WO2013017552A1

WO2013017552A1 - Process for refinishing a transportation vehicle

Info

Publication number: WO2013017552A1
Application number: PCT/EP2012/064844
Authority: WO
Inventors: Antonius Hendrikus Gerardus Van Engelen; Maarten Van Pul; Daniël Simon RUIGROK
Original assignee: Akzo Nobel Coatings International B.V.
Priority date: 2011-08-02
Filing date: 2012-07-30
Publication date: 2013-02-07

Abstract

The invention relates to a process of refinishing a transportation vehicle comprising the steps of a) Providing an actinic-radiation curable ready-to-spray liquid coating composition comprising an ethylenically unsaturated radically polymerizable binder and a photoinitiator in a collapsible container made of flexible material which is impermeable for actinic radiation, and which container has a connection member adapted for connection to a paint spray gun, b) Connecting the container to a paint spray gun, c) Applying the liquid coating composition to at least a part of the surface of the transportation vehicle by spraying, and d) Curing the applied coating composition by irradiating it with actinic radiation.

Description

Process for refinishing a transportation vehicle

The present invention relates to a process of refinishing a transportation vehicle.

US 2003/209573 A describes a spraying device using a collapsible reservoir which can be attached to and detached from a spray gun. The reservoir is equipped with a valve device which has to be opened and closed manually. WO 2009/086335 A describes a method for producing a coating layer on a substrate, wherein a first component is introduced into a spray gun and atomized, and a second component is siphoned into the atomized stream.

The object of the invention is to provide a process of refinishing a transportation vehicle or a part thereof in a simple and time-saving fashion, and wherein unused coating material can be used later on for further repair jobs. The invention also seeks to provide a process which allows easy attachment and replacement of a paint container without exposing the contents to ambient air, or light, and without requiring additional steps upon attaching or detaching the paint container, or handling multiple components.

The object of the invention is achieved by a process of refinishing a transportation vehicle comprising the steps of

a) Providing an actinic-radiation curable ready-to-spray liquid coating composition comprising an ethylenically unsaturated radically polymerizable binder and a photoinitiator in a collapsible container made of flexible material which is impermeable for actinic radiation, and which container has a connection member adapted for connection to a paint spray gun,

b) Connecting the container to a paint spray gun, c) Applying the liquid coating composition to at least a part of the surface of the transportation vehicle by spraying, and

d) Curing the applied coating composition by irradiating it with actinic radiation.

The actinic-radiation curable ready-to-spray liquid coating composition used in the process according to the invention has a practically unlimited pot life and does not require metering and mixing of its components prior to application. It is also not necessary to include additional components into the composition before or after atomization in the spray gun. The coating composition is cured under the influence of actinic radiation, such as UV light or visible light. Especially with visible light-curing materials the risk for light exposure during handling is high. Such exposure during handling and preparation leads to premature curing reactions. This disadvantage is avoided by the described process. The cured coating exhibits the properties required for automobile coatings, such as good hardness, scratch resistance, elasticity, durability, resistance to water and solvents, and a good appearance, e.g. gloss. The cured coatings have also been found to be free of defects. Suitable actinic-radiation curable ready-to-spray liquid coating compositions comprise an ethylenically unsaturated radically polymerizable binder or binder solution and a photoinitiator. The coating composition is ready-to-spray. This means that all components required for application and curing are already present, including catalysts or initiators, optional additives, and optional diluents. Therefore, it is not required to mix in any further components prior to application to a substrate. This makes the process of the invention very convenient for the user, because the handling of multiple components is not required, and the exposure to potentially hazardous ingredients is minimized. Furthermore, because no mixing is required, any risk of mixing ratio errors is excluded. In the process according to the present invention, the curable composition applied can be a conventional UV-curable composition, for instance a UV- curable composition having a low volatile organic content (VOC), i.e. less than 450 grams solvent per litre, or preferably less than 420 grams solvent per litre of the composition.

Preferably, the curable composition comprises less than 40 wt.% volatile organic compounds, more preferably less than 30 wt.%. The composition can also contain water as volatile diluent.

If the curable composition comprises a volatile organic compound and/or water, this should be evaporated after the application of the composition.

Reactive diluents can be used instead of (part) of any water and/or volatile organic compounds, for example to adjust the viscosity of the curable composition. A reactive diluent usually is a monomer or a mixture of monomers that reacts with one or more of the other components in the composition. Well- known reactive diluents are esters of acrylic and/or methacrylic acid. Hereinafter the wording (meth)acrylic is used to indicate acrylic and/or methacrylic acid and their derivatives. Examples of reactive diluents are (meth)acrylic diluents, e.g., tripropylene glycol diacrylate (TPGDA), hexanediol diacrylate (HDDA), acrylated pentaerythritolethoxylate (PPTTA), and hydroxyethyl methacrylate (HEMA). Preferred reactive diluents are esters of (meth)acrylic acid and an alcohol having at least two hydroxyl groups and a molecular weight below 500. The use of reactive diluents reduces or eliminates VOC emission, as they are incorporated into the final film.

The actinic-radiation curable liquid composition may comprise oligomers or resins with a medium or relatively high molecular weight, for instance radiation- curable oligomers or resins. Polyester acrylate oligomers and resins were found to be suitable for use in the curable composition in the process according to the present invention. Examples of suitable commercially available polyester acrylate resins are: Craynor^® UVP-215, Craynor^® UVP-220 (both ex Cray Valley), Genomer^® 3302, Genomer^® 3316 (both ex Rahn), Laromer^® PE 44F, Laromer PE 56F, Laromer 8992, Laromer 8800 (ex BASF), Ebecryl^® 800, Ebecryl^® 810, Viaktin^® 5979, Viaktin^® VTE 5969, and Viaktin^® 6164 (100%) (all ex UCB).

Epoxy acrylate oligomers and resins were also found to be very useful in the curable composition in the process according to the present invention. Examples of commercially available epoxy acrylate resins are: Craynor^® UVE- 107 (100%), Craynor^® UVE-130, Craynor^® UVE-151 , CN^® 104 (all ex Cray Valley), Actilan 300, Actilan 320, Actilan 330, Actilan 360 (all ex Akzo Nobel), Photocryl^® 201 (ex PC resins), Genomer^® 2254, Genomer^® 2258, Genomer^® 2260, Genomer^® 2263 (all ex Rahn), UVP^® 6000 (ex Polymer technologies), and Ebecryl^® 3500 (ex UCB).

Polyether acrylate resins can also be used in the curable composition in the process according to the present invention. Examples of commercially available polyether acrylate resins are: Genomer^® 3456 (ex Rahn), Laromer^® PO33F (ex BASF), Viaktin^® 5968, Viaktin^® 5978, and Viaktin^® VTE 6154 (all ex Vianova).

Urethane acrylate oligomers and resins can also be used with great advantage in the curable composition in the process according to the present invention. Examples of commercially available urethane acrylate resins are: CN^® 934, CN^® 936, CN^® 976, CN^® 981 (all ex Cray Valley), Ebecryl^® 210, Ebecryl^® 230, Ebecryl^® 270, Ebecryl^® 2000, Ebecryl 8402, Ebecryl^® 8800 (all ex Cytec), UA VPLS^® 2308, UA VPLS^® 2989, Desmolux XP2738, Desmolux D200XP (all ex Bayer), Genomer^® 4258, Genomer^® 4312, Genomer^® 4652, and Genomer^® 4675 (all ex Rahn), NeoRad U25 (ex DSM). Other actinic radiation-curable compounds that are suitable to be used in the curable composition in the process according to the present invention are, e.g., unsaturated polyester resins, acrylated polyetherpolyol compounds, (meth)acrylated epoxidised oils, (meth)acrylated hyperbranched polyesters, silicon acrylates, maleimide-functional compounds, unsaturated imide resins, compounds suitable for use in photo-induced cationic curing, or mixtures thereof.

Further compounds that are suitable to be used are polyisocyanates like trimers of HDI, silane or epoxy compounds, phosphoric acid derivatives or compounds combining these functionality with ethylene unsaturationl functionality, which are known to improve adhesion or toughness.

In one embodiment, the coating composition comprises a (meth)acryloyl- functional polyurethane and an ester of (meth)acrylic acid and an alcohol having at least two hydroxyl groups and a molecular weight below 500.

In the radiation-curable composition also use may be made of a radiation- curable mixture of (a) photo-induced radical curing resin(s) and (b) photo- induced cationic curing resin(s). Such systems are sometimes called hybrid systems and may comprise, for example, acrylic oligomers as photo-induced radical curing resins, vinyl ethers as photo-induced cationic curing resins, and radical and cationic photoinitiators. In principle, all possible combinations of photo-induced radical curing resins and photo-induced cationic curing resins can be used in such hybrid systems.

Further, the actinic-radiation curable liquid composition comprises a photoinitiator or a mixture of photoinitiators. Examples of suitable photoinitiators that can be used in the radiation-curable composition according to the present invention are benzoin, benzoin ethers, benzylketals, α,α- dialkoxyacetophenones, a-hydroxyalkylphenones, a-aminoalkylphenones, acylphosphine oxides, benzophenone, thioxanthones, 1 ,2-diketones, and mixtures thereof. It is also possible to use copolymerisable bimolecular photoinitiators or maleimide-functional compounds. Co-initiators such as amine based co-initiators can also be present in the radiation-curable curable composition. Examples of suitable commercially available photoinitiators are: Esacure^® KIP 100F and Esacure^® KIP 150 (both ex Lamberti), Genocure^® BDK, Genocure^® CQ, Genocure^® CQ SE, Genocure^® EHA, Velsicure^® BTF, Quantacure^® BMS, Quantacure^® EPD (all ex Rahn), Speedcure^® EDB, Speedcure^® ITX, Speedcure^® BKL, Speedcure^® BMDS, Speedcure^® PBZ, Speedcure^® BEDB, Speedcure^® DETX (all ex Lambson), Cyracure^® UVI-6990, Cyracure^® UVI-6974, Cyracure^® UVI-6976, Cyracure^® UVI-6992 (all ex Union Carbide), CGI-901 , Irgacure^® 184, Irgacure^® 369, Irgacure^® 500, Irgacure^® 754, Irgacure^® 819, Darocur^® 1000, Darocur^® 1 173 (all ex Ciba Chemicals), and Lucirin^® TPO (ex BASF).

The total amount of photoinitiator in the composition is not critical; it should be sufficient to achieve acceptable curing of the composition when it is irradiated. However, the amount should not be so large that it affects the properties of the cured composition in a negative way. In general, the composition comprises between 0.1 and 10 wt.% of photoinitiator, calculated on the total weight of the composition.

In addition to the above-described materials, the coating composition used according to the invention may optionally comprise other polymeric and/or oligomeric binders and resins. Examples of suitable materials are vinyl polymers, i.e. polymers which are obtainable by the polymerization of olefinically unsaturated monomers; polyesters; polyamides; polycarbonates; polyurethanes; and modified cellulose based materials.

Examples of suitable organic solvents for the coating composition to be used according to the invention are hydrocarbons, such as toluene, xylene, Solvesso 100; ketones, such as acetone, 2-butanone, methyl amyl ketone, and methyl iso-amyl ketone; terpenes, such as dipentene or pine oil; halogenated hydrocarbons, such as dichloromethane or para-chlorobenzotrifluoride; ethers, such as ethylene glycol dimethyl ether, dipropyl ether, dibutyl ether, dipentyl ether, dioctyl ether; esters, such as ethyl acetate, ethyl propionate, n-butyl formate, n-butyl acetate, n-butyl propionate, n-butyl butyrate, the corresponding tert. -butyl, sec. -butyl, and iso-butyl esters, esters of linear or branched pentanol, hexanol, or octanol, such as 2-ethyl-hexanol; or ether esters, such as methoxypropyl acetate or ethoxyethyl propionate. Also mixtures of these compounds can be used.

In view of current and future legislation it is preferred that the composition used according to the invention has a low content of volatile organic compounds (VOC). Examples of suitable VOC values are 500 g/l or less, 420 g/l or less, or 250 g/l or less.

The coating composition used according to the invention may further comprise other ingredients, additives or auxiliaries commonly used in coating compositions, such as pigments, dyes, surfactants, pigment dispersion aids, levelling agents, wetting agents, anti-cratering agents, antifoaming agents, antisagging agents, heat stabilizers, light stabilizers, UV absorbers, antioxidants, and fillers. When the process is implemented to apply the coating composition as a primer or primer-surfacer, the composition preferably also comprises an adhesion promoting agent. Examples of adhesion promoting agents are carboxylic acid-functional materials, silanes, and phosphoric acid functional materials. In the process of refinishing of a transportation vehicle according to the invention, the coating composition can be applied to an automobile or a part thereof. The process is suitable for refinishing the entire automobile. Alternatively, it is possible to refinish damaged panels or replacement parts. In still another embodiment, refinishing can be carried out to repair small scratches or dents without refinishing an entire body panel. The latter method is generally referred to as spot repair. Application of the coating composition is accomplished by spraying with a paint spray gun. The term transportation vehicle includes, without limitation, automobiles, trucks, buses, airplanes, railroad vehicles, and agricultural machines. Coatings on automobiles generally are multi-layer coating systems. The coating composition can be used according to the invention in any of the layers applied during the process of refinishing. In one embodiment, the coating composition is applied as a top coat in a multi-layer lacquer coating. The top coat may be a pigmented top coat. In this case pigments are included in the coating composition. Alternatively, the top coat may be a clear coat. Clear coats are generally applied on top of a colour- and/or effect-imparting base coat layer. In still another embodiment, the coating composition is applied as a primer and/or filler, or as a so-called primer-surfacer. In the latter case, the coating composition suitably comprises anti-corrosive pigments, optionally in combination with fillers.

After application of the coating composition the coating layer cures under the influence of actinic radiation. Curing is generally carried out in a temperature range of 0°C to 80°C. In one embodiment, curing is carried out at ambient temperature, i.e. in the range of about 15°C to about 25°C. In another embodiment, curing is carried out in a heated curing chamber, for example at a temperature of 40°C to 60°C. The curable composition used in the process according to the present invention is actinic radiation-curable. Within the framework of the present invention, an actinic radiation-curable composition is a composition which is cured using electromagnetic radiation having a wavelength λ≤ 500 nm or electron beam radiation. An example of electromagnetic radiation having a wavelength λ≤ 500 nm is UV radiation. Radiation sources which may be used are those customary for electron beam and UV. For example, UV sources such as high-, medium-, and low-pressure mercury lamps can be used. Also, for instance, gallium and other doped lamps can be used, especially for pigmented compositions. Also (UV) light emitting diodes (LEDs) can be used as source of actinic radiation. It is also possible to cure the composition by means of short light pulses and by daylight curing.

In a particular embodiment, the coating composition is applied with a spraying device comprising a spray nozzle, a feed line, and a collapsible paint container, wherein the feed line extends between the spray nozzle and an open end surrounded by a first connection member to connect the open end of the feed line to a corresponding second connection member surrounding an opening of the collapsible paint container, wherein the paint container is provided with a closing valve to close off the opening of the paint container and wherein the first connection member is provided with a member acting on the valve to cause its being opened when the first and second connection members are mutually connected and to cause its being closed when the the first and second connection members are mutually disconnected.

This way, the paint contents in the container are effectively protected against open air influences, even when the paint container is temporarily replaced by a paint container containing paint of another type or colour. When the paint container is attached to the spraying device, the valve automatically opens. When the paint container is taken off the spraying device, the closing valve is automatically closed again. Later on, it can be used again to spray out the rest of the paint contents, which are still unaffected by oxygen or moisture. Due to the compressibility or collapsibility of the paint container, it can be emptied without air supply, and so during spraying the paint in the container is not contacted with air or moisture either.

The process according to the invention requires less time to prepare the spraying device before painting. The paint containers, which can be used as disposable cartridges, do not have to be cleaned. Paint which is not sprayed out is left in the air-tight paint container, and since the paint containers can be re- closed in an air-tight fashion, they can be stored for further use next time, so waste and spoiling of paint is minimized. The container and the paint spray gun are suitably disconnected after the coating composition has been applied by spraying. In one embodiment, the container and the paint spray gun remain connected until the entire content of the container has been applied, either in the course of a single repair job, or in the course of several repair jobs, between which the container and the spray gun remain connected.

Alternatively, the spray gun and the container may also be disconnected before the entire content of the container has been applied. Due to the fact that the opening of the container is automatically closed when the container is disconnected from the spray gun, the content of the container remains sealed. Neither components from the surrounding atmosphere, nor UV light can deteriorate the actinic-radiation curable liquid coating composition in the container, and the partly emptied container can be stored until required for a following repair job.

The closing valve can for example comprise a closing member which is tightly pressed onto an inner ledge or shoulder along the inner diameter of the opening by a resilient member, such as a coil spring. For better closing off of the opening, the closing member can have a convex surface to be pressed against the shoulder. Optionally, the closing member may have the shape of a ball. To open the container, the first connection member can be provided with a protrusion or finger to press the closing member away from the shoulder surrounding the opening of the paint container.

In an alternative embodiment, the closing valve may comprise a nipple with an outer screw thread and a cap with an inner screw thread cooperating with the outer screw thread of the nipple, the nipple having a top end provided with at least one opening and a protrusion which is in register with an opening in the top end of the cap, the opening being dimensioned to fit tightly over the protrusion. The first connection member has an opening to receive the cap. When the cap is put into the opening in the first connection member, the bag can be turned to screw the nipple out off the cap to open the valve. In order to prevent the cap from being rotated together with the nipple, the connection between the cap and the first connection member may be provided with a stop, or the outline of the cap may be made non-circular, matching a corresponding shape of the opening in the first connection member, or the cap may be held in place by friction. A bayonet catch can be used to prevent removal of the bag while it is still open.

In a further alternative embodiment, the closing valve can include a plug with a central bore leading from an outlet opening to an outer end provided with a narrowing inner diameter and a cap comprising a closed end and an open end defined by a profiled edge apt to form a snap joint in cooperation with the narrowing inner diameter of the plug's outer end, the cap being attached to the plug by flexible spokes. The first connection member at the inlet of the spray gun's feed line can then be provided with a hollow protrusion with a head dimensioned to fit tightly into the plug's cap and radial openings below the head. The hollow protrusion can be provided with a shoulder to cooperate with the narrowing inner diameter in the plug's inner bore to prevent further intrusion of the protrusion than is required for opening the plug's cap.

The first connection member can for example be a collar provided with an outer screw thread apt to cooperate with an inner screw thread of a collar around the paint container opening forming the second connection member. Alternatively, the first connection member can be a collar provided with an inner screw thread apt to cooperate with an outer screw thread of a collar around the paint container opening forming the second connection member. In a further alternative embodiment, the first and second connection members can form a bayonet catch. It is preferred that the connection members are implemented to allow for a closed system at any time, when connecting the container to a paint spray gun, during application of the coating composition, and when the container is disconnected from the paint spray gun.

The paint container can hang below the air supply line of the paint spray gun, or it can be located on top of it. In either case, the paint container may be stabilized by a supporting frame or holder made of rigid material. Alternatively, the paint container itself can be provided with one or more rigid parts to maintain it in the upright position when it is evacuated. If the paint container is used in the upright position, use can be made of gravity feed in addition to suction feed.

The container can be configured as a pouch of two or more walls of foil material, sealed along the outlines, leaving free only the outlet opening. The foil material can be made of polymeric material or of metal foil, such as aluminium, or it can be made of layers of different materials. As mentioned above, the container is collapsible. Preferably, the container can be completely emptied without creating a vacuum inside. This can be achieved by designing the container as a flat pouch made of flexible material.

Since the paint containers according to the present invention can be temporarily replaced and stored to be used again, the system allows the paint containers to be designed as easily replaceable cartridges. This way, modular sets of cartridges can be used, each cartridge containing a paint of a different type or colour. Such systems can for example include cartridges for a primer or various types of primers, base coats, clear coats, and the like.

The use of the collapsible container in the process of the invention can provide additional advantages in the factory where the radiation-curable liquid coating composition is prepared and filled into the container. The radiation-curable liquid coating composition may be introduced into the collapsible container either through the connection member, or through an additional filling port. In any case, the liquid coating composition can be introduced in to the container directly from the equipment wherein it is manufactured, without exposure to air, UV light, or day light. Hence, production of the coating composition and filling of the container can be carried out in a closed system. This is beneficial for the quality and consistency of properties of the delivered radiation-curable liquid coating composition. Furthermore, exposure of factory operators to components of the radiation-curable liquid coating composition, such as organic solvents, can be minimized or entirely avoided. The process allows handling of the coating composition in a closed system from production up to application. A UV-curable primer surfacer, Sikkens Autosurfacer UV, commercially available from Akzo Nobel Car Refinishes, was provided in a collapsible container as described above. The same coating material was also placed in commercial plastic cups (Sata Quick Cups) suitable for attachment to a paint spray gun. The plastic cups and the collapsible container filled with Sikkens Autosurfacer UV were stored for 5 minutes in a laboratory illuminated by daylight. The collapsible container and one of the plastic cups were stored at a distance of 0.5 m from the window, where the sum of UV A and UV B light intensity was 1 .5 mW/cm². A second plastic cup was stored for 5 minutes at a distance of 2.5 m from the window, where the sum of UV A and UV B light intensity was 0.8 mW/cm².

The coating material in the collapsible container was unchanged after this time. The same coating composition in the commercial plastic cup at 0.5 m distance from the window had increased in viscosity and contained visible gelled particles.

The same coating composition in the commercial plastic cup at 2.5 m from the window contained some thickened material on the walls of the container.

Hence, in the process of the invention unused coating material can be used later on for further repair jobs, while a process using standard paint spray equipment leads to deterioration of the UV curable coating material.

Claims

1 . A process of refinishing a transportation vehicle comprising the steps of a) Providing an actinic-radiation curable ready-to-spray liquid coating composition comprising an ethylenically unsaturated radically polymerizable binder and a photoinitiator in a collapsible container made of flexible material which is impermeable for actinic radiation, and which container has a first connection member adapted for connection to a paint spray gun having a second connection member, b) Connecting the container to a paint spray gun,

c) Applying the liquid coating composition to at least a part of the surface of the transportation vehicle by spraying, and

2. The process according to claim 1 , wherein the first connection member is provided with a closing valve to close off the opening of the container and wherein the second connection member is provided with a member acting on the valve to cause its being opened when the container is connected to the paint spray gun, and to cause its being closed when the connector is disconnected from the paint spray gun.

3. The process according to claim 1 or 2, wherein the container is provided in a frame made of rigid material.

4. The process according to any one of the preceding claims, comprising the additional step e) of disconnecting the container and the paint spray gun.

5. The process according to claim 4, wherein step e) is carried out after the entire content of the container has been applied to the surface of the transportation vehicle.

6. The process according to any one of the preceding claims, wherein the coating composition comprises a (meth)acryloyl-functional polyurethane and an ester of (meth)acrylic acid and an alcohol having at least two hydroxyl groups and a molecular weight below 500.

7. The process according to any one of the preceding claims, wherein the actinic radiation is ultraviolet light or visible light.

8. The process according to any one of the preceding claims, wherein the photoinitiator has absorption above a wavelength of 360 nm.

9. The process according to any one of the preceding claims, wherein the photoinitiator has absorption above a wavelength of 380 nm.

10. A process according to any one of the preceding claims, wherein the coating composition is a clear coat.

1 1 . A process according to any one of the preceding claims 1 to 6, wherein the coating composition is a primer-surfacer, and wherein after curing of the coating composition to a cured primer-surfacer layer, a pigmented base coat and a clear top coat are applied on the cured primer-surfacer layer.

12. A process according to any one of the preceding claims, wherein production of the radiation-curable liquid coating composition and filling of the collapsible container are carried out in a closed system.