SU1456410A1 - Method of separating a mixture of diphenylmethane diisocyanate isomers - Google Patents

Abstract

The invention relates to the production of isocyanates, in particular the separation of isomers of diphenylmethane diisocyanate used in the synthesis of urethanes and herbicides. The goal is to increase the yield of target sizes. The separation of the latter includes: a) fractional crystallization of the melt of the initial mixture of isomers at 15–30 ° C with the formation of a crystalline product and the first mother liquor; b) film crystallization of the molten crystalline product with a temperature of 40-45 ° C supplied from step a, and 20-50 wt.% is added to it, which is obtained at this stage of crystals; c) crystallization at 0-15 ° C of the first mother liquor, to which the second mother liquor from step b is added in an amount of 50-200 wt.%. The third mother liquor thus formed, together with part of the crystals from step b, is returned to step a. The amount of Erisalisate from step B, necessary to return to step a, is determined graphically, starting from the composition of the initial mixture of isomers. These conditions allow an increase in the yield of basic 4,4-diphenyl methane diisocyanate from 76 to 85%. 2 ill., 1 tab. SS UIICTI-.

Description

one

The invention relates to industrial production methods, specifically to an improved method for separating a mixture of isomers of diphenyl methane diisocyanate (MDI), which are used to prepare urethanes and herbicides.

The aim of the invention is to increase the yield of the target products.

Separation of a mixture of isomers of diphente-methane diisocyanate by multi-stage fractional crystallization into a melt includes a primary crystallization stage, in which the initial mixture is separated into a crystalline product and the first mother liquid at 15-30 ° C, the primary crystallization of the molten crystalline product with a temperature of 40-45 ° C filed from the stage of primary crystallization, and the crystals obtained at this stage are added to the product supplied to this stage in an amount of 25-50% of its mass, allizatsii the first mother liquor,

the second mother liquor obtained at this stage, the return of the third mother liquor from the recrystallization stage and part of the crystals from the crystallization stage of the first mother liquor to the primary crystallization stage are added to the liquid supplied to this stage in an amount of 50-200%.

Figure 1 shows a graph by which the amount of crystallisate from the crystallization stage of the first mother liquor is determined, which must be returned to the primary stage. depending on the composition of the initial mixture fed to the primary crystallization stage in the form of its ratio to the flow of MDI supplied to the crystallization stage of the mother liquor; on. Fig. 2 is a diagram explaining the method.

Example 1. 100 mach. the initial mixture of MDI isomers (69.5% of the 4.4 - isomer, 26.2% of the 2.4 isomer and 4.3% of the 2.2 isomer) —flow 1 is fed to stage 2 of the primary crystallization (FIG. 2) . Mixtures of isomers are recycled to this stage, from 10 to 10

60 mAh, 4.4 -MDI containing 0.4% of the 2,4-isomer as impurities and 0.1% of the 2.2 -isomer, of which 40 m.h. the target product is stream 8, and 20 wt.h. - stream 9 is returned to mixing with stream 5 (the mass flow of stream 9 is 29% of that of stream 5).

The third mother liquor of stage 7 (stream 3) is returned to stage 2 of the primary crystallization.

On Etadia 10 crystallization of the first mother liquor stream 6 is subjected to

15 crystallization at 7 ° C. From stage 10, the mixture of isomers of OR (57.3% 4.4 -MDI, 38.2% 2.4 -MDI, 4.8% 2.2 -MDI) is removed as crythalls, part of which — stream 11 (35 wt.h.) is used as a target product, and another part — stream 4 (70 wt.h.) is returned to stage 2 of the primary crystallization. In the form of a second uterine fluid in etadia 10, they receive emeee

25 isomers with increased content

2.2 -VDI (38.6% 4.4 -NDI, 50.7% 2.4- -MDI, 10.7% 2.2 -MDI), the stream of which is stream 12 (25 parts per hour) removed from the cycle as a side fraction

isimewio mixtures, j i - t j - - - / nto l

the following stages: stream 3 (30 ma.h .; 30 and the other part - stream 13 (128 ma.h.)

86.9% 4.4 -MDI, 12.7% 2.4 -MDI, 0.4% 2.2 -MDI and stream 4 (70 parts per hour; 57.3% 4.4 -VDI, 38.2% 2.4-MDI, 4.8% 2.2-MDI). In this etadi, the process is carried out at, with the result that they receive (after melting) 70 wt. the crystalline phase - stream 5 (94.1% 4.4-MDI, 5.7% 2.4-MDI and 0.2% 2.2-MDI) and 130 mas. the first mother liquor - stream 6 (53.7% 4.4-MDI, 40.6% 2.4-MDI. and 5.9% 2.2-MDI). Stream 5 is fed to the rotary recrystallization stage 7 to obtain pure 4.4-MDI from melt back to mixing with stream 6 (lower stream 13 is 98% of the mass of stream 6).

PRI me R s 2-18. 100 ma.ch.

PG mixture of MDI isomers is treated with anao5

logical for example 1, but the temperatures at stages 2, 7, 10 and the ratios between streams 9 and 5, 13 and 6 vary. These examples are given in table 40.

Approximately 19 (comparative). 100 ma.ch. The isomers of MDI (93.6% 4.4 -MDI, 5.9% 2.4 -MDI, 0.5% 2.2 -MDI) are sent to the first

60 mAh, 4.4 -MDI containing 0.4% of the 2,4-isomer as impurities and 0.1% of the 2.2 -isomer, of which 40 m.h. the target product is stream 8, and 20 wt.h. - stream 9 is returned to mixing with stream 5 (the mass flow of stream 9 is 29% of that of stream 5).

The third mother liquor of stage 7 (stream 3) is returned to stage 2 of the primary crystallization.

On Etadia 10 crystallization of the first mother liquor stream 6 is subjected to

5 crystallization at 7 ° C. From stage 10, the mixture of isomers of OR (57.3% 4.4 -MDI, 38.2% 2.4 -MDI, 4.8% 2.2 -MDI) is removed as crythalls, part of which — stream 11 (35 wt.h.) is used as the target product, and the other part — stream 4 (70 wt.h.) is returned to stage 2 of the primary crystallization. In the form of a second uterine fluid in etadia 10, they receive eemey

5 isomers e high content

2.2 -VDI (38.6% 4.4 -NDI, 50.7% 2.4- -MDI, 10.7% 2.2 -MDI), the stream of which is stream 12 (25 parts per hour) removed from the cycle as a side fraction.

about / this l

the other part is the stream 13 (128 ma.h.)

return to mixing with stream 6 (under stream 13 makes up 98% of the mass of stream 6).

PRI me R s 2-18. 100 ma.ch.

mixtures of MDI isomers are treated with ana

It is logical to Example 1, but the temperatures at stages 2, 7, 10 and the ratios between streams 9 and 5, 13 and 6 vary. The data of the examples are given in the table.

Approximately 19 (comparative). 100 ma.ch. The isomers of MDI (93.6% 4.4 -MDI, 5.9% 2.4 -MDI, 0.5% 2.2 -MDI) are sent to the first

123 43 7 69.5 26.2 A, 3

215 40. O 69.5 26.2 4.3

330 45 15 69.5 26.2 4i3

40 99.5 3557.3 38.2 4.8

42 99.1 4055.0 40.0 5.0

35 99.7 3261.5 35.3 3.2

At this stage, 10 mae. are separated, mixtures of isomers as the mother liquor MDI (57.8% 4.4-MDI, 37.7% 2.4-MDI, 4.5% 2.2-MDI), which is used as a target product. As a crystalline product, 90 wt. Parts are obtained. 4,4-MDI, which contains as an impurity 1.7% 2,4-MDI and 0.2% 2.2-MDI. The crystals are 5 ma.h. a melt of pure 4.4-MDI (washing liquid in the amount of 9 wt. hours. contains 90.5% 4.4-MDI, 9.3% 2.4 MDI and 0.2% 2.2 MDI) and subjected to recrystallization at 38 ° C. Get 81 ma.h. pure 4.4-MDI (0.2% 2.4-MDI, 0.1% 2.2-MDI) and 5 ma.h. stock solution (91.2% 4.4 -MDI, 8.7% 2.4. -MDI, 0.1% 2.2-MDI). 5 ma.ch. 4.4-MDI was used as described above for washing the crystals after the initial crystallization, and the remaining 76 parts by weight represented the desired product. The side fraction (14 ma.h ,; 90.8% 4.4 -MDI, 9.1% 2.4 -MDI, 0.1% 2.2 -MDI) cannot be used according to its intended purpose. m for which use 4,4 -MD

and its isomers, containing 35-40% of 2,4-MDI.

Example 20 (L-Avniteln). 100 ma.ch. The MDI isomers (69.5% 4.4 -MDI, 26.2% 2.4 -MDI, 4.3% 2.2--MDI) are treated as in Example 1, except that the repetition is carried out at, the recrystallized product is washed with a melt of pure 4.4-MDI and returns the bulk liquid to the recrystallization stage. As target products receive 30 ma. 4.4 PM-MDI (0.6% 2.4 -MDI, 0.1% 2.2 -MDI) and 5 ma.h. areomers (60.5% 4.4 -MDI, 38.5% 2.4 -MDI, 1% 2.2 -MDI

five

0

five

0

35

40 45

as a secondary fraction, 65 mAh., emei isomers (56.2% 4.4-MDI, 37.3% 2.4-MDI, 6.5% 2.2-MDI).

Thus, the proposed technique allows increasing the yield of the main substance to 85 versus 76% for the known substance when separating the mixture with a high content of 4.4 -MDI and up to 40 against 30% by a known method for the initial mixture with a low content of 4. 4-mdi

Claims (1)

Invention Formula Solving the separation of the isomers of diphenylmethane diisocyanate with the use of etiadium of primary fractional crystallization from the melt of the initial mixture and the stage of subsequent recrystallization of the crystalline product obtained in the method of primary crystallization, characterized in that, in order to increase the degree of extraction of the target products, the primary crystallization is obtained in the method of primary crystallization, characterized by the fact that, in order to increase the degree of extraction of the target products, the primary crystallization is obtained in order to increase the degree of extraction of the target products, the primary crystallization is the initial crystallization, characterized in that 30 C, the recrystallization is carried out from a flowing film of a melt with a temperature of 40-45 ° C, with the addition of the crythalls obtained in this method in quantities E 25-50% of the mass of the supplied crystalline product, the mother liquor from the primary crystallization stage is directed to the crystallization stage of the first mother liquor. bones, which is carried out at 0-15 ° C, add the second mother liquor obtained at this stage in the amount of 50-200% by weight of the first mother liquor, and the third mother liquor obtained at the recrystallization stage and 50-75% of the crystals from the crystallization stage of the first mother liquor liquids return to the stage of primary crystallization. 423 43 7 69.5 26.2. 4.3 "O 99.5 30 57.3 38.2 4.8 525 45 7 93.6 5.9 0.5 85 99.8 12 62.5 35.9 1.5 625 45 7 93.6 5.9 0.5 7B 99.8 12 62.5 34.8 2.7 7 25 45 7 93.6 5.5 0.5 85 99.8 Yu 62.5 35.9 1.5 8 13 45 - 69.5 26.2 4.3 35 96.2 9, 32 - 15 69.5 2b, 2 4.3 55 92.7 10 15 45 2 69.5 26.2 4.3 30 99.2 eleven 30 45 17 69.5 26.2 4.3 30 99.5 12 15 38 O 69.5 26 , 2 4.3 40 94.1 40 55.6 39.4 5.0 13 30 48 15 69.5 26 4.3 28 99.8 32 62.0 35.6 4.2 14 23 43 7 69.5 26.2 4.3 40 98.6 35 60.2 36.0 3.8 15 23 43 7 69.5 26.2 4.3 42 99.5 9 5 50.4 42.8 7.0 65 55.1 38.4 6.5 45 41.1 49.6 9.3 70 56.9 37, 6.1 70 56.6 37.3, 1 20 48 40,8 11,1 40 55.7 37.0 7.3 25 36.0 52.5 11.5 36 38.1 52.7 9.2 1456410 ten . Table continuation to stream 5 more than 50x results at the level of example 19 220 56 With respect to flow 13 to stream 6 .more than 2 OX results at the level of example 5 - - When the temperature at stage 2 is below 15 ° C, it is fully cured. - - At a temperature in stage 2 above 30 ° C, crystallization does not proceed - - At stage temperature 10 below "details full cure 120 - At a temperature at stage 10 above 15 ° C, crystallization does not occur. 80 50 When the temperature on Stage 7 below is fully cured I 120 65 When the temperature at stage 7 is above 45 ° C, the yield of pure 4.4-MDI is lower than in example 20 100 65 With respect to flow 9 to stream 5 less than 25x, the quality of 4.4 -MDI is deteriorating 35 60 With respect to flow 13 to stream 6 less than 50%. mixture of isomers, which should have been used does not satisfy technical requirements for 2.2-MDI content 20 23 43 7 69.5 26.2 A, 3 50 99.2. 59.3 37.5 3.2 13 7O F / f / -ffuM concentration mixtures / „ 1456410 14 Continuation of the table 80 90 t but. / Fi9.1