SU825511A1 - Method of preparing diisocyanates - Google Patents

Description

The invention relates to the synthesis of organic compounds, in particular to the improvement of the method of synthesis of diisocyanates of the general formula (where R is an organic radical - (CHg) or J which can be -HaC used in the chemical industry, namely, in the synthesis of organic compounds - xylylene diisocyanates (CDI) and Hexamethylenediisocyanate (HMDI), A method is known for the production of CDI and HMDI by phosgenating the corresponding diamines by the reaction R (, cH2NHj. :) sose,; - –HсSnz),; - 2ns at atmospheric pressure l. The disadvantage of the method is the presence in the resulting product of chlorinated impurities: chloromethyl benzyl isocyanate (C I) in CDI and chlorhexyl isocyanate (HGI) in HMDI. polymer chain and the impossibility of obtaining polyurethane foams. Other urethane products obtained on the basis of KDI with a high content of chlorine, have worse mechanical properties and lower resistance in relation to low temperatures than, for example, products obtained on the basis of toluylene diisocyanate. The purpose of the invention is to improve the quality of the target product. This goal is achieved by the fact that in the method of producing diisocyanates of the indicated general formula by phosgenating the corresponding diamines, phosgenation is carried out in the presence of ammonia in an amount from 0.2 to 1.5% relative to the starting diamine. Ammonia is introduced into the reaction mixture in the form of ammonium chloride in an amount of from 1.6 to 3.2% relative to the starting diamine. The introduction of NH in the form in many cases is technologically more convenient and leads to the same effect as the introduction of free ammonia due to the decomposition of INDS1 on NH and HCI under conditions

phosgenation at elevated temperatures. The hydrogen chloride released during the decomposition of MNDS is removed along with the hydrogen chloride formed during phosgenation.

Example lB four-necked flask with a capacity of 3000 ml, equipped with a stirrer, a thermometer, a reflux condenser and a bubbler for supplying phosgene gas, loading rt 1300 g of chlorobenzene, chill the last mixture of ice-salt to -15 to -12 ° C, load 500 g of phosgene and feeding a solution of 170 g of xylylenediamine-KDA (a mixture of m- and p-isomers in a ratio of 70:30) in 700 g of chlorobenzene at a temperature of from -2 to OC. At the end of the amine solution supply, the temperature in the reactor is slowly raised to 130G while simultaneously feeding 800 g of gaseous phosgene (at a rate of 90-100 g / h) and withdrawal. live at this temperature until the precipitate of carbamoyl chloride and hydrochloric acid salt of KDA disappears. Throughout the entire hot phosgenation step, 70 g of a 0.5% chlorobenzene solution of ammonia (prepared by saturating a portion of the solvent for synthesis, at room temperature) is added to the reaction mixture. The total amount of ammonia added is 0.20% with respect to the diamine.

 After synthesis, the mixture is blown dry with nitrogen to release residual phosgene and hydrogen chloride. 210.2 g (89.6% yield) of product with a total chlorine content of 0.6% was isolated by vacuum distillation.

For comparison, the process is carried out without the addition of ammonia. In this case, 217.0 g (92.5%) of KDI with a total chlorine content of 1.2% is recovered.

Example 2. The method of synthesis of KDI is the same as in Example 1. The solvent used is o-dichlorobeneol. The temperature of the first stage of the process (-2) is 0 ° C, the second stage is 170 ° C. When conducting the second (hot) phosgenation step, 100 g of a 2% solution of NH in o-dichlorobenzene is added to the reaction mixture. The amount of missed phosgene gas at the hot season is 420 g (120 g / h). The reaction dares to blow off, distill and get 213, .5 g (91.0%) KDI with a total chlorine content of 0.5 The total amount of ammonia introduced is 1.17% relative to the diamine. For comparison, the process is carried out without the addition of ammonia. After isolating the CDI, 223.3 g (95.2%) of product is obtained with a total chlorine content of 2.7%.

Example 3. The method of synthesis of CDI is the same as in example 1, with

the difference is that at the stage of hot phosgenation, a 0.5 h of each 0.5 h (0.25%) NH4CI is added to the reaction mixture.

The total weight of I added during hot phosgenation varies between 1.0-2.5% by weight of the amine, taken for synthesis.

After synthesis, the reaction mixture is vented and distilled.

In tab. 1 shows the total chlorine content in the pure product, depending on the amount of added

- 0.15

0.63 0.79 0.18

As can be seen from the table, the chlorine content in the product with the addition of 1.6-2.0% of NN401 is 0.15-0.18% without decreasing with an increase in the additive to 2.5% and age when the additive is reduced to 1 , 0%.

The product yield is 211 g (90%. Content of the main substance is 99.2%.

Example 4. The method of synthesis of KDI is the same as in example 3. As the solvent used o-dichlorobenzene. The temperature of the second reaction stage is 170 ° C. The amount of added is from 3.5 to 6.3 g (2.0-3.7% by weight of the amine, taken for synthesis).

Table 2 shows the total chlorine content in the product, depending on the amount of NH, C1 added.

2

The average product yield is 212 g (90%). Content of the main substance is 99.0%.

Example 5. A reactor with a capacity of 1.0 l, equipped with a stirrer, a thermometer, a reflux condenser and a bubbler for supplying phosgene gas, was charged with 400 g of o-dichlorobenzene, the latter was cooled with an ice-salt mixture, 200 g of phosphorus was added, and a solution of 60 g was added hexamethylenediamine (HMDA) in 400 g of o-dichlorobenzene at such a rate that the temperature in the reactor does not exceed (-2) -0s. After the supply of the amine solution is completed, the temperature in the reactor is raised to and maintained at this temperature until the precipitate of carbamoyl chloride and the hydrochloric acid salt of HMDA disappears, while 720 g (111.0 g / h) of phosgene gas are simultaneously supplied. 90 g of a 1% aqueous solution of NH in o-dichlorobenzene is introduced into the reaction mixture at the stage of hot phosgenation. After completion of the reaction, the reaction mixture is vented from the residual COS, 2 and her, subjected to vacuum distillation and 70.5 g (yield 81%) of HMDI with a total chlorine content of 0.25% is obtained. The total amount of NH injected is 1.50% with respect to diamine.

For comparison, the process was carried out without the addition of NHj and 75.7 g of HMDI was isolated (yield 87.0%) with a total chlorine content of 0.75%.

Example 6. The method of synthesis according to example 5. The solvent used is diethylbenzene. To a mixture of 200 g of diethylbenzene and 155 g of phosgene at a temperature of from -2 to 60 g of HMDA solution in 311 g of diethylbenzene is added. The temperature of the second stage is 170 ° C. At the stage of hot phosgenation, 1.9 / g portions of 0.4-0.5 g are introduced into the reaction mixture at equal intervals of time (1 hour). After isolation, 70.5 g (yield: 80.9%) of 1MDI with a total chlorine content of 0.4% are obtained. The total amount injected with .- 3.16% relative to the starting diamine (in terms of NH, 1.01%). For comparison, the synthesis was carried out without the addition of NN401 and 67.7 g (yield 78.0%) of HMDI with a total chlorine content of 1.4% were obtained.

0

Example 7. The method of synthesis is the same as Example 6, with the difference that at the stage of hot phosgenation, the additives are added in equal portions of 0.25 g every 5 0.5 hours. 71.2 g (yield 81.8%) of HMDI with a total chlorine content of 0.3% were recovered.

Claims (2)

1. A process for preparing diisocyanates: of the general formula R () 2, where 25 R-- - (sn2) 4-;  by -HgC phosphating the corresponding diamines, different 0 in order to improve the quality of the target product, phosgenation is carried out in the presence of ammonia, introduced in an amount of from 0.2 to 1.5% relative to the starting diamine. 2. The method according to Claim 1, about tl and h a5 shch and so that ammonia is introduced into the reaction mixture in the form of ammonium chloride in an amount of from 1.6 to 3.2% relative to the original diamine. 0 Sources of information taken into account in the examination 1. US Patent No. 3658656, cl. 203-49, published. 1972 (prototype).