M-toluenediamine composition, purification method of m-toluenediamine and application of m-toluenediamine composition

Abstract

The invention belongs to the technical field of product purification and organic synthesis, and particularly relates to an m-toluenediamine composition, a purification method of m-toluenediamine and application of m-toluenediamine. Through repeated research, the applicant finds that m-toluenediamine, 4-methyl-5-amino-1-cyclohexene-1-formaldehyde and 4-methyl-5-amino-2-cyclohexene-1-ketone can be subjected to a Schiff base reaction under the catalytic action to generate Schiff base tar, and then m-toluenediamine and 4-methyl-5-amino-2-cyclohexene-1-ketone are removed from m-toluenediamine in the form of heavy components; the contents are respectively reduced to below 50ppm; the purified m-toluenediamine is used for preparing crude TDI, the purity of the TDI product obtained through rectification and purification can reach 99.99 wt% or above, and the content of chlorine-containing impurities such as hydrolyzed chlorine is lower than 5 ppm. The polyurethane flexible foam prepared by adopting the TDI provided by the invention has the advantages that the foam hole structure is fine and smooth, the comfort level of a user is obviously improved, and the content of free monomers and volatile VOCs (Volatile Organic Compounds) is obviously reduced.

Description

Technical Field

[0001] This application belongs to the field of product purification and organic synthesis technology, specifically relating to a m-toluenediamine composition, a method for purifying m-toluenediamine, and its application. Background Technology

[0002] Toluene diisocyanate (TDI) is an important organic chemical raw material widely used in polyurethane flexible foam, coatings, and adhesives. Among existing TDI preparation technologies, the liquid-phase phosgenation and gas-phase phosgenation methods using m-toluenediamine (MTDA) as a raw material are currently the most mature production processes. Research and practice have shown that in existing TDI production methods, the high content of difficult-to-separate impurities in m-toluenediamine, such as 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde and 4-methyl-5-amino-2-cyclohexene-1-one, results in a high content of volatile light components in the TDI product prepared by the reaction of MTDA and phosgene. This leads to lower TDI purity and insufficient reactivity, severely affecting the quality and application performance of the TDI product. Especially with increasingly stringent VOCs requirements for polyurethane products, the TDI products produced by current processes no longer meet the needs of high-end customers in the market.

[0003] To address the technical challenges of improving the quality of downstream TDI products and reducing the high content of volatile VOCs, the industry is currently making unremitting efforts and attempts to improve TDI quality. The main methods used are controlling the impurity content of MTDA, optimizing phosgenation reaction conditions, and using multi-stage distillation purification to reduce the impurity content of products and continuously improve the purity of TDI products.

[0004] However, existing technologies for directly phosgenating m-toluenediamine to produce TDI products have limited solutions to problems such as low purity and high content of chlorine-containing light components, resulting in polyurethane flexible foams that do not meet VOCs requirements. These solutions still cannot guarantee that the quality of downstream products meets the demands of high-end applications, or they present challenges in engineering implementation and low feasibility. Therefore, there is an urgent need to develop a high-purity, low-impurity toluene diisocyanate preparation technology. Summary of the Invention

[0005] Therefore, the technical problem to be solved by this application is to overcome the defects of the prior art, such as low purity of TDI products and high content of chlorine-containing light component impurities, which leads to high content of volatile VOCs in downstream products, thereby providing a m-toluenediamine composition, a purification method for m-toluenediamine and its application.

[0006] Therefore, this application provides the following technical solution:

[0007] According to one aspect of this application, a m-toluenediamine composition is provided, comprising 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde and 4-methyl-5-amino-2-cyclohexene-1-one, wherein the 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde has a mass content of 1-100 ppm, preferably 1-30 ppm, and the 4-methyl-5-amino-2-cyclohexene-1-one has a mass content of 3-100 ppm, preferably 3-50 ppm.

[0008] Optionally, the m-toluenediamine composition contains ≥99.990% m-toluenediamine by mass.

[0009] In this application, by controlling the content of 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde and 4-methyl-5-amino-2-cyclohexene-1-one in the m-toluenediamine composition, the content of chlorine impurities in the TDI product prepared therefrom can be reduced, the purity of the product can be improved, and the reactivity of TDI can be increased, thereby reducing the content of residual monomers and volatile VOCs in polyurethane flexible foam products.

[0010] This application also provides a method for purifying m-toluenediamine, comprising the following steps:

[0011] S1, the catalyst is activated in a reducing atmosphere; the catalyst includes a support and an active metal component supported on the support, the active metal component includes nickel, chromium and zinc, and the loading of the active metal component is 45-60% based on the total mass of the catalyst.

[0012] Based on the total mass of the active metal components, the content of nickel is 80%-95%, the content of chromium is 2%-15%, and the content of zinc is 0.1%-8%.

[0013] S2, the m-toluenediamine to be purified is reacted in the presence of a catalyst to remove tar and obtain purified m-toluenediamine.

[0014] In the purification method of this application, the catalyst composition is a key factor affecting the conversion rate of the reaction between 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde and 4-methyl-5-amino-2-cyclohexene-1-one and m-toluenediamine, especially the nickel content, which has a significant impact.

[0015] In existing toluene diisocyanate production processes, the high impurity content of the raw material m-toluenediamine, especially 4-methyl-5-amino-1-cyclohexen-1-carboxaldehyde and 4-methyl-5-amino-2-cyclohexen-1-one, whose boiling points are very close to those of m-toluenediamine, makes complete separation impossible using conventional distillation methods. During the reaction of m-toluenediamine with phosgene, the entrained impurities 4-methyl-5-amino-1-cyclohexen-1-carboxaldehyde and 4-methyl-5-amino-2-cyclohexen-1-one undergo chlorination reactions with phosgene, generating chlorinated impurities such as chloroisocyanurate-methylcyclohexenal and cyclohexenone. When crude TDI is processed in single or multi-stage methods such as distillation or rectification, chloroisocyanuric methylcyclohexenal and cyclohexenone have lower boiling points than TDI and are mostly enriched and recycled as light components in the overhead stream. This results in high chlorine impurity content and low purity in the TDI product, which in turn affects the reactivity of TDI, leading to increased residual monomer content and excessive volatile organic compound (VOC) content in flexible foam products. To address these issues, this application involves reacting m-toluenediamine with 4-methyl-5-amino-1-cyclohexen-1-carboxaldehyde and 4-methyl-5-amino-2-cyclohexen-1-one impurities via a Schiff base reaction under a catalyst before the reaction with phosgene to generate Schiff tar. The Schiff tar is then removed as a heavy component along with the distillation residue of m-toluenediamine. The treated m-toluenediamine reacts with phosgene to produce TDI. After subsequent distillation and purification, the purity of the product increases and the chlorine impurity content is significantly reduced. When used to prepare flexible polyurethane foam, it can significantly reduce the volatile organic compound (VOC) content of the foam product.

[0016] In some optional embodiments, in S1, the content of nickel in the catalyst is preferably 85%-95% based on the total mass of the active metal components, the content of chromium is preferably 4%-10%, and the content of zinc is preferably 0.6%-6%.

[0017] And / or, the catalyst support includes at least one of α-alumina, diatomaceous earth, activated carbon, or carbon black.

[0018] In some alternative embodiments, in S2, the reaction temperature is 125-195°C and the reaction time is 0.5-6h; alternatively, the reaction temperature is 155-175°C and the reaction time is 1.5-3h.

[0019] If the reaction temperature is below 125℃, 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde and 4-methyl-5-amino-2-cyclohexene-1-one will not react with m-toluenediamine and cannot be effectively removed; if the temperature is above 195℃, m-toluenediamine will undergo polymerization at high temperature under the action of a catalyst, resulting in product loss and economic loss.

[0020] In some alternative implementations, in S2, the pressure of the reaction only needs to be greater than 3 barg, optionally 3-5 barg.

[0021] In some optional embodiments, in S1, the activation temperature of the catalyst is 300-550°C, and the activation time is 2-6 hours;

[0022] Optionally, the activation temperature of the catalyst is 350-400℃, and the activation time is 2.4-4.5h.

[0023] In this application, tar removal is preferably achieved by means of a distillation column with a reboiler and a condenser. The distillation column has a top pressure of 4-6 kPaA and a top temperature of 150-170°C; a bottom pressure of 7-10 kPaA and a bottom temperature of 185-195°C; and the theoretical number of plates of the distillation column is preferably 25-30.

[0024] In this application, the catalyst used can be obtained commercially or prepared in-house. The preparation method of the catalyst is conventional in the art, for example, it can be obtained by impregnation and calcination of the active component. Specifically, it may include the following steps:

[0025] 1) Add the required amount of soluble metal salt (such as nickel sulfate, chromium sulfate, zinc sulfate) to a 1-5 wt% hydrochloric acid aqueous solution to obtain an impregnation solution; the use of hydrochloric acid aqueous solution in this application can further ensure the impregnation effect of active metal elements;

[0026] 2) Then the support (e.g., α-Al2O3) is impregnated in hydrochloric acid aqueous solution for 4-10 hours, filtered, and dried to obtain the catalyst intermediate;

[0027] 3) The catalyst intermediate was calcined at 600-800℃ for 4-8 hours to obtain the catalyst.

[0028] In this application, the reactor used for the reaction can be one or a combination of a batch reactor, a fixed-bed reactor, or a tower reactor, with a fixed-bed reactor being preferred.

[0029] In this application, the content of 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde in the m-toluenediamine to be treated is 200-2000 ppm, and the content of 4-methyl-5-amino-2-cyclohexene-1-one is 300-3000 ppm. Both 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde and 4-methyl-5-amino-2-cyclohexene-1-one in the m-toluenediamine are byproducts of the hydrogenation of dinitrotoluene, and their structural formulas are as follows:

[0030]

[0031] After purification, the m-toluenediamine has a content of 1-100 ppm for 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde, preferably less than 30 ppm, and a content of 3-100 ppm for 4-methyl-5-amino-2-cyclohexene-1-one, preferably less than 50 ppm.

[0032] According to another aspect of this application, a toluene diisocyanate is also provided, the preparation method of which includes the following steps:

[0033] The above-mentioned m-toluenediamine composition or the purified m-toluenediamine obtained by the above purification method is subjected to phosgenation reaction with phosgene, followed by post-treatment to obtain toluene diisocyanate.

[0034] In some alternative embodiments, the post-processing includes dephosgenesis, desolventization, and purification.

[0035] In this application, the operating parameters for phosgene removal, solvent removal, and purification are all conventional in the field, and those skilled in the art can select them according to actual operating conditions. For example, a plate column is used for phosgene removal, with an operating pressure of 45-75 kPaG and a reboiler temperature of 190-210℃. A packed column is used for solvent removal, with an operating pressure of 7-12 kPaA and a reboiler temperature of 175-190℃; a packed column is used for the purification step, with an operating pressure of 3-8 kPaA and a reboiler temperature of 160-185℃.

[0036] According to another aspect of this application, the use of the above-mentioned toluene diisocyanate in polyurethane flexible foam, coatings or adhesives is also provided.

[0037] In some optional embodiments, the raw materials of the polyurethane flexible foam include component A and component B, wherein,

[0038] Component A comprises the following components in parts by weight: 5-60 parts of polyether polyol, 2.5-6 parts of foaming agent, 1-2.5 parts of foam stabilizer, 0.2-0.5 parts of amine catalyst, 0.05-0.2 parts of metal catalyst, and 3-10 parts of flame retardant.

[0039] Component B is the toluene diisocyanate provided in this application;

[0040] The mass ratio of component A to component B is 100:40-60.

[0041] In this application, the method for preparing polyurethane flexible foam is conventional in the art, and may include, for example, the following steps:

[0042] 1) In container A, add 5-60 parts of polyether polyol, 2.5-6 parts of foaming agent, 1-2.5 parts of foam stabilizer, 0.2-0.5 parts of amine catalyst, 0.05-0.2 parts of metal catalyst, and 3-10 parts of flame retardant according to the weight proportions. After thorough mixing, obtain component A.

[0043] 2) First, add TDI to container B. Then, add component A to container B at a TDI to component A mass ratio of 40-60:100. Stir at 2000-5000 rpm for 4-10 seconds to obtain material B.

[0044] 3) Quickly pour material B into the foaming box for foaming and curing. The curing time is 10-72 hours. After curing, polyurethane flexible foam material can be obtained.

[0045] In this application, the raw materials used in the preparation of polyurethane flexible foam are all conventional in the art. For example, the polyether polyol includes at least one of polypropylene glycol, polytetrahydrofuran glycol, or polytetramethylene ether glycol, with a hydroxyl value of 40 mgKOH / g-80 mgKOH / g, preferably 45 mgKOH / g-60 mgKOH / g. The foam stabilizer is a polysiloxane-oxidized olefin block or graft copolymer. The amine catalyst is selected from at least one of foaming tertiary amine catalysts, gel tertiary amine catalysts, or balanced tertiary amine catalysts. The flame retardant is one or both of halogenated flame retardants, phosphorus-based flame retardants, or nitrogen-based flame retardants.

[0046] In some alternative embodiments, the foaming agent may be water and / or dichloromethane, preferably water as a physical foaming agent, and the amount added is preferably 2.8-4 parts by weight.

[0047] In some alternative implementations, the polyurethane flexible foam is used in automotive interiors or furniture.

[0048] The TDI provided in this application is used in the preparation of polyurethane flexible foam, and can be optionally used for flexible foam for automotive seats, interiors and furniture. The tested volatile organic compound (VOC) content is less than 20 ppm, preferably less than 10 ppm.

[0049] The technical solution of this application has the following advantages:

[0050] The m-toluenediamine composition provided in this application, by controlling the content of 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde and 4-methyl-5-amino-2-cyclohexene-1-one in the m-toluenediamine composition, can reduce the content of chlorine impurities in the TDI product prepared therefrom, improve the purity of the product, thereby improving the reactivity of TDI, and reducing the content of residual monomers and volatile VOCs in polyurethane flexible foam products.

[0051] The purification method for m-toluenediamine provided in this application includes the following steps: S1, activating the catalyst in a reducing atmosphere; the catalyst includes a support and an active metal component supported on the support, the active metal component includes nickel, chromium, and zinc, and the loading of the active metal component is 45-60% based on the total mass of the catalyst; the content of nickel is 80%-95%, the content of chromium is 2%-15%, and the content of zinc is 0.1%-8% based on the total mass of the active metal component; S2, reacting the m-toluenediamine to be purified in the presence of the catalyst at a reaction temperature of 125-195℃ for a reaction time of 0.5-6 h to remove tar and obtain purified m-toluenediamine. Through repeated research, the applicant discovered that m-toluenediamine can undergo a Schiff base reaction with 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde and 4-methyl-5-amino-2-cyclohexene-1-one under catalysis to generate Schiff tar. These tars are then removed from m-toluenediamine as heavy components, reducing the content of 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde and 4-methyl-5-amino-2-cyclohexene-1-one to below 50 ppm. The purified m-toluenediamine reacts with phosgene via liquid-phase phosgenation to generate crude TDI. After distillation purification, the TDI product obtained achieves a purity of over 99.99 wt%, with chlorine impurities such as hydrolyzed chlorine below 5 ppm. Polyurethane flexible foam prepared using the TDI provided in this application exhibits advantages such as a fine pore structure, significantly improved user comfort, and a marked reduction in free monomers and volatile organic compounds (VOCs).

[0052] The purification method for m-toluenediamine provided in this application limits the reaction pressure, maintaining a positive pressure of more than 3 barg in the reaction system to prevent oxygen and moisture in the air from entering the system, which would cause m-toluenediamine to oxidize and deteriorate at high temperatures when exposed to oxygen, leading to corrosion of the subsequent photochemical reaction system.

[0053] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0055] Figure 1 This is a schematic diagram of the device structure used in the embodiments of this application;

[0056] Figure label:

[0057] E1, Preheater; E2, Thermal oil heating system; R1, Fixed bed reactor; C1, Tar removal tower; R2, Phosgene reaction vessel; C2, Phosgene removal tower; C3, Solvent removal tower; C4, Refining tower. Detailed Implementation

[0058] The following embodiments are provided to better understand this application and are not limited to the preferred embodiments described herein. They do not constitute a limitation on the content and scope of protection of this application. Any product that is the same as or similar to this application, derived by anyone under the guidance of this application or by combining features of this application with other prior art, falls within the scope of protection of this application.

[0059] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having” and any variations thereof in the text of this application are intended to cover non-exclusive inclusion.

[0060] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0061] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers from a to b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed herein, and "0-5" is merely a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that the parameter can be, for example, integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0062] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0063] In the description of the embodiments of this application, the term "at least one" refers to one or more (including two).

[0064] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0065] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0066] The present application will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present application in any way.

[0067] The raw materials and measurement methods involved in the following examples and comparative examples are as follows:

[0068] The m-toluenediamine (MTDA) to be purified: comes from the TDI unit of Fujian Wanhua Industrial Park, and is an industrial product.

[0069] o-Dichlorobenzene (ODCB): Purchased from Jiangsu Yangnong Chemical Co., Ltd., with a purity greater than 99.95 wt%, industrial grade.

[0070] Phosgene: Originates from the TDI unit in Fujian Wanhua Industrial Park; an industrial product.

[0071] The catalyst was prepared in-house. The support used for catalyst preparation was α-Al₂O₃ purchased from the market (analyzed as D50 = 40 μm, specific surface area 268 m²). 2 g), the preparation of the catalyst includes the following three steps:

[0072] 1) According to the required metal content of α-Al2O3, add the required metal salts nickel sulfate, chromium sulfate and zinc sulfate to a 5% hydrochloric acid aqueous solution;

[0073] 2) Then, the α-Al2O3 support was impregnated in hydrochloric acid aqueous solution for 4 hours, filtered, and dried to obtain the catalyst intermediate;

[0074] 3) The catalyst intermediate was calcined at 600℃ for 4 hours to obtain the nickel / chromium / aluminum-α-Al2O3 catalyst.

[0075] Using the above method, five catalysts with different nickel / chromium / zinc active metal contents, A / B / C / D / E, were prepared:

[0076] Catalyst A: The active metal component content is 60%, of which nickel content is 94 wt%, chromium content is 5 wt%, and zinc content is 1 wt%.

[0077] Catalyst B: The active metal component content is 55%, of which nickel content is 90 wt%, chromium content is 8 wt%, and zinc content is 2 wt%.

[0078] Catalyst C: The active metal component content is 51%, of which nickel content is 86 wt%, chromium content is 9 wt%, and zinc content is 5 wt%.

[0079] Catalyst D: The active metal component content is 45%, of which nickel content is 80 wt%, chromium content is 15 wt%, and zinc content is 5 wt%.

[0080] Catalyst E: The active metal component content is 31%, of which nickel content is 60 wt%, chromium content is 30 wt%, and zinc content is 10 wt%.

[0081] The contents of 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde and 4-methyl-5-amino-2-cyclohexene-1-one in m-toluenediamine were quantitatively analyzed by gas chromatography (manufacturer: Agilent). The chromatographic column was a weakly polar column. The initial temperature of the column oven was 50℃, held for 1 min, and then increased to 320℃ at a rate of 50℃ / min, held for 30 min. The detector type was an FID detector.

[0082] The purity of TDI products conforms to the standard GB / T 32469-2016 "Plastic Polyurethane Raw Materials Toluene Diisocyanate".

[0083] Hydrolyzed chlorine in TDI products was analyzed according to standard GB / T 12009.2-2016.

[0084] The method for determining the free TDI monomer content in polyurethane flexible foam is based on EN ISO 10283:2014 "Plastics - Aromatic isocyanates for polyurethane production - Toluene diisocyanate (TDI)" standard.

[0085] The method for determining the volatile organic compound (VOC) content of polyurethane flexible foam products is based on EN ISO 11890-2:2020 "Paints and varnishes - Determination of volatile organic compound (VOC) content - Part 2: Gas chromatography".

[0086] Example 1

[0087] This embodiment provides a method for purifying m-toluenediamine and preparing toluene diisocyanate, using... Figure 1 The specific steps and operating parameters of the apparatus shown are as follows:

[0088] Weigh 1000g of solid catalyst A and load it into the tubes of fixed-bed reactor R1. Reactor R1 has tube dimensions of Φ80×2000mm, with 112 tubes and an effective volume of approximately 1.5L. Activate the shell-side heat transfer oil heating system E2, setting the circulating hot oil temperature to 350℃. After the hot oil temperature stabilizes, introduce hydrogen gas to activate the catalyst. Control the hydrogen feed rate to 20Nm³. 3 / h, activation time is 2.5h, after activation is completed, stop adding hydrogen and cool the heat transfer oil to 160℃.

[0089] With a catalyst-to-material loading ratio of 2%, the purified m-toluenediamine feedstock, after removing the ortho-isomer, was preheated to 160°C in preheater E1 and introduced into reactor R1 from the bottom. The residence time was controlled at 2.3 h. Under the action of the catalyst, it underwent a Schiff base reaction with 4-methyl-5-amino-1-cyclohexen-1-carboxaldehyde and 4-methyl-5-amino-2-cyclohexen-1-one. The material from the reactor outlet entered the detarting tower C1 to remove heavy components from the bottom of the tower. The pressure at the top of tower C1 was 5 kPaA, the pressure at the bottom of tower C1 was 8 kPaA, the temperature at the top of tower C1 was 165°C, and the temperature at the bottom of tower C1 was 188°C. Analysis showed that the purified MTDA contained 2 ppm of 4-methyl-5-amino-1-cyclohexen-1-carboxaldehyde and 4 ppm of 4-methyl-5-amino-2-cyclohexen-1-one.

[0090] The structural confirmation data for 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde are as follows:

[0091] GCMS: Injector split ratio 30:1, temperature 280℃, column oven temperature: 50℃, elution position 16.1 min; mass spectrometry fragments: 139, 124, 122, 109, 97, 83, 71, 55, 43.

[0092] The structural confirmation data for 4-methyl-5-amino-2-cyclohexene-1-one are as follows:

[0093] GCMS: Injector split ratio 40:1, temperature 300℃, column oven temperature: 50℃, peak position 18.5 min; mass spectrometry fragments: 125, 121, 108, 97, 82, 69, 54, 41.

[0094] The structural data in other embodiments and comparative examples are consistent with this embodiment, and will not be described one by one.

[0095] Purified MTDA was reacted with phosgene according to industrial TDI production methods. Specifically, MTDA and o-dichlorobenzene (ODCB) were prepared into a mixed solution (amine concentration 25 wt%), which was then mixed with phosgene in a reactor and subjected to a cold / hot phosgenation reaction to produce crude TDI. The cold reaction temperature was 85℃, and the hot reaction temperature was 158℃. After passing through a phosgene removal tower C2, a solvent removal tower C3, and a purification tower C4, TDI-80 product with a purity of 99.998 wt% and a hydrolyzed chlorine content of 1.5 ppm was obtained. The operating pressure of the phosgene removal tower C2 was 45 kPaG, and the reboiler temperature was 205℃; the operating pressure of the solvent removal tower C3 was 10 kPaA, and the reboiler temperature was 185℃; and the operating pressure of the purification tower C4 was 5 kPaA, and the reboiler temperature was 165℃.

[0096] This embodiment also provides a polyurethane flexible foam, the composition of which and its preparation method are as follows:

[0097] In container A, according to the following weight proportions, add 60 parts of polypropylene glycol (molecular weight 3000, hydroxyl value 60 mg KOH / g), 3 parts of water, 2 parts of Momentive L-580 polysiloxane oxidized olefin block foam stabilizer, 0.2 parts of tertiary amine catalyst XD-104, 0.1 parts of metal catalyst T-12, and 3 parts of phosphorus flame retardant OP-935, respectively, and stir thoroughly to obtain component A;

[0098] Component A and TDI-80 product were added to container B at a mass ratio of 40:60. After stirring at 2000 rpm for 6 seconds, the mixture was quickly poured into a foaming chamber for curing for 36 hours. The resulting polyurethane flexible foam material was then prepared.

[0099] The polyurethane flexible foam prepared by the above method was tested, and the free TDI monomer content was 0.01 wt% and the volatile VOCs content was 1.8 ppm.

[0100] Example 2

[0101] This embodiment provides a method for purifying m-toluenediamine and preparing toluene diisocyanate, using... Figure 1 The specific steps and operating parameters of the apparatus shown are as follows:

[0102] 1000g of solid catalyst B was weighed and loaded into the tubes of fixed-bed reactor R1. The tubes of reactor R1 are Φ80×2000mm in size, with 112 tubes and an effective volume of approximately 1.5L. The shell-side heat transfer oil heating system E2 was activated, and the circulating hot oil temperature was set to 350℃. After the hot oil temperature stabilized, hydrogen was introduced to activate the catalyst. The hydrogen feed rate was controlled at 20Nm³. 3 / h, activation time is 2.5h, after activation is completed, stop adding hydrogen and cool the heat transfer oil to 160℃.

[0103] With a catalyst-to-material loading ratio of 2%, the m-toluenediamine to be purified after removal of the ortho-isomer was preheated to 160°C in preheater E1 and then introduced into reactor R1 from the bottom. The residence time was controlled at 3 hours. Under the action of the catalyst, it underwent a Schiff base reaction with 4-methyl-5-amino-1-cyclohexen-1-carboxaldehyde and 4-methyl-5-amino-2-cyclohexen-1-one. The material from the reactor outlet entered the detarting tower C1 to remove the heavy components from the bottom of the tower. The top pressure of C1 was 5 kPaA, the bottom pressure was 8 kPaA, the top temperature was 165°C, and the bottom temperature was 188°C. Analysis showed that the purified MTDA contained 4 ppm of 4-methyl-5-amino-1-cyclohexen-1-carboxaldehyde and 7 ppm of 4-methyl-5-amino-2-cyclohexen-1-one.

[0104] Purified MTDA and ODCB were mixed into a solution (amine concentration 25 wt%), which was then mixed with phosgene in a reactor and subjected to a cold / hot phosgenation reaction to produce crude TDI. The cold reaction temperature was 85℃, and the hot reaction temperature was 158℃. After passing through a phosgene removal tower C2, a solvent removal tower C3, and a purification tower C4, a TDI-80 product with a purity of 99.996 wt% and a hydrolyzed chlorine content of 2.4 ppm was obtained. The operating pressure of the phosgene removal tower C2 was 45 kPaG, and the reboiler temperature was 205℃; the operating pressure of the solvent removal tower C3 was 10 kPaA, and the reboiler temperature was 185℃; and the operating pressure of the purification tower C4 was 5 kPaA, and the reboiler temperature was 165℃.

[0105] Polyurethane flexible foam was prepared according to the foaming method of Example 1 and tested. The free TDI monomer content was 0.03 wt% and the volatile VOCs content was 2.5 ppm.

[0106] Example 3

[0107] This embodiment provides a method for purifying m-toluenediamine and preparing toluene diisocyanate, using... Figure 1 The specific steps and operating parameters of the apparatus shown are as follows:

[0108] 1000g of solid catalyst C was weighed and loaded into the tubes of fixed-bed reactor R1. The tubes of reactor R1 are Φ80×2000mm in size, with 112 tubes and an effective volume of approximately 1.5L. The shell-side heat transfer oil heating system E2 was activated, and the circulating hot oil temperature was set to 350℃. After the hot oil temperature stabilized, hydrogen was introduced to activate the catalyst. The hydrogen feed rate was controlled at 20Nm³. 3 / h, activation time is 2.5h, after activation is completed, stop adding hydrogen and cool the heat transfer oil to 160℃.

[0109] With a catalyst-to-material loading ratio of 2%, m-toluenediamine, after the removal of its ortho-isomer, was preheated to 160°C in preheater E1 and introduced into reactor R1 from the bottom. The residence time was controlled at 2.8 h. Under the action of the catalyst, it underwent a Schiff base reaction with 4-methyl-5-amino-1-cyclohexen-1-carboxaldehyde and 4-methyl-5-amino-2-cyclohexen-1-one. The material from the reactor outlet entered detarting tower C1 to remove heavy components from the bottom of the tower. The pressure at the top of tower C1 was 5 kPaA, the pressure at the bottom was 8 kPaA, the temperature at the top was 165°C, and the temperature at the bottom was 190°C. Analysis showed that the purified MTDA contained 5 ppm of 4-methyl-5-amino-1-cyclohexen-1-carboxaldehyde and 9 ppm of 4-methyl-5-amino-2-cyclohexen-1-one.

[0110] Purified MTDA and ODCB were mixed into a solution (amine concentration 25 wt%), which was then mixed with phosgene in a reactor and subjected to a cold / hot phosgenation reaction to produce crude TDI. The cold reaction temperature was 85℃, and the hot reaction temperature was 158℃. After passing through a phosgene removal tower C2, a solvent removal tower C3, and a purification tower C4, a TDI-80 product with a purity of 99.994 wt% and a hydrolyzed chlorine content of 3.1 ppm was obtained. The operating pressure of the phosgene removal tower C2 was 45 kPaG, and the reboiler temperature was 205℃; the operating pressure of the solvent removal tower C3 was 10 kPaA, and the reboiler temperature was 185℃; and the operating pressure of the purification tower C4 was 5 kPaA, and the reboiler temperature was 165℃.

[0111] Polyurethane flexible foam was prepared according to the method of Example 1 and tested, wherein the free TDI monomer content was 0.05 wt% and the volatile VOCs content was 3.1 ppm.

[0112] Example 4

[0113] This embodiment provides a method for purifying m-toluenediamine and preparing toluene diisocyanate, using... Figure 1 The specific steps and operating parameters of the apparatus shown are as follows:

[0114] Weigh 1000g of solid catalyst A and load it into the tubes of fixed-bed reactor R1. Reactor R1 has tube dimensions of Φ80×2000mm, with 112 tubes and an effective volume of approximately 1.5L. Activate the shell-side heat transfer oil heating system E2, setting the circulating hot oil temperature to 350℃. After the hot oil temperature stabilizes, introduce hydrogen gas to activate the catalyst. Control the hydrogen feed rate to 20Nm³. 3 / h, activation time is 2.5h, after activation is completed, stop adding hydrogen and cool the heat transfer oil to 160℃.

[0115] With a catalyst-to-material loading ratio of 2%, the m-toluenediamine to be purified (after removing the ortho-isomer) was preheated to 160°C in preheater E1 and introduced into reactor R1 from the bottom. The residence time was controlled at 1.5 h. Under the action of the catalyst, it underwent a Schiff base reaction with 4-methyl-5-amino-1-cyclohexen-1-carboxaldehyde and 4-methyl-5-amino-2-cyclohexen-1-one. The material from the reactor outlet entered the detarting tower C1 to remove the heavy components from the bottom of the tower. The pressure at the top of tower C1 was 5 kPaA, the pressure at the bottom of tower C1 was 8 kPaA, the temperature at the top of tower C1 was 170°C, and the temperature at the bottom of tower C1 was 190°C. Analysis showed that the purified MTDA contained 10 ppm of 4-methyl-5-amino-1-cyclohexen-1-carboxaldehyde and 12 ppm of 4-methyl-5-amino-2-cyclohexen-1-one.

[0116] Purified MTDA and ODCB were mixed into a solution (amine concentration 25 wt%), which was then mixed with phosgene in a reactor and subjected to a cold / hot phosgenation reaction to produce crude TDI. The cold reaction temperature was 85℃, and the hot reaction temperature was 158℃. After passing through a phosgene removal tower C2, a solvent removal tower C3, and a purification tower C4, a TDI-80 product with a purity of 99.993 wt% and a hydrolyzed chlorine content of 3.5 ppm was obtained. The operating pressure of the phosgene removal tower C2 was 45 kPaG, and the reboiler temperature was 205℃; the operating pressure of the solvent removal tower C3 was 10 kPaA, and the reboiler temperature was 185℃; and the operating pressure of the purification tower C4 was 5 kPaA, and the reboiler temperature was 165℃.

[0117] Polyurethane flexible foam was prepared according to the foaming method of Example 1 and tested. The free TDI monomer content was 0.15 wt% and the volatile VOCs content was 4.5 ppm.

[0118] Example 5

[0119] This embodiment provides a method for purifying m-toluenediamine and preparing toluene diisocyanate, using... Figure 1 The specific steps and operating parameters of the apparatus shown are as follows:

[0120] 1000g of solid catalyst B was weighed and loaded into the tubes of fixed-bed reactor R1. The tubes of reactor R1 are Φ80×2000mm in size, with 112 tubes and an effective volume of approximately 1.5L. The shell-side heat transfer oil heating system E2 was activated, and the circulating hot oil temperature was set to 350℃. After the hot oil temperature stabilized, hydrogen was introduced to activate the catalyst. The hydrogen feed rate was controlled at 20Nm³. 3 / h, activation time is 2.5h, after activation is completed, stop adding hydrogen and cool the heat transfer oil to 135℃.

[0121] With a catalyst-to-material loading ratio of 2%, the m-toluenediamine to be purified after removal of the ortho-isomer was preheated to 135°C in preheater E1 and then introduced into reactor R1 from the bottom. The residence time was controlled at 2.3 h. Under the action of the catalyst, it reacted with 4-methyl-5-amino-1-cyclohexen-1-carboxaldehyde and 4-methyl-5-amino-2-cyclohexen-1-one in a Schiff base reaction. The material from the reactor outlet entered the detarting tower C1 to remove the heavy components from the bottom of the tower. The pressure at the top of tower C1 was 5 kPaA, the pressure at the bottom of tower C1 was 8 kPaA, the temperature at the top of tower C1 was 170°C, and the temperature at the bottom of tower C1 was 190°C. Analysis showed that the purified MTDA contained 20 ppm of 4-methyl-5-amino-1-cyclohexen-1-carboxaldehyde and 40 ppm of 4-methyl-5-amino-2-cyclohexen-1-one.

[0122] Purified MTDA and ODCB were mixed into a solution (amine concentration 25 wt%), which was then mixed with phosgene in a reactor and subjected to a cold / hot phosgenation reaction to produce crude TDI. The cold reaction temperature was 85℃, and the hot reaction temperature was 158℃. After passing through a phosgene removal tower C2, a solvent removal tower C3, and a purification tower C4, TDI-80 product with a purity of 99.990 wt% and a hydrolyzed chlorine content of 4.9 ppm was obtained. The operating pressure of the phosgene removal tower C2 was 45 kPaG, and the reboiler temperature was 205℃; the operating pressure of the solvent removal tower C3 was 10 kPaA, and the reboiler temperature was 185℃; and the operating pressure of the purification tower C4 was 5 kPaA, and the reboiler temperature was 165℃.

[0123] Polyurethane flexible foam was prepared according to the foaming method of Example 1 and tested. The free TDI monomer content was 0.28 wt% and the volatile VOCs content was 9.8 ppm.

[0124] Example 6

[0125] This embodiment provides a method for purifying m-toluenediamine and preparing toluene diisocyanate. The difference from Example 1 is that catalyst D is used instead of catalyst A. After analysis, the content of 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde in the purified MTDA is 10 ppm, and the content of 4-methyl-5-amino-2-cyclohexene-1-one is 20 ppm.

[0126] Purified MTDA and ODCB were mixed into a solution (amine concentration 25 wt%), which was then mixed with phosgene in a reactor and subjected to a cold / hot phosgenation reaction to produce crude TDI. The cold reaction temperature was 85℃, and the hot reaction temperature was 158℃. After passing through a phosgene removal tower C2, a solvent removal tower C3, and a purification tower C4, a TDI-80 product with a purity of 99.992 wt% and a hydrolyzed chlorine content of 4.2 ppm was obtained. The operating pressure of the phosgene removal tower C2 was 45 kPaG, and the reboiler temperature was 205℃; the operating pressure of the solvent removal tower C3 was 10 kPaA, and the reboiler temperature was 185℃; and the operating pressure of the purification tower C4 was 5 kPaA, and the reboiler temperature was 165℃.

[0127] Polyurethane flexible foam was prepared according to the method in Example 1 and tested. The free TDI monomer content was 0.20 wt% and the volatile VOCs content was 8.1 ppm.

[0128] Example 7

[0129] This embodiment provides a purification method for m-toluenediamine and a preparation method for toluene diisocyanate. The difference from Example 1 is that the residence time is controlled to be 1 hour during the purification process. After analysis, the content of 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde in the purified MTDA is 15 ppm, and the content of 4-methyl-5-amino-2-cyclohexene-1-one is 36 ppm.

[0130] Purified MTDA and ODCB were mixed into a solution (amine concentration 25 wt%), which was then mixed with phosgene in a reactor and subjected to a cold / hot phosgenation reaction to produce crude TDI. The cold reaction temperature was 85℃, and the hot reaction temperature was 158℃. After passing through a phosgene removal tower C2, a solvent removal tower C3, and a purification tower C4, a TDI-80 product with a purity of 99.991 wt% and a hydrolyzed chlorine content of 4.6 ppm was obtained. The operating pressure of the phosgene removal tower C2 was 45 kPaG, and the reboiler temperature was 205℃; the operating pressure of the solvent removal tower C3 was 10 kPaA, and the reboiler temperature was 185℃; and the operating pressure of the purification tower C4 was 5 kPaA, and the reboiler temperature was 165℃.

[0131] Polyurethane flexible foam was prepared according to the method in Example 1 and tested. The free TDI monomer content was 0.24 wt% and the volatile VOCs content was 8.6 ppm.

[0132] Comparative Example 1

[0133] The difference between this comparative example and Example 6 is that an unpurified MTDA sample was prepared using existing equipment. Analysis showed that the content of 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde was 800 ppm and the content of 4-methyl-5-amino-2-cyclohexene-1-one was 1400 ppm.

[0134] TDI was prepared according to the method in Example 1, and the TDI-80 product had a purity of 99.410 wt% and a hydrolyzed chlorine content of 75 ppm.

[0135] Polyurethane flexible foam was prepared according to the method of Example 1 and tested, wherein the free TDI monomer content was 1.1 wt% and the volatile VOCs content was 300 ppm.

[0136] Comparative Example 2

[0137] The difference between this comparative example and Example 6 is that it uses a commercially available brand name. A comparison was made with TDI-80 (measured TDI purity of 99.92wt%, hydrolyzed chlorine of 12ppm), and commercially available brands... Using TDI (measured 2,4-monomer content of 80.2 wt%) as raw material, and with other conditions consistent with Example 1, polyurethane flexible foam was prepared and tested, wherein the free TDI monomer content was 0.55 wt% and the volatile VOCs content was 60 ppm.

[0138] Comparative Example 3

[0139] This comparative example provides a method for purifying m-toluenediamine and preparing toluene diisocyanate. The difference from Example 6 is that the residence time during the purification process is controlled to be 0.2 h. After analysis, the content of 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde in the purified MTDA is 600 ppm and the content of 4-methyl-5-amino-2-cyclohexene-1-one is 800 ppm.

[0140] The purified MTDA was reacted with phosgene according to the method in Example 1 to generate crude TDI, and then post-processed to obtain TDI-80 product with a purity of 99.720 wt% and a hydrolyzed chlorine content of 39 ppm.

[0141] Polyurethane flexible foam was prepared according to the method in Example 1 and tested. The free TDI monomer content was 0.66 wt% and the volatile VOCs content was 140 ppm.

[0142] Comparative Example 4

[0143] This embodiment provides a purification method for m-toluenediamine and a preparation method for toluene diisocyanate. The difference from Example 6 is that the residence time is controlled to be 8 hours during the purification process. After analysis, the content of 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde in the purified MTDA is 10 ppm, and the content of 4-methyl-5-amino-2-cyclohexene-1-one is 1300 ppm.

[0144] The purified MTDA was reacted with phosgene according to the method in Example 1 to generate crude TDI, and then post-processed to obtain TDI-80 product with a purity of 99.510 wt% and a hydrolyzed chlorine content of 50 ppm.

[0145] Polyurethane flexible foam was prepared according to the method in Example 1 and tested. The free TDI monomer content was 0.71 wt% and the volatile VOCs content was 180 ppm.

[0146] Comparative Example 5

[0147] This embodiment provides a method for purifying m-toluenediamine and preparing toluene diisocyanate. The difference from Example 6 is that the preheating temperature during the purification process is 110°C. After analysis, the content of 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde in the purified MTDA is 500 ppm, and the content of 4-methyl-5-amino-2-cyclohexene-1-one is 200 ppm.

[0148] After purification, MTDA was reacted with phosgene according to the method in Example 1 to generate crude TDI, and then post-processed to obtain TDI-80 product with a purity of 99.810 wt% and a hydrolyzed chlorine content of 23 ppm.

[0149] Polyurethane flexible foam was prepared according to the method in Example 1 and tested. The free TDI monomer content was 0.58 wt% and the volatile VOCs content was 98 ppm.

[0150] Comparative Example 6

[0151] This comparative example provides a method for purifying m-toluenediamine and preparing toluene diisocyanate. The difference from Example 6 is that the preheating temperature during the purification process is 190°C. After analysis, the content of 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde in the purified MTDA is 80 ppm, and the content of 4-methyl-5-amino-2-cyclohexene-1-one is 160 ppm.

[0152] After purification, MTDA was reacted with phosgene according to the method in Example 1 to generate crude TDI, and then post-processed to obtain TDI-80 product with a purity of 99.886 wt% and a hydrolyzed chlorine content of 8.9 ppm.

[0153] Polyurethane flexible foam was prepared according to the method in Example 1 and tested, wherein the free TDI monomer content was 0.48 wt% and the volatile VOCs content was 55 ppm.

[0154] Comparative Example 7

[0155] This comparative example provides a method for purifying m-toluenediamine and preparing toluene diisocyanate. The difference from Example 6 is that catalyst E is used instead of catalyst A. After analysis, the content of 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde in the purified MTDA is 760 ppm, and the content of 4-methyl-5-amino-2-cyclohexene-1-one is 1300 ppm.

[0156] The purified MTDA was reacted with phosgene according to the method in Example 1 to generate crude TDI, and then post-processed to obtain TDI-80 product with a purity of 99.623 wt% and a hydrolyzed chlorine content of 72 ppm.

[0157] Polyurethane flexible foam was prepared according to the method in Example 1 and tested. The free TDI monomer content was 0.77 wt% and the volatile VOCs content was 195 ppm.

[0158] Table 1: Comparison of results between the examples and comparative examples

[0159]

[0160]

[0161] As can be seen from the data in Table 1, the method of the embodiments of this application for purifying m-toluenediamine and using the purified product for the preparation of toluene diisocyanate and polyurethane flexible foam shows that, compared with the comparative example, the MTDA treated in the embodiments has lower contents of 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde and 4-methyl-5-amino-2-cyclohexene-1-one impurities, higher TDI product, and lower chlorine impurity content. This also indicates that the implementation of this application can improve the quality of polyurethane flexible foam materials, and significantly reduce the content of free monomers and volatile VOCs.

[0162] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A m-toluenediamine composition, characterized in that, It includes 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde and 4-methyl-5-amino-2-cyclohexene-1-one, wherein the mass content of 4-methyl-5-amino-1-cyclohexene-1-carboxaldehyde is 1-100 ppm, preferably 1-30 ppm, and the mass content of 4-methyl-5-amino-2-cyclohexene-1-one is 3-100 ppm, preferably 3-50 ppm; Optionally, the m-toluenediamine composition contains ≥99.990% m-toluenediamine by mass.

2. A method for purifying m-toluenediamine, characterized in that, Includes the following steps: S1, the catalyst is activated in a reducing atmosphere; the catalyst includes a support and an active metal component supported on the support, the active metal component includes nickel, chromium and zinc, and the loading of the active metal component is 45-60% based on the total mass of the catalyst. Based on the total mass of the active metal components, the content of nickel is 80%-95%, the content of chromium is 2%-15%, and the content of zinc is 0.1%-8%. S2, the m-toluenediamine to be purified is reacted in the presence of a catalyst to remove tar and obtain purified m-toluenediamine.

3. The purification method for m-toluenediamine according to claim 2, characterized in that, In S1, based on the total mass of the active metal components, the catalyst contains 85%-95% nickel, 4%-10% chromium, and 0.6%-6% zinc. And / or, the catalyst support includes at least one of α-alumina, diatomaceous earth, activated carbon, or carbon black.

4. The purification method for m-toluenediamine according to claim 2, characterized in that, In S2, the reaction temperature is 125-195℃ and the reaction time is 0.5-6h; Optionally, the reaction temperature is 155-175℃, and the reaction time is 1.5-3h; And / or, in S2, the reaction pressure is greater than or equal to 3 barg, optionally 3-5 barg.

5. The purification method for m-toluenediamine according to any one of claims 2-4, characterized in that, In S1, the activation temperature of the catalyst is 300-550℃, and the activation time is 2-6h; Optionally, the activation temperature of the catalyst is 350-400℃, and the activation time is 2.4-4.5h.

6. A toluene diisocyanate, characterized in that, The preparation method includes the following steps: reacting the m-toluenediamine of claim 1 or the purified m-toluenediamine obtained by the purification method of any one of claims 2-5 with phosgene, followed by post-treatment to obtain toluene diisocyanate.

7. The toluene diisocyanate according to claim 6, characterized in that, The post-processing includes phosgene removal, solvent removal, and purification.

8. The use of the toluene diisocyanate as described in claim 6 or 7 in polyurethane flexible foam, coatings or adhesives.

9. The application according to claim 7, characterized in that, The raw materials for the polyurethane flexible foam include component A and component B, wherein, Component A comprises the following components in parts by weight: 5-60 parts of polyether polyol, 2.5-6 parts of foaming agent, 1-2.5 parts of foam stabilizer, 0.2-0.5 parts of amine catalyst, 0.05-0.2 parts of metal catalyst, and 3-10 parts of flame retardant. Component B is the toluene diisocyanate according to claim 6 or 7; The mass ratio of component A to component B is 100:40-60.

10. The application according to any one of claims 8-9, characterized in that, The polyurethane flexible foam is used in automotive interiors or furniture.

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