METHOD FOR THE PURIFICATION OF ALCOHOL-CONTAINING SOLVENTS

Description

[0001] The present invention relates to a method for purifying an alcohol-containing solvent. The method according to the invention is particularly suitable for the processing of alcohol-containing solvents, which are used, for example, for cleaning, especially degreasing, metal parts. Further aspects of the present invention include compositions suitable for the aforementioned purpose, as well as the use of specific compositions for purifying alcohol-containing solvents.

[0002] GB 675 995 A discloses that aqueous solutions of alcohols produced from olefins containing aldehydic impurities can be purified by adding alkali metal hydroxide (e.g. NaOH or KOH), refluxing for at least half an hour, and then distilling off the alcohol in a largely aldehyde-free form.

[0003] When degreasing metal parts using alcohol-based solvents, the solvents can become acidic. This acidification can lead to corrosion damage in the equipment used and damage to the metal parts being degreased during subsequent use.

[0004] To avoid these disadvantages in the prior art, so-called stabilizers are often added to the alcohol-containing solvents, which reduce acid formation or bind the acid that has been formed.

[0005] Various stabilizers are known from the prior art, for example compositions based on amines and hydrocarbons (see EP 1 042 257 A and EP 1 907 505 A, where EP 1 042 257 A describes the use of amines for stabilization only for halogenated hydrocarbons, such as perchloroethylene, and EP 1 907 505 A describes stabilizers for mixtures of modified alcohols and hydrocarbons).

[0006] Furthermore, EP 3 088 429 A discloses a package containing a cleaning agent encapsulated in a water-soluble film, wherein the film consists of polyvinyl alcohol and may contain other materials, e.g. polyvinyl butyral.

[0007] WO 2019 / 027635 A discloses a cleaning agent composition containing diamines (TAED) in a polyvinyl butyral matrix.

[0008] WO 03 / 062363 A discloses a combination of cellulases and special cellulose in detergents.

[0009] DE 28 31 210 A discloses a process for purifying ethylene diglycol using metal hydrides and distillation. Nevertheless, after certain production cycles, it is necessary to either recycle or discard the alcohol-containing solvent. Users sometimes discard the solvent bath once a certain threshold concentration of impurities (acids, esters, etc.) is reached, leading to plant downtime and costs for disposal and refilling. New, innovative processes are needed for recycling the alcohol-containing solvent; these processes must be efficient and easy to implement.

[0010] The object of the present invention is therefore to provide an efficient and easy-to-implement method for purifying an alcohol-containing solvent, which is particularly useful in the degreasing of metal parts.

[0011] This problem is solved by a process for purifying an alcohol-containing solvent, characterized in that a cleaning agent is introduced into the alcohol-containing solvent, the cleaning agent being contained in an encapsulation that substantially completely surrounds the cleaning agent. The encapsulation consists of a material that dissolves in the alcohol-containing solvent without forming interfering impurities, and the alcohol-containing solvent comprises a modified alcohol or mixtures of modified alcohols. The encapsulated cleaning agent serves to purify the alcohol-containing solvent and, in particular, to remove the acidification of the alcohol-containing solvent.

[0012] Within the scope of the present invention, it has been found that the effectiveness of the cleaning agent in purifying the alcoholic solvent can be efficiently improved if the cleaning agent is not introduced directly into the alcoholic solvent, but is contained in an encapsulation, is introduced into the alcoholic solvent to be purified in this encapsulation, and is only released there by dissolving the encapsulation.

[0013] Without being bound to any theory, it is assumed that the efficiency of the cleaning agent provided according to the invention is improved compared to an unencapsulated material, since there is a slow release of the cleaning agent in the alcohol-containing solvent.

[0014] In the context of the present invention, it is provided that the cleaning agent is contained in an encapsulation material which is soluble in the alcoholic solvent, so that the substantially encapsulated cleaning agent is released in the alcoholic solvent by dissolving the encapsulation.

[0015] The rate of release of the cleaning agent and thus the rate of dissolution of the encapsulation does not play a significant role for the method according to the invention, but under usual application temperatures of approximately 100 °C it is 1 to 120 minutes, more preferably 1 to 60 minutes, even more preferably 1 to 30 minutes, even more preferably 1 to 10 minutes, even more preferably 3 to 5 minutes.

[0016] Within the scope of the present invention, the correct selection of a suitable encapsulation material is particularly important. The encapsulation material provided according to the invention must first dissolve in the alcohol-containing solvent, optionally at an elevated temperature. A further requirement placed on the encapsulation material within the scope of the present invention is that it dissolves in the alcohol-containing solvent without forming any interfering impurities. Furthermore, it is advantageous for the present invention if the encapsulation material can be produced easily and enables simple and efficient, and as complete as possible, encapsulation of the cleaning agent according to the invention.

[0017] Stabilizers, such as those known from the prior art, are in liquid form and consist of mixtures of liquids or of solids dissolved in liquids.

[0018] Powdered substances, on the other hand, are not yet used on a large scale. These can cause a dust explosion if the substance is stirred up in the air and ignition sources are present. With dusts, preventing explosive mixtures by limiting the dust concentration is difficult to achieve.

[0019] The encapsulation of the powdered cleaning agent therefore creates a novel way of purifying alcohol-containing solvents, as the encapsulation prevents dangerous turbulence of the substance in the air.

[0020] The encapsulation material should ideally be non-toxic, so that users of the inventive method can add the encapsulation material to the solvent without explosion protection measures or minimal safety precautions – i.e., without wearing personal protective equipment to prevent dermal and inhalation exposure. Furthermore, it is advantageous for selecting a suitable encapsulation material if the material is transparent, allowing for easy visual inspection of the cleaning agent before its use in the alcohol-containing solvent.

[0021] Finally, the encapsulation material should be able to contain different amounts of cleaning agent, so that the user of the inventive method can easily carry out the appropriate dosage.

[0022] Within the scope of the present invention, numerous different encapsulation materials were investigated for this purpose and suitable materials for forming the encapsulation are, for example, cellulose derivatives, in particular cellulose esters, such as cellulose nitrate, cellulose acetate or cellulose acetate butyrate, as well as polyvinyl butyral.

[0023] With regard to the cellulose derivatives, the person skilled in the art can, based on the solubility behavior, the type of substituents, the average degree of substitution, the substitution distribution in the chain and its distribution to the primary and secondary alcohol groups, find suitable cellulose derivatives for different alcohol-containing solvents which are soluble in alcohol-containing solvents under the conditions to be applied according to the invention.

[0024] Another suitable material for forming the encapsulation is polyvinyl butyral (PVB). Polyvinyl butyrals with a high degree of acetalization are particularly soluble in alcohol. For the formation of the packaging material, it is especially preferred if the polyvinyl butyral can be processed into films with a low dynamic viscosity. Suitable commercially available starting materials for the production of the encapsulation are, for example, distributed by Kuraray Europe GmbH. Suitable commercial products include, for example, Mowital® < B30H or Mowital® < B20H.

[0025] Within the scope of the present invention, polyvinyl butyral is particularly preferred as the encapsulation material. The reasons for this are explained below: Firstly, polyvinyl butyral is thermoplastic, light-stable, and heat-sealable at temperatures above 120 °C. Therefore, within the scope of the present invention, it is easy to produce film materials for the manufacture of encapsulated cleaning agents from these encapsulation materials, for example, in the form of pouches.

[0026] Furthermore, the desired encapsulation based on polyvinyl butyral has the advantage that the resulting encapsulation is clear and transparent, so that it is possible to inspect the encapsulated cleaning agent before its use in treating the alcohol-containing solvent.

[0027] Another significant advantage of using polyvinyl butyral as an encapsulation material is that the polyvinyl butyral dissolves easily under the applied process conditions without introducing any interfering by-products into the alcohol-containing solvent to be purified.

[0028] In a preferred embodiment of the present invention, the encapsulation material comprises not only polyvinyl butyral and other polymers, but consists essentially, and in particular exclusively, of polyvinyl butyral. Therefore, in a preferred embodiment of the present invention, an encapsulation material consisting of polyvinyl butyral is provided.

[0029] In the following, particularly preferred embodiments of the polyvinyl butyral preferred according to the invention as an encapsulation material are described.

[0030] The polyvinyl butyral preferably used in the context of the present invention generally has a polyvinyl alcohol content of 11 to 27 wt.%, based on the total mass of polyvinyl butyral.

[0031] Furthermore, and independently of this, it is preferred if the polyvinyl butyral contains polyvinyl acetate. It is even more preferred if the polyvinyl acetate content in the polyvinyl butyral is up to 8 wt.%, based on the total mass of polyvinyl butyral.

[0032] Regardless of the foregoing properties of the polyvinyl butyral preferably used, this encapsulation material preferably has a dynamic viscosity of 9 to 330 mPa • s in a 10% solution in ethanol.

[0033] Regardless of the aforementioned properties of the polyvinyl butyral preferably used, this encapsulation material preferably has a water absorption capacity of the polyvinyl butyral after 24 hours at 20 °C of 200 to 340 g / l.

[0034] Regardless of the foregoing properties of the polyvinyl butyral preferably used, this encapsulation material preferably has a glass transition temperature, determined according to DSC, ISO11357-1, of 60 to 92 °C.

[0035] Regardless of the foregoing properties of the polyvinyl butyral preferably used, this encapsulation material preferably has a solids content of more than 97.5 wt.%.

[0036] The properties of polyvinyl butyral described above make polyvinyl butyral particularly suitable for use as a capsule material in the process according to the invention.

[0037] Particularly preferred embodiments of the present invention use polyvinyl butyral which has more than one of the properties described above. In particular, the polyvinyl butyral to be used according to the invention has at least 2, more preferably at least 3, and more preferably at least 4, further preferably at least 5 of the previously described properties.

[0038] The cleaning agent present in the encapsulation according to the present invention preferably comprises a base. Using the base as a cleaning agent, acidic impurities that arise during the use of the alcohol-containing solvent are neutralized and thus rendered harmless for further use of the alcohol-containing solvent.

[0039] In a preferred embodiment, the cleaning agent consists essentially, and in particular exclusively, of a base.

[0040] The use of multiple bases as cleaning agents is also included in the present invention.

[0041] Furthermore, the cleaning agent may contain other components that are also used to clean the alcohol-based solvent.

[0042] If a base is used as a cleaning agent within the scope of the present invention, the alcohol-containing solvent preferably contains an acid as an impurity. Furthermore, non-specific esterification products can also form from the acid present as an impurity, which are removed from the alcohol-containing solvent by the plastic cleaning agent.

[0043] In a further embodiment of the present invention, the cleaning agent used in the encapsulation is hygroscopic. By using a hygroscopic cleaning agent, aqueous impurities, as well as acidic impurities, can be efficiently separated using the method according to the invention. Aqueous impurities can form, for example, through non-specific esterification of the acidic impurities with the alcohol in the alcoholic solvent.

[0044] However, the use of a hygroscopic cleaning agent and the presence of water as an impurity in the alcoholic solvent are not essential for the present invention.

[0045] In a preferred embodiment of the present invention, the cleaning agent is preferably a base from the group consisting of alkali or alkaline earth hydroxides and mixtures thereof. In a preferred embodiment of the present invention, 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 aforementioned cleaning agents.

[0046] In a further preferred embodiment of the present invention, the cleaning agent is selected from the group consisting of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide and mixtures of the aforementioned cleaning agents.

[0047] According to the present invention, after bringing the alcoholic solvent to be purified into contact with the encapsulated cleaning agent, the alcoholic solvent to be purified is distilled (refluxed).

[0048] This distillation or reflux of the alcoholic solvent is preferably carried out for a period of at least 1 hour, preferably at least 2 hours, more preferably at least 3 hours, more preferably at least 6 hours, more preferably at least 12 hours, and more preferably at least 24 hours. Due to the temperatures used in combination with the cleaning agent, the impurities are efficiently removed from the alcoholic solvent.

[0049] In practice, the inventive method can be carried out by adding the encapsulated cleaning agent to the sump of a distillation unit (refluxing device) supplied with the solvent to be purified and then using it at the temperatures provided according to the invention.

[0050] Alternatively, encapsulated cleaning agents can be added to any other point within the unit or device. For example, a water separator could be used.

[0051] However, within the scope of the present invention, it has proven to be technically most advantageous to add the encapsulated cleaning agent to the sump, since a solid must be separated.

[0052] In accordance with the present invention, at least one or more antioxidants can be used in addition to the encapsulated cleaning agent. This antioxidant is added to the alcohol-containing solvent before or during contact with the encapsulated cleaning agent.

[0053] Suitable antioxidants that can be additionally used during the purification of the alcohol-containing solvent according to the invention are, for example, phenolic antioxidants, amine-containing antioxidants, antioxidants based on organic sulfur compounds, antioxidants based on organic phosphorus compounds and mixtures of the aforementioned antioxidants.

[0054] Suitable antioxidants are known to those skilled in the art from Ullmann's Encyclopedia of Industrial Chemistry, Chapter: Antioxidants (2015, Wiley-VCH Verlag GmbH & Co. KG, Weinheim). In particular, suitable antioxidants can be found in Chapters 4.2, 4.3, 4.4 and 4.5.

[0055] In a first embodiment, the antioxidant is a phenolic antioxidant. In a second embodiment, the antioxidant is an amine-containing antioxidant.

[0056] In a third embodiment, the antioxidant is an antioxidant based on organic sulfur compounds.

[0057] In a fourth embodiment, the antioxidant is an antioxidant based on organic phosphorus compounds.

[0058] Particularly suitable antioxidants are selected from the group consisting of 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butylphenol and mixtures thereof.

[0059] Other suitable antioxidants are selected from the group consisting of p,p'-dioctyl-diphenylamine, oligomeric 1,2-dihydro-2,2,4-trimethylquinoline, 1-naphthylphenylamine, derivatives of diphenylamine and mixtures thereof.

[0060] These antioxidants are preferably used together with the cleaning agent in the encapsulation which essentially completely surrounds the cleaning agent, or added separately to the alcoholic solvent.

[0061] In a further embodiment of the present invention, the cleaning agent is encapsulated and optionally used in combination with at least one antioxidant and additionally with silica gel as a surfactant.

[0062] The method according to the invention is particularly applicable to alcohol-containing solvents resulting from (metal) degreasing systems. (Metal) degreasing systems are closed systems comprising a cleaning chamber, a varying number of solvent tanks, and a distillation unit. Contaminated parts are cleaned using a solvent, preferably with modified alcohols as defined below.

[0063] The contaminated, alcohol-based solvent, enriched with the residues removed from the cleaned and degreased components, then flows back into the solvent tanks. These tanks continuously supply the distillation unit integrated into the degreasing system with the contaminated solvent. During the distillation process, the solvent, which boils at a lower temperature, is separated from the previously removed residues. This distillation process can lead to acidification due to the solvent's self-decomposition. For example, when modified alcohol is used as a solvent, low-boiling components and, in particular, acids can be formed. This acidification can, in turn, cause corrosion damage in the cleaning system and surface corrosion on the cleaned parts.

[0064] To counteract acid formation in the distillation apparatus, the encapsulated cleaning agent provided according to the invention is added to the distillation process during purification. The cleaning agent binds the acids formed in the distillation sump and remains there. Thus, the cleaning agent remains in the distillation apparatus throughout the entire purification and preparation process of the solvent.

[0065] The distillate, i.e., the distilled and purified alcoholic solvent, is subsequently returned to the solvent tanks via a water separator. The distillation sump is emptied and disposed of at regular intervals. The used cleaning agent, along with any non-interfering residues from the encapsulation material, is removed together with the cleaned residues from the components.

[0066] Using a rapid test procedure for solvent verification, the user can determine the quality, i.e. the acid content, of the solvent used directly at the system.

[0067] Knowing the determined acidity of the alcoholic solvent, i.e., the proportion of free acids in the alcoholic solvent, and the system volume of the degreasing system, the required amount of cleaning agent according to the invention can be determined by means of stoichiometric calculation in order to neutralize the acid content.

[0068] In the context of the present invention, the alcohol-containing solvent generally comprises individual modified alcohols or mixtures of modified alcohols.

[0069] Modified alcohols include, for example, propanols to which an ether group has been added (alkoxy propanols). By varying the ether group, the solubility of the modified alcohols can be tailored to the type of impurity being removed (degreasing).

[0070] The modified alcohols include, for example, glycol ether mixtures and / or glycol ether hydrocarbon mixtures.

[0071] Particularly preferred within the scope of the present invention are 1-butoxy-2-propanol and butoxy-1-propanol. Mixtures of these two aforementioned modified alcohols are also particularly preferred within the scope of the present invention.

[0072] In another aspect, the present invention relates to a composition of a cleaning agent and an encapsulation, which is preferably used in the method described above according to the invention.

[0073] Therefore, the present invention also relates to a composition comprising a cleaning agent in an encapsulation made of a polymer material containing polyvinyl butyral, wherein the cleaning agent in the encapsulation comprises or consists of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide and mixtures of the aforementioned cleaning agents.

[0074] According to the foregoing explanations of the inventive method, the cleaning agent in the encapsulation preferably comprises a base or consists essentially, in particular exclusively, of a base.

[0075] The encapsulation essentially completely surrounds the cleaning agent.

[0076] As already stated above, it is preferred if the cleaning agent in the encapsulation is hygroscopic.

[0077] In a preferred embodiment of the present invention, the composition is 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 aforementioned cleaning agents.

[0078] In a further preferred embodiment of the present invention, the cleaning agent is selected from the group consisting of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide and mixtures of the aforementioned cleaning agents.

[0079] As already stated above, the capsule material preferably comprises polyvinyl butyral.

[0080] In a further preferred embodiment of the present invention, the capsule material consists essentially, and in particular exclusively, of polyvinyl butyral.

[0081] For the stated purpose of degreasing metal parts according to the above method, it is further preferred if the polyvinyl butyral has a polyvinyl alcohol content of 11 to 27 wt.%, based on the total mass of polyvinyl butyral.

[0082] In a further embodiment, the composition according to the invention is characterized in that the polyvinyl butyral contains polyvinyl acetate.

[0083] If the polyvinyl butyral in the composition according to the invention contains polyvinyl acetate, the polyvinyl acetate content in the polyvinyl butyral is preferably up to 8 wt.%, based on the total mass of polyvinyl butyral.

[0084] The dynamic viscosity of the polyvinyl butyral to be used according to the invention is preferably 9 to 330 mPa • s in a 10% solution in ethanol.

[0085] The water absorption capacity of the polyvinyl butyral to be used according to the invention is preferably 200 to 340 g / l after 24 hours at 20 °C.

[0086] The glass transition temperature of the polyvinyl butyral to be used according to the invention, determined according to DSC, ISO11357-1, is preferably 60 to 92 °C.

[0087] The solids content of the polyvinyl butyral to be used according to the invention is preferably more than 97.5 wt.%.

[0088] In the composition according to the invention, in addition to the actual cleaning agent, the base described in more detail above, at least one or more antioxidants can be used.

[0089] Suitable antioxidants are known to experts from Ullmann's Encyclopedia of Industrial Chemistry, Chapter: Antioxidants (2015, Wiley-VCH Verlag GmbH & Co. KG, Weinheim). Particularly suitable antioxidants can be found in Chapters 4.2, 4.3, 4.4 and 4.5.

[0090] In a first embodiment, the antioxidant is a phenolic antioxidant.

[0091] In a second embodiment, the antioxidant is an amine-containing antioxidant.

[0092] In a third embodiment, the antioxidant is an antioxidant based on organic sulfur compounds.

[0093] In a fourth embodiment, the antioxidant is an antioxidant based on organic phosphorus compounds.

[0094] Particularly suitable antioxidants are selected from the group consisting of 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butylphenol and mixtures thereof.

[0095] Other suitable antioxidants are selected from the group consisting of p,p'-dio-ctyldiphenylamine, oligomeric 1,2-dihydro-2,2,4-trimethylquinoline, 1-naphthylphenylamine, derivatives of diphenylamine and mixtures thereof.

[0096] Furthermore, the present invention relates to the use of the composition described above for the purification of a solvent that is used in particular for degreasing metal parts. Reference is made to the above statements.

[0097] Furthermore, the present invention relates to a method for producing a composition according to the invention, which has been described in detail above. The method according to the invention is characterized by the following process steps: i. Provision of a film comprising polyvinyl butyral; ii. Provision of a cleaning agent; iii. Sealing the substance in the film comprising polyvinyl butyral, such that the substance is in a substantially complete encapsulation.

[0098] In this process, encapsulation is carried out by welding the film at a temperature of at least 120 °C.

[0099] For further details, please refer to the above statements.

[0100] The following examples illustrate the present invention in detail: Examples of implementation Experiment 1: Simple mixing experiment and evaporation behavior

[0101] A sheet of Mowital Thin Film 100 is mixed with solvent (DOWCLENE ®< 1601) at room temperature; then the solvent is evaporated.

[0102] Analytical results: 1. Solubility: Without agitation, complete dissolution of the plastic was observed after approximately 30 minutes. 2. Appearance after evaporation: The solvent was evaporated overnight at 80 °C. A uniform, colorless Mowital film formed in the container.

[0103] Assessment: The solubility of the film is good, and the recovery shows that the plastic does not exhibit any obvious degradation reactions due to the combination of temperature and solvent. Experiment 2: Continuous test in laboratory distillation apparatus with fresh DOWCLENE® < 1601

[0104] Mowital Thin Film 100 in solvent (DOWCLENE® < 1601) is mixed in the distillation sump of the laboratory apparatus. Metal strips made of aluminum, steel, copper, and brass are suspended in the vapor chamber of the apparatus. The solvent is refluxed continuously under reduced pressure (100 mbar) for 6 days.

[0105] Analytical results: 1. GC / FID analysis of the distillate: Solvent was recovered in unchanged purity. Volatile organic degradation products from the plastic were not identified. 2. Acidity of the distillate (titration method): The solvent remained unchanged and within specifications. 3. Visual inspection of the metal strips: The metal strips showed no coating or similar plastic-like deposits. 4. Assessment of the residue: The residue appeared viscous, which was caused by the high concentration of PVB. No clumping or caking of the plastic was observed. The color remained unchanged. 5. FT-IR analysis of the residue: After the experiment, the solvent in the distillation residue evaporated. An FT-IR spectrum of the plastic remaining in the residue was recorded and compared with an unused plastic film.No difference was observed between the dissolved, heated plastic after the test and the new film. Evaluation:

[0106] Even at consistently high temperatures in the boiling solvent, no potentially problematic degradation products were observed. The plastic was dissolved by the solvent but remained chemically unchanged. The solvent distilled from the residue is identical to the virgin material used and can be used without restriction for cleaning. Experiment 3: Continuous test in laboratory distillation apparatus with acidic DOWCLENE® < 1601

[0107] The above-mentioned experiment 2 was repeated with Mowital granules B30H and with acidic solvent (acidity value approx. 6000 ppm). Analytical results:

[0108] 1. GC / FID analysis of the distillate: Only solvent of unchanged quality was recovered. Volatile organic degradation products from the plastic were not identified. 2. Acidity of the distillate (titration method): The acid value remained constant. 3. Visual inspection of the metal strips: The metal strips showed no coating or similar plastic-like deposits. 4. Assessment of the residue: The residue showed discoloration. This is frequently observed when distilling acidic samples. No clumping or caking of the plastic was observed. Evaluation:

[0109] The findings obtained for fresh solvent also apply to acidic solvents: no degradation products of the plastic were observed; the solvent distillate is of the same quality as the solvent used and can be used for cleaning. Experiment 4: Acid reduction using encapsulated cleaning agent - Sample 1

[0110] Acidic DOWCLENE 1601 (solvent taken from a customer's cleaning system as a realistic example) is refluxed overnight at 100 mbar. Metal strips made of aluminum, steel, copper, and brass are suspended in the vapor chamber of the apparatus. The following day, a sample is taken from the distillate at the sampling point to determine the baseline value.

[0111] The encapsulated cleaning agent is produced by sealing anhydrous sodium carbonate and adding an antioxidant into Mowital Thin Film 100 film.

[0112] To reduce the acidity, the encapsulated cleaning agent is added to the solution. The film dissolves in hot solvent within 3 to 5 minutes, releasing the solid, which disperses in a fine dispersion.

[0113] The solvent is refluxed for a further 6 hours, during which time the cleaning agent complexes the acid in the sump. Further samples are taken after 2, 4, and 6 hours to assess the success of the distillation. The distillation rate of the apparatus is approximately 1 / 3 of the total solvent volume per hour. Analytical results:

[0114] 1. Acidity of the distillate (titration method): Baseline: 9853 ppm as acetic acid. After 2 hours (2 / 3 volume turnover): 2761 ppm. After 4 hours (4 / 3 volume turnover): 1510 ppm. After 6 hours (2 volume turnover): 578 ppm. 2. GC / FID analysis: The distillate showed consistent quality at all sampling times, except that the acetic acid signal showed a decrease in intensity after 6 hours, corresponding to the titration result. 3. Ionic chromatographic analysis of the distillate after 2 hours: Acetate and formate concentrations corresponding to the acid concentration (2761 ppm) were measured (2190 mg / L acetate, 440 mg / L formate). No other anions were identified. 4. Visual inspection of the metal strips: The metal strips showed no coating or similar plastic-like deposits. 5. Assessment of the sludge: The sludge contained finely dispersed, white solid material.No clumping or adhesion of the solid or plastic was observed. The solid is water-soluble. Evaluation:

[0115] The encapsulated cleaning agent showed a significant reduction in acid value after only a short test period. The solid did not clump, and its water solubility made disposal easy.

[0116] The solvent distillate remains unchanged from the starting material, except that the acid has been removed. The solvent can therefore be used further for cleaning and gains significantly in value through acid removal, as corrosive components are eliminated. Experiment 5: Acid reduction using encapsulated cleaning agent - Sample 2

[0117] acidic DOWCLENE ®<Solvent 1601 (taken from a customer's cleaning system as a realistic example) is refluxed for 2 hours at 100 mbar. Metal strips made of aluminum, steel, copper, and brass are suspended in the vapor chamber of the apparatus. After 2 hours, a sample is taken from the distillate at the sampling point to determine the baseline value.

[0118] The encapsulated cleaning agent is produced by sealing anhydrous sodium carbonate and adding an antioxidant into Mowital Thin Film 100 film.

[0119] To reduce the acidity, the encapsulated cleaning agent is added to the solution. The film dissolves in hot solvent within 3 to 5 minutes, releasing the solid, which disperses in a fine dispersion.

[0120] The solvent is refluxed for a further 24 hours, during which time the cleaning agent complexes the acid in the sump. Further samples are taken after 2 and 24 hours to assess the success of the distillation. The distillation rate of the apparatus is approximately 1 / 3 of the total solvent volume per hour. Analytical results

[0121] 1. Acidity of the distillate (titration method): Baseline: 6303 ppm as acetic acid. After 2 hours (2 / 3 volume turnover): 3009 ppm. After 24 hours (8 volume turnover): <10 ppm. 2. GC / FID analysis: The distillate showed consistent quality at all sampling times, except that the acetic acid signal showed a decrease in intensity after 24 hours, corresponding to the titration result. 3. Ionic chromatographic analysis of the distillate after 2 hours: A quantity of acetate and formate approximately corresponding to the acid concentration (3009 ppm) was identified (1550 mg / L acetate, 940 mg / L formate). No other anions were identified. 4. Visual inspection of the metal strips: The metal strips showed no coating or similar plastic-like deposits. 5. Assessment of the swamp: The swamp showed finely dispersed, white solids.No clumping or adhesion of the solid or plastic was observed. The solid is water-soluble. Evaluation:

[0122] The encapsulated cleaning agent also showed a significant reduction in acid number, even achieving complete removal after 24 hours. The solid did not clump in the test, and its water solubility made disposal easy.

[0123] The solvent distillate remains unchanged from the starting material, except that the acid has been removed. The solvent can therefore be used further for cleaning and gains significantly in value through acid removal, as corrosive components are eliminated. Experiment 6: Acid reduction using encapsulated cleaning agent - Sample 3

[0124] acidic DOWCLENE ®<1601 units are refluxed overnight at 100 mbar. Metal strips made of aluminum, steel, copper, and brass are suspended in the vapor chamber of the apparatus. The next day, a sample is taken from the distillate at the sampling point to determine the baseline value.

[0125] The encapsulated cleaning agent is produced by sealing anhydrous sodium carbonate and adding an antioxidant into Mowital Thin Film 100 film.

[0126] To reduce the acidity, the encapsulated cleaning agent is added to the solution. The film dissolves in hot solvent within 3 to 5 minutes, releasing the solid, which disperses in a fine dispersion.

[0127] The solvent is refluxed for a further 6 hours, during which time the cleaning agent complexes the acid in the sump. Further samples are taken after 2, 4, and 6 hours to assess the success of the distillation. The distillation rate of the apparatus is approximately 1 / 3 of the total solvent volume per hour. Analytical results:

[0128] 1. Acidity of the distillate (titration method): Baseline: 13391 ppm as acetic acid. After 2 hours (2 / 3 volume turnover): 3724 ppm. After 4 hours (4 / 3 volume turnover): 1529 ppm. After 6 hours (2 volume turnover): 537 ppm. 2. GC / FID analysis: The distillate showed consistent quality at all sampling times, except that the acetic acid signal showed a decrease in intensity after 6 hours, corresponding to the titration result. 3. Ionic chromatographic analysis of the distillate after 2 hours: Acetate and formate concentrations were measured that were on the order of magnitude of the acid concentration (3724 ppm) (3300 mg / L acetate, 1700 mg / L formate). No other anions were identified. 4. Visual inspection of the metal strips: The metal strips showed no coating or similar plastic-like deposits. 5. Assessment of the sludge: The sludge contained finely dispersed, white solid material.No clumping or adhesion of the solid or plastic was observed. The solid is water-soluble. Evaluation:

[0129] The encapsulated cleaning agent showed a significant reduction in acid value after only a short test period. The solid did not clump, and its water solubility made disposal easy.

[0130] The solvent distillate remains unchanged from the starting material, except that the acid has been removed. The solvent can therefore be used further for cleaning and gains significantly in value through acid removal, as corrosive components are eliminated. Comparative experiment 7: Acid reduction using unencapsulated stabilizer

[0131] The same amount (as in the experiments above) of acidic DOWCLENE ®< Samples 1601 are refluxed overnight at 100 mbar, using the same solvent as in the previous samples.

[0132] Experiments. Metal strips made of aluminum, steel, copper, and brass are suspended in the steam chamber of the apparatus. The next day, a sample is taken from the distillate at the sampling point to determine the baseline value.

[0133] The cleaning agent is produced 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 cleaning agent is added to the sump in powder form.

[0134] The solvent is refluxed for a further 6 hours, during which time the cleaning agent complexes the acid in the sump. Further samples are taken after 2, 4, and 6 hours to assess the success of the distillation. The distillation rate of the apparatus is approximately 1 / 3 of the total solvent volume per hour. Analytical results

[0135] 1. Acidity of the distillate (titration method): Baseline: 12327 ppm as acetic acid. After 2 hours (2 / 3 volume turnover): 10239 ppm. After 4 hours (4 / 3 volume turnover): 9916 ppm. After 6 hours (2 volume turnover): 9813 ppm. 2. GC / FID analysis: The distillate showed consistent quality at all sampling times, except that the acetic acid signal showed a slight decrease in intensity after 6 hours, corresponding to the titration result. 3. Ionic chromatographic analysis of the distillate after 2 hours: Acetate and formate concentrations approximately corresponding to the acid concentration (10239 ppm) were measured (6900 mg / L acetate, 3400 mg / L formate). No other anions were identified. 4. Visual inspection of the metal strips: The metal strips showed no coating or similar plastic-like deposits. 5. Assessment of the sludge: The sludge contained finely dispersed, white solid material.No clumping or adhesion of the solid or plastic was observed. The solid is water-soluble. Overall rating:

[0136] The encapsulated cleaning agent showed a significantly higher reduction in acid number than the unencapsulated version. It can therefore be assumed that encapsulation offers a technical advantage in terms of controlled release of the cleaning agent.

Claims

1. Method for purifying an alcohol-containing solvent, characterised in that a cleaning agent, which is present in an encapsulation that essentially completely surrounds the substance, is introduced into the alcohol-containing solvent, wherein the encapsulation consists of a material that dissolves in the alcohol-containing solvent without forming disruptive impurities and wherein the alcohol-containing solvent comprises a modified alcohol or mixtures of modified alcohols.

2. Method according to claim 1, characterised in that the encapsulation material comprises cellulose derivatives and / or polyvinyl butyral.

3. Method according to claim 1 or 2, characterised in that the cleaning agent in the encapsulation comprises a base or consists of a base.

4. Method according to one of claims 1 to 3, characterised 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. Method according to one of claims 1 to 4, characterised in that the alcoholic solvent is refluxed after being brought into contact with the substantially encapsulated cleaning agent.

6. Method according to one of claims 1 to 5, characterised in that during the process of purifying the alcohol-containing solvent, at least one antioxidant is added to the solvent.

7. Method according to one of claims 1 to 6, characterised in that the alcohol-containing solvent contains modified alcohols, in particular glycol ether mixtures.

8. Composition containing a cleaning agent in a substantially encapsulation made of a polymer material containing polyvinyl butyral, characterised in that the cleaning agent in the encapsulation comprises or consists of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide and mixtures of the above cleaning agents.

9. Composition according to claim 8, characterised in that the cleaning agent in the encapsulation is hygroscopic.

10. Composition according to claim 8 or 9, characterised 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.

11. Use of a composition according to any one of claims 8 to 10 for treating alcohol-containing solvents, wherein the alcohol-containing solvent comprises a modified alcohol or mixtures of modified alcohols.

12. Use according to claim 11 for the processing of modified alcohols, in particular glycol ether mixtures.

13. Method for producing a composition according to one of claims 8 to 10, characterised by the following process steps: i. providing a film comprising polyvinyl butyral; ii. providing a cleaning agent; iii. sealing the agent into the film comprising polyvinyl butyral so that the agent is present in a substantially completely surrounding encapsulation.

14. Method according to claim 13, characterised in that the encapsulation is carried out by sealing the film at a temperature of at least 120 °C.