Method for treating phenyl isocyanate byproduct and use thereof

Abstract

The present invention relates to a method for treating a phenyl isocyanate byproduct and a use thereof. The method comprises the following steps: S1: subjecting a phenyl isocyanate byproduct to first separation treatment, and obtaining a diphenylmethane series diisocyanate and polyisocyanate mixture and a phenyl isocyanate mixture; S2: subjecting the phenyl isocyanate mixture to second separation treatment, and obtaining a phenyl isocyanate concentrate and a solvent; and S3: reacting the phenyl isocyanate concentrate with hydrochloric acid in a reactor, and obtaining aniline hydrochloride. In the method for treating a phenyl isocyanate byproduct according to one embodiment of the present invention, byproducts containing phenyl isocyanate produced in an MDI production process can be efficiently treated, separated phenyl isocyanate can be converted, by means of reaction, into aniline hydrochloride, and the aniline hydrochloride is reused in the MDI production process, which not only reduces the impact of phenyl isocyanate on said production process but also saves production costs.

Description

A method for treating phenyl isocyanate by-product and its application Technical Field

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

[0002] Diphenylmethane-based diisocyanates and polyisocyanates (MDI) are important raw materials for the production of polyurethane. Currently, the main production method for MDI involves the following steps: condensing aniline with formaldehyde in the presence of an acid catalyst to produce diphenylmethane-based diamines and polyamines (MDA); phosgenating MDA with liquid phosgene in an inert solvent to produce a reaction solution; and removing phosgene, stripping with hydrogen chloride, removing the solvent, and refining and separating the reaction solution to obtain the corresponding MDI product.

[0003] Research has found that because the MDA product contains small amounts of phenyl isocyanate (PI) precursor impurities (such as formanilide, acetanilide, methylformanilide, methylacetanilide, and aniline), PI is inevitably generated after phosgenation and hydrogen chloride stripping. Most of this PI enters the circulating solvent, where it mixes with the raw amine to form urea or uret-like substances, reducing product yield. Furthermore, since urea is insoluble in the solvent, it precipitates in the reaction apparatus and adheres to the equipment walls, causing scaling. This scaling impairs heat transfer in the reaction system equipment and can exacerbate clogging, thus hindering the long-term operation of the production system. Furthermore, a small amount of PI enters the crude MDI and enters the vacuum unit (vacuum pump combination) during the product refining and separation process. Because the system is not completely sealed, trace amounts of moisture inevitably enter the vacuum unit. PI reacts with water to form urea, which accumulates in the unit, ultimately causing blockage and blocking, impacting the long-term operation of the desolventizing unit. Furthermore, PI is a highly toxic substance. If left untreated, its accumulation in the system can lead to potential toxicological issues.

[0004] There are two main methods for reducing the PI content in the production system in the existing technology. 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 it into a reaction before processing.

[0005] However, these methods all have significant drawbacks. Controlling PI precursor impurities in DAM requires adding a new catalyst system to the MDA production process, introducing new impurities and altering existing process conditions, all of which inevitably lead to other adverse effects and increased costs. Furthermore, methods that utilize the reaction characteristics of PI for conversion not only increase the amount of circulating solvent in the production system and the burden of the new treatment process, but also require the introduction of new impurities (catalysts or active hydrogen compounds) into the circulating solvent of the photochemical reaction unit. These impurities, if not removed, will accumulate in the system and react with or catalyze MDI reactions. Improper handling can have a greater impact on the system than PI.

[0006] Summary of the Invention

[0007] To overcome at least one of the above-mentioned defects of the prior art, in a first aspect, one 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 diphenylmethane series diisocyanates and polyisocyanates, and the method comprises the diphenylmethane series diisocyanates and polyisocyanates, phenyl isocyanate and a solvent, and the treatment method comprises the following steps:

[0008] S1: performing a first separation treatment on the phenyl isocyanate by-product to obtain a diphenylmethane series diisocyanate and polyisocyanate mixture and a phenyl isocyanate mixture;

[0009] S2: performing a second separation treatment on the phenyl isocyanate mixture to obtain a phenyl isocyanate concentrate and the solvent; and

[0010] S3: reacting the phenyl isocyanate concentrate with hydrochloric acid in a reactor to obtain aniline hydrochloride.

[0011] In a second aspect, an embodiment of the present invention provides a device for processing phenyl isocyanate by-products, comprising:

[0012] an evaporator for performing a first separation treatment on the phenyl isocyanate by-product to obtain a diphenylmethane series diisocyanate and polyisocyanate mixture and a phenyl isocyanate mixture;

[0013] a distillation tower for performing a second separation treatment on the phenyl isocyanate mixture to obtain a phenyl isocyanate concentrate and a solvent;

[0014] a mixer for mixing the phenyl isocyanate concentrate with hydrochloric acid; and

[0015] A reaction kettle is used to carry out the reaction between the phenyl isocyanate concentrate and the hydrochloric acid.

[0016] In a third aspect, an embodiment of the present invention provides a process for producing diisocyanates and polyisocyanates of a diphenylmethane series, comprising the following steps:

[0017] Carrying out a phosgenation reaction between a diphenylmethane series diamine and a polyamine and phosgene in a solvent to obtain a first mixture;

[0018] removing phosgene from the first mixture to obtain a second mixture;

[0019] stripping the second mixture with HCl gas to obtain a third mixture; and

[0020] The third mixture is subjected to a solvent removal treatment to obtain crude diisocyanates and polyisocyanates of the diphenylmethane series and a gas phase condensate;

[0021] Wherein, the gas phase condensate includes phenyl isocyanate by-product, and the gas phase condensate is treated by the above-mentioned treatment method.

[0022] A method for treating phenyl isocyanate byproducts according to one embodiment of the present invention can efficiently treat phenyl isocyanate-containing byproducts generated in the production process of diphenylmethane series diisocyanates and polyisocyanates. The separated phenyl isocyanate can be converted into aniline hydrochloride through a reaction, and the aniline hydrochloride can be reused in the production process of diphenylmethane series diisocyanates and polyisocyanates, thereby reducing the impact of phenyl isocyanate on the above-mentioned production process and saving production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are only used to illustrate specific embodiments and are not to be considered as limiting the present invention.

[0024] FIG1 is a schematic structural diagram of a device for treating phenyl isocyanate by-products according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] Typical embodiments embodying the features and advantages of the present invention are described in detail in the following description. It should be understood that the present invention is capable of various variations in various embodiments without departing from the scope of the present invention, and that the descriptions herein are intended to be illustrative rather than limiting. All pressures referred to herein are absolute pressures.

[0026] 1 , 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 diphenylmethane series diisocyanates and polyisocyanates (MDI), and the phenyl isocyanate by-products include MDI, phenyl isocyanate (PI) and a solvent. The treatment method comprises the following steps:

[0027] S1: performing a first separation treatment on the phenyl isocyanate by-product to obtain an MDI mixture and a phenyl isocyanate mixture;

[0028] S2: performing a second separation treatment on the phenyl isocyanate mixture to obtain a phenyl isocyanate concentrate and a solvent; and

[0029] S3: reacting the phenyl isocyanate concentrate with hydrochloric acid in a reaction vessel 50 to obtain aniline hydrochloride.

[0030] In one embodiment, the reaction temperature T of the reaction of phenyl isocyanate concentrate with 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.

[0031] In one embodiment, the reaction of phenyl isocyanate with hydrochloric acid is as follows:

[0032] Main reaction:

[0033] Side effects:

[0034] By regulating parameters such as reaction temperature, reactant ratio, reaction time, and residence time, more than 95 wt% of PI can be converted into aniline hydrochloride, thereby reducing the PI content in the product.

[0035] In one embodiment, step S3 comprises: mixing the phenyl isocyanate concentrate with hydrochloric acid through a mixer 40 to obtain a reaction mixture; and

[0036] The reaction mixture is reacted in a reaction vessel 50;

[0037] 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.

[0038] In one embodiment, the mixer 40 may be a static mixer or a dynamic mixer, preferably a static mixer.

[0039] In one embodiment, the reaction temperature T of the reaction of the phenyl isocyanate concentrate with hydrochloric acid is preferably 30-60°C, more preferably 40-50°C, such as 35°C or 45°C.

[0040] 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.

[0041] In one embodiment, the ratio of the mass (or mass flow) m1 of hydrogen chloride in hydrochloric acid to the mass (or mass flow) m2 of phenyl isocyanate in the phenyl isocyanate concentrate is preferably m1:m2=(2-5):1, more preferably (3-5):1, further preferably (3-4):1, further preferably (3.5-4):1.

[0042] 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 , more preferably 4 to 6 kW / m 3 .

[0043] In one embodiment, the reactor 50 may use an external circulation cooler to remove heat.

[0044] In one embodiment, the parameters w, t1, t2, T, m1, and m2 satisfy the following relationship:

[0045] The unit of w is kW / m 3 , t1 is in seconds, t2 is in minutes, T is in °C, and m1 and m2 are in kg / h. The above formula only represents the numerical relationship between the above parameters; the units on either side of the inequality do not correspond. Parameters such as w that satisfy the above relationship can improve the conversion rate of the phenyl isocyanate reaction, increase the aniline hydrochloride content in the product, and reduce the PI content.

[0046] 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, or 4000 ppm.

[0047] 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.

[0048] 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 even more preferably 0.01-0.05%, for example 0.02%, 0.03%, 0.04%, 0.06%, 0.07%, and 0.09%.

[0049] In one embodiment, the mass concentration of the phenyl isocyanate concentrate is 80-98%, preferably 90-95%, for example 85% or 93%.

[0050] In one embodiment, the mass concentration of hydrochloric acid may be 10-35%, preferably 30-35%.

[0051] 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.

[0052] In one embodiment, the first separation treatment is carried out in the evaporator 10, which 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 to 60 kPa, preferably 40 to 50 kPa; the temperature can be 90 to 130°C, preferably 100 to 120°C, for example, 105°C, 110°C, 115°C.

[0053] In one embodiment, after the first separation process, 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.

[0054] In one embodiment, the second separation process is performed in the distillation column 20, producing a phenyl isocyanate concentrate in the bottom of the column and a gaseous solvent at the top of the column. The gaseous solvent can be partially refluxed after condensation in the first condenser 21, and the remaining portion can be sent to the refined solvent tank of the production system.

[0055] 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.

[0056] 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.

[0057] In one embodiment, a reboiler 22 is provided 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%.

[0058] In one embodiment, a second condenser 30 is provided outside the bottom of the distillation tower 20 . The temperature of the second condenser 30 may be 10° C. to 50° C., preferably 30° C. to 40° C.

[0059] 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.

[0060] 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 in 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.

[0061] In one embodiment, the mixture of aniline hydrochloride and hydrochloric acid in the reaction kettle 50 can be sent to the condensation reaction step.

[0062] 1 , an embodiment of the present invention provides a device for processing phenyl isocyanate byproducts, which can be used to implement the above method, and the device comprises:

[0063] an evaporator 10 for performing a first separation treatment on the phenyl isocyanate by-product to obtain an MDI mixture and a phenyl isocyanate mixture;

[0064] a distillation tower 20 for performing a second separation treatment on the phenyl isocyanate mixture to obtain a phenyl isocyanate concentrate and a solvent;

[0065] A mixer 40 for mixing the phenyl isocyanate concentrate with hydrochloric acid; and

[0066] The reaction kettle 50 is used for reacting the phenyl isocyanate concentrate with hydrochloric acid.

[0067] In one embodiment, the processing device further includes a first condenser 21 connected to the top of the distillation tower 20 for condensing the gaseous solvent discharged from the top of the tower.

[0068] 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 .

[0069] In one embodiment, the processing device further includes a reboiler 22 and a pump 23. The reboiler 22 is connected to the bottom of the distillation column 20 and the pump 23, respectively. The pump 23 is also connected to the mixer 40. Under the action of the pump 23, part of the material discharged from the bottom of the column is circulated back to the bottom of the column through the reboiler 22, and the other part enters the mixer 40.

[0070] In one embodiment, the reactor 50 may be a vertical reactor equipped with a stirring component.

[0071] In one embodiment, the functioning of each component in the processing device is applicable to the description in the aforementioned processing method section.

[0072] One embodiment of the present invention provides an MDI production process, comprising the following steps:

[0073] Carrying out a phosgenation reaction between MDA and phosgene in a solvent to obtain a first mixture;

[0074] removing phosgene from the first mixture to obtain a second mixture;

[0075] stripping the second mixture with HCl gas to obtain a third mixture; and

[0076] The third mixture is subjected to a treatment for removing the solvent to obtain a crude MDI product and a gas phase condensate;

[0077] The gas phase condensate includes phenyl isocyanate as a by-product, and the gas phase condensate can be treated by the above-mentioned treatment method.

[0078] In one embodiment, the process for removing the solvent comprises:

[0079] subjecting the third mixture to a first solvent removal treatment to obtain a fourth mixture; and

[0080] The fourth mixture is subjected to a second solvent removal treatment to obtain a crude MDI product and a gas phase condensate.

[0081] In one embodiment, the first or second desolventizing treatment may be performed by a desolventizing tower, which may be a distillation tower.

[0082] In one embodiment, the second desolventizing treatment may be performed by a nitrogen stripping tower or a solvent removal tower, and the gas phase condensate is the condensate of the gas from the top of the stripping tower or the solvent removal tower.

[0083] 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 as a circulating solvent for use.

[0084] 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.

[0085] 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.

[0086] One embodiment of the present invention provides an MDI production system that can be used to implement the above-mentioned MDI production process, including a phosgene reaction unit, a phosgene removal unit, a stripping treatment unit, and a solvent removal unit; wherein the phosgene reaction unit is used to perform a phosgenation reaction of MDA and phosgene to obtain a first mixture; the phosgene removal unit is used to remove phosgene from the first mixture to obtain a second mixture; the stripping treatment unit is used to strip the second mixture using HCl gas to obtain a third mixture; and the solvent removal unit is used to remove the solvent from the third mixture.

[0087] In one embodiment, the desolventizing device includes 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.

[0088] In one embodiment, the MDI production system includes a refined solvent tank, which can be connected to a desolventizing device, and the solvent discharged from the desolventizing device can be introduced into the refined solvent tank.

[0089] In one embodiment, the MDI production system includes a refining and separation device for refining the crude MDI product.

[0090] In one embodiment, the MDI production system includes a vacuum unit, which may include multiple vacuum pumps for regulating the pressure of the system.

[0091] By sampling and evaluating various liquid streams in the MDI production process, the inventors discovered the presence of a PI-enriched liquid (or PI-enriched liquid stream) within the production system. This PI-enriched liquid is the aforementioned vapor phase condensate. This PI-enriched liquid primarily consists of solvent, MDI, and PI, with a PI concentration more than 10 times that of the circulating solvent. Furthermore, the flow rate of this enriched PI liquid is relatively low. Due to the high value of the MDI it contains, existing processes recycle this PI stream back to the phosgene removal unit, causing a large amount of PI in this stream to circulate within the production system (a small amount of PI is carried away by the crude MDI). Consequently, PI accumulates in the system, ultimately increasing the PI content in both the circulating solvent and the crude MDI, which in turn affects the system's long-term operation and product yield.

[0092] 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 passed into the refined solvent tank of the production system, and the phenyl isocyanate concentrate 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.

[0093] One embodiment of the present invention reduces the rate of decrease in the heat transfer coefficient within the photochemical reaction device by treating the PI-enriched solution (or phenyl isocyanate byproduct), reduces the frequency of blockage of the aforementioned vacuum unit, and extends the operating cycle of the production system. Furthermore, PI is converted into aniline hydrochloride through a simple reaction and then used as a raw material for MDA production, achieving material recycling and increasing efficiency. Furthermore, this method does not increase energy consumption compared to existing processes, saving operating costs.

[0094] The method for treating phenyl isocyanate byproducts 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 operating cycle of the production system, and realize the reuse of PI.

[0095] The method for treating phenyl isocyanate byproducts according to one embodiment of the present invention has a simple process flow and operation. 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.

[0096] In an MDI production process according to one embodiment of the present invention, the PI mass content in the circulating solvent after treatment by the above-mentioned treatment method is 30 to 100 ppm, and the PI mass content 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 impact 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 MDI production, the product yield is improved, thereby increasing additional economic benefits.

[0097] The following is a further description of a method for treating phenyl isocyanate byproducts according to one embodiment of the present invention, using specific examples. The PI mass content herein is determined by direct analysis using gas chromatography, using dichloromethane as the solvent; the 1,3-diphenylurea mass content is determined by liquid chromatography using methanol as the dispersant.

[0098] Example 1

[0099] (1) Diphenylmethane series diamines and polyamines (MDA) are mixed with chlorobenzene to obtain a mixed solution with an MDA concentration of 30 w %; then, the mixed solution with a mass ratio of 1:4 is reacted with liquid phosgene at 3 barg and 100° C. to obtain a first mixture.

[0100] (2) Phosgene was removed from the first mixture at 0.1 MPa and 150° C. to obtain a second mixture.

[0101] (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.

[0102] (4) The third mixture is subjected to a dechlorobenzene treatment to obtain a fourth mixture; the fourth mixture contains 3.1 wt% of chlorobenzene.

[0103] (5) The fourth mixture is sent to 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 gaseous condensate at the top of the tower; wherein the PI content in the gaseous condensate at the top of the tower (phenyl isocyanate by-product) is 3000 ppm by mass.

[0104] (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).

[0105] (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.

[0106] (8) A phenyl isocyanate concentrate having a PI concentration of 90 wt% is mixed with hydrochloric acid (concentration 32 wt%), a by-product 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 rate ratio of HCl in the hydrochloric acid to the mass flow rate of PI in the phenyl isocyanate concentrate is 3.5:1.

[0107] (9) The reaction mixture was fed into the reactor, and the stirring power density of the reactor was 5 kW / m 3 , the temperature is 40°C, and the residence time of the mixture in the reactor is 20 min.

[0108] 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%.

[0109] Example 1-1

[0110] This embodiment uses substantially the same raw materials and process steps as 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.

[0111] 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 0.2%.

[0112] Example 1-2

[0113] This embodiment uses substantially the same raw materials and process steps as 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.

[0114] 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%.

[0115] Examples 1-3

[0116] This embodiment uses substantially the same raw materials and process steps as 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.

[0117] 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%.

[0118] Examples 1-4

[0119] This embodiment uses substantially the same raw materials and process steps as 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.

[0120] 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 0.03%.

[0121] Example 2

[0122] This embodiment uses substantially the same raw materials and process steps as in Example 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 1 second.

[0123] 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 by-product 1,3-diphenylurea was 0.15%.

[0124] Example 2-1

[0125] This embodiment uses substantially the same raw materials and process steps as in Example 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.

[0126] 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 by-product 1,3-diphenylurea was 0.08%.

[0127] Example 2-2

[0128] This embodiment uses substantially the same raw materials and process steps as in Example 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 4 seconds.

[0129] 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%.

[0130] Example 2-3

[0131] This embodiment uses substantially the same raw materials and process steps as in Example 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 5 seconds.

[0132] 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 0.025%.

[0133] Examples 2-4

[0134] This embodiment uses substantially the same raw materials and process steps as in Example 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.

[0135] 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 0.03%.

[0136] Example 3

[0137] This embodiment uses substantially the same raw materials and process steps as in Example 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.

[0138] 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 0.25%.

[0139] Example 3-1

[0140] This embodiment uses substantially the same raw materials and process steps as in Example 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the temperature in step (9) is 30°C.

[0141] 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 0.03%.

[0142] Example 3-2

[0143] This embodiment uses substantially the same raw materials and process steps as in Example 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the temperature in step (9) is 50°C.

[0144] 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 0.025%.

[0145] Example 3-3

[0146] This embodiment uses substantially the same raw materials and process steps as in Example 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the temperature in step (9) is 60°C.

[0147] 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 0.07%.

[0148] Example 4

[0149] This embodiment uses the same raw materials and process steps as in Example 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the stirring power density of the reactor in step (9) is 1 kW / m 3 .

[0150] The mass content of PI 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%.

[0151] Example 4-1

[0152] This embodiment adopts the same raw materials and process steps as those in Example 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the stirring power density of the reactor in step (9) is 2 kW / m 3 .

[0153] 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%.

[0154] Example 4-2

[0155] This embodiment adopts the same raw materials and process steps as those in Example 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the stirring power density of the reactor in step (9) is 4 kW / m 3 .

[0156] 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 0.025%.

[0157] Example 4-3

[0158] This embodiment adopts the same raw materials and process steps as those in Example 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the stirring power density of the reactor in step (9) is 6 kW / m 3 .

[0159] 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 0.023%.

[0160] Example 4-4

[0161] This embodiment adopts the same raw materials and process steps as those in Example 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the stirring power density of the reactor in step (9) is 10 kW / m 3 .

[0162] 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%.

[0163] Example 5

[0164] This embodiment uses substantially the same raw materials and process steps as in Example 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the residence time of the mixture in step (9) in the reactor is 5 min.

[0165] 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%.

[0166] Example 5-1

[0167] This embodiment uses substantially the same raw materials and process steps as in Example 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the residence time of the mixture in step (9) in the reactor is 10 min.

[0168] 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 by-product 1,3-diphenylurea was 0.019%.

[0169] Example 5-2

[0170] This embodiment uses substantially the same raw materials and process steps as in Example 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the residence time of the mixture in step (9) in the reactor is 15 min.

[0171] 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%.

[0172] Example 5-3

[0173] This embodiment uses substantially the same raw materials and process steps as in Example 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the residence time of the mixture in step (9) in the reactor is 25 min.

[0174] 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 0.03%.

[0175] Example 5-4

[0176] This embodiment uses substantially the same raw materials and process steps as in Example 1 to produce MDI and treat the phenyl isocyanate by-product, with the only difference being that the residence time of the mixture in step (9) in the reactor is 35 min.

[0177] 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%.

[0178] 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 outlet of the reactor, 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.

[0179] The difference between Examples 1 and 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 reactor outlet, t1 affects the PI content and 1,3-diphenylurea content in the outlet material. Based on 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.

[0180] The difference between Examples 1, 3, and 3-3 is that the reaction temperature T in step (9) is different. According to the test results of the liquid material at the reactor outlet, the reaction temperature T affects the PI content and 1,3-diphenylurea content in the outlet material. Based on the above test results, the reaction temperature T is preferably 30-60°C, more preferably 40-50°C.

[0181] The difference between Examples 1, 4 and 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 above test results, w is preferably 2 to 10 kW / m 3 , more preferably 4 to 10 kW / m 3 , more preferably 4 to 6 kW / m 3 .

[0182] The difference between Examples 1, 5, and 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 even more preferably 15 to 20 minutes.

[0183] Unless otherwise defined, the terms used in the present invention have the same meanings as those commonly understood by those skilled in the art.

[0184] 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-mentioned 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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