A green process for the preparation of 1,4-cyclohexane dimethyldiisocyanate

Abstract

The application belongs to the field of organic synthesis and provides a green preparation method of 1,4-cyclohexane dimethyl diisocyanate, wherein a non-polar solvent is used to prepare a solid light solution and a 1,4-cyclohexanedimethylamine solution respectively; the 1,4-cyclohexanedimethylamine solution is added dropwise into the solid light solution at 0-50 DEG C to perform a cold light reaction; the temperature is increased to 30-100 DEG C to perform a warm light reaction; the solid light solution is supplemented, the temperature is increased to 120-180 DEG C, and a hot light reaction is performed; wherein the total molar ratio of bis(trichloromethyl) carbonate and 1,4-cyclohexanedimethylamine is 0.5-2:1. Through the synergistic effect of the segmented supplementing process and the gradient temperature control, the problems of poor safety, many side reactions and low yield in the prior art are solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of organic synthesis, and particularly relates to a green preparation method of 1,4-cyclohexanedimethyl diisocyanate. BACKGROUND

[0002] 1,4-cyclohexanedimethyl diisocyanate (H6XDI) is a high-performance alicyclic diisocyanate, and the polyurethane material prepared therefrom has the characteristics of yellowing resistance and high mechanical strength, and is widely used in high-end coatings, elastomers and other fields. At present, the industrial preparation method of alicyclic diisocyanate is mainly a toxic phosgene method, but in this process type, toxic phosgene is used, which has great danger in use, transportation and storage, and needs to adopt various strict safety measures. The requirements for equipment in the production process are particularly high, the service life of the equipment is short, and there are various defects or hidden dangers. For example, CN106674056B discloses that 1,3-cyclohexanedimethylamine is salted with hydrogen chloride in a two-phase reaction solvent, and then the amine salt is reacted with phosgene in an inert solvent to prepare H6XDI. Although the target product is successfully obtained, the reaction of 1,3-cyclohexanedimethylamine with hydrogen chloride is rapid, and the amine salt is wrapped and caked, which leads to uneven stirring and incomplete salting, and urea is easily generated when reacting with phosgene, and the color of the solution becomes dark. In addition, the process needs to prepare 1,3-cyclohexanedimethylamine hydrochloride first, which increases the energy consumption, and has many operation steps, and has the defects of large solvent consumption and complex operation.

[0003] The reaction of the non-phosgene process has high energy consumption and many by-products. CN111108094A, US20060025626A1 and JPH07165696A introduce a multi-stage process for continuously preparing alicyclic diisocyanate, in which alicyclic diamine is reacted with carbonic acid derivatives (urea and dimethyl carbonate, respectively) and alcohol to obtain alicyclic diaminoformic acid ester, and then the alicyclic diaminoformic acid ester is thermally cracked to obtain alicyclic diisocyanate. The method needs to be carried out at high temperature, and high-boiling-point impurities are easily generated, which adversely affects the overall yield.

[0004] JP2011111424 discloses that 1,3-cyclohexanedimethylamine is reacted with solid phosgene under low temperature conditions to prepare 1,3-dimethyl isocyanate cyclohexane. However, this method has the defects of many reaction by-products, long reaction time and low yield, and is not suitable for industrial production.

[0005] Therefore, it is of great significance to continue to research and develop a new method which can solve the defects of the prior art.

[0006] In view of this, the present application is proposed. SUMMARY

[0007] The present application aims to solve the problems of poor safety, multiple side reactions and low yield in the existing preparation method of 1,4-cyclohexane dimethyl diisocyanate, and provides an efficient preparation method by replacing phosgene with solid light, and through the synergistic effect of staged supplementing process and gradient temperature control.

[0008] The basic concept of the technical solution adopted by the present application is as follows:

[0009] A green preparation method of 1,4-cyclohexane dimethyl diisocyanate, comprising: preparing a solid light solution and a 1,4-cyclohexanedimethylamine solution with a non-polar solvent respectively; dropping the 1,4-cyclohexanedimethylamine solution into the solid light solution at 0-50℃ to carry out a cold light reaction, then warming up to 30-100℃ to carry out a warm light reaction; further adding the solid light solution, and warming up to 120-180℃ to carry out a hot light reaction; wherein the total molar ratio of bis(trichloromethyl) carbonate to 1,4-cyclohexanedimethylamine is 0.5-2:1.

[0010] As one way, the solid light solution is dynamically added in the hot light reaction stage, and the addition time of the solid light solution is 1-6h. The time of the cold light reaction is 0.5-3h; the time of the warm light reaction is 0.5-8h; and the time of the hot light reaction is 1-6h.

[0011] As one way, the content of bis(trichloromethyl) carbonate in the added solid light solution accounts for 40%-70% of the total amount of bis(trichloromethyl) carbonate.

[0012] As one way, the hot light reaction is carried out in two stages, first at 120℃ for 0.5-4h, and then at 160℃ for 0.5-2h.

[0013] As one way, stirring is carried out in the cold light reaction stage, the warm light reaction stage and the hot light reaction stage, and the stirring rate is controlled to be 200-500rpm.

[0014] As one way, in the cold light reaction stage, the initial molar feeding ratio of bis(trichloromethyl) carbonate in the solid light solution to 1,4-cyclohexanedimethylamine is 0.3-1.2:1.

[0015] As one way, after the hot light reaction, the reaction liquid is filtered, desolventized, and purified by reduced pressure distillation, and the fraction at 120-160℃ / 5mmHg is collected.

[0016] As one way, the prepared 1,4-cyclohexane dimethyl diisocyanate has a purity of ≥99.8% and a hydrolysis chlorine content of ≤0.1% detected by GC-MS.

[0017] As one way, the gas generated in the cold light reaction stage, the warm light reaction stage and the hot light reaction stage is collected and introduced into lye, and then dehydrated, boiled with salt and recovered.

[0018] As a way, the non-polar solvent obtained after the reaction solution is desolventized is recovered and reused; the non-polar solvent is 1,2-dichlorobenzene, xylene, n-hexane or cyclohexane.

[0019] Compared with the prior art, the present application has the following advantages:

[0020] 1. The method of the present application uses 1,4-cyclohexanedimethylamine and bis(trichloromethyl) carbonate (also known as solid light or triphosgene) as reaction raw materials, uses a non-polar solvent (such as 1,2-dichlorobenzene, xylene, n-hexane or cyclohexane) as a solvent, and obtains a 1,4-cyclohexane diisocyanate reaction solution by mixing, cold light, warm light and hot light (additional solid light stabilizes the solid light concentration, so that the reaction proceeds in the forward direction).

[0021] By dynamically adding solid light in the hot light stage, the problem of side reactions caused by concentration fluctuations is solved, and in combination with three-stage gradient temperature control (matching reaction / by-product decomposition kinetics), the yield is increased from the traditional 40%~70% to more than 90% based on the replacement of phosgene with solid light.

[0022] 2. The method of the present application is simple, avoids the use of highly toxic phosgene, avoids the problems of phosgene production, transportation and storage, has high safety, long service life of equipment, and is easy to scale up production.

[0023] 3. The method of the present application reduces the amount of solid light added in the cold light stage, continuously and slowly adds solid light during the reaction, stabilizes the solid light content in the reaction solution, and makes the reaction proceed in the forward direction. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a flowchart of the preparation method of 1,4-cyclohexane diisocyanate according to the present application.

[0025] Figure 2 is the total ion current chromatogram of the GC-MS of the product prepared in Example 1.

[0026] Figure 3 is a partial enlarged view of Figure 2 .

[0027] Figure 4 is a partial enlarged view of Figure 2 .

[0028] Figure 5 is a partial enlarged view of Figure 2 .

[0029] Figure 6 is a partial enlarged view of Figure 2 .

[0030] wherein, Figure 1 1,4-H6XDI is 1,4-cyclohexane diisocyanate. DETAILED DESCRIPTION

[0031] The technical solutions of the embodiments of the present application are described below clearly and completely. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the described embodiments of the present application, all other embodiments obtained by those skilled in the art without any creative effort are within the scope of protection of the present application.

[0032] The raw materials used in the present application are all commercially available goods or samples prepared by the methods disclosed in the prior art.

[0033] The basic concept of the method described in the present application is as shown in Figure 1 The 1,4-cyclohexane diisocyanate reaction liquid is obtained by mixing, cold light, warm light and hot light (additional solid light) using 1,4-cyclohexanedimethylamine and solid light (bis(trichloromethyl) carbonate, also known as triphosgene) as the raw materials and 1,2-dichlorobenzene, dimethylbenzene, n-hexane or cyclohexane as the solvent. The reaction liquid is filtered to separate the insoluble by-products, and the solvent is recovered to obtain a crude liquid. The crude liquid is separated from the remaining by-products by distillation to obtain colorless and transparent finished 1,4-cyclohexane diisocyanate.

[0034] The 1,4-cyclohexane diisocyanate obtained in each case is tested and analyzed, and the specific method is described as follows.

[0035] (1) GC analysis of 1,4-cyclohexane diisocyanate

[0036] Shimadzu GC2030 with FID detector; microsyringe: 10 μL.

[0037] Chromatographic column: RTX-5, 30 m*0.32 mm*0.25 um

[0038] Inlet temperature: 280℃

[0039] Detector temperature: 280℃

[0040] Split ratio: 20:1

[0041] Injection volume: 0.5 uL

[0042] Carrier gas (nitrogen) pressure: 45 kPa

[0043] Hydrogen: 32 mL / min

[0044] Air: 200 mL / min

[0045] Tail gas: 24 mL / min

[0046] Column temperature: initial temperature 40 °C, hold for 1 min; increase to 280 °C at a rate of 20 °C / min, hold for 5 min.

[0047] (II) Hydrolysis rate analysis

[0048] A 0.01 mol / L silver nitrate standard titration solution was used in the hydrolysis rate determination;

[0049] A certain amount of sample was weighed into a clean and dry flask, and acetone was added to dissolve the sample;

[0050] A rotor was added to the flask, and stirring was performed until the sample was completely dissolved. Methyl alcohol (for sample hydrolysis reaction) was added, and continuous stirring was performed until the reaction solution heated up and white crystals precipitated, indicating the start of the reaction. Stirring was continued until the solution became turbid. Some isocyanates were not easy to react, and heating was required to start the reaction;

[0051] Pure water was added to the flask, and stirring and heating were continued to a slight boil for 30 min. The solution was cooled to room temperature, 10 drops of nitric acid were added, and potential titration was performed using a 0.01 mol / L silver nitrate standard titration solution.

[0052] (III) NCO content determination

[0053] (1) A 25 ml solution of di-n-butylamine was added to an iodometric flask using a pipette, and the flask walls were washed with 10 ml of toluene;

[0054] (2) The sample was weighed to an accuracy of 0.1 mg, and was added to the iodometric flask containing di-n-butylamine. After gently shaking to completely dissolve the sample, the solution was allowed to stand at room temperature for 15 min. The reaction caused the solution to heat up, and the sample for analysis should be completely liquefied. If the sample contained crystalline isocyanate, it was carefully heated until the sample was a homogeneous liquid;

[0055] (3) When the sample solution cooled to room temperature, 150 ml of acetone was added using a graduated cylinder, and the flask walls and stopper were rinsed;

[0056] (4) The excess di-n-butylamine was titrated using a colorimetric titration method;

[0057] Colorimetric titration: the iodometric flask was placed on a magnetic stirrer, 0.8 ml of bromophenol blue indicator was added using a pipette, and the solution was titrated with a hydrochloric acid standard titration solution until it changed from blue to yellow, and was maintained for 15 s, which was the end point of the titration.

[0058] (5) A blank test was also performed, and each group of samples was titrated twice to obtain an average value.

[0059] Example 1

[0060] (1) In a four-necked flask with thermometer and stirring element, 49 g of solid light and 100 g of 1,2-dichlorobenzene were dissolved to form a solid light solution, with a stirring rate of 200-300 rpm;

[0061] (2) In a constant pressure funnel, 20 g of 1,4-cyclohexanedimethylamine and 50 g of 1,2-dichlorobenzene were added to form a 1,4-cyclohexanedimethylamine solution;

[0062] (3) The 1,4-cyclohexanedimethylamine solution was added dropwise to the solid light solution obtained in step (1) (ice water bath 10-20℃), and the cold light reaction was carried out at 15-25℃ for 3h;

[0063] (4) The warm light reaction was carried out at 80℃ for 5h;

[0064] (5) A solution of 35 g of solid light and 100 g of 1,2-dichlorobenzene was added at one time, and then the temperature was raised to 120℃ for the hot light reaction, and then the temperature was raised to 160℃ for 2h;

[0065] (6) Filtration was carried out to remove solid impurities (the filter cake was dried for 10.32 g), and the filtrate was collected and evaporated to remove the solvent. The crude product after evaporation was subjected to vacuum distillation, and the fraction at 120-160℃ / 5mmHg was collected to obtain a colorless transparent liquid product 15.3 g.

[0066] The yield of the product was 56%, the purity was 99.4%, the hydrolysis rate was 534ppm, and the NCO value was 42.95%.

[0067] Example 2

[0068] (1) In a four-necked flask with thermometer and stirring element, 49 g of solid light and 100 g of 1,2-dichlorobenzene were dissolved to form a solid light solution, with a stirring rate of 400-500 rpm;

[0069] (2) In a constant pressure funnel, 20 g of 1,4-cyclohexanedimethylamine and 50 g of 1,2-dichlorobenzene were added to form a 1,4-cyclohexanedimethylamine solution;

[0070] (3) The 1,4-cyclohexanedimethylamine solution was added dropwise to the solid light solution obtained in step (1) (ice water bath 10-20℃), and the cold light reaction was carried out at 15-25℃ for 3h;

[0071] (4) The warm light reaction was carried out at 80℃ for 5h;

[0072] (5) A solution of 35 g of solid light and 100 g of 1,2-dichlorobenzene was added at one time, and then the temperature was raised to 120℃ for the hot light reaction, and then the temperature was raised to 160℃ for 2h;

[0073] (6) filtration, filter out solid impurities (filter residue is dried to obtain 8.53 g), collect the filtrate, remove the solvent by rotary evaporation, and perform vacuum distillation on the desolventized crude product to collect the fraction at 120-160°C / 5mmHg to obtain 15.6 g of colorless transparent liquid product.

[0074] The product yield is 57.1%, the purity is 98.6%, the hydrolysis rate is 323 ppm, and the NCO value is 42.9%.

[0075] Example 3

[0076] (1) Add 49 g of solid light and 100 g of 1,2-dichlorobenzene to a four-necked flask with a thermometer and a stirring element to form a solid light solution, and the stirring rate is 300-400 rpm;

[0077] (2) Add 20 g of 1,4-cyclohexanedimethylamine and 50 g of 1,2-dichlorobenzene to a constant pressure funnel to form a 1,4-cyclohexanedimethylamine solution;

[0078] (3) Add the 1,4-cyclohexanedimethylamine solution dropwise to the solid light solution obtained in step (1) (ice water bath 10-20°C), and perform a cold light reaction at 15-25°C for 3 h;

[0079] (4) Perform a warm light reaction at 80°C for 5 h;

[0080] (5) First, increase the temperature to 120°C, start to supplement the solution obtained by adding 35 g of solid light and 100 g of 1,2-dichlorobenzene (dropwise addition time 3 h) to perform a hot light reaction, and keep the temperature for 3 h, then increase the temperature to 160°C, and keep the temperature for 2 h;

[0081] (6) filtration, filter out solid impurities (filter residue is dried to obtain 5.12 g), collect the filtrate, remove the solvent by rotary evaporation, and perform vacuum distillation on the desolventized crude product to collect the fraction at 120-160°C / 5mmHg to obtain 19 g of colorless transparent liquid product.

[0082] The product yield is 69.6%, the purity is 99.1%, the hydrolysis rate is 213 ppm, and the NCO value is 43.2%.

[0083] Example 4

[0084] (1) Add 49 g of solid light and 100 g of 1,2-dichlorobenzene to a four-necked flask with a thermometer and a stirring element to form a solid light solution, and the stirring rate is 300-400 rpm;

[0085] (2) Add 20 g of 1,4-cyclohexanedimethylamine and 50 g of 1,2-dichlorobenzene to a constant pressure funnel to form a 1,4-cyclohexanedimethylamine solution;

[0086] (3) The 1,4-cyclohexanedimethylamine solution is added dropwise into the solid light solution obtained in step (1) (ice water bath 10-20 °C), and a cold light reaction is carried out at 15-25 °C for 3 h;

[0087] (4) A warm light reaction is carried out at 80 °C for 5 h;

[0088] (5) First, the temperature is raised to 120 °C, and a solution obtained from 35 g of solid light and 100 g of 1,2-dichlorobenzene is added dropwise (dropwise addition time 5 h) to carry out a hot light reaction, and the temperature is kept for 3 h, and then the temperature is raised to 160 °C, and the temperature is kept for 2 h;

[0089] (6) Filtration is carried out to remove solid impurities (0.2 g of filter residue is obtained after drying), and the filtrate is collected, desolvated by rotary evaporation, and the desolvated crude product is distilled under reduced pressure to collect a 120-160 °C / 5 mmHg fraction to obtain 25.19 g of colorless transparent liquid product.

[0090] The product yield is 91.3%, the purity is 99.8%, the hydrolysis rate is 76 ppm, and the NCO value is 43.21%.

[0091] Example 5

[0092] (1) A four-necked flask with a thermometer and a stirring element is added with 20 g of solid light and 100 g of 1,2-dichlorobenzene to form a solid light solution, and the stirring rate is 300-400 rpm;

[0093] (2) A constant pressure funnel is added with 20 g of 1,4-cyclohexanedimethylamine and 50 g of 1,2-dichlorobenzene to form a 1,4-cyclohexanedimethylamine solution;

[0094] (3) The 1,4-cyclohexanedimethylamine solution is added dropwise into the solid light solution obtained in step (1) (ice water bath 10-20 °C), and a cold light reaction is carried out at 15-25 °C for 3 h;

[0095] (4) A warm light reaction is carried out at 80 °C for 5 h;

[0096] (5) First, the temperature is raised to 120 °C, and a solution obtained from 35 g of solid light and 100 g of 1,2-dichlorobenzene is added dropwise (dropwise addition time 5 h) to carry out a hot light reaction, and the temperature is kept for 3 h, and then the temperature is raised to 160 °C, and the temperature is kept for 2 h;

[0097] (6) Filtration is carried out to remove solid impurities (0.2 g of filter residue is obtained after drying), and the filtrate is collected, desolvated by rotary evaporation, and the desolvated crude product is distilled under reduced pressure to collect a 120-160 °C / 5 mmHg fraction to obtain 25.19 g of colorless transparent liquid product.

[0098] The product yield is 91.3%, the purity is 99.8%, the hydrolysis rate is 76 ppm, and the NCO value is 43.21%.

[0099] Example 6

[0100] The recovered solvent, with a purity of 99.8%, contains 1,4-cyclohexane dimethyl diisocyanate at a content of 0.12%.

[0101] (1) A four-necked flask with a thermometer and a stirring element was used to dissolve 20 g of solid light and 100 g of recovered 1,2-dichlorobenzene, with a stirring rate of 300-400 rpm to form a solid light solution;

[0102] (2) A constant pressure funnel was used to add 20 g of 1,4-cyclohexanedimethylamine and 50 g of recovered 1,2-dichlorobenzene to form a 1,4-cyclohexanedimethylamine solution;

[0103] (3) The 1,4-cyclohexanedimethylamine solution was added dropwise to the solid light solution obtained in step (1) (ice water bath 10-20°C), and a cold light reaction was carried out at 15-25°C for 3 h;

[0104] (4) A warm light reaction was carried out at 80°C for 5 h;

[0105] (5) First, the temperature was raised to 120°C, and a solution obtained by adding 35 g of solid light and 100 g of recovered 1,2-dichlorobenzene was added dropwise (dropwise addition time 5 h) to carry out a hot light reaction, and then the temperature was raised to 160°C for 2 h;

[0106] (6) Filtration was carried out to remove solid impurities (0.2 g of filter residue was obtained after drying), and the filtrate was collected, desolvated by rotary evaporation, and the crude product after desolvation was subjected to vacuum distillation to collect a 120-160°C / 5 mmHg fraction to obtain a colorless transparent liquid product 23.12 g.

[0107] The product yield was 84.7%, the purity was 99.6%, the hydrolysis rate was 95 ppm, and the NCO value was 43.1%.

[0108] Example 7

[0109] (1) A four-necked flask with a thermometer and a stirring element was used to dissolve 20 g of solid light and 100 g of 1,2-dichlorobenzene, with a stirring rate of 300-400 rpm to form a solid light solution;

[0110] (2) A constant pressure funnel was used to add 20 g of 1,4-cyclohexanedimethylamine and 50 g of 1,2-dichlorobenzene to form a 1,4-cyclohexanedimethylamine solution;

[0111] (3) The 1,4-cyclohexanedimethylamine solution was added dropwise to the solid light solution obtained in step (1) (ice water bath 10-20°C), and a cold light reaction was carried out at 15-25°C for 3 h;

[0112] (4) Warm photoreaction at 80 °C for 5 h;

[0113] (5) Warm photoreaction at 120 °C for 5 h by adding a solution of 35 g of solid light and 100 g of 1,2-dichlorobenzene dropwise (dropwise time 5 h);

[0114] (6) Filtration to remove solid impurities (the filter residue was dried to obtain 12.6 g), and the filtrate was collected, desolvated by rotary evaporation, and the desolvated crude product was distilled under reduced pressure to collect the 120-160 °C / 5 mmHg fraction to obtain 13.2 g of colorless transparent liquid product.

[0115] The product yield was 46.4%, the purity was 99.3%, the hydrolysis rate was 117 ppm, and the NCO value was 43.08%.

[0116] Comparative Example 1

[0117] (1) In a four-necked flask with a thermometer and a stirring element, 43.75 g of solid light was dissolved in 100 g of 1,2-dichlorobenzene to form a solid light solution, and the stirring rate was 300-400 rpm;

[0118] (2) In a constant pressure funnel, 20 g of 1,4-cyclohexanedimethylamine and 50 g of 1,2-dichlorobenzene were added to form a 1,4-cyclohexanedimethylamine solution;

[0119] (3) The 1,4-cyclohexanedimethylamine solution was added dropwise to the solid light solution obtained in step (1) (ice water bath 10-20 °C), and cold photoreaction was carried out at 15-25 °C for 3 h;

[0120] (4) Warm photoreaction at 80 °C for 5 h;

[0121] (5) Warm photoreaction at 120 °C for 3 h, and then warm photoreaction at 160 °C for 2 h;

[0122] (6) Filtration to remove solid impurities (the filter residue was dried to obtain 13.46 g), and the filtrate was collected, desolvated by rotary evaporation, and the desolvated crude product was distilled under reduced pressure to collect the 120-160 °C / 5 mmHg fraction to obtain 11.09 g of colorless transparent liquid product.

[0123] The product yield was 40.9%, the purity was 98.6%, the hydrolysis rate was 1500 ppm, and the NCO value was 42.93%.

[0124] Comparative Example 2

[0125] In a four-necked flask with thermometer and stirring element, 87.5 g of solid light and 190 g of 1,2-dichlorobenzene were dissolved, the stirring rate was 300-400 rpm, 20 g of 1,4-cyclohexanedimethylamine and 50 g of 1,2-dichlorobenzene were added to the constant pressure funnel. The 1,4-cyclohexanedimethylamine solution was added dropwise to the solid light solution (ice water bath 10-20°C), and the light was kept at 15-25°C for 3 h, the light was kept at 80°C for 5 h, and the light was kept at 120°C and 160°C for 3 h and 2 h respectively. Filter, filter out solid impurities (oven dried 9.75 g), collect the filtrate, rotary evaporation, after desolventization, the crude product was distilled under reduced pressure, and the fraction of 120-160°C / 5mmHg was collected to obtain 16 g of colorless transparent liquid product.

[0126] The product yield was 58.6%, the purity was 98.8%, the hydrolysis rate was 1800 ppm, and the NCO value was 42.89%.

[0127] Test Example 1

[0128] In this test, the content of solid light at different reaction stages was detected by using aniline derivation method, taking Example 1 and Example 4 as examples.

[0129] 1 mL of reaction solution was taken into a 50 mL volumetric flask, 10 mL of acetonitrile solvent and 10 drops of aniline were added, and ultrasonic was performed for 30 min to generate bisphenyl urea, and then acetonitrile was added to the scale, and then it was shaken uniformly. The bisphenyl urea was quantitatively determined by liquid phase method.

[0130] Liquid phase conditions:

[0131] Chromatographic column: InertSustain C18 (250mm*4.6mm, 5mm)

[0132] Mobile phase: 70% methanol aqueous solution

[0133] Column temperature: 35°C

[0134] Wavelength: 254 nm

[0135] Flow rate: 1 mL / min

[0136] Injection volume: 3 uL

[0137] Analysis time: 30 min.

[0138] The results of the test are shown in Table 1. The % in Table 1 is mass fraction.

[0139] Table 1

[0140]

[0141] By comparing example 1 and example 4, it is found that there is a big difference in reaction effect between adding all solid light at one time before thermal photo reaction and dynamic supplementing under the condition of same solid light.

[0142] The reason is that: in the thermal photo reaction stage, the solid light is rapidly decomposed, which affects the forward progress of the reaction. Combined with the determination of the reaction end point, when the mass fraction of solid light is less than 0.2%, the reaction cannot continue to proceed in the direction of product.

Claims

1. A green process for the preparation of 1,4-cyclohexane dimethyldiisocyanate, characterized in that, The non-polar solvent is used to prepare the solid light solution and the 1,4-cyclohexanedimethylamine solution respectively; the 1,4-cyclohexanedimethylamine solution is added dropwise into the solid light solution at 0-50℃ to perform the cold light reaction, then the temperature is increased to 30-100℃ to perform the warm light reaction; the solid light solution is added again, and the temperature is increased to 120-180℃ to perform the hot light reaction; wherein the total molar ratio of the bis(trichloromethyl) carbonate and the 1,4-cyclohexanedimethylamine is 0.5-2:1; The content of the bis(trichloromethyl) carbonate in the added solid light solution accounts for 40%-70% of the total amount of the bis(trichloromethyl) carbonate; In the cold light reaction stage, the initial molar ratio of the bis(trichloromethyl) carbonate in the solid light solution to the 1,4-cyclohexanedimethylamine is 0.3-1.2:1; The non-polar solvent is 1,2-dichlorobenzene, xylene, n-hexane or cyclohexane.

2. The process for green preparation of 1,4-cyclohexane dimethanol diisocyanate as claimed in claim 1, wherein, The solid light solution is dynamically added in the hot light reaction stage, and the addition time of the solid light solution is 1-6h; The time of the cold light reaction is 0.5-3h; the time of the warm light reaction is 0.5-8h; and the time of the hot light reaction is 1-6h.

3. The process for green preparation of 1,4-cyclohexane dimethanol diisocyanate as claimed in claim 1, wherein, The hot light reaction is divided into two stages, first at 120℃ for 0.5-4h, and then at 160℃ for 0.5-2h.

4. The process for green preparation of 1,4-cyclohexane dimethanol diisocyanate as claimed in claim 1, wherein, The cold light reaction stage, the warm light reaction stage and the hot light reaction stage are all stirred, and the stirring speed is controlled to be 200-500rpm.

5. The process for green preparation of 1,4-cyclohexane dimethanol diisocyanate as claimed in claim 1, wherein, After the hot light reaction is completed, the reaction liquid is filtered, desolventized and purified by vacuum distillation, and the fraction at 120-160℃ / 5mmHg is collected to obtain the 1,4-cyclohexanedimethyl diisocyanate.

6. The process for green preparation of 1,4-cyclohexane dimethanol diisocyanate as claimed in claim 5 wherein, The purity of the obtained 1,4-cyclohexanedimethyl diisocyanate detected by GC-MS is ≥99.8%, and the hydrolysis chlorine content is ≤0.1%.

7. The process for the green preparation of 1,4-cyclohexane dimethyldiisocyanate according to any one of claims 1 to 6, characterized in that, The gas generated in the cold light reaction stage, the warm light reaction stage and the hot light reaction stage is collected and introduced into lye, then dehydrated, boiled and recovered.

8. The process for green preparation of 1,4-cyclohexane dimethanol diisocyanate as claimed in claim 5 wherein, The non-polar solvent obtained after the reaction liquid is desolventized is recovered and reused.

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