Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D9/00—Chemical paint or ink removers
  • C09D9/005—Chemical paint or ink removers containing organic solvents
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/14—Cleaning or pickling metallic material with solutions or molten salts with alkaline solutions
  • C23G1/22—Light metals
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G5/00—Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents

Definitions

• the painting industry stands, i.a. due to increasing quality requirements, increasingly faced with the problem of stripping coating aids such as racks and conveyors and incorrectly coated production parts.
• stripping coating aids such as racks and conveyors and incorrectly coated production parts.
• the difficulties in stripping are that the coating materials to be removed have different structures and thereby also react differently to the stripping chemicals and the multi-layered structure requires a relatively high amount of coating to be cleaned, resulting in a high consumption of descaling chemicals and long stripping times.
• the invention proposes that for the stripping of the contaminated with paint, varnish and other organic coatings workpieces, tools, aids or devices, a total cleaning process is made of at least two successive Ent fürungsvons Kunststoffen.
• the individual process steps can be carried out either in individual batch systems or in fully automatic continuous systems.
• the invention is suitable to be integrated easily and decentrally in the user in the production.
• coatings are to be understood as meaning paints, powder coatings, paints or similar coatings on parts. These are summarized in the following description usually under the term “paint” summarized.
• Stripping agents which are to be used for paint stripping of objects made of chemically reactive metals such as aluminum or magnesium, the surfaces of these metals after peeling not chemically attack.
• Anhydrous or at least low-water removal agents are therefore used for this purpose. These may additionally contain corrosion inhibitors for the metals mentioned, such as silicates.
• paint strippers contain both active ingredients that penetrate into the paint layer and swelling, as well as those that split the binder by chemical attack.
• DE-A-10014579 contains the following information:
• paint strippers consist of sodium or potassium hydroxide solution and a mixture of high-boiling components of the classes alcohols, glycols, glycol ethers and other high boilers.
• the pool filling a Entlackungsbeckens divides into a lower phase, consisting of aqueous alkali and dissolved organic solvents to saturation concentration and an upper phase consisting of organic solvents that are saturated with soda or potassium hydroxide solution.
• the volume fraction of this lower phase is usually from 30% to 80%.
• aqueous phase the Entlackungs für based on a combination of saponification and swelling.
• the saponification is a hydrolytic cleavage of the binders contained in the paint, for example fatty acids, oils or the like, in particular in an alkaline medium, in which the alkali metal salts known as so-called soaps of the corresponding binders are formed in the paint.
• the improved (according to this DE-A-10014579) method is characterized in that the coating agent is removed by immersing the coated therewith parts in a stripping bath of almost uniformly saturated solution of organic phase in the aqueous phase during the stripping, wherein a continuous phase in the pickling bath is formed exclusively by the aqueous phase.
• the organic phase is therefore not present as a continuous phase but as dissolved in the aqueous phase. This prevents that it comes to a two-layer, ie a phase separation in an organic and an aqueous layer in the pickling bath.
• the aqueous phase and the organics dissolved therein preferably form a homogeneous mixture.
• organic phase and aqueous phase may be mixed together.
• the mixing of organic and aqueous phase can take place inside and / or outside of the stripping bath occur.
• at least one phase may be in dispersed form.
• Organic phase and aqueous phase can form a heterogeneous mixture.
• the preferred mixing in the bath can be carried out by passing organic solvent in disperse form, in particular in drop form, through the continuous aqueous phase. Due to the lower density of the organic solvents, the drops of the dispersed organic solvents can rise above the aqueous phase and thereby dissolve in the aqueous phase.
• the continuous aqueous phase preferably takes up so much organic phase until its saturation concentration is reached. It is also possible that part of the continuous aqueous phase dissolves in the dispersed organic phase. Undissolved dispersed organic phase may rise to the surface of the pickling bath and flow back into a supply via the overflow.
• DE-A-19861133 proposes that for cleaning the tools, auxiliaries, devices or other objects contaminated with paint and varnishes and other organic coatings, an overall cleaning process is carried out, consisting of the two process steps of cleaning and rinsing, wherein both operations are integrated in a single-module system are.
• a cleaning agent which consists exclusively of glycol ethers.
• Alkali-supplying additives are added to this cleaning agent to increase the cleaning power.
• a volatile hydrocarbon medium is used, which does not mix with the glycol ether-solvent mixture, dries without residue and can be recovered by phase separation.
• DE-A-19861133 In the process step cleaning, a solvent mixture is used which consists exclusively of glycol ether.
• additives containing alkalinity preferably alkali metal hydroxides and / or alkanolamines, are added as required.
• the dissolution of alkalinity-containing additives is considerably accelerated by the injection process. This will be the poorly soluble additives dissolved only in an economically meaningful way.
• the possibly resulting undesirable reaction product water is quickly evaporated by the injection process and discharged through the system vent.
• the emergence of a liquor which would be harmful to various types of metals, can be avoided.
• the glycol ether solvent mixtures used can be used in high temperature ranges well above 100 ° C without risk of explosion due to their property to have high boiling and flash points. In addition, a higher temperature considerably speeds up the cleaning process or even allows cleaning. After the cleaning process, the parts must still be washed off the adhering detergent residues. This takes place in the subsequent process step rinsing.
• the rinse aid used here is a volatile hydrocarbon medium which dries without residue from the workpiece surface. The decisive factor here is that the rinse aid does not mix with the glycol ether solvent mixture. "
• the object of the present invention is to improve the state of the art, in particular with regard to the consumption of desizing chemicals.
• the present invention is a process for paint stripping of objects, characterized in that it takes place in at least two steps, wherein in a first step a) using a first Entlackungsstoffs split off a portion of the paint in the form of paint particles from the substrate and in a second step b) is removed by means of a second Entlackungsstoffs of after the step a) still adhering to the workpiece portion of the paint by at least partial dissolution.
• the first and the second step can also be carried out repeatedly in each case.
• This stripping process in at least two separate steps can be carried out batchwise or in a continuous flow system. In batch-wise processes, the two process steps can be carried out in the same or preferably in different paint removal containers. If both steps take place in the same paint removal container, the first paint removal agent is removed after a sufficient exposure time and replaced by the second paint removal agent. For receiving a new batch, the second stripping agent then has to be exchanged again for the first stripping agent. It is more advantageous to provide two separate Entlackungs investigatinger, wherein in the first container, the first stripping and in the second container is the second stripping.
• the objects to be painted are then brought into contact first in the first paint removal container and then in the second paint removal container with the respective paint removal agent. This can be done by dipping or spraying.
• the process can also run quasi-continuously in a continuous flow system.
• the articles to be desmutted come into contact with the first stripping agent in a first zone of the continuous flow system and then in a second zone of the flow plant with the second stripping agent. This contact can also be made by immersion in containers with the stripping agent or by spraying with the stripping agent.
• the paint is at least partially split off from the substrate in the form of macroscopically visible particles. These are of such size that they can be mechanically separated from the paint stripping agent, for example by sieving or filtration, sedimentation or centrifuging. For example, these particles may be in the form of pancakes or scales.
• This splitting off is mainly done by diffusing the paint stripping agent into the lacquer layer or lacquer layers, causing them to swell and jump off the substrate. A dissolution of paint to a true or colloidal solution is not or at best to a small extent. This jumping off can take place in the boundary layer between the paint and the substrate surface, for example the metal surface, or at the boundary between different paint layers.
• the first stripping agent can therefore essentially be kept ready for use by mechanically or continuously removing the splintering paint particles from it continuously or discontinuously. This can be done for example by centrifuging or by suitable screening or filtering devices. Or one removes the paint particles by sedimentation. Since the first stripping agent practically does not chemically consume, only as much stripping agent has to be added, as is lost when the paint particles are discharged.
• the remaining lacquer layer is at least partially dissolved under the action of the second Entlackungsstoffs to a true or colloidal solution.
• This can be done by physical dissolution of paint components or by their chemical cleavage.
• insoluble coating components such as pigments can be released from the dissolved lacquer layer, which can be deposited as sludge.
• a part of the paint may also detach particulate.
• the (chemical) consumption of the second paint removal agent is significantly reduced compared to conventional processes. This reduces the total consumption of Entlackungsffenn and usually also the time required for a complete Entlackung time.
• the temperature of the respective Entlackungsmittels can be a compromise between Entlackungsrial and Energy consumption for each step can be optimized separately.
• the first paint stripper preferably has a temperature in the range of about 30 0 C to about 80 0 C.
• the temperature of the second Entlackungsstoffs is preferably in the range of 50 ° C to 1 0 C below its flash point, preferably to 13O 0 C when the flash point is higher. It is generally favorable to set a higher temperature in the second stripping agent than in the first stripping agent.
• the stripping time for practical applications is preferably between about 10 and about 60 minutes in each of the two steps. However, times may also be lower or higher for particularly simple or particularly difficult paint stripping processes.
• the process is carried out in such a way that in the first step more than 50%, in particular more than 70% of the total paint is removed. This is advantageous with regard to the total consumption of paint stripping agent. This can be controlled by a suitable choice of Entlackungsdauer and Entlackungstemperatur in the first step.
• a stripping agent which contains substituted or unsubstituted methylpyrrolidone.
• a substituted methylpyrrolidone is understood as meaning such a compound in which one or more hydrogen atoms of the pyrrolidone ring have been replaced by other atomic groups.
• the unsubstituted or substituted methylpyrrolidone can represent the complete first stripping agent.
• the methylpyrrolidone can be treated with other organic solvents such as unsubstituted or substituted benzyl alcohol and / or with glycol ether.
• the glycol ethers preferably represent polyethylene glycols or polypropylene glycols.
• the terminal OH groups may be capped by end groups such as alkyl groups.
• organic solvents which have a flash point of above 6O 0 C.
• the effect of the first stripping agent can be improved by the addition of alkaline substances such as alkali metal hydroxides or amines.
• the first stripping agent should retain its ability to act, preferably by blasting off the varnish from the underlay, in particular due to swelling, and less by physical or chemical dissolution of varnish constituents, such as chemical attack on the binder system of the varnish.
• the second stripping agent consists exclusively of glycol ether and these alkaline compounds.
• the alkaline compounds may, for example, be selected from alkali metal hydroxides, amines and alkanolamines.
• the glycol ethers preferably represent polyethylene glycols or polypropylene glycols.
• the terminal OH groups may be capped by end groups such as alkyl groups.
• Mechanical release of paint particles as particles can also be done in the second step in addition to a physical or chemical dissolution of paint constituents. This happens, for example, in that the second stripping agent more easily infiltrates the lacquer layer already attacked in the first step. By dissolving paint components in the sub-migration zone, the overlying paint layer can be blasted off.
• the process according to the invention can be used, for example, for removing paint from objects made of aluminum and / or magnesium.
• the first and in particular the second stripping agent contain as little, preferably not more than about 1% by weight of water. At least should the first and second paint stripping agents do not contain more than 10% by weight, preferably not more than 5% by weight, of water.
• corrosion inhibitors such as, for example, silicates, borates or organic phosphonic acids, can be added to the first and the second stripping agent, in particular the second stripping agent.
• An undesirable accumulation of water in the first and in particular in the second stripping agent can be prevented, for example, by keeping the temperature of the stripping agent in the upper third of the abovementioned temperature range. In this case, especially in spraying, water is evaporated and thereby removed from the paint stripping.
• the stripped articles are rinsed after the second step.
• Hydrocarbons for example, can be used for this purpose, as described in more detail in DE-A-1986133.
• the two-step process according to the invention is particularly suitable for stripping articles which at least partially consist of aluminum, magnesium, alloys of aluminum or alloys of magnesium.
• the objects to be painted can be parts of vehicles, in particular wheel rims.
• a special field of application is the Entlackung of wheel rims, which consist of aluminum, magnesium, aluminum alloys or magnesium alloys.
• the paint to be removed on these objects may have a multilayer structure and consist for example of primer, basecoat and clearcoat.
• the proposed two-step process can be considered more cumbersome than the known one-step process when viewed superficially. Thereby, however, that one the two basic processes at the Entlacken, the rather physical swelling and jumping off the lacquer layer on the one hand and that rather On the other hand, by optimizing chemical dissolution of the binder in each case in two separate stages, the overall consumption of paint stripping chemicals is reduced. This is due in particular to the fact that the first step takes place at most a low chemical attack and thus a low chemical consumption of Entlackungschemikalien. In the second step, the lacquer component which is physically removed in the first step no longer comes into contact with the more chemically active second paint stripping agent. He therefore no longer contributes to the chemical consumption of the second Entlackungsstoffs. As a result, the total consumption of paint stripping agent is reduced by up to a factor of 5 in comparison to conventional processes. If the process is carried out favorably, the overall time for the stripping process is also reduced.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Metallurgy (AREA)
• Mechanical Engineering (AREA)
• Life Sciences & Earth Sciences (AREA)
• Wood Science & Technology (AREA)
• Paints Or Removers (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Detergent Compositions (AREA)
• Road Signs Or Road Markings (AREA)

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Citations (4)

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• 2006
  • 2006-02-15 DE DE102006007246A patent/DE102006007246B4/de not_active Expired - Fee Related
• 2007
  • 2007-01-30 AT AT07703128T patent/ATE537227T1/de active
  • 2007-01-30 EP EP07703128A patent/EP1989266B1/de active Active
  • 2007-01-30 WO PCT/EP2007/000773 patent/WO2007093278A1/de active Application Filing
  • 2007-01-30 ES ES07703128T patent/ES2377835T3/es active Active
  • 2007-01-30 PL PL07703128T patent/PL1989266T3/pl unknown

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