Method and device for cleaning industrially produced components

Abstract

The invention relates to a method and to a device for cleaning industrially produced metal and / or plastic components using a cleaning agent, characterised in that a mixture of at least two organic solvents and water is used as the cleaning agent, said mixture comprising at least one non-water soluble organic solvent and at least one water-soluble organic solvent. The invention also relates to a device (1) which is suitable for carrying out the method, comprising a working chamber (2) for the components to be cleaned and at least one tank (3, 4) for feeding the working chamber (2) with a solvent mixture by means of at least one supply means (5, 11) for cleaning the components.

Description

[0001] The invention relates to a method for cleaning industrially manufactured parts made of metal and / or plastic.

[0002] Furthermore, a device for cleaning industrially manufactured parts made of metal and / or plastic is described, in particular for carrying out the method according to the invention.

[0003] A previously known method of the type mentioned is described in DE 43 29 178 B4. In this method, the parts or objects to be cleaned are placed in an evacuated cleaning chamber and flooded with a liquid organic solvent at a pressure of 200 mbar or below. The liquid solvent is then withdrawn from the cleaning chamber, and subsequently, the solvent vapor is fed into the cleaning chamber at a pressure of 200 mbar or below and at a temperature at or above the solvent's flash point. This allows the cleaning of the objects to be completed by condensation of the solvent vapor onto the objects.

[0004] US Patent 5,716,458 describes a cleaning process using an azeotropic mixture of at least two different solvents.

[0005] DE 43 14 365 A1 describes a cleaning composition comprising a hydrocarbon, a glycol ether compound, a surfactant, and water. PCT / EP00 / 01565 discloses cleaning fluids consisting of water and a solvent, wherein the solvent forms a miscibility gap with the water.

[0006] Hybrid cleaning systems or processes are also known, in which the parts to be cleaned are treated with an organic solvent and water in a chamber. For example, water can be introduced into the cleaning or working chamber first, followed—in a further process step—by an organic solvent, and then water again. Alternatively, the organic solvent can be used first, followed by water, and then the organic solvent again. According to the current state of the art, a particularly time-consuming drying process takes place between each of these steps.

[0007] Furthermore, with the previously known systems or processes, all steps are carried out one after the other, which can each take about 20 minutes, resulting in a relatively long cleaning process overall.

[0008] If the solvent is applied first, a disadvantage can arise: due to the relatively high drying temperature, any inorganic substances remaining on the parts to be cleaned may adhere strongly and be difficult to remove. Conversely, if water is applied first, it becomes heavily contaminated, leading to a shorter service life and increased effort.

[0009] Using an evaporator to purify the process water according to the state of the art requires a considerable amount of energy, or results in a relatively large amount of wastewater that needs to be disposed of.

[0010] In view of these disadvantages, the invention is based on the objective of providing a method of the type mentioned at the outset with which an improved cleaning result can be achieved in a shorter time and with reduced effort.

[0011] This problem is solved according to the invention by a method having the features of claim 1. Advantageous further developments of the idea according to the invention are the subject of dependent claims.

[0012] A method according to the invention for cleaning industrially manufactured parts made of metal and / or plastic using a cleaning agent is characterized in that a mixture of at least two organic solvents and water is used as the cleaning agent, the mixture comprising at least a first water-insoluble organic solvent and at least a second water-soluble organic solvent.

[0013] With such a cleaning agent, both non-water-soluble (fat-soluble) and water-soluble contaminants can be removed from the components to be cleaned in one step.

[0014] The inventive method comprises the following steps: a) Placing the parts to be cleaned into a work chamber; b) Filling the work chamber with the cleaning agent; c) Cleaning the parts in the work chamber using the cleaning agent.

[0015] The method according to the invention provides that subsequently, i.e., after step c), the working chamber is evacuated and at least one organic solvent in a liquid, vaporous, or mixed liquid-vaporous state is introduced into the evacuated working chamber at a reduced pressure relative to the surroundings, preferably at a pressure of 400 mbar or 200 mbar or lower, and at a temperature at or above the flash point of the solvent in question. The cleaning process is then completed by condensation of the solvent vapor onto the parts, wherein the reduced pressure and / or the temperature is selected such that no explosive mixture is formed. This essentially corresponds to step b) of claim 1 from DE 43 29 178 B4, which has proven to be particularly effective and advantageous in achieving a good cleaning result.

[0016] According to the invention, a cleaning agent is a mixture of at least two organic solvents and water. The cleaning agent contains a water content of at least approximately 30% by volume, preferably at least approximately 50% by volume, based on the proportion of the water-soluble organic solvent.

[0017] A further development of the method according to the invention provides that the water-solvent mixture or the cleaning agent additionally contains a cleaning enhancer, for example a surfactant and / or an amine. In this way, the cleaning effect can be further enhanced in a manner known per se.

[0018] A device for cleaning industrially manufactured parts made of metal and / or plastic, in particular for carrying out the method according to the invention, comprises: a) a working chamber for receiving parts to be cleaned; b) tank means for supplying water and a solvent mixture containing at least a first water-insoluble organic solvent and at least a second water-soluble organic solvent, which tank means for supplying the working chamber with the water and the solvent mixture in fluid communication with the working chamber; c) conveying means for conveying the water and the solvent mixture into the working chamber for cleaning the parts in the working chamber by means of the water-solvent mixture; as well as separating means, in particular for oil and / or for water, in fluid communication with evaporator and condenser means for recovering the water-insoluble solvent and for recovering the water-soluble solvent and the water.

[0019] Extensive tests conducted by the applicant have surprisingly revealed that the process according to the invention leads to a separation (demulsification) of the water-solvent mixture (hereinafter also referred to as cleaning agent), whereby the second, water-soluble organic solvent becomes oil-free upon the addition of water. In this way, both greasy and oily (organic) soiling and inorganic soiling can be removed in essentially a single step, resulting in corresponding time and cost savings. The process according to the invention is also advantageous from an energy perspective, as it eliminates the need for the repeated drying processes known from the prior art, which are correspondingly energy-intensive.

[0020] A further development of the inventive method provides that in step c) the parts and / or the water-solvent mixture are circulated in the working chamber in order to improve the cleaning effect and to create a dispersion (in the case of liquid components, specifically an emulsion) of the components of the water-solvent mixture for this purpose.

[0021] In another embodiment of the inventive process, it is provided that, following step c), the parts are removed from the working chamber or the water-solvent mixture (the cleaning agent) is drained from the working chamber. The water-solvent mixture can, in particular, be fed to an evaporator to recover all components of the cleaning agent (first solvent, second solvent, and water). Alternatively, however, several evaporators can be used to accelerate the recovery process.

[0022] Yet another further development of the process provides that the parts to be cleaned are optionally pre-cleaned with an organic solvent, in particular the first solvent, the second solvent or another solvent, before or after they are or have been placed in the working chamber according to step a).

[0023] Furthermore, it can be provided that in step b) the water-solvent mixture or the cleaning agent is introduced into the working chamber in liquid form. Preferably, the temperature is below the flash point of at least one of the two solvents.

[0024] A particularly preferred embodiment of the method according to the invention provides that, at least during steps b) and c), a pressure and temperature are generated and maintained in the working chamber so that no explosive mixture of air and solvent vapor is formed.

[0025] It is generally not necessary to introduce the water and solvents into the work chamber in already mixed form; rather, separate feeding of the water and / or solvents into the work chamber is also possible.

[0026] Additionally or alternatively, it can be provided that, following step c), hot water with a temperature of preferably above 50 °C is introduced into the working chamber, wherein preferably in both cases the water-solvent mixture has first been drained from the working chamber.

[0027] To complete the cleaning process, the cleaned parts can then be dried. This drying can take place in the work chamber itself, although the invention is not limited to this.

[0028] As already mentioned, in the further development of the inventive method it can be provided that, after cleaning, the water-solvent mixture or the cleaning agent is purified by evaporation and / or filtration and prepared for reuse.

[0029] A corresponding further development of the device is characterized by filter media for the water and for the first and second solvents in fluid connection with the tank medium and the working chamber.

[0030] Although treatment using one or more evaporators may be preferred, purification or treatment, particularly by ion exchange or (reverse) osmosis, is also within the scope of the invention. In principle, techniques used for water desalination, which are known to those skilled in the art, can be applied for this purpose.

[0031] One advantage of using evaporators over ion exchangers or similar devices is that any cleaning enhancer additives can also be recovered.

[0032] The cleaning agent preferably contains, based on the total amount of water-soluble organic solvent and water, 10 to 90 vol% non-water-soluble organic solvent.

[0033] A mixing ratio of approximately 10:90, preferably 30:70, most preferably 50:50, is particularly suitable between the non-water-soluble solvent and the total amount of the water-soluble solvent and water.

[0034] In particular, the ratio of the first solvent, the second solvent and water can be approximately 1:1:1, whereby it can generally be assumed that the mixture remains functional in the sense of the invention for a longer time the more water it contains.

[0035] As mentioned, the mixing ratios can be adjusted when filling the working chamber. This is done by pumping the individual components of the cleaning agent, such as the organic solvents, water, and any other substances, from separate (storage) containers or tanks in the required quantities and combining them to create the desired cleaning agent mixture.

[0036] In a further embodiment of the process according to the invention, it can be provided that the first solvent and / or the second solvent are each a solvent mixture, wherein the components of the mixture then exhibit the fundamental properties of the first solvent (water-insoluble) and the second solvent (water-soluble), respectively. Furthermore, certain additives, such as surfactants, amines, or the like, can be added to the water used.

[0037] Since the first and second solvents separate after parts cleaning due to their respective properties—with the first solvent absorbing organic contaminants (oils, greases) and the second solvent absorbing inorganic contaminants—a physical-mechanical separation of the mixture is also possible, for example, by means of an overflow or controlled downward drainage. Such separation can be used in addition to the previously mentioned evaporation and / or filtration.

[0038] Specifically for the first, water-insoluble solvent, the ratio or absolute quantity can be chosen such that a sufficient phase thickness (after separation) results to correspond to a known or assumed degree of contamination of the parts to be cleaned, i.e., to completely absorb the contamination in question.

[0039] Another embodiment of the method according to the invention may involve generating and maintaining a negative pressure relative to the environment in the working chamber, at least during steps e) and c). If the ambient pressure is approximately 1 bar, it may be provided – without limitation – that a negative pressure with an absolute value of approximately 100 mbar or approximately 200 mbar to 400 mbar is generated in the working chamber. This serves in particular to protect against explosions.

[0040] A corresponding further development of the device is characterized by pressure generating means in fluid connection with the evaporator and condenser means and / or with the working chamber.

[0041] Alternatively, it can also be provided that an overpressure relative to the environment is generated and maintained in the working chamber, at least during steps b) and c). This overpressure can, for example, be up to 1 bar above ambient pressure.

[0042] The cleaning agent comprises – as already mentioned – preferably at least one water-soluble organic solvent, wherein the water-soluble organic solvent dissolves in water at a concentration of more than 5 vol% (20 vol%, 30 vol%, 50 vol%), and at least one non-water-soluble organic solvent, wherein the non-water-soluble organic solvent dissolves in water at a concentration of less than 5 vol%, preferably < 1 vol%, particularly preferably < 0.1 vol%. Such a cleaning agent can remove both non-water-soluble (fat-soluble) and water-soluble contaminants from the components to be cleaned.

[0043] Organic solvents are used as solvents in the cleaning agent, such as: Hydrocarbons (RH), such as n-hexane, petroleum, benzene, benzene homologs, such as styrene, suitably aliphatic hydrocarbons containing 5 to 20 hydrocarbon atoms, such as cyclic saturated hydrocarbons and straight-chain or branched saturated or unsaturated hydrocarbons, preferably cycloalkanes, n-paraffins, isoparaffins or (test) gasolines (such as Stoddard Solvent), or aromatic hydrocarbons, such as toluene or xylene; alcohols (R-OH), such as methanol, ethanol, isobutanol, propanol, isopropanol, phenol, hexanol, alkoxypropanols or alkoxyethanols; ketones (R-CO), such as acetone, methylene ketone (MEK), methyl isobutyl ketone (MIBK); esters, such as alkyl lactates, dibasic esters, commercially available mixtures of dibasic esters; Ethers, such as dipropylene glycol monomethyl ether (DPM), diethyl ether or hydroxy ether; carboxylic acids (R-COOH), such as formic acid, acetic acid;Glycols (HO-R-OH), such as ethanediol (ethylene glycol, glycol), propanediol (propylene glycol), diethylene glycol, triethylene glycol; amino compounds (R-NCOH), such as aniline, β-naphthylamine, benzidine; amides, such as dimethylformamide (DMF), hydrocarbon-sulfur compounds, such as dimethyl sulfoxide (DMSO), carbon disulfide, and cyclic siloxanes, which, suitably, contain 6 to 8 ring atoms, or a mixture of two or more such compounds.

[0044] Suitable organic solvents are used which have a flash point below their boiling point at atmospheric pressure and which have a boiling point of 100 °C or less at an absolute pressure of 1 mbar or more.

[0045] The organic solvents preferably have a flash point in the range of 40 °C to 100 °C. The flash point of particularly suitable organic solvents is in the range of 55 °C to 100 °C and especially in the range of 61 °C to 100 °C.

[0046] The cleaning agent or the water-solvent mixture preferably also comprises one or more additives selected from the group consisting of surfactants, amines, pH buffers, dispersants, inorganic solvents such as ammonia solutions or inorganic acids, as already mentioned.

[0047] In a preferred embodiment of the invention, a mixture comprising a cleaning agent is used. 30-35% by volume aliphatic hydrocarbon with 9 to 13 carbon atoms; 30-35% by volume DPM; 1-5% by volume Diethylamine; rest Water used.

[0048] In the cleaning process according to the invention, pressure and temperature are preferably selected such that no explosive mixture of air and solvent vapors can form.

[0049] Preferably, in a further embodiment of the inventive method, it can be provided that, at least during step c), the working chamber and its contents are subjected to ultrasound in order to promote the dispersion of the cleaning agent components and improve the cleaning effect. In this way, the achievable cleaning effect can be further enhanced.

[0050] A further development of the device is characterized by ultrasound generating means in operative connection with the working chamber in order to subject the working chamber and its contents to ultrasound.

[0051] A preferred "minimum equipment" of the device comprises at least one tank (tank medium) for the water-solvent mixture, a working chamber for carrying out the actual cleaning, preferably with a circulation system for producing a dispersion from the added solvents and the water, and an evaporator to recover the solvents and water used.

[0052] Further features and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the drawing.

[0053] The single figure schematically shows an embodiment of device 1, with optional components indicated by dashes.

[0054] The device 1 comprises, in addition to a working chamber 2, at least one cleaning agent tank 3 containing the cleaning agent used (two different solvents and water) ("Tank 1"); the further tank 4 ("Tank 2"), shown with a dashed line, is optional, as are the corresponding lines, conveying devices, filters, and valves (also shown with a dashed line). At least Tank 3 is in fluid communication with the working chamber 2 via suitable lines, conveying devices 5, filters 6.1, 6.2, and valves (not all labeled), so that the cleaning agent can be introduced from Tank 3 into the working chamber 2, for example, by flooding (especially via the fine filter 6.2) or by injection. The working chamber 2 can also be loaded with the parts to be cleaned (not shown).Furthermore, it can be designed to implement a circulation process so that no separation of the cleaning agent takes place, by conveying the cleaning agent from the working chamber 2 via the filter means 6.1, 6.2 by means of the conveying means (pump) 5 and returning it to the working chamber 2 (or the tank 3), for which the valve means must be appropriately controlled, which is known to those skilled in the art.

[0055] According to the design shown in Figure 1 An evaporator 7 is arranged in fluidic interaction with the working chamber 2, enabling the cleaning and recovery of the individual components of the cleaning agent. The filter media 6.1 and 6.2, which are integrated into the cleaning agent circuit, serve to remove contaminants from the cleaning agent. A separate coarse filter 6.1 is not strictly necessary.

[0056] Tank 1 has an overflow at reference numeral 3a for the first, water-insoluble solvent containing oil during the cleaning of parts in the operation of the device 1, which overflow 3a is in operative connection with the evaporator 7 in order to enable continuous processing in particular of the solvent in question during operation.

[0057] For the purpose of recovering the water-solvent mixture used, or its components, the evaporator 7 is connected to a condenser 8, which in turn is operatively connected to separators 9 and a vacuum pump 10. One separator 9a can be provided for the recovery of the water-insoluble solvent, and the other separator 9b for the recovery of the water-soluble solvent (and the water), without the invention being limited to such a configuration.

[0058] Ultrasonic devices (not shown) may be arranged in working chamber 2 to subject the contents of working chamber 2 to ultrasound during the cleaning process. Furthermore, at least the working chamber includes devices for setting a working temperature (not shown).

[0059] The working chamber 2 is also directly connected to the evaporator 7 (reference numeral 7a) to carry out vapor phase cleaning of parts to be cleaned - preferably after they have already been cleaned with the cleaning agent, as described above.

[0060] The vacuum pump 10 can then be used to (vacuum) dry the parts in the working chamber 2. It can also be used to set a specific pressure in the working chamber 2.

[0061] In an advantageous optional embodiment of the device 1 with a second tank 4, this tank ("Tank 2") can be filled with an organic solvent, preferably a water-insoluble solvent, most preferably the first solvent, which is also contained in the cleaning agent used. The solvent in Tank 4 can contain additives, e.g., anti-corrosive agents or re-fatting agents. Tank 4 is operatively connected to corresponding lines, conveying elements 11, filters 12, and valves (shown in dashed lines, not all labeled). Tank 4 and Tank 3 can be cascaded together, as shown. Otherwise, the system section with Tank 3 and the optional system section with Tank 4 share at least the working chamber 2, the evaporator 7, the coarse filter 6.1, and the condenser-separator arrangement 8, 9 with the vacuum pump 10, without the invention being limited thereto.

[0062] In operation, the described variant of device 1 initially functions analogously to the variant without tank 4 and the associated additional means to perform cleaning. Subsequently, the relevant solvent can be introduced from tank 4 into the working chamber 2, for example by injection, to minimize consumption. This allows for the removal of residual water, a process known as "dewatering." The used solvent can be discharged via the filter media 6.1 and 6.2 into tank 3 and / or tank 4. Additionally or alternatively, the used solvent can be routed through the water separator 9a. If tank 3 is used, it is advantageous to introduce the solvent from the top, as this is where the relevant solvent layer from the first solvent will be located.Afterwards, the working chamber 2 can be (partially) filled with the solvent from tank 4, whereby the solvent can be heated to a temperature above its flash point. For this purpose, the working chamber 2 can be (partially) evacuated, preferably by means of the vacuum pump 10. This helps to evaporate any residual water remaining on the cleaned parts. Preferably, the solvent is circulated at least through the coarse filter 6.1. For recovery purposes, the used solvent can be passed through the evaporator 7 and the condenser-separator assembly 8, 9 (the water separator 9a).

[0063] An additional (hot) water tank for rinsing purposes may be provided, which is not shown in the figure. Alternatively, tank 4 can be used accordingly. In conjunction with tank components 3, 4 and / or working chamber 2, temperature control devices (not shown) may be provided to precisely adjust the temperature of the cleaning agent / solvent.

Claims

1. Method for cleaning industrially manufactured parts made of metal and / or plastic using a cleaning agent, with the steps of: a) introducing parts to be cleaned into a working chamber (2); b) charging the working chamber (2) with the cleaning agent; c) cleaning the parts in the working chamber (2) by means of the cleaning agent; wherein preferably in step c) the parts and / or the cleaning agent are circulated in the working chamber (2); in which the working chamber (2) is subsequently evacuated and at least one organic solvent is fed into the evacuated working chamber (2) in the vaporous state at a negative pressure relative to the environment, preferably at a pressure of 400 mbar, 200 mbar or lower, at a temperature at or above the flash point of the solvent in question, and the cleaning is completed by condensation of the solvent vapor on the parts, wherein the negative pressure and / or the temperature is selected such that no explosive mixture is created; characterised in that a mixture of at least two organic solvents and water is used as the cleaning agent, which mixture comprises at least one first water-insoluble organic solvent and at least one second water-soluble organic solvent, and in that, following step c), the water-solvent mixture is drained from the working chamber (2), wherein the cleaning agent contains, based on the proportion of the water-soluble organic solvent, a water content of at least about 30 % by volume, preferably at least about 50 % by volume.

2. Method according to claim 1, characterised in that subsequently hot water at a temperature preferably above 50 °C is introduced into the working chamber (2).

3. Method according to claim 1 or 2, characterised in that subsequently the cleaned parts are subjected to drying, wherein preferably the drying takes place in the working chamber (2).

4. Method according to any one of claims 1 to 3, characterised in that after cleaning, the water-solvent mixture is cleaned by evaporation and / or filtration and prepared for reuse.

5. Method according to any one of claims 1 to 4, characterised in that the first solvent is soluble in water in a proportion of less than 5 % by volume, preferably less than 1 % by volume, most preferably less than 0.1 % by volume, and the second solvent is soluble in water in a proportion of more than 5 % by volume, preferably more than 20 % by volume, most preferably more than 30 % by volume or more than 50 % by volume.

6. Method according to any one of claims 1 to 5, characterised in that the water-solvent mixture has a mixing ratio between non-water-soluble solvent and the total amount of the water-soluble solvent and water of about 10:90, preferably 30:70, most preferably 50:50.

7. Method according to any one of claims 1 to 6, characterised in that before step b) the parts are pre-cleaned with a solvent, preferably an organic solvent.

8. Method according to any one of claims 1 to 7, characterised in that at least during the steps b) and c), a negative pressure is generated and maintained in the working chamber (2) relative to the environment; or at least during the steps b) and c), an overpressure relative to the environment is generated and maintained in the working chamber (2); wherein preferably, at least during the steps b) and c), a pressure and a temperature are generated and maintained in the working chamber (2) so that no explosive mixture of air and solvent vapor is created.

9. Method according to any one of claims 1 to 8, characterised in that the organic solvents have a flash point in the range from 40 °C to 100 °C, preferably 55 °C to 100 °C, at most 61 °C to 100°C.

10. Method according to any one of claims 1 to 9, characterised in that as water-solvent mixture, a mixture comprising 30-35 %by volume aliphatic hydrocarbon with 9 to 13 carbon atoms,30-35 %by volume DPM,1-5 %by volume diethylamine, andremainderwater is used.

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