Method for producing isocyanate compounds

Abstract

The present invention relates to a method for producing an isocyanate compound, which can recover and reuse materials used in the reaction when producing an isocyanate compound using phosgene, and minimizes thermal degradation of the reaction product and the generation of by-products.

Description

[Technical field]

[0001] The present invention relates to a method for producing an isocyanate compound. [Background technology]

[0002] Xylylene diisocyanate (XDI) contains an aromatic ring in the molecule, but is classified as an aliphatic isocyanate. XDI is a very useful compound as a raw material for polyurethane-based materials, polyurea-based materials, and polyisocyanurate-based materials in the chemical, resin, and paint industries.

[0003] Generally, since isocyanate compounds undergo many side reactions during the synthesis process, they are produced by reacting them with anhydrous hydrochloric acid or carbonic acid to form a salt of an amine compound, which is then reacted with phosgene.

[0004] For example, XDI is produced by reacting xylylene diamine (hereinafter referred to as XDA) with anhydrous hydrochloric acid to form amine hydrochloride, which is then reacted with phosgene. More specifically, in the past, a liquid raw material amine, for example, a solution containing XDA, was reacted with anhydrous hydrochloric acid to form XDA-HCl hydrochloride, which was then heated at a high temperature of at least 100°C, and then gaseous phosgene was injected to carry out a gas-liquid reaction to produce isocyanate compounds such as XDI.

[0005] The reaction for forming the isocyanate compound is a typical endothermic reaction, and in order to increase the yield, continuous heating and maintenance of a high temperature are required during the reaction.

[0006] However, isocyanate compounds such as XDI often have highly reactive amino groups, which causes many side reactions during the phosgenation reaction. The by-products formed by the side reactions affect processes in which the isocyanate compound is used as a raw material (e.g., processes for producing polyurethane resins), resulting in a decrease in quality.

[0007] Due to the need to maintain high temperatures during the production of isocyanate compounds and the high reactivity of the generated isocyanate compounds such as XDI, there is a high risk of by-products being generated or side reactions occurring due to thermal denaturation of the product, which often places a heavy burden on the purification process.

[0008] Due to these problems, various attempts have been made to suppress side reactions and the generation of by-products during the production of isocyanate compounds, but no effective technology has yet been developed.

[0009] Attempts have been made to recover and reuse compounds such as phosgene and hydrogen chloride from exhaust gases generated in the process of producing isocyanate compounds, but there are limitations to the efficiency of such attempts. Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention provides a method for producing an isocyanate compound using phosgene, which can recover and reuse materials used in the reaction and minimize thermal denaturation of the reaction product and generation of by-products. [Means for solving the problem]

[0011] According to one embodiment of the invention, a phosgene reaction step in which the salt of the amine compound is reacted with phosgene in the presence of a solvent to obtain a reaction product containing an isocyanate compound; a degassing step for removing the gas phase from the reaction product; a gas compression stage for compressing the gas phase obtained in the degassing stage to obtain a condensate of the gas phase; and distilling said condensate to separate phosgene from said condensate; The present invention provides a method for producing an isocyanate compound, comprising:

[0012] Hereinafter, a method for producing an isocyanate compound according to an embodiment of the present invention will be described.

[0013] Unless otherwise defined herein, all technical and scientific terms have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention belongs. The terms used in the description of the present invention are merely for the purpose of effectively describing a specific embodiment and are not intended to limit the present invention.

[0014] As used herein, the singular forms "a," "an," and "the" include the plural forms as well, unless the context clearly indicates to the contrary.

[0015] As used herein, the meaning of "comprising" is to embody certain properties, regions, integers, steps, operations, elements, components and / or components, and does not exclude the presence or addition of other certain properties, regions, integers, steps, operations, elements, components and / or groups.

[0016] Since the present invention can be modified in various ways and can have various forms, specific embodiments are exemplified and described in detail below, but this is not intended to limit the present invention to the specific disclosed forms, and it should be understood that the present invention includes all modifications, equivalents, and alternatives within the above-mentioned idea and technical scope.

[0017] In this specification, when the positional relationship of two parts is described, for example, "on," "upper," "lower," "adjacent," etc., one or more other parts may be located between the two parts, unless the words "immediately" or "directly" are used.

[0018] In this specification, when a temporal context is described, for example, "after," "following," "next to," or "before," this can also include non-consecutive cases, unless the words "immediately" or "directly" are used.

[0019] As used herein, "low boiling point material" means a material having a lower boiling point than the isocyanate compound which is the target product of the present invention; and "high boiling point material" means a material having a higher boiling point than the isocyanate compound which is the target product of the present invention.

[0020] As used herein, the term "bottom" of a distillation column refers to an outlet through which a lower discharge from the distillation column is discharged to the outside of the distillation column, and the term "top" of a distillation column refers to an outlet through which an upper discharge from the distillation column is discharged to the outside of the distillation column.

[0021] According to one embodiment of the invention, a phosgene reaction step in which the salt of the amine compound is reacted with phosgene in the presence of a solvent to obtain a reaction product containing an isocyanate compound; a degassing step for removing the gas phase from the reaction product; a gas compression stage for compressing the gas phase obtained in the degassing stage to obtain a condensate of the gas phase; and distilling said condensate to separate phosgene from said condensate; The present invention provides a method for producing an isocyanate compound, comprising:

[0022] According to another embodiment of the invention, a salt-forming reaction step of reacting an amine compound with hydrochloric acid in a solvent to obtain a salt of the amine compound; a phosgene reaction step in which the salt of the amine compound is reacted with phosgene in a solvent to obtain a reaction product containing an isocyanate compound; a degassing step for removing the gas phase from the reaction product; a gas compression step for compressing the gas phase obtained from the salt formation reaction step, the phosgene reaction step and the degassing step to obtain a condensate of the gas phase; a distillation step of distilling the condensate to separate phosgene and hydrochloric acid from the condensate; and The hydrochloric acid obtained in the distillation step is supplied as a reactant in the salt formation reaction step, and the phosgene is supplied as a reactant in the phosgene reaction step. A method for producing an isocyanate compound is provided.

[0023] According to yet another embodiment of the invention, a desolvation step for removing the solvent from the reaction product from which the gas phase has been removed, obtained in the degassing step; a low boiling point material removal step for removing low boiling point materials (lights) from the reaction product from which the solvent has been removed; A high boiling point material removing step of removing high boiling point materials (heavies) from the reaction product from which the low boiling point materials have been removed. The present invention provides a method for producing an isocyanate compound, further comprising:

[0024] During the main reaction and purification processes in the production of isocyanate compounds using phosgene, exhaust gases containing phosgene, hydrogen chloride, etc. Due to environmental regulations, the exhaust gases are discharged into the atmosphere after being post-treated to remove harmful substances.

[0025] As a result of the inventors' research, it has been found that when exhaust gas from the entire process including the gas phase obtained in the degassing step is treated in the gas compression step and the distillation step, phosgene, hydrogen chloride, etc. contained in the exhaust gas can be recovered more effectively, and the recovered compounds can be supplied to a step requiring them, thereby reducing costs and increasing process efficiency.

[0026] Furthermore, it has been confirmed that, when an isocyanate compound is produced by carrying out the reaction step, the degassing step, the desolvation step, the low boiling point removal step, and the high boiling point removal step, particularly when the steps are carried out under the above temperature and pressure conditions, it is possible to minimize thermal denaturation of the reaction product and the generation of by-products, and thus it is possible to obtain an isocyanate compound of high purity.

[0027] Fig. 1 is a diagram showing a schematic diagram of the steps and apparatus used in the method for producing an isocyanate compound according to an embodiment of the present invention. Each step that may be included in the method for producing an isocyanate compound according to an embodiment of the present invention will be described below with reference to Fig. 1.

[0028] (Phosgene Reaction Step) A phosgene reaction step is carried out in which the salt of an amine compound is reacted with phosgene in the presence of a solvent to obtain a reaction product containing an isocyanate compound, the solvent and unreacted phosgene.

[0029] According to an embodiment of the present invention, in order to suppress the rapid reaction and side reactions of the amine compound and phosgene, the amine compound is preferably applied as a salt of the amine compound, for example, the salt of the amine compound may be a hydrochloride or carbonate of the amine compound.

[0030] The salt of the amine compound is prepared by neutralizing the amine compound with anhydrous hydrochloric acid or carbonic acid at a temperature of 20 to 80°C.

[0031] The salt of the amine compound is obtained by reacting the amine compound with anhydrous hydrochloric acid or carbonic acid in a solvent in the salt-formation reactor 1. The salt of the amine compound obtained in the salt-formation reactor 1 is supplied to the phosgene reactor 110 of the phosgene reaction unit 100 through an amine compound salt supply line 10. The gas phase discharged from the salt-formation reactor 1 is transferred to the surge drum 251 of the gas compression unit 250 through a gas phase discharge line 9.

[0032] The supply ratio of the anhydrous hydrochloric acid or carbonic acid may be, for example, 2 to 10 moles, or 2 to 6 moles, or 2 to 4 moles, per mole of the amine compound.

[0033] Preferably, the amine compound is an aliphatic amine having an aliphatic group in the molecule. Specifically, the aliphatic amine may be a linear or cyclic aliphatic amine. More specifically, the aliphatic amine may be a bifunctional or more linear or cyclic aliphatic amine having two or more amino groups in the molecule.

[0034] For example, the amine compound may be hexamethylenediamine, 2,2-dimethylpentanediamine, 2,2,4-trimethylhexanediamine, butenediamine, 1,3-butadiene-1,4-diamine, 2,4,4-trimethylhexamethylenediamine, 1,6,11-undecatriamine, 1,3,6-hexamethylenetriamine, 1,8-diisocyanato-4-isocyanatomethyloctane, bis(aminoethyl)carbonate, bis(aminoethyl)ether, xylylenediamine, α,α,α',α'-tetramethylxylylenediamine, bis(aminoethyl)phthalate, bis(aminomethyl)cyclohexane, dicyclohexylmethylamine, bis(aminoethyl ... The diamine may be one or more compounds selected from the group consisting of benzenediamine, cyclohexanediamine, methylcyclohexanediamine, dicyclohexyldimethylmethanediamine, 2,2-dimethyldicyclohexylmethanediamine, 2,5-bis(aminomethyl)bicyclo-[2,2,1]-heptane, 2,6-bis(aminomethyl)bicyclo-[2,2,1]-heptane, 3,8-bis(aminomethyl)tricyclodecane, 3,9-bis(aminomethyl)tricyclodecane, 4,8-bis(aminomethyl)tricyclodecane, 4,9-bis(aminomethyl)tricyclodecane, bis(aminomethyl)norbornene, and xylylenediamine. In the present invention, the xylylenediamine is classified as an aliphatic diamine.

[0035] The amine compound may be one or more sulfur-containing aliphatic amines selected from the group consisting of bis(aminomethyl)sulfide, bis(aminoethyl)sulfide, bis(aminopropyl)sulfide, bis(aminohexyl)sulfide, bis(aminomethyl)sulfone, bis(aminomethyl)disulfide, bis(aminoethyl)disulfide, bis(aminopropyl)disulfide, bis(aminomethylthio)methane, bis(aminoethylthio)methane, bis(aminoethylthio)ethane, bis(aminomethylthio)ethane, and 1,5-diamino-2-aminomethyl-3-thiapentane.

[0036] Among the amine compounds, xylylenediamine (XDA) can show superior effects when applied to a method for producing an isocyanate compound according to an embodiment of the present invention. Preferably, the amine compound may be one or more compounds selected from the group consisting of m-xylylenediamine, p-xylylenediamine, and o-xylylenediamine.

[0037] According to one embodiment of the present invention, the phosgene reaction step is carried out as a gas-liquid-solid three-phase reaction in which a solid amine compound salt is reacted with gaseous phosgene in the presence of a solvent, thereby effectively suppressing a rapid reaction and minimizing the generation of side reactions and by-products.

[0038] When the salt of the amine compound and phosgene are reacted in a solvent, the phosgene can be added at once or in portions. For example, a small amount of phosgene is added first at a relatively low temperature to react with the salt of the amine compound to produce an intermediate. Then, the remaining amount of phosgene is added secondly at a relatively high temperature to react with the intermediate, thereby obtaining a reaction liquid containing an isocyanate compound. For example, a small amount of phosgene is reacted with xylylenediamine to produce an intermediate in the form of a carbamoyl salt, and the remaining amount of phosgene is added to react the intermediate in the form of a carbamoyl salt with phosgene to form an aliphatic isocyanate such as xylylenediisocyanate.

[0039] This phosgene reaction step can minimize the time that the final product, the isocyanate compound, is exposed to high temperatures. Furthermore, by forming the intermediate at a relatively low temperature, the time required to maintain high temperatures in the entire reaction process can be reduced. Furthermore, the amount of heat input to the entire process can be reduced. In addition, the high-temperature reaction time of phosgene can be relatively shortened, thereby reducing the risk of explosive vaporization of phosgene.

[0040] The phosgene reaction step is carried out in a solvent containing at least one of an aromatic hydrocarbon solvent and an ester solvent, and the solvent may be selected in consideration of the temperature at which the phosgene reaction step is carried out.

[0041] The aromatic hydrocarbon solvent may be a halogenated aromatic hydrocarbon solvent such as monochlorobenzene, 1,2-dichlorobenzene, and 1,2,4-trichlorobenzene.

[0042] The ester solvent may be a fatty acid ester such as amyl formate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, methyl isoamyl acetate, methoxybutyl acetate, sec-hexyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, cyclohexyl acetate, methylcyclohexyl acetate, benzyl acetate, ethyl propionate, n-butyl propionate, isoamyl propionate, ethyl acetate, butyl stearate, butyl lactate, and amyl lactate; or an aromatic carboxylic acid ester such as methyl salicylate, dimethyl phthalate, and methyl benzoate.

[0043] According to an embodiment of the invention, the salt of the amine compound may be contained in the solvent at a concentration of 20 vol% or less, for example, 1 to 20 vol%, or 5 to 20 vol% in the phosgene reaction step. If the concentration of the salt of the amine compound contained in the solvent exceeds 20 vol%, a large amount of salt may be precipitated in the phosgene reaction step.

[0044] The phosgene reaction step is carried out at a temperature of 165°C or less, preferably 80°C to 165°C.

[0045] According to one embodiment of the invention, when phosgene is added in portions in the phosgene reaction step, 10-30 wt%, 12-30 wt%, or 15-28 wt% of the total amount of phosgene is added at a temperature of 80°C to 100°C or 85°C to 95°C. Under these reaction conditions, a rapid reaction is suppressed and an intermediate in the form of a carbamoyl salt can be selectively and effectively formed. Next, the intermediate is reacted with phosgene while the remaining amount of phosgene is added at a temperature of 110°C to 165°C or 120°C to 150°C to obtain a reaction product containing an isocyanate compound.

[0046] The isocyanate compound varies depending on the type of the amine compound used in the salt formation reaction step. For example, the isocyanate compound may be one or more compounds selected from the group consisting of n-pentyl isocyanate, 6-methyl-2-heptane isocyanate, cyclopentyl isocyanate, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), diisocyanatomethylcyclohexane (H6TDI), xylylene diisocyanate (XDI), diisocyanatocyclohexane (t-CHDI), and di(isocyanatocyclohexyl)methane (H12MDI).

[0047] In particular, the method for producing an isocyanate compound according to an embodiment of the present invention is useful for producing xylylene diisocyanate (XDI). XDI includes structural isomers such as 1,2-XDI (o-XDI), 1,3-XDI (m-XDI), and 1,4-XDI (p-XDI).

[0048] The phosgene reaction step can be carried out in either a batch or continuous manner. The phosgene reaction step can be carried out in a phosgene reaction unit 100 including a reactor 110 having a rotating shaft, an amine compound salt supply line 10 and a phosgene supply line 20 for supplying reactants to the inside of the reactor, a heat source for supplying heat to the reactor, a reaction product transfer line 102 for transferring the reaction product obtained in the reactor to a subsequent process, and a gas phase discharge line 109 for transferring the gas phase obtained in the reactor to a surge drum 251 of a gas compression unit 250.

[0049] (Degassing stage) This is followed by a degassing step in which the gas phase is removed from the reaction product.

[0050] In the degassing step, gas phase components such as excess phosgene and by-product hydrogen chloride are removed from the reaction product in a known degassing unit 200 .

[0051] The gas phase can be removed from the reaction product by aeration using a gas supply or by separating the gas phase from the reaction product using a flash tank or a distillation column.

[0052] In particular, according to one embodiment of the present invention, in order to minimize the generation of by-products during the degassing step, the degassing step is preferably performed at a temperature of 145° C. to 165° C. and a pressure of 100 torr to 600 torr.

[0053] As an example, the degassing step is performed in a distillation tower, and it is advantageous to operate the distillation tower at a temperature of 145°C to 165°C at the bottom and a pressure of 100 torr to 600 torr at the top in order to minimize the production of by-products. Here, the temperature at the bottom of the distillation tower refers to the temperature of a reboiler connected to the bottom of the distillation tower. And, the pressure at the top of the distillation tower refers to the pressure of a condenser connected to the top of the distillation tower.

[0054] Preferably, the degassing step is performed at a temperature of 145° C. to 165° C., alternatively 150° C. to 165° C., alternatively 150° C. to 160° C., alternatively 155° C. to 160° C. And preferably, the degassing step is performed at a pressure of 100 torr to 600 torr, alternatively 200 torr to 500 torr, alternatively 300 torr to 450 torr, alternatively 350 torr to 450 torr.

[0055] If the temperature and pressure at which the degassing step is performed do not satisfy the above ranges, the amount of by-products produced in the degassing step may increase and the efficiency of gas phase removal may decrease, thereby decreasing the concentration of isocyanate compounds in the reaction product obtained from the degassing step.

[0056] As an example, the degassing step is performed in a degassing unit 200 including a distillation column 220 configured to remove a gas phase from the reaction product supplied through a reaction product transfer line 102 of the reaction unit 100; a gas phase discharge line 209 for discharging the gas phase to the top of the distillation column; and a reaction product transfer line 203 for discharging the reaction product from which the gas phase has been removed to the bottom of the distillation column and transferring it to a subsequent step.

[0057] (Gas Compression Stage) This is followed by a gas compression step in which the gas phase obtained in the degassing step is compressed to obtain a condensate of the gas phase.

[0058] In the gas compression stage, the gas phase obtained in the degassing stage is compressed under a gas compression unit 250 to obtain a condensate of the gas phase.

[0059] Preferably, in the gas compression stage, the gas phase obtained in the phosgene reaction stage together with the gas phase obtained in the degassing stage is compressed in a gas compression unit 250 to obtain a condensate of the gas phase.

[0060] More preferably, in the gas compression step, the gas phase obtained in the salt formation reaction step, the phosgene reaction step and the degassing step is compressed in a gas compression unit 250 to obtain a condensate of the gas phase.

[0061] Preferably, the gas compression stage is performed under a gas compression unit 250 including three or more gas compressors to ensure the compression efficiency of the gas phase and the pressure of the condensate. Preferably, the gas compression stage is performed under a gas compression unit 250 including three or more primary compressors. Preferably, the gas compression unit 250 includes three or more subunits including a surge drum 251, a gas compressor 254, and a condenser 257.

[0062] As an example, Figure 1 shows a process including three such sub-units connected in series. Referring to Figure 1, a gas compression unit 250 includes three gas compressors 254, 264, 274 arranged in series, surge drums 251, 261, 271 connected via gas phase transfer lines 253, 263, 273 before each gas compressor, and condensers 257, 267, 277 connected via compressed gas transfer lines 256, 266, 276 after each gas compressor.

[0063] The surge drum 251 of the first subunit is supplied with the gas phase from the gas phase discharge line 209 of the degassing unit 200. Optionally, the surge drum 251 can be further supplied with the gas phase transferred from the gas phase discharge line 9 of the salt formation reactor 1 and the gas phase discharge line 109 of the phosgene reaction unit 100.

[0064] At the bottom of surge drum 251, liquid droplets are separated through liquid droplet discharge line 252 to prevent the liquid phase from flowing into gas compression unit 250. The gas phase is discharged to the top of surge drum 251 and is supplied to gas compressor 254 through gas phase transfer line 253. The gas phase is compressed in gas compressor 254. The compressed gas obtained in gas compressor 254 is supplied to condenser 257 through compressed gas transfer line 256.

[0065] When the operation of the gas compressor 254 is interrupted due to a power outage or other reasons, in order to prevent a surge phenomenon, a portion of the gas phase that is not compressed in the gas compressor 254 is supplied to the surge drum 251 through a gas recirculation line 255. The compressed gas is supplied to a condenser 257 to reduce the temperature, and is supplied to the surge drum 261 of the second sub-unit through a transfer line 259.

[0066] The second and third subunits compress gas in the same manner as the corresponding devices in the first subunit.

[0067] Finally, the condensate obtained in the condenser 277 of the third unit is transferred to a buffer drum 280 through a condensate transfer line 279. The condensate collected in the buffer drum 280 is supplied to a distillation column 291 of a distillation unit 290 as a feed.

[0068] In the gas compression unit 250, the surge drums 251, 261, and 271 are devices for preventing surges during the gas compression process. Although not shown in FIG 1, the gas recirculation lines 255, 265, and 275 are provided with anti-surge valves for preventing surges during the gas compression process.

[0069] Gas compressors 254, 264, 274 in gas compression unit 250 are devices for compressing the gas phase to form compressed gas. Preferably, in the gas compression step, the gas phase is compressed to a pressure of 16 bar or more to ensure efficient compression of the gas phase and sufficient pressure of the condensate.

[0070] For example, the gas phase entering the first subunit preferably exhibits a pressure of 16 bar or more at the last subunit after passing through each subunit.

[0071] More preferably, in the gas compression step the gas phase may be compressed to a pressure of from 16 bar to 19 bar, alternatively from 16.5 bar to 18.5 bar, alternatively from 16.5 bar to 18 bar.

[0072] (Distillation stage) A distillation step is then carried out in which the condensate obtained from the gas compression step is distilled to separate phosgene from the condensate.

[0073] In the distillation step, phosgene is separated and recovered from the condensate by a distillation unit 290 including a distillation column 291 .

[0074] According to one embodiment of the invention, in order to ensure the distillation efficiency of the condensate and the energy efficiency of the entire process, the distillation step is preferably carried out in a distillation column 291 having a top temperature of −15° C. or higher. Preferably, the top temperature of the distillation column 291 may be −15° C. to 0° C., alternatively −12° C. to −3° C., alternatively −10° C. to −5° C.

[0075] According to one embodiment of the invention, the temperature of the top of the distillation column 291 is determined by the pressure of the condensate supplied to the distillation stage in the gas compression stage. For example, when the final pressure of the condensate supplied to the distillation stage in the gas compression stage (i.e., the pressure of the condensate discharged from the last subunit of the gas compression unit 250) is 16 bar or more, the temperature of the top of the distillation column 291 is operated at -15°C or more. When the temperature of the top of the distillation column 291 is set lower, a larger amount of energy is consumed during the operation of the distillation column 291, and therefore energy efficiency and process efficiency may decrease.

[0076] In the distillation step, the condensate collected in the buffer drum 280 is supplied to the distillation column 291 as a feed. A phosgene-containing fraction separated from the condensate by the distillation in the distillation column 291 is discharged through a column bottom stream line 292 to the bottom of the distillation column 291. The phosgene-containing fraction is supplied to a reboiler 294. In the reboiler 294, the low boiling point fraction is re-supplied to the bottom of the distillation column 291, and the remaining fraction, phosgene, is recovered through a phosgene discharge line 296. The recovered phosgene is used as a reactant in the reaction step. That is, the phosgene recovered through the phosgene discharge line 296 in the distillation step is supplied to the reactor 110 through the phosgene supply line 20 of the reaction unit 100.

[0077] During the distillation step, a gas phase (e.g., hydrochloric acid gas or carbon dioxide gas) separated from the condensate is discharged to the top of the distillation column through a top stream line 293. The discharged gas phase is supplied to a condenser 295. A portion of the gas phase condensed in the condenser 295 is re-supplied to the top of the distillation column 291, and the remainder is recovered through a gas phase discharge line 297. The recovered gas phase is used as a reactant for forming a salt of the amine compound.

[0078] According to another embodiment of the present invention, the method for producing an isocyanate compound may further include a desolvation step of removing the solvent from the reaction product from which the gas phase obtained in the degassing step has been removed, a low boiling point removal step of removing low boiling point materials (lights) from the reaction product from which the solvent has been removed, and a high boiling point removal step of removing high boiling point materials (heavies) from the reaction product from which the low boiling point materials have been removed.

[0079] 2 is a diagram showing a schematic diagram of a process and an apparatus used in the method for producing an isocyanate compound according to the embodiment. Hereinafter, a step that may be additionally included in the method for producing an isocyanate compound according to the embodiment will be described with reference to FIG.

[0080] (Desolvation step) A desolvation step is carried out to remove the solvent from the reaction product from which the gas phase has been removed, obtained in the degassing step.

[0081] In the desolvation step, the solvent is distilled off from the reaction product from which the gas phase has been removed by a known desolvation unit 300.

[0082] According to one embodiment of the present invention, in order to minimize thermal denaturation of the reaction product and generation of by-products during the desolvation step, the desolvation step is preferably performed at a temperature of 100° C. to 165° C. and under a pressure of 30 torr or less.

[0083] As an example, the desolvation step is performed in a distillation tower, and it is advantageous to operate the distillation tower at a temperature of 100°C to 165°C at the bottom and at a pressure of 30 torr or less at the top in order to minimize the thermal degradation and the generation of by-products. Here, the temperature at the bottom of the distillation tower refers to the temperature of a reboiler connected to the bottom of the distillation tower. And, the pressure at the top of the distillation tower refers to the pressure of a condenser connected to the top of the distillation tower.

[0084] Preferably, the desolvation step is carried out at a temperature of 100° C. to 165° C., alternatively 115° C. to 165° C., alternatively 115° C. to 160° C., alternatively 130° C. to 160° C. And preferably, the desolvation step is carried out at a pressure of 5 torr to 30 torr, alternatively 5 torr to 25 torr, alternatively 10 torr to 20 torr, alternatively 10 torr to 15 torr.

[0085] If the temperature and pressure at which the desolventization step is carried out do not satisfy the above ranges, the amount of thermal denaturation and by-products produced in the desolventization step may increase, and the efficiency of removing the solvent may decrease, thereby causing a decrease in the concentration of isocyanate compounds in the reaction product obtained from the desolventization step.

[0086] As an example, the desolvation step is performed in a desolvation unit 300 including a distillation column 330 configured to remove the solvent from the reaction product supplied through the reaction product transfer line 203 of the degassing unit 200; a solvent discharge line 309 for discharging the solvent to the top of the distillation column; and a reaction product transfer line 304 for discharging the reaction product from which the solvent has been removed to the bottom of the distillation column and transferring it to a subsequent step.

[0087] In order to minimize the high temperature residence time of the reaction product in the desolvation step, a distillation column 440 equipped with devices such as a kettle type reboiler, a thin film evaporator, a force circulated reboiler, and a jacketed vessel type reboiler is used.

[0088] (Low boiling point removal stage) Next, a low boiling point material removal step is performed to remove low boiling point materials (lights) from the reaction product obtained from the solvent removal step.

[0089] In the low boiler removal step, low boiling point materials (lights) are removed from the reaction product from which the solvent has been removed by a known low boiler removal unit 400.

[0090] The low boiling point material means a material having a boiling point lower than that of the isocyanate compound, which is the main product in the reaction step. The low boiling point material may be a material produced by a side reaction in the process of obtaining the main product. For example, in the process of producing XDI from the isocyanate compound, the low boiling point material may include monoisocyanates such as (chloromethyl)benzyl isocyanate (CBI) and ethylphenyl isocyanate (EBI).

[0091] According to one embodiment of the invention, in order to minimize thermal degradation of the reaction product and generation of by-products in the low boiler removal step, the low boiler removal step is preferably performed with a temperature of the bottom of the distillation column 440 of 150°C to 165°C and a pressure of the top of the distillation column of 5 torr or less. Here, the temperature of the bottom of the distillation column means the temperature of a reboiler connected to the bottom of the distillation column.

[0092] Preferably, the low boiler removal step is performed at a temperature of 150° C. to 165° C., alternatively 155° C. to 165° C., alternatively 155° C. to 162° C., alternatively 160° C. to 162° C. And preferably, the upper pressure at which the low boiler removal step is performed is 1 torr to 5 torr, alternatively 2 torr to 5 torr, alternatively 2 torr to 4 torr.

[0093] If the operating temperature and pressure of the low boiler removal step do not satisfy the above ranges, the amount of thermal degradation and by-products produced in the low boiler removal step may increase, and the efficiency of removing low boiling point materials may decrease, thereby decreasing the concentration of isocyanate compounds in the reaction product obtained from the low boiler removal step.

[0094] As an example, the low boiler removal step is performed in a low boiler removal unit 400 including a distillation column 440 configured to remove low boiling point materials from the reaction product supplied through the reaction product transfer line 304 of the desolvation unit 300; a low boiler discharge line 409 for discharging the low boiling point materials to the top of the distillation column; and a reaction product transfer line 405 for discharging the reaction product from which the low boiling point materials have been removed to the bottom of the distillation column and transferring it to a subsequent step.

[0095] In order to minimize the high-temperature residence time of the reaction product in the low boiler removal step, a distillation column 440 equipped with devices such as a kettle type reboiler, a thin film evaporator, a force circulated reboiler, and a jacketed vessel type reboiler is used.

[0096] (High boiling point removal stage) Next, a high boiler removal step is carried out to remove high boilers from the reaction product from which the low boilers have been removed.

[0097] In the high boiler removal step, high boilers are removed from the reaction product from which the low boilers have been removed by a known high boiler removal unit 500.

[0098] The high boiling point substance means a substance having a boiling point higher than that of the isocyanate compound which is the main product in the reaction step. Examples of the high boiling point substance include by-products in the form of high molecular weight such as oligomers including dimers, trimers or higher multimers of the isocyanate compound formed in the process of obtaining the main product, or polymers.

[0099] According to one embodiment of the present invention, in order to minimize thermal denaturation of the reaction product and generation of by-products in the high boiler removal step, the high boiler removal step is preferably carried out at a temperature of 145°C to 165°C and under a pressure of 1 torr or less.

[0100] For example, the high boiling point removal step is carried out in a thin-film evaporator, and it is advantageous to operate the thin-film evaporator at a bottom temperature of 145°C to 165°C and a bottom pressure of 1 torr or less in order to minimize the thermal denaturation and the generation of by-products.

[0101] Preferably, the high boiler removal step is performed at a temperature of 145° C. to 165° C., alternatively 150° C. to 165° C., alternatively 150° C. to 160° C., alternatively 155° C. to 160° C. And preferably, the high boiler removal step is performed at a pressure of 0.1 torr to 1 torr, alternatively 0.5 torr to 1 torr.

[0102] If the operating temperature and pressure of the high boiler removal step do not satisfy the above ranges, the amount of thermal degradation and by-products produced in the high boiler removal step may increase, and the efficiency of removing high boiling point substances may decrease, thereby decreasing the concentration of isocyanate compounds obtained from the high boiler removal step.

[0103] As an example, the high boiling point removal step is performed in a high boiling point removal unit 500 including a thin film distillation apparatus 550 configured to remove high boiling point substances from the reaction product supplied through a reaction product transfer line 405 of the low boiling point removal unit 400; an isocyanate compound discharge line 509 for discharging an isocyanate compound to the condensation section of the thin film distillation apparatus; and a high boiling point substance discharge line 506 for discharging the high boiling point substances to the bottom of the thin film distillation apparatus. Effect of the Invention

[0104] The present invention provides a method for producing an isocyanate compound using phosgene, which can recover and reuse materials used in the reaction and minimize thermal denaturation of the reaction product and generation of by-products. [Brief description of the drawings]

[0105] [Figure 1] FIG. 1 is a diagram showing a schematic diagram of steps and apparatus used in a method for producing an isocyanate compound according to an embodiment of the invention. [Diagram 2] FIG. 1 is a diagram showing a schematic diagram of steps and apparatus used in a method for producing an isocyanate compound according to an embodiment of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0106] The functions and effects of the present invention will be described in more detail below with reference to specific examples of the present invention, however, these are presented as examples to aid in understanding the invention and do not in any way limit the scope of the invention. EXAMPLES

[0107] Example 1 Using the apparatus shown in Figures 1 and 2, 1,3-XDI (m-XDI) was produced according to the following steps.

[0108] (Phosgene Reaction Step) Under normal temperature and pressure conditions, 500 kg of hydrochloric acid and 560 kg of m-xylylenediamine (m-XDA) were reacted in 6,500 kg of 1,2-dichlorobenzene (o-DCB) solvent for 4 hours to form 870 kg of m-xylylenediamine hydrochloride. At this time, the unreacted hydrochloric acid gas discharged through gas phase discharge line 9 was transferred to surge drum 251 of gas compression unit 250.

[0109] 870 kg of the m-xylylenediamine hydrochloride was fed into the reactor 110 through the feed line 10, and the temperature of the reactor was raised to 125°C. During the reaction time, a total of 1,359 kg of phosgene was fed into the reactor through the feed line 20 and stirred. A dry ice-acetone condenser was used from the time of feeding phosgene to the time of the end of the reaction to prevent phosgene from leaking outside. The reaction was carried out at a temperature of 90°C for 1.5 hours.

[0110] Thereafter, the reactor was heated to an internal temperature of 125°C, and 6,000 kg of phosgene was added. The temperature of the reactor was maintained at 125°C, and the reaction solution was further stirred for 4.5 hours until it became transparent. After the reaction solution became transparent, heating was stopped. The reaction product obtained by the above method was transferred to the degassing unit 200 through the transfer line 102. At this time, the unreacted phosgene and hydrochloric acid gas discharged through the gas phase discharge line 109 were transferred to the surge drum 251 of the gas compression unit 250.

[0111] (Degassing stage) The distillation column 220 of the degassing unit 200 is configured to remove a gas phase from the reaction product provided via the transfer line 102 .

[0112] Specifically, the distillation column 220 is a packed column filled with Mellapak, a type of structured packing, and has a height of about 6 m.

[0113] The temperature at the bottom of the distillation column 220 was 155° C. and the pressure at the top of the distillation column 220 was operated at 400 torr.

[0114] About 150 kg / hr of the reflux stream is recharged to the distillation column 220, which corresponds to a reflux ratio to the overhead of about 3.2.

[0115] A gas phase containing phosgene was discharged through a gas phase discharge line 209 connected to the top of the distillation column 220. The gas phase discharged through the gas phase discharge line 209 was transferred to a surge drum 251 of a gas compression unit 250. The reaction product from which the gas phase was removed was transferred to a desolvation unit 300 through a transfer line 203 connected to the bottom of the distillation column 220.

[0116] (Gas Compression Stage) The gas phase supplied to the surge drum 251 of the first subunit in the gas compression unit 250 was supplied to the gas compressor 254 through a transfer line 253. In the gas compressor 254, the gas phase was compressed under a pressure of 2.7 bar. The compressed gas obtained in the gas compressor 254 was supplied to the condenser 257 through a transfer line 256. The temperature of the compressed gas supplied to the condenser 257 was lowered to 15°C, and the compressed gas was supplied to the surge drum 261 of the second subunit through a transfer line 259.

[0117] The compressed gas supplied to the surge drum 261 of the second sub-unit was supplied to a gas compressor 264 through a transfer line 263. In the gas compressor 264, the compressed gas was further compressed under a pressure of 7.6 bar. The compressed gas obtained in the gas compressor 264 was supplied to a condenser 267 through a transfer line 266. The temperature of the compressed gas supplied to the condenser 267 was lowered to 41°C, and the compressed gas was supplied to a surge drum 271 of the third sub-unit through a transfer line 269.

[0118] The compressed gas supplied to the surge drum 271 of the third subunit was supplied to a gas compressor 274 through a transfer line 273. In the gas compressor 274, the compressed gas was further compressed under a pressure of 16.86 bar (12,644 torr). The compressed gas obtained in the gas compressor 274 was supplied to a condenser 277 through a transfer line 276. The temperature of the condensed water supplied to the condenser 277 was lowered to -5°C to form a condensate, and the condensate was transferred to a buffer drum 280 through a transfer line 279.

[0119] (Distillation stage) The condensate collected in the buffer drum 280 is supplied as a feed to a distillation column 291 of a distillation unit 290. The distillation column 291 is configured so as to be able to separate phosgene from the condensate.

[0120] Specifically, distillation column 291 is an approximately 8 m column consisting of 12 bubble cap trays. Approximately 710 kg / hr of reflux stream is recharged to distillation column 291, which corresponds to a reflux ratio of approximately 3 to the overhead.

[0121] The condensate from the gas compression stage was fed to the distillation column 291 at a pressure of 16.86 bar, so that the condenser 295 connected to the top of the distillation column 291 was operated at a temperature of -15°C.

[0122] At the bottom of the distillation column 291, a phosgene-containing fraction separated from the condensate was discharged through a bottom streamline 292. The phosgene-containing fraction was supplied to a reboiler 294. In the reboiler 294, the low boiling point fraction was re-supplied to the bottom of the distillation column 291, and the remaining fraction, phosgene, was recovered through a phosgene discharge line 296. The recovered phosgene was supplied to the reactor 110 through a phosgene supply line 20 of the reaction unit 100.

[0123] A hydrochloric acid gas-containing fraction separated from the condensate was discharged from the top of the distillation column 291 through a top stream line 293. The discharged hydrochloric acid gas-containing fraction was supplied to a condenser 295. A part of the fraction condensed in the condenser 295 was re-supplied to the top of the distillation column 291, and the remaining hydrochloric acid gas was recovered through a gas phase discharge line 297. The recovered hydrochloric acid gas was supplied to the reaction step as a reactant for forming a salt of an amine compound.

[0124] (Desolvation step) Distillation column 330 of desolvation unit 300 is configured to remove solvent from the reaction product provided via transfer line 203 .

[0125] Specifically, the distillation column 330 is a packed column filled with Mellapak, a type of structured packing, and has a height of about 7 m.

[0126] The temperature at the bottom of the distillation column 330 was 160° C., and the pressure at the top of the distillation column 330 was operated at 15 torr.

[0127] About 600 kg / hr of reflux stream is recharged to distillation column 330, which corresponds to a reflux ratio to overhead of about 0.5.

[0128] A solvent containing 1,2-dichlorobenzene (o-DCB) was discharged through a solvent discharge line 309 connected to the top of the distillation column 330. The reaction product from which the solvent was removed was transferred to a low boiler removal unit 400 through a transfer line 304 connected to the bottom of the distillation column 330.

[0129] (Low boiling point removal stage) Distillation column 440 of low boiler removal unit 400 is configured to remove low boiling materials from the reaction product provided via transfer line 304 .

[0130] Specifically, the distillation column 440 is a packed column filled with Mellapak, a type of structured packing, and has a height of about 13 m.

[0131] The temperature at the bottom of the distillation column 440 was 160° C. and the pressure at the top of the distillation column 440 was operated at 5 torr.

[0132] About 40 kg / hr of reflux stream is recharged to distillation column 440, which corresponds to a reflux ratio to overhead of about 2.0.

[0133] Low boiling point materials including (chloromethyl)benzyl isocyanate (CBI) were discharged through low boiling point material discharge line 409 connected to the top of distillation column 440. The reaction product from which the low boiling point materials were removed was transferred to high boiler removal unit 500 through transfer line 405 connected to the bottom of distillation column 440.

[0134] (High boiling point removal stage) The thin film distillation apparatus 550 of the high boiler removal unit 500 is configured to remove high boiling point materials from the reaction product supplied through the transfer line 405 .

[0135] Specifically, the thin film distillation apparatus 550 used was a short path evaporator having a condenser installed therein.

[0136] The temperature at the bottom of the thin film distillation apparatus 550 was set to 160° C., and the pressure at the bottom of the thin film distillation apparatus 550 was set to 0.5 torr.

[0137] About 13 kg / hr of high boiling point condensate was separated at the bottom of the thin film distillation apparatus.

[0138] Isocyanate compounds including 1,3-XDI (m-XDI) were discharged through a discharge line 509 connected to the top of the thin film distillation apparatus 550. High boiling point substances separated from the reaction product were discharged through a discharge line 506 connected to the bottom of the thin film distillation apparatus 550.

[0139] Example 2 An isocyanate compound containing 1,3-XDI (m-XDI) was obtained in the same manner as in Example 1, except that in the gas compression step, the compression in the gas compressor 274 of the last subunit was carried out under 20 bar.

[0140] The condensate from the gas compression stage was fed to the distillation column 291 at a pressure of 20 bar, so that the condenser 295 connected to the top of the distillation column 291 was operated at a temperature of -9.2°C.

[0141] Reference example An isocyanate compound containing 1,3-XDI (m-XDI) was obtained in the same manner as in Example 1, except that in the gas compression step, compression in the gas compressor 274 of the last subunit was carried out under 10 bar.

[0142] The condensate from the gas compression stage was fed to the distillation column 291 at a pressure of 10 bar, so that the condenser 295 connected to the top of the distillation column 291 was operated at a temperature of -32°C.

[0143] Test Example In the above examples and reference examples, a part of the stream from the gas phase discharge line 297 and the phosgene discharge line 296 of the distillation unit 290 was collected and analyzed by gel permeation chromatography. The contents of the main components confirmed by the above analysis are shown in Tables 1 to 3 below.

[0144] The energy per unit time (kcal / hr) inputted in carrying out the gas compression step and the distillation step in the examples and comparative examples was measured and is shown in Tables 1 to 3 below.

[0145] [Table 1]

[0146] [Table 2]

[0147] [Table 3]

[0148] Referring to Tables 1 to 3, it was confirmed that the method for preparing an isocyanate compound according to the embodiment can efficiently recover and reuse the phosgene and hydrochloric acid used in the reaction step with a relatively low energy consumption.

[0149] In the Reference Example, phosgene and hydrochloric acid could be recovered in the distillation unit by the gas compression step, but the compressed gas could not be kept at a sufficient pressure in the gas compression step, and a large amount of energy was consumed per unit time. In particular, in the Reference Example, a large amount of expensive refrigerant had to be used to maintain a low temperature at the top of the distillation column during operation, and the difference in economic effect was large compared to the Examples. [Explanation of symbols]

[0150] 1. Salt production reactor 9 Gas phase discharge line 10. Amine compound salt supply line 20 Phosgene supply line 100 Phosgene Reaction Unit 110 Phosgene Reactor 102 Reaction product transfer line 109 Gas Phase Discharge Line 200 Degassing Unit 220 Distillation Tower 209 Gas Phase Discharge Line 203 Reaction product transfer line 250 Gas Compression Unit 251,261,271 surg drum 252,262,272 Droplet discharge line 253,263,273 Gas Phase Transfer Lines 254,264,274 Gas Compressors 255,265,275 Gas recirculation lines 256,266,276 Compressed gas transfer lines 257,267,277 Condenser 259,269,279 Condensate transfer line 280 Buffer Drum 290 Distillation Unit 291 Distillation Tower 293 Tower Top Streamline 295 Condenser 297 Gas Phase Discharge Line 292 Tower Bottom Streamline 294 Reboiler 296 Phosgene discharge line 300 Desolvation Unit 330 Distillation Tower 309 Solvent discharge line 304 Reaction product transfer line 400 Low boiling point removal unit 440 Distillation Tower 409 Low boiling point substance discharge line 405 Reaction product transfer line 500 High boiling point removal unit 550 Thin Film Distillation Apparatus 506 High boiling point substance discharge line 509 Isocyanate compound discharge line

Claims

1. A salt-forming reaction step in which an amine compound is reacted with hydrochloric acid in a solvent to obtain a salt of the amine compound; a phosgene reaction step in which the salt of the amine compound is reacted with phosgene in a solvent to obtain a reaction product containing an isocyanate compound; a degassing step for removing the gas phase from the reaction product; a gas compression step for compressing the gas phase obtained in the salt formation reaction step, the phosgene reaction step and the degassing step to obtain a condensate of the gas phase; and a distillation step of distilling the condensate to separate phosgene from the condensate; The hydrochloric acid obtained in the distillation step is supplied as a reactant in the salt formation reaction step, and the phosgene is supplied as a reactant in the phosgene reaction step; In the gas compression step, the gas phase is compressed to a pressure of 16 bar or more, The distillation step is carried out in a distillation column having a temperature at the top of the column of -15°C to 0°C; A method for producing an isocyanate compound.

2. The method for producing an isocyanate compound according to claim 1, wherein the degassing step is carried out at a temperature of 145° C. to 165° C. and a pressure of 100 torr to 600 torr.

3. The method for producing an isocyanate compound according to claim 1, wherein the gas compression step is carried out under a gas compression unit including three or more gas compressors.

4. a desolvation step for removing the solvent from the reaction product from which the gas phase has been removed, obtained in the degassing step; a low boiling point material removal step for removing low boiling points from the reaction product from which the solvent has been removed; and A high boiling point material removing step of removing high boiling point materials (heavies) from the reaction product from which the low boiling point materials have been removed. The method for producing an isocyanate compound according to claim 1, further comprising:

5. The method for producing an isocyanate compound according to claim 4, wherein the degassing step, the solvent removal step, the low boiling substance removal step, and the high boiling substance removal step are each performed at a temperature of 165° C. or less.

6. The method for producing an isocyanate compound according to claim 1, wherein the amine compound is an aliphatic amine having an aliphatic group in the molecule.

7. The method for producing an isocyanate compound according to claim 1, wherein the amine compound is a difunctional or more functional chain or cyclic aliphatic amine containing two or more amino groups in the molecule.

8. The amine compounds include hexamethylenediamine, 2,2-dimethylpentanediamine, 2,2,4-trimethylhexanediamine, butenediamine, 1,3-butadiene-1,4-diamine, 2,4,4-trimethylhexamethylenediamine, 1,6,11-undecatriamine, 1,3,6-hexamethylenetriamine, 1,8-diisocyanato-4-isocyanatomethyloctane, bis(aminoethyl)carbonate, bis(aminoethyl)ether, xylylenediamine, α,α,α',α'-tetramethylxylylenediamine, bis(aminoethyl)phthalate, bis(aminomethyl)cyclohexane, dicyclohexylmethanediamine, cyclohexamethyldiamine, bis(aminoethyl)cyclohexane, dicyclohexylmethanediamine, bis(aminoethyl)cyclohexane ...

2. The method for producing an isocyanate compound according to claim 1, wherein the isocyanate is one or more compounds selected from the group consisting of 2,5-bis(aminomethyl)bicyclo-[2,2,1]-heptane, 2,6-bis(aminomethyl)bicyclo-[2,2,1]-heptane, 3,8-bis(aminomethyl)tricyclodecane, 3,9-bis(aminomethyl)tricyclodecane, 4,8-bis(aminomethyl)tricyclodecane, 4,9-bis(aminomethyl)tricyclodecane, bis(aminomethyl)norbornene, and xylylenediamine.

9. The method for producing an isocyanate compound according to claim 1, wherein the amine compound is one or more sulfur-containing aliphatic amines selected from the group consisting of bis(aminomethyl)sulfide, bis(aminoethyl)sulfide, bis(aminopropyl)sulfide, bis(aminohexyl)sulfide, bis(aminomethyl)sulfone, bis(aminomethyl)disulfide, bis(aminoethyl)disulfide, bis(aminopropyl)disulfide, bis(aminomethylthio)methane, bis(aminoethylthio)methane, bis(aminoethylthio)ethane, bis(aminomethylthio)ethane, and 1,5-diamino-2-aminomethyl-3-thiapentane.

10. The method for producing an isocyanate compound according to claim 1, wherein the amine compound is one or more compounds selected from the group consisting of m-xylylenediamine, p-xylylenediamine and o-xylylenediamine.

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