Preparation method and application of diamine and polyamine of diphenylmethane series

Abstract

The invention relates to a preparation method and application of diphenylmethane series diamine and polyamine, and the preparation method comprises the following steps: reacting aniline with an acidic compound to obtain aniline salt; reacting the aniline salt with formaldehyde, and neutralizing the obtained product with alkali liquor to obtain a DAM crude product; wherein the total content of oxidizing substances in the raw materials is less than or equal to 50 ppm, and the total content of metal ions is 0-10 ppm; the raw materials comprise the aniline, the formaldehyde, the acidic compound and the alkali liquor. According to the preparation method of diphenylmethane series diamine and polyamine in one embodiment, the content of impurities, especially metal ions, in the raw materials is regulated and controlled, so that the color number of the prepared DAM product can be reduced, and the quality of the DAM product can be improved.

Description

Technical Field

[0001] The present invention relates to diphenylmethane series diamines and polyamines, and in particular to the preparation and application of diphenylmethane series diamines and polyamines. Background Art

[0002] Diamines and polyamines of the diphenylmethane series (DAM) are amines and mixtures of amines having the following structure:

[0003]

[0004] Wherein, n represents an integer ≥ 0, and the compound when n = 0 is called "diaminodiphenylmethane", referred to as "diamine"; when n>0, it is called "polyaminopolyphenylmethane", referred to as "polyamine", and the mixture of these two types is called diamine and polyamine of diaminodiphenylmethane series (referred to as "diamine and polyamine"). Among them, the product derived from the replacement of all -NH2 groups in DAM with -NCO groups is diisocyanate of diaminodiphenylmethane series, polyisocyanate of diaminodiphenylmethane series or polyiminopolyphenylenepolymethylene polyisocyanate or diisocyanate and polyisocyanate of diaminodiphenylmethane series (hereinafter referred to as MDI), which can be used to produce polyurethane.

[0005] The preparation method of DAM is well known. It can be prepared by a continuous, semi-continuous or discontinuous reaction process. Usually, aniline is reacted with hydrochloric acid to form aniline acid salt, and then formaldehyde is added to the reactor to form DAM acid salt. The crude DAM is obtained through neutralization and water washing processes and separation of the organic phase and the inorganic phase. The DAM product is obtained through a refining process, and then a phosgenation reaction is performed to generate monomer or polymer MDI.

[0006] The color number of DAM products is a key indicator that affects the quality of the final MDI product. If the color number of DAM increases, the quality of the MDI series products after the phosgenation reaction will decrease, and ultimately lead to insufficient color quality of downstream polyurethane foam materials or other polyurethane (PU) materials. Therefore, the preparation technology of low-color DAM is the key to the preparation method of high-quality MDI. Summary of the invention

[0007] In order to overcome at least one defect of the above-mentioned prior art, in a first aspect, one embodiment of the present invention provides a method for preparing diamines and polyamines of a diphenylmethane series, comprising the following steps:

[0008] reacting aniline with an acidic compound to obtain an aniline salt;

[0009] The aniline salt is reacted with formaldehyde and then the obtained product is neutralized with alkali solution to obtain a crude DAM product;

[0010] The total content of oxidizing substances in the raw materials is ≤50 ppm, and the total content of metal ions is 0-10 ppm; the raw materials include aniline, formaldehyde, acidic compounds and alkali solution.

[0011] In a second aspect, an embodiment of the present invention provides a method for preparing diphenylmethane series diisocyanates and polyisocyanates, comprising preparing diphenylmethane series diisocyanates and polyisocyanates using diphenylmethane series diamines and polyamine products prepared by the above-mentioned preparation method.

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

[0013] reacting aniline with an acidic compound to obtain an aniline salt;

[0014] The aniline salt is reacted with formaldehyde and then the obtained product is neutralized with alkali solution to obtain a crude DAM product;

[0015] Refining the crude DAM product to obtain a DAM product; and

[0016] The DAM product is subjected to a phosgenation reaction to prepare diisocyanates and polyisocyanates of the diphenylmethane series;

[0017] The total content of oxidizing substances in the raw materials is ≤50ppm, and the total content of metal ions is 0-10ppm; the raw materials include the aniline, the formaldehyde, the acidic compound and the alkali solution; the color index I is ≤1.0, and the color index I is calculated by the following formula:

[0018] I=0.0024c1+0.2421lnc2-0.0003T+0.0013t+0.1279

[0019] Wherein, c1 is the total content of oxidizing substances in the raw material in ppm, c2 is the total content of metal ions in the raw material in ppm, T is the temperature of the refining treatment in ° C, and t is the time interval from the completion of the preparation of the diphenylmethane series diamine and polyamine products to their use in the phosgenation reaction, and the time interval is in hours.

[0020] The method for preparing diphenylmethane series diamines and polyamines according to one embodiment of the present invention can reduce the color number of the obtained DAM product and improve the quality of the DAM product by regulating the content of impurities, especially metal ions, in the raw materials. DETAILED DESCRIPTION

[0021] 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.

[0022] One embodiment of the present invention provides a method for preparing diamines and polyamines of a diphenylmethane series, comprising the following steps:

[0023] reacting aniline with an acidic compound to obtain an aniline salt;

[0024] After reacting aniline salt with formaldehyde, the resulting product is neutralized with alkali solution to obtain crude diamines and polyamines of the diphenylmethane series (crude DAM);

[0025] The total content of oxidizing substances in the raw materials is ≤50ppm, and the total content of metal ions is ≤10ppm; the raw materials include aniline, formaldehyde, acidic compounds and alkali solution.

[0026] In one embodiment, the crude DAM product is subjected to a refining treatment to obtain diphenylmethane series diamine and polyamine products (DAM products).

[0027] One embodiment of the present invention provides a method for preparing diphenylmethane series diisocyanates and polyisocyanates (MDI), comprising preparing diphenylmethane series diisocyanates and polyisocyanates using the DAM product prepared by the above method.

[0028] In one embodiment, during the preparation of MDI, the color index I≤1.0, where I is calculated by the following formula:

[0029] I=0.0024c1+0.2421lnc2-0.0003T+0.0013t+0.1279

[0030] Wherein, c1 is the total content of oxidizing substances in the raw materials for preparing the DAM product in ppm, c2 is the total content of metal ions in the raw materials for preparing the DAM product in ppm, T is the temperature of the refining treatment in °C, and t is the time interval from the refining treatment to the use of the DAM product for phosgenation reaction, and the time interval is in hours.

[0031] In one embodiment, the color index I≤1.0, and further, the value of I can be 0.08-1.0, for example, 0.08, 0.09, 0.1, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9.

[0032] In one embodiment, the total content of oxidizing substances in the raw material is ≤50ppm, and further can be 2-43ppm, such as 2ppm, 4ppm, 5ppm, 8ppm, 10ppm, 15ppm, 20ppm, 25ppm, 30ppm, 31ppm, 35ppm, 40ppm, 43ppm. Correspondingly, the value of c1 can be ≤50, and further can be 2-43, such as 2, 4, 5, 8, 10, 15, 20, 25, 30, 31, 35, 40, 43.

[0033] In one embodiment, the oxidizing substance in the raw material can be oxygen or a chlorine-containing compound. Further, the oxidizing substance includes one or more of chlorine, hypochlorous acid, perchloric acid, hypochlorite, chlorate, perchlorate, benzoquinone, imine, and azobenzene.

[0034] In one embodiment, aniline, the acidic compound and the alkali solution all contain oxidizing substances, wherein the oxidizing substance in the acidic compound can be one or more of chlorine, hypochlorous acid, and perchloric acid; the oxidizing substance in the alkali solution can be one or more of hypochlorite, chlorate, and perchlorate; the oxidizing substance in the aniline can be one or more of benzoquinone, imine, and azobenzene.

[0035] In one embodiment, the mass of the oxidizing substance in the acidic compound and the alkali solution can be measured by potentiometric titration, for example, by reacting the oxidizing substance with potassium iodide to convert iodine ions into elemental iodine, and then using sodium thiosulfate to titrate and measure the amount (moles) of the elemental iodine, and then calculating the moles of the oxidizing substance reacting with it according to the moles of the elemental iodine, and multiplying the moles of the oxidizing substance by its relative molecular mass to obtain the mass of the oxidizing substance. Wherein, the moles and relative molecular mass of the oxidizing substance in the acidic compound and the alkali solution are calculated according to the moles and relative molecular mass of the chloride ions.

[0036] In one embodiment, the oxidizing substance content in aniline can be measured by gas chromatography analysis.

[0037] In one embodiment, the total content of oxidizing substances in the raw materials refers to the sum of the contents of oxidizing substances in aniline, acidic compounds and alkali solution, that is, the sum of the content of oxidizing substances in aniline, the content of oxidizing substances in acidic compounds and the content of oxidizing substances in alkali solution.

[0038] In one embodiment, the oxidizing substances can be removed by mixing the raw materials with a reducing agent or an antioxidant (such as sodium sulfite, hydrogen peroxide, etc.) to control their content; wherein the amount of the reducing agent can be 1.2 to 2.0 times the content of the oxidizing substances.

[0039] In one embodiment, raw materials such as aniline, acidic compounds, formaldehyde and alkali solution may contain metal ions that are easy to coordinate or complex with organic matter, such as one or more of iron ions, chromium ions, nickel ions, copper ions and aluminum ions. These metal ions are easy to coordinate or complex with organic amine compounds to form color-forming substances, thereby affecting the color number of the DAM product.

[0040] In one embodiment, the content of metal ions in the raw material can be regulated by using demetallizing resins, chelating agents, flocculants, etc.

[0041] In one embodiment, the total content of metal ions in the raw materials refers to the sum of the content of metal ions in aniline, acidic compounds, formaldehyde, and alkali solution.

[0042] In one embodiment, the total content of metal ions in the raw material is 0 to 10 ppm, such as 1 ppm, 2 ppm, 2.5 ppm, 4 ppm, 5 ppm, 6 ppm, 8 ppm, 10 ppm. Accordingly, the value of c2 can be 0 to 10, and further can be 1 to 10, such as 1, 2, 2.5, 4, 5, 6, 8, 10. When c2 is 0, the value of lnc2 is equal to 0.

[0043] In one embodiment, the crude DAM product may be subjected to a refining treatment to remove impurities such as aniline and water to obtain a DAM product. Further, the refining treatment includes a distillation treatment.

[0044] In one embodiment, the refining treatment of the crude DAM product includes distillation treatment through a distillation tower, and may further be vacuum distillation treatment.

[0045] In one embodiment, the temperature of the refining treatment (or the temperature of the bottom of the distillation tower) can be 180-210° C., for example, 183° C., 185° C., 188° C., 190° C., 193° C., 195° C., 198° C., 200° C., 203° C., 205° C., 208° C., 210° C. Correspondingly, the value of T can be 180-210, for example, 183, 185, 188, 190, 193, 195, 198, 200, 203, 205, 208, 210.

[0046] In one embodiment, the pressure of the refining treatment (or the pressure at the top of the distillation tower) can be 6 to 10 kPa (absolute pressure), for example, 6.5 kPa, 6.9 kPa, 7.0 kPa, 7.4 kPa, 7.5 kPa, 8.0 kPa, 8.5 kPa, 8.8 kPa, 9.0 kPa, 9.4 kPa, and 10 kPa.

[0047] In one embodiment, the time interval between the preparation of the DAM product and the delivery to the downstream for phosgenation reaction to prepare MDI is t hours, which includes the transportation time and the possible storage time, which can be ≤192 hours, and further can be 10 to 192 hours, such as 10 hours, 20 hours, 30 hours, 50 hours, 60 hours, 62 hours, 70 hours, 80 hours, 90 hours, 100 hours, 103 hours, 110 hours, 130 hours, 135 hours, 140 hours, 150 hours, 180 hours, 190 hours. Accordingly, the value of t can be ≤192, and further can be 10 to 192, such as 10, 20, 30, 50, 60, 62, 70, 80, 90, 100, 103, 110, 130, 135, 140, 150, 180, 190.

[0048] In one embodiment, the acidic compound includes one or more of hydrogen chloride, sulfuric acid, phosphoric acid, and methanesulfonic acid; wherein the acidic compound may exist in the form of a solution, for example, hydrogen chloride may exist in the form of hydrochloric acid, and the mass percentage of HCl in the hydrochloric acid may be 10 to 37%, for example, 15%, 20%, 25%, 30%, 34%, 35%.

[0049] In one embodiment, the acidic compound is hydrogen chloride, which may be present in the form of hydrochloric acid or HCl gas, and the molar ratio of HCl (or HCl gas) in the hydrochloric acid to aniline may be 0.03 to 1.0, and may further be 0.05 to 0.40, for example 0.04, 0.08, 0.1, 0.2, 0.25, 0.30, 0.35, 0.38, 0.50, 0.80.

[0050] In one embodiment, formaldehyde exists in the form of gas or aqueous solution, and the mass concentration of the formaldehyde aqueous solution can be 20-55%, for example, 25%, 30%, 35%, 37%, 40%, 45%, 50%; the molar ratio of formaldehyde to aniline can be 0.1-0.8, for example, 0.2, 0.4, 0.5, 0.6, 0.7.

[0051] In one embodiment, the alkali solution is an aqueous solution of an alkaline substance, and the alkaline substance includes hydroxides of alkali metals and / or alkaline earth metals, such as sodium hydroxide and potassium hydroxide.

[0052] In one embodiment, the alkali solution may be a sodium hydroxide aqueous solution, and its mass concentration may be 30-55%, and further may be 40-50%, for example, 32%, 35%, 42%, 45%, or 48%.

[0053] In one embodiment, the OH contained in the alkali solution - H+ The molar ratio of sodium hydroxide added to the alkali solution to hydrogen chloride added to the hydrochloric acid can be 1.02 to 1.40, and can further be 1.04 to 1.30, such as 1.05, 1.1, or 1.2. That is, the molar ratio of sodium hydroxide added to the alkali solution to hydrogen chloride added to the hydrochloric acid can be 1.02 to 1.40, and can further be 1.04 to 1.30.

[0054] In one embodiment, the preparation of diamines and polyamines of the diphenylmethane series comprises the following steps:

[0055] S1: reacting aniline with an acidic compound to obtain an aniline salt;

[0056] S2: performing condensation reaction and transposition reaction on the aniline salt and formaldehyde to obtain a reaction solution including a reaction product;

[0057] S3: mixing the reaction solution with an alkali solution for neutralization reaction, and then washing with water to obtain a crude DAM product;

[0058] S4: Refining the crude DAM product to obtain a DAM product.

[0059] In one embodiment, the reaction temperature of the condensation reaction in step S2 can be 40-100°C, for example, 50°C, 60°C, 70°C, 75°C, 80°C, 85°C, 90°C; the reaction time of the condensation reaction can be 1-2 hours, for example, 1.5 hours.

[0060] In one embodiment, the reaction temperature of the transposition reaction in step S2 can be 80-150°C, and can further be 105-140°C, for example, 100°C, 110°C, 120°C, 130°C; the reaction time of the transposition reaction can be 1-5 hours, for example, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 4 hours.

[0061] In one embodiment, the platinum-cobalt color number of the prepared DAM product is ≤200#, and can further be ≤180#, such as 80#, 118#, 120#, 140#, 160#, 163#, 165#. The platinum-cobalt color number of the DAM product is measured by the platinum-cobalt color number method.

[0062] In one embodiment, the platinum-cobalt color number of the prepared DAM product is 80-200#, and can further be 80-180#.

[0063] One embodiment of the present invention provides a method for preparing and applying diphenylmethane series diamines and polyamines, comprising the following steps:

[0064] reacting aniline with an acidic compound to obtain an aniline salt;

[0065] After reacting aniline salt with formaldehyde, the resulting product is neutralized with alkali solution to obtain crude diamines and polyamines of the diphenylmethane series (i.e. crude DAM);

[0066] Refining the crude DAM product to obtain a DAM product; and

[0067] Phosgenation of DAM products to prepare diisocyanates and polyisocyanates (MDI) of the diphenylmethane series;

[0068] The total content of oxidizing substances in the raw materials is ≤50ppm, and the total content of metal ions is ≤10ppm; the raw materials include aniline, formaldehyde, acidic compounds and alkali solution.

[0069] In one embodiment, in the preparation and application of DAM products, the color index I≤1.0, where I is calculated by the following formula:

[0070] I=0.0024c1+0.2421lnc2-0.0003T+0.0013t+0.1279

[0071] Wherein, c1 is the total content of oxidizing substances in the raw material in ppm, c2 is the total content of metal ions in the raw material in ppm, T is the temperature of the refining treatment in ° C, and t is the time interval from the refining treatment to the use of the DAM product for phosgenation reaction, and the time interval is in hours.

[0072] In one embodiment, the raw materials and processes involved in the preparation and application of diphenylmethane series diamines and polyamines can refer to the above description.

[0073] The preparation method of one embodiment of the present invention can obtain high-quality DAM products by controlling key parameters such as the content of impurities such as oxidizing substances and metal ions in the preparation raw materials and the refining treatment temperature.

[0074] The method of one embodiment of the present invention can keep the platinum-cobalt color number of the DAM product used to prepare MDI at ≤200# by controlling the color number index I within the range of ≤1.0. As an important raw material in the MDI production process, the use of low-color number DAM products plays a key role in reducing the process complexity or energy consumption in the MDI preparation process.

[0075] A method according to one embodiment of the present invention controls the color index I within a range of ≤1.0. The calculation formula of the color index I covers important indicators that affect the quality of DAM products during the production and use of DAM, such as the content of specific impurities in the raw materials, the refining treatment temperature, and the specific interval time, thereby avoiding the incompleteness of single indicator control; at the same time, the generation control of color-forming substances that affect the color number of DAM products is reduced from the source, and the subsequent process of removing impurities through complex processes and operations is avoided.

[0076] The method of one embodiment of the present invention improves the flexibility of quality control of DAM products in MDI preparation. For example, if the impurities such as metal ions in the preparation raw materials are high, the color number of the DAM product can be reduced by adjusting the refining temperature and / or the interval time of application.

[0077] The preparation and application of diphenylmethane series diamines and polyamines according to one embodiment of the present invention are further described below in conjunction with examples. The raw materials and test methods involved in each example and comparative example are as follows.

[0078] raw material

[0079] Aniline, formaldehyde, hydrochloric acid, sodium hydroxide: all from Wanhua Chemical Co., Ltd.

[0080] Test Method

[0081] 1. Determination of oxidizing substances in acidic compounds and alkali solutions

[0082] Take 100ml of clean water, accurately weigh 1g of raw material as m; add the raw material into the clean water, add excess potassium iodide into it, and store it in the dark for ten minutes to obtain the test mixture. After that, use sodium thiosulfate solution to directly titrate the test mixture. The concentration of sodium thiosulfate solution is C (mol / L), and the volume of sodium thiosulfate solution used for titration is V (ml). The calculation formula of oxidizing substances is: X = (C*V*0.001*71*0.5) / m%.

[0083] 2. Determination of oxidizing substances in aniline

[0084] The content of oxidizing substances in aniline was measured by gas chromatography, and the contents of benzoquinone, imine and azobenzene in aniline were determined by external standard method using Agilent 7890BHP-5 (30m*0.53mm*1.5um) chromatographic column.

[0085] 3. Determination method of metal ion content

[0086] ICP was used to determine the metal ion content of the raw materials. The instrument used was Agilent (ICP-OES-725), the plasma flow rate was 15 L / min, the auxiliary gas flow rate was 1.5 L / min, the observation height was 10 mm, and the content of the corresponding metal was obtained according to the corresponding wavelengths of different metal elements (such as Fe-238.204 nm, Cu-327.395 nm).

[0087] 4. Measurement of platinum-cobalt color number

[0088] The color number of DAM product is determined by platinum-cobalt color number method. Use a measuring cylinder to measure 10mL of chlorobenzene and add it to a 50mL colorimetric tube. Use a disposable dropper to weigh 10.00g (accurate to 0.01g) of DAM product into the colorimetric tube. Use chlorobenzene to make up to the scale and then compare the color with the standard color scale. Report the result with the platinum-cobalt color number of the standard color scale that is closest to it.

[0089] Example 1

[0090] S1: adding hydrochloric acid solution (mass concentration of 34%) and aniline (mass concentration of 93.5%) into a reactor at a molar ratio of 0.38:1 to react and generate aniline hydrochloride.

[0091] S2: Add formaldehyde aqueous solution (mass concentration is 30%) dropwise into the reactor of step S1, the molar ratio of formaldehyde to aniline is 0.4, and carry out condensation reaction at 80°C for 1.5 hours; then add the material to the transfer kettle and transfer at 80°C for 5 hours to obtain a transfer liquid (reaction liquid).

[0092] S3: The translocation liquid obtained in step S2 is mixed with 50% sodium hydroxide solution, and the molar ratio of alkali solution (calculated as sodium hydroxide) to hydrochloric acid (hydrochloric acid in step S1, calculated as hydrogen chloride) is 1.20; the obtained mixed solution is allowed to stand in a phase separator for phase separation, and the upper organic phase is washed with pure water to obtain a crude DAM product.

[0093] S4: The crude DAM product is passed through a negative pressure distillation tower to remove impurities such as water and aniline to obtain a DAM product; wherein the top pressure of the distillation tower is 6.5 kPa and the bottom temperature of the tower is 210° C. The DAM product is subjected to a phosgenation reaction 10 hours after the preparation to prepare MDI.

[0094] The total content of oxidizing substances in the raw materials aniline, formaldehyde, hydrochloric acid and alkali solution is 2ppm, and the total content of metal ions that are easily coordinated or complexed with organic matter is 1.0ppm. Before the phosgenation reaction (i.e., 10h after the preparation), the DAM product is tested for platinum-cobalt color number. The color index I and platinum-cobalt color number results are shown in Table 1.

[0095] Example 2

[0096] S1: adding hydrochloric acid solution (mass concentration of 20%) and aniline (mass concentration of 94%) into a reactor at a molar ratio of 0.5:1 to react and generate aniline hydrochloride.

[0097] S2: Add formaldehyde aqueous solution (mass concentration is 37%) dropwise into the reactor of step S1, the molar ratio of formaldehyde to aniline is 0.8, and carry out condensation reaction at 60°C for 1 hour; then add the material to the transfer kettle and transfer at 100°C for 2 hours to obtain a transfer liquid (reaction liquid).

[0098] S3: The translocation liquid obtained in step S2 is mixed with 30% sodium hydroxide solution, and the molar ratio of alkali solution (calculated as sodium hydroxide) to hydrochloric acid (hydrochloric acid in step S1, calculated as hydrogen chloride) is 1.30; the obtained mixed solution is allowed to stand in a phase separator for phase separation, and the upper organic phase is washed with pure water to obtain a crude DAM product.

[0099] S4: The crude DAM product is passed through a negative pressure distillation tower to remove impurities such as water and aniline to obtain a DAM product; wherein the top pressure of the distillation tower is 6.9 kPa and the bottom temperature of the tower is 203° C. The DAM product is subjected to a phosgenation reaction 30 hours after the preparation to prepare MDI.

[0100] Among them, the total content of oxidizing substances in the above raw materials aniline, formaldehyde, hydrochloric acid and alkali solution is 10ppm, and the total content of metal ions that are easily coordinated or complexed with organic matter is 2.5ppm. Before the phosgenation reaction (i.e. 30h after the preparation is completed), the DAM product is tested for platinum-cobalt color number. The color number index I and platinum-cobalt color number results are shown in Table 1.

[0101] Example 3

[0102] S1: HCl gas and aniline (mass concentration is 93%) are added into a reactor at a molar ratio of 0.30:1 to react and generate aniline hydrochloride.

[0103] S2: Add formaldehyde aqueous solution (mass concentration is 55%) dropwise into the reactor of step S1, the molar ratio of formaldehyde to aniline is 0.5, and carry out condensation reaction at 40°C for 2h; then add the material to the transfer kettle and transfer at 140°C for 1h to obtain a transfer liquid (reaction liquid).

[0104] S3: The translocation liquid obtained in step S2 is mixed with 40% sodium hydroxide solution, and the molar ratio of the alkali solution (calculated as sodium hydroxide) to the hydrogen chloride in step S1 is 1.40; the obtained mixed solution is allowed to stand in a phase separator for phase separation, and the upper organic phase is washed with pure water to obtain a crude DAM product.

[0105] S4: The crude DAM product is passed through a negative pressure distillation tower to remove impurities such as water and aniline to obtain a DAM product; wherein the top pressure of the distillation tower is 7.4 kPa and the bottom temperature of the tower is 200° C. The DAM product is subjected to a phosgenation reaction 62 hours after the preparation to prepare MDI.

[0106] Among them, the total content of oxidizing substances in the above raw materials aniline, formaldehyde, hydrogen chloride and alkali solution is 22ppm, and the total content of metal ions that are easily coordinated or complexed with organic matter is 4.0ppm. Before the phosgenation reaction (i.e. 62h after the preparation is completed), the DAM product is tested for platinum-cobalt color number. The color index I and platinum-cobalt color number results are shown in Table 1.

[0107] Example 4

[0108] S1: HCl gas and aniline (mass concentration is 93%) are added into a reactor at a molar ratio of 0.04:1 to react and generate aniline hydrochloride.

[0109] S2: Add formaldehyde gas into the reactor of step S1, the molar ratio of formaldehyde to aniline is 0.2, and carry out condensation reaction at 50°C for 2h; then add the material into the transfer kettle and transfer at 150°C for 1h to obtain a transfer liquid (reaction liquid).

[0110] S3: The translocation liquid obtained in step S2 is mixed with 40% sodium hydroxide solution, and the molar ratio of the alkali solution (calculated as sodium hydroxide) to the hydrogen chloride in step S1 is 1.20; the obtained mixed solution is allowed to stand in a phase separator for phase separation, and the upper organic phase is washed with pure water to obtain a crude DAM product.

[0111] S4: The crude DAM product is passed through a negative pressure distillation tower to remove impurities such as water and aniline to obtain a DAM product; wherein the top pressure of the distillation tower is 8.8 kPa and the bottom temperature of the tower is 195° C. The DAM product is subjected to a phosgenation reaction 103 hours after the preparation to prepare MDI.

[0112] Among them, the total content of oxidizing substances in the above raw materials aniline, formaldehyde, hydrogen chloride and alkali solution is 31ppm, and the total content of metal ions that are easily coordinated or complexed with organic matter is 6.0ppm. Before the phosgenation reaction (i.e., 103h after the preparation is completed), the DAM product is tested for platinum-cobalt color number. The color number index I and platinum-cobalt color number results are shown in Table 1.

[0113] Example 5

[0114] S1: adding hydrochloric acid solution (mass concentration of 34%) and aniline (mass concentration of 93%) into a reactor at a molar ratio of 0.25:1 to react and generate aniline hydrochloride.

[0115] S2: Add formaldehyde aqueous solution (mass concentration is 40%) dropwise into the reactor of step S1, the molar ratio of formaldehyde to aniline is 0.6, and carry out condensation reaction at 100°C for 1 hour; then add the material to the transfer kettle and transfer at 120°C for 1 hour to obtain a transfer liquid (reaction liquid).

[0116] S3: The translocation liquid obtained in step S2 is mixed with 55% sodium hydroxide solution, and the molar ratio of alkali solution (calculated as sodium hydroxide) to hydrochloric acid (hydrochloric acid in step S1, calculated as hydrogen chloride) is 1.10; the obtained mixed solution is allowed to stand in a phase separator for phase separation, and the upper organic phase is washed with pure water to obtain a crude DAM product.

[0117] S4: The crude DAM product is passed through a negative pressure distillation tower to remove impurities such as water and aniline to obtain a DAM product; wherein the top pressure of the distillation tower is 9.4 kPa and the bottom temperature of the tower is 188°C. The DAM product is subjected to phosgenation reaction 135 hours after the preparation to prepare MDI.

[0118] Among them, the total content of oxidizing substances in the above raw materials aniline, formaldehyde, hydrochloric acid and alkali solution is 43ppm, and the total content of metal ions that are easily coordinated or complexed with organic matter is 8.0ppm. Before the phosgenation reaction (i.e., 135h after the preparation is completed), the DAM product is tested for platinum-cobalt color number. The color index I and platinum-cobalt color number results are shown in Table 1.

[0119] Example 6

[0120] S1: adding hydrochloric acid solution (mass concentration of 10%) and aniline (mass concentration of 93%) into a reactor at a molar ratio of 0.8:1 to react and generate aniline hydrochloride.

[0121] S2: Add formaldehyde aqueous solution (mass concentration is 20%) dropwise into the reactor of step S1, the molar ratio of formaldehyde to aniline is 0.7, and carry out condensation reaction at 60°C for 1 hour; then add the material to the transfer kettle and transfer at 110°C for 2 hours to obtain a transfer liquid (reaction liquid).

[0122] S3: The translocation liquid obtained in step S2 is mixed with 32% sodium hydroxide solution, and the molar ratio of alkali solution (calculated as sodium hydroxide) to hydrochloric acid (hydrochloric acid in step S1, calculated as hydrogen chloride) is 1.05; the obtained mixed solution is allowed to stand in a phase separator for phase separation, and the upper organic phase is washed with pure water to obtain a crude DAM product.

[0123] S4: The crude DAM product is passed through a negative pressure distillation tower to remove impurities such as water and aniline to obtain a DAM product; wherein the top pressure of the distillation tower is 10 kPa and the bottom temperature of the tower is 183°C. The DAM product is subjected to a phosgenation reaction 192 hours after the preparation to prepare MDI.

[0124] The total content of oxidizing substances in the raw materials aniline, formaldehyde, hydrochloric acid and alkali solution is 50ppm, and the total content of metal ions that are easily coordinated or complexed with organic matter is 10ppm. Before the phosgenation reaction (i.e., 192h after the preparation), the DAM product was tested for platinum-cobalt color number. The color index I and platinum-cobalt color number results are shown in Table 1.

[0125] Comparative Example 1

[0126] S1: adding hydrochloric acid solution (mass concentration of 10%) and aniline (mass concentration of 93%) into a reactor at a molar ratio of 0.8:1 to react and generate aniline hydrochloride.

[0127] S2: Add formaldehyde aqueous solution (mass concentration is 20%) dropwise into the reactor of step S1, the molar ratio of formaldehyde to aniline is 0.7, and carry out condensation reaction at 60°C for 1 hour; then add the material to the transfer kettle and transfer at 110°C for 2 hours to obtain a transfer liquid (reaction liquid).

[0128] S3: The translocation liquid obtained in step S2 is mixed with 32% sodium hydroxide solution, and the molar ratio of alkali solution (calculated as sodium hydroxide) to hydrochloric acid (hydrochloric acid in step S1, calculated as hydrogen chloride) is 1.05; the obtained mixed solution is allowed to stand in a phase separator for phase separation, and the upper organic phase is washed with pure water to obtain a crude DAM product.

[0129] S4: The crude DAM product is passed through a negative pressure distillation tower to remove impurities such as water and aniline to obtain a DAM product; wherein the top pressure of the distillation tower is 10 kPa and the bottom temperature of the tower is 183°C. The DAM product is subjected to a phosgenation reaction 192 hours after the preparation to prepare MDI.

[0130] Among them, the total content of oxidizing substances in the above raw materials aniline, formaldehyde, hydrochloric acid and alkali solution is 58ppm, and the total content of metal ions that are easily coordinated or complexed with organic matter is 10ppm. Before the phosgenation reaction (i.e., 192h after the preparation is completed), the DAM product is tested for platinum-cobalt color number. The color number index I and platinum-cobalt color number results are shown in Table 1.

[0131] Comparative Example 2

[0132] S1: adding hydrochloric acid solution (mass concentration of 10%) and aniline (mass concentration of 93%) into a reactor at a molar ratio of 0.8:1 to react and generate aniline hydrochloride.

[0133] S2: Add formaldehyde aqueous solution (mass concentration is 20%) dropwise into the reactor of step S1, the molar ratio of formaldehyde to aniline is 0.7, and carry out condensation reaction at 60°C for 1 hour; then add the material to the transfer kettle and transfer at 110°C for 2 hours to obtain a transfer liquid (reaction liquid).

[0134] S3: The translocation liquid obtained in step S2 is mixed with 32% sodium hydroxide solution, and the molar ratio of alkali solution (calculated as sodium hydroxide) to hydrochloric acid (hydrochloric acid in step S1, calculated as hydrogen chloride) is 1.05; the obtained mixed solution is allowed to stand in a phase separator for phase separation, and the upper organic phase is washed with pure water to obtain a crude DAM product.

[0135] S4: The crude DAM product is passed through a negative pressure distillation tower to remove impurities such as water and aniline to obtain a DAM product; wherein the top pressure of the distillation tower is 10 kPa and the bottom temperature of the tower is 183°C. The DAM product is subjected to a phosgenation reaction 192 hours after the preparation to prepare MDI.

[0136] Among them, the total content of oxidizing substances in the above raw materials aniline, formaldehyde, hydrochloric acid and alkali solution is 50ppm, and the total content of metal ions that are easily coordinated or complexed with organic matter is 13ppm. Before the phosgenation reaction (i.e., 192h after the preparation is completed), the DAM product is tested for platinum-cobalt color number. The color index I and platinum-cobalt color number results are shown in Table 1.

[0137] Comparative Example 3

[0138] S1: adding hydrochloric acid solution (mass concentration of 10%) and aniline (mass concentration of 93%) into a reactor at a molar ratio of 0.8:1 to react and generate aniline hydrochloride.

[0139] S2: Add formaldehyde aqueous solution (mass concentration is 20%) dropwise into the reactor of step S1, the molar ratio of formaldehyde to aniline is 0.7, and carry out condensation reaction at 60°C for 1 hour; then add the material to the transfer kettle and transfer at 110°C for 2 hours to obtain a transfer liquid (reaction liquid).

[0140] S3: The translocation liquid obtained in step S2 is mixed with 32% sodium hydroxide solution, and the molar ratio of alkali solution (calculated as sodium hydroxide) to hydrochloric acid (hydrochloric acid in step S1, calculated as hydrogen chloride) is 1.05; the obtained mixed solution is allowed to stand in a phase separator for phase separation, and the upper organic phase is washed with pure water to obtain a crude DAM product.

[0141] S4: The crude DAM product is passed through a negative pressure distillation tower to remove impurities such as water and aniline to obtain a DAM product; wherein the top pressure of the distillation tower is 10 kPa and the bottom temperature of the tower is 183°C. The DAM product is subjected to a phosgenation reaction 216 hours after the preparation to prepare MDI.

[0142] The total content of oxidizing substances in the raw materials aniline, formaldehyde, hydrochloric acid and alkali solution is 50ppm, and the total content of metal ions that are easily coordinated or complexed with organic matter is 10ppm. Before the phosgenation reaction (i.e., 216h after the preparation), the DAM product is tested for platinum-cobalt color number. The color index I and platinum-cobalt color number results are shown in Table 1.

[0143] Comparative Example 4

[0144] S1: adding hydrochloric acid solution (mass concentration of 10%) and aniline (mass concentration of 93%) into a reactor at a molar ratio of 0.8:1 to react and generate aniline hydrochloride.

[0145] S2: Add formaldehyde aqueous solution (mass concentration is 20%) dropwise into the reactor of step S1, the molar ratio of formaldehyde to aniline is 0.7, and carry out condensation reaction at 60°C for 1 hour; then add the material to the transfer kettle and transfer at 110°C for 2 hours to obtain a transfer liquid (reaction liquid).

[0146] S3: The translocation liquid obtained in step S2 is mixed with 32% sodium hydroxide solution, and the molar ratio of alkali solution (calculated as sodium hydroxide) to hydrochloric acid (hydrochloric acid in step S1, calculated as hydrogen chloride) is 1.05; the obtained mixed solution is allowed to stand in a phase separator for phase separation, and the upper organic phase is washed with pure water to obtain a crude DAM product.

[0147] S4: The crude DAM product is passed through a negative pressure distillation tower to remove impurities such as water and aniline to obtain a DAM product; wherein the top pressure of the distillation tower is 17 kPa and the bottom temperature of the tower is 170°C. The DAM product is subjected to phosgenation reaction 192 hours after the preparation to prepare MDI.

[0148] The total content of oxidizing substances in the raw materials aniline, formaldehyde, hydrochloric acid and alkali solution is 50ppm, and the total content of metal ions that are easily coordinated or complexed with organic matter is 10ppm. Before the phosgenation reaction (i.e., 192h after the preparation), the DAM product was tested for platinum-cobalt color number. The color index I and platinum-cobalt color number results are shown in Table 1.

[0149] Table 1

[0150] Color Index I DAM platinum cobalt color number, # Example 1 0.0827 80 Example 2 0.352 118 Example 3 0.537 140 Example 4 0.711 163 Example 5 0.854 180 Example 6 1.000 200 Comparative Example 1 1.020 220 Comparative Example 2 1.064 245 Comparative Example 3 1.031 230 Comparative Example 4 1.004 205

[0151] According to the results in Table 1, by controlling the color index I of the MDI prepared in the embodiment of the present invention within 1.0, the platinum-cobalt color number of the raw material DAM product can be reduced.

[0152] Further, referring to Example 6 and Comparative Examples 1 to 4, it can be seen that the difference between Comparative Example 1 and Example 6 is that the total content of oxidizing substances in the raw materials of Comparative Example 1 is 58 ppm, and that in Example 6 is 50 ppm; the difference between Comparative Example 2 and Example 6 is that the total content of metal ions in the raw materials of Comparative Example 2 is 13 ppm, and that in Example 6 is 10 ppm; the difference between Comparative Example 3 and Example 6 is that the interval time from the completion of the preparation of the DAM product to the phosgenation reaction is different, which is 216 h for Comparative Example 3 and 192 h for Example 6; the difference between Comparative Example 4 and Example 6 mainly lies in that the temperature of the bottom of the distillation tower is different, which is 170°C for Comparative Example 4 and 183°C for Example 6.

[0153] Combining the above description and the results in Table 1, it can be seen that by controlling the content of oxidizing substances and metal ions in the raw materials for preparing DAM, the platinum-cobalt color number of the prepared DAM product can be reduced. Furthermore, by regulating the refining temperature and interval time, the value of the color index I can be adjusted, and the platinum-cobalt color number of the DAM product can be further reduced, thereby improving the quality of the DAM product.

[0154] Unless otherwise defined, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0155] 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 diamines and polyamines of a diphenylmethane series, comprising the following steps: reacting aniline with an acidic compound to obtain an aniline salt; The aniline salt is reacted with formaldehyde and then the obtained product is neutralized with alkali solution to obtain a crude DAM product; in, The total content of oxidizing substances in the raw materials is ≤50ppm, and the total content of metal ions is 0-10ppm; the raw materials include aniline, formaldehyde, acidic compounds and alkali solution.

2. The preparation method according to claim 1, wherein The crude DAM product is subjected to a refining treatment to obtain diphenylmethane series diamine and polyamine products; the refining treatment includes a distillation treatment, and the refining treatment temperature is 180-210°C.

3. A method for preparing diphenylmethane series diisocyanates and polyisocyanates, comprising preparing diphenylmethane series diisocyanates and polyisocyanates from diphenylmethane series diamines and polyamines obtained by the preparation method according to claim 1 or 2.

4. The preparation method according to claim 3, wherein: The color index I≤1.0, and the color index I is calculated by the following formula: I=0.0024c1+0.2421lnc2-0.0003T+0.0013t+0.1279 Wherein, c1 is the total content of oxidizing substances in the raw materials in ppm, c2 is the total content of metal ions in the raw materials in ppm, T is the temperature of the refining treatment in ° C, and t is the time interval from the completion of the preparation of the diphenylmethane series diamine and polyamine products to their use in the preparation of the diphenylmethane series diisocyanates and polyisocyanates, and the time interval is in hours.

5. The preparation method according to claim 4, wherein c1 is ≤50; and / or, c2 is 0 to 10; and / or, T is 180 to 210; and / or, t is ≤ 192; and / or, The alkali solution is an aqueous solution of an alkaline substance, wherein the alkaline substance includes hydroxides of alkali metals and / or alkaline earth metals; and / or, The aniline, the acidic compound and the alkali solution all contain oxidizing substances. The oxidizing substances in the acidic compound include one or more of chlorine, hypochlorous acid and perchloric acid. The oxidizing substances in the alkali solution include one or more of hypochlorite, chlorate and perchlorate. The oxidizing substances in the aniline include one or more of benzoquinone, imine and azobenzene.

6. The preparation method according to claim 5, wherein: c1 is 2 to 43; and / or, c2 is 1 to 10; and / or, t is 10 to 192; and / or, The sum of the content of oxidizing substances in the aniline, the content of oxidizing substances in the acidic compound and the content of oxidizing substances in the alkali solution is ≤50ppm; and / or, The alkaline substance includes sodium hydroxide and / or potassium hydroxide; and / or, The refining treatment includes distillation treatment using a distillation tower.

7. The preparation method according to claim 3, wherein: The oxidizing substance comprises one or more of chlorine, hypochlorous acid, perchloric acid, hypochlorite, chlorate, perchlorate, benzoquinone, imine, and azobenzene; and / or, The acidic compound includes one or more of hydrogen chloride, sulfuric acid, phosphoric acid, and methanesulfonic acid; and / or, The metal ions include one or more of iron ions, chromium ions, nickel ions, copper ions, and aluminum ions; and / or, The refining treatment includes performing vacuum distillation treatment using a distillation tower.

8. The preparation method according to claim 3, comprising: reacting the aniline with the acidic compound to obtain an aniline salt; The aniline salt and formaldehyde are subjected to condensation reaction and transposition reaction to obtain a reaction solution including a reaction product; The reaction solution is mixed with the alkali solution for neutralization reaction, and then washed with water to obtain the crude DAM product; The crude DAM product is subjected to a refining treatment to obtain diphenylmethane series diamine and polyamine products.

9. The preparation method according to claim 8, wherein: The platinum-cobalt color number of the DAM product is ≤200#; and / or, The reaction temperature of the condensation reaction is 40 to 100° C.; and / or, The reaction time of the condensation reaction is 1 to 2 hours; and / or, The reaction temperature of the metathesis reaction is 80-150° C.; and / or, The reaction time of the transposition reaction is 1 to 5 hours.

10. A method for preparing and applying diamines and polyamines of a diphenylmethane series, comprising the following steps: reacting aniline with an acidic compound to obtain an aniline salt; The aniline salt is reacted with formaldehyde and then the obtained product is neutralized with alkali solution to obtain a crude DAM product; Refining the crude DAM product to obtain a DAM product; and The DAM product is subjected to a phosgenation reaction to prepare diisocyanates and polyisocyanates of the diphenylmethane series; in, The total content of oxidizing substances in the raw materials is ≤50ppm, and the total content of metal ions is 0-10ppm; the raw materials include the aniline, the formaldehyde, the acidic compound and the alkali solution; the color index I is ≤1.0, and the color index I is calculated by the following formula: I=0.0024c1+0.2421lnc2-0.0003T+0.0013t+0.1279 Wherein, c1 is the total content of oxidizing substances in the raw material in ppm, c2 is the total content of metal ions in the raw material in ppm, T is the temperature of the refining treatment in ° C, and t is the time interval from the completion of the preparation of the diphenylmethane series diamine and polyamine products to their use in the phosgenation reaction, and the time interval is in hours.

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