Preparation method of isocyanate, cold reaction mixer and preparation device of isocyanate

Abstract

The invention relates to an isocyanate preparation method, a cold reaction mixer and an isocyanate preparation device.The preparation method comprises a cold reaction, a thermal reaction and aftertreatment, the cold reaction comprises the steps that a phosgene solution and an amine solution are mixed in a static mixing pipe and react, and an intermediate mixed solution is obtained; the intermediate mixed solution enters a dynamic mixing pipe, a dynamic mixing assembly is driven by a driving part to rotate, and a cold reaction mixed solution is obtained after the intermediate mixed solution is sheared by the dynamic mixing assembly; wherein the crystallization index Q of the cold reaction is greater than or equal to 175.52. According to the invention, by controlling the crystallization index of the cold reaction stage, the average particle size of intermediate particles in the cold reaction mixed liquid is reduced, so that the obtained isocyanate has low impurity content, the product chromaticity is obviously reduced, and the quality of the isocyanate is effectively improved.

Description

Technical Field

[0001] This invention relates to the field of isocyanate technology, and in particular to methods for preparing isocyanates, cold reaction mixers, and apparatus for preparing isocyanates. Background Technology

[0002] The liquid-phase phosgene method is an effective and crucial step in the preparation of isocyanates, typically consisting of two stages: a cold reaction and a hot reaction. According to the reaction mechanism (Equation 1, taking aromatic amines as an example): in the cold reaction stage, the amine reacts with phosgene to produce carbamoyl chloride and hydrogen chloride, which then reacts with the amine to form amine hydrochloride; in the hot reaction stage, the carbamoyl chloride directly decomposes into isocyanate, while the amine hydrochloride first decomposes into amine, which then further reacts with phosgene to form isocyanate.

[0003]

[0004] Since the generated carbamoyl chloride and amine hydrochloride are both solid particles, they will partially encapsulate the amine during the cold reaction stage; the larger the particle, the more amine it encapsulates. During the hot reaction stage, as the carbamoyl chloride and amine hydrochloride react, the encapsulated amine is released and reacts with isocyanate or carbamoyl chloride to generate impurities such as urea (Equation 2). Urea is a solid with extremely poor solubility. Its formation will not only clog the reactor and downstream equipment, affecting the continuous operation of the equipment, but also reduce product quality and affect the application of subsequent products (such as foaming performance).

[0005]

[0006] In addition, urea, as an intermediate, can further react with phosgene to generate impurities such as carbodiimide, urea ketimide, and phosgene adducts (colored substances) (Equation 3), which increases the types of impurities, product color, acid value, and hydrolytic chlorine, further reducing product quality.

[0007]

[0008] Moreover, existing research (Equation 4) shows that particle size also affects the thermal reaction rate of intermediates. The larger the particle size, the slower the reaction rate, the higher the selectivity of by-products, and the longer the reaction residence time.

[0009]

[0010] As can be seen from the above, minimizing the particle size of intermediate particles during the cold reaction stage is key to controlling the generation of impurities such as urea, improving product quality, shortening residence time, and extending the operating cycle of the equipment during isocyanate synthesis.

[0011] To reduce the particle size of the generated intermediate particles and thus mitigate the adverse effects of large-particle intermediates, the prior art discloses the following methods:

[0012] Patent CN101811018A discloses a tilting paddle-type cold photochemical reactor, which uses a rotating blade-equipped stirring paddle to pulverize the solid particles trapped in the reaction, thus avoiding the formation of solid agglomerates containing unreacted materials. However, the effect of controlling particle size with only one stirring paddle is limited, making it difficult to obtain uniformly distributed small-diameter particles.

[0013] Patent CN115286535A discloses a coupling device that reduces the probability of large hydrochloride particles being generated by improving the gas-liquid mixing effect of the salt formation reaction, and further disperses and breaks up the generated large hydrochloride particles through strong stirring. However, this device only has a certain effect on reducing the formation of large solid particles, and requires maintaining a high rotation speed, which places high demands on the equipment.

[0014] Patent CN113181859A discloses a salt-forming reactor equipped with a rotating grinding cylinder and grinding discs to obtain amine hydrochloride particles with a relatively uniform particle size distribution through grinding. However, this process is only applicable to the salt-forming method, and the average particle size of the obtained hydrochloride particles can only be controlled at around 90 μm. It still encapsulates a large amount of the raw material amine, leading to the formation of subsequent by-products.

[0015] It is evident that current technologies mainly focus on controlling the particle size of intermediate particles by considering factors such as reactor type and internal components. Although these technologies have achieved certain results, they all have some problems, such as high equipment requirements and unsatisfactory control of small particles. Summary of the Invention

[0016] Therefore, it is necessary to provide a method for preparing isocyanate, a cold reaction mixer, and an apparatus for preparing isocyanate to address the above problems. The preparation method can reduce the average particle size of intermediate particles and obtain high-quality isocyanate.

[0017] A method for preparing an isocyanate includes a cold reaction, a hot reaction, and a post-treatment, wherein the cold reaction step includes:

[0018] Phosgene solution and amine solution are mixed and reacted in a static mixing tube to obtain an intermediate mixture, wherein chlorobenzene is used as a solvent for both phosgene solution and amine solution;

[0019] The intermediate mixture enters the dynamic mixing tube, and the dynamic mixing assembly is driven to rotate by the driving component. After being sheared by the dynamic mixing assembly, a cold reaction mixture is obtained.

[0020] Wherein, the crystallinity index Q of the cold reaction is ≥175.52, and Q is calculated as follows:

[0021]

[0022] In the formula, C p The mass concentration of the phosgene solution is expressed in wt%; P b The outlet pressure of the dynamic mixing tube, in bar; W e Input power per unit volume of the dynamic mixing tube, in kW / m 3 ;T p R represents the feed temperature of the phosgene solution, in °C. s The ratio of the total mass of the chlorobenzene solvent used in the amine solution and the chlorobenzene solvent used in the phosgene solution to the mass of the amine in the amine solution.

[0023] In one embodiment, 175.52 ≤ Q ≤ 405.15.

[0024] In one embodiment, the cold reaction step simultaneously satisfies the following conditions:

[0025] (1) Input power W per unit volume of dynamic mixing tube e 10kw / m 3 -15kw / m 3 ;

[0026] (2) Mass concentration C of phosgene solution p 40wt%-50wt%;

[0027] (3) The outlet pressure P of the dynamic mixing pipe b 15-20 bar;

[0028] (4) Feed temperature T of phosgene solution p The temperature is 4℃-6℃;

[0029] (5) The mass ratio of the first solvent used in the amine solution and the second solvent used in the phosgene solution to the mass of the amine in the amine solution, R s It is 4-8;

[0030] (6) The feed temperature of the amine solution is constant and controlled at 80°C;

[0031] (7) The mixing time in the static mixing tube is >150ms, and the mixing time in the dynamic mixing tube is >60ms.

[0032] In one embodiment, the cold reaction step further includes adding a phosgene solution at a temperature of 4°C-6°C to the dynamic mixing tube, the amount of which is 10wt%-30wt% of the amount of phosgene solution used in the static mixing tube.

[0033] In one embodiment, the average particle size of the cold reaction mixture obtained from the dynamic mixing tube is also detected using an online particle size analyzer.

[0034] In one embodiment, the amine in the amine solution is selected from methylene diphenyl diamine, polymethylene polyphenyl polyamine, a mixture of methylene diphenyl diamine and polymethylene polyphenyl polyamine, 2,4-toluenediamine, a mixture of 2,4-toluenediamine and 2,6-toluenediamine, m-phenylenediamine and its isomers, p-phenylenediamine and its isomers, tetramethylxylenediamine, 1,3-dimethylaminocyclohexane, 2,6-dimethylamine, 1,5-naphthyldiamine, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 4,4'-dicyclohexylmethanediamine, 2,4'-dicyclohexylmethanediamine, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 2,2-dimethyl-1,5-diaminopentane, 2-methyl-1,5-pentane Diamine, 2,4,4 (or 2,2,4)-trimethyl-1,6-diaminocyclohexane, 1,3- and 1,4-diaminocyclohexane, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane, 2,4- or 2,6-diamino-1-methylcyclohexane, 1-amino-1-methyl-4(3)-aminomethylcyclohexane, 1,3 (and / or 1,4)-bis(aminomethyl)cyclohexane Alkane, at least one of bis(aminomethyl)norbornene, triaminocyclohexane, tri(aminomethyl)cyclohexane, triamino-methylcyclohexane, 1,8-diamino-4-(aminomethyl)octane, 1,6,11-undecanetriamine, 1,7-diamino-4-(3-aminopropyl)heptane, 1,6-diamino-3-(aminomethyl)hexane, or 1,3,5-tri(aminomethyl)cyclohexane.

[0035] A cold reaction mixer used in the method for preparing the isocyanate, the cold reaction mixer comprising:

[0036] A static mixing tube having an amine solution inlet and a phosgene solution inlet;

[0037] A dynamic mixing tube is provided inside the dynamic mixing tube. The dynamic mixing component includes a stator and a rotor. The stator is fixedly connected to the inner wall of the dynamic mixing tube. The rotor is arranged opposite to the stator and is connected to a driving component. The rotor is driven to rotate by the driving component. The outlet end of the dynamic mixing tube is connected to the outlet end of the static mixing tube, and the dynamic mixing tube is provided with a cold reaction mixture outlet.

[0038] In one embodiment, the cold reaction mixer further includes a phosgene solution silo with a phosgene solution inlet, and the static mixing pipe is disposed in the phosgene solution silo, with the phosgene solution inlet of the static mixing pipe connected to the phosgene solution silo.

[0039] In one embodiment, the dynamic mixing tube is connected to the phosgene solution silo via a channel.

[0040] In one embodiment, the cold reaction mixer further includes an amine solution mixing section having an amine inlet, a first solvent inlet, and an amine solution outlet, the amine solution outlet being connected to the amine solution inlet of the static mixing tube.

[0041] In one embodiment, the stator has a first serration on the side facing the rotor, and the rotor has a second serration on the side facing the stator that matches the first serration.

[0042] In one embodiment, the dynamic hybrid assembly has two or more sets of stators and rotors.

[0043] An apparatus for preparing isocyanate, the apparatus comprising at least the aforementioned cold reaction mixer and a hot reactor connected to the cold reaction mixer.

[0044] In one embodiment, the outlet of the dynamic mixing tube is also equipped with an online particle size analyzer.

[0045] This invention reduces the average particle size of intermediate particles in the cold reaction mixture by controlling the crystallization index during the cold reaction stage, specifically by simultaneously controlling the reaction crystallization process in the static mixing tube and the shearing and crushing process in the dynamic reaction tube. As a result, the obtained isocyanate has less impurity content and significantly reduced product color, effectively improving the quality of isocyanate. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a flow chart of the preparation process of the isocyanate of the present invention;

[0048] Figure 2 This is a schematic diagram of the cold reaction mixer of the present invention;

[0049] Figure 3 This is an enlarged view of point A in the cold reaction mixer;

[0050] Figure 4 This is an enlarged view of the cold reaction mixer B.

[0051] In the diagram: 12, Phosgene solution silo; 13, Dynamic mixing tube; 14, Static mixing tube; 15, Amine solution mixing section; 16, Phosgene solution inlet; 17, Dynamic mixing assembly; 18, Drive unit; 101, Phosgene solution feed inlet; 102, Cold reaction mixture outlet; 111, Channel; 151, Amine feed inlet; 152, First solvent feed inlet; 153, Amine solution outlet; 171, Stator; 172, Rotor. Detailed Implementation

[0052] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0053] 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 invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional scope of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0054] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe features or characteristics, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0055] like Figure 1 As shown, the method for preparing isocyanate provided by the present invention includes the following steps:

[0056] S1. Cold reaction: Phosgene solution and amine solution undergo a cold reaction in a cold reaction mixer to obtain a cold reaction mixture;

[0057] S2, Thermal reaction: The cold reaction mixture enters a thermal reactor to undergo a thermal reaction, resulting in a thermal reaction liquid;

[0058] S3. Post-processing: The hot reaction liquid is sequentially subjected to dephosgene, desolventization and purification to obtain isocyanate.

[0059] Specifically, the cold reaction mixer used in step S1 of this invention includes a connected static mixing tube and a dynamic mixing tube. The dynamic mixing tube contains a dynamic mixing component, which is driven by a driving element. Furthermore, the cold reaction step includes:

[0060] Phosgene solution and amine solution were mixed and reacted in a static mixing tube to obtain an intermediate mixture;

[0061] The intermediate mixture enters the dynamic mixing tube, and the dynamic mixing component is driven to rotate by the driving component. After being sheared by the dynamic mixing component, a cold reaction mixture is obtained.

[0062] Both the amine solution and the phosgene solution were prepared by mixing chlorobenzene as a solvent.

[0063] The amine is selected from methylene diphenyl diamine (mMDA), polymethylene polyphenyl polyamine (pMDA), a mixture of methylene diphenyl diamine and polymethylene polyphenyl polyamine (MDA), 2,4-toluenediamine (TDA-100), a mixture of 2,4-toluenediamine and 2,6-toluenediamine (TDA-80 or TDA-65), m-phenylenediamine (XDA) and its isomers, p-phenylenediamine (PPDA) and its isomers, tetramethylxylenediamine (... TMXDA), 1,3-dimethylaminocyclohexane (H6XDA), 2,6-dimethylamine, 1,5-naphthyldiamine (1,5-NDA), 1,4-diaminobutane, 1,5-diaminopentane (PDA), 1,6-diaminohexane (HDA), 4,4'-dicyclohexylmethanediamine (H12MDA), 2,4'-dicyclohexylmethanediamine, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 2,2-dimethylaminocyclohexane (DMC) 1,5-diaminopentane, 2-methyl-1,5-pentanediamine (MPDA), 2,4,4 (or 2,2,4)-trimethyl-1,6-diaminohexane (TMDA), 1,3- and 1,4-diaminocyclohexane, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane (IPDA), 2,4- or 2,6-diamino-1-methylcyclohexane (H6-TDA), 1-amino-1-methyl-4(3)-aminomethylcyclohexane ( AMCA), 1,3 (and / or 1,4)-bis(aminomethyl)cyclohexane, bis(aminomethyl)norbornene (NBDA), triaminocyclohexane, tri(aminomethyl)cyclohexane, triamino-methylcyclohexane, 1,8-diamino-4-(aminomethyl)octane, 1,6,11-undecanetriamine, 1,7-diamino-4-(3-aminopropyl)heptane, 1,6-diamino-3-(aminomethyl)hexane, or 1,3,5-tri(aminomethyl)cyclohexane.

[0064] When amine and phosgene solutions react in a cold reaction mixer, a cold reaction mixture comprising intermediates amine hydrochloride and carbamoyl chloride is obtained. In this invention, a reaction crystallization process occurs in the static mixing tube, while a shearing and fragmentation process occurs in the dynamic mixing tube. The reaction crystallization process is a combination of reaction kinetics and crystallization kinetics. As shown in Equation 5, when the reaction rate of the intermediate is increased by controlling the reaction conditions, the supersaturation of the corresponding intermediate increases, thereby increasing the nucleation rate and producing intermediates with smaller particle sizes. High supersaturation often results in ultrafine particles. Increasing the phosgene feed concentration and reactor outlet pressure helps control the phosgene concentration during the reaction, thereby increasing the reaction rate and supersaturation. In addition, the amount of chlorobenzene solvent must be controlled, as a large amount is not conducive to increasing supersaturation.

[0065]

[0066] In Equation 5, r refers to the rate, k refers to the rate constant, C refers to the reactant concentration, ΔC refers to the supersaturation, and p refers to the nucleation index. According to Equation 5, by controlling parameters such as phosgene concentration to increase the reaction rate of the intermediate, the supersaturation ΔC of the intermediate will increase, thereby increasing its nucleation rate and resulting in fine intermediate particles.

[0067] Crystallization rate is usually slower than reaction rate. In order to allow intermediates to crystallize and precipitate fully, mixing time needs to be controlled to >150ms in static mixing tube.

[0068] The cold reaction is an adiabatic exothermic process. Excessive temperature is detrimental to product quality. In order to control the cold reaction temperature, it is necessary to control the feed temperature of the phosgene solution and the amine solution.

[0069] In the dynamic mixing tube, the resulting solid intermediate particles are further broken down under shearing action. The greater the input power per unit volume of the cold reactor, the stronger the shearing action, and the smaller the particle size. To ensure sufficient breakage of the solid intermediates, the mixing time needs to be controlled to >60ms.

[0070] Therefore, this invention obtains a cold reaction mixture with smaller particle size by simultaneously controlling multiple parameters during the cold reaction stage. The crystallization index Q is used to reflect the above control effect, and the calculation formula is as follows:

[0071]

[0072] In the formula, C p P represents the mass concentration of the phosgene solution, expressed in wt%, i.e., the mass concentration of the phosgene solution entering the static mixing tube. b W represents the outlet pressure of the dynamic mixing tube, in bar, i.e., the outlet pressure of the cold reaction mixture; e Input power per unit volume of the dynamic mixing tube, in kW / m 3 That is, the ratio of the power of the dynamic mixing tube drive to the volume of the dynamic mixing tube; T p R represents the feed temperature of the phosgene solution, in °C, i.e., the temperature of the phosgene solution entering the static mixing tube; s The ratio of the total mass of chlorobenzene solvent used in the amine solution and the chlorobenzene solvent used in the phosgene solution to the mass of amine in the amine solution, i.e., the ratio of all solvents to amine after the phosgene solution and amine solution enter the static mixing tube and before they react.

[0073] Furthermore, to further control the cold reaction temperature, the amine solution feed temperature is controlled at 80°C. At this temperature, the amine solution is homogeneous and does not easily precipitate solids. The mass concentration of the amine solution is 30wt%-40wt%. Further, during the cold reaction, the molar ratio of phosgene to amine (phosgene-amine ratio) is preferably 2:1-8:1.

[0074] Based on the above calculation method of Q, the smaller the Q value, the larger the average particle size of the intermediate particles. Therefore, by controlling the crystallization index Q≥175.52, the present invention can obtain intermediate particles with a smaller average particle size. Specifically, the average particle size of the intermediate particles can be controlled below 13μm, resulting in less isocyanate impurity content and significantly reduced product color, effectively improving the quality of isocyanate.

[0075] However, considering that if the Q value is too large, the amount of phosgene and the system pressure need to be increased, and when the amount of phosgene and the system pressure are too high, it will lead to an increase in the load of the cold reaction mixer, a decrease in production capacity and an increase in safety risks. Therefore, it is preferable to control the Q value in the range of 175.52-405.15.

[0076] Optionally, in the cold reaction stage of step S1, the input power W per unit volume of the dynamic mixing tube... e The preferred value is 10 kW / m 3 -15kw / m 3 ; Mass concentration C of phosgene solution p The preferred value is 40wt%-50wt%; the outlet pressure P of the dynamic mixing tube b The preferred temperature is 15-20 bar; the feed temperature T of the phosgene solution is... p Preferably, the temperature is 4℃-6℃; the ratio of the total mass of the chlorobenzene solvent used in the amine solution and the chlorobenzene solvent used in the phosgene solution to the mass of the amine in the amine solution is R. s The preferred value is 4-8.

[0077] Optionally, the cold reaction step further includes adding a phosgene solution at a temperature of 4°C-6°C to the dynamic mixing tube, the amount of which is 10wt%-30wt% of the amount of phosgene solution used in the static mixing tube. This increases the phosgene concentration in the dynamic mixing tube, allowing the released amine to react with phosgene to form carbamoyl chloride at a lower temperature, further reducing the formation of byproducts such as urea.

[0078] See also Figure 1In the preparation method of the present invention, an online particle size analyzer can also be used to detect the average particle size of the intermediate particles in the cold reaction mixture obtained from the dynamic mixing tube. Therefore, online particle size detection can be used to determine whether the cold reaction is normal. For example, if the Q value is within the normal range, but the average particle size of the detected intermediate particles is greater than 13 μm, it indicates a problem in the cold reaction stage, requiring timely adjustment and repair to restore the cold reaction to normal.

[0079] The present invention does not have special requirements for the thermal reaction in step S2 and the post-processing in step S3, and will not be described in detail here.

[0080] Preferably, the present invention also provides a cold reaction mixer, such as Figures 2-4 As shown, the cold reaction mixer includes a static mixing tube 14 and a dynamic mixing tube 13. The static mixing tube 14 has an amine solution inlet and a phosgene solution inlet 16. The dynamic mixing tube 13 is equipped with a dynamic mixing assembly 17, which includes a stator 171 and a rotor 172. The stator 171 is fixedly connected to the inner wall of the dynamic mixing tube 13, and the rotor 172 is disposed opposite to the stator 171. The rotor 172 is connected to a driving member 18, which drives the rotor 172 to rotate. The dynamic mixing tube 13 is connected to the outlet end of the static mixing tube 14, and the dynamic mixing tube 13 is provided with a cold reaction mixture outlet 102. It can be understood that in the calculation of the crystallinity index Q, the outlet pressure P of the dynamic mixing tube... b This refers to the pressure here.

[0081] Optionally, the cold reaction mixer further includes a phosgene solution silo 12, the phosgene solution silo 12 having a phosgene solution inlet 101, the static mixing pipe 14 being disposed in the phosgene solution silo 12, and the phosgene solution inlet 16 of the static mixing pipe 14 being connected to the phosgene solution silo 12.

[0082] Optionally, the cold reaction mixer further includes an amine solution mixing section 15, which has an amine inlet 151, a first solvent inlet 152, and an amine solution outlet 153, wherein the amine solution outlet 153 is connected to the amine solution inlet of the static mixing tube 14.

[0083] When using the cold reaction mixer of the present invention, the amine and the first solvent enter the amine solution mixing section 15 from the amine inlet 151 and the first solvent inlet 152, respectively, and are mixed in the amine solution mixing section 15 to obtain an amine solution. At the same time, the phosgene solution enters the phosgene solution hopper 12 from the phosgene solution inlet 101 and fills the entire phosgene solution hopper 12. Then, the amine solution and the phosgene solution enter the static mixing tube 14 through the amine solution inlet and the phosgene solution inlet 16, respectively, and react in the static mixing tube 14 to generate an intermediate mixture of amine hydrochloride and carbamoyl chloride. Then, the intermediate mixture enters the dynamic mixing tube 13 and is sheared and broken by the dynamic mixing component 17 in the dynamic mixing tube 13 to obtain a cold reaction mixture. The cold reaction mixture is discharged from the cold reaction mixture outlet 102 of the dynamic mixing tube 13 as a product of the cold reaction and enters the thermal reactor for thermal reaction.

[0084] Optionally, the stator 171 has a first serration on the side facing the rotor 172, and the rotor 172 has a second serration on the side facing the stator 171 that matches the first serration. This arrangement is beneficial for further crushing the average particle size of the intermediate particles.

[0085] Optionally, the dynamic mixing component may have two or more sets of stators 171 and rotors 172, such as two or three sets, for better results.

[0086] In this invention, the driving component 18 is configured as a motor.

[0087] Since the reaction products are sheared and crushed by the dynamic mixing component 17, the encapsulated raw material amine will be released. At this time, it is preferable to also add cold phosgene solution to the dynamic mixing tube 13. For example, the dynamic mixing tube 13 is connected to the phosgene solution hopper 12 through the channel 111. Cold phosgene solution is added from the phosgene solution hopper 12 to the dynamic mixing tube 13 through the channel 111, thereby increasing the phosgene concentration in the dynamic mixing tube 13, so that the released raw material amine reacts with phosgene at the lowest possible temperature, reducing the generation of by-products.

[0088] Furthermore, the present invention also provides an apparatus for preparing isocyanates, comprising at least the aforementioned cold reaction mixer and a hot reactor connected to the cold reaction mixer. It is understood that the apparatus also includes equipment such as a decolorization tower for post-processing steps.

[0089] The thermal reactor can be a tower reactor, a stirred tank reactor, a stirred tankless reactor, or a combination thereof. Preferably, the thermal reactor is a multi-stage series reactor, with 1 to 6 stages connected in series, and the temperature is controlled at 100℃-180℃ and the pressure is controlled at 2 bar-10 bar.

[0090] Optionally, the outlet of the dynamic mixing tube is also equipped with an online particle size analyzer to detect the average particle size of the intermediate particles and determine whether the cold reaction is normal.

[0091] The following specific embodiments will further illustrate the preparation method of the isocyanate, the cold reaction mixer, and the isocyanate preparation apparatus. The yield is calculated based on the amount of isocyanate generated, i.e.: Yield % = (Molar amount of isocyanate measured in the product / Theoretically, the molar amount of isocyanate generated from amino groups in the raw material) × 100.

[0092] Example 1:

[0093] This embodiment uses a mixture of methylene diphenyl diamine and polymethylene polyphenyl polyamine (MDA) as raw materials to prepare MDI products.

[0094] First, MDA and chlorobenzene are mixed in an amine solution mixing section to form an MDA solution. Then, the phosgene solution and MDA solution are injected into a static mixing tube to react and obtain an intermediate mixture. The static mixing time is 300 ms. The intermediate mixture then enters a dynamic mixing tube, which has a dynamic mixing assembly consisting of two sets of stators and rotors. After being sheared by the dynamic mixing assembly, a cold reaction mixture is obtained. The dynamic mixing time is 130 ms. The phosgene solution uses chlorobenzene as the solvent with a mass concentration of 40 wt%. The outlet pressure of the dynamic mixing tube is 15 bar, and the input power per unit volume of the dynamic mixing tube is 10 kW / m³. 3 The feed temperature of the phosgene solution is 4. o C, the concentration of MDA and chlorobenzene after mixing is 30wt%, the feed temperature of the amine solution is 80℃, the mass ratio of the total mass of chlorobenzene to the mass of MDA in the static mixing tube before reaction is 4, at this time Q value = 175.52, the average particle size of intermediate particles in the cold reaction mixture measured by an online particle size analyzer is 11.51μm.

[0095] Next, the cold reaction mixture from the cold reaction mixer enters a four-tank hot reactor connected in series, with the temperature controlled at 120°C. o At temperature C, the thermal reaction was carried out at a pressure of 3 bar to obtain a thermal reaction solution. Finally, the thermal reaction solution underwent operations such as dephosgenesis, desolventization, and purification to obtain various MDI products with an overall product yield of 98.8%, of which MDI-50 had a color intensity (APHA) of 15 and MDI-100 had a color intensity (APHA) of 13.

[0096] Example 2:

[0097] The only difference between Example 2 and Example 1 is that the solvent for the phosgene solution is chlorobenzene with a mass concentration of 48 wt%, the outlet pressure of the dynamic mixing tube is 18 bar, and the input power per unit volume of the dynamic mixing tube is 14 kW / m³.3 The feed temperature of the phosgene solution is 5. o C, the ratio of the total mass of chlorobenzene to the mass of MDA in the static mixing tube before reaction is 8, at which point Q = 210.05, and the average particle size of the intermediate particles in the cold reaction mixture, as measured by an online particle size analyzer, is 9.56 μm.

[0098] In this embodiment, the total product yield is 99.1%, with MDI-50 chromaticity (APHA) of 12 and MDI-100 chromaticity (APHA) of 9.

[0099] Example 3:

[0100] The only difference between Example 3 and Example 1 is that the solvent for the phosgene solution is chlorobenzene with a mass concentration of 50 wt%, the outlet pressure of the dynamic mixing tube is 20 bar, and the input power per unit volume of the cold reaction mixer is 15 kW / m³. 3 The feed temperature of the phosgene solution is 4. o C, the mass ratio of the total mass of chlorobenzene to the mass of MDA in the static mixing tube before reaction is 4, at which point the Q value is 405.15, and the average particle size of the intermediate particles in the cold reaction mixture, as measured by an online particle size analyzer, is 7.62 μm.

[0101] In this embodiment, the total product yield is 99.5%, with MDI-50 chromaticity (APHA) of 9 and MDI-100 chromaticity (APHA) of 7.

[0102] Example 4:

[0103] The only difference between Example 4 and Example 1 is that the solvent for the phosgene solution is chlorobenzene with a mass concentration of 60 wt%, the outlet pressure of the dynamic mixing tube is 30 bar, and the input power per unit volume of the dynamic mixing tube is 20 kW / m³. 3 The feed temperature of the phosgene solution is 5. o C, the ratio of the total mass of chlorobenzene to the mass of MDA in the static mixing tube before reaction is 6, at which point the Q value is 515.46, and the average particle size of the intermediate particles in the cold reaction mixture, as measured by an online particle size analyzer, is 7.04 μm.

[0104] In this embodiment, the total product yield is 99.6%, with MDI-50 chromaticity (APHA) of 8 and MDI-100 chromaticity (APHA) of 7.

[0105] Comparative Example 1:

[0106] The only difference between Comparative Example 1 and Example 1 is that the solvent for the phosgene solution is chlorobenzene with a mass concentration of 40 wt%, the outlet pressure of the dynamic mixing tube is 10 bar, and the input power per unit volume of the dynamic mixing tube is 5 kW / m. 3The feed temperature of the phosgene solution is 5. o C, the mass ratio of the total mass of chlorobenzene to the mass of MDA in the static mixing tube before reaction is 6, at which point the Q value is 37.34, and the average particle size of the intermediate particles in the cold reaction mixture, as measured by an online particle size analyzer, is 21.72 μm.

[0107] The total product yield in this comparative example was 97.4%, with MDI-50 colorimetric index (APHA) of 36 and MDI-100 colorimetric index (APHA) of 40.

[0108] Example 5:

[0109] This embodiment uses toluene diamine (TDA-80) as a raw material to prepare toluene diisocyanate (TDI-80).

[0110] First, TDA-80 and chlorobenzene are mixed in an amine solution mixing section to form a TDA-80 solution. Then, the phosgene solution and TDA-80 solution are injected into a static mixing tube to react and obtain an intermediate mixture. The static mixing time is 300 ms. The intermediate mixture then enters a dynamic mixing tube, which has a dynamic mixing assembly consisting of two sets of stators and rotors. After being sheared by the dynamic mixing assembly, a cold reaction mixture is obtained. The dynamic mixing time is 130 ms. The phosgene solution uses chlorobenzene as the solvent with a mass concentration of 50 wt%. The outlet pressure of the dynamic mixing tube is 20 bar, and the input power per unit volume of the dynamic mixing tube is 15 kW / m³. 3 The feed temperature of the phosgene solution is 6. o C, the concentration of TDA-80 after mixing with chlorobenzene is 35wt%, the feed temperature of the amine solution is 80℃, the mass ratio of the total mass of chlorobenzene to the mass of TDA-80 in the static mixing tube before reaction is 4, at this time Q value = 176.36, the average particle size of intermediate particles in the cold reaction mixture measured by an online particle size analyzer is 12.24μm.

[0111] Next, the cold reaction mixture from the cold reaction mixer enters a tower-type thermal reactor, with the temperature controlled at 120°C. o At temperature C, and pressure 3 bar, a thermal reaction was carried out to obtain a thermal reaction solution. Finally, the thermal reaction solution underwent operations such as dephosgenesis, desolventization, and purification to obtain the TDI-80 product, with an overall product yield of 98.4% and a color (APHA) of 13.

[0112] Example 6:

[0113] The only difference between Example 6 and Example 5 is that the solvent for the phosgene solution is chlorobenzene with a mass concentration of 45 wt%, the outlet pressure of the dynamic mixing tube is 18 bar, and the input power per unit volume of the dynamic mixing tube is 15 kW / m³. 3 The feed temperature of the phosgene solution is 4.o C, the ratio of the total mass of chlorobenzene to the mass of TDA-80 in the static mixing tube before reaction is 7, at which point Q value = 335.89, and the average particle size of the intermediate particles in the cold reaction mixture, as measured by an online particle size analyzer, is 10.53 μm.

[0114] In this embodiment, the total product yield is 98.9%, and the colorimetric achromaticity (APHA) is 8.

[0115] Example 7:

[0116] The only difference between Example 7 and Example 5 is that the solvent for the phosgene solution is chlorobenzene with a mass concentration of 47 wt%, the outlet pressure of the dynamic mixing tube is 16 bar, and the input power per unit volume of the dynamic mixing tube is 14 kW / m³. 3 The feed temperature of the phosgene solution is 5. o C, the ratio of the total mass of chlorobenzene to the mass of TDA-80 in the static mixing tube before reaction is 8, at which point Q value = 194.21, and the average particle size of the intermediate particles in the cold reaction mixture, as measured by an online particle size analyzer, is 11.51 μm.

[0117] In this embodiment, the total product yield is 98.6%, and the colorimetric aura (APHA) is 10.

[0118] Example 8:

[0119] The only difference between Example 8 and Example 5 is that the solvent for the phosgene solution is chlorobenzene with a mass concentration of 60 wt%, the outlet pressure of the dynamic mixing tube is 30 bar, and the input power per unit volume of the dynamic mixing tube is 20 kW / m³. 3 The feed temperature of the phosgene solution is 5. o C, the ratio of the total mass of chlorobenzene to the mass of TDA-80 in the static mixing tube before reaction is 8, at which point Q value = 512.12, and the average particle size of the intermediate particles in the cold reaction mixture, as measured by an online particle size analyzer, is 9.97 μm.

[0120] In this embodiment, the total product yield is 99.1%, and the colorimetric achromaticity (APHA) is 7.

[0121] Comparative Example 2:

[0122] The only difference between Comparative Example 2 and Example 5 is that the solvent for the phosgene solution is chlorobenzene with a mass concentration of 35 wt%, the outlet pressure of the dynamic mixing tube is 15 bar, and the input power per unit volume of the dynamic mixing tube is 6 kW / m. 3 The feed temperature of the phosgene solution is 5. oC, the ratio of the total mass of chlorobenzene to the mass of TDA-80 in the static mixing tube before reaction is 8, at which point the Q value is 44.45, and the average particle size of the intermediate particles in the cold reaction mixture, as measured by an online particle size analyzer, is 27.31 μm.

[0123] In this comparative example, the total product yield was 96.7%, and the colorimetric index (APHA) was 34.

[0124] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0125] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing an isocyanate, comprising a cold reaction, a hot reaction, and a post-treatment, characterized in that, The steps of the cold reaction include: Phosgene solution and amine solution are mixed and reacted in a static mixing tube to obtain an intermediate mixture, wherein chlorobenzene is used as a solvent for both phosgene solution and amine solution; The intermediate mixture enters the dynamic mixing tube, and the dynamic mixing assembly is driven to rotate by the driving component. After being sheared by the dynamic mixing assembly, a cold reaction mixture is obtained. Wherein, the crystallinity index Q of the cold reaction is ≥175.52, and Q is calculated as follows: In the formula, C p The concentration of the phosgene solution is expressed in wt%; P b The outlet pressure of the dynamic mixing tube, in bar; W e Input power per unit volume of the dynamic mixing tube, in kW / m 3 ;T p R represents the feed temperature of the phosgene solution, in °C. s The ratio of the total mass of the chlorobenzene solvent used in the amine solution and the chlorobenzene solvent used in the phosgene solution to the mass of the amine in the amine solution.

2. The method for preparing isocyanate according to claim 1, characterized in that, 175.52≤Q≤405.15。 3. The method for preparing isocyanate according to claim 1, characterized in that, The cold reaction step simultaneously satisfies the following conditions: (1) Input power W per unit volume of dynamic mixing tube e 10kw / m 3 -15kw / m 3 ; (2) Mass concentration C of phosgene solution p 40wt%-50wt%; (3) The outlet pressure P of the dynamic mixing pipe b 15-20 bar; (4) Feed temperature T of phosgene solution p The temperature is 4℃-6℃; (5) The ratio of the total mass of the chlorobenzene solvent used in the amine solution and the chlorobenzene solvent used in the phosgene solution to the mass of the amine in the amine solution, R s It is 4-8; (6) The feed temperature of the amine solution is constant and controlled at 80°C; (7) The mixing time in the static mixing tube is >150ms, and the mixing time in the dynamic mixing tube is >60ms.

4. The method for preparing isocyanate according to claim 1, characterized in that, The cold reaction step also includes adding a phosgene solution at a temperature of 4°C-6°C to the dynamic mixing tube, with the amount added being 10wt%-30wt% of the amount of phosgene solution used in the static mixing tube.

5. The method for preparing isocyanate according to any one of claims 1-4, characterized in that, The cold reaction step also includes using an online particle size analyzer to detect the average particle size of the cold reaction mixture obtained from the dynamic mixing tube.

6. The method for preparing isocyanate according to any one of claims 1-4, characterized in that, The amine in the amine solution is selected from methylene diphenyl diamine, polymethylene polyphenyl polyamine, a mixture of methylene diphenyl diamine and polymethylene polyphenyl polyamine, 2,4-toluenediamine, a mixture of 2,4-toluenediamine and 2,6-toluenediamine, m-phenylenediamine and its isomers, p-phenylenediamine and its isomers, tetramethylxylenediamine, 1,3-dimethylaminocyclohexane, 2,6-dimethylamine, 1,5-naphthyldiamine, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 4,4'-dicyclohexylmethanediamine, 2,4'-dicyclohexylmethanediamine, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 2,2-dimethyl-1,5-diaminopentane, 2-methyl-1,5-pentanediamine, 2, 4,4 (or 2,2,4)-trimethyl-1,6-diaminocyclohexane, 1,3- and 1,4-diaminocyclohexane, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane, 2,4- or 2,6-diamino-1-methylcyclohexane, 1-amino-1-methyl-4(3)-aminomethylcyclohexane, 1,3 (and / or 1,4)-bis(aminomethyl)cyclohexane, bis At least one of (aminomethyl)norbornene, triaminocyclohexane, tri(aminomethyl)cyclohexane, triamino-methylcyclohexane, 1,8-diamino-4-(aminomethyl)octane, 1,6,11-undecanetriamine, 1,7-diamino-4-(3-aminopropyl)heptane, 1,6-diamino-3-(aminomethyl)hexane, or 1,3,5-tri(aminomethyl)cyclohexane.

7. A cold reaction mixer used in the method for preparing isocyanate according to any one of claims 1-6, characterized in that, The cold reaction mixer includes: A static mixing tube having an amine solution inlet and a phosgene solution inlet; A dynamic mixing tube is provided inside the dynamic mixing tube. The dynamic mixing component includes a stator and a rotor. The stator is fixedly connected to the inner wall of the dynamic mixing tube. The rotor is arranged opposite to the stator and is connected to a driving component. The rotor is driven to rotate by the driving component. The outlet end of the dynamic mixing tube is connected to the outlet end of the static mixing tube, and the dynamic mixing tube is provided with a cold reaction mixture outlet.

8. The cold reaction mixer according to claim 7, characterized in that, The cold reaction mixer also includes a phosgene solution silo, which has a phosgene solution inlet. The static mixing pipe is located in the phosgene solution silo, and the phosgene solution inlet of the static mixing pipe is connected to the phosgene solution silo.

9. The cold reaction mixer according to claim 8, characterized in that, The dynamic mixing pipe is connected to the phosgene solution silo via a channel.

10. The cold reaction mixer according to claim 7, characterized in that, The cold reaction mixer further includes an amine solution mixing section, which has an amine inlet, a first solvent inlet, and an amine solution outlet. The amine solution outlet is connected to the amine solution inlet of the static mixing tube.

11. The cold reaction mixer according to claim 7, characterized in that, The stator has a first serration on the side facing the rotor, and the rotor has a second serration on the side facing the stator that matches the first serration.

12. The cold reaction mixer according to claim 7, characterized in that, The dynamic hybrid assembly has two or more sets of stators and rotors.

13. An apparatus for preparing isocyanate, characterized in that, The preparation apparatus includes at least a cold reaction mixer as described in any one of claims 7-12, and a hot reactor in communication with the cold reaction mixer.

14. The isocyanate preparation apparatus according to claim 13, characterized in that, The outlet of the dynamic mixing tube is also equipped with an online particle size analyzer.

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