Method for producing isocyanate compounds

Abstract

The present invention relates to a method for producing an isocyanate compound. The present invention provides a method for producing an isocyanate compound that can minimize thermal denaturation of a reaction product and generation of by-products when producing an isocyanate compound using phosgene, and can provide a high-purity isocyanate compound.

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 many side reactions occur during the synthesis of an isocyanate compound, it is produced by reacting it 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 an 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 or higher, 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, since isocyanate compounds such as XDI generally have highly reactive amino groups, many side reactions occur during the phosgenation reaction, and the by-products formed by the side reactions affect processes in which the isocyanate compound is used as a raw material (for example, 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, the risk of by-products being generated or side reactions occurring due to thermal denaturation of the product is increased, 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 the reality is that no effective technology has yet been developed. Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention provides a method for producing an isocyanate compound, which can minimize thermal denaturation of a reaction product and generation of by-products during the production of an isocyanate compound using phosgene, and can provide a high-purity isocyanate compound. [Means for solving the problem]

[0010] According to one embodiment of the present invention, a reaction step of reacting the salt of the amine compound with phosgene in a solvent to obtain a reaction product containing an isocyanate compound; and a degassing step for removing a gas phase from the reaction product, The reaction product from which the gas phase has been removed may include, in any order, a desolvation step for removing solvent, a low boiler removal step for removing lights, and a high boiler removal step for removing heavies; Each of the steps is carried out at a temperature of 165° C. or less, The low boiling point removal step is carried out at a temperature of 150°C to 165°C, thereby providing a method for producing an isocyanate compound.

[0011] Hereinafter, a method for producing an isocyanate compound according to an embodiment of the present invention will be described.

[0012] 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.

[0013] As used herein, the singular forms "a," "an," and "the" include the plural forms as well, unless the context clearly indicates to the contrary.

[0014] 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.

[0015] 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 concept and technical scope.

[0016] In this specification, when the location of two parts is described, for example, by "on," "upper," "lower," or "adjacent," one or more other parts may be located between the two parts, unless the words "immediately" or "directly" are used.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] According to one embodiment of the invention, a reaction step of reacting the salt of the amine compound with phosgene in a solvent to obtain a reaction product containing an isocyanate compound; and a degassing step for removing a gas phase from the reaction product, The reaction product from which the gas phase has been removed may include, in any order, a desolvation step for removing solvent, a low boiler removal step for removing lights, and a high boiler removal step for removing heavies; Each of the steps is carried out at a temperature of 165° C. or less, The low boiling point removal step is carried out at a temperature of 150°C to 165°C, thereby providing a method for producing an isocyanate compound.

[0021] Isocyanate compounds are required to have high purity in order to be used as raw materials for fine chemical products such as optical materials.

[0022] However, in general, many side reactions occur during the synthesis of isocyanate compounds containing XDI, and there is a problem that the purity of the isocyanate compounds decreases due to reactions between reaction products and thermal denaturation.

[0023] For example, aliphatic diisocyanates can be produced by reacting aliphatic diamines with phosgene. At this time, side reactions occur, and by-products such as monoisocyanates, such as (chloromethyl)benzyl isocyanate, are produced. It is known that the occurrence of such side reactions and the production of by-products are caused by the need to maintain high temperatures during the production process of aliphatic diisocyanates and the high reactivity of the produced aliphatic diisocyanates, such as XDI. In particular, when the final product, aliphatic diisocyanates, is exposed to high temperatures for a certain period of time, side reactions occur or polymeric by-products such as oligomers and polymers containing dimers or higher polymers are formed.

[0024] As a result of extensive research, the inventors have 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, and particularly when the steps are carried out under the above-mentioned temperature and pressure conditions, it is possible to minimize thermal denaturation of the reaction product and the generation of by-products, and to obtain a high-purity isocyanate compound.

[0025] The method for producing an isocyanate compound includes the reaction step, the degassing step, the solvent removal step, the low boiling point removal step, and the high boiling point removal step.

[0026] Among the steps, the desolvation step, the low boiler removal step, and the high boiler removal step may be performed in any order after the degassing step.

[0027] As an example, the method for producing the isocyanate compound includes the steps of: a reaction step of reacting a salt of an amine compound 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 desolvation step for removing the solvent from the reaction product from which the gas phase has been removed; a low boiler removal step for removing low boilers from the reaction product from which the solvent has been removed; and The high boiler removal step may include removing high boilers from the reaction product from which the low boilers have been removed.

[0028] As another example, the method for producing the isocyanate compound includes the steps of: a reaction step of reacting a salt of an amine compound 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 desolvation step for removing the solvent from the reaction product from which the gas phase has been removed; removing high boilers from the solvent-removed reaction product; and The low boiler removal step may include removing low boilers from the reaction product from which the high boilers have been removed.

[0029] As yet another example, the method for producing the isocyanate compound includes the steps of: a reaction step of reacting a salt of an amine compound 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; the high boiler removal step for removing high boilers from the reaction product from which the gas phase has been removed; removing the solvent from the reaction product from which the high boiling point materials have been removed; and The low boiler removal step may include removing low boiling lights from the reaction product from which the solvent has been removed.

[0030] 1 to 3 are diagrams that diagrammatically show steps and devices used in a method for producing an isocyanate compound according to an embodiment of the present invention. FIG. 1 relates to a production method in which the reaction step, the degassing step, the solvent removal step, the low boiler removal step, and the high boiler removal step are carried out in this order. FIG. 2 relates to a production method in which the reaction step, the degassing step, the solvent removal step, the high boiler removal step, and the low boiler removal step are carried out in this order. FIG. 3 relates to a production method in which the reaction step, the degassing step, the high boiling point substance removal step, the solvent removal step, and the low boiling point substance removal step are carried out in this order.

[0031] Hereinafter, 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 with reference to FIG.

[0032] (Reaction Step) First, a reaction step is carried out in which a salt of an amine compound is reacted with phosgene in a solvent to obtain a reaction product containing an isocyanate compound.

[0033] According to an embodiment of the present invention, in order to suppress the rapid reaction and side reaction of the amine compound with 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.

[0034] 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.

[0035] 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.

[0036] Preferably, the amine compound can be an aliphatic amine having an aliphatic group in the molecule. Specifically, the aliphatic amine can be a chain or cyclic aliphatic amine. More specifically, the aliphatic amine can be a chain or cyclic aliphatic amine having two or more functionalities and containing two or more amino groups in the molecule.

[0037] 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.

[0038] 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.

[0039] Among the amine compounds, xylylenediamine (XDA) can show more excellent effects when applied to the method for producing an isocyanate compound according to one 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.

[0040] According to one embodiment of the present invention, the reaction step is carried out as a gas-liquid-solid three-phase reaction in which a solid amine 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.

[0041] 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 first added 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 secondly added 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 then added to react the intermediate in the form of a carbamoyl salt with phosgene to form an aliphatic isocyanate such as xylylenediisocyanate.

[0042] This 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. This reduces the amount of heat input to the entire process. In addition, the high-temperature reaction time of phosgene can be relatively shortened, reducing the risk of explosive vaporization of phosgene.

[0043] The reaction step is carried out in a solvent including 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 reaction step is carried out.

[0044] The aromatic hydrocarbon solvent may be a halogenated aromatic hydrocarbon solvent such as monochlorobenzene, 1,2-dichlorobenzene, and 1,2,4-trichlorobenzene.

[0045] 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.

[0046] According to one embodiment of the present invention, the salt of the amine compound may be contained in the solvent at a concentration of 20% by volume or less, for example, 1 to 20% by volume, or 5 to 20% by volume, in the reaction step. If the concentration of the salt of the amine compound contained in the solvent exceeds 20% by volume, a large amount of salt may be precipitated in the reaction step.

[0047] The reaction step is carried out at a temperature of 165°C or less, preferably 80°C to 165°C.

[0048] According to one embodiment of the present invention, when phosgene is added in portions in the 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. Such reaction conditions suppress a rapid reaction, and an intermediate in the form of a carbamoyl salt can be selectively and effectively formed. Next, the intermediate is reacted with phosgene while adding the remaining amount of phosgene at a temperature of 110°C to 165°C or 120°C to 150°C to obtain a reaction product containing an isocyanate compound.

[0049] The isocyanate compound varies depending on the type of the amine compound used in the 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).

[0050] 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).

[0051] The reaction step can be carried out either by batch or continuous. The reaction step can be carried out in a 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, and a transfer line 102 for transferring the reaction product obtained in the reactor to a subsequent purification process.

[0052] (Degassing stage) This is followed by a degassing step in which the gas phase is removed from the reaction product.

[0053] In the degassing step, gas phase substances such as excess phosgene and hydrogen chloride by-product are removed from the reaction product by a known degassing unit 200 .

[0054] The method for removing the gas phase from the reaction product includes a method of supplying a gas and venting it, and a method of separating the gas phase from the reaction product using a flash tank or a distillation column.

[0055] 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.

[0056] 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 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.

[0057] 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.

[0058] If the temperature and pressure at which the degassing step is carried out do not satisfy the above ranges, the amount of by-products produced in the degassing step increases and the efficiency of gas phase removal decreases, thereby decreasing the concentration of isocyanate compounds in the reaction product obtained from the degassing step.

[0059] As an example, the degassing step can be performed in a degassing unit 200 including a distillation column 220 configured to remove a gas phase from the reaction product supplied via a transfer line 102 of the reaction unit 100; a gas phase discharge line 209 for discharging the gas phase from the top of the distillation column; and a transfer line 203 for discharging the reaction product from which the gas phase has been removed from the bottom of the distillation column and transferring it to a subsequent stage.

[0060] (Desolvation step) Next, a desolvation step is performed to remove the solvent from the reaction product from which the gas phase has been removed.

[0061] 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.

[0062] 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.

[0063] For 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.

[0064] 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 2 torr to 30 torr, alternatively 2 torr to 25 torr, alternatively 5 torr to 25 torr, alternatively 5 torr to 20 torr.

[0065] If the temperature and pressure at which the desolvation step is carried out do not satisfy the above ranges, the amount of thermal denaturation and by-products produced during the desolvation step increases, and the efficiency of solvent removal decreases, thereby decreasing the concentration of isocyanate compounds in the reaction product obtained from the desolvation step.

[0066] As an example, the desolvation step can be performed in a desolvation unit 300 including a distillation column 330 configured to remove the solvent from the reaction product supplied via a transfer line 203 of the degassing unit 200; a solvent discharge line 309 for discharging the solvent from the top of the distillation column; and a transfer line 304 for discharging the reaction product from which the solvent has been removed from the bottom of the distillation column and transferring it to a subsequent step.

[0067] In order to minimize the residence time of the reaction product at high temperatures in the desolvation step, a distillation column 330 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.

[0068] (Low boiling point removal stage) Next, a low boiler removal step is carried out to remove low boiling lights from the reaction product from which the solvent has been removed.

[0069] In the low boiler removal step, low boiling materials (lights) are removed from the reaction product from which the solvent has been removed by a known low boiler removal unit 400.

[0070] The low boiling point substance refers to a substance having a boiling point lower than that of the isocyanate compound, which is the main product in the reaction step. The low boiling point substance may be a substance 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 substance may include monoisocyanates such as (chloromethyl)benzyl isocyanate (CBI) and ethylphenyl isocyanate (EBI).

[0071] According to an embodiment of the present invention, in order to minimize thermal denaturation of the reaction product and generation of by-products in the low boiler removal step, the low boiler removal step is preferably performed at a temperature of 150° C. to 165° C. And, the low boiler removal step is preferably performed under a pressure of 5 torr or less.

[0072] For example, the low boiling point removal step is performed in a distillation tower, and it is advantageous to operate the distillation tower at a bottom temperature of 150°C to 165°C and a top pressure of 5 torr or less 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.

[0073] Preferably, the low boiler removal step is performed at a temperature of 150° C. to 165° C., or 155° C. to 165° C. And, preferably, the low boiler removal step is performed at an upper pressure of 1 torr to 5 torr, or 2 torr to 5 torr, or 2 torr to 4 torr.

[0074] 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 increases, and the efficiency of removing low boiling materials decreases, thereby decreasing the concentration of isocyanate compounds in the reaction product obtained from the low boiler removal step.

[0075] As an example, the low boiler removal step can be performed in a low boiler removal unit 400 including a distillation column 440 configured to remove low boiling materials from the reaction product supplied via transfer line 304 of the desolvation unit 300; a low boiler discharge line 409 for discharging the low boiling materials from the top of the distillation column; and a transfer line 405 for discharging the reaction product from which the low boiling materials have been removed from the bottom of the distillation column and transferring it to a subsequent step.

[0076] In order to minimize the residence time of the reaction product at high temperatures 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.

[0077] (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.

[0078] 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.

[0079] 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, and examples of the high boiling point substance include by-products in the form of high molecular weight such as oligomers including dimers or trimers or higher polymers of the isocyanate compound formed in the process of obtaining the main product.

[0080] According to an 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.

[0081] 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.

[0082] Preferably, the high boiler removal step may be 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 may be performed at a pressure of 0.1 torr to 1 torr, alternatively 0.5 torr to 1 torr.

[0083] 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 increases, and the efficiency of removing high boiling materials decreases, thereby decreasing the concentration of isocyanate compounds obtained from the high boiler removal step.

[0084] As an example, the high boiling point removal step can be 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 via a transfer line 405 of the low boiling point removal unit 400; a transfer line 509 for transferring an isocyanate compound to a condensation section of the thin film distillation apparatus; and a high boiling point substance discharge line 506 for discharging the high boiling point substances from the bottom of the thin film distillation apparatus.

[0085] FIG. 2 relates to a production method in which the reaction step, the degassing step, the solvent removal step, the high boiler removal step, and the low boiler removal step are carried out in this order.

[0086] 2, high boiling materials are removed from the reaction product from which the solvent has been removed by a known high boiling materials removal unit 500. The high boiling materials removal step can be performed by a thin film distillation apparatus 550 configured to remove high boiling materials from the reaction product supplied through a transfer line 304 of the desolvation unit 300, a high boiling materials discharge line 509 for discharging high boiling materials from a condenser of the thin film distillation apparatus, and a transfer line 506 for discharging the reaction product from which the high boiling materials have been removed from another condenser of the thin film distillation apparatus and transferring it to a subsequent step.

[0087] In the low boiler removal step of Fig. 2, low boilers (lights) are removed from the reaction product from which the high boilers have been removed by a known low boiler removal unit 400. The low boiler removal step can be performed in a low boiler removal unit 400 including a distillation column 440 configured to remove low boilers from the reaction product supplied via a transfer line 506 of the high boiler removal unit 500; a low boiler discharge line 409 for discharging the low boilers from the top of the distillation column; and a transfer line 405 for discharging the reaction product from which the low boilers have been removed from the bottom of the distillation column.

[0088] FIG. 3 relates to a production method in which the reaction step, the degassing step, the high boiling point substance removal step, the solvent removal step, and the low boiling point substance removal step are carried out in sequence.

[0089] 3, high boilers are removed from the reaction product from which the gas phase has been removed by a known high boilers removal unit 500. The high boilers removal step can be performed by a thin film distillation apparatus 550 configured to remove high boilers from the reaction product supplied through a transfer line 203 of the degassing unit 200; a high boiler discharge line 509 for discharging high boilers from a condenser of the thin film distillation apparatus; and a transfer line 506 for discharging the reaction product from which the high boilers have been removed from another condenser of the thin film distillation apparatus and transferring it to a subsequent step.

[0090] 3, the solvent is distilled off from the reaction product from which the high boiling point materials have been removed by a known desolvation unit 300. The desolvation step can be performed in a desolvation unit 300 including a distillation column 330 configured to remove the solvent from the reaction product supplied through a transfer line 506 of the high boiler removal unit 500, a solvent discharge line 309 for discharging the solvent from the top of the distillation column, and a transfer line 304 for discharging the reaction product from which the solvent has been removed from the bottom of the distillation column and transferring it to a subsequent step.

[0091] 3, low boiling point materials (lights) are removed from the reaction product from which the solvent has been removed by a known low boiling point material removal unit 400. The low boiling point material removal step can be performed in a low boiling point material removal unit 400 including a distillation column 440 configured to remove low boiling point materials from the reaction product supplied via a transfer line 304 of the desolvation unit 300, a low boiling point material discharge line 409 for discharging the low boiling point materials from the top of the distillation column, and a transfer line 405 for discharging the reaction product from which the low boiling point materials have been removed from the bottom of the distillation column. Effect of the Invention

[0092] According to the present invention, there is provided a method for producing an isocyanate compound, which can minimize thermal denaturation of a reaction product and generation of by-products when producing an isocyanate compound using phosgene, and can produce a high-purity isocyanate compound. [Brief description of the drawings]

[0093] [Figure 1] FIG. 1 is a diagram illustrating a process and an apparatus used in a method for producing an isocyanate compound according to one embodiment of the present invention. [Diagram 2] FIG. 1 is a diagram illustrating a process and an apparatus used in a method for producing an isocyanate compound according to one embodiment of the present invention. [Diagram 3] FIG. 1 is a diagram illustrating a process and an apparatus used in a method for producing an isocyanate compound according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0094] The functions and effects of the present invention will be described in more detail below with reference to specific embodiments of the present invention, however, these are presented as examples to aid in understanding the invention and are not intended to limit the scope of the invention in any way.

[0095] Example 1 1,3-XDI (m-XDI) was produced using the apparatus shown in FIG. 1 and the following steps.

[0096] (Reaction Step) Under normal temperature and pressure conditions, 500 kg of hydrochloric acid and 560 kg of m-xylylenediamine (m-XDA) were reacted in a solvent of 6,500 kg of 1,2-dichlorobenzene (o-DCB) for 4 hours to form 870 kg of m-xylylenediamine hydrochloride.

[0097] 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 1359 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.

[0098] Then, the reactor was heated to an internal temperature of 125° C., and 6,000 kg of phosgene was further 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 via the transfer line 102.

[0099] (Degassing stage) The distillation column 220 of the degassing unit 200 is configured to remove a gas phase from the reaction product supplied via the transfer line 102 .

[0100] Specifically, the distillation column 220 uses a packing tower packed with pall rings, which is a type of random packing, and has a height of about 6 m.

[0101] 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.

[0102] A reflux stream of about 150 kg / hr was recharged to distillation column 220, corresponding to a reflux ratio to the overhead output of about 3.2.

[0103] A gas phase containing phosgene was discharged through a gas phase discharge line 209 connected to the top of the distillation column 220. 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.

[0104] (Desolvation step) The distillation column 330 of the desolvation unit 300 was configured to remove the solvent from the reaction product supplied via the transfer line 203 .

[0105] Specifically, the distillation column 330 uses a packing tower packed with pall rings, which are a type of random packing, and has a height of about 7 m.

[0106] 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.

[0107] About 600 kg / hr of reflux stream is recharged to distillation column 330, which corresponds to a reflux ratio of about 0.5 to the overhead output.

[0108] A solvent containing 1,2-dichlorobenzene (o-DCB) was discharged through a gas phase 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.

[0109] (Low boiling point removal stage) The distillation column 440 of the low boiler removal unit 400 was configured to remove low boiling materials from the reaction product supplied via the transfer line 304 .

[0110] Specifically, the distillation column 330 uses a packing tower packed with pall rings, which is a type of random packing, and has a height of about 13 m.

[0111] 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 3 torr.

[0112] A reflux stream of about 40 kg / hr was recharged to distillation column 440, corresponding to a reflux ratio to the overhead output of about 2.0.

[0113] Low boiling materials including (chloromethyl)benzyl isocyanate (CBI) were discharged through low boiling material discharge line 409 connected to the top of distillation column 440. The reaction product from which the low boiling materials were removed was transferred to high boiler removal unit 500 through transfer line 405 connected to the bottom of distillation column 440.

[0114] (High boiling point removal stage) The thin film distillation apparatus 550 of the high boiler removal unit 500 was configured to be capable of removing high boiling point substances from the reaction product supplied via the transfer line 405 .

[0115] Specifically, the thin film distillation apparatus 550 used was an evaporator in the form of a short path evaporator having a condenser installed therein.

[0116] The temperature at the bottom of the thin film distillation apparatus 550 was set to 135° C., and the pressure at the bottom of the thin film distillation apparatus 550 was set to 0.5 torr.

[0117] About 13 kg / hr of high boiling point condensate was separated at the bottom of the thin film distillation apparatus.

[0118] Isocyanate compounds including 1,3-XDI (m-XDI) were discharged through a discharge line 509 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.

[0119] Example 2 In the low boiler removal step, the distillation column 220 was operated at a bottom temperature of 155° C., and an isocyanate compound including 1,3-XDI (m-XDI) was obtained in the same manner as in Example 1.

[0120] Example 3 In the low boiler removal step, the distillation column 220 was operated at a bottom temperature of 165° C., and an isocyanate compound including 1,3-XDI (m-XDI) was obtained in the same manner as in Example 1.

[0121] Example 4 An isocyanate compound containing 1,3-XDI (m-XDI) was obtained in the same manner as in Example 1, except that the reaction step, the degassing step, the solvent removal step, the high boiling point substance removal step, and the low boiling point substance removal step were carried out in this order using an apparatus as shown in FIG. 2.

[0122] In Example 4 of Table 2 below, the data for the high boiler removal stage is the composition at the top of the column, and the data for the remaining stages is the composition at the bottom of the column.

[0123] Example 5 An isocyanate compound containing 1,3-XDI (m-XDI) was obtained in the same manner as in Example 1, except that the reaction step, the degassing step, the high boiling point substance removal step, the solvent removal step, and the low boiling point substance removal step were carried out in this order using an apparatus as shown in FIG. 3.

[0124] In Example 5 of Table 3 below, the data for the high boiler removal stage is the composition at the top of the column, and the data for the remaining stages is the composition at the bottom of the column.

[0125] Comparative Example 1 An isocyanate compound containing 1,3-XDI (m-XDI) was obtained in the same manner as in Example 1, except that the temperature of the bottom of the distillation column 440 in the low boiler removal step was 145° C. In the above-mentioned preparation method, the amount of residual low boilers in the low boiler removal step was relatively high.

[0126] Comparative Example 2 An isocyanate compound containing 1,3-XDI (m-XDI) was obtained in the same manner as in Example 1, except that the temperature at the bottom of the distillation column 440 in the low boiler removal step was 170° C. In the above preparation method, the content of 1,3-XDI was significantly reduced due to thermal decomposition of the reaction product.

[0127] Reference example 1 In the degassing step, the temperature at the bottom of the distillation column 220 was set to 155° C., and the pressure at the top of the distillation column 220 was set to 760 torr, but the same procedure as in Example 1 was used to obtain an isocyanate compound containing 1,3-XDI (m-XDI). In the above-mentioned production method, phosgene leaked out in the degassing step.

[0128] Reference example 2 In the degassing step, the temperature at the bottom of the distillation column 220 was set to 140° C., and the pressure at the top of the distillation column 220 was set to 400 torr, but the same procedure as in Example 1 was used to obtain an isocyanate compound containing 1,3-XDI (m-XDI). In the above-mentioned production method, phosgene leaked out in the degassing step.

[0129] Reference example 3 An isocyanate compound containing 1,3-XDI (m-XDI) was obtained in the same manner as in Example 1, except that in the desolvation step, the temperature at the bottom of the distillation column 330 was set to 160° C. and the pressure at the top of the distillation column 330 was set to 50 torr. In the above-mentioned preparation method, the amount of residual low boilers in the low boiler removal step was relatively high.

[0130] Reference example 4 In the desolvation step, the temperature at the bottom of the distillation column 330 was set to 95° C., and the pressure at the top of the distillation column 330 was set to 15 torr, and an isocyanate compound containing 1,3-XDI (m-XDI) was obtained in the same manner as in Example 1. In the above-mentioned preparation method, the amount of residual low boilers in the low boilers removal step was relatively high.

[0131] Reference example 5 In the high boiling point removal step, the temperature of the bottom of the thin film distillation apparatus 550 was set to 160° C., and the pressure of the bottom of the thin film distillation apparatus 550 was set to 2 torr, and an isocyanate compound containing 1,3-XDI (m-XDI) was obtained in the same manner as in Example 1. In the above-mentioned preparation method, the amount of residual high boiling point materials in the high boiling point removal step was relatively high.

[0132] Test Example A portion of the reaction product obtained at each step of the Examples and Comparative Examples was collected and analyzed by gel permeation chromatography. The contents of the main components confirmed by the analysis are shown in Table 1 below.

[0133] [Table 1]

[0134] [Table 2]

[0135] [Table 3]

[0136] Referring to Tables 1 to 3 above, it was confirmed that the method for producing an isocyanate compound according to the above examples can minimize thermal denaturation of the reaction product and the generation of by-products, and can obtain a high-purity isocyanate compound.

[0137] In contrast, in the above-mentioned Reference Example, phosgene leaked out or low-boiling or high-boiling substances remained. Also, in the above-mentioned Reference Example, it was confirmed that the amount of thermal denaturation and by-products produced increased, and the concentration of the finally obtained isocyanate compound was relatively low. [Explanation of symbols]

[0138] 10. Amine compound salt supply line 20 Phosgene supply line 100 reaction units 110 Reactor 102 Transfer Line 200 Degassing Unit 220 Distillation Tower 209 Gas Phase Discharge Line 203 Transfer Line 300 Desolvation Unit 330 Distillation Tower 309 Solvent discharge line 304 Transfer Line 400 Low boiling point removal unit 440 Distillation Tower 409 Low boiling point substance discharge line 405 Transfer Line 500 High boiling point removal unit 550 Thin Film Distillation Apparatus 506 High boiling point substance discharge line 509 Transfer Line

Claims

1. a reaction step of reacting the salt of the amine compound with phosgene in a solvent to obtain a reaction product containing an isocyanate compound; and a degassing step for removing a gas phase from the reaction product, The method includes, in any order, a desolvation step for removing solvent from the reaction product from which the gas phase has been removed, a low boiler removal step for removing lights, and a high boiler removal step for removing heavies; The degassing step is carried out at a temperature of 145° C. to 165° C. and a pressure of 100 torr to 600 torr; The desolvation step is carried out at a temperature of 100° C. to 165° C. and a pressure of 2 torr to 30 torr; The low boiler removal step is carried out at a temperature of 150° C. to 165° C. and a pressure of 1 torr to 5 torr; The high boiler removal step is carried out at a temperature of 145° C. to 165° C. and a pressure of 0.5 torr to 1 torr; The amine compound is one or more compounds selected from the group consisting of m-xylylenediamine, p-xylylenediamine, and o-xylylenediamine. A method for producing an isocyanate compound.

2. a reaction step of reacting a salt of an amine compound with phosgene in a solvent to obtain a reaction product containing an isocyanate compound; said degassing step removing a gas phase from said reaction product; the desolvation step of removing the solvent from the reaction product from which the gas phase has been removed; the low boiler removal step of removing low boiling points from the reaction product from which the solvent has been removed; and 2. The method for producing an isocyanate compound according to claim 1, further comprising the step of removing high boilers from the reaction product from which the low boilers have been removed.

3. a reaction step of reacting a salt of an amine compound with phosgene in a solvent to obtain a reaction product containing an isocyanate compound; said degassing step removing a gas phase from said reaction product; the desolvation step of removing the solvent from the reaction product from which the gas phase has been removed; the high boiler removal step, which removes heavy materials from the solvent-removed reaction product; and The method for producing an isocyanate compound according to claim 1, further comprising removing low boilers from the reaction product from which the high boilers have been removed.

4. a reaction step of reacting a salt of an amine compound with phosgene in a solvent to obtain a reaction product containing an isocyanate compound; said degassing step removing a gas phase from said reaction product; a high boiler removal step for removing heavy materials from the reaction product from which the gas phase has been removed; removing the solvent from the reaction product from which the high boiling point materials have been removed; and 2. The method for producing an isocyanate compound according to claim 1, further comprising removing low boilers from the reaction product from which the solvent has been removed.

5. The method for producing an isocyanate compound according to claim 1 , wherein the salt of the amine compound is a hydrochloride or a carbonate of the amine compound.

6. The method for producing an isocyanate compound according to claim 1, wherein the high boiler removal step is carried out in a thin-film evaporator.

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