The present invention relates to the field of coating objects. More specifically, the invention relates to a method for continuously cleaning and pre-treating objects made of plastic materials and/or metallic materials followed by a coating step. The invention also provides a system designed for carrying our said method. Finally, the invention provides a specific cleaning preparation to be used in the initial pre-treatment step and in the total coating process.

Technical Background

Methods for coating objects made by plastic materials and/or metallic materials are widely used in modern society. There is also a continuous and increasing demand for advanced products comprising such coated plastic and/or metallic objects. However, such methods are quite often associated with substantial drawbacks.

Accordingly, standard methods for coating such objects are quite energy consuming and release large quantities of paint comprising organic solvents into the atmosphere. Furthermore, such coating processes are often unreliable and large amounts of coated objects are discarded due to problems in the coating process. Plastic parts or objects are typically manufactured in several steps. The first step comprises moulding or extrusion of the plastic object by any known plastic injection method, the second step comprises lacquering of the object by any generally known method, and the third step comprises any generally known printing method. In previously known methods, plastic and/or metallic parts are typically manufactured in several steps. The first step comprises moulding by any known method. The product is packed on tape on reel, in container, or any other known packaging method after moulding. The parts are then moved to the next station which is directed to surface treatment where the parts could be treated by any known method such as plasma treatment, and/or lacquering and/or decoration of the parts.

Products that are handled in free atmosphere are exposed to contamination due to logistic processes before surface treatment. They may accordingly be exposed to dust, fibres, protein, bacteria, hair, etc. The product itself is typically electrically loaded due to friction etc, which increases adhesion of contaminating objects and compounds. There are different methods in use for cleaning of surfaces. Examples of devices and methods in use are carbon fibre brushes, cupper wires, antistatic polarisation equipment, dry cleaning including surfactants, and blasting with fluids, ice crystals or sand. US 6030663, US 6200943, US 6297206,

US6763840, and US 6099396 all describe examples of dry cleaning surface treatment methods and blasting with a fluid and where surfactants as well as carbon dioxide are involved.

Contamination before coating causes reject of finished parts for estetical reasons (for example loss of coating, uneven surface, etc.), optical reasons (for example lenses and displays are not transparent and/or does not have specified optical characteristics) and functional reasons (for example not specified isolation characteristics leading to battery and electricity problems). Using technology according to the state of the art could lead to a rejection level of 50 % of the coated products. Contamination before coating is thus a serious and substantial problem.

The plastics objects are conventionally lacquered in an open spray system, a dip system, Inmould labeling or Inmould Decoration Moulding system. These systems are open to the atmosphere. During the spray lacquering process, over-spray of paint occur. Such over-spray of paint constitutes an

environmental problem and thus additional equipment is necessary to prevent the paint from being released to the atmosphere as well as keeping the system itself clean from over-sprayed paint.

In WO 03/049929 a single tool for injection moulding as well as painting of an object is disclosed. In an injection moulding station the object is moulded between a turnable mould part and a stationary mould part. The turnable mould part with the object is rotated 90° to another station where paint is applied to the object, with the object still placed on the turnable mould part. In additional stations the paint applied to the object is UV hardened and then the object is ejected from the turnable mould part. Finally, the turnable mould part is rotated back to the injection moulding station to start the cycle again.

The advantage of the system of WO 03/049929 is that there is only one machine for production and painting of the plastic object without the need to transport the object from an injection moulding machine. However, the injection moulding step is essentially faster than the painting and hardening step. Thus, by using such a combined injection moulding and painting machine, cycle times are expanded and productivity reduced. Furthermore, the turnable movable part might be contaminated with paint and thus has to be cleaned from time to time in order to avoid damages of the objects during the injection moulding step.

WO 2005/075170 discloses a system for producing and coating an object, comprising a manufacturing machine and an object treatment device wherein said object treatment device comprises a painting station with means for applying a coating to a surface of said object, at least another station for treating said object and a conveyor which allows said object to move between the stations. Most stations (except the loading station) are typically located within an enclosure comprising means for creating a controlled atmosphere. Accordingly, the system of WO 2005/075170 is more efficient compared to the disclosure of WO 03/049929.

As already mentioned, a major problem in this field that remains to be solved is to reduce the amount of finished coated products and parts that are rejected. Contamination before coating causes reject for esthetical, optical (malfunctioning lenses and displays), and functional (isolation of batteries and electrical items) reasons. As already mentioned, reject due to contamination could reach the level of 50 % of the coated products. A recent proposed solution to this problem is to add a primer layer to the surface to be coated before the actual coating operation begins. This primer layer covers any remaining contamination. However, the chemical compounds required for applying such a layer are harmful and environmellaly unfriendly. Accordingly, there is a need for improved systems and methods for which the amount of rejects could be reduced and the environmental impact would be minimized.

Summary of the invention

In a first aspect, the present invention provides a method for producing and coating a specific surface of moulded plastic object, comprising the steps of: a) producing said object in a manufacturing machine according to per se known methods;

b) transferring said object into and through a tunnel comprising at least three, optionally four or five consecutive partially separated chambers in the direction A to E, where chambers A and E each comprises an opening to the surroundings, the consecutive chambers of the tunnel having a controlled atmosphere obtained by injection, said injection of controlled atmosphere being set up in such a way that the net air transport in said tunnel is directed from chamber B to A and out to the surroundings as well as from chamber E and out to the surroundings, during which transferring the object receives a treatment comprising: applying, in chamber A, a microemulsion comprising a cleaning agent to said specific surface;

rinsing, in chamber B, said specific surface with a volatile rinsing agent capable of removing said microemulsion from said specific surface;

optionally drying, in optional chamber C, in such a way that said volatile rinsing agent is removed from said specific surface; and

optionally adjusting, in optional chamber D, the temperature of said specific surface to the temperature of subsequent coating step; and

c) transferring said moulded plastic object from any of chambers B - D to chamber E and coating said specific surface according to per se known methods.

In a second aspect, the invention provides an apparatus for coating a surface of a moulded plastic object in accordance with the method of the first aspect, said apparatus comprising a tunnel comprising at least three, optionally four or five consecutive partially separated chambers in the direction A to E, where chambers A and E each comprises an opening to the surroundings, the consecutive chambers of the tunnel having means for achieving a controlled atmosphere obtained by injection, said injection of controlled atmosphere being set up in such a way that the net air transport in said tunnel is directed from chamber B to A and out to the surroundings as well as from chamber E and out to the surroundings,

said tunnel having a means for transferring a moulded plastic object to be coated from the entrance opening outside chamber A to the exit opening outside chamber E,

chamber A having means, such as one or more nozzles, for applying a microemulsion comprising a cleaning agent,

chamber B having means, such as one or more nozzles, for injecting a rinsing agent,

optional chamber C having drying means such as a source of infrared radiation or means for injecting a drying agent, such as one or more nozzles, optional chamber D having temperature adjusting means such as heating or cooling means, and chamber E having per se known coating means.

In a third aspect, the present invention provides a system for controlling an apparatus according any of claims 8 and 9, said system comprising:

a plurality of sensors for detecting presence and/or motion of an object to be coated;

a plurality of sensors for detecting flow and direction of a gas stream; means for controlling application of a microemulsion comprising a cleaning agent in chamber A;

means for controlling injection means, such as one or more nozzles, for injecting a rinsing agent in chamber B;

a plurality of temperature sensors;

optionally means for controlling drying means in optional chamber C; optionally means for controlling temperature adjusting means in optional chamber D; and

a control and calculation means;

said plurality of sensors for detecting presence and/or motion of an object to be coated being set up to send information to the control and calculation means regarding when such an object is in a pre-determined position;

said plurality of sensors for detecting flow and direction of a gas stream being set up to send information to the control and calculation means regarding the gas flow in the chambers;

said plurality of temperature sensors being set up to send information to the control and calculation means regarding temperature in the chambers; said control and calculation means being set up to instruct said means for controlling application of a microemulsion comprising a cleaning agent in chamber A to apply said microemulsion when an object to be coated is transferred through chamber A;

said control and calculation means being set up to instruct said means for controlling said injection means in chamber B to provide injection of said rinsing agent when an object to be coated is transferred through chamber B; optionally said control and calculation means being set up to instruct said means for controlling drying means in optional chamber C to provide drying when an object to be coated is transferred through chamber C;

optionally said control and calculation means being set up to instruct said means for controlling temperature adjusting means to provide a predetermined temperature adjustment using data from said plurality of temperature sensors when an object to be coated is transferred through optional chamber D. In a fourth aspect, the present invention provides a composition for cleaning a plastic surface when preparing said surface for coating and/or printing, said composition being useful in the method of the first aspect, said composition being an oil-in-water microemulsion comprising:

a) 19 - 25% (wt) of a non-ionic surfactant component;

b) 2 - 6% (wt) of a hydrophobic component selected from hydrocarbons and/or fatty esters which are liquid at room temperature; and

c) 70 - 80% (wt) of a mixture of water and 0 - 80% (wt) of a lower alcohol such as butanol. In a fifth aspect, the present invention provides use of a composition according to the fourth aspect for cleaning a plastic surface when preparing said surface for coating and/or printing.

Detailed description of the invention

In a first aspect, the present invention provides a method for producing and coating a specific surface of moulded plastic object, comprising the steps of: a) producing said object in a manufacturing machine according to per se known methods;

b) transferring said object into and through a tunnel comprising at least three, optionally four or five consecutive partially separated chambers in the direction A to E, where chambers A and E each comprise an opening to the surroundings, the consecutive chambers of the tunnel having a controlled atmosphere obtained by injection, said injection of controlled atmosphere being set up in such a way that the net air transport in said tunnel is directed from chamber B to A and out to the surroundings as well as from chamber E and out to the surroundings, during which transferring the object receives a treatment comprising:

applying, in chamber A, a microemulsion comprising a cleaning agent to said specific surface;

rinsing, in chamber B, said specific surface with a volatile rinsing agent capable of removing said microemulsion from said specific surface;

optionally drying, in optional chamber C, in such a way that said volatile rinsing agent is removed from said specific surface; and

optionally adjusting, in optional chamber D, the temperature of said specific surface to the temperature of subsequent coating step; and c) transferring said moulded plastic object from any of chambers B - D to chamber E and coating said specific surface according to per se known methods.

The term "moulded plastic object" relates to any kind of moulded plastic object intended to be coated such an outer cover of an electronic device such as a mobile phone, spectacle frames, or packages intended for containing cosmetics. The present invention is well suited for production of coated plastic objects the surfaces of which have a high gloss. The moulded plastic objects may be produced by any per se known method for producing a moulded plastic object, such as injection moulding, extrusion moulding, metal pouring or rolling mill.

According to the method of the present invention, the object is transferred through a tunnel comprising at least three and optionally four or five consecutive partially separated chambers. Typically, when carrying out the method, the tunnel is arranged in an area have a controlled atmosphere such as a clean room. The tunnel is also adapted for containing a controlled atmosphere. By the expression "consecutive partially separated chambers" is meant that the chambers are not isolated from each other or from the surroundings. Typically, they are separated by walls containing openings. These openings may in turn typically be partially sealed by air knives or slidable doors, which slidable doors may be automatic. The controlled atmosphere may hence flow from one chamber to another and out into the clean room where the tunnel typically is located.

As already mentioned, the net air transport in the tunnel is directed from chamber B through chamber A and out to the surroundings. In case the tunnel comprises a chamber C and/or a chamber D the net air transport is directed from the chamber closest to chamber E, through remaining consecutive chambers and out to the surroundings through the partial opening in chamber A

The term "volatile rinsing agent" relates to an agent capable of removing the microemulsion comprising a cleaning agent. As the microemulsion typically is of the oil-in-water type, it is advantageous for cost and environmental reasons to use clean water and/or ethanol as a rinsing agent. Carbon dioxide in liquid and/or gaseous form and nitrogen are two other examples of rinsing agents. Clean water is preferred. In case gaseous agent is used as volatile rinsing agent, chamber C as well as the drying step carried out there can be dispensed with. In that case the object to be coated is directly transferred to chamber D, in case temperature adjustment is needed, or directly to chamber E in case no temperature adjustment is needed. It is advantageous that all of the microemusion applied in chamber A is removed from the object to be coated during the rinsing step in chamber B.

The drying step optionally carried out in optional chamber C is typically carried out by one or more mechanisms selected from ethanol spraying, streams of air or nitrogen, heat typically produced by infrared radiation or other conventional heating sources. In case a liquid rinsing agent is used in the rinsing step in chamber B, it is advantageous that the liquid rinsing agent is completely removed during the drying step in chamber C. The temperature adjustment step optionally carried out in optional chamber D is carried out using conventional heating or cooling means. What is important to consider are the temperature requirements of the final coating step in chamber E.

The term "controlled atmosphere" relates to gas compositions normally used in clean rooms, for instance when manufacturing semiconductor structures. Hence, the amount of particles in the controlled atmosphere should be very low. Clean air or inert gasses such as nitrogen or argon or mixtures thereof could be used. The skilled person knows how to select a suitable controlled atmosphere for a given situation.

Regarding methods for manufacturing, coating and printing said object according to per se known methods it is referred to the disclosure of WO 2005/075170 and methods referred to therein.

In a preferred embodiment the transferring of the moulded plastic object through said tunnel comprising chambers A - E is done in such a way that no reloading is carried out during the whole transfer operation and that the specific surface is only exposed to said microemulsion comprising a cleaning agent, said volatile rinsing agent, gaseous agents and the coating

composition of step c) during the whole transfer operation.

Typically, the object to be coated is hung under a conveyor (in case the object to be coated is to be coated from many directions). The object may be hung in such a way that it can be rotated in order to further improve coating from many different directions. Furthermore, the object can be arranged on a transporter such as a transport belt (in case the coating is to be applied from above). The conveyor or transport belt typically runs through the whole tunnel and no reloading is therefore necessary.

In a preferred embodiment, the microemulsion comprising a cleaning agent that is applied in chamber A is an oil-in-water microemulsion comprising: a) 19 - 25% (wt) of a non-ionic surfactant component;

b) 2 - 6% (wt) of a hydrophobic component selected from hydrocarbons and/or fatty esters which are liquid at room temperature; and

c) 70 - 80% (wt) of a mixture of water and 0 - 80% (wt) of a lower alcohol such as butanol.

Preferably, the non-ionic surfactant component is selected from the group of Berol 533, Berol 535, Berol 537, Berol Ox 91 -4, Berol OX 91 -6, AG6202, 2EH2PO4EO, Span 20, Span 80, Span 65, Span 85, Tween 20, Tween 80, Tween 65, Tween 85, Ethylan 1003, and Ethylan 1005.

Preferably, the hydrophobic component is selected from the group of isopropyl myristate, Methyl octanoate, heptane and cyclohexane. Preferably, the volatile rinsing agent in chamber B that is capable of removing said microemulsion from said specific surface is selected from pure water, pure ethanol, nitrogen, and liquid or gaseous carbon dioxide.

Preferably, the drying step in chamber C is carried out in a stream of air, nitrogen and/or carbon dioxide, optionally in combination with heat.

All chemicals used in relation to the present invention are of high, and preferably the highest commercially available quality and purity. It is especially important that the rinsing agent has a high purity.

In a second embodiment the present invention provides an apparatus for coating a surface of a moulded plastic object in accordance with the method of the first aspect,

said apparatus comprising a tunnel comprising at least three and optionally four or five consecutive partially separated chambers in the direction A to E, where chambers A and E each comprise an opening to the surroundings, the consecutive chambers of the tunnel having means for achieving a controlled atmosphere obtained by injection, said injection of controlled atmosphere being set up in such a way that the net air transport in said tunnel is directed from chamber B to A and out to the surroundings as well as from chamber E and out to the surroundings,

said tunnel having a means for transferring a moulded plastic object to be coated from the entrance opening outside chamber A to the exit opening outside chamber E,

chamber A having means, such as one or more nozzles, for applying a microemulsion comprising a cleaning agent,

chamber B having means, such as one or more nozzles, for injecting a rinsing agent,

chamber C having drying means such as a source of infrared radiation or means for injecting a drying agent, such as one or more nozzles,

chamber D having temperature adjusting means such as heating or cooling means, and

chamber E having per se known coating means.

The term "means for achieving a controlled atmosphere" typically relates to means for specific injection of said atmosphere in defined locations, Typically, such means could be nozzles for injecting gasses. In order to achieve the desired net transport of controlled atmosphere, such nozzles are arranged close to the opening between chambers D and E (or alternatively C and E in case chamber D is missing, or B and E in case both chambers C and D re missing). Hence an elevated pressure is obtained which initiates the gas transport.

The means for transporting the objects to be coated has been described in relation to the first aspect of the invention.

The means for injecting a microemulsion comprising a cleaning agent, as well as the means for injecting a rinsing agent could be any nozzle suitable for injecting liquids, preferably aqueous liquids. The nozzles are arranges in any suitable way in order to facilitate application of the microemulsion/rinsing agent. Likewise any means for injecting gasses in chambers B and C are ordinary nozzles that could be arranged in any suitable way. Typically, the drying means in chamber C is any suitable source of infrared radiation that is arranged in such a way that the area to be coated is efficiently dried.

The heating and/or cooling means of chamber E are also of standard type.

Preferably, chambers A - E are separated by separation means selected from the group of air knives and automatic sliding doors set up to open when an object to be coated is about to pass. In a third embodiment, the present invention provides a system for controlling an apparatus according any of claims 8 and 9, said system comprising:

a plurality of sensors for detecting presence and/or motion of an object to be coated;

a plurality of sensors for detecting flow and direction of a gas stream; means for controlling application of a microemulsion comprising a cleaning agent in chamber A;

means for controlling injection means, such as one or more nozzles, for injecting a rinsing agent in chamber B;

a plurality of temperature sensors;

means for controlling drying means in chamber C;

means for controlling temperature adjusting means in chamber D; and a control and calculation means;

said plurality of sensors for detecting presence and/or motion of an object to be coated being set up to send information to the control and calculation means regarding when such an object is in a pre-determined position; said plurality of sensors for detecting flow and direction of a gas stream being set up to send information to the control and calculation means regarding the gas flow in the chambers;

said plurality of temperature sensors being set up to send information to the control and calculation means regarding temperature in the chambers; said control and calculation means being set up to instruct said means for controlling application of a microemulsion comprising a cleaning agent in chamber A to apply said microemulsion when an object to be coated is transferred through chamber A;

said control and calculation means being set up to instruct said means for controlling said injection means in chamber B to provide injection of said rinsing agent when an object to be coated is transferred through chamber B; said control and calculation means being set up to instruct said means for controlling drying means in chamber C to provide drying when an object to be coated is transferred through chamber C;

said control and calculation means being set up to instruct said means for controlling temperature adjusting means to provide a pre-determined temperature adjustment using data from said plurality of temperature sensors when an object to be coated is transferred through chamber D.

The motion sensors, sensors for detecting flow and direction of gas streams as well as different control means are all standard components. The skilled person could easily select suitable such components. The control and calculation means is typically a micro-computer or a personal computer using standard interfaces.

In a fourth embodiment, the present invention provides a composition for cleaning a plastic surface when preparing said surface for coating and/or printing, said composition being useful in the method of the first aspect, said composition being an oil-in-water microemulsion comprising:

a) 19 - 25% (wt) of a non-ionic surfactant component;

b) 2 - 6% (wt) of a hydrophobic component selected from hydrocarbons and/or fatty esters which are liquid at room temperature; and c) 70 - 80% (wt) of a mixture of water and 0 - 80% (wt) of a lower alcohol such as butanol.

Preferably, the non-ionic surfactant component is selected from the group of Berol 533, Berol 535, Berol 537, Berol Ox 91 -4, Berol OX 91 -6, AG6202, 2EH2PO4EO, Span 20, Span 80, Span 65, Span 85, Tween 20, Tween 80, Tween 65, Tween 85, Ethylan 1003, and Ethylan 1005.

In principle it should be possible to include any non-ionic surfactant

component. However, it has turned out that good result can be obtained with non-ionic surfactants selected from the group of Berol 533, Berol 535, Berol 537, Berol Ox 91 -4, Berol OX 91 -6, AG6202, 2EH2PO4EO, Span 20, Span 80, Span 65, Span 85, Tween 20, Tween 80, Tween 65, Tween 85, Ethylan 1003, and Ethylan 1005. All these non-ionic surfactants are easy to obtail. Berol 533, Berol 535, Berol 537, Berol OX 91 -4, Berol OX 91 -6, Ethylan 1003, Ethylan 1005, AG6202 and 2EH2PO4EO are all readily available from Akzo Nobel Surface Chemistry AB, SE. Span 20, Span 80, Span 65, Span 85, Tween 20, Tween 80, Tween 65 and Tween 85 are all readily available from Croda International PLC. Particularly good results have been obtained for Berol 535, Berol OX 91 -4 and Berol OX 91 -6.

Preferably, the hydrophobic component is selected from the group of isopropyl myristate, Methyl octanoate, heptane and cyclohexane. In a fifth aspect the present invention provides use of a composition according to the fourth aspect, for cleaning a plastic surface when preparing said surface for coating and/or printing.

The present invention will now be further described with reference to the enclosed figures in which:

Figure 1 discloses an apparatus according to the second embodiment of the present invention; and

Figure 2 outlines a system for controlling the apparatus of Figure 1 . Referring now to Figure 1 , an apparatus 10 according for carrying out the method of the first aspect of the present invention is shown. An object to be coated 12 is attached to a conveyor 14. The conveyor 14 typically transports said object 12 through the whole apparatus 10 without any reloading operation. It is advantageous that the object 12 is hung under the conveyor 14 as it then is possible to coat the object 12 from several directions at the same time. In certain cases the object is mounted on a holder enabling rotation of the object (embodiment not shown). The holder is then transported through the tunnel by the conveyor. It is of course also possible to arrange the object 12 on top of the conveyor 14, or on a transport belt, especially if it is only desirable to coat the object 12 from above. Furthermore, irrespective of how the objects are transported through the tunnel, it is of course possible to treat more than one object at a time in a chamber of the tunnel.

The apparatus 10 shown in Figure 1 is a tunnel comprised of five consecutive chambers A, B, C, D and E. Chambers A and E both have partial openings 16, 18 to the surroundings outside the apparatus 10. There is a partial opening 20 between chambers A and B, a partial opening 22 between chambers B and C, a partial opening 24 between chambers C and D and a partial opening between chamber D and E. As already indicated, the term "partial opening" indicates that the openings are not completely sealed.

Typically, these openings 16, 18, 20, 22, 24, 26 may be partially sealed by air knives or slidable doors, which slidable doors may be automatic. The controlled atmosphere may hence flow from one chamber to another and out into the clean room where the tunnel typically is located. Object detectors 28, 30, 32, 34, 36, 38 monitor the presence of an object to be coated and typically sends signals to a control and calculation means 202 (only shown in Figure 2) in order to initiate door openings and/or treatment steps in the different chambers A - E. Chambers A, B, C and D are all associated with pre-treatment of the surface of the object 12 to be coated. Chamber E is associated with the actual coating operation. The pre-treatment of the object 12 to be coated that is carried out in chamber A is application of a microemulsion comprising a cleaning agent. The advantage of applying such a microemulsion is that such an emulsion is a good solvent for any kind of contamination that may be present on the surface to be coated. Microemulsions that could be used in connection with the present invention will be further described later on. The microemulsion is injected into chamber A from different nozzles 40. The embodiment shown in Figure 1 is focused on injection of the microemulsion as such an application is very efficient. However, it is of course possible to apply the microemulsion in other ways such as dipping the object into the emulsion or pouring the emulsion over the object.

The pre-treatment carried out in chamber B is rinsing. The rinsing step can be carried out by injecting liquid or gaseous rinsing agents through rinsing nozzles 42. As already mentioned, suitable liquid rinsing agents are clean water, ethanol or liquid carbon dioxide. Suitable gaseous rinsing agents are nitrogen or gaseous carbon dioxide.

In case a liquid rinsing agent such as water or ethanol has been used, it is advantageous to include a drying step. Typically, such a drying step is carried out in chamber C. Any suitable means for drying can be used. Typical examples of drying means are a source 44 of infrared radiation or gas streams blowing over the object 12 to be coated. In case carbon dioxide or another gaseous rinsing agent has been used in chamber B, it is not necessary to include any chamber C or the associated drying step.

After the drying step it is advantageous to adjust the temperature of the object 12 to be coated in case the temperature of the object differs substantially from what is recommended during the coating step. This temperature adjustment step, if needed, is carried out in chamber D and involves using means 48 for increasing the temperature as well as means 46 for reducing the temperature. Any suitable means adapted for the particular controlled atmosphere of the tunnel may be used. However, in case the object already has a suitable temperature it is also possible to exclude chamber D and the associated temperature adjustment treatment.

The actual coating treatment is carried out in chamber E by any suitable coating method.

There are two main net flows 52, 54 for the controlled atmosphere in the apparatus 10 and they are each associated with the two parts of the coating process. Accordingly flow 52 is associated with the pre-treatment part of the process. The flow starts from nozzles 56 close to the partial opening into chamber E. In case the apparatus 10 comprises a chamber D, nozzles 56 are located there. In case there is a chamber C but no chamber D, nozzles 56 are located in chamber C. In case both chambers C and D are absent, nozzles 56 are located in chamber B. Nozzles 58 for starting flow 54 are always located in chamber E.

Referring now to Figure 2, a simplified schetch of a control system 200 for the apparatus 10 shown in Figure 1 is shown. Accordingly, the central part system 200 is a control and calculation means 202. The control and

calculation means 202 is typically a personal computer or a microcomputer, and receives information from a variety of sensors. Examples of such sensors that are shown in Figure 2 are a location or motion sensor 204 for detecting and monitoring position and movement of an object to be coated, gas flow detection means 206 for determining amount and direction of a gas flow and temperature sensors 212. The control and calculation means 202 uses the information obtained from these sensors for controlling the apparatus 10 by sending instructions to a plurality of means, such as means 208 for controlling application of a microemulsion comprising a cleaning agent, means 210 for controlling injection of rinsing agent, means 214 for controlling drying means and means 216 for controlling temperature adjustment means. The sensors and means used in the system are of standard type and any commercially available such means and sensors could be included. The system renders it possible to automatize the process shown in Figure 1 . Furthermore, such a system also leads to increased efficiency and reduced environmental impact as chemicals are only injected when needed, and temperature is only adjusted when needed. Another important part of the present invention is the microemulsion comprising a cleaning agent that is applied in chamber A. In order to minimize the amount of rejects it is believed that it is important to remove all

contaminations of the surface to be coated before the final coating step is initiated. Furthermore, it is important to note that anything may contaminate such a surface. Water droplets, dust particles and traces of organic chemicals are all examples of contaminations that should be removed before the coating operation. Consequently, it is important that the cleaning compositions used in connection with the present invention has the ability of dissolving and/or physically removing a broad range of potential contaminations. It has turned out that microemulsions comprising a cleaning agent have such broad dissolving and removing characteristics.

Without wishing to be bound by at specific theory, it is assumed that the cleaning water-in-oil microemulsion or oil in water composition according to the present invention affects the surface of plastic and metallic objects in such a way that adhesion is prevented. Inclusion of a cleaning step using the cleaning composition of the invention before coating leads to higher productivity, higher yield but lower manufacturing costs. The fact that the combined cleaning and coating process is carried out in an enclosure and in a controlled atmosphere decreases environmental problems and hazards as well as energy consumption. In a verification test, yield increased from 69 % to 97%. The yield was measure on wear resistance (Ericsen test), optical effect (permeable for UV/visual light), surface defects per mm ² (measured by optical equipment) and influence of adhesion in the interface between coating and substrate (steel wool test).

After cleaning with the microemulsion comprising a cleaning agent, a rinsing step is carried out with a volatile rinsing agent in order to remove the microemulsion. As already mentioned, suitable rinsing agents may be pure water and ethanol as well as air, nitrogen and carbon dioxide in gaseous and supercritical form. A supercritical liquid is under such a high pressure that the border between liquid and gas has disappeared. The pressure and

temperature point above which supercritical liquids are formed is called the thermodynamical critical point. When conditions are approaching the critical point, the density of the gas phase becomes more and more similar to the density of the liquid phase until they are indistinguishable. Supercritical liquids may diffuse through solid materials as a gas but they may also dissolve other compounds as a liquid. Moreover, the density of a supercritical liquid may be regulated by changing temperature and/or pressure. Supercritical C02 may occur at pressures above 70 bar and at temperatures above room

temperature. It has turned out to be advantageous to use rinsing agents that easy to remove from the surface to be coated. Liquid rinsing agents such as water and ethanol are removed in a separate drying step that may comprise drying by heating or by a gas flow. In case gaseous or supercritical rinsing agents are used it is possible to dispense with a separate drying step.

Because of the reduced environmental impact, oil-in-water microemulsions are preferred in connection with the present invention in comparison with water-in-oil microemulsions. Oil-in-water microemulsions contains a

considerably lower amout of organic solvents. Furthermore excellent results are obtained when rinsing away oil-in-water microemulsions using pure water. The consumption of organic solvents is then very low indeed.

The present invention will now be further disclosed with reference to the following examples. Examples 1 - 7

The following microemulsions were formed mixing the ingredients followed by vigorous shaking. All percentages in the table are % (wt):

Plastic objects were dipped into one of the microemulsions above. Then they were immersed twice in ethanol. After each immersion, the objects were flushed with air. Finally, the objects were coated with lacquer.

The results were excellent and none of the objects were discarded.

Example 8: Pre-treatment and subsequent coating of plastic objects Surfaces of some plastic objects (10 surfaces of polycarbonate and 10 surfaces of polyamide 12, size: 100 x 35 mm, grooves in a square pattern) were processed in a tunnel comprising five consecutive chambers A - E. The following steps were carried out: Chamber A: The surfaces were each sprayed with 0.8 ml of the

microemulsion of example 7 for 1 .5 seconds at a temperature of 20°C. The microemulsions were allowed to interact with the surfaces for 20 seconds. Chamber B: The surfaces were sprayed three times and each time during 2 seconds with totally 450 ml water at a temperature of 20°C.

Chamber C: The surfaces were heated by infrared radiation during 140 seconds at a temperature of 40 °C. Chamber D: The surfaces were cooled in a controlled atmosphere comprising pure air for 180 seconds. Their temperature after cooling was 20 °C. There was a steady flow of pure air from chamber D through chambers C, B, and A out to the surroundings. The dryness of the surfaces were checked before the final coating step. Furthermore, one polycarbonate surface and one polyamide 12 surface were removed for further measurements.

Chamber E: The surfaces were coated with an organic solvent-based lacquer and thereafter cured in a heated chamber. There was a steady flow of pure air from chamber E out to the surroundings.

An inspection of the final result revealed that coatings on surfaces that were completely dry when the coating step in chamber E was initiated were of excellent quality. They were also unexpectedly glossy. Coatings on surfaces comprising taces of water/microemusion were not acceptable.

Example 9 Comparison of wetting angles for polycarbonate and polyamide 12 with and without pre-treatment with microemulsion/rinsing/drying

The wetting angle Φ for water was measured polycarbonate and polyamide 12 surfaces were some had been treated in accordance with what has been described in example 8, chambers A - D, and some had not been treated. The results are shown in Table 1 . Table 1

It is evident from Table 1 that the pre-treatment according to Example 8 results in reduction of the wetting angle for both materials. Without wishing to be bound by a particular theory it is presently believed that such change of the wetting characteristics is important for obtaining good coating results.