METHOD FOR PRESERVING A DISPERSION IN A DOSING SYSTEM AND DOSING SYSTEM

Description

[0001] The invention relates to a method for preserving an emulsion paint or a pigment paste in a dosing system and a dosing system for preserving an emulsion paint or pigment paste.

[0002] Dosing systems enable the precise delivery of a specific amount of a dispersion on demand. Whenever dosing systems are mentioned here or elsewhere, this generally refers to any system that enables the metered delivery of a material. Dosing systems in this sense comprise at least a container and a closable valve.

[0003] Dosing systems are used, for example, in paint mixing systems. An example of a dosing system for paints is described in DE 196 54 829 A1.

[0004] The dispersion stored in a dosing system remains in a container within the dosing system for several weeks or even months. To prevent the quality of the dispersion from deteriorating during this time due to microbial contamination by bacteria or fungi, preservatives are added to the dispersion. Common preservatives for this purpose include isothiazolines or formaldehyde releasers. The amount of preservative required exceeds the typically tolerable concentrations in water-based coating systems.

[0005] There is therefore a need for processes that enable long-term protection of dispersions in containers of dosing systems against microbial contamination without having to resort to preservatives.

[0006] As a possible approach, EP 1 541 225 A1 describes a dosing system for mixing emulsion paint. A container is provided for each paint component, which is connected via a conveying line to a dosing valve arranged in the feed area of ​​a mixing vessel. The containers for the aqueous paint components are formed by water- and gas-tight bags. The internal volume of the watertight bags shrinks when the container is emptied, corresponding to the volume of the container contents, preventing the paint from drying on the inner wall and preventing microbial contamination in the gas space above the liquid level.

[0007] However, the dosing system described in EP 1 541 225 A1 cannot be easily refilled with new emulsion paint. Furthermore, existing microbial contamination in the bags cannot be eliminated, and the dosing flow must be constantly adjusted to the changing internal pressure in the bags for accurate dosing. Furthermore, the bags described in EP 1 541 225 A1 cannot be easily attached to an existing paint mixing system or similar and must be disposed of after use, generating packaging waste.

[0008] GB 2 292 695 A discloses a process for producing an acrylic emulsion paint. The acrylic emulsion resin is emptied from one of two storage containers into one of two mixing containers and mixed with a stirrer. Pigments, thickeners, dispersants, extenders, and pH adjusters are dispersed in a water base in a dispersion container, and the pigment dispersion is introduced into the resin in the mixing container.

[0009] The document US 2 883 343 A discloses a method and an apparatus for analyzing a lubricating oil stock containing an additive and a method and an apparatus for controlling the mixing of additives with lubricating oil stocks.

[0010] The document EP 1 189 995 A2 describes a preserved water-based paint composition containing an oxidoreductase, an oxidizing agent, a binder and at least 10 wt% water.

[0011] The document US 2015 / 151957 A1 describes a water dispenser comprising a cold water tank, a fresh water line, a replaceable fresh water container, a pump, an air intake line and an ozone generator connected to the air intake line, as well as a control device configured to activate the ozone generator.

[0012] The document DE 199 42 284 A1 describes a device for producing liquid preparations with at least one gaseous volatile anesthetic, wherein the device contains a premixing stage and a downstream fine mixing or homogenization stage.

[0013] Document WO 02 / 13774 A2 describes a process for preparing an aqueous suspension of calcium carbonate for use in the manufacture of toothpaste compositions, comprising adding a dispersant and a preservative to a suspension of calcium carbonate and adding water to the suspension, wherein the water has been treated by a process to reduce the microbiological activity therein.

[0014] The present invention therefore has the object of providing a method in which preservative-free or low-preservative emulsion paints or pigment pastes in containers of dosing systems are protected against microbial attack in the long term.

[0015] In addition, the invention aims to provide a particularly sustainable process for preserving emulsion paints or pigment pastes in containers of dosing systems without having to resort to conventional preservatives, in particular isothiazolinones.

[0016] A further object of the present invention is to provide a method that can be flexibly applied to existing dosing systems and / or paint mixing systems.

[0017] Furthermore, the invention aims to provide a dosing system for preserving an emulsion paint or pigment paste in which an emulsion paint or pigment paste can be stored for a long time without being exposed to the risk of microbial contamination.

[0018] Further tasks arise from the following explanations and are partly listed below.

[0019] All or some of these objects are achieved according to the invention by the method according to claim 1 and the dosing system according to claim 8.

[0020] Advantageous embodiments of the invention are specified in the dependent claims and are explained in detail below.

[0021] According to the method according to the invention, for preserving an emulsion paint or pigment paste in a container that is part of a dosing system, a gaseous oxidizing agent is introduced into the container, wherein the gaseous oxidizing agent is introduced into the gas space above the surface of the emulsion paint or pigment paste in the container. Preferably, the emulsion paint or pigment paste is thoroughly mixed after introduction into the container, e.g., by stirring.

[0022] Surprisingly, it has been shown that, using a method according to claim 1, an emulsion paint or pigment paste can be protected from microbial contamination for months. The emulsion paint or pigment paste can be free of preservatives and yet still offers long-lasting protection against microbial contamination. Even with frequent use of the dosing system and repeated refilling of the container with fresh emulsion paint or pigment paste, the method according to the invention ensures protection against fungal and bacterial contamination.

[0023] Without wishing to be bound to any particular scientific theory, the oxidizing agent introduced into the container appears to provide complete protection against microbial contamination by killing microbes such as fungi and bacteria.

[0024] The oxidizing agent provides the emulsion paint or pigment paste with long-lasting protection against microbial contamination. Particularly when the emulsion paint or pigment paste is frequently removed from the dosing system container, it may be advisable to add new oxidizing agent to the container to renew the protection against microbial contamination. According to a preferred embodiment of the invention, the oxidizing agent is added to the container at periodic intervals, preferably at least once a month or at least twice a month, more preferably at least three times a month, even more preferably at least once a week, and most preferably once a day. By adding the oxidizing agent to the container at periodic intervals, the emulsion paint or pigment paste retains particularly long-lasting protection against microbial contamination.If the oxidizing agent is applied periodically at least once a day, the emulsion paint or pigment paste can retain protection against fungal and bacterial attack for several years.

[0025] It is expedient to introduce 0.1 to 200 mg, preferably 0.5 to 100 mg, or particularly preferably 1 to 50 mg, calculated per liter of container volume of the oxidizing agent per introduction. It has been found that these amounts achieve a particularly good balance between effective preservative protection provided by the oxidizing agent and the lowest possible consumption of resources. Furthermore, efficient process control can be achieved with gaseous oxidizing agents. For example, when using ozone as the oxidizing agent, which is generated with an ozone generator with a generator output of 500 mg / h, an effective amount of oxidizing agent can be introduced into the containers within 5 minutes for a system comprising twenty containers containing an emulsion paint or pigment paste.

[0026] According to the invention, the oxidizing agent is introduced into the gas space above the surface of the emulsion paint or pigment paste in the container. This effectively preserves the particularly problematic area for microbial infestation in the gas space above the surface of the emulsion paint or pigment paste.

[0027] In principle, very different oxidizing agents are suitable for preserving the dispersion.

[0028] Preferably, the oxidizing agent has a standard potential of 0.1 V or higher, preferably 0.5 V or higher, more preferably 1 V or higher, relative to the standard hydrogen electrode at a temperature of 25°C and an effective concentration of 1 mol l -1 and / or an ionic activity of 1, or in the case of gaseous reactants at a partial pressure of 101.325 kPa. Stronger oxidizing agents combat microbial infestation more effectively. In particular, isothiazolines are not oxidizing agents within the meaning of the invention.

[0029] Advantageously, the oxidizing agent is an oxygen- or chlorine-based oxidizing agent or a mixture thereof, preferably an oxygen-based oxidizing agent. The oxidizing agent is preferably selected from the group consisting of sodium hypochlorite, potassium hypochlorite, bleach, chlorine, ozone, hydrogen peroxide, peracetic acid, perborate, percarbonate, and mixtures thereof. These oxidizing agents are powerful oxidizing agents that effectively inhibit the growth of microbial organisms.

[0030] The oxidizing agent is particularly preferably selected from the group consisting of sodium hypochlorite, hydrogen peroxide, ozone, and mixtures thereof. The oxidizing agents from this group have proven particularly suitable for protecting the emulsion paint or pigment paste from microbial attack, as they are effective oxidizing agents. Furthermore, these oxidizing agents are essentially unproblematic for the emulsion paint or pigment paste, particularly at the appropriately intended amounts. In particular, the aforementioned oxidizing agents do not cause any significant change in the color and / or quality of the emulsion paint or pigment paste at the appropriately intended amounts.

[0031] According to the invention, the oxidizing agent is gaseous. Gaseous oxidizing agents can be easily introduced into the container and create a protective atmosphere in the gas space above the surface of the emulsion paint or pigment paste. This results in particularly long-lasting protection of the emulsion paint or pigment paste against microbial contamination. The addition of a gaseous oxidizing agent is particularly advantageous because, even over long periods of storage of a emulsion batch, only minimal dilution effects occur.

[0032] According to a particularly preferred embodiment of the invention, the oxidizing agent is ozone. When ozone is used as the oxidizing agent in the process according to the invention, a particularly long-lasting antimicrobial effect is achieved. Furthermore, ozone is compatible with the common components of emulsion paints or pigment pastes, particularly in the appropriately provided amounts. Furthermore, ozone can be easily produced at the site of use.

[0033] Ozone can be generated in various ways. Preferably, ozone can be generated in a generator or in the lid of the container, particularly by corona discharge.

[0034] Ozone can be generated externally, i.e., outside the container, which is part of a dosing system, and then introduced into the container. Ozone can be generated, for example, from a chemical reaction of potassium permanganate with concentrated sulfuric acid or by electrolysis of diluted sulfuric acid, especially at low temperatures. Ozone can also be generated from air or oxygen under the influence of UV radiation.

[0035] According to a preferred embodiment of the method according to the invention, the ozone is generated in an ozone generator comprising a voltage source, in particular a high-voltage generator, and a discharge unit starting from air, in particular dried air, oxygen or an oxygen mixture with argon or carbon dioxide. The structure of common ozone generators is known to the person skilled in the art. In the discharge unit, oxygen molecules are preferably generated by silent electrical discharge, so-called " Corona discharge", dissociates into oxygen atoms, after which ozone synthesis and ozone enrichment take place in the plasma of the discharge filaments. The resulting ozone content of the final concentration of the gas mixture can be 1 to 5 wt.% with air as the starting gas and 6 to 13 wt.% with oxygen as the starting gas. Air is preferably used as the starting gas for ozone generation. When ozone is generated in a generator, ozone is thus produced in a clean manner starting from inexpensive starting materials.

[0036] A possible construction of a discharge unit referred to as an ozonizer, which is suitable for the method according to the invention for generating ozone, is described in DE 197 14 176 A1.

[0037] According to a preferred embodiment of the invention, the ozone is generated in the container lid. Generating ozone in the container lid has the significant advantage that the ozone has a shorter path to travel to the emulsion paint or pigment paste and thus to the site of action. This embodiment ensures that as little of the generated ozone as possible is lost due to ozone instability. Furthermore, generating ozone in the container lid is a particularly space-saving and flexible approach.

[0038] According to one embodiment of the inventive method, the ozone can be generated in the container lid by a device arranged in the container lid, in which ozone is generated from air or oxygen using UV light. For this purpose, the lid comprises, for example, UV-C light-emitting diodes. According to a specific embodiment of this approach, the lid has an induction plate, a control LED, several UV-C LEDs, preferably from 2 to 8 LEDs, more preferably from 3 to 5 LEDs, several blue light LEDs, a battery, and an on / off switch. However, lids with a different specific structure than the container lid are also suitable for generating ozone using UV radiation.

[0039] According to a more preferred embodiment of the invention, the ozone in the container lid is generated by corona discharge. Preferably, air or oxygen passes through a tube that is attached directly to the container lid via an adapter and comprises a metal foil, a metal rod, and a cavity. The air passes through the cavity while the metal foil and metal rod are energized, leading to corona discharge. In this way, ozone is generated in the tube, which enters the container directly. This embodiment provides particularly effective protection for the emulsion paint or pigment paste against microbial contamination.

[0040] In a further preferred embodiment, ozone is generated by corona discharge outside the container, but in the immediate vicinity of the container. In this embodiment, the ozone is preferably introduced into the at least one container by means of a pump, in particular a diaphragm pump.

[0041] Preferably, the ozone is introduced evenly into the container. The pump advantageously generates positive pressure. The pump and the containers are preferably connected via a supply line, such as a hose system. This ensures that, when using an ozone generator in the immediate vicinity of the containers, all containers can be supplied with a sufficient amount of ozone.

[0042] Preferably, the emulsion paint or pigment paste is thoroughly mixed after the introduction of the oxidizing agent. According to a preferred embodiment of the inventive method, the emulsion paint or pigment paste is thoroughly mixed by stirring after the introduction of the oxidizing agent. In this way, the antimicrobial protection provided by the oxidizing agent is distributed throughout the emulsion paint or pigment paste. Furthermore, the thorough mixing of the emulsion paint or pigment paste ensures a stable, homogeneous appearance of the emulsion paint or pigment paste.

[0043] Pigment pastes are described, for example, in EP 2 243 808 B1. Dispersion paints and pigment pastes are particularly suitable for the process according to the invention because, firstly, they can be particularly well protected against microbial attack by the oxidizing agent and, secondly, because they are of particular economic importance. If a pigment paste is involved, it can be used, for example, for tinting paints, preferably emulsion paints. Pigment pastes preferably do not contain binders such as polymer dispersions.

[0044] According to a particularly preferred embodiment of the invention, the emulsion paint or pigment paste is essentially free of preservatives. "Essentially free of preservatives" means that the pigment paste contains preservatives at most in trace amounts, in particular in an amount of less than 2 ppm.

[0045] EP 1 297 079 B1, DE 1 031 910, DE 10 2014 013 455 A1, and DE 10 2016 002 221 A1 each describe emulsion paints that are essentially free of preservatives. The emulsion paints described therein are outstandingly suitable for the process according to the invention.

[0046] A further aspect of the invention also relates to a dosing system.

[0047] The dosing system according to the invention for preserving an emulsion paint or pigment paste comprises at least one container which is designed for storing an emulsion paint or pigment paste and has a maximum fill level for the emulsion paint or pigment paste, a closable dosing valve and at least one supply line for a gaseous oxidizing agent leading into the container, wherein the supply line leading into the container leads into the container above a maximum fill level.

[0048] The dosing system according to the invention is ideally suited for the antimicrobial protection of the emulsion paint or pigment paste and for carrying out the method according to the invention.

[0049] According to a preferred embodiment of the invention, the container of the dosing system according to the invention comprises means for thoroughly mixing an emulsion paint or pigment paste. In this way, the antimicrobial protection provided by the oxidizing agent is distributed throughout the emulsion paint or pigment paste. Furthermore, the thorough mixing of the emulsion paint or pigment paste ensures a stable, homogeneous appearance of the emulsion paint or pigment paste. Preferably, the container comprises an agitator as a means for thorough mixing. A agitator is particularly well suited for effectively mixing the emulsion paint or pigment paste.

[0050] The supply line leading into the container can enter at different heights. According to the invention, the supply line leads above the maximum fill level of the container. This effectively preserves the particularly problematic area for microbial contamination in the gas space above the surface of the emulsion paint or pigment paste. Furthermore, the design effort for the supply line is reduced, as penetration of the emulsion paint or pigment paste into the supply line does not need to be prevented.

[0051] Preferably, the feed line leading into the container ends in a nozzle. This allows the oxidizing agent to be introduced effectively into the container or directly into the emulsion paint or pigment paste, depending on the height at which the feed line enters the container. The nozzle is preferably directed towards the bottom of the container. This nozzle arrangement prevents contamination of the nozzle when filling the container with new emulsion paint or pigment paste. According to an alternative preferred embodiment, the feed line leading into the container can be provided with a protective cap at its outlet opening that opens towards the bottom of the container. The protective cap prevents contamination and the resulting blockage of the outlet opening when filling the container with emulsion paint or pigment paste.

[0052] According to one embodiment, the supply line leading into the container leads into the container above its maximum fill level and ends in a nozzle.

[0053] The oxidizing agent is preferably introduced into the interior of the container via an adapter, which is essentially tightly sealed at its top with the lid part of the container and at its bottom with the side wall of the container, e.g. in the form of an extension piece for a pipe. The adapter can be designed as a component of the container lid. The adapter comprises a supply line with an outlet opening through which the oxidizing agent can be fed into the interior of the container. The outlet opening can be designed as a nozzle. According to a preferred embodiment of the invention, a protective cap is located at the outlet opening in the adapter, which opens towards the container bottom. The protective cap prevents contamination and the resulting blockage of the outlet opening when filling the container with new emulsion paint or pigment paste. Suitable adapters are described, for example, in the

[0054] Figures 3 to 8 and the corresponding character descriptions. While the Figures 3 to 8 Although the adapters shown are optimized for operation with ozone as the oxidizing agent, they can also be operated with any other liquid or gaseous oxidizing agents. The advantage of using adapters is that existing dosing systems can be easily converted for operation with the method according to the invention without complex measures (such as drilling holes in the container walls for the oxidizing agent supply).

[0055] It is also conceivable for the at least one container to have more than one supply line leading into the container. For example, the container can have two or more supply lines leading into the container. The supply lines can lead into the container at the same height, above the maximum fill level. This leads to a more even distribution. However, multiple supply lines per container can also lead into the container at different heights, for example, above and below the maximum fill level. This makes it possible to directly introduce the oxidizing agent into the emulsion paint or pigment paste and to treat the container above the maximum fill level. The supply lines can also each end in a nozzle.

[0056] According to a preferred embodiment of the invention, the at least one container is made of plastic. Plastics are well-suited as a material for containers because they are resistant to many oxidizing agents. The container is preferably made of polyoxymethylene (POM), polypropylene, polyethylene, polyethylene terephthalate, polyamide, or mixtures or blends thereof. These plastics have proven to be particularly resistant and durable. In addition to the aforementioned plastics, stainless steel can also be used as a material for the at least one container.

[0057] The at least one container can have a wide variety of shapes. According to one possible embodiment of the invention, the at least one container is cuboid-shaped. According to a preferred embodiment of the invention, the container is essentially cylindrical. A substantially cylindrical design of the container prevents deposits in the corners or edges of the container and increases protection against microbial contamination.

[0058] According to a further embodiment of the invention, the dosing system comprises at least two, preferably at least three or at least four containers. The containers can contain different emulsion paints or pigment pastes and be controlled via a common control device. In this way, different emulsion paints or pigment pastes can be handled from one control system, and the emulsion paints or pigment pastes can be precisely mixed with one another.

[0059] If the dosing system has multiple containers, the containers can be arranged in a carousel-like manner or stationary. Preferably, the multiple containers are arranged in a carousel-like manner. One or more buckets for holding the emulsion paints or pigment pastes can then be arranged concentrically along a central axis on a carousel. In this embodiment, the emulsion paints or pigment pastes from the multiple containers can be mixed particularly well with one another.

[0060] According to a further preferred embodiment of the invention, the supply line is made of a material containing at least one plastic selected from the group consisting of polyurethane (PUR), polytetrafluoroethylene (PTFE), perfluoroalkoxy polymer (PFA), polyvinylidene fluoride, perfluoro rubber, ethylene-tetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-chlorotrifluoroethylene, ethylene-propylene-diene rubber, and mixtures thereof. The material of the supply line can also consist of one of the aforementioned plastics. Materials containing or consisting of the aforementioned plastics are characterized by high stability against strong oxidizing agents. A supply line made of these materials thus has a long service life and a high degree of flexibility. In particular, a supply line made of the aforementioned materials is suitable for supplying hydrogen peroxide, sodium hypochlorite solutions, and / or ozone.

[0061] The supply line can, for example, comprise or consist of one or more hoses. The supply line can be formed by a hose system.

[0062] If the dosing system contains more than one container, the dosing system can also have more than one supply line leading into the container. Preferably, each container of the dosing system designed to store an emulsion paint or pigment paste has a supply line leading into the container.

[0063] According to a preferred embodiment, the dosing system according to the invention comprises an ozone generator. The ozone generator preferably comprises a voltage source, in particular a high-voltage generator, and a discharge unit. Ozone is preferably generated in the discharge unit by means of corona discharge. This form of ozone generation has proven particularly efficient.

[0064] According to one embodiment of the invention, the voltage source, in particular the high-voltage generator, and the discharge unit are arranged in the same device housing. This makes it possible for the corona discharge to take place at a central location in the dosing system and thus spatially separate from the at least one container. Ozone can thus be generated at a central location in the dosing system. The centrally generated ozone can then be distributed in the dosing system, preferably via the supply line leading to the at least one container. This embodiment generally comprises at least one ozone generator and optionally at least one pump, in particular a diaphragm pump, for transporting the ozone into the at least one container, preferably via the supply line. With the help of the pump, the at least one container is supplied with ozone via the supply line. The pump preferably generates an overpressure.The pump advantageously supplies at least one container evenly with the generated ozone.

[0065] The optional pump can be used to ensure that, in a dosing system with more than one container and when using an ozone generator in the immediate vicinity of the containers, all containers can be supplied with a sufficient amount of ozone.

[0066] According to a further embodiment of the invention, the voltage source, in particular the high-voltage generator, and the discharge unit are not arranged in the same device housing. Preferably, the discharge unit is in the container lid, preferably in an adapter of the container lid. According to this embodiment of the invention, ozone is preferably generated by means of corona discharge in the respective container lids. The container lids preferably have a lid part and an adapter for this purpose. In these adapters, the ozone is then generated by means of corona discharge. In this way, the path that the in situ generated ozone has to travel, thus maximizing the amount of reactive ozone available for preserving the emulsion paint or pigment paste.

[0067] What has been said above in connection with the process according to the invention applies accordingly to the production of ozone.

[0068] According to a particularly preferred embodiment of the invention, the dosing system is connected to a control device, preferably a computer, for the precise dosing of the emulsion paint or pigment paste.

[0069] The dosing system may further comprise a dosing valve. Preferably, the closable valve is a dosing valve. Furthermore, the dosing system may comprise a delivery line. The dosing system may also comprise a delivery pump. The emulsion paint or pigment paste can be introduced into the delivery line using the delivery pump. The dosing valve is preferably attached to the delivery line. If the dosing system comprises a dosing valve, the dosing valve is preferably connected to the control device. The emulsion paint or pigment paste can be conveyed through the delivery line from the container, preferably via a filling head, to a scale or into a bucket resting on the scale with the aid of a delivery pump, which is preferably also connected to the control device.Preferably, the scale is also connected to the control device to enable control of the feed pump and the dosing valve depending on the weighed amount of emulsion paint or pigment paste. In addition to gravimetric dosing, the quantity can alternatively be defined volumetrically via pumps, in particular dosing pumps such as gear pumps, reciprocating piston pumps, progressing cavity pumps, or diaphragm pumps. The advantage of this embodiment is that a scale can be dispensed with entirely.

[0070] The described dosing system enables particularly precise dosing of the emulsion paint or pigment paste, which can be used flexibly.

[0071] To ensure thorough mixing of the emulsion paint or pigment paste in the bucket on the scale, the scale can either be connected to a vibrator for homogeneous mixing, the bucket can be equipped with a stirring system, or the scale itself can have an integrated motion control system. A separate vibrating machine can also be used for homogeneous mixing. A pre-dosed bucket can be clamped into a vibrating machine and vigorously mixed using oscillating and rotating movements.

[0072] A keyboard or similar input device is connected to the control unit. This allows the dosing system to be controlled, and in particular, the dosing valves and feed pumps for the emulsion paint or pigment paste to be controlled according to the desired quantities.

[0073] In addition, the control device can be provided with a printer for a label to be attached to a bucket, with which the data can be printed on the label in a machine-readable format, for example as a barcode, in order to bill the emulsion paint filled into the bucket at the cash register after the label has been affixed.

[0074] The dosing system according to the invention is particularly suitable as a mixing system for paints, also " Paint mixing system ". A further aspect of the invention therefore relates to a paint mixing system with a dosing system according to one of claims 8 to 13.

[0075] In a dosing system for mixing paints, several containers are preferably controlled by a control system so that different emulsion paints or pigment pastes can be combined. For example, some containers may contain dispersions with fillers and / or polymer dispersions, while others contain dispersions with pigment. However, it is also possible for a container to already contain all the essential components for an emulsion paint as a concentrate and then become an emulsion paint by dilution with water. Furthermore, each of the containers can contain a pigment paste. Using the pigment pastes in the various containers, a base color, for example a white emulsion paint, can be tinted until the desired shade is achieved.

[0076] According to a preferred embodiment, the dispersion paints or pigment pastes consist of different colored pigment pastes, which are volumetrically combined in a prefabricated base material, which is already present in the sales container as a defined amount of material, in order to achieve the desired color tone.

[0077] Computer-assisted consultation and product selection result in a multitude of combination possibilities. For example, if a matte red interior paint is to be mixed, a high proportion of pigment red paste can be set using the input device, with smaller proportions of pigment blue paste and pigment black paste depending on the shade. The amount of base paint in the bucket is first tared on the scales using the input device. The control unit then controls the dosing valves and feed pumps accordingly. When the predetermined amount of pigment paste added to the bucket, as measured by the scales, is reached, the dosing valves close and the feed pumps switch off. The same process can also be carried out using volumetric dosing, although in this case the scales are omitted.

[0078] What has been said in connection with the method according to the invention for the oxidizing agent and for the introduction of the oxidizing agent also applies equally to the dosing system according to the invention.

[0079] What has been said in connection with the process according to the invention for emulsion paint or pigment paste also applies equally to the dosing system according to the invention.

[0080] The dosing system according to the invention is particularly suitable for carrying out the method according to the invention.

[0081] The invention is explained in more detail below with reference to the drawings, which, however, serve only for illustrative purposes and are not limiting. Fig. 1 shows an embodiment of the dosing system according to the invention, Fig. 2 shows a container in cross section according to an embodiment of the dosing system according to the invention with a central ozone generator, Fig. 3 shows a container in cross section according to an embodiment of the dosing system according to the invention with ozone generation in the lid of the container, Fig. 4 shows a container in cross section according to an embodiment of the dosing system according to the invention with a central ozone generator, Fig. 5 shows a container in cross section according to an embodiment of the dosing system according to the invention with ozone generation in the lid of the container, Fig. 6 shows a container in cross section according to an embodiment of the dosing system according to the invention with a central ozone generator, Fig. 7a shows a perspective view of an adapter of the container lid according to an embodiment of the invention with ozone generation in a central ozone generator, Fig.7bshows the container lid adapter. Fig. 7a in cross-section, Fig. 8a shows a perspective view of an adapter of the container lid according to an embodiment of the invention with ozone generation in the lid of the container, Fig. 8b shows the adapter of the container lid from Fig. 8a in cross section.

[0082] Fig. 1 shows a preferred embodiment of the dosing system according to the invention comprising several containers 1. The containers 1 each have a maximum fill level for an emulsion paint or pigment paste (in Fig. 1(not shown). Each container 1 also has a closable dosing valve 7 and a supply line for an oxidizing agent leading into the container 1, each supply line branching off from a ring line 4 feeding the individual supply lines. The ring line 4 and the supply lines are made of polyurethane. In the present case, eight cylindrical containers 1 made of polyoxymethylene, each with a volume of one liter, are arranged in a carousel-like manner, with the ozone being introduced into the respective container 1 through a nozzle 2 arranged at the end of each supply line. The ozone is generated centrally in an ozone generator 3, comprising a voltage source, in particular a high-voltage generator, and a discharge unit, with an output of 200 mg of ozone per hour and, as mentioned, is fed into the cylindrical containers 1 via the supply line through the nozzles 2 with the aid of a diaphragm pump 14.This allows approximately 2 mg of ozone to be introduced into each container 1 within five minutes. The emulsion paint or pigment paste contained in the cylindrical containers 1 is pumped out via feed pumps 5 and discharged along feed lines 6. The dosing valves 7 built into the feed lines 6 enable the precise dosing of the emulsion paint or pigment paste contained in the containers 1. After passing through the dosing valve 7, the emulsion paints or pigment pastes are transported via the feed lines 6 to a filling head 8 and from there into a bucket 9. The bucket 9 rests on a scale 10. The feed pumps 5, the dosing valves 7, and the scale 10 are connected via the control line 11 to a computer 12, which controls the precise dosing of the emulsion paint or pigment paste. The computer 12 is also connected to a printer 13, which is suitable for printing labels.

[0083] Fig. 2shows a container in longitudinal section according to an embodiment of the dosing system according to the invention with an external ozone generator. In the external ozone generator 103, comprising a voltage source, in particular a high-voltage generator, and a discharge unit, the oxidizing agent ozone is generated and, with the aid of a diaphragm pump 118, passes via the polyurethane supply line 104 through the nozzle 102 into the cylindrical container 101 made of polyoxymethylene into the gas space above the surface 114 of an emulsion paint or pigment paste located in the container 101. The surface 114 of the emulsion paint or pigment paste coincides here with the maximum fill level of the container 101. The cylindrical container 101 is equipped with a lid 115 and a side wall 116. The emulsion paint or pigment paste located inside the cylindrical container 101 is mixed by the agitator 117.The emulsion paint or pigment paste is pumped out of the container 101 along the feed line 106 using the feed pump 105.

[0084] Fig. 3shows a container 201 in longitudinal section according to an embodiment of the dosing system according to the invention with ozone generation in an adapter 215b as a component of the container lid 218. For this purpose, air, oxygen, or an oxygen-containing gas mixture, hereinafter referred to as the "oxygen gas mixture," is introduced through the opening 219 into the interior of the adapter 215b, in which a discharge unit 203 is arranged, which is connected to a high-voltage generator via the high-voltage connection 220. The ozone / air, ozone / oxygen, or ozone / oxygen gas mixture produced in the discharge unit passes along the supply line 221 into the interior of the cylindrical container 201 and there into the area above the surface 214 of an emulsion paint or pigment paste located in the container 201. The cylindrical container 201 is equipped with a lid 218 comprising lid part 215a and, as mentioned above, adapter 215b as well as with a side wall 216.The emulsion paint or pigment paste contained inside the cylindrical container 201 is mixed by the agitator 217. The emulsion paint or pigment paste is pumped out of the container 201 along the delivery line 206 by means of the feed pump 205.

[0085] Fig. 4shows a container in longitudinal section according to an embodiment of the dosing system according to the invention with an external ozone generator. In the external ozone generator 103, comprising a voltage source, in particular a high-voltage generator, and a discharge unit, the oxidizing agent ozone is generated and, with the aid of a diaphragm pump 118, passes via the polyurethane supply line 104 through the nozzle 102 into the cylindrical container 101 made of polyoxymethylene into the gas space above the surface 114 of a dispersion contained in the container 101. The nozzle 102 is directed towards the container bottom. This nozzle arrangement prevents contamination of the nozzle 102 when filling the container 101 with the emulsion paint or pigment paste. The surface 114 of the emulsion paint or pigment paste coincides here with the maximum fill level of the container 101. The cylindrical container 101 is equipped with a lid 115 and a side wall 116.The emulsion paint or pigment paste contained inside the cylindrical container 101 is mixed by the agitator 117. The emulsion paint or pigment paste is pumped out of the container 101 along the delivery line 106 by means of the feed pump 105.

[0086] Fig. 5shows a container 201 in longitudinal section according to an embodiment of the dosing system according to the invention with ozone generation in an adapter 215b as a component of the container lid 218. For this purpose, the oxygen gas mixture is introduced through the opening 219 into the interior of the adapter 215b, in which a discharge unit 203 is arranged, which is connected to a high-voltage generator via the high-voltage connection 220. The ozone / air, ozone / oxygen, or ozone / oxygen gas mixture produced in the discharge unit passes along the supply line 221 into the interior of the cylindrical container 201 and there into the area above the surface 214 of an emulsion paint or pigment paste located in the container 201. At the outlet opening 215e of the supply line 221, through which the ozone / air, ozone / oxygen or ozone / oxygen gas mixture enters the interior of the cylindrical container 201, there is a downwardly open protective cap 222.The protective cap 222 prevents contamination and the resulting blockage of the outlet opening 215e when filling the container 101 with emulsion paint or pigment paste. The cylindrical container 201 is equipped with a lid 218 comprising a lid part 215a and, as mentioned above, adapter 215b, as well as a side wall 216. The emulsion paint or pigment paste located inside the cylindrical container 201 is mixed by the agitator 217. The emulsion paint or pigment paste is pumped out of the container 201 along the feed line 206 by means of the feed pump 205.

[0087] Fig. 6shows a container in longitudinal section according to an embodiment of the dosing system according to the invention with an external ozone generator. The ozone is introduced into the interior of the container 201 via an adapter 215b as a component of the container lid 218. In the external ozone generator 203, comprising a voltage source, in particular a high-voltage generator, and a discharge unit, the oxidizing agent ozone is generated and, with the aid of a diaphragm pump 218, reaches the adapter 215b via the polyurethane supply line 204. The supply line 204 is connected to the adapter 215b via a connecting piece 223. The ozone passes through the supply line 221 into the cylindrical container 201 made of polyoxymethylene, into the gas space above the surface 214 of an emulsion paint or pigment paste located in the container 201.At the outlet opening 215e of the supply line 221, through which the ozone enters the interior of the cylindrical container 201, there is a downwardly opening protective cap 222. The protective cap 222 prevents contamination and the resulting blockage of the outlet opening 215e when filling the container 101 with emulsion paint or pigment paste. The cylindrical container 201 is equipped with a lid 218 comprising a lid part 215a and, as mentioned above, adapter 215b, as well as a side wall 216. The side wall 216 located inside the cylindrical container 201.

[0088] Dispersion paint or pigment paste is mixed by the agitator 217. The dispersion paint or pigment paste is pumped out of the container 201 along the conveying line 206 by means of the conveying pump 205.

[0089] Fig. 7a and 7bshow an adapter 215b for use in a dosing system according to the invention with an external ozone generator. The adapter 215b comprises a connecting section 215c and an annular section 215d connected thereto. The annular section 215d is designed such that it is substantially tightly sealed at its top with the lid part 215a and at its bottom with the side wall of the container 201. The connecting section 215c has a connecting piece 223 for a gas supply line, via which the adapter 215b can be connected to the ozone supply line 204. The connecting section 215c comprises a supply line 221, via which the ozone is guided through the outlet opening 215e into the interior space defined by the annular section. At the outlet opening 215e there is a downwardly opening protective cap 222 which prevents emulsion paint or pigment paste from entering the outlet opening when the container 201 is filled.

[0090] Fig. 8a and 8bshow an adapter 215b for use in a dosing system according to the invention with ozone generation in the adapter 215b as a component of the container lid 218. The adapter 215b comprises a connection section 215c and an annular section 215d connected thereto. The annular section 215d is designed such that it is substantially tightly sealed at its top with the lid part 215a and at its bottom with the side wall of the container 201. A discharge unit 203 is arranged inside the connection section 215c and is connected to a high-voltage generator via the high-voltage connection 220. The connection section 215c comprises a supply line 221, via which the ozone / air, ozone / oxygen, or ozone / oxygen gas mixture formed in the discharge unit is guided through the outlet opening 215e into the interior space defined by the annular section.At the outlet opening 215e there is a downwardly opening protective cap 222 which prevents emulsion paint or pigment paste from entering the outlet opening when the container 201 is filled.

[0091] The Figures 2 to 8The containers and adapters shown are suitable for operation with gaseous oxidizing agents such as ozone. However, they can also be operated with any other oxidizing agents described herein, in particular with liquid oxidizing agents. The material information contained in the figure descriptions (such as polyoxymethylene for the container or polyurethane for the supply line) is not essential for the implementation of the invention and can be replaced by any other suitable materials, in particular the materials described herein. The shape information contained in the figure descriptions (such as cylindrical container) is also not essential for the implementation of the invention and can be replaced by any other suitable shapes (such as cuboid containers, etc.).Nor, for example, are the exact number and position of the oxidant supply lines inside the container or adapter indicated in the descriptions of the figures essential for the implementation of the invention and can be varied accordingly, in particular as described herein. List of reference symbols

[0092] 1Container 2Nozzle 3Ozone generator 4Supply line 5Feed pump 6Feed line 7Dosing valve 8Filling head 9Bucket 10Scale 11Control lines 12Computer 13Printer 14Diaphragm pump 101Vessel 102Nozzle 103Ozone generator 104Feed line 105Feed pump 106Feed line 114Dispersion surface 115Cover 116Side wall 117Agitator 118Diaphragm pump 201Vessel 203Discharge unit 205Feed pump 206Feed line 214Dispersion surface 215aCover part 215bAdapter 215cConnection section 215Densing section 215eOutlet opening 216Side wall 217Agitator 218Vessel cover 219Opening 220High-voltage connection 221Feed line 222Protective cap 223Connection nozzle

Claims

1. Process for preserving an emulsion paint or a pigment paste in a metering apparatus, the emulsion paint or pigment paste being stored in a container (1, 101, 201) which is part of the metering apparatus, in which a gaseous oxidant is introduced into the container (1, 101, 201), characterized in that the gaseous oxidant is introduced into the gas space above the surface (114, 214) of the emulsion paint or pigment paste into the container (1, 101, 201).

2. Process according to claim 1, characterized in that the oxidant is introduced into the container at periodic intervals, in particular at least once a month or at least twice a month or at least three times a month or at least once a week, or at least once a day, and / or characterized in that 0.1 to 200 mg, in particular 0.5 to 100 mg or 1 to 50 mg, calculated per liter of container volume, of the oxidant is introduced per introduction.

3. Process according to either of the preceding claims, characterized in that the emulsion paint or pigment paste is mixed after the introduction of the oxidant, in particular by stirring.

4. Process according to any of the preceding claims, characterized in that the oxidant has a standard potential of 0.1 V or higher, preferably 0.5 V or higher, more preferably 1 V or higher with respect to the standard hydrogen electrode at a temperature of 25°C and at an effective concentration of 1 mol l-1 and / or at an ion activity of 1 or, in the case of gaseous reactants, at a partial pressure of 101.325 kPa.

5. Process according to any of the preceding claims, characterized in that the oxidant is an oxygen- or chlorine-based oxidant or a mixture thereof, in particular is selected from the group consisting of sodium hypochlorite, potassium hypochlorite, Javel water, chlorine, hydrogen peroxide, ozone, peroxyacetic acid, perborate, percarbonate, and mixtures thereof.

6. Process according to any of the preceding claims, characterized in that the oxidant is ozone, the ozone optionally being generated centrally in the metering apparatus or in the lid (218) of the at least one container (201), in particular by means of corona discharge.

7. Process according to any of the preceding claims, characterized in that the emulsion paint or pigment paste is substantially free of preservatives before the introduction of the oxidant.

8. Metering apparatus for preserving an emulsion paint or pigment paste, comprising at least one container (1, 101, 201) designed for storing an emulsion paint or pigment paste and having a maximum fill level (114, 214) for the emulsion paint or pigment paste, a closable metering valve (7) and at least one supply line (4, 104, 221) for a gaseous oxidant leading into the container (1, 101, 201), characterized in that the supply line (104, 221) leading into the container (1, 101, 201) leads into the container (1, 101, 201) above its maximum fill level (114, 214).

9. Metering apparatus according to claim 8, characterized in that the container (1, 101, 201) has means for mixing (117, 217) an emulsion paint or pigment paste, in particular an agitator.

10. Metering apparatus according to either of claims 8 or 9, characterized in that the supply line (104, 221) leading into the container (1, 101, 201) ends in a nozzle (102).

11. Metering apparatus according to any of claims 8 to 10, characterized in that the at least one container has more than one supply line leading into the container, the supply lines leading into the container at the same level or leading into the container at different levels, preferably above and below the maximum fill level.

12. Metering apparatus according to any of claims 8 to 11, characterized in that the at least one container (1, 101, 201) is made of plastics material or stainless steel, in particular of polyoxymethylene (POM), polypropylene, polyethylene, polyethylene terephthalate, polyamide, or mixtures or blends thereof, and / or characterized in that the supply line (104, 221) is made of a material containing a plastics material selected from the group consisting of polyurethane (PUR), polytetrafluoroethylene (PTFE), perfluoroalkoxy polymer (PFA), polyvinylidene fluoride, perfluoro rubber, ethylene-tetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-chlorotrifluoroethylene, ethylene-propylene-diene rubber, and mixtures thereof.

13. Metering apparatus according to any of claims 8 to 12, characterized in that the metering apparatus comprises an ozone generator (3, 103) which, in particular, comprises a voltage source, in particular a high-voltage generator, and a discharge unit (203) which in particular generates ozone by means of corona discharge, the voltage source, in particular the high-voltage generator, and the discharge unit (203) optionally not being arranged in the same device housing, the discharge unit (203) in particular being in an adapter (215b) of the container lid (218).

14. Paint mixing apparatus comprising a metering apparatus according to any of claims 8 to 13.