阅读说明：本技术 一种基于成盐光气化制备低氯代杂质含量异氰酸酯的方法 (Method for preparing isocyanate with low chlorinated impurity content based on salification phosgenation ) 是由 李同和 王京旭 孙淑常 崔学磊 郝超 张翼强 何伟 郭耀允 方婷 尚永华 于 2020-06-30 设计创作，主要内容包括：本发明提供一种基于成盐光气化法制备低氯代杂质含量异氰酸酯的方法。该方法成盐反应获得的盐颗粒粒径分布在平均粒径±30％范围内的比例占总粒径分布的70％以上,无搅拌的平均停留时间小于60min。相对于传统的方法,该方法获得的产品具有更低的氯代杂质含量。(The invention provides a method for preparing isocyanate with low content of chlorinated impurities based on a salifying phosgenation method. The proportion of the salt particle size distribution obtained by the salt forming reaction in the range of average particle size +/-30% accounts for more than 70% of the total particle size distribution, and the average retention time without stirring is less than 60 min. The process results in a product having a lower level of chlorinated impurities relative to conventional processes.)

1. A process for the preparation of isocyanates having a low chlorinated impurity content, said process comprising the steps of:

a. salt forming reaction: reacting the amine stream with hydrogen chloride and/or carbon dioxide to obtain amine hydrochloride and/or amine carbonate slurry;

b. and (3) carrying out phosgenation reaction: introducing phosgene into the amine hydrochloride and/or amine carbonate slurry to react to obtain photochemical reaction liquid;

c. separation: phosgene removal, refining and separation are carried out on photochemical reaction liquid to obtain an isocyanate product;

the method is characterized in that in the amine hydrochloride and/or amine carbonate slurry obtained in the step a, the proportion of the particle size of the amine hydrochloride and/or amine carbonate particles within the range of the average particle size +/-30 percent accounts for more than 70 percent, preferably more than 75 percent and more preferably more than 80 percent of the total particle size distribution; and the mean residence time of the amine hydrochloride and/or amine carbonate particles without stirring before starting the phosgenation reaction of step b is less than 60min, preferably less than 30min, more preferably less than 10 min.

2. The method according to claim 1, wherein step a is performed in any one of a batch mode, a semi-batch mode and a continuous mode, preferably in a continuous mode.

3. The process according to claim 1 or 2, characterized in that the amine of step a is added in the form of a separate stream or is previously brought into solution or suspension with an inert organic solvent.

4. The method of any one of claims 1-3, wherein the amine of step a has R (NH)₂)_nThe structure is shown in the specification, wherein R is an aliphatic or aromatic hydrocarbon group of C4-C15, and n is an integer of 1-10; the amine is preferably one or more of aniline, cyclohexylamine, 1, 4-butanediamine, 1, 5-naphthalenediamine, 1, 3-cyclohexyldimethylamine, 1, 6-hexamethylenediamine, 1, 4-diaminocyclohexane, 1-amino-3, 3, 5-trimethyl-5-aminomethylcyclohexane, 4' -diaminodicyclohexylmethanediamine, p-phenylenediamine, m-xylylenediamine, 2, 4-toluylenediamine, 2, 6-toluylenediamine, 1, 8-diamino-4- (aminomethyl) octane and triaminononane.

5. The process according to any one of claims 1 to 4, wherein, when the amine with a melting point of not higher than 60 ℃ is used in the step a, the salt-forming reaction temperature is-20 ℃ to 80 ℃, preferably 0 ℃ to 50 ℃; when amine with the melting point higher than 60 ℃ is adopted, the salt forming reaction temperature is 40-150 ℃, and preferably 60-130 ℃;

and/or the reaction pressure is between 0.03MPa and 0.50MPa (absolute pressure), preferably between 0.07MPa and 0.3MPa (absolute pressure);

and/or, the concentration of the reaction liquid is controlled between 5 and 40 percent (based on the mass of the amine);

and/or the dosage of the hydrogen chloride and/or carbon dioxide stream is 1.05-5 times of the theoretical dosage, preferably 1.5-3 times.

6. The process according to any one of claims 1 to 5, wherein the temperature of the reaction in step b is 90 to 180 ℃, preferably 100 to 150 ℃;

and/or the reaction pressure is between 0.05 and 0.80MPa (absolute pressure), preferably between 0.08 and 0.50MPa (absolute pressure);

and/or the reaction time is 1-8 h, preferably 2-4 h;

and/or the using amount of the phosgene is 1.1-6 times of the theoretical using amount, and preferably 1.5-4 times.

7. The process according to any one of claims 1 to 6, wherein an inert solvent is used in steps a and b, preferably one or more of chlorinated aromatic hydrocarbons, dialkyl terephthalates, diethyl phthalate, toluene and xylenes, more preferably one or more of aromatic hydrocarbons, and even more preferably one or more of chlorobenzene, dichlorobenzene, toluene and xylenes.

8. An isocyanate having a low level of chlorinated impurities prepared by the process of any one of claims 1 to 7 wherein the isocyanate is a polyisocyanate having R (NCO)_nAliphatic or aromatic isocyanate with a structure, wherein R is aliphatic or aromatic hydrocarbon radical of C4-C15, and n is an integer of 1-10; preferred isocyanates are one or more of phenyl isocyanate, cyclohexyl isocyanate, 1, 4-tetramethylene diisocyanate, 1, 5-naphthalene diisocyanate, 1, 3-dimethylene isocyanate cyclohexane, 1, 6-hexamethylene diisocyanate, 1, 4-cyclohexane diisocyanate, isophorone diisocyanate, 4' -dicyclohexylmethane diisocyanate, p-phenylene diisocyanate, m-xylylene diisocyanate, 2, 4-toluene diisocyanate, 2, 6-toluene diisocyanate, 1, 8-diisocyanato-4- (isocyanatomethyl) octane and nonane triisocyanate.

9. The isocyanate according to claim 8, wherein the chlorinated impurity in the isocyanate is R (NCO)_nA structure wherein one or more NCO groups are substituted with chlorine atoms.

Technical Field

The invention belongs to the field of isocyanate, and particularly relates to a method for preparing isocyanate with low chlorinated impurity content based on a salifying phosgenation method.

Background

Disclosure of Invention

The invention aims to provide a method for preparing isocyanate based on salification phosgenation, and compared with the traditional method, the obtained product has lower content of chlorinated impurities. In the process of preparing isocyanate by a salt-forming phosgene method, different control parameters in the salt-forming process can obtain hydrochloride or carbonate with different index parameters, the hydrochloride or carbonate with different parameters needs to correspond to different photochemical reaction conditions, the influence of different parameters is greatly different, and the different control parameters are very complicated, so that the key factors influencing the quality of reaction liquid or products in the salt-forming reaction or the photochemical reaction process are difficult to determine.

In the multiple reaction processes, the surprising discovery shows that the particle size of the hydrochloride or the carbonate can be used as a key influence factor for controlling the salification reaction and the photochemical reaction processes, the proportion of the particle size of salt particles obtained by the salification reaction within the range of the average particle size of +/-30 percent accounts for more than 70 percent of the total particle size distribution, the average retention time of the salification reaction liquid in a stirring-free state is less than 60min, and the content of chlorinated products in the reaction liquid or products can be effectively reduced. By controlling the particle size distribution of the salt in the salt forming reaction, the method can effectively control the over-high viscosity increase of the hydrochloride, reduce the problem of amine coating of the hydrochloride or the carbonate, and simultaneously can effectively control the photochemical reaction time, reduce the occurrence of various side reactions and reduce the content of chlorinated impurities in the product.

The mechanism of action of the particle size distribution of the amine salt particles, which is presumed to influence the chlorinated impurity content, is as follows:

in the process of salifying, if the particle size distribution is not well controlled, the problem of amine salt coating is very easy to exist, in photochemical reaction, along with the gradual reaction of surface salt into isocyanate, the coated amine is very easy to react with the generated isocyanate to generate urea (substance 1), the urea reacts with phosgene to generate substance 3 through substance 2, carbon dioxide is removed at the reaction temperature to generate substance 4, substance 4 continues to react with phosgene, and chlorinated impurities 7 and substance 8 are generated through dehydrochlorination, addition with hydrogen chloride and dehydrochlorination. The physical properties of the chlorinated impurities 7 are close to those of the target isocyanate, so that the difficulty of subsequent separation and purification is greatly increased, a certain amount of chlorinated impurities are contained in the product, and the application of the product in downstream industries is limited.

The particle size distribution of the hydrochloride is controlled in the salt forming reaction, so that the proportion of the particle size distribution within plus or minus 30 percent of the average particle size accounts for more than 70 percent of the total particle size distribution, the photochemical time of the hydrochloride or the carbonate can be ensured to be relatively uniform, the difference of different particle size reaction time caused by uneven distribution of the hydrochloride particles is reduced, the polymerization probability of isocyanate is reduced, and the reaction yield is improved.

The salt-forming reaction does not appear to be as good as the smaller the particle size distribution of the hydrochloride or carbonate salt as disclosed in the prior patents, although a smaller salt-forming particle size increases the specific surface area of the particles, shortens the time for photochemical reaction, and increases the conversion rate of the reaction. However, the salt-forming particle size is too small, the viscosity of the hydrochloride or carbonate can be increased rapidly, the reaction liquid can lose fluidity under partial working conditions, great challenges are brought to equipment of a production device, the conveying pipeline is easy to block, and great safety risks are brought to production. In addition, if the particle size of the hydrochloride generated by the reaction is concentrated in a very narrow particle size distribution range, the reaction needs to be controlled very accurately, so that very high requirements on production equipment, operators and parameter control are provided, and industrialization is difficult to realize.

After the salt-forming reaction is finished, the salt-forming reaction liquid is in an unstable suspension state, and salt particles and a solvent are in a layered settlement state under the condition of no stirring. The particles of these salts are in an unstable state and are more prone to agglomeration or caking, which is more likely to cause a deterioration in the result of the photochemical reaction, with a direct effect of causing an increase in the level of chlorinated impurities. During the course of the reaction, there are a lot of states of no stirring, and many states of no stirring are easily overlooked. Such as the conveying of the reaction liquid between the salification reaction kettle and the photochemical reaction kettle, or a buffer tank between the salification reaction kettle and the photochemical reaction kettle, or the retention of the salification reaction liquid in a pipeline in the intermittent reaction process, or the stop of stirring caused by abnormal reaction, etc.

The invention aims to be realized by the following scheme:

a process for the preparation of isocyanates having a low chlorinated impurity content, said process comprising the steps of:

a. salt forming reaction: reacting the amine stream with hydrogen chloride and/or carbon dioxide to obtain amine hydrochloride and/or amine carbonate slurry;

b. and (3) carrying out phosgenation reaction: introducing phosgene into the amine hydrochloride and/or amine carbonate slurry to react to obtain photochemical reaction liquid;

c. separation: phosgene removal, refining and separation are carried out on photochemical reaction liquid to obtain an isocyanate product;

in the method, in the amine hydrochloride and/or amine carbonate slurry obtained in the step a, the proportion of the particle size of the amine hydrochloride and/or amine carbonate particles within the range of the average particle size +/-30 percent accounts for more than 70 percent, preferably more than 75 percent and more preferably more than 80 percent of the total particle size distribution; and the mean residence time of the amine hydrochloride and/or amine carbonate particles without stirring before starting the phosgenation reaction of step b is less than 60min, preferably less than 30min, more preferably less than 10 min.

Step a preferably employs a hydrogen chloride stream having a faster reaction rate. To reduce the production of urea by-products and corrosion of the equipment in photochemical reactions, a hydrogen chloride stream employs dry hydrogen chloride.

The particle size distribution of the amine hydrochloride and/or amine carbonate particles obtained in step a is determined by a laser particle sizer.

The stir-free mean residence time of the hydrochloride obtained in step a consists of the following fractions. The average residence time of the salification reaction liquid transferred from the salification reaction kettle to the photochemical reaction kettle is that if the reaction is an intermittent reaction, the average residence time comprises the time t of starting stirring of the photochemical reaction kettle after the salification reaction liquid is fed into the photochemical reaction kettle from the beginning to reach a certain liquid level₁Transfer time t obtained from the volumes of the piping and the buffer tank and the transfer flow rate of the reaction solution₂And stopping stirring until the time t after the liquid level in the salt-forming reaction kettle is reduced to a certain degree and the salt-forming reaction liquid is discharged₃. If the salt-forming reaction liquid in the pipeline is not completely discharged in the batch reaction process, the average residence time t from the part of the residence volume to the whole reaction liquid needs to be increased before the salt-forming reaction kettle and the photochemical reaction kettle of one batch are transferred₄. If the reaction is continuous reaction, the average residence time is calculated by the volume of the pipeline and the buffer tank and the transfer flow rate of the reaction liquid to obtain the transfer time t₅. Abnormal stopping time t of stirring during and after salt-forming reaction₆. The residence time t of the unstirred maturation reaction set after the end of the salt formation reaction₇And other residence times t without agitation as can be determined by one skilled in the art₈And the like. In general, for a batch reaction, the residence time without stirring is from t_{Intermittent type}＝t₁+t₂+t₃+t₄+t₆+t₇+t₈Average residence time t without stirring for continuous reaction_Continuous＝t₅+t₆+t₇+t₈。

In the reaction process, t is used for ensuring the reaction effect_{Intermittent type}Or t_ContinuousLess than 60min, preferably t_{Intermittent type}Or t_ContinuousLess than 30min is required, more preferably t_{Intermittent type}Or t_ContinuousLess than 20min is required. Through the medium without stirring working conditionThe control measures for reducing the average residence time of the salification reaction liquid are taken, such as adopting higher transfer flow speed in the process of transferring the salification reaction kettle to the photochemical reaction kettle, increasing stirring in a middle buffer tank, reducing the curing time without stirring or increasing stirring in the curing process, and the like.

In the present invention, the step a is carried out by any of a batch system, a semi-batch system and a continuous system, and preferably by a continuous system.

In the present invention, the amine of step a is added in the form of a separate stream, or is previously mixed with an inert organic solvent to form a solution or suspension of the amine. The amine is in the liquid state under the process conditions of the reaction and can be added in a separate stream, preferably premixed with an inert organic solvent to form a solution of the amine. The amine is solid under the reaction process conditions and can be added as a separate stream by heating the amine stream above its melting point, preferably as a solution which is premixed with an inert organic solvent to form the amine, and which is less soluble in the inert solvent and which is added in suspension with the amine. The amine stream (either as a separate amine stream or as a solution or suspension with an inert solvent) can be fed into the reactor at once, preferably in a continuous manner.

In the present invention, the amine in step a has R (NH)₂)_nThe structure is shown in the specification, wherein R is an aliphatic or aromatic hydrocarbon group of C4-C15, and n is an integer of 1-10; the amine is preferably one or more of aniline, cyclohexylamine, 1, 4-butanediamine, 1, 5-naphthalenediamine, 1, 3-cyclohexyldimethylamine, 1, 6-hexamethylenediamine, 1, 4-diaminocyclohexane, 1-amino-3, 3, 5-trimethyl-5-aminomethylcyclohexane, 4' -diaminodicyclohexylmethanediamine, p-phenylenediamine, m-xylylenediamine, 2, 4-toluylenediamine, 2, 6-toluylenediamine, 1, 8-diamino-4- (aminomethyl) octane and triaminononane.

In the invention, when amine with the melting point not higher than 60 ℃ is adopted in the step a, the salt forming reaction temperature is-20-80 ℃, and preferably 0-50 ℃; when amine with the melting point higher than 60 ℃ is adopted, the salt forming reaction temperature is 40-150 ℃, and preferably 60-130 ℃.

In the present invention, the reaction pressure in step a is 0.03MPa to 0.50MPa (absolute), preferably 0.07MPa to 0.3MPa (absolute).

In the invention, the concentration of the reaction liquid in the step a is controlled to be 5-40% (based on the mass of the amine).

In the invention, the consumption of the hydrogen chloride and/or carbon dioxide stream in the step a is 1.05-5 times of the theoretical consumption, and preferably 1.5-3 times.

In the invention, the reaction temperature in the step b is 90-180 ℃, and preferably 100-150 ℃.

In the present invention, the reaction pressure in step b is 0.05MPa to 0.80MPa (absolute), preferably 0.08MPa to 0.50MPa (absolute).

In the invention, the reaction time in the step b is 1-8 h, preferably 2-4 h.

In the invention, the phosgene usage amount in the step b is 1.1-6 times of the theoretical usage amount, and preferably 1.5-4 times.

In the present invention, an inert solvent is used in the steps a and b, preferably one or more of chlorinated aromatic hydrocarbon, dialkyl terephthalate, diethyl phthalate, toluene and xylene, more preferably one or more of aromatic hydrocarbon, and further preferably one or more of chlorobenzene, dichlorobenzene, toluene and xylene.

The proportions of the raw materials in the steps a and b are in the conventional proportions known in the art.

The method for obtaining the isocyanate product from the photochemical reaction liquid in the step c is well known in the art, and the isocyanate product can be obtained by the methods of phosgene removal, refining and separation of the photochemical reaction liquid by adopting known methods, such as separation methods of gas stripping, crystallization, distillation, rectification and the like.

It is another object of the present invention to provide an isocyanate prepared by the method.

An isocyanate having a low level of chlorinated impurities prepared by the process, said isocyanate having R (NCO)_nAliphatic or aromatic isocyanate with a structure, wherein R is aliphatic or aromatic hydrocarbon radical of C4-C15, and n is an integer of 1-10; preferred isocyanates are phenyl isocyanate, cyclohexyl isocyanate, 1, 4-tetramethylene isocyanate, 1, 5-naphthalene diisocyanate, 1, 3-dimethylene isocyanate cyclohexane, 1,6-hexamethylene diisocyanate, 1, 4-cyclohexane diisocyanate, isophorone diisocyanate, 4' -dicyclohexylmethane diisocyanate, p-phenylene diisocyanate, m-xylylene diisocyanate, 2, 4-toluene diisocyanate, 2, 6-toluene diisocyanate, 1, 8-diisocyanato-4- (isocyanatomethyl) octane and nonane triisocyanate.

In the invention, the chlorinated impurity in the isocyanate is R (NCO)_nA structure wherein one or more NCO groups are substituted with chlorine atoms.

It should be noted that the method of the present invention reduces the content of chlorinated impurities in the same kind of isocyanate, but the absolute value of the content of chlorinated impurities in different kinds of isocyanate is very different, and the related comparison is limited to the same kind of isocyanate.

Compared with the prior art, the invention has the following positive effects:

(1) under the same separation conditions, isocyanate products with lower chlorinated impurity content can be obtained, and the separated products have higher yield, for example, when comparing the XDI obtained in the example 1 and the comparative example 1, the chlorinated impurity content of the XDI in the example 1 is reduced by 4 percentage points, the reduction is 44%, and the yield is also improved to 98.5%.

(2) The control method is simple to operate and can realize instant control.

Drawings

FIG. 1 is a graph showing the particle size distribution of hydrochloride particles of example 1.

FIG. 2 is a graph showing the particle size distribution of hydrochloride particles of example 2.

Fig. 3 is a graph showing a particle size distribution of hydrochloride particles of comparative example 1.

Detailed Description

The following examples are provided to further illustrate the technical solutions provided by the present invention, but the present invention is not limited to the listed examples, and includes any other known modifications within the scope of the claims of the present invention.

The main raw material sources and specifications are as follows:

chlorobenzene, industrial product, purity 99.8%, chemical industry of Jiangxi Longchang;

1, 6-Hexanediamine (HDA), industrial, 99.9% pure, usa, indovida;

isophorone diamine (IPDA), industrial, 99.7% purity, Vanhua Chemicals;

m-Xylylenediamine (XDA), industrial, 99.8% pure, mitsubishi japan;

p-phenylenediamine (PPDA), industrial product, purity 99.7%, Shanghai' an no arylamine;

1, 5-Naphthalene Diamine (NDA), industrial product, purity 99.8%, Nantong Haidi.

The main equipment is as follows: a reaction vessel equipped with a pressure regulator and equipped with a reflux condenser, a stirrer, a thermometer, a raw material feeder, a raw material tank, and a raw material pump was used. The volume of the reaction vessel was 80L, and the stirring speed was 200 rpm.

The particle size distribution of the obtained hydrochloride or carbonate particles is determined by a laser granulometer: taking out a small amount of slurry after the salt forming reaction is finished, further diluting the slurry by using acetonitrile as a solvent until the concentration is between 0.1 and 0.3 percent, measuring the slurry by using a laser diffraction type particle size distribution measuring device SALD-2201 manufactured by Shimadzu, and measuring the laser wavelength by 680 nm. The average particle size, the particle size distribution, and the proportion of the particle size within. + -. 30% of the average particle size in all the particle size distributions were measured.

The purity of the reaction liquid and isocyanate products and the content of chlorinated impurities in the reaction liquid are tested by an instrument and conditions as follows: gas chromatography, shimadzu GC-2010, column: DB-530X 0.25mm X0.25 μm sample size: 1 μ L, vaporizer temperature: 260 ℃, column flow: 1mL/min, split ratio: 50:1, column temperature: 50 ℃, keeping for 2min, heating to 80 ℃ at the rate of 5 ℃/min, keeping for 5min, heating to 280 ℃ at the rate of 20 ℃/min, keeping for 10min, and the detector temperature: at 300 ℃. Firstly, determining the retention time of target isocyanate and chlorinated impurities in a gas chromatography by adopting a gas chromatography-mass spectrometry method, and determining the mass fractions of the chlorinated impurities in reaction liquid and products by an area normalization method.