Process for the purification of alcohol-containing solvents

Abstract

A process for processing an alcohol-containing solvent is described. The process according to the invention is used in particular for the treatment of alcohol-containing solvents which are used, for example, for cleaning metal parts. Further subject matter of the present invention are compositions which are suitable for the aforementioned intended use, as well as the use of certain compositions for the purification of alcohol-containing solvents.

Claims

1. A process for purifying an alcohol-containing solvent comprising: introducing a cleaning agent into the alcohol-containing solvent, and refluxing the alcohol-containing solvent, wherein the cleaning agent is in an encapsulation material, and wherein the encapsulation material completely surrounds the cleaning agent.

2. The process according to claim 1, wherein the encapsulation material comprises at least one of cellulose derivatives and polyvinyl butyral.

3. The process according to claim 2, wherein the encapsulation material comprises polyvinyl butyral and the cleaning agent comprises a base.

4. The process according to claim 3, wherein the base is selected from the group consisting of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate, calcium hydroxide, magnesium carbonate and mixtures of the foregoing.

5. The process according to claim 4, wherein the alcohol-containing solvent comprises modified alcohols.

6. The process according to claim 5, wherein the alcohol-containing solvent comprises glycol ether mixtures.

7. The process according to claim 3, wherein the alcohol-containing solvent comprises modified alcohols.

8. The process according to claim 7, wherein the alcohol-containing solvent comprises glycol ether mixtures.

9. The process according to claim 1, wherein the cleaning agent comprises a base.

10. The process according to claim 1, wherein the cleaning agent is selected from the group consisting of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate, calcium hydroxide, magnesium carbonate and mixtures of the foregoing.

11. The process according to claim 1, further comprising adding at least one antioxidant to the alcohol-containing solvent.

12. The process according to claim 1, wherein the alcohol-containing solvent comprises modified alcohols.

13. The process according to claim 12, wherein the alcohol-containing solvent comprises glycol ether mixtures.

Description

EXAMPLES

(1) Test 1: Simple Mixing Test and Evaporation Behavior

(2) A film of Mowital Thin Film 100 is mixed with solvent (DOWCLENE® 1601) at room temperature; the solvent is then evaporated.

(3) Analytical Results:

(4) 1. Solubility: Without agitation, complete dissolution of the plastic was observed after approximately 30 minutes.

(5) 2. Appearance after evaporation: The solvent was evaporated at 80° C. overnight. A uniform, colorless Mowital film formed in the container.

(6) Evaluation:

(7) The solubility of the film is good and the recovery shows that the plastic shows no obvious degradation reactions due to the applied temperature and solvent and the combination thereof.

(8) Test 2: Endurance Test in Laboratory Distillation Apparatus with Fresh DOWCLENE® 1601

(9) Mowital Thin Film 100 in a solvent (DOWCLENE® 1601) are mixed in the distillation sump of the laboratory apparatus. Metal strips made of aluminum, steel, copper and brass are suspended in the steam space of the apparatus. The solvent is continuously refluxed in negative pressure (100 mbar) for 6 days.

(10) Evaluation:

(11) 1. GC/FID analysis of the distillate: solvent was recovered in unchanged purity. Volatile organic degradation products from the plastic were not identified.

(12) 2. Acidity of the distillate (titration method): The solvent was unchanged and within specification.

(13) 3. Optical inspection of the metal strips: The metal strips showed no coating, or similar plastic-like precipitation.

(14) 4. Assessment of the sump: The sump appeared viscous, which was triggered by the high concentration of PVB. Clumping or caking of the plastic was not observed. The color was unchanged.

(15) 5. FT-IR analysis of the sump: After the experiment, the solvent in the distillation residue was evaporated. An FT-IR spectrum of the plastic remaining in the sump was recorded and compared to an unused plastic film. There was no change between the dissolved, heated plastic after the test and the originally unused film.

(16) Evaluation:

(17) No potentially troublesome degradation products show up even at permanently high temperatures in the boiling solvent. The plastic was dissolved by the solvent, but was chemically unchanged. The solvent distilled from the sump corresponds to the fresh material used and can be used without restriction for cleaning.

(18) Test 3: Endurance Test in Laboratory Distillation Apparatus with Acidic DOWCLENE® 1601

(19) The above experiment 2 was repeated with Mowital granules B30H and with acid solvent (acid number about 6000 ppm).

(20) Analytical Results:

(21) 1. GC/FID analysis of the distillate: Only solvent of unchanged quality was recovered. Volatile organic degradation products from the plastic were not identified.

(22) 2. Acidity of the distillate (titration method): The acid number remained constant.

(23) 3. Optical inspection of the metal strips: The metal strips showed no coating, or similar plastic-like precipitation.

(24) 4. Assessment of the sump: The sump showed discoloration. This is often observed during distillation of acidic samples. Clumping or caking of the plastic was not observed.

(25) Evaluation:

(26) The findings obtained for a fresh solvent are identical for an acidic solvent: No degradation products of the plastic were observed; the solvent distillate corresponds in quality to the solvent used and can be used for cleaning.

(27) Experiment 4: Acid Reduction Using Encapsulated Detergent—Sample 1

(28) Acidic DOWCLENE® 1601 (solvent taken from customer cleaning plant as the most realistic example possible) are refluxed overnight at 100 mbar. Metal strips of aluminum, steel, copper and brass are suspended in the steam space of the apparatus. The next day, a sample is taken at the sampling point in the distillate for zero determination.

(29) The encapsulated cleaning material is produced by sealing anhydrous sodium carbonate and adding an antioxidant in a Mowital Thin Film 100 film.

(30) The encapsulated detergent is added to the sump to reduce the acid. The film dissolves in hot solvent within 3 to 5 minutes and releases the solid, which disperses finely.

(31) The solvent is refluxed for an additional 6 hours, at which time the detergent complexes the acid in the sump. To evaluate the success, further samples are taken after 2, 4 and 6 hours. The distillation capacity of the apparatus is approx. ⅓ of the total solvent volume per hour.

(32) Analytical Results:

(33) 1. Acidity of the distillate (titration method): Zero value: 9853 ppm as acetic acid After 2 h (⅔ times circulation of the volume): 2761 ppm After 4 h ( 4/3 times circulation of the volume): 1510 ppm After 6 h (2-fold circulation of the volume): 578 ppm

(34) 2. GC/FID analysis: The distillate showed consistent quality at all sampling times, with the exception that the acetic acid signal showed a drop in intensity after 6 hours that was associated with the titration result.

(35) 3. Ion chromatographic analysis of the distillate after 2 hours: A concentration of acetate and formate matching the acid concentration (2761 ppm) was measured (2190 mg/L acetate, 440 mg/L formate). No other anions were identified.

(36) 4. Optical inspection of the metal strips: The metal strips showed no coating or similar plastic-like deposits.

(37) 5. Assessment of the sump: The sump showed finely dispersed white solid. No clumping or caking of the solid or plastic was observed. The solid is soluble in water.

(38) Evaluation:

(39) The encapsulated detergent showed a significant reduction in acid number after even a short test period. The solid did not clump and disposal of the solid was easy due to its water solubility.

(40) The solvent distillate is unchanged from the starting material, with the exception that the acid has been removed. The solvent can thus continue to be used for cleaning and gains significantly in value due to the acid removal, since corrosive components are removed.

(41) Experiment 5: Acid Reduction Using Encapsulated Detergent—Sample 2

(42) Acidic DOWCLENE® 1601 (solvent taken from customer's cleaning plant as the most realistic example possible) is refluorinated for 2 hours at 100 mbar. Metal strips made of aluminum, steel, copper and brass are suspended in the steam space of the apparatus. After 2 hours, a sample is taken at the sampling point in the distillate for zero determination.

(43) The encapsulated detergent is produced by sealing anhydrous sodium carbonate and adding an antioxidant in Mowital Thin Film 100 film.

(44) The encapsulated detergent is added to the sump to reduce the acid. The film dissolves in hot solvent within 3 to 5 minutes and releases the solid, which disperses finely.

(45) The solvent is refluxed for a further 24 hours, with the detergent complexing the acid in the sump. Further samples are taken after 2 and 24 hours to assess success. The distillation capacity of the apparatus is approximately ⅓ of the total solvent volume per hour.

(46) Analytical Results

(47) 1. Acidity of the distillate (titration method): Zero value: 6303 ppm as acetic acid After 2 h (⅔ times circulation of the volume): 3009 ppm After 24 hrs (8 times circulation of the volume): <10 ppm

(48) 2. GC/FID analysis: The distillate showed consistent quality at all sampling times, with the exception that the acetic acid signal showed a drop in intensity after 24 hours that was associated with the titration result.

(49) 3. Ion chromatographic analysis of the distillate after 2 hours: An amount of acetate and formate approximately matching the acid concentration (3009 ppm) was identified (1550 mg/L acetate, 940 mg/L formate). No other anions were identified.

(50) 4. Optical inspection of the metal strips: The metal strips showed no coating, or similar plastic-like precipitation.

(51) 5. Assessment of the sump: The sump showed finely dispersed white solid. No clumping or caking of the solid or plastic was observed. The solid is soluble in water.

(52) Evaluation:

(53) The encapsulated detergent also showed a clear reduction of the acid number up to complete removal after 24 hours. The solid did not clump in the test and disposal of the solid was easy due to its water solubility.

(54) The solvent distillate is unchanged from the starting material, with the exception that the acid has been removed. The solvent can thus continue to be used for cleaning and gains significantly in value due to the acid removal, since corrosive components are removed.

(55) Experiment 6: Acid Reduction Using Encapsulated Detergent—Sample 3

(56) Acidic DOWCLENE® 1601 are refluxed overnight at 100 mbar. Metal strips made of aluminum, steel, copper and brass are suspended in the steam space of the apparatus. The next day, a sample is taken at the sampling point in the distillate for zero determination.

(57) The encapsulated detergent is produced by sealing anhydrous sodium carbonate and adding an antioxidant in Mowital Thin Film 100 film.

(58) To reduce the acid, the encapsulated detergent is added to the sump. The film dissolves in hot solvent within 3 to 5 minutes and releases the solid, which disperses finely.

(59) The solvent is refluxed for a further 6 hours, with the detergent complexing the acid in the sump. Further samples are taken after 2, 4 and 6 hours to assess success. The distillation capacity of the apparatus is approximately ⅓ of the total solvent volume per hour.

(60) Analytical Results:

(61) 1. Acidity of the distillate (titration method): Zero value: 13391 ppm as acetic acid After 2 h (⅔ times circulation of the volume): 3724 ppm After 4 h ( 4/3 times circulation of the volume): 1529 ppm After 6 h (2-fold circulation of the volume): 537 ppm

(62) 2. GC/FID analysis: The distillate showed consistent quality at all sampling times with the exception that the acetic acid signal after 6 hours showed a drop in intensity associated with the titration result.

(63) 3. Ion chromatographic analysis of the distillate after 2 hours: A concentration of acetate and formate matching the acid concentration (3724 ppm) in magnitude was measured (3300 mg/L acetate, 1700 mg/L formate). No other anions were identified.

(64) 4. Optical inspection of the metal strips: The metal strips showed no coating, or similar plastic-like precipitation.

(65) 5. Assessment of the sump: The sump showed finely dispersed white solid. No clumping or caking of the solid or plastic was observed. The solid is soluble in water.

(66) Evaluation:

(67) The encapsulated detergent showed a significant reduction in acid number after even a short test period. The solid did not clump and disposal of the solid was easy due to its water solubility.

(68) The solvent distillate is unchanged from the starting material with the exception that the acid has been removed. The solvent can thus continue to be used for cleaning and gains significantly in value due to the acid removal, since corrosive components are removed.

(69) Comparative Experiment 7: Acid Reduction with the Aid of Unencapsulated Stabilizer

(70) The same amount (as in the above experiments) of acidic DOWCLENE® 1601 is refluxed overnight at 100 mbar, with the solvent being the same as in the previous experiments. Metal strips made of aluminum, steel, copper and brass are suspended in the steam space of the apparatus as above. The next day, a sample is taken at the sampling point in the distillate for zero determination.

(71) The detergent is prepared by mixing anhydrous sodium carbonate and an antioxidant. The amounts of anhydrous sodium carbonate and antioxidant are identical to those used in the experiments described above. The detergent is added to the sump in powder form.

(72) The solvent is refluxed for a further 6 hours, with the detergent complexing the acid in the sump. Further samples are taken after 2, 4 and 6 hours to assess success. The distillation capacity of the apparatus is approximately ⅓ of the total solvent volume per hour.

(73) Analytical Results

(74) 1. Acidity of the distillate (titration method): Zero value: 12327 ppm as acetic acid After 2 h (⅔ times circulation of the volume): 10239 ppm After 4 h ( 4/3 times circulation of the volume): 9916 ppm After 6 h (2-fold circulation of the volume): 9813 ppm

(75) 2. GC/FID analysis: The distillate showed consistent quality at all sampling times, with the exception that the acetic acid signal showed a small drop in intensity after 6 hours, which was associated with the titration result.

(76) 3. Ion chromatographic analysis of the distillate after 2 hours: A concentration of acetate and formate approximately matching the acid concentration (10239 ppm) was measured (6900 mg/L acetate, 3400 mg/L formate). Further anions were not identified.

(77) 4. Optical inspection of the metal strips: The metal strips showed no coating, or similar plastic-like precipitation.

(78) 5. Assessment of the sump: The sump showed finely dispersed white solid. No clumping or caking of the solid or plastic was observed. The solid is soluble in water.

(79) Overall Evaluation:

(80) The encapsulated detergent showed a significantly higher reduction of the acid number than the non-encapsulated version. It can therefore be assumed that the encapsulation represents a technical advantage in terms of controlled release of the cleaning agent. Moreover, the encapsulated cleaning agent according to the present invention is easier to be used and does not require any additional safety measurements (due to the encapsulation.

(81) The present invention is once again summarized by the following items: 1. A process for purifying an alcohol-containing solvent, which comprises introducing into the alcohol-containing solvent a cleaning agent which is present in an encapsulation which substantially completely surrounds the cleaning agent. 2. The process according to item 1, characterized in that the capsule material comprises cellulose derivatives and/or polyvinyl butyral. 3. The process according to item 1 or 2, characterized in that the cleaning agent in the encapsulation comprises a base or consists of a base. 4. The process according to any one of items 1 to 3, characterized in that the cleaning agent is selected from the group consisting of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate, calcium hydroxide, magnesium carbonate and mixtures of the above cleaning agents. 5. The process according to any one of items 1 to 4, characterized in that the alcoholic solvent is refluxed after being brought into contact with the substantially encapsulated cleaning agent. 6. The process according to any one of items 1 to 5, characterized in that at least one antioxidant is added to the solvent during the process of purifying the alcohol-containing solvent. 7. The process according to any one of items 1 to 6, characterized in that the alcohol-containing solvent contains modified alcohols, in particular glycol ether mixtures. 8. A composition comprising a cleaning agent in a substantially encapsulation of a polymeric material comprising polyvinyl butyral. 9. The composition according to item 8, characterized in that the cleaning agent in the encapsulation comprises or consists of a base. 10. The composition according to item 8 or 9, characterized in that the cleaning agent in the encapsulation is hygroscopic. 11. The composition according to any one of items 8 to 10, characterized in that the cleaning agent is selected from the group consisting of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate, calcium hydroxide, magnesium carbonate and mixtures of the above cleaning agents. 12. Use of a composition according to any one of items 8 to 11 for processing alcohol-containing solvents, in particular for cleaning alcohol-containing solvents. 13. The use according to item 12 for cleaning modified alcohols, in particular glycol ether mixtures. 14. A process for preparing a composition according to any one of items 8 to 11, characterized by the following process steps: i. providing a film comprising polyvinyl butyral; ii. providing a cleaning agent; iii. sealing the cleaning agent into the film comprising polyvinyl butyral such that the cleaning agent is in a substantially completely surrounding encapsulation. 15. The process according to item 14, characterized in that the encapsulation is carried out by welding the film at a temperature of at least 120° C.