce by-products. For example, when acrylic acid is used as the carboxylic acid monomer and ethanol is used as the polar co-solvent, ethyl acrylate and water may be produced as by-products through an esterification reaction.

[0044] In addition, when acrylic acid is used as the carboxylic acid monomer and ethyl acetate is used as the polar co-solvent, ethyl acrylate may be produced as a by-product by trans-esterification.

[0045] Ethyl acrylate is a polymerizable material, so it can reduce the amount of acrylic acid in the chain when producing ethyl-acrylic acid copolymer (EAA). Also, when ethyl acrylate is involved in polymerization in place of acrylic acid in the chain, it can reduce the adhesive strength of the resulting copolymer product, and due to its bulky properties, it can inhibit the formation of polymer crystals and lower the melting point. A low melting point can induce a blocking phenomenon in which pellet-shaped polymer products stick together.

[0046] Ethyl acrylate can react with water and release ethanol through hydrolysis when exposed to high temperatures, and if it is included as a by-product in copolymer products, it can cause bubbles or other residues inside or on the surface of processed products.

[0047] Furthermore, ethyl acrylate is an odorous substance and can emit a foul odor even in small amounts, and when a large amount is contained as a by-product, it can be difficult to use it for applications such as food packaging. Therefore, when ethylene-carboxylic acid copolymers are used as food packaging materials, the residual content of ethyl acrylate in the product is regulated to less than 6 ppm based on the EU food contact regulations.

[0048] In addition, in order to ensure the controllability of the by-products in advance, calculations are made assuming that 6 ppm of by-products remain in the final product as a plant process replica model, and it is found that the actual by-products need to be controlled in the discharge section 40 to a level of, for example, 600 ppm or less.

[0049] In addition, when ethyl acrylate is produced by the esterification reaction, water is also produced, which may accelerate the dimerization and self-polymerization of the carboxylic acid monomer, as described above.

[0050] In order to suppress or reduce side effects resulting from side reactions due to the introduction of the polar co-solvent, according to an exemplary embodiment, as described below, it is possible to adjust the mixing and transport characteristics of the carboxylic acid monomer and the polar co-solvent in a flow path through which the carboxylic acid monomer and the polar co-solvent are transported together, for example, by including a mixing section 30 and a discharge section 40.

[0051] It is not easy to predict the degree of side reaction products generated by the introduction of co-solvents in the manufacturing process of ethylene-carboxylic acid copolymers using pilot / experimental equipment. In fact, when the side reaction products caused by the introduction of ethanol were evaluated in a pilot / laboratory test for the manufacture of ethylene-carboxylic acid copolymers, no residual amount of side reaction products could be detected in the product. In contrast, when the same molar ratio of ethanol was used as a co-solvent and injected into an actual polymerization process, it was confirmed that a significant level of ethyl acrylate was detected in the final product.

[0052] Therefore, control and design of process variables is necessary to suppress side reaction products without separate analytical equipment and reaction analysis of analytical results.

[0053] Therefore, according to an exemplary embodiment, in order to suppress side reactions of the carboxylic acid monomer and the polar co-solvent, the reaction progress index (RPI) described below can be adjusted.

[0054]

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[0055]

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[0056] t indicates the contact time of the carboxylic acid monomer and the polar co-solvent. For example, t may refer to the time from when the carboxylic acid monomer and the polar co-solvent are introduced together into the mixing section 30 until they are discharged from the discharge section 40 and meet with the ethylene stream 55.

[0057] T can refer to the average contact temperature of the carboxylic acid monomer and the polar co-solvent. For example, T can refer to the average temperature of the initial temperature when the carboxylic acid monomer and the polar co-solvent are mixed in the mixing section 30 and the temperature to which they are elevated by pressurization before being discharged from the discharge section 40 and meeting with the ethylene stream. For example, T can refer to the arithmetic average of the temperature at the mixing section 30 and the temperature at the discharge line 45, or the arithmetic average of the temperature at the storage tank 65 (see FIG. 2) and the temperature at the discharge line 80.

[0058]

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[0059] According to an exemplary embodiment, the RPI is 1.5 to 1.3 x 10 7sec·K range. If the RPI is less than 1.5 sec·K, the effect of reducing the crystallization temperature by the polar cosolvent may not be fully realized. 7 If the sec·K is exceeded, the esterification reaction will proceed too far, causing the aforementioned side effects, and the side reaction products may exceed the regulated range and not be realized as a commercial product.

[0060] In a preferred embodiment, the value of RPI is 14.9 to 1.3 × 10 5 It can be adjusted in the range of sec·K.

[0061]

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[0062] As described above, the RPI, which combines the process factors that affect the reaction rate and the process time during which the reaction can proceed at that reaction rate, can be used as a process control variable in processes using various polar co-solvents, as shown in Equation 1. This allows comprehensive control of side reactions to be achieved without the need to install separate analytical equipment or perform reaction analysis of the analytical results in order to suppress side reactions of the carboxylic acid monomer.

[0063] In addition, the amount of the by-product can be easily controlled to a desired level by adjusting the RPI. For example, as illustrated in Figures 3 to 11, the relationship between the RPI and the by-product (e.g., ethyl acrylate) can be substantially linear. Thus, the amount of the by-product can be easily and reliably fine-tuned by adjusting the value of the RPI.

[0064] Returning to FIG. 1, the carboxylic acid monomer and the polar co-solvent can be separated from the carboxylic acid monomer supply section 10 and the co-solvent supply section 20, respectively, and fed individually to the mixing section 30.

[0065] For example, the carboxylic acid monomer and the polar co-solvent can enter the mixing section 30 separately via the first flow path 15 and the second flow path 25, respectively, thereby reducing the contact time of the carboxylic acid monomer and the polar co-solvent and suppressing the esterification reaction.

[0066] In some embodiments, mixing section 30 or storage tank 65 may also be co-fed with one or more additives, such as polymerization initiators, reaction inhibitors, antioxidants, and the like.

[0067] The polymerization initiator may be any initiator known in the field of polymer polymerization, such as peroxides or peroxy compounds, and azobis compounds.

[0068] A reaction inhibitor may additionally be included to suppress side reactions of the carboxylic acid monomer and the polar co-solvent, for example, the reaction inhibitor may suppress the formation of esters by competing reactions with alcohols.

[0069] In some embodiments, an amine-based compound can be used as a reaction inhibitor, such as an alkyl amine, such as trimethylamine.

[0070] In some embodiments, the molar ratio of the reaction inhibitor to the carboxylic acid monomer is 10 -6 ~10 -3 Within the above range, the efficiency of the polymerization reaction is not reduced, and the esterification can be sufficiently suppressed.

[0071] The carboxylic acid monomer and the polar co-solvent mixed by the mixing section 30 can move to the discharge section 40 via the transfer flow path 35 and be discharged through the discharge flow path 45 for copolymerization with ethylene.

[0072] The discharge section 40 may include, for example, a discharge device such as a pump or a compressor.

[0073] According to an exemplary embodiment, the temperatures (e.g., mixing temperature and discharge temperature) in the mixing section 30 and the discharge section 40 may be higher than the crystallization temperature of the carboxylic acid monomer and lower than the temperature at which self-polymerization of the carboxylic acid occurs.

[0074] For example, the temperatures in the mixing section 30 and the discharge section 40 can be adjusted within the range of 20 to 100°C, respectively.

[0075] According to an exemplary embodiment, the discharge pressure (eg, the exit pressure from discharge section 40 ) of the carboxylic acid monomer and polar co-solvent may be greater than the entry pressure or mixing pressure at mixing section 30 .

[0076] In some embodiments, the discharge pressure may be greater than the pressure of the copolymerization reaction in reactor 60.

[0077] For example, the discharge pressure may be maintained in the range of 1100 to 2500 bar. Preferably, the discharge pressure may be in the range of 1300 to 2300 bar.

[0078] Ethylene can move through third flow path 55 and contact the mixture of carboxylic acid monomer and polar co-solvent supplied through discharge flow path 45. Then, copolymerization of the carboxylic acid monomer and ethylene proceeds in reactor 60 to produce an ethylene-carboxylic acid copolymer (e.g., EAA copolymer).

[0079] In some embodiments, the polymerization initiators mentioned above can be co-introduced into the reactor 60 via the third flow path 55 or another flow path.

[0080] In one embodiment, the polymerization initiator may be introduced only into the reactor 60, not into the mixing section 30. This can prevent the polymerization initiator from promoting the self-polymerization of the carboxylic acid monomer first.

[0081] In some embodiments, a chain transfer agent can be introduced during the polymerization process, for example, via the third line 55. The chain transfer agent can facilitate controlling the molecular weight and molecular weight distribution of the polymer product to a desired range.

[0082] Polar co-solvents can also have a chain transfer effect on the polymerization reaction of ethylene-carboxylic acid comonomers. Therefore, by adjusting the amount of chain transfer agent and polar co-solvent added in consideration of the chain transfer coefficient (Cs) of polar co-solvent, the molecular weight and molecular weight distribution of ethylene-carboxylic acid copolymers can be effectively controlled and the effect of polar co-solvent injection can be realized.

[0083] Chain transfer agents can include, for example, non-polar organic compounds such as isobutane, propyne, or polar organic compounds such as methyl ethyl ketone, isopropyl aldehyde, vinyl acetate, and the like.

[0084] In some embodiments, the polar co-solvent can also interact with the chain transfer agent in the reactor to affect molecular weight control.

[0085] In some embodiments, the input concentration of polar co-solvent (C solvent ) can be adjusted to satisfy the range of formula 2, taking into consideration the concentrations of the polar cosolvent and the chain transfer agent in the upstream flow path (e.g., the third flow path 55) of the reactor and their respective chain transfer coefficients.

[0086]

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[0088] The chain transfer coefficient is a constant that indicates the reactivity of a chain transfer agent to terminate a polymer polymerization reaction; the higher the value of the chain transfer coefficient, the less amount of chain transfer agent is required to reduce the molecular weight of a polymer during the polymer polymerization process.

[0089] Specific values ​​of the chain transfer coefficient are described in such literature as Polymer science & Technology, Joel R. Fried, 2006, 2nd edition, pp. 34-39, Handbook of polymer synthesis part A, Hans R. Kricheldorf, 1991, pp. 3-5, and Polymer science and engineering, David J. Williams, pp. 103-104.

[0090] For example, outside the numerical range for chain transfer shown in formula 2, chain termination may be too active or chain extension may proceed too far, making it difficult to control the molecular weight.

[0091] According to an exemplary embodiment,

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[0092] 1, the mixture of carboxylic acid monomer and polar co-solvent can be mixed with ethylene before being injected into reactor 60 to improve the polymerization efficiency in reactor 60. In one embodiment, the mixture of carboxylic acid monomer and polar co-solvent and ethylene can be injected into reactor 60 together.

[0093] For example, the polymerization temperature in the reactor 60 may be 170 to 270° C. The pressure in the reactor 60 may be 1100 to 2500 bar.

[0094] According to an exemplary embodiment, the ethylene content (e.g., the content of ethylene-derived units or blocks) may be 60-98 wt % and the carboxylic acid content (e.g., the content of carboxylic acid-derived units or blocks) may be 2-40 wt % based on the total weight of the ethylene-carboxylic acid copolymer. Within the above ranges, the reduction in purity due to self-polymerization of the carboxylic acid monomer and ester by-products can be sufficiently prevented. In a preferred embodiment, the ethylene content may be 75-97.5 wt % and the carboxylic acid content (e.g., the content of carboxylic acid-derived units or blocks) may be 2.5-25 wt %.

[0095] For example, the weight average molecular weight of the copolymer produced from the reactor 60 may be 8,000 to 1,000,000.

[0096] According to the above exemplary embodiment, the reaction kinetics between the carboxylic acid monomer and the polar co-solvent can be controlled to suppress side reactions and reduce crystallization and self-polymerization of the carboxylic acid monomer, thereby improving the yield and purity of the ethylene-carboxylic acid copolymer and preventing or reducing the above side effects caused by by-products such as ethyl acrylate.

[0097] The above-mentioned ethylene-carboxylic acid copolymer can be commercialized, for example, in the form of pellets and used for applications such as adhesive films, sealing materials, insulating coating layers, and packaging films.

[0098] FIG. 2 is a schematic process flow diagram illustrating a method for producing an ethylene-carboxylic acid copolymer according to some exemplary embodiments.

[0099] 2, the carboxylic acid monomer and the polar co-solvent may be supplied by being stored together in a storage tank 65. For example, a mixture of the carboxylic acid monomer and the polar co-solvent may be delivered from the storage tank 65 to the discharge portion 75 via a transfer flow path 70. The mixture may be discharged from the discharge portion 75 via a discharge flow path 80.

[0100] The ethylene stored in the ethylene supply unit 50 moves through the third flow path 55 and can be contacted with a mixture of a carboxylic acid monomer and a polar co-solvent supplied through the discharge flow path 80. Then, copolymerization of the carboxylic acid monomer and ethylene proceeds in the reactor 60 to produce an ethylene-carboxylic acid copolymer (e.g., an EAA copolymer).

[0101] 2, the process can be designed and implemented to meet the RPI range according to the exemplary embodiment described above. For example, t in Equation 1 can represent the contact time of the carboxylic acid monomer and the polar co-solvent after being introduced into the storage tank 65 before combining with the ethylene.

[0102] In some embodiments, the chain transfer agent can also be provided via the third flow path 55 to satisfy Equation 2.

[0103] Hereinafter, the embodiments of the present invention will be described in more detail with reference to experimental examples. However, the examples and comparative examples included in the experimental examples are merely illustrative of the present invention and do not limit the scope of the appended claims. It is clear to those skilled in the art that various changes and modifications can be made to these examples within the scope of the scope and technical ideas of the present invention, and it is natural that these changes and modifications fall within the scope of the appended claims.

[0104] Experimental Example 1 In order to mimic the generation of by-products due to contact between carboxylic acid monomers and polar co-solvents, the amount of ethyl acrylate generated in a mixture of acrylic acid (AA) (containing 200 ppm of MEHQ (mono methyl ether hydroquinone) as an inhibitor, purity 99.5%, Alfa Aeser) and ethanol (EtOH) (purity 99.5%, Sigma-Aldrich) was measured by gas chromatography-flame ionization detector (GC-FID) after taking samples at various times and adding an internal standard.

[0105] In Experimental Examples 1-1 to 1-9, the mixing ratio of EtOH / AA and the contact temperature were adjusted as shown in Table 1.

[0106] 3 to 11 are graphs showing the amount of ethyl acrylate generated over time in Experimental Examples 1-1 to 1-9, respectively.

[0107] 3 to 11, it can be seen that ethyl acrylate tends to be generated linearly with time. The amount of ethyl acrylate generated (y) with time (x) derived based on linear regression analysis is shown in FIGS. 3 to 11, respectively.

[0108] Specifically, under the same temperature conditions, the production of ethyl acrylate was promoted with a larger EtOH / AA molar ratio, and also promoted with a higher reaction temperature under the same EtOH / AA molar ratio.

[0109] The introduction of the polar co-solvent is required to lower the crystallization temperature of the mixture in the discharge section 40 to ensure a process operation range that can prevent self-polymerization and crystallization of the carboxylic acid monomer. For this reason, in order to properly mix the carboxylic acid monomer and the polar co-solvent before being introduced into the reactor 60, the minimum contact time (or residence time) of the mixture was set to 0.1 seconds.

[0110] As mentioned above, in order to meet the regulatory standard of 6 ppm for a by-product (ethyl acrylate) in the final product, the allowable level of ethyl acrylate at the discharge section 40 in the plant process replica model was set to 600 ppm.

[0111] The reaction progress index (RPI) (lower limit) based on the minimum contact time of 0.1 seconds and the RPI (upper limit) based on the contact time corresponding to the upper limit of ethyl acrylate generation of 600 ppm were calculated for each experiment and are shown in Table 1.

[0112] [Table 1]

[0113] Referring to Table 1, RPI is 1.5 and 1.3Х10 7 sec·K, it can be confirmed that the introduction of the polar co-solvent ensures a wide process operating range and easily controls the amount of the by-product (ethyl acrylate) below the target value. When the RPI is less than 1.5, the polar co-solvent cannot be effectively introduced into the reactor. When the RPI is adjusted to 1.3X10 7 Exceeding sec·K may result in exceeding the manageable regulatory limits of ethyl acrylate in the final product, which may result in the side effects mentioned above.

[0114] Meanwhile, in order to ensure a sufficient process operating range by the polar co-solvent, the RPI (lower limit) was set at a minimum contact time of 1 second, and the RPI (upper limit) for the contact time to meet the actual ethyl acrylate regulatory standard of 6 ppm was calculated and shown in Table 2. Specifically, the contact time corresponding to 6 ppm was calculated from the relationship of the amount of ethyl acrylate generated (y) by the time (x) shown in Figures 3 to 11, respectively.

[0115] [Table 2]

[0116] Referring to Table 2, RPI is 14.9 and 1.3Х105 When the time sec·K is adjusted, it is possible to practically increase the contact time of the polar co-solvent and to suppress the amount of side reaction products to less than the practical standard.

[0117] Experimental Example 2 Using a process replica model of the ethylene-acrylic acid copolymer polymerization process, the molar concentrations of the chain transfer agent and polar co-solvent in the front-stage flow path of reactor 60 were measured and used to calculate the value of Equation 2 above.

[0118] [Table 3]

[0119] As described above, the molecular weight and molecular weight distribution of the copolymer can be appropriately adjusted within the numerical range of formula 2. In addition, the effect of the use of a polar cosolvent on the molecular weight distribution can be appropriately controlled within the numerical range of formula 2.

[0120] For example, if the value of formula 2 is less than the lower limit (0.003 mol / L), the total amount of compounds that perform chain transfer in the reactor will be insufficient, and the average molecular weight of the product may be too high or the molecular weight distribution may be too broad. If the value of formula 2 is greater than the upper limit (0.01 mol / L), the total amount of compounds that perform chain transfer in the reactor will be too high, and the average molecular weight of the product may be too low or the molecular weight distribution may be too narrow.

[0121] Referring to Table 3, it can be seen that due to the action of the chain transfer agent in the polar cosolvent itself, even when a polar cosolvent is newly introduced, the content of the chain transfer agent can be reduced and the calculated value of Equation 2 can be maintained within the range of Equation 2.

Claims

1. forming a mixture of a carboxylic acid monomer and an organic solvent-based polar co-solvent; and injecting the mixture and ethylene into a reactor to copolymerize; the carboxylic acid monomer is (meth)acrylic acid, and the polar co-solvent is an alcoholic solvent or ethyl acetate; The step of forming a mixture of the carboxylic acid monomer and the organic solvent-based polar co-solvent has a reaction progress index (RPI) defined by the following Equation 1 of 1.5 to 1.3×10 ７ and adjusting the temperature in the range of sec·K to control the amount of by-products of the carboxylic acid monomer and the polar co-solvent. [0010] [0025] are the initial molar concentrations of the polar co-solvent and the carboxylic acid monomer, respectively; t is the contact time of the carboxylic acid monomer and the polar co-solvent; and T is the average contact temperature of the carboxylic acid monomer and the polar co-solvent before reacting with ethylene.

2. The reaction progress index is 14.9 to 1.3 × 10 ５ 2. The method for producing an ethylene-carboxylic acid copolymer according to claim 1, wherein the polymerization temperature is in the range of sec·K.

3. The method for producing an ethylene-carboxylic acid copolymer according to claim 1, further comprising the step of discharging the mixture.

4. The method for producing an ethylene-carboxylic acid copolymer according to claim 3, wherein the discharge pressure of the mixture is greater than the mixing pressure of the carboxylic acid monomer and the polar co-solvent.

5. The method for producing an ethylene-carboxylic acid copolymer according to claim 4, wherein the discharge pressure is higher than a pressure inside the reactor.

6. The step of forming the mixture includes introducing the carboxylic acid monomer and the polar co-solvent into a mixing section, The step of discharging the mixture includes moving the mixture from the mixing section to a discharge section through a transfer flow path; and The method for producing an ethylene-carboxylic acid copolymer according to claim 3, further comprising discharging the mixture from the discharge portion through a discharge flow path.

7. The method for producing an ethylene-carboxylic acid copolymer according to claim 1, wherein the temperature of the mixture is maintained at a temperature equal to or higher than a crystallization temperature of the carboxylic acid monomer and equal to or lower than a self-polymerization temperature of the carboxylic acid monomer.

8. The method for producing ethylene-carboxylic acid copolymers according to claim 1, wherein the mixture is contacted with ethylene before being injected into the reactor.

9. The method for producing an ethylene-carboxylic acid copolymer according to claim 1, further comprising the step of injecting into the mixture an inhibitor for the reaction between the carboxylic acid monomer and the polar co-solvent.

10. The method for producing an ethylene-carboxylic acid copolymer according to claim 9, wherein the reaction inhibitor comprises an amine compound.

11. The method for producing an ethylene-carboxylic acid copolymer according to claim 1, further comprising the step of injecting a chain transfer agent into the mixture through a pre-stage flow path of the reactor.

12. The method for producing an ethylene-carboxylic acid copolymer according to claim 11, wherein the chain transfer agent comprises a non-polar organic compound.

13. The method for producing an ethylene-carboxylic acid copolymer according to claim 12, wherein the chain transfer agent comprises methyl ethyl ketone or isobutane.

14. The method for producing an ethylene-carboxylic acid copolymer according to claim 11, which satisfies the following formula 2: [0030] [0045] are the molar concentrations of the polar co-solvent and the chain transfer agent in the pre-pass of the reactor, respectively; [0050] is the chain transfer coefficient (Cs) of the polar co-solvent and the chain transfer agent to ethylene at 200°C.

15. the carboxylic acid monomer is acrylic acid; The method for producing an ethylene-carboxylic acid copolymer according to claim 1, wherein the polar co-solvent is ethanol.

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