Treatment method of phenyl isocyanate by-product and application of phenyl isocyanate by-product

Abstract

The invention relates to a phenyl isocyanate by-product treatment method and application thereof, the method comprises the following steps: S1, carrying out first separation treatment on a phenyl isocyanate by-product to obtain a diphenylmethane series diisocyanate and polyisocyanate mixture and a phenyl isocyanate mixture; s2, carrying out second separation treatment on the phenyl isocyanate mixture to obtain a phenyl isocyanate concentrated solution and a solvent; s3, the phenyl isocyanate concentrated solution and hydrochloric acid are subjected to a reaction in a reaction kettle, and aniline hydrochloride is obtained. According to the treatment method of the phenyl isocyanate by-product, the phenyl isocyanate-containing by-product generated in the MDI production process can be efficiently treated, the separated phenyl isocyanate can be converted into aniline hydrochloride through reaction, the aniline hydrochloride is reused in the MDI production process, the production efficiency is improved, and the production cost is reduced. Not only is the influence of phenyl isocyanate on the production process reduced, but also the production cost is saved.

Description

Technical Field

[0001] The invention relates to diphenylmethane series diisocyanates and polyisocyanates, and in particular to the treatment of phenyl isocyanate byproducts produced in the production process of diphenylmethane series diisocyanates and polyisocyanates. Background Art

[0002] Diisocyanates and polyisocyanates of the diphenylmethane series (MDI) are one of the important raw materials for preparing polyurethane. At present, the main production method of MDI includes the following steps: condensing aniline and formaldehyde in the presence of an acid catalyst to generate diamines and polyamines of the diphenylmethane series (MDA); phosgenating MDA with liquid phosgene in an inert solvent to obtain a reaction liquid; and removing phosgene, stripping hydrogen chloride, removing solvents and refining and separating the reaction liquid to obtain the corresponding MDI product.

[0003] The study found that since the MDA product contains a small amount of precursor impurities of phenyl isocyanate (PI) (formanilide, acetanilide, methylformanilide, methylacetanilide, aniline, etc.), PI will inevitably be generated after phosgenation reaction and hydrogen chloride stripping. Most of the PI enters the circulating solvent and mixes with the raw material amine to form urea or uret-like substances, which reduces 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 wall of the equipment to cause scaling. After scaling, it will affect the heat transfer effect of the reaction system equipment and aggravate the blockage 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 enter the vacuum unit (combination of vacuum pumps) during the refining and separation process of the product. Since the system cannot be absolutely sealed, it is inevitable that a small amount of water will enter the vacuum unit. PI will react with water to form urea and accumulate in the unit, eventually causing the unit to block and lock, affecting the long-term operation of the desolventizing device, etc. At the same time, PI is a highly toxic substance. If it is not treated, it will accumulate in the system and cause some potential toxicological problems.

[0004] There are two main methods for reducing the PI content in the production system in the prior art. One is to reduce the amount of PI finally generated by controlling the impurity content of the PI precursor in MDA; the other is to utilize the reaction characteristics of PI to convert its reaction and then process it.

[0005] However, these methods all have obvious disadvantages. For the method of controlling the PI precursor impurities in DAM, it is necessary to add a new catalyst system to the MDA production process, introduce new impurities, and change the existing process conditions, which will inevitably bring other adverse effects and increase costs. For the method of using the reaction characteristics of PI to transform it, not only does it make the production system have a large amount of circulating solvent and a high load of the new treatment process, but it also needs to introduce new impurities (catalysts or active hydrogen compounds) into the circulating solvent of the photochemical reaction device. If these impurities are not removed, they will also accumulate in the system. At the same time, they will also react with MDI or catalyze the MDI reaction. Improper treatment may have a greater impact on the system than PI. Summary of the invention

[0006] In order to overcome at least one defect of the above-mentioned prior art, in a first aspect, an embodiment of the present invention provides a method for treating phenyl isocyanate by-products, wherein the phenyl isocyanate by-products are produced in the production process of diisocyanates and polyisocyanates of the diphenylmethane series, including the diisocyanates and polyisocyanates of the diphenylmethane series, phenyl isocyanate and a solvent, and the treatment method comprises the following steps:

[0007] S1: subjecting the phenyl isocyanate by-product to a first separation treatment to obtain a diphenylmethane series diisocyanate and polyisocyanate mixture and a phenyl isocyanate mixture;

[0008] S2: subjecting the phenyl isocyanate mixture to a second separation treatment to obtain a phenyl isocyanate concentrate and the solvent; and

[0009] S3: reacting the phenyl isocyanate concentrate with hydrochloric acid in a reactor to obtain aniline hydrochloride.

[0010] In a second aspect, an embodiment of the present invention provides a device for treating phenyl isocyanate byproducts, comprising:

[0011] An evaporator is used to perform a first separation treatment on the phenyl isocyanate byproduct to obtain a diphenylmethane series diisocyanate and polyisocyanate mixture and a phenyl isocyanate mixture;

[0012] A distillation tower, used for performing a second separation treatment on the phenyl isocyanate mixture to obtain a phenyl isocyanate concentrate and a solvent;

[0013] A mixer for mixing the phenyl isocyanate concentrate with hydrochloric acid; and

[0014] A reaction kettle is used to carry out the reaction between the phenyl isocyanate concentrate and the hydrochloric acid.

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

[0016] Carrying out a phosgenation reaction between a diphenylmethane series diamine and a polyamine and phosgene in a solvent to obtain a first mixture;

[0017] removing phosgene from the first mixture to obtain a second mixture;

[0018] stripping the second mixture with HCl gas to obtain a third mixture; and

[0019] The third mixture is subjected to a treatment for removing the solvent to obtain crude diisocyanates and polyisocyanates of the diphenylmethane series and a gas phase condensate;

[0020] Wherein, the gas phase condensate includes phenyl isocyanate by-product, and the gas phase condensate is treated by the above-mentioned treatment method.

[0021] The method for treating phenyl isocyanate by-products according to one embodiment of the present invention can efficiently treat phenyl isocyanate-containing by-products produced in the production process of diphenylmethane series diisocyanates and polyisocyanates, and can convert the separated phenyl isocyanate into aniline hydrochloride through reaction, and the aniline hydrochloride can be recycled into the production process of diphenylmethane series diisocyanates and polyisocyanates, thereby reducing the influence of phenyl isocyanate on the above-mentioned production process and saving production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are only used to illustrate specific embodiments and are not to be considered as limiting the present invention.

[0023] Figure 1 The present invention is a schematic structural diagram of a device for treating phenyl isocyanate by-products according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] Typical embodiments that embody the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various variations in different embodiments without departing from the scope of the present invention, and the descriptions therein are essentially for the purpose of illustration rather than for limiting the present invention. All pressures referred to herein are absolute pressures.

[0025] Reference Figure 1As shown, one embodiment of the present invention provides a method for treating phenyl isocyanate byproducts, wherein the phenyl isocyanate byproducts are produced in the production process of diphenylmethane series diisocyanates and polyisocyanates (MDI), and the phenyl isocyanate byproducts include MDI, phenyl isocyanate (PI) and solvents. The treatment method includes the following steps:

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

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

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

[0029] In one embodiment, the reaction temperature T of the reaction of phenyl isocyanate concentrate and hydrochloric acid can be 30 to 60° C., and the stirring power density w of the reactor 50 can be 2 to 10 kW / m 3 ; 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 effects:

[0034]

[0035] By regulating parameters such as reaction temperature, reactant ratio, reaction time, residence time, etc., more than 95 wt% 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] The reaction mixture is reacted in a reaction vessel 50;

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

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

[0040] In one embodiment, the reaction temperature T of the reaction of the phenyl isocyanate concentrate with hydrochloric acid is preferably 30 to 60°C, more preferably 40 to 50°C, such as 35°C or 45°C.

[0041] In one embodiment, the reaction time t2 (or the reactor residence time) of the reaction of the phenyl isocyanate concentrate with hydrochloric acid can be 10 to 35 minutes, preferably 10 to 30 minutes, more preferably 15 to 25 minutes, and even more preferably 15 to 20 minutes.

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

[0043] In one embodiment, the stirring power density w of the reactor 50 is preferably 2 to 10 kW / m 3 , more preferably 4 to 10 kW / m 3 , and more preferably 4 to 6 kW / m 3 .

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

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

[0046]

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

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

[0049] In one 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, more preferably less than or equal to 50 ppm, and even more preferably less than or equal to 1 ppm.

[0050] In one embodiment, the mass content of the by-product 1,3-diphenylurea in the product of the reactor 50 is less than or equal to 0.2%, preferably less than or equal to 0.1%, more preferably 0.01-0.08%, and 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%, such as 85%, 93%.

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

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

[0054] In one embodiment, the first separation treatment is carried out in the evaporator 10, and the evaporator 10 can be a rising film evaporator or a falling film evaporator, preferably a rising film evaporator; during the first separation treatment, the pressure of the rising 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 process of the MDI production process for reuse.

[0056] In one embodiment, the second separation treatment is performed in the distillation tower 20, and the phenyl isocyanate concentrate in the tower bottom and the gas solvent at the top of the tower are obtained through the second separation treatment. The gas solvent can be partially refluxed after condensation in the first condenser 21, and the remaining part can be sent to the refined solvent tank of the production system.

[0057] In one embodiment, the distillation tower 20 is a packed tower, and the theoretical number of packing plates may be 15 to 35, preferably 20 to 30; the reflux ratio of the distillation tower 20 may be 0.2 to 0.5, preferably 0.3 to 0.4.

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

[0059] In one embodiment, a reboiler 22 is disposed outside the bottom of the distillation tower 20, and the gas phase fraction at the outlet of the reboiler 22 is 10-20%, preferably 12-16%.

[0060] In one embodiment, a second condenser 30 is disposed outside the bottom of the distillation tower 20, and the temperature of the second condenser 30 may be 10°C to 50°C, preferably 30 to 40°C.

[0061] In one embodiment, the phenyl isocyanate concentrated solution in the bottom of the tower can be cooled and then mixed with hydrochloric acid for reaction; further, the phenyl isocyanate concentrated solution 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 by the reaction can be used as a raw material for the MDI production process; further, aniline hydrochloride is an intermediate product for the production of MDA, so the aniline hydrochloride obtained by 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 may be sent to the condensation reaction step.

[0064] Reference Figure 1 As shown, one embodiment of the present invention provides a device for treating phenyl isocyanate byproducts, which can be used to implement the above method, and the device comprises:

[0065] An evaporator 10 is used to perform a first separation treatment on the phenyl isocyanate by-product to obtain an MDI mixture and a phenyl isocyanate mixture;

[0066] A distillation tower 20 is used to perform a second separation treatment 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] The reaction kettle 50 is used for carrying out the reaction between the phenyl isocyanate concentrate and the hydrochloric acid.

[0069] In one embodiment, the processing device further includes a first condenser 21 connected to the top of the distillation tower 20, and used for condensing the gaseous solvent discharged from the top of the tower.

[0070] In one embodiment, the processing device further includes a second condenser 30 disposed between the bottom of the distillation tower 20 and the mixer 40 for cooling the phenyl isocyanate concentrated liquid discharged from the bottom of the distillation tower 20.

[0071] In one embodiment, the processing device further includes a reboiler 22 and a pump 23, wherein the reboiler 22 is connected to the bottom of the distillation tower 20 and the pump 23 respectively, and the pump 23 is also connected to the mixer 40. Under the action of the pump 23, a part of the material discharged from the bottom of the tower is circulated back to the bottom of the tower through the reboiler 22, and the other part enters the mixer 40.

[0072] In one embodiment, the reactor 50 may be a vertical reactor equipped with a stirring component.

[0073] In one embodiment, the functioning mode of each component in the processing device is applicable to the description of the aforementioned processing method section.

[0074] One embodiment of the present invention provides a MDI production process, comprising the following steps:

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

[0076] removing phosgene from the first mixture to obtain a second mixture;

[0077] stripping the second mixture with HCl gas to obtain a third mixture; and

[0078] The third mixture is subjected to a treatment for removing the solvent to obtain a crude MDI product and a gas phase condensate;

[0079] The gas phase condensate includes phenyl isocyanate by-product, and the gas phase condensate can be treated by the above-mentioned treatment method.

[0080] In one embodiment, the process of removing the solvent comprises:

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

[0082] The fourth mixture is subjected to a second solvent removal treatment to obtain a crude MDI product and a gas phase condensate.

[0083] In one embodiment, the first or second desolventizing treatment may be performed by a desolventizing tower, which may be a distillation tower.

[0084] In one embodiment, the second solvent removal treatment can be performed by a nitrogen stripping tower or a solvent removal tower, and the gas phase condensate is the condensate of the stripping tower top or the solvent removal tower gas.

[0085] In one embodiment, the solvent obtained by the solvent removal process can be collected in a refined solvent tank and re-entered into the production system for use as a circulating solvent.

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

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

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

[0089] In one embodiment, the desolventizing device comprises a first desolventizing tower for performing a first desolventizing treatment and a second desolventizing tower for performing a second desolventizing treatment; both the first and second desolventizing towers can be distillation towers.

[0090] In one embodiment, the MDI production system includes a refining solvent tank, which can be connected to a desolventizing device, and the solvent discharged from the desolventizing device can be introduced into the refining solvent tank.

[0091] In one embodiment, the MDI production system includes a refining and separation device for refining the crude MDI product.

[0092] In one embodiment, the MDI production system includes a vacuum unit, which may include a plurality of vacuum pumps for adjusting the pressure of the system.

[0093] The inventors sampled and evaluated each liquid flow in the MDI production process and found that there was a PI-enriched liquid (or PI-enriched liquid flow) in the production system, and the PI-enriched liquid was the above-mentioned gas phase condensate. The main components of the PI-enriched liquid are solvent, MDI and PI, and the PI concentration therein is more than 10 times the PI concentration in the circulating solvent, and the flow rate of the enriched PI liquid is small. Due to the high value of the MDI contained therein, the existing process circulates it back to the phosgene removal device, so that a large amount of PI in the liquid flow circulates in the production system (a small amount of PI will be taken away by the crude MDI), so PI continues to accumulate in the system, eventually leading to an increase in the PI content in the circulating solvent and the crude MDI, thereby affecting the long-term operation of the system and the product yield.

[0094] In one embodiment of the present invention, the PI-enriched liquid (or phenyl isocyanate by-product) is treated separately and no longer recycled to the production system; wherein the MDI, solvent and PI in the PI-enriched liquid are separated; the separated MDI is recycled back to the production system, the solvent is introduced into the refined solvent tank of the production system, and the phenyl isocyanate concentrated liquid is mixed with hydrochloric acid to react to obtain aniline hydrochloride, and then the aniline hydrochloride is recycled back to the preparation process of MDA.

[0095] One embodiment of the present invention reduces the rate of decrease of the heat transfer coefficient in the photochemical reaction device by treating the PI enriched solution (or phenyl isocyanate byproduct), reduces the blocking frequency of the aforementioned vacuum unit, and prolongs the operation cycle of the production system; in addition, PI is converted into aniline hydrochloride through a simple reaction and then used as a raw material for the production of MDA, thereby realizing the recycling of materials and increasing benefits. In addition, compared with the existing process, this method does not increase energy consumption and saves operating costs.

[0096] The method for treating phenyl isocyanate by-products according to one embodiment of the present invention can effectively reduce the circulating solvent of the MDI production process and the PI content in the MDI crude product, extend the operation cycle of the production system, and realize the reuse of PI.

[0097] The method for treating phenyl isocyanate byproducts according to one embodiment of the present invention has a simple process flow and operation, and the components constituting the corresponding treatment device can all be existing components, and fully automated operation can be achieved without adversely affecting the MDI process.

[0098] In an MDI production process according to one embodiment of the present invention, the mass content of PI in the circulating solvent after being treated by the above-mentioned treatment method is 30 to 100 ppm, and the mass content of PI in the MDI crude product is 5 to 20 ppm, thereby reducing the blockage problem of PI on 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 the production raw material of MDI, the product yield is improved and additional economic benefits are added.

[0099] The following is a further description of a method for treating phenyl isocyanate byproducts according to an embodiment of the present invention in conjunction with a specific example. The mass content of PI in this article is directly measured by gas chromatography, and the solvent used in the test is dichloromethane; the mass content of 1,3-diphenylurea is measured by liquid chromatography using methanol as a dispersant.

[0100] Example 1

[0101] (1) Mixing diphenylmethane series diamines and polyamines (MDA) with chlorobenzene to obtain a mixed solution with an MDA concentration of 30w%; then, reacting the mixed solution with a mass ratio of 1:4 with liquid phosgene at 3 barg and 100° C. to obtain a first mixture.

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

[0103] (3) stripping the second mixture with hydrogen chloride 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 subjected to a dechlorobenzene treatment to obtain a fourth mixture; the fourth mixture contains 3.1 wt % of chlorobenzene.

[0105] (5) sending the fourth mixture into a nitrogen stripping tower to remove the solvent, thereby obtaining a crude MDI product having a chlorobenzene content of 600 ppm by mass and a gas condensate at the top of the tower; wherein the PI content in the gas condensate at the top of the tower (phenyl isocyanate by-product) is 3000 ppm by mass.

[0106] (6) sending the gaseous condensate from the top of the tower to a rising film evaporator at an operating pressure of 40 kPa and a temperature of 115° C. to obtain a liquid MDI mixture and a gaseous phenyl isocyanate mixture; and mixing the MDI mixture with the first mixture of step (1).

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

[0108] (8) A phenyl isocyanate concentrate having a PI concentration of 90 wt % and hydrochloric acid (concentration 32 wt %), a by-product of a photochemical reaction, are mixed 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 rate ratio of HCl in the hydrochloric acid to the mass flow rate of PI in the phenyl isocyanate concentrate is 3.5:1.

[0109] (9) The reaction mixture is fed into a reactor, and the stirring power density of the reactor is 5 kW / m 3 , the temperature is 40°C, and the residence time of the mixture in the reactor is 20 min.

[0110] 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 by-product 1,3-diphenylurea was 0.02%.

[0111] Example 1-1

[0112] This embodiment adopts the raw materials and process steps that are basically the same as those in Example 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the mass flow rate ratio of HCl in the hydrochloric acid in step (8) to the mass flow rate ratio of PI in the phenyl isocyanate concentrate is 1:1.

[0113] The mass content of PI in the liquid material at the reactor outlet was measured to be <1 ppm, and the mass content of the by-product 1,3-diphenylurea was 0.2%.

[0114] Example 1-2

[0115] This embodiment adopts the raw materials and process steps that are basically the same as those in Example 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the mass flow rate ratio of HCl in the hydrochloric acid in step (8) to the mass flow rate ratio of PI in the phenyl isocyanate concentrate is 2:1.

[0116] The mass content of PI in the liquid material at the reactor outlet was measured to be <1 ppm, and the mass content of the by-product 1,3-diphenylurea was 0.06%.

[0117] Examples 1-3

[0118] This embodiment adopts the raw materials and process steps that are basically the same as those in Example 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the mass flow rate ratio of HCl in the hydrochloric acid in step (8) to the mass flow rate ratio of PI in the phenyl isocyanate concentrate 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 by-product 1,3-diphenylurea was 0.021%.

[0120] Examples 1-4

[0121] This embodiment adopts the raw materials and process steps that are basically the same as those in Example 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the mass flow rate ratio of HCl in the hydrochloric acid in step (8) to the mass flow rate ratio of PI in the phenyl isocyanate concentrate is 5:1.

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

[0123] Example 2

[0124] This embodiment adopts substantially the same raw materials and process steps as those of Embodiment 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being 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 reactor outlet was measured to be 300 ppm, and the mass content of the by-product 1,3-diphenylurea was 0.15%.

[0126] Example 2-1

[0127] This embodiment adopts the raw materials and process steps that are basically the same as those in Embodiment 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the residence time of the reaction mixture in step (8) in the static mixer is 2 seconds.

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

[0129] Example 2-2

[0130] This embodiment adopts the raw materials and process steps basically the same as those in Embodiment 1 to produce MDI and treat the phenyl isocyanate by-product, the only difference being that the residence time of the reaction mixture in the static mixer in step (8) is 4 seconds.

[0131] 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 by-product 1,3-diphenylurea was 0.019%.

[0132] Example 2-3

[0133] This embodiment adopts the raw materials and process steps that are basically the same as those in Embodiment 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the residence time of the reaction mixture in the static mixer in step (8) is 5 seconds.

[0134] 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 by-product 1,3-diphenylurea was 0.025%.

[0135] Embodiment 2-4

[0136] This embodiment adopts the raw materials and process steps that are basically the same as those in Embodiment 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the residence time of the reaction mixture in step (8) in the static mixer is 6 seconds.

[0137] The mass content of PI in the liquid material at the reactor outlet 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 embodiment adopts the same raw materials and process steps as those in Embodiment 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the temperature in step (9) is 70°C.

[0140] 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 by-product 1,3-diphenylurea was 0.25%.

[0141] Example 3-1

[0142] This embodiment adopts the raw materials and process steps basically the same as those in Embodiment 1 to produce MDI and treat the phenyl isocyanate by-product, the only difference being that the temperature in step (9) is 30°C.

[0143] The mass content of PI in the liquid material at the reactor outlet 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 embodiment adopts the raw materials and process steps basically the same as those in Embodiment 1 to produce MDI and treat the phenyl isocyanate by-product, the only difference being that the temperature in step (9) is 50°C.

[0146] 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 by-product 1,3-diphenylurea was 0.025%.

[0147] Example 3-3

[0148] This embodiment adopts substantially the same raw materials and process steps as those of embodiment 1 to produce MDI and treat the phenyl isocyanate by-product, the only difference being that the temperature in step (9) is 60°C.

[0149] The mass content of PI in the liquid material at the reactor outlet was measured to be <1 ppm, and the mass content of the by-product 1,3-diphenylurea was 0.07%.

[0150] Example 4

[0151] This embodiment adopts the same raw materials and process steps as those in Embodiment 1 to produce MDI and treat the phenyl isocyanate byproduct, except that the stirring power density of the reactor in step (9) is 1 kW / m 3 .

[0152] The mass content of PI in the liquid material at the reactor outlet 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 embodiment adopts the same raw materials and process steps as those in Embodiment 1 to produce MDI and treat the phenyl isocyanate by-product, except that the stirring power density of the reactor in step (9) is 2 kW / m 3 .

[0155] The mass content of PI 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 embodiment adopts the same raw materials and process steps as those in Embodiment 1 to produce MDI and treat the phenyl isocyanate byproduct, except that the stirring power density of the reactor in step (9) is 4 kW / m 3 .

[0158] 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 by-product 1,3-diphenylurea was 0.025%.

[0159] Example 4-3

[0160] This embodiment adopts the same raw materials and process steps as those in Embodiment 1 to produce MDI and treat the phenyl isocyanate by-product, except that the stirring power density of the reactor in step (9) is 6 kW / m 3 .

[0161] 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 by-product 1,3-diphenylurea was 0.023%.

[0162] Example 4-4

[0163] This embodiment adopts the same raw materials and process steps as those in Embodiment 1 to produce MDI and treat the phenyl isocyanate by-product, except that the stirring power density of the reactor in step (9) is 10 kW / m 3 .

[0164] 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 by-product 1,3-diphenylurea was 0.04%.

[0165] Example 5

[0166] This embodiment adopts the raw materials and process steps basically the same as those in Embodiment 1 to produce MDI and treat the phenyl isocyanate by-product, the only difference being that the residence time of the mixture in step (9) in the reactor is 5 min.

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

[0168] Example 5-1

[0169] This embodiment adopts the raw materials and process steps basically the same as those in Embodiment 1 to produce MDI and treat the phenyl isocyanate by-product, the only difference being that the residence time of the mixture in step (9) in the reactor is 10 min.

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

[0171] Example 5-2

[0172] This embodiment adopts the raw materials and process steps basically the same as those in Embodiment 1 to produce MDI and treat the phenyl isocyanate by-product, the only difference being that the residence time of the mixture in step (9) in the reactor is 15 min.

[0173] 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 by-product 1,3-diphenylurea was 0.019%.

[0174] Example 5-3

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

[0176] The mass content of PI in the liquid material at the reactor outlet was measured to be <1 ppm, and the mass content of the by-product 1,3-diphenylurea was 0.03%.

[0177] Example 5-4

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

[0179] 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 by-product 1,3-diphenylurea was 0.05%.

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

[0181] The difference between Examples 1, 2 and 2-4 is that the residence time t1 of the reaction mixture in step (8) in the static mixer is different. According to the test results of the liquid material at the outlet of the reactor, t1 affects the PI content and 1,3-diphenylurea content in the outlet material. According to the above test results, t1 is preferably 2 to 5 seconds, more preferably 3 to 5 seconds, and even more preferably 3 to 4 seconds.

[0182] The difference between Examples 1, 3 to 3-3 is that the reaction temperature T of step (9) is different. According to the test results of the liquid material at the outlet of the reactor, the reaction temperature T affects the PI content and 1,3-diphenylurea content in the outlet material. According to the above test results, the reaction temperature T is preferably 30 to 60°C, and more preferably 40 to 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 reactor outlet, the stirring power density w will affect the PI content and 1,3-diphenylurea content in the outlet material. According to the above test results, w is preferably 2 to 10 kW / m 3 , more preferably 4 to 10 kW / m 3 , and more preferably 4 to 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 step (9) in the reactor is different. According to the test results of the liquid material at the reactor outlet, the reaction time t2 affects the PI content and 1,3-diphenylurea content in the outlet material. According to the above test results, the reaction time t2 can be 10 to 35 minutes, preferably 10 to 30 minutes, more preferably 15 to 25 minutes, and more preferably 15 to 20 minutes.

[0185] Unless otherwise defined, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0186] The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Those skilled in the art may make various other substitutions, changes and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above embodiments, but is only limited by the claims.

Claims

1. A method for treating phenyl isocyanate by-products, wherein: The phenyl isocyanate by-product is produced in the production process of diisocyanates and polyisocyanates of the diphenylmethane series, and comprises the diisocyanates and polyisocyanates of the diphenylmethane series, phenyl isocyanate and a solvent. The treatment method comprises the following steps: S1: subjecting the phenyl isocyanate by-product to a first separation treatment to obtain a diphenylmethane series diisocyanate and polyisocyanate mixture and a phenyl isocyanate mixture; S2: subjecting the phenyl isocyanate mixture to a second separation treatment to obtain a phenyl isocyanate concentrate and the solvent; and S3: reacting the phenyl isocyanate concentrate with hydrochloric acid in a reactor to obtain aniline hydrochloride.

2. The processing method according to claim 1, wherein: Step S3 comprises: mixing the phenyl isocyanate concentrate and the hydrochloric acid in a mixer to obtain a reaction mixture; and reacting the reaction mixture in the reactor; the residence time t1 of the reaction mixture in the mixer is 2 to 5 seconds; and / or, The ratio of the mass m1 of hydrogen chloride in the hydrochloric acid to the mass m2 of phenyl isocyanate in the phenyl isocyanate concentrate is m1:m2=(2-5):1; and / or, The reaction temperature T of the reaction of the phenyl isocyanate concentrate and the hydrochloric acid is 30-60° C., and the stirring power density w of the reactor is 2-10 kW / m 3 .

3. The processing method according to claim 2, wherein: The mixer is a static mixer or a dynamic mixer; and / or, The residence time t1 is 3 to 4 seconds; and / or, The reaction time t2 of the reaction between the phenyl isocyanate concentrate and the hydrochloric acid is 10 to 35 minutes.

4. The processing method according to claim 3, wherein: The reaction temperature T of the reaction of the phenyl isocyanate concentrate with the hydrochloric acid is 40 to 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 to 25 minutes; and / or, Parameters w, t1, t2, T, m1, and m2 satisfy the following relationship:

5. The processing method according to claim 1, wherein: Using the aniline hydrochloride as a raw material for the production process of diisocyanates and polyisocyanates of the diphenylmethane series; and / or, The diphenylmethane series diisocyanate and polyisocyanate mixture is transported to the process of the diphenylmethane series diisocyanate and polyisocyanate production process; and / or, The solvent includes one or more of benzene, toluene, chlorobenzene, and diethyl carbonate; and / or, The mass content of phenyl isocyanate in the phenyl isocyanate by-product is 500 to 5000 ppm.

6. The processing method according to claim 1, wherein: The first separation process is performed in an evaporator; and / or, The second separation treatment is carried out in a distillation tower; and / or, The mass concentration of the phenyl isocyanate concentrated solution is 80-98%; and / or, The mass concentration of the hydrochloric acid is 10-35%; and / or, The mass content of phenyl isocyanate in the reaction kettle product is less than or equal to 300 ppm; and / or, The mass content of 1,3-diphenylurea in the reaction kettle product is less than or equal to 0.2%.

7. The processing method according to claim 6, wherein: The evaporator is a rising film evaporator or a falling film evaporator; in the first separation process, the pressure of the rising film evaporator is 30-60 kPa and the temperature is 90-130° C.; and / or, The distillation tower adopts a packed tower, the reflux ratio is 0.2-0.5, the tower top pressure is 30-50 kPa, and the tower bottom temperature is 110-140°C.

8. A device for treating phenyl isocyanate byproducts, comprising: An evaporator is used to perform a first separation treatment on the phenyl isocyanate byproduct to obtain a diphenylmethane series diisocyanate and polyisocyanate mixture and a phenyl isocyanate mixture; A distillation tower, used for performing a second separation treatment on the phenyl isocyanate mixture to obtain a phenyl isocyanate concentrate and a solvent; A mixer for mixing the phenyl isocyanate concentrate with hydrochloric acid; and A reaction kettle is used to carry out the reaction between the phenyl isocyanate concentrate and the hydrochloric acid.

9. A process for producing diisocyanates and polyisocyanates of a diphenylmethane series, comprising the following steps: Carrying out a phosgenation reaction between a diphenylmethane series diamine and a polyamine and phosgene in a solvent to obtain a first mixture; removing phosgene from the first mixture to obtain a second mixture; stripping the second mixture with HCl gas to obtain a third mixture; and The third mixture is subjected to a treatment for removing the solvent to obtain crude diisocyanates and polyisocyanates of the diphenylmethane series and a gas phase condensate; in, The gas phase condensate includes phenyl isocyanate by-product, and the gas phase condensate is treated by the treatment method according to any one of claims 1 to 8.

10. The production process according to claim 9, wherein: The solvent removal process includes: performing a first solvent removal process on the third mixture to obtain a fourth mixture; and performing a second solvent removal process on the fourth mixture to obtain crude diisocyanates and polyisocyanates of a diphenylmethane series and a gas phase condensate; The second desolventizing treatment is performed by nitrogen stripping or a distillation tower; and / or, The diphenylmethane series diisocyanate and polyisocyanate mixture is mixed with the first mixture.

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