Title of Invention

A PROCESS FOR PREPARAING A MIXTURE OF CHLORINATED VIOLANTHRONE AND ISOVIOLANTHRONE

Abstract

ABSTRACT A process for preparing a compound selected from chlorinated violanthrone and its isomers comprising reacting a compound selected from violanthrone and its isomers with chlorine in the presence of a diluent selected from a C2-C5 aliphatic carboxylic acids, a C2-C5 aliphatic halo carboxylic acids and mixtures thereof at a temperature in the range of 60-160°C and recovering said chlorinated violanthrone and its isomers from the reaction mixture by blown manner.

Full Text

The present invention relates to a process for preparing a mixture of chlorinated violanthrone and isoviolanthrone by reacting a mixture of violanthrone and isoviolanthrone with chlorine in the presence of a diluent. Chlorinated violanthrones (la) and isoviolanthrones (lb) are important vat dyes for the blue to violet range of hues (la: C.I. Vat Blue 18 (n=3), C.I. Vat Blue 22 (n=4); lb: C.I. Vat Violet 1 (m=2)). In the generally known processes for preparing these vat dyes, the chlorination takes place in nitrobenzene (DE-A-177 574 and 465 988). However, unwanted byproducts are often formed thereby. In addition, the use of nitrobenzene requires, because of its damaging effects on health, special safety measures and complete removal from the products. Furthermore, chlorination in molten phthalic anhydride is described in US-A-1 842 694. In this reaction, the recovery of the phthalic anhydride on working up the reaction mixture pres¬ents difficulties because phthalate is formed and must be con¬verted back into the anhydride by acidification and ring closure. Finally, DE-A 177 574 also discloses the bromination of violan¬throne in glacial acetic acid, but the reaction conditions are not stated. The chlorination reactions mentioned are, however, always carried out in nitrobenzene. It is an object of the present invention to provide a process for preparing high-purity chlorinated violanthrones and isoviolan¬thrones in good yields and purity in a way which is economic and -does not pollute the environment. Accordingly the present invention theretbre provides a process for preparing a mixture of chlorinated violanthrone and isoviolanthrone comprising reacting a mixture of violanthrone and isoviolanthrone with chlorine in the presence of a diluent selected from a C2-C5 aliphatic carboxylic acids, a C2-C5 aliphatic halo carboxylic acids and mixtures thereof at a temperature in the range of 60-160°'C , optionally in the presence of a halogenation catalyst such as herein described and recovering said chlorinated violanthrone and isoviolanthrone from the reaction mixture by known manner. The number of carbon atoms in the aliphatic carboxylic acids is not in principle important but those acids which are liquid at the reaction temperature are to be preferred. Hence C2-C5-carboxylic acids, especially C:-C3-carboxylic acids, and veiy particularly acetic acid, are preferred. Examples of suitable carboxylic acids are moreover propionic acid, mono-, di- and trichloroacetic acid and mixtures thereof As a rule, the non-halogenated acids are to be preferred to the halogenaled acids because they are easier lo handle, but the halogenated acids, especially the chlorine derivatives, can also be used. In this connection, it has proven beneficial for the acid used, in particular acetic acid, to be virtually anhydrous. A water content of up to 10°0 by weight does not, as a rule, have an adverse effect, however. It is particularly advantageous to use anliydrous acids such as glacial acetic acid.It is surprising that the carboxylic acid which is acting as diluent undergoes negligible chlorination under the reaction conditions and is virtually unchanged after the reaction has taken place (cf in this connection Ullmanns Encyklopadie der Technischen Chemie, 4th edition, volume 9,page 395(1975)). In general, from 4 to 15 kg, preferably 8 to 12 kg, of carboxylic acid are employed per kg of chlorination product. In some cases, especially for preparing more highly chlorinated products (n or m > 3), it is advisable for a halogenation catalyst to be present. Suitable agents are those customarily used for this purpose, such as iron powder, iron compounds, especially anhydrous iron (III) compounds such as iron (III) chloride, and iodine. The amount of halogenation catalyst is expediently about 0.5 to 10% of the weight of violanthrone or isoviolanthrone. The necessary amount of chlorine depends on the required degree of chlorination, ie. on the average number of chlorine atoms to be incorporated in the violanthrone or isoviolanthrone molecule. As a rule, from 1 to 4 mol, preferably 2 to 3 mol, of chlorine (C12) are used per chlorine atom to be incorporated, in each case based on 1 mol of violanthrone or isoviolanthrone. Suitable reaction temperatures are, in general, from 40 to 160°C, especially 40 to 140"C, and very particularly 90 to 120'C. The reaction can normally be carried out under atmospheric pres¬sure, but it can also be carried out under slightly elevated pressure, as a rule up to about 5 bar. The chlorination according to the invention can be carried out either continuously or batchwise. The procedure for the process according to the invention is expediently as follows: the diluent is introduced first in liquid form (room temperature or elevated temperature, eg. about 60°C for chloroacetic acid) and, while stirring, violanthrone or isovio¬lanthrone and, if desired, the halogenation catalyst are added and, after heating to the required temperature, the addition of chlorine is started. In this connection it is advisable to introduce the stream of chlorine under the surface of the reac¬tion mixture. After the introduction of chlorine is complete, which generally takes from 4 to 18 h, the reaction is normally completed by stir¬ring further at the reaction temperature for up to 3 hours. The reaction mixture can be worked up to the chlorination prod¬ucts in a conventional way, where appropriate after slight cooling, by filtration, washing with the particular diluent and hot water and subsequently drying. The process according to the invention can be used to prepare chlorinated violanthrones and isoviolanthrones in high purity and good yield, and even the more highly chlorinated products can be obtained without difficulty. Another advantage is the economy of the process. The diluents, especially acetic acid, can easily be regenerated by distillation, and can thus be returned to the process, but are also readily biodegradable so that costly treat¬ment of the wastewater is unnecessary. Examples A mixture of x g of violanthrone (la) or isoviolanthrone (lb) (100% calculated), a g of diluent D, b g of water and c g of halogenation catalyst C was heated with stirring to T*C (in the case of Example 8, the diluent was heated to 60°C before introducing the other components). Then, y g of chlorine were passed into the mixture over the course of t1 h. After svibsequently stirring for t2 h at T°C and cooling to about 70°C, the product was removed by filtration, washed first with glacial acetic acid and then with hot water, and subsequently dried. Further details of these experiments and their results are com¬piled in the following Table. The present invention relates to a process for preparing a mixture of chlorinated violanthrone and isoviolanthrone by reacting a mixture of violanthrones and isoviolanthrone with chlorine in the presence of a diluent. are important vat dyes for the blue to violet range of hues (la: C.I. Vat Blue 18 (n=3), C.I. Vat Blue 22 (n=4); lb: C.I. Vat Violet 1 (m=2)). In the generally known processes for preparing these vat dyes, the chlorination takes place in nitrobenzene (DE-A-177 574 and 465 988). However, unwanted byproducts are often formed thereby. In addition, the use of nitrobenzene requires, because of its damaging effects on health, special safety measures and complete removal from the products. Furthermore, chlorination in molten phthalic anhydride is described in US—A—1 842 694. In this reaction, the recovery of the phthalic anhydride on working up the reaction mixture pres¬ents difficulties because phthalate is formed and must be con¬verted back into the anhydride by acidification and ring closure. Finally, DE-A 177 574 also discloses the bromination of violan¬throne in glacial acetic acid, but the reaction conditions are not stated. The chlorination reactions mentioned are, however, always carried out in nitrobenzene. It is an object of the present invention to provide a process for preparing high-purity chlorinated violanthrones and isoviolan-thrones in good yields and purity in a way which is economic and does not pollute the environment. We claim: 1. A process for preparing chlorinated violanthrones or isovio- lanthxones by reacting violanthrone or isoviolanthrone with chlorine in the presence of a diluent, wherein aliphatic carboxylic acids and/or aliphatic halo carboxylic acids are used as diluent for this purpose. 2. A process as claimed in claim 1, wherein C2—C5—carboxylic acids or their halogen derivatives are used as diluents. 3. A process as claimed in claim 1, wherein acetic acid is used as diluent. 4. A process as claimed in claim 1, wherein acetic acid with a water content 5. A process as claimed in claim 1, wherein the reaction is car¬ried out in the presence of a halogenation catalyst. 6. A process as claimed in claim 1, wherein the reaction is car¬ ried out in the presence of iron powder, iron(III) chloride or iodine as halogenation catalyst. 7. A process as claimed in claim 1, wherein the reaction is car¬ ried out at from 60 to 160°c.

Documents:

150-mas-95 abstract.pdf

150-mas-95 claims.pdf

150-mas-95 correspondence-others.pdf

150-mas-95 correspondence-po.pdf

150-mas-95 description (complete).pdf

150-mas-95 form-1.pdf

150-mas-95 form-26.pdf

150-mas-95 form-4.pdf

150-mas-95 others document.pdf

150-mas-95 others.pdf