DE1493360B1 - Process for the preparation of aliphatic, cycloaliphatic or araliphatic polyisocyanates low in chlorine-containing impurities - Google Patents

Description

Process for the production of impurities poor in chlorine aliphatic, cycloaliphatic or araliphatic polyisocyanates.

Diisocyanates are usually made in two ways Art. In the first, the so-called hydrochloric acid method, the amine is converted into the hydrochloride transferred and the slurry thus obtained stirred and heated through introduced phosgene converted to diisocyanate. The second, the so-called cold Hot phosgenation method, consists in turning excess free amine Entering phosgene, which is preferably dissolved in the cold in an inert solvent is, the resulting slurry is heated and at the same time for the purpose of completion of the conversion initiates further phosgene.

In the previous embodiments of both methods, the Diisocyanate production at temperatures between 145 and 175 "C and in inert Solvents various composition at a weight ratio of 8 to 10 parts by weight Solvent per part by weight of amine. These temperature and dilution ratios not only required longer implementation times, but also led to education of a considerable amount of chlorine monoisocyanates, depending on the type of amine and the other Temperature in amounts of 1 to 50 /, incurred as an impurity. The patent literature contains with the exception of the production of hexamethylene diisocyanate, where a content of at least 501,6-chlorohexyl isocyanate is given, no evidence of formation of these impurities.

In both procedures, however, in addition to the desired diisocyanate, alkyl chlorides are actually formed from monoamines and monochloroisocyanate and / or dichloroalkane from the diamine according to the following reactions: The formation of these three impurities is probably based on the displacement of an --NHCOCI - or NC = O - group by a chloride ion which is unavoidably present in the reaction mixture. Experience has shown that this side reaction occurs independently of the conversion method, that is to say both in the hydrochloride and in the cold-hot phosgenation method.

The same difficulties are encountered in the extraction of Isocyanates from cycloaliphatic polyamines, i.e. those with their amino groups either directly to a ring carbon atom or via an aliphatic chain one or more carbon atoms bonded to a cycloaliphatic radical are, as well as araliphatic polyamines, z. B. such polyamines, their amino groups via an aliphatic chain of one or more carbon atoms are bound to an aromatic nucleus. It is also known that the conversion of aliphatic, cycloaliphatic and araliphatic diamines to the corresponding Diisocyanates is more difficult than that of aromatic amines and has longer reaction times and higher temperatures required.

The presence of co-formed aliphatic chloromonoisocyanate in the diisocyanates is very undesirable for the production of high molecular weight polyurethanes, since the monoisocyanate undoubtedly acts as a chain stopper and contributes to the formation of low an Place of the desired high molecular weight polyurethanes leads. Also, the polyurethanes Due to the presence of chlorine, they are susceptible to discoloration through exposure to light and as a result limited in their usability for the production of lightfast polyurethanes.

It was found generally true that in all species aliphatic diisocyanates that have been produced, e.g. B. Hexa-, Nona- and decamethylene diisocyanate and much more with m-xylylene, p-xylylene and with p-1,8-Menthandiisocyanaten, chloroisocyanates are formed. It turned out also find out that the boiling points of the diisocyanates and those derived from them Chlorides are so close together that they can be separated by fractional distillation difficult and economically point is impractical. this applies especially to those high molecular weight compounds because of their sensitivity require a high vacuum against, in particular, prolonged heating for their distillation. It is well known that when isocyanates are heated to 150 to 200 "C carbon dioxide and amorphous substances, namely carbodiimides, are formed.

The main object of the invention is to provide a practical one Working method in which the formation of these impurities is reduced to a minimum so that they are harmless for the various forms of use mentioned earlier are. Another aim of the invention is to create an economical one stimulating process for the synthesis of aliphatic, cycloaliphatic and araliphatic Diisocyanates in high yield and purity. The invention further aims the Development of a process in which the diisocyanates are highly pure for the purpose of obtaining them Material does not need to be fractionally distilled.

It has now been found according to the invention that one has the disadvantages the known processes and avoid aliphatic, low-chlorine impurities cycloaliphatic or araliphatic polyisocyanates in a short time, in high yield and in highly pure form by reacting the corresponding polyamines or their hydrochlorides in the presence of an inert organic solvent, with excess phosgene, Can be prepared at elevated temperature by phosgenation at temperatures between about ta 110 and about 130 "C and with a solvent to polyamine weight ratio between about 18: 1 and about 30: 1.

The improvements according to the invention can be used both in the hydrochloride as well as with the cold-hot phosgenation method, but with the former more beneficial. In this case, the solvent-polyamine ratio will be on the Calculated based on the free base.

Experience has shown that the temperature range between 120 and 1280 C the purest products and with a solvent-polyamine ratio between 18: 1 and 30: 1 the highest yields.

When working with lower solvent polyamine -Relationship you need longer implementation times that are not only impractical, but also contribute to the decomposition of the polyisocyanate, and consequently a deterioration in the yield cause.

Which solvent is used in the process according to the invention, is of no importance as long as it is inert, i.e. neither with HCl nor reacts with COCl2 or the isocyanates formed.

Generally solvents with a boiling point of at least 110 ° C usable. Chlorobenzene, o-dichlorobenzene, Toluene, xylene, n-octane and anisole mentioned as examples.

Even if the following examples include the preparation of diisocyanates show, the process according to the invention can obviously also be used for Obtaining tri- or higher molecular weight polyisocyanates in high yield and purity exploit.

Understandably, can of course with the method according to the invention also substituted diamines, i.e. those with nitro groups, alkyl radicals and halogens, to be used.

The improved, inventive method can advantageously for converting the most varied of aliphatic, cycloaliphatic or araliphatic Polyamines can be used in the corresponding polyisocyanates, provided that the amino groups can be converted to isocyanate groups by phosgenation, ie present, for example, as primary amino groups.

The polyamine should preferably also be obtained from others containing phosgene responding groups be free.

Otherwise there are no further restrictions on the type of according to the invention processable aliphatic, cycloaliphatic and araliphatic Amines. However, the process of the invention is for the conversion of polyamines with less than 5 carbon atoms of little practical value since they are too long Request implementation times. Even so, the invention also applies to short chain polyamines applicable with comparatively large alkyl groups attached to the carbon chain, because the presence of these groups increases the solubility of the polyamine hydrochloride improved in the solvent and thus the phosgenation is accelerated. The inventive Process is on both straight and branched chain and furthermore as well Applicable to both saturated and unsaturated polyamines. With the higher molecular weight, So about 11 to 20 carbon atoms containing hydrochlorides, which in the solvents More soluble than the C5 to C10 polyamine hydrochlorides are dependent on the reaction temperature a more important role than the dilution ratio. Even so, it also increased in these If the dilution clearly increases the rate of conversion to a considerable extent.

The following examples illustrate the invention.

Example 1 Describe the experimental details below the recommended process for the preparation of m-xylylene diisocyanate.

In one with stirrer, high-performance cooler, thermometer and gas inlet tube 5-1 round bottom flasks equipped with 136 g (1 mole) of commercially available m-xylylenediamine and 3100 ml of chlorobenzene accordingly a solvent to diamine weight ratio of 24.6: 1 entered. Thereafter, dry hydrogen chloride was released at one rate of 1690 ml / min passed and a temperature increase to 60 ° C allowed. After one hour the diamine was completely converted to its hydrochloride. the the resulting, comparatively thin slurry was with gentle stirring to the Heated to reflux, 70 ml of chlorobenzene-water were distilled off azeotropically ,, so that the dilution ratio now decreased to 24: 1. After that was phosgene at a flow rate of 221 ml / min via a flow meter in the dry reaction mixture, which was kept at 120 to 125 ° C., was initiated.

After 10 to 12 hours a clear, yellow solution had formed, which contained very little, very fluffy, white solid. She was 1 to Flushed with dry nitrogen for 2 hours at reflux temperature, to room temperature, d. H. 25 to 30 "C, cooled and suction filtered. Analysis of a 50 g sample of the filtrate produced a total yield of m-xylylene diisocyanate of 183 g or 98, according to the Theory. The chlorobenzene was then stripped off in vacuo and the residue after transfer distilled in a 300 ml flask in vacuo. The m-xylylene diisocyanate fraction boiling at 126 ° C./1 mm was collected; it weighed 178 g, which corresponds to a 91. ole yield. The analysis showed a purity of 99.3% and a content of 0.08% total chlorine.

Examples 2 to 4 These examples were carried out as in Example 1 with the modification that o-dichlorobenzene was used instead of chlorobenzene and the various temperatures indicated below. The results are compiled in the list below and compared with those from Example 1 in order to show the influence of temperature on product quality. Temperature purity total Example Abusbeute chlorine ° C%% 2 160 90.0 # 97.2 1.24 3,150 89.3 97.7 1.00 4,140 91.2 98.9 0.70 1 120 to 125 91.4 99.3 0.08 Examples 5 to 8 These examples were carried out as in Example 1 with the modification that different mixing ratios of chlorobenzene to m-xylylenediamine and in the temperature range between 124 and 128 ° C were used. The results are compiled in the list below, and the influence the dilution on the yield of m-xylylene diisocyanate and the duration of the reaction. Dilution conversion Example ratio yield duration ~ in hours 5 10: 1 80 46 6 15: 1 84.5 33 7 20: 1 87.5 20 8 24: 1 91 <4 12 Example 9 This example depicts the preparation of p-1,8-menthane diisocyanate. In the usual apparatus described earlier, 85 g (0.5 mol) of 1,8-diamino-p-menthane were dissolved in 1615 ml of chlorobenzene and converted into the hydrochloride. The slurry was then heated to reflux and made sure to anhydrous by distilling off 100 ml of chlorobenzene, reducing the dilution ratio to 20. Phosgene was then passed through at a rate of 220 ml / min and the unconverted phosgene was caught in a dry ice-acetone cold trap. The reaction temperature was kept at 125 to 126 ° C. After 1200 / c of the theoretical amount of phosgene had been introduced, captured phosgene plus HCl were again passed through the reaction mixture. This measure was repeated three to four times over the course of 18 hours. At the end of this time the reaction mixture was clear and amber in color.

The chlorobenzene was then distilled off, the residue at 0.4 Distilled to 0.5 mm vacuum and collected the fraction passing over at 94 to 110 ° C.

It weighed 98.5 g, corresponding to a yield of 88.70 / 0 according to theory. Her Analysis showed that it consisted of 99.1% pure p-1,8-menthane diisocyanate and 0.09 % Total chlorine.

Example 10 This example illustrates the preparation of hexamethylene diisocyanate.

Following the procedure of Example 1, 116 g (1 mol) of hexamethylenediamine were obtained in 2940 g of chlorobenzene, i.e. at a dilution ratio of 25, to hexamethylene diisocyanate implemented. The yield of hexamethylene diisocyanate was 151 g, corresponding to 900 / o according to the theory. The isocyanate has a boiling point of 101 to 103 ° C / 2.7 mm; nD25 = 1.4501. It had a purity of 99%.

Example 11 This example also illustrates the preparation of Hexamethylene diisocyanate.

Following the procedure of Example 1, 116 g (1 mol) of hexamethylenediamine were obtained in 1000 g of o-dichlorobenzene, i.e. at a dilution ratio of 8, at 165 to 170 ° C converted into hexamethylene diisocyanate. The yield was only 115.8 g accordingly 69% by theory and the product was only 97.00 / o pure.

Example 12 This example describes the production of mixed, namely 4,6- and 2,4-dimethyl-m-xylylene diisocyanates.

100 g of the corresponding diamine mixture with a melting point of 120 to 124 ° C were in 2400 g of anisole, i.e. H. corresponding to a dilution ratio of 24, resolved. The solution became more anhydrous by means of a flow meter Hydrogen chloride was passed in until all the diamine had been converted to the hydrochloride. The hydrogen chloride was then replaced with phosgene and the solution slowly increased heated to 125 to 135 ° C and then for so long, namely 7 hours, on this Temperature hold until the completeness of the solution becomes clear Implementation indicated. The clear, rather dark solution was initially used for removal all dissolved phosgene was flushed through with dry nitrogen and then distilled in vacuo. The fraction boiling at 160 to 165 ° C and 3.0 mm pressure was collected. The yield of colorless, liquid diisocyanate (nD20 = 1.5424) was 90 ° / 0 according to theory.

Calculated equivalent weight 108, found equivalent weight 109.

A small portion of it was converted into the corresponding mixed diurethane of the formulas using dry methanol converted, which was separated by fractional crystallization from chlorobenzene into the compound (Ia) of F. 189C and (IIa) of F. 1300 C. The mixed diisocyanates and their urethane derivatives gave the following analytical values: For the diisocyanates C12H12N2O2: Calculated C 66.6, C66.6, H5.5, N13, O0 / 0; found .......... C 66, 5, H 5, 7, N 13.1 0h For the dimethyl urethanes C14H20N2O4: Calculated .......... C 60.0, H 7, 2, N 10.0%; found .......... C 60.2, H 7.1, N 10.1 0 / o.

Example 13 This example illustrates the preparation of 4,6-dimethyl-1,3-xylylene diisocyanate.

In much the same way as in Example 1; H. with the modification, that n-octane was used as a solvent, 100g of pure diamine isomer (F. 129 bis 130 "C), which had previously been purified by recrystallization from chlorobenzene, converted into the diisocyanate, with 93% yield as a colorless liquid from bp. 140 to 142 ° C / 0.88 mm and nD20 = 1.5435.

Calculated equivalent weight 108, found equivalent weight 109.

A small sample was converted into dimethyl urethane using methanol (Ta) converted from F. 1800C to that contained in Example 12 from the mixture identical was. The diisocyanate and its urethane gave the following analysis values: For C12H12N2O2: Calculated .......... C 66.6, H 5.6, N 13.00 / o; found .......... C 66.7, H 5, 5, N 12.8 O / o.

For Cl4H20N202: Calculated .......... C 60.6, H 7.2, N 10.00 / o; found .......... C 59.8, H 7.3, N 10.1%.

Example 14 This example illustrates the preparation of pentamethylene diisocyanate.

Following the procedure of Example 1, 51 g (0.5 mol) of pentamethylenediamine were obtained in 1500 g of anhydrous chlorobenzene, d. H. at a dilution ratio of 29, converted to pentamethylene diisocyanate, which in an amount of 69 g accordingly 900 / o accrued according to the theory; Bp 105 ° C / 4.0 mm.

Calculated equivalent weight 77.1, found equivalent weight 76.3, corresponding to 99% purity.

Example 15 This example illustrates the preparation of nonamethylene diisocyanate.

Following the procedure of Example 1, 158 g (1 mol) of nonamethylenediamine were obtained in 3950 g of anhydrous chlorobenzene, d. H. at a dilution ratio of 25, converted to nonamethylene diisocyanate, which distilled off at 134 ° C./0.6 mm. the The theoretical yield was 91%.

Calculated equivalent weight 105, found equivalent weight 104, corresponding to 99% purity.

Example 16 This example illustrates the preparation of decamethylene diisocyanate at.

Following the procedure of Example 1, 172 g (1 mol) of decamethylenediamine were obtained in 4300 g of anisole, d. H. at a dilution ratio of 25, with a 930 / ger yield converted to decamethylene diisocyanate; Bp 132 "C / 0.2 mm.

Calculated equivalent weight 112.2, found equivalent weight 113.1, corresponding to 99% purity.

Example 17 In one with mechanical stirrer, condenser, thermometer and a 5-liter flask equipped with a dropping funnel were initially filled with 3030 ml of dry chlorobenzene filled. The flask was then cooled to 0-5 "C in an ice-salt bath, and then about 250 g of phosgene were condensed into it in the course of about 90 minutes. Afterward were stirred vigorously and the temperature of the mixture was kept below 10 ° C 136 g (1 mol) of m-xylylenediamine dropwise, i.e. at a dilution ratio of 24, added. The ice bath was then removed and the reaction mixture heated to 110.degree warmed and phosgene in slow flow, d. H. at a speed of about 220ml / min, initiated. The temperature was then increased to 125 ° C and so long hold until a clear, slightly brownish solution was obtained. Well was flush the apparatus with dry nitrogen for about 1 hour and remove the solvent distilled off in vacuo. The residue was then distilled off at 0.1-0.2 mm Hg and delivered 163 g corresponding to 870 /, according to theory, of m-xylyldiisocyanate, the 0, Contained 4% chlorine.

Claims (3)

Claims: 1 process for the production of chlorine-containing Impurities of poor aliphatic, cycloaliphatic or araliphatic polyisocyanates by reacting the corresponding primary polyamines or their hydrochlorides, in the presence of an inert organic solvent, with excess phosgene at elevated temperature, characterized in that the reaction is carried out at temperatures between about 110 and about 135 ° C and a solvent to amine weight ratio between about 18: 1 and about 30: 1. 2. The method according to claim 1, characterized in that one is a polyamine containing at least 5 carbon atoms is used. 3. The method according to claim 1 and 2, characterized in that one as the primary polyamine, a polymethylenediamine with at least 5 carbon atoms used.