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Preparing method of MDI

An organic solvent and solution technology, applied in the field of preparation of organic compounds, can solve the problems of non-phosgene method retention, difficulty in large-scale production, and many side reactions, and achieve the effects of accelerating the reaction rate, shortening the production cycle, and reducing the reaction temperature

Inactive Publication Date: 2017-03-15
JIANGSU JIALONG CHEM
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] 2. Non-phosgene method: non-phosgene method includes carbamate method, direct method (nitro compound reacts directly with carbon monoxide to form isocyanate) and triphosgene method, but currently the non-phosgene method is still in the lab. Or the pilot test was interrupted, and large-scale workshop production could not be carried out
[0006] 1. The reaction temperature of the phosgene method is high, and there are many side reactions. It is difficult to obtain pure MDI in one step. Only after splitting can MDI monomer and polymer be obtained.
[0007] 2. The non-phosgene reaction conditions are harsh, most of which require high temperature, noble metal catalysts and other conditions, and it is currently difficult to achieve large-scale production

Method used

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  • Preparing method of MDI

Examples

Experimental program
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Effect test

Embodiment 1

[0034] Put 30g of diphenylmethanediamine and 360g of o-dichlorobenzene into a 500ml four-neck flask equipped with a stirring, thermometer, gas guide tube and condenser tube, raise the temperature to 40~45°C, and pass in dry HCl gas while stirring , adjust the system pH=2~3. Add 0.3g of benzyltriethylammonium chloride, raise the temperature to 105~110℃, and pass phosgene under vigorous stirring, pass phosgene at 105~110℃ for 1.5h, Pass phosgene at ~140°C for 2 hours, and finally pass phosgene at 155-160°C until the solution is transparent. Then cool down to 40~45°C, and pass through dry nitrogen for 2h. Then the solvent is removed under reduced pressure, and then rectified under reduced pressure to obtain pure MDI.

[0035] 32.5g of pure MDI was obtained in the experiment, the content was 99.3% by gas spectrometry analysis, and the yield was 85.8%.

Embodiment 2

[0037] The process steps are the same as in Example 1, except that the feeding amount of diphenylmethanediamine is 50 g, that of o-dichlorobenzene is 600 g, and that of benzyltriethylammonium chloride is 0.5 g.

[0038] 55.6g of pure MDI was obtained in the experiment, the content was 99.4% by gas spectrometry analysis, and the yield was 88.1%.

Embodiment 3

[0040] The process steps are the same as in Example 1, except that the feeding amount of n-diphenylmethanediamine is 100 g, that of xylene is 1200 g, and that of benzyltriethylammonium chloride is 1 g.

[0041] 113g of pure MDI was obtained in the experiment, the content was 99.4% by gas spectrometry analysis, and the yield was 89.5%.

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Abstract

The invention discloses a preparing method of MDI. The method comprises the steps of dissolving diphenylmethane toluene diamine in an organic solvent, introducing acid gas into the solvent to salify, conducting phosgenation reaction on the solvent under the action of a catalyst to obtain a MDI solution, and then conducting distilling, desolventizing and rectification on the MDI solution to obtain MDI with a high purity. According to the method, a phosgenation method is adopted to prepare MDI, firstly diphenylmethane toluene diamine is made into hydrochloride, and thus the situation that isocyanate and acyl chloride generated in the photochemical reaction react with amine again and generate a polymer compound is avoided; meanwhile, the catalyst is added, thus the reaction temperature is lowered and the reaction rate is quickened; in addition, gradient temperature raising is adopted to conduct the photochemical reaction, thus the disadvantages that in a traditional phosgenation method, side reactions are easily generated when the temperature is too high, and the reaction time is too long when the temperature is too low are avoided, not only the production phase is shortened, but also MDI with high purity can be obtained. According to the preparing method of MDI, MDI monomer can be directly obtained in the photochemical reaction, and purified MDI can be obtained without flow separating.

Description

technical field [0001] The invention relates to a method for preparing an organic compound, in particular to a method for preparing MDI. Background technique [0002] MDI is the abbreviation of diphenylmethane diisocyanate. MDI is one of the most important raw materials for the production of polyurethane. A small amount of MDI is used in other aspects except polyurethane. At present, the methods for producing MDI are mainly divided into two categories: phosgene method and non-phosgene method: [0003] 1. Phosgene method: use aniline and formaldehyde to react under an acidic catalyst to generate diphenylmethanediamine (MDA), dissolve MDA in a solvent, and then carry out phosgenation reaction to produce polyphenyl polyisocyanate 4,4- MDI, 2,2-MDI or mixed PMDI, and then refined by distillation to obtain pure MDI. This process is a fully mature technical route for the production of MDI abroad. [0004] 2. Non-phosgene method: non-phosgene method includes carbamate method, di...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07C263/10C07C265/14
CPCC07C263/10C07C209/00
Inventor 牛安忠杨佳佳刘超张洪峰
Owner JIANGSU JIALONG CHEM
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