GB1570741A - Process for teh production of diisocyanatodiphenyl methaneisomers with an adjusted content of chlorine compounds - Google Patents
Process for teh production of diisocyanatodiphenyl methaneisomers with an adjusted content of chlorine compounds Download PDFInfo
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- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C263/00—Preparation of derivatives of isocyanic acid
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Description
(54) PROCESS FOR THE PRODUCTION OF
DIISOCYANATODIPHENYL METHANE ISOMERS WITH AN
ADJUSTED CONTENT OF CHLORINE COMPOUNDS
(71) We, BAYER AKTIENGESELLSCHAFT, a body corporate organised under the laws of
Germany, of 5090 Leverkusen, Germany; do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:
2,4'-diisocyanatodiphenyl methane and, in particular, 4,4'-diisocyanatodiphenyl methane are important starting materials for the production of polyurethane plastics.
In the condensation of aniline and formaldehyde in the presence of acid catalysts, followed by reaction of the polyamine mixtures formed with phosgene, the isomeric compounds 2,2'-, 2,4'- and 4,4'-diisocyanatodiphenyl methane are always formed at the same time.
These isomers have been found to contain varying amounts of impurities, including those which contain some of the organicallybound chlorine in the form of hydrolysable chlorine. Varying amounts of compounds containing hydrolysable chlorine adversely affect the reaction of isocyanates with polyols to form polyurethanes because these chlorine compounds influence the velocity of this reaction. In general, they retard it. Accordingly, the hydrolysable chlorine content of isocyanates is an important parameter when considering the purity thereof. Compounds containing hydrolysable chlorine are, for example, the reaction products of phosgene with secondary products from the condensation of aniline and formaldehyde, such as p-aminobenzyl aniline, N-methyl-amino compounds, also acridane and acridine (acridine being obtainable from acridane by a redox reaction).
It is known that impurities may be removed from distillable isocyanates by processes which are either based on the addition of substances capable of converting chlorinecontaining impurities into a less volatile form, for example in accordance with DT-PS No.
1,138,040, or on a technically complex physical separation process, for example crystallisation in accordance with DT-OS No.
1,938,384. As commercial products, both 2,4'- and 4,4'-diisocyanatodiphenyl methane, obtained by fractional distillation from a polyisocyanate mixture, are mixtures of isomers. The ratio of the isomers is governed by the composition of the polyamine mixture used and by the effort involved in the fractionation of the isocyanates.
On account of the low concentration thereof, the multiplicity thereof and also, to a certain extent, on account of the sensitivity thereof to heat and changes caused by inter-reaction, the chlorine-containing compounds in the commercially produced diisocyanates are difficult to analyse. The literature describes splitting reactions of N,N-disubstituted carbamic acid chlorides which, depending on the substituents and the presence of catalysts, may take place at temperatures above 150"C, at which temperature diphenyl methane diisocyanates are distilled. Such splitting reactions, in which substantially involatile chlorine containing compounds are converted into lower boiling compounds, such as conversion of the acid chloride formed from phosgene and paminobenzyl aniline into p-isocyanatobenzyl chloride and phenyl isocyanate (J. Org. Chem.
39 (1974), 2897-2899), also alter the chlorine function. A readily hydrolysable chlorine in a carbamic acid chloride becomes a more firmly bound chlorine in a benzyl chloride function.
In conventional distillation-based purification processes (DT-AS No. 1,923,214), separation of the solvents used for the amine/phosgene reaction was followed by purification in the following stages:
Removal of diisocyanate from a polyisocyanate mixture by distillation, separation of the isomeric diphenyl methane diisocyanates by fractional distillation in a column and distilling off diisocyanate of reduced 2,4'-diisocyanatodiphenyl methane content from polymerisation products which are reformed during distillation by the action of heat on isocyanates.
The chlorine-containing impurity may only be unsatisfactorily separated off by this process, probably because reactions of the type described above continuously take place in view of the thermal stressing of the distillation process.
It has now suprisingly been found that these difficulties may be obviated and that highly pure diisocyanates, which may be exactly adjusted in regard to their chlorine content, may be obtained by initially freeing the isomer mixture obtained by distillation-based separation from a polyisocyanate mixture of the diphenyl methane series obtained by the phosgenation of aniline/formaldehyde condensates, and consisting essentially of 2,4'- and 4,4'-diisocyanatodiphenyl methane, apart from small quantities of 2,2'-diiso cyanatodiphenyl methane, from most of the impurities boiling at higher temperatures than 4,4'-diisocyanatodiphenyl methane in a distillation column (2) using a recycle ratio (= ratio, by volume, of recycle to distillate removed) of from 0.1 to 10 and subsequenctly freeing the distillate obtained from the impurities boiling at lower temperatures than 2,4'-diiso cyanatodiphenyl methane.
Accordingly, the present invention relates to a process for the production of diisocyanatodiphenyl methane isomers with an adjusted content of chlorine compounds by the distillation-based separation of diisocyanatodiphenyl methane and isomers from a polyisocyanate mixture of the diphenyl methane series obtained by the phosgenation of aniline/formaldehyde condensates in a distillation stage (1) and further distillation-based purification of the resulting fraction (I), distinguished by the fact that the fraction (I) is distilled in a distillation column (2) using a recycle ratio of from 0.1 to 10, from 0.5 to 10%, by weight, of the total amount of fraction (I) introduced into the column (2) being run off as the sump product of column (2), after which the fraction (II) obtained as the head product of column (2) is freed in the following distillation stage from readily volatile impurities and, optionally, from 2,4'-diisocyanatodiphenyl methane as well and, finally, the sump product obtained is distilled in a further distillation stage to give purified 4,4'-diisocyanatodiphenyl methane and optionally purified 2,4'-diusocyanatodiphen methane.
The most important embodiments of the process according to the present invention are described in more detail below with reference to the accompanying drawings.
Figure 1 shows the conventional process.
The reference (1) denotes the distillation stage in which the dusocyanatodiphenyl methane isomers are separated from the polyisocyanate mixture of the diphenyl methane series. In a distillation column (3), the isomers are then separated into a head product, which contains most of the 2,2'- and 2,4'-isomers, and a sump product from which pure 4,4'-diisocyanatodiphenyl methane (head product) and polymers formed during distillation (sump) are obtained in a distillation column (4).
Figure 2 shows an embodiment of the process according to the present invention, in which an isomer mixture obtained as fraction (I) by distillation from a polyisocyanate mixture of the diphenyl methane series (distillation stage (1)) and consisting essentially of 2,4'- and 4,4'-isomers, apart from small quantities of 2,2'-diisocyanatodiphenyl methane, is split in a distillation column (2) into a fraction (II) (head product) and a sump, most of the impurities boiling at higher temperatures than 4,4' dusocyanatodiphenyl methane remaining in the sump (2), whilst the impurities boiling at lower temperatures than 4,4'-diisocyanatodiphenyl methane which are already present in fraction (I) and which are formed thermally in (2) are delivered together with fraction (II) into a distillation column (3) where separation into a fraction (III) and a sump (IV) takes place. The fraction (III) obtained contains most of the 2,2'- and 2,4'-isomers in addition to the impurities boiling at lower temperatures than 4,4'-diisocyanatodiphenyl methane.
Finally, the sump (W) is split in a last column (4) into pure 4,4'-diisocyanatodiphenyl methane (V) (head product) and a residue (IV) formed by polymerisation (sump).
Figure 3 shows another embodiment of the process according to the present invention, in which the fraction (II) obtained from column (2) is first separated by distillation in another column (2') in such a way that most of the impurities boiling at lower temperatures than 2,4'-diisocyanatodiphenyl methane are separated off as head product, whilst most of the 2,4'- and 4,4'-diisocyanatodiphenyl methane remains in the sump and, finally is separated in columns (3) and (4) into 2,4'diisocyanatodiphenyl methane having a depleted content of chlorine-containing impurities (head product of column (3)), 4,4'-diisocyanatodiphenyl methane having a depleted content of chlorine-containing impurities (head product of column (4)) and residue (sump product of column (4)).
Finally, Figure 4 shows another possible embodiment of the process according to the present invention relating to a possible division of the fraction (II) emanating from column (2). In this embodiment, a column (2") is arranged at the head of the column (3), which enables the chlorine compounds boiling at lower temperatures than 2,4'-diisocyanatodiphenyl methane together with small quantities of 2,2'-dllsocyanatodiphenyl methane to be separated off at the head of the column (2"), whilst 2,4'-diisocyanatodiphenyl methane largely freed from chlorine-containing impurities is obtained as a side stream of the column (2"). The column (4) enables the sump from column (3) to be separated into 4,4'-diisocyanatodiphenyl methane substantially free of chlorine-containing impurities and a distillation residue.
The process according to the present invention is not just a simple distillation-based separation of the chlorine-containing impurities.
On the contrary, partial conversion of the substantially involatile impurities originally present into readily volatile impurities is obtained in column (2), the thus-obtained readily voltaile impurities being subsequently removed in columns (2'), (2") or (3). The separation effect obtained in the process according to the present invention is quite clearly also attributable to this separate conversion of substantially involatile chlorine compounds into readily volatile chlorine compounds The distillation column (3) used in the abovedescribed conventional process was obviously redundant because this conversion cannot be carried out simultaneously with a clean separation of the end products and impurities in a single column.
In all the embodiments of the process according to the present invention, high-boiling impurities are removed from the diisocyanate mixture (fraction (I)) in another distillation step of fractionation in a column (2) to such an extent that the end-products are obtained with a substantially reduced, adjusted content of hydrolysable chlorine and may be brought after or in combination with the separation of the isomers to a content of less than 10 ppm of total chlorine and less than 10 ppm of hydrlysable chlorine. It is important to separate off impurities boiling at higher temperatures than 4,4'-diisocyanatodiphenyl methane or to convert them at least partly into lower boiling impurities in column (2), because these substantially involatile impurities generally contain most of the hydrolysable chlorine in the distillate from separation of the diisocyanate higher polyisocyanate mixture.
Some of the compounds containing hydrolysable chlorine boil at lower temperatures than 2,4'-diisocyanatodiphenyl methane.
Since the high-boiling chlorine compounds are separated off and since low-boiling chlorine compounds cannot be continually reformed by rearrangements and other secondary reactions, the separation of these secondary products in the columns (2'), (2") and (3) is possible with considerably more effect and to a far greater extent than in the conventional process. Accordingly, in order to adjust a certain content of hydrolysable chlorine, it is now sufficient, in principle, to run off sump product containing chlorine to a greater or lesser extent in a column (2) which precedes the column (3) for the separation of 2,4'- and 4,4'-diisocyanatodiphenyl methane. The outcome of such a measure must be regarded as suprising because it could be neither calculated nor predicted from experience on account of the relatively high volatility of the compounds which distil over with the diisocyanate during separation of the diisocyanate/polyisocyanate mixture, on account of the tendency thereof to decompose.
on account of the possibility of a back reaction of chlorine-containing cleavage products with
NCO-groups to form adducts, including the formation of carbamic acid chloride from isocyanate and hydrogen chloride, and finally on account of the absence of accurate analytical methods for all the various individual chemical compounds. Despite the inclusion of a column (2) and thesesulling additional thermal stressing of the product introduced into stages (3) and (4), the total amount of polymer obtained in the sumps of (2) and (4) is not considerably increased, which is indicative of the fact that substances accelerating the catalytic polymerisation during isomer separation are also removed in the sump of column (2).
It is also possible by the process according to the present invention, following separation of the compounds containing hydrolysable chlorine and boiling at higher temperatures than 4,4'-diisocyanatodiphenyl methane, to run off the compounds containing hydrolysable chlorine and boiling at lower temperature than 2,4'-diisocyanatodiphenyl methane as head product by fractionation in another column (2') and in this way to obtain a product enriched with 2 ,4'diiso cyanatodipheny methane and containing less than 50 ppm of total chlorine and less than 10 ppm of hydrolysable chlorine (Figure 3). It is also possible to obtain either in the same operation or in an additional operation 2,2'-difsocyanato- diphenyl methane which boils at a lower temperature than 2,4'-diisocyanatodiphenyl methane and whose separation from 2,4' diisocyanatodiphenyl methane may be carried out in basically the same way as the separation of 2,4'-/4,4'-diisocyanatodiphenyl methane.
In all cases the separation of diisocyanates from a polyisocyanate mixture in the distillation stage (1) takes place under the most moderate conditions possible in a good vacuum of less than 15 millibars and without fractionation in order not unnecessarily to damage the mixtures of MDI-polymer obtained as secondary yield as the sump of (1). It is known that decomposition reactions take place more quickly in nonpurified polyiso cyanate mixtures, produced from non-distilled aniline/formaldehyde condensates by reaction with phosgene, than in diphenyl methane diisocyanates which have been obtained by distillation from such polyisocyanate mixtures. A large amount of those compounds which would promote thermal decomposition of the required diisocyantes and the formation of carbodiimides during the subsequent distillation steps is separated off in the distillation stage (1).
However, the distillate inevitably also contains small quantities of compounds which boil at higher temperatures than the isomeric diphenyl methane diisocyanates, for example the reaction product of phosgene and hydrogen chloride with p-aminobenzyl aniline, N-methyl amino compounds and acridine.
The higher boiling compounds are removed by fractional distillation (2) in a column with a low pressure loss to such an extent that chlorine compounds remain in the distillate in the required concentration. Suitable low pressure loss columns are, inter alia, columns having fabric packings or helical springs.
This column may either be fed in the vapour phase from the preceding separation of diisocyanate and higher boiling polyisocyantes, or even in the liquid phase after intermediate condensation of the in-flowing diisocyanate.
In addition to the distillation section, the column may also have a concentrating section.
The column is preferably operated under a vacuum of less than 20 mbar. The sump temperature is generally from 170 to 240 C, preferably from 180 to 21 50C. In the column (2), from 0.5 to 10%, by weight, of the fraction (I) obtained from the distillation stage (1) are generally run off as sump. The recycle ratio in column (2) is from 0.1 to 10. The head distillate removed from this distillation stage still contains those compounds containing hydrolysable chlorine which boil at lower temperatures than the isomeric diphenyl methane diisocyanates.
The recovery of 2,4'-diisocyanatodiphenyl methane, optionally in admixture with isomers, takes place by fractional distillation in another low pressure loss column (3) and under similar temperatures and pressures to those prevailing in column (2). In general the distillation column (3) is operated using a recycle ratio of from 1 to 10.
Another fractionation column (2') may optionally be arranged between these two columns for separating off 2,2'-diisocyanatodiphenyl methane. By virtue of this arrangement, it is also possible to remove chlorinecontaining compounds which boil at lower temperatures than 2,4'-diisocyanatodiphenyl methane and to obtain in the column (3) a head product with enriched 2,4'-diisocyanatodiphenyl methane and a content of less than 50 ppm of total chlorine and less than 10 ppm of hydrolysable chlorine.
Other possible arrangements are, in principle, column structures having several distillate outlets, for example at the head for a small quantity of 2,2'-diisocyanatodiphenyl methane and chlorine compounds, and at an underlying plate for a side stream outlet for a product which, by comparison with the head product, contains less 2,2'-diisocyanatodi- phenyl methane and chlorine compounds and more 2,4'-diisocyanatodiphenyl methane.
This arrangement corresponds to a combination of columns (2) and (3) arranged one above the other with a common evaporator at the sump of column (3) (Figure 4).
By virtue of the process according to the present invention, it is possible to produce 2,4'-diisocyanatodiphenyl methane in pure form having a content of more than 97% of the pure isomer and less than 50 ppm of chlorine.
Working-up of the sump product of column (3), which gives 2,4'-diisocyanatodiphenyl methane as head product, is carried out in the conventional way in another following.distilla- tion column (4), in which polymer formed during distillation is separated from pure 4,4'-diisocyanatodiphenyl methane, optionally in admixture with isomers.
The sump of the distillation column (4), in which the diisocyanate is left by virtue of better flow properties and on account of the danger of the auto-catalytically accelerated formation of relatively high molecular weight products on enrichment with carbodiimides, may with advantage be recycled to the distillation stage (1) where it is mixed with the polyisocyanate mixture from the phosgenation stage and separated into diisocyanate as distillate and a sump containing the relatively high boiling components. If the sump product from (4), containing carbodiimide and other basic compounds, is added with the input for column (2), the reactions which take place in (2), such as the splitting of chlorine compound on the one hand and the binding of acid chlorides with basic compounds on the other hand, and hence the controlled separation of chlorine-containing compounds from diphenyl methane diisocyanate may be promoted. In this case, the sump from (4) is removed from the system together with the sump from (2).
Basically, it is possible to produce from the sump products of all the distillation stages mixtures which may be used as valuable starting materials for the production of polyure thane plastics, especially foams.
The extreme purification of 4,4'-diisocyanatodiphenyl methane and 2,4'-diisocyanatodiphenyl methane obtainable by the process according to the present invention is of considerable commercial significance because 4P'-diisocyanato- diphenyl methane, like 2,4'-diisocyanatodiphenyl methane of low chlorine content, is particularly resistant to yellowing and to the effects of light and air so that, in many cases, there is no need to add stabilisers which prevent discolouration.
Another significant advantage of the process according to the present invention is that it is also possible, for obtaining 2,4'- and 4,4'diisocyanatodiphenyl methane or mixtures thereof with an adjusted content of chlorine compounds, to use aniline-formaldehyde condensates produced by a variety of different processes and containing a varying amount of compounds containing secondary or tertiary nitrogen, such as p-aminobenzyl aniline, Nmethylamino compounds, acridine and acridane. Accordingly, the quality of the end-products is largely independent of the quality of the polyamine and polyisocyanate mixtures used as starting products.
The process according to the present invention is illustrated by the following Examples.
Unless stated to the contrary, the percentages quoted in the Examples are expressed in terms of weight.
EXAMPLE 1
a. Comparison: conventional process
A polyisocyanate mixture of the diphenyl methane series containing approximately:
2.3% of 2,4'-diisocyanatodiphenyl methane,
81.9% of 4,4'-diisocyanatodiphenyl methane,
11.7% of 3-nuclear compounds
0.9% of 4-nuclear compounds as determined by gas chromatography, is worked-up in a continuously operated distillation unit with the sections (1), (3) and (4) (Figure 1).
(1), (3) amd (4) are apparatus with evaporators, pumps for delivering product, condensers for the distillate and connection to a vacuum system which maintains a pressure of 10 mbar for (1) and a pressure of 5 mbar for (3) and (4), as measured at the product inlet to the consenser.
A column consisting of six 2 metre long drops filled with helical springs (Montz system) is arranged at (3) between the evaporator and condenser.
The product flows in at the fourth drop, counting upwards. The column load, i.e. the total of recycle and distillate removed, is adjusted to 1000 kg/h.
A separation of diisocyante/polyisocyanate mixture takes place in distillation stage (1).
(3) receives distillate from (1) as input, the head product being an isocyanate mixture enriched with 2,4'-diisocyanatodiphenyl methane.
A distillate predominantly containing 4,4'-diisocyanato-diphenyl methane is obtained in (4), the sump running back to the entrance to the distillation stage (1).
950 kg per hour of a distillate containing
400 ppm of hydrolysable chlorine (=HC) and
1280 ppm of total chlorine (=TC) are obtained in the distillation stage (1). This distillate from (1) is the starting product for the distillation (3) in which a separation of isomers takes place:
Distillate from (3) 75 kg/h with
240 ppm of HC
570 ppm of TC
Purification in the distillation stage (4) produces a distillate (760 kg/h) with
80 ppm of HC
280 ppm of TC and 115 kg/h of sump product which is recycled to (1).
If a polyurethane test specimen is produced from this distillate with 1.0% of 2,4'-diisocyana todiphenyl methane and 98.9% of 4,4'-diiso cyanatodiphenyl methane and heat treated at 2000 C, it undergoes discolouration, becoming yellow-brown in colour.
b. Comparison: new process
In the existing distillation unit with the sections (1), (3) and (4), another column (2) which is identical in equipment and size with column (3) is connected between (1) and (3) (Figure 2). The quality of the starting product and distillate from (1) are the same as in comparison (a), the quantity of distillate from (1), is, however, only 920 kg/h.
A distillate (850 kg/h) with
160 ppm of HC
280 ppm of TC is removed at the head of column (2), whilst a sump product (70 kg/h) with
2200 ppm of HC
3200 ppm of TC is removed at the foot of this column.
A distillate enriched with 2,4'-diisocyanatodiphenyl methane and containing 115 ppm of HC
280 ppm of TC is obtained at a rate of 75 kg/h in the distillation (3).
4,4'-diisocyanatodiphenyl methane containing 1.2% of 2,4'-diisocyanatodiphenyl methane and
4 ppm of HC
12 ppm of TC distills from the final stage (4).
A polyurethane test specimen produced and tested in the same way as in test (a) remains almost white after the heat treatment.
EXAMPLE 2
The arrangement of the distillation apparatus is the same as in Example l(b). A polyisocyanate mixture of the diphenyl methane series is used, containing approximately:
61.6% of 2-nuclear compounds
25.1% of 3-nuclear compounds
10.9% of 4-nuclear compounds
1.5% of 5-nuclear compounds approximately 3.3% of the 2-nuclear compounds consisting of 2 ,2'-diisocyanatodiphenyl methane, 25.2% of 2,4'-diisocyanatodiphenyl methane, 70.1% of 4,4'-diisocyanatodiphenyl methane and 1.3% of N-methyl compounds.
The following products were obtained:
Distillate Content ppm Content % from kg/h HC TC 2,2'- 2,4' (1) 400 770 1350 3.5 25.3 (2) 380 240 460 3.8 26.1 (3) 180 190 960 7.9 554 (4) 180 20 70 0.1 1.2 Part of the distillate from (3) is distilled a second time through the columns (2) and (3), the only difference being that, corresponding to the arrangement (Figure 3), the sump product from (2') is delivered to the distillation stage (3):
Input to (2') 400 kg/h with
7.9% of 2,2'-diisocyanatodiphenyl methane 55.4% of 2,4'-diisocyanatodiphenyl methane
190 ppm of HC
960 ppm of TC
Distillate from (3) 180 kg/h with
0.6% of 2,2'-diisocyanatodiphenyl methane
97.7% of 2A'-diisocyanatodiphenyl methane
8 ppm of HC
30 ppm of TC
EXAMPLE 3
A polyisocyanate mixture is produced from a polyamide mixture, obtained by aniline/formaldehyde condensation, containing approximately 60% of 2-nuclear compounds, of which 0.5% consist of acridane, 5.9% of 2,2'-diiso cyanatodiphepyl methane, 46.6% of 2,4'diaminodiphenyl methane, 46.6% of 4,4'diaminodiphenyl methane and 0.5% of Nmethyl-substituted diamine, and processed in the same way as described in Example lb.
Distillate from (1) 400 kg/h with
6.1% of 2,2'-diisocyanatodiphenyl methane
46.9% of 2,4'-diisocyanatodiphenyl methane
550 ppm of HC
Distillate from (2) 380 kg/h
Distillate from (3) 250 kg/h with
9.7% of 2,2'-diisocyanatodiphenyl methane
74.2% of 2,4'-diisocyanatodiphenyl methane
150 ppm of HC
Distillate from (4) 150 kg/h with 02% of 2,2'-diisocyanatodiphenyl methane
2.2% of 2,4'-diisocyanatodiphenyl methane
97.6% of 4,4'-diisocyanatodiphenyl methane
10 ppm of HC
EXAMPLE 4
A polyisocyanate mixture of the diphenyl methane series having a viscosity of 70 mPas/ 25 C.
0.2% of 2,2'-diisocyanatodiphenyl methane
4.8% of 2,4'-dlisocyanatodiphenyl methane
65.9% of 4,4'-diisocyanatodiphenyl methane
0.3% of N-methyl compounds
21.0% of 3-nuclear compounds
1300 ppm of HC
2700 ppm of TC is processed by distillation in the same way as described in the preceding Examples.
Input to (1) 1200 kg/h;
Distillate from (1) 480 kg/h with
0.3% of 2,2'-diisocyanatodiphenyl methane
6.1% of 2,4'-diisocyanatodiphenyl methane
93.5% of 4,4'-diisocyanatodiphenyl methane
0.1% of N-methyl compounds 360ppmHC 570 ppm of TC
Sump from (1) 720 kg/h having a viscosity of 290 mPas/25 C 3.9% of 2,4'-diisocyanatodiphenyl methane
48.8% of 4,4'-diisocyanatodiphenyl methane 0.4% of N-methyl compounds
34.0% of 3-nuclear compounds
1400 ppm of HC 3900 ppm of TC
Sump from (2) 30 kg/h with
1650 ppm of HC
2840 ppm of TC
Distillate from (3) 30 kg/h with 19% of 2,4'-diisocyanatodiphenyl methane,
98.0% of 4,4'-diisocyanatodiphenyl methane,
4 ppm of HC
12 ppm of TC
Colour after storage for 10 days under nitrogen at 400C:
APHA 5.
The sump from (4) goes back into column (2) together with distillate from (1).
4,4'-diisocyanatodiphenyl methane from comparable starting product, produced without the processing stage (2), contains
55 ppm of HC
135 ppm of TC and after 10 days gives colour values of APHA 70.
WHAT WE CLAIM IS:
1. Aprocess for separating the components of a mixture obtained by phosgenating aniline/ formaldehyde condensation products which
**WARNING** end of DESC field may overlap start of C
Claims (1)
- **WARNING** start of CLMS field may overlap end of DESC **.approximately 3.3% of the 2-nuclear compounds consisting of 2 ,2'-diisocyanatodiphenyl methane, 25.2% of 2,4'-diisocyanatodiphenyl methane, 70.1% of 4,4'-diisocyanatodiphenyl methane and 1.3% of N-methyl compounds.The following products were obtained:Distillate Content ppm Content % from kg/h HC TC 2,2'- 2,4' (1) 400 770 1350 3.5 25.3 (2) 380 240 460 3.8 26.1 (3) 180 190 960 7.9 554 (4) 180 20 70 0.1 1.2 Part of the distillate from (3) is distilled a second time through the columns (2) and (3), the only difference being that, corresponding to the arrangement (Figure 3), the sump product from (2') is delivered to the distillation stage (3): Input to (2') 400 kg/h with7.9% of 2,2'-diisocyanatodiphenyl methane 55.4% of 2,4'-diisocyanatodiphenyl methane 190 ppm of HC 960 ppm of TC Distillate from (3) 180 kg/h with 0.6% of 2,2'-diisocyanatodiphenyl methane97.7% of 2A'-diisocyanatodiphenyl methane 8 ppm of HC 30 ppm of TC EXAMPLE 3 A polyisocyanate mixture is produced from a polyamide mixture, obtained by aniline/formaldehyde condensation, containing approximately 60% of 2-nuclear compounds, of which 0.5% consist of acridane, 5.9% of 2,2'-diiso cyanatodiphepyl methane, 46.6% of 2,4'diaminodiphenyl methane, 46.6% of 4,4'diaminodiphenyl methane and 0.5% of Nmethyl-substituted diamine, and processed in the same way as described in Example lb.Distillate from (1) 400 kg/h with6.1% of 2,2'-diisocyanatodiphenyl methane46.9% of 2,4'-diisocyanatodiphenyl methane 550 ppm of HC Distillate from (2) 380 kg/h Distillate from (3) 250 kg/h with9.7% of 2,2'-diisocyanatodiphenyl methane74.2% of 2,4'-diisocyanatodiphenyl methane 150 ppm of HC Distillate from (4) 150 kg/h with 02% of 2,2'-diisocyanatodiphenyl methane2.2% of 2,4'-diisocyanatodiphenyl methane97.6% of 4,4'-diisocyanatodiphenyl methane 10 ppm of HC EXAMPLE 4 A polyisocyanate mixture of the diphenyl methane series having a viscosity of 70 mPas/ 25 C.0.2% of 2,2'-diisocyanatodiphenyl methane4.8% of 2,4'-dlisocyanatodiphenyl methane65.9% of 4,4'-diisocyanatodiphenyl methane 0.3% of N-methyl compounds21.0% of 3-nuclear compounds 1300 ppm of HC 2700 ppm of TC is processed by distillation in the same way as described in the preceding Examples.Input to (1) 1200 kg/h; Distillate from (1) 480 kg/h with 0.3% of 2,2'-diisocyanatodiphenyl methane6.1% of 2,4'-diisocyanatodiphenyl methane93.5% of 4,4'-diisocyanatodiphenyl methane 0.1% of N-methyl compounds 360ppmHC 570 ppm of TC Sump from (1) 720 kg/h having a viscosity of 290 mPas/25 C3.9% of 2,4'-diisocyanatodiphenyl methane48.8% of 4,4'-diisocyanatodiphenyl methane 0.4% of N-methyl compounds34.0% of 3-nuclear compounds 1400 ppm of HC 3900 ppm of TC Sump from (2) 30 kg/h with 1650 ppm of HC 2840 ppm of TC Distillate from (3) 30 kg/h with 19% of 2,4'-diisocyanatodiphenyl methane,98.0% of 4,4'-diisocyanatodiphenyl methane, 4 ppm of HC 12 ppm of TC Colour after storage for 10 days under nitrogen at 400C: APHA 5.The sump from (4) goes back into column (2) together with distillate from (1).4,4'-diisocyanatodiphenyl methane from comparable starting product, produced without the processing stage (2), contains 55 ppm of HC 135 ppm of TC and after 10 days gives colour values of APHA 70.WHAT WE CLAIM IS:1. Aprocess for separating the components of a mixture obtained by phosgenating aniline/ formaldehyde condensation products whichcomprises: distilling the said mixture comprising diphenyl methane polyisocyanates in a first distillation stage in order to separate a disocyanate fraction from a higher polyisocyanate fraction; distilling the said diisocyanate fraction in a second distillation stage using a recycle ratio of from 0.1 to 10 in order to separate a head fraction from a sump fraction, the said sump fraction, consisting of from 0.5 to 10%, by weight, of the said diisocyanate fraction introduced into the said second distillation stage, being removed from the said second distillation stage, the said sump fraction comprising material having a boiling point in excess of that of 4,4'-diisocyanatodiphenyl methane; distilling the said head fradtion in a third distillation stage in order to obtain, as a head fraction, low boiling material and, optionally, 2,4'diisocyanatodiphenyl methane and, as a sump fraction, 4i4'-diisocyanatodiphenyl methane and, optionally, 2,4'-diisocyanatodiphenyl methane; and distilling the said sump fraction from the said third distillation stage in a fourth distillation stage in order to separate 4,4'-diisocyanatodiphenyl methane from any other material present.2. A process as claimed in Claim 1 in which the said head fraction from the said second distillation stage is distilled in a further distillation stage using a recycle ratio of from 0.1 to 10 in order to remove, as a head fraction, low boiling material from a sump fraction, which sump fraction is subsequently distilled in order to obtain 2,4'- and 4,4'-diisocyanatodiphenyl methane.3. A process as claimed in Claim 1 in which the said head fraction from the said second distillation stage is distilled in a further distillation stage using a recycle ratio of from 1 to 10 in order to obtain, as a sump fraction, 4,4'-diisocyanatodiphenyl methane and any material having a boiling point in excess of that of 4,4'diisocyanatodiphenyl methane, which sump fraction is subsequently distilled in order to obtain 4,4'-diisocyanatodiphenyl methane4. A process as claimed in Claim 1 substantially as herein described.5. A process as claimed in Claim 1 substantially as herein described with reference to any one of the Examples and/or the accompanying drawings.6. The individual components of a mixture as defined in Claim 1 when separated by a process as claimed in any of Claims 1 to 5.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19762631168 DE2631168B2 (en) | 1976-07-10 | 1976-07-10 | Process for the preparation of diisocyanatodiphenylmethane isomers with an adjusted content of chlorine compounds |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB1570741A true GB1570741A (en) | 1980-07-09 |
Family
ID=5982715
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB2851477A Expired GB1570741A (en) | 1976-07-10 | 1977-07-07 | Process for teh production of diisocyanatodiphenyl methaneisomers with an adjusted content of chlorine compounds |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS539750A (en) |
| BE (1) | BE856617A (en) |
| DE (1) | DE2631168B2 (en) |
| ES (1) | ES460560A1 (en) |
| FR (1) | FR2357532A1 (en) |
| GB (1) | GB1570741A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6222066B1 (en) | 1999-03-30 | 2001-04-24 | Bayer Aktiengesellschaft | Process for decreasing the chlorine content of organic isocyanates |
| US6391161B1 (en) | 1999-03-30 | 2002-05-21 | Bayer Aktiengesellschaft | Method for reducing the chlorine content of low molecular weight isocyanates |
| CN100434417C (en) * | 2004-02-04 | 2008-11-19 | 拜尔材料科学股份公司 | Process for the production of very pure 2,4'-methylene diphenyl diisocyanate |
| US11613518B2 (en) | 2017-12-14 | 2023-03-28 | Sulzer Management Ag | Plant and method for purifying an isomeric monomer |
Families Citing this family (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS54103415A (en) * | 1978-01-31 | 1979-08-14 | Ricoh Kk | Lens bonding |
| JPS54102320A (en) * | 1978-01-31 | 1979-08-11 | Ricoh Kk | Lens bonding and apparatus therefor |
| JPS54102321A (en) * | 1978-01-31 | 1979-08-11 | Ricoh Kk | Removing bubbles in lens bonding |
| DE2935318A1 (en) * | 1979-08-31 | 1981-03-26 | Bayer Ag, 51373 Leverkusen | NEW DIISOCYANATES OR DIISOCYANATE MIXTURES OF THE DIPHENYLMETHANE SERIES, METHOD FOR THE PRODUCTION THEREOF, AND THEIR USE AS CONSTRUCTION COMPONENT IN THE PRODUCTION OF POLYURETHANE PLASTICS BY THE ISOCYANATE POLYADDITION METHOD |
| JPH02311452A (en) * | 1989-05-26 | 1990-12-27 | Daicel Chem Ind Ltd | Diisocyanate compound |
| JP2875877B2 (en) * | 1990-10-23 | 1999-03-31 | 三井化学株式会社 | Method for producing methylene-crosslinked polyphenylene polyisocyanate |
| EP1475367B1 (en) * | 2003-05-08 | 2010-07-07 | Bayer MaterialScience AG | Distillation process for separating diisocyanatodiphenylmethane isomers |
| DE102005004170A1 (en) * | 2005-01-29 | 2006-08-03 | Bayer Materialscience Ag | Process for the distillation of a mixture of isomeric diisocyanatodiphenylmethanes |
| DE102005026864A1 (en) | 2005-06-10 | 2006-12-14 | Bayer Materialscience Ag | Process for the preparation of 4,4'-diphenylmethane diisocyanate |
| DE102005053065A1 (en) * | 2005-11-04 | 2007-05-10 | Basf Ag | Process for the preparation of polyisocyanate mixtures |
| US8907124B2 (en) | 2010-11-17 | 2014-12-09 | Basf Se | Process for preparing methylenedi(phenyl isocyanate) |
| EP2640694B1 (en) | 2010-11-17 | 2019-01-09 | Basf Se | Process for the production of methylenediphenyldiisocyanate |
| US9505711B2 (en) | 2010-11-17 | 2016-11-29 | Basf Se | Method for purifying mixtures comprising 4,4′-methylenediphenyl diisocyanate |
| KR101898743B1 (en) * | 2010-11-17 | 2018-09-13 | 바스프 에스이 | Method for purifying mixtures comprising 4,4'-methylenediphenyl diisocyanate |
| EP2640696B1 (en) * | 2010-11-17 | 2016-08-10 | Basf Se | Process for purifying mixtures comprising 4,4'-methylene diphenyl diisocyanate |
| JP2015010183A (en) * | 2013-06-28 | 2015-01-19 | 旭化成ケミカルズ株式会社 | Diisocyanate composition |
| JP6731929B2 (en) | 2015-01-30 | 2020-07-29 | ビーエーエスエフ ソシエタス・ヨーロピアＢａｓｆ Ｓｅ | Polyphenylene polymethylene polyisocyanate with low by-product content |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3219678A (en) * | 1963-02-28 | 1965-11-23 | Olin Mathieson | Process for reducing the hydrolyzable chlorine content of organic isocyanates |
| GB1194459A (en) * | 1967-10-31 | 1970-06-10 | Takeda Chemical Industries Ltd | Method for the Purification of Isocyanates |
| GB1398975A (en) * | 1971-08-16 | 1975-06-25 | Ici Ltd | Heat treatment and distillation of methylene bridged polyphenyl polyisocyanates |
| GB1384065A (en) * | 1971-11-30 | 1975-02-19 | Ici Ltd | Process for the purification of organic isocyanates |
| US3853936A (en) * | 1973-02-05 | 1974-12-10 | Olin Corp | Process for distillation of toluene diisocyanate |
| US3912600A (en) * | 1974-05-09 | 1975-10-14 | Upjohn Co | Recovery of polymethylene polyphenyl polyisocyanate from a phoshenosed polyamine feed |
-
1976
- 1976-07-10 DE DE19762631168 patent/DE2631168B2/en not_active Ceased
-
1977
- 1977-07-07 GB GB2851477A patent/GB1570741A/en not_active Expired
- 1977-07-08 JP JP8111477A patent/JPS539750A/en active Pending
- 1977-07-08 BE BE179183A patent/BE856617A/en not_active IP Right Cessation
- 1977-07-08 FR FR7721174A patent/FR2357532A1/en active Granted
- 1977-07-08 ES ES460560A patent/ES460560A1/en not_active Expired
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6222066B1 (en) | 1999-03-30 | 2001-04-24 | Bayer Aktiengesellschaft | Process for decreasing the chlorine content of organic isocyanates |
| US6391161B1 (en) | 1999-03-30 | 2002-05-21 | Bayer Aktiengesellschaft | Method for reducing the chlorine content of low molecular weight isocyanates |
| CN100434417C (en) * | 2004-02-04 | 2008-11-19 | 拜尔材料科学股份公司 | Process for the production of very pure 2,4'-methylene diphenyl diisocyanate |
| CN101117375B (en) * | 2004-02-04 | 2010-11-24 | 拜尔材料科学股份公司 | Process for producing polyurethane and/or prepolymer |
| KR101142714B1 (en) | 2004-02-04 | 2012-05-03 | 바이엘 머티리얼사이언스 아게 | Process for the production of very pure 2,4'-methylenediphenyl diisocyanate |
| US11613518B2 (en) | 2017-12-14 | 2023-03-28 | Sulzer Management Ag | Plant and method for purifying an isomeric monomer |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS539750A (en) | 1978-01-28 |
| FR2357532A1 (en) | 1978-02-03 |
| DE2631168A1 (en) | 1978-01-12 |
| FR2357532B1 (en) | 1980-10-17 |
| DE2631168B2 (en) | 1979-03-08 |
| ES460560A1 (en) | 1978-05-16 |
| BE856617A (en) | 1978-01-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PS | Patent sealed | ||
| PCNP | Patent ceased through non-payment of renewal fee |