Method for preparing polymer

Abstract

The present invention provides a method for preparing a polymer, wherein a feed stream comprising water and a polymer solution is supplied to a first stripper, a bottom discharge stream from the first stripper, comprising a polymer and water, is supplied to a second stripper, and a bottom discharge stream from the second stripper is supplied to a third stripper so as to obtain a polymer from the bottom discharge stream from the third stripper.

Description

Method for manufacturing polymers

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0000796, filed January 3, 2024, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a method for producing a polymer, and more particularly, to a method for obtaining a polymer from a polymer solution using a small amount of steam.

[0005] Solution polymerization is a method of dissolving monomers in a solvent and polymerizing them in a solution state. It is used in radical polymerization and ionic polymerization. A representative example of the production of polymers through solution polymerization is the production of styrene-butadiene copolymers through the anionic polymerization of styrene and butadiene. The anionic polymerization initiator typically used is n-butyl lithium, and the solvent is cyclohexane.

[0006] Since a large amount of solvent is used in the process of producing a polymer using the above solution polymerization method, a process is required to separate and recover the solvent within the reaction product generated through the solution polymerization reaction to obtain the polymer. Thus, a steam stripping process using a stripper was applied to obtain a high-purity polymer within the reaction product.

[0007] In general, the steam stripping process requires a large amount of steam, which can increase energy consumption. If the amount of steam supplied to the steam stripping process is insufficient, the amount of solvent remaining in the polymer increases, which can cause problems such as failure to solidify the polymer or an increase in the total volatile organic compounds (tVOC) of the polymer, which have a negative impact on the product.

[0008] The problem to be solved in the present invention is to provide an effect of obtaining a high-purity polymer while reducing the amount of steam used in the process in order to solve the problem mentioned in the technology that is the background of the above invention.

[0009] According to one embodiment of the present invention for solving the above problem, the present invention comprises the steps of: supplying a feed stream containing water and a polymer solution to a first stripper to obtain a first stripper overhead discharge stream containing a solvent and a first stripper bottom discharge stream containing a polymer and water; supplying the first stripper bottom discharge stream to a second stripper to obtain a second stripper overhead discharge stream and a second stripper bottom discharge stream, supplying the second stripper overhead discharge stream to the first stripper and supplying the second stripper bottom discharge stream to a third stripper; separating the second stripper bottom discharge stream into a third stripper overhead discharge stream and a third stripper bottom discharge stream in the third stripper; A method for producing a polymer is provided, comprising the steps of: supplying a third steam stream containing steam to an ejector, allowing the ejector to suck the third stripper top discharge stream to obtain an ejector discharge stream containing the third steam stream and the third stripper top discharge stream; and supplying a mixed stream obtained by mixing the ejector discharge stream with a second steam stream containing steam to a second stripper; and obtaining a polymer from the third stripper bottom discharge stream.

[0010] According to the method for producing a polymer of the present invention, by increasing the gas generated in the third stripper by the ejector provided on the upper portion of the third stripper, the efficiency of stripping, which vaporizes the solvent remaining in the polymer in the third stripper, can be increased even without supplying steam to the third stripper. In addition, by supplying an ejector discharge stream containing a motive fluid for operating the ejector and a suction fluid sucked by the ejector to a second stripper, and mixing the ejector discharge stream with a second steam stream containing steam and supplying the mixed stream to the second stripper, the polymer existing in the liquid phase in the second stripper is smoothly dispersed, and the mixing efficiency of the polymer and steam is increased, so that the solvent remaining in the polymer can be effectively vaporized.

[0011] Accordingly, the solvent evaporated by the steam included in the mixed stream can be supplied to the first stripper together with the steam in the second stripper top discharge stream, and the solvent can also be vaporized in the first stripper by the steam included in the second stripper top discharge stream. That is, since the steam included in the mixed stream can be used as a heat source for heating the second stripper and the first stripper, there is an effect of reducing the total amount of steam used in the process.

[0012] Figure 1 is a process diagram showing a steam stripping process among the methods for manufacturing a polymer according to one embodiment of the present invention.

[0013] Figures 2 to 4 are process diagrams showing a steam stripping process among the methods for manufacturing a polymer according to comparative examples of the present invention.

[0014] The terms or words used in the description and claims of the present invention should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0015] In the present invention, the term "stream" may refer to the flow of fluid within a process, and may also refer to the fluid itself flowing within a pipe. Specifically, the stream may refer to both the fluid itself flowing within the pipe connecting each device and the flow of the fluid. Furthermore, the fluid may refer to a gas or a liquid, and cases where the fluid includes a solid component are not excluded.

[0016] Meanwhile, in the present invention, in devices such as strippers, the "lower part" of the device, unless otherwise specified, refers to a point 80% to 100% in height downward from the top of the device, and may specifically refer to the lowest part (bottom of the tower). Similarly, the "upper part" of the device, unless otherwise specified, refers to a point 0% to 20% in height downward from the top of the device, and may specifically refer to the top (top of the tower).

[0017] Meanwhile, in the present invention, in the device such as a stripper, the operating temperature of the device may refer to the temperature at the bottom of the device unless otherwise specified. Similarly, the operating pressure of the device may refer to the pressure at the top of the device unless otherwise specified. Specifically, the operating temperature of the stripper may refer to the temperature in the region of 0 to 20% height downward from the top of the stripper, and the upper pressure of the stripper may refer to the pressure in the region of 80 to 100% height downward from the top of the column.

[0018] In the present invention, the term 'crumb' may mean a polymer in the form of droplets that is produced through a steam stripping process by supplying a polymer solution to a stripper and removing the solvent by volatilization.

[0019] Hereinafter, to help understand the present invention, the present invention will be described in more detail with reference to FIG. 1.

[0020] A method for producing a polymer according to one embodiment of the present invention comprises the steps of: supplying a feed stream containing water and a polymer solution to a first stripper (100) to obtain a first stripper top discharge stream containing a solvent and a first stripper bottom discharge stream containing a polymer and water; supplying the first stripper bottom discharge stream to a second stripper (200) to obtain a second stripper top discharge stream and a second stripper bottom discharge stream, supplying the second stripper top discharge stream to the first stripper (100) and supplying the second stripper bottom discharge stream to a third stripper (300); separating the second stripper bottom discharge stream into a third stripper top discharge stream and a third stripper bottom discharge stream in the third stripper (300); The method may include the steps of: supplying a third steam stream containing steam to an ejector, allowing the ejector to suck the third stripper top discharge stream to obtain an ejector discharge stream containing the third steam stream and the third stripper top discharge stream; and supplying a mixed stream obtained by mixing the ejector discharge stream with a second steam stream (210) containing steam to a second stripper; and obtaining a polymer from the third stripper bottom discharge stream.

[0021] According to one embodiment of the present invention, the polymer solution may be derived from a reaction product produced by supplying a monomer stream and a solvent stream to a reactor and subjecting them to a polymerization reaction. Specifically, the reaction product may be obtained by subjecting the monomer to a polymerization reaction in the presence of a solvent in the reactor. The reaction product may include a polymer formed by the monomer polymerization reaction, unreacted monomer, and a solvent.

[0022] The monomer is an aromatic vinyl monomer comprising at least one selected from the group consisting of styrene, alpha-methyl styrene, 3-methyl styrene, 4-methyl styrene, 4-propyl styrene, isopropenylnaphthalene, 1-vinylnaphthalene, styrene substituted with an alkyl group having 1 to 3 carbon atoms, 4-cyclohexylstyrene, 4-(p-methylphenyl)styrene, and styrene substituted with a halogen; And it may include a conjugated diene monomer including at least one selected from the group consisting of 1,3-butadiene, 1,4-butadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene, piperylene, 3-butyl-1,3-octadiene, 2-phenyl-1,3-butadiene, and isoprene. As a specific example, the monomer may include styrene and butadiene, and thus the polymer produced by the polymerization reaction may be a styrene-butadiene copolymer.

[0023] The solvent may include a hydrocarbon solvent, and specifically may include at least one selected from the group consisting of cyclohexane, normal hexane, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, 1,3-dialkyl-2-imidazolidinone, tetramethyl urea, and hexamethylphosphoric acid triamide. As a specific example, the solvent may include cyclohexane. In this case, polymerization of a styrene-butadiene copolymer can be effectively performed.

[0024] Meanwhile, the polymerization reaction may be performed by further including additives such as ion exchange water, an initiator, a molecular weight regulator, an activator, and a redox catalyst.

[0025] The initiator may include, for example, at least one selected from the group consisting of n-butyl lithium, diisopropylbenzene hydroperoxide, t-butyl hydroperoxide, cumene hydroperoxide, p-menthane hydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, acetyl peroxide, isobutyl peroxide, octanoyl peroxide, dibenzoyl peroxide, 3,5,5-trimethylhexanol peroxide, and t-butyl peroxy isobutyrate.

[0026] Meanwhile, the reaction product obtained by a solution polymerization reaction that polymerizes a monomer using a solvent can be transferred to, for example, a blowdown tank, where the residual heat of the solution polymerization reaction can be used to volatilize the solvent contained in the reaction product. Through this, a polymer solution with a higher polymer composition compared to the reaction product can be obtained.

[0027] In this way, even if the solvent included in the reaction product is volatilized in the blow down tank, some of the solvent is not volatilized and remains in the polymer. Therefore, the present invention aims to provide a method for effectively separating the solvent included in the polymer solution to obtain a high-purity polymer while reducing the amount of energy used in this process.

[0028] Although there are various methods for separating the solvent from the polymer solution, the present invention may employ a steam stripping process, which removes the solvent contained in the polymer solution by volatilization and solidifies the polymer contained in the polymer solution to obtain it as crumb. This steam stripping process may be performed using a multi-stage stripper.

[0029] A method for producing a polymer according to one embodiment of the present invention may include a step of supplying a feed stream containing water and a polymer solution to a first stripper (100) to obtain a first stripper top discharge stream containing a solvent and a first stripper bottom discharge stream containing a polymer and water.

[0030] Specifically, the polymer solution and water may be mixed, and a feed stream containing the polymer solution and water may be supplied to the first stripper (100). As another example, the polymer solution and water may each be supplied to the first stripper (100) through separate pipes. The water may be high-temperature water, and specifically, may be at a temperature of 90 to 110°C.

[0031] The polymer solution included in the feed stream (1) may be heated by steam introduced into the first stripper (100). Here, the steam introduced into the first stripper (100) may be from the first steam stream (110) described below and / or the upper discharge stream of the second stripper. When the polymer solution is heated in this manner, the solvent included in the polymer solution evaporates, and the polymer may be solidified. At this time, the solidification of the polymer may be performed by an antisolvent precipitation mechanism and solvent evaporation. Specifically, the solidification of the polymer may be performed because the amount of solvent remaining in the polymer decreases due to solvent evaporation, and the polymer is precipitated in water, which is an antisolvent for the polymer.

[0032] Meanwhile, the high-temperature water supplied to the first stripper (100) can also heat the polymer solution like steam. Furthermore, the water can also function as an antisolvent and a dispersion medium that disperses the polymer as much as possible within the liquid phase. Accordingly, the polymer contained in the polymer solution can be solidified by the steam and water, and the solvent and unreacted monomer contained in the polymer solution can be evaporated and discharged to the upper portion of the first stripper (100).

[0033] According to one embodiment of the present invention, a first steam stream (110) containing steam can be supplied to the first stripper (100) through a line connected to the first stripper (100). Specifically, the first steam stream (110) can be introduced into the first stripper (100) through a line connected to the lower portion of the first stripper (100). More specifically, the first steam stream (110) can be supplied as a heat source for heating the first stripper (100), thereby allowing the temperature of the first stripper (100) to be finely controlled to a desired level. Furthermore, by controlling the operating temperature of the first stripper (100) in this way, the stripping efficiency of the process can be maximized, thereby reducing the content of total volatile organic compounds (tVOC) in the final product. Here, the total volatile organic compounds may collectively refer to liquid or gaseous organic compounds that are easily evaporated into the air when the final product is heated, and may include, for example, a solvent.

[0034] Specifically, the temperature of the first steam stream (110) may be 120 to 280° C., and the pressure may be 2 to 100 bar. When the temperature and pressure ranges of the first steam stream (110) are within the above ranges, the efficiency of stripping performed in the first stripper (100) may be maximized.

[0035] According to one embodiment of the present invention, the operating temperature of the first stripper (100) may be 5°C or more higher than the glass transition temperature (Tg) of the polymer and 10°C or more higher than the azeotropic point of water and the solvent. Specifically, when the operating temperature of the first stripper (100) is 5°C or more higher than the glass transition temperature of the polymer, the amorphous portion of the polymer may be in a state in which it is easy to move. Accordingly, the solvent remaining in the polymer may be diffused in the liquid phase, and the state in which the solvent is easily vaporized may be achieved. Meanwhile, when the operating temperature of the first stripper (100) is 10°C or more higher than the azeotropic point of water and the solvent, it may be an appropriate temperature level for sufficiently volatilizing the solvent present in the polymer solution. Here, the azeotropic point of water and the solvent may mean the boiling point of an azeotropic mixture including water and the solvent.

[0036] According to the present invention, the operating temperature of the first stripper (100) may be 85 to 95°C, specifically 85 to 90°C. When the operating temperature of the first stripper (100) is less than 80°C, the efficiency of stripping, which vaporizes the solvent remaining in the polymer to separate the polymer and the solvent, may rapidly decrease in the first stripper (100), and polymer aggregates called mats may be generated in the water phase, making it impossible to operate the steam stripping process. On the other hand, when the operating temperature of the first stripper (100) exceeds 95°C, the amount of heat that must be supplied to the first stripper (100) excessively increases, which may be undesirable in terms of energy.

[0037] By heating performed by steam and high-temperature water in the first stripper (100), a first stripper top discharge stream in a gaseous state containing a solvent and a first stripper bottom discharge stream in a liquid state containing a polymer and water can be obtained. Specifically, the first stripper bottom discharge stream may contain a solidified polymer, and the solidified polymer may be transported by water. Meanwhile, the first stripper top discharge stream may further contain steam (water vapor) and unreacted monomers.

[0038] Meanwhile, the first stripper top discharge stream may be cooled through a condenser (10) and then introduced into a purification process (20). In the purification process (20), the solvent and unreacted monomers contained in the cooled first stripper top discharge stream may be separated and recovered. The solvent and unreacted monomers recovered in the purification process (20) may be reused as raw materials for the aforementioned polymerization reaction.

[0039] A method for producing a polymer according to one embodiment of the present invention may include the steps of supplying the first stripper bottom discharge stream to a second stripper (200) to obtain a second stripper top discharge stream and a second stripper bottom discharge stream, supplying the second stripper top discharge stream to the first stripper (100), and supplying the second stripper bottom discharge stream to a third stripper (300).

[0040] Specifically, the first stripper bottom discharge stream containing polymer and water can be supplied to the second stripper (200) and heated by steam. At this time, the steam used in the second stripper (200) may be introduced from the mixed stream described below.

[0041] Meanwhile, the first stripper bottom discharge stream may contain solvent and unreacted monomers that were not volatilized in the first stripper (100). Therefore, the solvent and unreacted monomers contained in the first stripper bottom discharge stream may be additionally vaporized by steam in the second stripper (200) and separated into the upper portion of the second stripper (200). Through this, a gaseous second stripper top discharge stream containing the solvent and unreacted monomers volatilized in the second stripper (200) and a liquid second stripper bottom discharge stream containing a polymer and water may be obtained.

[0042] Specifically, the polymer content in the second stripper bottom discharge stream may be higher than the polymer content in the first stripper bottom discharge stream. That is, the second stripper bottom discharge stream may be supplied to the third stripper (300) as a stream with a higher polymer content by removing unreacted monomers and solvents as much as possible.

[0043] Meanwhile, the second stripper top discharge stream may be supplied to the first stripper (100) and may further include steam in addition to the solvent and unreacted monomer. As described above, the steam contained in the second stripper top discharge stream may be used as a heat source for heating the first stripper (100).

[0044] According to one embodiment of the present invention, the first stripper (100) and the second stripper (200) can be operated while satisfying the following mathematical expressions 1 and 2.

[0045] [Mathematical Formula 1]

[0046] P2 - P1 ≥ 0.2 bar

[0047] [Equation 2]

[0048] 1.8 bar ≥ P1 ≥ 1.1 bar

[0049] In the above mathematical expressions 1 and 2, P1 is the operating pressure of the first stripper (100), and P2 is the operating pressure of the second stripper (200). Specifically, the operating pressure of the second stripper (200) may be operated at a pressure higher than that of the first stripper (100) by 0.2 bar or more, 0.2 bar to 0.8 bar, or 0.2 bar to 0.5 bar. By operating the first stripper (100) and the second stripper (200) while satisfying the above mathematical expression 1, the upper discharge stream of the second stripper can be supplied to the first stripper (100) without a separate compression device.

[0050] Specifically, when the above mathematical expression 1 is satisfied, it may be sufficiently possible to supply the second stripper upper discharge stream to the first stripper (100) due to the operating pressure difference between the first stripper (100) and the second stripper (200). Therefore, it may not be necessary to provide a separate device, such as an ejector, to the second stripper (200) to supply the second stripper upper discharge stream to the first stripper (100). In this way, by not providing an ejector at the upper portion of the second stripper (200), additional use of steam supplied to operate the ejector can be prevented, and it may also be desirable from an economical perspective, such as device costs and process equipment costs for the ejector.

[0051] That is, according to the present invention, the operating pressure of the second stripper (200) is operated at a level 0.2 bar or higher than the operating pressure of the first stripper (100), so that the upper discharge stream of the second stripper can be supplied to the first stripper (100) without the use of a separate device and additional energy accordingly. The condition control of the operating pressure according to the mathematical expression 1 may be influenced by the operating temperatures of the first stripper (100) and the second stripper (200).

[0052] Meanwhile, the operating pressure of the first stripper (100) may be 1.1 to 1.8 bar, specifically 1.1 to 1.5 bar. Specifically, when the operating pressure of the first stripper (100) is less than 1.1 bar, the stripping efficiency may be reduced due to the low operating pressure of the first stripper (100). In this case, the amount of steam supplied to the first stripper (100) may be increased to increase the stripping efficiency of the first stripper (100), but this may cause entrainment due to the excessive volume flow rate of gas in the upper discharge stream of the first stripper, which may cause fouling in the condenser (10). Meanwhile, if the operating pressure of the first stripper (100) exceeds 1.8 bar, energy consumption may increase to satisfy these operating conditions, and due to the high operating pressure, the operating temperature of the first stripper (100) may also excessively increase, which may cause problems such as local polymer chain scission.

[0053] A method for producing a polymer according to one embodiment of the present invention may include a step of separating the second stripper bottom discharge stream from the third stripper (300) into a third stripper top discharge stream and a third stripper bottom discharge stream.

[0054] As described above, the second stripper bottom discharge stream may include water and solidified polymer, and may further include a solvent remaining in the solidified polymer. Accordingly, in the third stripper (300), the second stripper bottom discharge stream may be heated to undergo gas-liquid separation into a gaseous third stripper top discharge stream containing unreacted monomer and solvent, and a liquid third stripper bottom discharge stream containing water and polymer.

[0055] Specifically, heating of the second stripper bottom discharge stream in the third stripper (300) can be performed by the pressure difference between the second stripper (200) and the third stripper (300). More specifically, since the operating pressure of the second stripper (200) is higher than the operating pressure of the third stripper (300), heating of the second stripper bottom discharge stream can be performed in the third stripper (300) by utilizing the residual heat resulting from the pressure drop while the second stripper bottom discharge stream is supplied to the third stripper (300).

[0056] Meanwhile, the third stripper (300) may perform a role of uniformly transporting the third stripper bottom discharge stream containing the solidified polymer to the dehydration process (40) subsequent to the third stripper (300). For this purpose, it may be preferable that steam is not supplied to the third stripper (300). For example, when steam is supplied to the third stripper (300), the stirring efficiency of the third stripper (300) is reduced by the steam, so that the polymer present in the water phase may be transported in the third stripper bottom discharge stream without being uniformly mixed with the water. In this case, a hunting problem may occur in the dehydration process (40) due to the uneven mixing of water and polymer included in the third stripper bottom discharge stream, and the quality of the final product may deteriorate. Therefore, in the third stripper (300), it may be desirable to separate the second stripper bottom discharge stream into the third stripper top discharge stream and the third stripper bottom discharge stream by the residual heat resulting from the pressure difference between the second stripper (200) and the third stripper (300) without the introduction of steam.

[0057] According to one embodiment of the present invention, no steam is directly introduced into the third stripper (300), and the temperature of the steam may be 120 to 280°C and the pressure may be 2 to 100 bar. Specifically, the steam is in a gaseous state and may be distinguished from the water contained in the third stripper bottom discharge stream according to the state of matter. The water contained in the third stripper bottom discharge stream is in a liquid state and may have a temperature of 90 to 110°C.

[0058] Meanwhile, the operating pressure of the third stripper (300) may be 0.9 to 1.0 bar. Specifically, when the operating pressure of the third stripper (300) is less than 0.9 bar, intermittent inflow of outside air (oxygen) may occur due to the vacuum atmosphere inside the third stripper (300), which may cause discoloration of the polymer. When the operating pressure of the third stripper (300) exceeds 1.0 bar, the third stripper bottom discharge stream is introduced into the dehydration process (40) at a high temperature and high pressure, which may cause heat loss due to superheated steam in the dehydration process (40). Specifically, the dehydration process (40) can be performed under pressure conditions (approximately 0.9 to 1.0 bar) similar to the operating pressure of the third stripper (300), and when the high-pressure and high-temperature third stripper bottom discharge stream is introduced into the dehydration process (40), residual heat is generated due to the pressure difference, and superheated steam is generated due to the residual heat, resulting in heat loss.

[0059] A method for producing a polymer according to one embodiment of the present invention may include the steps of supplying a third steam stream containing steam to an ejector, causing the ejector to suck the third stripper top discharge stream to obtain an ejector discharge stream containing the third steam stream and the third stripper top discharge stream, and supplying a mixed stream obtained by mixing the ejector discharge stream with a second steam stream (210) containing steam to a second stripper (200).

[0060] Specifically, the ejector (30) is a device that sucks in and moves a suction fluid by utilizing the pressure energy of a high-pressure motive fluid, and may be provided on the upper portion of the third stripper (300). In this way, by providing the ejector (30) on the upper portion of the third stripper (300), the gas volatilized to the upper portion of the third stripper (300) may be included in the upper discharge stream of the third stripper and may be sucked into the ejector (30). More specifically, since the gas generated within the third stripper (300) may increase by the ejector (30), the stripping efficiency of the third stripper (300) may be increased even without newly supplied steam to the third stripper (300).

[0061] Meanwhile, the third steam stream (310) can be used as a motive fluid for operating the ejector (30). In addition, since the third steam stream (310), which is a motive fluid, and the third stripper upper discharge stream, which is a suction fluid, are mixed in the ejector (30), the third stripper upper discharge stream can be heated by the third steam stream (310), and flowability to the second stripper (200) or the first stripper (100) can be secured. Meanwhile, the flow rate of the third steam stream (310) can be controlled to maintain the operating pressure of the third stripper (300) at 0.9 to 1.0 bar.

[0062] In other words, the third steam stream (310) is supplied to the ejector (30), and the ejector (30) sucks the third stripper upper stream, thereby obtaining an ejector discharge stream including the third stripper upper discharge stream and the third steam stream (310).

[0063] Thereafter, the ejector discharge stream can be mixed with a second steam stream (210) containing steam to obtain a mixed stream, and the mixed stream can be supplied to the second stripper (200). In this way, by mixing the ejector discharge stream with the second steam stream (210), the steam contained in the ejector discharge stream and the steam contained in the second steam stream (210) are mixed together into the second stripper (200), so that dispersion of the polymer existing in the liquid phase in the second stripper (200) can be smoothly performed. Through this, the mixing efficiency between the polymer and the steam can be maximized, so that vaporization of the solvent remaining in the polymer can be performed more effectively. Therefore, the effect of volatilization of the solvent, i.e., stripping, performed in the second stripper (200) can be maximized.

[0064] Meanwhile, referring to FIG. 3, conventionally, the second steam stream (210) containing steam was not mixed with the ejector discharge stream, but was supplied to the second stripper (200) through a separate line connected to the lower portion of the second stripper (200). In this case, since the second stripper (200) must be equipped with separate devices such as nozzles and distributors, it was not desirable from the economical viewpoints such as process equipment costs and device costs. In addition, when the second steam stream (210) and the ejector discharge stream are supplied to the lower portion of the second stripper (200) through separate lines, the second steam stream (210) and the ejector discharge stream may be mixed in the liquid phase within the second stripper (200). In this case, high-temperature heat sources are introduced into the second stripper (200) in two places, causing an imbalance (maldistribution) in material transfer and heat transfer, which makes the temperature of the polymer in the second stripper (200) uneven, thereby causing unevenness in the quality of the final product.

[0065] Accordingly, according to the present invention, by mixing the second steam stream (210) with the ejector discharge stream in the gas phase, a mixed stream in which the second steam stream (210) and the ejector discharge stream are mixed is formed as a uniform heat source through rapid heat transfer and material transfer, and this is supplied to the second stripper (200), thereby improving the thermal mixing efficiency and stripping efficiency of the second stripper (200).

[0066] Meanwhile, the solvent evaporated by the steam included in the mixed stream can be supplied to the first stripper (100) together with the steam in the second stripper upper discharge stream, and the solvent can also be vaporized in the first stripper (100) by the steam included in the second stripper upper discharge stream. That is, since the steam included in the mixed stream can be used as a heat source to vaporize the solvent in the second stripper (200) and the first stripper (100), the total amount of steam used in the process can be expected to be reduced.

[0067] Meanwhile, in general, the aforementioned ejector (30) is a device whose operating conditions are fixed, and the flow rate of the third steam stream (310), which is the motive fluid of the ejector (30), can be supplied to the ejector (30) at a constant rate without fluctuation. Therefore, when controlling the amount of steam supplied to the first stripper (100) and the second stripper (200) according to the process situation, it may be difficult to control the amount of steam by the third steam stream (310). Therefore, by supplementing the steam by the second steam stream (210), it is possible to flexibly respond to the steam supply within the process, thereby preventing a decrease in the stripping efficiency of the process due to process control instability (hunting).

[0068] Meanwhile, the temperature of the second steam stream (210) may be 120 to 280° C., and the pressure may be 2 to 100 bar. The temperature of the third steam stream (310) may be 140 to 280° C., and the pressure may be 4 to 100 bar. Specifically, the pressure of the third steam stream (310) may be preferably higher than the pressures of the second steam stream (210) and the first steam stream (110). Through this, the third steam stream (310) may increase the suction efficiency of the ejector (30) as a high-pressure motive fluid.

[0069] According to one embodiment of the present invention, the mass flow rate of the second steam stream (210) may be 0.15 to 0.40 or 0.29 to 0.33 relative to the total mass flow rate of the first steam stream (110), the second steam stream (210), and the third steam stream (310). Here, since the third steam stream (310) serves as a motive fluid of the ejector (30) as described above, it may be necessary to secure the flow rate of the third steam stream (310) to a certain level or higher in order to operate the ejector (30).

[0070] Specifically, when the mass flow rate of the second steam stream (210) is 0.40 or less compared to the total mass flow rate of the first to third steam streams, the design and manufacturing of the ejector (30) can be facilitated when the ejector (30) is provided on the upper portion of the second stripper (200). In addition, since the mass flow rate of the second steam stream (210) is not excessively high, the performance degradation of the ejector (30) that supplies the upper discharge stream of the third stripper to the second stripper (200) can be prevented. Meanwhile, when the mass flow rate of the second steam stream (210) is 0.15 or more compared to the total mass flow rate of the first to third steam streams, when the production amount of the product in the process changes, the temperatures of the second stripper (200) and the first stripper (100) can be easily controlled by the second steam stream (210).

[0071] A method for producing a polymer according to one embodiment of the present invention may include a step of obtaining a polymer from the third stripper bottom discharge stream.

[0072] Specifically, in the method for producing a polymer according to the present invention, the step of obtaining a polymer from the third stripper bottom discharge stream may be performed by including the step of supplying the third stripper bottom discharge stream to a dehydration process and dehydrating it to obtain a polymer.

[0073] More specifically, by the steam stripping process performed in the first stripper (100) to the third stripper (300), the third stripper bottom discharge stream may have a minimized content of solvent and unreacted monomer. In addition, the content of polymer in the third stripper bottom discharge stream may be higher than the content of polymer in the second stripper bottom discharge stream.

[0074] This third stripper bottom discharge stream can be introduced into a dehydration process (40), and the dehydration process (40) can be a process for obtaining a high-purity polymer by solid-liquid separating liquid water and solid polymer contained in the third stripper bottom discharge stream. Specifically, in the present invention, the dehydration process (40) can be performed in an open system, and the third stripper bottom discharge stream can be dehydrated by a filtration method.

[0075] According to the present invention, the water included in the feed stream (1) may be derived from water separated from the polymer by dehydrating the third stripper bottom discharge stream in the dehydration process (40). When the third stripper bottom discharge stream is dehydrated in the dehydration process (40), a large amount of water may be separated from the polymer. At this time, the water may be high-temperature water of approximately 100°C, and by circulating this high-temperature water to the first stripper (100) and reusing it, the amount of steam used as a heat source in the steam stripping process may be reduced. That is, the water separated from the polymer in the dehydration process (40) may be mixed with the polymer solution and included in the feed stream (1).

[0076] The mass flow rate of water included in the feed stream (1) may be 11 to 15 times the mass flow rate of the polymer included in the feed stream (1), and specifically, may be 11 to 13 times. Here, the water included in the feed stream (1) may include water separated from the polymer in the dehydration process (40).

[0077] Specifically, when the mass flow rate of water included in the feed stream (1) is less than 11 times the mass flow rate of the polymer included in the feed stream (1), the polymer may not be dispersed in the liquid phase due to the small amount of water and may coagulate as polymer aggregates, making it difficult to operate the steam stripping process. On the other hand, when the mass flow rate of water included in the feed stream (1) is more than 15 times the mass flow rate of the polymer included in the feed stream (1), the mass flow rate of water included in the feed stream (1) may excessively increase, and the residual heat generated in the third stripper (300) may excessively increase due to the pressure difference between the second stripper (200) and the third stripper (300). Accordingly, it may be difficult for the ejector (30) provided on the upper portion of the third stripper (300) to absorb this excessive residual heat in the form of steam, which may cause a problem in that the operating pressure of the third stripper (300) increases. In addition, in the above dehydration process (40), there is a problem that the size of the device for circulating the water separated from the polymer to the first stripper (100) must be increased, which may be undesirable from an economic perspective such as process equipment cost and device cost.

[0078] Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are intended to illustrate the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and technical spirit of the present invention, and the scope of the present invention is not limited to these examples alone.

[0079] Example

[0080] Example 1

[0081] The polymer manufacturing process was performed according to the process flow shown in Fig. 1.

[0082] Specifically, a polymerization reaction was performed in a reactor using styrene and butadiene as monomers and cyclohexane as a solvent to produce a reaction product. Subsequently, the reaction product was heated in a blowdown tank to obtain a polymer solution from which the solvent had partially evaporated. The polymer solution contained a styrene-butadiene copolymer, cyclohexane, and unreacted monomers.

[0083] A feed stream containing the polymer solution and water was supplied to a first stripper (100). Specifically, the feed stream contained a styrene-butadiene copolymer (flow rate: 10 ton / hr), cyclohexane (flow rate: 35 ton / hr), unreacted monomer (flow rate: 0.01 ton / hr), and water (temperature: 100°C, flow rate: 120 ton / hr). In the first stripper (100), the feed stream was heated using steam to obtain a first stripper top discharge stream containing steam and a solvent and a first stripper bottom discharge stream containing a polymer and water. At this time, the operating temperature of the first stripper (100) was 85°C, and the operating pressure was 1.2 bar.

[0084] The first stripper upper discharge stream was cooled through a condenser (10) and then introduced into a purification process (20). Meanwhile, the first stripper lower discharge stream was supplied to a second stripper (200).

[0085] In the second stripper (200), the first stripper bottom discharge stream was heated using steam to obtain a second stripper top discharge stream containing steam and solvent and a second stripper bottom discharge stream containing polymer and water. At this time, the operating temperature of the second stripper (200) was 112°C, and the operating pressure was 1.5 bar.

[0086] The upper discharge stream of the second stripper was supplied to the first stripper (100), and the lower discharge stream of the second stripper was supplied to the third stripper (300).

[0087] The second stripper bottom discharge stream was heated in the third stripper (300) to obtain a third stripper top discharge stream containing a solvent and a third stripper bottom discharge stream containing a polymer and water. At this time, the operating pressure of the third stripper (300) was 1 bar.

[0088] A third steam stream (310) containing steam (flow rate: 8 ton / hr, temperature: 220°C, pressure: 13 bar) and the third stripper top discharge stream were supplied to an ejector (30) to obtain an ejector discharge stream. A mixed stream obtained by mixing the ejector discharge stream with a second steam stream (210) containing steam (flow rate: 4 ton / hr, temperature: 200°C, pressure: 11 bar) was supplied to a second stripper (200).

[0089] Meanwhile, the third stripper bottom discharge stream was supplied to a dehydration process (40) and dehydrated, thereby separating the water contained in the third stripper top discharge stream from the polymer. Through this, the water separated from the polymer was circulated to the first stripper (100) as a circulation stream (41), and specifically, was included in the feed stream (1). Meanwhile, the polymer dehydrated in the dehydration process (40) was obtained as a high-purity polymer as a final product.

[0090] As a result, in the above Example 1, a total of 12 tons / hr of steam was used, the content of tVOC in the final product was 10 ppm based on 1 part by weight of the total final product, and the variation in the content of tVOC in the final product over a month (the difference between the highest and lowest values ​​of the content of tVOC in the final product measured over a month) was approximately 0.1% based on 10 ppm. Here, the content of tVOC in the final product may refer to the content of solvent and unreacted monomer included in the final obtained polymer, and it can be seen that the lower the content of tVOC in the final product, the more effectively stripping was performed in the process.

[0091] Example 2

[0092] Example 2 produced a polymer using the same process flow as Example 1, except that the flow rate of the second steam stream was controlled to 3.7 ton / hr, the first steam stream (110) was supplied through a line connected to the first stripper, and the flow rate of the first steam stream was controlled to 0.3 ton / hr, the temperature to 200°C, and the pressure to 11 bar.

[0093] As a result, in the above Example 2, a total of 12 ton / hr of steam was used, the content of tVOC in the final product was 10 ppm based on 1 part by weight of the total final product, and the variation in the content of tVOC in the final product over a month was approximately 0.01% based on 10 ppm.

[0094] In the above Example 2, the temperature of the first stripper was most easily controlled by additionally supplying the first steam stream to the first stripper compared to Example 1, and accordingly, it was confirmed that the variation in the content of tVOC in the final product over a period of one month was the lowest.

[0095] Example 3

[0096] Example 3 produced a polymer using the same process flow as Example 2, except that the operating pressure of the first stripper was controlled to 1.0 bar and the flow rate of the third steam stream was controlled to 9 ton / hr.

[0097] As a result, in order to maintain the operating temperature of the first stripper at 85°C in Example 3, the flow rate of the third steam stream was increased compared to Example 2, and the excessive volume flow rate of gas in the upper discharge stream of the first stripper caused a condenser clogging phenomenon due to entrainment, making long-term operation of the process impossible.

[0098] Example 4

[0099] Example 4 produced a polymer using the same process flow as Example 2, except that the operating pressure of the first stripper was controlled to 1.9 bar and the operating temperature of the first stripper was 96°C.

[0100] As a result, in Example 4, problems related to product quality such as local polymer chain scission and polymer discoloration occurred due to high-temperature operation of the first stripper.

[0101] Example 5

[0102] Example 5 produced a polymer using the same process flow as Example 2, except that the flow rate of the third steam stream was controlled to 7 ton / hr and the operating temperature of the first stripper was controlled to 82°C.

[0103] As a result, in Example 5, the stripping efficiency of the first stripper rapidly decreased and polymer aggregates were generated, making it impossible to operate the steam stripping process.

[0104] Specifically, the reason why this problem occurred is that the operating temperature of the first stripper must be 5°C or higher than the glass transition temperature (78°C) of the polymer so that diffusion of the solvent within the first stripper can occur actively, creating an appropriate condition for vaporizing the solvent. In addition, the operating temperature of the first stripper must be 10°C or higher than the azeotropic point (73°C) of water and the solvent (cyclohexane) so that it can become a temperature level capable of sufficiently vaporizing the solvent.

[0105] Comparative example

[0106] Comparative Example 1

[0107] The polymer manufacturing process was performed according to the process flow shown in Fig. 2.

[0108] Specifically, a polymer solution was obtained in the same manner as in Example 1. A feed stream containing the polymer solution and water was supplied to the first stripper (100). Specifically, the feed stream contained a styrene-butadiene copolymer (flow rate: 10 ton / hr), cyclohexane (flow rate: 35 ton / hr), and water (temperature: 100°C, flow rate: 120 ton / hr).

[0109] Meanwhile, a first steam stream (110) containing steam (10 ton / hr) was supplied to the first stripper (100) through a line connected to the first stripper (100). The feed stream was heated using steam in the first stripper (100), thereby obtaining a first stripper top discharge stream containing steam and solvent and a first stripper bottom discharge stream containing polymer and water. At this time, the operating temperature of the first stripper (100) was 92°C, and the operating pressure was 1.2 bar. Meanwhile, the first stripper bottom discharge stream was supplied to the second stripper (200).

[0110] Meanwhile, a second steam stream (210) containing steam (10 ton / hr) was supplied to the second stripper (200) through a line connected to the second stripper (200). In the second stripper (200), the first stripper bottom discharge stream was heated using steam to obtain a second stripper top discharge stream containing steam and solvent and a second stripper bottom discharge stream containing polymer and water. At this time, the operating temperature of the second stripper (200) was 112°C, and the operating pressure was 1.5 bar. Meanwhile, the second stripper bottom discharge stream was supplied to the third stripper (300).

[0111] The second stripper bottom discharge stream was heated in the third stripper (300) to obtain a third stripper top discharge stream containing a solvent and a third stripper bottom discharge stream containing a polymer and water. At this time, the operating pressure of the third stripper (300) was 1 bar.

[0112] The third stripper top discharge stream is mixed with the first stripper top discharge stream and the second stripper top discharge stream described above, cooled as a mixed stream through a condenser (10), and then introduced into a purification process (20).

[0113] Meanwhile, the third stripper bottom discharge stream was supplied to a dehydration process (40) and dehydrated, thereby separating the water contained in the third stripper top discharge stream from the polymer. Through this, the water separated from the polymer was circulated to the first stripper (100) as a circulation stream (41), and specifically, was included in the feed stream (1). Meanwhile, the polymer dehydrated in the dehydration process (40) was obtained as a high-purity polymer as a final product.

[0114] As a result, in the above comparative example 1, a total of 20 tons / hr of steam was used, the content of tVOC in the final product was 10 ppm based on 1 part by weight of the total final product, and the variation in the content of tVOC in the final product over a month was approximately 3% based on 10 ppm.

[0115] In the above comparative example 1, the total amount of steam used increased compared to example 1, and it was also confirmed that the variation in the content of tVOC in the final product over a period of one month increased significantly.

[0116] Comparative Example 2

[0117] Comparative Example 2 produced a polymer using the same process flow as Example 1, except that there was no supply of the second steam stream and the flow rate of the third steam stream was 12 ton / hr.

[0118] As a result, in the above comparative example 2, a total of 12 ton / hr of steam was used, the content of tVOC in the final product was 10 ppm based on 1 part by weight of the total final product, and the fluctuation range of the content of tVOC in the final product over a month was approximately 1% based on 10 ppm.

[0119] Comparative Example 2 is a case where the second steam stream was not provided compared to Example 1, and it was difficult to control the operating temperature of the first stripper, and it was confirmed that the fluctuation range of the tVOC content in the final product increased over a period of one month compared to Example 1.

[0120] Comparative Example 3

[0121] The polymer manufacturing process was performed according to the process flow shown in Fig. 3.

[0122] Comparative Example 3 produced a polymer using the same process flow as Example 2, except that the second steam stream was not mixed with the ejector discharge stream, but was supplied directly to the second stripper through a line connected to the second stripper.

[0123] As a result, in the above comparative example 3, a total of 12 ton / hr of steam was used, the content of tVOC in the final product was 37 ppm based on 1 part by weight of the total final product, and the variation in the content of tVOC in the final product over a month was approximately 2.6% based on 37 ppm.

[0124] In the above comparative example 3, the second steam stream was supplied directly to the second stripper without being mixed with the ejector discharge stream, and an imbalance (maldistribution) of material transfer and heat transfer occurred within the second stripper (200), resulting in difficulty in controlling the operating temperature of the first stripper and causing a deterioration in the quality and unevenness of the final product.

[0125] Comparative Example 4

[0126] The polymer manufacturing process was performed according to the process flow shown in Fig. 4.

[0127] Comparative Example 4 did not have an ejector on the top of the third stripper (300), supplied the third steam stream (310) to the third stripper (300) instead of the ejector, mixed the second stripper upper discharge stream with the second steam stream (210) and supplied it to the second stripper (200), and controlled the flow rate of the first steam stream (110) to 1 ton / hr, the flow rate of the second steam stream (210) to 7 ton / hr, and the flow rate of the third steam stream (310) to 8 ton / hr, except that a polymer was manufactured using the same process flow as Example 2.

[0128] As a result, in order to maintain the operating temperature of the first stripper (100) at 85°C in Comparative Example 4, an additional 4 ton / hr of steam was required compared to Example 3. In addition, due to the absence of an ejector at the top of the third stripper (300), the overpressure of the third stripper (300) could not be relieved, and since the pipe for moving the upper discharge stream of the third stripper connects the upper part of the third stripper (300) and the lower part of the second stripper (200), the pressure of the third stripper naturally formed 1.8 bar. As a result, a problem occurred in which the operating temperature of the third stripper increased to 117°C. Therefore, the lower discharge stream of the third stripper was introduced into the dehydration process (30) at a high temperature and high pressure, and residual heat was generated due to the temperature difference. However, since the dehydration process (30) is performed in an open system, it is difficult to recover the superheated steam generated by the residual heat, resulting in heat loss in the dehydration process (30). In addition, this superheated steam condenses into white due to the cold air of the outside air, resulting in a white smoke phenomenon that obscures the view, making it impossible to work in the dehydration process (30).

[0129] [Explanation of symbols]

[0130] 10: Condenser

[0131] 20: Refining process

[0132] 100: The First Stripper

[0133] 200: The Second Stripper

[0134] 300: The Third Stripper

[0135] 110: First Steam Stream

[0136] 120: Second Steam Stream

[0137] 130: Third Steam Stream

[0138] 30: Ejector

[0139] 40: Dehydration process

[0140] 41: Circular stream

Claims

1. A step of supplying a feed stream containing water and a polymer solution to a first stripper to obtain a first stripper top discharge stream containing a solvent and a first stripper bottom discharge stream containing a polymer and water; A step of supplying the first stripper bottom discharge stream to a second stripper to obtain a second stripper top discharge stream and a second stripper bottom discharge stream, supplying the second stripper top discharge stream to the first stripper and supplying the second stripper bottom discharge stream to a third stripper; A step of separating the second stripper bottom discharge stream from the third stripper into a third stripper top discharge stream and a third stripper bottom discharge stream; A step of supplying a third steam stream containing steam to an ejector, wherein the ejector sucks the third stripper top discharge stream to obtain an ejector discharge stream containing the third steam stream and the third stripper top discharge stream, and supplying a mixed stream obtained by mixing the ejector discharge stream with a second steam stream containing steam to a second stripper; and A method for producing a polymer, comprising the step of obtaining a polymer from the third stripper bottom discharge stream.

2. In paragraph 1, The second stripper top discharge stream and the third stripper top discharge stream contain solvent, The second stripper bottom discharge stream and the third stripper bottom discharge stream are a method for producing a polymer comprising a polymer and water.

3. In paragraph 1, A method for producing a polymer, comprising supplying a first steam stream containing steam to the first stripper through a line connected to the first stripper.

4. In paragraph 3, The mass flow rate of the second steam stream is: A method for producing a polymer, wherein the total mass flow rate of the first steam stream, the second steam stream and the third steam stream is 0.15 to 0.

40.

5. In paragraph 1, A method for producing a polymer, wherein the operating temperature of the first stripper is 5°C or higher than the glass transition temperature (Tg) of the polymer and 10°C or higher than the azeotropic point of water and the solvent.

6. In paragraph 5, A method for producing a polymer, wherein the operating temperature of the first stripper is 85 to 95°C.

7. In paragraph 1, A method for producing a polymer satisfying the following mathematical formulas 1 and 2; [Mathematical formula 1] P2 - P1 ≥ 0.2 bar [Mathematical formula 2] 1.8 bar ≥ P1 ≥ 1.1 bar In the above mathematical expressions 1 and 2, P1 is the operating pressure of the first stripper, and P2 is the operating pressure of the second stripper.

8. In paragraph 1, A method for producing a polymer, wherein the step of obtaining a polymer from the third stripper bottom discharge stream comprises the step of supplying the third stripper bottom discharge stream to a dehydration process and dehydrating it to obtain a polymer.

9. In paragraph 8, The water contained in the above feed stream is derived from water separated from the polymer by dehydrating the third stripper bottom discharge stream in the above dehydration process, A method for producing a polymer, wherein the mass flow rate of water contained in the feed stream is 11 to 15 times the mass flow rate of the polymer contained in the feed stream.

10. In paragraph 1, The above polymer solution is derived from a reaction product produced by supplying a monomer stream and a solvent stream to a reactor and performing a polymerization reaction. The above polymer solution is a method for producing a polymer comprising a polymer and a solvent.

11. In paragraph 1, A method for producing a polymer, wherein the solvent comprises at least one selected from the group consisting of cyclohexane, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-cyclohexyl2-pyrrolidone, 1,3-dialkyl-2-imidazolidinone, tetramethyl urea, and hexamethylphosphoric acid triamide.

12. In paragraph 1, The above polymer is a method for producing a polymer including a styrene-butadiene copolymer.

13. In paragraph 1, There is no steam introduced into the third stripper above, A method for producing a polymer, wherein the temperature of the steam is 120 to 280 ℃ and the pressure is 2 to 100 bar.

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