Preparation method of diphenylmethane series diisocyanate and polyisocyanate

Abstract

The invention relates to a preparation method of diphenylmethane series diisocyanate and polyisocyanate, which comprises the following steps: S1, carrying out phosgenation reaction on diphenylmethane series diamine and polyamine and phosgene in a solvent to obtain a first mixed solution; s2, the first mixed solution is subjected to phosgene removal treatment, and a second mixed solution is obtained; s3, carrying out steam stripping treatment on the second mixed solution by adopting HCl gas to obtain a third mixed solution; s4, the third mixed solution is subjected to solvent removal treatment, and diphenylmethane series diisocyanate and polyisocyanate crude products are obtained. According to the preparation method of the diphenylmethane series diisocyanate and polyisocyanate in one embodiment of the invention, by optimizing the process parameters of the steam stripping treatment step, diphenylmethane series diisocyanate and polyisocyanate products with light colors can be prepared.

Description

Technical Field

[0001] The invention relates to isocyanate, in particular to the preparation of diisocyanate and polyisocyanate of a light-colored diphenylmethane series. Background Art

[0002] Diisocyanates and polyisocyanates (MDI) of diphenylmethane series are one of the important raw materials for producing rigid polyurethane foams, and are mainly used in the fields of household appliances, cold storage, containers, building insulation materials, etc. At present, the production of diisocyanates and polyisocyanates of diphenylmethane series is well-known in the art. The main industrial preparation method is: first, aniline and formaldehyde are subjected to condensation reaction under the action of an acid catalyst to generate DAM (diamines and polyamines of diphenylmethane series, referred to as polyamines), DAM is reacted with phosgene in a solvent under an inert solvent environment through liquid phase phosgenation to obtain a reaction mixture, and the reaction mixture can obtain a corresponding pure MDI product after phosgene removal, hydrogen chloride stripping, solvent removal and refined separation.

[0003] In the phosgenation reaction process and the solvent removal step, dark products are usually formed due to various factors, which cannot be removed during the separation process, resulting in the subsequent polyurethane foam material having a light yellow discoloration effect, which has an adverse effect on its actual application effect. Therefore, it is hoped that isocyanates with light colors or containing less dark components can be prepared as raw materials for polyurethane production.

[0004] At present, there are many studies on the preparation methods of light-colored isocyanates, especially diphenylmethane series isocyanates. In the disclosed methods for improving the color of polymerized MDI, it is often necessary to introduce new materials into the system, which not only increases the operating cost, but also brings new impurities, which is easy to bring other adverse effects. In addition, the control of raw materials is difficult to achieve, and it is often necessary to increase the procurement cost. Summary of the invention

[0005] 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 preparing diisocyanates and polyisocyanates of a diphenylmethane series, comprising the following steps:

[0006] S1: performing a phosgenation reaction on a diphenylmethane series diamine and polyamine with phosgene in a solvent to obtain a first mixed solution;

[0007] S2: removing phosgene from the first mixed solution to obtain a second mixed solution;

[0008] S3: stripping the second mixed liquid with HCl gas to obtain a third mixed liquid; and

[0009] S4: removing the solvent from the third mixed liquid to obtain crude diisocyanates and polyisocyanates of the diphenylmethane series;

[0010] The stripping treatment in step S3 is carried out in a stripping tower, the reflux ratio R of the stripping tower is 0.05-0.3, the contact time t between the second mixed liquid and the gaseous substance containing HCl gas in the stripping tower is 1-10 min, the flow rate v of the gaseous substance in the stripping tower is 2-15 m / s, the mass ratio of the HCl gas to the solute of the second mixed liquid is m1:m2=(0.03-0.2):1; the mass percentage c1 of the solute of the second mixed liquid is 15-35%; the mass percentage c2 of the solute of the third mixed liquid is 40-65%.

[0011] In a second aspect, an embodiment of the present invention provides a diphenylmethane series of diisocyanate and polyisocyanate products, which are prepared by the above-mentioned preparation method.

[0012] In a third aspect, an embodiment of the present invention provides a method for preparing diisocyanates and polyisocyanates of a diphenylmethane series, comprising the following steps:

[0013] S1: performing a phosgenation reaction on a diphenylmethane series diamine and polyamine with phosgene in a solvent to obtain a first mixed solution;

[0014] S2: removing phosgene from the first mixed solution to obtain a second mixed solution;

[0015] S3: stripping the second mixed liquid with HCl gas to obtain a third mixed liquid; and

[0016] S4: removing the solvent from the third mixed liquid to obtain crude diisocyanates and polyisocyanates of the diphenylmethane series;

[0017] The stripping treatment in step S3 is carried out in a stripping tower, R represents the reflux ratio of the stripping tower; t represents the contact time between the second mixed liquid and the gaseous substance containing HCl gas in the stripping tower, in minutes; v represents the flow rate of the gaseous substance in the stripping tower, in m / s; m1 represents the mass flow rate of HCl gas during the stripping treatment, in t / h; m2 represents the mass flow rate of the solute in the second mixed liquid during the stripping treatment, in t / h; c1 represents the mass percentage of the solute in the second mixed liquid, and c2 represents the mass percentage of the solute in the third mixed liquid; R, t, v, m1, m2, c1, and c2 satisfy the following relationship:

[0018]

[0019] The method for preparing diphenylmethane series diisocyanates and polyisocyanates according to one embodiment of the present invention can produce diphenylmethane series diisocyanates and polyisocyanates products with higher L* values ​​and lighter colors by optimizing the process parameters of the stripping treatment step, thereby reducing the impact on the subsequently produced polyurethane products. DETAILED DESCRIPTION

[0020] 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 changes in different embodiments without departing from the scope of the present invention, and the descriptions therein are essentially used as illustrations rather than to limit the present invention.

[0021] One embodiment of the present invention provides a method for preparing diisocyanates and polyisocyanates (MDI) of a diphenylmethane series, comprising the following steps:

[0022] S1: performing a phosgenation reaction of diphenylmethane series diamines and polyamines (DAM) with phosgene in a solvent to obtain a first mixed solution;

[0023] S2: removing phosgene from the first mixed solution to obtain a second mixed solution;

[0024] S3: stripping the second mixed liquid with HCl gas to obtain a third mixed liquid; and

[0025] S4: removing the solvent from the third mixed liquid to obtain crude diisocyanates and polyisocyanates of diphenylmethane series (crude MDI);

[0026] The stripping treatment in step S3 is carried out in a stripping tower, the reflux ratio R of the stripping tower is 0.05-0.3, the contact time t between the second mixed liquid and the gaseous material containing HCl gas in the stripping tower is 1-10 min, the flow rate v of the gaseous material in the stripping tower is 2-15 m / s, the mass ratio of HCl gas to the solute of the second mixed liquid is m1:m2=(0.03-0.2):1; the mass percentage c1 of the solute of the second mixed liquid is 15-35%; and the mass percentage c2 of the solute of the third mixed liquid is 40-65%.

[0027] In one embodiment, the solvent used for the liquid phase phosgenation reaction in step S1 can be one or more of chlorobenzene, dichlorobenzene, diethyl carbonate, and toluene, preferably chlorobenzene.

[0028] In one embodiment, in step S1, the reaction temperature can be 60-160°C, for example, 80°C, 90°C, 95°C, 100°C, 120°C, 140°C, 150°C; the reaction pressure can be 2-30 bar, for example, 5 bar, 8 bar, 10 bar, 15 bar, 20 bar, 25 bar; the mass ratio of DAM to the solvent can be 1:(1.1-5), for example, 1:1.5, 1:2, 1:3, 1:4; the mass ratio of DAM to phosgene can be 1:(1.1-5), for example, 1:1.5, 1:2, 1:2.5, 1:3, 1:4.

[0029] In one embodiment, in step S2, the first mixed liquid may be treated to remove phosgene in a distillation tower, and the phosgene is discharged from the top of the tower in a gaseous form.

[0030] In one embodiment, in step S2, the temperature of the phosgene removal treatment (e.g., bottom temperature) can be 100-180°C, for example, 120°C, 140°C, 150°C, 160°C; the pressure (e.g., top pressure) can be 1-5 bar, for example, 2 bar, 3 bar, 4 bar.

[0031] In one embodiment, the gaseous material (gas) in the stripping tower includes evaporated solvent and HCl gas, and the flow rate v of the gaseous material can be 5-15 m / s, and further can be 5-10 m / s, for example 3 m / s, 4 m / s, 6 m / s, 7 m / s, 8 m / s, 9 m / s, 11 m / s, 12 m / s, 13 m / s, 14 m / s.

[0032] In one embodiment, HCl gas enters the stripping tower from the lower part, and the second mixed liquid enters the stripping tower from the upper part. The gas phase material containing HCl gas moves from bottom to top, and the second mixed liquid moves from top to bottom. The two contact and react in the tower.

[0033] In one embodiment, the contact time t between the second mixed liquid and the gas phase material containing HCl gas in the stripping tower can be 3 to 6 minutes, and further can be 5 to 6 minutes, for example, can be 2 minutes, 4 minutes, 5 minutes, 7 minutes, 8 minutes, 9 minutes. The contact time t is obtained according to the residence time of the second mixed liquid in the stripping tower; in other words, the contact time t can also be described as the residence time of the second mixed liquid in the stripping tower.

[0034] In one embodiment, the stripping column can be an existing distillation column.

[0035] In one embodiment, the operating temperature of the stripping tower (bottom temperature) can be 130-210°C, further 160-190°C, for example 150°C, 170°C, 180°C, 200°C; the operating pressure of the stripping tower (tower top pressure) can be 1-5 bar, further 2-4 bar, for example 3 bar.

[0036] In one embodiment, the reflux ratio R of the stripping tower may be 0.05 to 0.2, and further may be 0.08 to 0.15, for example, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.2, or 0.25.

[0037] In one embodiment, c1 and c2 are measured according to the gel permeation chromatography described below, that is, the mass percentage of the solvent in the mixed solution (the second mixed solution or the third mixed solution) is measured by gel permeation chromatography, and then the mass percentage of the corresponding solvent is subtracted from 100% to obtain c1 or c2. In other words, c3 is the mass percentage of the solvent in the second mixed solution, c1 = 100% - c3; c4 is the mass percentage of the solvent in the third mixed solution, c2 = 100% - c4.

[0038] In one embodiment, c1 and c2 refer to the total content of solutes in the mixed solution. For example, the second mixed solution may include a solvent, MDI and a small amount of impurities, and c1 may be the sum of the mass contents of MDI and impurities. Similarly, the third mixed solution may include a solvent, MDI and a small amount of impurities, and c2 may be the sum of the mass contents of MDI and impurities.

[0039] In one embodiment, in the second mixed solution, the mass percentage c1 of the solute may be 23-35%, further may be 23-30%, for example, 18%, 20%, 25%, 26%, 28%, 33%.

[0040] In one embodiment, in the third mixed solution, the mass percentage c2 of the solute can be 45-65%, and can further be 50-60%, for example, 42%, 45%, 48%, 52%, 54%, 55%, 56%, 58%.

[0041] In one embodiment, the ratio of the mass flow rate m1 of the HCl gas in step S3 to the mass flow rate m2 of the solute in the second mixed solution can be m1:m2=(0.05-0.25):1, further can be (0.05-0.2):1, further can be (0.05-0.15):1, and further can be (0.08-0.1):1, for example, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.12:1, 0.15:1, 0.18:1. Wherein, m1 is measured by a flow meter; m2 is first measured by a mass flow meter to measure the total mass flow rate of the second mixed solution, and then obtained by multiplying the total mass flow rate by the concentration of the solute.

[0042] In one embodiment, R represents the reflux ratio of the stripping tower; t represents the contact time between the second mixed liquid and the gaseous material containing HCl gas in the stripping tower, in minutes; v represents the flow rate of the gaseous material in the stripping tower, in m / s; m1 represents the mass flow rate of HCl gas during the stripping treatment, in t / h; m2 represents the mass flow rate of the solute in the second mixed liquid during the stripping treatment, in t / h; c1 represents the mass percentage of the solute in the second mixed liquid, and c2 represents the mass percentage of the solute in the third mixed liquid; c1, c2 and R are all dimensionless numbers; R, t, v, m1, m2, c1, c2 satisfy the following relationship:

[0043]

[0044] 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 t that satisfy the above relationship can improve the stripping effect of the HCl stripper and make the final product MDI crude product have a higher L* and a lighter color.

[0045] In one embodiment, the desolventizing treatment includes a first desolventizing treatment and a second desolventizing treatment. The first desolventizing treatment can be performed in a distillation tower. The specific process can be: the third mixed liquid is sent to the distillation tower kettle, and the distillation tower kettle produced liquid is sent to the evaporator, and the gas phase substance produced by the evaporator is sent back to the distillation tower. The liquid phase substance is the reaction liquid after desolventizing. Further, the reaction liquid after desolventizing can be subjected to a second desolventizing treatment to remove trace solvents therein, and the second desolventizing treatment can be performed by a nitrogen stripping tower.

[0046] In one embodiment, the method for preparing MDI further comprises the step of separating the crude MDI product. The separation step may be: refining and separating the crude MDI product in a distillation tower, the tower bottom temperature of the distillation tower may be 180-250°C, such as 180°C, 200°C, 230°C, 250°C, etc., the tower top pressure may be 10-1000Pa, such as 10Pa, 50Pa, 100Pa, 1000Pa, etc., and obtaining a polymerized MDI product in the tower bottom.

[0047] In one embodiment, the solvent content in the crude MDI product is less than 1 wt %, further less than 2000 ppm, further less than 1500 ppm, for example, 1200-1400 ppm.

[0048] One embodiment of the present invention provides an MDI product, which is prepared by the above-mentioned preparation method.

[0049] In one embodiment, the L* of the MDI product is 85-93, such as 86, 87, 88, 90, 91, 92.

[0050] Unless otherwise specified, the raw materials, steps, process conditions, etc. of the method for preparing diphenylmethane series diisocyanates and polyisocyanates of the present invention can all be prior art. For example, the diphenylmethane series diisocyanates and polyisocyanates can be prepared by referring to the methods disclosed in CN116217439A, CN108147979B, CN116034102A, CN102471241A, and CN111630027B.

[0051] Unless otherwise specified, the pressures involved in the present invention refer to absolute pressures.

[0052] The inventors have found that in the HCl stripping step of the preparation method of MDI, in addition to parameters such as operating temperature and pressure, the gas velocity in the stripping tower, the reflux ratio of the stripping tower, the concentration of the mixed liquid before and after stripping, and the contact time of the mixed liquid with the stripping HCl in the stripping tower all have a certain influence on the stripping effect; by optimizing the combination of other influencing factors except temperature and pressure, the stripping effect can be further improved, and the L* of the crude MDI product can be improved.

[0053] A method for preparing diphenylmethane series diisocyanates and polyisocyanates according to an embodiment of the present invention reduces the content of impurities by optimizing relevant parameters of the HCl stripping process, and can obtain a crude MDI product with higher L* and lighter color; and the method does not require modification of the existing MDI process and will not have adverse effects on the existing process and products.

[0054] The method for preparing diphenylmethane series diisocyanates and polyisocyanates according to one embodiment of the present invention can produce a crude MDI product with an L* of 85 to 93, thereby improving the quality of the product and the downstream application effect.

[0055] The following is a further description of the preparation method of diphenylmethane series diisocyanates and polyisocyanates according to an embodiment of the present invention in conjunction with examples. The raw materials and test methods used are as follows:

[0056] 1. Raw materials

[0057] Diphenylmethane series diamines and polyamines (DAM): Wanhua Chemical (Ningbo) Co., Ltd., purity> 99.99%. The preparation method of DAM is: aniline and hydrochloric acid are reacted at 60°C and 1 bar to generate aniline hydrochloride, which is then reacted with formaldehyde to obtain a condensation transfer process to obtain a transfer liquid, which is neutralized and washed with water to obtain polyamines, and then distilled and stripped to obtain DAM.

[0058] Chlorobenzene: Wanhua Chemical (Ningbo) Co., Ltd., purity >99.9%.

[0059] Phosgene: Wanhua Chemical (Ningbo) Co., Ltd., purity>95.0%.

[0060] 2. Determination of L* of crude MDI

[0061] The VTS spectrophotometer from Hunterlab was used for the measurement. The specific process was as follows: the colorimetric cell was placed in the instrument detection slot for blank calibration. After the calibration was completed, the sample to be tested was placed in the colorimetric cell and placed in the instrument detection slot for reading.

[0062] 3. Determination of the mass percentage of solute in a mixed solution (e.g. c1 or c2)

[0063] The mass percentage of the solute in the mixed solution is determined and calculated by gel permeation chromatography (GPC). The analysis method is as follows: take the mixed solution and directly inject it for analysis, with an injection volume of 10uL. Chromatographic columns: Waters HR01*1, Waters HR01*3, column box temperature 35°C; detector type is FID detector, detector temperature is 35°C, mobile phase is tetrahydrofuran, flow rate 1ml / min. The mass percentage of the solvent in the mixed solution can be obtained by integrating the chromatogram, and the mass content of the solute is: 100%-the mass percentage of the solvent.

[0064] 4. The solvent content in the crude MDI product was determined by gel permeation chromatography (GPC). The crude MDI product was diluted 10 times with dichloromethane and then sampled and analyzed. The rest of the method was the same as above.

[0065] Example 1

[0066] S1: DAM and chlorobenzene are mixed to obtain a mixed solution with a DAM concentration of 33 wt%, a phosgene chlorobenzene solution with a phosgene concentration of 65 wt% (the mass ratio of DAM to phosgene is 1:2.5) is added to the mixed solution, and the mixture is reacted at 5 bar and 95° C. for 0.5 h to obtain a first mixed solution.

[0067] S2: removing phosgene from the first mixed solution at 1 bar and 130° C. to obtain a second mixed solution; in the second mixed solution, the mass percentage c1 of the solute containing MDI is 27%.

[0068] S3: The second mixed liquid is fed into a hydrogen chloride stripping tower, the operating pressure of the stripping tower is 2 bar, the tower bottom temperature is 180°C, and the tower top reflux ratio R is 0.1. HCl gas is introduced from the tower bottom for stripping, and the mass ratio of the stripped HCl gas to the mass ratio of the solute in the second mixed liquid fed is m1:m2=0.08:1; the contact time t of the gas containing stripped HCl in the tower and the second mixed liquid is controlled to be 5min, and the gas phase flow rate v in the tower is 7m / s, and a third mixed liquid after stripping treatment is obtained in the tower bottom. Among them, the mass percentage c2 of the solute containing MDI in the third mixed liquid is 55%.

[0069] S4: The third mixed liquid is subjected to dechlorobenzene treatment in a distillation tower, the tower top pressure is 30 kPa, the tower bottom temperature is 195°C, and the dechlorobenzene MDI (i.e., the reaction liquid after desolventization) is obtained; the dechlorobenzene MDI is sent to a nitrogen stripping tower for further treatment at 35 kPa and 190°C to remove trace solvents therein, and the mass ratio of nitrogen to the reaction liquid after desolventization is controlled to be 0.04, and a crude MDI product is obtained in the tower bottom. The crude MDI product is tested by a colorimeter, and its L* is measured to be 92; the solvent content in the crude MDI product is 1200 ppm.

[0070] Example 1-1

[0071] This embodiment uses substantially the same raw materials and process as in Embodiment 1 to prepare MDI, with the only difference being that in step S3, the reflux ratio R of the stripping tower is 0.05.

[0072] The L* of the obtained crude MDI was 88; the solvent content in the crude MDI was 1200 ppm.

[0073] Example 1-2

[0074] This embodiment uses substantially the same raw materials and process as in Embodiment 1 to prepare MDI, with the only difference being that in step S3, the reflux ratio R of the stripping tower is 0.08.

[0075] The L* of the obtained crude MDI was 91; the solvent content in the crude MDI was 1200 ppm.

[0076] Examples 1-3

[0077] This embodiment uses substantially the same raw materials and process as in Embodiment 1 to prepare MDI, with the only difference being that in step S3, the reflux ratio R of the stripping tower is 0.15.

[0078] The L* of the obtained crude MDI was 91; the solvent content in the crude MDI was 1200 ppm.

[0079] Examples 1-4

[0080] This embodiment uses substantially the same raw materials and process as in Embodiment 1 to prepare MDI, with the only difference being that in step S3, the reflux ratio R of the stripping tower is 0.2.

[0081] The L* of the obtained crude MDI was 87; the solvent content in the crude MDI was 1200 ppm.

[0082] Examples 1-5

[0083] This embodiment uses substantially the same raw materials and process as in Embodiment 1 to prepare MDI, with the only difference being that in step S3, the reflux ratio R of the stripping tower is 0.3.

[0084] The L* of the obtained crude MDI was 86; the solvent content in the crude MDI was 1200 ppm.

[0085] Examples 1-6

[0086] This embodiment uses substantially the same raw materials and process as in Embodiment 1 to prepare MDI, with the only difference being that in step S3, the reflux ratio R of the stripping tower is 0.35.

[0087] The L* of the obtained crude MDI was 84; the solvent content in the crude MDI was 1200 ppm.

[0088] Example 2

[0089] This embodiment uses substantially the same raw materials and process as those of Embodiment 1 to prepare MDI, with the only difference being that in step S3, the contact time t between the second mixed liquid and the gas phase material containing HCl gas is 1 min.

[0090] The L* of the obtained crude MDI was 83; the solvent content in the crude MDI was 1200 ppm.

[0091] Example 2-1

[0092] This embodiment uses substantially the same raw materials and process as those of Embodiment 1 to prepare MDI, with the only difference being that in step S3, the contact time t between the second mixed liquid and the gas phase material containing HCl gas is 3 min.

[0093] The L* of the obtained crude MDI was 91; the solvent content in the crude MDI was 1200 ppm.

[0094] Example 2-2

[0095] This embodiment uses substantially the same raw materials and process as in Embodiment 1 to prepare MDI, with the only difference being that in step S3, the contact time t between the second mixed liquid and the gas phase material containing HCl gas is 6 min.

[0096] The L* of the obtained crude MDI was 92; the solvent content in the crude MDI was 1200 ppm.

[0097] Example 2-3

[0098] This embodiment uses substantially the same raw materials and process as those of Embodiment 1 to prepare MDI, with the only difference being that in step S3, the contact time t between the second mixed liquid and the gas phase material containing HCl gas is 8 min.

[0099] The L* of the obtained crude MDI was 88; the solvent content in the crude MDI was 1200 ppm.

[0100] Embodiment 2-4

[0101] This embodiment uses substantially the same raw materials and process as in Embodiment 1 to prepare MDI, with the only difference being that in step S3, the contact time t between the second mixed liquid and the gas phase material containing HCl gas is 10 min.

[0102] The L* of the obtained crude MDI was 86; the solvent content in the crude MDI was 1200 ppm.

[0103] Embodiment 2-5

[0104] This embodiment uses substantially the same raw materials and process as in Embodiment 1 to prepare MDI, with the only difference being that in step S3, the contact time t between the second mixed liquid and the gas phase material containing HCl gas is 11 min.

[0105] The L* of the obtained crude MDI was 85; the solvent content in the crude MDI was 1200 ppm.

[0106] Example 3

[0107] This embodiment uses substantially the same raw materials and process as in Embodiment 1 to prepare MDI, with the only difference being that in step S3, the flow rate v of the gas phase material in the stripping tower is 2 m / s.

[0108] The L* of the obtained crude MDI was 86; the solvent content in the crude MDI was 1200 ppm.

[0109] Example 3-1

[0110] This embodiment uses substantially the same raw materials and process as in Embodiment 1 to prepare MDI, with the only difference being that in step S3, the flow rate v of the gas phase material in the stripping tower is 5 m / s.

[0111] The L* of the obtained crude MDI was 91; the solvent content in the crude MDI was 1200 ppm.

[0112] Example 3-2

[0113] This embodiment uses substantially the same raw materials and process as in Embodiment 1 to prepare MDI, with the only difference being that in step S3, the flow rate v of the gas phase material in the stripping tower is 10 m / s.

[0114] The L* of the obtained crude MDI was 91; the solvent content in the crude MDI was 1200 ppm.

[0115] Example 3-3

[0116] This embodiment uses substantially the same raw materials and process as in Embodiment 1 to prepare MDI, with the only difference being that in step S3, the flow rate v of the gas phase material in the stripping tower is 15 m / s.

[0117] The L* of the obtained crude MDI was 87; the solvent content in the crude MDI was 1200 ppm.

[0118] Embodiment 3-4

[0119] This embodiment adopts substantially the same raw materials and process as those of embodiment 1 to prepare MDI, with the only difference being that in step S3, the flow rate v of the gas phase material in the stripping tower is 17 m / s.

[0120] The L* of the obtained crude MDI was 83; the solvent content in the crude MDI was 1200 ppm.

[0121] Example 4

[0122] This embodiment uses substantially the same raw materials and process as in Embodiment 1 to prepare MDI, with the only difference being that in step S3, the mass ratio of the stripping HCl gas to the mass ratio of the solute in the second mixed liquid fed is m1:m2=0.02:1.

[0123] The L* of the obtained crude MDI was 84; the solvent content in the crude MDI was 1200 ppm.

[0124] Example 4-1

[0125] This embodiment uses substantially the same raw materials and process as in Embodiment 1 to prepare MDI, with the only difference being that in step S3, the mass ratio of the stripping HCl gas to the mass ratio of the solute in the second mixed liquid fed is m1:m2=0.03:1.

[0126] The L* of the obtained crude MDI was 85; the solvent content in the crude MDI was 1200 ppm.

[0127] Example 4-2

[0128] This embodiment uses substantially the same raw materials and process as in Embodiment 1 to prepare MDI, with the only difference being that in step S3, the mass ratio of the stripping HCl gas to the mass ratio of the solute in the second mixed liquid fed is m1:m2=0.05:1.

[0129] The L* of the obtained crude MDI was 90; the solvent content in the crude MDI was 1200 ppm.

[0130] Example 4-3

[0131] This embodiment uses substantially the same raw materials and process as in Embodiment 1 to prepare MDI, with the only difference being that in step S3, the mass ratio of the stripping HCl gas to the mass ratio of the solute in the second mixed liquid fed is m1:m2=0.1:1.

[0132] The L* of the obtained crude MDI was 92; the solvent content in the crude MDI was 1200 ppm.

[0133] Example 4-4

[0134] This embodiment uses substantially the same raw materials and process as in Embodiment 1 to prepare MDI, with the only difference being that in step S3, the mass ratio of the stripping HCl gas to the mass ratio of the solute in the second mixed liquid fed is m1:m2=0.15:1.

[0135] The L* of the obtained crude MDI was 91; the solvent content in the crude MDI was 1200 ppm.

[0136] Embodiment 4-5

[0137] This embodiment uses substantially the same raw materials and process as in Embodiment 1 to prepare MDI, with the only difference being that in step S3, the mass ratio of the stripped HCl gas to the mass ratio of the solute in the fed second mixed liquid is m1:m2=0.2:1.

[0138] The L* of the obtained crude MDI was 90; the solvent content in the crude MDI was 1200 ppm.

[0139] Embodiment 4-6

[0140] This embodiment uses substantially the same raw materials and process as in Embodiment 1 to prepare MDI, with the only difference being that in step S3, the mass ratio of the stripping HCl gas to the mass ratio of the solute in the second mixed liquid fed is m1:m2=0.25:1.

[0141] The L* of the obtained crude MDI was 89; the solvent content in the crude MDI was 1200 ppm.

[0142] Example 5

[0143] This embodiment uses substantially the same raw materials and process as those of Embodiment 1 to prepare MDI, with the only difference being that the mass percentage content c1 of the solute in the second mixed solution is 13%.

[0144] The L* of the obtained crude MDI was 85; the solvent content in the crude MDI was 1200 ppm.

[0145] Example 5-1

[0146] This embodiment uses substantially the same raw materials and process as those of Embodiment 1 to prepare MDI, with the only difference being that the mass percentage content c1 of the solute in the second mixed solution is 15%.

[0147] The L* of the obtained crude MDI was 86; the solvent content in the crude MDI was 1200 ppm.

[0148] Example 5-2

[0149] This embodiment uses substantially the same raw materials and process as those of embodiment 1 to prepare MDI, with the only difference being that the mass percentage c1 of the solute in the second mixed solution is 23%.

[0150] The L* of the obtained crude MDI was 90; the solvent content in the crude MDI was 1200 ppm.

[0151] Example 5-3

[0152] This embodiment uses substantially the same raw materials and process as those of embodiment 1 to prepare MDI, with the only difference being that the mass percentage content c1 of the solute in the second mixed solution is 30%.

[0153] The L* of the obtained crude MDI was 91; the solvent content in the crude MDI was 1200 ppm.

[0154] Example 5-4

[0155] This embodiment uses substantially the same raw materials and process as those of Embodiment 1 to prepare MDI, with the only difference being that the mass percentage content c1 of the solute in the second mixed solution is 35%.

[0156] The L* of the obtained crude MDI was 88; the solvent content in the crude MDI was 1200 ppm.

[0157] Example 5-5

[0158] This embodiment uses substantially the same raw materials and process as those of embodiment 1 to prepare MDI, with the only difference being that the mass percentage c1 of the solute in the second mixed solution is 38%.

[0159] The L* of the obtained crude MDI was 84; the solvent content in the crude MDI was 1200 ppm.

[0160] Example 6

[0161] This embodiment uses substantially the same raw materials and process as those of embodiment 1 to prepare MDI, with the only difference being that the mass percentage content c2 of the solute in the third mixed solution is 38%.

[0162] The L* of the obtained crude MDI was 83; the solvent content in the crude MDI was 1200 ppm.

[0163] Example 6-1

[0164] This embodiment uses substantially the same raw materials and process as those of embodiment 1 to prepare MDI, with the only difference being that the mass percentage content c2 of the solute in the third mixed solution is 40%.

[0165] The L* of the obtained crude MDI was 85; the solvent content in the crude MDI was 1200 ppm.

[0166] Example 6-2

[0167] This embodiment uses substantially the same raw materials and process as those of Embodiment 1 to prepare MDI, with the only difference being that the mass percentage content c2 of the solute in the third mixed solution is 45%.

[0168] The L* of the obtained crude MDI was 88; the solvent content in the crude MDI was 1200 ppm.

[0169] Example 6-3

[0170] This embodiment uses substantially the same raw materials and process as those of embodiment 1 to prepare MDI, with the only difference being that the mass percentage content c2 of the solute in the third mixed solution is 50%.

[0171] The L* of the obtained crude MDI was 91; the solvent content in the crude MDI was 1200 ppm.

[0172] Example 6-4

[0173] This embodiment uses substantially the same raw materials and process as those of embodiment 1 to prepare MDI, with the only difference being that the mass percentage content c2 of the solute in the third mixed solution is 60%.

[0174] The L* of the obtained crude MDI was 92; the solvent content in the crude MDI was 1200 ppm.

[0175] Example 6-5

[0176] This embodiment uses substantially the same raw materials and process as those of embodiment 1 to prepare MDI, with the only difference being that the mass percentage content c2 of the solute in the third mixed solution is 65%.

[0177] The L* of the obtained crude MDI was 88; the solvent content in the crude MDI was 1200 ppm.

[0178] Example 6-6

[0179] This embodiment uses substantially the same raw materials and process as those of embodiment 1 to prepare MDI, with the only difference being that the mass percentage content c2 of the solute in the third mixed solution is 68%.

[0180] The L* of the obtained crude MDI was 84; the solvent content in the crude MDI was 1200 ppm.

[0181] Example 7

[0182] S1: DAM and chlorobenzene are mixed to obtain a mixed solution with a DAM concentration of 20 wt%, a phosgene chlorobenzene solution with a phosgene concentration of 65 wt% (the mass ratio of DAM to phosgene is 1:3) is added to the mixed solution, and the mixture is reacted at 5 bar and 95° C. for 0.5 h to obtain a first mixed solution.

[0183] S2: removing phosgene from the first mixed solution at 1 bar and 130° C. to obtain a second mixed solution; in the second mixed solution, the mass percentage c1 of the solute containing MDI is 18%.

[0184] S3: The second mixed liquid is fed into a hydrogen chloride stripping tower, the operating pressure of the stripping tower is 6 bar, the tower bottom temperature is 215°C, and the tower top reflux ratio R is 0.04. HCl gas is introduced from the tower bottom for stripping, and the mass ratio of the stripped HCl gas to the mass of the solute in the second mixed liquid fed is m1:m2=0.02:1; the contact time t of the gas containing stripped HCl in the tower and the second mixed liquid is controlled to be 0.5min, and the gas phase flow rate v in the tower is 16m / s, and a third mixed liquid after stripping treatment is obtained in the tower bottom. Among them, the mass percentage c2 of the solute containing MDI in the third mixed liquid is 45%.

[0185] S4: The third mixed liquid is subjected to dechlorobenzene treatment under the conditions of 30 kPa and 195° C., and the dechlorobenzeneed MDI (i.e., the reaction liquid after desolventization) is sent to a nitrogen stripping tower for treatment at 35 kPa and 190° C., and the mass ratio of nitrogen to the reaction liquid after desolventization is controlled to be 0.04, and a crude MDI product is obtained in the bottom of the tower. The crude MDI product is tested by a colorimeter, and its L* is measured to be 80; the solvent content in the crude MDI product is 1400 ppm.

[0186] Table 1 below lists the parameters related to the stripping process and the L* values ​​of the obtained products of various examples.

[0187] Table 1

[0188]

[0189]

[0190] The difference between Examples 1 to 1-6 is that the reflux ratio R of the stripping tower in step S3 is different. According to the results in Table 1, the L* of the products obtained in Examples 1 to 1-4 is higher than the L* of the products in Examples 1-5 and 1-6, and further, the L* of the products obtained in Examples 1, 1-2, and 1-3 is higher than the L* of the products in Examples 1-1 and 1-4. Therefore, the reflux ratio R of the stripping tower in step S3 is preferably 0.05 to 0.2, and more preferably 0.08 to 0.15.

[0191] The difference between Examples 1, 2 to 2-5 is that in step S3, the contact time t between the second mixed liquid and the gaseous substance containing HCl gas is different. According to the results in Table 1, the L* of the products obtained in Examples 1, 2-1 to 2-4 is higher than the L* of the products in Examples 2 and 2-5, and further, the L* of the products obtained in Examples 1, 2-1 and 2-2 is higher than the L* of the products in Examples 2-3 and 2-4. Therefore, in step S3, the contact time t between the second mixed liquid and the gaseous substance containing HCl gas is preferably 3 to 10 minutes, more preferably 3 to 6 minutes, and even more preferably 5 to 6 minutes.

[0192] The difference between Examples 1, 3 to 3-4 is that in step S3, the flow rate v of the gas phase material in the stripping tower is different. According to the results in Table 1, the L* of the products obtained in Examples 1, 3 to 3-3 is higher than the L* of the product in Example 3-4, further, the L* of the products obtained in Examples 1, 3-1 to 3-3 is higher than the L* of the product in Example 3, and further, the L* of the products obtained in Examples 1, 3-1 and 3-2 is higher than the L* of the product in Example 3-3. Therefore, in step S3, the flow rate v of the gas phase material is preferably 2 to 15 m / s, more preferably 5 to 15 m / s, and even more preferably 5 to 10 m / s.

[0193] The difference between Examples 1, 4 to 4-6 is that in step S3, the mass ratio m1:m2 of the stripping HCl gas to the mass ratio of the solute in the second mixed solution of the feed is different. According to the results in Table 1, the L* of the products obtained in Examples 1, 4-2 to 4-6 is higher than the L* of the products in Examples 4 and 4-1, and further, the L* of the products obtained in Examples 1, 4-2 to 4-5 is higher than the L* of the products in Example 4-6, and further, the L* of the products obtained in Examples 1, 4-3 and 4-4 is higher than the L* of the products in Examples 4-2 and 4-5. Therefore, the value of m1:m2 is preferably (0.05-0.25):1, further preferably (0.05-0.2):1, further preferably (0.05-0.15):1, and further preferably (0.08-0.1):1.

[0194] The difference between Examples 1, 5 to 5-5 is that the mass percentage c1 of the solute in the second mixed solution is different. According to the results in Table 1, the L* of the products obtained in Examples 1, 5-1 to 5-4 is higher than the L* of the product in Example 5, 5-1. Further, the L* of the products obtained in Examples 1, 5-2 to 5-4 is higher than the L* of the product in Example 5-1. Further, the L* of the products obtained in Examples 1, 5-2 and 5-3 is higher than the L* of the product in Example 5-4. Therefore, c1 is preferably 15 to 35%, more preferably 23 to 35%, and even more preferably 23 to 30%.

[0195] The difference between Examples 1, 6 to 6-6 is that the mass percentage c2 of the solute in the third mixed solution is different. According to the results in Table 1, the L* of the products obtained in Examples 1, 6-1 to 6-5 is higher than the L* of the products in Examples 6 and 6-6, and further, the L* of the products obtained in Examples 1, 6-2 to 6-5 is higher than the L* of the product in Example 6-1, and further, the L* of the products obtained in Examples 1, 6-3 and 6-4 is higher than the L* of the products in Examples 6-2 and 6-5. Therefore, c2 is preferably 40 to 65%, more preferably 45 to 65%, and even more preferably 50 to 60%.

[0196] Unless otherwise defined, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0197] 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 preparing diisocyanates and polyisocyanates of a diphenylmethane series, comprising the following steps: S1: performing a phosgenation reaction on a diphenylmethane series diamine and polyamine with phosgene in a solvent to obtain a first mixed solution; S2: removing phosgene from the first mixed solution to obtain a second mixed solution; S3: stripping the second mixed liquid with HCl gas to obtain a third mixed liquid; and S4: removing the solvent from the third mixed liquid to obtain crude diisocyanates and polyisocyanates of the diphenylmethane series; in, The stripping treatment in step S3 is carried out in a stripping tower, the reflux ratio R of the stripping tower is 0.05-0.3, the contact time t between the second mixed liquid and the gaseous material containing HCl gas in the stripping tower is 1-10 min, the flow rate v of the gaseous material in the stripping tower is 2-15 m / s, the mass ratio of the HCl gas to the solute of the second mixed liquid is m1:m2=(0.03-0.2):1; the mass percentage content c1 of the solute of the second mixed liquid is 15-35%; the mass percentage content c2 of the solute of the third mixed liquid is 40-65%.

2. The preparation method according to claim 1, wherein The contact time t between the second mixed liquid and the gas phase material containing HCl gas in the stripping tower is 3 to 6 minutes, and can further be 5 to 6 minutes.

3. The preparation method according to claim 1, wherein The reflux ratio R of the stripping tower is 0.05 to 0.2, and can further be 0.08 to 0.

15.

4. The preparation method according to claim 1, wherein The flow velocity v of the gas phase material in the stripping tower may be 5 to 15 m / s, and further may be 5 to 10 m / s.

5. The preparation method according to claim 1, wherein c1 is 23-35%, and can further be 23-30%; c3 is the mass percentage of the solvent in the second mixed solution, and the sum of c1 and c3 is 100%; and / or, c2 is 45-65%, and can further be 50-60%; c4 is the mass percentage of the solvent in the third mixed liquid, and the sum of c2 and c4 is 100%.

6. The preparation method according to claim 1, wherein The mass ratio of the HCl gas to the solute of the second mixed liquid is m1:m2=(0.05-0.25):1, further can be (0.05-0.2):1, further can be (0.05-0.15):1, and further can be (0.08-0.1):

1.

7. The preparation method according to claim 6, wherein: R, t, v, m1, m2, c1, c2 satisfy the following relationship:

8. The preparation method according to claim 1, wherein The operating temperature of the stripping tower is 130-210° C., further 160-190° C.; and / or, The operating pressure of the stripping tower is 1 to 5 bar, further 2 to 4 bar; and / or, The L* of the crude diisocyanate and polyisocyanate of the diphenylmethane series is 85-93.

9. A method for preparing diisocyanates and polyisocyanates of a diphenylmethane series, comprising the following steps: S1: performing a phosgenation reaction on a diphenylmethane series diamine and polyamine with phosgene in a solvent to obtain a first mixed solution; S2: removing phosgene from the first mixed solution to obtain a second mixed solution; S3: stripping the second mixed liquid with HCl gas to obtain a third mixed liquid; and S4: removing the solvent from the third mixed liquid to obtain crude diisocyanates and polyisocyanates of the diphenylmethane series; in, The stripping treatment in step S3 is carried out in a stripping tower, R represents the reflux ratio of the stripping tower; t represents the contact time between the second mixed liquid and the gaseous substance containing HCl gas in the stripping tower, in minutes; v represents the flow rate of the gaseous substance in the stripping tower, in m / s; m1 represents the mass flow rate of HCl gas during the stripping treatment, in t / h; m2 represents the mass flow rate of the solute in the second mixed liquid during the stripping treatment, in t / h; c1 represents the mass percentage of the solute in the second mixed liquid, and c2 represents the mass percentage of the solute in the third mixed liquid; R, t, v, m1, m2, c1, and c2 satisfy the following relationship:

10. A diphenylmethane series of diisocyanate and polyisocyanate products, prepared by the preparation method according to any one of claims 1 to 9.

Images