Europaisches Patentamt (19) European Patent Office Office europeenpeen des brevets EP 0 601 458 B1 (12) EUROPEAN PATENT SPECIFICATION (45) Date of publication and mention (51) intci.6: C08J 11/02, B01D 3/14, of the grant of the patent: B01D3/36, D01F 13/04 26.08.1998 Bulletin 1998/35 // C08G63/81 (21) Application number: 93119353.6 (22) Date of filing: 01.12.1993 (54) Separation process of a mixture acetone , dichloromethane and trifluoroacetic acid/acetone azeotrope Verfahren zurTrennung einer Mischung aus Aceton, Dichlormethan und dem Azeotrop Aceton/ Trifluoressigsaure Procede de separation d'un melange acetone, dichloromethane et azeotrope acetone/acide trifluoroacetique (84) Designated Contracting States: • Maier, Thomas Robert DE FR GB IT Brecksville, Ohio 44141 (US) • Chawla, Surendra Kumar (30) Priority: 07.12.1992 US 986201 Copley, Ohio 44321 (US) (43) Date of publication of application: (74) Representative: Leitz, Paul 15.06.1994 Bulletin 1994/24 Goodyear Technical Center-Luxembourg Patent-Department (73) Proprietor: THE GOODYEAR TIRE & RUBBER L-7750 Colmar-Berg (LU) COMPANY Akron, Ohio 44316-0001 (US) (56) References cited: EP-A- 0 359 692 (72) Inventors: • Hahn, Bruce Raymond • DATABASE WPIL, no. 88-212 207, DERWENT Hudson, Ohio 44236 (US) PUBLICATIONS LTD., London; & SU-A-1 366 173 (MOSCOW FINE CHEM. TECHN.) DO 00 o CO Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice the Patent Office of the Notice of shall be filed in o to European opposition to European patent granted. opposition a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. a. 99(1) European Patent Convention). LU Printed by Jouve, 75001 PARIS (FR) 1 EP 0 601 458 B1 2 Description trope to break the water/trifluoroacetic acid azeo- trope producing a mixture of trifluoroacetic acid and Background of the Invention a water/sulfuric acid complex; (6) fractionally distilling the mixture of trifluoroacetic United States Patent 5,061 ,425 discloses a process 5 acid and the water/sulfuric acid complex to separate for producing high modulus, high tenacity polyethylene the trifluoroacetic acid from the water/sulfuric acid terephthalate (PET) filament by spinning a solution of complex. PET in a mixed solvent system containing trifluoroacetic acid and dichloromethane through a die and into a co- Detailed Description of the Invention agulation medium containing acetone. This results in 10 the formation of a mixture of acetone, trifluoroacetic ac- Mixtures of acetone, dichloromethane, and trifluor- id, and dichloromethane. United States Patent oacetic acid are technically comprised of free acetone, 4,792,573, United States Patent 4,917,845, and United free dichloromethane, and a trifluoroacetic acid/acetone States Patent 4,957,945 disclose a technique for pro- azeotrope. There is no free trifluoroacetic acid in such ducing ultra-high molecular weight polyester resin. One is mixtures (all of the trifluoroacetic acid is in the trifluoro- of the techniques disclosed in these patents also results acetic acid/acetone azeotrope). In the first step of the in the formation of a mixture of acetone, trifluoroacetic process of this invention, the three component mixture acid, and dichloromethane. In commercial operations it is fractionally distilled to recover the dichloromethane. is important to be able to recycle such solvent mixtures This fractional distillation is typically conducted at a tem- to make the process commercially and environmentally 20 perature of 41 °C (the boiling point of dichloromethane). feasible. In other words, the organic solvents must be However, this temperature will vary if the fractional dis- used, collected, separated, and re-used in a closed con- tillation is not carried out under atmospheric pressure. tinuous system. For instance, the dichloromethane will boil at a lower It is unfortunately not an easy task to separate the temperature at reduced pressures and will boil at higher three organic solvents present in such mixtures. This is 25 temperatures under increased pressures. In any case, because a trifluoroacetic acid/acetone azeotrope forms the dichloromethane is boiled off and recovered in this making quantitative separation by fractional distillation fractional distillation step. Afterthe dichloromethane has impossible. been removed, the remaining components in the solvent mixture are the free acetone and the trifluoroacetic acid/ Summary of the Invention 30 acetone azeotrope. In the second step of the process, the mixture of This invention discloses a process for separating trifluoroacetic acid/acetone azeotrope and free acetone acetone, dichloromethane and trifluoroacetic acid from remaining after the first step is fractionally distilled to re- a mixture of acetone, dichloromethane, and a trifluoro- move and recover the free acetone from the mixture. acetic acid/acetone azeotrope comprising the steps of: 35 Since acetone has a boiling point of 56°C, this fractional distillation step will typically be carried out at that tem- (1) fractionally distilling the mixture of acetone, perature under atmospheric pressure. After all of the dichloromethane, and the trifluoroacetic acid/ace- free acetone has been recovered, only the trifluoroace- tone azeotrope to separate the dichloromethane tic acid/acetone azeotrope remains. from a mixture of the trifluoroacetic acid/acetone 40 At this point, at least about 1 6 parts of water is add- azeotrope and free acetone; ed to the trifluoroacetic acid/acetone azeotrope per 1 00 (2) fractionally distilling the mixture of the trifluoro- parts by volume of the trifluoroacetic acid/acetone aze- acetic acid/acetone azeotrope and free acetone to otrope. The water breaks the trifluoroacetic acid/ace- separate the free acetone from the trifluoroacetic tone azeotrope and produces a mixture of free acetone acid/acetone azeotrope; 45 and a water/trifluoroacetic acid azeotrope. This will typ- (3) adding at least 1 6 parts of water to the trifluoro- ically be accomplished by adding from 16 parts to 350 acetic acid/acetone azeotrope per 100 parts by vol- parts of water per 100 parts by volume of the trifluoro- ume of the trifluoroacetic acid/acetone azeotrope to acetic acid/acetone azeotrope. It is more typical to add break the trifluoroacetic acid/acetone azeotrope from 1 6 parts to 1 00 parts of water to the trifluoroacetic producing a mixture of free acetone and a water/ so acid/acetone azeotrope per 1 00 parts by volume of the trifluoroacetic acid azeotrope; azeotrope. It is normally preferred to add from 16 parts (4) fractionally distilling the mixture of free acetone to 30 parts of water to the trifluoroacetic acid/acetone and the water/trifluoroacetic acid azeotrope to sep- azeotrope per 100 parts by volume of the azeotrope. It arate the free acetone from the water/trifluoroacetic is beneficial to minimize the amount of water added acid azeotrope; 55 while still using an amount which ensures that the trif- (5) adding at least 10 parts of sulfuric acid to the luoroacetic acid/acetone azeotrope is completely bro- water/trifluoroacetic acid azeotrope per 100 parts ken. by volume of the water/trifluoroacetic acid azeo- The mixture of free acetone and the water/trifluoro- 2 3 EP 0 601 458 B1 4 acetic acid azeotrope can then be fractionally distilled of the mixture of acetone, dichloromethane and the tri- to recover the free acetone from the mixture. This frac- fluoroacetic acid/acetone azeotrope was then heated in tional distillation is, of course, preferably carried out un- a round bottom flask equipped with a small Vigreux col- der atmospheric pressure at a temperature of 56°C. Af- umn. The mixture was fractionally distilled and at a tem- ter the free acetone is removed and recovered, only the 5 perature of about 40°C, a dichloromethane fraction was water/trifluoroacetic acid azeotrope remains. collected. After all of the dichloromethane had been sep- The water/trifluoroacetic acid azeotrope is broken arated from the mixture, the temperature was allowed by the addition of sulfuric acid. This is carried out by add- to increase to about 56°C. At that point, an acetone frac- ing at least 10 parts by volume of sulfuric acid to the tion was collected. Titrations of the dichloromethane water/trifluoroacetic acid azeotrope per 1 00 parts by vol- 10 fraction and the acetone fraction collected with a sodium ume of the water/trifluoroacetic acid azeotrope. Typical- hydroxide (NaOH) solution showed only a trace amount ly, from 10 parts to 140 parts of sulfuric acid is added of acid. The 111 .5 ml of residue in the pot was found to per 1 00 parts by volume of the water/trifluoroacetic acid be 5.01 molar trifluoroacetic acid. This showed that the azeotrope. Preferably, from 20 parts to 70 parts of sul- residue in the pot was a 3/2 by volume trifluoroacetic furic acid will be added to the water/trifluoroacetic acid is acid/acetone azeotrope (within experimental error). azeotrope per 100 parts by volume of the azeotrope. It At this point 20 ml of water was added to the trifluor- is normally most preferred to add from 30 parts to 50 oacetic acid/acetone azeotrope in the round bottom parts of sulfuric acid to the water/trifluoroacetic acid aze- flask. The distillation was continued and additional ace- otrope per 100 parts by volume of the azeotrope. After tone was collected at a temperature of 56°C. The tem- the water/trifluoroacetic acid azeotrope is broken by the 20 perature was then increased and a small fraction was addition of sulfuric acid, a mixture of free trifluoroacetic collected at a temperature over the range of 70°C to acid and a water/sulfuric acid complex is formed. 78°C. The fraction collected at 56°C contained only a The free trifluoroacetic acid can then be removed trace amount of acid and the small fraction collected from the mixture of free trifluoroacetic acid and the wa- from 70°C to 78°C contained 2.8% trifluoroacetic acid ter/sulfuric acid complex by fractional distillation.