A method for treating phenyl isocyanate by-product and application thereof

Abstract

The present application relates to a kind of phenyl isocyanate byproduct processing method and its application, the method includes the following steps: S1: the phenyl isocyanate byproduct is carried out first separation processing, obtains the diisocyanate and polyisocyanate mixture of diphenylmethane series and phenyl isocyanate mixture;S2: the phenyl isocyanate mixture is carried out second separation processing, obtains phenyl isocyanate concentrated solution and solvent;And S3: the phenyl isocyanate concentrated solution is reacted with hydrochloric acid in reaction kettle, obtains aniline hydrochloride salt.The phenyl isocyanate byproduct processing method of one embodiment of the present application, the byproduct containing phenyl isocyanate generated in MDI production process can be efficiently treated, the separated phenyl isocyanate can be converted into aniline hydrochloride salt by reaction, and aniline hydrochloride salt is reused to MDI production process, both reduce the influence of phenyl isocyanate on the above production process and save production cost.

Description

TECHNICAL FIELD

[0001] The present application relates to diisocyanates and polyisocyanates of the diphenylmethane series, and in particular to the treatment of phenyl isocyanate by-products produced in the production process of diisocyanates and polyisocyanates of the diphenylmethane series. BACKGROUND

[0002] Diisocyanates and polyisocyanates of the diphenylmethane series (MDI) are one of the important raw materials for the preparation of polyurethanes. The main production method of MDI currently includes the following steps: condensation reaction of aniline and formaldehyde under the action of an acid catalyst to generate di- and polyamines of the diphenylmethane series (MDA); phosgenation reaction of MDA with liquid phosgene in an inert solvent to obtain a reaction liquid; and removal of phosgene, hydrogen chloride stripping, solvent removal, and purification and separation of the reaction liquid to obtain the corresponding MDI product.

[0003] Research has found that due to the presence of a small amount of phenyl isocyanate (PI) precursor impurities (formanilide, acetanilide, methylformanilide, methylacetanilide, aniline, etc.) in the MDA product, PI is inevitably generated after phosgenation and hydrogen chloride stripping. Most of the PI enters the circulating solvent and, after mixing with the raw material amine, generates urea or urea derivatives, reducing the product yield. At the same time, since urea is insoluble in the solvent, it will precipitate in the reaction device and adhere to the device wall, causing fouling, which will affect the heat transfer effect of the reaction system equipment and exacerbate the plugging of the reaction device, thereby affecting the long-term operation of the production system. In addition, a small amount of PI will enter the crude MDI and, during the purification and separation process of the product, will enter the vacuum unit (combination of vacuum pumps), since the system cannot be absolutely sealed, a small amount of moisture will inevitably enter the vacuum unit, PI will react with water to generate urea and accumulate in the unit, ultimately causing the unit to be blocked and seized, affecting the long-term operation of the solvent removal device, etc. At the same time, PI is a highly toxic substance, if not treated, its accumulation in the system will pose some potential toxicological problems.

[0004] The existing technology has two main methods for reducing the content of PI in the production system, one is to control the content of PI precursor impurities in MDA to reduce the amount of PI ultimately generated, and the other is to use the reaction characteristics of PI to convert it and then treat it.

[0005] However, these methods have obvious shortcomings. For the method of controlling the PI precursor impurities in the DAM, new catalyst systems need to be added in the MDA production process, new impurities are introduced, and the existing process conditions need to be changed, which inevitably brings other adverse effects and increases the cost. For the method of converting PI by using its reaction characteristics, not only does it increase the circulating solvent amount of the production system and the load of the new processing process, but also new impurities (catalysts or compounds containing active hydrogen) need to be introduced into the circulating solvent of the photochemical reaction device. These impurities will also accumulate in the system if they are not removed, and they will also react with MDI or catalyze the reaction of MDI. If not handled properly, they may have a greater impact on the system than PI. SUMMARY

[0006] To overcome at least one of the above-mentioned deficiencies of the prior art, in a first aspect, an embodiment of the present application provides a method for treating phenyl isocyanate by-products, wherein the phenyl isocyanate by-products are produced in a production process of diisocyanates and polyisocyanates of a diphenylmethane series, and the phenyl isocyanate by-products, diisocyanates and polyisocyanates of the diphenylmethane series, phenyl isocyanate and a solvent, the method comprising the following steps:

[0007] S1: performing a first separation treatment on the phenyl isocyanate by-products to obtain a mixture of diisocyanates and polyisocyanates of the diphenylmethane series and a mixture of phenyl isocyanate;

[0008] S2: performing a second separation treatment on the mixture of phenyl isocyanate to obtain a concentrated solution of phenyl isocyanate and the solvent; and

[0009] S3: performing a reaction between the concentrated solution of phenyl isocyanate and hydrochloric acid in a reaction kettle to obtain aniline hydrochloride.

[0010] In a second aspect, an embodiment of the present application provides a device for treating phenyl isocyanate by-products, comprising:

[0011] an evaporator for performing a first separation treatment on the phenyl isocyanate by-products to obtain a mixture of diisocyanates and polyisocyanates of the diphenylmethane series and a mixture of phenyl isocyanate;

[0012] a rectifying column for performing a second separation treatment on the mixture of phenyl isocyanate to obtain a concentrated solution of phenyl isocyanate and the solvent;

[0013] a mixer for mixing the concentrated solution of phenyl isocyanate and hydrochloric acid; and

[0014] a reaction kettle for performing a reaction between the concentrated solution of phenyl isocyanate and the hydrochloric acid.

[0015] In a third aspect, one embodiment of the present application provides a production process of diisocyanates and polyisocyanates of diphenylmethane series, comprising the following steps:

[0016] carrying out a phosgenation reaction of the diamines and polyamines of diphenylmethane series with phosgene in a solvent to obtain a first mixture;

[0017] carrying out a phosgene removal treatment on the first mixture to obtain a second mixture;

[0018] carrying out a stripping treatment on the second mixture by means of HCl gas to obtain a third mixture; and

[0019] carrying out a solvent removal treatment on the third mixture to obtain a crude product of diisocyanates and polyisocyanates of diphenylmethane series and a gas phase condensate;

[0020] wherein the gas phase condensate comprises a phenyl isocyanate by-product, and the phenyl isocyanate by-product is treated by means of the treatment method described above.

[0021] The treatment method of the phenyl isocyanate by-product of one embodiment of the present application can efficiently treat the phenyl isocyanate-containing by-product generated in the production process of diisocyanates and polyisocyanates of diphenylmethane series, and can convert the separated phenyl isocyanate into aniline hydrochloride through a reaction, and reuse the aniline hydrochloride to the production process of diisocyanates and polyisocyanates of diphenylmethane series, thereby reducing the influence of phenyl isocyanate on the production process and saving production costs. BRIEF DESCRIPTION OF DRAWINGS

[0022] The accompanying drawings are included to provide a further understanding of the present application, and are incorporated in and constitute a part of this specification. It will be appreciated that the drawings are only for

[0023] Figure 1 FIG. 1 is a structural schematic diagram of a phenyl isocyanate by-product treatment device according to one embodiment of the present application. DETAILED DESCRIPTION

[0024] The typical embodiments embodying the features and advantages of the present application will be described in detail hereinafter with reference to the accompanying drawings. It should be understood that the present application can have various modifications on different embodiments, and all of which do not deviate from the scope of the present application, and the description herein is essentially used for illustration, but not to limit the present application. Herein, all the pressures involved herein are absolute pressures.

[0025] REFERENCE Figure 1As shown, one embodiment of the present application provides a method for treating phenyl isocyanate by-products, wherein the phenyl isocyanate by-products are produced in a production process of diisocyanates and polyisocyanates (MDI) in a diphenylmethane series, the phenyl isocyanate by-products including MDI, phenyl isocyanate (PI) and solvent, the method comprising the following steps:

[0026] S1: performing a first separation treatment on the phenyl isocyanate by-products to obtain an MDI mixture and a phenyl isocyanate mixture;

[0027] S2: performing a second separation treatment on the phenyl isocyanate mixture to obtain a phenyl isocyanate concentrate and a solvent; and

[0028] S3: reacting the phenyl isocyanate concentrate with hydrochloric acid in a reaction kettle 50 to obtain aniline hydrochloride.

[0029] In one embodiment, the reaction temperature T of the reaction of the phenyl isocyanate concentrate with hydrochloric acid can be 30-60℃, and the stirring power density w of the reaction kettle 50 can be 2-10 kW / m 3 ; the stirring power density refers to the power used by the stirrer per unit volume of solution.

[0030] In one embodiment, the reaction of phenyl isocyanate with hydrochloric acid is as follows:

[0031] Main reaction:

[0032]

[0033] Side reaction:

[0034]

[0035] By adjusting the reaction temperature, the ratio of reactants, the reaction time, the residence time and other parameters, more than 95wt% of PI can be converted into aniline hydrochloride, thereby reducing the PI content in the product.

[0036] In one embodiment, step S3 comprises: mixing the phenyl isocyanate concentrate with hydrochloric acid through a mixer 40 to obtain a reaction mixture; and

[0037] reacting the reaction mixture in the reaction kettle 50;

[0038] Preferably, the residence time t1 of the reaction mixture in the mixer 40 is 2-5 seconds, further preferably 3-5 seconds, and more preferably 3-4 seconds.

[0039] In one embodiment, the mixer 40 can be a static mixer or a dynamic mixer, and is preferably a static mixer.

[0040] In an embodiment, the reaction temperature T of the reaction of the phenyl isocyanate concentrate with hydrochloric acid is preferably 30-60°C, further preferably 40-50°C, for example 35°C, 45°C.

[0041] In an embodiment, the reaction time t2 (or residence time of the reactor) of the reaction of the phenyl isocyanate concentrate with hydrochloric acid can be 10-35 minutes, preferably 10-30 minutes, further preferably 15-25 minutes, still further preferably 15-20 minutes.

[0042] In an embodiment, the ratio of the mass (or mass flow) m1 of hydrogen chloride in the hydrochloric acid to the mass (or mass flow) m2 of phenyl isocyanate in the phenyl isocyanate concentrate is preferably m1 :m2 = (2-5):1, further preferably (3-5):1, still further preferably (3-4):1, still further preferably (3.5-4):1.

[0043] In an embodiment, the stirring power density w of the reactor 50 is preferably 2-10 kW / m 3 , further preferably 4-10 kW / m 3 , still further preferably 4-6 kW / m 3 .

[0044] In an embodiment, the reactor 50 can use an external circulation cooler to remove heat.

[0045] In an embodiment, the parameters w, t1, t2, T, m1, m2 satisfy the following relationship:

[0046]

[0047] wherein the unit of w is kW / m 3 , the unit of t1 is second, the unit of t2 is minute, the unit of T is °C, and the units of m1 and m2 are kg / h. The above formula represents only the numerical relationship between the above parameters, and there is no corresponding relationship between the units on both sides of the inequality. The parameters such as w satisfying the above relationship can improve the conversion rate of phenyl isocyanate reaction, and can increase the content of aniline hydrochloride in the product and reduce the content of PI.

[0048] In an embodiment, the mass content of PI in the phenyl isocyanate by-product is 500-5000 ppm, for example 1000 ppm, 2000 ppm, 3000 ppm, 4000 ppm.

[0049] In an embodiment, the mass content of PI in the product of the reactor 50 is less than or equal to 300 ppm, preferably less than or equal to 200 ppm, further preferably less than or equal to 50 ppm, still further preferably less than or equal to 1 ppm.

[0050] In one embodiment, the mass content of by-product 1,3-diphenylurea in the reactor 50 product is less than or equal to 0.2%, preferably less than or equal to 0.1%, further preferably 0.01-0.08%, still further preferably 0.01-0.05%, for example 0.02%, 0.03%, 0.04%, 0.06%, 0.07%, 0.09%.

[0051] In one embodiment, the mass concentration of the phenyl isocyanate concentrate is 80-98%, preferably 90-95%, for example 85%, 93%.

[0052] In one embodiment, the mass concentration of the hydrochloric acid can be 10-35%, preferably 30-35%.

[0053] In one embodiment, the solvent in the phenyl isocyanate by-product is the solvent used in the MDI production process, including one or more of benzene, toluene, chlorobenzene, diethyl carbonate, preferably chlorobenzene.

[0054] In one embodiment, the first separation treatment is carried out in an evaporator 10, which can be a climbing film evaporator or a falling film evaporator, preferably a climbing film evaporator; during the first separation treatment, the pressure of the climbing film evaporator can be 30-60 kPa, preferably 40-50 kPa; the temperature can be 90-130°C, preferably 100-120°C, for example 105°C, 110°C, 115°C.

[0055] In one embodiment, after the first separation treatment, the liquid material in the evaporator 10 is an MDI mixture, and the gaseous material is a gaseous phenyl isocyanate mixture. The MDI mixture can be sent to the MDI production process for reuse.

[0056] In one embodiment, the second separation treatment is carried out in a rectifying column 20, and the phenyl isocyanate concentrate in the column bottom and the gaseous solvent in the column top are obtained after the second separation treatment. The gaseous solvent can be partially refluxed after being condensed by the first condenser 21, and the remaining part is sent to the refined solvent tank of the production system.

[0057] In one embodiment, the rectifying column 20 is a packed column, and the theoretical plate number of the packing can be 15-35, preferably 20-30; the reflux ratio of the rectifying column 20 can be 0.2-0.5, preferably 0.3-0.4.

[0058] In one embodiment, the overhead pressure of the rectification column 20 can be 30-50 kPa, preferably 35-40 kPa, during the second separation process; the overhead temperature can be 85-115°C, for example 90°C, 100°C, 110°C; and the column bottom temperature can be 110-140°C, preferably 120-130°C.

[0059] In one embodiment, a reboiler 22 is provided outside the column bottom of the rectification column 20, and the gas phase fraction of the outlet of the reboiler 22 can be 10-20%, preferably 12-16%.

[0060] In one embodiment, a second condenser 30 is provided outside the column bottom of the rectification column 20, and the temperature of the second condenser 30 can be 10-50°C, preferably 30-40°C.

[0061] In one embodiment, the phenyl isocyanate concentrate from the column bottom can be cooled before being mixed with hydrochloric acid; further, the phenyl isocyanate concentrate can be cooled to 0-50°C, preferably 10-30°C, for example 15°C, 20°C, 25°C.

[0062] In one embodiment, the aniline hydrochloride obtained from the reaction can be used as a raw material for the production of MDI; further, the aniline hydrochloride is an intermediate product for the production of MDA, and thus the aniline hydrochloride obtained from the reaction can be used as a raw material for the production of MDA, thereby improving the yield and economic benefits of the product.

[0063] In one embodiment, the mixture of aniline hydrochloride and hydrochloric acid in the reaction kettle 50 can be sent to the condensation reaction step.

[0064] Referring to Figure 1 An embodiment of the present application provides a device for processing phenyl isocyanate by-products, which can be used to implement the above method, and the device comprises:

[0065] An evaporator 10 for performing first separation on the phenyl isocyanate by-products to obtain a MDI mixture and a phenyl isocyanate mixture;

[0066] A rectification column 20 for performing second separation on the phenyl isocyanate mixture to obtain a phenyl isocyanate concentrate and a solvent;

[0067] A mixer 40 for mixing the phenyl isocyanate concentrate with hydrochloric acid; and

[0068] A reaction kettle 50 for performing a reaction between the phenyl isocyanate concentrate and hydrochloric acid.

[0069] In one embodiment, the device further comprises a first condenser 21 connected to the overhead of the rectification column 20, for condensing the gaseous solvent discharged from the overhead.

[0070] In one embodiment, the processing device further comprises a second condenser 30, which is arranged between the column still of the rectifying column 20 and the mixer 40, and is used to cool the phenyl isocyanate concentrate discharged from the column still of the rectifying column 20.

[0071] In one embodiment, the processing device further comprises a reboiler 22 and a pump 23, the reboiler 22 is connected to the column still of the rectifying column 20 and the pump 23 respectively, and the pump 23 is further connected to the mixer 40. Under the action of the pump 23, part of the material discharged from the column still is circulated back to the column still through the reboiler 22, and the other part enters the mixer 40.

[0072] In one embodiment, the reaction kettle 50 can be a vertical reaction kettle configured with stirring components.

[0073] In one embodiment, the working modes of the components in the processing device are applicable to the descriptions of the aforementioned processing method part.

[0074] One embodiment of the present application provides an MDI production process, which comprises the following steps:

[0075] carrying out a phosgenation reaction of MDA and phosgene in a solvent to obtain a first mixture;

[0076] carrying out a phosgene removal treatment on the first mixture to obtain a second mixture;

[0077] carrying out a stripping treatment on the second mixture by using HCl gas to obtain a third mixture; and

[0078] carrying out a solvent removal treatment on the third mixture to obtain an MDI crude product and a gas phase condensate;

[0079] The gas phase condensate comprises a phenyl isocyanate by-product, and the gas phase condensate can be treated by using the aforementioned processing method.

[0080] In one embodiment, the solvent removal treatment comprises:

[0081] carrying out a first solvent removal treatment on the third mixture to obtain a fourth mixture; and

[0082] carrying out a second solvent removal treatment on the fourth mixture to obtain the MDI crude product and the gas phase condensate.

[0083] In one embodiment, the first or second solvent removal treatment can be carried out by using a desolventizing column, and the desolventizing column can be a rectifying column.

[0084] In one embodiment, the second solvent removal treatment can be carried out by using a nitrogen stripping column or a solvent removal column, and the gas phase condensate is a condensate of the gas at the top of the stripping column or the solvent removal column.

[0085] In one embodiment, the solvent obtained by the solvent removal treatment can be collected in a refined solvent tank and reused in the production system as circulating solvent.

[0086] In one embodiment, the PI mass content in the circulating solvent is 30-100 ppm, and the PI mass content in the MDI crude product is 5-20 ppm.

[0087] In one embodiment, the MDI mixture separated in step S1 can be mixed with the first mixture of step (1) and reused in the production process.

[0088] One embodiment of the present application provides an MDI production system which can be used to implement the above-mentioned MDI production process, comprising a phosgene reaction device, a phosgene removal device, a stripping treatment device and a solvent removal device; wherein the phosgene reaction device is used to perform the phosgenation reaction of MDA and phosgene to obtain a first mixture; the phosgene removal device is used to perform the phosgene removal treatment of the first mixture to obtain a second mixture; the stripping treatment device is used to perform the stripping treatment of the second mixture by HCl gas to obtain a third mixture; and the solvent removal device is used to perform the solvent removal treatment of the third mixture.

[0089] In one embodiment, the solvent removal device comprises a first solvent removal column for performing a first solvent removal treatment and a second solvent removal column for performing a second solvent removal treatment; and the first and second solvent removal columns can both be rectification columns.

[0090] In one embodiment, the MDI production system comprises a refined solvent tank which can be connected to the solvent removal device and through which the solvent discharged from the solvent removal device can be introduced into the refined solvent tank.

[0091] In one embodiment, the MDI production system comprises a refined separation device which is used to perform the refined treatment of the MDI crude product.

[0092] In one embodiment, the MDI production system comprises a vacuum unit which can comprise a plurality of vacuum pumps and is used to adjust the pressure of the system.

[0093] The inventors find that there is PI-rich liquid (or PI-rich liquid stream) in the production system by sampling and evaluating each liquid stream in the MDI production process. The PI-rich liquid is the gas phase condensate liquid as described above. The main components of the PI-rich liquid are solvent, MDI and PI. The PI concentration in the PI-rich liquid is more than 10 times of the PI concentration in the circulating solvent. The flow of the PI-rich liquid is small. The PI-rich liquid contains a high value of MDI. The existing process circulates the PI-rich liquid back to the phosgene removal device, so that a large amount of PI in the liquid stream circulates in the production system (a small amount of PI is carried away by the crude MDI), and thus PI accumulates in the system, which eventually leads to an increase of the PI content in the circulating solvent and the crude MDI, and further affects the long-period operation of the system and the product yield.

[0094] In an embodiment of the present application, the PI-rich liquid (or phenyl isocyanate by-product) is separately treated and is not circulated back to the production system. In the embodiment, the MDI, solvent and PI in the PI-rich liquid are separated. The separated MDI is circulated back to the production system. The solvent is fed into a refined solvent tank of the production system. The phenyl isocyanate concentrated liquid is mixed with hydrochloric acid to obtain aniline hydrochloride. The aniline hydrochloride is circulated back to the preparation process of MDA.

[0095] In an embodiment of the present application, the PI-rich liquid (or phenyl isocyanate by-product) is treated, which reduces the reduction rate of the heat transfer coefficient in the phosgenation device, reduces the plugging frequency of the vacuum unit, and prolongs the operation period of the production system. In addition, the PI is converted into aniline hydrochloride through a simple reaction, and then the aniline hydrochloride is used as a raw material for the production of MDA, which realizes the recycling of materials and increases the benefit. In addition, the method does not increase the energy consumption compared with the existing process, and saves the operation cost.

[0096] The treatment method of the phenyl isocyanate by-product in an embodiment of the present application can effectively reduce the PI content in the circulating solvent and the crude MDI in the MDI production process, prolong the operation period of the production system, and realize the reuse of PI.

[0097] The treatment method of the phenyl isocyanate by-product in an embodiment of the present application has simple process flow and operation, the components of the corresponding treatment device can be existing components, the automatic operation can be completely realized, and the method does not have adverse effects on the process of MDI.

[0098] The PI mass content in the circulating solvent after the treatment method is 30-100 ppm, and the PI mass content in the MDI crude product is 5-20 ppm, which reduces the plugging problem of the PI to the photochemical reaction device and the vacuum unit and the influence on the heat exchange effect of the reaction device; at the same time, by converting the by-product PI into aniline hydrochloride and using it as a raw material for the production of MDI, the product yield is improved, and additional economic benefits are increased.

[0099] The treatment method of the phenyl isocyanate by-product according to one embodiment of the present application will be further described below in combination with specific examples. The PI mass content herein is directly analyzed and measured by gas chromatography, and the solvent used for testing is dichloromethane; the mass content of 1,3-diphenyl urea is measured by liquid chromatography with methanol as a dispersant.

[0100] Example 1

[0101] (1) Diphenylmethane series diamines and polyamines (MDA) are mixed with chlorobenzene to obtain a mixed solution with a MDA concentration of 30 w%; then, the mixed solution with a mass ratio of 1:4 is reacted with liquid phosgene under the conditions of 3 barg and 100°C to obtain a first mixture.

[0102] (2) The first mixture is dephosgenated at 0.1 MPa and 150°C to obtain a second mixture.

[0103] (3) The second mixture is treated by hydrogen chloride stripping at 170°C to obtain a third mixture; wherein the stripping mass ratio is 0.05, and the residence time is 5 min.

[0104] (4) The third mixture is treated by dechlorobenzene to obtain a fourth mixture; the fourth mixture contains 3.1 wt% of chlorobenzene.

[0105] (5) The fourth mixture is sent to a nitrogen stripping tower to remove the solvent to obtain an MDI crude product with a chlorobenzene mass content of 600 ppm and a top gas phase condensate; wherein the PI mass content in the top gas phase condensate (phenyl isocyanate by-product) is 3000 ppm.

[0106] (6) The top gas phase condensate is sent to a climbing film evaporator with an operating pressure of 40 kPa and a temperature of 115°C to obtain a liquid MDI mixture and a gaseous phenyl isocyanate mixture; the MDI mixture is mixed with the first mixture of step (1).

[0107] (7) The gaseous phenyl isocyanate mixture is sent into a rectifying tower to separate a phenyl isocyanate concentrated solution at the tower bottom and gaseous chlorobenzene at the tower top; the gaseous chlorobenzene is condensed at 35℃ and then sent into a refined solvent tank; wherein the rectifying tower has 25 theoretical plates, a reflux ratio of 0.3, a tower top pressure of 35 kPa, and a tower bottom temperature of 130℃.

[0108] (8) The phenyl isocyanate concentrated solution with a PI concentration of 90wt% is mixed with hydrochloric acid (concentration of 32wt%) as a byproduct of the photochemical reaction in a static mixer to obtain a reaction mixture; wherein the residence time of the reaction mixture in the static mixer is 3 seconds, and the mass flow ratio of HCl in the hydrochloric acid to PI in the phenyl isocyanate concentrated solution is 3.5:1.

[0109] (9) The reaction mixture is sent into a reaction kettle, which has a stirring power density of 5kW / m 3 , a temperature of 40℃, and a residence time of the mixture in the reaction kettle of 20min.

[0110] The PI mass content in the liquid material at the outlet of the reaction kettle is measured to be <1ppm, and the mass content of the byproduct 1,3-diphenyl urea is 0.02%.

[0111] Example 1-1

[0112] This example uses the same raw materials and process steps as Example 1 to produce MDI and treat the phenyl isocyanate byproduct, with the only difference being that the mass flow ratio of HCl in the hydrochloric acid to PI in the phenyl isocyanate concentrated solution in step (8) is 1:1.

[0113] The PI mass content in the liquid material at the outlet of the reaction kettle is measured to be <1ppm, and the mass content of the byproduct 1,3-diphenyl urea is 0.2%.

[0114] Example 1-2

[0115] This example uses the same raw materials and process steps as Example 1 to produce MDI and treat the phenyl isocyanate byproduct, with the only difference being that the mass flow ratio of HCl in the hydrochloric acid to PI in the phenyl isocyanate concentrated solution in step (8) is 2:1.

[0116] The PI mass content in the liquid material at the outlet of the reaction kettle is measured to be <1ppm, and the mass content of the byproduct 1,3-diphenyl urea is 0.06%.

[0117] Example 1-3

[0118] The present example uses the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate byproduct, with the exception that the ratio of the mass flow rate of HCl in the hydrochloric acid to the mass flow rate of PI in the phenyl isocyanate concentrate in step (8) is 4:1.

[0119] The mass content of PI in the liquid material at the outlet of the reactor was measured to be <1 ppm, and the mass content of the byproduct 1,3-diphenylurea was 0.021%.

[0120] Example 1-4

[0121] The present example uses the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate byproduct, with the exception that the ratio of the mass flow rate of HCl in the hydrochloric acid to the mass flow rate of PI in the phenyl isocyanate concentrate in step (8) is 5:1.

[0122] The mass content of PI in the liquid material at the outlet of the reactor was measured to be <1 ppm, and the mass content of the byproduct 1,3-diphenylurea was 0.03%.

[0123] Example 2

[0124] The present example uses the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate byproduct, with the exception that the residence time of the reaction mixture in the static mixer in step (8) is 1 second.

[0125] The mass content of PI in the liquid material at the outlet of the reactor was measured to be 300 ppm, and the mass content of the byproduct 1,3-diphenylurea was 0.15%.

[0126] Example 2-1

[0127] The present example uses the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate byproduct, with the exception that the residence time of the reaction mixture in the static mixer in step (8) is 2 seconds.

[0128] The mass content of PI in the liquid material at the outlet of the reactor was measured to be 50 ppm, and the mass content of the byproduct 1,3-diphenylurea was 0.08%.

[0129] Example 2-2

[0130] The present example uses the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate byproduct, with the exception that the residence time of the reaction mixture in the static mixer in step (8) is 4 seconds.

[0131] The PI mass content in the liquid material at the outlet of the reactor was measured to be <1 ppm and the mass content of the by-product 1,3-diphenylurea was 0.019%.

[0132] Example 2-3

[0133] This example uses the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate by-product, with the exception that the residence time of the reaction mixture in the static mixer in step (8) is 5 seconds.

[0134] The PI mass content in the liquid material at the outlet of the reactor was measured to be <1 ppm and the mass content of the by-product 1,3-diphenylurea was 0.025%.

[0135] Example 2-4

[0136] This example uses the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate by-product, with the exception that the residence time of the reaction mixture in the static mixer in step (8) is 6 seconds.

[0137] The PI mass content in the liquid material at the outlet of the reactor was measured to be <1 ppm and the mass content of the by-product 1,3-diphenylurea was 0.03%.

[0138] Example 3

[0139] This example uses the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate by-product, with the exception that the temperature in step (9) is 70°C.

[0140] The PI mass content in the liquid material at the outlet of the reactor was measured to be <1 ppm and the mass content of the by-product 1,3-diphenylurea was 0.25%.

[0141] Example 3-1

[0142] This example uses the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate by-product, with the exception that the temperature in step (9) is 30°C.

[0143] The PI mass content in the liquid material at the outlet of the reactor was measured to be 200 ppm and the mass content of the by-product 1,3-diphenylurea was 0.03%.

[0144] Example 3-2

[0145] This example uses the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate by-product, with the exception that the temperature in step (9) is 50°C.

[0146] The PI mass content in the liquid material at the outlet of the reactor was measured to be <1 ppm, and the mass content of the by-product 1,3-diphenylurea was 0.025%.

[0147] Example 3-3

[0148] This example used the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate by-product, except that the temperature in step (9) was 60°C.

[0149] The PI mass content in the liquid material at the outlet of the reactor was measured to be <1 ppm, and the mass content of the by-product 1,3-diphenylurea was 0.025%.

[0150] Example 4

[0151] This example used the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate by-product, except that the stirring power density of the reactor in step (9) was 1 kW / m 3 .

[0152] The PI mass content in the liquid material at the outlet of the reactor was measured to be 800 ppm, and the mass content of the by-product 1,3-diphenylurea was 0.2%.

[0153] Example 4-1

[0154] This example used the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate by-product, except that the stirring power density of the reactor in step (9) was 2 kW / m 3 .

[0155] The PI mass content in the liquid material at the outlet of the reactor was measured to be 200 ppm, and the mass content of the by-product 1,3-diphenylurea was 0.10%.

[0156] Example 4-2

[0157] This example used the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate by-product, except that the stirring power density of the reactor in step (9) was 4 kW / m 3 .

[0158] The PI mass content in the liquid material at the outlet of the reactor was measured to be <1 ppm, and the mass content of the by-product 1,3-diphenylurea was 0.025%.

[0159] Example 4-3

[0160] This example uses the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate byproduct, with the exception that the agitator power density in the reactor of step (9) is 6 kW / m 3 .

[0161] The PI mass content in the liquid material at the outlet of the reactor was measured to be <1 ppm, and the mass content of the byproduct 1,3-diphenylurea was 0.023%.

[0162] Example 4-4

[0163] This example uses the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate byproduct, with the exception that the agitator power density in the reactor of step (9) is 10 kW / m 3 .

[0164] The PI mass content in the liquid material at the outlet of the reactor was measured to be <1 ppm, and the mass content of the byproduct 1,3-diphenylurea was 0.04%.

[0165] Example 5

[0166] This example uses the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate byproduct, with the exception that the residence time of the mixture in the reactor of step (9) is 5 min.

[0167] The PI mass content in the liquid material at the outlet of the reactor was measured to be 2000 ppm, and the mass content of the byproduct 1,3-diphenylurea was 0.016%.

[0168] Example 5-1

[0169] This example uses the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate byproduct, with the exception that the residence time of the mixture in the reactor of step (9) is 10 min.

[0170] The PI mass content in the liquid material at the outlet of the reactor was measured to be 300 ppm, and the mass content of the byproduct 1,3-diphenylurea was 0.019%.

[0171] Example 5-2

[0172] This example uses the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate byproduct, with the exception that the residence time of the mixture in the reactor of step (9) is 15 min.

[0173] The mass content of PI in the liquid material at the outlet of the reactor is <1 ppm, and the mass content of the by-product 1,3-diphenyl urea is 0.019%.

[0174] Example 5-3

[0175] This example uses the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate by-product, with the only difference being that the residence time of the mixture in the reactor in step (9) is 25 min.

[0176] The mass content of PI in the liquid material at the outlet of the reactor is <1 ppm, and the mass content of the by-product 1,3-diphenyl urea is 0.03%.

[0177] Example 5-4

[0178] This example uses the same raw materials and process steps as Example 1 to produce MDI and to treat the phenyl isocyanate by-product, with the only difference being that the residence time of the mixture in the reactor in step (9) is 35 min.

[0179] The mass content of PI in the liquid material at the outlet of the reactor is <1 ppm, and the mass content of the by-product 1,3-diphenyl urea is 0.05%.

[0180] Examples 1 to 1-4 differ in that the mass ratio (m1:m2) of the mass flow rate of HCl in step (8) to the mass content of PI in the phenyl isocyanate concentrate is different. According to the test results of the liquid material at the outlet of the reactor, the ratio of m1:m2 will affect the content of 1,3-diphenyl urea in the outlet material. According to the above test results, the ratio of m1:m2 is preferably (2-5):1, further preferably (3-5):1, more preferably (3-4):1, and more preferably (3.5-4):1.

[0181] Examples 1, 2 to 2-4 differ in that the residence time t1 of the reaction mixture in the static mixer in step (8) is different. According to the test results of the liquid material at the outlet of the reactor, t1 will affect the content of PI and the content of 1,3-diphenyl urea in the outlet material. According to the above test results, t1 is preferably 2-5 seconds, further preferably 3-5 seconds, and more preferably 3-4 seconds.

[0182] Examples 1, 3 to 3-3 differ in that the reaction temperature T in step (9) is different. According to the test results of the liquid material at the outlet of the reactor, the reaction temperature T will affect the content of PI and the content of 1,3-diphenyl urea in the outlet material. According to the above test results, the reaction temperature T is preferably 30-60°C, and further preferably 40-50°C.

[0183] The difference between Examples 1, 4 to 4-4 is that the stirring power density w of the reactor in step (9) is different. According to the test results of the liquid material at the outlet of the reactor, the stirring power density w will affect the PI content and 1,3-diphenylurea content in the outlet material. According to the test results, the w is preferably 2-10 kW / m 3 , further preferably 4-10 kW / m 3 , more preferably 4-6 kW / m 3 .

[0184] The difference between Examples 1, 5 to 5-4 is that the residence time (or reaction time t2) of the mixture in the reactor in step (9) is different. According to the test results of the liquid material at the outlet of the reactor, the reaction time t2 will affect the PI content and 1,3-diphenylurea content in the outlet material. According to the test results, the reaction time t2 can be 10-35 minutes, preferably 10-30 minutes, further preferably 15-25 minutes, more preferably 15-20 minutes.

[0185] Unless specifically defined, the terms used in the present application are understood to have the meanings commonly used by those skilled in the art.

[0186] The embodiments described in the present application are only for illustrative purposes, not to limit the protection scope of the present application, and those skilled in the art can make various other replacements, changes and improvements within the scope of the present application, therefore, the present application is not limited to the above embodiments, but is limited by the claims.

Claims

1. A method for the treatment of phenyl isocyanate by-products, wherein, The phenyl isocyanate by-product is generated in a production process of diisocyanates and polyisocyanates of a diphenylmethane series, including the diisocyanates and polyisocyanates of the diphenylmethane series, phenyl isocyanate and a solvent, and the treatment method comprises the following steps: S1: the phenyl isocyanate by-product is subjected to a first separation treatment to obtain a mixture of diisocyanates and polyisocyanates of a diphenylmethane series and a mixture of phenyl isocyanate; S2: the mixture of phenyl isocyanate is subjected to a second separation treatment to obtain a phenyl isocyanate concentrate and the solvent; and S3: the phenyl isocyanate concentrate is mixed with hydrochloric acid through a mixer to obtain a reaction mixture; and the reaction mixture is reacted in a reaction kettle to obtain aniline hydrochloride; The mass concentration of the phenyl isocyanate concentrated solution is 80-98%; the residence time t1 of the reaction mixture in the mixer is 3-5 seconds; the ratio of the mass m1 of hydrogen chloride in the hydrochloric acid to the mass m2 of phenyl isocyanate in the phenyl isocyanate concentrated solution is m1:m2=(2-4):1; the reaction temperature T of the reaction of the phenyl isocyanate concentrated solution with the hydrochloric acid is 40-60 DEG C, the reaction time t2 of the reaction of the phenyl isocyanate concentrated solution with the hydrochloric acid is 15-35 minutes, and the stirring power density w of the reactor is 4-10 kW / m 3 .

2. The treatment method of claim 1, wherein, The mixer is a static mixer or a dynamic mixer; and / or, The residence time t1 is 3-4 seconds.

3. The treatment method of claim 2, wherein, The reaction temperature T of the reaction of the phenyl isocyanate concentrate with the hydrochloric acid is 40-50°C; and / or, The stirring power density w of the reactor is 4-6 kW / m 3 ; and / or, m1:m2=(3-4):1; and / or, t2 is 15-25 minutes; and / or, The parameters w, t1, t2, T, m1, m2 satisfy the following relationship:

4. The treatment method of claim 1, wherein, The aniline hydrochloride is used as a raw material of the production process of diisocyanates and polyisocyanates of a diphenylmethane series; And / or, The mixture of diisocyanates and polyisocyanates of a diphenylmethane series is delivered to a flow of the production process of diisocyanates and polyisocyanates of a diphenylmethane series; and / or, The solvent includes one or more of benzene, toluene, chlorobenzene, diethyl carbonate; and / or, The mass content of phenyl isocyanate in the phenyl isocyanate by-product is 500-5000 ppm.

5. The treatment method of claim 1, wherein, The first separation treatment is performed in an evaporator; and / or, The second separation treatment is performed in a rectifying column; and / or, The mass concentration of the hydrochloric acid is 10-35%; and / or, The mass content of phenyl isocyanate in the product of the reaction kettle is less than or equal to 300 ppm; and / or, The mass content of 1,3-diphenylurea in the product of the reaction kettle is less than or equal to 0.2%.

6. The treatment method of claim 5, wherein, The evaporator is a climbing film evaporator or a falling film evaporator; in the first separation treatment process, the pressure of the climbing film evaporator is 30-60 kPa, and the temperature is 90-130°C; and / or, The rectifying column adopts a packed column, the reflux ratio is 0.2-0.5, the overhead pressure is 30-50 kPa, and the column bottom temperature is 110-140°C.

7. A production process of diisocyanates and polyisocyanates of a diphenylmethane series, comprising the following steps: Diphenylmethane series diamines and polyamines are subjected to a phosgenation reaction with phosgene in a solvent to obtain a first mixture; The first mixture is subjected to a phosgene removal treatment to obtain a second mixture; The second mixture is subjected to a stripping treatment with HCl gas to obtain a third mixture; and The third mixture is subjected to a solvent removal treatment to obtain a crude product of diisocyanates and polyisocyanates of a diphenylmethane series and a gas phase condensate. wherein, The gas phase condensate includes phenyl isocyanate by-product, and the gas phase condensate is treated by the treatment method in any one of claims 1 to 6.

8. The production process according to claim 7, wherein, The solvent removal treatment includes: performing a first solvent removal treatment on the third mixture to obtain a fourth mixture; and performing a second solvent removal treatment on the fourth mixture to obtain a crude product of a diphenyl methane series diisocyanate and polyisocyanate and a gas phase condensate; The second solvent removal treatment is performed by nitrogen stripping or a rectification column; and / or, The diphenyl methane series diisocyanate and polyisocyanate mixture is mixed with the first mixture.

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