Light-colored isocyanate and preparation method and application thereof

Abstract

The present application provides a kind of light color isocyanate and its preparation method and application, the preparation method first carries out phosgene reaction to amine substance, phosgene solution and inert solvent, obtains liquid phase material A, then removes hydrogen chloride and phosgene in liquid phase material A, obtains liquid phase material B, removes part of inert solvent in liquid phase material B again, obtains isocyanate crude product, removes remaining part of inert solvent and pure isocyanate in isocyanate crude product again, obtains light color polymeric isocyanate, and condenses pure removed inert solvent and pure isocyanate, obtains liquid phase material C, finally removes inert solvent in liquid phase material C, obtains light color pure isocyanate;By controlling the residence time of phosgene-containing material at 120-180 DEG C is 0.5-12h, and then effectively avoids the generation of phosgene adduct and polycyclic polymer, successfully prepared light color isocyanate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of isocyanate, and particularly relates to a light-colored isocyanate and a preparation method and application thereof. BACKGROUND

[0002] As an organic reaction intermediate, isocyanate is widely used in various industries such as industry, agriculture, construction, automobile and thermal insulation, because it can be further synthesized into polyisocyanate, polyurethane, polyurea, spandex and other materials. At present, the mainstream method for synthesizing isocyanate in industry is phosgenation, but the disadvantage of phosgenation is that discoloration occurs in the phosgenation process, which is due to a large amount of colored substances produced in the phosgenation reaction of diamines or polyamines, and the colored substances are not removed in the subsequent separation and treatment process and remain in the process of further processing of isocyanate into polyurethane.

[0003] At present, the following methods are mainly used to solve the color problem of isocyanate: (1) control of engineering process parameters of phosgenation reaction. US5364958 discloses a method for preparing light-colored isocyanate, in which phosgene is completely removed at low temperature after phosgenation, and then the reaction solution is treated with hot HCl gas to reduce the color number of the product. (2) Addition of an additive for lightening color to the crude isocyanate after phosgenation; US4465639 discloses a method for preparing light-colored isocyanate, in which water is added after phosgenation and before removal of the solvent to obtain a light-colored product. EP0581100 discloses a method for preparing polyisocyanate, in which a chemical reducing agent is added after phosgenation and before removal of the solvent to obtain light-colored isocyanate. (3) Treatment of the final obtained isocyanate; EP0561225 discloses that the phosgenated isocyanate is subjected to hydrogen treatment under the conditions of a pressure of 1-150 bar and a temperature of 100-180℃, so that the color of the final product is improved. EP0133528 discloses that isocyanate is subjected to extraction purification to obtain a light-colored MDI component. (4) Pretreatment of the raw material amine; EP0866057 and US5872278 disclose a method for treating amine with a Lewis acid or Bronsted acid solid substance before phosgenation of the amine to obtain light-colored isocyanate. (5) Control of the quality of raw material phosgene; CN102317255A discloses a method for adjusting the molar excess of the adjustable carbon monoxide to adjust the color of isocyanate.

[0004] However, the coloring of isocyanate is not only caused by impurities, but also caused by by-products generated in the phosgenation process. In the above five methods, color treatment is performed after phosgenation, which requires a large amount of engineering cost and is not obvious for color number improvement. In addition, the color treatment after phosgenation requires the introduction of other impurities, which form unwanted by-products in the downstream application of isocyanate. The upstream treatment of phosgenation requires strict limitation of the content of certain specific components, which is high in cost.

[0005] In summary, it can be found that developing a method for adjusting the phosgenation process to prepare light-colored isocyanate is a technical problem urgently needed to be solved in the art. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide a light-colored isocyanate and a preparation method and method thereof. The preparation method successfully prepares light-colored isocyanate by limiting the residence time of the phosgene-containing material at 120-180℃ and controlling the step of removing inert solvent.

[0007] To achieve this purpose, the technical scheme adopted by the present application is as follows:

[0008] (1) phosgenation reaction of amine, phosgene solution and inert solvent to obtain liquid phase material A containing isocyanate;

[0009] (2) removing hydrogen chloride and phosgene from the liquid phase material A obtained in step (1) to obtain liquid phase material B;

[0010] (3) removing part of the inert solvent from the liquid phase material B obtained in step (2) to obtain crude isocyanate product; (4) removing the remaining part of the inert solvent and pure isocyanate from the crude isocyanate product obtained in step (3) to obtain light-colored polymeric isocyanate; condensing the removed inert solvent and pure isocyanate to obtain liquid phase material C;

[0011] (5) removing the inert solvent from the liquid phase material C obtained in step (4) to obtain light-colored pure isocyanate.

[0012] The temperature of the phosgenation reaction in step (1) is 60-160℃, for example, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃ or 150℃, etc.

[0013] The removal temperature of hydrogen chloride and phosgene from the liquid phase material obtained in step (1) in step (2) is 100-180℃, for example, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃ or 170℃, etc.

[0014] In the steps (1) and (2), the residence time of the phosgene-containing material at 120-180℃ (for example, 130℃, 140℃, 150℃, 160℃ or 170℃, etc.) is 0.5-12h, for example, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h or 11h, etc.

[0015] The method for preparing light-colored isocyanate provided by the application comprises the following steps: firstly, carrying out phosgenation reaction on amine, phosgene solution and inert solvent at 60-160℃ to obtain liquid-phase material A containing isocyanate, and hydrogen chloride and phosgene are also generated in the process; secondly, removing hydrogen chloride and phosgene in the liquid-phase material A containing isocyanate obtained in the above step at 100-180℃ to obtain liquid-phase material B, and hydrogen chloride and phosgene are also generated in the process; thirdly, removing part of the inert solvent in the liquid-phase material B to obtain crude isocyanate, and the removed inert solvent can be reused after being cooled; fourthly, removing the remaining inert solvent and pure isocyanate in the crude isocyanate to obtain polymeric isocyanate, and the removed inert solvent and pure isocyanate are condensed to obtain liquid-phase material C; and finally, removing the inert solvent in the liquid-phase material C to obtain light-colored pure isocyanate.

[0016] The application limits the residence time of the phosgene-containing material in the above process to 0.5-12h at 120-180℃, and limits the removal of the inert solvent in the liquid-phase material in two steps, so that the content of the inert solvent in the liquid-phase material is controlled, the generation of phosgene adduct and polycyclic polymer in the preparation process is effectively avoided, and the color number of the isocyanate product is effectively reduced, and the whole preparation method has the advantages of simple process, convenient operation, energy saving, low cost, high efficiency and environmental friendliness.

[0017] Specifically, if the residence time of the phosgene-containing material at 120-180℃ is higher than 12h, the generation amount of phosgene adduct will increase, which will deteriorate the color number of the isocyanate product, and if the residence time at 120-180℃ is less than 0.5h, the reaction requirement cannot be met.

[0018] The "light-colored isocyanate" in the application refers to pure isocyanate with platinum-cobalt color number less than 10 and polymeric isocyanate with L color higher than 75.

[0019] In the present application, the gaseous material is produced after the phosgenation reaction of step (1) and the step of removing hydrogen chloride and phosgene from the liquid material A of step (2) are completed. The gaseous material is first condensed and then reused. The condensed liquid from the gaseous material of step (1) is refluxed into the reaction kettle of the phosgenation reaction (preferably the reaction kettle of the thermal phosgenation reaction). The non-condensable gas is sent to the gaseous absorption system, in which the phosgene is absorbed by an inert solvent, and the phosgene solution is reused in the phosgenation reaction. At the same time, the gaseous hydrogen chloride is absorbed by hydrochloric acid in the gaseous absorption system.

[0020] Preferably, the gaseous absorption system can use any absorption tower known in the art, preferably a packed tower or a plate tower, more preferably a packed tower.

[0021] Preferably, the temperature of the gaseous absorption system is -15 to 15°C, such as -13°C, -11°C, -9°C, -7°C, -5°C, -3°C, -1°C, 3°C, 5°C, 7°C, or 9°C, etc.

[0022] Preferably, the pressure of the gaseous absorption system is 0 to 10 barg, such as 2 barg, 4 barg, 6 barg, 8 barg, or 10 barg, etc.

[0023] Preferably, the inert solvent in the gaseous absorption system includes any one or a combination of at least two of chlorobenzene, dichlorobenzene, trichlorobenzene, toluene, xylene, benzene, and diethyl phthalate, further preferably chlorobenzene and / or o-dichlorobenzene.

[0024] Preferably, the mass percentage of phosgene in the phosgene solution obtained in the gaseous absorption system is 50 to 90%, such as 55%, 60%, 65%, 70%, 75%, 80%, or 85%, etc.

[0025] Preferably, the mass ratio of the amine substance to the phosgene solution in step (1) is 1: (2 to 8), such as 1:3, 1:4, 1:5, 1:6, or 1:7, etc., further preferably 1: (3 to 5).

[0026] Preferably, the mass ratio of the amine substance to the inert solvent in step (1) is 1: (2 to 6), such as 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, or 1:5.5, etc., further preferably 1: (2.5 to 5), and more further preferably 1: (3 to 4).

[0027] Preferably, the amine in step (1) comprises any one of or a combination of at least two of diaminodiphenylmethane, polymethylene polyphenyl polyamine, diaminotoluene, isophorone diamine, hexanediamine, cyclohexanediamine, p-phenylenediamine, naphthalenediamine, xylylenediamine, cyclohexanedimethylene diamine, tetramethyl-m-xylylenediamine or dimethylbenzidiamine.

[0028] Preferably, the inert solvent in step (1) comprises any one of or a combination of at least two of chlorobenzene, dichlorobenzene, trichlorobenzene, toluene, xylene, benzene or diethyl phthalate, and is further preferably chlorobenzene and / or o-dichlorobenzene.

[0029] Preferably, the mass percentage of phosgene in the phosgene solution in step (1) is 50-90%, such as 55%, 60%, 65%, 70%, 75%, 80%, 85% or 90%, etc.

[0030] The amine and the inert solvent can be mixed before the phosgenation reaction in step (1), and the mixing can be performed using a mixing device known in the art, preferably a static mixer.

[0031] Preferably, the phosgenation reaction in step (1) comprises a cold phosgenation reaction and a hot phosgenation reaction.

[0032] The reactor used for the cold phosgenation reaction and the hot phosgenation reaction is not particularly limited, and a reactor known in the art can be selected; preferably, the cold phosgenation reaction is performed in a jet reactor, and the hot phosgenation reaction is performed in a tank reactor.

[0033] Preferably, the temperature of the cold phosgenation reaction is 60-140°C, such as 70°C, 80°C, 90°C, 100°C, 110°C, 120°C or 130°C, etc.

[0034] Preferably, the pressure of the cold phosgenation reaction is 1-30 barg, such as 5 barg, 10 barg, 15 barg, 20 barg, 25 barg or 30 barg, etc.

[0035] Preferably, the time of the cold phosgenation reaction is 1-90 min, such as 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min or 80 min, etc.

[0036] Preferably, the temperature of the hot phosgenation reaction is 110-160°C, such as 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C or 155°C, etc.

[0037] Preferably, the pressure of the thermal phosgene reaction is 2 to 20 barg, such as 4 barg, 6 barg, 8 barg, 10 barg, 12 barg, 14 barg, 16 barg or 18 barg, etc.

[0038] Preferably, the time of the thermal phosgene reaction is 1 to 8 h, such as 2 h, 3 h, 4 h, 5 h, 6 h or 7 h, etc.

[0039] Preferably, the temperature of removing the hydrogen chloride and phosgene in the liquid phase material A obtained from step (1) in step (2) is 120 to 170 °C, such as 130 °C, 140 °C, 150 °C or 160 °C, etc., further preferably 140 to 160 °C.

[0040] Preferably, the pressure of removing the hydrogen chloride and phosgene in the liquid phase material A obtained from step (1) in step (2) is -0.2 to 3 barg, such as -0.15 barg, -0.1 barg, -0.05 barg, 0 barg, 0.05 barg, 0.1 barg or 0.15 barg, etc., further preferably -0.1 to 2 barg, and still further preferably 0 to 0.5 barg.

[0041] Preferably, the temperature of removing part of the inert solvent in the liquid phase material B obtained from step (2) in step (3) is 100 to 220 °C, such as 120 °C, 140 °C, 160 °C, 180 °C or 200 °C, etc., further preferably 130 to 200 °C, and still further preferably 150 to 180 °C.

[0042] Preferably, the pressure of removing the liquid phase material B obtained from step (2) in step (3) is -1 to 0 barg, such as -0.9 barg, -0.8 barg, -0.7 barg, -0.6 barg, -0.5 barg, -0.4 barg, -0.3 barg, -0.2 barg or -0.1 barg, etc., further preferably -0.9 to -0.2 barg, and still further preferably -0.7 to -0.4 barg.

[0043] Preferably, the mass percentage content of the inert solvent in the crude isocyanate product in step (3) is 5 to 30%, such as 7%, 9%, 11%, 13%, 15%, 17%, 19%, 21%, 23%, 25% or 27%, etc., further preferably 10 to 15%.

[0044] Preferably, the removal temperature of the remaining part of the inert solvent and the pure isocyanate in the crude isocyanate product obtained from step (3) in step (4) is 150-300℃, such as 170℃, 190℃, 210℃, 230℃, 250℃, 270℃ or 290℃, and further preferably 150-250℃.

[0045] Preferably, the removal pressure of the remaining part of the inert solvent and the pure isocyanate in the crude isocyanate product obtained from step (3) in step (4) is -1-1 barg, such as -0.8 barg, -0.6 barg, -0.4 barg, -0.2 barg, 0 barg, 0.2 barg, 0.4 barg, 0.6 barg or 0.8 barg, and further preferably -10.5--0.5 barg.

[0046] Preferably, the removal temperature of the inert solvent in the liquid phase material C obtained from step (4) in step (5) is 100-220℃, such as 120℃, 140℃, 160℃, 180℃ or 200℃, and further preferably 130-200℃, and more further preferably 150-180℃.

[0047] Preferably, the removal pressure of the inert solvent in the liquid phase material C obtained from step (4) in step (5) is -1-0 barg, such as -0.9 barg, -0.8 barg, -0.7 barg, -0.6 barg, -0.5 barg, -0.4 barg or -0.2 barg, and further preferably -0.9--0.2 barg, and more further preferably -0.7--0.4 barg.

[0048] As a preferred technical solution of the present application, the preparation method comprises the following steps:

[0049] (1) carrying out a cold phosgenation reaction of the amine substance, the phosgene solution and the inert solvent at 60-140℃ and 1-30 barg for 1-90 min, and then carrying out a hot phosgenation reaction at 110-160℃ and 2-20 barg for 1-8 h, to obtain a liquid phase material A containing isocyanate;

[0050] (2) removing the hydrogen chloride and the phosgene in the liquid phase material A obtained from step (1) at 100-180℃ and -0.2-3 barg, to obtain a liquid phase material B; and in steps (1) and (2), the residence time of the phosgene-containing material at 120-180℃ is 0.5-12 h;

[0051] (3) removing part of the inert solvent in the liquid phase material B obtained in step (2) at 100-220℃, -1-0 barg, to obtain a crude isocyanate product with the mass percentage of the inert solvent being 5-30%;

[0052] (4) removing the remaining part of the inert solvent and pure isocyanate in the crude isocyanate product obtained in step (3) at 150-300℃, -1-1 barg, to obtain a light-colored polymeric isocyanate; condensing the removed inert solvent and pure isocyanate to obtain a liquid phase material C;

[0053] (5) removing the inert solvent in the liquid phase material C obtained in step (4) at 100-220℃, -1-0 barg, to obtain a light-colored pure isocyanate product.

[0054] In the second aspect, the present application provides a light-colored polymeric isocyanate, which is prepared by the preparation method as described in the first aspect.

[0055] Preferably, the L color of the light-colored polymeric isocyanate is higher than 75, such as 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, etc.

[0056] In the third aspect, the present application provides a light-colored pure isocyanate, which is prepared by the preparation method as described in the first aspect.

[0057] Preferably, the platinum-cobalt color number of the light-colored pure isocyanate is less than 10, such as 9, 8, 7, 6, 5, 4, 3, 2 or 1, etc.

[0058] In the fourth aspect, the present application provides an application of the light-colored polymeric isocyanate as described in the second aspect in the synthesis of polyisocyanate, polyurethane, polyurea or spandex.

[0059] In the fifth aspect, the present application provides an application of the light-colored pure isocyanate as described in the third aspect in the synthesis of polyisocyanate, polyurethane, polyurea or spandex.

[0060] Compared with the prior art, the present application has the following beneficial effects:

[0061] The preparation method of the light-colored isocyanate provided by the present application first carries out a phosgenation reaction on an amine substance, a phosgene solution and an inert solvent to obtain a liquid-phase material A containing isocyanate, then removes hydrogen chloride and phosgene in the liquid-phase material A to obtain a liquid-phase material B, further removes part of the inert solvent in the liquid-phase material B to obtain a crude isocyanate product, then removes the inert solvent and pure isocyanate in the crude isocyanate product to obtain a polymeric isocyanate, and at the same time, condenses the removed inert solvent and pure isocyanate to obtain a liquid-phase material C; finally, removes the inert solvent in the liquid-phase material C to obtain a light-colored pure isocyanate; by limiting the temperature of the phosgenation reaction to 60-160℃, the removal temperature of hydrogen chloride and phosgene in the liquid-phase material to 100-180℃ and the residence time of the phosgene-containing material at 120-180℃ to 0.5-12h, the generation of phosgene adducts and polymers is effectively avoided, and the color number of the prepared isocyanate is effectively reduced, and a light-colored pure isocyanate with a platinum-cobalt color number less than 10 and a light-colored polymeric isocyanate with an L color higher than 75 are successfully prepared. BRIEF DESCRIPTION OF DRAWINGS

[0062] Figure 1 A preparation process flow chart of the light-colored isocyanate provided for the embodiment 1 of the present application is shown in the figure.

[0063] Among them, 1 is a static mixer, 2 is a jet reactor, 3 is a kettle reactor, 4 is a de-phosgenation tower, 5 is a phosgene absorption tower, 6 is a primary solvent removal tower, 7 is a component separation tower, 8 is a secondary solvent removal tower and 9 is an isocyanate condenser. DETAILED DESCRIPTION

[0064] The technical solutions of the present application are further illustrated by specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations on the present application.

[0065] Embodiment 1

[0066] A preparation method of a light-colored isocyanate, the process flow of which is shown in the figure, specifically includes the following steps: Figure 1

[0067] ​(1) Diphenylmethanediamine with a flow rate of 30 t / h and a pressure of 20 barg and chlorobenzene with a flow rate of 25 t / h and a pressure of 20 barg are mixed uniformly in static mixer 1, and then enter jet reactor 2 with a flow rate of 35 t / h and a pressure of 20 barg of phosgene solution (phosgene mass percentage of 70%, solvent chlorobenzene) to carry out cold phosgenation reaction at 100°C and 10 barg for 5 min, and then enter kettle reactor 3 to carry out hot phosgenation reaction at 130°C and 3 barg for 2.5 h to obtain isocyanate-containing liquid phase material A and gas phase material containing phosgene and hydrogen chloride;

[0068] (2) The isocyanate-containing liquid phase material A obtained in step (1) enters dephosgenation column 4 to remove hydrogen chloride and phosgene at a column bottom temperature of 140°C and a column top pressure of 0.2 barg (in steps (1) and (2), the material containing phosgene stays in the temperature range of 120-180°C for 3 h), which produces gas phase material and liquid phase material B;

[0069] (3) The liquid phase material B obtained in step (2) enters primary solvent removal column 6 to remove part of chlorobenzene at a column bottom temperature of 180°C and a column top pressure of -0.6 barg, and the solution collected from the column bottom of primary solvent removal column 6 is obtained as crude isocyanate product, and the mass percentage of chlorobenzene in the crude isocyanate product is 10%;

[0070] The gas phase material obtained in step (2) and the gas phase material produced after the hot phosgenation reaction in step (1) are simultaneously introduced into phosgene recovery column 5 for recovery and reuse, and chlorobenzene is introduced into phosgene recovery column 5 to contact with phosgene in the gas phase material in countercurrent to absorb the phosgene to produce phosgene solution, the column bottom temperature of phosgene absorption column 5 is -2°C, and the column top temperature is 3 barg;

[0071] (4) The crude isocyanate product obtained in step (3) is introduced into component separation column 7 for component separation at a column bottom temperature of 220°C and a column top pressure of -0.2 barg, and light-colored polymeric isocyanate is collected from the column bottom, and pure isocyanate and chlorobenzene are collected from the column top to enter isocyanate condenser 9 for condensation to obtain liquid phase material C containing a small amount of chlorobenzene;

[0072] (5) The liquid phase material C obtained in step (4) is introduced into secondary solvent removal column 8 to remove chlorobenzene at a column bottom temperature of 200°C and a column top pressure of -0.6 barg, and the removed chlorobenzene is collected from the column top, and light-colored pure isocyanate is obtained from the column bottom.

[0073] Example 2

[0074] A method for preparing a light color isocyanate, which differs from example 1 only in that the time of the thermal phosgene reaction in step (1) is 4h, and the total time of the phosgene-containing material in step (1) and step (2) staying in the temperature range of 120-180℃ is 5h, and other conditions, parameters and steps are the same as example 1.

[0075] Example 3

[0076] A method for preparing a light color isocyanate, which differs from example 1 only in that the time of the thermal phosgene reaction in step (1) is 9h, and the total time of the phosgene-containing material in step (1) and step (2) staying in the temperature range of 120-180℃ is 10h, and other conditions, parameters and steps are the same as example 1.

[0077] Example 4

[0078] A method for preparing a light color isocyanate, which differs from example 1 only in that the time of the thermal phosgene reaction in step (1) is 10.5h, and the total time of the phosgene-containing material in step (1) and step (2) staying in the temperature range of 120-180℃ is 12h, and other conditions, parameters and steps are the same as example 1.

[0079] Example 5

[0080] A method for preparing a light color isocyanate, which differs from example 1 only in that the temperature of removing hydrogen chloride and phosgene in the dephosgene column in step (2) is 180℃, and other conditions, parameters and steps are the same as example 1.

[0081] Example 6

[0082] A method for preparing a light color isocyanate, which differs from example 1 only in that the temperature of the thermal phosgene reaction in step (1) is 120℃, and other conditions, parameters and steps are the same as example 1.

[0083] Example 7

[0084] A method for preparing a light color isocyanate, which differs from example 1 only in that the temperature of the thermal phosgene reaction in step (1) is 180℃, and other conditions, parameters and steps are the same as example 1.

[0085] Examples 8-12

[0086] A method for preparing a light color isocyanate, which differs from example 1 only in that the mass percentage of chlorobenzene in the crude isocyanate product obtained in the primary solvent removal column in step (2) is 15%, 5%, 30%, 35% and 2% respectively, and other conditions, parameters and steps are the same as example 1.

[0087] Comparative Example 1

[0088] A method for preparing a light-colored isocyanate, specifically comprising the following steps:

[0089] (1) Diphenylmethane diamine with a flow rate of 30 t / h and a pressure of 20 barg and chlorobenzene with a flow rate of 25 t / h and a pressure of 20 barg are mixed uniformly in a static mixer, and then enter a jet reactor with a phosgene solution (phosgene mass percentage of 70%, solvent chlorobenzene) with a flow rate of 35 t / h and a pressure of 20 barg to perform a cold phosgenation reaction at 100°C and 10 barg for 30 min, and then enter a kettle reactor to perform a hot phosgenation reaction at 130°C and 3 barg for 13 h to obtain an isocyanate-containing liquid phase material A and a gas phase material containing phosgene and hydrogen chloride;

[0090] (2) The isocyanate-containing liquid phase material A obtained in step (1) enters a dephosgenation tower to remove hydrogen chloride and phosgene under the conditions of a tower bottom temperature of 140°C and a tower top pressure of 0.2 barg (the material containing phosgene in steps (1) and (2) stays in the temperature range of 120-180°C for 14 h), which produces a gas phase material and a liquid phase material B;

[0091] (3) The liquid phase material B obtained in step (2) is introduced into a primary solvent removal tower to remove part of the chlorobenzene under the conditions of a tower bottom temperature of 180°C and a tower top pressure of -0.6 barg, and the solution collected from the tower bottom of the primary solvent removal tower is an isocyanate crude product, and the mass percentage of chlorobenzene in the isocyanate crude product is 0.1%;

[0092] The gas phase material and the gas phase material produced after the hot phosgenation reaction in step (1) are simultaneously introduced into a phosgene recovery tower for recycling, chlorobenzene is introduced into the phosgene recovery tower, and the chlorobenzene and the phosgene in the gas phase material are countercurrently contacted to absorb the phosgene to produce a phosgene solution, the tower bottom temperature of the phosgene absorption tower is -2°C, and the tower top temperature is 3 barg;

[0093] (4) The isocyanate crude product obtained in step (3) is introduced into a component separation tower 7 for component separation under the conditions of a tower bottom temperature of 220°C and a tower top pressure of -0.2 barg, a light-colored polymeric isocyanate is collected from the tower bottom, and pure isocyanate and chlorobenzene are collected from the tower top and introduced into an isocyanate condenser for condensation to obtain a liquid phase material C containing a small amount of chlorobenzene;

[0094] (5) The liquid phase material C obtained in step (4) is introduced into a secondary solvent removal tower to remove chlorobenzene under the conditions of a tower bottom temperature of 200°C and a tower top pressure of -0.6 barg, the removed chlorobenzene is collected from the tower top, and a light-colored isocyanate is obtained from the tower bottom.

[0095] Performance test:

[0096] (1) Platinum-cobalt color number of pure isocyanate: test according to the test method provided in GB / T 3143-1982, test the platinum-cobalt color number of initial isocyanate and the platinum-cobalt color number after deterioration at 110℃ for 4h;

[0097] (2) L chroma of polyisocyanate: use integrating sphere spectrophotometer, dichloromethane as standard substance to determine.

[0098] Test the light-colored pure isocyanate and light-colored polyisocyanate provided by examples 1-12 and comparative example 1 according to the above test method, and the test results are shown in table 1:

[0099] Table 1

[0100]

[0101]

[0102] According to the data in table 1, it can be seen that:

[0103] The present application effectively avoids the generation of color-producing substances in the preparation process by controlling the residence time of the phosgene-containing material at 120-180℃, fundamentally reduces the color of the isocyanate product, and further reduces the color depth of the isocyanate product by using the two-step method to remove the solvent and using the remaining solvent to protect the isocyanate product during high-temperature separation.

[0104] Specifically, the initial platinum-cobalt color number of the pure isocyanate product obtained by the preparation method provided in examples 1-10 is 4.6-8.2#, the platinum-cobalt color number after deterioration at 110℃ for 4h is 5.8-9.6#, and the L chroma of the polyisocyanate product obtained by the preparation method provided in examples 1-10 is 75-85.

[0105] Comparing the data of comparative example 1 and comparative example 1, it can be found that the residence time of the phosgene-containing material at 120-180℃ is too long, which will result in an increase in the platinum-cobalt color number of the pure isocyanate obtained, and also result in a decrease in the L chroma of the pure isocyanate product.

[0106] Comparing the data of example 1 and examples 11-12, it can also be found that the mass percentage content of the solvent in the crude isocyanate product will also affect the color of the final obtained pure isocyanate and polyisocyanate product.

[0107] Applicants declare that the present invention illustrates a light color isocyanate and its preparation method and application by the above-mentioned examples, but the present invention is not limited to the above-mentioned examples, namely does not mean that the present invention must rely on the above-mentioned examples to be implemented. The skilled in the art should understand that any improvement of the present invention, equivalent replacement of each raw material of the product of the present invention and addition of auxiliary ingredients, selection of specific mode, etc. fall within the protection scope and disclosure scope of the present invention.

Claims

1. A process for the preparation of a light-colored isocyanate, characterized in that, The preparation method comprises the following steps: (1) performing a phosgenation reaction on an amine substance, a phosgene solution and an inert solvent to obtain a liquid-phase material A containing isocyanate; (2) removing hydrogen chloride and phosgene in the liquid-phase material A obtained in step (1) to obtain a liquid-phase material B; (3) removing part of the inert solvent in the liquid-phase material B obtained in step (2) to obtain a crude isocyanate product; (4) removing the remaining part of the inert solvent and pure isocyanate in the crude isocyanate product obtained in step (3) to obtain a light-colored polymeric isocyanate; condensing the removed inert solvent and pure isocyanate to obtain a liquid-phase material C; (5) removing the inert solvent in the liquid-phase material C obtained in step (4) to obtain light-colored pure isocyanate; The phosgenation reaction in step (1) comprises a cold phosgenation reaction and a hot phosgenation reaction. The temperature of the cold phosgenation reaction is 60-140 ℃, and the time is 1-90 min. The temperature of the hot phosgenation reaction is 110-160 ℃, and the time is 1-8 h. The removal temperature of hydrogen chloride and phosgene in the liquid-phase material A obtained in step (1) in step (2) is 100-180 ℃, and the residence time of the phosgene-containing material at 120-180 ℃ in the steps (1) and (2) is 0.5-12 h. The mass percentage content of the inert solvent in the crude isocyanate product in step (3) is 5-30%.

2. The production method according to claim 1, characterized by, The mass ratio of the amine substance to the phosgene solution in step (1) is 1:(2-8).

3. The preparation method according to claim 2, characterized in that, The mass ratio of the amine substance to the phosgene solution in step (1) is 1:(3-5).

4. The method of claim 1, wherein, The mass ratio of the amine substance to the inert solvent in step (1) is 1:(2-6).

5. The preparation method according to claim 4, characterized in that, The mass ratio of the amine substance to the inert solvent in step (1) is 1:(2.5-5).

6. The production method according to claim 5, wherein The mass ratio of the amine substance to the inert solvent in step (1) is 1:(3-4).

7. The preparation method according to claim 1, characterized in that, The amine substance in step (1) comprises any one or a combination of at least two of diaminodiphenylmethane, polymethylene polyphenyl polyamine, diaminotoluene, isophorone diamine, hexanediamine, cyclohexanediamine, p-phenylenediamine, naphthalenediamine, benzene dimethylene diamine, cyclohexane dimethylene diamine, tetramethyl m-xylylene diamine or dimethyl diphenyl diamine.

8. The method of claim 1, wherein, The inert solvent in step (1) comprises any one or a combination of at least two of chlorobenzene, dichlorobenzene, trichlorobenzene, toluene, xylene, benzene or diethyl isophthalate.

9. The production method according to claim 8, characterized by, The inert solvent in step (1) comprises chlorobenzene and / or o-dichlorobenzene.

10. The method of claim 1, wherein, The mass percentage content of phosgene in the phosgene solution in step (1) is 50-90%.

11. The method of claim 1, wherein, The pressure of the cold phosgenation reaction is 1-30 barg.

12. The method of claim 1, wherein, The pressure of the hot phosgenation reaction is 2-20 barg.

13. The method of claim 1, wherein, The removal temperature of hydrogen chloride and phosgene in the liquid-phase material A obtained in step (1) in step (2) is 120-170 ℃.

14. The method of claim 13, wherein, The removal temperature of hydrogen chloride and phosgene in the liquid-phase material A obtained in step (1) in step (2) is 140-160 ℃.

15. The method of claim 1, wherein, The removal pressure of hydrogen chloride and phosgene in the liquid phase material A obtained in step (1) is -0.2-3 barg.

16. The method of claim 15, wherein, The removal pressure of hydrogen chloride and phosgene in the liquid phase material A obtained in step (1) is -0.1-2 barg.

17. The preparation method according to claim 15, characterized in that, The removal pressure of hydrogen chloride and phosgene in the liquid phase material A obtained in step (1) is 0-0.5 barg.

18. The method of claim 1, wherein, The removal temperature of part of the inert solvent in the liquid phase material B obtained in step (2) is 100-220 ℃.

19. The method of claim 18, wherein, The removal temperature of part of the inert solvent in the liquid phase material B obtained in step (2) is 130-200 ℃.

20. The method of claim 19, wherein, The removal temperature of part of the inert solvent in the liquid phase material B obtained in step (2) is 150-180 ℃.

21. The method of claim 1, wherein, The removal pressure of part of the inert solvent in the liquid phase material B obtained in step (2) is -1-0 barg.

22. The method of claim 21, wherein, The removal pressure of part of the inert solvent in the liquid phase material B obtained in step (2) is -0.9--0.2 barg.

23. The method of claim 22, wherein, The removal pressure of part of the inert solvent in the liquid phase material B obtained in step (2) is -0.7--0.4 barg.

24. The method of claim 1, wherein, The mass percentage content of the inert solvent in the crude isocyanate product in step (3) is 10-15%.

25. The method of claim 1, wherein, The removal temperature of the remaining part of the inert solvent and the pure isocyanate in the crude isocyanate product obtained in step (3) is 150-300 ℃.

26. The method of claim 25, wherein, The removal temperature of the remaining part of the inert solvent and the pure isocyanate in the crude isocyanate product obtained in step (3) is 150-250 ℃.

27. The method of claim 1, wherein, The removal pressure of the remaining part of the inert solvent and the pure isocyanate in the crude isocyanate product obtained in step (3) is -1-1 barg.

28. The method of claim 27, wherein, The removal pressure of the remaining part of the inert solvent and the pure isocyanate in the crude isocyanate product obtained in step (3) is -1--0.5 barg.

29. The method of claim 1, wherein, The removal temperature of the inert solvent in the liquid phase material C obtained in step (4) is 100-220 ℃.

30. The method of claim 29, wherein, The removal temperature of the inert solvent in the liquid phase material C obtained in step (4) is 130-200 ℃.

31. The method of claim 30, wherein, The removal temperature of the inert solvent in the liquid phase material C obtained in step (4) is 150-180 ℃.

32. The method of claim 1, wherein, The removal pressure of the inert solvent in the liquid phase material C obtained in step (4) is -1-0 barg.

33. The method of claim 32, wherein the method is performed in a single step. The removal pressure of the inert solvent in the liquid phase material C obtained in step (4) is -0.9--0.2 barg.

34. The method of claim 33, wherein the method further comprises, The removal pressure of the inert solvent in the liquid phase material C obtained in step (4) is -0.7--0.4 barg.

35. The method of claim 1, wherein, The preparation method comprises the following steps: (1) carrying out a cold phosgenation reaction of the amine substance, the phosgene solution and the inert solvent at 60-140℃ and 1-30 barg for 1-90 min, and then carrying out a hot phosgenation reaction at 110-160℃ and 2-20 barg for 1-8 h to obtain a liquid-phase material A containing isocyanate; (2) removing hydrogen chloride and phosgene in the liquid-phase material A obtained in step (1) at 100-180℃ and -0.2-3 barg to obtain a liquid-phase material B; and in steps (1) and (2), the residence time of the phosgene-containing material at 120-180℃ is 0.5-12 h; (3) removing part of the inert solvent in the liquid-phase material B obtained in step (2) at 100-220℃ and -1-0 barg to obtain an isocyanate crude product with a mass percentage of inert solvent of 5-30%; (4) removing the remaining part of the inert solvent and pure isocyanate in the isocyanate crude product obtained in step (3) at 150-300℃ and -1-1 barg, the light-colored polymerized isocyanate; condensing the removed inert solvent and pure isocyanate to obtain a liquid-phase material C; (5) removing the inert solvent in the liquid-phase material C obtained in step (4) at 100-220℃ and -1-0 barg to obtain a light-colored pure isocyanate.

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