Preparation method of m-xylylene diisocyanate

Abstract

The invention discloses a preparation method of m-xylylenediamine, which comprises the following steps: adding m-xylylenediamine into a reaction bottle filled with a hydrochloric acid solution, carrying out heat preservation reaction, carrying out reduced pressure distillation to remove water to obtain dry amine hydrochloride, preparing the amine hydrochloride and a solvent into slurry, adding the slurry into the reaction bottle filled with the solvent, introducing phosgene for reaction, and after the reaction, carrying out reduced pressure distillation to obtain m-xylylenediamine. And cooling the reaction liquid, filtering, carrying out reduced pressure distillation on the filtrate, and rectifying a crude product to obtain m-xylylene diisocyanate. According to the method disclosed by the invention, the m-xylylenediamine is good in dispersion and free from wrapping during salifying, the conversion rate of the amine hydrochloride is high, the amine hydrochloride slurry is continuously fed for photochemical reaction, the selectivity is high, the content of a key byproduct chlorinated derivative is less than 0.5%, and the method effectively improves the reaction conversion rate and selectivity and is suitable for industrial production. And the m-xylylene diisocyanate with high yield and high purity can be rapidly and simply prepared.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and particularly relates to a method for preparing m-xylylene diisocyanate. Background Art

[0002] Meta-xylylene diisocyanate (XDI) is a colorless and transparent liquid. XDI and its polyurethane products have excellent weather resistance, color stability and adhesion, and are widely used in high-end polyurethane coatings and paints, eyeglass lenses, flexible packaging, outdoor sealants, elastomers, leather and adhesives, etc. As an optical material such as a substitute for glass lenses, the content of impurities in meta-xylylene diisocyanate needs to be strictly limited to reduce the color and transparency problems caused by the presence of impurities.

[0003] In the prior art, the mainstream method for preparing m-xylylene diisocyanate is to use primary amine as raw material and react with phosgene to synthesize isocyanate. The phosgene method is mainly divided into a direct method and a salt-forming method. The direct method is to directly react primary amine and phosgene to prepare isocyanate. Due to the high activity of the amine group, urea by-products are easily generated. In the salt-forming method, the primary amine is first reacted with acidic gases such as hydrogen chloride and carbon dioxide to obtain the corresponding amine salt, and then reacted with phosgene to prepare isocyanate, which effectively avoids the generation of urea by-products. However, the amine salt will cause the system viscosity to be higher, and it is easy to cause wrapping and generate by-products such as chlorinated derivatives in the photochemical process, and affect mass transfer, so that the high-temperature photochemical reaction time is long, which brings the problem of increased polymer.

[0004] In the prior art, some researchers have proposed to increase the solvent ratio (usually controlled between 18 and 30:1) to make the amine salt uniformly dispersed and improve the salt conversion rate. Some have also proposed to use esters as solvents to increase the solubility of the amine salt and solve the problem of salt conversion rate. However, in these technologies, the encapsulation problem in the amine salt formation process has not been completely solved, the content of the chloro derivatives generated by the reaction is more than 1%, and the chloro derivatives and XDI have similar physical and chemical properties and are difficult to separate, which will lead to a decrease in the purity of XDI and reduce the yield of XDI. In addition, excessive solvent ratios and ester solvents increase the energy consumption of solvent recovery. Patent document CN101203488A solves the salt viscosity problem by increasing the temperature and gas phase salt formation, but the reaction temperature is too high to increase the content of the chloro derivatives, and the boiling points of the chloro derivatives and XDI are close, which is not conducive to subsequent distillation and purification. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for preparing m-xylylene diisocyanate with high yield, high purity, few impurities and strong industrial practicability.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0007] A method for preparing m-xylylene diisocyanate comprises the following steps:

[0008] (1) adding m-xylylenediamine to a reaction vessel containing a hydrochloric acid solution, controlling the reaction temperature to be 30° C. to 80° C. (salt-forming reaction), keeping the temperature for reaction after the addition of m-xylylenediamine, and then removing water by distillation under reduced pressure to obtain a dry amine hydrochloride;

[0009] (2) The dried amine hydrochloride obtained above is mixed with a solvent to form a slurry, the slurry is added to a reaction vessel containing a solvent, phosgene is introduced, and the temperature is raised to 130° C. to 180° C. for reaction (photochemical reaction). After the reaction, the reaction solution is cooled to 20° C. to 50° C., filtered, and the crude product is distilled to obtain m-xylylene diisocyanate.

[0010] In the above-mentioned method for preparing meta-xylylene diisocyanate, preferably, in step (1), the molar ratio of the meta-xylylenediamine to HCl in the hydrochloric acid solution is 1:2-4, and the mass fraction of the hydrochloric acid solution is 10%-36%.

[0011] In the above-mentioned method for preparing meta-xylylene diisocyanate, preferably, in step (1), the molar ratio of the meta-xylylenediamine to HCl in the hydrochloric acid solution is 1:2.2-3, and the mass fraction of the hydrochloric acid solution is 20%-30%.

[0012] The above-mentioned method for preparing m-xylylene diisocyanate, preferably, in step (2), the mass ratio of the amine hydrochloride to the phosgene is 1:3-12, the mass ratio of the amine hydrochloride to the total mass of the solvent is 1:4-18, and the solvent includes one of chlorobenzene, xylene and o-dichlorobenzene; the solvent of the slurry is the same as the solvent in the reaction container, and the mass ratio of the solvent of the slurry to the solvent in the reaction container is 3-1:1.

[0013] In the above-mentioned method for preparing m-xylylene diisocyanate, preferably, in step (2), the molar ratio of the amine hydrochloride to the phosgene is 1:4-8, and the ratio of the mass of the amine hydrochloride to the total mass of the solvent is 1:8-15.

[0014] The above-mentioned method for preparing meta-xylylene diisocyanate, preferably, in step (1), the meta-xylylenediamine is added dropwise or by a peristaltic pump (continuous feeding), and the addition rate is 0.005mol / min~0.015mol / min; in step (2), the slurry is added dropwise or by a peristaltic pump (continuous feeding), and the addition rate is 0.001mol / min~0.005mol / min, and the introduction rate of the phosgene is 0.006mol / min~0.02mol / min.

[0015] In the above-mentioned method for preparing m-xylylene diisocyanate, preferably, in step (1), the reaction temperature is 50°C to 70°C.

[0016] In the above-mentioned method for preparing m-xylylene diisocyanate, preferably, in step (1), the insulation reaction time is 0.5h to 1h.

[0017] In the above-mentioned method for preparing m-xylylene diisocyanate, preferably, in step (2), the reaction is carried out until the reaction liquid is transparent, and the filtrate obtained after filtering is subjected to reduced pressure distillation to recover the solvent.

[0018] In the above-mentioned method for preparing m-xylylene diisocyanate, preferably, in step (2), the temperature is raised to 140° C. to 170° C. for reaction.

[0019] In the above-mentioned method for preparing m-xylylene diisocyanate, preferably, in step (2), the heating and reaction time is 7h to 15h in total.

[0020] In the above-mentioned method for preparing isocyanate, preferably, in step (2), the content of isocyanate is ≥99.5%, the yield is ≥90%, and the content of chlorinated derivatives is <0.5%.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] In the preparation method of m-xylylenediisocyanate of the present invention, m-xylylenediamine and hydrochloric acid solution (aqueous solution) generate amine hydrochloride, which is soluble in water, has fast salt formation, good dispersion and no wrapping, while other technologies use HCl in an organic solvent to form salt, then the amine hydrochloride is insoluble, dispersed in the solvent, has slow salt formation, poor dispersion and easy wrapping, and m-xylylenediamine will be wrapped in the hydrochloride, and in the later high-temperature photochemical reaction of the amine hydrochloride and phosgene, urea, chloro derivatives and other by-products are easily generated, which reduces the reaction selectivity and the reaction yield. The hydrochloric acid salt formation method of the present invention has few by-products, the content of the key by-product chloro derivative is less than 0.5%, the reaction selectivity is more than 99%, the reaction yield is more than 98%, the product content is ≥99.5%, and the product yield is ≥90%.

[0023] In the preparation method of m-xylylene diisocyanate of the present invention, the amine hydrochloride and the solvent are not added at once after being prepared into a slurry, but are fed while reacting (preferably by dripping or continuous feeding with a peristaltic pump), the total amount of unreacted amine hydrochloride online is small, a small amount of solvent can effectively maintain the appropriate solvent ratio and material concentration of the reaction material amine hydrochloride, reduce the viscosity of the reaction liquid, facilitate the gas-solid-liquid three-phase mixing of phosgene, amine hydrochloride and solvent, accelerate mass transfer, improve reaction rate and shorten reaction time.

[0024] The invention effectively improves the reaction conversion rate and selectivity by optimizing the process, and can quickly and simply prepare high-purity meta-xylylene diisocyanate with a high yield, a content of ≥99.5%, and a yield of ≥90%. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with specific preferred embodiments, but the protection scope of the present invention is not limited thereby. The materials and instruments used in the following embodiments are all commercially available.

[0026] Example 1

[0027] A method for preparing m-xylylene diisocyanate of the present invention comprises the following steps:

[0028] (1) Add 300 mL of 30 wt% hydrochloric acid solution (containing 3 mol HCl) to a reaction flask, add 136 g (1 mol) of m-phenylenediamine dropwise at 0.01 mol / min to 0.015 mol / min, maintain the reaction temperature at 60-70°C, and add the solution for about 1.5 h. Keep the temperature for 0.5 h, and remove water by distillation under reduced pressure to obtain 209 g (1 mol) of dry amine hydrochloride.

[0029] (2) 209 g (1 mol) of dried amine hydrochloride and 1045 g of o-dichlorobenzene were prepared into a slurry, and added dropwise to a reaction bottle containing 1045 g of o-dichlorobenzene at a rate of 4-5 g / min (0.003 mol / min to 0.004 mol / min), phosgene was introduced at a rate of 1.3 g / min (0.013 mol / min), and the temperature was raised to 150-160° C. for reaction. The heating and reaction time was 9 h (i.e., the phosgene introduction time), and the reaction was stopped. The reaction liquid was light yellow and transparent. The content of chloro derivatives in the reaction liquid was monitored by gas chromatography and was 0.3%. The obtained reaction liquid was cooled to 30° C. and filtered. The obtained filtrate was distilled under reduced pressure to recover the solvent o-dichlorobenzene. The crude product was rectified to obtain a colorless transparent liquid, namely, m-xylylene diisocyanate, with a content of 99.5% and a yield of 95.5%.

[0030] Comparative Example 1

[0031] A method for preparing m-xylylene diisocyanate comprises the following steps:

[0032] (1) In a reaction bottle containing 300 g of o-dichlorobenzene, HCl gas was introduced at a rate of 1 g / min (0.028 mol / min), and 136 g (1 mol) of m-phenylenediamine was added dropwise. The reaction temperature was maintained at 60-70° C. The addition was completed in about 1.5 h. The reaction was kept warm for 0.5 h, and the solvent was removed by distillation under reduced pressure to obtain 209 g (1 mol) of dry amine hydrochloride.

[0033] (2) 209 g (1 mol) of dried amine hydrochloride and 1045 g of o-dichlorobenzene were prepared into a slurry, which was added dropwise at 4-5 g / min to a reaction bottle containing 1045 g of o-dichlorobenzene, phosgene was introduced at 1.3 g / min (0.013 mol / min), the temperature was raised to 150-160°C for reaction, and the heating and reaction time was 9 hours. The reaction was stopped, and the reaction liquid was light yellow and transparent. The content of chloro derivatives in the reaction liquid was 3.7% as monitored by gas chromatography. The obtained reaction liquid was cooled by 30°C, filtered, and the filtrate was distilled under reduced pressure to recover the solvent o-dichlorobenzene. The crude product was rectified to obtain a colorless transparent liquid, namely, m-xylylene diisocyanate, with a content of 98.5% and a yield of 80.3%.

[0034] Comparative Example 2

[0035] A method for preparing m-xylylene diisocyanate comprises the following steps:

[0036] (1) Add 300 mL of 30 wt% hydrochloric acid solution (containing 3 mol HCl) to a reaction flask, add 136 g (1 mol) of m-phenylenediamine dropwise at 0.01 mol / min to 0.015 mol / min, maintain the reaction temperature at 60-70°C, and add the solution for about 1.5 h. Keep the temperature for 0.5 h, and remove water by distillation under reduced pressure to obtain 209 g (1 mol) of dry amine hydrochloride.

[0037] (2) Add 209g (1mol) of dry amine hydrochloride and 2090g of o-dichlorobenzene into the reaction flask, introduce phosgene at 1.3g / min (0.013mol / min), heat to 150-160°C for reaction, heat and react for 15h, stop the reaction, the reaction liquid is light yellow and transparent, and the content of chloro derivatives in the reaction liquid is 1.5% as monitored by gas chromatography. The obtained reaction liquid is cooled to 30°C, filtered, and the filtrate is distilled under reduced pressure to recover the solvent o-dichlorobenzene. The crude product is rectified to obtain a colorless transparent liquid, which is m-xylylene diisocyanate, with a content of 99.0% and a yield of 85.6%.

[0038] Example 2

[0039] A method for preparing m-xylylene diisocyanate of the present invention comprises the following steps:

[0040] (1) Add 250 mL of 36 wt% hydrochloric acid solution (containing 3 mol HCl) to a reaction flask, add 136 g (1 mol) of m-phenylenediamine dropwise at 0.01 mol / min to 0.015 mol / min, maintain the reaction temperature at 70-80°C, and add the solution for about 1.5 h. Keep the temperature for 0.5 h, and remove water by distillation under reduced pressure to obtain 209 g (1 mol) of dry amine hydrochloride.

[0041] (2) 209 g (1 mol) of dried amine hydrochloride and 1045 g of o-dichlorobenzene were prepared into a slurry, and added dropwise to a reaction bottle containing 1045 g of o-dichlorobenzene at a rate of 4-5 g / min (0.003 mol / min to 0.004 mol / min), phosgene was introduced at a rate of 1.3 g / min (0.013 mol / min), and the temperature was raised to 150-160° C. for reaction. The total time of the temperature rise and reaction was 9 h (i.e., the phosgene was introduced for 9 h), and the reaction was stopped. The reaction liquid was light yellow and transparent, and the content of chloro derivatives in the reaction liquid was 0.4% as monitored by gas chromatography. The obtained reaction liquid was cooled to 30° C., filtered, and the filtrate was distilled under reduced pressure to recover the solvent o-dichlorobenzene. The crude product was rectified to obtain a colorless transparent liquid, namely, m-xylylene diisocyanate, with a content of 99.7% and a yield of 93.4%.

[0042] Example 3

[0043] A method for preparing m-xylylene diisocyanate of the present invention comprises the following steps:

[0044] (1) Add 300 mL of 30 wt% hydrochloric acid solution (containing 3 mol HCl) to a reaction flask, add 136 g (1 mol) of m-phenylenediamine dropwise at 0.01 mol / min to 0.015 mol / min, maintain the reaction temperature at 60-70°C, and add the solution for about 1.5 h. Keep the temperature for 0.5 h, and remove water by distillation under reduced pressure to obtain 209 g (1 mol) of dry amine hydrochloride.

[0045] (2) 209 g (1 mol) of dried amine hydrochloride and 418 g of o-dichlorobenzene were prepared into a slurry, and added dropwise at 2 g / min (0.0016 mol / min) to a reaction bottle containing 418 g of o-dichlorobenzene, and phosgene was introduced at 1.3 g / min (0.013 mol / min). The temperature was raised to 150-160° C. for reaction, and the temperature and reaction lasted for 13 hours. The reaction was stopped, and the reaction liquid was light yellow and transparent. The content of chloro derivatives in the reaction liquid was 0.4% as monitored by gas chromatography. The obtained reaction liquid was cooled to 30° C., filtered, and the filtrate was distilled under reduced pressure to recover the solvent o-dichlorobenzene. The crude product was rectified to obtain a colorless transparent liquid, namely, m-xylylene diisocyanate, with a content of 99.5% and a yield of 90.5%.

[0046] Example 4

[0047] A method for preparing m-xylylene diisocyanate of the present invention comprises the following steps:

[0048] (1) Add 300 mL of 30 wt% hydrochloric acid solution (containing 3 mol HCl) to a reaction flask, add 136 g (1 mol) of m-phenylenediamine dropwise at 0.01 mol / min to 0.015 mol / min, maintain the reaction temperature at 60-70°C, and add the solution for about 1.5 h. Keep the temperature for 0.5 h, and remove water by distillation under reduced pressure to obtain 209 g (1 mol) of dry amine hydrochloride.

[0049] (2) 209 g (1 mol) of dried amine hydrochloride and 1045 g of xylene were prepared into a slurry, and added dropwise at 4-5 g / min (0.003 mol / min to 0.004 mol / min) to a reaction bottle containing 1045 g of xylene. Phosgene was continuously introduced at 1.3 g / min (0.013 mol / min), and the temperature was raised to 130-140°C for reaction. The temperature and reaction lasted for 15 hours. The reaction was stopped, and the reaction liquid was light yellow and transparent. The content of chloro derivatives in the reaction liquid was 0.2% as monitored by gas chromatography. The obtained reaction liquid was cooled to 30°C, filtered, and the filtrate was distilled under reduced pressure to recover the solvent xylene. The crude product was rectified to obtain a colorless transparent liquid, namely, m-xylylene diisocyanate, with a content of 99.6% and a yield of 92.8%.

[0050] Example 5

[0051] A method for preparing m-xylylene diisocyanate of the present invention comprises the following steps:

[0052] (1) Add 300 mL of 30 wt% hydrochloric acid solution (containing 3 mol HCl) to a reaction flask, add 136 g (1 mol) of m-phenylenediamine dropwise at 0.01 mol / min to 0.015 mol / min, maintain the reaction temperature at 60-70°C, and add the solution for about 1.5 h. Keep the temperature for 0.5 h, and remove water by distillation under reduced pressure to obtain 209 g (1 mol) of dry amine hydrochloride.

[0053] (2) 209 g (1 mol) of dried amine hydrochloride and 1045 g of o-dichlorobenzene were prepared into a slurry, and added dropwise to a reaction bottle containing 1045 g of o-dichlorobenzene at a rate of 4-5 g / min (0.003 mol / min to 0.004 mol / min), phosgene was introduced at a rate of 1.3 g / min (0.013 mol / min), and the temperature was raised to 170-180°C for reaction. The temperature and reaction lasted for 7 hours, and the reaction was stopped. The reaction liquid was yellow and transparent. The content of chloro derivatives in the reaction liquid was 0.4% as monitored by gas chromatography. The obtained reaction liquid was cooled to 30°C, filtered, and the filtrate was distilled under reduced pressure to recover the solvent o-dichlorobenzene. The crude product was rectified to obtain a colorless transparent liquid, namely, m-xylylene diisocyanate, with a content of 99.5% and a yield of 94.1%.

[0054] Example 6

[0055] A method for preparing m-xylylene diisocyanate of the present invention comprises the following steps:

[0056] (1) Add 300 mL of 30 wt% hydrochloric acid solution (containing 3 mol HCl) to a reaction flask, add 136 g (1 mol) of m-phenylenediamine dropwise at 0.01 mol / min to 0.015 mol / min, maintain the reaction temperature at 30-40°C, and add the solution for about 1.5 h. Keep the temperature for 0.5 h, and remove water by distillation under reduced pressure to obtain 209 g (1 mol) of dry amine hydrochloride.

[0057] (2) 209 g (1 mol) of dried amine hydrochloride and 1045 g of o-dichlorobenzene were prepared into a slurry, which was added dropwise to a reaction bottle containing 1045 g of o-dichlorobenzene at a rate of 4-5 g / min (0.003 mol / min to 0.004 mol / min), phosgene was introduced at a rate of 1.3 g / min (0.013 mol / min), and the temperature was raised to 150-160° C. for reaction. The total time of the temperature rise and reaction was 9 hours. The reaction was stopped, and the reaction liquid was light yellow and transparent. The content of chloro derivatives in the reaction liquid was monitored by gas chromatography and was 0.3%. The obtained reaction liquid was cooled to 30° C. and filtered. The obtained filtrate was distilled under reduced pressure to recover the solvent o-dichlorobenzene. The crude product was rectified to obtain a colorless transparent liquid, namely, m-xylylene diisocyanate, with a content of 99.7% and a yield of 93.5%.

[0058] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as above in the preferred embodiment, it is not used to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing m-xylylene diisocyanate, characterized in that: The following steps are involved: (1) adding m-xylylenediamine to a reaction vessel containing a hydrochloric acid solution, controlling the reaction temperature to be 30° C. to 80° C., and after the addition of m-xylylenediamine, maintaining the temperature for reaction, and then removing water by distillation under reduced pressure to obtain a dry amine hydrochloride; (2) The dried amine hydrochloride obtained above is mixed with a solvent to form a slurry, the slurry is added to a reaction vessel containing a solvent, phosgene is introduced, and the temperature is raised to 130° C. to 180° C. for reaction. After the reaction, the reaction solution is cooled to 20° C. to 50° C., filtered, and the crude product is distilled to obtain m-xylylene diisocyanate.

2. The method for preparing meta-xylylene diisocyanate according to claim 1, characterized in that: In step (1), the molar ratio of the m-phenylenediamine to HCl in the hydrochloric acid solution is 1:2-4, and the mass fraction of the hydrochloric acid solution is 10%-36%.

3. The method for preparing meta-xylylene diisocyanate according to claim 2, characterized in that: In step (1), the molar ratio of the m-phenylenediamine to HCl in the hydrochloric acid solution is 1:2.2-3, and the mass fraction of the hydrochloric acid solution is 20%-30%.

4. The method for preparing meta-xylylene diisocyanate according to claim 1, characterized in that: In step (2), the molar ratio of the amine hydrochloride to the phosgene is 1:3-12, the mass ratio of the amine hydrochloride to the total mass of the solvent is 1:4-18, and the solvent comprises one of chlorobenzene, xylene and o-dichlorobenzene; the solvent of the slurry is the same as the solvent in the reaction container, and the mass ratio of the solvent of the slurry to the solvent in the reaction container is 3-1:

1.

5. The method for preparing meta-xylylene diisocyanate according to claim 4, characterized in that: In step (2), the molar ratio of the amine hydrochloride to the phosgene is 1:4-8, and the ratio of the mass of the amine hydrochloride to the total mass of the solvent is 1:8-15.

6. The method for preparing meta-xylylene diisocyanate according to any one of claims 1 to 5, characterized in that: In step (1), the m-phenylenediamine is added dropwise or by a peristaltic pump at a rate of 0.005 mol / min to 0.015 mol / min; in step (2), the slurry is added dropwise or by a peristaltic pump at a rate of 0.001 mol / min to 0.005 mol / min, and the phosgene is introduced at a rate of 0.006 mol / min to 0.02 mol / min.

7. The method for preparing meta-xylylene diisocyanate according to any one of claims 1 to 3, characterized in that: In step (1), the reaction temperature is 50° C. to 70° C.; and / or, in step (1), the insulation reaction time is 0.5 h to 1 h.

8. The method for preparing meta-xylylene diisocyanate according to any one of claims 1 to 3, characterized in that: In step (2), the reaction is carried out until the reaction solution is transparent, and the filtrate obtained after filtering is subjected to reduced pressure distillation to recover the solvent.

9. The method for preparing meta-xylylene diisocyanate according to any one of claims 1 to 3, characterized in that: In step (2), the temperature is raised to 140° C. to 170° C. for reaction; and / or, in step (2), the heating and reaction time is 7 h to 15 h in total.

10. The method for preparing meta-xylylene diisocyanate according to any one of claims 1 to 3, characterized in that: In step (2), the content of m-xylylene diisocyanate is ≥99.5%, the yield is ≥90%, and the content of chlorinated derivatives is <0.5%.