DE1045394B - Process for the production of pure 1, 4, 5, 6, 7, 7-hexachlorobicyclo- [2, 2, 1] -5-hepten-2, 3-dicarboxylic acid - Google Patents

Description

Process for obtaining pure 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1 ] -5-hepten-2,3-dicarboxylic acid The invention relates to the recovery of 1,4,5,6,7,7-Hexachlorbicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid of high purity and useful color in very good yields.

The anhydride of 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid was previously obtained by reacting hexachlorocyclopentadiene with maleic anhydride in xylene solution under reflux cooling. This method is described in U.S. Patent 2606910 (Herzfeld et al .). 1,4,5,6,7,7-Hexachlorobicyclo- [2,2,1] -5 = hepten-2,3-dicarboxylic acid, which is formed by hydrolysis of the anhydride, is dibasic and contains a large amount of stable chlorine. It has found use on an industrial scale for the manufacture of fire-resistant polyester resins.

As far as it could be determined, 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid was used for the production so far only one process described (P r i 11, J. Am. Chem. Soc., Vol. 69, 1947, P. 62). Then hexachloropentadiene was made with maleic anhydride in toluene Anhydride of 1,4,5,6,7,7-hexachlorobicyclo- [2,2,11-5-hepten-2,3-dicarboxylic acid implemented. The unreacted hexachlorocyclopentadiene and toluene were removed by steam distillation. The dicarboxylic acid formed by hydrolysis was mostly in the form of a heavy in the distillation residue (about 1500 cm3 of water) Obtained oil layer, which crystallized after cooling to room temperature. That Product was purified by recrystallization from water or toluene. declarations There is no information about the yield and purity. Although 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid can be produced, arise upon application this process has numerous difficulties on an industrial scale.

The 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-heptene-2,3-dicarboxylic acid prepared in this way has an undesirable color, which is why it is used for making very brightly colored Polyester resins cannot be used. In addition, the procedure must follow P r i 11 the steam distillation of the reaction mixture for an uneconomically long time continued to remove all of the unreacted hexachloropentadiene to remove. The Dien has a very strong, unpleasant odor and gives, if not removed, the acid has undesirable properties. Repetitive Crystallization by known methods only improves the color of the acid a lot slow. It also brings about a decrease in the yield and makes it difficult the exercise of the process on an industrial scale.

The invention now relates to a process for the production of 1,4,5,6,7,7-Hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid in a simple way, which can also be taken on a large scale without difficulty. Included is the product obtained for the manufacture of very light colored polyester resins good usable.

According to the method according to the invention, 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -heptane-2,3-dicarboxylic acid from a solvent pair, the components of which namely water and an organic solvent, practically immiscible with one another are crystallized. This is followed by filtration, washing the crystals with the used ones Solvents and usual drying. The method according to the invention is particularly useful for the preparation of 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -heptane-2,3-dicarboxylic acid from a reaction mixture containing the anhydride. The reaction mixture becomes mixed with a pair of solvents, which water in excess over the hydrolysis of the anhydride contains the required amount as well as practically none with water miscible solvent. This mixture is kept at an elevated temperature as long as until the formation of 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid the end the anhydride is complete by hydrolysis. The resulting Crystals are released from the liquid, e.g. B. by filtering or centrifuging, separated, then washed both with the organic solvent and with water and freed from adhering solvent residue by drying. That way 1,4,5,6,7,7-hexachlorob.icyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid obtained in high yield has a degree of purity exceeding 99% and a degree of purity for the production of light-colored, high quality polyester resin suitable paint.

The color is determined as follows: 3 g of acid are dissolved in 17 cm3 of acetone, and the color of this solution is measured in a test device, e.g. B. with a water tester according to T ay 1 or, determined by comparing the acid solution with the Hazen standard values from -0 to 70. For darker colors than the value -70, the solution is diluted and the value determined with multiplied by the corresponding factor. With regard to the Hazen color test, reference is made to the work "Examination of Water" by Mason, 5th edition, publisher john Wiley and Son, Inc., New York, in particular on page 21. With regard to the color standardization, the Am. Journ. of Chem., Vol. 14, 1892, pp. 300-310, reprinted article by Allen Hazen.

The following examples serve to explain the process in more detail according to the invention. For the preparation of 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid anhydride protection is not claimed within the scope of the present invention. Example 1 260g (0.93 mol) hexachlorocyclopentadiene (purity 97%) were placed in a round bottom flask, the one with a reflux condenser, a stirring device and a heating and / or cooling device was equipped. Over a period of 2 hours, 90 g (0.92 Mol) maleic anhydride, dissolved in 45 g of monochlorobenzene, slowly added, whereby the temperature of the mixture was maintained at 135 to 140 ° C. Subsequently was the temperature of the mixture increased and 8 hours to 140 to 150 ° C held to complete the condensation reaction.

Then more monochlorobenzene (27 g) was added. The received liquid reaction mixture contained 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic anhydride, theoretically an amount of 358 g of 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid corresponding. The mixture was cooled to 80 ° C and then slowly added to 217 g of water of 80 ° C added, which in one with a stirrer and heating and / or cooling device fitted round bottom flask was included. During this addition, something had to be chilled to keep the reaction temperature at 85 to 90 ° C. The hydrolysis of the 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic anhydride was included quickly ahead of this temperature range. After the addition mentioned, the mixture existed from a layer of oil and an overlying layer of water. She was still 1/2 Hour while maintaining the temperature chilled to be sure a full To achieve hydrolysis.

The contents of the bottle were cooled with stirring, whereby 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-heptene-2,3-dicarboxylic acid monohydrate precipitated mainly at a temperature between 39 and 35 ° C. Finally it was the obtained crystal slurry is cooled to about 20 ° C and at this temperature below kept stirring for 15 minutes.

The 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-heptene-2,3-dicarboxylic acid crystals contained 1 mole of water of crystallization. They were sucked off with a Büchner funnel. The filtrate consisted of 59 g of a monochlorobenzene layer and 142 g of a water layer. Analysis of the monochlorobenzene and water layers showed 1.5 and 4.6 g in Contaminants in the solution. The crystals were once with as much monochlorobenzene washed so that they were just covered by it. The obtained filtrate consisted of a monochlorobenzene layer (106 g) containing 2.6 g of impurities in solution, and a layer of water (11 g). Washing was done with a second serving Monochlorobenzene repeated to give a filtrate (97 g) consisting of a monochlorobenzene layer (92.5 g with 0.9 g of soluble impurities) and a water layer (4.5 g). The combined water layers from the first and second washes with monobenzene contained 0.75 g of soluble impurities. The one after the second wash with monochlorobenzene Crystals obtained on the funnel showed a color of 70 (H a z e n).

These crystals were then mixed in the same way with 100 g of water washed. The filtrate consisted of a water layer (96 g) which was 1.3 g of water soluble Containing impurities, and from a monochlorobenzene layer (10 g). The one in the funnel The crystals inside had a Hazen stain of 30. They became a second Washed times with 100 g of water. The filtrate consisted of a layer of water (103 g), which contained 0.4 g of water-soluble impurities, and of a monochlorobenzene layer (2.4 g). The combined monochlorobenzene layers from the first and second wash with water weighed 12.4 g and contained 0.1 g of impurities soluble in monochlorobenzene. The Hazen coloration of the crystals after the second washing with water was 15. These crystals were air dried and then to remove the water of hydration Heated to 100 to 105 ° C for 1 hour. Finally, there was 322 g of 1,4,5,6,7,7-hexachlorobicyclo- [2.2.1] -5-heptene-2,3-dicarboxylic acid obtained in 901% yield and 99% purity.

Example 1 gives a preferred embodiment of the process according to the invention again and shows that the following factors for obtaining purer 1,4,5,6,7,7-Hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid are important: 1. Both the water phase and that of the organic solvent of the mother liquor absorb in them soluble impurities.

2. In order to obtain a light colored product, you must use both solvents getting washed.

3. The total of the filtrate combined with the washing liquids dissolved impurities including dissolved 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-heptene-2,3-dicarboxylic acid amounted to 12.15 g, which is only 3.41% of the theoretically possible yield. In which Process according to the invention is thus 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-heptene-2,3-dicarboxylic acid obtained in high yield without the product in a complicated manner from the Filtrates must be recovered.

Example 2 Part A: A 75 ° C solution of 546 g of maleic anhydride in 263 g of monochlorobenzene, an amount of 1516 g of hexachlorocyclopentadiene was added within 2 hours added. Before the addition, the hexachlorocyclopentadiene was heated to 145 ° C and during the 2 hour addition as well as during further for the completion of the condensation Maintain a temperature of 145 ± 5 ° C for 8 hours. The mixture was then cooled to 130 ° C, and certain amounts of it were in two crystallization dishes poured. After the crystallization was complete, a crystal cake was weighed, to determine the loss of monochlorobenzene. This was 13% of the original Lot. The cake was crushed and to avoid further monochlorobenzene losses kept tightly closed in a bottle.

Part B: 200 g of the condensation product prepared according to Part A, which 184.4 g of 1,4,5,6,7,7-hexachlorobicyclo- [2.2.1] -5 heptene-2,3-dicarboxylic acid and 22.1 g of monochlorobenzene were added by introducing into a mixture of 43.7 g of water and 84.4 g of monochlorobenzene while stirring and maintaining a temperature hydrolyzed at 85 ° C. Of this mixture, 8.2 g of water were used for the hydrolysis, so that a solvent with 36.5 g of water and 106.5 g of monochlorobenzene for the later Crystallization was present. In order to achieve complete hydrolysis, was the mixture was stirred for 1/2 hour at 85 to 90 ° C. and then by cooling the crystallization subject. The mixture was inoculated with success at 44 ° C, the main part crystallized at 42 to 43.5 ° C. Finally the mixture was cooled to 25 ° C and after further stirring at this temperature in a Buchner funnel. The filtrate consisted of two layers. After washing twice with 50 cm3 monochlorobenzene each time the product had a coloration of 80 (H a z en). The crystal cake was then washed twice with 50 cm3 of water each time. The product now had a coloration of 30 (H a z e n). After air drying the product overnight at room temperature dried it in the oven at 105 ° C to constant weight (2 hours). This Product contained 99,219 / o 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid and had a coloration of 30 (H a z e n). The yield (taking into account the samples taken for the color test) was 96.6% of theory. Example 3 Another, 200g weighing part of the condensation product prepared according to Example 2, Part A was hydrolyzed in a similar manner and from a medium containing 116.4 g of water and 25.6 g of monochlorobenzene crystallized. These 25.6 g of monochlorobenzene sat down together from 22.1 g, which was introduced with the condensation product, and from 3.5 g, which is used to correct the losses during the crystallization stage according to example 2 were added. They correspond to those at the end of the condensation stage in the mixture the amount of monochlorobenzene present. After filtering and washing twice with each 60 cm3 of monochlorobenzene, the wet cake had a coloration of 70 (H 19z en). It was then washed twice with 60 cm3 of water each time and gave one when wet Coloring of 30 (H a z e n). After air drying overnight at room temperature and oven drying at 105 ° C to constant weight became a product obtained that 99.3% of 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid and gave a coloration of 35 (Hazen). The yield was 97.0% Theory. In Examples 2 and 3, the 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid from a practically immiscible solvent pair, namely water and monochlorobenzene, crystallizes. The ratio of water to different organic solvents were chosen. Example 4 200 g des condensation product prepared according to Example 2, Part A, were similar Way hydrolyzed and composed of a 35.5 g monochlorobenzene and 106.5 g water Solvent mixture crystallizes. After filtering with a deer funnel the wet, unwashed cake had a coloration of 130 (H a z e n). Dei7 Cake was made with an intimate mixture of 130 cm3 monochlorobenzene and 130 cm3 Water washed. The washing was carried out with the aid of a shake flask in such a way that that there is no layer of liquid over the surface of the cake during the washing process could form. During the washing process, the cake was continuously under Kept negative pressure. The washed, wet cake had a coloration of 30 (H a z e n). After air drying at room temperature overnight and oven drying for 2 hours at 105 ° C. (to constant weight) a product with 99.50% 1,4,5,6,7,7-hexachlorobicyclo- [2.2.1] -5-hepten-2,3-dicarboxylic acid was obtained obtained, the color of which corresponded to 50 (H a z en). The yield was 97.0% Theory. Example 4 illustrates the use of an intimate mixture of water with an organic solvent, especially monochlorobenzene, after washing crystallization from the same medium.

The following examples 5 to 12 are further explanations of the subject matter of the invention and in particular show the use of various organic solvents together with water as a solvent pair for the crystallization of the desired product.

Examples 5, 6 and 7 explain in particular the crystallization of 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid from a practically immiscible solvent pair (water and organic solvent), of which the organic solvent of benzene, carbon tetrachloride and perchlorethylene in the presence of monochlorobenzene. Example 5 Another weighing 200 g Part of the condensation product prepared according to Example 2, Part A, was through Adding to 99 g of water at 85 ° C with stirring hydrolyzed. At the end of the hydrolysis the mixture was cooled to 77 ° C. By adding 25.6 g of benzene, a Crystallization medium from 80.9 g of water, 25.6 g of benzene and 15.6 g of monochlorobenzene obtain. The mixture was cooled for crystallization. She was at 45 ° C inoculated with success, the main part crystallized between 35 and 437 ° C. The Mixture was held at 25 ° C for a further 15 minutes and then through a Buchner funnel filtered. After washing twice with 60 cm3 of benzene each time, the cake was wet a coloration of 70 (H a z e n). The cake was then twice with 60 cm3 of water washed and gave a 30 color (H a z e n) when wet. That according to the usual Product obtained from drying contained 99.22% 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten- 2,3-dicarboxylic acid and had a coloration of 25 (knuckles). The yield was 97.0% of theory. example 6 In a similar manner, another part (200 g) of the according to Example 2, part A, produced condensation product hydrolyzed and after cooling to 75 ° C with Carbon tetrachloride added. It was a crystallization medium from 80.9 g of water, 25.6 g carbon tetrachloride and 25.6 g monochlorobenzene produced. The mixture was then crystallized by cooling. She was vaccinated with success at 45 ° C, the main part crystallized between 37 and 40 ° C, the mixture was still 15 Maintained at 25 ° C for minutes and then filtered through a Buchner funnel. To The wet cake was washed twice with 60 cm3 carbon tetrachloride each time Coloring of 70 (H a z e n). The cake was then twice with 60 cm3 of water washed and gave a 30 color (H a z en) when wet. That after the usual drying The resulting product contained 99.38% 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid and had a coloration of 35 (H a z en). The yield was 98.1% of theory.

Example 7 In a similar manner, another portion (200 g) of the hydrolyzed and hydrolyzed condensation product prepared according to Example 2, Part A au_s a medium consisting of 80.9 g of water, 25.6 g of perchlorethylene and 25.6 g of monochlorobenzene existed, crystallized. The mixture was inoculated with success at 45 ° C, the bulk of it crystallized between 39 and 41 ° C. After the crystallization was complete, the The mixture was filtered through a Buchner funnel. The cake was made twice with each 60 cm3 perchlorethylene washed and then shows a wet color of 70 (H a z e n). It was then washed twice with 60 cm3 each and gave a color of 35 (H a z e n). The product obtained after the usual drying contained 99.16% 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid and had a Coloring of 40 (H a z c n). The yield was 98.7% of theory. Example 8 Part A: Part of the cake made according to Example? -, Part A, was mixed with a Porcelain spatula crushed and air-dried at room temperature to constant Weight brought. During the drying process, the crystals were moved around diligently. Of the The weight loss corresponded to 97.0% of the amount of monochlorobenzene present in the starting material. The condensation product, dried in the air, had a coloration of 360 (H a z e n).

Part B: 182 g of the air-dry product were at 85 ° C in 114.2 g of water stirred in, after the hydrolysis and cooling to 75 ° C was through Addition of carbon tetrachloride produced a crystallization medium that 36 g of carbon tetrachloride and 106 g of water. The mixture was made by cooling subjected to crystallization. It was inoculated successfully at 45 ° C, the main crystallization took place at 39 to 41.5 ° C. The mixture was then cooled to 25 ° C., the mixture Stirred for 15 minutes at 23 to 25 ° C and filtered through a Buchner funnel. Of the unwashed cakes had a coloration of 220 (knuckle). After washing twice with 60 cm3 carbon tetrachloride each, the wet cake had a coloration of 90 (H. a z e n). The cake was then washed twice with 60 cm3 of water each time and yielded thereafter a coloration of 40 (Haxen), after drying in the usual way it had The end product had a coloration of 45 (H a z en) and contained 99.4 "/ a 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid. The yield was 97.8% of theory.

Example 9 182g of the dry prepared according to Example 8, Part A Condensation product were hydrolyzed in water. After cooling the solution up At 75 ° C., the addition of benzene resulted in a mixture consisting of 36 g of benzene and 106 g of water Crystallization medium produced. The mixture was allowed to crystallize in the usual manner brought. It was inoculated with success at 37 ° C, the majority of which crystallized at 34.5 to 36 ° C. After cooling to 25 ° C and stirring for 15 minutes at 24 to 25 ° C, the mixture was filtered through a Buchner funnel, the unwashed Cake had a coloration of 180 (knuckle). After washing twice with 60cm3 each Benzene, the wet cake had a coloration of 90 (H a z e n). He was then twice washed with 60 em3 water each and then had a coloration of 25 (knuckle). To Drying in the usual way, the end product had a coloration of 35 (knuckle) and contained 99.7% 1,4,5,6,7,7-hexachlorobicyclo- [2.2.1] -5-heptene-2,3-dicarboxylic acid. The yield was 96.2 "/ o of theory. Example 10 182g of that according to Example 8, Part A, the dry condensation product produced was hydrolyzed in water. After cooling the solution to 75 ° C., nitromethane became a crystallization medium produced containing 36 g of nitromethane and 106 g of water. The crystallization was carried out in the usual manner. The mixture was inoculated with success at 18 ° C; the majority of the crystals were obtained at 15 to 16 ° C. The mixture was 15 minutes stirred at 10 to 11 ° C and then filtered through a Buchner funnel, after Washing with nitromethane and then with water the cake became more usual Way dried. The product had a color of 40 (Haxen) and contained 99.92% 1,4,5,6,7,7-hexaehlorbicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid. According to the Solubility of the moist 1,4,5,6,7,7-Hexachlo @ rbicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid in nitromethane the yield was only 21.0% of theory. Example 11 182g of the according to Example 8, Part A, air dry condensation product prepared in Hydrolyzed water. After cooling the solution to 75 ° C was by adding n-butyl ether produced a crystallization medium containing 36 g of n-butyl ether and 106 g of water. The crystallization was carried out in the usual manner. the Mixture was inoculated with success at 38 ° C, the main crystallization occurred at 30 to 32 ° C. The mixture was stirred for 15 minutes at 20 to 22 ° C and then through filtered through a Buchner funnel. After washing with n-butyl ether and then with water the cake was dried in the usual way. The product showed a color of 50 (Haxen), analysis showed 100.14% 1,4,5,6,7,7-hexachlorobicyclo- [2.2.1] -5-hepten-2,3-dicarboxylic acid. Due to the solubility of moist 1,4,5,6, 7,7 - hexachlorobicyclo - [2,2,1] - 5 -hepten-2,3-dicarboxylic acid in In n-butyl ether, the yield was only 37.4% of theory.

Example 12 182 g of the air-dry condensation product prepared according to Example 8, Part A, were hydrolyzed in water. After cooling the solution to 75 ° C., a crystallization medium was produced by adding thiophene, which consisted of 36 g of thiophene and 106 g of water. The crystallization was carried out in the usual manner. The mixture was successfully inoculated at 38 ° C., the main crystallization occurred at 29 to 32 ° C. The mixture was stirred for 15 minutes at 20 to 21 ° C. and then filtered through a Buchner funnel. After washing with thiophene and then with water, the cake was dried in the usual manner. The product had a color of 35 (sharks) and contained 99.619 / o 1,4,5,6, 7.7 - hexachlorobicyclo - [2,2,11- 5 - heptene-2,3-dicarboxylic acid. The yield was 95.0% of theory. EXAMPLE 13 871.3 kg, that is 3.084 kg-moles of hexachlorocyclopentadiene, were placed in a glass-lined reaction vessel which had a capacity of 1,892.5 liters and was equipped with reflux cooling, a stirrer and heating and cooling device. The temperature was increased to 140 to 145 ° C and a molten mixture of 313.13 kg, that is 3.175 kg-moles of maleic anhydride and 192.61 kg, that is 174.11 kg of monochlorobenzene gradually in a period of 1.5 to 3 hours entered the reaction vessel. The reaction temperature was maintained at a temperature of 140 to 145 ° C. After this addition, the feed lines were flushed through with 37.85 liters, that is 42.2 kg of monochlorobenzene. The temperature in the reaction vessel was kept at the specified level for 8 hours in order to achieve complete completion of the reaction, then 75.7 liters, that is 843.8 kg, of monochlorobenzene were added.

A glass-lined 1892.51 capacity was used as the crystallization vessel Boiler used with a stirrer and adjustable heating and cooling devices was provided. 643.45 liters of water were placed in this crystallization vessel. the The water temperature was increased to 80 ° C and the contents of the reaction vessel gradually brought into the crystallization vessel, keeping the temperature in this was kept at 83 to 90 ° C. At this temperature the hydrolysis of the 1st, 4,5,6,7,7-hexachlorobicyclo took place - [2,2,1] -5 - hepten-2,3-dicarboxylic acid anhydride quickly in front of you. After overcrowding the line was flushed with 56.77 liters, that is 64.2 kg of monochlorobenzene. the The temperature in the crystallization vessel was kept at 83 to 90 ° C for another 10 minutes, to achieve complete hydrolysis.

The crystallization vessel now contained a theoretical amount of 1192.3 kg, that is 30.93 kg-mol 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid, dissolved in a pair of solvents consisting of 344,431, that is 381.55 kg of monochlorobenzene and 643.51 composed of water. Crystallized on cooling and simultaneous stirring 1,4,5,6,7,7-Hexachlorobicyclo- [2,2,1] -5 -hepten-dicarboxylic acid monohydrate from, namely mainly at 44 to 39 ° C. The mixture finally became with stirring cooled to 25 ° C. The total time required for the crystallization process was about 7 hours. The 1,4,5; 6,7,7-hexachlorobicyclo- [2,2,1] -5-heptene-2,3-dicarboxylic acid crystals were made from the mother liquor consisting of a monochlorobenzene and a water phase separated with the help of a filter. The wet crystals obtained in the filter (each Approach about 9.17 to 11.48 kg) were first mixed with 3.78 to 7.571 monochlorobenzene and then washed with 3.78 to 7.57 liters of water and placed in a rotating oven. There they were removed from the adhering solvent residues with the help of a stream of hot air freed and finally heated to 85 ° C to remove the last water of crystallization. There were 1118.96 kg 1,4,5,6,7,7-Hexachlo @ rbicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid obtain; this corresponds to a yield of 93.7% of theory. The product had a color of 35 (sharks) and a purity of 99.7%. It was for making very light colored polyester resins suitable.

The mother liquor consisted of a water phase, which separated and was discarded, and from a monochlorobenzene phase, from which the monochlorobenzene recovered by distillation and reused in the process. The residue this distillation was drained.

Example 13 illustrates a convenient embodiment of the process according to the invention for a process running on an industrial scale.

The preferred organic solvents for the process according to the invention are benzene, monochlorobenzene, carbon tetrachloride and perchlorethylene. As in Example 1 is shown, 1,4,5,6, 7,7 - hexachlorobicyclo - [2,2,1] - 5 - heptene-2,3-dicarboxylic acid by condensation of Hexachl (> rpentadien and maleic anhydride in the presence .from monochlorobenzene as a solvent. The use of a common organic solvent for both the condensation reaction and the crystallization is more practical than working with two solvents, which requires a more complicated recovery facility. Monochlorobenzene is a preferred organic solvent for both the condensation reaction and also for crystallization. A preferred crystallization medium consisting of an immiscible solvent pair contains between 25 and 75 percent by weight (of the total solvent) water. With a crystallization medium consisting of 75% water and 25 percent by weight organic solvent, the organic solvent losses occurring during drying are minimal, and the method ka nn can be carried out with the greatest economic efficiency.

The advantages of the procedure according to the invention are evident from the following Comparative tests clearly show: a) 273 g of that prepared according to Example 8, Part A air-dry condensation product was hydrolyzed in 227 cm3 of water at 85 ° C, then cooled with stirring and inoculated to give 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-heptene-2,3-dicarboxylic acid monohydrate crystallize out. The inoculation took place at 56 ° C, the main part crystallized at 53 to 54 ° C. The mixture was cooled to 25 ° C and 15 minutes at 23 to Stirred at 25 ° C., then filtered through a Buchner funnel. The one not washed Cake had a coloration of 315 (H a z e n). After washing twice with each 100 cm3 of water, the moist product had a coloration of 270 (H a z e n). The cake was then recrystallized from 210 cm3 of water. After cooling to 25 ° C, filter and twice Washing with 100 cm3 of water each gave the coloration still 270 (Hazen). This product was again poured onto the 210 cms of water recrystallized in the same way. The washed product now had a color of 240 (H a z en). The odor clearly indicated that the product was still hexachlorocyclopentadiene and other impurities. Even after three recrystallization the product could not yet be used from water.

b) The starting point was 272 g of the hexachlorocyclopentadiene according to Example 2 and maleic anhydride, the content of which is 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-heptene-2,3-dicarboxylic anhydride (0.63 mol) theoretical 246g of 1,4,5,6,7,7-hexachlorobicyclo- [2.2.1] -5-heptene-2,3-dicarboxylic acid corresponded. This condensation product was dissolved in 167 g of monochlorobenzene (total available 198 g) and 14.3 g (0.79 mol) of water, that is 25% more than for hydrolysis of 1,4,5,6,7,7-hexachlorobicyclo- [2,2,11-5-hepten-2,3-dicarboxylic anhydride theoretically required is given. This mix was made for the full The course of the hydrolysis is stirred at 90 to 95 ° C for 1 hour, with a considerable Amount of 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-heptene-2,3-dicarboxylic acid crystals formed. The mixture was cooled to 20 ° C. and stirred for 15 minutes kept this temperature. The 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-heptene-2,3-dicarboxylic acid crystals were sucked off. The filtrate was clear and there was no separate aqueous phase.

The crystals were washed twice with 100 g of monochlorobenzene each time. The filtrate combined with the washing liquids contained 4.4 g of dissolved substance, which is only 1.8% of the theoretical 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid yield is equivalent to. The washed 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-heptene-2,3-dicarboxylic acid crystals had a coloration of 220 (H a z e n).

Example a) shows that the purification of 1,4,5, 6,7,7-Hexachlorbicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid unsatisfactory as a result of crystallization from water alone is. Example b) shows that the purification of 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-heptene-2,3-dicarboxylic acid by crystallization from monochlorobenzene alone, which is only 25% more than water those for the hydrolysis of 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-heptene-2,3-dicarboxylic anhydride theoretically required amount does not correspond. The reason for that last The result mentioned is that the excess water present in the crystallization medium is too low to form an effective solvent pair with the monochlorobenzene. It is therefore understandable that the previously widespread mode of operation for cleaning organic compounds, namely crystallization from a single solvent and the subsequent washing with this solvent, to a 1,4,5,6, 7,7 - Hexachlorobicyclo- [2,2,1] - 5 -hepten-2,3-dicarboxylic acid leads, which for the production light-colored polyester resins are not suitable. It is surprising that im In contrast to the normal crystallization practice, in which a product is made with the help of a single solvent is to be purified, the crystallization from one Solvent pair, its components, namely water and organic solvent, are practically immiscible with one another, leads to a product which has the for The production of very light-colored polyester resins has to be met quite corresponds.

Claims (4)

PATE NTANSPRt'CIIE: 1. Process for the extraction of pure 1,4,5.6, 7,7-Hexachlorobicyclo- [2,2,1] -5 -hepten-2,3-dicarboxylic acid, characterized in that that the hydrolysis of 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic anhydride 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic acid obtained at elevated temperature in the presence of a sufficient amount of water and one that is practically immiscible with it organic solvent, such as in the proportion of at least 1 part by weight of water per part by weight of organic solvent, crystallized, the 1,4,5, 6,7,7 -Hexachlorbicyclb- [2,2,1] - 5 -hepten-2,3 - dicarboxylic acid crystals filtered off, with water and the organic solvent washes and the crystals dried at elevated temperature. 2. The method according to claim 1, characterized in that there is used as starting material a 1,4,5, 6,7,7 - hexachlorobicyclo - [2,2,1] - 5 -heptene-2,3 = dicarboxylic acid or a mixture containing 1,4,5,6,7,7-hekachlorobicyclo- [2,2,1] -5-heptene-2,3-dicarboxylic acid used, which is made by reacting hexachlorocyclopentadiene and maleic anhydride at elevated temperature in monochlorobenzene and hydrolysis of the reaction mixture with one is the water requirement for the hydrolysis of the 1,4,5,6,7,7-hexachlorobicyclo- [2,2,1] -5-hepten-2,3-dicarboxylic anhydride formed excessive amount of water was obtained. 3. The method according to claim 1, characterized characterized in that monochlorobenzene and or or as the organic solvent another organic solvent is used. 4. The method according to claim 1, 2 or 3, characterized in that in the serving as the crystallization medium Solvent pair the weight ratio of water to monochlorobenzene about 3: 1 up to 1: 3, based on the total weight of the solvent present, preferably 3 parts by weight of water applied to 1 part by weight of monochlorobenzene will.